Pangaea: Difference between revisions
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It friggin' sucked. |
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[[Image:Pangaea continents.png|right|250px|thumb|Map of Pangaea]] |
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'''Pangaea''', '''Pangæa''', or '''Pangea''' ({{pron-en|pænˈdʒiːə}}<ref>OED</ref>, from [[Ancient Greek]] πᾶν ''pan'' "entire", and Γαῖα ''Gaia'' "Earth", Latinized as ''Gæa'') was the [[supercontinent]] that existed during the [[Paleozoic]] and [[Mesozoic]] eras about 250 million years ago, before the component [[continent]]s were separated into their current configuration.<ref>Plate Tectonics and Crustal Evolution, Third Ed., 1989, by Kent C. Condie, Pergamon Press</ref> |
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One continent for EVERYBODY to live on, is not fun for ANYONE. |
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The name was first used by the [[German people|German]] originator of the [[continental drift]] theory, [[Alfred Wegener]], in the 1920 edition of his book ''The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane)'', in which a postulated [[supercontinent]] Pangaea played a key role. |
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The single [[Superocean|enormous ocean]] which surrounded Pangaea is known as [[Panthalassa]]. |
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==Formation== |
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The breaking up and formation of supercontinents appears to be [[supercontinent cycle|cyclical]] through Earth's 4.6 billion year history. There may have been [[List of supercontinents|several others]] before Pangaea. The next-to-last one, [[Pannotia]], formed about 600 million years ago (Ma) during the [[Proterozoic]] eon, and lasted until 540 Ma. Before Pannotia, there was [[Rodinia]], which lasted from about 1.1 billion years ago (Ga) until about 750 million years ago. The exact configuration and geodynamic history of Rodinia are not nearly as well understood as for Pannotia and Pangaea. |
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When Rodinia broke up, it split into three pieces, the supercontinent of [[Proto-Laurasia]] and the supercontinent of [[Proto-Gondwana]], and the smaller [[Congo craton]]. Proto-Laurasia and Proto-Gondwana were separated by the [[Proto-Tethys Ocean]]. Soon thereafter [[Proto-Laurasia]] itself split apart to form the continents of [[Laurentia]], [[Siberia (continent)|Siberia]] and [[Baltica]]. The rifting also spawned two new oceans, the [[Iapetus Ocean]] and [[Indian Ocean]]. Baltica was situated east of Laurentia, and Siberia northeast of Laurentia. |
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Around 600 Ma, most of these masses came back together to form the relatively short-lived supercontinent of [[Pannotia]], which included large amounts of land near the poles and only a relatively small strip near the equator connecting the polar masses. |
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Only 60 million years after its formation, about 540 Ma, near the beginning of the [[Cambrian]] epoch, Pannotia in turn broke up, giving rise to the continents of [[Laurentia]], [[Baltica]], and the southern supercontinent of [[Gondwana]]. |
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In the [[Cambrian]] period the independent continent of [[Laurentia]], which would become [[North America]], sat on the [[equator]], with three bordering oceans: the [[Panthalassic Ocean]] to the north and west, the [[Iapetus Ocean]] to the south and the [[Khanty Ocean]] to the east. In the Earliest [[Ordovician]], around 480 Ma, the microcontinent of [[Avalonia]], a landmass that would become the northeastern [[United States]], [[Nova Scotia]] and [[England]], broke free from Gondwana and began its journey to [[Laurentia]].<ref>{{cite book| last =Stanley| first = Steven| authorlink = Steven M. Stanley| title = Earth System History| date = 1998| location = USA| pages = 355–359 }}</ref> |
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[[Image:Euramerica en.svg|245px|thumb|right|Euramerica's formation]] |
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[[Image:Appalachian orogeny.jpg|thumb|235px|right|Appalachian orogeny]] |
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Baltica, Laurentia, and Avalonia all came together by the end of the Ordovician to form a minor supercontinent called [[Euramerica]] or Laurussia, closing the Iapetus Ocean. The collision also resulted in the formation of the northern [[Appalachians]]. [[Siberia (continent)|Siberia]] sat near Euramerica, with the [[Khanty Ocean]] between the two continents. While all this was happening, Gondwana drifted slowly towards the South Pole. This was the first step of the formation of Pangaea.<ref>{{cite book| last =Stanley| first = Steven| authorlink = Steven M. Stanley| title = Earth System History| date = 1998| location = USA| pages = 386–392 }}</ref> |
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The second step in the formation of Pangaea was the collision of Gondwana with [[Euramerica]]. By [[Silurian]] time, 440 Ma, Baltica had already collided with Laurentia to form Euramerica. [[Avalonia]] had not collided with [[Laurentia]] yet, and a seaway between them, a remnant of the [[Iapetus Ocean]], was still shrinking as Avalonia slowly inched towards Laurentia. |
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Meanwhile, [[southern Europe]] fragmented from Gondwana and started to head towards Euramerica across the newly formed [[Rheic Ocean]] and collided with southern [[Baltica]] in the [[Devonian]], though this microcontinent was an underwater plate. The Iapetus Ocean's sister ocean, the Khanty Ocean, was also shrinking as an island arc from Siberia collided with eastern Baltica (now part of Euramerica). Behind this [[island arc]] was a new ocean, the [[Ural Ocean]]. |
