Churning Cauldron - Geothermal Area of Yellowstone

The thermal features at Mud Volcano and Sulfur cauldron (Mud Volcano) are primarily mud pots and fumaroles because the area is situated on a parched water system with little water available. Fumaroles or "steam vents" occur when the ground water boils away faster than it can be recharged. Also, the vapors are rich in sulfuric acid that leaches the rock, breaking it down into clay.