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
Gaafu Dhaalu Atoll Gaafu Dhaalu Atoll Gaafu Dhaalu (also known as Southern Huvadhu Atoll or Huvadhu Atholhu Dhekunuburi) is an administrative district of the Maldives formed by the southwestern section of Huvadhu Atoll. It was created on February 8, 1962 when Huvadhu Atoll was divided into two districts. Gaafu Dhaalu corresponds to the Southwestern section of this large natural atoll, south of the line extending between the channels of Footukandu and Vaarulu Kandu. The capital of this region is Thinadhoo (formerly known as Havaru Thinadhu). There are 153 islands in this district, 10 of which are inhabited. This district is located about 340