238 Updates in Volcanology - New Advances in Understanding Volcanic Systems

they are unstable and effervesce as they decompose.

**3. The gas hydrates**

The phase diagram reported in Figure 4 shows a typical situation on continental shelves. As‐ suming a seafloor depth of 1,200 m, temperature steadily decreases with water depth, and a minimum value near 0° C is reached at the ocean bottom. Below the sea floor, temperatures steadily increase, so the top of the gas hydrate stability zone (GHSZ) occurs at roughly 400 m, while the base of the GHSZ is at 1,500 m. From the phase diagram, it appears that hy‐ drates should accumulate anywhere in the ocean-bottom sediments where water depth ex‐ ceeds about 400 m. Very deep (abyssal) sediments are generally not thought to house hydrates in large quantities. In fact deep oceans lack both the high biologic productivity (necessary to produce the organic matter that is converted to methane) and rapid sedimenta‐ tion rates (necessary to bury the organic matter) that support hydrate formation on the con‐ tinental shelves. Note that the conditions for gas hydrate formations are present also in sea water, but gas concentration is always not sufficient for their formations.

The gas hydrate phase is affected by gas mixture and pore-fluids composition (salinity). It is known that the presence of only a small percentage of higher hydrocarbons (such as ethane and propane) shifts the phase boundary to higher temperature (at constant pressure). The effect is that the base of GHSZ is shifted to greater depths [100,103]. Analogous to the effect of salt on the freezing point of water, if pore-fluids composition is brine, the phase boundary is shifted to lower temperatures at a given pressure and thus base of GHSZ will be shallow‐ er, as demonstrated by different authors [i.e., 204. Figure 5] shows a comparison among sev‐ eral gas hydrate stability models proposed in literature. The black line indicates the methane hydrate stability in brine water with a salinity of 3.5 % [105]. The red lines are evaluated by using the equations reported in [100] which consider fresh water. The solid red line indicates the methane hydrate stability curve and the dashed red line the hydrate stability curve con‐ sidering a mixture of methane (90%), ethane (5%) and propane (5%). The blue lines are the hydrate stability in fresh water considering pure methane (solid line) and a mixture of meth‐ ane (90%) and ethane (10%) by using the empirical expression proposed by [106]. Reference [107] obtained empirical equation for methane hydrate system in function of salinity. The green lines represent the gas hydrate stability considering the following salinity values: 0.0% ( i.e. fresh water; solid line), 2 % (dotted line), 3.5 % (dashed line), and 5 % (dashed-dotted line). Finally, the magenta line indicates the stability for system of pure methane and water, following the approach of Reference [108]. Note that the methane hydrate stability curves in fresh water obtained from the proposed models are almost coincident, while the case con‐ sidering salt water shows differences between the considered approaches.

The stability of methane hydrates on the sea floor has several implications [i.e., 109,110]. First, they may constitute a huge energy resource [111]. Second, natural and man-made dis‐ turbances may cause their destabilization causing the release of huge amounts of fluids (gas and water) and affecting slope stability. Finally, methane is an effective greenhouse gas (26 times more powerful than carbone dioxide), and large methane releases may explain sudden episodes of climatic warming in the geologic past. Some authors suggested that gas hydrate dissociation influenced significantly climate changes in the late Quaternary period [112-115]. The Clathrate Gun Hypothesis [116] suggests that past increases in water temperatures near the seafloor may have induced such a large-scale dissociation, with the methane spike and isotopic anomalies reflected in polar ice cores and in benthic foraminifera [115]. Reference [117] suggested that methane would oxidize fairly quickly in the atmosphere, but could cause enough warming that other mechanisms (for example, release of carbon dioxide from carbonate rocks and decaying biomass) could keep the temperatures elevated.

erate methane gas from hydrate in sediments, and in the process lock up CO2 in CO2 hydrate [i.e., 131]. The CO2 storage program is a further reason to assess the feasibility of mapping and monitoring the reservoir by means of an efficient seismic analysis [132,133] and to ob‐

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241

tain information about hydrate and free gas concentrations in a time-effective way.

**Figure 5.** Comparison among different gas hydrate stability models. See text for details.

**Figure 6.** Comparison between two models: the Biot theory (solid red lines; [129]) and the approximation for seismic frequency (green dashed lines; [128]). (a) Compressional (Vp) and shear (Vs) velocity versus gas hydrate concentration

Finally, it is worth to mention that gas hydrates cannot survive for long geological times ei‐ ther because buried sediments are submitted to increasing geothermal conditions or are tec‐ tonically uplifted. In fossil sediments, the study of the interaction between seep-carbonates, hydrate destabilization and sediment instability is particularly difficult, owing to the lack of

in pore space. (b) Vp and Vs versus free gas saturation in pore space, supposing uniform distribution.

Gas hydrates in marine environments have been mostly detected from analysis of seismic reflection profiles, where they produce remarkable bottom-simulating reflectors (BSRs; [100,118]). Generally, the BSR is a very high-amplitude reflector that is associated with a phase reversal that approximately parallels the seafloor [119]. This phase reversal, which re‐ sults from a strong acoustic impedance contrast between the layers, may indicate that sedi‐ ments above the BSR are extensively filled with gas hydrates and sediments below it are filled with free gas in the pore space [i.e., 120-122]. Because the BSR follows a thermobaric surface rather than a structural or stratigraphic interface, it is normally observed to crosscut other reflectors [123].

Several studies [i.e. 30] revealed a seismic reflector below the BSR that can be associated with the base of the free gas zone, called base of the free gas reflector (BGR). The scientific community have been devoted much effort in studying marine sediments containing gas hydrates to characterize the hydrate reservoir and to quantify the gas trapped within sedi‐ ments from seismic data analysis [i.e., 31,122,124,125]. To reach this goal advanced techni‐ ques have been developed. In fact, the BSR, detected from seismic data, is an easily recognizable indicator of the presence of hydrate, but it does not provide information direct‐ ly on the concentration of hydrate and free gas or their distribution. One approach to esti‐ mate hydrate and free gas concentration is from seismic velocity (primarily P-wave velocity, Vp), obtained through advanced seismic analysis and/or modeling of data from a multichannel seismic streamer, using techniques such as common-image gathers analysis [i.e., 32], one dimensional waveform inversion [i.e., 126], and amplitude versus offset analysis [i.e., 127]. The obtained velocity can be translated in terms of concentration by using theoret‐ ical models [i.e., 127,128]. Figure 6 reports an example of compressional and the shear (Vs) velocity versus gas hydrate and free gas saturation in pore space by using two models: the Biot theory [129] and the approximation for seismic frequency [128]. Note that in presence of high hydrate concentration, the velocity increases significantly, while, if we suppose uni‐ form distribution of free gas in the pore space, it is sufficient a small content of free gas to reduce drastically the velocity.

Recently, the international community has considered CO2 sequestration as a possible means of offsetting the emission of greenhouse gases into the atmosphere [130]. Some stud‐ ies have considered confining CO2 hydrate directly to shallow sediments on the deep sea floor, but this approach would not be permissible under the above international conven‐ tions. In the case of hydrates, several studies have investigated the use of injected CO2 to lib‐ erate methane gas from hydrate in sediments, and in the process lock up CO2 in CO2 hydrate [i.e., 131]. The CO2 storage program is a further reason to assess the feasibility of mapping and monitoring the reservoir by means of an efficient seismic analysis [132,133] and to ob‐ tain information about hydrate and free gas concentrations in a time-effective way.

times more powerful than carbone dioxide), and large methane releases may explain sudden episodes of climatic warming in the geologic past. Some authors suggested that gas hydrate dissociation influenced significantly climate changes in the late Quaternary period [112-115]. The Clathrate Gun Hypothesis [116] suggests that past increases in water temperatures near the seafloor may have induced such a large-scale dissociation, with the methane spike and isotopic anomalies reflected in polar ice cores and in benthic foraminifera [115]. Reference [117] suggested that methane would oxidize fairly quickly in the atmosphere, but could cause enough warming that other mechanisms (for example, release of carbon dioxide from

Gas hydrates in marine environments have been mostly detected from analysis of seismic reflection profiles, where they produce remarkable bottom-simulating reflectors (BSRs; [100,118]). Generally, the BSR is a very high-amplitude reflector that is associated with a phase reversal that approximately parallels the seafloor [119]. This phase reversal, which re‐ sults from a strong acoustic impedance contrast between the layers, may indicate that sedi‐ ments above the BSR are extensively filled with gas hydrates and sediments below it are filled with free gas in the pore space [i.e., 120-122]. Because the BSR follows a thermobaric surface rather than a structural or stratigraphic interface, it is normally observed to crosscut

Several studies [i.e. 30] revealed a seismic reflector below the BSR that can be associated with the base of the free gas zone, called base of the free gas reflector (BGR). The scientific community have been devoted much effort in studying marine sediments containing gas hydrates to characterize the hydrate reservoir and to quantify the gas trapped within sedi‐ ments from seismic data analysis [i.e., 31,122,124,125]. To reach this goal advanced techni‐ ques have been developed. In fact, the BSR, detected from seismic data, is an easily recognizable indicator of the presence of hydrate, but it does not provide information direct‐ ly on the concentration of hydrate and free gas or their distribution. One approach to esti‐ mate hydrate and free gas concentration is from seismic velocity (primarily P-wave velocity, Vp), obtained through advanced seismic analysis and/or modeling of data from a multichannel seismic streamer, using techniques such as common-image gathers analysis [i.e., 32], one dimensional waveform inversion [i.e., 126], and amplitude versus offset analysis [i.e., 127]. The obtained velocity can be translated in terms of concentration by using theoret‐ ical models [i.e., 127,128]. Figure 6 reports an example of compressional and the shear (Vs) velocity versus gas hydrate and free gas saturation in pore space by using two models: the Biot theory [129] and the approximation for seismic frequency [128]. Note that in presence of high hydrate concentration, the velocity increases significantly, while, if we suppose uni‐ form distribution of free gas in the pore space, it is sufficient a small content of free gas to

Recently, the international community has considered CO2 sequestration as a possible means of offsetting the emission of greenhouse gases into the atmosphere [130]. Some stud‐ ies have considered confining CO2 hydrate directly to shallow sediments on the deep sea floor, but this approach would not be permissible under the above international conven‐ tions. In the case of hydrates, several studies have investigated the use of injected CO2 to lib‐

carbonate rocks and decaying biomass) could keep the temperatures elevated.

240 Updates in Volcanology - New Advances in Understanding Volcanic Systems

other reflectors [123].

reduce drastically the velocity.

**Figure 5.** Comparison among different gas hydrate stability models. See text for details.

**Figure 6.** Comparison between two models: the Biot theory (solid red lines; [129]) and the approximation for seismic frequency (green dashed lines; [128]). (a) Compressional (Vp) and shear (Vs) velocity versus gas hydrate concentration in pore space. (b) Vp and Vs versus free gas saturation in pore space, supposing uniform distribution.

Finally, it is worth to mention that gas hydrates cannot survive for long geological times ei‐ ther because buried sediments are submitted to increasing geothermal conditions or are tec‐ tonically uplifted. In fossil sediments, the study of the interaction between seep-carbonates, hydrate destabilization and sediment instability is particularly difficult, owing to the lack of a direct recognition of fluid seepages and to the absence of precise quantifications of paleo‐ environmental factors (pressure, temperature, paleodepth) conditioning hydrate stability conditions [134]. Following present-day analogues, the only means to infer a possible role of gas hydrates in fossil seep-carbonates are geochemical (oxygen isotope signature) and tex‐ tural (presence of distinctive sedimentary features such as breccias, pervasive non-systemat‐ ic fractures, soft sediment deformation) described in clathrites. Additional evidences can derive from the close association between seep-carbonates and sedimentary instability, and the large dimensions of seep-carbonate masses bearing brecciated structures. Recently, [134] studied cold seep-carbonates and associated lithologies in the northern Apennines and high‐ lighted the seepage activity and the possible relationships with gas hydrate destabilization. In this geological context, many seep-carbonates are characterized by negative ∂13C and positive ∂18O values, by various types of brecciated structures and fluid-flow conduits, and are associated with intense sediment instability such as slumps, intraformational breccias and olistostromes.

the gas supply is large enough to create a separate gas phase that migrates upward by buoy‐ ancy. The changes in salinity during hydrate formation are too small for a three-phase zone to develop, and hence all free gas is crystallized as hydrate at the base of the GHSZ (Figure 7, number 3, inset). As hydrate forms, the permeability drops and a capillary seal to gas is formed. In these circumstances, either the gas pressure will build until it frac‐ tures the overlying column, or if there is another pathway present, the gas will flow up‐ ward but underneath the low-permeability cap of the base of the GHSZ (Figure 7). Finally, far from where any methane gas flow is focused but where there is upward flow of wa‐ ter, low concentrations of hydrate may be deposited within the RHSZ but not at its base

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**Figure 7.** Cartoon of the gas hydrate reservoir system. Four characteristic forms of hydrate deposit are shown. (1) Gas chimney sourced by permeable conduits. Gas is focused along permeable conduits beneath the hydrate stability zone. Focused flow penetrates the GHSZ and self-generates a three-phase pathway to vent gas to the seafloor. (2) Gas chim‐ ney sourced by gas trapped beneath the GHSZ. Gas is focused along the base of the GHSZ and trapped beneath the crest of the structure. Gas builds up until it begins to form a chimney through the GHSZ. (3) Capillary sealing and later‐ al migration. On the flanks of the structure, hydrate formation rapidly forms capillary seals to gas and the gas is driven laterally to the highest structural point. (4) Aqueous flow and hydrate formation. Far from the crest, water with dis‐

The simulations of [109] provide insight into how gas chimneys form and sustain them‐ selves within the GHSZ. The penetration of gas into the GHSZ is controlled by a competi‐ tion between the basal supply of gas and the lateral diffusion of salt. The gas flow is driven primarily by buoyancy: as a result, the natural tendency for gas is to flow vertically even when permeability is reduced by hydrate formation. In addition, salt diffusivity is extremely low; thus high salinity zones within chimneys can be maintained for long times, particularly if there is continued supply of gas to form more hydrate and maintain salinity. Finally, later‐ al salt diffusion concentrates hydrate at the margins of the chimney; this further lowers the

solved methane migrates upward and deposits hydrate within the GHSZ. Modified after [109].

salt diffusivity and further limits salt loss.

