Geology of Sandhill Wildlife Area

Sandhill Wildlife Area lies within the bed of historic Glacial Lake Wisconsin, which covered parts of Wood County and six neighboring counties. The lake formed out of the yearly runoff of meltwater from the great continental glaciers that covered much of eastern and northern Wisconsin from 60,000 to 10,000 years ago. With the retreat and disappearance of the glaciers, the lake drained, leaving a vast expanse of sandy soils covered by marshes in low-lying areas and by forests on the slightly higher, undulating sand ridges. Scattered across the landscape are outliers or "mounds," remnants of a sandstone plateau deposited on the floor of seas that covered central North America 500 million years ago. North Bluff, which rises 200 feet above the surrounding plain, is composed of very ancient Precambrian quartzite rock that was sealed in sandstone for hundreds of millions of years.