U-shaped valleys are formed by the erosion of glaciers as they move through mountainous regions. The powerful ice carves out a distinct U shape, characterized by steep sides and a flat bottom. This process occurs over thousands of years, resulting in wide valleys that are often found in areas previously covered by glaciers. These valleys are commonly seen in places like the Alps and the Rocky Mountains. They can also contain features such as hanging valleys, which are smaller valleys that join the main U-shaped valley at a higher elevation. U-shaped valleys are important indicators of past glacial activity.