(Figure 7, number 4, inset).

Many authors have focused their attention on the possible modes of gas hydrate formations. Here, we report the study proposed by [135], which clearly summarized the possible mode of gas hydrate formation and produced a cartoon of gas hydrate system (Figure 7). They en‐ visioned three possible modes of hydrate formation.

First, dipping permeable layers may focus gas flow and drive large amounts of free gas into the regional gas hydrate stability zone (Figure 7, number 1, inset). This is illustrated with a dipping stratigraphic layer in Figure 7; however, the permeability conduit could also be a fault or fracture. Beneath the GHSZ, the permeable layer draws gas from the surrounding material over an extensive source region, because of its high permeability and resultant low capillary entry pressure [136]. In this environment, gas rapidly enters the GHSZ and salinity rises as hydrate forms. The increased salinity inhibits further hydrate formation, which al‐ lows free gas to coexist with hydrate within the GHSZ. This process is repeated and the gas chimney rapidly propagates to the seafloor. Within the chimney, hydrate concentration in‐ creases upward toward the seafloor, where the system is furthest from equilibrium (Figure 7, number 1, inset). At the base of the gas chimney, the BSR will be diminished because gas is continuously present across the base of the GHSZ. These types of gas chimneys may be present, for example, at South Hydrate Ridge [109,137,138], at Blake Ridge [139-142] and along the Norwegian margin [143,144].

A second form of focused gas flow is illustrated in Figure 7 (number 2, inset). In this case, gas concentrates beneath the topographic crest of the seafloor structure. On the flanks of the structure, gas is trapped beneath the low-permeability base of the hydrate stability zone. Buoyancy drives the gas laterally toward the shallowest zone beneath the regional hydrate stability zone. The gas pressure is at a maximum at this location and ultimately the gas will drive its way through the GHSZ creating a gas chimney. As illustrated, the gas vent does not penetrate to the seafloor.

At the flanks of the topographic structures, a low permeability hydrate seal rapidly devel‐ ops at the base of the GHSZ as illustrated in case 3 (Figure 7, number 3, inset). Hy‐ drates are formed when water flows up through the GHSZ. Even in this low-flux example, the gas supply is large enough to create a separate gas phase that migrates upward by buoy‐ ancy. The changes in salinity during hydrate formation are too small for a three-phase zone to develop, and hence all free gas is crystallized as hydrate at the base of the GHSZ (Figure 7, number 3, inset). As hydrate forms, the permeability drops and a capillary seal to gas is formed. In these circumstances, either the gas pressure will build until it frac‐ tures the overlying column, or if there is another pathway present, the gas will flow up‐ ward but underneath the low-permeability cap of the base of the GHSZ (Figure 7). Finally, far from where any methane gas flow is focused but where there is upward flow of wa‐ ter, low concentrations of hydrate may be deposited within the RHSZ but not at its base (Figure 7, number 4, inset).

a direct recognition of fluid seepages and to the absence of precise quantifications of paleo‐ environmental factors (pressure, temperature, paleodepth) conditioning hydrate stability conditions [134]. Following present-day analogues, the only means to infer a possible role of gas hydrates in fossil seep-carbonates are geochemical (oxygen isotope signature) and tex‐ tural (presence of distinctive sedimentary features such as breccias, pervasive non-systemat‐ ic fractures, soft sediment deformation) described in clathrites. Additional evidences can derive from the close association between seep-carbonates and sedimentary instability, and the large dimensions of seep-carbonate masses bearing brecciated structures. Recently, [134] studied cold seep-carbonates and associated lithologies in the northern Apennines and high‐ lighted the seepage activity and the possible relationships with gas hydrate destabilization. In this geological context, many seep-carbonates are characterized by negative ∂13C and positive ∂18O values, by various types of brecciated structures and fluid-flow conduits, and are associated with intense sediment instability such as slumps, intraformational breccias

Many authors have focused their attention on the possible modes of gas hydrate formations. Here, we report the study proposed by [135], which clearly summarized the possible mode of gas hydrate formation and produced a cartoon of gas hydrate system (Figure 7). They en‐

First, dipping permeable layers may focus gas flow and drive large amounts of free gas into the regional gas hydrate stability zone (Figure 7, number 1, inset). This is illustrated with a dipping stratigraphic layer in Figure 7; however, the permeability conduit could also be a fault or fracture. Beneath the GHSZ, the permeable layer draws gas from the surrounding material over an extensive source region, because of its high permeability and resultant low capillary entry pressure [136]. In this environment, gas rapidly enters the GHSZ and salinity rises as hydrate forms. The increased salinity inhibits further hydrate formation, which al‐ lows free gas to coexist with hydrate within the GHSZ. This process is repeated and the gas chimney rapidly propagates to the seafloor. Within the chimney, hydrate concentration in‐ creases upward toward the seafloor, where the system is furthest from equilibrium (Figure 7, number 1, inset). At the base of the gas chimney, the BSR will be diminished because gas is continuously present across the base of the GHSZ. These types of gas chimneys may be present, for example, at South Hydrate Ridge [109,137,138], at Blake Ridge [139-142] and

A second form of focused gas flow is illustrated in Figure 7 (number 2, inset). In this case, gas concentrates beneath the topographic crest of the seafloor structure. On the flanks of the structure, gas is trapped beneath the low-permeability base of the hydrate stability zone. Buoyancy drives the gas laterally toward the shallowest zone beneath the regional hydrate stability zone. The gas pressure is at a maximum at this location and ultimately the gas will drive its way through the GHSZ creating a gas chimney. As illustrated, the gas vent does

At the flanks of the topographic structures, a low permeability hydrate seal rapidly devel‐ ops at the base of the GHSZ as illustrated in case 3 (Figure 7, number 3, inset). Hy‐ drates are formed when water flows up through the GHSZ. Even in this low-flux example,

and olistostromes.

visioned three possible modes of hydrate formation.

242 Updates in Volcanology - New Advances in Understanding Volcanic Systems

along the Norwegian margin [143,144].

not penetrate to the seafloor.

**Figure 7.** Cartoon of the gas hydrate reservoir system. Four characteristic forms of hydrate deposit are shown. (1) Gas chimney sourced by permeable conduits. Gas is focused along permeable conduits beneath the hydrate stability zone. Focused flow penetrates the GHSZ and self-generates a three-phase pathway to vent gas to the seafloor. (2) Gas chim‐ ney sourced by gas trapped beneath the GHSZ. Gas is focused along the base of the GHSZ and trapped beneath the crest of the structure. Gas builds up until it begins to form a chimney through the GHSZ. (3) Capillary sealing and later‐ al migration. On the flanks of the structure, hydrate formation rapidly forms capillary seals to gas and the gas is driven laterally to the highest structural point. (4) Aqueous flow and hydrate formation. Far from the crest, water with dis‐ solved methane migrates upward and deposits hydrate within the GHSZ. Modified after [109].

The simulations of [109] provide insight into how gas chimneys form and sustain them‐ selves within the GHSZ. The penetration of gas into the GHSZ is controlled by a competi‐ tion between the basal supply of gas and the lateral diffusion of salt. The gas flow is driven primarily by buoyancy: as a result, the natural tendency for gas is to flow vertically even when permeability is reduced by hydrate formation. In addition, salt diffusivity is extremely low; thus high salinity zones within chimneys can be maintained for long times, particularly if there is continued supply of gas to form more hydrate and maintain salinity. Finally, later‐ al salt diffusion concentrates hydrate at the margins of the chimney; this further lowers the salt diffusivity and further limits salt loss.

Reference [135] showed that at South Hydrate Ridge, gas is supplied at a rate 10 times great‐ er than is depleted by hydrate formation due to salt diffusion. Salt loss by diffusion, and hence the amount of methane needed to form hydrate to replace the salt, is independent of the vent half-width. In general, if the flux of methane supplied is greater than the loss due to diffusion, a chimney will be created and maintained at three-phase equilibrium (Figure 7, number 1, inset). However if the gas flux supplied is less than the loss due to diffusion, the chimney will only penetrate a short distance within GHSZ and free gas will not reach the seafloor (Figure 7, number 2, inset).

pies) with central 'mud lakes' and elongated, radial mud-flow tongues. In both types, the mud is found to have a plastic behavior in which its yield strength decreases with increasing porosity. Thixotropy is associated with high porosity (e.g. more than 70%), which is often related to the dissociation of gas hydrate [151]. Often, mud volcanoes are associated with methane fluxes, either as free gas or, depending on ambient temperature and pressure con‐ ditions, as gas hydrate [54,152]. On this basis, Reference [14] argue that the global flux of methane to the atmosphere from the world's terrestrial and submarine mud volcanoes is highly significant. The relative difficulty in studying submarine mud volcanoes, compared with their terrestrial counterparts, leaves substantial gaps in our knowledge about their modes of formation, the duration and frequency of eruptions and the fluxes of mud and vol‐ atile phases from the subsurface. For this reason, several efforts are spend to simulate nu‐

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At the present time, evidence for submarine mud volcanoes has been found in all oceans (Figure 1). For instance, in shallow water areas (shelves) where mud islands are recorded, submarine mud volcanoes are likely to be present. However, there are regions where the ex‐ istence of submarine mud volcanoes is unexpected, such as in the Baltic Sea, where sedi‐ ments are only 10 m thick, but miniature mud diapirs/volcanoes (1.5 m in diameter, 30 cm high above the surrounding seafloor) are reported [154,155]. Figure 1 includes sediment dia‐ pirs reported in [33]; however, it is unclear whether all these sediment diapirs are mud vol‐

canoes. Submarine mud volcanoes are more extensive than their sub-aerial analogs.

All the regions where submarine mud volcanoes or evidence for them have been ob‐ served are confined to shelves, continental and insular slopes, and abyssal parts of in‐ land seas (e.g. Black and Caspian). The examination of geologic and tectonic features of these areas is crucial for the understanding of the mechanisms of mud volcanic ac‐ tivity. In the abyssal parts of inland seas, mud volcanoes have been found in the Cas‐ pian Sea and in the Black Sea where the sedimentary cover is typically thick (10–20 km) for these regions. Sediments are mostly terrigenous and were deposited during Ter‐ tiary and recent times under high subsidence and accumulation rates. Shale diapirs and

On the continental slopes of passive margins, submarine mud volcanoes have been found in the Norwegian Sea, offshore Nigeria and in the Gulf of Mexico. In the first two cases, mud volcanic activity is confined to submarine fans (the Bear Island Trough mouth fan and the Niger Delta are notable examples), composed of Tertiary terrigenous sediments deposited at a high accumulation rate. In the Niger Delta there are many diapirs and faults [156]. The continental slope of the Gulf of Mexico is an extremely complex deep-water region charac‐ terized by a combination of rapid sediment influx, faulting, and diapiric (salt and shale) tec‐

At active margins, submarine mud volcanoes have been reliably identified in the Mediterra‐ nean Sea and offshore Barbados, both characterized by different geologic and tectonic set‐ tings. In the Mediterranean Sea, mud volcanoes have been found only within the limits of the accretionary prism, characterized by a complex fabric composed of many thrusts [28]. Offshore Barbados mud volcanoes are located within the limits of the accretionary prism as

merically the formation of submarine mud volcanoes [i.e., 153].

faults deform many sedimentary sequences.

tonism [157].

### **4. The gas hydrate in submarine mud volcanoes**

The jointly occurrence of submarine mud volcanoes and gas hydrate has been reported by many authors in world-wide [i.e. 26,42,145-148]. For example, on the upper continental slope of the Gulf of Mexico, active gas migrations along faults or at mud volcanoes have been identified and their sources attributed to accumulated gas hydrates [53,149]. Reference [12] estimated that methane accumulated in gas hydrate associated with mud volcanoes is about 1010 ~ 1012 m3 at normal temperature and pressure. Reference [150] estimated that up to 40% of total United Kingdom methane emission was from the continental shelf around UK. It is therefore important to investigate marine gassy sediments and submarine mud vol‐ canoes to better understand the dynamics of shallow-water methane transport, fluid migra‐ tion and the relationship of these phenomena to gas hydrate.

Firstly, we recall an important review of submarine mud volcanoes reported in Reference [12], reporting the main points. Evidence for submarine mud volcanoes exists in many re‐ gions showing the following features:

Submarine mud volcanoes occur world-wide on continental shelves, slopes and in the abys‐ sal parts of inland seas. Some studies (i.e. from the Barbados accretionary complex [54,151]) have linked the morphology of submarine mud volcanoes to different development stages and processes of mud liquefaction. Conical-shaped mud volcanoes ('mud-mounds' or gry‐ phons), which do not have any central summit 'mud lakes' (or salses), are formed by the ex‐ pulsion of plastic mud breccia in concentric radial flows. In contrast, shearing with the feeder conduit liquefies the mud leading to the formation of flat-top mud volcanoes (mudpies) with central 'mud lakes' and elongated, radial mud-flow tongues. In both types, the mud is found to have a plastic behavior in which its yield strength decreases with increasing porosity. Thixotropy is associated with high porosity (e.g. more than 70%), which is often related to the dissociation of gas hydrate [151]. Often, mud volcanoes are associated with methane fluxes, either as free gas or, depending on ambient temperature and pressure con‐ ditions, as gas hydrate [54,152]. On this basis, Reference [14] argue that the global flux of methane to the atmosphere from the world's terrestrial and submarine mud volcanoes is highly significant. The relative difficulty in studying submarine mud volcanoes, compared with their terrestrial counterparts, leaves substantial gaps in our knowledge about their modes of formation, the duration and frequency of eruptions and the fluxes of mud and vol‐ atile phases from the subsurface. For this reason, several efforts are spend to simulate nu‐ merically the formation of submarine mud volcanoes [i.e., 153].

