43. A sense of time – Earth history and the London Marathon

In geology, you learn about time. About a lot of time.

As I look from my window upon the Surrey Downs, I see the Chalk and Greensand hills, walked by pilgrims heading east to Canterbury for eight hundred years and more. That seems a lot of time.

But to the Earth, it’s nothing. Our planet is around 4.6 billion years old, give or take a few. That IS a lot of time.

A new perspective is required, so let’s imagine the Earth’s own lifetime as a marathon course. The longest journey, but even in this unimaginable race, every 100 million years meant just one kilometre en route from Greenwich to The Mall.

If the first half of any marathon is 20 miles long, and the second ‘only’ six, then the Earth’s was much the same. Those early miles are largely lost to her geological biographers, and she has herself all but forgotten. Only the meteorites’ vague radioactive memory recalls her startline euphoria from the birth of the solar system. Just a few fragments of battered crust in Greenland and South Africa remain to witness the long time of cooling when her race was warming up. The first 10 km to the Cutty Sark, virtually wiped for ever.

And after that, through South London’s streets, it was pretty quiet. For a very long time. Barren, wild, volcanic landscapes rose and were worn away, separated by empty oceans which opened, closed and re-opened unseen throughout long and lonely miles. There was no free oxygen in the air, but we’ve found microscopic filaments and strange bacteria-like structures in sedimentary rocks around 3 billion years old. Did they really live, or form as mineral aggregates ? A question to fuel a live debate amongst geologists: since how could we confirm such simple life on Mars, when we’re not quite sure what to recognise as life at home ?

Maybe it was around the twelve mile mark, or 20 km, by Tower Bridge, that saw the pattern for Earth’s race set at last. Primitive algae had appeared, forming mounds and crusts to drape those Precambrian shields. They ruled the Earth for ten kilometres more, through Poplar, past Canary Wharf, and into Docklands. A slow release of oxygen was liberated by their photosynthesis, and a few soft-bodied creatures emerged to glimpse St Katharine’s Dock, with less than seven kilometres still to race. Such old and squidgy life forms have an understandably patchy fossil record and remain preserved in soft soupy muds like the Burgess Shale of Canada.

Almost four billion years elapsed, and only slime and worms to show ? But the pace was hotting up, and our weary Earth was lifted by a sudden crowd as several new animal groups arose at the Tower of London with 5.5 km left to run. Amongst them are many shells like those we find today. But these molluscs and corals would see no fish to swim between them for another long kilometre’s course – since young Nemo’s ancestors can trace their line back only to St Paul’s.

For almost twenty four miles along her run, Earth’s continents had been all but bare of life, and then the plants appeared. Giant forests rose and fell, leaving coal behind. Flowering species, and insects, graced the land when Mother Earth reached Blackfriars, three kilometres from The Mall. And she was already on The Embankment when supercontinent Pangaea was formed, its vast red desert roamed by giant reptiles whilst the Triassic seas ebbed and flowed around its shores.

Soon after, the dinosaurs reached their Jurassic peak as the Atlantic Ocean began to open, near Big Ben, with 2 km still to go. America drifted west across a widening sea, floored at first by stagnant muds later to form the North Sea oil which I and other geologists seek today.

Sea levels fell again, along Birdcage Walk, as giant rivers and deltas plied the European coast, winnowing the orange tidal sands of Guildford’s golden ford which lies below me now. The encroaching waters then rose once more, as the tiny plankton of a warm Cretaceous sea laid down the Chalk beneath my feet.

The Earth had almost reached Buckingham Palace, 60 million years ago with just 600 metres left to plod, when a mid-sized meteorite landed in southeastern Mexico, threatening and in part extinguishing life in Yucatan and across the world. And so the dinosaurs would never live to see The Mall, which instead belonged to the tiny mammals which survived that global storm.

The next hundred steps saw the Downs below my house rise up as gentle folds above a primaeval crustal fault, a far-flung rolling Alpine ripple made as Africa collided with Europe far beyond my Surrey vale.

With 30 metres left, some man-like hunter apes left their footprints across a drying African lake shore, shortly before the Ice Age began to rack our more northern climes. Those apes’ descendant species were then usurped five paces from the line by Homo sapiens, who invented agriculture a metre from the tape.

Inside the last 10 cm, old Moses led his people across the Red Sea’s developing rift, long before a young carpenter named Jesus preached on a Middle Eastern hill, with just a finger’s width of the marathon left to run. The Spanish Armada set sail half a centimetre back, with the Industrial Revolution still unborn inside the final quarter inch.

The last exultant millimetre of our Earthly race has seen man learn to fly across the atmosphere and beyond, those flights to reach the Moon within my lifetime, which so far spans four tenthousandths of a metre along Earth’s marathon course.

I look again from the window upon my Surrey hill, over this landscape etched by unimaginable time. From the London Massif, across the Weald Basin towards the South Downs beyond.

A geologist’s view, to scratch the surface truths of Earth profound.

With grateful homage to Nigel Calder’s ‘Restless Earth’.

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