laboratory calibration of chemical volcanic gas sampling techniques using an artificial fumarole abstract we have constructed an artificial laboratory fumarole to calibrate the most common chemical volcanic gas sampling techniques and obtain a quantitative measure of their efficacy we have also developed and tested a new rugged and portable venturi spray gas sampler the venturi sampler reproduced the output gas composition most accurately followed by the giggenbach bottles filter packs and lastly alkaline traps passive alkaline traps however did better than filter packs when sampling more concentrated fumarole gases under ideal conditions the accuracy of the giggenbach bottles was identical to the venturi sampler although there was slightly more scatter the giggenbach sampler was more susceptible to problems with condensation on the input train even in a laboratory setting and this technique was only effective in relatively concentrated gas streams filter packs are also effective but extreme care must be exercised to maintain strong undersaturation with respect to the acid gas if strong undersaturation high ph is not maintained the filter packs return erroneously low s cl and s f ratios use of a ph indicator is an effective way of avoiding this problem the passive alkaline traps also under sample sulfur resulting in low reported s cl and s f ratios it appears that the overall sampling efficiency of all techniques was not strongly affected by oxygen fugacity over the limited range tested when detecting sulfate and sulfite simultaneously we found no difference in total sulfur before and after oxidation this suggests that all sulfur from the gas regardless of oxidation state was absorbed as sulfite or sulfate and or was quickly oxidized in solution this conclusion is supported by ic hs reference samples

selenium in volcanic environments a review abstract selenium is a chemical element with major environmental implications due to the extremely narrow range between essential and toxic concentrations volcanoes emit significant amounts of se which has an enormous impact on the se cycle and potentially human and animal health this paper presents a broad overview of the current state of knowledge of major aspects of volcanic derived se focussing on the processes in soils and aquifers volcanic soils formed when volcanic products weather rapidly display peculiar characteristics selenium contents can be relatively high 1 2 orders of magnitude higher compared to the worldwide average 0 4 mg kg but often with low mobility the soils can be impacted by local deposition of volcanic emissions which are enriched in se due to volatilization in the magma chamber it seems that the chemical fate of se in volcanic soils is controlled by sorption processes on poorly crystalline phases which presence depends on the parental materials and weathering these sorption processes also determine leaching to groundwaters some volcanic aquifers have se concentrations above the who guideline of 10 g l this might also be related to geothermal activity in spite of the well documented interest on se during the last decades a significant number of uncertainties exist on the behavior of this fascinating element a preliminary model of the se cycle around volcanoes can be constructed but the well known analytical problems associated with se determinations have produced a lack of reliable information on some processes involved in the chemical interaction between soils and water this review therefore also aims to identify the processes where new efforts are needed to produce good quality data to be compared and integrated in global models

particle transport in the bari canyon southern adriatic sea to define the sediment transport pathways along the southern adriatic shelf and slope two oceanographic cruises were carried out in the southern adriatic in july 2004 and in march april 2005 to study the role of the bari canyon system on sediment dispersal three moorings including sediment traps and current meters have been deployed near the bottom at depths of 600 m for one year march 2004 march 2005 two moorings were deployed within the canyon station b in the northern branch and station c in the southern branch and one on the adjacent open slope north of the canyon system station a total mass fluxes tmfs measured by sediment traps were always higher in the canyon than on the adjacent slope the highest values were measured at station c average 8 07 g m 2 d 1 roughly double those of station b 3 07 g m 2 d 1 and the lowest outside the canyon at station a 1 69 g m 2 d 1 the highest tmf were recorded in spring 2004 a period characterized by the lowest water temperatures and the highest current speeds up to 72 cm 1 which were associated with the highest across slope current component along the canyon axes the simultaneous variations of fluxes occurring at the three stations imply that similar processes are active along the entire southern adriatic margin and that they are amplified inside the canyon in spring a vein of southward flowing north adriatic dense water naddw was observed along the adriatic shelf this was related to an enhanced across slope current component which was responsible for the higher particle fluxes both on the open slope and at the canyon stations these data suggest that the bari canyon is an efficient conduit for sediment from the adriatic continental shelf to the deep basin downcore profiles of 210 pb in sediments collected below the traps have been used to estimate sediment mass accumulation rates mars on a century scale on the open slope the annual trap flux recorded in 2004 2005 was lower than mar on the contrary in the bari canyon the annual trap flux was higher than mar indicating that the lateral advection of particles becomes predominant and that a fraction of the particles intercepted by sediment traps was only in transit through the canyon 2007 elsevier b v all rights reserved