Reference [135] showed that at South Hydrate Ridge, gas is supplied at a rate 10 times great‐ er than is depleted by hydrate formation due to salt diffusion. Salt loss by diffusion, and hence the amount of methane needed to form hydrate to replace the salt, is independent of the vent half-width. In general, if the flux of methane supplied is greater than the loss due to diffusion, a chimney will be created and maintained at three-phase equilibrium (Figure 7, number 1, inset). However if the gas flux supplied is less than the loss due to diffusion, the chimney will only penetrate a short distance within GHSZ and free gas will not reach the

The jointly occurrence of submarine mud volcanoes and gas hydrate has been reported by many authors in world-wide [i.e. 26,42,145-148]. For example, on the upper continental slope of the Gulf of Mexico, active gas migrations along faults or at mud volcanoes have been identified and their sources attributed to accumulated gas hydrates [53,149]. Reference [12] estimated that methane accumulated in gas hydrate associated with mud volcanoes is

to 40% of total United Kingdom methane emission was from the continental shelf around UK. It is therefore important to investigate marine gassy sediments and submarine mud vol‐ canoes to better understand the dynamics of shallow-water methane transport, fluid migra‐

Firstly, we recall an important review of submarine mud volcanoes reported in Reference [12], reporting the main points. Evidence for submarine mud volcanoes exists in many re‐

**1.** subcircular structures up to several kilometers in diameter elevated above the sur‐

**3.** fluid expulsion above elevated seafloor structures revealed by acoustic profiles and through visual observations from a submersible, remote operated vehicle (ROV), or by

Submarine mud volcanoes occur world-wide on continental shelves, slopes and in the abys‐ sal parts of inland seas. Some studies (i.e. from the Barbados accretionary complex [54,151]) have linked the morphology of submarine mud volcanoes to different development stages and processes of mud liquefaction. Conical-shaped mud volcanoes ('mud-mounds' or gry‐ phons), which do not have any central summit 'mud lakes' (or salses), are formed by the ex‐ pulsion of plastic mud breccia in concentric radial flows. In contrast, shearing with the feeder conduit liquefies the mud leading to the formation of flat-top mud volcanoes (mud-

rounding seafloor and visible on bathymetric maps and/or sonar images;

**5.** gas bubbles at the surface of water that may be related to mud volcanoes.

at normal temperature and pressure. Reference [150] estimated that up

seafloor (Figure 7, number 2, inset).

gions showing the following features:

underwater video-camera;

**4.** transient mud islands in shallow waters;

about 1010 ~ 1012 m3

**4. The gas hydrate in submarine mud volcanoes**

244 Updates in Volcanology - New Advances in Understanding Volcanic Systems

tion and the relationship of these phenomena to gas hydrate.

**2.** seafloor-piercing shale diapirs visible on seismic profiles;

At the present time, evidence for submarine mud volcanoes has been found in all oceans (Figure 1). For instance, in shallow water areas (shelves) where mud islands are recorded, submarine mud volcanoes are likely to be present. However, there are regions where the ex‐ istence of submarine mud volcanoes is unexpected, such as in the Baltic Sea, where sedi‐ ments are only 10 m thick, but miniature mud diapirs/volcanoes (1.5 m in diameter, 30 cm high above the surrounding seafloor) are reported [154,155]. Figure 1 includes sediment dia‐ pirs reported in [33]; however, it is unclear whether all these sediment diapirs are mud vol‐ canoes. Submarine mud volcanoes are more extensive than their sub-aerial analogs.

All the regions where submarine mud volcanoes or evidence for them have been ob‐ served are confined to shelves, continental and insular slopes, and abyssal parts of in‐ land seas (e.g. Black and Caspian). The examination of geologic and tectonic features of these areas is crucial for the understanding of the mechanisms of mud volcanic ac‐ tivity. In the abyssal parts of inland seas, mud volcanoes have been found in the Cas‐ pian Sea and in the Black Sea where the sedimentary cover is typically thick (10–20 km) for these regions. Sediments are mostly terrigenous and were deposited during Ter‐ tiary and recent times under high subsidence and accumulation rates. Shale diapirs and faults deform many sedimentary sequences.

On the continental slopes of passive margins, submarine mud volcanoes have been found in the Norwegian Sea, offshore Nigeria and in the Gulf of Mexico. In the first two cases, mud volcanic activity is confined to submarine fans (the Bear Island Trough mouth fan and the Niger Delta are notable examples), composed of Tertiary terrigenous sediments deposited at a high accumulation rate. In the Niger Delta there are many diapirs and faults [156]. The continental slope of the Gulf of Mexico is an extremely complex deep-water region charac‐ terized by a combination of rapid sediment influx, faulting, and diapiric (salt and shale) tec‐ tonism [157].

At active margins, submarine mud volcanoes have been reliably identified in the Mediterra‐ nean Sea and offshore Barbados, both characterized by different geologic and tectonic set‐ tings. In the Mediterranean Sea, mud volcanoes have been found only within the limits of the accretionary prism, characterized by a complex fabric composed of many thrusts [28]. Offshore Barbados mud volcanoes are located within the limits of the accretionary prism as well as in front of the prism where the thickness of sedimentary cover is only 2.3 km [158]. The majority of reported evidence of submarine mud volcanoes presents at active margins.

fluids that have risen from the deep subsurface. This fluid is warmer than the surrounding sediments (by up to 15–20° C at the sub-bottom depth of 1 m) and contains gas in solution and perhaps as a free phase. Gas hydrates crystallize from this warm fluid when it becomes cold and the solubility of gas decreases [164]. Both water and gas participating in the forma‐ tion of gas hydrates have come from the deep, external fluid that filters through mud vol‐ canic sediments. This process is analogous to the conventional low-temperature

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247

At the peripheral part of the mud volcano, gas hydrates form from the gas that emanates from the central part of the mud volcano, and is transported in solution by diffusion. On the other hand, the water participating in the formation of gas hydrates is contained in the host sediments (local water). In addition, some local biochemical gas may be captured in gas hy‐ drates. Thus, in this case the local water is partly replaced by gas hydrates due to the supply of gas from an external source (mud volcanic fluid). This process of gas hydrate formation is analogous to the conventional metasomatic process of mineral formation [165]. At any point between the central and peripheral parts of the mud volcano, mixing of hydrothermal and metasomatic processes is possible. The source of water (mud volcanic or local) determines

The close proximity of mud volcanoes to zones where BSRs crop out on the seafloor de‐ serves particular attention. Seismic records strongly suggest that much of the gas in mud volcanoes originates from levels deeper than that of the gas hydrates and faulting could be responsible for this unique situation. It has been argued that, in the case that a concentric zonal distribution of hydrate is present, the gas hydrates have probably been formed by gas emanating from the central part of the mud volcano, and transported into solution by diffu‐ sion [12]. For example, a strong BSR and the presence of mud volcanoes have recently been detected by seismic data along the southwest African margin, which is a passive margin [166]. This region, located in the distal part of the Orange River delta, is also characterized by overpressure which results in active fluid expulsion, as shown by the existence of mud volcanoes, pockmarks, and possibly cold-water corals thriving on methane gas seeps [167].

The global climate change is particularly amplified in transition zones, such as the peri-Ant‐ arctic regions. For this reason, the gas hydrate reservoir present offshore Antarctic Peninsula was studied in the last 20 years acquiring a quite extensive geophysical dataset. The pres‐ ence of a diffused and discontinuous BSR was discovered during the Italian Antarctic cruis‐ es of 1989–1990 [i.e., 30] and 1996–1997 [122], onboard the R/V OGS Explora. Seismic data showed the existence of a potential gas hydrate reservoir [32,168] along the South Shetland margin. Along this margin, the extent of the BSR was mapped based on about 1,000 km of seismic lines [e.g.,168 and references therein]. Ocean bottom seismometers (OBSs) deployed during the 1996–1997 cruise provided energy arrivals from the BSR and the refraction and the converted waves from the base of the free-gas zone, the so-called base of the free gas re‐

hydrothermal process of mineral formation [165].

which of these two processes is dominant.

**5. An example: The Antarctic Peninsula**

The association of gas hydrates with submarine mud volcanoes was first noted by Reference [145] and has since observed in the Caspian [42], Black [27,146-148], Mediterranean [57,148], Norwegian seas [48,58], offshore Barbados [159], offshore Nigeria [160] and in the Gulf of Mexico [161,162].

**Figure 8.** Cartoon showing the proposed model of the formation of gas hydrates within a mud volcano: (a) hydrother‐ mal process dominates around the central part of the mud volcano; (b) metasomatic process dominates at the periph‐ erical part of the mud volcano. Modified after [12].

There are many common features of gas hydrates associated with mud volcanoes. Gas hy‐ drate content in sediments varies from 1–2% to 35% by volume and changes through a mud volcano area as well as through depth. Methane is the major gas component of gas hydrates and can be thermogenic, biogenic or mixed in origin. Reference [12] proposed a model for the formation of gas hydrates within a mud volcano: (a) hydrothermal process dominates around the central part of the mud volcano; (b) metasomatic process dominates at the pe‐ ripherical part of the mud volcano (Figure 8). This generalized model is based mainly on da‐ ta from the Haakon Mosby mud volcano in the Norwegian Sea, which is the most famous mud volcano characterized by a concentric-zonal distribution of gas hydrates [58,163]. Gas hydrate accumulation is controlled by the ascending flow of warm fluids. The water from the mud volcanic fluid as well as from the surrounding recent sediments is involved in the formation of gas hydrates. So, gas hydrates can occur within the edifice of a mud volcano (crater and hummocky periphery) as well as outside in the host marine sediments. Howev‐ er, the processes that are responsible for the formation of gas hydrates differ from point to point. Note that in Figure 8 there are no gas hydrates in the central part of the model mud volcano (usually in the central part of a crater where mud and fluid flow out) because of the high temperature. Around the central part of the mud volcano, gas hydrates form from the fluids that have risen from the deep subsurface. This fluid is warmer than the surrounding sediments (by up to 15–20° C at the sub-bottom depth of 1 m) and contains gas in solution and perhaps as a free phase. Gas hydrates crystallize from this warm fluid when it becomes cold and the solubility of gas decreases [164]. Both water and gas participating in the forma‐ tion of gas hydrates have come from the deep, external fluid that filters through mud vol‐ canic sediments. This process is analogous to the conventional low-temperature hydrothermal process of mineral formation [165].

At the peripheral part of the mud volcano, gas hydrates form from the gas that emanates from the central part of the mud volcano, and is transported in solution by diffusion. On the other hand, the water participating in the formation of gas hydrates is contained in the host sediments (local water). In addition, some local biochemical gas may be captured in gas hy‐ drates. Thus, in this case the local water is partly replaced by gas hydrates due to the supply of gas from an external source (mud volcanic fluid). This process of gas hydrate formation is analogous to the conventional metasomatic process of mineral formation [165]. At any point between the central and peripheral parts of the mud volcano, mixing of hydrothermal and metasomatic processes is possible. The source of water (mud volcanic or local) determines which of these two processes is dominant.

The close proximity of mud volcanoes to zones where BSRs crop out on the seafloor de‐ serves particular attention. Seismic records strongly suggest that much of the gas in mud volcanoes originates from levels deeper than that of the gas hydrates and faulting could be responsible for this unique situation. It has been argued that, in the case that a concentric zonal distribution of hydrate is present, the gas hydrates have probably been formed by gas emanating from the central part of the mud volcano, and transported into solution by diffu‐ sion [12]. For example, a strong BSR and the presence of mud volcanoes have recently been detected by seismic data along the southwest African margin, which is a passive margin [166]. This region, located in the distal part of the Orange River delta, is also characterized by overpressure which results in active fluid expulsion, as shown by the existence of mud volcanoes, pockmarks, and possibly cold-water corals thriving on methane gas seeps [167].

### **5. An example: The Antarctic Peninsula**

well as in front of the prism where the thickness of sedimentary cover is only 2.3 km [158]. The majority of reported evidence of submarine mud volcanoes presents at active margins.

246 Updates in Volcanology - New Advances in Understanding Volcanic Systems

The association of gas hydrates with submarine mud volcanoes was first noted by Reference [145] and has since observed in the Caspian [42], Black [27,146-148], Mediterranean [57,148], Norwegian seas [48,58], offshore Barbados [159], offshore Nigeria [160] and in the Gulf of

**Figure 8.** Cartoon showing the proposed model of the formation of gas hydrates within a mud volcano: (a) hydrother‐ mal process dominates around the central part of the mud volcano; (b) metasomatic process dominates at the periph‐

There are many common features of gas hydrates associated with mud volcanoes. Gas hy‐ drate content in sediments varies from 1–2% to 35% by volume and changes through a mud volcano area as well as through depth. Methane is the major gas component of gas hydrates and can be thermogenic, biogenic or mixed in origin. Reference [12] proposed a model for the formation of gas hydrates within a mud volcano: (a) hydrothermal process dominates around the central part of the mud volcano; (b) metasomatic process dominates at the pe‐ ripherical part of the mud volcano (Figure 8). This generalized model is based mainly on da‐ ta from the Haakon Mosby mud volcano in the Norwegian Sea, which is the most famous mud volcano characterized by a concentric-zonal distribution of gas hydrates [58,163]. Gas hydrate accumulation is controlled by the ascending flow of warm fluids. The water from the mud volcanic fluid as well as from the surrounding recent sediments is involved in the formation of gas hydrates. So, gas hydrates can occur within the edifice of a mud volcano (crater and hummocky periphery) as well as outside in the host marine sediments. Howev‐ er, the processes that are responsible for the formation of gas hydrates differ from point to point. Note that in Figure 8 there are no gas hydrates in the central part of the model mud volcano (usually in the central part of a crater where mud and fluid flow out) because of the high temperature. Around the central part of the mud volcano, gas hydrates form from the

Mexico [161,162].

erical part of the mud volcano. Modified after [12].

