Atoll

An atoll is a type of low, coral island found in tropical oceans and consisting of a coral-algal reef surrounding a central depression. The depression may be part of the emergent island, but more typically is a part of the sea (that is, a lagoon), or very rarely is an enclosed body of fresh, brackish, or highly saline water.

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The word atoll comes from the Dhivehi (Indo-Aryan language of the Maldive Islands) word atholhu (Dhivehi: އަތޮޅު). Its first recorded use in English was in 1625. However, the term was popularised by Charles Darwin (1842, p. 2), who described atolls as a subset in a special class of islands, the unique property of which is the presence of an organic reef. More modern definitions of atoll are those of McNeil (1954, p. 396) as "...an annular reef enclosing a lagoon in which there are no promontories other than reefs and composed of reef detritus" and Fairbridge (1950, p. 341) "...in an exclusively morphological sense, ...a ring-shaped ribbon reef enclosing a lagoon in the centre."

Coral: see Anthozoa...

Island: An island or isle is any piece of land smaller than a continent and larger than a rock that is completely surrounded by water. Very small islands are called islets. Although seldom adhered to, it is also proper to call an emergent land feature on an atoll an islet, since an atoll is a type of islan...

Tropical: REDIRECT Tropics...

Atoll related Images and Photos (experimental)

South Male Atoll Maldives	Tepuka Islet. Funafuti Atoll Tuvalu	Woman Snorkelling Kurumba Island North Male Atoll Kaafu Maldives	Underwater Vista of a Reef Off Bikini Atoll Reveals a Giant Clam and Various Corals
White Tern on its Nest with an Egg Gygis Alba Midway Atoll National Wildlife Refuge USA	A Tree Floats in the Crystal-Clear Waters of Palmyra Atoll