Mud volcanoes are associated with subduction zones and about 1100 have been identified on or near land. The temperature of any given active mud volcano generally remains fairly steady and is much lower than the typical temperatures found in igneous volcanoes. Mud volcano temperatures can range from near 100 C to occasionally 2 C, some being used as popular "mud baths".

About 86% of the gas released from these structures is methane, with much less carbon dioxide