co 2 degassing in the hartousov mofette area western eger rift imaged by co 2 mapping and geoelectrical and gravity surveys strong subcontinental mantle dominated co2 degassing occurs in the hartousov and bublak mofette fields in the western eger rift the combination of co2 gas flux and soil gas measurements as well as gravity and geoelectric surveys provides insight into the surface and subsurface of this unique mofette area co2 soil gas and gas flux measurements reveal that large amounts of carbon dioxide are released via channels with diameters below 1 m carbon dioxide emissions of several tens and up to more than 100 kg day 1 are ejected via these small seeps measurements with small spacings are necessary to account for the point like focused gas discharge in the lesser degassing surrounding we estimate that between 23 and 97 tons of co2 are released over an area of about 350 000 m2 each day in the hartousov mofette field the application of widely used geostatistical tools leads to estimations of the co2 discharge with very high standard deviations due to the strong positive skewness of the data distribution geophysical investigations via electrical resistivity tomography and gravity measurements were carried out over areas of strong seepage and reveal distinct anomalies in the subsurface below mofettes indicating rock and sediment alterations and or sediment transport by pressurised ascending co2 and water mobilised by it this study reveals that the gas emanations only occur west of a morphological step which is related to a n s oriented fault zone the pocatky plesna fault zone the results of co2 mapping and the geophysical studies can track the course of this fault zone in this area our results fit into a tectonic model in which the mofette fields are in the centres of two independent pull apart basin like structures we hypothesise that the sinistral strike slip movement of the pocatky plesna fault zone leads to a pull apart basin like opening at which the strong mantle derived co2 degassing occurs nowadays since the hartousov and bublak mofette fields only illustrate examples along the n s striking pocatky plesna fault zone its role and other n s striking faults roles of the regensburg leipzig rostock zone for upper mantle degassing might have been underestimated previously

pyrometamorphic processes at the magma hydrothermal system interface of active volcanoes evidence from buchite ejecta of stromboli aeolian islands italy pyrometamorphic ejecta erupted during recent paroxysmal explosions and hydrothermally altered volcanic and subvolcanic rocks from stromboli volcano aeolian islands italy were studied by combined polarizing microscopy electron microprobe scanning electron microscope x ray diffraction transmission electron microscope and whole rock inductively coupled plasma optical emission spectrometry mass spectrometry analysis the pyrometamorphic ejecta are compositionally heterogeneous at the macroand micro scale and are classified as buchites that is glass coupled with a high temperature low pressure modal mineralogy three distinct facies i e cordierite plagioclase mullite plagioclase palisade and tridymite clinopyroxene are recognized among the buchites whose bulk rock chemistry is compatible with aluminousto silica rich protoliths abundant mineral growth e g plagioclase palisades and clinopyroxene coronae occurs at the contact between the ejecta and the crystal rich host shoshonitic basalt which typically coats the pyrometamorphic blocks mineral constraints pseudoporphyritic microstructures plagioclase relict phenocrysts and major and trace element compositions strongly support the origin of the buchite ejecta as hydrothermally altered rocks from thevancori edifice a period of activity spanning 410 kyr which underwent high temperature low pressure contact metamorphism in the uppermost magmatic system of an active island arc volcano such as stromboli volcanic and subvolcanic rocks usually undergo alteration processes induced by acid sulphate hydrothermal systems the circulation of acidic fluids results in leaching of the stromboli rocks in the upper part of the volcano edifice and depending on the ph temperature and exposure time to the hydrothermal fluids production of different alteration facies the hydrothermally altered stromboli rocks show facies consistent with argillic to silicic alteration containing abundant hydrous sulphate and hydroxy sulphate minerals such as the alunite group minerals hexahydrite millosevichite pickeringite and kieserite the hydrothermally altered wall rocks heated by contact with the basaltic magma of the feeder dyke system of stromboli can easily undergo pyrometamorphic processes inducing partial melting and subsolidus crystallization of the volcanic protoliths this results in the development of buchite rocks at the magma hydrothermal system interface

diffuse carbon dioxide emissions from hidden subsurface structures at asama volcano japan we measured diffuse carbon dioxide co2 flux and soil temperature around the summit of asama volcano japan to assess the diffuse degassing structure around the summit area soil co2 flux was measured using an accumulation chamber method and the spatial distributions of co2 flux and soil temperature were derived from the mean of 100 sequential gaussian simulations results show that soil co2 flux was high on the eastern flank of kamayama cone and the eastern rim of maekake crater the outer cone these areas mostly correspond to high temperature anomalies the average emission rate of diffuse co2 was calculated to be 12 6 t day 1 12 2 14 6 t day 1 such diffuse emissions account for 12 of the total diffuse and plume co2 emissions from the summit area the diffuse co2 anomalies probably reflect permeable zones controlled by local topography and hidden fractures bordering maekake crater the permeable zones are connected to the low electrical resistivity zone inferred to indicate both a hydrothermal fluid layer and an upper sealed layer made of clay minerals magmatic gas from the main conduit ascends to the volcano surface through this fluid layer and the permeable zones these insights emphasize that the pathways and the connection between the pathways and the source of diffuse co2 combine to create the pattern of heterogeneous diffuse co2 emission seen at the surface only by using a combination of gas measurements and geophysical tools can we begin to understand the dynamics of this system as a whole

streaming potential measurements 1 properties of the electrical double layer from crushed rock samples the potential has been inferred from streaming potential measurements with crushed rock samples as a function of ph and electrolyte concentration for various salts the value obtained for crushed fontainebleau sandstone at ph 5 7 and a kcl solution with a resistivity of 400 m is 40 5 mv where the error is dominated by sample to sample variations the sensitivity of the potential to the electrolyte resistivity for kcl is given experimentally by f 0 23 0 014 where f is the electrolyte resistivity the point of zero charge pzc is observed for ph 2 5 0 1 and the potential is positive for ph pzc for ph 5 the variations of the potential with ph can be approximated by ph 5 7 1 0 068 0 004 ph 5 7 for f 100 m the potential has been observed to be sensitive to the valence of the ions and is approximately reduced by the charge of the cation unless specific adsorption takes place like in the case of al 3 the experimental results are well accounted for by a three layer numerical model of the electrical double layer and the parameters of this model can be evaluated from the experimental data the sensitivity of the potential to the rock minerals has also been studied the potential obtained for granitic rocks is comparable to that obtained for fontainebleau sandstone but can be reduced by a factor of 2 4 for sandstones containing significant fractions of carbonates or clay to take into account the effect of the chemical composition of the electrolyte a chemical efficiency is defined as the ratio of the potential to the potential measured for kcl this chemical efficiency is measured to be 80 for typical groundwater but can be as low as 40 for a water with a high dissolved carbonate content the set of empirical laws derived from our measurements can be used to assess the magnitude of the streaming potentials expected in natural geophysical systems

