Environmental Science and Engineering Subseries: Environmental Science Series Editors: R. Allan · U. Förstner · W. Salomons
Lambert A. Rivard With contributions by Q. Hugh J. Gwyn
Geohazardassociated Geounits Atlas and Glossary
With 995 Images and CD-ROM
Author Lambert A. Rivard 201-300 St-Georges St-Lambert QC J4P 3P9 CANADA
[email protected] Contributor Q. Hugh J. Gwyn, Ph.D 445, rue Woodward North Hatley QC J0B 2C0 CANADA
[email protected]
ISBN 978-3-540-20296-7
e-ISBN 978-3-540-68885-3
Environmental Science and Engineering ISSN: 1863-5520 Library of Congress Control Number: 2008936682 © 2009 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitations, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: deblik, Berlin Typesetting: Stasch · Bayreuth Production: Agata Oelschläger, Heidelberg Printed on acid-free paper 9 8 7 6 5 4 3 2 1 springer.com
30/2132/AO
To Carla Hehner-Rivard on whom great personal stress was imposed in this endeavour. Her selfless devotion, her arduous coordinating effort in dealing with the often re-ordered digital data base of the atlas’ illustrations and text, her protracted correspondence in obtaining permissions for close to 1 000 illustrations, and her endless patience with her husband’s importunities, contributed immeasurably to the book’s realization.
Preface
The media now broadcast loss of life and property damage caused by a variety of geologic hazards and geologic terrains worldwide on a near-daily frequency and in near-real-time.
Themes This Atlas and Glossary is the result of the author’s lifetime vocation, practice and research worldwide on the application of vertical air photography and Earth Observation satellite images to geomorphology. His teaching experience and consulting for civil engineers led him to increasingly emphasize the links between specific geounits and their inherent geologic hazards. The idea of producing an atlas documenting these links was inspired by the activities of the International Decade for Natural Disaster Reduction, and he began work on the book in 1998. The integrity of any structure has to rely on the ground on which it stands. There is a general awareness that such common hazards as rock falls, rock slides, and floods are associated with certain geologic formations, structures, and topographic situations. However, this knowledge is not as widespread as a dozen other destructive hazards that threaten human life and property, and are functionally associated with particular geologic processes and formations. These relationships have been established by distilling a selection of geounits as agents of, or susceptible to, specific geohazards, from a comprehensive photogeologic classification and photographic archive that was developed during the author’s training and consultancy work.
Objectives The Atlas and Glossary is a portfolio approach that aims to provide an accessible source of concise information for earth science professionals and students who need to understand the hazards that are associated with specific geological units and geostructures that are mappable using airphotos and satellite images. All the material is presented as integrated data sets whose texts and figures of world wide coverage characterizing a geounit and its geohazards, are a convenient synthesis of information providing a rapid insight for the user from frequently widely scattered sources.
The Illustrations The Atlas and Glossary includes 995 satellite images, vertical airphotos, air perspective views, ground photos and line-art figures that depict and document the classified geounits in their varied photogeologic appearances in diverse biophysical environments on a planet that is too easily thought of as small. Eighty-nine countries are represented.
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Preface
Characterization of Geounits The descriptions of geounit data sets are concise syntheses of current geoscience knowledge. A geounit, as an agent of a geohazard or its susceptibility to other geohazards is discussed in relation to a set of fifteen hazard types detectable on air photos and images under the heading geohazard relations.
Photogeologic Interpretation The Classification provides a set of descriptor codes for the identification of photogeologic units. Interpretations delineate and annotate geounits on the majority of the satellite images and airphotos.
Stereo Viewing The Presentation section of the Introduction explains the inclusion of a CD-ROM to provide stereo viewing of airphoto figures in the Atlas.
Copyright Every effort was made to obtain permission to reproduce copyright material throughout this book. The illustrations are all drawn from an archive of over 400 files. Because some date back more than four decades, the provenance of some has been lost and their source is listed as unattributed. If any proper acknowledgment has not been made, this oversight will be corrected in subsequent editions of the Atlas and Glossary.
Acknowledgments
Preparation of a book, especially a first edition, needs the help and expertise of many people. First among those to whom we are most greatly indebted is Nicholas W. E. Lee. This civil engineer and life-long friend who long presided a photographic survey company, actively promoted the application airphoto interpretation to site selection in civil engineering projects. Nicholas strongly encouraged and supported the author at critical moments in his career. He saw to it that his early experience was developed within international projects. We are particularly grateful to the staff of the Earth Science Information Centre of Natural Resources Canada in Ottawa, especially Penny Minter and Irène Kumar of the Map Library, for their unstinting and prompt response to endless requests. The National Air Photo Library generously permitted the reproduction of numerous stereo and other airphotos, and its staff constantly responded to urgent requests for information. Dr. Stéphane Péloquin, consultant in remote sensing for mineral exploration and a specialist in the development of computer programs for applied earth science made contributions in the methodical formulations that were used for some of the processing of digital data. The initial scanning and processing of the mass of illustrations was performed by Sophie Gaudreau, Micheline Léger and Carl Garneau under the supervision of Martin Trépanier who organized this phase of the book production at Groupe BGJLR Inc. in Québec City. At Springer-Verlag, Dr. Christian Witschel, Executive-Editor Geosciences recognized the merit of our concept of an airphoto and satelite image based atlas relating specific geounits to specific geohazards and made the commitment to see it published. Agata Oelschläger efficiently and with indulgence coordinated the production process. Armin Stasch of Stasch Verlagsservice reconciled our layout and presentation ideals with publishing realities. Lastly, the true source of this atlas are the students of Civil Engineering Courses 303 and 439 in the Civil Engineering Department, McGill University. Their successive classes over the years constituted a persistent challenge to the author to continually refine the content of the sets of pedagogic data, collected, organized and re-organized, for a more effective characterization and presentation of the environmentally varied appearance of given photogeologic units. These cumulative data sets became the basis of the Atlas.
Author and Contributors
Mr. Rivard takes responsibility for the full content of the book, any mistakes, omissions or errors are his. He performed the photogeological interpretations and wrote the comments of the figures of the Part IV atlas. Dr. Q. Hugh J. Gwyn did the initial copy-editing and vetting of the texts of Part I, Part II, Part III and the 160 geounit characterizations of the Glossary sections of the data sets of Part IV. His continued support and technical expertise contributed greatly to the final publication. Major contributions were made by Carla Hehner-Rivard in the overall production control and coordination, figure/text matching and editing, adaptation of line art, image enhancement and picture quality control.
Contents
Part I Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Definition of a Geohazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Geohazard Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Definition of a Geounit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Selection of Geounits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Airphotos and Satellite Images as Sources of Geohazard Information . . . . . . . . . . . . . . . . 2 Presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Part II User’s Guide to the Atlas and Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 II-1 Classification Basis of the Photogeologic Geounits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 II-2 Selection Criteria of the Geounits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 II-3 Characterization of the Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 II-3.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 II-3.2 Mappability of Photogeologic Geounits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 II-3.3 Relationship to Other Image-Based Geo-Science Terrain Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 II-3.4 Present Professional Context of the Classification . . . . . . . . . . . . . . . . . . . . . . . . 6 II-4 Organization of the Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 II-4.1 Division 1: Magmatic Rocks and Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 II-4.2 Division 2: Sedimentary Rocks and Duricrusts . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 II-4.3 Division 3: Geostructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 II-4.4 Division 4: Surficial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 II-5 Geounit Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 II-5.1 Geostructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 II-5.2 Geounit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 II-5.3 Variant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 II-5.4 Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 II-5.5 Relative Chronology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 II-6 Mode of Designation of Mapped Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 General Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Select Bibliography of Remote Sensing Technology for Geologic Interpretation . . . . . . . . . 9
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Part III Classification of Geohazard-Related Geounits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Division 1 Division 2 Division 3 Division 4 Division 4 Division 4 Division 4 Division 4 Division 4 Division 4
Magmatic Rocks and Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Sedimentary Rocks and Duricrusts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Geostructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Surficial Deposits · Group – Aeolian Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Surficial Deposits · Group – Basinal Sediments . . . . . . . . . . . . . . . . . . . . . . . . . 17 Surficial Deposits · Group – Fluvial System Sediments . . . . . . . . . . . . . . . . 18 Surficial Deposits · Group – Marine Littoral Systems . . . . . . . . . . . . . . . . . . 19 Surficial Deposits · Group – Paraglacial Geosystems . . . . . . . . . . . . . . . . . . 20 Surficial Deposits · Group – Periglacial-Related Forms . . . . . . . . . . . . . . . 20 Surficial Deposits · Group – Mass Movement Materials . . . . . . . . . . . . . . . 21
Part IV Data Sets of the Atlas and Glossary of the Geounits and Variants . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Division 1 Magmatic Rocks and Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Group X Extrusive Magmas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 X1 Basaltic Flows, Flow Fields, or Plateaus (Trapps) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 X1.1 Local Slope Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 X1.2 Local Valley Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 X1.3 Disturbed-Dissected Basalts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 X1.4 Dissected Alkaline Basalts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 X2 Interbedded Lavas and Pyroclastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 X2.1 Interbedded Lavas and Pyroclastics, Disturbed Facies . . . . . . . . . . . . . . . . . 58 X2.2 Interbedded Lavas and Pyroclastics, Dissected Facies . . . . . . . . . . . . . . . . . . 60 Group P Tephra Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Sub-group Pf · Falls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Pf1 Pyroclastic Falls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Pf1.1 Ash-Tuff Hills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Pf1.3 Ash-Tuff Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Sub-group Ps · Pyroclastic Density Current Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Ps1 Pyroclastic Flows and Surges, Undifferentiated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Ps1.1 Macroscopic Ignimbrite Outflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Group V Cenozoic Volcanic Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Sub-group Vs · Viscous Lava Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Vs1 Autonomous Domes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Vs1.1 Domes in Cones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Vs1.2 Flow-Dome Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Vs2 Coulées . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Sub-group Vc · Major Conical Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Vc1 Stratovolcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Vc1.1 Dissected Cones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
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Vc2 Shield Volcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vc3 Calderas and Tectonic Depressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vc3.1 Calderas on Stratovolcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vc3.2 Calderas with Post-Caldera Cones and Domes . . . . . . . . . . . . . . . . . . . . . . . . . Vc3.3 Large Silicic Calderas with Resurgent Domes . . . . . . . . . . . . . . . . . . . . . . . . . . Vc3.4 Calderas on Shield Volcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vc4 Volcanic Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
141 146 146 156 166 170 174
Group A Modern Volcanic-Epliclastic Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1 Lahars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2 Volcanic Debris Avalanches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3 Hydrocinerite Plain Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
183 183 188 196
Division 2 Sedimentary Rocks and Duricrusts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 Group K Carbonates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 K3 Karst Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Sub-group Kp · Holokarst Residual Terrains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kp1 Karst Plateaus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kp1.1 Corridored Plateaus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kp2 Pyramid-Labyrinth Karst Terrains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
211 211 222 228
Sub-group Kn · Holokarst Erosional Terrains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Kn1 Poljes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Kn2 Fluviokarst Terrains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Sub-group Kc · Amorphous Carbonates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 Kc2 Chalk and Marl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 Kc4 Interbedded Carbonates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Group H Saline and Phosphatic Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 H1 Cemented Evaporites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Group S Detrital Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S1.2 Weak Rudites-Arenites, Upland Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S1.5 Weak Rudites-Arenites, Lowland Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S2 Siltstones and Lutites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S2.1 Siltstones and Lutites, Dissected Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
266 266 276 284 290
Group W Interbedded Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W1 Interbedded Sedimentary Rocks, Undivided . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W1.1 Coal Seams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W4 Interbedded Weak Rock Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
302 302 310 315
Group D Duricrusts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 D1 Ferricretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
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Division 3 Geostructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Group Gravity Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Stock Salt-Evaporite Diapirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Pillow Domes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Duplex Stocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Extrusive Salt Diapirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Elongate Diapirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
334 334 340 346 348 351
Group Fault Line Traces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Dip-Slip Normal Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 Multidirectional Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Strike-slip Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Thrust Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Composite Lineaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Horst Dip-Slip Fault Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Graben Dip-Slip Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1 Graben Conjugate Fault Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Single Fault Asymmetric Grabens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
357 357 367 370 378 387 390 398 398 407
Group General Lineaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Mesoscale Fracture Traces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Macroscale Discontinuities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.1 Geomorphologic Discontinuities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 Radiometric Discontinuities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Synergic Lineaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
410 410 419 419 427 431
Division 4 Surficial Deposits · Group E – Aeolian Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 Sub-group Et · Inland Aeolian Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434 Et1.1 Blanket Loess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434 Sub-group Ef · Duneless Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 Ef1 Sand Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 Ef2 Sand Streaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 Sub-group Ed · Sand Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1 Free Inland Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.1 Linear Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.2 Transverse Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.3 Barchanoid Ridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.4 Barkhan Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.5 Star Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.6 Dome Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.7 Parabolic Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed1.8 Dune Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ed2 Dune Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
452 452 453 462 465 471 475 479 481 485 486
Contents
Sub-group Eo · Obstacle Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eo1 Shadow Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eo3 Climbing Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eo4 Falling Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
491 491 496 500
Sub-group Ec · Coastal Beach Backshore Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ec1 Parallel Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ec2 Transgressive Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ec3 Free Dunes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
504 504 509 518
Division 4 Surficial Deposits · Group L – Basinal Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525 L1 L2 L3
Pleistocene Glaciolacustrine Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526 Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments . . . . . . 540 Quaternary Drained Lakebeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
Division 4 Surficial Deposits · Group F – Fluvial System Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 Sub-group Fu · Upland Margin Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556 Fu1 Alluvial Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556 Fu1/Mv1.2 Alluvial Fan and Talus Cone Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572 Sub-group Fv · Valley Fill Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fv1 Braided Alluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fv1.1 High Gradient Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fv1.2 Low Gradient Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fv2 Meandering Alluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
580 581 582 587 599
Sub-group Fv · Valley Fill Composite Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637 Fv1.1/Fv2 Meandering-Braided Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637 Sub-group Fw · Holocene Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fw1 Arcuate Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fw2 Elongate Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fw3 Estuarine Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fw3.1 Macrotidal Estuaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fw4 Cuspate Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
644 645 651 657 661 668
Sub-group Fr · Climatic Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675 Fr2 Inland Deltas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675 Division 4 Surficial Deposits · Group B – Marine Littoral Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681 Sub-group Br · Bedrock Littorals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Br2.1 High Rock Cliffs Unstable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Br3.1 Low Rock Cliffs Weak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Br4.1 Bedrock Hills Weak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Br6 Tectonic Eustatic Marine Terraces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Br7 Bedrock Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
682 683 686 689 691 695
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XVIII Contents
Sub-group Bb · Residual Shorelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 Bb1 Bluffs in Unconsolidated Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 Bb1.1 Bluffs in Frozen Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704 Sub-group Bw · Wave and Current-formed Littoral Sediments . . . . . . . . . . . . . . . . . . Bw2 Offshore Bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bw3 Near-Shore Barrier Beaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bw3.1 Bay Barrier Beaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bw4 Attached Beaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bw5 Spits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bw6 Tombolos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
709 709 712 720 729 732 736
Sub-group Bl · Sea Ice and Sea Ice Related Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741 Bl1 Sea Ice Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741 Sub-group Bt · Tidal Regime Deposits and Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745 Bt1 Lagoons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745 Sub-group Bc · Coastal Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bc1 Plains of Marine Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bc2 Passive Margin Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bc3 Glaciomarine Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bc4 Fluviomarine Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
778 778 792 795 806
Sub-group Bp · Low Latitude Offshore Carbonate Platforms . . . . . . . . . . . . . . . . . . . . 815 Bp1 Subtidal Banks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 815 Division 4 Surficial Deposits · Group G – Paraglacial Geosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819 Sub-group Gl · Ice Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820 Gl4 Outlet Tidewater Glaciers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820 Gl5 Valley Glaciers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 Sub-group Gf · Glaciofluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845 Gf4 Eroded Till Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845 Gf5 Boulder Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 851 Division 4 Surficial Deposits · Group Z – Periglacial-Related Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855 Sub-group Zi · Ground Ice Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857 Zi4 Ice Wedge Polygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857 Sub-group Zm · Cryoturbated Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zm1 Gelifluction Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zm1.1 Gelifluction Sheets and Lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zm1.2 Gelifluction Stripes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zm2 Rock Glaciers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zm5 Detachment Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
869 869 869 879 885 893
Sub-group Zk · Thermokarst Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895 Zk1 Subsidence Terrains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895 Zk2 Retrogressive Thaw-Flow Slides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904
Contents
Division 4 Surficial Deposits · Group M – Mass Movement Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907 Sub-group Mv · Falls and Subsidences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv1 Talus-Rockfalls Undifferentiated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv1.1 Talus Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv1.2 Talus Cones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv2 Rock Avalanches (Sturzströmen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv2.1 Rock Avalanches, Inactive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv3 Toppled Rock Slabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv4 Subsidences, Sudden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mv5 Subsidence Zones, Gradual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
908 908 912 922 926 930 936 938 944
Sub-group Ml · Lateral Spreads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953 Ml1 Rock Block Glides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953 Sub-group Mc · Diagonal Creeps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 956 Mc1 Colluvial Mantle Movement Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 956 Sub-group Ms · Slides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms1 Planar Rock Slides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms1.1 Planar Rock Slides, Inactive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms2 Debris Slides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms2.1 Debris Avalanches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms3 Rotational Rock Slumps, Undifferentiated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms3.1 Rotational Rock Slumps, Inactive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms4 Snow Avalanches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ms5 Ice Avalanches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
959 959 964 969 972 977 984 986 992
Sub-group Mf · Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 998 Mf1 Retrogressive Flows in Unconsolidated Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 998 Mf1.1 Retrogressive Slides in Unconsolidated Sediments and Detrital Rocks Substrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1007 Mf2 Earth Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010 Mf2.1 Slow Earth Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017 Mf3 Debris-Mud Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021 Mf4 Mountain Valley Natural Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036 Mf4.1 Landslide Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036 Mf4.2 Moraine Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043 Mf4.3 Glacier Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1048 Appendix Abbreviations and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053
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I Part I Introduction
This book is an Atlas and Glossary of data sets of geounits associated with geohazards that are detectable in optical and radar airphotos and satellite images. These sets are intended to provide a reference and instructional aid for geoscience professionals and students in physical, engineering, environmental geology as well as hydrogeology, geomorphology and physical geography. Its geographical reach is global. Hazard mitigation measures are illustrated incidentally where they happen to be evident in the airphotos and space images or within characterizing photos of geounits.
Background The approach to environmental studies used in the Atlas and Glossary is a result of the author’s more than three decades of consultancy practice worldwide, and teaching of photogeology and remote sensing in engineering geology and physical geography. During that time a scheme was evolved to order and classify geological units as they are resolved spatially and spectrally on airphotos and images. This has resulted in a comprehensive updated glossary of photogeological units comprising 177 basic units and 178 variants. The present Atlas Glossary was derived from the more general glossary by applying the method described below to identify geohazard-associated geounits. It comprises autonomous data sets of 94 basic units and 70 facies.
Definition of a Geohazard The following definition of a geohazard is extracted from that as given by Gares et al. (1994, p 5): “Geomorphic hazards must be regarded as the suite of threats to human resources arising from instability of the surface features of the earth. The threat arises from landform response to surficial processes, although the initiating processes may originate at great distances from the surface.”
Geohazard Types The geounits have been evaluated as associated with 15 principal hazard types. They are either agents of a particular hazard or are susceptible to particular hazards including three hydrologic hazards. The hazard types are listed in Table I.1. This dual evaluation of a geounit incorporates both hazard process and landform response as proposed by Gare et al. (1994).
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_1, © Springer-Verlag Berlin Heidelberg 2009
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Airphotos and Satellite Images as Sources of Geohazard Information
A well-illustrated general overview of geological processes and related geohazards is presented in United States Geological Survey Bull. 2149, Geologic Processes at the Land Surface (1996).
Definition of a Geounit A Geounit is a portion of a tract of land having recognizable lithologic contact boundaries at scales related to airphotos and space imagery, and whose overall homogeneity is a function of its genesis, composition, geologic structure and relief type.
Selection of Geounits The methodology to produce the list of geounits associated with geohazards consisted of a sequence of empirical selective questions and decisions. Considering the intrinsic geologic characteristics of a given unit and its typical topographic situation relative to surrounding geounits is the unit judged to be stable or unstable with respect to the listed geohazard types For which of the geohazard types is the unstable unit intrinsically a potential agent? (e.g. flow/liquefaction hazard is intrinsic to a glaciomarine plain; solution hazard is intrinsic to the karst plateau) To which of the hazard types extrinsic to the geounit is it potentially susceptible? (e.g. a glaciomarine plain is potentially susceptible to the flooding hazard; the karst plateau is susceptible to the fall and subsidence hazards) A useful two-page spread overview of ground geohazard associations is presented in T. Waltham, Foundations of Engineering Geology, Spon Press, 2002; Topic 37 – Understanding Ground Conditions.
Detection and identification of geounits and their associated geohazards is a geomorphological science method based on spatial and spectral attributes of landforms visible on stereoscopic airphotos or high resolution stereoscopic Earth Observation satellite images. The attributes (relief, shape, size, reflectance, locational context) are based on concepts and principles which were developed by photogeologists eighty years ago. Monoscopic satellite images are generally less suitable for detailed mapping of geohazard types presented in this atlas. Brown et al. 2007 reported predictive mapping of surficial materials in the arctic using Landsat TM and digital elevation data. The maps produced in advance of field work were found to be approximately 50% accurate. The literature on hazard types per se is voluminous while that on the use of aerospace data as sources of geohazard information is uneven. A concise overview of the former, where use of airphotos is mentioned frequently, is the monograph by Legget and Karrow (1983) on geology and civil engineering. Referring to such problems, and leaving costs aside, Waltham states “Civil engineering design can accommodate almost any ground conditions which are correctly assessed and understood.” (Spon Press 2002). A guide to special problems limited to slope instabilities of hazard types 3 to 8, is given by Soeters and van Westen (1996). The detection and interpretability of hazard types 3 to 8 in that report is summarized as follows: “Experience at the International Institute for Aerospace Survey and Earth Sciences with the use of photointerpretation techniques in support of landslide hazard investigations in various climatic zones and for a considerable variety of terrain conditions suggests that a scale of 1 : 15 000 appears to be the optimum scale for aerial photographs, whereas a scale of 1 : 25 000 should be considered the smallest useful scale for analysing slope instability phenomena with aerial photographs. A slope failure may be recognized on smaller scale photography provided that the failure is large enough and the photographic contrast is sufficient.” (Soeters and van Westen 1996, p 159). Discussions of aerospace data applications to hazard types 9 to 12 are scattered in the geological and civil engineering literature pertaining to the description of geounits related to those hazards. Hydrologic hazards 13, 14, and 15 are particularly amenable to monitoring and mapping by satellite optical and cloud penetrating microwave sensors. Published information on the subject is abundant and readily available (search keywords “floodplains”, “barrier beaches”, “lagoons”, “coastal plains”).
Presentation
Much of current R&D on geologic remote sensing systems focuses on spectral attributes of lithologies. Recent systems of note are ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) which captures data in 14 spectral bands in 15, 30 and 90 m pixels and in 60 × 60 km scenes. The Shuttle Radar Topography Mission (STRM) used radar interferometry to derive elevation models for 80% of the Earth’s landmass (±60 degrees latitude) with 30 and 90 m pixels depending on locations and 20 m vertical accuracy. Table I.2 illustrates the usefulness and the principal characteristics of satellite images for the purpose of geohazard study. The currently Internet accessible Global Earth EO satellite imaging system is a highly useful coverage complementary to the scenes and airphotos that make up this Atlas. The coordinates of some Figures differ from those of that system.
Presentation The 160 Geounits and Variants are ordered as data sets of each unit which include a Glossary of descriptive text and figures, an Atlas of interpreted satellite images and vertical airphotos and a select bibliography.
The Glossary portion includes a concise monograph that characterizes the unit, states its geohazard relations and provides a select bibliography of key texts and primary papers. The text is supported by various graphics – cross sections, block diagrams, maps – ground and air perspective photos. A total of 477 of such characterizing figures are presented. Some reproductions, though of less than top quality, are included because they were considered vital for proper documentation of a particular geounit. The Atlas portion consists of a set of geographically and geologically located vertical airphotos and/or satellite images each of which is accompanied by interpretative comments and the majority of which are overlaid with unit delineations and/or annotations. A total of 518 figures make up the Atlas including 142 EO satellite images, 20 satellite radar images, 54 monoscopic vertical airphotos, 90 mounted stereograms and 212 CD-ROM based free and mounted stereo airphoto pairs and triplets. The scales given are those of the figures as published by the source and, in individual cases, may not be exactly as reproduced in the Atlas.
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The CD-ROM contains the air photos that complete those in the body of the book for stereo viewing as indicated by Soeters and van Westen, p 158. “Landforms are among the most conspicuous phenomena appearing in the imagery obtained from aerospace. This is particularly the case if a three-dimensional image suitable for stereoscopic study is involved and provides a basis for deductive interpretation on the basis of morphogenetical reasoning”. (Verstappen 1977). Such stereo viewing of terrain is so valuable for the detection and interpretation of geounits that stereo capability has been incorporated into the more recent EO satellites. Both stereopairs and stereotriplets are included in the CD-ROM, from which paper copies of the airphotos can be printed to match those in the book. Stereo viewing is accomplished by laying a print beside its mate photo in the book and viewing them with the use of a simple pocket stereoscope. A useful comparison may be made of the CD-ROM sets with their monoscopic Google Earth image on the Internet. Bibliographies. The following text paraphrases that of Ernst Breisach in On the Future of History (Chicago 2003). In the age of extensive electronic databases and access to online catalogues of numerous libraries, the
ideal of comprehensiveness can yield its place to other objectives in the compilation of bibliographies. The select bibliographies of each geounit and variant support the purpose of this glossary; to be a guide to the characterization of geounits. Besides documenting the resources used by the author, the selected works will facilitate the reader’s own interests and explorations.
References Brown O, Harris JR, Utting D, Little EC (2007) Remote predictive mapping on surficial materials on nothern Baffin Island: Developing and testing techniques using Landsat TM and digital elevation data. GSC, Current Research 2007-B1, p 12 Gares PA, Sherman J, Nordstrom KF (1994) Geomorphology and natural hazards. Geomorphology 10 Hutchinson JN (2001) Reading the ground: Morphology and geology in site appraisal. Quarterly Journal of Engineering Geology and Hydrogeology 34:7–50 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York Soeters R, van Westen CJ (1996) Slope instability recognition, analysis, and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Special Report 247. Transportation Research Board, National Research Council, Washington, D.C., p 158–159 Verstappen HTh (1977) Remote sensing in geomorphology. Elsevier Scientific Publishing Co., NY Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 74–75
II Part II User’s Guide to the Atlas and Glossary
II-1 Classification Basis of the Photogeologic Geounits The logic underlying the classification of the geounits is essentially the same as that which supports other forms of geologic mapping. Varnes (1974) has stated “Four fundamental categories of attributes apply to (geologic) maps; these pertain to time, space, the inherent qualities or properties of real matter, and the relations of objects. Geologic units commonly are defined by combinations of these four kinds of attributes.” The typological individuals of the classification conform to these attributes and their nomenclature conforms to accepted geoscience usage.
II-2 Selection Criteria of the Geounits The following criteria were used in selecting the specific geohazard related geounits from the general classification. That the typological individuals be detectable and recognizable in current operational civil satellite images and airphotos with a spatial resolution range of submetric to 1 km, subject to other factors conditioning observability (Sect. II-3.2). That the classification includes all the major terrestrial environments. That the units possess a compositional homogeneity with respect to a number of observable and inferred attributes. That the units be significant in broader engineering and environmental terms. The approach chosen to document the type units has been to examine airphoto coverage and satellite images of known lithologies and structures located in the various terrestrial environments. Reproductions of representative photos and images studied were thus progressively incorporated in the data sets of the geounit files as the group of illustrations in support of their textual characterizations.
II-3 Characterization of the Classification II-3.1 Purpose Geological and geomorphological interpretation and mapping requires the use of a set of descriptor codes to designate geounits. The codes best consist of combinations L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_2, © Springer-Verlag Berlin Heidelberg 2009
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of alpha-numeric symbols (Fulton 1993). The complete set of descriptors constitutes a terrain classification system. When the units are compiled as a photogeologic map these codes can also become the map legend.
II-3.4 Present Professional Context of the Classification In his advanced text on the use of remote sensing in the geological sciences Scanvic (1993) stated:
II-3.2 Mappability of Photogeologic Geounits
(the geoscience community) “… can anticipate methodological developments whose aims are to optimize the application of remote sensing techniques to the traditional activities of the (field) geologist. This applies particularly to the photo-image analyst who is attempting to gain an understanding of the geological environment of a given area. It proceeds from the normal synthesizing of multi bits of photo-image and extra-image evidence (integrated as distinct terrain units), currently the most operational photo-image interpretation method directed to the goal of an objective characterization of the terrain.” (author’s translation).
The expression of a geounit within a photo or image, and hence its mappability, is conditioned by a number of factors: sufficient distinction in lithologic composition or structure occurring in a terrain nature of the denudational processes that act or have acted on it environment in which it presently occurs spectral characteristics of geologic materials in outcrop spectral characteristics of associated vegetation or land-use spatial, spectral and temporal resolutions of the sensor system that acquired the imagery or airphoto data processing techniques employed to generate the image available background information aptitude of the person performing the interpretation Subject to the above factors, a given photogeologic interpretation or map will result in geologic information of differing specificity and accuracy.
II-3.3 Relationship to Other Image-Based Geo-Science Terrain Classifications Beginning in the 1950s a number of systematic treatments of genetic terrain units were formulated for the interpretation of stereoscopic vertical air photographs in what has become recognized as the field of Photogeology. A notable example of this is the manual by Howes and Kenk (1988). Since the advent of multispectral scanners aboard EarthObservation satellites in the 1970s, a number of texts dealing with remote sensing in geology and geomorphology have appeared. A comprehensive lexicon of lithologic geology was not central to the purposes of these works. Only Meijerink (1988) and Short and Blair (1986) contain classifications approximating the systematization introduced here. The listings of Terrain Mapping Units in Meijerink (1988) is incidental to the presentation of a GIS-compatible methodology, while Short and Blair (1986) focus on structural (rather than lithologic) patterns associated with tectonic terranes and selected denudational landform categories as they appear on the early Landsat images. Mesoscale units best resolved on airphotos are not considered in that book.
II-4 Organization of the Classification The classification is ordered in 4 lithologic and structural Divisions and 19 Genetic Groups.
II-4.1 Division 1: Magmatic Rocks and Structures The Units of this Division are primary igneous rock bodies lithified or welded. Genetic Groups of this Division include:
extrusive microlithic magmas pyro- and volcaniclastic deposits modern volcanic structures modern epiclastic deposits
II-4.2 Division 2: Sedimentary Rocks and Duricrusts This Division consists of 5 Genetic Groups:
carbonates saline and phosphatic rocks detrital rocks interbedded sequences duricrusts
Note: No metamorphic rocks appear in the present classification. As stated by Ehlen (1983) none of the three common classifications for predicting metamorphic rocks, textural, facies and formational, were found adequate for use on airphotos. Subsequent remote sensing
II 5 · Geounit Terminology
research indicates a potential possibility for identification of these rock types spectrally. Pre-Phanerozoic cratonic metamorphic rocks, like intrusive magmatic rocks, do not have geohazard relations as defined in this glossary. Non-cratonic metamorphic rocks that have geohazard relations are low-grade slate and schist. Due to their cleavages and foliations these rocks are susceptible to mechanical weathering and erosion in the same manner as siltstones and lutites among detrital and interbedded rocks.
II-4.3 Division 3: Geostructures The Structural Units are areas of deformation and displacement of rocks of Divisions 2, 3 and 4. Three structural Groups include: gravity structures fault line traces general lineaments
II-4.4 Division 4: Surficial Deposits With the exception of the basinal sediments and paraglacial groups, Geounits of this Division result from the transport and deposition in an unconsolidated state of materials eroded from the rocks and structures of the other Divisions by subaerial and marine denudation processes. Genetic Groups of Surficial Deposits include:
aeolian deposits basinal sediments fluvial system sediments marine littoral systems paraglacial geosystems periglacial-related forms mass movement materials
II-5 Geounit Terminology The Classification contains four types of typological individuals: Geostructures, Geounits, Variants and Components. They are defined and symbolically designated as follows.
II-5.1 Geostructure Definition. A Geostructure is a geounit of macro or meso scale which occurs in one of two modes:
as a portion of or all of the mass of a rock Unit which has been subjected to particular diastrophic processes as a macroscopic scale Unit in its own right Designation. A Geostructure is designated by conventional geological map symbols and by numeric codes as indicated for individual units in the Division.
II-5.2 Geounit Definition. Photogeologically a geounit is a portion of a tract of land having recognizable boundaries at appropriate photo or imagery scales and whose overall homogeneity is a function of its genesis, composition, geologic structure and relief type. A geounit approximates in conception the pedologist’s “polypedon” (Gerrard 1981, pp 6–7) and the engineering geologist’s “lithologic type” (IAEG 1981, pp 252–253). Designation. A geounit is identified by a pairing of a single upper case letter code and number, when it is part of a Group (e.g. X1 for a (undisturbed) basalt flow); or by an upper and lower case letter combination and number when it is part of a Sub-group (e.g. Ed1 for linear dunes). The alpha character codes for Genetic Groups are given in Table II.1.
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Part II · User’s Guide to the Atlas and Glossary
II-5.3 Variant
II-5.4 Component
Definition. The Variant is a photo-image distinguishable ‘facies’ resulting from the action of one of a number of geologic or environmental factors. It is genetically assignable to a parent geounit. A variety of geologic factors are illustrated in the following examples. (Refer to the classification tables for the geological designations.)
Definition. A Component is a mesoscale deposit or landform produced by genetic, structural or erosional processes. It has the following attributes:
genesis, e.g. Fv1.2, Zm1.2 diagenesis, e.g. Ps1.1, S1.2 tectonism, e.g. X1.3 relative age, e.g. Ms1.1 morphology, e.g. Mv1.1, Ed1.1 topographic site, e.g. X1.2 climatic occurrence, e.g. Bb1.1
Designation. A Variant is identified by a number following the Unit designation, (e.g. Variant S2.1 – lutite dissected facies of Unit S2 – lutites undifferentiated).
functionally integrated with the parent Unit dimensions are smaller than the parent Unit Designation. Components are indicated by a qualifying lower case letter descriptor following the Unit or Variant designation (e.g. Fv2b – a levee within a low energy alluvial deposit Unit polygon; L3c clay-salt temporal wet zone).
II-5.5 Relative Chronology Existing geological maps may enable interpreters to specify the age relations of adjacent geounits or superposed sequences of units. Suggested symbols of a general temporal nomenclature that may be used in such cases are listed in Table II.2.
Select Bibliography of Remote Sensing Technology for Geologic Interpretation
II-6 Mode of Designation of Mapped Units The degree of certainty of identification and designation of geounits that is achievable in any photo-image interpretation is conditioned by the factors listed in Sect. II-3.2: Subject to those factors, an interpreter may combine descriptor codes of the classification to geounits that have been delineated and about which he/she can be more specific. For example, composition codes may be added to structural rock units or other deposits. Some specific examples are: 2-S1.1 designates not only a cuesta in layered rocks, but more specifically one in stabilised cemented sandstones Br2.1-X1 designates an unstable high rock cliff of basalt Mv2-S2/S1.2 designates a rock avalanche in shale beds overlying a mass of weakly-cemented sandstones relative thickness and superposition of certain surficial deposits (fluvial, lacustrine, glacial) when interpretable may be designated by use of a fractional code: – Zi4/L2 designates ice wedge polygons developed on glaciolacustrine sediments – Ef1/X1 designates sand sheets flowing over a basalt flow field
References Fulton RJ (1993) Surficial geology mapping at the Geological Survey of Canada: Its evolution to meet Canada’s changing needs. Canadian Journal of Earth Sciences, vol 30, p 237 Gerrard AJ (1981) Soils and landforms. George Allen and Unwin, London Matula M (1981) Rock and soil description and classification for engineering geological mapping. Report by the IAEG Commission on Engineering Geological Mapping. Bull. IAEG no 24, pp 235–274 Meijerink AMJ (1988) Data acquisition and data capture through terrain mapping units. ITC Jour., 1988-1. Scanvic J-Y (1983) Utilisation de la télédétection dans les sciences de la terre, BRGM, France, Manuel et méthodes, no 7 Short NM, Blair RW Jr (eds) (1986) Geomorphology from Space. NASA SP 486 Varnes DJ (1974) The logic of geological maps, with reference to their interpretation and use for engineering purposes. USGS Professional Paper 837
Soeters R, van Westen C (1996) Landslides: investigation and mitigation. Special Report 247. Transportation Research Board, National Research Council, Washington, D.C. Thomas MF (1974) Tropical geomorphology. Macmillan, London, pp 158–159 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 74–75
Select Bibliography of Remote Sensing Technology for Geologic Interpretation Optical Airphotogeology Allum JAE (1966) Photogeology and regional mapping. Pergamon Press, Oxford Ehlen J (1981) The identification of rock types in an arid region by air photo patterns. US Army Corps of Engineers Topographic Labs, ETL-0261 Ehlen J (1983) The classification of metamorphic rocks and their applications to air photo interpretation procedures. US Army Corps of Engineers, Topographic Labs, ETL-0341 Ehlers M, Hermann J, Kaufmann UM (2004) Remote sensing for environmental monitoring, GIS applications and geology. Society of Photographic Instrumentation Engineering Keser N (1976) Interpretation of landforms from aerial photographs. Province of British Columbia, Ministry of Forests Lueder DR (1959) Aerial photographic interpretation. McGraw-Hill, New York Mekel JFM (1970) The use of aerial photos in geology and engineering. ITC Textbook of Photo Interpretation, vol VIII. International Institute for Aerial Survey and Earth Sciences Miller VC (1961) Photogeology. McGraw-Hill, New York Mollard JD, Janes JR (1983) Airphoto interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy Mines and Resources, Canada Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS Professional Paper 373 Summerson CH (1954) A philosophy for photo interpreters. Photogrammeric Engineering 20(3):396 Townshend JRG (ed) (1981) Terrain analysis and remote sensing. George Allen & Unwin, London Tricart JS, Rimbert S, Lutz G (1970) Introduction a l’utilisation des Photographies Aériennes en Géographie, Géologie Écologie. SEDES, France Verstappen HTh (1977) Remote sensing in geomorphology. Elsevier Scientific Publishing Co., NY van Zuidam RA (1985/86) Aerial photo interpretation in terrain analysis and geomorphological mapping. Smits Publishers/ITC, The Hague von Bandat HF (1962) Aerogeology. Gulf Publishing Company, Houston, Texas
General Bibliography Electro-Optical Satellite Imageries Bell FG (1999) Geological hazards: Their assessment, avoidance and mitigation. Taylor & Francis Hayden RS (1985) Geomorphological similarity and uniqueness. NASA Conference Publ. 2312, Global Mega-Geomorphology, pp 21–22 Howard JA, Mitchell CW (1985) Phytogeomorphology. John Wiley & Sons, New York Hunt RE (2007) Geologic hazards: A field guide for geotechnical engineers. Taylor & Francis IAEG Bull (1981) No 23, pp 235–274 Kusky TM (2003) Geological hazards: A sourcebook. Greenwood Publishing Group
Amaral G (1984) Remote sensing systems comparisons for geological mapping in Brazil. Proceedings, IUGS/UNESCO Seminar, Remote Sensing for Geological Mapping, pp 91–106 Berger Z (1994) Satellite hydrocarbon exploration. Springer-Verlag, Berlin Blodget HW, Brown GF (1982) Geological mapping by use of computer enhanced imagery in Western Saudi Arabia. USGS Professional Paper 1153 de Silva S, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin
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Part II · User’s Guide to the Atlas and Glossary Drury SA (1987) Image interpretation in geology. Allen & Unwin, London Gupta RP (1991) Remote sensing geology. Springer-Verlag, Heidelberg Prost GL (2002) Remote sensing for geologists: A guide to image interpretation. Gordon & Breach Williams RS, Marsh SE (1983) Geological applications. Manual of remote sensing 2nd edn, Chap. 31. American Society of Photogrammetry
Radar Geology Dallemand JF, Lichtenegge J, Raney RK, Schumann R (1993) Radar imagery: Theory and interpretation. Remote Sensing Centre, Food and Agriculture Organization, United Nations, RSC Series No 67 RADARSAT International (1996) RADARSAT geology handbook, Client Services
Sabins FF (1999) Geologic mapping and remote sensing. Proceedings, Thirteenth International Conference on Applied Geologic Remote Sensing, Vancouver. pp I-41, I-42 Scanvic JY (1993) Télédétection aérospatiale et informations géologiques. BRGM, France, Manuel et méthodes, no. 24 Siegal BS, Gillespie AR (1980) Remote sensing in geology. John Wiley & Sons, New York Singhroy VH (ed) (1994) Special issue on radar geology. Canadian Journal of Remote Sensing 20(3): 197–349 Singhroy VH, Kenny FM, Barnett PJ (1989) Radar imagery for Quaternary geological mapping in glaciated terrains. Proceedings, 7th Thematic Conference on Remote Sensing for Exploration Geology, pp 591–600 Trautwein CM, Taranik JV (1978) Analytic and interpretive procedures for remote sensing data. USGS, Sioux Falls, S.D. van Sleen LA (1984) Analysis of MSS Landsat data for small-scale soil surveys in the humid tropics. Proceedings, 18th ERIM Remote Sensing Symposium, pp 1973–1982
III Part III Classification of Geohazard-Related Geounits
This classification establishes the position of geounits as typological individuals in an ordered genetic grouping of 4 lithologic and structural Divisions, 19 Groups and 32 Sub-groups. Its characterization is explained in Sect. 4, of the User’s Guide to the Atlas and Glossary and its organization is outlined in Sect. 5. The term facies has been used in the sense of the distinctive appearance of a unit or variant rather than its composition or stratigraphy. Hiatuses in the numbering of Geounit descriptor codes are due to their derivation from the comprehensive classification developed by the author. For ease of reference see Table III.1 (a reproduction of Table I.1), which contains the principal hazard types.
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_3, © Springer-Verlag Berlin Heidelberg 2009
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Part III · Classification of Geohazard Related Geounits
Division 1 Magmatic Rocks and Structures
Division 1 · Magmatic Rocks and Structures
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Part III · Classification of Geohazard Related Geounits
Division 2 Sedimentary Rocks and Duricrusts
Division 3 · Geostructures
Division 3 Geostructures
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Division 4 Surficial Deposits · Group – Aeolian Deposits
Division 4 · Group Basinal Sediments
Division 4 Surficial Deposits · Group – Basinal Sediments
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Division 4 Surficial Deposits · Group – Fluvial System Sediments
Division 4 · Group Marine Littoral Systems
Division 4 Surficial Deposits · Group – Marine Littoral Systems
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Division 4 Surficial Deposits · Group – Paraglacial Geosystems
Division 4 Surficial Deposits · Group – Periglacial-Related Forms
Division 4 · Group Mass Movement Materials
Division 4 Surficial Deposits · Group – Mass Movement Materials
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IV Part IV Data Sets of the Atlas and Glossary of the Geounits and Variants
Division 1 Magmatic Rocks and Structures
Group X Extrusive Magmas Group P Tephra Deposits Sub-group Pf Falls Sub-group Ps Pyroclastic Density Current Deposits Group V Cenozoic Volcanic Structures Sub-group Vs Viscous Lava Structures Sub-group Vc Major Conical Structures Group A Modern VolcanicEpliclastic Deposits
General Notes of Geohazard Relations The variety of Quaternary volcanic geounits is greater than that of any other Earth subaerial rock type.The units that have geohazard relations are ordered in four Groups: Extrusive lavas. These have two Units and six Variants that are agents of eruption and deposition and are susceptible to rockfalls, sliding and slumping. Tephra deposits include two Units and three Variants; they are also agents of eruption and deposition but are highly susceptible to flowing and erosion. Volcanic structures have seven Units and seven Variants divided into viscous lava domes and conical structures proper. The viscous lavas are agents of eruption and flowing, and are susceptible to erosion,while volcanic cones and calderas are agents of eruption and are susceptible to seismicity and erosion. Epiclastic deposits consist of three Units that are the result of secondary surface processes of erosion and transportation operating on the units of the other volcanic groups. They are agents of flowing, and deposition, and are susceptible to erosion. Although these rocks occur on approximately 3% of the Earth’s land surface, their destructiveness is out of all proportion to their extent. “Fully 80% of the world’s population lives in, and presumably pays taxes to, nations with responsibility for at least one Holocene volcano” (Simkin T, Siebert L (2000) Encyclopedia of volcanoes. Academic Press, p 252).
Occurrence The patterns of occurrence of extrusive magmatic rocks on the Earth’s surface are associated with five principal tectonic settings: The linear orogenic belts of convergent tectonic plates. Divergent continental rifts, (most eruptions along divergent plate boundaries are submarine mid-ocean and are undetected). Passive intra-plate fault zones. Stationary “hot spots” of upwelling magma over which continental or oceanic portions of lithospheric plates move. Intraplate magmatism (18 illustrations) is poorly understood.
Usefulness of Volcanoes Volcanoes may however be benevolent in a number of ways by
creating new land which can be used for agricultural or urban development providing building materials (e.g. welded tuffs) contributing to the formation of certain ore deposits (sulphur,alum,boric acid,perlite) providing a source of energy (geothermal power plants)
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_4, © Springer-Verlag Berlin Heidelberg 2009
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Division 1 · Magmatic Rocks and Structures
Group X Extrusive Magmas X1
X1 Basaltic Flows, Flow Fields, or Plateaus (Trapps) Characterization Basalt lava flows are discreet bodies of hot silicate liquids emplaced non-explosively as dynamically continuous units. Flow fields are a collection of lava flows produced by the same effusion (Kilburn 2000). They are the meso- and macroscale equivalent of regionally extensive plateau basalts. Basalt flows are erupted from central vents to produce narrow streams (Variant X1.1) or low coalescing shields, or from fissures to produce sheets in units up to 10 m thick. Edlgjá (AD 934, 30 km east of Hetkla in southern Iceland) at 30 km is the longest fissure on Earth. It is paralleled 5 km to the east by the catastrophic Lakagigar Fissure 1783 25 km in length which erupted 20 million tonnes of toxic tephra along with 565 km2 of lavas. The rate of effusion of basaltic lava, and the slope of the surface onto which it is erupted determine the morphology of the extrusions. Because of their fluidity basalt flows are capable of extending to great distances from the vent or fissure and often form thick piles as one flow builds on another to develop flow fields which can widen until halted by topography or by the end of effusion. Flows are characteristically highly jointed, the result of shrinkage during cooling in the form of both columnar and contraction joints. These flows are porous and have few surface streams. Basalt rock is itself impermeable, and where it is not highly jointed runoff develops relatively dense drainage patterns as seen in Variant X1.3. The terms Aa, Pahoehoe, and Blocky that are frequently encountered in discussions of fresh lava flows refer to a field classification of the lava crust appearance and distinct styles of flow growth. These features are poorly resolved at usual airphoto scales, i.e. 1:30 000 and smaller, however, they can be detected in radar images because of differences in surface roughness. Fresh lava flows are among the volcanic geounits that have distinctive thermal characteristics.
Geohazard Relations Property damage rather than loss of life is the principal hazard associated with basalt flows during an eruption. Secondary hazards include the expulsion of toxic gases accompanying eruption. Forest fires may be started. Thick lava blankets sterilize agricultural land for years, though the rate of land recovery is relatively fast in wet tropical zones. Weathering of columnar joints, seepage and erosion of underlying weaker rocks contribute to a susceptibility to massive slumping along plateau scarps. Early detection and monitoring of active lava flows using satellite sensors is being rapidly developed by remote sensing specialists, volcanologists and operating agencies.
Select Bibliography Cas RAF, Wright JV (1987) Volcanic successions. Allen and Unwin, London, p 73 Flynn LP, Harris AJL, Rothery DA, Oppenheimer C (2000) High spatial-resolution thermal remote sensing of active volcanic features using landsat and hyperspectral data. Remote Sensing of Active Volcanism, Geophysical Monograph 116. American Geophysical Union, pp 161–176 Hickson CJ, Edwards BR (2001) Volcanoes and volcanic hazards in Canada. In: Brooks GR (ed) A synthesis of geological hazards. GSC Bull 548:145–181 Kilburn CRJ (2000) Lava flows and flow fields. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 291–305 Krafft M, de Larouzière FD (1999) Guide des Volcans d’Europe et des Canaries. Delachaux et Niestlé Macdonald GA, Abbott AI, Peterson FL (1983) Volcanoes in the sea: The geology of Hawaii. Univ. of Hawaii Press, Honolulu, pp 162–163 Peterson DW, Tilling RI (2000) Lava flow hazards. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 957–971 Rothery DA, Pieri DC (1993) Remote sensing of active lava. In: Kilburn CRJ, Luongo G (eds) Active lava. University College London Press, pp 203–323 Scarpa R, Tilling RI (eds) (1996) Monitoring and mitigation of volcano hazards. Springer-Verlag, Heidelberg Smith K (1996) Environmental hazards, 2nd edn. Routledge, London, pp 161–165 Walker GPL (1973) Lengths of lava flows. Phil Trans R Soc London, A274:107–118
X1 · Basaltic Flows, Flow Fields, or Plateaus (Trapps)
Fig. X1-1. Source. USGS Comments. The block diagram depicts the characteristic mode of effusion and extended flow of successive sheets of basaltic lava from a fissure to form thick piles as one flow builds on another. See a ground photo of such a pile in Fig. X1-3.
Fig. X1-2. Source. USGS Comments. The photo shows a basaltic lava flow encroaching on a road in the Hawaii Volcanoes National Park.
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Fig. X1-3. Source. Courtesy of Natural Resources Canada, GSC 74079 Comments. Photo shows a succession of Tertiary basalt flows with characteristic columnar jointing at Mission Creek, British Columbia.
28 Division 1 · Magmatic Rocks and Structures
X1 · Basaltic Flows, Flow Fields, or Plateaus (Trapps)
Fig. X1-4. Location. Geographic. 03°40' E, 45°04' N, south central France Source. LAR, October 1976 Comments. View of a road cut 22 km northwest of Le Puy in the Massif Central that exposes Upper Pleistocene brecciated basalt 15 000 BP overlying Lower Pleistocene, 1 500 000 BP lacustrine fine sands, reddened at the lava contact. This site is 95 km southeast of the columnar basalt of Fig. X1-6. The regional geologic context of this figure is described in Fig. Pf1-6. See also Figs. Vs1-2 and Vs1-3.
Fig. X1-5. Source. Hamblin WK (1974) Late Cenozoic volcanism in the Western Grand Canyon. In: Breed WJ, Road EC (eds) Geology of the Grand Canyon. Northern Arizona Society of Science and Art Inc., p 166, fig 17 Comments. An air perspective view shows typical basalt flows in one of the areas of Cenozoic volcanism that occur around the margins of the Colorado Plateau. The location is near the western edge of the Plateau, north of the Colorado River. The flows were extruded from numerous craters that lie from 100 to 200 m above the underlying Lower Triassic shales. The dark mound on the left is a scoria/ash cone.
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Division 1 · Magmatic Rocks and Structures
Fig. X1-6. Source. Deffontaines P, Delamarre MJ-B (1958) Atlas Aérien, France, Tome III. Gallimard, p 152, fig 253 Comments. An air view at Bort in the western part of the Massif Central of France shows the characteristic columnar structure of a 90 m high basalt flow. The flow is Tertiary phonolite, an outlier of the extensive Cantal volcanic centers to the east. This site is 95 km northwest of the brecciated basalt of Fig. X1-4 and 60 km southwest of the trachyte dome of Fig. Vs1-3. A description of the regional geologic context of this figure is given in Fig. Pf1-6.
Fig. X1-7.
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Location. Geographic. 130°04' W, 57°28' N, north central British Columbia Klastline Plateau Geologic. Stikinia Terrane of intermontane belt of Cor-dillera Vertical Airphoto/Image. Type. b/w, pan airphoto Scale. 1:30 000 approx Acquisition date. Not given Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada. BC 1251-105, 104 Comments. This stereomodel in the northern Skeena Mountains shows the dissected margin of Late Cenozoic lava flows from adjacent Edziza volcanic complex in Edziza Provincial Park (Fig. Vc2-4) or from local fissures. The massive dissected rock unit underlying the lavas is Mid to Upper Jurassic sedimentary rock. An Ms3 rock slump occurs along the west-facing scarp. The Zm2 rock glaciers in north-facing cirque scarps are in the present zone of Alpine permafrost. Their situation near the upper limit (2 000 m) of semi-independent glacier systems of the late Wisconsinan (Würm) Cordilleran glaciation suggests that they may also be relics of that time.
X1 · Basaltic Flows, Flow Fields, or Plateaus (Trapps)
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X1.1 · Local Slope Flows ▼
Fig. X1-8. Location. Geographic. 03°22' E, 43°40' N, Languedoc, France Geologic. Southern Jurassic Causse basins Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1970 Source. IGN–Photothèque Nationale, France Comments. The stereomodel shows the Po/Pl basalt flows surrounding the Salagou hydro-electric power reservoir. They are part of the regional Escandorgue fissure eruptions related to Neogene volcanic activity of the Massif Central 100 km to the north. The area consists of Permian/ Triassic detrital sediments on the southern periphery of the limestone Causses. Four Ms1.1 rock slides are associated with the basalt scarps. Cultivated terraced fluvial deposits fill the Lorgue River valley.
X1.1 Local Slope Flows Characterization A local slope flow extends for long distances as a relatively narrow stream that outpours from fissures or extends from a vent well beyond the steep depositional slopes of stratovolcanoes. In response to slope relief the flow will channel into existing erosional ravines and may spread out at valley margins. The morphology of young slope flows reflects the process of flow. In addition to Component ‘b’ marginal flow levees of this Variant flow lines, superimposed flows and gas pocket depressions combine to produce characteristic rugged flow surfaces. These relief details are detected in both airphoto and satellite imagery.
Geohazard Relations In addition to the hazards related to the parent unit, slope flows that come into contact with ice and snow can generate Mf3 debris-mud flows. Kilburn (2000) has developed flow equations related to slope angle which provide reliable estimates of potential flow length and can be used for preparation of hazard maps.
Reference Kilburn CRJ (2000) Lava flows and flow fields. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 291–305
Select Bibliography Eisbacher GH, Clague JJ (1984) Destructive Mass Movements in High Mountains: Hazard and Management. GSC Paper 84–16, pp 29–36 Hulme G (1974) The interpretation of lava flow morphology. Geophys J R Astr Soc 39:361–383 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology: Volume 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, pp 9–22
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X1.1
Division 1 · Magmatic Rocks and Structures
Fig. X1.1-1. Location. Geographic. 130°32' W, 57°51' N, north central British Columbia Geologic. Stikinia Terrane of Intermontane Belt of Cordillera Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 40 000 Acquisition date. August 1949 Source. Courtesy of Natural Resources Canada, NAPL, A12184, 131, 132 Comments. The stereomodel shows the lower 5 km of a 13 km long by 1 to 2 km wide ropy basalt slope flow. This flow is on the north slope of Edziza Volcano, 2 590 m, pictured in the stereo photo pair of Fig. Vc2-5. Figure Vc2-4 is a perspective view of the volcano. The flow, which postdates the last episode of regional glaciation, descended 1 160 m in elevation from its point of origin. The relatively low resolution of the photo print fails to reveal that there are sparse stunted trees rooted in pockets of soil among the blocks of lava which are as old or older than the trees in the adjacent mature forest. The trees on the soilless flow surface have a slow rate of reforestation.
Fig. X1.1-2.
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Location. Geographic. 137°22' W, 62°55' N, central Yukon Geologic. Nisutlin Terrane of Omineca Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL, A12106-129, 130 Comments. Two slope flows in opposite directions and a valley flow that issued from a local breached stratovolcano are pictured in this stereomodel 40 km west of Pelly Crossing. The barren volcano has evidently erupted recently from a vent that existed earlier and was the source of the mainly vegetated older flows. (The white stripe across the photo is a blemish in the original photo negative.)
X1.1 · Local Slope Flows
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Division 1 · Magmatic Rocks and Structures
Fig. X1.1-3. Location. Geographic. 103°30' E, 11°30' N, Southwest Cambodia Geologic. Lower Jurassic craton cover sandstones Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. 5 November 1958 Source. Journal Photo Interprétation, Editions ESKA, Paris, 67-6.3 Comments. A stereomodel shows that the characteristic and diagnostic morphology of certain Cenozoic photogeologic
units permits them to be detected and identified under dense forest cover. Location is in the Elephant Chain, of the Cardomon Mountains. The crater area of the Vc1 volcano and the X1.1 basalt slope flows are distinguishable. It is noted that such geologic unit recognition under forest cover also applies to the surrounding S1 interbedded sandstones. The lavas are one of three local outpourings – Ambel, Tatey, or Veal Veng, 150 km west of Phnom Penh. They are probably associated with tectonic movements at the western end of the Indochina Uplift.
X1.1 · Local Slope Flows
Fig. X1.1-4. Location. Geographic: 67°53' W, 22°50' S, southwest Bolivia. Vertical Airphoto/Image. Type. TM Acquisition date. 2007
Source. MDA EarthSat. Comments. This satellite image shows well-developed youthful lava flows that extend up to 6 km on the flanks of Vc1 Licancabur Volcano (5 916 m) in the Cordillera Occidental on the Chilean border.
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X1.2
Division 1 · Magmatic Rocks and Structures
X1.2 Local Valley Flows Local valley flows are further characterized by two Components: X1.2a – residual lava ridge X1.2b – Interstratified flows and fluvial-lacustrine sediments
Characterization A valley flow travels down the valley axis, filling it partially or wholly, burying fluvial deposits and causing some streams displaced by the lava to etch out new channels along the margins of the encroaching flow.
Geohazard Relations Local valley flows can dam the valley and tributaries and cause upstream flooding. Many lava flow dams are so permeable that the impounded lakes do not overflow; the dams remain stable prolonging the flooding.
Select Bibliography Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology: Volume 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, p 9
See also Unit X1.1.
Fig. X1.2-1. Source. Roche Brésole J (undated) Parc Naturel Régional des Volcans d’Auvergne. Copyright éditions G. de Bussac. Dessin Roche et Brésole, p 51 Comments. The schematic block diagram shows the topographic relationships of Variants of basaltic lava flows.
X1.2 · Local Valley Flows
Fig. X1.2-2. Source. Green J, Short NM (eds) (1971) Volcanic Landforms and Surface Features. Springer-Verlag, plate 139A Comments. An air perspective photo shows a blocky Quaternary lava valley flow in the volcanic Modoc Plateau of northern California. The flow surface is about 30 m above the surrounding terrain which lies in one of a number of regional block-faulted basins. The smooth white deposits in foreground are Pf1 ash.
Location. Geographic. 119°50' W, 52°08' N, southern British Columbia Geologic. Barkerville Terrane of Omineca Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 62 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL, A133318-92, 93 Comments. The lava valley flows of Quaternary Clearwater basalts in this stereomodel of Upper Paleozoic metasediments in Wells Gray Provincial Park erupted from a vent in the upper left corner of the interpreted photo and flowed 60 km down valley.A scoria/ash cone has erupted from the vent more recently. The lake portion visible behind the vent site resulted from the damming of the stream (File Creek) by the lavas. Two prominent fault-suggestive geolineaments have been drawn.
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Fig. X1.2-4.
Location. Geographic. 130°37' W, 56°45' N, northern British Columbia Geologic. Stikinia Superterrane of Cordilleran Intermontaine Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL, A12198 – 170, 171 Comments. This stereomodel in the lower Iskut River valley shows forested Quaternary lava flows that issued from a 1 km diameter cone located near the base of a steep mountain slope marked by both old and recent-appearing mass movements and a strong geolineament 1 km south of the failures. The flows fill the valley floor and continue 15 km beyond the western edge of the model. This figure is located 40 km south of Fig. Fv1.1-5.
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Fig. X1.2-3.
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Division 1 · Magmatic Rocks and Structures
Fig. X1.2-3. (Caption on p. 39)
X1.2 · Local Valley Flows
Fig. X1.2-4. (Caption on p. 39)
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Division 1 · Magmatic Rocks and Structures
X1.3 · Disturbed Dissected Basalts ▼
Fig. X1.2-5. Location. Geographic. 05°11' E, 22°58' N, southeast Algeria Geologic. Weathered Upper Proterozoic granites of Hoggar cratonic massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 87 000 Acquisition date. 1969 Source. IGN–Photothèque Nationale, France Comments. The stereomodel at Tit, 40 km northwest of Tamanrasset shows narrow Tertiary (possibly Eocene) residual lava ridges extending 14 km along the margin of a wadi valley. They are erosional remnants of flows from sources eastward in the Atakor volcanic massif.
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jointed flows and segments display relatively dense surface drainage systems and dissection. Resistant units of older flows may be disproportionately preserved, but in general “Only those relatively undeformed flows, mainly of Tertiary age and younger, are readily identifiable from aerial photographs without some knowledge from ground surveys.” (Ray 1960). Pre-Cenozoic and ancient weathered, dissected, variably deformed and metamorphosed successions can be significantly modified in their morphologic appearance.
Geohazard Relations The geohazards associated with solidified, stabilized flows relate principally to sliding, slumping and rockfalls.
Reference
X1.3 Disturbed-Dissected Basalts
Ray RG (1960) Aerial photographs in geologic interpretation and mapping, USGS Professional Paper 373, p 17
Characterization
Select Bibliography
The more permeable highly jointed flows tend to be more resistant to weathering and erosion in contrast to other crystalline rocks. As a consequence the more impermeable, less
Drury SA (1987) Image interpretation in geology. Allen & Unwin, London, pp 81–83 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 142–144
Fig. X1.3-1. Location. Geographic. 70°21' W, 23°37' S, north Chile Source. Rich JL (1942) The Face of South America. In: Weaver JC (ed) Special Publication No. 26. American Geographic Society, New York, photo 233 Comments. This air perspective view southward 10 km northeast of the port of Antofogasta shows a monoclinal
fault block of thick Lower Jurassic lava sequences of the Sierra Ancla on the arid north coast. The disturbed beds are part of the 1 000 km long Lower Cretaceous Atacama Fault System which parallels the subducting Mazca Plate from Iquique at 21° S to La Serena at 30° S. Renewed tectonic deformation in the fault system in this latitude occurred during the last subduction earthquake 30 June 1995.
X1.3
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Division 1 · Magmatic Rocks and Structures
X1.4 · Dissected Alkaline Basalts ▼
Fig. X1.3-2. Location. Geographic. 65°43' W, 21°26' S, southern Bolivia Geologic. Polygenetic Cordillera oriental Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 50 000 Acquisition date. 30 August 1967 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 94 Comments. This stereomodel shows the rugged upland topography of dissected Tertiary basalts and dacites of a local extrusion associated with the rift-like Tupiza Valley containing shaly and sandy S2.1 Ordovician sediments.
X1.4 Dissected Alkaline Basalts Characterization Denudation and weathering produces the distinctive aspects of this facies from the dissected facies X1.3. The distinctiveness is due to enhanced dissection resulting from in-situ deep chemical weathering in humid tropical environments (see Mc1). Typical morphology is steepsided ridges and spurs and generally straight steep slopes. In engineering work the weathered rock and residual soil can be ripped with power equipment.
Geohazard Relations Fluvial erosion of impermeable soils and a number of mass movements are associated with the relative instability of this facies: Creep, Mc1; Surficial material debris slides, Ms2; and Debris-mud flows, Mf3. The possible irregularity of the weathering front can be an important factor in engineering excavations.
References Drury SA (1987) Image interpretation in geology. Alen & Unwin, London Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS Professional Paper 373
Select Bibliography Bellamy JA (1986) Papua New Guinea inventory of natural resources,population distribution and land use. Natural Resources Series No. 6, Division of Water and Land Resources. CSIRO, Australia, pp 59–61, 70–81 Blake DH, Paijmans K (1973) Landform types and vegetation of Eastern Papua. Land Research Ser. No. 32, CSIRO, Australia, pp 36–40 Dizier JL, Olivier L (1982) Photo-Interpretation et Cartographie en Haiti. Faculté d’Agronomie et Médecine Vétérinaire,Université d’État d’Haiti, pp 185, 191, 265
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Drury SA (1987) Image interpretation in Geology. Alen & Unwin, London, pp 81–82 Erb DK (1982) Geologic remote sensing in “difficult terrain”, photogeomorphology and photogeology in the humid tropics. Proceedings, Second Thematic Conference, Remote Sensing for Exploration Geology, ERIM, pp 365–374 Hardjoprawiro S, Sidarto (1987) The geology of the area surrounding Lake Kerinci Indonesia as interpreted through SIR-B imageries. Geological Research and Development Centre, Bandung Macdonald GA, Abbott AI, Peterson FL (1983) Volcanoes in the sea: The geology of Hawaii. University of Hawaii Press, Honolulu Thomas MF (1974) Tropical geomorphology. Macmillan, London
Photogeological Note Photogeologically Cretaceous volcanic X1.4 and Tertiary sedimentary Kp1 rocks occurring in disturbed settings have proven difficult to distinguish and delineate on both airphotos and satellite images. The problem has been defined as follows: “Only those relatively undeformed flows, mainly of Tertiary age and younger, are readily identified from aerial photographs without some knowledge from ground surveys … where flows have been strongly tilted, folded, or otherwise disturbed, recognition and interpretation from aerial photographs may be extremely difficult or impossible.” (Ray 1960, p 17). “Lavas, unless they are undissected and show distinctive surface features, are difficult to distinguish from sediments with which they may be interbedded.” (Drury 1987, p 81). To illustrate the difficulty, the following are the main photo and image morphologic criteria observed to distinguish lithologies in Figs. X1.4–6 and 9. The intense dissection of the volcanic rocks. The higher, less dissected plateau-like condition of the carbonates. The conformable stratigraphic position of the carbonates overlying the volcanics. The presence of apparent solution features on plateau surfaces. Slope failure at plateau margins suggesting contact with weaker underlying volcanics. Similar failures are also characteristic of basalt plateau scarps. Divides in dissected carbonate areas are less frequent and less sharply defined than in the volcanics. Some dissection zones in the volcanics, which have not been isolated in this interpretation, display a form that is very suggestive of pyroclastic materials: knife-edge ridges and steep uniform sideslopes.
X1.4
Division 1 · Magmatic Rocks and Structures
Fig. X1.4-1. Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Bellamy JA (ed). Inventory of Natural Resources, Population Distribution and Land Use, Papua New Guinea. CSIRO Natural Resources Series No. 6, p 59, fig 5.31 © CSIRO 1986 Comments. An air perspective photo shows the dissection and weathering of alkaline volcanic rocks in a tropical humid climate. These are massive Oligo and Miocene plate tectonic island arc basalts and andesites at 146°06' E, 05°50' S 140 km northwest of Lae in the Finisterre Range of the eastern PPNG coast ranges. Many landslides are present.
Fig. X1.4-2. Source. Macdonald GA and others (1983) Volcanoes in the Sea, 2nd edition. University of Hawaii Press, Honolulu, p 210, fig 10.10 Comments. The air view shows strongly dissected Tertiary basalts at the east end of Molokai Island. In the lower right an airstrip has been emplaced on an undissected interfluve. Molokai is 15 km north of Lanai Island of Fig. Vc3.4-3.
Fig. X1.4-3.
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Location. Geographic. 156°38' W, 20°49' N, Hawaii Vertical Airphoto/Image. Type. Colour infrared airphotos Scale. 1: 165 000 Acquisition date. Not given Source. Upper photo – NASA Lower photo – Lillesand TM, Kiefer RW (1979) Remote Sensing and Image Interpretation. ©John Wiley & Sons, plate IV. Reproduced with permission.
X1.4 · Dissected Alkaline Basalts
Comments. These two photos of the same locality on the southwest coast of west Maui show the deep dissection of Tertiary alkaline surficial basalt flows, (Wailuku Series). The dissection reflects the relatively high surface runoff on more weathered, less permeable lavas. West Maui is a Vc2 shield volcano with a Vc3.4 caldera in its center. The inset frame on the vertical photo shows the coverage of the air perspective stereo pair. Slightly brighter small Vs1 trachyte domes with a lo-
cally anomalous morphology are visible just west of the fan on both photos. The cloud cover 10 km inland in the caldera vicinity is over the red coloured 1 500 m elevation West Maui Forest Reserve with average annual rainfall of 1 000 cm. The barren-looking hills near the coast receive 40 to 80 cm annual rain. This bioclimatic pattern is typical of Hawaiian Islands with their northeast trade winds. Red zones along the coast are irrigated plantations (pineapple/sugar). West Maui is 15 km east of Lanai Island of Fig. 17.2-2.
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Division 1 · Magmatic Rocks and Structures
Fig. X1.4-4. Location. Geographic. 55°37' W, 27°46' S, northeast Argentina Geologic. Volcanic craton cover of southern diabase Brazilian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1 : 33 000 Acquisition date. 14 March 1962 Source. Journal Photo Interprétation. Editions ESKA, Paris, 64-4.3 Comments. Mesozoic basalt flows and Variants are delineated in this stereomodel oriented northeast/southwest in
a partly forested area in the vicinity of Posadas Missiones Province. Areas of X1 plateau basalts are surrounded by forested slopes labelled X1.1. These areas may just be slopes of the plateau sequences rather than distinct slope flows. The valley areas consist of X1.4 weathered and possibly alkaline basalt. The bright unforested area in the upper plateau area is a zone of shallow unweathered basalt that may be abandoned agricultural land. The cleared land in the weathered basalts in lower left of the model is interpreted as agricultural use.
X1.4 · Dissected Alkaline Basalts
Fig. X1.4-5. Location. Geographic. 09°15' E, 05°45' N, southwest Cameroon Geologic. Cretaceous tectonic trough Vertical Airphoto/Image. Type. b/w infrared, stereo pair Scale. 1: 50 000 Acquisition date. Not given Source. IGN–Photothèque Nationale, France Comments. This stereomodel near Mamfé shows a Cretaceous lava flow overlying Cretaceous detrital sediments. The lavas are associated with volcanic massifs of the regional Mount Cameroon rift valley type trough.
The distinction between the respective morphologies is subdued by the dense forest cover. The S1K area has low, rounded, uniform topography. The weathered mantle relief of the X1-4 Cn higher overlying basalts has slightly coarser textured and dissected terrain. Lake Nyos (10°33' E, 05°48' N) occupies the crater of one of a number of Vc3 calderas that occur in this range. In August 1986, a rapid, massive release of carbon dioxide from this lake killed over 1 700 people. Most victims were asphyxiated in the cold CO2 cloud that travelled a gaseous density current from the lake down the valleys.
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Division 1 · Magmatic Rocks and Structures
Fig. X1.4-6. (Caption on p. 52)
X1.4 · Dissected Alkaline Basalts
Fig. X1.4-7. (Caption on p. 52)
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Division 1 · Magmatic Rocks and Structures ▼
Fig. X1.4-6. Location. Geographic. Southwest Haïti Geologic. Greater Antilles Disturbed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. Not given Source. IGN–Photothèque Nationale, France Comments. A stereomodel in the Massif de la Selle 30 km southwest of Port au Prince covers high relief Lower Cretaceous basaltic rocks whose strong dissection is characteristic of alkaline facies with weathered mantle in tropical climate. The Landsat subscene of Fig. X1.4-9. shows the regional setting of these lavas. Old rock slides (Ms1.1) and the karst terrain in which they occur are delineated.
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Fig. X1.4-7. Location. Geographic. 106°05' E, 15°07' N, south Laos Geologic. Craton cover sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. 1981 Source. Personal archive Comments. The stereomodel on the southwest part of the Bolovens Plateau shows X1.4-PL flows of weathered alkaline Pleistocene basalts in the northern half of the model associated with north-northeast trending fractures. Surface streams have eroded gullies parallel to local flow lines. The flows have developed good iron-rich soils and are relatively densely cultivated. In marked contrast, the poorer soils of W4-J Mid Jurassic quartzitic sandstones of the plateau to the south are forested and uncultivated. The location of the photos is shown on the satellite image of Fig. X1.4-8.
X1.4 · Dissected Alkaline Basalts
Fig. X1.4-8. Location. Geographic. 106°E, 15°10' N, south Laos Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. This image of the southwest portion of the Bolovens Plateau in southern Laos shows bright green basaltic lava flowing off the plateau through a depression between plateau scarps. Lower Pleistocene basalts issued from north-east trending fissures cover 75 km of the plateau at an elevation of 1 000 to 1 200 m with flows occupying the valleys that radiate from the plateau center.
The underlying plateau, which is exposed in the scarps and eastward in Fig. W1-5 consists of Mid-Jurassic sedimentary rocks epeirogenetically uplifted at the time of the lava outflows. The vegetation cover is monsoonal humid tropical forest. The Mekong River near Paksé is in the lower left. The inset frame locates the stereo photopair of Fig. X1.4-7. Some land use changes are observable within this frame area in the quarter century following the air photography. The agricultural occupance visible on the lavas in the airphotos is not evident in the satellite image, but land clearing can be seen on the plateau basalts in the lower right of the photo cover frame.
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Division 1 · Magmatic Rocks and Structures
Fig. X1.4-9. Location. Geographic. 72°30' W, 18°24' N image center, south Haiti Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 250 000 Acquisition date. January 1979 Source. USGS
Comments. The typically strongly dissected Lower Cretaceous alkaline lavas in a tropical humid climate are detectable and delineated on this Landsat image. The massif is bordered to north and south by Kp1 limestones. This figure shows the regional setting of the stereo photopair of Fig. X1.4-6. Altitudes in the X1.4 unit range from 600 m a.s.l. to 1 500 m a.s.l. at the east. Bordering limestone ridges are about 600 m elevation.
X2 · Interbedded Lavas and Pyroclastics
X2 Interbedded Lavas and Pyroclastics
ments produces a distinct topography displayed in Variant X2.2.
Characterization
Geohazard Relations
The basic characteristic of interbedded lavas and pyroclastics is a plateau-like sequence of horizontally bedded and low dipping strata in a terraced or stair-stepped pattern of compound slopes. Scarps and gentle slopes develop on resistant and weak beds respectively. Lavas have scarps and steep slopes. Non-cohesive unwelded tuffs have gentler slopes and a wider outcrop belt. In lavas the ground slope is governed by its composition, while in the tuffs it is governed by grain size. Interbedded sedimentary rocks (W1) and interbedded sedimentary and volcanic rocks (W2) have photogeologic characteristics similar to this geounit. Distinction of X2 is supported by close association with other volcanism. As with Variant X1.4, climatic denudation in more humid tropical environ-
Interbedded flows are highly unstable due to the presence of the weak tuff beds. Undermining of the tuffs can lead to collapse or landsliding of the overlying lavas (e.g. see Fig. Bc4–6). Vertical jointing in the lavas presents a potential for large slides along the scarps. Tunnelling through these rocks is hazardous because of the risk of collapse.
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Fig. X2-1.
Source. Way DS (1978) Terrain Analysis 2nd edn. Dowden, Hutchinson & Ross, p 166, fig 6.9 Comments. A schematic section shows the characteristic differential erosion of interbedded resistant lavas and weaker pyroclastic beds.
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Fig. X2-2.
Location. Geographic. 05°32' E, 23°15' N, southeast Algeria Source. LAR, April 1974 Comments. The photo shows a repetition of beds of Miocene basalts and tephra at 2 500 m elevation on the eastern side of the Ilamane viscous dome in the 2 150 km2 Atakor volcanic Highland of the Hoggar Cratonic Massif. The lavas and tephra cover a granitic and gneissic basement. The angular rubble in the foreground is probably frost riven. Location is just off the western edge of the map of Fig. Vc4-1.
Select Bibliography Drury SA (1987) Image interpretation in geology. Allen & Unwin, London, p 81 Rognon p (1967) Le Massif de l’Atakor et ses Bordures. Centre National de la Recherche Scientifique, Paris, pp 166–169 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 166–175
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X2
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Division 1 · Magmatic Rocks and Structures
Fig. X2-3. Location. Geographic. 66°52' W, 19°25' S, southwest Bolivia Vertical Airphoto/Image. Type. TM Acquisition date. 2007
Source. MDA EarthSat. Comments. This satellite image shows a deposit of Tertiary interbedded lavas and tephra of the Los Frailes Formation on the Altiplano at the Laguna Sevaruyo near Rio Mulata.
X2 · Interbedded Lavas and Pyroclastics
Fig. X2-4. Location. Geographic. Western USA Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 31 680 Acquisition date. 1946 Source. Personal archive Comments. The code “B” in this stereomodel points to faint bedding traces in interbedded rhyolite and tuff at an unspecified location.
Fig. X2-5. Location. Geographic. Southern Arizona Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 31 680 Acquisition date. Not given Source. Personal archive Comments. This stereomodel shows the typical erosion response pattern of resistant lavas, X2a, and weaker pyroclastics X2b.
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X2.1
Division 1 · Magmatic Rocks and Structures
X2.1 Interbedded Lavas and Pyroclastics, Disturbed Facies
have the continuity of interbedded sedimentary and volcanic rocks.
Characterization
Geohazard Relations
This variant show a dissected relief in stereo-photos, and dips of lava beds are discernable. The sequences do not
See Geounit X2.
Fig. X2.1-1. Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 25 000 Acquisition date. Not given Source. Personal archive Comments. These stereomodels of localities in western State of Utah, USA show occurences of deformed interbedded Tertiary andesites and tuffs on the northwest margin of the Colorado Plateau. Diagnostic evidence of interbedding in such areas becomes obscured, but other associated indicators are generally present. In the upper model, the micro relief and topo site of exposed tuffs, labelled “b”, allows their delineation. In the higher, more rugged “a” area some bedding traces are visible and local mass movements at contacts are indicative. In the lower model diagnostic indicators are lacking, the single rock slump is inconclusive. Field evidence is required in such areas.
X2.1 · Interbedded Lavas and Pyroclastics, Disturbed Facies
Fig. X2.1-2. Location. Geographic. Southeast Arizona Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 31 680 Acquisition date. Not given Source. Personal archive Comments. These stereomodels are in areas of disturbed and dissected interbedded Tertiary lavas and pyroclastic rocks on the southern margin of the Colorado plateau. Diagnostic features are limited by the structural and erosive morphology, but some bedding traces are evident at “B” in the upper model and at “1” in the lower. The contact drawn at “2” in the lower model is between interbedded lavas and pyroclastics that overlie basalt, possibly in a thrust fault relation. The gully area in the upper model is in pyroclastics.
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X2.2
Division 1 · Magmatic Rocks and Structures
X2.2 Interbedded Lavas and Pyroclastics, Dissected Facies
aerial photographs without some knowledge from ground surveys”.
Characterization
Geohazard Relations
Lava beds tend to be indistinguishable in strongly dissected sequences of this geounit. The greater the proportion of pyroclastics present, the greater the dissection. Stereo-photo interpretation reveals a morphology similar to that of dissected alpine and pre-alpine orogenic batholiths (masses of intrusive igneous rocks), and dissected facies of non-cratonic massive metamorphic rocks. Ray (1960) stated “Only those relatively undeformed flows, mainly of Tertiary age and younger, are identifiable from
See Geounit X2.
References Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS Professional Paper 373, p 17
Select Bibliography See Geounit X2.
Fig. X2.2-1. Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 31 680 Acquisition date. Not given Source. Personal archive Comments. The stereomodel is of a locality in the Central Rocky Mountains of Wyoming, USA, probably in the Tertiary Absaroka Mountains in the northwest corner of the state. The interpretation, based on relative differences of erosional relief, makes a tentative distinction between areas composed mainly of breccias – b, and those of basalt flows – a. White codes “D” indicate intrusive dykes, not tilted basalts. These mountains were extensively glaciated, obscuring lithological contacts in addition to the erosion normally resulting from steep slopes in high relief.
Fig. X2.2-2.
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Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 40 000 Acquisition date. Not given Source. van Zuidam RA, van Zuidam-Cancelado FL (1978–1979). ITC Textbook of Photo-Interpretation Vol.VII. Use of aerial detection in geomorphology and geographical landscape analysis. Chapter 6 Terrain Analysis and Classification Using Aerial Photographs. A geomorphological approach. International Institute for Aerial Surveys and Earth Sciences (ITC), The Netherlands, p 79, photo 45 Comments. A stereomodel shows dissected tephra and interbedded minor lavas at an unidentified location in a Far East humid tropical climate.
X2.2 · Interbedded Lavas and Pyroclastics, Dissected Facies
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X2.2 · Interbedded Lavas and Pyroclastics, Dissected Facies ▼
Fig. X2.2-3.
Location. Geographic. 81°17' W, 08°29' N, western Panama Geologic. Isthmus Ranges volcanic arc Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. March 1979 Source. Personal archive Comments. The stereomodel covers the upper reaches of the Rio Cañazas at a general elevation of 600 m a.s.l. The continental divide is in the forested mountains at the north end of the photo cover. The model displays the intense dissection in a dry climate (100–200 cm av. annual rainfall) typical of weak, interbedded, in this case Miocene, lavas and pyroclastic sediments, with the latter probably dominant. The red X2a areas are mapped as inliers of the more resistant lavas on the overlay. Two Ms1 rock slides are also delineated. See also Figs. Ms3-4 and Ms3-5.
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Division 1 · Magmatic Rocks and Structures
Group P Tephra Deposits Sub-group Pf Falls Pf1
Pf1 Pyroclastic Falls Characterization Pyroclastic falls are a rain-out of clasts during an explosive eruption of high viscosity magmas. The geometry and size of deposits reflect the eruption column height and the velocity and direction of winds. Clasts fall back to Earth at varying distances downwind from the source depending on their size and density. All fall deposits show some diminution in grain size between vent proximal and distal areas. Agglomerate and breccia pyroclasts are >64 mm; lapilli and scoria are between 2 and 30 mm, while ash is <2 mm. The more extensive, and common, lapilli and ash blanket deposits (Variant Pf1.1) and tuff blankets (Variant Pf1.3) are generally mappable using photogeology methods. The agglomerate and breccia deposits are typically less extensive, and tend to be restricted to relatively less hazardous vent proximal zones. When such zones occur at high altitudes they may be obscured by more or less perennial snow or ice which inhibit interpretation. Landsat TM bands 5 and 7 permit detection of subtle morphological details on snow-covered parts of volcanoes but do not allow complete interpretation of the materials (de Silva and Francis 1991). The general photogeological mappability is less difficult and quite as useful as field mapping techniques. Among the half dozen geoscientific properties of pyroclastic deposits measured in the field, an isopach map of the thickness of a fall deposit provides a meaningful indication of vent location, dispersal and volume of the deposit. However, the map does not trace lithological boundaries between deposits. These are usually so complex in the field that no attempt is made to draw them (Cas and Wright 1987). An isopach map shows the inferred original distribution of a deposit, not its present outcrop pattern. In outcrop sections, fall deposits show mantle bedding.
Geohazard Relations Scott (1989) discussed the geohazhard relations presented by this Geounit. Tephra fall poses the widestranging direct hazard from volcanic eruptions. Pyroclastic falls endanger life and property by burial, producing a suspension of fine-grained particles in air and water, and carrying noxious gases and acids. Burial by tephra can collapse roofs of buildings, break power and communication lines and damage or kill vegetation. Wet compacted tephra has a greater density than
dry uncompacted tephra and creates a greater load on buildings. The suspension of fine-grained particles affects visibility and health. An additional hazard of eruption-related ash clouds is their presence at the normal cruising altitudes for commercial jet airplane traffic. In the past 15 years more than 90 jet aircraft have been damaged as a result of encounters with drifting clouds of volcanic ash. The ash clouds are not detectable by the present generation of radar instrumentation onboard aircraft, but are detectable by sensors aboard some EO satellites including geostationary meteorological satellites. The detection and tracking of ash clouds is now accomplished by a network of Volcanic Ash Advisory Centers (VAACs) and Meteorological Watch Offices (NWOs). The purpose of USGS map I-2700 “World Map of Volcanoes and Principal Aeronautical Features” is to increase awareness about the close spatial relation between volcanoes and aviation operations. The transport of fine-grained tephra by wind, especially in dry climates, can prolong many problems. Even thin (<2 cm) falls of ash can damage such critical facilities as hospitals, electric generating plants, pumping plants, storm sewers and surface drainage systems, and water and sewage treatment facilities. Fine ash can also cause short circuits in electric-transmission facilities. In addition communications can be affected greatly by damage to telephone lines and radio and television transmitters. Magma contains dissolved gases that are released to the atmosphere during eruptions. By far the most abundant volcanic gas is water vapour but there is a group of acid aerosols absorbed as compounds on tephra. Sulfur compounds and chlorine and fluorine react with water to form acids that are poisonous and, even in low concentrations, are damaging to eyes, skin and respiratory systems of animals. These acids can damage or kill vegetation depending on their concentration; they can also damage fabrics and metals. Carbon monoxide is poisonous, odorless and unlike the noxious gases cannot be detected by humans. Harmful effects of volcanic gas are usually restricted to within 10 km of vents except under exceptional circumstances. Early detection and tracking of the dispersal of eruption plumes using existing and planned satellite sensors is under development by remote sensing specialists, volcanologists and operating agencies. Hazards related to older deposits are described for Variant Pf1.1.
References Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, London, p 469 de Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin, p 7 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards, short course in geology. American Geophysical Union, pp 9–23
Pf1 · Pyroclastic Falls
Select Bibliography Casadevall TJ (1994) Volcanic ash and aviation safety. USGS Bull 2047 Constantine EK, Bluth GJ, Rose WI (2000) TOMS and AVHRR observations of drifting volcanic clouds from the August 1991 eruption of Cerro Hudson. Geophysical monograph 116, Remote Sensing of Active Volcanism, American Geophysical Union, pp 45–64 Hickson CJ, Edwards BR (2001) Volcanoes and volcanic hazards. In: Brooks GR (ed) A synthesis of geological hazards. GSC Bull 548:145–181
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Fig. Pf1-1.
Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p220, fig 7.46(1) Comments. The schematic section shows eruption plumederived and ash cloud-derived tephra deposits. The near-vent deposits at “1” are the large pyroclastic fragments – agglomerates, breccia and lapilli (ballistic clasts) unaffected by the wind. The ash/tuff fines are dispersing downwind.
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Fig. Pf1-2.
Source. Scott WE Volcanic and Related Hazards. In: Tilling RI (ed) Volcanic Hazards, Short Course in Geology. © 1989American Geophysical Union, p 19, Fig. 2.9 Comments. This graph gives the percentage of thickness of tephra deposits plotted against the distance from the vent, measured along the axis of the plume.
Houghton BF, Wilson CJN, Pyle DM (2000) Pyroclastic fall deposits. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 555–570 Schneider DJ, Dean KG, Dehn J, Miller TP, Kirianov VYu (2000) Monitoring and analyses of volcanic activity using remote sensing data at the Alaska Volcano Observatory: Case study for Kamchatka, Russia, December 1997. Geophysical Monograph 116, Remote Sensing of Active Volcanism. American Geophysical Union, pp 65–85
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Fig. Pf1-3. Location. Geographic. West Java Island Geologic. Active stratovolcanoes arrayed along a median zone of an islandarc structural belt Source. Compost A (undated) Indonesia from the Air. PT Humpuss & Times Editions, p 105 Comments. Photo shows the effects of ash fall on downwind structures and vegetation from an August 1982 eruption of Mt. Galunggung 60 km southeast of Bandung.
Fig. Pf1-4. Location. Geographic. 20°16' W, 63°25' N, south Iceland Geologic. Shield volcano at junction of Mid-Atlantic Ridge and Iceland – Faeroe Hot Spot Track Source. Green J, Short NM (eds) (1971) Volcanic Landforms and Surface Features. Springer Verlag, plate 8 Comments. This photo captured a rain-out of tephra from eruption clouds of Surtsey Island, 26 November 1963. The volcano of submarine origin is the southwesternmost island of the Vestmannaeyjar Archipelago, a neovolcanic system which is part of the Mid-Atlantic Ridge fis-
sure that is continued north-ward in a supramarine belt across Iceland. It developed from episodic eruptions which began on 8 November 1963 and ended on 5 June 1967. The volcano has been dormant ever since, and has an elevation of 174 m. The photo shows subaerially depositing tephra which overlie submarine deposited tephra. Lava flows of the last effusive activity now cover the early explosive activity tephra. Heimaey Island, 23 km to the north in the same archipelago is shown in Fig. Pf1.1-2. See also Fig. Vc1.1–4. Contrast this figure with the pyroclastic flow of Fig. Ps1-6.
Pf1 · Pyroclastic Falls
Fig. Pf1-5. Location. Geographic. 105°27' E, S 06°10' S, Indonesia Geologic. Active stratovolcano in island-arc structural belt Source. Edmaier B (1997) Volcans. Nathan, Paris, p 12 Comments. Photo of a pyroclastic eruption plume from Vc1 Anak Krakatau Volcano, now 813 m elevation, in the Sunda Strait between Java and Sumatra. The volcano originated in 1927 in the center of the earlier Vc3.2 Krakatau Caldera. Krakatau Caldera is an exceptional representative of volcanic geohazards. In AD 416 caldera collapse destroyed an original volcano and formed a 7 km diameter wide caldera. It erupted on 20 May 1883 and produced tsunamis that ran up coasts to heights of 35 m, killed 36 000 people, and totally or partly destroyed close to 300 villages. Ps1 pyroclastic flows travelled over the sea surface, ships 65 to 80 km away were engulfed by ash clouds. Ash falls settled up to 500 km away and travelled right around the world. On 27 August 1883 the volcano cracked and a submarine caldera 300 m deep and 5 km in diameter was open to the sea. The resulting blast was heard as far as
4 800 km away; it was the largest explosion in recorded history, and is reported to have been 5 000 greater than that of the Hiroshima atomic bomb. Ps1.1 ignimbrite outflows were subaqueous and shallowed the sea floor up to 15 km north of the caldera. The most recent episode of activity began in March 1994 and continued to at least March 1995, the period when this photo was taken. This is the westernmost of the six Indonesian volcanic island arc figures in this Atlas (others are Pf1-3; Vc1-8, Vc1.1-7; Vc3.1-10 and Vc3.2-9). The occurrence of volcanoes on this type of collisional plate tectonic boundary is explained by the fact that the oceanic crust that is subducted beneath the overriding plate of the continental shelf (basement) of the shallow Java Sea descends into the mantle carrying “with it entrained sea water … Hydrating a portion of the mantle causes mineralogic phase changes and some partial melting. This process produces the explosive volcanoes that lie above subduction zones”. (Howell DG (1989) Tectonics of Suspect Terranes. Chapman and Hall, p 33.) There are over 130 active volcanoes in the Indonesian Arc.
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Fig. Pf1-6. Location. Geographic. South central France Geologic. In center of 45 km chain of Vp1 pyroclastic cones and Vs1 viscous domes erupted along north-south fractures in the Central Hercynian Massif. Fractures are associated with MidTertiary movements related to Alpine orogeny Source. Bardintzeff J-M (1997) Les Volcans. Liber, Genève, p 160 Comments. Photo in a quarry 10 km west of ClermontFerrand on the north side of a small scoria/ash cone shows the main range of tephra grainsizes. Ash at base; lapilli and scoria in the center; blocks and agglomerates at the top. This quarry is 3 km west of the trachyte dome of Fig. Vs1-3. They are at the north end of the Auvergne and Cantal Mid-Tertiary volcanic area that rests on the Hercynian Massif Central. The associated volcanic rocks extend 200 km to the south and are 100 km at their broadest. Figures X1-4 and X1-6 illustrate basalt flows in this volcanic complex region.
Fig. Pf1-7. Source. Macdonald GA et al. (1983) Volcanoes in the Sea, 2nd edn. University of Hawaii Press, Honolulu, p 432, fig 21.9 Comments. The bright surficial beds in this photo, suggestive of tephra, are probably X1.4 post-shield erupted alkaline basalts. The underlying basalts are part of the residual remnant of Kaala Vc2 (1 208 m) shield volcano in the Pliocene Waianae Range of western Oahu Island.
Pf1 · Pyroclastic Falls
Fig. Pf1-8. Location. Geographic. 45°56' S, 72°57' W, southern Chile Geologic. Cerro Hudson Andean volcano Vertical Airphoto/Image. Type. AVHRR Scale. 1: 16 million Acquisition date. 13 August 1991 Source. Constantine et al TOMS and AVHRR Observations of Drifting Volcanic Clouds From the August 1991 Eruptions of Cerro Hudson. Remote Sensing of Active Volcanism. Geophysical Monograph 116. © 2000 American Geophysical Union, pp 45–64, plate 4B. Reproduced by permission of American Geophysical Union Comments. This figure is the first of a set which includes Pf1-9 and Pf1-10. This band 4 (11 μm near-infrared) image (of 5) was acquired an undetermined number of hours after the end of the eruption of Cerro Hudson Volcano. The 8 000 km2 volcanic cloud containing aerosols and gases is outlined by red dots. Meteorological clouds are also visible in the scene. Volcanic clouds can be discriminated from met clouds by subtracting band 5 12 μm brightness temperatures from band 4 11 μm brightness temperatures. The negative brightness temperature difference (BTD) will represent volcanic cloud pixels because of optical effects associated with the refractive index of ash and H2S04 aerosols
at infrared wavelengths. Positive brightness temperature values are generally associated with met clouds containing water. AVHRR on NOAA-11 and 12 satellites have a nominal repeat cover of 6 hours increasing with increasing latitude. The 1 100 m AVHRR field of view makes it an effective data set for recording large features such as volcanic clouds. The following information is extracted from Rosi M, Papale P, Lupi L, Stoppato M (2003) Volcanoes. Firefly Books, p 308, 309. “Cerro Hudson is composed of a 10 km wide caldera located at the far southern end of the Chilean Andes. The volcano is located at the point where the oceanic Nazca plate is being subducted beneath the South American and Antarctica continental plates. The origin of the caldera is related to two large explosive eruptions that took place roughly 7 000 and 5 400 years ago. The last eruptive cycle was in 1991 and consisted of two explosive phases, the first on August 8 and 9, and the second from August 12 to 15. During the second phase the fluorine contained in the volcanic ash fell to the ground in rain, poisoning pasturelands in the Argentinian and Chilean Patagonia and as faraway as Australia, eventually causing the deaths of thousands of head of cattle”. Cerro Hudson is 570 km north of Torres del Paine National Park of Fig. Gl4-1.
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Fig. Pf1-9. Location. Geographic. 45°56' S, 72°57' W, southern Chile Geologic. Cerro Hudson, Andean volcano Vertical Airphoto/Image. Type. TOMS Scale. 1:16 million Acquisition date. 13 August 1991 Source. Constantine et al TOMS and AVHRR Observations of Drifting Volcanic Clouds From the August 1991 Eruptions of Cerro Hudson. Remote Sensing of Active Volcanism. Geophysical Monograph 116. © 2000 American Geophysical Union, pp 45–64. Reproduced by permission of American Geophysical Union Comments. This spectral contrast image, between 339.66 and 379.55μ channels (of 6) is Plate 4C in the Constantine paper. These bands are sensitive to absorbing particulates such as desert dust, smoke and volcanic ash. The image was acquired 9 hours after the AVHRR. The latter relies on upwelling thermal infrared energy from the earth’s surface that is absorbed and scattered by the volcanic ash in volcanic clouds. The TOMS AI detects volcanic ash by its scattering of solar energy, which means that it is limited to daylight operation. The TOMS has a repeat cover of 1 day and has a 39 km field of view.
Pf1 · Pyroclastic Falls
Fig. Pf1-10. Location. Geographic. 90° S, 0° W/E Geologic. Cerro Hudson, Andean volcano Vertical Airphoto/Image. Type. AVHRR Scale. 1:16 million Acquisition date. 13 August 1991 Source. Constantine et al TOMS and AVHRR Observations of Drifting Volcanic Clouds From the August 1991 Eruptions of Cerro Hudson. Remote Sensing of Active Volcanism. Geophysical Monograph 116. © 2000 American Geophysical Union, pp 45–64, plate 14. Reproduced by permission of American Geophysical Union Comments. The composite image integrates the position data of TOMS AI drifting cloud over many days surrounding the South Pole.
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Pf1.1
Division 1 · Magmatic Rocks and Structures
Pf1.1 Ash-Tuff Hills Characterization Mode of emplacement and composition of this Variant is the same as for the tephra falls unit Pf1. The relative thickness of a blanket deposit is revealed by a masking of the underlying topography. The relief of this Variant is typically hilly and strongly-dissected.
Geohazard Relations The principal hazards associated with thick ash-tuff deposits are burial, erodability and slope instability. Burial by tephra can collapse roofs of buildings, snap power and communication lines and damage or kill vegetation. Because the deposits are porous and friable, especially when they are young, or loosely conso-
lidated, they are easily eroded. Tephra deposits are unstable because of the steepness of slopes and the movement of groundwater in the naturally porous material. Local faults occur which are caused by settling and compaction.
References Houghton BF, Wilson CJN, Pyle DM (2000) Pyroclastic fall deposits. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 555–570 Mollard JD, Janes JR (1983) Airphoto interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, p 16 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology: Volume 1. Presented at the 28th International Geological Congress, Washington, D.C. American Geophysical Union, pp 9–23 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 160–75
Fig. Pf1.1-1. Source. Way DS (1978) Terrain Analysis 2nd edn. Dowden, Hutchinson & Ross, Inc. Stroudsburg, Pennsylvania, p 163, fig 6.17 Comments. Block diagram shows characteristic hilly topography produced by the intense dissection of weak poorly consolidated tephra.
Pf1.1 · Ash Tuff Hills
Fig. Pf1.1-2. Source. Courtesy of Saemundur Ingolfsson c/o www.vulkaner.no Comments. A view of part of the town of Vestmannaeyjar (5 300 inhabitants) buried by 2 million m3 of tephra during a 5 month eruption from end January to June 1973 at the north end of Heimaey Island off the south coast of Iceland. During that period 80 houses were buried and burned by ash and scoria and 300 by lava. A 220 m high stratocone developed from an 1 800 m long fissure eruption at the east end of town. One third of the town was destroyed, with only one fatality, and 5 km2 of lava were emplaced. The tephra falls were from strong winds that carried them from the 9 km high eruption column east of the town. Heimaey Island is part of the same neovolcanic archipelago as Surtsey Island of Fig. Pf1-4 23 km to the southwest.
Fig. Pf1.1-3. Location. Geographic. 147°28' E, 09°27' S, southeast Papua New Guinea Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Bellamy JA (ed). Inventory of Natural Resources, Population Distribution and Land Use, Papua New Guinea. CSIRO Natural Resources Series No. 6, p 60, fig 5.32 © CSIRO 1986 Comments. Photo of the low undulating hilly topography of deeply-weathered Pliocene andesitic tuffs in a humid tropical environment 30 km east of Port Moresby. The local vegetation is eucalypt savanna. The forest density increases with increasing altitude and rainfall on the horizon.
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Fig. Pf1.1-4. Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 30 000 Acquisition date. Not given Source. Personal archive Comments. Stereomodel shows the intense erosional relief of deeply-weathered Cretaceous to Eocene tephra in the tropical climate of Puerto Rico in the Greater Antilles Deformed Belt of the Caribbean Plate. Ridges are sharp with steep sideslopes and hilltops are at varying elevations, unlike those in dissected S2.1 shales. The relatively sparse vegetation indicates that this area is on the rain shadow south side of the island, away from the high rainfall windward north side.
Fig. Pf1.1-5. Location. Type.
b/w pan airphoto Scale. 1:35 000 approx Acquisition date. Not given Source. Personal archive Comments. A stereomodel at an unspecified location in Japan shows the severe erosional topography with a dense drainage system and hilltops at different elevations that is characteristic of tephra hills in all climates.
Pf1.1 · Ash Tuff Hills
Fig. Pf1.1-6. Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 250 000 Acquisition date. 11 October 1985 Source. Unattributed Comments. The Tertiary tephra of the southern part of the Alban Hills south of Rome are pictured in a spectral red in the northwest sector of the image, reflecting beech forest cover and perennial crops. These hills are part of the greatest plateau area of volcanic tuffs in Europe, covering some 5 000 km². The spectral contrast of bluish soils on the Pontine Plain of Fig. Bc4-5 indicates harvested crops at the autumn image acquisition date.
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Pf1.3
Division 1 · Magmatic Rocks and Structures
Pf1.3 Ash-Tuff Plains Characterization In contrast to ash-tuff hills, the Ash-tuff plains Variant is characterized by a generally level deposition surface. Fluvial erosion of the plains deposits develops a relatively dense network of steep, deep, loess-like nearly vertical-sided gullies (e.g., the extensive plains of south Etruria associated with the volcanoes north of Rome).
Geohazard Relations The geohazards of these tuffs relate primarily to engineering construction activities. The gully dissection of the
erosive material may require major cuts and tunnelling for transport corridors. Cuts can generally be excavated safely in near-vertical slopes, but tunnelling may encounter zones of groundwater movement due to the porosity of the mass. Surficial clay soils resulting from weathering can be susceptible to volume changes and affect building foundations, particularly in humid tropical environments.
Select Bibliography Conrey RM, Taylor EM, Sherrod DR, Donnelly-Nolan JM, Bullen TD (2002) Desert spring tuff, central Oregon Cascade Range; new perspectives on source, genesis and hazards. Proc GSA Annual Meeting von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, p 140 See also variant Pf1.1.
Fig. Pf1.3-1. Source. Courtesy of Natural Resources Canada, Geological Survey of Canada, GSC 95660 Comments. Exposure of a distal deposit of tephra overlying gravel diamicton in southern Yukon Territory. The thin white fine pumice-like layer marks the contact. Age is approximately 1 400 BP.
Pf1.3 · Ash Tuff Plains
Fig. Pf1.3-2. Location. Geographic. Guatemala Geologic. Middle America Deformed Belt Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. April 1961 Source. Personal archive
Comments. The stereomodel of typically dissected ash/tuff covers a local area of the tephra-filled down-faulted basin of Guatemala City. The probable source of the tephra are the Quaternary twin volcanoes Acatenango, 3 976 m and Fuego 3 763 m, 20 km southwest of the city. The former last erupted in 1926–1927 and Fuego in October 1974. See Fig. Ps1-3. See similar terrain in the Philippines in Fig. Pf1.3-4.
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Fig. Pf1.3-3. Location. Geographic. Salvador Geologic. Middle America Deformed Belt Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given Acquisition date. Not given
Source. Personal archive Comments. Stereomodel of a typically dissected Quaternary ash/tuff plain is near San Salvador city in Salvador. The city is at the southeast foot slope of 15 km diameter, 2 000 m elevation San Salvador Vc1 stratovolcano, which is the probable source of this tephra. See similar terrain in the Philippines in Fig. Pf1.3-4.
Pf1.3 · Ash Tuff Plains
Fig. Pf1.3-4. Location. Geographic. 123°08' E, 10°34' N, southern Philippines Geologic. Magmatic island arc Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given Acquisition date. February 1952
Source. Personal archive Comments. The location of this stereomodel is in an area of tephra from one of three active Vc1 stratovolcanoes on Negros Island. The best known is Can Laon 2 465 m. Ash/tuff plains are characterized by a general level deposition surface. The depth of gullies gives an indication of the thickness of the deposits. See similar terrain in Central America in Figs. Pf1.3-2 and Pf1.3-3.
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Division 1 · Magmatic Rocks and Structures
Sub-group Ps Pyroclastic Density Current Deposits
bedded dissection, but is not evident in the available airphotos.
Ps1 Pyroclastic Flows and Surges, Undifferentiated
Geohazard Relations
Characterization Flows and surges originate as explosive eruptions of high viscosity magmas which expel fragments of materials from a conduit as a high-speed jet that interacts with the atmosphere. Although they have distinct origins and internal characteristics, the resulting deposits are difficult to differentiate in airphotos. There are two main eruption mechanisms as described by Cas and Wright (1987) lava-dome collapse and eruption column collapse. The former operates on steep-sided andesitic volcanic cones (Vc1). Fragment flows are generated when an unstable, actively growing lava-dome (Vs1) collapses at the summit or high on the flanks of the volcano. Eruption column collapse occurs when the effective density of a vertical ash-laden column becomes greater than that of the atmosphere; gravitational collapse occurs, generating a pyroclastic flow. In contrast to Pf1 pyroclastic falls which are generated from buoyant vertical trajectory plumes, flow and surge behaviours are non-buoyant and ground-hugging where the trajectory of motion is sideways to the ground surface. The pyroclastic flow travels along the ground as a high particle concentration gas-solid dispersion at velocities ranging from 10 to several hundred meters per second. It is composed of poorly sorted particle sizes ranging from pumice to 1m diameter scoria to blocks that can attain 5 m in diameter. The deposit, generally consisting of multiple flow units, does not drape the landscape but fills depressions. The pyroclastic surge generally travels ahead of the flow as a low particle pumice-ash concentration expanded by ingestion of air. The deposits are crossbedded, slightly-mantling beds that thicken into depressions in thicknesses that range from 1 to 5 m. Fresh pyroclastic flows are among the volcanic geounits that have distinctive thermal characteristics. Airphotos show the possible confusion in photogeological identification of this geounit with other similar appearing, and similarly sited, volcanic geounits including lava slope flows (X1.1); epiclastic lahars (A1); debris avalanches (A2). Welding in pyroclastic flow deposits, which is controlled by emplacement temperatures and load thickness compaction, affect their erodability as overall or inter-
“Pyroclastic density currents pose a variety of hazards including destruction by high-velocity ash-laden clouds, impact by rock fragments, and burial by surge deposits. Hot pyroclastic surges present several additional hazards, including incineration, noxious gases, and asphyxiation. Owing to their high velocities and great mobility, escape is impossible once pyroclastic density currents are generated.” (Scott 1989). These flows have been responsible for more than 70% of all deaths in volcanic eruptions this century, e.g. Pelée (1902), Lamington (1951). “… modeling scenarios of pyroclastic density currents as a basis for hazard assessment and emergency planning during eruptions are still problematic – a fundamental understanding of the compressible flow dynamics of rapidly moving hot gas-particulate currents is necessary.” (Freundt et al. 2000).
References Bordet P (1952) Les appareils volcaniques récents de l’Ahaggar. Monographies Régionales, XIXème Congrès Géologique International, pp 37–38 Brantley SR, Waitt RB (1988) Interrelations among pyroclastic surge, pyroclastic flow, and lahars in Smith Creek valley during the first minutes of 18 May 1980 eruption of Mount St. Helens, USA. Bull of Volcanology 50:304–326 Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 107–108 Freundt A, Wilson CJN, Carey SN (2000) Ignimbrites and blockand-ash flow deposits. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 581–599 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology: Volume 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, pp 9–23
Select Bibliography Fisher RV (1979) Models for pyroclastic surges and pyroclastic flows. Journal of Volcanology and Geothermal Research 6:305–318 Sheridan MF (1979) Emplacement of pyroclastic flows: A review. GSA Special Paper 180 Smith K (1996) Environmental hazards, 2nd edn. Routledge, London, p 160 Sparks RSJ, Walker GPL (1973) The ground surge deposit: A third type of pyroclastic rock. Nature 241:62–64 Valentine GA, Fisher RV (2000) Pyroclastic surges and blasts. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 571–580 Wilson CJN, Houghton BF (2000) Pyroclast transport and deposition. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 545–554
Ps1 · Pyroclastic Flows and Surges, Undifferentiated
Fig. Ps1-1. Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 94, fig 5.1 Comments. Schematic section shows the terrain differences of tephra deposits overlying the same topography. The fall deposit maintains a uniform thickness draping all the topography. The flow deposit is shown as poorly-sorted and confined to valleys. The surge deposit is thinner, cross-bedded, slightly mantles the ground, and thickens into low-lying areas.
Fig. Ps1-2. Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 106, fig 5.11e Comments. This schematic diagram shows the structure and idealized deposits of one pyroclastic flow. The detail sketch on the left is an enlargement of the boxed area on the right.
Fig. Ps1-3. Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 96, fig 5.5 Comments. Sketch map of Fuego Volcano, Guatemala showing tongues of Ps1 pyroclastic flows filling gullies and valleys on the lower slopes and Pf1 pyroclastic falls (stipple pattern) mantling the open slopes from the 1974 eruption. See Fig. Pf1.3-2.
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Fig. Ps1-4. Location. Geographic. North Island, New Zealand Geologic. Pleistocene volcano of emergent part of a fragment of Gondwana supercontinent Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 178, fig 7.1a Comments. A ground view of the pyroclastic flow from the vent of the 1975 eruption of Ngauruhoe Volcano in Tongariro National Park. Surface ridges are evident on the flow and there is a superficial photo resemblance to a X1.1 lava flow. This volcano is 13 km north of Ruapehu in the belt of volcanic activity described in Fig. A1-3. At 2 292 m elevation Ngauruhoe is the youngest and most active volcano in New Zealand. It has erupted 45 times in the 20th century. See also Fig. A2-2.
Fig. Ps1-5. Source. Bardintzeff J-M (1997) Les Volcans. Liber, Suisse, p 96 Comments. Closeup photo shows the typically poorly sorted deposit of a pyroclastic flow. This flow was emplaced during the 1929 eruption of Mont Pelée on Martinique Island in the eastern Caribbean Plate margin. The boulders are probably lava blocks. See the associated dome of Fig. Vs1.1-8.
Ps1 · Pyroclastic Flows and Surges, Undifferentiated
Fig. Ps1-6. Location. Geographic. 145°02' E, 04°05' S, Papua New Guinea Source. Ollier C (1969) Volcanoes. MIT Press, Cambridge, plate 5 Comments. This photo records a pyroclastic flow and surge from an eruption of the volcano on Manam Island, on the northeast coast, 17 March 1960. This volcano is active, it erupted again in January 2005. Figure Vc1.1-7 is a vertical airphoto of the island. Contrast this figure with the pyroclastic fall of Fig. Pf1-4.
Fig. Ps1-7. Location. Geographic. unspecified Source. USGS Comments. Photo shows the vertical ash-laden eruption column and the basal density current debris of a pyroclastic flow.
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Fig. Ps1-8. (Caption on p. 86)
Ps1 · Pyroclastic Flows and Surges, Undifferentiated
Fig. Ps1-9. (Caption on p. 86)
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Ps1.1 Macroscopic Ignimbrite Outflow
Ps1.1
Characterization ▼
Fig. Ps1-8. Location. Geographic. 05°21' E, 22°40' N, south Algeria Geologic. Hoggar Massif of African craton Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 78 000 Acquisition date. 1969 Source. IGN–Photothèque Nationale, France Comments. Based on Bordet’s 1952 regional field observations (p 12) the large, approximately 10 km2, bright area delimited in the center of the photo is interpreted as a composite deposit of Ps1/A1 pyroclastic flow and laharic material. The deposit is located 20 km southwest of Tamanrasset, at the eastern end of the 120 km long × 20 km wide Quaternary Tahalra Vc4 volcanic field, one of four extensive volcanic fields that occur in the Hoggar Massif (R3 in the photo). In stereo the deposit has the morphologic characteristics of pyroclastic density currents and epiclastic debris flow volcanic units. The flows evidently issue from one of a number of scoria cones occurring in the photo area, 2 km to the northeast. Smaller similar-appearing deposits have been delineated. The circular white deposit in the figure unit is possibly pumiceous A3 hydrocinerite. Vp1 are scoria/ash cones. This figure is 60 km east of the hydrocinerite deposits of Fig. A3-5.
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Fig. Ps1-9. Vertical Airphoto/Image. Type. TM, 30 m resolution Scale. 1: 740 000 Acquisition date. Not given Source. Applications of Remote Sensing in Asia & Oceania – Environmental Change Monitoring (1991) Murai S (ed). Asian Association on Remote Sensing, Murai Laboratory, Institute of Industrial Science, University of Tokyo, p 356 Comments. The complex distribution pattern of large-scale Pleistocene pyroclastic flows appears beige on this satellite image of the southern part of Kyushu Island, Japan. Sources of the flows were vents associated with each of the three outlined Vc3.2 calderas. The flow from the central, active caldera, began erupting about 22 000 BP. Among its many eruptions the one of 1914 was particularly catastrophic. See Fig. Vc3.2-7. The bright pink area west of the central caldera is Kagoshima City, population >500 000. The green areas are mainly subtropical semi-natural or plantation mixed forests in the uplands.
Ignimbrite outflows are the results of the most cataclysmic of all geologic phenomena. Notable catastrophes include Santorini 1470 bc, Vesuvius ad 79, Tambora 1815, Krakatau 1883, St. Helens 1980, Chichon 1982. Ignimbrites are the most voluminous of volcanic products, and occur in all geotectonic settings on land. They are understood to be formed by the eruption column collapse mechanism described for pyroclastic flows and surges (Ps1) but over a larger area, involving continuous gravitational collapse of a plinian (violent) eruption column from heights of several kilometers. The general transportation and depositional mechanisms of ignimbrites are also described in the characterization of Ps1. A characteristic photogeologic feature of ignimbrite flows is the deep grooving of the surface parallel to the direction of flow which is related to the high outflow energy. Related local airfall welded ash-tuff facies are difficult to detect and map photogeologically. Ignimbrite source vents, which are often hidden by associated structural collapse or fill, can be linear fissures (e.g. Novarupta Vs1 dome), ring fissures (e.g. Valles, Galan Vc3.3 Calderas) or central (e.g. Santorini, Vc3.1 caldera). Dimensions: areas covered – a few hundred m2 to 45 000 km2 volumes – a few km3 to 5 000 m3 (large volume ignimbrites are commonly associated with caldera collapse, Vc3 thicknesses – 1 m to 150 m (a single flow unit can range from 0.5 m to more than 40 m) runout distances – a few hundred m to as much as 200 km The morphologic expression and detectability of internal characteristics of ignimbrites, such as deposition facies (related for example to magma discharge rates), fallflow, welding and secondary deposits interbedding, could be subjects for additional photogeologic research.
Geohazard Relations See Geounit Ps1. Concerning the geohazards in relation to eleven large silicic systems of the central Andes, de Silva and Francis (1991) have stated “… even though many caldera systems have been inactive for periods as long as hundreds of thousands of years, from a geological perspective there is no compelling reason to believe that activity has ended.” A hazard potential remains related to these systems.
Ps1.1 · Macroscopic Ignimbrite Outflow
Reference de Silva S, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin, pp 157–176
Select Bibliography Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, Chap. 8 Christiansen RL (1979) Ash-flow tuffs. GSA Spec. Paper 180, pp 29–42 Crown DA, Greeley R, Sheridan M, Carrasco R (1989) Spectral and morphologic characteristics of ignimbrites: The Frailes
Fig. Ps1.1-1. Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 231, fig 8.8 Comments. These models show the eruption phases of ignimbrite-forming volcanism. In (a) a violent eruption column termed plinian produces Pf1 pumice fall deposits. In (b) gravity collapse of the overloaded column produces ignimbrite pumice outflows.
Fig. Ps1.1-2. Source. Green J, Short NM (eds) (1971) Volcanic Landforms and Surface Features. Springer-Verlag, pl 167A Comments. A view of exposures of ash flow deposits of the Lower Pleistocene Bandelier Tuffs. This site is indicated by arrows in Fig. Ps1.1-5. The darker flows are more densely welded than the lighter beds.
Formation, Bolivia. New Mexico Bureau of Mines, Miner Res Bull 131 Freundt A, Wilson CJN, Carey SN (2000) Ignimbrites and blockand-ashflow deposits. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 581–599 Hill DP (2002) A color code for communicating volcanic hazard information in the Long Valley Caldera-Mono Craters region, eastern California. GSA 34(5) Self S (2006) Defining super-eruptions: Purpose, prejudices and limitations. AGU Fall Meeting 2006, Abstract V23G-02 Sheridan MF (1979) Emplacement of pyroclastic flows: A review. GSA Special Paper 180, pp 125–136
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Fig. Ps1.1-3. Location. Geographic. 118°27' W, 37°26' N, central California Geologic. western Basin and Range Province Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 140 000 Acquisition date. Not given Source. Sharp RP (1972) Geology Field Guide to Southern California. Wm. C. Brown Co. Publishers, Dubuque, Iowa, p 152, photo 3-30 Comments. Subscene of a highaltitude photo of the Bishop Tuff in the Owens Valley Fault Zone pictured in the satellite image of Fig. Ps1.1-7. The tuff is 150 m thick at Bishop and has been dated at 0.74 Ma. Fracture traces in the lower right of the deposit are post-depositional faulting not fluting. The streams crossing the tuff are entrenched 60–70 m into it. North is on the right of the photo.
Fig. Ps1.1-4.
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Location. Geographic. 67°39' W, 21°26' S, southwest Bolivia Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 11 August 1964 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 105 Comments. The stereomodel shows part of a Quaternary ignimbrite flow, with its characteristic grooved surface, overlying Tertiary X1 basalt flows. Location is on the Altiplano. Fu2 is a piedmont apron type of alluvial fan cover.
Ps1.1 · Macroscopic Ignimbrite Outflow
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Fig. Ps1.1-5. (Caption on p. 92)
Ps1.1 · Macroscopic Ignimbrite Outflow
Fig. Ps1.1-6. (Caption on p. 92)
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Fig. Ps1.1-5.
Location. Geographic. 106°33' W, 35°52' N scene center, northen New Mexico, USA Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 360 000 Acquisition date. Not given Source. USGS Comments. Wide, shallow-dipping ignimbrite deposits known as the Bandelier Tuffs are delineated surrounding the Vc3.3 Valles Caldera, west of Santa Fe in this Landsat subscene. They are at about 3 000 m elevation, and display the characteristic fluting parallel to the direction of flow. The tuffs are of Lower Pleistocene age, and are the products of two eruptions dated 1.4 and 1.1 Ma. The lower deposit with its volume of 100 km3 and the upper with its volume of 70 km2 are two of the most voluminous yet recognized. (Cas & Wright 1987, pp 244, 245). Ash from the eruption of the lower tuff is known to have been dispersed 500 km. The small arrows on the eastern deposit locate the site of the ground photo of Fig. Ps1.1-2 along the Route 4 Los Alamos Canyon. The town of Los Alamos is just west of the small arrows. ▼
Fig. Ps1.1-6.
Location. Geographic. 66°15' W, 19°30' S scene center, southwest Bolivia Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 590 000 Acquisition date. Not given Source. deSilva S, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, p 161, fig S2 Comments. This Landsat mosaic covers the vast, >8 500 km2, Frailes ignimbrite plateau at an average elevation of 4 500 m, west of Potosi. Radiometric ages for the flows range from 20 Ma to 7 Ma. Characteristic radial fluting patterns are conspicuous. White codes indicate local place names:. HP is Cerro Huanapa Pampa; NM is a Holocene Nuevo Mundo complex; CN is Cerro Condor Nasa. Because of sheer size the existence of this structure and other large silicic calderas as Pastos Grandes of Fig. Vc3.3-3 and Cerro Galan of Fig. Vc3.3-4 were only discovered by the synoptic view provided by Earth Observation satellites in the mid to late 1970s when they became immediately obvious.
Ps1.1 · Macroscopic Ignimbrite Outflow
Fig. Ps1.1-7. Location. Geographic. 118°30' W, 37°27' N at inset frame, central California Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 04 October 1979 Source. USGS Comments. This Landsat image is annotated to show the regional setting of the Bishop Tuff of Fig. Ps1.1-3 airphoto. The inset frame locates the coverage of the airphoto. The tuff originally extended 40 km northward to Mono Lake, but has been partly eroded or covered by more recent volcanic deposits.
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Group V Cenozoic Volcanic Structures Sub-group Vs Viscous Lava Structures Vs1
Vs1 Autonomous Domes
Geohazard Relations The cooled outer carapace of a dome can contribute to a buildup of pressure in the dome’s interior releasing a violent explosion when the dome front collapses, giving rise to Ps1 pyroclastic flows and surges. Repeated injections of magma beneath the dome can also cause further eruptions.
Reference Characterization Autonomous domes occur in isolation as relatively smallvolume, circular, generally convex accumulations of rhyolitic lavas erupted at low rates, resting in-situ above their source vent. Lateral flow is inhibited by the lava viscosity and quick cooling following extrusion. The dome diameters vary from a few meters to several kilometers. Heights vary from a few meters to greater than 1 km. Domes grow by repeated injections of lavas which create internal foliate structures. Their surfaces range from nearly level (Fig. Vs1-2 and 3). to irregular ridges and troughs (Fig. Vs1-4), to strongly dissected (Fig. Vs1-5). These variations may relate to eruption and cooling rates and subaerial erosion. Photogeologically some domes could be confused with non-geohazardous granitic stocks (intrusions of local extent). The stocks are generally more conical than the convex domes, and display jointing not characteristic of domes.
Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 81–87, 294, 391
Select Bibliography Fink J (ed) (1987) The emplacement of silicic domes and lava flows. GSA Special Paper 212 Fink JH, Anderson SW (2000) Lava domes and coulees. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 307–319 Miller CD, Mullineaux DR, Crandell DR, Bailey RC (1982) Potential hazards from future volcanic eruptions in the Long Valley-Mono Lake area, East-Central California and Southwest Nevada – A preliminary assessment. USGS Circular 877 Nakada S, Miyake Y, Sato H, Oshima O, Fujinawa A (1995) Endogenous growth of dacite dome at Unzen Volcano (Japan), 1993–1994. Geology 23(2):157–160 Rose WI (1989) Volcanic activity at Santiaguito Volcano, 1976–1984. GSA Special Paper 212, pp 17–27 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology: Volume 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, pp 9–10
Fig. Vs1-1. Location. Geographic. 05°41' E, 23°15' N, SE Algeria Source. Girod M (1971) Le Massif Volcanique de l’Atakor (Hoggar, Sahara Algérien) Etude pétrographique, structurale et volcanique. IGN France, plate 9 (groundview), p 97, fig 40 (cross section) Comments. The figure shows a ground view and a cross section of the Upper Miocene Essa trachyte lava dome in the Atakor Highland. Interbanded flows are visible in the photo. The cross section illustrates the viscous extrusion from a central vent, and the development of the concentric structure of flow foliations moving outward both radially and tangentially as lava is repeatedly injected into the growing dome. This dome is 300 m high and has a diameter of 750 m. A deposit of precursor pyroclastics is visible at the base of the structure.
Vs1 · Autonomous Domes
Fig. Vs1-2. Location. Geographic. 02°59' E, 45°49' N, south central France Source. LAR, October 1976 Comments. This is a view of the east face of the 200 m high and 1 km diameter Grand Sarcoui trachyte dome which erupted 8 300 BP. The cave entrance near the center of the dome is an abandoned adit type quarry dating from the late 18th century. (The stone’s ease of excavation and porosity, favouring dessication, led to its use for coffins and as a local building stone.). There is evidence of a small Ms1.1 rock slide to the left of the adit entrance. Location is 7 km west of Clermont-Ferrand in the Auvergne of the Massif Central. A vertical airphoto stereogram of the dome is in Fig. Vs1-3. Figure Pf1-6 gives a description of the regional geologic context of this figure.
Fig. Vs1-3. Location. Geographic. 02°59' E, 45°49' N, south central France Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 25 000 Acquisition date. Not given
Source. Personal archive Comments. The Upper Pleistocene dome marked “T2” and “4” in the center of this stereomodel is pictured and described in the ground view of Fig. Vs1-2. The bordering cones north and south are typically small parasitic scoria/ ash cones from mildly explosive conduits. This site is 3 km east of the quarry in tephra of Fig. Pf1-6.
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Fig. Vs1-4. (Caption on p. 98)
Vs1 · Autonomous Domes
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Division 1 · Magmatic Rocks and Structures ▼
Fig. Vs1-4. Location. Geographic. 67°43' W, 20°54' S, southwest Bolivia Geologic. Altiplano Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 3 June 1964 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 69 Comments. A stereomodel shows a 1 km diameter Tertiary/Quaternary autonomous viscous dome 12 km west of Julaca.
Fig. Vs1-5.
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Location. Geographic. 16°59' E, 20°59' N, northern Chad Vertical Airphoto/Image. Type. MSS7. 80 m resolution Scale. 1: 650 000 Acquisition date. 26 January 1976 Source. USGS Comments. The 20 km broad Tarso Abouki siliceous (rhyolite/trachyte) dome, 2 135 m elevation is delineated on this Landsat subscene. The dome stands in marked contrast to the Ps1.1 ignimbrite fields of the adjacent calderas. See Fig. Vc3.1-11. Location is south of Bardai, in the Cenozoic volcanic cap of the Tibesti Precambrian crustal block. Boundary faults are associated with the dome, and radial dykes also occur in the structure. Neither are image-resolved. Photogeologically volcanic domes could be confused with intrusive granitic stocks, but the latter usually display a less dense jointing system, and relief that frequently reflects associated arid climate exfoliation. Physical weathering has played its part in the dissection visible on the dome, but fluvial erosion may have been effective in earlier pluvial periods.
Vs1.1 · Domes in Cones
Vs1.1 Domes in Cones
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Vs1.1
Characterization The Dome in cones Variant, commonly called a tholoid, occurs within the craters of stratovolcanoes (Vc1), shield volcanoes (Vc2), and within caldera Variant Vc3.3. General characterization is the same as autonomous domes, Vs1. Fresh domes are among the volcanic geounits that have distinctive thermal characteristics.
Geohazard Relations Lava dome emplacement has been among the most deadly types of volcanic eruptions. “Most hazards associated with domes originate when a part of a dome front collapses giving rise to pyroclastic flows. The flows may travel tens of kilometres at very high speeds.” (Fink and Anderson 2000).
Reference Fink JH, Anderson SW (2000) Lava domes and coulees. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 307–319
Select Bibliography See Geounit Vs1.
Fig. Vs1.1-1. Location. Geographic. 91°35' W, 14°30' N, western Guatemala Source. Fink J (ed). (1987) The Emplacement of Silicic Domes and Lava Flows. Geological Society of America Special Paper 212, p 24, fig 8 Comments. The map shows the areas devastated by large pyroclastic flows at Santiaguito Dome below 3 771 m Santa Maria Volcano, in 1929 and in 1973. The 1929 flow is now forested and eroded by a parallel drainage system. A ground photo of the dome is in Fig. Vs1.1-2.
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Fig. Vs1.1-2. Source. Bardintzeff J-M (1997) Les Volcans. Liber, Suisse, p 43 Comments. A ground view of a small explosion at Santiaguito Dome in western Guatemala which caused approximately 1 000 deaths in 1929. A map of the devastated areas of the 1929 and 1973 explosions is in Fig. Vs1.1-1.
Vs1.1 · Domes in Cones
Fig. Vs1.1-3. Source. Rittman A-L (1976) Les Volcans. Editions Atlas s.a.r.l. Paris, p 54 Comments. Air perspective photo shows a classic tholoid dome in the Vc1 crater of fumarolic Tarumai Volcano, 1 320 m, photo date is not given. The visible slopes are covered with Pf1 tephra. The volcano is at 141°22' E, 42°41' N on the south rim of Shikotsku Caldera near the southwest coast of Hokkaido, Japan. It has been dormant since a last minor eruption on 28 February 1981.
Fig. Vs1.1-4.
Fig. Vs1.1-5.
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Source. Bardintzeff JM (1997) Les Volcans. Liber, Suisse, p 95 Comments. A closeup view of the tholoid which rose in the crater of 1 234 m Soufrière Volcano, in May 1979 following the pyroclastic flow and surge in April, at the north end of St. Vincent Island, St. Vincent and Grenadines, Antilles.
Location. Geographic. 153°16' E, 28°24' S, eastern Highlands, Australia Vertical Airphoto/Image. Type. b/w pan airphoto Scale. reduced from 1:38 000 Acquisition date. Not given Source. Twidale CR, Foale MR (1969) Landforms Illustrated. Thomas Nelson (Australia) Ltd., p 71, ill 22
Comments. Stereomodel quadruplet in the northern Tablelands shows a 1 156 m tholoid in the inactive early Tertiary Vc2 in Mt. Warning National Park shield volcano 85 km south of Brisbane. This volcano forms the central complex of the 100 km wide Tweed Volcano.
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Fig. Vs1.1-5. (Caption on p. 101)
Vs1.1 · Domes in Cones
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Division 1 · Magmatic Rocks and Structures
Fig. Vs1.1-6. Source. USGS/Cascades Volcano Observatory, photo by Dan Dzurisin Comments. This photo taken on April 28, 2006, shows the growing dome 100 m high emerged from the crater of Mt. St. Helens (Fig. Vs1.1-7) with a collapse of part of the dome front. The dome is related to a renewed activity of the volcano in the autumn of 2004.
Fig. Vs1.1-7.
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Vertical Airphoto/Image. Type. colour infrared airphoto Scale. 1: 14 000 ± Acquisition date. Not given Source. USGS Comments. The stereomodel shows a viscous dome growing in the crater of the decapitated stratocone of Mount St. Helens, now 2 250 m elevation, in the northern Cascade Range of the western cordillera, Washington State, USA. The photo was taken about one year following the catastrophic 18 May 1980 eruption. See the dome’s height and form on 28 April 2006 in Fig. Vs1.1-6. Mt. Rainier of Fig. A2-3 is 80 km to the north. The Cascade range, within the United States, is an 1 100 km long narrow linear chain, which in plate tectonic terms, is a sliver of continental margin volcanic arc.
Vs1.1 · Domes in Cones
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Fig. Vs1.1-8. Location. Geographic. 61°10' W, 14°49' N, Martinique Island, France Geologic. Neogene volcanic belt on the east margin of the Caribbean Plate Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 33 000 Acquisition date. 1950
Source. IGN-Photothèque Nationale, France Comments. A photo shows the tholoid-type lava dome in the crater of Mt. Pelée at the north end of the island. On 8 May 1902 the dome exploded and collapsed and a Ps1 pyroclastic flow filled the Rivière Blanche Valley killing 29000 people in a minute.Another eruption followed on 20 May. The Pf1 area east of the crater consists of undifferentiated vent proximal deposits, probably tephra. The volcano has been K-Ar dated at Mid-Pleistocene 400 000 BP.
Vs1.2 · Flow Dome Complexes
Vs1.2 Flow-Dome Complexes
described by Miller et al. (1982) who evaluated the hazard potential of the Mono Craters complex and inferred both ashfall hazard and flowage hazard.
Characterization Reference The characterization of flow-domes complexes is essentially the same as that for the parent unit. The distinction lies in the outflow of viscous coulées which flow from the dome as relatively short lobes or accumulate as corrugated aprons around the base of the dome. Flow lobes lying on a sloping surface are the most extensive. Their morphology is related to flow viscosity and flow rate.
Geohazard Relations The geohazards of flow-dome complexes are also essentially similar to those of the parent unit Vs1. They are
Miller CD, Mullineaux DR, Crandell DR, Bailey RC (1982) Potential hazards from future volcanic eruptions in the Long Valley – Mono Lake Area, East-Central California and Southwest Nevada – A preliminary assessment. USGS Circular 877
Select Bibliography Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 81–87 Fink JH, Anderson SW (2000) Lava domes and coulées. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 317–319 Weaver BL (2000) The geology of Ascension Island. Proceedings of the American Academy of Arts and Sciences 60:1–80
Fig. Vs1.2-1. Source. Green J, Short NM (eds) (1971) Volcanic Landforms and Surface Features. Springer-Verlag, pl 90B Comments. An air view shows a rhyolite flow that emanated from a central dome. Big Obsidian Flow which erupted 1 300 years ago is located on a fracture bounding the south side of Newberry Caldera on the Columbia Volcanic Plateau in central Oregon. The corrugated apron pattern of the flow is particularly well expressed. Compare with the vertical airphoto of Fig. Vs1.2-3 in Kenya, and Fig. Vs1.2-5 in California’s Modoc Plateau.
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Division 1 · Magmatic Rocks and Structures
Fig. Vs1.2-2. Source. Putnam WC (1938) Geographical Review. American Geographical Society, vol 28, pp 68–82 Comments. The schematic diagram adapted from Putnam shows the outflow of a short lobe of lava from a dome onto a level surface. Vs1.1 is the dome in the crater; Vs1.2 is the flow-dome out from the crater.
Fig. Vs1.2-3.
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Vertical Airphoto/Image. Type. b/w pan Scale. Not given Acquisition date. Not given Source. Green J, Short NM eds. (1971) Volcanic Landfords and Surface Features. Springer-Verlag, pl 91A Comments. The photo shows the flow-dome complex of Pakka 20 km north of Lake Baringo in the eastern Rift Valley, Kenya. The trachyte flow emanates from a breached cone. The lobes, with concentric pressure ridges, lying on a flat surface, are short and are typically arrayed as an apron around the base of the cone. Compare with the air perspective view of Fig. Vs1.2-1 in Oregon.
Vs1.2 · Flow Dome Complexes
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Fig. Vs1.2-4. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. Ray RG (1960) Aerial Photographs in Geologic Interpretation & Mapping. USGS PP 373. p 142, fig 76
Comments. Stereomodel shows a flow-dome complex at “E” and “D” that extruded from the breached Vc1 volcano, now inactive, amid faulted NW-trending belts of Lower Triassic metamorphic rocks. Location is 131°W, 55°25' N, in densely forested land on the southeast side of Revillagigedo Island on the Behm Canal in coastal foothills at the extreme south end of the Alaska Panhandle, 60 km west of the Canadian border.
Vs1.2 · Flow Dome Complexes
Fig. Vs1.2-5. Location. Geographic. 121°30' W, 41°36' N, Northern California Geologic. Quaternary/Tertiary lavas of Modoc volcanic plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 31 July 1955 Source. USGS Comments. The stereomodel shows the flow-dome complex of Glass Mountain which consists of two obsidian
flows, the younger of which runs northeast (towards upper right) from a 3 395 m summit dome. Flow structure and steep margins of flows stand out. The older flow, named Hoffman, lies to the west and supports a moderate growth of pines. Its vent, Mount Hoffman, is outside the area of the photograph. The white patches on the Hoffman flow are pumice up to 18 m thick that has filled depressions on the flow surface. A line of small domes trends 30° NW from Glass Mountain. The flows are probably less than 1 000 years old.
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Division 1 · Magmatic Rocks and Structures
Vs2 Coulées
their slow rate of movement. Also the extrusions typically produce short thick flows that seldom move as far as 5 km.
Characterization
Reference
“Coulées are extrusions of lava that have aspects of both lava domes and lava flows. They are elongated extrusions of viscous lava concentrated to one side of a vent. Ridge patterns, similar to those visible on flows of flow-dome complexes, are frequently prominent on coulée surfaces. They are said to have formed in response to compression parallel to flow during advance.” (Fink and Anderson 2000).
Geohazard Relations Coulées geohazard relations are indirect. They are in common association with other geohazard-related viscous lava structures, domes (Vs1) and flow-dome complexes (Vs1.2). The flows seldom threaten human life directly because of
Fink JH, Anderson SW (2000) Lava domes and coulees. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 307–319
Select Bibliography Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 81, 87 Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos. Tomo II. Universidad Mayor de San Andres, pp 493–494 de Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin, p 143 Krafft M, de Larouzière FD (1999) Guide des Volcans d’Europe et des Canaries. Delachaux et Niestlé, Paris, pp 290–296 Souther JG (1992) Ornostay and Koosick centres, 182. The Late Cenozoic Mount Edziza volcanic complex, British Columbia. GSC Memoir 420, p 155
Vs2 · Coulées ▼
Fig. Vs2-2.
Location. Geographic. Eolian Island Group, south Italy Geologic. Part of Mid-Paleozoic metamorphic Calabrian Massif of the Italian toe and northeast Sicily Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 86, figs 4.27 and 4.28 Comments. The photograph shows the frontal mass of the Rocche Obsidian (volcanic glass) Holocene coulée on North Lipari Island. The graphic is a cross section through the length of the coulée, with generalised internal flow foliation.
