Mud Volcano area
The Mud Volcano thermal area is an area of muddy hot springs and fumaroles located near one of the Yellowstone Volcano’s vents. To reach it, drive 5.9 miles north of Fishing Bridge Junction, or 9.7 miles south of Canyon Junction on the Canyon to Fishing Bridge section of the Grand Loop Road. The Sulphur Cauldron, one of the most acidic features in the park with a pH of battery acid, is located just 0.2 miles north of the Mud Volcano parking area.
The Mud Cauldron is viewable from the pathway right in front of the parking area. It is a large area of mud and water heated by steam escaping from far below.
Head left from the parking area towards a steep climb. Before the climb begins, a short side path leads to the Mud Geyser. This feature used to erupt muddy water up to 50 feet in the air in the 1800s. It has long since stopped this activity, although it has went through a series of movements and explosions since. It is at present a sizzling mudpot area.
Continue up the pathway, climbing the Cooking Hillside, which is quite steep but relatively short. The boardwalk trail resumes at the top and soon comes to the Churning Cauldron. This area was a cool pool filled with bacteria until earthquakes in 1978 and 1979 greatly increased the temperature. It tosses muddy water three to five feet high.
Black Dragon Cauldron
Further ahead the boardwalk goes to the left and right. To the left is a short side path leading to the Black Dragon’s Cauldron. It is a large, sizzling lake of mud. It was created in 1948 along a crack in the earth, and coated nearby trees in mud when it exploded into existence.
Return to the main boardwalk and take the right turn back towards the parking area. A short distance down the walk is the Grizzly Fumarole. This feature’s appearance varies widely depending on recent precipitation. It can be a watery mudpot, a thick mudpot, or simply a steam vent (fumarole). It is dry in the picture to the left.
Descend down a steep section of pathway to the Mud Volcano itself. Early visitors reported this as a 30 foot high cone erupting mud high enough to cover nearby trees. By the time the park was established in 1872 however, it had apparently blown itself apart and become a crater filled with bubbling mud, as it appears today.
Dragon’s Mouth Spring
From Mud Volcano a short side boardwalk leads to the Dragon’s Mouth Spring. This is one of the more interesting features in the park. Boiling water rolls out of a small cave-like opening, steam bellowing from within. Bizarre noises emit from the opening, making the idea of a dragon’s mouth rather believable.