Supercontinent: 10 Billion Years In The Life Of Our Planet Read online

  ‘The four dimensional complexities of our happy little planet – “earth’s immeasurable surprise” – are made elegantly accessible by Ted Nield in this truly exceptional book. At least until the next major discovery it deserves to become the standard work, ideal for students of the subject, and hugely enjoyable to those for whom the world remains an unfathomable enigma’ Simon Winchester

  ‘Ted Nield tells the fascinating story of how the world has been made – and re-made – through billions of years of geological time. Geology underpins everything, yet the history of the continents on which we live has remained almost neglected. Nield has put this right with his imaginative and dynamic account of the movements of plates, and the assembly of the familiar world from an unfamiliar past’ Richard Fortey

  ‘As a geologist turned science journalist, editor and provocative blogger, Ted Nield has a complex view of life and science. His skills as a writer successfully convey in Supercontinent the recent exciting work in grand-scale geoscience … To handle it without oversimplification or getting lost in a maze of detail is no small accomplishment. I know of no other attempt to reduce the complexities of the relevant primary literature to the confines of a single popular-science book’ Nature

  ‘Entrenched in daily life, we all crave a little perspective: in Supercontinent we find more than a little, as Ted Nield takes us into the vistas of “deep time”’ Financial Times

  ‘Both informative and entertaining. He has thought well outside the academic box, touching on a huge diversity of topics … lively and stimulating’ Science

  SUPERCONTINENT

  Ten Billion Years in the Life of Our Planet

  TED NIELD

  GRANTA

  The mind must believe in the existence of a law, and yet have a mystery to move about in.

  JAMES CLERK MAXWELL

  CONTENTS

  Title Page

  Epigraph

  Acknowledgements

  Foreword – Big crunch

  PART ONE – MOVING IN MYSTERY

  1 Lost worlds

  2 Ice at the Equator

  3 Queens of Mu

  4 Land of the Gonds

  5 From out the azure main

  PART TWO – EXISTENCE OF LAW

  6 Wonderland

  7 World wars

  8 Wrong-way telescope

  9 Motherland

  10 Birth

  Epilogue – Life, the universe and the puddle

  Further reading

  Index

  About the Author

  Copyright

  ACKNOWLEDGEMENTS

  For particular help with this book and with previous writings of mine that have contributed to it, I gladly acknowledge the following persons (who are, of course, in no way responsible for remaining omissions and errors, for all of which responsibility rests with me).

  Professor Philip Allen, Professor Mike Benton, Ms Vivianne Berg-Madsen, Professor Kevin Burke, Dr Tony Cooper, Professor John C. W. Cope, Professor Charles Curtis, Professor Ian Dalziel, Dr Wolfgang Eder, Professor Michael Ellis, Professor John Grotzinger, Dr Gordon Herries-Davies, Professor Paul Hoffman, Mr Robert Howells, Dr Patrick Wyse Jackson, Dr Werner Janoschek, Dr Sven Laufeld, Dr Roy Livermore, Dr Bryan Lovell, Dr Joe McCall, Professor Mark McMenamin, Dr John Milsom, Professor Eldridge Moores, Dr Bettina Reichenbacher, Professor John J. W. Rogers, Dr Mike Romano, Professor Mike Russell, Dr Gaby Schneider, Professor Chris Scotese, Professor Dick Selley, Professor Bruce Sellwood, Professor Dr Klaus Weber, Dr Jeffrey Huw Williams, Mr Simon Winchester and Dr Rachel Wood. My special thanks go to those in this list who critically read parts of the book in manuscript.

  I should like to acknowledge the Geological Society of London for its enlightenment in encouraging private enterprise among its employees; but I also owe an immense debt to the Society as a Fellow. Fellowship has provided me with invaluable access to one of the great geological libraries of the world; and to the services of my colleague, Wendy Cawthorne. Wendy, like all the best Assistant Librarians, assists in finding the things readers ask for, but then goes the extra mile to find the things they actually need.

  The idea for this book came to me very early one happy summer morning in 2003, among the chestnut trees of Vallée Française, Lozère, France. I made the first outline in a letter I was writing to my dear friend since student days, Professor Mike Ellis, now at the US National Science Foundation. Had he and I not been corresponding in this old-fashioned way since he selfishly removed himself to the other side of the Atlantic, I might never have begun this project. I also thank my editor, George Miller at Granta, who took me to lunch and made editorial suggestions that greatly improved the text.

  I should pay homage to the late and great Professors Janet Watson and Mike Coward of Imperial College, London. They never taught me in the strict sense, but after reading their work as a student I eventually met Janet and came to count Mike as a friend. In this group must also be numbered Dr Rod Graham (still vigorously extant), who did teach me, but who has since, I hope, forgiven me.

  To all I owe my sense of awe at their achievements in untangling the rocks of the Precambrian. I must also acknowledge two more of my personal giants, the late Professors Derek Ager and Dick Owen, both of whom taught me by example that the most complicated science ought to be explicable in language everyone can understand: a lesson that stood me well in my subsequent career as a science journalist.

