What are the different types of coral reefs?
The evolution of coral reefs from fringing reef (left) to barrier reef (centre) and atoll (right). Illustration by Michael King. Fringing reefs lie near emergent land. They are fairly shallow, narrow and are recently formed. They can be separated from the coast by a navigable channel (which is sometimes incorrectly termed a ‘lagoon’). Barrier reefs are broader and lie farther away from the coast. They are separated from the coast by a stretch of water which can be up to several miles wide and several tens of metres deep. Sandy islands covered with characteristic patterns of vegetation sometimes form on top of barrier reefs. The coastlines of these islands are broken by passes, which occupy beds of former rivers. Atolls are large, ring-shaped reefs lying off the coast, with a lagoon in their middle. The emergent part of the reef is often covered with accumulated sediment and the most characteristic vegetation growing on these reefs consists of coconut trees. Atolls develop near the sea
