A U-shaped valley is a type of valley characterized by its distinct U-like shape, formed primarily by the erosion of glaciers. As glaciers move through mountainous regions, they carve out the landscape, creating steep sides and a flat bottom. This process can take thousands of years, resulting in valleys that are wider and deeper than those formed by rivers. These valleys are often 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 for understanding glacial geology and the effects of climate change.