Waves may have beaten against their shores, making beaches. Subsequently it was uplifted and submerged several times. Two hundred million years or so ago this part of the United States was uplifted for the last time, and has since remained dry land. The peneplain on the site of the ancient lofty mountains of Wisconsin was completely hidden beneath the limestones and sandstones. The work of weather and streams recommenced, and continued till the state was fashioned into something similar to its present form.
Cambrian mountains lie deep beneath the present surface.
In the northern part of Wisconsin the worn down mountains have been revealed. We know the visible portion of these worn- down, buried and exhume d mountains as the Northern Highland of Wisconsin. The Northern Highland belongs to a great upland area that stretches northward in Canada to Labrador and Hudson Bay. It has a strong southward slope and, as the highland is shield- shaped and gently arches, it also has east and west components of slope. The slant of a medial line from the northern to the southern border is less than six feet to the mile.