unusual lapilli tuff ejecta erupted at stromboli during the 15 march 2007 explosion shed light on the nature and thermal state of rocks forming the crater system of the volcano abstract textural and mineralogical study of high temperature angular blocks erupted during the stromboli explosion of 15 march 2007 was used to make inferences on the nature and thermal state of rocks forming the subsurface of the volcano summit crater terrace the studied ejecta consist of lapilli tuff that formed as a result of the transformation and high temperature induration sintering of the basaltic scoriae lapilli and ash originally accumulated as loose tephra during the current activity of the volcano the main processes leading to the tephra transformation were investigated through microstructural observations mineral and glass analyses sem eds and emp analyses investigations revealed that subsolidus reactions and partial melting of the tephra occurred at temperatures higher than 600 c and under variable fo 2 conditions from qfm to hm buffering curves in some blocks evidence of high t reheating and partial melting at the expense of secondary hydrothermal minerals was also observed in order to track the subsolidus reheating history of the basaltic pyroclasts a detailed study of the pseudomorphic phases and reactions after olivine driven by iron oxidation under high t conditions was performed the observed mineralogical transformation suggests that the lapilli tuff material originating from the burial of tephra routinely accumulated by persistent strombolian explosions within the crater terrace were in some cases altered by the circulation of acidic fluids and were in any case reheated due to isotherm rise forced by high heat flux and gas streaming delivered by the underlying magma system it is worth noting that the ejection of these unusual volcanic lithotypes was possible because a few days before the 15 march 2007 event the craters were clogged with lapilli tuff material that slid into the crater bottom between 7 and 9 march findings of this study suggest that the scattered permanently active vents and shallow conduits of stromboli are surrounded sideways and underneath the crater terrace by a fairly large volume of high temperature rocks with variable degree of compaction sintering up to partially melted such a spectrum of rock types is in good agreement with the conceptual model of prominent thermal zoning all around sideway and upwards the active magmatic system we speculate that continuous migration upwards of isotherms led to transformation and partial melting of the normal strombolian tephra

fluid flow in the resurgent dome of long valley caldera implications from thermal data and deep electrical sounding abstract temperatures of 100 c are measured at 3 km depth in a well located on the resurgent dome in the center of long valley caldera california despite an assumed 800 c magma chamber at 6 8 km depth local downflow of cold meteoric water as a process for cooling the resurgent dome is ruled out by a peclet number analysis of temperature logs these analyses reveal zones with fluid circulation at the upper and lower boundaries of the bishop tuff and an upflow zone in the metasedimentary rocks vertical darcy velocities range from 10 to 70 cm a 1 a 21 km long geoelectrical profile across the caldera provides resistivity values to the order of 10 0 to 10 3 m down to a depth of 6 km as well as variations of self potential interpretation of the electrical data with respect to hydrothermal fluid movement confirms that there is no downflow beneath the resurgent dome to explain the unexpectedly low temperatures in the resurgent dome we challenge the common view that the caldera as a whole is a regime of high temperatures and the resurgent dome is a local cold anomaly instead we suggest that the caldera was cooled to normal thermal conditions by vigorous hydrothermal activity in the past and that a present day hot water flow system is responsible for local hot anomalies such as hot creek and the area of the casa diablo geothermal power plant the source of hot water has been associated with recent shallow intrusions into the west moat the focus of planning for future power plants should be to locate this present day flow system instead of relying on heat from the old magma chamber

structure of an active volcano associated with a resurgent block inferred from thermal mapping the yasur yenkahe volcanic complex vanuatu subsurface thermal measurements provide a valuable tool to map hydrothermal fluid release zones in active volcanic areas on the yasur yenkahe volcanic complex tanna island vanuatu archipelago fumaroles and hot springs abound signs of upraising heat fluxes associated to a well developed hydrothermal activity combination of high resolution mapping of ground thermal anomalies with geomorphological analysis allows the characterization of the structural relationships between the active yasur volcano and the yenkahe resurgent block a complex system of heat release and hydrothermal fluid circulation below the yasur yenkahe complex is evidenced circulation though propagating vertically as a whole is funneled by stratification thus the main thermal fluid released is almost exclusively concentrated along structural limits that break the seals induced by the stratified nature of the ground three types of medium high temperature anomalies have been evidenced 1 broad hydrothermalized areas linked with planar stratification that favor lateral spreading 2 linear segments that represent active faults and 3 arcuate segments related to paleo crater rims the limit between the yasur volcano and the yenkahe resurgent block is characterized by an active fault system accommodating both the rapid uplift of the yenkahe block and the overloading induced by the volcano weight in such a setting faults converge below the cone of yasur which acts as a focus for the faults evidence of such structures sometimes hidden in the landscape but detected by thermal measurements is critical for risk assessment of flank landslides

importance of structural history in the summit area of stromboli during the 2002 2003 eruptive crisis inferred from temperature soil co2 self potential and electrical resistivity tomography the 2002 2003 eruptive crisis of stromboli volcano in the aeolian islands raised the question of how to assess the stability of the flanks of this volcanic edifice during such a crisis to provide a response to this question we analyzed a detailed fluid flow mapping plus the reiteration of a profile located in the vicinity of the active vents using the self potential method temperature data soil gas co2 measurements and electric resistivity tomography coupling the interpretation of these methods that are sensitive to the flow of gas and water in the ground indicates the position of areas of mechanical weakness in addition they can be used to monitor the change in the discharge of fluids associated with these features before and during the 2002 2003 eruptive crisis our results emphasize the importance of old structural boundaries such as the large fossa crater in the development of the new set of fractures observed during the 2002 2003 eruptive crisis between october 2002 and january 2003 the use of co2 soil gas technique evidenced an increase in the discharge of co2 outside the large fossa crater boundaries along the failure boundary of the southern sciara del fuoco area self potential and temperature measurements made before the 2002 2003 eruptive crisis reveal significant changes along the main structural boundaries of the fossa area the development of these anomalies is interpreted as an increase of the permeability of the structure from may 2000 to may 2002 between january 2003 and march 2003 the reiteration of self potential temperature and co2 measurements shows an increase of fluid discharge along weakness planes located inside the large fossa crater boundary they evidence no change outside this structural boundary the importance of the large fossa crater boundary in controlling the deformation and fluid flow from january to march 2003 has been attested by the development of the fractures inside the large fossa crater boundary and also with a network of electrooptical distance measurement stations located inside and outside this ancient crater this multidisciplinary approach to fluid flow assessment before and during an eruptive crisis is complementary to geodetic measurements of the deformation of the edifice it demonstrates for the first time the powerful potential of combining electrical resistivity tomography self potential temperature and soil co2 measurements in assessing the position of the planes of mechanical weakness in a volcanic edifice

insights into the dynamic processes of the 2007 stromboli eruption and possible meteorological influences on the magmatic system 1 the unrest of stromboli volcano leading to the february 27 april 2 2007 eruptive period and to the march 15 paroxysm is constrained by combining broad band seismic data and 1 hz gps high rate gps hereinafter hrgps measurements during the pre eruptive stage the simultaneous examination of seismic and hrgps data together with weather parameters suggests the possible influence of external perturbations on the magmatic system which evolved toward a critical state after january 2007 some days after the onset of the eruption a sudden change of the seismic and eruptive behaviour was recognized while ground deformation began to show a deflation the march 15 paroxysm was preceded about two days before by a peak of the hrgps spectral power densities a small inflation and by the occurrence of a few vt earthquakes located at depths down to 3 5 km b s l these findings constrain for the first time at stromboli volcano the deep origin of a fast rising magma batch rich in gas that led to a strong explosive event

