Dragon's Mouth Spring

Steam rises from a vent next to a cloudy pool of water with green vegetation on the pool edges
Steam vent

Quick Facts
Mud Volcano area

Historical/Interpretive Information/Exhibits

The Crow saw the steam from this mudpt as snorts of an angry bull bison. An unknown European American gave it the current name. Its previous names include Gothic Grotto, Blowing Cavern, and The Belcher.

The surging action has decreased since 1994, though no one is sure why. In 1999, more dramatic changes occurred: the water temperature dropped 10 degrees and the color changed from green to chalky white.

Hot Springs

Hot springs are the most common hydrothermal features in Yellowstone. Their plumbing has no constrictions.

Superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below.

This circulation prevents water from reaching the temperature needed to set off an eruption.

The Smell

Mudpots are acidic features with a limited water supply. Some microorganisms use hydrogen sulfide, which rises from deep within the earth, as an energy source. They help convert the gas to sulfuric acid, which breaks down rock to wet clay mud and creates the area’s smell. The pungent odor of rotten eggs is caused by the hydrogen sulfide gas.

Various gases escape through the wet clay mud, causing it to bubble. Mudpot consistency and activity vary with the seasons and precipitation.

Mud Volcano Area

The Mud Volcano area has many mudpots and hillsides strewn with trees cooked by steam. The hydrothermal features here are some of the most acidic in the park.

Mud Volcano is near the greatest uplift and sinking of the Yellowstone Caldera floor. Many faults converge here and earthquakes are common.

The areas surrounding the Mud Volcano vent and the other major vent near Old Faithful are called resurgent domes. Resurgent domes are active ground deformation, where the land moves up or down with the fluctuation of the magma chamber below. Scientists monitor these domes closely for information about ongoing volcanic activity.

Use Caution in Hydrothermal Areas

  • Stay on boardwalks and designated trails.
  • Hydrothermal water can severely burn you.
  • Never run, push, or shove.
  • Supervise children at all times.
  • Do not scratch hydrothermal mats.

You are responsible for your safety.

Think safety, act safely. Yellowstone is a dangerous place.

Yellowstone National Park

Last updated: March 3, 2021