Stresses in the tectonic plates, the moving sections that make up the earth's outer crust, can cause the plate to stretch or compress and create faults. The tectonic plates move due to the pressure of molten rock beneath them.
Normal faults occur when two masses of rock are pulling apart. Reverse faults occur when two rocks are compressing together. When two rocks are not moving up or down in relation to each other, but move past each other laterally, this is called a transform or strike-slip fault.
The San Andreas Fault is causing the California coast to move away from the mainland at the rate of 2 inches per year. This rate will cause Los Angeles and San Francisco to move next to each other in 15 million years, according to the United States Geological Survey.