Supercontinent: Ten Billion Years in the Life of Our Planet

by Ted Nield

  The thing about volcanoes is that they erupt from time to time, and as Professor Zichichi knew well, when they do this they tend to swell up as the magma rises (and subsequently down after it erupts). The new activity of 2003 was just the latest phase in the life of the Graham Bank volcano. The previous time it had appeared above the water was in 1831. In the very year that Eduard Suess was born, a small Mediterranean island a few hundred metres across was also coming into the world, just off Italy’s toe.

  Location of Ferdinandea, or Graham Bank as the British have it.

  The British name derives from Admiral Sir James Robert George Graham, First Lord of the Admiralty, who claimed the newly emerged island for Britain by planting a flag on it. This did not stop competing colonial claims by France, Spain and of course the Kingdom of the Two Sicilies. The Italians, whose nation now encompasses the Two Sicilies, still refer to Graham Bank as Ferdinandea, after King Ferdinand II, who ruled the Two Sicilies from 1830 to 1859. The competing colonial nations only gave up their territorial squabble when they realized that the sea had eroded the island away completely while their backs were turned.

  Graham Bank sometimes seems to have been put on Earth simply to make fools out of men. As recently as 1987 US warplanes spotted it, believed it to be a Libyan submarine and dropped depths charges on it. Even more recently the two surviving relatives of Ferdinand II commissioned a plaque to be affixed to the then still submerged volcanic reef, claiming it for Italy should it ever rise again. Astute readers will not miss the logical difficulty inherent in the concept of a ‘submerged island’. For is not a ‘submerged island’ just another bit of the seabed? But neither national sentiment nor fin de race royals find much use for logic.

  The prime mover in the affair with the plaque was one Domenico Macaluso, surgeon, voluntary ‘Inspector of Sicilian Cultural Riches’ and, as luck would have it, a keen diver. He first became interested in Ferdinandea in February 2000, when news of fresh eruptions first broke. These reports were all couched in terms of the reappearance of a ‘lost corner of the British Empire’, thus ruffling some Italian plumage. The well-connected Macalusa successfully persuaded Charles and Camilla de Bourbon to commission a 150kg marble tablet, which he and some friends duly installed, twenty metres under the waves, in March 2002. (Mysteriously, it was later smashed into twelve pieces by a person or persons unknown.)

  That year Filippo D’Arpa, a journalist on a Sicilian newspaper, published a timely novel about the events of 1831: L’isola che se ne andò (The island that went away). He summed up the fiasco well when he told the Independent: ‘[Ferdinandea] is a metaphor on the ridiculousness of power. This rock is worth nothing, it’s no use as a territorial possession, and yet the French and the Bourbons … nearly came to war [and] 160 years later, England and Italy are still fighting.’

  If only politicians would listen to geologists, perhaps they would learn to curb their enthusiasm. For alongside this grand opera buffa, the geology of Graham Bank is really rather boring. Today the volcanic scoria that surrounded the vent in 1831 have been planed off: to thirty metres deep. A column of rock twenty metres in diameter – the lava-choked neck of the old volcano – rises to a dangerous eight metres below sea level (and looks, one must suppose, rather like the conning tower of a submarine to the pilot of a B52). To a geologist it is just alkali olivine Hawaiite basalt, a typical piece of ocean floor. Most of our planet is covered in similar stuff. No wonder geologists were so nonplussed by the public interest in this here-today-gonetomorrow island.

  But in 1831 men of science exhibited no such disdain. Its emergence was greeted as an amazing prodigy, and the most advanced scientific thinkers of the time seized on it with glee. The man who founded the Société Géologique de France, Louis Constant Prévost, wrote a lengthy scientific paper about the island (which he called L’Isle Julia); though by the time it finally appeared in print, in 1835, the island itself had long vanished. Meanwhile in England there was another geologist for whom the movement of the Earth’s crust was a source of interest.

