mineral and gas chemistry of hydrothermal fluids on an ultrafast spreading ridge east pacific rise 17 to 19 s naudur cruise 1993 phase separation processes controlled by volcanic and tectonic activity during the naudur cruise in december 1993 23 dives using the french submersible nautile were conducted on the axis of the east pacific rise between 17 and 19 s where the spreading rate is among the fastest in the ocean 14 to 16 cm yr twenty hydrothermal fluids located at the topographic high of each segment in the axial domain were collected between 2573 and 2669 m depth on three segments centered respectively at 17 25 s 18 15 s and 18 26 s the fluids exhibit a very wide range of temperature chemical and gas compositions on the 17 25 s and 18 26 s segments fluids have quite uniform compositions low chlorinities are gas enriched and are low in dissolved metals relative to fluids from the 18 15 s segment which show high chlorinities are less gas enriched and show high metal concentrations chloride and metal depletion associated with gas enrichment is consistent with phase separation whereas ch 4 end members show large variations between sites the 13 ch 4 data are very similar with 13 c values in a narrow range 22 0 to 23 9 versus pee dee belemnite pdb 13 co 2 measured in fluids within the 18 15 s and 18 26 s segments are respectively 7 9 and 5 8 versus pdb similar to 13 c of co 2 trapped in mid oceanic ridge basalts suggesting a magmatic origin the variability in fluid composition is linked to the variability of the accretion process observed on the three segments the uniform venting of low chlorinity fluids in the 17 25 s and 18 26 s segments is connected with volcanic activity which causes boiling with preferential venting of vapor enriched fluids high salinity fluids are emitted on the 18 15 s segment where the ridge is tectonics dominated and subseafloor circulation controlled by faults phase separated effluents induced by volcanic and tectonic activity are delivered to the deep ocean in this area as previously observed on the juan de fuca ridge or in the north fiji basin ridge

interaction of viscous free surface flows with topography the interaction of gravitationally driven free surface flows of viscous fluid with topographic features is investigated theoretically the motion is studied in the regime where the depth of the flow is much smaller than the streamwise extent of the topography a lubrication model of the motion is developed integrated numerically and analysed asymptotically for small mounds it is shown that the flow surmounts the obstacles but for larger mounds the flow is deflected around it and can form dry zones in its wake into which fluid does not flow as well as forming deeper ponded regions upstream which of these phenomena prevails is shown to depend upon the amplitude of the mound height and the thickness of the oncoming flow relative to the streamwise length scale over which the topography varies by using numerical and asymptotic results we demonstrate that relatively wide mounds lead to the development of deep ponds of material upstream which may lead to flow overtopping if the mound is not sufficiently high these insights can be used to inform the design of barriers that defend built infrastructures from lava flows and it is shown how this model can also provide an upper bound on the force exerted by the flow on them

long submarine lava flows observations and results from numerical modeling long 100 km lava flows are relatively common on mars and venus and have been identified on the moon but they are rarely documented on earth however although 75 of the earth s surface is covered by water only a small percentage of the ocean floor has been investigated at a resolution sufficient to unequivocally identify the boundaries of long submarine lava flows even so basaltic lava flows as long as 110 km have been identified on the deep 1500 m seafloor near hawaii and the east pacific rise ambient conditions on the deep ocean floor may favor the development of long lava flows for the following reasons first high pressures 15 mpa keep volatiles dissolved in basaltic lavas preventing viscosity increases associated with exsolution and vesiculation second seawater rapidly quenches the surface of submarine basalt flows so that an insulating glass layer 1 5 cm thick encases submarine flows within seconds after their emplacement this glass rind effectively insulates the molten flow interior from additional heat loss making submarine basalt flows behave as well insulated subaerial tube fed flows thus for identical basalt flows emplaced on the deep seafloor and subaerially a submarine flow could advance farther before stopping results of numerical modeling indicate that thin 1 m submarine basalt flows behave similarly to identical subaerial flows but thicker submarine flows may advance significantly farther than their subaerial counterparts

microbial sulfate reduction within the iheya north subseafloor hydrothermal system constrained by quadruple sulfur isotopes abstract subseafloor hydrothermal systems may host spatially extended and numerically abundant microbial communities sustained by sulfate reduction as one of the important terminal electron accepting metabolisms in order to estimate microbial sulfate reduction in a subseafloor hydrothermal regime we analyzed sulfur isotopes s 32 s 33 s 34 s 36 of pore water sulfate and mineralized sulfide in the upper 100 m of sedimentary sequences at the iheya north hydrothermal field in the okinawa trough recovered in integrated ocean drilling program expedition 331 iodp exp 331 on the basis of the pore water chemistry and temperature profiles the subseafloor environment is divided into three hydrogeologic units in the topmost unit 1 relatively fresh seawater is recharged and the bottommost unit 3 is characterized by predominance of endmember like high temperature hydrothermal fluid 300 c underlying the impermeable cap rock layers intermediate unit 2 is subject to mixing between the hydrothermal fluid and seawater the 34 s values of sulfate in the unit 2 mixing zone were found to be more 34s enriched than the values expected from simple mixing model of seawater sulfate in the unit 1 with the hydrothermal fluid in the unit 3 the observed s so 4 34 enrichment and sulfate concentration so2 4 depletion suggest sulfate reduction is taking place below the seafloor based on our model calculation the isotope discrimination e 34 is estimated to be 21 this large isotope discrimination together with slight 33 s enrichment and 36 s depletion reveals that sulfate reduction is caused by microbial processes but not by thermochemical processes in addition our numerical simulation points out that sulfate may be reduced prior to presently undergoing mixing with high temperature fluid probably within the seawater recharge zone despite the abundant input of hydrothermal h2s mineralized sulfide below 10 m seafloor mbsf shows characteristic sulfur isotopic signatures that support the significant contribution of subseafloor microbial sulfate reduction potentially corresponding to approximately 20 of the total sulfide mineral formation active microbial sulfate reduction below the seafloor may be promoted by significant input of seawater to the habitats through the vigorous hydrothermal circulation in vicinity of iheya north field

hydrothermal activity on near arc sections of back arc ridges results from the mariana trough and lau basin 1 the spatial density of hydrothermal venting is strongly correlated with spreading rate on mid ocean ridges with the interesting exception of hot spot affected ridges evidently because spreading rate is a reliable proxy for the magma budget this correlation remains untested on spreading ridges in back arc basins where the magma budget may be complicated by subduction induced variations of the melt supply to address this uncertainty we conducted hydrothermal plume surveys along slow spreading 40 60 mm yr and arc proximal 10 60 km distant sections of the southern mariana trough and the valu fa ridge lau basin on both sections we found multiple plumes overlying 15 20 of the total length of each section a coverage comparable to mid ocean ridges spreading at similar rates these conditions contrast with earlier reported results from the two nearest arc segments of a faster spreading 60 70 mm yr back arc ridge the east scotia ridge which approaches no closer than 100 km to its arc there hydrothermal venting is relatively scarce 5 plume coverage and the ridge characteristics are distinctly slow spreading small central volcanic highs bookended by deep median valleys and axial melt lenses restricted to the volcanic highs two factors may contribute to an unexpectedly low hydrothermal budget on these east scotia ridge segments they may lie too far from the adjacent arc to benefit from near arc sources of melt supply and subduction aided migration of mantle from the bouvet hot spot may reduce hydrothermal circulation by local crustal warming and thickening analogous to the reykjanes ridge thus the pattern among these three ridge sections appears to mirror the larger global pattern defined by mid ocean ridges a well defined trend of spreading rate versus hydrothermal activity on most ridge sections plus a subset of ridge sections where unusual melt delivery conditions diminish the expected hydrothermal activity

reservoir monitoring and characterization using satellite geodetic data interferometric synthetic aperture radar observations from the krechba field algeria deformation in the material overlying an active reservoir is used to monitor pressure change at depth a sequence of 11 field estimates allows us to construct a measure of diffusive traveltime throughout a reservoir the dense distribution of traveltime values means that we can construct an exactly linear inverse problem for reservoir flow properties application to interferometric synthetic aperture radar insar data gathered over a carbon dioxide c o2 injection site in algeria reveals pressure propagation along two northwest trending corridors an inversion of the traveltimes indicates the existence of two northwest trending high permeability zones the high permeability features trend in the same direction as the regional fault and fracture zones model parameter resolution estimates indicate the features are well resolved

redox state of seafloor hydrothermal fluids and its effect on sulfide mineralization abstract the redox conditions f o 2 f s 2 of seafloor hydrothermal fluids were calculated from dissolved h 2 and h 2 s concentrations at conditions of 300 and 350 c 71 409 bars and seawater salinity the results were compared with f o 2 f s 2 conditions estimated from black smoker mineralogy as reported by previous studies and our own investigations for various geological settings including the okinawa trough sediment rich hakurei and sediment poor jade fields the manus back arc basin felsic hosted pacmanus and basalt hosted vienna woods fields and the central indian ridge mafic ultramafic hosted kairei and basalt hosted edmond fields in most cases the calculated fluid f o 2 f s 2 conditions agree well with estimates from primary mineral assemblages and fes contents in sphalerite wurtzite this correlation suggests that the redox states of sulfide mineralization in chimneys typically reflect dissolved h 2 and h 2 s concentrations in vent fluids it should be noted that variable h 2 concentrations in vent fluids 0 01 19 mmol kg dominantly control not only fluid f o 2 but also f s 2 whereas the more uniform h 2 s concentrations 1 20 mmol kg have less of an influence on fluid f s 2 fluid sediment interaction elevates h 2 concentrations to over 1 mmol kg which sufficiently lowers f o 2 f s 2 to the pyrrhotite stability field however low h 2 s concentrations do not necessarily account for low f s 2 calculations for the h 2 poor 0 1 mmol kg and h 2 s rich 10 mmol kg fluids in some felsic hosted arc backarc systems indicate relatively high f o 2 f s 2 states consistent with the bornite pyrite chalcopyrite assemblages these redox conditions result from a combination of fluid mineral equilibria at relatively oxidizing conditions elevated h 2 s concentrations from magmatic degassing redox calculations at 350 c indicate that neither pyrite nor pyrrhotite is stable in the initial hot fluids of the tag and ultramafic hosted mid atlantic ridge systems due to the low h 2 s concentrations with cooling of these fluids either conductively or by interacting with seawater higher f s 2 and f o 2 result and fe sulfides are stable in agreement with the higher f o 2 f s 2 mineral assemblages observed

