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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 date 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 grad
uation 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.
The Rocks Don't Lie: A Geologist Investigates Noah's Flood Page 10