Aerial photograph of the San Andreas Fault as it crosses the Carrizo Plain in California, USA. The San Andreas Fault extends almost the full length of California. It marks the boundary between the Pacific Plate to the west and the North American Plate to the east. These tectonic plates are moving past each other, making this a transform fault. The plates' movements cause stress that builds up until it is released by their sudden movement, which causes earthquakes. The desolate landscape consists of pressure ridges formed as a result of hundreds of fault movements. The Carrizo Plain is at right, the elevated Elkhorn Scarp at left.