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Annabelle Cheng

Wegener and Continental Drift Theory - 15 views

  • 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
Rima Touya

Alfred Wegener - Wikipedia, the free encyclopedia - 8 views

  • Alfred Wegener first thought of this idea by noticing that the different large landmasses of the Earth almost fit together like a jigsaw.
  • The Continental shelf of the Americas fit closely to Africa and Europe, and Antarctica, Australia, India and Madagascar fit next to the tip of Southern Africa.
  • He analyzed either side of the Atlantic Ocean for rock type, geological structures and fossils. He noticed that there was a significant similarity between matching sides of the continents, especially in fossil plants.
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  • From 1912, Wegener publicly advocated the theory of "continental drift", arguing that all the continents were once joined together in a single landmass and have drifted apart.
  • In his work, Wegener presented a large amount of very strong
  • In 1943 George Gaylord Simpson wrote a vehement attack on the theory
  • evidence in support of continental drift, but the mechanism remained elusive. While his ideas attracted a few early supporters such as Alexander Du Toit from South Africa and Arthur Holmes in England, the hypothesis was generally met with skepticism from largely conservative scientists, who were resistant to any change in the status quo.
  • but G.G.Simpson's influence was so powerful that even in countries previously sympathetic towards continental drift, like Australia
  • Wegener's hypothesis fell out of favour.
    • Annabelle Cheng
       
      Diagram to show evidence
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    How Alfred W. first came up with this theory...
Annabelle Cheng

Alfred Wegener - 9 views

  • Reaction to Wegener's theory was almost uniformly hostile, and often exceptionally harsh and scathing; Dr. Rollin T
  • Part of the problem was that Wegener had no convincing mechanism for how the continents might move. Wegener thought that the continents were moving through the earth's crust, like icebreakers plowing through ice sheets, and that centrifugal and tidal forces were responsible for moving the continents.
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    Part of the problem no one believed his theory
Annabelle Cheng

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

  • 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
       
      clear slideshow that explains wegener's theory
Simon Scoones

Alfred Wegener: Great Minds - YouTube - 22 views

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    A five minute video all about Alfred Wegener and his theory of plate tectonics
Rima Touya

What evidence did Alfred Wegener use to support his theory of continental drift - 18 views

  • Alfred Wegener's fully developed theory of continental drift attempted to point out evidences that the continents were once joined into a single continent he called Pangea. Wegener's theory hypothesized that the continents were able to push through the rock of the seafloor to their present positions. As evidence, he noted, as had others before him, of the geographic correlation in coastline perimeters of South America and Africa. This was the feature that led Wegener to investigate for other evidences. His investigations revealed that mountain ranges in South America and Africa, and strata and composition of coal fields in Europe and North America matched or lined up. Additionally, matching reptilian fossils were found on either side of the ocean, indicating that the continents were once joined together. Although he was unable to find a mechanism for his proposed continental drift theory, he also observed that the more shallow an ocean, the younger its geologic age. It wasn't until the 1950's and 1960's, with the discovery of the Mid-Atlantic Ridge, and other sea floor mapping discoveries that Wegener's hypothesis started to become more accepted. The newer science of plate tectonics owes much to Wegener's scientific groundwork.
Rima Touya

Plate tectonics | Article | World Book Student - 10 views

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    mantle rock as it rises to the top of the asthenosphere, cools, and then sinks is known as a
Rima Touya

Earth's Continental Plates - ZoomSchool.com - 4 views

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    Information about plate tectonics
Simon Scoones

Topographic map of Mid-Oceanic Ridge [This Dynamic Earth, USGS] - 11 views

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    USGS Dynamic Earth pamphlet
pbranston

A Science Odyssey: You Try It: Plate Tectonics - 11 views

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    Useful pages on Wegener and the people that helped to prove his theory of Continental Drift.
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    I agree. I recommend this website as a quick and easy read, learn something new and catch up on the things we have been doing in class.
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