Laurasia

Laurasia

Map of Pangea with Laurasia and Gondwana.
Historical continent
Formed 500 Mya
Type Geological supercontinent
Today part of Europe (without Balkans)
Asia (without India)
North America
Smaller continents Laurentia
Baltica
Kazakhstania
Siberia
North China
South China
East China
Tectonic plate Eurasian Plate
North American Plate

Laurasia (pronunciation: /lɔːˈreɪʒə/ or /lɔːˈreɪʃiə/)[1] was the more northern of two supercontinents (the other being Gondwana) that formed part of the Pangaea supercontinent around 300 to 200 million years ago (Mya). It separated from Gondwana 200 to 180 Mya (beginning in the late Triassic period) during the breakup of Pangaea, drifting farther 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 land masses which make up today's continents of the Northern Hemisphere, chiefly Laurentia, Baltica, Siberia, Kazakhstania, and the North China and East China cratons.

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.

Breakup 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. No evidence, though, exists for any large-scale Carboniferous glaciation of the northern continents. This cold period saw the rejoining of Laurentia and Baltica with the formation of the Appalachian Mountains and the vast coal deposits, which are a mainstay of the economies of such regions as West Virginia, Britain, 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.

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, 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 the Indian subcontinent).

See also

References

Look up laurasia in Wiktionary, the free dictionary.
  1. ↑ OED
  2. ↑ Houseman, Greg. "Dispersal of Gondwanaland". University of Leeds. Retrieved 21 Oct 2008.
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