Fig. Vs2-3.
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Fig. Vs2-1.
Location. Geographic. 119°01' W, 37°53' N, eastern California Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image covers the 12 km long line of Late Pleistocene silicic Vs1 (obsidian) Vs2 coulees and Vs1 domes misnamed Mono Craters. The larger coulees, with cliff-like marginal slopes, are arrayed normal to the trend of the range. The ruggedness of their surfaces is due to the fact that they hardened at the surface while the still molten interior continued to flow. These structures lie within a 55 km wide large complex volcanic-filled graben, Long Valley, bounded on the west by the Sierra Nevada and on the east by the White Mountains, the westernmost ranges of the Basin and Range Province. The extrusion of these structures within the last 35 000 years, chiefly about 10 000 years ago, followed a repetitous sequence in different parts of the complex. Shallow explosion pits developed, followed by a rise of viscous lavas which formed domes inside the pits. As the lavas continued to ascend they spilled over the pit rims forming coulees. The youngest feature is only 600 years old. The Vs1 dome complex in the center stands 820 m above the surrounding plain. The main encircled area encloses Johnson, Russell, and a cluster of five other domes. Volcanic unrest continues in Long Valley, a sequence of earthquakes which began in 1978 culminated in 1980. The white areas are loose fine pumice particles blown out of the craters by a series of explosions.
Location. Geographic. 39°55' E, 09°00' N, western Ethiopia Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. Not given Source. Green J, Short ND eds (1971) Volcanic Landforms and Surface Features. Springer-Verlag, plate 91B Comments. Photo shows a 2 km long coulee flowed from a vent down the northeast flank of Fantale Volcano of Fig. Vc3.1-7 near the eastern Rift Valley. The curved ridges reflect the main directions of movement.
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Fig. Vs2-2. (Caption on p. 113)
Vs2 · Coulées
Fig. Vs2-3. (Caption on p. 113)
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Fig. Vs2-4. (Caption on p. 118)
Vs2 · Coulées
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Fig. Vs2-4. Location. Geographic. 66°29' W, 19°51' S, southwest Bolivia Geologic. Central Andes Volcanic Zone Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 1 January 1961 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 11 Comments. A stereomodel on the Cordillera Oriental at Laguna Khasilla south of Rio Mulatos covers a 5 km long by 2 km wide viscous, relatively thick, coulée of Tertiary rhyolite with the characteristic ridge pattern.
Fig. Vs2-5. Location. Geographic. 68°09' W, 22°07' S, northern Chile Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 100 000 Acquisition date. Not given Source. deSilva SL, Francis PW (1991) Volcanoes of the Central Andes. SpringerVerlag, p 142, fig M4 Comments. The Landsat subscene covers the discrete Chao coulee. The flow is 15 km long by 7 km wide, occupying a saddle between two volcanoes. It is the largest of its type in the world. It has been dated in the Upper Pleistocene at less than 100 000 years old. The structure is made up of three lobes of lava, shown as I, II, and III respectively. The flow fronts are 350 to 400 m high. Characteristic features of this coulee are the prominent 30 m high flow ridges on its surface. A and PF are tephra fall precursors to lobe III. Points P and L are unidentified in the source.
Vc1 · Stratovolcanoes
Sub-group Vc Major Conical Structures Vc1 Stratovolcanoes Characterization Origin and Composition The stratovolcano is the most abundant type of volcano on the Earth’s surface. More than 1 300 have been active in the last 10 000 years. The mechanism of emplacement begins when magma, normally less dense than surrounding rock, rises buoyantly toward the surface following a line or network of lines of weakness, resulting in a pipelike vertical conduit building a symmetrical cone. “The most influential factor in shaping volcano landform is the manner in which gas exits the magma. As magma nears the surface, the attendant decrease in pressure permits exsolution of dissolved gases, which then drive the eruption vertically (the only direction in which it is free to expand).” (Simkin and Siebert 2000). Repeated eruption of primary volcanic products, tephra (Pf1) and lavas (principally andesitic X1) “complement each other in building a stable structure. Outpourings of lava mix with fragmental ejecta to construct a reinforced conical landform” (Short and Blair 1986). The layering may be seen exposed by erosion on the cone flanks. Stratovolcanoes are thus also referred to as composite volcanoes.
Morphometry Stratovolcanoes can be topographically impressive, rising steeply from about 400 m to as high as 5 km above their bases. Basal diameters can range from 1 to 60 km. Average slopes range from 15° to 30°. Ollier 1981 has written that as with other crustal loadings (glacial, sedimentary) volcanoes are subject to isostatic forces and settle under their own weight. The settlement of volcanic cones causes various deformations at the base of the structure. Suzuki (1968) found that fault type settlement tends to occur when underlying sediments are thin (<200 m). Where sedimentary rocks are thicker – several hundred to thousands of meters, fold type settlement results.
Morphology Initially the cone is symmetrical; however it is soon modified by volcaniclastic geounits, principally pyroclastic explosions (Pf, Ps geounits) and of a number of epiclastic
surface process geounits. Many of these are hazardous phenomena. Photogeologically, such a modified cone structure is classed and characterized as Variant Vc1.1. A volcanic lake is a cap of meteoric water over the vent of an active volcano. Only 12% of the world’s 714 Holocene aged or younger volcanoes have such a lake. What makes these lakes rare is that their occurrence requires a special balance of volcanic heat flux versus atmospheric cooling, and precipitation versus evaporation. Figure Vc1–9 shows a volcano which could be susceptible to volcanic lake hazards. Other such lakes are Bolsena, Vico and Bracciano north of Rome and Albano and Nemi south of the city. (The latter two are shallow maar explosion craters.)
Occurrence Suzuki (1977) determined that stratovolcanoes make up the largest group (62%) of the global population of volcanoes. Maps showing boundaries of tectonic plates and volcanoes show that most stratovolcanoes occur near the edges of tectonic plates. Subduction of one plate beneath another causes most of the evident volcanism. More than 90% of known historical eruptions have occurred within subduction zone belts encircling the Pacific Ocean. Other stratovolcanoes occur in association with some intracontinental fault zones and rifts.
Geohazard Relations “All volcanoes which have erupted within the last 25 000 years should be regarded as at least potentially active. In an average year around fifty volcanoes actually erupt. Thus the eruptive, hazardous phases are very short in comparison to the long periods of relative inactivity. The infrequency of volcanic events, within the short time-scale of human history, is one of their most dangerous features and can make average figures misleading”. “As with most environmental hazards, the impact of volcanic eruptions depends heavily on the local population density and building type.” (Smith 1996). There are at least 1 000 identified magma systems – on land alone – (including shield Vc2 and calderas Vc3) likely to erupt in the future. “The most common eruptions observed by humans, and by far the most dangerous to human populations, are those from volcanoes overlying the world’s subduction zones. (i.e. stratovolcanoes) Because of their explosive nature, these are also the eruptions most likely to affect our climate.” (Simkin and Siebert 2000). Erupting volcanoes can generate a variety of primary hazards including pyroclastic flow geouints, Ps1, air fall
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tephra, Pf1 and lava flows, X1.1, which are directly related to an eruption episode. Secondary hazards associated with stratovolcanoes are the epiclastic geounits including debris avalanches, A2, and dome collapse, Vs1. The harmful effect of dissolved gases released during eruptions are discussed in Geounit Pf1 Pyroclastic falls. Volcanic eruptions through lakes can cause failure of a retaining wall and a resulting flood of the lake waters. Many eruptions through lakes lead to massive A1 lahar flows, e.g., Fig. A1–3. True lake explosions may be thermal in origin or may be related to catastrophic degassing of the lake waters, e.g., in Fig. X1.4–5. An additional, and major, hazard associated with some stratovolcanoes is caldera forming eruptions following stratovolcanic activity. The altered structures and their related hazards are characterized as Variant geounit Vc3.1.
References Ollier CD (1981) Tectonics and landforms. Longman, London, pp 113–114 Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Volcanic landforms. Geomorphology from space. NASA SP 486, pp 185–253 Simkin T, Siebert L (2000) Earth’s volcanoes and eruptions: An overview. In: Sigurdsson H (ed). Encyclopedia of volcanoes. Academic Press, pp 249–261 Smith K (1996) Environmental hazards, 2nd edn. Routledge, pp 155–181 Suzuki T (1968) Settlement of volcanic cones. Bull Volcanol Soc Japan 13:95–108 Suzuki T (1977) Geomorphological aspects of volcanoes. Bull Volcanol Soc Japan 2(20):241–246
Select Bibliography Photogeology and Remote Sensing de Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin Dehn J, Dean K, Engle K (2000) Thermal monitoring of North Pacific volcanoes from space. Geology 28(8):755–758 Elder DF, Sides SC, Chavez PS (1991) Discriminating lithologic units and structural features in volcanic terrain using Landsat Thematic Mapper and 3 cm airborne radar data. GSA, Abstracts, vol. 23, no. 4, p 18 Hartono, Baharuddin A (1987) The use of aerial photographs in Quaternary volcanic terrains. Geological Research and Development Centre, Bandung, Indonesia, pp D-23–1 – D-23–15 Massonet D, Sigmundsson F (2000) Remote sensing of volcano deformation by radar interferometry from various satellites. Remote Sensing of Active Volcanism, Geophysical Monograph 116, American Geophysical Union, pp 207–221 Mouginis-Mark PJ, Domergue-Schmidt N (2000) Acquisition of satellite data for volcano studies. Remote Sensing of Active Volcanism, Geophysical Monograph 116, American Geophysical Union, pp 9–24 van Zuidam RA (1985/86) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC, The Hague, pp 16–186
Verstappen HTh (1983) Applied geomorphology. Elsevier Scientific Publishing Co., NY, pp 417–422
Hazards Blong RJ (1984) Volcanic hazards. A sourcebook on the effects of eruptions. Academic Press, Sydney Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management, GSC Paper 84 – 16, pp 29–43 Guffanti MC, Bacon CR, Hanks TC,Scott WE (eds) (1999) Proceedings of the workshop on present and future directions in volcano hazard assessments, Sept. 1998. USGS Open File 99–0339 Hickson CJ, Edwards BR (2001) Volcanoes and volcanic hazards. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:145–181 Major JJ, Mark LE, Pierson TC, Spicer KR (2002) Geomorphic response to widespread catastrophic disturbance by volcanic eruption. 2002 Denver Annual Meeting (October 27–30, 2002) GSA vol. 34, no 6 Nathensen M (2001) Publications of the Volcano Hazards Program 2000. USGS Open File Report 01–464 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology: Volume 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, pp 9–23 Scott WE (1984) Assessments of long-term volcanic hazards. USGS Open File Report 84–760, pp 447–498 Wright TL, Pierson TC (1992) Living with volcanoes. USGS Volcano Hazards Program, Circular 1073
Genesis Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 383–393 Fisher RV, Heiken G, Hulen JB (1987) Volcanoes: Crucibles of change. Princeton University Press, Princeton, NJ Gerrard AJ (1990) Mountain environments. The MIT Press Cambridge, Mass., pp 192–223 Putirka K, Condit CD (2003) Cross section of a magma conduit system at the margin of the Colorado Plateau. Geology 31(8): 701–704 Simkin T, Unger JD, Tilling RI, Vogt PR, Spall H. (1994) This dynamic planet – World map of volcanoes, earthquakes, impact craters and plate tectonics, 2nd edn. USGS Map Simkin T, Siebert L (1994) Volcanoes of the world. Geoscience Press, Tucson, AZ
Classification and Distribution Casadevall TJ, Thompson TB (1995) World map of volcanoes and principal aeronautical features, 1 : 34 268 000. Jeppeson Sanderson Inc., USGS GP-1011 Green J, Short NM (eds) (1971) Volcanic landforms and surface features. Springer-Verlag, Berlin, plates 28–36 International Association of Volcanology and Chemistry of Earth’s Interior (1994) Catalogue of active volcanoes of the world. Pike RJ, Clow GD (1981) Revised classification of terrestrial volcanoes and a catalogue of topographic dimensions with new results on edifice volume. USGS Open File 81–1038 Suzuki T (1977) Volcano types and their global population percentages. Bull Volcanol Soc Japan 22:27–40 Whitford-Stark JL (1987) A survey of Cenozoic volcanism on mainland Asia. GSA Special Paper 213, Appendix 5, p 46
Vc1 · Stratovolcanoes
Fig. Vc1-1. Source. Selby MJ (1985) Earth’s Changing Surface. Clarendon Press, Oxford, p 140, fig 5.4a. By permission of Oxford University Press Comments. Block diagram showing the interstratification of lavas and pyroclastics that typically make up the structure of a stratovolcano.
Fig. Vc1-2. Source. Hickson CJ, Edwards BR (2001) Volcanoes and Volcanic Hazards. A synthesis of Geological Hazards in Cana-da, Brooks GR (ed) Geological Survey of Canada Bulletin 548, p 158, fig 22. Courtesy of Natural Resources Canada, Geological Survey of Canada Comments. This modified schematic figure illustrates the hazards associated with different types of volcanic eruptions.
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Fig. Vc1-3. Location. Geographic. 152°12' E, 04°14' S, eastern Papua, New Guinea Geologic. See Vc1-8 Source. Bardintzeff J-M (1997) Les Volcans. Liber, Suisse, p 123 Comments. A photo taken during the August 1996 eruption period of Tavurvur Volcano at Rabaul on the north end of New Britain Island. See vertical stereo photos of Fig. Vc1-7. The dense eruption column of Pf tephra is accompanied by a grey cloud of Pf1 clasts beginning to fall on the right.
Fig. Vc1-4. Source. Edmaier B (1997) Volcans. Nathan, Paris, p 112 Comments. A closeup photo of the interior wall of the 7 km diameter crater wall of Stubel Volcano also known as Ksudach in the Kamchatka volcanic chain on the north Pacific coast of eastern Siberia. The photo shows the interbedding of lavas and tephra that register the structure’s emplacement activity. Its main eruption was in 1907. The regional setting of this volcano is shown in the Landsat mosaic of Fig. Vc1-9.
Vc1 · Stratovolcanoes
Fig. Vc1-5. Location. Geographic. 153°26' W, 59°22' N, southern Alaska, USA Geologic. Northeast end of the Tertiary Aleutian volcanic island arc Source. Unattributed Comments. This is an air perspective view looking south of the 8 by 11 km Augustine Island stratovolcano 1260 m at the entrance of Cook Inlet. The bright area in the foreground is a ‘y’collapse scar being filled with Pf1 pyroclastics and X1.1 lava flows. Augustine is one of
Fig. Vc1-6. Location. Geographic. 161°53' W, 55°25' N, Aleutian Peninsula Alaska, USA Geologic. Aleutian Trench island arc Source. Unattributed Comments. Air perspective view shows adjacent stratovolcanoes in the Aleutian Range at different stages of activity: Pavlov 2 714 m; Pavlov Sister cone 2 142 m, appears inactive. These cones are 275 km southwest of Aniakchak caldera of Fig. Vc3.2-6.
Alaska’s greatest hazards. It is the most active volcano in the eastern Aleutian Arc. Recent episodic activity has been recorded in January and November 2006. The volcano, which is seismicaly monitored, is 275 km from Anchorage in the most populated region of the state. It is also in the middle of a major shipping corridor. The debris avalanches resulting from flank collapses such as is visible in this photo extend offshore and raise tsunamis. Augustine’s setting is described in Fig. Vc3.2-6 of Aniakchak Caldera 375 km to the southwest.
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Vc1 · Stratovolcanoes ▼
Fig. Vc1-7.
Location. Geographic. 152°12' E, 04°14' S, east Papua New Guinea Geologic. Paleogene island arc fault system of North Bismarck micro plate, between Pacific and Australian Plates Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 15 300 Acquisition date. 14 January 1944 Source. University of Illinois Air Photo Repository, 1967, Stereogram Aerial Photographs # 102 Comments. The stereomodel shows Tavurvur, a 200 m high dormant composite volcano at Rabaul on the east side of the 8 by 14 km diameter drowned Blanche Bay caldera at the northeast tip of New Britain Island. The footslopes are X3 andesite and dacite – see Fig. Vc1-3. Turbidity is seen to originate near the bare footslopes on the west side of the volcano, and is carried southward by local currents. This turbidity is visible on current satellite imagery. Tavurvur erupted in the last two weeks of September 1994 and forced the abandonment of the town of Rabaul on the other side of the bay (the new town, Kokopo, is 20 km away). The volcano continues to erupt, ash is deposited daily in the caldera. This volcano is one of four dormant post-caldera units and two extinct pre-caldera cones which are sited around the margins of the caldera. This structure in turn is inside a 688 m high pyroclastic shield volcano. The entire surrounding area is covered with Pf1 dacitic pyroclastic falls. The Rabaul Volcanological Observatory was established in 1937 to monitor the activity of this and 14 active and 22 dormant volcanoes that are spread along three regional volcanic arcs.
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Fig. Vc1-8. Location. Geographic. 120°57' E, 08°53' S, central Indonesia Vertical Airphoto/Image. Type. X band SLAR Scale. 1: 100 000 Acquisition date. Not given Source. Aero Service. Division of Litton Industries Comments. This is an Airsar view of Late Quaternary active Ineri Volcano, 2 245 m elevation on the south shore of Flores Island, part of the inner volcanic island arc of the Indonesian Archipelago. The image was acquired from 12 km altitude through ten tenths cloud cover. Surrounding dissected terrain is undivided Quaternary volcanic rocks. The smooth area in the center of the shoreline is probably the toe of a Ps1 pyroclastic flow.
Vc1 · Stratovolcanoes
Fig. Vc1-9. Location. Geographic. 157°25' E, 52°10' N mosaic center, Kamchatka Peninsula, eastern Siberia, Russia Geologic. Pacific/Eurasian subduction Plates boundary Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. This image at the southern tip of the peninsula shows the large Pauzhetka Vc3 Caldera with Kurile Crater lake.
The caldera northward with crater lakes is Ksudach with bright eruptive products north and south of the crater. The other unvegetated area to the north is Asacha stratovolcano. The structures are chain-aligned in the typical Circum-Pacific style, with the Kuriles to the south and the Aleutians to the east, see Figs. Vc3.2-6 and Vc3.3-2. The peninsula has parallel ranges of volcanoes east and west of a central lowland valley. Of 74 volcanoes present in the eastern range, 13 are still active.
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Vc1.1 Dissected Cones Characterization In general stratovolcanoes are highly erodable. A number of erosion features are visible on stratovolcanoes that are the result of the action of lava flows X1.1 and pyroclastic flows Ps1, and debris flows and debris avalanches of Group A Epiclastic deposits:
d – a breached cone g – glaciation x – barranco gullies y – sector breach and collapse scar
Fig. Vc1.1-1. Source. Ollier C (1969) Volcanoes. MIT Press, Cambridge, Mass, p 118, fig 41 Comments. This figure depicts the stages in the erosion of a volcano as they relate to the Variants of the geounit. The bottom stage is either a residual Vs1.1 dome in cone, or neck of other intrusive fill coded Vc1. 2.
Geohazard Relations The geohazard relations of dissected cones are those of the above- mentioned geounits, X1.1 lava flows, Ps1 pyroclastic flows, A1 debris flows and A2 debris avalanches.
Reference Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 293–330
Select Bibliography Driedger C, Stout T (2002) Geohazards interpretation at Mount Rainier National Park. Proceedings, Geol. Soc. of Am., 98th Annual Meeting Rothery DA, Francis PW (1984) A remote sensing study of a sector collapse volcano. Proceedings International Symposium Remote Sensing Environment 18:57–63
Vc1.1 · Dissected Cones
Fig. Vc1.1-2. Location. Geographic. 177°10' E, 37°30' S, New Zealand Geologic. Pacific-Australian Collision Plates margin Source. Roberts-Ostman Agency Comments. An air pespective view eastward illustrates well the breached cone erosion feature on the dissected stratovolcano of White Island, on the outer edge of the Bay of Plenty, North Island.
Fig. Vc1.1-3. Location. Geographic. Japanese Ryukyu island chain (128°34' E, 27°21' N) Geologic. Ruykyu Trench island arc between Philippine and Eurasian plates
The volcano is estimated to be between 100 000 and 200 000 years old, its present state dates from approximately 16 000 BP. The crater, over 100 m deep holds a lake. This is new Zealand’s only active marine volcano, and it is monitored constantly by the IGNS (Institute of Geology and Nuclear Sciences). The structural setting of this volcano is described in Fig. A1-3.
Source. Putnam WC et al. (1960) Natural coastal environments of the world. U. of California, Los Angeles, p 127, fig 56 Comments. The air perspective view shows the active 217 m Iwo Shima stratovolcano with slopes dissected by barranco gullies. Its last eruption was 1964 or later.
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Fig. Vc1.1-4. Location. Geographic. 08°10' W, 71°05' N, Jan Mayen Island, Norway Source. Orheim O (1993) Glaciers of Jan Mayen, Norway. In: Williams RS, Ferrigno JG (eds) Glaciers of Europe, Satellite image atlas of glaciers of the world, USGS, PP 1386 – E, p E159, fig 8 Comments. An air view to the southeast shows part of the northwest side of Beerenberg Volcano, 2 277 m high, on Nord-Jan sector of 373km2 Jan Mayen, the northernmost island of the Mid-Atlantic Ridge. The volcano is active; a 1993 report mentioned the most recent effusive eruptions occurred on 6–9 January 1985. The Gl4 outlet glacier in the photo is Weyprechtbreen; it is one of 20 outlet glaciers that emanate from the ice cap which surrounds the volcano. The sector collapse scar to the left of the glacier is the site of a new vent from which steam billowed on 7 April 1985. See also Fig. Pf1-4.
Fig. Vc1.1-5. Source. Personal archive Comments. An apparent barranco erosion feature is delineated on the south flank of dormant Fujiyama Volcano (3 776 m) Japan’s highest mountain, 110 km west of Tokyo. The last eruption was in AD 1707. Geologists have identified four phases of volcanic activity in the formation of Mt. Fuji; the modern New Fuji is believed to have formed over the top of the older structures about 10 000 BP. Fuji is at the place where the Eurasian Plate, the Okhotsk Plate and the Philippine Plate meet.
Vc1.1 · Dissected Cones
Fig. Vc1.1-6. Location. Geographic. 15°13' E, 38°47' N, Aeolian Islands, southern Italy Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 38 000 Acquisition date. Not given Source. Green J, Short ND eds (1971) Volcanic Landforms & Surface Features Springer-Verlag, plate 34B Comments. The arrows on this photo of the 12 km2, 924 m Stromboli Volcano of the Lipari Island Group show a 1 km wide sector collapse on the west and barranco gullies on the east side of the island. Stromboli is the only continuously active volcano in Europe. Two thirds of the structure, 2 200 m, are below sea level. Initial eruptions were in the Early Pleistocene, 100 000 BP. The sector collapse with a steep, 35° slope, is Sciara del Fuoco, which occurred 5 000 BP, and has since been a channel for successive lava and scoria flows.
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Fig. Vc1.1-7.
Fig. Vc1.1-8.
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Location. Geographic. 145°02' E, 04°05' S, Papua New Guinea Geologic. Island arc boundary of the North Bismarck and Indo/Eurasian Plates Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 55 000 Acquisition date. Not given Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Löffler E, Explanatory Note to the Geomorphological Map of Papua New Guinea. CSIRO Land Research Series No. 33, plate 10. © CSIRO 1974 Comments. The photo shows the partly dissected 1 807 m, 10 km diameter active volcano of Manam Island off the northeast coast of the island. The youngest lava flows are unvegetated light-toned. The white masses are clouds, not tephra. A pyroclastic flow and surge from this vent is in Fig. Ps1-6. The circular crater off-center is the remnant of an old caldera.
Location. Geographic. 45° E, 12°45' N, southwest Yemen Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. Perrin RMS, Mitchell CW (1969) An Appraisal of Physiographic Units for Predicting Site Conditions in Arid Areas (MEXE Report No. IIII) Volume 2. Military Engineering Experimental Establishment, Christchurch, Hampshire, England, p 13, photo P4 Comments. The stereomodel covers the breached cones of twin Pleistocene or Recent craters, 350 m, at Aden Island (also labelled P4) with the south part of the Bw 5 spit curving northeastward. The regional setting of the site is pictured in the satellite images of Figs. Vc1.1-13. and Bc4-4. The Aden Volcano consists of lava flows and tephra intruded by trachyte plugs. Adan, town, is in the crater. A settlement, Kraytown, now exists on the beach just north of the volcano.
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Fig. Vc1.1-7. (Caption on p. 131) Fig. Vc1.1-8. (Caption on p. 131)
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Fig. Vc1.1-9. (Caption on p. 136)
Vc1.1 · Dissected Cones
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Fig. Vc1.1-9.
Location. Geographic. 67°36' W, 21°14' S, southwest Bolivia Geologic. Altiplano Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 14 June 1964 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 53 Comments. Stereomodel shows the Tertiary/Quaternary stratovolcano Cerro Khala Katin at San Agustin north of Fig. Vc3.3-3, with a “d” breached cone and a “y” sector collapse. A Vc1c adventive cone has developed on its western flank.
Fig. Vc1.1-10.
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Location. Geographic. 98°37' W, 19°01' N, central Mexico Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1:20 000 approx Acquisition date. Not given Source. Personal archive Comments. A stereomodel covers the active Popocatepetl Volcano 5 452 m, 60 km southeast of Mexico City, in the Trans Mexico neo-volcanic belt. The steep-walled crater is 612 m by 400 m wide and is 250 m to 450 m deep. Hundreds of thousands of people would be endangered by hazards associated with a large explosive eruption of the volcano. In addition ash from such an eruption could endanger aircraft using the Mexico City International Airport. Tertiary age cone is built on an older volcano. A large x barranco is delineated also, lower on the north slope. Most of the slopes appear covered by Pf1 tephra. X1.1 are lavas; ‘a’ is the central crater. A glacier lies on the north side of this currrently highest active volcano in the Northern Hemisphere.
Vc1.1 · Dissected Cones
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Fig. Vc1.1-11. Location. Geographic. 78°26' W, 0°41' S, Ecuador Geologic. Paleozoic and Mesozoic metamorphic and igneous rocks of the Andes Central Cordillera Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 30 000 Acquisition date. 22 June 1963
Source. USGS Comments. This stereomodel shows Cotopaxi stratovolcano which rises to 5 896 m a.s.l. just south of the equator. Above 5 000 m the volcano is covered by permanent ice field type glaciers. Its activity status is fumarolic, i.e. dormant. The summit crater is 600 m by 800 m in diameter. ‘C’ is an adventive cone; Gt4.1 are moraines.
Vc1.1 · Dissected Cones
Fig. Vc1.1-12. Location. Geographic. 144°00' E, 06°45' S, eastern Papua New Guinea Vertical Airphoto/Image. Type. Airsar Scale. 1: 250 000 Acquisition date. Not given Source. Dow DB (1977) A Geological Synthesis of Papua New Guinea. Dept. of Natural Resources Bulletin 201, Australian Government Publishing Service, p 23, fig 24 Comments. A radar image of the Late Pliocene or Quaternary dissected volcano of Mount Murray in the Eastern Highlands. The structure surmounts strike ridges of folded Miocene limestones. The regional vegetation cover is dense forest with canopies, between 20 and 30 m high. The radar image does not penetrate the forest canopy, it images the variations of the heights of treetops which mimick the geomorphology.
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Fig. Vc1.1-13.
Vertical Airphoto/Image. Type. MSS 80 resolution Scale. 1: 368 000 Acquisition date. April 2002 Source. USGS Comments. This is the same scene area of southwest Yemen as Fig. Bc4-4 to provide the regional setting of the volcanoes of Fig. Vc1.1-8.
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Fig. Vc1.1-13. (Caption on p. 139)
Vc2 · Shield Volcanoes
Vc2 Shield Volcanoes
which continental and oceanic portions of lithospheric plate move. Gravity sliding and slumping occurs on shield flanks.
Characterization Geohazard Relations Shield volcanoes are domes that form by repeated eruptions of almost solely basaltic lavas of low viscosity (see X1) that can flow for tens of kilometers. While the basic mechanism of emplacement is similar, shield volcanoes are different in composition and in shape from stratovolcanoes Vc1. The eruptions “are not confined to [a central vent] but occur also along fissures extending across the summit and far down the flanks” (Macdonald et al. 1983). The shields are built by a great pile of successive flows with gentle slopes (<10°). Because the lava is not viscous it cannot form steep flanked cones typical of stratovolcanic (Vc1). In plan view they tend to be elongate, due to eruptions from lateral rifts. Their height is about 1/20 of basal diameter. Shield structures can be divided into two size types: Hawaiian large shields Icelandic small shields Hawaiian shields can attain basal diameters of over 100 km. Icelandic type shields have basal diameters <15 km, built by large numbers of thin flows, and are probably monogenetic. Both types are considered to be surface expressions of stationary “hot spots” of upwelling mantle magma over
Fig. Vc2-1. Source. Selby MJ (1985) Earth’s Changing Surface. Clarendon Press, Oxford, p 140, fig 5.4c. By permission of Oxford University Press Comments. The block diagram shows the characteristic form and the interstratification of basaltic lavas and tephras that compose a shield volcano.
The principal hazard associated with shield volcanoes is from lava flows because eruptions tend to be gentle and non-explosive. The flows tend to advance slowly; property damage rather than loss of life is the principal concern. Hazards from epiclastic phenomena are rare because of the gentle slopes and the absence of pyroclastic materials and loose debris that often make up the bulk of lahars and debris avalanches.
Reference Macdonald GA, Abbott AT, Peterson FL (1992) Volcanoes in the sea: The geology of Hawaii. University of Hawaii Press, Honolulu, pp 35–46; 146–148, 163–164
Select Bibliography Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 365–369 Monroe JS, Wicander R (1994) The changing Earth. West Publishing Co., St. Paul, Minn., pp 78, 79, 82 Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Geomorphology from space. NASA SP 486, pp 212–213 Souther JG (1992) Ornostay and Koosick centres, 182. The Late Cenozoic Mount Edziza volcanic complex, British Columbia. GSC Memoir 420 Wentworth CK, Macdonald GA (1953) Structures and forms of basaltic rocks in Hawaii. USGS Bull 994 Whitford-Stark JL (1987) A survey of Cenozoic volcanism on mainland Asia. GSASpecial Paper 213, appendix 5, p 46
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Fig. Vc2-2. Source. Bardintzeff JM (1997) Les Volcans. Liber, Suisse, p 34
Comments. The photo pictures the characteristic shield volcano profile of 1 060 m Pleistocene Skjaldbreidur formed 9 500 years ago, 70 km northeast of Reykjavik, Iceland.
Fig. Vc2-3. Source. Macdonald GA et al. (1983) Volcanoes in the Sea, 2nd edition. University of Hawaii Press, Honolulu, p 456, fig 22.3 Comments. This air perspective photo is a view westward over the northwest end of Kauai Tertiary shield volcano island, a single great shield volcano which is deeply eroded.
At the top of the shield was a caldera 15 to 20 km across – the largest in the Hawaiian Islands. The dissected relief in the foreground consists of lavas (Olekole formation) that erupted in the caldera and ponded within it. Figure Bc1-7 at Mana on the coast is 15 km west of this site.
Vc2 · Shield Volcanoes
Fig. Vc2-4. Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada. BC 538, 75 Comments. This is a perspective view westward of Edziza Volcano in Edziza Provincial Park. The draping of the X1 lavas over the underlying Meso and Paleozoic sedimentary and volcanic rocks coded W2-M/PZ is well shown in the view. The flow in the center of the photo is dated at 1.1 Ma, the flow on the right is ~1 Ma. Zone d is a breach in the shield. Figure Vc2-5 is a stereomodel of Edziza. Fig. X1.1-1 showing a Holocene basalt flow on the north flank of the volcano.
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Fig. Vc2-5.
Location. Geographic. 130°38' W, 57°43' N, north-central British Columbia Geologic. Late Cenozoic volcanic complex of the Stikinia Superterrane of the Intermontane Cordilleran Belt Vertical Airphoto/Image. Type. Natural colour, stereo pair Scale. 1: 103 000 Acquisition date. 21 August 1972 Source. Courtesy of Natural Resources Canada, NAPL, A30552-16, 17 Comments. The stereomodel covers the ice-filled 2 km diameter crater of Edziza trachyte shield volcano at 2 590 m elevation and its associated Gl5 valley glaciers. “c” spots are adventive cones; “d” is a breach in the cone. Gt4 are moraines; W2 Paleozoic and Mesozoic sedimentary and volcanic rocks. The inset frame shows the coverage of Fig. Vc2-4 perspective view. This figure is 110 km north of Fig. X1.2-3.
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Fig. Vc2-5. (Caption on p. 143)
Vc2 · Shield Volcanoes
Fig. Vc2-6. Location. Geographic. 112°05' W,76°17' S, west Antarctica Source. Swithinbank CS (1988) Antarctica. In: Williams RS, Ferrignano JG (eds) Satellite image atlas of glaciers of the world. USGS PP1386-B, p B131, fig 96 Comments. An air perspective view of Post-Eocene Mount Takahe shield volcano, one of a chain of volcanoes that parallel this coast of the continent. With an altitude of 3 460 m the cone stands 2 200 m above the surface of the local ice sheet. It is approximately 30 km in diameter, with an 8 km diameter ice filled caldera. Fig. Vc2-7 is a satellite image of the volcano.
Fig. Vc2-7. Location. Geographic. 112°05' W,76°17' S, west Antarctica Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 250 000 Acquisition date. 19 November 1972 Source. USGS Comments. This Landsat subscene shows the partly buried Mount Takahe shield volcano of Fig. Vc2–6. 500 meter ice surface contours have been added to the figure.
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Vc3 Calderas and Tectonic Depressions Characterization “Calderas are large volcanic depressions, more or less circular in form, the diameter of which is many times greater than that of included vents.” (Lipman 2000).
proportions of the caldera volume being generated by explosive ejection and removal of older rocks.” Thus once the batholith chamber is evacuated by eruption the summit starts to sink along bounding ring faults. A single eruptive unit may be hundreds of meters thick within the caldera, including landslide breccia from the caldera wall, but no more than tens of meters thick outside.
Geohazard Relations They are a form of igneous tectonism where igneous activity at depth results in the near destruction of a strato or shield volcano. The caldera geounit is characterized by four Variants:
Vc3.1, calderas on Vc1 stratovolcanoes Vc3.2, calderas with post-caldera cones and domes Vc3.3, large silicic calderas with resurgent domes Vc3.4, calderas on Vc2 shield volcanoes
Geohazard Relations
“They represent the most catastrophic geological events that affect the Earth’s surface other than large meteorite impacts. The potential societal impact of a future eruption comparable in size to large prehistoric events, should it involve a heavily populated area is so enormous as to defy comprehension.” (Lipman 2000).
Vc3.1 Calderas on Stratovolcanoes
Smaller historical caldera forming eruptions, Tambora 1815, Krakatau 1883, Pinatubo 1991, may have modified global climate including anomalously cold weather. The dominant factors were believed to be the injection of sulphur aerosols into the stratosphere (see Geounit Pf1). See Geounit Vc1 for hazards related to volcanic lakes. Figures Vc3.1–3, Vc3.1–8 and Vc3.1–9 show crater lakes that could be susceptible to volcanic lake hazards.
Characterization
References
Calderas are “depressions formed largely by collapse into a magma reservoir” (Newhall and Dzurisin 1988). Chorley (1984) describes caldera formation as igneous tectonism, usually late in the history of a stratovolcano, involving foundering of the top of the edifice. Their formation remains incompletely understood and controversial. It is thought that calderas are the final surface expression of shallow depth batholiths that are emplaced preceding an eruption. Suppe (1985) mentions volume increase on melting, density differences between magma and surrounding rock, and boiling of magma, as factors resulting in excess pressure that drives magma toward the surface to produce the eruption. Lipman (2000) states “Origin dominantly by (post-eruptive) subsidence has been overwhelmingly recognized, with only minor
Chorley RJ, Schumm SA, Sugden DE (1984) Geomorphology. Methuen, London Lipman PW (2000) Calderas. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 661, 643–662 Newhall CG, Dzurisin D (1988) Historical unrest at large calderas of the world. USGS Bull 1855:143–146, 991–993 Suppe J (1985) Principles of structural geology. Prentice-Hall, Englewood Cliffs, NJ, pp 227, 237–239
See Geounit Variants.
References See Geounit Variants.
Vc3.1
As with other magmatic geohazard-related geounits, large caldera forming explosive eruptions involve obvious hazards to people and property.
Select Bibliography Lipman PW, Self S, Heiken G (eds) (1984) Calderas and associated igneous rocks. J Geophys Res 89(B10) Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Geomorphology from space. NASA Special Publication 486, plates V-13, V-18 and V-19 Williams H (1941) Calderas and their origin. University of California. Department of Geological Sciences, publication 25, pp 239–346
Vc3.1 · Calderas on Stratovolcanoes
Fig. Vc3.1-1. Source. Putnam WC (1971) Geology, 2nd ed. Oxford University Press, p 68, fig 4.2. By permission of Oxford University Press Comments. The diagram shows the sequence of eruptive events in the development of a Vc3 caldera from a Vc1 stratovolcano, as put forth by Willams, 1941. Stage I at top , mild explosions of pyroclatics from a filled magma chamber. Stage II, culminating tephra explosions clear out the volcanic conduit, and the magma level is rapidly lowered in the chamber. Stage III, with removal of support the volcanic cone collapses into the magma chamber below, leaving the wide, bowl-shaped caldera. Stage IV, after a quiet period, minor post-caldera cones of Variant Vc3.2 appear on the crater floor.
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Fig. Vc3.1-2. Location. Geographic. 27°02' E, 36°42' N, Greece, Southern Sporades island group off the western coast of Turkey Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 401, fig 13.44 Comments. A sketch map shows the inferred caldera ring outline off the south coast of Kos Island, and the coverage of the photo of Fig. Vc3.1-6.
Fig. Vc3.1-3. Location. Geographic. 25°19' W, 37°45' N, Azores Geologic. Possible hot spot of WNW-ESE-trending Azores Fracture Zone Source. Newhall CG, Dzurisin D (1988) Historical unrest at large calderas of the world. USGS Bulletin 1855, 2 vols, pp 991–993, fig 18.3.1 Comments. A map of Furnas Caldera with a crater lake on its west side,and extinct Povoacao Caldera on Sao Miguel Island. Furnas formed about 1 200 BP. The island has experienced numerous eruptions since, the latest unrest was in AD 1630. An air perspective view of Povoacao is in Fig. Vc3.1-5. The north part of the caldera is agriculturally developed around the town of Caldeiras.
Vc3.1 · Calderas on Stratovolcanoes
Fig. Vc 3.1-4. Location. Geographic. 36° E, 03° S, north central Tanzania Source. Aeronautical Chart and Information Center, U.S. Air Force Comments. This fragment of an air navigation chart gives the topography of the large caldera-bearing massif of Fig. Vc3.1-9. in the eastern Rift Valley.
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Fig. Vc3.1-5. Source. Unattributed Comments. An air view of the 6 km wide cultivated extinct Povoacao Caldera adjacent to the Furnas Caldera, 805 m, on Sao Miguel Island of the Azores. See map, Fig. Vc3.1-3. The Azores cluster of volcanic islands has a high level of activity due to its location on a microplate which is at
the junction of three major tectonic plates. These plates, which are in effect pulling apart, are the north American Plate to the northwest; the Euroasian Plate to the northeast and the African plate. The Azores are 1 400 km northwest of the Canary Islands of Fig. Vc3.2-8.
Fig. Vc3.1-6. Location. Geographic. 27°02' E, 36°42' N, southeast Greece Geologic. Near subduction zone on continental terrane of African basement Source. Unattributed Comments. A high altitude view to northeast of 40 km long Kos Island in the Southern Sporades off the southwest coast of Turkey. The sketch map of Fig. Vc3.1-2 delimits the waters off the south coast of the island as concealing a Quaternary submarine rhyolitic caldera. The west half of the island is a Ps1.1 ignimbrite plateau, 160 000 BP, associated with the caldera eruption, covers sedimentary rocks. The Vs1 area delineates a pair of rhyolite domes, Latra 427 m and Zini 362 m. The ignimbrite is mainly gullied badland, the cultivated part of the island is on the north side in the photo background. (Kos is 140 km east of and stucturally unrelated to the Santorini Caldera in a Neogene island arc.)
Vc3.1 · Calderas on Stratovolcanoes
Fig. Vc3.1-7. Location. Geographic. 39°55' E, 09°00' N, central Ethiopia Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. Not given
Source. Green J, Short ND eds (1971) Volcanic Landforms and Surface Features. Springer-Verlag, plate 22A Comments. Photo shows the Quaternary 2 007 m elevation Fantale Caldera in the East African Rift Valley System. The crater has dimensions of 4.5 by 3.5 km. The short coulee visible near the northeast edge of the caldera is pictured in detail on Fig. Vs2-3.
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Fig. Vc3.1-8. Location. Geographic. 91°08' W, 0°50' S, Galapagos Islands, Ecuador Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1 : 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. A 110-km segment of a radar image covers the southern half of Isabela Island, the largest of the 3 Myr volcanic cluster of the Archipelago, 900 km west of South America. Three of the Island’s active coalescing shield volcanoes, with their 3 km diameter calderas appear in the image: Alcedo, to the north is 1 130 m; Negra in the center is 1 080 m, and Azul in the southwest is 1 689 m. Negra Caldera is 5 × 4 km diameter. The islands may have been formed within the Nazca Plate which has moved over a hotspot fed by a mantle plume.
Vc3.1 · Calderas on Stratovolcanoes
Fig. Vc3.1-9. Location. Geographic. 35°31' E, 03°12' S scene center, north central Tanzania Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The bright green area on this image is a volcanic highland massif 230 km south of Nairobi, which includes three calderas coded 3, and five extinct stratovolcanoes coded 1. The massif has developed within the 1 000 m elevation floor of the southern extension of the east arm of the African Rift Valley system. The rifts lie along a line of faults in the Precambrian basement rocks (e.g. Fig. 12-2). Arching of the crust followed by volcanism and rifting began in Late Cretaceous and continued through the Tertiary. The massif is located between bright evaporite-rich Lake Natron to the north and Lake Eyasi on the south. It has an average elevation of 2 150 to 2 450 m with the stratovolcanoes rising to 3 648 m.
The largest caldera is 20 km diameter Ngorongoro, the brown depression with smaller Lake Makat off-center. Another crater lake is in the 5 km diameter Embagai Caldera at the north end of the massif. The massif is the greater part of the Ngorongoro Conservation Area adjacent to Serengeti National Park on the west. Lake Manyara National Park is to the southeast. The topography of the massif is given on the fragment of the air navigation chart of Fig. Vc3.1-4. Altitudinal vegetation zoning is well expressed in this image contrasting the green forest, woodland and bushland of the massif with the brown of the semi-arid surrounding grass-lands. The dark zone on the east side of the massif is moist evergreen forest covering 3 648 m high Loolmalasin Volcano. The three other stratovolcanoes on the east are, from north to south, Gelai, 2 942 m; Kitumbeine, 2 942 m; Losiminguri, 2 300 m. The Olduvai Gorge archaeological site is visible on the Serengeti Plain 20 km west of the massif.
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Fig. Vc3.1-10. Location. Geographic. 117°33' E, 08°25' S scene center, eastern Indonesia Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 5 September 1972 Source. USGS Comments. Landsat scene covers the west half of Sumbawa Island. As with Flores Island of Fig. Vc1-8 Sumbawa is part of the inner volcanic island arc, and has the same regional geology of mafic rocks.
Tambora Caldera 2 850 m, on the northeast Sanggar Peninsula is active. Its crater diameter is 6 km. This volcano erupted cataclysmically in 1815, causing directly and indirectly the deaths of more than 70 000 people. Tambora’s slopes are mantled with Ps1.1 ignimbrite outflow related to that event. A subsidiary crater, resolved on higher resolution imagery, exists to the northeast. Batulantee Caldera, 1 923 m, on the north side of the large peninsula in the lower left is a Late Quaternary volcano with a vegetated caldera also of 6 km diameter.
Vc3.1 · Calderas on Stratovolcanoes
Fig. Vc3.1-11. Location. Geographic. 17°15' E, 20°55' N crater center, northern Chad Vertical Airphoto/Image . Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. This image is centered on Tarso Voon Caldera, one of a 30 000 km2 group of co-extensive volcanic structures that are a Cenozoic cap on the 100 000 km2 Tibesti Precambrian basement upwarp. Adjacent volcanic structures include the Tarso Toon Caldera on the east and TarsoYega Caldera on the south-
east side, with Ehi-Létébi stratocone in between. Abouki siliceous dome pictured in Fig. Vs1-5 is on the west. The 18 × 11 km diameter Tarso Toon Crater is at 2 400 m elevation (summit elevation is 3 100 m). The caldera’s most prominent component is the light-toned, grey, 20 km broad surrounding Ps1.1 poorly indurated pumiceous ignimbrite outflow apron with characteristic flutings. The deposit slopes down 900 m from the crater rim to 1 500 m elevation. It has the typical well-developed radial fluting, also seen in Figs. Vc3.3-4 of Cerro Galan and Ps1.1-5 of Valles Caldera. The ravined beige zone in the lower left corner of the image consists of monoclinal Lower Paleozoic sandstones of the Djado Basin. The contact with the basement upwarp is marked by a probable fault 200 m escarpment.
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Division 1 · Magmatic Rocks and Structures
Vc3.2 Calderas with Post-Caldera Cones and Domes
Figure Vc3.2–4 shows a susceptibility to volcanic lake hazards.
Characterization
Reference
Cones and domes in calderas are slow incremental extrusions of viscous magma that follows explosive eruptions.
De Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin, p 13
Select Bibliography Geohazard Relations Young domes and cones in calderas “are extremely important as they indicate active magmatic systems beneath these calderas that – should be considered as likely to erupt in the future perhaps catastrophically, or more probably in minor eruptions of silicic lavas and pyroclastic rocks.” (de Silva and Francis 1991).
Lipman PW, Self S, Heiken G (eds) (1984) Calderas and associated igneous rocks. J Geophys Res 89(B10) Newhall CG, Dzurisin D (1988) Historical unrest at large calderas of the world. USGS Bull 1855:87, 219, 285, 358, 380, 386, 416, 429, 483, 639, 713, 721, 836, 880, 994 Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Geomorphology from space. NASA Spec. Pub. 486, pl. V-6; V-9; V-13; V-18 Whitford-Stark JL (1987) A survey of Cenozoic volcanism on mainland Asia. GSA Special Paper 213, App. 5, p 46
Fig. Vc3.2-1. Source. Thornbury WD (1965) Regional Geomorphology of the United States. John Wiley & Sons, Inc., p 519, fig 25.9 Comments. Photo is a view north from Lake Helen to active Lassen Peak, 3 189 m in the southern Cascade Range of the western cordilleras, northern California. Lassen is the largest silicic lava dome volcano in the world. It formed from 0.35 Myr to about 11 000 years ago and is 2.4 km in diameter. 20th century eruptive activity began in 1914 and ended in 1917.
Crags of dacite project through A2 debris avalanche and Ps1 tephra deposits on the upper slopes. Lassen appears today as a Vs1 autonomous dome on the northern flank of the present Brokeof Caldera. The original caldera – Tehama, has a diameter of 18 to 24 km which would place Lassen within that structure. The dome rests on a sequence of Brokeoff andesite flows. Mt. St. Helens of Fig. Vs1.1-7 is 62 km to the north in the same range.
Vc3.2 · Calderas with Post Caldera Cones and Domes
Fig. Vc3.2-2. Source. Green J, Short NM (eds.) (1971) Volcanic Landforms and Surface Features. Springer-Verlag, pl. 23B Comments. This air perspective photo is another view of Mihara Yama cone within O Shima Caldera pictured in the vertical airphoto and section of Fig. Vc3.2-3. The photo was taken 23 March 1951 and shows a basalt flow spilling over the cone crater margin and advancing northward on the caldera floor.
Location. Geographic. 116°25' E, 08°25' S, central Indonesia Vertical Airphoto/Image. Type. b/w infrared airphoto Scale. 1: 60 000 Acquisition date. 1970 Source. Verstappen HTh (1977) ITC Textbook of PhotoInterpretation, Volume VII. Chapter 5, An Atlas Illustrating the Use of Aerial Photographs in Geomorphological Mapping. International Institute for Aerial Surveys and Earth Sciences (ITC), The Netherlands, photo II-10 Comments. The stereomodel at the north end of Lombok Island covers the twin post-caldera cinder cones and associated lava flows at 2 876 m, in 3 726 m Rinjani Crater of the 6 by 8.5 km diameter Segara Anak Caldera, the second highest volcano in Indonesia. The lake has a depth of 230 m. The partly cloud covered major straight ravine to the north of the lake is fault-controlled. Figure Vc3.2-9 is a satellite image of the greater part of the island. The volcano has erupted in 1994, 1995 and 1996.
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Fig. Vc3.2-4.
Location. Geographic. 139°25' E, 34°45' N, east central Honshu, Japan Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 30 000 Acquisition date. 1947 Source. Green J, Short ND eds (1971) Volcanic Landforms and Surface Features. Springer-Verlag, plate 23A Comments. The photo and cross section show the center of the 14 km diameter O Shima Island at the entrance to Sagami Bay, south of Tokyo, Japan. The 3 km diameter caldera is pictured with the crater walls open to the northeast. Mihara Yama cone in the caldera is 800 m wide and rises to an altitude of 755 m. The pit crater within the cone is 300 m wide. The location of a magma column, in 1953 or 1954, is shown in the central pit. The cross section is fig 8.10.2 in USGS Bulletin 1855. An air perspective view of Mihara Yama cone is Fig. Vc3.2-2.
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Fig. Vc3.2-3.
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Fig. Vc3.2-3. (Caption on p. 157)
Vc3.2 · Calderas with Post Caldera Cones and Domes
Fig. Vc3.2-4. (Caption on p. 157)
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Fig. Vc3.2-5. Location. Geographic. 158°09' W, 56°53' N, southern Alaska Vertical Airphoto/Image. Type. Natural colour, Hasselblad, photo, Challenger 6 Scale. 1: 200 000 Acquisition date. 13 October 1984 Source. USGS
Comments. This astronaut photo gives a clear view of the post-caldera cratered Vent Mountain cone in Aniakchak Caldera (1 341 m) of Fig. Vc3.2-6. The cone is 2.5 km in diameter and rises 430 m above the caldera floor. The caldera is 10 km in diameter and is a maximum of 1 km deep. Its most recent activity was in 1942. Surprise Lake, at elevation 335 m, is 3.2 km long in the northeast part of the caldera.
Vc3.2 · Calderas with Post Caldera Cones and Domes
Fig. Vc3.2-6. Location. Geographic. 158°09' W, 56°53' N at structure, southern Alaska Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1:706 000 Acquisition date. 9 February 1979 Source. USGS Comments. A Landsat view locates Aniakchak Caldera, circled in red, in the Aleutian Range. The range is on the Aleutian Peninsula between Bristol Bay on the left of the scene and Chelikof Strait on the right. The Aleutian Range extends as the 2 400 km long chain of the Aleutian Islands across the North Pacific to eastern Siberia, see Figs. Vc1-9 and Vc3.3-2. The inset frame locates Fig. Vc3.2-5.
Aniakchak is located between Augustine stratovolcano of Fig. Vc1-5 375 km to the northeast, and the Pavlov cones of Fig. Vc1-6 275 km to the southwest along the peninsula. The mountains consist of folded and faulted Mesozoic and Cenozoic rocks locally intruded by granitic stocks. Gt/Gf indicates lower terrain covered by glacial deposits. Some prominent geolineaments are traced in red. Chelikof Strait, which is about 50 km wide, is the south end of a 300 km long graben-like structure, the Cook InletSusitna Lowland. The Lowland had been modified by glaciers that extended along the entire length. During the earthquake of 27 March 1964 described in Fig. Mf1-1, the Lowland became a trough of subsidence. In plate tectonics the strait is an island arc forearc basin.
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Vc3.2 · Calderas with Post Caldera Cones and Domes ▼
Fig. Vc3.2-7. Vertical Airphoto/Image. Type. TM, 30 m resolution Scale. 1: 740 000 Acquisition date. Not given Source. Applications of Remote Sensing in Asia & Oceania – Environmental Change Monitoring (1991) Murai S (ed). Asian Association on Remote Sensing, Murai Laboratory, Institute of Industrial Science, University of Tokyo, p 356 Comments. This is the same Landsat image as Fig. Ps1-9; it covers the Aira Caldera in Kagoshima Bay, circled in red, in the southern part of Honshu Island, Japan. The cone on the southern side of the caldera is active; a fumarolic plume can be seen extending south from the vent. The black outlines locate other V3.2 calderas north and southward from Aira.
Fig. Vc3.2-8. Location. Geographic. 16°38' W, 28°15' N, Canary Islands, Spain Vertical Airphoto/Image. Type. Shuttle 9, natural colour photo Scale. 1:450 000 Acquisition date. December 1983 Source. USGS Comments. The photograph covers most of Tenerife Island the largest of the seven islands of the Canary hot spot chain. The capital city of Santa Cruz is just off the photo edge on the south shore at upper right. Tenerife has records of eruptions in the last 500 yr, but the chain has been active along its entire length during the last million years. The 17 km diameter Canadas Caldera, 1.54 Ma, one of the Earth’s largest, dominates the island center. The crater floor, covered with recent syenite lava, is at elevation 2 000 to 2 250 m. The caldera rim is 550 m high. The post caldera cone, Teide is 3 718 m elevation, snow-covered in winter. It is flanked by the smaller Viejo cone, 3 103 m. The islands developed in a geodynamic setting now involving several genetic hypotheses, but it is generally assumed that the archipelago originated from residual old plume material in the upper mantle and that its growth involved submarine and subaerial stages.
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Vc3.2 · Calderas with Post Caldera Cones and Domes ▼
Fig. Vc3.2-9. Location. Geographic. 116°25' E, 08°25' S, central Indonesia Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 374 000 Acquisition date. July 1976 Source. USGS Comments. This Landsat image shows perennially cloudencirled Rinjani Crater of Segana Anak Caldera at the north end of Lombok Island.
Fig. Vc3.2-10. Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 165 000 Acquisition date. Not given Source. USGS Comments. This Landsat subscene of the southern Apennine fold-and-thrust chain is centered on the active Vesuvius cone and caldera structure 7 km east of Naples, Italy.
The image shows the typical topography of the islands of the inner volcanic arc that carry the structural and volcanic belts of Java eastward along strike into the Banda Arc. These islands consist of young and active volcanoes in the north part, whereas the rocks older than Late Miocene occur only near the southern coast. Segara Anak is flanked on the west by the Late Tertiary volcano Punikan, 1 489 m, and on the east by the cloud-covered Batulan, 2 330 m. The stereomodel of Figure Vc3.2-4 is centered on Rinjani Crater.
The barren blue of the lavas and Vesuvius cone and crater are 1.5 km from the caldera rim of Monte Somma with the orange vegetated Pf1 ash and breccia slopes. The Somma rim was formed by the collapse of a stratovolcano about 17 000 years ago. Vesuvius began to form after the Somma collapse. The Roman city of Pompeii, shown in Fig. A3-3, that was buried by the AD 79 ignimbrite outflow is located in the southeast sector of the image. See also Fig. A3-6.
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Vc3.3
Division 1 · Magmatic Rocks and Structures
Vc3.3 Large Silicic Calderas with Resurgent Domes Characterization Large calderas with resurgent domes have dimensions up to 100 km in diameter and are the source of ignimbrites with volumes considerably in excess of 1 000 km3 as described by de Silva and Francis (1991) “These are extremely long-lived magmatic systems, with histories spanning several millions of years. Their activity may be cyclic, related to the evolution of batholithic scale magmatic systems that underlie the calderas”. The dominant characteristic of this Variant is the presence of a prominent dome (or domes) in the central part of the caldera. The rise results from a surge of new magma into the intracaldera ignimbrite following the initial collapse and surrounding ignimbrite sheet outflows. The intracaldera ignimbrite is uplifted to produce the resurgent dome.
Geohazard Relations Resurgent calderas are regarded as being potentially active. Specific hazards of this Variant include those described for its associated Variants Ps1.1 and Vc3.1.
Reference de Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin, pp 157–176
Select Bibliography Lipman PW (2000) Calderas. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 643–662 Lipman PW, Self S, Heiken G (1984) Introduction to calderas. J Geophys Res 89(10) Newhall CG, Dzurisin D (1988) Historical unrest at large calderas of the world. USGS Bull 1855 Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Geomorphology from space. NASA Special Publication 486, plates V-2, V-14, V-25 Smith RL, Bailey RA (1968) Resurgent cauldrons. GSA Memorandum 116, pp 83–104, 613–662
Fig. Vc3.3-1. Source. Reprinted from Encyclopedia of Volcanoes. H. Sigurdsson (ed). ©2000, p 648, from fig 2, with permission from Elsevier Comments. These sectional diagrams show the evolution of a resurgent dome in a caldera. The upper section is the caldera following initial collapse. In the lower section resurgence occurs by a rise of a new magma body into the volcanic pile and doming up of the intracaldera ignimbrite.
Vc3.3 · Large Silicic Calderas with Resurgent Domes
Fig. Vc3.3-2. Location. Geographic. 158°02' E, 52°33' N, eastern Siberia Russia Vertical Airphoto/Image. Type. Natural colour Shuttle 9 photo Scale. 1: 400 000 Acquisition date. December 1983 Source. USGS
Comments. This is a winter photo of 1 829 m elevation Gorely Khrebet active caldera 150 km southwest of Petropavlosk on the Kamchatka Peninsula. Location is 50 km north of the Landsat image coverage of Fig. Vc1-9. The delineated caldera rim is12 km in diameter. The 10 km diameter post-caldera cone almost fills the crater. Ps1.1 Ignimbrite outflow deposits are also delineated. Nearby Asacha Volcano is currently inactive.
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Fig. Vc3.3-3. (Caption on p. 170)
Vc3.3 · Large Silicic Calderas with Resurgent Domes
Fig. Vc3.3-4. (Caption on p. 170)
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Vc3.4 Calderas on Shield Volcanoes
Vc3.4 ▼
Fig. Vc3.3-3.
Location. Geographic. 67°51' W, 21°40' S, southwest Bolivia Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 537 000 Acquisition date. Not given Source. deSilva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, fig S.5, p 164 Comments. Landsat subscene covers the 8 Ma old Pastos Grandes caldera complex just southwest of Alota and south of Fig. Vc1.1-9. It is one of a number of large calderas in the central Andes which, because of their magnitude, were not discovered until the advent of synoptic coverage satellite imagery in the mid 1970s. The Vs1.1 dome of Cerro Pastos Grandes (CPG) was first recognized as the resurgent center of a major caldera in 1981. The complex, which includes other minor eruptive centers, extensive Ps1.1 ignimbrite outflow deposits and residual lakes is 50 km long and 40 km wide, and covers 5 000 km2. The highest point on the resurgent dome is 5 800 m, and the base elevation is at 4 600 m. The caldera is bounded by a 400 m high arcuate fault zone, labelled CS on the image. The bright white surfaces of the lakes are H1 evaporite deposits, not ice. LPG and K are remnants of a lake that may have filled most of the moat of the caldera. Az and SP identify Azufre and San Pedro stratovolcanoes. ▼
Fig. Vc3.3-4. Location. Geographic. 66°56' W, 25°59' S, northwest Argentina Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 715 000 Acquisition date. Not given Source. deSilva S, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, p 172, fig S11 Comments. A Landsat image pictures Cerro Galan, the best exposed large caldera in the world. The structure is 16 000 km2 in extent. At least nine major ignimbrite eruptions occurred between 7 and 4 Ma. de Silva and Francis 1991 report that about 2.2 Ma an eruption of more than 1 000 km2 of intermediate dacitic magma formed the present 35 by 25 km caldera and the resulting ignimbrite that extends for up to 100 km radially from the caldera rim. Caldera formation was followed by resurgence of the central part of the caldera to the present elevation of 6 100 m. The ignimbrite outflows are readily recognized by the characteristic radial fluting as in Figs. Vc3.1-11 of Tarso Voon and Ps1.1-5 of Valles.
Characterization “Basic shield calderas are large circular or elliptical sunken craters on the crests of volcanic domes bounded by high-angle faults without raised rims.” Chorley et al. (1984). “Caldera formation can occur at any time during the shield building stage; the only condition required being the loss of support from beneath the summit area by withdrawal of magma during flank eruptions.” (Macdonald et al. 1983). Thus shield calderas can undergo repeated collapse and refilling on the main shield volcano dome (Vc2).
Geohazard Relations Shield caldera formation does not involve direct hazards; these are described for the Vc2 volcano itself.
References Chorley RJ, Schumm SA, Sugden DE (1984) Geomorphology. Methuen, London, p 144 Macdonald GA, Abbott AT, Peterson FL (1983) Volcanoes in the sea: The geology of Hawaii. University of Hawaii Press, Honolulu, p 148
Select Bibliography Gaddis L, Mouginis-Mark P, Singer R, Kaupp V (1989) Geologic analyses of shuttle imaging radar (SIR-B) data of Kilauea Volcano, Hawaii. GSA Bull 101:317–332 Greely R (1974) Aerial reconnaissance over the island of Hawaii. NASA CR-152416, pp 113–184 Macdonald GA, Hubbard DH (1970) Volcanoes of the national parks of Hawaii. Hawaii Natural History Assn, 5th edn Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Geomorphology from space. NASA SP 486, pp 212, 213
Vc3.4 · Calderas on Shield Volcanoes
Fig. Vc3.4-1. Source. USGS Comments. This is an air perspective view northward over the summit of Kilauea Caldera in Hawaii Volcanoes National Park, on the southeast side of Hawaii Island. Its elevation is 1 247 m, it is 5 km long, 3 km wide, 120 m deep. The crater in the floor of the caldera is Halemaumau, 2 km diameter and 150 m deep. The caldera area is made up of volcanic series of Pleistocene to Recent age. The caldera floor is entirely covered by lavas, while the surrounding slopes are covered with ash deposits ranging in thickness from 2 m at the rim to 0.1 m 2 to 4 km distant. The dark lava in the caldera, the patch to the northeast and the larger deposit to the south all flowed in 1982.
Topographically, Kilauea actually forms only a slight independent protuberance on the southeast flank of Vc2 Mauna Loa shield 4 170 m elevation, probably the largest volcanic mountain on Earth (Macdonald et al. 1983, p 348). Hawaii is the largest and at 0.7 Ma youngest of the Hawaiian chain of hot spot islands. The average depth of the ocean floor in the Hawaiian region is 4 900 meters. When measured from the sea floor these volcanoes approach 9 000 meters, higher than Mount Everest. Figure Vc3.4-2 is a stereomodel of this caldera area. The bare surface results from acid rain and rain shadow of the northeast trade winds.
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Vc3.4 · Calderas on Shield Volcanoes ▼
Fig. Vc3.4-2. Location. Geographic. 155°17' W, 19°25' N, Hawaii Island Geologic. Kilauea Vc2 Holocene shield volcano Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. 14 October 1954 Source. USGS Comments. This stereomodel of the air perspective view of Fig. Vc3.4-1 shows the summit caldera of Kilauea shield volcano bordered by fault scarps and floored by lava flows
Fig. Vc3.4-3. Vertical Airphoto/Image. Type. Colour infrared airphoto Scale. 1: 145 000 Acquisition date. Not given Source. USGS Comments. The Pliocene shield volcano of Lanai Island Hawaii pictured in this photo is described in Fig. 17.2-2. The inset frame locates the perspective photo of that figure. Graben faults are drawn to mark rift zones. The circled area is the lava-filled 4 km Palawai Caldera. Red areas are pineapple plantations; blue reflects the dry climate. Lanai is 10 km south of Molokai Island of Fig. X1.4-2.
erupted within the last century. Along the western and northern edges are step faults. Near the southwest edge of the caldera floor is the “Fire Pit” Halemaumau, a crater about 150 m deep that is the focus of Kilauea’s eruptive activity. In these photographs the spatter cone of a 1952 eruption stands above the floor of Halemaumau, which is covered with lava formed in 1952 and 1954. A fissure that extends east-northeast from the northeast side of the crater fed the 1954 lava flow, whose dark color on the aerial photographs contrasts with the surrounding lighter colored weathered flows. Open fissures that extend southwest from Halemaumau are the surface expression of the north end of the southwest rift of Kilauea.
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Vc4 Volcanic Fields Characterization The following are taken from Karapetian (1963) “Areal (polyorifice) volcanism is characterized by the absence of a localisation tendency of eruption centers in definite points for any lengthy period of time. Here lies the main, fundamental difference between areal volcanism and volcanicity of other types.” “Eruption centers form structures of small sizes; their basement diameters usually do not exceed 2 000 m and the heights rarely reach 400–450 m. Volcanic edifices can consist of slag and lava cones (Vc1) domes and maars” (low-relief volcanic craters). “The activity of areal volcanoes is limited by a short period of time, never exceeding a dozen years. Sometimes the active life of an eruption center is actually several weeks.” “The location of eruption centers can be disorderly, in clusters or linear.” “Volcanoes originate directly on fissures.” The extent of areal volcanic centers ranges from 1 000 to 8 000 km2.
Tuttle ML, Lockwood JP, Evans WC (1990) Natural hazards associated with Lake Kivu and adjoining areas of the Birunga volcanic field, Rwanda and Zaire, Central Africa. Final Report, 37 p, USGS OF 90-0691 Ulrich GE, Billingsley GH, Hereford R, Wolfe EW, Nealy LD, Sutton Rl (1984) Map showing geology, structure, and uranium deposits of the Flagstaff 1×2° quadrangle, Arizona, USGS Map I – 1446, 1 : 250 000 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, p 248
Fig. Vc4-1.
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Vc4
Division 1 · Magmatic Rocks and Structures
Source. Girod M (1968) Carte géologique du centre de l’Atakor. C.N.R.S., Paris Comments. A 30 km by 18 km fragment of a geological map covers the area framed on the astronaut photo of Fig. Vc4-6 over the center of the Algerian Hoggar Massif. The figure center is at 05°40' E, 23°15' N. The background white areas are Neogene XI basalt lavas; green units are Plio-Pleistocene Vs1.2 siliceous flow domes and Vs3 phonolitic extrusive columns. Areas coded R 3 are outcrops of crystalline basement rocks.
Geohazard Relations Some currently active volcanic fields are in the Congo and Iceland. The hazards associated with this geounit are the same as those described for lava flows X1, pyroclastic falls Pf1 and domes Vs1, but on a scale related to the reduced dimensions of the specific units.
Reference Karapetian KI (1964) Some regularities in areal volcanism. Bull Volcanologique, IUGG Tome XXVII, pp 381–383
Select Bibliography Condit CD, Morrison RB (1991) Quaternary volcanic fields of the Colorado Plateau. Quaternary Nonglacial Geology: Conterminous US, GSA, pp 378, 379 Dubertret L (1929) Etudes des régions volcaniques du Haouran, du Djebel Druze et du Diret et Toulloue (Syrie). Revue de géographie et de géologie dynamique Joyce EB (1975) Quaternary volcanism and tectonics in Southeastern Australia. In: Suggate RP, Cresswell MM (eds) Quaternary studies. The Royal Society of New Zealand Bulletin 13:169–176 Krafft M, de Larouzière FD (1999) Guide des Volcans d’Europe et des Canaries, 2nd edn. Delachaux et Niestlé, Paris, pp 51, 119, 154, 188 Newhall CG, Dzurisin D (1988) Historical unrest at large calderas of the world. U.S. Geological Survey Bull 1855 Newhall CG, Dzurisin D (1988) Phlegraean Fields. Historical unrest at large calderas of the world. USGS Bull 1855 Short NM (1986) Volcanic landforms. In: Short NM, Blair RW Jr. (eds) Geomorphology from space. NASA SP 486, plates V-3, V-4, T-38
Fig. Vc4-2.
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Source. Newhall CG, Dzurisin (1988) Historical unrest at large calderas of the world. USGS Bulletin 1855, vol 1, fig 1.4.2 Comments. This is a volcano-tectonic sketch map of the 13 km diameter caldera of the Phlegrean Fields multi-vent complex west of Naples Italy. This structure collapsed 35 000 BP. The caldera is set in an uplifted seabed; some of the post-caldera activity was Vc3.1 submarine and a number of the craters are phreatic tuff rings. These are low, broad, shallow monogenetic craters formed by explosive eruption of mainly basaltic lava that interacts with groundwater, i.e. a type of hydrovolcanic eruption. Other circular vents are scoria cones. From 1983–1985 an area of 80 km² was uplifted, in places up to 1.8 m, damaging homes, the harbour and the tourist industry. Ultimately 36 000 people were relocated. The Argo Project for the Bay of Naples, designed to control seismic risk and monitor potential for an eruption, measures preeruptive ground inflation, geochemical, and seismic data for the Ministry of Civil Defence at three sites around this caldera and at others in the Vesuvius Volcano area of Fig. Vc3.2-10, 20 km to the east. The data are transmitted by way of a parabolic antenna to a stationary global positioning satellite.
Vc4 · Volcanic Fields
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Fig. Vc4-3. Location. Geographic. 110°13' W, 35°24' N, north central Arizona, USA Source. Green J, Short NM (eds) (1971) Volcanic Landforms and Surface Features. Springer-Verlag, pl 73 Comments. This air view shows some of the association of volcanic units in the satellite Fig. Vc4-9 of the 1 800 km2 Tertiary Hopi Buttes volcanic field 150 km east-southeast of the Grand Canyon. Tephra and lava deposits are distinguished in the foreground. X1 are basalt flows with veneers of windblown sand or tephra; Pf1 are tephra deposits. The buttes in the background are diatremes – volcaniclastic debris that filled pipe-like Volcanic conduits. See also Fig. Vc4-4.
Fig. Vc4-4. Location. Geographic. 113°36' W, 31°50' N, northwest Mexico Source. Green J, Short NM (eds) (1971) Volcanic Landforms and Surface Features. Springer-Verlag, plate 92B Comments. An air perspective view over the western portion of Pinacate volcanic field in Sonora, shows some of the variety of geounits that generally occur in such a collective macro-scale unit. A Vc1 stratovolcano is on the left horizon; breached cinder cones occur below, and X1 basaltic flows are in the foreground. The entire field is shown in satellite images of Fig. Vc4-5 where some of the variety is expressed, particularly in the radar subscene. See also Fig. Vc4-3.
Vc4 · Volcanic Fields
Fig. Vc4-5. (Caption on p. 178)
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Division 1 · Magmatic Rocks and Structures ▼
Fig. Vc4-5. Location. Geographic. 113°30' W, 31°45' N, northwest Mexico Vertical Airphoto/Image. Type. SIR-A ; Gemini IV, b/w of Ektachromes Scale. SIR-A: 1:467 000; Gemini IV: 1:550 000 Acquisition date. SIR-A 13 November 1981, Gemini IV 4 June 1965 Source. USGS Comments. The composite image presents comparisons of the Pinacate volcanic field captured by different sensors. This field, in Sonora State is 35 km by 40 km, has a maximum elevation of 1 300 m. and covers 1 500 km2. It is located in the Salton Trough at the head of the Gulf of California. and is one of 18 Tertiary and Quaternary volcanic fields in the adjacent Basin and Range physiographic province of the southwest USA. The field includes coalescing basalt lava flows, tephra deposits, numerous volcanic vents, cinder cones, and several maar craters. It is pictured in air perspective in Fig. Vc4-4. The radar image on the left is spectrally almost a negative rendition of the visible band black and white photo on the right, e.g. the youngest lavas are brightest in the radar image due to their surface roughness; they are the darkest in the black and white photo. Pinacate is surrounded by sands of a part of the Gran Desierto Ed1.8 dune field, of Figs. Fw3.1-2 and Fv2-29, North America’s largest field of active dunes. The dunes are typically black in the radar image and bright in the visible band photo.
Fig. Vc4-6.
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Location. Geographic. 05°40' E, 23°15' N center of inset frame, southeast Algeria Geologic. Caledonian Craton of Trans-Saharan Mobile Belt Vertical Airphoto/Image. Type. Apollo 9 spacecraft Ektachrome film Scale. 1: 535 000 Acquisition date. March 1969 Source. Lowman PD Jr (1972) The Third Planet. Weltflugbild Reinhold A. Müller, Feldmeilen/Zürich, CH, p 115, picture 52 Comments. An extensive X1 basaltic volcanic field, Atakor, 80 km by 40 km is clearly delineated on this astronaut photograph. It covers a basement complex of late Precambrian (Neohadrynian) crystalline rocks of the Hoggar Massif also called the Tuareg Shield, labelled R3. Extrusion of the lavas was associated with epeirogenic uplift (>1 000 m) and fracturing of the basement since Early Pliocene. The field now lies at a general range of elevation from 1 800 m to 2 200 m. The highest point is the 2 918 m Vs1 Tahat dome on the western edge of the field. The inset frame locates coverage of the 30 km by 20 km geologic map extract of Fig. Vc4-1 which shows the typical distribution of the occurring lavas and numerous domal structures.
Vc4 · Volcanic Fields
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Fig. Vc4-7. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 270 000 Acquisition date. Not given Source. NASA Special Publ. 486 (1986) p 113, plate T-38 Comments. This Landsat mosaic shows the relation of the dark Tertiary and Quaternary Jebel Druze volcanic field of basalt and andesite in southern Syria to the Levant Fault Zone, a major transform type strike slip fault (regionally named the Jordan Rift Valley). The mosaic covers 340 km, from the Dead Sea to north of Beirut, of the 1 000 km long structure, stretching from the Gulf of Akeba to southern Turkey, which is the northwestern edge of the Arabian Plate. See also Fig. 13-1. Damascus and its surrounding red cultivated zone is just north of the volcanic field.
Vc4 · Volcanic Fields
Fig. Vc4-8. Location. Geographic. 107°26' W, 35°19' N, northwest New Mexico Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image shows the dark mass of a Neogene volcanic field 80 km west of Albuquerque, lying 400 m to 700 m above bright Upper Cretaceous shale of the southeast Colorado Plateau. The 70 km long by 30 km wide field is made of two epochs of volcanism; the dark-green Late Miocene pine forested mass of Vc1 Mt. Taylor stratovolcano, 3 445 m with more than 1 600 m of relief and the brown, drier, Late Pliocene mesa of X1 basaltic lavas that erupted from scores of widely scattered, little visible low eroded vents.
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Fig. Vc4-9. Location. Geographic. 110°13' W, 35°24' N, north central Arizona Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image shows the scattered small dark basaltic lava buttes of the 50 km diameter Tertiary Hopi
Buttes volcanic field against the pale-brown Cretaceous sandstones and shales of the southern Colorado Plateau. About 200 narrow diatreme columns (volcaniclastic debris that filled pipe-like volcanic conduits) appear as small dark points amid the buttes. Larger basalt flows appear as small mesas on the east side of the field. An air perspective view of the field is in Fig. Vc4-3.
A1 · Lahars
Group A Modern Volcanic-Epliclastic Deposits A1 – Lahars Characterization Origin Lahars are mass movements generated on the flanks of volcanoes, the detritus consisting of contemporaneous volcanic debris. They are also referred to as volcanic mudflows or debris flows. Their origin and composition distinguish lahar transport processes and deposits from those of comparable debris flow deposits (Mf3) which consist of substrate-related surficial materials. Lahars may be primary (eruptive) or secondary (posteruptive) or unrelated to eruptions. They are essentially viscous flows and can originate in a variety of ways; Eisbacher and Clague (1984) list six of the more common mechanisms:
Geohazard Relations “Lahars threaten lives and property both on volcanoes and in the valleys that drain them. Because of their high bulk density and velocity lahars can destroy vegetation and even substantial structures in their paths, such as bridges. The deposits of lahars can deeply bury crops and developments. They can also fill stream channels, thus decreasing the channel’s capacity to carry flood flows. In contrast to pyroclastic flows and surges (Ps1), lahars and floods have sharply defined upper limits along valleys and in many cases people can quickly climb to safety if safe areas are identified beforehand.” (Scott 2000). “… abundant liquid contained in lahars allows them to inundate areas far away from their sources. People in such distal areas commonly neither expect the danger nor anticipate the destructive power of lahars.” (Vallance 2000). Rock fragments carried by lahars make them especially destructive.
References emptying of crater lakes; by violent expelling or by failure of enclosing walls (see Geounit Vc1) rapid melting of snow or ice (jokulhlaup); lava flows come into contact with snow-ice explosion-induced avalanches of volcanic debris into streams; damming of streams movement of Ps1 pyroclastic flows along river valleys; addition of river water to mass failure of the flank or summit of a volcano; portion slides away and transforms into a lahar heavy rain on newly fallen pyroclastic deposits Pf1; lack of protective vegetation cover
Composition “Generally lahar deposits may be massive to crudely stratified and graded to ungraded, depending on the proportion of water that the flows contained.” (Vallance 2000). Lahar units typically incorporate exotic sediment by eroding and undercutting steep slopes of active stream banks and by scouring their beds.
Deposits The flows usually follow river valleys, but on reaching distal footslopes they spread out as broad sheets. Thick deposits (30–70 m) occur in valley bottoms and lowlands, with thinner deposits on slopes. Scattered large boulders on the surface of many deposits give rise to a landscape of mound fields.
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Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 33–36 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology, Vol 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, p 15 Vallance JW (2000) Lahars. In: Sigurdsson H (ed) Encyclopaedia of volcanoes. Academic Press
Select Bibliography Genesis Bordet P (1952) Les appareils volcaniques récents de l’Ahaggar. Monograpies Régionales, XIXème Congrès Géologique International, pp 37–38 Brantley SR, Waitt RB (1988) Interrelations among pyroclastic surge, pyroclastic flow, and lahars in Smith Creek valley during the first minutes of 18 May 1980 eruption of Mount St. Helens, USA. Bull of Volcanology 50:304–326 Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 323–328 Coe JA, Ellis WL, Godt JW, Savage Wz, Savage JE, Michael JA, Kibler JD, Powers PS, Lidke DJ, Debray S (2003) Seasonal movement of the Slumgullion Landslide determined from global positioning system surveys and field instrumentation. Engineering Geology 68(1–2):67–101 Pierson TC, Scott KM (1985) Downstream dilution of a lahar – Transition from debris flow to hyperconcentrated streamflow. Water Resources Research 21:1511–1524
Remote Sensing Tighe LM, Irving R (1995) Volcanic flow mapping of Mount Pinatubo, Philippines using radar texture analysis. Proceedings, 17th Canadian Symposium on Remote Sensing, pp 756–761 Verstappen HTh (1983) Applied geomorphology. Elsevier Scientific Publishing Co., NY, pp 121–125
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Geohazards Iverson RM (1994) Lahar dynamics. GSA Abstracts, vol 26, no 7, pp 376–377 MacPhail DD (1973) The geomorphology of the Rio Teno Lahar, Central Chile. Geographical Review (US) 63(4):517–532
Scarpa R, Tilling RI (eds) (1996) Monitoring and mitigation of volcano hazards. Springer-Verlag, Heidelberg Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology, Vol 1. 28th International Geological Congress, Washington D.C., American Geophysical Union, pp 16–17 Smith WK (1998) Photogrammetric determination and analysis of landslide displacement, Slumgullion Slide, Colorado. Association of Engineering Geologists, 37th annual meeting Vallance JW (2000) Lahars. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, p 602
Fig. A1-1. Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, p 327, fig 10.30 Comments. A schematic diagram shows the site of initiation of a lahar on the flank of a Vc1 stratovolcano; the section shows the poorly sorted texture of large clasts in a fine matrix, typical of the geounit. See Fig. A1-2.
Fig. A1-2. Source. Crandell DR & Mullineaux DR (1967). Volcanic Hazards at Mount Rainier Washington. USGS Bulletin 1238, p 13, fig 4 Comments. Photo shows the heterogeneous unstructured composition typical of lahar debris flows. This deposit is on the northwest flank of the Early Pleistocene 4392 m Mount Rainier Vc1 Volcano. This is the highest volcano in the USA, in the Middle Cascade Ranges of the western cordilleras. A lahar (Osceola) on the eastern side of this volcano is one of the largest in the world. It extended from 65 to 100 km and covered an area of some 250 km2, 5 700 BP.
A1 · Lahars
Fig. A1-3. Location. Geographic. New Zealand Geologic. Pleistocene eruption through Late Paleozoic and Early Mesozoic sediments of emergent part of a fragment of Gondwana supercontinent Source. New Zealand Geological Survey, photo by T. Ulyatt Comments. The photo shows one of three lahars that swept down the slopes of Ruapehu Volcano 2 796 m a.s.l. in the center of North Island in June 1969. Water in the lahar came from the crater lake at a temperature of 45 °C and melted snow and ice. Eruptions through this lake occur relatively frequently changing the physical dimensions of the lake and posing a constant threat to human activities in the area. The volcano is located in the popular recreational and winter sports area of Tongariro National Park. It lies at the southern end of a belt of volcanic activity that extends northeast for 2000 km along the Pacific-Australian
Plates boundary, parallel to the White Island (Fig. Vc1.1-2), Kermadec and Tonga Trenches. The broad summit of Ruapehu consists of a main depression within which are four overlapping smaller craters; the youngest is occupied by Crater Lake. Eruptions through this lake and weak tephra barriers occur relatively frequently changing the physical dimensions of the lake and posing a constant threat to human activities throughout the area. Lake level rises are caused mainly by snow and ice melt, heavy precipitation and by input of hydrothermal fluids. Lahar tracks have flowed out in northeast, northwest, south and west directions. The latest flow occurred on 19 March 2007. The last previous eruption was in June 1996. Regular monitoring and data collection on this volcano and its lake is carried out by the New Zealand Geonet Project. Figures Ps.1-4 and A2-2 show a pyroclastic flow and a debris avalanche on Ngauruhoe Volcano, 13 km to the north.
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Fig. A1-4. Source. Macdonald GA et al. (1983) Volcanoes in the Sea, 2nd edn. University of Hawaii Press, Honolulu, p 397, fig 20.16
Fig. A1-5.
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Location. Geographic. 120°19' E, 15°09' N, Zambales Mtns Luzon, Philippines Geologic. Subduction complex of magmatic arc terrane Vertical Airphoto/Image. Type. SIR – C/X-SAR Acquisition date. 14 April 1994, left / 5 October 1994, right Source. NASA Comments. Colour composite radar images showing the area around Mount Pinatubo cover an area of approximately 40 km by 65 km. Red on the high slopes shows the distribution of the ash deposited during the June 1991 eruption. The dark drainages radiating from the summit are the lahars which even three years after the eruption continue to flood the river valleys after heavy rains.
Comments. Air perspective photo shows recent lahar and older X1.1 lava flows located in one of a number of stream eroded valleys on the south east and north slopes of Haleakala Volcano on east Maui Island.
Three weeks before the second image was obtained, devastating lahars more than doubled the affected area in the Pasig – Potrero Rivers, which is clearly visible as the increase in the dark zone on the lower right of the images. Deposition has affected many communities where thousands of homes were buried in meters of hot mud and rock as 80 000 people fled the lahar stricken district. The 1991 eruption of this volcano is well known for its near-global effects on the atmosphere and short-term climate due to the large amount of sulfur dioxide that was injected into the upper atmosphere. Pinatubo is located in the volcanic zone of the Manila arc system. It is composed of a collection of lava domes surrounded by thick deposits of tephra. A 2 km diameter caldera occupied by a lake came into being following the destruction of the summit by the 1991 euption.
A1 · Lahars
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Division 1 · Magmatic Rocks and Structures
A2 – Volcanic Debris Avalanches Characterization Origin “A sector collapse of a volcanic edifice produces a debris avalanche. A debris avalanche is triggered typically by intrusion of new magma, a phreatic explosion, or an earthquake.” Ui et al. (2000).
Geohazard Relations “Debris avalanches bury and destroy everything in their paths and greatly alter pre-existing topography.” “Debris avalanches can also dam streams and form lakes that can drain catastrophically and generate lahars and floods.” “Finally, debris avalanches that enter a body of water and suddenly displace large volumes of water can form waves.” (Scott 2000).
References Debris avalanches have occurred at numerous stratovolcanoes (Vc1) in historical time. Numerous dynamic emplacement models have been proposed, including air, mechanical, acoustic, and seismic energy fluidization; granular and biviscous flow, and basal low-density layers and mass loss models.
Composition Volcanic debris avalanches are composed of debris avalanche blocks derived from the source volcano surrounded by a debris avalanche matrix consisting of a mixture of smaller volcanic fragments from various units within the volcano. Exotic materials are eroded and mixed with the primary matrix material during flow.
Morphology The following comments which summarize clearly the morphology of volcanic debris avalanches are taken from Ui et al. (2000): “Hummocky topography, natural levees, a marginal cliff, a distal cliff, remnants of temporary river channels, and an amphitheatre at the source are characteristic geomorphic features of a debris avalanche deposit. Hummocky topography is perhaps the most significant geomorphic feature.” “Block facies and matrix facies are terms used to define (field) mappable areas of a debris avalanche deposit. In the block facies many debris avalanche blocks are assembled to form hummocky terrain. Matrix facies … are topographically flat.” “Some glacial terminal moraines show a similar topographic expression. Due to irregularity in form and composition, it is often hard to discriminate debris avalanche deposits based on topography alone. Similar undulating topography is also known in the case of small-scale pyroclastic flow deposits (Ps1). However, their gentle and regularly undulating pattern differs from the hummocky topography of debris avalanche deposits.” Known debris avalanches extend up to 85 km from their sources and cover tens to 1 000 km2.
Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology, vol 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, p 15 Ui T, Takarada S, Yoshimoto M (2000) Debris avalanches. In: Sigurdsson H (ed) Encyclopedia of volcanoes. Academic Press, pp 617–626
Select Bibliography Origin-Characterization Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 300–303, Gerrard AJ (1990) Mountain environments. The MIT Press Cambridge, Mass., pp 212–219 Glicken H (1982) Criteria for identification of large volcanic debris avalanches (abstr). EOS Trans Am Geophys Union 63:1141 Scott WE (1989) Volcanic and related hazards. In: Tilling RI (ed) Volcanic hazards. Short course in geology, vol 1. Presented at the 28th International Geological Congress, Washington D.C., American Geophysical Union, pp 14–15 Siebert L (1984) Large volcanic debris avalanches: Characteristics of source areas, deposits and associated eruptions. Journal Volcanol Geotherm Res 22:163–197 Ui T (1989) Discrimination between debris avalanche and other volcaniclastic deposits. In: Latter JH (ed) Volcanic hazards. IAVCEI Proceedings, Volcano, vol 1, pp 201–209 Ui T (1983) Volcanic dry avalanche deposits – Identification and comparison with nonvolcanic debris stream deposits. Journal Volcan Geotherm Res 18:135–150
Remote Sensing de Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, Berlin, pp 13, 20, 33, 34 Francis PW, Wells GL (1988) Landsat thematic mapper observations of debris avalanche deposits in the Central Andes. Bull of Volcanology 50:258–278 Francis PW, Self S (1987) Collapsing volcanoes. Sci. Am. 256:91–97 Molnia BF, Hallam CA (1999) Open skies aerial photography of selected areas in Central America affected by hurricane Mitch. USGS Circular 1181:44–66 Singhroy V, Molch K, Bulmer M (2002) Characterterization of landslide deposits using SAR images. Geoscience & Remote Sens. Symp., IGARSS apos; 02, 2002 IEEE International, vol. 1, issue 2002, pp 185–187
Geohazards Siebert L (1996) Hazards of large volcanic debris avalanches and associated eruptive phenomena. In: Scarpa R, Tilling RI (eds) Monitoring and mitigation of volcano hazards. Springer-Verlag, Berlin, pp 541–572
A2 · Volcanic Debris Avalanches
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Fig. A2-1. Source. Reprinted from Encyclopedia of Volcanoes, H. Sigurdsson (ed), Ui T, Takarada S, Yoshimoto M, Debris Avalanches, p 617, Fig. 1 © 2000, with permission from Elsevier Comments. Schematic diagram of a debris avalanche deposit, shows the decreasing size of hummocks toward the distal end of the deposit.
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Fig. A2-2.
Source. Gregg DR (1961) Volcanoes of Tongariro National Park Information Series – No. 28. New Zealand Department of Scientific & Industrial Research, p 40, Fig. 19 Comments. A close view of the block and ash composition of the debris avalanche of 16 September 1954 on the western slopes of Ngauruhoe Volcano, in North Island’s Tongariro National Park. The tectonic setting of this volcano is described in Fig. A1-3 of Ruapehu Volcano 13 km to the south. See also Fig. Ps1-4.
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Fig. A2-3. (Caption on p. 192)
A2 · Volcanic Debris Avalanches
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Fig. A2-3.
Location. Geographic. 121°45' W, 46°52' N, Washington State Geologic. Middle northern Cascade Range of Western Cordillera Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 50 000 Acquisition date. 3 September 1955 Source. USGS Comments. Stereomodel shows the upper 3 km of a 5 km long by 1 km wide debris avalanche (Paradise Park) that occurred between 5 800 and 6 600 BP on the south flank of 4 400 m Mount Rainier Vc1 Volcano of this Quaternary volcanic range. The avalanche changed into an A1 lahar flow more than 200 m deep as it spread out at lower elevation. Gl5 are valley glaciers. Gt4.1 are lateral moraines (see Gl5) from a previous advance of that glacier. Mt. St. Helens of Fig. Vs1.1-7 is 80 km to the south.
Fig. A2-4.
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Location. Geographic. 68°16' W, 24°24' S scene center, northeast Chile, – southwest Bolivia Vertical Airphoto/Image. Type. TM, 30 m resolution Scale. 1: 303 000 Acquisition date. Not given Source. deSilva S, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, p 105, Fig. 33.1 Comments. Landsat subscene shows a massive debris avalanche labelled DF covering more than 600 km2. It is the world’s best exposed example of this geounit. The deposit formed 7 200 BP when the northwestern sector “A” of the ancestral cone of Socompa Volcano, on the Chilean-Argentinian border collapsed. The amphitheater at “A” has steep cliffs 400 m high in places. The inset frame locates the air perspective view of the bottom photo.
A2 · Volcanic Debris Avalanches
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Fig. A2-5. Vertical Airphoto/Image. Type. TM, 30 m resolution Scale. indicated Acquisition date. Not given Source. De Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, p 109, Fig. 34.1 Comments. This Landsat subscene is centered on a major debris avalanche, DF, that originated on the eastern flank
of Pleistocene Llullaillaco Volcano, L, on the ChileanArgentine border 68°32' W, 23°43' S. (At 6 723 m this is the second highest volcano in the world.). The avalanche split into two lobes around Cerro Rosado (CR) 17 km east of its source and traveled a further 5 km terminating on the shores of L3 Salar de Llullaillaco (SL). FM are the distal margins of the avalanche. (LF are young lava flows; FL are flow levees).
A2 · Volcanic Debris Avalanches
Fig. A2-6. Vertical Airphoto/Image. Type. TM 30m resolution Scale. Indicated Acquisition date. Not given Source. De Silva SL, Francis PW (1991) Volcanoes of the Central Andes. Springer-Verlag, p 53, Fig. 13.1 Comments. Landsat subscene shows at DF a large Holocene volcanic debris avalanche that flowed southward from Tata
Sabaya Volcano onto the L3 Salar de Coipasa, SC, on the Bolivian Altiplano 68°32' W, 19°08' S. ADS is the avalanche detachment scarp. The distal margin of the deposit has been removed by erosion but probably extends under the small islands at the edge of the image. (LF on the western slope of the volcano are young X1.1 lava flows). A vehicular roadway crosses the deposit from northeast to southwest.
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A3 – Hydrocinerite Plain Deposits Characterization Hyrocinerites are primarily unconsolidated stratified tephra, frequently interbedded with non-volcanic sediments, occurring in exposed ponded depressions in distal volcano footslopes, in basinal sites (Group L) and in Coastal plains Sub-group Bc. The cinerites are emplaced in these environments by epiclastic processes either directly by airfall (Pf1) or pyroclastic flows (Ps1), or transported off slopes and redeposited by overland or channeled water flow. Identification of this geounit is indirect, inferred by association with the above-mentioned deposition sites that may occur in the vicinity of tephra-producing volcanic structures.
Geohazard Relations The geohazards of hydrocinerites are those related to the deposits of the geounits in which they occur – lacustrine sediments (Group L) and coastal plain sediments (Subgroup Bc). These geounits are agents of slumping, flowing
and flooding, and are susceptible to subsidences. Agricultural activities and their infrastructures (irrigation etc.) are commonly located on the soils derived from these sediments.
Select Bibliography Bordet P (1952) Les appareils volcaniques récents de l’Ahaggar. Monographies Régionales, XIXème Congrès Géologique International, pp 12, 37–38 Campy M, Macaire JJ (1989) Géologie des formations superficielles. Masson, pp 306–307 Cas RAF, Wright JV (1987) Volcanic successions: Modern and ancient. Allen and Unwin, London, pp 312–315, 360, 402–403 Clough BJ (1981) The geology of La Primavera Volcano, Mexico. Unpublished Ph.D. Thesis. Imperial College, University of London Haberle SG (1999) Late Quaternary environmental dynamics of southwestern Chile. Monash University Houston JM (1964) The Western Mediterranean world. Longmans, London, p 411 Lettis WR, Unruh JR (1991) Quaternary geology of the Great Valley, California. Quaternary Nonglacial Geology: Conterminous U.S., GSA, p 173 Moxey L (2001) Late Quaternary deposits of Mt. Hudson Volcano, Southern Argentina. University of Florida Journal of Undergraduate Research, vol. 2, issue 5, Feb. 2001 Tricart J (1974) Structural geomorphology. Longman, New York, pp 258–261
Fig. A3-1. Location. Geographic. 103°34' W, 20°39' N, south-central Mexico Source. Cas RAF, Wright JV (1987) Volcanic Successions. Allen & Unwin, London, p 395, Fig. 13.37
Comments. The map of this figure shows 95 000 BP hydrocinerite deposits filling the shallow 11 km wide La Primavera Caldera in the Trans Mexico Neo-Volcanic Belt.
A3 · Hydrocinerite Plain Deposits
Fig. A3-2. Source. MDA EarthSat Comments. This Google Earth image shows the topographic setting of part of Mexico city in the 900 km2 Basin of Mexico. The basin lies at an elevation of 2 239 m in the central part of the Trans Mexico Volcanic Belt. The scene includes some surface water and the type of agricultural land use depicted in Fig. A3-4. The circular structure which is a type of explosion crater is partly surrounded by a moat-like area of water. Hydrocinerite deposits, infilled from surrounding volcanic piedmont and mountain slopes occur in some subbasins of the depression. Basin of Mexico is an area whose partly block-faulted geologic setting and stratigraphy result in a zone of high susceptibility to a combination of Mv5 subsidence, flooding and seismic geohazards. The stratigraphy consists essentially of 800 m of interbedded L2 lacustrine, Fu1 alluvial and X1 volcanic sediments. Hydrologically the basin is a closed depression, sources of groundwater are from infiltrated precipitation and
snowmelt from the surrounding volcanic highlands. Modern pumping of the groundwater for domestic use and industry has resulted in subsidence rates of up to 46 cm yr–1 in some districts. Now pumping of groundwater is controlled by law. The net subsidence over the last 100 years has lowered the central organized area of the city by an average of 7.5 m. The result has been extensive damage to the city’s infrastructure including building foundations and the sewer system (floating foundations and pile construction must be used). Remarkably, despite these conditions, the presumed introduction of stabilizing measures has enabled the construction of a subway system since the 1960s that now reaches 207 km in service. The site of Mexico City on the valley floor has always been subject to flooding. By 1950 the sinking of the city was such that dykes had to be built to confine stormwater flow. This subsidence has also lowered the elevation of the city relative to the Lake Texoco area east of the international airport. By 1974 the lake bottom was 2 m higher than the city. Dyking and drainage works are evident in the lake area. Finally, Mexico City is well within the seismic region of southern North America.
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Fig. A3-3. Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1:4 330 approx. Acquisition date. Not given Source. Personal archive
Comments. Large scale photo shows the excavated city of Pompeii near Naples buried in ad 79 by an ash fall from a Vesuvius eruption. The tuffs were deposited in water. The regional context of this city is shown in Fig. A3-6.
A3 · Hydrocinerite Plain Deposits
Fig. A3-4. Location. Geographic. Central Mexico Geologic. Neovolcanic plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 41 000 Acquisition date. April 1959 Source. Journal Photo Interprétation, Editions ESKA, Paris, 67-3, 4 Comments. The stereomodel covers 40 km2 of the Basin of Mexico described in Fig. A3-2. The land use/land cover contrasts of basin and hillslopes is clear evidence of relative agricultural capacities.
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A3 · Hydrocinerite Plain Deposits ▼
Fig. A3-5.
Fig. A3-6.
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Location. Geographic. 04 45' E, 22°39' N, southeast Algeria Geologic. Hoggar cratonic massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 78 000 Acquisition date. 1969 Source. IGN–Photothèque Nationale, France Comments. The bright, possibly pumiceous hydrocinerite deposits delineated in this stereomodel are in the Tahalra Quaternary volcanic field 80 km west of Tamanrasset are reported by Bordet (1952) p 37. The semi-circular units are scoria/ash cones that are the sources of the deposits. The drainage patterns traced in blue are the channels that transported the tephra through fluvially dissected lavas. This stereomodel covers 20 km of the 120 km long × 20 km wide Vc4 volcanic field. The area comprises a built-up sequence of basic flows overlying older ones. The strong dissection of the lavas is due in part to interbedded latosols (weathered laterite) from Quaternary climatic variations in the Hoggar (a pluvial in the Neolithic 3 000 ka). The semi-circular inliers are clusters of scoria/ash cones. Vs1.2 is a classic flow-dome complex. (Note: The contact prints from which this stereo model was reproduced have a low contrast; the model is included in the atlas because of the remarkable occurrences of the delineated volcanic units). This figure is 60 km west of the pyroclastic flow deposits of Fig. Ps1-8.
Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 155 000 Acquisition date. Not given Source. Unattributed Comments. Landsat subscene of the southern Apennine fold-and-thrust chain shows the general extent of fertile tephra and hydrocinerite deposits marked Pf/A3-Q on the Campanian Plain surrounding Mount Vesuvius and Naples, Italy. Kc3-M are dolomites. Fvk are fluvial terrace lands. An airphoto of excavated Pompeii is Fig. A3-3. See also Fig. Vc3.2-10.
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Fig. A3-6. (Caption on p. 201)
Division 2 Sedimentary Rocks and Duricrusts
Group K Carbonates
General Note Concerning Geohazard Relations The geohazard-related lithotypes described in this Atlas are classified in five groups:
Sub-group Kp Holokarst Residual Terrains Sub-group Kn Holokarst Erosional Terrains Sub-group Kc Amorphous Carbonates
Carbonate rocks are primarily agents of solution and are susceptible to seismicity, rockfalls, and subsidences. Saline and phosphatic rocks are agents of subsidence and solution, and are susceptible to flooding. Detrital rocks are susceptible to seismicity, sliding, slumping and erosion. Interbedded sequences are susceptible to seismicity, rockfalls, sliding, creep, and erosion. Duricrust ferricretes are agents of encroachment deposition and are susceptible to rockfalls.
Group H Saline and Phosphatic Rocks Group S Detrital Rocks Group W Interbedded Sequences Group D Duricrusts
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_5, © Springer-Verlag Berlin Heidelberg 2009
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Group K Carbonates Characterization Carbonate rocks are formed from marine shell debris and chemical precipitate, lithified by recrystallization. They are composed of variable sized calcite (93%) dolomite (5%) and clay minerals (2%). The strata can be massive or thin bedded, commonly with thin shale partings. They may also include large massive fossil reefs of strong limestone. Beds may contain nodules or lenses of silica: flint in chalk and chert in limestone. “Limestone is the only common rock soluble in water. It dissolves in rainwater enriched by carbon dioxide derived from organic soils so the processes and results are on a large scale in areas of warm, wet climate. Karst features are erosional forms produced by solution on bare rock surfaces, beneath the soil at rockhead, and within the rock.” (Waltham 2002).
Reference Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 58–59
Select Bibliography Characterization Back W, Arenas AD (1989) Karst terrains; resources and problems. Nature and Resources, Special Issue, pp 19–26 Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Natural Resources Ser. no 6, Division of Water and Land Resources, CSIRO, Australia, pp 66–69 Bonacci O, Vidovic-Kulic Z (1987) Karst hydrology. Springer-Verlag, New York Herak M, Springfield VT (eds) (1972) Karst (important karst regions of the Northern Hemisphere). Elsevier, Amsterdam Hoffmeister JE, Ladd HS (1945) Solution effects on elevated limestone terraces. GSA Bull 56:809–818 Jakucs L (1978) Morphogenetics of karst regions: Variants of karst evolution. Halstead Press, John Wiley and Sons, New York Jennings JN (1972) Karst. An introduction to systematic geomorphology. MIT Press, Cambridge, Mass Jennings JN (1985) Karst geomorphology. Blackwell, Oxford Monroe WH (1970) A glossary of karst terminology. USGS Water Supply Paper 1899-k Monroe WH (1976) The karst landforms of Puerto Rico. USGS Professional Paper 899 Selby MJ (1985) Earth’s changing surface. Clarendon Press, Oxford, pp 303–323 Smith DI, Atkinson TC (1976) Process, landforms and climate in limestone regions. In: Derbyshire E (ed) Geomorphology and climate. Wiley, London, p 369–409
Sweeting MM (ed) (1981) Karst geomorphology. Benchmark Papers in Geomorphology, vol 59, Hutchison Ross
Geohazards Brink ABA, Partridge TC, Williams AAB (1982) Soil survey for engineering. Oxford Science Publications, Oxford, pp 124–129 Calembert L (ed) (1975) Engineering problems in karstic regions. International Association of Engineering Geology, Bull. no 12 Daoxian Y (1983) Problems of environmental protection of karst areas. Ministry of Geology and Mineral Resources, Institute of Karst Geology, China Foose RM (1968) Surface subsidence and collapse caused by ground water withdrawal in carbonate rock areas. Proceedings, XXIII International Geological Congress, pp 155–166 Newton JG (1980) Induced sinkholes; An engineering problem in carbonate terrains. Proceedings, Third Annual Applied Geography Conference, pp 185–194
Airphoto Interpretation Blair RW JR (1986) Karst landforms and lakes. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, chap 7 Desaunettes JR (1977) Catalogue of landforms of Indonesia. FAO Working Paper no 13, AGL-TF-INS-44, Soil Research Institute, Bogor, pp 55–57, Stereograms S17, S23, S24, S25 Dizier J-L, Léo O (1982) Photo-Interpretation et Cartographie en Haiti. Faculté d’Agronomie et de Médecine Vétérinaire, Université d’État d’Haiti, p 185, fig 101, pl 8 Doherty E, Brahana JV (1996) Use of remote-sensing data and GIS models for mapping hydrogeology and structure in karst terrain of northwestern Arkansas. Abstracts, GSA Bull 28(1):11 Drury SA (1987) Image interpretation in geology. Allen & Unwin, London, p 79 Erb DK (1968) Geomorphology of Jamaica. Photogrammetric Engineering 34:1148–1160 Gupta RP (1991) Remote sensing geology. Springer-Verlag, Berlin, p 257 Mekel JFM (1970) The use of aerial photographs in geological mapping. ITC Textbook of Photo-Interpretation, vol VIII, pp 15–16, stereo photo 14, p 30 Norman JW, Waltham AC (1969) The use of airphotographs in the study of karst features. Trans. Cave Research Group, of G.B., Symposium on Cave Photography, pp 245–254 Sabins FF (1983) Geologic interpretation of Space Shuttle radar images of Indonesia. Bull AAPG 67(11):2076–2099 van Zuidam RA (1985/86) Aerial photo-interpretation in terrain analysis and geomorphological mapping. Smits Publ./ITC, The Hague, p 125 Verstappen HTh (1977) The use of aerial photographs in geomorphological mapping. ITC Textbook of Photo-Interpretation, vol VII, pp 141–154 von Bandat H (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 104–125, fig 8–2, p 65 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 102–116
K3 · Karst Plains
K3 – Karst Plains Characterization Karst plains are tracts of relatively flat land of Cambrian to mid-Tertiary sediments of Br7 marine bedrock plains or interior continental shelves. Other than on the Florida Arch karst plains occur at a number of localities in the Caribbean, southeast Asia and southeast Australia: on the Pliocene Miocene Yucatan Carbonate Platform on the south coast of Puerto Rico, in Miocene rocks west of Ponce at Longitude at 66°50' at the east end of Java Island in the Neogene rocks of the Madura Basin at Surabaya in southwest Malaysia, at Port Dickson, 70 km south of Kuala Lumpur in southeast Australia, eastern Gippsland, between longitudes East 149° and 150°
Geohazard Relations The subsidence potential for all engineering structures is a major geohazard in karst plains. “Solution is highly selective, so that joints are etched out to create fissures, gullies and caves; they may be full of air, water or soil, between remnants of strong, unweathered rock. This creates highly variable ground conditions.” (Waltham 2002).
Reference Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 58–59
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Fig. K3-1. Location. Geographic. Guadeloupe, French Antilles Geologic. Neogene Volcanic Belt and Lesser Antilles Deformed Belt of eastern Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 10 000 Acquisition date. 12 December 1955 Source. Journal Photo Interprétation, Editions ESKA, Paris, 63-2-4
Comments. In this large-scale stereomodel of post-Eocene marine limestone on GrandeTerre the karst plain partly overlies X1 volcanic base rocks, and is distinguished from them by topography and land use. The volcanic soil, bottom left, growing sugar cane, is both more fertile and level than the limestone at top, the latter is comparatively less densely cultivated. The dark vegetated mass on the right is mangrove swamp Bt1c, associated with the Rivière Salée tidal channel that separates the island pair.
K3 · Karst Plains
Fig. K3-2. Source. Unspecified U.S. government agency Comments. This 1: 63 360 airphoto mosaic example of the era preceding synoptic hyperaltitude photography and Earth observation satellites covers a 96 km2 area of the Florida karst plain imaged in Fig. K3-4.
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Fig. K3-3. Location. Geographic. 81°35' W, 28°35' N scene center, central Florida Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 9 September 1972
Source. USGS Comments. Landsat scene is centered on the 50 m a.s.l. Ocala Arch of the Florida Carbonate Platform. The concentration of solution dolines near the crest of the arch in the center of the scene is notable. The inset frame locates the coverage of Fig. K3-4.
K3 · Karst Plains
Fig. K3-4. (Caption on p. 210)
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Fig. K3-4.
Location. Geographic. 81°35' W, 28°35' N image center, central Florida Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 375 000 Acquisition date. 8 April 1992 Source. USGS Comments. The Landsat subscene was acquired by a 2.5 times better spatial and spectral resolutions successor sensor system 20 years after that of Fig. K3-3 which shows the coverage of this image at Orlando east of the large Lake Apopka. The zone of doline concentrations on the Cretaceous and Paleogene carbonates of the Ocala Arch have been delineated. This area has a long history of collapsing foundations of houses, other buildings and structures. Lands to the northeast and southwest are Miocene and Pliocene beach ridges and other marine sediments. The inset frame locates the coverage of the airphoto mosaic of Fig. K3-2. The bright green areas are interpreted as wetlands.
Kp1 · Karst Plateaus
Sub-group Kp Holokarst Residual Terrains Kp1 – Karst Plateaus Characterization
The karst plateau surface is also subject to solution by rainwater (CO2 charged) which results in the collapse to produce characteristic surface depressions called dolines or sinkholes. Such collapses are responsible for most of the catastrophic collapses involving dwellings or engineering structures (Dearman 1981). “Because of their mode of formation, natural sinkholes will be irregular in occurrence. The solution channels in carbonate rocks may start out along joint planes but thereafter develop in quite heterogeneous fashion. There can be no certainty, therefore, about the absence of sinkholes on building sites in ‘sinkhole country’.” (Legget and Karrow 1983).
The plateau is distinguished from Karst plain K3 by its elevated topographic situation. Limestone sequences frequently form high relief because they are structurally resistant, or have been epeirogenetically uplifted (uplift of large areas of the Earth’s crust without significant deformation). As with the karst plain the surface is typically “pock marked” with sinkholes; no surface drainage system develops on the plateau, drainage is underground. The rate of groundwater movement is a major factor in the development of solution topography. High relief and abundant precipitation promotes rapid movement through the flow net.
Karst terrains yield large water supplies but the water may be contaminated. A special engineering hazard is leakage from reservoirs.
Geohazard Relations
References
Kp1 is an agent of geohazard types; rock fall 3; subsidence 4, and solution 9. Rock falls occur in zones of joint widening at plateau margin scarps. Subsidence is a ubiquitous hazard of Kp1 due to the cavernous nature of limestone in other than arid environments. Circulating groundwater dissolves the carbonate rock, and seasonal fluctuation in water levels may be sufficient to cause collapse.
Dearman WR (1981) Engineering properties of carbonate rocks. Symposium on Engineering Geological Problems of Construction on Soluble Rocks. Bull. of International Association of Engineering Geology, no 24, pp 3–17 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 38–3–38–5
Select Bibliography See Select Karst General Bibliography.
Fig. Kp1-1. Source. a and b: Jennings JN (1972) An introduction to systematic geomorphology. MIT Press, Cambridge Mass, p 121, fig 36. c: Personal archive Comments. These are block diagrams of doline type solution which are one of the most characteristic diagnostic surface features of karst plateaux on airphotos. Diagram a depicts a doline that has been produced by widening of joints by CO2-charged rainwater. Diagram b is a collapse doline caused by groundwater solution circulating along joints and subsidence of the overlying rock. Diagram c shows the situation of Figs. Kp1-2, Kp1-3 and Kp1-4, infilling of a doline with insoluble oxide-rich clayey soil (syn. terra rossa).
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Fig. Kp1-2. Location. Geographic. 03°32' E, 44°15' N, south central France Geologic. Uplifted Jurassic marine carbonate basin – see Kp1-10 Source. Larousse (1975) Découvrir la France No 64, BasLanguedoc, Causses Cévennes Comments. A ground view of a terra rossa-filled doline as shown in c of Fig. Kp1-1. The photo was taken during the growing season and the crop is located in the only arable soil. The surrounding ground is skeletal soil on 3–4 m of periglacial weathered limestone. See also Fig. Kp1-3 and stereomodel of Fig. Kp1-9.
Fig. Kp1-3. Source. Larousse (1975) Découvrir la France No 64, BasLanguedoc, Causses Cévennes Comments. An air perspective view shows dolines sharply defined by land use (yellow ripened cereal crops on the only locally arable soils) on the karst plateau shown in the vertical stereo airphotos of Fig. Kp1-9. Arrows indicate other dolines. See also Fig. Kp1-2.
Fig. Kp1-4.
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Location. Geographic. 01°44' E, 44°29' N, Quercy, southwest France Geologic. Gently westward-dipping plateau of Upper Jurassic marine carbonates Vertical Airphoto/Image. Type. b/w infrared, airphoto Scale. 1: 20 000 Acquisition date. 1977 Source. IGN – Photothèque Nationale, France Comments. This photo subframe shows solutional doline features labelled with descriptor code “7”. These features are described in Geounits Kp1-1, Kp1-2 and Kp1-3. The variably-toned rectangular areas in the dolines are agricultural fields. Code “4” is rough pasture land on the skeletal plateau soils.
Kp1 · Karst Plateaus
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Fig. Kp1-5. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. Not given Source. Unspecified U.S. government agency Comments. The stereomodel shows a group of dry valleys, characteristic of karst limestone traced in a local 1 km × 3 km area of Ordovician limestones in the inverted topographic basin eroded into the crest of the Nashville Dome 86°30' W, 35°30' N of the Interior Low Plateaus near Shelbyville in central Tennessee. See also Fig. Kn2-3.
Kp1 · Karst Plateaus
Fig. Kp1-6. Location. Geographic. Northern Dalmatia, Croatia Geologic. Cretaceous and Paleogene limestone in marginal zone of Alpine belt of continental terrane of African basement Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 63 000 Acquisition date. Not given Source. Personal archive Comments. A stereomodel pair from the classic karst region illustrates the control of doline shapes by the attitude of limestone bedding. Zones labelled “B” and emphasized by “S” are evidently aligned along an axis of gentle folding. Dolines in the “A” zone are more typically irregularly distributed, suggesting less disturbed strata. The isolated low hill mass “C” has a reduced doline density possibly due to a limestone type that is less susceptible to karstification. Elsewhere in the Dinaric zone relatively thick beds of flysch cover (marine sandstones, shales, marls and clays) impede karst development.
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Fig. Kp1-7. Location. Geographic. 22°04' E, 37°34' N, central Peloponnese, Greece Geologic. Parnassos Zone of Hellenides of continental terranes of African basement Vertical Airphoto/Image. Type. b/w, pan, stereo pair Scale. 1: 32 000 Acquisition date. 25 May 1960
Source. Journal Photo Interprétation, Editions ESKA Paris, 68-2, 2 Comments. This stereomodel shows a thrust sheet of Cretaceous karst limestone over W1 Eocene and Oligocene sedimentary rocks north of the town of Ipsous. The limestone surface is barren, while the slide area and the sedimentary rocks westward are fairly-densely vegetated. A Ms1.1 rock slide is on the scarp front.
Kp1 · Karst Plateaus
Fig. Kp1-8. (Caption on p. 218)
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Division 2 · Sedimentary Rocks and Duricrusts
Fig. Kp1-9.
Location. Geographic. 57°00' W, 51°30' N, south Labrador Geologic. Cambrian sediments of Foreland of Appalachian Orogen Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 53 000 Acquisition date. 16 July 1950 Source. Courtesy of Natural Resources Canada, NAPL LAB 77, 040, 041, 042 Comments. The stereomodel on the Strait of Belle Isle shows the photogeological contrast of Cambrian karst plateau rocks resting unconformably on PR Proterozoic granite gneisses of the Interior Magmatic Belt of the Shield Grenville Orogen. The plateau elevation in the photo is 180 m a.s.l. It lies 30 m above the gneisses and 150 m above the lake. Bedding traces are visible on the lake-facing scarp. Characteristic doline lakes are evident on the plateau surface. Northeast trending lineaments on the plateau are rock fracture traces, while the smaller north-south set are elongate bog-filled depressions produced by glacial scour of the last ice age which withdrew from the region 11 000 bp. Bc3 unit is glaciomarine deposit.
Location. Geographic. 03°30' E, 44°12' N, south central France Geologic. Regional basin in a Jurassic epicontinental sea Vertical Airphoto/Image. Type. b/w pan stereo triplet Scale. 1: 81 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. A stereomodel covers a 195-km2 area of the northeast margin of an extensive fault-bounded and MidTertiary uplifted plateau of Lower, Middle and Upper Jurassic carbonate sequences. As shown in Fig. Kp1-10 Landsat mosaic, the carbonates accumulated in a basin within the crystalline rocks of the French Central Hercynian Massif. The two lithotectonic terranes are distinctive morphologically and spectrally in the stereomodel. Spectrally the carbonates are bright due to a very low vegetation cover, while massive, metamorphic rocks are dark due to a dense scrub and forest cover. A number of structures and other carbonate rocks have been interpreted in the stereomodel. Oligocene tectonism produced several regional normal faults with throws of some 50 m, trending northnortheast. This relief has been attenuated by erosion but some lineaments associated with the faults are traceable. The only local areas of cultivable soil occur in Kn1 poljes (dolines structurally controlled by the faulting). Karstification of the plateau occurred in early Tertiary and Pliocene and 3–4 m of periglacially weathered (Zm1) limestone developed during Late Pleistocene. Numerous small dolines about 100 m in diameter are visible as the dark-toned dots, evidence of the terra rossa infill. Three carbonate lithologies are mappable in the model:
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Fig. Kp1-8.
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Kc2 Lower Jurassic marls are adjacent to the streams below the plateau Kc3 Mid Jurassic massive dolomites, occur as a limited darker-toned band within the karst limestones Kp1 main plateau-forming Upper Jurassic karst limestone The plateau surface, at 1 150 m a.s.l. is excessively droughty locally, even for a normally drainage-poor rock, due to the deeply entrenched major local streams which are at 600 m a.s.l. Figure Kc2-8 is in similar terrain 20 km to the north.
Kp1 · Karst Plateaus
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Fig. Kp1-10. Location. Geographic. 03°31' E, 44°12' N scene center, south-central France Geologic. Regional basin in a Jurassic epicontinental sea Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. Morphology and land cover clearly distinguish two lithotectonic suites on this image. Beige terrain is a near-barren Kp1 karst plateau. The dark zone in the center of the plateau is a 20 km2 area of afforestation which was in early stages in the 1979 photos. The adjacent dissected and green vegetated unit consists of Lower Paleozoic metamorphic rocks of a Hercynian massif. The inset frame locates the stereomodel of Fig. Kp1-9. The dark zone in the center is a 20-km2 area of afforestation which was in early stages in the 1979 photos.
Kp1 · Karst Plateaus
Fig. Kp1-11. Location. Geographic. 133°30' E, 01°30' S scene center, West Papua Indonesia Geologic. Central monocline of carbonates between high metamorphic rocks to the north and overlying clastic basinal sediments to the south Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1: 500 000 Acquisition date. Data Take 32–33, 14 November 1981 Source. USGS Comments. This radar scene covers an area of 674 km2 on the Vogelkop Peninsula (Jazirah Doberai). The radar image does not penetrate the forest canopy, it images the variation of the heights of treetops which mimick the geomorphology. The smooth appearing Kp1 Paleogene to Cretaceous continental shelf of the Australian-New Guinea landmass karst terrain with little surface drainage dips south from an elevation of 600 m a.s.l. to 300 m. The rugged terrain to the north is the Kemun Block of dissected Devonian and Silurian metamorphic rocks at elevations of 1 500 to 2 000 m. To the south the limestones dip beneath Plio-Pleistocene W1 clastic rocks on the Bintuni Basin. Although the contact line is drawn between Kp1 and W1 units to the south, at the image scale and radar response clastic and carbonate areas cannot be distinguished.
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Kp1.1
Division 2 · Sedimentary Rocks and Duricrusts
Kp1.1 – Corridored Plateaus
Karst plateaus on low resolution Landsat images display geomorphic Unit 19.1.
Characterization Geohazard Relations The corridored plateau is a morphological Variant of the karst plateau Kp1, distinguished from it by a surface that is marked by a system of linear solution along joints, faults and other fracture trace Unit 18 lines of weakness (tectonically controlled), or solution along bedding planes (stratigraphically controlled). Selective solution produces narrow, often discontinuous parallel trenches (corridors) generally oriented in the same direction. In Puerto Rico the trenches were noted to be up to 1 000 m long, ranging in width from a few centimetres to 3 m, and in depth from 1 to 4 m. Spacing is 5 to 10 m. Minor solution trenches, termed lapiez and karren, are only detectable on large-scale airphotos, but larger joint systems resolve well on photos of 1: 80 000.
See Geounit Kp1.
Select Bibliography Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Natural Resources Series no 6, Division of Water and Land Resources, CSIRO, Australia, p 67 Blair RW Jr (1986) Karst landforms and lakes. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 414–441 Demangeot J (1985) Nouvel atlas des formes du relief. Nathan, Paris, p 36 Monroe WH (1970) A glossary of karst terminology. USGS Water Supply Paper 1899, p 48–50 Williams PW (1966) Limestone pavements. Transactions, Institute of British Geographers, no 38, pp 155–172
Fig. Kp1.1-1. Source. La France par-dessus les toits (1972) Sélection du Reader’s Digest, Montreal, p 238 Comments. An air perspective view to the northwest at 04°21' E, 44°29' N shows a karst limestone surface marked by typical solution corridors on the Ardèche River at the Cirque de Chauzon north of Ruoms. The site is 70 km northwest of Avignon in the narrow Upper Jurassic Gras Plateau on the fault-bounded southeast margin of the Central Massif. The incision of the river results from a fall in baselevel in the Pliocene when the Mediterranean Sea was characterized by a sea level fall.
Kp1.1 · Corridored Plateaus
Fig. Kp1.1-2. Location. Geographic. 66°55' W, 18°20' N, northwest Puerto Rico Source. Monroe WH (1976) The karst landforms of Puerto Rico. USGS PP 899, p 48, fig 31
Comments. A 1:20 000 stereomodel taken in 1964, shows the classic pattern of solution along joints that characterizes a corridored plateau. Location is in Mio- and Oligocene limestone. This area is now forested by a reforestation project. See also Fig. Kp2-7.
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Fig. Kp1.1-3. (Caption on p. 226)
Kp1.1 · Corridored Plateaus
Fig. Kp1.1-4. (Caption on p. 226)
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Fig. Kp1.1-3. Location. Geographic. Chaine de Matheux, Central Haïti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. This stereomodel shows a density of linear solutional fracture traces on a Tertiary limestone plateau 20 km east-southeast of St. Marc. The locality is a 1 200 m high ridge. Dolines are red circles, possible fault lineaments are drawn near the top of the model.
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Fig. Kp1.1-4. Location. Geographic. 0°43' W,42°58' N, western Pyrénées, France/ Spain Geologic. Hercynian/Alpine tectogenic belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 80 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows a 215 km2 area of complex geology at the contact of the Mid-Paleozoic, Lower Devonian and Lower Carboniferous sedimentary rocks of the Axial Zone of the mountains with the stronglycorridored and barren Upper Cretaceous Arre Planère karst plateau of the Interior Sierras at 2 000 m a.s.l. The southwest sector of the model (lower left) is the Sierra Anabacardia in Spain. Prominent fracture traces are drawn in red.
Kp1.1 · Corridored Plateaus
Fig. Kp1.1-5. Location. Geographic. 108°E, 24°30' N scene center, southeastern China Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 29 December 1973 Source. USGS Comments. Landsat scene shows extensive occurrences of corridored limestone in striking spectral and spatial con-
trasts – tonality and morphology – with surrounding dissected Paleozoic sedimentary rocks. Structurally the scene is located in the Tien-Ch’-ien Kuei Platform of the greater South China Platform. These carbonates consist of a continuous age sequence from Devonian through Triassic with a cumulative thickness of 3 000 m. The present solution topography along the regional jointing developed during the Cenozoic. Pyramid karst terrain also occurs in this region, as shown in Fig. Kp2-3.
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Kp2
Division 2 · Sedimentary Rocks and Duricrusts
Kp2 – Pyramid-Labyrinth Karst Terrains
Select Bibliography
Characterization
Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Natural Resources Series no 6, Division of Water and Land Resources, CSIRO, Australia, pp 68–69 Brook GA, Ford DC (1978) The origin of labyrinth and tower karst and the climatic conditions necessary to their development. Nature 275(5680):493–496 Demangeot J (1985) Nouvel atlas des formes du relief. Nathan, Paris, p 38 Desaunettes JR (1977) Catalogue of landforms for Indonesia. AGL–TF–INS–44, Working paper no 13, FAO Trust Fund Ford JP, Cimino C, Elachi C (1983) Space Shuttle Columbia views the world with imaging radar: The SIR-A Experiment. NASA JPL Publication 82–95, pp 82–85 Loffler E (1974) Explanatory note to the geomorphological map of Papua New Guinea. CSIRO, Australia, p 12, plate 7 Monroe WH (1976) The karst landforms of Puerto Rico. USGS Professional Paper 899, p 37 Sweeting MM (1978) The landscape of one-seventh of China. The Geographical Magazine, March, pp 293–400 Verstappen HTh (1977). The use of aerial photographs in geomorphological mapping. ITC Textbook of Photo-Interpretation, vol VII, pp 148–154
Hilly forms predominate in the pyramid-labyrinth karst terrain, in contrast to the Kp1 karst plateau. These include conical rounded hills up to 150 m high, canyon-like labyrinths of deep intersecting solution trenches, and dissected isolated steep-sided tower-shaped hills 30 to 200 m high. These landforms are grouped as a single geounit because they have common karst geohazard relations, are typical of and often closely associated in warm, wet climatic regions, and are readily distinguished on airphotos and images. An added cause of intense karstification in such climates is vegetation cover. CO2 increases the dissolving potential of CaCO3 20 times over pure rain water.
Geohazard Relations See Geounit K3.
Fig. Kp2-1. Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Bleeker P (1983) Soils of Papua New Guinea. p 113, pl 7.3, © CSIRO 1983 Comments. A ground view of the classic morphology of Neogene pyramid karst terrain. Location is in the Southern Highlands Province of Papua New Guinea.
Fig. Kp2-2.
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Source. Verstappen HTh (1977) ITC Textbook of photointerpretation, vol. VII. Chapter 5 An atlas illustrating the use of aerial photographs in geomorphological mapping. International Institute for Aerial Surveys and Earth Sciences (ITC), The Netherlands, p 155, photo VIII-7 Comments. This air perspective view from 6 000 m shows pyramid-labyrinth karst terrain in Oligocene and early Miocene limestones in the Central Mountains of West Papua, Indonesia. The alignment of joints in the right half of the photo suggest elements of Kp1.1 corridored plateau.
Kp2 · Pyramid Labyrinth Karst Terrains
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Fig. Kp2-3. Source. Unattributed Comments. An air perspective view of pyramid karst terrain in the Mid to Upper Paleozoic structural TienCh’ien–Kuei Platform of Guangxi, in southeast China. The towers are about 200 m high. The satellite image of Fig. Kp1.1-5 shows the extensive occurrence of this geounit in the region.
Fig. Kp2-4.
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Location. Geographic. 124°15' E, 10° N, southern Philippines Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given Acquisition date. November 1951 Source. Personal archive Comments. The stereomodel of Tertiary/Quaternary pyramid/labyrinth karst is on Bohol Island.
Kp2 · Pyramid Labyrinth Karst Terrains
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Fig. Kp2-5. (Caption on p. 234)
Kp2 · Pyramid Labyrinth Karst Terrains
Fig. Kp2-6. (Caption on p. 234)
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Division 2 · Sedimentary Rocks and Duricrusts ▼
Fig. Kp2-5. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. Not given Source. Verstappen HTh (1977) ITC textbook of photointerpretation, vol. VII. Chapter 5 An atlas illustrating the use of aerial photographs in geomorphological mapping. International Institute for Aerial Surveys and Earth Sciences (ITC), The Netherlands, photo VIII-3 Comments. Stereomodel at 110°48' E, 08°10' S shows the morphology of pyramid (cone) karst terrain in Upper Miocene carbonates, and the tectonically disturbed drainage of the dry Giritontro River valley area on the southeast coast of Java Island, Indonesia. A 7.7 magnitude earthquake killed 700 people and displaced 74 000 others along this coast on 17 July 2006.
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Fig. Kp2-6. Location. Geographic. North central Jamaica Geologic. Paleogene carbonates of Nicaraguan Rise of the Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 15 March 1961 Source. Personal archive Comments. The stereomodel of pyramid karst morphology in the Jamaican “cockpit country” is marked by a set of strong parallel fracture traces expressing regional jointing or faulting.
Fig. Kp2-7.
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Location. Geographic. 60°26' W, 18°24' N, Puerto Rico Geologic. Greater Antilles Deformed Belt of the Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 12 February 1963 Source. Unspecified U.S. government agency Comments. The stereomodel depicts classic pyramid karst terrain in Miocene limestones at Manati near the north coast. The haystack hills average 30 m in height and they are locally surrounded by alluvial sands near the coast. North is to the right. Plantations at the north are sugar cane on a K3 karst plain.
Kp2 · Pyramid Labyrinth Karst Terrains
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Fig. Kp2-8. Location. Geographic. 124°18' E, 06°29' N image center, southern Philippines Vertical Airphoto/Image. Type. SIR-A 40 m resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. The fine textured surface of this local Neogene karst plateau in southwestern Mindanao of the magmatic island arc is the typical radar return of these little disturbed carbonate rocks in a humid tropical climate. The two northward draining streams are deeply incised in the plateau. The radar image does not penetrate the forest canopy, it images the variation of the heights of treetops which mimick the geomorphology. The surrounding mountainous terrain consists of Neogene calcalkaline intermediate to basic volcanic rocks. The abrupt contact on the east between the karst plateau and the mountainous terrain is suggestive of structural control from a fault about 15 km to the east but not detected on this image.
Kn1 · Poljes
Sub-group Kn Holokarst Erosional Terrains Kn1 – Poljes Characterization “The very diverse nature of poljes prevents a definition based on genesis; they are truly polygenetic features.” (Goudie et al. 1994). Morphologically, poljes are large, generally elongated, closed depressions aligned along structural trends, frequently along axes of folds, in areas of karst topography having a flat floor generally veneered by alluvium, and surrounded by steep walls of limestone. The wall boundaries of many poljes are controlled by faulting. Water drains into a polje from springs at the polje edge or from stream channels passing over marginal impermeable rocks. Water drains from a polje into stream sinks called ponors.
Fig. Kn1-1. Source. Selby MJ (1985) Earth’s changing surface. Clarendon Press, Oxford, p 312, fig 11.4, by permission of Oxford University Press Comments. Block diagrams illustrate the relation of structural poljes to faulting and folding. The structural features guide, but do not control, the erosion which is generally caused by laterally directed corrasion in these geounits.
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Geohazard Relations Many poljes are periodically inundated by floodwaters when rainfall and runoff exceed the capacity of the ponors to drain them. Flooding may also be increased by a rise of groundwater table, and the ponors then feed water into the temporary lakes of the polje floor (Selby 1985).
References Goudie A, Atkinson BW, Gregory KJ, Simmons IG, Stoddart RR, Sugden D (eds) (1994) The encyclopedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, p 394 Selby MJ (1985) Earth’s changing surface. Clarendon Press, Oxford, pp 311–313
Select Bibliography Blair RW Jr (1986) Karst landforms and lakes. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, p 422–423 Gams I (1969) Some morphological characteristics of the Dinaric karst. Geographical Journal 35:563–572 Machatschek F (1966) Geomorphology, 9th edn. American Elsevier, New York, pp 104–107
Kn1
Division 2 · Sedimentary Rocks and Duricrusts
Fig. Kn1-2.
Fig. Kn1-3.
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Location. Geographic. 14°38' E, 45°14' N, western Croatia Source. Unattributed Comments. A cultivated structured polje in folded Mesozoic carbonates of the Dinaric Alps. A fault wall boundary is visible on the left. Location is 3 km inland and parallel to the Adriatic coast 25 km southeast of Rijeka.
Location. Geographic. 25°28' E, 35°11' N, eastern Crete Geologic. Island arc of Alpine folding Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 2 August 1960 Source. Journal Photo Interprétation, Éditions ESKA, Paris, 68-2-5 Comments. A stereomodel in east Lassithi covers a 20-km2 structural polje in Mesozoic carbonates in an intermont basin. The Unit is sharply delimited by topography and land use. Periodic inundation is a characteristic of such poljes, so local villages (black circled) are located on the basin margins.
Fig. Kn1-4.
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Location. Geographic. Western Provence, France Geologic. Upper-Jurassic and Cretaceous carbonates folded by Paleogene Pyrenean movements Source. IGN – Photothèque Nationale, France (1956) Atlas des Formes du Relief. p 117 Comments. This is a cross-section of one of a series of regional structural poljes in Provence, the monoclinal Cuges polje 25 km east of Marseilles. This polje is also pictured in Figs. Kn1-5 and Kn1-6. The internally-drained limestone floor has a veneer of fluvial sediments, not shown in the section, that provides a local pump irrigated agricultural site amid surrounding bare hills.
Kn1 · Poljes
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Fig. Kn1-5. Source. Perceval A (date unknown) Documentation Française Comments. Air perspective view of Cuges polje in the Provence Alps of southern France, shown in the cross section Fig. Kn1-4 and stereomodel of Fig. Kn1-6. Vineyards constitute three quarters of the land use in the polje.
Fig. Kn1-6.
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Location. Geographic. 05°41' E, 43°15' N, Cuges, Basse Provence Geologic. Pyrenean-Provence Alpine structures Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 75 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. The Cuges Depression shown in this stereomodel is an 18-km2 intensely cultivated polje pictured in Fig. Kn1-5. It is one of three graben-like depressions in Lower Cretaceous carbonates aligned WSW–ENE conformably with the direction of local structures. The polje is bounded on the north by the south slopes of the regional Sainte-Baume thrust and on the south by the stepped scarps of the coastal Beausset synclinal structure as seen on satellite image Fig. 14-11. The N-S line locates the cross-section of Fig. Kn1-4.
Kn1 · Poljes
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Kn2
Division 2 · Sedimentary Rocks and Duricrusts
Kn2 – Fluviokarst Terrains
limestones, dolomitic, siliceous, e.g. Fig. Kn2-4, with less opportunity for deep circulation.
Characterization Geohazard Relations Fluviokarst terrain is developed in limestone areas by a combination of fluvial and karst processes resulting in gorges and dry valleys. A number of hypotheses exist to account for the formation of dry valleys:
The geohazard relations of fluviokarst terrains are similar to those of holokarst plateau Kp1.
Select Bibliography Normal erosion processes include: – Joint enlargement by solution – Cavern collapse – Cutting down by major through-flowing streams A marine hypothesis relates to base-level changes where streams are unadjusted to falling Pleistocene sea levels Paleoclimatic hypotheses include: – Erosion by glacial meltwater – Spring snowmelt under periglacial conditions – Run-off from impermeable permafrost
Demangeot J (1985) Nouvel atlas des formes du relief. Nathan, Paris, p 34 Goudie A, Atkinson BW, Gregory KJ, Simmons IG, Stoddart RR, Sugden D (eds) (1994) The encyclopedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, pp 157, 213 Selby MJ (1985) Earth’s changing surface. Clarendon Press, Oxford, pp 314–315 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphological mapping. Smits Publishers/ITC, The Hague, pp 217–219
Dry valleys result from loss of water into stream sinks as in Kn1 poljes. These are not exclusive to karst terrain. Parakarstic, they may also occur on chalk and on impure
Fig. Kn2-1. Location. Geographic. 01°37' E, 44°48' N, southwest France Source. LAR, September 1978 Comments. The view shows a sequence of platy, compact and massive Mid-Jurassic Dogger limestones in the 110 m deep gorge of the through-flowing Alzou River at Rocamadour on the Kp1 karst plateau of Causse Gramat. The gorge was incised at the time of a Pliocene epeirogeny and during the Würm (Wisconsinan) glaciation.
Fig. Kn2-2. Location. Geographic. 01°37' E, 44°48' N, southwest France Source. LAR, September 1978 Comments. This photo shows the infill of Würm alluvium in the Alzou River gorge of Fig. Kn2-1. Sloping platy facies of the limestone sequence are visible.
Fig. Kn2-3.
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Kn2 · Fluviokarst Terrains
Fig. Kn2-4.
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Location. Geographic. 01°32' 48'' E, 44°31' 20'' N, Quercy, southwest France Geologic. Upper Jurassic carbonates of Aquitaine Basin Source. Deffontaines P, Delamarre Mj-B (1962) Atlas Aérian, France, Tome III. Gallimard, p 132, photo 218 Comments. An air perspective view shows dry valleys with agricultural land use in a “causse” karst plateau at Le Barry, northeast of Cahors. The plateau surfaces are in scrub vegetation and some forest. See also Fig. Kp1-5.
Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 25 000 Acquisition date. May 1954 Source. Deffontaines P, Delamarre MJ-B (1962) Atlas Aérien, France, Tome IV. Gallimard, p 83, photo 108 Comments. This fragment of an airphoto is an example of a parakarst valley. It shows 4 km of a 100 m wide slightly entrenched valley occupied by dark humid meadows, in siliceous Oligocene limestone 60 km south of Paris.
