A Tale of Two Eons
This month’s prez letter comes from northern Idaho, where I am spending a long Thanksgiving visit with family. I have visited this area on a number of occasions even before family members recently transplanted themselves here in the Coeur d’Alene area-mainly due to my fascination with the mega- sedimentary deposits to the west from a large glacial flood that originated just north of here. Between 15-13,000 years ago the sudden emptying of 500 cu mile, (300 sq mile) proglacial Lake Missoula occurred. Its cause was the instant melting of an ice dam located at the site of the southern end of present-day Lake Pend Oreille, resulting in a 2000 ft wave of water that washed over much of eastern Washington and northern Oregon. The scablands topography downstream provides dramatic evidence of that dramatic event , but it turns out to have been only the latest such flood as it obliterated evidence from previous (45-50) such floods.
The spectacular nature of this event almost takes a back seat to the backstory of how a catastrophic origin came to be accepted by the geologic community over 40 years of debate. Initial proposals came from J. Harlon Bretz in 1922, who shocked the geologic community by claiming the surface features came from a large scale cataclysmic flooding event... incurring the derision of the geologic community. The young science of geology was in the process of establishing its claim of slow constant change over unimaginably long periods of time. This was seen as defiance of centuries-old church authority, which controlled interpretation of physical phenomena using literal translation of Scripture. The anti-catastrophist scientific “consensus” wasn’t about to hand control back to religious-based institutions and fought back against Bretz’s proposal. (He didn’t help his own case by referring to it in scientific journals as a flood of ”Biblical proportions”). But eventually he was vindicated, as the scientific community further debated the issue, uncovering more evidence of large scale flooding, and it came even to acknowledge its own former biases. The resolution of the cause of the “Bretz floods” provides an example of how real scientific debate occurs.
The almost absurd use of Phanerozoic (current) Eon to categorize an event merely 15 thousand years ago nevertheless provides the context to circle back to the title of this letter. The northern Idaho area is also the site of deposition of sediments from a completely different Eon. It provided me the opportunity to investigate 1400 million year old rocks from the Proterozoic Eon. The entire surface of the Idaho panhandle is comprised of these sedimentary rocks of the Belt Supergroup. This area was the site of a continental rifting that allowed 10,000 feet of deposition of these fine grained sediments. The source of deposition came from the west of the rift (the current western edge of the northern Idaho boundary), but it has been transported by transform rifting to other areas. Candidates for the source are the Siberian craton, Australia, and eastern Antarctica. Lively debate is occurring, but the lack of fossil assemblages make correlation difficult.
Despite their vast age, the rocks contain sedimentary structures, (ripples, mudcracks, etc.) that are often well preserved. Partly this is due to the complete lack of burrowing and other disruptions, as such life forms that would be 800 million years in the future. It is always thrilling to touch ancient rocks (as most field geologists sense), especially when they also have same sedimentary structures as today and yet were formed when the atmosphere was so different. Most of it was methane and CO2, containing only 1-2% Oxygen. Yet those sedimentary structures are nearly identical to those forming today. To me it is comforting to sense the permanence of our planet. It helps puts into perspective all the discussion about the irreversible nature of tipping points.
Musings on these two eons suggest the opportunity we geologists have to inspire and educate the larger community about the nature of science and its advancement, (using evidence of the changing earth as the enticement). Historically, scientific debate among accredited colleagues has sought to objectively apply critical analysis, leaving the outcome open to further data collection and evaluation of that newer data. In the traditional Scientific Method, theories are proposed, and not claimed from the outset to be “facts”. The true Scientific Method objectively evaluates current and evolving theories, whether or not they are held by consensus. It follows then that open, technical debate guided by the Scientific Method allows theories to be evolved by integrating verifiable data into more accurate and comprehensive understandings of the subject.
As scientists, we have not only the opportunity to explain these concepts to our nonscientific fellow citizens, but to many of us it is an obligation, to evaluate and explain in the most objective and accurate manner possible. To the HGS it is in fact, mission-critical. This is how we Serve the Science.
Please consider joining our outreach efforts. The HGS Educational Outreach committee has redoubled its commitment to reach out to local public and private educational institutions. Committee chairs Steve Johansen and Letha Slagle are seeking new members and new ideas. Help us find you. Contact Steve Johansen at geosjjohansen@gmail.com.
Mike Erpenbeck, President