Complex sentence: The Cordilleran, Laurentide, Innuitian, and the currently existing Greenland Ice Sheet all made up the North American ice sheet complex, which covered present day Canada and much of the northern U.S. This cold glaciated time for North America was called the Wisconsin glaciation.
Split into simpler sentences: The Cordilleran, Laurentide, Greenland, and the Innuitian ice sheet all made up the North American ice sheet complex. The North American ice sheet complex covered present day Canada and much of the northern U.S. This cold glaciated time for North America was called the Wisconsin glaciation.