Mississippi River History

Bob Melchior, an emeritus professor of geology from Bemidji State University, has studied the geological history of the Mississippi headwater region in rich detail. He introduced me to the wonders of paleontology in a course some twenty years ago. Yesterday, Bob stopped by and shared a powerpoint presentation that he used for a public talk earlier this summer. It includes some fascinating prehistory of our region. The two slides reproduced above (click to enlarge) are especially intriguing and are directly relevant to understanding the current dissolved oxygen impairment of the Mississippi between Itasca and the confluence with the Schoolcraft River.

The top image relates the establishment of the Mississippi River to a global temperature record from the Greenland ice sheet. As the Laurentide Itasca Phase Glacier begins a slow northward retreat during a warm period commencing roughly 14,500 years ago, the river flowed north through a tunnel valley laden with intermittent masses of glacial debris which acted as dams, forming a series of at least eight shallow lakes which exist as visible relicts even today.

As the second figure clearly reveals, these eight relict lakes comprise most of the Mississippi's course from Itasca to Lake Bemidji; modern day Lake Irving is situated in the last of these eight basins. Seems to me these relict lake should have some catchy names -- Bob simply uses the numbers 1 though 8 on one of his slides -- so how about (1) something mundane like the days of the week plus Irving, (2) something earthy like the eight spokes (sabbats) in the Wiccan Wheel of the Year, or (3) perhaps something really exotic based on the elements of the Eightfold Path or the Eight Great Bodhisattvas of Buddhism or the Eight Immortals from Chinese mythology. Just a thought -- for my purposes I think I'll adopt the sabbats -- Samhain, Yule, Imbolc, Ostara, Beltaine, Midsummer, Lunasagh, and Mabon -- as a nod to the cycles of change that gave rise to the river itself. In any case, I am looking forward to paddling this stretch of the river next summer with a new perspective.

The second slide also shows how the course of the Mississippi changed between 4000 and 8000 years ago from (1) an exit out the south end of modern day Lake Bemidji through the Necktie River then on to Leech Lake to (2) the modern course out the east side of Lake Bemidji though the Cass Lake chain. Interestingly enough this also relevant to a contemporary issue facing the city of Bemidji since the peat occlusion that re-routed the river are in the vicinity of the controversial former Georgia Pacific site, a prime piece of urban real estate. Fascinating stuff. /dps