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WEGENER

vs

JEFFREYS, et al.

FEUDING PARTIES

Alfred Lothar Wegener (1880–1930) – German meteorologist and astronomer, architect of continental drift theory

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Sir Harold Jeffreys (1891–1989) – geophysicist;

most of the rest of the geological world

DATE

1915–60s

CAUSE OF FEUD

The theory of continental drift

The story of Alfred Wegener and the theory of continental drift is often cited as a prime example of how theories that are beyond the pale can rapidly become accepted scientific dogma and of the way in which the real narrative of science (messy, contradictory and contentious) is quite different from the ‘classical’ picture of a serene progress from ignorance to enlightenment. In truth, the Wegener case is not a brilliant illustration of either of these, but it remains a popular and fascinating story.

The shrinking Earth

The most obvious evidence for the notion that the continents were once joined is the apparent fit between the coastlines of eastern South America and western Africa, which became apparent almost as soon as the first maps of the New World were produced. As early as 1596, Dutch map-maker Abraham Ortelius suggested that the Americas had once been joined to Europe and Africa, until they had been ‘torn away ... by earthquakes and floods’.

In 1881, pioneer geophysicist Osmond Fisher proposed a model of the Earth in which a crust of hard rock sat atop a fluid mantle, even suggesting that the ocean floor expanded through volcanic production of new rock, and that contraction of the continents gave rise to mountain ranges. This was a remarkably prescient prototype of modern plate tectonics theory, which went unheralded. Fisher was going against the grain of an Anglo–American tradition that emphasized the relative permanence of the oceans and continents. While in the German-speaking world the notion that the crust of the planet was mobile and the interior fluid had some currency, the mainstream hypothesis was that the Earth was cooling from an initial molten state (see page 17), and in the process contracting, so that its skin rumpled and creased, creating mountain ranges and oceanic basins.

Scientific adventurer

Onto this scene burst Alfred Wegener, an intrepid meteorologist and astronomer. Struck, like many, by the jigsaw-like fit of the South American and African coastlines, Wegener was intrigued when, in 1911, he came across a report outlining palaeontological connections between Brazil and Africa (such as fossils of the same species on both continents). Many other such connections between far-flung regions were known, but they were generally presumed to indicate the former existence of land bridges, now sunk beneath the oceans.

TIMELINE

Wegener claimed not to be aware of the ‘continental drift’ hypothesis of the American geographer F.B. Taylor, published in 1910, and in 1912 he came up with his own, similar theory. He fleshed out this theory in a 1915 book, Die Entstehung der Kontinente und Ozeane (The Origin of the Continents and Oceans), in which he laid out several strands of evidence for his theory of ‘Die Verschiebung der Kontinente’, properly translated as ‘continental displacement’.

Meteorological expedition in the Arctic. Wegener’s research background was in meteorology rather than geology. The vitriolic response to his geological theories was partly motivated by his outsider status.

Wegener, left, on one of his research trips in the Arctic.

Wegener’s theory

Wegener began by discussing flaws in the current contraction model: for instance, if the globe was uniformly contracting, why were the mountain ranges and ocean basins so unevenly distributed? He pointed to clear evidence that there were two distinct types of crustal rock – continental and oceanic – and tried to show how the strata underlying continental crust could deform under great pressure over long periods of time until it acted almost like a fluid (much as ice will). He collated evidence of similarities in rock types and strata on either side of the Atlantic, which suggested former contiguity, arguing: ‘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 run smoothly across.’

To this evidence he added the mounting evidence from the fossil record of species found on both sides of the Atlantic, such as Mesosaurus, a small reptile from the Permian era, and Glossopteris, a plant from the Permo-Carboniferous era. These distributions could not be explained by now-sunken land bridges, he pointed out, because such land bridges were an impossibility: continental granite was less dense than oceanic basalt, and therefore could not sink into the ocean floor. The prevailing belief in these land bridges was, he wrote, ‘a perfectly preposterous attitude’.

Wegener was particularly impressed by the presence at high latitudes of rock types and coal deposits that must have formed in the tropics. All this evidence suggested to him that the continents must once have been joined, and must, over time, have wandered across the face of the globe, like huge icebergs slowly forcing their way through thinner pack ice. He retraced their wanderings to a point where they were all joined together in a super-continent he termed Pangaea (from the Greek for ‘all land’). What force might conceivably drive such epic migrations he could not say for sure. Perhaps foolishly, however, he was willing to speculate that a Pohlfluct (‘flight from the Poles’) and some form of tidal friction might be jointly responsible.

