The Cocos (Keeling) Islands lie in the eastern Indian Ocean, about 2,900 km (1,800 mi) northwest of the Australian city of Perth. Comprised of coral atolls and islands, the archipelago includes North Keeling Island and the South Keeling Islands. This natural-color satellite image of the South Keeling Islands dates to 31 July 2009.
Coral atolls - which are largely composed of huge colonies of tiny animals - form atop islands. Over time the islands may subside, but the coral remains growing upward and generally forming complete or partial rings. Only some parts of the South Keeling Islands still stand above the water surface. In the north, the ocean overtops the coral.
Along the southern rim of this coral atoll, the shallow water appears aquamarine. The water darkens to navy blue as it deepens toward the central lagoon. Above the water line, coconut palms and other plants form a thick carpet of vegetation.
In 2005, the Australian Government issued a report on the Cocos (Keeling) Islands, summarizing field research conducted between 1997 and 2005. Overall, the report noted, "the coral reef community at Cocos (Keeling) Islands is very healthy and in a stable period, with little impact from anthropogenic activities." Image courtesy of NASA.