concomitant evolution of tectonic environment and magma geochemistry ambrym volcano vanuatu new hebrides arc ambrym volcano lies in the central part of the new hebrides island arc near the latitude where the d entrecasteaux zone is colliding with the arc it is a 35 km x 50 km mainly basaltic stratovolcano constructed in four distinct parts i well preserved remnants of an old edifice in the north ii a nloo aligned oval shaped basal hawaiian type shield volcano iii apyroclasticcone cut by aconcentric 12 kmwide caldera and iv post caldera basaltic suites both intra and extra caldera considering kzo la and zr variations three major trends characterize the geochemistry of ambrym one medium k mk to high k hk tholeiitic to calc alkaline basaltic trend and two more evolved trends respectively mk and hk from basaltic to dacitic and rhyodacitic compositions these magmatic suites correspond to several volcanic phases 1 older mk basalts forming the tuvio vetlam dalahum edifice 2 mk to hk basalts forming the basal shield volcano 3 mk andesites and rhyodacites forming the first pyroclastic sequence of the ambrym pyroclastic series aps which probably initiated the formation of the caldera 4 mk to hk basalts and andesites forming surtseyan then strombolian pyroclastic sequences 2 3 and 4 of the aps and 5 post caldera mk to hk basalts forming the recent olivine porphyritic and plagioclase porphyritic suites locally associated with more evolved hk andesitic volcanic rocks in the eastern part of the caldera la yb n and la k n ratios 2 5 9 and 1 3 2 2 respectively and zr contents indicate that the parental magmas originated from incremental batch melting or fractional melting 21 25 during uplift of a single spinel lherzolite source from at least60 to 45 km depth in response to modifications in the tectonicenvironment due to ongoing collision with the d entrecasteaux zone however k and la contents require prior enrichments by possible mantle metasomatism associated with subduction fractionation of olivine plagioclase clinopyroxene and fe ti oxides explain most of the major and trace element variations in the resulting liquids and interaction between magmas rising from two distinct chambers combined with massive introduction of seawater into the edifice appear to be the major causes of the giant eruption leading to caldera formation more recent activity of the volcano is principally related to shallow incremental batch melting or fractional melting and to fractionation in magma chambers associated with n100 rifting

periodic volcanic degassing behavior the mount etna example 1 in contrast to the seismic and infrasonic energy released from quiescent and erupting volcanoes which have long been known to manifest episodes of highly periodic behavior the spectral properties of volcanic gas flux time series remain poorly constrained due to a previous lack of hightemporal resolution gas sensing techniques here we report on so2 flux measurements performed on mount etna with a novel uv imaging technique of unprecedented sampling frequency 0 5hz which reveal for the first time a rapid periodic structure in degassing from this target these gas flux modulations have considerable temporal variability in their characteristics and involve two period bands 40 250 and 500 1200s a notable correlation between gas flux fluctuations in the latter band and contemporaneous seismic root mean square values suggests that this degassing behavior may be generated by periodic bursting of rising gas bubble trains at the magma air interface citation tamburello g a aiuppa a j s mcgonigle p allard a cannata g giudice e p kantzas and t d pering 2013 periodic volcanic degassing behavior the mount etna example geophys res lett 40 4818 4822 doi 10 1002 grl 50924

observation of so2 degassing at stromboli volcano using a hyperspectral thermal infrared imager abstract thermal infrared tir imaging is a common tool for the monitoring of volcanic activity broadband cameras with increasing sampling frequency give great insight into the physical processes taking place during effusive and explosive event while fourier transform infrared ftir methods provide high resolution spectral information used to assess the composition of volcanic gases but are often limited to a single point of interest continuing developments in detector technology have given rise to a new class of hyperspectral imagers combining the advantages of both approaches in this work we present the results of our observations of volcanic activity at stromboli volcano with a ground based imager the telops hyper cam lw when used to detect emissions of sulfur dioxide so2 produced at the vent with data acquired at stromboli volcano italy in early october of 2015 we have developed an innovative technique based on a curve fitting algorithm to quickly extract spectral information from high resolution datasets allowing fast and reliable identification of so2 we show in particular that weak so2 emissions such as inter eruptive gas puffing can be easily detected using this technology even with poor weather conditions during acquisition e g high relative humidity presence of fog and or ash then artificially reducing the spectral resolution of the instrument we recreated a variety of commonly used multispectral configurations to examine the efficiency of four qualitative so2 indicators based on simple brightness temperature difference btd our results show that quickly changing conditions at the vent including but not limited to the presence of summit fog render the establishment of meaningful thresholds for btd indicators difficult building on those results we propose recommendations on the use of multispectral imaging for so2 monitoring and routine measurements from ground based instruments