geochemical observations within the water column at the co2 rich hydrothermal systems hatoma knoll and yonaguni knoll iv in the southern okinawa trough the okinawa trough is one of three known hydrothermal sites worldwide where liquid carbon dioxide is emitted from the seafloor into the water column in march 2008 investigations were performed at two active areas yonaguni knoll iv and hatoma knoll in order to identify impacts of hydrothermal venting on the water column chemistry vertical profiles of ph and redox potential eh were recorded and discrete water samples were taken for the analysis of total carbon dioxide ct and helium 3he 4he anomalies with respect to reference stations ct ph and 3he with respect to saturation with the atmosphere 3heexcess were used to characterize the impact of hydrothermal vents these data indicate that the flux of co2 into the water column is dominated by hot hydrothermal co2 rich vents located in close proximity to the liquid co2 emission sites bubbles and droplets sampled at the cold gas outlets at hatoma knoll differed considerably from the water column regarding co2 3he ratios and thus provide additional evidence that cold liquid phase co2 is of minor importance for the total co2 flux at both hydrothermal systems although hydrothermal vents at back arc basins are known to emit large amounts of acids other than co2 the correlation between ph and ct at both research areas clearly suggests that the observed ph reduction is mainly caused by the addition of co2 deviating ct 3he and ct ph ratios and the prevailing water currents indicate a yet undiscovered vent site at the flank of a seamount in the northeast

the 4 d microgravity method for waterflood surveillance a model study for the prudhoe bay reservoir alaska forward and inverse gravity modeling is carried out on a suite of reservoir simulations of a proposed water injection in the prudhoe bay reservoir alaska a novel surveillance technique is developed in which surface gravity observations are used to monitor the progress of a gas cap waterflood in the reservoir at 8200 ft 2500 m depth this cost effective method requires that high precision gravity surveys be repeated over periods of years differences in the gravity field with time reflect changes in the reservoir fluid densities preliminary field tests at prudhoe bay indicates survey accuracy of 5 10 gal can be achieved for gravity data using a modified lacoste romberg g type meter or scintrex cg 3m combined with the navstar global positioning system gps forward gravity modeling predicts variations in surface measurements of 100 gal after 5 years of water injection and 180 250 gal after 15 years we use a constrained least squares method to invert synthetic gravity data for subsurface densi

mineralogical characterization and formation of fe si oxyhydroxide deposits from modern seafloor hydrothermal vents we have studied mineralogical characteristics of fe si oxide precipitates from hydrothermal fields of the valu fa ridge lau basin especially the role that the neutrophilic fe oxidizing bacteria played in their formation using various analytical techniques xrd sem epma tg dta and ftir according to this examination the fe si oxide formation can be divided into two stages at the initial stage the fe oxidizing bacteria bound and oxidized fe2 into fe3 to fix co2 triggering precipitation of fe oxyhydroxide ferrihydrite and construction of a loose network of fe rich filaments subsequently the decreased porosity of the network resulting from the gradual growth of the filaments led to a decline in the mixing between seawater and the hydrothermal fluids then the conductive cooling of the network resulted in saturation of the dissolved si with respect to amorphous silica as a result significant precipitation of opal a occurred through inorganic polymerization however part of the silica was immobilized by bonding to fe oh functional groups and yielded unpolymerized silica which is characterized by fe o si bond owing to the incorporation of si into the ferrihydrite structure and its adsorption on the ferrihydrite surface the modern hydrothermal fe si oxides are thermally stable dsc measurements indicate the full segregation of cristobalite from hematite at about 800 c in an o2 atmosphere these observations indicate that primary alternating si and fe rich layers may be absent in the archean ocean and that alternating bands in bifs represent a diagenetic process our work thus provides a potential clue that can be used to unravel the precipitation and diagenetic mechanisms of precambrian banded iron formations bif

submarine venting of magmatic volatiles in the eastern manus basin papua new guinea abstract the susu knolls and desmos hydrothermal fields are located in the back arc extensional transform zone of the eastern manus basin in 2006 highly acidic and so4 rich vent fluids were collected at both sites and analyzed for the chemical and isotopic composition of major and trace species fluids exiting the seafloor have measured temperatures from 48 to 215 c and are milky white in appearance due to precipitation of elemental s0 vent fluid concentrations of na k and mg are depleted by as much as 30 relative to seawater but have the same relative abundance in contrast the fluids are highly enriched in dissolved co2 cl sio2 aq fe and al relative to seawater measured ph 25 c ranged from 0 95 to 1 87 and aqueous so4 ranged from 35 to 135 mmol kg the chemical and isotopic composition points to formation via subsurface mixing of seawater with a na k mg and ca free volatile rich magmatic fluid exsolved from subsurface magma bodies during a process analogous to subaerial fumarole discharge estimates of the magmatic end member composition indicate a fluid phase where h2o so2 co2 cl f the hydrogen and oxygen isotopic composition of h2o and carbon isotopic composition of co2 in the vent fluids strongly suggest a contribution of slab derived h2o and co2 to melts generated in the mantle beneath the eastern manus volcanic zone abundant magmatically derived so2 undergoes disproportionation during cooling in upflow zones and contributes abundant acidity so42 and s0 to the venting fluids interaction of these highly acidic fluids with highly altered mineral assemblages in the upflow zone are responsible for extensive aqueous mobilization of sio2 aq fe and al temporal variability in the speciation and abundance of aqueous s species between 1995 and 2006 at the desmos vent field suggests an increase in the relative abundance of so2 in the magmatic end member that has mixed with seawater in the subsurface results of this study constrain processes responsible for the formation of hot spring fluids in magmatically active back arc environments and the resulting chemical exchange between the lithosphere and water column

formation of fe mn si oxide and nontronite deposits in hydrothermal fields on the valu fa ridge lau basin abstract hydrothermal fe mn si oxides and nontronite are pervasive in the hine hina vai lili and mariner hydrothermal fields along the central valu fa ridge lau basin morphometric and mineralogical analyses reveal that the iron rich filaments are the most important constituents of these fe mn si oxide deposits both the morphologies and chemical composition of the filaments indicate that neutrophilic fe oxidizing bacteria have played a key role in the formation of these deposits a key process of the formation of these deposits is the creation of a complicated filamentous network in which a series of metabolic activities and passive sorption and nucleation processes occur the precipitation of dissolved si in unsaturated and saturated states leads to a two generation growth model in the hydrothermal vents the precipitation of amorphous opal occurs in a relatively narrow temperature range 41 1 42 9 c based on oxygen isotope analyses indicating a fast precipitation rate of opal a when conductive cooling of the hydrothermal fluid occurrs patchy nontronite in the mariner fields is a product of the direct precipitation from hydrothermal fluids at a temperature of 87 9 c whereas the scattered nontronite at the hine hina field is the product of the replacement of hydrothermal fe si oxides at a temperature of 46 2 c

formation of gas discharging from taketomi submarine hot spring off ishigaki island in the southern ryukyu islands japan abstract taketomi submarine hot spring lies off ishigaki island in the southern ryukyu islands and vents hot spring waters at temperatures up to 50 c from the seafloor at a depth of 20 m we investigated the chemical and isotopic composition of gases discharging from taketomi hot spring the gases were composed mainly of methane with secondary nitrogen at higher than atmospheric concentration carbon and hydrogen isotope data suggest that the methane in the discharging gases was derived mainly from thermal decomposition of organic matter helium isotopes were enriched in 3 he relative to the atmosphere suggesting a supply of mantle derived helium to the discharging gases the mantle derived gases transfer the deep originated thermal energy to the hot spring and thermogenesis of organic matter the hydrocarbons in the venting gas could be sourced from sedimentary rocks of the yaeyama or shimajiri groups or yaeyama metamorphic rocks and added to the ascending gases as they pass through those source rocks on their way to the surface because the pleistocene rocks of the ryukyu group beneath the hot spring have been altered by the spring activity the taketomi hot spring began venting after the pleistocene

chemical characteristics of newly discovered black smoker fluids and associated hydrothermal plumes at the rodriguez triple junction central indian ridge abstract the chemical characteristics of hydrothermal fluids in the indian ocean have been revealed for the first time a hydrothermal field called the kairei field including active black smoker chimneys was discovered by rov kaiko dives at 25 19 17 s 70 02 40 e 2450 m depth on the southwestern flank of an off axis knoll located 15 miles north of the rodriguez triple junction central indian ridge after detailed tow yo surveys of the hydrothermal plume distribution the temperature of the fluid expelled from the most active chimney was almost stable 359 360 c throughout three successive days of fluid sampling the endmember fluid has a chemical composition similar to the hydrothermal fluids sampled from sediment starved mid ocean ridges in the pacific and the atlantic oceans suggesting typical interactions between hot fluid and mid ocean ridge basalts in the subseafloor reaction zone

atmospheric noble gases in volcanic glasses from the southern lau basin origin from the subducting slab abstract noble gas concentrations and isotopic compositions have been determined for four submarine volcanic glasses from the valu fa ridge vfr in the southern lau basin the samples are the least differentiated ones from this area and they display enrichments in fluid mobile elements similar to the nearby island arc 3he 4he ratios are slightly below average morb 6 8 7 8 times atmospheric whereas ne ar kr and xe have isotopic compositions very similar to air together with previously published data from the valu fa ridge and other spreading segments in the lau basin our data show a systematic latitudinal variation of increasing ne ar kr and xe abundances from north to south as well as ne and ar isotopic compositions changing from morb like to atmosphere like in the same direction moreover isotopic compositions and noble gas abundances of the lavas correlate strongly with ba nb ratios and h2o concentrations based on these observations and mass balance arguments we propose that the atmospheric noble gases come from the subducting oceanic crust and are not due to shallow contamination with air dissolved in seawater or assimilation of old crust our data suggest that the noble gases released from the subducting slab are atmospheric and thus contain little or no solar he and ne in addition to the fact that ratios of he to heavy noble gases are small in aged ocean crust he has possibly fractionated from the other noble gases due to its higher diffusivity and thus he transport from the subducting slab into the mantle wedge is probably insignificant we propose that the 3he 4he ratios lower than morb observed in the vfr lavas result from radiogenic ingrowth of he in a highly depleted and hence degassed mantle wedge after the enrichment of u and th released from the downgoing slab

geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the kermadec intraoceanic arc abstract during the r v sonne cruise so253 in 2016 2017 hydrothermal vent sites along the kermadec intraoceanic arc were sampled for hydrothermal fluids at four active volcanoes macauley haungaroa brothers and rumble iii respectively water depths ranged between 290 m and 1700 m a new vent field was discovered at haungaroa the samples were taken from diffuse flow sites as well as from white and black smokers rich in metals and gases with discharge temperatures as high as 311 c their fluid composition is very variable but basically divides into two types one that indicates distinct magmatic input and another that shows evidence for intense water rock interaction under hot acidic conditions fluid samples from macauley the shallowest sampling site 300 m had fe concentrations as high as 1 7 mm al concentrations up to 122 m and h2s up to 10 mm at a ph of only 1 2 at brothers the deepest sampling site down to 1600 m we identified two different fluid types 1 a magmatically influenced type at the upper and lower cone with highest temperatures of 115 c up to 95 6 mm mg the highest mg concentration measured in fluids from intraoceanic arc systems so far elevated so42 76 9 mm high h2s 5 0 mm but fe concentrations of only 15 m and 2 a fluid with low mg 5 4 mm low h2s 1 1 mm temperatures reaching 311 c and high fe contents 12 4 mm at the upper caldera and nw caldera wall typical of a black smoker fluid chloride concentrations in all fluids were similar or highly enriched when compared to seawater e g up to 787 mm brine fluids with also one low chlorinity vapor phase fluid sample recovered indicating that phase separation is occurring at brothers unusual highly elevated mg concentrations in fluids from the brothers lower cone 95 6 mm compared to 53 2 mm in ambient seawater combined with highly elevated concentrations of so42 76 9 mm compared to 29 0 mm in ambient seawater indicate dissolution of mg and so42 bearing minerals in the subsurface such as caminite our data show how highly diverse and variable island arc systems can be with respect to their fluid chemistry both spatially and temporally it adds to the still limited data set of arc systems compared to mid ocean ridges and supplies an important contribution towards a better understanding of geochemical processes along arc volcanoes the higher range in fluid chemistry together with shallower water depth implies that the fluids from intraoceanic arcs may contribute a significant fraction of dissolved metals not only to the global oceanic biogeochemical cycle but also into the photic zone the area of highest bioproductivity

