Analog SFF, May 2009

by Dell Magazine Authors

  Now that I know what to look for, there's plenty of evidence here, as well. On my hike, I found water-rounded pebbles hundreds of feet above the present-day river, with no creek in the vicinity to explain them.

  Back in Portland, my own neighborhood also fits Bretz's theory. Not far away is an extinct volcano called Rocky Butte. Its east side—upstream at the time of Bretz's flood—is steep, eroded, stripped of soil. The west side has more soil, and downstream extends a residential area known as Alameda Ridge. In aerial views, the ridge has the classic shape of gravel bars I've encountered on many a canoe trip. But it's a gravel bar writ large, 200 feet above the present-day river.

  One of my best friends once lived there. Digging a vegetable garden one spring, we kept coming up with rocks the size of hubcaps. Not only were they obviously water-rounded, they were made of granite or granite-derived metamorphics. But there's no granite bedrock in our part of Oregon. Her garden was full of chunks of somewhere far away, washed downstream by Bretz's flood and deposited in a gravel bar 200 feet high.

  I have a book on my shelves about Bretz and his “HumongousFlood.” Humongous barely begins to describe it.

  * * * *

  Even Bretz was a reluctant catastrophist. “He kept trying to explain that he'd gone back and looked again and again, and the only way [he could] account for this is [by] huge quantities of water,” says Soennichsen.

  He also had a problem: He couldn't figure out where all of that water came from.

  If you're a geologist looking for a mechanism that might create big floods, one place to look is Iceland. The Icelandic floods are called jokulhlaups, and they're common enough to satisfy even the most ardent uniformitarian. The most recent, in 1996, produced three cubic kilometers of water in two days, crushing that country's largest bridge like a used tissue paper.

  Jokulhlaups occur when volcanoes erupt beneath glaciers. Meltwater collects in ponds beneath the ice until there's enough of it to lift the ice high enough to give the water a way out. Then, poof, no more bridges, farms, or anything else that happens to be in the way.

  But no jokulhlaup has ever come close to the scale needed to account for Bretz's scour channels. Nor could he find a place where big volcanoes might have erupted beneath ice—and fully aware of jokulhlaups, he looked.

  Then, in 1927, he was invited to Washington, D. C., to speak before an elite gathering of geologists. At last, he must have thought, he'd been given a chance to prove his case.

  “He did a great deal of preparation,” says Soennichsen. “He had all sorts of visuals, maps. It would have taken an hour and a half or more to make the presentation.”

  But he'd walked into an ambush. The assembled scientists had no intention of being persuaded, and one after another, they rose to squash his outrageous theory. Caught by surprise, Bretz made a poor defense, then, depressed, boarded a train and went back to Chicago.

  * * * *

  The problem with grand theories like uniformitarianism is that they blind you to what the data itself might be trying to say. “The grounding for a science is not a principle,” Baker says. “The grounding is that you are open to what nature has to tell you. If you dismiss something as impossible, you will not learn anything about it. It's like being a detective. If you ignore a clue, it's the critical one.”

  In physics, scientists generally form hypotheses, then conduct experiments to test them. But geology is an observational science, in which experiments involve forming a hypothesis, then going out into the field to see whether you can find other things that are consistent (or inconsistent) with it.

  “Again, it's like a detective at a crime scene,” Baker says. “When they're on the right tack, things begin to fit a pattern that wasn't obvious before.”

  * * * *

  It appeared that the uniformitarians had won. But Bretz had a secret supporter, a man named Joseph T. Pardee. During Bretz's presentation, Pardee reputedly turned to someone sitting near him and confided: “I know where Bretz's water came from.”

  Bretz had figured that it had to have had something to do with melting Ice Age glaciers, not far to the north. Pardee believed the source was father east, in Montana. But the uniformitarian/catastrophist divide was strong, and Pardee wasn't willing to risk his career supporting a catastrophist. Not yet.

  Then, in 1940, as he was retiring, Pardee dropped his bombshell in a vaguely titled paper about ripple marks in the bed of glacial Lake Missoula.

