Reading the Rocks

In the early summer of 1788, a small boat noses along the Berwickshire coast, rocking under a grey Scottish sky, and three men aboard it are looking for a particular cliff. One is a farmer-physician with a restless mind and a reputation for talking too fast to follow; his name is James Hutton. With him are a mathematician, John Playfair, and a chemist, Sir James Hall. They round a headland at a place called Siccar Point, and there it is — exactly the thing Hutton had predicted he would find, the way one predicts a sunrise. The lower rock is grey, and it stands on end, its layers driven nearly vertical, scoured flat across the top as if by a colossal plane. Lying atop it, gently tilted, runs a second set of layers, red, sandy, and altogether different. Between the two, pressed thin as a closed book, is a line. And in that line, Hutton tells his companions, sits a gulf of time so vast the human mind has no rope long enough to lower into it.

The grey rock had once been mud on a sea floor, hardened, buckled upright by the heat of the Earth's interior, hoisted into mountains, and then ground away again by wind and rain across an unimaginable span — and only after all of that had the red sand begun, layer by patient layer, to bury what was left. The seam between them is not a thing but an absence: an entire vanished mountain range, dissolved into the gap, leaving no record except the gap itself. Playfair never forgot what it did to him. "The mind," he wrote years later, "seemed to grow giddy by looking so far into the abyss of time." That giddiness is the whole of it, because deep time is not a fact you are told. It is a vertigo you survive.

To feel why three grown men stood dizzy on a beach, you have to know what clock they had been raised on. In the Christian West, the age of the Earth was read straight from the genealogies of Genesis, and in 1650 Archbishop James Ussher had pinned it down with terrible precision: creation in 4004 BC, a world some six thousand years old and, since the sixth day, essentially finished. This was not the belief of cranks. It was the educated consensus, the schoolroom default, the frame inside which every European naturalist had learned to think.

And yet the frame was already cracking, and not only in Scotland. A century before Hutton, a Danish anatomist named Nicolas Steno had worked out the grammar of rock — that lower layers are older than the ones above, that strata begin as flat sheets — giving the world a way to read stone as a sequence in time. The French count Buffon, heating iron balls and timing their cooling, had calculated an Earth of seventy-five thousand years and privately suspected millions, severing the planet's age from scripture and making it, for the first time, a question a thermometer might answer. Georges Cuvier, laying fossil elephants beside living ones, had forced science to swallow the unsettling truth that whole kinds of creature simply end — that the living world has a history of loss. The young, fixed Earth was being taken apart by a Catholic, a French nobleman, and the father of paleontology before the Scotsman ever reached his boat.

And it had been taken apart, partly, long before any of them. Reading the same evidence — seashells stranded high on mountains — the Persian polymath Avicenna had concluded around 1027 that peaks rise slowly and erode slower still, over spans too great to count, and that those shells were the signature of vanished seas. His contemporary al-Biruni, studying the plains of India, decided the subcontinent had once been ocean and that the Earth's age lay simply beyond measure. In China, Shen Kuo found petrified bamboo in a dry northern province where no bamboo could grow, and read in it whole climates rising and falling across deep time. The Hindu cosmologists had gone further still, counting the days of Brahma in units of 4.32 billion years — a scale that, almost alone among the world's ancient reckonings, lands in the same vast neighbourhood as the modern figure. These were not quaint anticipations to be graded against an Edinburgh finish line. They were other windows onto the same rock, and the honest story names them as windows, not footnotes.

What Hutton added was a theory — a cyclic, self-renewing Earth in which mountains erode to sediment, sediment hardens and lifts and erodes again, forever, driven by the planet's inner fire. It needed oceans of time, far more than any scripture allowed, and Hutton offered it without flinching: in the Earth's machinery, he wrote, "we find no vestige of a beginning — no prospect of an end." His own prose was so dense it was nearly unread; it fell to his friend Playfair, the giddy mathematician, to translate Hutton into sentences a person could follow, and so to carry the idea forward — the first of this chapter's uncredited hands, the expositor who makes the genius legible.

There would be others, and the establishment that honoured the genius was less kind to them. The man who turned deep time into a working tool was William Smith, a blacksmith's son and canal surveyor who, crawling through the mud of England, noticed that each layer of rock carries its own signature company of fossils, always in the same order — so that a stratum in Yorkshire could be matched to its twin in Somerset by the shells inside it. On this principle he drew, in 1815, the first geological map of an entire nation, a hand-tinted thing eight feet tall. The gentlemen of the Geological Society, who would not have a man of his birth among them, watched a cheaper rival map undercut his sales, watched him ruined, and watched him jailed for debt. Only in old age did they award him their first medal and call him, at last, the Father of English Geology.