spectroscopic evidence for a lava fountain driven by previously accumulated magmatic gas the eruption of mount etna in 2000 was notable for an exceptional series of 64 periodic lava fountains propelling lava fragments to heights of up to 900 metres it has been difficult to determine which of two suggested sources of power gas release from the magma itself during its rapid ascent or a build up of pressure from gas accumulated at depth is the driving force for these dramatic jets but one of the etna fountains provided volcanologists with the opportunity to use remote sensing not that remote see picture on the following page to determine the infrared spectra of the gas phase this revealed the chemical composition of the gas that powered this fountain as consistent with an origin in an accumulated gas layer lava fountains are spectacular continuous gas jets propelling lava fragments to heights of several hundred metres which occasionally occur during eruptions of low viscosity magmas1 2 3 4 5 whether they are generated by the effervescent disruption of fast rising bubbly melt2 3 4 5 or by the separate ascent of a bubble foam layer accumulated at depth6 7 still remains a matter of debate8 no field measurement has yet allowed firm discrimination between these two models a key insight into the origin of lava fountains may be gained by measuring the chemical composition of the driving gas phase this composition should differ markedly depending on whether the magma degassing occurs before or during eruption9 10 here we report the analysis of magmatic gas during a powerful 250 600 m high lava fountain measured with fourier transform infrared spectroscopy11 12 13 14 on mount etna sicily the abundances of volcanic gas species determined from absorption spectra of lava radiation reveal a fountain gas having higher co2 s and s cl ratios than other etnean emissions14 15 16 17 18 and which cannot derive from syn eruptive bulk degassing of etna basalt19 20 instead its composition suggests violent emptying of a gas bubble layer previously accumulated at about 1 5 km depth below the erupting crater

conduit convection driving persistent degassing at basaltic volcanoes abstract the persistent release of gas at basaltic volcanoes where there is a low magma eruption rate can be driven by an exchange flow of magma in the conduit in which gas rich magma ascends degasses and crystallises and then sinks back down the conduit the driving force of the flow is provided by the density difference between the buoyant bubble rich magma at depth and the dense degassed crystallised magma at shallow levels in this study we attempt to constrain the physical and chemical processes driving an exchange flow of magma at stromboli aeolian archipelago italy the model uses a simple cylindrical geometry we define degassing and crystallisation paths of the ascending and descending magmas constrained by gas flux and melt inclusion data given in the literature to produce a three phase model of ascending and descending magmas driving persistent gas fluxes we calculate the viscosity of the three phase magma using end member rheological models for bubble and crystal suspensions combining our modelled magma properties with analogue exchange flow experiments we can relate the regime of magma flow driving persistent degassing to pressure at pressures 90 mpa 3 km the viscosity ratio is 100 and the regime is predicted to be side by side flow with both ascending and descending magmas adjacent to a portion of the conduit wall at pressures 90 mpa 3 km the viscosity ratio between the ascending and descending magma is 100 and the flow is predicted to be core annular flow with the ascending vesiculating magma in the inner core and the more crystalline degassed magma flowing down along the conduit wall by analogy we hypothesise that degassed magma would flow down along the walls in dike like plumbing geometries that have been proposed for the deeper strombolian system analogue experiments suggest that exchange flows do not overturn under conditions of maximum volume flux we use an empirical relationship to characterise the volume flux of the exchange flow and show that the radius of a cylindrical conduit required to account for the observed persistent gas flux at stromboli at 0 1 mpa is 1 m

cyclic degassing of erebus volcano antarctica field observations have previously identified rapid cyclic changes in the behaviour of the lava lake of erebus volcano in order to understand more fully the nature and origins of these cycles we present here a wavelet based frequency analysis of time series measurements of gas emissions from the lava lake obtained by open path fourier transform infrared spectroscopy this reveals i a cyclic change in total gas column amount a likely proxy for gas flux with a period of about 10 min and ii a similarly phased cyclic change in proportions of volcanic gases which can be explained in terms of chemical equilibria and pressure dependent solubilities notably the wavelet analysis shows a persistent periodicity in the co2 co ratio and strong periodicity in h2o and so2 degassing the peaks of the cycles defined by maxima in h2o and so2 column amounts coincide with high co2 co ratios and proportionally smaller increases in column amounts of co2 co and ocs we interpret the cycles to arise from recharge of the lake by intermittent pulses of magma from shallow depths which degas h2o at low pressure combined with a background gas flux that is decoupled from this very shallow magma degassing

stability of lava lakes a physical model of a generic lava lake system is developed we derive the requisite conditions for the existence of an equilibrium lava lake in which magmastatic pressure at the base of the conduit balances the pressure in the underlying magmatic reservoir the stability of this lava lake system is tested by investigating the response of the system to perturbation we develop a graphical method based on the system s pressure depth profile to predict the subsequent behaviour of the system despite the simplicity of the modelled system we find a broad behavioural spectrum initially the rise of bubbles through the magma is ignored in this case both stable long lived lava lakes and unstable lakes that are prone to sudden draining are predicted the stability of the system is shown to be controlled by lake conduit geometry the solubility and gas expansion laws and the magma s volatile content we show that an unstable lake must collapse to a new stable equilibrium subsequent recharge of the system by for example conduit overturn would promote a return to the original equilibrium giving rise to cyclic behaviour such a mechanism is consistent with lava lake behaviour during the 1983 1984 pu u o o eruption of kilauea when the rise of bubbles through the magma is considered our model predicts that stable lakes must drain over time we therefore deduce that persistently degassing stable lava lakes such as those observed at mt erebus antarctica and mauna ulu kilauea hawaii must have an effective conduit convection mechanism or an exogenous supply of bubbles from depth