geochemical origin of hydrothermal fluid methane in sediment associated fields and its relevance to the geographical distribution of whole hydrothermal circulation abstract we investigated the chemical composition of hydrothermal fluids and deduced the origin of hydrothermal fluid methane in a sediment associated minami ensei me hydrothermal field the okinawa trough the endmember hydrothermal fluid of the me field contained isotopically 13 c enriched methane 26 0 to 24 7 which suggested a thermogenic origin however the observed methane dominating hydrocarbon compositions c 1 c 2 10 3 suggested that biogenic methane not thermogenic hydrocarbons is predominant the conflict between these geochemical indications can be resolved by the hypothesis that the thermal reaction of sedimentary organic matter initially generates the primary source of hydrocarbons and the secondary thermal decomposition of hydrocarbons increases the c 1 c 2 ratio as high as that of biogenic methane the low molecular hydrogen concentration 0 04 mmol kg in the me fluid suggests that the thermal fluid sediment interaction occurred in the recharge stage not the discharge stage of hydrothermal circulation less biogenic methane in the me fluid implies a laterally shrunken hydrothermal fluid circulation that reduced biogenic methane incorporation at the recharge stage a comparison of hydrothermal fluid chemistry and geological geographical settings among the global sediment associated hydrothermal systems also suggests representative patterns in the geochemical origins of hydrothermal fluid methane and their relevance to hydrothermal fluid circulation as a whole

simulating the thermorheological evolution of channel contained lava flowgo and its implementation in excel flowgo is a one dimensional model that tracks the thermorheological evolution of lava flowing down a channel the model does not spread the lava but instead follows a control volume as it descends a line of steepest descent centred on the channel axis the model basis is the jeffreys equation for newtonian flow modified for a bingham fluid and a series of heat loss equations adjustable relationships are used to calculate cooling crystallization and down channel increases in viscosity and yield strength as well as the resultant decrease in velocity here we provide a guide that allows flowgo to be set up in excel in doing so we show how the model can be executed using a slope profile derived from google tm earth model simplicity and ease of source term input from google tm earth means that this exercise allows i easy access to the model ii quick global application and iii use in a teaching role output is tested using measurements made for the 2010 eruption of piton de la fournaise la reunion island the model is also set up for rapid syneruptive hazard assessment at piton de la fournaise as we show using the example of the response to the june 2014 eruption

gradients in the composition of hydrothermal fluids from the endeavour segment vent field phase separation and brine loss hydrothermal fluid samples collected in 1984 1987 and 1988 from a large vent field near 47 57 n on the endeavour segment of the juan de fuca ridge jfr have been analyzed for major and minor elements and gases there are of the order of 100 individual smoker vents on 10 large sulfide structures which are localized along faults and fault intersections across the vent field each sulfide structure has a characteristic fluid composition which varies very little from one vent orifice to the next or from year to year on a given structure however there are large gradients in fluid composition across the vent field with endmember chlorinity increasing from 255 mmol kg in the sw to 505 mmol kg in the ne end member concentrations of major elements are well correlated with chlorinity and endmember volatile concentrations in the lowest chlorinity fluids are approximately twice as high as in the highest chlorinity fluids the gradients in composition across the vent field and measured vent fluid temperatures 400 c are consistent with supercritical phase separation and loss of brine phase below the seafloor the factor of 2 variation in co2 and h2s is larger than expected for loss of a very high chlorinity brine concentrations of iron and manganese are not positively correlated with chlorinity suggesting that temperature and ph are more important in controlling metal solubility elevated ammonia and bromide chloride ratios indicate that there has been subseafloor interaction between the hydrothermal fluids and organic matter and high boron concentrations point to a sedimentary source

on the role of thermal conductivity on thermal erosion by lava lava channels are abundant on the surface of both the moon and venus there is evidence that erosion may have played a part in their formation here a study of the relationship between thermal conductivity and erosion rate is presented a numerical model is used to investigate the sensitivity of the erosion rate to the relative value of the thermal conductivity of the lava solid substrate and liquid substrate boundary layer results show that the highest rates for thermal erosion are achieved by a high liquid substrate and low solid substrate thermal conductivity and that the thermal erosion process is most sensitive to the liquid substrate s thermal conductivity

calculated effect of vesicles on the thermal properties of cooling basaltic lava flows abstract this paper investigates the effects of porosity in the form of vesicles and bubbles on the transfer of heat within basaltic lava this study was undertaken to provide input for realistic cooling models of basaltic lava flows and to help explain some recent field measurements by jones 1992 1993 these field observations indicate that the surfaces of vesicular pahoehoe flows cool significantly more rapidly than that of dense flows it has been suggested that thermal radiation across vesicles is responsible for this enhanced cooling rate it is shown here that for vesicles in typical pahoehoe flows radiation across vesicles may enhance the effective thermal conductivity and thermal diffusivity but only at high temperatures t 800 c and high vesicularities 40 it is also found that convection of the gas phase within bubbles will not occur unless the cavities are larger than about 1 cm furthermore previous work has demonstrated that porosity greatly reduces the thermal conductivity and thermal inertia of cold lava it is shown here that this should also be true at high temperatures examining only radiation across vesicles severely understates the effect of porosity on the cooling of the surface of lava flows thermal inertia developed to describe diurnal surface temperature variations is the most appropriate thermal parameter in this case thermal inertia is a measure of how quickly surface temperature responds to heating or cooling with low thermal inertia materials responding more quickly it is shown here that porosity greatly reduces thermal inertia at all temperatures and that this provides a more general explanation for the field observation

dynamics of a confined lava flow on kilauea volcano hawaii this paper presents a new method of analysing lava flow deposits which allows the velocity discharge rate and rheological properties of channelled moving lavas to be calculated the theory is applied to a lava flow which was erupted on kilauea in july 1974 this flow came from a line of fissures on the edge of the caldera and was confined to a pre existing gully within 50 m of leaving the vent the lava drained onto the floor of the caldera when the activity stopped but left wall and floor deposits which showed that the lava banked up as it flowed around each of the bends field surveys established the radius of curvature of each bend and the associated lava levels and these data together with related field and laboratory measurements are used to study the rheology of the lava the results show the flow to have been fast moving but still laminar with a mean velocity of just over 8 m s 1 the lava had a low or negligible yield strength and viscosities in the range 85 140 pa s an extension of the basic method is considered and the possibility of supercritical flow discussed

risk evaluation detection and simulation during effusive eruption disasters lava ingress into a vulnerable population will be difficult to control so that evacuation will be necessary for communities in the path of the active lava followed by post event population infrastructural societal and community replacement and or relocation there is a pressing need to set up a response chain that bridges scientists and responders during an effusive crisis to allow near real time delivery of globally standard products for a timely and adequate humanitarian response in this chain the scientific research groups investigating lava remote sensing and modelling need to provide products that are both useful to and trusted by the crisis response community requirements for these products include a formats that can be immediately integrated into a crisis management procedure and b in an agreed and stable standard a review of current capability reveals that we are at a point where the community can provide such a response as is the aim of the red seed risk evaluation detection and simulation during effusive eruption disasters working group this book is the first production of this group and is intended not only as a directory of current capabilities and operational service providers but also as a statement of intent and need while providing a simulation designed to demonstrate how a truly pan disciplinary response to an effusive crisis could work

chemical composition of hydrothermal fluids in the central and southern mariana trough backarc basin abstract we present a geochemical data set from hydrothermal fluids collected from the central and southern mariana trough during dive programs conducted in the 1990s the fluid samples were collected from two hydrothermal fields 1 the alice springs field 18 13 n 144 42 e water depth 3600 m on the axial ridge crest of the central marana trough and 2 the forecast field 13 24 n 143 55 e water depth 1470 m on peak b seamount one of a cluster of small volcanic seamounts which represents a unique tectonic setting in the southern mariana trough gas geochemistry of the alice springs fluid showed he and c isotope ratios in the range of morb whereas that of the forecast fluid showed a higher co 2 3 he ratio and 13 c enriched isotope ratio both of which are commonly recognized in hydrothermal fluids from intraoceanic arc volcanoes the major and minor element composition of the alice springs fluid is characterized by enrichment in mobile alkali elements such as k rb and cs this geochemical signature is in accordance with the well known characteristics of basaltic lava collected from the same area which show substantial enrichment in incompatible elements as interpreted in previous petrological studies this signature is considered to be an arc geochemical signal reflecting contribution from the subduction component the b concentration of the alice springs fluid is also high and is another arc geochemical signal the forecast fluid by contrast did not show enrichment in the mobile alkali elements although its b concentration is high the forecast fluid is characterized instead by enrichment in ca and sr coupled with depletion in na and li as discussed in previous studies this signature is attributed to hydrothermal reactions at rather low temperature due to the shallow water depth we recognize two different arc geochemical signals in these two hydrothermal fluids mobile alkali elements in the alice spring fluid and gaseous species in the forecast fluid this difference could reflect different behaviors of these species during magmatic processes in the mantle wedge beneath the mariana trough backarc spreading center

