Editing Mid-Atlantic Ridge (section)

==Discovery==
[[Image:Pangea animation 03.gif|thumb|200px|[[Pangaea|Pangaea'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 (1836)|USS ''Dolphin'']]. The existence of the ridge and its extension into the South Atlantic was confirmed during the [[Challenger expedition|expedition of HMS ''Challenger'']] in 1872.<ref name="Searle_2013">{{Cite book |last=Searle |first=R. |title=Mid-Ocean Ridges |publisher=[[Cambridge University Press]] |year=2013 |url = https://books.google.com/books?id=VdSaAAAAQBAJ&q=%22Tizard%22+1876+map&pg=PA4|isbn=9781107017528 |pages=3–4}}</ref><ref>{{cite book|last1=Hsü|first1=Kenneth J.|title=Challenger at Sea: A Ship That Revolutionized Earth Science|date=1992|publisher=[[Princeton University Press]]|isbn=978-0-691-08735-1|page=57|url=https://books.google.com/books?id=ZlQABAAAQBAJ&pg=PA57}}</ref> 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]].<ref>Redfern, R.; 2001: ''Origins, the Evolution of Continents, Oceans and Life'', [[University of Oklahoma]] Press, {{ISBN|1-84188-192-9}}, p. 26</ref> The existence of such a ridge was confirmed by sonar in 1925<ref>Alexander Hellemans and Brian Bunch, 1989, ''Timeline of Science'', Sidgwick and Jackson, London</ref> and was found to extend around [[Cape Agulhas]] into the [[Indian Ocean]] by the [[German Meteor expedition]].<ref name=Stein>{{Cite web |url=http://ipy.arcticportal.org/ipy-blogs/item/831-a-victory-in-peace-the-german-atlantic-expedition-1925-27 |title=Stein, Glenn, ''A Victory in Peace: The German Atlantic Expedition 1925–27,'' June 2007 |access-date=2010-06-23 |archive-url=https://web.archive.org/web/20160309101405/http://ipy.arcticportal.org/ipy-blogs/item/831-a-victory-in-peace-the-german-atlantic-expedition-1925-27 |archive-date=2016-03-09 |url-status=dead }}</ref>

In the 1950s, [[seafloor mapping|mapping of the Earth's ocean floors]] by [[Marie Tharp]], [[Bruce C. Heezen|Bruce Heezen]], [[Maurice Ewing]], and others revealed that the Mid-Atlantic Ridge had a strange [[bathymetry]] of valleys and ridges,<ref>{{cite journal | last1 = Ewing | first1 = W.M. | author-link = Maurice Ewing | author-link4 = Bruce Heezen | last2 = Dorman | first2 = H.J. | last3 = Ericson | first3 = J.N. | last4 = Heezen | first4 = B.C. | year = 1953 | title = Exploration of the northwest Atlantic mid-ocean canyon | journal = [[Bulletin of the Geological Society of America]] | volume = 64 | issue = 7| pages = 865–868 | doi=10.1130/0016-7606(1953)64[865:eotnam]2.0.co;2}}</ref> with its central valley being [[seismology|seismologically]] active and the [[epicenter]] of many [[earthquake]]s.<ref>{{cite journal | last1 = Heezen | first1 = B. C. | author-link2 = Marie Tharp | last2 = Tharp | first2 = M. | year = 1954 | title = Physiographic diagram of the western North Atlantic | journal = [[Bulletin of the Geological Society of America]] | volume = 65 | page = 1261 }}</ref><ref>{{cite journal | last1 = Hill | first1 = M.N. | last2 = Laughton | first2 = A.S. | year = 1954 | title =  Seismic Observations in the Eastern Atlantic, 1952 | journal = Proceedings of the Royal Society of London A: Mathematical and Physical Sciences | volume = 222 | issue = 1150| pages = 348–356 | doi=10.1098/rspa.1954.0078| bibcode = 1954RSPSA.222..348H | s2cid = 140604584 }}</ref> Ewing, Heezen and Tharp discovered that the ridge is part of a {{convert|40,000|km|mi|abbr=on|adj=on}} long essentially continuous system of [[mid-ocean ridge]]s on the floors of all the Earth's oceans.<ref>{{cite book |first=Edgar W. |last=Spencer |year=1977 |title=Introduction to the Structure of the Earth |edition=2nd |publisher=McGraw-Hill |location=Tokyo |isbn=978-0-07-085751-3 |url=https://books.google.com/books?id=uAi0AAAAIAAJ }}</ref> 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 a feature whose contribution to the breakup of the [[supercontinent]] of [[Pangaea]], in the period from about 200 to 160 million years ago, is considered in the modelling of such breakup in modern tectonic theory, where subduction and mantle plumes mechanisms are hypothesised to be primary, although historically this was contentious.<ref>{{cite journal|last=Keppie|first=D.F.|year=2015|title=How the closure of paleo-Tethys and Tethys oceans controlled the early breakup of Pangaea|journal=Geology|volume=43|issue=4|pages=335–338|doi=10.1144/SP424.8|doi-access=free}}</ref><ref>{{cite journal|last1=Dang|first1=Z.|last2=Zhang|first2=N.|last3=Li|first3=Z.X.|last4=Yan|first4=P.|year=2023|title=Pangaea's breakup: the roles of mantle plumes, orogens and subduction retreat|journal=Geological Society, London, Special Publications| volume=542|issue=1|at=345|doi=10.1144/SP542-2022-345|bibcode=2023GSLSP.542..345D}}</ref>