• Visitors stand on the boardwalk of Grand Prismatic, the park's largest hot spring which is ringed with orange, brown and yellow runoff channels.

    Yellowstone

    National Park ID,MT,WY

Fumaroles and How They Work

A fumarole emits a jet of hot steam in Porcelain Basin.

Black Growler Steam Vent
Norris Geyser Basin

Fumaroles, or steam vents, are the hottest hydrothermal features in the park. They have so little water that it all flashes into steam before reaching the surface. At places like Roaring Mountain, the result is a lot of hissing of steam and gases.

Did You Know?

Upper Geyser Basin Hydrothermal Features on a Winter Day.

Yellowstone contains approximately one-half of the world’s hydrothermal features. There are over 10,000 hydrothermal features, including over 300 geysers, in the park.