Blowhole is a hole in a sea cliff from which columns of spray are forced upward, often accompanied by noise. Blowholes are formed by wave erosion that extends sea caves along joints or cracks to the surface. The expansion and compression of air in the hole forced out as waves enter, creates the driving force that ejects water. There are many blowholes located around the California Channel Islands. There is a large blowhole to the west of Coches Prietos, Santa Cruz Island.