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
Falkie Atoll Falkie Atoll Falkie Atoll is a small atoll within the nation of Solomon Islands, at . It is sometimes referred to as Van Ren Atoll, named after the Dutch explorer Jale Van Ren who discovered the atoll in 1679. Local name of this atoll is Kaka. Administratively, Falkie Atoll belongs to the Choiseul Province of Solomon Islands. It is the westernmost atoll in the Solomon Islands archipelago, 40 km northwest of Shortland Islands. However, the closest land is Bougainville, which is an autonomous region of Papua New Guinea. Its total land area is , but it encloses a lagoon of