noun \ˈa-ˌtl, -ˌtäl, -ˌtōl, ˈā-\

: an island that is made of coral and shaped like a ring

Full Definition of ATOLL

:  a coral island consisting of a reef surrounding a lagoon

Illustration of ATOLL

Origin of ATOLL

Divehi (Indo-Aryan language of the Maldive Islands) atolu
First Known Use: 1625

Other Geology Terms

anthracite, boulder, cwm, erratic, igneous, intrusive, mesa, sedimentary, silt, swale


noun    (Concise Encyclopedia)

Coral reef enclosing a lagoon. Atolls consist of ribbons of reef that may not be circular but that are closed shapes, sometimes miles across, around a lagoon that may be 160 ft (50 m) deep or more. Most of the reef itself is usually below the water surface; around the rim along the top are usually low, flat islands or more continuous strips of low, flat land.


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