The global climate change is particularly amplified in transition zones, such as the peri-Ant‐ arctic regions. For this reason, the gas hydrate reservoir present offshore Antarctic Peninsula was studied in the last 20 years acquiring a quite extensive geophysical dataset. The pres‐ ence of a diffused and discontinuous BSR was discovered during the Italian Antarctic cruis‐ es of 1989–1990 [i.e., 30] and 1996–1997 [122], onboard the R/V OGS Explora. Seismic data showed the existence of a potential gas hydrate reservoir [32,168] along the South Shetland margin. Along this margin, the extent of the BSR was mapped based on about 1,000 km of seismic lines [e.g.,168 and references therein]. Ocean bottom seismometers (OBSs) deployed during the 1996–1997 cruise provided energy arrivals from the BSR and the refraction and the converted waves from the base of the free-gas zone, the so-called base of the free gas re‐ flector or BGR [122]. During the austral summer 2003-2004, additional data were acquired in the same area: multibeam bathymetry, seismic profiles, chirp, and sediment gravity cores [31]. Figure 9 summarizes the position of the three acquisition legs.

**Figure 9.** Left: Multibeam bathymetry map after [169], showing the locations of the seismic lines acquired in 1990 (dashed lines) and 1997 (continuous lines). The dot indicates the location of the OBS data acquired in 1997. The yel‐ low box presents the 2004 study area. Right: 2004 study area. Continuous blue lines: locations of the airgun seismic lines. Dotted black lines: location of seismic lines of 1990 and 1997 legs. Thick dashed segments indicate the presence of particularly well developed BSRs. Also annotated are the CTD measurements (red stars), and the two coring sites (grey and black arrows cores GC01 and GC02 respectively). Modified after [31].

**Figure 10.** Multibeam bathymetry map of the study area, showing evidence of mud volcanoes (open arrows), collapse troughs (closed arrows) and slides (dashed arrows). The numbers indicate the four mud volcano ridges described in

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249

Reference [31] reported the main results obtained by the analysis of bathymetric data, CHIRP data and gravity core analysis. In particular, the bathymetric map provided the evi‐ dences of mud volcanoes, collapse troughs and slides (Figure 10). It is well known [i.e., 172] that these features are generally associated to the presence of gas hydrate, as already ex‐ plained. Reference [31] have recognized five main mud volcano ridges, named Chiavalz, Flop, Grauzaria, Sernio and Vualt (see location map in Figure 10). Table 1 reports the main characteristics of the mud volcanoes (Figures 11-15). The Vualt mud volcano is the highest detected in our study area; its top is at 2,216 m below sea level, with an elevation of about 255 m above the seafloor and an extension of 9.4 km2 (Figure 10, label 5; Figure 11). On the flank, a gravity core (GC02) was recovered. The Flop mud volcano has its top at 2,363 m be‐ low sea level and a relief of about 115 m. Its extension is 7.5 km2 (Figure 10, label 2; Figure 12). The Grauzaria ridge, oriented W–E and located at around 61 S–57 W (Figure 10; label 3; Figure 13), can be considered an alignment with several culminations and a total extension

. The highest culmination is at 2,594 m below sea level and exhibits a relief of

about 185 m above the seafloor. The Sernio mud volcano ridge is located in the proximity of core GC01 and is oriented SW–NE (Figure 10, label 4; Figure 14). Its top is at 1,990 m below sea level with an elevation of about 185 m. It presents several culminations for a total exten‐

the text and in Table 1. Modified after [31]*.*

of 45.9 km2

As already explained, seismic velocity obtained from advanced seismic analysis can be translated in terms of concentrations of gas hydrate and free gas. This procedure has been applied in the Antarctic Peninsula, where seismic velocities obtained from advanced analy‐ sis of multichannel seismic data were analyzed to determine gas hydrate and free-gas distri‐ butions and to estimate the methane volumetric fraction trapped in the sediments [170]. The elastic properties of the layers across the BSR were modeled applying the approximation of the Biot equations for seismic frequency in order to quantify the concentrations of gas hy‐ drate and free gas in the pore space [128]. This theory considers two solid phases - grains and hydrates - and two fluid phases - water and free gas - including an explicit dependence on differential pressure and depth, and the effects of cementation by hydration on the shear modulus of the sediment matrix. So, the seismic velocities of the 2D seismic lines were trans‐ lated in terms of concentrations of gas hydrate and free gas in the pore space, obtaining 2D models. The jointly interpolation of the 2D models allowed obtaining a 3D model of gas hy‐ drate concentration from the seafloor to the BSR. The total volume of hydrate, estimated in the area (600 km2 ) where the interpolation is reliable, is 16 × 109 m3 . The gas hydrate concen‐ tration is affected by errors that could be equal to about ±25%, as deduced from sensitivity tests [31,171] and from error analysis related to the interpolation procedure. The estimated amount of gas hydrate can vary in a range of 12 × 109 - 20 × 109 m3 . Moreover, considering that 1 m3 of gas hydrate corresponds to 140 m3 of free gas in standard conditions, the total free gas trapped in this reservoir ranges between 1.68 × 1012 and 2.8 × 1012 m3 . This estima‐ tion does not take into account the free gas contained within pore space below the hydrate layer, so this values could be underestimated.

flector or BGR [122]. During the austral summer 2003-2004, additional data were acquired in the same area: multibeam bathymetry, seismic profiles, chirp, and sediment gravity cores

**Figure 9.** Left: Multibeam bathymetry map after [169], showing the locations of the seismic lines acquired in 1990 (dashed lines) and 1997 (continuous lines). The dot indicates the location of the OBS data acquired in 1997. The yel‐ low box presents the 2004 study area. Right: 2004 study area. Continuous blue lines: locations of the airgun seismic lines. Dotted black lines: location of seismic lines of 1990 and 1997 legs. Thick dashed segments indicate the presence of particularly well developed BSRs. Also annotated are the CTD measurements (red stars), and the two coring sites

As already explained, seismic velocity obtained from advanced seismic analysis can be translated in terms of concentrations of gas hydrate and free gas. This procedure has been applied in the Antarctic Peninsula, where seismic velocities obtained from advanced analy‐ sis of multichannel seismic data were analyzed to determine gas hydrate and free-gas distri‐ butions and to estimate the methane volumetric fraction trapped in the sediments [170]. The elastic properties of the layers across the BSR were modeled applying the approximation of the Biot equations for seismic frequency in order to quantify the concentrations of gas hy‐ drate and free gas in the pore space [128]. This theory considers two solid phases - grains and hydrates - and two fluid phases - water and free gas - including an explicit dependence on differential pressure and depth, and the effects of cementation by hydration on the shear modulus of the sediment matrix. So, the seismic velocities of the 2D seismic lines were trans‐ lated in terms of concentrations of gas hydrate and free gas in the pore space, obtaining 2D models. The jointly interpolation of the 2D models allowed obtaining a 3D model of gas hy‐ drate concentration from the seafloor to the BSR. The total volume of hydrate, estimated in

) where the interpolation is reliable, is 16 × 109

free gas trapped in this reservoir ranges between 1.68 × 1012 and 2.8 × 1012 m3

amount of gas hydrate can vary in a range of 12 × 109

layer, so this values could be underestimated.

of gas hydrate corresponds to 140 m3

tration is affected by errors that could be equal to about ±25%, as deduced from sensitivity tests [31,171] and from error analysis related to the interpolation procedure. The estimated

tion does not take into account the free gas contained within pore space below the hydrate

m3

of free gas in standard conditions, the total

. The gas hydrate concen‐

. Moreover, considering

. This estima‐

[31]. Figure 9 summarizes the position of the three acquisition legs.

248 Updates in Volcanology - New Advances in Understanding Volcanic Systems

(grey and black arrows cores GC01 and GC02 respectively). Modified after [31].

the area (600 km2

that 1 m3

**Figure 10.** Multibeam bathymetry map of the study area, showing evidence of mud volcanoes (open arrows), collapse troughs (closed arrows) and slides (dashed arrows). The numbers indicate the four mud volcano ridges described in the text and in Table 1. Modified after [31]*.*

Reference [31] reported the main results obtained by the analysis of bathymetric data, CHIRP data and gravity core analysis. In particular, the bathymetric map provided the evi‐ dences of mud volcanoes, collapse troughs and slides (Figure 10). It is well known [i.e., 172] that these features are generally associated to the presence of gas hydrate, as already ex‐ plained. Reference [31] have recognized five main mud volcano ridges, named Chiavalz, Flop, Grauzaria, Sernio and Vualt (see location map in Figure 10). Table 1 reports the main characteristics of the mud volcanoes (Figures 11-15). The Vualt mud volcano is the highest detected in our study area; its top is at 2,216 m below sea level, with an elevation of about 255 m above the seafloor and an extension of 9.4 km2 (Figure 10, label 5; Figure 11). On the flank, a gravity core (GC02) was recovered. The Flop mud volcano has its top at 2,363 m be‐ low sea level and a relief of about 115 m. Its extension is 7.5 km2 (Figure 10, label 2; Figure 12). The Grauzaria ridge, oriented W–E and located at around 61 S–57 W (Figure 10; label 3; Figure 13), can be considered an alignment with several culminations and a total extension of 45.9 km2 . The highest culmination is at 2,594 m below sea level and exhibits a relief of about 185 m above the seafloor. The Sernio mud volcano ridge is located in the proximity of core GC01 and is oriented SW–NE (Figure 10, label 4; Figure 14). Its top is at 1,990 m below sea level with an elevation of about 185 m. It presents several culminations for a total exten‐ sion of 23.9 km2 . Finally, the Chiavalz mud volcano ridge is located in the northeast of our survey area (Figure 10; label 1; Figure 15) and is oriented S–NE. It has its top at 1,615 m be‐ low sea level, a maximum elevation of about 210 m, and an extension of 14.5 km2 .

depths in both cores, with quite similar contents. Below the upper 1 m of sediment in core GC02, the interstitial gases are essentially composed of pentane. The average total gas con‐ tent amounts to 150.54 and 49.30 µg/kg for the two cores, respectively. The gas content measured in core GC01 is therefore about three times higher than that measured in core GC02. Downcore profiles for specific gases showed that core GC01 has a quite uniform gas type and content along the whole core; on the contrary, core GC02 has variable gas content. Even if both cores are located in the proximity of mud volcanoes, Reference [31] suggested that the sediment permeability of core GC01 is lower than that of core GC02, in which the fluids can easily escape and produce a collapse trough (see closed arrows in Figure 10). Moreover, the sediment stiffness in core GC01 is higher than that of core GC02, as suggested also by the different core length (1.07 and 2.98 m respectively); this is in agreement with the

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251

In conclusion, interpretation of the data acquired on the South Shetland margin confirmed the crucial role of tectonics controlling the extent of the hydrate reservoir, and active venting of fluids and mud through faults bordering and crossing the gas hydrate field. Mud volca‐ noes and fluid expulsion events are likely located in close association with faults, through which they are connected to the reservoir located beneath the BSR. Their activity is probably episodic [31]. Moreover, the different sediment stiffness at the two coring sites can be related to the temporal frequency of expulsion events, where the hardness of the mud volcano flanks is directly proportional to the interval between expulsion events, as suggested by [173]. Finally, the hydrocarbons trapped in our sediment cores possibly indicate the exis‐

**Figure 12.** CHIRP image of the Flop. Insert: Bathymetric map after BSR project. The red line indicates the CHIRP loca‐

hypothesis of different permeability values between the two cores.

tence of deeper reserves.

tion.

**Table 1.** Details of the mud volcanoes offshore Antarctic Peninsula: latitude and longitude of the midpoint, water depth at the top, elevation with respect to the bathymetry and extension. Grauzaria is a group of several mud volcanoes.

**Figure 11.** Comparison between chirp (a) and airgun (b) data across the Vualt mud volcano, in which the BSR is evi‐ dent. The arrow indicates the location of core GC02. CHIRP image of the Vualt. Insert: Bathymetric map after BSR project. The red line indicates the CHIRP location. After [31].

Fluid analyses performed on the two gravity cores [31] revealed the presence of several hy‐ drocarbon gases, i.e. methane, ethane, propane, butane, pentane and hexane, and traces of aromatic hydrocarbons of > C12 carbon chain length, suggesting a thermogenic origin of the gas. The major difference in gas contents between the two cores is that methane and pro‐ pane are totally absent in core GC02. On the contrary, pentane is present at all analyzed depths in both cores, with quite similar contents. Below the upper 1 m of sediment in core GC02, the interstitial gases are essentially composed of pentane. The average total gas con‐ tent amounts to 150.54 and 49.30 µg/kg for the two cores, respectively. The gas content measured in core GC01 is therefore about three times higher than that measured in core GC02. Downcore profiles for specific gases showed that core GC01 has a quite uniform gas type and content along the whole core; on the contrary, core GC02 has variable gas content. Even if both cores are located in the proximity of mud volcanoes, Reference [31] suggested that the sediment permeability of core GC01 is lower than that of core GC02, in which the fluids can easily escape and produce a collapse trough (see closed arrows in Figure 10). Moreover, the sediment stiffness in core GC01 is higher than that of core GC02, as suggested also by the different core length (1.07 and 2.98 m respectively); this is in agreement with the hypothesis of different permeability values between the two cores.

sion of 23.9 km2

volcanoes.

