the 2009 2010 eruption of gaua volcano vanuatu archipelago eruptive dynamics and unsuspected strong halogens source gaua a little known volcano in the northern part of vanuatu archipelago went through a long term eruptive activity between september 2009 and july 2010 the eruption started by a phreatic to phreatomagmatic activity which progressively shifted into a magmatic discharge the first eruptive phase involved the hydrothermal system in place the latter was likely influenced by seawater seepage leading to the formation of anhydrite magma involved hereafter this opening phase is of basaltic andesite and basaltic trachyandesite composition high k calc alkaline series typical of the northern part of the vanuatu archipelago the 2009 2010 activity discharged at least 184 kt of so2 and a significant amount of halogens 72 kt cl and 217 kt f such halogen releases indicate that gaua is a strong source of halogens into the atmosphere high and sustained amount of f discharges are known to induce health issues and should not be ignored on gaua island during this eruption the quiescent and voluminous lake letas was slightly affected by the eruption nevertheless the hydrothermal discharge point into the lake situated on the southeastern part of mt garet appeared to be relatively active at this particular location rock forming elements leached out from volcanic rock by acid fluids released by the new intrusion of magma were discharged along with anions into lake letas this release has triggered localized chemistry changes in the lake we speculate that this discharge has also disturbed the bottom water in a limited perimeter remobilizing reduced fe to the surface and subsequently triggering the change in the water color by fe oxidation

potential vorticity in hurricane gloria abstract potential vorticity pv analysts for hurricane gloria of 1985 are derived from nested objective wind analyses of omega dropwindsonde and airborne doppler radar data the analyses resolve eyewall scale features in the inner vortex core and embed analyses of these features within the larger scale environment since three dimensional geopotential height fields required for evaluation of pv are not available in the core they are derived using the balance equation in the process of deriving the heights the degree of gradient balance is evaluated the 500 mb tangential winds in the core averaged azimuthally on the four cardinal points are close to gradient balance outside the radius of maximum wind the resulting depiction of pv is the first presented for a real hurricane due to data deficiencies immediately outside the doppler region as well as inside the eye smoothing of the wind data using a filter with a minimum 25 km spatial scale is required to derive a balanced geopotential height distr

alteration of hawaiian basalts under sulfur rich conditions applications to understanding surface atmosphere interactions on mars and venus a suite of hawaiian basalts that were variably altered in the presence of so 2 rich gases during the current summit eruptive episode at halemaumau crater kilauea were studied to determine their alteration phase assemblage and reactive pathways using electron microscopy mossbauer spectroscopy and x ray diffraction the alteration conditions represent an acid fog environment alteration rinds on the basalts vary in thickness from tens of micrometers to the entirety of the rock and are composed of amorphous silica rims 85 95 wt sio 2 overlain by sulfates sulfate mineralogy consisted of gypsum anhydrite and natroalunite jarosite no phyllosilicates were observed in any alteration assemblages phenocrysts and glass were both observed to be extensively reacted during alteration the halemaumau samples may provide good analogs for basalt alteration on other rocky planetary bodies i e mars venus and mercury where s is ubiquitous and low fluid rock ratios are common

geochemical studies of thermal waters from kanlaon volcano negros island philippines abstract kanlaon is a stratovolcano situated in central negros island philippines it has a record of 30 eruptions since 1866 ranging from phreatic to phreatomagmatic vei 1 2 events geothermal manifestations in kanlaon volcano are evidenced by the presence of hot springs boiling mud pools and warm rivers with temperatures up to 95 c it has developed a significant hydrothermal system within the volcanic edifice through time it evolved into two distinct hydrothermal systems independent of each other a mature hydrothermal system represented by pataan thermal area is characterized by neutral na k chloride bicarbonate fluids and an immature system represented by hagdan spring is characterized by the presence of acid sulfate waters representative water samples were collected between 2014 and 2017 to further characterize the two systems chemical and sulfur isotopic analyses were performed on thermal waters to classify the samples that are linked to the co existence of these two hydrothermal systems results show that thermal spring s ph ranges between 2 5 and 8 1 and conductivity ranges between 88 s cm to 3930 s cm based on their cl so4 hco3 relative abundances the thermal waters are classified as acid sulfate acid sulfate chloride neutral chloride and neutral bicarbonate waters temperatures of deep water hydrothermal reservoirs were calculated using fluid mineral geothermometers and correlated with available borehole temperatures the na k mg geothermometer was used to evaluate equilibrium between water and reservoir rocks results show that the samples are not in equilibrium with the minerals in the reservoir temperature of equilibrium for the mature hydrothermal system was extrapolated to 270 c based on available borehole temperatures the linear trend towards the equilibrium temperature in the na k mg geothermometer can be explained by either groundwater meteoric dilution this is consistent with the light sulfur isotopic signatures between 34s 3 4 and 1 2 of the mature hydrothermal system mambucal which imply that the origin of sulfates is linked to surficial oxidation of h2s or dilution and mixing of meteoric water on the other hand immature hydrothermal system hagdan shows a significantly higher sulfur isotopic composition 34s 8 2 which could either result from the disproportionation of magmatic so2 or from the hydrolysis of elemental sulfur at high temperature between 100 and 350 c

light toned salty soils and coexisting si rich species discovered by the mars exploration rover spirit in columbia hills 1 light toned soils were exposed through serendipitous excavations by spirit rover wheels at eight locations in the columbia hills their occurrences were grouped into four types on the basis of geomorphic settings at three major exposures the light toned soils are hydrous and sulfate rich the spatial distributions of distinct types of salty soils vary substantially with centimeter scaled heterogeneities at paso robles dead sea shredded and champagne penny a well mixed nature for light toned soils occurring near and at the summit of husband hill and relatively homogeneous distributions in the two layers at the tyrone site aeolian fumarolic and hydrothermal fluid processes are suggested to be responsible for the deposition transportation and accumulation of these light toned soils in addition a change in pancam spectra of tyrone yellowish soils was observed after being exposed to current martian surface conditions for 175 sols this change is interpreted to be caused by the dehydration of ferric sulfates on the basis of laboratory simulations and suggests a relative humidity gradient beneath the surface si rich nodules and soils were observed near the major exposures of s rich soils they possess a characteristic feature in pancam visible near infrared vis nir spectra that may be diagnostic of hydrated species and this spectral feature can be used to search for additional si rich species the exposures of hydrated salty soils within various geomorphic settings imply the potential existence of hydrous minerals in similar settings over a much wider area hydrous sulfates represent one of the candidates that may contribute the high level of water equivalent hydrogen in equatorial regions detected by the neutron spectrometer on mars odyssey

experimental study of acid sulfate alteration of basalt and implications for sulfate deposits on mars 1 acid sulfate alteration of basalt by so2 bearing volcanic vapors has been proposed as one possible origin for sulfate rich deposits on mars to better define mineralogical signatures of acid sulfate alteration laboratory experiments were performed to investigate alteration pathways and geochemical processes during reaction of basalt with sulfuric acid pyroclastic cinders composed of phenocrysts including plagioclase olivine and augite embedded in glass were reacted with sulfuric acid at 145 c for up to 137 days at a range of fluid rock ratios during the experiments the phenocrysts reacted rapidly to form secondary products while the glass was unreactive major products included amorphous silica anhydrite and fe rich natroalunite along with minor iron oxides oxyhydroxides probably hematite and trace levels of other sulfates at the lowest fluid rock ratio hexahydrite and an unidentified fe silicate phase also occurred as major products reaction path models indicated that formation of the products required both slow dissolution of glass and kinetic inhibitions to precipitation of a number of minerals including phyllosilicates and other aluminosilicates as well as al and fe oxides oxyhydroxides similar models performed for martian basalt compositions predict that the initial stages of acid sulfate alteration of pyroclastic deposits on mars should result in formation of amorphous silica anhydrite fe bearing natroalunite and kieserite along with relict basaltic glass in addition analysis of the experimental products indicates that fe bearing natroalunite produces a mossbauer spectrum closely resembling that of jarosite suggesting that it should be considered an alternative to the component in sulfate rich bedrocks at meridiani planum that has previously been identified as jarosite

argillic alteration in the novarupta vent region katmai national park alaska secondary mineralogy in the 1912 vent region at novarupta illustrates an alteration history that evolved from high temperature degassing of ejecta through surficial argillic alteration to near neutral wet steam alteration as the posteruptive volcanic system cooled the locallized distribution of surficial argillization appears to have been controlled mainly by fractures related to slumping and compaction in the near surface fallback ejecta the fractures guiding the surviving warm near neutral fumarolic fluids however must be connected with deeper vent structures that reach a subsurface heat source perhaps the boiling zone of a hydrothermal system trace metals including mo pb cu cd and zn concentrated by high temperature vapor phase mobilization have subsequently been partly removed by argillization processes in contrast hg sb tl bi and as remain high even though the fumaroles now emit only low temperature near neutral wet steam

extreme alteration by hyperacidic brines at kawah ijen volcano east java indonesia i textural and mineralogical imprint article kawah ijen volcano located on the eastern tip of java and renowned for its large hyperacidic crater lake poses significant volcanic and environmental hazards to its immediate surroundings crater lake brines seep through the flanks of the volcano to form the banyu pahit river which is used in irrigation downstream resulting in extensive pollution sharply reduced crop yields and health problems the impact on the environment comes mainly from the high element load which is derived from leaching of rocks by the acid fluids and transported downstream our detailed study of water rock interaction in different parts of the kawah ijen system indicates that there are three settings for this alteration the crater lake and banyu pahit riverbed the hydrothermal system below the lake and the solfatara of the active rhyolite dome in all three settings the silicates are leached and altered to amorphous silica in the order olivine glassnan rich plagioclasenortho pyroxenenclino pyroxenenab rich plagioclase in contrast the alteration of titanomag netite is characterised by dissolution in the surficial setting replacement by pyrite and ti oxide in the hydrothermal system and pyritisation ti mobility in the fumarole conduits alteration progresses along crystallographically controlled planes in all phases and shows strong compositional control in plagioclase and titanomagnetite no secondary minerals develop except for minor barite cristobalite pyrite and jarosite this indicates that despite its high element load the waters are undersaturated with respect to most secondary minerals typically produced during alteration of these magmatic rocks by acid chloride sulphate brines and that water rock interaction at kawah ijen is not a sink of elements but rather contributes to the element load transported downstream

