se7enW
Back to What
📖 what

What Is a Coral Atoll?

geographynature

Quick Answer

A coral atoll is a ring-shaped reef encircling a shallow lagoon, formed as coral grows around a volcanic island that gradually sinks.

The Full Story

Charles Darwin first explained atoll formation in 1842. A volcanic island rises from the ocean floor, and coral begins growing around its coast. Over millions of years, the volcano subsides, but the coral keeps growing upward to stay near the sunlit surface. Eventually the volcano disappears beneath the sea, leaving a ring of coral reef surrounding a central lagoon. The Maldives, Marshall Islands, and Kiribati are nations built almost entirely on atolls. Kwajalein Atoll in the Marshall Islands is the world largest, enclosing a lagoon of over 2,170 km².

Key Facts

1.There are approximately 440 atolls worldwide, mostly in the Pacific and Indian Oceans.
2.The average elevation of the Maldives is just 1.5 metres above sea level, making it extremely vulnerable to rising seas.
3.Darwin atoll theory was confirmed by deep drilling at Bikini Atoll in 1952, which found volcanic rock beneath over 1,400 metres of coral.

YouTube Angle

Suggested video title for this topic:

"Rings in the Ocean — How Coral Atolls Form Over Millions of Years"