Valley Formation

Movement at the San Andreas Fault stretched the land east of the Sierra Nevada. As this region expanded, the lightweight Sierra crust began to rise and tilt to the west while at the same time the basin to the east dropped down.

On the western slope of the Sierra Nevada, a once gently rolling landscape became steeper, causing meandering streams to flow faster. These faster flowing streams cut more deeply through the landscape, carving V-shaped canyons up to 2,000 feet deep.

The processes of uplift, tilt, and erosion continue along the steep eastern border of the Sierra Nevada range, although at a less dramatic rate. Uplift of the Sierra Nevada is approximately 3.8 cm (1½ inches) per 100 years in the Yosemite region; erosion is wearing down these mountains at about the same rate.