Coral reef is the mass of corals build-up by the accumulation of skeletons of coral polyps and other marine organisms.
The following are 3 types of coral reefs.
this is the platform of corals attached to the coastline and extending seaward for a distance of a few hundred meters.
The surface of the reef is highly irregular with many broken corals and many large hollows resulting from selective solution; however, the inner lagoon is absent or weakly developed.
Fringing reefs grow near coastlines around islands or continents. They are separated from the shores by shallow and narrow lagoons.
An example of a fringing reef can be found along the coast of East Africa from Somalia to Mozambique.
this is a large coral reef running parallel to the coastline, from which it is separated by the deep and deep lagoons.
The most famous example of a barrier reef is the Great Barrier Reef of Eastern Australia, which extends for over 2000 kilometers.
A barrier reef is a massive and complex structure, comprising an outer line of coral reef, innumerable cays, and a larger island laying some 50 – 200 kilometers off shore, together with many inner reefs.
this is the coral reef surrounding a central lagoon, commonly found among the island of the Southern Pacific.
It is believed that atoll has been formed above the former island; as these submerged either as the result of subsidence of ocean floor or the rise of sea level, these submerged islands provided the base for coral growth which grew seaward and outward to form atoll.