Supercontinent: Ten Billion Years in the Life of Our Planet by Ted Nield

Author:Ted Nield
Language: eng
Format: mobi, epub, azw3, pdf
Tags: Non-Fiction, Science
ISBN: 9780674026599
Publisher: Harvard University Press
Published: 2007-11-15T00:00:00+00:00

Non posse

The reason for du Toit’s failure lay in the nature of the evidence itself, of the ‘proofs’, as Skerl would have translated it. Both du Toit and Wegener were aware of this problem, which was that by their nature, geological correlations did not compel drift. In fact, du Toit committed a PR blunder of his own by admitting in his monograph that the similarities between the fossils of Africa and South America ‘can generally be explained equally well, even if less neatly, by the orthodox view that assumes the existence of extended land bridges …’. This was putting weapons in the hands of his enemies; but his point was that fossils on their own could not decide anything because fossils are remains of living things and living things can move. Instead, he concentrated on the rocks themselves.

Sedimentary rocks change their character from place to place, depending on the environment that lays them down. Beach sediments change as the bay merges with, say, a river estuary. What du Toit showed was that sediments of the same age in South America and Africa often showed greater changes within their outcrops in those continents than they did across the wide expanse of the South Atlantic. This, for him, was far more compelling evidence than the fossil similarities that the two continents were once close together and hence probably joined along their now distant coastlines.

But this evidence was also circumstantial. Geophysicists persisted with their non posse, ‘it’s impossible’, line of argument (it is a well-known fact that a scientist always finds evidence from his own field most convincing). If you wanted to win over physicists, it was little use drawing their attention to fossils and sediments. For that group, drift didn’t happen because it couldn’t happen.

Writers of popular science are often accused of ‘hardening up’ stories to make them simpler, clearer or more exciting. This sometimes gets them into trouble with scientists, who tend to favour caution. Charles Ray was writing The World of Wonder, my father’s unwieldy science encyclopaedia, in the early 1930s. Wegener, referred to throughout as ‘the late Professor Wegener’, had not long perished on the Greenland icecap. Continental drift theory had been around for eighteen years but was still highly controversial. Yet undaunted, after an excellent summary of the theory, Ray writes: ‘It seems a startling theory to think of the continents sliding or drifting over their foundations; but distinguished geologists say there is nothing at all impossible in the theory from a mechanical point of view …’

When I first read this as a boy, of course I believed it. When I came across it again later, having by then read the conventional textbook histories of plate tectonics, it made me laugh. Surely, the situation was quite the reverse? Was it not precisely the ‘mechanical point of view’ (the mechanism) that gave even the most eminent geologists the greatest difficulty of all? No amount of evidence based on animal or fossil distributions, or similarities in sequences of strata, or

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