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
Bikini Atoll Bikini Atoll Bikini Atoll (pronounced or ; Marshallese: ", , meaning "coconut place") is an atoll in the Marshall Islands which consists of 23 islands totalling surrounding a central lagoon. It is at the northern end of the Ralik Chain, approximately northwest of Ailinginae Atoll and northwest of Majuro. Within Bikini Atoll, Bikini, Eneu, Namu and Enidrik islands comprise just over 70% of the land area. Bikini and Eneu are the only islands of the atoll that hosted a permanent population. Bikini Island is the northeastern most and largest islet. Before World War II, the atoll was known by its