Why Do Giant Rocks Suddenly Fall From Cliffs?

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"In Yosemite Valley, rockfalls can happen every four to five days, where boulders that can be larger than your average car or apartment building thunder down steep mountainsides." - Seeker

guy standing on cliff edge watching rockfall below

Screenshot from Seeker Video called "Why Do Giant Rocks Suddenly Fall From Cliffs?" featuring Brian Collins.

(Public domain.)

A video filmed in Yosemite National Park discussing rockfalls and what triggers them. Featuring USGS engineer Brian Collins and National Park geomorphologist Greg Stock.

View the video.