Changing Landscapes Through Time

Changing Landscapes Through Time. . , Ancient oceans, glaciers, and the powerful action of rivers carved the landscape of this region. Millions of years ago, Minnesota was covered by a shallow sea teeming with corals, sponges and shellfish. At the close of the Pleistocene, a time of Ice Ages which ended about 13,000 years ago, the glaciers receded, leaving behind Glacial Lake Agassiz, which covered much of Canada and the northern United States. For thousands of years, the mighty River Warren was the only outlet of Glacial Lake Agassiz. The river cut a powerful course through Minnesota, forming the Mississippi Valley, and the Falls at St. Anthony and Minnehaha upstream., Large Pleistocene - era animals such as giant bison, mastodon, mammoth, and giant beavers the size of bears still roamed the spruce forests of Minnesota after the glaciers receded. As temperatures rose, spruce forests were replaced by elm and oak, and later by prairie. Populations of bison, elk and deer emerged with the gradual disappearance of the Pleistocene creatures. By 5000 years ago, the deciduous forests and prairie openings that we see today were well established.