Friday, December 15, 2006

World Changes during the Triassic, Jurassic and Cretatious Era's

The super-continent of Pangea

During the Triassic era, 240 million years ago, one hemisphere was dominated by a vast ocean while the other hemisphere was dominated by a great super-continent. Pangea. This great landmass included all of what is now known as North America, Europe, North Asia. Africa, South America, India, Australia and Antartica

During Triassic times, Pangea moved gradually northwards. At the end of the permian period, very low sea levels and climate change coincided with a major extinction event. Since then sea levels have risen again allowing a slow recovery of marine life such as corals on land - tropical coal forming forests and swamps diminished as climates got warmer and drier

During the Jurassic era, 170 million years ago, the world was a warmer, less varied place than it is today. There were probably no ice caps at the poles for much of this time. The mild conditions made for much higher sea levels resulting in a smaller area of dry land but extensive shallow continental seas, which teemed with life.

The huge continent of Pangea was splitting up, and familiar modern landmasses such as North America and Eurasia were begginning to appear. Both the North and South Atlantic oceans began to open up. At the same time the ancient tethys ocean began to close

The Cretatious period spanned almost 80 million years from 142 million to 65 million years ago. During this time the world began to take on a familiar look as lands that had once made up the super-continent of Pangea pulled apart. The newly formed Atlantic Ocean extended north and southwards, seperating Africa and Eurasia from the Americas. The continents of Africa, India, Antartica and Australia began to move apart about 120 million years ago as new oceans formed between these constiuents of ancient Gondwana. Asia still had an unfamilliar form, with lands that are now part of its southern edge, such as Indochina and India, still seperate islands.

By about 90 million years ago, the distribution of the contients was looking more familiar. The Atlantic ocean seperated the new world of of the Americas from the old world of Europe, Asia, and Africa. Much of Asia was assembled, except for India. Australia still languished in the deep south, attached to Antartica and India was still attached to Madagascar

Source: The Atlas of the Prehistoric World and Wikipaedia

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