  Lake Missoula was an Ice Age lake about the size of one of the Great Lakes. It had formed south of the great ice sheets, in western Montana, when ice blocked what is now the Clark Fork River, causing water to impound, up to 2,000 feet deep. Geologists had long known about it: Pardee himself had mapped its shorelines in 1909 and published his findings in 1910. But he'd not mentioned the ripple marks. Those, he'd kept to himself.

  They were a lot like the ripples ordinary streams leave in sandbars. But they were enormous: thirty feet tall, a mile long, and spaced at intervals of 200 to 300 feet. Such features could only be created by an enormous current: the type of current that could only be produced if the entire lake emptied, practically overnight.

  * * * *

  Today, scientists know that ice dams are notoriously unstable. When the one that formed this lake broke, they estimate, water roared down the canyons at fifty to sixty miles per hour. It was, quite simply, one of the greatest flash floods of all times.

  Pardee never bothered to say where all of that water went. He didn't need to. Anyone who'd heard of Bretz knew.

  Today, scientists have found signs that ancient Lake Missoula may have formed and drained dozens of times over the course of several thousand years. Others have found traces of additional superfloods in Canada, Siberia, Mongolia, and Europe. Then in 1973, Mariner 9 returned the first good, close-up photos of Mars. One of the people who saw them was Baker, who'd done his doctoral research studying the Eastern Washington scablands. What he saw looked familiar. “It was pretty obvious that the features were similar,” Baker says. Today, most planetary scientists believe that Mars too had enormous floods sometime in its history, though they are still searching for the source of the water.

  Bretz himself lived to 98, old enough to watch the Martian discoveries and be pleased at hearing the newly discovered features referred to as scablands. Better yet, in 1979, the Geological Society of America (the very organization that had arranged the D. C. meeting at which he had been so thoroughly excoriated) awarded him its highest scientific honor, the Penrose Medal.

  Bretz reportedly had only one complaint: “All my enemies are dead, so I have no one to gloat over.”

  * * * *

  Today's question isn't whether there was a big flood in the scablands: It's whether even Lake Missoula was big enough to account for everything Bretz saw.

  Today's “outrageous” hypothesis, Baker says, is that additional water came from beneath the ice caps—like a jokulhlaup but without a volcano.

  The idea stems from findings in Antarctica, where scientists have discovered large subglacial lakes, one of them enormous.[3] More recently, they've discovered that water can flow from one lake to another via subglacial channels. Could a similar lake, perhaps filling part of the great trough of British Columbia's Okanogan Valley, have belched water big time?

  The idea, Baker admits, is a long shot. “A lot of people would have thought the ice sheet was stable,” he says. But, he adds, “it's a principle of science that if you dismiss something as impossible, you will not learn anything about it.”

  That sounds like a pretty good principle for any scientific endeavor. And in the wake of Bretz's vindication—not to mention subsequent studies regarding dino-killing asteroids—you might think the old gradualism/catastrophism debate would be finally put to rest.

  But that's not the case. It's alive and kicking in history and archaeology. There are plenty of examples, but the one we'll look at is the eastern Mediterranean.

  * * * *

  Big Bang in the A
egean

  For hundreds of years, the Minoan culture thrived on the island of Crete, dominating the entire region. Its most famous ruin is the palace of Knossos, whose warren of passageways probably gave rise to the legends of the Labyrinth and the Minotaur.

  But then, about 3,500 years ago, Minoan civilization came crashing down. The ruins show clear evidence of fire and violent destruction, but what was the cause? Some early excavators suggested a cataclysmic event, but the idea fell into disrepute. By the late twentieth century, archaeologists tended to reflexively blame such cultural collapses on internal decay, possibly opening the door to invasion, says Amos Nur, a geophysicist at Stanford University.[4]

  Nur attributes that attitude to one of the twentieth century's leading historians, Arnold J. Toynbee, who in 1939 argued that for the twenty-plus civilizations he examined, the cause of collapse was internal, not external. “The breakdowns of civilization are not catastrophes of the same order as famines and floods and fires and shipwrecks and railway accidents; and they are not the equivalent, in the experiences of bodies social, of mortal injuries inflicted in homicidal assaults,” Toynbee wrote.[5]

  In other words, in Toynbee's view you can't kill a culture with a single blow, (unless, perhaps, it is already dying of internal causes). It's basically a gradualist view, not all that different from that of the uniformitarians of Bretz's time.

