The San Andreas fault system is the boundary between the huge Pacific and North American plates. These two plates first came into contact offshore of southern California about 25 million years ago. The boundary first formed at the edge of the continental shelf, then moved inland as pieces of the continent broke off and joined the Pacific plate. Events during this plate boundary development formed our complex offshore basins and islands, our on-land mish-mash of mountain ranges and valleys, and our east-west coastlines. They set the stage for our unique climate and ocean currents and our rich oil and marine life resources. Present day earthquakes, landslides, and rugged landscapes attest to the continuing deformations in this system.
Dr. Tanya Atwater is an Emeritus Professor at the University of California, Santa Barbara. She received her education at the M.I.T., U.C. Berkeley, and Scripps Institute of Oceanography, completing her PhD in 1972. Dr. Atwater is especially well known for her research on the plate tectonic history of the San Andreas Fault and western North America. She is devoted to science communication, working with teachers, parks, museums and the media. She has received many honors, most recently a Geological Society of America Lifetime Achievement Award and an Emmy. She was elected to the National Academy of Sciences in 1997.