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By late Silurian time, [[North China (continent)|North]] and [[South China (continent)|South China]] rifted away from Gondwana and started to head northward across the shrinking Proto-Tethys Ocean, and on its southern end the new [[Paleo-Tethys Ocean]] was opening. In the Devonian Period, Gondwana itself headed towards Euramerica, which caused the Rheic Ocean to shrink. |
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In the Early [[Carboniferous]], northwest [[Africa]] had touched the southeastern coast of [[Euramerica]], creating the southern portion of the [[Appalachian Mountains]], and the [[Meseta Mountains]]. [[South America]] moved northward to southern Euramerica, while the eastern portion of Gondwana ([[India]], [[Antarctica]] and [[Australia]]) headed towards the South Pole from the [[equator]]. |
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North China and South China were on independent continents. The [[Kazakhstania]] microcontinent had collided with [[Siberia (continent)|Siberia]] (Siberia had been a separate continent for millions of years since the deformation of the supercontinent [[Pannotia]]) in the Middle Carboniferous. |
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Western [[Kazakhstania]] collided with [[Baltica]] in the Late Carboniferous, closing the [[Ural Ocean]] between them, and the western Proto-Tethys in them ([[Uralian orogeny]]), causing the formation of the [[Ural Mountains]], and the formation of the supercontinent of Laurasia. This was the last step of the formation of Pangaea. |
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Meanwhile, South America had collided with southern [[Laurentia]], closing the [[Rheic Ocean]], and forming the southernmost part of the [[Appalachians]] and [[Ouachita Mountains]]. By this time, Gondwana was positioned near the South Pole, and glaciers were forming in Antarctica, India, Australia, southern Africa and South America. The [[North China]] block collided with [[Siberia]] by Late Carboniferous time, completely closing the Proto-Tethys Ocean. |
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By Early [[Permian]] time, the [[Cimmerian plate]] rifted away from Gondwana and headed towards Laurasia, with a new ocean forming in its southern end, the [[Tethys Ocean]], and the closure of the [[Paleo-Tethys Ocean]]. Most of the landmasses were all in one. By the [[Triassic]] Period, Pangaea rotated a little, in a southwest direction. The Cimmerian plate was still travelling across the shrinking Paleo-Tethys, until the [[Middle Jurassic]] time. The Paleo-Tethys had closed from west to east, creating the [[Cimmerian Orogeny]]. Pangaea looked like a ''C'', with an ocean inside the ''C'', the new Tethys Ocean. Pangaea had rifted by the Middle Jurassic, and its deformation is explained below. |
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==Evidence of existence== |
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[[Fossil]] evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. For example, fossils of the [[therapsid]] ''[[Lystrosaurus]]'' have been found in [[Gandu]], [[South Africa]], [[India]] and [[Australia]], alongside members of the ''[[Glossopteris]]'' flora, whose distribution would have ranged from the polar circle to the equator if the continents had been in their present position; similarly, the freshwater reptile ''[[Mesosaurus]]'' has only been found in localized regions of the coasts of [[Brazil]] and [[West Africa]].<ref>Benton, M.J. ''Vertebrate Palaeontology''. Third edition (Oxford 2005), 25.</ref> |
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Additional evidence for Pangaea is found in the [[geology]] of adjacent continents, including matching geological trends between the eastern coast of [[South America]] and the western coast of [[Africa]]. |
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The [[polar ice cap]] of the [[Carboniferous]] Period covered the southern end of Pangaea. Glacial deposits, specifically [[till]], of the same age and structure are found on many separate continents which would have been together in the continent of Pangaea.<ref>Barbara W. Murck, Brian J. Skinner, ''Geology Today: Understanding Our Planet, Study Guide'', Wiley, ISBN 978-0-471-32323-5</ref> |
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Apparent polar wandering paths also support the theory of a super-continent. Geologists can determine the movement of continental plates by examining the orientation of magnetic minerals in rocks; when rocks are formed, they take on the magnetic properties of the Earth and indicate in which direction the poles lie relative to the rock. Because we know that the poles do not move more than a few degrees, magnetic anomalies in rocks can only be explained by the drifting of continents. |
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The continuity of mountain chains also provide evidence for Pangea. One example of this is the [[Appalachian Mountains]] chain which extends from the northeastern [[United States]] to the [[Caledonides]] of Ireland, Britain, Greenland, and Scandinavia.<ref>Zeeya Merali, Brian J. Skinner, ''Visualizing Earth Science'', Wiley, ISBN 978-0470-41847-5</ref> |
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==Rifting and break-up== |
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[[Image:Pangea animation 03.gif|thumb|240px|Pangaea separation animation]] |
