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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 and seas where ...
Eventually the island completely subsides beneath the water, leaving a ring of growing coral with an open lagoon in its center. The process of atoll formation may take as long as 30,000,000 years to occur. Reason Not many people know what an atoll is. This is a simple explanation in a picture. Also, it is original. Articles this image appears ...
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 reefs , and atolls which are exposed to moderate wave energy. [ 1 ]
Reefs were formed by corals living in shallow depths of water. Darwin's theory set out a sequence of coral reef formation around an extinct volcanic island, becoming an atoll as the island and ocean floor subsided. Courtesy of the US Geological Survey. When the Beagle set out in 1831, the formation of coral atolls was a scientific puzzle.
Being a true atoll structure, it is believed that the atolls of Tubbataha were formed as fringing reefs and volcanic islands. This follows the classical Charles Darwin's theory that atolls are formed around an existing volcanic island. When the volcanoes became extinct and the islands subsided over a long time, only the corals remained which ...
The shelf usually ends at a point of increasing slope [3] (called the shelf break).The sea floor below the break is the continental slope. [4] Below the slope is the continental rise, which finally merges into the deep ocean floor, the abyssal plain. [5]
Objects in the water column can include structures from shipwrecks, dense biology, and bubble plumes. The importance of objects in the water column to marine geology is identifying specific features as bubble plumes can indicate the presence of hydrothermal vents and cold seeps. [13] There are limitations to this technique.
Conversely, an atoll is a ring reef with no land present. The reef front, facing the ocean, is a high energy locale. Whereas, the internal lagoon will be at a lower energy with fine grained sediments.