The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North American from the Eurasian plate and the African plate, north and south of the Azores triple junction. In the South Atlantic, it separates the African and South American plates. The ridge extends from a junction with the Gakkel Ridge (Mid-Arctic Ridge) northeast of Greenland southward to the Bouvet triple junction in the South Atlantic. Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level, for example in Iceland. The ridge has an average spreading rate of about 2.5 centimetres (1 in) per year.
Discovery
A ridge under the northern Atlantic Ocean was first inferred by Matthew Fontaine Maury in 1853, based on soundings by the USS Dolphin. The existence of the ridge and its extension into the South Atlantic was confirmed during the expedition of HMS Challenger in 1872. A team of scientists on board, led by Charles Wyville Thomson, discovered a large rise in the middle of the Atlantic while investigating the future location for a transatlantic telegraph cable. The existence of such a ridge was confirmed by sonar in 1925 and was found to extend around Cape Agulhas into the Indian Ocean by the German Meteor expedition.
In the 1950s, mapping of the Earth's ocean floors by Marie Tharp, Bruce Heezen, Maurice Ewing, and others revealed that the Mid-Atlantic Ridge had a strange bathymetry of valleys and ridges, with its central valley being seismologically active and the epicenter of many earthquakes. Ewing, Heezen and Tharp discovered that the ridge is part of a 40,000-km (25,000 mile) long essentially continuous system of mid-ocean ridges on the floors of all the Earth's oceans. The discovery of this worldwide ridge system led to the theory of seafloor spreading and general acceptance of Alfred Wegener's theory of continental drift and expansion in the modified form of plate tectonics. The ridge is central to the breakup of the hypothetical supercontinent of Pangaea that began some 180 million years ago.
Notable features
The Mid-Atlantic Ridge includes a deep rift valley that runs along the axis of the ridge for nearly its entire length. This rift marks the actual boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava and producing new crustal material for the plates.
Near the equator, the Mid-Atlantic Ridge is divided into the North Atlantic Ridge and the South Atlantic Ridge by the Romanche Trench, a narrow submarine trench with a maximum depth of 7,758 m (25,453 ft), one of the deepest locations of the Atlantic Ocean. This trench, however, is not regarded as the boundary between the North and South American plates, nor the Eurasian and African plates.
Islands
The islands on or near the Mid-Atlantic Ridge, from north to south, with their respective highest peaks and location, are:
Northern Hemisphere (North Atlantic Ridge):
- Jan Mayen (Beerenberg, 2277 metres (7470') (at 71°06′N 08°12′W / 71.100°N 8.200°W), in the Arctic Ocean
- Iceland (Hvannadalshnúkur at Vatnajökull, 2109.6 metres (6921') (at 64°01′N 16°41′W / 64.017°N 16.683°W), through which the ridge runs
- Azores (Ponta do Pico or Pico Alto, on Pico Island, 2351 metres (7713'), (at 38°28′0″N 28°24′0″W / 38.46667°N 28.40000°W)
- Saint Peter and Paul Rocks (Southwest Rock, 22.5 metres (74'), at 00°55′08″N 29°20′35″W / 0.91889°N 29.34306°W)
Southern Hemisphere (South Atlantic Ridge):
- Ascension Island (The Peak, Green Mountain, 859 metres (2818'), at 07°59′S 14°25′W / 7.983°S 14.417°W)
- Saint Helena (Diana's Peak, 818 metres (2684') at 15°57′S 5°41′W / 15.950°S 5.683°W)
- Tristan da Cunha (Queen Mary's Peak, 2062 metres (6765'), at 37°05′S 12°17′W / 37.083°S 12.283°W)
- Gough Island (Edinburgh Peak, 909 metres (2982'), at 40°20′S 10°00′W / 40.333°S 10.000°W)
- Bouvet Island (Olavtoppen, 780 metres (2560'), at 54°24′S 03°21′E / 54.400°S 3.350°E)
Iceland
The submarine section of the Mid-Atlantic Ridge close to southwest Iceland is known as the Reykjanes Ridge. The Mid-Atlantic Ridge runs through Iceland where the ridge is also known as the Neovolcanic Zone. In northern Iceland the Tjörnes fracture zone connects Iceland to the Kolbeinsey Ridge.
