Coral island
A coral island is the result of an atoll
An atoll is a coral island that encircles a lagoon partially or completely.- Usage :The word atoll comes from the Dhivehi word atholhu OED...

 whose lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

 has dried up or been filled in with coral sand
Coral sand
Coral sand is sand of particles originating in tropical and sub-tropical marine environments from bioerosion of limestone skeletal material of marine organisms. One example of this process is that of parrot fishes which bite off pieces of coral, digest the living tissue, and excrete the inorganic...

 and detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...

. This state is typically the last in the life cycle of an island, the first being volcanic and the second being an atoll. Most of the world's coral islands are in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

. The American territories
United States Minor Outlying Islands
The United States Minor Outlying Islands, a statistical designation defined by the International Organization for Standardization's ISO 3166-1 code, consists of nine United States insular areas in the Pacific Ocean and Caribbean Sea: Baker Island, Howland Island, Jarvis Island, Johnston Atoll,...

 of Jarvis
Jarvis Island
Jarvis Island is an uninhabited 4.5 square kilometer coral island located in the South Pacific Ocean at , about halfway between Hawaii and the Cook Islands...

, Baker
Baker Island
Baker Island is an uninhabited atoll located just north of the equator in the central Pacific Ocean about southwest of Honolulu. The island lies almost halfway between Hawaii and Australia, and is a possession of the United States. Its nearest neighbor is Howland Island, to the north.Located at...

 and Howland Island
Howland Island
Howland Island is an uninhabited coral island located just north of the equator in the central Pacific Ocean, about southwest of Honolulu. The island lies almost halfway between Hawaii and Australia and is an unincorporated, unorganized territory of the United States. Geographically, it is part...

s are clear examples of coral islands. Also, some of the islands belonging to Kiribati
Kiribati , officially the Republic of Kiribati, is an island nation located in the central tropical Pacific Ocean. The permanent population exceeds just over 100,000 , and is composed of 32 atolls and one raised coral island, dispersed over 3.5 million square kilometres, straddling the...

are considered coral islands.

A coral island is an island that forms a ring and partially or totally encloses a shallow body of water,or lagoon. It is formed by a build up of depositing lava on top of lava from a volcano that rises up out of the sea. Living organisms begin living around the shores of the new islands. The volcano becomes inactive and sinks,the coral dies, the island forms. The formation is a hard rock like material formed by the skeleton of marine polyps and sand. Most of the coral islands are located in the Pacific Ocean, some of the islands have been designated as a National Monument. Their surrounding waters contain objects of historic or scientific interest. They consist of Wake, Baker, Howland, and Jarvis Islands.

A coral island is formed by small organisms called polyps (pa-lips). Polyps are the builders of coral. These tiny organisms protect themselves by building small walls of limestone around their bodies. These creatures live in small colonies, and over millions of years, these ‘settlements’ become reefs, and then turn into islands.
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