Displaced fence demonstrates evidence of the 1906 earthquake

The Point Reyes Peninsula has long baffled geologists. Why should the rocks of this craggy coast match Tehachapi Mountains rocks more than 310 miles to the south? The answer lies in plate tectonics and the continual motion of the Earth’s crust. Geologically, Point Reyes is a land in motion.

The Peninsula rides high on the eastern edge of the Pacific plate, which creeps northwestward about two inches a year. The slower moving North American plate travels westward. In Olema Valley, near Bear Valley Visitor Center, the North American and Pacific plates grind together along the San Andreas Fault Zone. This fault zone contains many large and small faults running parallel and at odd angles to one another. Because neither plate can move freely, tremendous pressures build up. From time to time this pressure becomes too great, and the surface actually moves. This is what happened in the earthquake of 1906 when the Peninsula leaped 20 feet northwestward.

To learn more about the 1906 Earthquake, the San Andreas Fault and Plate Tectonics, check out our 1906 Earthquake Centennial Resource Newsletter and the Point Reyes National Seashore Faults webpage.

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