By John Eliot Allen
The formation of the Grand Coulee remained a secret for a few years, till J Harlen Bretz proved that the Columbia River basin used to be the positioning of big floods 15,000 years in the past that created the panorama we see this present day.
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Extra resources for Cataclysms on the Columbia: a layman's guide to the features produced by the catastrophic Bretz floods in the Pacific Northwest
It's a phenomenon familiar to geologists and the only one that logically explains the Columbia erratics (though nowhere else had erratics of this size been attributed to iceberg drift). It should also be pointed out that Bretz was not the first geologist to suggest that vast amounts of water had once inundated the Northwest. Forty years earlier in 1871, Thomas Condon, Oregon's pioneer geologist, had proposed a Pleistocene flooding of Oregon's Willamette Valley, but Bretz would carry these ideas further and in doing so would formulate theories that would bring him into extended and bitter conflict with the geological community.
And the potholes themselveslarge pit-like depressions lying beyond the fallswere of a size beyond anything known elsewhere: hundreds of feet across, much longer than they were wide, and deeper than a house is tall. Now what did all this mean? Why, for example, should Bretz find the cataract so particularly surprising? First of all there was the matter of the falls being "dry," in itself puzzling, but the principal mystery lay in explaining the very existence of a waterfall in this unlikely spot.
Though, ideally, geological discovery is a continual play-off between speculation and proof, between the ivory tower and the field, ultimately the site itself must serve as the final check. " A rock proven by lab tests to contain gold or oil does not necessarily mean that the area it came from is rich in these materials, any more than a trace of arsenic in a corpse is proof that the host at last night's dinner party ought to be arrested. It's a matter of puzzle work, of using all available techniques to rebuild the scenario.