The Rocks Don't Lie: A Geologist Investigates Noah's Flood (30 page)

In 1979, the Geological Society of America awarded Bretz its highest honor, the Penrose Medal. He was ninety-seven years old and is reported to have jokingly complained to his son, “All my enemies are dead, I have no one to gloat over.” In hindsight, he described his work as a struggle against the dominance of uniformitarian thinking that prejudiced his colleagues against the idea of a great flood:

Was not this debacle that had been deduced from the Channeled Scabland simply a return, a retreat to catastrophism, to the dark ages of geology? It could not, it must not be tolerated… . They demanded, in effect, a return to sanity and Uniformitarianism.
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Later fieldwork by others revealed evidence for many floods, each of which left a single thin layer in thick stacks of backwater sediments. The ice dam had failed over and over again. When an advancing glacier dams a river, it can prove stable until the water backs up deep enough to float the ice, catastrophically undermining the dam. Once the lake drains, the ice can readvance, repeating the whole process again and again until the glacier finally retreats. The ice dam blocking Lake Missoula’s only outlet had become a virtual flood machine.

Calculations accounting for the estimated rate of flow into the lake indicated that it took three to seven decades to fill, the same time interval between lake-draining floods revealed by the number of annual sediment layers in the lake bottom sediments. Downstream, careful stratigraphic analyses showed that each layer of flood-deposited sediment represented a separate event with velocities exceeding twenty feet per second. Radiocarbon dating of organic matter deposited in the flood sediments revealed there were as many as 100 separate floods as the ice dam formed, failed, and reformed every few decades from 15,300 to 12,700 years ago.

In a way, the finding that Lake Missoula failed scores of times brought Bretz’s heretical idea back into line with uniformitarian thinking. Glacial dam failure is a simple process to understand. It works via the mechanics of floating an ice dam. Fill up a glacially dammed lake enough to float the dam and, presto, you get an instant catastrophe. Keep filling it up and you get a repeating series of catastrophes.

Recognition of the Missoula Floods helped identify similar landforms in Asia, Europe, Alaska, and the American Midwest, as well as on Mars. There is now compelling evidence for many gigantic ancient floods where glacial ice dams failed time and again on the margins of great ice sheets. In hindsight, it’s obvious that ice dams are not all that intelligently designed for the simplest of reasons—they float.

At the end of the last glaciation, giant ice-dammed lakes along glacial margins in Eurasia and North America repeatedly produced catastrophic outburst floods. Ice dammed north-flowing Siberian rivers, spilling them over drainage divides and changing their courses. England’s destiny as an island was sealed by erosion from glacial outburst floods that carved the English Channel. Devastating floods were a fact of life on the margins of the world’s great ice sheets.

We now know that large ice dam failures were common in pre-historic North America and Eurasia. And since ice dams tend to fail catastrophically, people living around ice sheet margins probably witnessed giant floods. Could survivors of such events have passed their stories down through the ages?

A campsite with charred bones and stone artifacts buried under pre-flood deposits along with a stone artifact recovered from a giant flood-deposited gravel bar along the Columbia River provide the only reported physical evidence I could find that anyone could have witnessed a thousand-foot-high wall of water crashing through the Columbia River gorge—and no indication of whether or not any possible human witness lived to tell about it. Early missionaries in eastern Washington reported that Yakama and Spokane Indians had oral traditions of a great flood that described locations where survivors sought refuge. The native inhabitants of the lower Columbia River also reportedly had a legend of a catastrophic flood. Upstream in Idaho, the Nez Perce and Shoshone also had flood stories. Downstream, the Santiam Kalapuya people of the southern Willamette Valley, Oregon, had a story of a time the valley filled with water, forcing all the people to flee up a mountainside west of Corvallis before the waters receded.

One problem with attributing such stories to the Lake Missoula floods has been that the floods occurred before the generally accepted time of human arrival in North America. However, the recent discovery of human coprolites (fossilized excrement) radiocarbon dated to 14,000 to 14,270 years ago at Paisley Caves, in south-central Oregon, places human populations in the region during the time of the Missoula Floods. If the region’s flood stories do record the Missoula Flood and backwater flooding of the Willamette Valley, then it means that science is only now catching up with folklore.

In North America, glacial dam failures were not restricted to the Pacific Northwest. Catastrophic drainage of glacial Lake Agassiz, a vast lake that formed in a moatlike depression on the edge of the retreating Canadian ice sheet, happened numerous times as the lake’s shoreline kept shifting as the ice melted off. Exposure of new outlets sent great floods cascading off in different directions, south to the Mississippi, north through Hudson’s Bay, and east down the St. Lawrence River to the Atlantic. When the lake finally emptied for the last time more than eight thousand years ago, it was still a hundred times larger than Lake Missoula, releasing a pulse of freshwater big enough to change ocean circulation and shut down the current of the Gulf Stream, which brings warm water to the North Atlantic and keeps northern Europe habitable (without it Britain would have a climate like Siberia’s). It’s no coincidence that cold periods recorded in Greenland ice cores correspond to major drainage events from Lake Agassiz.

Given that the ancestors of Native Americans from Alaska to Tierra del Fuego are thought to have come from Asia via the Bering Strait (whether overland or by paddling along the coast), they would have passed near the ice sheet margin. The Native American Clovis culture overlaps with the great outburst floods in the Midwest and Northeast that continued to occur until glacial Lake Agassiz drained for the last time around 8,400 years ago. Algonquin flood stories center around the Great Lakes region, along the shifting outlets of ice-dammed Lake Agassiz. Downstream, in Nebraska and Kansas, Pawnee stories associate the bones of giant bison with catastrophic floods along the Missouri River. Do these stories relate ancestral tales of dramatic disasters, or attempt to explain puzzling features of the local environment, or both?

