Mid-Atlantic Ridge


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Mid-Atlantic Ridge:

see Atlantic OceanAtlantic Ocean
[Lat.,=of Atlas], second largest ocean (c.31,800,000 sq mi/82,362,000 sq km; c.36,000,000 sq mi/93,240,000 sq km with marginal seas). Physical Geography
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Mid-Atlantic Ridge

 

the largest mountain system on the floor of the Atlantic Ocean, one of the links in the system of mid-oceanic ridges. The Mid-Atlantic Ridge is more than 18,000 km long and includes several smaller ridges. The Knipovich Ridge is situated in the basins of the Norwegian and Greenland seas, from 81° to 73° N lat. Mohns Ridge is located to the south, and the Jan Mayen Ridge even further south. The Reykjanes Ridge and the Northern Mid-Atlantic Ridge are south of Iceland, the former extending up to 52° N lat. The Southern Mid-Atlantic Ridge is situated south of the equator.

The transverse fractures of the Mid-Atlantic Ridge break the ridge into segments displaced by as much as 300–600 km from one another. Data from deepwater drilling, seismic profiling, and dredging done in the rift zone have shown that the geological cross section of the ridge is composed of two complexes: an upper complex consisting of tholeiite basalt with interlayers of carbonate sedimentary rocks, and a lower complex composed of am-phibolites and ophiolites (from anorthosites to ultrabasites). The rocks of the upper complex, which date to the Oligocene-Anthro-pogene, are broken into numerous blocks by young faults. The rocks of the lower complex, belonging to the Jurassic-Oligocene, are dislocated and metamorphosed regionally; the age of the ser-pentinized ultrabasites and gabbros that frequently occur in the metamorphic complex as flakes and protrusions may be Precam-brian. In the southern hemisphere the Mid-Atlantic Ridge is more monolithic; its slopes include a series of underwater volcanoes, some of whose peaks form islands (for example, Ascension Island and St. Helena). There is an active volcano in the Tristan da Cunha island group.

The meridional strike of the Mid-Atlantic Ridge changes to sublatitudinal near Bouvet Island (approximately 55° S lat.); the eastern segment is called the African-Antarctic Ridge.

REFERENCES

Hazen, B., M. Tarf, and M. Ewing. Dno Atlanticheskogo okeana. Moscow, 1962. (Translated from English.)
Leont’ev, O. K. Dno okeana. Moscow, 1968.
Il’in, A. V. “Osnovnye cherty geomorfologii dna Atlanticheskogo okeana.” In Usloviia sedimentatsii v Atlanticheskom okeane. Moscow, 1971.

O. K. LEONTEV

mid-Atlantic ridge

[‚mid·ət′lan·tik ′rij]
(geology)
The mid-oceanic ridge in the Atlantic.
References in periodicals archive ?
The Azores triple junction evolution since 10 Ma from an aeromagnetic survey of the Mid-Atlantic Ridge. Earth and Planetary Science Letters, 125(1-4), 439-459.
Douville et al., "Compared geochemical signatures and the evolution of Menez Gwen (35[degrees]50N) and Lucky Strike (37[degrees]17N) hydrothermal fluids, south of the Azores Triple Junction on the Mid-Atlantic Ridge," Chemical Geology, vol.
The South-Equatorial Mid-Atlantic Ridge Sector (SEMS) grouped a total of four superstations; the Tropical Mid-Atlantic Ridge Sector (TMS) grouped two of them, and the Walvis Ridge Sector (WRS) grouped other four.
Rimicaris was originally established for two species discovered from hydrothermally influenced vent field, TAG (Tans-Atlantic Geotraverse) on the MAR (Mid-Atlantic Ridge), Rimicaris exoculata Williams and Rona 1985 and R.
The relationships among relative symbiont density, relative availability of C[H.sub.4] and dissolved [H.sub.2]S, and carbon stable-isotopic compositions may prove to be relatively straightforward in mussels with dual symbionts on the Mid-Atlantic Ridge, and independent of the mussel species (Trask and Van Dover, 1999; Colaco et al., 2002; Fiala-Medioni et al., 2002).
The rock-climbing column was made to resemble the local five-sided basalt columns exposed by the Mid-Atlantic ridge, and introduces Nanoq to mall traffic.
Iceland sits astride the Mid-Atlantic Ridge where the Eurasian and North American tectonic plates meet.
He forecast the tunnel will reach a depth of 21/2 miles below the sea, and would need special construction techniques to cope with minor earth tremors around the Mid-Atlantic Ridge.
At a site known as TAG between the Kane and Atlantis fracture zones at 26 [degrees] North on the Mid-Atlantic Ridge, scientists have discovered a hydrothermal mound of massive sulphide deposits occupying an area 200 m in diameter and standing 40 m above the surrounding sea bed.
Peter Shaw, an associate scientist in the Department of Geology and Geophysics at Woods Hole Oceanographic Institution (Woods Hole, Mass.), has been mapping portions of the Mid-Atlantic Ridge in the Atlantic Ocean.
Wilson, "Detection of hydrothermal plumes on the northern Mid-Atlantic Ridge: Results from optical measurements," Earth and Planetary Science Letters, vol.
The other joint winner was Patrick O'Driscoll, who submitted Standard Definition video footage from the Kongsberg Maritime OE14-366 Colour Zoom Camera acquired using the Irish Marine Institute's ROV Holland 1 during the 2011 Venture expedition, which located a new mid-Atlantic ridge vent field to the North of the Azores in 3000m of water.

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