noble gases and nitrogen mixing and temporal evolution in the fumarolic fluids of vulcano italy abstract since 1979 noble gases he ne ar and n 2 in the medium temperature fumaroles of vulcano crater have been analyzed repeatedly during these 10 years of surveillance variations have been noticed in fluid composition until 1986 40 ar 36 ar ratios up to 2000 were found n 2 ar was 1600 and he ar was 1 9 indicating the presence of a deep component as the result of a mixing between mantle and crustal fluids since 1987 the atmospheric component has increased and the fluid composition has evolved towards an air saturated groundwater asw this change is considered to be the result of mixing between magmatic fluids and meteoric waters that release their atmospheric gases on entering the volcanic system these gases thus mask the magmatic component which has remained more or less constant in the last decade

factors controlling the geochemical evolution of fumarolic encrustations valley of ten thousand smokes alaska abstract factor and canonical correlation analysis of geochemical data from eight fossil fumaroles suggest that six major factors controlled the formation and evolution of fumarolic encrustations on the 1912 ash flow sheet in the valley of ten thousand smokes vtts the six factor solution model explains a large proportion low of 74 for ni to high of 99 for si of the individual element data variance although the primary fumarolic deposits have been degraded by secondary alteration reactions and up to 75 years of weathering the relict encrustations still preserve a signature of vapor phase element transport this vapor phase transport probably occurred as halide or oxyhalide species and was significant for as sb and br at least three and possibly four varied temperature leaching events affected the fumarolic deposits high temperature gases liquids heavily altered the ejecta glass and mineral phases adjacent to the fumarolic conduit as the fumaroles cooled fe rich acidic condensate leached the ejecta and primary fumarolic deposits and resulted in the subsequent precipitation of fe hydroxides and or fe oxides low to ambient temperature leaching and hydration reactions generated abundant hydrated amorphous phases up to 87 of the individual element data variance is apparently controlled by the chemistry of the ejecta on which the relict encrustations are found this matrix chemistry factor illustrates that the primary fumarolic minerals surrounding the active vtts vents observed by earlier workers have been effectively removed by the dissolution reactions element enrichment factors calculated for the vtts relict encrustations support the statistical factor interpretations on the average the relict encrustations are enriched relative to visibly unaltered matrix protolith in as br cr sb cu ni pb fe and loi an indirect measure of sample h 2 o content

environmental changes during isolation processes from the litorina sea as reflected by diatoms and geochemical parameters a case study the aim with the present case study was to detect environmental changes during the isolation of a lake from the baltic sea elemental and stable isotope ratios of carbon and nitrogen are presented as well as results of a diatom analysis of a sedimentary sequence from lake skaren in southeastern sweden the dated part of the analysed sequence covers the period c 8200 to 7000 cal years bp i e the late ancylus lake to early litorina sea stages it is concluded that subtle environmental changes due to uctuations in input of organic material from different sources cannot be detected by diatom analysis alone but that chemostratigraphy is an important complement to diatom stratigraphy when interpreting the isolation process we also conclude that even though 13c is highly variable in baltic sea sediment it is most useful in isolation studies for recording the contribution of organic carbon derived from benthic macro algae and or terrestrial sources as a proxy for shore displacement it is especially

polar motions excited by a convecting viscous mantle the role played by time dependent mantle convection on exciting long term polar motions is examined by means of a viscous model for sufficiently low effective viscosity polar wander speeds of 0 1 deg myr would require contributions from the off diagonal elements of the inertia tensor with magnitudes around 105 times smaller than those found in viscoelastic models used for postglacial rebound contributions from the large scale mantle flow to the angular momentum vector can be comparable to those due to changes in moment of inertia tensor for non linear rheology or for young planets the relative roles of the two contributions depend on the non linear rheology of the mantle and its convective vigor

the effect of variations in rainfall on the chemical composition of vulcano fumaroles italy analytical data for samples collected over a period of 17 months at the crater fumaroles of vulcano are given

marine and limnic radiocarbon reservoir corrections for studies of late and postglacial environments in georgia basin and puget lowland british columbia canada and washington usa models of late glacial environmental change in coastal areas are commonly based on radiocarbon ages on marine shell and basal lake sediments both of which may be compromised by reservoir effects the magnitude of the oceanic reservoir age in the inland waters of the georgia basin and puget lowland of northwestern north america is inferred from radiocarbon ages on shell wood pairs in saanich inlet and previously published estimates the weighted mean oceanic reservoir correction in the early and mid holocene is 720 90 yr slightly smaller than but not significantly different from the modern value the correction in late glacial time is 950 50 yr valley head sites yield higher reservoir values 1200 130 yr immediately after deglaciation the magnitude of the gyttja reservoir effect is inferred from pairs of bulk gyttja and plant macrofossil ages from four lakes in the region incorporation of old carbon into basal gyttja yields ages from bulk samples that are initially about 600 yr too old the reservoir age declines to less than 100 yr after the first millennium of lake development when these corrections are accounted for dates of deglaciation and late glacial sea level change in the study area are pushed forward in time by more than 500 yr

genesis and evolution of the fumaroles of vulcano aeolian islands italy a geochemical model a geochemical model explaining the presence of fumaroles having different gas composition and temperature at the top of the crater and along the northeastern coast of vulcano island is proposed a pressurized biphase liquid vapor reservoir at the depth of about 2 km is hypothesized energy and mass balance sheets controlp t conditions in the system p t must vary along a boiling curve of brine as liquid is present the co2 content in the steam is governed by the thermodynamic properties of the fluids in the h2 nacl co2 system on the assumption that oxygen fugacity in the system is between the hm fmq oxygen buffers observed so2 h2s co2 co co ch4 ratios in the fumarolic gases at the fossa crater appear in equilibrium with a temperature higher than that observed such as may exist at depth the more reduced gas phases present on the sea side may result from re equilibrium processes in shallower aquifers the suggested model would help in monitoring changes in volcanic activity by analyzing fumarolic gases

polar wandering and paleomagnetism an important hypothesis of paleomagnetism is that apparent polar wander the motion of the paleomagnetic pole relative to a continent or plate is caused entirely by plate motion relative to the mesosphere which is the relatively stronger and slowly deforming mantle beneath the astheno sphere recent research has challenged this hypothesis and suggests that polar wandering i e true polar wandering affects apparent polar wander apw paths the debate about polar wandering has been revived by studies comparing paleomagnetic poles to plate motion relative to hotspots morgan 1 98 1 what makes the new work interesting is that the under lying hotspot model makes many predictions that are testable by available and obtainable data one prediction that the hawaiian hotspot has shifted southward over cenozoic time has been severely tested and confirmed kana et al 1 978 kana 1 980 gordon cape 1 98 1 gordon 1 982 recent tests have mainly but not entirely taken the form of a reexamination of existing data in the light of the new model future tests can and should be made however by obtaining high quality data from paleomagnetic study of critical time intervals already identified by analysis of existing data this paper discusses what polar wandering is and reviews how the available paleomagnetic data and plate reconstructions have been used to investigate past polar wandering implications of work to date possible causes of polar wandering and promising directions of future research are also discussed

dynamics of vulcano island tyrrhenian sea italy investigated by long term 40 years geophysical data abstract vulcano island is a composite volcanic edifice located in the south central sector of the aeolian archipelago tyrrhenian sea italy historic activity has been characterized by frequent transitions from phreatomagmatic to minor magmatic activity the last eruption in 1888 90 saw powerful explosive pulses and this eruption defines what we call vulcanian also for other volcanoes since then volcanic activity has been in the form of fumarolic emanations of variable intensity and temperature mainly concentrated at la fossa crater we investigated vulcano dynamics through ca 40 years of ground deformation and seismicity data collected by the discrete and continuous ingv monitoring networks we considered levelling gps edm seismic and tilt data edm and levelling measurements began in the middle of the 1970s since the late 1990s the edm benchmarks have been measured using gps we performed a data inversion identifying for the 1999 2013 period the action of a deflating magmatic source located under vulcanello at 4 5 km a s l just at the top of a wide regional tectonic tabular source we analyzed data on different time space scales distinguishing the dynamics of different sectors of vulcano piano vulcanello la fossa cone and caldera and three periods 1974 1984 1984 1999 1999 2013 and the time evolution of the dynamics of the island we also show how the regional tectonic stress plays an important role in the transition of the volcanic system from a phase of stability to one of unrest inducing the heating and expansion of shallow hydrothermal fluids

the potential influence of radiative heat transfer on the formation of megaplumes in the lower mantle abstract recent seismic tomographic models have revealed broad low velocity anomalies in the lower mantle beneath africa and the central pacific which suggest a break in the symmetry between hot and cold regions in lower mantle dynamics we have considered the possible impact from radiative heat transfer which can be described by a nonlinear temperature dependent coefficient in the thermal conductivity in 2d numerical simulations results for rayleigh numbers up to 106 show a strong stabilizing influence from radiative heat transfer on mantle upwellings and the production of extremely hot thermal anomalies in the interior this nonlinearity is responsible for producing a strong attractor in the mantle convective system which greatly simplifies its time dependent dynamics the possible link of the simplified lower mantle time dependent dynamics with polar wander is discussed the main point here is that slow time dependence of the huge anomalies in the lower mantle can be the main mechanism controlling long term rotational dynamics

a revised chronology for the fjord stade moraine in disko bugt west greenland this paper re evaluates the age of the fjord stade moraine in disko bugt a large marine embayment in west greenland previous work suggests that this moraine is part of a widespread moraine complex present throughout west greenland which formed ca 9300 cal yr bp in response to either a regional climate change or the effects of topographic controls on ice sheet recession we present the results of a relative sea level study using data from eight isolation basins that straddle the fjord stade moraine in southeast disko bugt our results suggest that the moraine here formed between ca 8400 and 7700 cal yr bp this is later than previously thought and similar in timing to a widespread cooling event recorded in the greenland ice core records this chronological similarity raises the possibility that the fjord stade moraine in the study area records an ice marginal response to a major short lived climatic cooling during the early holocene the so called 8200 event

