Geology, Catastrophism and Lake Missoula

In the late 18th and early 19th Centuries, there was a mighty struggle in the nascent science of geology. Biblical literalism had insisted on a young earth, created less than 10,000 year earlier, and a literal, world-spanning Noachian flood. As the evidence for a much older earth accumulated, and the evidence against a global flood emerged, early geologists like Alexander von Humboldt and Charles Lyell argued that the geologic forces they observed today were the same forces acting in the past, what became known as uniformitarianism. The terms uniformitarianism for this idea, and catastrophism for the opposing viewpoint, was coined by William Whewell in a review of George Lyell’s book, Principles of Geology. That treatise was the most influential geological work in the middle of the 19th century. By the late 19th Century, geology had emerged as a rejection of catastrophism.

That battle, a battle viewed as blasphemy in many religious quarters, was fresh in the collective recollection of the Geological Society of America when in 1927 the Society invited a mostly unknown Washington state geologist named J. Harlan Bretz to present his paper on what Bretz called the Spokane Floods. The invitation was in some senses an ambush: the Society had lined up half a dozen members to argue against Bretz’s theory.

What Bretz proposed was that a monstrous flood had created the Channelled Scablands in Eastern Washington. “Channeled Scablands” was a phrase coined by Bretz to describe extensive areas in Eastern Washington where along riverine channels all of the top soil had been eroded away down to bedrock. There were massive cuts through basalt walls, and obvious waterfall locations that were bone dry.

Bretz was making a direct challenge to the theory of uniformitarianism and, worse he was raising the specter of the recently defeated idea of epic floods. His theory was not well received. In fact, it set off a forty year absolute firestorm of bitter, acrimonious debate among geologists. It was a classic scientific revolution, as described by Thomas Kuhn, a paradigm shift, suggesting that uniformitarianism could not account for observed scientific facts. Many geologists refused Brett’s invitation for them to view the Scablands themselves.

Bretz’s theory received additional support when Joseph T. Pardee, a U.S. Geological Survey geologist from Missoula, Montana, described glacial lake features in western Montana consistent with an immense lake created by glacial damming of the Clark Fork River. The lake was as much as 2,150 feet deep, and held a volume of water greater than modern day Lake Erie and Lake Ontario combined. The dam was a glacier, a lobe of the Cordilleran Ice Shield, specifically the Purcell Lobe. The Lobe of the continental glacier had to have been at least 2,000 feet high. When the water behind the Purcell Lobe was high enough, the Purcell Lobe lifted up, because, after all, ice floats in water. The dam failed and an astonishing flood ensued.

But despite that corroborating evidence, for decades the Strict Uniformitarianism School of geology resisted the idea. In 1979, when the Geological Society of America finally recognized Bretz’s work by awarding him the Penrose Medal, the field’s highest honor, it Bretz was 96 years old. He joked to his son, “All my enemies are dead, so I have no one to gloat over.”

The debate today has shifted to how many flood events occurred. The thing about glacier-dammed lakes is that, after the dammed waters have all run away, the glacier is still there, and can still advance and dam the river again. Which is pretty clearly what happened with the Missoula Floods. The difficulty with counting the number of times it happened, of course, is that subsequent floods tend to destroy the evidence of earlier floods. Current estimates are as many as 50 flood events of varying sizes.

But the point WC wants to make in this blog post is that the unthinking, uncritical acceptance of one theory, especially one that was hard won, like the victory of uniformitarianism over catastrophism, can make it very hard to accept even a partial change back, even in the face of very clear evidence. In fact, the line between uniformitarianism and catastrophism is blurred, not absolute. There are catastrophic floods; they are part of that uniform process.

If you think about it, the lesson has broader implications, far beyond geology.