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Fig. Kn2-5. Location. Geographic. 01°43' W, 51°46' N, Gloucestershire, England Geologic. Mid Jurassic limestones of the Scarplands Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 22 October 1963 Source. Journal Photo Interprétation, Editions ESKA, Paris, 65-1-4 Comments. A stereomodel of fluviokarst terrain is characterized by a dry valley and some tributaries at Eastleach in the Cotswolds. North is at the bottom of the model.
Fig. Kn2-6.
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Location. Geographic. 02°18' E, 43°32' N, inland Languedoc Geologic. Upper Eocene carbonates of southeastern extremity of Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1971 Source. IGN – Photothèque Nationale, France Comments. The stereomodel at La Brugière 9 km south of Castres shows a system of dry valleys on a Kp1 karst plateau east of the river Agout Valley. A partly vegetated military reservation extends across the plateau as a broadening rectangle. An airstrip is also visible on the limestone. Note the contrast in land use between the dry karst and the S1.2 molassic terrain south of the river.
Kn2 · Fluviokarst Terrains
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Sub-group Kc Amorphous Carbonates Kc2
Kc2 – Chalk and Marl Characterization Chalk is a mechanically weak, soft, fine-grained, porous (20 to 50% vs. 5% in limestone) and poorly indurated variety of limestone. Solution features develop but on a smaller scale than in strong limestone. Solution spreads uniformly throughout the rock mass because water transmits through the porous body of the rock rather than along fracture-controlled solution channels. Chalk, though soft is cohesive and forms vertical escarpments in outcrop. Seepage generally dries up the few valleys. Stable cutting slopes range from 45° to 80°. Where chalk adjoins karst limestone in agricultural regions, the boundary between them can often be drawn on the basis of associated land uses and land covers alone as seen in airphotos and satellite images. Chalk surfaces are rather smooth with incised flatbottomed steep-sided gullies. Marl is a S2 mudstone with significant calcite content. In contrast to chalk marls do not have sharp breaks in slope at gully margins. The morphology is typically rounded hills in humid regions, with steep dissecting slopes in arid and humid tropical regions.
Geohazard Relations Small solution depressions are caused by settlement of the overlying material into solution cavities in the chalk below, as in karst limestone. Layers of insoluble siliceous nodules (flint) occur locally along bedding planes in some chalk sequences.Water traverses the chalk along these bands causing differential weathering. Uplifted chalk strata underlain by impervious rock occur in coastal cliffs. Pore water pressure at potential slip surfaces at cliff tops will provoke small subsidences which develop into large rock falls Mv1. The geohazard relations of marls are similar to those of S2 siltstones and lutites.
Select Bibliography Blyth FGH, de Freitas MH (1976) A geology for engineers, 7th edn. Edward Arnold, London, pp 190–191, 193, 395–396 Drury SA (1986) Remote sensing of geological structure in temperate agricultural terrains. Geol Mag (GB) 123(2):113–121 Dumbleton MJ, West G (1970) On air-photograph interpretation for road engineers in Britain. RRL Report LR 369, Min. of Transport, pl. 5–6 Higginbottom IE (1966) The engineering geology of chalk. Proceedings, Symposium on Chalk in Earthworks and Foundations. Inst. of Civil Engineers, London Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 8–7, 38–3, 40–6 Parsons AW (1967) Earthworks in soft chalk. A study of some factors affecting construction. RRL Report LR 112, Ministry of Transport Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London
Fig. Kc2-1. Geographic. 06°37' E, 44°10' N, southeast France Source. Ricou (1975) Découvrir la France, no 63, 64. Larousse Comments. The photo shows typical erosion morphology of monoclinal soft carbonates in a humid climate. The strata are Lower Cretaceous of the southern SubAlpine chain at Colmars in the upper Verdon Valley. A recent Ms1 down-dip rock slide is in the lower left of the photo.
Kc2 · Chalk and Marl
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Fig. Kc2-2.
Fig. Kc2-3.
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Location. Geographic. Southern Apennines, Italy Source. Touring Club Italiano (undated) Comments. This photo shows the locally named “calanchi” terrain of differential weathering in Pliocene chalk and marl in the hill lands of the Bradano Trough on the Gulf of Taranto.
Location. Geographic. 09°58' E, 33°32' N, southern Tunisia Source. Unattributed Comments. The photo illustrates the relative ease of excavation of soft carbonate rocks with a minimum of mechanical equipment. This is one of over 700 “troglodyte” dwellings of Matmata at the north end of the cuesta-like Ksour Plateau (Jebel Dahar). The plateau consists of interbedded Upper Cretaceous (Turonian) marls and limestones. Numbers of these dwellings are now uninhabited. Figure S1.5-1 shows similar dwellings in weak sandstones in Spain.
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Fig. Kc2-4. Location. Geographic. 01°36' E, 45°00' N, Périgord Geologic. Southeastern Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Source. IGN – Photothèque Nationale, France Comments. A segment of a photo illustrates the distinction, based essentially on associated land uses and land covers, between two flat-lying Jurassic carbonate rocks in a west European context. The light-toned area of agricultural fields consists of Mid-Jurassic (Dogger) marls at 230 m elevation. The darker area is dominantly forested with some bright, mainly pasture, fields, frequently associated with solutional depressions. It is part of the Kp1 Causse Martel Plateau of Upper Jurassic (Malm) karstic limestone at Cazillac, at an elevation ranging from 240 to 300 m.
Fig. Kc2-5.
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Location. Geographic. 03°27' W, 40°07' N, central Spain Geologic. New Castile Basin on Hercynian basement Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1:40 000 approx. Acquisition date. Not given Source. Personal archive Comments. The photo of an area 40 km southeast of Madrid shows the morphological and land use contrasts of compact and weak carbonates of Miocene age. The uniform area to the left, south of the town of Chinchon, consists of K1 strong coeval lacustrine limestone. The delineated, densely cultivated areas are exposures of the weaker underlying calcareous and gypsiferous marls. North is at the bottom of the photo.
Kc2 · Chalk and Marl
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Fig. Kc2-6. Location. Geographic. 119°25' E, 09°30' S, eastern Indonesia Vertical Airphoto/Image. Type. b/w pan, single photo Scale. 1: 40 000 Acquisition date. Not given Source. Verstappen HTh (1983) Applied geomorphology. Elsevier, p 37, fig 3.6 Comments. This photo shows the intense dissection characteristic of soft carbonates in a tropical environment. The rocks are Upper Miocene and Pliocene shallow marine and non-marine chalk and marls on the volcanic arc aberrant non-volcanic Sumba Island. The island has a dry season from May to November and a wet season from December to April.
Fig. Kc2-7.
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Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 33 000 Acquisition date. Not given Source. Verstappen HTh (1977) ITC textbook of photointerpretation, vol. VII. Chapter 5 An atlas illustrating the use of aerial photographs in geomorphological mapping. International Institute for Aerial Surveys and Earth Sciences (ITC), The Netherlands, photo III-4 Comments. Stereomodel at 0°44' W, 41°26' N shows the intense dissection of weak, sub-horizontal Miocene marls and gypsum 20 km southeast of Zaragoza in the sediments of the dry climate of the Ebro Basin in northeastern Spain. The dissection dates from climatic fluctuations in the Pleistocene and is no longer active. The Ebro is Spain’s largest basin, 350 km long by 160 km wide. It lies as an extensive plateau 180 to 300 m a.s.l., largely infilled by sediments eroded from the Pyrenees. North is to the right. See also Fig. Kc2-10.
Kc2 · Chalk and Marl
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Kc2 · Chalk and Marl ▼
Fig. Kc2-8. Location. Geographic. 03°30' E, 44°30' N, Causse Sauveterre Geologic. Regional basin in a Jurassic epicontinental sea Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 65 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. Carbonate rocks of two Sub-groups are pictured in this stereomodel. The southward-sloping cultivated Gévaudan Plateau north of the town of Mende is at the northern margin of the Grandes Causses Basin where it contacts with micaschists, labelled J3.2, of the southern extremity of the Massif Central. The area consists of Lower Jurassic chalky carbonates. Its fluvially eroded mass is in contrast to the massive partly forested, Upper Jurassic less agriculturally attractive partly forested Kp1 karst plateau which is continued in Fig. Kp1-9 20 km to the south.
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Fig. Kc2-9. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 800 000 Acquisition date. Not given Source. USGS Comments. This Landsat mosaic of part of the eastern Paris Basin is dominated by the bright 60–70 km wide belt of the Upper Cretaceous stratigraphic chalk cuesta of Champagne. The delineated portion extends through 360 km of outcrop from Sens on the Yonne River in the south to 25 km below Amiens on the Somme River in the north. The cuesta altitude rises from 75 m a.s.l. at the foot of the Ile de France Escarpment on the west to 200 m at its eastern rim which is 40–50 m above the underlying Lower Cretaceous shales of the Argonne Valley.
The relatively bare appearing porous chalk has a cover of shallow rendzina-type lithosols that have been persistently enriched with commercial fertilizers. Land uses are cereals, fodder crops and some field crops. The three dark patches are partly afforested military reservations and training grounds. On the west are agricultural and forest lands of Lower Tertiary marls, clays, sandstones and limestones of Beauce, Brie and Valois regions. The chalk cuesta is crossed by the dark, 1 km broad trenches of the Seine, Aube and Marne River valleys. These were eroded during Pleistocene times when their volume was much greater. The essential shortage of water on the chalk has local settlements located in these valleys at the spring line at the foot of the chalk bluffs.
Kc2 · Chalk and Marl
Fig. Kc2-10. (Caption on p. 256)
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Fig. Kc2-10.
Location. Geographic. 01°W, 41°30' N, northeast Spain Geologic. Ebro Tertiary molassic Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 28 July 1956 Source. van Zuidan RA, van Zuidam-Cancelado FI (1978–1979) ITC textbook of photo-interpretation, vol VII. Use of aerial detection in geomorphology and geographical landscape analysis. Chapter 6: Terrain analysis and classification using aerial photographs. A geomorphological approach. International Institute for Aerial Surveys and Earth Sciences (ITC), The Netherlands, stereomodel XVII Comments. The stereomodel shows the dissected edge of a plateau of W4 Miocene marls and gypsum at Muel on the Rio Huerva, 20 km south of Zaragoza. Fu2.1 indicates a piedmont apron of large coalesced alluvial fans of the Llanos de la Plana. Arrays of soil and water retention terraces are visible in the larger gullies. See also Fig. Kc2-7.
Kc4 · Interbedded Carbonates
Kc4 – Interbedded Carbonates
Kc4
Characterization Interbedded carbonates constitute photomorphologically mappable flat-lying sequences which are composed of beds greater than 8 m in thickness. Thinly bedded sequences provide comparatively little morphologic evidence of their occurrence particularly in humid climates. Contour-like scarp outcropping of resistant limestone alternates with the more gradual slopes of weaker marls. The resistant-weak stair-like outcrop patterns are generally similar to those of interbedded sedimentary rocks W1, including detrital arenites and shales. The morphology of the unit is typically emphasized by vegetation or tonal-colour associations and differences as seen on airphotos and satellite images.
Geohazard Relations The main geohazards in this unit are related to the loss of support of resistant limestone beds underlain by weak marls leading to falls Mv1, slides Ms1 and slumps Ms3. Deep cuts in the sequences intersecting weak beds are a source of landslides in engineering work. Stratigraphic conformities-unconformities at litholigic contacts are of relatively little concern as geohazards.
Select Bibliography
Fig. Kc4-1.
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Ehlen J (1981) The identification of rock types in an arid region by air photo patterns. U.S. Army Corps of Engineers, Engineer Topographic Labs., Report ETL–0261, p 27 Glennie KW (2005) The geology of the Oman Mountains, 2nd ed. Scientific Press Gupta RP (1991) Remote sensing geology. Springer-Verlag, Berlin, pp 255–256 Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS Professional Paper 373, fig 61, p 112, 113; fig 77, p 144, 145; fig 78, p 146, 147 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC, The Hague, pp 130–131 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 166–167
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Location. Geographic. 01°21' W, 43°23' N, Southwest France Geologic. Southwest extremity of Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. 1977 Source. IGN – Photothèque Nationale, France Comments. This stereomodel in Basse Pyrénée Department shows a sequence of interbedded Upper Cretaceous limestones, marls and some conglomerates strongly dissected by Pyrenean tectonics to the south. Bedding traces are not evident. The roadways and tracks in the district 15 km southeast of Bayonne are located on interfluves as favourable construction routes. This area is being increasingly cleared for agriculture.
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Fig. Kc4-1. (Caption on p. 257)
Kc4 · Interbedded Carbonates
Fig. Kc4-2. Location. Geographic. 56° 04' E, 25° 47' N, northern Oman Geologic. Mid to Late Tertiary orogeny of Mesozoic sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 9 June 1968 Source. Journal Photo Interprétation, Editions ESKA, Paris, 68-5-4
Comments. This stereomodel in the Musandam Peninsula (Ruus al Jibal) shows an intricately dissected and clearly interbedded sequence of weak and resistant carbonate shelf sediment formations of the Mesozoic Hajar Supergroup. These strata are traversed by an Fv1 wadi system. Some Unit 18 fracture traces are drawn. The peninsula’s location is the north end of the Oman Mountains which were raised by horizontal compression and thrusting of plate collision tectonics, including a nappe of ophiolites from the Eurasian continent across the Gulf of Oman.
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Fig. Kc4-3. Location. Geographic. 24°52' E, 35°14' N, central Crete Geologic. Island arc of Alpine folding Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 53 000 Acquisition date. 2 August 1960 Source. Journal Photo Interprétation, Editions ESKA, Paris, 68-2-1 Comments. The stereomodel northeast of Mount Ida (Psiloritis) provides a comparative model of three distinct Mesozoic carbonate geounits. Kc4 in the upper half of the model is a unit of interbedded limestone and marls and has a well-integrated drainage system. A segment of this unit shows evidence of disturbance. Kp1 is typical karst plateau with no surface drainage and numerous locally agriculturally valuable accumulations of terra rossa infilling the sinkholes. Kc3 is a dolomitic massif.
Kc4 · Interbedded Carbonates
Fig. Kc4-4. Location. Geographic. 46°37' E, 23°25' N image center, central Saudi Arabia Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 335 000 Acquisition date. 14 February 1985
Source. USGS Comments. A Landsat subscene shows the differential erosion of interbedded Jurassic limestone and marl at Hillah in the western ridges of the Jebel Tuwaiq cuestas. The red circles in the south part of the image are areas of central pivot irrigation in the local valleys.
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Group H Saline and Phosphatic Rocks H1 – Cemented Evaporites Characterization Outcrops of evaporite rocks other than Geostructure Unit 11 are comparatively rare. They vary from flat to undulating to irregular hummocky terrain of plains or low plateaus with depressions. Extensive subsurface occurrences of recrystallized evaporites of most Phanerozoic ages are the deposits that primarily produce the related features and conditions in overlying rocks and surficial deposits that are detectable on airphotos and satellite images. The following descriptions are from Martinez et al. (1998). “Evaporite deposits form when various salts precipitate from evaporating water, mainly seawater. The principal evaporite rocks include gypsum (or anhydrite, its anhydrous form) and salt (halite), although potash and other rarer salts are locally important. Evaporites have the highest solubility of common rocks – gypsum and salt are, respectively, about 150 and 7 500 times more soluble than limestone.” When percolating fresh groundwater encounters salt beds “dissolution of the salt forms brines and also creates underground cavities into which the overlying rock settles or collapses.” Modern evaporites are Bt1e sabkhas that occur in coastal lagoons and L2 inland playas and have efflorescent crusts. Hydrycarbon accumulations occur in many ancient evaporite-related basins.
Fig. H1-1.
The high solubilities of evaporites “enable subsurface dissolution channels and sinkholes to form in a matter of only days, weeks or years, and catastrophic collapse can result.” (Martinez JD et al. 1998). “The mining of rock salt, or the drilling of boreholes into or through rock salt have accidentally created a number of large, man-made sinkholes. Regardless of their origin, sinkholes in evaporites pose significant hazards and are costly to society – Industrial development, transportation and human habitation are all constrained by the presence of such features.”
Reference Martinez JD, Johnson KS, Neal JT (1998) Sinkholes in evaporite rocks. American Scientist 86:38–51
Select Bibliography Bell FG (1981) Geotechnical properties of some evaporitic rocks. IAEG Bull 24:137–144 Dean WE, Johnson KS (eds) (1989) Anhydrite deposits of the United States and characteristics of anhydrite important for storage of radioactive wastes. USGS Bull 1794 Johnson KS, Neal JT (coordinators) (1997) Symposium, evaporite karst: Origins, processes, landforms, examples, and impacts. Carbonates and Evaporites 12:1–116 Martinez JD (1971) Environmental significance of salt. AAPG Bull 55:810–825 Neal JT (1994) Surface features indicative of subsurface evaporite dissolution: Implications for storage and mining. Solution Mining Research Institute, Annual Meeting, Houston, 25 April 1994 Warren JK (2006) Evaporites: Sediments. Resources & Hydrocarbons, Springer-Verlag
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H1
Geohazard Relations
Location. Geographic. 68°32' W, 17°15' S, western Bolivia Geologic. Altiplano of central Andes Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 14 June 1955 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 62
Comments. The stereomodel shows Tertiary and Quaternary gypsum and shale in the glaciomarine lake Tauca basin 75 km southeast of residual Lake Titicaca. The solution pitting is diagnostic and the water in the pits is an indicator of local groundwater conditions; this terrain is uncultivated. The cultivated surface to the north is in unpitted shales. This figure is 50 km west of Fig. L1-7. See also Figs. Mv5-5 and L1-2.
H1 · Cemented Evaporites
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Fig. H1-2.
Fig. H1-3.
Location. Geographic. 07°54' E, 34°22' N, central Tunisia Geologic. Tunisian Atlas Foreland Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 28 October 1952 Source. Journal Photo Interprétation, Editions ESKA, Paris, 63-6, 2 Comments. Stereomodel of a barren anticlinal Mid-Cretaceous gypsum unit at Tamerza on the Wadi Khanga on the Algerian border 90 km west of Gafsa. The unit is readily distinguishable from the adjacent Kc2 marls by its characteristic morphology darker toned and more intense dissection. S1.5-T are tilted detrital rocks. Part of a large Fu1 alluvial fan is at the bottom of the photo.
Location. Geographic. 84°55' W, 76°35' N, S Ellesmere Island, Nunavut Geologic. Franklinian Mobile Belt Platform of the Queen Elizabeth Islands Subplate Vertical Airphoto/Image. Type. Natural colour, stereo triplet Scale. 1: 20 000 Acquisition date. Unspecified Source. Courtesy of Natural Resources Canada, NAPL 3100, 166-167-168. Comments. The recessive slope outlined in red in this stereo-model at South Cape Fjord consists of a formation of 350 m of weak Ordovician gypsum, anhydrite and limestone underlying a cap of K1 resistant Ordovician carbonates. A characteristic Ms3 rock slump within the Unit formation is delineated. See also Fig. Fu1/Mv1.2-4.
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Group S Detrital Rocks Characterization
S1.2
Detrital, or clastic, rocks are the most common rocks exposed at the Earth’s surface. They are formed from grains of river, desert or marine origin broken from preexisting rocks. The particles are released by weathering, physically eroded, mechanically transported by gravity, principally by running water and wind, and ultimately deposited in units lithified by cementation by minerals precipitated in the interstices between grains. The particles are mechanically well sorted by long travel distance, or poorly sorted by short travel distances, and are classified mainly on the basis of size:
Boulder: Cobble: Gravel: Sand: Silt: Clay:
256 mm 64 mm 4 mm 2 mm 0.06 mm <0.004 mm
The products of consolidation of cobbles, gravels and sands are S1 rudites and arenites (conglomerates and sandstones); units composed of silts and clays are S2 siltstones and lutites (shales and mudstones).
Geohazard Relations The detrital rocks that are related to geohazards are poorly cemented rudites and arenites which are susceptible to debris slides and rockfalls, while siltstones and lutites are susceptible to sliding and slumping.
Select Bibliography General Murray JW (1981) A guide to classification in geology. John Wiley & Sons, pp 14–24 Pettijohn FJ, Potter PE (1964) Atlas and glossary of primary sedimentary structures. Springer-Verlag, Berlin, plates 5B, 6B, 9B, 10A, 10B, 11A, 11B, 19B, 30B Waltham T (2002) Foundations of engineering geology. Spon Press, p 9, p 48
Airphoto Interpretation Allum JAE (1966) Photogeology and regional mapping. Pergamon Press, p 55 Drury SA (1987) Image interpretation in geology. Allen & Unwin, pp 73–78 Ehlen J (1981) The identification of rock types in an arid region by air photo patterns. U.S. Army Corps of Engineers, Engineering Topographic Laboratories Report ETL-0261, p 15
Mainguet M (1972) Le Modelé des Grès. Études de Photo Interprétation. IGN, 2 vols, pp 1–657 Mekel JFM (1970) ITC textbook of photo-interpretation, vol VIII: Use of aerial photographs in geology and engineering. Institute for Aerial Survey and Earth Sciences, pp 13–15 Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS Professional Paper 373, p 16 and figs 42, 49, 62, 63, 79, 91 ,92 van Zuidam RA (1985/1986) Aerial photo interpretation in terrain analysis and geomorphological mapping. ITC/Smits Publishers, the Hague, pp 123–125 von Bandat HF (1962) Aergeology. Gulf Publishing Company, pp 91–104
S1.2 – Weak Rudites-Arenites, Upland Facies Characterization Units of this Variant consist mainly of coarse and medium sands that have a matrix and may or may not have a cement. They are associated with areas of active tectonic processes, rapid uplift, intense erosion and tend to be extremely thick successions of conglomerate, sandstone, flysch and turbidites in marine deposits. These tecto facies termed molasse occur in foreland basins north of the European Alps. Their unconfined compressive strength is low, 0.5–20 Mpa, and they are sensitive to changes in moisture content, compressive strengths are greatly reduced at saturation. Morphologically occurrences of this Variant appear as fluvially dissected hills with many narrow ridges and relatively steep gullies and valleys.
Geohazard Relations Sheet and gully erosion can provoke Mv1 rockfalls and Ms1 slides. In cold climates erosion can be by frost wedging of fractures on slopes and scarps. Headward erosion and scarp collapse on these hills threaten any hilltop structures. Molasse is susceptible to large scale bedrock failures and debris slides involving weathered blocky bedrock.
Select Bibliography Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Natural Resources Series no 6, Division of Water and Land Resources, CSIRO, Australia, pp 54–55, 58 Blake DH, Paijmans K, McAlpine JR, Saunders JC (1973) Landform types and vegetation of eastern Papua. CSIRO Land Research Series no 32, plate 13, fig 1 Cordova EV (1992) La fotografia aerea y su aplicacion a estudios geologicos y geomorfologicocs, Tomo II. Universidad Mayor de San Andres stereo models, 10, 41, 96, 100, 101
S1.2 · Weak Rudites Arenites, Upland Facies Desaunettes JR (1977) Catalogue of landforms of Indonesia. FAO, Trust Fund of the Government of Indonesia, stereogram no 9 Dobereiner L, Oliveira R (1986) Site investigations on weak sandstones. Proceedings, 5th International IAEG Congress, 2.1.2, pp 411–421 Everett JR, Morisawa M, Short NM (1986) In: Short NM, Blair RW Jr (eds) Geomorphology from Space. NASA SP 486, plate T-46, pp 134–135
Fig. S1.2-1. Location. Geographic. 07°43' E, 46°43' N, central Switzerland Source. LAR, September 1976 Comments. Photo at a road cut in Oligocene molasse from the Wildhorn Helvetic Nappes on the east shore of Lake Thun. The exposure shows a flysch deposit of large conglomerate clasts in a matrix of clays. The hand on the right provides scale.
Mainguet M (1972) Le Modelé des Grès, Études de Photo-Interprétation. IGN, Paris, pp 13–26 Scholle PA (1979) A colour illustrated guide to constituents, textures, cements and porosities of sandstones and associated rocks. AAPG Memoir 28 van Houten FB (1973) Meaning of molasse. GSA Bull 84:1973–1976 Verstappen HTh (1983) Applied geomorphology. Elsevier Scientific Publishing Co., NY, pp 153–154
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Fig. S1.2-2. Location. Geographic. 16°14' E, 40°18' N, southern Italy Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 17 000 Acquisition date. Not given Source. Verstappen HTh (1983) Applied geomorphology. Elsevier, p 168, fig 7.25 Comments. A stereomodel shows the site of the town of Aliano in the southern Apennine Lucanian Upland of Basilicata. The local lithology consists of fine Upper Tertiary sandstones. The strongly dissected badland relief, known regionally as calanche, is widespread in bare weak sediments in a dry climate. The erosion in these badlands is enhanced by a system of intersecting small faults which govern the growth of deep ravines. These are now endangering the townsite.
S1.2 · Weak Rudites Arenites, Upland Facies
Fig. S1.2-3. (Caption on p. 270)
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Fig. S1.2-3. Location. Geographic. 64°56' W, 19°05' S, southern Bolivia Geologic. Central Andes Cordillera Oriental Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 29 May 1963 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 16 Comments. This stereomodel shows strongly dissected Tertiary conglomerates lying in a probably down-faulted basin of Paleozoic arenites northeast of Tarabuco. W3 is an area of relatively resistant interbedded sedimentary rocks. North is on the left of the model.
Fig. S1.2-4. Location. Geographic. 04°03' W, 40°19' N, south central Spain Geologic. New Castile Basin on Hercynian basement Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 30 000 Acquisition date. September 1956 Source. Personal archive Comments. The stereomodel and accompanying profile show the erosional morphology of Miocene argillaceous sandstones. In this semi-arid climate the surface strata become saturated with water in the rainy season, and intensely hardened in the dry season. Mechanical analysis shows 30% silt and clay in the A/B pedological horizon and 37% in the B horizon. The clays also contain fine seams of calcium carbonate.
S1.2 · Weak Rudites Arenites, Upland Facies
Fig. S1.2-5. Location. Geographic. 01°55' E, 43°10' N, Haut-Languedoc, southern France Geologic. Southeast Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 23 May 1953 Source. Journal Photo Interprétation, Editions ESKA, Paris, 63-2-3
Comments. The stereomodel shows typical dissection of weakly cemented sedimentary rocks. This is a sequence of clearly interbedded flat-lying Oligocene sandstones. The area is at the western extremity of the same structural basin as Fig. S1.5-4 near the Mediterranean 100 km to the northeast. It lies 25 km southeast of the Col de Naurouze which, at 190 m elevation, forms the watershed between the Bay of Biscay and the Mediterranean. The principal lowlands and valley-fill alluvial deposits are delineated.
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Fig. S1.2-6. Location. Geographic. 72°03' E, 33°06' N scene center, north Pakistan Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 13 December 1976 Source. USGS Comments. Two areas of weak Miocene and Pliocene molassic sandstones are delineated on this Landsat scene of the Potwar Uplands.
The northern area is characterized by broad folds and lies just south of the west Himalayan foothill ridges of the Safed Kohat range. The southern area is a plateau with the fractional code Et1/S1.2 to indicate that it is overlain by a veneer of loess sediments. The plateau is bounded on the southeast by the compact folded Salt Range. The fluvial dissection of this area is enhanced by its topographic site which is 300 m higher than the adjacent lowlands. The red strike-slip faults of the horseshoe shaped Surghar anticline in the south center of the scene are described in Fig. 13-6.
S1.2 · Weak Rudites Arenites, Upland Facies
Fig. S1.2-7. Location. Geographic. 149°50' E, 09°59' S, southeast Papua New Guinea Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 100 000 Acquisition date. Not given Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Blake DH et al. (1973) Landform types and vegetation of Eastern Papua. Land Research Series no 32, upper Fig 1, pl 13, lower Fig 2, pl 22, © CSIRO 1973
Comments. This stereomodel and low air perspective view show the landform of chemically immaturely-weathered, steep-sided knife-edge ridges and V-shaped valleys in moderately-dipping, Upper Tertiary, poorly consolidated conglomerates and sandstones, coded ZSv in the model. Area FSt is a Fu1 alluvial fan-delta. The locality is at Raba Raba Village on Goodenough Bay south of Cape Vogel. The vegetation is a mosaic of grassland and seasonal Hopea and Araucaria rainforest climate. Compare this model with that of mechanically-weathered arenites in an arid climate in Fig. 18-5.
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S1.2 · Weak Rudites Arenites, Upland Facies ▼
Fig. S1.2-8. Location. Geographic. 82°35' W, 38°25' N, image center, West Virginia Geologic. Allegheny Plateau of Acadian Appalachian Highlands Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 600 000 Acquisition date. 12 February 1976 Source. USGS Comments. This Landsat image covers 12 500 km2 of dissected flat-lying Mid and Lower Carboniferous sandstones, shales and minor limestone, easily eroded in a humid temperate climate. Interbedding is not evident. Regional elevations range from 320 to 420 m on the Ohio and West Virginia sides of the Ohio River. The broad wavy band on the right is the 200 m broad Tertiary Teays paleovalley, now filled with Mid-Pleistocene glacial and postglacial deposits. The area is largely forested with the exception of the Teays Valley which is densely developed as mainly residential land use.
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S1.5 – Weak Rudites-Arenites, Lowland Facies
Select Bibliography
Characterization
Demangeot J (1985) Nouvel atlas des formes du relief. Nathan, Paris, p 31 Dobereiner L, Oliveira R (1986) Site investigations on weak sandstones. In Proceedings, 5th International IAEG Congress, 2.1.2, pp 411–421 Scholle PA (1979) A colour illustrated guide to constituents, textures, cements and porosities of sandstones and associated rocks. AAPG Memoir 28 Tozer ET, Thorsteinsson R (1964) Western Queen Elizabeth Islands, Arctic Archipelago. GSC Memoir 332, pp 167–171 Vincent JS (1983) La Géologie du Quaternaire et la Géomorphologie de l’ile Banks, Arctique Canadien. GSC Memoir 405, pp 13–14 Williams RBG, Robinson DA (1981) Weathering of sandstone by the combined action of frost and salts. Earth Surface Processes, vol. 6, pp 1–9
This Variant is morphologically a dissected plain in distinction from Variant S1.2 upland facies. The morphology is relatively more subduced. Weakness is generally due to the degree and nature of cementation, e.g. carbonate cements rather than silica or iron compounds.
Geohazard Relations The lowland facies is specifically susceptible to Ms1 slides and Ms3 slumps which are relatively common.
Fig. S1.5-1. Source. Unattributed Comments. The low ground in this photo with excavated dwellings near Guadix consists of weak Paleogene argillaceous sandstones in a foothill steppe zone of the Baetic Cordillera of Andalusia in southern Spain. The dissected hills are probably a sequence of Mesozoic limestones. Figure Kc2-3 shows similar dwellings fashioned in marls in Tunisia.
Fig. S1.5-2. Location. Geographic. 121°22' W, 76°19' N, Arctic Archipelago Source. Tozer ET, Thorsteinsson R (1964) Western Queen Elizabeth Islands, Arctic Archipelago. GSC Memoir 332, p 202, pl LV. Courtesy of Natural Resources Canada, Geological Survey of Canada Comments. An air view northwestward from 6 000 m altitude across the Arctic Coastal Plain of southern Prince Patrick Island. The materials are poorly lithified to unconsolidated alluvial coarse-grained quartzose sandstones with some conglomerate seams of the Miocene Beaufort Formation. The fluvial dissection probably relates to a concurrence of the weak sediments, a permafrost table close to surface, and local gelifluction. Glacial deposits are sparse due to the regional predominance of cold based Pleistocene glacier systems, see Fig. S1.5-3.
S1.5 · Weak Rudites Arenites, Lowland Facies
Fig. S1.5-3.
Fig. S1.5-4.
patches within mainly unconsolidated rock. The hill in the center, Castel Butte, is capped by the arenites. The surface deposits in the photos consist of colluvial sand derived from physical disaggregation of the bedrock, to a depth of several meters, which greatly exceeds the present thickness of the active permafrost layer. As in the Miocene sandstones of Fig. S1.5-2, the drainage pattern probably reflects the impermeability of the underlying permafrost. These islands were hypothetically glaciated by a “Innuitian” ice sheet (9 ka) but glacial deposits are sparse. (As late as 1989 glacial deposits were unmapped on this and neighbouring islands.) The absence of relatively fresh, or even any, glacial landforms in the central and western islands was explained as being due to a cold thermal regime at the base of the ice sheet.
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Location. Geographic. 111°25' W, 77°40' N, Queen Elisabeth Islands, Arctic Archipelago Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 60 000 Acquisition date. 16 August 1960 Source. Courtesy of Natural Resources Canada, NAPL A17242, 28, 29 Comments. Stereomodel shows variably-cemented Lower Cretaceous coarse-grained sandstones and conglomerates of the Innuitian Sverdrup Basin on Mackenzie King Island. Local elevation is ≈ 150 m. The formation (Isachsen) consists of hard and soft facies with the hard occurring as irregularly distributed
Location. Geographic. 03°14' E, 43°24' N, Languedoc Geologic. Piedmont sediments of Central Massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1974 Source. IGN – Photothèque Nationale, France Comments. The vineyard-covered terrain on either side of the terraced Libron River 5 km north of Béziers in this
stereomodel consists of moderately dissected poorly-cemented Pliocene sands and gravels at the foot of the southern edge of the Central Massif. The location is on the northern margin of an extensive depo basin depicted in the Landsat subscene of Fig. S1.5-8. The dark strip of land adjacent to the valley covered in scrub vegetation appears to be too dissected for current agricultural practices. Figure S1.2-5 depicts similar sediments at the western extremity of this depo basin 100 km to the southwest.
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Fig. S1.5-4. (Caption on p. 277)
S1.5 · Weak Rudites Arenites, Lowland Facies
Fig. S1.5-5. Location. Geographic. 02°23' E, 07°12' N, southeast Bénin Geologic. Craton cover sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 1954–1955 Source. IGN – Photothèque Nationale, France
Comments. A stereomodel in the Ouémé River area shows the southerly occurrence of poorly cemented Tertiary sandstones termed “Continental terminal” that are widespread in West Africa and the Sahara. The surface is silty sand and the relief is gently rolling and undissected compared to upland facies. Regional population pressures are evident by attempts to grow crops on the relatively infertile cap of D1 ferricretes. This model is a continuation westward of Fig. Fv2-24. North is at the bottom of the photo.
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Fig. S1.5-6. (Caption on p. 282)
S1.5 · Weak Rudites Arenites, Lowland Facies
Fig. S1.5-7. (Caption on p. 282)
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Fig. S1.5-6. Location. Geographic. 06°24' E, 43°22' N, lower Provence Geologic. Intermontane depression between Triassic limestone uplands and Hercynian massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. 10 July 1979 Source. IGN – Photothèque Nationale, France Comments. This stereomodel at Le Luc-Vidauban, shows essentially the entire area, 20 km long × 10 km wide, of a topographically and geologically distinct geounit named the Luc Trough, a low plain with microrelief surface. The unit consists of Permian detrital argillites and conglomerates with generally poor soils, excepting a 10 km2 cultivated area on the north. The south half of the model marked “J1.1-PZ” is part of the coastal Maures gneissic massif. The model area is shown on satellite image Fig. S1.5-7.
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Fig. S1.5-7. Location. Geographic. 06°12' E, 43°21' N scene center, Lower Provence, France Vertical Airphoto/Image. Type. MSS 50 m resampled resolution Scale. 1: 500 000 Acquisition date. Not given Source. Personal archive Comments. The 100 km × 70 km Landsat subscene provides the regional structural setting of the depression in which the Permian detrital sediments of Fig. S1.5-6 are located – see inset frame. The massive and dissected morphology of the 20 km broad 600 m high coastal Maures Massif contrasts with the inland east-trending Pyreno-Provençal relief in Mesozoic and Eocene carbonates of subtabular plateaus with surfaces at 200, 300 and 400 m, separated by fold and thrust ridges. Some of the cultivated alluvial depressions are poljes. The poor Permian soils appear blue in contrast to the red forested slopes of the adjacent massif. The port of Toulon, the largest naval base in France, and the naval air station and resort town of Hyères are visible on their respective coastal promontories 40 km to the southwest. This figure is an extension eastward of Fig. 14-11.
Fig. S1.5-8.
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282
Location. Geographic. 02°50' E, 43°15' N image center, Lower Languedoc, southern France Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 500 000 Acquisition date. 22 November 1981 Source. Personal archive Comments. The west-central beige/pink part of this Landsat subscene covers the greater part of a 150 km long by 30 km broad depo basin of the Bas Languedoc that merges eastward with the coastal plain of Fig. Bc4-3. The basin consists of a sequence of early Tertiary marine sediments over which have spread detrital Eocene to Miocene molassic sediments (S1.2) derived from the red forested Montagne Noire of the uplifted Hercynian Central Massif on the north and the also forested Paleozoic Mouthoumet and Cretaceous Corbières Massifs to the south (Mouthoumet is structurally a part of the Central Massif). The stereomodel of Fig. S1.5-4 is located near the eastern end of the image.
S1.5 · Weak Rudites Arenites, Lowland Facies
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Division 2 · Sedimentary Rocks and Duricrusts
S2 – Siltstones and Lutites Characterization This geounit includes laminated clay shales (with calcite as the most common cementing material), unlaminated mudstones, and marls (clays mixed with calcium carbonate). Sandy shales appear similar to sandstones, and limy shales resemble clay shales. They are of marine origin, lithified by compaction and water explusion. The poor permeability of fine clastics means that, irrespective of cementation and climate, these rocks are prone to erosion by surface runoff. The characteristically described parent unit is associated with occurrences in the humid climates. In such regions shales have moderately sloping (<8°) rolling landscapes with low relief. The fine-grained deposits act like homogeneous bodies when exposed to erosion and denudation, so bedding planes and attitudes are little evident in airphotos. The drainage pattern tends to be dendritic in both undisturbed and disturbed sequences. As clay-rich rock they deform plastically, so joint systems are also little visible. The material weathers so quickly that relatively few fresh exposures are found. Development of a soil profile in humid regions results in a surface with greater infiltration capacity than bare shale, hence the drainage density on shale is usually lower in humid climates than in dry climates. Siltstones, due to their quartz content, are essentially finegrained sandstones and are relatively more resistant to erosion than other lutites.
Geohazard Relations Hazards associated with shales are essentially related to their low resistance to mechanical weathering and ero-
sion. Their variable strength is related largely to their water content. They are susceptible to sliding and slumping and generally provide poor subgrade support for structures due to high compaction potential. Frost-heave potential, however, is high in colder climates. A particular hazard relates to two mineral products of lutite rock weathering; montmorrillonite and bentonite. These minerals are of the smectite class of clay minerals that are very fine-grained and are highly reactive with water. Smectite normally constitutes about proportionally 10% of the mineralogy of shales, but hazard develops where these smectite minerals are present in either residual (e.g., South Africa) or transported (e.g., Canada, USA) soils. “These minerals have a layered structure; if water enters into the individual minerals, it can vary the basal spacing and swelling will result. The damage they are able to cause (such as to paved roads and reinforced concrete foundations) stems from the great pressures which they can exert as they swell when water has gained access to them.” (Legget and Karrow 1983).
Reference Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 42–16–17
Select Bibliography Drury SA (1987) Image interpretation in geology. Allen & Unwin, London, pp 76–78 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 102–104 Waltham T (2002) Foundations of engineering geology. Spon Press, London, pp 48–49 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 94–101
Fig. S2-1. Location. Geographic. 12°10' E, 46°32' N, northern Italy Source. Touring Club Italiano Comments. View of marly and shaly limestones of the Upper Triassic basin of Cortina d’Ampezzo amid the Triassic crystalline Dolomite Massifs.
S2 · Siltstones and Lutites
Fig. S2-2. Location. Geographic. 132°45' W, 65°46' N, east central Yukon Territory Source. Courtesy of Natural Resources Canada, NAPL T5-185R Comments. An air perspective view southward from 6 000 m altitude on 4 August 1944 of the fluvially dissected Mid-Cretaceous shales at 800 m elevation of the southern part of the Peel Plateau in the Cordilleran Foreland Belt. The bright S1-Ku capping strata in mesa form are Upper Cretaceous sandstone and minor shale. The mountains on the horizon are the thrusted Mackenzie Mountains, the first ranges of the Western Cordillera. This area, at the extreme limit of Laurentide Ice, shows little evidence of glaciation. An area of Zm1.2 gelifluction stripes is also delineated.
Fig. S2-3. Source. Putnam WC, et al. (1960) Natural Coastal environments of the world. University of California, Los Angeles, p 83, fig 12 Comments. Photo shows two shale units of slightly different age, composition and contrasting morphology, 25 km west of Santa Barbara in southern California, USA. The Br-7 plain with low white cliffs in the foreground consists of siliceous Mid-Miocene shale (Monterey Formation). The inland sloping S2-Mc unit is composed of softer Lower Miocene shale (Rincon Formation). The break in slope contact between these units may be a strike-slip fault. The forested W1-Pg mountains in the background are Eocene sandstones and shales of the Santa Ynez Range.
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Fig. S2-4. Location. Geographic. 67°13' W, 47°12' N, northwest New Brunswick Geologic. Acadian (Hercynian) Belt of the Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. Rampton VN, et al. (1984) Quaternary geology of New Brunswick. GSC Memoir 416, p 71, fig 39. Cour-
tesy of Natural Resources Canada, Geological Survey of Canada Comments. North is to the right on this stereomodel of deeply dissected Devonian siltstones at an elevation of 270 to 370 m in the Chaleur Uplands. The northeast-southwest oriented subparallel drainage, with a local relief of 30 to 60 m, is structurally controlled. The plateau-like forested surface relates to a Cretaceous peneplain that truncates the rocks and extended throughout much of Atlantic Canada.
S2 · Siltstones and Lutites
Fig. S2-5. Location. Geographic. 75°03' W, 40°31' N, northwest New Jersey Geologic. Piedmont Province of Acadian Appalachain Highlands Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. 3 August 1956 Source. Way DS (1973) Terrain analysis. Dowden, Hutchinson & Ross, Inc. Stroudsburg, Penn, p 93, fig 6.14
Comments. This stereomodel shows Triassic shales in one of a number of downfaulted lowlands in the crystalline rocks of the Piedmont Province. The locality is Frenchtown on the Delaware River. As in Fig. S2-6 the stereo displays the moderately sloping, smoothly rounded, low relief typical of shale in humid climates. The relatively lower drainage density than in S2.1 dissected Variant common in drier climates is also evident. The steeper gully slopes in this model are forested.
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Fig. S2-6. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 25 000 Acquisition date. November 1937 Source. Personal archive Comments. Stereomodel shows the dissection of shale in a humid climate as in Fig. S2-5 relatively less intense than in drier zones. This occurrence is in Upper Carboniferous shales in Berkeley County, West Virginia, U.S.A. in the Valley and Ridge Province of the Acadian Appalachian Highlands. The “c” annotation indicates steep slopes resulting from undercutting at stream bends, “s” indicates sinkholes related to adjacent limestones. The entire area is evidently in agricultural land use.
Fig. S2-7.
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Location. Geographic. 01°05' E, 11°00' N, Bénin Geologic. Downfolded basin of West African Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. This stereomodel on the Pendjari River (Gourma) covers 80 km2 of undissected Cambrian shales of the Voltaian Oti Basin of northwestern Bénin, Togo and Ghana. The lack of dissection is attributed to the rocks lying close to local base level. Some evidently relict stream channels are traced in the model area. An underfit stream is in the Fv2 valley. An underfit stream is one that is much smaller than the valley in which it flows, probably a result of climatic change.
S2 · Siltstones and Lutites
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Division 2 · Sedimentary Rocks and Duricrusts
S2.1 – Siltstones and Lutites, Dissected Facies
References
Characterization
Guerricchio A, Melidoro G (1982) New views on the origin of badlands in the Plio-Pleistocenic clays of Italy. Proceedings, IV Congress, IAEG, pp II, 227-II, 238
These soft argillaceous rocks occur mainly in arid and semi-arid areas. They are distinguished from the parent unit S2 by topography which is dissected to a high degree and frequently referred to as “badlands”. The typical morphology is “haystack” hills, sharp-crested ridges and steep slopes produced by the high runoff of a dense drainage pattern. High swelling clay minerals in the shales tend to produce rounded dome-like hills.
Geohazard Relations The strongly dissected topography is almost impossible to travel across, and the terrain is notorious for landslide activity. These are mainly debris slides Ms2 and slumps Ms3. Some retrogressive slides Mf1.1 develop along river valley slopes. Clay shales tend to expand greatly upon rapid unloading, producing differential movements and difficult foundation conditions. In some shale sequences bentonite layers containing sodium are zones of high plasticity and high swelling pressures when exposed to air during excavation. They can absorb up to eight times their volume of water. Guerricchio and Melidoro (1982) stated that “the badlands cause severe economic consequences: heavy losses of large expanses of land to agriculture; considerable expenses for the building of important works (dams, highways, etc.); instability phenomena and destruction of ancient villages, … contribution of a great quantity of solid transport by the river water which produce rapid silting up of reservoirs and of the channels of irrigation or drainage, etc.”
Select Bibliography Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Natural Resources Series no 6, Division of Water and Land Resources, CSIRO, Australia, pp 55, 56 Christiansen EA (1983) The Denholm Landslide, Saskatchewan. Part 1: Geology. Canadian Geotechnical Journal 20:197–207 Cordova EV (1992) La fotografia aerea y su aplication a estudios geologicos y geomorfologicos. ORSTOM, stereo models 5, 17, 26, 48, 85, 99 Crosta AP, Moore JMcM (1989) Geological mapping using Landsat Thematic Mapper imagery in Almeria Province, south-east Spain. Int J Remote Sensing 10(3):505–514 Kienholz H (1978) Maps of geomorphology and natural hazards of Grindelwald, Switzerland, scale 1 : 10 000. Arctic and Alpine Research 10:169–184 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 43–2, 43–3 Moore JMcM, Mason PJ, Davis AM, Eyers R, Liu JG (1999) Geohazard monitoring in southeast Spain using integrated imagery and digital elevation model. Proceedings, Thirteenth International Conference on Applied Geologic Remote Sensing, pp 1–47–1–54 Ray RG (1960) Aerial photographs in geological interpretation and mapping. USGS Professional Paper 373, fig 63, p 116, fig 64, p 118 Scott JS, Brooker EW (1968) Geological and engineering aspects of Upper Cretaceous shales in Western Canada. GSC Paper 66–37, pp 23–55, 58 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 102–104 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 94–101
Fig. S2.1-1. Location. Geographic. 116°45' W, 36°10' N, southeast California, U.S.A. Source. LAR, January 1975 Comments. This photo shows characteristic strong fluvial dissection of Tertiary lacustrine mudstone near Zabriskie Point in Death Valley National Monument. See Figs. Fu1-3 and L2-7 for other features of Death Valley.
S2.1 · Siltstones and Lutites, Dissected Facies
Fig. S2.1-2. Location. Geographic. 145°E, 06°S, east central Papua New Guinea Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Bellamy JA (ed) (1986) Inventory of natural resources, population distribution and land use, Papua New Guinea. CSIRO Natural Resources Series no 6, p 57, fig 5.29, © CSIRO 1986 Comments. This ground view and block diagram show the erosional topography in indurated Neogene shales of the Central Highlands. “1” in the diagram indicates the narrow sharp-crested ridges; “2” are the steep slopes, and “3” is the dissection pattern. Bellamy reports that Ms3 slumping and Ms2 debris slides are common on the steep slopes, particularly in areas of thinly laminated but relatively hard mudstones and shales.
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Fig. S2.1-3. Location. Geographic. 08°05' E, 46°38' N, central Switzerland Source. LAR Comments. The photo shows gully erosion in low dipping,unstable Mid Jurassic marly shales in a humid climate at Grindelwald in the Helvetic Nappes. The local erosion processes are fluvial combined with frost action. The stands of conifers may be local forest relics or have been planted as a slope stabilization measure. Mass movements in these sediments are pictured in Figs. Ms3-3, Mf3-4 and Mc1-3.
Fig. S2.1-4. Location. Geographic. 108°48' W, 43°35' N, northwest Wyoming, USA Source. Courtesy of Lou Maher Comments. A photo of characteristic dissection morphology of shales in an arid climate. These Permian shales are in the homoclinal Owl Creek Uplift at the south end of the Bighorn Basin in the Middle Rocky Mountains.
Fig. S2.1-5. Location. Geographic. Northern Territory, Australia Geologic. Craton cover sedimentary basin Source. Twidale CF, Foale MR (1969) Landforms illustrated. Thomas Nelson (Australia) Ltd., p 11, photo 10 Comments. This air perspective view near the MacDonnell Ranges shows the dissected morphology of Late Proterozoic siltstones.
S2.1 · Siltstones and Lutites, Dissected Facies
Fig. S2.1-6. (Caption on p. 294)
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Fig. S2.1-6. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Indicated Acquisition date. Not given Source. Unattributed Comments. The large scale photo at an undisclosed location in Turkey clearly expresses the comparative classic photogeologic morphologies of detrital and carbonate sedimentary rocks in a semi-arid region. The bright, strongly stream-dissected shales are overlain by the darker karstic limestones with no surface drainage, but abundant characteristic black-toned solution sinkholes.
Fig. S2.1-7.
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Location. Geographic. 66°19' W, 20°35' S, southwest Bolivia Geographic. Polygenetic Andes Cordillera Oriental Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 05 April 1964 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 98 Comments. Headward stream erosion from westward in this stereomodel has exposed and dissected S2.1- O interbedded Lower Paleozoic shales and sandstones that are overlain by south-dipping resistant interbedded Cretaceous rocks designated W3 south of Ubina. Evident fault fracture traces have been drawn in black, e.g., at the contact of W3 with a west-dipping homocline on the left. The site is at 4 000 m elevation.
S2.1 · Siltstones and Lutites, Dissected Facies
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Fig. S2.1-8. Location. Geographic. 79°28' W, 38°41' N, eastern West Virginia Geologic. Ridge and Valley Province of Acadian Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 30 000 Acquisition date. Not given Source. Schultz AP, Southworth CS (1989) In: Schultz P, Jibson RW (eds) Landslide processes of the eastern United States and Puerto Rico. Geological Society of America Special Paper 236, p 8, fig 7 Comments. The stereomodel is centered on an exposure of dissected Ordovician shale, labelled “Or”, in a breached anticline.“Ojo” are the resistant sandstone limbs of the structure. Numerous Ms2 debris slides developed on thin regolith on the wetter unforested north-facing slopes on these shales following the passage of a sustained rainfall cell over the area November 3–5, 1985. The model is oriented to northwest. The strike of the valley and the St ridge is northeast.
Fig. S2.1-9.
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S2.1 · Siltstones and Lutites, Dissected Facies
Location. Geographic. 03°07' E, 42°30' N, Languedoc-Roussillon Geologic. Cambrian lutites of Pyrenean Orogen Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1972 Source. IGN – Photothèque Nationale, France Comments. A stereomodel shows a 2 km wide belt of strongly dissected Cambrian lutites on the Mediterranean coast at the eastern extremity of the Pyrenees. The rectangular Port of Vendres at the north end of the photos is a fishing and general cargo port; the recreational and marine biological research Port of Banyuls is near the south, 5 km from the Spanish border. The area with “J3.1” descriptor inland consist of also dissected but more elevated and less cultivated Precambrian metamorphic rocks. ▼
Fig. S2.1-10.
Location. Geographic. 06°17' E, 44°46' N, Alps Geologic. Pelvoux Hercynian Massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1970 Source. IGN – Photothèque Nationale, France Comments. The stereomodel 60 km southeast of Grenoble shows dominantly fine detrital sediments of Liassic (lower Jurassic) age, S2.1-J, with diagnostic dissected morphology and Mv1.1 associated talus sheets. The occurrence is an inlier in the crystalline massif, labelled J3.1–Pm. The Upper Drac River crosses the lower southern half of the photos.
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Fig. S2.1-9. (Caption on p. 297)
S2.1 · Siltstones and Lutites, Dissected Facies
Fig. S2.1-10. (Caption on p. 297)
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S2.1 · Siltstones and Lutites, Dissected Facies ▼
Fig. S2.1-11.
Location. Geographic. 06°30' E, 26°07' N, eastern Algeria Vertical Airphoto/Image. Type. MSS, 80 m resolution Scale. Indicated Acquisition date. Not given Source. Personal archive Comments. A Landsat subscene shows the clear photogeologic morphology of two lithologies of detrital rocks in a hyperarid climate. The labelled units are part of the northern belt of Lower Paleozoic Tassili sedimentary rocks that surround the PreCambrian Hoggar Massif. S1.1-C/O are resistant Cambro/ Ordovician sandstones with the characteristic fracture pattern controlling the drainage network. The darker and typically dissected unit to the north, S2.1-D consists of Lower Devonian sandy shales. Ef1 areas are sand sheets; Ed5 are star dunes at the south end of the regional 120 km long sand sea of Erg Tifernine which is enclosed by extensions of these Tassilian rocks.
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Group W Interbedded Sequences W1
W1 – Interbedded Sedimentary Rocks, Undivided Characterization As erosion proceeds in horizontal strata, the fluvial system cuts canyons and valleys in which a succession of older, silicate, carbonate, and phosphatic rock units (and/ or lavas) becomes exposed. In this situation topographic forms are largely dependent on the sequence and relative thickness of strata of different composition, and their differential resistance to weathering and erosion. The compositional layering results in compound slopes; with varying thickness ratios of soft to hard rock strata, and a resistant caprock. In sequences of thin interbeds the materials do not have the characteristic terraced slopes. In these horizontal sequences there is a near-coincidence of bedding traces and topographic contours, with steeper resistant slopes separated by gentle slopes of weaker rocks (shales).
Fig. W1-1. Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Bellamy JA (ed) (1986) Inventory of natural resources, population distribution and land use, Papua New Guinea. CSIRO Natural Resources Ser. no 6, p 64, fig 5.36, © CSIRO 1986
Geohazard Relations The main geohazard associated with these rock sequences is the risk of landslides due to the lack of support of resistant rocks (K limestone, S1 sandstone) underlain by weak (S2 generally shale) strata. Seepage between bedding planes is a further indication of possible slide areas.
Select Bibliography Ehlen J (1981) The identification of rock types in an arid region by air photo patterns. U.S. Army Corps of Engineers, Engineer Topographic Labs., Report ETL–0261, p 27 Gupta RP (1991) Remote sensing geology. Springer-Verlag, Berlin, pp 255–256 Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS Professional Paper 373, fig 61, p 112, 113; fig 77, p 144, 145; fig 78, p 146, 147 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC, The Hague, pp 130–131 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 166–167
Comments. Photo shows a moderately-dipping (homoclinal) sequence of Neogene marine and continental interbedded sedimentary rocks covered by humid tropical forest. The resistant beds are S1 sandstones; the weak beds S2 siltstone and mudstone. Local relief is 150 m to 300 m. Location is at approximately 146° E, 07°45' S in the Gulf district of southern Papua New Guinea.
W1 · Interbedded Sedimentary Rocks, Undivided
Fig. W1-2. Location. Geographic. 56°E, 26°50' N, southern Iran Source. Putnam WC, et al. (1960) Natural coastal environments of the world. University of California Los Angeles, p 117, fig 46 Comments. An air view shows differential erosion in interbedded Late Miocene sandstones, marls and siltstones on the south shore of Qishm Island, Hormuz Strait. The recessive outcrop of the shales is notable. A Shuttle astronaut’s view of the island is in Fig. W1-6.
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Fig. W1-3.
Fig. W1-4.
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Location. Geographic. 01°37' W, 43°19' N, western Pyrenees Geologic. Contact of axial and foothill rocks Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1977 Source. IGN – Photothèque Nationale, France Comments. The stereomodel covers an area of occurrence of Pyrenean orogeny affecting Mesozoic rocks of the foothills and Paleozoic rocks of the axial zone. The area is located in the Basque Country on the French/Spanish border 10 km inland from the coast. The telecommunication and tourist structures visible on the la Rhune Peak (900 m) are on the border at the terminus of a winding mountain railway. The agricultural land at the north is on Upper Cretaceous sediments in the Nivelle Valley at the southern limit of the Aquitaine Basin. The mixed forest and pasture land on the south is on Carboniferous sediments of the axial zone. The extensive central area of the model is an association of disturbed relatively weak Permian interbedded sediments and scarp-forming Triassic sandstones. Intersecting fracture traces may be discerned throughout this area as well as a number of slope failures in the Permian rocks. Two large failures are evident in the Carbonifeorus sediments.
Location. Geographic. 106°44' E, 14°57' N, South Laos Geologic. Craton cover sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. Not given Source. Personal archive Comments. The stereomodel shows an area of interbedded sandstones and shales on the southeast sector of the Mid-Jurassic Bolovens structural Plateau. S2 shales are typically low weathering, with some Ms3.1 slumps in lower left. S1 sandstones are scarp forming with some bedding traces evident. The generally bare terrain in the center of the model is interpreted as S1.2 weak sandstones. The location of this model is given on the space image subscene of Fig.W1-5. The possible land use relationship of the non-forested areas are discussed in the description of that figure of more recent date.
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Fig. W1-3. (Caption on p. 303)
W1 · Interbedded Sedimentary Rocks, Undivided
Fig. W1-4. (Caption on p. 303)
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Fig. W1-5. (Caption on p. 308)
W1 · Interbedded Sedimentary Rocks, Undivided
Fig. W1-6. (Caption on p. 308)
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Fig. W1-5.
Location. Geographic. 106°40' E, 15° N, south Laos Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. Image covers southeast scarp of the Bolovens Plateau. The structure consists of a sequence of MidJurassic sedimentary rocks epeirogenetically uplifted in Lower Pleistocene. The sediments are interbedded Mid-Jurassic quartzite and sandstone with some conglomerate and shale (the regional Thai Phra Wihan Formation). The inset frame locates the stereo photo pair of Fig. W1-4. A reservoir, created since 1987, is northeast of the photo area. The central part of this gently synclinal plateau is covered by Lower Pleistocene basalts shown in Fig. X1.4-8. The brown areas are bare ground, possibly related to clearing by fire. ▼
Fig. W1-6.
Location. Geographic. 56°E, 26°50' N, south Iran Vertical Airphoto/Image. Type. Challenger 6, Hasselblad photo Scale. 1: 394 000 Acquisition date. October 1984 Source. NASA Comments. This photograph is a partial frame of a handheld photo taken by an astronaut. The photo covers 65 km of the 110 km long, 170 m elevation, barren Qishm Island at the Hormuz Strait. The sediments of the main part of the island are gently warped 3000 m thick interbedded Late Miocene sandstones, marls and siltstones. The near-obliterating anticline (erosion has eliminated most of the structural relief) consists of 700 m of Early to Mid-Miocene marls and limestones. The pear-shaped structure on the island center is interpreted as a probable 11.1 pillow dome diapir in an anticline. The dark circular structure on the mainland is the large inactive 100 km2 250 m high Gachin diapir. There is much extraction of non-evaporite rocks which occur on the plug’s surface. Shore installations of the Bandar Abbas oil refinery and naval complex are located adjacent to the Gachin structure. This area is 50 km east of Fig. 11.3-2. Figure W1-2 is an air perspective view of the center of the island.
W1 · Interbedded Sedimentary Rocks, Undivided
Fig. W1-7. Location. Geographic. 114°59' E, 0°31' N, Kalimantan, Indonesia Vertical Airphoto/Image. Type. SIR-B 25 m resolution Acquisition date. 11 October 1984 Source. USGS Comments. A plateau of Paleogene interbedded clastic sedimentary rocks is pictured in this 1:500 000 image of an 80 km × 45 km segment of a radar image. The area is located in the center of the thickly forested island. The dip and strike of the rocks are readily visible, as is the differential resistance of the strata. The terrain to the right is marked by numerous closely spaced volcanic cones. The radar image does not penetrate the forest canopy, it images the variation of the heights of treetops which mimick the geomorphology.
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Division 2 · Sedimentary Rocks and Duricrusts
W1.1 – Coal Seams
Geohazard Relations
Characterization
The surface features related to underground mining are the geohazard zones of land subsidence. Strip and contour mines are a source of significant pollution. Runoff from spoil materials may sterilize local soils and contaminate surface and groundwater, toxic concentrations called “acid drainage”. Removal of topsoil increases the potential for erosion of an area and may result in increased sediment loads in nearby streams. Current underground coal extraction practices allow the unsupported roof to fail and cause predictable and controlled surface subsidence. The ground over older mined coal beds is prone to subside – in some places gradually but in others suddenly and without warning – months, years, or decades after the coal has been removed.
The strata of this Variant occur relatively near to the surface in interbedded sequences. They are rarely directly visible on air photos or satellite images; rather their presence is inferred by the features of associated surface and underground mining activities. Characteristic imagery patterns of surface mining result from “area” or “strip” mining and “contour” mining. Strip mining is normally used for surface mining in low relief terrain where the overburden can be totally removed and all the coal extracted, thus large areas are uniformly disturbed. Contour mining is restricted to areas of high relief and the coal is uncovered in a narrow band around the mountain. As many of the coal beds where this technique is used lie nearly horizontal, the stripping essentially follows the contour of the mountain, thus the name. The identification features for strip mining are the spoil ridges of overburden, the lack of vegetation on active mines, and deep trenches. Active strip mines use large mechanical drag lines, shovels and other heavy equipment. The equipment removes the overburden, the coal is removed, and the trench where the coal was extracted is then filled with overburden, The sequence of operation is repeated along the length of the seam to produce a characteristic surface pattern.
Select Bibliography Crosby EJ, Hansen WR, Pendleton JA (1978) Nature to be commanded. USGS Prof Paper 950:40–41 Loelkes GL Jr, Howard GE Jr, Schwertz EL Jr, Lampert PD, Miller SW (1983) Land use-land cover and environmental photointerpretation keys. USGS Bull 1600:105–106 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 62–63
Fig. W1.1-1. Location. Geographic. 69°W, 81°55' N, northeast Ellesmere Island, Nunavut Source. Courtesy of Natural Resources Canada, GSC 146772
Comments. The photo shows a dark coal seam in an interbedded sequence of Upper Tertiary sandy shales of an outlier of Sverdrup Basin sediments at the north end of Lake Hazen in the Hazen Fold Belt, in Quttinirpaaq National Park.
W1.1 · Coal Seams
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Fig. W1.1-2.
Source. Thorbecke F, Fehn H, Terhalle W (1963). Luftbilder aus Bayern. Thorbecke Verlag, Konstanz, photo 34 Comments. The photo shows the Wackersdorf open pit mining of lignite in an outlier of Miocene S1.5 molasse near Schwandorf, Bavaria, 35 km north of Regensburg, 12°13' E, 49°19' N near the contact of the Mesozoic scarplands with the Bohemian Massif. Abandoned pits are now filled with water. This lignite contains uranium but atmospheric radioactivity is at low levels. ▼
Fig. W1.1-3.
Source. Thornbury WD (1965) Regional geomorphology of the United States. John Wiley & Sons Inc., p 110, fig 7.1 Comments. The mining of coal seams interbedded with sedimentary rocks in this air perspective view expresses the strike of the beds of folded Paleozoic rocks in the Ridge and Valley Province of the Acadian Appalachian Highlands Orogen.
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Fig. W1.1-4. (Caption on p. 314)
W1.1 · Coal Seams
Fig. W1.1-5. (Caption on p. 314)
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Fig. W1.1-4.
Location. Geographic. 65°58' W, 46°07' N, southern New Brunswick Geologic. Central Basin of Acadian Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. June 1966 Source. Courtesy of Natural Resources Canada, NAPL A19414-62, 63 Comments. A stereomodel at Chipman on Grand Lake 60 km east of Fredericton covers multiple strip mines in the north part of the Minto coal field. The rectangular area in the center is 3 km × 1 km. A relatively small black slurry pond is visible in each of the three mining areas. The source beds are in Upper Carboniferous (Pennsylvanian) arenites of the Grand Lake Basin. The bedrock in this area is covered by a veneer of glacial till. Recent space imagery reveals considerable changes in mining activity at this site. Mining has extended into the southwest corner of the photo and on the east of the outlet of Salmon River in lower right. Mining has ceased in the circular area on the west bank of the river, and the ground has been reclaimed. The ridges may have been graded, the entire surface is now revegetated and a network of waterways has been developed. The mined areas on the north have also been reclaimed. ▼
Fig. W1.1-5. Vertical Airphoto/Image. Type. Colour infrared airphoto Scale. Not given – estimated 1:20 000 Acquisition date. Not given Source. Manual of color aerial photography (1968) American Society of Photogrammetry, p 420, fig 10.20 Comments. This large scale photo shows blue snake-like patterns. These are spoil ridges of overburden adjacent to coal extraction trenches. Denuded soil areas register in Cyan hues when C.I.R. film is used. The area is a segment of a contour coal mining operation in subhorizontal Late Paleozoic sandstones and shales in the Allegheny Plateau of the Acadian Appalachain Highlands of the eastern USA. The coal beds are bituminous, 2.5 to 3 m thick. The water in the sinuous channel of a throughgoing river also appears blue, indicating a relatively high level of suspended sediment from the local watersheds. Toxicity of soil and water relates to sulphuric acid from decomposed pyrite and sulphur minerals associated with coal-bearing formations. The brown background areas are leafless deciduous forests of the evidently autumn season of photography. Agricultural fields with some standing crops appear pink.
W4 · Interbedded Weak Rock Sequences
W4 – Interbedded Weak Rock Sequences Characterization The Interbedded weak rock sequences geounit distinctiveness lies in the photogeomorphology, which results from the proportions of the occurring lithologies, their relative induration, and the climatic zones in which they occur. The rocks that make up this unit consist of the same suites as those of undivided interbedded sedimentary rocks W1. The morphology is generally similar to that of the dissected silstones and lutites of S2.1. The distinction of these two types in arid and tropical climates may be difficult to make depending on ancillary information. In addition to the fluvial erosion of W1 interbeds the principal geomorphic processes that develop the topography of weak interbeds are mechanical weathering (thermal) and wind erosion in arid climates, strong chemical weathering and mass wasting in humid tropical climates, and mass wasting and frost weathering in humid temperate climates. Dissection relief is notably more subdued in the latter areas. With a dominance of weak rocks, and their relatively strong dissection, bedding traces are essentially absent in W4 sediments, so the compound slope of W1 rocks is not present.
Ms1 and slides Ms2, creeps Mc1, earth flows Mf2, and debris-mud flows Mf3 in episodic torrential rainfalls in arid zones.
Select Bibliography See Geounits W1 and S2.1.
Fig. W4-1.
Fig. W4-2.
Fig. W4-3.
Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given Acquisition date. Not given Source. Van Zuidam RA, van Zuidam-Cancelado FL (1978/ 1979) ITC textbook of photo-interpretation, vol VII, Terrain analysis and classification using aerial photographs. ITC, chap 6, p 83, photo 47 Comments. The stereomodel shows typical morphology of thin interbedded sedimentary rocks, well-exposed in a unspecified semi-arid climate. The model dominant dissected beds are siltstones and lutites; the arenaceous or carbonate resistant strata are narrow residual ridges that do not provide sufficient unit surface to develop diagnostic photo-geomorphic indicators such as drainage patterns to distinguish them.
Location. Geographic. 67°57' W, 15°32' S, approx., northwest Bolivia Geologic. Andean front ranges Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 25 June 1963 Source. Cordova EV (1992) La Fotografia Aerea y su Aplication a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 72 Comments. A stereomodel shows dissected Ordovician sandstones and shales unconformably overlain by Miocene conglomerates. The latter occur only as light-toned residual ridge crests. Location is in the forested Cerros de Bela, the northern sector of the Yungas, 150 km east of Lake Titicaca. Figure Fu1-5 shows a large alluvial fan further south in the same front ranges.
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Geohazard Relations
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The inherent engineering instability of weak interbedded sedimentary rocks is related to mass movements
Location. Geographic. 109°05' W, 37°08' N, southwest U.S.A. Source. LAR, January 1975 Comments. A closeup photo shows an unstable minor scarp of Mid-Jurassic weakly cemented Entrada Fm sandstone overlying grey fine-grained Carmel Fm shale near Aneth in the Blanding Basin in southeast Utah on the eastern Colorado Plateau.
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Fig. W4-2. (Caption on p. 316)
W4 · Interbedded Weak Rock Sequences
Fig. W4-3. (Caption on p. 316)
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Fig. W4-4. Location. Geographic. 68°05' W, 16°28' S, southern Bolivia Geologic. Central Andes Cordillera Oriental Vertical Airphoto/Image. Type. TM Acquisition date. 2007 Source. MDA EarthSat Comments. The satellite image oriented to northeast just northeast of La Paz shows weak Tertiary and Quaternary interbedded sediments east of La Paz being dissected by headward erosion of streams.
W4 · Interbedded Weak Rock Sequences
Fig. W4-5. (Caption on p. 320)
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Division 2 · Sedimentary Rocks and Duricrusts ▼
Fig. W4-5. Location. Geographic. French Riviera Geologic. Pre-Alps of Maritime Alps Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. The deformed and dissected Pliocene marls and conglomerates in this stereomodel are part of an intermont basin fill just west of Nice. The quarry is probably in conglomerates. In common with many weak interbedded sedimentary rock sequences, photogeologic bedding traces and dips are not visible, particularly at smaller photo scales.
Fig. W4-6.
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Location. Geographic. 71°42' W, 19°05' N, Haïti/Dominican Republic Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The intensely dissected Paleocene and Eocene clastic sediments occur in the upper (north) part of this stereomodel on the Central Plateau of Haïti. Those, less deforested, south of this reach of the upper Artibonite River are in the Dominican Republic; the river constitutes the international boundary. Unit K2 are undifferentiated Cretaceous carbonates.
W4 · Interbedded Weak Rock Sequences
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W4 · Interbedded Weak Rock Sequences ▼
Fig. W4-7. Location. Geographic. 64°39' W, 17°44' N, Virgin Islands Geologic. North Caribbean Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 24 000 Acquisition date. 28 January 1954 Source. Unspecified U.S. government agency Comments. The stereomodel at Seven Hills on eastern St. Croix shows the dissected relief of weak interbedded Cretaceous marine sedimentary rocks in a warm humid environment. Local colluvial and fluvial infilled gullies and lowlands are delineated as in Fig. Bc1-13. See also Fig. Bw3.1-5.
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Fig. W4-8.
Location. Geographic. 110°50' W, 40°25' N scene center, central Utah Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 18 October 1977 Source. USGS Comments. Dissected Eocene interbedded shales and sandstones of the aptly-named Badland Cliffs are delineated on this Landsat scene. The unit is the western part of the Uinta Basin of the northern Colorado Plateau. The structure is a cuesta that was uplifted in late Cenozoic and dips north from 3 000 down to 2 000 m elevation. The glaciated Uinta Mountains to the north are a broad anticline of Precambrian sediments, rising to over 4 000 m. Both the Badland Cliffs and the Uinta Mountains are parts of national forests. Their respective elevations in this arid climate attract sufficient precipitation, 20 to 90 cm per year, to support conifer woodlands (pinyon, juniper) and forests. Also, streams flowing from the Uintas are a source of irrigation water for the arid basin zone.
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Fig. W4-8. (Caption on p. 323)
W4 · Interbedded Weak Rock Sequences
Fig. W4-9. (Caption on p. 326)
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Fig. W4-9. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 385 000 Acquisition date. Not given Source. USGS Comments. The 65 km × 20 km rust dark brown geounit in this Landsat subscene is eucalyptus and acacia open forest covering a cuesta-like structure, the Woronara Plateau, in southeast Australia, extending from Sydney to Wollongong. The high point of the structure is 840 m at the Nepean Monocline west of Wollongong. The Mid-Triassic shales and sandstones dip to the northwest from 400 to 75 m elevation. The structure was warped in the Tertiary. The elongate black drainageways on the cuesta are dammed river reservoirs. The pink lowland west of the structure is the dairying and market gardening Cumberland Plain.
D1 · Ferricretes
Group D Duricrusts
these areas expand they reduce the land available for agriculture in often marginally productive regions. Mv1 rockfalls are associated with escarpment ledges.
D1 – Ferricretes
D1 References
Characterization Ferricretes are iron-oxide cemented crusts also known as laterite resulting from weathering and pedogenesis of mainly basic igneous rocks under humid tropical climate conditions. Ferricretes occurring in arid and semi-arid environments are relict. Ferricrete profiles vary considerably in thickness. The ferricrete can be from a few centimeters to tens of meters thick, below which is a weathered zone also varying from a few centimeters to over 100 m. Induration occurs after exposure of the weathered horizons as a result of erosional stripping of the topsoil. As shown in Fig. D1–2, this erosion may be due to climate change or to the influence of man. Ferricrete crusts consist of a continuous, homogeneous, massive unit of a hard, high strength incompressible fabric. They may become harder than many rocks and can be quarried. They typically occur as relatively high plateaus, mesas or residual buttes that conspicuously cap underlying country rocks and whose extensions are marked by a generally prominent escarpment. The surfaces are very poorly vegetated and uncultivated. Other residual or transported pedological occurrences are lateritic soils and laterite “colluvial” gravels popularly used for road construction (Atkinson and Brown 1962; Holden 1968; Malomo 1982; and Zongyuan 1986). The mineral resource potential of some laterite weathered profile deposits (aluminous bauxite, nickel, cobalt) is noted. Photogeomorphically, there is a similarity with basalt X1 and sandstone plateau surfaces with laterite plateaus. Additional information might resolve such possible confusions.
Geohazard Relations Exposed, hardened laterite is a surface which does not decompose, on which chemical erosion has no effect. As
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Atkinson JR, Brown NB (1962) Airphoto interpretation study for the division of roads and road traffic of the Southern Rhodesian Government. Proceedings 1st International Symposium on Photo Interpretation, Delft, pp 487–491 Holden A (1968) Engineering soil mapping from airphotos. Photogrammetria 23:185–199 Malomo S (1982) The use of the word ‘laterite’ in engineering geology – A review. Proceedings, IV Congress, IAEG, pp II 201–208 Zongyuan L (1986) On the engineering classification of laterite. Proceedings, 5th International IAEG Congress, pp 811–820
Select Bibliography General Dixon JC (1994) Duricrusts. In: Abrahams AD, Parsons AJ (eds) Geomorphology of desert environments. Chapman and Hall, London, pp 82–105 Dury GH (1969) Rational descriptive classification of duricrusts. Earth Science Journal 3(2):77–86 Gidigasu MD (1976) Laterite soil engineering. Elsevier Scientific, Amsterdam Goudie A (1973) Duricrusts in tropical and subtropical landscapes. Clarendon Press, Oxford Goudie A (1985) Duricrusts and landforms. In: Richards KS, Arnett RR, Ellis S (eds) Geomorphology and soils. Allen and Unwin, London, pp 37–57 McFarlane MC (1976) Laterite and landscape. Academic Press Petit M (1985) A provisional world map of duricrust. In: Douglas I, Spencer T (eds) Environmental change and tropical geomorphology. Allen and Unwin, London, pp 269–279 Tardy Y (1997) Petrology of laterite and tropical soils. Balkema, Rotterdam Young A (1976) Tropical soils and soil survey. Cambridge University Press, Cambridge, pp 154–170
Airphoto Interpretation Dowling JWF (1964) The use of aerial photography and land-form analysis in the location of laterites. Proceedings UNESCO Toulouse Conference – Aerial Surveys and Integrated Studies, pp 425–429 Drury SA, Hunt GA (1988) Remote sensing of laterized Archaean greenston terrain: Marshall Pool Area, Northeastern Yilgarn Block, Western Australia. Photogrammetric Engineering and Remote Sensing 54(12):1717–1725 Persons BS (1970) Laterite, genesis, location, use. Plenum Press, New York
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Fig. D1-1. Location. Geographic. 80°05' E, 21°55' N, northeast India Source. University of Alaska Comments. The photo shows a Tertiary laterite crust capping Archean rocks of the Indian Shield in the vicinity of Balaghat approximately 100 km northeast of Nagpur.
Fig. D1-2. Source. Thomas MF (1974) Tropical geomorphology. MacMillan, p 54, Fig. 12 Comments. A sectional diagram shows profiles of covered D1 ferricretes in a forested environment and later exposed and photogeologically mappable in a truncated eroded profile.
D1 · Ferricretes
Fig. D1-3. Source. Mainguet M (1972) Le Modelé de Grès, Tome II. IGN – Photothèque Nationale, France, p 247 Comments. The 1: 50 000 stereomodel delineates laterite cap marked “D1.1” over fractured, eroding craton cover S1.1 Ordovician sandstones east of Conakry, western Guinée, West Africa.
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Fig. D1-4. Location. Geographic. 02°35' 13'' E, 11°19' 24'' N, northern Benin Source. IGN – Photothèque Nationale France Comments. 1:50 000 stereomodel taken in 1950, shows residual areas of deep, darker-toned, typically uncultivated laterite caps marked “D1.1” on Archaean rocks of the West African Shield.
D1 · Ferricretes
Fig. D1-5. Location. Geographic. 54°30' W, 04°30' N, east Surinam Geologic. Guyana Proterozoic Shield Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 40 000 Acquisition date. Unspecified Source. Courtesy of KLM Aerocarto
Comments. The stereomodel in the Nassau Mountains area near the Maroni River shows a mesa covered by tropical forest that is part of an uplifted Plio-Pleistocene X1 basalt surface with a 2–15 m thick layer of laterite, ferrobauxite and bauxite.
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Fig. D1-6. Vertical Airphoto/Image. Type. TM 30 m resolution Scale. Indicated Acquisition date. 30 October 1987
Source. USGS Comments. This Landsat scene shows typical occurrences of dark grey laterite crusts covering Tertiary sandstones in the sub-Saharan Sahel along the Niger River at Tillabery, southwest Niger, 01°24' E, 14°18' N, image center.
Division 3 Geostructures
Group Gravity Structures Group Fault Line Traces Group General Lineaments
General Note of Geohazard Relations Geostructures are mainly endogenetic features of photogeologic bedrock units that have been variously modified by exogenetic weathering processes. They are ordered in three groups: Gravity structures are diapiric stocks of saline evaporites classified in four Variants. Fault line traces are fractures in consolidated rocks resulting from tectonic stresses along which displacement of adjacent rocks has taken place. They are classified in eight Units and Variants. General lineaments are non-genetically classified as four types of linear arrangements of geomorphic and or radiometric features. Fault line traces and general lineaments are detectable on small scale stereoscopic airphotos and on various scales and resolutions of monoscopic low sun elevation satellite imageries and that are not near-parallel to radar look direction.
Image Interpretation of Exposed Geostructures The following notes are taken from Berger, 1994 p 53 and 68 (see Unit 12 Select Bibliography): “The ability to recognize and map geological structures from remote sensing data is dependent primarily on two main factors: the level of bedrock exposure of the mapped structures and their magnitude of deformation. Exposed structures are recognized and analysed from image data by the unique expressions of their inclined bedrock strata and fault-line traces. … fault lines are rarely found in nature because their initial surface expression is modified by erosional processes shortly after faulting has occurred. The resulting fault-line traces, however, preserve several diagnostic surface attributes which can be recognized on imagery – e.g. springs, lakes, sag ponds, linear valleys, offset drainage.’’
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_6, © Springer-Verlag Berlin Heidelberg 2009
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Group Gravity Structures 11
11 Stock Salt-Evaporite Diapirs Characterization Diapiric stocks are plastic intrusive structures that originate in sediments accumulated in continental playa (L2), coastal sabkha (Bt1e) and marine evaporite basins throughout Phanerozoic time. They are a distortion of such tabular source sediments into vertical-walled cylindrical stocks driven upward by buoyant forces due to the contrast in density between the evaporites and the overlying strata. The stocks rise episodically through thicknesses of 2 to 8 km of overlying strata. Periods of growth, between 0.1 and 1 mm yr–1 for several million years, alternate with periods of dormancy. At outcrop the diapirs have a generally circular symmetry range from nil to 500 m in height and from 1 to 10 km and more in diameter. The composing anhydrite and gypsum are differentially eroded by dense drainage networks. Five Variants are based on their modes of emplacement.
Geohazard Relations The evaporites are weak rocks and are subject to dissolution and collapse. Potential engineering geological problems also relate to the fact that anhydrite will readily combine with water to form gypsum and in so doing will expand rapidly in volume, in some cases over 50%. Seismic shocks greater than 6 MM can also result from shear fracturing of the country rock caused by the drag of rising salt.
Select Bibliography Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, Central Iran. GSA Memoir 177:28 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 43–46, 43–47 Scheidegger A (2004) Morphotectonics. Springer-Verlag, Berlin Scott RB, Bryant B, Perry WJ (2000) Neogene deformation related to evaporite dissolution and diapirism along the southwest flank of the White River Uplift, northwestern Colorado. Proc. GSA Annual Meeting, vol 32, no 7 Suppe J (1985) Principles of structural geology. Prentice-Hall, Englewood Cliffs, NJ, pp 242–249 Talbot CJ, Jackson MPA (1987) Salt tectonics. Scientific American 256(2):70–79
11 · Stock Salt Evaporite Diapirs
Fig. 11-1. Location. Geographic. 102° W, 78°30' N, Ellef Ringnes Island, Queen Elizabeth Islands, Nunavut, Canada Geologic. Lower Cretaceous Sverdrup Basin Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 500 000 Acquisition date. 20 August 1974 Source. USGS Comments. This Landsat subscene covers 75% of the 11 295 km2 of Ellef Ringnes Island. The island is a low plateau with elevations <300 m consisting of interbedded Lower Cretaceous sandstones (bright) and siltstones (dark). These rocks are moderately disturbed, mainly as monocli-
nal flanks, in relation to a group of six Upper Carboniferous and Permian anhydrite and gypsum diapirs. Five of the structures are located by arrows. Fluvial dissection of the gypsum has relief in the order of 100 to 125 m. The ground surface consists of a veneer of substantially weathered and colluviated bedrocks little disturbed by glaciation. The only vegetation in this high arctic ecoclimate is a sparse cover of mosses and lichens on the dark siltstones, the sandstones and gypsum are barren. The east side of the brown zone surrounding Hoodoo dome in the lower right of the image is the location of the experimental procedure related to an exploratory oil well described in geounit Zk1. Figures 11-2 and 11-3 are stereomodels of two of these domes.
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Fig. 11-2. (Caption on p. 338)
11 · Stock Salt Evaporite Diapirs
Fig. 11-3. (Caption on p. 338)
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Fig. 11-2. Location. Geographic. 102°10' W, 78°30' N, Ellef Ringnes Island, Nunavut Geologic. Lower Cretaceous Sverdrup Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A16192-20, 21 Comments. This stereomodel covers the 6.5 km long × 3.7 km wide Isachsen Dome which is located on the west side of Fig. 11-1. The diapir is located 15 km west of the Dumbells structure of Fig. 11-3. The intense and deep fluvial dissection of the gypsum is striking. The monoclinal dips of the rim rocks 65° to 80° near the domes are characterized by the bright sandstones and the dark siltstones.
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Fig. 11-3. Location. Geographic. 101° W, 78°30' N, Ellef Ringnes Island, Nunavut Geologic. Lower Cretaceous Sverdrup Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A16192-103, 104 Comments. This delineated stereomodel located in the north of Fig. 11-1 covers 20 km of the 50 km long joint Dumbells Dome diapir structure. The label 11.5-cb is an early reclassified descriptor. The associated W4/5.1 antiform of the surrounding sedimentary rocks is well displayed. This location is just west of the polygons in shales of Fig. Zi4-9.
11 · Stock Salt Evaporite Diapirs
Fig. 11-4. Location. Geographic. 01°52' E, 33°39' N, Algeria Geologic. Sahara, south Atlas Piedmont Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 20 August 1959
Source. Journal Photo Interprétation, Éditions ESKA Paris, 63-4, 2 Comments. This stereomodel shows the Kef el Melah Diapir of Upper Triassic/Liassic salt and gypsum 90 km south-west of Laghouat. 11.1 denotes the cap rock portion. This is one of a number of diapiric events which pierced through the folded Jurassico/Cretaceous sediments of the Sahara Atlas ranges.
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11.1 Pillow Domes Characterization Pillow domes have the same genetic characteristics as their parent unit; they differ in the fact that they have domed up but not pierced the overlying strata.
Geohazard Relations
Fig. 11.1-2.
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11.1
Division 3 · Geostructures
Source. John S. Shelton Comments. An air perspective view of a Jurassic pillow dome, Avery Island at Vermilion Bay on the coast of the Gulf of Mexico in southern Louisiana USA. The dome is approximately 3 km in diameter and 45 m in elevation in structure center. The top of the diapir stock is 5 m below the surface. Figure 11.1-4 is a stereogram of the northeast margin of the dome.
Withdrawal of hydrocarbons trapped against the flanks of upwelling salt diapirs can induce substantial earthquakes in associated faults. Crude oil and natural gas that have been extracted are sometimes stored in caverns in large diapirs, and caverns are being evaluated as possible permanent disposal sites for radioactive wastes. The presence of permeable rocks that could compromise the seal of such storage caverns is a potential hazard.
Select Bibliography Ala MA (1974) Salt diapirism in Southern Iran. AAPG Bull 58(9): 1758–1770 Autin WJ, McCulloh RP, Davison AT (1986) Quaternary geology of Avery Island, Louisiana. Gulf Coast Association of Geological Societies Transactions 36:379–390 Ewing TE (1991) Quaternary tectonic history of the Gulf of Mexico Coastal Plain. Quaternary Nonglacial Geology: Coterminous U.S. GSA Geology of North America K-2:584 Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, Central Iran. GSA Memoir 177:38 Miller VC (1961) Photogeology. McGraw-Hill, New York, pp 158–161
Fig. 11.1-3.
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Location. Geographic. 54°21' E, 32°46' N, Zarin Basin of Kalut Diapir Province central Iran Geologic. Intermontane basin of Alpine orogeny Source. Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, central Iran. Geological Society of America Memoir 177, p 33, fig 1.28, photo by J. Stöcklin Comments. These are ground and air perspective views of a small diapir of Eocene salt: a in ground view A is a gypsum rim a in air view B to southeast is the same rim b is early morning shadow Ground view A misleads with the appearance of a pillow dome cap rock.
Fig. 11.1-1. Source. Unattributed Comments. This is a simplified section of the pillow dome Variant of the salt diapir. The salt has domed up but not pierced the overlying strata. The relation of hydrocarbons is indicated.
11.1 · Pillow Domes
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Fig. 11.1-4. Location. Geographic. 91°54' W, 29°54' N, southern Louisiana, USA Geologic. Gulf of Mexico coastal plain Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 20 000 Acquisition date. 9 December 1963 Source. Way DS (1973) Terrain analysis. Dowden Hutchinson & Ross Inc., p 77, fig 6.3 Comments. The stereomodel covers a 1 250 m by 3 000 m strip of the north margin of the 3 km diameter, 45 m high Avery Dome of Fig. 11.1-2. The top of the Jurassic diapir is 5 m below Pleistocene fluvial sediments that cover this portion of the plain. The dissection of the dome indicates that uplift has continued to the present.
11.1 · Pillow Domes ▼
Fig. 11.1-5.
Location. Geographic. 53°35' E, 29°15' N, southern Iran Vertical Airphoto/Image. Type. MSS subscene, 80 m resolution Scale. 1: 500 000 Acquisition date. 20 September 1972 Source. USGS Comments. The Kharman Pillow Dome, 3 184 m just south of the 1 900 km2 Neriz Playa, is delimited in this Landsat subscene in the Zagros Mountains of southern Iran. The dome is 12 by 15 km broad, rises 1 800 m above the local valley floor, and is adjacent to the plunge of an anticlinal structure, with which other Zagros diapirs are typically associated. The dome and anticline consist of Early Tertiary dolomite; the intruding salt is Precambrian. The inset frame locates map fig. 5 in Ala (1974). Figure 11.3-2 discusses the Zagros Mountain Belt. ▼
Fig. 11.1-6.
Location. Geographic. 53°53' E, 27°20' N, southern Iran Vertical Airphoto/Image. Type. MSS subscene, 80 m resolution Scale. 1: 500 000 Acquisition date. 28 February 1973 Source. USGS Comments. Landsat subscene in the Zagros Mountains covers Gavbast Dome 210 km south of the Kharman Dome of Fig. 11.1-5. It has the same plane dimensions, but is 1 000 m lower in elevation. It is located more typically in the crestal region of the fold, and consists of Jurassic carbonates. Anticline rocks are Mid-Cretaceous to Lower Tertiary carbonates and shale. The underlying diapir salt is Precambrian. Inset frame locates map, fig. 4 in Ala (1974). White zones in the interfold depressions are L2 evaporites with partly irrigated Fu1 fans on their margins. Figure 11.3-2 discusses the Zagros Mountain Belt.
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Fig. 11.1-5. (Caption on p. 343)
11.1 · Pillow Domes
Fig. 11.1-6. (Caption on p. 343)
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Division 3 · Geostructures
11.2 Duplex Stocks Characterization Duplex stocks are distinguished from the parent simple stock geounit in airphotos by at least three-fold circumferential pattern which is a composite of two source layers. The primary diapir material forms the core of the duplex structure. Peripheral rings are composed of both overlying deposits (evaporites and/or other sediments) which have been dragged up during diapir formation and diapir material itself. The entrainment of overburden can occur when its viscosity is similar to that of the salt. The combined materials upwell, mushroom out and overhang as infolded lobes. The airphoto pattern is the exposure of the structure as truncated by erosion.
Fig. 11.2-1. Location. Geographic. 53°45' E, 34°57' N, central Iran Geologic. Intracontinental basin of Alpine orogeny Source. Jackson MPA et al. (1990) Salt diapirs of the Great Kavir, central Iran. Geological Society of America Memoir 177, pl 13
Geohazard Relations “One of the reasons salt deposits have been proposed as storage sites for radioactive waste is that they are relatively impermeable. If a waste-storage cavern were built in a duplex stock entrained layers of permeable sedimentary rocks could act as conduits, channeling water through the cavern. The water could potentially carry radionuclides into the environment”. (Talbot and Jackson 1987).
Reference Talbot CJ, Jackson MPA (1987) Salt tectonics. Scientific American 256(2):70–79
Select Bibliography Eardley AJ (1962) Structural geology of North America, 2nd edn. Harper and Row, New York, p 659 Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, Central Iran. GSA Memoir 177, pp 71–82
Comments. The figure is an inferred cross section through a duplex stock above and below present erosion level. Spn (Oligocene-Miocene) younger salt is shown dragged up by the upwelling spe older (Eocene) salt. M1, M2 and M3 are bedded Miocene gypsiferous salts; EOg is Eocene massive rock salt generally not exposed in this region. See vertical airphoto Fig. 11.2-2.
11.2 · Duplex Stocks
Fig. 11.2-2. Location. Geographic. 53°45' E, 34°57' N, central Iran Source. Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, central Iran. Geological Society of America Memoir 177, p 47, fig 1.42, photo by Worldwide Aerial Surveys, Inc. Comments. Airphoto of a single Mid Tertiary diapir shows the dark-toned finely-banded repeated cycles of salt, gypsum, mudstone of the younger Miocene Spn salt series of
Fig. 11.2-1 around the mottled brighter Spe older salt of the same figure. The broken line locates the cross section of Fig. 11.2-1. The striped rocks into which the dome is intruded are part of the Great Kavir Neogene evaporite basin. They consist of folded saline mudstones with interbeds of rock salt. Code a is a small normal fault in the evaporites. Code b indicates a segment of an anticline. Code c is a regional syncline.
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11.3 Extrusive Salt Diapirs Characterization This Variant occurs as a further stage of development of the self-standing 11.1 pillow dome variant or of a dome in an anti or synformal fold. The diapir breaks through the dome surface and a mass of salt flows from the emerging plug as a tongue-shaped body resembling viscous lava that flows over the ground by gravity flow. The extrusion is a sign of active diapirism; the salt is evidently upwelling more rapidly than the extrusive plug is being eroded.
Geohazard Relations The potential hazards of this Variant are those of the pillow dome 11.1. The salt flow itself presents no hazard with flow rates of sub to 2 or 3 mm yr–1.
Select Bibliography Ala MA (1974) Salt diapirism in Southern Iran. American Association of Petroleum Geologists Bull. 58(9):1758–1770 Berger Z (1994) Satellite hydrocarbon exploration. Springer-Verlag, Berlin, p 63 Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, Central Iran. GSA Memoir 177:57–58, 66–67 Koyi H (1988) Experimental modeling of role of gravity with lateral shortening in Zagros Mountain Belt. AAPG Bull 72(11):1381–1394
Fig. 11.3-1.
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Location. Geographic. 54°28' E, 27°33' N, Fars Province, southern Iran Geologic. Zagros Alpine belt of Arabian/Eurasian Plate collision Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 55 000 Acquisition date. 28 May 1956 Source. USGS Comments. The stereomodel 20 km southeast of Lar in Fars Province shows extrusive late Proterozoic salt and gypsum flowing as a tongue-shaped ridged mass 300 m downhill and 5 km long from a diapiric plug which rose syntectonically with the Pliocene Gach anticline of Upper Cretaceous and Mid Tertiary carbonates. The satellite synoptic view of Fig. 11.3-2 provides the regional setting of this structure.
11.3 · Extrusive Salt Diapirs
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Fig. 11.3-2. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 28 February 1973 Source. USGS Comments. The coverage of the extrusive diapir of the stereomodel of Fig. 11.3-1 is shown in the inset frame of this Landsat scene. Seventeen other spectrally black Late Proterozoic extrusive diapirs are readily located within anticlinal folds, the characteristic structural style of the
Mid-Pliocene sedimentary rocks of the Iranian Zagros Mountains. The white areas are L2 evaporites in interfold depressions. The image covers 180 km of the southern part of the 1 300 km long mountain chain which is the Arabian Shield–Eurasian Plate collision boundary. The positive expression of the anticlinal (convex upwards) fold ridges is due to a slow rate of denudation in a region of extreme aridity and the young age of the fold belt. The salt diapirs are syntectonic with the folding process of the anticlines. See also Fig. W1-6.
11.4 · Elongate Diapirs
11.4 Elongate Diapirs
Geohazard Relations See Geounit 11.
Characterization Select Bibliography Elongated diapirs develop by association with anticlinal (geological strata folded in arch form) and normal fault (Geostructure Unit 12) tectonism. The shape of the latter is controlled by local or regional normal faults. Salt rises into anticlines by being squeezed from adjacent sediment loaded synclinal sites or into folds that are cut by basement faults. The salt and gypsum become exposed and dissected or dissolved by erosion of the overlying confining strata on the crests of the anticlines. The flanks of some anticlines can collapse along graben faults that result from removal of the supporting salt by flowage andor solution.
Cater FW (1970) Geology of the Salt Anticline Region in Southwestern Colorado. USGS Professional Paper 637:50, 51, 63–67 Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, Central Iran. GSA Memoir 177:46 Patton PC, Biggar N, Condit CD, Gillam ML, Love DW, Machette MN, Mayer L, Morrison RB, Roshold JN (1991) Quaternary geology of the Colorado Plateau. In: Morrison RB (ed) Quaternary nonglacial geology: Conterminous U.S. GSA Geology of North America K-2:384 Talbot CJ, Jackson MPA (1987) Salt tectonics. Scientific American 256(2):70–79 Trettin HP (1991) Geology of the Innuitian Orogen and Arctic Platform of Canada and Greenland. Geology of Canada 3:346–348
Fig. 11.4-1. Source. Cater FW (1970) Geology of the salt anticline region in southwestern Colorado. USGS, pp 636, fig 13 Comments. The figure is a cross-section of the elongate diapirs of Gypsum and Paradox Valleys, Colorado shown on the Landsat image of Fig. 11.4-6.
Fig. 11.4-2. Location. Geographic. 108°45' W, 36°00' N, southwest Colorado, USA Geologic. Upper Carboniferous piercements of Mesozoic sediments of northeast Colorado Plateau Source. Cater FW (1970) Geology of the salt anticline region in southwestern Colorado. USGS, pp 637, fig 2, pp 8, 50–51, 63–67 Comments. A ground view north across the Paradox elongate diapir of Figs. 11.4-1 and 11.4-6 showing collapse of flank along graben faults resulting from flowage or solution of supporting salt.
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Fig. 11.4-3. Source. Thornbury WD (1965) Regional geomorphology of the United States. John Wiley & Sons Inc., p 431, fig 22.17 Comments. An air perspective view of the Gypsum Valley elongate diapir in southwestern Colorado pictured in the satellite image subscene of Fig. 11.4-6.
Fig. 11.4-4.
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Location. Geographic. 54°21' E, 35°02' N, central Iran Geologic. Intracontinental basin of Alpine orogeny Vertical Airphoto/Image. Type. pan b/w, airphoto Scale. 1: 58 000 Acquisition date. 1955 Source. Jackson MPA, Cornelius RR, Craig CH, Gansser A, Stocklin J, Talbot CJ (1990) Salt diapirs of the Great Kavir, central Iran. Geological Society of America, Memoir 177, p 46, fig 1.41, photo by Worldwide Aerial Surveys, Inc. Comments. This airphoto shows one of a cluster of 50 diapirs in the north part of the Kavir Megaplaya. The diapir delineated in red is elongate and controlled by a regional fault and is flanked by local splay faults. The Oligocene-Miocene playa bedding traces have of 15–20° dip. a is a regional fault; b are two piercing spines of Eocene salt which also occurs in the core of the structure.
11.4 · Elongate Diapirs
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11.4 · Elongate Diapirs ▼
Fig. 11.4-5. Location. Geographic. 67°09' W, 19°26' S, southwest Bolivia Geologic. Altiplano Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 1 September 1961 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 30 Comments. This stereomodel shows the elongate shape of a 2 300 m long by 900 m wide Miocene to Eocene gypsum diapir that is controlled by its location along the strike of a belt of synclinal W1 Cretaceous sediments. The belt is an inlier of Cordilleran structures located between the Coipasa Salar and Lago Poopo. The only Fu1 alluvial fans occurring on the flanks of this foldbelt are evidently derived from the erosion of the overlying sediments by the rising plug. The fans have spread eastward onto the adjacent plain. An igneous intrusion, in the form of a multi domal unit, delineated in dashed lines and associated with a fault, lies normal to the strike of the fold belt.
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Fig. 11.4-6.
Location. Geographic. 108°40' W, 38°15' N, southwest Colorado Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 350 000 Acquisition date. Not given Source. USGS Comments. The Landsat subscene is centered on a set of elongate northwest trending breached salt anticlines and synclines about 40 km long in the northeast part of the Colorado Plateau. The strike of the folds is parallel with that of a large uplift (Uncompahgre) to the north. The structures are part of a group of eight in the region and are unique in North America. They consist of Jurassic rocks cored with Upper Carboniferous salt. Though not visible in the image, the floors of the anticlines have collapsed due to flowage and solution of the underlying salt, producing “anticlinal valleys”. The red inset frame locates the air perspective view of Fig. 11.4-3. The broken line locates the cross-section of Fig. 11.4-1.
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Fig. 11.4-6. (Caption on p. 355)
12 · Dip Slip Normal Faults
Group Fault Line Traces 12 Dip-Slip Normal Faults Characterization A normal fault is a planar fracture in a consolidated rock mass or coherent surficial material resulting from movement reflecting tensional stress. Movement is parallel to the dip of the fault plane which is typically in the range of 45 to 90 degrees. Differential displacements are observable on opposite sides of the rock masses. Faults in post-Paleozoic bedded rocks which have not been severely eroded generally exhibit positive or negative relief. Once developed a fault forms a zone of weakness, many are infilled with weathered gouge and are often major sources of groundwater. The length of normal faults on airphotos and satellite images varies from local of a few kilometers, to regional and to continental. Fault-related terminology applicable to photogeology includes (Ollier 1988): Fault complex: A system of interconnecting faults. Fault line: The intersection of a fault with the Earth’s surface. Fault-line scarp: A scarp that results from differential erosion of rocks of different resistance on either side of a fault rather than resulting directly from fault movement. Fault scarp: A scarp formed as direct result of faulting at the Earth’s surface. Fault set: Two or more parallel faults in an area. Fault system: Two or more fault sets that were formed at the same time. (Difficult to establish without field evidence).
Geohazard Relations Active faults are those which are liable to recurrent movement; they are related to seismic activity and present major environmental hazards. Faults which have been
active in the last few thousand years still preserve features which can be seen on air photos and space images. The most obvious sign of the activity of a fault is its disturbance of cultural features and younger surficial deposits. Active normal faults with important vertical components of movement are easily recognized by the scarps they produce. Many small faults which can be a hazard to structures can only be detected during site investigations by civil engineers.
Reference Ollier CD (1988) Glossary of morphotectonics. Dept. of Geography and Planning. University of New England, Australia
Select Bibliography Photogeology Allum JAE (1966) Photogeology and regional mapping. Pergamon Press, Oxford, pp 45–49 Berger Z (1994) Satellite hydrocarbon exploration. Springer-Verlag, Berlin, pp 66–69 Budkewitsch P (2002) Software tools for geological mapping. Remote Sensing in Canada 30(2) Drury SA (1987) Image interpretation in geology. Allen & Unwin, London, pp 92–98 Miller VC (1961) Photogeology. McGraw Hill, New York, pp 108–109, 156, 188–191, 196–201, 220–223, 230–231 van Zuidam RA (1985/86) Aerial photo interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC, The Hague, pp 143, 148, 149 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, p 199
Other Allen CR (1975) Geological criteria for evaluating seismicity. GSA Bull 86, Aug 1975, doc no 50801, pp 1041–1057 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 44–1–44–13 Slemmons DB (1979) Evaluation of geomorphic features of active faults for engineering design and siting studies, Course Syllabus. Dept. of Geological Sciences, MacKay School of Mines, University of Nevada Suppe J (1985) Principles of structural geology. Prentice-Hall, Englewood Cliffs, NJ, pp 270–276
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Fig. 12-1. Source. Krynine DP, Judd WR (1957) Principles of engineering geology and geotechnics. McGraw-Hill, p 73, fig 2.19a. Reproduced with permission of The McGrawHill Companies Comments. A modified block diagram shows rock mass displacement and a typical angle of dip of a normal fault.
Fig. 12-2. Source. Burton J (1972) Animals of the African year. Holt, Rinehart & Winston, NY Eurobook Ltd., p 39 Comments. The cliff in this photo is the plane of a normal fault in volcanic rocks of the East African Rift Valley System with vegetated Mv1.2 talus deposits at the base. The regional setting is shown in Fig. Vc3.1-9.
12 · Dip Slip Normal Faults
Fig. 12-3. Source. Huntoon PW (1974) The Post-Paleozoic Structural Geology of the Eastern Grand Canyon, Arizona. In: Breed WJ, Road EC (eds) Geology of the Grand Canyon. Northern Arizona Society of Science and Art Inc., p 97, fig 12 Comments. Black and white arrows locate the Sinyala Cenozoic Fault where it crosses the Colorado River at Longitude 112°35' in the center of this high-altitude perspective airphoto. The view is to the south-west across Upper Permian limestones and sandstones.
Huntoon (1974) states that this fault “clearly illustrates a tendency for faults to dampen out with elevation in the Paleozoic rocks of the Grand Canyon. The largest displacement found on the fault is 3.6 m, west down, in the Precambrian rocks along the Colorado River. As the fault is traced upward in the cliffs, the displacement diminishes to 1.5 m in a vertical distance of 610 m. At that rate the fault would die out before reaching the Upper Paleozoic units if they were present. The mechanism that adequately accounts for this phenomenon is flowage and flexing of the rocks in the vicinity of the fault”.
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Location. Geographic. 115°14' W, 75°28' N, Arctic Archipelago Source. Tozer ET, Thorsteinsson RT (1964) Western Queen Elizabeth Islands, Arctic Archipelago. GSC Memoir 332, p 189, pl L. Courtesy of Natural Resources Canada, Geological Survey of Canada Comments. The black arrows on this air perspective view to the southeast indicate a fault line scarp on southwest Melville Island. The lower Dg rocks in foreground are Upper Devonian thinly interbedded sandstones, siltstones and shales (i.e., W4 geounit). The scarp-forming Dh rocks are Mid-Devonian thickbedded sandstones (S1). A small icefield occupies the higher ground.
Fig. 12-5.
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Fig. 12-4.
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Location. Geographic. 68°33' W, 16°02' S northwest Bolivia Geologic. Andes Cordillera Oriental Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 10 August 1953 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 61 Comments. The stereomodel shows a northwest/southeast oriented neotectonic normal fault in Quaternary glacial till (Gf4) sediments. The fault is in southern prolongation of the structural eastern margin of Lake Titicaca.
12 · Dip Slip Normal Faults
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Division 3 · Geostructures
Fig. 12-6. Location. Geographic. Southeast Sri Lanka Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. Personal archive Comments. Stereomodel shows massive northeast trending faulting and jointing in parallel strike ridges of a circum island peneplain of Archean gneisses. The faults are strongly etched out by deep weathering where moisture is concentrated and retained, while it is shallow on the exposed surfaces of the resistant bedrock. The terrain is under dense forest cover. A regional faultrelated rock avalanche is depicted in Fig. Mv2.1-5.
Fig. 12-7.
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Location. Geographic. 70°02' W, 47°45' N, north shore, lower St. Lawrence River Geologic. Mid Proterozoic granite in Grenville Province of eastern Canadian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 1979 Source. © Gouvernement du Québec, tous droits réservés Comments. The normal fault drawn on this stereomodel at St. Fidèle de Mont Murray in Charlevoix-Est County has a throw of 180 m. It is probably a northeast prolongation of the fault system bounding the north side of the St. Lawrence Lowlands, an ancient rift system. The bright delineated square is a piece of cleared land used as a control point. The 180 m wide bright parallel band is a hydroelectric power transmission line corridor.
12 · Dip Slip Normal Faults
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Fig. 12-8. (Caption on p. 366)
12 · Dip Slip Normal Faults
Fig. 12-9. (Caption on p. 366)
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Fig. 12-8. Location. Geographic. 06°49' E, 43°35' N, Alpes de Provence Geologic. Contact of Lower Permian gneiss massif and Kp1 Jurassic carbonate plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. This stereomodel at Lac de St. Cassien reservoir near Grasse in the Massif du Tanneron shows a fieldmapped normal fault and associated photo inferred fracture trace. The gneiss massif is forested and dissected in contrast to the morphology and land use of the adjacent carbonate rocks.
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Fig. 12-9.
Location. Geographic. 03°14' E, 25°55' N, southeast Algeria Geologic. Hoggar Massif of African Craton Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 85 000 Acquisition date. 1969 Source. IGN – Photothèque Nationale, France Comments. A stereomodel at Adrar Tibaradine shows normal faults occurring at the north end of a fault system that marks the zone of contact of the Hoggar cratonic massif with Ordovician sandstones and Silurian shale cover rocks in this area. The R3 unit is outcrop of Proterozoic basement rocks with a cluster of Ed1.5 star dunes.
12.1 · Multidirectional Faults
12.1 Multidirectional Faults
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12.1
Characterization Normal fault line traces of regional extent visible on satellite images can be composed of segments of individual faults that intersect at oblique angles. Traces that exhibit positive relief, reflecting vertical movement along the fault or differential erosion, are relatively easy to map on lower resolution but synoptic coverage satellite images.
Geohazard Relations See Geounit 12 Dip slip normal fault.
Select Bibliography Berger Z (1994) Satellite hydrocarbon exploration. Springer-Verlag, Berlin, p 68 ▼
Fig. 12.1-1.
Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 09 October 1972 Source. MDA EarthSat Comments. Segments of multidirectional faults are clearlyexpressed in this Landsat image. They mark the west margin of the Tertiary rifting (a huge graben produced by subsidence between deep-seated parallel faults) middle Rhine Graben, from the Hercynian Vosges Massif in the south to the Triassic sandstones of the Pfälzer Wald in the north. ▼
Fig. 12.1-2.
Location. Geographic. 112°50' W 37°50' N scene center, southwest Utah Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 920 000 Acquisition date. October 1975, August 1976, June 1977 Source. USGS Comments. This multidate Landsat mosaic covers 200 km of the multidirectional Hurricane Fault which marks part of the western margin of the Colorado Plateau. Along most of its course in the image the fault consists of a zone of fractures as much as 1.5 km wide. At the south edge of the scene the fault is a single, scarped fracture. Known movements on the fault are of Miocene age. The irrigated areas near the northern arrows are at Cedar City and Parowan in the fault margin upper Virgin River valley. The fault in this area is known as the Hurricane Cliffs. The bright red area on the plateau east of the fault is yellow pine forest and pinyon-juniper woodland.
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Fig. 12.1-1. (Caption on p. 367)
12.1 · Multidirectional Faults
Fig. 12.1-2. (Caption on p. 367)
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13 Strike-slip Faults Characterization A strike-slip fault is a fault with a horizontal to sub-horizontal displacement of blocks. It is distinguished from the normal fault by a number of features:
Fault block movements are rarely strictly vertical or horizontal, they are generally a combination of, Geostructures 12 and 13, but such relations may not be detectable on airphotos. The relation of strike-slip faults to the macroscale structures of continental plate margins is discussed in Fig. 13-1.
Geohazard Relations It is relatively straight, without multidirectional segments. It does not cause scarping. Rocks do not match across the fault – offset effect. Major faults frequently have negative expressions; occupied by valleys. Major faults on satellite images often show fault line traces splaying obliquely from the master fault as related extensional or compressional features. Resolution limitations in both satellite images and many airphotos frequently do not permit identification of the relative sense of movement along strike-slip faults. Synonyms for strike slip fault are wrench, tear and transcurrent fault.
See normal fault Unit 12.
Select Bibliography Berger Z (1994) Satellite hydrocarbon exploration. Springer-Verlag, Berlin, p 69 Campagna DJ, Lewandowski DW (1991) The recognition of strikeslip fault systems using imagery, gravity, and topographic data sets. Photogrammetric Engineering & Remote Sensing 57(9):1195–1201 Everett JR, Morisawa M, Short NM (1986) Tectonic landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP486, pp 146–147 Rothery DA, Drury SA (1984) The neotectonics of the Tibetan Plateau. Tectonics 3:19–26 Shelton JS (1966) Geology illustrated. W.H. Freeman, San Francisco, pp 96–101
Fig. 13-1. Source. Von Bandat HF (1962) Aerogeology. Gulf Publishing Co., p 201, fig 18-3 Comments. A block diagram showing the geometry of displacement of rock masses affected by a strike slip fault, in this case with right lateral movement parallel to the fault’s strike. In plate tectonics one of three types of plate boundaries is the transform boundary or transform fault on continental plate margins This is a type of macroscale discontinuity of Geounit 19. As with the strike-slip fault a transform fault is parallel to the direction of relative horizontal motion of the continental plates on either side, with the exception that there is a lack of a continuous planar fault surface; instead the fault zone is composed of branching splay type fault segments. Major transform fault zones include
Dead Sea (see Fig. Vc4-7) San Andreas Anatolia in Turkey Philippines Denali in Alaska Alpine in New Zealand Great Glen in Scotland
Many of such boundaries are locked in tension before suddenly releasing and causing earthquakes which have triggered some of the world’s most destructive mass movements.
Fig. 13-2.
▼
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Location. Geographic. 65°56' W, 54°46' N, north central Labrador/ Quebec Geologic. Paleoproterozoic metasediments and metavolcanic rocks of Labrador Trough of the eastern shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 31 680 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL, A 11404-128 and 130 Comments. The stereomodel shows a strike-slip fault that displaced folded interbedded sedimentary and volcanic rocks. See a composite lineament in this same orogen in Fig. 15-1.
13 · Strike slip Faults
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13 · Strike slip Faults ▼
Fig. 13-3.
Location. Geographic. 05°23' E, 23°01' N, Southeast Algeria Geologic. Hoggar Massif of African Craton Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. 1969 Source. IGN – Photothèque Nationale, France Comments. Complex sets of strike-slip and normal faults occur in this stereomodel of Upper Proterozoic rocks. NW/SE oriented lineaments in the dark grey migmatitic granite in the center of the model are interpreted as normal faults. E/W lineaments in the same rock unit are strike-slip faults. The multi-oriented linears in the white granite plain are dykes – sheet-like tabular bodies of igneous rock that cut massive rocks. This plain is visible in the southwest quadrant of the space photo of Fig. Vc4-6 between Units Nr3 and Ef1. The rocks on the left margin of the model are foliated metamorphics. The light-grey rocks to the right of the faulted granite are undifferentiated granite. The smooth dark grey units on the far right are X1 Holocene basalt flows.
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Fig. 13-4. Location. Geographic. 01°59' E, 25°28' N central Algeria Geologic. Mid Paleozoic craton cover sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 30 March 1952
Source. Journal Photo Interprétation, Editions ESKA, Paris, 62-2-6 Comments. The stereomodel shows a set of east-west strike-slip faults displacing Devonian sediments of northward-dipping resistant cuesta scarps between two possibly fracture-related valleys in the Ahnet Basin. North is at the bottom of this model.
13 · Strike slip Faults
Fig. 13-5. Location. Geographic. 78°20' E, 40°12' N, northwest China Source. USGS Comments. The location of this 100 km by 50 km segment of a 1:500 000 Shuttle image of 14 November 1981 is shown in the inset frame of the Landsat scene of Fig. 14-10. The larger scale, and spatial and microwave resolutions permit a clearer detection and mapping of local strike slip faults (red) across the bright cuestas of fold and thrust ridges of Lower Paleozoic carbonate and clastic sediments.
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Fig. 13-6. Location. Geographic. 71°30' E, 32°30' N, north Pakistan Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 500 000 Acquisition date. 13 December 1976 Source. USGS Comments. Landsat subscene in north Pakistan shows 60 km of strike-slip faulting associated with detachment and tec-
tonic transport of a block of Permian sediments (the Salt Range) off-scene to the southeast along a salt layer. The horseshoe narrow anticlines are Jurassic/Triassic rocks of the Surghar Range. They enclose a reach of the northern Indus Valley and the reservoir of the Taunsa Barrage, designed for agricultural irrigation and also generating 100 kW of electricity. The area in the northeast of the image is part of the Upper Tertiary rocks of Fig. S1.2-6.
13 · Strike slip Faults
Fig. 13-7. Location. Geographic. 135°W, 62°40' N scene center, southern Yukon Territory, Canada Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 13 September 1973 Source. USGS Comments. This Landsat scene covers 180 km of the 725 km long Tintina Trench strike-slip fault; the arrows on the right point to a 2 km wide section of the trench occupied by the Pelly River.
The fault is the boundary between two major tectonic regions of the Cordillera, and is one of the world’s major fault zones. The rocks north of the trench range in elevation between 1 800 and 2 000 m. They are Mid Proterozoic and Lower Paleozoic sediments of the deformed western margin of the Ancestral North American Craton. The rocks south of the trench range in elevation between 600 m in the southwest near the Yukon River to 2 100 m in the Glenlyon Range of the Pelly Mountains in the northeast. These are Mesozoic intrusive and volcanic rocks which are part of an assemblage of pericratonic terranes (mainly Nisutlin Terrane in scene) accreted to the North American Craton.
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14 Thrust Faults
thrust may be either less or more deformed than the lower. Field mapping would be required to make the distinction.
Characterization
Geohazard Relations
Thrust or reverse faults are primarily developed in mega and macroscopic tectonic belts along compressive continental plate boundaries (two plates moving towards each other). Elsewhere they are less common than dip- and strike-slip faults. As a class thrust faults are the most difficult to recognize on airphotos or images because the low angle of the fault causes the trace to follow topography and resemble bedding rather than from a discordant lineament. Detachment (décollement – independent styles of deformation in the rocks above and below) segments occur along stratigraphic horizons of low rock strength or high fluid pressures. Thrusts have some of the same characteristics as angular unconformities. Bedding above an unconformity is less deformed than below; whereas the upper sheet of a
See Geounit 12.
Fig. 14-1.
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378
Source. Prost GL (1989) Recognizing thrust faults and exploration implications. Proceedings Seventh Thematic Conference on Remote Sensing for Exploration Geology, ERIM, p 1116, fig 1 Comments. The block diagram shows the sinuous irregular trace of a thrust fault, with discordant strikes and dips across the fault.
Fig. 14-2. Source. Oakeshott GB (1971) California’s changing landscapes. McGraw-Hill Book Co., p 108, fig 7-3. Reproduced with permission of the McGraw-Hill Companies Comments. Photo shows a thrust fault separating two Cambrian sedimentary rock formations in California’s Death Valley region.
Select Bibliography Dekker F, Balkwill H, Slater A, Herner R, Kampschuur W (1989) Hydrocarbon exploration through remote sensing and field work in the onshore eastern Papuan Fold Belt, Gulf Province, Papua New Guinea. Proceedings, Seventh Thematic Conference on Remote Sensing for Exploration Geology, (ERIM), pp 65–80 Miller VC (1961) Photogeology. McGraw-Hill, New York, pp 202–203, 218–219 Prost GL (1989) Recognizing thrust faults, and exploration implications. Proceedings, Seventh Thematic Conference on Remote Sensing for Exploration Geology (ERIM), pp 1111–1123 Suppe J (1985) Principles of structural geology. Prentice-Hall, Englewood Cliffs, NJ, pp 280–286 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 200–201
14 · Thrust Faults
Fig. 14-3. Location. Geographic. 115°31' W, 36°10' N, southeast Nevada, USA Geologic. Adjacent to shear zone in southeast margin of Basin and Range shield margin assemblage Source. John S. Shelton Comments. Air perspective photo shows the Spring Mountains Keystone Thrust, a fault that is atypical of Basin and
Fig. 14-4. Location. Geographic. 84° W, 78°50' N, central Ellesmere Island, Nunavut Geologic. Mesozoic sediments of central Ellesmere Fold Belt
Range faulting. Dark Paleozoic sediments are thrust over resistant light-toned Mesozoic sandstones. The bright beds that appear like talus underlying the sandstones are weak Triassic sediments. The structure is further illustrated in the stereomodel of Fig. 14-8 and the satellite image of Fig. 14-9.
Source. Courtesy of Natural Resources Canada, NAPL – RR 114L-53, 27 April 1952 Comments. Air perspective photo is a view south from 1 500 m at a thrust fault over an overturned fold on the south side of Bay Fjord.
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Fig. 14-5. Source. Fen H, Beckel L (1973) Luftbild-Atlas Bayern. Paul List-Verlag, München, p 138, photo 60 Comments. This closeup air perspective view shows stacked thrust faulting of the Miocene Alpine orogeny. Triassic carbonates are thrust over Mv1-talus and forest concealed weak Paleogene flysch (interbedded marine sediments) in lower left. Location is in the Bavarian Pre-Alps 37 km southeast of Bregenz, Austria.
Fig. 14-6. Location. Geographic. French Riviera Geologic. Jurassic and Cretaceous carbonates of Maritime Alps Source. Unattributed Comments. This air perspective view northward at Villefranche east of Nice emphasizes the thrust faulting of Upper Jurassic carbonate strata over Upper Cretaceous marls and limestones. This location is also pictured in stereo in Fig. 14-7.
14 · Thrust Faults
▼
Fig. 14-7.
Location. Geographic. Nice Geologic. Maritime Alps of High Sedimentary Alps Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows the Jurassic limestones thrusted over the Cretaceous marls and limestones of Fig. 14-6. The Cap Ferrat Peninsula and Mont Boron to its left are anticlinal ridges of Upper Jurassic limestones striking normal to the coastline. They may be related to the similarly oriented folds of the Chaine de Férion off the model, 10 km to the north behind the thrust sheets. ▼
Fig. 14-8.
Location. Geographic. 115°31' W, 36°10' N, Southern Nevada Geologic. Shield margin rift zone with episodic magmatism Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 63 360 Acquisition date. 16 July 1950 Source. Unspecified U.S. government agency Comments. A stereomodel of the Keystone Thrust of Fig. 14-3. The stereo coverage is indicated on the satellite image of Fig. 14-9. ▼
Fig. 14-9.
Location. Geographic. 115°30' W, 36°05' N, southeast Nevada, USA Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 520 000 Acquisition date. 5 April 1977 Source. Personal archive Comments. The Keystone Thrust west of Las Vegas is traced on this Landsat subscene. Comments for this structure are in Fig. 14-3. Inset frame locates the stereogram of Fig. 14-8. Red lines emphasize Units 18 or 19.1 lineaments.
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Fig. 14-7. (Caption on p. 381)
14 · Thrust Faults
Fig. 14-8. (Caption on p. 381)
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Fig. 14-9. (Caption on p. 381)
14 · Thrust Faults
Fig. 14-10. Location. Geographic. 78°20' E, 40°12' N scene center, western China Vertical Airphoto/Image. Type. MSS infrared, 80 m resolution Scale. 1: 1 000 000 Acquisition date. 14 February 1973 Source. USGS Comments. The Landsat scene shows conspicuous Late Tertiary to Quaternary southeast-facing thrust faults of the 2 500 to 3 000 m high Kelpin Tagh Fold Belt of Lower Paleozoic carbonate and clastic sediments.
The belt is in a zone of active compressive deformation between the Quaternary covered basement shield rocks of the Tarim Basin, lower right, elevation 1 000 m and the 4 000 m to 6 000 m ranges of the Tien Shan Mountains, upper left. In the northwesternmost corner of the scene (upper left) the glaciated peaks are in Kirghizistan. Coalesced Fu1 alluvial fans fill the flats between the thrust ridges. The 15 km wide bright zone at the Tarim Basin contact consists of evaporite saline deposits. The inset frame shows the coverage of the radar image of Fig. 13-5 on which local strike-slip faults are mapped.
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Fig. 14-11. Location. Geographic. Mediterranean France Source. Personal archive Comments. Major detectable south-thrusting fault scarps have been traced on this 50 m resolution Landsat subscene of a 60 km section of the ridges in Mesozoic and Eocene calcareous rocks of the subalpine Pyreno-Provençal alpine chain east of Marseille. Other image-prominent Unit 12 normal faults are traced in red. The structures are related to a regional uplift in the Upper Miocene together with a regional topography which favoured southward gravity tectonics. This figure is an extension westward of Fig. S1.5-7.
15 · Composite Lineaments
15 Composite Lineaments
15
Characterization
Geohazard Relations Related geohazards include those of the fault activity status subsequently determined by higher resolution stereo airphoto or stereo satellite images interpretation or field work.
Select Bibliography Bagheri S, Kiefer RW (1986) Regional geologic mapping of digitally enhanced Landsat imagery in the south central Alborz Mountains of northern Iran. Proceedings, Symposium on Remote Sensing for Resources Development and Environmental Management – Enschede, pp 555–559 Gregory AF, Moore HD, Thirlwall SL (1983) An application of Landsat data to exploration in the NEA-IAEA Athabaska Test Area. GSC Paper 82–11, pp 111–115 Miller JB (1975) Landsat image studies as applied to petroleum exploration in Kenya. Research Conference on Remote Sensing, University of Kansas Scanvic J-Y (1983) Utilisation de la télédétection dans les Sciences de la Terre. BRGM, France, Manuels et méthodes, no 7, pp 37–46, 76–88
▼
Fig. 15-1.
Location. Geographic. 66°18' W, 55°20' N scene center, northern Québec Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. Image covers a segment of the deformed Proterozoic orogen of the Labrador Trough, resting unconformably on the Archean basement of the eastern Canadian Shield. Glacial scour along bedding contacts produced most of the linear lakes emphasizing the form of folding in basalts and gabbro sills in the southwest half of the mosaic. The beige striped area to the northeast are foliated paraschists and gneisses. See a strike-slip fault in this same regional structure in Fig. 13-2. North is on the left.
Fig. 15-2.
▼
A composite lineament is generally of macroscopic scale and consists of aligned segments of relief, drainage, vegetation or spectral tonality detectable on satellite imageries. The lineament is evidence of fault line trace Units 12, 13 and 14, and can be indicative of dykes (sheet like intrusions of igneous rock), sedimentary and metasedimentary bedding (W1), schistocity or gneissocity of foliated metamorphic rocks and brittle or ductile shear zones (tabular zones that have been crushed by many parallel fractures).
387
Location. Geographic. 58°37' W, 51°18' N scene center, eastern Québec Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image covers a sector of Mid-Proterozoic gneisses of the Interior Magmatic Belt of the Grenville Orogen of the Canadian Shield along the Saint Augustin River on the Lower Gulf of St. Lawrence. The terrain in this area is mainly denuded rock, areally scoured by glacial erosion which etched out the structural fabric. The large lineaments that dominate the scene are essentially fjord-like lakes near the coast. Many are also water-filled inland. See a stereomodel of fracture traces 90 km to the west in Fig. 18-8. North is on the left.
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Division 3 · Geostructures
Fig. 15-1. (Caption on p. 387)
15 · Composite Lineaments
Fig. 15-2. (Caption on p. 387)
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Division 3 · Geostructures
16 Horst Dip-Slip Fault Set
The dominantly extensional nature of these faults can lead to volcanic activity and emplacement of units of magmatic groups X, P and V.
Characterization Select Bibliography A horst is a terrain unit elevated above adjacent terrain along conjugate bounding normal faults. Typical morphology describes an elongate and relatively narrow structure with parallel faults, but the unit may also be irregularly shaped. The structure may be meso to macroscale.
Geohazard Relations The principal geohazard is seismicity related to the activity status of the bounding faults.
Park RG (1989) Foundations of structural geology. Blackie, London, p 6 Spate OHK, Learmouth ATA, Farmer BH (1967) India, Pakistan & Ceylon, The Regions. Methuen, London, pp 740, 751 Twidale CR, Foale MR (1969) Landforms illustrated. Nelson, Melbourne, pp 54–61 van Zuidam RA (1985/1986) Aerial photo interpretation in terrain analysis and geomorphological mapping. Smits Publishers/ITC, The Hague, p149 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 201, 203, 209 ▼
Fig. 16-1. Source. Park RG (1989) Foundations of structural geology, 2nd edn. Blackie, p 6, fig 1.9B Comments. A block diagram of a horst. An elevated block bounded by geounit 12 normal faults.
▼
Fig. 16-2. Location. Geographic. 149°23' E, 35°08' S, New South Wales, Australia Source. Ollier CD (1981) Tectonics and landforms. Longman, p 173, fig 12.14 Comments. A sketch map showing the 200 m high Cullarin horst structure and its modifications of local drainage at Lake George (the antecedent Molonglo River kept pace with uplift, Taylor’s Creek was beheaded). See the ground view of Fig. 16-6, the stereomodel of Fig. 16-7 and the Landsat scene of Fig. 16-8.
16 · Horst Dip Slip Fault Set
Fig. 16-3. Location. Geographic. Southern Honshu, Japan Source. Twidale CR (1971) Structural landforms. MIT Press, p 120, fig 51 Comments. This is a regional map and section of the horst and graben structures of the Landsat image of Fig. 16-9.
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Fig. 16-4. Location. Geographic. Kerala and Tamil Nadu States, southwest India Geologic. South Deccan Craton Source. Spate OHK, Learmouth ATA, Farmer BH (1967)
India, Pakistan and Ceylon, the Regions, 3rd edn. Methuen, p 674, fig 22.7 Comments. Map shows the Palni Hills Cretaceous horst in gneissic cratonic rocks, and coverage of the satellite image of Fig. 16-10.
16 · Horst Dip Slip Fault Set
Fig. 16-5. Location. Geographic. 107°25' W, 75°54' N, Arctic Islands, Nunavut Source. Courtesy of Natural Resources Canada, NAPL T149R-200 Comments. An air view westward over a small, 19 km by 4.5 km, horst structure on eastern Melville Island. The horst rocks are Devonian limestones (K1-D) dipping north 20°, flanked on the south by W4 Carboniferous arenites. The horst elevation, at about 350 m, is approximately 150 m above the W4 ground. Structurally it is a westward continuation of the Towson Point anticline. The ice-covered water body, on 2 August 1950, is the western arm of Weatherall Bay.
Fig. 16-6. Source. Twidale CR, Foale MR (1969). Landforms illustrated. Thomas Nelson (Australia) Ltd., p 60, fig 13 Comments. Ground view looking south along the Lake George horst fault of the stereomodel of Fig. 16-7 in southern New South Wales; see the sketch map of Fig. 16-2.
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Fig. 16-7. Location. Geographic. 149°22' E, 35°05' S, southeast Australia Geologic. Metasediments of the Southern Tablelands of the Eastern elevated continental margin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. Not given
Source. Twidale CR, Foale MR (1969) Landforms illustrated. Thomas Nelson (Australia) Ltd., p 60 fig 12 and 13 Comments. The stereomodel shows the eastern edge of the 200 m high Lake George/Cullarin. Horst developed in Lower Paleozoic sedimentary rocks. Down-fault Lake George is 150 km2 and <5 m deep. Occasionally dries but is not saline. Location is framed on satellite image of Fig. 16-8. See ground photo of Fig. 16-6 and diagram of Fig. 16-2.
16 · Horst Dip Slip Fault Set
Fig. 16-8. Location. Geographic. 149°22' E, 35°05' S scene center, eastern Australia Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. Not given Source. USGS Comments. This image shows a number of fault scarps that are related to regional Tertiary block faulting in the elevated plateaus of New South Wales.
The inset frame locates the stereo photopair of Fig. 16-7. The photos show the dip-slip fault of the 200 m high Cullarin Horst at Lake George, diagrammed in Fig. 16-2, 25 km northeast of Canberra. The rocks of Cullarin Horst are Ordovician quartzite, phyllite, slate and metagreywacke. Adjacent rocks are Silurian dacite in the lake depression, and Ordovician sandstone and shale on the west. The dark areas are eucalyptus forests.
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Fig. 16-9. Location. Geographic. 135°26' E, 34°29' N scene center, southern Honshu, Japan Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 24 October 1972 Source. USGS
Comments. The fault lines drawn on this Landsat scene locate horsts and grabens in Paleozoic basement rocks. See regional map of Fig. 16-3. The east-west lineament bounding the Osaka Graben on the south and equally dividing the scene is a major fault that has had both vertical (Unit 12) and right-lateral slip (Unit 13) in Quaternary time. The fault, which is capable of being the focus of large earthquakes, could be recognized as an active feature over a length of 600 km.
16 · Horst Dip Slip Fault Set
Fig. 16-10. Location. Geographic. 77°12' E, 09°57' N scene center, southern India Geologic. Cretaceous horst of Indian Shield Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 02 September 1973 Source. USGS
Comments. The dark grey area in this image reflects forest and plantation covers which are co-extensive with the Palni/Cardamom Hills in the Archean gneisses. The area is in Kerala and Tamil Nadu States. The horst elevations are from 1 000 to 2 000 m; the surrounding bright, drier land of the Noyil Plains, is at about 600 to 700 m elevation. The highest peak in the peninsula is just west of the scene center, at 2 695 m. The coverage of this scene is framed in Fig. 16-4.
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Division 3 · Geostructures
17 Graben Dip-Slip Faults
Table IV.1. Location, dimensions and age of active rift valleys
Characterization See Variants 17.1 and 17.2.
Geohazard Relations See Variants 17.1 and 17.2.
Select Bibliography See Variants 17.1 and 17.2.
17.1
17.1 Graben Conjugate Fault Pairs Characterization A graben is tectonically the inverse of the horst Geostructure Unit 16. It is a terrain unit depressed below the adjacent terrain along conjugate bounding normal faults. Morphologically they form an elongate and relatively narrow structure with parallel faults, but the unit may also be irregularly shaped. The propagation of large faults with formation of scarps can occur only in brittle rocks. Elongate graben structures at regional to continental macro scales are termed rift valleys. Rifts frequently include Unit 13 transform faulting. Some have successions of fault blocks at each edge, possibly resulting from multiple episodes of faulting, dropping the land surface down to the rift floor. In addition to the common fluvial and lacustrine sediment fills, rift floors can contain lakes and be studded with
volcanic cones and lavas which can themselves be faulted. The volcanism associated with rift faulting results from partial melting of both crustal rocks, producing viscous lavas (Vs1) and mantle rocks, producing basaltic lavas (X1). Shallow focus earthquakes are associated with rift faulting. There are numerous extinct rifts on different continents. Slips on these faults can result in damaging earthquakes today. The principle neotectonic currently active rift valleys are shown in Table IV.1.
Geohazard Relations Volcanism and seismicity are hazards related to the activity status of the bounding faults. The extensional nature of these faults can be associated with volcanic activity and emplacement of units of magmatic Groups X, P and V. Graben depressions are depositional environments for fluvial and lacustrine sediments, interbedded with volcanic deposits. The sites are susceptible to seasonal or episodic flooding.
Select Bibliography
Fig. 17.1-1. Source. Goudie A, et al. (eds) (1994) The encyclopedic dictionary of physical geography, 2nd edn. Blackwell Publishers Inc., p 427, schematic A Comments. A modified highly schematic representation of a symmetric graben structure. The number of faults in real grabens is much greater than shown here.
Illies JH, Baumann H (1982) Crustal dynamics and morphodynamics of the western European Rift system. Zeitschrift für Geomorphologie, Suppl 42:135–165 McCall GJH (1967) Geology of the Nakuru-Thomson’s Falls-Lake Harrington Area. Geological Survey of Kenya, Report no 78, pp 93–102 Ollier CD (1981) Tectonics and landforms. Longman, London, pp 63–65, 80–81, 174–176 Park RG (1989) Foundations of structural geology. Blackie, London, p 6 Rothery DA, Drury SA (1984) The neotectonics of the Tibetan Plateau. Tectonics 3(1):19–26 Selby MJ (1985) Earth’s changing surface. Clarendon Press, Oxford, pp 106–110 Townsend TE (1987) A comparison of Landsat MSS and TM imagery for interpretation of geologic structure. Photogrammetric Engineering and Remote Sensing 53(9):1245–1249 Twidale CR (1971) Structural landforms. The MIT Press, Cambridge, Mass., pp 120–131 van Zuidam RA (1985/86) Aerial photo interpretation in terrain analysis and geomorphological mapping. Smits Publishers/ITC, The Hague, p 149
17.1 · Graben Conjugate Fault Pairs
Fig. 17.1-2. Location. Geographic. 59°50' W, 53°30' N, south Labrador Geologic. Neoproterozoic graben sediments in Late Paleoproterozoic Grenville Craton Source. Courtesy of Natural Resources Canada, NAPL, T3730 R-26
Fig. 17.1-3. Source. Light RU, Light M (1944) Focus on Africa. American Geographic Society, New York, photo 86 Comments. An air perspective view of the Zambesi Escarpment in north Zimbabwe, 50 km downstream from the Kariba Dam and 100 km west of the satellite view of Fig. 17.1-8. The view is to the south, the escarpment strike is west-southwest. The morphology of the upland is granitic rocks with a weathered mantle.
Comments. A view eastward from 6 000 m to the 200 m high southern bounding fault of the Lake Melville Graben and the snow-covered Mealy Mountains Terrane. The location of the photo is indicated on the Landsat mosaic of Fig. 17.1-5.
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Fig. 17.1-4. (Caption on p. 402)
17.1 · Graben Conjugate Fault Pairs
Fig. 17.1-5. (Caption on p. 402)
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Fig. 17.1-4. Location. Geographic. 05°57' E, 43°16' N, lower Provence Geologic. Mesozoic Maritime Alps Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 70 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. A stereomodel covers a graben at Le Gapeau, 15 km north of Toulon. The structure occurs along the crest of a faulted anticline in Upper Jurassic carbonates exposing Upper Triassic shales and marls. The east-west strike is conformable with that of the regional Maritime Alps. The faults are traced in black; red lines are photogeologically associated geolineaments. This structure is delineated in red on the east margin of Landsat Fig. 14-11.
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Fig. 17.1-5.
Location. Geographic. 59°50' W, 53°30' N at lake, southeast Labrador Vertical Airphoto/Image. Type. MSS mosaic, 100 m resolution Scale. 1: 1 250 000 Acquisition date. Not given Source. Personal archive Comments. The conjugate faults of the Lake Melville Graben in the Exterior Thrust Belt of the Grenville Orogen of the Canadian Shield have been traced on this Landsat mosaic. Some 17.2 asymmetric grabens have also been located. The inset frame locates the air perspective view of Fig. 17.1-2. The fault scarps of the graben are 200 m high on the south and 180 m on the north.
