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San Gorgonio Pass

Oblique aerial photograph looking east through San Gorgonio Pass. To the south (right) are Peninsular Ranges-type basement rock of the San Jacinto Mountains; to the north (left) are San Gabriel Mountains-type basement rocks of the San Bernardino Mountains that rise above foothills of Tertiary and Quaternary sedimentary materials. Young Quaternary alluvial deposits occupy the center of San Gorgonio Pass. These mainly are derived from easily eroded bedrock to the north of the Pass; note the large alluvial-fan cones sloping gently from left to right from the San Bernardino Mountains. Interstate Highway 10 snakes east-west through the lowland between the two mountain masses. Some workers propose that a significant east-trending buried fault must lie concealed beneath alluvial deposits in the center of San Gorgonio Pass in order to account for the steep northern front of the San Jacinto Mountains. Evidence for such a structure is not compelling, however. Photo by J.C. Matti, USGS, December, 1979.

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This site last updated September 3, 2004 (ps)

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