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 ?
Two new caridean shrimps (Bresiliidae) from a hydrothermal field on the Mid-Atlantic ridge.
However, in 1985, a large hydrothermal vent field was discovered on the Mid-Atlantic Ridge.
Retinal anatomy of Chorocaris chacei, a deep-sea hydrothermal vent shrimp from the Mid-Atlantic ridge.
The eyes of the bresiliid shrimp that live on the sides of black smoker chimneys at sites along the Mid-Atlantic Ridge have all enlarged (Chamberlain et al.
A cruise in 2005 will investigate a telltale area of high seismicity that we discovered 70 kilometers west of the Mid-Atlantic Ridge between 12.
Oceanographic Institution completed a 900-kilometer-long survey of the Mid-Atlantic Ridge in January.
OPUS was deployed using Alvin at black smoker chimneys on the Mid-Atlantic Ridge and the East Pacific Rise during four cruises between 1993 and 1997.
Several months before, scientists had discovered and collected these animals around underwater geysers that sporadically dot the surface of the mid-Atlantic ridge at depths of about 3.
01 A comparison of characteristics and chemical composition shows the distinct differences between seawater and hydrothermal vent fluid, in this case fluid from the TAG hydrothermal site on the Mid-Atlantic Ridge at 26 [degrees] N.
Researchers at the meeting also highlightedstudies of vents on the Mid-Atlantic Ridge, which spreads much more slowly than its Pacific cousins.
His research has focused on seismic studies of mid-ocean ridges, including the East Pacific Rise and the Mid-Atlantic Ridge.
The JOIDES Resolution, now in the middle of Leg 109, is currently deepening a hole started at the Mid-Atlantic Ridge during Leg 106 last fall.

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