Also by David R. Montgomery
Dirt: The Erosion of Civilizations
King of Fish: The Thousand-Year Run of Salmon
THE
ROCKS
DON’T LIE
A Geologist Investigates
Noah’s Flood
David R. Montgomery
W. W. Norton & Company
New York London
For my parents, Dave and Toby, with thanks for encouraging me to think.
Contents
Preface
1 Buddha’s Dam
Discovering evidence for an immense Tibetan flood shows the author that folktales can have an element of truth.
2 A Grand Canyon
A hike out of the deepest hole in North America reveals Earth’s antiquity and fundamental problems with the creationist view of earth history.
3 Bones in the Mountains
Early Christians see evidence for Noah’s Flood in fossils and rocks.
4 World in Ruins
Seventeenth-century savants lay the foundation for modern geology through imaginative theories of how God triggered the Flood.
5 A Mammoth Problem
Recognition of fossils as the bones of extinct animals invalidates grand Flood theories.
6 The Test of Time
An eighteenth-century Scottish farmer discovers geologic time and Christians reinterpret Genesis to accommodate an ancient world.
7 Catastrophic Revelations
Nineteenth-century geologists refute the idea of a global flood as the most recent of a series of world-shattering catastrophes.
8 Fragmented Stories
An introverted Englishman zealously reassembles cuneiform puzzles, proving that the biblical flood story is a Babylonian hand-me-down.
9 Recycled Tales
Scholars uncover the evolution of the Bible as anthropologists probe the roots of flood stories around the world.
10 Dinosaurs in Paradise
A trip to the Creation Museum sheds light on the twentieth-century resurrection of creationism.
11 The Heretic’s Flood
A geologist rediscovers grand catastrophes and creationists refuse to believe geologists have discovered Noah’s Flood.
12 Phantom Deluge
Modern creationists recycle seventeenth-century ideas to explain geological problems and miss the plate tectonics revolution.
13 The Nature of Faith
The greatest story never told—the way we read earth history shapes how we see the world.
Notes
Sources
Acknowledgments
Index
Preface
ALL AROUND THE WORLD, mythology and folktales address the origin of topography, the form of the land itself. How should we read ancient stories, like accounts of great floods purporting to explain the origin of landforms? Can we regard them as tales of prehistoric events, or should we dismiss them as archaic superstition? As a geologist trained to read the history of the world from rocks and landforms, I’m curious about the geological basis of folktales and how geography, culture, and tradition shape the way people see and interpret the land.
Investigating the origin of the world’s flood stories, some of humanity’s oldest and most widely spread traditions, presents an intriguing challenge. Geologists tend to explain the prevalence of flood stories among ancient societies as simply reflecting the fact that floods are common natural disasters. But could there be more to stories of really big floods, or even the flood to end all floods, Noah’s Flood?
Of all the sciences, geology is especially bound to the story of Noah’s Flood. Historically, few things on the frontier between science and religion proved as contentious as the biblical stories of the Creation and Noah’s Flood, the age of the world, and the genesis of topography. For two centuries, Christians have wrestled with contradictions between traditional biblical interpretations and geological discoveries. At the same time, debate over interpreting supposed signs of Noah’s Flood made surprising contributions to the development of geology. This back-and-forth also proved central to the rise of modern creationism and its perception of geology as a fundamental threat to faith.
I started writing this book intending to present a straightforward refutation of creationism, the belief that the world is a few thousand years old and that all the world’s topography—every mountain, hill, and valley—was formed by the biblical Flood. But as I read through old books I learned how stories about enormous floods shaped both scientific and religious views. I also came upon a different story about the nature of faith.
In looking into the origins of flood stories, and the story of Noah’s Flood in particular, I thought I’d find the standard conflict between reason and faith. Instead, I found a much richer story of people struggling to explain the world—and our place in it. The initial development of the discipline of geology was premised on the Flood as fact, which naturally led to imaginative theories of how to interpret the story of Noah’s Flood. Later, with evidence literally in their hands and beneath their feet, geologists began to influence theology, showing that a global flood fell short when tested against the rocks that make up our world. Along the way, scientists were as apt to be blinded by faith in conventional wisdom as Christians proved adept at reinterpreting biblical stories to account for scientific findings. The historical relationship between science and religion was far more fluid, far more cross-pollinating than I ever thought—or was taught at Sunday school or in college.
Little did I expect to learn that Niels Stensen, also known as Steno, the seventeenth-century grandfather of modern geology, invoked Noah’s Flood to explain the origin of the landscape around Florence in his influential treatise on the nature of fossils. All too frequently, the history of science is simplified into a story of the light of reason dispelling the shadows of myth and superstition.
