By Macy Jenkins

SACRAMENTO, Calif. (CBS13) – Yosemite National Park is now using high-resolution photography, laser-mapping of cliffs, and computer modeling to try to identify potential rock slides.

According to geologists, if one happens in a certain location, they like to keep an eye out for any others that may follow close by.

“Well the cause is nature,” said Mike Oskin, professor of geology at UC Davis. “Yosemite is a very deep and beautiful valley because it was carved by glaciers that have occupied it repeatedly. But without the ice to hold up those rocks, they come down. It’s just natural geologic process.”

ALSO READ: Climber: Latest Rockfall At Yosemite’s El Capitan ‘Massive’

Roughly 80 rockfalls happen every year in Yosemite Valley, but geologists estimate that even more go unreported. Oskin says rockfall happens when large debris becomes detached from the face of a rock. It’s debris that looks small from a distance, but in reality could be dozens of feet wide.

“We’re talking vehicle-sized boulders that can come off of these,” Oskin said.

This week, Yosemite Valley saw seven rockfalls on Wednesday and another Thursday afternoon — both on the Southeast face of El Capitan.

“It was in the same place, so it’s possible that the rocks were destabilized from the event that happened yesterday,” Oskin said.

Rocks can be dislodged by a myriad of factors, including water seeping between the rocks, erosion, earthquakes and vegetation growth.

The National Park Service has a map showing documented rockfalls in Yosemite Valley from 1857 to 2011.

“It certainly helps to appreciate how far they go into the valley,” Oskin said.

But with the entire mountain ridge lined with dots, it truly goes to show that rockfall can happen anywhere during any season.

Geologists say rock fall often happens at the end of the rainy season, yet the last two events happened this week, during the end of the dry season.

Click here to visit Yosemite’s rockfall website.


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