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Canton Island typifies the isolated coral atolls dotting the Pacific Ocean. The Structure and Distribution of Coral Reefs, Being the first part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836, was published in 1842 as Charles Darwin's first monograph, and set out his theory of the formation of coral reefs and atolls.
Spur and groove formations are a geomorphic feature of many coral reefs. They are ridges of reef formed by coral ("spurs") separated by channels ("grooves") which often have sediment or rubble bed. Spur and groove formations vary in their size and distribution worldwide but are a common feature on many forereefs of fringing reefs , barrier ...
The atoll of Tetiʻaroa in French Polynesia. An atoll (/ ˈ æ t. ɒ l,-ɔː l,-oʊ l, ə ˈ t ɒ l,-ˈ t ɔː l,-ˈ t oʊ l /) [1] is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. [2] [3] Atolls are located in warm tropical or subtropical parts of the oceans
There are two types of lagoons, coastal and oceanic/atoll lagoons. [23] A coastal lagoon is, as the definition above, simply a body of water that is separated from the ocean by a barrier. An atoll lagoon is a circular coral reef or several coral islands that surround a lagoon. Atoll lagoons are often much deeper than coastal lagoons. [24]
The Amirante Islands (Les Amirantes) are a group of coral islands and atolls that belong to the Outer Islands of the Seychelles.. They stretch about 155 km from the African Banks (African Islands) in the north to Desnœufs (Isle des Noeufs) in the south, all on the shallow Amirantes Bank (Amirantes Plateau, with depths of mostly 25 to 70 m), except the main island Île Desroches in the east ...
As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef. Darwin's theory starts with a volcanic island which becomes extinct As the island and ocean floor subside, coral growth builds a fringing reef , often including a shallow lagoon between the land and the main reef.
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. [55] Many reefs result from natural, abiotic processes but there are also reefs such as the coral reefs of tropical waters formed by biotic processes dominated by corals and coralline algae.
The coral reefs of Tuvalu consist of three reef islands and six atolls, [1] containing approximately 710 km 2 (270 sq mi) of reef platforms. [2] The islands of the Tuvalu archipelago are spread out between the latitude of 5° to 10° south and longitude of 176° to 180°, west of the International Date Line. [1] The islands of Tuvalu are ...