The Changing Earth

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     Alfred Wegener (1880-1930) was a climatologist and geophysicist who proposed the idea that a single supercontinent, Pangaea had existed in the past and  broke up 200 million years ago. The pieces then ``drifted'' to their present positions.

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Germany 9N541 commemorates Alfred Wegener and shows the configuration as he believed it was in the Eocene epoch (54.8 to 33.7 million years ago). Most of the modern orders of mammals appear in the early Eocene.

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The carefully considered reassembly of Gondwana was published by the South African geologist Alex du Toit in 1937. His reconstruction relied on available geological data and “best-fits” of continental pieces. In 1967, as a result of the discovery and interpretations of paleomagnetic anomalies on ocean floors, it was shown that the movement of continents on the earth’s surface could be defined by a set of simple algebraic equations which described the dispersal of Gondwana during the past one hundred fifty million years. November 30, 2001

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The Mid-Atlantic Ridge

Mid-oceanic ridges are the places of geological creation. The Midatlantic Ridge snakes down the center of that ocean from Jan Mayen off Greenland to the latitude of Cape Horn. Other ridges are found in the Indian and Pacific Oceans. The stamp from Ascension shows the shape of Gondwanaland in the Jurassic period, about 180 million years ago, and the Mid-Atlantic Ridge.

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