Old Faithful Virtual Visitor Center

Lobby > Exhibits > Hot Spring Ecology > Microbes > Meet the Microbes > Sulfide-rich Carbonate Springs

Meet the Microbes


The water at Mammoth Hot Springs, although rich in sulfate, is neither very acidic nor very alkaline because the underlying bedrock of calcium carbonate acts as a buffer and keeps the water’s pH near neutral. Some of the sulfate in the water is converted to hydrogen sulfide underground, most likely by microorganisms. Sulfide strongly influences the types of microorganisms found at Mammoth Hot Springs. Some microbes thrive on sulfide, whereas others find this chemical poisonous. The latter live downstream in areas where the sulfide has already been removed by their hungry neighbors. Becoming coated with calcium carbonate, the microorganisms also help build the travertine terraces.

Reds, blues and greens color the runoff channel of a hot spring in Norris Geyser Basin

Alkaline Siliceous Springs

Two people observe the many colors of Grand Prismatic Spring
   Acidic Springs

Microbes color the runoff channel from a hot spring in Norris Geyser Basin
Neutral Sulfide-rich Carbonate Springs
Microbes add bands of color to this formation at Mammoth Hot Springs

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Drawing of the outside of the visitor center
Young Scientists
Yellowstone Express
Why Geysers Erupt
Hot Water Treasures
Hot Spring Ecology
Scientific Research

This work is supported by

National Science Foundation    Yellowstone Park Foundation
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