Glacial valleys are U-shaped valleys formed by the movement of glaciers over time. As glaciers advance, they carve out the landscape, creating wide, flat bottoms and steep sides. This process can take thousands of years, resulting in distinct geological features. These valleys often contain features such as moraines, which are piles of debris left behind by glaciers, and glacial lakes, formed by melting ice. Glacial valleys are commonly found in mountainous regions, such as the Rocky Mountains and the Alps, showcasing the powerful effects of glacial erosion on the Earth's surface.