Opal Pool
Opal Pool is a hot spring in the Midway Geyser Basin of Yellowstone National Park, Wyoming.[1] Though usually active as a hot spring, Opal Pool is considered a fountain-type geyser.Eruptions occur suddenly following visible convection in the pool, but are unpredictable.Much smaller splashes seconds apart stretch the total duration to about 1 minute.In 2005 Opal completely drained, but refilled as a vivid green pool in 2008.