joint inversions of seismic and geodynamic data for models of three dimensional mantle heterogeneity the seismic models of three dimensional 3 d mantle heterogeneity may be interpreted in terms of the density perturbations which drive mantle flow and thus provide important predictions of flow related observables such as the nonhydrostatic geoid the current models of global scale shear velocity heterogeneity provide reasonably good fits to the long wavelength nonhydrostatic geoid data 60 70 variance reductions but rather poor fits to the corresponding free air gravity anomalies 30 40 variance reductions this major difference is due to two factors 1 the very different amplitude spectrum of the gravity anomalies which is nearly flat for degrees l 3 the largest mismatch between the pattern of predicted and observed gravity anomalies is in the southern hemisphere this observation suggests that one reason for the poor overall match between the two fields may be that the global seismic data are not resolving sufficiently well the heterogeneity in the southern hemisphere portion of the deep mantle in contrast the gravity data provide accurate and geographically uniform constraints on the vertically integrated heterogeneity in the mantle we therefore perform a series of experiments in which we simultaneously invert a large set of seismic data which includes long period waveforms ss s and scs s differential travel times and normal mode structure coefficients and the long wavelength gravity anomaly data we thus determine whether it is possible to derive new 3 d heterogeneity models which satisfy both data sets the gravity anomaly data are interpreted in the context of spherically symmetric viscous flow models of the mantle in these inversion experiments we test several radial viscosity and ln ln profiles and thereby assess their plausibility the joint seismic geodynamic inversions reveal that it is indeed possible to greatly improve the fit to the free air gravity anomalies with variance reductions of 80 90 readily accessible while preserving the fit to the seismic data this improvement is achieved with some adjustment to the heterogeneity in the depth range 1500 2500 km where the seismic data constraints appear to be weakest the joint inversions also reveal new structures in the southern hemisphere portion of the lower mantle which apparently are not resolved by the seismic data alone

geochemical mapping of magmatic gas water rock interactions in the aquifer of mount etna volcano abstract systematic analysis of major and minor elements in groundwaters from springs and wells on the slopes of mt etna in 1995 1998 provides a detailed geochemical mapping of the aquifer of the volcano and of the interactions between magmatic gas water bodies and their host rocks strong spatial correlations between the largest anomalies in pco2 ph and alkalinity k rb mg ca and sr suggest a dominating control by magmatic gas co2 and consequent basalt leaching by acidified waters of the shallow meteoric etnean aquifer most groundwaters displaying this magmatic type interaction discharge within active faulted zones on the s sw and e lower flanks of the volcanic pile but also in a newly recognised area on the northern flank possibly tracking a main n s volcano tectonic structure in the same time the spatial distribution of t c tds na li cl and b allows us to identify the existence of a deeper thermal brine with high salinity high content of b cl and gases co2 h2s ch4 and low k na ratio which is likely hosted in the sedimentary basement this hot brine reaches the surface only at the periphery of the volcano near the village of paterno where it gives rise to mud volcanoes called salinelle di paterno however the contribution of similar brines to shallower groundwaters is also detected in other sectors to the w bronte maletto sw adrano and se acireale suggesting its possible widespread occurrence beneath etna this thermal brine is also closely associated with hydrocarbon fields all around the volcano and its rise generally masked by the high outflow of the shallow aquifer may be driven by the ascent of mixed sedimentary magmatic gases through the main faults cutting the sedimentary basement

high temperature elasticity of iron bearing olivines the first high temperature data on the nine adiabatic elastic moduli for iron bearing olivine are reported these measurements are on two single crystal specimens of natural olivine at ambient pressure and from room temperature to a maximum of 1500 k the two specimens contain 8 and 9 modal percent fayalite which required the oxygen fugacity be controlled at high temperature to preserve their chemical stability the rectangular parallelepiped resonance apparatus was adapted to buffer the specimens from the atmosphere with a mixture of co and co2 gas a small increase 1 2 gpa in the adiabatic bulk modulus of each specimen over that of end member forsterite was found the data are high quality to extreme temperatures with good agreement found when comparing the temperature derivatives of the elastic moduli of the two specimens neither specimen exhibits measurable nonlinear temperature dependence in the computed isotropic bulk and shear moduli which is in contrast to published forsterite data the temperature derivatives of the isotropic bulk modulus ks are 1 69 1 80 10 2 gpa k 1 for the two olivine specimens and the shear modulus g derivatives are 1 38 1 36 10 2 gpa k 1 these derivatives are only slightly larger in magnitude than ks t p 1 56 10 2 and g t p 1 30 10 2 gpa k 1 found previously for iron bearing olivine over a very small temperature range there are also no significant differences between the temperature derivatives found here and the average derivatives of end member forsterite from data retrieved over a slightly larger temperature range several dimensionless parameters have been calculated from these results and are discussed in view of systematics which bear on high pressure phases in earth s transition zone one result from these systematics related to the seismic velocities in the earth and especially the shear wave velocities is that an olivine content of less than 50 is implied at the 400 km discontinuity if earth s upper mantle is isochemical furthermore the substitution of almost 10 iron for magnesium at the forsterite end of the olivine solid solution series has little effect on the dimensionless parameters or on the temperature derivatives of the elastic moduli at high temperature

global anisotropic phase velocity maps for higher mode love and rayleigh waves summary it is well established that the earth s uppermost mantle is anisotropic but there are no clear observations of anisotropy in the deeper parts of the mantle surface waves are well suited to observe anisotropy since they carry information about both radial and azimuthal anisotropy fundamental mode surface waves for commonly used periods up to 200 s are sensitive to structure in the first few hundred kilometres and therefore do not provide information on anisotropy below higher mode surface waves have sensitivities that extend to and beyond the transition zone and should thus give insight about azimuthal anisotropy at greater depths we have measured higher mode love and rayleigh phase velocities using a model space search approach which provides us with consistent relative uncertainties from measurement to measurement and from mode to mode from these phase velocity measurements we constructed global anisotropic phase velocity maps prior to inversion we determine the optimum relative weighting for anisotropy we present global azimuthal phase velocity maps for higher mode rayleigh waves up to the sixth higher mode and love waves up to the fifth higher mode with corresponding average model uncertainties the anisotropy we derive is robust within the uncertainties for all modes given the ray theoretical sensitivity kernels of rayleigh and love wave modes the source of anisotropy is complex but mainly located in the asthenosphere and deeper our models show a good correspondence with other studies for the fundamental mode but we have been able to achieve higher resolution

co2 output and δ13c co2 from mount etna as indicators of degassing of shallow asthenosphere an estimated average co2 output from etna s summit craters in the range of 13 3 mt a has recently been determined from the measured so2 output and measured co2 so2 molar ratios to this amount the co2 output emitted diffusely from the soil 1 mt a and the amount of co2 dissolved in etna s aquifers 0 25 mt a must be added data on the solubility of co2 in etnean magmas at high temperature and pressure allow the volume of magma involved in the release of such an amount of this gas to be estimated this volume of magma 0 7 km3 a is approximately 20 times greater than the volume of magma erupted annually during the period 1971 1995 on the basis of c isotopic data of co2 collected in the etna area and of new hypotheses on the source of mediterranean magmas significant contributions of co2 from non magmatic sources to the total output from etna are unlikely such large outputs of co2 and also of so2 from etna could be due to an anomalously shallow asthenosphere beneath the volcano that allows a continuous escape of gases toward the surface even without migration of magma

thermal and chemical heterogeneity in the mantle a seismic and geodynamic study of continental roots abstract chemical differences in the mantle below continents and oceans are investigated in the context of a recent seismic model of three dimensional mantle structure this analysis of the existence and magnitude of deep continent ocean chemical differences is based on a model of a viscous flowing mantle and it suggests that this continent ocean heterogeneity is internally supported and thus produces little flow this stabilization reduces the vertical flow of mass and heat across the upper mantle and results in a large continent ocean signal in the surface gravity and topography fields the stabilization of continent ocean heterogeneity also provides an explanation for the large amplitude of the nonhydrostatic ellipticity in the earth s geoid

fluids along the north anatolian fault niksar basin north central turkey insight from stable isotopic and geochemical analysis of calcite veins abstract six limestone assemblages along the north anatolian fault naf niksar pull apart basin in northern turkey were analyzed for 18opdb and 13cpdb using bulk isotope ratio mass spectrometry irms matrix vein differences in 18opdb 2 1 to 6 3 and 13cpdb 0 9 to 4 6 suggest a closed fluid system and rock buffering veins in one travertine and two limestone assemblages were further subjected to cathodoluminescence trace element laser ablation inductively coupled plasma mass spectrometry and 18opdb secondary ion mass spectrometry sims analyses fluid inclusions in one limestone sample yield th of 83 8 7 3 c 1 mean average sims 18opdb values across veins show fine scale variations interpreted as evolving thermal conditions during growth and limited rock buffering seen at a higher resolution than irms rare earth element data suggest calcite veins precipitated from seawater whereas the travertine has a hydrothermal source the 18osmow fluid for the mineralizing fluid that reproduces th is 2 in range of cretaceous brines as opposed to negative 18osmow fluid from meteoric groundwater and geothermal sites in the region and highly positive 18osmow fluid expected for mantle derived fluids calcite veins at this location do not record evidence for deeply sourced metamorphic and magmatic fluids an observation that differs from what is reported for the naf elsewhere along strike

novel applications of fluid inclusions and isotope geochemistry in unravelling the genesis of fossil travertine systems the denizli basin is a fault bounded neogene quaternary depression located in the western anatolian extensional province western turkey the basin is a unique geological site with abundant active and fossil quaternary travertine and tufa deposits fluid inclusion microthermometry and isotopic analysis were applied to study the genesis of the ballk fossil travertine deposits located in the south eastern part of the basin microthermometry on fluid inclusions indicates that the main travertine precipitating and cementing fluids are characterized by low salinity 07wt nacl equivalent and variable temperatures that cluster at 50 degrees c and ca 100 degrees c fluids of meteoric origin have been heated by migration to the deeper subsurface possibly in a local high geothermal gradient setting a later uncommon cementation phase is related to a fluid with a significantly higher salinity 255 to 260wt bulk the fluid obtained its salinity by interaction with late triassic evaporite layers strontium isotopes indicate that the parent carbonate source rock of the different travertine precipitates is very likely to be the triassic limestone of the lycian nappes carbon isotopes suggest that the parent co2 gas originated from thermal decarbonation of the lycian limestones with minor contributions of magmatic degassing and organic soil co2 oxygen isotopes confirm the meteoric origin of the fluids and indicate disequilibrium precipitation because of evaporation and degassing results were integrated within the available geological data of the denizli basin in a generalized travertine precipitation model which enhanced the understanding of fossil travertine systems the study highlights the novel application of fluid inclusion research in unravelling the genesis of continental carbonates and provides several recommendations for hydrocarbon exploration in travertine bearing sedimentary basins the findings suggest that travertine bodies and their parent carbonate source rocks have the potential to constitute interesting subsurface hydrocarbon reservoirs

experimental determination of drag coefficient for volcanic materials calibration and application of a model to popocatepetl volcano mexico ballistic projectiles 1 this study shows the results of experiments performed in a subsonic wind tunnel to measure drag coefficients cd for volcanic particles emitted by popocatepetl volcano mexico the results indicate that volcanic projectiles move in a range of reynolds number re values where cd is independent of re drag coefficients of volcanic fragments were found between the values of spheres and cubes with low values in this study initial conditions of the ballistic equations were calibrated with the launching kinetic energy from ballistics expelled by popocatepetl volcano during the eruptive event of december 17 1998 the maximum range of the projectiles calculated with the experimentally measured drag coefficient is in better agreement with the field and observational data reported here than using the values of geometrical bodies as in previous studies our study can be useful for definition of safety zones around volcanoes to protect people and infrastructure adequately