  Charles Lyell is undoubtedly one of the most influential geologists who ever lived, even outstretching Suess’s shadow over subsequent ages. When you read Suess’s obituaries you are struck by the way all of them reach for comparisons; for writers with comparable scope, who published great books that will stand for ever as their monument. The one name they all quote is Charles Lyell, author of Principles of Geology.

  Through his Principles, which Darwin took aboard the Beagle as his bedtime reading, Lyell had come to dominate the way geologists (especially English geologists) in the nineteenth century thought about Earth history. He preached a strict version of a creed known as uniformitarianism, the concept credited with putting an end to wild speculation about the past and turning geology into a science.

  So what is it? The essence of the principle is simple. It says that to understand what the rocks are trying to tell you, you should look around at the causes operating today and find an explanation among them. Geologists constrain their interpretations of the rock record by looking at the way the modern world works. The modern world is the control on geologists’ thought experiments.

  This is how it works. If you were to see me in the street with a black eye and grazed elbows, you could devise a number of possible scenarios to explain how I got that way. You might conclude I had been abducted by aliens and used as a guinea pig in their experiments. That explanation would not be uniformitarian because, although some pretty unusual things do happen in Stoke Newington, alien abductions are not among them. On the other hand you might surmise that after one glass of Pinot Grigio too many I had missed my footing and measured my length in the gutter. This would be a uniformitarian conclusion, because similar events happen almost every day (though not to me, you understand).

  As well as urging present-day processes upon geologists, uniformitarianism also has something to say about their intensity. In addition to looking around for modern-day causes, the strict Lyellian assumption is that those processes have also always operated at a comparable rate. Thus deep time becomes paramount. The raindrop falling on the stone can, given enough time, move the mountain. Tiny changes, all but imperceptible to us, can achieve everything geologists might want because time is almost infinitely available. There is therefore no need to appeal to great upheavals or catastrophes; the gradual ups and downs of the Earth’s crust, as in the Baltic or the Graham Bank, will be enough.

  This view of uniformity is an extreme one, but it was the prevailing view in Suess’s time, especially in England. The third (1834) edition of Lyell’s Principles devoted six pages to Graham Bank. It provided Lyell (who trained as a lawyer, and it showed) with a convincing courtroom argument against his catastrophist opponents. But Suess, who also subscribed to uniformitarian principles, had a different mind: one with mountains in it. Geologists who work among the world’s great ranges will tell you they leave an indelible stamp on the imagination. The Alps lay at the root of the Romantic revolution, as artists turned to them for inspiration. Mountains were no longer merely inconvenient obstacles but meaningful. Suess had cut his geological teeth mapping the Alps and wrote an early book about them.

  By contrast, Lyell hardly mentioned mountain building at all in his magnum opus. Today this seems very curious. It is almost as though he thought of mountains as a bit embarrassing, a sort of unsavoury fracas from which an English gentleman should avert his eyes. European geologists like Suess found the Alps much less easy to ignore. They knew in their bones that the Alps had something very important to say about the world and how it worked. Something about the beginning and the end of the world seemed locked up in their tumult.

  So geologists are still struggling with two types of change: gradual, repetitive Lyellian ones that go in cycles, and secular – one might even say ‘Suessian’ – changes: progressive, revolutionary once-and-for-all changes after which there is no going back. The history of the Earth is made of both.

  In nature, cyclicity is g
oing around all the time. Our Earth goes around the Sun and we have cycles called seasons. The Moon goes round the Earth and we have cycles called tides. Our planet rotates and we get cycles of day and night. This book is about the greatest cycle of nature: from one supercontinent, through phases of breakup, to the reassembly of a new supercontinent over a period of between 500 and 750 million years.

  But there are plenty of examples of Suessian change too. Owing to the friction caused by the tides of the global ocean, the Earth is rotating more slowly today than it did yesterday. The moon’s orbit takes it a little further away from us each day. Days are longer now than they were 500 million years ago, which also means there were more days in the year back then. The Sun is gradually becoming hotter as it uses up its hydrogen fuel. And despite the delaying tactics of radioactivity, the Earth is indeed very gradually cooling down. Changes like this are one-way-only.