aqueous volatiles in hydrothermal fluids from the main endeavour field northern juan de fuca ridge temporal variability following earthquake activity the main endeavour field northern juan de fuca ridge experienced intense seismic activity in june 1999 hydrothermal vent fluids were collected from sulfide structures in september 1999 and july 2000 and analyzed for the abundance of h2 h2s ch4 co2 nh3 mg and cl to document temporal and spatial changes following the earthquakes dissolved concentrations of co2 h2 and h2s increased dramatically in the september 1999 samples relative to pre earthquake abundances and subsequently decreased during the following year in contrast dissolved nh3 and ch4 concentrations in 1999 and 2000 were similar to or less than pre earthquake values aqueous cl abundances showed large decreases immediately following the earthquakes followed by increases to near pre earthquake values the abundances of volatile species at the main endeavour field were characterized by strong inverse correlations with chlorinity phase separation can account for 20 50 enrichments of co2 ch4 and nh3 in low chlorinity fluids while temperature and pressure dependent fluid mineral equilibria at near critical conditions are responsible for order of magnitude greater enrichments in dissolved h2s and h2 the systematic variation of dissolved gas concentrations with chlorinity likely reflects mixing of a low chlorinity volatile enriched vapor generated by supercritical phase separation with a cooler gas poor hydrothermal fluid of seawater chlorinity decreased abundances of sediment derived nh3 and ch4 in 1999 indicate an earthquake induced change in subsurface hydrology elevated co2 abundances in vent fluids collected in september 1999 provide evidence that supports a magmatic origin for the earthquakes temperature salinity relationships are consistent with intrusion of a shallow dike and suggest that the earthquakes were associated with movement of magma beneath the ridge crest these data demonstrate the large and rapid response of chemical fluxes at mid ocean ridges to magmatic activity and associated changes in subsurface temperature and pressure

carbon isotopic distribution of methane in deep sea hydrothermal plume myojin knoll caldera izu bonin arc implications for microbial methane oxidation in the oceans and applications to heat flux estimation the concentration and stable carbon isotopic composition 13c of methane have been measured for both seafloor hydrothermal venting fluids and effluent plume waters supplied from the vents at the myojin knoll caldera izu bonin arc in the western north pacific the hydrothermal end member concentrations and 13c of methane show near homogeneity among vents 41 2 mol kg and 16 3 0 8 pdb respectively while those in the effluent plume are stratified in the caldera and vertically exhibit a large variation 2 1 11 nmol kg and 29 0 to 11 3 pdb respectively comparison of concentration and 13c data between vent fluids and plume waters suggest that the methane is not conserved but microbially oxidized along with the plume gradual decrease of diffusive methane flux in proportion to distance from the vent fields supports the occurrence of significant microbial oxidation within the plume assuming steady state emission of methane from the vents 1 kinetic isotope effect due to the microbial oxidation k12 k13 2 methane flux from the vents fvents 3 heat flux from the vents q and 4 average turnover time of hydrothermal methane tall are estimated to be k12 k13 1 005 0 001 fvents 90 340 mol d q 30 110 mw and tall 60 240 d respectively the estimated turnover times however are not uniform within the water column around the vents a turnover time of less than 50 d for methane is one of the shortest values in the pelagic ocean while those at the distant points correspond to values more typical for deep ocean water

geochemistry of hydrothermal fluids from the pacmanus northeast pual and vienna woods hydrothermal fields manus basin papua new guinea abstract processes controlling the composition of seafloor hydrothermal fluids in silicic back arc or near arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic hydrothermal activity in such environments we conducted a survey of vent fluid compositions from two contrasting sites in the manus back arc basin papua new guinea to examine the influence of variations in host rock composition and magmatic inputs both a function of arc proximity on hydrothermal fluid chemistry fluid samples were collected from felsic hosted hydrothermal vent fields located on pual ridge pacmanus and northeast ne pual near the active new britain arc and a basalt hosted vent field vienna woods located farther from the arc on the manus spreading center vienna woods fluids were characterized by relatively uniform endmember temperatures 273 285 c and major element compositions low dissolved co 2 concentrations 4 4 mmol kg and high measured ph 4 2 4 9 at 25 c temperatures and compositions were highly variable at pacmanus ne pual and a large newly discovered vent area fenway was observed to be vigorously venting boiling 358 c fluid all pacmanus fluids are characterized by negative d h 2 o values in contrast to positive values at vienna woods suggesting substantial magmatic water input to circulating fluids at pual ridge low measured ph 25 c values 2 6 2 7 high endmember co 2 up to 274 mmol kg and negative 34 s h 2 s values down to 2 7 in some vent fluids are also consistent with degassing of acid volatile species from evolved magma dissolved co 2 at pacmanus is more enriched in 13 c 4 1 to 2 3 than vienna woods 5 2 to 5 7 suggesting a contribution of slab derived carbon the mobile elements e g li k rb cs and b are also greatly enriched in pacmanus fluids reflecting increased abundances in the crust there relative to the manus spreading center variations in alkali and dissolved gas abundances with cl at pacmanus and ne pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents in further contrast to vienna woods substantial modification of pacmanus ne pual fluids has taken place as a result of seawater ingress into the upflow zone consistently high measured mg concentrations as well as trends of increasingly non conservative so 4 behavior decreasing endmember ca cl and sr cl ratios with increased mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment decreased ph and endmember fe mn ratios in higher mg fluids indicate that the associated mixing cooling gives rise to sulfide deposition and secondary acidity production several low temperature 80 c fluids at pacmanus ne pual also show evidence for anhydrite dissolution and water rock interaction fixation of b subsequent to seawater entrainment hence the evolution of fluid compositions at pual ridge reflects the cumulative effects of water rock interaction admixing and reaction of fluids exsolved from silicic magma phase separation segregation and seawater ingress into upflow zones

the 4d microgravity method for waterflood surveillance part iv modeling and interpretation of early epoch 4d gravity surveys at prudhoe bay alaska between march 2003 and march 2007 four high precision 4d absolute microgravity surveys were performed at prudhoe bay alaska these surveys are part of an ongoing effort to monitor the progress of a very large water injection project in the gas cap of the prudhoe bay reservoir at a depth of 2 5 km these carefully acquired gravity data must be modeled and interpreted in terms of water movement within the reservoir a constrained linear inversion scheme was tested on reservoir simulations during the planning and development phase of this project preinjection the inver sion methodology has been applied to data for three epochs 2005 2003 2006 2003 and 2007 2003 and mass distribution models have been produced for the reservoir the time evolution of the water mass distribution in the reservoir is visualized from these three snapshot models the waterflood is expanding into the gas cap at the expected rate but is exhibiting nonsymmetric behavior that is consistent with a greater degree of structural

a year of lava fountaining at etna volumes from seviri 1 we present a new method that uses cooling curves apparent in high temporal resolution thermal data acquired by geostationary sensors to estimate erupted volumes and mean output rates during short lava fountaining events the 15 minute temporal resolution of the data allows phases of waxing and peak activity to be identified during short 150 to 810 minute long events cooling curves which decay over 8 to 21 hour periods following the fountaining event can also be identified application to 19 fountaining events recorded at etna by msg s seviri sensor between 10 january 2011 and 9 january 2012 yields a total erupted dense rock lava volume of 28 106 m3 with a maximum intensity of 227 m3 s 1being obtained for the 12 august 2011 event the time averaged output over the year was 0 9 m3 s 1 this being the same as the rate that has characterized etna s effusive activity for the last 40 years

prokaryote communities at active chimney and in situ colonization devices after a magmatic degassing event 37 n mar emso azores deep sea observatory the mixing zone between high temperature hydrothermal fluids and seawater produces redox gradients promoting the development of unique ecosystems based on chemotrophy the structure of microbial communities depends on their environment which can vary according to space and time hydrothermal circulation within the oceanic crust determines the chemical composition and flow of fluids depending on underground events earthquakes volcanic episodes and impacts the development of microbial communities this link between hydrothermal vent communities and deep geological events is the focus of the present study the first of its kind for slow spreading ridge in this study we present a unique set of multidisciplinary data collected from 2008 to 2011 on the eiffel tower hydrothermal site lucky strike vent field mid atlantic ridge we benefit from continuous geophysical monitoring temperature seismicity of the site annual sampling of hydrothermal fluids hot and diffuse for geochemistry analyses sampling of hydrothermal chimneys and an in situ microbial colonization experiments over a year for microbial study the high co2 content and concentrations of major elements cl ca si and so4 in the end member fluids collected in 2010 indicate that a magmatic degassing occurred between 2009 and 2010 under the lucky strike hydrothermal field this is supported by the large temperature variations observed in march april 2010 these magmatic co2 inputs seem to have affected microbial communities colonizing the high temperature chimney as well as the basalts in the more diffuse and mixed zone promoting the development of thermophilic anaerobic archaea and bacteria archaeoglobales nautiliales nitratiruptoraceae

submarine venting of phase separated hydrothermal fluids at axial volcano juan de fuca ridge since the discovery of high temperature venting on the east pacific rise in 19791 it has been expected2 3 because of the physical properties of sea water at pressures and temperatures encountered during submarine hydrothermal circulation4 5 that phase separated fluids would discharge from ridgecrest vents although this notion is supported by the reported large deviations in vent fluid chlorinity relative to that of sea water 40 200 6 7 by observations of venting at p t conditions clearly within the two phase region 220 bar and 420 c 8 and by fluid inclusion data9 10 unequivocal identification11 of phase separated venting fluids has remained elusive here we report observations of chloride and metal depleted gas enriched fluids from a shallow vent field on the juan de fuca ridge which confirm the expectation that phase separated effluents are delivered to the deep ocean from some sea floor venting systems

gravimetric monitoring of gas production from the troll field four surveys of relative gravity and depth measurements have been conducted over the troll field since gas production began in 1996 precision in gravity intrasurvey repeatability measured as standard deviation has improved from 26 gal to 4 5 gal in two surveys in 2002 and 2005 the scatter of 74 station depth differences standard deviation has improved to 1 0 cm with modeled subsidence removed for the same two surveys subsidence of up to 3 cm is observed above the thickest reservoir of troll east between 2002 and 2005 time lapse gravity shows a general slight average increase in troll east 95 confidence for the interval centered at 5 2 4 4 gal which is likely caused by edgewater influx one gravity station close to troll a shows a 9 gal gravity increase indicating 2 2 m water rise repeated logging in a nearby well indicates 2 8 m rise these two observations agree within uncertainty bounds gravity decrease in troll west is explained by oil production and a downward moving gas oil con

forecasting lava flow paths by a stochastic approach 1 a stochastic model named downflow is presented to forecast possible lava flow paths with the aim of hazard assessment and mitigation the model relies on the fact that lava flow emplacement is in many cases controlled by topography the potential inundation area of the flow is determined by considering a number of steepest paths over stochastic perturbations of the original topography since the code requires very short computational time and few input data the model proved to be a very useful tool to obtain real time predictions during the initial phase of an eruption the necessary topographic information can be obtained by photogrammetry radar altimetry or laser scanning techniques downflow has been successfully applied to a number of flows including the september 2004 lava flow where updated topographies were available

low temperature volatile production at the lost city hydrothermal field evidence from a hydrogen stable isotope geothermometer although commonly utilized in continental geothermal work the water hydrogen and methane hydrogen isotope geothermometers have been neglected in hydrothermal studies here we report d ch4 and d h2 values from high temperature black smoker type hydrothermal vents and low temperature carbonate hosted samples from the recently discovered lost city hydrothermal field methane deuterium content is uniform across the dataset at 120 12 hydrogen d values vary from 420 to 330 at high temperature vents to 700 to 600 at lost city the application of several geothermometer equations to a suite of hydrothermal vent volatile samples reveals that predicted temperatures are similar to measured vent temperatures at high temperature vents and 20 60 c higher than those measured at the lost city vents we conclude that the overestimation of temperature at lost city reflects 1 that methane and hydrogen are produced by serpentinization at n110 c and 2 that isotopic equilibrium at temperatures b70 c is mediated by microbial sulfate reduction the successful application of hydrogen isotope geothermometers to low temperature lost city hydrothermal samples encourages its employment with lowtemperature diffuse hydrothermal fluids 2005 elsevier b v all rights reserved

