The San Andreas Fault superimposed over a shuttle photo of California (click to enlarge and read explanation below).

The San Andreas Fault is a continental transform fault that extends roughly 1,200 kilometers (750 mi) through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate. It has three segments, each with different characteristics and a different degree of earthquake risk.

The fault is best known for producing large and destructive earthquakes due to the horizontal movement of the plates. As the Pacific Plate moves northwest relative to the North American Plate, stress builds up along the fault, eventually releasing as seismic activity.

The image highlights key geological features, such as the Great Valley, Sierra Nevada, and the Gulf of California, showing how the fault extends from northern California down to the Baja California region. Over millions of years, this movement has shaped the landscape, influencing everything from mountain formation to river courses.