The Shaping of North America The discovery of nearly identical species of fish in various bodies of water has proven that 225 million years ago, a single supercontinent of dryland began to drift apart, creating the different oceans and landmasses. 2 million years ago the Great Ice-Age, a two-mile thick ice sheet, crept from the polar regions into North America and the other continents. 10,000 years ago the glaciers retreated the North American landscape, leaving behind the lakes and river systems…
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