Modelling eruption cycles and decay of mud volcanoes

Recent debates about the eruptive behavior of mud volcanoes and their activation mechanisms have been driven particularly by the LUSI eruption in Indonesia that resulted in huge commercial and cultural damages. Numerical modeling of mud volcanoes, of which few exist, can provide insight into eruptive behavior and contribute to hazard evaluation. In this paper, we present a simple model to describe fluid escape from an underground reservoir through a conduit, extruded as a mud volcano at the surface. The governing equations result in oscillatory behavior, and we study the influence of changes in rheological properties of surrounding rock and fluid characteristics of the mud on extrusion dynamics. We focus on understanding long-term eruption behavior, flow cycles, and decay factors. Model results can be used to estimate the discharge rates and extruded volume from assumptions on the mud reservoir and conduit, or conversely, the reservoir or conduit properties from discharge rates.     

Earthquake triggering of mud volcanoes

Mud volcanoes sometimes erupt within days after nearby earthquakes. The number of such nearly coincident events is larger than would be expected by chance and the eruptions are thus assumed to be triggered by earthquakes. Here we compile observations of the response of mud volcanoes and other geologic systems (earthquakes, volcanoes, liquefaction, ground water, and geysers) to earthquakes. The compilation shows a clear magnitude–distance threshold for triggering, suggesting that these seemingly disparate phenomena may share similar underlying triggering mechanisms. The compilation also shows that pre-existing geysers and already-erupting volcanoes and mud volcanoes are much more sensitive to earthquakes than quiescent systems.     

When mud volcanoes sleep: Insight from seep geochemistry at the Dashgil mud volcano,Azerbaijan

The worlds >1500 mud volcanoes are normally in a dormant stage due to the short duration of eruptions. Their dormant stage activity is often characterized by vigorous seepage of water, gas, and petroleum. However, the source of the fluids and the fluid–rock interactions within the mud volcano conduit remain poorly understood. In order to investigate this type of activity, we have combined satellite images with fieldwork and extensive sampling of water and gas at seeping gryphons, pools and salsa lakes at the Dashgil mud volcano in Azerbaijan. We find that caldera collapse faults and E–W oriented faults determine the location of the seeps. The seeping gas is dominated by methane (94.9–99.6%), with a δ¹³C (‰ V-PDB) in the −43.9 to −40.4‰ range, consistent throughout the 12 analysed seeps. Ethane and carbon dioxide occur in minor amounts. Seventeen samples of seeping water show a wide range in solute content and isotopic composition. Pools and salsa lakes have the highest salinities (up to 101,043 ppm Cl) and the lowest δ¹⁸O (‰ V-SMOW) values (1–4‰). The mud-rich gryphons have low salinities (<18,000 ppm Cl) and are enriched in ¹⁸O (δ¹⁸O = 4–6‰).     

Terrestrial methane seeps and mud volcanoes: A global perspective of gas origin

A global database of gas composition and methane stable isotopes of 143 terrestrial mud volcanoes from 12 countries and 60 seeps independent from mud volcanism from eight countries, was compiled and examined in order to provide the first worldwide statistics on the origin of methane seeping at the earth's surface. Sixteen seep data were coupled with their associated subsurface reservoirs.     

Modeling study of growth and potential geohazard for LUSI mud volcano: East Java,Indonesia

The mud volcano known as LUSI first erupted in May 2006 in East Java, Indonesia. The eruption has continued for over two years, and potentially will continue for many years to come, impacting an ever larger area. An obvious and significant question is how extensive the impacted area will become in the coming years. The answer is important for planning scenarios for the relocation of people and infrastructure and for managing the environment and economy. To make such a prediction, an understanding of the geological processes controlling the mud volcanic evolution is needed.     