  I hope that this book will be seen as one long homage to all those great geologists whom I have met over the years and who have helped me. I lay no claim to having seen further, but in the thirty years that have passed since I began studying Earth science, too many giants have offered me their shoulders as footstools for me to be able to acknowledge them all by name. However, for the dedication of this book I would like to single out my fellow members of the Management Team of the International Year of Planet Earth, with whom discussions on the way that Earth sciences benefit society in general have played a major role in the development of this book.

  Most of all, my thanks go to my wife Fabienne, who has continued to provide that without which nothing would be possible.

  Ted Nield

  FOREWORD

  BIG CRUNCH

  Different living is not living in different places

  But making in the mind a map.

  STEPHEN SPENDER

  The drifting continents of the Earth are heading for collision. Two hundred and fifty million years from now, all landmasses will come together in a single, gigantic supercontinent. It already has a name (in fact, it has three) even though human eyes will, in all probability, never see it.

  That future supercontinent will not be the first to have formed on Earth, nor will it be the last. The continents we know today – Africa, the Americas, Asia, Australia, Europe and the Antarctic – are fragments of the previous supercontinent Pangaea, which gave birth to dinosaurs, and whose break-up was first understood barely a century ago, in 1912. Yet 750 million years before Pangaea formed, yet another one broke up; and before that another, and so on and on, back into the almost indecipherable past. The Earth’s landmasses are locked in a stately quadrille that geologists call the Supercontinent Cycle, the grandest of all the patterns in nature.

  Men and women have been imagining lost or undiscovered continents for centuries. For early mapmakers they filled in gaps, forming a bridge from the uncertain to the unknown. Nineteenth-century zoologists and botanists speculated about sunken lands to explain odd distributions of animals and plants. Early evolutionists peopled their hypothetical lost lands with the ancestors of mankind. Fringe religions adopted
them and embattled minority cultures latched on to them to bolster their myths. All had one thing in common: the basic human urge to understand and make sense of the world.

  Today geography has no room for lost continents. The world is ringed by satellites that reveal no undiscovered country. But lost continents have found, at last, a true science of their own. This book is about how that science emerged and how Earth scientists are using the most modern techniques to wring as much information as they can out of the oldest rocks on Earth and predict what the next supercontinent will look like.

  Supercontinent Earths, salvaged from oblivion or projected into the future by today’s geologists, share one thing with all the lost continents that were ever dreamt of, whether by other scientists, mystics or madmen. All lost lands truly exist only in one place: the human mind, the only eye that can see through time.

  But why should we care? We human latecomers evolved a mere six million years ago, halfway through the present cycle, when today’s moving continents were barely a few hundred kilometres from where they are now. And if what we understand of other species can be applied to ours, there is very little chance that humans will survive the 250 million years that will pass before a new supercontinent assembles.

  Yet the supercontinents of modern geology are no exotic fruit from some esoteric branch of science. Their discovery began with an innate urge to explore; it was boosted by the spur of Empire in the nineteenth century as science reached out through the third dimension to map the world and its living things. It continued as the patterns of today were seen to hold meaning for their evolution through the fourth dimension, time. And as the human mind has reached out it has also drawn together.

  Without science the Earth could not sustain us in anything like our present numbers. Our continued life on the planet that gave rise to us will depend upon our ability to use our science to protect and feed ourselves in the face of what threatens us (chiefly ourselves). Understanding the Supercontinent Cycle is nothing less than finally knowing how our planet works. This can be to our benefit – we have, after all, made it thus far – or our detriment.

  If scientific knowledge had been properly deployed many, perhaps most, of the quarter of a million people who died around the Indian Ocean on Boxing Day 2004 could have been saved. The knowledge that makes that possible is the same knowledge that reconstructs landscapes that washed into oblivion hundreds of millions of years before our species existed.

  London, 2006

  PART ONE

  MOVING IN MYSTERY

  1

  LOST WORLDS

  Far out in the uncharted backwaters of the unfashionable end of the Western Spiral Arm of the Galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet …

  DOUGLAS ADAMS

  Novopangaea – a science fiction

  A blue planet hangs in space. You have seen many planets as you have searched the cosmos for signs of life far from your own small planet somewhere in the vicinity of Betelgeuse. But as you approach this one, something about it impresses and excites you. It’s the third planet from an unremarkable star, and the largest of the rocky inner ones. But as you approach it from below the plane of the ecliptic, it shines like an opal, streaked with white.

  The galaxy is full of the common oxide of dihydrogen that appears to cover this planet, but almost everywhere else it is a solid. Here it exists as a liquid and there are traces of its vapour in the atmosphere. The liquid phase can only exist within a very small range of temperatures; temperatures you, as a space explorer, expend a lot of energy maintaining inside your craft. Yet here these equable conditions seem to cover the entire planet. There isn’t even an icecap at the pole, where the temperatures should be at their lowest. It is almost inconceivable that a planet’s temperature should be so constant over its entire surface. It must be that the deep atmosphere is trapping the star’s heat, and then, with the help of the ocean, spreading it around.