gas aerosol ash interaction in volcanic plumes new insights from surface analyses of fine ash particles the reactions occurring between gases aerosols and silicate ash particles in volcanic eruption plumes remain poorly understood despite the fact that they are at the origin of a range of volcanic environmental atmospheric and health effects in this study we apply x ray photoelectron spectroscopy xps a surface sensitive technique to determine the chemical composition of the nearsurface region 2 10 nm of nine ash samples collected from eight volcanoes in addition atomic force microscopy afm is used to image the nanometer scale surface structure of individual ash particles isolated from three samples we demonstrate that rapid acid dissolution of ash occurs within eruption plumes this process is favoured by the presence of fluoride and is believed to supply the cations involved in the deposition of sulphate and halide salts onto ash afm imaging also has permitted the detection of extremely thin 10 nm coatings on the surface of ash this material is probably composed of soluble sulphate and halide salts mixed with sparingly soluble fluoride compounds the surface approach developed here offers promising aspects for better appraising the role of gas aerosol ash interaction in dictating the ability of ash to act as sinks for various volcanic and atmospheric chemical species as well as sources for others c 2007 elsevier b v all rights reserved

trajectories of thermospheric air parcels flowing over alaska reconstructed from ground based wind measurements it is widely presumed that the convective stability and enormous kinematic viscosity of earth s upper thermosphere hinders development of both horizontal and vertical wind shears and other gradients any strong local structure over scale sizes of several hundreds of kilometers that might somehow form would be expected to dissipate rapidly air flow in such an atmosphere should be relatively simple and transport effects only slowly disperse and mix air masses however our observations show that wind fields in earth s thermosphere have much more local scale structure than usually predicated by current modeling techniques at least at auroral latitudes they complicate air parcel trajectories enormously relative to typical expectations for tracing air parcels we used wind measurements of an all sky scanning doppler fabry perot interferometer and reconstructed time resolved two dimensional maps of the horizontal vector wind field to infer forward and backward air parcel trajectories over time this is the first comprehensive study to visualize the complex motions of thermospheric air parcels carried through the actual observed local scale structures in the high latitude winds results show that thermospheric air parcel transport is a very difficult observational problem because the trajectories followed are very sensitive to the detailed features of the driving wind field to reconstruct the actual motion of a given air parcel requires wind measurements everywhere along the trajectory followed with spatial resolutions of 100 km or less and temporal resolutions of a few minutes or better understanding such transport is important for example in predicting the global scale impacts of aurorally generated composition perturbations

neutral thermospheric dynamics observed with two scanning doppler imagers 3 horizontal wind gradients 1 this is the third and final article in a series of papers reporting on observations of the 630 0 nm thermospheric airglow emission by two spatially separated scanning doppler imagers sdi s in alaska in this article bistatic winds derived from the combined measurements of both instruments in a region of field of view overlap were used to derive local scale maps of horizontal neutral wind gradients averaged over the bistatic field of view these gradient estimates were compared with the monostatic gradient estimates routinely produced by the two sdi s the key findings to emerge from this study include 1 the bistatic gradient estimate agreed very well with monostatic estimates for the majority of the time which given the very different methods involved in each technique gives us great confidence in our ability to measure f region neutral wind gradients 2 the strongest gradient was that which describes the magnetic meridional shear of the zonal wind which is driven by momentum deposition from convecting ions 3 vortical flow was more often observed than divergent flow and both types of flow showed systematic variations with magnetic local time 4 viscous heating due to non negligible gradients was on the order of 10 11 wm 3 which while small compared to typical f region joule heating rates may be comparable to particle heating and in a time integrated sense may be an appreciable source of heating

mineralogical analyses and in vitro screening tests for the rapid evaluation of the health hazard of volcanic ash at rabaul volcano papua new guinea the continuous ash and gas emissions from the tavurvur cone in rabaul caldera papua new guinea during 2007 08 raised concerns regarding how exposure would affect the respiratory health of nearby populations and impact on the environment as part of a formal evaluation of the effects of volcanic emissions on public health we investigated the potential health hazard of the ash using a suite of selected mineralogical analyses and in vitro toxicity screening tests the trachy andesitic ash comprised 2 1 6 7 vol respirable sub 4 m diameter particles the crystalline silica content was 1 9 5 0 wt cristobalite in the bulk sample with trace amounts of quartz and or tridymite scanning electron microscopy showed that the ash particles were angular with sparse fibre like particles 3 60 m max diameter observed in some samples which we confirmed to be caso4 gypsum at 6 wt in the bulk samples and not asbestiform fibres the ash specific surface area was low 0 1 2 7 m2 g 1 the leached solution from one of the ash samples was slightly acidic ph 5 6 but did not contain high levels of toxic metals such as f cu zn mn as ni and cd when compared to previously tested volcanic ash leachates ash samples generated potentially harmful hydroxyl radicals through an iron mediated catalytic reaction in the range of 0 15 2 47 mol m 2 after 30 min of reaction however measurement of particle oxidative capacity potential oxidative stress reaction using ascorbic acid and silica like injury to red blood cells erythrolysis assay i e measurement of cell death nevertheless revealed low biological reactivity the findings suggest that acute exposure to the ash would have a limited potential to exacerbate pre existing conditions such as asthma or chronic bronchitis and the potential for chronic exposure leading to silicosis was low

origin of native sulfur ball from the kueishantao hydrothermal field offshore northeast taiwan evidence from trace and rare earth element composition we first report the trace and rare earth element compositions of native sulfur ball with sulfur contents varying from 97 08 wt to 99 85 wt from the kueishantao hydrothermal field off ne taiwan we then discuss the sources of trace and rare earth elements incorporated into the native sulfur ball during formation comparison of our results with native sulfur from crater lakes and other volcanic areas shows the sulfur content of native sulfur ball from the kueishantao hydrothermal field is very high and that the rare earth element ree and trace element constituents of the native sulfur balls are very low sigma ree 35 ppb in the native sulfur ball v cr co ni nb rb cs ba pb th u al ti and ree are mostly derived from andesite mg k and mn are mostly derived from seawater and fe cu zn and ni are partly derived from magma based on the sulfur contents trace and rare earth element compositions and local environment we suggest that the growth of the native sulfur ball is significantly slower than that of native sulfur chimneys which results in the relatively higher contents of trace and rare earth element contents in the native sulfur ball than in the native sulfur chimneys from the kueishantao hydrothermal field finally we suggest a glue pudding growth model for understanding the origin of the native sulfur ball in the kueishantao hydrothermal field whereby the native sulfur ball forms from a mixture of oxygenated seawater and acidic low temperature hydrothermal fluid with h 2 s and so 2 gases and is subsequently shaped by tidal and or bottom currents c 2010 elsevier ltd all rights reserved

magmatic vapor expansion and the formation of high sulfidation gold deposits chemical controls on alteration and mineralization abstract large bulk tonnage high sulfidation gold deposits such as yanacocha peru are the surface expression of structurally controlled lode gold deposits such as el indio chile both formed in active andesite dacite volcanic terranes fluid inclusion stable isotope and geologic data show that lode deposits formed within 1500 m of the paleo surface as a consequence of the expansion of low salinity low density magmatic vapor with very limited if any groundwater mixing they are characterized by an initial sulfate stage of advanced argillic wallrock alteration alunite commonly with intense silicification followed by a sulfide stage a succession of discrete sulfide sulfosalt veins that may be ore grade in gold and silver fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 c and preserve a record of a vapor rich environment recent data for el indio and similar deposits show that at the commencement of the sulfide stage condensation of cu as s sulfosalt melts with trace concentrations of sb te bi ag and au occurred at 600 c following pyrite deposition euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor saturated melt occurs to fe tennantite with progressive non equilibrium fractionation of heavy metals between melt vapor and solid vugs containing a range of sulfides sulfosalts and gold record the changing composition of the vapor published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock this sulfate stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays from any external contemporary hydrothermal activity subsequent fracturing is localized by the embrittled wallrock to provide high permeability fracture arrays that constrain vapor expansion with minimization of heat loss the sulfide stage vein sequence is then a consequence of destabilization of metal vapor species in response to depressurization and decrease in vapor density the geology mineralogy fluid inclusion and stable isotope data and geothermometry for high sulfidation bulk tonnage and lode deposits are quite different from those for epithermal gold silver deposits such as mclaughlin california that formed near surface in groundwater dominated hydrothermal systems where magmatic fluid has been diluted to less than about 30 high sulfidation gold deposits are better termed solfataric gold deposits to emphasize this distinction the magmatic vapor expansion hypothesis also applies to the phenomenology of acidic geothermal systems in active volcanic systems and equivalent magmatic vapor discharges on the flanks of submarine volcanoes

geochemistry and isotope composition sr pb δ 66 zn of vulcano fumaroles aeolian islands italy abstract we present and discuss temperatures major and trace element gas geochemistry radiogenic isotopes pb sr and the first zn isotope data of fumarole condensates and altered rocks from the vulcano fumarolic field the fumaroles of the la fossa cone sampled on 5th may 2015 have temperatures ranging between 233 and 427 c they plot compositionally on the mixing trend between the magmatic and hydrothermal end members defined by previous studies but are strongly displaced towards the hydrothermal component correlations of radiogenic sr pb and stable isotopes of zn with 13 c co2 and several trace elements of the fumarolic acid condensates support mixing between the above mentioned distinct magmatic and hydrothermal fluids the magmatic end member has a less radiogenic sr 87 sr 86 sr 0 7045 and heavier zn isotope composition 66 zn 0 3 the hydrothermal fluid end member has a more radiogenic 87 sr 86 sr signature 0 7055 which could be due to leaching of radiogenic sr from the crystalline basement rocks or reflect seawater sr it is also characterized by lighter zn isotope composition 66 zn pb isotope compositions of the fumaroles sampled in this study show a shift towards less radiogenic values compared to pre 2001 fumaroles this could indicate either a change in the hydrothermal circulation pattern leading to leaching of rocks with different isotopic compositions or the involvement of a new isotopically distinct magmatic fluid the alteration zones around the fumarole vents are also characterized by systematic correlations of pb and zn isotopes with major and trace elements we interpret these as the result of the addition onto the substratum volcanic rock of pb and zn from the fumaroles zn isotope signatures of the alteration zones are significantly heavier than those of the corresponding fumaroles 66 zn 0 3 1 6 probably due to equilibrium fractionation occurring during sphalerite precipitation at the vent discharge