the summit hydrothermal system of stromboli new insights from self potential temperature co2 and fumarolic fluid measurements with structural and monitoring implications accurate and precisely located self potential sp temperature t and co2 measurements were carried out in the summit area of stromboli along 72 straight profiles sp data were acquired every metre and t data every 2 5 m co2 concentrations were acquired with the same density as t but only along seven profiles the high density of data and the diversity of the measured parameters allows us to study structures and phenomena at a scale rarely investigated the shallow summit hydrothermal activity pizzo fossa area is indicated by large positive sp t and co2 anomalies these anomalies are focused on crater faults suggesting that the fracture zones are more permeable than surrounding rocks at stromboli the analysis of the distribution of these linear anomalies coupled with the examination of the geologic photographic and topographic data has led us to propose a new structural interpretation of the summit of stromboli this newly defined structural framework comprises 1 a large pizzo circular crater about 350 m in diameter 2 a complex of two concealed craters nested within the pizzo crater the large and the small fossa craters thought to have formed during the eruption of the pizzo pyroclastites unit the small fossa crater is filled with highly impermeable material that totally impedes the upward flow of hydrothermal fluids and 3 the present complex of active craters on the floor of the fossa short wavelength sp lows are organized in drainage like networks diverging from the main thermal anomalies and converging toward the topographic low in the fossa area inside the small fossa crater they are interpreted as the subsurface downhill flow of water condensed above the thermal anomalies we suspect that water accumulates below the small fossa crater as a perched water body representing a high threat of strong phreatic and phreatomagmatic paroxysms t and co2 anomalies are highly correlated the two types of anomalies have very similar shapes but the sensitivity of co2 measurements seems higher for lowest hydrothermal flux above t anomalies a pronounced high frequency sp signal is observed isotopic analyses of the fluids show similar compositions between the gases rising through the faults of the pizzo and large fossa craters this suggests a common origin for gases emerging along different structural paths within the summit of stromboli a site was found along the large fossa crater fault where high gas flux and low air contamination made gas monitoring possible near the active vents using the alkaline bottle sampling technique

streaming potential measurements 2 relationship between electrical and hydraulic flow patterns from rock samples during deformation streaming potential and resistivity measurements have been performed on fontainebleau sandstone and villejust quartzite samples in a triaxial device during compaction uniaxial compression and rupture measurements on individual samples do not show any clear intrinsic dependence of the streaming potential coefficient with permeability an apparent dependence of the streaming potential coefficient with permeability is however observed during deformation the effect of surface conductivity is taken into account and is small compared with the observed changes in the streaming potential coefficient the observed dependence is therefore interpreted in terms of a difference in the evolution of the electrical and hydraulic connectivity patterns during deformation this effect causes the streaming potential coefficient and consequently the inferred potential to be reduced by a geometrical factor r g representing the electrical efficiency of the hydraulic network estimates of the r g factor varying between 0 2 and 0 8 for electrolyte resistivity larger than 100 m are obtained by comparing the values of the potential inferred from intact rock samples with the values obtained from crushed rock samples where the geometrical effects are assumed to be negligible the reduction of the streaming potential coefficient observed during compaction or uniaxial compression suggests that the tortuosity of the hydraulic network increases faster than the tortuosity of the electrical network before rupture an increase in the streaming potential coefficient associated with the onset of dilatancy was observed for three samples of fontainebleau sandstone and one sample of villejust quartzite the changes in streaming potential coefficient prior to failure range from 30 to 50 during one experiment an increase in the concentration of sulfate ions was also observed before failure these experiments suggest that observable streaming potential and geochemical variations could occur before earthquakes

fluid circulation at stromboli volcano aeolian islands italy from self potential and co2 surveys this work addresses the study of fluid circulation of the stromboli island using a dense coverage of self potential sp and soil co2 data a marked difference exists between the northern flank and the other flanks of the island the northern flank exhibits 1 a typical negative sp altitude gradient not observed on the other flanks and 2 higher levels of co2 the general sp pattern suggests that the northern flank is composed of porous layers through which vadose water flows down to a basal water table in contrast to the other flanks where impermeable layers impede the vertical flow of vadose water in the sciara del fuoco and rina grande le schicciole landslide complexes breccias of shallow gliding planes may constitute such impermeable layers whereas elsewhere poorly permeable fine grained pyroclastites or altered lava flows may be present this general model of the flanks also explains the main co2 patterns concentration of co2 at the surface is high on the porous north flank and lower on the other flanks where impermeable layers can block the upward co2 flux the active upper part of the island is underlain by a well defined hydrothermal system bounded by short wavelength negative sp anomalies and high peaks of co2 these boundaries coincide with faults limiting ancient collapses of calderas craters and flank landslides the hydrothermal system is not homogeneous but composed of three main subsystems and of a fourth minor one and is not centered on the active craters the latter are located near its border this divergence between the location of the active craters and the extent of the hydrothermal system suggests that the internal heat sources may not be limited to sources below the active craters if the heat source strictly corresponds to intrusions at depth around the active conduits the geometry of the hydrothermal subsystems must be strongly controlled by heterogeneities within the edifice such as craters caldera walls or gliding planes of flank collapse as suggested by the correspondence between sp co2 anomalies and structural limits the inner zone of the hydrothermal subsystems is characterized by positive sp anomalies indicating upward movements of fluids and by very low values of co2 emanation this pattern suggests that the hydrothermal zone becomes self sealed at depth thus creating a barrier to the co2 flux in this hypothesis the observed hydrothermal system is a shallow one and it involves mostly convection of infiltrated meteoric water above the sealed zone finally on the base of co2 degassing measurements we present evidence for the presence of two regional faults oriented n41 and n64 and decoupled from the volcanic structures

experimental measurements of the sp response to concentration and temperature gradients in sandstones with application to subsurface geophysical monitoring exclusion diffusion potentials arising from temperature gradients are widely neglected in self potential sp surveys despite the ubiquitous presence of temperature gradients in subsurface settings such as volcanoes and hot springs geothermal fields and oil reservoirs during production via water or steam injection likewise with the exception of borehole sp logging exclusion diffusion potentials arising from concentration gradients are also neglected or at best it is assumed that the diffusion potential dominates to better interpret these sp sources requires well constrained measurements of the various coupling terms we report measurements of thermoelectric and electrochemical exclusion diffusion potentials across sandstones saturated with nacl brine and find that electrode effects can dominate the measured voltage after correcting for these we find that hittorf transport numbers are the same within experimental error regardless of whether ion transport occurs in response to temperature or concentration gradients over the range of nacl concentration investigated that is typical of natural systems diffusion potentials dominate only if the pore throat radius is more than approximately 4000 times larger than the diffuse layer thickness in fine grained sandstones with small pore throat diameter this condition is likely to be met only if the saturating brine is of relatively high salinity thus in many cases of interest to earth scientists exclusion diffusion potentials will comprise significant contributions from both ionic diffusion through and ionic exclusion from the pore space of the rock however in coarse grained sandstones or sandstones saturated with high salinity brine exclusion diffusion potentials can be described using end member models in which ionic exclusion is neglected exclusion diffusion potentials in sandstones depend upon pore size and salinity in a complex way they may be positive negative or zero depending upon sandstone rock texture expressed here by the pore radius r and salinity

diagenesis or dire genesis the origin of columnar spar in tufa stromatolites of central greece and the role of chironomid larvae two greek pleistocene tufa stromatolites were examined petrographically and with stable isotope geochemistry to determine whether calcite spar is of primary or diagenetic origin the younger ca 100 ka tufa from zemeno primarily is micritic with primary columnar calcite spar restricted to areas immediately above chironomid larval tubes this relationship suggests that chironomid larval feeding behaviour is responsible for the development of zemeno tufa columnar calcite probably involving biological substances smeared onto the tufa surface most micritic crystals are not suitably oriented to allow later post depositional growth resulting in columnar fabrics the older ca 1 ma predominantly sparry tufa from nemea contains some chironomid tubes and organic cyanobacterial filaments preserved in crystal fans but also contains many fabrics found in primary speleothem spar columnar spar here is unlikely to be the result of post depositional crystal growth a comparison of stable isotopic trends between the two tufa deposits suggests that both contain interpretable seasonal trends and implies little or minor post depositional alteration of either tufa consequently there is no basis for the common assumption that sparry tufa fabrics must be of diagenetic origin

dynamics of the december 2002 flank failure and tsunami at stromboli volcano inferred by volcanological and geophysical observations 1 the 2002 effusive flank eruption at stromboli volcano started on december 28 after several months of strong explosive activity at the summit craters on december 30 the seismic network recorded two large flank failures and associated tsunami waves this is the first time that a flank collapse and tsunami and their associated phenomena have been recorded by a multi disciplinary monitoring system volcanological and geophysical monitoring as well as thermal surveys performed immediately before and after the failure allowed us to define and interpret the sequence of events the still on going eruption has provided for the first time the opportunity to look into the dynamics of stromboli s effusive eruptions flank failure and landslide formation and their potential hazard