toroidal poloidal energy partitioning and global lithospheric rotation during cenozoic time the motion of surficial plates can be split into two terms the toroidal field related to shear between plates or to spin around their centres and the poloidal field associated with horizontal divergence at ridges and subductions recent papers have suggested that the present day plate motion minimizes the ratio of toroidal to poloidal energies 1 and that the existence of a global lithospheric rotation results from viscosity variations between oceans and continents 2 this paper tests and confirms these two hypotheses using plate reconstructions during cenozoic time the partition of energy between the two modes always favours the poloidal velocities the global rotation computed using a viscosity one order of magnitude lower below oceans than below continents agrees with observations the existence of a non linear rheology in a uniform asthenosphere leads to a satisfactory location of the global lithospheric rotation but with too small an amplitude

signs of potential renewal of eruptive activity at la fossa vulcano aeolian islands since the end of the last magmatic eruption 1890 activity of la fossa southern tyrrhenian sea italy has consisted of fumarolic emissions of fluctuating intensity fluids are discharged principally at two fumarolic fields located in the northern rim of the active crater and at the beach sited at its northern foot increased thermal seismic and geochemical activity has been recorded since 1978 when an earthquake of m 5 5 occurred in the region this paper combines available geophysical and geochemical information in order to develop a tentative interpretation of two episodes of apparent unrest which occurred in 1985 and 1987 1988 enhancing the risk of renewal of the eruptive activity the 1985 unrest consisted essentially of a sharp build up of the internal pressure in the shallow hydrothermal system which was induced by the injection of hot gases of magmatic origin the crater fumaroles displayed significant increases in co2 and other acid species but their outlet temperature did not change conversely the 1987 1988 episode was characterized by appreciable modifications at the crater fumaroles with only secondary effects at the fumarole system of the beach the sliding of part of the eastern flank of the la fossa cone into the sea occurred on 20 april 1988 when the region was affected by crustal dilatation producing a seismic sequence of relatively high intensity both episodes of unrest were accompanied by increases of local microseismic activity which affected the nothern sector of the island in 1985 and the southern one in 1988 finally a phase of appreciable areal contraction was detected in 1990 probably due to the effect of the cooling and crystallization of magma at relatively shallow depths accompanying the increased thermal activity at the crater fumaroles regional tectonic stress seems to play an important role in the transition of the volcanic system from a phase of relative stability to a phase of apparent unrest inducing the heating and the expansion of shallow hydrothermal fluids available information is insufficient to indicate whether or not the volcano is building towards the renewal of a magmatic eruption and there is no evidence to hypothesize episodes of significant magma migration the frequency of measurements of many parameters needs to be increased in order to learn more about the temporal relationships between geochemical and geophysical variations preceding and accompanying periods of increased thermal activity this will probably be a valid tool for recognizing short term precursors of a future eruption reducing the risk of false alarms

thermal expansion measurements at very high pressure systematics and a case for a chemically homogeneous mantle new data on thermal expansivity of iron to over 400 kbar in laser and electrically heated diamond anvil cells and on mgo and forsterite from spectroscopic data to over 200 kbar and previously measured adiabats boehler 1982 imply that at high pressure may be described by a constant value of 1n 1nv t 5 5 0 5 this behavior is supported by previous measurements at lower pressures on a large variety of materials densities of magnesio wustite and silicate perovskite in a pyrolitic ratio calculated at lower mantle conditions using a finite strain equation and at high pressures using the above systematics match those in prem through the entire lower mantle making a strong case for a uniform mantle

thermal infrared satellite measurements of volcanic activity at stromboli and vulcano the use of landsat thermal infrared imagery gives a direct way of quantitatively monitoring the evolution of low amplitude thermal anomalies using nighttime landsat thematic mapper images of vulcano and stromboli volcanoes on october 23 1986 we have developed a simplified method for correcting atmospheric effects we were then able to identify thermal anomalies around the craters part of the stromboli lava flow formed 1 year earlier was also still warm enough to be detected we obtained fairly accurate estimates of relative surface anomaly radiative heat fluxes 29 5 w m 2 21 4 w m 2 and 37 5 w m 2 for the stromboli craters stromboli lava flow and vulcano crater respectively accounting for the convective heat loss significantly increases the estimates of the relative internal heat flux of geothermal origin we found values of 370 60 w m 2 for the stromboli crater region 220 50 w m 2 for the stromboli lava flow and 270 60 w m 2 for the vulcano crater despite the low precision these values are much higher than the 53 62 w m 2 limit defined by cassinis and lechi 1974 as the threshold where the geothermal flux can affect ground temperatures our study provides a unique systematic definition of thermal volcanic features found on stromboli and vulcano the spatial extents of the anomalies and their fluxes and associated errors

pleistocene deglaciation and the earth s rotation implications for mantle viscosity summary recent results from the analysis of postglacial rebound data suggest that the viscosity of the earth s mantle increases through the transition region models which fit both relative sea level and free air gravity data have viscosities which increase from a value near 1022 poise in the upper mantle beneath the lithosphere to a value of about 1023 poise in the lower mantle in this paper we analyse the effect of deglaciation upon the earth s rotation and thereby show that the observed secular trend polar wander evident in the ils ipms pole path and measurements of the non tidal acceleration of the length of day are both consistent with the viscosity profile deduced from postglacial rebound the two analyses are therefore mutually reinforcing

the evolution of a dynamic geological system the support of a gis for geochemical measurements at the fumarole field of vulcano italy abstract the island of vulcano aeolian arc southern italy has displayed several periods of volcanic unrest since the end of the last eruption 1890 we report here results obtained from a long term survey concerning variations of both the steam output and the exhaling surface area at the summit crater fumarolic field of la fossa the field measurements analysed in a geographical information system gis show a highly dynamic volcanic system in which deep variations in the geochemistry and the temperature of the released fluids were accompanied by fluctuations in the mass output of steam and the topography of the crater field the use of a gis facilitated digitized reconstructions of maps of the crater field in addition to analysis of the steam flux data the fumarolic field expanded its surface area from 50 m 2 in 1983 to more than 2400 m 2 in 1995 accompanied by an increase in steam output from 152 to about 1400 tonnes per day the possibility that the observed phenomena are related to volcano tectonic activity and to magma uprising is taken into consideration

geothermal energy release at the solfatara of pozzuoli phlegraean fields phreatic and phreatomagmatic explosion risk implications the h2o co2 and h2s outputs at the solfatara of pozzuoli have been measured and a map of the exhaling areas has also been made the energy released at the surface by the fluids has been estimated to be 1019 ergs day

the monzogabbroic intrusion in the island of vulcano aeolian archipelago italy two drill holes were carried out during 1983 84 by the joint venture agip ems enel on the island of vulcano southwest of the cratere della fossa after passing through pyroclastics and lavas of the young volcanic centres of vulcano the drill holes penetrated an intrusion of monzogabbro to leuco monzogabbro composition in one of the holes the top of the intrusion occurs at 1360 m and the intrusive rocks are found to the bottom of the well at 2050 m at this depth the temperature exceeds 419 c and the temperature gradients are sufficiently steep that magma could well be reached only a few hundred metres deeper lava of the south vulcano centre is metamorphosed by the intrusion

time series analysis of high temperature fumaroles monitored on the island of vulcano aeolian archipelago italy abstract the exhalation activity at the la fossa cone vulcano island aeolian archipelago italy has been ongoing for more than 1 century many of the monitored geochemical and geophysical parameters have showed transient variations of energy release the time series analyses of fumarole temperatures presented in this paper enabled the sequence of observations to be defined and information from different monitoring stations to be integrated the motion of fluids feeding the fumaroles of the la fossa cone is driven by the thermal and kinetic energies that balance the seismic and volcanic forces active in the region and the temperatures of the fumaroles reflect the local response of the hydrothermal system to these forces during a 14 year period of observation from 1998 to 2012 fumarole temperatures showed various trends but also cyclic variations characterized by sharp increases the repetition of these variations during periods with different trends indicates that no physical variation occurred from the hydrothermal source to the surface during the analyzed period and after each periodic geochemical crisis the previous thermal conditions were restored although the continuous monitoring of high temperature fumaroles was limited to only a few sites the observed trends characterized the most important fumaroles in the area of vulcano island an evaluation of thermal energy release based on these spatially discrete measurements would be a speculative exercise in thermodynamics but the analyses of the recorded data represent a step forward in interpreting the signals from ongoing volcanic activity and in assessing the seismic risk

improving gloria images using sea beam data gloria and sea beam data are processed together with a number of benefits the sea beam data allow an improved slant to ground range projection of the imagery that results in less of the distortions such as layover and foreshortening that are produced when the seafloor is assumed to be flat a calculation originally intended to quantify side scan sonar data has also been found to improve the images in an image enhancement sense this calculation involves estimating the seafloor s backscatter strength from gloria side scan sonar data using a simple physical model and the characteristics of the gloria instrument the backscatter strength is the ratio of backscattered to incident sonar intensity on the sea bottom normalized to the surface area covered by the acoustic pulse it is computed by correcting the gloria data for propagation losses beam directivity pattern time varied amplifier gain and other factors the calculation is improved by accounting for refraction in the water column and for some topographic effects using sea beam data a gloria image from a mid ocean ridge crest is shown to have a large 60 db range that is due to the effect of the system response such as the beam pattern on the images the corresponding image of the seafloor backscatter strength has an almost gaussian distribution of picture element digital numbers with a narrow range 20 db showing that most of the system effects have been removed cross sections through the backscatter strength image show flat trends superimposed with finer variations due to the seafloor geology the conversion of gloria data into seafloor backscatter strength serves two purposes it provides quantitative information that can be used to determine the likely causes of particular features in the images and it performs what is effectively a deterministic shading correction

