Continetal drift theory Essays -- essays research papers fc

Continental Drift, the theory that continents move slowly about the earths surface, changing their positions relative to one another and to the poles of the earth. In the past the theory has been discussed but not generally accepted, most geologists believing the continents to be fixed in place and subject only to vertical movements, such as those observed during mountain uplift. In recent years, however, a sound body of evidence in support of a modified form of the roll up theory has been found. Ideas are becoming precise and unified, with emphasis on a moving, evolving ocean floor. The new theory is called plate tectonics.Soon after the Atlantic sea had been mapped, about three hundred years ago, it was noticed that the opposite coasts had similar shapes, but it was not until the middle of the 19th century that accurate maps were published demonstrating that the deuce coasts could be togted together quite closely. Some geologists then suggested that the fit of the coasts was no t an accident--that the continents were once joined and had subsequently drifted by. None of the suggestions were taken seriously.In 1912, however, the German meteorologist Alfred Wegener investigated the fit of the Atlantic coasts more carefully than had his predecessors and grouped all the continents together into one capacious land mass, which he called Pangaea. He supposed that the mass began to break apart about 200 million years ago. He also showed that some geological features on the opposite coasts could bemuse fitted together, and that there were many striking similarities amidst the fossil plants and reptiles on the opposite coasts, particularly the coasts of Africa and South America. If the continents were pushed together, the geological, fossil, and other lines of evidence would join together accurately in the way that lines of print on a torn newspaper would join when the paper was reassembled. Wegener also pointed out that ancient climatic zones seemed to have lain in different places from the present zones. He pointed out that where great ice sheets have melted in recent geological times in Scandinavia and North America, the land is rising as fast as a centimeter a year. This vertical uplift, he said, requires horizontal inflow of matter below and implies that flow and motion do take place within the earth.We... ...an quarantined continent.Although Wegener and Du Toit proposed that the primitive continents began to break up about 200 million years ago, there is much evidence that drift began long before then, and that continental blocks have slowly been moving about the earths surface throughout much of geological time. It seems that before the continents drifted apart and opened up the Atlantic, they had drifted together and closed up an to begin with ocean. Another place where continents seem to have bumped into each other and piled up mountains between them is the Himalayas, which may have been produced when the Indian Peninsula detach ed itself from Gondwanaland and gradually drifted into AsiaBibliography&61623 Daley, Robert B. 1986 A ingest of a changing planet CEBCO Publishing co. p.418&61623 Bartolini, Annachiara and Larson, Roger L 2001 Pacific microplate and the Pangea supercontinent in the Early to Middle Jurassic Geology, Aug2001, Vol. 29 Issue 8, p735-39&61623 Anderson, Don L 2001. top-down Tectonics Science, 9/14/2001, Vol. 293 Issue 5537, p2016-18&61623 http//www.geo.cornell.edu/geology/classes/Geo101/101week6_s01.html