Atoll facts for kids

The atoll of Nukuoro in the Federated States of Micronesia.

An atoll is a kind of island. It is made when a coral reef forms around an island that sinks over many years. In the end, the land is gone, and only the coral reef continues to grow until it becomes an atoll, a group of islands shaped like a doughnut.

Charles Darwin, who is most famous for his theory of evolution, was the first person to find out how atolls form. He said that volcanoes in the ocean sometimes wear away or sink deeper. Coral growing on a volcano likes to be near the surface, and it keeps growing to stay there.

Most atolls are in the warm parts of the Pacific Ocean or the Indian Ocean.

Some island nations like Kiribati, Tuvalu, and the Federated States of Micronesia have atolls as all or part of their country.

How an atoll forms.

• Darwin, C. 1842. The structure and distribution of coral reefs, being the first part of the voyage of the Beagle under the command of Capt. Vitzroy R.N. during the years 1832 to 1834. Smith, Elder and Co.: London. 214 pp.

Images for kids

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  Satellite picture of the Atafu atoll in Tokelau in the Pacific Ocean

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  Penrhyn atoll

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  NASA satellite image of some of the atolls of the Maldives, which consists of 1,322 islands arranged into 26 atolls

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  Los Roques Archipelago in Venezuela, the largest marine national park in Latin America, from space. Courtesy NASA

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  View of the coast of Bikini Atoll from above

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  Raa Atoll in Maldives

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  Kaafu Atoll in Maldives

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  Map from Charles Darwin’s 1842 The Structure and Distribution of Coral Reefs showing the world’s major groups of atolls and coral reefs

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  Aerial view of Bora Bora

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  Tarawa Atoll

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  Bikini Atoll

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  Aerial overview of the Wake Island atoll, part of the Pacific Remote Islands Marine National Monument

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  Darwin's theory starts with a volcanic island which becomes extinct

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  As the island and ocean floor subside, coral growth builds a fringing reef, often including a shallow lagoon between the land and the main reef

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  As the subsidence continues the fringing reef becomes a larger barrier reef farther from the shore with a bigger and deeper lagoon inside

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  Ultimately the island sinks below the sea, and the barrier reef becomes an atoll enclosing an open lagoon

See also

In Spanish: Atolón para niños