Missoula Floods

The Missoula Floods are large scale flooding that occurred at the end of the last ice age in the Pacific Northwest of North America. They are the result of repeated, catastrophic drainage of a series of Eisstauseen at Clark Fork. The Eisstauseen arose before the great ice sheet of the North American ice sheet. Progress of the Laurentide ice sheet led to the damming of a network of large glacial lakes, the largest of which was the Lake Missoula.

The water was looking his way over Clark Fork and the Columbia River and flooded the eastern Washington and the Valley Willamette Valley in Western Oregon. The water carried the ground up on the rocks off, cut deep into the hard basalt of the mighty Columbia flood basalt, and created a special, barren landscape, the Channeled Scablands.

Geologists estimate that the flooding 13,000 and 15,000 years ago over two millennia, repeated about 40 times, each with about 55 years long intervals, where the Lake Missoula auffüllte again.

The Missoula Floods are considered as the basis for the fertility of the soil in the Willamette Valley.

The theory of the Missoula floods was first formulated in the 1920s by J Harlen Bretz.