Rockfall triggering by cyclic thermal stressing of exfoliation fractures

Nature Geoscience
National Park Service
By:  and 

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Abstract

Exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cliff in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the efficacy of other, more typical rockfall triggers.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Rockfall triggering by cyclic thermal stressing of exfoliation fractures
Series title Nature Geoscience
DOI 10.1038/ngeo2686
Volume 9
Year Published 2016
Language English
Publisher Nature Publishing Group
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 7 p.
First page 395
Last page 400
Country United States
State California
Other Geospatial Yosemite National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N