Golden Gate Photo Geotour Garage
The San Andreas Fault Tour
The San Andreas Fault is the surface expression of the boundary between the Pacific and North American Tectonic Plates. In general, the Pacific Plate (on the west side of the fault) is moving northwest relative to the North American Plate (on the east side of the fault). Each sudden movement of a segment of the boundary is expressed as an earthquake along the fault. The San Andreas Fault extends from the Gulf of California (Mexico), through most of California, skipping along the coastline from San Francisco to its northern extent in the northern part of the state, a distance of over 800 miles (1,280 Km). The San Andreas Fault extends to a depth of at least 10 miles (16 Km) and since its beginning about 15 to 20 million years ago, the offset across the fault has been 350+ miles (560+ Km). At its northernmost point where it dramatically curves to the west and changes characteristics is the Mendocino Triple Junction. To the south of this point, the San Andreas Fault pushes the Pacific Plate to the northwest relative to the North American Plate. North of this junction, ocean seafloor is spreading out from the Gorda Ridge (#1) in the Pacific Ocean, and is forcing the Gorda Plate eastward and beneath the North American Plate along the Cascadia Subduction Zone (#2). The southern edge of the Gorda Plate is that west-trending extension of the San Andreas Fault, now called the Mendocino Fault (#3). The golden arrows show the locations of the current set of images.
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