Dry Falls, A Basalt Cliff That Rimmed Glacial Lake Missoula, in Eastern Washington State: A Rare Case Where Catastrophism is the Explanation

      The recent glacial collapse flood in Nepal was a reminder that catastrophism, though quite rare, does happen in geology, whether influenced by anthropogenic actions or not. Those waters and debris were estimated to have flowed at about 104 miles per hour, extraordinarily fast and destructive. In contrast, the Dry Falls basalt cliff rim of Lake Missoula, a glacial lake in Eastern Washington, is thought to have been cut by waters moving at 65 miles per hour. Both events are examples of catastrophism in geology, which does happen, although such events are quite rare; of course, gradualism, or gradual change, is by far the main mechanism in geology. The reality is that while some processes, like floods, storms, and surface-affecting earthquakes in geology, happen faster than others, the vast majority are slow and gradual, including most tectonism, sedimentation, and erosion.

     Dry Falls is thought to have been created by catastrophic flooding caused by glacial melt about 20,000 years ago at the end of the last glaciation. Wikipedia describes Dry Falls as:

“…a 3.5-mile-long (5.6 km) scalloped precipice with four major alcoves, in central Washington scablands. This cataract complex is on the opposite side of the Upper Grand Coulee from the Columbia River, and at the head of the Lower Grand Coulee, northern end of Lenore Canyon. According to the current geological model, catastrophic flooding channeled water at 65 miles per hour (105 kph) through the Upper Grand Coulee and over this 400-foot (120 m) rock face at the end of the last glaciation. It is estimated that the falls were five times the width of Niagara Falls,: 116  with ten times the flow of all the current rivers in the world combined.”

     In the case of Dry Falls, there is thought to have been a series of repeating catastrophic events, as the Lake repeatedly filled due to ice damming followed by rising waters floating the ice over the dam:

“It is generally accepted that this process of ice-damming of the Clark Fork, refilling of Lake Missoula and subsequent cataclysmic flooding happened dozens of times over the years of the last Ice Age.”

     The massive flow rates of the falls after these events put land affected under hundreds of feet of water in a short time. There is evidence of multiple plunge pools, signifying individual catastrophic ice dam breaches. Once the ice sheet fully melted and the rivers returned to their normal flow, the falls area was left dry and has been ever since.

     As noted below, the glacial lake ice dam collapse explanation for Dry Falls was first proposed in 1923 by geologist J. Harlen Bretz but not widely accepted until 1965.

 

  

    

 

References:

 

Dry Falls, the Missoula flood cataract, in bare-earth lidar [OC]. r/geology. u/Northing_ Labs. Reddit. October 2, 2026. Dry Falls, the Missoula flood cataract, in bare-earth lidar [OC] : r/geology

Dry Falls. Wikipedia. Dry Falls - Wikipedia