observation of the eruption sequence and formation process of a temporary lava lake during the june august 2015 mt raung eruption indonesia using high resolution and high frequency satellite image datasets abstract from june to august 2015 mt raung located at the east end of java indonesia erupted effusively with strombolian activity at the intra caldera cinder cone the effused lava from the base of the cone entirely buried the caldera floor with a lava bed and ultimately formed a temporary lava lake in this study details of the eruption sequence and formation process of the temporary lava lake are analyzed based on a series of high resolution images combined with the high frequency thermal observation results of himawari 8 the volume of effused lava was also estimated using a digital elevation model aster gdem based on the lava bed bathymetry in the caldera and lava bed distribution at several points over the course of the eruption the total effusion volume was estimated to be 7 5 107 m3 and the average effusion rate was 1 4 106 m3 day the activity consisted of four stages the precursory stage was characterized by low level thermal anomalies which are thought to result from high temperature spots at the bottom of several pits formed in the buried vent probably due to magma head partial exposure or gas emission pulses 1 and 2 were effusive stages that formed the lava bed the pattern recognized in the time series variation of thermal anomalies was confirmed to reflect the lava effusion rate using the volumes estimated in this study the lava bed is divided into the lower and upper lava groups which were generated in pulses 1 and 2 respectively except for the fine lobes formed around the margin of the lower lava group the terminal stage also showed low level thermal anomalies most likely caused by gas emissions the intra caldera cone grew to approximately 100 m higher than its initial height by mid august and then collapsed into the conduit at the end of the terminal stage the lava bed increased in thickness through lobe multi layering and later through the addition of lava directly from the vent into the lava bed interior over the course of the lava bed growth the bed outline nearly matched the caldera contours uplift of the lava bed surface caused lateral fluidization of the bed and molten lava was extruded at the bed margins forming fine lobes this process enlarged the zone of fine lobes around the lava bed thus the lava bed growth resulted in the appearance of a lava lake in the middle of pulse 1 a small amount of hot material was thrown onto the slope beyond the caldera rim in the future the caldera floor uplift caused by this activity approximately 49 m will increase the risk of erupted material ejection outside the caldera in a comparison with the 2013 15 nishinoshima eruption which was a similar effusive eruption mt raung was shown to have predominantly large lobes over most of the lava bed while in nishinoshima narrow medium scale lobes occupied the majority of the surface this may be attributed to the high effusion rate of lava for mt raung which was approximately seven times higher on average than the lava effusion rate for nishinoshima

polar mesosphere and lower thermosphere dynamics 1 mean wind and gravity wave climatologies 1 mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere mlt the data were derived using mf radars at davis 69 s 78 e and syowa 69 s 40 e in the antarctic and poker flat 65 n 147 w and andenes 69 n 16 e in the arctic the dynamics of the antarctic mlt are found to be significantly different from the arctic mlt summer maxima in both the westward and equatorward winds occur closer to the solstice in the antarctic than in the arctic the greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the antarctic mlt than in the arctic where dynamical effects appear to be more important gravity wave observations also suggest that wave drag may be greater in the arctic than in the antarctic the equatorward flow near the mesopause persists later in summer in the arctic than in the antarctic as do observations of polar mesospheric clouds and polar mesospheric summer echoes all three phenomena begin at about the same time in each hemisphere but end later in the arctic than in the antarctic it is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the mlt seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations

on the nature of short period mesospheric gravity wave propagation over halley antarctica 1 as part of a collaborative program between british antarctic survey and utah state university measurements were made using an all sky airglow imager located at the u k halley station 76 s 27 w during the 2000 and 2001 austral winter seasons from april through to early september a co located imaging doppler interferometer was utilized to obtain coincident wind measurements for a total of 171 wave events this study comprises the first detailed climatological investigation of the propagation nature freely propagating doppler ducted or evanescent of individual quasi monochromatic short period wave events at a high southern latitude distributions of the derived vertical wavelength exhibit an interquartile range from 16 48 km with a median vertical wavelength of 21 km the majority of the wave events were found to be freely propagating waves with only 5 exhibiting a clear doppler ducted signature while 15 of the waves were found to be evanescent in nature although no coincident temperature measurements were available subsequent saber temperature measurements suggest that up to 28 of the measured temperature profiles are capable of providing a ducted environment for the observed wave field this is in sharp contrast to findings at mid and low latitudes where these waves have been shown to be prone to doppler ducted motion it is suggested that the relatively weak wind field and associated tidal wind amplitudes over halley are not capable of forming a significant doppler ducted region to sustain a substantial amount of ducted waves belonging to the detectable spectrum of the airglow imager as these wind fields are comparable to wind fields found at other polar latitudes we hypothesize that the majority of short period gravity waves observed in the polar mesosphere are freely propagating and thus an important source of energy transfer into the mlt region

gas and aerosol emissions from villarrica volcano chile here we report results from a multidisciplinary field campaign at villarrica volcano chile in march 2009 a range of direct sampling and remote sensing techniques was employed to assess gas and aerosol emissions from the volcano and extend the time series of measurements that have been made during recent years airborne traverses beneath the plume with an ultraviolet spectrometer yielded an average so2 flux of 3 7 kg s 1 this value is similar to previous measurements made at villarrica during periods of quiescent activity the composition of the plume was measured at the crater rim using electrochemical sensors and for the first time open path fourier transform infrared spectroscopy yielding a composition of 90 5 mol h2o 5 7 co2 2 6 so2 0 9 hcl 0 3 hf and 0 01 h2s comparison with previous gas measurements made between 2000 and 2004 shows a correlation between increased so2 hcl ratios and periods of increased activity base treated filter packs were also employed during our campaign yielding molar ratios of hbr so2 1 1 10 4 hi so2 1 4 10 5 and hno3 so2 1 1 10 3 in the gas phase our data represent the most comprehensive gas inventory at villarrica to date and the first evaluation of hbr and hi emissions from a south american volcano sun photometry of the plume showed the near source aerosol size distributions were bimodal with maxima at 0 1 and 1 m these findings are consistent with results from analyses in 2003 electron microscope analysis of particulate matter collected on filters showed an abundance of spherical micron sized particles that are rich in si mg and al non spherical s rich particles were also observed