the use of 7 lioh impregnated filters for the collection of acidic gases and analysis by instrumental neutron activation analysis a simple system was designed using7lioh impregnated filters to collect acidic gases from ambient air and from highly concentrated volcanic plumes or gas streams these filters were developed for analysis using instrumental neutron activation analysis but other analytical techniques could be used as well the sampling system was designed to use a series of 1 3 m7lioh impregnated filters to collect high concentrations of acidic gases found in gas plumes of active volcanoes the filters are quantitative for so2 and the halide acids when sufficient base is present to neutralize the acidic species extremely high concentrations of so2 may not be collected quantitatively since so2 is a relatively weak lewis acid compared to the halide acids the acidic oxides of sb as and se were also collected quantitatively a particle filter preceded the impregnated filters in order to remove particles from the fumes this system has proven effective under difficult sampling conditions and since it is portable and light weight it could be used for many volcanological applications where high levels of acidic gaseous phase species need to be collected

simulating the formation and fate of dense water in a midlatitude marginal sea during normal and warm winter conditions 1 dense shelf water production and the deep convection process in the adriatic sea are investigated considering two case studies the first is representative of the present climatic situation whereas the second may be expected in a scenario characterized by mild winter conditions over the basin dense water production and spreading are studied using a high resolution implementation of the massachusetts institute of technology general circulation model that is initialized and forced with realistic conditions this paper provides qualitative and quantitative information on mass transport dense water pathways thermohaline structures and the mixing properties of the basin in the northern adriatic shelf seawater temperature is the key element for winter dense water production because it contributes more relevantly than salinity in determining density in the southern adriatic sea a small amount of dense water that cascades directly into the pit can be formed on the narrow western shelf only during cold winter conditions moreover open ocean deepwater formation occurs in the middle of the southern basin in late winter and spring although only when winter conditions have been sufficiently cold northern adriatic dense shelf water forms a subsurface stream of which the densest part rapidly sinks in the southern pit along the shelf break whereas its lighter part flows southward and reaches the otranto strait the frequent occurrence of mild winter conditions could lead to lower dense water production with a reduced dense water flow from the adriatic sea to the ionian sea and a potential great impact on the eastern mediterranean thermohaline circulation

modeling the northern adriatic double gyre response to intense bora wind a revisit 1 a combination of recent intensive observations and simulations with two numerical models is used to revisit the issue of the northern adriatic response to strong bora episodes new observed and simulated data reinforce the view that an episode of strong bora wind provokes a double gyre cyclonic trieste and anticyclonic rovinj response north of the po delta pula line during an intense bora episode both measured and modeled statistics picture a downwind highly polarized and almost depth independent flow within the trieste gyre nw arm its ne arm maintains a sharp polarization and strong depth dependence while exhibiting lower speeds with models in good accord with observations the current statistics for rovinj gyre provide lower maximum and average speed values and less polarized but still rather depth independent flow while exhibiting clockwise rotation the north arm of the senj gyre positioned south of the po delta pula line enjoys more lateral freedom and exhibits less rectilinear flow our review reinforces the notion that modeling studies based on ecmwf wind forcing fail to properly take into account the orographic control of the dinaric alps and to produce correct bora induced gyral pattern the coamps model successfully simulated the onset duration and decay of the wind peaks but exhibited a tendency to overpredict the strength of the bora wind our simulations have identified the shallow nw coastal strip as an important source of colder water observed in a sequence of remotely sensed sst fields derived from avhrr data

mid devonian tectonics and sedimentation in the bristol channel area the hangman sandstone group eifelian of north devon contains two continental 9old red sandstone9 formations the trentishoe formation is some 1000 m thick and consists of lithic arenites which petrographically match closely with those in the higher parts of the lower old red sandstone in south wales this formation was derived mainly from erosion of the highest lower old red sandstone in early mid devonian times as a result of end caledonian uplift and erosion in s wales the rawns formation which follows contains 120 m of conglomerates and pebbly sandstones with angular clasts of porphyry tuff quartzite and lithic arenite which do not match with rocks in possible source areas in wales but could have been derived from the lower palaeozoic and precambrian rocks believed to lie at shallow depth to the north of the bristol channel fault zone fault movements along this zone are believed to have generated relatively short lived coarse clastic supply at various times and places around the bristol channel in lower to early mid devonian times in response to end caledonian movements the later production of late namurian to westphalian sands from the bristol channel area was unrelated to these devonian events and represents uplift in response to variscan events in sw england

