Crater lakes are most likely to occur in regions of extinct volcanoes. These are the areas where the volcanoes have stopped erupting and have become dormant or extinct. Crater lakes are formed when the crater or caldera of a volcano fills with water. The water in the crater lake may come from precipitation, groundwater, or from streams and rivers that flow into the crater. The water in the crater lake is often deep and clear, with a blue or green tint due to the minerals and other substances that are dissolved in it. Crater lakes are important features of the landscape and can provide habitats for a variety of plant and animal species. They are also popular tourist destinations and are often surrounded by scenic views of mountains and other natural features.