San Francisco Bay Region Geology and Geologic Hazards

Stories > Crystal Springs Reservoir, San Mateo County - Faulted Landscape

Crystal Springs Reservoir, San Mateo County - Faulted Landscape

Faults generate recognizable shapes in the landscape. One of these faulted landscape shapes (the technical term is "fault geomorphology", which literally means "fault Earth-shape") is a long, straight valley called a "linear valley". In San Mateo County, the waters of Crystal Springs Reservoir, west of I-280, fill the linear valley of the San Andreas Fault.

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Crystal Springs Reservoir fills a linear valley on the San Andreas Fault.

Other prominent linear valleys in the San Francisco Bay region include Tomales Bay in Marin County along the San Andreas Fault and Montclair Valley in Oakland along the Hayward Fault.

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Tomales Bay fills another linear valley on the San Andreas Fault

Many of the faulted landscape shapes, including linear valleys, are the result of enhanced erosion along faults. As faults repeatedly rupture, the rocks near them are broken and ground down. These rocks are more easily eroded than the more coherent rocks away from the fault.

Learn more about the San Andreas Fault at:


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Page Last Modified: 8/18/2006