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with his ideas.
    University of Chicago professor J Harlen Bretz, however, was not convinced of that theory and spent years combing the dry side of Washington State, carefully examining and reexamining the evidence. He came to believe that the ice stopped well north of Spokane, and that many of the distinctive features of the Inland Northwest were not the result of the slow advance and retreat of glaciers, but rather had been sculpted by a sudden massive flood. Harlen Bretz was not the first to entertain the notion of water as a major player in the drama. A century earlier,naturalist David Douglas and missionary Samuel Parker had both surmised that the Grand Coulee west of Spokane must have been carved by some dramatic flow. In 1899, geologist and foresterJ. B. Leiberg postulated that an ice plug had dammed the Clark Fork River near its mouth on Lake Pend Oreille. In 1910, another geologist,J. T. Pardee, reckoned that this ice dam must have attained a thickness of several thousand feet. He visualized how it would have impounded tributaries all the way upstream to Flathead Lake and the Bitterroot Valley, creating a vast body of water that he called Glacial Lake Missoula.
    Pardee’s work helped Harlen Bretz to envision a credible mechanism for a flood of biblical scale, and in 1923, Bretz published the first of more than a dozen technical papers detailing his ideas. He theorized that as the climate warmed at the end of the Pleistocene, the ice dam had come apart. Its sudden failure allowed the totality of the lake’s water to flush the ice from Lake Pend Oreille’s basin, then fan out with devastating speed, crashing through the Spokane countryside and across the Columbia Basin.The deluge backed up behind the constriction of Wallula Gap before tearing through the Columbia River Gorge with renewed force. This single jet of floodwater split again at the Willamette Valley, forking to find separate ways to the sea.
    Few of Harlen Bretz’s fellow geologists bought into the notion of the cataclysmic event that he called the Spokane or Lake Missoula Flood, and decades passed before the theory gained wide acceptance. But by the early twenty-first century, the saga of the Ice Age floods stood as a defining chapter in the region’s history. To gain any sense of the Inland Northwest landscape, you have to comprehend these immense forces at work. You must try and picture how the dam failed within a matter of hours, and how the whole event played out over the course of a few days. You have to realize that, after the first apocalyptic deluge, global weather cycled back toward the cold. Within a few decades, a lobe of the continental glacier again crept south to form another thick dam across the Clark Fork delta and Lake Pend Oreille. A new Glacial Lake Missoula filled, lapping at levels clearly visible today on bare hillsides. Another warming trend and catastrophic ice failure followed, releasing another torrent to pound its way to the sea. You have to imagine this happening dozens of times as the climate wobbled toward the warmth of the Holocene epoch. Today we have accepted the spectacle of these floods washing over our earth as common knowledge, and we marvel that it took geologists so long to figure it out.
Inside the Icebox
    Even though the basics of this story have been available for almost a century, the devil, as Roy Breckenridge continually points out, is in the details. He and his colleagues study theevents that took place around Lake Pend Oreille and the lower Clark Fork River at the end of the Pleistocene, trying to figure out how the Cordilleran Ice Sheet formed a wall that was tall enough and strong enough to back up an enormous Glacial Lake Missoula. They want to know how such a massive dam could have failed so catastrophically, and exactly what happened when three thousand square miles of deep water roared away. They are curious as to how the ice then re-formed to replay the same scene, with subtle variations, many times