The idea of Continental Drift was the forerunner of Plate Tectonics Theory. At the time that Wegener proposed the idea of Continental Drift, he did not have sufficient information to explain the physical mechanisms that would have allowed continents to break apart and drift apart. He did have fossil evidence, and shape-of-the continents evidence, and matching-rocks-on-both-sides evidence that the continents had indeed been juxtaposed. "A fatal weakness in Wegener's theory was that it could not satisfactorily answer the most fundamental question raised by his critics: What kind of forces could be strong enough to move such large masses of solid rock over such great distances? Wegener suggested that the continents simply plowed through the ocean floor, but Harold Jeffreys, a noted English geophysicist, argued correctly that it was physically impossible for a large mass of solid rock to plow through the ocean floor without breaking up."http://pubs.usgs.gov/gip/dynamic/historical.html
Later, when scientists discovered magnetic striped on the ocean floor, learned more about the seismicity at trenches, and so forth, they were able to put together a more comprehensive model of the actual physical processes that could and do cause the continents to "drift" apart, or collide together. These processes come under the heading of Plate Tectonics--which includes the ideas of three types of plate boundaries, including the divergent boundaries with spreading ridges required for continents to "drift" apart.
The website below will give you illustrations and discusses both continental drift and plate tectonics.
2006-11-09 02:34:49
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answer #1
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answered by luka d 5
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