Umpteen thousand years ago a glacier from Canada flowed down into northern Idaho blocking the Clark Fork of the Columbia River. Water backed up to a depth of 200 feet creating a lake several hundred miles up into Montana through Missoula, Deer Lodge nearly to Butte. Eventually, the ice dam floated creating a catastrophic flood which emptied the lake in a couple days. Rocks unique to Bonner, MT, just upstream from Missoula, were found in the Willamette Valley as a result of the extreme erosion which carved parts of the Columbia Gorge.
The glacier continued and blocked the river 10 or 15 more times resulting in evidence of the subsequent shorelines of the lake in Missoula and throughout the Clark Fork Valley.
In 1989, the Northwest Mining Association in Spokane awarded the Exploration Geologist of the Year award to the recently landed Mars Rover which explored an area on Mars for water in an area on the planet which replicated the outwash plain from Lake Missoula through the Columbia Gorge. The Rover trained in the State of Washington as it is the most pronounced example of this type of outwash plain on earth.

Jeff Stabnow
Clitherall MN