Emerald Pool, Yellowstone National Park

Taken on the third day (13 September 2012) of a week's trip with great friends from England, down to Yellowstone National Park and Grand Teton National Park. This beautiful pool is located at the Black Sand Basin. I still have so many photos to go through from this holiday, and am trying to slip the occasional one on to my photostream.

"Temperature 154.6°F Dimensions 27x38 feet. Depth 25 feet. Named for its emerald green color, it is one of the main attractions at Black Sand Basin. The color is the result of lower temperatures which have allowed yellow bacteria and algae to grow on the lining of the pool. The clear water of the pool reflects the blues but absorbs the other hues of the color spectrum. The combination of blue and yellow then produces green. Objects thrown into the pool and natural debris have caused a further decrease in temperature, resulting in a change of bacteria and algae growth and thus a change of color. The edge of the pool is now orange and brown. If the temperature continues to decrease, the pool may lose its emerald color."

www.yellowstonenationalpark.com/blacksand.htm