Which two tectonic plates meet along California’s San Andreas Fault?

California’s San Andreas Fault marks the boundary between the Pacific Plate and the North American Plate.

It is a transform boundary, where the two plates move mainly sideways past one another. The Pacific Plate moves generally northwest relative to the North American Plate. This motion is not smooth everywhere; friction can lock sections of the fault until stress is released in earthquakes.

The fault system extends for roughly 1,200 kilometres through California, from the Salton Sea region toward the coast north of San Francisco. It forms part of a broader network of faults that accommodates plate motion along the western edge of North America.

The San Andreas is not the only active fault in California, and it is not a single perfectly straight crack. It includes bends, branches, and connected fault strands. Earthquake hazard depends on the whole fault system, local ground conditions, building design, and how much strain has accumulated since previous ruptures.