acid alteration in the fumarolic environment of usu volcano hokkaido japan abstract the last eruptive activity of usu volcano in 1977 78 involved the development of high temperature 550 710 c fumaroles the gases emitted were h2o rich 95 99 mol with cl s 0 05 0 9 f cl 0 3 0 2 and with rh 2 5 close to the rock buffer feo feo1 5 cooling and oxidation of the high temperature gases resulted in the formation of acidic condensates ph 1 6 that interacted with the wall rock complete leaching of the cations ca na mg al and fe from the primary minerals and matrix glass occurred leaving in place only silica these mobilized cations precipitated as secondary minerals from acidic fluids that circulated in microcracks sem study shows mineral associations reflecting increasing fluid oxidation a al fluorides such as ralstonite namgalf6 h2o pyrite and anhydrite gypsum b an al hydroxide hematite gypsum and amorphous silica or cristobalite c al sulfates such as hydronium alunite h3o al3 so4 2 oh 6 alunite kal3 so4 2 oh 6 amorphous silica cristobalite hematite and anhydrite gypsum d al sulfates al fluorides amorphous silica cristobalite pyrite and anhydrite gypsum a ti oxide a fe mg sulfate and barite are present in minor amounts clay minerals are absent from the observed assemblages primary phenocrysts and matrix glass undergo a complete transformation to silica enriched in fluorine 1 7 wt this fluorine enrichment in the silicified parts of silicates and in silica incrustations suggests that f may play a role in silica mobilization modeling of the cooling of the high temperature gases was performed with the program gasworks the calculations suggest that 66 of the total sulfur from the gases may be lost by deposition as native sulfur at temperatures below 160 c thermochemical modeling of condensate rock interaction using chiller indicates that the cooling of gases was the source of the altering solutions oxidation by atmospheric o2 of the sulfur reduced species in the volcanic gas condensates resulted in their extreme acidification condensate rock interactions produce supersaturation with respect to the following mineral assemblages at 95 c 1 pyrite native sulfur cristobalite barite anhydrite diaspore log m h 2 s aq 2 32 2 cristobalite anhydrite hematite alunite diaspore log m h 2 s aq gypsum replaces anhydrite at t 25 c the calculated mineral assemblages are in agreement with those observed in the field

mapping thermospheric winds in the auroral zone a new all sky imaging fabry perot asifp spectrometer has been developed for ground based mapping of upper atmospheric wind and temperature fields in the auroral zone although several other asifp spectrometers exist for atmospheric studies rees et al 1984 sekar et al 1993 biondi et al 1995 these instruments have all operated with etalons of fixed optical gap a method potentially subject to errors in the presence of auroral intensity gradients in this instrument the etalon plate spacing is scanned periodically over one order of interference and each photon detected is assigned to a wavelength interval which is determined from both its arrival location on the detector and the etalon plate spacing prevailing at the detection time spectra accumulated this way are not distorted by spatial intensity gradients preliminary 630 nm observations were made during the winter of 1994 95 from poker flat research range alaska to illustrate some of the features we have observed in this study we present line of sight wind estimates derived for the night of december 7 1994 the background wind matches averages presented previously by sica et al 1986 and is consistent with winds driven principally by momentum deposition from ionospheric plasma convection through ion drag smaller scale curvature and divergence features are also discernable and are discussed

neutral thermospheric dynamics observed with two scanning doppler imagers 1 monostatic and bistatic winds 1 doppler shift measurements of the thermospheric 630 0 nm emission recorded by two spatially separated imaging fabry perot spectrometers in alaska have been combined to infer f region horizontal wind vectors at approximately 75 locations across their overlapping fields of view these bistatic horizontal wind estimates rely only on an assumption regarding the local vertical wind and assume a common observing volume and thus represent a more direct measurement of the wind than do the monostatic single station vector wind fields routinely inferred by these instruments here we present comparisons between both the independently derived monostatic wind fields from each instrument and the bistatic wind estimates inferred in their common observing volumes data are presented from observations on three nights during 2010 two principal findings have emerged from this study first the monostatic technique was found to be capable of estimating the actual large scale wind field reliably under a large range of geophysical conditions and is well suited to applications requiring only a large scale big picture approximation of the wind flow secondly the bistatic or tristatic technique is essential for applications requiring detailed knowledge of the small scale behavior of the wind as for example is required when searching for gravity waves

superficial alteration mineralogy in active volcanic systems an example of poas volcano costa rica abstract the alteration mineralogy in the crater area of poas volcano costa rica has been studied to constrain acid fluid rock interaction processes and conditions relevant for the formation of sulphate bearing mineral assemblages found on the surface of mars individual sub environments which include the hyperacid lake laguna caliente ephemeral hot springs fumarole vents and areas affected by acid rain and or spray from the lake are marked by distinct secondary mineral associations with sulphates commonly as prevailing component the sulphates occur in a wide mineralogical diversity comprising gypsum anhydrite various polyhydrated al sulphates alunite jarosite group minerals halotrichite voltaite and copiapite group minerals epsomite and romerite depending on the sub environment they are variably associated with clay minerals kaolinite group and smectite group zeolites sio 2 polymorphs fe hydro oxides ti oxides native sulphur sulphides chlorides fluorides phosphates and carbonates geochemical modelling was performed to identify mechanisms responsible for the formation of the secondary minerals found in the field and to predict their possible stability under conditions not seen at the surface the results indicate that the appearance of amorphous silica hematite anhydrite gypsum pyrite anatase and kaolinite is relatively insensitive to the degree of acidity of the local aqueous system on the other hand alunite jarosite group minerals elemental sulphur and al oh so 4 only form under acidic conditions ph 2 sulphates is restricted to olivine bearing rocks exposed to acid rain or brine spray modelling suggests that their formation required a repetitive sequence of olivine dissolution and evaporation in an open system involving limited amounts of fluid the mineral variety in the crater of poas is remarkably similar to sulphate bearing assemblages considered to be the product of acid sulphate alteration on mars the analogy suggests that comparable fluid rock interaction controls operated in martian volcanic environments

volcano hydrothermal system and activity of sirung volcano pantar island indonesia abstract sirung is a frequently active volcano located in the remote parts of western timor indonesia sirung has a crater with several hydrothermal features including a crater lake we present a timeseries of satellite images of the lake and chemical and isotope data from the hyperacid hydrothermal system the fluids sampled in the crater present the typical features of hyperacidic systems with high tds low ph and 34s h s o 4 34s s 0 among the highest for such lakes the cations concentrations are predominantly controlled by the precipitation of alunite jarosite silica phases native sulfur and pyrite which dominate the shallow portions of the hydrothermal system these minerals may control shallow sealing processes thought to trigger phreatic eruptions elsewhere sparse mg cl and so4 cl ratios and lake parameters derived from satellite images suggest gradual increase in heat and gas flux most likely so2 rich prior to the 2012 phreatic eruption an acidic river was sampled 8 km far from the crater and is genetically linked with the fluids rising toward the active crater this river would therefore be a relevant target for future remote monitoring purposes finally several wells and springs largely exceeded the world health organization toxicity limits in total arsenic and fluoride

spatial structure in the thermospheric horizontal wind above poker flat alaska during solar minimum a new all sky imaging wavelength scanning fabry perot spectrometer was used to record high resolution r 200 000 spectra of the 630 nm thermospheric optical emission above poker flat alaska these spectra were used to derive spatially resolved maps of the horizontal wind vector at approximately 250 km altitude we describe the procedure used to infer vector winds from line of sight doppler shifts along with its limitations we present the time evolution of the vector wind fields obtained from this method for 6 nights of observation five of the 6 nights contained periods when we inferred the existence of significant curvature divergence or shear in the thermospheric wind across our instrument s 1000 km diameter field of view the sixth night exhibited little spatial structure and is shown for comparison we compare these results with a generic solar minimum winter time run of the national center for atmospheric research s thermosphere ionosphere and electrodynamics general circulation model while agreement was good at the start and end of the night considerable differences were found in the late evening and midnight sectors some possible origins for these discrepancies are proposed in particular we suggest that the f region horizontal wind may be deflected by upwelling vertical winds which are in turn driven by e region heating in the auroral zone we note that both the instrument used and our high latitude implementation of the analysis procedure are new experimental techniques thus the data presented here should be regarded as preliminary and if possible be validated by comparison with results from other techniques

a potential vorticity based study of the role of diabatic heating and friction in a numerically simulated baroclinic cyclone abstract a particularly intense case of western atlantic baroclinic cyclogenesis was investigated in this study specifically the roles of latent heat of condensation and surface friction were examined from the potential vorticity or pv thinking perspective the methodology used for this study involves three key components 1 a full physics mesoscale model which provides a continuous and dynamically consistent dataset and provides full user control over physical processes 2 a partitioned pv integration which temporally integrates the accumulation of pv due to various physical processes in the model s eulerian framework and 3 the piecewise inversion method of davis and emanuel which calculates the balanced wind and mass field associated with particular pv anomalies potential vorticity features obtained through the partitioned integration technique were inverted to yield their direct contributions to the total circulation in addition sensitivity studies were carried out to determine the overal