geology and tectonics of the southwestern boundary of the unstable sector of mt etna italy abstract the etna volcano is known to be unstable and gradually moving downslope toward east and south the study of the local geology and structure of these unstable flanks and of their boundaries is important to understand the evolution of the flank instability and the stress field driving the spreading of the edifice in this paper we present the geological evolution of the lower south western sector of mount etna base on a detailed field survey at 1 10 000 scale this area located at the boundary of the unstable south eastern flank of the volcano is affected by the active ragalna fault and by distinctive eruptive fissures monte calvario formation 18 15 ka the monte calvario formation is made of viscous lavas often associated to breccia and autoclastic lava facies fed by a set of eruptive fissures ne sw oriented their emplacement occurred immediately before the ellitico caldera collapse marking a previously poorly constrained shift in the feeding system of the volcano the orientation of these eruptive fissures and lineaments and the geometry of the sedimentary substratum modeled from subsurface data indicate that the area was dominated by a local stress field consistent with the lateral spreading of mount etna since at least from the final ellittico phase about 18 ka with a nearly constant mean displacement rate these data give new insights into the geology and structure of the flank instability at etna the main geologic hazard of the studied area is not related to the opening of a new eruptive fissures but it is posed by the presence into il calvario quarry of fluoro edenite an asbestiform mineral that caused an high mortality rate for respiratory system cancer in biancavilla town in fact the monte calvario formation groups other eruptive fissures with similar volcanological and geochemical characteristics where hydrothermal alteration occurred with the likely formation of health threatening minerals

an upper mantle s wave velocity model for northern europe from love and rayleigh group velocities summary a model of upper mantle s wave velocity and transverse anisotropy beneath northwestern europe is presented based on regional surface wave observations group velocities for both love and rayleigh surface waves are measured on waveform data from international and regional data archives including temporary deployments and then inverted for group velocity maps using a method accounting for fresnel zone sensitivity the group velocity variations are larger than in global reference maps and we are able to resolve unprecedented details we then apply a linear inversion scheme to invert for local 1 d shear wave velocity profiles which are consequently assembled to a 3 d model by choosing conservative regularization parameters in the 2 d inversion we ensure the smoothness of the group velocity maps and hence of the resulting 3 d shear wave speed model to account for the different tectonic regimes in the study region and investigate the sensitivity of the 1 d inversions to inaccuracies in crustal parameters we analyse inversions with different reference models of increasing complexity pure 1 d 3 d crust 1 d mantle and pure 3 d we find that all inverted models are very consistent at depths below 70 km at shallower depths the constraints put by the reference models primarily moho depth which we do not invert for remain the main cause for uncertainty in our inversion the final 3 d model shows large variations in s wave velocity of up to 12 per cent we image an intriguing low velocity anomaly in the depth range 70 150 km that extends from the iceland plume beneath the north atlantic and in a more than 400 km wide channel under southern scandinavia beneath southern norway the negative perturbations are around 10 per cent with respect to ak135 and a shallowing of the anomaly is indicated which could be related to the sustained uplift of southern scandinavia in neogene times furthermore our upper mantle model reveals good alignment to ancient plate boundaries and first order crustal fronts around the triple junction of the baltica avalonia laurentia collision in the north sea

searching for travertines calcretes and speleothems in deep time processes appearances predictions and the impact of plants common models for modern calcite precipitation in and around caves soils springs and streams involve co 2 supplied by thick high p co 2 biogenic soils which were probably thin or non existent before vascular plants indeed plant influenced chemical weathering might have caused accelerated terrestrial carbonate production from the devonian onwards however terrestrial carbonates have also been documented from the archaean proterozoic cambrian ordovician and silurian mechanisms which could have caused non marine carbonates to precipitate without organic rich soils are described and some geological events likely to have influenced non marine carbonate precipitation up to the origin of vascular plants are highlighted as organisms have evolved so have the petrographic characteristics of non marine carbonates some examples of this are also given here

dynamic topography gravity and the role of lateral viscosity variations from inversion of global mantle flow lateral viscosity variations lvvs in the mantle influence geodynamic processes and their surface expressions with the observed long wavelength geoid free air anomaly gravity gradient in three directions and discrete high accuracy residual topography we invert for depth and temperature dependent and tectonically regionalized mantle viscosity with a mantle flow model the inversions suggest that long wavelength gravitational and topographic signals are mainly controlled by the radial viscosity profile the pre cambrian lithosphere viscosity is slightly one order of magnitude higher than that of oceanic and phanerozoic lithosphere plate margins are substantially weaker than plate interiors and viscosity has only a weak apparent dependence on temperature suggesting either a balancing between factors or a smoothing of actual higher amplitude but short wavelength lvvs the predicted large scale lithospheric stress regime compression or extension is consistent with the world stress map thrust or normal faulting both recent compiled high accuracy residual topography and the predicted dynamic topography yield 1 km amplitude long wavelength dynamic topography inconsistent with recent studies suggesting amplitudes of 100 to 500 m such studies use a constant positive admittance transfer function between topography and gravity in contrast to the evidence which shows that the earth has a spatially and wavelength dependent admittance with large negative admittances between 4000 and 10 4 km wavelengths

hydrothermal co2 degassing in seismically active zones during the late quaternary natural co2 discharges are abundant in turkey as evident from ongoing deposition of recent terrace mound travertines and emplacement of significant travertine vein and breccia deposits in fractured damage zones of active fault systems we report high precision u series age data for the vein carbonates combined with important field observations and geochemical data to evaluate the travertine veining and co2 degassing history in seismically active areas field evidence suggests that travertine filled veins and associated breccias represent hydrothermal eruption products which probably formed by hydraulic fracturing in response to overpressure of co2 rich fluids stable isotope and ree data support the field observations and indicate that travertine veins formed as thermogene deposits from rapidly ascending co2 rich fluids travertine veins from the kirsehir geothermal field give u series ages in a range from 10 6 0 3 ka to 86 16 1 24 ka with a majority of ages failing between 10 6 0 3 and 11 3 0 2 ka vein samples from the pamukkale geothermal field yield u series ages between 21 1 0 1 ka and 73 6 0 6 ka two major age groups are evident in pamukkale that cluster coherently around 21 ka and 25 ka a large number of travertine veins we dated by high precision u series technique coincide with times of cold dry climate events this is different from surface sinter deposits in geothermal fields which more frequently form during warm and wet periods we propose that a significant reduction in surface discharge of co2 by spring or geothermal waters during dry climate periods may promote oversaturation of co2 in deep reservoirs host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas and may lead to hydrothermal eruptions crown copyright c 2009 published by elsevier b v all rights reserved

radial profile of mantle viscosity results from the joint inversion of convection and postglacial rebound observables we present new inferences of the radial profile of mantle viscosity that simultaneously fit long wavelength free air gravity harmonics associated with mantle convection and a large set of decay times estimated from the postglacial uplift of sites within previously glaciated regions hudson bay arctic canada and fennoscandia the relative sea level variation at these latter sites is constrained by age height pairs obtained by geological survey rather than the subjective trends which are commonly used in glacial isostatic adjustment gia studies our viscosity inferences are generated using two approaches first we adopt a relative viscosity profile which is known to provide a good fit to the free air gravity harmonics and determine an absolute scaling which yields a best fit to the gia decay time constraints second we perform an iterative nonlinear joint inversion of the two data sets in both cases our inferred profiles are characterized by a significant increase of viscosity 2 orders of magnitude with depth to values of 1022 pa s in the bottom half of the lower mantle the new viscosity profiles are shown to satisfy constraints based on the postglacial uplift of both fennoscandia the classic haskell 1935 number and hudson bay which have commonly been invoked to argue for an isoviscous mantle furthermore the models are used to predict a set of long wavelength signatures of the gia process these include predictions of gia induced variations in 1 the length of day over the late holocene period 2 the earth s precession constant and obliquity over the last 2 6 myr and 3 the present day zonal harmonics of the geopotential jl l 7 the predictions 1 and 3 bound the late holocene and ongoing mass flux between the large polar ice sheets greenland and antarctic and the global oceans to small values 0 4 mm yr equivalent eustatic sea level rise

anisotropic rayleigh wave phase velocity maps of eastern china we explore the variations of rayleigh wave phase velocity beneath eastern china in a broad period range 20 200 s rayleigh wave dispersion curves are measured by the two station technique for a total of 734 interstation paths using vertical component broadband waveforms at 39 seismic stations in eastern china from 466 global earthquakes in addition 599 waveform inversion interstation measurements were added to this data set the interstation dispersion curves are then inverted for high resolution isotropic and azimuthally anisotropic phase velocity maps at periods between 20 and 200 s at shorter periods sampling the crustal depth range phase velocities are higher in the southeastern part of the region reflecting the thinner crust there the jiangnan belt separates cathaysia from the yangtze craton the latter with thicker crust and a deep high velocity cratonic root the eastern part of yangtze craton however east of 115 116 e does not display a deep root and has a thin lithosphere azimuthal anisotropy at long periods 120 s shows fast propagation directions broadly similar to that of the absolute plate motion beneath cathaysia and eastern yangtze craton anisotropy in the asthenosphere is strong and suggests coast perpendicular flow asthenospheric flow from beneath china s thick continental lithosphere toward the thinner lithosphere of the margin and the resulting decompression melting may be the fundamental causes of the intraplate basaltic volcanism along the eastern coast of china

gravity field over northern eurasia and variations in the strength of the upper mantle the correlation of long wavelength gravity anomalies in northern eurasia with seismic velocity anomalies in the upper mantle reverses in sign between western and eastern eurasia the difference between western and eastern eurasia can be explained by the presence of a low viscosity zone in the uppermost mantle beneath eastern eurasia that is absent to the west the location of the lateral change in viscosity corresponds with the geologic boundary between the older shields and platforms of the baltics russia and siberia and the younger geologically active mountain belts of eastern asia this relation provides evidence that differences in the strength of the upper mantle control the locus of intracontinental deformation

automated multimode phase speed measurements for high resolution regional scale tomography application to north america summary a fully automated method for obtaining multimode phase speed measurements from a single seismogram has been developed and applied to a large data set of three component longperiod seismograms in north america constructing high resolution phase speed maps on a continental scale the method of our phase speed estimation is based on a fully non linear waveform inversion by yoshizawa kennett working with a global search method the neighbourhood algorithm the entire process of waveform fitting and the evaluation of the estimated phase speed have been fully automated employing several empirical quantitative measures assessing the quality of waveform fit and the relative contributions of each mode in a chosen time window the measured phase speed data undergo automatic screening for quality control comprising the threshold evaluation of their reliability and outlier detection and removal this new automated method has been applied to a large data set recorded at north american stations including the latest transportable stations of usarray using long period three component seismograms recorded during the past eight years we have successfully retrieved large numbers of regional surface wave paths including over 20000 paths for the fundamental mode rayleigh waves over a wide range of frequencies and over 10000 paths for the higher mode rayleigh as well as the fundamental mode love waves the consistentresultsoftheautomatedmeasurementproceduresuggestthatthemethodworkswell at regional distances allowing us to perform a high resolution mapping of multimode phase speeds in north america the results of the automated waveform analysis also indicate some intrinsic limitations in the higher mode phase speed measurements from a single seismogram particularly in the short period range mainly due to the overlapping of higher mode arrivals as well as coupling between mode branches despite such an innate difficulty in the higher mode dispersion measurements the automated method allows us to construct reliable multimode phase speed maps the current data set of ray paths is significantly biased towards the western half of north america resulting in non uniform horizontal resolution across the continent this issue will be resolved by the future migration of the usarray stations to cover the central and eastern united states the new automated method can be a useful tool for high resolution mapping of regional 3 d shear wave structure including possible anisotropy

