Lake Agassiz

s Jack McDevitt explains in a note at the end of Ancient Shores, Lake Agassiz really existed. It once covered 110,000 square miles in what is now Manitoba, Saskatchewan, Ontario, North Dakota and Minnesota. By comparison, Lake Superior, now the largest lake in North America, has an area of only 32,700 square miles.

Lake Agassiz formed when glaciers blocked the drainage to Hudson Bay. When the glaciers receded at the end of the last ice age, the Nelson River formed to drained the basin. Significant remnants of Lake Agassiz remain, however. The largest, Lake Winnipeg in Manitoba, Canada, is bigger than Lake Ontario. Other major remnants include Lakes Winnepegosis and Manitoba (both within Manitoba) and the Lake of the Woods on the Manitoba-Ontario-Minnesota border), as well as many smaller lakes in the region.

McDevitt includes a map at the beginning of the book showing the extent of Lake Agassiz.

ack to Off the Shelf.