The Slumgullion Earth Flow: A Large-Scale Natural Laboratory U.S. GEOLOGICAL SURVEY BULLETIN 2130 AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications re­ leased prior to the current year are listed in the most recent annual "Price and Availability List." Publications that may be listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" may no longer be available. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. 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Eaton, Director For sale by U.S. Geological Survey, Information Services Box 25286, Federal Center Denver, CO 80225 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government Library of Congress Cataloging-in-Publication Data The Slumgullion earth flow : A large-scale natural laboratory / edited by D.J. Varnesand W.Z. Savage. p. cm. (U.S. Geological Survey bulletin ; 2130) Summaries of presentations at a meeting held in Golden, Colo., Jan. 26-27, 1994. Includes bibliographical references. Supt. of Docs, no.: I 19.2:2130 1. Earth flows Colorado Lake City Region. I. Varnes, David J. (David Joseph), 1919- . II. Savage, William Z. III. Series. QE75.B9 no. 2130 [QE599.U5] 557.3 s dc20 [551.3'07] 95-32788 CIP CONTENTS Introduction ByDJ. Varnes and W.Z. Savage....................................................................................................................I 1. Preliminary chronology of the Slumgullion landslide, Hinsdale County, Colorado By Richard F. Madole.....................................................................................................................................5 2. Kinematic studies of the Slumgullion landslide, Hinsdale County, Colorado By Rex L. Baum and Robert W Fleming.......................................................................................................9 3. Preliminary geologic map and alteration mineralogy of the main scarp of the Slumgullion landslide By Sharon F. Diehl and Robert L. Schuster..................................................................................................13 4. Retreat of the Slumgullion main scarp By Robert L. Schuster and William K. Smith.............................................................................................21 5. Radiocarbon age of a newly identified Slumgullion landslide deposit By Alan F. Chleborad ...................................................................................................................................29 6. Slumgullion landslide dam and its effects on the Lake Fork By Robert L. Schuster...................................................................................................................................35 7. Deformation and control surveys, Slumgullion landslide By David J. Varnes, William K. Smith, William Z. Savage, and Philip S. Powers......................................43 8. A digital photogrammetric method to measure horizontal surficial movements on the Slumgullion landslide, Hinsdale, County, Colorado By Philip S. Powers and Maria Chiarle........................................................................................................51 9. Photogrammetric determination of slope movements on the Slumgullion landslide fly William K. Smith ............................................................................................................... 10. Modeling deformation at the active toe of the Slumgullion landslide By William Z. Savage, David J. Varnes, William K. Smith, and Philip S. Powers......................................61 11. Geotechnical properties of selected materials from the Slumgullion landslide By Alan F. Chleborad, Sharon F. Diehl, and Susan H. Cannon ...................................................................67 12. Slumgullion landslide fault creep studies By William Z. Savage and Robert W. Fleming ............................................................................................73 ill IV CONTENTS 13. Detection of the base of Slumgullion landslide, Colorado, by seismic reflection and refraction methods 5y Robert A. Williams and Thomas L. Pratt................................................................................................77 14. Slidequakes and fault creep at the Slumgullion landslide: An analog to crustal tectonics By Joan S. Gomberg, Paul W. Bodin, William Z. Savage, and Michael E. Jackson....................................85 15. Measurement of local horizontal velocities on the Slumgullion landslide using the Global Positioning System By Michael E. Jackson, Paul W. Bodin, Willian Z. Savage, and Elizabeth M. Nel.....................................93 INTRODUCTION By DJ. Varnes and W.Z. Savage In 1990, the U.S. Geological Survey (USGS), with the slide movement and determining what information about assistance of scientists provided by a cooperative agreement flow processes within the slide can be obtained from the between the USGS and the Istituto di Ricerca per la Protezi- study of features at the ground surface. Chapters 3 and 4 con­ one Idrogeologica (IRPI) of the Italian National Research tain the results of field studies on the geology of the main Council, began a new study of the Slumgullion earth flow in scarp of the Slumgullion landslide and its retreat. As part of the San Juan Mountains near Lake City, Colo. This famous these studies, photogrammetric measurements are being landslide (figs. 1 and 2) has been described by numerous made to establish the rate of retreat of the main scarp of the investigators (Endlich, 1876; Howe, 1909; Atwood and slide. These studies are of interest, because the main scarp Mather, 1932; Burbank, 1947; Crandell and Varnes, 1960, provided material for the older, inactive slide and still pro­ 1961; Keefer and Johnson, 1983). It was chosen for a com­ vides material for the newer, active slide. Chapter 5 presents prehensive study of landslide processes because part of it the results of recent field investigations of a newly identified apparently has been moving continuously for the past 300 yr, Slumgullion landslide deposit. This deposit, which may be transporting material hundreds of meters and repeatedly cre­ the result of a "spill-over" of Slumgullion landslide material, ating and destroying surface features such as folds and faults. may be critical to understanding the slide's early history. Also, movement data have been collected periodically on the Chapter 6 pertains to the 700-yr-old natural dam formed by flow for more than 30 yr. the toe of the inactive slide. The continued stability of this The Slumgullion earth flow occurs in altered Tertiary dam, which created Lake San Cristobal, is of great impor­ volcanic rocks