Idaho Librarian

Contents

On My Mind...

Review

Humongous is the operative word here.  It is estimated that the glacial lake covered about 2900 square miles and contained about 500 cubic miles of water.  That’s about half the water in Lake Michigan.  We’re not talking about a fishing hole here.  It was formed from the meltwater of enormous glaciers that had covered vast stretches of Alberta and British Columbia.  At the end of the last ice age, from about 15000 to 13000 years ago, the rapid cycles of melting and reforming of glaciers and ice dams caused dramatic changes in the geology of the area from the lake around Missoula downstream through Idaho, Washington, and Oregon, all the way to the Pacific Ocean.   

David Alt explores the geologic developments through the writings of many geologists who studied the area:  T.C. Chamberlain, who first noted the existence of watermarks in the Mission Valley in western Montana in 1886; Joseph T. Pardee, who first described the lake in 1910; and J. Harlan Bretz, who in 1923 presented his catastrophic theory about the formation of the scablands in eastern Washington, causing a major controversy among geologists for approximately forty years.  Many of the scientists simply could not comprehend the vastness of the lakes that formed behind the ice dams, the tremendous volume of water that escaped each time a dam melted enough to float, or the speed and power with which that water roared across the land.  Alt and fellow geologist R. L. Chambers have determined that these gigantic floods scoured the land at least 36 times during a few thousand years.  Each flood could involve 500 cubic miles of water powering its way from Montana to the Pacific in a week or less. 

Alt brings these scientific findings up close and personal to the modern reader. Although he is a geology professor at the University of Montana, he intended this book for the use of laymen.  He wrote it in the clear, easy-reading style of his roadside geology series and supplemented the text with ample use of maps, photos and drawings.   He makes the geologic events comprehensible and guides the reader, literally, to some of the features in the landscape.  For example, he tells the reader to note some geologic feature while traveling west on I-90 toward East Missoula (p 66) or to observe the lakes in the Lower Grand Coulee that make for dramatic scenery along Washington Highway 17 (p119).  Alt selected  “a few of the most spectacular, the most accessible, the most typical and the most perplexing” geological features (p vii) to discuss in the book.  He visited each site and includes information from scientific sources as well as his own observations.  At each point of interest he describes the formation and how it might have been created, often including photos to help the reader recognize the feature. 

Alt has written another interesting book that brings geology to the general public.   He includes a glossary for the amateur and a bibliography that should give everyone some further reading.  This book will be of interest to public and academic libraries.

Readers who enjoy Glacial Lake Missoula will want to read Northwest Exposures: a Geologic Story of the Northwest by David Alt and Donald W. Hyndman and Fire, Faults and Floods: a Road and Trail Guide Exploring the Origins of the Columbia River Basin by Marge and Ted Mueller.