rain plume interactions at nyiragongo and nyamulagira volcanoes and associated rainwater hazards east africa abstract a rain gauge network consisting of 13 stations was installed on the volcanic fields around nyiragongo and nyamulagira volcanoes as well as in the surrounding villages and goma city dr congo from december 2013 to october 2015 the rain gauges were then sampled on a monthly basis in order to evaluate the influence of volcanic emissions on rain chemistry and rainwater quality this is the first temporally distributed dataset of rain chemistry from this densely populated region where the two africa s most active volcanoes 14 km apart continuously eject gases and ash to the atmosphere and where rainwater represents an important water resource the results revealed that volcanic emissions are the primary source of the dissolved loads wind blown dust dissolution is in fact occasionally the dominant source of major cations at cities and villages that are remote with respect to the volcano summits a few sites located in the forested virunga national park are neither significantly impacted by volcanic emissions nor wind blown dust the combined contribution of volcanic gases and the dissolution of volcanic ash and soil dust determined the ph of the rainwater thus areas with limited volcanic impact showed higher ph values up to 7 6 while those that experience major volcanic impact showed lower ph values as low as 3 1 as a consequence of the continuous input of acidic volcanic gases the chemical composition of rain varies according to location and was driven by changes in wind direction nearly all the sites showed prominent temporal variations in dissolved loads which were essentially related to the variations in precipitation amount due to seasonal changes the rain dissolved loads the bulk atmospheric deposition fluxes e g 0 5 24 6 t km 2 yr 1 for fluoride and 22 6 176 6 t km 2 yr 1 for total dissolved substances and the spatial variations converged to show that localities to the west and southwest of mt nyiragongo are the most strongly impacted by volcanic emissions these areas to the west and southwest which experience higher rates of f deposition also coincide with the locations of villages and small cities where endemic dental fluorosis occurs such a relationship is explained by the use of f rich water in all domestic activities including as drinking water in the region

slug stability in flaring geometries and ramifications for lava lake degassing long lived persistently active lava lakes are rare but have been studied extensively because they may provide a natural laboratory for studying magmatic convection in basaltic and other low viscosity volcanoes however lava lakes differ from other volcanic systems in various ways particularly geometry the presence of the lava lake requires a sudden and significant flaring of the conduit the goal of this paper is to advance our understanding of the effect that a sudden increase in the conduit width has on the stability of large gas slugs and bubbles ascending from the plumbing system we investigate this question by linking analog laboratory experiments to direct numerical simulations in two dimensions we find that the rapid change in the geometry associated with the transition from the conduit to the lava lake causes large gas slugs to break up the nondimensional regime over which we observe the breakup depends sensitively on the flare angle of the lava lake and the importance of inertial effects in the flow implying that degassing related eruptive activity at open system volcanoes is sensitive to the upper conduit and lake geometries applying this idea to the likely geometries and viscosities of actual lava lakes our study suggests that all lava lakes except erebus fall well within the regime where large gas slugs are prone to breakup

magmatic degassing at erta ale volcano ethiopia abstract here we report measurements of the chemical composition and flux of gas emitted from the central lava lake at erta ale volcano ethiopia made on 15 october 2005 we determined an average so 2 flux of 0 69 0 17 kg s 1 using zenith sky ultraviolet spectroscopy of the plume and molar proportions of magmatic h 2 o co 2 so 2 co hcl and hf gases to be 93 58 3 66 2 47 0 06 0 19 and 0 04 respectively by open path fourier transform infrared ftir spectrometry together these data imply fluxes of 7 3 0 7 0 008 0 03 and 0 004 kg s 1 for h 2 o co 2 co hcl and hf respectively these are the first ftir spectroscopic observations at erta ale and are also some of the very few gas measurements made at the volcano since the early 1970s gerlach t m 1980b investigation of volcanic gas analyses and magma outgassing from erta ale lava lake afar ethiopia journal of volcanology and geothermal research 7 3 4 415 441 we identify significant increases in the proportion of h 2 o in the plume with respect to both co 2 and so 2 across this 30 year interval which we attribute to the depletion of volatiles in magma that sourced effusive eruptions during the early 1970s and or to fractional magma degassing between the two active pit craters located in the summit caldera

rheological behavior of bubble bearing magmas abstract the vesiculation of the rising magma in a volcanic conduit results in a large change in the viscosity of magma understanding the effect of bubbles on the viscous behavior of bubble melt mixtures over a wide range of bubble volume fractions is essential for accurate modeling of the volcanic processes in this study new equations for the relative viscosity of concentrated bubble bearing suspensions are developed using a differential scheme along with the solution of an infinitely dilute suspension of bubbles out of the four models developed in the paper two models predict the relative viscosity to be a function of only two variables capillary number and volume fraction of bubbles there are no adjustable parameters in these models the remaining two models include an additional parameter that is the maximum packing volume fraction of bubbles the proposed models are evaluated using published numerical and experimental data on the relative viscosity of concentrated suspensions of bubbles the viscosity models for bubble bearing suspensions developed in this study are useful in modeling of the volcanic processes