17.1 · Graben Conjugate Fault Pairs
Fig. 17.1-6. Location. Geographic. 78°30' W, 73°20' N scene center, north Baffin Island, Nunavut Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 10 August 1974 Source. USGS Comments. The large graben of the Eclipse Trough is drawn on the Landsat image of Sirmilik National Park on Bylot Island and Borden Peninsula.
The structure is one of a number that make up the North Baffin Rift Zone, a region in which block faulting has occurred periodically from Late Proterozoic time to perhaps the present. The country rocks are Ar Archean and Proterozoic crystallines of the northeast Shield. The trough rocks are Upper Cretaceous and Tertiary sandstones and siltstones of the Arctic Platform. See also Figs. 19.1-7 and Gl4-10.
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Fig. 17.1-7. Location. Geographic. 113°30' W, 44°25' N scene center, central Idaho Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 27 August 1972 Source. USGS Comments. The Landsat scene shows grabens of block faulting in the Carboniferous limestone and shale Lost
River and Lemhi Ranges of the Northern Rocky Mountains. These structures are similar to the Basin and Range structures to the south in Nevada in Fig. L2-7. Code 16 indicates the faults bounding the horst ranges. The horst mountains rise to 3 500 m, the alluvium-filled grabens are at about 1 800 m elevation. Irrigated agriculture (red) lines the rivers in the arid grabens. The mountains are national forests.
17.1 · Graben Conjugate Fault Pairs
Fig. 17.1-8. Location. Geographic.31° E, 16° S scene center, western Mozambique Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 1 000 000 Acquisition date. 31 August 1986 Source. Pesonal archive Comments. A Landsat TM scene covers the central third of the 500 km long Zambezi Trough in southeast Africa. The southern escarpment which is 750 to 800 m high, is topographically more in evidence than the north scarp in the scene.
The western end of the 250 km long Cahora Bassa Reservoir at 310 m elevation is visible by the red riverine vegetation in the upper part of the depression. Land covers and land uses associated with the seasonally barren and fire-marked W1, Pm Permian (Karroo) sedimentary rocks in the Trough and on the upland plateau are spectrally distinct. The air perspective view of Fig. 17.1-3 in north Zimbabwe shows the southern scarp of the graben 100 km west of the image margin. Descriptor Np3.4 on the south designates the peneplain of the Zimbabwe Craton. Descriptor R3.2 Pr on the north designates the basement complex of the Moravia Plateau.
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Fig. 17.1-9. Location. Geographic. 111°40' E, 36°17' N image center, eastern China Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 500 000 Acquisition date. 29 December 1973, upper; 23 October 1979, lower Source. USGS Comments. This Landsat mosaic covers 220 km of the 30 to 40 km wide down-faulted multi-directional graben of the Fen Ho River on the Shanxi Platform. The depression, at approximately 300 m elevation, is filled with a mixture of loess and alluvium. The bright, dissected land on the west, at an elevation of about 1 500 m, is Et1.1 loess of the Ordos Plateau. The dark grey zone consists of a range of forested Triassic sedimentary and basement rocks of the Luliang Shan that rise to about 2 500 m in elevation. The delineated areas on the east of the graben are the Taiching Mountains and the western limit of the Liliang Mountains. The Shanxi Platform is a Permo Carboniferous structural basin. The W1.1 coal seams in these sediments are among the largest reserves in China. Intensive mining is resulting in extensive Mv4 and Mv5 ground subsidences, affecting infrastructures and agricultural land. Google Earth imagery presents some possible evidence of such subsidence at 111°00' E, 35°56' N in the southwest sector of this image just above the bend in the graben.
17.2 · Single Fault Asymmetric Grabens
17.2 Single Fault Asymmetric Grabens
Geohazard Relations See Geounit 17.1.
Characterization Select Bibliography An asymmetric graben differs from the classic one in having much of the downthrow on one side only, with the normal fault often becoming listric at depth. (A lisric fault is a deep-seated normal fault associated with crustal extension that passes downward into a low-angle zone of plastic flow.)
Goudie A, Atkinson BW, Gregory KJ, Simmons IG, Stoddart RR, Sugden D (eds) (1994) The Encyclopedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, pp 426–427 Summerfield MA (1991) Global geomorphology. Longman, London, fig 4.9 Suppe J (1985) Principles of structural geology. Prentice-Hall, Englewood Cliffs, NJ, p 271
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Fig. 17.2-1.
Source. Goudie A, et al. (eds) (1994) The encyclopedic dictionary of physical geography, 2nd edn. Blackwell Publishers Inc., p 427 Comments. This highly schematic modified diagram shows the single fault asymmetric graben Variant.
Fig. 17.2-2. Source. Macdonald GA, et al. (1983) Volcanoes in the sea, 2nd edn. University of Hawaii Press, Honolulu, p 408, fig 20.28 Comments. The line of cliffs in the background of this photo are part of a set of asymmetric grabens that cut across the center of the Pliocene Vc3.4 shield
volcano of Lanai Island, Hawaii, of the hot spot island chain. Displacements on these faults have allowed the central part of the volcano to sink in relation to its outer slopes. The foreground consists of lavas that accumulated in the graben. The graben faults have been drawn on the vertical airphoto of Fig. Vc3.4-3.
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17.2 · Single Fault Asymmetric Grabens
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Fig. 17.2-4.
Location. Geographic. 03°45' E, 43°56' N, Languedoc Geologic. Jurassic carbonate plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 62 500 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The stereomodel covers the Ganges asymmetric graben. At the Causses Larzac and Blanda. The associated faults are drawn in red. This structure is part of the faulting along the southeast contact of Mesozoic sediments with the Paleozoic crystalline and Tertiary volcanic rocks of the Central Massif. The brighter cultivated Cretaceous chalk beds of the Ganges Depression define the structure in marked contrast with the soil-poor enclosing Jurassic upland limestones, in the manner of a pseudo geobotanical association.
Location. Geographic. 116°40' E, 30°18' N scene center, eastern China Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 24 December 1973 Source. MDA EarthSat Comments. This Landsat image is centered on a 70 km wide probable asymmetric graben in the Yangzi Fold Belt of eastern China. Location is the 30 to 60 m elevation alluvial/lacustrine plain of the lower Yangzi Jiang River, 570 km upstream from Shanghai. The flanking crystalline uplands, Dabie (Ta-Pieh) Shan on the northwest, and Huang Chan on the east are respectively 300 m and 750 m in elevation. The large lakes on the plain are not blocked valleys (see Figs. Fv2-33 and Fv2-34) as they do not have tributary streams. They are shallow and being gradually infilled by sediments.
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Fig. 17.2-3.
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Group General Lineaments 18
18 Mesoscale Fracture Traces Characterization A mesoscale fracture trace is a natural linear feature “not obviously related to outcrop pattern of tilted beds, lineation and foliation, and stratigraphic contacts … Included in this term are joints mapped on aerial photographs where bare rock is observed.” (Lattman 1958). It is expressed as alignments of drainage, vegetation, or spectral tonality. Brittle rocks deform by fracturing in release of stored stress or cooling contraction in igneous bodies. The term joint is used where fault displacement evidence is lacking. In geologic mapping fractures are distinguished as sets of parallel fractures and systems of intersecting fractures. Conjugate sets of joints are two sets, at oblique angles, thought to be generated at the same time. Fracture traces may further be classified by their orientations, their lengths, microfractures being less than 4 km and macrofractures extending from 4 to 50 km, and their densities, e.g. , a high density is greater than 24 linear km per km2. A Mechanical Classification refers to shear joints which are relatively tightly closed and tension joints which are more open and may contain infilling materials. Hydrogeologically, some of the most productive aquifers are fracture zones in bedrock where the fractured rock has good porosity and permeability. Differences in well yields tend to reflect differences in degree of fracturing and weathering.
Geohazard Relations Surface patterns of joints are a reliable indication of pattern at depth. They affect the strength and stability of the rock mass, and the voids associated with their presence allow increased circulation of groundwater through them. This may be crucial in drainage of a deep excavation or in leakage through the sides or floor of a reservoir.
Reference Lattman LH (1958) Technique of mapping geologic fracture traces and lineaments on aerial photographs. Photogrammetric Engineering 24:568–576
Select Bibliography Boyer RE, McQueen JE (1964) Comparison of mapped rock fractures and airphoto linear features. Photogrammetric Engineering 30:630–635 Lattman LH, Matzke RH (1961) Geological significance of fracture traces. Photogrammetric Engineering 27:435–438 Norman JW (1976) Photogeological fracture trace analysis as a subsurface exploration technique. Transactions, Institution of Mining and Metallurgy, (Sect. B: Applied Earth science), February ’76, Professional Paper B52-B62, vol 24, pp 568–576 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, p 219 Wheeler RL (1983) Linesmanship and the practice of linear geo-art: Discussion and reply. GSA Bull 94:1377–1379 Wise DU (1982) Linesmanship and the practice of linear geo-art. GSA Bull 93:886–888
Fig. 18-1. Source. Personal archive Comments. Graphic of a plan view of a coastal plateau escarpment edge in brittle layered rocks showing the relation of photo fracture traces (in this case conjugate sets) to the strength and stability of rock masses. Zones of high density of fracturing are backwasted (cliff retreat) at accelerated rates compared to relatively less fractured zones A, B, C. Area E will be left as an outlying sea stack. Line 1 on the plan is the present coastline; line 2 will be the eventual shoreline position resulting from continued selective erosion.
18 · Mesoscale Fracture Traces
Fig. 18-2. Location. Geographic. 127°41' W, 51°42' N, southwest British Columbia Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada, BC 1231:73 Comments. Air pespective view to northeast shows a prominent set of fracture traces striking diagonally across the photo in diorite rocks of the Coast Mountains. A subsidiary, less prominent, set of fractures in the lower part of the photo is oriented normal to, and crosses, the lakedefined major Owikeno system.
Vertical Airphoto/Image. Type. b/w pan, single photo Scale. 1: 12 000 Acquisition date. 1958 Source. Personal archive Comments. The large-scale airphoto 6 km south of the St. Lawrence River at Montreal, Canada, reveals a network of dark-toned linear traces ranging from 100 to 800 m in length and 1 to 20 m wide in agricultural fields. The stratigraphy of the site consists of 6 to 10 m of Bc3 Champlain Sea glaciomarine clay overlying K3 Ordovician limestone. The wooded and uncultivated 300 m wide zone on the left, of much less value agriculturally, consists of a veneer of Gt glacial till overlying the limestone. The fracture traces are interpreted as narrow to wide solutional joints of the grike/karren type (macro grikes) in the underlying limestone. The high moisture content in the joints is maintained upward into the naturally poorly-draining clays. Tile drainage, commented on in Fig. Bc3-6, is clearly visible in the fields.
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Fig. 18-4.
Vertical Airphoto/Image. Type. b/w pan, single photo Scale. 1: 40 000 Acquisition date. 1945 Source. IGN – Photothèque Nationale, France Comments. Conjugate sets of sand-filled tension joints with some block separation clearly expressed in white in this airphoto in darker Proterozoic metamorphic rocks of the Hoggar Saharan Massif of southeastern Algeria.
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Fig. 18-3.
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Fig. 18-3. (Caption on p. 411)
18 · Mesoscale Fracture Traces
Fig. 18-4. (Caption on p. 411)
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Fig. 18-5. Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 20 000 Acquisition date. Not given Source. Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS pp 373, p 80, fig 42 Comments. The well-expressed fracture traces in this stereomodel are a joint set which is diagnostic of mechanically-weathered, well-cemented S1 sandstones in an arid climate of the southwestern USA. The internal drainage reduces the number of surface streams. Compare with chemicallyweathered arenites in a humid tropical climate, Fig. S1.2-7. See also Fig. Mv1-1.
Fig. 18-6.
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Location. Geographic. West Corsica, 25 km north of Ajaccio Geologic. Paleozoic granite of terrane of European basement Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1982 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows the detectability of fracture traces in dissected, glaciated, high relief and partly-forested terrain. Red lines are possible Unit 12 normal faults.
18 · Mesoscale Fracture Traces
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Fig. 18-7. (Caption on p. 418)
18 · Mesoscale Fracture Traces
Fig. 18-8. (Caption on p. 418)
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Fig. 18-7. Location. Geographic. 70°37' W 47°32' N, Massif des Laurentides, Québec Geologic. Interior Magmatic Belt of Grenville Orogen of Canadian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 1979 Source. ©Gouvernement du Québec, tous droits réservés Comments. This stereomodel and that of Fig. 18-8 are both situated in cratonic terrains of the Grenville Province of the Canadian Shield. The present model shows that fracture traces can be detected and mapped in well-forested metamorphic hilly glaciated terrain as readily as in the bare, relatively plateau-like terrain of intrusive igneous rocks of essentially the same age. The R3.1–PR descriptor indicates that the country rock is glaciated basement complex. The Gf3 unit is a glaciofluvial deposit.
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Fig. 18-8. Location. Geographic. 59°49' W, 51°29' N, eastern Québec Geologic. Interior Magmatic Belt of Grenville Orogen of Canadian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A20788 – 113, 114 Comments. The stereomodel in ultrabasic anorthosite rocks (an intrusive igneous rock of plagioclase composition) reveals its characteristic pattern of sets of fracture traces prominently due to the absence of the natural forest cover, resulting from a severe regional forest fire (see Google Earth) – compare with Fig. 18-7. These systems of intersecting fractures are a strong photogeologic diagnostic feature of this type of rock. Two classes of fractures are readily distinguished by their relative photo prominence. The major fractures could be regional joints or faults although photo evidence alone does not permit such distinctions, nor that between certain shear and tension joints. Selective erosion by continental glaciation and postglacial frost shattering along the fractures enhanced their expression. The resulting drainage system of linear lakes is strongly controlled by the fracture pattern. See a regional Landsat subscene of composite lineaments centered 90 km to the east in Fig. 15-2.
19.1 · Geomorphologic Discontinuities
19 Macroscale Discontinuities Characterization These discontinuities are anomalous point or segment, straight or slightly curved alignments, revealed geomorphologically (Variant 19.1) or radiometrically (Variant 19.2) visible in the synoptic coverage of satellite images. Humaninduced lineaments and lineaments produced by ice flow in Quaternary glaciated regions are excluded. These lineaments are generally indicators of the occurrence of fault line trace units 12, 13, 14 and 15. See Fig. 13-1 discussion.
tion, of landforms, shadows or drainages, of regional extent. As with Unit 15 the discontinuity is an indicator of the fault line trace Units 12, 13 or 14, as well as of intrusive dykes, metasedimentary bedding, schistocity and gneissocity of foliated rocks, and brittle or ductile shear zones. These discontinuities must not be confused with lineaments produced by ice flow in Quaternary glaciated regions or with manmade lineaments.
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Geohazard Relations Related geohazards include those of the fault activity status subsequently determined by higher resolution stereo airphoto or stereo satellite images interpretation or field work.
Geohazard Relations Select Bibliography See Variants 19.1 and 19.2.
Select Bibliography See Geounit Variants 19.1 and 19.2.
19.1 Geomorphologic Discontinuities Characterization A geomorphic image discontinuity is expressed in synoptic coverage satellite images. It is the optical and radar equivalent of the lineaments detectable on macroscale optical airphotos of Unit 15. The discontinuity consists of an anomalous point or segment alignment, subject to the directional bias of the sun angle and radar look direc-
Fig. 19.1-1. Location. Geographic. 81°40' W, 70°07' N, northwest Baffin Island, Nunavut Source. Courtesy of Natural Resources Canada, NAPL T241R-9 Comments. An air perspective view shows a geolineament forming the north side of Murray Maxwell Bay. The location is shown on the interpretation of the Landsat image of Fig. 19.1-7.
Harris J, Bercha FG, Bruce B (1984) Cobalt-Abitibi Project – Landsat image analysis in the Canadian Shield. Proceedings, 8th Canadian Symposium on Remote Sensing, pp 697–703 Larson BS (1982) Examination of some factors used in selecting Landsat imagery for lineament interpretation. Proceedings, Second Thematic Conference, Remote Sensing for Exploration Geology, pp 293–302 Masuoka PM, Harris J, Lowman PD Jr., Blodget HW (1988) Digital processing of orbital radar data to enhance geologic structure: Examples from the Canadian Shield. Photogrammetric Engineering and Remote Sensing 54(5):621–632 Misra KS, Slaney VR, Graham D, Harris J (1991) Mapping of basement and other tectonic features using Seasat and Thematic Mapper in hydrocarbon-producing areas of the Western Sedimentary Basin of Canada. Can J Remote Sens, vol 17, no 2, April 1991, pp 137–151 Saadi A, Machette MN, Haller KM, Dart RL, Bradley L-A, de Souza AMPD (2002) Map and data base of Quaternary faults and lineaments in Brazil. USGS Open File 02–0230 Walsh GJ (2000) Geologic controls on remotely sensed lineaments in southeastern New Hampshire. GSA Bull 32(1)
19.1
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Fig. 19.1-2. Location. Geographic. 118°10' W, 52°52' N, southern Rocky Mountains, Alberta Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 65 000 Acquisition date. Not given Source. Smith DG (1987) Landforms of Alberta. University of Calgary Publ. 87-1, p 39
Comments. The linears in the stereomodel are located in a mountain valley at the town of Jasper in the national park of that name. The lineaments were produced by the erosive action of a glacier that flowed eastward across relatively weak Upper Proterozoic sandstones, shales and siltstones in a range of rocks of the same age down the valley toward the town. Figure 19.1-3 shows the detectability of these lineaments on an 80 m resolution satellite image.
19.1 · Geomorphologic Discontinuities
Fig. 19.1-3. Location. Geographic. 118°05' W, 52°53' N, southern Alberta Geologic. Foreland of Alpine tectogenic belt. West dipping thrust faults and NW-trending folds Vertical Airphoto/Image. Type. MSS subscene, 80 m resolution Scale. 1: 430 000 Acquisition date. Not given Source. NASA Comments. Landsat image in the Canadian Jasper National Park shows low resolution detectability of geolineaments of carbonate bedrock ridges in a broad valley that have been oriented by iceflow grooving at an angle to the regional trend of the main thrust ridges. The inset square locates the coverage of the stereomodel of Fig. 19.1-2.
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Fig. 19.1-4. Vertical Airphoto/Image. Type. C/X AirSAR Scale. 1 : 240 000 Acquisition date. Not given Source. Her Majesty the Queen in Right of Canada with permission of the Canada Center for Remote Sensing, Natural Resources Canada © 1995. Reproduced with the permission of the Minister of Public Works and Government Services (2005) Comments. Zones of lineaments exhibiting brittle fracture and ductile deformation (rocks that are able to sustain 5 to 10%
plastic deformation before fracturing or faulting) in crystalline rocks are delineated on this radar image. The area is Stormy Lake at 92°17' W, 49°20' N in western Ontario. Geologically the areas is in the Late Archean Wabigoon Greenstone Belt of the Superior Province of the southwest Canadian Shield. The brittle fractured rocks are intrusive granitic. The linear belt is an association of tightly folded and sheared volcanic and sedimentary rocks termed greenstone due to the chlorite mineral in the volcanics which gives them a greenish cast. North is on the left of the image.
19.1 · Geomorphologic Discontinuities
Fig. 19.1-5. Location. Geographic. 71°00' W, 48°09' N, southeastern Québec Vertical Airphoto/Image. Type. airborne SAR Scale. 1: 330 000 Acquisition date. Not given Source. Her Majesty the Queen in Right of Canada with permission of the Canada Center for Remote Sensing Natural Resources Canada © 2005. Reproduced with the
permission of the Minister of Public Works and Government Services, 2005 Comments. The Airsar image in the Laurentide Provincial Park of Québec strongly expresses fracturing of Precambrian rocks of the Interior Magmatic Belt of the Grenville Orogen of the eastern Canadian Shield south of the Saguenay Graben. The NE-SW oriented major lineament is parallel to the Saguenay Graben faults and may be associated with that structure. This image covers the eastern 25 km of the Landsat scene of Fig. Bc3-10.
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Fig. 19.1-6. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 500 000 Acquisition date. Not given Source. USGS Comments. This Landsat subscene showing a distinct set of parallel fractures occurs in the 1 000 m high Chugoku Mountains of southwest Honshu east and west of Hiroshima (blue), Japan. The geolineaments are in Cretaceous granites and volcanic rocks and include metamorphic rocks of the Permian/Triassic Akiyoshi Orogen and the Sangun accretionary terrrane. Landsat Fig. 16-9 shows horst and graben faulting at Osaka 275 km to the east. North is to the left.
19.1 · Geomorphologic Discontinuities
Fig. 19.1-7. Location. Geographic. 81° W, 70°40' N scene center, Baffin Island,Nunavut Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 31 August 1973 Source. USGS Comments. This Landsat scene is at the south end of the block-faulted North Baffin Rift Zone of the northeast Canadian Shield of Fig. 17.1-6. A number of geomorphic geolineaments are indicated by arrows. The lineament labelled 12 is a mapped normal fault. Two other lineaments are parallel to Unit 12. The remaining linear is at an angled relation to the southern one, which could be suggestive of a possible branching splay type fault.
The inset frame locates the air perspective view of Fig. 19.1-1. The lake-filled area in the center of the scene is underlain by Ordovician sediments and covered with hummocky glacial till. The country rocks to south and north are crystalline basement complex covered with a veneer of till. The bright area in the northwest are the Ordovician/Silurian limestone Katiktok Hills with a veneer of glacial till (Gf4). The hills are part of a fault-bounded upland, part of the rift zone, with an average elevation of 400 m that is a craton cover platform. The white colour reflects the generally barren surface of the upland. This is due to the high alkalinity and lack of basic plant nutrients in carbonates. This spectral reflectance is common to many occurrences of carbonates in the Canadian Arctic.
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Fig. 19.1-8. Location. Geographic. 11° E, 07° N scene center, southeast Nigeria Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 17 November 1978 Source. USGS
Comments. The Landsat scene shows multiple systems of fractures on the 1 500 m surface of the northern portion of the Cameroon Highlands Precambrian Craton. The generally uncultivable terrain of the scarp slopes appears in red forest cover. The bluish area in the northwest of the scene reflects the local dry season in the Cretaceous Benue Trough at about 250 m elevation.
19.2 · Radiometric Discontinuities
19.2 Radiometric Discontinuities
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19.2
Characterization A radiometric image discontinuity is expressed in satellite images. It is detectable as differences in the radiometric response of the surface materials. It is the optical and radar equivalent of the lineaments detectable on macroscale airphotos of Unit 15. The discontinuity consists of an anomalous alignment of points or segments, in relation to the solar sun angle, vegetation, rock-mineral colour and moisture patterns of local or regional extent. As with Unit 15 the discontinuity is an indicator of the fault line trace Units 12, 13 or 14.
Geohazard Relations Related geohazards would be those of the fault activity status subsequently determined by higher resolution stereo airphoto or stereo satellite image interpretation or field work.
Select Bibliography Bagheri S, Kiefer RW (1986) Regional geologic mapping of digitally enhanced Landsat imagery in the south central Alborz Mountains of northern Iran. Proceedings, Symposium on Remote Sensing for Resources Development and Environmental Management – Enschede, pp 555–559 Gregory AF, Moore HD, Thirlwall SL (1983) An application of Landsat data to exploration in the NEA-IAEA Athabaska Test Area. GSC Paper 82–11:111–115 Miller JB (1975) Landsat image studies as applied to petroleum exploration in Kenya. Research Conference on Remote Sensing, University of Kansas ▼
Fig. 19.2-1.
Location. Geographic. 111°00' W, 29°00' N scene center, northwest Mexico Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 1 000 000 Acquisition date. 2 April 1990 Source. USGS Comments. Landsat subscene is centered on the city of Hermosillo on the Sonora River. The river is crossing the Basin and Range neotectonic Province and has built a delta of irrigated land on the Pacific Coastal Plain. The ranges are Early Cretaceous volcanic rocks. The linearity of Sonora River Valley suggests a lineament at an angle to the regional basin and range trends. This evidence is not provided by morphology in the image but by the spectral red ribbon of irrigated land that lines the river along its straight course.
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Fig. 19.2-1. (Caption on p. 427)
19.2 · Radiometric Discontinuities
Fig. 19.2-2. Location. Geographic. 89°11' W, 20°09' N scene center, southeast Mexico Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 15 January 1978 Source. USGS Comments. Arrows on this Landsat scene locate the radiometric expression of the Ticul Fault in the central Yucatan Peninsula.
The fault is an arcuate ridge with a relief of 50 m but it is resolved spectrally, poorly vegetated, rather than morphologically in this image. The entire area, mixed forested and unforested landcover, is Eocene Miocene and Pliocene K3 karstic limestone and movement on the fault has been sporadic through that time. The peninsula is the emergent portion of the Yucatan Carbonate Platform (Campeche Bank) which extends halfway across the Gulf of Mexico to within 300 km of the Florida Carbonate Platform.
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Fig. 19.2-3. Location. Geographic. 29°41' E, 20°33' S, southern Africa Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. This image in the Zimbabwe craton shows a geomorphologic and radiometric discontinuity. A short segment of the 6 km wide Great Dyke, the largest known on Earth, 440 km long, traverses the central
part of the image. It is resolved in this image by its brown colour and by its morphology. The dyke extends from 100 km south of the Zambezi Escarpment south to Mberengwa 160 km east of Bulawayo. The structure is actually the feeder conduit for four contiguous lopoliths (masses of concordant intrusive rocks which dome up the overlying strata) that intruded about 2.5 Ga ago. Subsequent erosion has stripped off the lopolithic masses leaving only the feeder root in the form of the dyke. A Unit 13 strike-slip fault is visible near the bottom of the image.
20 · Synergic Lineaments
20 Synergic Lineaments Characterization A synergic lineament is an anomalous alignment detected as a result of some combination of:
solar sun angle radar look direction landforms shadows drainage pattern vegetation rock-mineral colours moisture pattern
and coincident:
geophysical geochemical metallogenic hydrocarbon lineaments
of any of the fault line trace units 12, 13, 14, 15 and brittle or ductile shear zones as resolved in electro-optical or radar airborne or satellite images.
Geohazard Relations Related geohazards would be those of the fault activity status subsequently determined by higher resolution stereo airphoto or stereo satellite image interpretation or field work.
Select Bibliography Hildenbrand TG, Mc Bride J, Ravat D, Wheeler R (1999) Crustal studies and central U.S. hazard mapping; Characterization of the source of the commerce geophysical lineament in 3-D. Abstracts – GSA, North-Central Section, 33rd annual meeting, vol 31, no 5, p 21 Lamontagne M, Graham DF (1993) Remote sensing looks at an intraplate earthquake surface rupture. EOS Transactions, American Geophysical Union 74(32):353–357 Miller JB (1975) Landsat image studies as applied to petroleum exploration in Kenya. Research Conference on Remote Sensing, University of Kansas Qureshy MN (1982) Geophysical and Landsat lineament mapping – An approach illustrated from West-Central and South India. Photogrammetria 37:161–184 Tassell GW (1985) A study of lineaments and mineralisation north of Mount Isa. ALS Newsletter (Australia), Nov. 1985, pp 27–29 Tighe LM (1995) Structural mapping of northern mainland Nova Scotia with radar and other remotely sensed data. Proceedings, 17th Canadian Symposium on Remote Sensing, pp 762–767
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Division 4 Surficial Deposits Group E · Aeolian Deposits
Sub-group Et Inland Aeolian Deposits Sub-group Ef Duneless Deposits Sub-group Ed Sand Dunes Sub-group Eo Obstacle Dunes Sub-group Ec Coastal Beach Backshore Dunes
General Note of Geohazard Relations Aeolian deposits with geohazard relations occur as geounits within five Subgroups:
Et Ef Ed Eo Ec
– – – – –
Inland aeolian deposits Duneless deposits Sand dunes Obstacle dunes Coastal beach backshore dunes
Thick inland deposits are susceptible to seismicity, subsidence, flowing, and erosion. Coastal dunes are susceptible to storm surges, tsunamis and erosion. All other dunal Sub-groups are agents of deposition and susceptible to erosion.
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_7, © Springer-Verlag Berlin Heidelberg 2009
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Division 4 · Surficial Deposits
Sub-group Et Inland Aeolian Deposits Et1.1
Et1.1 Blanket Loess Characterization Composition Loess is an unconsolidated, unstratified silt and clayeysilt sediment.
Origin The source of loess is surface sediments deflated during the Pleistocene from periglacial desert surfaces and glacial outwash and alluvial plains.
Occurrence Loess covered wide areas with steppe climates during the Pleistocene in China, Europe, North and South America, downwind from the desert and fluvioglacial sources. It is more widespread than sand because it is principally transported in suspension rather than by saltation.
Deposition The silts range in thickness from more than 200 m to a few centimeters. Deposits decrease in thickness and increase in fineness and cohesion (clay content) with distance from their source. Variant Et1.1 includes only deposits which, because of their thickness, mask underlying sediments or bedrock. Deposits in China consist mainly of a maximum of 120 m laid down in Mid Pleistocene and 40 m in Late Pleistocene. European deposits are 2 to 15 m thick, North American maxima are 35 m and those in South America 30 m.
Morphology Loess can maintain a stable vertical face due to a vertical cleavage resulting from tension cracks and incorporated plant roots, but sloping surfaces are highly susceptible to fluvial erosion. Deposits are porous and are vertically well drained. Original plateau surfaces show no drainage pattern because precipitation is absorbed by the porous surface layers. Residual gullied terrain is morphologically very distinct from an undissected zone. Individual gullies are U-shaped, a characteristic that will not be resolved in smaller-scale photos and images.
Group E · Aeolian Deposits
Geohazard Relations Loess is susceptible to erosion by wind and water; headward dissection develops from the drainage of infiltrated water at footslopes. Addition of water generally destroys the internal structure and the material will collapse on saturation. Loess is also susceptible to mass movements (e.g. minor slumps of catsteps); undercutting by streams is a common cause of debris slides in vertical faces. External loading such as imposed by earthquakes also causes loss of strength of loess during the period of vibration. Such a catastrophic event killed 246 000 cave dwelling people in thick loess in China on 16 December 1920.
Select Bibliography General Anonymous (1986) Explanatory notes to geomorphologic map of the Loess Plateau in China. Geological Publishing House, China Cressey GB (1955) Land of the 500 million, A geography of China. McGraw-Hill, New York, pp 255–267 Derbyshire E (1977) Periglacial environments. In: Hails JR (ed) Applied geomorphology. Elsevier, Amsterdam, pp 253–258 Flint RF (1971) Glacial and Quaternary geology. John Wiley & Sons, Ltd., New York, pp 251–266 Hunt CB (1972) Geology of soils. W. Freeman, San Francisco, pp 138–141 Lutenegger AJ (1983) Engineering properties and zoning of loess and loess-like soils in China. Canadian Geotechnical Journal 20:192–193 Middleton NJ (1989) Arid zone geomorphology. Belhaven Press, Halsted Press, London, p 275 Osterkamp WR, Fenton MM, Gustavson TC, Hadley RF, Holliday VT, Morrison RB, Toy TJ (1987) Great Plains. In: Graf WL (ed) Geomorphic systems of North America. GSA Centennial Special vol 2, pp 172–173 Smalley IJ (1975) Loess lithology and genesis. Dowden, Hutchinson & Ross, Stroudsburg Wayne WJ, Aber JS, Agard SS, Bergantino RN, Cluemie JP, Coates DA, Cooley ME, Madole RF, Martin JE, Brainerd M Jr, Morrison RB, Sutherland WM (1991) Quaternary geology of the Northern Great Plains. In: Morrison RB (ed) Quaternary nonglacial geology: Conterminous U.S. GSA, The Geology of North America, vol K-2, p 467
Geohazard Relations Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 42–10 Lin Z, Liang W (1982) Engineering properties and zoning of loess and loess-like soils in China. Canadian Geotechnical Journal 19:76–90 Okuda S, Rapp A, Linyuan Z (1991) Loess. Geomorphological hazards and processes. Catena Supplement 20, Catena Verlag, Cremlingen. Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 54
Air Photo Interpretation von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 326–329 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 280–285
Et1.1 · Blanket Loess
Fig. Et1.1-1. Location. Geographic. 109°30' E, 35°50' N, Shanxi, China Source. IRZ München Comments. Photo shows the dissection into steep gorges of the 50 m to 150 m thick blanket loess near Luochan in the southeast of the Ordos Plateau. Vertical cleavage is evident as interbedding by successive layers of fossil soil. Stratrigraphically the beds range in age from early Pleistocene to Holocene. These deposits were accumulated by cold dry winds blowing across desert basins of central Asia. See also Fig. Et1.1-5. ▼
Fig. Et1.1-2.
Location. Geographic. 07°42' E, 48°04' N, southwest Germany Source. Personal archive Comments. The photo illustrates the characteristic property of loess to stand in vertical slopes and cuts due to its peculiar vertical columnar structure. Location is an outlier of the loess terraces of the Miocene 17.1 Upper Rhine graben 60 km southwest. It is adjacent to and covers some of the local Kaiserstuhl Miocene volcanic complex. This part of the graben is at a moderate altitude of about 200 m, the thickness of Quaternary sediment infills is up to 70 m. This loess is 10 m to 40 m thick. It was derived by southwest winds from the postglacial vegetation-free surfaces of Alpine outwash sediments in the valley.
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Fig. Et1.1-3. Location. Geographic. North China Geologic. Ordos Basin Source. Personal archive Comments. This air perspective photo of residual loess terrain on either side of an Fv2 alluvial plain is analogous to the area depicted in the U.S. High Plains of Fig. Et1.1-4.
Group E · Aeolian Deposits
Et1.1 · Blanket Loess
Fig. Et1.1-4. Location. Geographic. 100°40' W, 40°50' N, south central Nebraska Geologic. Pleistocene cover on Tertiary piedmont plain Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 29 November 1938 Source. Personal archive Comments. This stereomodel shows the characteristic fluvial dissection into sharp-crested hills of loess when adjacent to streams. The high density drainage pattern is a result of the uniform nature of the material. Location is in the semi-arid High Plains of the USA. C, P, and G codes indicate points of characteristic micro-relief in loess deposits. C are side-sloped slumped “cat steps”; P are remnental pinnacles, and G are U-shaped gullies where material stands in vertical slopes. Loess deposits in this region are 15 to 30 m thick.
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Group E · Aeolian Deposits
Et1.1 · Blanket Loess ▼
Fig. Et1.1-5. Location. Geographic. 112° E, 38° N, Shanxi Province Geologic. Ordos Basin of North China-Korean Platform Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 27 March 1947 Source. USGS Comments. This stereomodel covers an area where thick loess blankets a region where rainfall is sufficient to support vegetation that can catch and hold dust deflated from the Gobi Desert, to the west. The loess is deeply stream dissected. Every hill and gully slope is terraced for cultivation along with the undissected surfaces. See also Fig. Et1.1-1.
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Ef1
Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Sub-group Ef Duneless Deposits
activities. Abrasion can undercut structures close to ground level.
Ef1 Sand Sheets
Select Bibliography
Characterization Sand sheets are accumulations in essentially flat laminae forming a sheetlike deposit with no prominent topographic expression. Deposits range in thickness from 1 to 10 cm. They have distinct local or extensive geographic boundaries, e.g., they can occupy from 15 to 65% of sand seas. The sheets consist of grains too large to be moved into dunes, they are formed by moderate effective winds of constant direction. Less extensive occurrences, e.g. Fig. Ef1-8, may develop from localized deep weathering of some crystalline rocks. Coarse sand sheets lying upwind of a dune field are deflational lag deposits comparable to reg (hamada) pavements (closely packed stones, one or two stones thick).
Geohazard Relations Sand sheets encroach on vehicular roadways and agricultural land. Obstruction of roads reduces trafficability. Zones of persistent encroachment require constant clearing
Fig. Ef1-1. Source. Verstappen HTh (1983) Applied Geomorphology. Elsevier, p 362, fig 14.20 Comments. These cross sections depict the interactions of sand sheet encroachment with various vehicular roadway construction designs. As sand accumulates downwind of structures, the upper section shows how a road raised tilted upwind is selfclearing.
Berlin GL, Tarabzouni MA, Sheikho KM, Al-nasser A (1985) SIR-A and Landsat MSS observations on the Al Labbah Plateau, Saudi Arabia. Proceedings, 19th International Symposium on Remote Sensing of Environment, ERIM, Ann Arbor, pp 311–321 Breed CS, McCauley JF, Davis PA (1987) Sand sheets of the eastern Sahara and ripple blankets on Mars. In: Frostick L, Reid I (eds) Desert sediments ancient and modern. Geological Society of London special publication 35, Blackwell, Oxford, pp 337–359 Holm DA (1957) Sand pavement in the Rub Al Khali. GSA Bull 68:1746 Holm DA (1960) Desert geomorphology of the Arabian Peninsula. Science 132(3437):1369 Kocurek G, Nielson J (1986) Conditions favourable for the formation of warm-climate eolian sand sheets. Sedimentology 33:795–816 Lancaster N (1995) Geomorphylogy of desert dunes, Routledge Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., p 226 Maxwell RA, Haynes CV (2001) Sandsheet dynamics and Quaternary landscape evolution of the Selima Sand Sheet, southern Egypt. Quaternary Science Reviews, vol 1, issue 15, Sept. 2001, pp 1623–1643 McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 11, 261, 281, 282, 293, 294 Muhs DR, Maat PB (1993) The potential response of eaolian sands to greenhouse warming and precipitation reduction on the Great Plains of the United States. Journal of Arid Environments 25:351–361 Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, pp 232, 233, 236 Verstappen HTh (1983) Applied geomorphology. Elsevier Scientific Publishing Co., NY, pp 361–362
Ef1 · Sand Sheets
Fig. Ef1-2. Location. Geographic. 02°58' E, 30°04' N, central Algeria Source. LAR, March 1975 Comments. This photo shows a section of the paved highway 60 km south of El Golea that traverses a sand sheet area where the roadway is repeatedly encroached by sand,
Fig. Ef1-3. Location. Geographic. 03°14' E, 25°01' N, southeast Algeria Source. LAR, March 1975
as signalled by the warning panel. The line of massive Ed dunes in the background is at the eastern edge of the Grand Erg Occidental sand sea basin. Just southward beyond this sand sheet zone the road is at the beginning of a 275 km traverse of the dune-free hamada (Fig. Eo4-2) surface of Tertiary and Cretaceous calcareous sediments of the Tademait Plateau.
Comments. The characteristic grain size of sand sheet sedimentation can be seen in the foreground of this photo. The plain is backed by a line of Ed dunes. See stereo photos of Fig. Ef1-6.
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Group E · Aeolian Deposits
Fig. Ef1-4. Source. Wilshire HG et al. (1996) Geologic processes at the land surface. USGS Bulletin 2149, p 25, fig 15c Comments. An air perspective photo over a section of the San Joaquin Valley, California. The dark fore-
ground is a field of forage crop. It is partly covered by a sand sheet that was eroded from grazing land in the background by a severe windstorm of 24 hours duration.
Fig. Ef1-5. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 25 000 Acquisition date. Not given
Source. Verstappen HTh (1983) Applied geomorphology. Elsevier, p 363, fig 14.23 Comments. This photo shows sand sheet deposits encroaching on agricultural fields of Aboud oasis in Algeria.
Ef1 · Sand Sheets
Fig. Ef1-6. Location. Geographic. 04°26' E, 24°25' N, south Algeria Geologic. Hoggar Massif of African Craton Vertical Airphoto/Image. Type. b/w, pan stereo triplet Scale. 1: 50 000 Acquisition date. Unspecified
Source. IGN – Photothèque Nationale, France Comments. Stereomodel covers an area of 50 km2 sand sheet. A ground view is on Fig. Ef1-3. Linear outcrops are intrusive igneous dykes (vertically-oriented sheets of intrusive rocks). Ed3 is a limited occurrence of barchanoid dunes.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Ef1 · Sand Sheets ▼
Fig. Ef1-7.
Location. Geographic. 11°41' E, 25°21' N scene center, southwest Libya Vertical Airphoto/Image. Type. Earth-Terrain Camera, Skylab Acquisition date. 1973/1974 Source. NASA Comments. This image covers a segment of the Mesozoic sedimentary cuesta of the western edge of the Marzuk Basin. The extensive deposits of mainly Ed1.3 barchanoid dunes are part of the Marzuk sand sea. Note the contrast with the smooth adjacent Ef1 sand sheets.
Fig. Ef1-8. Location. Geographic. 35° 55' E, 21° 27' N, northeast Sudan Geologic. Basement complex on a line of rift in the African Plate Source. USGS Comments. This 1: 500 000 Landsat subscene shows sand sheet deposits in depressions of the Red Sea Hills at the eastern extremity of the Sahara.
Fractional code Ef1/R1 refers to underlying foliated basement rocks. Ef1/R4 refers to more massive rocks, Precambrian gneisses and batholithic granites have developed from deep weathering of surrounding crystalline rocks. If the deposits are thick enough they could form potential aquifers. Zoomed images reveal fossil drainage patterns in the sand from a pluvial period in late Quaternary (8 000 BP).
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Fig. Ef1-9. Location. Geographic. 0°20' E, 15°38' N image center, eastern Mali Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 650 000 Acquisition date. Not given Source. USGS
Group E · Aeolian Deposits
Comments. McKee (1979) p 325, using 80 m resolution Landsat images mapped the aeolian deposits on this Landsat subscene as undivided occurrences of Ef1 sand sheets and Ef2 sand streaks. Examination of current high resolution imagery reveals patterns of Ed1.3 barchanoid ridges and Ed1.2 transverse dunes oriented to a wind direction from west/northwest, e.g. at 0°20' E, 15°33' N.
Ef2 · Sand Streaks
Ef2 Sand Streaks Characterization Streaks are thin elongate sand bodies with a stringlike shape with no slip faces extended downwind from a localized source area or a topographic obstruction. Their thicknesses are similar to those of Ef1 sand sheets. They are formed by strong effective winds of constant direction similar to related sand sheets Ef1. Deposits identified as streaks on early low resolution Landsat images are now known to have included aligned barkhan dunes Ed1.4 and other small dunes.
Geohazard Relations Sand streaks encroach on agricultural, vegetated lands and roadways in the same manner as sand sheets.
Select Bibliography Arvidson RE, Jacobberger PA (1982) Mapping oases and soil types from Landsat digital multispectral scanner data – Kharga Depression, Western Desert, Egypt. Proceedings ERIM First Thematic Conference, Remote Sensing of Arid and Semi-Arid Lands, pp 565–569 Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 281, 293, 294 Greeley R, Christensen P, Carrasco R (1989) Shuttle radar images of wind streaks in the Altiplano, Bolivia. Geology 17:665–668 Norris RM, Norris KS (1961) Algodunes of southeastern California. GSA Bull 72(4):605–620 Strain PL, Farouk El-Baz (1982) Sand distribution in the Kharga Depression of Egypt: Observations from Landsat images. Proceedings, ERIM First Thematic Conference, Remote sensing of Arid and Semi-Arid Lands, pp 765–774 Verstappen HTh, van Zeedam RA (1970) Orbital photography and the geosciences – A geomorphological example from the Central Sahara. Geoforum 2:33–47
Fig. Ef2-1. Location. Geographic. 78°22' W, 09°24' S, north Peru Source. Rich JL (1942) The face of South America. In: Weaver JC (ed) Special publication no 26, American Geographic Society, photo 267 Comments. The airphoto shows adjacent patterns of smooth darker-toned Ef1 sand sheets and Ef2 sand streaks on a probable Br6 wave-cut terrace just north of Casma.
Although it appears so, this is not a vertical photograph, aircraft altitude not given. Ed1.4 are scattered occurrences of barkhan dunes amid the sand streaks. Dark cloud shadows partially obscure detail in unit Ef2/Ed1.4. This site is 140 km south of Fig. Ed1.4-3 on the same coast.
447
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits ▼
Fig. Ef2-2. Source. Personal archive Comments. An air perspective view from 6 000 m of sand streaks over flat-lying Phanerozoic craton cover sedimentary rocks in the Algerian western Sahara.
Ef2 · Sand Streaks
▼
Fig. Ef2-4.
Location. Geographic. 17°42' E, 18°42' N northern Chad Geologic. Craton platform cover sediments Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 1956/1957 Source. IGN – Photothèque Nationale, France Comments. The arrow on the right in this photo indicates the wind direction moving Ef2 sand streaks from east to west across poorly-cemented fine grained S1.2 Devonian sandstones at an elevation of 450 m a.s.l. The streaks direction results from a deflection of winds from the northeast in Lybia southwestward and westward around the 3 300–3 500 m Tibesti Massif of Precambrian basement north of the photo area. Ef1 sand sheet deposits fill an elongate shallow depression. See windward dune of Fig. Eo1-2 and falling dunes in Fig. Eo4-5 from the same wind system in the region. The system of sand-filled stream channels is fossil from Tertiary and Quaternary pluvial stages.
Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 588 000 Acquisition date. January 1976 Source. USGS Comments. This Landsat subscene is a black and white copy of the colour composite image of Fig. Fv2-28. Arrows point to bright, parallel 20 km long, northwest to southeast-oriented sand streaks. The streaks are crossing K1 Eocene limestones in the bend of the Nile River, 20 km west of Luxor in southeast Egypt. The bright zone in the southwest of the image is Ef1 sand sheets. The source of the streak sands appears to be probably Paleocene sands immediately to the northwest, between the limestones and the river floodplain.
Fig. Ef2-5.
▼
▼
Fig. Ef2-3.
Location. Geographic. 30°30' E, 25°30' N image center, south central Egypt Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 588 000 Acquisition date. November 1975 Source. USGS Comments. Sand streaks are well-displayed in this Landsat subscene of the northeast sector of the closed bedrock Kharga Depression. Arrows indicate wind direction. The depression is itself partly developed by wind deflation of Tertiary and Cretaceous interbedded sediments in episodes of Quaternary aridity. These streaks of sand constantly encroach on inhabited and irrigated lands of 40 000 pop. in the depression. The local elevation is about 50 m. The bordering escarpment height ranges from 200 m to 350 m. The depression is 190 km long and ranges in width from 20 km in the north to 80 km in the south.
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Division 4 · Surficial Deposits
Fig. Ef2-4. (Caption on p. 449)
Group E · Aeolian Deposits
Ef2 · Sand Streaks
Fig. Ef2-5. (Caption on p. 449)
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Sub-group Ed Sand Dunes Ed1
Group E · Aeolian Deposits
Ed1 Free Inland Dunes
tional drift of active migrating dunes buries agricultural land, overrides linear facilities such as roadways, pipelines and airfields, and clogs irrigation canals. In recent decades many areas of the African Sahel zone have been affected by increased sand migration related to continental desertification.
Characterization
Reference
About 20% of the world’s arid zones (<100 mm rain per year) are covered by aeolian sands where wind action effectively moves loose sediments (quartzos, minor carbonates and gypsiferous). The principal sources of dune sands are from bahada (desert alluvial) fans, dry river valleys Fv1.2, marginal playa deposits L3, and weathered desert sandstones. The dunes have a wide range of dimensions, from a few centimeters to several kilometers and heights exceeding 250 m. The height range for typical dunes is 0.1 to 100 m. Deposits that are resolved on large scale airphotos for example are 20 m wide and 500 m long for transverse dunes and are mappable at 1:20 000. Viewed stereoscopically the windward and slipface slopes of dunes are detectable on large scale airphotos but with difficulty at smaller scales. Extensive deposits observable on low to medium resolution synoptic satellite images are documented in McKee (1979). The dune sands are transported principally close to the ground by traction and saltation (particles dislodged by the impact of descending grains), and accumulate by fall deposition in sheltered sites of reduced velocity of sand-laden winds. Fine sands can become windborne over much greater distances. Dunes develop asymmetrically by movement of sand up the gentle windward slope toward the crest. As sand crosses the crest from windward to the lee side it avalanches down the slipface which is near to the angle of repose for sand 33° to 35°. As avalanching continues the dune migrates in the direction of the wind. Rates of migration average 6 to 10 m per year and can exceed 25 m per year. Eight dune Variants describe the simple basic types classified according to the form of the dune and the position and number of slipfaces. This parent characterization is common to all the Variants. McKee (1979) noted in studying satellite images and airphotos that there are a large number of combinations of dunes types. These are classed as a dune complex Ed2.
McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 4, 6, 8–14, 137–169, 253–281
Geohazard Relations Wind erosion and deposition go hand in hand. Sand abrasion undercuts structures close to ground level. The direc-
Select Bibliography Alsharhan AS (1998) Quaternary deserts and climate change. Taylor & Francis Clos-Arceduc A (1969) Essai d’explication des formes dunaires sahariennes. Etudes de Photo Interprétation no 4, IGN France Coaldrake JE (1954) The sand dunes of the Ninety-Mile Plain, Southeastern Australia. Geographical Review (U.S.), pp 394–407 Cooke RU (1977) Aeolian sand control in Saudi Arabia. Applied Geomorphology, pp 216–218 Cooke RU, Doornkamp JC (1974) Soil erosion by wind. Geomorphology in Environmental Management. Clarendon Press, Oxford, pp 51–73 Doornkamp JC, Brunsden D, Jones DKC, Cooke RU, Bush PR (1979) Rapid geomorphological assessments for engineering. Quarterly Journal of Engineering Geology 12:189–204 Glennie KW (1970) Desert sedimentary environments. Elsevier, New York, pp 21–24, 81–89 Goudie AS, Atkinson BW, Gregory KJ, Simmons IG, Stoddart DR, Sugden D (eds) (1994) The encyclopaedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, p 159 Huadong G, Schaber GG, Breed CS, Lewis AJ (1986), Shuttle imaging radar response from sand dunes and subsurface rocks of Alashan Plateau in north-central China. Symposium on Remote Sensing for Resources Development and Environmental Management, Enshede, pp 137–143 Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., pp 215–249 Ohamobi SI, Ofoegbu CO (1999) Mapping cover sand encroachment in northwestern Nigeria from Landsat MSS and aerial photography. Proc., 13th Intern. Conf. on Applied Geologic Remote Sensing Pye K, Tsoa H (1990) Aeolian sand and sand dunes. Unwin Hyman, London Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, pp 232–261 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC The Hague, pp 275–294 Verstappen HTh (1983) Applied geomorphology. Elsevier Scientific Publishing Co., NY, pp 357–364 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 321–328 Walker AS (1986) Eolian landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 447–520 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 32 Wolfe SA (2001) Eolian activity. In: Brooks GR (ed) A synthesis of geological hazards in Canada. Geological Survey of Canada, Bulletin 548, pp 231–240 Zeitschrift für Geomorphologie (1983) Supplement Band 45
Ed1.1 · Linear Dunes
Ed1.1 Linear Dunes
Geohazard Relations See Geounit Ed1.
Characterization Select Bibliography Linear dunes, also named longitudinal and seif, are the most common desert dune type. They are elongate, sharp-crested parallel ridges with slipfaces on both sides, and with the long axis extending in the direction of sand movement, which is the result of (controversial) bidirectional winds. They generally occur in evenlyspaced systems. Individual linear dunes average 20 m in height with a basal width 5–10 times the height and are spaced up to 1 km apart, and can attain great (100 km) lengths and heights.
Fig. Ed1.1-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 13, fig 10 Comments. A block diagram shows the typical morphology of linear dunes. The arrows show the probable dominant winds.
Fig. Ed1.1-2. Source. Warren A, Mainguet M (1982) The Geographical Magazine, March 1982, p 166 Comments. The sketch map shows surveyed dune hazard at the proposed site for Dubai Airport. Zones of distinct dune form were related to wind roses of velocity and direction. The data permitted assessment of dune hazard and stabilization work required in each zone.
Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., pp 234, 241, 244 McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 13, 155–165, 261 Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, p 250 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publ./ITC The Hague, p 278 Walker AS (1986) Eolian landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 454, 466, 467, 492, 493, 494, 495
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed1.1-3. Location. Geographic. 138° E, 24° S approx. central Australia Geologic. Cretaceous Eyre downwarp basin Vertical Airphoto/Image. Type. b/w pan air and ground photos Scale. 1: 50 000 approx. Acquisition date. Not given Source. Twidale CR, Foale MR (1969) Landforms illustrated. Thomas Nelson (Australia) Ltd., Sydney, p 121, photos 35, 36 Comments. The air and ground photo pair of this figure show linear dunes migrating slowly north-northwest in the Simpson Desert. Individual dunes here are 10 to 38 m high, generally 160 to 200 m apart and average 40 to 50 km in length. Interdunal vegetation is visible in both photos. As in the Landsat images of Figs. Ed1.1-9 and Ed1.1-10, the characteristic form, bounded on both sides by opposite-facing slipfaces, is readily visible.
Ed1.1 · Linear Dunes
Fig. Ed1.1-4. Location. Geographic. 110°52' W, 35°39' N, northern Arizona Geologic. Triassic sediments of southern Colorado Plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. Not given Source. Unspecified U.S. government agency
Comments. Two Variants of Inland dunes occur in this stereomodel on Garces Mesa, 20 km north of Red Lake: extensive deposits of Ed1.1 linear dunes a limited occurrence of Ed1.2 transverse dunes Two local units of Ef1 sand sheets are located within the linear dune areas. The probable source of these dunes is the friable sandstones of the regional Black Mesa to the southwest.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Ed1.1 · Linear Dunes
Fig. Ed1.1-7.
Location. Geographic. 07° W, 26° N image center, north Mauritania/ west Algeria Vertical Airphoto/Image. Type. Ektachrome, 70 mm photo, Gemini VI Spacecraft Scale. 1:1 260 000 approx. Acquisition date. 16 December 1965 Source. USGS Comments. Hand-held astronaut photo pictures the rustcoloured 30 km wide by 250 km long northeast-trending Erg Iguidi belt of linear dunes located at G on Fig. Ed1.1-8.
Fig. Ed1.1-8.
Fig. Ed1.1-6. Location. Geographic. 13° W, 20° N photo center, northwest Mauritania Vertical Airphoto/Image. Type. Hasselblad 500C Kodachrome Gemini VI photo Scale. 1:2 500 000 in foreground Acquisition date. 16 December 1965 Source. USGS Comments. An astronaut view westward from approximately 200 km altitude shows linear dunes as much as 20 km long deposited in a high energy wind environment effective from the northeast. The dark rock outcrops are interbedded Lower Paleozoic sediments low dipping to southeast. They are the northwest limbs of one of the largest synclines in the world, the Taoudeni intracratonic basin. The dunes flow along the strike of the weaker sediments.
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Location. Geographic. 69°34' E, 25°34' N, southeast Pakistan Geologic. Un2 alluvial plain Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. 1953 Source. USGS Comments. This stereomodel is at the southern contact of the extensive Thar Desert with the central Sind plain of the Indus Valley. Lakes occupy depressions between long linear dunes that trend north-northeast under the influence of a regional unimodal wind regime. Surface wind flow in summer is from the southwest and from northeast in winter. The dunes are evidently stabilized, but a stabilizing agent is not obvious. They are older than the lakes. A broad depression to northwest is occupied by irrigated land extending from the Indus flood plain.
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Fig. Ed1.1-5.
Location. Geographic. 04° W, 27° N scene center, northwest Africa Vertical Airphoto/Image. Type. HCMM day vis, 500 m resolution Scale. 1: 4 000 000 Acquisition date. 1 March 1979 Source. USGS Comments. Extensive linear dune fields are well-resolved by spectral contrast at 500 m spatial resolution in this subcontinent scale image that covers an area in west central Algeria, northeast Mauritania and north Mali 700 by 700 km, the equivalent of 15 Landsat scenes. The dunes surround the east end of the extensive Precambrian craton (Dorsal Reguibat), and the north margin of the Taoudeni Basin of Fig. Ed1.1-6. The latter are the dark band in the lower part of the image. The dark grey of the craton area consists of metamorphic basement rocks. The lighter-toned areas are later granitic intrusive masses. The west (left) inset frame, marked “G” locates an early astronaut photograph of Fig. Ed1.1-7. The eastern frame, marked “L” locates a Landsat scene of Fig. Ed1.1-9. The image was acquired by NASA’s Heat Capacity Mapping Mission which operated from 1978 to 1980. The sensor system consisted of a detector in the visible and reflected IR spectral range, and a detector in the thermal IR range. Data were acquired in day and night times at 13 hour intervals. The present image is from the day vis detector.
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Division 4 · Surficial Deposits
Fig. Ed1.1-7. (Caption on p. 457)
Group E · Aeolian Deposits
Ed1.1 · Linear Dunes
Fig. Ed1.1-8. (Caption on p. 457)
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed1.1-9. Location. Geographic. 01° W, 26° N scene center, central Algeria Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 8 February 1974 Source. USGS Comments. This Landsat scene covers the center of Erg Chech dune field.
The very large dunes have a mean width of 1.0 km and an interdunal spacing of 2–10 km in this scene. The image area is located at L on Fig. Ed1.1-8. This dune field, which occupies a depression between the Reguibat Craton on the west and the Tademait sedimentary plateau to the east, carries sand from the Grand Erg Oriental basis 400 km to the north to the Taoudeni Basin to the southwest.
Ed1.1 · Linear Dunes
Fig. Ed1.1-10. Location. Geographic. 48°50' E, 17°28' N image center, north central Yemen Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 25 January 1973 Source. USGS Comments. Landsat subscene, at the southwest limit of the Rub Al Khali sand sea in Saudi Arabia, shows part of an extensive zone of linear dunes at the margin of their cover of fluvially dissected Lower Eocene S2.1 calcareous shales. The characteristic form of linear dunes, bounded on both sides by opposite-facing slipfaces is visible in the image.
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Ed1.2
Division 4 · Surficial Deposits
Ed1.2 Transverse Dunes
Group E · Aeolian Deposits
Geohazard Relations See Geounit Ed1.
Characterization Transverse dunes, also known as zibars, are elongate ridges transverse to the dominant wind direction. The cross profile is asymmetric, with one slipface. They commonly occur up to 5 m high, parallel and closely spaced, sometimes overriding one another. Transverse dunes are difficult to distinguish from smaller barchanoid ridges Ed1.3 on moderate resolution images.
Select Bibliography Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 9–11, 257 Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., pp 245–248 Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, pp 240–248 van Zuidam RA (1985/86) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publ./ITC The Hague, pp 278–288
Fig. Ed1.2-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 5, fig 11 Comments. Block diagram to show the typical morphology of transverse dunes. The arrow indicates the prevailing wind direction.
Fig. Ed1.2-2.
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462
Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given; estimate 1: 30 000–1: 40 000 Acquisition date. Not given Source. Personal archive Comments. The typical asymmetry of transverse dune ridges is well displayed in this photo at an undisclosed location in north Africa. The smooth areas are flat interdune basins. Wind direction is from the left. Comparison with Fig. Ed1.3-5 shows the relative indistinguishability of these dunes from barchanoid dunes on small scale or low resolution satellite images.
Ed1.2 · Transverse Dunes
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed1.2-3. Location. Geographic. 04°38' E, 24°56' N, southeast Algeria Geologic. Upper Proterozoic metamorphic rocks of Hoggar cratonic massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. Not given
Source. IGN – Photothèque Nationale, France Comments. The transverse dunes in this stereomodel are named Amadhel Néner on the 1 : 200 000 topo map. They have locally impeded and ponded the sporadic flow of an east-flowing wadi tributary of Oued Tazouine. As labeled, the smooth-appearing surface of the eastern portion of the photo is a typical Ef1 sand sheet.
Ed1.3 · Barchanoid Ridges
Ed1.3 Barchanoid Ridges Characterization Many segments of transverse dune ridges Ed1.2 are curved and the term barchanoid has been used in reference to the similar appearing crescentic shape of barchan dunes Ed1.4 when they occur in parallel coalesced rows.
Geohazard Relations See Geounit Ed1.
Fig. Ed1.3-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 11, fig 4 Comments. Block diagram to show the typical morphology of barchanoid ridges. The arrow indicates the prevailing wind direction.
Select Bibliography Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 265–268 Fryberger SG, Dean G (1979) Dune forms and wind regime. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 151–155 Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., p 244 McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 11 Walker AS (1986) Eolian landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 510, 511
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Ed1.3
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Division 4 · Surficial Deposits
Fig. Ed1.3-2. Source. Personal archive Comments. A high altitude view of a field of barchanoid
Group E · Aeolian Deposits
ridges elongated in a possible shallow depression at an unspecified location in the Sahara Desert. Wind direction is from the bottom.
Ed1.3 · Barchanoid Ridges
Fig. Ed1.3-3. Location. Geographic. 77°07' W, 11°46' S, central Peru Coast Geologic. Holocene coastal plain terrace, 50 m elev. over Lower Cretaceous arenites Source. Johnson GR (1930) Peru from the air. American Geographical Society, p 84, fig 77
Comments. This air perspective photo shows 2 m high barchanoid dunes moved by winds from the south, from the right of the photo. Location is on the 5 km wide inner coastal terrace (Bc1a) near the foothills of the Andes back of Ancon 40 km north of Lima.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Ed1.3 · Barchanoid Ridges ▼
Fig. Ed1.3-4.
Location. Geographic. 32°45' N, 114°50' W, southeastern California Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. 30 March 1953 Source. Perrin RMS, Mitchell CW (1969) An appraisal of physiographic units for predicting site conditions in arid areas. Military Engineering Experimental Establishment, Christchurch, Hampshire, England. Report no IIII, vol II, p 483, fig 33 Comments. This stereomodel area covers 11 km2, of the 350 km2 surface of the southern part of the elongate barchanoid Algodones dune field, one of the largest active dune fields in the United States. They are located in the fault-bounded Salton Trough which is a continuation of the Gulf of California. The dunes range in height from 30 to 90 m. They consist of sand reworked from the delta plain deposits of the Colorado River. The river separates Algodones from the other large dune field of the Salton Trough, the Gran Desierto in Mexico in Fig. Fw3.1-2. The canal is 130 km long and 60 m wide, it carries water from the lower Colorado River on the Arizona border west to the irrigated Imperial Valley in the Salton Trough at the head of the Gulf of California.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed1.3-5. Location. Geographic. 87°22' E, 40°06' N, scene center, northwest China Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 7 October 1972 Source. USGS Comments. Landsat image is centered on the northeast end of the Takla-Makan Desert in the structural Tarim Basin. The clearly-diplayed barchanoid ridges are among the largest known. Their reported dimensions according to
Short and Blair (1986) are – mean length 2.2 km, spacing 3 km, height 100 to 150 m. Aeolian action brings sand into the eastern part of the basin from dune fields east of the Lop Nor mega playa. Fv2 is the valley of the intermittently eastward-flowing Tarim River with saline wetlands on its floodplain. Ef1 is an area of sand sheets along the north margin of the basin. Compare this synoptic image with the morphology of transverse dune ridges on the medium scale airphoto of Fig. Ed1.2-2.
Ed1.4 · Barkhan Dunes
Ed1.4 Barkhan Dunes
Geohazard Relations See Geounit Ed1.
Characterization References Barkhan dunes are crescentic accumulations up to 10 m high. They develop on initially small patches of sand which, as soft patches on stony ground, entrap particles arriving from upwind. “Sand accumulation is least at the edges of the original patch, where saltation transport is greatest, so the dune and its slipface downwind become highest in the middle. This leads to the development of the barkhan horns.” (Thomas 1989). “The wings (horns) of the slipface will advance downwind faster than the higher center, giving the crescentic form.” (Mabbutt 1979). Barkhan migration rates range from 5 to 30 m yr–1 for smaller dunes. Large barkhans are observable on synoptic satellite imagery. Compound (overlapping) barkhan ridges are more common than solitary dunes.
Fig. Ed1.4-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 11, fig 3 Comments. Block diagram to show the typical morphology of barkhan dunes. The arrow shows the prevailing wind direction.
Fig. Ed1.4-2. Source. Perrin RMS, Mitchell CW (1969) An appraisal of physiographic units for predicting site conditions in arid areas. Military Engineering Experimental Establishment, Christchurch, Hampshire, England, Report no 1111, vol II, p 487, photo F134 Comments. Photo of a typical barchan dune at Buraimi Oasis, Oman, 55°47' E, 24°15' N. Wind is from the right. As is characteristic of this dune unit, the wings of the slipface are advancing downwind faster than the higher center.
Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., pp 229–233 Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, pp 248–250
Select Bibliography Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 265–268 Hersen P, Douady S (2004) Stability of barchan dunes. Geophysical Research Abstracts, vol 6, 05195 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC The Hague, p 278
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Ed1.4
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed1.4-3. Location. Geographic. 78°52' W, 08°24' S, north Peru Source. Rich JL (1942) The face of South America. In: Weaver JC (ed) Special Publication no 26, American Geographical Society, photo 274
Comments. Air perspective view of a relatively large classic barkhan dune (horns downwind) on the coastal plain. The roadway near the top of the photo gives scale. Small Ed1.3 barchanoid ridges cover the dune’s surface. This site is 140 km north of Fig. Ef2-1 on the same coast.
Fig. Ed1.4-4. Location. Geographic. 29° E, 25°30' N, central Egypt Geologic. Sand sea overlying thick craton cover Phanerozoic sedimentary sequences Source. Goerster/Comstock
Comments. An air perspective photo shows dunes at Dakhla which are outliers of the Great Sand Sea of the Western Desert, advancing from right to left across the irrigated fields of an artesian spring oasis. Direction of movement is determined by the location of the slipface of the dunes, i.e. from lower right.
Ed1.4 · Barkhan Dunes
Fig. Ed1.4-5. Location. Geographic. 50°04 E, 26°10' N approx., eastern Saudi Arabia Source. Personal archive Comments. A group of barchan dunes formed by winds from the north are in the center of this airphoto
They have drifted onto the surface of a moist (darktoned) Bt1e sabkha on the east shore of the bay south of Dharan. Bw4.1 are a raised beaches.
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Division 4 · Surficial Deposits
Fig. Ed1.4-6. Vertical Airphoto/Image. Type. b/w pan, single photo Scale. Not given; estimate: 1:40 000–1:50 000 Acquisition date. Not given Source. Personal archive
Group E · Aeolian Deposits
Comments. Barchan dunes of different sizes are seen in this airphoto of an undisclosed location in north Africa. A group of dunes are inside a delineated wind scour deflation hollow, possibly eroded to the underlying bedrock. The wind direction is from the bottom right of the photo, the orientation is unknown.
Ed1.5 · Star Dunes
Ed1.5 Star Dunes Characterization Star dunes are pyramidal sand mounds with a culminating peak from which branching ridges radiate out on all sides. They grow vertically rather than migrate laterally. They develop by the interaction of winds from multiple directions. Individual dunes can be up to 150 m high and have diameters of 1 to 2 km.
Geohazard Relations See Geounit Ed1.
Fig. Ed1.5-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 13, fig 13 Comments. Block diagram to show the typical morphology of star dunes. The arrows show the effective wind directions.
Fig. Ed1.5-2. Location. Geographic. 03°40' E, 25°09' N, central Algeria Source. LAR, March 1975 Comments. Photo of a large star dune, over 150 m high, at the south end of the Ahnet craton cover Basin northwest of the Ahaggar Massif. The vehicles are on a Ef1 sand sheet plain.
Select Bibliography Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 275–277 Fryberger SG, Dean G (1979) Dune forms and wind regime. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 165–169 Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., p 245 McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 12–13, 275–277 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC The Hague, p 290 Walker AS (1986) Eolian landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 454, 468–469, 480–481
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Ed1.5
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Ed1.5 · Star Dunes
Location. Geographic. 03°11' E, 25°40' N, southeast Algeria Geologic. Ahnet Upper Paleozoic basin carbonates of north Saharan Craton covers Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 88 000 Acquisition date. 1969 Source. IGN – Photothèque Nationale, France Comments. The delineated area in this stereomodel is an 8 km broad grouping of multiple star dunes. The small white patch in one of the interdune depressions is a deposit of L2 evaporites. The mesa structure to the north consists of interbedded Upper Paleozoic sediments; the dark rocks to the east are Lower Paleozoic sandstones. This dune unit is at the eastern edge of a 20 km broad field (Ed1.8) of similar dunes.
Fig. Ed1.5-4. Source. Personal archive Comments. This is a near-vertical view of a cluster of star dunes in a structural basin of the southwest USA.
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Fig. Ed1.5-5.
Vertical Airphoto/Image. Type. b/w pan, single photo Scale. Not given Acquisition date. Not given Source. Personal archive Comments. This photo shows widely-spaced star dunes with the characteristic central peak and multiple radially extending arms. The dunes of different sizes are surrounded by minor barkhanoid-appearing dunes of low relief and bare flat ground. The smaller peaks may represent embryonic forms. Location is undisclosed in north Africa.
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Fig. Ed1.5-3.
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Division 4 · Surficial Deposits
Fig. Ed1.5-5. (Caption on p. 477)
Group E · Aeolian Deposits
Ed1.6 · Dome Dunes
Ed1.6 Dome Dunes
Geohazard Relations See Geounit Ed1.
Characterization Select Bibliography Dome dunes are a subdued variant of star dunes Ed1.5. Typical shape is a broad mass of sand roughly circular in plan view which lacks slipfaces. Large dome mounds can attain a height of 150 m and a diameter of 1 km. Dome dunes are rare and tend to occur at the far upwind margins of sand seas.
Fig. Ed1.6-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 12, fig 7 Comments. Block diagram to show the subdued morphology and lack of slip faces of dome dunes.
Fig. Ed1.6-2. Source. Personal archive Comments. An air perspective view shows an occurrence of dome dunes with superimposed Ed1.3 barchanoid ridges. Location is unspecified in the Sahara Desert.
Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 278–281 McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 11–12 Walker AS (1986) Eolian landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 455, 458–459
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Ed1.6
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed1.6-3. Location. Geographic. 44° E, 26° N image center, central Saudi Arabia Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 7 December 1972 Source. USGS Comments. The large dome dunes in this Landsat scene are located in the elongate sand seas (nefuds) that occupy
low areas between the Permian and Triassic limestone and sandstone cuestas (hamada bare rock surfaces) of the western edge of the Jebel Tuwaiq at its contact with the craton granite of the Najd Plateau visible in the southwest sector of the scene. The cuestas rise about 50 m above the dunes. The mean diameter of the domes is 1.2 km. The city of Buraydah is located just north of the center of the scene.
Ed1.7 · Parabolic Dunes
Ed1.7 Parabolic Dunes Characterization
van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publ./ITC The Hague, p 278 Walker AS (1986) Eolian landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486,pp 455, 486–487
Parabolic dunes are a result of deflation by wind in semiarid environments. Similar to Ed1.4 barkhan dunes, parabolics are crescentic in shape, but in contrast to them the wings point to windward. These dunes develop where anchoring vegetation is locally eroded by strong winds. As they are partially fixed by vegetation or moisture, their movement is slow. Migration is by the convex nose of sand which advances downwind leaving paired wings which trail the centre of the dune on either side.
Geohazard Relations See Geounit Ed1.
Select Bibliography Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 277–278 Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., p 249 McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 11–12 Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, p 246
Fig. Ed1.7-2. Source. This picture has been reproduced with the kind permission of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The original picture appears at Gill ED (1982) Eight coasts of Australia. Technical Report 119, Division of Applied Mechanics, CSIRO, p 50, fig 10, © CSIRO 1982 Comments. This air perspective view to southeast at 123°44' E, 17°17' S near Derby at the head of King Sound of parabolic dunes is on the northwest tropical coast of Australia, evidently developed by onshore winds.They adjoin tidal flats of the Flandrian Transgression (last postglacial sea level rise) which partly drowned them. These dunes are not classed as Ec2 transgressive coastal dunes due to their position at the shoreline, and the absence of parallel dunes with which transgressive dunes are generally associated genetically.
Fig. Ed1.7-1. Source. McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, p 11, fig 9 Comments. Block diagram to show the typical morphology of parabolic dunes. The arrow shows the prevailing wind direction.
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Ed1.7
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Division 4 · Surficial Deposits
Fig. Ed1.7-3. (Caption on p. 484)
Group E · Aeolian Deposits
Ed1.7 · Parabolic Dunes
Fig. Ed1.7-4. (Caption on p. 484)
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Division 4 · Surficial Deposits ▼
Fig. Ed1.7-3. Location. Geographic. 61°08' W 53°03' N, southern Labrador Geologic. 17.1 graben in eastern Grenville Shield Province Vertical Airphoto/Image. Type. Colour infrared, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 30885-25, 26 Comments. The stereomodel is at the same locality as Fig. Mf1-3 on the Lower Churchill River. Winds from the west-south-west had re-worked the surface of Fw3 estuarial sand terraces on the south bank of the river into parabolic dunes, now stabilized, but poorly vegetated. Old river channels are visible between the dunes. Another group of these dunes occurs on a similar terrace in Fig. Fv2-19 33 km downstream.
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Fig. Ed1.7-4. Location. Geographic. 118°35' W, N 55°07' N, northwest Alberta Geologic. Glaciolacustrine sediments of Canadian Interior Plains Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 14 August 1945 Source. Courtesy of Natural Resources Canada, NAPL A 9109-76, 77 Comments. A stereomodel east of the town of Grande Prairie shows parabolic dunes developed on veneer deposits of glaciofluvial outwash sands and silts (in Paraglacial Geosystems General note on geohazard relations) over L1 glaciolacustrine sediments.
Group E · Aeolian Deposits
Ed1.8 · Dune Fields
Ed1.8 Dune Fields
fied due to low image resolution. Identification is based on dune spatial pattern rather than form as within the other Variants.
Characterization Geohazard Relations This descriptor is utilized where sand accumulations are evident on images but occurring units cannot be identi-
See Geounit Ed1.
Fig. Ed1.8-1. Location. Geographic. 17°40' E, 28°35' N scene center, north central Libya Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 567 000 Acquisition date. 8 June 1987
Source. USGS Comments. Landsat subscene shows a bright 15 km wide dune field oriented parallel to the NW-SE oriented fault-controlled (red lineaments) strike of Kc2 and W1 Post-Paleozoic sediments at Zella, west of oil fields, in the coastal Syrte Basin. A bright L2 playa is in the northeast corner of the image.
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Ed1.8
486
Ed2
Division 4 · Surficial Deposits
Ed2 Dune Complexes
Group E · Aeolian Deposits
The term compound dunes refers to a situation where two or more of the same unit combined by overlapping or by being superimposed on one another.
Characterization Geohazard Relations This unit class is used for delineations on satellite images and small scale airphotos (1: 50 000–1: 200 000) of sand seas. The name was proposed by McKee (1979) “Complex dunes in which two different basic types have coalesced or grown together are represented in most sand seas by various combinations. Generally, complex forms consist of a main dune type and a secondary dune type and can be classed as mainly linear, mainly crescentic, and so forth. However, some complex dunes have approximately equal components of different dune types.”
See Geounit Ed1.
Reference McKee ED (1979) A study of global sand seas. USGS Professional Paper 1052, pp 13, 15
Select Bibliography Breed CS, Grow T (1979) Morphology and distribution of dunes in sand seas observed by remote sensing. In: McKee ED (ed) A study of global sand seas. USGS Professional Paper 1052, pp 260
Fig. Ed2-1. Source. Personal archive Comments. An air perspective view of a hybrid dune complex in the Sahara.
In this occurrence the main dune Variant is the Ed1.1 linear dune ridges with superimposed Ed1.5 star dunes as a secondary Variant.
Ed2 · Dune Complexes
Fig. Ed2-2. Location. Geographic. 04°23' E, 23°33' N, southeast Algeria Geologic. Upper Proterozoic metamorphic rocks of Hoggar cratonic massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 1954 Source. IGN – Photothèque Nationale, France
Comments. This stereomodel shows a regional example of complex aeolian sedimentation associated with wadi depressions 140 km northwest of Tamanrasset. The photos are situated along wadi Tekouyat, another of the drainages westward off the Atakor Highland. This dune belt extends 20 km upstream from the photo location. Ed1.1 points to linear dunes, Ed1.5 points to star dunes. The surrounding ground is a plain of basement rocks covered by Ef1 sand sheets.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Ed2 · Dune Complexes ▼
Fig. Ed2-3. Location. Geographic. 04°29' E, 24°15' N, south Algeria Geologic. Hoggar Massif of African Craton Vertical Airphoto/Image. Type. b/w pan stereo triplet Scale. 1: 50 000 Acquisition date. Unspecified Source. IGN – Photothèque Nationale, France Comments. A stereomodel of a complex dune field illustrates a relation between fluvial and aeolian sedimentation and regional topography in deserts. The topographic setting of the photos is analogous to that described by Glennie in the southeast Arabian Peninsula: “Any highland area within a desert is likely to receive a higher rainfall than the adjacent lowland areas and hence to be surrounded by a fairly well-defined belt of wadi sediments. Since its elevation exposes it to the erosive action of the wind, it will not be covered with dune sand. In contrast, the surrounding plains may have a covering of dune sands which will compete with the water-borne wadi sediments for a site of deposition.” This pattern of an erosional highland bordered by wadi and dune sediments is replicated by the wadis draining off the Atakor Highland and the dune sands choking Wadi Ihr. Assouf Mellène over a distance of 25 km and creating a local zone of intermittent ponding in the wadi valley. “The erosion caused by the short period of flowing water is easily compensated for by the intermittent aeolian deposition during the remainder of the year.” Glennie KW (1970) Desert sedimentary environments. Elsevier Publishing Company, Amsterdam London New York, pp 36–37, 45.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ed2-4. Location. Geographic. 01°30' W, 30°30' N image center, western Algeria Vertical Airphoto/Image. Type. SIR-A 40 m resolution Scale. 1: 500 000 Acquisition date. 13 November 1981 Source. USGS Comments. This radar image segment covers a 100 km by 50 km area northeast of Beni Abbes near the western margin of the Grand Erg Occidental of western Algeria. The compound dunes have relatively smooth surfaces that return no radar signal. The surface roughness of the outcrops of W1 Paleozoic interbedded sedimentary rocks returns a strong radar signal. The complex dunes on the lower outcrop of W1 sediments occur in linear chains that are poorly resolved. This image should be compared to the same area in Google Earth.
Eo1 · Shadow Dunes
Sub-group Eo Obstacle Dunes
Geohazard Relations See Geounit Ed1.
Eo1 Shadow Dunes
Reference
Characterization
Smith HTU (1963) Eolian geomorphology, wind direction and climatic change in North Africa. Contract no AF 19 (628)–298, Geophysics Directorate, Air Force Cambridge Res. Laboratories, USAF, p 15
“Lee dunes are long, narrow, tapering sand ridges attached to and extending downwind from rock knobs or salient points, the wind shadows of which initiate sand accumulation.” (Smith 1963).
Fig. Eo1-1. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given Acquisition date. Not given Source. Personal archive Comments. Six elongate ridges of lee, wind shadow dunes, are well-expressed in this photo at an undisclosed location in north Africa. In the absence of background information,the flat obstacle bedrock outlier in this part of Africa is tentatively classed as W1 interbedded sedimentary rocks or X1 basalt flow.
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Select Bibliography Hesp PA (1981) The formation of shadow dunes. Journal of Sedimentary Research, vol 51, no 1, pp 101–112
Eo1
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Eo1 · Shadow Dunes ▼
Fig. Eo1-2.
Vertical Airphoto/Image. Type. b/w pan airphoto Acquisition date. Not given Source. Verstappen HTh (1977) ITC textbook of photointerpretation, vol VII, chap 5. An Atlas Illustrating the Use of Aerial Photographs in Geomorphological Mapping. ITC, Enschede, The Netherlands, photo VII-6 Comments. This stereomodel shows numerous windward dunes in an area of residual Cambrian sedimentary rocks in the Borkou region of northern Chad. See falling dunes in Fig. Eo4-5 and sand streaks in Fig. Ef2-3 from the same wind system in the region.
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Division 4 · Surficial Deposits
Fig. Eo1-3. Location. Geographic. 04 32' E 24°36' N, southeast Algeria Geologic. Hoggar Massif of African Craton Source. IGN, France Comments. This is a fragment of a 1: 200 000 topo map sheet NG 31V, Tesnou, annotated to show the site of a 6 km long dune in the wind shadow of local hills. Regional dominant winds are from the northeast.
Group E · Aeolian Deposits
The obstacle hills range from 200 m to 700 m in height. They are the northeast-southwest faulted core of one of a dozen Lower Cambrian (about 560 Ma) post-tectonic intrusive granite stocks with concentric structures, known as the Taourirt Granites. (These occur along a 525 km north-south contact of two successive emplacements of a Proterozoic orogen Kibarian.) The red inset frame locates the coverage of stereo photos of Fig. Eo1-4.
Eo1 · Shadow Dunes
Fig. Eo1-4. Location. Geographic. 04°28' E, 24°31' N, south Algeria Geologic. Hoggar Massif of African Craton Vertical Airphoto/Image. Type. b/w pan stereo triplet Scale. 1: 50 000 Acquisition date. Unspecified
Source. IGN – Photothèque Nationale, France Comments. A stereomodel covers a 2 km × 6 km long dune mass that is a sand shadow accumulation in the lee of the 22 km long elongate granite ridges of Adrars Tesnou and Ezzouiage, 2 km northeast, see the map of Fig. Eo1-3. The obstacle ridges range in height from 200 to 700 m.
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Division 4 · Surficial Deposits
Eo3 Climbing Dunes Characterization A climbing dune forms when a sand-laden wind or migrating dune encounters opposing hillslopes. Depending on the height of the obstacle and a sufficient sand supply, the dune will cover any occurring talus sheets Mv1 or cones and bedrock crest scarp.
Geohazard Relations See Geounit Ed1.
Fig. Eo3-1. Source. Perrin RMS, Mitchell CW (1969) An appraisal of physiographic units for predicting site conditions in arid areas. Military Engineering Experimental Estab-
Group E · Aeolian Deposits
Select Bibliography Baker VR, Greeley R, Komar PD, Swanson DA, Waitt RB (1987) Columbia and Snake River Plains. In: Graf WL (ed) Geomorphic systems of North America. GSA Centennial Special, vol 2, pp 457–459 Goldsmith V (1985) Coastal dunes. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 343–344 Mabbutt JA (1979) Desert landforms. MIT Press, Cambridge, Mass., p 248 Perrin RMS, Mitchell CW (1969) An appraisal of physiographic units for predicting site conditions in arid areas. Military Engineering Experimental Establishment, Christchurch, England, p 407 Smith HTU (1963) Eolian geomorphology, wind direction and climatic change in North Africa. Contract no AF 19 (628)–298, Geophysics Directorate, Air Force Cambridge Research Laboratories, USAF, p 15 Thomas DSG (1989) Aeolian sand deposits. In: Thomas DGS (ed) Arid zone geomorphology. Halstead Press, London, pp 246–247
lishment, Christchurch, England, MEXE Report no IIII, vol 2, p 407 Comments. This sketch shows the topographic sites of Eo-3 climbing and Eo-4 falling dunes in relation to wind direction.
Fig. Eo3-2. Location. Geographic. 03°39' E, 24°59' N, southeast Algeria Source. LAR, March 1975 Comments. Photo of a large climbing dune on a hillslope on the northwest margin of the Hoggar Massif. The vehicles are on a Ef1 sand sheet corridor along the edge of a lower trafficability Ed1.8 dune field, thin distal deposits of which are in the foreground.
Eo3 · Climbing Dunes
Fig. Eo3-3. Location. Geographic. 02°52' E, 29°48' N, northern Algeria Source. LAR, March 1975
Fig. Eo3-4. Location. Geographic. 121°49' W, 36°14' N, southwest California, USA
Comments. Photo of a dune climbing a slope toward an escarpment of Cretaceous sediments south of El Goléa. The dune is an outlier from the Grand Erg Occidental sand sea in the Mac-Mahon structural basin to the south-west.
Source. LAR, January 1975 Comments. Photo of a dune climbing an inland slope beyond a tidal pool, from a beach source 10 km south of Point Sur Lighthouse.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Eo3-5. Location. Geographic. 78°45' W, 08°33' S, northern Peru Source. Rich JL (1942) The face of South America. In: Weaver JC (ed) Special Publication no 26, American Geographical Society, photo 273 Comments. Air perspective photo shows climbing dunes that have progressed far inland up the slopes of the Cordillera Occidental coastal ranges over an abandoned Br6 wave-cut terrace. Other photos of aeolian geounits in this same region are in Figs. Ef2-1, Ed1.4-3 and Eo3-6.
Fig. Eo3-6. Location. Geographic. 78°55' W, 08°12' S, northern Peru Source. Johnson GR (1930) Peru from the air. American Geographical Society, p 49, fig 42
Comments. The air perspective view shows large dunes climbing the slopes of the first coastal range of the Cordillera Occidental just south of Trujillo. Bw4 is a beach, and Bc1e is a marine plain terrace. Figures Eo3-5, Ef2-1 and Ed1.4-3 are in the same region.
Eo3 · Climbing Dunes
Fig. Eo3-7. Location. Geographic. 06°18' W 34°52' N, northwest Morocco Geologic. Sous Quaternary structural basin of intermontane west coast lowlands Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 10 000 Acquisition date. 14 May 1962 Source. Journal Photo Interprétation, Edit. ESKA, Paris, 64-2, 4
Comments. The main climbing dune in this stereomodel at Moulay bou Selham is 50 m to 150 m wide and 750 m long. The dunes extending 200 m to 300 m inland are poorly cemented dunes named aeolianites. The sand sources of these dunes are the nearshore and foreshore zones and the Bw4 beach. The town is sited on a Br4 bedrock bench of horizontal probably Miocene sedimentary rocks. Ec3 are free dunes.
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Division 4 · Surficial Deposits
Eo4 Falling Dunes
Group E · Aeolian Deposits
Geohazard Relations See Geounit Ed1.
Characterization Select Bibliography A falling dune results from a climbing dune Eo3 growing sufficiently in height to enter the airstream over the obstacle. Sand will then be transported over the obstacle and the falling dune develops.
See Geounit Eo3.
Fig. Eo4-1. Source. Thomas DSG (ed) (1989) Arid zone geomorphology. Chap.: Aeolian sand deposits. Halsted Press, © John Wiley & Sons Ltd., reproduced with permission, p 247, fig 119a
Comments. The profile shows the topographic site of Eo4 falling dunes, and Eo3 climbing dunes in relation to the direction of dune migration.
Fig. Eo4-2. Source. Krinsley DB (1970) A geomorphological and paleoclimatological study of the playas of Iran. USGS, fig 108, p 413 Comments. Photo (August 1967) of a 600 m high falling dune in central Iran. The sand has been blown southward through a low point in the ridge of volcanic rocks. The
immediate source of the sand appears on vertical airphotos to be from deflation of the surface of extensive bahada Fu1.3 piedmont alluvial fans behind the ridge. The coarse gravel surface in the foreground coded Ea2 is a unclassified hamada reg, i.e. a plain from which the fine particles have been stripped, also by aeolian deflation.
Eo4 · Falling Dunes
Fig. Eo4-3. Source. Abrahams AD, Parsons AJ (eds) (1994) Geomorphology of desert environments. Chapman & Hall, p 635 Comments. Photo of falling dunes on the Cronese Mountains into an L2 playa pond at 116°12' W, 35°11' N in the eastern Mojave Desert of southeastern California, USA.
Fig. Eo4-4. Location. Geographic. 111°51' W, 44°04' N, northwest USA Source. Baker VR, et al. (1987) Geomorphic systems of North America. Geological Society of America Centennial Special vol 2, p 458, fig 65 Comments. Air perspective view to southwest of an active imbricating falling dune following a path across a depression in an obstacle hill mass. The hill mass is the Quaternary basaltic Juniper Buttes located at the north end of the volcanic Snake River Plain of the Columbia Plateaus in southeastern Idaho. The dune is advancing northeastwards at the rate of 3 m per year, driven by prevailing southwesterly winds which pick up sand from L2 playas on the north and from the Fv2 floodplain of the Snake River on the south.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Eo4 · Falling Dunes ▼
Fig. Eo4-5. Location. Geographic. 19°31' E, 19°32' N northern Chad Geologic. Craton platform cover sediments Vertical Airphoto/Image. Type. b/w stereogram Scale. 1:50 000 in CD-ROM Acquisition date. Not given Source. Mainguet M (1972) Le Modelé de Grès, Tome II. IGN, p 367 Comments. The falling dunes at F and C in this stereomodel in the Borkou area are accompanied by Ef2 sand streaks at D and E and a line of Ed1.4 barkhan dunes at G. All the unit deposits are oriented common to an extensive regional trend of dunes that are formed by winds from the northeast flowing around the volcanic Tibesti Highlands. The falling dunes have traversed part of the regional Devonian craton cover S1.1 sandstone plateau. See windward dunes in the same area in Fig. Eo1-2.
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Division 4 · Surficial Deposits
Sub-group Ec Coastal Beach Backshore Dunes Ec1
Ec1 Parallel Dunes Characterization Parallel sand dunes are the primary dune type in the coastal zone. They are composed of beach sand blown by onshore winds. They form in the back beach areas where there is a large supply of sand. Such supplies “are commonly associated with a large tidal range, which exposes an extensive sand area at low tide and results in storm overwash at higher levels during high water. Coastal dunes are widespread along humid temperate and arid tropical coasts, but are much less common on humid tropical coasts. Suggested reasons for this are the tendency of tropical weathering to produce silts rather than sands, an excess of vegetation near shore, the inhibition of sand movement in the damp climate and the generally low mean wind velocities.” (Chorley et al. 1984). When a beach is widened on an emerging coast a succession of parallel dune ridges are added on the seaward side. The height attained by primary dunes depends essentially on the velocities of the prevailing onshore winds.
Geohazard Relations Parallel dunes will be susceptible to erosion by sea-level rise which causes an upward shift in the reach of coastal processes and resultant erosion, e.g., the Gulf of St. Lawrence coasts of Prince Edward Island; eastern coast of Baffin Island, Canada (Shaw et al. 1998).
Group E · Aeolian Deposits
At present, as storm surges approach shores, wind velocities and wave heights increase and dunes can be destroyed along with beaches. Dune ecosystems are also very sensitive to the effects of human occupation. The abrasive action of foot and vehicular traffic is especially destructive. With the anchoring of grasses gone, wind blows away sand causing breaches in dunes. Storm driven waves cut channels through the breaches and penetrate deep into the dunes.
References Chorley RJ, Schumm SA, Sugden DE (1984) Geomorphology. Methuen, London, p 425 Shaw J, Taylor RB, Forbes DL, Ruz M-H, Solomon S (1998) Sensitivity of the coasts of Canada to sea-level rise. GSC Bull 505:29, fig 17; p 53, fig 35
Select Bibliography Bird ECF (1976) Coasts. Australian National University Press, pp 152–171 Bloom A (1986) Coastal landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 394–395 Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 146–161 Gares PA, Nordstrom KF, Psuty NP (1979) Coastal dunes; Their function, delineation and management. Center for Coastal Studies, University of New Jersey Goldsmith V (1985) Coastal dunes. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 303–378 Jennings JN (1965) Further discussion of factors affecting coastal dune formation in the tropics. Australian Journal of Science 28:166–167 Jones JR (1984) Coastal dune management: A quantitative approach. In: Costa JE, Fleisher PJ (eds) Developments and applications of geomorphology. Springer-Verlag, Berlin, pp 58–67 Nordstrom KF, Psity NP, Carter RWG (eds) (1990) Coastal dunes: Processes and morphology. John Wiley & Sons, Ltd., London Norrman JO (1981) Coastal dune systems. In: Bird ECF, Koike K (eds) Coastal dynamics and scientific sites. Commission on the Coastal Environment, IGU, pp 119–158 Paskoff R (1985) Les littoraux. Masson, Paris, pp 50–69 Zenkovich ZP (1967) Aeolian processes on sea coasts. In: Steers JA (ed) Processes of coastal development. Interscience, N.Y., pp 586–617
Ec1 · Parallel Dunes
Fig. Ec1-1. Location. Geographic. 70°46' W, 41°21' N, northeast USA Source. LAR, October 1980 Comments. Photo of shore dunes being stabilized by American beachgrass, Ammophila brevigulata, at Menemsha
Beach on the west coast of Martha’s Vineyard Island, Massachusetts. The brown bluff on the left is glacial till (Gf4) of a major continental end moraine. The bluff is shown in Fig. Bb1-4.
Fig. Ec1-2. Location. Geographic. 140°22' E, 08°30' S, southeast Papua, Indonesia Source. LAR, January 1987 Comments. This photo shows an uncommon ocurrence of parallel shore dunes on a humid tropical coast, the Arafura Sea Bc1 coast, at Merauke (Fig. Bc1-2). A tidal foreshore is in left foreground.
The treed area is on the main belt of backshore dunes. As Jennings (1965) and Bird (1976) have pointed out, strong winds are rare in the humid tropics in comparison with other climatic zones, and the occasional violence of tropical storms is usually accompanied by torrential rainfall which saturates the beach surface and impedes sand transportation by temporarily strong wind action.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ec1-3. Location. Geographic. 12°52' E, 56°40' N, southwest Sweden Source. Gullers KW (1952) Nordiska museet, Sweden Comments. A view north of a belt of recreationally trodden parallel dunes at Tylösand beach 8 km west of Halmstad on the eastern shore of the Kattegat. The dunes are also affected by some deflation. The broad beach is on a coast with a tide range of <2 m.
Fig. Ec1-4.
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Location. Geographic. 01°15' W, 45°51' N, Atlantic Coast Geologic. Upper Cretaceous arenites of Saintonge Arch Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows a 400 m broad belt of parallel backshore dunes tapering to 100 m northward lining the west coast of Ile d’Oléron. A 100 m wide strip of Bw4 attached beach lies seaward of the dune belt. Two sets of Bw4.1 raised beaches lie between the Ec1 dunes and a broad belt of conifer planted Ec3 free dunes inland. See free dunes on the east side of the island in Fig. Ec3-8.
Ec1 · Parallel Dunes
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ec1-5. Location. Geographic. 99°50' W, 16°47' N, southern Mexico Vertical Airphoto/Image. Type. b/w pan, single photo Scale. 1: 32 000 Acquisition date. 10 October 1951 Source. Journal Photo Interprétation, Edit. ESKA, Paris, 66-4, 1 Comments. This photo is just south of the city of Acapulco. Two sets of dune ridges are delineated. The inland set,
being cleared of its scrub vegetation cover, marks the shoreline of an earlier, Flandrian type, marine transgression, to which the raised beaches are also related. This transgression was a rise in world-wide sea levels as a result of the melting of the ice sheets of the last glacial period. Golf courses now occupy the raised beaches and vacation cottages have been built in the area immediately behind the dunes.
Ec2 · Transgressive Dunes
Ec2 Transgressive Dunes Characterization
Goldsmith V (1985) Coastal dunes. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 337–340 Paskoff R (1985) Les littoraux. Masson, Paris, pp 57–58 Roy PS, Cowell PJ, Ferland MA, Thom BG (1994) Wave-dominated coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 148–151
Transgressive dunes are usually associated with vegetated parallel dunes Ec1. Their dynamics also give them the names transgressive and blowout. The dunes are initiated by destruction of vegetation cover in the same manner as for Parallel dunes Ec1, and they evolve under the force of consistent strong onshore winds in excess of 25 km hr–1 to which they are parallel. The dune becomes enlarged by erosive wind blowout and begins to migrate through the dune field. The typical transgressive dune is similar in shape and origin to the inland Ed1.7 parabolic dune and moves in the same manner, with the nose advancing downwind trailing paired wings on either side. These dunes require a large level ground area over which they can move. “Many transgressive dune barriers occur where sand is supplied by waves in such large quantities to an exposed, windy coast that the local pioneer plants are inundated and killed before they can stabilize the sand in incipient foredunes.” (Hesp and Thom 1990).
Geohazard Relations Transgressive dunes effectively erode primary dunes and encroach on any natural vegetation, man-made structures, transport facilities or agricultural land located in the hinterland over which they progress. Their seaward ends are susceptible to storm surge erosion.
Reference Hesp PA, Thom BG (1990) Geomorphology and evolution of erosional dunefields. In: Nordstrom KF, Psuty NP, Carter RWG (eds) Coastal dunes: Processes and morphology. John Wiley & Sons, Ltd., London, pp 253–288
Select Bibliography Bird ECF (1976) Coasts. Australian National University Press, pp 163–167 Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 158–159
Fig. Ec2-1. Location. Geographic. 120°51' W, 35°22' N, southwest California, USA Source. Personal archive Comments. This air perspective view northward shows transgressive dunes driven by winds from northwest on a 5 km long by 500 m wide Bw3 barrier beach enclosing the Bt1 lagoon of Morro Bay. Symbol X locates the dune segment of Fig. Ec2-2.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ec2-2. Location. Geographic. 120°51' W, 35°22' N, central California, USA Source. Personal archive Comments. A vertical airphoto shows 500 m wide and 15 m high transgressive dunes on the Morro Bay Barrier beach of Fig. Ec2-1. The steep slipface of the dunes is toward the lagoon on which they are encroaching.
Ec2 · Transgressive Dunes
Fig. Ec2-3. Location. Geographic. 160°12' W, 21°45' N, Hawaii Source. Macdonald GA, et al. (1983) Volcanoes in the sea, 2nd ed. University of Hawaii Press, Honolulu, p 248, fig 12.1 Comments. An air perspective view northward shows calcareous, partly consolidated transgressive dunes covering and crossing Pleistocene lavas and pyroclastics at Kawaihoa Point, at the south tip of Niihau Island. The cementation of the dunes (syn. aeolianite) comes from the calcite of the washed up detrital sediments of offshore corals and shells. Ec1 parallel dunes form the shoreline; Pf1.1 is an ashtuff hill; Pf1.3 is part of the ash-tuff plain that is covered by the dunes.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ec2-4. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 80 000 Acquisition date. Not given Source. Twidale CR, Foale MR (1969) Landforms illustrated. Thomas Nelson (Australia) Ltd., p 142, photo 16 Comments. Photo at 150°47' E, 22°52' S on a coastal plain of northeast Queensland, Australia, shows the classic pattern of transgressive coastal dunes, now stabilized, that had been moved by southeasterly onshore winds. They vary in length from 1 to 4 km. The climate is subtropical humid.
Fig. Ec2-5.
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Location. Geographic. 57°40' W, 54°37' N, central Labrador Geologic. Glaciomarine sediments on Late Proterozoic granites of the eastern Shield, Grenville Province Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL Lab-10, 200, 201 Comments. The two main areas of active transgressive dunes in this stereomodel at Byron Bay are respectively 1 300 m long × 400 m wide and 1 500 m long × 500 m wide. They are developed by northwest onshore winds that are eroding through a 250 m wide active beach and a 300 m wide raised beach. Two narrow, 1 200 m long × 100 m wide active zones are visible at the east end of the beach zone. The same area is pictured in Fig. Ec2–6 at smaller scale. The Bw4 raised beaches mark the limit of postglacial marine submergence at 60 m elevation, 3.5 km inland.
Ec2 · Transgressive Dunes
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Division 4 · Surficial Deposits
Fig. Ec2-6. (Caption on p. 516)
Group E · Aeolian Deposits
Ec2 · Transgressive Dunes
Fig. Ec2-7. (Caption on p. 516)
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Division 4 · Surficial Deposits ▼
Fig. Ec2-6. Location. Geographic. 57°40' W, 54°37' N, central Labrador Geologic. Glaciomarine sediments on Late Proterozoic granites of the eastern Shield, Grenville Province Vertical Airphoto/Image. Type. Colour infrared, stereo pair Scale. 1: 122 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL 30466 IR-41, 42 Comments. The inset frame on this small scale stereomodel in the Byron Bay area locates the coverage of Fig. Ec2-5. The brightness of the active dunes makes them readily detectable at this reduced scale. Np3.1 indicates the granitic basement rocks. The delineated areas are glacial and organic deposits in lower ground. Vertical airphotography at this photo scale with the proper camera system, three times smaller than Fig. Ec2-5, covers 10 times the area, providing regional terrain coverage at higher resolution.
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Fig. Ec2-7. Location. Geographic. 120°38' W, 34°58' N, Southern California Geologic. Intermontane Quaternary basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. Not given Source. Unspecified U.S. government agency Comments. The stereomodel shows two cycles of transgressive dune formation at the outlet of Santa Maria Valley 100 km northwest of Santa Barbara. The beach is oriented north-south, and the prevailing onshore winds are from northwest. The bright, active dunes, a number of which have stabilized since photo date, vary in length from 800 m to 1 300 m. The older, vegetated dunes extend off the model and continue a further 16 km up the Santa Maria Valley. They are locally named the Hairpin Dunes, and may date back to an interglacial time of higher sea level. North is to the left.
Group E · Aeolian Deposits
Ec2 · Transgressive Dunes
Fig. Ec2/Ec3-8. Location. Geographic. 34°37' E, 31°45' N, Israel Vertical Airphoto/Image. Type. Landsat Scale. 1:500 000 approx. Acquisition date. 2006
Source. MDA EarthSat Comments. This satellite image shows a complex of dunes occurring in the 12 km section of the Negev coastal plain between Ashdod and Asqelon. The free dune belt is succeeded inland by the cultivated land of the coastal plain proper. See stereo photo pair of Fig. Ec3-7.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Ec3 Free Dunes
In some cases winds may transport sands directly off beaches and carry them inland over a primary dune belt.
Characterization
Geohazard Relations
Free dunes occur in the form of inland type transverse Ed1.2 and barkhan dunes Ed1.4 within the Coastal Zone environment. The stabilisation produced by vegetation in humid climates is overcome where large supplies of shore sands are available and onshore winds are strong and persistent enough to exploit the deflations of transgressive Ec2 dunes, and carry loose sands farther inland where they continue their advance. On arid coasts, sands move inland from the shore as barkhan dunes. Absence of vegetation, a relatively hard substrate and level terrain inland facilitate the advance.
In inhabited regions in humid climates migrating dunes can completely bury the terrain over which they advance including vegetation, houses, roads and fields. Local streams and wetlands are similarly encroached.
Select Bibliography Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 151–153 Goldsmith V (1985) Coastal dunes. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 330, 331, 337–342 Paskoff R (1985) Les littoraux. Masson, Paris, pp 53, 57, 66
Fig. Ec3-1. Location. Geographic. 70°12' W, 42°04' N, southeast Massachusetts, USA Source. LAR, June 1973 Comments. A site on the Race Point Road from Provincetown to the Coast Guard station at the northern tip of Cape Cod. The roadway at this point traverses a 1 200 m wide belt of active free dunes, as much as 20 m high, which persistently encroach over the roadway. Under the influence of winter winds from the north, thousands of tons of sand sweep annually from windward to lee sides of these dunes, requiring constant clearing activities. Biotechnical stabilization pitch pine plantations are seen on either side of the road.
Fig. Ec3-2. Location. Geographic. 03°42' E, 51°42' N, southwest Netherlands Geologic. Bc1 marine sediments of North Sea Lowlands Source. Van de Kam J (undated) Spectrum Atlas van de Nederlandse Landschappen. Uitgeverij Het Spectrum. Utrecht/Antwerpen, p 214 Comments. A photo of the west end of Schouwen Island shows live-staked biotechnical stabilization of free dunes by plantings of esparto grass – see air views in Fig. Ec3-3.
Ec3 · Free Dunes
Fig. Ec3-3. Source. Personal archive Comments. These air perspective and vertical airphotos dating from circa 1942 cover the southwest end of Schouwen Island, Netherlands at the mouth of the dammed East Scheldt estuary. The vertical photo is oriented to northeast.
The photos show areas of 15 to 40 m high free dunes that have been planted in grids of stabilizing esparto grass as in the ground photo of Fig. Ec3-2. Today a 150 ha (conifer) forest occupies the area. The dune areas adjacent to the forest to the northwest are in continuous grass cover except for some persistent zones of wind deflation blowouts. The original plantation grid has obliterated.
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Group E · Aeolian Deposits
Fig. Ec3-4. Location. Geographic. 43°12' W, 02°27' S, northern Brazil Source. Rich JL (1942) The face of South America. In: Weaver JC (ed) Special Publication no 26, American Geographical Society, photo 39 Comments. An air perspecive view northward of free dunes on the Bc4 coastal plain near its merge with the Fw3 Amazon Delta plain. The area is in Lencois Maranhenses National Park 120 km east of the port of Sao Luis. The shoreline is just visible at the top edge of the photo.
Fig. Ec3-5. Location. Geographic. 08°20' E, 54°40' N, northwest Germany Source. Degn C, Muus U (1972) Luftbildatlas Schleswig-Holstein. Karl Wachholtz Verlag, Neumünster, p 168, no 77 Comments. This air perspective view looks northward over the 1 km wide inland belt of free dunes on the North Frisian Amrum Island of the Wadden Sea. The photograph illustrates well the morphologic distinction between parallel Ec1 dunes in the foreground and Ec3 free dunes inland. The Gf3/Bc1 cultivated land in the background is a Pleistocene sand and gravel outwash plain over marine sediments. The fractional code Ec3/Gt2 indicates a probable substrate of glacial till (Gf4). The fractional coded Bc1/Gt2 area is marine sediments overlying glacial till. Amrum is 80 km north of the Trischen headland of Fig. Bw2-2.
Ec3 · Free Dunes
Fig. Ec3-6. Location. Geographic. 08°20' E, 54°40' N, northwest Germany Vertical Airphoto/Image. Type. Natural colour airphoto Scale. 1: 5 000 Acqusition date: Not given Source. Wattenmeer (1976) Karl Wachholtz, Neumunster, p 309, photo 391 Comments. A very large scale photo shows a recreational area in the dunes of Amrum Island of Fig. Ec3-5. The dark tones are dense cover of beach grasses. Where the cover is destroyed by vehicle and excessive pedestrian traffic, the exposed sand is quickly remobilized by the wind, and erosional “blowouts” develop in addition to those naturally produced.
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Division 4 · Surficial Deposits
Group E · Aeolian Deposits
Fig. Ec3-7. Location. Geographic. 34°30' E, 31°32' N, Palestinian Israel Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. Personal archive Comments. Stereomodel shows free dunes inland from the beach at Gaza at the south end of the Israeli coastal plain. Only the southernmost sectors of these dunes, near the Egyptian border, remain in the natural state in which they are pictured here. The rest of the belt of dunes northward have been settled and cultivated. See the satellite image of Fig. Ec2/ Ec3-8 and the associated bluffs of Fig. Bb1-3.
Fig. Ec3-8.
▼
522
Location. Geographic. 01°15' W, 45°59' N, Atlantic Coast Geologic. Jurassic/Cretaceous arch of Charente Plateau north extremity of Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows a 5.5 km long × 1 to 2 km wide belt of now forested free dunes of a roughly parabolic shape at Boyardville on the northeast coast of Oléron Island. A similar belt occurs on the west coast of the island in Fig. Ec1-4. The source of these sands has probably been from broad foreshores exposed at low tide. The sands overlie regional Upper Jurassic carbonates. The local Bw4 beach sands are supplied by longshore currents from the west. Bw4-1 are raised beaches. The rest of the photo area is a lagoonal zone of intensive aquaculture.
Ec3 · Free Dunes
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Division 4 · Surficial Deposits
Fig. Ec3-9. Location. Geographic. 69°39' W, 11°26' N, north west Venezuela Geologic. Coastal ranges of Venezuelan Andes Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 63 000 Acquisition date. 9 February 1960
Group E · Aeolian Deposits
Source. Journal Photo Interprétation, Edit. ESKA, Paris, 63-3, 8 Comments. Stereomodel shows a local coastal plain with a well-expanded mass of active free dunes occurring over an older base of vegetated Ec2a transgressive dunes. The city Coro lies just south of these aeolian deposits on the inner portion of the plain. The open arrows on the right indicate the prevailing wind direction.
Division 4 Surficial Deposits Group L · Basinal Sediments
Component L1 Pleistocene Glaciolacustrine Sediments Component L2 Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments
General Note of Geohazard Relations of Three Classed Geounits Glaciolacustrine sediments are susceptible to subsidence, flowing and flooding. Arid zone playas are agents of soil salinization, are susceptible to flooding and have vehicle and aircraft trafficability limitations. Quaternary drained lakebeds are susceptible to flooding.
Component L3 Quaternary Drained Lakebeds
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_8, © Springer-Verlag Berlin Heidelberg 2009
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L1
Division 4 · Surficial Deposits
L1 Pleistocene Glaciolacustrine Sediments Characterization The sediments of this geounit were deposited “… in temporary basins of which one side consisted of glacier ice, (the other being) ice-free ground that sloped down toward the glacier.” (Flint 1971). These proglacial and postglacial situations from which waters subsequently drained occurred commonly on broad regional slopes and in mountain valleys. The facies suites of glacial lakes are essentially the same as those of other Quaternary lacustrine sediments: ranging from deeper water clays to littoral sands and proximal icemargin sands and gravels. Sediment thicknesses range from a few to several hundred meters. The topography is generally flat, but gullies develop in thick deposits where the regional base level has lowered. Where the deposits are thin the underlying material and topography are reflected at surface. Marginal strand lines appear as beach ridges that mark different lake stages along the limits of lakes which subsisted longer. Common indicators on photos and images of the lakes in agricultural areas are associated with intensive land uses, regular field patterns compared to adjacent geounit lands, and a strong pattern of tile drainage.
Geohazard Relations Glaciolacustrine sediments are susceptible to several processes that may constitute hazards or severe constraints on construction. General geotechnical properties are usually poor, bearing capacities are poor; shear strengths are low and can decrease with depth. Susceptibility to frost in cold win-
Fig. L1-1. Location. Geographic. Central Great Plains Geologic. Tertiary craton cover sediments Source. Thornbury WD (1965) Regional geomorphology of the United States. Wiley & Sons, Ltd., p 295, fig 16.5 Comments. This regional map shows the relation of glaciolacustrine basins to the Wisconsinan Ice Sheet, 18 ka, in the central United States near the Canadian border. The southward advance of the ice sheet resulted in the damming of northward-flowing streams and formation of the ice-marginal lakes.
Group L · Basinal Sediments
ter temperatures can be high. The soils can have high moisture contents and can be difficult to handle and compact. Clay sediments with minimal over-consolidation gradually subside by dewater and compaction from imposed structural loads as in a gradual subsidence geounit Mv5. Some of these clays with montmorillonite as a main clay mineral can expand or contract markedly upon changes in moisture content. Shallow foundations on such clays may be subject to structurally damaging movements. Where these lake sediments are underlain by weak sedimentary rocks they can be entrained in retrogressive slides Mf1.1 that occur in them.
Reference Flint RF (1971) Glacial and Quaternary geology. John Wiley & Sons, Ltd., New York, pp 192–195; 611–612
Select Bibliography Blodgett TA, Isacks BL, Lenters JD (1997) Constraints on the origin of paleolake expansions in the Central Andes. American Meteorological Society Journal 1:1–28 Clague JJ, Evans SG (2003) Geological framework of large historical landslides in Thompson River Valley, British Columbia. Environmental and Engineering Geoscience 9:201–212 Froese CR, Cruden DM (2000) Landslides in weakly cemented glaciolacustrine sediments, Morkill River valley, British Columbia. NRC Research Press Web site http://cgj.nrc.ca, 21 August 2001 Kenny TC (1976) Formation and geotechnical characteristics of glacial-lake varved soils. In: Janbu N, Jorstad F, Kjaernsli B (eds) Laurits Bjerrum memorial volume. Norwegian Geotechnical Institute, Oslo, Contributions to Soil Mechanics, pp 15–39 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 42–15–42–17 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 54–55 Quigley RM (1983) Glaciolacustrine and glaciomarine clay deposition; A North American perspective. In: Eyles N (ed) Glacial geology. Pergamon Press, Oxford, pp 140–167
L1 · Pleistocene Glaciolacustrine Sediments
Fig. L1-2. Source. deSilva SL, Francis PW (1991) Volcanoes of the Central Andes. SpringerVerlag, p 12, fig 10 Comments. A regional map of parts of western Bolivia, southeast Peru and northeast Chile shows the extent attained by Pleistocene Glacial Lake Tauca and residual major lakes and playas on the Andean Altiplano. The internally drained paleolake Tauca occupied about 50% of the Altiplano basin between 13 000 and 11 000 b.c. The origin of the lake is attributed by some researchers to deglaciation, while others suggest that the expansion of the lake was produced by a change in pluvial conditions in response to increased moisture onto the Altiplano by strengthened trade winds. See airphotos of Figs. H1-1, Mv5-5 and L1-7.
Fig. L1-3. Location. Geographic. 75°15' W, 46°33' N, southern Laurentian Hills, Quebec, Canada Geologic. Southeastern Canadian Shield Source. LAR, 10 August 1991
Comments. This photo shows a marginal strand line of a freshwater extension of the Champlain Sea in the valley of the Lièvre River. The beach trace here consists of lag boulders of glacial till, the fine fractions having been washed away from the surrounding till by wave action.
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Division 4 · Surficial Deposits
Fig. L1-4. Source. Courtesy of Natural Resources Canada, GSC 119242 Comments. Photo shows the rhythmic beds of varved clays of glacial Lake Barlow-Ojibway overlying glacial deposits (Gf4) of the eastern Canadian Shield in northern Ontario. The penknife provides scale.
Group L · Basinal Sediments
The thick pale layers were laid down in summer and consist of coarse silt produced by ice melt. The thin dark bands are clays deposited from suspension in quiet winter water when input streams are frozen. The folded sediments below the varves were probably deformed at the base of retreating ice.
Fig. L1-5. Location. Geographic. 148°10' W, 62°52' N, southern Alaska Source. LAR, October 1980 Comments. An air view shows an exposure of shallow, ±2 m, silty glaciolacus-trine veneer at elevation 600 m over glacial till (Gf4) in the upper Susitna Valley of the Talkeetna Mountains. The sediments were deposited by waters that spilled through a 30 km long interlowland gorge from the Pleistocene proglacial lake of the Copper River Basin to the east. The Basin’s deposits are the largest occurrence (14 000 km2) in Alaska. This site is in the same area as Fig. Zi4-6.
L1 · Pleistocene Glaciolacustrine Sediments
Fig. L1-6. Location. Geographic. 86°09' W, 42°34' N, southwest Michigan Geologic. Lower Carboniferous craton cover Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 25 000 Acquisition date. Not given
Source. Unspecified U.S. government agency Comments. Photo shows the strong contrast in tonalities, land use, and micro relief between the flat, dark agricultural fields of market gardening crops on the glaciolacustrine sediments, and the orchards and vineyards on the brighter rolling glacial till soils, coded Gt2. The locality is 9 km east of the eastern shore of Lake Michigan. Unit Y4 is a wetland.
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Division 4 · Surficial Deposits
Group L · Basinal Sediments
L1 · Pleistocene Glaciolacustrine Sediments ▼
Fig. L1-7. Location. Geographic. 67°54' W, 17°08' S, southern Bolivia Geologic. Central Andes Altiplano Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1:50 000 (in CD ROM) Acquisition date. 14 June 1966 Source. Cordova EV (1992) La Fotografia Aerea y su Aplication a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 19 Comments. The stereomodel shows dissection by fluviatile gullying of fine sediments of the Altiplano glacial lake Tauca. The undissected surfaces are cultivated. This figure is 50 km east of Fig. H1-1. See the regional map of this lake in Fig. L1-2.
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Fig. L1-8. (Caption on p. 534)
Group L · Basinal Sediments
L1 · Pleistocene Glaciolacustrine Sediments
Fig. L1-9. (Caption on p. 534)
533
Division 4 · Surficial Deposits
Group L · Basinal Sediments
▼
Fig. L1-8.
Location. Geographic. 72°35' W, 44°32' N, north central Vermont USA Geologic. Acadian New England, Province of Appalachian Orogen Vertical Airphoto/Image. Type. Natural colour, stereo pair Scale. 1: 60 000 Acquisition date. October 1971 Source. Courtesy of Natural Resources Canada, NAPL A 30382-166, 167 Comments. The stereomodel covers 14 km of the central portion of the 70 km long Glacial Lake Mansfield, one of a series of similar lakes that occupied the high valleys of the Green Mountains. The lake elevation stood at 315 m a.s.l. The lake bed here is quite dissected and is composed mainly of near-shore sands. The lakebed surface is about equally occupied by agricultural and forest land. Gt2 units are areas of glacial till; Fv are fluvial sediments. ▼
Fig. L1-9. Location. Geographic. 113°45' W, 52°17' N, southern Alberta Geologic. Glaciated Cretaceous and Tertiary sediments of Interior Plains Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 76 300 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 21755-15, 16 Comments. An annotated stereomodel covers the southern 15 km of Glacial Lake Red Deer, whose deposits extend 70 km northward and are 10 km wide. The deposits in the center, between the river reaches, are about 15 m thick. The fractional descriptor L1/Gt indicates areas of evidently thin veneer of lake sediments over glacial till. The surface topography of the lacustrine deposits mimics that of the underlying till. The Ed1.7 area in the upper left corner is a field of little cultivated parabolic dunes.
Fig. L1-10.
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534
Location. Geographic. 79°29' W, 71°18' N, North Baffin Island, Nunavut Geologic. Archean granite gneiss of the northeastern shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 16107-156, 157 Comments. A stereomodel at Mary River shows glaciolacustrine sediments with Zi4 ice wedge polygons in the active layer. In this local basin polygons have not developed at L1/Gt1 where the sediments are thin over glacial diamicton (unsorted terrigenous deposit containing a wide range of particle sizes). This site is 30 km south of Fig. Zi4-15.
L1 · Pleistocene Glaciolacustrine Sediments
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Division 4 · Surficial Deposits
Group L · Basinal Sediments
L1 · Pleistocene Glaciolacustrine Sediments ▼
Fig. L1-11. Location. Geographic. 106°40' W, 50°25' N, south central Saskatchewan Geologic. Glaciated southern Interior Plains over Upper Cretaceous shales Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 38 000 Acquisition date. 12 September 1956 Source. Courtesy of Natural Resources Canada, NAPL A 15497-70, 71, 72 Comments. This stereomodel covers Chaplin Lake, the second largest saline water body in Canada. It is situated in a subhumid (grassland) climate with a mean annual precipitation of 560 mm. The mean precipitation for September, when the airphotos were taken, is 50 mm. The lake margins are ringed with extensive zones of white evaporites.
The delineations mark the upper limit of the lake’s fluctuations. The surrounding land is Gf glaciofluvial sands and gravel with pitted surface. The presence of these deposits suggests that Chaplin Lake is sited in a segment of a postglacial outwash channel (see Paraglacial Geosystem). The group of dark squares at the north edge of the photo are ponds for extraction of sodium sulphate deposits. Brine shrimp that thrive in the salt water are also caught and packaged.
Fig. L1-12.
▼
“Although summer is barely three months long, warm temperatures (mean July 19 °C) combined with strong winds and extended daylight, create highly evaporative conditions.” Lemmen DS, et al. (1998) in GSC Bulletin 521, p 20.
Location. Geographic. 96°03' W, 45°49' N, western Minnesota, eastern South Dakota Geologic. Glaciated southern shield Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 825 000 Acquisition date. 2 May 1975 Source. USGS Comments. Landsat image covers the segment of glaciolacustrine Lake Agassiz near its southern extremity, at the eastern margin of the Interior Plains. The lake at its greatest extent covered approximately 500 000 km2 in the Canadian Province of Manitoba. The extent of both deeper and patchy lacustrine sediments is readily delineated in this image due to it being generated from the near-infrared Band 7 of the MSS system. In this electromagnetic wavelength water absorbs virtually all incident energy. This image was acquired in early May which is the season when soil moistures are high at the end of the spring runoff. The southern limit of Lake Agassiz proper is at Brown’s Valley at the southern end of Lake Traverse on the elbow of the Red River. The southern half of the delineated area consists of patchy lacustrine sediments overlying glacial tills (Gf4) coded Gt2 to the west. The relative impermeability of the fine sediments results in their sharp tonal contrast with the better drained adjacent glacial till sediments. The area east of the lake sediments coded Gt4.2 is part of the Alexandria Moraine, a lobe of Gl5 terminal moraine of the Wisconsinan continental glaciation, 11.8 ka. This hummocky moraine is regionally named the Small Lakes Section.
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Division 4 · Surficial Deposits
Fig. L1-12. (Caption on p. 537)
Group L · Basinal Sediments
L1 · Pleistocene Glaciolacustrine Sediments
Fig. L1-13. Location. Geographic. 117° W, 56° N image center, Interior Plains of north central Alberta Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 500 000 Acquisition date. 4 June 1985 Source. Smith DG (1987) Landforms of Alberta. University of Calgary Publ. 87-1, pl. 1, p1
Comments. The Landsat subscene covers a part of an extensive system of glaciolacustrine sediments that occupy regional lowlands of Lower Cretaceous sediments of the Peace River Valley, surrounded by slightly higher ground of Upper Cretaceous sediments. The pictured agricultural areas are near the most northerly extension of commercial farmlands in Canada. The dark zones amid the light blue fields are watersaturated. The red zones along the river banks are largely old Mf1.2 slides now covered with deciduous tree growth.
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L2
Division 4 · Surficial Deposits
L2 Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments Characterization This composite Late Cenozoic geounit is among the most common of desert landforms. It occupies the widespread and numerous flat floors of structurally or erosionally generated inland basins with the exception of ephemeral salt blisters and salt polygons. It is the flattest of all landforms, and is very conspicuous spectrally and spatially on both satellite images and airphotos. Occurrences have great variations in size and physical characteristics, ranging from a few to hundreds square kilometers. The water in playas is derived from groundwater and direct precipitation in the catchment area. The mechanical and chemical deposition of evaporite and non-evaporite minerals is controlled by the hydrology of the basin. These occur as lateral and vertical alterations of relatively insoluble, soft and friable siliclastic muds and clays, and soluble surface efflorescent crusts of evaporite salines which do not persist as sedimentary strata. “Only when the groundwater table is above the surface of the deepest part of a closed basin playa, so that groundwater input is constant, can subaqueous evaporites accumulate in a hydrologically closed basin.” (Rosen 1994). Multitemporal images make it possible to observe and measure variations in salt content of arid zone playas and seasonal inundations of basins in semi-arid regions. Comparable landforms are Bt1e marine lagoon sabkhas.
Geohazard Relations Playas may support aircraft landings or be totally impassable to vehicles.
Group L · Basinal Sediments
“Giant desiccation fissures, up to 1 m wide and 10 m deep occur preferentially on hard, dry playa crusts, especially where long-term drought has occurred, or where humans have lowered groundwater levels over protracted intervals …(elsewhere) salt ridges form from thermal expansion of salt and from the capillary rise of brine; they may be 60 cm high in places and are a clear hazard to traffic of any kind.” (Neal 1998). “Capillary rise in fine soils may lift salt 3 m above water table into road and building structures.” (Waltham 2002).
References Neal JT (1998) Playas and military operations. GAS, Reviews in Engineering Geology, vol XIII:166–168 Rosen MR (1994) The importance of groundwater in playas: A review of playa classifications and the sedimentology and hydrology of playas. GSA Special Paper 289, pp 1–18 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 32
Select Bibliography Genetic Emphasis Dohrenwend JC, Bull WB, McFadden ID, Smith GL, Smith RSU, Wells SG (1991) Quarternary geology of the Basin and Range Province in California. In: Morrison RB (ed) Quarternary nonglacial geology, Conterminous U.S.: Boulder, Colorado. Geological Society of America, The Geology of North America, K-2 Einsele G (1992) Sedimentary basins. Springer-Verlag. Henley JP (1987) Methods of determining playa surface conditions using remote sensing. Army Engineer Topographic Labs Fort Belvoir, VA. Neal JT (ed) (1975) Playas and dried lakes: Occurrence and development. Dowden, Hutchinson & Ross, Stroudsburg Peryt TM (1987) Evaporite basins. Springer-Verlag, Berlin Schuster M, Roquin C, Duringer P, Brunet M, Caugy M, Fontugne M, Mackaye HT, Vignaud P, Ghienne J-F (2005) Holocene Lake MegaChat palaeshorelines from space. Quaternary Science Reviews, vol 24, issues 16-17, pp 1821–1827 Warren JK (2006) Evaporites. Springer-Verlag
Fig. L2-1. Source. Shaw PA, Thomas DSG (1989) Playas, pans and salt lakes. In: Thomas DSG (ed) Arid zone geomorphology. Halsted Press, p 188, fig 9.9. ©John Wiley & Sons Ltd., Reproduced with permission Comments. An idealised diagram of the depositional subenvironments which can occur in closed arid zone playa basins.
L2 · Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments
Fig. L2-2. Location. Geographic. 37°14' E, 02°40' S, south Kenya Source. LAR, November 1975 Comments. A view north, from a 75 m elevation, of the bed of Amboseli Lake in the regional dry tropical climate. The sediments consist of 90 m of Pleistocene clays, covered with a veneer of 10–15 cm of windblown silts. The lake, at elevation 1130 m lies in a 40 km long broad eastwest trending basin bounded by Precambrian rocks in the north and by Kilimanjaro volcanic rocks to the south.
Fig. L2-3. Location. Geographic. 69°49' W, 19°58' S, north Chile Source. Rich JL (1942) The face of South America. In: Weaver JC (ed) Special Publication no 26, American Geographical Society, photo 246 Comments. This air view shows one of several extraction sites of nitrate in 1939, from evaporite sequences at Salar de Pintados in the Atacama Desert.
The desert is a longitudinal trough at 1 000 m a.s.l., with playa basins, between the Coastal Range and the western slopes of the Andes. Regional aridity results from onshore south and southwest winds which pick up little moisture crossing the low evaporating very cold waters of the Peruvian Oceanic and Coastal Currents.
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Division 4 · Surficial Deposits
Fig. L2-4. (Caption on p. 544)
Group L · Basinal Sediments
L2 · Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments
Fig. L2-5. (Caption on p. 544)
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Division 4 · Surficial Deposits
Group L · Basinal Sediments
▼
Fig. L2-4.
Location. Geographic. 118°43' W, 39°28' N, west central Nevada Geologic. Basin and Range Province Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 63 360 Acquisition date. June 1964 Source. Unspecified U.S. government agency Comments. The interpreted photo mosaic at Fallon covers a 150 km2 area of the Carson Sink sub-basin of the 13 000 km2 Pleistocene Pluvial Lake Lahontan. The dark-toned irrigated land, standing water surfaces (W) and Lc are temporal wet zones and are readily distinguished from surrounding dry zones. The latter have a veneer cover of Ef1 sand sheets and low dunes – fractional code Ef/L. The location of this mosaic is drawn on the Landsat mosaic of Fig. L2-7.
Fig. L2-6.
Location. Geographic. 51° 06' E, 31° 31' N, Central Zagros, Iran Geologic. Alpine belt of Arabian/Eurasian Plates collision Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 55 000 Acquisition date. Circa 1955 Source. Personal archive Comments. The stereomodel covers the southern half of a 20 km long by 10 km wide intermont structural basin infilled by playa sediments on the eastern margin of the Zagros fold belt. The largest part is irrigated cropland. The village at its north end is Deh Sasra. The uncultivated L2b dry zone Component area has since been brought under irrigation. Only the central part of the dark L2c wet zone is still unused. The rest has now been drained and irrigated. A stream drains unused playa groundwater. Fu1.3 are coalesced bahada alluvial fans, little cultivated at the time, but now intensely used. This site is 35 km south of the playa area of Fig. L2-6.
Location. Geographic. 51° 06' E., 31° 51' N, Central Zagros, Iran Geologic. Alpine belt of Arabian/Eurasian Plates collision Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 55 000 Acquisition date. Circa 1955 Source. Personal archive Comments. Basin fill sediments of three Quaternary epochs of surface and groundwater hydrologic regimes, are associated in this stereomodel on the eastern margin of the Zagros fold belt:
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Fig. L2-5.
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544
L2 are Pleistocene pluvial lacustrine deposits. They are characterized by a level surface and intense groundwater irrigation. L2b and c are saline (b) and wet (c) zones, remnants of a Holocene arid playa. The saline area in the center is still uncultivated today; the wet zones have been brought into cultivation. Fv1.2 are Recent coarser-grained alluvial deposits of a perennial stream that flows from a catchment to the northwest in the higher precipitation (400–500 mm yr–1) Zagros Mountains. The stream has cut through the Pleistocene beds to provide inflow to the lake. In the photo these alluvial deposits appear more lightly cultivated than the lacustrine sediments, but are now more densely managed. Fu2 these are piedmont apron alluvial deposits that are now also more intensely cultivated. This site adjoins Fig. Fu1-10 on the south; it is 35 km north of Fig. L2-5, and is 12 km south of the town of Boldaji.
L2 · Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments
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Division 4 · Surficial Deposits
Group L · Basinal Sediments
L2 · Holocene Playa Basins and Pleistocene Pluvial Lacustrine Sediments ▼
Fig. L2-7.
Fig. L2-8.
▼
Location. Geographic. 117° W, 39° N mosaic center, eastern California, western Nevada Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1 : 3 225 000 Acquisition date. Not given Source. USGS Comments. This Landsat mosaic covering 280 000 km2 in Nevada and southeastern California shows the extent and distribution, in white, of playas of the lakes that occupied many of the internally drained intermontane basins of the Basin and Range physiographic province during the Pleistocene Epoch. These pluvial lakes have radiometrically dated evidence of perennial lake stands younger than 50 ka. In Death Valley several carbon-14 ages on organic material in the lacustrine deposits range from about 26 ka to 11 ka. The valley contains over 2 700 m of alluvial infill overlying the solid strata. In the central part of the mosaic the basins and ridges are subparallel, formed by Unit 12 high angle block faulting of horsts (Unit 16) and grabens (Unit 17) that took place during the Late Tertiary with broad epeirogenic uplift and regional extension. In the southern Death Valley sector the valleys and ridges trend north-northwestward and are characterized by both normal (Unit 12) and strike-slip (Unit 13) fault displacements. Tectonically the Death Valley sector is one of the youngest and most active areas in the basin and Range Province. Continuing deformation is indicated by the presence of numerous fault scarps in Quaternary alluvium along most of the range fronts of the area. In Death Valley the 3 454 m relief separating Badwater, –86 m, in the valley floor from Telescope Peak, 3 368 m, represents the greatest amount of local relief within the southwest United States. The snow-covered mountain range in lower left is the Sierra Nevada, and the green area is the southeast portion of California’s Great Valley. The small green inset frame locates the airphoto mosaic of Fig. L2-4. See also Landsat image of Fig. 17.1-7. Figures Fu1-3, Fu1-9 and S2.1-1 are also located in Death Valley.
Location. Geographic. 52° E, 34°30' N, north central Iran Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1 : 1 000 000 Acquisition date. 22 September 1972/14 May 1973 Source. Krinsley DB (1970) A geomorphological and paleoclimatological study of the playas of Iran. USGS, pp 63–74 Comments. A multi-date montage of two Landsat subscenes shows Qom Playa (Namak), 120 km south of Tehran, Iran. The playa is a large evaporite basin 2 715 km2, 765 m a.s.l. The following comments are based on Krinsley 1970. This playa originated as tectonic basin. Seismic data indicate a thickness of sediments of more than 400 m in the middle of the playa. 350 m of silt and clay are covered by 45 m of salt beds, separated by beds of clay and silt. Filling of the basin continued through the whole of the Pleistocene. During the spring, rain and snow melt feed a number of streams that flow to the playa from the west and cover the lower northwest part of the basin with a shallow sheet of water (May image). This water evaporates by mid-summer (September image). Prospecting for brines and potash is being carried out in this and a number of other playas in Iran by the Potash Exploration and Equipping Project.
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Division 4 · Surficial Deposits
Fig. L2-8. (Caption on p. 547)
Group L · Basinal Sediments
L3 · Quaternary Drained Lakebeds
L3 Quaternary Drained Lakebeds Characterization Former lake water bodies, of variable shape and size, have been artificially drained and the groundwater tables lowered to produce areas of fertile sediments for generally visibly intense agricultural uses. Surfaces are exceptionally flat and are characterized by closely-integrated systems of tiles and open drains. The sediments were originally deposited in water bodies standing in closed basin environments. Their deposition was climatically controlled by seasonal fluctuations of discharge from inflowing streams. The laminated sediments range from deep water clays to littoral sands and deltaic sands and gravels.
Fig. L3-1. Location. Geographic. 16°52' E, 47°46' N, eastern Austria Source. Unattributed Comments. An air view of reclaimed portions of a Quaternary lake bed at Neusiedler See in the Danubian Plain. This is a 315 km2 alkaline turbid lake at elevation 115 m, its average depth of 1.5 m varies considerably with the seasons. The water body is transboundary, shared with Hungary where it is named Ferto. A portion is also a bilateral national park and the area is now a World Heritage Site. Restoration measures are currently underway to counter the adverse effects of a water table lowered by earler drainage and irrigation.
Geohazard Relations Engineering construction in land use designated zones of this geounit would have to deal with sediments of high compressibility and low bearing capacity. Frost heave potential would exist in cold winter climates. Risk of flooding exists in extreme rainstorm events that would exceed a particular sedimentary unit’s draining capacity.
Select Bibliography Blair RW Jr (1986) Karst landforms and lakes. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 411–413 Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, New York, pp 213–24
549
L3
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Division 4 · Surficial Deposits
Fig. L3-2. (Caption on p. 552)
Group L · Basinal Sediments
L3 · Quaternary Drained Lakebeds
Fig. L3-3. (Caption on p. 552)
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Division 4 · Surficial Deposits
Group L · Basinal Sediments
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Fig. L3-2. Location. Geographic. 113°02' W, 53°12' N, Interior Plains of central Alberta Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 31 680 Acquisition date. Not given Source. Smith DG (1987) Landforms of Alberta. University of Calgary Publ. 871, p 76 Comments. The stereomodel shows a 6 km2, drained lakebed in the midst of an extensive plain of hummocky glacial till, 50 km southeast of Edmonton, Alberta. Topography and land use both distinguish the geounits.
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Fig. L3-3. Location. Geographic. 03°07' E, 43°19' N, Languedoc Geologic. Synclinal basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 1971 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows the 600 ha depression of Montady 7 km west of Béziers on the fluviomarine plain of Fig. Bc4-3. It was produced as one of 300 regional deflation hollows developed during the Würm (Wisconsinan) cold dry climate in Miocene marine sediments. This depression is 35 km east of the smaller unit of Fig. L3-4. The depression is drained by a central slump, since the 18th century, with a distinctive centripetal field pattern. A dark rail line traverses the southeastern part of the unit. The Gallo Roman fortified site (oppidum), Enserune, occupies an outcrop rise of gravels on the southwest edge of the depression.
Fig. L3-4.
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552
Location. Geographic. 02°42' E, 43°16' N, western Languedoc Geologic. Synclinal lowland Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 1976 Source. IGN – Photothèque Nationale, France Comments. A stereomodel shows a 60 ha drained bed and distinct land use near Homps, 2 km southwest of Olonzac in the Aude Valley 35 km west of a larger bed in Fig. L3-3. The depression is one of a number of regional deflation hollows in Upper Eocene molassic coarse detrital sediments developed during the Würm (Wisconsinan) cold dry climate. The southern margin of the depression abuts the Canal du Midi which parallels the Aude River in this district. The canal is a 240 km long, 2 m draught, 20 m wide waterway that negotiates the watershed between the Atlantic at Toulouse and the Mediterranean at Agde in Fig. Bt1g-4. It is the oldest functioning canal in Europe. The drain ditch does not empty into the canal but passes under it in a 1 km long cut to join the Aude River. Recent space imagery shows this lakebed flooded.
