Yosemite National Park’s Geologic History
The City of Merced is the gateway to Yosemite National Park. Today, let’s dig a little deeper into the geology of this wonderful park and its interesting development through the ages. Yosemite has a simple geologic history compared to many other mountain parks. Most all of the rock that you see in Yosemite is part of the Sierra Nevada Batholith, a large body of magma that intruded, crystallized, and lay buried as granitic material beneath a thick layer of metamorphic rock.
Geologists have estimated that the batholith was about six miles below the surface and it took about 100 million years for it to form. Inside Yosemite, dozens of plutons of different ages and composition were emplaced. Most of the rock in Yosemite was thrust up between 80 and 120 million years ago. Some were intruded between 150 and 210 million years ago.
The entire Yosemite region rose and has been extensively eroded. Over time, almost all of the overlying metamorphic rock was eroded away and the batholithic granite remained. The latest period of uplifting occurred around 10 million years ago which created the Sierra Nevada range, which has a distinct westward tilt, steep east face, and gentle western slopes.