There is a history behind the appearance of the Minnesota landscape. A warming trend began about 13,000 years ago. This set off many events related to glaciers and water. Water returned to the oceans, the levels of which rose. Flood from meltwater (from the retreating Laurentide Ice Sheet) created a system of streams and rivers. As the glaciers retreated, they left behind piles of sediment called recessional moraines. Around this time, underground caverns formed where the ice flow was stalled. When finally this dead ice melted and the caverns collapsed, a landscape of hills and kettle lakes emerged. In Minnesota, this process was comparatively swift.
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