National Geographic : 2015 Jan
Ancient Worlds EXPLORE JEROME N. COOKSON, NGM STAFF. SOURCE: RON BLAKEY, COLORADO PLATEAU GEOSYSTEMS PANTHALASSIC OCEAN EQUATOR INDIA AUSTRALIA AFGHANISTAN U.S. SPAIN CHINA RUSSIA SOUTH AFRICA ARGENTINA BRAZIL CANADA JAPAN Hot off the presses in 1915, Alfred Wegener’s book The Origin of Continents and Oceans sent tremors through the foundations of earth science. The German meteorologist was the first to weave together multidisciplinary evidence to support a then controversial theory of continental drift. While perusing a world atlas in 1910, Wegener pondered whether the shapes of the continents corresponded by mere coincidence. He later pieced them into a single “primordial continent” he called Pangaea, Greek for “all Earth.” Wegener theorized that this massive landform had existed until roughly 250 million to 200 million years ago, when today’s continents began to creep apart. For biologists, this explained the related plant and animal species on lands divided by oceans. For paleontologists, the theory fit with mesosaur fossils found in both South Africa and Brazil. To geologists, Wegener pointed out similar land formations on separate continents and suggested, among other things, that South Africa’s Cape Fold Belt range once joined up with Argentina’s Sierra de la Ventana. Wegener’s work was rejected by leading geologists who had a stake in long-standing, competing theories of Earth’s evolution. Critics complained that he had failed to explain the exact mechanism that would have driven the drifting motion. Wegener agreed with that point, writing in 1929 that “the Newton of drift theory has not yet appeared.” The next year Wegener died, at age 50. It would take 30 more years—and geophysicists’ conclusion that plate tectonics results in continental drift—for Wegener’s theory to be vindicated. —Karen de Seve First Came Pangaea Present-day country boundaries and shorelines are superimposed on the Pangaea of 250 million years ago. Some areas of the modern world aren’t seen; their continental crust formed later.