L3 · Quaternary Drained Lakebeds
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Division 4 · Surficial Deposits
Group L · Basinal Sediments
Fig. L3-5. Location. Geographic. 23°10' E, 38°30' N, central Greece Geologic. Parnassos Zone of Hellenides of continental terranes of African Basement Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 4 August 1960 Source. Journal Photo Interprétation, Edit. ESKA, Paris, 68-2, 3
Comments. This stereomodel covers a 10 km × 4 km extent of a Quaternary drained lakebed in an intermont basin 75 km northwest of Athens at Kastron at the northeast end of 200 km2 Lake Copais (Iliki Limni). The unit is readily distinguishable by its topographic site and land use. The island is 67 m above the lake elevation and the 14th –12th century BC Mycenaean fortified city Gla is in its center.
Division 4 Surficial Deposits Group F · Fluvial System Sediments
Sub-group Fu Upland Margin Units
General Note of Geohazard Relations Fluvial sediments include 13 geounits and variants ordered in five Sub-groups:
Sub-group Fv Valley Fill Units Sub-group Fv1/Fv2 Valley Fill Composite Units Sub-group Fw Holocene Deltas Sub-group Fr Climatic Deltas
Sub-group Upland Margin Units are of two types of alluvial fans Sub-group Valley Fill Units distinguishes high and low energy deposits and two variants which, in turn, include 13 Components in the classification list Sub-group Valley Fill Composite Unit is a bimodal unit that combines both high and low energy deposits Sub-group Holocene Deltas includes four classic geounits and a variant Sub-group Climatic Deltas are five examples of an inland geounit In addition to being agents of deposition, the Sub-groups of Fluvial System Sediments are both agents of and susceptible to flooding and erosion. Upland Margin Alluvial Fans can become agents of Mf3 debris flows, while marine margin Deltas are susceptible to flooding, storm surges and tsunamis. Cooke and Doornkamp (1974, pp 112–113) explain that flooding is characterized by three groups of interrelated factors: transient phenomena – heavy precipitation, snowmelt – precipitation loss by evaporation – soil moisture preceding precipitation basic characteristics – area – network properties – density, length of streams – nature of drainage channels– slope, roughness, width, depth land use – urbanization
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_9, © Springer-Verlag Berlin Heidelberg 2009
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Division 4 · Surficial Deposits
Sub-group Fu Upland Margin Units Fu1
Fu1 Alluvial Fans Characterization Alluvial fans are cone-shaped sediment bodies deposited subaerially, mainly by swift streams and debris flows, at the base of tectonically active mountain fronts. The apex of a fan is the point at which a stream emerges from a mountain canyon. The most important factors influencing fan area in addition to tectonic history are the size and lithology of the provenance area and climate. The geounit includes the Variants paraglacial fan, the rapid rate of fan building following the last deglaciation; fan-delta, which is built into a standing and permanent body of water; and bajada, which is a coalescing of many fans to form a depositional piedmont. The Variants are grouped into the parent unit because they have essentially similar geohazard relations. Fan surface slopes vary greatly, but are generally <10°. Talus deposits Mv1 appear similar but have slopes close to 40°. Modern fans range in typical size from 1 km2 to 1 000 km2 (e.g. Fig. Fu1-14) and occcasionally they have been mapped up to 15 000 km2 on satellite images. The radius of fans, the horizontal distance between fan apex and receiving river valley, ranges from a few hundred meters to 100 km. Fans are up to about 700 m thick, considerably less than ancient fan deposits. The texture of alluvial fans is coarse detrital sediments as a rule. Particles size ranges from boulders to clay size, and it decreases from fan head to fan base, see Fig. Fu1-1. Fans can be built of Mf3 debris flow material (see) as well as fluvial sediments in variable proportions. Deposition on fans is the result mainly of the decrease in depth and velocity of flow that results from the increase in width as the flow spreads out on the fan. It is not caused by an abrupt decrease in gradient, as the slopes of the upper parts of most fans are about the same as the stream channel gradients immediately upstream from the fan apexes (Spearing 1971). Two types of water-laid sediments occur on alluvial fans: 1. Unconfined sheets of sand and silt deposited by a network of braided streams. 2. Sand and gravel deposited in the main stream channels.
Group F · Fluvial System Sediments
Geohazard Relations Fans are hazardous environments for structures and transport lines. They are subject to unpredictable flash flooding, erosion and sedimentation. Road washouts and plugging of culverts result from flash floods. The sporadic addition of debris masses to the surface and along the outer fringe of a fan modify the geometry and flood potential of the receiving river on the valley floor; accumulations of debris create lakes on the upstream side; at the toe of the fan the river channel is pushed against the far embankment and causes erosion (Eisbacher and Clague 1984).
References Eisbacher GH, Clague J (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16 Nilsen TH, Moore TE (1984) Bibliography of alluvial fans. Geo Books, Norwich Rust BR (1979) Facies models 2: Coarse alluvial deposits. In: Walker RG (ed) Facies models. Geological Association of Canada, Geoscience Canada, Reprint Series 1, pp 9–22 Spearing DR (1971) A concise summary sheet of alluvial fan deposits. GSA, chart 1
Select Bibliography General The origin and characteristics of alluvial fans are described in all general geoscience, geomorphology and engineering geology texts published in the last several decades. A voluminous literature was compiled up to 1984 by T. H. Nilsen and T. E. Moore and published as Bibliography of alluvial fans by Geo books,Norwich.Representative examples of alluvial fans described in texts published since 1984 are Marshak (2001), Harvey (1989). Discussion of alluvial fans in current engineering geology texts is exemplified by Waltham (2002).
Recent Papers Field JJ (1997) Geomorphic flood-hazard assessment of alluvial fans and piedmonts. Journal Geoscience Education (USA) 45:27–37 Guzzetti F, Marchetti M, Reichenbach P (1997) Large alluvial fans in the central Po Plain, (Italy). Geomorphology 18(2):119–136 Harvey AM (1989) The occurrence and role of arid zone alluvial fans. In: Thomas DSG (ed) Arid zone geomorphology. Belhaven Press, London, pp 136–158 Larsen MC, Wieczorek GF (2002) Debris-flow hazards on alluvial fans. GSA Bull 34(6):47 Marshak S (2001) Earth, portrait of a planet. W. Norton, New York Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 6, 28, 32
Airhoto and Imagery Interpretation Low angle (<10°) weathered bedrock erosion surfaces, termed pediments, flank many mountain ranges in arid zones. These surfaces are frequently covered by a veneer thickness of alluvial gravels and sands, and can be difficult to distinguish from low angle alluvial fan deposits on airphotos or satellite images of arid environments.
Baker VR (1986) Fluvial landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pl F-12, F-17, F-18, F-1, F-21 Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Division of Water and Land Resources, CSIRO, Australia, Natural Resources Series no 6, pp 27, 41–49
Fu1 · Alluvial Fans Crouvi O, Ben-Or E, Beyth M, Avigad D, Amit R (2006) Quantitative mapping of arid alluvial fan surfaces using field spectrometer and hyperspectral remote sensing. Remote Sensing of Environment, vol 104, issue 1, pp 103–117 Drury SA (1987) Image interpretation in geology. Allen & Unwin, London, p 109, fig 4.47 Farr TG, Chadwick OA (1996) Geomorphic processes and remote sensing signatures of alluvial fans in the Kun Lun Mountains, China. Journal of Geophysical Research, vol 101, no E10, pp 23091–23100 Miller VC (1961) Photogeology. McGraw-Hill, New York, p 119, figs 9–1, 9–2 Mollard JD, Janes JR (1983) Airphoto Interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, pp 82–83, pl 5–8, 5–9, 5–10
Fig. Fu1-1. Source. Unattributed Comments. A block diagram shows the typical morphology and sediment bedding of alluvial fans. “Because of their topographic setting and hydraulic characteristics, alluvial fans are typified by coarse gravel in proximal reaches and rapidly decreasing grain size downfan.” (Rust 1979, p 11). The diagram shows the sedimentary response to faulting along a mountain front.
Fig. Fu1-2. Source. Courtesy of Natural Resources Canada,GSC 115836 Comments. A photo shows some of the internal bedding of an alluvial fan exposed by road construction along the bank of the Nicola River at 120°56' W, 50°08' N, 11 km west of Merritt, southern British Columbia.
Pelletier JD, Mayer L, Pearthree PA, House PK, Demsey KA, Klawon JE, Vincent KR (2005) An integrated approach to flood hazard assessment on alluvial fans using numerical modeling, field mapping, and remote sensing. GSA Bulletin, vol 117, no 9–10, pp 1167–1180 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC The Hague, p 116 von Bandat HF (1962) Aerogeology. Gulf Publishing Co., Houston, Texas, pp 290–291, figs 11–25, 11–35, 18–8, 18–10, 18–20, 18–22, 23–28, 23–29 Way DS (1978) Terrain analysis: A guide to site selection using aerial photographic interpretation, 2nd edn. Dowden, Hutchinson & Ross, Stroudsburg, pp 312–321 White KH (1986) Large-scale geomorphological mapping of alluvial fans in south-central Tunisia using Thematic Mapper data. Proceedings, Symposium Mapping from Modern Imagery, ISPRS, pp 594–599
557
Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fig. Fu1-3.
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Location. Geographic. 116°52'22'' W, 36°29'42'' N, southeastern California Source. LAR, January 1975 Comments. This photo was taken at the base of a 800 m long fan, 1.3 km north of furnace Creek Ranch at the north end of the Death Valley tectonic depression. The distal deposits, at elevation minus 55 m, are covering the faulted scarp of L.2 lacustrine sediments. The upper ridges are at sea level. The relatively smooth surface of the fan, resulting from the breaking down of coarse material and the development of desert varnish, suggests that it is of an older generation of regional fans, probably of Mid-Pleistocene age, but younger than 70 ka. See Figs. Fu1-9, S2.1-1 and L2-7 for other features of Death Valley.
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Fig. Fu1-4. Location. Geographic. Engadine southeast Switzerland Geologic. Glaciated longitudinal fault valley across preTriassic granites Source. Photograph 22-300, Photo Furter, Davos Comments. The air perspective photo view westward shows the 1 km broad fan-delta built into Silvaplana Lake from the short glaciated valley, with its own sideslope fans, of the eastern segment of the Julier Pass route in granite rocks of a basement nappe. The stream leaves the valley through a gorge cut in response to isostatic rebound of the land following deglaciation.
Fu1 · Alluvial Fans
Fig. Fu1-5. (Caption on p. 560)
559
Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
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Fig. Fu1-5.
Location. Geographic. 65°48' W, 17°31' S, central Bolivia Geoligic. Central Andes front range Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 26 August 1961 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 59 Comments. Stereomodel covers the large alluvial fan of the river Tiraque in the Yungas (hot valleys) of the dissected Cordilleran foreland north of Cochabamba. Agricultural land use on the fan is concentrated near the apex between the active braided stream channels, with different uses at mid and distal fan sectors. Figure W4-3 shows dissected sedimentary rocks in the same front ranges.
Fig. Fu1-6.
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560
Location. Geographic. 132°06' W, 58°26' N, northwest British Columbia Geologic. Cordillera Boundary Ranges Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 9 July 1949 Source. Courtesy of Natural Resources Canada, NAPL A 12077-194, 195 Comments. The stereomodel covers a 10 km reach of the south-flowing (north at top) Fv1 braided Sheslay River. Four inactive paraglacial fans are delineated on the west side of the valley; the largest, in the north, is 2 000 m broad and 1 500 m to apex. This fan has significantly displaced the river channel.
Fu1 · Alluvial Fans
561
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Division 4 · Surficial Deposits
Fig. Fu1-7. (Caption on p. 564)
Group F · Fluvial System Sediments
Fu1 · Alluvial Fans
Fig. Fu1-8. (Caption on p. 564)
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
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Fig. Fu1-7. Location. Geographic. 72°18' W, 18°13' N, south Haiti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The stereomodel displays three successive alluvial deposits in a short upland valley at Marigot on the south coast. Fu1 upstream is built into the valley, while Fu1.2 is a fan-delta built into the sea. Fv1.2 is a low gradient high energy braided stream deposit. An intense cultivation of tree crops, possibly coffee or cocoa, appears to be the principal land use on all of the units.
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Fig. Fu1-8. Location. Geographic. 72°23' W, 19°01' N, central Haïti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. A stereomodel shows a classic alluvial fan built onto the floodplain of the longitudinal valley of the Artibonite River which flows along the strike of northwest trending ranges. It is 2.5 km broad at the toe and 2.5 km long to its apex. One of the main distributary channels has entrenched itself into the fan surface. Such incision can be attributed to one of a number of causes: decrease in sediment supply; variability of storm events; climatic change; base level change. The village near the bottom of the fan is Savane-àRoche. See also Fig. Fv2-18.
Fig. Fu1-9.
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Location. Geographic. 116°46' W, 36°09' N, southeastern California Geologic. Fault zone of Basin and Range Province Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 48 000 Acquisition date. 27 November 1948 Source. Unspecified U.S. government agency Comments. This stereomodel shows a series of six lowangled fine-grained Pleistocene bajada fans debouching from gullies in precipitous tectonically active fault scarps into the saline valley of the Amargosa River in Death Valley. The two largest are 3 km broad at the toes. Badwater Road now runs around the largest fans. Elevations range from –85 m to +1 800 m See also Figs. Fu1-3 and L2-7.
Fu1 · Alluvial Fans
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fu1 · Alluvial Fans ▼
Fig. Fu1-10.
Fig. Fu1-11.
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Location. Geographic. 51°08' E, 31°48' N, Central Zagros Iran Geologic. Alpine belt of Arabian/Eurasian Plates collision Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 55 000 Acquisition date. Circa 1955 Source. Personal archive Comments. A stereomodel shows extensive coalesced fans infilling an intermont basin on the eastern margin of the Zagros fold belt. Fu1.2 fan-delta Variant, is intensively cultivated. The larger of the zones of ‘active’ deposition is now cultivated. The bright lake margin area was apparently little used at the time of photography, probably due to waterlogging and some soil salinization. Recent space imaging shows the zone to have been improved and productive. The smaller apparently unused Fu1.2 deposit on the east is now also cultivated. The Fu1 areas remain unused. The L2 areas are irrigated Pleistocene pluvial lacustrine sediments. The tell site just east of the lake at the north testifies to ancient occupation of this basin. The village at the southwset margin is Dasht-e Gum. This photo adjoins that of Fig. L2-6 on the north.
Location. Geographic. 47°37' E, 40°30' N scene center, central Azerbaijan Vertical Airphoto/Image. Type. Sir-A, 40 m resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. This 120 km by 60 km radar image shows three large alluvial fans near the upper end of the 35 000 km2 Upper Tertiary and Quaternary Kura (Kurskaya) lowland between the Caucasus and Armenian Mountains. Two coalesced fans each 30 km by 30 km dimensions and a third eastward with a 20 km width are visible on the image by the relative brightness of the characteristic morphology of their distributaries, and their typical position at the base of a highland front, in this case the bright band of Paleocene sedimentary rocks on the south flank of the Caucasus. The climate is hot and semi-arid, and the staple regional cotton crop (and some rice) is based on two sources of water. Cropping on the fans uses water directly from surface and groundwater. The rectangular patterns of bright lines visible on the dark valley floor reflect the irrigation systems based on both fan and probable groundwater sources. The dependence on these traditional sources of water has probably been eased by the provision of regulated flows from the 65 km long Mingacevir Reservoir beyond the image at the head of the lowland.
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fu1 · Alluvial Fans ▼
Fig. Fu1-12.
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Fig. Fu1-13.
Vertical Airphoto/Image. Type. MSS 50 m resolution Scale. 1: 500 000 Acquisition date. Not given Source. Personal archive Comments. The Fu1.2 area on this Landsat subscene is the Crau, an abandoned Mid and Upper Pleistocene ‘dry-delta’ of the Durance River adjacent to the present Rhone Delta of Fig. Fw4-3. The unit is 35 km broad at its distal end from Arles to the sea, and 25 km long from its apex. It consists of coarse gravels and cobbles ranging in thickness from a few meters at apex to 50 m near the Rhone. The unit is composed of a pair of alluvial fans: The distinctive red pattern of intense market gardening in the north is of Riss (Illinoian) age. It is irrigated due to high permeabilities on calcareous gravels. The barren-looking south part is composed of siliceous sediments of Würm (Wisconsinan) age.
Fig. Fu1-14.
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Location. Geographic. 69°32' E, 37°33' N, Tajikistan/Afghanistan Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. This 105 km by 60 km radar image covers a delineated macro-scale alluvial fan filling the 35 km wide valley of the Panj River for 50 km on the Tajikistan/ Afghanistan border near its junction with the Amu Darya River. The flanking mountains are the first western ranges of the Pamirs. The fan surface presents contrasting patterns on either side of the green-marked international boundary. In the Tajik territory the fan is occupied with the regular bright/dark returns of the field patterns of staple cotton cropping, while the Afghan portion is relatively undeveloped agriculturally.
Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 500 000 Acquisition date. April 1975 Source. USGS Comments. This Landsat subscene shows red agricultural land use on 20 and 30 km diameter alluvial fans deposited by streams flowing from the snow and rainfed Elburz Mountains in Iran. The fans are delineated southeast and west of Tehran (1 230 m a.s.l.) on the older piedmont apron (a gently sloping zone of weakly consolidated coarse sediments). Agricultural land use is limited to the narrow (30 km) foothill transition belt between the mountains and the rain-shadow plateau desert to the south. The concentration on the fans is complemented by irrigation on the flatter piedmont apron.
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Division 4 · Surficial Deposits
Fig. Fu1-13. (Caption on p. 569)
Group F · Fluvial System Sediments
Fu1 · Alluvial Fans
Fig. Fu1-14. (Caption on p. 569)
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fu1/Mv1.2 Fu1/Mv1.2 Alluvial Fan and Talus Cone Complexes Characterization This geounit is a composite of alluvial fans Fu1 and talus cones Mv1.2 with evidence of sporadic alluvial runoff activity on its surface. Tracks, absent on simple gravity cones are visible on these cone surfaces. They are attributable to water rills and streams or small debris-mud flows Mf3 that have flowed down the ravine or gully of talus transport and across the cone slope. The alluvial sediments probably originate as fine-grained weathered or densely fractured bedrock particles on slopes and cliffs above the cones.
Geohazard Relations See Geounits Mv1.2 and Fu1.
Select Bibliography See Geounits Mv1.2 and Fu1.
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Fig. Fu1/Mv1.2-1. Location. Geographic. 10°49' E, 47°28' N, Tyrol, west Austria Source. LAR, October 1974 Comments. The forested portion of this photo of a fan/talus deposit on the south shore of the Plansee in Triassic carbonates of the Lechtaler Alps is evidence of its paraglacial origin (shortly after deglaciation) and a period of inactivity. The cause of the renewed activity is unspecified, but testifies to the latent geohazard potential of this geounit.
Fu1 Mv1.2 · Alluvial Fan and Talus Cone Complexes
Fig. Fu1/Mv1.2-2.
Location. Geographic. 69°23' W, 68°53' N, east Baffin Island, Nunavut Geologic. Archean granite gneiss of northern Canadian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 27 000 Acquisition date. 28 August 1967 Source. Courtesy of Natural Resources Canada, NAPL A 20199-49, 50 Comments. The stereomodel in large-scale airphotos at Ekalugad Fjord provides a view of morphological details of two adjacent slope-related geounits. They are both roughly 200 m wide × 500 m long and drop 250 m from 300 m upslope. The detachment scarp and individual blocks of the Mv2 rock avalanche mass are clearly visible, while alluvial runoff channels are visible on the relatively smoother surface of the smaller particle size fan/talus unit. Segments of a terminal moraine (Gl5) extend across the fjord. See also Fig. Mv2-4.
Fig. Fu1/Mv1.2-4.
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Fig. Fu1/Mv1.2-3.
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Source. Friedli W (1969) Alpenflug. Kümmerly + Frey Geographischer Verlag, Bern, photo 39 Comments. An extensive suite of composite alluvial/talus cones are delineated on the dip slope of the Montagne de Ferrand, 30 km south of Grenoble, France. This is a north-south striking Alpine border cuesta ridge of Lower Jurassic carbonate rocks.
Location. Geographic. 85°00' W, 76°38' N, south Ellesmere Island, Nunavut Geologic. Franklian Mobile Belt Platform of the Queen Elizabeth Islands Subplate Vertical Airphoto/Image. Type. Normal colour, stereo pair Scale. 1: 20 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 31000-167, 168 Comments. The stereomodel allows a comparison of adjacent deposits of alluvial fan and fan/talus cone complex geounits at South Cape Fjord. Both are 600 m broad at their toes, the fan is 450 m long to its apex, and the complex is 600 m long. The complex unit has steeper slope and coarses material, it is fed from the sides of a 400 m wide gully (faulted) eroding in interbedded Ordovician massive and argillaceous Kc limestones at 500 m elevation. The fan source material is from the lower talus slopes. See also Fig. H1-3 at same locality.
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Division 4 · Surficial Deposits
Fig. Fu1/Mv1.2-3. (Caption on p. 573)
Group F · Fluvial System Sediments
Fu1 Mv1.2 · Alluvial Fan and Talus Cone Complexes
Fig. Fu1/Mv1.2-4. (Caption on p. 573)
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Division 4 · Surficial Deposits
Fig. Fu1/Mv1.2-5. (Caption on p. 578)
Group F · Fluvial System Sediments
Fu1 Mv1.2 · Alluvial Fan and Talus Cone Complexes
Fig. Fu1/Mv1.2-6. (Caption on p. 578)
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Division 4 · Surficial Deposits ▼
Fig. Fu1/Mv1.2-5. Location. Geographic. 130°41' W, 57°15' N, northwest British Columbia Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 31 680 Acquisition date. Not given Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada BC 5160-092,093 Comments. The interpretation of this stereomodel of a valley in an alpine terrain delineates the distinction of juxtaposed occurrences of purely gravitational MV1.2 talus cone deposits and Fu1/Mv1.2 alluvial fan and talus complexes.
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Fig. Fu1/Mv1.2-6. Location. Geographic. 63°53' W, 58°53' N, north Labrador Geologic. Uplifted eastern Rim of Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL LAB92,-153, 154 Comments. The two groups of fan/talus complexes on either side of Palmer River Valley in this stereomodel at Nachvak Fjord in the Torngat Mountains are situated in their characteristic topographic site at the foot of cliffs or high steep slopes. They vary in width from 400 to 500 m, and issue from small notch gullies etched into the headwalls of this strongly glaciated valley. The cliff edges are at 800 m high relief from the valley bottom. The much larger, 2 km broad active Fu1 alluvial fans are developed from the catchments of tributary streams. The delineation of the Mv1.2 talus fan areas are groupings of closely coalesced deposits. Gt1 is a deposit of glacial till (see Gf4).
Group F · Fluvial System Sediments
Fu1 Mv1.2 · Alluvial Fan and Talus Cone Complexes
Fig. Fu1/Mv1.2-7. Location. Geographic. 06°18' E, 44°57' N, Dauphiné Alps Geologic. Granites of Hercynian Massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 1967 Source. IGN – Photothèque Nationale, France
Comments. A stereomodel in the Écrins National Park of the Pelvoux Massif shows a red delineated well-developed fan/talus complex unit varying in width from 900 m upslope to 1 300 m at valley toe. A large Mf3 debris flow has displaced the stream channel at the north end of the model. Other Mv1.1 talus sheet units are delineated. Mv2 is a rock avalanche with masses of rock debris visible on the rupture surface.
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Sub-group Fv Valley Fill Units General Note and Select Bibliography for Valley Fill Units The two photogeomorphic basic channel pattern units and their gradient-based Variants classified as Valley Fills incorporate the numerous hydrodynamic variables of concern to the engineering geology of river valleys and their related geohazards. “… only a tiny portion of the total water on Earth is in streams (1255 km3 or 0.0001% of the total) but running water is nevertheless the most important erosional agent modifying the Earth’s surface.” (Monroe and Wicander 1994). The distribution of alluvial deposits within river valleys is at first glance complex. However, sedimentary models of the general patterns have been developed which make their interpretation regular and predictable. In the hydrologic continuum of fluvial system sediments Group F, these Geounits are situated between the upland alluvial fans Fu1 and the deltaic units Fw. The units are composed of sediments derived from sheet, gully and channel erosion and include all grain sizes from clay to boulders. They are transported by traction and in suspension and ultimately deposited in stretches of the valley as a result of reduction of gradients, water volumes and velocities.
Table IV.2. Comparison of Characterization of main valley fill geounits
Group F · Fluvial System Sediments
Stream flow acts as a sort of giant centrifuge on the sediment particles; it sorts them by density, grades them by size, and stratifies them in successive beds. The valley deposits are landforms of low relief whose outstanding characteristics, as seen in photos and images, are their location, shape and extent. The photogeomorphic aspects of the deposits have been well-documented (e.g., Meijerink 1970, 1989). Large rivers are particularly well imaged by satellites providing synoptic coverage. Such rivers have lengths of 4 000 to over 6 000 km, water discharges (volume of water passing a river section per unit time) ranging from 500 to 6 000 km 3 yr –1 and sediment from 90 000 to 900 000 × 103 t yr–1 (Milliman and Meade 1983). Table IV.2 provides a comparison of the characteristics of the high energy Fv1 and low energy alluvial Fv2 geounits serves to highlight their distinctiveness.
References Meijerink AMJ (1970) Photo-interpretation in hydrology, a geomorphological approach. ITC Textbook, pp 34–48 Meijerink AMJ (1989) Remote sensing application in watershed management. Remote Sensing Applications to Water Resources, FAO Remote Sensing Centre Series 50, pp 229–280 Milliman JD, Meade RH (1983) World-wide delivery of river sediment to the oceans. Journal of Geology 91:1–21 Monroe JS, Wicander R (1994) The changing Earth. West Publishing Co., St. Paul, Minn., p 300
Select Bibliography Baker VR (1978) Adjustment of fluvial systems to climate and source terrain in tropical and subtropical environments. CSPG Memoir 5:211–230 Cooke RU, Doornkamp JC (1974) Geomorphology and environmental management. Oxford University Press, Oxford, pp 74–127 Knighton D (1984) Fluvial forms and processes. Edward Arnold, London Martini IP, Baker VR, Garzon G (2002) Flood and megaflood processes and deposits (SP 32). BlackwellRichards K (1982) Rivers: Form and process in alluvial channels. Methuen, London Rust BR (1978) A classification of alluvial channel systems. CSPG Memorandum 5, pp 187–198 Schumm SA (1977) Applied fluvial geomorphology. In: Hails JR (ed) Applied geomorphology. Elsevier, Amsterdam, pp 119–156 Schumm SA (1985) Patterns of alluvial rivers. Annual Review of Earth and Planetary Sciences 13:5–27 Wohl EE (2000) Inland flood hazards: Human, riparian, and aquatic communities. Cambridge University Press Wright LD (1985) River deltas. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York
Fv1 · Braided Alluvial Deposits
Fv1 Braided Alluvial Deposits Characterization The basic characteristics of this unit are given in Table IV.2 of the General Note for Valley Fill Units. The specific characteristics are given in Variants Fv1.1 and Fv1.2.
Geohazard Relations See Variant Fv1.1.
Select Bibliography See the Select bibliographies of Variants Fv1.1 and Fv1.2.
Fig. Fv1-1. Source. Selby MJ (1986) Earth’s changing surface: An introduction to geomorphology. Clarendon Press, Oxford, p 277, fig 10.12 Comments. The block diagram shows the main depositional Components of braided alluvial deposits. Cross-stratified coarse deposits; large sediment load of Component “x” elongate channel bars parallel to flow, and Component “k” marginal terraces are the emphasized dominant characteristics.
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Division 4 · Surficial Deposits
Fv1.1 High Gradient Setting Characterization The dominant morphological characteristic of this alluvial valley Variant is a close association of multiple well-defined active stream channels and bars in an interlaced braided pattern of channels meeting and redividing. As defined by its setting the Variant is best developed in the reaches where sediment supply is greater than the transport capacity of a river. Braiding of broad shallow channels depends on an intermittent flow when sediment erosion and deposition occur simultaneously during runoff. Sediments are non-cohesive coarse sands, gravels and cobbles transported as bedload. Very few fines are present. Braiding develops when a river is overloaded with bed material. Bars are imbricated lag deposits which could not be carried by the flow. They are elongate in shape and parallel to the flow. Typical geometries are 10 to 12 m width and 100 m length. These characteristics are similar to those of Paraglacial glaciofluvial deposits.
Group F · Fluvial System Sediments
Many vehicular access roads in mountainous terrain in deserts (e.g. the Egyptian Sinai) are constrained to be located in wadis. These sites are susceptible to unexpected storm-fed torrential flash floods which result from short high intensity rainfalls in the mountains. Their velocity can be difficult to outrun.
Flood Mechanisms Flood mechanisms are grouped in two categories: Hydrometeorological – storm rainfall (especially infrequent and intense in arid regions) – snow melt runoff (in mountainous regions) – ice jams Natural dams – landslides – glaciers – glacial moraines
Flood Damage See Geounit Fv2.
Geohazard Relations Select Bibliography Engineering Characteristics High energy high gradient alluvial deposits are notoriously unstable and provide poor foundation conditions. They present an active depositional environment with rapid and continuous shifting of the sediment and the position of channels which are difficult for engineers to control. Distinguishing between sandy, gravelly and bouldery stream beds can be important for engineering and environmental studies. Such mapping by airphoto interpretation best depends on large scale airphotos taken at low flow stages or sequential sets taken over several months.
Baker VR (1986) Fluvial landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 284–285 Bathurst JC (1987) Critical conditions for bed material movement in steep, boulder-bed streams. Erosion and Sedimentation in the Pacific Rim. IAHS Publication 165, pp 309–318 Brooks GR, Evans SG, Clague JJ (2001) Floods. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:101–112 Johnson PA, Simon A (1995) Reliability of bridge foundations in unstable alluvial channels. In: Espey WH Combs PG (eds) Proceedings First International Conference on Water Resources Engineering. ASCE, pp 1041–1045 Mollard JD (1973) Airphoto interpretation of fluvial features. NRC, Fluvial Processes and Sedimentation, pp 341–380
Fig. Fv1.1-1. Source. Unattributed Comments. Ground view of a typical active channel bar, Component “x” of braided alluvial deposits. Cobbles and coarse gravel bed load are prominent.
Fv1.1 · High Gradient Setting ▼
Fig. Fv1.1-2.
Location. Geographic. 08°53' W,30°38' N, western Morocco Geologic. High Atlas Mountains Source. LAR, August 1992 Comments. This photo shows rounded channel bar cobbles of a seasonally dry high energy stream flowing from Upper Cretaceous sediments in the mountains north of the Souss basin 25 km north of Taroudant. This deposit appears to be initiating a bar at this site as such cobbles are normally the lower part of the vertical sequence of sedimentary structures of a channel bar in mountain streams.
Fig. Fv1.1-3. Location. Geographic. Southern Alaska Source. Personal archive Comments. This air perspective photo provides a close-up view of a common technique of placer gold dredging as it is practiced in valley fill alluvial deposits. Figure Fv2-21 is a stereomodel of the possible extent of such mining operations.
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Group F · Fluvial System Sediments
Fig. Fv1.1-4. Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 25 000 Acquisition date. Not given Source. Personal archive Comments. Stereomodel of one side of a high energy river valley in the Phillipines shows three levels, A, B, C, of the terrace Component of alluvial deposits. The “C” low terrace, though the only one with evidence of cultivation, is susceptable to erosion during floods, “D” is the active channel bar, “E” is an area of rice paddy.
Fig. Fv1.1-5.
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Location. Geographic. 130°37' W, 57°03' N, northern British Columbia Geologic. Stikinia Superterrane of Cordilleran Intermontane Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 31 680 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, BC 5158-247, 248 Comments. This stereomodel shows the lower reach of More Creek. The floodplain elevation is 600 m with surrounding peaks averaging 1 800 m, and Hankin Peak rising to 2 556 m. The Creek’s catchment area is 1 600 km2 in Cretaceous felsic igneous rocks. Fv1.1x are the active 500 m wide high bedload channel bar components; Fv1.1k are the forested terrace component evidently above the flood level of the last 20 years. Two large Mf3 debris flows of different ages are located in the southeast corner of the model (at the top). A large unconfirmed Ms1.1 old rock slide is delineated on the northern valley slope. This figure is located just west of Fig. Mf3-11 and is 40 km north of Fig. X1.2-3.
Fv1.1 · High Gradient Setting
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fig. Fv1.1-6. Location. Geographic. Nepal Vertical Airphoto/Image. Type. MSS, 80 m resolution Scale. Not given
Acquisition date. Not given Source. USGS Comments. A Landsat subscene shows an unidentified high energy braided alluvial plain in the mountain belt south of the Great Himalaya.
Fv1.2 · Low Gradient Setting
Fv1.2 Low Gradient Setting Characterization The valley deposit morphological characteristics of this Variant are the same as those of the high gradient Variant Fv1.1. The distinction is in its location. These are piedmont plains or broad valleys in mountainous regions. Such sites can be in any latitudinal belt, but are determined by climatic conditions that produce seasonal high discharge fluctuations that favour aggradation (e.g. , monsoonal in low latitudes, snowmelt in high latitudes, wet-dry seasons in savannah zones, vicinity of tectonically active zones.) Erodible or weathered provenance rocks and poor vegetation cover within the drainage basin are also significant factors which promote erosion and sedimentation.
Fig. Fv1.2-1. Location. Geographic. 74°30' W, 11°45' S, central Peru Source. Johnson GR (1930) Peru from the air. American Geographical Society NYC, p 153, fig 147 Comments. This air perspective photo shows stabilized and active portions of channel bars in the braided Perené River on the forested eastern foothills of the Andes. The vegetated bars, with relict bar/channel forms are inactive and lie slightly above the active tract. They have received deposition of fine sediments on the coarser gravels when submerged during the river’s high discharge stages. These sediments facilitate the colonization of the bars by vegetation.
Fig. Fv1.2-2. Location. Geographic. 72°43'15'' W, 44°28'24'' N, northeast USA Source. LAR, August 1976 Comments. A view upstream of a bedload channel bar of coarse gravel and cobbles of the West Branch of the Waterbury River 3.5 km west of Stowe in northern Vermont in the Acadian Appalachian Highlands. An earth and vegetation clod is slumping from above the cutbank on the left foreground at the usual erosion site on the outsides of channel bends.
The sediments are generally finer-grained than the high gradient suites Fv1.1. The channel bedload bars are sands rather than gravels and cobbles. During a flood stage the bars are generally eroded on their upstream end, with deposition on the downstream end, causing significant downstream migration of the bars from flood to flood. Many of the world’s largest rivers have braided lower courses including the Brahmaputra, Hwang Ho, Amazon, and Congo.
Geohazard Relations See Geounit Fv1.1.
Select Bibliography Coleman JM (1969) Brahmaputra River channel processes and sedimentation. Sedimentary Geology 3:129–239
See also Geounit Fv1.1.
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fig. Fv1.2-3. Location. Geographic. 04°51' E, 44°46' N, southeast France Geologic. Tertiary-Quaternary infill of Miocene RhôneSaône Valley Source. Deffontaines P, Delamarre MJ-B (1955) Atlas Aérian, France, Tome I. Gallimard, p 114, photo 110 Comments. An air perspective view eastward upstream of the Drome River at Livron 6 km upstream from its junction with the Rhone between Valence and Montélimar. The view shows the characteristic geomorphic setting of a 75 m wide by 1 km long alluvial terrace. The agricultural land use is also distinctive. Bright, active gravel bars are visible in the high energy channel flowing down from the Vercors and Dévoluy Fore Alps.
Fig. Fv1.2-4. Source. LAR Comments. These are ground views of dykes that line the 110 m wide channel in the upper Rhine Valley appearing in the air perspective view of Fig. Fv1.2-5 and in the stereo airphotos of Fig. Fv1.2-6. A second set of dykes, 75 m back from these, was constructed during the period 1892–1923 to contain the overbank flood zone, within which the auto is stationed, for a distance of 25 km downstream to Lake Constance (Bodensee).
Fv1.2 · Low Gradient Setting
Fig. Fv1.2-5. Source. Ernst E (1972) Der Rhein. Konkordia AG für Druck und Verlag. Bühl/ Baden, p 11 Comments. An air perspective view northward at Vaduz of the 110 m wide dyked upper Rhine Valley pictured in ground views of Fig. Fv1.2-4 and stereomodel of Fig. Fv1.2-6. The white gravel bars are part of an excessive bedload. They are regularly dredged, and the excavated material is stockpiled, as seen near the bottom of the photo, to be subsequently used in road construction. A large Fu1 alluvial fan (outlined) off the east bank may have had an effect in deflecting the river channel at this point.
▼
Fig. Fv1.2-6.
Fig. Fv1.2-7.
▼
Location. Geographic. Eastern Switzerland/Austria Geologic. Lower Cretaceous sediments of Alpine Säntis Nappe Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Personal archive Comments. A stereomodel shows a 10 km reach of the Rhine River at Ruthi, at the junction of the tributary Ill River from Feldkirch in Austria. In the 25 km reach of the river from this point to Lake Constance the river traverses a low L1 basinal area (see Fig. Fv1.2-4). In this reach it is lined by dykes 75 m back from each bank to contain a 260 m wide overbank floodzone. The “S” arrow points to channel bars. An air perspective view of the area is in Fig. Fv1.2-5. A 10 m wide canal, visible near the west bank, parallels the river for 55 km from streams in hills above Bad Ragaz to Lake Constance. See similar engineered stream channel control in southern France in Fig. Fv1.2-9.
Location. Geographic. 105°50' E,14°01' N, south Laos, at Cambodian border Geologic. Alluvial plain on craton cover rocks Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. February–March, 1981 Source. Personal archive Comments. The stereomodel covers an 11 km × 5 km reach of the Mekong River shown in the Landsat scene of Fig. Fv1.2-13. These photos were necessarily taken during the dry season when local cultivation is extended into the onto the floodplain islands which are not channel bars. At the height of the monsoon season many of the smaller islands are submerged, their presence indicated only by emergent tall vegetation.
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Fig. Fv1.2-6. (Caption on p. 589)
Group F · Fluvial System Sediments
Fv1.2 · Low Gradient Setting
Fig. Fv1.2-7. (Caption on p. 589)
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Division 4 · Surficial Deposits
Location. Geographic. 04°55' E, 23°36' N, southeast Algeria Geologic. Ahaggar cratonic massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 1955 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows a 10 km reach of a typical wadi channel of Oued Amguel. The channel is 500 m wide and is peppered by phreatophytes (plants that send roots that tap the saturated groundwater zone). The tributary channel marked “inactif” and other bright fracture depressions have a smooth appearing veneer of Ef1 sand sheet deposits.
Fig. Fv1.2-9.
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Fig. Fv1.2-8.
Group F · Fluvial System Sediments
▼
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Location. Geographic. Nice, France Geologic. Pre-Alps of Maritime Alps Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. A stereomodel presents a river valley environment, the Lower Var, on the Mediterranean coast analogous to that of the Upper Rhine in Fig. Fv1.2-6. The dyked channel of this 15 km reach of the lower Var is twice as wide, 210 m, as that of the Rhine locality.
Fv1.2 · Low Gradient Setting
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Group F · Fluvial System Sediments
Fv1.2 · Low Gradient Setting ▼
Fig. Fv1.2-10. Location. Geographic. 139°30' W, 69°27' N, north Yukon Geologic. Landward extension of Beaufort Shelf Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 68 000 Acquisition date. 1952 Source. Courtesy of Natural Resources Canada, NAPL A 13751-114, 115 Comments. The stereomodel shows the lower 15 km reach of the strongly coarse grain bedload-braided channel of Firth River in Ivvavik National Park on the coastal plain 3 km from its mouth at the Beaufort Sea. In this location it traverses with little incision an older Fu1.1 alluvial fan. Firth River has extensive winter icings, sheetlike masses of layered ice, upstream. These icings are indicative of continued groundwater discharge through the winter. Gt2 areas are deposits of glacial till (see Gf4). This site is 80 km west of the bluffs of Fig. Bb1.1-4.
Fig. Fv1.2-11. Location. Geographic. 84°15' E, 24°58' N, northeast India Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image shows a 50 km reach of the 4 km wide floodplain of the Son River in Bihar, 110 km south of its entry into the Ganges Plains. A system of water control and irrigation canals is just south of Dehri City. Bedload channel bars are well exposed downstream of the control area and are partly drowned upsteam. The brown area west of the river is the eastern end escarpments of the extensive Rewah Plateau of Archean massive sandstones with some limestone and shale.
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Group F · Fluvial System Sediments
Fv1.2 · Low Gradient Setting ▼
Fig. Fv1.2-12.
Fig. Fv1.2-13.
▼
Location. Geographic. 60° W, 03° S, north Brazil Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 665 000 Acquisition date. 12 July 1987 Source. USGS Comments. 140 by 140 km multiband Landsat scene reveals the different sediment loads of two major rivers whose confluence at Manaus on the right margin of the image becomes the Amazon River proper. The Rio Negro, which may be fault-controlled, is so named because it carries little suspended sediment load and is thus less susceptible to meandering. It drains the area of north-central South America. The last Andean orogeny took place in early Pleistocene. Streams have eroded deep valleys and transported their sediments downstream. Neogene sediments in the Amazon Basin which lies between the Guyana and Brazilian Shields are overlain by 10 to 120 m of kaolinitic clay (Balterra) which has been dissected during the Quaternary leaving terraces common along major streams. The blue Solimoes carries the suspended sediment load from all the tributaries that drain the Andes, which is more than 75% of the suspended sediment provided by more than 200 tributaries to the Amazon system. The average discharge of the Amazon is 219 000 m3 s–1, i.e. 20% of the total volume of freshwater entering oceans worldwide. Its daily flow is 14 times that of the Mississippi. Navigation note – The river has an extremely shallow gradient, Manaus, at 1 600 km from the sea, is only 44 m above sea level. Both rivers are more than 8 km wide at Manaus. The Amazon can be navigated by ships of 3 000 tons (4 m draught) 2 100 km further upstream to Iquitos Peru (1 469 km Great Circle), and 725 km up the Rio Negro. The average depth of the Amazon in the rainy season is 40 m. Biomass note – The Amazonian tropical rainforest cover extends beyond the Amazon Basin to cover all of the Guyana Shield to the north and impinges up to 500 km onto the north margin of the Brazilian Shield. North is to the left.
Location. Geographic. 105°50' E, 14°05' N, south Laos Geologic. Alluvial plain on craton cover rocks Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image is centered on the 50 km long mainly cultivated complex of the dissected river floodplain islands and rapids in the lower middle course of the Mekong River. The inset frame locates coverage of the stereo photos of Fig. Fv1.2-7. The area is known as Siphandon or Four Thousand Islands. Topographically the complex lies at the head of the Cambodian Plain but hydrologically, at Khone Falls, at the south end of the zone, it concentrates the flow of the Mekong to make it, according to different sources, the second or third largest falls site in the world, with flow volumes varying from double to four times those of Niagara. The Khone Falls which are outcrops of Triassic rhyolites and tuffs are 10 km broad and drop 18 m in 6 km. The islands result from the backing up of the river flow onto the floodplain upstream of the falls. Khone is the site of one of a number of multi-purpose projects, including hydro-electric power, irrigation, and navigational improvements, to develop the Mekong River. As John Keay has written, these developments “combined with the relentless deforestation of the whole basin could easily spell disaster for the hydraulic economies of Cambodia and the delta. If the Mekong rises too high or too fast, people drown. If it rises too little or too late people starve,” (Mad about the Mekong, Harper Collins Publishers, 2005, p 26).
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Fig. Fv1.2-13. (Caption on p. 597)
Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits
Fv2 Meandering Alluvial Deposits Characterization These deposits are one of the most ubiquitous of geounits, and their associated floods are one of the most ubiquitous geohazards. The term low energy is somewhat of a misnomer for this geounit where flood events are concerned. The expression is used for its normal flow discharges in comparison to those of Fv1 geounit. The unit is characterized by a number of hydrologic attributes and by a distinctive suite of morphologic sediment bodies that have differing engineering properties and are agents of or susceptible to specific geohazards. These bodies are classified in Table III.7 as Components of the geounit and are illustrated and described in the supporting illustrations. The origin and occurrence of the Components are closely related to two hydrologic discharge stages: In the bank-full stage water flow velocities on the outside and insides of channel bends produce discrete sites of erosion and deposition by a complementary hydraulic cut-and fill process. This results in the gradual migration of the meanders down stream. The resulting sinuosity of the channel is what has given the floodplain the geomorphologic appellation of a meandering floodplain. The over-bank flood stage produces discharges that exceed the channel capacity, cause floodwaters and the suspended sediment load to leave the channel to be initially deposited as levees immediately bordering the channel and eventually be deposited on the adjacent plain. This results in successive vertically accreting parallel laminae in the forms of the other unit Components. In a purely hydrological sense, a flood is just a very high discharge above the bank-full stage standard. Statistically, a flood is defined by the return period. For a geohazard perspective it is convenient to define a flood as any over-bank flow.
Flood Mapping with Airphoto and Satellite Images Electro-Optical Where the meandering unit is well-defined, i.e., bounded by relatively higher adjacent geounits, all the components of the alluvial plain can be detected and mapped on conventional black and white panchromatic stereoscopic vertical airphotos, but they are not well suited for flood mapping. Colour infrared film provides much better discrimi-
nation of inundations and allows the affected area to be mapped after recession of floodwaters. Where floodplains are extremely flat (e.g., Río Llanos in South America, Kafue, Zambesi) airphoto interpretation based on stereo relief is less practical, few of the characterizing components occur or are detectable. Such floodplains are mapped by techniques developed using data from various optical and radar sensors. The multispectral, multispatial, and multitemporal resolution capabilities of the various EO satellites permit flood extent mapping and flood monitoring with high reliability subject to cloud-free conditions.
Radar Cloud cover which typically occurs during many flood events and persistent cloud cover over floodplains in humid tropical environments prevent using optical sensors for mapping and monitoring. Radar data are a key source of information at such times due to their all-weather capability.
Geohazard Relations “Flooding is the most common of all environmental hazards. It regularly claims over 20 000 lives per year and adversely affects around 75 million people worldwide. The reason lies in the widespread geographical distribution of river floodplains … together with their long-standing attractions for human settlement.” (Smith 1996). Remote sensing is the only cost effective method to monitor the spatial extent of flooding.
Engineering Problems The sediments of this geounit generally provide poor foundation conditions for construction: extensive piling or deep footings are frequently required due to depth to bedrock and low bearing capacity of sediments saturated subgrades – moisture content often approaches the liquid limit high vertical and horizontal variability of sediments scouring of fills channel instability. “Large floods cause large-scale erosion and deposition completely altering the character of the pre-flood river and valley bottom.” (Brooks et al. 2001)
Flood Mechanisms The magnitude of a flood is defined by the depth of water outside the channel and the length of time the floodwa-
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Division 4 · Surficial Deposits
ters remain out of the channel. Flood mechanisms are hydrometeorological: storm rainfall snow melt runoff in cold climates ice jams in cold climates
Flood Damage As Brooks et al. (2001) have clearly explained: “Flooding causes loss of life and damages property and infrastructure. Buildings and infrastructure (e.g., bridges and pipelines) can be damaged structurally or destroyed by fastflowing water and/or impacts from debris (ice, trees) carried by the current. In extreme circumstances, buildings and bridges may be washed off their foundations and carried downstream. Lateral bank erosion can damage or destroy buildings and infrastructure by undermining them, even when they are situated above the level of inundation. Bridge abutments or pier supports may be scoured and undermined in areas where they constrict and accelerate the flow. Bridges can also partly dam flow and be overtopped by water, causing the approaches to be washed out. Floodwaters can wash out roads, highways and railway lines. Artificial dams may be breached by overtopping flood flows. In addition to causing flooding, jammed and floating ice during breakup can be very destructive along rivers prone to ice jamming. Ice may pile up along the channel margins and be pushed along and thrust onto the banks or floodplain to heights well above the water level. A shearing and thrusting ice mass is a threat to structures adjacent to or spanning a river. Bridges can be damaged or destroyed by ice jams that form behind them.” Damage to crops, livestock and the agricultural infrastructure can also be high in intensively cultivated areas. Water-borne pollution is frequently associated with floods as are water borne diseases in tropical countries.
Salinization Soil salinization is a significant geohazard associated with irrigation schemes in river valleys in arid and semi-arid areas, e.g., Figs. Fv2-11 and Fv2-25. The principal effects are reduced infiltration, increased runoff and erosion, and impairment of biological activity. “Soil salinization is spreading at a rate of up to 20 000 km2 yr–1 globally, offsetting a significant portion of the increased production achieved by expanding irrigation.” (Umali 1993).
Group F · Fluvial System Sediments
References Brooks GR, Evans SG, Clague JJ (2001) Floods. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548: 101–125 Smith K (1996) Environmental hazards, 2nd edn. Routledge, London, p 256 Umali DL (1993) Irrigation-induced salinity. World Bank, Washington, D.C.
Select Bibliography General Bellamy JA (1986) Papua New Guinea inventory of natural resources, population distribution and land use. Division of Water and Land Resources, CSIRO, Australia, Natural Resources Series no 6, pp 27–38 Church M (1988) Floods in cold climates. In: Baker VR, Kochel RC, Paton PC (eds) Flood geomorphology. John Wiley & Sons, Ltd., New York, pp 205–229 Nanson GC, Croke JC (1992) A genetic classification of floodplains. Geomorphology 4:459–486 Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, New York, pp 225–263 Spearing DR (1971) Alluvial valley deposits, summary sheets of sedimentary deposits. GSA, Chart 2 Stevenson IM (1967) Goose Bay map-area, Labrador (13F) (Report and Map 7–1967). GSA Paper 67–33 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 28–29
Airphoto and Image Interpretation Baker VR (1986) Fluvial landforms. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pl F-10, F11, F-12, F 22, F 23, F-24, F 25 Coloma JR, Valverde AM (1998) Morphologic dynamic of Amazon River – Iquitos, Peru. Geomatics in the Era of RADARSAT International Conference May 1997, Ottawa, Canada, pp 131–138 Costa MP de F, de Moraes Novo EML, Ahern FJ, Pietsch RW (1998a) Seasonal dynamics of the Amazon Floodplain through RADAR eyes: Lago Grande de Monte Alegre Case Study. Geomatics in the Era of RARARSAT, International Conference, May 1997, Ottawa, Canada, pp 163–171 Costa MP de F, de Moraes Novo EML, Mituso II F, Mantovani JE, Ballester MV, Ahern FJ (1998b) Classification of floodplain habitats (Lago Grande, Brazilian Amazon) with RADARSAT and JERS1 data. Geomatics in the Era of RADARSAT, International Conference May 1997, Ottawa, Canada, pp 149–161 Meijerink AMJ (1970) Photo-interpretation in hydrology, a geomorphological approach. ITC Textbook, pp 16, 17, 20–22, 37, 38, 43, 44, 53–59 Meijerink AMJ (1989) Remote sensing application in watershed management. Remote Sensing Applications to Water Resources, FAO Remote Sensing Centre Series 50, pp 265–271 Yath YA, van Gils HAM (1986) Multi-temporal Landsat for land unit mapping on project scale of the Sudd-floodplain, Southern Sudan. Symposium on Remote Sensing for Resources Development and Environmental Management, ITC, pp 531–534
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-1. Source. Allen JRL (1964) Studies in fluviatile sedimentation: Six cyclothems from the Lower Old Red Sandstone, AngloWelsh Basin. Blackwell Publ. Ltd., Sedimentology 3:168, fig 4
Fig. Fv2-2. Source. Hamblin WK, Christiansen EH (2004) Earth’s dynamic systems, 10 th ed. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, N.J., p 321, figs 12.29b,c Comments. These block diagrams show the development of Component ‘k’ of Fv1 or Fv2 alluvial deposits. The upper diagram is an undissected alluvial deposit. The lower diagram shows terraces which result from a lowering of base level or an increase of discharge, causing a stream to downcut through its alluvium. The terraces are alluvial deposit remnants. They are separated from one another by erosional scarps.
Comments. A block diagram shows the main depositional Components of meandering low energy stream floodplains.
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Group F · Fluvial System Sediments
Fig. Fv2-3. Location. Geographic. 33°56' E, 09°36' S, south Tanzania Geologic. Alluvial plains in shield rift Source. Light RV (1944) Focus on Africa. American Geographical Society, Special Publication no 25, photo 137 Comments. An air perspective view looking west shows land use defining the levee ridges bordering stream channels in the center of the Mbeka Delta Plain at the head of Lake Malawi in the West African Rift Valley system. See analogous levees in Fig. Fv2-16 in Haiti.
Fig. Fv2-4. Source. Beckel L, Stenzel G (1973) Flug über Österreich. Otto Müller Verlag, Salzburg, photo 92 Comments. The air perspective view looking west shows abandoned meander channels of the Salzach River at Furth near Zell in central Austria at 12°44'34'' E, 47°17'08'' N. The straight regulated channel of the river on the left was engineered in the 19th century to reduce the constant heavy flooding in this part of the valley. Dark-toned zones in the floodplain adjacent to the channels indicate the usual high groundwater levels in such plains.
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-5. Source. LAR, August 1963 Comments. An air perspective view shows progressively drier, higher sandy terrace levels (Fig. Fv2-2) of the Naskaupi
River flowing onto the Bc3 glaciomarine sediments near the head of Grand Lake, 60 km north northwest of Goose Bay, Labrador in the Lake Melville Graben of Fig. 17.1-5.
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Fig. Fv2-6. Location. Geographic. 139°E, 35°36' N, Honshu, Japan Geologic. Active margin of island arc Source. Unattributed
Group F · Fluvial System Sediments
Comments. Air perspective view shows a high Holocene terrace (Fig. Fv2-2) of the Sagami River 60 km west of Tokyo is here flowing though Cretaceous-Lower Miocene sedimentary rocks of the Shimanto Belt. The railway viaduct over the valley gives a scale.
Fig. Fv2-7. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Not given Acquisition date. Not given Source. Personal archive Comments. This photo, at an unnamed location in the Philippine Islands, gives by tonality a clear expression of bright natural levees (L) with distictive land use bordering both active and abandoned stream channels.
Fv2 · Meandering Alluvial Deposits ▼
Fig. Fv2-8. Vertical Airphoto/Image. Type. b/w pan airphotos Scale. Not given Acquisition date. Not given Source. Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, p 247, figs 368, 369 Comments. These two unscaled photos show typical patterns of recent “c” crevasse splay Component deposits of alluvial plains at unspecified sites along the Brahmaputra River, in Assam of northeast India. (Fig. Fv1/Fv2-3). Crevasse splays are a type of overbank discharge of channel bedload material that breaches low or weak points in Component b levees (long-narrow-crested ridges that line many river floodplains).
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Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits ▼
Fig. Fv2-9. Location. Geographic. 107°05' E, 06°04' S, western Java Island Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 8 000 Acquisition date. Not given Source. Verstappen HTh (1977) Remote sensing in geomorphology. Elsevier, p 123, fig 6.10 Comments. This large-scale photo shows the destruction of rice paddies by deposits of a Component “c” crevasse splay on the Citarum River, 40 km east of Jakarta.
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Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits ▼
Fig. Fv2-10.
Location. Geographic. 138°25' E, 02°52' S, northern Papua, Indonesia Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. Not given Acquisition date. Not given Source. Verstappen HTh (1977) Remote sensing in geomorphology. Elsevier, p 125, fig 6.12 Comments. In this photo at the confluence of the Mamberamo and Tariku (Rouffaeir) Rivers in the Quaternary Meerlakta Basin between the central and northern ranges abandoned channels marked “d”, one temporarily dry, are delineated on the river floodplain of a low energy river. There is a controversial hydroelectric project that would dam the Mamberamo, Papua’s largest river in an environmentally valued region, to supply electricity to all of Papua.
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Fig. Fv2-11. Location. Geographic. 68°47' E, 28°15' N, central Pakistan, Upper Sind Plain, Indus Valley Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 1953/1954 Source. Personal archive
Group F · Fluvial System Sediments
Comments. The dark-toned U-shaped band delineated and marked “CR” in this photo indicates relatively high groundwater and associated denser agricultural land use in a 1.5 km wide Component “d” abandoned channel fill of the meandering alluvial plain. The channel lies 6 m below the level of the plain. Descriptor “L” indicates local levees. Levee sands have been worked into dunes at “1”. Salt crusts are at “2”. Crevasse splays (see Fv2-8) are at “3”. Irrigation canals are at “4”. Compare Fig. Fv2-13.
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-12. Location. Geographic. 101°12' W, 50°18' N, southwest Manitoba Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 33 000–1: 40 000 Acquisition date. 18 May 1955, 7 October 1956 Source. Courtesy of Natural Resources Canada, NAPL A 15215-73; A 15528-109 Comments. These twin photos show the same reach of the Assiniboine River south of St. Lazare at two flood stages:
mid-May overbank spring runoff, and early October bankfull. The meaning of the term floodplain is graphically expressed. The occupance of the floodplain can be seen to be about evenly divided between cropland and natural vegetation, probably trembling aspen. This reach of the river is 50 km upstream of Fig. Fv2-32. Figure Fv2-22 shows seasonal flooding in southeast Manitoba.
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Group F · Fluvial System Sediments
Fig. Fv2-13. Location. Geographic. 0°02' E, 45°50' N, northern Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 40 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France
Comments. This photo of a 15 km reach of the Charente River shows the extent of a floodplain clearly expressed by its tonality. The darkness relates to the higher soil moisture of the relatively deeper alluvial sediments in contrast to the shallower and drier adjacent soils. The river flows across a local plateau of Kc2-J Upper Jurassic limestones. Compare Fig. Fv2-11.
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-14. Geographic. 0°01' E, 41°17' N, northeast Spain Geologic. Molassic (S1.2) Tertiary Ebro Basin Source. Personal archive Comments. An air perspective view of an abandoned channel of the Ebro River 100 km downstream from Zaragoza.
The channel is well defined by its distinctive intense land use, the “huerta” type of market garden crops. The fertile and well-watered alluvial soils are in contrast to the surrounding sandy soils in this dry region. This location has since been submerged by the construction of the Mequinenza Reservoir.
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Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits ▼
Fig. Fv2-15. Location. Geographic. 68°23' W, 16°41' S, western Bolivia Geologic. Central Andes Alti-plano Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1:40 000 (in CD ROM) Acquisition date. 27 August 1955 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 68 Comments. The stereomodel shows bright-toned saline deposits, Fv2i, that have accumulated on the floodplain of the meandering Catari River that flows into the east end of Lake Titicaca. Location is near Viacha southwest of La Paz.
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Fig. Fv2-16. (Caption on p. 618)
Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-17. (Caption on p. 618)
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Group F · Fluvial System Sediments
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Fig. Fv2-16. Location. Geographic. 72°35' W, 19°15' N, west-central Haïti Geologic. Fluvio-deltaic plain in synclinal basin Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. This stereomodel illustrates levees at Gonaives/ Dessaline. The levees are clearly visible by their location and bright tones, bordering a tributary channel, dry at photo date, of the Artibonite River. The tonality is due to both morphology and land use. The levee soils are more elevated and drier than the adjacent darker poorly-drained flood plain soils. Land uses associated with the levees also contrast in brightness with the mono culture of irrigated rice on the floodplain. The levees are occupied by housing, garden crops and local access tracks. The linear patterns of the floodplain are not vehicular roadways, they are systems of locally poorly-maintained irrigation and drainage canals. An analogous levee pattern, occurring on a similar fluvio-deltaic plain in southern Tanzania, is well shown in the air perspective photo of Fig. Fv2-3. The low-lying Gonaives area was flooded by a tropical storm on 18 September 2004 with over a thousand deaths.
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Fig. Fv2-17. Location. Geographic. 72°06' W, 18°50' N, central Haïti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows a reach of the Artibonite River at Mirebalais which is underfit, possibly related to climatic change. Its present flood plain varies from 300 to 700 m in width, but its intensely cultivated bordering terraces indicate (Fig. Fv2-2) a valley 2.5 km wide, i.e. 3.5 to 8 times broader. The surrounding ground consists of dissected W4 weak Tertiary sedimentary rocks. Mirebalais is 30 km upstream from the valley reach of Fig. Fv2-18.
Fig. Fv2-18.
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Location. Geographic. 72°23' W, 19° 01' N, central Haïti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. This stereomodel shows a 9 km reach of a 1 to 1.5 km wide Fv2j floodplain meander belt with abandoned meander scrolls and abandoned channel oxbow lakes of the Artibonite River 15 km downstream from La Chapelle and 30 km down from Mirebalais of Fig. Fv2-17. Fu1 alluvial fans border each bank for most of the reach. This is the same locality as Fig. Fu1-8.
Fv2 · Meandering Alluvial Deposits
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Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits ▼
Fig. Fv2-19.
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Fig. Fv2-20.
Location. Geographic. 133°59' W, 62°10' N, Glenlyon Range, central Yukon Geologic. Late Proterozoic sandstones and shales of Omineca Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 15 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada NAPL A 11450-175, 176 Comments. This stereomodel shows terrace components “k” (Fig. Fv2-2) of alluvial plains of the Magundy River above the Fv2j meander belt.
Fig. Fv2-21.
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Location. Geographic. 60°46' W, 53°15' N, southern Labrador Geologic. 17.1 graben in eastern Grenville Shield Province Vertical Airphoto/Image. Type. Colour infrared, stereo pair Scale. 1: 36 000 Acquisition date. 8 August 1973 Source. Courtesy of Natural Resources Canada, NAPL A 30885-36, 37 Comments. The delineated areas bearing the descriptor “h” on this stereomodel at Muskrat Falls are interpreted as buried valleys under Fw3 estuarial sand terraces (Fig. Fv2-2) and into Bc3 glaciomarine clays, down to bedrock as reported by Stevenson, GSC Paper 67-33, p 2. This is one of two neighbouring sites on the lower Churchill River that comprise a hydro-electric power development project that can generate 7 000 megawatts of electricity. The geohazard relations of the unstable materials at this site are discussed in Geounits Bc3, Glaciomarine plains, and Mf2, Earth flows. A group of poorly vegetated and bare parabolic dunes are on the terrace surface on the north bank of the river. They are of the same origin as the dunes in Fig. Ed1.7-3, 33 km upstream.
Location. Geographic. 139°22' W, 64°02' N, western Yukon Geologic. Nisutlin Terrane of Cordilleran Omineca Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. 27 June 1951 Source. Courtesy of Natural Resources Canada, NAPL A 13134-2, 3 Comments. A stereomodel shows 8.5 km of the floodplains of Klondike River and Bonanza Creek which flow into the Yukon River near Dawson. The bright wormlike patterns on the floodplains are tailings from dredge mining of placer gold which is present in the valley gravels. The source of the placers is in uplift and erosion of deeply weathered gold-bearing schists in late Tertiary time. The gold bearing gravels accumulated in the valleys cut into the uplands. A close air perspective view of this type of dredging is in Fig. Fv1.1-3. J3.3 code indicates Paleozoic stratified rocks. Despite its location Dawson is situated in the unglaciated western Yukon, the forested uplands are covered with weathered rock and colluvium.
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Fig. Fv2-20. (Caption on p. 621)
Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-21. (Caption on p. 621)
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Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits ▼
Fig. Fv2-22. Location. Geographic. 97°13' W, 49°00' N, southern Manitoba Geologic. Glaciolacustrine Lake Agassiz of Interior Plains Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 15 000 Acquisition date. 7 May 1950 Source. Courtesy of Natural Resources Canada NAPL A 12445-242, 243 Comments. The stereomodel shows springtime overbank flooding of a lower reach of the Red River at Emerson on the border with Minnesota. The entire residential area of the town is underwater. Some bordering levees are emergent and locate the channel. North is on the right. Other photos of seasonal flooding in Manitoba are in Figs. Fv2-12 and Fv2-32.
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Fig. Fv2-23.
Location. Geographic. 116°48' W, 51°09' N, Kootenay Ranges of southeast British Columbia Geologic. Cretaceous thrusting of Cambrian shales of the Cordilleran Craton Foreland Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 35 000 Acquisition date. 24 July 1950 Source. Courtesy of Natural Resources Canada, NAPL A 12795-16, 17 Comments. This stereomodel on the Columbia River 13 km southeast of Golden, shows two floodplain components on a 7 km reach of the upper Columbia River: “b” are levees; “f” are floodbasin backswamps. The large alluvial fan has the river channel deflected around it.
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Fig. Fv2-23. (Caption on p. 625)
Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-24. Location. Geographic. 02°27' E, 07°13' N, south Benin Geologic. Alluvial valley in west African Craton Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 1954/1955
Source. IGN – Photothèque Nationale, France Comments. A stereomodel shows the greater surface of a 5 to 6 km wide alluvial plain of the Ouémé River 95 km north of Cotonou occupied by “f” flood basin backswamps. Other components are the meander belt “j” and stabilized channel bars “s”. This model is a continuation eastward of Fig. S1.5-5.
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fig. Fv2-25. Location. Geographic. Southwest Chad Geologic. Chad downwarp basin of craton cover Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 50 000 Acquisition date. 8 February 1951 Source. Journal Photo Interprétation, Editions ESKA, Paris, 62-2-4
Comments. The stereomodel shows an 8 km × 8 km area of the Logone-Chari alluvial plains in the Lake Chad basin about 40 km south of N’Djamena. The climate is semi-arid, with 600 mm annual rainfalls. The photos illustrate the occurrence of saline evaporite concentrations, the bright areas, on low terraces. The lake itself is currently dessiccating; this location now 140 km from the present water line, used to be 120 km.
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-26. (Caption on p. 630)
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Group F · Fluvial System Sediments
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Fig. Fv2-26.
Location. Geographic. 140°55' E, 06°51' S, southeast Papua, Indonesia Geologic. Phanerozoic sedimentary cover of northern Australian Shield Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 50 000 Source. Personal archive Comments. This stereomodel in the Digul/Fly River lowlands emphasizes Component “j” floodplain meander belt, of an alluvial plain. This is the area of channel cut-and-fill erosion and deposition that is related to the lateral migration of the river floodplain over time. As the terminology indicates the plain is subject to periodic flooding during which fines suspended in the flood waters are deposited in areas marginal to the main channel. Other alluvial plain components include “x” channel pointbar scrolls; “b” natural levees; and “d” abandoned channels (oxbows). Higher pointbars and levees which are above seasonal flood levels are frequently forested. Fv2f is swamp forest in flood basin.
Fig. Fv2-27.
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Location. Geographic. 140°56' E, 07°52' S, Digul-Fly Lowlands, southeast Papua, Indonesia Geologic. Phanerozoic sedimentary cover of northern Australian shields Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 50 000 Source. Personal archive Comments. The stereomodel shows numerous blocked valley “g” tributaries of the main Merauke River. They are characterized by their locations and marsh and swamp vegetation. These components develop when relatively more rapid sedimentation along the main stream cuts the tributaries off at their outlet. ‘f’ are backswamps in the river floodplain. See satellite radar image in the same area in Fig. Fv2-33.
Fv2 · Meandering Alluvial Deposits
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Group F · Fluvial System Sediments
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-29. ▼
Vertical Airphoto/Image. Type. Landsat Scale. Indicated Acquisition date. January 1976 Source. USGS Comments. This satellite subscene covers 175 km of the completely irrigated floodplain (canals, sprinklers, drips, surface drains) of the Nile at Luxor in southeast Egypt. There, it snakes around the possible extension of the southern end of a 500 km long north-south fault in Tertiary craton cover sediments that begins at the latitude of Cairo and borders the Pre-Cambrian Red Sea Hills Rift structure. See also the image of Fig. Ef2-4.
Location. Geographic. 114°35' W, 31°50' N scene center, northwest Mexico Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. Not given Source. USGS Comments. Descriptor ‘i’ indicates bright salt pans in this Landsat image of the macrotidal estuarine delta of the Colorado River at the head of the Gulf of California in Sonora State. The irrigated portion of the delta is at the north of the scene. The large beige area to the northeast is the Ed1.8 Gran Desierto/Altar Dune Field. See also Fig. Fw3.1-2.
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Fig. Fv2-28.
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Group F · Fluvial System Sediments
Fig. Fv2-30. Location. Geographic. 60°40' W, 33°00' S, eastern Argentina Source. USGS Comments. A Landsat MSS 80 m resolution scene of November 1981 shows a 150 km segment of the 35 to 60 km wide meander belt floodplain of the Parana River crossing the Pampa at Rosario, 250 km upstream from its delta at Buenos Aires. The Parana is South America’s second largest drainage basin. It occupies the Chaco-Pampa depression which lies between the Andes, the Patagonia Shield and the Brazilian Shield.
This Fv2 floodplain extends 320 km from the head of the estuarine Fw3 Rio de la Plata Delta, 100 km upstream from Buenos Aires, to the town of Parana 60 km north of the image cover. Beyond Parana the river flows as a 30 km broad Fv1 braided stream for a further 500 km north to Corrientes. In the image the floodplain is essentially a large meander belt with abandoned channels, backswamps, and extensive wetlands. It is subject to periodic flooding which greatly enlarges the backswamp lakes. The land cover of the floodplain is in distinct contrast with the pastoral and crop land uses of the adjacent pampa.
Fv2 · Meandering Alluvial Deposits
Fig. Fv2-31. Location. Geographic. 105°51' E, 21° N, northern Viet Nam Vertical Airphoto/Image. Type. Sir-A 40 m spatial resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. A 120 km by 60 km segment of a radar image is centered on the densely inhabited reach of the Unit 13 strike-
Fig. Fv2-32. Vertical Airphoto/Image. Type. C/X SAR Scale. Area is approximately 10 × 15 km Acquisition date. 22 April/4 May 1995 Source. Her Majesty the Queen in Right of Canada with permission of the Canada Center for Remote Sensing, Natural Resources Canada © 1995. Reproduced with the permission of the Minister of Public Works and Government Services, 2005 Comments. This image shows overbank flood stage on the Assiniboine River from spring season snowmelt at Virden in southwest Manitoba in the Interior Plains. The “B” levees are clearly distinguished from the floodbasin backswamps “A”. This reach of the river is 50 km downstream of Fig. Fv2-12. Figure Fv2-22 shows seasonal flooding in southeast Manitoba.
slip fault of Red (Son Hong) River valley floodplain at Hanoi. Bright levees along tributaries and dark abandoned channels are resolved. The southeast end of this image is continued in Fig. Fw4-5. The average elevation at Hanoi is 7 to 8 m a.s.l., the highest water level in flood season is 14 m a.s.l. Flood protection consists of extensive dyke and canal systems which are visible on zoomed Google Earth images. Much of the floodplain land use is double cropping wet rice cultivation.
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Fig. Fv2-33. Location. Geographic. 139°22' E, 06°38' S, southeast West Papua, Indonesia Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. North is at the bottom in this reproduction of a segment of a radar image.
Fig. Fv2-34. Location. Geographic. 28°38' E, 45°23' N scene center, south Ukraine Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 14 Aug. 1977 Source. USGS Comments. This Landsat image shows the outlets of four valleys tributary to the Danube River near its delta plain that have been blocked by the river’s sedimentation. The local appellation of these water bodies is Ozero. The largest, Ozero Yalpug, is 45 km long. See also Fig. Fw4-2.
Group F · Fluvial System Sediments
The area covered is 100 km × 50 km on the southern Papuan coastal plain. Local relief is 0 to 10 m. The area is entirely covered with uniform grey toned closed to open canopy rain and swamp forest. The narrow bright strips are swamp grasses and sedges or swamp woodland bordering drainageways. The black and white areas are Component g blocked valleys described in the stereo photos of Fig. Fv2-27 in the same region. The radar image does not penetrate the forest canopy, it images the variation of the heights of tree tops.
Fv1.1/Fv2 · Meandering Braided Complexes
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Sub-group Fv Valley Fill Composite Units Fv1.1/Fv2 Meandering-Braided Complexes
Fv1.1/Fv2
Characterization At given reaches of a river photos and images display a composite pattern of superimposed and closely adjacent channels of both the Fv1.1 high gradient Variant and Fv2 low energy alluvial deposits, and their related load and discharge variations. The bimodal pattern records the stream’s local response to hydrometeorological change – lower or greater discharge – or human factors – deforestation in the river watershed, with increased sediment load and higher discharges.
Geohazard Relations See Geounits Fv1.1 and Fv2.
Select Bibliography Baker VR (1986) Fluvial landforms. In: Short NM, Blair RW Jr (eds) Geo-morphology from space. NASA SP-486, pl F-11, F12, F-13, F-24, F-25 Coleman JM (1969) Brahmaputra River: Channel processes and sedimentation. Sedimentary Geology, vol 3, pp 129–239 Meijerink AMJ (1989) Remote sensing application in watershed management. Remote Sensing Applications to Water Resources, FAO Remote Sensing Centre Series 50, pp 265–268 ▼
Fig. Fv1/Fv2-1.
Location. Geographic. 74°13' W, 18°18' N, southwest peninsula Haïti Geologic. Greater Antilles Disturbed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows the delta-like outlet with intense land use of a short, unnamed, about 15 km in length stream valley that displays the characteristics of a dual plain. The locality is named Les Anglais. The stream rises in the 2 000 m a.s.l. high Tertiary karstic Southern Massif Range. The lower hill lands on either side of the valley are dissected volcanic rocks. Despite the high energy setting, the abandoned channel east of the active one has a meandering pattern. The present braiding channel is probably due to accelerated erosion in the uplands. High population density and deforestation have been a common condition favouring erosion regionally for decades.
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Fig. Fv1/Fv2-1. (Caption on p. 637)
Group F · Fluvial System Sediments
Fv1.1/Fv2 · Meandering Braided Complexes
Fig. Fv1/Fv2-2. Location. Geographic. 03°25' E, 11°53' N, northeast Bénin/southwest Niger Geologic. Craton cover plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 1950
Source. IGN – Photothèque Nationale, France Comments. The stereomodel provides a good comparison of the two basic alluvial valley geounit photo patterns. Fv1x are channel bars of the Niger River – a braided high energy stream. Fv2j is the flood plain meander belt of the tributary Sota (Kakigourou) River. S15-T are weak Tertiary sandstones in southwest Niger. The river is the international boundary.
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Group F · Fluvial System Sediments
Fig. Fv1/Fv2-3. Location. Geographic. 94°50' E, 27°29' N scene center, northeast India Geologic. Lowland between subduction zones of E/W Himalaya and N/S Naga/Patkai Ranges of Tethyan Fold Belt Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. Indicated Acquisition date. 14 November 1981 Source. USGS Comments. Radar image covers a 90 km broad × 55 km long reach of the Upper Brahmaputra River Valley in northeast Asssam. The 10 to 15 km broad braided Fv1 floodplain has a low radar backscatter due to the specular reflection of radar beams on the evidently smooth river surface two months following the end of the monsoon period.
The great rises and falls of the river (e.g. after snowmelt and monsoon) lead to a dynamic sequence of channel adjustment throughout the year. Channel movement as great as 800 m per year (Coleman 1969) has resulted in 863 km2 of bank area lost to erosion during the twentieth century. In contrast, the 50 km wide plain on the southern side of the valley in the river’s own alluvium displays evidence of an earlier distinct flow regime – the characteristic pattern of the Fv2 low energy meandering fluvial system with its typical oxbow-shaped abandoned channels. This bimodality probably relates to both historic and recent climatic and/or tectonic factors in the watershed.
Fv1.1/Fv2 · Meandering Braided Complexes
Fig. Fv1/Fv2-4. Location. Geographic. 0°33' W, 43°22' N, southern Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. The photo covers a bimodal 10 km reach of the Gave de Pau River downstream from Pau. This valley segment is typical of those of a number of turbulent streams that flow out from the central Pyrenees over vast deposits of mountain-derived S1.5 Miocene molasse sandstone.
Three Components of alluvial valley fill geounits are well expressed in the photo – “x” channel bars; “j” floodplain; “k” terraces: The x channel bars on the upstream (right) reach of the valley are braided, while those in the downstream reach are meandering. The dark-toned j floodplain is covered with alder thickets, willows and poplars on either side of the braided channel bars. It is unusable for agriculture because of yearly flooding by very high flows in winter and spring. Agricultural land use occupies the k bordering terraces. Recent space imagery shows two small reservoirs developed within the floodplain.
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Group F · Fluvial System Sediments
Fv1.1/Fv2 · Meandering Braided Complexes ▼
Fig. Fv1/Fv2-5. Location. Geographic. 113°13' W, 49°07' N, southwest Alberta Geologic. Till veneer over poorly cemented Paleocene sandstone and shale of the Interior Plains Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 23 000 Acquisition date. 8 October 1939 Source. Courtesy of Natural Resources Canada, NAPL A 6722-52, 53 Comments. This stereomodel covers a 6 km reach of the St. Mary River, 40 km downstream from it source in the St. Mary L1 glacial lakes at the foot of the Northern Rocky Mountains in the State of Montana. The dual plain characteristics of the valley evidently relate to two distinct flow regime periods. The 1.5 to 2 km wide original Fv2 low energy terraced meander plain had cut its valley into the glacial till cover. The present river valley is underfit, flowing in a 500 m broad floodplain, slightly entrenched into the meander floodplain deposits. It has channel bar deposits resembling braiding, that are formed by higher energy flows. The altered discharge may result from now regulated flow at the Sherborne Reservoir on one of the headwater lakes. It may also be caused by a gradual erosion of the moraine dam at the outlet of the other lake. An irrigation canal paralleling the valley on the left is a feature of the regional arid grassland climate.
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Sub-group Fw Holocene Deltas Note and Select Bibliography for Holocene Deltas Deltas are classified in two Sub-groups: Fw – Holocene deltas and Fr – inland deltas. The latter are described as Geounit Fr2. (Fr1 is a raised glacial delta with no geohazard relations, associated with L1 glacio-lacustrine deposits). This note discusses the Fw Sub-group. Regarding Holocene deltas Wright (1985) states “Deltas may occur wherever a stream debouches into a receiving basin. This statement holds whether the receiving basis is an ocean, gulf, inland sea, bay, estuary or lake. Consequently, deltas of various sizes can be found throughout the world.” Deposition and flooding hazards are common to all deltas. These notes apply particularly to marine deltas which are additionally subject to storm surges and tsunamis. Marine deltas are broadly defined as coastal accumulations of sediment extending both above and below sea level, formed where a river enters marine waters. A fluvial system delivers sediment faster than marine processes can rework it, resulting in progradation of the shoreline into delta forms. Deltaic sediments accumulate in three main environments: the delta plain dominated by fluvial processes; the sub-aqueous delta front with topset sediments, reflecting river-marine interaction and the prodelta fully marine sub-aqueous delta slope foreset beds. The delta plain is a mosaic of distributary channel and interchannel environments. The upper plain is essentially a fluvial environment – deposition by fluvial processes. The lower plain is a typically brackish to saline environment and is the scene of more active deposition. Most of the active deposition in a delta takes place in the delta front, a transition zone from the fluvial to the marine environment. The coarsest material is deposited at the mouths of the distributaries as bars. “The mouths are the most fundamental element of a delta system because it is the dynamic dissemination point for sediments that contribute to delta progradation.” (Wright 1985). The prodelta is entirely sub-aqueous and is the finestgrained portion of a delta, with sedimentation mostly from suspension. The varied expression of these environments as the four geounits of the Sub-group have been ordered according to the use by Galloway (1975) of delta front morphology, but including consideration of the deltaic plain. Essentially the units are the result of the interaction of the fluvial system (drainage basin, climate, discharge, sediment grain size and load), river-mouth processes, and marine reworking by wave trains and tidal currents. Deltaic geounits are generally very extensive. Only synoptic coverage of satellite images can display major portions or the entire extent of some deltas.
Group F · Fluvial System Sediments
Airphotos display local areas of a delta plain or the topset beds of the sub-aerial delta front. Some film filters and spectral scanner channels will penetrate the water, where not impeded by turbidity, to record the upper facies of the prodelta slope foreset sediments.
Geohazard Relations Fluvial flooding, tidal flooding, storm surges and sea level rise are geohazards common to all marine deltas. Shoreline harbours, seaport facilities and associated maritime infrastructures located on distributary channels are all subject to these hazards as are extensive agricultural and reclaimed lands, aquaculture installations, and other fisheries. Channel siltation has continuous unfavourable effects on navigation and flood dispersal. Widespread forest clearing and agricultural activity has resulted in greatly increased sediment supply in some deltas. Global climate changes and associated sea-level rise are a serious threat to all deltaic environments.
References and Select Bibliography for Fw Sub-Group Delta Geounits These references and bibliography are common to all the Fw Sub-group units.
References Galloway WE (1975) Process framework for describing the morphology and stratigraphic evolution of the deltaic depositional systems. In: Broussard ML (ed) Deltas: Models for exploration. Houston Geological Society, pp 87–98 Wright LD (1985) River deltas. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 1–76
Select Bibliography Allison MA, Khan SR, Goodbred Jr SL, Kuehl SA (2003) Stratigraphic evolution of the late Holocene Ganges-Brahmaputra lower delta plain. Sedimentary Geology, vol 155, issues 3–4, pp 317–342 Asian A, White WA, Warne AG, Guevara EH (2003) Holocene evolution of the western Orinoco Delta, Venezuela. GSA Bulletin, vol 115, issue 4, pp 479–498 Bird ECF (1976) Coasts. Australian National University Press, pp 205–218 Boyd RL, Dalrymple RW, Zaitlin BA (1992) Classification of clastic coastal depositional environments. Sedimentary Geology 80:139–150 Chorley RJ, Schumm SA, Sugden DE (1984) Geomorphology. Methuen, London, pp 359–370 Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 167–172 Fisher WL, Brown LF Jr (1972) Clastic depositonal systems – A genetic apprroach to facies analysis. Bureau of Economic Geology, The Universty of Texas, pp 40–96 Kakani NR, Takayasu K, Sadakata N, Bandaru HM (1993) Studies on the holocene evolution of the east coast deltas of India: Present status and future prospects. Proceedings, International Conference on Deltas of the World
Fw1 · Arcuate Deltas
Airphoto and Imagery Interpretation Coleman JM, Roberts HH, Huh OK (1986) Deltaic landform. In: Short NM, Blair RW Jr (eds) Geomorphology from space. NASA SP 486, pp 317–352 Nath AN, Rao MV, Reddy SR (1991) Coastal morphological features, and their changes in Krishna Delta Region, (India). In: Murai S (ed) Applications of remote sensing in Asia and Oceania. Asian Assoc. on Remote Sens., Geocarto International Centre, Hong Kong, pp 305–310 Shepard FP, Wanless HR (1971) Our changing coastlines. McGrawHill, New York, pp 199–225, 458–465, 486–491 van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC The Hague, pp 238–241 Xiangxiang X, Xuelian C, Jianjui Z, Dan L (1991) Monitoring the water-sediment dynamics in Lingdingyang Bay, Pearl River. In: Murai S (ed) Applications of remote sensing in Asia and Oceania. Asian Assoc. on Remote Sens., Geocarto International Centre, Hong Kong, pp 299–304
Fw1 Arcuate Deltas Characterization In plan view the arcuate delta is fan-shaped, and so it is also termed lobate. It is formed by deposition and progradation of river-derived sediment into a receiving body of water, ocean or lake. A compact form, over which distributaries constantly change position as on an alluvial fan, develops chiefly through fluvial processes, by pronounced progradation of large streams with large, relatively coarse sediment loads. The distributary channels are bounded by well-developed levees. There is little contemporaneous wave, tidal or current influence limiting the progradation.
Geohazard Relations See Note and Select Bibliography for Holocene Deltas for Sub-group Fw.
Select Bibliography See Note and Select Bibliography for Holocene Deltas for Sub-group Fw.
Fig. Fw1-1.
▼
Nemec W (1990) Deltas; remarks on terminology and classification. In: Colella A, Prior DB (eds) Coarse-grained deltas. IAS Special Publication 10, pp 3–12 Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, New York, pp 264–279 Suter JR (1994) Deltaic coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 87–119 Van Straaten LMJU (2007) Some recent advances in the study of deltaic sedimentation. Geological Journal, vol 2, issue 3, pp 411–442
Location. Geographic. 62°28' W, 57°28' N, north Labrador Geologic. Archean metaplutonic rocks of Nain Province of the eastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 65 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 18299-149, 150 Comments. A stereomodel shows an arcuate delta actively prograding 1.6 km half way across Okak Bay. The delta sediments are deposited by Ikinet Brook which is cutting into the early Holocene glaciofluvial outwash terraces in the Brook Valley. The fjord-head estuarine delta is described in Fig. Fw3-2. In recent space imagery the deposit appears more subaqueous than in this photo, due probably to tide level.
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Fig. Fw1-1. (Caption on p. 645)
Group F · Fluvial System Sediments
Fw1 · Arcuate Deltas
Fig. Fw1-2. Location. Geographic. 118°30' E, 37°40' N image center, northeast China Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1:430 000 approx. Acquisition date. Not given Source. USGS Comments. The single band, low resolution Landsat subscene covers the greater part of the 8 000 km2 Huang Ho River Delta. It is included in this atlas for comparison with the TM image of Fig. Fw1-3.
Huang Ho is one of four deltas that occupy the structural North China Basin, one of the larger alluvial lowlands of the world. The sediment load of the Huang Ho is the largest of any river in the world, 1 600 million tons per year of which 800 million tons are deposited in the delta. The basin has extended into the low tide, low wave energy of the Gulf of Chihli by the great quantity of sediment carried by the river, especially loess from the Et1.1 Loess Plateau in Shansi Province. It is the loess in the suspended sediment that gives the river its other name, Yellow River. The bright areas along the northern distributary of the delta indicate local land use development.
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Fig. Fw1-3. Location. Geographic. 118°30' E, 37°40' N image center, northeast China Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1:430 000 approx. Acquisition date. Ca. 1997 Source. USGS Comments. This multiband Landsat subscene covers the same area of the Huang Ho Delta as Fig. Fw1-2. Both land
Group F · Fluvial System Sediments
use and natural features are visible in this image that are not present in the single band scene. A large 9 km square dyked area on the eastern shore is most evident. Development of that structure has displaced and reduced the importance of the northeast trending distributary that is clearly expressed on the older image. The flow of that channel diverted into an entirely new and major east-flowing distributary cut in 1997 that is creating its own satellite delta which now extends a further southeastwards 9 km into the Gulf of Bohai (Chihli) beyond the margin of the scene.
Fw1 · Arcuate Deltas
Fig. Fw1-4. Location. Geographic. 164° W, 62°30' N scene center, western Alaska Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 10 June 1976 Source. USGS Comments. The 80 km broad Yukon River Delta on the Bering Sea Coast is pictured in this Landsat scene. The river flows at an extremely low gradient across the north end of an extensive, unglaciated Bc1 coastal plain underlain by discontinuous permafrost.
Because of the shifting sand and mudbanks of the delta distributaries, the river is only navigable by shallow-draft river boats, but it was used extensively to transport prospectors during the Klondike gold rush of 1898. The delta began to form only 2 500 years ago when the Yukon River shifted its course from the southern part of the coastal plain. The offshore delta region is ice-bound from late October through late May. Short and Blair (1986) state that “During break-up much of the sediment bypasses the delta fringe and is deposited offshore by a combination of over-ice flow and sub-ice flow through a series of channels that extend up to 25 km offshore.”
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Group F · Fluvial System Sediments
Fig. Fw1-5. Location. Geographic. 113°38' W, 61°16' N, Northwest Territories, Canada Geologic. Devonian evaporite basin of northern Interior Plains (H1) Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The dominant pattern in this image is the bright zone of turbidity in the waters of the southern shore of Great Slave Lake in the prodelta zone of the Slave River, the largest river draining into the lake.
The 50 km broad delta front just north of the white airstrip of Fort Resolution consists of a 20 km, green, active segment on the west, and an inactive segment on the east traversed by an active major distributary. The turbid zone is the suspended load of sediments of the 40 to 55 km wide plain of L1 Glacial Lake McConnell that the river flows through from its origin at the juncture of Peace and Athabaska Rivers 430 km to the south. The sediment load is increased by the volumes of clay that are deposited in the river channel by numerous Mf1 retrogressive flows that occur along the banks of low stability.
Fw2 · Elongate Deltas
Fw2 Elongate Deltas Characterization The Elongate delta, also known as a birdsfoot delta, is developed by fluvial processes that deliver large quantities of fine sediments as suspended load to a fresh water lake or a sea that has low tidal range, low wave energy and low gradient offshore slopes. The distributary channels are elongate protrusions, fairly stable and confined by well-developed levees.
Geohazard Relations See Note and Select Bibliography for Holocene Deltas for Sub-group Fw.
Select Bibliography See Note and Select Bibliography for Holocene Deltas for Sub-group Fw.
Fig. Fw2-1. Location. Geographic. 137°51' E, 01°51' S, Papua, Indonesia Source. Verstappen HTh (1964) Geomorphology in delta studies. Publications of ITC, ser B, no 24, photo B Comments. The 1:20 000 vertical airphoto shows a minor delta built into a lake at the northern tip of the island, 40 km south of its main delta into the sea.
Photo annotations: “M”: Mamberano River; “R”: Rombebai Lake; “ML”: levees; “OD”: older delta; “YD”: younger delta. Google Earth image shows YD has disappeared, while the northeast extremity has prolonged with a bend eastward.
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Group F · Fluvial System Sediments
Fw2 · Elongate Deltas ▼
Fig. Fw2-2. Location. Geographic. 112°34' E, 06°54' S, east Java, Indonesia Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 32 500 Acquisition date. 1943 Source. Verstappen HTh (1964) Geomorphology in delta Studies. ITC ser B, no 24, photo A Comments. This photo of the south part of the Solo Delta was taken in 1943, 27 years earlier than the infrared photo of Fig. Fw2-3 on which its coverage is framed. The suspended load of the five numbered distributary channels and the turbidity in offshore waters are visible in contrast to the infrared film.
The principal observable evolutionary changes in the delta’s morphology are:
the disappearance of distributary 3 the shortening of distributaries 2 and 2a the extension of distributary 4 the broadening of the base of the delta on both shores
Visible land cover and land use changes are the disappearance of mangove swamp woodlands and their replacement by fish ponds. The photo has been annotated as follows: “L”: Fw2b natural levees; “B”: Fw2c floodbasin backswamp; “S”: Bw4 beach area; “M”: Bt1c mangroves; “R”: Bt1c rice paddies; “F”: Bt1c aquaculture area (fish ponds); “OC”: old Bw4 coast line.
Fig. Fw2-3. Location. Geographic. 112°34' E, 06°54' S, east Java, Indonesia Vertical Airphoto/Image. Type. b/w infrared airphoto Scale. 1: 70 000 Acquisition date. 1970 Source. Verstappen HTh (1977) Remote sensing in geomorphology. Elsevier, p 128, fig 6.15 Comments. Photo shows 12 km of the elongate delta of the Solo River extending into the Java Sea, 40 km north of Surabaya. Near the northern edge of the photo only the natural levees are above sea level. Verstappen, states that the delta growth started at the beginning of the 20th century when an artificial new outlet was dug for the Solo River. Other than the levees, the delta is fully utilized as fish ponds. The inset frame shows the coverage of the airphoto of Fig. Fw2-2.
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Fig. Fw2-4. (Caption on p. 656)
Group F · Fluvial System Sediments
Fw2 · Elongate Deltas
Fig. Fw2-5. (Caption on p. 656)
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Fig. Fw2-4. Location. Geographic. 112°16' W, 58°34' N, northeast Alberta Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 60 000 Acquisition date. Not given Source. Smith DG (1987) Landforms of Alberta. Alberta Remote Sensing Center, pub 87-1, p 74 Comments. The steremodel shows the 9 km long birdfoot delta of the local Birch River, built into Lake Claire on the northeast margin of the Canadian Interior Plains. The lake is pictured in the 11 August 1981 satellite image of Fig. Fr2-3.
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Fig. Fw2-5. Location. Geographic. 76°54' W, 48°47' N, Abitibi, central Québec Geologic. Grenville Province of the eastern Shield Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 60 000 Acquisition date. 13 June 1953 Source. Courtesy of Natural Resources Canada, NAPL A 13658, 42 Comments. The single photo shows a composite elongate delta formed by the confluence of three rivers, built into the head of a large lake. The characteristic bordering levees are well developed. The rivers are flowing in a region of L1 glaciolacustrine sediments, the delta suspended load thus consists of a high proportion of clay. The area was deglaciated 8 400 years ago, so the elevation of the sub-aerial sediments is still near lake water level, with a marsh vegetation growth.
Group F · Fluvial System Sediments
Fw3 · Estuarine Deltas
Characterization
Fig. Fw3-1.
▼
An Estuarine delta is a tide-dominated bayhead deposit, situated in the lower reach of valleys which have been drowned by marine submergence; distributary channels are usually funnel-shaped, with sediments deposited as linear sand ridges. River water is less dense than the saline tidal water, for this reason fresh water spreads as a narrow plume above the salt-water wedge of the inflowing and outflowing tidal currents. Flood tides may extend inland up the distributary channels for a considerable distance. Sediments in estuaries are thus accumulated by both fluvial and marine mechanisms. Fluvial sediment is trapped by estuarine circulation and reduced current competence, while marine sediment is brought in by flood currents. Intertidal mud or sand flats and salt marshes of marine lagoons Variant Bt1c may also be associated with the other Components of estuarine deltas. Estuarine deltas can be grouped geologically into 4 types:
Barrier island, e.g., Fig. Bc1-9 Tectonic, where the sea floods a subsident region, e.g., Figs. Fw3.1-2, Bt1e-6 Coastal plain, a flooded river valley, e.g., Fig. Bc2-1 Fjords – e.g., Figs. Gl4-8, Fw1-1
Geohazard Relations See Note and Select Bibliography for Holocene Deltas for Sub-group Fw.
Select Bibliography Dalrymple RW, Zaitlin BA, Boyd R (1992) Estuarine facies models: Conceptual basis and stratigraphic implications. Journal of Sedimentary Petrology 62:1030–1043 Heap AD, Bryce S, Ryan DA (2004) Facies evolution of Holocene estuaries and deltas: A large-sample statistical study from Australia. Sedimentary Geology 168:1–17 Nichols MM, Biggs R (1985) Estuaries. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 76–186 Silvester R (1974) Coastal engineering II. Elsevier, Amsterdam, pp 203–237
See Note and Select Bibliography for Holocene Deltas for Sub-group Fw.
Fig. Fw3-2.
▼
Fw3 Estuarine Deltas
Location. Geographic. 56°05' W, 49 29' N, north Newfoundland coast Geologic. Silurian sediments of Springdale Belt of Dunnage Zone Terrane of Acadian Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 18984-152, 153 Comments. This stereomodel shows subaerial and subaqueous beds of an estuarine delta at the town of Springdale on Halls Bay with a visible distinction of its subaerial and subaqueous portions, each with a length of 700 m. The front of the subaerial portion is 1 km wide. Adjacent paraglacial coastal geounits are also delineated:
Location. Geographic. 62°32' W, 57°30' N, north Labrador Geologic. Archean metaplutonic rocks of Nain Province of the eastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL LAB52-09, 10, 11 Comments. This stereomodel shows a mostly subaqueous estuarine fjord-head delta of North River in Okak Bay. The delta is 4.5 km long × 2.5 km broad at water margin including the brighter subaerial distributaries. Local tides are approximately 3 meters. Other delineated geounits occurring in this local coverage of a paraglacial coastal environment are:
Fr1
– isostatic glaciomarine deltas at 5 m, 15 m and 70 m a.s.l. Bt2.1 – intertidal flat Bw4.1 – raised beaches Bc3 – glaciomarine sediments The first three of these coded units are not currently geohazard related, but they could be susceptible to long term sea level rise.
– salt marsh – interdistributary plains – Alluvial fan – raised delta (unclassified, no immediate geohazard relation) Bw4.1 – raised beaches, 90 m a.s.l. Gf3 – valley fill is pitted glaciofluvial outwash sands and gravels (see general note of Geohazard relations for paraglacial geosystems) Bt1c Fw3c Fu1 Fr1
See also Fig. Fw1-1.
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Division 4 · Surficial Deposits
Fig. Fw3-1. (Caption on p. 657)
Group F · Fluvial System Sediments
Fw3 · Estuarine Deltas
Fig. Fw3-2. (Caption on p. 657)
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Fig. Fw3-3. Location. Geographic. 30° E, 59°55' N image center, northwest Russia Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 250 000 Acquisition date. 8 June 1987 Source. Personal archive Comments. A Landsat mid-summer subscene shows the estuarine delta islands of the Neva River at the east end
Group F · Fluvial System Sediments
of the Gulf of Finland at St. Petersburg in the last glaciated Baltic Lowlands. Kotlin Island on the west edge of the image is the site of Kronstadt naval base. The barriers projecting from Kotlin Island are part of a 25 km dam project to protect the city from storm surges. The structures have been under construction since 2003 and are due for completion in 2008. The Neva is only 74 km long but drains lakes Ladoga and Onega, the two largest lakes in Europe.This arm of the Gulf of Finland is ice-bound from December through March.
Fw3.1 · Macrotidal Estuaries
Fw3.1 Macrotidal Estuaries
Select Bibliography
Smith DG, Reinson GE, Zaitlin BA, Rahman RA (eds) Clastic tidal sedimentology. CSPG Memoir 16:29–39 Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 49–51 Klein deVries G (1985) Intertidal flats and intertidal sand bodies. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 189–190 Leveoy F, Avoine J (1993) Large scale sediment movement in a macrotidal high-energy coastal area: The French coast of the English Channel. In: List JH (ed) Large-scale coastal behaviour ’93. USGS Open File Report 93–381, pp 105–108 Morgan PF, McIntire GW (1959) Quaternary geology of the Bengal Basin, East Pakistan and India. GSA Bull 70:319–342 Nichols MM, Biggs R (1985) Estuaries. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 81–82, 89–90 Silvester R (1974) Coastal engineering II. Elsevier, Amsterdam, pp 146–147, 224–229 Wright LD (1985) River deltas. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 33–37
Allen GP (1991) Sedimentary processes and facies in the Gironde Estuary: A recent model for macrotidal estuarine systems. In:
See also Fw3 bibliography and bibliography of General notes for Sub-group Fw.
Characterization Macrotidal estuaries are similar to the parent geounit in their essential characteristics. The macrotidal distinction refers to deltas that are dominated by extreme tides, e.g., semi-diurnal tides with ranges of over 4 m at springs. For at least part of the year, tides account for a larger fraction of the sediment-transporting energy than the river. Extensive intertidal flats occur in macrotidal areas.
Geohazard Relations See Note and Select Bibliography for Holocene Deltas.
Fig. Fw3.1-1. Source. Unattributed Comments. This infrared air perspective photo looking east shows the Biesboch Marshes in the upper right, 8 km southeast of Dordrecht, in south Holland. The Biesboch is a local
now tide controlled delta at the head of the Hollandsch Diep Channel of the Rhine Delta distributaries. The transportation lines crossing the Diep Channel are road and rail from Dordrecht and Breda.
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Fig. Fw3.1-2. Location. Geographic. 115°10' W, 32°00' N scene center, northwest Mexico Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 9 June 1973 Source. USGS Comments. The Landsat scene in Sonora State clearly distinguishes two deltas, the modern macrotidal segment at the head of the Gulf of California and the older inland Colorado River Delta.
Group F · Fluvial System Sediments
The tidal delta, known as the Laguna Salada, consists of bare flats subject to tides ranging up to 10 m, with local Bt1e evaporite deposits, while the Fr2 Colorado Delta is the Mexicali irrigated area. Both segments are located where the transform San Andreas Fault connects to the spreading ridge segments of the Gulf of California. They are separated by the barren 1 100 m high fault-aligned Sierra Cucopas. The yellowish northeast quadrant of the scene is the hamada bedrock pavement of the Desierto del Altar covered inland by the extensive Gran Desierto Ed1.8 dune field. L2 are playa sediments. Fu1 are bahada type alluvial fans. See also Fig. Fv2-29.
Fw3.1 · Macrotidal Estuaries
Fig. Fw3.1-3. (Caption on p. 664)
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Fig. Fw3.1-4.
Vertical Airphoto/Image. Type. TM 30 m resolution Scale. Indicated Acquisition date. Not given Source. This Landsat image is supplied by the Canada Center for Remote Sensing and is reproduced with the permission of the Minister of Public Works and Government Services, Canada (2005) Comments. The subscene is centered on the 200 m thick Late Pleistocene and Holocene estuarine delta of the Fraser River at the Strait of Georgia in southwestern British Columbia, Canada. It is 25 km broad at its front and extends 50 km upstream to Pitt Lake. The Fraser River, with a length of 2 800 km, is one of the great rivers of North America. It has the third largest average mean flow in Canada. The sediment load discharged annually by the river varies from about 11 to 26 million tonnes. The delta is bounded on the north and south by areas of glacial till, Gt on the figure. The north area is the Burrard Upland on which Greater Vancouver is situated. The southern area is the Surrey Uplands. The portion of the delta north of the main channel is Lulu Island. It is largely reclaimed peat bog and, as with the southern delta, is mainly agricultural land. The 9 km by 5 km dark brown area on the southern delta plain is the Burns Bog Wetland, the rain-fed bog covering 4 000 ha is the largest domed peat bog on the west coast of North America. Red areas in the bog mark sphagnum moss extraction. The flat areas bordering the river and the delta plain are subject to flooding. An extensive system of dykes has been built along the river. Because of these dykes and regular dredging of the river (to maintain navigation to New Westminster 25 km upstream) much of the delta is receiving no new sediment. The Fraser River is now a conduit funnelling transported sediment past the delta and into the sea as pictured here.
Vertical Airphoto/Image. Type. TM 30 m resolution Scale. Indicated Acquisition date. January–March 1984 Source. Personal archive Comments. This Landsat mosaic of the Ganges-Brahmaputra Delta in south Bangladesh covers the area framed in Fig. Fw3.1-5. The forest covered fold belt on the east side of the mosaic is the Chittagong Hills, which are part of the orogenic interface of the Indian and Eurasian Plates. The combined delta covers an area of 130 000 km2, one of the largest deltas in the world. The drainage basin of the rivers is geologically young, with large volumes of unconsolidated sediment available for transport. The combined river sediment load discharge is extremely high, 4.4 × 106 t d–1. Blue subaqueous plumes are visible in the bay. The red area is the Sundarbans Bt1c mangrove National Park. The following descriptions are based on Morgan and McIntire (1959). The delta region is constantly subsiding, owing mainly to compaction of Recent sediments and possibly to structural downwarping. The Ganges has abandoned numerous deltaic distributaries to the southwest in favour of joining the Brahmaputra in the subsidence zone. Sediment and water of the combined rivers have been pouring into the eastern part of the delta for the last 200 years or more with no appreciable build-out of the deltaic front. This suggests that the rate of subsidence has kept pace with the rate of sedimentary deposition. The intricate network of tidal channels are nonriverine; they are a common feature of many macrotidal deltas. The large whitish area between the rivers to the northwest is the Fu1 type Barind Pleistocene piedmont alluvial plain. The smaller bright area east of the Brahmaputra, known as Madhupur, is the same type of plain. These slightly elevated Pleistocene plains, and some river terraces of the same age, are essentially the only parts of Bangladesh that have no major flood or drainage problems. The rest of the country is close to sea level and is regularly exposed to storm surges from tropical cyclones from the southwest, tsunami runups, and river flooding from heavy rains or snowmelt in the upper catchments. The problem with dykes along the lower river is that they cannot be protected from lateral sapping by the huge river. In July and August 2004 half of the country was inundated by rains, and river flooding killed more than 760 people, affected more than 30 million, and washed away untold numbers of homes, roads and vital subsistence crops. In September the country endured its heaviest rain in 50 years, inundating the already saturated land and devastating recovery efforts.
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Fig. Fw3.1-3.
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Group F · Fluvial System Sediments
Fig. Fw3.1-5. Vertical Airphoto/Image. Type. AVHRR channel 4 (10.3–11.3 μm) Scale. 1: 9 000 000 Acquisition date. Not given Source. USGS Comments. This supersynoptic image covers an area 1 500 by 1 500 km, from the Bay of Bengal to the Tibetan Plateau, and from western Burma to Eastern India, 2 250 000 km2.
Hydrologically, the image includes a major part of the drainage basins of the Ganges and Brahmaputra Rivers joining in their recent deltaic plain in the image center. The exposure of this plain, one of the most densely populated regions on Earth, to flooding, storm surge and tsumani runups is recorded historically. The inset frame shows the coverage of the Landsat mosaic of Fig. Fw3.1-4.
Fw3.1 · Macrotidal Estuaries
Fig. Fw3.1-6. Location. Geographic. 122° E, 32° N, eastern China Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 102 000 Acquisition date. 11 May 1978 Source. USGS Comments. A near-infrared image provides a view of the lower Yangzi Jiang Estuary with the funnel shape typical of long macrotidal estuaries. Shanghai is visible as a dark area on tributary Whangpoo River in the lower center of the image. The Yangzi is building a delta that is prograding into the East China Sea at an estimated rate of 1.5 to 2 km per century. Short and Blair (1986) state that the Yangzi River discharge is about 690 km3 yr–1 (22 000 m 3 s–1) at its mouth. Associated with this discharge is a heavy load of
silt. It is estimated that more than 142 million m3 of sediments pass down the Yangzi every year. Although subsidence is taking place in the delta, deposition occurs at a more rapid rate, resulting in progradation. From the point of view of ship navigation, this estuary is so broad that there is no safe anchorage. The water is shallow and sand bars out of sight of land require continual dredging. Only the 4.5 m tidal range enables large vessels to enter the river. These facts are suggested by a remarkable feature of this image: Despite the fact that MSS band 7 has almost no water penetration capability, the very high suspended sediment load and areas of shallow water of this river are evident as related patterns of turbidity extending as much as 80 km east of Shanghai.
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Division 4 · Surficial Deposits
Group F · Fluvial System Sediments
Fw4 Cuspate Deltas
are parallel to the coast in contrast to those of the riverdominant estuarine delta Fw3.
Characterization
Geohazard Relations
Cuspate deltas are characterized by marine processes which dominate over fluvial processes. Fluvially introduced sediments are reworked and redistributed contemporaneously with active progradation. Waves sort and redistribute the sediments debouched by rivers, and remould them into wave-built shoreline geounits – nearshore barrier beaches Bw3 and attached beaches Bw4 which are included in the cuspate delta Fw4. The beaches
See Note and Select Bibliography for Holocene Deltas.
Select Bibliography Stafani M, Vincenzi S (2005) The interplay of eustasy, climate and human activity in the late Quaternary depositional evolution and sedimentary architecture of the Po Delta system. Mar Geol 222–223:19–48
See also Note and Select Bibliography for Holocene Deltas.
Fig. Fw4-1. Location. Geographic. 94°25' W, 74°07' N, east central Arctic Archipelago Source. Courtesy of Natural Resources Canada, GSC 164732 Comments. Air perspective view looking east of an arcuate delta 11 km broad by 1 km long with braided drainage on a narrow Bc3 plain with Bw4.2 raised beaches (9 000–9 600 BP) on the north shore of Somerset Island, Nunavut.
The delta is enclosed by a Bw5 spit beach and a Bw3 barrier beach (foreground) on which some B1 ice thrust ridges are visible. Braiding results from high flood discharges during the short spring melt flows. In late summer when discharge is minimal marine processes dominate over fluvial and streams are closed off at their mouths by beach ridges.
Fw4 · Cuspate Deltas
Fig. Fw4-2. Location. Geographic. 29°22' E, 45°07' N, eastern Romania Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. The image shows the green mass of the 100 km broad cuspate delta of the Danube River on the west shore of the Black Sea, the second largest river in Europe, with a delta area of 4 345 km2.
The delta has three major distributary channels ranging from 100 to 120 km in length. The narrow, and straighter central channel was artificially dyked for navigation purposes. The delta consists of an older upstream part and a younger seaward part. These are separated by large beach ridge complex, visible on the image as a bright feathery line crossing the center of the delta. The delta is bordered on the south by Lake Razim which is a Bt1 lagoon enclosed by faintly visible Bw3 barrier beaches. Figure Fv2-34 shows blocked tributary valleys north of the river.
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Fig. Fw4-3. Vertical Airphoto/Image. Type. MSS resampled 50 m resolution Scale. 1: 500 000 Acquisition date. August–September 1980 Source. USGS Comments. The west half of this Landsat mosaic covers the French Rhone cuspate delta at the head of the northwest Mediterranean Gulf of Lions. The delta is a Plio-Quaternary subsidence structure.
Group F · Fluvial System Sediments
The Petit Rhone is the smaller western distributary that flows southwestward on the left margin of the image. The bluish Camargue Regional Park wetlands and the Vaccares Zoological/Botanical Reserve between the two distributaries are lagoonal, enclosed by a line of Bw3 barrier beaches and dykes. Some bright blue rectangular component e salt evaporite basins are visible on the west side of the delta mouth. The industrial Port St Louis-du-Rhone has been developed on the eastern side of the delta. See Fig. Fu1-13, which discusses the adjacent Crau “dry-delta”.
Fw4 · Cuspate Deltas
Fig. Fw4-4. Location. Geographic. 12°40' E, 44°40' N scene center, northeast Italy Vertical Airphoto/Image. Type. TM, 30 m resolution Scale. 1: 825 000 Acquisition date. Not given Source. USGS Comments. Landsat scene covers 160 km of the coastline of the northwest Adriatic Sea, from Chioggia, at the south end of the Venice Lagoon, to the Marches at Pesaro.
The delta of the Po River is prominent, with the sharply resolved Bw3 barrier and Bw4 attached beaches that border cuspate deltas. The barrier beach-enclosed coastal lagoons southward include the small Volano Lido, the large Comacchio Valli, a wetland area near Ravenna, and the small salt pan area at Cervia. Bright red plankton blooms, lying at probably 5–10 m below the surface, are stretched along the entire offshore zone. The red colour is caused by the chlorophyll contained within the plankton. See also Stafani and Vincenzi (2005) and Fig. Bt1g-6.
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Group F · Fluvial System Sediments
Fig. Fw4-5. Location. Geographic. 106°25' E, 20°20' N, northern Viet Nam Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. A 70 km long segment of a radar image covers the densely populated cuspate delta of the Red River at Thai Binh 50 km south of the port of Haiphong on the delta’s north branch on the Gulf of Tonkin. Deltaic sediments prograde at a rate of 100 m yr–1 into the gulf. Bright linear traces of raised beaches are visible on the delta up to 35 km inland. This region is no more than three meters above sea level and is subject to frequent flooding. This image is the continuation of the coverage of Fig. Fv2-31. The delta mouth is 110 km southeast of Hanoi.
Fig. Fw4-6.
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Location. Geographic. 109°11' E, 0°13' S, northern Indonesia Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 12 September 1972; 14 July 1972 Source. USGS Comments. This mosaic of Landsat images shows the cuspate delta of the Kapuas River flowing across its coastal plain in western Kalimantan Island. The inset frame locates the coverage of the radar image of Fig. Fw 4-7. This is one of the main coastal plains of the island of Borneo shown on Fig. Bc1-11. The plain is an emergent part of the shallow Sunda Shelf. It received marine sediments during post-glacial submergence and later clastic alluvial sedimentation, and is now a Bc4 fluviomarine plain. The delineated bright-toned area along the coast and rivers is cleared land distinct from the rest of the densely forested plain. It is one of the most densely populated regions of Kalimantan. The cleared land has since extended up the Kapuas Valley.
Fw4 · Cuspate Deltas
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Fig. Fw4-7. Location. Geographic. 109°11' E, 0°13' S, northern Indonesia Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1: 500 000 Acquisition date. 14 November 1981 Source. USGS Comments. The 100 km by 50 km segment of a radar image covers the lower reach and cuspate delta of the Kapuas River in western Kalimantan (Borneo). The delta is part of a larger coastal plain mapped on the satellite image of Fig. Fw4-6. The Kapuas River is the main river draining western Kalimantan and is also, with its length of 1 143 km, the longest in Indonesia. The alluvial plain of the lower Kapuas River is increasingly subject to flooding as a result of extensive deforestation for palm oil production and illegal logging. The medium grey tones of the image are due to the canopy of the dense swamp forest that covers most of the coastal plain. The darker grey tones are clear-cuts in the forest. Recent imagery reveals that these areas have now extended to cover nearly half of the land area of this scene. A concurrent environmental effect of forest and swamp clearance by burning (illegal) is the release of tonnes of carbon dioxide into the atmosphere. The bright return at the north edge of the image is the town of Pontianac, which is practically on the equator.
Fr2 · Inland Deltas
Sub-group Fr Climatic Deltas
construction that must design, build and maintain roadways located in or crossing zones susceptible to floods.
Fr2 Inland Deltas
Select Bibliography
Characterization Inland deltas occur in rivers entering into lakes in structural intracratonic and intermontaine basins. In arid and semi-arid areas with internal drainage, sediments are deposited during floods whose frequency and magnitude relate to annual wet-dry rainfall cycles in upland headwater areas. During the rainy season(s) floodwaters spread out over the floodplain and basin, and are gradually lost to evaporation and seepage. These deltas have most of the morphological characteristics of Fw Holocene deltas, including braided distributary channels, interdistributary bars, marshes and small lakes. The figures illustrate four inland deltas. Other notable arid climate occurrences are Wadi Hanifa in the Riyad area of Saudi Arabia; Zayandeh Rud near Isfahan, Iran; Helmand on the Iranian Afghan border; and Damascus, Syria.
Geohazard Relations The dominant geohazard for inland deltas relates to foundations and transportation and infrastructure engineering
Brivio PA, Dessena MA, Zilioli E (1989) Detection of geomorphological units from Landsat images for the Inland Delta of the Niger River. Report of the Thirteenth UN/FAO International Training Course, Remote Sensing Applications to Water Resources. FAO Remote Sensing Centre Report RSC Series 50, pp 167–185 Csaplovics E (2003) Environmental monitoring of tropical wetlands in semi-arid Sub-Saharan Africa – what about remote sensing? Geoscience and Remote Sensing Symposium, IGARSS apos, 03rd Proceedings 2003 IEEE International, vol 5 Dumont H, Pensaert J (1988) The inner Niger Delta. In: Davies B, Gasse F (eds) African wetlands and shallow water bodies. Travaux et Documents de l’ORSTOM 1988, pp 159–176 McCarthy TS (1993) The great inland deltas of Africa. Journal of African Earth Sciences 17(3):275–291 NASA Space Station On-Orbit Status Report, 7 December 2003 Pietroniro A, Prowse T, Peters DL (1999) Hydrologic assessment of an inland freshwater delta using multi-temporal satellite remote sensing. Hydrological Processes, vol 13, issue 16, pp 2483–2498 Ringrose S, Matheson W, Boyle T (1988) Differentiation of ecological zones in the Okavango Delta, Botswana by classification and contextual analyses of Landsat MSS data. Photogrammetric Engineering and Remote Sensing 54(5):601–608 Schmidt J (2007) Multi-temporal analysis in the Niger inland delta using ERS 1/2 and ASAR data. Proceedings Envisat Symposium 2007, ESA SP 636, July 2007 Wolski P, Murray-Hudson (2006) Flooding dynamics in a large low gradient alluvial fan, the Okavango Delta, Botswana, from analysis and interpretation of a 30-year hydrometric record. Hydrology and Earth Systems Sciences 10, pp127–137
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Group F · Fluvial System Sediments
Fig. Fr2-1. Location. Geographic. 22°45' E, 19°22' S, northwest Botswana, southern Africa Geologic. Cretaceous to Quaternary sediments of Kalahari downwarp of south African Plateau Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. This image shows the 200 km broad Okavango Delta which is part of the internal drainage system of the Kalahari Basin.
Okavango is comparable in size to the Nile Delta. The dark zones of distributary channels are permanently inundated with surfaces of open water and aquatic vegetation. The bright interchannel plains are seasonally inundated, with a cover of mixed herbaceous and sparse acacia vegetation. The linear stream occurring at the delta extremity is the Thamalakane Fault, (Unit 12). The delta region receives a mean annual rainfall of 500 mm during the October to May wet season.
Fr2 · Inland Deltas
Fig. Fr2-2. Vertical Airphoto/Image. Type. b/w pan airphotos Scale. 1:20 000 approx (reduced) Acquisition date. 1923, 1950, 1960 Source. Naturräumliche Gefüge im Luftbild (1973) Selbstverlag der Bundesforschungsanstalt für Landeskunde und Raumordnung Bonn-Bad Godesberg, p 59, photo 3 Comments. This three photo sequence documents the dynamics of a 35 year evolution period of the Tiroler Ache Delta building into the south shore of the glacial moraine-enclosed (Gl5) Chiemsee in eastern Bavaria, Germany. a Delta in 1923; b delta in 1950; c delta in 1960. In the more than 45 years since 1960 the delta front has continued to prograde northward several hundred meters.
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Group F · Fluvial System Sediments
Fig. Fr2-3. Location. Geographic. 111°30' W, 58°35' N, northeast Alberta Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 22 May 1974/ 11 Aug. 1981 Source. Smith DG (1987) Landforms of Alberta. Alberta Remote Sensing Center, publ 87-1, pp 4, 94 Comments. This multi-date montage of Landsat subscenes is centered on the delta of the Peace River between Lakes Claire and Athabaska on the eastern edge of the Canadian Interior Plains. The delta is one of the world’s largest inland freshwater deltas. The May image (top) shows the delta in spring flood stage and an off-scene ice-blocked outlet, with the distributary levees visible due to the high water levels. The August (bottom) image, acquired at normal water levels, shows the brown wetlands of the delta plains. The small Fw2 elongate Birch River Delta of the stereo photo triplet of Fig. Fw2-4 is visible on the southwest side of Lake Claire in the August 1981 image.
Fr2 · Inland Deltas
Fig. Fr2-4. Location. Geographic. 04°40' W, 13°30' N, central Mali, Africa Geologic. Quaternary sediments over Late Proterozoic craton cover sediments Source. Images of the world (1983) Rand McNally, p 100 Comments. This map shows the Niger Delta in the Macina Depression. The red inset frame locates the coverage of satellite image Fig. Fr2-5 of the southern part of the delta.
The map shows the belt of dunes mentioned in Fig. Fr2-5 that had blocked the river flow. These had extended southward from the Sahara as a result of increasing aridity and higher wind velocities. A change has occurred in the delta since this 1974 image. Many of the northern lakes no longer receive the flood waters and have become dry. The primary cause is low rainfall since the late 1960s.
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Fig. Fr2-5. Location. Geographic. 04°40' W, 13°’30' N scene center, central Mali Vertical Airphoto/Image. Type. MSS 80 m resolution Acquisition date. 3 January 1974 Source. USGS Comments. The area delineated on this Landsat scene covers 10 000 km2, comprising the dry season upstream 25% of the total area of the Niger Inland Delta in central Mali, west Africa. The extent of the delta is shown on the locator map of Fig. Fr 2-4 with the coverage of this scene indicated. This is one of the greatest examples of fluvial morphology in the world. Structurally the delta is located in a basin (Macina) of Paleozoic craton cover sediments. Climatically
Group F · Fluvial System Sediments
it is in the Sahelian semi-arid belt on the south margin of the Sahara with a mean annual local rainfall of ca. 500 mm. The delta extends 450 km northeastwards to Tombouktou, where southward migrating sand dunes in the Upper Pleistocene had blocked the Niger River, creating a Pluvial lake (Araouane). The river eroded the dunes about 5 000 years ago draining the lake. The present delta dates from that time. Brivio et al., 1989 state that only 2% of the incoming waters at Ségou (see map) at the head of the delta, succeeds in reaching Gao, 900 km downstream, the site of the first gauging station after the delta, largely through evaporation. Hydrographic records show that a noticeable contribution of water is provided by local aquifers. The dark and red tones in the scene correspond to wetland vegetation which provides vital grazing during the dry season.
Division 4 Surficial Deposits Group B · Marine Littoral Systems
Sub-group Br Bedrock Littorals Sub-group Bb Residual Shorelines Sub-group Bw Wave and Current formed Littoral Sediments Sub-group Bl Sea Ice and Sea Ice Related Forms Sub-group Bt Tidal Regime Deposits and Forms Sub-group Bc Coastal Plains Sub-group Bp Low Latitude Offshore Carbonate Platforms
The coast is a zone of interaction between processes of erosion and deposition in the sea and on the land. The changes which various coasts are undergoing, long term retreat and short term cliff erosion, are dependent on the character of the coasts. A classification of coastal geounits involves the disciplines of oceanography and climatology in addition to geology. The classification of geohazard-related Geounits comprises seven Sub-groups, the first of which is automorphic and the others allomorphic:
Br Bb Bw Bl Bt Bc Bp
– – – – – – –
Bedrock littorals Residual shorelines Wave and current formed littoral sediments Sea ice forms and sea ice related deposits Tidal regime deposits and forms Coastal plains Low latitude offshore carbonate platforms
General Note of Geohazard Relations All units of the littoral system Sub-groups other than bedrock, but including bedrock plains, are susceptible to flooding, storm surges and tsunamis. Residual shorelines in unconsolidated sediments are additionally susceptible to slumping. Barrier beaches and shore beaches are also susceptible to erosion. Coastal plains are additionally susceptible to subsidence, slumping and flowing. Sea ice deposits are agents of beach encroachment.
Note on Airphoto Interpretation “Because the shore zone is usually quite narrow, details of its appearance in small- and medium-scale airphotos are not always obvious. In addition, vertical exaggeration distorts the perception of the profile across the shore zone, making the cliffs look much higher and their slopes much steeper than they really are.” (Mollard JD, Janes JR(1983) Airphoto Interpretation and the Canadian Landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, p 102).
Select Bibliography Schwartz M (ed) (2005) Encyclopedia of coastal science. Springer-Verlag
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_10, © Springer-Verlag Berlin Heidelberg 2009
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Sub-group Br Bedrock Littorals General Description and Select Bibliography of Bedrock Littorals Origin Rock cliffs occur along approximately 80% of the marine shores of the Earth. As structural units they result from sustained regional scale tectonic uplift and transitory isostatic rebound. Lithologically they include magmatic, sedimentary and metamorphic rocks or associations of any of these.
Morphology Steep cliffs occur in homogeneous rocks that have either horizontal, steeply-dipping or vertical bedding planes; they are typical of wave-dominated environments. Steep cliffs do not form in parts of the humid tropics where deep weathering has decreased the resistance to erosion.
Processes Locally cliffs are products of the combination of marine and subaerial processes. Mechanical wave action at cliff foot during storms is the primary marine erosion agent. This is accomplished by quarrying, abrasion and corrasion. Quarrying requires the presence of air and water. Shock pressure from breaking waves is followed by compression of pockets of air within rock crevices. Abrasion and corrasion are accomplished by wave energy armed with the tools provided by coarse granular material lying on cliff foot shore platforms Br6. Salt crystal growth, freeze-thaw, hydration, oxidation and solution are the principal sub-aerial weathering processes. They exploit the internal structural weaknesses of cliffs, (i.e. , fault line traces 12 and 13, lineaments 18 and 19) and ultimately result in the high intensity and low frequency mass movement failures.
Geohazards Rockfalls Mv1, rock slides Ms1 and rock slumps Ms3 are the mass movements to which rock cliffs are susceptible, as a function of the lithology, structure, and environmental conditions in which a particular cliff occurs. Some low rock cliffs Br4.1 low rock hills, Br6 marine terraces and Br7 bedrock plains are susceptible to storm surge as well as tsunami runup damages. Falls occur in well-fractured rocks, e.g., rudites and arenite S1.2; slides occur in argillaceous S2 and other easily sheared rocks with low bearing strength, as are interbedded permeable and impermeable W1 sequences, and massive rocks overlying weak rocks.
Group B · Marine Littoral Systems
Rotational slumps are typical of thick, homogeneous beds of siltstones and lutites S2. Deep-seated mass movements generally result from undercutting at the base of the cliff. The displacing masses and deposits obviously endanger human life and property. Human activity on more accessible coastal bedrock hills Br4.1, construction on hilltops, landscaping and watering, increase pore pressures in the cliff materials, decreasing strengths and accelerating failures.
Select Bibliography Bird ECF (1976) Coasts. Australian National University Press, pp 59–95 Emery KO, Kuhn GG (1982) Sea cliffs: Processes, profiles, classification. GSA Bull 93:644–653 Fletcher CH, Grossman EE, Richmond BM, Gibbs AE (2002) Atlas of natural hazards in the Hawaiian coastal zone. University of Hawaii/NOAA, USGS I-2761 Grainger P, Kalaugher PG (1987) Intermittent surging movements of a coastal landslide. Earth Surface Processes and Landforms 12:597–603 Griggs GB, Trenhaile AS (1994) Coastal cliffs and platforms. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 425–450 Hampton MA, Griggs GB (2004) Formation, evolution, and stability of coastal cliffs: Status and trends. USGS Professional Paper 1693 Hapke CJ, Reid D (2007) National assessment of shoreline change, Part 4: Historical coastal cliff retreat along the California coast. USGS Open-File 2007-1133 Hapke CJ, Richmond BM, D’Iorio MM (2002) Map showing seacliff response to climate and seismic events, Depot Hill, Santa Cruz County, California. USGS, MF-2398 Horikawa K, Sunamura T (1967) A study on erosion of coastal cliffs, by using aerial photographs. Coastal Engineering Japan 10:67–83 Lajoie KR (1986) Coastal tectonics. Active Tectonics, Studies in Geophysics. National Academy Press, Washington, D.C., pp 95–124 Nordstrom KF, Renwick WH (1984) A coastal cliff management district for protection of eroding high relief coasts. Environmental Management, vol 8, no 3. Springer-Verlag, New York Pirazzoli PA (1994) Tectonic shorelines. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 451–476 Pitts J (1986) The form and stability of a double undercliff: An example from south-west England. Engineering Geology 22: 209–216 Reefe D, Chadwick A (2004) Coastal engineering. Taylor & Francis So CL (1987) Coastal forms in granite, Hong Kong. In: Gardiner VE (ed) International geomorphology. John Wiley & Sons, Ltd., New York, pp 1213–1229 Sunamura T (1977) A relationship between wave-induced cliff erosion and erosive force of wave. Journal of Geology 85:613–618 Sunamura T (1992) Geomorphology of Rocky coasts. John Wiley & Sons, Ltd., Chichester Terzaghi K (1962) Stability of steep slopes on hard unweathered bedrock. Geotechnique 12:251–270 Trenhaile AS (1987) The geomorphology of rock coasts. Oxford University Press, New York Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 34 Woodroffe C (2002) Coasts. Cambridge University Press
Br2.1 · High Rock Cliffs Unstable
Br2.1 High Rock Cliffs Unstable
Br2.1
Characterization
Select Bibliography
See General Description and Select Bibliography of Bedrock Littorals.
See General Description and Select Bibliography of Bedrock Littorals.
Geohazard Relations See General Description and Select Bibliography of Bedrock Littorals.
Fig. Br2.1-1. Location. Geographic. 13°34' E, 43°35' N, eastern Italy Source. Touring Club Italiano (undated) Comments. A view of 100 m high cliffs in plateaus of poorly-cemented Plio-Pleistocene sands and clays at the Numana Beach of Ancona on the Marche Coast. The sediments are Apennine foreland deposits in the Adriatic Trough. A large Ms3 rock slump is delineated, probably caused by wave erosion at a higher sea level. See also Fig. Br2.1-3.
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Group B · Marine Littoral Systems ▼
Fig. Br2.1-2.
Location. Geographic. 0°02' E, 49°20' N, northern France Geologic. Mesozoic carbonates of the western Paris Basin Source. Deffontaines P, Delamarre MJ-B (1962) In Atlas Aérian, France, Tome IV. Gallimard, p 128, photo 190 Comments. The photo of a 100 m high cliff on the Baie de la Seine 10 km west of Deauville illustrates the geohazard situation described in the geounit description. Kc2 chalk strata (Upper Cretaceous) are underlain by 25–30 m of impervious rock (Mid Jurassic) along 8 km of shoreline. The dark S2.1 marls show strong erosion. A line of springs occur at the contact of the two sets of beds. High tide waves erode the marls here at the rate of 50 cm yr–1 cliff recession. Mv1 talus at the foot of cliff is a mix of failed chalk and Mf3 debris-mud flow of the eroded marl. The latter is quickly removed by waves.
Fig. Br2.1-3. Source. Putnam WC, et al. (1960) Natural coastal environments of the world. University of California, Los Angeles, p 108, fig 37 Comments. An air perspective view at 12°53' E, 43°55' N of high cliffs near Pesaro on the Italian Adriatic Coast in the same geologic formation as that of the Ms3 rock slump of Fig. Br2.1-1 at Ancona, 60 km to the south. The toe of the large Ms1.1 old rock slide covers the narrow Bw4 fringing beach.
Fig. Br2.1-4.
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684
Location. Geographic. 61°46' W 47°24' N, Magdalen Islands, Québec Geologic. Volcanism accompanying development of Carboniferous basins resting uncomformably on deformed rocks of Acadian orogeny Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 12 000 Acquisition date. 1970 Source. Courtesy of Natural Resources Canada, NAPL A 21672-158, 159, 160 Comments. A stereomodel shows marine action and resulting Ms1 slides on shore cliffs on the south coast of Ile du Havre aux Maisons on the east central side of the island group. They are composed of pyroclastics interbedded with lavas.
Br2.1 · High Rock Cliffs Unstable
685
Br3.1
Division 4 · Surficial Deposits
Br3.1 Low Rock Cliffs Weak Characterization See General Description and Select Bibliography of Bedrock Littorals.
Group B · Marine Littoral Systems
Geohazard Relations See General Description and Select Bibliography of Bedrock Littorals.
Select Bibliography See General Description and Select Bibliography of Bedrock Littorals.
Fig. Br3.1-2.
Fig. Br3.1-1. Source. Steers JA (1960) The coast of England and Wales in pictures. Cambridge University Press, pl 33, by permission of Oxford University Press Comments. An air perspective view of Ms3 rotational rock slumps in weak low rock cliffs approximately 150 m high, at 02°50' W, 50°43' N. Location is Black Ven, Dorset, between Lyme Regis and Bridport in the middle part of the southern English Coast. Failure-prone bedding at the site consists of horizontal Lower Cretaceous marly clay, sandstone and clay sliding over lower Jurassic overconsolidated argillaceous limestone and shale. In the upper half of the photo the accumulation zone at the toe overrode the beach.
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686
Location. Geographic. 59°08' W, 48°36' N, southwestern Newfoundland Geologic. Foreland basin of the Appalachian Orogen Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 14 000 Acquisition date. Unspecified Source. Courtesy of Natural Resources Canada, NAPL A 20830, 24, 25, 26 Comments. The stereomodel at the Port au Port Peninsula shows with white arrows weak low rock cliffs, evidenced by the Ms3 rock slumps at the west shoreline of a plateau dissected in K Mid-Ordovician limestones and S1 sandstones. The cliffs are 25 m high at protruding Crow Head. The weakness is attributed to wave attack at the foot of rocks (marked by a Bw2 offshore bar which may be a bedrock or sand shoal) that have been folded and faulted parallel to the shore and normal to wave approach. Code Gf4.2/W4 indicates a veneer of raised beach gravel over glacial till (Gf4) and bedrock. Code Y4/W4 indicates a deposit of bog peat over bedrock. Gt2.3/W4 are glacial till (Gf4) deposits over the bedrock. (The offshore zone from the cliffs is a fishery area for groundfish and a spawning ground for herring).
Br3.1 · Low Rock Cliffs Weak
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Division 4 · Surficial Deposits
Fig. Br3.1-3. Location. Geographic. Southern Aquitaine Basin Geologic. Western Pyrenees Foothills Vertical Airphoto/Image. Type. b/w pan, single photo Scale. 1: 25 000 Acquisition date. 17 March 1961
Group B · Marine Littoral Systems
Source. Journal Photo Interprétation, Editions ESKA, Paris, 62-1, 9 Comments. This photo near Bidart 4 km south of the center of Biarritz shows a 3 km length of shoreline on low rock cliffs of weak Kc4 Oligocene limestone and marl. The material eroded from the foot of the cliffs by breaking waves is seen in suspension as a strong turbid zone offshore.
Br4.1 · Bedrock Hills Weak
Br4.1 Bedrock Hills Weak
ably an important erosive mechanism in shales and other argillaceous rocks subjected to tidally induced cycles of wetting and drying.” (Griggs and Trenhaile 1994).
Characterization
See General Description of Br Geounits.
These bedrock hills are mainly composed of friable rocks such as poorly lithified rudites and arenites S1.2, and lutites and siltstones S2. See General Description of Bedrock Littorals.
Reference
Geohazard Relations
Select Bibliography See General Description and Select Bibliography of Bedrock Littorals. ▼
Fig. Br4.1-1.
Location. Geographic. 121° W, 35°29' N, central California, USA Source. Personal archive Comments. This colour vertical airphoto shows turbidity in the offshore waters at Point Estero of the Santa Lucia Range of the continental borderland. The turbidity is evidence of erosion of the Late Jurassic and Cretaceous rocks of the Franciscan Melange suite (fault-zone related chaotic rock bodies – blocks of all sizes with little or no stratigraphic continuity embedded in a matrix of finer-grained material) by marine processes and by local streams emptying into the sea. The 19.1 geolineaments of the coastline and the parallel adjacent lineament inland are suggestive of local faulting. See also Figs. Bc1-3 and Br6-2.
Fig. Br4.1-2.
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“The expansion and contraction of certain clay minerals such as the montmorillonite/smectite group is prob-
Griggs GB, Trenhaile AS (1994) Coastal cliffs and platforms. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, p 430
Location. Geographic. 09°12' E, 44°19' N, Liguria, northern Italy Geologic. Paleogene Apennine fold-and-thrust chain within Apulia continental terrane of African Basement Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 35 000 Acquisition date. Not given Source. Personal archive Comments. The photo covers 5.5 km of the north-south coastline of the Gulf of Tigullio on the Ligurian Coast, from Portofino Peninsula in the south to Rapallo in the north. The annotations delimit two lithologies of Upper Cretaceous bedrock hills. The southern unit, with northwest-trending lineaments, consists of relatively resistant limestone with ridges that rise inland to 600 m. The rest of the area, with a distinctive pattern of dissection, and the town of Santa Margherita in its center, is composed of weaker marls that rise to 300 m inland. Two zones of limestone between fractures appear relatively undissected.
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Br4.1
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Division 4 · Surficial Deposits
Fig. Br4.1-2. (Caption on p. 689)
Group B · Marine Littoral Systems
Br6 · Tectonic Eustatic Marine Terraces
Br6 Tectonic Eustatic Marine Terraces
Where uplift has been episodic rather than continuous, multiple terraces develop, as in the case of the Huon Terraces.
Characterization Geohazard Relations Occurrences of this geounit are uplifted Pleistocene marine terraces. They are shorelines elevated by “glacioeustatic sea-level highstands superimposed on a rising coastline” (Griggs and Trenhaile 1994) and are common along subducting plate coasts where uplift is taking place. Their surfaces are wave-cut, generally truncating the bedrock, and can rise several hundred meters above sea level. The extreme occurrence is the coral reef terraces on the Huon Peninsula of eastern New Guinea which are uplifted to 750 m above sea level.
Terraces below 30 m elevation are susceptible to the principal related geohazard, tsunami runups. See Note concerning tsunami runups following Geounit Bp1, carbonate platforms.
Reference Griggs GB, Trenhaile AS (1994) Coastal cliffs and platforms. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 425–449
Fig. Br6-1. Location. Geographic. 06°11' W, 55°55' N, west central Scotland Source. Dudley Stamp L (1946) Britain’s structure and scenery, 2nd edn. Collins London, pl XI
Comments. A photo taken on a 25–30 m marine terrace with a small offshore stack cut in Precambrian quartzites on the north shore of Islay of the Inner Hebrides.
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Br6
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Br6-2. Source. Putnam WC et al. (1960) Natural coastal environments of the world. University of California, Los Angeles, p 86, fig 15 Comments. This air perspective view shows a 30 m high marine terrace just north of Point San Luis at Latitude 35°10' N on the California Coast.