shallowly driven fluctuations in lava lake outgassing gas pistoning kīlauea volcano abstract lava lakes provide ideal venues for directly observing and understanding the nature of outgassing in basaltic magmatic systems k lauea volcano s summit lava lake has persisted for several years during which seismic and infrasonic tremor amplitudes have exhibited episodic behavior associated with a rise and fall of the lava surface gas pistoning since 2010 the outgassing regime of the lake has been tied to the presence or absence of gas pistoning during normal behavior no gas pistoning the lake is in a spattering regime consisting of higher tremor amplitudes and gas emissions in comparison gas piston events are associated with an abrupt rise in lava level up to 20 m during which the lake enters a non spattering regime with greatly decreased tremor and gas emissions we study this episodic behavior using long term multidisciplinary monitoring of the lake including seismicity infrasound gas emission and geochemistry and time lapse camera observations the non spattering regime i e rise phase of a gas piston cycle reflects gas bubbles accumulating near the top of the lake perhaps as a shallow foam while spattering regimes represent more efficient decoupling of gas from the lake we speculate that the gas pistoning might be controlled by time varying porosity and or permeability in the upper portions of the lava lake which may modulate foam formation and collapse competing models for gas pistoning such as deeply sourced gas slugs or dynamic pressure balances are not consistent with our observations unlike other lava lakes which have cyclic behavior that is thought to be controlled by deeply sourced processes external to the lake itself we show an example of lava lake fluctuations driven by cycles of activity at shallow depth and close to the lake s surface these observations highlight the complex and unsteady nature of outgassing from basaltic magmatic systems

halogen cycling and precious metal enrichment in sub volcanic magmatic systems insights from the rum layered intrusion scotland abstract the cycling of the halogens in sub volcanic systems may play an important role in magmatic ore deposit formation and the emission of climate altering gases via volcanic outgassing however the mobile and reactive nature of the halogens as well as their typically low abundances in most intrusive igneous rocks means that their behaviour in shallow crustal level magmatic systems is difficult to constrain we present data from the 60 ma rum layered suite nw scotland utilising the neutron irradiation noble gas mass spectrometry ni ngms technique to provide insight into the provenance and behaviour of cl br and i in magma chamber and precious metal enrichment processes as a well characterised and superbly exposed example of an open system sub volcanic magmatic body the rum intrusion is an ideal locality to investigate halogen behaviour in this context our data reveal concentrations of

the role of large bubbles detected from acoustic measurements on the dynamics of erta ale lava lake ethiopia the activity at the surface of the lava lake on erta ale volcano ethiopia shows that large bubbles are regularly breaking at a fixed position on the lava lake this is also where the small lava fountains are sometimes produced since this location is likely to be directly above the volcanic conduit feeding the lava lake we have done continuous measurements between march 22 and 26 2003 to understand the degassing of a volcano in permanent activity the bubble size has been first estimated from videos which once combined with the acoustic pressure can constrain the source of the sound the gas volume and overpressure stayed roughly constant between 36 700 m3 and 4 103 1 8 104 pa respectively simultaneous thermal measurements showed regular peaks which occurred when the crust was broken by a large bubble hence gave a direct indication on the typical return time between the bubbles 1 h these spherical cap bubbles had a high reynolds number 4600 20000 therefore a wake periodically unstable formed and detached from the bubble bottom the bubbly wake if the detachment occurs close to the surface can explain the duration of lava fountains measured on the videos the periodic arrival of bubbly wakes which mostly detach from the driving spherical cap within the lava lake could explain the absence of cooling at erta ale erebus antartica villarica chile and nyiragongo democratic republic of congo without invoking a convective downflow of magma in the conduit as previously done

degassing dynamics of basaltic lava lake at a top ranking volatile emitter ambrym volcano vanuatu arc persistent lava lakes are rare on earth and provide volcanologists with a remarkable opportunity to directly investigate magma dynamics and degassing at the open air ambrym volcano in vanuatu is one of the very few basaltic arc volcanoes displaying such an activity and voluminous gas emission but whose study has long remained hampered by challenging accessibility here we report the first high temporal resolution every 5 s measurements of vigorous lava lake degassing inside its 300 m deep benbow crater using op ftir spectroscopy our results reveal a highly dynamic degassing pattern involving i recurrent 100 200 s short period oscillations of the volcanic gas composition and temperature correlating with pulsated gas emission and sourced in the upper part of the lava lake ii a continuous long period 8 min modulation probably due to the influx of fresh magma at the bottom of the lake and iii discrete co2 spike events occurring in coincidence with the sequential bursting of meter sized bubbles which indicates the separate ascent of large gas bubbles or slugs in a feeder conduit with estimated diameter of 6 1 m this complex degassing pattern measured with unprecedented detail and involving both coupled and decoupled magma gas ascent over short time scales markedly differs from that of quieter lava lakes at erebus and kilauea it can be accounted for by a modest size of benbow lava lake and its very high basalt supply rate 20 m3 s 1 favouring its rapid overturn and renewal we verify a typical basaltic arc signature for ambrym volcanic gas and based on contemporaneous so2 flux measurements we evaluate huge emission rates of 160 gg d 1 of h2o 10 gg d 1 of co2 and 8 gg d 1 of total acid gas so2 hcl and hf during medium activity of the volcano in 2008 such rates make ambrym one of the three most powerful volcanic gas emitters at global scale whose atmospheric impact at local and regional scale may be considerable