anthropogenic versus natural control on trace element and sr nd pb isotope stratigraphy in peat sediments of southeast florida usa 1500 ad to present abstract analysis of a well dated peat core from blue cypress marsh bcm provides a detailed record of natural and anthropogenic factors that controlled the geochemical cycles of a number of trace elements in florida over the last five centuries the trace elements were divided into natural and anthropogenic groups using concentration trends from the bottom to the top of the core the natural group includes li sc cr co ga ge zr nb cs ba hf y ta th and ree rare earth elements these elements show similar concentrations throughout the core indicating that changes in human activities after european arrival in the new world did not affect their geochemical cycles the anthropogenic group includes pb cu zn v sb sn bi and cd upcore enrichment of these elements indicates enhancement by anthropogenic activities from the early 1500s to present fluxes of the anthropogenic metals to the marsh increased significantly with modern accumulation rates several fold e g v to hundreds of times e g zn greater than pre colonial rates the dominant input mechanism for trace elements from both groups to the marsh has been atmospheric deposition atmospheric input of a number of the elements including the anthropogenic metals was dominated by local sources during the last century for several elements long distant transport may be important for instance ree and nd isotopes provide evidence for long range atmospheric transport dominated by saharan dust the greatest increase in flux of the anthropogenic metals occurred during the 20th century and was caused by changes in the chemical composition of atmospheric deposition entering the marsh increased atmospheric inputs were a consequence of several anthropogenic activities including fossil fuel combustion coal and oil agricultural activities and quarrying and mining operations pb and v exhibit similar trends with peak accumulation rates in 1970 the principal anthropogenic source of v is oil combustion the decline in v accumulation after 1970 in the bcm peat corresponds to the introduction of low sulfur fuels and the change from heavy to distilled oils since the 1970s after the 1920s pb distribution in the peat follows closely the history of alkyl lead consumption in the us which peaked in the 1970s pb isotopes support this inference and furthermore record changes in the ore sources used to produce leaded gasoline idaho ores dominated the peat pb isotope record until the 1960s followed by pb from mississippi valley type deposits from the 1960s to the 1980s enhanced fluxes of cu zn cd sn sb bi and to some extent ni during the last century are likely also related to fossil fuel combustion local agricultural activities may also have influenced the geochemical cycles of cu and zn the peat record shows enhanced u accumulation during the last century possibly related to phosphate mining in western florida sr isotopes in the peat core also reflect anthropogenic influence the 87sr 86sr ratio decreases from natural background values in the basal part of the core to lower values in the upper part of the core the sr isotope shift is probably related to quarrying operations in florida and marks the first time an anthropogenic signal has been detected using the sr isotope record in a peat core

dense water flow and carbonate system in the southern adriatic a focus on the 2012 event abstract the active deep overturning circulation of the mediterranean is emerging as one of the most effective mechanisms in transporting the atmospheric imprint on the carbon cycle to the interior of the basin there is growing evidence that sites of dense water formation over the continental shelf such as the northern adriatic sea play a key role in this process nevertheless little is known about the inorganic carbon chemistry of the adriatic sea and co2 absorption and its fate the winter of 2012 experienced peculiar meteorological conditions with an extended period of cold weather with strong winds that triggered in february a massive formation of an extremely cold and dense potential density anomaly 30 00 kg m 3 northern adriatic dense water naddw water mass this event provided a unique opportunity to study this process at sub basin scale taking into account co2 adsorption within the naddw source area the gulf of trieste in the northern adriatic and its spreading over the shelf and into the southern adriatic pit the northern adriatic and the gulf of trieste during winter act as a co2 sink the average air sea co2 flux of 60 mmol m 2 d 1 estimated during the exceptional 2012 event was at least 3 times higher than the flux measured in winter 2008 when dense water was produced through the same mechanism but under less extreme conditions in winter 2012 absorbed co2 resulted in the decrease of pht25 down to 7 907 0 034 pht units and the strong evaporation induced by wind increased total alkalinity ta to 2673 16 mol kg 1 following its formation in the north the naddw plume entering the southern adriatic observed in march 2012 exhibited significantly modified values the plume was characterized by colder temperature 10 c lower pht25 7 947 pht units and higher alkalinity 2635 mol kg 1 than the surrounding water masses along the western adriatic shelf however the signal of atmospheric co2 enrichment was weaker than in the northern adriatic source region as well as positive apparent oxygen utilization aou values 20 mol kg 1 were recorded this is suggestive of oxygen consumption in the water mass observed changes in both physical and biogeochemical properties were similar to those observed in 2008 suggesting that mixing with levantine intermediate waters liw was the main driver modulating the changes of aou and inorganic carbon chemistry in both winters the rising of pht25 and aou due to the mixing indicates that naddw at its origin was richer in atmospheric co2 than the liw was thus confirming the relevance of the northern adriatic sea for co2 adsorption the study provides the first characterization of inorganic carbon chemistry including carbonate minerals saturation states ar and ca in the bottom waters both on the slope and along the expected pathways of dense water cascading in the adriatic sea therefore it can represent a baseline to improve the knowledge on the acidification process and impacts as well as being useful for comparison with other benthic environments

alkalinity of the mediterranean sea total alkalinity at was measured during the meteor 51 2 cruise crossing the mediterranean sea from west to east at concentrations were high 2600 mol kg 1 and alkalinity salinity correlations had negative intercepts these results are explained by evaporation coupled with high freshwater at inputs into coastal areas salinity adjustment of at revealed excess alkalinity throughout the water column compared to mid basin surface waters since mediterranean waters are supersaturated with respect to calcite and aragonite the excess alkalinity likely reflects alkalinity inputs to coastal areas close to regions of deep and intermediate water formation an alkalinity budget shows that main alkalinity inputs come from the black sea and from rivers whereas the strait of gibraltar is a net sink the major sink appears to be carbonate sedimentation the basin average net calcification rate and caco3 sedimentation was estimated to be 0 38 mol m 2 yr 1 the estimated residence time of at is 160 yr

