The term mud volcano or mud dome are used to refer to formations created by geo-excreted liquids and gases, although there are several different processes which may cause such activity. Hot water mixes with mud and surface deposits. Mud volcanoes are associated with subduction zones and about 700 have been identified. Temperatures are much cooler in these processes than found at igneous volcanoes. The largest mud volcano structures are 10 kilometres (6 mi) in diameter and reach 700 metres (2,300 ft) in height.[where?]