Atoll Atoll An atoll (, , , , or ), sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the volcanic crater or caldera while the higher rim remains above water(s) or at shallow depths that permit the coral to grow and form the reefs. For the atoll to persist,
Baa Atoll Maldives, including large mangroves and a unique diversity of fauna, such as the benthic fauna. Furthermore, the ring-shaped reef forms known as "faru" in the Dhivehi language is a reef structure which is unique to the Maldives. The southernmost uninhabited island of Olhugiri in the North Maalhosmadulu Atoll lies 13 km north of Goifulhafehendhu Atoll. Olhugiri is well known for its unique natural vegetation and for providing two of the only perching sites for the great frigatebird in the Maldives. Likewise, other marine creatures such as seaturtles and hawksbill turtles can be encountered. The Fisheries Ministry of the Maldives has