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.

Approximately 0.6 mile (1 km) loop trail. The clockwise route is less steep than the counterclockwise route. Start at the south trailhead for a more gradual incline up the hillside.

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.

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.

Resurgent Domes

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.

Accessibility

Designated accessible parking and wheelchair-accessible restrooms. The lower loop is wheelchair-accessible. Start at the northeast end of the parking area. At the boardwalk junction beyond the Mud Volcano, turn left and return to the parking area.

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.