boiling vapour type fluids from the nifonea vent field new hebrides back arc vanuatu sw pacific geochemistry of an early stage post eruptive hydrothermal system in 2013 high temperature vent fluids were sampled in the nifonea vent field this field is located within the caldera of a large shield type volcano of the vate trough a young extensional rift in the new hebrides back arc hydrothermal venting occurs as clear and black smoker fluids with temperatures up to 368 c the hottest temperatures measured so far in the western pacific the physico chemical conditions place the fluids within the two phase field of nacl h2o and venting is dominated by vapour phase fluids with cl concentrations as low as 25 mm the fluid composition which differs between the individual vent sites is interpreted to reflect the specific geochemical fluid signature of a hydrothermal system in its initial post eruptive stage the strong cl depletion is accompanied by low alkali cl ratios compared to more evolved hydrothermal systems and very high fe cl ratios the concentrations of rey 180 nm and as 21 m in the most cl depleted fluid are among the highest reported so far for submarine hydrothermal fluids whereas the inter element rey fractionation is only minor the fluid signature which has been described here for the first time in a back arc setting is controlled by fast fluid passage through basaltic volcanic rocks with extremely high water rock ratios and only limited water rock exchange phase separation and segregation and at least two component fluid mixing metals and metalloids are unexpectedly mobile in the vapour phase fluids and the strong enrichments of fe rey and as highlight the metal transport capacity of low salinity low density vapours at the specific physico chemical conditions at nifonea one possible scenario is that the fluids boiled before the separated vapour phase continued to react with fresh glassy lavas the mobilization of metals is likely to occur by leaching from fresh glass and grain boundaries and is supported by the high water rock ratios the enrichment of b and as is further controlled by their high volatility whereas the strong enrichment of rey is also a consequence of the elevated concentrations in the host rocks however a direct contribution of metals such as as from magmatic degassing cannot be ruled out the different fluid end member composition of individual vent sites could be explained by mixing of vapour phase fluids with another fluid phase of different water rock interaction history

the control of lava flow during the 1991 1992 eruption of mt etna abstract all the actions carried out in 1992 to protect the village of zafferana etnea from being invaded by lava are described an earthen barrier 234 m long and 21 m high was firstly built in january 1992 by accumulating with mechanical escavators 370 000 m 3 of earth scoriae and stones this embankment contained the lava for about one month and was overflowed by april 9 1992 three additional smaller earthen barriers lenght 90 160 m height 6 12 m were built in april to gain time while the lava front was descending towards zafferana from the overflowed first embankment the major effort of the 1992 operation consisted of several attempts at stopping the lava front advance by diverting the flow out from the natural and extensively tunnelled channel through a skylight near the vent the main intervention point was located in valle del bove at an elevation of 2000 m at 8 km from zafferana in a zone almost unaccessible from land helicopters were hence extensively used during the whole operation initial interventions called for attempts at plugging a tunnel by dumping into it linked concrete blocks hedgehogs and blasted portions of the solid levee each intervention caused the partial obstruction of the tunnelled channel which determined major increases of lava overflow in valle del bove and the consequent halt of the most advanced fronts however benefits were of brief duration at the most two weeks of respite before new lava fronts approached again and again the outskirts of zafferana the final successful intervention was carried out on may 27 29 an artificial channel was dug departing from the natural one the solid separation levee was thinned to 3 m and blasted by 7000 kg of explosives after the explosion 2 3 of the lava flowed spontaneously in the artificial channel and then the total diversion was obtained the tunnel being plugged by dumping into the natural flow 230 m 3 of lava boulders as a consequence of the intervention the active natural lava front that on may 27 was only 850 m from zafferana came to an halt as did the entire flow downhill from the diversion point bringing back the situation as it was five months earlier a few days after the beginning of the eruption with the new front of the diverted flow at 6 7 km from zafferana in june 1992 the effusion rate halved from 30 to 15 m 3 s and with this reduced thrust the lava was no longer capable of covering long distances five months after the conclusive intervention the diverted lava continues to flow over its initial natural field but remaining confined in the upper valle del bove without any new threat to zafferana

gravity changes and natural gas extraction in groningen gravity observations made over the groningen gasfield from 1978 onwards are available the existing gravity data were reanalysed and a new survey was carried out the observed gravity changes obtained during four surveys spanning an 18 year period were compared with the gravity effect due to natural gas extraction computed from the reservoir model and the production data the random error in the gravity values is small enough to detect the effect of gas extraction after a few years up to 2 gal year the trends obtained from observed and calculated gravity changes agree well within their expected error margins after statistical data snooping due to the inadequate measurement set up of the previous surveys systematic errors present in the gravity data hampered the use of this data for refinement of the reservoir and the production models however with improved gravity monitoring in particular a very systematic network set up and well calibrated instruments this should now be feasible by using the network analysis from the 1996 measurements for the planning of a network in space and time most of the current problems can be avoided

flow and convective cooling in lava tubes tube fed basaltic lava flows with lengths ranging from 10 to 200 km are inferred to exhibit similar amounts of cooling to explain the wide range of implied cooling rates we consider forced convection as a dominant cooling process in lava tubes and present solutions that express mean temperature versus distance down the tube as a function of flow rate and flow cross section our models treat forced convective thermal losses in steady laminar flow through a lava tube with constant temperature walls and constant material properties we explore the effects of different wall temperature and heat flux rate boundary conditions for circular tube and parallel plate flows over a range of tube sizes plate spacings eruption temperatures and volume flow rates results show that nonlinear cooling rates over distance are characteristic of constant wall temperature for a piecewise parallel plate circular tube model this provides the best fit to temperature observations for hawaiian tubes such a model may also provide an explanation for the very low 10 c cooling observed in 10 km long hawaii tube flows and inferred in longer 50 to 150 km tube fed flows in queensland the forced convective cooling model may also explain similar flow morphologies for long tube fed basaltic lava flows in a wide variety of locations since small variations in eruption temperature or flow rate can accommodate the entire range of flow lengths and cooling rates considered our results are consistent with previous suggestions that long basaltic flows may be a reflection of low slopes a particularly steady moderate eruption rate and well insulated flow rather than of high discharge rates

constraints on the formation of submarine lava flows from numerical model calculations abstract to constrain life time and flow rates in a submarine lava tube pillow 3d finite element calculations were carried out for a simplified fixed geometry model tube the principal parameters included into the model are a temperature dependent newtonian viscosity of the lava whereby viscosity is also dependent on composition temperature and crystallinity of the lava cooling by seawater and the release of latent heat of crystallization time dependent model runs suggest the longevity of the tube flow is constrained by the competition of advective heat flow along the tube axis and the conduction of heat towards the margins of the flow in order to keep the lava flowing a minimum critical pressure gradient along the tube is required otherwise the amount of thermal energy brought in by the influx of hot lava is less than the amount lost at the outer boundaries and the tube will solidify providing an exponentially decaying driving pressure at the tube inlet this critical pressure gradient has been calculated for different tube lengths and diameters and is compared to critical pressure values resulting from a more simplistic solution assuming constant viscosity and pure conductive or convective cooling an analysis of the difference between pressure gradients obtained through the numerical and simplified model is used to derive an appropriate power law for the critical pressure gradient in bodies cooled by convection and conduction including the effect of temperature dependent viscosity that gradient scales with the tube radius r as r3 85 this law is valid for tube style lava flows and lava viscosities in the basaltic range

inverting multispectral thermal time series images of volcanic eruptions for lava emplacement models we present a novel method for interpreting time series of multispectral observations of volcanic eruptions we show how existing models relating to radiance and area emplacement can be generalized into an integration convolution of a net area emplacement nae function and a coolingfunction assumingallsurfacesfollowthesamecoolingcurve thenaedescribesthevari ation in the rate of emplacement of hot material with time and temperature while the cooling func tion describes the cooling of a hot surface with time discretizing the integration convolution equation yields an underdetermined matrix equation that we solve using second order tikhonov regularization to stabilize the solution we test the inversion by modelling plausible nae surfaces calculating the radiances adding noise and inverting for the original surface three or more spec tralbands are requiredtocapture theoverallshapeofthenae andrecovering specificquantitiesis difficult single wavebands that yield flat kernels recover the total area emplacement curve rate of increase of hot area the integral of the nae with respect to temperature surprisingly well due to their property of conserving nae suggesting novel methods for calculating area emplacement rates and effusion rates from time series of satellite images and radiometer measurements gold open access this article is published under the terms of the cc by 3 0 license

variability in the microbial communities and hydrothermal fluid chemistry at the newly discovered mariner hydrothermal field southern lau basin 1 a newly discovered hydrothermal field called the mariner field on the valu fa ridge in the southern lau basin was explored and characterized with geochemical and microbiological analyses the hydrothermal fluid discharging from the most vigorous vent snow chimney maximum discharge temperature 365 c was boiling at the seafloor at a depth of 1908 m and two distinct end member hydrothermal fluids were identified the fluid chemistry of the typical cl enriched and cl depleted hydrothermal fluids was analyzed as was the mineralogy of the host chimney structures the variability in the fluid chemistry was potentially controlled by the subseafloor phase separation vapor loss process and the microbial community activities microbial community structures in three chimney structures were investigated using culture dependent and independent techniques the small subunit ssu rrna gene clone analysis revealed that both bacterial and archaeal rrna gene communities on the chimney surfaces differed among three chimneys cultivation analysis demonstrated significant variation in the culturability of various microbial components among the chimneys particularly of thermophilic h2 oxidizing and s oxidizing chemolithoautotrophs such as the genera aquifex and persephonella the physical and chemical environments of chimney surface habitats are still unresolved and do not directly extrapolate the environments of possible subseafloor habitats however the variability in microbial community found in the chimneys also provides an insight into the different biogeochemical interactions potentially affected by the phase separation of the hydrothermal fluids in the subseafloor hydrothermal habitats in addition comparison with other deep sea hydrothermal systems revealed that the mariner field microbial communities have unusual characteristics