u th age evidence from carbonate veins for episodic crustal deformation of central anatolian volcanic province abstract central anatolia represents one of the most outstanding examples of intraplate deformation related to both continental collision and back arc extension generating non uniformly distributed stress fields in this study we provide direct field evidence of various stress directions and investigate carbonate filled fracture systems in the central anatolian volcanic province using u th geochronology and isotope geochemistry for evaluating the episodes of latest volcanic activity under regional stress field data reveal two independent fracture systems in the region successive fracture development has been controlled by two different volcanic eruption centers hasandag composite volcano and acigol caldera trace element and stable c and o and radiogenic sr isotope compositions of carbonate veins indicate different fluid migration pathways for two different fracture systems the u th age data for carbonate veins of two independent fracture systems indicate that the crustal deformation intensified during 7 episodic periods in the last 150 ka the nne trending first fracture system was formed as a result of strain cycles in a period from 149 2 5 through 91 1 5 to 83 2 5 ka bp subsequent deformation events represented by the ene trending second fracture zone have been triggered during the period of 53 3 5 44 0 6 and 34 1 ka bp before the first fracture zone resumed the activity at about 4 7 0 15 ka bp although further studies are needed to evaluate statistical significance of age correlations the periods of carbonate precipitation inferred from u th age distributions in this study are comparable with the previous dating results of surrounding volcanic eruption events

dynamics of strombolian explosions inferences from field and laboratory studies of erupted bombs from stromboli volcano strombolian activity is characterized by repeated low energy explosions and is named after the volcano where such activity has persisted for around 2000 years i e stromboli aeolian islands italy stromboli represents an excellent laboratory where measurements of such explosions can be made from safe but close distances during a field campaign in 2008 two 15 cm diameter bombs were quenched and collected shortly after a normal explosion the bombs were characterized in terms of their textural chemical rheological and geophysical signatures the vesicle and crystal size distribution of the samples coupled with the glass chemistry enabled us to quantify variations in the degassing history and rheology of the magma resident in the shallow i e in last 250 m of conduit length the different textural facies observed in these bombs showed that fresh magma was mingled with batches of partially to completely degassed oxidized high crystallinity high viscosity evolved magma this magma sat at the top of the conduit and played only a passive role in the explosive process the fresh microlite poor vesiculated batch however experienced a response to the explosive event by undergoing rapid decompression integration of geophysical measurements with sample analyses indicates that popular bubble bursting models may not fit this case we suggest that the degassed magma forms a plug or rheological layer at the top of the conduit through which the fresh magma bursts in this model we need to consider the paradox of a slug ascending too fast through a magma of varying viscosity and yield strength

statistical analysis reveals spatial and temporal anomalies of soil co2 efflux on mount etna volcano italy abstract extensive geochemical surveys were carried out on the western flank of mt etna volcano for the determination of soil co 2 effluxes in order to study the relationship between soil gas anomalies faults and volcanic activity the areas of santa maria di licodia sml and w rift wr were selected because of their importance within the volcano tectonic framework of etna two gas surveys were performed in each area in different periods november 2005 and may 2006 in sml september 2007 and june 2008 in wr with 2140 measurements in total in each survey data were log normally distributed and were statistically different from the other surveys therefore their standard normal form was used to compare them log probability plots revealed five populations of data in each survey due to varying degrees of mixing between biogenic and magmatic co 2 and indicated anomalous co 2 effluxes for values 36 g m 2 d 1 magmatic output was 39 2 t d 1 in november 2005 15 8 t d 1 in may 2006 98 4 t d 1 in september 2007 and 234 1 t d 1 in june 2008 natural neighbor interpolation of standardized data produced distribution maps that showed some clustering of anomalous values along directions possibly related to hidden faults compatible with volcanic or regional structural trends analysis of magmatic co 2 emissions in time suggested a possible influence from seasonal variations but comparison with volcanic activity of etna also indicated a volcanic influence accompanying the 2008 2009 flank eruption

bombs behaving badly unexpected trajectories and cooling of volcanic projectiles we collected thermal infrared video of two explosive eruptions at stromboli in june 2008 and manually traced the trajectories of 95 particles launched during two eruptions we found that 10 15 of the analyzed trajectories deviated from predicted curves due to collisions causing one particle to travel horizontally more than twice as far as expected furthermore we observed an oscillatory cooling behavior for the airborne pyroclasts with a median period of 0 46 s measured cooling was typically much faster than model predicted cooling with discrepancies of up to 40 between measured cooling and theoretical modeling we interpret the measured cooling curves as resulting from the spinning and twisting and tearing of particles during travel the periodic re exposing of the hotter core of the pyroclasts to the atmosphere may cause the observed oscillations and the spinning may accelerate cooling by enhancing convective heat transfer current volcanic trajectory and cooling models do not account for projectile collisions spinning or tearing and can thus severely underestimate the maximum landing distance and cooling rates of large pyroclasts

origins of elements building travertine and tufa new perspectives provided by isotopic and geochemical tracers fluid rock interaction represents a major process in the formation of calcitic or aragonitic travertine and tufa catt in most cases catt is associated to limestone dissolution somewhere along the hydrogeological pathway however a wide array of other substratum basalts rhyolites carbonatites ultramafics granites dolomites evaporites can act as potential source of elements involved in the formation of catt this study reports on the evaluation of potential geochemical tracers linking catt to their substratum and unravelling the origin of elements a large database was established from available literature data as well as new data acquired in the frame of this study for a set of modern to recent catt ligurian ophiolites italy the chaine des puys limagne graben and paris basin france reunion island indian ocean jebel oust tunisia four most reliable tracing methods are identified 1 13c and 18o cross plot allows distinguishing epigean min 13c 27 2 max 13c 0 9 mean 13c 12 3 for n 314 from hypogean systems min 13c 4 max 13c 11 7 mean 13c 2 87 for n 198 very low 13c values 4 associated to negative 13c values are specifically indicative of an ultramafic source rock 2 barium and strontium cross plot helps to discriminate different groups of source rocks amongst the hypogean catt i source rocks composed of mixed limestones evaporites and dolomites are characterised by low barium 400 ppm contents ii mafic and granitic source rocks are undifferentiated and display similar barium from 15 to 930 ppm and high strontium 200 ppm contents iii the carbonatite group is characterised by its exceptional high barium and strontium values in epigean catt a pure limestone source rock usually relates to very low barium and strontium contents 50 ppm 3 relatively high beryllium content 30 ppm in catt seems to indicate a pure granitoid source 4 high chromium concentrations 20 ppm are systematically documented in modern catt located on an ultramafic substratum the definition of diagnostic compositional fields for actively forming or recently formed catt is influenced by many factors including water composition water temperature dissolved gas composition and concentration biological activity position in the sedimentary body and early diagenesis in addition to substratum lithology however the results of this study illustrate that despite these many factors the combined use of ba sr be cr 13c and 18o may be valuable to discriminate the rock lithology prevailing in the hydrogeological or palaeo hydrogeological reservoir of catt

the azuaje travertine an example of aragonite deposition in a recent volcanic setting n gran canaria island spain the azuaje travertines in the north of gran canary island crop out in the azuaje gorge which is incised into miocene volcanic breccias of the roque nublo formation this travertine is interesting because of the scarcity of travertines in the canary islands and its close relationship with recent volcanic events part of the travertine overlies a lava flow dated at 2420 40 years bp the travertine is composed mainly of aragonite in both perched systems on the gorge walls and in gorge bottom deposits parallel to the present stream perched systems include deposits from the feeder conduits within the roque nublo formation that spilled out through waterfalls and over barriers the gorge valley bottom system includes barrier and pool deposits the main laminated facies are composed mostly of large fibrous aragonite crystals while there are also common micritic and porous microfabrics shrubs coated grains coated bubbles and rafts are present in many of the deposits detailed study of the microfacies shows the presence of sparsely distributed biogenic features the 13c values are between 4 0 and 11 0 and the 18o values range between 11 0 and 2 0 vpdb these 13c values lie within the range of those of thermogene travertines fed by thermal waters that cooled downstream as indicated by the increase of the carbon and oxygen isotope values in that direction the common occurrence of fibrous radial fabrics is interpreted to be due to disequilibrium conditions during aragonite precipitation disequilibrium was likely caused by rapid co2 degassing of the thermalwaters that led to a rapid increase in the degree of aragonite saturation thus themorphology of the aragonite crystals and the isotopic composition indicate that the formation of the azuaje travertine was mostly due to abiogenic processes induced by rapid degassing of thermalwaters linked to the presence of a recent lava flow within the gorge in short the azuaje travertine shows the important role of volcanic activity in travertine deposition in the facies distribution as well as in the geochemical signatures of the deposits and so can be used as a recent analogue for ancient travertine deposits in volcanic settings

the 15 march 2007 explosive crisis at stromboli volcano italy assessing physical parameters through a multidisciplinary approach basaltic volcanoes are dominated by lava emission and mild explosive activity nevertheless many basaltic systems exhibit from time to time poorly documented and little understood violent explosions a short lived multiblast explosive crisis paroxysmal explosion occurred on 15 march 2007 during an effusive eruptive crisis at stromboli italy the explosive crisis which started at 20 38 14 ut had a total duration of 5 min the combined use of multiparametric data collected by the permanent instrumental networks seismic acoustic and thermal records and a field survey carried out immediately after the event enabled us to constrain the eruptive dynamics and quantify physical parameters the eruption consisted of three major pulses in the first lithic blocks and ash were ejected at speeds of 100 155 m s and 130 210 m s respectively the high solid load of the eruptive jet resulted in the partial collapse of the column with the formation of a small volume pyroclastic density current the second 12 s long pulse emitted 2 2 2 7 107 kg of tephra mass discharge rate 1 9 2 3 106 kg s forming a 3 km high convective plume dispersing tephra up to the west coast and a dilute density current with limited dispersal downslope of the craters a final 30 s long phase formed a scoria flow with a volume of 1 5 1 7 104 m3 mass discharge rate 5 9 6 7 105 kg s a total runout of 200 m and a velocity of 45 m s the total gas volume involved in the explosion was 1 3 1 9 104 m3 with an initial overpressure of 7 9 0 4 mpa we compared the 15 march 2007 event with historical paroxysms in particular with that of 5 april 2003 which was remarkably similar

thermal seismic and infrasonic evidences of variable degassing rates at stromboli volcano abstract during june 1999 we measured the amplitude and rate number of events per second at which gas exited the vent at stromboli volcano as discrete gas bursts or puffs this allowed us to identify two styles of gas burst puffing activity the first is characterized by frequent rapidly rising puffs the second by less frequent slowly rising puffs each style persisted over 5 40 min long durations and was associated with a high and low number of strombolian explosions per hour respectively each period was also associated with characteristic delay times between the arrival of the infrasonic and thermal signals during strombolian explosions the delays were longer during vigorous puffing periods to explain our observations we propose a model in which the degassing process cycles between vigorous and weak degassing phases during vigorous degassing phases bubble layers ascend the conduit at a frequency of 0 5 1 0 s 1 this high degassing level reflects a gas rich magma column and leads to an increased rate in the formation of shallow foams and hence an increase in puffing and explosive activity as well as a higher free surface level and or gas jet velocity during weak phases bubble layers ascend the conduit at a reduced frequency of 0 2 0 3 s 1 during such times the magma column is poor in gas this leads to a decreased rate of foam layer formation and hence a reduction in puffing and explosive activity as well as a lower free surface level and or gas jet velocity variations in puffing activity can thus be used to track changes in the rate at which the shallow system is supplied by fresh gas rich magma our observations indicate that the two degassing styles last from 5 to 40 min and that the switch from one to the other occurs over a matter of minutes

