GLACIAL LAKE AGASSIZ

As the Wisconsin Glacier slowly began to melt some 12,000 years ago, it created Glacial Lake Agassiz, the largest known glacial lake in North America. At its maximum the lake covered an area of over 110,000 square miles—more than the area of the combined

Great Lakes—spread over parts of areas known today as Minnesota, North and South Dakota, Manitoba, Saskatchewan, and Ontario. Over 400 feet deep in places it extended over 700 miles from its southern tip near Browns Valley to its northern tip near Hudson Bay.

While the glacier moved south during its advance, it built up a moraine on its southern end which ponded the melt waters when the ice began its retreat. Eventually the water overflowed, cutting an outlet which created the present Minnesota River valley. Over approximately 3,000 years, as the glacier continued to melt, numerous beaches were created along the lake's shores. Still visible today, these beaches are named after towns such as Herman, Tintah, Norcross, and Campbell.

About 7,500 years ago, when the glacier had receded far enough north that the melt waters began to drain into Hudson Bay, Glacial Lake Agassiz disappeared. A few undrained depressions—Upper and Lower Red Lake, Lake of the Woods, and Lake Winnipeg—remain today to remind us of the site of the glacial lake. The area it covered in northwestern Minnesota is almost flat and lakeless, and the rich land produces bountiful yields of wheat, sugar beets, potatoes, sunflowers, and other crops. Thanks to Glacial Lake Agassiz, the region is sometimes called "the breadbasket of the world." 1989