opposing trends in crustal thickness and spreading rate along the back arc eastern lau spreading center implications for controls on ridge morphology faulting and hydrothermal activity abstract along back arc ridges located near the arc volcanic front crustal thickness is observed to vary systematically with arc proximity independent of spreading rate this effect is especially well expressed by the 400 km long eastern lau spreading center elsc where approaching the arc volcanic front from 100 to 40 km crustal thickness nearly doubles 5 5 9 km as spreading rates decrease by more than half 97 39 mm yr the crustal thickness variations at the elsc appear to result primarily from changes in mantle wedge composition caused by subduction we investigated the effects of these large and opposed crustal thickness and spreading rate variations on ridge morphology faulting and hydrothermal activity as part of the first phase of ridge2000 integrated studies in the lau back arc basin we used deep towed side scan sonar instruments dsl120a and imi30 to continuously map the near axis region within broader coverage ship multibeam bathymetry and acoustic imagery swaths an array of optical sensors maprs concurrently surveyed the near bottom water for hydrothermal plume anomalies hydrocasts made at identified plume sites confirmed their hydrothermal origin the data show that as spreading rates increase and crustal thicknesses decrease along the elsc 1 morphology transitions from shallow peaked volcanic highs to a deeper flat axis 2 faults become larger and more widely spaced 3 hydrothermal activity as measured by plume incidence increases and appears to reach levels higher than the global mid ocean ridge trend with spreading rate the observations indicate that crustal thickness magma supply has a greater control on ridge morphology and faulting than spreading rate even at fast rates where the thermal lithosphere should be thin however heat input from mantle advection proportional to spreading rate perhaps in combination with increased fault permeability appears to have a greater control on hydrothermal activity than crustal thickness and the magmatic robustness of the ridge although subduction effects give rise to the opposed trends in crustal thickness and spreading rate at the elsc the observed effects may have generic implications for controls of seafloor spreading characteristics at mid ocean ridges

methanogens in h2 rich hydrothermal fluids resulting from phase separation in a sediment starved basalt hosted hydrothermal system abstract we here report on specific chemical and microbial compositions observed at the archaean hydrothermal site in the southern mariana backarc spreading center which produces two remarkably different hydrothermal fluids one was black smoker hydrothermal fluid at 340 c containing a low concentration of methane with a relatively high carbon isotope ratio 13 c of methane relative to vpdb 7 8 indicating that methane originated from a magmatic source thus this is a fairly ordinary hydrothermal fluid for basalt hosted hydrothermal activity in contrast the other fluid was clear smoker hydrothermal fluid at 117 c containing a high concentration of methane with a very low carbon isotope ratio 49 7 the host rock of the archaean hydrothermal site is basalt and therefore fischer tropsch type reactions resulting from serpentinization of mantle rocks are not feasible as a source for the light carbon in methane additionally the carbon isotope ratio of carbon dioxide demonstrated that the sources of co 2 and ch 4 were not organic materials the remaining possibility biogenic methane was confirmed by cultivation of hyperthermophilic hydrogen oxidizing methanogens from both rocks covering the vent of clear smoker hydrothermal fluids and in situ cultivation systems although the dominance and abundance of methanogens were very low in this ecosystem the number was consistent with the relationship between hydrogen concentration and methanogen abundance takai et al 2015 these results suggest that phase separation led to concentration of hydrogen and subsequent persistence of a hyperthermophilic subsurface lithoautotrophic microbial ecosystem in both serpentine hosted and basalt hosted hydrothermal systems this type of ecosystem may occur in similar settings elsewhere on modern earth in addition similar communities may have existed in other types of deep sea hydrothermal systems in the geological past

diversity and distribution of subseafloor thermococcales populations in diffuse hydrothermal vents at an active deep sea volcano in the northeast pacific ocean received 30 august 2005 revised 28 july 2006 accepted 5 september 2006 published 20 december 2006 1 the presence diversity and distribution of a key group of subseafloor archaea the thermococcales was examined in multiple diffuse flow hydrothermal vents at axial seamount an active deep sea volcano located in the northeast pacific ocean a polymerase chain reaction pcr approach was used to determine if this group of subseafloor indicator organisms showed any phylogenetic distribution that may indicate distinct subseafloor communities at vents with different physical and chemical characteristics targeted primers for the thermococcales 16s rrna small subunit ribosomal rna gene and intergenic transcribed spacer its region were designed and applied to organisms filtered directly from a variety of diffuse flow vents thermococcales were amplified from 9 of 11 samples examined and it was determined that the its region is a better phylogenetic marker than the 16s rrna in defining consistent groups of closely related sequences results show a relationship between environmental clone distribution and source vent chemistry the most highly diluted vents with elevated iron and alkalinity contained a distinct group of thermococcales as defined by the its region suggesting separate subseafloor thermococcales populations at diffuse vents within the axial caldera

geochemistry of hydrothermal fluids from axial seamount hydrothermal emissions study vent field juan de fuca ridge subseafloor boiling and subsequent fluid rock interaction hydrothermal fluids collected from the ashes vent field in 1986 1987 and 1988 exhibit a very wide range of chemical composition over a small area 60 m in diameter compositions range from a 300 c gas enriched 285 mmol kg co2 low chlorinity 33 of seawater fluid to a 328 c relatively gas depleted 50 mmol kg co2 high chlorinity 116 of seawater fluid the entire range of measured compositions at ashes is best explained by a single hydrothermal fluid undergoing phase separation while rising through the ocean crust followed by partial segregation of the vapor and brine phases other mechanisms proposed to produce chlorinity variations in hydrothermal fluids precipitation dissolution of a chloride bearing mineral or crustal hydration cannot produce the covariation of chlorinity and gas content observed at ashes there is good agreement of the measured fluid compositions with compositions generated by a simple model of phase separation in which gases are partitioned according to henry s law and all salt remains in the liquid phase significant enrichments in silica lithium and boron in the low chlorinity fluids over levels predicted by the model are attributed to fluid rock interaction in the upflow zone depletions in iron and calcium suggest that these elements have been removed by iron sulfide and anhydrite precipitation at some time in the history of the low chlorinity fluids the distribution of low and high chlorinity venting is consistent with mechanisms of phase segregation based on differential buoyancy or relative permeability the relatively shallow depth of the seafloor 1540 m and the observed chemistry of ashes fluids are consistent with phase separation in the sub critical or near critical region

the 4d microgravity method for waterflood surveillance part ii gravity measurements for the prudhoe bay reservoir alaska between 1994 and 2002 a series of experiments was conducted at prudhoe bay alaska aimed at the development of an effective 4d or time lapse gravity technique theoretical investigations had pointed out the potential for monitoring water injection in the 2500 m deep reservoir but it was not clear that gravity measurements of sufficient accuracy could be made in the arctic environment during the course of these experiments new techniques and instrumentation were introduced and perfected for both gravity and position measurements gravity stations are located using high precision global positioning system gps techniques without permanent monuments robust methods for meter drift control have improved noise resistance in relative gravimeter surveys absolute gravity measurements with a field portable instrument maintain absolute gravity levels among surveys a 4d gravity difference noise of 12 gal standard deviation has been established at prudhoe bay for gps controlled relative gravimeter surveys

poroelasticity efficient modeling of strongly coupled slow deformation processes in a multilayered half space we present a fast powerful numerical scheme to compute poroelastic solutions for excess pore pressure and displacements in a multilayered half space the solutions are based on the mirror image technique and use an extension of haskell s propagator method they can be applied to assess in situ formation parameters from the surface deformation field when fluids are injected into or extracted from a subsurface reservoir or they can be used to simulate changes in pore fluid pressure resulting from matrix displacements induced by an earthquake the performance of the numerical scheme is tested through comparison with observations of the surface deformation as recorded by tiltmeters in the vicinity of an iteratively pumped well modeling of near surface tilt data around a productive well is useful in constraining hydraulic diffusivity in the layered subsurface

earthen barriers to control lava flows in the 2001 eruption of mt etna abstract preceded by four days of intense seismicity and marked ground deformation a new eruption of mt etna started on 17 july and lasted until 9 august 2001 it produced lava emission and strombolian and phreatomagmatic activity from four different main vents located on a complex fracture system extending from the southeast summit cone for about 4 5 km southwards from 3000 to 2100 m elevation a s l the lava emitted from the lowest vent cut up an important road on the volcano and destroyed other rural roads and a few isolated country houses its front descended southwards to about 4 km distance from the villages of nicolosi and belpasso a plan of intervention including diversion and retaining barriers and possibly lava flow interruption was prepared but not activated because the flow front stopped as a consequence of a decrease in the effusion rate extensive interventions were carried out in order to protect some important tourist facilities of the sapienza and mts silvestri zones 1900 m elevation from being destroyed by the lava emitted from vents located at 2700 m and 2550 m elevation thirteen earthen barriers with a maximum length of 370 m height of 10 12 m base width of 15 m and volume of 25 000 m3 were built to divert the lava flow away from the facilities towards a path implying considerably less damage most of the barriers were oriented diagonally 110 135 to the direction of the flow they were made of loose material excavated nearby and worked very nicely resisting the thrust of the lava without any difficulty after the interventions carried out on mt etna in 1983 and in 1991 1992 those of 2001 confirm that earthen barriers can be very effective in controlling lava flows

influences of the tonga subduction zone on seafloor massive sulfide deposits along the eastern lau spreading center and valu fa ridge abstract this study investigates the morphology mineralogy and geochemistry of seafloor massive sulfide sms deposits from six back arc hydrothermal vent fields along the eastern lau spreading center elsc and valu fa ridge vfr in the context of endmember vent fluid chemistry and proximity to the tonga subduction zone to complement deposit geochemistry vent fluid analyses of cu zn ba pb and h 2 aq were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions results document southward increases in the abundance of mantle incompatible elements in hydrothermal fluids ba and pb and sms deposits ba pb as and sb which is also expressed in the abundance of barite baso 4 and galena pbs in sms deposits these increases correspond to a decrease in distance between the elsc vfr and the tonga subduction zone that correlates with a change in crustal lithology from back arc basin basalt in the north to mixed andesite rhyolite and dacite in the south barite influences deposit morphology contributing to the formation of horizontal flanges and squat terraces results are also consistent with a regional scale lowering of hydrothermal reaction zone temperatures from north to south except at the southernmost mariner vent field that leads to lower temperature higher ph vent fluids relative to mid ocean ridges of similar spreading rates mottl et al 2011 these fluids are cu and zn poor and the deposits formed from these fluids are cu poor but zn rich in contrast at the mariner vent field higher temperature and lower ph vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles mottl et al 2011 the mariner fluids are cu and zn rich and vent from sms deposits that are rich in cu but poor in zn with moderate amounts of pb thermodynamic calculations indicate that the contrasting metal contents of vent fluids and sms deposits can be accounted for by vent fluid ph wurtzite sphalerite zn fe s and galena pbs are saturated at higher temperatures in higher ph zn cu and pb poor elsc vfr vent fluids but are undersaturated at similar temperatures in low ph zn cu and pb rich vent fluids from the mariner vent field indicators of ph in the elsc and vfr sms deposits include the presence of co precipitated wurtzite and chalcopyrite along conduit linings in deposits formed from higher ph fluids and different correlations between concentrations of zn and ag in bulk geochemical analyses significant positive bulk geochemical zn ag correlations occur for deposits at vent fields where hydrothermal fluids have a minimum ph at 25 c 3 6 data show that the compositions of the mineral linings of open conduit chimneys minerals present mol fes in zn fe s that precipitate directly from hydrothermal fluids closely reflect the temperature and sulfur fugacity of sampled hydrothermal fluids these mineral lining compositions thus can be used as indicators of hydrothermal fluid temperature and composition ph metal content sulfur fugacity

