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.
A coral island in Maldives
Healthy reef system
Bleached coral due to rising sea temperature, increased acidity, and/or pollution.
The Moruroa atoll, composed of low islands on the reef encircling a central lagoon
Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal thickening, changes in the density distribution of the crust and underlying mantle, and flexural support due to the bending of rigid lithosphere.
Former sea bottom that raised during the 2013 Bohol earthquake - the water used to extend to the mangroves at right