Grand Prismatic Spring, Yellowstone National Park, Wyoming
Another view taken at Grand Prismatic Spring. This is such an amazing hot spring, photographed on 13 September 2012, during my recent week's trip with friends down to Yellowstone National Park and Grand Teton National Park. This photo was taken from the boardwalk, but there is also a hill you can climb to get a higher view over the whole spring - we ran out of time to do this.
"The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world, after Frying Pan Lake in New Zealand and Boiling Lake in Dominica. It is located in the Midway Geyser Basin.
Grand Prismatic Spring was noted by geologists working in the Hayden Geological Survey of 1871, and named by them for its striking coloration. Its colors include blue, green, yellow, orange, red and brown, and recall the rainbow disperson of white light by an optical prism.
The vivid colors in the spring are the result of pigmented bacteria in the microbial mats that grow around the edges of the mineral-rich water. The bacteria produce colors ranging from green to red; the amount of color in the microbial mats depends on the ratio of chlorophyll to carotenoids and on the temperature of the water which favors one bacterium over another. In the summer, the mats tend to be orange and red, whereas in the winter the mats are usually dark green. The center of the pool is sterile due to extreme heat.... The spring is approximately 250 by 300 feet (80 by 90 m) in size and is 160 feet (50 m) deep. The spring discharges an estimated 560 US gallons (2,100 L) of 160 °F (70 °C) water per minute." From Wikipedia.