A glacial tarn is a small mountain lake formed by the melting of glaciers. These lakes often appear in depressions left behind by the retreating ice, creating a picturesque setting in rugged landscapes. The water in glacial tarns is typically cold and can be quite clear, reflecting the surrounding mountains and sky. Glacial tarns are commonly found in areas with past glacial activity, such as the Rocky Mountains or the Alps. They can vary in size and depth, and their colors often range from deep blue to green, depending on the minerals and sediments in the water.