Mid-Atlantic ridge - wikipedia Mid-Atlantic ridge A map of the Mid-Atlantic Ridge The Mid-Atlantic Ridge ( MAR ) is a mid-ocean ridge, a divergent tectonic plate 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 it separates the Eurasian and North American Plates, and 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. The section of the ridge that includes the island of Iceland is also known as the Reykjanes Ridge. The ridge has an average spreading rate of about 2.5 centimetres ( 0.98 in ) per year. Contents 1 Discovery 2 Notable features 3 Islands 4 Geology 5 See also 6 References 7 Bibliography 8 External links Discovery Pangaea 's separation animated A ridge under the Atlantic Ocean was first inferred by Matthew Fontaine Maury in 1850. The existence of the ridge was discovered 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 the Cape of Good Hope into the Indian Ocean by the German Meteor expedition. In the 1950s, mapping of the Earth 's ocean floors by Bruce Heezen, Maurice Ewing, Marie Tharp 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 - 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 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 In Iceland the Mid-Atlantic Ridge passes across the Þingvellir National Park, a popular destination for tourists The Mid-Atlantic Ridge includes a deep rift valley that runs along the axis of the ridge along 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 m ( at 71 ° 06 ′ N 08 ° 12 ′ W ﻿ / ﻿ 71.100 ° N 8.200 ° W ﻿ / 71.100 ; - 8.200 ), in the Arctic Ocean Iceland ( Hvannadalshnúkur in the Vatnajökull, 2109.6 m ( 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 m, ( 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 m, 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 m, at 07 ° 59 ′ S 14 ° 25 ′ W ﻿ / ﻿ 7.983 ° S 14.417 ° W ﻿ / - 7.983 ; - 14.417 ) Saint Helena ( Diana 's Peak, 818 m 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 m, at 37 ° 05 ′ S 12 ° 17 ′ W ﻿ / ﻿ 37.083 ° S 12.283 ° W ﻿ / - 37.083 ; - 12.283 ) Gough Island ( Edinburgh Peak, 909 m, at 40 ° 20 ′ S 10 ° 00 ′ W ﻿ / ﻿ 40.333 ° S 10.000 ° W ﻿ / - 40.333 ; - 10.000 ) Bouvet Island ( Olavtoppen, 780 m, at 54 ° 24 ′ S 03 ° 21 ′ E ﻿ / ﻿ 54.400 ° S 3.350 ° E ﻿ / - 54.400 ; 3.350 ) Geology. Basaltic rocks of the MAR collected by the Hercules ROV during the 2005 Lost City Expedition. For a general explanation of mid-oceanic ridges, see mid-oceanic ridge and seafloor spreading 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 Central Atlantic Magmatic Province Fifteen - Twenty Fracture Zone References Jump up ^ USGS ( 5 May 1999 ). `` Understanding plate motions ''. Retrieved 13 March 2011. Jump up ^ Hsü, Kenneth J. ( 1992 ). Challenger at Sea : A Ship That Revolutionized Earth Science. Princeton University Press. p. 57. ISBN 0 - 691 - 08735 - 0. Jump up ^ Redfern, R. ; 2001 : Origins, the Evolution of Continents, Oceans and Life, University of Oklahoma Press, ISBN 1 - 84188 - 192 - 9, p. 26 Jump up ^ Alexander Hellemans and Brian Bunch, 1989, Timeline of Science, Sidgwick and Jackson, London Jump up ^ Stein, Glenn, A Victory in Peace : The German Atlantic Expedition 1925 - 27, June 2007 Jump up ^ 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. Jump up ^ Heezen, B.C. ; Tharp, M. ( 1954 ). `` Physiographic diagram of the western North Atlantic ''. Bulletin of the Geological Society of America. 65 : 1261. Jump up ^ 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. doi : 10.1098 / rspa. 1954.0078. Jump up ^ Spencer, Edgar W. ( 1977 ). Introduction to the Structure of the Earth ( 2nd ed. ). Tokyo : McGraw - Hill. ISBN 0 - 07 - 085751 - 2. Jump up ^ 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. doi : 10.1086 / 627882. JSTOR 30070631. Jump up ^ Burke, K. ( 1976 ). `` Development of graben associated with the initial ruptures of the Atlantic Ocean ''. Tectonophysics. 36 ( 1 -- 3 ) : 93 -- 112. 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 Mid-ocean ridges Present Central Indian Chile East Pacific Explorer Gakkel Gorda Juan de Fuca Mid-Atlantic Pacific - Antarctic South American - Antarctic Southeast Indian Southwest Indian Former Aegir Alpha Kula - Farallon Pacific - Farallon Pacific - Kula Phoenix GND : 4039662 - 9 VIAF : 242531964 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Mid-Atlantic_Ridge&oldid=836998701 '' Categories : Underwater ridges of the Atlantic Ocean Geology of the Atlantic Ocean Plate tectonics Geology of Iceland Geology of Saint Helena, Ascension and Tristan da Cunha Geology of the Azores Hidden categories : Wikipedia articles with GND identifiers Wikipedia articles with VIAF identifiers Talk Contents About Wikipedia Asturianu Azərbaycanca Български Català Čeština Dansk Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Gaeilge Galego 한국어 Íslenska Italiano עברית ქართული Kiswahili Latviešu Lietuvių Magyar Bahasa Melayu Nederlands 日本 語 Нохчийн Norsk Norsk nynorsk Polski Português Română Русский Sicilianu Simple English Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Türkçe Українська Tiếng Việt 粵語 中文 39 more Edit links This page was last edited on 18 April 2018, at 03 : 23. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: what four major plates make up the floor of the atlantic ocean
Answer: Eurasian