A U-shaped valley is a type of valley formed by the erosion of glaciers. As glaciers move through mountainous regions, they carve out a distinct U shape, characterized by steep sides and a flat bottom. This process can take thousands of years, resulting in valleys that are often wider and deeper than those formed by rivers. These valleys are commonly found in areas that were once covered by ice during the last Ice Age. Famous examples of U-shaped valleys include the Yosemite Valley in California and the Glacier National Park in Montana. They are important features in understanding glacial geology and landscape evolution.