马里亚纳弧前蛇纹岩泥火山角砾蛇纹岩流体流动性元素富集特征及影响因素

马里亚纳弧前蛇纹岩泥火山被认为是认识俯冲作用的直接窗口,其发育的角砾状蛇纹岩富含的流体流动性元素（FMEs）记录了引起蛇纹石化作用的流体和俯冲带的流体-岩石相互作用及元素循环等信息。本文整理了马里亚纳弧前物源深度逐渐增加的5座蛇纹岩泥火山（Yinazao、Fantangisña、Asùt Tesoru、South Chamorro和Conical）发育角砾蛇纹岩的FMEs数据,通过不同泥火山、同一泥火山不同深度样品及同一块状样微区子样品间的FMEs特征对比,分析了蛇纹岩泥火山引起的蛇纹石化作用的流体性质、来源和形成机制。5座蛇纹岩泥火山角砾蛇纹岩的FMEs均较亏损地幔（DM）显示富集特征：B、Cs、As强烈富集（常＞100×DM）,Li、Rb、Sb中等富集（＞10×DM）,Ba、Sr、Pb弱富集（＜10×DM）。浅源泥火山角砾蛇纹岩中B、Sr、Ba、Pb含量最高,且由浅源至深源泥火山其含量呈逐渐减少的趋势。而Li、Rb、Cs、As、Sb含量显示相反特征,浅源泥火山的角砾蛇纹岩中含量最低,且从浅源到深源泥火山其含量逐渐增加。不同泥火山角砾蛇纹岩FMEs具有系统性变化特征,反映了俯冲板片衍生流体是其发生蛇纹石化作用的主要流体。离海沟较近的泥火山下部俯冲板片成岩作用以蛋白石脱水为主,形成的板片衍生流体极富B,略富Li、Ba、Sr、Pb;离海沟较远的泥火山下部俯冲板片成岩或进变质作用主要为碳酸盐矿物分解和少量蚀变洋壳脱水及黏土矿物转化,板片衍生流体富Ba、Sr、Li、Rb、Cs;居于上述2类泥火山之间的泥火山,下部俯冲板片主要成岩作用为黏土矿物脱水及转化,板片衍生流体以富集B、Li、Rb、Cs、Ba为特征。海底以下深度＜50 m的样品FMEs含量最高,指示海水风化对FMEs含量有一定影响,尤其是B、Sr。同一块角砾蛇纹岩不同微区结构的FMEs含量不同,纯蛇纹石区域其含量最高,指示蛇纹石化产物对FMEs有一定影响;绢石结构中Li、Rb、Cs含量高于橄榄石蚀变的蛇纹石,说明原始矿物类型也对部分FMEs富集有一定影响。     

Active mud volcanism in the West Alboran Basin: Geochemical evidence of hydrocarbon seepage

The West Alboran Basin was previously classified as a mud volcanic province consisting of two mud volcano (MV) fields that are inactive at the present day: the Northern (Spanish) and the Southern (Moroccan) fields. The discovery of the first active mud volcano (Carmen; cruise TTR-17) in 2008, along with several pockmarks at the central part of the basin, motivates more careful geological and geochemical analysis of previous data and comparison to new observations.Gas bubbling from the crater of Carmen MV was observed and recorded using an underwater TV-system and a large TV-grab sample. The gas mainly consisted of methane with less than 1% wetness. However, all sets of homologues up to pentane were detected in the mud breccia of Carmen MV. Both molecular and stable carbon isotopic compositions, and their distribution along the core length, suggest a deep thermogenic source of hydrocarbons (HCs). Composition of the pore water from Carmen MV also points to a deep source of mud volcanic water. The isotopic results indicate that the source of mud volcanic water is the dehydration of clay minerals in the thermal zone of the smectite-to-illite transformation. Our observations allow us to infer the presence of structure II gas hydrates in mud breccia on the top of Carmen MV.High HC gas saturation in sediments in some pockmarks accompanied with live chemosynthetic fauna directly indicates the strong seepage activity of these structures. For the first time, authigenic carbonate crusts and chimneys with associated living chemosynthetic bivalves and tubeworms were sampled from a seep site in the West Alboran Sea. Authigenic carbonates consist of aragonite and calcite, and are characterized by a light carbon isotopic signature, up to −37.2‰ PDB, which points to their methane-derived origin.     

