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What is the Voyage of the Odyssey Track the Voyage Interactive Ocean Class from the Sea Patrick Stewart
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Atolls are found in the open sea. They are formed by a prolific group of animals called corals, which when concentrated in masses, form coral reefs. These reefs are formed during the slow sinking of an extinct volcano. Entering the water from the edge of a sandy white beach, one can swim in shallow water to the edge of the table reef which will then drop off directly into very deep water. In essence, the volcanic island is buried beneath the atoll.
Photo: Josh Jones

October 23, 2000
Formation of a Coral Atoll
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Log Transcript

This is Genevieve Johnson, talking to you from the Odyssey. Our present search for sperm whales takes the Odyssey around an area in the central pacific known as the Republic of Kiribas, which encompasses from west to east, the Gilbert, Phoenix and Line Island groups. Covering 3.5 million sq.km of ocean, Kiribas is made up of 1 raised coral island and 33 low lying coral atolls that straddle the equator. The warm waters of the equatorial pacific we are currently exploring, favor the growth of a prolific group of animals called corals. Tiny soft-bodied animals housed in limestone shelters of their own making, which when concentrated in masses, form coral reefs. Coral will only grow in clear, unpolluted, well-aerated shallow water, and as coral atolls are only found in open ocean, they are often surrounded by very deep water. So the question arises, how did these corals get a foothold in the Pacific? Since the beginning of our planets history, volcanic islands have risen from the sea floor and then disappeared beneath the waves. Once a volcano becomes extinct, it slowly subsides, dragging its fringing reef, a thin coral band formed along its coastline, downward into the water. The actively growing coral keeps pace with the subsidence, as it must to keep thriving in the upper sunlit waters, continuously building the reef upward and outward. Eventually a barrier reef forms, separated from the shoreline of the protruding volcanic peak or seamount. Continual erosion or an increase in sea level or both, ultimately cause the volcanic crest to be engulfed. A ring shaped coral reef or atoll is then left encircling a lagoon, providing the coral continues to grow. New coral polyps form on top of the skeletons of the previous generation, burying ancient corals, which in turn overlay an even older base of volcanic rock. In essence, the volcanic island is buried beneath the atoll. The atoll becomes a haven for animals, supporting one of the richest and most diverse ecosystems on the planet. The Odyssey crew is looking forward to exploring some of these remote atolls, with their abundance of thriving bird colonies and dazzling array of reef fishes.

Log by Genevieve Johnson

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