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

comparative study of geophysical and soil gas investigations at the hartousov czech republic natural co2 degassing site our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of co2 degassing it supports the development of an effective monitoring concept for geological co2 storage sites carbon capture and storage as one of the pillars of the european climate change efforts this study presents results of comprehensive investigations along a 500 m long profile within the hartousov czech republic natural co2 degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured measurements of co2 concentrations and investigation of the subsurface using electrical resistivity tomography and self potential methods provide information about subsurface properties for their successful application it is necessary to take seasonal variations e g soil moisture temperature meteorological conditions into consideration due to their influence on these parameters locations of high co2 concentration in shallow depths are related to positive self potential anomalies low soil moistures and high resistivity distributions as well as high 13c values and increased radon concentrations co2 ascends from deep geological sources via preferential pathways and accumulates in coarser sediments repetition of measurements which includes the effects of seasonal variations revealed similar trends and allows us to identify a clear prominent zone of anomalous values coarser unconsolidated sedimentary layers are beneficial for the accumulation of co2 gas the distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs

influence of rainfalls on heat and steam fluxes of fumarolic zones six months records along the ty fault soufriere of guadeloupe lesser antilles fumarolic zones are permeable areas where both steam and heat are expelled to the atmosphere surface fluxes and flows which are representative of the intensity of the hydrothermal circulation in depth can be monitored by thermometers thermal infrared cameras spectrometers or condensers however the superficial activity of fumarolic zones can be modified by the meteorological conditions in particular the rainfalls which might result in erroneous estimations from this perspective we developed a set of physical equations to quantify the effects of rainfalls on the thermal behavior of fumarolic zones results were faced to continuous measurements achieved at the ty fault fumarolic zone la soufriere volcano guadeloupe lesser antilles during six months in 2010 using six vertical series of thermometers measuring the heat transfer in the ground and one condenser measuring the rising steam flux results demonstrate that in the absence of rainfalls heat and steam flux reach an equilibrium that is representa tive of the geothermal flux in depth conversely after the rainfalls the cooling of the ground provokes a deepening of the condensation level the related soil temperature drop can be estimated by computing the heat required to warm the infiltrated water up to boiling temperature while the recovery rate is directly linked to the geothermal flux our observations allow defining in which conditions flux are at steady state but also to build a first order numer ical model allowing estimating both the physical parameters of the ground thermal conductivity precipitation efficiency coefficient and surface flux constant and the long term thermal behavior of the hydrothermal system in particular our results predict that the hydrothermal activity must vanish on the zones where the geothermal flux drops under a certain threshold 60 w m 2 at la soufriere the existence of this limit may have strong implications for the precipitation rate of minerals and the possible reactivation of the fumarolic zones during volcanic crises

chronology of the 2007 eruption of stromboli and the activity of the scientific synthesis group abstract on 27 february 2007 at 12 49 gmt a new eruption of stromboli took place with the effusion of a lava flow from a fracture cutting the flank of the ne cone which rapidly reached the sea the eruption had been heralded by an increase in the amplitude of tremor and flank movement since at least the 14th of february short term precursors were an increase in the rate of occurrence of small landslides within the sciara del fuoco scar on the north western flank of the volcano a new effusive vent opened at 18 30 gmt on the sciara del fuoco at an height of 400 m asl the new lava emission caused the sudden termination of the summit flow and initiated a period of non stationary lava outpouring which ended on 2 april 2007 the eruption has been characterized by a rapid decrease in the eruption rate after the first days and subsequently by episodic pulse increases on the 15th of march the increase in lava outpouring monitored by a thermal camera heralded by 9 min the occurrence of a violent paroxysmal explosion with the formation of an impulsive eruption column and the emission of small pumices mingled with black scoriae the pumice had a bulk composition similar to that of the lava and of the black scoriae but with a distinct lower content of phenocrysts a similar feature has been repeatedly observed during the major explosive paroxysms of stromboli short term precursors of the paroxysm were recorded by strainmeter and tiltmeter stations the volcano monitoring activity has been made by a joint team of researchers from the ingv sections of catania napoli palermo and rome along with researchers from the universities of florence pisa roma tre and palermo the scientific activity was coordinated by a synthesis group made up by scientists responsible for the different monitoring techniques of ingv and universities and by the volcanic experts of commissione nazionale grandi rischi of the prime minister office civil protection department the group made a daily evaluation of the state of the volcano and transmitted its recommendations to the civil protection department dpc several prevention measures were adopted by dpc the main of which were the evacuation of the coast zone when strong acceleration of the sciara del fuoco slope motion occurred twice could led to a dangerous tsunami by flank collapse as last occurred on 30 december 2002 and four days before the 15 march paroxysm when access was prohibited to the part of the volcano above 290 m asl

the evolution of the sciara del fuoco subaerial slope during the 2007 stromboli eruption relation between deformation processes and effusive activity abstract focusing on the island of stromboli this research investigates whether airborne remote sensing systems such as those based on digital photogrammetry and laser scanner sensors can be adopted to monitor slope deformation and lava emplacement processes in active volcanic areas thanks to the capability of extracting accurate topographic data and working on flexible time schedules these methods can be used to constrain the regular and more frequent measurements derived from satellite observations this work is dedicated to the monitoring of stromboli s volcanic edifice which is beneficial when obtaining quantitative data on the geometry of deformation features and the displaced failures and landslides and emplaced lava flows volumes in particular we focus on the capability of extracting average effusion rates from volume measurements that can be used to validate or integrate satellite derived estimates since 2001 a number of airborne remote sensing surveys namely digital photogrammetry dp and airborne laser scanning als have been carried out on stromboli s volcano to obtain high resolution digital elevation models dem and orthophotos with sub meter spatial resolution and a time schedule suitable for monitoring the morphological evolution of the surface during the quiescent phases during the last two effusive eruptions 2002 2003 and 2007 the surface modifications created on the sciara del fuoco slope and on the crater area as a consequence of effusive activity were quantified and monitored using the same methodologies this work which is based on the results obtained from the multi temporal quantitative analysis of the data collected from 2001 to 2007 mainly focuses on the 2007 eruption but also accounts for analogies and differences regarding the 2002 2003 event the 2007 eruption on the sciara del fuoco slope from 27 february until 2 april produced a compound lava field including a lava delta on the shoreline discharging most of the lava into the sea the comparison of the 2007 dems with a pre eruption surface 2006 lidar survey allowed for the evaluation of the total lava volume that accumulated on the subaerial slope while two syn eruption dems were used to calculate the average effusion rates during the eruption since the evolution of a lava field produced during an eruption can be seen as a proxy for the magma intrusion mechanism hypotheses are formulated on the connection between the lava discharge and the instabilities suffered by the slope

