Half Dome

Half Dome is a granite dome rising about 1,444 meters above Yosemite Valley in the Sierra Nevada of California, formed from granite of the Sierra Nevada Batholith that crystallized deep underground roughly 87 million years ago before millions of years of uplift and erosion exposed it at the surface. Its rounded shape is a product of exfoliation, in which curved sheets of rock progressively split away from the dome's surface as the overlying rock eroded away and pressure on the deeply buried granite was gradually released; its dramatic sheer northwest face, which gives the formation its "half dome" appearance, was carved by glacial ice that plucked away jointed rock along a pre-existing vertical fracture during past ice ages, though geologists estimate erosion removed at most twenty percent of the original dome rather than a literal half. It is among the most recognizable granite domes in the Sierra Nevada and a defining symbol of Yosemite National Park.