Regions of Minnesota - Geology and Terrain

Geology and Terrain

Main article: Geology of Minnesota See also: List of lakes in Minnesota and List of Minnesota rivers

Minnesota contains some of the oldest rocks found on earth, gneisses some 3.6 billion years old, or 80% as old as the planet. About 2.7 billion years ago, basaltic lava poured out of cracks in the floor of the primordial ocean; the remains of this volcanic rock formed the Canadian Shield in northeast Minnesota. The roots of these volcanic mountains and the action of Precambrian seas formed the Iron Range of northern Minnesota. Following a period of volcanism 1.1 billion years ago, Minnesota's geological activity has been more subdued, with no volcanism or mountain formation, but with repeated incursions of the sea which left behind multiple strata of sedimentary rock.

In more recent times, massive ice sheets at least one kilometer thick ravaged the landscape of the state and sculpted its current terrain. The Wisconsin glaciation left 12,000 years ago. These glaciers covered all of Minnesota except the far southeast, an area characterized by steep hills and streams that cut into the bedrock. This area is known as the Driftless Zone for its absence of glacial drift. Much of the remainder of the state outside of the northeast has 50 feet (15 m) or more of glacial till left behind as the last glaciers retreated. 13,000 years ago gigantic Lake Agassiz formed in the northwest; the lake's outflow, the glacial River Warren, carved the valley of the Minnesota River, and its bottom created the fertile lands of the Red River valley. Minnesota is geologically quiet today; it experiences earthquakes infrequently, and most of them are minor.

The state's high point is Eagle Mountain at 2,301 feet (701 m), which is only 13 miles (20.9 km) away from the low of 602 feet (183 m) at the shore of Lake Superior. Notwithstanding dramatic local differences in elevation, much of the state is a gently rolling peneplain.

Two continental divides meet in the northeastern part of Minnesota in rural Hibbing, forming a triple watershed. Precipitation can follow the Mississippi River south to the Gulf of Mexico, the St. Lawrence Seaway east to the Atlantic Ocean, or the Hudson Bay watershed to the Arctic Ocean.

The state's nickname, The Land of 10,000 Lakes, is no exaggeration; there are 11,842 lakes over 10 acres in size. The Minnesota portion of Lake Superior is the largest at 962,700 acres (3,896 km2) and deepest (at 1,290 ft (390 m), 393 m) body of water in the state. Minnesota has 6,564 natural rivers and streams that cumulatively flow for 69,000 miles (111,000 km). The Mississippi River begins its journey from its headwaters at Lake Itasca and crosses the Iowa border 680 miles (1,094 km) downstream. It is joined by the Minnesota River at Fort Snelling, by the St. Croix River near Hastings, by the Chippewa River at Wabasha, and by many smaller streams. The Red River, in the bed of glacial Lake Agassiz, drains the northwest part of the state northward toward Canada's Hudson Bay. Approximately 10.6 million acres (42,900 km²) of wetlands are contained within Minnesota's borders, the most of any state except Alaska.