a global synthesis of lava lake dynamics abstract active lava lakes represent a variety of open vent volcanism in which a sizable body of lava accumulates at the top of the magma column constrained by the vent and or crater geometry the longevity of lava lakes reflects a balancing of cooling and outgassing occurring at the surface and input of hot and gas rich magma from below due to their longevity and relative accessibility lava lakes provide a natural laboratory for studying fundamental volcanic processes such as degassing convection and cooling this article examines all seven lakes that existed at the time of writing in 2018 located in the pacific antarctica africa and south and central america these lakes span all tectonic environments and a range of magma compositions we focus on analysis of the lake surface motion using image velocimetry which reveals both similarities and contrasts in outgassing and lake dynamics when comparing the different lakes we identify two categories of lake behavior organized erta ale nyiragongo k lauea after 2011 and erebus and chaotic villarrica masaya marum this division does not map directly to lake size viscosity gas emission rate or temperature instead when examined together we find that the lakes follow a linear relationship between average surface speed and the ratio of total gas flux to lake surface area this relationship points to the combined importance of both flux and lake size in addition to the total volume of gas emission and suggests that a shared deep mechanism controls the supply of heat and gas to all lakes on the other hand the differences between chaotic and organized lakes highlight the important role of the geometry of the conduit lake transition which superimposes a shallow signal on that of the deep circulation the spatial patterns of surface motion we document suggest that the release of gas bubbles at chaotic lakes is more efficient i e bubbles are less likely to be retained and recycled compared with organized lakes in addition the data presented here indicate that the solidified crust of organized lakes plays a role in regulating convection and outgassing in lava lakes

distribution of sulfur aerosol precursors in the spcz released by continuous volcanic degassing at ambrym vanuatu abstract the melanesian volcanic arc mva emits about 12 kt d 1 of sulfur dioxide so2 to the atmosphere from continuous passive non explosive volcanic degassing which contributes 20 of the global so2 emission from volcanoes here we assess from up to date and long term observations the so2 emission of the ambrym volcano one of the dominant volcanoes in the mva and we investigate its role as sulfate precursor on the regional distribution of aerosols using both satellite observations and model results at 1 1 spatial resolution from wrf chem gocart without considering aerosol forcing on clouds our model parameterizations for convection vertical mixing and cloud properties provide a reliable chemical weather representation making possible a cross examination of model solution and observations this preliminary work enables the identification of biases and limitations affecting both the model missing sources and satellite sensors and algorithms for aerosol detection and classification and leads to the implementation of improved transport and aerosol processes in the modeling system on the one hand the model confirms a 50 underestimation of so2 emissions due to satellite swath sampling of the ozone monitoring instrument omi consistent with field studies the omi irregular sampling also produces a level of noise that impairs its monitoring capacity during short term volcanic events on the other hand the model reveals a large sensitivity on aerosol composition and aerosol optical depth aod due to choices of both the source function in wrf chem and size parameters for sea salt in flexaod the post processor used to compute offline the simulated aod we then proceed to diagnosing the role of so2 volcanic emission in the regional aerosol composition the model shows that both dynamics and cloud properties associated with the south pacific convergence zone spcz have a large influence on the oxidation of so2 and on the transport pathways of volcanic species across the south pacific atmosphere for example in the tropical cloudy air the sulfate production in the aqueous phase is very efficient resulting in the formation of a large cloud of highly scattering sulfate aerosols advected horizontally to eastern indonesia in agreement with the aod feature captured by modis aqua but missed in caliop calipso lidar products model sensitivity experiments indicate that aerosol re suspension due to evaporating droplets is a significant pathway for the supply of volcanic sulfur species in the remote marine boundary layer by strongly modulating the irreversible loss due to wet scavenging this aerosol process has a similar influence on the sulfur burden as natural emission from volcanoes or biogenic sources like dimethyl sulfate dms the results emphasize the importance of mva passive degassing and spcz dynamics on the aerosol background and raise questions about potential impacts on the local climate and marine ecosystems

megacrystals track magma convection between reservoir and surface abstract active volcanoes are typically fed by magmatic reservoirs situated within the upper crust the development of thermal and or compositional gradients in such magma chambers may lead to vigorous convection as inferred from theoretical models and evidence for magma mixing recorded in volcanic rocks bi directional flow is also inferred to prevail in the conduits of numerous persistently active volcanoes based on observed gas and thermal emissions at the surface as well as experiments with analogue models however more direct evidence for such exchange flows has hitherto been lacking here we analyse the remarkable oscillatory zoning of anorthoclase feldspar megacrystals erupted from the lava lake of erebus volcano antarctica a comprehensive approach combining phase equilibria solubility experiments and melt inclusion and textural analyses shows that the chemical profiles are best explained as a result of multiple episodes of magma transport between a deeper reservoir and the lava lake at the surface individual crystals have repeatedly travelled up and down the plumbing system over distances of up to several kilometers presumably as a consequence of entrainment in the bulk magma flow our findings thus corroborate the model of bi directional flow in magmatic conduits they also imply contrasting flow regimes in reservoir and conduit with vigorous convection in the former regular convective cycles of 150 days at a speed of 0 5 mm s 1 and more complex cycles of exchange flow and re entrainment in the latter we estimate that typical 1 cm wide crystals should be at least 14 years old and can record several from 1 to 3 complete cycles between the reservoir and the lava lake via the conduit this persistent recycling of phonolitic magma is likely sustained by co 2 fluxing suggesting that accumulation of mafic magma in the lower crust is volumetrically more significant than that of evolved magma within the edifice

magma and volatile supply to post collapse volcanism and block resurgence in siwi caldera tanna island vanuatu arc v24c 04 allen s r 2005 complex spatterand pumice rich pyroclastic deposits from an andesitic caldera forming eruption the siwi pyroclastic sequence tanna vanuatu bulletin of volcanology 67

