The Test of Time
THIRTY MILES EAST OF Edinburgh lies Siccar Point, a holy site of sorts. The farmer whose fields surround it is said to complain about an endless stream of geologists trampling his turnips. Rock hounds plague this windswept headland because it’s celebrated as the place where Scottish farmer James Hutton discovered geologic time—the place he found the key to unlocking time enough for geological forces to reshape the world. Tucked in along the rocky shore below the turnips are the clear signs of two rounds of mountain building, erosion, and deposition recorded in two sandstones, one gray and the other red.
On a rare sunny Scottish day six of us pulled up at the trailhead and parked just out of view from the farm. We skirted the fields and walked toward the sea cliff, passing by the ruins of a crumbling building amid glowing yellow gorse bushes. I could see striking beds of red sandstone diving down toward the sea to the west. To the east lay planed-off vertical beds of gray sandstone exposed along the shore. Walking out to the headland, we stood above where the two rock formations should meet before starting down a steep grass-covered slope pitching off to the surf below.
Map of Siccar Point, Scotland, showing its position on the coast east of Edinburgh.
At the bottom lay a jewel of an outcrop. The two rock formations sat there just as textbooks showed. Here, in front of me, were the rocks that helped inspire geology’s core concept of deep time, that the world is billions of years old. Over lunch I read the story in the rocks, laid out plain as day.
The older gray sandstone formed as debris eroded off an ancient upland and settled to the bed of an adjacent sea until the sand eventually lay buried deep enough that heat and pressure turned it into solid rock. Then, something caused the rocks to buckle, lifting them back above sea level and tipping them into their now vertical orientation. Gazing along the shore, I could see how the contact between the two sandstones defined the surface of an ancient valley carved into the gray sandstone. As this new land sank back down beneath the waves of an ancient sea, red sand settled on top, eventually accumulating into enough of a pile to turn it, too, into bona fide rock. After all that, another round of tilting and uplift brought the works back to the surface, where waves peeled the cliff back to expose a low shelf of red sandstone dipping out to sea at a jaunty angle and truncating the underlying vertical beds of gray sandstone.
Hutton’s unconformity at Siccar Point showing the inclined beds of the Silurian Old Red Sandstone truncating vertical beds of Devonian graywacke sandstone (by Alan Witschonke based on a photograph by the author).
When Hutton discovered this outcrop in 1788, it confirmed his suspicion that mountains could be recycled into sand and remade into new rock. I had the advantage of having my colleagues from the University of Edinburgh explain how the gray rock, four-to-eight-inch-thick beds of sandstone separated by thin layers of mudstone, recorded erosion of the mountains that formed the geologic suture from the closing of the ancestral Atlantic Ocean. This collision united England and Scotland 425 million years ago during the Silurian Period, several hundred million years before the days of the dinosaurs. The upper formation, the Old Red Sandstone, formed when the younger Caledonian mountains eroded 345 million years ago in the Devonian Period, with the resulting sand deposited in what is now modern Scotland. The other half of the sandstone derived from erosion of the Caledonian mountains lies across the Atlantic, in New England, as the Catskill Formation in New York and Maine. The present far-flung distribution of the two halves of the red sandstone records the reopening of the Atlantic Ocean well after the life and death of the mountains testified to by the rocks themselves.
Although I’m well versed in thinking about geologic time, I still have a hard time grasping how long it must have taken to raise and erode a mountain range, deposit the resulting sand in the sea, fold up the seabed into another mountain range, and then erode it all back into a new ocean. Siccar Point stands as a natural monument to the unimaginable expanse of time required to account for geologic events.
Of course, in Hutton’s day general consensus placed the world at a mere six thousand years old. The crazy notion of a world old enough to be shaped by the slow accumulation of day-to-day change was beyond radical, it was dangerously pagan.
Nowhere does the Bible say, “the earth is six thousand years old.” This curious belief comes from literally adding up years gleaned from biblical chronology to arrive at how far back the world was created. The second-century historian Julius Africanus was the first Christian to date the Creation by drawing on Egyptian, Greek, and Persian histories. His urgency in dating the dawn of time stemmed from the belief that Christ would return to begin his thousand-year reign before the end of the world precisely six thousand years after it all began. The only way to be sure about when the world would end was to figure out when it started.
