Laurasia
Map of Pangaea with Laurasia and Gondwana. |
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| Historical continents | |
|---|---|
| Type | Geological supercontinent |
| Today part of | Europe (without Balkans) Asia North America |
| Smaller continents | Laurentia Baltica Kazakhstania Siberia North China South China East China |
| Tectonic plate | Eurasian Plate North American Plate |
In paleogeography, Laurasia (
/lɔːˈreɪʒə/ or /lɔːˈreɪʃiə/)[1] was the northernmost of two supercontinents (the other being Gondwana) that formed part of the Pangaea supercontinent from approximately 510 to 200 million years ago (Mya). It separated from Gondwana 200 to 180 Mya (the late Triassic era) during the breakup of Pangaea, drifting further north after the split.[2]
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.
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[edit] 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.
[edit] 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 Carboniferous 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.
Siberia moved southwards and joined with Kazakhstania, a small continental region believed today to have been created during the Silurian by extensive volcanism. When these two continents joined together, Laurasia was nearly reformed, and by the beginning of the Triassic, the East China craton had rejoined the redeveloping Laurasia as it collided with Gondwana to form Pangaea. North China became, as it drifted southwards from near-Arctic latitudes, the last continent to join with Pangaea.
[edit] Final split
Around 200 million years ago, Pangaea started to break up. Between eastern North America and northwest Africa, a new ocean formed - the Atlantic Ocean, even though Greenland (attached to North America) and Europe were still joined together. The separation of Europe and Greenland occurred around 55 million years ago (at the end of the Paleocene). Laurasia finally divided into the continents after which it is named: Laurentia (now North America) and Eurasia (excluding India).
[edit] See also
[edit] References
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Look up laurasia in Wiktionary, the free dictionary. |
- ^ OED
- ^ Houseman, Greg. "Dispersal of Gondwanaland". University of Leeds. http://homepages.see.leeds.ac.uk/~eargah/Gond.html. Retrieved 21 Oct 2008.
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