  And just as Bretz ran into trouble for proposing his gigantic flood, historians or archaeologists who suggested that civilizations may have fallen due to natural cataclysms have been mocked and may well have damaged their careers. The fear is so deep seated, Nur notes, that when one archaeologist suggested that an earthquake played a role in one city's collapse, she felt compelled to add: “Archaeologists of my generation ... were brought up to view earthquakes, like religion, as an explanation ... to be avoided if at all possible."[6]

  But the Aegean and eastern Mediterranean lie in an extremely active tectonic zone near the boundaries between the African plate, the Eurasian plate, the Arabian plate, and the Anatolian (Turkish) platelet. As much as five percent of the earthquake energy released on the entire planet is concentrated in this zone, says Jelle Zeilinga de Boer of Wesleyan University in Middletown, Connecticut.[7]

  There are also a few widely scattered volcanoes, the most famous of which is (or was) Thera, in the Aegean archipelago of Santorini.

  Thera lies about seventy miles north of Crete. Sometime about 3,600 years ago, it erupted in the biggest volcanic blast in the history of civilization: an order of magnitude bigger than the one that in 1883 destroyed the Indonesian island of Krakatoa.

  It's a little hard to determine when, precisely, the eruption occurred, but Zeilinga de Boer notes that sulfur deposits in Greenland ice cores date the event to about 1645 B.C.E. Tree-ring data from California, Turkey, Sweden, and Ireland, he says, all show a decade-long period of severe global cooling at about the same time,[8] while Chinese records show “yellow fogs,” probably from sulfuric acid, as well as frost in July.

  Nobody doubts that Thera produced a big, nasty bang. But the demise of Minoan civilization is normally dated at about 1450 B.C.E., nearly two centuries later.

  For gradualists, that's proof that in the long haul, volcanoes are irrelevant. Healthy civilizations weather whatever disaster befalls them; unhealthy ones are collapsing anyway.

  Zeilinga de Boer has a different theory. He calls it the “vibrating string,” and argues that natural cataclysms can have impacts that ripple through history for years, decades, and centuries. Crop failures, for example, lead to famine and disease; ecosystem changes alter economies and, ultimately, cultures. It's a bit like chaos theory's famous “butterfly effect” or Ray Bradbury's classic short story, “A Sound of Thunder."[9]

  Consider, de Boer suggests, a temblor that in 464 B.C.E. damaged the ancient Greek city-state of Sparta.

  The Spartans were a relatively small warrior caste, supported by a much larger slave population. The earthquake, whose magnitude is estimated to have been 7.2, had an epicenter directly beneath the city. It knocked down many buildings and killed many soldiers. It also killed women and children, depleting the ranks of the next generations of soldiers. Thus, the Spartans had to fill out their army with slaves, “which wasn't so good,” Zeilinga de Boer says, “because those people weren't as interested in fighting for Sparta.”

  Sparta limped on this way for several decades, but eventually was defeated: an event that was one of the most momentous in ancient history because it opened the door for the rise of Athens and the ensuing Golden Age of Greek culture. Without the earthquake, he argues, the history of Western civilization might have been unimaginably different.

  Nor are such changes limited to ancient history. In 1972, Zeilinga de Boer says, a magnitude 6.2 temblor in Managua precipitated revolution in Nicaragua by exposing the corruption of the government, whose officials used relief money to line their own pockets. That led to the leftist Sandinista regime, with major influences on U.S. Central American policies.

  “Disasters have long-ranging after-effects,” Zeilinga de Boer says. “If a major earthquake occurred in California, there would be so many social and economic impacts that people couldn't comprehend it.”

  It's a sobering thought. Then he carries it one step further: “We've already seen what a simple hurricane has done. Imagine when the earthquake that will occur finally raises havoc in San Francisco.”

  * * * *

  So, what did happen in ancient Crete?