rheology and topography control the path of a lava flow insight from numerical simulations over a preexisting topography 1 determination of flow path is strongly controlled by both the preexisting topography and rheology of the lava flow using the okmok 1997 eruption as an example lava flow we perform numerical simulations of bingham fluids flowing over preexisting topography and find that flow rheology determines whether or not new lobe formation or bifurcation occurs from the main flow at a topographic divide or remains confined by local topography therefore lobe or branch length may increase for higher viscosity flows when considering the effect of topographic control also even one order of magnitude difference in the rheological properties allows lava flows to move in completely different paths which may suggest that flow bifurcation due to topographic control provides insight to the local rheological properties of a lava flow the effect reported here should be taken into account in risk assessments of future volcanic hazards

submarine hydrothermal activity and gold rich mineralization at brothers volcano kermadec arc new zealand brothers volcano of the kermadec intraoceanic arc is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world it has two distinct vent fields known as the nw caldera and cone sites whose geology permeability vent fluid compositions mineralogy and ore forming conditions are in stark contrast to each other the nw caldera site strikes for 600 m in a sw ne direction with chimneys occurring over a 145 m depth interval between 1 690 and 1 545 m at least 100 dead and active sulfide chimney spires occur in this field and are typically 2 3 m in height with some reaching 6 7 m their ages at time of sampling fall broadly into three groups 4 23 and 35 years old the chimneys typically occur near the base of individual fault controlled benches on the caldera wall striking in lines orthogonal to the slopes rarer are massive sulfide crusts 2 3 m thick two main types of chimney predominate cu rich up to 28 5 wt cu and more commonly zn rich up to 43 8 wt zn geochemical results show that mo bi co se sn and au up to 91 ppm are correlated with the cu mineralization whereas cd hg sb ag and as are associated with the dominant zn rich mineralization the cone site comprises the upper cone site atop the summit of the recent main dacite cone and the lower cone site that straddles the summit of an older smaller more degraded dacite cone on the ne flank of the main cone huge volumes of diffuse venting are seen at the lower cone site in contrast to venting at both the upper cone and nw caldera sites individual vents are marked by low relief 0 5 m mounds comprising predominately native sulfur with bacterial mats vent fluids of the nw caldera field are focused hot 300 c acidic ph 2 8 metal rich and gas poor calculated end member fluids from nw caldera vents indicate that phase separation has occurred with cl values ranging from 93 to 137 of seawater values by contrast vent fluids at the cone site are diffuse noticeably cooler 122 c more acidic ph 1 9 metal poor and gas rich higher than seawater values of so4 and mg in the cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water rock interactions iron oxide crusts 3 years in age cover the main cone summit and appear to have formed from fe rich brines evidence for magmatic contributions to the hydrothermal system at brothers includes high concentrations of dissolved co2 e g 206 mm kg at the cone site high co2 3he negative d and 18oh2o for vent fluids negative 34s for sulfides to 4 6 sulfur to 10 2 and 15n2 to 3 5 vent fluid ph values to 1 9 and mineral assemblages common to high sulfidation systems changing physicochemical conditions at the brothers hydrothermal system and especially the cone site occur over periods of months to hundreds of years as shown by interlayered cu au and zn rich zones in chimneys variable fluid and isotopic compositions similar shifts in 3he 4he values for both cone and nw caldera sites and overprinting of magmatic mineral assemblages by water rock dominated assemblages metals especially cu and possibly au may be entering the hydrothermal system via the dissolution of metal rich glasses they are then transported rapidly up into the system via magmatic volatiles utilizing vertical 2 5 km long narrow 300 m diameter pipes consistent with evidence of vent fluids forming at relatively shallow depths the nw caldera and cone sites are considered to represent stages along a continuum between water rock and magmatic hydrothermal dominated end members

mitigation of lava flow invasion hazard through optimized barrier configuration aided by numerical simulation the case of the 2001 etna eruption abstract lava flow spreading along the flanks of etna volcano often produces damages to the land and proprieties the impact of these eruptions could be mitigated by building artificial barriers for controlling and slowing down the lava as recently experienced in 1983 1991 1993 2001 and 2002 this study investigates how numerical simulations can be adopted for evaluating the effectiveness of barrier construction and for optimizing their geometry considering as test case the lava flows emplaced on etna s south flank during 2001 the flow temporal evolutions were reconstructed deriving the effusion rate trends together with the pre eruption topography were adopted as input data of the magflow simulation code three simulations were then conducted to simulate lava flow with and without barriers the first aimed at verifying the reconstruction of the effusion rate trends while the others at assessing the performance of the barrier system realized during the eruption in comparison with an alternative solution here proposed a quantitative analysis carried out on the first simulation confirms the suitability of the selected test case the comparison of the three simulated thickness distributions showed both the effectiveness of the barriers in slowing down the lava flow and the sensitivity of the magflow code to the topographical variations represented by the barriers finally for reducing both the time necessary to erect the barrier and the barrier environmental impact the gabion s barrier construction was analyzed the implemented and tested procedure enforces the capability of using numerical simulations for designing optimized lava flow barriers aimed at making swifter mitigatory actions upon lava flows and improving the effectiveness of civil protection interventions during emergencies

abundant hydrothermal venting along melt rich and melt free ridge segments in the lau back arc basin 1 the relationship between the spatial density of hydrothermal venting ph and spreading rate us is undefined along back arc ridges here we report a continuous survey of hydrothermal plumes along the 400 km long eastern lau spreading center the mean ph us ratio for each of three tectonic segments followed the global midocean ridge trend with ph doubling as us increased northward from 39 to 96 mm yr however we found little correlation between ph and the previously imaged distribution of axial melt lenses which are near continuous along the southern two segments but wholly absent along the northernmost segment we infer that venting on the southern segments is melt driven whereas venting on the northern elsc is entirely powered with heat extracted by deep circulation through hot rock this segment may be a rare example of an entire fast spreading segment where hydrothermal convection cells are powered by downward migrating cracking fronts

emplacement and erosion by archean komatiite lava flows at kambalda revisited we have developed a mathematical model to evaluate the flow and erosional potential of submarine channelized komatiite lavas at kambalda western australia field data from kambalda were used to constrain the choice of important input parameters and model results were compared with data from field studies and geochemical analyses our results suggest that thermal erosion is strongly dependent upon the nature and behavior of the substrate if the substrate is treated as an unconsolidated hydrous sediment that can be fluidized by vaporized seawater then our model predicts that an initially 10 m thick basal kambalda komatiite lava could have produced very high thermo mechanical erosion rates 23 10 m day crustal thicknesses of 5 20 cm at distances of 5 35 km from the source and a high degree of lava contamination 3 12 in contrast if the substrate is treated as a more consolidated anhydrous sediment that could not be fluidized then our model predicts that a kambalda komatiite flow would have had much lower thermal erosion rates 1 2 0 4 m day and degrees of contamination 1 3 and would have had crustal thicknesses of 5 20 cm at longer flow distances of 30 165 km field constraints are generally consistent with our predictions for a non fluidized substrate the reentrant embayments at kambalda are thought to form from either erosion of deep channels in a flat basaltic seafioor huppert et al 1984 or erosion of a thin 5 m sediment with minor undercutting of basalt in pre existing topography lesher et al 1984 our modeling indicates that the former was possible for long eruption durations months whereas the latter was possible for short eruption durations 2 weeks as the latter hypothesis is more consistent with the existing field evidence for thermal erosion at kambalda we believe it is the preferred interpretation

the perception of volcanic risk in kona communities from mauna loa and hualālai volcanoes hawai i abstract volcanic hazards in kona i e the western side of the island of hawai i stem primarily from mauna loa and hual lai volcanoes the former has erupted 39 times since 1832 lava flows were emplaced in kona during seven of these eruptions and last impacted kona in 1950 hual lai last erupted in ca 1800 society s proximity to potential eruptive sources and the potential for relatively fast moving lava flows coupled with relatively long time intervals since the last eruptions in kona are the underlying stimuli for this study of risk perception target populations were high school students and adults n 462 using these data we discuss threat knowledge as an influence on risk perception and perception as a driving mechanism for preparedness threat knowledge and perception of risk were found to be low to moderate on average fewer than two thirds of the residents were aware of the most recent eruptions that impacted kona and a minority felt that mauna loa and hual lai could ever erupt again furthermore only about one third were aware that lava flows could reach the coast in kona in less than 3 h lava flows and ash fall were perceived to be among the least likely hazards to affect the respondent s community within the next 10 years whereas vog volcanic smog was ranked the most likely less than 18 identified volcanic hazards as amongst the most likely hazards to affect them at home school or work not surprisingly individual preparedness measures were found on average to be limited to simple tasks of value in frequently occurring domestic emergencies whereas measures specific to infrequent hazard events such as volcanic eruptions were seldom adopted furthermore our data show that respondents exhibit an unrealistic optimism bias and infer that responsibility for community preparedness for future eruptions primarily rests with officials we infer that these respondents may be less likely to attend to hazard information react to warnings as directed and undertake preparedness measures than other populations who perceive responsibility to lie with themselves there are significant differences in hazard awareness and risk perception between students and adults between subpopulations representing local areas and between varying ethnicities we conclude that long time intervals since damaging lava flows have occurred in kona have contributed to lower levels of awareness and risk perceptions of the threat from lava flows and that the on going eruption at k lauea has facilitated greater awareness and perception of risk of vog but not of other volcanic hazards low levels of preparedness may be explained by low perceptions of threat and risk and perhaps by the lack of a clear motivation or incentive to seek new modes of adjustment

a relation between lava discharge rate thermal insulation and flow area set using lidar data 1 a simple linear relation can be used to link time averaged discharge rate tadr and lava flow area a the relation applies to given insulation conditions as described by the characteristic flow surface temperature te and will vary from case to case depending on rheological and topographic influences on flow spreading most flows have insulation conditions that change through time modifying the relationship between tadr and area as insulation conditions evolve using lidar data we can define tadr the flow area that the discharge feeds and te allowing generation of a case specific relation to convert satellite data derived flow areas to tadr for etna s 2006 lava flow field we obtain a relation whereby tadr 5 6 10 6 a for well insulated conditions te 100 c and tadr 1 5 10 4 a for poorly insulated conditions te 600 c

integrating gravimetric and interferometric synthetic aperture radar data for enhancing reservoir history matching of carbonate gas and volatile oil reservoirs reservoir history matching is assuming a critical role in understanding reservoir characteristics tracking water fronts and forecasting production while production data have been incorporated for matching reservoir production levels and estimating critical reservoir parameters the sparse spatial nature of this dataset limits the efficiency of the history matching process recently gravimetry techniques have significantly advanced to the point of providing measurement accuracy in the microgal range and consequently can be used for the tracking of gas displacement caused by water influx while gravity measurements provide information on subsurface density changes i e the composition of the reservoir these data do only yield marginal information about temporal displacements of oil and inflowing water we propose to complement gravimetric data with interferometric synthetic aperture radar surface deformation data to exploit the strong pressure deformation relationship for enhancing fluid flow direction forecasts we have developed an ensemble kalman filter based history matching framework for gas gas condensate and volatile oil reservoirs which synergizes time lapse gravity and interferometric synthetic aperture radar data for improved reservoir management and reservoir forecasts based on a dual state parameter estimation algorithm separating the estimation of static reservoir parameters from the dynamic reservoir parameters our numerical experiments demonstrate that history matching gravity measurements allow monitoring the density changes caused by oil gas phase transition and water influx to determine the saturation levels whereas the interferometric synthetic aperture radar measurements help to improve the forecasts of hydrocarbon production and water displacement directions the reservoir estimates resulting from the dual filtering scheme are on average 20 40 better than those from the joint estimation scheme but require about a 30 increase in computational cost

