San Joaquin Valley

The San Joaquin Valley is a sediment-filled depression, called a basin, that is bound to the west by the California Coast Ranges, and to the east by the Sierra Nevadas. It is classified as a forearc basin, which basically means that it is a basin that formed in front of a mountain range.

The Valley dates back more than 65 million years ago to the Mesozoic, when subduction was taking place off the coast of California. However, the plate tectonic configuration of western North America changed during the Tertiary, and the ancient trench that once characterized offshore California was transformed into a zone of right-lateral strike-slip motion that we know today as the San Andreas fault. Nonetheless, the Valley still retains many features that characterized it prior to formation of the San Andreas transform.

Dromos