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Mud Volcano / Sulphur Caldron, Yellowstone National Park
Fast Facts




Lake District
Yellowstone Nat'l Park
Wyoming 82190
Natural Wonder
Points of Interest Nearby

Mud Volcano


Photo by Harlan Kredit, courtesy of National Park Service

The sizzling basin known as Sulphur Caldron and Mud Volcano is one of the most volatile hydrothermal areas in Yellowstone National Park. And it is one of the most eerily intriguing. Sulfur is responsible for the peculiar sights, sounds and smells. - Iron sulfide paints mudpots and fumaroles shades of brown and gray. Hydrogen sulfide gurgles and hisses and produces a pungent rotten egg smell. Sulfuric acid, twice as acidic as battery acid, cooks the terrain creating a graveyard of skeleton trees. - Sour Creek Dome, a volcanic vent called a resurgent dome, is the source of instability. It's of little consequence that Mud Volcano, the hydrothermal feature for which the area is named, no longer throws mud nor rumbles noisily.
Getting There
Mud Volcano and Sulphur Caldron are located 6 miles (9.5 km) north of Fishing Bridge and 10 miles (16 km) south of Canyon. Mud Volcano is on the west side of the road; Sulphur Caldron is on the east. The road between Fishing Bridge and Canyon is accessible to wheeled vehicles from early May through October and oversnow vehicles from late December to early March.
Getting Around
Mud Volcano Trail is a moderate 0.7-mile (1 km) loop. To avoid the steepest ascent start at Mud Caldron and walk counterclockwise. The short loop to Mud Volcano and Dragon's Mouth Spring is wheelchair and stroller accessible; the boardwalk to Sour Lake is not.
Things to Keep in Mind
Keep to boardwalks and trails. Swimming and bathing is prohibited in all hot spring pools. Do not throw objects into geothermal features. Bison and elk frequent the area in spring, summer and fall.
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