I was equally surprised to learn that the development of modern creationism originates in arguments within the fundamentalist community over how Noah’s Flood explained geology. I did not expect to learn that the historic interplay between how Christians interpreted biblical stories and how scientists continually reinterpreted geological evidence helps explain the origin of modern creationism and why such beliefs arose in America. Neither did I realize that what we know today as creationism is one of the most recently evolved branches of Christianity, or that the founding fathers of modern creationism based their views, in part, on a perceptive critique of geology in the days right before the discovery of plate tectonics. Modern creationists had a rational basis for their arguments—even if they then recycled thoroughly discredited seventeenth-century theories to support their beliefs.
For readers seeking to delve deeper into the history of science and religion, and the topics touched upon in this book in particular, I have listed my sources at the end. I leave it to others to debate the long and fruitless search for Noah’s ark and where it came to rest (Mount Ararat being a relatively recent addition to a long list of candidate sites). I will also steer clear of arguments over the size, design, and logistics of the ark, despite all the wonderfully imaginative ideas about how to accommodate a world of animals on a handmade lifeboat. And I leave debate about the question of intelligent design to theologians in whose purview inherently untestable ideas properly reside. While my geological background and training provide me with insight into earth history—how to read stories archived in stone and etched upon the land—I have no better idea than anyone why the universe exists and runs the way it does. Such questions are unanswerable, at least in this lifetime.
I found r
eading the historic works of theologians, natural philosophers, and scientists a fascinating experience, one that left me with an appreciation for the rich and engaging interplay between biblical interpretation and the development of geology. Noah’s story is central to one of the longest-running debates between science and religion as people sought, and still seek, to reconcile scriptural interpretation with observations of the natural world. We mortals have long been struggling to understand who we are, and probably always will. Even today, interpretations of the biblical flood story remain central to understanding modern culture wars—no matter how one views them—because how we read ancient stories still defines the way we see the world, and thus ourselves.
1
Buddha’s Dam
AS A GEOLOGIST, I’ve had plenty of surprises in the field, but I never expected that an excursion to a remote corner of Tibet would lead me to a new appreciation for the biblical story of Noah’s Flood. My specialty is geomorphology, the study of processes that create and shape topography. Over the last several decades I’ve explored how landscapes evolve—where stream channels begin, how landslides sculpt hillslopes, and why rivers carve deep gorges through mountain ranges.
In the spring of 2002 I joined a research expedition to the Tsangpo River in southeastern Tibet. The team needed a geomorphologist with river experience to study how the Tsangpo had sawed down through kilometers of rock to carve the world’s deepest gorge. I couldn’t turn down the chance to visit the roof of the world.
As we drove down from the pass toward the Tsangpo on the newly paved road southeast of Lhasa, I noticed flat-topped piles of sediment rising above the valley floor. Known as topographic terraces, these elevated islands of flat ground can form in different ways, most commonly when an incising river abandons an old riverbed. I watched for clues to determine what created these.
Photograph of a topographic terrace, the top of which corresponds to the level of an ancient lake that once filled the valley of the Tsangpo River, Tibet (photograph by the author).
Over the course of our several-week expedition I collected the pieces of a landscape-scale puzzle. Flat-topped piles of loose sediment—gravel, sand, and silt—stuck up hundreds of feet into the air where tributary valleys entered the main valley. More terraces lay at about the same elevation at each confluence where smaller streams joined the river. From our hotel near the foot of the valley wall we could see a terrace rising above the edge of town a few blocks away. A short hike up a dirt road cut up through the side of the terrace revealed hundreds of alternating layers of silt and finer clay. Segregation into distinct layers sorted by size meant that these sediments were laid down in quiet water. Such fine material would not have settled out in a turbulent river. The implication was clear. An ancient lake once filled the valley.
Sketching the extent of the flat terrace surfaces onto our map as we drove along the valley, I badgered my compatriots into occasionally stopping for a closer look at these curious piles of sediment laid out like a giant’s playground. Some were dried-up gravel riverbeds perched well above the modern river. Others were lake terraces made of layered silt and clay. How did they get there?
A coherent picture began to emerge as we traversed up and down the valley. The terraces made of river gravel continued down the valley bottom to an elevation corresponding to the top of the lake sediments, defining the ancient shoreline where the rivers had entered the lake. In addition to prominent terraces that rose a few hundred feet above the modern river, the remnants of a second set of higher terraces preserved at a few remote locations halfway up the valley walls attested to an even deeper lake. At least twice in the recent geologic past a lake extended hundreds of kilometers upstream from the Tsangpo Gorge. I was onto something.
It was thrilling to have scientific sleuthing that started as little more than a hunch lead to a solid story. Once I saw the pieces and knew how they fit together, the story of ancient lakes that once filled the valley of the Tsangpo stood out plain as day in the form of the land.
What do you see when you look at the land? Something stable and reassuringly solid. A slope to ski down? A surface to pave over? Geologists see the world as incredibly dynamic and ever-changing—only change occurs slowly over immense spans of time.