double origin of hydrothermal convective flux variations in the fossa of vulcano italy soil temperature measurements can provide information on the distribution of degassing fissures their relationship to the internal structure of the volcano and the temporal evolution of the system at vulcano island italy heat flux from a 3 km deep magma body drives a hydrothermal system which extends across the main fossa crater this heat flux is also associated with variable magmatic gas flow a high density map of soil temperatures was made in 1996 at a constant depth of 30 cm on the central and southern inner flanks of the fossa crater these measurements extended over an area covering about 0 04 km2 across which the heat flux is predominantly associated with a shallow boiling aquifer the map shows that hot zones relate to structures of higher permeability mainly associated with a fissure system dating from the last eruptive cycle 1888 1890 from 1996 to january 2005 we studied the evolution of the heat flux for the high temperature part of the map both by repeating our measurements as part of 14 visits during which temperatures were measured at a constant depth and using data from permanent stations which allowed soil temperatures to be continuously measured for selected vertical profiles these data allowed us to calculate the heat flux and its variation with good precision for values lower than about 100 w m 2 which is generally the case in the study area above 100 w m 2 although the heat flux value is underestimated its variations are recorded with an error less than 10 during the period 1996 2004 two increases in the thermal flux were recorded the first one was related to the seismic crisis of november 1998 which opened existing or new fissures the second in november 2004 was probably due to magma migration and was associated with minor seismic activity

microbial communities near the oxic anoxic interface in the hydrothermal system of vulcano island italy abstract hydrothermal fluids and sediments from subaerial and shallow submarine sites at vulcano island italy were investigated for relations between the thermophilic microbial communities as analysed by fluorescence in situ hybridization and their geochemical environment as assessed by photometry chromatography and in situ microsensor measurements mixing between hydrothermal fluids and seawater in the sediment pore space was reflected in the chemical composition of the emitted fluids in depth profiles of pore water oxygen and sulfide concentrations and in the structure of the benthic microbial community organic compounds did not accumulate in the vent fluids

the holocene shore displacement of gastrikland eastern sweden a contribution to the knowledge of scandinavian glacio isostatic uplift the holocene shore displacement of gastrikland eastern sweden a contribution to the knowledge of scandinavian glacio isostatic uplift

volcanic steam output directly measured in fumaroles the observed variations at vulcano island italy between 1983 and 1987 the mass of steam emitted by the fumaroles of the crater of vulcano aeolian islands italy was evaluated by using a direct measuring method measurements were effected with this method between 1983 and 1987 in nine field campaigns the results of which are given in this paper the steam flux measurements were performed by an instrument expressly designed for steam condensation the estimates of the thermal energy transported daily by the steam gave values of up to 10e12 j the sharp variations in the total mass outputs recorded in 1984 and 1985 are here interpreted as being a consequence of the probable accumulation of fluid pressure at depth during the evolution of volcanic activity the different results obtained from the various areas of the fumarolic field during the evolutionary phases have led to the hypothesis that different subsystems exist that feed the fumaroles and that their activity is triggered by volcano tectonics this method can be applied in the evaluation of both fumarolic steam and thermal energy outputs and therefore it is particularly useful in geothermal exploration in the evaluation of the environmental impact of volcanic degassing and in the forecasting of volcanic eruptions the evaluation of the steam output is also useful for quantifying the release of other gaseous species and giving univocal interpretations regarding their variations in concentrations furthermore this direct method provides a new way of calibrating the flux estimates effected by other telemetric techniques lidar cospec etc

sulfur dioxide and particles in quiescent volcanic plumes from poas arenal and colima volcanos costa rica and mexico measurements of so2 emission rates and concentrations and of particle distribution size shape and composition were made in quiescent volcanic plumes emitted into the troposphere from poas and arenal volcanos costa rica and colima volcano mexico so2 emission rates were 700 180 metric tons per day t d for poas 210 30 t d for arenal and 320 50 t d for colima the concentrations of so2 calculated from the cospec lidar data were 5 380 ppb concentrations of so2 measured directly by flame photometry were 10 250 ppb particles collected in the plumes with a quartz crystal microbalance impactor were mostly less than 3 m in diameter and consisted of droplets of dilute sulfur bearing solutions and minor amounts of larger silicate particles coated with a sulfur bearing film or crust total particle concentrations were 4 7 g m3 for poas and 18 8 g m3 for colima comparison of concentrations of so2 in the plumes with gas samples collected at fumaroles on the ground suggests that the plumes are diluted by the atmosphere by factors of up to 105

hard turbulent thermal convection and thermal evolution of the mantle this article summarizes the results of hard turbulent convection obtained in laboratory experiments and numerical simulations its applications to mantle convection are illustrated by two dimensional numerical solutions to 1 newtonian 2 non newtonian convection and 3 newtonian convection with multiple phase transitions in newtonian mantle convection the transition from soft to hard turbulence is marked by the appearance of disconnected plumes spectral analysis of the time series of the nusselt number reveals the presence of a spectral scaling subrange for hard turbulence but not for soft turbulence in hard turbulence there is correspondence between the spectra in frequency and wavenumber domains the slope of the seismic wave spectra measured from seismology suggests that the mantle convection today is strongly time dependent the transition to hard turbulence takes place at much lower nusselt numbers for non newtonian than for newtonian rheology for the mantle this would have important ramifications non newtonian plumes behave quite differently from newtonian ones in that large curvatures are developed in their trajectories in the hard turbulent regime mantle convection with phase transitions tends to become more layered with increasing rayleigh numbers the style of mantle convection might have changed from a layered to a more whole mantle type of flow with time catastrophic overturns associated with strong gravitational instabilities in the transition zone could be responsible for superplume events

dynamical influences on the moment of inertia tensor from lateral viscosity variations inferred from seismic tomographic models abstract we have investigated the influences of lateral variations of viscosity on the moment of inertia tensor from viscous flows due to the density anomalies in the mantle inferred from seismic tomographic models the scaling relations between the density and the seismic anomalies is taken as either a constant or a function increasing with depth in accord with the recent high pressure experimental studies the viscosity is taken as an exponential function of the 3d density anomaly in models with an isoviscous background the effects on the perturbed moment of inertia tensor from the lateral viscosity variations are smaller than those due to variations in the radial viscosity profiles in mantle models with a background viscosity increasing with depth the influences of the lateral viscosity variations are significant the most striking feature in the latter case is that the two off diagonal elements i xz and i yz in the inertia tensor exhibit greatest sensitivity to lateral variations of the viscosity while the other elements of the inertia change by only about a few tens of percent in the range of lateral viscosity contrast considered i xz and i yz can vary up to 40 times even with a change in sign depending on the radial viscosity stratification and the location of the strongest lateral variations the increase in the velocity density scaling relation with depth can reduce the influences of the lateral viscosity variations but it does not change the overall sensitive nature of i xz and i yz this study demonstrates clearly that the lateral viscosity variations especially in the upper mantle must be considered in the determination of long term polar wander since the variations in the i xz and i yz terms are directly responsible for exciting rotational movements

a tensile shear crack model for the mechanism of volcanic earthquakes abstract temporary seismic observations were carried out for about 1 month at miyakejima island on the izu bonin arc after an eruption on october 3 1983 more than 3000 seismic events were observed and they are classified into 4 different categories short period earthquakes long period earthquakes isolated tremors and continuous tremors two active source regions of the short period earthquakes were located along the old caldera rim of the miyakejima volcano one region was very close to the eruptive fissures another was about 1 2 km northwest of the fissures almost all the earthquakes in the former region showed dilatant first motions of p waves at all the stations in the island on the other hand almost all events in the latter region showed compressive first motions of p waves at all the stations the first motions of p waves for these earthquakes cannot be explained by the quadrant type pattern due to a double couple force system nucleation of a tensile crack coupled with a shear crack a tensile shear crack model is proposed as a source mechanism of the short period earthquakes moment tensor elements of tensile and shear cracks have been determined by the least squares method using observed p and s wave data results suggest that tensile cracking opening or closing is dominant for generating those earthquakes in comparison with shear cracking the strikes of the tensile cracks for the earthquakes are shown to be nearly parallel to the strike of the fissures the earthquakes that occurred in the northwestern region of the fissures are considered to be generated by a sudden opening of tensile shear cracks due to the excess pressure of intrusive magma in contrast the earthquakes occurring beneath the fissures are probably generated by a sudden closing of tensile shear cracks and this suggests that the magmatic pressure under the fissures rapidly decreased after the eruption moment tensor analysis of the tensile shear crack model in this study demonstrates the non double couple source mechanism for volcanic earthquakes related to magmatic activity

chloropigments a in sediments of the gulf of gdansk deposited during the last 4000 years as indicators of eutrophication and climate change abstract the occurrence of chlorophyll a derivatives in a sediment core from the gulf of gdansk southern baltic sea was investigated the core 380 cm long was taken in the area with the highest sedimentation rate ninety five sub samples of the core were analysed for their pigment and organic carbon contents selected sections of the core were 14c dated and analysed for granulometry the results of the study are in agreement with previous observations for eastern gotland basin sediments that there are greater quantities of chloropigments in the deeper layers than in more recent sediments taken from the same site secondary diagenesis products pyrophaeophytin a and steryl chlorin esters are taken here as indicators of diagenetic processes under anoxic conditions and hence of sediment age these results endorse earlier hypotheses that past eutrophication in the baltic has occurred at a higher level than that observed nowadays and that climate may be a more important factor relative to anthropogenic impacts in influencing the combination of primary production and pigment preservation in sediments