an inversion for radial viscosity structure using seismic tomography using a uniform velocity density scaling we have inverted the seismically inferred 3 dimensional structure of the whole manfie for the radial viscosity structure which best fits the geoid we are able to obtain 60 72 variance reductions for three different s wave tomographic models the resulting viscosity structures are remarkably similar showing a high viscosity lid a low viscosity zone in the transition region and a high viscosity lower manfie a resolution analysis indcates that the viscosity structure in the upper manfie is well resolved by the data however the resolution in the lower manfie is poorer our models axe in general agreement with previous studies except that our inversions prefer a low viscosity layer at 400 670 km as opposed to 100 400 kin

a case history of paroxysmal explosion at stromboli timing and dynamics of the april 5 2003 event abstract on april 5 2003 stromboli volcano italy produced the most violent explosion of the past 50 years the event was exceptionally well documented thanks to the presence on the island of several scientists and a large number of instruments deployed over the preceding months to monitor the effusive eruption that began in december 2002 integration of visual documentation deposit features and geophysical data allowed an accurate reconstruction of the explosive event and its dynamics the eruption consisted of a 8 min long explosive event which evolved through four phases whose timing was precisely recorded by an infrared thermometer located about 450 m from the summit crater phases 2 and 3 lasted 39 and 42 s respectively both had an impulsive character were responsible for ejecting almost the entire mass of the pyroclastic products phases 1 and 4 represented respectively a short lived precursory event and a waning tale during phase 2 meter sized ballistic blocks were launched with velocities of 170 m s to altitudes of up to 1400 m above the craters these fell on the volcano flanks and on the village of ginostra about 2 km distant from the vent a vertical jet rose above the craters which developed to feed a convective plume that reached a height of up to 4 km the calculated mass of the phase 2 fallout deposit and mass discharge rate were 1 1 1 4 108 kg and 2 8 3 6 106 kg s respectively during phase 3 a scoria flow deposit with an estimated volume of 0 9 1 1 104 m3 was erupted from the same vent that fed the ongoing sustained lava flow the average mass discharge rate for this phase was 2 5 3 1 105 kg s products emitted during phases 2 and 3 consisted of lithic and fresh magmatic material in similar proportions the juvenile fraction consisted of a deep originated almost aphyric highly vesicular pumice mingled with a shallow derived crystal rich moderately vesicular scoria similarities with the eruption dynamics of other historical paroxysms at stromboli makes the april 5 2003 explosion representative of these highly energetic events that constitute the most hazardous volcanic phenomena at stromboli volcano

crustal thickness over the nw pacific and its tectonic implications abstract igneous emplacement on the nw pacific oceanic crust via mantle activity such as hot spots and mantle plumes results in perturbations of crustal thickness therefore mapping crustal thickness variations is key for understanding these mantle structures and processes improvements in resolution and accuracy of marine gravity anomalies promote the use of moho gravity inversion effects especially for large scale applications for improving the moho gravity inversion accuracy density variations of the lithospheric mantle are modelled via lithospheric age temperature density relationship since age grid with a resolution of 2 arc minutes is available and density variations of the mantle beneath lithosphere are modelled via seismic wave velocity density relationship since velocity structure with penetration to 700 km is available comparisons between the moho geometries by gravity inversion and seismic interpretation demonstrate that the mantle density modelling improves the moho inversion accuracy our crustal map shows that 1 the crustal thickness of 26 of the nw pacific region is thicker than 7 km 2 the southern end of the emperor seamounts was emplaced on the western flank of the hess rise and a part of the central hawaiian seamounts was emplaced on the eastern end of the mid pacific mountains 3 the magma production of hawaiian seamounts is greater than that of the emperor seamounts 4 the leakiness of the fracture along which the line islands formed decreases in the order of the central southern and northern segments

simultaneous inversion for 3 d variations in shear and bulk velocity in the mantle until recently most of the seismic tomographic modeling has been addressing the question of lateral heterogeneity either in p or s wave velocities the s wave velocity variations are larger and hence provide stronger signal on long period waveforms the direct p travel times being the first arrivals on the other hand are most frequently reported in the international seismological centre isc bulletins in mineral physics experiments the variation in bulk velocity is more often measured to better understand the differences between vp and vp patterns and better link the results from mineral physics to those of seismic tomography we formulate the inverse problem in terms of relative perturbations in the shear velocity vs 12 and bulk sound velocity v k 12 we use a large data set which consists of waveforms waveform derived travel times and travel times from the isc bulletins the earthquakes are relocated using corrections for lateral heterogeneity the events which cannot be reliably determined are discarded the model is defined as spherical harmonics to degree 12 horizontally and as chebyshev polynomials to order 13 radially for both shear and bulk sound velocity the inversion is performed under smoothness constraint the resolution tests and bootstrapping analysis indicate that the model is well recovered particularly at long wavelength the results indicate a much larger variability of shear than bulk sound velocity the model explains observations well the most intriguing result obtained in this study is that the variations in shear velocity and bulk sound velocity are negatively correlated in the lowermost mantle the explanation is not very clear from the mineral physics point of view it is not unlikely that this could be explained in terms of thermal variation even though we are unwilling to rule out the possibility of large wavelength compositional variations

pyroclast tracking velocimetry a particle tracking velocimetry based tool for the study of strombolian explosive eruptions image based techniques enable high resolution observation of the pyroclasts ejected during strombolian explosions and drawing inferences on the dynamics of volcanic activity however data extraction from high resolution videos is time consuming and operator dependent while automatic analysis is often challenging due to the highly variable quality of images collected in the field here we present a new set of algorithms to automatically analyze image sequences of explosive eruptions the pyroclast tracking velocimetry pytv toolbox first a significant preprocessing is used to remove the image background and to detect the pyroclasts then pyroclast tracking is achieved with a new particle tracking velocimetry algorithm featuring an original predictor of velocity based on the optical flow equation finally postprocessing corrects the systematic errors of measurements four high speed videos of strombolian explosions from yasur and stromboli volcanoes representing various observation conditions have been used to test the efficiency of the pytv against manual analysis in all cases 106 pyroclasts have been successfully detected and tracked by pytv with a precision of 1 m s for the velocity and 20 for the size of the pyroclast on each video more than 1000 tracks are several meters long enabling us to study pyroclast properties and trajectories compared to manual tracking 3 to 100 times more pyroclasts are analyzed pytv by providing time constrained information links physical properties and motion of individual pyroclasts it is a powerful tool for the study of explosive volcanic activity as well as an ideal complement for other geological and geophysical volcano observation systems

deep source co2 in natural waters and its role in extensive tufa deposition in the huanglong ravines sichuan china abstract the aqueous geochemistry of huanglong ravine sichuan china where tufa is being deposited extensively is discussed using chemical composition data together with the carbon and oxygen stable isotope ratios the water quality of tufa depositing surface streams in this area is basically controlled by the mixing of two source waters fault bounded spring water and snow and or glacier melt water the spring water contains high concentrations of co 2 supplied via faults the resulting high concentration of dissolved co 2 gives rise to much greater dissolution of carbonate rocks than is usual in karst springs and also to the dissolution of silicate rocks upstream spring waters in the ravine are close to equilibrium with respect to calcite concentrations of dissolved inorganic carbon dic and their 13 c values result from the interaction of about 0 02 mol l 1 co 2 aq of 13 c 3 with carbonate rocks of 13 c 3 under closed system conditions about 70 of the co 2 is estimated to be supplied from the upper mantle the data for all the springs fall in the kaolinite stability field in agreement with observed dissolutional aggressiveness towards na and ca feldspar and that the dissolution rates of these minerals are too slow to move the composition of these waters into the feldspar stability field the dic species in the surface streams are in isotopic equilibrium variations in 13 c dic found at different sites are mainly due to differences in the degree of co 2 degassing from the water there is a linear relationship between 18 o values and the altitude at which samples were collected the oxygen isotope composition of surface stream water in this area is controlled by evaporation water chemistry in daytime and nighttime and daily change of ph in the surface water flowing on the tufa deposition indicate that biological activities contribute to the carbonate precipitation although their extent is not great the daily precipitation rate in this area is estimated to be 4300 kg as caco 3 day 1 over a surface area of 0 9 km 2 i e 0 1 cm year 1

anomalies of temperature and iron in the uppermost mantle inferred from gravity data and tomographic models we propose a method to interpret seismic tomography in terms of thermal and compositional anomalies in addition to the tomographic model we use gravity data which provide information on the density expressed as a relative density to shear wave velocity scaling factor ln ln vs the inferred values of are not consistent with the presence of thermal anomalies alone however simultaneous anomalies of temperature and composition explain the observations compositional anomalies can have several origins but we find the most relevant parameter to be the global volumic fraction of iron xfe fe fe mg we invert the tomographic model s16rlbm woodhouse and trampert 1995 and the density anomalies correlated to vs anomalies 0 vs v0 for anomalies of temperature t and iron fe the partial derivatives are provided by a numerical method that reconstructs density and seismic velocity for given temperatures and petrologic models vacher et al 1998 down to z 300 km depth the distribution of temperature and iron anomalies strongly depends on the surface tectonics the continental mantle below old cratons and stable platforms is colder than average and depleted in iron whereas the oceanic mantle is mostly homogeneous due to uncertainties on the reference state of the mantle error bars on t and fe reach 10 of the inverted values finally we apply these results to the stability of continental roots and test the hypothesis that the negative buoyancy induced by lower than average temperatures is balanced by the positive buoyancy induced by the depletion in iron we find that continental roots are stable only if the viscosity of the mantle is strongly temperature dependent however some uncertainties remain on the real effects and importance of rheology 2002 elsevier science b v all rights reserved

geochemistry of carbon dioxide in six travertine depositing waters of italy abstract the chemical compositions of six travertine depositing hot spring waters in italy are described with emphasis on the carbon dioxide system all springs contained high concentrations of co 2 20 mm l 1 with equilibrium partial pressures well above those which could have been formed in contact with a soil atmosphere after surfacing the co 2 is rapidly lost to the atmosphere with evasion rates close to the springs ranging from 0 45 4 41 mm m 2 s 1 partial pressures of c02 showed an exponential decline with distance which is consistent with the static film model where temperature and turbulence are constant downstream co 2 transfer coefficients which ranged from 66 to 360 cm h 1 were consistent with moderately turbulent flow however there was no correlation between turbulence measured as the mean shear stress and co 2 evasion rate the channels investigated had all been modified by man and most possessed even widths and gradients all waters became increasingly supersaturated with aragonite and calcite downstream and both of these minerals were present in fresh travertine deposits the supersaturation was driven almost exclusively by gas evasion comparison of daytime and nighttime evasion rates demonstrated that photosynthetic activity was an insignificant source of co 2 flux in the reaches investigated carbon dioxide evasion is therefore primarily responsible for the supersaturation and probably also the deposition of travertine at these sites the caco 3 content of the travertines ranged from 91 3 to 96 0 wt with 1 7 4 1 caso 4 traces of organic matter and acid insoluble minerals

