Crater lakes are bodies of water that form in the depressions left by volcanic activity. When a volcano erupts, it can create a caldera, which is a large, bowl-shaped cavity. Over time, rainwater or melted snow fills this caldera, resulting in a lake. These lakes can vary in size and depth, depending on the volcano's characteristics. Many crater lakes are known for their stunning blue or green colors, which are often due to minerals in the water. Some famous examples include Crater Lake in Oregon and Lake Toba in Indonesia. These lakes can also be important ecosystems, supporting unique plant and animal life.