Mud volcano

Note:See the volcano article for information on magmatic volcanoes such as Mount St. Helens or Kilauea.

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. 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.

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.

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.

Features

• gryphon: steep-sided cone shorter than 3m. Extrude mud.
• mud cones : high cones shorter than 10m. Extrude mud and rock fragments.
• scoria cones: formed by heating of mud deposits during fires.
• hydrocarbon deposits.
• 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. How much of the powerful greenhouse gas methane reaches the atmosphere from submarine volcanoes is not known.

• 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." ^{10.1029/2002GL016358}

1. ^  "Global Distribution and Significance of Mud Volcanoes." AAPG Annual Meeting 2003: Energy - Our Monumental Task. Accessed on April 20, 2005.
2. ^  Achim J. Kopf (2003) "Global methane emission through mud volcanoes and its past and present impact on the Earths climate". International Journal of Earth Sciences 92 (5), 806-816. DOI:10.1007/s00531-003-0341-z ISSN 1437-3254 (Paper) ISSN 1437-3262 (Online)
3. ^  "Mud volcano." USGS Photo glossary of volcano terms. Accessed on April 20, 2005.

External links

• Gaia's Breath—Methane and the Future of Natural Gas - USGS, June 2003
• Azeri mud volcano flares - October 29 2001 BBC report
• Redondo Beach mud volcano with methane hydrate deposits
• Hydrocarbons Associated with Fluid Venting Process in Monterey Bay, California
• Hydrothermal Activity and Carbon-Dioxide Discharge at Shrub and Upper Klawasi Mud Volcanoes, Wrangell Mountains, Alaska - U.S. Geological Survey Water-Resources Investigations Report 00-4207
• Mud Volcano Eruption at Baratang, Middle Andamans