  Above the glowing blue ocean, especially over its equator, are streaks of white. Cloudy curlicues and spiralling weather systems track like miniature galaxies across the hemispheres. At first it all looks chaotic, but on your long approach, heading towards the planet’s southern pole, you have time to study time-lapse images. Suddenly the apparent chaos starts to make sense. The clouds’ movements are indeed complex, but do describe a sort of ragged mirror symmetry about the planet’s equator. What seemed like chaos now looks more like order: the atmosphere is convecting in six great cells arranged symmetrically about the equator.

  The planet’s moon is unusually large, though to an experienced space traveller little else is unusual about this satellite. No heat regulation there; with no atmosphere to distribute energy, temperatures can swing wildly through almost 300 degrees from sunlight to shade: quite normal for a space rock struck by starlight. A satellite as big as that must set up a tidal bulge in the ocean by the force of its gravity; you will be able to detect that once you are in orbit and can train your altimeter on the ocean surface.

  Already, using the spectrometer to analyse the light reflecting from the planet, you have detected, amid the dominant nitrogen signature gases like carbon dioxide, and the gas phase of dihydrogen oxide (which will also help to trap heat and keep the planet warm). Methane is there too, and does the same job.

  The unusually tall oxygen spike piques your interest, but just as you are thinking about that, something momentous distracts you. Your ship is now pulling level with the planet’s equator. Perhaps because the clouds had drawn all your attention you had missed it at first, but now you see that this is not a liquid-covered world after all. There, below, is a single, gigantic landmass. You can see it clearly, because the clouds obligingly part over it; few penetrate far beyond its coastline. As the hours go by you watch the landmass unroll as you enter a fixed equatorial orbit.

  It sits mostly in the Northern Hemisphere, covering perhaps 30 per cent of the planet’s total surface area. It is dry. Immense white and beige deserts occupy nearly all of it. Three ranges of mountains, low, desolate and worn down with age, stand out amid the dune seas and endless dazzling playas. Dry, wiggling canyons feed the arid interior wastes, dying into vast plains of white from which expanses of blown sand stretch far away beyond the shimmering mirages of the horizon.

  Most spectacular, apart from this terrifying barren waste, is the continent’s southern coast, maybe twelve or fifteen thousand kilometres long. It lies at a slight angle to the equator and crosses it near its southern end before taking a dogleg and heading back, reaching even greater heights, to the north-west. This entire coast presents a cordillera of jagged peaks up to eight thousand metres high (perhaps nearer ten thousand at its eastern end) punching into the cold upper atmosphere and capped with white. These mountains are young, active, still growing. There are volcanoes too. One of them is erupting now, its plume of ash sweeping offshore like a thin veil, carried by the winds of the topmost atmosphere. This planet’s surface is moving, geologically active; the planet is alive inside, powered by heat generated continuously by radioactive elements, so that the whole crust seethes like the scum on a boiling pot. As the largest of the rocky planets in this system, it is big enough not to have cooled down and died like the others, even after nearly five thousand million years.

  What excites you perhaps more than anything as a space explorer are the colours you can see at the coast of the supercontinent, especially where those coasts cross the tropics. The interior is parched; but the point at which the driest area comes closest to the ocean is behind the range of towering mountains on the south-east coast. Here the weather systems that sweep inshore stand little chance of breaching those massive battlements (even though some of those systems are thousands of kilometres across, with wind speeds of over three hundred kilometres per hour).

  But on the diametrically opposite north-west coast things are different. Here, where prevailing westerlies make lan
dfall, streamers of cloud obscure the land for thousands of kilometres. Beneath them, from time to time and around the edges of the cloud blanket, you detect a livid green stain. Other, narrower areas on the supercontinent’s coasts are green too, peeping out occasionally from the fringe of coastal clouds. This is the eureka moment. The oxygen spike! That huge ocean, and those coastal regions where moisture falls as rain, are teeming with living things.

  You have just topped the greatest scientific discovery by any member of your species since it first began to look up towards the stars. You have found another place in the universe where matter lives. You knew it must be possible. Some said probable. Growing numbers believed it inevitable. But would – indeed, could – anyone ever find such a place? Given the distances of space, would it be possible to travel to such a world? And then even if, somewhere else in that limitless abyss, matter had become imbued with life, would it necessarily coincide with yours? For there was another abyss to consider: the abyss of time.

  The universe is like a post-apocalyptic town: there appear to be other houses, but only yours is currently inhabited. Maybe all those other living worlds were marooned not only by impossible and untravellable distances, but also by duration; lost in time as well as space. Now you have an answer. You have found a neighbour alive.