Two major physiographic regions comprise Minnesota. Its northeastern portion falls within the Superior Upland province, part of the huge territory of ancient, long-stable continental bedrock called the Canadian Shield. The Precambrian rock of this province is among the oldest exposed on the continent. The Central Lowlands occupy the rest of Minnesota. The underlying bedrock here is younger than that of the Canadian Shield, laid down in the Paleozoic Era, and overlain in much of the state by thick glacial deposits of much more recent origin. The landforms in both speak to vast scales of time and great forces of volcanism and ice.
Minnesota’s landforms range from famously plentiful lakes to rolling glacial plains.
Because it has been tectonically inactive for so long, Minnesota is a relatively level state, its major irregularities having been smoothed out by forces of erosion and weathering over the eons. But low ranges of hills in the Superior Upland speak of its more violent, topographically dramatic past. These are remnants of Precambrian upheaval of volcanic flows and intrusions, mountain-building and tectonic buckling between 3.5 billion years ago and 600 million years ago. Such highlands include the Misquah Hills of northeastern Minnesota, composed of red granite of the Duluth Formation, an old magma intrusion, and including the state’s highest point, 2,301-foot Eagle Mountain.
Most of Minnesota was glaciated repeatedly during the Pleistocene, with the most recent ice-sheets retreating only about 10,000 years ago. They have massively influenced the state’s landscape. They scoured out the famous concentration of lakes in northeastern Minnesota’s Superior Upland and farther south created many kettle lakes formed by the melting of discrete blocks of ice. Part of the massive ancient lakebed of Glacial Lake Agassiz occupies northwestern Minnesota; this huge Pleistocene water body once sprawled across more than 100,000 square miles. Thick glacial-till deposits form the great plateau called the Coteau des Prairies, which edges into southwestern Minnesota, cresting as 1,995-foot Buffalo Ridge. Central and southerly parts of glaciated Minnesota showcase numerous landforms sculpted by ice, including drumlins, moraines and kames.
A relatively small portion of southeastern Minnesota falls within the Driftless Area, a pocket of the Midwest that was not invaded by ice during the most recent cycle of glaciation. Most of this area is in southwestern Wisconsin, with some acreage also in northeastern Iowa and northwestern Illinois. The landscape here tends to be more rugged than the rolling plains and hills of the glacier-impacted country. Drainages here, not widened and softened by ice, are steep and V-shaped, tumbling between bluffs to the Mississippi River.
Minnesota has plenty of public lands to entice the geologically minded outdoors enthusiast. Superior National Forest in the northeast offers chances to roam the remnants of some of the state’s ancient mountains. Voyageurs National Park in north-central Minnesota showcases spectacular Superior Upland country of glacier-polished rock platforms and lakes. Contrast the ice-impacted landscape of Glacial Lakes State Park near Starbuck with the broken Driftless Area valleys of Great River Bluffs State Park near Winona.
- “Natural Landscapes of the United States”; James A. Henry, Joann Mossa; 1995
- “Minnesota’s Geology”; Richard W. Ojakangas, Charles L. Matsch; 2004
- “A Sierra Club Naturalist’s Guide to the North Woods”; Glenda Daniel, Jerry Sullivan; 1981
- Minnesota Department of Natural Resources: Ecological Classification System – Inner Coteau Subsection
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