Geology
The ridge sits atop a geologic feature known as the Mid-Atlantic Rise, which is a progressive bulge that runs the length of the Atlantic Ocean, with the ridge resting on the highest point of this linear bulge. This bulge is thought to be caused by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere. This divergent boundary first formed in the Triassic period, when a series of three-armed grabens coalesced on the supercontinent Pangaea to form the ridge. Usually, only two arms of any given three-armed graben become part of a divergent plate boundary. The failed arms are called aulacogens, and the aulacogens of the Mid-Atlantic Ridge eventually became many of the large river valleys seen along the Americas and Africa (including the Mississippi River, Amazon River and Niger River). The Fundy Basin on the Atlantic coast of North America between New Brunswick and Nova Scotia in Canada is evidence of the ancestral Mid-Atlantic Ridge.
See also
- Atlantis Massif
- Canadian Arctic Rift System
- Central Atlantic Magmatic Province
- Charlie–Gibbs fracture zone
- East Pacific Rise
- Fifteen-Twenty fracture zone
- Project FAMOUS
- Researcher Ridge
References
- "Understanding plate motions". United States Geological Survey. 5 May 1999. Retrieved 13 March 2011.
- Searle, R. (2013). Mid-Ocean Ridges. Cambridge University Press. pp. 3–4. ISBN 9781107017528.
- Hsü, Kenneth J. (1992). Challenger at Sea: A Ship That Revolutionized Earth Science. Princeton University Press. p. 57. ISBN 978-0-691-08735-1.
- Redfern, R.; 2001: Origins, the Evolution of Continents, Oceans and Life, University of Oklahoma Press, ISBN 1-84188-192-9, p. 26
- Alexander Hellemans and Brian Bunch, 1989, Timeline of Science, Sidgwick and Jackson, London
- "Stein, Glenn, A Victory in Peace: The German Atlantic Expedition 1925–27, June 2007". Archived from the original on 2016-03-09. Retrieved 2010-06-23.
- Ewing, W.M.; Dorman, H.J.; Ericson, J.N.; Heezen, B.C. (1953). "Exploration of the northwest Atlantic mid-ocean canyon". Bulletin of the Geological Society of America. 64 (7): 865–868. doi:10.1130/0016-7606(1953)64[865:eotnam]2.0.co;2.
- Heezen, B. C.; Tharp, M. (1954). "Physiographic diagram of the western North Atlantic". Bulletin of the Geological Society of America. 65: 1261.
- Hill, M.N.; Laughton, A.S. (1954). "Seismic Observations in the Eastern Atlantic, 1952". Proceedings of the Royal Society of London A: Mathematical and Physical Sciences. 222 (1150): 348–356. Bibcode:1954RSPSA.222..348H. doi:10.1098/rspa.1954.0078. S2CID 140604584.
- Spencer, Edgar W. (1977). Introduction to the Structure of the Earth (2nd ed.). Tokyo: McGraw-Hill. ISBN 978-0-07-085751-3.
- General citations for named fracture zones are at page Wikipedia:Map data/Fracture zone and specific citations are in interactive detail.
- Burke, K.; Dewey, J. F. (1973). "Plume-generated triple junctions: key indicators in applying plate tectonics to old rocks" (PDF). The Journal of Geology. 81 (4): 406–433. Bibcode:1973JG.....81..406B. doi:10.1086/627882. JSTOR 30070631. S2CID 53392107. Archived from the original (PDF) on 2016-10-23. Retrieved 2022-02-26.
- Burke, K. (1976). "Development of graben associated with the initial ruptures of the Atlantic Ocean". Tectonophysics. 36 (1–3): 93–112. Bibcode:1976Tectp..36...93B. CiteSeerX 10.1.1.473.8997. doi:10.1016/0040-1951(76)90009-3.
Bibliography
- Evans, Rachel. "Plumbing Depths to Reach New Heights: Marie Tharp Explains Marine Geological Maps." The Library of Congress Information Bulletin. November 2002.
