A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases.Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce lava and are not necessarily driven by magmatic activity.
Mud volcanoes may range in size from merely 1 or 2 metres high and 1 or 2 metres wide, to 700 metres high and 10 kilometres wide. Smaller mud exudations are sometimes referred to as mud-pots.
The mud produced by mud volcanoes is mostly formed as hot water, which has been heated deep below the Earth’s surface, begins to mix and blend with subterranean mineral deposits, thus creating the mud slurry exudate.This material is then forced upwards through a geological fault or fissure due to local subterranean pressure imbalances.
The temperature of any given active mud volcano generally remains fairly steady and is much lower than the typical temperatures found in igneous volcanoes.
About 86% of the gas released from these structures is methane, with much less carbon dioxide and nitrogen emitted.
A mud volcano may be the result of a piercement structure created by a pressurized mud diapir that breaches the Earth’s surface or ocean bottom. Their temperatures may be as low as the freezing point of the ejected materials, particularly when venting is associated with the creation of hydrocarbon clathrate hydrate deposits.
Mud volcanoes are often associated with petroleum deposits and tectonic subduction zones and orogenic belts; hydrocarbon gases are often erupted.
Most liquid and solid material is released during eruptions, but seeps occur during dormant periods.The mud is rich in halite.
Dozens of mud volcanoes are located on the Taman Peninsula of Russia and the Kerch Peninsula of Crimea, Ukraine along with the south-western portion of Bulgaria near Rupite.
Many mud volcanoes exist on the shores of the Black Sea and Caspian Sea. Tectonic forces and large sedimentary deposits around the latter have created several fields of mud volcanoes, many of them emitting methane and other hydrocarbons.