. Finally, the Chiavalz mud volcano ridge is located in the northeast of our

**seafloor of the top**

.

**Elevation (m) Extension (km2)**

survey area (Figure 10; label 1; Figure 15) and is oriented S–NE. It has its top at 1,615 m be‐

low sea level, a maximum elevation of about 210 m, and an extension of 14.5 km2

*1 Chiavalz* 60 52 29.31 S 56 18 46.88 W 1615 210 14.5 *2 Flop* 61 01 40.52 S 56 45 11.88 W 2363 115 7.5 *3 Grauzaria* 61 01 31.44 S 56 56 36.64 W 2594 185 45.9 *4 Sernio* 60 51 54.73 S 56 28 19.10 W 1990 185 23.9 *5 Vualt* 61 04 30.63 S 56 43 02.71 W 2216 255 9.4

**Table 1.** Details of the mud volcanoes offshore Antarctic Peninsula: latitude and longitude of the midpoint, water depth at the top, elevation with respect to the bathymetry and extension. Grauzaria is a group of several mud

**Figure 11.** Comparison between chirp (a) and airgun (b) data across the Vualt mud volcano, in which the BSR is evi‐ dent. The arrow indicates the location of core GC02. CHIRP image of the Vualt. Insert: Bathymetric map after BSR

Fluid analyses performed on the two gravity cores [31] revealed the presence of several hy‐ drocarbon gases, i.e. methane, ethane, propane, butane, pentane and hexane, and traces of aromatic hydrocarbons of > C12 carbon chain length, suggesting a thermogenic origin of the gas. The major difference in gas contents between the two cores is that methane and pro‐ pane are totally absent in core GC02. On the contrary, pentane is present at all analyzed

project. The red line indicates the CHIRP location. After [31].

**Mud Volcano Lat. (WGS84) Lon. (WGS84) Meter below**

250 Updates in Volcanology - New Advances in Understanding Volcanic Systems

In conclusion, interpretation of the data acquired on the South Shetland margin confirmed the crucial role of tectonics controlling the extent of the hydrate reservoir, and active venting of fluids and mud through faults bordering and crossing the gas hydrate field. Mud volca‐ noes and fluid expulsion events are likely located in close association with faults, through which they are connected to the reservoir located beneath the BSR. Their activity is probably episodic [31]. Moreover, the different sediment stiffness at the two coring sites can be related to the temporal frequency of expulsion events, where the hardness of the mud volcano flanks is directly proportional to the interval between expulsion events, as suggested by [173]. Finally, the hydrocarbons trapped in our sediment cores possibly indicate the exis‐ tence of deeper reserves.

**Figure 12.** CHIRP image of the Flop. Insert: Bathymetric map after BSR project. The red line indicates the CHIRP loca‐ tion.

recovery [174]. In this context, the gas hydrate associated to mud volcanoes is a very inter‐ esting topic because this system contains high gas hydrate concentration in a very small area. In addition, gas hydrate accumulations related to fluid discharges sites (including mud volcanoes) occur at very shallow depths or on the seafloor and show the maximum hydrate content in their upper parts. These features may consider as natural reactors, in which part of the migrating gas from the surrounding areas is stabilized in gas hydrates. Gas resources in such accumulations are therefore renewable and could become important gas hydrate for‐

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

253

Moreover, the wide and extensive literature about hydrate, mud volcanism and their in‐ teraction suggests that this topic is timely because gas hydrates may play an impor‐ tant role in the global carbon cycle and global climate dynamics through emissions of methane and in affecting stability of geological features, including mud volcanoes. The role of gas hydrates in above-mentioned processes cannot be assessed accurately with‐ out a better understanding of the hydrate reservoir and their interactions with geolog‐ ical features and meaningful estimates of the amount of methane it contains. In conclusion, lack of knowledge hampers the evaluation of the resource potential of gas hydrates and the hazards related to gas hydrates, requiring efforts to improved knowledge about

**Figure 15.** CHIRP images of the Chiavalz mud volcano. Insert: Bathymetric map after BSR project. The red line indicates

We wish to thank Manuela Sedmach for graphic support. This work is partially supported

by Programma Nazionale di Ricerche in Antartide, project CLISM.

mations to be exploited [11].

the CHIRP location.

**Acknowledgements**

gas hydrate and their interaction with mud volcanoes.

**Figure 13.** CHIRP images of the Grauzaria group. Insert: Bathymetric map after BSR project. The red line indicates the CHIRP location.

**Figure 14.** CHIRP images of the Sernio mud volcano. Insert: Bathymetric map after BSR project. The red line indicates the CHIRP location.

### **6. Conclusions**

Knowledge of natural occurring gas hydrate is increasing rapidly in the last years; however commercialization of gas hydrate remains unproven. Great uncertainty of the global gas hy‐ drate resource and imitated estimates of hydrate system retard economic analysis of hydrate recovery [174]. In this context, the gas hydrate associated to mud volcanoes is a very inter‐ esting topic because this system contains high gas hydrate concentration in a very small area. In addition, gas hydrate accumulations related to fluid discharges sites (including mud volcanoes) occur at very shallow depths or on the seafloor and show the maximum hydrate content in their upper parts. These features may consider as natural reactors, in which part of the migrating gas from the surrounding areas is stabilized in gas hydrates. Gas resources in such accumulations are therefore renewable and could become important gas hydrate for‐ mations to be exploited [11].

Moreover, the wide and extensive literature about hydrate, mud volcanism and their in‐ teraction suggests that this topic is timely because gas hydrates may play an impor‐ tant role in the global carbon cycle and global climate dynamics through emissions of methane and in affecting stability of geological features, including mud volcanoes. The role of gas hydrates in above-mentioned processes cannot be assessed accurately with‐ out a better understanding of the hydrate reservoir and their interactions with geolog‐ ical features and meaningful estimates of the amount of methane it contains. In conclusion, lack of knowledge hampers the evaluation of the resource potential of gas hydrates and the hazards related to gas hydrates, requiring efforts to improved knowledge about gas hydrate and their interaction with mud volcanoes.

**Figure 15.** CHIRP images of the Chiavalz mud volcano. Insert: Bathymetric map after BSR project. The red line indicates the CHIRP location.

### **Acknowledgements**

**Figure 13.** CHIRP images of the Grauzaria group. Insert: Bathymetric map after BSR project. The red line indicates the

252 Updates in Volcanology - New Advances in Understanding Volcanic Systems

**Figure 14.** CHIRP images of the Sernio mud volcano. Insert: Bathymetric map after BSR project. The red line indicates

Knowledge of natural occurring gas hydrate is increasing rapidly in the last years; however commercialization of gas hydrate remains unproven. Great uncertainty of the global gas hy‐ drate resource and imitated estimates of hydrate system retard economic analysis of hydrate

CHIRP location.

the CHIRP location.

**6. Conclusions**

We wish to thank Manuela Sedmach for graphic support. This work is partially supported by Programma Nazionale di Ricerche in Antartide, project CLISM.

### **Author details**

Umberta Tinivella\* and Michela Giustiniani

\*Address all correspondence to<EMAIL_ADDRESS>
OGS – National Institute of Oceanography and Experimental Geophysics, Borgo Grotta Gi‐ gante 42C, 34010, Trieste, Italy

[11] Mazurenko, L. L., & Soloviev, V. A. (2003). Worldwide distribution of deep-water fluid venting and potential occurrences of gas hydrate accumulations. *Geo-Marine*

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

255

[12] Milkov, A. V. (2000). Worldwide distribution of submarine mud volcanoes and asso‐

[13] Dimitrov, L. I. (2002). Mud volcanoes-the most important pathway for degassing

[14] Hovland, M., Hill, A., & Stokes, D. (1997). The structure and geomorphology of the

[15] Kopf, A., Klaeschen, D., & Mascle, J. (2001). Extreme efficiency of mud volcanism in dewatering accretionary prisms. *Earth and Planetary Science Letters*, 189, 295-313.

[16] Delisle, G., von, Rad. U., Andruleit, H., von, Daniels. C. H., Tabrez, A. R., & Inam, A. (2002). Active mud volcanoes on- and offshore eastern Makran, Pakistan. Interna‐

[17] Etiope, G., Caracausi, A., Favara, R., Italiano, F., & Baciu, C. (2002). Methane emis‐ sions from the mud volcanoes of Sicily (Italy). *Geophysical Research Letters*, 29(8),

[18] Deville, E., Battani, A., Griboulard, R., Guerlais, S., Herbin, J. P., Houzay, J. P., Mul‐ ler, C., & Prinzhofer, A. (2003). The origin and processes of mud volcanism: new in‐ sights from Trinidad. *Van Rensbergen P, Hillis RR, Maltman AJ, Morley CK. (ed.)*

[19] Yassir, N. (2003). The role of shear stress in mobilizing deep-seated mud volcanoes: geological and geomechanical evidence from Trinidad and Taiwan. *Van Rensbergen P, Hillis RR, Maltman AJ, Morley CK. (ed.) Subsurface Sediment Mobilization. Geol. Soc. Lon‐*

[20] Shakirov, R., Obzhirov, A., Suess, E., Salyuk, A., & Biebow, N. (2004). Mud volcanoes

[21] Stewart, S. A., & Davies, R. J. (2006). Structure and emplacement of mud volcano sys‐

[22] Barber, A. J., Tjokrosapoetro, S., & Charlton, T. R. (1986). Mud volcanoes, shale dia‐ pirs, wrench faults and me´langes in accretionary complexes, eastern Indonesia.

[23] Orange, D. L. (1990). Criteria helpful in recognizing shear-zone and diapiric meleng‐ es, examples from the Hoh accretionary complex, Olympic Peninsula, Washington.

[24] Brown, K. M., & Orange, D. L. (1993). Structural aspects of diapiric melange emplace‐

ment: The Duck Creek diaper. *Journal of Structural Geology*, 13, 831-847.

and gas vents in the Okhotsk Sea area. *Geo-Marine Letters*, 24, 140-149.

tems in the South Caspian Basin. *AAPG Bulletin*, 90(5), 771-786.

*Subsurface Sediment Mobilization. Geol. Soc. London, Spec. Publs.*, 216, 475-490.

*Letters*, 23, 162-176.

56-1-56-4.

ciated gas hydrates. *Marine Geology*, 167, 29-42.

tional Journal of Earth Sciences. 91, 93-110.

*don, Spec. Publs.*, 216, 461-474.

*AAPG Bull*, 70, 1729-1741.

*Geol. Soc. Am. Bull.*, 102, 935-951.

deeply buried sediments. *Earth-Science Reviews*, 59, 49-76.

Dashgil mud volcano, Azerbaijan. *Geomorphology*, 21, 1-15.

### **References**

[11] Mazurenko, L. L., & Soloviev, V. A. (2003). Worldwide distribution of deep-water fluid venting and potential occurrences of gas hydrate accumulations. *Geo-Marine Letters*, 23, 162-176.

**Author details**

Umberta Tinivella\*

**References**

gante 42C, 34010, Trieste, Italy

Society of America. 140.

phere. *Chemosphere*, 49, 777-789.

*Geofluids*, 2, 109-126.

*gy*, 46, 997-1002.

chapter 4, 147-157.

and Michela Giustiniani

*Boulder, Colo.: Geological Society of America*, 31-41.

*Geo-Mar Lett*, 23, 155-161, doi: s00367-003-0140-3.

OGS – National Institute of Oceanography and Experimental Geophysics, Borgo Grotta Gi‐

[1] Canon-Tapia, E., & Szakacs, A. (2010). What is a volcano? Boulder, Colo.: Geological

[2] van Loon, A. J. (2010). Sedimentary volcanoes: Overview and implications for the definition of a volcano on Earth. *Canon-Tapia E, Szakacs A, Editors. What is a volcano?.*

[4] Hensen, C., Nuzzo, M., Hornibrook, E., Pinheiro, L.M., Bock, B., Magalhães, V. H., & Brückmann, W. (2007). Sources of mud volcano fluids in the Gulf of Cadiz- indica‐ tions for hydrothermal imprint. *Geochimica et Cosmochimica Acta*, 71, 1232-1248.

[5] Etiope, G., & Klusman, R. W. (2002). Geologic emissions of methane to the atmos‐

[6] Judd, A. G., Hovland, M., Dimitrov, L. I., García, Gil. S., & Jukes, V. (2002). The geo‐ logical methane budget at Continental Margins and its influence on climate change.

[7] Dimitrov, L. I. (2003). Mud volcanoes-a significant source of atmospheric methane.

[8] Milkov, A. V., Sassen, R., Apanasovich, T. V., & Dadashev, F. G. (2003). Global gas flux from mud volcanoes: a significant source of fossil methane in the atmosphere

[9] Etiope, G., & Milkov, A. V. (2004). A new estimate of global methane flux from on‐ shore and shallow submarine mud volcanoes to the atmosphere. *Environmental Geolo‐*

[10] Judd, A. (2005). Gas emissions from mud volcanoes. Significance to Global Climate Change. *Martinelli G., Panahi B., (ed.) Mud Volcanoes, Geodynamics and Seismicity*, 51,

and the ocean. *Geophysical Research Letters*, 30, doi:10.1029/2002GL016358.

