Sea basins are related in form and origin to dry land basins, such as that of Los Angeles. The Santa Barbara Basin lies between the four Northern Channel Islands and the adjacent mainland. The Santa Monica and San Pedro basins separate the Southern Channel Islands from the mainland. Coastal basins are more shallow than the deep water basins to the southwest of the Channel Islands. The Santa Barbara Basin is about 1500 feet deep, while the Santa Monica and San Pedro basins are about 2250 feet deep. The Catalina basin is about 3750 feet deep. Deep water basins which off Santa Cruz and San Nicolas islands reach depths over a mile.