Missoula Floods - Flood Hypothesis Proposed

Flood Hypothesis Proposed

Geologist J Harlen Bretz first recognized evidence of the catastrophic floods, which he called the Spokane Floods, in the 1920s. He was researching the Channeled Scablands in Eastern Washington, the Columbia Gorge and the Willamette Valley of Oregon. In the summer of 1922, and for the next seven years, Bretz conducted field research of the Columbia River Plateau. He had been interested in unusual erosion features in the area since 1910 after seeing a newly published topographic map of the Potholes Cataract. Bretz coined the term Channeled Scablands in 1923 to refer to the area near the Grand Coulee, where massive erosion had cut through basalt deposits. Bretz published a paper in 1923, arguing that the channeled scablands in Eastern Washington were caused by massive flooding in the distant past.

Bretz's view, which was seen as arguing for a catastrophic explanation of the geology, ran against the prevailing view of uniformitarianism, and Bretz's views were initially held in disregard. The Geological Society of Washington, D.C invited the young Bretz to present his previously published research at a January 12, 1927 meeting where several other geologists presented competing theories. Another geologist at the meeting, J.T. Pardee, had worked with Bretz and had evidence of an ancient glacial lake that lent credence to Bretz's theories. Bretz defended his theories and this kicked off an acrimonious forty year debate over the origin of the Scablands. Both Pardee and Bretz continued their research over the next 30 years, collecting and analyzing evidence that led them to identify Lake Missoula as the source of the Spokane Flood and creator of the Channeled Scablands.

After J.T. Pardee studied the canyon of the Flathead River, he estimated that flood waters in excess of 45 miles per hour (72 km/h) would be required to roll the largest of the boulders moved by the flood. He estimated the water flow was nine cubic miles per hour, more than the combined flow of every river in the world. Estimates place the flow at ten times the flow of all current rivers combined.

The Missoula Floods have also been referred to as the Bretz Floods in honor of Bretz.