Glacial Lake Missoula and the Ice Age Floods
to the Montana Natural History Center's Glacial Lake Missoula website.
Here you can learn about the great floods that
shaped the Pacific Northwest, take
a tour of the landscapes they created, revisit
the drama that unfolded as the story of the floods came to light,
and keep up-to-date on events focusing on
the floods--including the creation of a National Park Service trail following
the path of the flood waters.
The Short Story
About 12,000 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.
- The ice dam was over 2000 feet tall.
- Glacial Lake Missoula was as big as Lakes Erie and Ontario combined.
- The flood waters ran with the force equal to 60 Amazon Rivers.
- Car-sized boulders embedded in ice floated some 500 miles; they can
still be seen today!