If you approached the rim of a volcano and looked down into it, you might expect to see a lava pool, but if the volcano previously erupted and then the top of it collapsed into a huge bowl-shaped crater, or caldera, then what you might see when you peer over the rim is a beautiful crater lake. Sometimes the water is acidic and the lake has a bright greenish hue. Other times the water is a cloudy turquoise color, yet other times the lake may appear to be a very deep shade of blue. Crater Lake, Oregon, is one of the most well known, but crater lakes can be found all over the globe. If the volcano has been dormant for a long time, the water can be extremely clear because no river or streams flow into with sediment deposits.
Click through for descriptions, sources, and 30 more Crater Lakes.