Cataclysms on the Columbia: the great Missoula floods by John Eliot Allen

The story of the Missoula floods is dramatic. The floods themselves were almost inconceivably large and powerful, and it took academic geology nearly fifty years to fully accept the physical evidence of massive flooding.

Briefly, in 1919 J Harlen Bretz began exploring the Columbia Plateau of eastern Washington by car and on foot, discovering the scablands, an area marked by interconnecting channels scoured out of the earth. Imagine training a hose on a dry piece of ground. What happens first, before the water chooses one channel to deepen, is that a braid of multiple channels form.

In addition to these channels Bretz also found ripples like one sees in sand at the ocean. But, like the braided channels the ripples were on a massive scale: thirty-five feet high and two hundred to three hundred feet between crests. The only conclusion Bretz could come to, though even he was unwilling at first, was that a massive flood created these features.

In the 1920s the accepted academic thinking was that all geologic formations developed over time, slowly. The idea of catastrophe shaping the earth with the exceptions of earthquakes and volcanoes was out of favor. Keeping suspense alive, the book details the conflict between Bretz and other geologists as the field slowly changed.

It took someone with courage and imagination to make sense of the unusual geological formations–without the aid of a view from the air–and Bretz was finally awarded the Penrose Medal of the Geological Society, the nation’s highest geological honor, in 1979.

It is now known that at least 40 floods inundated the northwest between 18,000 and 15,000 years ago as the last ice age closed. Ice dams at the edge of a vast inland lake near Missoula, MT, periodically failed and water coursed across eastern Washington, the Columbia River, into the Willamette Valley as far south as Eugene, and to the ocean. The water would have filled the Gorge, been as high as Crown Point, and enveloped what is now Portland under 400 feet of water. Eugene was also, like Portland, intermittently submerged–under an estimated 380 feet.

The largest Missoula flood had a force of 10 times that of the volcano that created Crater Lake. The combined forces of all forty floods has no equal on earth, including the largest fusion bomb and the meteorite that landed 66 million years ago.

Because it had such force, it should be no surprise that the Missoula floods have left erratics, house-sized boulders in the Willamette Valley, as well as fertile top soil from eastern Washington state, deposited–in some places–100 feet deep.

Interested in learning more? The library has the book and a DVD, Ice Age Flood, and there are several good web sites.

Reviewed by Lily


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