Continental drift: Difference between revisions
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{{About|the development of the continental drift hypothesis before 1958|the contemporary theory|plate tectonics}} |
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[[File:Antonio Snider-Pellegrini Opening of the Atlantic.jpg|thumb|300px|Antonio Snider-Pellegrini's Illustration of the closed and opened Atlantic Ocean (1858).]] |
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'''Continental drift''' is the movement of the [[Earth]]'s [[continents]] relative to each other by drifting across the ocean bed.<ref name=usghistory>[http://pubs.usgs.gov/gip/dynamic/historical.html USGS: Historical perspective on plate tectonics, last updated 19 September 2011]</ref> The speculation that continents might have 'drifted' was first put forward by [[Abraham Ortelius]] in 1596. The concept was independently (and more fully) developed by [[Alfred Wegener]] in 1912. The theory of continental drift was superseded by the theory of [[plate tectonics]]. |
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==History== |
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{{Further|Timeline of the development of tectonophysics}} |
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===Early history=== |
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[[Abraham Ortelius]] {{Harv|Ortelius|1596}},<ref>{{Citation |last=Romm |first=James |title=A New Forerunner for Continental Drift |journal=Nature |date=February 3, 1994 |volume=367 |pages=407–408 |doi=10.1038/367407a0 |postscript=. |issue=6462}}</ref> Theodor Christoph Lilienthal (1756),<ref name=schmeling2004 >{{Cite web |first=Harro |last=Schmeling |url=http://www.geophysik.uni-frankfurt.de/~schmelin/skripte/Geodynn1-kap1-2-S1-S22-2004.pdf |title=Geodynamik |year=2004 |publisher=University of Frankfurt |language=German }}</ref> [[Alexander von Humboldt]] (1801 and 1845),<ref name=schmeling2004 /> [[Antonio Snider-Pellegrini]] {{Harv|Snider-Pellegrini|1858}}, and others had noted earlier that the shapes of [[continent]]s on opposite sides of the [[Atlantic Ocean]] (most notably, Africa and South America) seem to fit together.<ref>{{Citation |url=http://www.lib.uchicago.edu/e/crerar/crerar-prize/2003%2004%20Brusatte.pdf |title=Continents Adrift and Sea-Floors Spreading: The Revolution of Plate Tectonics |first=Stephen |last=Brusatte}}</ref> W. J. Kious described Ortelius' thoughts in this way:<ref>{{Citation |last=Kious |first=W.J. |coauthors=Tilling, R.I. |title=This Dynamic Earth: the Story of Plate Tectonics |origyeacontijntental to dwod somothin r=1996 |url=http://pubs.usgs.gov/gip/dynamic/dynamic.html |accessdate=2008-01-29 |edition=Online |publisher=U.S. Geological Survey |isbn=01hj n rgrjhguitghtigu60482208 |chapter=Historical perspective |chapterurl=http://pubs.usgs.gov/gip/dynamic/historical.html |year=2001 |month=February}}</ref> |
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{{quote|Abraham Ortelius in his work Thesaurus Geographicus ... suggested that the Americas were "torn away from Europe and Africa ... by earthquakes and floods" and went on to say: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents]."}} |
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Writing in 1889, [[Alfred Russel Wallace]] remarks "It was formerly a very general belief, even amongst geologists, that the great features of the earth's surface, no less than the smaller ones, were subject to continual mutations, and that during the course of known geological time the continents and great oceans had again and again changed places with each other."<ref> |
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{{citation|first=Alfred Russel|last=Wallace|title=Darwinism|year=1889|publisher=Macmillan}} |
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</ref> He quotes [[Charles Lyell]] as saying "Continents, therefore, although permanent for whole geological epochs, shift their positions entirely in the course of ages"<ref> |
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{{citation|first=Charles|last=Lyell|title=Principles of Geology|year=1872|edition=11|publisher=John Murray}} |
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</ref> and claims that the first to throw doubt on this was [[James D. Dana]] in 1849. |
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In his ''Manual of Geology'', 1863, Dana says "The continents and oceans had their general outline or form defined in earliest time. This has been proved with respect to North America from the position and distribution of the first beds of the Silurian - those of the Potsdam epoch - and this will probably prove to the case in Primordial time with the other continents also".<ref> |
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{{citation|first=James D.|last=Dana|title=Manual of Geology|year=1863|publisher=Theodore Bliss & Co, Philadelphia}} |
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</ref> Dana was enormously influential in America - his ''Manual of Mineralogy'' is still in print in revised form - and the theory became known as ''Permanence theory''.<ref> |
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{{citation|first=Naomi|last=Oreskes|title=Continental Drift|year=2002|url=http://historyweb.ucsd.edu/oreskes/Papers/Continentaldrift2002.pdf}} |
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</ref> |
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=== Wegener and his predecessors === |
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[[File:Alfred Wegener 1910.jpg|thumb|140px|Alfred Wegener]] |
