Glacial Lake Missoula: Book Review of Glacial Lake Missoula and its Humongous Floods

At the height of the most recent ice age, from around 17,000 to 10,000 years ago, the northern half of North America was buried beneath a massive ice sheet. Up to three miles thick at its center, the ice sheet sent lobes of glacial ice down into the northern tier of states in the United States. One of these lobes of ice flowed down the Purcell Valley in northern Idaho. As the ice crossed, and eventually blocked the Clark Fork River, it became an ice dam. Behind this dam was formed one of the largest glacial lakes to have existed during the last ice age. Known as Glacial Lake Missoula, it covered an area over 2,900 square miles, and was nearly 2,000 feet deep at its deepest point by the ice dam.

As the lake filled with water, the water was able to eventually float the dam, releasing a catastrophic flood. It is estimated that over 500 cubic miles of water was released emptied from the lake in only a few days time. This flood raced across much of Idaho, Washington, and Oregon through much of the Colombia River basin, creating the spectacular scabland terrain that characterizes eastern Washington.

The flood was amazing, and we can only imagine at what it was like to have seen or experienced this flood. What is even more amazing is that this flood didn't happen once or twice, but at least thirty-six times! Each successive flood was slightly less massive than the one preceding it, but even the last and smallest flood, was still one of the largest floods to have been recorded.

This amazing lake, and the floods it spawned, is the subject of a recently published book, Glacial Lake Missoula and its Humongous Floods written by David Alt. Alt is professor of geology at the University of Missoula and has studied Glacial Lake Missoula and its floods since the 1960's.

Glacial Lake Missoula and its Humongous Floods takes the reader on a journey examining the lake from its source in the valleys of Montana, and down the path of its flood to the coast at the mouth of the Columbia River. The book is well illustrated with photos and maps of Lake Missoula and the scablands that were created by the humongous floods.

Now, I admit that I wasn't sure what to expect when I began reading this book. I have known about Lake Missoula, and I knew it had catastrophically drained, but not much else. The books back cover tells the reader that this is "the story of geologists grappling with scientific controversy - 'of how personalities, pride, and prejudice sometimes supersede scientific evidence.'" This grabbed my attention.

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