Coral reefs

(Phys. Geog.)

reefs, often of great extent, made up chiefly of fragments of corals, coral sands, and the solid limestone resulting from their consolidation. They are classed as fringing reefs, when they border the land; barrier reefs, when separated from the shore by a broad belt of water; atolls, when they constitute separate islands, usually inclosing a lagoon. See Atoll.

See also: Coral