  Cycles, however, were the essence of uniformitarianism as presented by Lyell. They allowed nature to repeat herself endlessly to the last syllable of time. What attracted Lyell to cases like the Graham Bank volcano and the ups and downs of the Bay of Naples was that they allowed him to make a subtly different point, namely that even if the rocks do speak of catastrophe, gradualism still dominates time.

  The Vesuvius eruption of AD 79 left a lot of geological evidence behind. Catastrophes often give rise to more evidence than the uneventful ages that pass between them. But this does not mean that the past was more violent than today; it just means that the rocks are unrepresentative. Like a scandal sheet called the Geological Record, rocks scurrilously report everything lurid and gruesome but leave out the everyday stuff. Lyell’s Earth was cyclic, placid even, and there was no progression, wave following on wave.

  Suess wasn’t having this. His was a uniformitarianism for revolutionaries. For Suess there was more to existence than endless repetition. Not everything that goes around comes around. What happens today can make a difference, for ever. Suess rejected the idea that processes going on around us now are the only yardstick against which to measure the Earth’s massive history.

  In reconstructing supercontinents even older than Gondwanaland, lands that existed when the Earth was very different, Earth scientists today are able to envision much stranger things than Lyell’s philosophy would ever allow them to dream of, and yet still keep their scientific heads. Suess, who also peered deeply into time, lacked the true Englishman’s fondness for the status quo. This man, who had stood on mountains and barricades, built aqueducts, tamed rivers and discovered a supercontinent, understood something Lyell did not: things need not always have been the way they are.

  Endeth the world … (not)

  In mid-1960, engineers were carving out the Mont Blanc tunnel, which connects France and Italy, through the roots of the tallest Alpine massif. But on 14 July a small band gathered nearby to witness the End of the World, which was supposed to take place at 1.45pm. As the moment approached, women began wailing. A bugler in lederhosen stood up and delivered an impression of the final trump.

  Then, unexpectedly, 2.46 arrived.

  The cult leader, Elio Bianca, who before becoming a prophet had worked as a paediatrician with the Milan Electric Company, said afterwards: ‘We made a mistake.’ The next day the New York Times ran a story under the headline ‘WORLD FAILS TO END’. You could hardly ask for a more succinct statement of strict Lyellian uniformitarianism.

  By contrast, the first people to climb Mont Blanc did so at the behest of a geologist, who was more anxious to know about how the Earth began. Horace Bénédict de Saussure (1740–99) put up two guineas for the first person to find a route to the top of ‘la montagne maudite’ (‘the accursed mountain’) after visiting Chamonix for the first time in 1760. It was twenty-five years before anyone made a claim, but in the end it was chamois hunter and crystal gatherer Jacques Balmat, together with a local physician, Michel-Gabriel Paccard, who became the first humans to stand at the summit, on 8 August 1786.

  De Saussure himself gained the summit himself a year later and verified its height as 4785 metres (twenty-five metres short, but enough to put it in the record books). And although he later gave up trying to disentangle the fearsome structural complexity of the Alps, de Saussure summed up a whole tradition of European geology when he wrote: ‘It is the study of mountains which above all else can quicken the progress of the theory of the Earth.’ Understanding mountains and the processes that build them was to unlock the tectonic enigma of how supercontinents form and break up. Crucially, mountains were soon to demonstrate the impossibility of up-and-down tectonics and foundered continents.

  In almost his first geological assignment, Suess had discovered evidence of large lateral displacements in the Alps, which seemed to show that massive terrains had been moved sideways for large distances. In doing so he unwittingly planted the seeds of an idea that would unravel not only the structure of mountains but help lead eventually to the idea that continents themselves can move laterally. In later work and his magnum opus Suess did not ignore lateral displacement; instead he said it was a side effect of ups and downs. For him the basic force governing all tectonics was shrinkage, which caused large sections of the planet’s contracting crust to founder. As he put it, ‘The collapse of the Earth is what we are witnessing.’

