The 1871 Hayden Expedition named this thermal feature. At that time Mud Volcano was a very active mud spring with bellowing and exploding mud. In later years since its discovery it has not shown the same forcefulness. However, minor earthquake tremors during 1979 increased heat and water activity and Mud Volcano began bursting from the crater, spilling mud across the boardwalks. This activity decreased shortly thereafter and it has since been a quiet caldron with occasional churning caused by rising gases.