“Lake Superior, they say, never gives up her dead, when the winds of November blow early.” – Gordon Lightfoot
Superior is quite different from the other Great Lakes. For one thing it does not sit on that hard dolostone basin I described earlier. Its local geology allowed the ice sheet of the last glacial maximum to scour out Superior to a depth of 1,300 feet, making it by far the deepest of the Great lakes. In fact, the bottom of Superior is the lowest point of the North American continent.
The five Great Lakes contain 20% of all the (unfrozen) fresh water in the world. So it’s probably a really a good idea to keep the Lakes clean.