Mid-Atlantic Ridge


Mid-Atlantic Ridge
/mid"at lan"tik, mid'at lan"-/
a north-south suboceanic ridge in the Atlantic Ocean from Iceland to Antarctica on whose crest are several groups of islands; shown by plate tectonics to be the axis along which North America has split away from Eurasia, and along which South America has split away from Africa.

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Submarine ridge lying along the floor of the central Atlantic Ocean.

It is a long mountain chain running about 10,000 mi (16,000 km) in a north-south direction, curving from the Arctic Ocean to the southern tip of Africa. The mountains sometimes reach above sea level, forming such islands or island groups as Ascension, Saint Helena, and Tristan da Cunha.

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      submarine ridge lying along the north-south axis of the Atlantic Ocean; it occupies the central part of the basin between a series of flat abyssal plains that continue to the margins of the continental coasts. The Mid-Atlantic Ridge is in effect an immensely long mountain chain extending for about 10,000 miles (16,000 km) in a curving path from the Arctic Ocean to near the southern tip of Africa. The ridge is equidistant between the continents on either side of it. The mountains forming the ridge reach a width of 1,000 miles. These mountains sometimes reach above sea level, thus forming the islands or island groups of the Azores, Ascension, St. Helena, and Tristan da Cunha, among others.

      The Mid-Atlantic Ridge is located at the juncture of crustal plates that form the floor of the Atlantic Ocean; it is considered a "slow-spreading" ridge by earth scientists. Running along the crest of the ridge is a long valley that is about 50 to 75 miles (80 to 120 km) wide. This rift contains the zone of seafloor spreading, in which molten magma from beneath the Earth's crust continuously wells up, cools, and is progressively pushed away from the ridge's flanks. This phenomenon is evinced by the fact that the crustal material on either side of the Mid-Atlantic Ridge is notably younger than that farther away from the ridge. Because of seafloor spreading and the movement of the ocean floor and of the continents outward from the ridge, the Atlantic Basin is widening at an estimated rate of 1 to 10 cm (0.5 to 4 inches) a year. Apart from seafloor spreading, the Mid-Atlantic Ridge is also the site of volcanic activity and earthquakes along some portions of its length. Scientific research on the ridge and its geological and biological characteristics, although at an early stage, has revealed a number of active hydrothermal fields that tend to be larger than active sites at other mid-ocean ridges and appear to exhibit periodic hydrothermal activity (release of vent fluids).

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Universalium. 2010.

Look at other dictionaries:

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  • Mid-Atlantic Ridge — Mid′ Atlan′tic Ridge′ n. oce a north south suboceanic ridge in the Atlantic Ocean from Iceland to Antarctica on whose crest are several groups of islands …   From formal English to slang

  • Mid-Atlantic Ridge — noun a very long narrow elevation on the ocean floor that runs all the way from Iceland in the North Atlantic to Bouvet Island in the South Atlantic • Instance Hypernyms: ↑ridge • Part Holonyms: ↑Atlantic, ↑Atlantic Ocean …   Useful english dictionary

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  • Mid-Indian Ridge — ▪ ridge, Indian Ocean       submarine ridge of the Indian Ocean that is a direct continuance of the Mid Atlantic Ridge; both are segments of the worldwide midoceanic ridge system. Entering the Indian Ocean from the South Atlantic, the Mid Indian… …   Universalium

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  • mid-ocean ridge — /mid oh sheuhn/ any of several seismically active submarine mountain ranges that extend through the Atlantic, Indian, and South Pacific oceans: each is hypothesized to be the locus of seafloor spreading. [1960 65] * * * mid ocean ridge noun… …   Useful english dictionary

  • mid-oceanic ridge — [mid ō′shənmid ō΄shē an′ik] n. the continuous, double ridged chain of mountains on the ocean floor, extending through the middle of the Atlantic Ocean and into the Indian and Pacific oceans: also called mid ocean ridge [mid ō′shən] * * * …   Universalium

  • mid-oceanic ridge — [mid ō′shənmid ō΄shē an′ik] n. the continuous, double ridged chain of mountains on the ocean floor, extending through the middle of the Atlantic Ocean and into the Indian and Pacific oceans: also called mid ocean ridge [mid ō′shən] …   English World dictionary

  • mid-ocean ridge — /mid oh sheuhn/ any of several seismically active submarine mountain ranges that extend through the Atlantic, Indian, and South Pacific oceans: each is hypothesized to be the locus of seafloor spreading. [1960 65] * * * …   Universalium


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