tropical storm formation in a baroclinic environment abstract an analysis is presented of the large scale conditions associated with the initial development of tropical storm diana september 1984 in a baroclinic environment ordinary extratropical wave cyclogenesis began along an old frontal boundary east of florida after 0000 utc 7 september and culminated in tropical cyclogenesis 48 h later water vapor satellite imagery showed that the initial cyclogenesis and incipient tropical storm formation was nearly indistinguishable from a classical midlatitude development cyclogenesis occurred in three stages a large scale cold trough and associated frontal system crossed the atlantic coast while a small potential vorticity maximum aloft fractured off the main trough and stalled over central florida in the first stage as the main trough sheared off eastward cyclogenesis began along the southwestern end of the stalled frontal zone east of florida anticyclogenesis to the north in the wake of the shearing trough allowed a surge of cooler and drier air to flo

alunite dissolution rates dissolution mechanisms and implications for mars abstract alunite kal 3 so 4 2 oh 6 is a hydrated aluminous sulfate mineral associated with acidic oxidizing aqueous environments on earth additionally orbiting spacecraft and rovers on mars have reported spectral data that indicate a range of mono and polyhydrated sulfate phases and hydroxysulfate phases suggesting such conditions also existed on mars in the past this study examines alunite dissolution rates in aqueous systems with varying ph temperature and solution chemistry conditions alunite dissolution rates in dilute solutions are 2 3 orders of magnitude slower than jarosite dissolution rates measured under analogous conditions similar to jarosite alunite dissolution rates vary as a function of activity of h and oh following the rate law log r mol m 2 s 1 0 133 0 02 ph 10 65 0 07 at ph r 0 194 0 04 ph 12 53 0 26 at ph 5 however minimum alunite dissolution rates are shifted to higher ph 5 5 5 likely due to differences in fe and al speciation alunite and jarosite rates converge in saturated nacl and cacl 2 brines as the activity of water decreases suggesting that differences in water exchange rates with fe 3 and al 3 control dissolution rates in dilute solutions while metal cl complexation occurs at similar rates within the brines particle lifetimes based on measured dissolution rates in dilute solutions show that alunite particles are expected to be preserved two orders of magnitude longer than jarosite particles over a range of ph and temperature conditions in particular alunite is more likely to be preserved in neutral to moderately alkaline systems compared to jarosite which is expected to be preserved in more acidic conditions alunite dissolution produced amorphous al rich alteration products at moderate to high ph unlike jarosite alunite dissolution does not show a clear trend as a function of temperature alunite dissolution rates do not increase with increasing temperature likely due to lower alunite solubility at higher temperature therefore alunite is expected to be more prevalent in hydrothermal systems compared to jarosite

lithium isotope fractionation during magma degassing constraints from silicic differentiates and natural gas condensates from piton de la fournaise volcano reunion island abstract recent volcanic products from the piton de la fournaise volcano reunion show pronounced depletion or enrichment in lithium and significant isotopic fractionation related to degassing 1 trachytic pumices from the april 2007 eruption show extreme li depletion 90 and isotopic fractionation 7 li of 21 the depletion of water and volatiles cl f b cs in these samples suggests that li loss occurred in response to degassing which most likely occurred as the small isolated volume of magma underwent extensive differentiation near the surface because the pre degassing composition is relatively well known the composition of the degassed pumice constrains the partition coefficient to 60 v m v m to 1 010 at magmatic temperatures unlike d v m v m does not depend on whether crystallization and degassing occurred successively or concomitantly 2 basaltic samples from the interior wall of the long lived 1998 piton kapor were extensively altered by acidic gas they also show extreme li depletion but barely significant isotopic fractionation 7 li 4 5 suggesting that high temperature leaching of li by volcanic gas does not significantly fractionate li isotopes 3 high temperature 400 325 c gas condensates formed during degassing of the thick lava flow of april 2007 display high li contents 50 100 ppm which are consistent with li being as volatile as zn and sn their isotopically light li signature average of 1 7 is consistent with their derivation from isotopically heavy vapor 13 5 if the factor of isotopic fractionation between condensate and vapor is less than 0 985 a degassing crystallization model accounts for the evolution of trace species which like lithium are volatile but also moderately incompatible

extreme alteration in an acid sulphate geothermal field sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the soufriere volcanic centre in southern saint lucia intensely altered rocks occur over an area of at least 200 400 m together with bubbling hot pools and fumaroles the pools are sodium calcium sulphate type with phs of 3 7 and temperatures of 41 97 c fumaroles have temperatures up to and at times above 100 c gases collected from both fumaroles and bubbling pools have high contents of co2 601 993 mmol mol and commonly high h2s 3 190 mmol mol least altered host rocks surrounding sulphur springs comprise calc alkaline feldspar quartz porphyritic dacites of near uniform chemical composition these rocks which form massive domes and volcaniclastic units were emplaced 13 30 ka ago lindsay et al 2013 within the geothermal field the dacites have been moderately to highly altered to acid sulphate assemblages of kaolinite illite smectite alunite natroalunite cristobalite opaline silica native sulphur jarosite and amorphous compounds muddy sediments from grey to blackish thermal pools additionally contain iron sulphides despite intense alteration of the volcanic rocks and derived volcaniclastic sediments zr and ti have remained essentially immobile which allows identification of the precursors dacites and calculation of mass changes many of the altered rocks and sediments show major depletions of fe mg ca na extremely altered samples additionally show notable losses of al p k ree and y implying leaching by highly acidic waters a few of the highly altered rocks however have gained al together with p presumably due to neutralization or evaporation of acidic thermal waters also present within the geothermal field are metre scale zones with very high contents of silica and native sulphur and surface thermal waters define a linear trend in a plot of 18o vs d and reach high levels of isotopic enrichment the enrichment trend is ascribed to progressive evaporation in the thermal pools the low slope of the isotopic trend 1 4 is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 c from the deep brine that underlies the geothermal field the whole rock o h isotopic composition of four highly altered samples kaolinite smectite opal sulphates can be accounted for if the alteration fluid was a 50 50 mixture of steam and meteoric water and alteration occurred at 50 125 c whole rock 34s values of samples containing variable amounts of sulphates sulphides and native s are all notably negative 5 to 16 consistent with derivation of sulphur from volcanic gases such as so2 and h2s altered rocks and thermal pool sediments in the geothermal field are commonly enriched in hg and se up to 50 mg kg at sulphur springs primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters in many cases this has led to substantial mass losses or gains in al p and rees regardless of the degree of alteration however the precursor rocks can still be identified using ti zr relations

optical observations of thermospheric dynamics at arecibo observations of thermospheric neutral winds have been made at arecibo puerto rico by using a fabry perot interferometer to measure the doppler shift of the nighttime o d 630 nm emission we have developed a scheme of making observations at eight equally spaced azimuth positions with a constant zenith angle this technique allows us to determine the mean neutral wind velocities in the meridional and zonal directions as well as any horizontal gradients in the wind field it also provides a good means of simultaneously monitoring any spatial variations in neutral temperature and the intensity of the o d emission in general the highest equatorward wind velocity is observed at about 2100 lst the meridional wind velocity usually lessens as midnight approaches and sometimes but by no means always reverses after midnight the magnitude of the equatorward velocity is greater in summer than in winter months for winter and spring months the zonal wind blows eastward throughout the night with the velocity tending to decrease in a fairly regular fashion from about 125 m s 1 at 2100 lst towards zero by 0400 lst in summer the pattern is similar but the eastward flow usually reverses earlier and a westward velocity of some 50 m s 1 may be attained by 0400 lst significant horizontal wind gradients are often observed in the meridional direction but not in the zonal direction near midnight especially during both the equinox and summer months the equatorward wind is often greater to the north of arecibo than to the south we interpret this as being an effect of the passage of the midnight equatorial pressure maximum to the south of the station measurements of neutral temperature with the interferometer do indeed show that between 0100 0200 lst the neutral temperature to the south of arecibo is enhanced by some 40 k over that to the north

modeling tropical precipitation in a single column abstract a modified formulation of the traditional single column model for representing a limited area near the equator is proposed this formulation can also be considered a two column model in the limit as the area represented by one of the columns becomes very large compared to the other only a single column is explicitly modeled but its free tropospheric temperature rather than its mean vertical velocity is prescribed this allows the precipitation and vertical velocity to be true prognostic variables as in prior analytical theories of tropical precipitation two models developed by other authors are modified according to the proposed formulation the first is the intermediate atmospheric model of j d neelin and n zeng but with the horizontal connections between columns broken rendering it a set of disconnected column models the second is the column model of n o renno k a emanuel and p h stone in the first model the set of disconnected column models is run with a fixed temperature

assimilated observations of thermospheric winds the aurora and ionospheric currents over alaska we present simultaneous measurements of thermospheric winds auroral emissions and ionospheric currents over alaska obtained from four separate instruments thermospheric f region wind maps were recorded by an all sky imaging fabry perot spectrometer located at poker flat and observing at 630 0 nm auroral images at 557 7 nm were obtained from the low resolution visible imager on board the polar satellite white light all sky auroral images were recorded by ground based all sky cameras located in alaska at poker flat 65 07 n 212 34 e and at kaktovik 70 06 n 217 24 e finally the east west component of the ionospheric f region plasma convection was inferred using the alaskan meridian chain of magnetometers montage images of these four data sets are presented projected onto a geographic map of the alaskan region we examine a 10 hour period during the alaskan local nighttime of february 10 1997 these montages illustrate a close relationship between spatial structures occurring in the aurora in the ionospheric plasma convection and in the f region wind field latitudinal shear of the geomagnetic zonal wind often observed in the premidnight time sector was seen to be associated with both the equatorward and poleward boundaries of the discrete aurora we focus particularly on a period commencing just after 0900 ut when a strong shear in the zonal wind was observed to sweep southward across alaska after magnetic midnight the wind field was dominated by the emergence of the cross polar jet from the polar cap this overwhelmed any wind features associated with local auroral processes

simultaneous fpi and tma measurements of the lower thermospheric wind in the vicinity of the poleward expanding aurora after substorm onset

