The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and one of the largest in the world.Yellowstone National Park contains the most concentrated array of hot springs and geysers in the world. It is 90 meters (300 feet) across and 50 meters (160 feet) deep. In the center of the pool the water is 87° C (188° F)—too hot to support life. In the cooler water along the edges of the pool, however, colonies of thermophilic (heat-loving) cyano-bacteria and algae thrive. Yellow, orange, and red pigments are produced by the bacteria as a natural sunscreen. As a result, the pool displays a spectrum of colors from the bright blue of the center to the orange, red, and brown algal mats along the edges.