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The hypothesis that the continents had once formed [[Pangea|a single landmass]] before breaking apart and drifting to their present locations was first presented by [[Alfred Wegener]] to the German Geological Society on 6 January 1912.<ref name=weg>{{Citation |
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|last= Wegener|first= Alfred |coauthors= |date= 6 January 1912 |title= Die Herausbildung der Grossformen der Erdrinde (Kontinente und Ozeane), auf geophysikalischer Grundlage |journal= Petermanns Geographische Mitteilungen |volume= 63 |issue= |pages= 185–195, 253–256, 305–309 |url= http://epic.awi.de/Publications/Polarforsch2005_1_3.pdf |accessdate= |doi = |
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|postscript= . }}</ref> |
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Although Wegener's theory was formed independently and was more complete than those of his predecessors, Wegener later credited a number of past authors with similar ideas:<ref name=wegb>{{Citation | author=Wegener, A. | title = The Origin of Continents and Oceans | year=1929/1966 |publisher=Courier Dover Publications|isbn=0-486-61708-4}}</ref><ref>{{Citation | author=Wegener, A. | title = [[:s:de:Die Entstehung der Kontinente und Ozeane|Die Entstehung der Kontinente und Ozeane]]|edition= 4 | year=1929 |publisher=Friedrich Vieweg & Sohn Akt. Ges.| place=Braunschweig}}</ref> |
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Franklin Coxworthy (between 1848 and 1890),<ref>{{Citation | author=Coxworthy, F.| title = Electrical Condition or How and Where our Earth was created | place=London | publisher=W. J. S. Phillips| year=1848/1924 | url=http://www.dcd.zju.edu.cn/cgi-bin/udlcgi/ulibreader_iisc/bookReader.cgi?barcode=99999991946789&format=ptiff&curPage=1}}</ref> |
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[[Roberto Mantovani]] (between 1889 and 1909), [[William Henry Pickering]] (1907)<ref>{{Citation | author=Pickering, W.H| title = The Place of Origin of the Moon - The Volcani Problems | journal= Popular Astronomy | pages=274–287| year=1907 | bibcode=1907PA.....15..274P}}</ref> |
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and [[Frank Bursley Taylor]] (1908). [[Eduard Suess]] had proposed a supercontinent [[Gondwana]] in 1858 and the [[Tethys Ocean]] in 1893, from a sunken [[Land_bridge#Land_bridge_theory|land-bridge]]/ [[geosyncline theory]] point-of-view, though. [[John Perry (engineer)|John Perry]] had written an 1895 paper proposing that the earth's interior was fluid, and disagreeing with [[Lord Kelvin]] on the age of the earth. |
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For example: the similarity of southern continent geological formations had led [[Roberto Mantovani]] to conjecture in 1889 and 1909 that all the continents had once been joined into a [[supercontinent]] (now known as [[Pangaea]]); Wegener noted the similarity of Mantovani's and his own maps of the former positions of the southern continents. Through [[Volcanism|volcanic]] activity due to [[thermal expansion]] this continent broke and the new continents drifted away from each other because of further expansion of the rip-zones, where the oceans now lie. This led Mantovani to propose an [[Expanding Earth theory]] which has since been shown to be incorrect.<ref>{{Citation | author=Mantovani, R.| author-link =| title = Les fractures de l’écorce terrestre et la théorie de Laplace | journal= Bull. Soc. Sc. Et Arts Réunion | pages=41–53| year=1889}}</ref><ref>{{Citation | author=Mantovani, R.| title = L’Antarctide |journal= Je m’instruis. La science pour tous |volume=38 | pages=595–597| year=1909}}</ref><ref>{{Citation | author=Scalera, G. | contribution =Roberto Mantovani an Italian defender of the continental drift and planetary expansion | contribution-url=http://hdl.handle.net/2122/2017 | editor=Scalera, G. and Jacob, K.-H. |title =Why expanding Earth? – A book in honour of O.C. Hilgenberg | year=2003 | place=Rome | publisher= Istituto Nazionale di Geofisica e Vulcanologia |pages= 71–74}}</ref> |
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Some sort of continental drift without expansion was proposed by [[Frank Bursley Taylor]], who suggested in 1908 (published in 1910) that the continents were dragged towards the equator by increased lunar gravity during the [[Cretaceous]], thus forming the Himalayas and Alps on the southern faces. Wegener said that of all those theories, Taylor's, although not fully developed, had the most similarities to his own.<ref>{{Citation | author=Taylor, F.B. | title = Bearing of the tertiary mountain belt on the origin of the earth's plan | journal= GSA Bulletin | volume=21 |issue=2| pages=179–226| year=1910 | doi=10.1130/1052-5173(2005)015[29b:WTCCA]2.0.CO;2 | url=http://www.gsajournals.org/perlserv/?request=get-document&doi=10.1130%2F1052-5173(2005)015%5B29b%3AWTCCA%5D2.0.CO%3B2}}</ref> |