anthracitization of coals in the south wales coalfield abstract investigations by the institute of geological sciences on potential geothermal water sites in the coalfield of south wales have been reported they are of considerable interest and revive the controversy about the nature of the heat source responsible for the anthracitization of some coals in this classic area in the absence of exposed post carboniferous igneous rocks in the coalfield general opinion has favoured heat generation by friction along faults or disturbances we re examine the evidence in the light of more recent geophysical and geochemical investigations which suggest the possibility of igneous intrusions at a depth of about 3 5 km or shallower the likely age of such intrusions is also considered high seismic velocity basement rocks rise to only 2 5 km beneath the surface of the carboniferous in the northwestern anthracitized zone of the coalfield and we suggest that anthracitization in south wales is not the result of depth of burial nor of frictional heat but of proximity to a magmatic heat source associated with crystalline rocks of the basement

seismicity and tectonics in wales the distribution of instrumental and historical seismicity in wales is described including two events in 1984 for which good hypocentral locations were determined most of central wales is aseismic throughout the historic record suggesting that this is not a feature of reporting bias or population distribution alone there appears to be a relation between the epicentres and some of the major fault structures of wales including the bala fault and the swansea valley disturbance the relationship between faults and seismicity is examined in detail for the two recent events and more generally for the rest of the data which have much lower locational accuracy stress measurements for nw europe are shown to give a consistent nw se direction for the maximum horizontal stress this is appropriate for sinistral strike slip on n s vertical faults first motion data for both 1984 events also give a nodal plane in this orientation in the first case the event can be clearly attributed to mapped n s vertical faults se of newtown and in the second a deep n s normal fault under the lleyn peninsula is inferred as the most likely fault plane orientation from regional geological considerations the proposed activity of the bala fault and the swansea valley disturbance can also be explained within this stress field by their thrust reactivation as low angle structures the general difficulty of relating the remaining seismicity to geological structures is demonstrated by the fact that the second 1984 event could not be directly connected with any surface structure or even with known structures at depth

ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western arctic ocean calcium carbonate caco3 mineral saturation states for aragonite aragonite and calcite calcite are calculated for waters of the chukchi sea shelf and canada basin of the western arctic ocean during the shelf basin interactions project from 2002 to 2004 on the chukchi sea shelf a strong seasonality and vertical differentiation of aragonite and calcite saturation states was observed during the summertime sea ice retreat period high rates of phytoplankton primary production and net community production act to increase the aragonite and calcite of surface waters while subsurface waters become undersaturated with respect to aragonite due primarily to remineralization of organic matter to co2 this seasonal phytoplankton carbonate saturation state interaction induces strong undersaturation of aragonite aragonite 10 the seasonal aragonite undersaturation of waters observed on the chukchi sea shelf is likely a recent phenomenon that results from the uptake of anthropogenic co2 and subsequent ocean acidification with seasonality of saturation states superimposed by biological processes these undersaturated waters are potentially highly corrosive to calcifying benthic fauna e g bivalves and echinoderms found on the shelf with implications for the food sources of large benthic feeding mammals e g walrus gray whales and bearded seals the benthic ecosystem of the chukchi sea and other arctic ocean shelves is thus potentially vulnerable to future ocean acidification and suppression of caco3 saturation states

role of the mid adriatic deep in dense water interception and modification abstract this study set out to gain insights into i the route of dense water dw which leaves a morphological signature including large scale erosion moats and contourite sediment drifts and ii the physical and chemical modifications undergone by northern adriatic dense water naddw due to its entrapment in the mid adriatic deep mad for one or more years which leads to biogeochemical transformation into mid adriatic dense water maddw a less dense and colder water mass with reduced oxygen content as a result of prolonged biological consumption the paper provides an accurate description of how naddw on its way to the southern adriatic basin mixes with maddw on palagru a sill analysis of water column data ctd collected in spring 2005 and 2012 showed that part of the naddw flowing down the western adriatic shelf swerves left splitting into a branch that fills the western mad pit and another flowing along the 170 m contour towards the eastern pit and then south through palagru a sill due to the density difference the recently formed naddw flows as a bottom trapped current underneath the older maddw lifting and pushing it over palagru a sill thereby promoting water exchange among the mad pits the two water masses eventually mix as they flow over palagru a sill in proportions that depend on naddw volume and the changes undergone by maddw thus generating a new mixed bottom flowing dw with a distinctive chemical signal the bottom water pattern disclosed by ctd transects is consistent with seafloor and sub seafloor morphologies detected on high resolution seismic profiles which show both erosion and deposition features along bottom water routes moreover confinement of the mixed water within structural highs as it flows southward through palagru a sill promotes formation of shallow water contourites and giant sediment drifts demonstrating a significant role for topography in the flow of all adriatic dw

