The San Andreas Fault is a continental right-lateral strike-slip transform fault that extends roughly 750 mi (1,210 km) through the U.S. state of California. It forms part of the tectonic boundary between the Pacific plate and the North American plate. Traditionally, for scientific purposes, the fault has been classified into three main segments, each with different characteristics and a different degree of earthquake risk. The average slip rate along the entire fault ranges from 0.79 to 1.38 inches per year.