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Wegener was the first to use the phrase "continental drift" (1912, 1915)<ref name=weg /><ref name=wegb /> (in German "die Verschiebung der Kontinente" – translated into English in 1922) and formally publish the hypothesis that the continents had somehow "drifted" apart. Although he presented much evidence for continental drift, he was unable to provide a convincing explanation for the physical processes which might have caused this drift. His suggestion that the continents had been pulled apart by the [[Centrifugal force (fictitious)|centrifugal pseudoforce]] (''Polflucht'') of the Earth's rotation or by a small component of astronomical [[precession]] was rejected as calculations showed that the force was not sufficient.<ref>{{cite web |url=http://www.ucmp.berkeley.edu/geology/techist.html |title=Plate Tectonics: The Rocky History of an Idea |quote=Wegener's inability to provide an adequate explanation of the forces responsible for continental drift and the prevailing belief that the earth was solid and immovable resulted in the scientific dismissal of his theories.}}</ref> The [[Polflucht]] hypothesis was also studied by [[Paul Sophus Epstein]] in 1920 and found to be implausible. |
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FROG BLAST THE VENT CORE |
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==Rejection of Wegener's theory, and subsequent vindication== |
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The theory of continental drift was not accepted for many years. One problem was that a plausible driving force was missing.<ref name=usghistory/> And it did not help that Wegener was not a geologist. It is now accepted that the plates carrying the continents do move across the Earth's surface; ironically one of the chief outstanding questions is the one Wegener failed to resolve: what is the nature of the forces propelling the plates?<ref name=usghistory/> |
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The British geologist [[Arthur Holmes]] championed the theory of continental drift at a time when it was deeply unfashionable. He proposed that the Earth's mantle contained convection cells that dissipated radioactive heat and moved the crust at the surface. His ''Principles of Physical Geology'', ending with a chapter on continental drift, was published in 1944.<ref>{{Cite book |last=Holmes |first=Arthur |title=Principles of Physical Geology |edition=1 |place=Edinburgh |publisher=Thomas Nelson & Sons |year=1944 |isbn=0-17-448020-2 }}</ref> |
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As late as 1953 – just five years before [[Samuel Warren Carey|Carey]]<ref>{{Citation |
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|last1=Carey |first1=S. W. |year=1958 |contribution=The tectonic approach to continental drift |editor1-last=Carey |editor1-first=S. W. |title=Continental Drift—A symposium |publisher=Univ. of Tasmania |place=Hobart |pages=177–363}}</ref> introduced the theory of [[plate tectonics]] – the theory of continental drift was rejected by the physicist Scheiddiger on the following grounds.<ref>{{citation|last= Scheidegger|first= |title= Examination of the physics of theories of orogenesis|journal= GSA Bulletin|year= 1953|volume= 64|pages= 127–150|doi= 10.1130/0016-7606(1953)64[127:EOTPOT]2.0.CO;2|first1= Adrian E.}}</ref> |
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[[Image:Pangea animation 03.gif|thumb|Simplified animation of the break-up of [[Pangaea]] and the formation of modern continents.]] |
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* First, it had been shown that floating masses on a rotating geoid would collect at the equator, and stay there. This would explain one, but only one, mountain building episode between any pair of continents; it failed to account for earlier orogenic episodes. |
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* Second, masses floating freely in a fluid substratum, like icebergs in the ocean, should be in [[isostatic]] equilibrium (where the forces of gravity and buoyancy are in balance). Gravitational measurements were showing that many areas are not in isostatic equilibrium. |
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* Third, there was the problem of why some parts of the Earth's surface (crust) should have solidifed while other parts were still fluid. Various attempts to explain this foundered on other difficulties. |
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Geophysicist [[Jack Oliver (scientist)|Jack Oliver]] is credited with providing seismologic evidence supporting plate tectonics which encompassed and superseded continental drift with “Seismology and the New Global Tectonics,” published in 1968, using data collected from seismologic stations, including those he set up in the South Pacific.<ref>[http://www.nytimes.com/2011/01/12/science/earth/12oliver.html?ref=science Jack Oliver, Who Proved Continental Drift, Dies at 87, New York Times on-line, January 12, 2011]</ref> |
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It is now known that there are two kinds of crust, [[continental crust]] and [[oceanic crust]]. Continental crust is inherently lighter and of a different composition to oceanic crust, but both kinds reside above a much deeper fluid mantle. Oceanic crust is created at [[Seafloor spreading|spreading centers]], and this, along with [[subduction]], drives the system of plates in a chaotic manner, resulting in continuous [[orogeny]] and areas of isostatic imbalance. The theory of [[plate tectonics]] explains all this, including the movement of the continents, better than Wegener's theory. |
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==Bibliography== |
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'''Notes''': |
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{{Reflist|2}} |
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'''References''': |
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* {{Citation |last=Le Grand |first=Homer Eugene |authorlink= |title=Drifting Continents and Shifting Theories |edition= |year=1988 |publisher=Cambridge University |isbn=0-521-31105-5 }} |