insect trace fossils in aeolian deposits and calcretes from the canary islands their ichnotaxonomy producers and palaeoenvironmental significance insect trace fossils from canary islands have been known and discussed since the beginnings of the last century the most common and widespread morphologies have been tentatively referred to the ichnogenera celliforma palmiraichnus or rebuffoichnus and attributed to bees coleopterans and locusts until now herein they are included in a new single ichnospecies rebuffoichnus guanche isp nov which can be distinguished from other ichnospecies by the presence of an antechamber r guanche are considered herein as coleopteran curculionidae or scarabaeidae pupation chambers this is supported by themostly horizontal orientation in soils ellipsoid shape dispersion of sizes and particularly the internal surface of the wall chamber that is completely smoothed even in both extremes in addition it is supported by the finding of one adult weevil in a similar trace fossil and palaeoenvironment of australia all these characters argue against their assignation neither to egg pods of a locust species nor to bee cells the latter also contradicted by the lack of spiral closure the wall of r guanche shows the same petrological features of those of the palaeosol in which specimens are found in those specimens found in aeolian deposits the wall is composed of sand grains similar to those found in the dunes or sand sheets the diversity of microfabrics found in calcretes is higher and depends on the calcrete hostrock and the degree of development of the calcretes in poorly developed calcretes the trace fossils reflect very well the calcrete hostrock whereas in more developed ones they usually show peloidal ooidal or laminar microfabrics these similarities indicate that in contrast to some previous reports insects utilised as building material that of the surrounding soil as expectable for a coleopteran pupation chamber lower numbers of r guanche are recorded in calcretes from the western canary islands where no aeolian deposits are present in contrast to the high densities in the aeolian deposits of the eastern islands coleopterans would first colonise thin soils with calcretes developed on basaltic or sedimentary rocks in young islands and later colonise dunes as they appear when the islands aged the widespread presence of calcretes aeolian deposits and trace fossils in the easternmost and older canary islands is driven by both the geological evolution of the islands and climatic conditions both the calcretes and pupation chambers formed during the relatively wetter periods within otherwise prevailing arid to semiarid conditions

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

geochemical monitoring of the 2002 2003 eruption at stromboli volcano italy precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters significant changes in the helium and carbon isotopic composition of shallow thermal waters vs gas and a crater fumarolic gas have been recorded at stromboli prior and during the 2002 2003 eruption the3he 4he ratios corrected for air contamination rc ra and 13c of fumarolic gases gradually increased from may to november 2002 before the eruption onset these variations imply early degassing of a gas rich magma at depth that likely fed both the intense strombolian activity and small lava overflows recorded during that period the lava effusion of late december 2002 was shortly preceded by a marked rc ra decrease both in water and fumarolic gases comparison of he co2 and ch4 co2 ratios in dissolved gas and with rm delta 13 rm c rm co 2 values rules out the rc ra decrease due to an increasing input of radiogenic4he the rc ra decrease is attributed to the he isotope fractionation during rapid magma ascent and degassing a new uprising of 3he rich magma probably occurred in january to february 2003 when rc ra ratios displayed the highest values in dissolved gases ever measured before 4 56 rc ra the increase in he co2 and ch4 co2 ratios and decrease in 13c of dissolved co2 was recorded after the 5 april 2003 explosive paroxysm likely caused by enhanced gas water interaction inducing co2 dissolution no anomalous rc ra values were recorded in the same period when usual strombolian activity gradually resumed

architecture and temporal variations of a terrestrial co2 degassing site using electric resistivity tomography and self potential the hartousov mofette field in nw bohemia czech republic is characterized by strong co2 degassing from the lithospheric mantle in a test survey using electrical resistivity tomography we observed changes over time in the subsurface structure beneath heavily co2 degassing spots to depths of about 40 m and compared them to co2 gas flux and soil gas mappings from previous studies changes in the electrical resistivity were measured between september 2012 and october 2013 at irregular intervals and highlight large variations in the resistivity distribution where the co2 degassing was strongest 56 103 g m 2 day 1 indicating a fluid induced change of properties of the underlying clayey sediments positive and negative anomalies in the electric self potential parallel to the erts can be found where co2 degassing occurs which indicates varying ascent or descent of fluids within these spots some degassing spots seem not to be actively degassing continuously over time which can also be observed by other studies in the same area we suggest that future gas mappings are accompanied by methods that observe the state of fluid systems at subsurface over time e g electric resistivity tomography and self potential

insights into fluid circulation across the pernicana fault mt etna italy and implications for flank instability article i nfo we conducted geophysical geochemical measurements on a 2k m n s profile cutting across the pernicana fault one of the most active tectonic features on the ne flank of mt etna the profile passes from the unstable e flank of the volcano to the south to the stable n flank and significant fluctuations in electrical resistivity self potential and soil gas emissions co2 rn and th are found the detailed multidisciplinary analysis reveals a complex interplay between the structural setting uprising hydrothermal fluids meteoric fluids percolating downwards ground permeability and surface topography in particular the recovered fluid circulation model highlights that the southern sector is heavily fractured and faulted allowing the formation of convective hydrothermal cells although the existence of a hydrothermal system in a volcanic area does not surprise these results have great implications in terms of flank dynamics at mt etna indeed the hydrothermal activity interacting with the pernicana fault activity could enhance the flank instability our approach should be further extended along the full extent of the boundary between the stable and unstable sectors of etna for a better evaluation of the geohazard in this active tectonic area

hydroelectric coupling in a clayey material the hydroelectric coupling generating self potential anomalies recorded on the earth s surface has received a considerable attention in the last four years geophysical applications include the use of this phenomenon for mapping subsurface fluid flow the study of hydrothermal activity and the use of self potential anomalies to monitor volcanic activity and the possibility still debated of seismic activity forecasting through the use of electromagnetic precursors of electrokinetic nature we model here two key parameters relevant of the hydroelectric coupling in clayey porous rocks these two parameters are the potential and the specific surface conductivity which depend on the electrochemistry of the pore water mineral interface they are modeled in the case of a kaolinite saturated by a nacl brine using a triple layer model tlm in which the parameters are optimized using the simplex algorithm

the structure of a hydrothermal system from an integrated geochemical geophysical and geological approach the ischia island case study the complexity of volcano hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work we use here an integrated multidisciplinary approach combining geological investigations with hydrogeochemical and soil degassing prospecting and resistivity surveys to provide a comprehensive characterization of the shallow structure of the southwestern ischia s hydrothermal system we show that the investigated area is characterized by a structural setting that although very complex can be schematized in three sectors namely the extra caldera sector ecs caldera floor sector cfs and resurgent caldera sector rcs this contrasted structural setting governs fluid circulation geochemical prospecting shows in fact that the caldera floor sector a structural and topographic low is the area where co2 rich 40 cm3 l hydrothermally mature log mg na ratios 150 g m 2 d 1 is clearly captured by electrical resistivity tomography ert and transient electromagnetic tem surveys as a highly conductive resistivity 10 000 mg l and poorly conductive meteoric derived tds 4 000 mg l waters are observed respectively we finally integrate our observations to build a general model for fluid circulation in the shallowest 0 5 km part of ischia s hydrothermal system