  One possibility is simply that we've got the date for the collapse of Minoan civilization wrong, and that it actually occurred earlier, in the immediate aftermath of Thera. The generally accepted date for the end of Minoan civilization comes from matching up pottery styles in Crete and Egypt. But that's not rocket science. There could be problems, Zeilinga de Boer suggests, with either the matching or the Egyptian dates.

  But there's no obvious reason to suppose the accepted date for Minoan collapse is wrong. More likely, if Thera did deliver the mortal blow, it simply took a long time to play out.

  Zeilinga de Boer's hypothesis is that the eruption and associated earthquakes damaged Minoan cities, while the tsunami ruined harbors and boats, vital to a seafaring civilization. This opened the door for Mycenaeans (Greeks) to move in as the surviving Minoans dispersed. In an interesting side effect, he argues, the Minoan written language was adapted for use by the Greeks. Pre-Thera they had no writing. Post-Thera, they did. That ripple, far down Zeilinga de Boer's vibrating string from its initial source, might mean that the very philosophy and science of Western Civilization owes its genesis to a single volcanic blast. At the least, it's an interesting idea.

  * * * *

  Mycenae and other early Greek cities were not themselves immune to destruction. In 1993, Robert Drews listed forty-seven major archaeological sites in Greece, Asia Minor, Syria, and Israel that show clear signs of collapse, fire, and/or abandonment somewhere between 1225 and 1175 B.C.E. “Within a period of forty or fifty years ... almost every significant city or palace in the eastern Mediterranean world was destroyed, many of them never to be occupied again,” he wrote.[10]

  One was Mycenae itself.

  Traditionally, blame for all of this destruction is laid at the feet of mysterious, marauding “Sea Peoples” who attacked, pillaged, then vanished. There's just one problem: Nobody has a clue who the Sea Peoples were or why they didn't hang around to enjoy their spoils. In fact, the reason they're called Sea Peoples is that nobody can figure out where else they might have come from.

  In 1993 Nur visited the ruins of ancient Mycenae, where he was immediately impressed by the fact that the city's fortifications had been built atop an obvious fault scarp. Obvious to him, at least. To the ancient Greeks, it probably looked like any other cliff, which they happily incorporated into their fortifications. Nor, he realized, had archaeologists appreciated the significance of that cliff, whose surface was smooth, polished: a clear sign of geologically recent seism
ic activity.[11]

  Thanks to their anti-catastrophist mindset, Nur adds, archaeologists haven't been all that good at actually looking for evidence of earthquake damage. That's unfortunate, because earthquakes and marauders leave different types of ruins. If a fault line cuts directly across a wall or fence, for example, movement of the fault will put a distinctive kink into it. And that's not the only smoking gun for earthquake damage. If raiders were to destroy a temple by pulling down its columns, the columns would probably fall every which way, depending on the angle at which they were pulled. The same would probably occur if abandoned buildings collapsed of old age. But when columns or pillars are knocked down by earthquakes, they tend to fall in parallel rows.

  At least as tellingly, valuables—ranging from grain to gold—may lie beneath earthquake-collapsed walls: not likely if looters were instead responsible. In addition, crushed skeletons indicate that something brought everything crashing down a good deal more quickly than warfare was capable of doing in the millennia before gunpowder.

  Nur believes that Drews’ cites were actually devastated by a “storm” of earthquakes that struck one after another (though war may also have played a role, as rival kingdoms took advantage of the holes knocked in their enemies’ defenses).

  One of the arguments that had led archaeologists to dismiss earthquakes as a crackpot explanation is that Drews’ devastated cities are spread over a 900-mile radius, a vastly larger area than could be affected by any single earthquake. But we now know that earthquakes can occur in sequence, as stresses shift along fault lines. That's exactly what happened in Indonesia after the mammoth Sumatran earthquake of December 26, 2004.[12] Barely three months later, an adjacent segment of the same fault was hit by another gigantic earthquake. And in Turkey, from 1939 to 1967, a string of seven earthquakes (magnitude 5.6 and larger) progressed westward along 500 miles of the North Anatolian Fault, which runs south of the Black Sea. That's just one of several faults that could have contributed to Nur's 3,200-year-old earthquake storm.