fractional crystallization of the basaltic suite of usu volcano southwest hokkaido japan and its relationships with the associated felsic suite abstract ree concentrations were determined for four basalts two basaltic andesites three dacites and one rhyolite from usu volcano sw hokkaido japan and are reported with their mineralogical data the basic rocks are tholeiitic whereas the felsic rocks are calc alkaline no intermediate andesite has been erupted the ree abundances of the basic rocks increase with increasing feo mgo ratios and the mineral compositions are consistent with low pressure fractionation the variation of the ree concentrations can also be explained by low pressure fractionation in contrast the chemical features of the felsic rocks can be hardly accounted for by low or high pressure fractionation the felsic rocks are more depleted in hree than the most differentiated basaltic andesite a model calculation is suggestive of their origin the felsic rocks can be produced by remelting of an intrusive body of tholeiitic basic magma

geochemistry and mineralogy of fumarolic deposits valley of ten thousand smokes alaska bulk chemical and mineralogical evolution of dacite rich protolith assrracr samples from a fossil fumarole originating in the 1912 ash flow tuffin the valley of ten thousand smokes have been analyzed to ascertain chemical changes resulting from high temperature fumarolic alteration and subsequent cooling and weathering of the protolith samples of the underlying dominantly leached dacite rich portion of the ash flow tuff adjacent to the fumarolic conduit and samples of encrusted fallout from the shallow part of the fossil fumarole were interpreted using the isocon method of grant 1986 the results show that relative to unaltered l9l2 dacite chosen as a standard composition for the protolith in this fossil fumarole mass was conserved during the alteration reactions for most of the system but mass gains of l4 2do o were determined for three samples in the leached ash flow tuff relative to unaltered dacite protolith significant enrichments occurred in sor loi hro cl f zn pb cu sn cr ni as sb au br in various parts of the fossil fumarole some of these were during the high temperature part of the alteration and some were during cooling processes when acid alteration becomes prominent the rees indicate some depletion in highly altered samples relative to dacite protolith and differential mobility of eu2 relative to trivalent rees this is manifested by positive eu anomalies in ree patterns normalized against ree in the dacite protolith mineral phases introduced in the alteration assemblages include alunite reflecting high so activity hydrated aluminum hydroxy fluoride a ralstonite like phase and fluorite reflecting high f activity smectite magnetite hematite and goethite reflecting oxidation and hydration reactions opal and a portion of the a cristobalite reflect sio mobility however the abundance of a cristobalite is formed from pumice leached during hightemperature vapor phase processes and devitrification of the altered glass

convective contribution to the genesis of hurricane ophelia 2005 abstract the convection occurring in the tropical depression that became hurricane ophelia 2005 was investigated just prior to tropical storm formation doppler radar showed a deep wide intense convective cell of a type that has been previously thought to occur in intensifying tropical depressions but has not heretofore been documented in detail the updraft of the cell was 10 km wide 17 km deep had updrafts of 10 20 m s 1 throughout its mid to upper levels and contained a cyclonic vorticity maximum the massive convective updraft was maintained by strong positive buoyancy which was maximum at about the 10 km level probably aided by latent heat of freezing evaporative cooling and precipitation drag occurred in the rain shower of the cell but were insufficient to produce a strong downdraft or gust front outflow to force the updraft the convective updraft was fed by a layer of strong inflow that was several kilometers deep wind induced turbulence just above the ocean surface enriched the equi

halogens in volcanic systems the transport degassing and atmospheric release of halogens from active volcanism on earth have been the focus of increasing interest over the last few decades and have recently been the subject of the 1st workshop on halogens in volcanic systems and their environmental impacts that was held in december of 2007 at yosemite lodge in yosemite national park california as an introduction to this chemical geology special issue collecting contributions from many of the participants at the workshop we review here recent advances in this field including experimental and theoretical investigations of halogen behaviour in volcanic and related magmatic systems we discuss previous research on several aspects of halogen geochemistry including halogen abundances in the mantle and magmas on earth the effects of halogens on phase equilibria and melt viscosities their partitioning between melt and fluid phase s upon decompression cooling and crystallisation of magmas in the earth s crust and their final atmospheric release as volcanic gases the role of halogens in the genesis of hydrothermal systems and in the transport of ore forming metals is also reviewed and we discuss our current understanding of atmospheric processing of volcanic halogens in both the troposphere and stratosphere and their consequent impacts in spite of these recent advancements our current understanding of halogen geochemistry at active volcanoes is still far too fragmentary and the key questions that require answers from future research are summarised in our conclusions

estimation of mesoscale thermospheric wind structure using a network of interferometers we introduce a technique for estimating the regional thermospheric wind field from measurements made by a network of interferometers unlike previous work this technique does not make assumptions about the functional form of the wind field and instead uses inverse theory to find the smoothest wind field that agrees with the measurements this technique is general and applies to any network making radial velocity measurements we show reconstructions of the thermospheric wind field over the eastern united states and over eastern brazil using data from two distinct networks of fabry perot interferometers measuring the doppler shift of the 630 0 nm airglow emission in brazil we find direct evidence of a convergent wind field during the period of rapid thermospheric temperature increase associated with the equatorial midnight temperature maximum

the valley of ten thousand smokes katmai klaska a unique geochemistry laboratory abstract during june 6 8 1912 a new vent novarupta near mt katmai in the aleutian range of alaska released the largest volcanic eruption of this century and the largest rhyolitic eruption in nearly twenty centuries spectacular fumaroles developed in the ash flow sheet prompting robert f griggs who discovered the steaming valley in 1916 to name it the valley of ten thousand smokes vtts the katmai scientific drilling project was developed to advance understanding of the physical and chemical processes involved with explosive volcanism through an interdisciplinary investigation of the novarupta vent and fissure fumaroles present in the ash flow sheet novarupta vent represents a unique target for subsurface geophysical and coring studies of structures and lithologies produced by explosive volcanism panel on volcanic studies at katmai national academy of sciences 1989 scientific expeditions sponsored by the department of energy the national science foundation and the u s geological survey were conducted during the summers of 1989 and 1990 most of the surface studies are now complete and drilling is planned for 1994 contingent on successful completion of the national environmental policy act process one of the main objectives of this ambitious study is to determine the source mechanisms and thermal and chemical conditions of the fumarolic transport of elements that occurred following ash flow emplacement as part of the surface investigation prior to drilling a detailed geochemical study has been initiated involving the mass flux of nearly fifty major minor and trace elements using samples from fumarolic deposits located in distal rhyolitic and proximal dacitic and andesitic portions of the ash flow sheet significant enrichments are observed in s br cl f zn pb cu sn cr ni as sb and au in various portions of the fossil fumaroles these enrichments correlate well with those determined in active high temperature fumarolic sublimates and indicate that most of these elements were transported to the surface early in the vapor phase

fossil and active fumaroles in the 1912 eruptive deposits valley of ten thousand smokes alaska fumaroles in the ash flow sheet emplaced during the 1912 eruption of novarupta were intensely active throughout the valley of ten thousand smokes vtts when first studied in 1917 fumarole temperatures recorded in 1919 were as hot as 645 c influx of surface waters into the hot ash flow sheet provided the fluid flow to sustain the fumaroles but also enhanced cooling so that by the mid 1930 s vigorous activity survived only in the vent region configuration and distribution of high temperature fissure fumaroles tens of meters long that are prevalent in the middle and upper vtts were controlled largely by sintering and degree of welding which in turn controlled fracturing and permeability of the ash flow tuff one fracture type developed parallel to the enclosing valley walls during compaction of the ash flow sheet another type extends across the vtts nearly perpendicular to the flow direction a third type of randomly oriented fractures developed as cooling contraction cracks during vapor phase devitrification in distal parts of the ash flow sheet where the tuff is nonwelded prominent fumaroles have irregular funnel shaped morphologies fumarole distribution in the nonwelded part of the ash flow sheet is concentrated above pre emplacement river channels the hottest longest lived fumaroles occurred in the upper vtts near the 1912 vent where the ash flow sheet is thicker more indurated and on average more mafic richer in dacite and andesite in contrast to the thinner nonwelded rhyolitic tuff in the distal part of the sheet fumarolic activity was less intense in the distal part of the tuff because of lower emplacement temperatures more diffuse fumarole conduits in the nonwelded tuff and the thinness of the ash flow sheet chemical leaching of ash flow tuff by hot rising fluids took place adjacent to fumarolic conduits in deep parts of the fumaroles deposition of incrustation minerals the components of which were carried upward by fumarolic gases took place in the upper part of the ejecta mostly in the fallout layers the permeability difference between the ash flow tuff and the overlying coarse dacite fallout was a critical factor in promoting the abrupt gradients in temperature pressure and fo2 that resulted in deposition of minerals from the fumarolic gases the permeability difference between nonwelded ash flow tuff and overlying fine grained fall layers in the lower vtts is less pronounced the total mass of fumarolically deposited minerals appears large at first glance owing to the conspicuous coloration by fe minerals the mass is appreciably less than is apparent however because most incrustations are composed largely of ejecta coated or cemented by fine grained fumarolic minerals a large mass of unstable incrustation minerals mainly chlorides and sulfates reported during the 1917 1919 studies have since been removed by dissolution and weathering in the vent region argillic alteration that followed high temperature degassing is localized along arcuate subsidence fractures in fallback ejecta at widely scattered residual orifices fumarolic gases presently are near neutral steam and temperatures are as hot as 90 c

time dependent permeability evolution in compacting volcanic fracture systems and implications for gas overpressure abstract volcanic eruptions are driven by the ascent of volatile laden magma the capacity of a volcano system to outgas these volatiles its permeability controls the explosive potential and fractures at volcanic conduit margins play a crucial role in tempering eruption explosivity by acting as outgassing pathways however these fractures are often filled with hot volcanic debris that welds and compacts over time meaning that these permeable pathways have a finite lifetime while numerous studies emphasize that permeability evolution is important for regulating pressure in shallow volcanic systems how and when this occurs remains an outstanding question in volcanology in this contribution we show that different pressure evolution regimes can be expected across a range of silicic systems as a function of the width and distribution of fractures in the system the timescales over which they can outgas a function of depth and temperature and the permeability of the host material we define outgassing diffusive relaxation and pressure increase regimes which are distinguished by comparing the characteristic timescales over which they operate moreover we define a critical permeability threshold which determines in concert with characteristic timescales of diffusive mass exchange between the pore and melt phases whether systems fracture and outgas efficiently or if a volcano will be prone to pressure increases incomplete healing and explosive failure