electrical conductivity and induced polarization investigations at krafla volcano iceland abstract electrical conductivity and polarization properties of 6 samples from krafla volcano iceland were measured in the frequency range 1 mhz 45 khz and compared to the data obtained on various basaltic rock samples from hawaii the results indicate that for altered samples the surface conductivity normalized chargeability and quadrature conductivity of the core samples scales linearly with the cation exchange capacity taken as a proxy of the alteration facies the surface conductivity of fresh samples is also controlled by the cation exchange capacity but their normalized chargeability is influenced by the presence of magnetite especially for unaltered samples the temperature dependence of quadrature conductivity and normalized chargeability can be modeled with an arrhenius equation with an activation energy of 16 19 kj mol 1 the experimental results agree with a model in which the polarization of the metallic and non metallic grains are both considered in a unified framework these results are used to interpret two 3d induced polarization surveys performed in the south and east parts of krafla volcano using two 1 3 km long cables with 32 electrodes each the electrical conductivity is in the range 0 3 clay cap to 5 10 5 s m 1 unaltered rock while the normalized chargeability is typically comprised between 10 2 clay cap and 10 5 s m 1 unaltered rock induced polarization is used to image porosity and the cation exchange capacity a long 5 6 km electrical conductivity profile was also performed connecting the two 3d sites and crossing a rhyolitic obsidian ridge called hrafntinnuhryggur hrafntinnuhryggur is characterized by very low conductivity values on the order of 10 4 s m 1 the long conductivity profile shows the position of the inner and outer caldera rims and the feeder dike of hrafntinnuhryggur a self potential survey performed along this long profile shows no shallow active geothermal features in this area as expected from the low permeability of the clay cap

adventive hydrothermal circulation on stromboli volcano aeolian islands italy revealed by geophysical and geochemical approaches implications for general fluid flow models on volcanoes on march 15th 2007 a paroxysmal explosion occurred at the stromboli volcano this event generated a large amount of products mostly lithic blocks some of which impacted the ground as far as down to 200 m a s l about 1 5 km far away from the active vents two days after the explosion a new vapour emission was discovered on the north eastern flank of the volcanic edifice at 560 m a s l just above the area called nel cannestra this new vapour emission was due to a block impact in order to investigate the block impact area to understand the appearance of the vapour emission we conducted on may 2008 a multidisciplinary study involving electrical resistivity tomography ert ground penetrating radar gpr self potential sp co2 soil diffuse degassing and soil temperature surveys this complementary data set revealed the presence of an anomalous conductive body probably related to a shallow hydrothermal level at about 10 15 m depth more or less parallel to the topography it is the first time that such a hydrothermal fluid flow with a temperature close to the water boiling point 76 c has been evidenced at stromboli at this low elevation on the flank of the edifice the ert results suggest a possible link between 1 the main central hydrothermal system of stromboli located just above the plumbing system feeding the active vents with a maximum of subsurface soil temperature close to 90 c and limited by the neostromboli summit crater boundary and 2 the investigated area of nel cannestra at 500 m a s l a buried eruptive fissure active 9 ka ago in parallel sp and co2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the n41 regional fault a complementary ert profile on may 2009 carried out from the neostromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system the concept of shallow hydrothermal level have been compared to similar ert results recently obtained on mount etna and la fossa cone of vulcano this information needs to be taken into account in general fluid flow models on volcanoes in particular peripheral thermal waters as those bordering the north eastern coast of stromboli could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit

new geological insights and structural control on fluid circulation in la fossa cone vulcano aeolian islands italy accepted 1 june 2009 available online 21 june 2009 keywords electrical resistivity self potential soil co2 degassing temperature fluid circulation hydrothermal system structural boundary vulcano la fossa cone electric resistivity tomography ert self potential sp soil co2 ux and temperature are used to study the inner structure of la fossa cone vulcano aeolian islands nine profiles were performed across the cone with a measurement spacing of 20 m the crater rims of la fossa cone are underlined by sharp horizontal resistivity contrasts sp co2 flux and temperature anomalies underline these boundaries which we interpret as structural limits associated to preferential circulation of fluids the pietre cotte crater and gran cratere crater enclose the main hydrothermal system identified at the centre of the edifice on the base of low electrical resistivity values b20 m and strong co2 degassing sp and temperature anomalies in the periphery the hydrothermal activity is also visible along structural boundaries such as the punte nere forgia vecchia and palizzi crater rims and at the base of the cone on the southern side of the edifice along a fault attributed to the nwmain tectonic trend of the island inside the punte nere crater the ert sections show an electrical resistive body that we interpret as an intrusion or a dome this magmatic body is reconstructed in 3d using the available ert profiles its shape and position with respect to the pietre cotte crater fault allows replacing this structure in the chronology of the development of the volcano it corresponds to a late phase of activity of the punte nere edifice considering the position of the sp soil co2 flux and temperature maxima and the repartition of conductive zones related to hydrothermal circulation with respect to the main structural features la fossa cone could be considered as a relevant example of the strong influence of preexisting structures on hydrothermal fluid circulation at the scale of a volcanic edifice

the 5 april 2003 vulcanian paroxysmal explosion at stromboli volcano italy from field observations and thermal data abstract the 5 april 2003 paroxysmal explosion at stromboli volcano was one of the strongest explosive events of the last century it occurred while the effusive eruption begun on 28 december 2002 and finished on 22 july 2003 was still on going and the summit craters of the volcano were obstructed in this paper we present a reconstruction of the sequence of events based on thermal and visual images collected from helicopter before during and immediately after the paroxysm one month before the blast ash emission and temperature increase at the bottom of the summit craters were observed an increasing amount of juvenile components in the emitted ash during march suggested that the magma level within the crater was rising accordingly hot degassing vents at the bottom of the summit craters were not persistent and the craters remained almost entirely obstructed by talus accumulation until the paroxysm occurred three minutes before the explosion we recorded a significant increase in temperature inside crater 1 accompanied by a thicker gas plume thirty two seconds before the blast reddish ash was emitted from crater 1 the paroxysm produced a vulcanian explosion that opened the feeder conduit obstructed for over three months the blast was accompanied by a shock wave recorded by the ingv seismic network at 07 13 37 gmt explosions with hot material started from crater 1 and after 15 s propagated to crater 3 about 100 m away the velocity of ejecta was 80 m s 1 and increased when the eruptive plumes from both craters merged together during the vulcanian phase an eruptive column rose 1 km above the top of the volcano and explosions continued mainly at crater 3 the paroxysm lasted about 9 min with bombs up to 4 m wide falling on the village of ginostra on the west flank of the island and destroying two houses this event signalled the start of the declining phase of the effusive eruption suggesting that the feeder conduit was returning to its former steady conditions with open vents and continuous mild strombolian activity

characterization of volcanic deposits with ground penetrating radar field based studies of surficial volcanic deposits are commonly complicated by a combination of poor exposure and rapid lateral variations controlled by unknown paleotopography the potential of ground penetrating radar gpr as an aid to volcanological studies is shown using data collected from traverses over four well exposed recent volcanic deposits in western canada the deposits comprise a pumice airfall deposit 3 4 m thick a basalt lava flow 3 6 m thick a pyroclastic flow deposit 15 m thick and an internally stratified pumice talus deposit 60 m thick results show that gpr is effective in delineating major stratigraphic contacts and hence can be used to map unexposed deposits different volcanic deposits also exhibit different radar stratigraphic character suggesting that deposit type may be determined from radar images in addition large blocks within the pyroclastic deposits are detected as distinctive point diffractor patterns in the profiles showing that the technique has potential for providing important grain size information in coarse poorly sorted deposits laboratory measurements of dielectric constant k are reported for samples of the main rock types and are compared with values of k for the bulk deposit as inferred from the field data the laboratory values differ significantly from the field values of k these results suggest that the effectiveness of gpr at any site can be substantially improved by initial calibration of well exposed locations