I’ve learned to see what the land used to look like, and what it might look like in the future. Reading a landscape is an ongoing process of combining curiosity and inquiry. Why is that hillside bare and rocky? Why is that one covered with soil? Deciphering topography makes geologists natural storytellers. We piece together fragmentary clues in rocks and landforms to connect dots across landscapes, mountain ranges, and continents and tell stories with whole chapters lost to erosion and time. And here in the valley of the Tsangpo was a great story, except for one big loose end.
Map of the Tsangpo River, Tibet, showing the Nyang River, the town of Bayi (where our hotel was located), and the moraine dam at head of Tsangpo Gorge. The reconstructed extent of the lower paleo-lake is shown in black.
Looking at the map, there was no obvious dam to hold back our newly discovered ancient lakes. What kept them from draining down into the Tsangpo Gorge? Many miles downstream, right at the head of the gorge, we discovered glacial debris plastered on both sides of the valley confirming that a massive tongue of ice had once plunged down the 25,000-foot-high peak of Namche Barwa and blocked the river. The two levels of terraces extending far upstream indicated that a wall of ice and mud dammed the river, not just once but time and again, backing up a great lake that filled the valley.
As you might imagine, ice doesn’t make a very good dam. Once the lake filled enough to float or breach the dam, a rush of liberated water roared down the gorge, scouring out everything in its path. Upstream of the gorge, we found horizontal stripes of silt plastered onto the valley walls. Here were old shorelines confirming that the ice advanced to block the river over and over again, most likely during cold glacial periods or at times when strong monsoons delivered extra snow to the glacier’s source on the high peak. As the glacier repeatedly dammed the throat of the gorge, ice-dam failures generated catastrophic floods that drained ancient lakes impounded in the valley upstream.
One day as we drove down the valley toward the gorge, one of my graduate students relayed information from a guidebook he’d brought along. Local folklore told of a traditional kora—a Buddhist pilgrimage trek—that circled a small peak ringed by lake terraces. Pilgrims walk the kora to commemorate how Guru Rimpoche brought Buddhism to Tibet through defeating a powerful lake demon, draining its home to reveal fertile valley-bottom farmland. It was a feat impressive enough to convert the locals. I began to think that an oral tradition might record our glacial dam-break flood.
Suspicion moved beyond idle speculation when we got the radiocarbon dates from wood fragments I’d painstakingly collected from the lake terraces. Radiocarbon dating uses the ratio of carbon isotopes in once-living matter to determine how long ago it died.1 The technique works because carbon-14 (C) decays to carbon-12 (C) at a known rate, and all living things start with a C/C ratio equal to that in the atmosphere from which the carbon was originally taken up by photosynthesis. Wood fragments from the higher terraces of the older lake were almost ten thousand years old, dating from the tail end of the last glaciation of what’s popularly known as the ice age. Fragments from the younger lake were only about twelve hundred years old—dating from around the eighth century AD.
This was about the time that Guru Rimpoche arrived in Tibet. Did the geologic story I read in the landforms really support a Tibetan folktale? Or was it that the folktale told the geologic story?
Two years later, in 2004, I returned to Tibet to explore the story of the lake-draining flood. On our first trip we had hired a local farming couple to collect monthly samples of river water. When I told the farmer’s wife how we’d discovered that the whole valley was once an ancient lake, she replied that yes, she knew about that. Caught off guard, I listened to her. She pointed out a steep hillside
across the valley and described how three boats had been stranded there as the lake drained to reveal the farmland of the modern river bottom. She told me she’d heard the story from the Lamas at the local temple.
The temple sat right on top of a stack of ancient lake sediments, one of the terraces that rose to the elevation of the lower lake shoreline. A painted temple wall along an exterior walkway even had a striking portrayal of Guru Rimpoche above a lake floating before the distinctive peaks flanking the gorge entrance. Asked how Guru Rimpoche had drained the lake, the head Lama said he cared not how the great master did it. What was important was the fact that Guru Rimpoche had. Besides, he continued, the story we should be interested in was how the ocean once covered all of Tibet. He described how he had seen water-rounded rocks perched on mountainsides high above the valley. He assured us that the ocean once covered the high peaks. His story of a flood that submerged the world sounded familiar.
Photograph of the truncated glacial moraine where an ancient ice dam extended down off the flanks of Namche Barwa (the high peak in the background at right) to dam the Tsangpo River immediately upstream of the Tsangpo Gorge (photograph courtesy of Bernard Hallet).
People around the world tell stories to explain distinctive landforms and geological phenomena. The global distribution of folklore associated with topography and great floods makes me suspect that people are hard-wired to be fascinated by and to question the origin of landscapes. I know I am. I think I was a geomorphologist before I knew what one was.
As a kid I could stare at maps for hours, examining geographical details of places I’d never been. Seduced by the lay of the land, I grew up intrigued by how topography shaped historic battles, controlled the locations and form of cities, and forged the character of civilizations.
The Rocks Don't Lie: A Geologist Investigates Noah's Flood Page 1
