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.
WILLIAMS
vs
CHOUET
FEUDING PARTIES
Stanley Williams (born 1952) – volcanologist, professor of geology
vs
Bernard Chouet (born 1945) – volcanologist with the US Geological Survey
DATE
1993
CAUSE OF FEUD
Whether the best predictors of an imminent eruption – specifically, the eruption of Galeras volcano in Colombia – are seismological events or levels of gas emissions
The protagonists of this ‘feud’ never really faced off in person or in the arenas of scientific debate. In fact, it is probably a little unfair to describe their relationship as a feud, although Williams is on record as saying that he and Chouet ‘never really got along’. The two men are volcano experts, men whose driving ambition has been to work out how to predict an eruption. They differed sharply on their answers to this question, differences reflected in the ways they have approached their topic and in their views of what constitutes a ‘real’ volcanologist. These differences would be brutally and tragically highlighted in 1993, when Williams led a group of scientists and others into a volcanic crater, only for it to erupt, killing nine and severely injuring Williams himself.
Desk jockeys vs volcano jocks
Arguably, the world of volcanologists can be divided into jocks and nerds. The nerds work in laboratories and behind computers, poring over graphs, statistics and computer models. The jocks climb active volcanoes and get up close and personal with them. Williams has claimed that ‘the best work ... comes from those of us who walk into the crater’, so it is probably fair to describe him as a volcano jock. In the words of Dr Larry Malinconico of Lafayette College in Pennsylvania, ‘Stan’s a very aggressive scientist.’
Williams undertakes dangerous ventures into the volcano’s mouth, partly in order to study and collect samples of the noxious gases issuing from vents known as fumaroles. He believes that the make-up and volume of these emissions can be used to determine how close to an eruption the volcano is. Bernard Chouet, who trained as an engineer and rocket scientist before becoming a volcanologist, concentrates more on studying the seismology of volcanoes; he can be classed as one of the nerds. It was while studying seismographs in the early 1980s that he identified a hitherto unrecognized component of the vibrations produced by pre-eruption volcanoes: ‘It stared you in the face. “Wow, this is obviously different.” Embedded in the record among all these ... earthquakes were classic-looking quasi-monochromatic harmonic signatures, beautiful textbook examples.’
The ‘harmonic signatures’ were what is more commonly known as long-period events (LPEs), known in Spanish as tornillos (screws) because of their characteristic corkscrew shape. They are resonant frequencies produced by bottled-up lava and gas vibrating inside volcanic fissures like air in an organ pipe, and Chouet realized that their presence signalled an imminent eruption. He described his revelation as ‘a defining moment ... suddenly you realize the volcano is speaking to you and you understand the language.’
Bernard Chouet. Swiss geophysicist and seismologist who originally studied astronautics, making him, literally, a rocket scientist. Chouet is now best known for his pioneering research on Long Period Events.
Under the volcano
The pressing need for a reliable way to predict an eruption was driven home in 1985, when the Colombian volcano Nevado del Ruiz became highly active. Local volcanologists feared that when it erupted it would trigger catastrophic floods and mudslides that could threaten the nearby town of Armero, but without precise knowledge of when such an event might occur the authorities would not agree to evacuate over 20,000 people for an indefinite period. On 13 November the mountain blew, drowning Armero in a vast tide of mud, water and rubble that claimed 24,000 lives. Williams and Chouet continued work on their respective theories, hoping to prevent the next catastrophe.
In 1989, Chouet’s LPE model proved itself when he was able to