The basement rocks of the Laurentian Upland Province were metamorphosed about 2500 million years ago in a mountain-building collision of tectonic plates called the Kenoran orogeny. If we could strip away all of the younger rocks deposited on top of buried Precambrian basement, you would see a landscape of low relief. The topography of the Precambrian rocks is very subdued, with barely 500 feet difference between the highest point and the lowest. Clearly, this region was exposed to a very long period of erosion in the very distant past which beveled the original mountainous surface to a gently undulating surface. The present surface is not much different.
Hills rise just a few hundred feet above the surrounding countryside.
The highest of these, such as Rib Hill, Wisconsin, are made up mostly of resistant quartzite or granite. The structure of Superior Upland rock is quite complex. Folds and faults, most dating back to Precambrian time, record several episodes of mountain-building. The plate collisions that formed the core of our continent left behind a striking structural trend. Ridges and valleys are strongly aligned along this northeast-southwest trend.