a new collector for sampling volcanic aerosols abstract a new apparatus venturi effect system ves designed for sampling volcanic plumes is described and tested at vulcano italy this device together with purified basic nh 4 oh solutions supplies optimal conditions to obtain reliable s total cl f ratios and enrichment factors for metallic trace elements mte good concordance for acid gas ratios and metal enrichment factors in both the gas phase and the related plume allows the procedure to be validated the ves appears in vulcano conditions as a simple robust and easily portable apparatus that allows reliable collection of both acid gases and mte within a single sample and the analysis with current chemical methods high pressure liquid chromatography inductively coupled plasma mass spectrometry this apparatus may be suitable for more difficult volcanoes where only the plume can be sampled

dense water bottom currents in the southern adriatic sea in spring 2012 abstract in february 2012 a severe cold spell in the european region triggered a massive production of very dense water on the northern mediterranean sea shelves the spreading phase of the newly formed dense water was extensively studied in the adriatic sea by means of 2 ship surveys and 5 moorings fully equipped to monitor the flow of the bottom layer for the adriatic sea opposite to the gulf of lions the area of cascading is far from the source area and this implies substantial modifications adjustments and dilution of the source water mass along its path with a spreading phase lasting several months indeed all the moorings detected events although weaker than in the preceding months until june 2012 the surveys detected 2 branches of naddw on the shelf the first branch not denser than 29 7 kg m3 and the second branch not denser than 29 5 kg m3 despite the extremely dense water generated in the northern adriatic during events of dense water flow moorings recorded temperatures generally between 12 5 and 13 c seldom less temperatures along the shelf break also did not fall below 13 c at depths greater than 400 m turbulent mixing therefore heavily modified the cascading plumes which left the shelf with thicknesses between 10 and 30 m mooring data in the lowermost 100 mab suggest that the thickness of the cascading layer increased by several tens of meters downslope as a consequence of entrainment detraining frictional layers as well as locations of active cascading were identified mostly by isolated casts highlighting the submesoscale domain of the downsloping plumes the use of ladcp data allowed identification of very energetic bottom flow 40 50 cm s in many locations with otherwise little signature in tracers not previously observed the bari canyon system bcs was so far recognized as a hot spot for cascading in the southern adriatic however during the 2012 event this is not the only preferred site for cascading significant dense flow was detected in other locations the northernmost mooring site closer to the inception of the cascading process in particular showed active cascading and several dynamical differences from the bcs denser water with thinner boundary layer events organized in multiple pulses with sub inertial periodicity and with very short duration 12 h to 1 day that is generally not seen in other locations

steam output from fumaroles of an active volcano tectonic and magmatic hydrothermal controls on the degassing system at vulcano aeolian arc the results from measurements of extensive parameters steam output and exhaling surface area taken at the crater fumarolic field of vulcano island aeolian arc southern italy are reported along with a detailed description of the measuring method the steam emission rate increased by 1 order of magnitude during the observation time 1983 1995 while its concentration in the released gases was only slightly changed during the same period the total exhaling surface expanded from 50 m2 to more than 2400 m2 and evolved following preferential trends that coincide with the main tectonic structures of the island the observed peaks in steam output show a positive correlation with episodes of volcanic activity unrest the temporal increase of steam output and the observed development in the exhaling surface areas are consistent with a volcano tectonic triggering of the exhaling activity particularly the peaks in the steam output are interpreted as a consequence of degassing from an active magma slowly moving toward the surface

volatilization transport and sublimation of metallic and non metallic elements in high temperature gases at merapi volcano indonesia abstract condensates silica tube sublimates and incrustations were sampled from 500 800 c fumaroles and lava samples were collected at merapi volcano indonesia in jan feb 1984 with respect to the magma merapi gases are enriched by factors greater than 105 in se re bi and cd 104 105 in au br in pb and w 103 104 in mo cl cs s sn and ag 102 103 in as zn f and rb and 1 102 in cu k na sb ni ga v fe mn and li the fumaroles are transporting more than 106 grams day g d of s cl and f 104 106 g d of al br zn fe k and mg 103 104 g d of pb as mo mn v w and sr and less than 103 g d of ni cu cr ga sb bi cd li co and u with decreasing temperature 800 500 c there were five sublimate zones found in silica tubes 1 cristobalite and magnetite first deposition of si fe and al 2 k ca sulfate acmite halite sylvite and pyrite maximum deposition of cl na k si s fe mo br al rb cs mn w p ca re ag au and co 3 aphthitalite k na sulfate sphalerite galena and cs k sulfate maximum deposition of zn bi cd se and in higher deposition of pb and sn 4 pb k chloride and na k fe sulfate maximum deposition of pb sn and cu and 5 zn cu and k pb sulfates maximum deposition of pb sn ti as and sb the incrustations surrounding the fumaroles are also chemically zoned bi cd pb w mo zn cu k na v fe and mn are concentrated most in or very close to the vent as expected with cooling atmospheric contamination and dispersion the highly volatile elements br cl as and sb are transported primarily away from high temperature vents ba si p al ca and cr are derived from wall rock reactions incomplete degassing of shallow magma at 915 c is the origin of most of the elements in the merapi volcanic gas although it is partly contaminated by particles or wall rock reactions the metals are transported predominantly as chloride species as the gas cools in the fumarolic environment it becomes saturated with sublimate phases that fractionate from the gas in the order of their equilibrium saturation temperatures devolatilization of a cooling batholith could transport enough acids and metals to a hydrothermal system to play a significant role in forming an ore deposit however sublimation from a high temperature high velocity carrier gas is not efficient enough to form a large ore deposit re se cd and bi could be used as supporting evidence for magmatic fluid transport in an ore deposit

