Glaciers covered all of Canada, except for the northwest part of Yukon Territory, during a major glacial episode that reached a climax about 21,000 years ago. At that time, glaciers covered all of the Great Lakes, with the ice’s southern limit reaching into the United States.
These massive moving bodies of ice were incredibly thick, reaching depths of more than two kilometres in places. In 1968, the Geological Survey of Canada published the Glacial Map of Canada, which shows the passage of glaciers and the associated glacial meltwaters. It also shows the major imprint glaciers made on the Canadian landscape.
Aerial photography of the entire country was completed in the mid-1950s, and it provided a valuable new tool to map landforms in remote areas of the country. Indeed, aerial photographs were critical to the production of this map. While it was constructed using existing knowledge of Canada’s glacial deposits and landforms, the Glacial Map of Canada is mainly the result of meticulous interpretation of aerial photographs for regions where little was known about their glacial history. The map remains the benchmark in our understanding of the glacial landscape of the country.