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
Kaafu Atoll part of the administrative division of Kaafu Atoll. The two Malé Atolls are North Malé Atoll and South Malé Atoll which are separated by the Vaadhoo Kandu. Malé and Thulusdhoo are both located in North Malé Atoll. The Malé or Kaafu Atoll administrative division consists of the geographic or natural atolls of North Malé Atoll, South Malé Atoll, Gaafaru Atoll and Kaashidhoo Island. The atolls consists of Inhabited Islands and Uninhabited Island, a definition which includes resort islands, airport islands and industrial islands. Although Malé, Hulhulé, Hulhumalé and Villingili are geographically part of North Malé Atoll, they are not part