first lidar observations of middle atmosphere temperatures fe densities and polar mesospheric clouds over the north and south poles anfeboltzmanntemperaturelidarwasusedto obtaintherstmeasurementsofmiddleatmospheretemper atures fe densities and polar mesospheric clouds pmcs over the north and south poles during the 1999 2000 sum mer seasons the measured temperature structure of the mesopause and lower thermosphere regions in mid summer at both poles is consistent with the msis90 model the density proles of the normal fe layer between 80 100 km at summer solstice are similar at both the north and south poles with maximum densities of about 2000 cm 3 s po radic fe fes layers were observed at both poles with peak densities at 106 kmaltitude the maximum densities of the feslayers were 23210 3 cm 3 at north pole and 6 5210 3 cm 3 atsouthpole pmcsweredetectedabovebothpoles thealtitudesofpmcsoverthesouthpolewereconsistently 2 3 km higher than those observed over the north pole

continuous gravity measurements reveal a low density lava lake at kīlauea volcano hawai i abstract on 5 march 2011 the lava lake within the summit eruptive vent at k lauea volcano hawai i began to drain as magma withdrew to feed a dike intrusion and fissure eruption on the volcano s east rift zone the draining was monitored by a variety of continuous geological and geophysical measurements including deformation thermal and visual imagery and gravity over the first 14 hours of the draining the ground near the eruptive vent subsided by about 0 15 m gravity dropped by more than 100 gal and the lava lake retreated by over 120 m we used gps data to correct the gravity signal for the effects of subsurface mass loss and vertical deformation in order to isolate the change in gravity due to draining of the lava lake alone using a model of the eruptive vent geometry based on visual observations and the lava level over time determined from thermal camera data we calculated the best fit lava density to the observed gravity decrease to our knowledge the first geophysical determination of the density of a lava lake anywhere in the world our result 950 300 kg m 3 suggests a lava density less than that of water and indicates that k lauea s lava lake is gas rich which can explain why rockfalls that impact the lake trigger small explosions knowledge of such a fundamental material property as density is also critical to investigations of lava lake convection and degassing and can inform calculations of pressure change in the subsurface magma plumbing system

first estimate of volcanic so2 budget for vanuatu island arc abstract the spatial and temporal coverage of measurements of volcanic gas emissions remains patchy however over the last decade emissions inventories have improved thanks to new measurements of some of the lesser known volcanic areas we report on one such region the vanuatu island arc in the southwest pacific for which we now have sufficient systematic observations to offer a systematic emissions inventory our new estimate is based on so 2 flux measurements made in the period 2004 2009 with ultraviolet spectroscopy techniques for the following volcanoes yasur lopevi ambrym ambae gaua and vanua lava from south to north these are the first ever measurements for lopevi gaua and vanua lava the results reveal the vanuatu arc as one of earth s prominent sources of volcanic degassing with a characteristic annual emission to the atmosphere of 3 tg of so 2 representing about 20 of hitherto published global estimates our new dataset highlights the sustained prodigious degassing of ambrym volcano whose 5 gg day 1 mean flux of so 2 represents nearly two thirds of the total budget for the vanuatu arc this confirms ambrym as one of the largest volcanic sources worldwide comparable to etna often considered as the most vigorous source of volcanic emission on earth we also report a high degassing for ambae of 2 gg day 1 so 2 representing more than 28 of the vanuatu arc budget thus 90 of the so 2 output from vanuatu is focused in the central part of the arc from ambrym and ambae where magmas originate from enriched indian type mantle and where peculiar tectonic conditions could favor high magma production rates

surge in sulphur and halogen degassing from ambrym volcano vanuatu volcanoes provide important contributions to atmospheric budgets of so2 and reactive halogens which play significant roles in atmospheric oxidative capacity and radiation however the global source strengths of volcanic emissions remain poorly constrained these uncertainties are highlighted here by the first measurements of gas emission rates from ambrym volcano vanuatu our initial airborne ultraviolet spectroscopic measurements made in january 2005 indicate fluxes of 18 270 kg s 1 of so2 and 62 110 g s 1 of bro into the atmosphere placing ambrym amongst the largest known contemporary point sources of both these species on earth we also estimate high cl and f fluxes of 8 14 and 27 50 kg s 1 respectively for this period further observations using both airborne and spaceborne remote sensing reveal a fluctuating so2 output between 2004 and 2008 with a surge in the first half of 2005 and underline the substantial contribution that a single passively degassing volcano can make to the atmospheric budget of sulfur and halogens

observed temperature structure of the atmosphere above syowa station antarctica 69 s 39 e 1 by combining balloonsonde and na rayleigh temperature lidar observations made at syowa station 69 s 39 e during 2000 and 2001 a total of 176 observations 5 9 observations per week the winter temperature structure from 0 to 110 km is characterized from march to october the data are also compared with the temperature model of south pole from pan and gardner 2003 which was derived from observations made during the same period as the measurements at syowa although syowa and south pole are separated more than 2300 km the temperature structure is quite similar through the year below 30 km the annual temperature amplitude at syowa is about 6 7 k smaller than the south pole data because of the difference in seasonal solar flux variations between the two sites in spring when the polar vortex weakens and dissipates the stratospheric temperatures at syowa increase rapidly as a result of the inflow of warmer air from lower latitudes in the mesosphere the annual temperature amplitude is anticorrelated with the solar heating because of the strong adiabatic heating and cooling effects associated with the meridional circulation system the annual temperature amplitude at syowa is 5 k smaller than at south pole which is consistent with the smaller adiabatic heating and cooling expected at lower latitudes the semiannual amplitude at syowa is 5 7 k larger than at south pole between 30 and 60 km and it is 15 k smaller than at south pole between 80 and 100 km

