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Rock-fall potential in the Yosemite Valley, California

January 1, 1999

We used two methods of estimating rock-fall potential in the Yosemite Valley, California based on (1) physical evidence of previous rock-fall travel, in which the potential extends to the base of the talus, and (2) theoretical potential energy considerations, in which the potential can extend beyond the base of the talus, herein referred to as the rock-fall shadow. Rock falls in the valley commonly range in size from individual boulders of less than 1 m3 to moderate-sized falls with volumes of about 100,000 m3. Larger rock falls exceeding 100,000 m3, referred to as rock avalanches, are considered to be much less likely to occur based on the relatively few prehistoric rock-fall avalanche deposits in the Yosemite Valley. Because the valley has steep walls and is relatively narrow, there are no areas that are absolutely safe from large rock avalanches. The map shows areas of rock-fall potential, but does not predict when or how frequently a rock fall will occur. Consequently, neither the hazard in terms of probability of a rock fall at any specific location, nor the risk to people or facilities to such events can be assessed from this map.

Publication Year 1999
Title Rock-fall potential in the Yosemite Valley, California
DOI 10.3133/ofr99578
Authors Gerald F. Wieczorek, Meghan M. Morrissey, Giulio Iovine, Jonathan Godt
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 99-578
Index ID ofr99578
Record Source USGS Publications Warehouse
USGS Organization Geologic Hazards Science Center