Pirgel is a

mud volcano 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 ...

Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...

, in the province Sistan and Balochistan close to the town of

Khash Khash may refer to: *Khash (dish), South Caucasian dish *Khash Rod District, a district in Nimruz Province, Afghanistan **Khash, Nimruz, capital of Khash Rod District, Afghanistan * Khash District, a district in Badakhshan Province, Afghanistan *K ...

. The mud volcano is accessible via a foot track. Mud volcanoes are landforms where water and gas are extruded from the ground. In southeastern Iran they occur in two places, one close to

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

es such as

Bazman Bazman ( fa, بزمان, also known as Kuh-e Bazman) is a dormant stratovolcano in a remote desert region of Sistan and Baluchestan Province in south-eastern Iran. A 500-m-wide crater caps the summit of the dominantly andesitic-dacitic volcan ...

and

Taftan Taftan (in Persian: تفتان ''Taftân'') may refer to: * Taftan (volcano), located in Sistan and Baluchestan province of Iran * Taftan, Balochistan Taftan ( ur, ) ( bal, ) is a trunk road and railway town in Chagai District, Balochistan, ...

and are hot () effusions, the other is colder and linked to the extrusion of

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

and tectonic-sedimentary processes. Several theories have been proposed to explain cold mud volcanoes, one of which posits that water in

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

is trapped and thus pressurized, causing the clay to liquefy and erupt on the surface along faults. Despite its location close to the two aforementioned volcanoes, Pirgel is considered to be a cold mud volcano, with temperatures of . Pirgel contains a main cone with an elevation of above sea level, and above the terrain. This makes it a relatively high mud volcano, the highest and with width the biggest mud volcano in Iran. Venting occurs through cones, gryphons and pools. There are eleven individual craters, of which seven are active, but they are all relatively small. The mud volcano covers an area of on a

marl Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. Marl makes up the lower part o ...

hill, also a relatively large size.

Erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

from flowing water has affected both the surroundings as well as the mud volcano itself, forming gullies and ravines probably from the collapse of caverns. Eroded and inactive vents testify of past activity. The mud volcano was reported active in May 2003, with the extrusion of cold muddy water and the eruption of bubbles every 15-600 seconds. This mud is relatively liquid and fairly saline. The gas extruded at Pirgel is principally carbon dioxide; unlike other mud volcanoes in the region

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

is not a component. The mud volcano is considered to be a sacred place by local people, the site where a holy person manifests itself.

References

{{Reflist, 30em Mud volcanoes Geology of Iran Mud volcanoes of Iran