A large number of atolls also occur in the Lakshadweep islands. The Fiji atoll and the Funafuti atoll in the Ellice Island are well known examples of atolls. 3.14).Ītolls are far more common in the Pacific than any other ocean. The surface of a barrier reef is covered with coral debris, boulders and sand (Fig. A barrier reef is characterised by distant location of the reef from the coast with a broader and deeper lagoon, which is sometimes joined with the sea water through one or more channels cutting across the barrier reef.Ī barrier reef is very thick, going even below 180 metres from the surface with the seaward side sloping steeply into the deep sea.

It extends as a broken, irregular ring around the coast or an island, running almost parallel to it. This is the largest of the three reefs, runs for hundreds of kilometres and is several kilometres wide. Fringing reefs can be seen at the New Hebrides Society islands off Australia and off the southern coast of Florida (Fig. The surface of a fringing reef is rough, as it is covered with coral remains forming a boulder zone or reef flat. This type of reef grows from the deep sea bottom with the seaward side sloping steeply into the deep sea.Ĭoral polyps do not extend outwards because of sudden and large increase in depth. A fringing reef runs as a narrow belt, 0.5 km to 2.5 km wide. It is a coral platform attached to a continental coast or an island, sometimes separated by a narrow, shallow lagoon or channel (Fig.

Atoll reef