Alfred Lothar Wegener
1880-1930
German Meteorologist and Geophysicist
Alfred Lothar Wegener was a meteorologist and geophysicist best known for his theory of continental drift, according to which Earth's continents once formed a single landmass and over time drifted to their present positions. Largely rejected during his lifetime, Wegener's idea of continental motion is now universally accepted, although the details of his work have been superseded by plate tectonics.
Wegener was born in Berlin, Germany, on November 1, 1880, to Richard and Anna Schwarz Wegener. He attended the universities at Heidelberg and Innsbruck and received his doctorate in astronomy from Berlin in 1905. In 1906 he accompanied a Danish expedition to Greenland as their meteorologist. Upon returning Wegener lectured in meteorology at the Physical Institute in Marburg (1908-12). Wegener helped lead a second expedition to Greenland in 1912-13 to study glaciology and climatology. In 1924 a special chair of meteorology and geophysics was created for Wegener at the University of Graz. He again led expeditions to Greenland in 1929-30 and 1930-31. He died during the latter trip while attempting to resupply his party.
The idea of continental drift occurred to Wegener in 1910 when he noted the correspondence between the Atlantic shores of Africa and South America. He initially dismissed the idea as improbable. His interest was rekindled in 1911 when he learned paleontological evidence was being used to argue that a land bridge once connected Africa with Brazil.
Wegener became convinced the paleontological and geological similarities required explanation and presented a provisional account of his continental drift theory in 1912. An extended version appeared in 1915 under the title Die Entstehung der Kontinente und Ozeane ("The Origins of the Continents and Oceans") which was not widely read until the third edition appeared in 1924. Wegener was not the first to conceive of continental drift, but his account was the most fully developed and supported by extensive evidence.
Wegener proposed the existence of a supercontinent, which he named Pangaea, surrounded by a supersea, Panthalassa. He believed Pangaea began to split and move apart about 200 hundred million years ago. His strongest supports for the theory were the rocks and the flora and fauna on both sides of the Atlantic. Also, geodetic measurements indicated that Greenland was moving away from Europe. Finally, the separation of Earth's crust into a lighter granite floating on a heavier basalt suggested the possibility of continental horizontal transport.
The most serious problem for Wegener's theory was the lack of suitable mechanism. It was difficult to imagine a force strong enough to displace the continents through the solid mantle and oceanic crust. Wegener suggested two mechanisms that were later shown to be only one millionth as powerful as required. By 1928 Wegener's theory had been generally discounted.
Arthur Holmes suggested a viable driving mechanism in 1929. He argued that radioactive heating created convective currents within Earth's mantle, resulting in an internal zone of slippage. The motions thus generated were small but sufficient to account for the displacement of continental landmasses. Holmes' work drew little attention due to the disrepute of continental drift theory.
The discovery of mid-oceanic ridges after World War II renewed interest in Wegener's theory. Paleomagnetic studies in the early 1950s indicated that rocks have magnetic orientations that vary from continent to continent—consistent with continental drift. Wegener's work gained further support in the 1960s with the acceptance of sea-floor spreading and the discovery of subduction zones. Holmes's driving mechanism was then revived and is still widely accepted.
It was eventually recognized that Earth's crust is composed of plates moving relative to each other. Today, plate tectonics is the principal theory of the genesis, structure, and dynamics of Earth's continents.
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