Grand Prismatic Spring in Yellowstone National Park, Wyoming is one of the most dramatic and colorful features in Yellowstone and is located in the Midway Geyser Basin. Check out the Wikipedia link below for some aerial shots. This is the largest hot spring in the U.S. and third largest in the world. Every color of the rainbow as produced from sunlight on a prism is represented in over flow of the water from the spring. The spring is really a small boiling lake that is 250 by 300 feet (80 by 90 m) in diameter and 160 feet (50 m) deep. The intense blue color of the water is caused by absorbing the red colors of the spectrum as in all bodies of water, the purity of the water and the depth of the pool. The color of the steam is from the reflection of the water from the spring. When the wind was blowing the steam is takes on a yellow to orange color reflecting from colors on the out flow. The colors ranging from green to red of the outflow are caused by pigments in the bacteria that grow on the edges in the highly mineralized water. The ratio of chlorophyll to caroteniods and the temperature of the water causes the differences in colors. Some of the colors may also be due to oxides of iron, manganese, copper, and other metal elements. The first photo is the nearby Excelsior geyser pool (now dormant) and the last photo is the runoff from the spring going into the Firehole River.