Est. March 1, 1872
The Yellowstone Calderas were created during eruptions that took place 2.1 million, 1.3 million, and 630,000 years ago. The Grand Prismatic Spring measures 370 ft. in diameter and is over 121 ft. deep. The center of the spring lies above an underground water source, with temperatures as high as 189°F. The hot springs center is sterile due to the extreme temperature, but as the water spreads farther from the source, it changes the bacteria that can live there. Each band of color represents a new mini-ecosystem, created by individual pigmented microbes that have adapted to the various temperatures.