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Narissa Kunkudatharn

Volcanoes - 0 views

www.ussartf.org/volcanoes.htm

VOLCANOES

shared by Narissa Kunkudatharn on 02 Sep 11 - Cached
  • Narissa Kunkudatharn on 02 Sep 11
     
    Explains about volcanoes 
Annabelle Cheng

BBC - GCSE Bitesize: Wegener's theory - 11 views

www.bbc.co.uk/...continentaldriftrev1.shtml

Alfred Wegener Theory

shared by Annabelle Cheng on 05 Sep 11 - No Cached
  • Alfred Wegener proposed the theory of continental drift at the beginning of the 20th century. His idea was that the Earth's continents were once joined together, but gradually moved apart over millions of years. It offered an explanation of the existence of similar fossils and rocks on continents that are far apart from each other. But it took a long time for the idea to become accepted by other scientists.Before Weg
  • Wegener suggested that mountains were formed when the edge of a drifting continent collided with another, causing it to crumple and fold. For example, the Himalayas were formed when India came into contact with Asia.
  • se the Earth was cooling down, and in doing so contracted. This was believed to form wrinkles, or mountains, in the Earth's crust. If the idea was correct, however, mountains would be spread evenly over the Earth's surface. We know this is not the case.
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  • Wegener’s evidence for continental drift was that: the same types of fossilised animals and plants are found in South America and Africathe shape of the east coast of South America fits the west coast of Africa, like pieces in a jigsaw puzzlematching rock formations and mountain chains are found in South America and Africa
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    • Annabelle Cheng
      Annabelle Cheng on 06 Sep 11
       
      clear slideshow that explains wegener's theory
Annabelle Cheng

Wegener and Continental Drift Theory - 15 views

www.scientus.org/Wegener-Continental-Drift.html

Alfred Wegener ContinentalDrift Theory

shared by Annabelle Cheng on 05 Sep 11 - No Cached
  • Alfred Wegener was the scientist who championed the Continental Drift Theory through the first few decades of the twentieth century. Simply put, his hypothesis proposed that the continents had once been joined, and over time had drifted apart. The jigsaw fit that the continents make with each other can be seen by looking at any world map.
  • Since his ideas challenged scientists in geology, geophysics, zoogeography and paleontology, it demonstrates the reactions of different communities of scientists. The reactions by the leading authorities in the different disciplines was so strong and so negative that serious discussion of the concept stopped.
  • Why did Alfred Wegener's work produce such a reaction? He was much more diplomatic in presenting his theory than Galileo. Although he believed himself to be right and that some of his arguments were compelling, he knew he would need more support to convince others. His immediate goal was to have the concept openly discussed. Wegener did not even present Continental Drift as a proven theory. These modest goals did not spare him. The fact that his work crossed disciplines exposed him to the territoriality of scientific disciplines. The authorities in the various disciplines attacked him as an interloper that did not fully grasp their own subject. More importantly however, was that even the possibility of Continental Drift was a huge threat to the established authorities in each of the disciplines.
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  • One of Alfred Wegener's critics, the geologist R. Thomas Chamberlain, could not have summarized this threat any better : "If we are to believe in Wegener's hypothesis we must forget everything which has been learned in the past 70 years and start all over again." He was right.
  • In spite of the criticisms from several different disciplines Wegener was able to keep Continental Drift part of the discussion until his death. He knew that any argument based simply on the jigsaw fit of the continents could easily be explained away as a coincidence. To strengthen his case he drew from the fields of geology, geography, biology and paleontology. Wegener questioned why coal deposits, commonly associated with tropical climates, would be found near the North Pole and why the plains of Africa would show evidence of glaciation. Wegener also presented examples where fossils of exactly the same prehistoric species were distributed where you would expect them to be if there had been Continental Drift (e.g. one species occurred in western Africa and South America, and another in Antartica, India and central Africa) [_1_] . The graphic below shows the striking distribution of fossils on the different continents.
  • The main problem with Wegener's hypothesis of Continental Drift was the lack of a mechanism. He did not have an explanation for how the continents moved. Some argue that this failing justified the early reactions to his work and to its dismissal. But Charles Darwin was missing a mechanism for the inheritance of beneficial traits when he published the Origin of Species in 1859.
  • Wegener also shares much in common with Galileo. Wegener probably had at least as strong a case for Continental Drift in 1929 as Galileo had for the Copernican model in 1633
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