Adding up the ages of Adam’s descendants listed in Genesis, Julius convinced himself that 2,261 years passed between the Creation and Noah’s Flood. He then summed up the ages of Noah’s descendants and used extrabiblical sources to determine the dates of key events such as when Moses led the Jews out of Egypt and the destruction of the Temple in Jerusalem. In this way, Julius determined that Jesus was born precisely 5,500 years after God created the world. Adopting the tradition attributed to the prophet Elijah that the world would only last a thousand years for each day in the week of Creation, Julius predicted that Christ would return to end the world in 500 AD. His Chronologia served as the model for subsequent biblical chronologies, both in approach and motivation.
Centuries later, medieval and Renaissance chronologists generally agreed with Julius that the world would last a thousand years for each day of Creation. They disagreed about when the countdown to the end started, repeatedly pushing the date by which the world would end further into the future as predicted apocalypses came and went without incident. By the end of the seventeenth century, there were more than a hundred biblical chronologies to choose from that set differing dates for the beginning and end of everything.
The most venerated biblical chronology is Bishop Ussher’s influential Annals of the Old Testament. Published in 1650, it revealed Sunday, October 23, 4004 BC, as the first day of Creation. Archbishop of Armagh and Primate of All Ireland, James Ussher was a confidant of Charles I, with an international reputation as a brilliant scholar and one of the largest personal libraries in western Europe. Ussher’s prestige was such that he was buried with full honors in Westminster Abbey.
Ignoring Egyptian and Chinese histories that extended back before his preferred date for the Creation, Ussher concluded that Noah’s Flood occurred 1,656 years after the dawn of time. Noah and company embarked on Sunday, December 7, 2349 BC, spent a little over a year aboard, and disembarked on December 18 the following year.
How did he establish the year of Creation from the Bible? Like Julius, Ussher tallied up the lifespans of the biblical patriarchs listed in the unbroken male lineage of who begat whom from Adam to King Solomon. To fill in the gap from Solomon to the birth of Jesus, he had to cross-reference biblical events with those of a known age from Babylonian, Persian, or Roman history. Ussher also had to choose which translation of the Bible to use, as the genealogy in the Greek Bible pushes the date of Creation back almost another thousand years. Finally, he corrected for the awkward problem that the first-century Roman-Jewish historian Josephus indicated that Herod died in 4 BC, and thus that Jesus could not have been born after that since the Bible says that Herod tried to kill the newborn Jesus.
How could Ussher pinpoint the day it all started? He used reason. God rested on the seventh day after the Creation, and the Jewish Sabbath is traditionally Saturday. So, counting backwards six days from Saturday, God started making the world on a Sunday. Assuming that the Creation began near the autumn equinox, Ussher probably used astronomical tables to determine that the equinox occurred on Tuesday, October 25, making Sunday, October 23 the best fit for the day it all began. However he came up with it, in 1701, the Stationers’ Company inserted his 4004 BC date of Creation into a margin note for a new edition of the King James Bible. From then on, his calculated guess as to the age of the world became gospel for many Christians.
Despite the popularity of Ussher’s chronology, dozens of biblical analysts offered competing claims. Their disagreements illustrate the inherent difficulty in pinning down the meaning of even literal interpretations of the Bible. Depending on the reader and what else he or she brings to the table, two people may arrive at different meanings. After Steno, natural philosophers began to pursue increasingly independent approaches, piecing together earth history directly from reading the rocks.
The influential Baron Georges-Louis Leclerc, Comte de Buffon and director of the botanical gardens in Paris, argued that the world was at least ten times older. Born into a family of wealthy French aristocrats, Buffon inherited the family fortune at a young age, giving him the freedom to study law before he turned to mathematics and natural history. When he became keeper of the king’s garden in Paris in 1739, he converted it into a center to pursue his research interests.
In 1749, after a decade of study, Buffon proposed that Earth was created when a comet smashed into the Sun and knocked loose a molten fireball. The cooling of this piece of the Sun to form our world was described in the first installment of his massive thirty-four-volume Histoire Naturelle. After the flaming blob cooled into a rocky satellite, a universal ocean receded to expose the continents. Buffon denied that Noah’s Flood ever occurred and suggested that animals evolved based on otherwise enigmatic vestigial organs that served no apparent purpose, like the sightless eyes of a mole and the wings of flightless birds.
