Laurasia

Laurasia is the name given to the supercontinent that is thought to have arisen most recently during the late Mesozoic era, as part of the split of the Pangaean supercontinent. It also is believed that the same landmass existed much earlier, forming after the breakup of the hypothesize supercontinent Rodinia about 1 billion years ago, before reforming into Pangaea (or Pangea). The landmass of this earlier period is sometimes referred to as Proto-Laurasia to avoid confusion with the Mesozoic supercontinent.

The name Laurasia combines the names of Laurentia and Eurasia. It included most of the landmasses that make up today's continents of the northern hemisphere, chiefly Laurentia (the name given to the North American craton), as well as Baltica, Siberia, Kazakhstania, and the North China and East China cratons.

The existence of supercontinents such as Laurasia is explained by the theory of plate tectonics, which recognizes the earth to have a thin, solid crust, made up of several plates, that floats or rides on an inner layer of melted rock. The view of a supercontinent that is hundreds of millions of years old poses a problem for young-earth creationists, but plate tectonics is widely accepted today and backed by considerable scientific evidence.

Mesozoic era (251 - 65 mya)
Triassic	Jurassic	Cretaceous

Overview and 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.

Pangaea or Pangea is the name given to the supercontinent that is thought to have existed during the Paleozoic and Mesozoic eras, before the process of plate tectonics separated each of the component continents into their current configuration.

Pangaea broke apart during the Triassic and Jurassic periods of the Mesozoic, separating into Laurasia and Gondwana (or Gondwanaland).

The vast ocean that once surrounded the supercontinent of Pangaea has been named Panthalassa. Pangaea is believed to have broken up about 180 million years ago (mya) in the Jurassic period, first into two supercontinents (Gondwana to the south and Laurasia to the north), and thereafter into the continents as they are observed today.

(a supercontinent that also existed before and after Pangaea),

Another, earlier hypothesized supercontinent is Rodinia, believed to have formed approximately 1,100 mya and divided 750 mya. Tentative evidence suggests that the Columbia (supercontinent) existed between 1.8 and 1.5 billion years ago. There is also some evidence for an even earlier supercontinent named Kenorland, existing between ~2.7 billion years to ~2.1 billion years ago, and Earth's possibly first supercontinent named Vaalbara, existing between ~3.3 billion years to ~2.8 billion years ago.

Rodinia, believed to have formed 1.1 billion years ago during the Proterozoic, was the supercontinent from which all subsequent continents, sub or super, derived.

One simplified version holds that that Pangaea formed as a result of the collision of Gondwana and Laurasia (a supercontinent that also existed before and after Pangaea), while Laurasia was formed by the collision during the Carboniferous of the Siberia continent and the minor supercontinent Laurussia (or Euramerica). After these three major landmasses collided, during the Carboniferous, roughly 350 mya, other smaller landmasses collided as well.

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 a mainstay of the economy of such regions as West Virginia, 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.

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 60 million years ago (in the Paleocene). Laurasia finally divided into the continents after which it is named: Laurentia (now North America) and Eurasia (excluding India and Arabia).

See also

• Alexander du Toit
• Alfred Wegener
• Avalonia

References

ISBN links support NWE through referral fees

• Parrish, J. T. 1993. Climate of the supercontinent Pangea. Journal of Geology 101:215-233.
• Parrish, J. T., M. T. Bradshaw, A. T. Brakel, S. Mulholland, J. M. Totterdell, and A. N. Yeates. 1996. Paleoclimatology of Australia during the Pangaean interval. Palaeoclimates, Data and Modelling 1:241-281.
• Torsvik, T. H. 2003. The Rodina Jigsaw Puzzle. Science 300(5624):1379-1381.

Continents of the world

Africa-Eurasia

Americas

Eurasia

Oceania

Africa

Antarctica

Asia

Australia

Europe

N. America

S. America

Geological supercontinents Gondwana • Laurasia • Pangaea • Pannotia • Rodinia • Columbia • Kenorland • Ur • Vaalbara

Mythical and theorized continents Atlantis • Kerguelen Plateau • Lemuria • Mu • Terra Australis • Zealandia

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