Mega Flood

My favorite film from the past three labs is Mega Flood. While watching the video, I was surprised by how such a vast space could be transformed by a glacial flood and was struck by the story of how geologists determined the cause of the Scablands unique features.

Map of Glacial Lake Missoula and Flood Path

For a long period of time, geologists were unable to determine how the Scablands were created and why it featured eratics, but J Harlen Bretz proposed a giant flood washed over the area and carved out its unique features. The theory garnered little support from a group of respected geologists who did not believe a catastrophic event caused the formations in a short period of time. In the end, however, Bretz’ theory about a flood was proven correct.

Joseph Pardee was in the room when Bretz pitched his idea and believed the theory might prove true, but he did not help support the theory until several years later. After years of research, Pardee identified the source of Bretz’ flood as Glacial Lake Missoula. Based on the evidence of glacial activity, Pardee claimed the lake was formed when a glacier blocked water flow. When the glacial dam busted and let water flow through, the immense rush of flood water crashed over the land and carved out the Scablands, which were over 200 miles from the water source. Pardee pointed to ripple marks on the land in order to show the flood from Lake Missoula flowed towards the Scablands. Bretz’ theory was finally accepted by the geologic community.      

Joseph Pardee

The theory of a flood causing such extensive geologic formations has been solidified by more recent work. In the video, a current researcher pointed towards a flood in Iceland during the late 1990s as having similar characteristics as ancient glacial floods. The video explained that under glaciers lies super-cooled water which is below the freezing temperature but still liquid due to immense pressure, which is something I would have never thought to be possible. Eventually, the liquid water creates fissures in the dam that lead to its collapse after a long period of time.

Overview of Scablands

Ripples Left by Flood

In addition to the information about the nature of glacial dams, researchers in the film created a scale model of Lake Missoula and the Scablands pre-flood to see if similar features were created. Even on a smaller scale, the physical forces of the flood, including underwater tornadoes, formed features strikingly similar to the ones in the Scablands.

Underwater Tornado Example

At the end of the video, one current Scabland researched explained that the cause of the formations was flooding but that the theory of one giant flood might need changing. Due to composition of certain sediment layers found in the canyon walls, researches have determined that the sediments could not have settle to the bottom of flood waters so perfectly all at one time and that many floods deposited them separately.

Before viewing the film, I never would have thought about a series of giant floods creating the earth’s landscape, but apparently it happened quite often. As geologists perform future research on the Scablands and other areas, more information about ancient floods might shed more light on the creation of earth’s geologic features. I’m just glad we don’t see floods like that today!