upper mantle density modelling for large scale moho gravity inversion case study on the atlantic ocean moho geometry is an important parameter in geodynamic understanding seismic methods can provide accurate burial depths but the coverage is low the widely used crust1 0 model under oceans is greatly restricted by a low coverage of seismic data gravity inversion can provide high coverage of moho undulations but the accuracy is relatively low observed gravity anomalies integrate gravity effects induced by 3 d density perturbations in the earth for studies of the geometry of a specific density interface based on gravity all gravity effects caused by other interfaces should be removed from the total anomaly map based on 3 d density distributions we use temperature based and velocity based methods to model the lithospheric upper mantle density two temperature calculation parameter models psm and gdh1 three thermal expansion coefficients alpha and three scaling ratio models are tested for each method psm and gdh1 result in a similar mantle gravity anomaly mga pattern but different mga average values when the alpha model is the same different alpha and scaling ratio models result in different moho inversion results and the optimal result from the temperature based method has an rms of 3 2 km with the crust1 0 model a comparison between this inversion result and the crust1 0 model shows that the temperature based method performs well in reproducing moho geometry in the main part of the atlantic ocean especially in the central basin the optimal result from the velocity based method has an rms of 4 3 km with the crust1 0 model compared with the temperature based method the velocity based method performs worse in the central basin but better in regions with low velocity and low density mantle away from the mid ocean ridge

hydrothermal activity and its paleoecological implications in the latest miocene to middle pleistocene lacustrine environments of the baza basin betic cordillera se spain the continental sedimentary record of the baza basin guadix baza depression betic cordillera se spain shows six sedimentary units of lacustrine origin deposited from the latest miocene to the middle pleistocene depending on the interval considered the lacustrine deposits are mainly composed of marls carbonates or gypsiferous evaporites showing lithological mineralogical and geochemical features i e magnesium strontium and sulfur contents celestine deposits and travertine growths that are evidence of intense tectonically induced hydrothermal activity according to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays the supply of hot waters was greater during the zanclean the gelasian and the calabrian as a result of tectonic activity hydrothermal activity has continued until the present time and is responsible of the hot springs that are nowadays active in the guadix baza depression the paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table not subject to periodic desiccations in the dry season and warmer temperatures throughout the year this resulted in a high level of organic productivity especially for the calabrian which allowed the development of a rich and well diversified mammalian community similar to those of modern african savannas with tree patches in this mild environment the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo hippopotamus antiquus the high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings

the relative density to shear velocity scaling in the uppermost mantle we perform inversions of gravity data geopotential model egm96 and seismic tomography model s16rlbm for the scaling factor which relates relative density anomalies to relative s wave velocity anomalies the gravity data and tomographic model are anti correlated below continents down to a depth of z 200 km this anti correlation is not present below oceans except for smoothness which is controlled by a damping factor no a priori information is added to the inversion data are filtered between degrees 11 and 16 of the spherical harmonic expansion this spectral window is well suited for the study of intermediate size 2000 4000 km anomalies in the uppermost mantle calculations are made separately for sub continental and sub oceanic mantle the sub continental and sub oceanic scaling factors are significantly different at depths shallower than 260 km in both cases the magnitude of is around 0 05 the sub continental scaling factor has a positive root down to z 220 km whereas the sub oceanic scaling factor yields positive values down to z 140 km only at depth shallower than 350 km models of do not depend on the damping factor or the viscosity model at depths greater than 350 km the resolution of z decreases significantly and low degrees 2 4 add information from large scale anomalies and from the lower mantle as a result the shape and values of for 2 16 and 11 16 are significantly different at depths greater than 350 km a possible explanation of the discrepancies between the sub continental and sub oceanic scaling factor is that intermediate scale anomalies are more important in the continental uppermost mantle than in the oceanic uppermost mantle 2001 elsevier science b v all rights reserved

probability of radial anisotropy in the deep mantle article i nfo it is well established that the earth s uppermost mantle is anisotropic but observations of anisotropy in the deeper mantle have been more ambiguous radial anisotropy the discrepancy between love and rayleigh waves was included in the top 220 km of prem but there is no consensus whether anisotropy is present below that depth fundamental mode surface waves for commonly used periods up to 200 s are sensitive to structure in the first few hundred kilometers and therefore do not provide information on anisotropy below higher mode surface waves however have sensitivities that extend to and below the transition zone and should thus give insight about anisotropy at greater depths but they are very difficult to measure we previously developed a new technique to measure higher mode surface wave phase velocities with consistent uncertainties these data are used here to construct probability density functions of a radially anisotropic earth model down to approximately 1500 km in the uppermost mantle we obtain a high probability of faster horizontally polarized shear wave speed likely to be related to plate motion in the asthenosphere and transition zone however we find a high probability of faster vertically polarized shear wave speed to a depth of 1500 km in the lower mantle we see no significant shear wave anisotropy this is consistent with results from laboratory measurements which show that lower mantle minerals are anisotropic but lpo is unlikely to develop in the pressure temperature conditions present in the mid mantle 2008 elsevier b v all rights reserved

rapid low cost photogrammetry to monitor volcanic eruptions an example from mount st helens washington usa we describe a low cost application of digital photogrammetry using commercially available photogrammetric software and oblique photographs taken with an off the shelf digital camera to create sequential digital elevation models dems of a lava dome that grew during the 2004 2008 eruption of mount st helens msh volcano renewed activity at msh provided an opportunity to devise and test this method because it could be validated against other observations of this well monitored volcano the datasets consist of oblique aerial photographs snapshots taken from a helicopter using a digital single lens reflex camera twelve sets of overlapping digital images of the dome taken during 2004 2007 were used to produce dems and to calculate lava dome volumes and extrusion rates analyses of the digital images were carried out using photogrammetric software to produce three dimensional coordinates of points identified in multiple photos the evolving morphology of the dome was modeled by comparing successive dems results were validated by comparison to volume measurements derived from traditional vertical photogrammetric surveys by the us geological survey cascades volcano observatory our technique was significantly less expensive and required less time than traditional vertical photogrammetric techniques yet it consistently yielded volume estimates within 5 of the traditional method this technique provides an inexpensive rapid assessment tool for tracking lava dome growth or other topographic changes at restless volcanoes

global love wave overtone measurements 1 love wave phase velocities for fundamental and higher modes are difficult to measure because the different modes cannot easily be separated following yoshizawa and kennett 2002 we generate suites of path specific onedimensional shear wave velocity profiles using the neighbourhood algorithm of sambridge 1999a from this family of o 10 4 models both fundamental and higher mode phase velocities with mutually consistent uncertainties are calculated we have fully automated the method and analysed over forty thousand love wave seismograms from the gdsn and geoscope global networks from 1994 2004 our phase velocity measurements agree remarkably well with previous studies but we have been able to enlarge the available dataset dramatically we present global love wave phase velocity maps up to the fifth overtone with unprecedented resolution due to the improved path coverage comparing these maps to existing tomographic models we discern evidence of significant anisotropy inthe lower mantlearound a depth of 1000 km in the pacific citation visser k s lebedev j trampert and b l n kennett 2007 global love wave overtone measurements geophys res lett 34 l03302

controlling processes in a caco3 precipitating stream in huanglong natural scenic district sichuan china abstract huanglong scenic district is well known for its unusual and diversified landforms such as travertine pools travertine falls and travertine flows these landforms resulting from high altitude surface cold water caco 3 precipitation were chosen by unesco in 1994 as an entry in the world s nature heritage huanglong is a pristine region where there are limited human activities water analyses and thin section glass slide precipitation experiments were conducted to determine the aqueous processes controlling caco 3 precipitation and travertine landform formation results from the travertine flow indicate that the concentrations of hco 3 ca 2 and h decrease regularly along the flow paths chemical equilibrium modeling results demonstrate the importance of co 2 out gassing and caco 3 precipitation processes co 2 out gassing and caco 3 precipitation increase with increasing flow velocities in the pool area varying hydrodynamics are the primary factors which determine the extent of processes such as advection and diffusion and hence also control caco 3 precipitation and co 2 out gassing when the pool water circulation is very slow the ph of water flowing over the travertine dams increases significantly approximately 0 15 ph units downstream when the circulation is relatively fast the ph of stream water initially decreases followed by an increase of approximately 0 21 ph units as it flows past the travertine pool dams in both cases the ph rise is caused by sudden changes in the hydrodynamics of the pools despite the different initial flow conditions pool development is a consequence of spatial variations in ph which provide different conditions for caco 3 precipitation inside the travertine dam where less precipitation or even dissolution occurs compared to conditions at the top and downstream side of the dams precipitation experiments demonstrate that the top and downstream side of travertine dams are the locations of the most active precipitation particularly for pools having faster circulation precipitation experiments also reveal that vaterite a rare polymorph of caco 3 co precipitates with calcite in milky opalescent water near the upstream input portion of the pool groups thin sections covered by algae at the bottom of pools have 40 less caco 3 precipitation than those not covered by algae sem photographs of the surface of natural travertine deposits show that biofilms with diatom minimize caco 3 precipitation and that diatom adhered calcite surfaces show signs of etching suggesting that calcite dissolution may be aided by diatoms

mantle viscosity and ice age ice sheet topography ice age paleotopography and mantle viscosity can both be inferred from observations of earth s response to the most recent deglaciation event of the current ice age this procedure requires iterative application of a theoretical model of the global process of glacial isostatic adjustment results demonstrate that the iterative inversion procedure converges to a paleotopography that is extremely close to that from the ice 4g model the accompanying mantle viscosity profile is furthermore shown to reconcile the requirements of aspherical geoid anomalies related to the mantle convection process thus resolving a fundamental issue concerning mantle rheology the combined model also explains postglacial sea level histories for the east coast of the united states

linking variable explosion style and magma textures during 2002 at stromboli volcano italy microtextural characteristics of fresh ejecta from stromboli volcano were examined from three periods of differing eruption style and intensity in 2002 activity shifted from relatively weak and infrequent ash charged explosions during january through may into two broad cycles of waxing activity in june through late september and late september through december followed by the onset on 28 december of the 2002 2003 effusive eruption analyzed sets of lapilli from may september october and 28 december show contrasts in the physical properties of magma resident in the shallow conduit during this range of activity three distinct textures are observed among the analyzed pyroclasts low density ld with an abundance of subspherical bubbles the presence of large irregularly shaped bubbles and a light to transparent glass matrix transitional texture tt with an intermediate number of subspherical bubbles a high frequency of large irregularly shaped bubbles and a honey colored glass matrix and high density hd with sparse relatively small bubbles conspicuous large irregular bubbles and a dark glass matrix observational and quantitative data density vesicle size indicate that these textures are linked through variable residence time in stromboli s shallow conduit with an ongoing evolution from ld to hd magma calculations suggest that residual ld magma will evolve to hd texture in a period of hours to days contrasting amounts of the ld tt and hd magmas are present in each sample with the most tt in may the most ld in september october and the most hd in december this implies that the shallow magma had a different rheology at each collection period the viscosity of ld and hd magmas are calculated to be in the range of 2 000 to 2 600 and 3 000 to 5 000 pa s respectively which with their changing proportions must have implications for rates of bubble slug ascent and processes of fragmentation this study suggests that an increasing maturity of magma in stromboli s shallow conduit with resultant increase in viscosity feeds back to reduce the intensity of explosions whereas a steady flux of ld magma favors more powerful explosions

oceanic residual topography agrees with mantle flow predictions at long wavelengths dynamic topography the surface deflection induced by sublithosheric mantle flow is an important prediction made by geodynamic models but there is an apparent disparity between geodynamic model predictions and estimates of residual topography total topography minus lithospheric and crustal contributions we generate synthetic global topography fields with different power spectral slopes and spatial patterns to investigate how well the long wavelength spherical degrees 1 to 3 components can be recovered from a discrete set of samples where residual topography has been recently estimated an analysis of synthetic topography along with observed geoid and gravity anomalies demonstrates the reliability of signal recovery appropriate damping factors which depend on the maximum degree in the spherical harmonic expansion that is used to fit the samples must be applied to recover the long wavelength topography correctly large damping factors smooth the model excessively and suppress residual topography amplitude and power spectra unrealistically recovered long wavelength residual topographies based on recent oceanic point wise estimates with different spherical expansion degrees agree with each other and with the predicted dynamic topography from mantle flow models the peak amplitude of the long wavelength residual topography from oceanic observations is about 1 km suggesting an important influence of large scale deep mantle flow

