The idea that continents float deserves to rank alongside those of Galileo and Darwin as one of science’s most profound insights, argues Ted Nield
The gulf between Europe and North America is increasing every day. This is not a political or a cultural point, but a scientific fact. The Atlantic Ocean is expanding, growing, for the past 250 million years, at about the same rate as your fingernails. This is part of the complex process by which the surface of the Earth shifts and moves, forming, breaking up and reforming continents in a stately quadrille taking place over deep geological time.
The idea that the continents could “drift”, that the apparently solid ground in fact behaves like a liquid under the influence of the extreme heat within our planet, was so radical, so against our intuitive sense of the solidity of rock, it took a century to be accepted by the scientific community. Now, as part of the theory of plate tectonics, it is common currency within science, yet it has not sparked the popular imagination in the way we might have expected. We all seem to recognise the importance of Darwin’s theory of natural selection – the idea that we descended from apes, though once shocking, has become deeply ingrained, but the same is not true for the equally radical idea that continents float or that rock “flows”. The facts of plate tectonics itself and the story of how this shift in scientific orthodoxy came about, through the doggedness and enterprise of a series of scientific free thinkers, are as meaningful to our lives as Darwin’s adventures on the Beagle or Mendel’s meticulousness with sweet peas.
A white-backed vulture circling over the central deserts of Namibia in 1940 would have seen something odd in a rocky gorge in the Khomas Hochland pass, west of Windhoek. Two naked young Germans were wading through lingering pools of tepid, greenish water, catching carp with a makeshift fence-net made from a pair of string underpants. One intrepid hunter was Dr Hermann Korn; the other – owner of the sacrificed pants – Dr Henno Martin. Both were geologists. Both were on the run.
They studied together in Göttingen but rejected Nazism so they had fled to south-west Africa. Working on water exploration projects there, they got to know the geology of that remote country well. Finding freedom in South Africa, Martin and Korn became aligned with free geological thinking too. In Namibia they were surrounded by evidence of huge geological change, but also of strange correspondences between this continent and others thousands of miles away. For some prepared to think what was, in terms of the scientific orthodoxy of the day, the unthinkable, this evidence suggested that South America, Africa, India, Australia and Antarctica were the scattered fragments of one vanished megacontinent.
The evidence lay in similarities between types of rocks, fossil species, and living organisms like lemurs, now dispersed in Africa, Madagascar, Sri Lanka and the Far East. The prevailing scientific orthodoxy was a “fixist” one, which explained the spread of species with reference to long-vanished “land bridges”, and accounted for continental changes with the idea of land rising and falling. But Martin and Korn favoured a different notion – that the continents themselves had moved. It was a radical idea, but one with a history.
The original idea belonged to geologist Eduard Suess. Born in Islington in 1831, Suess had a varied and distinguished career which included manning Vienna’s barricades during the revolution of 1848 and masterminding the scheme to bring clean Alpine water to the city in 1873. In between he became a professor of geology and amassed the evidence for a vanished southern megacontinent, one he named Gondwanaland, in his massive four-volume book The Face of the Earth (1885-1901). We still use the name Suess gave the lost megacontinent, but in fact Suess did not quite follow the logic of his own discoveries. He argued that continents moved, but this movement was up and down, a consequence of the shrinking of the Earth as it cools. Gondwanaland, in his view, was fractured by this vertical motion, as mountains raised themselves and oceans flooded the sunken land. Where Suess did find evidence of lateral movement, as in his famous studies of the Alps, he explained this as a mere consequence of the vertical shift. He remained, to the end, a committed “fixist”. It took another scientist to take the next, lateral, step.
This came in 1912, when, having noticed that the continents appeared to fit together like a jigsaw, Alfred Wegener, the German meteorologist, geophysicist and champion balloonist, proposed the renegade theory of continental drift. Wegener used a combination of fossil, meteorological and geological evidence to push Suess’s research to its logical conclusion. He identified another, northern, megacontinent which had joined Gondwana at the equator, forming a true supercontinent which he called Pangaea. Rather than rising and sinking, the continents, he insisted, were moving sideways. He published his arguments in 1915 in The Origin of Continents and Oceans, which was greeted with derision and hostility in many quarters, particularly amongst the powerful American geophysicist community. Rollin T. Chamberlin of the University of Chicago called Wegener’s hypothesis “footloose”, and implied it was fanciful and unproven. In the face of such reactions Wegener became obsessed with finding the evidence which would prove his idea to the sceptics. He paid for his obsession with his life, expiring on the Greenland ice-cap, chasing confirmation of drift using eccentric radio-wave arrival-time methods that could never possibly have worked.
It wasn’t until the late 1960s that the ground shifted and Wegener’s theory started to predominate. This was in part due to the work Martin and Korn had done in the Namibian desert gathering evidence of ancient glaciation and Martin’s later work in Brazil, which matched correspondences with South Africa, on the other side of the South Atlantic. As important was the evidence coming from within geophysics itself that the Atlantic Ocean was young and is expanding. Finally came the evidence of exactly how continents moved, always a stumbling block for Wegener. He had proposed that they plow through the ocean floor rather like an ice-breaker. It was only later with more sophisticated tools at their disposal that geophysicists discovered that continents and the earth’s crust itself are actually floating on the asthenosphere, the underlying rock that is under such tremendous heat and pressure that it behaves as an extremely viscous liquid.
Geologists have now further deduced that plate tectonics is cyclic. For 3 billion years the world’s landmasses have been forming one supercontinent after another, each breaking up under the influence of natural heat, and re-forming 500 to 700 million years later. This “Supercontinent Cycle” is the grandest pattern in nature, up to three times slower than our solar system’s 200-million-year orbit around the galaxy. We are in the middle of one cycle now – we didn’t see the beginning and we’ll never see the end. But the human mind, the only eye that sees through time, has seen it. Some hundreds of millions of years in the future, according to projections made by Earth scientist Roy Livermore, the continents will all be joined back together again in a new supercontinent: Novopangaea.
Mapping the history of shifts in the tectonic plates is helping us to understand the future, and address the present. On 26 December 2004 a magnitude 9.3 earthquake, the largest for half a century, sent a tsunami rolling out across the Indian Ocean, killing a quarter of a million people. Less than a year later, a German research vessel had placed the first 15 earthquake sensors on the seabed. India set up a tsunami warning centre in Hyderabad and by December 2005 an interim Indian Ocean tsunami early warning system was nearing completion.
It is the research undertaken and tools developed by the pioneers of plate tectonics that allow us to develop these kinds of life-saving technologies. Like the profound scientific insights of Galileo and Darwin, plate tectonics can help us by revealing the true conditions under which we live: that nature was not made for us and works on a scale at which we are an irrelevance. This is the harsh message of all true science. It is for us to figure out what we do with this information.