Dean M. Chriss
Hot Color, Grand Prismatic Spring, Yellowstone National Park
(Click image to enlarge)
Yellowstone's Grand Prismatic Spring is the largest hot spring in the United States and the third largest in the world. Its vivid colors are the result of pigmented bacteria in the microbial mats that grow around the edges of the mineral-rich water. Grand Prismatic Spring discharges 560 gallons (2,100 L) of 160 °F (70 °C) water each minute. The pool is 160 feet (50 meters) deep and about 250 by 300 feet (80 by 90 meters). The pool is sterile due to the extreme heat and its extremely clear water appears a vivid blue.