Cascadia's Fault - Jerry Thompson [94]
Any one of these studies viewed in isolation might not have been enough to convince the most stubborn skeptics. Taken as a whole, however, and seeing that they all said basically the same thing, this united front of twelve top-level scientists looked like a critical mass. Having to equivocate a bit by including the phrase “or a series of lesser earthquakes” no doubt rankled those who wanted to make the clearest, least ambiguous statement possible. But counting the slow decay of carbon atoms to find out when something happened hundreds of years ago was just too imprecise. And there were many examples elsewhere of several earthquakes occurring in series, several years apart. So this remained an unsolved mystery and a real debate.
What they still needed was a more precise date and some way to show, convincingly, how big that mega-shockwave had been. If they could say that an earthquake happened in a specific year, or better yet on a specific day, the whole thing would become more real, more believable not only to skeptics in the science community but to elected officials, emergency planners, and the people who live within striking distance of Cascadia’s fault.
In all the mucking about along the coast, scientists had become increasingly aware that people had in fact been living on the edge of Cascadia’s rupture zone when it tore itself apart the last time. Beneath a thick layer of tidal mud in the Nehalem and Salmon River estuaries of northern Oregon, Rick Minor of Heritage Research Associates in Eugene and Wendy Grant of the USGS found fire pits full of charcoal and woven cedar mats. Near Willapa Bay in Washington State, fishing weirs and cobblestones modified by fire were found buried in submerged shorelines. Trying to figure out when the campfires had been doused or when coastal villages and their Aboriginal residents had been shaken from their sleep or perhaps drowned by killer waves turned out to be exceedingly difficult.
Anthropologists had been collecting flood and disaster stories from tribal elders since the 1850s but it was only in the 1980s that they began to compare notes with geologists, who found the oral histories intriguing and frustrating at the same time. Judge James Swan, who had lived among the Makah people of Neah Bay, Washington, for a time in the late 1860s published the family history of Billy Balch, a Makah leader, who told him about a catastrophic flood that had turned Cape Flattery into an island. The Balch story began “a long time ago” although “not at a very remote period,” when the water of the Pacific flowed like a swollen river through the swamp and prairie between his village and Neah Bay.
This, of course, was the same tide marsh where Brian Atwater found his first evidence of land subsidence caused by large seismic ruptures. Balch’s story does not mention the ground shaking, so perhaps the flooding he talks about was caused by a distant tsunami from across the Pacific. In any case, Balch told Swan that after the initial flooding, the ocean began to recede and left Neah Bay dry for four days. It then rose again “without any swell or waves” and submerged the whole of Cape Flattery.
“As the water rose, those who had canoes put their effects into them and floated off with the current which set strong to the north,” Swan paraphrased Balch. “Some drifted one way and some another; and when the waters again resumed their accustomed level, a portion of the tribe found themselves beyond Nootka [on Vancouver Island] where their descendants now reside ... Many canoes came down in the trees and were destroyed, and numerous lives were lost.”
“Could this be an account of a