Surprising cause of Yosemite rockfalls discovered Mar 29, 2016 4:40 PM EDT
More than four million people are expected to visit Yosemite National Park this year, and along with the park's natural beauty, they could encounter danger from its majestic granite cliffs, which experience dozens of rockfalls each season. Last year, the National Park Service says at least 25,000 tons of rock came crashing down.
Rockfalls can be caused by rain or snow, seismic activity, or the effects of freezing. But others had no obvious cause.
and coauthor of the study, said in a press release.