differential rotation between lithosphere and mantle a consequence of lateral mantle viscosity variations the description of plate motions in the so called hotspot reference frame introduces a global rotation of the lithosphere with respect to the mantle this rotation called toroidal field of degree 1 is roughly westward it reaches an amplitude of about 2 cm yr and has been consistently found in the different generation of plate tectonic models various authors have tried to relate this observation to the deceleration of the earth s rotation to polar wander or to tidal drag however these different physical mechanisms cannot explain the requested amplitude in this paper we compare the values of this rotation vector using different relative plate motion models expressed in the hotspot reference frame in a model earth with lateral viscosity variations a differential rotation is predicted the observed net lithospheric rotation is consistent with the dynamics of a model earth where the asthenospheric viscosity below the oceans is at least one order of magnitude lower than underneath the continents this relative westward drift of the lithosphere may account for the significant structural differences between east or west dipping subduction zones

geochemical and seismological investigations at vulcano aeolian islands during 1978 1989 both geochemical and geophysical evidence indicates that the activity of the fumarolic system of the fossa crater can be divided into two periods from 1978 to 1983 such activity has been mainly controlled by two competing processes which affect the permeability of the fumarolic system at deep levels 1 rock fracturing induced by faulting and 2 mineral deposition alteration the latter which causes a slow decrease of the permeability at deep levels through clogging of fractures and voids prevailed at the end of this period determining a fluid pressure increment in the deep parts of the system from 1984 to 1989 fluid pressure at deep levels remained persistently high triggering local microseismic swarms furthermore pt conditions much higher than before were attained in the zones where hydrothermal fluids seep into the conduits from lateral aquifers owing to an uprising of the isotherms a deepening of these seeping zones or both

the palaeoenvironments of coastal lagoons in the southern baltic sea ii δ13c and δ15n ratios of organic matter sources and sediments organic carbon and nitrogen isotope values 13c 15n and c n ratios of six sediment cores from six coastal lagoons including the oder estuary were measured to chart the coastal development and to reconstruct the local palaeoenvironments of the southern baltic sea region during the holocene in addition 13c 15n and c n values of major organic matter sources in the coastal lagoons and their drainage areas are investigated to determine the origin of organic matter i e terrigenous or marine in the sediments plankton aquatic macrophytes typical c3 shore plants and peat the 13c 15n and c n values of the samples collected show the clearly identifiable stages in the development of the water bodies post glacial lake stages with sandy sedimentation lacustrine phases with high autochthonous productivity terrestrial stages with peat formation sedimentation as a result of marine transgression and brackish sedimentation after the formation of sand spits and barrier islands these stages are the results of sea level changes in the region the values allow derivation of differences in the palaeoenvironments of the lagoons in the study area a distinct terrestrial input is evident in the sediments of the lagoonal oder estuary which can be attributed to the direct inflow of the oder river into the lagoon the isotope and c n values also suggest a contribution of c4 plant detritus for the water bodies in the northeastern part of the study area barther bodden grabow the burial of autochthonous organic matter i e plankton aquatic macrophytes in the sediment could be derived for all lagoons in this investigation

evolution of the fossa cone vulcano abstract in decreasing order of abundance the principal emplacement mechanisms for deposits of the fossa edifice of vulcano include dry surge wet surge pyroclastic fall lahar lava flow pyroclastic flow and epiclastic processes most samples from pyroclastic beds on fossa contain two grain size populations the coarser mode at 0 5 1 5 resulted from modified ballistic transport whereas the finer mode at 2 5 3 5 is related to surge transport reconstruction of the entire stratigraphy of the cone permits the beds to be grouped into five principal eruptive cycles all of which postdate the lower pilato ash of lipari dated at 11 000 to 8 500 y b p pte nere cycle palizzi cycle commenda cycle pietre cotte cycle and the modern cycle additional cycles may be present but exposures on the cone are insufficient for their adequate definition all cycles follow a similar stochastic pattern starting with surge eruptions and ending with effusion of lava from the crater rim the frequency of pyroclastic fall events increases with time throughout each cycle this progressive decrease in the efficiency of water melt interaction through the duration of each cycle may be due to a gradual rise of each new magma column coupled with an increase in magmatic volatiles tectonism and magma mixing both play a role in triggering eruptions on fossa the present crater lies at the intersection of two prominent tectonic trends a nnw fracture system parallels the main eruptive centers and an ene set aligns with the migration of minor vents the silicic lavas of fossa contain a mixture of two components xenocrysts of plagioclase augite and olivine surrounded by a dark glass are intimately dispersed into an evolved rhyolitic matrix

rates of sulfur dioxide and particle emissions from white island volcano new zealand and an estimate of the total flux of major gaseous species airborne correlation spectrometry cospec was used to measure the rate of so2 emission at white island on three dates i e november 1983 1230 300 t d november 1984 320 120 t d and january 1985 350 150 t d t metric tons the lower emission rates are likely to reflect the long term emission rates whereas the november 1983 rate probably reflects conditions prior to the eruption of december 1983 the particle flux in the white island plume as determined with a quartz crystal microbalance cascade in november 1983 was 1 3 t d unusually low for volcanic plumes the observed plume particles as shown from scanning electron microscopy include halite native sulfur and silicates and are broadly similar to other volcanic plumes

pre historic changes in natural and anthropogenic heavy metals deposition inferred from two contrasting swiss alpine lakes abstract continuous high resolution sedimentary record of heavy metals chromium cr copper cu lead pb zinc zn manganese mn and mercury hg from lakes lucerne and meidsee switzerland provides pollutant deposition history from two contrasting alpine environments over the last millennia the distribution of conservative elements thorium th scandium sc and titanium ti shows that in absence of human disturbances the trace element input is primarily controlled by weathering processes i e runoff and erosion nonetheless the enrichment factor ef of pb and hg that are measured by independent methods and the pb isotopic composition of sediments from the remote lake meidsee which are proportionally more enriched in anthropogenic heavy metals likely detect early mining activities during the bronze age meanwhile the deposition of trace elements remains close to the range of natural variations until the strong impact of roman activities on atmospheric metal emissions both sites display simultaneous increases in anthropogenic trace metal deposition during the greek and roman empires ca 300 bc to ad 400 the late middle ages ca ad 1400 and the early modern europe after ca ad 1600 however the greatest increases in anthropogenic metal pollution are evidenced after the industrial revolution of ca ad 1850 at low and high altitudes during the twentieth century industrial releases multiplied by ca 10 times heavy metal fluxes to hydrological systems located on both sides of the alps during the last decades the recent growing contribution of low radiogenic pb further highlights the contribution of industrial sources with respect to wood and coal burning emissions

seismic events at vulcano italy during 1988 1992 abstract a classification of seismic events is proposed that originate on vulcano aeolian islands southern tyrrhenian sea and adjacent regions into four broad classes 1 shocks that exhibit single peaked spectra 2 typical earthquakes with distinct p and s phases 3 irregular shaped events with ill defined to undetectable s phases and 4 long period events with dominant frequency peak less than 2 hz a hypothesis is put forward that the shocks occurring within the volcanic cone of la fossa are mainly related to intense fumarolic activity of high temperature more than 650 c in october 1992 estimation of seismic energy release within two distinct sectors one including la fossa cone the other external to it during 1988 1992 has been developed in order to evaluate the level of seismic activity of the system over the time here analysed the rate of seismic energy density release at la fossa was 4 71 1014 erg km 2 yr 1 that is significantly larger than that of the surrounding areas furthermore the energy partition estimate indicates that within la fossa seismic energy release associated with rock failure processes is on the whole about 3 6 times larger than that of fluid driven shocks the latter appear to be concentrated at rather shallow depths 400 1000 m where geochemical analyses and geothermal surveys indicate the sealing action of hydrothermal minerals estimated b values of the gutenberg richter magnitude frequency relation range between 0 81 0 27 and 1 45 0 29 within la fossa whereas a value around 1 6 has been calculated for the external sector the comparison between data presented in this paper and those from recent geophyical and geochemical investigations shows that appreciable increments in the rate of seismicity are accompanied with significant modifications in the chemistry of fumarolic gases and in the ground deformation pattern recorded at the base of the active cone

global tectonics under g having a minute westward tilt the convection seen to affect moon s mantle takes place under gravity having a component of asymmetry in the form of a minute westward slope or tilt constituting the external part of the field its effect is explored employing the equivalent potential denominated its nature is to bias convection of internal origin inducing east west polarization of a type prominent in global tectonics separately research at harvard has shown that by causing advection of non hydrostatic masses within the heterogeneous mantle deep seated convection inevitably displaces the axis of maximum moment compelling polar wander a reconstruction based on observed dissipation suggests that the combined effect of these factors is to contribute a not inconsiderable low latitude surface west component to the structure of the convection cumulative alteration in the direction west must eventually require global rearrangement of its cell structure offering explanation of the abrupt mesozoic tertiary transition and progressive net lithosphere rotation