complex caddisfly dominated bioherms from the eocene green river formation abstract complex caddisfly dominated insecta trichoptera carbonate mounds up to 9 m tall and 40 m in diameter formed in the nearshore environment of eocene lake gosiute the mounds outcrop for 70 km in reef like geometries along the northern margin of lake gosiute in wyoming the relationships among the caddisfly larvae the benthic microbial mat and physicochemical nearshore processes of eocene lake gosiute resulted in unique external and internal carbonate mound morphology externally the large carbonate mounds are formed by the lateral and vertical coalescence of several layers of smaller columns the smaller columns are generally 1 2 m tall and are 0 5 1 m in diameter each layer or generation of smaller columns tends to have a unique external morphology this suggests that variable paleoenvironmental conditions produced subtle differences in tufa and stromatolite morphology internally each of the smaller columns is composed of a core of caddisfly larval cases surrounded by layers of tufa and stromatolites the smaller column cores are characterized by centimeter thick microbial caddisfly couplets in which layers or packets of calcified caddisfly larval cases are covered by microbial mat mediated microlaminated carbonate the microbial caddisfly couplets suggest that both metazoans and microbes were responsible for column height and shape in this paper we propose a mechanism for the growth of these caddisfly dominated mounds the base of the laney member of the green river formation records a freshwater lacustrine transgression over the surrounding floodplains and mudflats of the cathedral bluffs tongue of the wasatch formation in nearshore areas of the lake s northern margin carbonate hardgrounds developed in some areas of the softer carbonate rich bottom muds these hardgrounds provided nucleation sites for the carbonate mounds and columns by providing a stable substrate for the benthic microbial mat and for caddisfly larval case attachment during pupation the larval cases became calcified and became a new stable substrate for the benthic microbial mat during or shortly after pupation the microbial caddisfly couplets may record a yearly cycle in which caddisfly pupation and aggregation behavior regularly interrupted the microbial mat mediated carbonate buildups in these unique carbonate mounds

diffuse emission of co2 from the fossa crater vulcano island italy numerous measurements of co2 degassing from the soil carried out with the accumulation chamber method indicate that in the period april july 1995 the upper part of the fossa cone released a total output of 200 t d 1 of co2 which corresponds to approximately 1000 t d 1 of steam these large amounts of fluids are of the same order of magnitude as those released by the high temperature fumarolic field located inside the crater the spatial distribution of soil gas fluxes shows that the main structures releasing co2 are the inner slopes of the crater and a nw se line located ne of the crater rim which correspond to the main direction of vulcano island active faults the comparison of the co2 maps with the soil temperature distribution derived from both direct measurements and airborne infrared images indicates the occurrence of extensive condensation of fumarolic steam within the upper part of the fossa cone whose total amount is comparable to the rainfall budget part of the condensate which originates from this process contributes to the recharge of the phreatic aquifer of porto plain modifying the chemical and isotopic composition of the groundwater

monitoring active fumaroles through time lapse electrical resistivity tomograms an application to the pisciarelli fumarolic field campi flegrei italy abstract volcanoes are usually monitored through observations of many physical and chemical phenomena in the most dangerous cases as the one of the campi flegrei caldera italy great amount of data are collected both in discrete or continuously and regularly stored however how to transform such mass of data in a deeper understanding of the volcano dynamics is still an open question dissimilar information are in fact always hard to compare but just integrating all the available knowledge hazardous events could be prevented in a reliable way fluids as water and gasses mobilized in the subsoil by the heat induced by deep magmatic sources are widely recognized as the first engine of similar occurrences and the volcanic gas emissions represent together with the seismic activity one of the most considered precursors at the same time the electrical geophysical methods are the most applied in order to detect and characterize the fluid patterns in the subsoil so the integration of geoelectrical and geochemical observations should represent one of the most pursued approach in volcanoes monitoring on the contrary standard way to compare such data has been not yet codified the ert tomograms capability to individuate that parts of the subsoil where gasses cumulate is well understood in literature however we look for indications about its proficiency in associating the electrical resistivity changes relative to these zones once compared to the geochemical time series to deep related contributes distinguishing them from the seasonal ones the electrical signature of the fluid patterns reconstructed through a time lapse ert approach could be of relevance to better characterize the volcanic phenomena and their origins in this paper a first test of ert and geochemical time series integration was performed to enhance the understanding of the pisciarelli fumarolic field evolution now the most active area in the whole campi flegrei caldera

geochemical and geo electrical study of mud pools at the mutnovsky volcano south kamchatka russia behavior of elements structures of feeding channels and a model of origin this study presents data on the geochemical composition of boiling mud pools at the mutnovsky volcano the physicochemical characteristics of the pools and the concentrations of major minor and trace elements in pool solutions vary widely a comparison of the geochemical compositions of host rocks and solutions indicates that leaching from rocks is not the only source of chemicals in thermal solutions geophysical studies reveal the inner structure of thermal fields which reflect the shapes of the underground reservoirs and feed channels using geophysical methods electrical resistivity tomography and frequency domain investigations it was shown that the vertical structure and complex geochemical zonation of the feed channels leads to a high contrast in the compositions of the mud solutions these findings answer questions about the origin and composition of surface manifestations to elucidate the mechanisms of solution formation an attempt was made to describe the magmatic fluid evolution and the resulting mixing of waters by physical and mathematical models the model illustrates fluid migration from a magma chamber to the surface it is shown that the formation of brines corresponding to the mud pool composition is possible during secondary boiling

earliest cretaceous cocoons or plant seed structures from the wealden group hastings uk we thank jason hilton university of birmingham and alan spencer imperial college for discussion rg is a member of the interdisciplinary centre for ancient life umri we are grateful for the reviews of both jorge genise and duncan mcilroy whose comments and guidance greatly improved the manuscript

geochemical precursors of the activity of an open conduit volcano the stromboli 2002 2003 eruptive events 1 marked increases of co2 h2 and he dissolved in thermal waters and changes in the dissolved carbon isotopic composition were observed at stromboli before the 28 december 2002 eruption and before a violent explosive paroxysm occurred on 5 april 2003 high anomalous co2 flux values were recorded at the crater rim since a week before the eruption onset the first anomalies in the thermal waters dissolved co2 amount appeared some months before the eruption when magma column rose at a very high level in the conduit high peaks of dissolved h2 and he were recorded a few days before the paroxysm carbon isotopic composition indicates a magmatic origin of the dissolved co2 whose increase together with those of h2 and he is attributed to an increasing output of deep gases likely produced by depressurization of a rising batch of a deep gas rich magma whose fragments have been emitted during the explosion

structural features of the 2007 stromboli eruption abstract on 27 february 2007 two ne sw and nnw sse dike fed effusive vents opened to the north at 650 and 400 m above sea level asl of the summit craters at stromboli forming a fissure parallel to the inner walls of the sciara del fuoco sdf sector collapse depression the formation of these vents was soon followed by rapid subsidence of the summit crater area this partly obstructed the central conduit temporarily choking the fissure and increasing the deformation of the upper part of sdf the reactivation of the nnw sse vent and the opening of a new vent located at 500 m asl fed by a second dike released the internal pressure and surface deformation ceased the eruption then continued again from the 400 m vent after a summit explosion on 15 march until ending in early april after a progressive decrease of magma output repeated ne sw dike intrusions have occurred in recent years close to the upper se limit of the sdf in that zone named bastimento the eruptive fractures traced the discontinuities that borders the sdf increasing the risk of triggering new sector collapse whereas the ne sw trending structures lie along the regional volcano structural trend of the aeolian arc through stromboli the nnw sse vents are oblique to this trend and may be controlled by the anomalous stress field within the unstable flank of the sdf another fundamental aspect of the 2007 eruption is the collapse of the central conduit due to the rapid and deep magma drainage linked to the opening of the 400 m vent the intrusion of dikes and development of flank vents during the 2007 eruption could possibly have triggered catastrophic landslides and related tsunami or eruptive paroxysms but the opening of new effusive vents released the internal pressures diminishing the hazard