The terrace is cut into disturbed Miocene marine shales and sandstones which rise 500 m on the right. It is mantled with a layer of marine and terrestrial poorly sorted sediments. The terrace, with some rock stacks, is being undercut by wave abrasion and erosion.
Fig. Br6-3. Location. Geographic. 131°23' E, 31°29' N, southern Japan Source. Putnam WC et al. (1960) Natural coastal environments of the world. University of California, L.A., p 126, fig 55 Comments. An air perspective view shows a wave-cut terrace truncating dipping strata on the southeast coast of Kyushu. The elevation of the terrace is difficult to estimate in the absence of a hydro chart or topo map. The 2 to 4 m high tide of the local meso tidal regime probably covers the terrace which could have been uplifted by a series of earthquakes.
Br6 · Tectonic Eustatic Marine Terraces
Fig. Br6-4. Vertical Airphoto/Image. Type. Natural colour stereogram Scale. 1: 20 000 Acquisition date. 25 May 1967 Source. Cravat HR, Glaser R (1971) Color aerial stereograms of selected coastal areas of the United States. NOAA/DOC, p 59 Comments. Stereomodel shows a coast of wave erosion at Fort Bragg at 39°35' N latitude on the coast of northern
California. The site is a 30 m high tectonic marine terrace cut into steeply-tilted Late Jurassic and Cretaceous rocks (Franciscan Mélange, see Fig. Br4.1-1). The terrace is overlain inland by Pleistocene marine sediments ranging from 1 to 40 m thick. The scarp-like indentation is characteristic of the cliffed shorelines of this region. The terrace is attributed more to a general upwarping of the coast rather than to a lowering of sea level. North is to the left.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Br6-5. Vertical Airphoto/Image. Type. b/w pan, airphoto Acquisition date. Not given Source. Personal archive
Comments. This stereo model shows a low marine terrace cut in Post-Eocene marine sediments 20 km east of Montego Bay on the north coast of Jamaica. The foreshore surf zone labelled Bl2 is on a coral reef.
Br7 · Bedrock Plains
Br7 Bedrock Plains
surfaces of Caledonian/Acadian and Hercynian orogenic complexes.
Characterization
Geohazard Relations
The Bedrock plains geounit is relatively close to sea level, with a low sloping or scarp shoreline. The local relief varies from smooth to rough in response to the near surface bedrock type. The geounit extends a variable distance inland from the limit of the marine processes. The constituent bedrock types can be of sedimentary rocks K, S or W Groups; igneous rocks; basalt flows of volcanic rock X Group; metamorphic rocks; or peneplaned
In common with other low-lying, low relief coastal geounits, bedrock plains are susceptible to flooding and damages from storm surges, tsunamis, and sea-level rise.
Fig. Br7-1.
ceous (119 Ma) argillaceous limestone and marl overlying folded and thrusted Lower Cretaceous (144 Ma) sediments of the same lithology. The area in lower right is now intensely urbanized around the fishing port of Carro. It is under the influence of pollutants from one of the most important petrochemical industries in France 15 km to the north in the Gulf of Fos, with its intense maritime traffic. The regional context of this plain is shown in the satellite images of Figs. Fw4-3 and Fu1-13.
Location. Geographic. 05°03' E, 43°20' N, southeast France Geologic. Pyrenean structures Source. Deffontaines P, Delamarre MJ-B (1955) Atlas Aérian, France, Tome I. Gallimard, p 139, photo 141 Comments. This air perspective view to north shows the rock plain of Cap Couronne at the western extremity of the Estaque Peninsula 25 km west of Marseille. The plain, of limited extent (8 km2) consists of 85 m of Mid-Creta-
Select Bibliography See notes concerning long term sea-level rise and tsunami runups following Geounit Bp1, carbonate platforms.
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Br7
Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Br7-2. Source. leBerre J, Guillemot E (1978) Guide de Croisière Bretagne. Editions J.-L. Roth SA, p 153 Comments. An air perspective view of the rock plain on Paleozoic granites of Pointe Courégan at 03°28' W, 47°42' N, 10 km southwest of Lorient, on the south coast of Brittany. The high macro tide line (>6 m) is clear at the upper limit of wavewashed bare bedrock.
Fig. Br7-4.
Fig. Br7-3. Source. Bardintzeff J-M (1997) Les Volcans. Liber, Suisse, p 122 Comments. A common warning panel on Pacific Ocean coasts of bedrock plains and other Littoral System SubGroups of low-lying geounits.
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696
Location. Geographic. 02°00' W, 48°33' N, northeast Brittany Geologic. Peneplaned Hercynian Massif Source. Personal archive Comments. Air perspective photo is over the low rock coast of northern Brittany at the Port of St Malo and the Rance ria type estuary. The area has a general elevation of 50 m with shorelines of low scarps and beaches. The scarps mark a slight late Tertiary uplift of this part of the peneplaned Hercynian Massif of Precambrian gneisses and granites. The Gulf of St. Malo is macrotidal (to 13 m). The Port of St. Malo is prominently characterized by its four locked tidal basins, and a tidal power station located in the Rance Estuary just off the bottom edge of the photo. The 3 km long Bw4 Rochebonne Beach is on the other side of the port.
Br7 · Bedrock Plains
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Division 4 · Surficial Deposits
Sub-group Bb Residual Shorelines Bb1
Group B · Marine Littoral Systems
Geohazard Relations
Bb1 Bluffs in Unconsolidated Sediments
Bluffs are susceptible to debris mud-flows and slumps Mf3; to coastal erosion processes; to storm surge floods; to tsunami runups and to eventual sea-level rise.
Characterization
Select Bibliography
Bluffs are relatively steep, unvegetated banks up to 100 m high, generally in glacial or marine sediments. They resulted from active erosion at the base. Debris blocks are frequently at the base of the bluff. Gullies and narrow beaches Bw4 at low tide are common.
Morton RA (2003) An overview of coastal land loss: with emphasis on the Southeastern United States. USGS Open File 03-337
See note and Select bibliography concerning long term sea-level rise.
Fig. Bb1-1. Location. Geographic. Central California, USA Source. Robinson GC, Spieker AM (eds) (1978) Nature to be commanded. USGS, p 12 Comments. A photo 25 km south of San Francisco shows bluffs in alluvial and beach sediments at El Granada on Half Moon Bay. Boulders are temporarily protecting the foundation of a structure in 1973. Local bluff retreat at historic rates has probably required additional protective measures or led to the demolition of this building.
Fig. Bb1-2. Location. Geographic. 58°40' W, 48°33' N, southwest Newfoundland Source. Courtesy of Natural Resources Canada, GSC. Photo by J. Shaw Comments. The photo shows 20 m high bluffs of ice-contact glaciofluvial deposits (Paraglacial Geosystem) being eroded by wave action west of Stephenville on St. George’s Bay. A Bw4 gravel beach is in the foreground. A bright recent slump is on the left. This bayhead site is 5 km east of the low rock cliffs of the tombolos of Fig. Bw6-3.
Bb1 · Bluffs in Unconsolidated Sediments
Fig. Bb1-3. Location. Geographic. Ashkelon, Israel Source. Unattributed Comments. A photo of bluffs at the north end of the Gaza Strip in the Sharon Coastal Plain. The plain is formed by extended Fu1 alluvial fans from the hills of Samaria and Judea. The fan deposits probably overlie eustatic marine sediments. A Bw4 beach is at the foot of the bluffs. The stereo model of Fig. Ec3-7 and the satellite image of Fig. Ec2/Ec3-8 show coastal dunes which commonly occur on these bluffs along this coast.
Fig. Bb1-4. Location. Geographic. 70°45' W, 41°20' N, southern Massachusetts, USA Source. LAR, October 1980 Comments. The view shows a 5 m high bluff in the Gf4 glacial till of a lobe of continental glacial terminal moraine (Gl5) of the Illinoian (Riss) Glacial Stage, 200 000 BP, on the western shore of Martha’s Vineyard Island (see Geounit Gl5 for description of glacial moraines). Wave and tide erosion of the till remove the fine matrix fractions and leave a mass of residual boulders on the inner edge of the beach. Nearby shore dunes appear in Fig. Ec1-1.
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Division 4 · Surficial Deposits
Fig. Bb1-5. Location. Geographic. 133°02' W, 69°27' N, Northwest Territories Source. Courtesy Natural Resources Canada, GSC 1995288A Comments. An air perspective view southward in 1995 shows protection works temporarily halting coastal erosion at Tuktoyaktuk, the major port of the western Canadian Arctic, at the mouth of a drowned valley on Kugmallit Bay of the Beaufort Sea Coast, current population 900. The port has a potential enhanced utility in the event of the developmement of offshore Arctic hydrocarbon resources. Coastal recession here has already caused significant property losses.
Group B · Marine Littoral Systems
Arrows point to plastic bags containing gravel dumped on the beach in attempts to arrest shoreline retreat, 75 m in a 20 year period. Additionally, Shaw et al. (1998) p 71 state “The most exposed part of the community will eventually have to be abandoned if sea level rise continues.” The unconsolidated materials here consist of 0.6 to 2.4 m of glaciofluvial outwash gravel (Paraglacial Geosystem) forming a low scarp, overlying ice-rich sands. Elevations range from 30 to 60 m, Tuktoyaktuk Airport elevation is 4.5 m. Shoreline retreat is mainly caused by intense storms with waves from the northwest that expose the ice-bonded sands at the base of the scarp. Depth to permafrost in this region is in excess of 350 m, the active layer ranges from 60 to 100 cm.
Bb1 · Bluffs in Unconsolidated Sediments
Fig. Bb1-6. Source. Wattenmeer (1976) Karl Wachholtz Verlag, Neumünster, p 94 Comments. This low air view shows unstable bluffs in postglacial outwash materials (Paraglacial Geosystem) or Pleistocene diamicton (unsorted terrigenous deposit containing a wide range of partical sizes regardless of origin), at 08°00' E, 55°33' N,southern Denmark in Ho lagoon 10 km north of Esbjerg.
Fig. Bb1-7. Source. Muus U, Petersen M (1974) Die Küsten SchleswigHolsteins. Karl Wachholtz Verlag, Neumünster, p 81, photo 49 Comments. This air perspective view east shows bluffs with local Ms3-like slumping evident in Pleistocene unconsolidated diamicton (see Bb1-6), 10°56' E, 54°23' N near Heiligenhafen at the east end of Kiel Bay, Germany.
Ms2 debris sliding here is evidently recurring, indicated by red arrows. Old, vegetated, slid material covers part of the Bw4 beach. The plantations of trees immediately behind the slideaffected bluffs appear to be attemps to stabilize the slopes. The brown turbidity offshore appears to be related to these slope movements.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bb1-8. Location. Geographic. 118°32' W, 34°02' N, southwest California, USA Source. Shepard FP (1971) Our changing coastlines. McGrawHill, p 280, fig 10.32. Reproduced with permission of The McGraw-Hill Companies Comments. A photo taken in 1932 shows 30 m bluffs at the turnoff of West Sunset Boulevard from the Pacific Coast Highway west of Santa Monica, southern California. These bluffs were last uplifted in late Miocene, they are composed of Pleistocene Fu1 fan deposits overlying Miocene shales. The fans are alluvium swept down from the south flank of the Santa Monica Mountains approximately 5 km inland. Westward toward Malibu, the shales occur as Br6 marine terraces; morphologically the bluffs and terraces are quite similar.
The surfaces of the bluffs are now completely developed residential areas. The bluffs are fronted by Bw4 beaches from which old groins have been removed. This site is 3 km west of the earth flow of Fig. Bb1-9.
Fig. Bb1-9. Source. Shepard FP,Wanless HR (1971) Our changing coastlines. McGraw-Hill Book Co., p 281, photo 10.33. Reproduced with permission of The McGraw-Hill Companies Comments. A photo at the west end of Santa Monica just east of Temescal Canyon in southern California shows a large Mf2 earth flow that occurred in April 1958 in 30 m high bluffs of Fu1 fan deposits from the Santa Monica Mountains following a period of heavy rains. The flow, with 600 000 cubic yards of debris, buried the coastal highway and extended slightly out into the sea. In recent EO satellite imagery, the displaced mass has been removed and the beach and the highway have been restored. The only trace of this slope failure is the vegetated material in the bowl of the rupture. Extensive measures have been taken to prevent sliding in these bluffs.
“Near-horizontal drainage tunnels were driven 100 to 200 feet (30 to 60 m) into the base of the cliff and outfitted with furnaces to dry the ground, where conditions were particularly hazardous and property values high.” Sharp RP (1978) Field guide coastal Southern California, p 37, Kendall/Hunt Publishing Company. This site is 3 km east of Fig. Bb1-8 in the same materials.
Bb1 · Bluffs in Unconsolidated Sediments
Fig. Bb1-10. Location. Geographic. 01°13' W, 45°44' N, Atlantic Coast Geologic. Saintonge Arch of Charente Cretaceous carbonate plateau Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 33 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. Shoreline bluffs in this stereomodel at La Coubre Point are the margin of a 20 km long by 5 km
broad belt of coastal dunes into which local tide and longshore drift are presently eroding as a result of sea level change. Longshore drift in this area is transporting sand southward and has resulted in a recession of 1 km of the coast in one century. The bluffs rise locally to 20 m; inland dunes are as high as 60 m. The latter date from the Flandrian Stage and rest on marine sediments of that transgression. The entire area covered by the photos, with the rectangular grid of access (and fire control) paths is part of the coniferous Foret domaniale de la Coubre.
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Bb1.1
Division 4 · Surficial Deposits
Bb1.1 Bluffs in Frozen Sediments Characterization This Variant of bluffs in unconsolidated materials is limited in occurrence to the circum-Arctic coastal margin dominated by cryological processes. It consists of finegrained ice-rich deposits of glacial, marine and lacustrine origin. The intersticial and massive ice in the bluffs provides transient strength to otherwise unlithified sediments allowing the development of over-steepened bluffs.
Geohazard Relations Arctic coastlines are the site of most of the human activity that occurs at high latitudes. Many settlements, airstrips, port and defence facilities are located on ice-rich terrain near sea level. Ice-rich coastal bluffs are undergoing rapid retreat by hydromechanical and thermodenudational erosional processes. Hydromechanical erosion is accomplished by waves that can attack shorelines only after they have been cleared of fast ice in the spring. Retreat of 2 to 18 m per year is accomplished entirely within an average three month openwater period. Such erosion rates are attributed primarily to the presence of ground ice in the coastal materials. The thermodenudational erosion processes acting on the ice-rich bluffs include debris slides, ground-ice slumps and thermoerosional falls:
Group B · Marine Littoral Systems
Debris sliding Ms2 occurs when the thawed surface layer fails as a result of oversteepening at the bluff base. Ground ice thaw-flow slides Zk2 result from exposure of the ice-rich soil during coastal retreat. A steep headwall retreats due to melting of the ice, and a mix of thawed sediment and water slides down the face of the headwall and flows seaward. Thermoerosional falls are block slumping mass movements Ms3. The slumped material, often bounded by ice-wedge Zi4, is removed mechanically by waves and long shore currents. Note: the thaw of frozen sediment may result in delayed but predictable subsidence, the thaw of massive ground ice in sediments may cause rapid subsidence.
Select Bibliography Algus M (1986) The development of coastal bluffs in a permafrost environment: Kivitoo Peninsula, Baffin Island. PhD thesis (unpublished), McGill University Carter LD, Heginbottom JA, Ming-ko Woo (1987) Arctic lowlands. In: Graf WL (ed) Geomorphic systems of North America. GSA, Cennial Special vol 2, pp 612–615 Dallimore SR, Wolfe S, Solomon SM (1996) Influence of ground ice and permafrost on coastal evolution, Richards Island, Beaufort Sea Coast, NWT. Canadian Journal of Earth Sciences 33:664–675 Harper JR (1978) The physical processes affecting the stability of tundra cliff coasts. PhD thesis. Louisiana State University Mackay JR (1986) Fifty years (1935 to 1985) of coastal retreat west of Tuktoyaktuk, District of Mackenzie. Current research Part A: GSC Paper 86–1A, pp 727–735
Fig. Bb1.1-1. Source. Taylor RB (1990) Geology of the continental margin of eastern Canada. In: Kean MJ, Williams GL (eds) GSC Geology of Canada, no 2, p 756, fig 14.11 Comments. These block diagrams show the various types of thermodenudational (thaw mass wasting) processes that affect bluffs in icebonded sediments.
Bb1.1 · Bluffs in Frozen Sediments Pollard W, Couture N, Strommer M, Solomon S (1999) Ground ice conditions along the Beaufort Sea coast. An International Workshop on Arctic Coastal Dynamics. GSC Open File 3929, p 21 Reimnitz E, Graves SM, Barnes PW (1985) Beaufort Sea coastal erosion, shoreline evolution, and sediment flux. USGS Open-File Rep. 85–380 Taylor RB, Mc Cann SB (1983) Coastal depositional landforms in northern Canada. In: Smith DE, Dawson AG (eds) Shorelines and isostasy. Academic Press, pp 53–75 Vasilief AA, Leibman MO (1999) Ground ice of the Baydarata Bay coast (Kara Sea) and its influence on the mechanisms of coastal destruction. An International Workshop on Arctic Coastal Dynamics, GSC Open File 3929, p 30 Wolfe S, Dallimore SR, Solomon SM (1998) Coastal permafrost investigations along a rapidly eroding shoreline, Tuktoyaktuk, NWT. Proc. 7th International Permafrost Conference, Presses de l’Université Laval, Québec, pp 1125–1131
Fig. Bb1.1-2. Location. Geographic. 137°57' W, 69°05' N, northern Yukon Territory, Canada Source. Courtesy of S. Dallimore, G.S.C Comments. A photo, taken in July 1987, shows thermoerosional block falls in bluffs of ice-bonded L1 glaciolacustrine and glacial till (Gf4) sediments. The location is on the Arctic Coastal Plain at King Point of Mackenzie Bay, 8 km west of the bluffs of Fig. Bb1.1-4.
Fig. Bb1.1-3. Source. Courtesy of Natural Resources Canada, GSC 202262E Comments. A ground level view of the Zk2 flow slide on the Yukon Coastal Plain shown in the airphotos of Fig. Bb1.1-4.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Bb1.1 · Bluffs in Frozen Sediments ▼
Fig. Bb1.1-4.
Location. Geographic. 137°54' W, 69°05' N, Yukon Territory Geologic. Paraglacial Geosystem coastal plain Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 26779-10, 11 Comments. A stereomodel shows a 7 km segment of the bluff shoreline of the King Plains on Mackenzie Bay. The bluffs are 60 m high and are composed of massive ground ice and ice-bonded Mid Pleistocene lacustrine and glacial sediments. The Zk 2 300 m × 200 m retrogressive thaw flow slide of Fig. Bb1.1-3 in the center is typical of active thermokarst in these arctic coastal sediments. This particular slide is reported to be stabilized: “Icy sediments and massive ice are exposed on a steep slope in the headwall… As they melt, the sediment and meltwater flow or slide down the headwall to its base where they form a soupy mixture and flow farther downslope on gentle slopes in the form of a mudflow. Where sediment is not removed from the base of the (slide), it will stabilize at a slope between 2° and 10°.” Rampton VN (1982) Quaternary geology of the Yukon Coastal Plain. GSC Bulletin 317, pp 29–30. ▼
Fig. Bb1.1-5. This location is the same as Fig. Zk1-9 and is 8 km east of the bluffs of Fig. Bb1.1-2.
Location. Geographic. 135°26' W, 69°37' N, North West Territories Geologic. Stony clayey Early Wisconsinan (Würm) (70 ka) glacial till Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 12857-408, 409 Comments. The stereomodel shows the northern end of 10 × 5 km Pelly Island off the north end of the Mackenzie Delta. The island’s shoreline is composed of ice-rich finegrained matrix of glacial till(Gf4). The indicated Bb1.1 location is a 200 m wide Mf1.2 retrogressive thaw flowslide affecting 1 900 m of shoreline in a 40 m bluff, the highest part of the island. The slide is one of 10 similar movements that occur around the shores of the island. A detached Bw5 spit beach extends 5 km eastward from the island’s north tip. Large Zk1 thermokarst lakes occupy the greater part of this island. Pelly Island is 125 km northeast of the bluffs of the Yukon Plain in Fig. Bb1.1-4. Dark patches in the sea are cloud shadows.
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Division 4 · Surficial Deposits
Fig. Bb1.1-5. (Caption on p. 707)
Group B · Marine Littoral Systems
Bw2 · Offshore Bars
Sub-group Bw Wave and Current-formed Littoral Sediments
are potentially hazardous to surface navigation and marine engineering activities if uncharted or mispositioned.
Bw2 Offshore Bars
Select Bibliography
Characterization Offshore bars are subtidal ridges of sand that parallel the shoreline and are continuously submerged even at low tide. They can occur singly or as multiple ridges. In eastern Canada the bars are typically located from 150 to 300 m offshore as a function of the bottom gradients, and their crests are from 1 to 4 m below mean water level. They can be continuous for distances of several kilometers, or be discontinuous and irregular in shape. The bars are produced by strong storm waves that rework the seabed sands. The location of the ridges can be detected directly on airphotos and some satellite images or by breaking wave patterns parallel to the shore. Such patterns are more prominent if the photos or images were acquired under relatively high energy conditions.
Alexander PS, Holman RA (2004) Quantification of nearshore morphology based on video imaging. Marine Geology 208(1):101–111 Bascom W (1980) Waves and beaches. Anchor Press/Doubleday, Garden City, New York, pp 262–265 Davidson-Arnott R (1990) Sandy beaches and nearshore bars. In: Keen MJ, Williams GL (eds) Geology of the continental margin of eastern Canada. GSC, Geology of Canada 2:642–645 Davis RA, Fox WT (1972) Coastal processes and nearshore sand bars. Journal of Sedimentary Petrology 42:401–412 Greenwood B, Davidson-Arnott RGD (1979) A tentative classification of bars. Canadian Journal of Earth Science, pp 312–332
Geohazard Relations Fig. Bw2-1. Offshore bars are subject to erosion by storm wave activity and storm surges which remobilize and redistribute the bar sediment. As submerged bottom features in areas normally dominated by dynamic marine conditions, they
Source. Bird ECF (1976) Coasts. Australian National University Press, p 1, fig 2 Comments. A schematic section shows the location of an offshore bar in relation to other units of a depositional coast.
Fig. Bw2-2. Source. Wattenmeer (1976) Karl Wachholtz Verlag, Neumünster, p 76, ill 95 Comments. This is a view northeastward at Trischen Island in Wadden See National Park, 20 km north of Cuxhaven, Schleswig Holstein, Germany, 08°41' E, 54°03' N. A sequence of four marine littoral geounits is displayed from west to east in this air perspective view: the Bw2 offshore bar, located by the breaking line of surf the smooth Bw4 beach the bright Ec2 transgressive dunes, 3 m in height the drained and undrained protected Bt1 lagoon deposits The island has migrated significantly. It is now 10 km east of its position 400 yr ago. It has also lost a quarter of its former size in 80 yr, its current area is 180 ha. See also Fig. Ec3-5.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bw2-3. Location. Geographic. Unspecified Geologic. Marine littoral systems Source. Davis RA (1985) In: Davis RA (ed) Coastal Sedimentary Environments, 2nd edn. Springer Verlag, p 390, fig 6-9 B
Comments. The air perspective view shows two offshore bars of a probable Bw3 barrier island located by the associated breaking wave patterns parallel to the shore on the USA southeast coast.
Fig. Bw2-4. Location. Geographic. 61°35' W, 47°36' N, Magdalen Islands, Québec Source. Owens EH, McCann SB (1980) The coastal geomorphology of the Magdalen Islands, Quebec. In: McCann SB (ed) The coastline of Canada. GSC Paper 80-10, p 63, fig 5.17
Comments. The air perspective photo shows the breaking wave pattern marking the position of offshore bars as in Fig. Bw2-3 parallel to the spilling breakers (see Bw4) of the Bw6 Dune du Nord Tombolo Beach.
Bw2 · Offshore Bars
Fig. Bw2-5. Location. Geographic. 75°31' W, 35°14' N, North Carolina Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 25 000 Acquisition date. 1958 Source. Shepard FP, Wanless HR (1971) Our changing Coastlines. McGraw-Hill, p 24, fig 2.23a. Reproduced with permission of The McGraw-Hill Companies Comments. Photo shows the linear pattern of breaking waves that locate the position of a submerged offshore bar paralleling the Cape Hatteras National Seashore of the Atlantic Coastal Plain.
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Bw3
Division 4 · Surficial Deposits
Bw3 Near-Shore Barrier Beaches Characterization A barrier beach is a sand bar parallel to the shore, not attached at either end, which has been built by upward shoaling wave action so that its crest rises above the normal highwater level. The barrier’s depositional environment includes the lagoon Bt1 which it encloses and protects. Another depositional environment of barrier beaches are the tidal delta channels which cut through the barrier and connect the lagoon to the open seas, see the block diagram of Fig. Bt1-1. Barrier beaches are ubiquitous along the gently sloping coastal plains Bc1 around the world. Carter et al. (1987) state that such barriers be divided into sand and gravel barriers. Sand barriers are widespread around the world’s coastlines; gravel barriers are restricted to high latitudes on glacial and paraglacial coasts (see Paraglacial Geosystems).
Geohazard Relations Barrier beaches can be mapped “in terms of risk zones defined on the basis of property damage vulnerability as derived from the known impact of coastal processes, protective vegetative cover, and the role of protective landforms.” (Bush et al. 1996). An example of this are coastal dunes Ec. The low height and narrow width of barrier beaches makes them particularly susceptible to sea-level rise. They would be subject to overwashing and the formation of new inlets during storms. Human impacts are also geohazard agents of coastal barrier beaches. There is no greater threat to them than extensive urbanization. As people develop the shore, the normal processes of island migration become problems of erosion. Many engineering solutions have been sought, seawalls, groins, jetties; but in the long run, coastal barriers respond only to the passage of time. They are dynamic features, always moving (Wells and Peterson 1986). Longshore currents play an important part in the dispersal of sewage effluent discharge into the sea. Beaches down-drift of the sewage discharge points may suffer pollution for this reason (King 1974). See notes concerning coastal erosion, tsunami runups, and long-term sea-level rise following Geounit Bp1, Carbonate platforms.
Group B · Marine Littoral Systems
Reference Bush DM, Neal WJ, Pilkey OH (1996) A rapid barrier island hazard mapping technique as a basis for property damage risk assessment and mitigation. Proceedings of Conference on Natural Disaster Reduction, ASCE, pp 185–186 Carter RWG, Forbes JD, Taylor RB (1987) Gravel barriers, headlands and lagoons: An evolutionary model. ASCE, Coastal Sediments ’87, vol 2 King CAM (1974) Geomorphology in environmental management. Oxford Press, London, p 197 Wells JT, Peterson CH (1986) Restless ribbons of sand, Atlantic & Gulf Coastal Barriers. Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC
Select Bibliography Andrew J, Cooper G, Pilkey OH (2002) The Barrier Islands of Southern Mozambique. Journal of Coastal Research, Spec. Iss. 36:164–172 Glaeser JD (1978) Global distribution of barrier islands in terms of tectonic setting. Journal of Geology 86:283–297 Hayes MO (1979) Barrier island morphology as a function of tidal and wave regime. In: Leatherman SP (ed) Barrier islands. Academic Press, pp 1–29 Hoyt JH (1967) Barrier island formation. GSA Bull 78:1123–1136 McBride RA, Byrnes MR (1993) Geomorphic response types along barrier coastlines: A regional perspective. Large Scale Coastal Behaviour ’93. USGS Open File Report 93–381, pp 119–122 Reinson GE (1980) Variations in tidal-inlet morphology and stability, northeast New Brunswick. The Coastline of Canada. GSC Paper 80–10, pp 23–39 Riggs SR, Cleary WJ (1993) Influence of inherited geologic framework upon barrier island morphology and shoreface dynamics. Large Scale Coastal Behaviour ’93. USGS Open File Report 93–381, pp 173–176 Schwartz ML (ed) (1973) Barrier islands. Dowden, Hutchinson and Ross, Stroudsburg Shepard FP, Wanless HR (1971) Our changing coastlines. McGrawHill, New York, pp 71–161
See also Select Bibliography for Marine Littoral Geounit Sub-groups following Geounit Bp1, Carbonate platforms.
Fig. Bw3-1.
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Source. Reinson GE (1980) The coastline of Canada. GSC Paper 80-10, fig 3.14, p 33 Comments. This map shows the characteristic depositional environment of barrier beaches – the beach itself in 1945; the enclosed Bt1 lagoon; and the tidal inlet breach area Bt1a existing in 1977. In the example, at Tabusintac on the northeast New Brunswick Coast, the barrier is migrating southward by strong longshore drift in response to short-period windgenerated storm waves from the northeast. This site is 22 km south of Fig. Bt1-2 at Tracadie.
Bw3 · Near Shore Barrier Beaches
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Fig. Bw3-2.
Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. Not given Source. IGN – Photothéque Nationale, France Comments. The photo is at the beach town of Palavas, 03°56' E, 43°32' N, in the photo center, 10 km south of Montpellier, covers 9 km of an extensive system of barrier beaches that line the Mediterranean coast of France from the Rhone Delta to the Pyrenees. The shallow brackish lagoons in the photo, Méjean and Arnel, are near-stagnant; streams that could disharge fresh water into them are seen to be channeled through them direct to the sea. Another water system that traverses the lagoons but is isolated from them by dykes, is the channel of a barge canal that links the navigation of the lower Rhone River 60 km to the northeast with the industrial port of Sète 16 km to the southwest. ▼
Fig. Bw3-3.
Location. Geographic. 82°40' W, 27°50' N, west central Florida Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 160 000 Acquisition date. Not given Source. USGS Comments. Large scale Landsat subscene covers the low, (<9 m elevation) K3 karstic Pleistocene plain of Pinellas Peninsula and the city of St. Petersburg on the eastern coast of the Gulf of Mexico. A chain of barrier beaches extends for 70 km along the Gulf side of the peninsula. Some mangrove swamps, see Fig. Bt1c-3, grow in the enclosed lagoons, they are evidently being dwarfed by the numerous marinas which are filling the lagoons. Tampa Bay is on the right.
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Division 4 · Surficial Deposits
Fig. Bw3-2. (Caption on p. 713)
Group B · Marine Littoral Systems
Bw3 · Near Shore Barrier Beaches
Fig. Bw3-3. (Caption on p. 713)
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Division 4 · Surficial Deposits
Fig. Bw3-4. (Caption on p. 718)
Group B · Marine Littoral Systems
Bw3 · Near Shore Barrier Beaches
Fig. Bw3-5. (Caption on p. 718)
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Division 4 · Surficial Deposits ▼
Fig. Bw3-4. Vertical Airphoto/Image. Type. TM, 30 m resolution Scale. 1: 800 000 Acquisition date. Not given Source. This Landsat image is supplied by the Canada Center for Remote Sensing and is reproduced by permission of the Minister of Public Works and Government Services, Canada (2005) Comments. This Landsat scene covers two extended sections of barrier beaches with Ec1 sand dunes that enclose lagoons on the Gulf of St. Lawrence Carboniferous basin coast of Prince Edward Island. The western 40 km long section comprises Cascumpec, Conway and Malpeque Sand Hills, while the eastern section is the Prince Edward Island National Park. The island is part of the region in Canada that is most sensitive to a rise in sea level. Such rise could increase retreat of the barrier beaches through overwashing. Rates of relative sea level rise obtained from tidal records at Rustico Harbour in the center of the north coast are 32.8 cm per century. North is on the left.
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Fig. Bw3-5. Location. Geographic. 81°05' W, 28°50' N scene center, east central Florida Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 1 000 000 Acquisition date. 2 April 1986 Source. USGS Comments. Landsat subscene covers a 170 km sector of the extended barrier beaches, with southward sediment movement, that parallel the Atlantic coastline of the Florida Carbonate Platform. A complex of lagoons, Indian River, Mosquito, and Banana River, lie behind the cuspate point of Cape Kennedy at lower right. These thin barriers are of great extent. The nearest natural inlets are 80 km north and 65 km south of Cape Kennedy. The city of Orlando is on the west side of the image. Bright green areas are wetlands. See also Figs. K3-3 and K3-4.
Group B · Marine Littoral Systems
Bw3 · Near Shore Barrier Beaches
Fig. Bw3-6. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 8 May 1974 Source. USGS Comments. Landsat scene of New York Bight shows the long barrier beaches of Long Island and New Jersey
developed by sand transport of waves (white arrows) from the open sea northwesterly to the New York Harbour area. Bw5 spit beaches of Rockaway on Long Island and Sandy Hook on the New Jersey shore are visible flanking the harbour entrance. The barrier coasts south of New York are all exposed to the full force of storm surge causing hurricanes.
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Bw3.1
Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Bw3.1 Bay Barrier Beaches Characterization
Geohazard Relations
The bay barrier beach differs from the parent unit by extending between headlands, or other topographic limits of a bay, lagoon or estuary, that separates or nearly separates them from the open ocean. They may develop by longshore growth or spits or by growth of emergent beaches offshore.
See Geounit Bw3.
Select Bibliography See Geounit Bw3.
Fig. Bw3.1-1. Source. Personal Archive Comments. This Landsat TM image shows the 20 km long bay barrier beach enclosing Sabkha Bou Aregat 02°50' W, 35°09' N on the northeast coast of Morocco. The iron and steel industrial city of Nador is on the south side of the bay near the hill mass. The Spanish enclave port of Melilla is at the northwest extremity of the image.
Fig. Bw3.1-2.
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Location. Geographic. 71°06' W, 41°30' N, southern Massachusetts Vertical Airphoto/Image. Type. Natural colour airphoto Scale. 1: 5 000 Acquisition date. 12 October 1960 Source. Unspecified U.S. government agency Comments. Large scale photo shows a 70 m wide, 400 m long bay barrier beach with Ec2 transgressive dunes at Acoaxet, 20 km west of New Bedford on outer Buzzard’s Bay. The adjacent land areas are glacial (Gf4) till of the last continental glaciation (Gl5).
Bw3.1 · Bay Barrier Beaches
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Division 4 · Surficial Deposits
Fig. Bw3.1-3. (Caption on p. 724)
Group B · Marine Littoral Systems
Bw3.1 · Bay Barrier Beaches
Fig. Bw3.1-4. (Caption on p. 724)
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
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Fig. Bw3.1-3. Location. Geographic. 125°00' W, 72°46' N, Arctic Archipelago Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 103 000 Acquisition date. 29 July 1961 Source. Courtesy of Natural Resources Canada, NAPL 17053-15 Comments. Small scale photo shows a series of six bay barrier beaches along a 20 km segment of the west shore of Banks Island. This part of the island consists of unlithified alluvial gravel and sand of the coastal plain Miocene Beaufort Formation with a veneer of glacial till (Gf4). The bluff at Meek Point at the north end of the photo is 90 m high. The coastal zones behind the lagoons are covered with a veneer of marine silt. In the brief summer when the offshore is relatively free of ice in the Beaufort Sea, northwesterly winds and wave action erode the weak Beaufort sediments, and redistribute these as barrier beaches by longshore drift. Other Bw5 spits are visible along the shore east of Meek Point. Pan ice remains offshore at photo date.
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Fig. Bw3.1-4.
Location. Geographic. 09°03' W, 05°01' N, southern Liberia Geologic. Quaternary coastal plain of west African Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 1964 Source. Personal archive Comments. A stereomodel at Greenville covers 4.6 km of a partly vegetated bay barrier beach shoreline 3.5 km west of the mangrove flat of Fig. Bt1c-8. The bay is narrow and shallow, varying in width from 100 m to 300 m. Raised beach forms beyond the bay are evident inland. Part of the local airstrip is oriented normal to the beach trends.
Fig. Bw3.1-5.
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Location. Geographic. 64°39' W, 17°43' N, Virgin Islands Geologic. North Caribbean Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 24 000 Acquisition date. 1954 Source. Unspecified U.S. government agency Comments. This stereomodel covers the area of 600 m shallow Great Pond Bay near Correy Drive on the southeast coast of St. Croix Island. The enclosing barrier beach is 1 300 m long and is covered with dense scrub vegetation. A coral reef marked Bl2 1 km offshore encloses a sandy shallow back reef flat or lagoon. The delineated alluvial lowland beyond the lagoon is cultivated. The bay is now being colonized by a Bt1c mangrove community. See also Figs. Bc1-13 and W4-7.
Bw3.1 · Bay Barrier Beaches
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Division 4 · Surficial Deposits
Fig. Bw3.1-6. (Caption on p. 728)
Group B · Marine Littoral Systems
Bw3.1 · Bay Barrier Beaches
Fig. Bw3.1-7. (Caption on p. 728)
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Division 4 · Surficial Deposits ▼
Fig. Bw3.1-6. Location. Geographic. 08°43' E, 42°04' N, Corsica Geologic. Prealpine basement rocks Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1982 Source. IGN – Photothèque Nationale, France Comments. The stereomodel shows a 2 km long bay barrier beach enclosing the cultivated lower Fv2 alluvial plain of Liamone River at Sagone Gulf on the west coast of the island. The north half of the beach is 90 m wide and the south half 210 m. The inland portion of this segment is marked by some aeolian deflation.
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Fig. Bw3.1-7.
Location. Geographic. 64°24' W, 48°47' N, eastern Québec Geologic. Devonian interbedded sediments of Appalachian orogeny Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. © Gouvernement du Québec, tous droits réservés Comments. This stereomodel covers part of the south side of Baie de Gaspé at Douglastown. A 3.7 km long × 200 m wide breached bay barrier beach, formed by a south-flowing longshore current, encloses a Bt1 lagoon system which includes the Fw3 estuarial delta of the Rivière St-Jean off the photo. The St-Jean breaches the barrier and the larger of the Bt1a double tidal deltas. A regional rail line, terminating at the town of Gaspé 13 km to the north, uses the barrier to bridge the lagoon.
Group B · Marine Littoral Systems
Bw4 · Attached Beaches
Bw4 Attached Beaches
or boulder beaches, all of which are generally not very laterally continuous.” (Davis 1985, pp 397, 399).
Characterization
Geohazard Relations
An attached beach is defined as “the zone of unconsolidated sediments that extends from the uppermost limit of wave action to the low-tide mark.” (Davis 1985). They are by far the most widely distributed of any of the coastal sediment geounits. The nature of the beach sediments is related to the characteristics of the materials derived from adjacent higher ground and foreshore, or brought in from offshore by alongshore currents. The sediments range in size from medium to fine sand, in thicknesses generally less than 5 m but locally they can be much thicker. Beaches consist of two depositional zones:
Beaches are very sensitive to the forces that act upon them – waves, currents, tides, winds. They are susceptible to coastal erosion, storm surges, tsunami runups and longterm sea-level rise. See particular notes following Geounit Bp1, Carbonate platforms.
The backshore zone extends from the uppermost limit of wave action to the mean highwater line. The zone is supratidal. The foreshore zone extends from the mean highwater line to the mean low water line. The zone is intertidal.
Bascom W (1980) Waves and beaches, 2 nd edn. Anchor Press/ Doubleday, Garden City, New York, pp 247–275 Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 109–129 Horn DP (2002) Mesoscale beach processes. Progress in Physical Geography 26:271–289 King CAM (1974) Geomorphology in environmental management. Oxford Press, London, pp 198–205 Lee JH, Takewaka S, Sakai T, Takano S (2004) Use of X-band radar for wave and beach morphology analysis. ICCE (Imaging Consumables Coalition of Europe) Conf. 2004 Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, New York, pp 285–289 Roy PS, Cowell PJ, Ferland MA, Thom BG (1994) Wave-dominated coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 159–160 Swan B (1979) Areal variations in textures of shore sands, Sri Lanka. The Journal of Tropical Geography 49:72–85 Wong PP (1973) Beach formation between breakwaters, southeast coast, Singapore. Journal of Tropical Geography 37:68–73
Beach profiles at any time are determined by wave conditions during the preceding period. In calm weather, low waves form ‘spilling’ breakers that move sand on to a beach. In rough weather, higher and steeper waves form ‘plunging’ breakers which scour sediment away from the beach (i.e., summer/winter cycles) (Bird 1976). Nonsand beaches – “Mud beaches occur but are not common because the normal relatively high energy associated with beaches disperses fine sediment seaward – the most common nonsand beaches are those comprised of gravel and coarser sediments. These include gravel, shingle, cobble
Fig. Bw4-1. Location. Geographic. 121°56' W, 36°31' N, California, USA Source. LAR, 1972 Comments. A typical pocket beach is at the foot of a granite headland near the east end of Point Lobos State Reserve. Coal Chute Point is in the background, and the ridge line on the horizon is the Big Sur coastal Range.
References Bird ECF (1976) Coasts. Australian National Univ. Press, pp 96–128 Davis RA Jr (1985) Beach and nearshore zone. In: Davis RA Jr (ed) Coastal sedimentary environments. Springer-Verlag, Heidelberg, pp 379–444
Select Bibliography
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Bw4
Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bw4-3. Location. Geographic. 11°12' E, 54°24' N, northwest Germany Source. Muus W, Petersen M (1974) Die Küsten SchleswigHolsteins. Karl Wachholtz Verlag, Neumünster, p 122, ph 78 Comments. This view to northwest shows a seasonally humanized 10 m wide beach with its related pressures on the local environment. This recreational development and land use is at Burgtiefe Marina on the southeast shore of Fehmarn Island. The island consists of glacial till (Gf4). This island is also the site of the largest repowered wind turbine park in Germany with an output of 160 megawatts.
Fig. Bw4-4.
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Fig. Bw4-2. Location. Geographic. 0°12'06'' E, 49°42'30'' N, northern France Source. LAR, 1979 Comments. A view southwest from a 70 m cliff of the 800 m long beach at Étretat, 24 km north of the port of Le Havre, on the Channel Coast. The grey colour of the beach material is from deposits of rounded cobbles of nodular flint (chert, siliceous concretions). The cobbles are residual from the erosion, by marine sapping of the Upper Cretaceous chalk cliffs. The flints occur as layers along some bedding planes and as concretions in joints in the chalk.
Location. Geographic. 77°46' W, 55°17' N, northwest Québec Geologic. Bienville Sub-province of Shield Superior Province Vertical Airphoto/Image. Type. Colour infrared, stereo pair Scale. 1: 15 000 Acquisition date. 17 August 1976 Source. Courtesy of Natural Resources Canada, NAPL A 374181R-12, 13 Comments. The stereomodel at Kuujuarapik on the east coast of Hudson Bay shows an attached beach and its Variant raised beaches with airstrip. The beach is 2.8 km long and 50 m wide. The sediments include concentrations of cobbles up to 1 m diameter. The set of Bw4.1 raised beaches reach 700 m inland. Fw3 deltaic sands are occupied by the main settlement. Grey-coloured ground is bedrock outcrop. An area of Eo3 climbing dunes onto bedrock is at the north end of the beach ridge complex. Dominant wind direction here is from the south. See also Fig. Mf1-4.
Bw4 · Attached Beaches
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Bw5
Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Bw5 Spits
Geohazard Relations
Characterization
References
Spit beaches are extended alongshore depositional features built above high-tide level. They are similar in composition to the other geounits of the Sub-group Bw. Spits grow from some point of attachment across an embayment, in response to a dominant littoral drift. A longshore growth occurs episodically during storms that erode the seaward face and overwash and recurve their exposed ends (Roy et al. 1994).
Ritter ME (2006) The physical environment: an introduction to physical geography. USGS Roy PS, Cowell PJ, Ferland MA, Thom BG (1994) Wave-dominated coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 159–160
“Spits often form when wave energy decreases as a result of wave refraction in a bay. When a coastline turns abruptly, wave energy is dissipated by divergence of wave trajectories, causing sediment to accumulate as the water loses its ability to transport.” (Ritter 2006).
Fig. Bw5-1. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Indicated Acquisition date. Not given Source. Shepard FP, Wanless HR (1971) Our changing coastlines. McGraw-Hill Inc., p 41, fig 3.11b. Reproduced with permission of The McGraw-Hill Companies Comments. This photo mosaic shows a spit beach enclosing Bt1 lagoonal muddy tidal flats at the south end of Plymouth Bay Massachusetts 40 km south of Boston, USA. “A” marks the historic Pilgrim’s landing site in 1620. The sand shoals to the east are in the main part of the bay.
See Geounit Bw4.
Select Bibliography See in particular notes of Bw4 geohazard relations. Bascom W (1980) Waves and beaches, 2nd edn. Anchor Press/Doubleday, Garden City, New York, pp 247–275 Bird ECF (1976) Coasts. Australian National University Press, pp 96–128 King CAM (1974) Geomorphology in environmental management. Oxford Press, London, pp 198–205 Shaw J, Forbes DL (1992) Barriers, barrier platforms, and spillover deposits in St. George’s Bay, Newfoundland: Paraglacial sedimentation on the flanks of a deep coastal basin.Marine Geology 105(1-4):119–140
Bw5 · Spits ▼
Fig. Bw5-2. Location. Geographic. 166°52' W, 65°15' N, western Alaska Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 100 000 Acquisition date. 1950 Source. Shepard FP, Wanless HR (1971) Our changing coastlines. McGraw-Hill, p 469, fig 14.12. Reproduced with permission of The McGraw-Hill Companies Comments. Photo mosaic shows the 12 km long Point Spencer spit on the Bering Strait Coast of the Paleozoic metamorphic rocks of the Seward Peninsula. A 2 km long airstrip is located on the 3 m high beach ridges of the enlarged spit terminus. The terminus point is very unstable, the position of the shoreline near the end changed as much as 30 m during one night as a result of wave and current action. ▼
Fig. Bw5-3.
Location. Geographic. 58°32' W, 48° 26' N, west Newfoundland Geologic. Paraglacial Geosystem deposits on late to post orogenic Carbonifeous sediments of the St. George Basin of the Acadian Appalachian Orogen Vertical Airphoto/Image. Type. Colour infrared, stereo pair Scale. 1: 110 000 Acquisition date. 19 July 1972 Source. Courtesy of Natural Resources Canada, NAPL RSA 305621R-16, 17 Comments. This stereomodel covers the inner end of St. George’s Bay and is centered on the spit beach of Flat Island and its enclosed Flat Bay. The following descriptions are based on Shaw and Forbes 1992, p 125: “The Flat Island barrier is about 12 km long and can be divided into three sections. Close to the attachment point, the western section is a narrow gravel ridge with elevation up to 2.8 m. Northeastward the ridge truncates older gravel beach ridges. The middle section’s morphology has been conditioned by outwashing. This has resulted in the destruction of the formerly continuous narrow barrier and its replacement by intertidal and shallow subtidal sand and gravel flats penetrated by numerous deeper channels.” The eastern section of the barrier, the island of Sandy Point, is more than 1 km wide and was developed by sets of gravel beach ridges. At least five documented shipwrecks are associated with this barrier structure. The white area about 3 km inland is a gypsum mine in the Lower Carboniferous sedimentary rocks underlying the till cover (Gf4). The conveyor belt to carry ore to the bulk carrier dock is visible.
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Division 4 · Surficial Deposits
Fig. Bw5-3. (Caption on p. 733)
Group B · Marine Littoral Systems
Bw5 · Spits
Fig. Bw5-4. Location. Geographic. 18°40' E, 54°41' N, southern Baltic Sea Vertical Airphoto/Image. Type. Shuttle 9, natural colour photo Scale. 1 : 2 500 000 Acquisition date. Nov. 1982 Source. USGS Comments. This is a segment of the synoptic coverage of an astronaut photo showing the 65 km long Hell Spit in the Gulf of Gdansk in northern Poland. Dark areas inland are reforestation on the Pleistocene northern continental glacial moraine belt (Gl5). The spit encloses the port of Gdynia whose piers are visible just south of image center.
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Bw6
Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Bw6 Tombolos Characterization
Geohazard Relations
A tombolo is a beach deposit that ties an island to the mainland or to another island. Some islands are attached to the mainland by two beaches – double tombolo. In all other respects tombolos have the same characteristics as beaches Bw4.
See Geounit Bw4.
Select Bibliography See Geounit Bw4.
Fig. Bw6-1. Source. Deffontaines P, Delamarre MJ-B (1956) Atlas Aérien, France, Tome II. Gallimard, p 61, photo 69 Comments. The arrow in this air perspective view looking northwest points to an approximately 350 m long by 5 m high tombolo joining the Paleozoic granite Quiberon Peninsula to the mainland on the south coast of Brittany, 25 km east of the port of Lorient. The beach is just wide enough to allow for the passage of a vehicular and rail line leading to Quiberon Town, and has required engineered wave and current erosion control structures. The western (left) side is exposed to the open sea.
Fig. Bw6-2.
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Location. Geographic. 64°24' W, 44°14' N, Nova Scotia Geologic. Peneplain of Meguma Zone Terrane of Acadian Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 27 000 Acquisition date. 28 June 1955 Source. Courtesy of Natural Resources Canada, NAPL A 14708-178 Comments. This airphoto shows a classic 2 km long by 100 m wide tombolo beach connecting Bush Island to the mainland at Green Bay on the Atlantic Upland 85 km south of Halifax. Local sea-level rise is in the order of 40 cm per century, mostly due to crustal subsidence. Wave approach is from the south, and a sand shoal has accumulated on the lee side of the tombolo.
Bw6 · Tombolos
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Division 4 · Surficial Deposits
Fig. Bw6-3. (Caption on p. 740)
Group B · Marine Littoral Systems
Bw6 · Tombolos
Fig. Bw6-4. (Caption on p. 740)
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Division 4 · Surficial Deposits ▼
Fig. Bw6-3. Location. Geographic. 58°43' W, 48°33' N, west Newfoundland Geologic. Cambrian-Ordovician sedimentary rocks of the Acadian Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 15339-154, 155 Comments. A stereomodel is centered on an isthmus of the Port au Port Peninsula consisting of twin tombolos 600 m long × 30 m wide which connects the peninsula with the mainland at Berry Head and Table Mountain. The beach-forming longshore currents are from the northwest and north for the north beach, and bidirectional east-west for the south. The mainland on the east (right) at Berry Head is a 40 m high Bc3 glaciomarine delta; the peninsula consists of limestones with a veneer of glacial till. This site is 5 km west of the bluffs of Fig. Bb1-2.
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Fig. Bw6-4. Location. Geographic. 81°15' E, 08°34' N, northeast Sri Lanka Geologic. Foliated Archean metasediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Personal archive Comments. The stereomodel shows the 600 m to 900 m wide tombolo which encloses the inner harbour of Koddiyar Bay at Trincomalee on the coastal plain of northeast Sri Lanka. The parallel rock ridges are the seaward projection of the Elahera Ridges of metamorphic rocks. This coastal area was overrun by a strong tsunami tidal wave on 26 December, 2004.
Group B · Marine Littoral Systems
Bl1 · Sea Ice Forms
Sub-group Bl Sea Ice and Sea Ice Related Forms Bl1 Sea Ice Forms
wells are particularly threatened. Overrides may take place in less than 30 minutes and are difficult to predict. Such motions have been known to bury houses along the coast, and can occur frequently enough to require the establishment of minimum setbacks for coastal installations (Forbes and Taylor 1994).
Characterization Reference This composite geounit incorporates the movements and geomorphic effects of sea ice motion in high latitudes. Sea ice can move sediments that are beyond the competence of other processes. Various types of shoreline and beach forms are developed during the short Arctic summer when mobile sea ice and waves strike the coast. Ice thrust ridges are composed of shore and beach material forced up from the water’s edge by ride-ups of sea pack ice across the beach. The process is particularly effective in shallow coastal waters. Sharp-crested or rounded ridge heights range from 3 to 4 m. Boulder barricades are ridges of boulders derived primarily from glacial deposits. They range from 5 to 20 m wide and 0.5 to 3 m high and are found at low water line of tidal flats. They originate from shoreline erosion by ice, and are concentrated where, during breakup, floating ice on tidal flats stands against the persistent ice cover offshore. Ice-rafted boulders occur scattered randomly on intertidal flats, they are typically 1 to 2 m in diameter. They become frozen into the ice at low tide and are then transported – rafted – in the ice and set down on the tidal flat as the ice melts. The dimensions of these forms requires airphotos or images at scales >1:5 000 to be resolved and mapped.
Forbes DL, Taylor RB (1994) Ice in the shore zone and the geomorphology of cold coasts. Progress in Physical Geography 18(1):59–89
Select Bibliography Harper JR (1985) Ice interaction with coastal processes. Short course lecture notes, coastal processes and engineering. Associate Committee for Research on Shoreline Erosion and Sedimentation, NRC, pp 91–114 Lauriol B, Gray JT (1980) Processes responsible for the concentration of boulders in the intertidal zone in Leaf Basin, Ungava. The coastline of Canada. GSC Paper 80–10, pp 281–292 McLaren P (1980) The coastal morphology and sedimentology of Labrador: A study of shoreline sensitivity to a potential oil spill. GSC Paper 79–28 Ogorodov SA (2003) The role of sea ice in the coastal zone dynamics of the arctic seas. Water Res. MAIK Nauka/Springer 30(5):509–518
Geohazard Relations Boulder barricades and ice-thrust ridges are impediments for landing operations in the nearshore zone, and ice rideups onshore are destructive of transport facilities and installations for resource development in high latitudes. Boulder barricades. Shores with boulder barricades are difficult to approach from the sea, they offer restrictions to boat travel, some can only be crossed at high tide. In oil spill events boulder barricade zones would be difficult to clean. Ice ride-ups and pile-ups. Sea ice is a major seasonal hazard to structures in the Arctic and also in more southern latitudes. During spring breakup ice floes composed of blocks 1 to 2 m thick are driven onshore by wind and waves and can pile up into ridges by buckling up to 30 m high. They override beaches and hit fixed objects with considerable force. Artificial islands used for oil and gas
Fig. Bl1-1. Location. Geographic. Northwestern Canadian Arctic Archipelago, Queen Elizabeth Islands Geologic. Cretaceous sediments of Sverdrup Basin of Queen Elizabeth Islands Sub-plate Source. Amos CL (1990) Geology of the continental margin of Eastern Canada. GSC Geology of Canada, no 2, fig 11.19B, p 640 Comments. Map shows coastal types in a region where shores are ice-locked for at least 11 months each year and dominated by the actions of sea ice and absence of wave action. The delineated ice push/override shore segments consist of ice ride-ups and pile-ups. The scarred shorelines are marked by boulder barricades and ice-rafted boulders.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bl1-2. Location. Geographic. 88°11' W, 80°26' N, Axel Heiberg Island, Nunavut Geologic. Triassic sediments of Sverdrup Basin of Innuitian Orogen Source. Bird JB (1967) The physiography of Arctic Canada, with special reference to the area south of Perry Channel.
Pl 40, © Johns Hopkins Press. Reprinted with permission of The Johns Hopkins University Press Comments. Ground view shows typical ice thrust ridges on the shores of the Schei Peninsula at the junction of Nansen and Eureka Sounds. In the northeast part of the island. Rucksack gives scale.
Fig. Bl1-3.
Comments. The arrows in this photo point to a boulder barricade concentrated at the low tide line on a narrow tidal flat on the eastern Shield coast of central Labrador at 58°55' W,54°55' N.
Source. Courtesy of Natural Resources Canada, GSC 203475W
Bl1 · Sea Ice Forms
Fig. Bl1-4. side of Pangnirtung Fjord, derived from Gf4 glacial till further up the fjord. The barricade is deposited on an intertidal flat at the south end of Auyuittuq National Park on Cumberland Peninsula. See the stereomodel of this site on Fig. Bl1–5.
Fig. Bl1-5.
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Location. Geographic. 65°50' W, 66°07' N, eastern Baffin Island, Nunavut Source. Courtesy of Natural Resources Canada, GSC. Photo by A. S. Dyke Comments. The arrows in this photo point to a 1 to 2 m high sea ice formed boulder barricade on the western
Location. Geographic. 65°50' W, 66°07' N, eastern Baffin Island, Nunavut Geologic. Eocene horst of the northeast shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 3 180 Acquisition date. 1 August 1980 Source. Courtesy of Natural Resources Canada, NAPL A 25553-93, 94 Comments. These very large scale photos at the site of Fig. Bl1-4 show a boulder barricade marked by arrows. The segment pictured in the photo is 950 m long and 50 m wide. The intertidal flat between the barricade and the shoreline marked Bt2.2 varies from 175 m to 275 m wide; its surface is strewn with lag boulders rolled in by ice flows.
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Division 4 · Surficial Deposits
Fig. Bl1-5. (Caption on p. 743)
Group B · Marine Littoral Systems
Bt1 · Lagoons
Sub-group Bt Tidal Regime Deposits and Forms Bt1 Lagoons Characterization Lagoons are sedimentary complexes that include barrier beaches Bw3. Typically, they occur where a low-gradient continental shelf is adjacent to a low-relief coastal plain Bc1. “Lagoons form where coastal embayments or depressions are separated from the adjacent sea by a barrier. Barriers comprise either clastic material (e.g., Bw3) or are created by vegetation, coral growth or tectonics.” (Cooper 1994). The evolutionary processes of lagoons overlap between estuaries Fw3 and tidal flats. Enclosure of a lagoon is accomplished by elongation of a spit Bw5, or by shoreward migration of a barrier ridge that originated offshore. Lagoon water occurs in three zones: a fresh-water zone from streams on the landward side; a salt water zone close to the inlets; and a transition brackish water zone. Within the lagoon water body a number of Component depositional geounits may occur: Component a. Tidal deltas – are sand bodies deposited from bi-directional flow located at inlet breaches in barrier beaches Bw3. “The ebb-tidal delta is a sand accumulation seaward of the inlet throat, formed primarily by ebb-tidal currents but modified by wave action. The flood-tidal delta is an accumulation of sand landward of the inlet throat, shaped chiefly by flood-tidal currents.” (Boothroyd 1985). Both types consist of channel and shoal systems in form. Component b. Washover fans – are created by wind-generated storm surges that overtop barrier beaches and deposit sand in the lagoon in relatively thin sheets, a few centimeters to two meters during each wash event, and a few hundred meters in width. “If the washover flow is unconfined, then the land surface is inundated by sheetwash. However, if the washover flow is confined to interdune lows or incised channels, then the energy of onshore flow is concentrated, flow velocities accelerate, and washover sediments are transported and deposited much farther inland.” (Morton 2002). Component c. Salt marshes and mangrove swamps – As with coral reefs, salt marshes exhibit a remarkable interplay between geological, hydrological, biological and chemical processes. Photographically and spectrally, the prime indicator of this component is the community of halophytic plants (strong near-infrared reflectance). This is a flora of reed type rushes and cord grasses.
As described in Fig. Bt1c-3, in low latitudes mangrove tree communities replace the marsh plants. These forests occur in similar situations along the coasts of many tropical coastal regions. They are readily identified by most sensor systems, including low resolution MSS Landsat images, particularly colour infrared wavelengths, in common with other biomasses. Swamp woodlands are associated wetlands. The marshes occur as low marshes corresponding to the upper intertidal zone with a muddy substrate, and high marshes which are supratidal and are more influenced by terrestrial conditions, with more permeable sands substrate. Both types are drained by a typical pattern of intricately meandering creeks. Sediment carried into a marsh by the rising tide, is trapped by the vegetation and retained as the tide ebbs. The marsh level is thus gradually built up. Salt marshes and mangrove swamps have been a striking instance of humankind acting as a geohazard agent in its own right. They have historically been greatly reduced in extent by draining for land development or transformed into garbage-based dry land. Mangrove forests are depleted for fuel wood and conversion into shrimp ponds. Mangroves can provide a buffer to storm surges and tsunami runups, while loosing some trees they can absorb most of the energy from the waves. Component e. Sabkhas – These deposits occur in subaerial or arid coastal environments just above normal high tide level where evaporation rates are high. They consist of silt, clay and muddy sand in shallow depressions. The deposits are commonly saturated with brine and are often salt encrusted. Salt crusts are spectrally revealed by their brightness on airphotos and images, similar to L2 inland playa surfaces. Component g. Polders – consist of zones in lagoons that have been dyked, drained by artificial means, and kept dry by pumping. The fertile lands are usually intensely developed for agriculture, and large ones are frequently under severe population pressure. Polders are readily visible on all types of airphotos and images by their geometric patterns which contrast strongly with the surrounding natural lagoon components.
Geohazard Relations As in the cases of littoral sediment and coastal plain geounits, lagoons are susceptible to storm surges, tsunami runups and long-term sea-level rise. “Under normal dry conditions the sabkha provides an excellent running surface for wheeled vehicles but under high water table conditions vehicles can break through the surface crust and find themselves up to the axles in a liquid mud.” (Ellis 1973).
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Division 4 · Surficial Deposits
References Boothroyd JC (1985) Tidal inlets and tidal deltas. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, p 448 Cooper JAG (1994) Coastal evolution. Cambridge University Press, Cambridge, p 221 Ellis CI (1973) Arabian salt-bearing soil (Sabkha) as an engineering material. Transport and Road Research Lab. , Report LR 523 Morton RA (2002) Factors controlling storm impacts on coastal barriers and beaches – A preliminary basis for near real-time forecasting. Journal of Coastal Research 18(3):486–501
Select Bibliography Althausen JD, Clark JS, Conroy CM (1995) Image processing techniques used in studying satellite images of the Arabian Gulf: Kuwait, Saudi Arabia, and the United Arab Emirates. Society of Economic Mineralogists and Paleontologists Congress Barth H-J, Boer B (2002) Sabkha ecosystems. Springer-Verlag Bubshait AA (2001) Quality of pavement construction in Saudi Arabia. Practice periodical on structural design and construction, Aug, pp 129–133
Group B · Marine Littoral Systems Bird ECF (1976) Coasts. Australian National University Press, pp 190–204 Commission on Mitigating Shore Erosion along Sheltered Coasts (2007) Ocean Studies Board, NRC (USA) Cooper JAG (1994) Lagoons and microtidal coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 219–266 Davies JL (1977) Geographical variation in coastal development. Longman, London, pp 162–180 Frey RW, Basan PB (1985) Coastal salt marshes. In: Davis RA (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 225–301 Hayes MO (1980) General morphology and sediment patterns in tidal inlets. Sedimentary Geology 26:139–156 Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, New York, pp 150–154 Reinson GE (1980) Barrier island systems. Facies models. GSA, Geoscience Canada, Reprint Series 1, pp 57–74
See Select bibliography for Marine Littoral Geounit Subgroups. See Note concerning long-term sea-level rise. See Note concerning tsunami runups following Geounit Bp1, Carbonate platforms.
Fig. Bt1-1. Source. Reinson GE (1980) Barrier island systems. In: Walker RG (ed) Facies models. Geological Association of Canada, p 58, fig 2 Comments. This modified block diagram locates the morphosedimentary Components of lagoons and the Geounits commonly associated with them.
Fig. Bt1-2.
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Location. Geographic. 64°53' W, 47°32' N, Acadian Peninsula, New Brunswick Geologic. Central platform of Acadian Appalachian Orogen Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 43 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 13143-57, 58 Comments. Stereomodel shows some morphosedimentary lagoon Components and units in a Bc3 glaciomarine plain at Tracadie: Bw3 is the barrier beach that encloses the lagoon; a are tidal deltas; c are salt marshes. This site is 22 km north of Fig. Bw3-1 at Tabusintac.
Bt1 · Lagoons
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Division 4 · Surficial Deposits
Fig. Bt1-3.
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Location. Geographic. 95°14' E, 05°29' N, Banda Aceh, north Sumatra, Indonesia Geologic. Bc1 coastal plain Source. Satellite image courtesy of Geo Eye Comments. A pair of images shows the before and after states of the tsunami runup of the Sumatra-Andaman earthquake at Longha Lagoon on the open coast west of Banda Aceh City on 10 January 2003 and 29 December 2004. 130 000 lives of the total 230 000 were lost in this region.
Fig. Bt1-4.
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748
Location. Geographic. 07°02' E, 53°21' N, north Germany Source. LAR, 1977 Comments. This panel plan describes the filling of a lagoon-like dyked area with sand dredged from a shipping channel. The location is 10 km seaward of the port of Emden on the Ems River Estuary in East Friesland. Strong tidal movements constantly silt up the estuary, and navigation to the port by large ore-carrying vessels requires constant dredging.
Group B · Marine Littoral Systems
Bt1 · Lagoons
Fig. Bt1b-1. Source. Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, p 298, fig 434 Comments. The air perspective photo shows washover fan sediments deposited onto the salt marsh area of a lagoon on the southeast coast of the United States. The Bw4 lagoon barrier beach is in the lower part of the photo. “One of the major agents modifying estuaries and lagoons (including the barriers to which the lagoons owe
their existence) is the hurricane.” (Authors’ storm surge geohazard). “It is probable that all of the province's lagoons have been affected by hurricanes at some time or other. Along some sections, especially the Gulf Coast and southern Atlantic Coast, they are of major importance.” (Walker HJ, Coleman JM (1987) Atlantic and Gulf Coastal Province In: Graf WL (ed) Geomorphic systems of North America. Geological Society of America, Centennial Special vol 2, p 94).
Fig. Bt1b-2. Source. Morton RA (2002) Factors controlling storm impacts on coastal barriers and beaches – A preliminary basis for near real-time forecasting. Journal of Coastal Research 18(3), p 496, fig 12
Comments. Washover deposits constructed by a 5.5 m storm surge near Cozumel Island on the east coast of Yucatan Peninsula, Mexico.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bt1b-3. Location. Geographic. 61° 58' W,47° 17' N, Magdalen Islands, Québec Source. Owens EH, McCann SB (1980) The coastal geomorphology of the Magdalen Islands, Quebec. In: McCann SB (ed) The coastline of Canada. GSC Paper 80-10, p 59, fig 5.11 Comments. An air perspective photo shows a washover fan that has reached 600 m into Havre aux Basques Lagoon on the west side of Ile du Havre-Aubert.
Fig. Bt1b-4. Location. Geographic. Maine, USA Geologic. Structurally controlled lowland of Acadian tectogenic belt Source. Morton RA (2002) Factors controlling storm impacts on coastal barriers and beaches – A preliminary basis for near real-time forecasting. Journal of Coastal Research 18(3), p 491, fig 6 Comments. In this photo a gravelly washover fan deposit constructed by waves of a 1 m storm surge lies just below the house balcony near Portland.
Fig. Bt1b-5.
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Location. Geographic. 97°11' W, 27º39' N, Northwest Gulf of Mexico, Texas Geologic. Bc1 coastal plain of Marine Quaternary sediments Vertical Airphoto/Image. Type. Pan, b/w airphoto Scale. Not indicated Acquisition date. Photo A: 1967; photo B: 1969
Source. Unspecified U.S. government agency Comments. The photo pair covers a short segment of Mustang Island Bw3 barrier beach that encloses Laguna Madre of Corpus Christi Bay. Photo A was taken immediately following a hurricane. It shows storm surge related breaching of the barrier and deposition of washover fan components in the lagoon. Photo B was taken 2 years later. The extent of the barrier recovery and persistence of the lagoon fans are evident.
Bt1 · Lagoons
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bt1b-6. Vertical Airphoto/Image. Type. b/w pan Scale. (see bar) Acquisition date. Not given Source. Morton RA (2002) Factors controlling storm impacts on coastal barriers and beaches – A preliminary basis for near real-time forecasting. Journal of Coastal Research 18(3), p 491, fig 5 Comments. A vertical airphoto shows a 700 m wide × 700 m length washover fan on the lagoon behind the low-lying Bw3 barrier beach of Cedar Island Virginia, USA. The fan was deposited in 1962 by a 2.5 m storm surge.
Fig. Bt1b-7.
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Location. Geographic. 69°56' W, 41°42' N, eastern Massachusetts Geologic. Bw3 barrier beach of a sub-lobe of Wisconsinan/ Würm continental ice Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 12 000 Acquisition date. April 1961 Source. Shepard FP, Wanless HR (1971) Our changing coastlines. McGraw-Hill, p 23, fig 2.21. Reproduced with permission of The McGraw-Hill Companies Comments. The photo fragment illustrates two generations of washover fans across Nauset Beach barrier near Chatham at the southeast tip of Cape Cod. The larger older fan, 1 400 m long by 650 m across, is in an eroded degraded-appearing condition. It is bounded on the lagoon side by a narrow barrier developed by tidal currents flowing through the locally narrow Chatham Harbour pass. The more recent, smaller washover to the north is 600 m wide by 400 m across. The washover form is similar to that of a Bt1a flood tidal delta, but lacks the breach channel through which delta flows pass. The old fan is now largely infilled and some hutments have been constructed on the bay side. The small fan has been eroded away.
Bt1 · Lagoons
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bt1c-1. Source. Reineck H-E, Singh IB (1973) Depositional sedimentary environments. Springer-Verlag, p 361, fig 518 Comments. The photo shows the bedding of fine-grained sediments with some bedding planes of shells that are normally accreted in a supratidal salt marsh.
Fig. Bt1c-2. Location. Geographic. 69°57'38'' W, 41°49'55'' N, Massachusetts, USA Source. LAR, 1975 Comments. A meadow of short, 20 to 30 cm Spartina patens salt hay on a tidal creek in Nauset Bay on the east coast of Cape Cod. This is one of the characteristic marsh halophyte grasses. The enclosing Bw3.1 Nauset barrier beach is in the background. Spartina alterniflora cordgrass appears as a fringe at the water’s edge. Spartina patens characteristically falls over when it ages, forming a mat through which next year’s growth emerges. It grows best on mud and sand flats where the seawater is diluted by rains or by freshwater coming into the saltwater at the mouth of a stream.
Bt1 · Lagoons
Fig. Bt1c-3. Location. Geographic. 167°30' E, 16°30' S, Vanuatu Source. Vocabulaire géographique, Tome 1 (1966) Masson et cie éditeurs, photo by Aubert de la Rüe Comments. This is a close ground view of the margin of a mangrove plant community on Malekula Island. Mangroves are tropical and subtropical shrubs and trees that grow in saline and brackish wetlands. They are homologous to higher latitude salt marsh ecosystems, but there are many shores in the tropics on which salt marsh and mangrove occur side by side. Mangroves range from pioneering low scrub on the seaward side to tall forest inland. They average from 6 to 12 m high, and in exceptional cases can be over 30 m tall. The photo shows the characteristic air absorbing root system which anchors the plant in the soft and shifting muddy substrate and promotes stabilization and accre-
Fig. Bt1c-4. Location. Geographic. 128°05' E, 15°25' S, northwest Australia Source. Kulmar S (1982) In: Kennedy T (ed) Australia’s beautiful coastline. Australia. Consolidated Press Ltd., pp 57–58 Comments. This air perspective view shows a mangrove community in the tidal reach of Wyndham River. A ground view and description are in Fig. Bt1c-3.
tion of sediment. Mangroves offer some protection against coast erosion and storm surge attack. In common with many types of wetland, mangroves are subject to man-induced disturbances and depletion; e.g., use for lumber; aquaculture development (shrimp farming in Thailand). See also Fig. Bt1c-4.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bt1c-5. Location. Geographic. 81°17' W, 31°28' N, southeast coast, USA Vertical Airphoto/Image. Type. Colour infrared, airphoto Scale. 1: 6 400 Acquisition date. 14 September 1971 Source. Reimold RJ, Gallagher JL, Thompson DE (1973) Remote sensing of tidal marsh. Photogrammetric Engi-
neering 39(5), p 483, pl 1, American Society of Photogrammetry Comments. Large-scale photo shows an area of salt marsh inside of Sapelo barrier island along the coast of Georgia. The blue-red colour of the marsh reflects the dominant presence of the tall Spartina alterniflora cordgrass of Fig. Bt1c-2. The bright red areas are trees on dry land.
Bt1 · Lagoons
Fig. Bt1c-6. Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 46 000 Acquisition date. February 1940 Source. Personal archive Comments. Stereomodel shows a typical occurrence of a lagoonal salt marsh (T descriptor) near latitude 39°50' N in Ocean County, New Jersey, USA. C and L indicate the Bc1 coastal plain, S is a disused flooded sand pit.
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Division 4 · Surficial Deposits
Fig. Bt1c-7. (Caption on p. 760)
Group B · Marine Littoral Systems
Bt1 · Lagoons
Fig. Bt1c-8. (Caption on p. 760)
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
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Fig. Bt1c-7. Location. Geographic. 77°56' W, 18°28' N, northwest Jamaica Geologic. Paleogene marine limestones of the Nicaraguan Rise of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 24 000 Acquisition date. Not given Source. Personal archive Comments. The stereomodel at Montego Bay shows a 2.5 km long zone of intertidal flat at the head of coralprotected Bogue Lagoon. The flat is occupied by mangrove swamp as in Figs. Bt1c-3 and Bt1c-4. The adjacent Bc1 coastal plain and terraces are densely cultivated with tropical crops such as bananas, sugar cane, or pineapple. The enclosing coral peninsulas were in the process of being developed when the photos were taken. The 300 m zone between the mangroves and the N/S road is now developed for aquaculture.
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Fig. Bt1c-8.
Location. Geographic. 09° 01' W, 05° 00' N, southern Liberia Geologic. Coastal plain of west African Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 1964 Source. Personal archive Comments. The stereomodel shows the mangrove-filled intertidal flat at the mouth of the Sinoe River at Greenville 3.5 km east of the barrier beach of Fig. Bw3.1-4. The town itself is sited on raised beach ridges. It is not a fishing port and is likely a residential center for outlying cocoa and palm production activities.
Fig. Bt1c-9.
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Location. Geographic. 02°49' E, 42°41' N scene center, Languedoc southern France Vertical Airphoto/Image. Type. MSS resampled to 50 m resolution Scale. 1: 500 000 Acquisition date. 13 October 1981 Source. USGS Comments. The inset frame on this Landsat subscene, which is a continuation southward of Fig. Bc4-3, locates the coverage of the stereo airphotos of Fig. Bt1g-3 with the red zone showing polders and salt marshes described in that figure. The image shows the location at the north end of the 30 km × 30 km plain of Perpignan near the Spanish border. The plain is Bc4 fluviomarine consisting of Pleistocene and Holocene terrestrial and interglacial marine sediments. The surrounding highlands are igneous and metamorphic rocks of the Pyrenees and Pre-Pyrenees, with Cretaceous folded sedimentary rocks to the north (Corbières).
Bt1 · Lagoons
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bt1e-1. Source. Personal archive Comments. A schematic profile locates the topographic site of a sabkha geounit in a desert coastal zone. Scale is approx. 1:250 000. Bubshait (2001) describes Arabian Peninsula sabkhas as being made up of nonuniform, variable, and highly compressible materials which lead to differential settlement of road pavements. Pavement cracking results from
salt crystallization near the surface and volume change of gypsum due to hydration and dehydration. Construction methods include 1 m high embankments and stabilization of the sabkha with asphalt admixtures. Also the high concentration of chlorides and sulfates in sabkha sediments makes it highly corrosive. Mobile sand encroachment as illustrated in Figs. Ef1-1 and Ef1-2 also occurs.
Fig. Bt1e-2. Location. Geographic. 54°20' E, 24°10' N, United Arab Emirates Source. Ellis CI (1973) Arabian saltbearing soil (sabkha) as an engineering material. Overseas Unit Transport and Road Research Laboratory, Crowthorne, Berkshire, Department of the Environment TRRL Report LR 523, pl 2 Comments. This view shows typical local trafficability along the Persian Gulf coasts of Abu Dhabi and Dubai. The bluffs in the background are interbedded, probably Pliocene sandy limestones and marls.
Fig. Bt1e-3. Location. Geographic. 52° E, 23°55' N, United Arab Emirates Geologic. Tertiary Rub at Khali Basin in the stable region of the Arabian Plate Source. Vesey-Fitzgerald D (1951) From Hasa to Oman by car. Geographical Review, American Geographic Society, October 1951, pp 544–560, figs 2 and 3 Comments. Photo shows a heavy vehicle that has broken through the salt crust and sunk up to the axles in mud on the Sabkha Mutti on the Persian Gulf coast.
Bt1 · Lagoons
Fig. Bt1e-4. Location. Geographic. 81°07' E, 06°08' N, southeastern Sri Lanka Geologic. Tanamalwila Archaean Peneplain of the sub-plate Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 40 000
Acquisition date. Not given Source. Personal archive Comments. The photo subscene covers a storm surge and tsumani-susceptible sabkha depression at Hambantota. The depression is enclosed by a Ec3 dune-crowned Bw3.1 bay barrier beach.
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Division 4 · Surficial Deposits
Fig. Bt1e-5. (Caption on p. 766)
Group B · Marine Littoral Systems
Bt1 · Lagoons
Fig. Bt1e-6. (Caption on p. 766)
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Division 4 · Surficial Deposits ▼
Fig. Bt1e-5. Location. Geographic. 72°45' W, 19°14' N, west coast Haiti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. This stereomodel at a locality named Grande Saline shows a dark band of Bt1c mangroves enclosing a turbid bay of the elongate delta of the south arm of Artibonite River. The mangroves screen a zone of wet Bt1e sabkha on the landward side. The bright peninsula on the left is a 24 m high raised coral reef. Grids of salt evaporation and extraction pans are located along the spit beach.
▼
Fig. Bt1e-6. Location. Geographic. 70°30' E, 23°10' N scene center, western India Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 29 January 1973 Source. USGS Comments. The bluish areas in this Landsat scene are partly inundated, supratidal deltaic saline mudflats in tectonic depressions in the Katchchh region at the southern end of the Thar Desert. The zone in the northwest is named Great Rann, and the estuarial shaped zone on the east is Little Rann which terminates in the Gulf of Kutch in the southwest. “The clay-rich sediments comprising these mudflats are transported into the Gulf of Kutch by strong longshore currents from the mouths of the Indus River, (200 km) to the northwest.” (Short and Blair, 1986, p 398). These flats are inundated only part of the year, the remaining time becoming regions of intense evaporation and deposition of evaporite minerals. The beige land area separating the Ranns is Kutch proper, consisting of flat-lying Jurassic to Miocene rocks, mainly sandstones, 275–335 m elevation. The brown area to the southeast appears to be dry thorn forest on the Late Cretaceous to Eocene Deccan lavas of the Kathiawar Peninsula. This is a tectonically controlled landscape whose elements are a manifestation of uplifts along major east-west normal faults reactivated from time to time, detectable in left center, and graben-like sabkha filled depressions reflecting oblique-cutting NE/SW subordinate faults developed during various tectonic events.
Group B · Marine Littoral Systems
Bt1 · Lagoons
Fig. Bt1g-1. Location. Geographic. 05°46' E, 52°38' N, central Netherlands Source. Unattributed Comments. These two perspective airphotos illustrate a result of the construction of a polder, in this case the 48 000 ha Northeast Polder. The upper photo looking south shows the 2.5 km long island of Schokland as it stood in the Ijsselmeer around 1939, with about 800 inhabitants.
In 1940, the four year project to construct the 54 km long dyke enclosing the polder area was completed. Pumping to drain the polder was completed in 1942. The lower photo looking north, probably taken around 1950, shows the island incorporated into the polder, kept as an undeveloped green space surrounded by agricultural land. See the Landsat scene of similar polders developed later to the south in Fig. Bt1g-8.
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Division 4 · Surficial Deposits
Fig. Bt1g-2. (Caption on p. 770)
Group B · Marine Littoral Systems
Bt1 · Lagoons
Fig. Bt1g-3. (Caption on p. 770)
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
▼
Fig. Bt1g-2.
Location. Geographic. 01°05' W, 46°22' N, Atlantic Coast Geologic. Embayment at contact of Brittany Massif and the Aunis Arch of the Jurassic northern Aquitaine Basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 1981 Source. IGN – Photothèque Nationale, France Comments. The stereomodel at Luçon-Puyravault in the Marais Poitevin covers the 38 km2 area of polder land in the center of Landsat MSS subscene Fig. Bt1g-7. The elongate outline is a 500 m wide ridge of limestone. In the Marais itself, individual farms are sited at intervals along the major collector drainage ditches such as the two that cut across the ridge. Field drainage ditches are both tiled and opened surface as in Figs. Bc3-6 and Bc3-7. ▼
Fig. Bt1g-3.
Location. Geographic. 02°57' E, 42°49' N, Languedoc Geologic. Quaternary Bc1 coastal sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1974 Source. IGN – Photothèque Nationale, France Comments. A stereomodel shows three areas of dark-toned wetland at the south west margin of the 40 km2 tideless Leucate Lagoon. The two north areas are reverting to salt marsh following their abandonment as drained agricultural zones. Abandonment has resulted from a condition of hyper salinity of the lagoon water brought about by engineered enlargement of the inlet (graus) to provide navigation to small ports at the north end of the lagoon. Regional salinity conditions are enhanced by desiccating winds from northwest in summer. (however, these salinity levels have led to a development of aquaculture – oysters, mussels – in the center of the lagoon – off photo cover). The high evaporation rates of summer temperatures lead to deoxygenation of water through enhanced bacterial activity and liberation of toxic substances. Harmful mosquito infestations are a related seasonal health hazard. Three short segments, 700 m to 1 000 m long of white, isolate Bw4 paleo-beach ridges occur in the second abandoned area. The town of Salses with its Spanish fortress (1497–1504) is visible on the west margin of the annotated photo. See Landsat subscene Fig. Bt1c-9.
Fig. Bt1g-4.
▼
770
Location. Geographic. 03°30' E, 43°19' N, Languedoc Geologic. Cretaceous and Pliocene sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 1968 Source. IGN – Photothèque Nationale, France Comments. The stereomodel at Agde is centered on the polderized lagoon of the 3 km2 Etang de Bagnas south of the Bassin de Thau. Photo evidence suggests it may have been a salt extraction area that was in an abandoned state at the time of photography. The smaller area also appears disused. Previous activity is undetermined. The canal that crosses the photo between the two areas is the eastern terminus of the Canal du Midi. The canal is a 240 km waterway that connects the Atlantic, via the Garonne River, to the Mediterranean. It was constructed between 1667 and 1681. It appears also in Fig. L3-4.
Bt1 · Lagoons
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Division 4 · Surficial Deposits
Fig. Bt1g-5. (Caption on p. 774)
Group B · Marine Littoral Systems
Bt1 · Lagoons
Fig. Bt1g-6. (Caption on p. 774)
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
▼
Fig. Bt1g-5.
Location. Geographic. 03°19' E, 43°17' N, Languedoc Geologic. Quaternary Bc1 coastal sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 1968 Source. IGN – Photothèque Nationale, France Comments. The stereomodel 10 km southeast of Béziers shows a group of artificially drained marsh areas in an analogous coastal setting to those occurring 60 km to the south, pictured in Fig. Bt1g-3. The poldered areas are on Quaternary sediments in the valley of the River Orb, with the Grande Maire lagoon separating active and inactive units. The northeast corner at the village of Portiragne consists of Pliocene marine sediments. The area along the Bw3 barrier beach has been developed for vacation homes. The coverage of these photos is shown on the Landsat image of Fig. Bc4-3.
Fig. Bt1g-7.
▼
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▼
Fig. Bt1g-6. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 555 000 Acquisition date. October 1975 Source. USGS Comments. Landsat subscene shows the setting of the Venice Lagoon and its enclosing Bw3 barrier beaches on a Bc1 coastal plain of the northeast section of the Po Plain of subsidence at the head of the Adriatic Sea. The lagoon is 50 km long by 10 km wide in the north and 15 km wide in the south. The blue colour reflects the shallow bottom muds. The blue patch of the city of Padua is visible 20 km inland, and the first ranges of the limestone Pre-Alps of the upper Piave Valley are in the northwest. See also Figs. Fw4-4 and Mv5-2.
Location. Geographic. 01° W, 46°20' N, western France Vertical Airphoto/Image. Type. MSS 50 m resampled resolution Scale. 1: 665 000 Acquisition date. September 1981 Source. Personal archive Comments. An extensive area of reclaimed land, indicated Bt1g, is delineated in the center of this Landsat subscene at the northern extremity of the Aquitaine Basin. The red band of land across the north of the image is the south margin of the Brittany Massif labelled J3.2. The reclaimed area is the Marais Poitevin, 70 km long by 25 km broad. It is a depression in the regional Upper Jurassic limestone plateau caused by reactivation during the Tertiary of faults in the Hercynian basement. Marine clays were deposited in the depression by the post-glacial Flandrian transgression. Drainage of the extensive salt marshes developed on the sediments was undertaken by the construction of sea dykes in the twelfth century and continued, following a period of disuse, by the cutting of a series of canals towards the end of the 18th century. The poldered area now consists of two zones, distinguished spectrally in the image; a bluish-speckled drier area of cropland and pasture covers 2/3 of the land; the remaining area, which appears bright red, consists of hedged, wetter market gardening fields. The higher moisture is maintained by surrounding dryland streams flowing into the margins of the depression, particularly at the east end. The inset frame locates the coverage of the stereomodel of Fig. Bt1g-2.
Bt1 · Lagoons
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Bt1 · Lagoons ▼
Fig. Bt1g-8. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 370 000 Acquisition date. August 1978 Source. USGS Comments. A major example of polder development is presented in this Landsat subscene of two contiguous units of four constructed to date in the Netherlands. The northern unit, densely agricultural, is 54 000 ha. East Flevoland, constructed between 1950 and 1957, enclosed by 90 km of dykes. The attached southern unit showing bare land in August 1978, is 43 000 ha South Flevoland, constructed from 1959 to 1968, enclosed by 70 km of dykes. The 4 km by 5 km bright rectangle on the west side of East Flevoland is Lelystad, the administrative and industrial center for the entire Dutch polder project, it is named after Dr. C. Lely, the project conceptor. The first two polders, off-scene, Wieringer, 20 000 ha, and Noordoost, 48 000 ha, were constructed between 1927 and 1930, and 1937 to 1942 respectively. A last unit, Markerwaard, to be 56 000 ha, northwest of South Flevoland, is still in planning and design stages. Collectively, these five polders will have increased the cultivated area of Holland by 10%. They lie from 2 to 6 m below sea level and are kept dry by a system of diesel and electric pumps, three around East Flevoland, and the same number for the South unit. In addition to dyking and pumping, another of the major requirements preceding usability of the reclaimed land has been desalination of the marine clay soil by leaching and spread of gypsum, which forms a highly soluble compound with the sodium chloride. Soil compaction brought about by land drainage has caused significant land subsidence. In a number of areas this can attain 50 to 100 cm. Local structures then require 5 m long piles. The marine environment in which the entire reclamation project is located in the tidal accumulation plain of the Zuider Zee, a basin of the North Sea, the remnant of which is now named Ijsselmeer and is protected from North Sea storms by the 30 km long Afsluitdijk 50 km northwest of these polders. Amsterdam, with its port installations on the North Sea Canal can be seen 20 km west of the South Polder. The extensive dark-toned land area on the east margin of the image is an infertile scrub and brush covered glacial morainic mass. See also Fig. Bt1g-1.
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Division 4 · Surficial Deposits
Sub-group Bc Coastal Plains Bc1
Bc1 Plains of Marine Sediments Characterization Coastal plains are underlain by repetitive sequences of Cenozoic marine deposits. These represent transgressiveregressive cycles of sedimentation caused by eustatic or tectonic changes in sea level. Plains of recent marine sediments occur on surfaces that are emerged portions of continental shelves. Lagoons Bt1 are a transitional zones between the plains and the present continental shelf. The sediments are not fixed in time and space and migrate laterally and vertically. They are relatively thin, overlying the older substrates. Typical thicknesses of about 10 m occur in the Netherlands and on the French Atlantic coast. They consist of various unconsolidated well-stratified beds of dominantly siliclastic fine sands, silts and cohesive clays. They were deposited during a eustatic marine transgression (Flandrian) following the last (Wisconsinan, Würm) continental glaciation, 30 000–10 000 a. In a regional setting the marine plains can often be seen to occur between embayed coastal river valleys. Strata have a gentle seaward dip generally <2°. The plain topography includes local occurrences of fluvial, aeolian, and organic (peat) deposits. The “a” and “e” terrace Components are frequent on many coastlines of marine plains. Geounits Bc2, Bc3, Bc4 characterize specific types of marine plains where over 60% of the global population live today.
Geohazard Relations Unless they are oxidized and preconsolidated these sediments have a generally low bearing capacity. Widespread subsidence problems occur on extensive soft clays. When confined and loaded, pore-water pressure increases and shear strength decreases. Where saturated, dewatering may cause consolidation over a large area. Settlement of structures increase with imposed load.
Group B · Marine Littoral Systems
As a result, slopes are generally unstable except in shallow dewatered cuts with gentle gradients. As with other low-lying coastal geounits marine plains are susceptible to storm surges and tsunami runups. A notable event occurred on 26 December 2004 in the northeast Indian Ocean. The tsunami was generated by a 9.0 Richter magnitude earthquake in the highly seismic subduction zone of the Indo-Australian and southeast Asian plates off the northwest coast of Sumatra. With no warning system in place the associated runups devastated the coast plains of northwest Sumatra, east India, east Sri Lanka and west Thailand. Losses in human lives exceeded 300 000. Property and infrastructure losses were estimated by insurers as being in the area of $14 billion. The susceptibility of these plains to sea-level rise is discussed in the Note on that topic.
Select Bibliography Gabilly J (1978) Poitou Vendée Charentes. Guides Geologiques Régionaux. Masson, Paris, p 136 Goudie AS (1992) Environmental change, 3rd edn. Clarendon Press, Oxford, chap 6 Goudie AS, Atkinson BW, Gregory KJ, Simmons IG, Stoddart DR, Sugden D (eds) (1994) The encyclopedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, pp 189–190 Harvey N (ed) (2006) Global change and integrated coastal management. The Asia-pacific region. Springer-Verlag Kraft JC, Chrzastowski MJ (1985) Coastal stratigraphic sequences. In: Davis RA Jr (ed) Coastal sedimentary environments, 2nd edn. Springer-Verlag, New York, pp 626, 638–640 Mörzer Bruijns MF (1979) Spectrum atlas van de Nederlandse landschappen, vierde druk. Uitgeverij Het Spectrum, Utrecht/ Antwerpen, p 13 Schwartz M (ed) (2005) Encyclopedia of coastal science. SpringerVerlag van Zuidam RA (1985/1986) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publishers/ITC The Hague, pp 232–274
See also Select bibliography for Marine Littoral Geounit Subgroups. Note concerning long-term sea-level rise. Note concerning tsunami runups following Geounit Bp1.
Bc1 · Plains of Marine Sediments ▼
Fig. Bc1-1.
Location. Geographic. 07° 22' E, 53°39' N, northwest Germany Source. LAR, 1977 Comments. This is a view of the flat agricultural land of the North Sea Coastal Plain of East Friesland. The farmstead in the center of the photo is located on a low, 2 to 3 m high mound. The site is one of numerous similar structures known as “terpen“ which are scattered about the coastal plains of northwest Germany and north Holland. They are relict storm surge refuge-mounds built prior to the dyking of the coasts in the 13th century. Other natural elevated ground areas which historically focused regional settlement are outcroppings of Pleis▼
Fig. Bc1-2.
Location. Geographic. 140°23' E, 08°30' S, southeast Papua, Indonesia Source. LAR, January 1987 Comments. The photo shows a system of drainage canals, some of which are concrete lined, that are located in the swales of a series of low Bw4 beach ridges on which the town of Merauke is sited at sea level on the Arafura Sea coastal plain. The town was founded by Dutch authorities in 1902 and now has a population of about 250 000.
tocene glacial till “halligen” and higher areas of outwash sands, “sand geest”.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bc1-3. Location. Geographic. 120°56' W, 35°27' N, central California, USA Source. LAR, January 1975 Comments. The photo shows a 30 m “e” Component, eu- or isostatic terrace, of a coastal plain 5 km east of Point Estero of Fig. Br4.1-1.
Fig. Bc1-4. Source. Personal archive Comments. View northeastward circa 1942 of the irrigated and now partly urbanized Sele Plain south of Salerno Italy. The plain is structurally a 35 km broad Quaternary Unit 17 graben structure infilled with 1 000 m of detrital sediments.
The Ec1 dune belt is now covered by pine plantations. The plain is backed by Fu1 piedmont fans of the first peaks of the southern Apennines. The circle encloses the 5th century bc Greek Poseidon Temple.
Bc1 · Plains of Marine Sediments
Fig. Bc1-5. Location. Geographic. 0°41' W, 37°38' N, southeast Spain Source. Putnam WC, et al. (1960) Natural coastal environments of the world. Univ. of California, Los Angeles, p 105, fig 34 Comments. An air perspective view westward shows a plain of marine sediments at Cabo Palos near Cartagena. The
cape itself is a Br7 bedrock plain. The Bt1g area appears to be a polderized zone behind an enclosing beach ridge. An area of free dunes is at Ec3. The agricultural land on the low plain of the cape in the photo is now completely urbanized.
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bc1-6. Source. Unattributed Comments. The air perspective view is a closeup of infilled trenches cut by placer diamond mining operations at Port Nolloth on the Namib Coastal Plain of Namaqualand, South Africa. The trenches are also resolved in the Landsat image of Fig. Bc1–12.
Fig. Bc1-7.
▼
782
Location. Geographic. 159°45' W, 22°00' N, Hawaii Vertical Airphoto/Image. Type. Colour infrared airphoto Scale. 1: 80 000 Acquisition date. Not given Source. NASA Comments. This photo covers the Mana Plain on the western coast of the Vc2 shield volcano of Kauai Island. The island is unique as a coastal plain in the Hawaiian Islands. It is 25 km long by 3 km at its widest; it is covered by pineapple plantations. The plain was formed by the combined effect of currents flowing northwest from the south coast
and southwest from the northwest coast. An area of raised beach ridges occupies the south part of the plain, and a 5 km long belt of Ec2 dunes up to 30 m high are blowing inland at the north end. In 1946 a tsunami with a runup of 11 m struck the plain, but caused little damage because of the lack of habitation. The bent-appearing linear feature in the center is a two-runway airstrip. Bw4.1 is an area of raised beaches. The dissected terrain inland consists of Lower Tertiary lavas (Napali Formation) rising from 200 to 500 m. Figure Vc2-3 is 15 km inland in a younger lava formation.
Bc1 · Plains of Marine Sediments
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Fig. Bc1-8. Source. NASA/JPL Comments. These images show a 27 km stretch of coast 80 km north of Phuket Airport. Grey areas are where vegetation was stripped away by the tsunami runup. The image on the right is a copy of the 31 December scene using SRTM data (Shuttle Radar Topographic Mission) highlighting in red areas that have elevations within 10 m of sea level.
Innundations and runups reached to 9.7 m in height at localities in the Phuket area. The seismic epicenter, at Simulue Island off the northwest coast of Sumatra, was a rapid slip along the fault plane of the interface of the India and Burma Plates. At 1 300 km this is the longest fault rupture ever observed. 230 000 lives were lost in this tsunami.
Bc1 · Plains of Marine Sediments
Fig. Bc1-9. Vertical Airphoto/Image. Type. SIR-A, 40 m resolution Scale. 1: 435 000 Acquisition date. 13 November 1981 Source. USGS Comments. The framed area of this segment of a radar image is the coverage of the TM subscene of Fig. Bc1-10. The different spatial resolutions should be kept in mind in comparing the two figures. (The spatial resolution of the TM image is the same as that of the wide beam mode of the current RADARSAT satellite whose other resolution 50 M – ScanSAR Narrow beam mode is similar to the older SIR-A satellite).
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Division 4 · Surficial Deposits
Group B · Marine Littoral Systems
Bc1 · Plains of Marine Sediments ▼
Fig. Bc1-10.
Location. Geographic. 76°59' W, 34°55' N, southeast coastal plain Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 286 000 Acquisition date. Not given Source. USGS Comments. This Landsat subscene is the framed area of Fig. Bc1-9, it covers a 65 km by 35 km segment of the Late Pleistocene to Holocene marine sediments of the lower coastal plain of North Carolina just north of Cape Lookout, and shows the typical regional pattern of landforms land cover and land use. At upper right is the south extremity of Pamlico Sound, an extensive Bt1 lagoon enclosed by the off-image Cape Hatteras Bw3.1 bay barrier complex. The 5 km wide Fw3 estuary of the Neuse River empties into the Sound. All the land is near sea level, and includes Bt1c salt marshes, (rusty, upper right), inland wetlands (smooth green upper center) and a 15 km by 10 km area of reclaimed wetland (bright checkerboard). This interpretation can be compared to the returns of the radar image in the framed area of Fig. Bc1-9.
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Division 4 · Surficial Deposits
Fig. Bc1-11. Vertical Airphoto/Image. Type. Radarsat Scan SAR, narrow, mosaic Scale. 1: 8 500 000 Acquisition date. Not given Source. RADARSAT-1 data © Canadian Space Agency/ Agence spatiale canadienne 1996. Received by the Canada Centre for Remote Sensing. Processed and distributed by RADARSAT International Comments. Three major Quaternary coastal plains are delineated on this mosaic of the 745 000 km2 island of Borneo, which is Indonesian Kalimantan territory on the south and Malaysian Sarawak on the northwest. The plains are emergent portions of the Sunda Shelf, the world’s largest continental shelf, which includes the Java Sea to the south and the South China Sea to the north-
Group B · Marine Littoral Systems
west. The shelf is shallow, everywhere less than 200 m deep. It is thought to be a Late Cretaceous peneplain of the tectonically more stable Indosinian Sub-plate. The largest, south central platform, is 575 km long and reaches 200 km inland. Its shores are largely Bt1c mangrove swamps, with dominantly evergreen tropical forest inland. The only major town on the south coast is Banjarmasin at its east end. Kuching and Sibu are the only towns of importance on the Sarawak Plain. Figures Fw4-6 and Fw4-7 are larger scale SIR-A and Landsat images of part of the Kapuas Plain on the west. The mountainous core of the island is a composite of Cretaceous continental terranes. The eastern sector consists of Cenozoic sedimentary basins (e.g. Kutei) which are the site of oil fields.
Bc1 · Plains of Marine Sediments
▼
Fig. Bc1-12.
Location. Geographic. 16°50' E, 29°07' S, Namaqualand, South Africa Vertical Airphoto/Image. Type. MSS, 80 m resolution Scale. 1: 692 000 Acquisition date. February 1981 Source. USGS Comments. A complex coastal plain is delineated on this Landsat subscene covering the southern part of the Namib Desert. The plain is a Bc1e Tertiary erosion surface cut on cratonic basement rocks. The partly Ef1 sand sheet and Ef2 sand streak-covered surface rises from beaches, eustatic shore platforms, and low cliffs to elevations of 300 m north of the Orange River whose mouth is at Alexander Bay. White arrows point to faintly discernible grid line patterns along the shore zone. These lines are the traces of extensive placer diamond mining operations in fossil marine sediments. These reserves have been almost completely exhausted. Figure Bc1-6 is a closeup of these parallel trenches at Port Nolloth at the southern arrow. The river is the boundary between South Africa and Namibia in northwest corner. ▼
Fig. Bc1-13.
Location. Geographic. 64°53' W, 17°41' N, Virgin Islands Geologic. North Caribbean Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 23 600 Acquisition date. 1954 Source. Unspecified U.S. government agency Comments. The stereomodel at Long Point on southwest St. Croix Island, shows a delimited (<10 km2) plain of marine Tertiary and Cretaceous sediments rising gradually to 30 m in an area of hill lands 120 to 250 m high. See also Figs. W4-7. and Bw3.1-5.
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Division 4 · Surficial Deposits
Fig. Bc1-12. (Caption on p. 789)
Group B · Marine Littoral Systems
Bc1 · Plains of Marine Sediments
Fig. Bc1-13. (Caption on p. 789)
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Bc2
Division 4 · Surficial Deposits
Bc2 Passive Margin Sediments Characterization In contrast to continental margins that are zones of active convergence, passive margins are characterized by low levels of tectonic activity once plate divergence has ceased. Marine terrestrial Tertiary and Cretaceous sedimentary sequences exposed on subaerial portions of broad passive margin continental shelves occur on the Atlantic and Gulf coasts of the United States, the Canadian Arctic Continental Terrace of the western Queen Elizabeth Islands and on some sectors of the Patagonian and African coasts. These sediments cover over 800 000 km2 in the U.S. (This is greater than the combined areas of the national territories of the United Kingdom and France.) The sediments consist of a thick (1 100 m) wedge of generally nonindurated (local ironstone and calcrete), seaward dipping sediments of dominantly marine origin. They are a succession of cyclic sediments deposited in transgressing and regressing seas. Upper Cretaceous are the dominant Cretaceous deposits; they include gravel, sand, clay, limestone, chalk, marl and some volcanic ash. Lower Tertiary sediments are mostly marine limestone and sand and some nonmarine clay and sand. The seaward boundary of the Unit is at the limit of Bc1 marine sediment unit. The inland boundary follows the boundary between Upper Cretaceous and older rocks. This inner edge is over 300 m a.s.l. The topography is marked by a succession of alternating cuestas on resistant rocks, and lowlands on weak rocks. Differential erosion has developed local reliefs of 30 to 75 m in a hilly landscape.
Group B · Marine Littoral Systems
Alluvial terraces Fv2k representing stages in an erosion sequence, overlie the Unit in some areas. In the west Gulf coast area in Texas, extremely large amounts of sediments were deposited during the Tertiary and contemporaneous growth faults were formed. Numerous salt diapirs, Geostructure 11, that have intruded through incompetent rocks occur in the Unit along the Gulf Coast.
Geohazard Relations Low sediment bearing capacities, landsliding, subsidence, flooding and storm surge are the main geohazards associated with this Unit. Bearing capacities are fair in sands and gravels and low in silts and clays. There is landsliding Ms1 susceptibility in the clay-rich Cretaceous deposits in Texas and Maryland. Lower-lying occurrences of the Unit are susceptible to flooding and storm surges. The susceptibility of the seaward boundary of these sediments to sea-level rise is discussed in the Note on that topic.
Select Bibliography Deschamps F, Braun J, Dauteuil O, Rouby D, Robin C, Guillocheau F (2007) 3D numerical modelling of the dynamic of the relief of African passive margins: Implications for sedimentary systems and surface transfers. Proceedings of the Evolution of the African Topography Converence, November 2007 Lowrie A, King Jr DT (2007) Roles of geologic processes along passive continental margins suggest dynamic interrelationships of cause and effect. Proceedings of AAPG and AAPG European Regional Energy Conference Lucazeau F, Brigaud F, Leturny P (2003) Dynamic interactions between the Gulf of Guinea passive margin and the Congo River drainage basin: 2. Isostasy and uplift. J Geophys Res 108(B8):2384 Walker HJ, Coleman JM (1987) Atlantic and Gulf Coastal Province. In: Graf WL (ed) Geomorphic systems of North America. GSA Centennial Special Volume 2, pp 51–110
Bc2 · Passive Margin Sediments
Fig. Bc2-1. Location. Geographic. 80° W, 33° N scene center, southeast coastal plain Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 500 000 Acquisition date. 3 October 1989 Source. USGS Comments. The red line on this Landsat subscene marks the seaward limit of the subaerial portion of passive mar-
gin sediments marked by traceable raised beaches of onlapped Late Pleistocene Bc1 sediments at Charleston, South Carolina. The rocks are Eocene and Oligocene sediments with local relief of <30 m. The two large water bodies are the Lake Marion and Lake Moultrie Resevoirs, at elevation 90 m, of a hydro-electric power project. The Fw3 estuaries of the Ashley, Cooper and adjacent rivers are prominent. This scene is 350 km south of Fig. Bc1-10.
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Division 4 · Surficial Deposits
Fig. Bc2-2. Location. Geographic. 96°15' W, 33°25' N, south Texas Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 25 000 Acquisition date. Not given Source. Unspecified U.S. government agency Comments. The photo shows two contrasting soils and associated land uses developed from Upper Cretaceous sedimentary rocks of the northwest extremity of the Gulf
Group B · Marine Littoral Systems
Coastal Plain, 80 km northeast of Dallas and 450 km inland from the Gulf shoreline. The area is in Black Prairie one of coastal plain belts, structurally it is the East Texas Embayment of the Gulf Coastal province. The location is at the White Rock Escarpment which divides the light-toned relatively resistant Kc2 chalk of the Austin Formation from the darker weak marly Bc2 clays and shales of the Taylor Formation. The clay-rich sediments, traditionally supporting cotton as a major crop, have a relatively high landslide susceptibility.
Bc3 · Glaciomarine Plains
Bc3 Glaciomarine Plains Characterization As continental ice margins withdrew in Late Wisconsinan/Würm at the end of the last glaciation (8–12 ka), marine incursion flooded lowlands that had been isostatically depressed by the ice sheets principally in Canada, Scandinavia and northern Germany. Deep water silts, clays and some fine sands, varying from massive to finely stratified, were deposited in the lowlands during the approximately 3 ka period that the sea remained. Isostatic readjusment caused progressive shoaling which exposed the sediments as glaciomarine plains. Relatively thin deposits near regressive shorelines consist of stratified sands and silts. Where glacial till is near the surface raised shorelines are washed bouldery or gravelly lag deposits (see Fig. L1-3). According to Aylsworth and Lawrence (2003) In eastern Canada the marine sediments average 30 to 50 m thick generally over glacial till, but may attain thicknesses of 100 m in a few areas.
loose shear strength and liquefy to produce Mf1 retrogressive flows and Mf2 earth flows. These are numerous in Champlain Sea plains in eastern Canada where more than 750 had been counted up to 1974. Data on 50 large failures indicated that loss of life exceeded 100 persons and loss of upland soil exceeded 40 000 ha.
Select Bibliography Aylsworth JM, Lawrence DE (2003) Earthquake-induced landsliding east of Ottawa. A contribution to the Ottawa Valley Landslide Project. 3rd Canadian Conference on Geotechnique and Natural Hazards, Edmonton, Alberta, pp 57–64 Danilov ID, Roujansky VE (1996) Late Pleistocene glaciation of the Arctic shelf and adjacent plains of northern Eurasia: Cryogenic and tectonic evidence. Permafrost and Periglacial Processes, vol 7, issue 1, pp 13-19 Occhietti S (1989) Quaternary geology of St. Lawrence Valley and adjacent Appalachian subregion. In: Fulton RJ (ed) Geology of Canada, no 1, Quaternary Geology of Canada and Greenland. GSC, pp 363, 364, 375–377 Vasiliev A, Kanevskiy M. Cherkashow G, Vanshtein B (2005) Coastal dynamics of the Barents and Kara Sea key sites. Geo-Marine Letters,pp 110-120 Weddle TK, Retelle MJ (2001) Deglacial history and relative sea-level changes, northern New England and adjacent Canada. GSA Special Paper 351
Geohazard Relations These clays have an unstable particle structure and a high natural moisture content. If disturbed, the sediments may
Fig. Bc3-1. Source. Transportation Research Board (1996) Landslides: Investigation and mitigation. National Research Council, Washington, D.C., Special Report 247, fig 24-2, p 606. Reproduced with permission Comments. This graphic is a simplified down-valley cross section of glaciomarine plain clay deposits of eastern Canada. The stratigraphy is of the massive clay formation, averaging 30 m thick, confined between two relatively pervious boundary layers. The surficial layer is 2 to 4 m thick and is composed of Fw fluviodeltaic sands (see Fig. Bc3-9).
See note concerning long-term sea-level rise following Geounit Bp1. See also Geounits Mf1 and Mf2.
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Fig. Bc3-2. Source. LAR Comments. The photo shows an open, main drainage ditch typically associated with agriculturally developed poorly-drained clays, in this case the glaciomarine Champlain Sea in the vicinity of Montreal in the upper St. Lawrence Valley, Quebec, Canada. See the feature in the vertical airphoto of Fig. Bc3-6.
Fig. Bc3-3. Location. Geographic. 128°35' W 54°30' N, western British Columbia Source. Clague JJ (1984) Quaternary geology and geomorphology, Smithers–Terrace– Prince Rupert Area, BC. GSC Memoir 413, p 39, fig 37 Comments. The photo shows a veneer of 2 m of lighttoned glaciomarine clays/ muds overlying deltaic sands, at 100 m elevation at Terrace in the Skeena River Valley, 110 km upstream from Chatham Sound.
Bc3 · Glaciomarine Plains
Fig. Bc3-4. Location. Geographic. 75°14' W, 45°37' N, southern Québec, Canada Source. LAR, August 1991 Comments. An exposure of glaciomarine sediments of the Champlain Sea in a stream cutbank north of Thurso on the Ottawa River. The vegetated scarp is unstable, probably being undercut by high volume spring flows.
Location. Geographic. 73°55' W, 45°15' N, southern Québec Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 12 000 Acquisition date. 1958 Source. Personal archive Comments. Photo shows the typical landscape of Holocene glaciomarine sediments in an agricultural region. The locality is in the eastern Canadian Champlain Sea sediments of the upper St. Lawrence River Valley as pictured in Fig. Bc3-5. The flat, uniform surface, the regular field pattern and the necessary system of parallel buried tile drainage in the impermeable clays, are all characteristic of the geounit. The arrow points to an open master drain ditch as pictured in Fig. Bc3-2. This photo should be compared to the photo in Fig. Bc3-7 in northwest Germany. See the stereo photos of Fig. Bc3-8 and single photo of Fig. 18-4. This tile pattern is also detectable on large scale high resolution satellite images.
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Fig. Bc3-6.
Source. Personal archive Comments. An air perspective photo looking northeast on 14 November 1956 over the upper St. Lawrence River Valley, Canada. The view is 20 km east of Montreal across the glaciomarine plain of the Champlain Sea that invaded the valley. The characteristic tile drainage lines in clay soils are visible in the agricultural fields. The mountain in upper left is Mont Bruno, one of a line of Cretaceous intrusive Monteregian Hills that occur in this part of the St. Lawrence Lowlands. See the related Figs. Bc 3.2, Bc3-6 and Bc3-8.
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Fig. Bc3-5.
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Fig. Bc3-5. (Caption on p. 797)
Group B · Marine Littoral Systems
Bc3 · Glaciomarine Plains
Fig. Bc3-6. (Caption on p. 797)
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Fig. Bc3-7. (Caption on p. 802)
Group B · Marine Littoral Systems
Bc3 · Glaciomarine Plains
Fig. Bc3-8. (Caption on p. 802)
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Fig. Bc3-7.
Location. Geographic. 09°12' E, 53 54' N, Schleswig-Holstein, Germany Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 13 400 Acquisition date. Not given Source. Zeiss-Aerotopograph München. Bayerisches Staatsministerium für Wirtschaft und Verkehr, Freigabe Nr. G10/312 Comments. This photo is near the North Sea entrance of the Nord-Ostsee (Kiel) Canal, just northeast of the port of Brunsbüttel on the estuary of the Elbe River. The site is on the Dithmarscher Marsch, on interbedded clays and sands of the glaciomarine sediments of northwest Germany. These coastal areas have been largely reclaimed by dyking (polderized) from the partial submergence of the coast during the postglacial Flandrian transgression. The photo is the same scale as that of Fig. Bc3-6 in eastern Canada. The same morphology is displayed, including the characteristic tile and ditch patterns. Google Earth shows significant changes in land use here. Nautical/industrial note: The canal, which saves 250 nautical miles of sailing to join the North Sea to the Baltic, was built between 1887 and 1895, it is 98 km long, 100 to 250 m wide and has an 11 m draught. It is the world’s busiest artificial waterway, with over 42 000 transits in 2005. The reservoir tanks, settling pond and loading dock are related to the regional Sasol chemical works. The settling pond has since been reclaimed and is now vegetated. Road vehicle ferry crossing boats can be seen in midchannel near the docking facility. ▼
Fig. Bc3-8. Location. Geographic. 73°36' W, 45°11' N, southern Québec Geologic. Champlain postglacial sea Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 12 000 Acquisition date. Unspecified (1975) Source. Personal archive Comments. A stereomodel oriented northeast of a location in the postglacial Champlain Sea of the St. Lawrence Lowlands near Montreal shows the dark flat uniform glaciomarine sediments with their characteristic intensive land use and associated drainage ditches and buried tile traces of Figs. Bc3-5, Bc3-6, and Bc3-7. These patterns are in marked contrast to those of the brighter outcropping undulating relief of glacial till, (Gf4), coded Gt2. The dark tone of the marine sediments is partly due to the organic and moisture content of these soils.
Fig. Bc3-9.
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Location. Geographic. 74°57' W, 45°31' N, Ottawa–St. Lawrence Lowlands, eastern Ontario Geologic. Glaciomarine plain on Paleozoic basin of ancient rift system Vertical Airphoto/Image. Type. Natural colour, stereo triplet Scale. 1: 40 000 Acquisition date. 11 May 1975 Source. Courtesy of Natural Resources Canada, NAPL A 31010-61, 62, 63 Comments. The stereomodel shows the characteristic level topography of glaciomarine clays at Plantagenet in the South Nation River Valley. The typical tile drainage is faintly discernible as patterns of parallel darker lines in some of the brighter fields. Closer views of this photo diagnostic artificial drainage are provided in Figs. Bc3-5, Bc3-6, Bc3-7 and Bc3-8. Overlying terraces of Fw3 deltaic sands (see Fig. Bc3-1) are distinguished by distinct land cover and land uses and brighter colour tones. Figure Mf2-6 discusses the old earth flows delineated here.
Bc3 · Glaciomarine Plains
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Bc3 · Glaciomarine Plains ▼
Fig. Bc3-10.
Location. Geographic. 72°00' W, 48°40' N scene center, central Québec Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1 800 000 Acquisition date. Not given Source. This Landsat image is supplied by the Canada Center for Remote Sensing and is reproduced with the permission of the Minister of Public Works and Government Services (2005) Comments. The Landsat subscene is centered on Lac St. Jean in the Saguenay Graben in the Grenville Province of the eastern Canadian Shield. The delineated areas are the glaciomarine sediments of the Laflamme Sea which invaded the depression 10 000 bp. Distinguishing spectral elements are the yellow of the agricultural zones which are coextensive with the glaciomarine sediments, and the blue of interspersed wetlands bearing the descriptor Y5/Bc3. Spatial elements are the geolineaments in the Proterozoic anorthosites north of the depression and contemporaneous granites to the south. See the large local retrogressive slide of Fig. Mf2-5. Figure 19.1-5 is a SAR image that covers the eastern 25 km of this image.
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Group B · Marine Littoral Systems
Bc4 Fluviomarine Plains
of geounits Fv2 or Fu1. Where both are in close association their respective geohazards should be considered.
Characterization
Select Bibliography
On some coastal plain areas Holocene marine sediments are crossed by a number of rivers that reflect the downward slope toward the sea, or are bordered or covered by piedmont alluvial aprons or fans.
Kuenzi WD, Horst OH, McGehee RV (1979) Effect of volcanic activity on fluvial-deltaic sedimentation in a modern arc-trench gap, southwestern Guatemala. GSA Bull 90:827–838 Monroe WH (1980) Some tropical landforms of Puerto Rico. USGS Prof Paper 1159, pp 24–25 Travaglia C, Mitchell CW (1982) Applications of satellite remote sensing for land and water resources appraisal in the People’s Democratic Republic of Yemen. FAO Remote Sensing Center Series 9, TCP/PDY/0104(Mi), Technical Report Zuquette LV, Pejon S-J, Quintos dos Santos Collares J (2004) Engineering geological mapping developed in the Fortaleza Metropolitan Region, State of Ceara, Brazil. Eng Geol 71(3–4):227–253
Geohazard Relations Where marine sediments are dominant in occurrence the geohazard relations will be those of geounit Bc1, where fluvial deposits dominate the geohazards will be those
Fig. Bc4-1. Location. Geographic. 140°50' E, 08° S, southeast Papua, Indonesia Geologic. Platform cover Papuan Shelf lowlands Source. LAR, 1987 Comments. An exposure of fluviomarine coastal plain sedimentation. Brown Fv2 alluvial deposits from the central mountains overlie grey Bc1 marine sediments of the Arafura Sea.
Fig. Bc4-2.
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Location. Geographic. 77°01' W, 12°10' S, central Peru Source. Johnson GR (1930) Peru from the air. American Geographical Society, p 106, fig 99 Comments. An air perspective view of the Pleistocene fluviomarine plain with a 30 m terrace, eustatic and/or related to Andean tectonics, at Chorrillos and Playa Agua Dulce, 12 km south of Lima. The sediments are coarse, of paleo alluvial fan of the Rimac River, overlying Pleistocene marine sediments. The hills on the right are Lower Cretaceous faulted sandstones. The photo was taken between June 1928 and January 1930. The entire plain is now urbanized beyond the coverage of the photo, including the site of the Lima International airport.
Bc4 · Fluviomarine Plains
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Group B · Marine Littoral Systems
Bc4 · Fluviomarine Plains ▼
Fig. Bc4-3.
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Fig. Bc4-4.
Location. Geographic. 44°53' E, 12°54' N, southwest Yemen Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 368 000 Acquisition date. October 1975 Source. USGS Comments. Landsat subscene covers 85 km of the arid 30 to 40 km wide fluviomarine plain at Aden with a 50 km long Bw5 spit beach The plain is overlain inland on the west and north by Ef1 sand sheets and Ed sand dunes. Irrigated cropping adjoins local (red) Fv1.2 wadis. A dark Bt1e sabkha occurs at the eastern end of the spit beach. The volcano island is depicted in the stereogram of Fig. Vc1.1-8. See also another landsat scene of this region in Fig. Vc1.1-13.
Fig. Bc4-5.
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Location. Geographic. 02°50' E, 43°15' N, southern France Vertical Airphoto/Image. Type. MSS 50 m resampled resolution Scale. 1: 500 000 Acquisition date. 22 November 1981 Source. Personal archive Comments. Landsat subscene which is a continuation northward of Fig. Bt1c-9 covers the 70 km long southern part of the northern 25 km wide Languedoc Coastal Plain of Tertiary and Quaternary sediments. The sediments of this plain reflect the fact that the region is an ancient gulf of the sea, several times covered by marine trangressions alternating with periods of emergence and terrestrial sedimentation. The deep red areas are interpreted as zones of high concentration of viticulture on Quaternary marine sediments. The speckled land is probably a mix of cereal, olive cultivation and fruit orchards. The inset frame locates the stereo photopair of Fig. Bt1g-5. The plain is enclosed on the north by the forested folds of Lower Paleozoic schists and limestones of Montagne Noire which is the southern extremity of the Central Massif, and on the south by the equally forested calcareous hills of the Cretaceous Corbières. The shallow Bt1 Sigean and Leucate lagoons at the south end of the plain are relicts of the Flandriain worldwide post-glacial sea level rise. Due to their occurrence in a tideless sea and the absence of water fluxes, these Mediterranean lagoons lack tidal flat, tidal delta, and washover fan morphosedimentary Components typical of other lagoons. Additionally, despite a limited input of freshwater from inland, engineered channels from the sea and the regional climate have rendered them hypersaline. The S1.2-E area of molassic sediments to the west is discussed in Fig. S15-8.
Location. Geographic. 13° E, 41°25' N, central Italy Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 320 000 Acquisition date. 11 October 1985 Source. Unattributed Comments. A Landsat subscene of the Apennine fold-andthrust chain covers the 55 km long by 15 to 30 km broad Pontine Plain 50 km south of Rome. It is bounded on the west by the Quaternary Pf1.3 tephra of the Alban foothills, and on the north and east by the Mesozoic karstic Lepini and Ausoni Mountains. Spectrally the plain is strikingly divided into two roughly equal parts which reflect hydrogeologic and land use differences. TM band 5 is an infrared water absorption band, while band 4 is the infrared peak vegetation reflectance band. The northern, dark half is composed of clastic deposits. These consist of residual clay from chemical weathering of carbonates, and have a high content of organic matter, both resulting in a concentration of high yield crops. The soil had a high moisture content at the date of scene acquisition, rainfall occurs in the region almost uninterruptedly from mid-autumn to late spring. The coastal half consists of marine lagoonal deposits of sand and sandy clay. Red rectangles of forest are the only growing vegetation in the zone. Wheat, fruit and wine crops have been harvested exposing a bare, light blue, soil. The red Sabaudia Forest of deciduous oak is a surviving tract of the Pontine forests destroyed by land reclamation. Three artificial lagoons were created just behind the shoreline. Each part of the plain is drained by extensive drainage systems for different reasons. Numerous springs emerge from the foot of the karst Lepini Mountains making drainage difficult in the northern zone, it has been drained piecemeal over time. The low-lying lagoonal zone required large-scale planned (75 000 ha) reclamation projects. Historically this was the most malarious area of continental Italy. For 2 000 years it defied reclamation efforts by former rulers, and was successfully reclaimed in the period 1928–1935. 2 683 km of canals were constructed, 700 km of roads, and four new towns were developed. See also Fig. Pf1.1-6.
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Fig. Bc4-4. (Caption on p. 809)
Group B · Marine Littoral Systems
Bc4 · Fluviomarine Plains
Fig. Bc4-5. (Caption on p. 809)
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Fig. Bc4-6. (Caption on p. 814)
Group B · Marine Littoral Systems
Bc4 · Fluviomarine Plains
Fig. Bc4-7. (Caption on p. 814)
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Fig. Bc4-6. Location. Geographic. 91° W, 14°29' N scene center, Guatemala Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 1 000 000 Acquisition date. 10 January 1979 Source. USGS Comments. This Landsat image covers 180 of the 850 km Pacific fluviomarine coastal plain of Guatemala and San Salvador. Although the plain is located at a convergent continental plate setting it is actively prograding. This is due to the large volumes of sediment that are carried to the plain by streams coming off an interior highland of Tertiary and preTertiary volcanic materials and a chain of active volcanoes in Guatemala and San Salvador. Eight Vc1 stratovolcanoes are visible along the volcanic front in the image. The most prominent structure is the 20 km diameter Vc3.2 Atitlan Caldera and Lake, with its three post caldera volcanoes. The volcano-derived fluvial sediments are deposited on the surface of the marine component. This component is part of the Cocos tectonic Plate island arc-trench that is terminated some 30 km inland. The coastline is characterized by a number of Bt1 lagoons and Bw3 barrier beaches. Other streams that build up this fluviomarine plain originate on the plain itself. Great loss of life, property and infrastructure was experienced along this coast in early October 2005 by the passage of a strong hurricane. This disaster is in large part attributable to the easily erodible volcanic rocks which occur in the entire Pacific watershed drained by torrential streams. In addition, the dense rural population is concentrated along the access of the Quaternary volcanoes. The image was acquired in the middle of the dry season. The darker grey areas on the east are alluvial fans with perennial grounwater sources at Escuintla and Guazacapan. The rectangular area on the coast, lower left is a zone of irrigated agriculture between Rios Coyolate and Madre Vieja.
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Fig. Bc4-7. Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 560 000 Acquisition date. June 1976 Source. USGS Comments. The Landsat subscene covers 160 of the 250 km long fluviomarine plain east and west of Jakarta (Jkt) on the Java Sea Coast of Indonesia. The Quaternary fluvial sediments, consisting mainly of volcanic materials, overlie Bc1 marine sediments. The plain is 250 km long and extends some 30 km inland to the island’s magmatic belt. Jakarta’s elevation is 8 m. Prolonged rainy season floods in early February 2007 killed 85 people in the city and surrounding districts and displaced more than 300 000.
Group B · Marine Littoral Systems
Bp1 · Subtidal Banks
Sub-group Bp Low Latitude Offshore Carbonate Platforms
which affect the populated low islands fringing the banks.
Bp1 Subtidal Banks
Reference
Characterization These banks occur in clear warm shallow water on continental shelf environments in low latitudes. They are clearly visible on various satellite images. Their world wide distribution includes occurrences in the Red Sea, Persian Gulf, northern Indian Ocean, Indonesia, Australia and the North American Carribbean. They can be source or reservoir rocks for petroleum. In the Bahamas Banks subtidal environments with normal marine waters and a limited range of salinities produce thick carbonate blankets that can be up to thousands of meters in thickness depending on rate of subsidence along the continental margin.
Geohazard Relations The principal hazards to which these bank environments are susceptible are hurricanes and flooding
Fig. Bp1-1. Location. Geographic. Caribbean region Geologic. Marine littoral systems Source. Mullins HT, Hine AC (1989) Scalloped banks margins: Beginning of the end for carbonate platforms? Geology 17:30–33, Geol Soc Am, fig 1 Comments. The map shows the bathymetry of Gulf of Mexico-Caribbean region and illustrates the related occurrence of carbonate platforms. The Bahama Banks consist of a thickness of about 200 m of raised Quaternary coral reefs and Holocene carbonate shoal sands resting on the Bahama Platform, a 4500 m sequence of carbonate sediments that have been developing since the Cretaceous. 700 low supratidal K3 karst islands make up the banks of which 26 are inhabited. The highest point in the group is 63 m Mount Alvernia on Cat Island, 50 km north of Fig. Bp1-2. The arrow and inset frame locate the coverage of Fig. Bp1-2.
Walker HJ, Coleman JM (1987) Atlantic and Gulf Coastal Province. In: Graf WL (ed) Geomorphic systems of North America. GSA Centennial Special Volume 2
Select Bibliography Cunningham KJ, Locker SD, Hine AC, Bukry D, Barron J, Guertin LA (2003) Interplay of late Cenozoic siliclastic supply and carbonate response on the Southeast Florida Platform. J Sediment Res 73:31–46 Ginsburg RN, James NP (1974) Holocene carbonate sediments on continental shelves. In: Burke CA, Drake CL (eds) The geology of coastal margins. Springer-Verlag, pp 137–156 Mullins HT, Hine AC (1989) Scalloped bank margins: Beginning of the end for carbonate platforms? Geology 17:30–33 Purdy EG, Bertram GT (1993) Carbonate concepts from the Maldives, Indian Ocean. AAPG Studies in Geology 34 Roberts HH, Murray SP (1984) Developing carbonate platforms: Southern Gulf of Suez, northern Red Sea. Marine Geology 59:165–185 Wilson JL (1974) Characteristics of carbonate platform margins. AAPG Bull 58(5):810–824 Wilson JL (1975) Carbonate facies in geological history. SpringerVerlag
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Note and Select Bibliography Concerning Long-Term Sea-Level Rise There are a number of factors that are responsible for the gradual rise in global sea levels. A significant factor is climate warming (e.g., greenhouse gas emissions into the atmosphere) which is melting ice from the Greenland and West Antarctica ice sheets and other outlet tidewater glaciers. See the Paraglacial Geosystems. Rignot and Kanagaratnam report that rising surface air temperatures appear to be triggering the increases in outlet glacier speed in the southern half of Greenland. Over the last 20 years the air temperature in southeast Greenland has risen by 3 °C. The warmer temperatures increase the amount of meltwater reaching the glacierrock interface where it serves as a lubricant that eases glacier flow to the ocean. Using satellite radar interferometry data from Radarsat-1, ERS1/2 and Envisat ASAR they measured ice velocity around the periphery of Greenland and deduced ice discharge by combining these data with ice thickness data. Taking higher glacier speeds into account, the authors calculate that Greenland contributes about 0.5 mm yr–1 to global sea rise which currently stands at 3 mm yr–1. Debates on the causes and effects of all aspects of climate change has been generating an extraordinary and continuous mass of research papers and reports on these subjects from all related scientific disciplines. The subject is additionally dramatized by news media (often inaccurately) on a daily basis. “The chief hazards associated with sea-level rise are the loss of property and infrastructure as a result of coastal erosion, and the damage to agricultural land, property, and infrastructure by flooding.” (Shaw et al. 2001).
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Fig. Bp1-2. Location. Geographic. 75°20' W, 23°20' N image center, Bahamas Vertical Airphoto/Image. Type. TM 30 m resolution Scale. 1: 420 000 Acquisition date. Not given Source. USGS Comments. The 30 by 50 km blue area on this Landsat subscene is the Long Island subtidal Bank of the Bahamas Carbonate Platform north of Cuba. 80 km of the 105 km long resort island is covered by the image. The location of the island and bank is shown as the inset frame on the map of Fig. Bp1-1. The lighter blue shoals are 3 to 8 m deep and consist of carbonate sands.
An already perceived result of this process is the rise of a new breed of displaced persons to be recognized as climatic refugees. About a third of the world’s 50 LDCs (less developed countries) are threatened by global warming and sea level rise including Bangladesh, Cambodia, Maldives and Samoa. Specific impacts include flooding due to surges in Bc1 and Bc2 units; beach migration in Bw Sub-group units and dune destabilization in Ec Sub-group units.
References Rignot F, Kanagaratnam P (2006) Changes in the velocity structure of the Greenland Ice Sheet. Science, American Association for the Advancement of Science, February 2006, pp 986–990 Shaw J, Taylor RB, Forbes DL, Ruz M-H, Solomon S (1998) Sensitivity of the coasts of Canada to sea-level rise. GSC Bull 505 Shaw J, Taylor RB, Forbes DL, Solomon S (2001) A synthesis of geological hazards in Canada. GSC Bull 548:225
Select Bibliography Bird ECF (1976) Coasts. Australian National University Press, pp 55–58 Bromwich F (2007) Insignificant change in Antarctica snowfall since the International Geophysical Year. Science 313:827–831 Gornitz V (1991) Global coastal hazards from future sea-level rise. Palaeogeography, Palaeoclimatology, Palaeoecology 89: 379–398 Intergovernmental Panel on Climate Change (IPCC) (2007) Climate change 2007: The physical science basis. Working Group I report Titus JG, Barth MC (1984) An overview of the causes and effects of sea level rise. In: Titus JG, Barth MC (eds) Greenhouse effects and sea level rise: A challenge for this generation. Van Nostrand Reinhold Ltd., New York
Note and Select Bibliography Concerning Tsunami Runups Tsunamis are ocean waves generated by sudden tectonic displacement of the sea bed associated with large, shallow focus earthquakes. The waves are very low amplitude in the open ocean, that move at up to 1 000 km h–1, and can reach heights of up to 30 m in shallow water. A tsunami breaks onto the shore as a series of waves separated by minutes to an hour or more. Wave runup is dependent on offshore bathymetry, shoreline orientation and onshore topography, being highest at heads of shallow bays when superimposed on a high tide. “Physical destruction from tsunamis occurs through a variety of mechanisms. Flotation and drag forces can move houses whilst inundation turns floating debris, such as boats, vehicles and timber, into projectiles which smash into structures. Strong wave currents undermine harbour foundations and lead to the collapse of bridges and seawalls.” (Smith 1996).
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A tsunami warning system utilizes linked seismographs that locate wave causing earthquakes, combined with estimated rates of wave travel across the open ocean. Tsunami hazard potential is not restricted to the coasts of the major oceans, it also exists along Mediterranean and Black Sea coasts. See Figs. Br7-9, Bt1-3 and Bc1-8.
Reference Smith K (1996) Environmental hazards, 2nd edn. Routledge, London, p 133
Select Bibliography Bernard EN (1991) Tsunami hazard. A practical guide to tsunami hazard reduction. Kluwer Academic Publishers, Boston Chiu W-T, Ho Y-S (2007) Bibliometric analysis of tsunami research. Scientometrics 73(1):3–17 Clague JJ (2001) Tsunamis. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:27–42 Lajoie KR (1986) Coastal tectonics. Active Tectonics, Studies in Geophysics. National Academy Press, Washington, D.C., pp 95–124 Lida K (1983) Some remarks on the occurrence of tsunamigenic earthquakes around the Pacific. In: Lida K, Iwasaki T (eds) Tsunamis – Their science and engineering. Terra Scientific Publishing Company, Tokyo, pp 61–76 Pirazzoli PA (1991) World atlas of Holocene sea level changes. Elsevier Oceanography Series 58 Pirazzoli PA (1994) Tectonic shorelines. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 451–476
Select Bibliography for Marine Littoral Geounit Sub-Groups Bascom W (1980) Waves and beaches. Anchor Press/Doubleday, Garden City, New York Bird E (2004) The world’s coasts online. Kluwer Electronic Publication Carter RWG (1988) Coastal environments. Academic Press
Group B · Marine Littoral Systems Carter RWG, Orford JD (1993) The morphodynamics of coarse clastic beaches and barriers: A short- and long-term perspective. Journal of Coastal Research, spec. issue 15, pp 158–179 Carter RWG, Forbes JD, Taylor RB (1987) Gravel barriers, headlands and lagoons: An evolutionary model. ASCE, Coastal Sediments ’87, vol 2, pp 1776–1792 Clifton HE, Hunter R (1982) Coastal sedimentary facies. In: Schwartz ML (ed) The encyclopedia of beaches and coastal environment. Hutchinson, Ross Publishing Company, Stroudsburg, PA, pp 314–322 Davis RA (1985) Coastal sedimentary environments, 2nd edn. SpringerVerlag Davis RA, Ethington RL (1976) Beach and nearshore sedimentation. Society of Economic Mineralogists and Paleontologists, spec. pub. 24 de Vriend HJ (1991) Coastal morphodynamics. ASCE, Coastal Sediments ’91, pp 356–370 Fisher JJ (1984) Regional long-term and localized short-term coastal environmental geomorphology inventories. In: Costa JE, Fleisher PJ (eds) Developments and applications of geomorphology. Springer-Verlag, Berlin, pp 68–96 Greenwood B, Davis RA (eds) (1984) Hydrodynamics and sedimentation in wave-dominated coastal environments. Elsevier, Developments in Sedimentology, vol 39 King CAM (1972) Beaches and coasts, 2nd edn. Edward Arnold Komar P (1976) Beach processes and sedimentation. Prentice-Hall, New Jersey Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 34–18, 34–9 Roy PS, Cowell PJ, Ferland MA, Thom BG (1994) Wave-dominated coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution. Cambridge University Press, Cambridge, pp 121–186 Short AD (1991) Macro-meso tidal beach morphodynamics; an overview. Journal of Coastal Research 7:417–436 Snead RE (1981) Coastal landforms and surface features. HutchinsonRoss Pennsylvania Steers JA (1962) The sea coast. Collins, London, pp 97–167 Terwindt JHJ, Battjes JA (1991) Research on large-scale coastal behaviour. ASCE, Proceedings, 22nd International Conference on Coastal Engineering, pp 1975–1983 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 34–35 Wright LD, Thom BG (1977) Coastal depositional landforms: A morphodynamic approach. Progress in Physical Geography 1:412–459
Division 4 Surficial Deposits Group G · Paraglacial Geosystems
Sub-group Gl Ice Bodies Sub-group Gf Glaciofluvial Deposits
The geounits of this Group which have geohazard relations include a Sub-group of glaciers, Gl ice bodies, and a Sub-group of glaciofluvial deposits, Gf. “We define paraglacial coasts to be those on or adjacent to formerly ice-covered terrain, where glacially excavated landforms or glaciogenic sediments have a recognizable influence on the character and evolution of the coast and nearshore deposits.” (Forbes and Syvitski 1994). We extend the term paraglacial to include inland terrains and deposits of possibly multiple glaciations in suitable distinction with the geounits of the Group Periglacial-related forms.
General Note of Geohazard Relations Tidewater glaciers calve navigation hazard icebergs. Valley glaciers are agents of deposition, flooding, falls, flows and water shortages related to their recessions. Glaciofluvial deposits are agents of erosion and deposition. Glaciofluvial deposits are the suspended and bed sediment loads of generally high energy streams of meltwater from Gl5 Valley glaciers. Their characteristics are similar to those of Fv1 braided alluvial deposits. “… meltwater discharges are characterized by violent summer floods superimposed on well-defined seasonal and diurnal discharge cycles posing costly river entrainment problems to engineers in modern glaciated areas … significant and expensive problem in construction and maintenance of road and rail networks close to modern ice margins is episodic, frequently periodic, flooding, following the failure of ice-dammed subglacial or sidevalley lakes (Mf4.3).” (Eyles 1985). An added geohazard relation of glaciers (and ice caps and ice sheets) is the effect of ice recession induced by climate change contributing to sea level rise – see Note on the subject in Group Marine Littoral Systems. At least one third of the observed sea level rise in the last 100 years has come from the melting of glaciers exclusive of the Greenland and Antarctic ice sheets. GLIMS (Global Land Ice Measurement from Space) data from the NSDIC (National Snow and Ice Data Center) of the University of Colorado Cooperative Institute for Research in Environmental Science represent the mass balances (a zero mass balance describes a situation where accumulation balances ablation, a positive mass balance describes an increase in glacier mass and a negative mass balL.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_11, © Springer-Verlag Berlin Heidelberg 2009
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ance a reduction in glacier mass) of more than 300 glaciers, on four continents, measured over the 1961–2003 time period. Although they make up only 4% of the total land ice area, they may have contributed to as much as 30% of sea level change in the 20th century due to rapid ice volume reduction connected with global warming.