High-resolution mapping of large gas emitting mud volcanoes on the Egyptian continental margin (Nile Deep Sea Fan) by AUV surveys

Two highly active mud volcanoes located in 990–1,265 m water depths were mapped on the northern Egyptian continental slope during the BIONIL expedition of R/V Meteor in October 2006. High-resolution swath bathymetry and backscatter imagery were acquired with an autonomous underwater vehicle (AUV)-mounted multibeam echosounder, operating at a frequency of 200 kHz. Data allowed for the construction of ~1 m pixel bathymetry and backscatter maps. The newly produced maps provide details of the seabed morphology and texture, and insights into the formation of the two mud volcanoes. They also contain key indicators on the distribution of seepage and its tectonic control. The acquisition of high-resolution seafloor bathymetry and acoustic imagery maps with an AUV-mounted multibeam echosounder fills the gap in spatial scale between conventional multibeam data collected from a surface vessel and in situ video observations made from a manned submersible or a remotely operating vehicle.     

Distinct activity phases during the recent geologic history of a Gulf of Mexico mud volcano

Laser line scan imaging and chirp sub-bottom profiling were used to detail the morphology of a submarine mud volcano and brine-filled crater at 652 m water depth in the northern Gulf of Mexico. The mud volcano has a relief of 6 m and a basal diameter of about 80 m. The feature comprises a central, brine-filled crater (253 m²) surrounded by a continuous bed of methanotrophic mussels (Bathymodiolus childressi) covering 434 m² and a patchy bed covering an additional 214 m² of the periphery. The brine pool was mostly <2 m deep, but there were two holes of >28 m and 12 m deep, respectively at the northern end of the pool which emitted continual streams of small clear bubbles. Sub-bottom profiles indicated three distinct strata beneath the present surface of the mud volcano. Integration of 17 profiles shows that the mud volcano has been built in at least three successive stages: the lowest stage deposited 35,400 m³, while the middle and upper stages deposited 7700 and 20,400 m³, respectively. Piston cores were taken at the northern edge of the mussel bed and a site ∼100 m southwest of the pool. Mussel and lucinid shells were recovered from the closer core, lucinid shells from the distant core. A mussel shell from 3.4 m sub-bottom had a Δ¹⁴C age of 16.2 ka. Mixture of modern carbon with “carbon dead” reservoir material would produce actual ages ∼2 ka less than the radiocarbon ages.     

High diversity of frenulates (Polychaeta: Siboglinidae) in the Gulf of Cadiz mud volcanoes: A DNA taxonomy analysis

Frenulates are the most poorly known members of the family Siboglinidae (Polychaeta: Canalipalpata). These thread-like worms occur in reducing marine sediments worldwide, but they are often overlooked in benthic samples or too poorly preserved for adequate taxonomic evaluations. We report on a remarkable diversity of frenulates that were recently sampled from 13 mud volcanoes (350–3902 m deep) in the Gulf of Cadiz, off southern Iberia. Sampled with benthic coring devices, the bodies of these long tubiculous worms were often broken or incomplete, making them difficult to identify morphologically. Consequently, we employed DNA taxonomic methods to assess their diversity. Mitochondrial cytochrome-c-oxidase subunit 1 (COI) sequences distinguished 15 evolutionary lineages inhabiting the Gulf of Cadiz. Only four of the lineages could be assigned to currently recognized Atlantic species; the remaining 11 may be new to science. This remarkable diversity of frenulates in a small geographical region is unprecedented and is hypothesized to result from environmental heterogeneity associated with the bathymetric and geochemical settings of these mud volcanoes.     