Two years later, in January 1751, the theological faculty of the Sorbonne sent Buffon a letter calling him out for more than a dozen reprehensible ideas. Among Buffon’s heretical notions were that currents scouring the bed of the primeval ocean shaped mountains and valleys, that topography was made by erosion rather than by God, and that eventually erosion would grind mountains down to sea level. Faced with the same choice that confronted Galileo, Buffon chose to recant and keep his prestigious position. He renounced everything in his book “respecting the formation of the earth, and in general all which may be contrary to the narrative of Moses.”1
Shaken but undeterred, Buffon experimented with how long it took to cool spheres of molten metal. He determined that the first day of Creation had to have lasted more than twenty-five thousand years for the planet to cool to the point where water could settle on it. Based on rainfall rates, he calculated that the second day must have lasted ten thousand years to build up the primordial seas. His concluding estimate was that the world must be about 75,000 years old to have cooled to its present temperature. This time, when Buffon included this estimate in his Introduction to the History of Minerals in 1775, he escaped theological condemnation.
Three years later, Buffon expanded on the idea of an ancient Earth in his Epochs of Nature. He argued that the days of Creation were figurative and corresponded to geological ages, while cautiously refraining from publishing his own opinion that the world was millions of years old. The first of his great epochs saw the formation of Earth and other planets. During the second epoch Earth’s rocky interior consolidated, releasing volatile substances to create the atmosphere. During the third epoch, about thirty-five thousand years after the planet formed, continent-covering seas deposited stratified rocks, coal, and marine fossils. Rushing currents circulating on the bottom of this great sea carved modern topography. Volcanoes became active in the fourth epoch. He offered Siberian fossil elephants (mammoths) as proof that even the poles enjoyed a tropical climate during the fifth epoch. In Buffon’s sixth epoch the modern continents formed as the intervening land collapsed to form ocean basins. Finally, the arrival of mankind ushered in the world we know roughly six thousand years ago.
Although he did not grant Noah’s Flood any place in his geologic history, Buffon did point out that there was no conflict between Genesis and geology if one did not take the days of Creation literally. He thought, just as some theologians had argued, that Genesis was written for uneducated people and should not be interpreted literally on matters pertaining to earth history. It was never intended to convey scientific truths.
Again, the church remained silent, torn by internal controversy over how to interpret Genesis. Unlike Galileo, this time Buffon escaped censure because influential theologians were themselves toying with the notion of an old Earth. Catholic opinion in France was divided about how to interpret Genesis. Even those in positions of authority were now willing to consider the idea that the six days of Creation might refer to geological ages.
Among Buffon’s correspondents was Joseph Needham, the first Roman Catholic priest elected to Britain’s Royal Society. In embracing Buffon’s view that each day in the week of Creation represented more than twenty-four hours, Needham pointed out that even sixty million years represents an infinitesimal portion of eternity. Theologians were starting to waver on a six-thousand-year-old Earth.
As the idea that geologic time involved more than a few thousand years became reasonable, Abraham Werner, a charismatic professor at the Freiberg Mining Academy, began popularizing the idea that the rocks revealed that earth history consisted of four periods. Werner’s father, a Saxon foundry inspector, had passed on to his son a keen interest in minerals, and at the age of twenty-five Werner published an influential field guide that landed him a professorship at the Freiburg School of Mines. Five years later he offered the first course in historical geology. A gifted lecturer, Werner’s influence grew as his students dutifully spread his ideas about geologic history across Europe.
A lab man who wanted to understand earth history from the study of minerals and rocks without all the bother of fieldwork, Werner adopted Buffon’s view that our planet formed when a stray comet smashed into the Sun, spinning off a fireball that slowly cooled to become covered by a universal ocean. He proposed that the primary (crystalline) rocks precipitated from this global sea, accounting for marine fossils found high in mountains. Neptunists, as Werner’s disciples were known, attributed deposition of the secondary (layered) rocks to material settling slowly to the bottom of the drying sea. They saw the signature of Noah’s Flood in the sculpting of topography, and the deposition of the tertiary rocks that were made of gravel, sand, and clay derived from erosion and redeposition of the primary and secondary rocks. On top of all this was a fourth, or quaternary, level of unconsolidated sand and gravel eroded off uplands by running water, like the deposits of modern rivers. In short order, these four divisions were found to adequately describe the rocks of other mountain ranges, like the Apennines and Caucasus.