the reshaping of the south west adriatic margin by cascading of dense shelf waters abstract the south west adriatic margin sam includes a steep and morphologically complex continental slope stretching about 600 km from the pelagosa sill to the otranto strait the margin is clearly dissected by submarine slides active fault systems e g the gondola deformation belt numerous shallowly incised and relatively straight canyons located south of bari canyon and a variety of large scale erosional and depositional features this area is seasonally impacted by dense shelf water forming in the north adriatic through wind forced winter cooling moving south along the western side of the basin and cascading across the south adriatic slope the area has been investigated through multibeam surveys integrated by high resolution seismic stratigraphic data resolving glacial and post glacial deposits this paper gives a detailed and comprehensive description of the sam seafloor morphology to document how the process of dense shelf water cascading concurs to a thorough restyling of the submarine landscape by interacting with the pre existing and markedly differentiated morphologies and sediment distribution we focus on depositional and erosional features such as giant sediment drifts down to 1200 m water depth muddy and sandy sediment waves comet marks against pre existing slide blocks furrow fields against steep slopes large scours at the shelf edge and large erosional moats adjacent to major morphological barriers the analysis of the bedform orientation and spatial distribution indicates that the downslope cascading bottom currents dominantly directed to the se encounter a straight upper slope oriented north south in the north and progressively more east west proceeding to the south as the slope orientation becomes more e w it also appears more dissected by small scale canyons active during glacial times in the latter area therefore the dense shelf waters follow a slope parallel direction almost perpendicular to the pre existing slope canyons as a consequence erosional furrows develop perpendicular to the canyon flanks and some of the canyon heads become disconnected from the main canyon downslope

vapor deposition of trace elements from degassed basaltic lava piton de la fournaise volcano reunion island abstract silica tube sublimates resulting from the cooling of high temperature volcanic gases from degassed lava in lava tunnels have been sampled at piton de la fournaise volcano mineral phases deposited in the tube are mainly halides na k and cu chlorides si and k fluorides the distribution of most of the chemical elements as a function of the temperature is mainly controlled by their volatility volatile elements such as rb cs se pb and tl are associated with low temperature deposits whereas refractory elements such as r e e alkaline earth sc ta hf th and zr are not detected the mineral assemblages are characterized by the lack of sulfides sulfates native sulfur and oxides in the same way numerous transition and semi metallic elements are lacking this is interpreted as the result of the magma transport in surface lava tunnels leading to extensive degassing upstream of the collection site

structural controls on upper palaeozoic sedimentation in south east wales marked thickness changes in early dinantian courceyan chadian sediments occur across the cardiff cowbridge anticline a major east west variscan fold in the vale of glamorgan they resulted from differential subsidence over an active concealed basement fault zone the vale of glamorgan axis which is coincident with the hinge of the anticline the latter formed in response to inversion on this basement fault a caledonian ancestry for the vale of glamorgan axis is indicated by pronounced upper old red sandstone overstep across it across the severn estuary between south wales and the bristol mendips region there is a significant offset of isopachs and facies belts in both the courceyan chadian and arundian sequences it is suggested that these result from intra carboniferous dextral strike slip along a major fault zone underlying the severn estuary the severn estuary fault zone and that the vale of glamorgan axis was a synthetic structure developed in conjunction with this strike slip movement by inference the severn estuary fault zone shares a common history with the vale of glamorgan axis extending back to the devonian and possibly earlier late dinantian holkerian facies distribution reflects uplift and emergence on the north south usk anticline and malvern lineament continued uplift is recorded in silesian sequences in south east wales and the bristol mendips area the orientation of structures bordering the severn estuary is consistent with their development in a right lateral strike slip zone

interaction of dense shelf water cascading and open sea convection in the northwestern mediterranean during winter 2012 the winter of 2012 experienced peculiar atmospheric conditions that triggered a massive formation of dense water on the continental shelf and in the deep basin of the gulf of lions multiplatforms observations enabled a synoptic view of dense water formation and spreading at basin scale five months after its formation the dense water of coastal origin created a distinct bottom layer up to a few hundreds of meters thick over the central part of the nw mediterranean basin which was overlaid by a layer of newly formed deep water produced by open sea convection these new observations highlight the role of intense episodes of both dense shelf water cascading and open sea convection to the progressive modification of the nw mediterranean deep waters

