Formation of continents

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Formation of Continenets Presentation PDFhttp://geowww.geo.tcu.edu/faculty/morgan/freshmanlectures/Drift.pdf

Alfred Lothar Wegener (1 November 1880 in Berlin – 2 November 1930) was a German scientist, geologist, and meteorologist.
He is most notable for his theory of continental drift (Kontinentalverschiebung), proposed in 1915, which hypothesized that the continents were slowly drifting around the Earth. However, Wegener was unable to demonstrate a mechanism for continental drift, which, combined with his mostly circumstantial evidence, meant that his hypothesis was not accepted until the 1950s, when numerous discoveries provided evidence of continental drift.[1]

Continental drift

From 1912 he publicly advocated the theory of "


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href="http://en.wikipedia.org/wiki/Continental_drift">continental drift", arguing that all the continents were once joined together in a single landmass and have drifted apart.
In 1915, in The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), Wegener published the theory that there had once been a giant continent, he named "Pangaea" (meaning "All-Lands" or "All-Earth") and drew together evidence from various fields. Expanded editions during the 1920s presented the accumulating evidence. The last edition, just before his untimely death, revealed the significant observation that shallower oceans were geologically younger

Pangaea, Panɡæa or Pangea (pronounced /pænˈdʒiːə/[1], from Ancient Greek παν pan "entire", and Γαῖα Gaia "Earth", Latinized as Gæa) was the supercontinent that is theorized to have existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration.[2]
The name was first used by the German originator of the continental drift theory, Alfred Wegener, in the 1920 edition of his book The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), in which a postulated supercontinent Pangaea played a key role.
The single enormous ocean which surrounded Pangaea is known as Panthalassa.

There were three major phases in the break-up of Pangaea. The first phase began in the Early-Middle Jurassic, when Pangaea created a rift from the Tethys Ocean in the east and the Pacific in the west. The rifting took place between North America and Africa, and produced multiple failed rifts. The rift resulted in a new ocean, the Atlantic Ocean.
The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The South Atlantic did not open until the Cretaceous. Laurasia started to rotate clockwise and moved northward with North America to the north, and Eurasia to the south. The clockwise motion of Laurasia also led to the closing of the Tethys Ocean. Meanwhile, on the other side of Africa, new rifts were also forming along the adjacent margins of east Africa, Antarctica and Madagascar that would lead to the formation of the southwestern Indian Ocean that would also open up in the Cretaceous.
The second major phase in the break-up of Pangaea began in the Early Cretaceous (150–140 Ma), when the minor supercontinent of Gondwana separated into four multiple continents (Africa, South America, India and Antarctica/Australia). About 200 Ma, the continent of Cimmeria, as mentioned above (see "Formation of Pangaea"), collided with Eurasia. However, a subduction zone was forming, as soon as Cimmeria collided.
This subduction zone was called the Tethyan Trench. This trench might have subducted what is called the Tethyan mid-ocean ridge, a ridge responsible for the Tethys Ocean's expansion. It probably caused Africa, India and Australia to move northward. In the Early Cretaceous, Atlantica, today's South America and Africa, finally separated from eastern Gondwana (Antarctica, India and Australia), causing the opening of a "South Indian Ocean". In the Middle Cretaceous, Gondwana fragmented to open up the South Atlantic Ocean as South America started to move westward away from Africa. The South Atlantic did not develop uniformly; rather, it rifted from south to north.
Also, at the same time, Madagascar and India began to separate from Antarctica and moved northward, opening up the Indian Ocean. Madagascar and India separated from each other 100–90 Ma in the Late Cretaceous. India continued to move northward toward Eurasia at 15 centimeters (6 in) per year (a plate tectonic record), closing the Tethys Ocean, while Madagascar stopped and became locked to the African Plate. New Zealand, New Caledonia and the rest of Zealandia began to separate from Australia, moving eastward towards the Pacific and opening the Coral Sea and Tasman Sea.
The third major and final phase of the break-up of Pangaea occurred in the early Cenozoic (Paleocene to Oligocene). North America/Greenland broke free from Eurasia, opening the Norwegian Sea about 60–55 Ma. The Atlantic and Indian Oceans continued to expand, closing the Tethys Ocean.
Meanwhile, Australia split from Antarctica and moved rapidly northward, just as India did more than 40 million years earlier, and is currently on a collision course with eastern Asia. Both Australia and India are currently moving in a northeastern direction at 5–6 centimeters (2–3 in) per year. Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma. India started to collide with Asia beginning about 35 Ma, forming the Himalayan orogeny, and also finally closing the Tethys Seaway; this collision continues today. The African Plate started to change directions, from west to northwest toward Europe, and South America began to move in a northward direction, separating it from Antarctica and allowing complete oceanic circulation around Antarctica for the first time, causing a rapid cooling of the continent and allowing glaciers to form. Other major events took place during the Cenozoic, including the opening of the Gulf of California, the uplift of the Alps, and the opening of the Sea of Japan. The break-up of Pangaea continues today in the Great Rift Valley

Gondwana (pronounced /ɡɒndˈwɑːnə/[1][2]), originally Gondwanaland, is the name given to a southern precursor-supercontinent (final ongoing joining occurred between ca. 570-510 Ma, joining East Gondwana to West Gondwana[3]) and then as a remnant separated from Laurasia 180-200 million years ago during the breakup of the Pangaea supercontinent that existed about 500 to 200 Ma ago into two large segments.[4] While the corresponding northern hemisphere continent Laurasia moved further north, the nearly equal in area Gondwana included most of the landmasses in today's southern hemisphere, including Antarctica, South America, Africa, Madagascar, Australia-New Guinea, and New Zealand, as well as Arabia and the Indian subcontinent, which have now moved into the Northern Hemisphere. The name is derived from the Gondwana region of central northern India (from Sanskrit gondavana "forest of Gond").
The adjective "Gondwanan" is in common use in biogeography when referring to patterns of distribution of living organisms, typically when the organisms are restricted to two or more of the now-discontinuous regions that were once part of Gondwana; e.g., the Proteaceae, a family of plants that is known only from Chile, South Africa, and Australia are considered to have a "Gondwanan distribution". This pattern is often considered to indicate an archaic, or relict lineage.