These plates slide horizontally. Most transform faults are found on the ocean floor, offsetting some of the active spreading ridges, producing zigzag plate margins. Shallow earthquakes are associated with them. The best-known example of a sliding plate is the San Andreas Fault in California. The San Andreas, which is 800 miles (1,300 km) long and in places up to 50-100 miles (80-160 km) wide, slices through two-thirds of the length of California. Here, the Pacific plate has been grinding horizontally past the North American plate for 10 million years, at an average rate of two inches (5 cm) per year. Land on the west side of the fault zone (Pacific plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (North American plate). Because the plates are internally rigid, moving as a solid mass, they interact mostly at their edges. All plates move relative to each other, by sliding past or subducting under each other.
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