fumarole distribution morphology and encrustation mineralogy associated with the 1986 eruptive deposits of mount st augustine alaska numerous rootless fumaroles were developed on pyroclastic flows and a lava flow generated during the march 1986 eruptive cycle of mount st augustine gases issued from fumarole vents with four different shapes fissure phreatic explosion crater single multiple ovoid opening and diffuse multiple opening fumarole distribution and morphology were controlled by preeruption drainage and topography as well as by the thickness compaction and settling of the flow deposits fumarole temperatures measured in june and july 1986 ranged from 75 394 c varying amounts of colorful and often roughly zoned encrustations are associated with all fumarole vent shapes only six types of crystalline phases were detected by x ray diffraction with gypsum the most abundant mineral followed by anhydrite sulfur tridymite halite and soda alum scanning electron microscopy and energy dispersive x ray analysis revealed a number of amorphous phases mainly halogen rich as well as other minor crystalline phases the mineral assemblages in the encrustations suggest formation conditions for these deposits within a general range of 25 250 c in an oxidizing environment many of the amorphous phases are metastable and upon cooling of the fumarole lose nonstructural water and crystallize to more stable forms the high halogen contents of the fumarole condensates and the mineralogy chemistry and morphology of the encrustations support leaching of the andesitic ash and lava flow by condensed acid vapors as the primary source for the chemical components contained in the encrustations comparison of traceelement sr ba v co ni and cr contents in unaltered and altered ash suggests that trace element distribution follows a pattern of isomorphic substitution in the encrustation phases

understanding the vertical structure of potential vorticity in tropical depressions author s murthy vs boos wr abstract 2019 royal meteorological society potential vorticity pv has been used to understand the intensification and motion of a variety of tropical vortices here atmospheric reanalyses and idealized models are used to understand how the vertical structures of moist convective heating and adiabatic advection jointly shape the vertical structures of pv in tropical depressions observationally based estimates reveal a top heavy pv structure in tropical depressions contrasting with bottom heavy structures of absolute vorticity and diabatic pv generation these distinct vertical structures are reproduced in an axisymmetric model which employs the weak temperature gradient approximation for conceptual simplicity and is forced by stratiform and deep convective heating when applied in isolation the stratiform and deep convective heatings produce pv maxima at 500 hpa and near the surface respectively when these two heatings are applied simultaneously interactions between the stratiform and deep convective modes enhance the adiabatic advective tendencies produced by the transverse circulation making the pv distribution more top heavy in the lower and middle troposphere radial advection also greatly reduces the radius of the pv structure relative to that of the imposed heating consistent with structures in observed tropical depressions the implications of these differences in radial structures for using the flux form of the relevant conservation equations e g for pv substance or absolute vorticity are discussed

primary igneous anhydrite progress since its recognition in the 1982 el chichon trachyandesite abstract primary igneous anhydrite was first identified in 1982 el chichon pumices analysis of the sulfur budget for the eruption provided compelling evidence that the pre eruptive magma contained a significant gas phase at 7 km depth in order to account for the excess gas release of 5 9 million tons of so2 to the stratosphere by the eruption primary igneous anhydrite and a larger excess gas release of 20 million tons of so2 were noted for the significantly larger eruption of mount pinatubo in 1991 for which a separate gas phase at 7 9 km depth was also required by the sulfur budget pumices from both eruptions have mineral assemblages dominated by plagioclase and hornblende with minor biotite and show evidence for co nucleation and mutual inclusions of anhydrite and apatite both magmas were also very water rich and highly oxidized with oxygen fugacities 1 log unit above the synthetic ni nio buffer furthering the similarities between these two eruptions ion microprobe analyses of sulfur isotopic compositions of anhydrites in pumices from el chichon and mount pinatubo both showed that individual crystals are isotopically homogeneous but inter crystalline variations in 34s are well beyond analytical error this study reviews the history of thought regarding primary igneous anhydrite ten volcanic and plutonic analogues to the el chichon and mount pinatubo magmas are discussed all were similarly water rich and highly oxidized magmas hornblende is the dominant mafic phenocryst in all but one plutonic example in that case so much early anhydrite precipitated that no calcium remained to form hornblende biotite is very abundant in that exceptional plutonic case and is present in six of the other examples with primary igneous anhydrite sphene is known as an indicator mineral of high magmatic oxygen fugacity it was present in the 1982 el chichon pumices and in 6 of the other anhydrite bearing samples hornblende and biotite phenocrysts are also characteristic of the intermediate to felsic plutonic rocks that typically host porphyry cu deposits such magmas are also known to be water rich and highly oxidized a close spatial and petrogenetic connection exists between magmas with primary igneous anhydrite and magmatic hydrothermal ore deposits

evaluation of gases condensates and so2 emissions from augustine volcano alaska the degassing of a cl rich volcanic system after the march april 1986 explosive eruption a comprehensive gas study at augustine was undertaken in the summers of 1986 and 1987 airborne cospec measurements indicate that passive so2 emission rates declined exponentially during this period from 380 45 metric tons day t d on 7 24 86 to 27 6 t d on 8 24 87 these data are consistent with the hypothesis that the augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption gas samples collected in 1987 from an 870 c fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation and loss of h2o in the intake tube of the sampling apparatus thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases although not conclusive this restoration is consistent with the idea that the gases were in equilibrium at 870 c with an oxygen fugacity near the ni nio buffer these restored gas compositions show that relative to other convergent plate volcanoes the augustine gases are very hcl rich 5 3 6 0 mol hcl s rich 7 1 mol total s and h2o poor 83 9 84 8 mol h2o values of d and 18o suggest that the h2o in the dome gases is a mixture of primary magmatic water pmw and local seawater part of the cl in the augustine volcanic gases probably comes from this shallow seawater source additional cl may come from subducted oceanic crust because data by johnston 1978 show that cl rich glass inclusions in olivine crystals contain hornblende which is evidence for a deep source 25km for part of the cl gas samples collected in 1986 from 390 642 c fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible h and o isotope data suggest that these gases are variable mixtures of seawater fmw and meteoric steam these samples are much more h2o rich 92 97 h2o than the dome gases possibly due to a larger meteoric steam component the 1986 samples also have higher cl s s c and f cl ratios which imply that the magmatic component in these gases is from the more degassed 1976 magma thus the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the augustine magma reservoir even though they were collected a year later and contain a significant seawater component future gas studies at augustine should emphasize fumaroles on active lava domes condensates collected from the same lava dome fumarole have enrichments ot 107 102 in cl br f b cd as s bi pb sb mo zn cu k li na si and ni lower temperature 200 650 c fumaroles around the volcano are generally less enriched in highly volatile elements however these lower termperature fumaroles have higher concentration of rock forming elements probably derived from the wall rock

neutral thermospheric dynamics observed with two scanning doppler imagers 2 vertical winds 1 this article is the second in a series of three papers reporting on observations of the 630 0 nm thermospheric airglow emission by two spatially separated scanning doppler imagers sdi s in alaska in this article line of sight wind measurements from these instruments in four common volume regions lying along the great circle joining the two observatories have been used to derive estimates of the vertical wind in those common volumes these estimates are combined with the vertical winds measured directly in each of the station zeniths to resolve both the spatial and temporal variations of the vertical wind field data from four nights are presented as examples of the wave like oscillations and frequently high spatial correlations that are observed a statistical study of data from the full 19 night data set showed that the frequency of observing statistically significant correlation between vertical winds measured at separate locations decreased linearly with increasing separation a linear fit to this trend indicated that for this particular location and orientation the largest separation over which statistically significant correlation would be expected to occur is approximately 540 km

chemical and mineralogical trends during acid sulfate alteration of pyroclastic basalt at cerro negro volcano and implications for early mars 1 acid sulfate alteration of pyroclastic basalts in active fumaroles at cerro negro volcano nicaragua was studied as a means to infer the mineralogical and chemical consequences of basalt alteration in analogous environments on early mars at this site recently erupted basaltic cinders are undergoing alteration by so2 bearing steam during alteration silicate phenocrysts including plagioclase olivine and augite react much more rapidly than basaltic glass secondary mineralogy is dominated by a very limited number of phases that include amorphous silica gypsum fe bearing natroalunite and fe oxides oxyhydroxides including hematite and magnetite the major element chemistry of the deposits is controlled by two processes gradual depletion of the major cations other than si as the basalt components decompose and elements are mobilized out of the deposits and enrichment in ca and s from precipitation of gypsum with ca apparently supplied from sources below the surface reaction path models constrained by these observations but extrapolated to martian conditions predict that alteration of pyroclastic deposits in similar environments on mars should produce a secondary mineral assemblage that includes amorphous silica fe bearing natroalunite anhydrite kieserite and hematite iron bearing natroalunite was found to produce a mossbauer signal similar to that of jarosite suggesting that this phase should be considered as an alternative to the jarosite component identified at meridiani planum spheroidal hematite formed in close association with natroalunite suggests a pathway for formation of hematite deposits on mars

the motion of hurricane gloria a potential vorticity diagnosis abstract multilevel multinested analyses of hurricane gloria of 1985 are the most comprehensive kinematic dataset yet developed for a single hurricane a piecewise inversion technique is used with these analyses and the nonlinear balance equation to deduce the three dimensional distribution of potential vorticity pv that contributed to the deep layer mean dlm flow that steered gloria toward the northwest the background state is taken to be the azimuthally averaged winds in balance with a geopotential distribution on an f plane advantage is taken of the near linearity of the weak asymmetries near the hurricane s core and of pv in the environment thus ad hoc aspects of the linearization required by other investigators are effectively eliminated removal of the hurricane vortex and the use of a climatological mean background state are avoided as well the insensitivity of the results to the imposed lateral boundary conditions is also demonstrated wind anomalies attributable to pieces of anomalous p