characterisation of the 1997 vulcanian explosions of soufriere hills volcano montserrat by video analysis the activity of convention at montserrat soufriere hills volcano montserrat during the period 1995 1999 included numerous violent explosions two major cycles of vulcanian explosions occurred in 1997 a first of 13 explosions between 4 and 12 august and a second of 75 between 22 september and 21 october the explosions were short lived events lasting a few tens of seconds during which partial fountain collapse generated pyroclastic surges and pyroclastic flows and buoyant plumes ascended 3 15 km into the atmosphere each explosion discharged on average 3 105 m3 dense rock equivalent dre of magma draining the conduit to depths of 1 2 km the paper focuses on the first few seconds of three explosions of the 75 that occurred in september october 1997 6 october 1997 at 17 50 7 october 1997 at 16 02 and 9 october 1997 at 12 32 physical parameters such as exit velocities magmatic water contents and magma pressures at fragmentation are estimated by following and modelling the ascent of individual momentum dominated finger jets visible on videos during the initial stages of each explosion the model treats each finger jet as an incompressible flow sustained by a steady flux of gas and particles during the few seconds of ascent and produces results that compare favourably with those using a multiphase compressible code run using similar eruptive parameters each explosion reveals a progressive increase in eruptive intensity with time jet exit velocities increasing from 40 m s 1 at the beginning of the explosion up to 140 m s 1 after a few seconds modelling suggests that the first magma to exit was largely degassed whereas that discharged after a few seconds contained up to 2 wt water magma overpressures up to 10 mpa are estimated to have existed in the conduit immediately prior to each explosion progressive increases in jet exit velocity with time over the first few seconds of each explosion provide direct evidence for strong pre eruptive gradients in water content and magma pressure in the upper reaches probably 100 500 m of the conduit fountain collapse occurred during the first 10 20 s of each explosion because the discharging jets had bulk densities up to 100 times that of the atmosphere and were unable to entrain enough air to become buoyant such high eruptive densities were due to the presence of partially degassed magma in the conduit

maximum horizontal range of volcanic ballistic projectiles ejected during explosive eruptions at santorini caldera abstract this study investigates the hazard posed by volcanic ballistic projectiles vbps to the santorini islands considering eruption scenarios that include low vei 2 3 and higher energy vei 3 eruptions a model that describes rapid decompression of pressurized magma below a caprock along with its fragmentation and acceleration of particles is utilized for estimating initial velocities during vulcanian style eruptions these initial velocities are inserted into the ballistic equations assuming that vbps have a cube like shape are subjected to gravity drag forces and are launched into a zone of reduced drag four different diameters of vbps are considered 0 35 m 1 0 m 2 0 m 3 0 m and also different values of gas fractions and extent of the reduced drag zone are investigated the results of these calculations show that an area of 1 2 km width along the western coast of thera will be within the maximum range of vbps provided that the eruptive vent will develop either on nea kameni or between nea kameni and thera initial velocities for higher energy eruptions are estimated by considering the conversion efficiency of thermal to kinetic energy for the case of an eruption with vei 4 and a number of vents centered between nea and palea kameni calculations show that the coastal areas of thera and therasia are within the maximum horizontal range of vbps with diameter larger than 0 35 m as the exact position of the eruptive vent seems to be of crucial importance for determining the areas at risk continuous seismic and geodetic monitoring of the caldera is needed in order to decipher its likely location

geochemistry and mineralogy of travertine deposits of the sw flank of mt etna italy relationships with past volcanic and degassing activity abstract travertine deposits outcropping in the lower sw flank of mt etna were studied for their mapping as well as for their chemical mineralogical and isotopic compositions these deposits are dated to about 24 to 5 ka in the adrano area located at the western limit of the study area in this area travertines show high mg contents and are composed mostly of dolomite thus apparently ruling out any primary deposition in favour of a diagenetic origin travertines outcropping near paterno in the east part of the study area should be younger than 18 ka those located to the ssw of paterno paterno diga show high sr contents and aragonite as dominant mineralogical phase thus suggesting primary deposition those located to the w of paterno paterno simeto stazione are instead poor both in mg and in sr and show calcite as dominant phase carbon isotope composition of travertines indicates a magmatic origin of co2 that formed them based on the estimated volume of travertines between 10 and 20 gg a of co2 were involved in their formation the time span of travertine formation coincided with the eruptive cycles of ellittico and the first part of mongibello which were probably characterised by a greater amount of co2 transported through groundwater circulation widespread travertine deposition probably ceased after the opening of the valle del bove depression that modified the volcanologic and hydrologic conditions in the summit crater area

anatomy of a strombolian eruption inferences from particle data recorded with thermal video over the past decade a proliferation of new technologies has pushed forward our ability to measure the dynamics of volcanic emissions as they exit and ascend above the vent measuring parameters of all particles as they exit the vent during an explosive eruption is the best way to gather parameters such as size shape velocity and mass for the solid particulate fraction of the plume in our case this being the lapilli and bomb component we compute particle velocities and size distributions using high spatial resolution centimeter sized pixel thermal infrared imagery collected at 200 hz for small explosive eruptions at stromboli italy our study covers 13 eruptions from stromboli s southwest crater that occured in october 2012 plus 13 eruptions from the southwest crater and 5 eruptions from the northeast crater in may 2014 we obtain a statistically robust database for size mass and velocity of 83 000 particles most particles have sizes of 5 to 15 cm so that the majority of individual particle masses are below 0 4 kg however 4950 6 of the particles are heavier than 5 kg and represent 59 of the total mass erupted we also show that the smallest particles detected have the highest velocities with the maximum recorded vent leaving velocity being 240 m s while the thermal data provide insights into particle emission and launch dynamics correlation with seismic data sheds light on the source mechanism our results lead us to suggest that pyroclast dominated explosions are a consequence of the presence of a viscous degassed cap at the head of the magma column whereas gas dominated events are a consequence of slug bursting in a cleaner conduit the cap having been lost by convective overturn

s wave velocity structure below central mexico using high resolution surface wave tomography shear wave velocity of the crust below central mexico is estimated using surface wave dispersion measurements from regional earthquakes recorded on a dense 500 km long linear seismic network vertical components of regional records from 90 well located earthquakes were used to compute rayleigh wave group velocity dispersion curves a tomographic inversion with high resolution in a zone close to the array obtained for periods between 5 and 50 s reveals significant differences relative to a reference model especially at larger periods 30 s a 2 d s wave velocity model is obtained from the inversion of local dispersion curves that were reconstructed from the tomographic solutions the results show large differences especially in the lower crust among back arc volcanic arc and fore arc regions they also show a well resolved low velocity zone just below the active part of the trans mexican volcanic belt tmvb suggesting the presence of a mantle wedge low densities in the back arc inferred from the low shear wave velocities can provide isostatic support for the tmvb

considerations on ejection velocity estimations from infrared radiometer data a case study at stromboli volcano abstract synchronous recordings of normal strombolian explosions with a thermal camera and infrared radiometers provide a unique opportunity to understand signals from less expensive radiometers using records from stromboli volcano we analyze in particular the limitations of using signals from infrared radiometers alone to quantify the plume ascent kinetics we conclude that infrared radiometers pointing close to the vent either single or coupled are often insufficient for velocity retrieval due to the complex structure and dynamics of the plumes and their evolution with time in addition to practical implementation difficulties in the field this is mainly due to the rapid succession and overlapping of thermal components in the radiometer s field of view optimized geometries of radiometer fields of view and new retrieval methodologies are proposed to improve velocity estimates from one or coupled radiometers

geochemistry of quaternary travertines in the region north of rome italy structural hydrologic and paleoclimatic implications in the tyrrhenian region of central italy late quaternary fossil travertines are widespread along two major regional structures the tiber valley and the ancona anzio line the origin and transport of spring waters from which travertines precipitate are elucidated by chemical and isotopic studies of the travertines and associated thermal springs and gas vents there are consistent differences in the geochemical and isotopic signatures of thermal spring waters gas vents and present and fossil travertines between east and west of the tiber valley west of the tiber valley 13c of co2 discharged from gas vents and 13c of fossil travertines are higher than those to the east to the west the travertines have higher strontium contents and gases emitted from vents have higher 3he 4he ratios and lower n2 contents than to the east fossil travertines to the west have characteristics typical of thermogene thermal spring origin whereas those to the east have meteogene low temperature characteristics including abundant plant casts and organic impurities the regional geochemical differences in travertines and fluid compositions across the tiber valley are interpreted with a model of regional fluid flow the regional mesozoic limestone aquifer is recharged in the main axis of the apennine chain and the groundwater flows westward and is discharged at springs the travertine precipitating waters east of the tiber valley have shallower flow paths than those to the west because of the comparatively short fluid flow paths and low normal heat flow the groundwaters to the east of the tiber valley are cold and have co2 isotopic signatures indicating a significant biogenic contribution acquired from soils in the recharge area and limited deeply derived co2 in contrast spring waters west of the tiber valley have been conductively heated during transit in these high heat flow areas and have incorporated a comparatively large quantity of co2 derived from decarbonation of limestone the elevated strontium content of the thermal spring water west of the tiber valley is attributed to deep circulation and dissolution of a triassic evaporite unit that is stratigraphically beneath the mesozoic limestone u series age dates of fossil travertines indicate three main periods of travertine formation ka 220 240 120 140 and 60 70 based on the regional flow model correlating travertine deposition at thermal springs and precipitation in the recharge area we suggest that pluvial activity was enhanced during these periods our study suggests that travertines preserve a valuable record of paleofluid composition and paleoprecipitation and are thus useful for reconstructing paleohydrology and paleoclimate

types and mechanisms of strombolian explosions characterization of a gas dominated explosion at stromboli textural and chemical analyses of bombs quenched directly from a normal explosion at stromboli volcano italy were integrated with coincident seismic acoustic and thermal data the data set defines a new gas dominated type of strombolian eruption named type 0 these events are characterized by high velocity emission 150 250 m s 1 of a few relatively small juvenile particles with entrained non juvenile clasts that previously fell back into the vent to be re erupted for the studied event the explosion depth was more than 250 m deep and the particles showed little residence time in the shallow system slug ascent velocities over the final 20 35 m of magma filled conduit and the low viscosity of the resident magma are all consistent with simple bubble burst in a clean conduit this conduit type and eruption style likely fit popular slug ascent and burst models used to explain strombolian eruptions in contrast the ballistic dominated type of explosions type 1 are associated with larger proportions of stagnant material in the shallow system magma mix we argue that the additional volume of this stagnant material pushes the free surface upward because of the larger volume of material available for entrainment into a type 1 slug burst which has to fragment through a thick cap of degassed material type 1 events tend to be rich in particles in contrast the less spectacular gas rich type 0 events have little material to entrain thus being poor in lapilli and bombs