‘If we are to believe Wegener’s hypothesis we must forget everything which has been learned in the last seventy years and start all over again.’

R.T. CHAMBERLAIN, 1926

The gathering storm

Right from the start, Wegener faced criticism for his bold attempt to cut across disciplines and forge a radical new theory. His father-in-law, who was a respected meteorologist, tried to dissuade him as early as 1911. Wegener defended himself: ‘I believe that you consider my primordial continent to be a figment of my imagination, but it is only a question of interpretation of observations ... Why should we delay in throwing the old concept overboard? Is this revolutionary? I don’t believe that the old ideas have more than a decade to live.’ His optimism was ill-founded.

Criticism began soon after publication and continued for decades. In 1922, Philip Lake dismissed him as ‘not seeking truth [but] advocating a cause ... blind to every fact and argument that tells against it.’ Lake savaged the attempt to reconstruct Pangaea by fitting together the coastlines of the continents: ‘It is easy to fit the pieces of a puzzle together if you distort their shape.’ In fact, the true fit is between the continental shelves, but these were not well mapped at this point. A year later, G.W. Lamplugh described Wegener’s theory as ‘vulnerable in almost every statement’, while R.D. Oldham wrote that ‘it was more than any man who valued his reputation for scientific sanity ought to venture on.’

Pangaea to present. A series of maps – showing equatorial and polar views – from Wegener’s book, The Origin of the Continents and Oceans, showing the positions of the continents at different periods in geological history, beginning with his hypothetical supercontinent.

One of the most influential, trenchant and unrelenting critics of continental drift was the geophysicist Harold Jeffreys, who was particularly unimpressed with Wegener’s notion of the continents sailing through a plastic ocean floor. He described it as ‘a very dangerous [idea], and liable to lead to serious error.’ Jeffreys calculated that the two forces Wegener had proposed as drivers of drift – a Pohlfluct and some form of tidal friction – could only provide one-millionth of the force that would be needed.

Opposition to continental drift came to a head at a symposium of the American Association of Petroleum Geologists held in New York in 1926, which both Wegener and Taylor attended. Attendees took turns to bash the theory. C.R. Longwell talked of, ‘the very completeness of the iconoclasm, this rebellion against the established order ... Its daring and spectacular character appeals to the imagination ... But [it] must have a sounder basis than imaginative appeal.’ Palaeontologist E.W. Berry accused Wegener of ‘a state of auto-intoxication in which the subjective idea comes to be considered an objective fact.’ T.C. Chamberlain accused Wegener of ‘taking considerable liberties with our globe’, and his son, R.T. Chamberlain, would later wonder, ‘Can we call geology a science when there exists such differences of opinion on fundamental matters as to make it possible for such a theory as this to run wild?’ Harsh words were still being aimed at Wegener long after his death. In 1949, the revered geological engineer Bailey Willis described continental drift as ‘a fairy tale’.

Continental margin, according to the modern day model of plate tectonics, developed in the 1960s.

‘And yet it moves’

Such vitriol, and the phrases deployed by his detractors, led many to compare Wegener to Galileo (see pages 166–171). Indeed, Our Mobile Earth, a book by a supporter of continental drift, Reginald Daly, included as an epigram Galileo’s famous alleged observation ‘E pur si Muove’ – ‘And yet it moves’. Wegener’s supporters felt vindicated when advances in oceanography and geology after the Second World War seemed to prove he had been correct after all. Bands of magnetic anomalies in ocean-floor rocks showed that the rocks had indeed been spreading, and the discovery of a network of mid-oceanic ridges where volcanic activity was pumping out new seabed explained why.

In 1960, Henry Hess proposed the spreading sea-floor hypothesis, explaining, ‘The continents do not plough through oceanic crust impelled by unknown forces, rather they ride passively on mantle material as it comes to the surface at the crest of the ridge and then moves laterally away from it.’ By 1965, Tuzo Wilson had synthesized the new discoveries into a comprehensive theory of plate tectonics, explaining how and why continents drifted, oceans spread, mountains were created, rift valleys opened, volcanoes erupted and islands formed.

So, was Wegener vindicated, like a latterday Galileo or Darwin? His overarching contention was proved correct – the continents had indeed come together to form super-continents in the distant past, and then had drifted apart to their current positions, and this did explain the distribution of mountain ranges, fossil and coal beds and much else besides. Yet Wegener had also been proved hopelessly wrong in many of the details of his theory, just as his critics contended. Although the plate tectonics model includes a form of continental drift theory, it is by no means the same as Wegener’s version. The story of science is always more complicated than one man triumphing over others.