Laurasia

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In paleogeography, Laurasia (pronounced /lɔːˈreɪʒə/, /lɔːˈreɪʃiə/[1]) was the northernmost of two nearly equal area supercontinents that came about around 200 Mya in the late Mesozoic era as a part of the split of the huge Pangaea supercontinent that is believed to have existed from its formation about 500 Mya[2]. Laurasia was located in the north after Pangaea split into two separate supercontinents, the other being Gondwanaland in the south.

The name combines the names of Laurentia, the name given to the North American craton, and Eurasia. As suggested by the geologic naming, 'Laurasia' included most of the landmasses which make up today's continents of the northern hemisphere, chiefly Laurentia (i.e. the core North American continent), Baltica, Siberia, Kazakhstania, and the North China and East China cratons.

Contents

Origin

Although Laurasia is known as a Mesozoic phenomenon, today it is believed that the same continents that formed the later Laurasia also existed as a coherent supercontinent after the breakup of Rodinia around 1 billion years ago. To avoid confusion with the Mesozoic continent, this is referred to as Proto-Laurasia. It is believed that Laurasia did not break up again before it recombined with the southern continents to form the late Precambrian supercontinent of Pannotia, which remained until the early Cambrian. Laurasia was assembled, then broken up, due to the actions of plate tectonics, continental drift and seafloor spreading.

Break up and reformation

During the Cambrian, Laurasia was largely located in equatorial latitudes and began to break up, with North China and Siberia drifting into latitudes further north than those occupied by continents during the previous 500 million years. By the Devonian, North China was located near the Arctic Circle and it remained the northernmost land in the world during the Carboniferous Ice Age between 300 and 280 million years ago. There is no evidence, though, for any large scale Carbonifeous glaciation of the northern continents. This cold period saw the re-joining of Laurentia and Baltica with the formation of the Appalachian Mountains and the vast coal deposits which are today, or were very recently, a mainstay of the economies of such regions as West Virginia, the parts of the United Kingdom and Germany.

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