The lake formed from glacial
Lake Algonquin as water levels dropped, occupying only the deepest parts of the
Lake Michigan basin. The waters drained through the
Straits of Mackinac, then across
Lake Stanley into either
Lake Hough and then to the
St. Lawrence River by way of the
Ottawa River valley, or through the
St. Clair and
Detroit rivers to an
Early Lake Erie and out the
Niagara River towards the St. Lawrence. Around 10,300 YBP, Lake Chippewa’s levels continued to drop, and the basin was a self-contained body of water without an outlet. Levels returned and Lake Chippewa again flowed through the canyon at Mackinac until around 7,500 YBP. At that time, the
Nipissing Great Lakes merged with the waters in the Michigan Basin and created a single lake encompassing all three of the upper
Great Lakes. ==Size==