As this crude geological system began to formalize the basis for evaluating the thickness, lateral extent, and relative age of rock formations, it became apparent that irregular boundaries (unconformities) separated geological eras. And yet individual layers within the secondary rocks could be traced across Europe. Delicate layers just a few centimeters thick could be traced across tens of kilometers, something impossible to attribute to a chaotic deluge that ripped apart and mixed up the world’s surface in the way that Burnet and Woodward had imagined. Werner’s dominant influence on geological thinking meant that layered rocks were no longer all thought to date from the Flood. Now it was just the tertiary rocks and the form of the land itself that testified to the Flood.
A few years later, in 1788, James Hutton’s startling discovery on a windswept stretch of Scottish coast went a step further in proving that earth history was more complicated than allowed by a literal reading of Genesis. At least two rounds of deposition and erosion were required to account for the deposition and deformation of the sandstone beds at Siccar Point—meaning that there were either two independent rounds of Creation, or Earth reshaped itself every now and again.
The son of a successful merchant, Hutton lived comfortably while studying at the University of Edinburgh. Upon graduation in 1743, at the age of seventeen, he apprenticed to a solicitor, offsetting the drudgery of copying wills and contracts by distracting coworkers with occasionally calamitous chemistry experiments. By the end of the summer Hutton’s experiments had exhausted his employer’s patience. That fall he reenrolled at the university, this time as a medical student. In 1747 he left Edinburgh to continue his studies, starting in Paris and finishing two years later with a medical degree from the University of Leiden (Steno’s alma mater).
Despite his medical training, Hutton never seriously considered practicing medicine. Insatiably curious, he continued studying chemistry before turning to geology. Inspired by a favorite experiment, Hutton started a company with a former classmate to use chimney soot to make sal ammoniac (ammonium chloride). This key component of metalworking flux otherwise had to be imported from Egypt. The scheme was brilliant. Chimney sweeps were thrilled to get rid of soot, and metalworkers were glad to have an affordable and reliable supply of an essential ingredient. In combination with his inheritance, the profits meant Hutton need not work, which left him plenty of time to pursue his many other interests.
At first, Hutton devoted himself to his family’s farm. Set on 140 acres just north of the English border, it lay on some of the best land in Scotland, where rolling hills carved out of volcanic rock produced rich, fertile soil. In contrast to Darwin’s epic voyage around the world, Hutton began forming his radical ideas about the age of the world by watching the dirt wash off his fields.
As he learned to read the land, he translated his love of chemistry to agriculture, developing ways to use calcium carbonate to enhance soil fertility. He also tried to retain the soil eroding off his bare, plowed fields by enclosing them behind stone walls. Stacking blocks of sandstone quarried from nearby hills, Hutton couldn’t help but recognize the similarity between the mineral grains leaving his fields and those that composed the rocks he piled.
There, in his hands, below his feet, and before his eyes, lay the keys to a grand cycle in which rocks eroded and the resulting sediment was deposited elsewhere and buried deep enough to reform into new rock. Most rocks in Britain are made of sediments eroded from somewhere else, and everywhere above sea level is eroding. Neither idea was new—Leonardo had long before recognized the nature of sedimentary rocks, and most farmers were familiar with erosion. But Hutton did something new: he put these ideas together, seeing them as two halves of a grand cycle. Here was the foundational insight behind his radically original concept of deep time.
Such a cycle presented a dilemma. Without a way to restore eroded material, the soil would eventually disappear and, along with it, the fertility of the land, something a benevolent creator would not allow. What could refresh the land after erosion wore it down?
After setting up his farm, Hutton moved back to Edinburgh in 1767. He arrived in a city on the cusp of an intellectual renaissance. The Scottish aristocracy that backed Bonnie Prince Charlie’s failed attempt to claim the throne had been purged, dismantling class distinctions and ushering in a new egalitarian spirit that fostered innovative thought. The new intellectual culture that sprang from the ruins of Edinburgh society nurtured Hutton’s curiosity and interests.
At the time, most natural philosophers thought rocks precipitated out of Werner’s drying primeval ocean in a global version of those grow-your-own crystal sets. But Hutton’s continual experimentation with mineral chemistry convinced him that rocks contained a lot of material that would not dissolve in water. How could rocks precipitate out of a drying sea if they could never be dissolved in the first place? And if Werner’s conventional wisdom about how minerals formed was wrong, then what could be responsible for solidifying rocks? Hutton theorized that the combined effects of heat and pressure offered the only viable alternative. Both would be available at the bottom of a pile of sediment—as long as the pile was thick enough.
