Water from the Gulf of Mexico in the Great Lakes?

Submitted by Deborah Cramer

Water from the Gulf of Mexico in the Great Lakes?

Sugarloaf Cove, Schroeder, Minnesota, on the North Shore of Lake Superior
© CK Sandberg 2009

The Great Lakes hold 90% of the fresh surface water in the U.S. It’s enough to put the lower continental U. S. under nine and a half feet of water.

Great Lakes water supports agriculture and industry, and supplies drinking water for the 33 million people living in the region. Each year, the lakes lose water – through evaporation, as water is removed for human use, and as it drains out from one lake to the next, and out through the Gulf of St. Lawrence into the sea. Each year, it is replenished. The water that refills the Great Lakes comes from a great distance. Evaporated from the Gulf of Mexico and adjacent Atlantic, it is blown in moisture-laden wind and storms 1000 miles to fall in the Great Lakes as rain and snow.

If things had gone differently, the Great Lakes might have been part of a large ocean. Over one billion years ago, heat rising from inside the earth stretched, thinned, and cracked the landscape around what is now Lake Superior, threatening to tear the terrain apart. The tear is known as the Keweenawan or MidContinent Rift. Some 22 million years of volcanic eruptions never widened the crack enough to let in the sea, or make Duluth a seaport, but the tremendous outpouring and subsequent sinking of volcanic rock – 10 miles thick in some places – sculpted the bowl that today holds Lake Superior. You can see evidence of the volcanoes that nearly tore the continent in two in the lava rock at Sugarloaf Cove on the north shore of Lake Superior in Minnesota.

References and more information

Source of rain and snow in the Great Lakes
Lewis, C.F.M., J.W. King, S.M. Blasco, et al. 2008. Dry Climate Disconnected the Laurentian Great Lakes. EOS 89:541-542.

Great Lakes Information Network

Lake Superior facts and figures

Sugarloaf Point – Minnesota Department of Natural Resources

Sugarloaf Cove – The North Shore Stewardship Associations

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