12/19/2025
These formations rock.🪨
Over millennia, glaciers, rivers, earthquakes, and even temperature swings have shaped Yosemite Valley, leaving massive monoliths of exposed rock in their wake. Can you name all five of these legendary rock formations? Find the answers (and some rockin’ facts) below:
🪨El Capitan
📍North Valley rim, opposite Bridalveil Fall
Soaring almost 3,000 feet above the valley floor, El Capitan is composed of varieties of granite– igneous rock formed from magma deep underground. As the molten rock cooled, different minerals crystallized within to give it that iconic ‘salt-and-pepper’ look.
🪨Three Brothers
📍North Valley Rim, east of El Capitan
Eagle Peak, Middle Brother, and Lower Brother’s steep peaks are formed from nearly parallel fractures in the granite that were broken off and pushed away by glaciers– colossal bulldozers of moving ice.
🪨Half Dome
📍Eastern Yosemite Valley
Half Dome began as magma that slowly hardened under high-pressure underground into granite. As this pluton rose to the surface and the overlying rock eroded away, tension cracks formed parallel to the surface, expanded, and peeled away in onion-like sheets to form a dome. This process is called exfoliation. As glaciers moved through the valley, they pushed against large vertical cracks on the dome’s sides, breaking off slabs of rock until a nearly smooth vertical face remained.
🪨Royal Arches
📍North Valley Rim, across from Half Dome
The Royal Arches are another example of exfoliation, in which fractures that form parallel to the surface cause large slabs to peel and fall off the rock. Water, ice, and earthquakes are strong contenders for pushing the rock over. But recent research suggests that extreme heat can also cause these slabs to expand and contract, adding stress that will eventually cause them to break off the rock.
🪨Sentinel Rock
📍South Valley Rim, opposite of Yosemite Falls
Standing guard over the valley, Sentinel Rock’s near-vertical north face was carved by dramatic rockfalls that split the cliffside. Weathering and erosion continue to sculpt Yosemite Valley, and rockfalls occur in the park every year.