clay mineral assemblages of the townsend tuff bed lower old red sandstone south wales and the welsh borders suites of samples from the townsend tuff bed possess widely varying clay mineralogies which may be divided into 5 major assemblages showing a general increase in diagenetic grade from smectite illite kaolinite to chlorite illite to the w this trend appears to be related to depth of burial fold style and proximity to basement illite crystallinity closely parallels cleavage development

cascading dense shelf water during the extremely cold winter of 2012 in the adriatic mediterranean sea formation flow and seafloor impact

assessment of a shallow magmatic system the 1888 90 eruption vulcano island italy the magmatic system feeding the last eruption of the volcano la fossa vulcano island italy was studied the petrogenetic mechanisms controlling the differentiation of erupted rocks were investigated through petrography mineral chemistry major trace and rare earth element and sr nd and pb isotopic geochemistry in addition melt inclusion and fluid inclusion data were collected on both juvenile material and xenolithic partially melted metamorphic clasts to quantify the p t conditions of the magma chamber feeding the eruption a regular and continuous chemical zoning has been highlighted rhyolites are the first erupted products followed by trachytes and latites whereas rhyolitic compositions were also found in the upper part of the sequence the chemical and isotopic composition of the rhyolites indicates that they originated by fractional crystallization from latitic magmas plus the assimilation of crustal material the trachytes represent hybrid magmas resulting from the mixing of latites and rhyolites contaminated in the shallow magmatic system the erupted products primarily compositionally zoned from latites to rhyolites are heterogeneous due to syn eruptive mingling the occurrence of magmacrust interaction processes evidenced by isotopic variations 87sr 86sr 0 70474 3 to 0 70511 3 143nd 144nd 0 512550 6 to 0 512614 8 206pb 204pb 19 318 19 489 207pb 204pb 15 642 15 782 208pb 204pb 39 175 39 613 is confirmed by the presence of partially melted metamorphic xenoliths with 87sr 86sr 0 71633 6 to 0 72505 2 and 143nd 144nd 0 51229 7 in rhyolites and trachytes afc calculations indicate a few percentage contribution of crustal material to the differentiating magmas thermometric measurements on melt inclusions indicate that the crystallization temperatures of the latites and trachytes were in the range of 1050 1100 c whereas the temperature of the rhyolites appears to have been around 1000 c at the time of the eruption compositional data on melt inclusions reveal that the magmas involved in the eruption contained about 1 1 5 wt dissolved h2o in pre eruptive conditions secondary fluid inclusions found in metamorphic xenoliths give low equilibration pressure data 30 60 mpa giving the location of the higher portions of the chamber at around 1500 2000 m of depth

lead isotope composition of the sublimates from the fumaroles of vulcano aeolian islands italy inferences on the deep fluid circulation the fumarolic fluids of vulcano aeolian islands italy consist of a mixture of both deep and shallow components the final products the fumarolic gases and the sublimates associated with them provide information on the complex interactions that occur at depth as radiogenic isotopes do not undergo fractionation after they are incorporated in a fumarolic gas they can be used directly to characterize the components that mixed lead isotopes are particularly suitable because seawater which plays an important part in the formation of the fumarolic fluids of vulcano contains only negligible amounts of it 10 12 g g therefore the lead present in the fumarolic gases and sublimates is derived from the magmatic component and a water rock interaction process the lead isotope compositions of the lead sulfosalt sublimates collected from the fossa crater of vulcano in 1924 and between 1989 and 1993 are given the lead isotope ratios of most of the samples are the same within the range of analytical error regardless of their collection date the only samples that display slight variations are those collected in 1993 on the whole the compositional trend of the lead isotopes of the sublimates coincides with that of the latitic rhyolitic activity of fossa and differs substantially from that of the pre fossa trachy basaltic activity the lead composition of the sublimates is very different from that of the calabrian basement rocks the data presented here show that the magma presently degassing at vulcano has the same lead isotopic composition as the products of the recent activity of fossa whereas the fumarolic fluid circulation of vulcano has not involved basement rocks similar to the calabrian metasediments

temporal geochemical variations in volatile emissions from mount st helens usa 1980 1994 abstract fumarole discharges 95 560 c collected from the dacite dome inside mount st helens crater show temporal changes in their isotopic and chemical compositions a d vs 18 o plot shows that condensed waters from the gases are mixtures of meteoric and magmatic components but that the apparent magmatic end member in 1994 was depleted by about 7 in d relative to the apparent end member in 1980 based on d modeling approximately 63 of shallow post 1980 magma has yet to degas surprisingly cl and f contents in the 1994 samples were only 0 47 and 3 8 respectively of the concentrations determined for end member magmatic fluid in 1980 the data indicate that cl and f and b is degassed from magma relatively quickly compared to water and or that most of the cl degassed in later years is dissolved into the shallow mount st helens hydrothermal system because metals are often transported in magmatic and hydrothermal fluids as cl complexes rapid changes in surface volatile compositions may have implications for the timing and location of metals transport and deposition in some volcanoes