External links
- MAR-ECO, a Census of Marine Life project on life along the Mid-Atlantic Ridge Archived 2015-04-02 at the Wayback Machine
The Mid Atlantic Ridge is a mid ocean ridge a divergent or constructive plate boundary located along the floor of the Atlantic Ocean and part of the longest mountain range in the world In the North Atlantic the ridge separates the North American from the Eurasian plate and the African plate north and south of the Azores triple junction In the South Atlantic it separates the African and South American plates The ridge extends from a junction with the Gakkel Ridge Mid Arctic Ridge northeast of Greenland southward to the Bouvet triple junction in the South Atlantic Although the Mid Atlantic Ridge is mostly an underwater feature portions of it have enough elevation to extend above sea level for example in Iceland The ridge has an average spreading rate of about 2 5 centimetres 1 in per year A bathymetric map of the Mid Atlantic Ridge shown in light blue in the middle of the Atlantic Ocean DiscoveryPangaea s separation animated A ridge under the northern Atlantic Ocean was first inferred by Matthew Fontaine Maury in 1853 based on soundings by the USS Dolphin The existence of the ridge and its extension into the South Atlantic was confirmed during the expedition of HMS Challenger in 1872 A team of scientists on board led by Charles Wyville Thomson discovered a large rise in the middle of the Atlantic while investigating the future location for a transatlantic telegraph cable The existence of such a ridge was confirmed by sonar in 1925 and was found to extend around Cape Agulhas into the Indian Ocean by the German Meteor expedition In the 1950s mapping of the Earth s ocean floors by Marie Tharp Bruce Heezen Maurice Ewing and others revealed that the Mid Atlantic Ridge had a strange bathymetry of valleys and ridges with its central valley being seismologically active and the epicenter of many earthquakes Ewing Heezen and Tharp discovered that the ridge is part of a 40 000 km 25 000 mile long essentially continuous system of mid ocean ridges on the floors of all the Earth s oceans The discovery of this worldwide ridge system led to the theory of seafloor spreading and general acceptance of Alfred Wegener s theory of continental drift and expansion in the modified form of plate tectonics The ridge is central to the breakup of the hypothetical supercontinent of Pangaea that began some 180 million years ago Notable featuresIn Iceland the Mid Atlantic Ridge passes across the THingvellir National Park a popular destination for tourists The Mid Atlantic Ridge includes a deep rift valley that runs along the axis of the ridge for nearly its entire length This rift marks the actual boundary between adjacent tectonic plates where magma from the mantle reaches the seafloor erupting as lava and producing new crustal material for the plates Near the equator the Mid Atlantic Ridge is divided into the North Atlantic Ridge and the South Atlantic Ridge by the Romanche Trench a narrow submarine trench with a maximum depth of 7 758 m 25 453 ft one of the deepest locations of the Atlantic Ocean This trench however is not regarded as the boundary between the North and South American plates nor the Eurasian and African plates IslandsApproximate surface projection on Atlantic Ocean of Mid Atlantic Ridge purple Associated fracture zones orange are also shown Click to expand map to obtain interactive details The islands on or near the Mid Atlantic Ridge from north to south with their respective highest peaks and location are Northern Hemisphere North Atlantic Ridge Jan Mayen Beerenberg 2277 metres 7470 at 71 06 N 08 12 W 71 100 N 8 200 W 71 100 8 200 in the Arctic Ocean Iceland Hvannadalshnukur at Vatnajokull 2109 6 metres 6921 at 64 01 N 16 41 W 64 017 N 16 683 W 64 017 16 683 through which the ridge runs Azores Ponta do Pico or Pico Alto on Pico Island 2351 metres 7713 at 38 28 0 N 28 24 0 W 38 46667 N 28 40000 W 38 46667 28 40000 Saint Peter and Paul Rocks Southwest Rock 22 5 metres 74 at 00 55 08 N 29 20 35 W 0 91889 N 29 34306 W 0 91889 29 34306 Southern Hemisphere South Atlantic Ridge Ascension Island The Peak Green Mountain 859 metres 2818 at 07 59 S 14 25 W 7 983 S 14 417 W 7 983 14 417 Saint Helena Diana