Cape Mendocino

Encyclopedia : C : CA : CAP : Cape Mendocino

Cape Mendocino in Humboldt County, California, USA, is the westernmost point on the coast of California. (Mendocino County lies to the south.) It has been a landmark since the 16th century Manila Galleons that would reach the coast here following the trade winds and make their way coastwise southwards. Its first lighthouse was lit December 1, 1868, standing on eight prefabricated panels sent up from San Francisco.

The Cape Mendocino region of California's north coast is one of the most seismically active regions in the "Lower Forty-eight" United States. Three earthquakes with epicenters nearby at Petrolia and offshore west of Cape Mendocino, 25–26 April, 1992, were outstanding, one reaching 7.0 on the Richter scale; they demonstrated that the Cascadia subduction zone is both capable of producing large earthquakes and generating tsunamis.

At Cape Mendocino, there is an unstable triple junction where three tectonic plates come together. The familiar San Andreas Fault, a strike-slip fault, approaches from the south; it separates the Pacific Plate and the North American Plate. To the north lies the Cascadia subduction zone, where the Juan de Fuca Plate and the last bit of its lower section, sometimes called the Gorda Plate, are being subducted under the margin of the North American plate. And west, along the continental shelf, lies the Mendocino fault zone, the strike-slip boundary between the main Juan de Fuca plate and the Pacific plate. Where the three come together, a geologically complex and highly unstable zone results.

Many geologists and seismologists believe that the main shock in the 1992 sequence may be a forerunner of a much more powerful earthquake in the Pacific Northwest.

Off the point, Sugarloaf Mountain is an isolated block of coastline eroded by surf.

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