THE ICE-AGE FLOODS LEAVE STARK EVIDENCE OF THEIR PASSAGE

In addition to the mammoth coulees of eastern Washington, direct evidence of the floods exist in several forms. Giant current ripples, such as those at West Bar, near Quincy, Wash., and at Camas Prairie, Mont. , offer some of the most conclusive proof that the massive flooding occurred. Other flood-caused phenomena include massive bars of sediment at various locations along the Snake and Columbia rivers...the scoured buttes, basins, and potholes of the scablands...impressive recessional cataracts at Dry Falls and Palouse Falls...and boulders transported hundreds of miles on ice rafts.

HOW DO WE KNOW THAT THESE DRAMATIC FLOODS OCCURRED?

The pioneering research carried out by geologist J Harlen Bretz in numerous treks through the Columbia Basin region beginning in the 1920s convinced him that only huge floods--not normal erosion processes--could have wreaked so much havoc upon the area's landscape. But most leading geologists scoffed at his findings. Not until the 1950s, after additional research by Bretz, coupled with that of geologists Joseph T. Pardee, did opinions begin to change. Pardee proved that glacial Lake Missoula was the source of the floods. Bretz's controversial thesis was vindicated fully by the mid-1960s.