Geology In Action: Ice Age Megafloods

In 1909, the Seattle teacher [Harley Bretz] visited the University of Washington to see the U.S. Geological Survey’s new topographic map of the Quincy Basin, a large area on the west side of the Columbia Plateau. He was 27, with no formal training in geology, but when he looked at the map, he noticed a striking feature: a huge cataract (much like Dry Falls) on the western edge of the basin, a place where water appeared to spill out of the basin and into the Columbia River, gouging a canyon several hundred feet deep. The falls would have been bigger than Niagara, but there was no apparent source of water for them—no signs whatsoever of a river leading to the cataract.

Bretz asked faculty in the department about the feature, called Potholes Coulee, but they had no answers for him. Nor could they explain many of the other unusual features of the region. That’s when, as legend has it, Bretz decided to become a geologist. He earned his Ph.D. in geology from the University of Chicago four years later, changed his professional name from Harley to “J Harlen” to sound more respectable, and in 1922 returned to eastern Washington to take a closer look at the plateau and its scablands. And after two seasons in the field, his conclusions shocked even himself: The only possible explanation for the all the region’s features was a massive flood, perhaps the largest in the Earth’s history—“a debacle which swept the Columbia Plateau,” ripping soil and rock from the landscape, carving canyons and cataracts in a matter of days. “All other hypotheses meet fatal objections,” he wrote in a 1923 paper.

read the rest at Natural Geographic

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