Abstract
A cave is a natural opening or cavity within the earth, generally extending from the earth's surface to beyond the zone of light. Three generic classes of caves can be recognized according to the major sculpturing process: (1) caves formed by pressure or flow, (2) caves carved by erosion, and (3) caves dissolved by solution. Those structures formed by mechanical pressure or flow include lava tunnels associated with volcanoes (e.g., Catacombs Cave in Lava Beds National Monument, California) and "badland caves" excavated from poorly consolidated rock by hydraulic pressure (e.g., small caves of the arid Badlands of South Dakota). The caves carved by erosion include shoreline grottos created by the mechanical action of waves (e.g., La Jolla sea caves near San Diego, California) and rock shelters cut by river meanders (e.g., the massive sandstone alcoves of the famed cliff-dwelling Pueblo Indians). The caves dissolved by solution include ice caves associated with glaciers and the familiar limestone caverns or caves. Limestone caves are, by far, the most common type of caves.