field temperature measurements at erta ale lava lake ethiopia the shield volcano erta ale situated in the danakil depression ethiopia is known for its active lava lake in february 2001 our team visited this lake located inside an 80 m deep pit to perform field temperature measurements the distribution and variation of temperature inside the lake were obtained on the basis of infrared radiation measurements performed from the rim of the pit and from the lake shores the crust temperature was also determined from the lake shores with a thermocouple to calibrate the pyrometer we estimated an emissivity of the basalt of 0 74 from this experiment through the application of the stefan boltzmann law we then obtained an estimate of the total radiative heat flux constrained by pyrometer measurements of the pit and visual observations of the lake activity taking into account the atmospheric convective heat flux the convected magma mass flux needed to balance the energy budget was subsequently derived and found to represent between 510 and 580 kg s 1 the surface circulation of this mass flux was also analyzed through motion processing techniques applied to video images of the lake electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00445 002 0224 3

continuous monitoring of fumarole temperatures at mount etna italy abstract in this paper we present the first data of temperature continuously recorded in two fumarole fields designated vor and hor located in the summit area of mount etna volcano italy the time series embraces two distinct periods 1 october 2007 to november 2009 during which an effusive eruption occurred from may 2008 to july 2009 and 2 november 2011 to june 2012 characterized by the occurrence of strong paroxysms fire fountains and lava flow the analysis of the temperature signal in both the time and frequency domains and its comparison with meteorological observations allowed us to separate the exogenous influences from the effects of variations in the activity state of the volcano the acquired data were weakly affected by seasonal cycles of the air temperature and strongly affected by the rainfall optimization of site conditions i e sensor depth and soil permeability markedly reduced meteorological disturbances the distance from the main degassing and or eruptive fractures was crucial to maximizing the probability of the technical survival of the monitoring apparatus which was seriously affected by the emission of acidic gases tephra fallout and lava flows apart from the exogenous influences the most appreciable variation was observed at vor where a huge increase in fumarole temperature was detected immediately after the onset of the 2008 2009 eruption such an anomalous increase was attributed to the rapid ascent of magma feeding the eruptive fracture another abrupt increase in temperature was recorded at hor in march and april 2012 during this period the frequency of paroxysm occurrence increased markedly and this led us to hypothesize that the thermal anomaly was due to the intrusion of a new batch of magma in the conduits of the southeast crater medium to long term monitoring weeks to months of fumarole temperatures revealed variations that were attributed to pressurization depressurization phases of the shallow volcanic system which varied between the various monitored sectors of the volcano our observations suggest that continuous monitoring of fumarole temperature can give useful information about the activity of mount etna moreover due to the complexity of its shallow plumbing system we conclude that the monitoring systems should be extended to cover the entire fumarole network of the summit area

observatory validation of neolithic tells magoules in the thessalian plain central greece using hyperspectral spectroradiometric data abstract this paper presents the results obtained from field spectroradiometric campaigns over neolithic tells magoules located at the thessalian region in greece in each one of the four archaeological sites selected three sections were carried out using the ger 1500 handheld spectroradiometer spectral profiles of the sections and several vegetation indices such as normalized difference vegetation indices ndvi and simple ratio sr have been examined in this study this is one of the first times that ground hyperspectral data are evaluated in such context of archaeological research for the spectral characterization of archaeological features as it was found ground spectroradiometric measurements can be efficiently used in order to support and validate satellite imagery results for the detection of archaeological sites

spectral and dynamical hints on the time scale of preparation of the 5 april 2003 explosion at stromboli volcano stromboli volcano is well known for its continuous strombolian activity moreover the volcano occasionally shows effusive phases the latest in 1985 1986 on 28 december 2002 stromboli entered a new effusive phase accompanied by different paroxysmal events that led to considerable hazards for inhabitants and tourists on the island of stromboli on 30 december 2002 a major sector collapse affected the sciara del fuoco slope and initiated a tsunami on 5 april 2003 a powerful explosion which can be compared in size with the most recent explosion in 1930 covered a large part of the normally tourist accessible summit area with bombs as this explosion was not forecasted although the island was by then effectively monitored by a dense deployment of instruments in this paper we tackle the problem of highlighting the time scale of preparation of this event and conduct a search for possible precursors for this purpose we analyze the seismic data preceding the paroxysm with spectral and dynamical methods

decomposition location and persistence of seismic signals recovered from continuous tremor at erta ale ethiopia abstract subband decomposition and reconstruction sdr provides a quantitative semi automated rapid means of analyzing volcanic tremor which can recover signals that dominate different parts of the frequency spectrum while preserving polarization and phase here applied to data from a two week experiment at erta ale in nov dec 2003 we demonstrate that the sdr method can identify signals corresponding to source processes active in several different physical regions of the erta ale caldera different recovered signals suggest that the continuous tremor at erta ale is a composite of several seismic sources including conduit resonance bubble bursting phenomena and degassing at fumaroles these signals are seen throughout the 2003 experiment suggesting that several competing source models of volcanic tremor can produce signals at the same volcanic conduit system simultaneously

lava lake surface characterization by thermal imaging erta ale volcano ethiopia the project sviluppo di sistemi di monitoraggio dipartimento di protezione civile di regione sicilia ingv catania section italy the leverhulme trust the bbc and the ethiopian air force

sustaining persistent lava lakes observations from high resolution gas measurements at villarrica volcano chile active lava lakes as the exposed upper part of magmatic columns are prime locations to investigate the conduit flow processes operating at active degassing volcanoes persistent lava lakes require a constant influx of heat to sustain a molten state at the earth s surface several mechanisms have been proposed to explain how such heat transfer can operate efficiently these models make contrasting predictions with respect to the flow dynamics in volcanic conduits and should result in dissimilar volatile emissions at the surface here we look at high frequency so2 fluxes plume composition thermal emissions and aerial video footage from the villarrica lava lake in order to determine the mechanism sustaining its activity we found that while fluctuations are apparent in all datasets none shows a stable periodic behaviour these observations suggest a continuous influx of volatiles and magma to the villarrica lava lake we suggest that ascending volatile rich and descending degassed magmas are efficiently mixed within the volcanic conduit resulting in no clear periodic oscillations in the plume composition and flux we compare our findings to those of other lava lakes where equivalent gas emission time series have been acquired and suggest that gas flux magma viscosity and conduit geometry are key parameters determining which flow mechanism operates in a given volcanic conduit the range of conduit flow regimes inferred from the few studied lava lakes gives a glimpse of the potentially wide spectrum of conduit flow dynamics operating at active volcanoes

subband decomposition and reconstruction of continuous volcanic tremor abstract a new method of analyzing volcanic tremor is presented which uses properties of undecimated wavelet packet transforms to filter decompose and recover signals from continuous multichannel data the method preserves many standard properties that are used to characterize tremor such as wavefield polarization and seismic energy in this way we can better understand the potentially many seismic sources that combine to form continuous volcanic tremor and we can specifically address the problem of what causes changing tremor spectral content tests on synthetic data suggest that sdr can recover multiple quasi continuous signals that differ from one another by an order of magnitude even in noisy environments tests on real data recorded at erta ale in 2002 suggest that sdr can recover signals with geophysically meaningful interpretations and corroborates existing seismic and multiparametric work by harris et al 2005 jones et al 2006 and harris 2008 we suggest that this algorithm could effectively detect subtle changes in the time frequency content of volcanic tremor and recover signals from real seismic sources that appear buried in background noise and or partly masked by one another such an algorithm could allow volcanologists much greater insight into the dynamics of volcanic systems and could detect subtle signals that might help address the possibility of unrest

correlations between so2 flux seismicity and outgassing activity at the open vent of villarrica volcano chile 1 the characteristics of the open vent activity of villarrica volcano chile were studied in detail by integrating visual observations of the lava lake analysis of the seismic tremor and measurements of so2 flux the outgassing activity comprises a persistent gas plume emission from the bottom of the crater as well as frequent explosive events three main styles of bubble bursting were identified at the surface of the active lava lake seething magma small short lived lava fountains and strombolian explosions seething magma consists of continual burst of relatively small bubbles a few meters in diameter with varying strength over the entire surface of the lava lake small lava fountains seen as a vigorous extension of seething magma commonly have durations of 20 120 s and reach 10 40 m high above the lava lake correlations between seismicity and visual observations indicate that the seismic tremor is mostly caused by the explosive outgassing activity furthermore for different periods between 2000 and 2006 during which the activity remained comparable the real time seismic amplitude measurement system rsam and so2 emission rates show a very good correlation higher so2 emissions appeared to be related to higher levels of the lava lake stronger bubble bursting activity and changes in the morphology and texture of the crater floor background low levels of activity correspond to a lava lake located 80 m below the crater rim small and or blocky morphology of the roof seismic amplitude rsam lower than 25 units few volcano tectonic earthquakes and daily averages of so2 emissions lower than 600 mg d

pulsed lava effusion at mount etna during 2001 effusion rate and degassing data collected at mt etna volcano italy in 2001 show variations occurring on time scales of hours to months we use both long and short term data sets spanning january to august to identify this variation the long data sets comprise a satellite and ground based time series of effusion rates and the latter include field based effusion rate and degassing data collected may 29 31 the satellite derived effusion rates for january through august reveal four volumetric pulses that are characterized by increasing mean effusion rate values and lead up to the 2001 flank eruption peak effusion rates during these 23 57 day pulses were 1 2 m 3 s 1 in pulse 1 1 jan 4 mar 1 1 m 3 s 1 in pulse 2 5 mar 21 apr 4 2 m 3 s 1 in pulse 3 24 apr 18 jun 8 8 m 3 s 1 in pulse 4 23 jun 16 jul and 22 2 m 3 s 1 during the flank eruption 17 jul 9 aug rank order analysis of the satellite data shows that effusion rate values during the 2001 flank eruption define a statistically different trend than etna s persistent activity from jan 1 to jul 17 data prior to the flank eruption obey a power law relationship that may define an effusion rate threshold of f3 5 m 3 s 1 for etna s typical persistent activity our short term data coincide with the satellite derived peak effusion period of pulse 3 degassing at vent puff frequency shows a general increase from may 29 to 31 with hour long variations in both puff frequency and lava flow velocity effusion rate we identify five 3 14 h degassing periods that contain 26 shorter 19 126 min long oscillations this variation shows some positive correlation with effusion rate measurements during the same time period if a relationship between puff frequency and effusion rate is valid we propose that their short term variation is the result of changes in the supply rate of magma to the near vent conduit system therefore these short term data provide some evidence that the clear weeks to months long variation in etna s effusive activity january august 2001 was overprinted by a minutes to hour scale oscillation in shallow supply d 2004 elsevier b v all rights reserved

pre and post failure spatial temporal deformation pattern of the baige landslide retrieved from multiple radar and optical satellite images abstract the baige landslide in southwest china has been active for at least 50 years and experienced two failure events on oct 10 and nov 3 2018 the rock mass and debris of the slope failure formed a landslide dam the discharge of the dammed lake plus the failure events caused significant socio economic losses many slow moving areas appeared after the two failure events and potential landslide risk still exists retrieving the long term spatial temporal pattern of landslide activity can help us to understand and mitigate landslide disasters however it is difficult to monitor all movement episodes of some landslides using single satellite dataset and method due to the different deformation characteristics employing multiple radar and optical images may solve this problem in this study the landsat 8 the alos palsar and alos 2 palsar 2 images are used to obtain the surface displacements before the first failure event by using the cross correlation technique for landsat 8 images and the pixel offset tracking technique the displacement velocity map after the second failure is derived by the multi temporal synthetic aperture radar interferometry mt insar method from the alos 2 palsar 2 and the sentinel 1 images the maximum radar line of sight los average velocity is 3 m yr between jan 2007 and feb 2011 and 12 m yr between jul 2015 and jul 2018 from oct 2013 to feb 2018 the maximum horizontal average velocity is 5 8 m yr the movement accelerated from jul 2017 a large deformation area appeared on the south of the failed slope after the second failure the unstable area observed by the mt insar is much larger than that obtained through the field measurements in the first month after the second failure the maximum los displacements are more than 20 cm the depletion area and the neighboring zones of the landslide are unstable even one year after the second failure this study shows how to use multiple satellite images and hybrid remote sensing techniques to investigate the landslide deformation history and illustrates the benefits of landslide monitoring based on images from multiple satellite sensors

regional and local tectonics at erta ale caldera afar ethiopia erta ale volcano lies along the on shore red sea rift northern afar ethiopia separating the nubia and danakil plates erta ale has a nnwesse elongated caldera with a subvertical rim scarp hosting a lava lake structural field work was aimed at defining the deformation pattern around the caldera the caldera consists of along rim and across rim structures resulting from local and regional maximum extension wneesw stress fields respectively these structures cross cut each other at high angles suggesting that the two stress fields remain distinct each prevailing during rifting or caldera collapse the local along rim extensional fractures are gravity driven structures that formed due to the retreat of the caldera wall after collapse and are confined to the region of caldera subsidence the across rim structures are mainly located to the n and s of the caldera where they form rift zones each accommodating a similar amount of extension w6 3 m but displaying different trends and extension directions analogue models of interacting fractures are consistent with the southern rift being representative of the regional fault kinematics while the northern rift is a local perturbation resulting from the interaction between two right stepping rift segments along the erta ale range 2006 elsevier ltd all rights reserved

marine electrical resistivity tomography for shipwreck detection in very shallow water a case study from agropoli salerno southern italy abstract a marine electric resistivity survey was carried out over a submerged beach along the agropoli shore salerno italy to detect buried objects of archaeological interest below the sandy seabed we found a shipwreck a military vessel that probably sunk during the salerno landing operations of the allied forces in the second world war resistivity data provide information on the vertical and horizontal extension of the shipwreck which is characterized by very low calculated resistivity values about 2 5 ohm m such values differ significantly from the sand and the bedrock values 5 40 ohm m although the presence of the shipwreck is clearly visible from geoelectric data the joint application of electric magnetic and multibeam bathymetric techniques reduces the ambiguities inherent in each method as shown in the electrical resistivity tomography ert and confirmed by the digital elevation model obtained from the processing of bathymetric data the shipwreck extends more than 30 m in ne sw direction and it is about 13 m wide the global extension of the relic is consistent with the magnetic data that are characterized by a magnetic anomaly with an amplitude of about 1800 nt and similar dimension as inferred from the estimation of source boundaries obtained from the computation of the analytic signal the results of our survey encourage the use of marine geoelectrical methods for the detection of buried archaeological targets particularly in locations where the use of seismic prospecting is not effective e g very shallow water with sandy sea bottoms the integration of different geophysical methods allows to better define the extension depth and thickness of buried objects suggesting that such an approach is the most effective for underwater archaeological investigations

comments on the paper automatic detection and discrimination of volcanic tremors and tectonic earthquakes an application to ambrym volcano vanuatu by daniel rouland denis legrand mikhail zhizhin and sylvie vergniolle j volcanol geotherm res 181 2009 196 206

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

subaqueous calderas in the archean abitibi greenstone belt an overview and new ideas abstract the 300 700 km abitibi greenstone belt in canada contains numerous world class archean volcanogenic massive sulfide vms deposits yet documentation of archean subaqueous calderas hosting such deposits is lacking the modern sunrise deposit in the myojin knoll caldera of the izu bonin arc shows that submarine calderas are first order sites for vms the hunter mine and normetal calderas as well as the blake river megacaldera complex are reviewed with respect to geometry regional geology physical volcanology dyke emplacement and hydrothermal carbonate alteration these subaqueous calderas are placed into the geodynamic context of the abitibi greenstone belt the abitibi belt displays a complex history of oceanic arc formation evolution collision and fragmentation with numerous types of volcanic edifices and sedimentary basins controlled by oblique subduction and mantle plumes analogue models yielding new insights into the sequence of caldera forming events and their synvolcanic fault patterns are applied to explain archean examples underpressure experiments develop a consistent sequence of fault patterns that compare favourably with natural caldera events during subsidence two sets of faults propagate from the magma chamber margin 1 early reverse outward dipping faults and 2 normal inward dipping faults the largest massive sulfide deposits form preferentially at the caldera margin based on experimental studies and detailed facies mapping the hunter mine caldera is of the segmented piecemeal variety and the normetal caldera is akin to a piston structure the blake river megacaldera contains 1 the e w trending misema 2 the nw trending new senator and 3 the ne trending noranda calderas with the latter two being nested graben type calderas consistent with oblique archean subduction the poorly documented hydrothermal carbonate alteration is discussed and a new exploration model for calderas is presented the alteration study was evaluated at three levels microprobe analysis geochemical staining of drill core and whole rock analyses there were two principal stages of alteration related to vms formation an early silicification phase developed either at depth and or at the seawater interface whereby silicification was bedding parallel in fine grained volcaniclastic deposits near the water surface a pervasive and extensive semi conformable carbonate alteration zone with a discordant focused root zone along faults evolved subsequently three distinct carbonate pairings were observed 1 proximal siderite sideroplesite fe ankerite next to the vms deposit 2 an intermediate ankerite fe dolomite zone and 3 a distal calcite dolomite zone the carbonate phase is associated with the mineralizing event transitions between carbonate species are subtle and changes are indicated by mineral assemblage overlap the silica carbonate hydrothermal alteration pattern is a replacement product and is far more widespread than has been documented this alteration can be easily confused with primary carbonates and chemical precipitation deposits e g banded iron formation if detailed volcano sedimentary facies mapping with alteration has not been conducted and if outcrop is insufficient

geophysical investigation of the temple of apollo hierapolis turkey abstract the ruins of hierapolis are located a few kilometres north of laodicea in the lycus valley western turkey this area is characterised by a large geothermic field that produces several hot water springs along tectonic structures fractures and faults inside hierapolis is the temple of apollo the principal deity of the city while the foundations of this temple go back to late hellenistic times the present remains of the upper structure are from the 3rd century ad next to it there is an underground chamber called the plutonion from which poisonous gases emerge this paper presents the results of a geophysical survey carried out to explore firstly the buried cavities or structures beneath the temple of apollo knowledge of which is important to understand whether the plutonion could be entered from the inside of the temple for completing the sacrifices secondly to contribute to the ongoing evaluation of ground penetrating radar gpr and electrical resistivity tomography ert as tools for research into subsurface archaeological features voids walls etc two dimensional ert imaging was used to detect the presence of an active normal fault passing under the temple of apollo as shown by geological geomorphological and archaeoseismological observations the resistivity profiles reveal the presence of conductive material clay covering the archaeological structures the presence of active normal faults is indicated by the displacement of the bedrock and the conductive material on top of it three dimensional gpr imaging was used to detect man made structures located under the temple of apollo the results of the two survey methods applied were compared assessing the relative merits and demerits of each technique their combined use is discussed in terms of providing enhanced views that are more informative than a single method

quantifying tomb geometries in resistivity images using watershed algorithms abstract quantifying the geometries defined here as width height and depth of burial of archeological structures within resistivity models produced as a result of the regularization constraints used in most inversion algorithms is difficult especially when structures are closely spaced here we apply the watershed by simulated immersion method of boundary detection to smooth 2d resistivity images generated for synthetic and field data over 3d targets the synthetic studies include a single cavity model a model for two widely spaced cavities spacing unit electrode spacing and a model for two closely spaced cavities spacing

volcanic hot spot detection from optical multispectral remote sensing data using artificial neural networks summary this paper describes an application of artificial neural networks for the recognition of volcanic lava flow hot spots using remote sensing data satellite remote sensing is a very effective and safe way to monitor volcanic eruptions in order to safeguard the environment and the people affected by such natural hazards neural networks are an effective and well established technique for the classification of satellite images in addition once well trained they prove to be very fast in the application stage in our study a back propagation neural network was used for the recognition of thermal anomalies affecting hot lava pixels the network was trained using the three thermal channels of the advanced very high resolution radiometer avhrr sensor as inputs and the corresponding values of heat flux estimated using a two thermal component model as reference outputs as a case study the volcano etna eastern sicily italy was chosen and in particular the effusive eruption which took place during the month of 2006 july the neural network was trained with a time series of 15 images 12 nighttime images and 3 daytime images and validated on three independent data sets of avhrr images of the same eruption and on two relative to an eruption occurred the following month while for both nighttime and daytime validation images the neural network identified the image pixels affected by hot lava with a 100 percent success rate for the daytime images also adjacentpixelswereincluded apparentlynotinterestedbylavaflow despitetheseperformance differences under different illumination conditions the proposed method can be considered effective both in terms of classification accuracy and generalization capability in particular our approach proved to be robust in the rejection of false positives often corresponding to noisy or cloudy pixels whose presence in multispectral images can often undermine the performance of traditional classification algorithms future work shall address application of the proposed method to data acquired with a high temporal resolution such as those provided by the spinning enhanced visible and infrared imager sensor on board the meteosat second generation geostationary satellite

cooling rate of some active lavas determined using an orbital imaging spectrometer 1 the surface temperature of an active lava flow is an important physical property to measure through its influence on lava crystallinity cooling exerts a fundamental control on lava rheology remotely sensed thermal radiance data acquired by multispectral sensors such as landsat thematic mapper and the terra advanced spaceborne thermal emission and reflection radiometer are of insufficient spectral and radiometric fidelity to allow for realistic determination of lava surface temperatures from earth orbit this paper presents results obtained from the analysis of active lava flows using hyperspectral data acquired by nasa s earth observing 1 hyperion imaging spectrometer the contiguous nature of the measured radiance spectrum in the 0 4 2 5 m region means that although sensor saturation most certainly occurs unsaturated radiance data are always available from even the hottest and most radiant active lava flow surfaces the increased number of wave bands available allows for the assumption of more complex flow surface temperature distributions in the radiance to temperature inversion processes the technique is illustrated by using a hyperspectral image of the active lava lake at erta ale volcano ethiopia a well characterized calibration target a time series of three hyperion images of an active lava flow acquired during a 4 day period at mount etna sicily as well as a lava flow erupted at nyamuragira democratic republic of congo the results provide insights into the temperature radiance mixture modeling problem that will aid in the analysis of data acquired by future hyperspectral remote sensing missions such as nasa s proposed hyspiri mission

gas driven lava lake fluctuations at erta ale volcano ethiopia revealed by modis measurements the long lived lava lake of erta ale volcano ethiopia is remotely monitored by moderate resolution imaging spectroradiometers modis installed on satellites the normalised thermal index nti wright et al remote sens environ 82 135 155 2002 is shown to be proportional to the volume of the lava lake based on visual observations the lava lake s variable level can be plausibly related to a stable foam i e a mixture composed of densely packed non coalescing bubbles in suspension within a liquid this foam is trapped at the top of the magma reservoir and its thickness changes in response to the gas flux feeding the foam being successively turned on and off the temporal evolution of the foam thickness and the resulting variation of the volume of the lava lake is calculated numerically by assuming that the gas flux feeding the foam initially constant and homogeneous since december 9 2002 is suddenly stopped on december 13 2002 and not restarted before may 2003 the best fit between the theoretical foam thickness and the level of the lava lake deduced from the nti provides an estimate of both the reservoir radius 155 170 m and the gas flux feeding the foam 5 5 10 3 7 2 10 3 m 3 s 1 when existing this is in agreement with previous estimates from acoustic measurements bouche et al earth planet sci lett 295 37 48 2010 the very good agreement between the theoretical foam thickness and that deduced from modis data shows for the first time the existence of a regime based on the behaviour of a stable foam whose spreading towards the conduit wide conduit condition can explain the long lived activity our predictive model which links the gas flux at the vent to the foam spreading could potentially be used on any volcano with a long lived activity the underlying gas flux and the horizontal surface area of the magma reservoir can then be deduced by combining modelling to continuous measurements of gas flux the lava lake when high often shows regular rise and fall of its level we have recognised a minimum of 26 very well marked cycles between january 2001 and december 13 2002 corresponding to a typical return time of 10 8 2 3 days and a gas volume of 8 3 105 2 0 105 m 3 this corresponds to a gas volume fraction in the reservoir equal to 0 023 0 063 the yearly gas flux estimated between december 13 2002 and september 27 2004 varies between 2 3 10 6 and 5 9 10 6 m 3 s 1 at the depth of the reservoir the long time series provided by infra red sensors mounted on satellites could be used on any persistent volcano to detect potential periodic variations in the level of lava lakes or lava columns providing that the vent has a funnel shape as often and is sufficiently large

