What is a plate boundary?
A plate boundary is a place where two tectonic plates meet. On the west coast of the United States, plate boundaries include the San Andreas fault in southern and central California (where the North American and Pacific plates slide past each other) and the Cascadia Subduction zone in northern California, Oregon, and Washington (where the Juan de Fuca plate slides under the North American plate). The closest plate boundary to the east coast is the Mid-Atlantic spreading ridge, in the center of the Atlantic Ocean. Watch this animation to learn more!