When the first maps of South America were made, cartographers and scientists noted that the shape of the eastern South American coast looked similar to the western coastline of Africa. People speculated that the two continents were once joined together.
Alfred Wegener was one of the first scientists to take this idea seriously. He reasoned that if the two continents had been joined together, fossil and rock patterns along each coastline would match. He began a series of studies to see if such patterns existed, and he discovered that they did.
If one were to place South America next to Africa, not only would the shapes match like two puzzle pieces, but the patterns of rock, minerals, and fossils would match, as well. This encouraged Wegener in his pursuit of the idea he called continental drift. He proposed that the two continents were once a single land mass that had somehow split in two. The two pieces had drifted to their present locations—nearly three thousand miles apart from one another.
Wegener searched for more evidence that continents had drifted over geologic time. He noticed that there were coal seams in the rock of Greenland. Today, Greenland is near the North Pole and is covered in ice. Coal forms from tropical swamps. Could the earth have been warm enough so that even regions near the North Pole were tropical? Or could it be that Greenland was once located near the equator and has since drifted to its present location near the pole? Wegener became convinced that the continents had, in fact, drifted to their present locations. Reassembling the continents by matching continental shapes, rock types, mountain ranges, and fossils, he proposed that the earth’s continents had once been one giant continent he called Pangaea. This landmass broke apart at some point, and the individual pieces drifted across the face of the earth to their current locations. The theory of continental drift was a result of Wegener’s hypothesis.
When Wegener presented his ideas, they were met with skepticism. How could continents drift thousands of miles? What force on Earth could do such a thing? Wegener was unable to explain in a plausible way how the continents had moved. As a result, most scientists of Wegener’s day dismissed his idea as a fantasy.
Read the following excerpt from NASA’s Earth Observatory program. In this excerpt, you will learn a little more about how scientists reacted to Alfred Wegener’s continental drift hypothesis. As you read, think about why scientists didn’t generally believe Wegener.
The Wrath of Science
Except for a few converts, and those like Cloos who couldn’t accept the concept, but was clearly fascinated by it, the international geological community’s reaction to Wegener’s theory was militantly hostile. American geologist Frank Taylor had published a similar theory in 1910, but most of his colleagues had simply ignored it. Wegener’s more cogent and comprehensive work, however, was impossible to ignore and ignited a firestorm of rage and rancor. Moreover, most of the blistering attacks were aimed at Wegener himself, an outsider who seemed to be attacking the very foundations of geology.
The idea of continental drift was not accepted easily by the scientific establishment. Even though Wegener assembled many interlocking pieces of evidence to support his ideas, they were so radical that he was often ridiculed. . . .
Because of this abuse, Wegener could not get a professorship at any German university. Fortunately, the University of Graz in Austria was more tolerant of controversy, and in 1924 it appointed him professor of meteorology and geophysics.
In 1926, Wegener was invited to an international symposium in New York called to discuss his theory. Though he found some supporters, many speakers were sarcastic to the point of insult. Wegener said little. He just sat smoking his pipe and listening. His attitude seems to have mirrored that of Galileo who, forced to recant Copernicus’ theory that the Earth moves around the sun, is said to have murmured, “Nevertheless, it moves!”
Scientifically, of course, Wegener’s case was not as good as Galileo’s, which was based on mathematics. His major problem was finding a force or forces that could make the continents “plow around in the mantle,” as one critic put it. Wegener tentatively suggested two candidates: centrifugal force caused by the rotation of the Earth, and tidal-type waves in the Earth itself generated by the gravitational pull of the sun and moon.
He realized these forces were inadequate. “It is probable the complete solution of the problem of the forces will be a long time coming,” he predicted in his last (1929) revision. “The Newton of drift theory has not yet appeared.”
Wegener noted, however, that one thing was certain:The forces which displace continents are the same as those which produce great fold-mountain ranges. Continental drift, faults and compressions, earthquakes, volcanicity, [ocean] transgression cycles and [apparent] polar wandering are undoubtedly connected on a grand scale.
Wegener’s final revision cited supporting evidence from many fields, including testimonials from scientists who found his hypothesis resolved difficulties in their disciplines much better than the old theories. Climatology was one such discipline.
Fossils and geologic evidence show that most of the continents used to have startlingly different climates than they do today. Wegener thought continental drift was the key to these climatic puzzles, so he and Vladimir Koppen plotted ancient deserts, jungles, and ice sheets on paleogeographic maps based on Wegener’s theory. Suddenly the pieces of the puzzles fell into place, producing simple, plausible pictures of past climates. Evidence of the Permo-Carboniferous ice-age era that peaked some 280 million years ago, for example, was scattered over almost half the Earth, including the hottest deserts. On Wegener’s map, however, it clustered neatly around the South Pole—because Africa, Antarctica, Australia, and India had once comprised a Southern Hemisphere supercontinent (Gondwanaland).
Wegener considered such paleoclimatic validation one of the strongest proofs of his theory. Conversely, continental drift has since become the organizing principle of paleoclimatology and other paleosciences.
Unfortunately, though Wegener’s explanation of the Permo-Carboniferous ice age impressed even his critics, the merit of much of the rest of his supporting evidence was not widely recognized at the time. As a result, most geologists eventually dismissed his theory as a fairy tale or “mere geopoetry.”
Wegener had evidence that the then-current theories about continents were not accurate, and he had evidence to support his own claim about continental drift. However, he wasn’t able to explain what force or mechanism moved the continents. Without a physical process that could move the continents, his idea remained in the scientific “dog house.” In the next lesson, you’ll learn how the theory of plate tectonics is similar to Wegener’s theory of continental drift and about the evidence that supports it.