evolution of fumarolic gases boundary conditions set by measured parameters case study at vulcano italy physical chemical and isotopic parameters were measured in fumaroles at the vulcano crater and in drowned fumaroles near the beach the data were used to define boundary conditions for possible conceptual models of the system crater fumaroles time variations of co2 and so2 concentrations indicate mixing of saline gas rich water with local fresh water cl br ratios of 300 400 favour sea water as a major source for cl brand part of the water in the fumaroles cl concentrations and d values revealed independently amixing of 0 75 sea water with 0 25 local freshwaterin furmarole f 5 during september 1982 patterns of parameter correlation and mass balances reveal that co2 s nh3 and b originate from sources other than sea water the co2 value of 13c 2 o favours at least partial origin from decomposition of sedimentary rocks rather than mantle derived material radiogenic4he 1 3 lo 3 ccstp g water and radiogenic40ar 10 6 10 4 ccstp g water are observed 4he 40ar radiogenic 1 2 well in the range of values observed in geothermal systems drowned fumaroles strongly bubbling gas at a pond and at the beachappears to have the same origin and initial compositionas the crater fumaroles 2 km away the fumarolic gas is modified by depletion of the reactive gases caused by dissolution in shallow water atmospheric ne ar kr and xe are addeden route some radiogenic he and ar are maintained the vulcano system seems to be strongly influenced by the contribution of sea water and decomposition of sedimentary rocks evidence of magmatic contributions is mainly derived from heat

predominance of long wavelength heterogeneity in the mantle analysis of travel time anomalies of long period shear waves recorded by the global digital seismographic network indicates that mantle heterogeneities which probably reflect patterns of mantle convection occur most prominently on length scales greater than about 6 000 km when projected onto a two dimensional map at the earth s surface models of mantle convection will need to be able to produce a similar power spectrum

chemical variations in fumarolic gases at vulcano island southern italy seasonal and volcanic effects abstract because of increasing in fumarolic activity at vulcano since september 1987 regular sampling and analysis is conducted on the well known f5 crater fumarole t 330 5 c significant chemical variations have been recorded over the period 1987 1989 variations of water vapour in the fumarolic fluid follow seasonal pattern and can be related to both external seasonal and internal volcanic influences suggesting a control by a shallow water aquifer significant variations of h 2 o and of some species in the anhydrous gas phase h 2 so 2 hcl hf n 2 he probably result from chemical or dynamic changes in the feeding system at depth several mechanism are considered for explaining the chemical trends results in relationship to the recent increase in activity a growing input of deep magmatic fluids is not supported by the low co content and the apparent constancy of the 3 he 4 he ratio apparent equilibrium temperatures close to the fumarolic outlet temperature 350 400 c were calculated suggesting isothermal expansion of the gas from a shallow equilibration zone comparison with the fumaroles at sea level porto di levante suggests that these latter may be fed a different hydrothermal systems variable interaction between both systems may account for some of the chemical variations observed at f5 fumarole

atmospheric dispersion of natural carbon dioxide emissions on vulcano island italy la fossa quiescent volcano and its surrounding area on the island of vulcano italy are characterized by intensive persistent degassing through both fumaroles and diffuse soil emissions periodic degassing crises occur with marked increase in temperature and steam and gas output mostly co2 from crater fumaroles and in co2 soil diffuse emission from the crater area as well as from the volcano flanks and base the gas hazard of the most inhabited part of the island vulcano porto was investigated by simulating the co2 dispersion in the atmosphere under different wind conditions the disgas dispersion of gas code an eulerian model based on advection diffusion equations was used together with the mass consistent diagnostic wind model numerical simulations were validated by measurements of air co2 concentration inside the village and along the crater s rim by means of a soil co2 automatic station and a tunable diode laser device the results show that in the village of vulcano porto the co2 air concentration is mostly due to local soil degassing while the contribution from the crater gas emission is negligible at the breathing height for humans and always remains well below the lowest indoor co2 concentration threshold recommended by the health authorities 1000 ppm outdoor excess co2 maxima up to 200 ppm above local background co2 air concentration are estimated in the center of the village and up to 100 ppm in other zones however in some ground excavations or in basements the health code threshold can be exceeded in the crater area because of the combined effect of fumaroles and diffuse soil emissions co2 air concentrations can reach 5000 7000 ppm in low wind conditions and pose a health hazard for visitors

excitation of true polar wander by subduction true polar wander the global motion of the mantle relative to the earth s rotation axis is known from the analysis of palaeomagnetic data hotspot tracks and plate motions to have occurred at velocities of up to 0 5 myr 1 since the late cretaceous period1 4 we address here the longstanding question of how fast episodes of true polar wander tpw can be excited5 by analysing the impact of the distribution and activity of subduction zones on polar motion using nonlinear liouville equations which allow us to treat large excursions of the polar axis we show that unrealistically fast tpw is excited by subduction episodes unless the lower mantle has a viscosity at least 10 times that of the upper mantle this need for a viscosity increase with depth in the mantle reinforces the conclusions of previous studies on post glacial rebound and geoid anomalies theoretical creep laws and some preliminary results on tpw induced by density anomalies embedded in the mantle6 10 the lower viscosity in the upper mantle means that upper mantle density anomalies are most effective in exciting tpw changes in the pattern of subduction through time may be responsible for both episodes of fast tpw and times of quiescence in polar motion

reservoir ages in baltic sea sediment a case study of an isolation sequence from the litorina sea stage abstract in order to quantify the reservoir age in baltic sea sediment one sedimentary sequence from an isostatically isolated basin was subject to high resolution ams radiocarbon dates diatom analysis confirmed deposition during the litorina sea stage and later in a freshwater lake macrofossils from well preserved seeds and other remnants from terrestrial plants were used for ams datings it is assumed that these fragile plant remains are not redeposited or affected by internal ages the ages obtained from the macrofossils range from 6460 125 to 5580 75 14c yr bp by comparing these radiocarbon ages with those obtained by bulk sediment dates it was obvious that the bulk samples were affected by reservoir ages resulting in too old ages the reservoir ages varied within the sediment column during the most saline phase the reservoir age was approximately 750 yr shortly after the isolation ca 400 yr and in the freshwater lake the age differences between the two series were neglectable

role of magma mixing during the recent activity of la fossa di vulcano aeolian islands italy abstract relatively homogeneous trachytes have been erupted for approximately 3800 years at la fossa di vulcano from the punte nere eruptive cycle up to the palizzi cycle the products varied little while after the palizzi cycle 1600 1000 a b p to the latest eruption 1888 1890 ad a spectrum of compositions with rhyolite dominating characterized the erupted products a stratigraphic sequence starting with the palizzi lava flow has been studied focussing the attention on lavas and volcanic bombs to define the role that magma mixing processes have played in the recent history of la fossa di vulcano textural and chemical analyses of whole rocks glass groundmass and mineral phases indicate that only the breadcrust bombs erupted during the 1888 1890 show evidence of mixing between trachytic and rhyolitic end members interestingly in the deposits of the same eruption trachytic bombs also occur the lava flows erupted before 1888 1890 display general features suggesting that they entrained crystals and lava fragments during magma ascent during the 1888 1890 eruption the trachytic bombs were erupted before the breadcrust bombs which have a more evolved and hybrid composition these characteristics together with the change of the nature of the products after the palizzi cycle require a complex volcanological model for the recent history of la fossa di vulcano

bulk sediment 14c dating in an estuarine environment how accurate can it be abstract due to a lack of marine macrofossils in many sediment cores from the estuarine baltic sea researchers are often forced to carry out 14c determinations on bulk sediment samples however ambiguity surrounding the carbon source pathways that contribute to bulk sediment formation introduces a large uncertainty into 14c geochronologies based on such samples and such uncertainty may not have been fully considered in previous baltic sea studies we quantify this uncertainty by analyzing bulk sediment 14c determinations carried out on densely spaced intervals in independently dated late holocene sediment sequences from two central baltic sea cores our results show a difference of 600 14c yr in median bulk sediment reservoir age or r t bulk between the two core locations 1200 14c yr for one core 620 14c yr for the other indicating large spatial variation furthermore we also find large downcore i e temporal r t bulk variation of at least 200 14c yr for both cores we also find a difference of 585 14c yr between two samples taken from the same core depth we propose that studies using bulk sediment 14c dating in large brackish water bodies should take such spatiotemporal variation in r t bulk into account when assessing uncertainties thus leading to a larger but more accurate calibrated age range less

visualization and modeling of sub populations of compositional data statistical methods illustrated by means of geochemical data from fumarolic fluids in the investigation of fluid samples of a volcanic system collected during a given period of time one of the main goals is to discover cause effect relationships that allow us to explain changes in the chemical composition they might be caused by physicochemical factors such as temperature pressure or non conservative behavior of some chemical constituents addition or subtraction of material among others the presence of subgroups of observations showing different behavior is evidence of unusually complex situations which might render even more difficult the analysis and interpretation of observed phenomena these cases require appropriate statistical techniques as well as sound a priori hypothesis concerning underlying geological processes the purpose of this article is to present the state of the art in the methodology for a better visualization of compositional data as well as for detecting statistically significant sub populations the scheme of this article is to present first the application and then the underlying methodology with the aim of the first motivating the second thus the first part has the goal to illustrate how to understand and interpret results whereas the second is devoted to expose how to perform a study of this kind the case study is related to the chemical composition of a fumarole of vulcano island southern italy called f14 the volcanic activity at vulcano island is subject to a continuous program of geochemical surveillance from 1978 up to now and the large data set of observations contains the main chemical composition of volcanic gases as well as trace element concentrations in the condensates of fumarolic gases out of the complete set of measured components the variables h2s hf and as determined in samples collected from 1978 to 1993 as is not available in recent samples are used to characterize two groups in the original population which proved to be statistically distinct the choice of the variables is motivated by the importance of investigating the behavior of well known toxicity elements which show like as a significant mobility under hydrothermal conditions the statistical methodology used for this study is based on models devised for compositional data they include 1 the perturbation approach for a better visualization 2 cluster analysis to detect groups 3 confidence regions for the center of the groups to obtain graphical evidence of differences between groups and 4 tests of hypothesis about centers and covariance structures to obtain statistical evidence about differences between groups the fact that only three components are used allows us to illustrate the results using ternary diagrams

