What is San Andreas Fault?
[[File:San Andreas Fault Aerial View.gif|thumb|right|The San Andreas Fault, a right-lateral strike-slip fault caused the massive 1906 [[San Francisco]] earthquake]] [[File:Sanandreas.jpg|thumb|Map of the San Andreas Fault, showing relative motion]] The '''San Andreas Fault''' is a right-moving ('dextral') strike-slip [[Fault (geology)|fault]]. It marks the boundary between the North American Plate on the east and the Pacific Plate on the west. The fault was the cause of the 1906 [[San Francisco]] [[earthquake]]. It first appeared about 20 million years ago.<ref>Atwater T. 1970. Implications of plate tectonics for the Cenozoic tectonic evolution of western North America.</ref><ref>Powell R.E. and Weldon,R.J. 1992. Evolution of the San Andreas fault. ''Annual Reviews of Earth and Planetary Science'', '''20''', 431–468.</ref> The San Andreas Fault is a zone several miles wide with multiple strands. The main active strand runs both on and off-shore between [[Cape Mendocino]] and the [[Sea of Cortez]]. From Cape Mendocino, it runs offshore to [[Tomales Bay]]. Then it goes southward through [[Bolinas Lagoon]], just west of the [[San Francisco]] Peninsula, to come onshore again at [[Daly City]], through the hills of the Peninsula. [[Crystal Springs|Crystal]] cum reservoir is formed by the fault itself. In the Santa Cruz mountains, it bends slightly eastward. This is the site of the 1989 [[Loma Prieta]] Earthquake. The fault continues south through the historic mission at [[San Juan Bautista]] and through the town of [[Hollister, California|Hollister]] (where active creep can be seen to offset sidewalks and even houses). The Transverse Ranges north of [[Santa Barbara]] are formed by compression. Strands of the fault snake under the [[Los Angeles]] Basin. From there it connects into the active spreading under the Sea of Cortez. The San Andreas fault was discovered by Professor Andrew Lawson in 1895, who climbed into the faulted [[serpentinite]] [[well]] where the south tower of the [[Golden Gate Bridge]] was being p