References Eyles N (ed) (1985) Glacial geology. Pergamon Press, p 108 Forbes DL, Syvitski (1994) Paraglacial coasts. In: Carter RWG, Woodroffe CD (eds) Coastal evolution Late Quaternary shoreline morphodynamics. Cambridge University Press, pp 373–423
Select Bibliography Ehlers J, Gibbard PL (2004) Quarternary glaciations. Elsevier Hambrey MJ (1994) Glacial environments. UBC Press Knight P (2006) Glacier science and environmental change. Blackwell Publishing
Sub-group Gl Ice Bodies Gl4
Gl4 Outlet Tidewater Glaciers Characterization An outlet tidewater glacier is a glacier that “flows from an accumulation area so large that even at sea level the volume of ice melt each year is much less than the volume of ice carried down from higher elevations”. (Post and La Chapelle 1971). The accumulation area is an ice cap or ice field. Lateral and terminal moraines are landforms composed of till of Geounit Gf-4 that are commonly associated with outlet glaciers. They are described in Geounit Gl-5 – Valley glaciers.
Frontal Component “c” – Calving Ocean near-shore movements weaken the ice tongue from below, causing it to break up, e.g., Figs. Gl4-1 and Gl4-9. The ice mass that breaks away from the front of the glacier is an iceberg. Thus the calving occurs in what is described as the frontal component of a glacier. Calving produces an infinite variety of icebergs. Glacier bergs may calve by spalling off of the entire glacier face from top to bottom, or a partial spalling of the glacial ice above the waterline. The densities of glacial ice and of sea water are such that about one-eight of the mass of the berg is above water. The deeper drafts are commonly in the range of 100 to 200 m. A berg’s motion due to currents is in the range of 18 km d–1 (0.2 m s–1).
Group G · Paraglacial Geosystems
The natural destruction of icebergs is accomplished in two ways – by sea temperature melting during southward flow, and by repeated calving into smaller fragments. The latter is more efficient, for every break that occurs the result is a greater surface area of ice on which melting can occur. Wave and swell action on a berg is also an important decay mechanism. These mechanisms will cause a shift in the center of gravity and consequent capsizing of the berg.
Geohazard Relations Icebergs are the most dangerous aspect of ice in the sea. They differ from sea ice in many ways, they are an intense local deep-drafted hazard to navigation as opposed to the limited but widespread problem offered by shallow draft sea ice. Furthermore “The keels of icebergs frequently strike and drag on the seafloor leaving scour marks on the sediment, and may damage structures and (bottom-mounted) installations such as cables, pipelines and wellheads.”“Icebergs can be tracked by the use of beacons transmitting to satellites and also by radar.” (Lewis and WoodworthLynas 1990). The grounding and the scouring are a hazard to submarine cables and communication links as well as oil and gas operations. The contribution of outlet glaciers from polar ice fields to sea-level rise is discussed in the Note and Select bibliography on that subject.
References Lewis CFM, Keen MJ (1990) Ice scour. In: Keen MJ, Williams GL (eds) Geology of Canada, no 2, Geology of the continental margin of eastern canada. GSC, pp 785–793 Post A, La Chapelle ER (1971) Glacier ice. University of Toronto Press, p 75
Select Bibliography Bea RG (1986) Engineering aspects of ice gouging. In: Lewis CFM, Parrott DR, Simpkin PG, Buckley JT (eds) Ice scour and seabed engineering. Environmental Studies Revolving Funds, Ottawa, Rep. 049, pp 18–28 ETH Zürich (ongoing) World Glacier Monitoring Service Green HP, Reddy AS, Char, TR (1983) Iceberg scouring and pipeline burial depth. Proceedings, 7th International Conference on Port and Ocean Engineering Under Arctic Conditions. Helsinki, pp 280–288 Hotzel IS, Miller JD (1983) Icebergs: Their physical dimensions and the presentation and application of measured data. Annals of Glaciology 4:116–123 Howat IM, Joughin I, Scambos TA (2007) Rapid changes in ice discharge from Greenland outlet glaciers. Science 315(5818): 1559–1561 Ommanney CSL, Clarkson J, Strome MM (1973) Information booklet for the inventory of Canadian glaciers. Glaciology Division, Inland Waters Directorate, Department of the Environment, Ottawa, p 40
Gl4 · Outlet Tidewater Glaciers
Fig. Gl4-1. Source. Perrottet T (ed) (1997) Chile. APA Publications, pp 10–11, photo by Daniel Bruhin Comments. A closeup photo shows one of the three terminal lobes of the 28 km long Grey Glacier on Lago Grey in Torres del Paine National Park in southern Chile at latitude 50°57' S, 73°15' W. Figures give scale to the ice mass.
Fig. Gl4-2. Source. Personal archive Comments. This air view shows the subaqueous portion of a small iceberg drifting south in the eastern Canadian North Atlantic iceberg drift route. See Fig. Gl4-9.
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Group G · Paraglacial Geosystems
Fig. Gl4-3. Location. Geographic. 21°46' E, 78°16' N, Svalbard, Norway Source. Liestol O (1993) Glaciers of Svalbard, Norway. In: Williams RS, Ferrigno JG (eds) Glaciers of Europe, Satellite image atlas of glaciers of the world. USGS, PP 1386-E, p E135, fig 7 Comments. An air perspective photo, in August 1956 shows the grounded front of Freemanbreen on the southern coast of Barentsoya, one of the smaller Svalbard Islands. The heavily crevassed section of the lower part of the glacier during a surge is visible. The approximate width of the glacier at its narrowest before the expanded foot (Fig. Gl4-7) is 2.5 km. The glacier’s icefield source is in the background.
Fig. Gl4-4. Location. Geographic. 84°55' W, 82°02' N, Queen Elizabeth Islands, Nunavut Geologic. Folded Lower Paleozoic clastic and carbonate rocks of the Late Cretaceous Franklinian Mobile Belt Source. Courtesy of Natural Resources Canada, NAPL RR113L-60 Comments. This is a view northward from 150 m of the floating front of a calving outlet glacier on 27 April 1952. The glacier is flowing south from an icefield at elevation 1 500 m onto the perennial sea ice cover of Philips Inlet on the northwest coast of Ellesmere Island. A Gl5 lateral moraine is prominent. Further advance of the glacier into the inlet tends to be constrained by the calving. At this latitude only the months of July and August have mean daily temperatures greater than 0 °C. The surrounding coastal highland is at about 1 100 m altitude.
Gl4 · Outlet Tidewater Glaciers
Fig. Gl4-5. Location. Geographic. 117°24' W, 52°10' N, western Alberta Source. Ommanney CSL (2002) Glaciers of the Canadian Rockies. In: Williams RS, Ferrigno JG (eds) Glaciers of North America, Satellite images of glaciers of the world. USGS PP 1386-J, p J252, fig 24 Comments. Air perspective view to southeast shows the Columbia Glacier in Alberta at the British Columbia border. It is a major inland outlet glacier from the northwest section of the Columbia Icefield and drops over a major icefall (center of photograph). The glacier receded rapidly from the 1920s to the 1960s but advanced about 2 km between 1966 and 1986. Red lines mark the trimlines of the highest moraines (Gl5). The water just visible at the bottom edge of the photo is the beginning of a Mf4.2 moraine dam lake.
Fig. Gl4-6. Location. Geographic. 134°30' W, 58°47' N, southeast Alaska Boundary Ranges Source. Courtesy of Natural Resources Canada, GSC 99475 Comments. The air perspective view shows a group of confluent outlet glaciers. Dark bands of lateral moraines (Gl5) are prominent on the glaciers. Where two glaciers join the lateral moraines come together to form a medial moraine. Such a complex is also visible in the upper right sector of the Landsat image of Fig. Gl5-11 in the Himalayas.
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Group G · Paraglacial Geosystems
Fig. Gl4-7. Location. Geographic. 79°23' W, 75°58' N, eastern Nunavut Source. Courtesy of Natural Resources Canada, NAPL T 505L-92 Comments. A view east from 6 000 m, on 30 June 1953, of multiple outlet glaciers coded Gl4.2a on the west coast of 40 km long Coburg Island. Glaciers with such a fan shape frontal characteristic, having issued from confining valley walls are named “Expanded Foot” glaciers, see Fig. Gl4-3. Gl3 is an icefield. The island is composed of Archaean shield rocks of the Ellesmere Uplift, and its elongate shape reflects the northeast orientation of shear zones and rifting in the Late Cretaceous and Tertiary.
Fig. Gl4-8.
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Location. Geographic. 76°12' W, 72°27' N, northeast Baffin Island, Nunavut Source. Courtesy of Natural Resources Canada, NAPL T 235R-70 Comments. A view looking east from 6 000 m, 28 July 1948, shows two outlet glaciers flowing into Erik Harbour Fjord from 1 500 m high ice fields. The Gt4.1 descriptor points to the terminal moraine (Gl5) of the foreground glacier, which created an Mf4.2 moraine dammed lake at the upper end of the fjord. This glacier’s recession since 1948 has created a dammed lake within its own moraine. The same situation is evident at the glacier further down the fjord. The Gl4a glacier in background has spread to a 14 km width onto an unconfined lowland. Such a fan shaped front is also referred to as an expanded foot. The front of the foreground glacier in the fjord is 2.5 km wide. Carbon-14 ages of the moraines range between 8 100 and 6 300 bp. The glacier in the middle ground has since retreated more than 500 m creating its own moraine dammed lake. The Gl3 unit in the lower right is part of an icefield.
Gl4 · Outlet Tidewater Glaciers
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Group G · Paraglacial Geosystems
Gl4 · Outlet Tidewater Glaciers ▼
Fig. Gl4-9.
Fig. Gl4-10.
1.5 m in diameter that have just spalled off the glacier face. They are surrounded by clusters of smaller fragments knows as bergy bits. This group is drifting into Smith Sound between Ellesmere Island and northwest Greenland. Those that do not ground will join the inventory of up to about 40 000 icebergs that is maintained in Baffin Bay from the major source area on the west Greenland Coast. The currents along the east coast of Baffin Island carry many of these bergs southward over the eastern Canadian margin. A classic 150 m wide lateral moraine (Gl5) is on the southeast (right hand) side of the glacier. Satellite imagery in April 2007 shows this glacier blocked by landfast sea ice extending 9 km seaward.
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Location. Geographic. 76°01' W, 78°28' N, east central Ellesmere Island, Nunavut Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 19 August 1971 Source. Courtesy of Natural Resources Canada, NAPL A 22542-53, 54 Comments. This stereomodel of the calving 3 km wide floating ice front of Tanquary outlet Glacier in the south arm of Baird Inlet shows 15 small icebergs as in Gl4-2, averaging
The island is at the entrance to the Northwest Passage and is part of a future Arctic transportation corridor. There are only two outlet glaciers on Bylot’s north coast, but icebergs from other sources drift in both easterly and westerly directions in Baffin Bay and Lancaster Sound. Most glaciers on the island appear to be either stationary at, or retreating from, positions attained during a Neoglacial maximum 120 years ago. Their terminal moraines (Gl5) are either close to, or in contact with, their margins. Marginal morainic ridges are poorly resolved in the image. See also Fig. 17.1-6. A remnant of sea ice, at this date, lies in Eclipse Sound, bottom right offshore of the developing iron ore shipment port of Pond Inlet in Fig. Zk1-5.
Fig. Gl4-11.
Larsen Ice Shelf is about 400 m thick at the grounding line, tapering to about 200 m at the Weddell Sea ice front. In the intervening quarter century from 1979 to 2004 the extents of both the ice shelf and the outlet glaciers have changed significantly. The ice shelf disintegrated in 1995, losing 1 600 km2, and a further 3 250 km2 in February 2002 after being weakened by temperatures that rose five times as fast as the global average over the previous five decades. The melting of an ice shelf does not affect sea level, but glaciers sliding off into the sea instantly affect sea level. The glaciers, once held up by the ice shelf, as in the image, are now flowing directly into the sea at speeds up to eight times faster than between 2000 and 2003. A controversial scientific contention states that the West Antarctica Peninsula is the only part of the continent that is experiencing temperature rises.
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Location. Geographic. 78°30' W, 73°15' N scene center, north Baffin Island, Nunavut Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 600 000 Acquisition date. 10 August 1971 Source. Klassen RA (1993) Quaternary geology and glacial history of Bylot Island, Northwest Territories. GSC Memoir 429 Comments. A Landsat image shows ice-capped Bylot Island in Sirmilik National Park which is a northern continuation of the Baffin Island Uplands of the northeast shield. About 45% of the island (4 859 km2) is covered by glaciers. Sixteen major outlet glaciers flow north and south from an icefield spine up to 1 800 m a.s.l. made up of a series of cirque basins.
Location. Geographic. 60°00' W, 64°15' S scene center, Antarctica Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 250 000 Acquisition date. 20 February 1979 Source. USGS Comments. The Landsat subscene covers two red delineated groups of 10 km long coalesced glaciers terminating at the grounding edge of the Larsen Ice Shelf, the most northerly ice shelf in the Southern Hemisphere. The glaciers are spilling down either side of Sobral Peninsula from the 1 500 to 2 000 m elevation of Graham Land on the West Antarctica Lower Paleozoic fold mountain peninsula.
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Fig. Gl4-10. (Caption on p. 827)
Group G · Paraglacial Geosystems
Gl4 · Outlet Tidewater Glaciers
Fig. Gl4-11. (Caption on p. 827)
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Gl5
Division 4 · Surficial Deposits
Gl5 Valley Glaciers
Group G · Paraglacial Geosystems
Debris flows are associated with downstream outbursts of lakes impounded by glacier ice or moraine ridges Units Mf4.2 and Mf4.3.
Characterization A valley glacier is an ice stream of recrystallized snow that has metamorphosed and deformed under its own accumulated weight and flows down and within a mountain valley. Transverse cracks – crevasses – commonly visible on the surface of advancing glaciers, occur in the brittle upper layers of ice which are placed in tension where the glacier flow is accelerated at a steepening of the bed. The glacier erodes by basal abrasion and deposits by ice basal flow, meltout and surface ablation. The tongues of valley glaciers are characterized by their activity status. They can be stationary, advancing, surging or retreating. The two states of notable photogeological interest are surging (given the descriptor h) and receding (given the qualifier i) in the classification. Lateral and terminal moraines are landforms composed of till, see Unit Gf4, that are commonly associated with valley and tidewater glaciers. Lateral moraines are ridges that result from the dumping of transported till debris in the trough between the glacier and valley sides, e.g., Figs. Gl4-5 and Gl5-9. Terminal, or end, moraines are crescent-shaped ridges of till across the valley at present day glacier margin, e.g., Gl4-8, Gl5-2 and Gl5-6. Terminal moraines beyond present day glacier margins become dams that pond water between them and the glacier. These deposits are classed as mass movement Mf4.2 moraine dams.
Geohazard Relations Glaciated valleys can contain some of the most difficult engineering ground conditions. Ms5 Ice avalanches originate from heavily crevassed glacier fronts overhanging steep bedrock slopes. A thin film of meltwater on the rock surface favours accelerated slippage of detaching ice blocks. The avalanches can be destructive by force of airblast knocking down trees and the ice mass demolishing buildings. Flooding, caused by glacier impounded lakes, Unit Mf4.3, inundates valley reaches upstream from glacier dams.
In addition to the hazard of long-term sea level rise from glacier recession related to climate warming – see Note on that subject at the end of Group Marine Littoral Systems – severe water shortages can be expected following the loss of land-based ice, with the disappearance of many valley glacier reservoirs, putting municipal water supplies and food supplies at risk in such regions as the Andean countries of South America.
Select Bibliography Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 44–47 Evans SG, Clague JJ (1992) Glacier-related hazards and climatic change. The world at risk: Natural hazards and climate change. American Institute of Physics Conference Proceedings 277, pp 48–60 Oerlemans J (2001) Glaciers and climate change. Swetz & Zeillinger Ryder JM (1998) Geomorphological processes in the alpine areas of Canada. GSC Bull 524:30–36 Tufnell L (1984) Glacier hazards. Longman, London
See also Gl4 Select Bibliography.
Remote Sensing Gratton DJ, Howarth PJ, Marceau DJ (1990) Combining DEM parameters with Landsat MSS and TM imagery. IEEE Transactions on Geosciences and Remote Sensing 28(4):766–769 Kulkarni AV, Bahuguna IM, Rathore BP, Singh SK, Randhawa SS, Sood RK, Dhar S (2007) Glacial retreat in Himalaya using Indian remote sensing satellite data. Current Science 92:1 Mohr JJ, Reeh N, Madsen SN (1998) Three-dimensional glacial flow and surface elevation measured with radar interferometry. Nature 391(3664):273–276 Reeh N, Madsen SN, Mohr JJ (1999) Combining SAR interferometry and the equation of continuity to estimate the three-dimensional glacier surface-velocity vector. Journal of Glaciology 45(151):532–538 Rees WG, Arnold NS (2007) Mass balance and dynamics of valley glacier measured by high-resolution LiDAR (Light detection and ranging – very similar to RADAR). Polar Record 43(227):311–319 Wheate RD, Sidjak RW, Whyte GT (2002) Mapping glaciers in the interior ranges and Rocky Mountains with Landsat Data. In: Williams RS Jr, Ferrigno JG (eds) Glaciers of North America, satellite image atlas of glaciers of the world. USGS Preofessional Paper 1386-J, p J101 Williams RS Jr, Ferrigno JG (2002) Glaciers of North America; Satellite image atlas of glaciers of the world. USGS Professional Paper 386-J, pp J20–J22
Gl5 · Valley Glaciers
Fig. Gl5-1. Location. Geographic. 08°21'17'' E, 46°27'02'' N, southern Switzerland Source. Schweizerische Verkehrszentrale, Zürich (1980) Die Schweiz und ihre Gletscher, 2 nd edn. Kümmerly +Frey Verlag, p 167, photo 1 Comments. Air view to southwest on 5 September 1973 at the 5 km long Griesgletscher, coalesced from two sources in its icefield, terminating since 1964 in the dammed Griessee. The glacier is in Mesozoic metamorphic rocks of the Lepontine Alps of Wallis Canton. It flowed from the 3 200 m Blinnenhorn Icefield at the top in Italy and terminates at elevation 2 387 m in the reservoir. The dam is 60 m high and 400 m long.
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Group G · Paraglacial Geosystems
Gl5 · Valley Glaciers ▼
Fig. Gl5-2. Location. Geographic. 06°46' E, 45°18' N, French Alps Vertical Airphoto/Image. Type. b/w pan, airphoto Scale. 1: 15 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. This enlarged photo fragment shows two alpine valley glaciers side by side in distinct activity stages.
Fig. Gl5-3. Location. Geographic. 147°08' W 63°27' N, southern Alaska Source. Post A, LaChapelle ER (1971) Glacier ice. University of Toronto Press, p 51, fig 60. Reprinted by permission of the University of Washington Press Comments. These sketch maps show the Susitna Glacier surge and moraine patterns. The red and green inset frames locate the coverages of Figs. Gl5-4 and Gl5-5.
The northern glacier, on the right, Arpont, coded Gl5h has a relatively steep terminus, crevassed tongue and no frontal moraine. These are marks of a newly advancing glacier. The neighbouring glacier Gl5i has a gently sloping terminus, crevasses are limited to an upper icefall zone, and it is misfitted in its wide moraine belt coded Gt4.1. The glacier is evidently in retreat, and decaying. Both flowed down from an icefield at about 3 000 m elevation in the Pennine Alps of the Vanoise National Park.
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Fig. Gl5-4. (Caption on p. 836)
Group G · Paraglacial Geosystems
Gl5 · Valley Glaciers
Fig. Gl5-5. (Caption on p. 836)
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Fig. Gl5-4. Location. Geographic. 147°08' W, 63°27' N, southern Alaska Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 9 September 1949 Source. Unspecified U.S. government agency Comments. This photo shows the terminal 6 km of the 2 km wide Susitna Glacier depicted in red outline on the sketch map of Fig. Gl5-3. The glacier was in a state of recession at the time of photography, and the ice surface was covered with morainic till and outwash deposits. The high-ice trimline is conspicuous. Unit Gf3.1 is a complex of englacial debris exposed by melting ice. The arrows locate common points on Fig. Gl5-5. A large pool of ponded meltwater is in the middle of the moraine areas. Red X codes are meltwater ponds existing at both dates.
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Fig. Gl5-5. Location. Geographic. 147°08' W, 63°27' N, southern Alaska Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 40 000 Acquisition date. 3 July 1954 Source. Unspecified U.S. government agency Comments. This photo shows the same area of the Susitna Glacier as Fig. Gl5-4 photogaphed 54 months later and is the green outline on the sketch map of Fig. Gl5-3. During 1952 or 1953 the glacier surged 3 km. The contorted darker bands of the medial moraines result from the surge movements. Unit B is a complex of englacial debris exposed by melting ice. The arrows locate common points on Fig. Gl5-4.
Group G · Paraglacial Geosystems
Gl5 · Valley Glaciers
Fig. Gl5-6 Location. Geographic. Eastern Alaska Vertical Airphoto/Image. Type. Colour infrared airphoto – reverse printed Scale. 1: 63 360 Acquisition date. Not given Source. U.S. Department of Agriculture
Comments. Stereomodel shows a 1 km wide decaying glacier at 141°06' W, 61°36' N that has retreated 3 km from its inner terminal moraines (red-coloured, now vegetated) and its 2 km wide front. The dark surface is attributed to valley-side debris falls or volcanic ash. North is at the bottom.
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Fig. Gl5-7. (Caption on p. 840)
Group G · Paraglacial Geosystems
Gl5 · Valley Glaciers
Fig. Gl5-8. (Caption on p. 840)
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Group G · Paraglacial Geosystems
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Fig. Gl5-7.
Location. Geographic. 82°43' W, 80°53' N, west central Ellesmere Island, Nunavut Geologic. Franklin Mobile Belt of Late Paleozoic Innuitian Orogen Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 17 August 1959 Source. Courtesy of Natural Resources Canada NAPL A 16785-23, 24 Comments. Stereomodel shows a parallel group of 6 valley glaciers, 500 to 600 m wide and 3 to 4 km long in Oobloyah Valley. They are located on the south side of a local Gl4 icefield (1 200 m a.s.l.) with its diverging outlet glaciers but only the first and fourth from left flow from it. The other four flow from their own cirques (hollows with a periglacially weakened glacier-eroded floor and basally undercut headwall). The tongues are at the approximate 300 m contour. ▼
Fig. Gl5-8. Location. Geographic. 140°10' W, 61°15' N, southwest Yukon Geologic. Tertiary Volcanic Belt of Cordilleran Wrangell Terrane Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 6 September 1955 Source. Courtesy of Natural Resources Canada, NAPL A 14960-17, 18 Comments. The stereomodel covers the lower 10 km of the 40 km long eastward curving Steele Glacier in the St. Elias Mountains. At date of photography the glacier was clearly stagnant. Its high-ice trimline is conspicuous. The full length pictured is debris-covered ice-cored moraine with a profusion of collapse pits as in Fig. Gl5-4. Steele Glacier is best known for its 1965–1966 surge which started in late 1965. By summer 1967, the total ice displacement was 9.5 km. Photos acquired 10 September 1966 show the terminus at 3 km up-valley from the deadice terminus which can be seen in the CD ROM mate photo. Terminal moraines of two receded tributary glaciers are visible upstream.
Fig. Gl5-9.
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Location. Geographic. 140°55' W, 61°35' N, west central Yukon Geologic. Tertiary Volcanic Belt of the Cordilleran Wrangell Terrane Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. 30 July 1957 Source. Courtesy of Natural Resources Canada, NAPL A 15728-75, 76 Comments. A stereomodel is centered on Natazhat Glacier which descends 2 800 m in 16 km from its source in a 4 000 m a.s.l. icefield just inside the Alaska border in the St. Elias Mountains which comprise the largest nonpolar icefield on Earth. Natazhat, in common with most present glaciers in the area, is stagnant and decaying. Its lower half is debriscovered and dotted with collapse pits and debris ice melt slumping. Its upper part consists of longitudinal furrows, also characteristic of debris-covered glaciers. The overall dark tones are probably due to volcanic ash cover from a 1 600 year old explosion center near the foot of the glacier. Lateral moraines have been delineated. An Ms1 rock slide is traced on the south slope of the valley.
Gl5 · Valley Glaciers
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Division 4 · Surficial Deposits
Fig. Gl5-10. (Caption on p. 844)
Group G · Paraglacial Geosystems
Gl5 · Valley Glaciers
Fig. Gl5-11. (Caption on p. 844)
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Fig. Gl5-10. Location. Geographic. 130°21' W, 56°36' N, northern British Columbia Geologic. Lower Jurassic sedimentary and volcanic rocks of the Stikinia Superterrane of the Cordilleran Intermontane Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 36 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 12226-122, 123 Comments. The stereomodel covers forest and alpine tundra zones in the Unuk River Valley area, with two moraineless un-
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Fig. Gl5-11. Location. Geographic. 75°30' E, 36° N at image center, western Himalayas Vertical Airphoto/Image. Type. MSS 80 m resolution Scale. 1: 550 000 Acquisition date. Not given Source. USGS Comments. A Landsat 115 km by 100 km subscene of part of the Karakoram Mountains shows numerous long
Group G · Paraglacial Geosystems
named short valley glaciers. Clear evidence of retreat of these glaciers are the abrupt transition zones from bare rock slopes to forested slopes. The high ice trimlines are delimited in red. Both glacier tongues are 1 300 m from their former termini, while the larger glacier has lost 40% of its width, to 1 080 m from 1 800 m. Additional evidence of recession is provided by the fully snow-covered small glacier and the gently sloping tongue of the large glacier with its surface broken by few crevasses. The crevasses visible at the south edge of the photo are at an icefall zone. No moraines flank these glaciers because they have flowed directly from their local icefield source at 2 000 m a.s.l. (30 to 40 km) Gl5 worm-patterned valley glaciers radiating from a central ice field on the Pakistan-China border. The ice field and surrounding peaks are at elevation 7 500 m rising to 8 600 m. Figure Gl5-12 covers the southeast quarter of the image. Medial moraines as in Fig. Gl4-6 are visible in these low resolution glaciers. Extended lower ablation zones of many of these glaciers appear stagnant and debris-covered in higher resolution images.
Fig. G15-12. Location. Geographic. 75°35' E 35°55' N, Karakoram Mountains, Pakistan Geologic. Himalayan Tethyan intercontinental tectogenic belt Source. USGS Comments. A pair of satellite subscenes of the east part of Fig. Gl5-11 provides comparison of images of valley glaciers in the region of Fig. Gl5-11 acquired by early NASA electro-optical and radar imaging systems. The multispectral Landsat image appears to have been ac-
quired by the 30 m resolution TM system. It also appears to be at a high summer solar elevation avoiding slope shadows. The SIR-A image was acquired 14 November 1981 at 40 m resolution. Glaciers are particularly well displayed in blue on the Landsat image, while they appear only marginally brighter than the weak, dark return backslopes that dominate the radar scene. The Karakoram Range contains some of the largest glaciers outside Greenland or Antarctica; the southeast trending glacier in the scene center is 35 km long.
Gf4 · Eroded Till Plains
Sub-group Gf Glaciofluvial Deposits Gf4 Eroded Till Plains
The relative scarcity of glaciofluvial deposits that could be anticipated to be associated with this geounit is believed to be attributable to cleaner ice and lower sediment loads in the runoff water in the central parts of the continental ice sheet which is a principal region of occurrence of the geounit.
Characterization Geohazard Relations Till is a heterogeneous unstratified mixture of boulders, gravel, sand, silt and some clay deposited by continental or alpine glaciers in two principal modes: 1. subglacially, compact, at and from the base of a moving glacier 2. supraglacially, loose, non-compacted, deposited from a stagnating glacier ice mass by flow or subsidence onto the ground Post-glacial meltwater streams eroded depressions between mounds and ridges of both tills, removing the coarse fractions. Occurrences of this geounit in glaciated terrain are distinct, they are usually elongate in the corridor depressions, and are characterized by sharp-crested hummocks and channel-like bouldery erosion depressions, with local lenses of water-sorted sand and gravel. Boulders, possibly derived from sheet flood subglacial meltwater erosion, frequently litter the tops of low ridges.
Fig. Gf4-1. Location. Geographic. 08°03' E, 46°37' N, central Switzerland Source. LAR, May 1976 Comments. The photo of lag cobbles illustrates the effect of dynamic fluvial erosion by removal of finer fractions from the surface matrix of glacial till.
Transportation corridors crossing eroded till areas necessitate much cutting and filling and can encounter concentrations of Gf5 boulders in the depressed zones.
Select Bibliography Bird and Hale Limited (1984) Development of remote sensing-based procedure to estimate boulder concentrations. The Research and Development Branch, Ontario Ministry of Transportation and Communications, Report no SP-019 Henderson EP (1959) A glacial study of central Quebec-Labrador. GSC Bull 50:19, 40 Hughes OL (1964) Surficial geology, Nichicun-Kaniapiskau map-area, Quebec. GSC Bull 106:10, 18, pl III Legget RF (1976) Glacial till: An interdisciplinary study. Royal Society of Canada, Special Publication 12 Matile GLD (2006) Surficial geological investigations in the KasmerePutahow Lakes area, northwestern Manitoba (parts of NTS 64N10, 11, 14 and 15). In: Report of Activities 2006 Manitoba Science, Technology, Energy and Mines, Manitoba Geological Survey, pp 148–154
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Division 4 · Surficial Deposits
Fig. Gf4-2. Location. Geographic. 75°25' W, 45°35' N, southern Quebec Source. LAR, 8 August 1991
Group G · Paraglacial Geosystems
Comments. Photo shows lag boulders and cobbles in a borrow pit of glacial till re-worked by glaciomarine shore waters of the Champlain Sea in the vicinity of Buckingham, north of the Ottawa River.
Fig. Gf4-3.
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Location. Geographic. 107°10' W, 63°48' N, Northwest Territories Geologic. Neoarchean intrusive rocks of the Bear-Slave Upland of the northwest Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 24 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada NAPL A 10335-6, 7 Comments. The stereomodel in the tundra of Clinton Golden Lake area shows a 5 km segment of a 700 m broad <9 ka glacial meltwater scour channel in an area of 23 ka glacial till, with an inclusion of an esker ridge (a subglacial stream of meltwater, gravel and sand) coded Gf1 along the margin of the south half. The channel is clearly revealed by its exposure of the local bedrock. The scour channel is located where the meltwater and esker stream flowed over a slight bedrock high between two lower areas.
Gf4 · Eroded Till Plains
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Division 4 · Surficial Deposits
Fig. Gf4-4. Location. Geographic. 70°28' W, 59°46' N, Ungava Peninsula, Quebec Geologic. Superior Province of the eastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 25 August 1953
Group G · Paraglacial Geosystems
Source. Courtesy of Natural Resources Canada, NAPL A 13844-71, 72 Comments. A subscene of a stereomodel near Peters Lake 40 km southwest of Kangirsuk on Arnaud River Estuary covers a 36 km2 area of drumlinized (ice-moulded) glacial till. Ice advance was from the southwest (lower left). The disrupted terrain in the 1 km wide band of till is a typical <7.5 ka meltwater erosion channel.
Gf4 · Eroded Till Plains
Fig. Gf4-5. (Caption on p.850)
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Division 4 · Surficial Deposits ▼
Fig. Gf4-5. Location. Geographic. 62°27' W, 52°05' N, south Labrador Geologic. Mid Proterozoic gneiss of Grenville Province of the eastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 15859-83, 84 Comments. The stereomodel is in the area of the headwaters of the Natashquan River covered by southeast flowing 25 ka drumlinized (ice-molded) Wisconsinan till. A 15 km segment of a 600 m wide <7.5 ka erosion channel crosses the photo. Descriptor Gf1/3 indicates an esker ridge (see Fig. Gf4-3) occupying the southeast portion of the channel. There is an S-shaped narrow channel interconnecting another parallel channel in the south part of the stereo model. “R” zones are bedrock exposed by scour.
Group G · Paraglacial Geosystems
Gf5 · Boulder Fields
Gf5 Boulder Fields Characterization Boulder fields occur in concentrations in topographic lows of Wiscosinan/Würm glacial till deposits. They are typically subangular to rounded and can be up to 2 m in diameter. The thickness of deposits varies as a function of the diameter of the boulders in the field. They have been observed up to 3 m in thickness but averaged 60 cm. in an extensive engineering project in central Labrador. The mode of origin of these concentrations is controversial but all are associated with deposits of glacial till. One hypothesis is dumping from ice transport on moraine surfaces. A second hypothesis posits a rolling in by gravity of boulders to depressions in glacial till from adjacent higher ground. In central Labrador boulder field occurrences are in elongate channel-like depressions of kilometer length and about 200 m width. Their origin appears related to a washing out of finer matrix particles from the till surface, as described for Unit Gf4, by glacial meltwaters, leaving the boulders as lag deposits. The densest concentrations are of the greatest engineering concern and can be identified and mapped on 1: 10 000 airphotos.
Geohazard Relations The presence of such boulder concentrations in engineering construction sites, e.g., foundations of earth and rockfill dykes to impound reservoirs, require additional cost items for under-seepage control, such as cut-off walls, or their removal, including drilling and blasting to pop the larger boulders. Additionally, maintenance cost at such sites can be considerable.
Select Bibliography Legget RF (1974) Glacial landforms in civil engineering. In: Coates DR (ed) Glacial geomorphology. State University of New York, Binghampton, pp 351–374 Legget RF (1979) Geology and geotechnical engineering. Journal Geotechnical Engineering, Div. ASCE 105:339–392 Matile GLD (2006) Surficial geological investigations in the KasmerePutahow Lakes area, northwestern Manitoba (parts of NTS 64N10, 11, 14 and 15). In: Report of Activities 2006 Manitoba Science, Technology, Energy and Mines, Manitoba Geological Survey, pp 148–154 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 30–31
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Division 4 · Surficial Deposits
Group G · Paraglacial Geosystems
Gf5 · Boulder Fields ▼
Fig. Gf5-1. Location. Geographic. 64° W, 53°35' N, central Labrador Plateau Geologic. Neoarchean gneisses of the eastern shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 10 000 Acquisition date. 1967 Source. Personal archive Comments. The stereomodel in the Smallwood Reservoir area covers a 370 ha area of a <7.5 ka field of erosion residual boulders of glaciated till. At this scale the boulders show up as white speckles and in this locality they are seen to occur on the low rises bordering the depressions as well as in them.
Fig. Gf5-3. Location. Geographic. 65°10' W, 53°44' N, central Labrador Plateau Source. LAR, 1968 Comments. This is a ground view of the boulder field of Fig. Gf5-2.
Fig. Gf5-2. Location. Geographic. 64°30' W, 54° N approx., central Labrador Plateau Source. Personal archive Comments. Helicopter view of a test trench, 10 m long and 60 cm deep, in a residual boulder field in the Smallwood
Reservoir area shown in the stereo photos of Fig. Gf5-1. A ground view is in Fig. Gf5-3. As a foundation condition (see the geohazard relations of this unit) such boulder fields occurred in up to 50% of the surface of some of the 68 linear kilometers of dykes that were constructed to create the reservoir.
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Division 4 Surficial Deposits Group Z · Periglacial-Related Forms
Sub-group Zi Ground Ice Units Sub-group Zm Cryoturbated Materials Sub-group Zk Thermokarst Terrain
Characterization The geounits of this Group are cold climate phenomena. They occur in seasonally unfrozen unconsolidated deposits and organic materials in polar and subpolar lowlands and in highlands; they are ordered in three Sub-groups: Sub-group Zi is a single unit that consists of segregated ice bodies in commonly, but not exclusively, fine-grained materials. Sub-group Zm are materials that have been moved or disturbed by frost action. Sub-group Zk are land surface areas that have been affected by the thawing of underlying ice-rich permafrost.
Geohazard Relations The geohazards associated with these units include localized creep, subsidences, slides and slumps. Engineering designs may require alternative approaches under warm ground thermal conditions to maintain terrain stability. A developing hazard of Sub-group Zk is related to global warming. The increase in global air temperatures in recent decades, due to known human greenhouse gas emissions, has initiated large scale thawing of permafrost, particularly in the extensive areas of peat bogs in western Siberia. A rise of 3 °C has been experienced there in the past 40 years. The consequent release of megatonnes of CO2 and methane into the atmosphere will further increase global air temperatures. Such increases can result in a spread of the process to all high latitudes, along with changes in the engineering behaviour of soils, necessitating increased maintenance of infrastructures and adaptive work on regional scales.
Select Bibliography for Periglacial-Related Forms The bibliography is restricted to key bench mark monographs and papers that are up-to-date and accessible.
Fundamental Science and Concepts Dixon JC, Abrahams AD (1992) Periglacial geomorphology. John Wiley & Sons, Ltd., Chichester French HM (ed) (1986) Permafrost geomorphology. Canadian Geographer 30(4):358–366 International Permafrost Association (1998) Permafrost bibliography 1978–1997; CAPS version 1.0 CD-ROM. National Snow and Ice Data Center, Boulder Colorado Nelson FE, Anisimov OA, Shiklomanov NI (2002) Climate change and hazard zonation in the CircumArctic permafrost regions. Natural Hazards 26(3):203–225
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_12, © Springer-Verlag Berlin Heidelberg 2009
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Division 4 · Surficial Deposits Paepe R, Mel’nikov VP (2001) Permafrost response on economic development, environmental security and natural resources. Springer-Verlag Smith DW, Low N (eds) (1996) Cold regions utilities monograph, 3rd edn. American Society of Civil Engineers and Cold Regions Engineering Division, Canadian Society for Civil Engineers, Technical Council on Cold Regions Engineering Washburn AL (1979) Geocryology. Edward Arnold, London Wei M, Fujan N, Satoshi A, Dewu J (2006) Slope instability phenomena in permafrost regions of Qinghai-Tibet Plateau, China. Landslides (On-Line) 3(3):260–264 Williams PJ, Smith MW (1989) The frozen earth; Fundamentals of geocryology. Cambridge University Press, Cambridge
Group Z · Periglacial Related Forms Kääb A, Huggel C, Fischer L (2006) Remote sensing technologies for monitoring climate change impacts on glacier-and permafrostrelated hazards. Proceedings 2006 Engineering Conferences International, USA, paper 2 Kreig RA, Reger RD (1976) Preconstruction terrain evaluation for the Trans-Alaska Pipeline Project. In: Coates DR (ed) Geomorphology and engineering. Dowden, Hutchinson, & Ross, Stroudsburg, pp 55–76 Mollard JD (1972) Airphoto terrain classification and mapping for northern feasibility studies. National Research Council Canada, Division of Building Research, Technical Memorandum 104, pp 105–127 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 117–137
Airphoto Interpretation and Remote Sensing Akerman HJ (1984) Notes on the use of aerial photographic interpretation in the study of periglacial geomorphology in Spitsbergen. Proceedings, 1st Int. Seminar on Methodology in Landscape Ecological Research and Planning, Theme II, Methodology and Techniques of Inventory and Survey, International Association for Landscape Ecology Brown RJE (1974) Some aspects of airphoto interpretation of permafrost in Canada. Division of Building Research, National Research Council Canada, Dept. of Energy, Mines and Resources, Technical Paper no 409 Etzelmüller B, Ødegard RS, Berhtling I, Sollid JL (2001) Terrain parameters and remote sensing data in the analysis of permafrost distribution and periglacial processes: Principles and examples from southern Norway. Permafrost & Periglacial Processes 12(1):79–92 Frohn RC, Hinkel KM, Eisner WR (2005) Satellite remote sensing classification of thaw lakes and drained thaw lake basins on the North Slope of Alaska. Remote Sensing of environment 97:116–126 Fulton RJ, Boydell AN, Barnett DM, Hodgson DA, Rampton VN (1974) Terrain mapping in northern environments. Proceedings, Technical Workshop on Canada’s Northlands, April 17–19. Lands Directorate, Environmental Management Service, Environment Canada, pp 14–60 Grosse G, Schirrmeister L, Kunitsky VV, Hubbertsen H-W (2005) The use of CORONA images in remote sensing of periglacial geomorphology: An illustration from the NE Siberian coast. Permafrost and Periglacial Processes 16:163–172
Note. Micro-scale cryoturbation features such as
earth hummocks frost-mud boils Non-sorted vegetation circles sorted stone circles vegetation stripes sorted stone stripes
which are commonly reported in field studies can only be detected at scales larger than 1:15 000.
General References, Geohazards for Z Group Units Andersland OB, Ladanyi B (2004) Frozen ground engineering. Wiley Brown RJE (1970) Permafrost in Canada. Canadian Building Series, University of Toronto Press Ferrians OJ, Kachadoorian R, Greene GW (1969) Permafrost and related engineering problems in Alaska. USGS Professional Paper 678 Johnson GH (1981) Permafrost, engineering design and construction. John Wiley & Sons, Ltd., Toronto Smith SL, Burgess MM, Heginbottom JA (2001) Permafrost in Canada, a challenge to northern development. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:241–264
Zi4 · Ice Wedge Polygons
Sub-group Zi Ground Ice Units Zi4 Ice Wedge Polygons Characterization Ice wedge polygons are a spatial network resulting from a type of ground ice that occurs in the freeze-thaw active layer of fine and coarse mineral and organic soils in permafrost regions. “Ice wedges develop from the repeated incursion of snow or water into cracks in the ground that form as a result of thermal contraction in winter. The resulting ice persists which localizes the point of cracking in subsequent years. Over decades, the ice wedge widens and ridges of displaced soil develop on either side of a trough, giving a distinctive microtopography.” (Smith et al. 2001). Two types of polygons are distinguishable: low and high center. Low centers occur in poorly-drained sites; the ridges of displaced soil enclose wet ground, dark on photos. High centers occur on better drained sites; the moist areas are the marginal troughs directly above the ice wedges. This situation can indicate thawing of the ice. The wedges are seldom more than 5 to 8 m deep and 2 to 3 m in maximum width. The size of individual polygons varies from 1 to 100 m, typically 10 to 40 m across. These dimensions limit the detectability of polygon patterned ground on high resolution photos and satellite images to scales of 1: 100 000; e.g., 50 m diameter high center polygons are detectable at scales of 1: 60 000 airphotos and same diameter low center polygons on 1: 28 000 airphotos. Some high latitude polygonal patterns on airphotos are suggestive of ice wedges but are only frost cracks with no infilling ice, e.g., Fig. Zi4–7.
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strips than for roads. Ice wedge polygons present an offroad trafficability problem for air-cushioned vehicles but are no problem for large tracked or large wheeled vehicles.
Zi4 Reference Smith SL, Burgess MM, Heginbottom JA (2001) Permafrost in Canada, a challenge to northern development. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:241–264
Select Bibliography Genetic Bovis MJ (1987) The Interior Mountains and Plateaus. In: Graf WL (ed) Geomorphic systems of North America. GSA, Centennial Special vol 2, p 490 Brown J, Solomon S (eds) (1999) Arctic coastal dynamics. Report of an International Workshop, GSC Open File 3929, p 17 Carter LD, Heginbottom JA, Ming-ko Woo (1987) Arctic lowlands. In: Graf WL (ed) Geomorphic systems of North America. GSA, Cennial Special vol 2, p 599 Dredge LA (2001) Where the river meets the sea: Geology and landforms of the lower Coppermine River Valley and Kugluktuk, Nunavut. GSC Miscellaneous Report 69, p 37 French HM (1989) A survey of geomorphic processes in Canada, In: Fulton RJ (ed) Geology of Canada, no 1, Quaternary geology of Canada and Greenland. GSC Permafrost Subcommittee, Associate Committee on Geotechnical Research (1988) Glossary of permafrost and related ground-ice terms. National Research Council of Canada, NRCC 27952, Technical Memorandum no 142, pp 73, 87
Airphoto Interpretation Friedman JD, Johansson CE, Oskarsson N, Svensson H, Thorarinsson S, Williams RS Jr (1971) Observations on Icelandic polygon surfaces and palsa areas, photo interpretation and field studies. Geografiska Annaler 53(A3–4):115–145 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 121–123 Thoren RVA (1960) Frost problems and photo interpretation of patterned ground. International Society of Photogrammetry, 1960 program of Commission VII (Photographic Interpretation) Velicko AA (1972) La morphologie cryogène relicte: Caractères fondamentaux et cartographie. Z Geomorph N.F., Suppl. Bd. 13, Berlin-Stuttgart, pp 59–72
Geohazard Relations
Geohazards
Ice wedge polygons are both hazards to construction and development in their own right and indicators of underlying problematic ground ice. The removal of insulating vegetation or organic cover and other disturbances to the ground surface can result in changes to the ground thermal regime, leading to warming and melting of ice wedges and permafrost. Initiation or acceleration of thawing is especially critical over ice wedges and will result in a polygonal pattern of trenches. Highways constructed on such areas suffer from severe settlement and pavement distress. Much less differential cracking and settlement can be tolerated for air-
Barnett DM, Edlund SA, Dredge LA (1977) Terrain characterization and evaluation: An example from eastern Melville Island. GSC Paper 76–23, p 17 Duk-Rodkin A, Hughes OL (1995) Quaternary geology of the northeastern part of the Central Mackenzie Valley Corridor, District of Mackenzie, Northwest Territories. GSC Bull 458:36 Ferrians OJ, Kachadoorian R, Greene GW (1969) Permafrost and related engineering problems in Alaska. USGS Professional Paper 678, p 23 Hodgson DA (1982) Surficial materials and geomorphological processes, western Sverdrup and adjacent Islands, District of Franklin. GSC Paper 81–9, pp 27, 31 Rampton VN (1988) Quaternary geology of the Tuktoyaktuk coastlands, Northwest Territories. GSC Memoir 423, p 77
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Fig. Zi 4-1. Source. Dredge LA (2001) Where the river meets the sea. GSC, Misc. Report 69, p 37, fig 39 Comments. These schematic sections show the thermal contraction process in the development of an ice wedge, i.e. tensile stresses caused by a reduction in ground temperature.
Fig. Zi4-2. Source. Velicko AA (1972) La morphologie cryogène relicte: caractères fondamentaux et cartographic. Zeitschrift für Geomorphologie, N.F., Suppl. Bd. 13, p 62, fig 1, www.schweizerbart.de Comments. These block diagrams illustrate the relation of stages of development of ice wedges to high and low center types. The upper diagram is the seasonally moist low center type; the lower diagram shows the degradation stage with resulting high drier center polygons. See Fig. Zi4-4. Zones 1 are the seasonally thawed ‘active’ surface layers, with the thicker layer in the degradation stage. Zones 2 are perennially frozen ground.
Group Z · Periglacial Related Forms
Zi4 · Ice Wedge Polygons
Fig. Zi4-3. Location. Geographic. 138°45' W, 69°20' N, northwest Yukon, Canada Source. Courtesy of S. R. Dallimore, GSC Comments. A ground photo shows an exposure of a large ice wedge in Late Wisconsinan morainic deposits near Stokes Point on the coastal plain. The wedge is about 1.5 m across at the top and extends about 3 m into the sediments. See also Fig. Zi4-11 at same site.
Fig. Zi4-4. Location. Geographic. Northeast Manitoba Source. Courtesy of Natural Resources Canada, GSC. Photo by L. Dredge Comments. This photo shows a person probing in a degrading ice wedge trough of a high center polygon net. See lower diagram of Fig. Zi4-2.
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Group Z · Periglacial Related Forms
Fig. Zi4-5. Location. Geographic. 152°10' W, 69°22' N, Arctic Foothills, Alaska Geologic. Residuum and colluvium of unglaciated Cretaceous sedimentary rocks Source. Ferrians OJ, et al. (1969) Permafrost and related engineering problems in Alaska. USGS PP 678, p 26, fig 25 Comments. This photo, taken in August 1958 at Umiat, shows successive troughs across a gravel road resulting from the degradation of ice wedges. The thickness of the fill at the time was insuffcient to prevent the thawing. The road was constructed in 1950 for mineral exploration access and was abandoned in 1953. This part of Alaska was unglaciated but is underlain by continuous permafrost.
Fig. Zi4-6. Location. Geographic. 148°30' W, 62°50' N, southern Alaska Source. LAR, September 1980 Comments. A photo of a roller-traction off-road vehicle on tundra terrain in the Talkeetna Mountains mounting a container of geotechnical equipment being used on glacial lacustrine sediments. The vehicle design was to reduce weight pressure on the sensitive active layer of permafrost ground. Compare with Fig. Zk1-3. This site is the same as Fig. L1-5.
Fig. Zi4-7.
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Vertical Airphoto/Image. Type. Ektachrome IR (35 mm) airphoto Scale. 1:1 000 approx. Acquisition date. Circa 1970 Source. Friedman JD, et al. (1971) Observations on Icelandic polygon surfaces and palsa areas, photo interpretation and field studies. Geografiska Annaler, vol 53, ser A,3-4, p 133, plate 3
Comments. The photograph is a low altitude air perspective view of a permafrost-free region in south-central Iceland. It shows that some polygons may be formed by seasonal frost cracking in areas of deep seasonal frost. The polygon pattern, revealed by the red vegetation filling the furrows, consists of 20–30 m spaced, 1 m deep furrows of frost cracks with no infilling ice in interbedded mineral soil and volcanic tephra.
Zi4 · Ice Wedge Polygons
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Division 4 · Surficial Deposits
Group Z · Periglacial Related Forms
Fig. Zi4-8. Source. French HM (1976) The periglacial environment. Longman, London, New York, p 237, fig 12.5 Comments. An air perspective view at 03°39' E, 52°08' N shows fossil (Weichsel/Würm/Wisconsinan 80 ka–10 ka bp) ice wedges in glacial deposits at the southern extremity of glaciation of the Great Eastern Ice Sheet revealed by soil moisture content and differential crop condition or ripening in a field northwest of Boxted, 10 km north of Colchester, Essex, England.
Fig. Zi4-9. Location. Geographic. 100°30' W, 78°40' N, Arctic Islands, Nunavut Source. Courtesy of Natural Resources Canada, GSC 203500-Z Comments. An air view shows high center polygons that average 25 m in diameter, in the active layer of Lower Cretaceous shales of the Sverdrup Basin on eastern Ellef Ringnes Island. This location is just east of the diapir structure of Fig. 11-3.
Zi4 · Ice Wedge Polygons
Fig. Zi4-10. Source. Courtesy of Natural Resources Canada, GSC 204063B Comments. This air view shows low center ice wedge polygons probably in glacial till (Gf4) on Banks Island of the northern interior plains, Arctic Archipelago. The muskox herd gives the scale.
Fig. Zi4-11. Source. Courtesy of Natural Resources Canada, GSC203452-1 Comments. An air view shows the unserviceable airstrip at Stokes Point on the Yukon Coastal Plain. At the date of photography removal of the vegetation cover on the glacial till (see Gf4) surface during construction of the airstrip exposed ice wedges in the till which melted, resulting in the observed differential settlement. Note that the access roads from the shore have also caused degradation of the active layer. See also Fig. Zi4-3 at same site.
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Group Z · Periglacial Related Forms
Fig. Zi4-12. Location. Geographic. 156°30' W, 70°50' N, northern Alaska Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 8 200 Acquisition date. July 1949 Source. Ferrians OJ, et al. (1969) Permafrost and related engineering problems in Alaska. USGS PP 678, p 9, fig 8
Comments. The large scale airphoto shows high center polygons, averaging 25–30 m in diameter in alluvial deposits of Meade River on the Beaufort Sea Coast about 55 km southeast of Barrow. The plain is underlain by up to 300 m of permafrost in Bc3 glaciomarine sediments and Cretaceous sedimentary rocks.
Zi4 · Ice Wedge Polygons
Fig. Zi4-13. Location. Geographic. 92°05' W, 63°17' N, Kazan Upland, Nunavut Geologic. Northwestern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 28 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL T160c-137
Comments. The stereomodel on the west coast of Hudson Bay shows delineated occurrences of ice wedge polygons shown as fractional code Zi4/Bc3 in marine overlap silts and clays, 70 km west of Chesterfield Inlet settlement. Local stratigraphy is: Bc3 glaciomarine sediments, –75 m a.s.l.; Gt2 veneer glacial till (see Gf4); R3 Archaean basement rocks (no outcrops in the stereomodel). The polygons are large, 40 m and more in diameter, and 2–3 m deep. The area was deglaciated 8 ka.
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Fig. Zi4-14. (Caption on p. 868)
Group Z · Periglacial Related Forms
Zi4 · Ice Wedge Polygons
Fig. Zi4-15. (Caption on p. 868)
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Fig. Zi4-14. Location. Geographic. 109°40' W, 68°42' N, Victoria Island, Nunavut Geologic. Arctic Interior Platform Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 1 July 1955 Source. Courtesy of Natural Resources Canada, NAPL A 14732-57, 58 Comments. The two rectangular patterns in this stereomodel on the south coast of Victoria Island are ice crack polygons that photographically resemble ice wedge polygons. The straight white lines, spaced at about 100 m, are ridges of frost-shattered and frost-thrusted sandstone rubble lifted out of joint fissures in the flat-lying rock. The site is on Cambrian sandstones covered by flights of Bw4 raised beaches from postglacial isostatic rebound. In this case a correct interpretation of the site of the polygons as bedrock rather than surficial material would have discounted ice wedge polygons. Lakes were still ice-covered at this date. This area was deglaciated 8.7 ka.
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Fig. Zi4-15. Location. Geographic. 79°21' W, 71°27' N, north Baffin Island, Nunavut Geologic. Archaean granite gneiss of the northeastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. 3 July 1958 Source. Courtesy of Natural Resources Canada, NAPL A 16107-161, 162 Comments. The ice-wedge polygons in stereoviewing of these photos at Mary River are developed and concentrated in the active layers of valley-fill glacial till coded Gt2. Much residual snow is on the adjacent higher ground at this latitude in mid-summer. Despite the small scale these polygons are readily identified as the high-center type. Compare with Figs. Zi4-12 and Zi4-13. This site is 30 km north of Fig. L1-10. It was deglaciated 6 ka.
Group Z · Periglacial Related Forms
Zm1.1 · Gelifluction Sheets and Lobes
Sub-group Zm Cryoturbated Materials Zm1 Gelifluction Slopes Characterization Gelifluction slopes occur on seasonally thawed materials lying over a frozen substrate. The parent soils include both residual and transported substrate. They are of variable thickness and flow downhill at imperceptible rates. Gelifluction activity is one of the most widespread processes of soil movement in periglacial environments. Geliflucted slopes are detectable on vertical airphotos as two Variants: Zm1.1 – Gelifluction sheets and lobes Zm1.2 – Gelifluction stripes
Zm1.1 Gelifluction Sheets and Lobes
areas the geomorphic effectiveness of this process is comparable to that of rockfalls (Geounit Mv1) and snow avalanches (Geounit Ms4). Using data from 15 m soil boring holes, Kreig (1976) calculated that only 8% of the gelifluction terrain along the 1 300 km Trans-Alaska Oil Pipe Line had ground ice content low enough to have less than 10% thaw strain. Thaw strain is the amount that frozen ground compresses upon thawing and exerts pressure on a structure, in this case a buried oil pipe line section. A structure resting on a gelifluction sheet or lobe will either be subjected to persistent earth pressure or will passively move downslope. For example, a segment of the Alaska Railroad on a slope above the Nenana River north of McKinley Station has had to be reconstructed a number of times at higher elevations as the entire roadbed was gradually displaced down the slope over many years (Linell and Johnston 1973). Another Alaskan rail line in Seward Peninsula was displaced 30 cm within a decade where the tracks crossed gelifluction lobes. In addition to their basic instability, seasonal melting of the pore ice and ice lenses in gelifluction sheets can result in local rapid soil slides (Geounit Ms2).
Characterization References Gelifluction sheets and lobes are best developed on finergrained materials on slopes varying from 2° to 20°. Displacement rates range from 0.50 to 4 cm yr–1 and tend to be concentrated into a few weeks of spring with little more perceptible for the remainder of the year. Movement is laminar in nature and decreases progressively with depth, usually restricted to the waterlogged uppermost 50 cm of the active mass. Increase in pore water pressure leads to decrease in shearing resistance. As the mass moves downhill any organic material is incorporated into the moving soil front. Sections usually show multiple buried organic layers over which the lobe has advanced. Tundra vegetation cover ranges from nil to discontinuous to complete, see Fig. Zm1.1-8. Lobes exist as tongue-shaped units up to 25 cm wide and 150 m long. Sheets and lobes frequently occur closely, will be confused on smaller scale photos, and are not easily distinguished in such associations on larger scales. They are generally mappable on airphotos in the scale range 1: 12 000–1: 40 000. Extensive sheets and lobes are large enough to be resolved on airphotos and images at 1: 60 000 to 1:100 000.
Geohazard Relations Due to their inherent seasonal instability, construction on gelifluction slopes is avoided wherever possible. Gelifluction is a ubiquitous and efficient geomorphic agent on slopes in periglacial environments. In alpine
Kreig RA,Reger RD (1976) Preconstruction terrain evaluation for the TransAlaska Pipeline Project. In: Coates DR (ed) Geomorphology and engineering. Dowden, Hutchinson, & Ross, Stroudsburg, pp 55–76
Select Bibliography Characterization Brown RJE (1974) Some aspects of airphoto interpretation of permafrost in Canada. Division of Building Research, National Research Council Canada, Dept. of Energy, Mines and Resources, Technical Paper no 409, p 8 Dredge LA (1995) Quaternary geology of northern Melville Peninsula, District of Franklin, Northwest Territories. GSC Bull 484:57 Eyles N, Paul MA (1983) Glacial geology. Pergamon Press, Oxford, p 126 French HM (1976) The periglacial environment. Longman, London, pp 135–141 French HM (1989) Cold climate processes. In: Fulton RJ (ed) Geology of Canada, no 1, Quaternary geology of Canada and Greenland. GSC, pp 592, 610 Furrer G, Bachman F (1972) Solifluktionsdecken im Schweizerischen Hochgebirge als Spiegel der postglazialen Landschaftsentwicklung. Zeitschrift für Geomorphologie Juli, pp 163–172 Gamper J (1983) Controls and rates of movement of solifluction lobes in the eastern Swiss Alps. Proceedings, 4th International Conference on Permafrost, pp 328–323 Gengnian L, Heigang Z, Zhijiu (1995) Gelifluction in the alpine periglacial environment of the Tianshan Mountains, China. Permafrost and Periglacial Processes 6(3):265–271 Gerrard AJ (1990) Mountain environments. The MIT Press Cambridge, Mass., p 91 Hamelin L-E, Cook F (1967) Illustrated glossary of periglacial phenomena. Les Presses de l’Université Laval, Quebec, pp 179–183
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Division 4 · Surficial Deposits Mollard JD, Janes JR (1983) Airphoto interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, pp 71, 124 Péwé T (1975) Quaternary geology of Alaska. USG Professional Paper 835, pp 62–83 Price LW (1970) Morphology and ecology of solifluction lobe development, Ruby Range, Yukon Territory. Ph.D. thesis, University of Illinois Rampton VN (1982) Quaternary geology of the Yukon Coastal Plain. GSC Bull 317:33–35, 41 Rapp A (1963) Solifluction and avalanches in the Scandinavian mountain. National Academy of Sciences-National Research Council Publication 1287, Permafrost Conference, Purdue University, November, pp 150–154 Ryder JM (1998) Geomorphological processes in the alpine areas of Canada. GSC Bull 524:24–25 Selby MJ (1985) Earth’s changing surface. Clarendon Press, Oxford, p 405 Smith DJ (1992) Long-term rates of contemporary solifluction in the Canadian Rockies. Periglacial geomorphology. John Wiley & Sons, Ltd., Chichester, pp 203–221 Strumquist L (1983) Gelifluction and surface wash, their importance and interactions on a periglacial slope. Geographiska Annaler 38:313–317 Tedrow JCF, Cantlon JE (1959) Concepts of soil formation and classification in Arctic regions. Arctic Institute of North America, pp 166–179
Group Z · Periglacial Related Forms
Geohazards Ferrians OJ, Kachadoorian R, Greene GW (1969) Permafrost and related engineering problems in Alaska. USGS Prof. Paper 678, p 9 Hanna AJ, McRoberts EC (1988) Permafrost design for a buried oil pipepline. Proc., 5th Intern. Permafrost Conf., pp 1247–1252 Hardy HM, Morrison HL (1972) Slope stability and drainage considerations for Arctic pipelines. Proceedings, Canadian Northern Pipeline Research Conference, NRC Technical Mem. 104, pp 249–266 Linell KA, Johnston GH (1973) Engineering design and construction in permafrost regions. Division of Building Research, NRC, Technical Paper no 412, p 566 Poulin A (1962) Measurement of frost formed soil patterns using air photo techniques. Photogrammetric Engineering 28:141–147 Sigafoos RS, Hopkins DM (1952) Soil instability on slopes in regions of perennially-frozen ground. Frost Action in Soils, A Symposium, Highway Research Board, Washington, D.C., pp 176–192 Smith DJ (1987) Late Holocene solifluction lobe activity in Mount Rae area, Southern Canadian Rocky Mountains. Canadian Journal of Earth Sciences 24:1634–1642 Tart RG (1996) Permafrost. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, pp 619–632
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Fig. Zm1.1-1. Location. Geographic. 164° W, 64°35' N, western Alaska Source. USGS Comments. Ground photo shows laminar movement of gelifluction sheets 70 km east of Nome on Norton Sound on the south coast of the Seward Peninsula. The area is near the north margin of discontinuous permafrost. Material is glacial till on footslopes of Paleozoic metamorphic rocks.
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Fig. Zm1.1-2. Location. Geographic. 164°35' W, 68°53' N, northwest Alaska, USA Geologic. Paleozoic/Mesozoic sedimentary rocks of Arctic Foothills of Arctic Mountains Source. Tedrow JCF, Cantlon JE (1959) Concepts of soil formation and classification in Arctic regions. Arctic Institute of North America, pp 166–179 Comments. Photo shows a gelifluction lobe with tundra vegetation that has covered part of a Fv2k fluvial terrace in the Pitmega River area in the zone of continuous permafrost.
Zm1.1 · Gelifluction Sheets and Lobes ▼
Fig. Zm1.1-3.
Source. Transportation Research Board (1996) Landslides: Investigation and mitigation. National Research Council, Washington, D.C., Special Report 247, p 31, fig 25-12. Reproduced with permission Comments. The photo shows solifluction flow around a 45 cm pipe pile. Inclinometers placed close to this pile showed the greatest movement at the surface with the magnitude of movement decreasing with depth.
Fig. Zm1.1-4. Location. Geographic. 134°45' W, 63°19' N, Nogold Plateau, central Yukon Territory Cordilleran Craton Foreland Belt Source. Courtesy of Natural Resources Canada, GSC 99473 Comments. Gelifluction lobes are clearly visible covering a slope of glacial till (see Gf4) veneer below 1 500 m elev. Nunatak hills of Upper Proterozoic sedimentary rocks on this high altitude air perspective photo. Compare this photo with the ground view of Fig. Zm1.1-1. The location is at the east limit of ice advance of the last Cordilleran glaciation. A Gl5 terminal moraine coded Gt4 is delineated at the foot of the slope.
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Group Z · Periglacial Related Forms
Fig. Zm1.1-5. Source. Furrer G, Bachmann F (1972) Solifluktionsdecken im Schweizerischen Hochgebirge als Spiegel der postglazialen Landschaftsentwicklung. Zeitschrift für Geomorphologie, Juli 1972, p 164, photo 1,www.schweizerbart.de Comments. This is a ground view of gelifluction lobes on a slope pictured in the vertical photo of Fig. Zm1.1-6.
Fig. Zm1.1-6. Vertical Airphoto/Image. Type. Colour infrared airphoto Scale. 1:8 000 (estimate) Acquisition date. 1974 Source. Schweizerische Verkehrszentrale, Zürich (1980) Die Schweiz und ihre Gletscher, 2nd edn. Kümmerly+Frey Verlag, Bern, p 36, photo 24
Comments. The photo shows bright unvegetated gelifluction lobes to the left on this slope overriding a group of partly-vegetated older lobes. The lobes are spread over Würm ground moraine at elevation 2 540 m. Location is in the National Park south of Zernez. Figure Zm1.1-5 is a ground view of the slope.
Zm1.1 · Gelifluction Sheets and Lobes
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Fig. Zm1.1-7.
Location. Geographic. 78°07' W, 78°45' N, east-central Ellesmere Island, Nunavut Geologic. Central Ellesmere fold belt of Queen Elizabeth Island Sub-plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 22542-14, 15 Comments. The Zm1 gelifluction terrain areas in this large scale stereomodel at the head of Hayes Fjord are incipient or poorly developed sheets and lobes on Mc1 colluvial veneer in comparison with the more characteristic slope expression of the adjacent Zm1.1 area. ▼
Fig. Zm1.1-8.
Location. Geographic. 63°55' W, 58°44' N, Torngat Mountains, Québec Geologic. Uplifted Shield eastern rim Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL LAB-55-114, 115 Comments. Two Variants of gelifluction deposits are distinguishable in this stereomodel of the glaciated valley of the west-flowing Korok River. Zm1 sheets and lobes occur on the steeper upper slopes, while Zm1.2 stripes are on the gentler lower slopes. Willow alder and dwarf birch vegetation on these deposits is not apparent on this panchromatic film, but is well expressed on the multispectral Google Earth image. A large paraglacial Fu1 alluvial fan has displaced the river channel southward. The small Gf unit is a deposit of glaciofluvial outwash sands and gravels. This figure is 40 km northwest of 1: 100 000 stereo photos of Fig. Zm1.1-9. The sheets and lobes, but not the stripes, are resolved on the evidently lower resolution Google imagery available in early 2008. Movement rates (normal, reduced, arrested) are not reflected in the vegetation cover. This area was deglaciated 10 ka.
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Fig. Zm1.1-7. (Caption on p. 873)
Group Z · Periglacial Related Forms
Zm1.1 · Gelifluction Sheets and Lobes
Fig. Zm1.1-8. (Caption on p. 873)
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Group Z · Periglacial Related Forms
Zm1.1 · Gelifluction Sheets and Lobes ▼
Fig. Zm1.1-9. Location. Geographic. 63°26' W, 58°27' N, Torngat Mountains, north Labrador Geologic. Uplifted Shield eastern rim Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 100 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 17815-90, 91 Comments. The stereomodel in the Saglek-Ujutok Fjords area illustrates the detectability of the characteristic microrelief pattern of gelifluction slopes on small scale airphotos. The regional setting of this area is shown in the Landsat image of Fig. Mv1.1-12. This figure is 40 km southeast of Fig. Zm1.1-8.
Fig. Zm1.1-10. Location. Geographic. 05°43' E, 23°12' N, south Algeria Geologic. Mio-Pliocene Atakor X1 lavas on Proterozoic Hoggar Massif of African Craton Source. Rognon P (1967) Le Massif de L’Atakor et ses Bordures. CNRS, p 201, fig 50
Comments. This figure is a cross-section of gelifluction deposits of basalt blocks described in Figs. Zm1.1-11 and Zm1.1-12. (1) is the X1 basalt source flow; (2) are frost-riven basalt fragments; (3) are other flows in the basalt sequence; (4) is weathered and disintegrated basalt and clay matrix; (5) is a recent X1.2 basalt valley flow; (6) is the footslope deposit.
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Group Z · Periglacial Related Forms
Fig. Zm1.1-11. Location. Geographic. 05°43' E 23°12' N, southeast Algeria Source. LAR, March 1975 Comments. The photo, at the site of the profile of Fig. Zm1.1-10, shows blocks of basalt rock lying near the base of a 250 m long slope of a 100 m high hill at an elevation of 2 100 m in the volcanic Atakor Highland of the Hoggar Massif. The blocks have moved on a slip surface of montmorillonite clay which is a contact between Pleistocene and weathered Miocene basalt flows. The movements date from the last pluvial epoch in the Sahara, about 30 ka (Upper Pleistocene Middle Wisconsinan/Middle Würm) when periglacial conditions existed in this highland. Water then percolated down through basalt joints to lubri-
Fig. Zm1.1-12. Location. Geographic. 05°43' E, 23°12' N, southeast Algeria Source. LAR, March 1975 Comments. This is a close-up view of Fig. Zm1.1-11, it shows 2 to 3 m long blocks of slid columnar-jointed basalt lying on and in a matrix of weathered and disintegrated basalt and clay with 5 to 50 cm angular lava slabs on the slide slope.
cate, and swell, the clay of the weathered Miocene basalt surface. A close-up view of these blocks is in Fig. Zm1.1-12.
Zm1.2 · Gelifluction Stripes
Zm1.2 Gelifluction Stripes
terrain damage is often self-perpetuating, as slumping and erosion expose more of the permafrost to thaw.
Characterization
Reference
Gelifluction stripes, also denoted as nonsorted stripes, develop on seasonally unfrozen materials over a frozen substrate. Frost heaving, frost sorting, differential thawing and rillwash processes are principal agents of formation in conjunction with gelifluction, snowmelt water and rainfall. The stripes consist of subparallel shallow vegetated runnels along which surface runoff is channelled. The runnels alternate with lines of less vegetated or bare ground 1–5 m apart. Movement is confined to the bare unvegetated areas. The stripes are oriented down slopes ranging from 3–15°. On airphotos, scale 1: 40 000 and larger, this gelifluction variant appears as a striated pattern also dubbed as “horsetail drainage”. Mollard (1983) states that “where stones are mixed with fines on bare slopes, frost heave and sorting shifts the coarser rubble into stony stripes, which alternate with stripes of finer soil”.
Mollard JD, Janes JR (1983) Airphoto interpretatio and the Canadian landscape. Surveys & Mapping Branch, Dept. of Energy, Mines and Resources, Canada, p 124
Geohazard Relations If transportation lines are placed on gelifluction striped slopes, severe ponding will develop on the upslope-side of the transportation line each spring, with the consequent risk of washouts and thermal effects in the soil. The sub-parallel drainage runnels are frequently sufficiently close to make the placement of highway culverts impractical. Striped slopes are susceptible to damage by off-road vehicles; these will fragment the vegetated surface and quickly produce slumping or gully erosion. This style of
Fig. Zm1.2-1. Source. French HM (1976) The periglacial environment. Longman, London and N.Y., p 187, fig 9.4 Comments. A ground view in eastern Banks Island, Canadian Arctic, provides the scale of typical gelifluction stripes.
Select Bibliography Crampton CB (1973) Studies of vegetation, Landform and permafrost in the Mackenzie Valley. Environmental-Social Committee Northern Pipelines, Task Force on Northern Oil Development Report no 73–8, pp 20, 21, 27, 33 Dyke AS (1983) Quaternary geology of Somerst Island, District of Franklin (Nunavut). GSC Memoir 404, pp 8, 18 French HM (1976) The periglacial environment. Longman, London, p 188 Frost RE (1960) Aerial photography in arctic and subarctic engineering. American Society of Civil Engineers, J Air Transport Div, pp 27–56 Hall K (1983) Sorted stripes on sub-Antarctic Kerguelen Island. Earth Surface Processes and Landforms 8:115–124 Hamelin L-E, Cook F (1967) Illustrated glossary of periglacial phenomena. Les Presses de l’Université Laval, Quebec, pp 156–159 Hughes OL, Veillette JJ, Pilion J, Hanley PT, van Everdingen RO (1973) Terrain evaluation with respect to pipeline construction, Mackenzie transportation corridor, Central Part, Lat. 64° to 68° N. Environmental-Social Committee Northern Pipelines Task Force on Northern Oil Development, Rep. 73–37, pp 13, 31 Mollard JD, Pihlainen JA (1963) Airphoto interpretation applied to road selection in the Arctic. Proc., Permafrost Conference, National Acad. of Sciences – National Research Council (USA) Publ. 1287, pp 381–387 Pérez FL (1984) Striated soil in an Andean Paramo of Venezuela: Its origin and orientation. Arctic and Alpine Research 16:277–289 Pérez FL (1992) Miniature sorted stripes in the Paramo de Piedras Blancas (Venezuelan Andes). Periglacial geomorphology. John Wiley & Sons, Ltd., Chichester, pp 152–157 Schubert C (1973) Striated ground in the Venezuelan Andes. Journal of Glaciology 12:461–468 van Zuidam RA (1985/86) Aerial photo-interpretation in terrain analysis and geomorphologic mapping. Smits Publ./ITC The Hague, pp 338–339
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Group Z · Periglacial Related Forms
Fig. Zm1.2-2. Source. Frost RE (1960) Aerial photography in Arctic and Subarctic engineering. Journal of Air Transport Division, American Society of Civil Engineers, © May 1960, p 47. Reproduced by permission of the publisher, ASCE
Comments. An air view of vegetation/soil cryoturbation stripes on a hill slope moving onto a more level zone of Zi4 ice wedge polygons (lower right) in Alaska.
Zm1.2 · Gelifluction Stripes
Fig. Zm1.2-3. Location. Geographic. 156°15' W, 68°40' N, northern Alaska Source. USGS Comments. The air view shows gelifluction stripes on the colluvium and residuum of soft, folded Paleozoic and Mesozoic rocks of the southern part of the Arctic Foothills of the Akaskan Rocky Mountain System.
Narrow ridges are outcroppings of steep dipping resistant strata. The area is unglaciated but is in the zone of continuous permafrost dating from Upper Pleistocene Wisconsinan/Würm time, with local permafrost thicknesses ranging from 200 to 230 m and active layer depths varying from 15 cm to 120 cm.
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Group Z · Periglacial Related Forms
Zm1.2 · Gelifluction Stripes ▼
Fig. Zm1.2-4.
Location. Geographic. 125°01' W, 65°56' N, Northwest Territories Geologic. Northern Interior Plains Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1:38 000 (in CD-ROM) Acquisition date. Not given Source. CB Crampton (1973) © Her Majesty the Queen in right of Canada, Canadian Forest Service Comments. This stereomodel shows the typical drainage pattern of gelifluction stripes on glacial till (see Gf4) 5 km west of Smith Arm of Great Bear Lake. The thickness of the active layer here varies from 25 to 50 cm. The slight lineation in the till in the upper western part of the model is due to the northward ice flow direction in this area which was deglaciated approx. 12 ka.
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Fig. Zm1.2-5.
Location. Geographic. 73°07' W, 60°47' N, northern Québec Geologic. Eastern Shield Superior Province Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 16790-29, 30 Comments. A stereomodel shows occurrences of gelifluction stripes in a veneer of glacial till (see Gf4) on the Ungava Plateau. The distribution of this gelifluction pattern evidently bears some relation to that of the local fracture traces. These traces, in conjunction with stereo-observable micro relief, suggest an area of some bedrock control of topography through the cover of a veneer of glacial deposits. The stripe areas are covered by dwarf tundra vegetation; while the drier bedrock outcrops are essentially barren. This area was deglaciated 7 ka. See also Fig. Zm1.1-8.
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Fig. Zm1.2-5. (Caption on p. 883)
Group Z · Periglacial Related Forms
Zm2 · Rock Glaciers
Zm2 Rock Glaciers Characterization Rock glaciers are masses of “rock debris deformed by the downslope flow in mountains of buried or insterstitial ice, forming pronounced transverse and longitudinal ridges and furrows.” (Smith 2003). They are lobate or tongue-shaped bodies 10–60 m thick that transport a copious supply of rock debris from the base of talus Mv1.1, or moraine (unstratified glacially-deposited material) in alpine environments under the influence of gravity, onto the floors of cirques and down outlet valleys. The masses move at surface velocities ranging from 0.5 to 1 m yr–1 rates of a few centimeters to a few decimeters per year by flow of intersticial ice. “Rock glaciers may appear to be insignificant features in the broader mountain landscape but they can account for 15–20 percent of periglacial mass transport.” (Gerrard 1990).
Geohazard Relations Geohazards of rock glaciers apply to structures sited on or that cross them. Active rock glaciers are inherently unstable and inactive units are potentially so. Even their slowest velocities are sufficient to destroy most structures built on them, (e.g., roadways, pipelines, power transmission lines). Damage is also caused by ice melting resulting in compression of the surface layer. Giardino et al. (1992) report postexcavation adjustment of a rock glacier to removal of material from its toe resulting in surface creep that progressed up to 100 m behind the cut during the next six years.
References Gerrard AJ (1990) Mountain environments. The MIT Press Cambridge, Mass., pp 80–82 Giardino JR, Vitek JD, DeMorett JL (1992) A model of water movement in rock glaciers and associated water characteristics. In: Dixon, Abrahams (eds) Periglacial geomorphology. John Wiley & Sons, Ltd., pp 159–184 Smith IR (2003) Surficial geology of Babiche Mountain, Yukon Territory, North West Territories. Map 1: 50 000, GSC Open File 1558
Select Bibliography General Brenning A (2005) Geomorphological, hydrological and climatic significance of rock glaciers in the Andes of Central Chile (33–35° S). Permafrost and Periglacial Processes 16(3):231–240
Burger KC, Degenhardt JJ, Giardino JR (1999) Engineering geomorphology on rock glaciers. Geomorphology 31(1):93–132 Campy M, Macaire JJ (1989) Géologie des formations superficielles. Masson, pp 108–110 Calkin P, Haworth LA, Ellis JM (1987) In: Giardino JR, Shroder JF Jr, Vitek J (eds) Rock glaciers. Allen & Unwin, London, p 82 Dyke AS (1990) Quaternary geology of the Frances Lake Map Area, Yukon, Northwest Territories. GSC Memoir 426, pp 26–29 Flint RF (1971) Glacial and Quaternary geology. John Wiley & Sons, Ltd., New York, pp 273–274, 607 Hamelin L-E, Cook F (1967) Illustrated glossary of periglacial phenomena. Les Presses de l’Université Laval, Quebec, pp 82–85 National Research Council (1988) Glossary of permafrost and related ground-ice terms. Technical Memorandum 142, Canada, p 75 Owen LA, England J (1998) Observations on rock glaciers in the Himalayas and Karakoram Mountains of northern Pakistan and India. Geomorphology 26(1–3):199–213 Ryder JM (1998) Geomorphological processes in the alpine areas of Canada. GSC Bull 524:20–21 Wahrhaftig C, Cox A (1959) Rock glaciers in the Alaska Range. GSA Bull 70:383–436 Washburn AL (1979) Geocryology. Edward Arnold, London Whalley WB (1974) Rock glaciers and the formation of part of a glacier transport system. Geography Paper 24, Reading University
Airphoto Interpretation Barsch D, Hell G (1975) Photogrammetrische Bewegunsmessungen am Blockgletscher Murtel I, Oberengadin, Schweizer Alpen. Z Gletscherkunde Glazialgeologie XI(2):111–142 Evin M, Assier A (1982) Mise en évidence de mouvements sur le glacier rocheux du Pic d’Asti, (Queyras – Alpes du Sud France). Revue de Géomorphologie Dynamique 31(4):127–136 Haeberli W (1985) Creep of mountain permafrost: Internal structure and flow of alpine rock glaciers. Mitt. der Versuch. für Wasserbau, Hydrol. und Glaziol. Zürich, no 77 Haeberli W, King L, Flotron A (1979) Surface movement and lichencover studies at the active rock glacier near Grubengletscher, Wallis, Swiss Alps. Arctic and Alpine Research 11:421–441 Luckman BH, Crockett KJ (1978) Distribution and characteristics of rock glaciers in the southern part of Jasper National Park, Alberta, Canada. Canadian Journal of Earth Sciences 15(4):540–550 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 72, 285–286 Outcalt SE, Benedict JB (1965) Photointerpretation of rock glaciers in the Colorado Front Range. Journal of Glaciology 5(42): 849–856 Schroder JF (1973) Movement of boulder deposits, Table Cliffs Plateau, Utah. Geological Society Abstracts 5:511–152 Serrat D (1979) Rock glacier morainic deposits in the eastern Pyrénées. In: Schluchter C (ed) Moraines and varves. A. A. Balkema, Rotterdam, pp 93–100 Smith HTU (1973) Photogeologic study of periglacial talus glaciers in northwestern Canada. Geografiska Annaler 55A:69–84 Vernon P, Hughes OL (1966) Surficial geology, Dawson, Larsen Creek, and Nash Creek Map Areas, Yukon Territory, GSC Bull 136:17–22 White PG (1979) Rock glacier morphometry, San Juan Mountains, Colorado. GSA Bull 90(6):1515–1518, Il924–Il952
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Group Z · Periglacial Related Forms
Fig. Zm2-1. Source. Giordano JR, Vitek JD, De Morett JL (1992) A model of water movement in rock glaciers and associated water characteristics, in periglacial geomorphology. John Wiley and Sons, fig 7.3, p 163 Comments. A longitudinal sectional diagram shows two pathways by which water flows through a rock glacier and the solid phase storage zone.
“A model for the hydrologic system of rock glaciers includes direct precipitation, runoff from adjacent slopes, ice and snow from avalanching, groundwater, and initial glacial and/or periglacial ice’’. (Giordano et al. 1992).
Fig. Zm2-2. Source. Giardino JR, Shroder JF, Vitek J (1987) Rock glaciers. Allen & Unwin, fig 14.21
Comments. The person in this ground view gives the scale of a basal push lobe of a rock glacier.
Zm2 · Rock Glaciers
Fig. Zm2-3. Location. Geographic. 128°30' W, 61°30' N, southeast Yukon Territory Source. Courtesy of Natural Resources Canada, GSC 204511–D Comments. A ground photo of a rock glacier 1 200 ka formed through flow off Mv1 talus slopes in the Upper Proterozoic sediments of the Logan Mountains in the Selwyn Group. The deposit exhibits the characteristic morphologies of the unit: lobate tongue-shaped downslope flow, transverse ridge and limited extent.
Fig. Zm2-4. Location. Geographic. 126°30' W, 60°30' N approx., southeast Yukon Territory Source. Gabrielse H, Blusson SL, Roddick JA (1973) Geology of Flat River, Glacier Lake, and Wrigley Lake map-areas, District of MacKenzie and Yukon Territory. Part I: General geology, structural geology, and economic geology. GSC Memoir 366, p 126, pl VI Comments. This air view shows twin relatively large northeast-facing rock glaciers flowed from talus in cirques on a mountain slope of the Upper Proterozoic sedimentary rocks in the Logan Mountains of the Hyland Highland.
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Division 4 · Surficial Deposits
Fig. Zm2-5. (Caption on p. 890)
Group Z · Periglacial Related Forms
Zm2 · Rock Glaciers
Fig. Zm2-6. (Caption on p. 890)
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Division 4 · Surficial Deposits
Group Z · Periglacial Related Forms
▼
Fig. Zm2-5. Location. Geographic. 06°40' E, 45°20' N, Vanoise National Park, France Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 14 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. A group of three rock glaciers flowing from Mv1.1 talus sheets, are delineated in red on this photo enlargement in Upper Carboniferous sediments of the High Alps 20 km northeast of Modane. Occurrences delineated in black, coded “Zm2.1” are vegetated and inactive, but their ridges are still evident. Adjacent active Mv1.1 and Mv1.2 talus sheets and cones are also delineated. This figure extends Fig. Mv1.2-5 westward.
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Fig. Zm2-6.
Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1:25 000 (approx.) Acquisition date. Not given Source. Snobble JK (1970) Stereoscopic aerial photographs for Earth science. Silver Burdett Co., Morristown, N.J., p 10 Comments. Stereomodel shows rock glaciers in their Mv1 talus and cirque floor sites at an unspecified location in the USA Rocky Mountains.
Fig. Zm2-7.
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890
Location. Geographic. 07°10' E, 44°07' N, southern Alps Geologic. Gneiss of Mercantour Hercynian Massif Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 30 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. This stereomodel shows a locality at an altitude of 1 400 m to 2 600 m a.s.l., 45 km north of Nice. Relief in the model records the limit of the southern margin of the Würm (Wisconsinan) Upper Pleistocene glaciation in this part of the Alps. The north facing slopes are glacial cirques below Mv1 talus slopes and forested at lower elevations, in contrast to the unglaciated and drier southern slopes. Three rock glaciers occur in the model area. The longest is 2 km and its upper half is active with the lower half vegetated. The adjacent deposit is 1.8 km long and is evidently inactive, being largely vegetated. The third deposit is on what had been a frost-affected south slope, and though unvegetated, appears inactive. This figure is 17 km west of Fig. Mv1-5 and 19 km east of Fig. Mv4-7.
Zm2 · Rock Glaciers
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Division 4 · Surficial Deposits
Group Z · Periglacial Related Forms
Fig. Zm2-8. Location. Geographic. 134°18' W, 64°47' N eastern Yukon Territory Geologic. Mid Proterozoic metasediments of Cordilleran Craton Foreland Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 32 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 12260–294, 295
Comments. A stereomodel in the Wernecke Mountains shows a rock glacier flowing north and west into a gorge. The upper part of the glacier is covered by later Mv1.2 talus cone and Mv2 rock avalanche deposits. This site is at the west limit of the continental Laurentide Ice Sheet, 18–25 ka. The area is 185 km northeast of the gelifluction lobes of Fig. Zm1.1-4 and 195 km south of the detachment failure of Fig. Zm5-5.
Zm5 · Detachment Failures
Zm5 Detachment Failures Characterization A detachment failure is a long and narrow thawed surface layer of mineral soil and vegetation mat that detaches from and slides rapidly along a plane that is the top of the underlying permafrost.
Lewkowicz AG (1992) Factors influencing the distribution and initiation of active-layer detachment slides on Ellesmere Island, Arctic Canada. In: Dixon JC, Abrahams AD (eds) Periglacial geomorphology. John Wiley & Sons, Ltd., Chichester, pp 223–250 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, p 73 Smith SL, Burgess MM, Heginbottom JA (2001) Permafrost in Canada, a challenge to northern development. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:249
“Movement may involve either sliding of a relatively intact thawed piece of ground … or flow of water-saturated sediment. They are generally triggered by unusually warm temperatures or some disturbance of the vegetation mat”. (Aylsworth and Kettles 2000). The sliding can take place on moderate slopes and slopes of less than 15°, with some records as low as 3°. These failures can be the commonest type of landslide in many permafrost areas. They are also frequently triggered following forest fires.
Geohazard Relations “If thaw continues into ice-rich ground, the original active layer detachment may evolve into a retrogressive thaw flow (geounit Zk2) where the slide deepens and develops a progressively thawing and retreating head-scarp.” (Dyke 2000). The potential impact of these failures is on local transportation facilities and other engineering structures.
Fig. Zm5-1. Source. Dyke LD (2000) The physical environment of the Mackenzie Valley, Northwest Territories. In: Dyke LD, Brooks GR (eds) A base line for the assessment of environmental change. GSC Bulletin 547, p 179, fig 1b Comments. These diagrams show the dynamics of a detachment failure where deep thaw in a permafrost terrain active layer continues to encounter ice-rich ground. The detachment failure evolves into a Zk2 retrogressive flow.
References Aylsworth JM, Kettles IM (2000) Distribution of peatlands. In: Dyke LD, Brooks GR (eds) The physical environment of the Mackenzie Valley, Northwest Territories: A base line for the assessment of environmental change. GSC Bull 547:170 Dyke LD (2000) Stability of permafrost slopes in the Mackenzie Valley. In: Dyke LD, Brooks GR (eds) The physical environment of the Mackenzie Valley, Northwest Territories: A base line for the assessment of environmental change. GSC Bull 547:183–186
Select Bibliography Carson MA, Bovis MJ (1989) Slope processes. In: Fulton RJ (ed) Geology of Canada, no 1, Quaternary Geology of Canada and Greenland. GSC, pp 591–592 Carter LD, Heginbottom JA, Ming-ko Woo (1987) Arctic lowlands. In: Graf WL (ed) Geomorphic systems of North America. GSA, Cennial Special vol 2, pp 603–604 Duguay CR, Lewkowicks AG (1995) Assessment of SPOT panchromatic imagery in the detection and identification of permafrost features, Fosheim Peninsula, Ellesmere Island, N.W.T. Proceedings 17th Canadian Symposium on Remote Sensing, pp 8–14 French HM (1989) Cold climate processes. In: Fulton RJ (ed) Geology of Canada,no 1,Quaternary geology of Canada and Greenland. GSC,p 611 Leibman MO (1995) Cryogenic landslides on the Yamal Peninsula, Russia: Preliminary observations. Permafrost and Periglacial Processes 6(3):259–264
Fig. Zm5-2. Location. Geographic. 123°20' W, 71°37' N, southern Banks Island, Northwest Territories, Canada Geologic. Cretaceous sediments of Arctic platform Source. French HM (1976) The periglacial environment. Longman, London and New York, p 146, fig 7.5 Comments. A ground view of a typical permafrost active layer detachment failure in poorly lithified Cretaceous sand, silt and clay in Masik Valley.
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Zm5
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Division 4 · Surficial Deposits
Group Z · Periglacial Related Forms
Fig. Zm5-3. Location. Geographic. 126°40' W, 65°20' N, Mackenzie River Valley, Northwest Territories Geologic. Pleistocene glaciation of thrusted mid-Paleozoic sedimentary rocks of the Northern Interior Plains Source. Fulton RJ (ed) (1989) Quaternary geology of Canada and Greenland. GSC Geology of Canada, no 1, p 591, fig 9.12 Comments. An air view of a Zm5 permafrost active layer detachment failure in colluvial rubble or glacial till (Gf4) curving off a rock ledge and through a forested zone. Approximate location is 10 km northeast of Norman Wells on Discovery Ridge of the Norman Range.
Fig. Zm5-4. Location. Geographic. Mackenzie Valley, Northwest Territories Geologic. Pleistocene glaciation of Paleozoic sedimentary rocks of the Northern Interior Plains. Source. Harris SA, et al. (1988) Glossary of permafrost and related ground-ice terms. Natural Resources Canada Technical Memorandum no 142, p 151, fig 21b Comments. Another air view of active-layer detachment failures on a forested slope.
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Fig. Zm5-5. Location. Geographic. 134°36' W, 66°35' N, northeast, Yukon Territory, Canada Geologic. Pleistocene glaciation of Mid Cretaceous arenites of the Northern Interior Plains Source. Unattributed Comments. This is an air perspective view of numerous detachment failures on sub-arctic forest-covered glacial till (see Gf4) and colluvium slopes capping little disturbed Mid Cretaceous sedimentary rocks in the central Peel Plateau. The area was deglaciated 18 ka.
Zk1 · Subsidence Terrains
Sub-group Zk Thermokarst Terrain Zk1 Subsidence Terrains
The surface of the tundra, although compact in places, remained essentially intact. It was concluded that terrain disturbances associated with the sumpless operation were considerably less than those that might have occurred if a sump had been constructed. Details of this experiment are given in French 1980 and 1985.
Characterization Reference Subsidence of the ground surface in surficial deposits that have a relatively high content of segregated ground ice results from the melting of the buried ice. “On level ground, in fine-grained, high ice-content deposits, surface disturbance (climate, fire, human) commonly leads to the development of thermokarst, extensive subsidence of the ground surface and the growth of (shallow to 5 m deep, flat-bottomed) thaw lakes.” (Heginbottom 2000). The thaw lakes are also termed alas depressions. Where thaw lakes have been drained (by headward eroding stream gullies) they are filled with recent sediments and organic deposits, e.g. Fig. Zk1-1. In deposits such as hummocky glacial till (Gf4 and Fig. Zk1-10) the melting of segregated ice produces settlement and slumping over the former ice bodies.
Geohazard Relations The principal hazards of thermokarst processes relate to damage or destruction of transportation corridor segments and other northern development engineering infrastructures. The thawing of peatlands underlain by permafrost releases methane and oxidized methane which increases the concentrations of greenhouse gases in the atmosphere and contributes to global warming. Hoodoo N-52 exploratory oil well located on Ellef Ringnes Island of Fig. 11-1 was drilled between September and November 1981. Waste drilling fluids were deliberately disposed of upon the adjacent tundra surface as an experimental procedure. At that time Territorial Arctic Land Use Regulations required that drill fluids be contained completely in below-ground sumps. It was assumed that upon burial in the permafrost the drill fluids would freeze in-situ. Since drill fluids commonly contains salts, sump fluids do not freeze at 0 °C. The thermal influence of sump fluids upon enclosing permafrost has led to sump enlargement and sump overburden weight has led to Zk1 thermokarst subsidence at other arctic sites. The surface materials at Hoodoo are at least 15 m of ice rich silty clay derived from the underlying shale rock. The active layer is 30–50 cm.
Heginbottom JA (2000) Permafrost distribution and ground ice in surficial materials. In: Dyke LD, Brooks GR (eds) The physical environment of the Mackenzie Valley, Northwest Territories: A base line for the assessment of environmental change. GSC Bull 547:31–39
Select Bibliography General Brown RJE (1970) Permafrost in Canada. Canadian Building Series, University of Toronto Press, pp 15, 23, 34, 55–179 Demangeot J (1987) Les milieux naturel du globe. Masson, Paris, pp 146–147 Dresch J (1985) Nouvel atlas des formes du relief. IGN/Nathan, Paris, p 120 Fedorov A, Konstantinov P, Bosikov N (2005) Surface subsidence in ice-rich permafrost landscapes during the years of climatic stress, Central Yakutia. Proc. of CliC (Climate and Cryosphere, a core project of World Climate Research Prog.) First Science Conf., Bejing French HM (1985) Terrain, land use and waste drilling fluid disposal problems in Arctic Canada. Arctic 33(4):794–806 French HM (1985) Surface disposal of waste fluids, Ellef Ringnes Island, N.W.T. : Short-term observations. Arctic 38(4):292–302 Hamelin L-E, Cook F (1967) Illustrated glossary of periglacial phenomena. Les Presses de l’Université Laval, Quebec, pp 37–41 Harris SA (2002) Causes and consequences of rapid thermokarst development in permafrost or glacial terrain. Permafrost and Periglacial Processes 13(3):237–242 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 36–14–36–18
Photogeology Barnett DM, Edlund SA, Dredge LA (1977) Terrain characterization and evaluation: An example from eastern Melville Island. GSC Paper 76–23, pp 9, 10, 16, 17 Dean KG, Morrissey LA (1988) Detection and identification of Arctic landforms: An assessment of remotely sensed data. Photogrammetric Engineering and Remote Sensing 54(3):363–371 Duk-Rodkin A, Hughes OL (1995) Quaternary geology of the northeastern part of the Central Mackenzie Valley Corridor. District of Mackenzie, Northwest Territories. GSC Bull 458:13, 34 Ferrians OJ, Kachadoorian R, Greene GW (1969) Permafrost and related engineering problems in Alaska. USGS Professional Paper 678, pp 17–34 Frost RE (1950) Evaluation of soils and permafrost conditions in the territory of Alaska by means of aerial photographs. U.S. Army Corps of Engineers, p 36 Kreig RA, Reger RD (1976) Preconstruction terrain evaluation for the Trans-Alaska Pipeline Project. In: Coates DR (ed) Geomorphology and engineering. Dowden, Hutchinson, & Ross, Stroudsburg, pp 55–76
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Zk1
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Division 4 · Surficial Deposits Lavkulich LM (1973) Soils, vegetation, landforms of the Wrigley Area, N.W.T. Northern Pipelines Task Force on Northern Oil Development, Report no 73–18, pp 68–96 Mollard JD (1972) Airphoto terrain classification and mapping for northern feasibility studies. National Research Council Canada, Division of Building Research, Technical Memorandum 104, pp 105–127 Mollard JD, Janes JR (1983) Airphoto interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, pp 125–129
Group Z · Periglacial Related Forms Morrissey LA, Strong LL (1986) Mapping permafrost in the boreal forest with thematic mapper satellite data. Photogrammetric Engineering and Remote Sensing 52(9):1513–1520 Rampton VN (1982) Quaternary geology of the Yukon Coastal Plain. GSC Bull 317:29–32 Rampton VN (1988) Quaternary geology of the Tuktoyaktuk coastlands, Northwest Territories. GSC Memoir 423, pp 21, 21, 77–79 Rutter NW (1977) Methods of terrain evaluation, Mackenzie Transportation Corridor, N.W.T., Canada. Earth Surface Processes 2:302–304
Fig. Zk1-1. Source. Photograph: Nouvel atlas des formes du relief (1985) Nathan, p 120; cross sections: Demangeot J (1987) Les milieux naturels du globe, 2e éd. Masson, p 146, fig 45 Comments. The photograph shows massive ground ice exposed in the wall of an alastype depression in the Aldan River Valley in eastern Siberia at general coordinates 135° E, 60° N. This site is situation A in the lower section below. Figures give scale. The upper cross section shows a mass of segregated ground ice P in the frozen state. The lower section shows the subsided depression A resulting from thawing of the ice mass. Such thawing often occurrs in association with a discontinuous cover of peat. These depressions can appear as thaw lakes on level ground in fine-grained deposits as in Fig. Zk1-8.
Zk1 · Subsidence Terrains
Fig. Zk1-2. Location. Geographic. 102° W, 72°45' N, Arctic Islands, Nunavut Source. Courtesy of Natural Resources Canada, GSC. Photo by A. S. Dyke Comments. The photo shows massive ground ice exposed in a sidewall of a thermokarst pond in 10 ka Bc3 glaciomarine sediment on the lowland of the western side of Prince of Wales Island.
Fig. Zk1-3. Location. Geographic. 108°29' W, 76°28' N, Arctic Islands, Nunavut Source. Courtesy of Natural Resources Canada, GSC 168280 Comments. This 1973 photo shows hydraulic erosion of surface materials by manmade disturbance at an oil and gas exploration site on northeast Melville Island. The soils are deeply-weathered, poorly lithified Lower Cretaceous marine shales and siltstones with a permafrost active layer thaw depth of 0.5–0.6 m. Erosion at this locality has resulted from a single pass by a tracked vehicle four years earlier. Some of the meltwater is draining away, but in the process is eroding the gullies. Figure Zi4-6 shows adaptation to this environment by overland transport technology.
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Division 4 · Surficial Deposits
Group Z · Periglacial Related Forms
Fig. Zk1-4. Location. Geographic. 81°13' W,68°45' N,Melville Peninsula, Nunavut, Can. Source. LAR, June 1972 Comments. Photo of buildings at a military installation on Bw4 raised beaches and Bc3 glaciomarine deposits on Mid Ordovician limestone at Hall Beach. The foreground shows a meter thick gravel pad laid over the continuous permafrost. The pad acts as the surface foundation for the structures. An air space to reduce heat flow into the ground from the building is visible in the background. The peninsula was deglaciated 7 ka. ▼
Fig. Zk1-5.
Location. Geographic. 77°57' W, 72°42' N, north Baffin Island, Nunavut, Canada Source. LAR, June 1972 Comments. The photo shows gravel pad foundations for residential housing over the continuous permafrost of glacial till (see Gf4) at Pond Inlet on the northeastern Shield. These pads are used for small buildings which can tolerate some movement. The highland northward in the background across Eclipse Sound is the south coast of Bylot Island of Fig. Gl4-10. Pond Inlet is to be developed as a base and port development for a nearby extensive iron mining operation, with expanded population and related housing construction.
Fig. Zk1-6. Location. Geographic. 114° W, 69°45' N, Victoria Island, Nunavut Geologic. Paleozoic sediments of Franklinian Mobile Belt Source. Sharpe DR (1992) In Quaternary geology of Wollaston Peninsula, Victoria Island, Northwest Territories. GSC Memoir 434, p 32, fig 22A Comments. The air view shows a buried ice thaw slump in hummocky glacial till (Gf4) on Wollaston Peninsula. The site is 70 km northwest of Fig. Zk1-10.
Zk1 · Subsidence Terrains
Fig. Zk1-7. (Caption on p. 900)
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Division 4 · Surficial Deposits
Group Z · Periglacial Related Forms
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Fig. Zk1-7. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. Not given Source. Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS PP 373, fig 112 Comments. This stereomodel in northern Alaska shows the beaded drainage pattern at indicator point A along a stream
course. This is a characteristic feature of thermokarst terrain. Other indicators, B through G, point to various occurrences of Zi4 ice wedge polygons. The course of the stream channel is controlled by the pattern of the wedges, with the beads occurring at the junctions of wedges.
Fig. Zk1-8. Location. Geographic. 131°35' W, 67°25' N, Mackenzie Valley, Northwest Territories Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 78 000 Acquisition date. 24 June 1971 Source. Duk-Rodkin A, Hughes OL (1995) Quaternary geology of the northeastern part of the Central Mackenzie Valley Corridor, District of Mackenzie, Northwest Territories. GSC Bull 458, p 13, fig 7 Comments. The thaw lakes in this stereomodel are located on typical topographic sites in a zone of continuous per-
mafrost: Lp-k, (L1) glaciolacustrine plain; Ap alluvial plain (Fv2). The location is on the Anderson Plain of the Northern Interior Plains, on the northern reach of the Mackenzie River 150 km from the head of the delta. The glaciolacustrine sediments are Late Wisconsinan, 3 to 30 m of ice-rich silt, clay and minor sand overlain by discontinuous veneer of organic deposits. The alluvial deposits are Holocene silt and fine grained sand up to 5 m or more thick. The fine grained sediments contain a high proportion of segegated ice. The part labeled Ap–k is marked with numerous thermokarst ponds.
Zk1 · Subsidence Terrains
▼
Fig. Zk1-9.
Location. Geographic. 137°50' W, 69°05' N, Yukon Coast Geologic. Arctic paraglacial coastal plain Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 40 000 Acquisition date. 8 August 1985 Source. Courtesy of Natural Resources Canada, NAPL A 26779, 11,12,13 Comments. This stereomodel at Sabine Point shows thermokarst basins with 3–9 m thick L1 glaciolacustrine and peat deposits that are inset 2 to 6 m into glacial till (see Gf4). The basins result from the melting of ice cores in the underlying till. A radiocarbon date for the peat is 14 400 ±180 bp. The combined Zk1 and Zi4 codes indicate that ice wedge polygons are developed on practically the entire surface of the basin sediments. This location is the same as Fig. Bb1.1-4. ▼
Fig. Zk1-10.
Location. Geographic. 112°20' W, 69°30' N, southwest Victoria Island, Nunavut Geologic. Paleozoic sediments of Franklinian Mobile Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 54 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 14901-111, 112 Comments. The hummocky relief in this stereomodel on the Wollaston Peninsula is being accentuated by Zk1 thermokarst subsidence of ice cores in a Gl5 end moraine. The site is 70 km southeast of Fig. Zk1-6. The peninsula was deglaciated 12 ka.
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Division 4 · Surficial Deposits
Fig. Zk1-9. (Caption on p. 901)
Group Z · Periglacial Related Forms
Zk1 · Subsidence Terrains
Fig. Zk1-10. (Caption on p. 901)
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Zk2
Division 4 · Surficial Deposits
Zk2 Retrogressive Thaw-Flow Slides Characterization These scooplike scar slides, also known as retrogressive thaw slumps or ground ice slumps are morphologically similar to Geounit Mf1, retrogressive flows in unconsolidated sediments, but are developed by periglacial processes in soil-ice mixtures. They occur where ice-rich scarps develop in a variety of geounits: detachment failures Zm5 if ground ice is exposed; glaciolacustrine sediments L2; fine-grained glacial till (Gf4) slopes; along coasts in bluffs in ice-bonded sediments Bb1.1; and around the edges of thermokarst depressions Zk1. They have a characteristic bowl shape and a longitudinal profile with a steep headwall ranging from 7 m to 60 m high and a low-angle tongue. Once exposed, the thawed material slides from the melting backwall in periodic bursts. The ice-rich scarp melts slowly backward (retrogression) until the sloping floor meets ground surface, or until the backwall intersects soil that is stable when thawed (Duk-Rodkin and Hughes 1995).
Group Z · Periglacial Related Forms Evans SG (2001) Landslides. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:65–66 Harris SA, French HM, Heginbottom JA, Johnston GH, Ladanyi B, Sego DC, van Everdingen RO (1988) Glossary of Permafrost and Related Ground-Ice Terms. Glossary of Permafrost and Related Ground-Ice Terms. NRC Technical Memorandum 142, p 75 Heginbottom JA (2000) Permafrost distribution and ground ice in surficial materials. In: Dyke LD, Brooks GR (eds) The physical environment of the Mackenzie Valley, Northwest Territories: A base line for the assessment of environmental change. GSC Bull 547:36 Lantuit H, Pollard WH (2004) Identification of stabilized and revegetated retrogressive thaw slumps floors on an ice-rich arctic coast using Landsat near-infrared imagery. 5th Internatioal Workshop of Arctic Coastal Dynamics. Mollard JD, Janes JR (1983) Airphoto interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, p 73 Rampton VN (1982) Quaternary geology of the Yukon Coastal Plain. GSC Bull 317:29–32 Wei M, Fujun N, Satoshi A, Dewu J (2006) Slope instability phenomena in permafrost regions of Qinghai-Tibet Plateau, China. Landslides 3(3):260–264
Geohazard Relations Retrogressive slides can be severely damaging to structures. “They take place naturally and continually, but the rate and resulting damage to human-made structures can be greatly increased by human activity that exposes the permanently frozen soil to thawing.” (Duk-Rodkin and Hughes 1995).
Reference Duk-Rodkin A, Hughes OL (1995) Quaternary geology of the northeastern part of the Central Mackenzie Valley Corridor. District of Mackenzie, Northwest Territories. GSC Bull 458:34
Select Bibliography Aylsworth JM, Duk-Rodkin A, Robertson T, Trainer JA (2000) Landslides of the Mackenzie Valley and adjacent mountainous and coastal regions. In: Dyke LD, Brooks GR (eds) The physical environment of the Mackenzie Valley, Northwest Territories: A base line for the assessment of environmental change. GSC Bull 547:170–171 Brown RJE (1974) Some aspects of airphoto interpretation of permafrost in Canada. Division of Building Research, National Research Council Canada, Dept. of Energy, Mines and Resources, Technical Paper no 409, p 14 Dyke LD (2000) Stability of permafrost slopes in the Mackenzie Valley. In: Dyke LD, Brooks GR (eds) The physical environment of the Mackenzie Valley, Northwest Territories: A base line for the assessment of environmental change. GSC Bull 547:179–183
Fig. Zk2-1. Location. Geographic. 119°45' W, 68°35' N approx., west Nunavut Source. St. Onge DA, Martin I (1995) Quaternary geology of the Inman River Area, Northwest Territories. GSC Bulletin 446, cover illustration Comments. An air view taken 23 July 1988 shows a large thawflow slide in hummocky glacial till (see Gf4) inland from the Arctic Coast, at the western extremity of Nunavut. The slumping has exposed 15 to 20 m ice-rich sediments beneath 2 to 5 m of till. The icy sediments appear as a lighter grey band in the slump face beneath the darker till surface just west of the center of the photo. This slump was observed to have enlarged substantially between 1986 and 1989. A similar slide in lacustrine sediments is in Fig. Zk2-2. The till and icy sediments rest on bright Ordovician dolomites of the Arctic Platform. The area was deglaciated about 12 ka.
Zk2 · Retrogressive Thaw Flow Slides
Fig. Zk2-2. Location. Geographic. 133°09' W, 69°24' N, Arctic Coastal Plain, Northwest Territories Source. Courtesy of Natural Resources Canada, GSC 204375S Comments. This air perspective photo shows a retrogressive thaw flow slide in massive ice-cored L1 glaciolacustrine sediments which range in thickness between 2 and 8 m at Pen-
insula Point 6 km southwest of Tuktoyaktuk on Kugmallit Bay of the Beaufort Sea. The scar of an older slide is visible behind the active slide. Figure Zk2-1 located 445 km to the east in Nunavut shows a similar slide in glacial till. Banding in the massive ice is visible in center foreground of the photo. This area was deglaciated about 16 ka.
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Division 4 Surficial Deposits Group M · Mass Movement Materials
Sub-group Mv Falls and Subsidences Sub-group Ml Lateral Spreads Sub-group Mc Diagonal Creeps
The 15 geounits and 10 Variants of this Group are ordered in five Sub-groups:
Mv Ml Mc Ms Mf
– – – – –
Falls and subsidences Lateral spreads Diagonal creeps Slides Flows
General Note of Geohazard Relations Sub-group Ms Slides Sub-group Mf Flows
The geounits of this Group are inherently agents of fall, creep, slide, slump, erosion and deposition acting on the units of the other groups. Additionally, geounits of Sub-groups Ms slides and Mf flows are agents of flooding. All of the geounits are susceptible to erosion, while units of Sub-groups Mv falls, Ms slides and Mf flows are particularly susceptible to seismicity. The following is a statement of background of landslides given by the ESA’s CEOS Disaster Management support Group. “Movement occurs when the shear stress exceeds the shear strength of the material.” “The factors contributing to an increase of the shear stress include removal of lateral and underlying support (erosion, previous slides, road cuts and quarries) increase of load (weight of rain/snow/ash, fills, vegetation) increase of lateral pressures (hydraulic pressures, roots, crystallization, swelling of clay) transitory stresses (earthquakes, vibrations of trucks, machinery, blasting) regional tilting (geological movements) Factors related to the decrease of the material strength include decrease of material strength (weathering, change in state of consistency) changes in intergranular forces (pore water pressure, solution, fracture and crack propogation) changes in structure (decreased strength in failure plane, fracturing due to unloading) Globally, landslides cause approximately 1 000 deaths per year, causing property damage of approximately U.S. $2 billion.” The 144 figures documenting this group include 54 stereo photo pairs with representations from 21 countries.
Select Bibliography Sinha PC (1998) Geological and mass movement disasters. Anmol Publications PVT Ltd.
L.A. Rivard, Geohazard-associated Geounits, Environmental Science and Engineering, DOI 10.1007/b93844_13, © Springer-Verlag Berlin Heidelberg 2009
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Division 4 · Surficial Deposits
Sub-group Mv Falls and Subsidences Mv1
Group M · Mass Movement Materials
Mv1 Talus-Rockfalls Undifferentiated
tation routes in rocky terrain, and when they hit buildings downslope. Talus accumulations can encroach on and bury land and buildings. Such deposits are susceptible to long term fluvial erosion of their distal portions.
Characterization
Select Bibliography
These are masses of broken rock blocks and angular rock fragments of any dimensions from the size of boulders to houses that detach from cliffs and steep slopes underlain by fractured but otherwise competent rock formations. The masses descend rapidly, mainly through the air, by falling, and by bouncing or rolling on the slope. Repeated falls from the same slope result in an unstructured accumulation of sub-angular boulders, cobbles and finer particles lying at the foot of the slope. The materials accumulate at angles of repose which reflect the size and roughness of the particles. The commonest causes of small rockfalls are high rainfall, freeze-thaw and desiccation weathering. Larger falls may be triggered by earthquakes, unloading or erosional undercutting. Hundreds of rockfalls have been recorded from young Alpine mountain ranges. Rockfall deposits appear as two Variants on airphotos: talus sheets, Mv1.1; and talus cones, Mv1.2. Pleistocene talus is inactive and generally appears vegetated.
Albjar G, Rehn, J, Stromquist L (1979) Notes on talus formation in different climates. Geografiska Annaler 61A:179–185 Chandler RJ (1973) The inclination of talus, arctic talus terraces and other slopes composed of granular material. Journal of Geology 81:1–14 Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 47–51 Evans SG, Hungr O (1993) The assessment of rockfall hazard at the base of talus slopes. Canadian Geographical Journal 30:620–636 Flageollet JC, Weber D (1996) Landslide recognition. John Wiley & Sons, Ltd., Chichester, p 13–29 Gardner J (1969) Observations on surficial talus movement. Zeitschrift für Geomorphologie 13:318–323 Jaboyedoff M, Labiouse V (2003) Preliminary assessment of rockfall hazard based on GIS data. International Society for Rock Mechanics – Technology roadmap for rock mechanics. South African Institute of Mining and Metallurgy Kalvoda J, Rosenfeld C (1998) Geomorphological hazards in high mountain areas. Springer-Verlag Marquinez J, Menéndez DR, Farias, Jinénez SM (2003) Predictive GISbased model of rockfall activity in mountain cliffs. Natural Hazards 30(3):341–360 Mc Saveney ER (1972) The surficial fabric of rockfall talus. Quantitative geomorphology: Some aspects and applications. Publications in Geomorphology, Binghamton, N.Y., pp 181–197 Moon BP, Selby MJ (1983) Rock mass strength and scarp forms in Southern Africa. Geografiska Annaler 65A:135–145 Sass O, Wollny K (2001) Investigations regarding Alpine talus slopes using ground-penetrating radar (GPR) in the Bavarian Alps, Germany. Earth Surface Processes and Landforms 26(10):1071–1086 Whalley WB (1974) The mechanics of high magnitude-low frequency rock failure and its importance in mountainous areas. Reading University Geography Paper 27
Geohazard Relations Rockfalls are agents of the fall hazard, #3, and the deposition hazard, #12. Boulders and even small stones, falling from a great height, attaining high velocities, can wreak much damage when they hit many types of man-made structures. They are a constant problem along transpor-
Fig. Mv1-1. Source. Courtesy ADMO Tours Comments. Photo of a large nearintact rockfall block of Jurassic cross-bedded sandstone on an unpaved road near Moab in eastern Utah, on the northern Colorado Plateau USA. In the absence of site-specific information concerning the nature of the detachment zone, the block appears to be from a scarp slope in massive or thick-bedded rocks. Failure may have proceeded by forward toppling from discontinuities or bedding planes inclined toward or parallel to the rock face. Figure 18-5 located in the same region shows the typical joint sets in these brittle rocks.
Mv1 · Talus Rockfalls Undifferentiated
Fig. Mv1-2. Location. Geographic. 07°47' E, 46°05' N, southern Switzerland Source. esa Service for Landslide Monitoring Comments. This photo shows the rupture scarp and rockfall mass of 30 million m3 from a slope of paragneiss and orthogneiss rocks. Location is near the village of Randa in the Mattertal, a busy alpine valley with rail and road lines connecting Zermatt to the Rhone Valley at Visp. The volume of rock fell from the face of the slope in two events three weeks apart. The first one occurred on 18 April 1991. It involved 22 million cubic meters of rock down 400 m of slope from elevation 2 000 m to 1 600 m. The second failure occurred on 9 May. It carried a further 7 million cubic meters of rock from upslope elevation 2 270 m to 2 000 m. The 18 April event interrupted the rail line. The 9 May failure was forecast by seismic and geodetic surveys and the area was evacuated. This rockfall buried 800 m of the rail line, 200 m of the roadway, and dammed the Vispa River (Mf4.1). About 30 houses were flooded. A channel was quickly dug to prevent overtopping and destruction of downstream villages. The unfavourable structural conditions consisted of three sets of joints that divided the rock slope into large blocks. These joint sets had promoted the development of two ancient landslides on the slope. These pre-existing instabilities increased the permeabilty of the substratum and the infiltration rate that favoured water overpressure.
The 1991 failures finally coincided with a period of heavy snowmelt.
909
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mv1-3. Location. Geographic. 123°14' W, 49°26' N, southern British Columbia Geologic. Lower Cretaceous tuff, breccia Source. Unattributed Comments. The photo shows rail and highways blocked by a rockfall that originated 300 m upslope at Howe Sound in the Coast Mountains 20 km north of Vancouver.
Fig. Mv1-4. Source. Unattributed Comments. A photo at an unidentified location shows sheds designed to deflect sites of persistent rockfalls over railway tracks in mountainous terrain.
Fig. Mv1-5.
▼
910
Location. Geographic. 07°22' E, 44°09' N, Mercantour, northwest Italy Geologic. Hercynian crystalline massif of Southern Alps Vertical Airphoto/Image. Type. b/w, pan, stereo pair Scale. 1: 30 000 Acquisition date. 30 August 1978 Source. IGN – Photothèque Nationale, France 93, 94 Comments. The stereomodel in the Parco Naturale delle Alpi Maritime shows a 3 km long by 0.5 km wide talus and rock complex. The avalanche that has flowed down from high and steep Mv1 talus slopes of glaciated migmatite peaks 30 km southwest of Cuneo. The rock mass
slid down a wide gully on the west side of the valley. Part flowed on down the valley, and a segment climbed part way up the opposite slope. Fortunately the valley track is not a vehicular roadway. In the upper left of the stereomodel is a hydro-electric power project, under construction at photo date, mid-way between the small lakes Rovine to the north and Brocan to the south. The high dam is readily visible. The well-known geotechnical factors involved in the design and construction of such a structure in sound foundation and abutment rocks in a glaciated valley are always challenging. This figure is 17 km east of Fig. Zm2-7.
Mv1 · Talus Rockfalls Undifferentiated
911
912
Mv1.1
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mv1.1 Talus Sheets
talus deposit. The hazard area covered by these boulders is termed a rockfall shadow.
Characterization
Geohazard Relations
Talus sheets are deposits of coarse angular rock fragments in mountain, plateau and coastal terrains that are not removed, and accumulate as sloping aprons with an angle of repose equal to 32–36° which reflects the shape and roughness of the particles at the base of cliffs or steep slopes from which they have been derived. As with the parent unit, weathering causes jointbounded blocks of rock to break off the rock scarps and cliffs. These sheets form against relatively straight cliffs. If the cliff is notched by gullies the debris will accumulate as the talus cone of Variant Mv1.2. Some scattered large boulders roll or bounce beyond the foot of the talus sheet onto materials that pre-date the
See Geounit Mv1.
Select Bibliography Gerrard AJ (1990) Mountain environments. The MIT Press Cambridge, Mass. Hungr O, Evans SG (1989) Engineering aspects of rockfall hazards in Canada. GSC and Transport Canada Research Project UP-T6–004–1 van Steijn H (2002) Long-term landform evolution: evidence from talus studies. Earth Surface Processes and Landforms 27(11): 1189–1199
See also Geounit Mv1.
Fig. Mv1.1-1. Source. Hungr O, Evans SG (1989) Engineering aspect of rockfall hazards in Canada. Report to the Geological Survey of Canada and Transport Canada (Research Project UP-T6-004-1) fig 4.3, p 24 Comments. This modified schematic diagram of a talus sheet slope shows the shadow zone of associated rollout rockfall deposits – see Fig. Mv1.1-2.
Fig. Mv1.1-2. Location. Geographic. 12°58' E, 47°31' N, southeast Bavaria, Germany Geologic. Upper Triassic dolomitic limestones Source. LAR, May 1976 Comments. Photo in the Königsee-Obersee glaciated fault valley in the Berchtesgaden National Park shows scattered sub-angular rollout boulders of a rockfall shadow zone (Fig. Mv1.1-1) lying on glacial till (Gf4).
Mv1.1 · Talus Sheets
Fig. Mv1.1-3. Location. Geographic. 56°09' W, 47°48' N, New foundland Island Geologic. Devonian granite in Inner Terrane Belt of Appalachian Orogen Source. Courtesy of Natural Resources Canada, GSC 201899 Comments. This photo on the western arm of Bay d’Espoir on the south central coast shows an unstructured deposit of angular boulders at the foot of a stabilized, possibly paraglacial (see Unit Fu1) partly forested talus sheet. Inactive and vegetated talus deposits evolve in a fashion similar to slopes with weathered mantles, see Unit Mc1.
Fig. Mv1.1-4. Location. Geographic. 08°03' E, 46°40' N, central Switzerland Geologic. Lower Jurassic sediments of the Wildhorn Nappe Source. LAR Comments. Photo just north of the First Bahn chair lift station above Grindelwald, shows new scree falls adding to older talus sheet deposits at the base of 40 m high cliffs of thinly bedded marly shales. The levee-like ridge form in the center may have been a Fu1/Mv1.2 fan/Talus cone complex.
913
914
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mv1.1-7.
Fig. Mv1.1-5. Location. Geographic. 07°54' E, 46°33' N, central Switzerland Geologic. Interbedded Mid-Jurassic sediments of the Wildhorn Nappe Source. LAR Comments. Photo at the upper end of the classic glaciated U-shaped Lauterbrunnen Valley shows 80 m high talus sheets of marly rocks and scattered limestone boulders at the valley footslope. The glacier-bevelled steep valley walls are 730 m high.
Location. Geographic. 03°45' E 25°17' N, southeast Algeria Geologic. Craton cover Ordovician sandstones Source. LAR, March 1975 Comments. The photo shows Mv1 rockfall flagged sandstone boulders lying on a talus sheet at Arak Gorge near the contact with the Hoggar Massif. As with Fig. Mv1.1-6 this talus appears climatically bimodal. Local relief is 450 m of which 250 m is the cliff free face and 200 m is the talus sheet slope masking the Late Archean basement rocks. This site is located on “y” the vertical airphoto of Fig. Mv1.1-8. The building at the base is a fortified hotel located at a point in the wadi course where groundwater is available. The water source is at a rock barrier buried in the valley fill which ponds up the groundwater in the coarse deposits, creating a raised aquifer immediately upstream. ▼
Fig. Mv1.1-6. Location. Geographic. Southeast Algeria Geologic. Stock of Neohadrynian granite in Hoggar cratonic massif Source. LAR, February 1975 Comments. The talus sheet in this photo is covering most of the slope of a well-jointed granite stock or domed inselberg. The sub-angular appears to be climatically bimodal, with the finer fraction being covered by joint-separated sub-angular boulders.
Mv1.1 · Talus Sheets
Fig. Mv1.1-8. Location. Geographic. 03°45' E, 25°17' N, southeast Algeria Geologic. Craton cover Ordovician sandstones Vertical Airphoto/Image. Type. Pan, b/w airphoto Scale. 1: 30 000 Acquisition date. December 1974 Source. Personal archive
Comments. A single photo shows extensive sandstone talus sheets masking the underlying basement rocks at Arak Gorge. The location and field of view of Fig. Mv1.1-7 is indicated on the interpretation sketch. The dark tones in the wadi bed are evidence of the groundwater source discussed in Fig. Mv1.1-7.
915
Division 4 · Surficial Deposits
Group M · Mass Movement Materials ▼
Fig. Mv1.1-9. Location. Geographic. 11°59' W,16°57' N, southern Mauritania Geologic. Lower Paleozoic craton cover sediments Vertical Airphoto/Image. Type. b/w airphoto Scale. 1:50 000 (in CD-ROM) Acquisition date. 1956/57 Source. IGN – Photothèque Nationale, France Comments. Stereomodel shows talus sheets surrounding the S1.4 Ordovician well-jointed surface of Assaba sandstone Plateau, elevation 470 m a.s.l. The talus sheets drop 250 m below the cliff free face. The rock blocks of these deposits coded “C” disintegrate in their fall, so that the largest boulders are at the upper end of the talus slope. The vegetation cover of the talus is due to the presence of springs in the scarp strata. The descriptor S1.4 originally designated an arid-zone facies.
Fig. Mv1.1-10.
▼
916
Location. Geographic. 63°27' W, 58°32' N, north Labrador Coast Geologic. K/T uplift of Late Proterozoic orogen of the eastern Shield Vertical Airphoto/Image. Type. Pan, b/w, mounted stereo pair Scale. 1: 100 000 Acquisition date. 11 October 1962 Source. Courtesy of Natural Resources Canada. NAPL A 17815-90, 91 Comments. The stereomodel in an area of multiple glaciations of the Torngat Mountains from Mid Pleistocene to 11 ka shows talus on a slope of gneisses of fault-controlled Nachvak Brook at the west end of Saglek Fjord. The site is poorly resolved due to the photo scale, the exaggerated relief from a short focal length wide-angle camera lens, and shadowing due to solar aximuth and elevation (October). However the same conditions, emphasize some structural control of this fjord type glaciated valley at the southern end of Torngat Mountains National Park. The inset frame locates the coverage of Fig. Mv1.1-11. Compare the model with the satellite image of Fig. Mv1.1-12.
Mv1.1 · Talus Sheets
917
918
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mv1.1 · Talus Sheets ▼
Fig. Mv1.1-11.
Location. Geographic. 63°27' W, 58°32' N, north Labrador Coast Geologic. K/T uplift of Late Proterozoic orogen of the eastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 15 August 1949 Source. Courtesy Natural Resources Canada, NAPL Lab48-192, 193 Comments. A stereomodel shows occurrences of talus sheets and related Mv1.2 talus cone and Mv2 rock avalanche on a fault-controlled fjord slope. Compare the same location photographed at a 2.5 times smaller scale in Fig. Mv1.1-10.
919
920
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mv1.1 · Talus Sheets ▼
Fig. Mv1.1-12. Location. Geographic. 63°27' W, 58°32' N, north Labrador coast Geologic. Late Proterozoic of the eastern Shield orogen Vertical Airphoto/Image. Type. Landsat Acquisition date. 2005 Source. MDA EarthSat Comments. This multispectral image is centered on the glaciated valleys of Saglek Fjord. The talus and rockfalls are not resolved at synoptic scale. The green strips are alder willow and dwarf shrub vegetation growing on the more moderately sloping and more solar exposed talus deposits of the valley footslopes. This vegetation is less clearly resolved as darker tonality in the panchromatic photos of Fig. Mv1.1-11. These valley floors are inundated seasonally by rapidly flowing streams, thus limiting vagetative colonization. The uplands are comparatively barren with a sparse cover of lichens and mosses. The inset frame locates coverage of the stereomodel of Fig. Mv1.1-10 in the fault valley of Nachvak Brook in the Torngat Mountains. See also Fig. Zm1.1-9.
921
Mv1.2
Division 4 · Surficial Deposits
Mv1.2 Talus Cones
Group M · Mass Movement Materials
Geohazard Relations See Geounit Mv1.
Characterization Select Bibliography In contrast to the talus sheet, the cone form variant occurs in confined situations where a rockfall is located in a ravine, funnel or chute.
See Geounit Mv1.
Fig. Mv1.2-1. Source. Clague JJ (1984) Quaternary geology and geomorphology, Smithers-Terrace-Prince Rupert Area, BC, Canada. GSC Memoir 413, p 21, fig 19 Comments. These block diagrams show the morphologic distinction between Mv1.1 talus sheet and Mv1.2 talus cone.
▼
Fig. Mv1.2-2. Location. Geographic. 85°40' W, 72°43' N (approx.), north Baffin Island, Nunavut Geologic. Mid-Proterozoic quartzites of the northeast Shield Source. Courtesy of Natural Resources Canada, GSC 142412 Comments. Photo of a classic talus cone issuing from a chute type gully on the east coast of Admiralty Inlet.
Fig. Mv1.2-3.
▼
922
Location. Geographic. 11°45' E, 46°30' N, western Dolomites, Italy Geologic. 1 000 m high Triassic fossil reef front Source. Friedli W (undated) Alpen Flugbild, Weltflugbild. R. A. Muller, Feldmeilen/Zh Schweiz, photo 58 Comments. An air perspective photo shows two large talus cones delineated at the foot of the Langkofelgruppe tract of reef limestone (Schlerndolomit) massif, 3 178 m between Bolzano and Cortina. A large Mv2.1 rock avalanche in the center lies below them near the Sella Pass Hotel 2 214 m. Mv1.1 talus sheets are at the right. See Fig. Mv2-1.
Mv1.2 · Talus Cones
923
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mv1.2-4. Location. Geographic. 73°15' W, 71°10' N, central Baffin Island, Nunavut Geologic. Archean metamorphic base ment rocks of the northeast Shield Source. Courtesy of Natural Resources Canada, RR 330-4200 Comments. An air view to the southeast in the Clyde Highland on the east coast shows an array of multiple talus cones at the foot of 600 m rock cliffs on the east side of Dexterity Fjord. The apices of the cones are at approx. 250 m elevation.
Fig. Mv1.2-5.
▼
924
Location. Geographic. 06°41' E 45°20' N, French Alps Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 14 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. This enlarged photo in the Vanoise National Park 5 km south of the winter sports resort of Pralognan shows a set of recurrently active talus cones. These descend to the Vallon Doron de Chauvière from below a ridge crest of west-dipping interbedded Triassic rocks at elevation 2 600 m to the valley at 2 100 m.
The arrow indicates a point at the toe of the largest movement where the valley track arcs way from a rollout boulder danger zone (see Variant Mv1.1). An active Mv1.1 talus sheet is also delineated northward. The smooth grey tones of the other parts of this eastfacing slope are probably covered by a veneer of glacial till. Talus-associated occurrences of some Zm2 rock glaciers are indicated on the west-facing slope of the ridge. This figure extends Fig. Zm2-5 eastward.
Mv1.2 · Talus Cones
925
926
Mv2
Division 4 · Surficial Deposits
Mv2 Rock Avalanches (Sturzströmen) Characterization Rock avalanches involve the initial failure and subsequent disintegration of a large rock mass on a valley-confined slope or on an unconfined high mountain slope. They differ from talus rockfalls in their mass, in their velocity of movement and in their efficiency of transport. These events involve much larger masses of rock than rockfalls, volumes are typically greater than 100 m3 which can trap enough air or snow and ice to facilitate very rapid flow. The avalanche masses can discharge into a valley and partly up the opposite slope in less than a minute; they
Group M · Mass Movement Materials
may also run-out long distances down-valley, up to 10 km from the source area. If the avalanche incorporates water-saturated sediments it may change into a Mf3 debris flow of great destructive power. Failures are related to bedding planes, joints, faults, cleavage or schistosity planes and caused by toe removal, head loading or seismicity.
Geohazard Relations The geohazards of rock avalanches are the same as for rockfalls, but their magnitudes and areas affected are greater. The stream of debris commonly blocks pre-existing drainage courses and forms lakes. Large masses of rock (>100 m3), once in motion, are almost impossible to control and protective works tend to be futile. In most densely settled mountain regions, where land is intensely used, the hazard from rare, single, large slope failures generally is accepted, but in the 20th century it has been estimated that 50 000 people have been killed by rock avalanches.
Select Bibliography
Fig. Mv2-1. Source. Eisbacher GH (1979) First-order regionalization of landslide characteristics in the Canadian Cordillera. Geoscience Canada, vol 6, no 2. Geological Association of Canada, p 71, fig 2 Comments. Figure shows simplified profiles of Mv1 rockfalls with free fall motion on a steep to vertical rock face, and the much larger mass of a Mv2 rock avalanche valley deposit below its source slope. See Fig. Mv1.2-3.
Dikau R, Brunsden D, Schrott L, Ibsen M-L (1996) Landslide recognition. John Wiley & Sons, Ltd., Chichester, pp 13–29 Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 148–149 Evans SG, DeGraff JV (2002) Catastrophic landlides. GSA Melosh HJ (1987) The mechanics of large rock avalanches. GSA Reviews in Engineering Geology, vol VII, pp 41–49 Mitchell WA (2006) Earthquake triggered rock avalanches in the western Himalaya. Geophysical Research Abstracts, vol 8, 04837 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 30–37 Soeters R, Cornelis J, van Westen CJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation.Transportation Research Board, National Research Council, Washington, D.C., Spec. Rep. 247, pp 142, 145
Fig. Mv2-2. Location. Geographic. 05°22' W, 35°24' N, western Rif Atlas, Morocco Geologic. Paleogene sediments of the Beni Ider nappe Source. LAR, 15 August 1992 Comments. Photo of the Amestrasse avalanche between Chefchaouen and Tetuan. The mass is 1.5 km long and 250 m wide. Its drop is 550 m from the main scarp to terminal boulders across a roadway. The trigger mechanism and date of the event are unspecified.
Mv2 · Rock Avalanches (Sturzströmen)
Fig. Mv2-3. (Caption on p. 928)
927
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
▼
Fig. Mv2-3.
Location. Geographic. 132° W, 64°23' N, east-central Yukon Territory Geologic. Early Alpine folding and faulting of Upper Proterozoic clastic sediments of the Cordilleran Craton Foreland Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 28 August 1949 Source. Courtesy of Natural Resources Canada, NAPL A 12251, 349, 350 Comments. The rock avalanche pictured in this stereomodel in the Selwyn Mountains is about 2 km wide and 3 km long. The debris mass has slid down from the south face of the mountain, crossed the valley and climbed 150 m up the opposite slope. The avalanche also became a temporary Mf4.1 landslide dam by blocking the outlet of a tributary stream, causing upstream L1 glaciolacustrine sedimentation. The debris mass still appears fresh after 58 years. See also Fig. Mf4.1-4.
Fig. Mv2-4.
▼
928
Location. Geographic. 69°22' W, 68°52' N, central Baffin Island Nunavut Geologic. Archean granite gneiss of northeastern Shield Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 27 000 Acquisition date. 28 August 1967 Source. Courtesy of Natural Resources Canada, NAPL A 20199, 48, 49, 50 Comments. The stereomodel features a 1 200 m long by 500 m wide Mv2 rock avalanche at the northwest extremity of Ekalugad Fjord in Davis Strait. A good comparison is afforded with the adjacent smoother appearing Mv1.2 talus cone of equal dimensions. Other prominent occurring geounits are: 1. Gf4 glacial till 2. Gl5 glacial terminal moraine 3. Fw3 glacial estuarine delta related to a marine limit between 10 and 5 ka 4. Fu1 fan delta 5. Bc3 marine sediments See also Fig. Fu1/Mv1.2-3.
Mv2 · Rock Avalanches (Sturzströmen)
929
930
Mv2.1
Division 4 · Surficial Deposits
Mv2.1 Rock Avalanches, Inactive Characterization Inactive avalanches are frequently overgrown by vegetation and can show some degradation of their form. Others retain their fresh appearance for long periods.
Group M · Mass Movement Materials
Geohazard Relations The most general difficulty with inactive rock avalanches is their unexpected reactivation due to human activity or exceptional natural conditions.
Select Bibliography See Geounit Mv2.
Fig. Mv2.1-1. Source. Courtesy of Natural Resources Canada, GSC 204167S Comments. View westward of the historic (1771) Monte Forca rock avalanche in the carbonate rocks of the Southern Alps in northern Italy. The following account is based on Eisbacher and Clague, 1984, p 148. Thick-bedded dolomites dipping 28° to the southeast failed above a horizon of thin-bedded argillaceous
limestone. The slide erased three hamlets and killed 49 people. The catastrophe did not remove all unstable rock from the failure surface. The southern section of the mountain is still a downward-tapering wedge of dolomite. Arrows indicate chalets recently constructed on the debris that crossed the local valley. See also Fig. Mv1.2-3.
Mv2.1 · Rock Avalanches, Inactive
Location. Geographic. 114°23' W, 49°35' N, southwestern Alberta, Canada Geologic. Thrusted Front Ranges of Laramide orogeny Source. Unattributed Comments. View from the distal limit of debris towards the detachment zone on Turtle Mountain at Frank. On 23 April 1903 the upper two thirds of the mountain suddenly slipped and buried part of the coal mining town of Frank, causing 75 deaths. The debris lobe of the avalanche stretches 1 km from the base of the mountain and extends 120 m up the opposite valley slope. More than a century after the disaster, the scar is still fresh. The slide slope is covered with whitish pulverized limestone blocks. The mountaintop scar remains an area of many post avalanche topples and rockfalls. A highway and railway cross the valley avalanche debris. See air perspective view of Fig. Mv2.1-3 and stereo photos of Fig. Mv2.1-4.
Fig. Mv2.1-3.
▼
Fig. Mv2.1-2.