Reproductive Cycle of the Caribbean Feather Star Nemaster rubiginosa (Echinodermata: Crinoidea)

Abstract. The reproductive cycle of the comatulid crinoid Nemaster rubiginosa from Discovery Bay, Jamaica is described histologically. The cycle is annual and may be divided into (1) a "resting" phase (summer) in which most adults possess immature, unsexable gonads, (2) a recovery phase (early fall) marked by the re-initiation of gametogenesis and rapid gonadal growth, (3) a breeding phase (late fall and winter) during which the gonads are mature and repeated spawning likely takes place, and (4) a post-spawning phase (spring) during which relict gametes are removed from the shrinking gonads. Although unsexable individuals predominate during the "resting" phase, a small proportion of the adult population is unsexable at all times of the year. The reproductive condition of animals in the same month in two successive years was very similar, suggesting that the timing of reproduction is quite predictable from year to year. The re-initiation of gametogenesis in the early fall is correlated with both rising sea temperature and shortening daylength, and the October to March breeding season corresponds to the period of short daylengths at the study site. The well-defined and synchronized annual reproductive cycle of Nemaster rubiginosa contrasts with the more prolonged and variable reproductive cycles reported for other tropical crinoids and points to a diversity of breeding patterns among tropical crinoids.     

抗菌类药物对锯缘青蟹N-乙酰-β-D氨基葡萄糖苷酶活力的影响

研究了几种抗菌类药物对锯缘青蟹（Scylla serrata）N-乙酰-β-D-氨基葡萄糖苷酶（简称NAGase,EC 3.2.1.52）活力的影响.其结果表明：链霉素、卡那霉素、青霉素钾、庆大霉素和磺胺嘧啶对该酶活力均没有明显的影响.头孢拉定对该酶有显著的激活作用,当其浓度为4.5mg/cm^3时,可使酶活力提高200%.而氟哌酸和恩诺沙星对该酶均有抑制作用,其中恩诺沙星对该酶的抑制作用较强,随着抑制剂浓度增大,酶活力呈指数下降,导致酶活力下降50%的抑制剂浓度（IC50）为0.44mg/cm^3.恩诺沙星对该酶的抑制作用类型表现为非竞争性可逆过程,抑制常数KI为0.35mg/cm^3.该研究对锯缘青蟹的人工养殖具有一定的参考价值.     

Phylogeographic patterns in Maguimithrax spinosissimus (Decapoda: Mithracidae) from Colombian Caribbean

The Caribbean king crab Maguimithrax spinosissimus is an important artisanal fisheries resource with a distribution range that includes the Florida Keys and Caribbean Sea islands. We carried out a phylogeographic analysis of M. spinosissimus in one oceanic (Old Providence) and two continental islands (Rosario and Tintipán). We analysed 89 and 49 Control Region (CR) and Cytochrome Oxidase I (COI) sequences, respectively. We found genetic differentiation between Old Providence and Rosario?+?Tintipán units (F_ST values of 0.84 for CR and 0.91 for COI gene), and gene flow between Rosario and Tintipán (F_ST values ?0.0085 for CR, P?>?.88; ?0.01 for COI gene, P?>?.99). Our analysis showed two genetic stocks and possibly an isolated biogeographic unit of M. spinosissimus. We suggest managing the species as different populations, and conducting more ecological and biological studies for the determination of possible cryptic species.     

Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Paola Ridge, along the NW Calabrian margin (southern Tyrrhenian Sea), is one of the few reported deep sea sites of precipitation of authigenic carbonates in the Tyrrhenian Sea. Here, the changing composition of the seeping fluids and the dynamic nature of the seepage induced the precipitation of pyrite, siderite and other carbonate phases. The occurrence of this array of authigenic precipitates is thought to be related to fluctuation of the sulfate-methane transition zone (SMTZ).Concretions of authigenic minerals formed in the near sub-bottom sediments of the Paola Ridge were investigated for their geochemical and isotopic composition. These concretions were collected in an area characterized by the presence of two alleged mud volcanoes and three mud diapirs. The mud diapirs are dotted by pockmarks and dissected by normal faults, and are known for having been a site of fluid seepage for at least the past 40 kyrs. Present-day venting activity occurs alongside the two alleged mud volcanoes and is dominated by CO₂-rich discharging fluids. This discover led us to question the hypothesis of the mud volcanoes and investigate the origin of the fluids in each different domed structure of the study area.In this study, we used stable isotopes (carbon and oxygen) of carbonates coupled with rare earth element (REE) composition of different carbonate and non-carbonate phases for tracing fluid composition and early diagenesis of authigenic precipitates. The analyses on authigenic precipitates were coupled with chemical investigation of venting gas and sea-water.Authigenic calcite/aragonite concretions, from surficial sediments on diapiric structures, have depleted ¹³C isotopic composition and slightly positive δ¹⁸O values. By contrast, siderite concretions, generally found within the first 6 m of sediments on the alleged mud volcanoes, yielded positive δ¹³C and δ¹⁸O values. The siderite REE pattern shows consistent LREE (light REE) fractionation, MREE (medium REE) enrichment and positive Gd and La anomalies. As shown by the REE distribution, the ¹³C-depleted composition and their association with chemosymbiotic fauna, calcite/aragonite precipitated at time of moderate to high methane flux close to the seafloor, under the influence of bottom seawater. Authigenic siderite, on the other hand, formed in the subseafloor, during periods of lower gas discharges under prolonged anoxic conditions within sediments in equilibrium with ¹³C-rich dissolved inorganic carbon (DIC) and ¹⁸O-rich water, likely related to methanogenesis and intermittent venting of deep-sourced CO₂.     

Sexual reproduction of Hippospongia communis (Lamarck, 1814) (Dictyoceratida,Demospongiae): comparison of two populations living under contrasting environmental conditions

The study of the reproductive processes of benthic invertebrates is essential to the understanding of their population dynamics and is also important in formulating conservation plans, especially for exploited species. The sexual reproduction of Hippospongia communis, the ‘honeycomb’ bath sponge, was studied at two locations in the Mediterranean Sea: the Kerkennah Islands (Tunisia, South Mediterranean), where the mean annual seawater temperature is 19 °C, and Marseille (France, Northwestern Mediterranean Sea), where the mean annual water temperature is 16 °C. The aim of this comparative study was to determine whether different environmental conditions could affect reproduction patterns. At both locations, H. communis was found to contain sexual reproductive elements year‐round. Oogenesis and embryogenesis occurred throughout the year, whereas spermatogenesis occurred during shorter periods between October and November, in both populations. While gametogenesis seemed to be synchronized, indicating that fertilization could occur at the same time at both locations, spawning was observed in late summer in Marseille, whereas it started in late spring for the Kerkennah population. Larval development of H. communis seems to take longer for sponges living at cooler locations such as Marseille. Reproductive effort calculated for both sexes showed significantly higher values for specimens from Kerkennah Islands. By comparing sexual reproductive patterns of populations living in two contrasted environments, we suggest that a change of thermal regime can affect H. communis phenology.     

Temperature Effects on Photosynthesis and Depth Distribution of the Seagrass Cymodocea nodosa (ucria) Ascherson in a Mediterranean Coastal Lagoon: the Mar Menor (SE Spain)

Abstract. Seasonal variation of temperature effects on photosynthesis and respiration of Cymodorea nodosa (Ucria) Ascherson was investigated in a 1 m depth meadow in the Mar Menor lagoon (SE Spain). Light-saturated net photosynthesis (P_max)and dark respiration (R) rates were linearly correlated with water temperature between 10 and 30°C. and 10 and 35°C, respectively, during the year. Water temperature had a similar effect on R rates in August, November, and February, but increased P_max rates in August vs. those in February, thus promoting a shift of the maximum P_max/R ratio values from 15°C in February to 30°C in August. P-I curves had higher P_max values in May and August than in November or February, while Ic values remained relatively constant throughout the year. Whole-plant carbon balances suggested that C. nodosa might not be able to survive in the central basin of the lagoon and that the spatial distribution of this seagrass in the Mar Menor might be controlled by light availability.     