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* {{Citation|first=Naomi|last=Oreskes|title=The Rejection of Continental Drift|publisher=Oxford University Press|year=1999|isbn= 0-19-511732-8|url=http://books.google.co.uk/books?id=EEQdk9GRfkoC&pg=PA14}}, (pb: {{ISBNT| 0-19-511733-6}}). |
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* {{Citation |last=Ortelius |first=Abraham |title=Thesaurus Geographicus |place=Antwerp |publisher=Plantin |year=1596 |language=Latin |edition=3 |ref=CITEREFOrtelius1596 |oclc=214324616 }} (First edition published 1570, [http://books.google.ca/books?id=YG1EAAAAcAAJ&dq=%22Thesaurus%20Geographicus%22&pg=PR4#v=onepage&q&f=false 1587 edition online]) |
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* {{Citation |title=La Création et ses mystères dévoilés |publisher=Frank and Dentu |place=Paris |first=Antonio |last=Snider-Pellegrini |year=1858 |ref=CITEREFSnider-Pellegrini1858 |url=http://books.google.ca/books?id=UZdKmF3iEdUC&dq=%22Cr%C3%A9ation%20et%20ses%20Myst%C3%A8res%20D%C3%A9voil%C3%A9s%22&pg=PA314-IA3#v=onepage&q=continent&f=false}} |
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==External links== |
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*[http://www.ux1.eiu.edu/~cfjps/1300/cont_drift.html A brief introduction to Plate Tectonics, based on the work of Alfred Wegener.] |
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*[http://www.scotese.com/earth.htm Maps of continental drift, from the Precambrian to the future] |
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*[http://kids.earth.nasa.gov/archive/pangaea/evidence.html Four main evidences of the Continental Drift theory] |
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*[http://www.bbm.me.uk/portsdown/PH_061_History_b.htm Wegener and his proofs] |
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{{DEFAULTSORT:Continental Drift}} |
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[[Category:Plate tectonics]] |
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[[Category:Geological history of Earth]] |
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{{Link GA|eo}} |
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[[ar:نظرية الانجراف القاري]] |
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[[bn:মহাদেশীয় প্রবাহ]] |
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[[bg:Континентален дрейф]] |
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[[br:Dilec'hiadur ar c'hevandiroù]] |
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[[ca:Deriva dels continents]] |
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[[cs:Kontinentální drift]] |
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[[da:Kontinentaldrift]] |
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[[de:Kontinentaldrift]] |
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[[et:Mandrite triiv]] |
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[[el:Μετατόπιση των ηπείρων]] |
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[[es:Deriva continental]] |
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[[eo:Kontinenta drivo]] |
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[[eu:Kontinenteen jitoa]] |
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[[fo:Meginlandarák]] |
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[[gl:Deriva continental]] |
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[[ko:대륙 이동설]] |
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[[hr:Pomicanje kontinenata]] |
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[[id:Pergeseran Benua]] |
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[[it:Deriva dei continenti]] |
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[[he:נדידת היבשות]] |
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[[kk:Вегенер гипотезасы]] |
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[[ht:Deriv kontinan]] |
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[[hu:Kontinensvándorlás]] |
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[[lt:Kontinentų dreifo teorija]] |
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[[ms:Teori hanyutan benua]] |
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[[nl:Continentverschuiving]] |
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[[ja:大陸移動説]] |
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[[no:Kontinentaldrift]] |
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[[pl:Wędrówka kontynentów]] |
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[[pt:Deriva continental]] |
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[[ru:Теория дрейфа материков]] |
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[[simple:Continental drift]] |
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[[sk:Pohyb kontinentov]] |
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[[sr:Померање континената]] |
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[[sh:Pomjeranje kontinenata]] |
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[[fi:Mannerliikunnot]] |
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[[sv:Kontinentaldrift]] |
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[[ta:கண்டப்பெயர்ச்சி]] |
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[[th:การเลื่อนไหลของทวีป]] |
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[[uk:Дрифтова гіпотеза]] |
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[[vi:Trôi dạt lục địa]] |
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[[zh:大陆漂移学说]] |
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