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Despite general rejection, Wegener's compelling concept continued to attract a few advocates over the next several decades. Then, beginning in the mid-1950s, a series of confirming discoveries in paleomagnetism and oceanography finally convinced most scientists that continents do indeed move. Moreover, as Wegener had predicted, the movement is part of a grandscale process that causes mountain-building, earthquakes, volcanic eruptions, sea-level fluctuations, and apparent polar wandering as it rearranges Earth's geography.
Some of the earliest evidence confirming Wegener's theories of continental drift was revealed when geologists measured the age of the ocean floor. Crustal rocks near the mid-ocean ridges are always very young, while the ocean crust along continental margins, furthest away from the ridges, is hundreds of millions of years older. New ocean floor is being created at the mid-ocean ridges—pushing the continents along. (Map courtesy Discovering Plate Boundaries, Rice University) Geologists call the process "plate tectonics," after the large moving plates that form the planet's outer shell. These plates carry both continents and sea floor, but unlike the sea floor, the less-dense, buoyant continents resist subduction into the mantle. Thus, despite significant differences in detail, Alfred Wegener was right in most of his major concepts. Plate tectonics also confirms the accuracy of many of his paleogeographic reconstructions. Ironically, though the lack of a credible driving force was the main objection to Wegener's theory, plate tectonics has been almost universally accepted despite the absence of scientific consensus as to its cause. Convection currents in the molten magma of the upper mantle are the favorite candidate; Wegener discussed this possibility in his 1929 revision. During the last few decades, Alfred Wegener has finally gotten the recognition he deserves. Unfortunately, as with most visionaries, it must be posthumous praise. next: The Obligation to Be a Hero
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 On the Shoulders of Giants
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