Geography of Minnesota
Minnesota is the most northern state outside of Alaska; its isolated Northwest Angle in Lake of the Woods is the only part of the 48 contiguous states lying north of the 49th parallel. Minnesota is in the U.S. region known as the Upper Midwest. The state shares a Lake Superior water border with Michigan and Wisconsin on the northeast; the remainder of the eastern border is with Wisconsin. Iowa is to the south, North Dakota and South Dakota are west, and the Canadian provinces of Ontario and Manitoba are north. With 87,014 square miles (225,370 km2), or approximately 2.26 % of the United States, Minnesota is the 12th largest state.
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.
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