Missoula floods
The Missoula Floods , also known as the Spokane Floods , are large-scale floods that occurred in the Pacific Northwest of North America at the end of the last glacial period . They are the result of the repeated, catastrophic runoff of a number of ice reservoirs on Clark Fork . The ice reservoirs formed in front of the large ice sheet of the North American inland ice. The advance of the Laurentide Ice Sheet led to the damming up of a network of large glacial lakes , the largest of which was Lake Missoula .
The water found its way across Clark Fork and the Columbia River , flooding eastern Washington and the Willamette Valley in western Oregon . The water carried the ground down to the rock, cut deep into the hard basalt of the mighty Columbia flood basalt , and created a special, barren landscape, the Channeled Scablands .
Geologists estimate that 15,000 to 13,000 years ago the floods were repeated about 40 times over two millennia, with intervals of about 55 years in which Lake Missoula filled up again.
The Missoula Floods are believed to be the foundation of soil fertility in the Willamette Valley.
The Missoula Flood theory was first formulated by J Harlen Bretz and Joseph Pardee in the 1920s .
See also
Individual evidence
- ↑ a b Joseph Thomas Pardee and the Spokane Flood Controversy ( Memento of the original from September 3, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ The Channeled Scablands of Eastern Washington, Fig. 10: The advance of glacial ice and the corking of the Clark Fork River. USGS
