While these states are for the most part relatively flat, consisting either of plains or of rolling and small hills, there is a measure of geographical variation. In particular, the following areas exhibit a high degree of topographical variety: the eastern Midwest near the foothills of the Appalachian Mountains; the Great Lakes Basin; the heavily glaciated uplands of the North Shore of Lake Superior in Minnesota, part of the ruggedly volcanic Canadian Shield; the Ozark Mountains of southern Missouri; and the deeply eroded Driftless Area of southwest Wisconsin, southeast Minnesota, northeast Iowa, and northwest Illinois.