Missoula floods
Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown south of the Cordilleran ice sheet. The areas inundated in the Columbia and Missoula floods are shown in red. | |
| Cause | Ice dam ruptures |
|---|---|
| Meteorological history | |
| Duration | Between 15,000 and 13,000 years ago |
| Flood | |
| Overall effects | |
| Areas affected | The current states of: Idaho, Washington, and Oregon |
The Missoula floods (also known as the Spokane floods, the Bretz floods, or Bretz's floods) were a series of cataclysmic glacial lake outburst floods that swept periodically across the area that would become eastern Washington, northern Idaho and northern Oregon, and down the Columbia River Gorge at the end of the last ice age. These floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, flooding much of eastern Washington and the Willamette Valley in western Oregon. After the lake drained, the ice would reform, creating glacial Lake Missoula again.