Next door to the Grand Prismatic Pool is the Excelsior Geyser Crater which is a very different sort of beast. Currently it expels a huge amount of boiling water (I recall 5,000 gallons per minute) into the Firehole River (see the cascade photo in the linked gallery). I guess with all of this water moving through the water remains a gorgeous blue, unlike the Grand Prismatic Pool with it rainbow of bacterial/algal "crud". Historically the pool not only boiled but "geysered" up to a height of 300 feet.

More to come... if you are interested, more photos from this area, you can find them Here

PLEASE CLICK ON ORIGINAL BELOW TO SEE AT FULL SIZE