Monday, March 3, 2014

Geology Lesson: the history behind Superior's clay soils

At the end of the Pleistocene (14,000 years ago) glaciers began to recede, with the melt and reduction of glaciers resulted in the loss and deposition of debris that had accumulated in the glacier and carried materials over very large distances. Leaving behind eskers, till, erratic’s as well as a very common mineral found in Northern Wisconsin, which happens to be part of what geologist call the Miller Creek Formation, this sediment was deposited at the end of our last glacial period. The reason we bring this up is because clay is a mineral that is not porous, when clay gets wet and compacted it creates tighter bonds with other clay minerals. When we in Superior receive high amounts of precipitation, especially during the spring when the ground is already saturated, these minerals cling together and form a sheet like structure in which water easily flows over. 

When looking at the lake the boundaries of the lake are angled towards Superior. So during heavy rain events, or those that happen while the ground is already saturated, direct everything to the lake. With the accumulation of undesirable wastes in our yards it is easy to see that it does not take much for water to run from our properties, into the road, and into the lake. The material that makes up Superior Wisconsin is not ideal for the natural filtration of rain water and melt, for this reason it is important to clean up pet waste, reduce salt in the winter and for you in the spring limit the amount of fertilizers used.
Remains of an esker often resembles an elongated hill formation

You can see this at the Sea Caves near Cornicopia, WI, where the till had been deposited on top of the sandstone formation. Red line represents the extent of the sandstone formation and the area represented in blue corresponds with glacial till.

Here is an example of an erratic, though sizes of these glacially dropped stones may vary, they were all deposited from the same processes

Written by Michael Krick.

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