[3] Kopf, A. J. (2011). Significance of mud volcanism. *Reviews of Geophysics*, 40(2).

\*Address all correspondence to<EMAIL_ADDRESS>
254 Updates in Volcanology - New Advances in Understanding Volcanic Systems

[25] Treves, B. (1985). Mud volcanoes and shale diapirs, their implications in accretionary processes. *A review. Acta Naturalia de l'Ateneo Parmense*, 21, 31-37.

[38] Martinelli, G. (1998). Mudvolcanoes of Italy: proceedings of V Int. *Conference on "Gas*

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

257

[39] Arhangelski, A. (1932). Some words about genesis of mud volcanoes on the Apsher‐ on peninsula and Kerch-Taman area. *Bull. MOIP, Ser. Geol.*, 3: 269-285 (in Russian).

[40] Gubkin, I., & Feodorov, S. (1932). Mud volcanoes of the USSR in connection with oil and gas prospects. Proceedings of 27th Int. Geol. Congr. Moscow -(in Russian) , 4,

[41] Jakubov, A. A., Ali-Zade, A. A., & Zeinalov, M.M. (1971). Mud volcanoes of the Azerbaijan, SSR-Atlas. *Baku: Publishing house of the Academy Sciences of the Azerbaijan*

[42] Ginsburg, G. D., & Soloviev, V. A. (1994). Mud volcano gas hydrates in the Caspian

[43] Higgins, G. E., & Saunders, J. B. (1973). Mud volcanoes-their nature and origin: con‐ tribution to the geology and paleobiology of the Carribbean and adjacent areas. *Verh.*

[44] Williams, P., Pigram, C., & Dow, D. (1984). Melange production and the importance

[45] Mazurenko, L. L., Soloviev, V. A., Belenkaya, I., Ivanov, M. K., & Pinheiro, L. M. (2002). Mud volcano gas hydrates in the Gulf of Cadiz. *Terra Nova*, 14, 321-329.

[46] Müller, C., Theilen, F., & Milkereit, B. (2001). Large gasprospective areas indicated by

[47] Perez-Belzuz, F., Alonso, B., & Ercilla, G. (1997). History of mud diapirism and trig‐ gering mechanisms in the Western Alboran Sea. *Tectonophysics*, 282, 399-423.

[48] Vogt, P. R., Cherkashev, G., Ginsburg, G., Ivanov, G., Milkov, A., Crane, K., Lein, A., Sunvor, E., Pimenov, N., & Egorov, A. (1997). Haakon Mosby mud volcano provides

[49] Paine, W. R. (1968). Recent peat diapirs in the Netherlands: A comparison with Gulf Coast salt structures. In: Braunstein G.,. O'Brien G.D. (ed.) Diapirism and Diapirs.,

[50] Neurauter, T. W., & Roberts, H. H. (1994). Three generations of mudvolcanoes on the

[51] Planke, S., Svensen, H., Hovland, M., Banks, D. A., & Jamtveit, B. (2003). Mud and fluid migration in active mud volcanoes in Azerbaijan. *Geo-Marine Letters*, 23,

[52] Etiope, G. (2005). Methane emission from mud volcanoes. *Martinelli G, Panahi B (ed.)*

Louisiana continental slope. *Geo-Mar. Lett.*, 14, 120-125.

*Mud Volcanoes, Geodynamics and Seismicity. Springer*.

unusual example of venting. *EOS Trans Am Geophys Union*, 78(48), 556-557.

of shale diapirism in accretionary terrains. *Nature*, 309, 145-146.

*in Marine Sediments"*, 40-42.

Sea. *Bull. Geol. Soc. Denm*, 41, 95-100.

*Naturforsch. Geschel. Basel*, 84, 101-152.

bright spots. *World Oil*, 222(1).

AAPG Mem., 8, 271-274.

258-268.

33-67.

*SSR*, 245.

[38] Martinelli, G. (1998). Mudvolcanoes of Italy: proceedings of V Int. *Conference on "Gas in Marine Sediments"*, 40-42.

[25] Treves, B. (1985). Mud volcanoes and shale diapirs, their implications in accretionary

[26] Guliyiev, I. S., & Feizullayev, A. A. (1997). All About Mud Volcanoes. *Azerbaijan, Ba‐*

[27] Ivanov, M. K., Limonov, A. F., & Woodside, J. M. (1998). Extensive deep fluid flux through the sea floor on the Crimean continental margin (Black Sea). *Henriet JP, Mie‐ nert J. (ed.) Gas hydrates: relevance to world margin stability and climate change. Geol. Soc.*

[28] Limonov, A. F., Woodside, J. M., Cita, M. B., & Ivanov, M. K. (1998). The Mediterra‐ nean Ridge and related mud diapirism: a background. *Mar. Geol.*, 132, 7-19.

[29] Kvenvolden, K. A., & Lorenson, T. D. (2000). The global occurrence of natural gas hy‐ drate. *Paull C.K., Dillon W. P. (ed.) Natural Gas Hydrates: Occurrence, Distribution, and*

[30] Tinivella, U., Lodolo, E., Camerlenghi, A., & Boehm, G. (1998). Seismic tomography study of a bottom simulating reflector off the South Shetland Islands (Antarctica). *Henriet J-P, Mienert J, (ed.) Gas hydrate: relevance to world margin stability and climate*

[31] Tinivella, U., Accaino, F., & Della Vedova, B. (2007). Gas hydrates and active mud volcanism on the South Shetland continental margin, Antarctic Peninsula. *Geo-Mar*

[32] Tinivella, U., Loreto, M. F., & Accaino, F. (2009). Regional versus detailed velocity analysis to quantify hydrate and free gas in marine sediments: the South Shetland margin target study. *Long D., Lovell M.A., Ress J.G., Rochelle CA. (ed.) Sediment-Hosted Gas Hydrates: New Insights on Natural and Synthetic Systems. Geol. Soc. London, Spec.*

[33] Rakhmanov, R. R. (1987). Mud volcanoes and their importance in forecasting of sub‐

[34] Lancelot, Y., & Embley, R. W. (1977). Piercement structures in deep oceans. *Bull.*

[35] Graue, K. (2000). Mud volcanoes in deep water Nigeria. Marine and Petroleum Geol‐

[36] Huguen, C., Mascle, J., Chaumillon, E., Kopf, A., Woodside, J., & Zitter, T. (2004). Structural setting and tectonic control of mud volcanoes from the Central Mediterra‐

[37] Huseynov, D. A., & Guliyev, I. S. (2004). Mud volcanic natural phenomena in the South Caspian Basin: geology, fluid dynamics and environmental impact. *Environ‐*

nean Ridge (Eastern Mediterranean). *Marine Geology*, 209, 245-263.

processes. *A review. Acta Naturalia de l'Ateneo Parmense*, 21, 31-37.

*ku: Publ. House, Nafta Press*.

*London, Spec. Publs.*, 137, 195-213.

256 Updates in Volcanology - New Advances in Understanding Volcanic Systems

*Dynamics, AGU Monograph*, 55.

*Lett*, doi s00367-007-0093-z.

*Publs.* , 319, 103-119.

ogy. 17, 959-974.

*change. Geol. Soc. London, Spec. Publs.*, 147, 141-151.

surface petroleum potential. *Nedra (in Russian).*

*Amer. Assoc. Pet. Geol.*, 61, 1991-2000.

*mental Geology*, 46, 1012-1023.

[53] Sassen, R., Losh, S. L., Cathles, L., Roberts, H. H., Whelan, J. K., Milkov, A. V., Sweet, S. T., & De Freitas, D. A. (2001). Massive vein filling gas hydrate: relation to ongoing migration from the deep subsurface in the Gulf of Mexico. *Mar. Pet. Geol.*, 18(5), 551-560.

[65] Svensen, H., Jamtveit, B., Planke, S., & Chevallier, L. (2006). Structure and evolution of hydrothermal vent complexes in the Karoo Basin,South Africa. *Journal of the Geo‐*

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

259

[66] Skogseid, J., Pedersen, T., Eldholm, O., & Larsen, B. T. (2010). Tectonism and magma‐ tism during NE Atlantic continental break-up: the Vøring Margin. *Storey B C, Alabast‐ er T, Pankhurst, R J, Editors. Magmatism and the Causes of Continental Break-up. London,*

[67] Svensen, H., Planke, S., Jamtveit, B., & Pedersen, T. (2003). Seep carbonate formation controlled by hydrothermal vent complexes: a case study from the Vøring Basin, the

[68] Planke, S., Rassmussen, T., Rey, S. S., & Myklebust, R. (2005). Seismic characteristics and distribution of volcanic intrusions and hydrothermal vent complexes in the Vøring and Møre basins. *Dore A, Vining B, Editors. Petroleum Geology: North-West Eu‐ rope and Global Perspectives. Proceedings of the 6th Geology Conference. London*, 833-844.

[69] Bell, B., & Butcher, H. (2002). On the emplacement of sill complexes: evidence from the Faroe-Shetland Basin. *Jolley D W, Bell B R, Editors. The North Atlantic Igneous Prov‐ ince: Stratigraphy, Tectonic, Volcanic and Magmatic Processes. London Geological Society,*

[70] Du, Toit. A. L. (2002). Geological Survey of Elliot and Xalanga, Tembuland. *Annual*

[71] Du, Toit. A. L. (1912). Geological Survey of Part of the Stormbergen. *Annual Report of*

[72] Gevers, T. W. (1928). The volcanic vents of the Western Stormberg. *Transactions of the*

[73] Stockley, G. M. (1947). Report on the Geology of Basutoland. Maseru, Authority of

[74] Dingle, R. V., Siesser, W. G., & Newton, A. R. (1983). Mesozoic and Tertiary Geology

[75] Jamtveit, B., Svensen, H., Podladchikov, Y. Y., & Planke, S. (2004). Hydrothermal vent complexes associated with sill intrusions in sedimentary basins. *Breitkreuz C, Petford N, Editors. Physical Geology of High-Level Magmatic Systems. London, Geological*

[76] Grapes, R. H., Reid, D. L., & Mc Pherson, J. G. (1973). Shallow dolerite intrusions and phreatic eruption in the Allan Hills region, Antarctica. New Zealand. *Journal of Geolo‐*

[77] Hanson, R. E., & Elliot, D. H. (1996). Rift-related Jurassic basaltic phreatomagmatic volcanism in the central Transantarctic Mountains: precursory stage to floodbasalt ef‐

*Report of the Geological Commission Cape of Good Hope for 1903*, 8, 169-205.

*the Geological Commission Cape of Good Hope for 1911*, 16, 112-136.

*logical Society*, 163, 671-682.

*Geological Society* , 68, 305-320.

*Special Publications*, 197, 307-329.

the Basutoland Government.

*gy and Geophysics*, 17, 563-577.

*Geological Society of South Africa*, 31, 43-62.

of Southern Africa. Rotterdam, Balkema.

fusion. *Bulletin of Volcanology*, 58, 327-347.

*Society of London, Special Publications*, 234, 233-241.

Norwegian Sea. *Geo-Marine Letters*, 23, 351-358.

[65] Svensen, H., Jamtveit, B., Planke, S., & Chevallier, L. (2006). Structure and evolution of hydrothermal vent complexes in the Karoo Basin,South Africa. *Journal of the Geo‐ logical Society*, 163, 671-682.

[53] Sassen, R., Losh, S. L., Cathles, L., Roberts, H. H., Whelan, J. K., Milkov, A. V., Sweet, S. T., & De Freitas, D. A. (2001). Massive vein filling gas hydrate: relation to ongoing migration from the deep subsurface in the Gulf of Mexico. *Mar. Pet. Geol.*, 18(5),

[54] Limonov, A. F., van Weering, T. C. E., Kenyon, N. H., Ivanov, M. K., & Meisner, L. B. (1997). Seabed morphology and gas venting in the Black Sea mudvolcano area: obser‐ vations with the MAK-1 deep-tow sidescan sonar and bottom profiler. *Mar. Geol.*,

[55] Foucher, J. P., & De Lange, G. (1999). Submersible observations of cold seeps on east‐ ern Mediterranean mud volcanoes. *Proceedings of J. Conf. Abstr. EUG 10, Strasbourg,*

[56] Reed, D. L., Silver, E. A., Tagudin, E., Shipley, H., & Volijk, P. (1990). Relations be‐ tween mud volcanoes, thrust deformation, slope sedimentation, and gas hydrate, off‐

[57] Woodside, J. M., Ivanov, M. K., & Limonov, A. F. (1998). Shipboard Scientists of the Anaxiprobe Expeditions. Shallow gas and gas hydrates in the Anaximander Moun‐ tains regions, eastern Mediterranean Sea. *Henriet JP, Mienert J. (ed.) Gas Hydrates: Rele‐ vance to World Margin Stability and Climate Change. Geol. Soc. London, Spec. Publ.* , 137,

[58] Ginsburg, G. D., Milkov, A. V., Soloviev, V. A., Egorov, A. V., Cherkashev, G. A., Crane, K., Lorenson, T. D., & Khutorskoy, . (1999). Gas hydrate accumulation at the

[59] Dimitrov, L. I., & Woodside, J. (2003). Deep sea pockmark environments in the east‐

[60] Evans, R. J., Davies, R. J., & Stewart, S. A. (2006). Internal structure and eruptive his‐ tory of a kilometrescale mud volcano system, South Caspian Sea. *Basin Research*, 19,

[61] Hedberg, H. D. (1974). Relation of methane generation to undercompacted shales,

[62] Ali-Zade, A. A., Shnyukov, E. F., Grigoryants, B. V., Aliyev, A. A., & Rakhmanov, R. R. (1984). Geotectonic conditions of mud volcano manifestation in the world and their role in prediction of gas and oil content in the earth's interior: proceedings of

[63] Guliyiev, I. S. (1992). A review of mud volcanism. *Translation of the report by: Azerbai‐*

[64] Manga, M., & Brodsky, E. (2006). Seismic triggering of Eruptions in the Far Field: Volcanoes and Geysers. *Annual Review of Earth and Planetary Science*, 34, 263-291.

shale diapirs and mud volcanoes. *Bull. Am. Assoc. Pet. Geol*, 58, 661-673.

