The shifting fortunes of drift

Continental Drift - The Rejection of Continental Drift

六月 23, 2000

The theory of plate tectonics - the idea that the outermost part of the earth is made up of a small number of mostly rigid blocks in relative motion - is to geology what the theory of evolution was to biology. The analogy is grand, but not overstated. Continental drift, and its mature form, plate tectonics, explain many seemingly disparate earth phenomena: earthquakes, volcanoes, sea-floor spreading, the global distribution of mountain ranges and the occurrence of fossils the same age on continents half the world apart. Not only is plate tectonics the most widely unifying concept in geology since Lyell's principle of uniformitarianism, it is also responsible for elevating geology from an observational science to a predictive one.

Of course we all believe it, and why not? As a student in the early 1980s,I never considered that it was anything but entirely right. But what if it is entirely wrong? Naomi Oreskes' scholarly account provides a fascinating and informative history of the debate that raged in the first part of the 20th century between American and European geologists over the scientific status of continental drift. In 1912, the German meteorologist Alfred Wegener proposed that the continents were not, as had been previously thought, fixed permanently in position, but had instead drifted over the face of the earth throughout geological time. Wegener's theory is convincingly traced back through a series of earlier ideas beginning with the contracting-earth models of Eduard Seuss and James Dwight Dana and ending with the discovery of radiogenic heat and the liberation of geological time from the thermal tyranny imposed by Lord Kelvin. Oreskes asks two simple but fundamental questions: why were leading American scientists so opposed to the idea, to the extent that it was labelled "unscientific", while their European colleagues were so receptive? And why,after such outright rejection, did they subsequently herald Wegener's theory as a major revolution?

Clearly, this volte face requires some explanation. The standard textbook answer is that continental drift was dismissed due to lack of a credible causal mechanism. Oreskes rejects this, contending instead that the theory of continental drift would have required American geologists to cast aside their deepest beliefs and scientific methodologies, something they were simply not prepared to do. But what were these methodologies? According to Oreskes, the methodologies that allowed them to practise utilitarian geology, geology that they believed worked and produced results. Many were also hindered by their belief in the Pratt model of isostasy, which would not allow for horizontal compression of the crust. The attitude of the day is best summarised by R. C. Chamberlin, who complained that (American) geologists would have to "forget everything that has been learned in the last 70 years and start all over again".

But change they did, and by the late 1960s it was an international mix of European and American geologists and geophysicists whose highly influential papers tipped the balance in favour of the "new global tectonics". But Oreskes' story does not have a clean ending. Some high-profile US academics still remained unconvinced late into the 1970s. In a series of papers published in 1974 by the American Association of Petroleum Geologists entitled Plate Tectonics, Assessments and Reassessments , A. A. and H. A. Meyerhoff, among others, were still critical of plate tectonics, arguing that the sea floor was Archaean in age and citing Harold Jeffreys's claim that his modified Lomnitz law was "fatal" to mantle convection.

The search for scientific truth is thus a central tenet in The Rejection of Continental Drift . Oreskes' book shows us clearly how this search can be a struggle against ideas as much as for them. But is geology really the best place to conduct an inquiry into the philosophy and sociology of science? Granted, its history provides a fascinatingly rich cultural backdrop against which to assess scientific methodology and the contingency of knowledge. But can the geosciences compete with the highbrow world of quantum physics and cosmology? Oreskes and her book show us that it can. Personally, I think this a good thing, and while the pragmatic nature of most geologists will undoubtedly save us from a raft of popular science books on whether God was an igneous petrologist, Oreskes is to be commended for redefining plate-tectonic theory in historical context.

The plate-tectonic theme is continued in Constantin Roman's Continental Drift: Colliding Continents, Converging Cultures . Roman, having escaped Ceausescu's Communist Romania in the late 1960s, arrived in Britain when, as in the United States, the theory of plate tectonics was finally coming of age. Set against the backdrop of Cambridge dons and college gardens, Roman's story is centred on the Bullard Laboratories where, in the company of some of the most eminent earth scientists of the day, he began a PhD on deep earthquakes in the Carpathians. Despite some initial reservations, I soon became absorbed in the twists and turns that befall poor Roman: bureaucratic hassles with entry visas, uncertainty about the academic credibility of his ideas on buffer plates and finally, just when he is confident that he is onto something big, he discovers that an American team have got there first. Nearly. But despite its human drama, I cannot help wondering who this book is aimed at. It is a strange mix. It is neither a textbook nor a history book in the sense of Oreskes' detailed work. Instead, it is an autobiographical account bordering on the self-indulgent and peppered with the kind of bizarre incidents that would not seem out of place in a Terry Pratchett novel.

It would nonetheless be surprising if the books did not share some common ground. I found it in Roman's account of the subdued response from much of the geological community to his idea of non-rigid plate margins: "geology remains a conservative profession where people view change with suspicion".A sentiment not out of place with the American mindset so thoroughly documented by Oreskes.

Nick Petford is senior lecturer in geology, Kingston University.

Continental Drift: Colliding Continents, Conberging Cultures

Author - Constantin Roman
ISBN - 0 7503 0686 6
Publisher - Institute of Physics Publishing
Price - £26.00
Pages - 211



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