What is the name of the area in Minnesota was not covered by massive ice sheets?
Minnesota has some of the earth's oldest rocks, gneisses that are about 3.6 billion years old (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 state's landscape and sculpted its 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 the northeast has 50 feet (15 m) or more of glacial till left behind as the last glaciers retreated. Gigantic Lake Agassiz formed in the northwest 13,000 years ago. Its bed created the fertile Red River valley, and its outflow, glacial River Warren, carved the valley of the Minnesota River and the Upper Mississippi downstream from Fort Snelling. Minnesota is geologically quiet today; it experiences earthquakes infrequently, and most of them are minor.
the Driftless Zone