Why are the Sierra Nevada mountains higher and steeper on their eastern side?

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map of western North America — Sierra Nevada Physical features of western North America.

The Sierra Nevada mountains are higher and steeper on their eastern side because the range is an upfaulted, tilted block of the Earth's crust. A major fault zone runs along the eastern edge, where the massive block was uplifted and tilted toward the west.1

This geological process created an abrupt, east-facing escarpment that has been further shaped by erosion from wind, rain, frost, and ice, resulting in steep-gradient canyons. In contrast, the western flank follows a gentle geologic dip slope where streams flow more gradually toward the Central Valley. This structural asymmetry is responsible for the dramatic relief found along the eastern slopes.1