Where does this come from, and can I check it?

Coral grows upward as its volcanic base sinks, leaving a ring of reef around a lagoon. The figure is taken from National Oceanic and Atmospheric Administration, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a world geography fact?

Yes. It sits on the World Geography shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

What else can I read about it?

The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

Atolls are the rims of sunken volcanoes

Coral grows upward as its volcanic base sinks, leaving a ring of reef around a lagoon Charles Darwin proposed the idea in 1842 and drilling at Enewetak in 1952 confirmed it, finding volcanic rock far beneath the reef. Coral only builds in shallow sunlit water, so the reef keeps pace as the old island subsides. The Maldives, Tuvalu and Kiribati are built almost entirely of such rings. It sits in Mondo's world geography collection, one of 200 facts that each trace back to the reference below.

Where this comes from

National Oceanic and Atmospheric Administration

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

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Tags: islands, oceans, coral

Atolls are the rims of sunken volcanoes: the short answers

Where does this come from, and can I check it?: Coral grows upward as its volcanic base sinks, leaving a ring of reef around a lagoon. The figure is taken from National Oceanic and Atmospheric Administration, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a world geography fact?: Yes. It sits on the World Geography shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.