Mapping

The shape of ice: Mapping North America’s glaciers

North America was created by ice, and its legacy covers the landscape
Map of North American glaciation Expand Image
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Ice created the landscape of North America that we’re all familiar with — even if we might not know much about how it happened.

At the height of the last glaciation, massive ice sheets spread across what is now Canada and northerly parts of the United States. When the Earth began to warm — about 19,000 years ago — that ice started to melt, leaving behind the Tyrrell and Champlain seas and many “proglacial” lakes, including Ojibway, Algonquin and McConnell. As the landscape drained, an enormous region of plains was created — spaces that would become populated by creatures such as mammoths.

Over thousands of years, the ice sheets went through thickening and thinning processes. Today, the continent is still rebounding from the weight of those sheets when they were at their thickest, which causes sea levels to fluctuate and can leave coastal regions in distress. (See the legend for more about ice-age remnants such as moraines, eskers, nunataks and water bodies.) The history of the movement of ice can be seen plainly on the Earth’s surface.

Map of North America's glaciation Expand Image
Map: Chris Brackley/Can Geo; Glacial, lake, ocean and land extents based on data by Arthur S. Dyke.
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This story is from the May/June 2020 Issue

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