Rethinking Lake Missoula Shorelines
Over 80 hardy souls braved record setting snow and cold to hear U Montana geology professor Jim Sears present “New Thoughts on Lake Missoula Shorelines” at the Montana Natural History Center in Missoula on February 27th. Sears discussed the traditional view put forth by David Alt and others that the shorelines were formed by wave action on the west facing slopes of successively lower levels of Glacial Lake Missoula during the most recent Ice Age. He clarified that all horizontal bands on Mt Jumbo and other locations are not shorelines. Some occur above the highest known flood level and are actually the result of soil creep or solifluction (those that meander are actually animal or cow trails).
A bigger question is the relationship between the shorelines visible in Missoula to the shorelines at the National Bison Range or other locations in the area. These elevations do not all match. Sears makes the suggestion that Lake Missoula was not a single large lake that drained all at once, but a series of lakes formed at narrow points such as Alberton Gorge and Hellgate Canyon. Each of these lakes may have experienced a back wash that formed the strandlines, possibly all in the same event.
Professor Sears also discussed the patterns of erratics fanning out from Hellgate Canyon, the polar vortex that may have occurred during the Ice Ages, and other topics of interest to students of geology.
The local chapter of the Ice Age Floods Institute is planning field trips for the spring and fall and will sponsor additional lectures in the future.