The Rocks Don't Lie: A Geologist Investigates Noah's Flood

by David R. Montgomery

  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 som
ething.

  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.