middle holocene to present sedimentary environment in the easternmost gulf of finland baltic sea and the birth of the neva river abstract the easternmost gulf of finland is the recipient of the neva river the largest river draining to the baltic sea the depositional history and endozoobenthic activity in the area have not been studied before based long sediment cores although such studies are desirable to provide a paleoenvironmental context for the recent environmental changes and the ecosystem projections for the future baltic sea two replicate long sediment cores from the easternmost gulf of finland record brackish water mud accumulation beginning at 5900 60 calendar years before present cal bp the brackish water muds are characterized by thin beds with erosional bases fining upward grain sizes and increasing upward organic contents a storm induced flow origin is inferred for the thin mud beds contrasting with previous interpretations that these muds accumulate by quiescent suspension settling the bed primary microstructures are overprinted by biodeformation and burrow mottling by incipient small planolites and arenicolites polykladichnus ichnofossils of the continental skolithos ichnofacies left behind by endobenthic oligochaetes and chironomid larvae the depositional succession is cut by a strong erosional hyperpycnal flow event at 3320 40 cal bp caused by the birth of the neva river which is now documented offshore for the first time mineral magnetic properties show pseudosingle domain magnetite as the main magnetic mineral present increased magnetic grain sizes and reduced loi values indicate a strong lithic influx immediately after the neva river birth the dominance of riverborne material in the accumulating sediments ever since highlights the strong influence of reworking in the shallow sea area increased diameters and the deeper penetration of biogenic sedimentary structures demonstrate improved seafloor oxygenation after the river birth during the medieval warm period ca 1000 700 cal bp and the last century increased sedimentary lithic contents and magnetic grain sizes indicate an elevated riverine influx due to increased precipitation and or the increased reworking of sediments by storms the results provide a paleoenvironmental context for the study area and deepen the understanding of storm induced sediment dispersal and the formation of sedimentary fabric in shallow wave dominated sea areas

dynamical consequences of depth dependent thermal expansivity and viscosity on mantle circulations and thermal structure the effects of both depth dependent thermal expansivity and depth dependent viscosity on mantle convection have been examined with two dimensional finite element simulations in aspect ratio ten boxes surface rayleigh numbers between 107 and 6 107 have been considered the effects of depth dependent properties acting singly or in concert are to produce large scale circulations with a few major upwellings the interior of the mantle is cooled by the many cold instabilities which are slowed down and eventually swept about by the large scale circulation the interior temperature of the mantle can be influenced by the trade off between depth dependent properties and internal heating for chondritic abundance of internal heating and depth dependent thermal expansivity the viscosity increase across the mantle can be no greater than a factor of around ten in order to keep the lower mantle adiabatic the thermal contrasts between the cold blobs and the surrounding mantle are strongly reduced by depth dependent properties whereas the lateral differences between the hot upwelling and the ambient lower mantle can be significant over several hundred degrees depth dependent properties also encourage the formation of a stronger mean flow in the upper mantle which may be important for promoting long term polar motions

seismic events under vulcano aeolian islands italy this paper describes the seismic activity of vulcano an active volcano of the aeolian islands group from 1977 to 1980 two main swarms of low energy seismic events are recognizable on the basis of the entire set of data the events localized very near the crater of vulcano where a fumarole field is present have been classified into two classes i very shallow events as far as 1 km in depth andii deeper events as far as 3 km in depth double events and small earthquakes localized on the rim of the old caldera have also been recorded in a little percentage the seismic events of vulcano can be attributed to an intensive fumarolic activity

thermal surveys of the vulcano fossa fumarole field 1994 1999 evidence for fumarole migration and sealing abstract between 1994 and 1999 we carried out five thermal surveys of the vulcano fossa fumarole field each consisted of 485 1213 vent temperature measurements distributed across the field these show that the field has been cooling and expanding where mean and maximum vent temperatures decreased from 216 to180 c and 541 to 428 c respectively between 1994 and 1997 however expansion of the field resulted in increased heat loss from 45 to 67 mw we suggest that cooling and expansion has been caused by increased gas flux and or permeability where increased flow of fluids of magmatic origin during 1996 is implied by chemical and isotopic data capasso g favara r francofonte s inguaggiato s 1999 chemical and isotopic variations in fumarolic discharge and thermal waters at vulcano island aeolian islands italy during 1996 evidence of resumed volcanic activity j volcanol geotherm res 88 1999 167 175 we propose that the size of the conduit has increased causing the fumarole field to expand and vent temperatures to generally decline as gas and heat losses become distributed over a wider area the increase in exhaling area has outweighed the modulating effect of cooling on total heat losses so that heat loss has increased due to an increased input from the magmatic source and or an increase in system permeability within these field wide trends the rim and then the middle zones have been cooling conversely the lower zone showed evidence of warming during 1994 98 before cooling in 1999 throughout the measurement period a se s thermal migration has been apparent and a new hot zone has developed on the field s southern edge we suggest that sealing of fumaroles by complete boiling of marine fluids on the northern edge of the system and higher permeability on the southern edge may have influenced this expansion direction if vent temperatures drop below 100 c then shallow sulfur sealing will quickly diminish fumarole life expectancy and contribute to the abandonment of vents in cooling zones in our model increased gas flux and or permeability e g due to increased magmatic degassing and or fracturing is the primary mechanism driving observed changes in the field temperature size and location deep and shallow conduit sealing are secondary mechanisms influencing the location of new zones once increased gas and heat fluxes have been triggered

seismic signals in geothermal areas of active volcanism a case study from la fossa vulcano italy since the last eruption 1888 1890 volcanism at vulcano aeolian archipelago southern tyrrhenian sea has taken the form of persistent fumarolic activity the gas vapour phases of the geothermal systems are mainly discharged within two restricted areas about 1 km apart from each other in the northern part of the island these areas are la fossa crater and the beach fumaroles of the baia di levante fluids released at the two main fumarolic fields display quite different chemical and temperature characteristics implying different origins the local seismicity essentially takes the form of discrete shocks of shallow origin depth 1 km at la fossa usually with energy 1013ergs they are thought to be related to the uprise of pressurized hot gases and vapours discharged at the crater fumaroles the present investigation points to the existence of two principal categories of seismic events called m shocks and n shocks these are short events normally 10 s m type shocks are thought to be due to resonance vibrations within the interior of the volcano probably driven by the excitation of shock waves within cavities deeply affected by deposition and alteration of self sealant hydrothermal minerals n type events display features that resemble those of volcano tectonic earthquakes but have no recognizable s phases here they are tentatively attributed to microfracturing of rocks which have been extensively hydrothermally altered results of the present study permit a preliminary conceptual model of the local shallow seismic processes in the framework of geochemical modelling of fumarolic activity and geological inferences from geothermal drilling

physical models of fumarolic flow abstract transport of gas from subsurface magma to the atmosphere is modelled as flow through a narrow rough pipe and through a wider conduit filled with spheres representing flow in a porous pipe macroscopic mass momentum and energy balances are written for a control volume representing a short vertical section of the pipe the balances are solved for a perfect gas with the approximate thermodynamic properties of steam losing heat by steady state radial conduction through the pipe walls with boundary conditions of magmatic temperature at the base of the pipe atmospheric pressure at the surface and an ambient geotherm at a specified distance from the conduit results yield the variation of exit temperature with magmatic source depth conduit radius mass flow rate per unit area distance to ambient temperatures vent porosity and porous particle size two ambient geotherms are used 1 a linear gradient from atmospheric to magmatic temperatures and 2 a hydrothermal geotherm based on water saturation temperatures assuming a hydrostatic pressure gradient because individual vents commonly cluster the porous pipe model is considered to be more realistic than the rough pipe model mainly because the conductive cooling approximation is more likely to remain valid exit temperatures fall as conductive losses increase i e as the source depth increases the conduit narrows the mass flow decreases the distance to ambient temperatures reduces or the ambient geotherm cools the porous pipe model is applied to data from two fumarole fields and indicates magmatic source depths of

origin of fumarolic fluids at vulcano italy insights from isotope data and numerical modeling of hydrothermal circulation abstract hydrothermal activity is often associated with active volcanic systems during quiescent times geochemical monitoring of discharged fluids commonly is carried out to gain insights on the state of evolution of the whole volcanic system the interest in geochemical monitoring derives from the observation that compositional variations of discharged fluids are commonly observed as a new eruptive phase is approaching in particular an increase in the gas components of direct magmatic origin may indicate a higher magma degassing rate at depth potentially related to a renewal of explosive activity surveillance programs devoted to hazard mitigation in active volcanic areas generally include periodic analyses of discharged fluids at various locations on the volcanic edifice unfortunately when significant changes are observed in gas composition their correct interpretation in terms of system evolution is not always clear and straightforward several mechanisms may in fact be responsible for differences in the proportion of magmatic gases and shallower fluid components and it is not always possible to recognize the magmatic gas fraction discrimination among fluids of different origin ideally is accomplished based on the isotope composition that each fluid acquires at the time of its generation however this isotope signature can be altered before the fluids reach the surface because of mixing between fluids of different origin or due to reactions that modify the original isotope composition thus the interpretation of isotope data sometimes is quite complex and it can be highly misleading in this work the origin of the steam discharged at the hydrothermal system of vulcano italy was investigated by the means of a dual approach first the available isotope data on the discharged steam were analyzed on the basis of on these and other data a conceptual model of the hydrothermal system was developed and numerical simulations of a multiphase multicomponent flow through a heterogeneous porous medium were carried out to evaluate the effects of various parameters on the system evolution results suggest that the hydrothermal system of vulcano is controlled by the entrance of large quantities of seawater whose original isotope composition has been altered by water rock interaction rock permeability and its distribution at depth were shown to be a primary parameter controlling the overall system evolution the fluid composition and fluid discharge rate at the surface

