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continental drift





continental drift: the break-up of Pangaea
Continental drift. A bout 200 million years ago, the original Pangea land mass began its split into two continental groups, which further separated over time to produce the present-day configuration
A theory first rigorously formulated by Alfred Wegener, later amplified by du Toit, to explain a number of geological and paleontological phenomena. It suggests that originally the land on Earth composed a single vast continent, Pangea, which broke up. Continental drift is now recognized to be a consequence of the theory of plate tectonics.

According to continental drift, the continents change position very slowly, moving over the Earth's surface at the rate of only a few centimeters per year, adding up to thousands of kilometers over geological time. Until the mid-20th century most scientists believed that the continents were in a fixed position, Early supporters of continental drift, like Wegener, claimed that the jigsaw shapes of the continents could be pieced together to form an ancient landmass which, at some time in the past, split and drifted apart. Evidence for the theory included matching the outlines of continents, rock types, geological structures, and fossils. Fossil magnetism in rocks is used to calculate the ancient latitude of continents over time. Continental drift became accepted with the development of plate tectonics in the 1960s. In recent years continental movement has been confirmed by direct measurements made by global positioning satellites using laser beams.


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   • GEOLOGY AND PLANETARY SCIENCE