551-560.

137, 121-136.

*France*, B13 4(1).

177-193.

153-163.

shore north Panama. *Mar. Pet. Geol.*, 7, 44-54.

258 Updates in Volcanology - New Advances in Understanding Volcanic Systems

Haakon Mosby mud volcano. *Geo-Mar. Lett.*, 19, 57-67.

ern Mediterranean. *Marine Geology*, 195, 263-276.

27th International Geological Congress. 13, 377-393.

*jan Academy of Sciences Institute of Geology*, 65.

[78] White, J. D. L., & Mc Clintock, M. K. (2001). Immense vent complex marks floodba‐ salt eruption in a wet, failed rift: Coombs Hills, Antarctica. *Geology*, 29, 935-938.

[92] Lorenz, V. (1985). Maars and diatremes of phreatomagmatic origin: a review. *Trans‐*

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

261

[93] Clement, C. R., & Reid, A. M. The origin of kimberlite pipes: an interpretation based

[94] Webb, K. J., Smith, B. H., Paul, J. L., & Hetman, C. M. (2004). Geology of the Victor Kimberlite, Attawapiskat, Northern Ontario, Canada: cross-cutting and nested cra‐

[95] Surtee southern African occurrences. (1989). *Ross, J. et al. Editors. Kimberlites and Relat‐*

[96] Mc Clintock, M. K., Houghton, B. F., Skilling, I. P., & White, J. D. L. (2002). The volca‐ niclastic opening phase of Karoo flood basalt volcanism, Drakensberg Formation,

[97] White, J. D. L., & Ross, P. S. (2011). Maar-diatreme volcanoes: A review. *J Volcanol Ge‐*

[98] Svensen, H., Planke, S., Chevallier, L., Malthe-Sorenssen, A., Corfu, F., & Jamtveit, B. (2007). Hydrothermal venting of greenhouse gases triggering Early Jurassic global

[99] Svensen, H., Planke, S., Polozov, A. G., Schmidbauer, N., Corfu, F., Podladchikov, Y. Y., & Jamtveit, B. (2009). Siberian gas venting and the end-Permian environmental

[100] Sloan, E. D., & Koh, C. A. (2008). Clathrate Hydrates of Natural Gases, third ed. CRC

[101] Smelik, E. A., & King, H. E. (1997). Crystal-growth studies of natural gas clathrate hydrates using a pressurized optical cell. *American Mineralogist*, 82, 88-98.

[102] Paull, C. K., & Dillon, W. (2001). Natural gas hydrates: occurrence, distribution, and

[103] Holder, G. D., Malone, R. D., & Lawson, W. F. (1987). Effects of gas composition and geothermal properties on the thickness and depth of natural-gas-hydrate zone. *Jour‐*

[104] Wright, J. F., Dallimore, S. R., Nixon, F. M., & Duchesne, C. (2005). In situ stability of gas hydrate in reservoir sediments of the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well. *Paper presented at Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program, Mackenzie Delta, Geol. Surv. Cana‐*

[105] Dickens, G. R., & Quinby-Hunt, M. S. (1994). Methane hydrate stability in seawater.

*ed Rocks. Geological Society of Australia, Special Publications*, 14, 632-646.

South Africa. *EOS Transactions of the American Geophysical Union*, 83(47).

*actions of the Geological Society of South Africa*, 88, 459-470.

on a synthesis of geological features displayed.

warming. *Earth Planet. Sci. Lett.*, 256, 3-4, 554-566.

crisis. *Earth Planet. Sci. Lett.*, 277(3-4), 490-500.

detection. *AGU Monogr*, 124, 1-315.

*nal of Petroleum Technology*, 1147-1152.

*da, Northwest Territories, Canada*.

*Geophys. Res. Lett*, 21, 2115-2118.

Press, New York, Taylor and Francis Group, Publishers.

ters. *Lithos*, 76, 29-50.

*otherm Res*, 201, 1-4, 1-29.

[92] Lorenz, V. (1985). Maars and diatremes of phreatomagmatic origin: a review. *Trans‐ actions of the Geological Society of South Africa*, 88, 459-470.

[78] White, J. D. L., & Mc Clintock, M. K. (2001). Immense vent complex marks floodba‐ salt eruption in a wet, failed rift: Coombs Hills, Antarctica. *Geology*, 29, 935-938.

[79] Zolotukhin, V. V., & Al'mukhamedov, A. I. (1988). Traps of the Siberian Platform. In: Macdougall JD, Editors. *Continental Flood Basalts. Kluwer, Dordrecht*, 273-310.

[80] Svensen, H., Planke, S., Malthe-Sørenssen, A., Jamtveit, B., Myklebust, R., Eidem, T., & Rey, S. S. (2004). Release of methane from a volcanic basin as a mechanism for ini‐

[81] Wignall, P. B. (2001). Large igneous provinces and mass extinctions. *Earth-Science Re‐*

[82] Courtillot, V. E., & Renne, P. R. (2003). On the ages of flood basalt events. Comptes

[83] Svensen, H., Bebout, G., Kronz, A., Li, L., Planke, S., Chevallier, L., & Jamtveit, B. (2008). Nitrogen geochemistry as a tracer of fluid flow in a hydrothermal vent com‐ plex in the Karoo Basin, South Africa. *Geochimica et Cosmochimica Acta*, 72, 4929-4947.

[84] Mazzini, A., Nermoen, A., Krotkiewski, M., Podladchikov, Y., Planke, S., & Svensen, H. (2009). Strike-slip faulting as a trigger mechanism for overpressure release through piercement structures. *Implications for the Lusi mud volcano, Indonesia. Marine*

[85] Mazzini, A., Svensen, H., Akhmanov, G. G., Aloisi, G., Planke, S., Malthe-Sorenssen, A., & Istadi, B. (2007). Triggering and dynamic evolution of the LUSI mud volcano,

[86] Botha, B. V. J., & Theron, J. C. (1966). New evidence for the early commencement of

[87] Coetzee, C. B. (1966). An ancient volcanic vent on Boschplaat 369 in the Bloemfontein district, Orange Free State. *Transactions of the Geological Society of South Africa*, 69,

[88] Taylor, N. C. (1970). The volcanic vents of the Stormberg series. *BSc(Hons) project,*

[89] Seme, U. T. (1997). Diatreme deposits near Rossouw, north Eastern Cape:sedimentol‐ ogy-volcanology and mode of origin. *BSc(Hons) project, Rhodes University, Grahams‐*

[90] Woodford, A. C., Botha, J. F., Chevallier, L., et al. (2001). Hydrogeology of the main Karoo Basin: Current Knowledge and Research Needs. *Water Research Commission*

[91] Navikov, L. A., & Slobodskoy, R. M. (1979). Mechanism of formation of diatremes.

tial Eocene global warming. *Nature*, 429, 542-545.

260 Updates in Volcanology - New Advances in Understanding Volcanic Systems

*and Petroleum Geology*, 26, 1751-1765.

*Rhodes University, Grahamstown, South Africa*.

*International Geology Review*, 21, 1131-1139.

Rendus de l'Acade´mie des Sciences. *Geoscience*, 335, 113-140.

Indonesia. *Earth and Planetary Science Letters*, 261(3-4), 375-388.

Stormberg volcanism. *Tydskrif vir Natuurwetenskappe*, 7, 469-473.

*views*, 53, 1-33.

127-137.

*town, South Africa*.

*Pretoria Report, 860*.

[106] Subramanian, S., Kini, R.A., Dec, S.F., & Sloan, E. D. (2000). Evidence of structure II hydrate formation from methane + ethane mixtures. *Chemical Engineering Science*, 55, 1981-1999.

[119] Shipley, T. H., & Didyk, B. M. (1982). Occurrence of methane hydrates offshore southern Mexico. *Watkins JS, Moore JC, et al., Editors. Init. Repts. DSDP, 66. Washing‐*

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

263

[120] Minshull, T. A., Singh, S. C., Westbrook, G. K., et al. (1994). Seismic velocitystructure at a gas hydrate reflector,offshore western Colombia, from full waveform inversion.

[121] Sain, K., Minshull, T. A., Singh, S. C., & Hobbs, R. W. (2000). Evidence for a thick free gas layer beneath the bottom simulating reflector in the Makran accretionary prism

[122] Tinivella, U., & Accaino, F. (2000). Compressional velocity structure and Poisson's ra‐ tio in marine sediments with gas hydrate and free gas by inversion of reflected and refracted seismic data (South Shetland Islands, Antarctica). *Mar Geol*, 164, 13-27.

[123] Dai, J,., Xu, H,., Snyder, F,., & Dutta, N. (2004). Detection and estimation of gas hy‐ drates using rock physics and seismic inversion: Examples from the northern deep‐

[124] Chand, S., & Minshull, T. A. (2003). Seismic constraints on the effects of gas hydrate on sediment physical properties and fluid flow: a review. *Geofluids*, 3, 1-15.

[125] Zillmer, M. (2006). A method for determining gas-hydrate or free-gas saturation of

[126] Singh, S. C., Minshull, T. A., & Spence, G. D. (1993). Velocity structure of a gas hy‐

[127] Tinivella, U. (2002). The seismic response to overpressure versus gas hydrate and

[128] Tinivella, U. (1999). A method to estimate gas hydrate and free gas concentrations in

[129] Tinivella, U., & Carcione, M. (2001). Estimation of gas-hydrate concentration and

[130] Ledley, T. S., Sundquist, E. T., Schwartz, S. E., Hall, D. K., Fellows, J. D., & Killeen, T. L. (1999). Climate Change and Greenhouse Gases. EOS, Transactions of the American

[131] Nakano, S., Moritoki, M., & Ohgaki, K. (1998). High-Pressure Phase Equilibrium and Raman Microprobe Spectroscopic Studies on CO2 Hydrate System. J. Chem. Eng.

[132] Lackner, K. S. (2003). A Guide to CO2 Sequestration. *Science*, 300, 1677-1678, doi: sci‐

*sica Teorica ed Applicata*, 40, 19-30.

fi

free-gas saturation from log and seismic data. *The Leading Edge*, 20.

porous media from seismic measurements. *Geophysics*, 71, 21-32.

*ton, U.S. Govt. Printing Office*, 547-556.

water Gulf of Mexico The Leading Edge. .

drate reflector. *Science*, 260, 204-207.

marine sediments. *Bollettino di Geo*

Geophysical Union. 80, 453-458.

Data; 43, 807-810.

ence.1079033.

free gas concentration. *J Seismic Explor*, 11, 283-305.

*J. Geophys. Res.*, 99, 4715-4733.

Marine Geology. 164, 37-51.

[119] Shipley, T. H., & Didyk, B. M. (1982). Occurrence of methane hydrates offshore southern Mexico. *Watkins JS, Moore JC, et al., Editors. Init. Repts. DSDP, 66. Washing‐ ton, U.S. Govt. Printing Office*, 547-556.

[106] Subramanian, S., Kini, R.A., Dec, S.F., & Sloan, E. D. (2000). Evidence of structure II hydrate formation from methane + ethane mixtures. *Chemical Engineering Science*, 55,

[107] Lu, Z., & Sultan, N. (2008). Empirical expressions for gas hydrate stability law, its volume fraction and mass-density at temperature 273.15 K to 290.15 K. *Geochemical*

[108] Sultan, N., Cochonat, P., Foucher, J. P., & Mienert, J. (2004). Effect of gas hydrates

[109] Liu, X., & Flemings, P. B. (2007). Dynamic multiphase flow model of hydrate forma‐ tion in marine sediments. *Journal of Geophysical Researcher*, 112( B03101), doi:

[110] Henriet, J. P., & Mienert, J. (1998). Gas hydrates: relevance to world margin stability

[111] Holder, G. D., & Bishnoi, P. R. (2000). Gas Hydrates: Challenges for the Future. Ann.

[112] Kennett, J. P., Cannariato, K. G., Hendy, I. L., & Behl, R. J. (2007). Carbon isotopic evi‐ dence for methane hydrate stability during Quaternary Interstadials. *Science*, 288,

[113] Brooks, J. M., Cox, H. B., Bryant, W. R., Kennicutt, M. C., Mann, R. G., & Mc Donald, T. J. (1986). Association of gas hydrates and oil seepage in the Gulf of Mexico. *Organ‐*

[114] Severinghaus, J. P., Sowers, T., Brook, E. J., Alley, R. B., & Bender, M. L. (1998). Tim‐ ing of abrupt climate change at the end of the Younger Dryas interval from thermally

[115] Reagan, M. T., & Moridis, G. J. (2007). Oceanic gas hydrate instability and dissocia‐ tion under climate change scenarios. *Geophysical Research Letters*, 34(L22709), doi:

[116] Kennett, J. P., Cannariato, K. G., Hendy, L. L., & Behl, R. J. (2002). Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. *Spec. Publ., 54, AGU,*

[117] Haq, B. U. (1998). Natural gas hydrates: searching for the long-term climatic and slope-stability records. *Geological Society, London, Special Publications*, 137, 303-318,

[118] Shipley, T. H., Houston, M. H., Buffler, R. T., et al. (1979). Seismic reflection evidence for widespread occurrence of possible gas-hydrate horizons on continental slopes

melting on seafloor slope instability. *Marine Geology*, 213, 379-401.