the contribution of fluid geochemistry to the volcano monitoring of stromboli abstract the persistent open vent mild explosive activity of stromboli volcano is episodically interrupted by more violent and dangerous explosive events major explosions and paroxysms according to the nature of erupted products paroxysms can be related either to the explosion of overpressured gas pockets located in the proximity of the magma column or to the sudden uprise of hot gas rich magma from a deep part of the plumbing system in both cases these more energetic explosive events should be preceded by an escape or a preferential uprise of the highly mobile volatiles which in turn should produce gas leakage anomalies at the surface in sites of high vertical permeability such as deep reaching faults in order to identify such gas leaking sites a systematic co2 soil flux survey has been carried out on the island using an accumulation chamber four hundred sixty one points have been measured with a high density in the summit crater area where high flux values have been found 10 3 10 2 cm s anomalous points are concentrated along the main ne sw axial feeding system of the volcano co2 soil flux decreases from the crater zone to the base of the volcanic cone where however an interesting gas leakage anomaly occurs pizzillo mofette in the pizzillo area thermal water wells also occur whose chemistry indicates an origin by sea water heated by hot gas soil gases have been sampled in the sites with the highest co2 flux in the crater area and at the base of the cone chemical and isotopic analyses indicate the presence of a deep gas component especially in the crater zone samples high co2 appreciable contents of he and h2 3he 4he values up to 3 55 13c of co2 2 the sc5 low flux fumarole on the crater rim has shown during six years a remarkable persistence of temperature 93 95 c with only minor fluctuations of chemistry appearance of anomalous peaks of h2 in correspondence with strombolian explosions was observed during a 2 h 30 min experiment of continuous recording of hydrogen content of the fumarole together with previous data on h2o co2 and he this experiment confirms that strombolian blasts produce rapid fluctuations in the fumarolic gas composition in the light of this study sc5 fumarole and pizzillo mofette look promising sites for the testing of a continuous geochemical monitoring system of stromboli volcano

structural control of collapse events inferred by self potential mapping on the piton de la fournaise volcano la reunion island abstract field surveys were performed on the terminal cone of piton de la fournaise in 2006 and 2008 to precisely map the self potential sp signal and determine the zonation of the hydrothermal activity both on the flanks of the cone and in the summit area including inside the bory and dolomieu craters sp maps inside the craters have been performed 8 months before the 5 7 april 2007 caldera collapse zonations appear both at the scale of the cone and of the summit and allow new interpretation of the electrical signal distribution on the terminal cone of piton de la fournaise superimposed to the sp maxima linked to the rift zones several areas of sp maxima associated with collapse structures have been detected 1 in the summit area the bory and dolomieu craters show the strongest sp values with amplitudes exceeding 2 v with respect to the base of the cone and with a sharp lateral variation to the east corresponding to the inner boundary of the dolomieu caldera collapsed on 5 7 april 2007 and 2 in the paleo pit craters surrounding the summit which show amplitudes similar to the dolomieu bory craters the analysis of the variations of the signal with time evidences a modification of the fluid flow pattern with a higher associated sp signature to the east in 2008 we interpret the amplification of fluid flow to the east in 2008 as a consequence of the eastward motion of the eastern flank of the volcano during the april 2007 eruption the acquisition of sp data during two periods separated by the april 2007 eruption turns out to be a good opportunity to correlate the sp signal to the piton de la fournaise structure and to its evolution in term of hydrothermal and eruptive activity

geochemical evaluation of observed changes in volcanic activity during the 2007 eruption at stromboli italy abstract on february 27 2007 a new eruption started at stromboli that lasted until april 2 and included a paroxysmal explosion on march 15 geochemical monitoring carried out over several years revealed some appreciable variations that preceded both the eruption onset and the explosion the carbon dioxide co 2 flux from the soil at pizzo sopra la fossa markedly increased a few days before the eruption onset and continued during lava effusion to reach its maximum value at 90 000 g m 2 d 1 a few days before the paroxysm almost contemporarily the 13 c co 2 of the sc5 fumarole located in the summit area increased markedly peaking just before the explosion 13 c co 2 1 8 following the paroxysm helium he isotopes measured in the gases dissolved in the basal thermal aquifer sharply increased almost contemporarily the automatic station of co 2 flux recorded an anomalous degassing rate also temperatures and the vertical thermal gradient which had been measured since november 2006 in the soil at pizzo sopra la fossa showed appreciable variabilities that lasted until the end of the eruption the geochemical variations indicated the degassing of a new batch of volatile rich magma that preceded and probably fed the paroxysm the anomalous 3 he 4 he ratio suggested that the ascent of a second batch of volatile rich magma toward the surface was probably responsible of the resumption of the ordinary activity a comparison with the geochemical variations observed during the 2002 2003 eruption indicated that the 2007 eruption was less energetic

gpr tdr and geochemistry measurements above an active gas vent to study near surface gas migration pathways the migration of deep gas to the atmosphere along faults and associated structures is important in many fields from studying the natural contribution of atmospheric greenhouse gases leaking from geothermal areas to ensuring the safety of man made natural gas and carbon dioxide c o2 geologic storage sites near surface geophysical and geochemical techniques were applied to a naturally occurring gas vent located along a deep terrestrial fault to better understand the structure and geophysical response of this gas migration pathway a number of ground penetrating radar gpr profiles were first conducted across the vent spot samples were then measured along one of these profiles for in situ apparent permittivity using time domain reflectometry tdr complex permittivity on dried samples using a capacitivecell soil gas composition and clay and bulk mineralogy results show how the migrating gas induces secondary effects that modify the signature of the vent as seen in the gpr profiles in particul

dissolved helium isotope ratios in ground waters a new technique based on gas water re equilibration and its application to stromboli volcanic system here a new technique for the determination of dissolved he isotope ratios in ground waters is presented this method is based on the extraction and subsequent equilibrium of dissolved gases in an added host gas phase ultra pure n2 is placed in glass flasks 250 cc containing water samples that were hermetically sealed after their collection after shaking in an ultrasonic bath for 10 min an aliquot of the separated gas phase was removed from the flask for ms analysis 3he 4he ratios are measured by using a modified double collector mass spectrometer vg 5400 tft helium and ne concentrations are calculated by comparing the partial pressures of masses 4 and 20 of the samples with those of the air standard measured by a quadrupole mass spectrometer qms vg quartz using he and ne equilibrium partitioning coefficients it is possible to calculate the amount of gas originally dissolved in the water the technique was tested on both air saturated waters asw and thermal waters from stromboli aeolian islands south italy the results of which confirmed good reproducibility 5 and accuracy 3 of the data the method was then applied to three thermal water samples collected from the same volcanic area and the results compared with those of a fumarolic and a soil gas the isotope ratios for dissolved he gave values of 4 06 4 23 ra which are significantly higher than those previously reported in the literature 3 0 3 5 and 2 9 ra and that measured at the fumarole 3 09 ra suggesting a newer and higher isotopic signature for the volcanic system the proposed method appears to be a useful tool in the determination of 3he 4he ratios in ground water systems especially when free gases are not available or are dangerous to collect