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Shutter Ridge, California

Pictures of Tectonic Landforms

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Shutter ridges are common on the San Andreas and other strike-slip faults. The rock ridge is moving to the right and blocking the stream. (more below)
Blocker in motion
Photo (c) 2008 Andrew Alden, licensed to About.com (fair use policy)
Shutter ridges occur where the fault carries high ground on one side past low ground on the other. In this case, the Hayward fault in Oakland carries the rocky ridge toward the right, blocking the course of Temescal Creek (here dammed to form Lake Temescal at the site of a former sag pond) and forcing it to flow rightward to get around it. (The result is a stream offset.) On the far side, the stream continues toward San Francisco Bay along the route of the freeway. The motion of the barrier is like the shutter of an old-fashioned box camera, hence the name. Compare this picture to the stream offset picture, which is exactly analogous.
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