s Peak 818 metres 2684 at 15 57 S 5 41 W 15 950 S 5 683 W 15 950 5 683 Tristan da Cunha Queen Mary s Peak 2062 metres 6765 at 37 05 S 12 17 W 37 083 S 12 283 W 37 083 12 283 Gough Island Edinburgh Peak 909 metres 2982 at 40 20 S 10 00 W 40 333 S 10 000 W 40 333 10 000 Bouvet Island Olavtoppen 780 metres 2560 at 54 24 S 03 21 E 54 400 S 3 350 E 54 400 3 350 Iceland The submarine section of the Mid Atlantic Ridge close to southwest Iceland is known as the Reykjanes Ridge The Mid Atlantic Ridge runs through Iceland where the ridge is also known as the Neovolcanic Zone In northern Iceland the Tjornes fracture zone connects Iceland to the Kolbeinsey Ridge GeologyBasaltic rocks of the Mid Atlantic Ridge observed by the Hercules ROV during the 2005 Lost City Expedition The ridge sits atop a geologic feature known as the Mid Atlantic Rise which is a progressive bulge that runs the length of the Atlantic Ocean with the ridge resting on the highest point of this linear bulge This bulge is thought to be caused by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere This divergent boundary first formed in the Triassic period when a series of three armed grabens coalesced on the supercontinent Pangaea to form the ridge Usually only two arms of any given three armed graben become part of a divergent plate boundary The failed arms are called aulacogens and the aulacogens of the Mid Atlantic Ridge eventually became many of the large river valleys seen along the Americas and Africa including the Mississippi River Amazon River and Niger River The Fundy Basin on the Atlantic coast of North America between New Brunswick and Nova Scotia in Canada is evidence of the ancestral Mid Atlantic Ridge See alsoVolcanoes portalGeography portalAtlantis Massif Canadian Arctic Rift System Central Atlantic Magmatic Province Charlie Gibbs fracture zone East Pacific Rise Fifteen Twenty fracture zone Project FAMOUS Researcher RidgeReferences Understanding plate motions United States Geological Survey 5 May 1999 Retrieved 13 March 2011 Searle R 2013 Mid Ocean Ridges Cambridge University Press pp 3 4 ISBN 9781107017528 Hsu Kenneth J 1992 Challenger at Sea A Ship That Revolutionized Earth Science Princeton University Press p 57 ISBN 978 0 691 08735 1 Redfern R 2001 Origins the Evolution of Continents Oceans and Life University of Oklahoma Press ISBN 1 84188 192 9 p 26 Alexander Hellemans and Brian Bunch 1989 Timeline of Science Sidgwick and Jackson London Stein Glenn A Victory in Peace The German Atlantic Expedition 1925 27 June 2007 Archived from the original on 2016 03 09 Retrieved 2010 06 23 Ewing W M Dorman H J Ericson J N Heezen B C 1953 Exploration of the northwest Atlantic mid ocean canyon Bulletin of the Geological Society of America 64 7 865 868 doi 10 1130 0016 7606 1953 64 865 eotnam 2 0 co 2 Heezen B C Tharp M 1954 Physiographic diagram of the western North Atlantic Bulletin of the Geological Society of America 65 1261 Hill M N Laughton A S 1954 Seismic Observations in the Eastern Atlantic 1952 Proceedings of the Royal Society of London A Mathematical and Physical Sciences 222 1150 348 356 Bibcode 1954RSPSA 222 348H doi 10 1098 rspa 1954 0078 S2CID 140604584 Spencer Edgar W 1977 Introduction to the Structure of the Earth 2nd ed Tokyo McGraw Hill ISBN 978 0 07 085751 3 General citations for named fracture zones are at page Wikipedia Map data Fracture zone and specific citations are in interactive detail Burke K Dewey J F 1973 Plume generated triple junctions key indicators in applying plate tectonics to old rocks PDF The Journal of Geology 81 4 406 433 Bibcode 1973JG 81 406B doi 10 1086 627882 JSTOR 30070631 S2CID 53392107 Archived from the original PDF on 2016 10 23 Retrieved 2022 02 26 Burke K 1976 Development of graben associated with the initial ruptures of the Atlantic Ocean Tectonophysics 36 1 3 93 112 Bibcode 1976Tectp 36 93B CiteSeerX 10 1 1 473 8997 doi 10 1016 0040 1951 76 90009 3 BibliographyEvans Rachel Plumbing Depths to Reach New Heights Marie Tharp Explains Marine Geological Maps The Library of Congress Information Bulletin November 2002 External linksWikimedia Commons has media related to Mid Atlantic Ridge MAR ECO a Census of Marine Life project on life along the Mid Atlantic Ridge Archived 2015 04 02 at the Wayback Machine
