This is the spring which is the source of the flow shown on the previous page.  This pool is fed by several hot springs and is one of the larger pools in the park.  Water boils at approximately 190° F at the surface elevations in Yellowstone, and this entire pool is boiling hot!  This was a warm Autumn day in the park.  On colder days, this entire area would be shrouded in fog and could not be photographed.  The Red and Yellow colors you see are the result of bacterial organisms which have adapted to life in near boiling temperatures.  Some of these organisms have become of interest to science in the treatment of diseases and the National Park Service is allowing limited harvesting of the bacteria.