Santa Rosa Island Beach Erosion

June 25, 2003

Roll1dx-21 copy

Provided by: Robert Moriarity
Summary authors & editors: Martin Ruzek; Robert Moriarity

This picture is of a north facing beach erosion zone on Santa Rosa Island off the southern California coast. The island is part of the northern Channel Islands, a westward extension of the Southern California Transverse Ranges. Distinctive clastic lithologies connect Sant Rosa Island to the California mainland near San Diego, 200 km to the southeast, in the distant past. The islands have been sliced, rotated and translated nothwestward as part of the San Andreas fault system. The photo above shows a layer of deformed fine grained sediment between coarse clastic deposits, now eroding on the beach. Unraveling the story told by these rocks is part of the challenge of geology - perhaps a slumping course debris flow compressed soft intertidal mud or volcanic ash deposits? The best way to find out is to get out your field notebook and hand lens and take a trip to Santa Rosa Island!

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