Map of glacial Lake Agassiz showing its maximum extent and outlet directions for various mega-floods during deglaciation.

An intriguing Ojibwa (Chippewa) legend from around Lake Superior tells of a devastating flood at the beginning of time when a great snow fell one September. A bag contained the sun’s heat until a mouse nibbled a hole in it. Spilled warmth instantly melted all the snow, producing a huge flood that rose above the tops of the highest pines. Everyone drowned except for an old man who drifted about in his canoe rescuing animals. It doesn’t take much imagination to see this as the story of an ice dam failure.

Stories about ice dam failures also come from Northern Europe. Nordic mythology tells of how a kingdom of ice, ruled by an ice giant, once covered Scandinavia. When the Norse god Odin and his brothers killed the frozen king, his blood (water) gushed forth to drown the other ice giants. In one story, Odin and his siblings used the frigid giant’s eyebrows to make a wall separating the land of ice from the land of people. This boundary sounds suspiciously like the snaking ridges of glacial debris (called moraines) left by ice retreating across Sweden and Finland. Viking songs and stories written down and preserved in Iceland before 1250
AD
also tell of how the modern world began when Odin and his brothers slew an ice giant, releasing a great flood that inundated the lowlands and drowned large mammals.

Flood stories from tropical climates have different narrative details. Accounts of big floods from throughout the Pacific Islands describe rapid inundation as a huge wave from the sea tears up trees and forces survivors to high ground. Many South Pacific flood stories fail to mention rain at all. Instead, in these accounts, the sea rose to flood all but the highest places. The remarkable tsunami stories from Sumatra, Borneo, New Guinea, Fiji, Tahiti, Tonga, New Zealand, and Hawaii show how tales of infrequent local disasters can become the stuff of legends.

Tsunamis come out of the blue, from over the horizon—sometimes from across an entire ocean. When a big shock like a landslide or an earthquake displaces a lot of water, the pressure wave travels. The surrounding ocean water doesn’t. Moving at tremendous speed, the resulting wave can cross an ocean in a few hours. Typically, the leading part of the wave arrives as a water-level depression when it grounds out as it approaches shore. So the water rushes out and then surges back in as the crest of the wave arrives. All too often, the initial mystery of the falling tide and the seductive exposure of bare seabed attract the curious before a surging wall of water sweeps away everyone in its path. With no local cause to invoke, divine displeasure might seem like the only reasonable way to explain monstrous rogue waves. Fijians are said to have only recently stopped keeping great canoes ready in case of a surprise flood from the sea.

The Indian Ocean tsunami resulting from the December 26, 2004, magnitude 9.3 earthquake killed more than a quarter-million people. Hard hit by the tsunami, Simeulue Island in Indonesia’s Aceh province lost only seven people out of a population of almost eighty thousand. What explains such a low casualty rate? The islanders had an oral history recounting another massive tsunami that struck in 1907, killing three-quarters of the island’s inhabitants and stranding bodies in the tops of coconut trees. Survivors of the 1907 disaster made up a new word for “the ocean coming onto the land.” Interviews after the 2004 tsunami revealed that the story did its job. When the ground shook the locals knew to flee their low-lying coastal villages and head for the hills. There were numerous casualties on the mainland, where the population had no such oral history of a previous tsunami.

Native American stories of a flood coming from the sea are common along the Cascadia subduction zone, from Northern California to the Oregon and Washington coasts and north to Vancouver Island. Tremendous earthquakes shake this region each time the oceanic crust beneath the Pacific gets shoved a little farther under North America. We know the last major subduction zone earthquake occurred on January 26, 1700 because Japanese temple records tell of a mysterious tsunami arriving without any ground shaking. The wave generated on the west coast of North America traveled all the way to Japan.

Early accounts from the Pacific Northwest record that flood traditions were common among coastal tribes. Missionaries were puzzled that some stories recounted floods just three or four generations back. One old man of the Clallam tribe said his grandfather had even met a survivor of the great flood. Missionaries wondered how native peoples could have been so confused about the timing of Noah’s Flood. They weren’t. Such stories read like eyewitness accounts because tsunamis devastated their ancestors’ coastal communities. Archaeological evidence documents that villages along the British Columbia, Washington, and Oregon coasts were inundated by tsunamis and abandoned after the 1700 earthquake. After the ground shook violently for more than three minutes, a thirty-foot wave smashed into the coast. The dramatic tale was sure to be retold by survivors.

Older traditional stories from throughout the region tell of ancient struggles between Thunderbird and Whale, graphically describing ground shaking and accompanying flooding from the sea. These stories depict Whale as a monster terrorizing animals and depriving people of food. Seeing that the people were starving, benevolent Thunderbird flew from his mountain home and dove into the ocean to battle Whale. During their struggle the sea fell and rose again, sending canoes into treetops and killing many people.

Even Western mythology has direct links to tsunami stories. An unusual Mediterranean tsunami may explain both the Greek story of Deucalion’s flood and the myth of Atlantis, the fabled city that sank into the sea. In 1960, Greek seismologist Angelos Galanopoulos proposed that the volcanic destruction of the island of Santorini (also known as Thera) was responsible for the story of Deucalion’s flood. Radiocarbon dating of the ash from the eruption of Santorini (as the volcano composing the island was also known) revealed it dated from 1500 to 1600
BC
, around the historical reign of King Deucalion. On the island of Paros, a marble pillar listing the kings of Greece implies Deucalion’s flood occurred in about 1539
BC
. The eruption destroyed a great city on Santorini and generated a tsunami that ravaged the Greek coast. In an early version of the Deucalion story the flood is even said to have come from the sea.