Mud volcanism presents one of the most interesting and unusual phenomena, with periodical eruptions of large amounts of gases (mainly hydrocarbons) and breccia with inclusions of rock fragments from small sizes up to blocks of several meters. Eruption products accumulate near the orifice and crater volcano cone. The size of the volcano cone depends on the eruption frequency and character of the erupted material
Mud volcano or mud dome refers to formations created by geo-exuded mud or slurries, water and gases. There are several geological processes that may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they produce no lava. The earth continuously exudes a mud-like substance, which may sometimes be referred to as a "mud volcano". Mud volcanoes may range in size from merely 1 or 2 meters high and 1 or 2 meters wide, to 700 meters high and 10 kilometers wide. Smaller mud exudations are sometimes referred to as mud-pots. The largest (man made) mud volcano is "Lusi" in Java, Indonesia, which is 10 kilometres (6 mi) in diameter. The mud produced by mud volcanoes is most typically 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. Mud volcanoes are associated with subduction zones and about 1100 have been identified on or near land. The temperature of any given active mud volcano generally remains fairly steady and is much lower than the typical temperatures found in igneous volcanoes. Mud volcano temperatures can range from near 100 °C (212 °F) to occasionally 2 °C (36 °F), some being used as popular "mud baths."
About 86% of the gas released from these structures is methane, with much less carbon dioxide and nitrogen emitted. Ejected materials are most often a slurry of fine solids suspended in water that may contain a mixture of salt, acids and various hydrocarbons.
Possible mud volcanoes have been identified on Mars.
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. They are also often associated with lava volcanoes; in the case of such close proximity, mud volcanoes emit incombustible gases including helium, whereas lone mud volcanoes are more likely to emit methane.
Approximately 1,100 mud volcanoes 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.
• Gryphon: steep-sided cone shorter than 3 meters that extrudes mud
• Mud cone: high cone shorter than 10 meters that extrudes mud and rock fragments
• Scoria cone: cone formed by heating of mud deposits during fires
• Salse: water-dominated pools with gas seeps
• Spring: water-dominated outlets smaller than 0.5 metres
• Mud shield
Most liquid and solid material is released during eruptions, but seeps occur during dormant periods.
The mud is rich in halite (rock salt)
First-order estimates of mud volcano emissions have been made (1 Tg = 1 million metric tonnes).
There are many mud volcanoes in Iran: in Hormozgan province, Sistan and Baluchestan Province and Golestan Province.
Mud volcanism and diapirism have puzzled geoscientists for 2 centuries. They have been described onshore and offshore in many places on Earth, and although they occur in various tectonic settings, the majority of the features known to date are located in compressional
Mud volcanoes show variable geometry (up to tens of kilometers in diameter and several hundred meters in height) and a great diversity regarding the origin of the fluid and solid phases. Gas (predominantly methane), water, and mud may be mobilized at sub bottom
depth of only a few meters but, in places, can originate from several kilometers depth (with minor crustal or mantle input). The possible contribution of mud extrusion to global budgets, both from quiescent fluid emission and from the extrusive processes themselves, is important. In regions where mud volcanoes are abundant, such as the collision zones between Africa and
Eurasia, fluid flux through mud extrusion exceeds the compaction-driven pore fluid expulsion of the accretion- ary wedge. Also, quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and, hence, to greenhouse climate Mud intrusion and extrusion are well-known phenomena whereby fluid-rich, fine-grained sediments ascend within a lithologic succession because of their buoyancy. These processes have long been recognized as related to the occurrence of petroleum, regional volcanic and earthquake activity, and orogenic belt
The term sedimentary volcanism refers to the similar geometry of many mud extrusions and igneous volcanoes, and only very rarely are MVs connected with igneous activity
., More often (and this is especially true for deep-seated features), MV occurrences have the following aspects in common:
(1) an origin from thick,
rapidly deposited sequences of marine clays;
(2) a Ter-tiary age;
(3) a structural association due to tectonic
shortening and/or earthquake activity;
(4) sediment overpressuring and accompanying
fluid emission (gas,
(5) polymictic assemblages of the surrounding rock present
in the ejected argillaceous matrix
http://sp.lyellcollection.org/content/2 ... 5.abstract
The mobilized sediments expelled by the mud volcanoes in Trinidad correspond to liquefied argillaceous and sandy material in which the solid fraction is systematically polygenic and originating from several formations (Cretaceous to Pliocene). The mud is notably rich in thin grained quartz that is angular and frequently mechanically damaged related to shearing at great depth, during the sedimentary burial, and/or hydraulic fracturing processes. The exotic clasts are mostly fractured fragments from various formations of the tectonic wedge (mostly Palaeocene to Miocene). The origin of the solid particles of the mud is polygenic, including deep Cretaceous-Palaeogene horizons close to the décollement, and various materials from the stratigraphic pile pierced by the mud conduits. Moreover, the fluids expelled by the mud volcanoes have a deep origin and notably the gas phase is thermogenic methane generated probably below a depth of 5000 m. The effusions occur either during cycles of moderate effusion of mud and fluids (quiescence regime), or during catastrophic events responsible for the expulsion of huge volumes of mud, clasts and fluids (transient regime).
Drilling during Ocean Drilling Program Leg 160 (April–May, 1995) revealed important new evidence concerning the internal composition, depositional processes, and age of two mud volcanoes within the Mediterranean Ridge accretionary complex. Holes were drilled at ca. 2000 m water depth on the crest areas, across the flanks of the mud volcanoes, and onto adjacent deep-sea sediments. The main depositional units forming the flanks of both mud volcanoes are debris flows (“mud breccias”) composed of a volumetrically dominant mud matrix, containing clasts of mainly clay, mudstone, siltstone, sandstone, and limestone. More variable muddy, silty, and sandy sediments were recovered from the crestal areas of both volcanoes. The lowest mud-volcano units drilled include well-sorted medium- to coarse-grained sediments, mainly composed of clay, that were deposited partly by turbidity currents. The mud-volcano sediments are associated with background deep-sea sediments that allow dating by using microfossils. The Milano mud volcano is at least 1.75 Ma, and is apparently now dormant, and the Napoli mud volcano started prior to, or during, 1.5–1.2 Ma and is currently active. Pore fluids at Napoli, and to a lesser extent at Milano, indicate the presence of halite of presumed latest Miocene age beneath the volcanoes. Hydrocarbon gas is venting from the crest of the Napoli mud volcano, and gas was also detected on the crest of the Milano mud volcano. Methane hydrates (clathrates) are also inferred to exist beneath the crest of the Milano mud volcano. The mud volcanoes are located above a shallowly dipping subduction zone in an area where the accretionary complex is apparently being thrust northward over a backstop of continental crust, related to initial collision of the African and Eurasian plates. Mud volcanism may have begun when backthrusting punctured a seal of latest Miocene evaporates, allowing the escape of overpressured materials.
The significance of mud volcanoes in research Mud volcanoes are of particular interest for several reasons.
Current research includes NASA who analyze satellite imagery of structures on Mars that closely resemble mud volcanoes. If the suggested analogies are true, it would help confirm the presence of water on Mars.
As Ronnie Gallagher wrote, his own research about the sea level changes of the Caspian Sea in the Late Pleistocene was helped by the mud volcanoes, because they create packages of soft strata that are easily eroded into strandlines. The mud volcanoes of the Caspian Sea area have thus provided evidence of uplift in excess of 100 m, which tectonic movements cannot be responsible for alone, as they are thought to be in the range of about 50 m only, as an accepted limit of uplift in the area because of DE glaciation.
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