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,
Northern Thiladhunmathi Atoll there are three Tourist resorts in the atoll. North Thiladhunmath is third largest atoll in the Maldives in terms of population and land area. The atoll being at the north tip of the Maldives is the closest to Sri Lanka and India. Northern Thiladhunmathi Atoll contains 42 islands, 16 of which are inhabited. NOTE: "Haa Alifu, Haa Dhaalu, Shaviyani, Noonu, Raa, Baa, Kaafu, etc. are code letters assigned to the present administrative divisions of the Maldives. They are not the proper names of the natural atolls that make up these divisions. Some atolls are divided into two administrative divisions while