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There were three major phases in the break-up of Pangaea. The first phase began in the [[Early Jurassic|Early]]-[[Middle Jurassic]] (about 175 Ma), when Pangaea began to rift from the Tethys Ocean in the east and the [[Pacific]] in the west, ultimately giving rise to the supercontinents Laurasia and Gondwana. The rifting that took place between North America and Africa produced multiple [[Eastern North America Rift Basins|failed rifts]]. One rift resulted in a new ocean, the North [[Atlantic Ocean]]. |
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The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The [[South Atlantic]] did not open until the [[Cretaceous]]. Laurasia started to rotate clockwise and moved northward with North America to the north, and [[Eurasia]] to the south. The clockwise motion of Laurasia also led to the closing of the Tethys Ocean. Meanwhile, on the other side of Africa, new rifts were also forming along the adjacent margins of east Africa, Antarctica and [[Madagascar]] that would lead to the formation of the southwestern [[Indian Ocean]] that would also open up in the Cretaceous. |
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The second major phase in the break-up of Pangaea began in the [[Early Cretaceous]] (150–140 Ma), when the minor supercontinent of Gondwana separated into four multiple continents (Africa, South America, India and Antarctica/Australia). About 200 Ma, the continent of [[Cimmerian Plate|Cimmeria]], as mentioned above (see "[[Pangaea#Formation of Pangaea|Formation of Pangaea]]"), collided with Eurasia. However, a subduction zone was forming, as soon as Cimmeria collided. |
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This subduction zone was called the [[Tethyan Trench]]. This trench might have subducted what is called the Tethyan [[mid-ocean ridge]], a ridge responsible for the Tethys Ocean's expansion. It probably caused Africa, India and Australia to move northward. In the Early Cretaceous, [[Atlantica]], today's South America and Africa, finally separated from eastern Gondwana (Antarctica, India and Australia), causing the opening of a "South Indian Ocean". In the Middle Cretaceous, Gondwana fragmented to open up the South Atlantic Ocean as South America started to move westward away from Africa. The South Atlantic did not develop uniformly; rather, it rifted from south to north. |
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Also, at the same time, [[Madagascar]] and India began to separate from Antarctica and moved northward, opening up the Indian Ocean. Madagascar and India separated from each other 100–90 Ma in the Late Cretaceous. India continued to move northward toward Eurasia at 15 centimeters (6 in) per year (a plate tectonic record), closing the Tethys Ocean, while Madagascar stopped and became locked to the [[African Plate]]. [[New Zealand]], [[New Caledonia]] and the rest of [[Zealandia (continent)|Zealandia]] began to separate from Australia, moving eastward towards the [[Pacific]] and opening the [[Coral Sea]] and [[Tasman Sea]]. |
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The third major and final phase of the break-up of Pangaea occurred in the early [[Cenozoic]] ([[Paleocene]] to [[Oligocene]]). [[Laurasia]] split when North America/Greenland (also called [[Laurentia]]) broke free from Eurasia, opening the [[Norwegian Sea]] about 60–55 Ma. The Atlantic and Indian Oceans continued to expand, closing the Tethys Ocean. |
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Meanwhile, Australia split from Antarctica and moved rapidly northward, just as India did more than 40 million years earlier, and is currently on a collision course with [[eastern Asia]]. Both Australia and India are currently moving in a northeastern direction at 5–6 centimeters (2–3 in) per year. Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma. India started to collide with [[Asia]] beginning about 35 Ma, forming the [[Himalayan orogeny]], and also finally closing the [[Tethys Ocean|Tethys Seaway]]; this collision continues today. The African Plate started to change directions, from west to northwest toward [[Europe]], and South America began to move in a northward direction, separating it from Antarctica and allowing complete oceanic circulation around Antarctica for the first time, causing a rapid cooling of the continent and allowing [[glacier]]s to form. Other major events took place during the [[Cenozoic]], including the opening of the [[Gulf of California]], the uplift of the [[Alps]], and the opening of the [[Sea of Japan]]. The break-up of Pangaea continues today in the [[Great Rift Valley]]. |
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==See also== |
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* [[List of supercontinents]] |
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* [[History of Earth]] |
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* [[Supercontinent cycle]] |
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* [[Plate tectonics]] |
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* [[Continental drift]] |
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==References== |
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{{reflist}} |
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== External links == |
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{{commons|Pangea|Pangaea}} |
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{{Wiktionary|Pangaea}} |
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* [http://pubs.usgs.gov/publications/text/historical.html USGS Overview] |