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

hydrothermal activity in the lau back arc basin sulfides and water chemistry the submersible nautile completed 22 dives during the nautilau cruise r v nadir april 17 may 10 1989 for a detailed investigation of the southern lau basin near tonga the objective of the scientific team from france germany and tonga was to understand the process of sea floor ore formation associated with hydrothermal circulation along the valu fa back arc ridge behind the tonga kermadec trench the four diving areas between lat 21 25 s and 22 40 s in water 2000 m deep were selected on the basis of results from cruises of the r v jeancharcot and r v sonne the nadir cruise provided proof of hydrothermal activity in all four areas over more than 100 km as indicated by the widespread occurrence of hydrothermal deposits and by heat flow conductivity and temperature measurements near the sea bottom the most spectacular findings were high temperature white and black smokers and associated fauna and ore deposits hydrothermal water chemistry and sulfide composition data presented here indicate that this hydrothermal field is very different from the hydrothermal fields in oceanic ridges this difference is seen in the water chemistry of the hydrothermal fluid ph 2 and high metal content and the chemical composition of sulfides enrichment in ba as and pb

volatile element isotopes of submarine hydrothermal mineral deposits in the western pacific the abundance and isotopic compositions of volatile elements trapped in fluid inclusions of submarine hydrothermal mineral deposits in western pacific subduction zones okinawa trough izu bonin arc mariana trough and lau basin and in kuroko ores in northeastern japan are presented the helium isotopic compositions corrected for air contribution of the okinawa and mariana troughs ranging 4 49 7 68 ra are lower than those of the izu bonin and lau basin 7 62 8 91 ra this characteristic might reflect the differences in regional tectonic setting the okinawa and mariana troughs are related to back arc spreading with strong graben sedimentary signature whereas the izu bonin arc is associated with island arc magmatism the arc contribution to the lau basin volcanism is significantly strong even though it is assigned to back arc spreading nitrogen isotopes can also be explained by a similar hypothesis whereas argon and carbon isotopes cannot be used to discriminate tectonic setting 13c co2 3he and 15n n2 36ar diagrams elucidate the source of carbon and nitrogen the mor type mantle contributions to carbon are mostly smaller in the okinawa and mariana troughs ranging 0 06 8 9 with the average of 2 4 than in the izu bonin and lau basin 2 1 25 with the average of 7 7 the sedimentary contributions to nitrogen are larger in the okinawa and mariana troughs 11 65 with the average of 35 than in the izu bonin and lau basin 4 24 with the average of 15 and the kuroko samples agree well with the latter carbon and nitrogen fluxes are again higher in okinawa trough than in izu bonin arc

gravimetric monitoring of the first field wide steam injection in a fractured carbonate field in oman a feasibility study gas oil gravity drainage is to be enhanced by steam injection in a highly fractured low permeability carbonate field in oman following a successful pilot field wide steam injection is being implemented first of this type in the world a dedicated monitoring program has been designed to track changes in the reservoir various observations are to be acquired including surface deformation temperature measurements microseismic well logs pressure and saturation measurements to monitor the reservoir because significant changes in the reservoir density are expected time lapse gravimetry is also being considered in this paper we investigate the feasibility of gravimetric monitoring of the thermally enhanced gravity drainage process at the carbonate field in oman for this purpose forward gravity modelling is performed based on field groundwater measurements the estimates of the hydrological signal are considered and it is investigated under what conditions the groundwater influences can be minimized using regularized inversion of synthetic gravity data we analyse the achievable accuracy of heat front position estimates in case of large groundwater variations at the field the gravity observations can be significantly affected and consequently the accuracy of heat front monitoring can be deteriorated we show that by applying gravity corrections based on local observations of groundwater the hydrological influences can to a large extent be reduced and the accuracy of estimates can be improved we conclude that gravimetric monitoring of the heat front evolution has a great potential 2015 european association of geoscientists engineers

methodology for the construction of earth barriers to divert lava flows the mt etna 1983 eruption this paper gives a critical analysis of the technical solutions adopted for erecting earthworks to divert lava flows on the basis of the experience obtained recently during the 1983 eruption of mount etna the purpose of the paper is to explain questions of general nature and throw light on problems that must still be solved which render it difficult to extrapolate the adopted solutions to other volcanic eruptions having radically different characteristics an account of the earthworks made at the various sites to the east and the west of the lava flow is given and an analysis is made of the planning choices the decisions taken during the work the daily output and thence the relative costs the works carried out are summarized in table 1 giving characteristics and costs of the works and times and sizes of the equipments used the following works were carried out during 50 days of 13 working hours per day a total volume of ca 750 000 m3 of material was moved and ca 10 km of service roads were built the total cost of the above mentioned works was 3 678 millions of italian liras the final result fulfilled the planning forecasts all the earthworks erected carried out their task of guiding and diverting the lava flows amongst other things the study of the evolution of eruption has shown that preventive and emergency works can successfully be programmed finally the technological aspects of the works are discussed with particular reference to their planning site organization determination of type and number of vehicles to be employed output to expect and thus for a correcta priori estimate of the advantage cost ratio a forecast of the expenses involved the paper aims at giving information that may be of use during emergency situations and at stimulating the study of an operations program for mitigating the effects of lava flows in areas of volcanic risk

mass dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles abstract sulfur isotope studies of post archean terrestrial materials have focused on the ratio 34s 32s because additional isotopes 33s and 36s were thought to carry little information beyond the well known mass dependent relationship among multiple isotope ratios we report high precision analyses of 33s and 36s values defined as deviations of 33s and 36s from ideal mass dependent relationships for international reference materials and sedimentary sulfides of phanerozoic age by using a fluorination technique with a dual inlet isotope ratio mass spectrometer measured variations in 33s and 36s are explained as resulting from processes involve branching reactions two or more reservoirs formed or mixing irreversible processes in closed systems rayleigh distillation amplify the isotope effect we outline how this new isotope proxy can be used to gain new insights into fundamental aspects of the sulfur biogeochemical cycle including additional constraints on seawater sulfate budget and processes in sedimentary sulfide formation the isotope systematics discussed here cannot explain the much larger variation of 33s and 36s observed in archean rock records furthermore phanerozoic samples we have studied show a characteristic 33s and 36s relationship that differs from those measured in archean rocks and laboratory photolysis experiments thus high precision analysis of 33s and 36s can be used to distinguish small non zero 33s and 36s produced by mass dependent processes from those produced by mass independent processes in archean rocks and extraterrestrial materials

chemistry of hot springs along the eastern lau spreading center abstract the eastern lau spreading center elsc is the southernmost part of the back arc spreading axis in the lau basin west of the tonga trench and the active tofua volcanic arc over its 397 km length it exhibits large and systematic changes in spreading rate magmatic tectonic processes and proximity to the volcanic arc in 2005 we collected 81 samples of vent water from six hydrothermal fields along the elsc the chemistry of these waters varies both within and between vent fields in response to changes in substrate composition temperature and pressure ph water rock ratio and input from magmatic gases and subducted sediment hot spring temperatures range from 229 to 363 c at the five northernmost fields with a general decrease to the south that is reversed at the mariner field the southernmost field vai lili emitted water at up to 334 c in 1989 but had a maximum venting temperature of only 121 c in 2005 due to waning activity and admixture of bottom seawater into the subseafloor plumbing system chloride varies both within fields and from one field to another from a low of 528 mmol kg to a high of 656 mmol kg and may be enriched by phase separation and or leaching of cl from the rock concentrations of the soluble elements k rb cs and b likewise increase southward as the volcanic substrate becomes more silica rich especially on the valu fa ridge iodine and 7li increase southward and 11b decreases as b increases apparently in response to increased input from subducted sediment as the arc is approached species that decrease southward as temperature falls are si h2s li na cl fe mn and 87sr 86sr whereas ph alkalinity ca and sr increase oxygen isotopes indicate a higher water rock ratio in the three systems on valu fa ridge consistent with higher porosity in more felsic volcanic rocks vent waters at the mariner vent field on the valu fa ridge are significantly hotter more acid and metal rich less saline and richer in dissolved gases and other volatiles including h2s co2 and f than the other vent fields consistent with input of magmatic gases the large variations in geologic and geophysical parameters produced by back arc spreading along the elsc which exceed those along mid ocean ridge spreading axes produce similar large variations in the composition of vent waters and thus provide new insights into the processes that control the chemistry of submarine hot springs

geochemistry of hot springs at the susu knolls hydrothermal field eastern manus basin advanced argillic alteration and vent fluid acidity abstract susu knolls is an area of ongoing magmatic activity and recent volcanism located in the back arc spreading environment of the manus basin in the bismarck sea papua new guinea in 2006 hydrothermal fluids were collected from three areas of submarine hot spring venting and analyzed for the chemical and isotopic composition of major and trace species fluids were characterized by temperatures that varied from 226 325 c and formed grey to black smoke as they mixed with bottom seawater the compositions of seawater derived vent fluids are regulated by the relative contributions of fluid rock and fluid sediment interaction phase separation and the addition of volatiles from magmatic degassing in addition to phase separation leaching of cl from felsic rocks that compose the lithosphere in back arc environments may produce cl concentrations in excess of seawater values the measured ph25 c of susu knolls smoker fluids varied from 1 5 3 7 a range that includes values substantially more acidic than typically observed in fluids at mid ocean ridge spreading centers late stage addition of magmatic volatiles in the shallow seafloor is directly responsible for the most acidic fluids ph25 c values below 2 in contrast the acidity of vent fluids characterized by ph25 c values between 2 and 3 is not the direct result of the direct addition of magmatically derived acidic species instead the ph of these fluids likely reflects reaction with rocks that were previously altered by highly acidic magmatic fluids to an advanced argillic alteration assemblage containing quartz illite pyrophyllite anhydrite alunite in hydrothermal upflow zones fluids that do not react with advanced argillic alteration assemblages during upflow have measured ph25 c values between 3 and 4