|Above, sheer granite wall of Yosemite National Park. Photo by Armand Vaquer.|
This is something that hikers and rock climbers should be aware of: heat triggers rockfalls.
According to The Mercury News:
When rocks get hot, they do what people do: shed a few layers.
And the hottest hours of the day — during the hottest months of the year — are prime time for unexplained rockfalls and cracking, according to a new study of the granite domes and cliffs in the Sierra Nevada, which finds that hikers, tourists and wildlife are at less risk of being flattened during cooler times from this mechanism.
“Cliffs move in and out, and detach,” said Menlo Park-based U.S. Geological Survey scientist Brian Collins, who uses instrumentation to measure restless rocks at Twain Harte reservoir and Yosemite National Park.
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