Glacial Lake Missoula

Glacial Lake Missoula, formed by the Cordilleran Ice Sheet blocking the Clark Fork River, was a vast prehistoric lake in Western Montana near present-day Lake Pend Oreille. Its repeated filling and emptying from 13,000 to 15,000 years ago left enduring marks on the landscape, evident in car-sized boulders and the Channeled Scablands of eastern Washington. Geologists have studied its impact since J.T. Pardee's 1910 discovery of shoreline marks around Missoula.

About 15,000 years ago, the valleys of western Montana lay beneath a lake nearly 2,000 feet deep. Glacial Lake Missoula formed as the Cordilleran Ice Sheet dammed the Clark Fork River just as it entered Idaho. The rising water behind the glacial dam weakened it until water burst through in a catastrophic flood that raced across Idaho, Oregon, and Washington toward the Pacific Ocean. Thundering waves and chunks of ice tore away soils and mountainsides, deposited giant ripple marks, created the scablands of eastern Washington and carved the Columbia River Gorge. Over the course of centuries, Glacial Lake Missoula filled and emptied in repeated cycles, leaving its story embedded in the land. Glacial Lake Missoula, the largest of several Cordilleran Ice Sheet impounded lakes, spanned about 2,900 square miles, holding over 500 cubic miles of water.

1) GLACIAL LAKE MISSOULA. (n.d.). GLACIAL LAKE MISSOULA. http://www.glaciallakemissoula.org/

2) Glacial Lake Missoula | Destination Missoula. (2019, May 20). Destination Missoula. https://destinationmissoula.org/glacial-lake-missoula

3) Glacial Lake Missoula National Natural Landmark (Camas Prairie Ripples) (U.S. National Park Service). (n.d.). https://www.nps.gov/places/glacial-lake-missoula-national-natural-landmark-camas-prairie-ripples.htm