deep structure and mechanical behavior of the lithosphere in the hangai hovsgol region mongolia new constraints from gravity modeling we investigate the deep structure and mechanical behavior of the lithosphere beneath the hangai ho vsgo l region central mongolia asia in order to explain the origin and support of large scale doming in this deforming area we propose a gravity and topography based model which accounts for constraints provided by other independent results from xenolith and tomography studies deviations of the measured gravity from the theoretical airy compensation model are examined a long wavelength low gravity anomaly is spatially correlated with low pressure and shear velocity anomalies in the mantle and with the extent of cenozoic volcanic outcrops we interpret it as a deep seated low density asthenosphere and model its effect on the bouguer gravity signal using a 600 km wide light asthenospheric body density reduction 310 kg m 33 located between 100 and 200 km north and south of the hangai ho vsgo l dome short wavelength highs and lows in the bouguer gravity field are clearly correlated with fault activity they seem to reflect opposite senses of flexure of a rigid lithosphere across two major active faults the sayan and bogd transpressional systems and are modeled by moho deflections of 10 and 5 km respectively finally a shortwavelength 200 km high amplitude 350 mgal gravity residual remains beneath the highest part of the mountain bulge namely the hangai dome based on previously published xenolith analyses we interpret it as an anomalous low density body which may represent underplated cumulates or mafic granulites at the uppermost mantle we conclude that upper mantle dynamics necessarily play an important role in the origin and evolution of the hangai ho vsgo l dome but without requiring significant thinning of the lithosphere fl 2002 elsevier science b v all rights reserved

pressure changes associated with the ascent and bursting of gas slugs in liquid filled vertical and inclined conduits at basaltic volcanoes the sources of long period and very long period seismicity and acoustic signals are frequently described in terms of fluid dynamic processes in particular the formation and ascent of gas slugs within the magma column and their bursting at the surface to investigate pressure changes associated with these processes two phase flow experiments have been carried out in vertical and inclined pipes with both single gas slugs and a continuously supplied gas phase the ascent of individual gas slugs is accompanied by strong dynamic pressure variations resulting from the flow of liquid around the slug these dynamic transients generate sub static pressures below the ascending slug in viscosity controlled systems and produce super static pressures when the slug reaches the surface and motion ceases in inertia dominated systems conduit inclination promotes a change of regime from bubbly to slug flow and favours an increase in size and velocity of the slugs at the expense of their frequency of occurrence during continuously supplied two phase flow the experimental pressure data support previous theoretical analyses of oscillatory sources in ascending slugs as the slugs approach the surface and burst pressure oscillations are also observed during the release of gas slugs and in their wake region

inferring radial models of mantle viscosity from gravity grace data and an evolutionary algorithm convective flow in the mantle can be thought of and modeled as exclusively driven by density heterogeneities in the mantle itself and the resulting lateral variations in the earth s gravity field with this assumption and a model of mantle rheology a theoretical relationship can be found between 3d mantle structure and flow related quantities that can be measured on the earth s surface like free air gravity anomalies this relationship can be used to set up an inverse problem with 1d mantle viscosity as a solution in the assumption that seismic velocity anomalies be of purely thermal origin and related to density anomalies by a simple scaling factor we invert the large scale length component of the above mentioned measurements jointly with seismic observations waveforms and or travel times to derive an accurate 5 layer spherically symmetric model of upper and lower mantle viscosity we attempt to account for non uniqueness in the inverse problem by exploring the solution space formed of all possible radial profiles of earth viscosity by means of a non deterministic global optimization method the evolutionary algorithm ea for each sampled point of the solution space a forward calculation is conducted to determine a map of gravity anomalies whose similarity to grace gravity recovery and climate experiment is then measured the procedure is iterated to convergence according to ea criteria the robustness of the inversion is tested by means of synthetic tests indicating that our gravity data set is able to constrain less than 6 radial layers each with uniform viscosity independently of the tomographic model or the scaling factor adopted to convert seismic velocity into density structure the ea optimization method finds viscosity profiles characterized by low viscosity in a depth range corresponding to the transition zone and relatively uniform elsewhere

evaluating the geogenic co2 flux from geothermal areas by analysing quaternary travertine masses new data from western central italy and review of previous co2 flux data abstract quantification of carbon fluxes between solid earth and its atmosphere is necessary to understand the global geological carbon cycle some of the main co2 contributors are metamorphism and magmatic mantle degassing co2 is discharged from active and quiescent volcanoes fault zones geothermal systems and co2 rich groundwater here a new method for the estimation of the geogenic flux of co2 from tectonically active regions based on the volume composition and age of travertine deposits is proposed the method is applied to the travertine deposits of western central italy where travertine deposition is driven by degassing of co2 charged groundwater results show that the study areas are characterized since middle pleistocene by diffuse co2 degassing processes with time averaged co2 fluxes ranging between 1 24 0 12 106 mol y 1 km 2 and 1 38 0 42 106 mol y 1 km 2 these values are of the same order of magnitude of carbon dioxide fluxes measured by different methods in western central italy and are higher than the global baseline co2 flux from high heat flow regions the review of the available 234u 230th and 14c data shows that the co2 degassing processes that affects western central italy nowadays were already active at least 350 ka ago proving that this region is a globally relevant case for the study of earth degassing considering the widespread occurrence of travertine deposits in tectonically active areas worldwide the proposed approach can be used as a reliable tool to estimate the co2 flux in different geodynamic settings within system earth

interpretation of geoid anomalies in the contact zone between the east european craton and the palaeozoic platform ii modelling of density in the lithospheric mantle summary we present analysis of lateral variations of density in the upper mantle in the area of contact of the precambrian east european craton eec and the palaeozoic platform pp in poland obtained by analysis of the gravimetric geoid undulations a precise 3 d density model of the crust in the study area down to a depth of 50 km discussed in the first part of this paper majdanski et al in press did not explain all features of the observed geoid this suggests that these features can be due to density inhomogeneities in the upper mantle to estimate them we performed inversion of a residual between the observed geoid and undulations caused by the 3 d density distribution in the crust basing on the assumption of local isostatic compensation and pratt hayford isostasy model the density distribution in the upper mantle was parametrized as a 40 km thick layer located above the assumed compensation depth of 140 km and subdivided into irregular blocks the boundaries of the blocks were defined according to boundaries of major tectonic units in the study area and position and shape of the most pronounced anomalies in the residual geoid a series of sensitivity tests calculated for such density heterogeneities in the upper mantle showed that they can produce geoid undulations of the order of several metres the density values in each unit were taken as model parameters for the inversion procedure and inverse problem was solved using global optimization with constraints the density variations in the upper mantle in the final model correlate well with the surface heat flow this suggests that these variations can be due to diversity in mantle temperature the trans european suture zone tesz which is a major suture separating the eec from the pp is not observed as a distinct unit in the mantle instead our study suggests continuation of the lithosphere of the eec beneath the pp and confirms subdivision of the tesz into terranes with distinctly different evolution a simple calculation shows that condition of local isostatic equilibrium is almost achieved at the assumed compensation depth with the exception of several small scale units however different loads and mass deficiencies in the lithosphere are compensated at different depth levels this proves that the lithosphere is alternation of mechanically strong and weak layers both in the crust and upper mantle and that different loads can be compensated at different depth however the total compensation of all lithospheric loads occurs in the upper mantle

lidar strip adjustment application to volcanic areas dems derived from lidar data are nowadays largely used for quantitative analyses and modelling in geology and geomorphology high quality dems are required for the accurate morphometric and volumetric measurement of land features we propose a rigorous automatic algorithm for correcting systematic errors in lidar data in order to assess sub metric variations in surface morphology over wide areas such as those associated with landslide slump and volcanic deposits our procedure does not require a priori knowledge of the surface such as the presence of known ground control points systematic errors are detected on the basis of distortions in the areas of overlap among different strips discrepancies between overlapping strips are assessed at a number of chosen computational tie points at each tie point a local surface is constructed for each strip containing the point displacements between different strips are then calculated at each tie point and minimization of these discrepancies allows the identification of major systematic errors these errors are identified as a function of the variables that describe the data acquisition system significant errors mainly caused by a non constant misestimation of the roll angle are highlighted and corrected comparison of dems constructed using first uncorrected and then corrected lidar data from different mt etna surveys shows a meaningful improvement in quality most of the systematic errors are removed and the accuracy of morphometric and volumetric measurements of volcanic features increases these corrections are particularly important for the following studies of mt etna calculation of lava flow volume calculation of erosion and deposition volume of pyroclastic cones mapping of areas newly covered by volcanic ash and morphological evolution of a portion of an active lava field over a short time span

interpretation of data from the monitoring thermal camera of stromboli volcano aeolian islands italy twenty eruptive events from the northeast crater of stromboli volcano recorded by a thermal monitoring camera in early 2004 were analysed in order to understand the eruptive dynamics selected events were chosen to be typical of explosions that characterize the steady activity of stromboli in terms of jet height and duration most of the explosions consisted of clast rich single bursts originating from the same vent inside the northeast crater conspicuous ash emission was scarce eruptions were preceded by the flashing of a perturbation wave characterized by low temperatures and an average propagation velocity of about 35 100 m s 1 this perturbation was thought to be caused by the bursting of the gas slug at the bottom of the crater and is interpreted as an air wave this was immediately followed by the expansion of a jet of hot gas and particles at a velocity of 35 75 m s 1 ejecta coarser than 138 cm appeared 1 6 2 s after the onset of the explosion moving at a variable velocity 30 60 m s 1 eruptive events were either vertical or inclined 7 13 towards the nnw this inclination is thought to be a consequence either of the morphology of the conduit following modest rock falls that partially obstructed the uppermost part of the crater or of the displacement of the internal conduit due to the explosive activity of the volcano the instability of the summit area is a further possible cause of the deformation of the conduit

computation of seismic profiles from mineral physics the importance of the non olivine components for explaining the 660 km depth discontinuity the recent increasing number of experimental works leads us to review the elastic properties and mineralogical transformations of mantle minerals the updated data set is used to compute seismic profiles for two petrological models along three adiabatic temperature profiles these profiles are chosen to stress out the influence of non olivine minerals on seismic parameters and to represent cold and horizontally averaged temperature profiles of the earth s mantle in a first part starting compositions of pyrolite and piclogite and a single layer convection are assumed the results clearly point out the importance of the non olivine part of the mineralogy two scenarios are found to explain the 660 km depth discontinuity

a method for 3d reconstruction of volcanic bomb trajectories reconstructing bomb trajectories resulting from strombolian activity can provide insights into near surface dynamics of the conduit system typically the high number of bombs involved represents a challenge for both automatic and manual bomb identification and tracking methods here we present a method for the automated recognition of hundreds of bombs 100 to 400 depending on the explosion observed and for the reconstruction of their trajectories in time and 3d space by stereophotogrammetry the data involve video collected at 30 hz with two synchronised cameras basler 1300 30 separated by 11 targeting explosions at stromboli aeolian islands italy in september october 2012 in total six data sets were collected for emissions lasting less than 15 s the 3d reconstructions provided more accurate velocity estimations error 10 than 2d analyses errors up to 90 100 for bombs moving parallel to the line of sight of the camera by coupling the measured trajectories with a numerical ballistic model we show that the method can be used to estimate the directional distribution of bombs and their velocities at the vent which in this case was 30 130 m s 1 the wind velocity 3 5 m s 1 from the nw and the drag coefficients 10 3 5 10 0 5 of the bombs the 3d reconstructions also provide a quantification of the directions of explosions and show that explosions can be radial oriented in a predominant direction of ejection or in several directions these dispersion patterns can change during a few seconds in a single explosion we relate the changing directions of ejections to rheological variations in the upper part of the magmatic system probably filled with a mixture of partially crystallised magma which can direct rising slugs along preferential paths

