About 20,000 years ago Ontario was covered by a great glacier, the fourth glaciation in this region within the past million years. The meltwaters from these gigantic ice-sheets filled the Lake Superior basin and progressively developed new drainag…
North of this watershed all flowing water eventually reaches Hudson Bay, while south of it all watercourses form part of the Great Lakes drainage system. The height of land follows an erratic course of some 1,400 miles across Ontario, ranging from…