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Note: See the volcano article for information on magmatic volcanoes such as Mount St. Helens or Kilauea.
The hydrothermal phenomenon known as "mud volcanoes" are not true mud volcanoes; see mud pot for more information.
The term mud volcano or mud dome is used to refer to formations created by geologically excreted liquids and gases, although there are several different processes which may cause such activity. Temperatures are much cooler than igneous processes. The largest structures are 10 km in diameter and reach 700 metres in height.

About 86% of released gases are methane, with much less carbon dioxide and nitrogen emitted. Ejected materials often are a slurry of fine solids suspended in liquids which may include water (frequently acidic or salty) and hydrocarbon fluids.

Details

A mud volcano may be the result of a piercement structure created by a pressurized mud diapir which breaches the Earth's surface or ocean bottom. Temperatures may be as low as the freezing point of 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 often are erupted. Mud volcanoes are often associated with lava volcanoes, and the typical relationship is that where they are close, the mud volcanoes emit incombustible gases, while the ones further away emit methane.

In Azerbaijan, eruptions are driven from a deep mud reservoir which is connected to the surface even during dormant periods, when seeping water still shows a deep origin. Seeps have temperatures up to 2–3 °C above the ambient temperature.

Approximately 1,100 have been identified on land and in shallow water. It has been estimated that well over 10,000 may exist on continental slopes and abyssal plains.

Features

  • gryphon: steep-sided cone shorter than 3 m. Extrude mud.
  • mud cones: high cones shorter than 10 m. Extrude mud and rock fragments.
  • scoria cones: formed by heating of mud deposits during fires.
  • salses: water-dominated pools with gas seeps.
  • springs: water-dominated outlets smaller than 0.5 m.
  • burning fires

Emissions

Most liquid and solid material is released during eruptions, but various seeps occur during dormant periods.

First order estimates of mud volcano emissions have been recently made.

  • 2002: L.I. Dimitrov estimated that 10.2–12.6 Tg/yr of methane is released from onshore and shallow offshore mud volcanoes.
  • 2002: Etiope and Klusman in 2002 estimated at least 1–2 and as much as 10–20 Tg/yr of methane may be emitted from onshore mud volcanoes.
  • 2003: Etiope, in an estimate based on 120 mud volcanoes: "The emission results to be conservatively between 5 and 9 Tg/yr, that is 3–6 % of the natural methane sources officially considered in the atmospheric methane budget. The total geologic source, including MVs (this work), seepage from seafloor (Kvenvolden et al., 2001), microseepage in hydrocarbon-prone areas and geothermal sources (Etiope and Klusman, 2002), would amount to 35–45 Tg/yr."
  • 2003: Milkov et al's analysis suggests that the global gas flux may be as high as 33 Tg/yr (15.9 Tg/yr during quiescent periods plus 17.1 Tg/yr during eruptions). 6 Tg/yr of greenhouse gases from onshore and shallow offshore mud volcanoes. Deep-water sources may emit 27 Tg/yr. Total may be 9% of fossil CH4 missing in the modern atmospheric CH4 budget, and 12% in the preindustrial budget.
  • 2003: Alexei Milkov estimated approximately 30.5 Tg/yr of gases (mainly methane and CO2) may escape from mud volcanoes to the atmosphere and the ocean.
  • 2003: Achim J. Kopf estimated 1.97 × 1011 to 1.23 × 1014 m3 of methane is released by all mud volcanoes per year, of which 4.66 × 107 to 3.28 × 1011 m3 is from surface volcanoes. That converts to 141–88,000 Tg/yr from all mud volcanoes, of which 0.033–235 Tg is from surface volcanoes.

Locations

Europe and Asia

Mud volcanoes are generally few in Europe, but dozens can be found on the Kerch Peninsula of southeastern Ukraine. In Italy they are common in the northern front of the Apennines and in Sicily.

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. Features over 200 meters high exist in Azerbaijan, with large eruptions sometimes producing flames of similar scale. Iran and Pakistan also possess mud volcanoes in the Makran range of mountains in the south of the two countries. China has a number of mud volcanoes in Xinjiang province.

North and South America

Mud volcanoes of the North American continent include:

South American mud volcanoes include:

  • Venezuela. The Eastern part of Venezuela contains several mud volcanoes, all of them, like in Trinidad, having an origin related to oil deposits. The image shows the Volcán de lodo de Yagrumito, about 6 km from Maturín, Venezuela. Its mud contains, not only certain amount of hydrocarbons, but an importan quantity of salt. This makes cows from the savanna to gather around to lick dried mud, since salt is very important in their feeding to produce milk. The Coriolis effect leaves a spiral flow clockwise around the crater.
  • El Totumo, which marks the division between Bolivar and Atlantico in Colombia. This volcano is currently under a legal fight between the Bolivar and the Atlantico because of its tourist value.

Yellowstone's Mud Volcano

The name of Yellowstone National Park's Mud Volcano feature and the surrounding area is misleading; it consists of hot springs, mud pots and fumaroles rather than a true mud volcano. The feature is much less active than in its first recorded description, although the area is quite dynamic. Yellowstone is an active geothermal area with a magma chamber near the surface, and active gases tend to be steam, carbon dioxide, and hydrogen sulfide.

The mud volcano in Yellowstone used to be an actual mound, until one day it literally tore itself apart into what is seen today.


Azerbaijan

It's estimated that 300 of the planet's estimated 700 mud volcanoes sit in Eastern Azerbaijan and the Caspian Sea.* Many geologists as well as locals and international mud tourists trek to such places as the Firuz Crater, Gobustan, Salyan and end up happily covered in mud which is thought to have medicinal qualities.In 2001 one mud volcano 15 kilometers from Baku made world headlines when it suddenly started spewing flames 15 meters high. [http://news.bbc.co.uk/2/hi/science/nature/1626310.stm

Other parts of the world

See also

References

  5. ISSN 1437-3254 (Paper) ISSN 1437-3262 (Online)

External links

Volcanology | Subduction volcanoes | Petrology | Hydrothermal vents

Vulcani di fango | 泥火山

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Mud volcano".

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