Supercontinent, by Ted Nield

The history of a break-up written deep in the Earth's heart
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In a stroke of serendipity that must have the publishers cooing, the cover of Ted Nield's book resembles the crack in Tate Modern's floor. It should make people pick it up. Doris Salcedo's artwork has struck a chord because fissures opening in our everyday world are both thrilling and shocking.

Despite this, geologists are the poor relations among scientists. How many people have heard of the great Alfred Wegener (1880-1930), author of the theory of continental drift, the subject of this book, proposed in 1912 and finally accepted in the 1960s?

Geology, with its complex minerals, its huge time-frame and confused strata, requires a great deal of patience. But the subject is climbing the agenda because we can now see how global warming is changing the world. The ice is retreating from the poles and glaciers at an alarming rate. But there are other changes, in deep geological time, of a different order. The present continents are the fragments of a supercontinent, named Pangaea, which started to break up 250 million years ago.

One reason the pattern the Earth had hundreds of millions of years ago matters is that the distant past has experienced climate change more severe than anything likely to be caused by human activities. For example, the rising concentration of oxygen in the atmosphere from the first plants caused a long crisis, in which vast deposits of iron turned to rust and then settled in huge beds now mined as iron ore.

The growing urgency of global warming will surely encourage us to try to understand the early history of the planet. Cue Nield's book, which tells how the continents were not only once joined as one, but how they periodically huddle together and fly apart. In this cycle – "a stately quadrille" – the next supercontinent is due in 250 million years.

Nield tells the story in the modern manner of popular science, which is one of maximum digressivity. This means that the reader sometimes has to piece together the complex story of supercontinents rather as the pioneers did – a fragment on one page linking with another much later.

Underpinning the theories are increasingly sophisticated geophysical techniques, especially studies of the magnetism of rocks and the radioisotopes they contain. Our own experiment in altering the climate and hence the geology of the Earth will one day also be written in the rocks. But will there still be anyone around to read these runes?

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