The word atoll comes from the Dhivehi word atholhu (Dhivehi: އަތޮޅު, [ˈat̪oɭu]), meaning the palm of the hand. Dhivehi is an Indo-Aryan language spoken in Maldives. The word's first recorded English use was in 1625 as atollon.

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 HMS Beagle from 1831 to 1836. Darwin's explanation suggests that several tropical island types: from high

• Baratal limestone, sometimes described as the oldest known atoll
• Low island
• Nukuoro Atoll
• Kapingamarangi Atoll

There are approximately 440 atolls in the world.
Most of the world's atolls are in the Pacific Ocean (with concentrations in the Caroline Islands, the Coral Sea Islands, the Marshall Islands, the Tuamotu Islands, Kiribati, Tokelau,

In 1896, 1897 and 1898, the Royal Society of London carried out drilling on Funafuti atoll in Tuvalu for the purpose of investigating the

On January 6, 2009, U.S. President George W. Bush announced the creation of the Pacific Remote Islands Marine National Monument,

• Formation of Bermuda reefs
• Darwin's Volcano – a short video discussing Darwin and Agassiz' coral reef formation debate