Department of the Interior U.S. Geological Survey Rock Falls in Yosemite Valley, California by Gerald F. Wieczorek1, James B. Sn
DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY ROCK FALLS IN YOSEMITE VALLEY, CALIFORNIA BY GERALD F. WIECZOREK1, JAMES B. SNYDER2, CHRISTOPHER S. ALGER3, AND KATHLEEN A. ISAACSON4 Open-File Report 92-387 This work was done with the cooperation and assistance of the National Park Service, Yosemite National Park, California. This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government 'USGS, Reston, VA 22092, 2NPS, Yosemite National Park, CA, 95389, 3McLaren/Hart, Alameda, CA 94501, 4Levine Fricke, Inc., Emeryville, CA 94608 Reston, Virginia December 31, 1992 CONTENTS Page Abstract ............................................... 1 Introduction .............................................. 1 Geologic History ........................................... 2 Methods of Investigation ..................................... 5 Inventory of historical slope movements ........................ 5 Location ............................................ 5 Time of occurrence .......:............................ 7 Size ............................................... 8 Triggering mechanisms ................................. 9 Types of slope movement ................................ 11 Debris flows ...................................... 11 Debris slides ...................................... 12 Rock slides ......................................
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