In 1784 the newly chartered Royal Society of Edinburgh invited Hutton, then nearly sixty, to present his theory of the Earth, forcing him to gather his thoughts into presentable form. He did not give his own lecture, whether due to illness or a bad case of nerves. His best friend, Joseph Black, who had recently discovered carbon dioxide, graciously read it—the tradition being that lectures were written up in advance and simply read aloud at the meeting. Black presented Hutton’s ideas about layered rocks being made of sediment eroded off of previous land, and how heat and pressure were required to form rocks, as well as the case for rejecting Werner’s ideas about rocks precipitating from an ancient sea. Ignoring the Bible and the Flood, Hutton had inferred that the world was unknowably old. Instead of a grand catastrophe to explain the world, he invoked the subtle day-to-day action of wind, rain, and waves that he himself had observed.
Four weeks later, Hutton personally read a second lecture. He finished his critique of Werner’s theory and focused on how to get stratified layers of rock back to the surface after they solidified at the base of a thick pile of sediment. If rocks just precipitated from a shrinking ocean, then they should all lay horizontal. Yet it was well known that some layered rocks lay steeply inclined. Instead of invoking worldwide collapse during Noah’s Flood to explain the tilted layers (as Steno had), Hutton literally turned the problem on its head and proposed a different action—Earth’s internal heat and volcanic action was what deformed rocks. The key to his argument was how granite veins cut across layered rocks. If, as he thought, granite began as molten rock that rises up from the overheated base of a sedimentary pile, granite veins in cracks and fissures should cut across the layers in the rocks they pushed up through before cooling. Hutton saw this basic process as the force driving a grand cycle of regeneration in which the sea and land continually changed places—continents eroding into oceans to form great piles of sediment that eventually melted at the base and rose anew.
Hutton’s ability to imagine an endless cycle of erosion and deposition that led to the formation of fresh rocks kicked open the door for serious consideration of the immensity of geologic time. He wasn’t arguing that the world was older than imagined; he flat-out argued that Earth was ancient beyond imagination. Who could know how many times rocks had been recycled? There was no way to know how many cycles of erosion and uplift the world had seen when each cycle destroyed evidence of prior ones. He must have shocked an audience that believed Werner’s ideas about rocks precipitating out of the ocean on a not quite six-thousand-year-old world. His extreme views even startled those willing to consider more expansive views of geologic time, like Buffon’s. The skeptical reception of those present spurred him to seek out more evidence to bolster his arguments.
When his lecture was finally published three years later, in 1788, it garnered dismissive reviews that mischaracterized his unknowably old Earth as a rewarmed version of Aristotle’s eternal world without beginning or end. Particularly controversial was the contention that the world evolved in a cyclical fashion. This was totally at odds with the Mosaic account in Genesis of the Creation and the Flood. Everyone knew that things hadn’t happened over and over again. The idea that new land was pushed up from beneath the sea by the force of Earth’s internal heat placed Hutton squarely at odds with both Werner’s Neptunist disciples, who believed in an aqueous origin for rocks, and the traditional Christian conception of a recently created, decaying world.
A simple test of Hutton’s idea lay in determining whether granite veins formed along with or were younger than the rocks they were found in. If precipitated together from an ancient sea, rocks and the veins they harbored should be the same age. If Hutton was right—that molten rock rose up from deep below the seafloor—then the veins should cut across the sedimentary layers.
Scouring the highlands on field excursions, Hutton sought out layered rock cut by veins of granite. He found what he was looking for in the boulders and exposed bedrock riverbed of idyllic Glen Tilt, a valley west of Aberdeen. There veins of red granite clearly passed through bed after bed of black sedimentary rock. The granite had intruded the sedimentary rock after it was formed. The thin stripes of granite were indeed younger than the rocks in which they were found.
The following summer, Hutton found more granite veins injected into sedimentary rocks in Galloway, in southwest Scotland. Even better than at Glen Tilt, these veins terminated within the exposed strata, only penetrating partway up into the stacked sediments. Not only was the granite younger, it came from below. Here was more evidence that granite did not precipitate out of an ancient sea. Hutton felt increasingly confident that what he was seeing revealed that Earth was far older than anyone believed.
