![]() ![]() ![]() The formation of supercontinents and their breakup appears to have been cyclical through Earth's history. Pangaea is only the most recent supercontinent reconstructed from the geologic record. One can subtract the polar wander component, which is identical for all contemporaneous samples, leaving the portion that shows continental drift and can be used to help reconstruct earlier continental latitudes and orientations. Magnetic differences between samples of sedimentary and intrusive igneous rock whose age varies by millions of years is due to a combination of magnetic polar wander (with a cycle of a few thousand years) and the drifting of continents over millions of years. When rocks are formed, they take on the magnetic orientation of the Earth, showing which direction the poles lie relative to the rock this determines latitudes and orientations (though not longitudes). ![]() Geologists can also determine the movement of continental plates by examining the orientation of magnetic minerals in rocks. For example, fossils of the therapsid Lystrosaurus have been found in South Africa, India and Antarctica, 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 been found in only localized regions of the coasts of Brazil and West Africa. įossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. The continuity of mountain chains provides further evidence, such as the Appalachian Mountains chain extending from the southeastern United States to the Caledonides of Ireland, Britain, Greenland, and Scandinavia. Glacial deposits, specifically till, of the same age and structure are found on many separate continents that would have been together in the continent of Pangaea. The polar ice cap of the Carboniferous Period covered the southern end of Pangaea. Īdditional 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. Careful reconstructions showed that the mismatch at the 500 fathoms (3,000 feet 910 meters) contour was less than 130 km (81 mi), and it was argued that this was much too good to be attributed to chance. The first to suggest that these continents were once joined and later separated may have been Abraham Ortelius in 1596. The seemingly close fit of the coastlines of North and South America with Europe and Africa was remarked on almost as soon as these coasts were charted. The geography of the continents bordering the Atlantic Ocean was the first evidence suggesting the existence of Pangaea. The distribution of fossils across the continents is one line of evidence pointing to the existence of Pangaea. This theory provides the now widely-accepted explanation for the existence and breakup of Pangaea. Arthur Holmes proposed the more plausible mechanism of mantle convection, which, together with evidence provided by the mapping of the ocean floor following the Second World War, led to the development and acceptance of the theory of plate tectonics. However, this mechanism was easily shown to be physically implausible, which delayed acceptance of the Pangaea hypothesis. Wegener originally proposed that the breakup of Pangaea was due to centripetal forces from the Earth's rotation acting on the high continents. Wegener used the Germanized form "Pangäa," but the name entered German and English scientific literature (in 19, respectively) in the Latinized form "Pangaea" (of the Greek "Pangaia"), especially due to a symposium of the American Association of Petroleum Geologists in November 1926. The name "Pangaea" occurs in the 1920 edition of Die Entstehung der Kontinente und Ozeane, but only once, when Wegener refers to the ancient supercontinent as "the Pangaea of the Carboniferous". He expanded upon his hypothesis in his 1915 book The Origin of Continents and Oceans ( Die Entstehung der Kontinente und Ozeane), in which he postulated that, before breaking up and drifting to their present locations, all the continents had formed a single supercontinent that he called the " Urkontinent". ![]() The concept that the continents once formed a contiguous land mass was hypothesised, with corroborating evidence, by Alfred Wegener, the originator of the scientific theory of continental drift, in his 1912 publication The Origin of Continents ( Die Entstehung der Kontinente). The name "Pangaea" is derived from Ancient Greek pan ( πᾶν, "all, entire, whole") and Gaia or Gaea ( Γαῖα, " Mother Earth, land"). World map of Pangaea created by Alfred Wegener to illustrate his concept ![]()
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