Triggering mechanisms and depositional rates of postglacial slope-movement processes in the Yosemite Valley, California

• Published in: Geomorphology (Amsterdam, Netherlands) Vol. 15; no. 1; pp. 17 - 31
• Main Authors: Wieczorek, Gerald F., Jäger, Stefan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.1996; Elsevier
• Subjects: Bgi / Prodig; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geomorphology; Marine and continental quaternary; Natural hazards: prediction, damages, etc; Physical geography; Slopes; Surficial geology; United States; North America; California; United States of America; Sierra Nevada; slumping; Quaternary; debris flows; slopes; earthquakes; human activity; Yosemite National Park; meltwater; volume; upper Pleistocene; rockfalls; Sierra Nevada; annual average; slope angle; Holocene; postglacial environment; valleys; slope stability; storms; Human impact; Freeze-thaw cycle; Glaciation; Debris flow; Postglacial; Mass movement; Slope; Precipitation; Earthquake; Rockfall; Landslide; Slope dynamics; Rainstorm
• ISSN: 0169-555X; 1872-695X
• DOI: 10.1016/0169-555X(95)00112-I

We examined information collected from 395 reports of slope-movement events during about the past 150 years in Yosemite National Park, central Sierra Nevada, California, to identify the most prevalent types of slope movements and their triggering mechanisms. Rock slides and rock falls have been more numerous than debris slides, debris flows, and miscellaneous slumps. Rock falls have produced the largest cumulative volume of deposits. About half of slope movements had unreported or unrecognized triggering events. Earthquakes and rain storms individually accounted for the greatest cumulative volumes of deposits from recognized triggers of all types of historical slope movements; snowmelt, human activities and freeze-thaw conditions accounted for only a small proportion of the volumes from reported triggers. A comparison of the historical and postglacial average annual rates of deposition from slope-movement processes in a portion of the Yosemite Valley indicates that, during the period 1851–1992, slope-movement processes have been producing about half the average rate of deposits than during the past 15,000 years.