YOSEMITE NATIONAL PARK, Calif. – National parks bring a plethora of beauty for all to enjoy year-round, but not without the risk of rockfall at some popular landmarks.
Rockfalls are a constant threat to be monitored at popular locations such as Yosemite National Park in California.
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According to the National Park Service (NPS), more than 1,000 rockfalls have occurred in the park in the last 150 years. Rockfalls are a natural and dynamic geologic process involving the detachment and rapid downward movement of rock.
Due to the steep, glacier-carved cliffs of Yosemite Valley, the national park experiences dozens of rockfalls each year.
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“2025 was a quiet year for rockfalls in Yosemite, with 43 documented events with a cumulative volume of approximately 478 cubic meters (1,423 tons),” a statement from the NPS reads. “As is typical, most of the documented rockfalls in 2025 consisted of relatively small rocks that fell onto park roadways during winter storms.”
Fortunately, the biggest rockfall events occurred at night, when there were no hikers in the area.
El Capitan, Yosemite, California, USA, 2022. The gigantic granite formation of El Capitan, one of the most famous landmarks in the valley, Yosemite National Park, California, USA. Creator: Ethel Davies.
(EMD/Then and Now Images/Heritage Images / Getty Images)
What causes a rockfall?
A number of geological processes can trigger rockfall, including glaciation and weathering. Tectonic stresses and erosion can cause granite rock to fracture as well.
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Other factors, such as earthquakes, water, ice and vegetation growth, can cause unstable rocks to fall.
“Recent research suggests that daily temperature variations and extreme heat can also cause rock slabs to become unstable,” a statement from the NPS reads.
What to do in the event of a rockfall
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Experts at the National Park Service suggest the following safety tips:
- If you witness a rockfall from the valley floor, quickly move away from the cliff toward the center of the valley. If you are near the base of a cliff or talus slope when a rockfall occurs above, immediately seek shelter behind the largest nearby boulder. After the rocks have stopped falling, move quickly away from the cliff toward the center of the valley. Be aware that rockfalls are inherently unpredictable and may happen at any time. Pay attention to warning signs, stay off closed trails, and, if unsure, keep away from the cliffs.
- Inform park staff if you witness a rockfall. If you witness or hear a rockfall of any size, please report it by calling 209-379-1420 or reporting it to one of the park’s visitor centers. This information is useful for assessing rockfall hazards and adds to the growing knowledge base of rockfall activity in the park.
- Understand this dynamic natural process and remember that Yosemite is a wild place. Rockfall is the most powerful geologic agent acting today in Yosemite. The dramatic cliffs of Yosemite are constantly being shaped by this potent natural force.
YOSEMITE, CA – FEBRUARY 23: A traffic sign show that the ”Horsetail Falls” closed due to rockfall as snow blankets Yosemite National Park in California, United States on February 23, 2023 as winter storm alerted in California.
(Tayfun Coskun/Anadolu Agency / Getty Images)
When a rockfall event occurs, park scientists, in collaboration with the U.S. Geological Survey, will actively study rockfalls using new technologies, such as high-resolution digital photography, laser mapping of cliffs and exposure dating of boulders.
These tools allow officials to accurately map rockfall zones and study the source areas of rockfall.
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In recent years, the NPS has reduced the risk of rockfalls in Yosemite Valley by removing or re-purposing high-risk buildings in hazardous areas. These actions have reduced rockfall-related risks by 95%, according to the NPS.
