Supercontinent: Ten Billion Years in the Life of Our Planet by Ted Nield

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 blackeye 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 hadcut 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 going 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