plate tectonics and aspherical earth structure the importance of poloidal toroidal coupling we derive poloidal flow internal loading green functions for incompressible fluid models of the mantle consisting either of a single constant viscosity spherical shell or of two adjacent spherical shells having different viscosities from the green function we obtain kernels connecting the surface divergence the geoid and the surface topography fields to the lateral density heterogeneity inferred on the basis of the application of seismic tomographic imaging techniques and with these kernels we argue that both the surface divergence and geoid fields consisting of harmonic degrees 2 5 may be reasonably fit with only a factor of 8 viscosity increase at a depth of 1200 km we point out however that the coupling from poloidal to toroidal flow which is required to understand surface velocity spectra may allow these observations to be understood in terms of a viscosity increase at depth which is smaller than required by nonhydrostatic geoid data in the context of pure poloidal models using the observed kinetic energy in the surface plate motions as a constraint allows us to infer a value for the steady state upper mantle viscosity of 2 0 0 5 1021 pa s we comment on the implication of the difference between this number and the somewhat lower value 1 1021 pa s which has been derived on the basis of analyses of signatures of the glacial isostatic adjustment process

volcanic plume fingerprint in the groundwater of a persistently degassing basaltic volcano mt etna abstract the chemical composition of the groundwater at mt etna was investigated in order to determine the extent to which the persistent plume affects the chemical composition of circulating waters samples from 31 springs and wells were collected during june and july 2014 and analyzed for their chemical compositions the content of dissolved elements derives from the bulk deposition wet and dry deposition at the recharge areas as well as from the weathering of volcanic rocks during the infiltration and transport of groundwater in its early phase the chemical weathering of volcanic rocks and ashes is promoted by the acid rain that characterizes the area and subsequently by the huge amount of deep magmatic carbon dioxide co 2 coming up through the volcanic edifice and dissolving in the water the high content of chlorine is mainly derived from interactions between the plume and rainwater while the total alkalinity can be completely ascribed to the dissociation of carbonic acid h 2 co 3 after the hydration of co 2 the relative contributions of plume derived elements weathering and co 2 driven weathering has been computed for each element in addition the comparison between the chemical compositions of the bulk deposition and of groundwater provides a new understanding about the mobility of volatile elements the proposed approach has revealed that the persistent plume strongly affects the chemical composition of groundwater at mt etna and probably also at other volcanoes characterized by huge open conduit degassing activity

the interaction of volcanic activity in quaternary times upon the evolution of the alcantara and simeto rivers mount etna sicily summary the interaction between volcanic and alluvial sequences is described for the alcantara and simeto valleys mount etna sicily this study provides valuable information on the stratigraphy for prehistoric lavas exposed on the lower western flanks of the volcano eight orders of terrace are recognised in the simeto valley the basal tholeiitic volcanics the oldest exposed lavas of etna are associated with terrace 7 of the simeto which is correlated with either the pre rianian nomentanan erosive phase or the early rianian stage of the pleistocene the earliest evidence of trachybasaltic volcanism in the simeto catchment occurs in terrace 4 which is considered to be of late maspinian age the oldest known volcanics in the north western part of the volcano are related to terrace 3 which is dated at around 20000 bp the alluvial deposits of these terraces provide a valuable sequence of italian quaternary sediments dating back over the last 300000 years the nature of these deposits is described and the probable conditions of their deposition considered the terraces in the upper part of the alcantara are quite different in their mode of formation from the lava capped cut and fill terraces of the simeto valley the current upper course of the alcantara river is considered to be quite youthful versilian in age and the terraces are bench features formed as the river cut down through the lava sequence

comparison between tomographic structures and models of convection in the upper mantle summary gruneisen s and third order finite strain theories are used to compute the density and seismic wave velocities of minerals assuming the minealogical model of ito takahashi 1987 seismic velocities of the upper mantle are calculated using the hashin shtrikman averaging procedure 1 d profiles are first obtained along adiabats and compared to the iasp91 model different adiabats are considered in order to take into account the thermal effect of phase transitions the best results are found with adiabats initiated at 1473 1573 and 1613 k for olivine and spinel respectively the incorporation of thermal effects resulting from phase transitions gives velocity jumps at discontinuities close to those of iasp91 next a model of convection constructed by dupeyrat sotin parmentier 1995 incorporating plate tectonics is used to compute 1 d profiles and 2 d fields of seismic anomalies in the upper mantle averaged profiles show seismic velocity gradients very close to those of iasp91 but individual values are much too high suggesting that the mean temperature profile of the convection model is too cold by 400 k when low pass filtered to the resolution scale of presently available tomogrphic models both the amplitude and shape of the computed seismic anomalies are consistent with the results of tomographic studies the amplitude of the anomalies ranges between 2 7 and 3 8 for p wave slownesses and from 3 3 to 4 5 for s wave slownesses these anomalies correspond to lateral temperature variations of 465 to 520 k these calculations are used 1 as an aid to the interpretation of global tomographic models for instance by computing spectra of lateral heterogeneities and 2 to test the adequacy of the basic assumptions used in the computation of numerical models of mantle convection and to build a theoretical temperature profile that would give the best fit to iasp91 in the uppermost mantle this theoretical model has a shape close to both the convection model and the 1473 k adiabat but in the transition zone the profile is highly subadiabatic the spectra obtained for the synthetic seismic anomalies resemble that of tomographic studies with most of the energy contained within gravest angular orders l and a fast decrease of energy with increasing l the spatial filtering has clearly different effects on heterogeneities depending on their respective wavelengths it is suggested that the change of decreasing rate observed in tomographic models at l 7 is closely related to the filter wavelength and may correspond at a lesser extent to a characteristic wavelength to mantle heterogeneities

geophysical evidence for chemical variations in the australian continental mantle 1 the relative density to shear velocity scaling provides a diagnostic for the presence of compositional variations in the mantle we invert shear wave velocity from a recent 3 d model and gravity anomalies for radial profiles of of the uppermost mantle beneath australia we performed calculations for the three major tectonic provinces that constitute the continent and found significant differences between them the profile for the phanerozoic region can be explained by thermal variations alone in contrast negative values of suggest that variations in composition are important between 75 and 150 km depth in the proterozoic continental lithosphere central australia it is likely that chemical variations are also required to explain the inferences for the archean craton west australia but poor tomographic resolution precludes a definitive conclusion the scaling factors found are consistent with chemical depletion of deep precambrian lithosphere which supports a tectosphere model for the australian continental roots

p and s waveform modeling of continental sub lithospheric detachment at the eastern edge of the rio grande rift 1 east of the rio grande rift tomographic images of teleseismic data have revealed a se dipping slab like structure underneath the western edge of the great plains in the southwestern united states however finite difference synthetics require an amplified tomographic model to reproduce the waveform distortions as observed in broadband waveform data recorded along the la ristra transect in addition to travel time anomalies song and helmberger 2007 demonstrated how to use s waveforms and their amplitude patterns to further constrain the magnitude of the anomalous structure their preferred s velocity model suggests that the slab like structure is about 4 fast 120 km thick and dipping 70 75 to the se to about a depth of 600 km we adapt the preferred s wave model from song and helmberger 2007 and scale the p wave model using a suite of scaling factors sf dlnvs dlnvp we find that synthetics from the p model generated by sf 1 25 can distort p waveforms and fit the amplitude pattern best such a low sf indicates that the slab like anomaly is not only cold but also compositionally distinct we make use of sf and the s wave anomaly simultaneously to obtain corresponding vp vs anomaly and infer the origin of the slab like anomaly our result suggests that the observed sub lithospheric detachment is 310 20 c colder and more depleted than the adjoining mantle asthenosphere by 3 units of mg mg mg fe 100 it is negatively buoyant and is geodynamically consistent with the observed foundering of the continental lithosphere at the eastern edge of the rio grande rift in short we demonstrate the importance of seismic waveform anomalies in geochemical and geodynamic inferences

global mantle shear velocity model developed using nonlinear asymptotic coupling theory we present a three dimensional shear velocity model of the whole mantle developed using s h waveform data the model is expressed horizontally in terms of spherical harmonics up to degree 12 and vertically in terms of legendre polynomials up to degrees 5 and 7 in the upper and lower mantle respectively what distinguishes this model from other tomographic models published to date is 1 the theoretical normal mode based wave propagation approach where we include across branch mode coupling terms in order to model the body wave sensitivity to structure along the path more accurately 2 the wave packet weighting scheme which allows to balance contributions from high amplitude and low amplitude phases increasing the resolution in some parts of the mantle we also relax the constraints on the moho depth which is allowed to vary in the inversion thus absorbing some uncertainties in crustal structure the resulting model is generally in good agreement with other recent global mantle s velocity models and with some regional models the rms profile with depth has more power than other models in the upper mantle lower mantle transition region and the zone of increased power and low degree structure near the base of the mantle is confined to the last 500 km in depth this model provides a particularly good fit to the non hydrostatic geoid through harmonic degree 12 79 variance reduction as well as good fits to observed splitting functions of s velocity sensitive mantle modes indicating that both large scale and small scale features are really well constrained

new images of the earth s upper mantle from measurements of surface wave phase velocity anomalies 1 the sensitivity of a surface wave to the lateral structure of the earth s mantle depends on the local structure and thickness of the crust particularly at short periods the strong lateral heterogeneity of the crust has a significant nonlinear effect on the surface wave sensitivity functions thus far this effect has not been quantified and tomographic studies of the upper mantle based on surface wave observations have not taken it into account on the basis of a jeffreys wentzel kramers brillouin jwkb description of surface wave propagation we find and discuss the lateral variations of the sensitivity of love and rayleigh waves to mantle seismic anomalies associated with a realistic model of the crust mooney et al 1998 we then use the resulting laterally varying sensitivity kernels to determine a new tomographic image of horizontally and vertically polarized shear velocity in the upper mantle from love and rayleigh wave phase velocity measurements periods from 35 to 300 s in terms of large scale patterns of high and low velocity our model is similar to previously published ones confirming among other features the anomalous anisotropy underlying the central pacific ekstrom and dziewonski 1998 we find however that the lateral dependence of the surface wave sensitivity kernels has a significant effect on the absolute amplitude of the anomalies which should not be neglected as we attempt to obtain higher resolution images of the upper mantle

thermodynamics of gas and steam blast eruptions eruptions of gas or steam and non juvenile debris are common in volcanic and hydrothermal areas from reports of non juvenile eruptions or eruptive sequences world wide at least three types or end members can be identified 1 those involving rock and liquid water initially at boiling point temperatures boiling point eruptions 2 those powered by gas primarily water vapor at initial temperatures approaching magmatic gas eruptions and 3 those caused by rapid mixing of hot rock and ground or surface water mixing eruptions for these eruption types the mechanical energy released final temperatures liquid water contents and maximum theoretical velocities are compared by assuming that the erupting mixtures of rock and fluid thermally equilibrate then decompress isentropically from initial near surface pressure 10 mpa to atmospheric pressure maximum mechanical energy release is by far greatest for gas eruptions 1 3 mj kg of fluid rock mixture about one half that of an equivalent mass of gunpowder and one fourth that of tnt it is somewhat less for mixing eruptions 0 4 mj kg and least for boiling point eruptions 0 25 mj kg the final water contents of crupted boiling point mixtures are usually high producing wet sloppy deposits final erupted mixtures from gas eruptions are nearly always dry whereas those from mixing eruptions vary from wet to dry if all the enthalpy released in the eruptions were converted to kinetic energy the final velocity v max of these mixtures could range up to 670 m s for boiling point eruptions and 1820 m s for gas eruptions highest for high initial pressure and mass fractions of rock m r near zero for mixing eruptions v max ranges up to 1150 m s all observed eruption velocities are less than 400 m s largely because 1 most solid material is expelled when m r is high hence v max is low 2 observations are made of large blocks the velocities of which may be less than the average for the mixture 3 heat from solid particles is not efficiently transferred to the fluid during the eruptions and 4 maximum velocities are reduced by choked flow or friction in the conduit