Long-Term Global Forecast? Fewer Continents

Geologists have long prided themselves on their ability to peer into the distant past and discern the slow movements of land and sea that have continuously revised the planet’s face over eons. Now, drawing on new insights, theories, measurements and technologies — and perhaps a bit of scientific bravado — they are forecasting the shape of terra firma in the distant future.

Forecasts of future continental motion developed slowly as offshoots of the theory of plate tectonics, which won acceptance in the 1960s and 1970s, shattering old dogmas of continental immobility.

In 1910, Wegener (note: at that time a professor of meteorology at the University of Marburg. GC) noticed the matching coastlines of the Atlantic continents -- they looked on maps like they had once been fit together. He was not the first to notice this, but it was an idea that would never leave his thoughts. In 1911, he published a textbook on the thermodynamics of atmosphere, but at the same time he pursued his studies of the continents. He first spoke on the topic in January of 1912, where he put forth the idea of "continental displacement" or what later was called continental drift. The year 1912 was busy for Wegener: he got married (to the daughter of Germany's leading meteorologist) and he returned to Greenland, making the longest crossing of the ice cap ever made on foot.

Though he served in World War I and was wounded twice, he published his ideas in 1915. They constituted the first focused and rational argument for continental drift, but still they veered radically from the accepted beliefs of the time. Some scientists supported him. Still more scientists opposed him -- including his father-in-law, who seemed annoyed that Wegener had strayed from meteorology into the unknown territory of geophysics. The established reputation of many of his detractors probably gave more weight to their criticisms than was merited. Wegener often complained of their narrow-mindedness.

Well after his death, and after World War II, Wegener's theories were vindicated by the work of Harry Hess and others. In 1960 Hess proposed the mechanism of sea-floor spreading, which would explain how the continents moved. Newly discovered expiration techniques were employed to prove this theory and ultimately, the correctness of Wegener's chief idea as well.

The Meteorologist Who Started a Revolution

By Patrick Hughes

"Utter, damned rot!" said the president of the prestigious American Philosophical Society.

"If we are to believe [this] hypothesis, we must forget everything we have learned in the last 70 years and start all over again," said another American scientist.

Anyone who "valued his reputation for scientific sanity" would never dare support such a theory, said a British geologist.

Thus did most in the scientific community ridicule the concept that would revolutionize the earth sciences and revile the man who dared to propose it, German meteorological pioneer and polar explorer Alfred Wegener. Science historians compare his story with the tribulations of Galileo.

German climatologist and geophysicist who, in 1915, published as expanded version of his 1912 book The Origin of Continents and Oceans. This work was one of the first to suggest continental drift and plate tectonics. He suggested that a supercontinent he called Pangaea had existed in the past, broke up starting 200 million years ago, and that the pieces ``drifted'' to their present positions. He cited the fit of South America and Africa, ancient climate similarities, fossil evidence (such as the fern Glossopteris and mesosaurus), and similarity of rock structures. The American F. B. Taylor had published a rather speculative paper suggesting continental drift in 1910 which, however, had attracted relatively little attention, as had previous such suggestions by Humbolt and Fisher . The book was translated to English in 1924, when it aroused hostile criticism. The proposal remained controversial until the 1960s.

...(that) when you fit Africa and South America together, mountain ranges (and coal deposits) run uninterrupted across both continents, writing:

"It is just as if we were to refit the torn pieces of a newspaper by matching their edges and then check whether the lines of print ran smoothly across. If they do, there is nothing left but to conclude that the pieces were in fact joined in this way."

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.

Because of this abuse, Wegener could not get a professorship at any German university.  (EA)

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."

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 grand scale process that causes mountain-building, earthquakes, volcanic eruptions, sea-level fluctuations, and apparent polar wandering as it rearranges Earth's geography.

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 candidates; 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.

“The most important thing to realize,” he said, “is that modern geology is just a snapshot of a continuous-action movie. When you zoom out and look over a long enough time, you realize everything is mobile.” -- J. Brendan Murphy, St Francis Xavier University

The change at the PETM was so large that it would have required a decrease in biological activity equivalent to roughly three times the total present-day terrestrial biosphere. In other words, if all of the terrestrial carbon today (in forests, animals, soils, etc.) were converted to carbon dioxide and returned to the global inorganic carbon pool, the change in the global carbon isotopic ratio would only be a third as big as that observed during the PETM!

During the Cretaceous Thermal Maximum (CTM), about 91 million years ago, the Earth's climate was extremely warm. Global surface temperatures averaged about 10^oC warmer than today.