I do not know English well.

The geothermal phenomena known as "mud volcanoes" are often not true mud volcanoes (pelovolcano). See mudpot for further information.
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 lower in these processes than found at igneous volcanoes. The largest mud volcano structure, Indonesia's Lusi, is 10 kilometres (6 mi) in diameter and reaches 700 metres (2,300 ft) in height.
About 86% of the gas released from these structures is methane, with much less carbon dioxide and nitrogen emitted. Ejected materials are often a slurry of fine solids suspended in liquids which may include water, which is frequently acidic or salty, and hydrocarbon fluids.
Possible mud volcanoes have been identified on Mars.
Another relatively accessible place where mud volcanoes can be found in Europe are the Berca Mud Volcanoes near Berca in Buzău County, Romania, close to the Carpathian Mountains.

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