Location. Geographic. 114°23' W, 49°35' N, southwestern Alberta Geologic. Thrusted Front Ranges of Laramide orogeny Source. Courtesy of Natural Resources Canada, NAPL T31L-213 Comments. A northward air perspective view shows the structural and topographic setting of the rock avalanche at Frank. The overthrust faulting (struc. 14) of Mid Paleozoic limestones over Upper Mesozoic shales are clearly evident. See the ground photo of Fig. Mv2.1-2 and the stereophotos of Fig. Mv2.1-4.
931
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Division 4 · Surficial Deposits
Fig. Mv2.1-3. (Caption on p. 931)
Group M · Mass Movement Materials
Mv2.1 · Rock Avalanches, Inactive
Fig. Mv2.1-4. (Caption on p. 934)
933
Division 4 · Surficial Deposits ▼
Fig. Mv2.1-4. Location. Geographic. 114°23' W, 49°35' N, southwestern Alberta Geologic. Thrusted Front Ranges of Laramide orogeny Vertical Airphoto/Image. Type. Pan b/w, stereo pair Scale. 1: 112 000 Acquisition date. 12 August 1970 Source. Courtesy of Natural Resources Canada, NAPL A 21850-13, 14
Group M · Mass Movement Materials
Comments. This stereomodel covers the site of Turtle Mountain at Frank shown on Figs. Mv2.1-2 and Mv2.1-3. Among the factors that caused this rock avalanche are the strong jointing of the ridge-forming Mid Paleozoic limestone strata. Seepage of groundwater, ice wedging and perhaps limestone solutions along the joints weakened the rocks. Mining of W1.1 coal seams at the base may have caused the Upper Mesozoic shales to yield by plastic flow. Some Mv3 toppling, not visible in the airphotos, occurs in the west-dipping limestones at the crown of the slide.
Fig. Mv2.1-5. Location. Geographic. Southern Sri Lanka Geologic. Cratonic metamorphic rocks Vertical Airphoto/Image. Type. b/w pan, stereogram Scale. 1: 40 000 Acquisition date. Unknown Source. Courtesy of D. K. Erb Comments. The stereomodel at 80°50' E, 07°25' N shows a large vegetation covered rock avalanche fallen from a local fault in the Knuckles Range on the northeast side of the Central Massif. Other regional faulting is depicted in Fig. 12-6.
Fig. Mv2.1-6.
▼
934
Location. Geographic. 06°20' E, 45°03' N, central High Alps Geologic. Contact zone of folded and thrusted Lower Jurassic S2.1-J sediments and Paleozoic J3.1-Pz gneisses Vertical Airphoto/Image. Type. Pan b/w, stereo pair Scale. 1: 20 000 Acquisition date. 1974 Source. IGN – Photothèque Nationale, France Comments. Multiple stabilized large paleo rock avalanches are associated with Liassic S2.1 interbedded shales and limestones in this stereomodel in the upper Romanche Valley. These sediments are now marked by large actively eroding, but not failing, slopes.
The village of Villar d’Arène and a concentration of alpine pastures (relatively gentler slopes, south facing) are located on the northern mass. The southern mass is partly forested on a north-facing slope. The N91 road to Briançon has required the construction of two tunnels, of 200 m and 400 m (Grand Clos) lengths respectively, to negotiate the section of the valley directly across from the southern rock avalanche. These works were evidently related to the steepness of the shale slopes in those areas. The road then traverses the 1 300 m broad toe of the adjacent stabilized rock avalanche. Numerous other, recent and inactive, rock avalanches and Mv1 rockfalls upslope of, and adjacent to, the older avalanche masses are also evident.
Mv2.1 · Rock Avalanches, Inactive
935
Mv3
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mv3 Toppled Rock Slabs Characterization Toppling of rock masses is favoured by the presence of a steeply inclined joint set with a strike aligned approximately parallel to the slope face. The topple is the forward rotation out of the slope of a mass of rock about a point below the center of gravity of the displaced mass. Toppling is sometimes driven by gravity exerted by material upslope of the displacing mass and sometimes by water or ice in cracks within the mass. Topples range from extremely slow to extremely rapid, sometimes accelerating throughout the movement. Toppling can occur in a number of primary and secondary modes and can be difficult to detect on airphotos. The toppled slabs themselves are less evident than the resultant Ms1 rock slides.
Geohazard Relations The geohazard relations of rock topples are the same as those for Mv1, but hazard zoning must include joint cracks at the top of the slope as well as the base run-out area.
Select Bibliography Dikau R, Schrott L, Dehn M (1996) Topple. In: Dikau R, Brunsden D, Schrott L, Ibsen MA (eds) Landslide recognition. John Wiley & Sons, Ltd., Chichester, pp 29–43 Goodman RE, Bray JW (1976) Toppling of rock slopes. Proc. Specialty Conference on Rock Engineering for Foundations and Slopes, ASCE, vol 2, pp 201–234 Pritchard MA, Savigny W, Evans SG (1988) Deep-seated slope movements in the Beaver River Valley, Glacier National Park, B.C. GSC Open File 2011 Soeters R, Cornelis J, van Westen CJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, p 145 Wyllie DC (1980) Toppling rock slope failures, examples of analysis and stabilization. Rock Mechanics 13:89–98 Wyllie DC, Mah CW (2004) Rock slope engineering. Taylor & Francis
Fig. Mv3-1. Source. Transportation Research Board (1996) Landslides: Investigation and mitigation. National Research Council, Washington, D.C., Special Report 247, fig 15-15, p 410. Reproduced with permission Comments. The figure shows sketches of two common rock toppling modes related to different types of discontinuities in hard rock masses. The upper sketch shows flexural toppling in slopes with steeply dipping closely spaced discontinuities. The lower sketch shows toppling in a rock mass with widely spaced orthogonal joints.
Fig. Mv3-2.
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936
Location. Geographic. 117°28' W, 51°26' N, British Columbia Geologic. Folded and thrusted Upper Proterozoic metasediments of the Cariboo Terrane of the Omineca Cordilleran Belt Vertical Airphoto/Image. Type. Pan b/w, stereo pair Scale. 1: 25 000 Acquisition date. 24 July 1978 Source. Courtesy of Natural Resources Canada, NAPL A 24972-74,75 Comments. Two forest-covered toppled rock masses are delineated in this stereomodel in Beaver Valley of the Selkirk Mountains. Pritchard et al. (1988) report that in the field “toppling is clearly visible in many backslope cuts. The process is locally active, resulting in ongoing shallow instability and related operational and maintenance problems”. Control structures are visible at the foot of the larger slide. An old Ms1 rock slide is delineated just south of the topples. The valley is part of a narrow rail and highway transport corridor.
Mv3 · Toppled Rock Slabs
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Mv4
Division 4 · Surficial Deposits
Mv4 Subsidences, Sudden Characterization Sudden subsidences result from seismic and faulting events, and the prolonged withdrawal of underlying solids by solution, lateral plastic flow or extraction of mineral deposit. Causes are schematized in Fig. Mv4-1.
Geohazard Relations Geounits in which sudden collapse subsidences frequently occur are karstic carbonate rocks; Geounits K3, Kp1, Kp1.1, Kp2, Kn1 and Kn2; deposits of blanket loess, Geounit Et1.1 and thermokarst, Zk1. Waltham (2002) states that “loess collapses most easily where it contains about 20% clay; with more or less clay it is less unstable.” Such composition, determined by field investigation, is not detectable on airphotos or satellite images.
Fig. Mv4-1. Source. Alexander D (1993) Natural disasters. Chapman & Hall, fig 4.19 Comments. A schematic ordering of the causes of subsidences.
Group M · Mass Movement Materials
Reference Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 54, 58
Select Bibliography Allen AS (1969) Geologic settings of subsidence. In: Varnes DJ, Kiersch GH (eds) Reviews in engineering geology. GSA Bull II:305–342 Hudnut KW, Pelzer G, Rosen PA, Fogez F, Galloway DL, Ikehara M, Phillips SP (1995) Land subsidence detection and monitoring with SAR interferometry. AGU, vol 77, no 46 Suppl., p F32 Johnson AI (1991) Land subsidence. International Association for Scientific Hydrology, Pub 200 Kuehn F, Trembich G, Hoerig B (1999) Satellite and airborne remote sensing to detect hazards caused by underground mining. Proceedings, 13th International Conference on Applied Geologic Remote Sensing, Vancouver, Canada, pp II-57–II-64 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 37–3–37–24
Fig. Mv4-2.
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Mv4 · Subsidences, Sudden
Source. Jennings JN (1972) An introduction to systematic geomorphology. MIT Press, p 121, fig 36 Comments. The diagram shows a collapse doline caused by groundwater solution circulating along joints in the Kp1 limestone.
Fig. Mv4-3. Source. Mathewson CC (1981) Engineering geology, 1st ed. © Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ, p 256, fig 14-14 Comments. Block diagram showing the surface characteristics of a subsided area resulting from the consolidation of a confined stratum of loose sand at depth.
Fig. Mv4-4. Location. Geographic. Southern Pennsylvania, USA Source. Pennsylvania Geology June 1980, vol 11, no 3, p 15. Photo by William H. Bolles Comments. Photo shows the result of a motorist going around a safety barrier near Hershey east of Harrisburg that had been erected at the site after a small depression over an unsuspected Kp1 limestone sinkhole. The depression gradually spread eventually leading to a complete collapse of the road.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mv4-5. Location. Geographic. 98° W, 38° N, central Lowlands, USA Geologic. Quaternary and Pliocene sediments overlying Permian sequences Source. Wichita Eagle and Beacon, 12 November 1974
Comments. Air view of a subsidence sinkhole 90 m in diameter on the west margin of the Osage Plains in central Kansas. The collapse resulted from man-induced dissolution of underlying H1 Permian salt.
Fig. Mv4-6.
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940
Location. Geographic. Central China Geologic. Mid to Late Pleistocene blanket loess of Shansi Platform Source. National Geographic Magazine (1938). Photo by H. Koester Comments. Air view on the Loess Plateau shows cave dwellings excavated in loess deposits which range from 40 m to 120 m in thickness. External loading, such as imposed by earthquakes, causes loss of strength and collapse of loess during the period of vibration. Such a catastrophic event killed 246 000 cave dwelling people in thick loess in this region on 16 December 1920.
Mv4 · Subsidences, Sudden
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mv4 · Subsidences, Sudden ▼
Fig. Mv4-7.
Location. Geographic. 06°56' E, 44°06' N, Maritime Alps Geologic. Mesozoic limestones Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 30 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The stereomodel at Valberg shows numerous circled subsidence sinkholes averaging 200 m in diameter visible within a Kp1-J unit of Mid-Jurassic marly limestone surrounding the Permian redbeds of the Barrot Dome. One depression to the southeast is 600 m in diameter. Strong fluvial erosion in the unit bordering the stream valley is in Kc4 Triassic marls and dolomites. Some photo fracture traces have been drawn in the carbonates. This figure is 19 km west of Fig. Zm2-7.
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Mv5
Division 4 · Surficial Deposits
Mv5 Subsidence Zones, Gradual Characterization Gradual subsidences are manifested by uniform or differential settlement of a ground surface in rocks and unconsolidated sediments that contain underground voids, e.g., macrovoids in karstic limestones; microvoids in clays and some silts and sands. They are dominantly humaninduced, the result of loading, pumping of underground fluids (water, hydrocarbons) that are held in the ground under pressure, and the removal of rock support at depth, such as underground coal mines. Hydrocompaction results when loose, dry, low-density deposits (e.g., dry alluvium; dry loess) with large void ratios become wet and compact. Rock salt (Sedimentary geounit H1; Gravity Geostructures geounit 11) dissolves in circulating groundwater rapidly enough to cause slow natural subsidence; associated gypsum deposits dissolves slower than salt. Young clay sediments and interbedded sands, with minimal over-consolidation, gradually subside by water expulsion and compaction from imposed structural loads. These clays are characteristic of Geounits L1, Quaternary lacustrine sediments; Bc1, plain of marine sediments; and Bc4, fluviomarine plain. Natural thawing of excess ground ice is classed as Geounit Zk1 in the Group Periglacial-related Forms. These activities and processes usually cause compaction whose surface expression is land subsidence.
Geohazard Relations There are numerous environmental, economic and legal problems in land subsidence due to fluid withdrawal. Gradual subsidences deteriorate surface drainage, and pose serious problems in the construction and maintenance of pipelines, power lines, highways, buildings, irrigation distribution systems and large canals. Airphoto evidence of gradual settlement zones within void-characterized geounits is limited and consists mainly of anomalous high groundwater or surface water areas in vicinity of subsurface extraction activities and surface loading structures. More effective remote sensing of gradual subsidence can be achieved by multitemporal radar interferometry monitoring of susceptible zones. These methods provide very precise measurements of small changes in surface relief.
Group M · Mass Movement Materials
Major cities where subsidence is due primarily to ground water removal are: Bangkok, Thailand; Osaka and Tokyo, Japan; Shanghai, China; Venice, Italy; London, England; Houston, Texas; LasVegas, Nevada; New Orleans, Louisiana; Long Beach/Los Angeles, California. Mexico City area is described in Figs. A3-2 and A3-4. The San Joaquin and Santa Clara Valleys in California are also significantly affected. More than 11 130 km2 of the San Joaquin Valley has subsided from 0.3 to 9 m due to withdrawal of water from confined aquifer systems for agricultural irrigation. Other regions similarly affected are in Iran (Bam in the south and the Shirin Rood Basin at Sari on the Caspian Coast) and Italy’s Northern Adriatic gas fields (lower Po Basin).
Select Bibliography Galloway DL, Jones DR, Ingebritsen SE (2000) Land subsidence in the United States. USGS Fact Sheet 0087–00 IASH-Unesco (1970) Land subsidence Ikehara ME, Galloway DL, Fielding E, Burgmann R (1998) SAR imagery reveals seasonal and long-term land-surface elevation changes influenced by ground-water levels and fault alignment in Santa Clara Valley, California. EOS Transactions, American Geophysical Union, vol 79, no 45 Suppl, p 37 Monroe JS, Wicander R (1994) The changing Earth. West Publishing Co., St. Paul, Minn., pp 342–344 National Environment Board, Thailand (1978) Investigation of land subsidence caused by deep well pumping in the Bangkok area, phase I: Geology. Division of Geotechnical & Transportation Engineering, Asian Institute of Technology Poland JF (Chairperson) (1984) Guidebook to studies of land subsidence due to groundwater withdrawal. UNESCO, International Hydrological Programme, Studies and Reports in Hydrology, vol 40 Poland JF, Evensen RE (1966) Hydrogeology and land subsidence, Great Valley, California. In: Bailey EH (ed) Geology of Northern California. California Division of Mines & Geology, Bull 190:239–247 Prokopovitch NP (1972) Land subsidence and population growth. Section 13, Proceedings, 24th International Geological Congress, pp 44–54 Selya RM (1995) Taipei. Wiley Shih SF, Engman ET, Neale C (1992) Applications of remote sensing to drainage. Proceedings of the Irrigation and Drainage Sessions at Water Forum ’92, ASCE Tsui PC, Cruden DM (1984) Deformation associated with gypsum karst in the Salt River Escarpment, Northeastern Alberta. Canadian Journal of Earth Sciences 21:949–959 Verbeek ER, Clanton US (1981) Historically active faults of the Houston Metropolitan Area, Texas. In: Etter EM (ed) Houston Area environmental geology: Surface faulting, ground subsidence, hazard liability. Houston Geological Society Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, pp 54, 56
See also Geounit Mv4.
Mv5 · Subsidence Zones, Gradual
Fig. Mv5-1. Source. Fisher WL, et al. (1972) Environmental geologic atlas of the Texas Coastal Zone Galveston-Houston Area. Bureau of Economic Geology, University of Texas, Austin, p 64, fig 18, derived from Turner, Collie, and Braden, Inc., Consulting Engineers (1966) Comments. The map of this figure covers an 80 km section of the West Coastal Plain of the Gulf of Mexico to show the result of half a century of urbanization and increased groundwater withdrawal.
Water-saturated clay beds separating the sand beds of the aquifers are compressible. Regional subsidences in this area range from 0.6 to >2 m. The subsidences are irreversible, with associated susceptibilities to flooding and storm surges in such low-lying coastal areas, as occurred just to the east in Sept. 2005. See Verbeek and Clanton (1981).
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mv5-2. Location. Geographic. 12°20' E, 45°26' N, at Venice Geologic. Fv2 alluvial plain and Bt1 lagoon Vertical Airphoto/Image. Type. InSAR Acquisition date. 1993–2000 Source. esa Comments. The satellite image shows subsidence (mm yr–1) on the Lido Bw3 barrier beaches and landward of the Venice Lagoon for the period 1993–2000.
Using differential interferometric SAR processing, subsidence rates can be monitored over time periods spanning several years. However, the technique can only be applied to areas that are stable in terms of phase coherence. In this scene these are towns and villages in the lower alluvial plain. See also Fig. Bt1g-6.
Mv5 · Subsidence Zones, Gradual
Fig. Mv 5-3. Location. Geographic. 118°14' W, 33°45' N, Southern California, USA Geologic. Bc4 fluviomarine plain Source. Courtesy City of Long Beach, California Comments. The photo shows flooding in the man-made harbour of Los Angeles. The flooding was caused by subsidence resulting from withdrawal of oil from the Wilmington oil sands that began in the 1930s near San Pedro Bay. By the 1940s and 1950s subsidence was progressing at the rate of 30 to 60 cm yr–1. As subsidence continued and reached 7 m lateral ground movements it broke oil, water and sewage pipes, pavements cracked and bridges had to be rebuilt to keep them above the invading sea water.
Fig. Mv5-4. Location. Geographic. 119°30 'W, 35°20' N, Great Valley, California Geologic. Upper Cretaceous and Cenozoic sedimentation in intermontane basin Vertical Airphoto/Image. Type. ERS 1,2 Source. Courtesy of Vexcel Canada Inc. Comments. This image shows land subsidence data from withdrawal of hydrocarbons from an oilfield near Belrige, California by applying a radar technique known as Interferometry to ERS 1 and 2 data. The DEM was then draped with colour imagery from Landsat and grey scale imagery from IRS.
The industrial harbour district became laced with dykes and retaining walls. Over 50 km2 of land were thus affected.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mv5 · Subsidence Zones, Gradual ▼
Fig. Mv5-5. Location. Geographic. 68°45' W, 16°49' S, western Bolivia Geologic. Altiplano of Central Andes Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1:40 000 (in CD-ROM) Acquisition date. 18 May 1958 Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Universidad Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 22 Comments. The stereomodel shows the pattern of pockmark waterhole solutional evidence of gradual subsidence in argillaceous gypsum evaporite sediments in a Holocene L1 paleolake. Location is in the tectonic trough of lake Titicaca, 20 km southeast of the lake. See also Figs. H1-1, L1-2, and karst solution in Fig. Mv5-7.
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Division 4 · Surficial Deposits
Fig. Mv5-6. (Caption on p. 952)
Group M · Mass Movement Materials
Mv5 · Subsidence Zones, Gradual
Fig. Mv5-7. (Caption on p. 952)
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Division 4 · Surficial Deposits ▼
Fig. Mv5-6. Location. Geographic. 112°12' W, 59°53' N, northeast Alberta Geologic. Craton cover sediments of Great Slave Plain Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 54 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 24075–86, 87 Comments. A stereomodel at Salt River shows salt flats that are related to Mid Devonian H1 gypsum and anhydrite evaporites which regionally underlie Kp1 karstic limestones of the same age (note the sink holes). The salt emerges from subterranean water flow locally as a spring at the base of the horizontally-bedded limestone escarpment in the north of the photos. Precipitation sinks through fractures in the limestone and dissolves the evaporites. This underground solution and associated rock deformation and collapse poses hazards to present and planned regional resource developments. These formations underlie the Athabaska oil sands and their deformations disturb the oil sand beds in places. The integrity of planned hydroelectric reservoirs on the Slave River to the south might also be affected by any disturbances in these rock formations.
▼
Fig. Mv5-7. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 63 360 Acquisition date. Not given Source. Ray RG (1960) Aerial photographs in geologic interpretation and mapping. USGS PP 373, p 126, fig 68 Comments. Stereomodel shows a K3 karst plain in Texas with a high concentration of solutional sinkholes. Area B consists of W1 sandstones and marls. Figure K3-2 at same scale illustrates the range in sizes of solutional sinkholes.
Group M · Mass Movement Materials
Ml1 · Rock Block Glides
Sub-group Ml Lateral Spreads Ml1 Rock Block Glides
“Fixed installations incapable of surviving increased tilt (e.g., towers) are frequently at risk from the typical block slide. All linear features such as roads, railways, power, gas and telephone lines crossing the block will be damaged beyond repair.” (Ibsen 1996).
Characterization
Reference
Rock block glide mass movement occurs on gentle slopes where a slow plastic deformation occurs in a subsurface material overlain by a more coherent thick surface rock mass. The upper layer is broken up into horst and grabenlike block structures by the movements of the underlying material and slides outward. The spreading of the surface rock is accompanied by its general subsidence into the softer underlying material.
Ibsen ML, Brunsden D, Bromhead E, Collison A (1996) Block slide. In: Dikau R, Brunsden D, Schrott L, Ibsen JL (eds) Landslide recognition. John Wiley & Sons, Ltd., Chichester, pp 64–77
Geohazard Relations The areal extent of block glides is often considerable and can narrow or block valleys and deflect streams. The drainage anomaly usually results in increased stream erosion at the point where the spread blocks the valley, which in turn results in development of numerous local smaller rotational slides.
Fig. Ml1-1. Location. Geographic. 102°35' E, 57°40' N, central Siberia, Russia Source. Zaruba Q, Mencl V (1969) Landslides and their control. Elsevier and Academia Publishing House of the Czechoslovak Academy of Sciences, p 72, fig 5-34 Comments. Figure is a section of the lateral extension of a now stabilized rock block glide at the junction of the Llima
Select Bibliography Cruden DM, Varnes DJ (1996) Landslide types and processes. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, p 62 McGill GE, Stromquist AW (1979) The grabens of Canyonlands National Park, Utah: Geometry, mechanics, and kinematics. J Geophys Res 84(B9):4547–4563 Rohn J, Resch M, Schneider H, Fernandez-Steeger TM, Czurda K (2004) Large-scale lateral spreading and related mass movements in the North Calcareous Alps. Bulletin of Engineering Geology and the Environment 63(1):71–75 Zaruba Q, Mencl V (1969) Landslides and their control. Elsevier, New York, pp 70–72
and Angara Rivers on the craton cover rocks of the Angara Plateau. A 100 m thick sheet of a diabase sill (“3” on section) (an intrusive igneous rock, also called dolerite) lies and glides on Carboniferous shales (“2” on section). The river cut through the diabase and exposed the shales. “1” on section are Carboniferous S1 sandstones; “s” are sites of borings.
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Ml1
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Ml1-2. Location. Geographic. 109°55' W, 38°10' N southeast Utah, USA Geologic. Fault zone in Permian sediments of central Colorado Plateau Source. Commins DC (2003) Reconstruction of fault growth using drainage development in the Canyonlands Graben, Utah. Ph.d. thesis, Imperial College, University of London, 336 p Comments. This figure is a DEM of the 17.1 Canyonlands Grabens also known as the Needles Fault Zone in Canyonlands National Park. One of North America’s largest landslides, it forms an active extensional fault array covering 200 km2 southeast of the Colorado River. The fault zone is a 450 m thick sequence of competent Paleozoic sedimentary rocks that have glided over evaporite salt beds down a 4° dip towards the Colorado River, off the west-dipping flank of the Monument Upwarp. Growth of this fault array within the last 0.5 to possibly 0.1 Ma has produced this group of linked normal fault geometries. Figure Ml1-3 is a stereo photo pair within the fault zone.
Fig. Ml1-3.
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954
Location. Geographic. 109°55' W, 38°10' N, southeast Utah Geologic. Fault zone in Permian sediments Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 82 000 Acquisition date. Not given Source. Unspecified U.S. government agency Comments. This stereomodel covers the central section of the DEM of Fig. Ml1-2. The faults are Structural Unit 17 grabens, formed by extension due to the flow of the underlying salt beds. They are 150 to 200 m in width and 25 to 75 m in depth.
Ml1 · Rock Block Glides
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Division 4 · Surficial Deposits
Sub-group Mc Diagonal Creeps Mc1
Mc1 Colluvial Mantle Movement Zones
Group M · Mass Movement Materials
Geohazard Relations Structures resting on slope creep zones are subjected to sustained lateral stresses and may be gradually displaced downslope. Use of digital terrain models (DTMs) to locate slopes >15° in Mc1 areas would be one method to avoid the hazard.
Characterization Select Bibliography Colluvium is a rock surface product of climate dependent factors (temperature conditions and availability of water) of mechanical disintegration and chemical decomposition weathering processes, e.g. see Unit Variant X1.4. Colluvial mantle-movement zone is the result of slow downslope movement of the sediments on hillsides under the influence of gravity, not carried by water, ice or wind. The movement is termed creep and consists of the deformation of an approximately 1 meter thick surface layer of colluvium by climatically-controlled expansion and contraction processes: wetting and drying; heating and cooling; freezing and thawing. Heavy rain can accelerate creep to landslips. As a photogeological facies, hillslopes zones affected by creep are generally only mappable on airphotos at scales of 1:10 000 to 1:5 000. As in mid-latitude environments, measurements of soil creep in deep-weathering wet tropical regions also show a drop to zero at a depth of less than one meter.
Bloom AL (1978) Geomorphology. Prentice Hall, Englewood Cliffs, NJ Brunsden D (1994) Mass movement types. In: Goudie A, Atkinson BW, Gregory KJ, Simmons IG, Stoddart DR, Sugden D (eds) Encyclopedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, p 325 Clarke ML, Vogel JC, Botha GA, Wintle AG (2003) Late Quaternary hillslope evolution recorded in eastern South African colluvial badlands.Palaeogeography,Palaeoclimatology,Palaeoecology 197:199–212 Finlayson BL (1985) Soil creep: A formidable fossil of misconception. In: Richards KL, Arnett RR, Ellis S (eds) Geomorphology and soils. Allen and Unwin, London, pp 141–158 Gerrard AJ (1981) Soils and landforms. Allen and Unwin, London, pp 55–59 Gray DH, Sotir RB (1996) Biotechnical and soil bioengineering slope stabilization: A practical guide. Wiley-IEEE Kienholz H (1978) Maps of geomorphology and natural hazards of Grindelwald, Switzerland, scale 1 : 10 000. Arctic and Alpine Research 10:169–84 Mollard JD, Janes JR (1983) Airphoto interpretation and the Canadian landscape. Surveys and Mapping Branch, Department of Energy, Mines and Resources, Canada, p 72 Okagbue CO (1984) Predicting landslips caused by rainstorms in residual/ colluvial soils of Nigerian hillside slopes. Natural Hazards 2(2):133–141 Shelton JS (1966) Geology illustrated. Freeman, San Francisco, p 126
Fig. Mc1-1. Source. Reprinted by permission of Waveland Press, Inc. from Bloom AL (1998) Geomorphology, 3rd edn. Waveland Press, Inc., Long Grove, IL, p 174, fig 9-5, (reissued 2004), all rights reserved Comments. Block diagram figure shows common field evidences of creep as a process of colluvial mantle movement (e.g., see Fig. Mc1-4).
Mc1 · Colluvial Mantle Movement Zones
Fig. Mc1-2. Source. John S. Shelton Comments. This photo shows how creep can deform weak sedimentary rocks. The road cut is in Miocene sandy shales near Los Angeles, California, it displays the bending of the outcropping strata in the upper part of the cut.
Fig. Mc1-3. Source. LAR, October 1991 Comments. This photo pair shows an area of rough-surfaced creep 40 m broad by 50 m long on a moderate slope in weak, locally frostsusceptible, Lower Jurassic marly shales. These zones of creep locally can be incipient Ms2 debris slides. The site is at the foot of Mt. Eiger at Grindelwald, in a broad valley of marly shales of the Helvetic Nappes in central Switzerland. The inset frame in the upper photo gives the coverage of the closeup view. See slumps and debris flows in this same weak formation in Figs. Ms3-3 and Mf3-4. These movements are common inconveniences in the local pasture lands associated with these rocks.
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Division 4 · Surficial Deposits
Fig. Mc1-4. Source. LAR, October 1974 Comments. This photo shows deformed tree trunk indicators of creep on a hillslope at Heiligenblut in the Pennine Alps of south central Austria.
Fig. Mc1-5. Source. LAR Comments. This photo shows biotechnical stabilization in the Austrian Alps using live staking on a graded slope.
Group M · Mass Movement Materials
Ms1 · Planar Rock Slides
Sub-group Ms Slides Ms1 Planar Rock Slides Characterization Rock slides may occur in any rock type; are largely related to slope-exposed bedding planes, joints, faults and cleavage or schistosity planes with unfavourable orientations relative to the slope. They occur because the forces creating movement exceed those resisting it. Slides are generally initiated by the coincidence of such inherently unstable slopes with a weather-related trigger or earthquake. The displaced masses consist of irregular and stacked bedrock blocks or coherent sheets of large rock blocks.
Geohazard Relation As agents of rapid sliding, deposition and flooding, landslides in areas with human resources can result in considerable property damage and significant loss of life. Direct annual cost of landslide damage has been estimated at $2 billion in the USA.
Select Bibliography Brabb EE (1991) The world landslide problem. Episodes 14:52–61 Bromhead EN (1997) The stability of slopes. Spon Press, London De La Ville N, Diaz AC, Ramirez D (2002) Remote sensing and GIS technologies as tools to support sustainable management of areas devastated by landslides. Environmenta, Development and Sustainability 4(2):221–229 Evans SG, DeGraff JV (2002) Catastrophic landslides: Effects, occurrence, and mechanisms. Geological Society of America Fookes PG, Dale SG, Land J (1991) Some observations on a comparative aerial photography interpretation of a landslipped area. Quarterly Journal of Engineering Geology 24:249–265
Fig. Ms1-1. Source. Howes DE, Kenk E (1988) Terrain classification system for British Columbia, rev. edn. MOE Man. 10. Recreational Fisheries Branch, Ministry of Environm., p 65, fig 34 Comments. Figure is a diagram that illustrates the common elements of a planar jointcontrolled rock slide with a weak layer failure surface. The detached blocks upslope are coherent, become disintegrated on the way downslope, and accumulate as stacked blocks at the foot of the slope.
Glade T, Crozier MJ (2005) Landslide hazard and risk. Wiley Hutchinson JN (1988) General report. Morphological and geotechnical parameters of landslides in relation to geology and geohydrology. Proceedings of the 5th International Symposium on Landslides, Lausanne, vol 1, pp 3–35 Lacerda WA (2004) Landslides: Evaluation and stabilization. Taylor & Francis Lee EM, Jones DKC (2004) Landslide risk assessment. Thomas Telford Leighton FB (1976) Geomorphology and engineering control of landslides. In: Coates DR (ed) Geomorphology and engineering. Dowden, Hutchinson & Ross, Inc. Mantovani F, Soeters R, van Westen CJ (1996) Remote sensing techniques for landslide studies and hazard zonation in Europe. Geomorphology 15:213–225 Nichol JE, Shaker A, Wong MS (2006) Application of high-resolution stereo satellite images to detailed landslide hazard assessment. Geomorphology 76(1–2):68–75 Poisel R, Bednarik M, Holzer R, Pavel L (2005) Geomechanics of hazardous landslides. Journal of Mountain Science 2(3)211–217 Rib TH, Liang T (1978) Terrain evaluation for landslide inves-tigations, 34 basic factors, recognition and identification, landslide analysis and control. Transportation Research Board, National Academy of Sciences, Washinton, D.C., Special Report 176 Schultz AP, Bartholomew MJ, Lewis SE (1991) Map showing surficial and generalized bedrock geology and accompanying sidelooking airborne radar image of the Radford 30' × 60' quadrangle Virginia and West Virginia. USGS Map 1–2170-A, 1 : 100 000 Schulz WH, Cotton W (2002) Use of detailed mapping and monitoring of a landslide to permit safe occupation of surrounding residences. GSA, vol 34, no 6 Singhroy V, Mattar KE, Gray AL (1998) Landslide characterization in Canada using interferometric SAR and combined SAR and TM images. Advances in Space Research 21(3): 465–476 Soeters R, Cornelis J, van Westen CJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, pp 147–149 Sorriso-Valvo M, Gulla G (1996) Rockslide. In: Dikau, R, Brunsden D, Schrott L, Ibsen ML (eds) Landslide recognition. John Wiley & Sons, Ltd., Chichester, pp 85–96 Voight B (ed) (1978) Rockslides and avalanches 1, Natural Phenomena. Elsevier
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Ms1
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Ms1-2. Source. LAR, April 1974 Comments. Photo of planar slide blocks and debris at the foot of a 200 m high stock of granite. The mass is of Late Proterozoic age in the Hoggar Massif of southeast Algeria. The blocks are spalling from stress release parallelbedded joints and vertical tension joints of geostructure Unit 18. The intrusive stock is in discordant contact with the foliated metamorhic country rock, syn or post tectonic emplacement is unspecified.
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Fig. Ms1-3. Source. USGS Comments. A planar rock slide of moderate displacement of intact blocks photographed at an undisclosed location. In the absence of site-specific information the slide is interpreted as consisting of coherent slabs in steep slopeexposed bedding plane surfaces of thin-bedded sedimentary rocks. The figure gives scale.
Ms1 · Planar Rock Slides
Fig. Ms1-4. Location. Geographic. 73°20' E, 34°30' N, Azad Kashmir, Pakistan Geologic. Alpinotype ranges of crystalline rocks with Himalayan overprint Vertical Airphoto/Image. Type. SPOT 4, pan, 10 m resolution Scale. 1:50 000 nominal Acquisition date. 21 September 2005 Source. International Charter for Space and Major disasters. CNES 2005, distribution by Spotimage
Comments. This interpreted image shows the occurrence of landslides generated on 8 October 2005 by an earthquake of magnitude 7.6 that struck on the India-Pakistan border. The epicenter was located about 95 km northeast of Islamabad. Shocks were felt over a radius of 300–400 km. On 21 October, Pakistani authorities reported casualties at 49 700 dead and over 74 000 injured. The UN estimated 1 million people have been left homeless. In this area at Balakot sites of newly detected Ms1 or Ms2 landslides are mapped in yellow. Sites of reactivated landslides are mapped in red.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Ms1 · Planar Rock Slides ▼
Fig. Ms1-5. Location. Geographic. 0°10' E, 42°47' N, central Pyrenees Geologic. Axial zone of Hercynian/Alpine tectogenic belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. 1980 Source. IGN – Photothèque Nationale, France Comments. This stereomodel 40 km southeast of Lourdes shows a group of slides delineated in interbedded Devonian limestones and shales at the Piau-Engaly ski development. The latter is located on a Paleozoic Np4.3 granitic stock, other small stocks occur in the area. Kidney-shaped Lac Cap-de-Long is a dammed reservoir. W1.3 – D are dissected Devonian folded interbedded limestones and shales. The larger Np4.2 – Pz is a Paleozoic glaciated granite batholith.
Fig. Ms1-6. Location. Geographic. 07°11'56'' E, 46°10'35'' N, Rhone Valley, Switzerland Geologic. Intermontane fault valley between Pennine basement Nappe and Helvetic cover alps Source. esa Service for Landslide Monitoring (SLAM) Comments. This ERS 2 image is at the village of Leytron, 485 m, in the middle Rhone Valley between Sion and Martigny. Local geology consists of the steep thrusted front of the Pennine basement Nappe in lower right, Fv alluvial valley fill and, on the north, folded Mid Jurassic (Aalénien) calcareous shales and slates with beds dipping 35° to southeast. In the very center of the scene, just left of the coloured patch is the historical Montagnon slide in the shales, it is not clearly evident topographically in this radar image, but is well resolved in electro optical imageries. This largest slide site in Valais Canton is one of eight in Switzerland chosen to develop landslide susceptibility mapping using esa SLAM techniques of mathematically combining multiple radar images of the same site in such a way that tiny changes in the landscape such as deformation of materials occurring between images are highlighted (interfereometry). The image shows preliminary SLAM results. The coloured points represent land movement measured via interferometry in millimeters per year: from –5 mm yr–1 in purple, on a scale up through red and orange, with light green around zero, up to blue at +1 mm yr–1.
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Ms1.1
Division 4 · Surficial Deposits
Ms1.1 Planar Rock Slides, Inactive Characterization Some old rock slides degrade to a state of ultimate stability but many retain low stability because the shear surface has been reduced to residual strength with little or no cohesion. Reactivation has no peak strength to overcome. Inactive slides may be more difficult to detect and map as their traces become less sharply defined and progressively attenuated. Weathering and revegetation obscure the original structure. “It takes of the order of a thousand years for a major rockslide to become sufficiently overgrown by natural vegetation in the Rockies to be obscured in a reconnaissance survey. The rate of growth depends on the climate and on the nature of the slide debris. Debris from mudstones, shales, schists and other materials that weather quickly to clay minerals promotes rapid recovery of the natural vegetation; slide debris with large blocks of limestone or sandstone is more persistent”. Cruden (1985).
Group M · Mass Movement Materials
Geohazard Relations Prediction of landslide hazard for areas not currently subject to movement is based on the assumption that hazardous phenomena that have occurred in the past can provide useful information for prediction of future occurrences. Proper field assessment of the dormant character is of considerable importance in construction areas because reactivation may begin if excavations decrease support from below by re-steepening any part of the slide, or by loading the slope to increase the pressure exerted on the slide mass.
Reference Cruden DM (1985) Rock slope movements in the Canadian Cordillera. Canadian Geotechnical Journal 22:528–540
Select Bibliography Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 70
See also Geounit Ms1.
Fig. Ms1.1-1.
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964
Location. Geographic. 08°54' E, 42°03' N, Corsica Geologic. Paleozoic granite of terrane of European basement Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 25 000 Acquisition date. 1982 Source. IGN – Photothèque Nationale, France Comments. A stereomodel 22 km northeast of Ajaccio shows a 1.5 × 1 km inactive slide in weathered and dissected intrusive granite rocks coded Np5 and Np5.1. The latter is interpreted as being more intensely weathered and dissected than the Np5 area. A strong fracture or fault trace bounds the north side of the failure which is situated within 0.5 km of the access road to Vero Village.
Ms1.1 · Planar Rock Slides, Inactive
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Division 4 · Surficial Deposits
Fig. Ms1.1-2. (Caption on p. 968)
Group M · Mass Movement Materials
Ms1.1 · Planar Rock Slides, Inactive
Fig. Ms1.1-3. (Caption on p. 968)
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Division 4 · Surficial Deposits ▼
Fig. Ms1.1-2. Location. Geographic. 72°14' W, 19°08' N, central Haïti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. Four types of apparently inactive mass movements are delineated in this stereomodel 50 km east of St. Marc, along the nose and limbs of a probably faulted anticline in Paleogene rocks: Ms1.1 rock slide; Ms2 debris slide; Ms3.1 rock slump; and Mv1 rock fall. The structure at 1 034 m elevation is composed of interbedded lavas and pyroclastics of the Chaine des Cahos. X2 – Pg are Paleogene lavas; S2 – Og are Oligocene silts and shales.
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Fig. Ms1.1-3.
Location. Geographic. 0°14' W, 42°58' N, western Pyrenees Geologic. Axial zone of Hercynian/Alpine tectogenic belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. 1979 Source. IGN – Photothèque Nationale, France Comments. A group of slides and gelifluction on glacial till and Lower Devonian sandy shales on the slopes above the Gave d’Arrens valley 20 km southwest of Lourdes. The lower part of the largest mass, 2 km long, is cultivated above the villages of Arrens and Marsous. The shales are relatively weak, dissected, and are bordered by steeply dipping limestone strata to north and south. This figure is 40 km east of Fig. Kp1.1-4 and 30 km west of Fig. Ms1-5.
Group M · Mass Movement Materials
Ms2 · Debris Slides
Ms2 Debris Slides Characterization Debris slides are the rapid translational downslope movement of relatively dry Mc1 colluvium generally on slopes ranging from 25° to 45°. The failure surface is generally at the contact between the regolith and the underlying bedrock.Where sufficient moisture is present, the slide may become a Mf3 mud flow. “Failures are commonly due to an increase in pore water pressure following heavy rains, which reduces the shear strength of surficial formations … A frequent observation with debris slides is that they can burst explosively out of a slope. This appears to be associated with throughflow water (downslope flow within the soil) in pedological horizons, piping or aquifers, which provide water quickly to a slope face.” (Corominas 1996). Debris slides are generally poorly detectable on vertical air photos unless the latter were acquired when the slides were fresh, shortly after the events.
Clark GM (1987) Debris flows-avalanches. GSA Reviews in Engineering Geology VII:125–138 Howell DG, Brabb EE, Pike RJ, Ransey DW, Roberts S, Hillhouse JW (1999) Landslide hazard information and the decision-making process. GSA, Annual Meeting, vol 31, no 6 Iverson RM (1998) Runout and runup of landslides with ordinary Coulomb friction. EOS Transactions, AGU 79(17) Morton DM, Alvarez, RM, Campbell RH (2003) Preliminary soil-slip susceptibility maps, southwestern California. USGS Open File 03–0017 Moser M (1978) Proposals for geotechnical maps concerning slope stability in mountain watersheds. International Association of Engineering Geologists Bull 17:100–108 Nagarajan R, Khire M (1998) Debris slides of Varandh Ghat, west coast of India. Bulletin of Engineering Geology and the Environment. Springer-Verlag, Berlin Heidelberg, vol 57, no 1 Radbruch-Hall DH, Colton RB, Davies WE, Skipp BA, Lucchitta I, Varnes D (1976) Preliminary landslide overview map of the coterminous United States. USGS, Misc. Field Studies Map MF–771 Reid E, Lahusen RG, Roering JJ (2000) Landslide dynamics captured by real-time monitoring. Abstract GSA Annual Meeting, vol 31, no 6, p 87 Reneau S, Dietrich WE (1987) Size and location of colluvial landslides in a steep forested landscape. Erosion and sedimentation in the Pacific Rim. Intern. Association of Hydrological Sciences, Publ. 165, pp 39–48 Sasaki Y, Fujii A, Asai K (2000) Soil creep process and its role in debris slide generation – Field measurements on the north side of Tsukuba Mountain in Japan. Engineering Geology 56( 1–2):163–183
“Debris slide scars are ephemeral because the scarps are smoothed by small-scale degradational processes and rill erosion and the surface of failure is blanketed with new debris. In humid climates vegetation spreads quickly over the source area. Under these conditions, recognition of debris slide scars can be made only by using large-scale aerial photographs and by detailed field work.” (Corominas 1996).
Geohazard Relations The hazard posed by a debris slide is mainly attributable to the movement of ground beneath a structure or to the physical impact of rapidly moving debris. Short and poorly vegetated slopes as well as forested areas destroyed by fire or logging generally exhibit frequent debris slides related to intense rainfall events or earthquakes. On forest-covered slopes where roots penetrate to the underlying rock, the cohesion imparted to the regolith can be significantly higher than the natural cohesion of unforested regolith. Use of DTMs to locate slopes >25° in Ms2 areas would be one method to avoid the hazard.
Reference Corominas J (1996) Debris slide. In: Dikau R, Brunsden D, Schrott L, Ibsen ML (eds) Landslide recognition. John Wiley & Sons, Ltd., Chichester, pp 97–103
Select Bibliography Bromhead EN (1997) The stability of slopes. Spon Press, London Chandler RJ (1977) The application of soil mechanics to the study of slopes. In: Hails JR (ed) Applied geomorphology. Elsevier Scientific Publishing Company, pp 157–181
Fig. Ms2-1. Location. Geographic. Eastern Nepal, southeast Tibet Source. Courtesy of Stephen and Klaudia Mandl Comments. Photo shows a debris slide site in a road cut at a point on the Friendship Highway from Kathmandu, Nepal to Lhasa, Tibet.
969
Ms2
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Ms2-2. Source. Wilshire HR, et al. (1996) Geologic processes at the land surface. USGS Bulletin 2149, p 3 Comments. An air perspective photo shows a debris slide at La Conchita on the coast of southern California. The slide destroyed nine homes on 4 March 1995 following a period of heavy rains. This photo was taken two days later. The movement occurred in a 120 m high Br6 marine terrace developed in hills of poorly consolidated Tertiary and Quaternary marine sediments. The town of la Conchita lies on a lower Bc1a marine terrace 6 to 12 m above mean sea level. The community is thus also susceptible to exceptionally large storm surges and tsunamis. These have undercut and oversteepened the slopes at the base of the cliffs, making them prone to landsliding. An additional hazard factor in this area is neotectonism produced by a rising of the land by 3 mm yr–1. The deformation is related to the Pacific crustal plate being compressed and thickened in the region. Destructive debris slides recurred here in January 2005, causing 10 human fatalities, the destruction of 15 houses and damage to 16 other buildings.
Fig. Ms2-3.
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970
Location. Geographic. 130°45' W, 57°04' N, northern British Columbia Geologic. Stikinia Superterrane of Intermontane Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 31 680 Acquisition date. Not given
Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada, BC 5157-260, 261 Comments. The stereomodel shows a 1.5 × 1.5 km debris slide in Lower Devonian volcanic rocks with a nested Ms2.1 debris avalanche that has displaced the east-flowing valley stream. An Ms1 rock slide in apparently similar rocks immediately adjoins the debris slide. Trimlines of three highland glaciers are traced. This figure is 15 km west of Fig. Mf3-11.
Ms2 · Debris Slides
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Ms2.1
Division 4 · Surficial Deposits
Ms2.1 Debris Avalanches Characterization Debris avalanches are extremely fast debris slides occurring on open very steep slopes (>35°), and as with the slide, involve only a thin (<2 m) layer of surficial materials. Heavy rains and earthquakes are the most common causes of these movements, but they are generally differentiated from Mf3 debris-mud flows by not being as water saturated and generally recurring in a stream channel path. See also Geounit A2 Volcanic Debris Avalanches.
Geohazard Relations Debris avalanches are common on logged or sparsely vegetated slopes, or where engineering work has disturbed the slope equilibrium. Large avalanches occur in alpine
Group M · Mass Movement Materials
environments where Gl5 hanging glaciers and ice caps rest on fractured bedrock infiltrated by meltwater from the base of the glacier. All debris avalanches are destructive of lives, land and structures located in their path and at the base of the failed slope.
Select Bibliography Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, p 47 Evans SG (2001) Landslides. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:49 Plafker G, Ericksen GE (1978) Natural phenomena. Nevado Huascaran avalanches. In: Voight B (ed) Rockslides and avalanches, Peru. Elsevier, Scientific Pub., Co., New York, pp 277–314 Soeters R, Cornelis J, van Westen CJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, p 150 ▼
Fig. Ms2.1-1. Source. Reprinted with permission of HKSAR Government Comments. An air view shows Hong Kong’s most destructive landslide up to the date of the event. This slide occurred on Po Shan Road on 18 June 1972. 25 000 m3 of debris moved 200 m in <1 min following a period of heavy rain. Sixty seven people were killed when a 68 m wide portion of the steep slope failed, destroying a four-story building and a 13 story apartment block. The hillside is in 15 m of weathered Mesozoic granite or rhyolite.
Ms2.1 · Debris Avalanches
Fig. Ms2.1-2. Location. Geographic. 77°44' W, 09°09' S, northern Peru Geologic. Early Alpine orogeny of Mesozoic rocks Source. Plafker G, Ericksen GE (1978) Nevado Huascaran avalanches. In: Voight B (ed) Rockslides and avalanches, vol 1, Natural phenomena, Peru. Elsevier, pp 277–314
Comments. The figure is a sketch map and profile of the catastrophic Nevado Huascaran debris avalanche 31 May 1970 in the present Huascaran National Park, pictured and described in Fig. Ms2.1-3.
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Division 4 · Surficial Deposits
Fig. Ms2.1-3. Source. Wilshire HG and others (1996) Geologic Processes at the Land Surface. USGS Bull 2149, p 24, fig 14 Comments. The devastation track of the debris avalanche of 31 May 1970 from Mt. Huascaran in the Cordillera Occidental of northern Peru is delineated on this photo taken three months after the earthquake. The town lay buried beneath the debris. The event was triggered by a magnitude 7.7 earthquake with epicenter 25 km offshore, 160 km northwest of Huascaran. A map and relief section of the event are in Fig. Ms2.1-2. The topographic and human occupation settings of this avalanche combined to produce a major catastrophe. Topographically, the movement originated at elevation 6 500 m, traversed a glacier,traveled 16 km to 3 000 m and lower. The avalanche had an average velocity of 280 km per hour. The towns of Yungay (18 000 deaths) and Ranrahirca (5 000 deaths) lay in the lower middle ground. The avalanche deposits are now re-vegetated and cultivated.
Fig. Ms2.1-4. Source. Evans SG, Clague JJ (1989) Rain-induced landslides in the Canadian Cordillera. Geoscience Canada, vol 16(3), Geological Association of Canada, p 197, fig 8 Comments. Site A in this air view south at 61°40' W, 61°–61°20' N in genissic Mc1 colluvium points to the larger of two debris avalanches that reached the road during heavy rains. The location is on the Alaska Highway at Kluane Lake, in southwest Yukon Territory. This is essentially the only vehicular access road in this part of the Territory.
Group M · Mass Movement Materials
Ms2.1 · Debris Avalanches
Fig. Ms 2.1-5. Vertical Airphoto/Image. Type. b/w pan, single photo Scale. See bar Acquisition date. 2 August 1993 Source. Evans SG (2001) A synthesis of geological hazards in Canada. GSC Bull 548, p 51, fig 10a Comments. Air view of a debris avalanche (estimated volume 23 000 m3) that occurred in 1990 at Belgo Creek in Paleogene volcanic rocks of the Okanagan Highland in southern British Columbia. Three people were killed when the avalanche crushed their home just upslope from the road.
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Fig. Ms2.1-6.
Location. Geographic. 55°49' W, 47°29' N, south coast Newfoundland, Canada Geologic. Avalon Zone Terrane of the Caledonian Appalachian Orogen Vertical Airphoto/Image. Type. Pan b/w airphoto Scale. Indicated Acquisition date. 1976 Source. Batterson M, Liverman D (1995) Landscapes of Newfoundland and Labrador. Department of Natural Resources, Report 95-3, p 117 Comments. The stereomodel shows a debris avalanche which occurred in Neoproterozoic intrusive rocks of Harbour Breton in August 1973 at point “3” on the photos. Glacial till (Gf4) on the steep slope was saturated by prolonged heavy rains. The avalanche destroyed four houses and resulted in four deaths.
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Division 4 · Surficial Deposits
Fig. Ms2.1-6. (Caption on p. 975)
Group M · Mass Movement Materials
Ms3 · Rotational Rock Slumps, Undifferentiated
Ms3 Rotational Rock Slumps, Undifferentiated Characterization Rotational rock slumps are backward-tilting, little deformed slide block(s) (internal structure may be retained), resting below a main scarp and cracked crown generally in homogeneous rocks. Block(s) move along a surface of
rupture that is curved and concave. A high proportion of the displaced block(s) remain on the rupture surface. Ponds may develop in depression(s) between slump unit(s) and/or rupture surface. Susceptible slopes may fail due to a variety of factors, but frequently result from fluvial erosion of the base of the slope or as consequence of even low-level seismic events. (Includes single, multiple and successive slides.)
Geohazard Relations Movement rates can vary by several orders of magnitude. The disruption of drainage may keep the displaced material wet and perpetuate slope movements. Permeable rocks overlying impermeable materials can result in multiple slides.
Select Bibliography
Fig. Ms3-1. Source. Howes DE, Kenk E (1988) Terrain classification system for British Columbia, rev. edn. MOE Manual 10. Recreational Fisheries Branch, Ministry of Environment, p 65, fig 34 Comments. The block diagram shows the concave rotational rupture surface and step-like morphology of the cohesive slide blocks of a rock slump. Slumps in coastal cliffs are shown in Figs. Br2.1-1 and Br3.1-1.
Fig. Ms3-2. Source. LAR, January 1975 Comments. Photo of a rotational slump at elevation 70 m in Upper Tertiary marine sediments (Monterey Formation) at Point Reyes National Seashore, 50 km north of San Francisco, California.
Cruden DM, Varnes DJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, p 56 Gallois RW, Edmunds FA (1965) The Wealden District, 4th edn. British Regional Geology, Natural Environment Research Council, Institute of Geological Sciences, pp 67–68 Kienholz H (1978) Maps of geomorphology and natural hazards of Grindelwald, Switzerland, scale 1 : 10 000. Arctic and Alpine Research Soeters R, Cornelis J, van Westen CJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, p 147 Yeend WE (1969) Quaternary geology of the Grand and Battlement Mesas Area, Colorado. USGS Professional Paper 617, pp 4–5, 30– 34, 38–40, 44–45
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Ms3
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Ms3-3. Source. LAR Comments. A view of one of a number of slump-type failures that frequently occur in unstable Mid-Jurassic marly shales of an alpine valley at Grindelwald in central Switzerland. See also in the same materials debris flows of Fig. Mf3-4, creep of Fig. Mc1-3, and gully erosion of Fig. S2.1-3.
Fig. Ms3-4.
▼
978
Location. Geographic. 81°36' W, 08°28' N, western Panama Geologic. Middle American Deformed Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 1971 Source. Personal archive Comments. This stereomodel in X2.2 interbedded lavas and pyroclastics in the upper Tabasara Valley shows a large scale representation of a 650 m wide by 1 500 m long rock slump. The model demonstrates the value of large scale airphotos in the study of some slope failures by a better resolution of the internal structures of the displaced mass as compared with Fig. Ms3-5. The surrounding hills remain nearly denuded but the slump mass is now vegetated. The site is in the same materials as the earth flow of Fig. Mf1-2, 115 km to the west. See also Fig. X2.2-3.
Ms3 · Rotational Rock Slumps, Undifferentiated
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980
Division 4 · Surficial Deposits
Fig. Ms3-5. (Caption on p. 982)
Group M · Mass Movement Materials
Ms3 · Rotational Rock Slumps, Undifferentiated
Fig. Ms3-6. (Caption on p. 982)
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
▼
Fig. Ms3-5. Location. Geographic. 81°37' W, 08°27' N, western Panama Geologic. Middle American Deformed Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 50 000 Acquisition date. 1954 Source. Personal archive Comments. The inset frame on this smaller scale stereomodel indicates the coverage of Fig. Ms3-4. The greater areal coverage of this scale shows the terrain context of the slope failure in typically dissected Tertiary X2.2 interbedded lavas and pyroclastics. See also Fig. X2.2-3.
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Fig. Ms3-6. Location. Geographic. 03°23' E, 43°58' N, north Languedoc Geologic. Contact of Hercynian massif and Jurassic sedimentary basin Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 28 500 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. The stereomodel is an enlargement of a portion of a 1:57 000 contact print. The location, at Le Vigan in Gard Department at the terminus of a regional railway from Montpellier, shows a roadway in a narrow valley curving around the foot of a 400 m broad pre-existing rock slump. The slump occurred in a narrow valley-parallel band of Lower Jurassic (Lias) marly limestones. The formation is in fault contact on the north with distinctly W1 Devonian sediments of a small local nappe structure at the southern extremity of the Cevennes Hercynian Massif. The plateau to the south is Upper Jurassic karstic Kp1 limestone of Causse Blandas.
Fig. Ms3-7.
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982
Location. Geographic. 123°24' W, 58°14' N, northeast British Columbia Geologic. Lower Cretaceous shales and sandstones of the Interior Plains Vertical Airphoto/Image. Type. b/w, pan, stereo triplet Scale. 1: 40 000 Acquisition date. Unspecified Source. Courtesy of Natural Resources Canada NAPL A 11364, 65, 66, 67 Comments. A stereomodel in the Fort Nelson Lowland shows six large rotational rock slumps associated with nearly flat-lying S2 shales underlying S1 sandstones. The failures average 0.5 to 1 km in width and 1.5 to 2 km in length. The largest is 5 km long within the photo cover and extends beyond. The two black delimited zones are less definitive than the other units.
Ms3 · Rotational Rock Slumps, Undifferentiated
983
Ms3.1
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Ms3.1 Rotational Rock Slumps, Inactive
ground. New high pore pressures and increases in loading could re-activate the slumps.
Characterization
Select Bibliography
See Geounit Ms3.
Dishaw H (1967) Massive landslides. Photogrammetric Engineering 33:603–608 Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 108–109
Geohazard Relations Morphology may be attenuated and re-vegetated, but the overall structure and shear surface remain beneath the
See also Geounit Ms3.
Fig. Ms3.1-1. Location. Geographic. 13°05' E, 47°10' N, central Austria Source. Courtesy of Natural Resources Canada, GSC 204166, O Comments. Photo of a rock slump in low grade metamorphic rocks and colluvium in the Gastein Valley. New chalet constructions are near the toe of the slide. The instability of these slopes is due to foliation in phyllites and calcareous shales which cover gneissic basement.
Fig. Ms3.1-2. Source. LAR, March 1972 Comments. The photo shows a succession of slumps with scarps and slide blocks in S2 Miocene marine shale 10 km northeast of San Jose south of San Francisco, California.
Fig. Ms3.1-3.
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984
Source. Unattributed Comments. A 1:45 000 stereomodel shows the typical morphology of rotational rock slumps. These are characteristic of escarpments in X1 basalt lava flows. Location is in Rio Grande Canyon, Taos County, New Mexico.
Ms3.1 · Rotational Rock Slumps, Inactive
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Ms4
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Ms4 Snow Avalanches
lanche motion ranges from 50 to 200 km h–1. Wet slides are denser and slower, 20 to 100 km h–1.
Characterization
Geohazard Relations
The formation of snow avalanches is the combined result of non-variable terrain factors (topography, orientation to wind, vegetation) and variable climatic factors (snowfall, wind, temperature). Most avalanches resulting from thermodynamic instability and structural collapse of the snow mass are ground-borne, slab or point release types. Slab avalanches are broad layers of cohesive snow that fail along a fracture line across a slope. Point-release avalanches start in cohesionless snow and move downslope creating a relatively narrow trough. In dry snow conditions avalanches can become airborne as powder avalanches. Avalanches recur in the same locations year after year and in certain places several times each year. They can also occur where they have not occurred before. Dry ava-
Slab avalanches cause most of the hazard to people, property and infrastructure. Fatalities. The number of recreational fatalities has increased dramatically in recent years. Damage to property and forests. “The most damaging events are often those which begin in snow accumulation or source areas above the tree line, traverse lower forested terrain, and run out onto valley floors where most engineered facilities related to human activities are located.”(Evans and Gardner 1989). Traffic delays. Avalanche-related closures of transportation corridors amount to many hours in average winters. Hazards are greatest on slopes in the range 25–40°; lower angles do not encourage failure of the snowpack, while at higher angles there is less opportunity for the snow to build up to unstable thicknesses. The location of common avalanche tracks can be mapped with accuracy from airphotos taken in the snow-free season. Reduction of encounter probabilities for avalanche damage is achieved mainly with snow sheds and with supporting structures such as fences in the avalanche release zone. These structures must be strong enough to support creep pressures reaching tons per square meter, while at the same time being light enough for economical transport and erection high on a mountainside.
Reference Evans SG, Gardner JS (1989) Geological hazards in the Canadian Cordillera. In: Fulton RJ (ed) Geology of Canada, no 1, Quaternary Geology of Canada and Greenland, p 702
Select Bibliography
Fig. Ms4-1. Location. Geographic. Canadian Cordillera Source. Unspecified Comments. Photo of a just-triggered large snow avalanche in its rapid motion down a mountain slope. Both the denser ground component and the airborne powder component are visible.
Butler DR (1986) Snow avalanche hazards in Glacier National Park, Montana: Meteorological and climatic aspects. Phys. Geogr. 7:72–87 Butler DR, Malanson G, Walsh SJ (1992) Snow-avalanche paths: Conduits from the periglacial-alpine to the subalpine-depositional zone. In: Dixon JC, Abrahams AD (eds) Periglacial geomorphology. John Wiley & Sons, Chichester, pp 185–202 Corner GD (1980) Avalanche impact landforms in Troms, north Norway. Geografiska Annaler 62A:1–10 Forsythe KW, Wheate RD, Waters NM (1995) Classification and mapping of avalanche slopes in Yoho National Park: An assessment using Landsat TM and digital elevation data. Proc., 17th Canadian Symposium on Remote Sensing, pp 108–113 Ganju A, Dimri AP (2004) Prevention and mitigation of avalanche disasters in western Himalayan region. Natural Hazards 31(2):357–371 Jamieson B (2001) Snow avalanches. In: Brooks GR (ed) Synthesis of geological hazards in Canada. GSC Bull 548A:81–100
Ms4 · Snow Avalanches Luckman BH (1977) The geomorphic activity of snow avalanches. Geografiska Annaler 59A:31–48 McClung D, Schaerer P (1993) The avalanche handbook. The Mountaineers, Seattle, Washington Peev CD (1966) Geomorphic activity of snow avalanches. International Association of Scientific Hydrology Publication 69, pp 357–358 Perla RI, Martinelli M Jr (1976) Avalanche handbook. U.S. Dept. of Agriculture Handbook 489 Salway AA (1979) Time series modelling of avalanche activity from meteorological data. Journal of Glaciology 22:513–528
Fig. Ms4-2. Location. Geographic. 129°30' W, 54°15' N, west central British Columbia Source. Courtesy of Natural Resources Canada,GSC 203257-H Comments. Photo shows a snow avalanche track that tore down a forested slope and crossed road and rail lines in the lower Skeena Valley of the Coast Mountans.
▼
Fig. Ms4-3.
Source. LAR Comments. This photo shows a wood and metal avalanche control snow retention fence unit of the array pictured in the vertical airphoto of Fig. Ms4-7.
Schaerer PA (1976) Analysis of snow avalanche terrain. Canadian Geotechnical Journal 14(3):281 Schild M (1972) Lawinen. Lehrmittelverlag des Kantons Zürich, CH Tuchinskiy GK (1966) Avalanche classification and rhythms in snow cover and glaciation of the Northern Hemisphere in historical times. Association Internationale d’Hydrologie Scientifique, vol 69, pp 382–393 Walsh SJ, Bian DG, Brown DG, Butler D, Malanson GP (1989) Image enhancement of Landsat Thematic Mapper digital data for terrain evaluation, Glacier National Park, Montana, USA. Geocarto International 4:55–58
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Ms4-4. Location. Geographic. Not specified Source. Courtesy of Respironics Inc., Murrysville, Pa., USA Comments. This photo shows a volunteer who has been buried in snow for an hour under simulated avalanche conditions. The person is instrumented with a complete set of vital signs sensors for core and skin temperatures, heart rate, and respiratory rate. He is in voice communication with the researchers and is free to request a ‘dig-out’ at any time, during the trial. The researchers are studying the physiology of avalanche victims and the efficacy of a new device called the Avalung that increases the survival time of buried individuals. “The motion of a snow avalanche fatally injures approximately 25% of avalanche victims, and after 30 minutes of burial the survival rate drops to 50%.
Consequently, to have a 50% chance of being found alive, his or her head and chest must be dug out within 30 minutes. Only about 15% of victims survive being buried two hours.” Jamieson B (2001) In: Brooks GR (ed) A synthesis of geological hazards in Canada. Geological Survey of Canada, Bull 548, p 94.
Fig. Ms4-5. Source. Société italo-suisse d’exploitation du tunnel du Grand-Saint Bernard Comments. View eastward across the Toules reservoir 07°12' E, 45°55' N at 1 810 m elevation of a section of 13 km of reinforced concrete snow avalanche protection sheds over the road in the PermoCarboniferous metamorphic rocks of the Pennine Nappes of the southern Swiss Alps. The road connects Aosta in Italy with Martigny in Switzerland and is one of only eight of 28 important alpine passes that are open all year. On the right the roadway is tunnelled through the mass of a Ms3.1 rock slump.
Ms4 · Snow Avalanches
▼
Fig. Ms4-7.
Location. Geographic. 06°55' E, 45°29' N, French Alps Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 15 000 Acquisition date. Not given Source. IGN – Photothèque Nationale, France Comments. The pattern of a myriad of short, regularlyspaced white lines enclosed by a red line in this airphoto enlargement is the expression of avalanche control snow retention fences of the type pictured in Fig. Ms4-3. The broken line traces the ridge crest of the slope leading down to the lake. Location is just below the winter sports center of Val d’Isère, the lake – Lac du Chevril – is the hydro-electric power reservoir of Tignes, elevation 1 790 m; at 2.8 km2, the largest such reservoir in the Alps. Such structures are so expensive that they are usually only installed to protect villages, and important roads. The protected road in this photo leads to another construction site and the Lac de Tignes winter sports center. ▼
Fig. Ms4-8.
Fig. Ms4-6. Source. Courtesy of Parks Canada/John Woods. G15-2880-336 Comments. This air view shows multiple avalanche tracks and runout deposits on both sides of the Rogers Pass Trans-Canada Highway and rail transportation corridor in Glacier National Park of southeast British Columbia, 117°36' W, 51°15' N. The pass elevation is 1 320 m, the average annual snowfall is 0.80 m. Several of the 6.5 km of snowsheds that cover the most dangerous pass sections are visible. Such sheds, and five long tunnels, are the most costly form of avalanche defense. In addition to the sheds earth dams, dikes, mounds and catch basins placed in avalanche paths contain or regulate snow slides. These static defenses are complemented by a mobile system of defense.
Location. Geographic. 128°29' W, 56°19' N, northern British Columbia Geologic. Bowser Basin of the Stikinia Superterrane of the Cordilleran Intermontane Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 31 680 Acquisition date. 12 July 1966 Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada. BC 5204-054, 055 Comments. The stereomodel in the Jurassic sediments of the Skeena Mountains shows two avalanche tracks, respectively 200 m and 300 m broad and 1 200 m long to the bottom of cleared forest. They are located on steep north-facing slopes with their rupture zones above timber line at the 1 700 m a.s.l. Many larger avalanches descend to valley bottoms, these stopped midway at a lower angle bench, perhaps due to their limited mass. The tracks are swaths cut through forest, completely destroying mature trees, they may also have removed organic soils which are important for forest regrowth. Red lines delimit postglacial valley fill and traces of earlier valley glaciation.
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Division 4 · Surficial Deposits
Fig. Ms4-7. (Caption on p. 989)
Group M · Mass Movement Materials
Ms4 · Snow Avalanches
Fig. Ms4-8. (Caption on p. 989)
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Ms5
Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Ms5 Ice Avalanches Characterization “Ice avalanches occur where a glacier terminates on a smooth bedrock slope inclined more than 30°. Failure of glacier snouts under such conditions is promoted by high ambient air temperatures leading to the development of a thin film of water along the base of the body of ice. This water triggers an increase in the rate of slippage of the glacier over its bed, which in turn leads to the widening of transverse crevasses above a zone of extension. Accelerated slippage may lead to failure concave transverse crevasses reaching to bedrock.” (Eisbacher and Clague 1984). Ice avalanches may be triggered by earthquakes.
Geohazard Relations Destructive ice avalanches have occurred in a number of localities in the relatively densely populated high alpine valleys of Europe. The same hazard exists for the development of settlements, mining, energy generation and tourism activities in proximity to valley and mountain glaciers in similar topographic sites in the high mountains of North and South America and Asia.
Reference Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, p 47
Fig. Ms5-1. Select Bibliography Ommanney CSL, Clarkson J, Strome MM (1973) Information booklet for the inventory of Canadian glaciers. Glaciology Division, Inland Waters Directorate, Department of the Environment, Ottawa, p 41 Post A, La Chapelle ER (1971) Glacier ice. University of Toronto Press, p 8 fig 12; p 34 fig 40a,b; p 35 fig 41a,b Röthlisberger H (1980) Die Schweiz und ihre Gletscher. Kummerly und Frey, Bern, pp 132–147 Ryder JM (1998) Geomorphological processes in the alpine areas of Canada. GSC Bull 524:35 Salzmann N, Kääb A, Huggel C, Allgöwer B, Haeberli W (2004) Assessment of the hazard potential of ice avalanches using remote sensing and GIS-modelling. Norwegian Journal of Geography 58(2):74–84
Source. Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. Geological Survey of Canada, Paper 84-16, p 44, fig 33 Comments. The profiles in this figure illustrate the principal situations in which ice avalanches occur. In the upper situation the avalanche is as characterized in the geounit description. The other profiles illustrate the situation where hanging glaciers rest on fractured bedrock. Infiltration of water from the base of such a glacier into open fractures may lead to failure involving both rock and ice.
Ms5 · Ice Avalanches
Fig. Ms5-2. Source. Post A, LaChapelle ER (1971) Glacier ice. University of Toronto Press, p 8, photo 12. Reprinted by permission of the University of Washington Press Comments. The three arrows at the bottom of this figure point to ice avalanches on the Mount Everest massif.
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Division 4 · Surficial Deposits
Fig. Ms5-3. Location. Geographic. 08°04' E, 46°36' N, central Switzerland Geologic. Autochton crystalline Aar Massif of Alpine tectogenic belt Vertical Airphoto/Image. Type. TM4/TM5 ratio Scale. Not given Acquisition date. 1998 Source. Courtesy of Zürich University, Geography Department Comments. The possibilities of remote sensing identification of potential ice avalanche sites are limited due to such
Group M · Mass Movement Materials
factors as snow cover, shadows, difficult topography and relatively small target dimensions. This figure is a ratio image of Landsat TM4/TM5 data overlain on a shaded DEM (DHM 25, L+T) just east of Eiger mountain at Grindelwald. Slope calculations in the DEM of the fused image allowed extraction of those glacier areas, in blue, which are steeper than 25°, recognized as potentially prone to ice avalanches assuming temperate thermal ice conditions. Both ice and snow-covered ground in the scene are white. Potential ice avalanche paths, shown in red, were calculated within the susceptible glacier areas based on hydrological flow modeling within a GIS.
Ms5 · Ice Avalanches
▼
Fig. Ms5-4.
Source. Die Schweiz und Ihre Gletscher, 2nd edn. (1980) Schweizerische Verkehrszentrale, Zürich, Kümmerly+Frey, Bern, p 145, photo 29 Comments. An air perspective photo, probably taken on 31 August 1965, of the ice avalanche zone of the Gl5 Allalin Glacier shown in the vertical airphoto of Fig. Ms5-5. The glacier is located at Mattmark at the head of Saas Valley, 7 km south of the Saas Fee ski center, in the Pennine Alps of Wallis Canton, southern Switzerland. Historically, Allalin Glacier posed a Mf4-3 glacier dam hazard. It frequently crossed the valley and blocked the torrential Saaser Vispa and impounded the Mattmarksee. Failure of the dam repeatedly flooded the valley destructively. In 1965 work was in progress at Mattmark to impound the Vispa stream for a major hydroelectric reservoir. The construction camp was established directly below the snout of the glacier. On the evening of 30 August, 1 000 000 m3 of ice at the heavily crevassed front of the hanging glacier slid away. The avalanche of ice 100 to 200 m across surged down and overwhelmed the construction camp. Air blast flattened structures before the ice hit, the camp disappeared under the blanket of pulverized ice. Eighty-eight workers lost their lives. Failure occurred during a phase of enhanced slippage along the ice-rock interface (Eisbacher and Clague, p 216, 217). ▼
Fig. Ms5-5.
Location. Type. b/w pan, subscene Scale. 1: 15 000 Acquisition date. September 1967 Source. Die Schweiz und Ihre Gletscher 2nd edn. (1980) Schweizerischen Verkehrszentrale, Zürich. Kümmerly+Frey, Bern, p 147, photo 37 Comments. The bare rock surface exposed by the ice avalanche is delineated on this segment of a photo of the Allalin Glacier of Fig. Ms5-4 taken two years after the catastrophe.
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Division 4 · Surficial Deposits
Fig. Ms5-4. (Caption on p. 995)
Group M · Mass Movement Materials
Ms5 · Ice Avalanches
Fig. Ms5-5. (Caption on p. 995)
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Division 4 · Surficial Deposits
Sub-group Mf Flows Mf1
Mf1 Retrogressive Flows in Unconsolidated Sediments Characterization These slides and flows are rapid movements that occur mainly in Bc3 glaciomarine and L1 glaciolacustrine clay deposits which have an unstable particle structure and a high natural moisture content. Liquefaction of these sensitive clays is generally triggered by spring snowmelt, vibration, blasting, or shaking response during earthquakes. The slide and flow process begins with a simple rotational slump resulting from fluvial erosion. It then progresses when the initial slide mass leaves the new slope unsupported and a new instability results. A sequence of failures are triggered resulting in the progressive removal of debris in the form of flows. The headwall failure surface can extend far beyond the crest of the initial bank failure. Vertical stereo airphoto mapping of slide flows can be carried out at photo scales of 1:20 000 to 1:30 000, but detection of the smallest slides requires a scale of 1:6 000 or larger.
Geohazard Relations Both the retrogressive and flow phases of these slides can be extremely rapid and very destructive (tens of minutes covering tens of hectares). In these sensitive clays, it is not just the risk of a slope failure that is of concern, but the enhanced destructiveness involved in the area that can be affected by the retrogressive failures. These spreads as they are sometimes called are agents of a number of hazard types: 6 – slide 8 – flow/liquefaction, and 12 – deposition
Select Bibliography Burn CR, Lewkowicz AG (1990) Retrogressive thaw slumps. Canadian Geographer 34:273–276 Evans SG (2001) Landslides. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:59–62 Lefebvre G (1996) Soft sensitive clays. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, pp 607–619
Group M · Mass Movement Materials Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 46–52 Poschmann AS (1978) Air photo classification and glossary of landslide problems in the Ottawa and St. Lawrence Lowlands. Bsc Thesis, Queen’s University, Ontario Poschmann AS, Klassen KE, Klugman MA, Goodings D (1983) Slope stability study of the South Nation River and Portions of the Ottawa River. Ontario Geological Survey Miscellaneous Paper 112 Updike RG, Olsen HW, Schmoll HR, Kharaka YK, Stokoe KH (1988) Geological and geotechnical conditions adjacent to the Turnagain landslide, Anchorage, Alaska. USGS Bull 1817 Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 69
Fig. Mf1-1.
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998
Location. Geographic. 149°57' W, 61°12' N, southern Alaska Geologic. Glaciomarine clay, 14 000 ka Vertical Airphoto/Image. Type. Natural colour airphoto Scale. 1:10 000 Acquisition date. 4 April 1964 Source. Cravat HR, Glaser R (1971) Color aerial stereograms of selected coastal areas of the United States. NOAA/DOC, p 71 Comments. A stereomodel of a retrogressive flow and multiple blocks at Turnagain Heights 3 km north of the international airport at Anchorage. The site is a 25 m high bluff of marine clay with an 8 m glacial outwash gravel cap on estuarine deposits of Knik Arm at the head of the grabenlike Cook Inlet – Susitna Lowland of Shelikof Strait. The clay may exceed 30 m in thickness. More than half of Alaska is seismically active today. A major earthquake of local intensity VIII with strong motion for >4 min occurred here on 27 March 1964. The clay in the lower 8 m liquefied. The slide moved forward 800 m along a front of 2.4 km and 270 m wide; the area extended to 50 ha causing 115 deaths, 75 houses wrecked, and some moved 150 m. In the heart of the city a drop in ground level of 6 m occurred and most buildings suffered serious structural damage and the loss of 135 lives. After 44 years the slide masses are now obliterated, largely forested and five large houses can be seen built on the disturbed material. The epicenter was 120 km east of Anchorage in the Chugach Mountains. The white flecks at the top of the stereogram are ice and snow stranded on mudflats by the 13 m (Fw3.1) tide. The tectonic setting of this lowland is described in Fig. Vc3.2-6.
Mf1 · Retrogressive Flows in Unconsolidated Sediments
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Division 4 · Surficial Deposits
Fig. Mf1-2. (Caption on p. 1002)
Group M · Mass Movement Materials
Mf1 · Retrogressive Flows in Unconsolidated Sediments
Fig. Mf1-3. (Caption on p. 1002)
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
▼
Fig. Mf1-2.
Location. Geographic. 82°36' W, 08°50' N, western Panama Geologic. Middle America Deformed Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 10 000 Acquisition date. April 1977 Source. Personal archive Comments. This large scale stereomodel in the Baru National Park covers a spectacular 2 km wide earth flow whose forested and shadowed rupture scarp is prominent. A characteristic series of parallel ridges and blocks of spoil flow are particularly well developed. The materials are Holocene X2 interbedded lavas and pyroclastic sediments in the northwest part of a 40 km broad regional footslope surrounding Baru Volcano, the only active volcano in Panama. Recent space imagery shows a large A1 lahar just south of this site that flowed down from the west flanc of the volcano 7 km south to the town of El Hato del Volcan. Baru Volcano is located near the locus of the triple junction of the Nazca and Cocos Plates and the Panama Fracture Zone. It is on the on-land projection of the P.F.Z. ▼
Fig. Mf1-3. Location. Geographic. 61°11' W, 53°02' N, southern Labrador Geologic. 17.1 graben in Exterior Thrust Belt of Grenville Orogen of Canadian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 11 October 1947 Source. Courtesy of Natural Resources Canada, NAPL LAB-5-175, 176 Comments. The stereomodel on a lower reach of the Churchill River shows a shallow-appearing retrogressive slide flow, 2 km long and 2 km wide at the riverbank, which is the result of the same postglacial events as in the Champlain Sea of the Ottawa-St. Lawrence Lowlands shown in Fig. Mf1-6. The failure occurred at the groundwater contact of the Fw3 pervious estuarial terrace sands and pore pressures in the impervious underlying Bc3 glaciomarine clays. Mollard (1977, p 46) states that “The reason old failures are usually larger and shallower than historic ones is that, at the time of high failure incidence, the freshly deposited sediments had neither drained nor consolidated to any significant degree. Accordingly, as a general condition, natural water content tended to be much higher and soil strengths much lower than they are today along the margins of abandoned terraces and river banks.” An analogous situation is depicted in Fig. Mf1-4. The parabolic dunes on the terrace surface are illustrated in the colour infrared photos of the same site in Fig. Ed1.7-3. This site is in the 17.2 graben of Fig. 17.1-5.
Fig. Mf1-4.
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1002
Location. Geographic. 77°44' W, 55°16' N, east coast Hudson Bay, Quebec Geologic. Archean granites of eastern Shield Vertical Airphoto/Image. Type. Colour infrared, stereo triplet Scale. 1: 15 000 Acquisition date. 17 August 1976 Source. Courtesy of Natural Resources Canada, NAPL A 37418IR, 24, 25, 26 Comments. The stereomodel in the estuary of the Grande Rivière de la Baleine just upstream from Fig. Bw4-4 shows a 1 km wide slide flow with 700 m of retrogression in 30 m high terraces at the contact of Fw3 deltaic sands overlying Bc3 marine sediments. The flow, which occurs 8 km downstream from a similar failure constricts the river channel here to less than 300 m. River current at high discharge rates undercuts the foot of the terrace. The marine sediments are stiff cohesive silty clays which in turn overlie massive to laminated highly sensitive clay of low strength. The surficial sands act as a groundwater reservoir that adds overburden weight and high pore pressures in the underlying silts and clays, particularly following heavy precipitation. The inland bedrock terrain is Archean granite. A small deposit of Ec2 dunes is on the left.
Mf1 · Retrogressive Flows in Unconsolidated Sediments
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mf1-5. Location. Geographic. 75°03' W, 45°24' N, eastern Ontario Source. Brooks GR and others (1994) The Lemieux Landslide of 10 June 1993. GSC Miscellaneous Report 56, fig 11b, p 16 Comments. This view shows the crater embankment and rotational blocks of a flow slide in Bc3 glaciomarine and deltaic sediments, 4.5 km downstream of the 1971 failure shown in the stereo airphotos of Fig. Mf1-6. Satellite imagery a dozen years later shows the crater condition as high soil moisture and slowly re-vegetating.
Fig. Mf1-6.
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Location. Geographic. 75°05'51'' W, 45°22'36'' N, eastern Ontario Geologic. Glaciomarine plain Vertical Airphoto/Image. Type. Natural colour, stereo pair Scale. 1: 10 000 Acquisition date. 1 September 1971 Source. Courtesy of Natural Resources Canada, NAPL A 30362, 150, 152 Comments. A stereomodel shows a flow slide with 400 m of retrogression and 650 m valley width in 20 m of deltaic sands and glaciomarine silty clay in the CasselmanLemieux reach of the South Nation River Valley. At least 13 historic and prehistoric slide scars are present along this valley. The pictured slide occurred on 16 May 1971. Fluidized debris flowed into the channel of the river and blocked its flow causing flooding upstream. Material that was not fluidized remains in the landslide crater. Compare this figure with Fig. Mf1-7 photo taken 7 years earlier. Increase in pore pressures in the sediments and steepening of banks by river erosion are believed to be the dominant causative factors of retrogressive flows in these sediments. The displaced mass is a succession of linear ridges of blocks of intact clay. The blocks, though vegetated, are still visible 36 years later with standing water in the intervening depressions. This site is 18 air km south-southwest of the 4 500 years older down-valley earth flows at Plantagenet in Fig. Mf2-6.
Mf1 · Retrogressive Flows in Unconsolidated Sediments
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Division 4 · Surficial Deposits
Fig. Mf1-7. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 10 000 Acquisition date. 18 May 1964
Group M · Mass Movement Materials
Source. Courtesy of Natural Resources Canada, NAPL A 18360, 214 Comments. The comparative photo fragment covers the same area seven years before the slide pictured in the stereo pair of Fig. Mf1-6.
Mf1.1 · Retrogressive Slides in Unconsolidated Sediments and Detrital Rocks Substrate
Mf1.1 Retrogressive Slides in Unconsolidated Sediments and Detrital Rocks Substrate Characterization As its name implies, this geounit is a characteristic of regions where river valley slopes are in unconsolidated sediments underlain by weak sedimentary rocks. This stratigraphic association predominates in the southern part of the mid-continent area of Canada between the Shield and the western Cordillera. Here, wide expanses of flatlying poorly consolidated Cretaceous sedimentary bedrock are covered by thick successions of Quaternary glacial and postglacial sediments. The failures are slow progressive backward-tilting blocks. They develop where river action rapidly downcut, as much as 100 m, through the upland cover, and thrusted, brecciated and relieved residual stresses in the upper shale strata at the base of the valley slopes. Tension cracks have formed in the Quaternary sediments near the top of the valley slopes. Continued downcutting causes slopes to exceed the critical maximum height consistent with slope angles.
Fig. Mf1.1-1. Source. Beaty CB (1972) Geographical distribution of post-glacial slumping in southern Alberta. Canadian Geotechnical Journal no 9, Natural Resources Canada, p 220, fig 2 Comments. Photo of a retrogressive slump involving glacial till (Gf4) and underlying Cretaceous shales on a bank of the Oldman River near Lethbridge. Lateral erosion by the river induces renewed movements of valley sides by gravity creep on pre-existing slip surfaces. A possible additional cause of the occurrence of this and adjacent slumps has been suggested as being their location on snow retentioning slopes of northerly and northeasterly aspect. See Figs. Mf1.1-2 and Mf1.1-3.
Geohazard Relations Although these slides are slow moving they can damage or destroy structures founded on the moving masses. Some slides exist that are more than 3 km in length and have retrogressed more than 1.5 km from a river edge.
Select Bibliography Beaty CB (1972) Geographical distribution of post-glacial slumping in southern Alberta. Canadian Geotechnical Journal 9:219–224 Carson MA, Bovi, MJ (1989) Slope processes. In: Fulton RJ (ed) Geology of Canada, no 1, Quaternary Geology of Canada and Greenland. GSC, pp 588–589 Christianson EA (1983) The Denholm Landslide, Saskatchewan, part 1: Geology. Canadian Geotechnical Journal 20:197–207 Evans SG (2001) Landslides. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:55–77 Haug MD, Saeur E, Fredlund DG (1977) Retrogressive slope failures at Beaver Creek, south of Saskatoon, Saskatchewan, Canada. Canadian Geotechnical Journal 14:288–301 Mollard JD (1977) Regional landslide types in Canada. GSA, Reviews in Engineering Geology, vol III, pp 38–46 Scott JS, Brooker EW (1968) Geological and engineering aspects of Upper Cretaceous shales in Western Canada. GSC Paper 66–37
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Mf1.1
Division 4 · Surficial Deposits
Fig. Mf1.1-2. Location. Geographic. 107°23' W, 50°45' N, southwest Saskatchewan Source. Scott JS, Brooker EW (1968) Geological and engineering aspects of upper Cretaceous shales in western Canada. GSC Paper 66-37, p 37, fig 15
Fig. Mf1.1-3.
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1008
Location. Geographic. 113°04' W, 52°15' N, southern Alberta Geologic. Glaciated Interior Plains Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL 116488-11,12 Comments. The annotated stereomodel shows the Red Deer River that has cut through 3 to 10 m of glacial till (Gf4) and approximately 100 m into underlying Paleocene and Upper Cretaceous poorly cemented, and/or densely jointed, interbedded argillaceous sandstones and shales.
Group M · Mass Movement Materials
Comments. The map and cross section of this figure show the characteristic stratigraphy of slide flows underlain by shale sediments, as in the stereo airphotos of Fig. Mf1.1-3. The linear arcuate ridges are separated by undrained depressions. Location is 3 km north of the north bank of Lake Diefenbaker. A succession of arcuate ridges at the till surface, parallel to the river, reveal a characteristic retrogressive slide topography. Undercutting of the valley sides by the river is a likely immediate cause of the slope failures. In such situations shear strength along slip surfaces is insufficient to resist the disturbing forces. The slides developed in postglacial time (13 ka) during unloading of the land and rapid stream erosion. The slide masses in this area appear stabilized, but fresh scarps and small stream channels are evident in them and along the valley slopes. S2 areas are interpreted as exposures of sandstone/shale. The knob and kettle topography in the lower right quarter of this photo is hummocky superglacial disintegration moraine, less consolidated than subglacial basal till. See a perspective view in Fig. Mf1.1-1.
Mf1.1 · Retrogressive Slides in Unconsolidated Sediments and Detrital Rocks Substrate
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Mf2
Division 4 · Surficial Deposits
Mf2 Earth Flows Characterization Earth flows are sudden translational movements of viscous cohesionless fine-grained sediments. They occur in two geomorphological settings and source materials: on moderate to steep slopes in rocks that produce debris rich in weak clay, e.g shales and volcaniclastics, in hilly and mountainous terrain; in normally consolidated L1 glaciolacustrine and Bc3 glaciomarine sediments which have an unstable particle structure and a high natural moisture content. The toe lobes of flows in weak rocks may rest at the foot of slopes or may extend to infill valleys or run out on flat land in larger events. Flows in the lacustrine and marine sediments occur without the rotational sliding of the retrogressive slides of the Mf1 unit. Remoulding of the clay in these flows results in almost complete conversion to fluid mud, often leaving “clean” flow bowls (Carson and Bovis 1989). “Earth flows (in glaciomarine sediments Bc3) terminate when the character of the uplands material changes, or when a balance is achieved between the spoil material and the backslope, or when the outlet becomes constricted.” (Poschmann et al. 1983).
Group M · Mass Movement Materials
References Carson MA, Bovis MJ (1989) Landslides. In: Fulton RJ (ed) Geology of Canada, 1, Quaternary Geology of Canada and Greenland. GSC, p 587 Poschmann AS, Klassen KE, Klugman MA, Goodings D (1983) Slope stability study of the South Nation River and Portions of the Ottawa River. Ontario Geological Survey Miscellaneous Paper 112
Select Bibliography Aylsworth JM, Lawrence DE (2003) Earthquake-induced landsliding east of Ottawa. A contribution to the Ottawa Valley Landslide Project. 3rd Canadian Conference on Geotechnique and Natural Hazards, Edmonton, Alberta, pp 57–64 Baum RL, Savage WZ, Wasowski J (2003) Mechanics of earth flows. USGS Brunsden D (1994) Mass movement types. In: Goudie A, Atkinson BW, Gregory KJ, Simmons IG, Stoddart DR, Sugden D (eds) Encyclopedic dictionary of physical geography, 2nd edn. Blackwell Reference, Oxford, p 322 Cruden DM, Varnes DJ (1996) Landslide types and processes. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, pp 64–66 Evans SG (2001) Landslides. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:57–58 Legget RF, Karrow PF (1983) Handbook of geology in civil engineering. McGraw-Hill, New York, pp 39–8–39–10 Ohlmacher GC (2007) Plan curvature and landslide probability in regions dominated by earth flows and earth slides. Engineering Geology 91(2–4):117–134 Soeters R, Cornelis J, van Westen CJ (1996) Slope instability recognition, analysis and zonation. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation.Transportation Research Board, National Research Council, Washington, D.C., Special Rep. 247, pp 144, 145, 150
In both cases the flows are typically triggered by heavy rainfall or shaking response in seismically moderate to major risk zones. Such flows have been known to be triggered by heavy rumbling traffic. With increased water content earth flows commonly grade into Mf3 debris-mud flows.
Geohazard Relations
Fig. Mf2-1.
Any part of a flow mass that remains in a rupture surface is susceptible to further movement following another heavy rainfall. A valley fill deposit may be a wet zone into which anything can sink. Many flows are too small to be detected in standard airphoto 1: 15 000–1: 40 000 scales.
Source. Eisbacher GH (1979) First-order regionalization of landslide characteristics in the Canadian Cordillera. Geological Association of Canada, Geoscience Canada 6(2):71, fig 2 Comments. This block diagram shows the translational movement of fluid mud and the residual bowl of a typical earth flow at a bluff site in Bc3 glaciomarine or L1 glaciolacustrine sediments.
Mf2 · Earth Flows
Fig. Mf2-2. Location. Geographic. 122°30' W, 52°57' N, eastern British Columbia Source. Brooks GR (ed) (2001) A synthesis of geological hazards in Canada. GSC Bull 548:59, fig 23 Comments. Air view of an earthflow that developed from disintegrated retrogressive slide blocks and slump scarps visible at the top of the photo. The failures occured in ±100 m of L1 glaciolacustrine sediments in the Fraser River Basin of the Interior Plateau. Surface movements as high as 271 m yr–1 have been measured on the flow. Trees in the lower left provide a scale.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mf2-3. Location. Geographic. 71°13' W, 48°28' N, Lac St. Jean lowland, Quebec, Canada Geologic. Glaciomarine sea in regional graben of eastern Shield Source. Unattributed
Comments. A view towards the headscarp of the flow bowl produced by the St. Jean Vianney earth flow in the Laflamme Sea sediments of Figs. Mf2-4 and Mf2-5 near Lac St. Jean. Much of the spoil has flowed out of the flow bowl and down the des Vases stream channel.
Fig. Mf2-4.
▼
1012
Location. Geographic. 71°13' W, 48°28' N, Saguenay, Québec Geographic. Laflamme Bc3 glaciomarine plain in regional graben of the eastern Shield Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 30 000 Acquisition date. May 1962 Source. Courtesy of Natural Resources Canada, NAPL A 17479, 19, 20, 21 Comments. A stereomodel covers an area at St. Jean Vianney in the Lac St. Jean region. The small black delineated area in the center marked Mf2 1971 is the flow area of Fig. Mf2-5. The red delineation defines the extent of a much greater earth flow circa 335 bp within which the comparatively small 1971 event is located. This flow occurred at a time when the area was practically uninhabited. The volume of material displaced by this event is estimated at 207 million m3, that is 30 times greater than 1971.
Mf2 · Earth Flows
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Division 4 · Surficial Deposits
Fig. Mf2-5. (Caption on p. 1016)
Group M · Mass Movement Materials
Mf2 · Earth Flows
Fig. Mf2-6. (Caption on p. 1016)
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Division 4 · Surficial Deposits
Location. Geographic. 71°13' W, 48°28' N, Saguenay, Québec Geologic. Laflamme Bc3 glaciomarine plain in anorthosite massif of Interior Magmatic Belt of Grenville Orogen of Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 38 000 Acquisition date. 20 September 1972 Source. Courtesy of Natural Resources Canada, NAPL 23075-30, 31 Comments. The bright triangular area indicated by an arrow in the stereo model is the scar of a retrogressive flow slide that occurred on 4 May 1971 at St. Jean Vianney in the Lac St. Jean region. These airphotos were acquired 17 months later. The rapid failure, followed a period of heavy rains, caused the loss of 31 lives and destroyed 40 single family homes. The 268 000 m2 slide area is located in the crater of a much larger (20 km2) slide of Fig. Mf2-4 that occurred 335 bp. The slide material consists essentially of debris of the ancient slide, marine clay, with pockets of overlying deltaic sands. Pore pressures within the sands were a probable cause of the failure, and the sliding material was subjected to complete liquefaction. An average depth of 22.5 m to the failure plane yields the volume of material involved at nearly 9 million cubic yards, of which 1.5 million cubic yards remain in the crater bowl. Figure Mf2-3 is a ground view of the headscarp of this flow slide. See the extent of the Laflamme Sea in Fig. Bc3-10.
Fig. Mf2-6.
▼
▼
Fig. Mf2-5.
Group M · Mass Movement Materials
Location. Geographic. 74°57' W, 45°31' N, eastern Ontario Geologic. Bc3 glaciomarine Champlain Sea Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 40 000 Acquisition date. 18 May 1964 Source. Courtesy of Natural Resources Canada, NAPL A 18360, 147, 148, 149 Comments. This stereomodel at Plantagenet in the South Nation River Valley shows multiple paleo earth flows that retrogressed 1.5 km into terraces and ran out up to 2 km across the floor of paleochannels of the Ottawa River that cut 20–30 m into Bc3 glaciomarine sediments. The terraces are capped by 2–10 m of Fw3 deltaic sand. Little spoil is left in the failure bowl because the clay flows as a viscous mud. The apron spreads of flow debris (now crossed by a rail line) are distinguishable by an irregular surface relief pattern and small wet depressions. Here, modern agricultural practices have slightly muted the surface relief on the aprons. The rougher-surfaced failure bowls remain in forest. Some current markings in the clays are visible on either side of the river. Area Bw4.1 is a series of raised beaches and channel point bars with local sand and gravel pits. Figure Bc3-9 is a stereo triplet of natural colour photos of this area which is 18 air km north-northeast of the 1971 retrogressive flow slide of Fig. Mf1-6. Based on radiocarbon dating of buried wood, these particular landslides are thought to have been triggered by a magnitude 6.5 to 7 earthquake circa 4 550 bp, which was 3 000 years after the Ottawa River had abandoned the channel (Aylsworth et al. 2003). The Ottawa-St. Lawrence Valley lies along the ancient rifted edge of the North American continent. Most of the large earthquakes in southern Canada are associated with this rift structure.
Mf2.1 · Slow Earth Flows
Mf2.1 Slow Earth Flows
Use of DTMs to locate slopes >15° in Mf2.1 areas would be one method to avoid the hazard.
Characterization
Reference
Slow Earth Flows are elongate, or tongue-shaped masses with dish-shaped scars and bulging toes, in valley incisions or on open slopes of 10° to 35°, in fine residual or colluvial soils containing a significant amount of entrained water. The flows “move episodically or by sustained, relatively steady movement, primarily by sliding on a basal shear surface, accompanied by internal deformation” (Baum et al 2003). They range in size from bodies a few meters wide and less than 1 m deep to bodies more than 6 km long, several hundred meters wide and more than 10 m deep. Many flows come to rest part way down apparently uniform slopes. Waltham (2002) describes progressive failure: “Clay soil in slopes too steep or too high is locally overstressed; deforms and loses strength, passes load to adjacent soil; shear zones grow and coalesce; overall strength declines to ultimate failure of slope”.
Baum RL, Savage WZ, Wasowski (2003) Mechanics of earth flows. USGS Waltham T (2002) Foundations of engineering geology, 2nd edn. Spon Press, London, p 68
Geohazard Relations Moisture content changes in earth flow deposits make them poor foundations for any permanent structures. The sustained or repeated movement of ground beneath transportation structures crossing the toe of slow earth flows present recurring maintenance problems.
Select Bibliography Bovis MJ (1985) Earthflows in the Interior Plateau, southwest British Columbia. Canadian Geotechnical Journal 22:313–334 Cruden DM, Varnes DJ (1996) Landslide types and processes. In: Turner AK, Schuster RL (eds) Landslides: Investigation and mitigation. Transportation Research Board, National Research Council, Washington, D.C., Special Report 247, pp 64–65 Evans SG (2001) A synthesis of geological hazards in Canada. GSC Bull 548:57–58 Keefer DK, Johnson AM (1983) Earth flows: Morphology, mobilization and movement. USGS Professional Paper 1264 van Asch TWJ (2005) Modelling the hysteresis in the velocity pattern of slow-moving earth flows: The role of excess pore pressure. Earth Surface Processes and Landforms 30(4):403–411 Zaruba Q, Mencl V (1969) Landslides and their control. Elsevier, New York, pp 39–42
Fig. Mf2.1-1. ▼ Source. Keefer DK, Johnson AM (1983) Earth flows: Morphology, mobilization and movement. USGS PP 1264, fig 4 Comments. The figure is an idealized model of an earth flow showing surface and subsurface features.
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Mf2.1
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Division 4 · Surficial Deposits
Fig. Mf2.1-2. Location. Geographic. North central Colorado, USA Geologic. Gf4 glacial till in Rocky Mountain intermontane basin Source. Transportation Research Board (1996) Landslides: Investigation and mitigation. National Research Council,
Group M · Mass Movement Materials
Washington, D.C., Special Report 247, fig 2-6, p 18. Reproduced with permission Comments. A photo shows an earth flow in 1985 that passed through the base of a railway embankment at Granby 75 km northwest of Denver derailing a passenger train. The flow moved another 70 m as an Mf3 debris flow and partially dammed the Fraser River in the foreground.
Mf2.1 · Slow Earth Flows
Fig. Mf2.1-3. Location. Geographic. 121°25' W, 50°20' N, southern British Columbia Source. Brooks GR (ed) (2001) A synthesis of geological hazards in Canada. GSC Bull 548, p 57, fig 21 Comments. Air view of a large volume, slow-moving (3 m yr–1 for the period 1951 to 1972) earthflow on the Thompson River in the ThompsonFraser Valley Corridor in the Interior Plateau. It is 5.3 km long and drops 710 m in elevation. It is 670 m wide at its toe and about 150 m wide in its middle sections. The flow has developed in poorly lithified Upper Cretaceous shale sandstone and coal. Well marked lateral shear deposits on the flow boundaries indicate a progressive reduction in the size of the flow over time. Flow deposit on one side has overridden tephra indicating that most of the flow developed after 6 600 bp. The photograph taken in 2000 shows that the TransCanada Highway and the Canadian Pacific Railway track cross the toe of the landslide. Both roadways have had to be realigned repeatedly since their construction, 1884 for the railway and 1957 for the highway. The Trans-Canada Highway, relocated again in 1961, has undergone little movement since because most of the failure plane was removed during construction. Note the small Ms2 debris slide at the base of the mass by the water’s edge.
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Division 4 · Surficial Deposits
Fig. Mf2.1-4. Vertical Airphoto/Image. Type. b/w pan airphoto Scale. Indicated Acquisition date. Not given Source. Evans SG (2001) A synthesis of geological hazards in Canada. GSC Bull 548, p 58, fig 22b
Group M · Mass Movement Materials
Comments. The photo shows an old, slow (45 cm yr–1), earth flow in south-central British Columbia. The flow is derived from Cretaceous sediments and incorporated glacial till (Gf4) and Mc1 colluvium (weathered bedrock) in its movement. The deposit below the bottleneck spread out in fan shape on the valley floor.
Mf3 · Debris Mud Flows
Mf3 Debris-Mud Flows Characterization Debris and mud flows are Ms2 debris slides and Mf2 earth flows that have been modified by increased water content. The hyphenated name debris-mud flow reflects the fact that “in many cases it is not easy to be specific about the mode of movement (of these flows). In addition, one movement mode often changes into another.” (Gerrard 1990). The mass consists of cobbles and boulders embedded in a matrix of fine material, with a quantity of water that forms a slurry and moves downslope very rapidly. Where coarse debris is absent the viscous mass becomes a mud flow. Debris-mud flows form elongated masses that commonly follow pre-existing drainage ways down steep mountain slopes covered with unconsolidated weathered rock and soil debris. Where they enter trunk valleys they frequently interstratify their deposits with the fluvial sediments of Fu1 fans (see). They have a high density and viscosity compared to stream flows and, because of their high viscosity, they do not flow as far down the fans as do water transported sediments. Debris-mud flow deposits are distinguished from fan sediments in the field by their unstratified structure and lack of sorting. The flows usually form during periods of intense rainfall or rapid snow melt. As is the case with Ms2 debris slides flow channels and deposits in vegetated areas quickly become less visible on airphotos due to the progressively masking effect of vegetation re-growth. These flows are comparable to A1 lahar flows in volcanic terrain.
Geohazard Relations Debris-mud flows are one of the most dangerous of mass movements. They occur suddenly, disrupt rail and highway lines, cover agricultural land and dam rivers in valleys. Ravines are dangerous conduits of failed debris; entrained logs become powerful tools of destruction. Culverts are often unable to convey flows, and distributaries continually shift their course. Activity recurs in inactive debris flows following intense downpours or rapid snowmelt. These meteorological events reactivate mobile debris accumulated in flow channels. In the Canadian Rocky Mountains older vegetated or forested deposits that have a fan stream entrenched along
the entire length of the deposit, and a truncation of the toe by the valley trunk stream are considered “safe sites … because debris flows and high water flows are naturally channellized (sic)”. (Jackson 1987).
References Gerrard AJ (1990) Mountain environments. The MIT Press Cambridge, Mass., p 85 Jackson LE Jr (1987) Debris flow hazard in the Canadian Rocky Mountains. GSC Paper 86–11, p 16
Select Bibliography Campbell RH, Bernknopf RL (1997) Debris-flow hazard map units from gridded probabilities. In: Chen-lung C (ed) First international conference on debris-flow hazards mitigation; mechanics, prediction and assessment. American Society of Civil Engineers, pp 165–175 Coates DR (1990) The relation of subsurface water to downslope movement and failure. In: Higgins CG, Coates DR (eds) Groundwater geomorphology. Geological Society of America Special Paper 252 Corominas J, Remondo J, Farias P, Estevao M, Zézere J, Diaz de Teran J, Dikau R, Schrott L, Moya J, Gonzales A (1996) Debris flow. In: Dikau R, Brunsden D, Schrott L, Ibsen ML (eds) Landslide recognition. John Wiley & Sons, Ltd., Chichester, pp 161–180 Costa JE (1984) Physical geomorphology of debris flows. In: Costa JE, Fleisher PJ (eds) Developments and applications of geomorphology. Springer-Verlag Costa JE, Wieczorek GF (eds) (1987) Debris flows and avalanches: Process, recognition and mitigation, reviews. GSA, Engineering Geology VII Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 15–19 Evans SG (2001) Landslides. In: Brooks GR (ed) A synthesis of geological hazards in Canada. GSC Bull 548:49–51 Jakob M (2005) A size classification for debris flows. Engineering Geology 79:151–161 Jakob M, Hungr O (2005) Debris-flow hazards and related phenomena. Springer-Verlag Jibson RB (1989) Debris flows in southern Puerto Rico. GSA Special Paper 236, pp 29–55 Kienholz H (1977) Kombinierte geomorphologische Gefahrenkarte 1 : 10 000 von Grindelwald. Catena 3:265–94 Kniveton DR, De Graff PJ, Granicas K, Hardy RJ (2000) The development of a remote sensing based technique to predict debris flow triggering conditions in the French Alps. International Journal of Remote Sensing 21(3):419–434 Phien-Wej N, Nutalaya P, Aung Z, Zhibin T (1993) Catastrophic landslides and debris flows in Thailand. Bulletin of Engineering Geology and the Environment 48(1):93–100 Rogers CT (1996) Geo-data system for landslide hazard assessment. In: Housner GW, Chung RM (eds) Natural disaster reduction. Proceedings of ASCE Conference, Washinton, Dec. 3–5, pp 70–71 Schrott L, Buechel S, Gaydos L (1996) Soil flow (mudflow). In: Dikau R, Brunsden D, Schrott L, Ibsen ML (eds) Landslide recognition. John Wiley & Sons, Ltd., Chichester, p 181–187
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Mf3
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mf3-1. Source. Corominas, et al. (1996) Landslide recognition. Report no 1 of the European Commission Environment Programme. Contract No. EV5V CT94-0454, Identification, Movement and Causes, Richard Dikau et al. (eds) © John Wiley & Sons, Ltd , p 163, fig 7.3 2. Reproduced with permission
Comments. An interpretive block diagram to show the morphological features of a debris-mud flow: A: scarp; B and F: surface of rupture; C: channel of erosion; D: depositional levee from previous debris flow activity; E: deposit.
Fig. Mf3-2.
▼
Mf3 · Debris Mud Flows
Source. Jibson RW (1989) Debris flows in southern Puerto Rico. In: Schultz P, Jibson RW (eds) Landslide processes of the eastern United States and Puerto Rico. Geological Society of America Special Paper 236, fig 27, pp 29-55 Comments. This photo taken in the same area as Fig. Mf3-3 exposes three successively older debris flow deposits in a gully. Distinctive differences in the texture, induration and degree of weathering suggest debris flow recurrence intervals of decades to centuries.
Fig. Mf3-3. Source. Jibson RW (1989) Debris flows in southern Puerto Rico. In: Schultz P, Jibson RW (eds) Landslide processes of the eastern United States and Puerto Rico. Geological Society of America Special Paper 236, pp 29–55, fig 14 Comments. Photo of a debris flow that entrained a house in its path on steep Mc1 colluvium and residuum-covered slopes in Mid-Tertiary limestones. This is one of numerous failures that were triggered by pore-pressure buildup at the colluvium/bedrock contact from the heavy precipitation of a tropical storm in October 1985.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mf3-4. Source. LAR, 1975 Comments. Photo of a debris flow on a mountain access road in Mid Jurassic marly shales at Grindelwald in central Switzerland. The flow overtopped wire mesh cribbing which attempted to stabilize the debris of an earlier flow.
The new flow had blocked the roadway, which was cleared shortly before the photo was taken. See also in the same materials slumping in Fig. Ms3-3 and creep in Fig. Mc1-3.
Fig. Mf3-5. Source. LAR Comments. This photo was taken at the mouth of a kilometer long mountain torrent gorge. The torrent intermittently feeds Mf3 debris and Fu1 alluvial fan deposits at a 1 700 m elevation from a gorge head at 2 100 m. Google location is at 08°03'43'' E, 46°35'35'' N in the Swiss Bernese Alps. The torrent is a hanging valley tributary to the U valley of the Lower Grindelwald Glacier at 1 500 m. In June 2005 the 200 m face of the thick deposit collapsed along the full length of its 800 m front. Person is standing on large debris-flow clasts.
Mf3 · Debris Mud Flows
Fig. Mf3-6. Source. LAR, October 1974 Comments. The photo shows masonry check dams arranged in a stacked array of the Gradenbach Torrent at Putschall in the Möll Valley 6.5 km south of Heiligenblut in the Pennine Alps of south central Austria. Torrent reaches in areas of recurrent debris flow activity are most effectively stabilized by such structures. “The rising wings of check dams keep the flow of the torrent to the central axis of the channel and thus prevent lateral and vertical erosion of the unstable bed; aggradation behind check dams adds stability to the toes of embankment slopes on the upstream side; the rush of water is broken by the stepped channel profile, and the gently curved discharge sections of the check dams facilitate unobstructed passage for minor debris floods and flows without endangering the stability of dam abutments”. Eisbacher and Clague (1984) p 26.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mf3-7. Source. Diack G (1961) Vancouver Sun Comments. An air view of a debris flow 106 m wide and 30 m deep of January 1961 that cut both the Trans-Canada Highway and the Canadian Pacific Railway in probably glacial till valley fill sediments, in the Fraser River Canyon 195 km northeast of Vancouver, British Columbia. The flow probably originated in Mc1 colluvium (weathered bedrock) in the valley slopes. It was one of seven such road cuts that occurred in southern B.C. caused by torrential downpours with added volumes of melting snow produced by southwesterly warm Chinook (föhn type) winds.
Fig. Mf3-8.
▼
1026
Location. Geographic. 107°17' W, 37°59' N, southwest Colorado, USA Geologic. Tertiary volcanic dome Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1:35 000 (approx.) Acquisition date. 27 September 1951 Source. Miller VC (1961) Photogeology. McGraw-Hill Book Co. Inc., p 129, fig 9-13 Comments. The stereomodel shows the inactive toe of Slumgullion debris/mudflow cum A1 lahar in the northwest part of the Miocene volcanic San Juan Mountains. The flow is 6 km long and descends 1 900 m, from 3 650 m to 2 750 m from the edge of a basaltic plateau. It is a compound structure, the original flow dates from 700 years ago. 300 years ago an Ms2 debris slide overrode the upper two thirds of the mass. This slide is active, moving at a rate of about 6 m a year. The flow has been the object of detailed investigations and monitoring since 1990; it is now designated as a National Natural Landmark. The flow dammed the Lake Fork of the Gunnison River to form Lake San Cristobal. C, D is bedding of lavas, E are Fu1 alluvial fans, and F is the narrow valley cut by the stream which drains the lake.
Mf3 · Debris Mud Flows
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Division 4 · Surficial Deposits
Fig. Mf3-9. Location. Geographic. 68°03' W, 16°32' S, western Bolivia Geologic. Cordillera Oriental of the central Andes
Group M · Mass Movement Materials
Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 50 000 Acquisition date. 28 November 1956
Mf3 · Debris Mud Flows
Source. Cordova EV (1992) La Fotografia Aerea y su Aplicacion a Estudios Geologicos y Geomorfologicos – Tomo II. Univ. Mayor de San Andres, La Paz, Bolivia, modelo estereoscopico 55 Comments. The stereomodel shows two stabilized debris flows in the valleys of the city of La Paz.
Satellite imagery now shows both deposits to have been built upon and completely urbanized. Urbanization also now completely occupies the beds of the Fv1 braided alluvial streams.
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Division 4 · Surficial Deposits
Fig. Mf3-10. Location. Geographic. Southern Brazil Geologic. Granitic rocks of Brazilian Shield Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 20 000 Acquisition date. 21 January 1953
Group M · Mass Movement Materials
Source. Journal Photo Interprétation, Editions ESKA, Paris, 68-3, 4 Comments. A stereomodel on the east flank of the Serra do Mar Mountains south of Sao Paulo near the coast between Paranagua and Sao José shows a debris flow in a Mc1 deeply weathered zone of granitic rocks in a tropical climate (Np3 descriptor). The dense forest canopy mimics the local topography.
Mf3 · Debris Mud Flows
▼
Fig. Mf3-11.
Location. Geographic. 130°32' W, 57°03' N, northern British Columbia Geologic. Stikinia Superterrane of Intermontane Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. Not given Source. Base Mapping and Geomatic Services Branch, Ministry of Sustainable Resources, Government of British Columbia, Canada. BC 5160-024, 025 Comments. The stereomodel shows two 1 km broad deposits of debris from slopes of Triassic andesite that have flowed into the south side of More Creek Valley (elev. ±600 m). The western flow is recent, poorly vegetated, and has partly displaced and blocked the stream channel. The adjacent flow is older, forested with regional subalpine conifers, but with a fresh gully. The source catchments at about 1 800 m are delineated. A smaller, morphologically comparative, Fu1 alluvial fan is at the mouth of a tributary stream east of the flows. The Gf areas are deltaic glaciofluvial deposits from icefield sources in the upper reaches of More Creek. This figure is just east of Fig. Fv1.1-5, and 15 km east of Fig. Ms2-3. ▼
Fig. Mf3-12.
Location. Geographic. 127°53' W, 65°07' N, Northwest Territories Geologic. Mid Cretaceous thrusted sediments of Cordilleran Craton Foreland Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 18 June 1950 Source. Courtesy of Natural Resources Canada, NAPL A 12599-281, 282 Comments. The stereomodel in Loretta Canyon of the Imperial River shows fresh (bright) debris flow deposits on the surfaces of a group of Fu1 alluvial fans. Debris flows are commonly deposited on fans and the latter can include a high proportion of interstartified debris flow materials. Fresh debris flows on fans generally have a surface relief of only a few centimeters to half a meter above the surrounding fan, so are not readily detectable at smaller photo scales. They are then concentrated on the slightly steeper gradient of the headward slopes of the fan cones. Flow source basins have been partly delineated in the model. The bare and forested covers on the flows are unchanged after more than half a century.
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Division 4 · Surficial Deposits
Fig. Mf3-11. (Caption on p. 1031)
Group M · Mass Movement Materials
Mf3 · Debris Mud Flows
Fig. Mf3-12. (Caption on p. 1031)
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Mf3 · Debris Mud Flows ▼
Fig. Mf3-13. Location. Geographic. 72°07' W, 18°31' N, southern Haïti Geologic. Greater Antilles Deformed Belt of Caribbean Plate Vertical Airphoto/Image. Type. b/w pan, stereo triplet Scale. 1: 44 000 Acquisition date. 1978 Source. IGN – Photothèque Nationale, France Comments. Three debris flows and their source basins are delineated in this stereomodel of the plaine du Cul de Sac east of Port-au-Prince. They are located on the south slopes of a unit Variant 17.1 graben-like block-faulted depression. A group of older Fu1 and Fu2 alluvial fans are also delineated at the foot of the slopes on the margin of the plain. Morphological distinctions between these deposits are evident between the relatively rough surfaces and steep slopes of the unstratified debris flows and the smoother low slopes of the bedded alluvial fans. An Ms1.1 rock slide occurs on the same regional slope. The Fu2 area, densely cultivated due to favourable groundwater conditions, is a macro scale alluvial fan occasionally termed a piedmont apron.
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Mf4
Division 4 · Surficial Deposits
Mf4 Mountain Valley Natural Dams Characterization Lakes dammed by landslides, late neoglacial moraines and glaciers in mountain regions, drain suddenly triggered by tectonic or climatic forces to produce floods that are orders of magnitude larger than normal streamflows. The floods may transform into Mf3 debris flows as they travel down steep valleys. Variants are based on the most unstable materials that form the dams which can be polygenetic. Overtopping is the most common cause of failure.
Geohazard Relations Natural dams may cause upstream flooding in a valley as the lake rises. The large discharges and long travel distances of outburst floods and debris flows cause widespread destruction and loss of life in downvalley settlements and developments. Global warming is increasing the frequency and hazardous effects of these types of failures in the alpine areas of North America, the Himalayas and the Andes.
Select Bibliography Clague JJ, Evans SG (1994) Formation and failure of natural dams in the Canadian Cordillera. GSC Bull 464 Costa JE, Schuster RL (1988) The formation and failure of natural dams. GSA Bull 100:1054–1068 Fort M (2006) Ephemeral natural dams in the Nepal Himalayas: Types, geomorphic impacts and risk induced. Geophysical Research Abstracts, vol 8, no 06904. Huber UM, Bugmann HK, Reasoner MA (2005) Global change and mountain regions: An overview of current knowledge. Springer-Verlag Kattelmann R (2003) Glacial lake outburst floods in the Nepal Himalaya: A manageable hazard? Natural Hazards 28(1):145–154
Mf4.1
Mf4.1 Landslide Dams Characterization Landslide dams form generally in two geomorphic settings: steep narrow mountain valleys broad open valleys and lowlands where rivers have incised in marine or lacustrine sediments A lake is formed by the damming of a valley by deposits of geounits Ms1, rock slides; Mv2 rock avalanches; Ms3
Group M · Mass Movement Materials
rock slumps; Mf3 debris-mud flows, and Mf1 rotational slides in unconsolidated sediments. The common processes causing these slope failures are excessive precipitation – rainfall and snowmelt, and earthquakes. The dams fail by overtopping and breaching.
Geohazard Relations Dams along small streams of small watersheds in mountainous terrain are relatively stable. Those blocking larger rivers can fail with catastrophic secondary effects. Dams impounding rivers upstream in lowlands filled with fine Quaternary sediments will be overtopped within a few days. Subsequent incision of the dam debris further reduces the level of impounded waters. Dams consisting of blocks of competent bedrock (e.g., from Ms1 slides, Mv2 avalanches, and Ms3 slumps) tend to be stable “because any overflowing water is incapable of eroding the coarse materials and because the dam slopes are unlikely to fail. In any case, these latter dams are so porous and permeable that there commonly is little or no overflow.” (Clague and Evans 1994). Rafted blocks of dam material can bury the valley bottom downstream, and high water turbidity pollute water supplies to farms and communities downstream for several days after river flow is restored.
Reference Clague JJ, Evans SG (1994) Formation and failure of natural dams in the Canadian Cordillera. GSC Bull 464:4–13
Select Bibliography Casagli N, Ermini L (1999) Geomorphic analysis of landslide dams in the Northern Appennine. Transactions Japanese Geomorphological Union 20(3):219–249 Costa JE, Schuster RL (1988) The formation and failure of natural dams. GSA Bull 100:1055–1060 Evans SG (1986) Landslide damming in the Cordillera of western Canada. Landslide dams; processes, risk, and mitigation. ASCE, Geotechnical Special Publication no 3, pp 111–130 King J, Loveday I, Schuster Rl (1989) The 1985 Bairaman landslide dam and resulting debris flow, Papua New Guinea. Quarterly Journal of Engineering Geology and Hydrogeology 22(4): 157–270 Korop O, Tweed FS (2007) Ice, moraine and landslide dams in mountainous terrain. Quaternary Science Reviews 26:3406–3422 Schuster RL, Costa JE (1986) A perspective on landslide dams. Landslide dams; processes, risk, and mitigation. ASCE, Geotechnical Special Publication no 3, pp 1–20
Mf4.1 · Landslide Dams
Location. Geographic. 122° W, 49°46' N (approx.), southern British Columbia Source. Courtesy of Natural Resources Canada, GSC 204047C Comments. The air perspective view shows a landslide dam formed by Mv2 rock avalanche debris in the vicinity of Mt. Mason in the southern Coast Mountains. The debris fill down-valley is spillout from the avalanche deposit; it is unrelated to the valley slopes. On 12 May 2008 a 7.9 Richter earthquake occurred in the Kunlun Mountains near the thrust-faulted western edge of the Sichuan basin in southern China. the event caused 34 landslide dams along faults in the mountains. Most collapsed by overtopping. These and thousands of associated other slope failures resulted in the deaths of 69 000 people, injury to 370 000 and left 5 000 000 homeless.
Fig. Mf4.1-2.
▼
Fig. Mf4.1-1.
Location. Geographic. 78°45' E, 31°50' N (approx.), Zaskar Mountains, southwest Tibet Geologic. Himalaya tectogenic belt Vertical Airphoto/Image. Type. ASTER, 15 m resolution Acquisition date. 01 October 2003/15 July 2004 Source. NASA – ASTER instrument team Comments. These comparative images acquired nine and a half months apart show a lake created by a landslide dam on the Pareechu River in Tibet, a tributary of the Sutlej River in India. The height of the dam is 35 m, the created lake is 6 000 m long by 1 500 m wide and the rate of rise in the water level is 0.5 m per day. Authorities in both countries had evacuated inhabitants from downstream villages as a precautionary measure.
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Division 4 · Surficial Deposits
Fig. Mf4.1-2. (Caption on p. 1037)
Group M · Mass Movement Materials
Mf4.1 · Landslide Dams
Fig. Mf4.1-3. Location. Geographic. 130°58' W, 61°24' N, southern Yukon Territory Vertical Airphoto/Image. Type. b/w pan airphoto Scale. 1: 20 000 Acquisition date. Not given
Source. Jackson LE (1994) Terrain inventory and Quaternary history of the Pelly River Area, Yukon Territory. GSC Memoir 437, p 37, fig 37 Comments. The stereomodel pictures a landslide of Upper Triassic S1 conglomeratic rocks damming a lake in the Campbell Range of the Pelly Mountains.
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Division 4 · Surficial Deposits
Fig. Mf4.1-4. (Caption on p.1042)
Group M · Mass Movement Materials
Mf4.1 · Landslide Dams
Fig. Mf4.1-5. (Caption on p. 1042)
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Division 4 · Surficial Deposits ▼
Fig. Mf4.1-4. Location. Geographic. 127°15' W, 62°25' N, Northwest Territories Geologic. Eastern Omineca Cordilleran Belt, Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 60 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 18044-51, 52 Comments. Multiple dam deposits are delineated in this stereomodel of Avalanche Lake in the Devonian miogeoclinal (a prograding wedge of shallow-water sediment at the continental margin) Backbone Ranges of the Mackenzie Mountains. They resulted from Ms1 rock slides along bedding planes of south-dipping (30°) dolomite delineated on the slopes surrounding the lake. The main failure occurred where the cliff collapsed on the north side of the valley and surged up the south wall. See also Fig. Mv2-3.
▼
Fig. Mf4.1-5.
Location. Geographic. 133°40' W, 59°06' N, northwest British Columbia Geologic. Cache Creek Terrane of the Intermontane Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 70 000 Acquisition date. Not given Source. Courtesy of Natural Resources Canada, NAPL A 25825-23, 24 Comments. A stereomodel in the Tagish Highland of the Yukon Plateau shows 12 km long Sloko Lake elevation 900 m and its outlet stream that carry the meltwaters of the Llewellyn Glacier and icefield to the Taku River. The landslide dam, which is 2 100 m wide, evidently consists of blocks of Eocene acidic and basic volcanic rocks and could be considered a large A1 lahar flow. As the Variant description explains, such dams tend to be stable due to the inability of overflowing water to erode the coarse material as well as to its porosity and permeability. The slide mass is holding the lake up, but a limited drainage is sustained around the toe of the slide. Increased meltwater discharge that would accompany recession of the Llewellyn Glacier due to climate warming could result in a sudden overtopping of the dam. A probable Ms2 debris slide is delineated on the east side of the dam slide.
Group M · Mass Movement Materials
Mf4.2 · Moraine Dams
Mf4.2 Moraine Dams Characterization Since the end of the nineteenth century many Gl5 mountain valley glaciers have retreated significantly, leaving behind many lakes dammed by their end moraines. The drainage area of moraine damsites is much smaller than that of Mf4.1 landslide dam sites. Moraine dams are commonly overtopped and breached by waves generated by the impact of an icefall from a crevassed glacier or a rockfall from the steep slopes above the lake. Overtopping can also result from increased stream-flow during periods of rapid glacier retreat, intense rainfall or snowmelt. Moraines with ice cores or intersticial ice are becoming susceptible to failure during a period of climatic warming.
Select Bibliography Clague JJ, Evans SG (1994) Formation and failure of natural dams in the Canadian Cordillera. GSC Bull 464:13–18 Clague JJ, Evans SG (2000) A review of catastrophic drainage of moraine-dammed lakes in British Columbia. Quaternary Science Reviews 19(17) Costa JE, Schuster RL (1988) The formation and failure of natural dams. GSA Bull 100:1063–1065 Dahms SH (2006) Moraine dam failure and glacial lake outburst floods. Quaternary Geology ES 767, Emporia State University Häusler, Payer T, Leber D, Brauner M, Wangda D, Rank D, Papesch W (2007) Hazard potential of seepages causing moraine dam break in the Bhutan Himalayas. Geophysical Research Abstracts 9(04048) Ryder JM (1998) Geomorphological processes in the alpine areas of Canada. GSC Bull 524:34–35
Geohazard Relations Water floods or debris flows downvalley can be catastrophic. “Debris flows from breached morainal dams have caused enormous damage in the mountains of north-central Peru – on 13 March 1941, Laguna Kohup in the Cordillera Blanca drained rapidly to produce a debris flow which erased a major section of the town of Huaraz, killing several thousand people.” (Eisbacher and Clague 1984).
Reference Eisbacher GH, Clague J (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, p 46
Fig. Mf4.2-1. Source. Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84-16, p 44, fig 33 Comments. Diagram shows a moraine damming a depression filled with meltwater from a glacier.
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Division 4 · Surficial Deposits
Group M · Mass Movement Materials
Fig. Mf4.2-2. Source. Post A, LaChapelle ER (1971) Glacier ice. University of Toronto Press, p 29, photo 35. Reprinted by permission of the University of Washington Press Comments. Photo of a moraine dammed lake below the snout of the retreated Pattullo Glacier circa 1970 in the Mt. Pattullo Massif of the northern Coast Mountains of British Columbia, Canada at 129°45' W, 56°14' N.
Mf4.2 · Moraine Dams
Fig. Mf4.2-3. Source. Clague JJ, Evans SG (1994) Formation and failure of natural dams in the Canadian Cordillera. GSC Bulletin 464, cover illustration Comments. Air view to southwest of August 1984 shows a breached moraine dam at 124°24' W, 51°12' N in the Coast Mountains of southern British Columbia, Canada. The moraine had been deposited by Cumberland Glacier (in shadow) in the upper left of the photo. The glacier has since receded to a cliff above Nostetuko Lake. On 19 July 1983 part of the toe of the glacier broke away and cascaded into the lake. Waves generated by the impact of the icefall overtopped and rapidly incised the moraine to a depth of almost 40 m, suddenly releasing 6 × 106 m3 of water producing a destructive flood that swept 115 km downstream, stripping large tracts of forest and sediments from the valley floor. The eroded material is seen deposited as a large fan directly downstream from the dam.
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Group M · Mass Movement Materials
Mf4.2 · Moraine Dams ▼
Fig. Mf4.2-4.
Vertical Airphoto/Image. Type. Normal colour airphoto Scale. 1: 20 000 Acquisition date. 19 May 1977 Source. Die Schweiz und ihre Gletscher, 2nd edn. Schweizerische Verkehrszentrale, Zürich, Kümmerly+Frey, Bern, p 115, photo 15 Comments. The photo shows a moraine from one glacier damming the lake in the valley of a neighbouring glacier at 09°52' E, 46°24' N. The westerly moraine of Tschierva Glacier dams the lake below Roseg Glacier, 12 km up-valley from Pontresina, Graubünden, southeast Switzerland. An outlet stream from the lake has eroded a small breach at the north end of the blocking moraine. Subsequent satellite imaging monitored the status of the lake. Additional details visible in the photo are a geostructure Unit 18 geolineament which parallels the east side of Roseg Glacier; and a Zm2 rock glacier in a cirque on the rock ridge dividing the glaciers.
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Mf4.3
Division 4 · Surficial Deposits
Mf4.3 Glacier Dams Characterization
Group M · Mass Movement Materials
“In rugged terrain glacier outburst floods can transform into rapidly moving debris flows (Mf3) if loose morainal or colluvial debris adjacent to the stream channel is incorporated into the floodwater.” (Ryder 1998, p 32).
Gl5 glaciers impound water in ice-free valleys. Meltwaters flow along crevasses and cavities at the base of the glacier to form interconnected tunnels. The flows melt the ice and enlarge the tunnel system. The process continues until the weakened ice dam can no longer support the water behind it and collapses.
References
Geohazard Relations
Ageta Y, Iwata S, Yabuki H, Naito N, Sakai A, Narama C, Karma (2000) Expansion of glacier lakes in recent decades in the Bhutan Himalayas. Debris-Covered Glaciers. IAHS Publication, pp 165–175 Costa JE, Schuster RL (1988) The formation and failure of natural dams. GSA Bull 100:1060–1063 Eisbacher GH, Clague JJ (1984) Destructive mass movements in high mountains: Hazard and management. GSC Paper 84–16, pp 45–46 Huggel C, Kääb C, Haeberli W, Teysseire P, Paul F (2002) Satellite and aerial imagery for analysing high mountain lake hazards. Canadian Geotechnical Journal 39(2):316–330 Iturrizaga L (2005) New observations on present and prehistorical glacier-dammed lakes in the Shimshal Valley (Karakoram Mountains). Journal of Asian Earth Sciences 25(4):545–555 Liestol O (1956) Glacier-dammed lakes in Norway. Norsk Geografisk Tiddskrift 15:122–149 Quincy DJ, Richardson SD, Luckman A, Lucas RM, Reynolds JM, Hambrey MJ, Glasser NF (2007) Early recognition of glacial lake hazards in the Himalaya using remote sensing data sets. Global and Planatary Change 56(1–2):137–152
The greatest potential hazard exists “as glacier recession occurs in accordance with climate warming. Drainage will occur for the first time at lakes that have not previously drained, releasing catastrophic flood discharges down valleys” (Ryder 1998, p 32), e.g., lake G in Fig. Mf4.3-1 in a trunk valley. Additionally, as shown in Fig. Mf4.3-2, the impounded waters resulting from a glacier surge across a mountain valley could inundate upstream settlements and transportation corridors. Clague estimates that there have been about 30 000 deaths from glacier-related catastrophes in the last 150 years. Ice dams prone to catastrophic leakage are often referred to by the Icelandic term jokulhlaup.
Fig. Mf4.3-1. Source. Costa JE, Schuster RL (1988) The formation and failure of natural dams. Geological Society of America Bulletin vol 100, fig 9 Comments. Sketch map showing the geomorphic settings and classification of icedammed lakes. Lake G in the trunk valley is potentially the most hazardous for a downstream flood (to the right) by a failure of the tributary glacier.
Clague JJ, Evans SG (1994) Formation and failure of natural dams in the Canadian Cordillera. GSC Bull 464:18–28 Ryder JM (1998) Geomorphological processes in the alpine areas of Canada. GSC Bull 524:31–32
Select Bibliography
Mf4.3 · Glacier Dams
Fig. Mf4.3-2. Location. Geographic. 137°59' W, 60°17' N, southwest Yukon Territory Source. ClagueJJ, Evans SG (1994) GSC Bull. 464, p 24, fig 28 Comments. Map showing the extent of a lake that inundated valleys during the late Holocene up to 95 km upstream from a glacier advance across the valley in the St. Elias Mountains
If Lowell Glacier were to surge about 1 km, the lake would reform and might inundate the town of Haines Junction and sections of the Alaska Highway upstream. The inset frame locates the coverage of vertical airphoto 176 of the stereopair Fig. Mf4.3-5 of the tongue of Lowell Glacier.
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Division 4 · Surficial Deposits
Fig. Mf4.3-3. Location. Geographic. 74°15' W, 71°35' N, northeast Baffin Island, Nunavut Source. Courtesy of Natural Resources Canada, NAPL RR325, 3193, 14 September 1953 Comments. Air view to southeast of a 8 km long by 2 km broad unnamed Gl4 outlet glacier damming the upper end
Group M · Mass Movement Materials
of Drever Arm Fjord in Buchan Gulf at the upper right of the photo. Icebergs are calving both into the dammed arm and northward towards Baffin Bay on the left. The icefield at the top of the photo is at 1 100 m elevation, the icefield source of the glacier is at 1 265 m. The moraine combines that from a coalescing glacier 4 km upstream. A meltwater spillway is at the contact of the glacier toe with the rockslope. The glacier’s recession has since opened up half the width of Drever Arm.
Mf4.3 · Glacier Dams
Fig. Mf4.3-4.
Fig. Mf4.3-5.
▼
Location. Geographic. 133°50' W, 58°49' N, northern Coast Mountains, British Columbia Source. Post A, LaChapelle ER (1971) Glacier ice. University of Toronto Press, p 85, photo 103. Reprinted by permission of the University of Washington Press Comments. The air perspective photo is a view southwest of 4 km long Lake Tulsequah. The lake is in a tributary valley of the Tulsequah Glacier Valley and is dammed by a short lobe of that glacier. The lake is effectively dammed by glaciers at both ends, the other is behind the mountain shoulder in the center, at the south end of the lake.
Location. Geographic. 137°59' W, 60°17' N, southwest Yukon Geologic. Alexander Superterrane of the Insular Cordilleran Belt Vertical Airphoto/Image. Type. b/w pan, stereo pair Scale. 1: 40 000 Acquisition date. 14 June 1948 Source. Courtesy of Natural Resources Canada, NAPL A 11521-175, 176 Comments. This stereomodel shows the 6 km broad terminus of Gl5 Lowell Glacier in Ordovician carbonates of
the St. Elias Mountains on 14 June 1948 at the channels of the south-flowing (to bottom) Alsek River Valley. At the date of photography the glacier was in recession and there is a temporary lake (with a few bergs) partly held up by Gf3.2a glaciofluvial valley fill deposits through which the river runs. The glacier’s lateral moraines (see Gl5) are coded Gt4.1. If the lower moraine had reached the other side of the valley the site would have been a Mf4.2 moraine dam variant. The potential for upstream flooding in the Alsek Valley is described in Fig. Mf4.3-2. The St. Elias Mountains contain the largest non-polar icefield on Earth.
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Fig. Mf4.3-5. (Caption on p. 1051)
Group M · Mass Movement Materials
A Appendix Abbreviations and Acronyms
AAPG AAG AGFG ap ASCE ASTER ATM AVHRR BC BGRG BRGM b/w CAN CCRS CEOS CGS CIR CNES CNRS COSPAR CRREL CSPG CSIRO DEM EDC EIA EO EOSAT ERS esa ESPON
American Association of Petroleum Geologists Association of American Geographers American Geomorphology Field Group air photograph American Society of Civil Engineers Advanced Spaceborne Thermal Emission and Reflection Radiometer Advanced Thematic Mapper Advanced Very High Resolution Radiometer MAPS – BC, British Columbia British Geomorphological Research Group Bureau de Recherches Géologiques et Minières (France) black and white Canada Canada Center for Remote Sensing Committee on Earth Observation Satellites (esa) Canadian Geotechnical Society colour infrared Centre National d’Études Spatiales (France) Centre National de la Recherche Scientifique Committee on Space research (of ICSU) Cold Regions Research and Engineering Laboratory (U.S. Army) Canadian Society of Petroleum Geologists Commonwealth Scientific and Industrial Research Organization (Australia) Digital Elevation Model Eros Data Center Environmental impact assessment Earth Observation Earth Observation Satellite Company European Remote Sensing Satellite European Space Agency European Spatial Planning Observation Network
FAO
Food and Agriculture Organization of the United Nations fcc False colour composite FR France GIS Geographic Information System GSA Geological Society of America GSC Geological Survey of Canada GSFC Goddard Space Flight Center HIRIS High Resolution Imaging Spectrometer IAEG International Association of Engineering Geology IAHS International Association of Hydrological Sciences IAS International Association of Sedimentologists IBG Institute of British Geographers IGCP International Geological Correlation Programme IGN Institut Géographique National (France) IGS Institute of Geological Sciences IGU International Geographical Union IKONOS Earth observation satellite INQUA International Quaternary Assciation InSAR Interferometric Synthetic Aperture Radar ISPRS International society for Photogrammetry and Remote Sensing ISRM International Society for Rock Mechanics ISSS International Society of Soil Science ITC International Institute for Aerospace Survey and Earth Sciences JPL Jet Propulsion Laboratory LAR Lambert Alfred Rivard LFC Large Format Camera MDA Earth Sat MDA Federal Inc. mono monoscopic MSS Multispectral Scanner NAPL National Air Photo Library (Canada) NAS National Academy of Sciences NASA National Aeronautics and Space Administration (USA) NOAA National Oceanic and Atmospheric Administration (USA)
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Appendix · Abbreviations and Acronyms
NRC NTIS ORSTOM pan RADAR RBV RGS RMS SAR SCS SIR-A, B, C SLAR
National Research Council (Canada) National Technical Information Service (USA) Office de la Recherche Scientifique et Technique Outre-Mer (France) panchromatic Radio detection and ranging Return Beam Vidicon Camera System Royal Geographical Society Rock mass strength Synthetic aperture radar Soil Conservation Service (USA) Shuttle Imaging Radar Side-looking airborne Radar
SPOT TM TOMS TRB UNDP UNEP USAF USDA USGS VEI vert
Satellite Pour l’Observation de la Terre Thematic Mapper Total ozone mapping spectrometer Transportation Research Board, National Academy (of Sciences) (USA) United Nations Development Programme United Nations Environment Programme United States Air Force United States Department of Agriculture United States Geological Survey Volcano explosivity index vertical
