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
Kure Atoll to restore the atoll to a more natural state. Jean-Michel Cousteau produced a video on a voyage to Kure which first aired in 2006. Since 2010 the Division of Forestry and Wildlife has had a year-round presence on Kure Atoll. Because of its particularly remote location, Kure Island has been the scene of several amateur radio DX expeditions, or DX-peditions. Because the radio propagation path between Kure and Europe runs right over the North Polar region, opportunities for distant communication with Kure are particularly popular among European amateurs. Some of the DXpeditions to Kure were: Kure Atoll The International Date