Fumaroles or steam vents are the hottest hydrothermal features in the park.
Mudpots are acidic features with a limited water supply. Microorganisms convert hydrogen sulfide gas coming up from deep within the earth to sulfuric acid, which breaks down rock into clay minerals.
Yellowstone National Park has approximately half of the world's geysers and most of them, including Old Faithful, are located in the Upper Geyser Basin.
Hot springs are the most common hydrothermal feature in the park.
Last updated: May 5, 2016
P.O. Box 168
Yellowstone National Park, WY