1981-1999.

*Journal*, 42, 163-175.

10.1029/2005JB004227.

N.Y. *Acad. Sci.*, 912.

*ic Geochemistry*, 10, 221-234.

10.1029/2007GL031671.

doi:10.1144/GSL.SP.19<IP_ADDRESS>.

and rises. *AAPG Bull*, 63, 2204-2213.

*Washington, D. C.*

128-133.

and climate change. *Geol Soc Spec Publ* , 137.

262 Updates in Volcanology - New Advances in Understanding Volcanic Systems

fractionated gases in polar ice. *Nature*, 391, 141.

[133] Chadwick, R. A., Arts, R., & Eiken, O. 4D seismic quantification of a growing CO2 plume at Sleipner, North Sea. *Geological Society, London, Petroleum Geology Conference series*, 6, 1385-1399, doi:.

[146] Ginsburg, G. D., Kremlev, A. N., Grigor'ev, M. N., Larkin, G. V., Pavlenkin, A. D., & Saltykova, N. A. (1990). Filtrogenic gas hydrates in the Black Sea (twenty-first voyage

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

265

[147] Limonov, A. F., Woodside, J. M., & Ivanov, M. K. (1994). Mud volcanism in the Medi‐ terranean and Black Seas and shallow structure of the Eratosthenes Seamount. *Initial results of the geological and geophysical investigations during the Third UNESCO-ESF "Training Through Research" Cruise of RV Gelendzhik, June-July 1993. UNESCO Rep.*

[148] Woodside, J. M., Ivanov, M. K., & Limonov, A. F. (1997). Neotectonics and fluid flow through seafloor sediments in the Eastern Mediterranean and Black Seas- Parts I and

[149] Mac, Donald. R. I., Sager, W. W., & Peccini, M. B. (2003). Gas hydrate and chemosyn‐ thetic biota in mounded bathymetry at mid-slope hydrocarbon seepsNorthern Gulf

[150] Judd, A., Davies, G., Wilson, J., Holmes, R., Baron, G., & Bryde, I. (1997). Contribu‐ tion to atmospheric methane by natural seepages on the UK continental shelf. *Mar.*

[151] Lance, S., Henry, P., Le Pichon, X., Lallemant, S., Chamley, H., Rostek, F., & Fau‐ geres-C, J. (1998). Submersible study of mud volcanoes seaward of the Barbados ac‐ cretionary wedge: sedimentology, structure and rheology. *Mar. Geol*, 145, 255-292.

[152] Cronin, B. T., Ivanov, M. K., Limonov, A. F., Egorov, A., Akhmanov, G. G., Akhmet‐ janov, A. M., & Kozlova, E. (1997). Shipboard Scientific Party TTR-5, New discoveries of mud volcanoes on the Eastern Mediterranean Ridge. *J. Geol. Soc.*, 154, 173-182.

[153] Murton, B. J., & Biggs, J. (2003). Numerical modelling of mud volcanoes and their flows using constraints from the Gulf of Cadiz. *Marine Geology*, 195, 223-236.

[154] Soderberg, P., & Floden, T. (1991). Pockmark developments along a deep crustal structure in the northern Stockholm Archipelago, Baltic Sea. *Beitr. Meereskd*, 62,

[155] Soderberg, P., & Floden, T. (1992). Gas seepages, gas eruptions and degassing struc‐ tures in the seafloor along the Stromma tectonic lineament in the crystalline Stock‐

[156] Cohen, H. A., & Mc Clay, K. (1996). Sedimentation and shale tectonics of the north‐

[157] Bouma A.H., Roberts H.H. (1990). Northern Gulf of Mexico continental slope. *Geo-*

[158] Langseth, M. G., Westbrook, G. K., & Hobart, A. (1988). Geophysical survey of mud volcano seaward of the Barbados Ridge Complex. *J. Geophys. Res.*, 93, 1049-1061.

holm Archipelago, east Sweden. *Cont. Shelf Res.*, 12, 1157-1171.

western Niger Delta front. *Mar. Pet. Geol.*, 13, 313-328.

of the research vessel Evpatoria). *Sov. Geol. Geophys*, 31, 8-16.

*Mar. Sci.*, 64.

II. *IOC Tech. Ser.*, 48.

*Geol*, 137, 165-189.

79-102.

*Mar. Lett.*, 10, 177-181.

of Mexico. *Marine Geology*, 198, 133-158.

[146] Ginsburg, G. D., Kremlev, A. N., Grigor'ev, M. N., Larkin, G. V., Pavlenkin, A. D., & Saltykova, N. A. (1990). Filtrogenic gas hydrates in the Black Sea (twenty-first voyage of the research vessel Evpatoria). *Sov. Geol. Geophys*, 31, 8-16.

[133] Chadwick, R. A., Arts, R., & Eiken, O. 4D seismic quantification of a growing CO2 plume at Sleipner, North Sea. *Geological Society, London, Petroleum Geology Conference*

[134] Conti, S., & Fontana, D. (2011). Possible Relationships between Seep Carbonates and Gas Hydrates in the Miocene of the Northern Apennines. *Journal of Geological Re‐*

[135] Liu, X., & Flemings, P. B. (2007). Dynamic multiphase flow model of hydrate forma‐ tion in marine sediments. *Journal of Geophysical Research*, 112: B03101, doi:

[136] Schowalter, T. T. (1979). Mechanics of secondary hydrocarbon migration and entrap‐

[137] Milkov, A. V., Claypool, G. E., Lee-J, Y., & Sassen, R. (2005). Gas hydrate systems at Hydrate Ridge offshore Oregon inferred from molecular and isotopic properties of

[138] Trehu, A. M., Flemings, P. B., Bangs, N. L., Chevallier, J., Gra`cia, E., Johnson, J. E., Liu-S, C., Liu, X., Riedel, M., & Torres, . (2004). Feeding methane vents and gas hy‐ drate deposits at south Hydrate Ridge. *Geophys. Res. Lett.*, 31: L23310, doi:

[139] Flemings, P. B., Liu, X., & Winter, W. (2003). Critical pressure and multiphase flow in

[140] Gorman, A. R., Holbrook, W. S., Hornbach, M. J., & Hackwith, K. L. (2002). Migration of methane gas through the hydrate stability zone in a low-flux hydrate province.

[141] Hornbach, M., Saffer, D. M., & Holbrook, W. S. (2003). Critically pressured free-gas

[142] Nimblett, J., & Ruppel, C. (2003). Permeability evolution during the formation of gas hydrates in marine sediments. *J. Geophys. Res.*, 108(B9), 2420, doi:

[143] Bouriak, S., Vanneste, M., & Saoutkine, A. (2000). Inferred gas hydrates and clay dia‐ pirs near the Storegga slide on the southern edge of the Voring Plateau, offshore

[144] Buenz, S., & Mienert, J. (2004). Acoustic imaging of gas hydrate and free gas at the

[145] Ginsburg, G. D., Ivanov, V. L., & Soloviev, V. A. (1984). Natural gas hydrates of the World's Oceans. In: Oil and gas content of the World's Oceans. PGO Sevmorgeologia

Storegga Slide. *J. Geophys. Res*, 109, B04102, doi:10.1029/2003JB002863.

reservoirs below gas-hydrate provinces. *Nature*, 427, 142-144.

ment. *American Association of Petroleum Geologists Bulletin*, 63, 723-760.

hydrate-bound and void gases, Geochim. *Cosmochim. Acta*, 69, 1007-1026.

*series*, 6, 1385-1399, doi:.

10.1029/2005JB004227.

10.1029/2004GL021286.

*Geology*, 30, 327-330.

10.1029/2001JB001650.

in Russian)., 141-158.

Norway. *Mar Geol*, 163, 125-148.

Blake Ridge gas hydrates. *Geology*, 31, 1057-1060.

*search*, 20727, doi:10.1155/2011/920727.

264 Updates in Volcanology - New Advances in Understanding Volcanic Systems

[159] Martin, J. B., Kastner, M., Henry, P., Le Pichon, X., & Lallemant, S. (1996). Chemical and isotopic evidence for sources of fluid in a mud volcano field seaward of the Bar‐ bados accretionary wedge. *J. Geophys. Res.*, 101, 20325-20345.

[171] Vargas-Cordero, I., Tinivella, U., Accaino, F., Loreto, M. F., & Fanucci, F. (2010). Ther‐

[172] Roberts, H. H. (2001). Fluid expulsion on the Northern Gulf of Mexico continental

[173] Roberts, H. H., Hardage, Shedd. W. W., & Hunt, J. (2006). Seafloor reflectivity-an im‐

[174] Milkov, A. V., & Sassen, R. (2002). Economic geology of offshore gas hydrate accu‐

*hydrates: occurrence, distribution, and detection. AGU Monogr 124*, 145-161.

mulations and provinces. *Marine and Petroleum Geology*, 19, 1-11.

gin (44°30′ S). *Marine and Petroleum Geology*, 27, 1148-1156.

ence of gas hydrate. *Leading Edge*, 25, 620-628.

mal state and concentration of gas hydrate and free gas of Coyhaique, Chilean Mar‐

An Overview of Mud Volcanoes Associated to Gas Hydrate System

http://dx.doi.org/10.5772/51270

267

slope: mud-prone to mineral-prone responses. *Paull CK, Dillon WP. (ed.) Natural gas*

portant seismic property for interpreting fluid/ gas expulsion geology and the pres‐

[171] Vargas-Cordero, I., Tinivella, U., Accaino, F., Loreto, M. F., & Fanucci, F. (2010). Ther‐ mal state and concentration of gas hydrate and free gas of Coyhaique, Chilean Mar‐ gin (44°30′ S). *Marine and Petroleum Geology*, 27, 1148-1156.

[159] Martin, J. B., Kastner, M., Henry, P., Le Pichon, X., & Lallemant, S. (1996). Chemical and isotopic evidence for sources of fluid in a mud volcano field seaward of the Bar‐

[160] Heggland, R., & Nygaard, E. (1998). Shale intrusions and associated surface expres‐ sions-examples from Nigerian and Norwegian deepwater areas: proceedings Off‐

[161] Corthay, J. E. (1998). Delineation of a massive seafloor hydrocarbon seep, overpres‐ sured aquifer sands, and shallow gas reservoir, Louisiana continental slope. *Proceed‐*

[162] Neurauter, T. W., & Bryant, W. R. (1998). Gas hydrates and their association with mud diapirs/mud volcanoes on the Louisiana continental slope. *Proceedings of Off‐*

[163] Milkov, A. V., Lee-J, Y., Borowski, W. S., Torres, Xu. W., Tomaru, H., Tre´hu, A. M., Schultheiss, P., Dickens, G. R., & Claypool, G. E. (2004). Co-existence of gas hydrate, free gas, and brine within the regional gas hydrate stability zone at Hydrate Ridge (Oregon margin): Evidence from prolonged degassing of a pressurized core. *Earth*

[164] Zatsepina, O. Y., & Buffett, B. A. (1997). Phase equilibrium of gas hydrate: Implica‐ tions for the formation of hydrate in the deep sea floor. *Geophys. Res. Lett.*, 24,

[166] Ben-Avraham, Z., Smith, G., Reshef, M., & Jungslager, E. (2002). Gas hydrate and mud volcanoes on the southwest African continental margin off South Africa. *Geolo‐*

[167] Jungslager, E. H. A. (1999). Petroleum habitats of the South Atlantic margin. *Cameron NR, Bate RH, Clure VS. (ed.) The Oil and Gas Habitats of the South Atlantic, Spec. Publ.*

[168] Tinivella, U., Accaino, F., & Camerlenghi, A. (2002). Gas hydrate and free gas distri‐ bution from inversion of seismic data on the South Shetland margin (Antarctica). *Mar*

[169] Klepeis, K., & Lowver, L. A. (1996). Tectonics of the Antarctic-Scotia plate boundary near Elephant and Clarence Islands, West Antarctica. *J. Geophys Res*, 101,

[170] Loreto, M. F., Tinivella, U., Accaino, F., & Giustiniani, M. (2011). Offshore Antarctic Peninsula Gas Hydrate Reservoir Characterization by Geophysical Data Analysis.

bados accretionary wedge. *J. Geophys. Res.*, 101, 20325-20345.

shore Technology Conference. *Houston, TX*, 1, 111-124.

266 Updates in Volcanology - New Advances in Understanding Volcanic Systems

*ings Of Offshore Technology Conference.Houston, Texas*, 37-56.

[165] Tomkeieff, S. I. (1983). Dictionary of Petrology. Wiley, New York.

*shore Technology Conference, Houston, Texas*, 1, 599-607.

*Planet. Sci. Lett.*, 222, 829-843.

*gy (Boulder)*, 30, 927-930.

*geol. Soc. Lond*, 153-168.

*Geophys Res*, 23, 109-123.

*Energies*, 4(11), 39-56, doi:10.3390/en4010039.

20211-20231.

1567-1570.

### *Edited by Károly Németh*

This book is the second volume of the Updates in Volcanology and presents review style chapters as well as stand alone research works on volcanological problems that could be used as valuable resource for both researchers and graduate research students. The book presents chapters arching over a broad field of volcanology among many are considered to be dynamically developing subject areas such as volcano morphology, volcanic terrain evolution or volcaniclastic-hosted mineral resource analysis. The book also takes the reader to areas such as the Russian Far East or sedimentary basins in China which are very remote and generally less known for the global community. This book demonstrates the dynamic evolution of volcanology in the past decades.

Updates in Volcanology - New Advances in Understanding Volcanic Systems

Updates in Volcanology

New Advances in Understanding

Volcanic Systems

*Edited by Károly Németh*

Photo by PRADEEP87 / iStock