“Rockfalls happen about 60 to 70 times per year in Yosemite, but usually they have an obvious cause. A winter storm has blown through, or there was an earthquake. But some, like the Happy Isles incident, happen on beautiful, clear summer days for no apparent reason. Now a pair of scientists says they know what’s behind these rockfalls—it’s the warm, sunny weather itself.” –Smithsonian Magazine
There’s a wide range of reasons behind these terrifying and spectacular natural occurrences, so to heap the explanation for when, where and why they happen into a single pile is impossible. With that said, better understanding the conditions that exist that make for a higher probability could be helpful to stay safe while exploring the mountains.
“Rockfalls are a natural and dynamic geologic process involving the detachment and rapid downward movement of rock. Historical records indicate that more than 1,000 rockfalls have occurred in the park during the past 150 years. Massive piles of “talus” or rock debris at the base of Yosemite Valley’s cliffs are reminders of these dramatic events.”-NPS
While rockfalls are relatively common in a place like Yosemite, they might stay off your radar because of how seldom they result in death:
“We have a lot of rockfalls in Yosemite because the cliffs are so big and steep. We’ve gotten lucky because in 150 years, only about 15 people have died as a result of rockfalls.” -Yosemite Geologist Greg Stock
Here’s a short video about rockfalls, their study, and how to avoid them while in mountainous terrain. Stay safe and share this with friends that frequent places where rockfalls are a potential: