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“There’s more to this paleomagnetism game than reversals,” Deffeyes said, “more than just determining when, and whether, the magnetic pole was in the north or south. The earth’s magnetic field is such that a compass needle at the equator will lie flat, while a compass needle at ‘the poles will want to stand straight up on end -with all possible gradations of that in the latitudes between. So by looking at the paleomagnetic compasses in rock you can tell not only whether the magnetic pole was in the north or south when the rock formed but also-from the more subtle positions ยท of the needles-the latitude of the rock at tlrn time it formed.” On the striated pavement of Algeria lies the till of polar glaciers. There are tropical atolls in Canada, tropical limestones zakelijke energie in Siberia, tropical limestones in Antarctica. From fossils; from climates preserved in stone, such facts were known long before paleomagnetism was discovered; but they were, to say the least, imperfectly understood. Paleomagnetism, first perceived in igo6, eventually confirmed what the paleoclimatologists and paleontologists had been saying about the latitudes of origins of rocks, but it did not resolve the mystery of the phenomenon, because there seemed to be two equally reasonable explanations. Either the rock had moved (and continents with it) or the whole earth had rolled, like a child’s top slowly turning on its side, and the poles and equator had wandered. Either the equator had gone to Minnesota or Minnesota had gone to the equator. As early as the sixteenth century, the specific movements of the earth’s surface that eventually became known as continental drift and plate tectonics had been hypothesized. The Flemish zakelijke energie vergelijken geographer Abraham Ortelius, in the third edition of his Thesaurus Geographicus (Antwerp, i596), postulated that the American continents were “torn away from Europe and Africa” by earthquakes and other catastrophic events.

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