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* In honor of [[Alfred Wegener]] a data library for earth system science, operated by the [[Alfred Wegener Institute for Polar and Marine Research]] (AWI), is named [[PANGAEA (data library)|PANGAEA]] |
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** [http://www.pangaea.de PANGAEA data library] |
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* [http://www.tectonic-forces.org An explanation of tectonic forces] |
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*[http://www.foxnews.com/story/0,2933,248979,00.html Europe's First Stegosaurus Boosts Pangaea Theory] |
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* [http://www.scotese.com/newpage8.htm Map of Triassic Pangaea at Paleomaps] |
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{{Continents of the world}} |
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[[Category:Geological history of Earth]] |
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[[Category:Historical continents]] |
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[[Category:Carboniferous]] |
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[[Category:Permian]] |
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[[Category:Triassic]] |
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[[Category:Jurassic]] |
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[[Category:Plate tectonics]] |
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[[Category:Supercontinents]] |
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[[ar:بانجيا]] |
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[[ast:Panxea]] |
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[[bs:Pangea]] |
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[[br:Pangea]] |
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[[bg:Пангея]] |
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[[ca:Pangea]] |
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[[ceb:Pangaea]] |
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[[cs:Pangea]] |
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[[cy:Pangaea]] |
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[[da:Pangæa]] |
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[[de:Pangaea]] |
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[[dv:ޕަންގިއާ]] |
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[[et:Pangaea]] |
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[[el:Παγγαία]] |
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[[es:Pangea]] |
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[[eo:Pangeo]] |
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[[eu:Pangea]] |
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[[fa:پانگئا]] |
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[[fr:Pangée]] |
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[[gd:Pangaea]] |
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[[gl:Panxea]] |
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[[ko:판게아]] |
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[[hr:Pangea]] |
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[[id:Pangea]] |
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[[it:Pangea]] |
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[[he:פנגיאה]] |
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[[ka:პანგეა]] |
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[[ht:Panje]] |
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[[la:Pangaea]] |
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[[lb:Pangäa]] |
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[[lt:Pangėja]] |
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[[hu:Pangea]] |
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[[ml:പാന്ജിയ]] |
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[[mt:Pangea]] |
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[[mr:पँजिआ]] |
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[[nl:Pangea]] |
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[[ja:パンゲア大陸]] |
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[[no:Pangea]] |
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[[nn:Pangea]] |
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[[nov:Pangea]] |
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[[pl:Pangea]] |
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[[pt:Pangeia]] |
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[[ru:Пангея]] |
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[[scn:Pangea]] |
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[[simple:Pangaea]] |
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[[sk:Pangea]] |
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[[sl:Pangea]] |
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[[sr:Пангеа]] |
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[[fi:Pangea]] |
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[[sv:Pangea]] |
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[[tl:Pangaea]] |
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[[ta:ஒருநிலக் கொள்கை]] |
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[[tt:Пангея]] |
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[[th:มหาทวีปแพนเจีย]] |
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[[tr:Pangea]] |
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[[uk:Пангея]] |
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[[vi:Pangaea]] |
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[[wa:Pandjêye]] |
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[[wuu:盘古大陆]] |
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[[zh:盤古大陸]] |
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Revision as of 13:58, 28 October 2009
It friggin' sucked.
One continent for EVERYBODY to live on, is not fun for ANYONE.