The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench under the North American Plate well north of San Francisco. In California, the plate borders the North American Plate along a transform boundary, the San Andreas Fault. The westward component of the North American Plate's motion and the irregularity of the San Andreas Fault results in some compressive force along the San Andreas and its associated faults, thus helping lift the Coast Ranges. The Mount Diablo Thrust Fault and the Great Valley Blind Thrust faults are consequences of this compression.