The fossils that anchored the whole enterprise were often dug, cleaned, and even drawn by Mary Anning, a carpenter's daughter from Lyme Regis who as a girl excavated the first ichthyosaur skeleton — her brother Joseph had spotted its skull in the cliff — then the first complete plesiosaur, then a British pterosaur, the very specimens that confirmed a world of vanished forms and a changing Earth. Gentlemen geologists published her finds, sometimes her anatomical drawings, under their own names; the Society that honoured Smith would not admit her, for she was a woman. Her companion Anna Pinney recorded the verdict with quiet fury: "these men of learning have sucked her brains." The map of who got the credit traced, with grim fidelity, the map of class and sex — never the map of who actually did the work.

And here the story you were probably taught needs correcting. We imagine deep time arriving as war — science against religion, the rock against the Book. It is a thrilling picture, and it is largely an invention, manufactured in the later nineteenth century by polemicists who read their own century's quarrels back into a past that did not hold them. The truth is stranger and quieter. Most theologians, from 1800 onward, simply accepted the old Earth. Many of the geologists doing the reading were themselves ordained clergymen — William Buckland, an Anglican priest; Adam Sedgwick, who took holy orders — devout men compelled to deep time by the rocks and untroubled in their faith. They built bridges rather than barricades: the "gap theory," tucking all the geological ages into an unrecorded silence between the first two verses of Genesis; the "day-age" reading, in which each day of creation is an epoch. Deep time was not resisted by mainstream religion. It was absorbed.

The irony has a sting in its tail. The young-Earth creationism that now presents itself as the ancient, unbroken Christian position is in fact a twentieth-century construction — built largely by a Seventh-day Adventist named George McCready Price and crystallized in 1961 by Whitcomb and Morris's The Genesis Flood. The "traditional" view is, in important respects, younger than Darwin. Its sharpest modern argument deserves a fair hearing: deep time, it says, rests on an assumption — that the slow processes of today have always held — rather than on direct sight. There is a real kernel there. Hutton did not measure the abyss; he inferred it.

But the inference did not stay an inference. Through the nineteenth century the physicist Lord Kelvin, reckoning from the Earth's cooling, insisted on a mere twenty to a hundred million years — too brief for the geologists, too brief for life — and he was wrong for reasons no one could yet account for: the heat of undiscovered radioactivity, and a churning planetary interior his simple cooling model never allowed for. That same radioactivity would, in the end, provide the true clock. Arthur Holmes learned to read the steady tick of decaying uranium in stone. And in 1956 Clair Patterson, measuring lead isotopes in a meteorite, fixed the age of the Earth at 4.55 billion years — a figure that has barely moved since, confirmed by independent radioactive clocks that have no reason to agree and agree anyway. What Hutton intuited on a beach, Patterson proved in a laboratory. The abyss is real, and now it is measured.

So what does it ask of us, this ocean of time in which a human life is a single dropped stitch? Stand again at Siccar Point and look at the seam. It appears to be a void — sixty-five million years simply missing. But the gap is not empty. It is full: full of an entire eroded mountain range, ground to sediment and folded into the red rock above, nothing lost, only transformed. The rock record is the compost cycle written in stone, and coherenceism did not invent the image of the leaf that falls and feeds the soil — it inherited it from Hutton's endlessly self-renewing Earth, where decay is never an ending but a turning. Deep time should make the mind grow giddy; Playfair's vertigo is the correct response, not a wound to be soothed away with cheap consolation. But the giddiness resolves, if you let it, into something other than despair. It is a re-scaling. The human pattern is real, brief, and precious — and it is nested, held inside rhythms vastly older than any clock we keep, which it neither centers nor commands. To live well in deep time is not to mourn our smallness but to align with cadences longer than a life.

Hutton had read the abyss of time the way Humboldt, a chapter ago on his Andean mountain, had read the web of space. But the rock held one more secret, and it was the one that would prove most disorienting of all. If the Earth was unthinkably old, and if whole kinds of creatures had come and gone in its long pages, then the door stood open to a question no six-thousand-year clock had ever left room for: given time enough — given all the time there was — what might the living world have slowly, patiently become? On a ship even then preparing to sail, a young man was packing the first volume of Lyell's geology into his cabin. His name was Charles Darwin, and he would need every year of Hutton's abyss.