Los Angeles is a very large city, and the edges of the city are very far from the center, going from the beaches to the mountains. The Santa Monica Mountains run through the city, separating it into the San Fernando Valley to the north and the Los Angeles Basin to the south. The Los Angeles River also runs through the city some . Los Angeles moves about one-quarter of an inch (6.3 millimeters) to the east every year. It is caused by the city's tectonic plates and rough ground geography and since Los Angeles is at a close distance with the San Andreas Fault. This brings Los Angeles and San Francisco 2.5 inches closer together each year.