Atoll remains of an ancient atoll as a hill in a limestone area is called a reef knoll. The second largest atoll by dry land area is Aldabra with 155 km². The largest atoll in terms of island numbers is Huvadhu Atoll in the south of the Maldives with 255 islands. In 1842, Charles Darwin explained the creation of coral atolls in the southern Pacific Ocean based upon observations made during a five-year voyage aboard from 1831 to 1836. Accepted as basically correct, his explanation involved considering that several tropical island types—from high volcanic island, through barrier reef island, to atoll—represented
Ari Atoll Ari Atoll Ari Atoll (also called Alif or Alifu Atoll) is one of the natural atolls of the Maldives. It is one of the biggest atolls and is located in the west of the archipelago. The almost rectangular alignment spreads the islands over an area of about . It has been divided in two sections for administrative purposes, Northern Ari Atoll and Southern Ari Atoll consisting of 105 islands. Ari Atoll is part of the zone designated for tourist development in the Maldives. It is roughly a 30-minute seaplane flight away from the Capital Malé. There are more than 20