This wasn’t enough to prove Hutton’s grand cycle. It only validated his mechanism for uplifting rocks through heat from below. Confident he was right about the larger story, he kept looking. Three years after he boldly announced that the world was immeasurably old, he sailed south from Edinburgh, searching the North Sea coastline for outcrops that would support his ideas. Two colleagues joined him: John Playfair, a professor of mathematics at the University of Edinburgh, and twenty-seven-year-old Sir James Hall, grandnephew of the influential president of the Royal Society. Playfair was a former Presbyterian minister steeped in the traditional views of the Scottish church. Hall, a wealthy young man, supplied a boat and crew for the day, allowing their party to cover far more ground that they could on foot. Both Playfair and Hall had initially rejected Hutton’s idea of an ancient Earth. Now, after years of discussions, Hutton had begun to convince them that he might be on to something.
Hutton picked this stretch of coast to explore because he knew the area was composed of two types of rock—fine-grained gray sandstone and coarser red sandstone. He was convinced that these strikingly different rocks represented two distinct cycles of uplift and sedimentation. Somewhere along the coast the two formations would meet, and the eroding sea cliffs could expose their contact.
They sailed south from Hall’s estate along the rocky coast, where high cliffs provided excellent exposures of the older gray rock. Several headlands down, they passed a sandy beach where the beds in a red sandstone cliff lay pitched at a twenty-degree angle. But where did the red rock meet gray rock? Around the next headland they struck gold. At the base of the cliff, vertical layers of gray rock jutted upward only to encounter the overlying red sandstone. In between the two rock formations lay gray rubble that looked like the modern beach deposits exposed along the shoreline.
Hutton was ecstatic. The contact between the gray and red rock lay exposed in striking clarity, and the story it told demolished conventional views. Here was proof of several rounds of Hutton’s grand cycles. Playfair later described the moment in dizzying terms that evoke a religious epiphany.
The mind seemed to grow giddy by looking so far into the abyss of time; and while we listened with earnestness and admiration to the philosopher who was now unfolding these wonderful events, we became sensible how much farther reason may sometimes go than imagination can venture to follow.2
Hutton had converted his field companions, but who else would believe that the world was unbelievably old? Who else would dare to imagine that cycles operating at a planetary scale could explain the origin of rocks and ultimately the world we see around us?
When Hutton published his Theory of the Earth in 1795, Werner’s Neptunism dominated geological opinion. Hutton’s near-vertical layers of once-horizontal secondary rock, by then widely acknowledged to predate the Flood, told of far more than Burnet’s collapsing crust or Werner’s gradually drying oceans. Hutton argued that mountains and oceans traded places over and over again in a global dance of erosion and sedimentation that demonstrated a divine design. He rejected the role of catastrophes like the biblical flood not only because they ran counter to his own observations but because periodic destruction of the world ran counter to his view of a divine design to everything on Earth. Faith in the perfection of God’s principles favored slow geological change—uniformity of action rather than violent catastrophes. Hutton saw Earth as a grand machine set in motion by natural laws that ran a perpetually self-renewing system he famously characterized as having “no vestige of a beginning,—no prospect of an end.”3
His peers thought him crazy.
To some degree, the cool reception of Hutton’s ideas reflected the politics of his time. Upper-class British intellectuals shocked by the excesses of revolutionary France saw a rising tide of atheism as fueling the horrors of the guillotine. Hutton’s rejection of both conventional biblical chronology and Noah’s Flood as the driving force of geologic history placed him in league with radicals set on overthrowing civilization. It hardly mattered that Hutton himself was deeply conservative. His ideas about an ancient Earth challenged tradition and authority.
Still, the rocks at Siccar Point simply did not fit into the model of a global flood as the singular event in earth history. The rocks were evidence of two geological eras separated by an abyss of time. Any way one looked at it, the eons necessary to explain the cycle of worlds apparent in Hutton’s two rounds of uplift and erosion did not fit with a literal reading of Genesis.
Hutton’s critics were not easily deterred. In 1793 one of Werner’s students, Richard Kirwan, savaged Hutton’s theory in the Transactions of the Royal Irish Academy, essentially accusing him of being an atheist. Hutton immediately began working on a greatly expanded version of his theory that would show how God established the world’s geological order at an unknowable date in the distant past and would terminate it at some unknowable date in the future. Just when the world began and when it would end were metaphysical issues beyond the reach of rational inquiry.
