Coral island

Island formed from coral and associated material

A coral island is a type of island formed from coral detritus and associated organic material. It occurs in tropical and sub-tropical areas, typically as part of a coral reef which has grown to cover a far larger area under the sea. The term low island can be used to distinguish such islands from high islands, which are formed through volcanic action. Low islands are formed as a result of sedimentation upon a coral reef or of the uplifting of such islands.

This keyword could refer to multiple things. Here are some suggestions: