exploring the explosive effusive transition using permanent ultra violet cameras understanding the mechanisms that cause effusive eruptions is the key to mitigating their associated hazard here we combine results from permanent ultra violet uv cameras and from other geophysical observations seismic very long period thermal and infrasonic activity to characterize volcanic so2 flux regime in the period prior during and after stromboli s august november 2014 effusive eruption we show that in the two months prior to effusion onset the so2 flux levels are two times average level we explain this anomalously high so2 regime as primarily determined by venting of rapidly rising pressurized so2 rich gas pockets produced by strombolian explosions being more frequent and intense than usual we develop a procedure to track and count in the uv camera record the so2 flux pulses produced by individual explosions and puffing activity active degassing we find that these so2 pulses are far more numerous 67 47 events hour before the effusion onset than during normal activity 20 15 events hour this observation combined with geophysical evidence demonstrates an elevated gas bubble supply to the shallow conduits causing elevated explosive and puffing activity this increase 0 1 m3s 1 in magma transport rate in the north east feeding conduits finally triggers effusion onset active degassing remains elevated also during the effusive phase supporting the persistence of explosive and puffing activity during the effusive eruption deep in the volcanic conduit our results demonstrate that permanent uv cameras can valuably contribute to monitoring at high sampling frequency gas dynamics and fluxes thus opening the way to direct comparison with more established geophysical observations

an automated so 2 camera system for continuous real time monitoring of gas emissions from kīlauea volcano s summit overlook crater abstract so 2 camera systems allow rapid two dimensional imaging of sulfur dioxide so 2 emitted from volcanic vents here we describe the development of an so 2 camera system specifically designed for semi permanent field installation and continuous use the integration of innovative but largely off the shelf components allowed us to assemble a robust and highly customizable instrument capable of continuous long term deployment at k lauea volcano s summit overlook crater recorded imagery is telemetered to the usgs hawaiian volcano observatory hvo where a novel automatic retrieval algorithm derives so 2 column densities and emission rates in real time imagery and corresponding emission rates displayed in the hvo operations center and on the internal observatory website provide hvo staff with useful information for assessing the volcano s current activity the ever growing archive of continuous imagery and high resolution emission rates in combination with continuous data from other monitoring techniques provides insight into shallow volcanic processes occurring at the overlook crater an exemplary dataset from september 2013 is discussed in which a variation in the efficiency of shallow circulation and convection the processes that transport volatile rich magma to the surface of the summit lava lake appears to have caused two distinctly different phases of lake activity and degassing this first successful deployment of an so 2 camera for continuous real time volcano monitoring shows how this versatile technique might soon be adapted and applied to monitor so 2 degassing at other volcanoes around the world

source mechanisms of explosions at stromboli volcano italy determined from moment tensor inversions of very long period data 1 seismic data recorded in the 2 30 s band at stromboli volcano italy are analyzed to quantify the source mechanisms of strombolian explosions during september 1997 to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous elastic medium that takes topography into account two source centroids are identified each representative of the distinct event types associated with explosive eruptions from two different vents the observed waveforms are well reproduced by our inversion and the two source centroids that best fit the data are offset 220 and 260 m beneath and 160 m northwest of the active vents the source mechanisms include both moment tensor and single force components the principal axes of the moment tensor have amplitude ratios 1 1 2 which can be interpreted as representative of a crack if one assumes the rock matrix at the source to have a poisson ratio n 1 3 a value appropriate for hot rock both imaged cracks dip 60 to the northwest and strike northeast southwest along a direction parallel to the elongation of the volcanic edifice and a prominent zone of structural weakness as expressed by lineaments dikes and brittle structures for our data set the volume changes estimated from the moments are 200 m 3 for the largest explosion from each vent together with the volumetric source is a dominantly vertical force with a magnitude of 10 8 n consistent with the inferred movement of the magma column perched above the source centroid in response to the piston like rise of a slug of gas in the conduit index terms 7215 seismology earthquake parameters 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms keywords very long period seismicity moment tensor inversions eruption mehanics

vesiculation in magmas from stromboli and implications for normal strombolian activity and paroxysmal explosions in basaltic systems 1 we performed a series of x ray tomographic experiments and lattice boltzmann permeability simulations on pyroclastic products from explosive activity at stromboli between december 2004 and may 2006 we reconstructed the 3 d textures of vesicles to investigate the relationship between the nature of vesiculation in the erupted products and the dynamics of gas transport in the shallow conduit in order to derive implications for the eruptive behavior of basaltic volcanoes scoriae from normal strombolian explosions display remarkably consistent vesicle volume distributions fit by power laws with an exponent of 1 0 2 we ascribe the origin of such distributions to the combined effect of coalescence and continuous nucleation events in the steady state shallow magma system that supplies normal strombolian activity volume distributions and textures of vesicles in pumice clasts from the 5 april 2003 and 15 march 2007 paroxysmal activity are markedly different from those in the scoriae besides a power law function with a higher exponent portions of these distributions can be also fit by an exponential function suggesting the attempt of the system to reach near equilibrium conditions the investigated pumice clasts also lack the large connecting vesicles responsible for the development of degassing pathways in the stromboli magma that erupts the scoriae this testifies to a decreased degassing efficiency of the magma associated with paroxysmal explosions and potential overpressure buildup at depth by comparison with degassing experiments on basaltic melts we derive a time constraint on the order of minutes to hours for the incubation of paroxysms at stromboli

atmospheric chemistry of an antarctic volcanic plume 1 we report measurements of the atmospheric plume emitted by erebus volcano antarctica renowned for its persistent lava lake the observations were made in december 2005 both at source with an infrared spectrometer sited on the crater rim and up to 56 km downwind using a twin otter aircraft with the two different measurement platforms plume ages were sampled ranging from 1 min to as long as 9 h three species co carbonyl sulfide ocs and so2 were measured from both air and ground while co and ocs were conserved in the plume consistent with their long atmospheric lifetimes the downwind measurements indicate a so2 co ratio about 20 of that observed at the crater rim suggesting rapid chemical conversion of so2 the aircraft measurements also identify volcanogenic h2so4 hno3 and recognized for the first time in a volcanic plume ho2no2 we did not find nox in the downwind plume despite previous detection of no2 above the crater this suggests that near source nox was quickly oxidized to hno3 and ho2no2 and probably no3 aq possibly in tandem with the conversion of so2 to sulfate these fast processes may have been facilitated by cloud processing in the dense plume immediately downwind from the crater a further striking observation was o3 depletion of up to 35 in parts of the downwind plume this is likely to be due to the presence of reactive halogens bro and clo formedthrough heterogeneous processes in the young plume our analysis adds to the growing evidence for the tropospheric reactivity of volcanic plumes and shows that erebus volcano has a significant impact on antarctic atmospheric chemistry at least locally in the southern ross sea area

so2 flux monitoring at stromboli with the new permanent ingv so2 camera system a comparison with the flame network and seismological data we installed a permanent so2 camera system on stromboli italy in may 2013 in order to improve our capacity to monitor the so2 emissions from this volcano the camera collects images of so2 concentrations with a period of similar to 10 s allowing quantification of short term processes such as the gas released during the frequent explosions which are synonymous with stromboli it also allows quantification of the quiescent gas flux and therefore comparison with the flame network of scanning ultraviolet spectrometers previously installed on the island analysis of results from the so2 camera demonstrated a good agreement with the flame network when the plume was blown fully into the field of view of the camera permanent volcano monitoring with so2 cameras is still very much in its infancy and therefore this finding is a significant step in the use of such cameras for monitoring whilst also highlighting the requirement of a favourable wind direction and strength we found that the explosion gas emissions are correlated with seismic events which have a very long period component there is a variable time lag between event onset time and the increase in gas flux observed by the camera as the explosion gas advects into the field of view of the camera this variable lag is related to the plume direction as shown by comparison with the plume location detected with the flame network the correlation between explosion gas emissions and seismic signal amplitude show is consistent with a gas slug driven mechanism for seismic event production comparison of the so2 camera measurements of the quiescent gas flux shows a fair quantitative agreement with the so2 flux measured with the flame network overall the so2 camera complements the flame network well as it allows frequent quantification of the explosion gas flux produced by stromboli whose signal is in general too brief to be measured with the flame network further work is required however to fully automate the calculation of so2 flux from the so2 images captured with the camera and to adequately account for scattering effects c 2015 elsevier b v all rights reserved

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

effects of monsoon trough intraseasonal oscillation on tropical cyclogenesis over the western north pacific abstractthe effects of intraseasonal oscillation iso of the western north pacific wnp monsoon trough on tropical cyclone tc formation were investigated using the advanced research weather research and forecasting arw model a weak vortex was specified initially and inserted into the background fields containing climatological mean anomalies associated with active and inactive phases of monsoon trough isos the diagnosis of simulations showed that monsoon trough iso can modulate tc development through both dynamic and thermodynamic processes the dynamic impact is attributed to the lower midtropospheric large scale vorticity associated with monsoon trough iso interactions between cyclonic vorticity in the lower middle troposphere during the active iso phase and a vortex lead to the generation of vortex scale outflow at the midlevel which promotes the upward penetration of friction induced ascending motion and thus upward moisture transport in addition the low level convergence associated with ac

continental slope processes off northern israel and southernmost lebanon and their relation to onshore tectonics abstract the continental terrace of israel and lebanon consists of a 1 2 km thick pliocene quaternary sediment wedge that narrows steepens and deepens from south to north the continental terrace is the product of 1 nile derived sediment accumulation whose bulk and rate of deposition decrease along the active levant continental margin with increasing distance from the nile mouths and 2 of the vertical tectonic uplift of israel and lebanon versus the subsidence of the adjacent submarine levantine basin which increases to the north collapse of the entire seaward facing part of the continental terrace off northern israel caused by large scale halokinetic rotational slumping has further accentuated its steep and narrow wedge form in the study area intensive mass wasting and canyon cutting over the steep continental slope have shaped its present furrowed morphology canyon incision is fault controlled the faults being submarine extensions of the continental fault system effected by drag of the sinai sub plate along the dead sea jordan beqa a transform that has controlled the tectonics and the structure of israel and lebanon since the late miocene the canyon heads at the continental shelf lie opposite the mouths of the continental rivers canyon cutting processes are not however connected to fluvial erosion of the emergent continental shelf during the last glacial lowered sea level stand canyon incision started on the continental slope and advanced downslope and upslope toward the shelf embryonic slope valleys canyons confined to the continental slope a canyon in the process of breaching the shelf break and mature canyons that indent the continental shelf to nearshore distances were mapped and are described

dynamics of the 5 april 2003 explosive paroxysm observed at stromboli by a near vent thermal seismic and infrasonic array 1 on 5 april 2003 an array of thermal infrasonic and seismic sensors tracked the dynamics of a major explosive paroxysmal event at stromboli the thermal signal recorded a decline 1 hour before the paroxysm which itself lasted 6 5 minutes and opened with a 14 s low thermal amplitude phase this was followed by three main explosive phases with gas and ejecta velocities of 324 and 185 m s being calculated for the first phase the delay time between thermal and infrasonic signals indicates a very shallow 150 m source for fragmentation a strong tilt component in the seismic signals shows that the conduit began to expand at least 90 s before the explosion large seismic amplitudes were recorded during the emission onset the seismic signal can thus be related to stress build up followed by release during the ejection of the gas particles mixture we calculate that the cloud of hot gas and ash emitted during the explosion had an overpressure of 3 8 mpa and involved 5 7 105 m3 2 9 106 kg of gas

volcanological applications of so2 cameras ground based volcanic gas and ash imaging has the potential to revolutionise the way in which volcanoes are monitored and studied the ability to track and quantify volcanic emissions in space and time with unprecedented fidelity opens the door to integration with geophysical measurements allowing breakthroughs in our understanding of the physical processes driving volcanic activity in may 2013 a european science foundation funded plume imaging workshop was conducted in strombolutaly with the objective of bringing the ground based volcanic plume imaging community together in order to examine the state of the art and move towards a best practice for volcanic ash and gas imaging techniques a particular focus was the development of so2 imaging systems or so2 cameras with six teams deploying and testing various designs of ultraviolet and infrared based imaging systems capable of imagining so2 one conclusion of the workshop was that the term so2 camera should be applied to any so2 imaging system regardless of wavelength of radiation used this special issue on volcanic plume imaging is the direct result of the stromboli workshop and together the papers presented here represent the state of the art of ground based volcano plume imaging science and technology in this work we examine in detail the volcanological applications of the so2 camera reviewing previous works and placing the new research contained in this special issue in context the development of the so2 camera and future developments extending imaging to other volcanic gases is one of the most exciting and novel research frontiers in volcanology today c 2014 published by elsevier b v

use of motion estimation algorithms for improved flux measurements using so 2 cameras abstract article history received 3 april 2014accepted 18 august 2014available online xxxxkeywords so 2 uxso 2 cameraplume speedplume modellingoptical owmotion estimation so 2 cameras are rapidly gaining popularity as a tool for monitoring so 2 emissions from volcanoes severaldifferent so 2 camera systems have been developed with varying patterns of image acquisition in space timeand wavelength despite this diversity there are two steps common to the work owsofmostofthesesystems aligning images of different wavelengths to calculate apparent absorbance and estimating plume transportspeeds both of which can be achieved using motion estimation algorithms here we present two suchalgorithms adualtreecomplexwavelettransform basedalgorithmandthefarnebackopticalflowalgorithm weassesstheiraccuracyusingasyntheticdatasetcreatedusingthenumericcloud resolvingmodelatham andthen apply them to real world data from villarrica volcano both algorithms are found to perform well and theatham simulations offer useful datasets for benchmarking and validating future algorithms 2014 the authors published by elsevier b v this is an open access article under the cc by license http creativecommons org licenses by 3 0

the so2 camera a simple fast and cheap method for ground based imaging of so2 in volcanic plumes 1 so2 flux is widely monitored on active volcanoes as it gives a window into the hidden subsurface magma dynamics we present here a new approach to so2 flux monitoring using ultraviolet imaging of the volcanic plume through carefully chosen filters to produce images of so2 column amount the so2 camera heralds a breakthrough in both our ability to measure so2 flux at unprecedented frequencies 2 hz and at unprecedented accuracy thanks to the application of correlation techniques to determine wind speed directly from the images and the ability to measure the whole profile simultaneously in this paper we detail the commercially available pieces required to construct the so2 camera introduce a retrieval scheme to determine so2 amounts from the images and present results from a field campaign in november 2005 on sakurajima volcano japan

array tracking of infrasonic sources at stromboli volcano 1 infrasonic arrays are a powerful tool for volcanic monitoring and hazard assessment explosions were recorded at stromboli using a small aperture array of 4 infrasonic stations allowing precise vent location the acoustic signals were delayed and summed revealing the existence of two main groups of infrasonic waves the ne crater produces short 3 s high amplitude 20 80 pa pressure waves while the sw crater produces small acoustic pressure 10 30 pa with long 5 15 s coda the two groups reflect different in explosive styles and similar spectral content centered on 5 6 hz when stacked together acoustic waveforms for each crater reveal the same pressure pulse which indicates a common source process we infer that the acoustic onset at both craters is generated by the burst of a large gas bubble while the acoustic coda is controlled by a sustained pressure release

high speed imaging of strombolian explosions the ejection velocity of pyroclasts explosive volcanic eruptions are defined as the violent ejection of gas and hot fragments from a vent in the earth s crust knowledge of ejection velocity is crucial for understanding and modeling relevant physical processes of an eruption and yet direct measurements are still a difficult task with largely variable results here we apply pioneering high speed imaging to measure the ejection velocity of pyroclasts from strombolian explosive eruptions with an unparalleled temporal resolution measured supersonic velocities up to 405 m s are twice higher than previously reported for such eruptions individual strombolian explosions include multiple sub second lasting ejection pulses characterized by an exponential decay of velocity when fitted with an empirical model from shock tube experiments literature this decay allows constraining the length of the pressurized gas pockets responsible for the ejection pulses these results directly impact eruption modeling and related hazard assessment as well as the interpretation of geophysical signals from monitoring networks

high frame rate thermal imagery of strombolian explosions implications for explosive and infrasonic source dynamics 1 explosive activity at stromboli volcano is analyzed using a high frame rate 50 hz thermal camera and differential pressure transducers we develop a thermal image based decomposition method to derive vertical and horizontal exit velocities of the explosive cloud peak vertical velocity ranges between 23 and 203 m s slightly higher than previous estimates and rapidly decreasing to a constant value of 30 50 m s within the first 0 1 s plume velocities are consistent with an elongated cloud expanding much faster vertically than horizontally and indicating the interaction with the conduit wall considering a vent radius of 2 m we estimate a volumetric flux of 200 600 m3 s which converts to total volumes of gas particles of 103 104 m3 for a single eruption these volumes are proportional to the thermal energy recorded by the camera providing a means to convert thermal radiance to volumes comparing the thermal onset of the explosions with the arrival time of the acoustic pressure we demonstrate that infrasound is propagating 0 14 1 7 s ahead of the explosive front the time difference between thermal and acoustic onsets constrains the infrasonic source within the conduit at 15 35 m below the crater rim peak amplitudes of acoustic pressure show a power law relationship p u2 with the exit vertical velocities consistent with the energy balance of a two phase flow rapidly accelerated in the conduit by gas decompression our results support monopole isotropic acoustic radiation of a source embedded within the conduit walls and indicate that explosive dynamics undergo strong accelerations of 103 104 m s2

relation between single very long period pulses and volcanic gas emissions at mt asama japan 1 multiple volcanic observations conducted at mt asama japan provide evidence of a link between single very long period vlp seismic pulses and volcanic gas emissions so2 flux measurements were conducted on 2 june 2009 when mt asama was producing ash free eruptions with vlp pulses gas bursts from a vent at the crater bottom following the vlp pulses provided an excellent opportunity to examine the relation directly the so2 emission for each eruption was calculated by integrating high temporal so2 flux data obtained by the so2 imaging system and subtracting the contribution from quiescent degassing from fumaroles around the crater bottom a seismic moment of vlp pulse was estimated by the waveform inversion we observed seven eruptions and obtained the proportional relation between vlp pulse moment and so2 emission the relation determined is consistent with the vlp source model these observational results are the first report of a quantitative comparison between single vlp pulse moment and volcanic gas emission

effusive to explosive transition during the 2003 eruption of stromboli volcano the persistent explosive activity of stromboli volcano italy ceased in december 2002 and correlated with the onset of a seven month long effusive eruption on the volcano flank from new vents that opened just below the summit craters we intensively monitored this effusive event collecting and interpreting in real time an extensive multiparametric geophysical data set the resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical strombolian activity we present a direct link between gas flux magma volume flux and seismicity supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity this insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity

so2 flux from stromboli during the 2007 eruption results from the flame network and traverse measurements abstract so 2 fluxes emitted by stromboli during the 27th february 2nd april 2007 effusive eruption were regularly measured both by an automatic network of scanning ultraviolet spectrometers and by traverse measurements conducted by boat and helicopter the results from both methodologies agree reasonably well providing a validation for the automatic flux calculations produced by the network approximately 22 000 t of so 2 were degassed during the course of the 35 day eruption at an average rate of 620 t per day such a degassing rate is much higher than that normally observed 150 200 t d because the cross sectional area occupied by ascending degassed magma is much greater than normal during the effusion as descending degassed magma that would normally occupy a large volume of the conduit is absent we propose that the hydrostatically controlled magma level within stromboli s conduit is the main control on eruptive activity and that a high effusion rate led to the depressurisation of an intermediate magma reservoir creating a decrease in the magma level until it dropped beneath the eruptive fissure causing the rapid end of the eruption a significant decrease in so 2 flux was observed prior to a paroxysm on 15th march 2007 suggesting that choking of the gas flowing in the conduit may have induced a coalescence event and consequent rapid ascent of gas and magma that produced the explosion