While frantically working to reframe and support his case, Hutton contracted a debilitating illness from which he never recovered. He completed two of three planned volumes of his Theory of the Earth despite great pain, which goes a long way toward explaining why the book is famously unreadable. Hutton died in March 1797, shortly after scathing reviews once again dismissed his ancient planet theory as a warmed-over version of Aristotle’s pagan eternal world.
Hutton’s Irish nemesis kept at it, marshaling geological evidence to defend Werner’s Neptunism against Hutton’s heat-driven theory and its heretically ceaseless cycles of uplift and erosion. Published in 1799, Kirwan’s Geological Essays attacked Hutton’s theory on moral and religious grounds. Kirwan thought the idea of an ancient Earth undermined society’s foundation: “how fatal the suspicion of the high antiquity of the globe has been to the credit of Mosaic history, and consequently to religion and morality.”4 Kirwan found Hutton’s arguments so absurd that in preparing his rebuttal he reportedly didn’t even bother to read the Scotsman’s book.
Instead, like others before him, he came up with another novel theory to explain Noah’s Flood. As Kirwan’s primitive Earth precipitated from primordial fluid, the water level gradually sank to that of the present oceans, leaving the continents high and dry. Misinterpreting frozen mammoth remains as drowned African elephants, Kirwan proposed a new idea to explain how their bones got to northern Europe and Siberia. In the beginning, long before the Flood, a globe-covering sea gradually retreated down into great rifts in Earth’s crust. Much later, all that water was released suddenly, triggering Noah’s Flood somewhere between India and the South Pole and transporting the remains of tropical animals to Siberia. No Northern Hemisphere creatures were found in the Southern Hemisphere, but elephants (mammoths) kept turning up in gravel deposits at high latitudes. Unaware that these enormous carcasses were almost always solitary (and quite hairy), Kirwan imagined that great piles of elephant bones showed how the beasts huddled together to face the oncoming flood before they were swept off to Siberia. He ignored the puzzling lack of lion, zebra, giraffe, and other bones of African animals in the Siberian deposits.
In Kirwan’s mind, floodwaters racing north reshaped continents, destroying an ancient landmass between Asia and North America and leaving Mongolia’s Gobi Desert a vast barren flat. He didn’t stop there, explaining how the Flood turned the Arabian Peninsula and North Africa into wasteland, and carved out the Bay of Bengal and the Red and Caspian seas. The planet’s shattered crust kept settling and producing earthquakes until around 2000 BC, creating Gibraltar, the Dardanelles, and the Straits of Dover. Putrefying remains of plants and animals sucked enough oxygen out of the atmosphere to reduce humanity to its present enfeebled state. And because carnivores would have been hard to manage on the ark, Kirwan proposed that God recreated them all after the Flood, along with the entire American fauna. He liked this idea so much he didn’t mind that the Bible neglected to mention this second round of creation.
Although Kirwan was fervent in his desire to defend the traditional literal interpretation of Noah’s Flood, he abandoned biblical literalism to bring in additional details and events not described in the Bible. He made up a geological story to preserve his preferred reading of the biblical story. Others, however, began to accept an older Earth in attempts to harmonize the biblical flood with the story told by the rocks.
Hutton’s influence would withstand the test of time, but he never had a chance to respond to Kirwan. Hutton’s impenetrable book was not compelling enough to convert skeptics to his side. Lacking the planned third volume that was to have related his discoveries at Glen Tilt and Siccar Point, his Theory of the Earth nearly died with him. Playfair and Hall, the primary witnesses to his field excursions, would not let Hutton’s work languish. They began spreading Hutton’s gospel of deep time. When sorting through his colleague’s papers while writing a memorial, Playfair realized just how much persuasive material Hutton had been working up for his unpublished third volume.
Determined to promote his friend’s ideas, Playfair did what Hutton had longed and meant to do and completed a compelling treatise about the antiquity of the Earth. He graciously credited his late friend by titling his work, published in 1802, Illustrations of the Huttonian Theory of the Earth. Here was an impressive, engaging work that included a distillation of Hutton’s theory followed by elaborations, examples, and responses to criticisms, much as Hutton himself had dreamed of presenting it.