relocation and focal mechanisms of earthquakes in the south central sector of the aeolian archipelago new structural and volcanological insights abstract to recognize possible spatial clusters and identify active seismogenic zones and structures in the aeolian archipelago in the south of italy we analyzed the spatial pattern of seismicity between 1993 and 2010 in a selected area comprising vulcano lipari salina and filicudi and calculated 22 fault plane solutions fpss for shocks with magnitude greater than 2 7 first we computed a 1 d velocity model for this area including information from recorded earthquakes by a joint hypocenter velocity inversion kissling et al 1994 successively we applied the double difference approach of waldhauser and ellsworth 2000 finding that a certain part of the scattered epicenter locations collapse in roughly linear features relocated seismicity evidenced three main alignments oriented nnw sse and ne sw at different depths that concur well with the known tectonic lineaments and focal mechanisms a detailed discussion is focused on a seismogenetic structure ne sw oriented 3 8 km deep located in the northern area of vulcano island this recognized element could represent a link between magma accumulation zones thus representing a possible preferential pathway along which magma may intrude two earthquake clusters located south west and east of vulcano with their focal mechanisms highlight the aeolian tindari letojanni fault system seismic activity and the existence of a transitional zone going from the n s compressive domain that dominates the aeolian islands to the nw se extensional domain characterizing the south eastern tyrrhenian

vertical ground deformation on vulcano aeolian islands southern italy observations and interpretations 1976 1986 abstract vertical ground deformation studies have continued on vulcano southern italy since 1976 as part of a broader geophysical and geochemical program to monitor activity on the island following a magnitude 5 5 earthquake on 15th april 1978 located a few kilometers south of vulcano the northern part of the island was found to have subsided relative to its southern part two further episodes of displacement the first of inflation and the second of deflation were recorded before september 1981 these displacements have been interpreted using a model that considers the effect of pressure change at the point source located at a depth centered at 6 5 km in the northern part of the island such pressure change according to other geophysical and geochemical data is due to increasing and subsequent decreasing pressure connected with the migration of high temperature fluids through fractures and channels beneath the fossa area opened as a result of the april 15 earthquake subsequent measurements until november 1986 detected only one additional significant movement a small inflation between may 1984 and may 1985 this uplift appears to be related to the shallow seismicity recorded beneath the fossa in this period

isotope composition of rain water well water and fumarole steam on the island of vulcano and their implications for volcanic surveillance abstract water samples from eight wells in the vulcano porto area and fumarole steam from the crater of vulcano southern italy were collected at monthly intervals over a two year period from february 1987 to january 1989 samples of bulk precipitation were also collected in three points at vulcano porto and vulcano piano island of vulcano and castroreale tyrrhenian coast of sicily again at monthly intervals the weighted mean isotopic composition of rain water on vulcano is d 32 and d 18 o 6 4 results for well waters tend to support the existence of at least two water bodies one of purely meteoric water and the other of brackish thermal water an intermediate water body probably the result of mixing of the other two was also recognized the isotope composition of fumarolic steam from the crater suggests the mixed contribution of both sea and rain waters although mixing is not the only process occurring the existence of a deep marine brine body is inferred characterized by d and 18o values more positive than those of mediterranean sea water a close relationship indicating common source effects is shown by temporal isotopic variations at some wells and the fumarolic steam wich may be used for volcano survey at distance from the active crater

mantle stratification and long term polar wander there is accumulating evidence1 2 that the average location of the earth s magnetic pole has moved relative to the deep mantle over the past 200 myr this phenomenon of true polar wander may be caused by the advance and retreat of ice sheets3 or by mass redistribution in the earth s interior due to changes in the pattern of mantle convection4 5 new analyses1 2 6 of polar wander data show a significant shift of the pole in the late cretaceous but this period is thought to have been too warm for glaciation to have occurred thus most of the true polar wander must be due to mass movements in the mantle here we show by analysing the appropriate equations for polar wander that both viscosity and chemical stratification in the mantle are important in determining the rate of polar wander the dynamical effects of chemical stratification and high viscosity 1023 poise in the lower mantle are to decrease polar wander speed to a level consistent with the averaged velocities inferred from palaeomagnetic data whole mantle convection models without non adiabatic density jumps at 670 km depth and with viscosities less than 1023 p would produce wandering rates in excess of 5 per myr

vent temperature trends at the vulcano fossa fumarole field the role of permeability between 1994 and 2010 we completed 16 thermal surveys of vulcano s fossa fumarole field aeolian islands italy in each survey between 400 and 1 200 vent temperatures were collected using a thermal infrared thermometer from distances of 1 m the results show a general decrease in average vent temperature during 1994 2003 with the average for the entire field falling from 220 c in 1994 to 150 c by 2003 however between 2004 and 2010 we witnessed heating with the average increasing to 190 c by 2010 alongside these annual scale field wide trends we record a spatial re organisation of the fumarole field characterised by shut down of vent zones towards the crater floor matched by rejuvenation of zones located towards the crater rim heating may be expected to be associated with deflation because increased amounts of vaporisation will remove volume from the hydrothermal system gambino and guglielmino j geophys res 113 b07402 2008 however over the 2004 2010 heating period no ground deformation was observed instead the number of seismic events increased from a typical rate of 37 events per month during 1994 2000 to 195 events per month during 2004 2010 as part of this increase we noticed a much greater number of high frequency events associated with rock fracturing we thus suggest that the heating event of 2004 2010 was the result of changed permeability conditions rather than change in the heat supply from the deeper magmatic source within this scenario cooling causes shut down of lower sectors and re establishment of pathways located towards the crater rim causing fracturing increased seismicity and heat flow in these regions this is consistent with the zone of rejuvenation which lies towards and at the rim being the most favourable location for fracturing given the stress field of the fossa cone schopa et al j volcanol geotherm res 203 133 145 2011 it is also the most established zone having been active at least since the early twentieth century our data show the value of deploying multi disciplinary geophysical campaigns at degassing fumarolic hydrothermal systems this allows more complete and constrained understanding of the true heat loss dynamics of the system in the case study presented here it allows us to distinguish true heating from apparent heating phases while the former are triggered from the bottom up i e they are driven by increases in heat supply from the magmatic source the latter are triggered from the top down i e by changing permeability conditions in the uppermost portion of the system to allow more efficient heat flow over zones predisposed to fracturing

fluids in early stage hydrothermal alteration of high sulfidation epithermal systems a view from the vulcano active hydrothermal system aeolian island italy abstract high sulfidation hs epithermal systems have elements in common with passively degassing volcanoes associated with high t acid fumarole fields or acid crater lakes they are considered to form in two stages the first of which involves advanced argillic alteration resulting from intense strongly acidic fluid rock interaction the la fossa hydrothermal system vulcano island represents a classic example of such an active hs system and can be considered as a modern analogue of this early stage of alteration resulting in a core of intense silicic 90 95 pure sio2 alteration surrounded by alunitic alteration zones this paper focuses on a geochemical and stable isotope study of the surficial alteration facies of vulcano particularly the horizon characterized by strong silicic alteration and on deep seated xenoliths ejected during the last eruption of la fossa volcano 1888 90 that can be considered as representative of fragments of the deep conduit system of la fossa volcano using directly measured temperatures at the sites of sampling we have calculated fluid composition in isotopic equilibrium with the alteration products the large range of measured silica 18o 12 3 to 29 reflects the wide range of formation temperatures 80 240 c the fluid compositions calculated for intense silicic alteration vary from 0 9 to 6 5 these are significantly heavier than local meteoric water 6 and are consistent with derivation from the condensation of high temperature fumarolic gases dominated by magmatic fluids and rich in acid gases so2 h2s hcl hf into shallow groundwaters of meteoric origin with dynamically variable ratios of fumarolic steam meteoric water the calculated 18o and d of water in equilibrium with alunite also suggest the mixing of magmatic and meteoric waters for the fluids involved in the genesis of advanced argillic alteration facies the calculated 18o of water in equilibrium with hedenbergitic clinopyroxene found in a veinlet in a metasomatized xenolith is 8 9 this value cannot reasonably result from water rock interaction between the host volcanic rocks and surface water instead it most likely represents a fluid brine exsolved from magma which was responsible for high temperature metasomatism in the deep conduit system

multiple phase transitions and the style of mantle convection abstract multiple phase transitions based on experimental and theoretical results have been incorporated into an extended boussinesq model of mantle convection a formulation is used which facilitates the numerical computations of convection with multiple phase transitions and a triple point near the 670 km discontinuity the propensity for layered convection is enhanced by including the additional phase transitions the location of the triple point of the spinel to perovskite phase transitions plays an important role in controlling the fate of the ascending hot plumes a plume with a core temperature above this triple point temperature t c tends to pass easily through the phase boundary at 670 km plumes with a core temperature lower than t c are blocked by the multiple phase transitions both depth dependent thermal expansivity and internal heating increase the tendency of the convective system to layering the dynamical time scales in the transition zone are much shorter than those of the top and bottom boundary layers simulations with increasing rayleigh number ra from 10 6 to 5 10 7 show unambiguously the increased tendency toward layering with larger ra in the early earth when ra was higher and internal heating was several times stronger layered convection might have been the preferred mode of mantle convection with time as both ra and radioactive heating decreased the style of mantle convection would have become less layered

