Large amounts of sand, gravel, and rock were left behind when the glaciers began to melt. This material is called glacial drift. Since the bedrock is buried under the glacial drift, geologists cannot look directly at it to see what kind of rock it is. Many features in Minnesota's landscape, such as most lakes, hills, and ridges, were formed by glacial activity. The wearing away of the surface is called erosion.
Erosion constantly attacks the land by wind, water, frost, and temperature changes.
Our land is being eroded and changed everyday. We see dust in the air. Streams have muddy water. Potholes appear in our streets. These are all signs of erosion.