The basins of Sundaland (SE Asia): Evolution and boundary conditions

Most of the basins developed in the continental core of SE Asia (Sundaland) evolved since the Late Cretaceous in a manner that may be correlated to the conditions of the subduction in the Sunda Trench. By the end of Mesozoic times Sundaland was an elevated area composed of granite and metamorphic basement on the rims; which suffered collapse and incipient extension, whereas the central part was stable. This promontory was surrounded by a large subduction zone, except in the north and was a free boundary in the Early Cenozoic. Starting from the Palaeogene and following fractures initiated during the India Eurasia collision, rifting began along large faults (mostly N–S and NNW–SSE strike-slip), which crosscut the whole region. The basins remained in a continental fluvio-lacustrine or shallow marine environment for a long time and some are marked by extremely stretched crust (Phu Khanh, Natuna, N. Makassar) or even reached the ocean floor spreading stage (Celebes, Flores). Western Sundaland was a combination of basin opening and strike-slip transpressional deformation. The configuration suggests a free boundary particularly to the east (trench pull associated with the Proto-South China Sea subduction; Java–Sulawesi trench subduction rollback). In the Early Miocene, Australian blocks reached the Sunda subduction zone and imposed local shortening in the south and southeast, whereas the western part was free from compression after the Indian continent had moved away to the north. This suggests an important coupling of the Sunda Plate with the Indo-Australian Plate both to SE and NW, possibly further west rollback had ceased in the Java–Sumatra subduction zone, and compressional stress was being transferred northwards across the plate boundary. The internal compression is expressed to the south by shortening which is transmitted as far as the Malay basin. In the Late Miocene, most of the Sunda Plate was under compression, except the tectonically isolated Andaman Sea and the Damar basins. In the Pliocene, collision north of Australia propagated toward the north and west causing subduction reversal and compression in the short-lived Damar Basin. Docking of the Philippine Plate confined the eastern side of Sundaland and created local compression and uplift such as in NW Borneo, Palawan and Taiwan. Transpressional deformation created extensive folding, strike-slip faulting and uplift of the Central Basin and Arakan Yoma in Myanmar. Minor inversion affected many Thailand rift basins. All the other basins record subsidence. The uplift is responsible for gravity tectonics where thick sediments were accumulated (Sarawak, NE Luconia, Bangladesh wedge).     

Circannual Cycle and Oxygen Consumption in Eudendrium glomeratum (Cnidaria, Anthomedusae): Studies on a Shallow Water Population

Abstract. The oxygen consumption of Eudendrium glomeratum was measured monthly, throughout the period of active presence of the species in the field, to obtain indications on its physiological condition in the different phases of the cycle. Sets of one hundred polyps were assayed in the laboratory under normothermic (according to field temperature: 14–19°C) and hyperthermic conditions (22–25°C). The different response to identical temperatures at the extremes of the cycle, together with a differential ability to face stressful conditions in the same periods, suggests that other factors, besides temperature, regulate the seasonal cycle of Eudendrium glomeratum.     

Seasonal variation in the reproductive activity and biochemical composition of the Pacific oyster (Crassostrea gigas) from the Marlborough Sounds,New Zealand

Reproductive cycles of the Pacific oyster Crassostrea gigas (Thunberg) from the Marlborough Sounds, New Zealand, were followed between June 1998 and January 2000. Histological examination of the gonad confirms an annual cycle with a winter inactive period followed by rapid gonad development and a single short spawning period. The population gonad index correlated with seawater temperature and changes in tissue dry weight, condition index, and biochemical components. In winter, few individuals with early gametogenic stages were present and rapid development of primary oocytes (diam. 11 μm) occurred during spring (September‐November). The developmental rate and the diameter of mature oocytes (37 μm) was similar for the 1998 and 1999 seasons. For a standard 110‐mm‐length oyster, maximal tissue body weight and condition index were recorded in December. Rapid weight loss in January was length dependent and was attributed to spawning. Temperature was the environmental variable which best correlated with the timing of gametogenesis. Food availability (phytoplankton biomass) may have been responsible for inter‐annual variations. The biochemical composition (% glycogen, lipid, protein) of separated gonad and somatic tissues were variable seasonally and annually. Gametogenesis (oocyte diameter) was associated with increased gonad protein and glycogen and a decrease in lipid concentrations. These changes are similar to those in Pacific oyster populations from other parts of the world.