Rock falls in California's Sierra Nevada

Pursuing explanations for exfoliation and seemingly spontaneous fracture of rock

by Brian D. Collins, USGS Research Civil Engineer, Landslide Hazards Program

• Exfoliation is a process by which layers of rock erode from the surface of landscapes.
• In California's Sierra Nevada, exfoliation in steep granite cliffs is common, sometimes leading to potentially hazardous rock falls.
• New research sheds light on how, where and when rock falls may occur from exfoliation, and the effect daily heating cycles may have on exfoliation itself.
• Recent rock fall studies by the USGS and National Park Service provide sound basis for risk reduction actions in Yosemite National Park.