Glacial lakes are bodies of water formed by the melting of glaciers. As glaciers retreat, they leave behind depressions that fill with water, creating these lakes. They can vary in size and depth, often appearing in mountainous regions where glaciers are present. These lakes are typically characterized by their clear, blue-green color, which is due to the fine particles of rock flour suspended in the water. Glacial lakes can also be found in areas like the Rocky Mountains and the Alps, and they play an important role in local ecosystems and water supply.