unaccounted role of mediterranean water in the drawdown of anthropogenic carbon a three sided box medbox comprising the strait of gibraltar 24 41 n east of 22 w was constructed using hydrographic and chemical data from three world ocean circulation experiment cruises in 1997 1998 an extended optimum multiparameter omp analysis resolves the water mass structure in the medbox the mass transport is estimated from data and models warranting mass conservation and no deep water formation within the region combining the mass transport the omp analysis and the spatial distribution of anthropogenic carbon cant some relevant questions about the mediterranean water mw formation transport and role in the global co2 cycle are resolved mw is produced at a rate of 2 7 0 2 sv in the eastern north atlantic it entrains 2 3 sv of central waters during its formation including also remnants of antarctic intermediate water the main advection route of mw is northward close to the iberian margin 2 2 sv while about 0 5 sv are exported into the subtropical eastern north atlantic the eastern north atlantic within the medbox is a strong region of air sea cant uptake 0 7 0 7 mmol m 2 d 1 where cant is accumulated at a rate of 66 21 kmol s 1 0 025 gtc yr 1 17 are taken up through the air sea interface and the rest is advected into the area by the circulation the entrainment of central waters to form mw drives a drawdown of 151 14 kmol s 1 0 06 gtc yr 1 from the surface to intermediate levels and 88 8 kmol s 1 0 03 gtc yr 1 are exported with mw into the north atlantic mainly by the horizontal eddy circulation

geochemical surveillance of magmatic volatiles at popocatepetl volcano mexico surveillance of popocatepetl volcanic plume geochemistry and so 2 flux began in early 1994 after fumarolic and seismic activity increased significantly during 1993 volatile traps placed around the summit were collected at near monthly intervals until the volcano erupted on december 21 1994 additional trap samples were obtained in early 1996 before the volcano erupted again emplacing a small dacite dome in the summit crater abundances of volatile constituents ppm day of cl s total f co 2 hg and as varied but most constituents were relatively high in early and late 1994 however ratios of these constituents to cl were highest in mid 1994 34 s s total in trap solutions ranged from 1 5 to 6 4 lowest values generally occurred during late 1994 13 c co 2 of trap solutions were greatly contaminated with atmospheric co 2 and affected by absorption kinetics when trap data are combined with so 2 flux measurements made through november 1996 popocatepetl released about 3 9 mt so 2 16 mt co 2 0 75 mt hcl 0 075 mt hf 260 t as 2 6 t hg and roughly 200 mt h 2 o near vent gas concentrations in the volcanic plume measured by correlation spectrometer cospec and fourier transform infrared ftir commonly exceed human recommended exposure limits and may constitute a potential health hazard volatile geochemistry combined with petrologic observations and melt inclusion studies show that mafic magma injection into a preexisting silicic chamber has accompanied renewed volcanism at popocatepetl minor assimilation of cretaceous wall rocks probably occurred in mid 1994

volcanic emission of se te and as from kilauea volcano hawaii abstract the se te and as content of the eruptive gas and of sulfur sublimates from the current jan 1983 through mar 1985 east rift eruption of kilauea volcano hawaii have been determined these data in combination with previous data suggest that most of the se and te in eruptive plumes occur in the particulate fraction while most of the as is in the gas phase eruptive emissions to the atmosphere have been estimated at 10 metric tons each of se and as and 2 tons of te over the first 14 months of the eruption material balance calculations suggest 0 28 ppm se and 0 017 ppm te for the initial kilauean magma content of these elements only one third of the original se and te is lost from the magma by degassing

the role of acids in electrical conduction through ice 1 electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly from sea salt biomass burning and volcanic eruptions the strongest conductivity response is to acids yet the mechanism causing this response has been unclear here we elucidate conduction mechanisms in ice using broadband dielectric spectroscopy of meteoric polar ice cores we find that conduction through polycrystalline polar ice is consistent with jaccard theory for migration of charged protonic point defects through single ice crystals except that bulk dc conduction is impeded by grain boundaries neither our observations nor modeling using archie s law support the hypothesis that grain boundary networks of unfrozen acids cause significant electrolytic conduction common electrical logs of ice cores by electrical conductivity measurement ecm or dielectric profiling dep and the attenuation of radio waves in ice sheets thus respond to protonic point defects only this response implies that joint interpretation of electrical and chemical logs can determine impurity partitioning between the lattice and grain boundaries or inclusions for example in the greenland ice core project grip ice core from central greenland on average more than half of the available lattice soluble impurities h cl nh4 create defects understanding this partitioning could help further resolve the nature of past changes in atmospheric chemistry