lidar observations of polar mesospheric clouds at south pole diurnal variations polar mesospheric clouds pmcs were observed by a ground based fe boltzmann temperature lidar for 65 h on 17 19 and 24 26 january 2000 above the geographic south pole the mean pmc backscatter ratio volume backscatter coefficient total backscatter coefficient layer centroid altitude and layer rms width are 53 5 2 9 l0 9 m 1sr 1 4 3 10 6 sr 1 85 37 km and 0 78 km respectively strong semidiurnal and diurnal oscillations were observed in the pmc backscatter ratio volume backscatter coefficient total backscatter coefficient and centroid altitude the oscillations are all maximum around 0630 and 1900 ut the variations appear to be linked to vertical advection of the pmc scattering layers by a persistent oscillation in the vertical wind velocity scattering is strongest when the pmcs are highest which suggests that the colder temperatures at higher altitudes near the mesopause facilitate the formation of larger pmc particles

hydraulic properties of a model dike from coupled bayesian and multi criteria hydrogeophysical inversion coupled hydrogeophysical inversion aims to improve the use of geophysical data for hydrological model parameterization several numerical studies have illustrated the feasibility and advantages of a coupled approach however there is still a lack of studies that apply the coupled inversion approach to actual field data in this paper we test the feasibility of coupled hydrogeophysical inversion for determining the hydraulic properties of a model dike using measurements of electrical resistance tomography ert our analysis uses a two dimensional 2d finite element hydrological model hydrus 2d coupled to a 2 5d finite element electrical resistivity code crmod and includes explicit recognition of parameter uncertainty by using a bayesian and multiple criteria framework with the dream and amalgam population based search algorithms to benchmark our inversion results soil hydraulic properties determined from ert data are compared with those separately obtained from detailed in situ soil water content measurements using time domain reflectometry tdr our most important results are as follows 1 tdr and ert data theoretically contain sufficient information to resolve most of the soil hydraulic properties 2 the dream derived posterior distributions of the hydraulic parameters are quite similar when estimated separately using tdr and ert measurements for model calibration 3 among all parameters the saturated hydraulic conductivity of the dike material is best constrained 4 the saturation exponent of the petrophysical model is well defined and matches independently measured values 5 measured ert data sufficiently constrain model predictions of water table dynamics within the model dike this finding demonstrates an innate ability of ert data to provide accurate hydrogeophysical parameterizations for flooding events which is of particular relevance to dike management and 6 the amalgam derived pareto front demonstrates trade off in the fitting of ert and tdr measurements altogether we conclude that coupled hydrogeophysical inversion using a bayesian approach is especially powerful for hydrological model calibration the posterior probability density functions of the model parameters and model output predictions contain important information to determine if geophysical measurements provide constraints on hydrological predictions

open path ftir spectroscopy of magma degassing processes during eight lava fountains on mount etna in june july 2001 a series of 16 discrete lava fountain paroxysms occurred at the southeast summit crater sec of mount etna preceding a 28 day long violent flank eruption each paroxysm was preceded by lava effusion growing seismic tremor and a crescendo of strombolian explosive activity culminating into powerful lava fountaining up to 500 m in height during 8 of these 16 events we could measure the chemical composition of the magmatic gas phase h2o co2 so2 hcl hf and co using open path fourier transform infrared op ftir spectrometry at 1 2 km distance from sec and absorption spectra of the radiation emitted by hot lava fragments we show that each fountaining episode was characterized by increasingly co2 rich gas release with co2 so2 and co2 hcl ratios peaking in coincidence with maxima in seismic tremor and fountain height whilst the so2 hcl ratio showed a weak inverse relationship with respect to eruption intensity moreover peak values in both co2 so2 ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval 2 6 days between lava fountains these observations together with a model of volatile degassing at etna support the following driving process prior to and during the june july 2001 lava fountain sequence the shallow 2 km magma reservoir feeding sec received an increasing influx of deeply derived carbon dioxide likely promoted by the deep ascent of volatile rich primitive basalt that produced the subsequent flank eruption this co2 rich gas supply led to gas accumulation and overpressure in sec reservoir generating a bubble foam layer whose periodical collapse powered the successive fountaining events the anti correlation between so2 hcl and eruption intensity is best explained by enhanced syn eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation

seasonal and latitudinal variation of noctilucent cloud altitudes 1 we present a summary of 1500 hours of lidar measurements of noctilucent cloud nlc altitudes at kuhlungsborn 54 n alomar 69 n and spitsbergen 78 n mean centroid altitudes zc are 82 75 km 83 33 km and 83 68 km respectively standard deviations representing geophysical variability are 0 7 1 6 km errors of mean heights zc are much smaller 60 340 m several processes which are not yet fully understood influence zc therefore is a better measure of uncertainties in zc compared to zc the increase of nlc heights with latitude is very small 43 65 m deg and statistically not significant at alomar zc varies with season by up to 1 1 5 km nlc heights accumulate around climatological temperatures of 145 k at 69 n and 78 n higher at 54 n the lima model nicely reproduces observations and indicates that non variation of nlc heights at polar latitudes is caused by temperature uniformity the 145 k isotherm varies in height by less than 250 m from the pole to 60 n