Like a fountain spewing water for infinity. There is a hole in the earth's crust under Vernon county. It spews up water from deep under the earth's core where it is heated up and sent upwards . This water follows the current of the aquifer into the great lakes then down into the ocean.
I mean why didn't the glaciers sheer the hills of the Driftless region anyway? Big rocks? Or maybe it was like one of those duck ponds with a fountain in the middle that keeps it from freezing.
Just a theory.