characterization of respirable volcanic ash from the soufriere hills volcano montserrat with implications for human health hazards volcanic ash generated in the long lived eruption of the soufriere hills volcano montserrat is shown to contain respirable sub 4 m particles and cristobalite a crystalline silica polymorph respirable particles of cristobalite can cause silicosis raising the possibility that volcanic ash is a respiratory health hazard this study considers some of the main factors which affect human exposure to respirable volcanic ash namely the composition and proportions of respirable ash and the composition and concentrations of airborne suspended particulates the composition size distribution and proportion by weight of respirable particles in representative samples of the soufriere hills tephra dome collapse ash fall deposits dome collapse pyroclastic flow matrix vulcanian explosion ash and mixed ash have been characterized dome collapse ash fall deposits are significantly richer in respirable particles 12 wt than the other tephra samples in particular the matrices of dome collapse pyroclastic flow deposits 3 wt within the respirable fraction dome collapse ash contains the highest proportion of crystalline silica particles 20 27 number of which 97 wt is cristobalite compared with other primary tephra types 0 4 5 6 number this enrichment of crystalline silica in the dome collapse ash is most pronounced in the very fine particle fraction sub 2 m the results are explained as being due to significant size fractionation during fragmentation of pyroclastic flows resulting in a fines depleted dome collapse matrix and a fines rich dome collapse ash deposit for all sample types the sub 4 m fraction comprises 45 55 wt of the sub 10 m fraction aeolian deposit lahar deposit and airborne samples of suspended ash collected on filters were characterized these samples show enrichment of crystalline silica in the respirable fraction 10 18 number the results are consistent with ash in the environment having a mixed origin but originating predominantly from dome collapse eruptions the reworked ash however contains low proportions of respirable ash 3 wt compared to primary ash samples the concentration of ash particles re suspended by road vehicles on montserrat is found to decrease exponentially with height above the ground indicating higher exposure for children compared with adults pm4 concentration at 0 9 m height of two year old child is 3 times that at 1 8 m adult height the composition of the re suspended road particles is similar to that re suspended by the wind

a multiscale numerical study of hurricane andrew 1992 part vi small scale inner core structures and wind streaks abstract the objectives of part vi of this series of papers are to a simulate the finescale features of hurricane andrew 1992 using a cloud resolving grid length of 2 km b diagnose the formation of small scale wind streaks and c perform sensitivity experiments of varying surface fluxes on changes in storm inner core structures and intensity as compared to observations and a previous 6 km model run the results show that a higher resolution explicit simulation could produce significant improvements in the structures and evolution of the inner core eyewall and spiral rainbands and in the organization of convection the eyewall becomes much more compact and symmetric with its width decreased by half and the radius of maximum wind is reduced by 10 to 20 km a zone of deep and intense potential vorticity pv is formed at the edge of the eye a ring of maximum pv is collocated in regions of maximum upward motion in the eyewall and interacts strongly with the eyewall convection the convective cor

escape of unradiogenic osmium during sub aerial lava degassing evidence from fumarolic deposits piton de la fournaise reunion island abstract this study presents new re os isotope and elemental data in gas condensates and corresponding lavas in order to examine the geochemical behavior of these two elements during magma degassing at piton de la fournaise reunion island gas sublimates formed between 2007 and 2011 at temperature ranging from 400 to ca 100 c include na k sulfate aphthitalite na sulfate thenardite ca cu sulfate e g gypsum ca mg al fe fluoride e g ralstonite and native sulfur the high temperature deposits show trace element typical of volcanic gas with high enrichment in re 24 to 79 ppb almost two order of magnitude higher than the corresponding lavas but with os abundances similar to those of the lavas 14 132 ppt in contrast the os contents of the low temperature fluoride deposits 13 77 ppb are higher than any of the other condensates the fluorides are also enriched in re albeit to lesser extent than os 2 9 15 3 ppb based on high temperature samples the fluid melt partition coefficients estimated for re and os are 100 80 and 1 2 respectively considering 1 of fluid loss these partition coefficients translate into emanation coefficients of 0 50 0 17 0 65 for re and 0 01 0 0 03 for os these results indicate that re unlike os is highly volatile at piton de la fournaise osmium isotopic compositions of samples collected at medium and low temperature 187 os 188 os between 0 130 0 135 and plot within the range of the april 2007 lava flow and the historical lavas of piton de la fournaise i e 0 130 0 137 however the highest temperature condensates na k sulfates with t of 384 400 c yield lower 187 os 188 os ratios i e 0 124 0 129 within the field of mantle signal such unradiogenic compositions are best explained if old mantle sulfides occur in lavas and contribute to volcanic gases within the general frame of osmium mantle geochemistry loss of unradiogenic os during magmas degassing could help to explain osmium isotope disequilibrium between lavas and melting residues

origin of the duvertepe kaolin alunite deposits in simav graben turkey timing and styles of hydrothermal mineralization abstract the duvertepe district located on the western end of the simav graben is the largest known fossil hydrothermal kaolin deposit in turkey active hot springs occur to the north of simav city eynal citgol nasa and geothermal fields occur to the west of the graben hisaralan kaolin in the duvertepe district formed at the expense of miocene rhyolites rhyodacites and tuffs emplaced in a tectonically active system undergoing n s extension upward fan shaped deposits of silicification and kaolin are found along fault zones and define areas of enhanced kaolinization silica sinters located above the kaolin zones suggest that hydrothermal fluids followed the fracture systems and mark outflow of geothermal waters fractured volcanic rocks rich in glass shards bear sufficient porosity and permeability for hydrothermal circulation two mineral facies kaolinite and alunite dominate the deposits which respectively include 1 kaolinite alunite quartz and 2 alunite opal ct quartz halloysite kaolinite crystals are well formed hexagonal vermiform habits and alunite crystals are idiomorphic rhombohedral forms needle and tubular shaped halloysites are common in the alunite facies the 34 s values for alunite range from 1 55 to 6 18 kaolinites have d ranging from 49 0 to 94 3 and the 18 o values range from 5 8 to 14 8 calculated formation temperatures of kaolin mineralization using 18 o values suggest that hydrothermal alteration occurred in the range of 38 to 129 c independent k ar and 40 ar 39 ar ages of alunite are concordant and indicate that alteration occurred from 20 1 to 20 6 ma in the southern part of the graben and 17 3 to 19 2 ma in the northern part these results suggest that metasomatism by steam heated hydrothermal fluids sourced by rhyolitic magma is responsible for the duvertepe kaolin and alunite deposit origins

mount st augustine volcano fumarole wall rock alteration mineralogy zoning composition and numerical models of its formation process abstract intensely altered wall rock was collected from high temperature 640 c and low temperature 375 c vents at augustine volcano in july 1989 the high temperature altered rock exhibits distinct mineral zoning differentiated by color bands in order of decreasing temperature the color bands and their mineral assemblages are a white to grey tridymite anhydrite b pink to red tridymite hematite fe hydroxide molysite fecl 3 with minor amounts of anhydrite and halite and c dark green to green anhydrite halite sylvite tridymite with minor amounts of molysite soda and potash alum and other sodium and potassium sulfates the alteration products around the low temperature vents are dominantly cristobalite and amorphous silica with minor potash and soda alum aphthitalite alunogen and anhydrite compared to fresh 1986 augustine lava the altered rocks exhibit enrichments in silica base metals halogens and sulfur and show very strong depletions in al in all alteration zones and in iron alkali and alkaline earth elements in some of the alteration zones to help understand the origins of the mineral assemblages in altered augustine rocks we applied the thermochemical modeling program gasworks in calculations of a reaction of the 1987 and 1989 gases with wall rock at 640 and 375 c b cooling of the 1987 gas from 870 to 100 c with and without mineral fractionation c cooling of the 1989 gas from 757 to 100 c with and without mineral fractionation and d mixing of the 1987 and 1989 gases with air the 640 c gas rock reaction produces an assemblage consisting of silicates tridymite albite diopside sanidine and andalusite oxides magnetite and hercynite and sulfides bornite chalcocite molybdenite and sphalerite the 375 c gas rock reaction produces dominantly silicates quartz albite andalusite microcline cordierite anorthite and tremolite and subordinate amounts of sulfides pyrite chalcocite and wurtzite oxides magnetite sulfates anhydrite and halides halite the cooling calculations produce a anhydrite halite sylvite b cu mo fe and zn sulfides c mg fluoride at high temperature 370 c d chlorides fluorides and sulfates of mn fe zn cu and al at intermediate temperature 170 370 c and e hydrated sulfates liquid sulfur crystalline sulfur hydrated sulfuric acid and water at low temperature

geochemistry mineralogy and chemical modeling of the acid crater lake of kawah ijen volcano indonesia the kawah ijen volcano with a record of phreatic eruptions has its 1000 m wide crater filled with a lake that has existed for at least one century at present the lake waters are hot t 37 c strongly mineralized tds 105 g l and extremely acidic ph 0 4 by its volume the javanese lake is probably the largest accumulation in the world of such acidic waters mineralogy of the suspended solids within the lake waters suggests that concentrations of si ca ti and ba are controlled by precipitation of silica gypsum anatase and barite lake sediment is composed of chemical precipitates with composition similar to the suspended solids thermodynamic calculations predict that the lake waters have reached equilibrium with respect to cristobalite barite gypsum anglesite celestite and amorphous silica in agreement with the analytical observations significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized sulfides are absent in the water column but are always present in the native s spherules that form porous aggregates which float on the lake the presence of native s provides direct evidence of more reduced conditions at the lake floor where h 2 s is probably being injected into the lake with progressive addition of h 2 s to the acid waters native s pyrite and enargite are theoretically predicted to be saturated reactions between upward streaming h 2 s bearing gases discharged by subaqueous fumaroles and metals dissolved in the acidic waters could initiate precipitation of these sulfides a model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake results show that strongly acidic sulfate rich solutions are formed under oxidizing conditions at high gas water ratios reactions between the acidic fluids and the ijen andesite were modeled to account for elevated cation concentrations in lake water current concentrations of conservative rockforming elements are produced by dissolution of approximately 60 g of andesite per kg of acid solution complete neutralization of the acid lake waters by reaction with the wallrock produces a theoretical alteration assemblage equivalent to that observed in volcano hosted acid sulfate epithermal ore deposits

