The San Andreas Fault is a transform plate boundary, meaning that the crust on either side of the fault is moving horizontally past each other.

Here's the breakdown:

* Pacific Plate: This plate is moving northward relative to the North American Plate.

* North American Plate: This plate is relatively stationary.

The San Andreas Fault itself is a continental-continental fault, as it runs through the continental crust of both the Pacific and North American Plates.

Important note: While the San Andreas Fault is a transform boundary, there are also areas along it where the movement is not purely horizontal. Some areas exhibit minor vertical movement as well, resulting in the formation of small mountains and valleys.