  As the Earth’s innards shrank, Suess believed, the crust was put under strain. From time to time parts of it would be forced to subside as the rocky outer shell accommodated to the collapsing planet within. The fragmentation of Gondwanaland, he reasoned, was caused by great subsidences, which left parts of the crust standing high as table-lands (Africa, India and South America) and parts deep below the sea. So the formerly connecting stretches of land in between, for example, Africa and South America, or India and Madagascar, had simply dropped and been lost beneath the waves. Gondwanaland had left fragments behind, but it had not fragmented. The lost parts of it were still there, sunk beneath the Indian and Atlantic oceans like the lost continents of myth. Because these foundered areas of new ocean were broadly elliptical, Suess said, they tended to leave behind landmasses with pointed ends: for the same reason that a round pastry cutter leaves you with triangular offcuts on the rolling board.

  The idea of a shrinking Earth was a powerful one, because it seemed to flow, with all the inevitability of physical law, from the simple observation that it is hot in mines. The further down in the crust you go, the warmer it gets. Heat is escaping from the Earth’s interior. And to nineteenth-century physicists this meant that the Earth was cooling. And if the Earth is cooling, it therefore must be shrinking because that is what happens when things cool. (The idea only finally lost support after the discovery of radioactivity, when scientists realized that, because of the heat generated by radioactive decay, the Earth was not in fact cooling at anything like the rate that had been assumed.)

  Although Suess was still alive when Alfred Wegener first proposed continental drift in 1912, he remained committed to fixed continents that occasionally sank below the waves. Yet his explanations of how the Earth’s contraction could lead to the very lateral displacements that he himself had noted as a young man were never wholly convincing, perhaps even to him.

  Later geologists, Wegener foremost among them, merely tipped their hats at his global observations, synthesis and deductions and, freed from the shackles of contraction theory, explained them away using another mechanism entirely: the notion that continents could move sideways. And that is how, rather paradoxically, Suess is numbered among the true precursors of continental drift, despite having remained resolutely ‘fixist’ all his life.

  Everest’s missing feet

  What finally killed off the age-old idea of sinking continents was the discovery that continents simply can’t sink: they are, in fact, already floating.

  Gravity is a property of matter. Every object exerts a certain gravitational attraction on every other, but the force is so weak that only truly massive objects exert it to a degree that we can meas
ure. Obviously the Earth and other planets exert gravity, but if you are using very sensitive instruments, even the extra mass of mountains could be expected to have an effect.

  Mapping can be said to be an act of colonization, and the British Raj was keen to reinforce its dominion by surveying the Empress’s possessions with the most modern techniques then available. Mapmakers criss-crossed India using two methods to determine their position, one providing a check on the other. The first of these fixed positions on the ground like a sailor at sea, using the stars, the horizon and a sextant. The other method was triangulation, whereby each point on the ground is fixed relative to another by measuring the intervening distance and taking the compass bearing from each triangulation point to two others. The rest is trigonometry.

  When, during the mapping of the Gangetic Plain, south of the Himalayas, these two methods were found to give widely differing results, the mapmakers found themselves in a spot of bother. It came to a head over the difference in latitude between the towns of Kalianpur and Kaliana. These were supposed to be 370 miles apart. But their latitude measurements, determined using the two methods, differed by 550 feet. This did not much please India’s Surveyor General, Colonel George Everest.

  Astronomical measurement depended on the use of a plumb bob to level the instrument before readings were taken, and Everest had the idea that the extra gravitational attraction of the Himalayas might have been pulling the plumb away from true vertical. The Archdeacon of Calcutta, John Pratt, a Cambridge-educated mathematician, was recruited to examine the conundrum; but his first results singularly failed to make things clearer. When Pratt compensated the astronomical readings for the expected extra gravitational attraction exerted by the mass of mountains that he could see, the observed discrepancy turned out to be much smaller than it should have been. The mountains were exerting less of a pull on the plumb bob than they should have done. It was as though they were hollow.