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

evolution of the monte negro acid sulfate au ag deposit pueblo viejo dominican republic important factors in grade development this study was undertaken to determine the geologic factors that were important in making pueblo viejo which contains over 600 000 kg of gold in relatively high grade ore one of the few acid sulfate deposits to be mined economically on a large scale orebodies at pueblo viejo including monte negro the focus of this study are found around a maar diatreme complex that formed in the upper part of the lower cretaceous los ranchos formation ore is hosted by spilite spilite derived conglomerate and intramaar carbonaceous sandstone and mudstone regional seawater alteration of these rocks was overprinted by two stages of advanced argillic alteration both of which are associated with precious metals stage i produced deep alunite quartz pyrite and overlying kaolinite quartz pyrite assemblages and deposited gold in association with disseminated pyrite in wall rock stage ii which overprinted stage i produced deep pyrophyllite or diaspore and an overlying recrystallized silica cap pyrite or sphalerite or enargite veins that probably formed in response to hydrofracturing of the silica cap contain gold grades of as much as 100 ppm vein density and assay data show that approximately 60 percent of the gold at monte negro is in disseminated stage i ore with the remainder in stage ii veins phase equilibria and sulfur isotope thermometry show that stage i alteration took place below 260 degrees c at ph values between 2 and 3 stage ii pyrophyllite or diaspore formation occurred above 285 degrees c from a fluid with an initial ph of 1 to 1 5 while the silica caps formed below 220 degrees c geologic constraints indicate that stage i wall rock gold at monte negro was deposited by sulfidation of fe rich wall rock whereas stage ii vein hosted gold could have formed by cooling boiling or mixing with overlying ground water use of the programs solveq and chiller to evaluate the relative efficiencies of these ore forming processes confirms that sulfidation was capable of depositing disseminated stage i gold whereas stage ii vein gold was probably deposited by boiling related to pressure release during hydrofracturing and subsequent mixing with ground water these observations indicate that development of grade and tonnage at pueblo viejo was greatly facilitated by 1 the porous permeable maar diatreme complex which hosted large shallow hydrothermal cells and probably served as a conduit for rising magmatic gases 2 the presence of iron rich wall rock which caused early deposition of background disseminated gold by sulfidation and 3 later hydrothermal activity which formed impermeable silica caps that hydrofractured to create the high grade vein overprint remobilization of stage i background gold into stage ii veins might also have been an important factor in upgrading the deposits exploration for similar deposits should focus on areas of explosive volcanism in andesitic island arc terranes

spatial sampling of the thermospheric vertical wind field at auroral latitudes 1 results are presented from two nights of bistatic doppler measurements of neutral thermospheric winds using fabry perot spectrometers at mawson and davis stations in antarctica a scanning doppler imager sdi at mawson and a narrow field fabry perot spectrometer fps at davis have been used to estimate the vertical wind at three locations along the great circle joining the two stations in addition to the vertical wind routinely observed above each station these data were obtained from observations of the 630 0 nm airglow line of atomic oxygen at a nominal altitude of 240 km low resolution all sky images produced by the mawson sdi have been used to relate disturbances in the measured vertical wind field to auroral activity and divergence in the horizontal wind field correlated vertical wind responses were observed on a range of horizontal scales from 150 to 480 km in general the behavior of the vertical wind was in agreement with earlier studies with strong upward winds observed poleward of the optical aurora and sustained though weak downward winds observed early in the night the relation between vertical wind and horizontal divergence was seen to follow the general trend predicted by burnside et al 1981 whereby upward vertical winds were associated with positive divergence and vice versa however a scale height approximately 3 4 times greater than that modeled by nrlmsise 00 was required to best fit the data using this relation

how does the hot core of a volcanic plume control the sulfur speciation in volcanic emission 1 volcanic eruptions inject sulfur into the atmosphere mainly in form of so2 and h2s the ratio of these species h2s so2 which is usually used as the mirror of the oxidation state of the source magma varies significantly according to the type of activity tectonic setting etc this study aims to investigate the role of the hot core of plinian and sub plinian volcanic plumes t 600 c in sulfur speciation based on the thermodynamic equilibrium in this temperature range we consider the hot core as a box model in which 1000 c magmatic gas and 25 c ambient air are mixed and show that it functions as a hot oxidizing reactor for s species processes inside the hot core usually decrease the h2s content of the system but can either increase or decrease so2 depending on initial oxidation state thus the so2 injected into the atmosphere is not essentially generated directly from the magma but it can be produced in the hot core as the result of h2s oxidation besides volcanic cloud compositions do not mirror the source conditions considering three types of tectonic settings convergent plate divergent plate and hot spot we propose that h2s emission is more likely under reduced conditions in divergent plate and hot spot volcanic settings

structure and formation of an annular hurricane simulated in a fully compressible nonhydrostatic model tcm4 abstract the structure and formation of an annular hurricane simulated in a fully compressible nonhydrostatic tropical cyclone model tcm4 are analyzed the model is initialized with an axisymmetric vortex on an f plane in a quiescent environment and thus the transition from the nonannular hurricane to the annular hurricane is attributed to the internal dynamics the simulated annular hurricane has all characteristics of those recently documented by knaff et al from satellite observations quasi axisymmetric structure large eye and wide eyewall high intensity and suppressed major spiral rainbands a striking feature of the simulated annular hurricane is its large outward tilt of the wide eyewall which is critical to the quasi steady high intensity and is responsible for the maintenance of the large size of the eye and eyewall of the storm although the annular hurricane has a quasi axisymmetric structure marked low wavenumber asymmetries exist in the eyewall region the formation of the simulated a

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere

lead isotopes behavior in the fumarolic environment of the piton de la fournaise volcano reunion island abstract the recent activity of the piton de la fournaise volcano offers a rare opportunity to address the issue of pb isotope behavior in volcanic fumaroles as the composition of the degassing source is accurately and precisely known gas sublimates formed between 2007 and 2011 at temperature ranging from 400 to ca 100 c include na k sulfate aphthitalite ca cu sulfate e g gypsum na sulfate thenardite ca mg al fe fluoride e g ralstonite and native sulfur the high temperature deposits show trace element patterns typical of volcanic gas with pb concentration up to 836 ppm while the low temperature deposits are depleted in most volatile elements pb only for low temperature fluoride samples do pb isotope compositions plot significantly outside the field of lavas the isotopic shift is ascribed to leaching ubiquitous unradiogenic phases e g sulfides by acidic gas condensates the similarity in pb isotope signature between lavas and sublimate samples more representative of the gas phase sulfates indicates that the net fractionation of pb isotopes resulting from volatilization and condensation processes is smaller than the precision of pb isotope measurements better than 60 ppm a m u the absence of net fractionation could result from negligible isotope fractionation during pb volatilization followed by extensive condensation of gaseous pb with possibly significant isotopic fractionation at this stage although this scenario has to be refined by more direct measurement of the gas phase and its general applicability tested it suggests that a small fraction resolving very small isotopic differences between magmas and their gaseous products remains an analytical challenge high precision pb isotope measurements rest not only on instrumental performance but also on high yield chemistry as pb isotopes drastically fractionate 800 ppm a m u upon elution on anionic resin for 50 pb recovery the estimated isotopic bias is plus or minus 60 80 ppm a m u depending on which of the early isotopically light or late isotopically heavy pb fraction is lost

seasonal dependence of northern high latitude upper thermospheric winds a quiet time climatological study based on ground based and space based measurements this paper investigates the large scale seasonal dependence of geomagnetically quiet time northern high latitude f region thermospheric winds by combining extensive observations from eight ground based optical remote sensing and three space based optical remote sensing and in situ instruments to provide a comprehensive picture of the wind morphology data are assimilated into a seasonal empirical vector wind model as a function of season latitude and local time in magnetic coordinates the model accurately represents the behavior of the constituent data sets there is good general agreement among the various data sets but there are some major offsets between goce and the other data sets especially on the duskside the assimilated wind patterns exhibit a strong and large duskside anticyclonic circulation cell sharp latitudinal gradients in the duskside auroral zone strong antisunward winds in the polar cap and a weaker tendency toward a dawnside cyclonic circulation cell the high latitude wind system shows a progressive intensification of wind patterns from winter to equinox to summer the latitudinal extent of the duskside circulation cell does not depend strongly on season zonal winds show a mainly diurnal variation two extrema around polar and middle latitudes and semidiurnal variation four extrema at auroral latitudes meridional winds are primarily diurnal at all high latitudes the strength of zonal winds channeling through the auroral zone on the duskside is strongest in the summer season the vorticity of the wind pattern increases from winter to summer whereas divergence is maximum in equinox in all three seasons divergence is weaker than vorticity

naturally acid waters from copahue volcano argentina volcanic acid sulfate chloride brines form through absorption of volcanic vapors in shallow reservoirs of meteoric water reaction with surrounding volcanic rocks leads to partial neutralization of the fluids and precipitation of secondary minerals chemical data of such acid waters from copahue volcano argentina covering 8 years of observations show evidence for changes in composition related to water rock interaction at depth prior to emergence of the fluids at the surface the chemical composition changed dramatically during the 2000 eruption of copahue with enhanced concentrations and fluxes of mg na fe and al followed in 2001 by rapidly declining concentrations and element fluxes the subsequent 5 years saw more variable element ratios and strong depletions in k and al most incompatible elements are released from the rock matrix stochiometrically whereas some elements are enriched through vapor input from the magma as pb zn most fluids have lree enrichments relative to the rock matrix but during periods of new magma intrusion the lree enrichment decreases as does the magnitude of the negative eu anomaly in the fluids these observations are interpreted assuming early dissolution of plagioclase olivine and volcanic glass that occurs during intrusion of new magma into the hydrothermal system the high field strength elements are virtually immobile even in these hot acid fluids with nb and ta more so than hf and zr the mobility of u and th in these fluids is comparable at variance with th behavior in neutral fluids the local rivers and lakes of copahue are fertilized by volcanic dissolved p and most surface waters with ph 3 have high levels of as the acid fluids from copahue may be surficial analogs for deep subduction fluids that evolve below zones of arc magma generation as well as for early mars environments that are thought to have had large acid lakes