In bringing Hutton’s ideas to the attention of mainstream scholars, Playfair also explained how rivers could carve topography—given enough time. He argued that “rivers have, in general, hollowed out their valleys” because “the general structure of valleys among mountains is highly unfavorable to the notion that they were produced by any single great torrent, which swept over the surface of the earth.”5 Playfair saw that valleys diverged in all directions from the center of mountain ranges, so a single current sweeping across the terrain could not have carved them all. Neither could a single current have carved valleys running at right angles to each other or perpendicular to the overall trend of the drainage from a mountain range. He went on to describe the division of landscapes into integrated networks of little valleys connected to larger valleys, each seamlessly connecting with the next at a common elevation regardless of size. Such a landscape could only be the signature of running water slowly eroding Earth’s surface. Ahead of his time by decades, Playfair made a compelling case that Noah’s Flood did not shape the world’s topography.
Playfair also addressed Siberian mammoths. He noted that their bones were always found in soil or alluvial deposits and never in the solid rock below. Writing in the style of his time, he rambled on a bit before pointedly demolishing Kirwan’s conception of the Flood.
If we consider attentively the facts that respect the Siberian fossil bones, there will appear insurmountable objections to every theory that supposes them to be exotic, and to have been brought into their present situation from a distant country. . . . Shall we ascribe it to some immense torrent, which, sweeping across the desarts of Tartary, and the mountains of Altai, transported the productions of India to the plains of Siberia, and interred in the mud of the Lena animals that had fed on the banks of the Barampooter or the Ganges? Were all other objections of so extraordinary a supposition removed, the preservation of the hide and muscles of a dead animal, and the adhesion of the parts, while it was dragged for 2000 miles over some of the highest and most rugged mountains in the world, is too absurd to be for a moment admitted.6
Playfair further noted how their carcasses would surely have rotted if these great beasts had died in a tropical climate. Whatever they were, mammoths were not relics of the Flood.
By the close of the eighteenth century, theologians had begun to recognize the lack of a unified explanation among natural philosophers for Noah’s Flood and the age of the world. The wide range of conflicting theories and interpretations fostered suspicions that perhaps it was the Bible that was being misinterpreted. The floodgates of heaven and the fountains of the deep had been interpreted to refer to comets, a great vapor canopy, water from alpine caves, and a vast subterranean sea—just about everywhere one might imagine finding enough water to drown the world. Theologians started to question whether scripture was meant to be a source of scientific information as well as a book of personal and moral redemption. Even conservative Christians began to question whether Noah’s Flood was all there was to earth history.
It is impossible to stand at Siccar Point and reasonably see how to fit what you can read in the rocks into just 6,000 years of time. When Roman ruins still stand after 2,000 years, how could raising and eroding off two mountain ranges happen in just twice as long before that? The virtually unimaginable amount of time required to form the two unconformable sandstones exposed along the Scottish coast offers a humbling glimpse of the infinite.
Hutton’s recognition of the concept we now call deep time laid the foundation for a new geological time scale. It was a turning point in our story and a huge development for the field of geology. Reinterpreting the days of the week of Creation as geological ages allowed earth history to accommodate vast expanses of geologic time. After all, who knew how long one of God’s working days lasted? Perhaps the rock record paralleled Genesis—if interpreted as consisting of six ages rather than six days. Maybe Moses only wrote about the part of the Flood that Noah witnessed. Although biblical interpretations were being reconsidered, there was still general faith that the rocks filled in the real story.
Then, as now, conventional wisdom guided interpretation of discoveries to the extent it could. Scientific revolutions happen when conventional views can no longer bend under the weight of new findings. Natural philosophers were still looking to prove Noah’s Flood because they viewed the world through the filter of religion, not because they feared theological condemnation. Despite the evidence Hutton and company marshaled to frame the geological story, natural philosophers were reluctant to abandon the biblical story. Only later did science start to modify and seriously undermine faith in biblical truth. Even so, it had become clear there was more to earth history and fossils than simple deposition of sedimentary rocks from a single flood over the span of a single year.
Soon geologists would unearth compelling evidence for multiple catastrophes, each of which ended a distinct period of earth history. As nagging questions and alternative ideas began to reshape how Christians interpreted the story of Noah’s Flood, natural philosophers shifted gears in looking for geological evidence of it. The search for Noah’s Flood moved from rocks into the overlying deposits of unconsolidated sediments that lay scattered across Earth’s surface.