relationships between diffuse co2 emissions and volcanic activity on the island of vulcano aeolian islands italy during the period 1984 1994 measurements of co2 flux from the ground were periodically carried out on the island of vulcano aeolian islands italy between 1984 and 1994 three high flux areas were identified at the foot of the volcanic cone la fossa either inside or very close to the main village effect of the choice of the sampling grid was evaluated a different sampling grid resulted in similar distribution patterns but with different co2 fluxes therefore the absolute estimate of the total flux from the investigated area includes a large degree of uncertainty but repeated measurements with permanent sampling sites are accurate and can detect small changes no correlation of the flux with atmospheric parameters was found at sites with high fluxes some periods characterized by high co2 fluxes were observed and a close correlation was found between the gas emissions from the ground and other geochemical and geophysical parameters such as temperature chemical composition steam and so2 flux from fumaroles seismic energy release and ground deformations the results show that major temporal variations of diffuse co2 flux are related to variations in volcanic activity

using an independent geochronology based on palaeomagnetic secular variation psv and atmospheric pb deposition to date baltic sea sediments and infer 14c reservoir age dating of sediment cores from the baltic sea has proven to be difficult due to uncertainties surrounding the c 14 reservoir age and a scarcity of macrofossils suitable for dating here we present the results of multiple dating methods carried out on cores in the gotland deep area of the baltic sea particular emphasis is placed on the littorina stage 8 ka ago to the present of the baltic sea and possible changes in the c 14 reservoir age of our dated samples three geochronological methods are used firstly palaeomagnetic secular variations psv are reconstructed whereby ages are transferred to psv features through comparison with varved lake sediment based psv records secondly lead pb content and stable isotope analysis are used to identify past peaks in anthropogenic atmospheric pb pollution lastly c 14 determinations were carried out on benthic foraminifera elphidium spec samples from the brackish littorina stage of the baltic sea determinations carried out on smaller samples as low as 4 mu g c employed an experimental state of the art method involving the direct measurement of co2 from samples by a gas ion source without the need for a graphitisation step the first time this method has been performed on foraminifera in an applied study the psv chronology based on the uppermost littorina stage sediments produced ten age constraints between 6 29 and 1 29 cal ka bp and the pb depositional analysis produced two age constraints associated with the medieval pollution peak analysis of psv data shows that adequate directional data can be derived from both the present littorina saline phase muds and baltic ice lake stage varved glacial sediments ferrimagnetic iron sulphides most likely authigenic greigite fe3s4 present in the intermediate ancylus lake freshwater stage sediments acquire a gyroremanent magnetisation during static alternating field af demagnetisation preventing the identification of a primary natural remanent magnetisation for these sediments an inferred marine reservoir age offset delta r is calculated by comparing the foraminifera c 14 determinations to a psv pb age model this delta r is found to trend towards younger values upwards in the core possibly due to a gradual change in hydrographic conditions brought about by a reduction in marine water exchange from the open sea due to continued isostatic rebound c 2012 elsevier ltd all rights reserved

salinity changes in the central baltic sea nw europe over the last 10000 years we attempt a reconstruction of salinity levels of the central baltic sea based on diatom assemblages the isotopic composition of organic matter and sedimentological expression of anoxia over the last 10 000 years we use the data to investigate the dependence of salinity levels on climate evolution and isostasy changes in salinity of surface and deep waters were most pronounced from 8400 to approximately 5000 cal bp density stratification between salty deep and fresher surface waters caused the frequent development of anoxic conditions and deposition of laminated sediments on large parts of the sea floor in the central baltic sea and dramatic changes in organic carbon accumulation rates from 5000 to 3100 cal bp the salinity of the basin decreased oxygenation of deep sea floors was improved and fertility of the sea surface was significantly reduced this is reflected by low accumulation rates of organic carbon in bioturbated sediments since 2800 cal bp salinity rose again and anoxic periods were more common even though the major steps in environmental evolution in the baltic sea coincide with known patterns of climatic change of the north atlantic realm over the last 10 000 years we find no conclusive evidence for synchronous changes or linear responses on submillennial timescales however we note that major variations in our salinity records agree with temporal patterns of reconstructed summer warmth and winter precipitation in southern scandinavia both types of record suggest that climate in the mid holocene was far from stable our data also confirm that climate evolution over the late holocene had significant impact on environmental conditions in the baltic sea

deep co2 release revealed by stable isotope and diffuse degassing surveys at vulcano aeolian islands in 2015 2018 abstract the partitioning of carbon dioxide co2 released by soils at vulcano island aeolian islands italy was performed by combining the co2 flux and the carbon isotope measurements based on this method the amount of co2 of volcanic origin was quantified six times during the period 2015 2018 the data analysis allowed us to establish the correlation between co2 soil degassing and changes in the contribution of volcanic fluids carbon isotope determinations were performed in situ to enhance the coverage of data collection in space and time these data were combined with both the co2 contents in the ground gases and the soil co2 flux the amount of volcanic co2 was distinguished from that of biogenic origin by implementing a three component mixing model the results of this study indicate that the increase in co2 output in september 2018 reflects the increase in volcanic gas emissions the measurement method and analysis presented in this work are sufficiently general to be applicable to the monitoring programs of active volcanoes

variable isostatic uplift patterns during the holocene in southeast sweden based on high resolution ams radiocarbon datings of lake isolations the construction of a new highway between uppsala and mehedeby in northern uppland southeastern sweden has motivated extensive archaeological excavations to describe changes in shoreline configuration over time the isolation of nine lake basins has been interpreted from diatom analysis their isolation ages were determined from 45 ams radiocarbon dates five per site of terrestrial macrofossils mainly betula and alnus seeds the isolation ages and the corresponding altitudes indicate a complicated pattern of isostatic uplift during the late holocene neither the present day isobases nor those for the neolithic sea seem to explain their isolation ages and corresponding altitudes in relation to their geographic distribution since at least some of the lakes are situated in a relatively pronounced topographic landscape we are inclined to explain the observations as the result of small scale irregular uplift earthquakes are rare in the area at present suggesting short term tectonic activities along e

organic and inorganic geochemistry of low temperature gas discharges at the baia di levante beach vulcano island italy abstract discharge from subaereal and submarine gas vents of the baia di levante beach gases from the vulcano island were sampled for major and trace gas components in may and november 1995 chemical compositions and equilibrium calculations suggest three different groups of co 2 rich gas emissions depending on their distance from the la fossa crater 1 gas vents close to the faraglione area are characterised by high h 2 s contents high calculated equilibrium temperatures based on inorganic species and relatively high proportion of alkene compounds 2 gas vents close to vulcanello are characterised by low calculated equilibrium temperatures and low amounts of alkenes and 3 pontile sample has the highest equilibrium co 2 pressure up to 68 bars which may account for the observed absence of benzene the relative large variability of h 2 s in the baia di levante beach gas discharge may be attributed to either different interactions between iron sulphides and weakly acid waters or catalytic effect of elemental sulphur on the de hydrogenation of cyclo hexane thermodynamic calculations suggest that the main inorganic species and ch 4 may have re equilibrated at relatively shallow depth 10 200 m b s l and 30 600 m b s l for a lithostatic and hydrostatic pressure respectively the slow kinetics of reactions in the c n h 2 n c n h 2 n 2 systems with respect to that of ch 4 co co 2 may explain the observed propene propane ratios which can only be reached at reaction temperatures of 300 350 c this low speed of reactions can also explain the observed disequilibrium of c1 c4 alkanes

u series disequilibrium radionuclides in sulphur incrustations from the fumarolic field of vulcano island abstract u series disequilibrium radionuclides 238 u 234 u 210 pb 210 po in sulphur incrustations deposited at la fossa cone vulcano island italy were measured over the period 1990 1995 to collect information about changes in the feeding system of the fumarolic field the 210 po 210 pb and 210 pb pb ratios of the sulphur incrustations allowed the identification of a fumarolic vent which is free from magmatic contribution and remobilized sublimate contamination in spite of the low temperature of the selected fumarole 280 350 c kinetic data show that 210 po is almost fully volatilized due to the relatively high velocity of the gas as a result the 210 po 222 rn activity ratio of the gas can be used to estimate fluid rising times about 100 days 234 u 238 u activity ratios of sulphur incrustations deposited in 1991 1993 showed a shift toward high values typical of nonmagmatic fluids both short lived and long lived u series disequilibrium radionuclides contribute to volcanic forecasting and give information on fluid sources and rising times as well as the residence times of the aquifers involved in the degassing process of the fumarolic field

rotational instabilities of the earth induced by mantle density anomalies from the seismic tomographic models the authors estimate the offset between the geographic pole and the main inertial axis this offset which is large for a static earth is drastically reduced when the dynamical behavior of the mantle is taken into account for a mantle stratification with a viscosity increase by a factor of about 50 this offset is comparable to what can be estimated on the basis of remanent post glacial depression the authors also discuss the rate of polar drift induced by both internal mass heterogeneities and pleistocenic deglaciation contributions from internal sources and ice sheets disintegration are consistent with the observed secular trend for high viscosity contrasts the results are quite insensitive to the phase transition of chemical nature of the upper lower mantle interface this study shows that there is no contradiction between the tomographic models of the earth and their implications for the rotational stability of our planet the findings also agree with recent analyses of paleomagnetic data

helium isotopes and tectonics in southern italy geodynamic evolution of southern italy can be understood within the framework of the mediterranean alpine system subduction of a plate along the sicily calabrian forearc under the tyrrhenian sea has been suggested by many geophysicists although it is not yet confirmed and remains somewhat controversial helium isotope ratios provide useful information on the geotectonic structure of the region the authors report here the sup 3 h sup 4 he ratios of terrestrial gas samples from southern italy the observed sup 3 he sup 4 he ratios are relatively high in the eolian volcanic arc region and low in the other areas dichotomous explanations are presented firstly volcanic arc forearc hypothesis suggests the subduction along the sicily calabrian forearc secondly horizontal transport hypothesis is described based on the relationship between the ratios and radial distance from the recent spreading basin in southern tyrrhenian sea