estimating 3d variation in active layer thickness beneath arctic streams using ground penetrating radar we acquired three dimensional 3d ground penetrating radar gpr data across three stream sites on the north slope ak in august 2005 to investigate the dependence of thaw depth on channel morphology data were migrated with mean velocities derived from multi offset gpr profiles collected across a stream section within each of the 3d survey areas gpr data interpretations from the alluvial lined stream site illustrate greater thaw depths beneath riffle and gravel bar features relative to neighboring pool features the peat lined stream sites indicate the opposite greater thaw depths beneath pools and shallower thaw beneath the connecting runs results provide detailed 3d geometry of active layer thaw depths that can support hydrological studies seeking to quantify transport and biogeochemical processes that occur within the hyporheic zone

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

possible interaction between tectonic events and seismic noise at las canadas volcanic caldera tenerife spain continuous seismic noise is recorded in the volcanic island of tenerife canary islands spain the origin of this noise strongly augmented by anthropogenic contamination is still under debate in this paper we discuss the relationship between this noise and the occurrence of local tectonic events in the same area in particular transitions are sought in the time evolution of dynamic parameters computed on the seismic noise and examples are shown where abrupt transitions may be associated with the occurrence of tectonic events these transitions provide further evidence of the existence of a natural origin for at least part of the seismic noise which is strongly contaminated if not dominated by anthropogenic sources

satellite observations reveal little inter annual variability in the radiant flux from the mount erebus lava lake abstract satellite remote sensing represents a mature technology for long term monitoring of volcanic activity at mount erebus either independently or as a complement to field instrumentation observations made on 4290 discrete occasions over a six year period by nasa s moderate resolution imaging spectroradiometer modis indicate that the radiant flux from the volcano s summit crater and by inference the lava lake contained therein while variable on the time scale of days to weeks has varied little on an inter annual basis over this period the average radiant flux from the lake during this time was 15 mw with a maximum flux of 100 mw such heat flux time series have been shown to act as a reliable proxy for general levels of activity at erupting volcanoes around the world particularly when these time series are of a long duration the apparent stability of erebus power output is in marked contrast to fluxes observed at three other terrestrial volcanoes erta ale ethiopia nyiragongo democratic republic of congo and ambrym vanuatu which while also hosting active lava lakes all exhibit much greater variability in radiant flux over the same period of time the results presented in this paper are confluent with those obtained from geochemical considerations of the erebus degassing regime and confirm that remarkably stable open system volcanism appears to be characteristic of this long active volcano

using so 2 camera imagery and seismicity to examine degassing and gas accumulation at kīlauea volcano may 2010 abstract so 2 camera measurements at k lauea volcano hawaii in may of 2010 captured two occurrences of lava lake rise and fall within the halema um au crater summit vent during high lava stands we observed diminished so 2 emission rates and decreased seismic tremor similar events at k lauea have been described as the result of sporadic degassing following gas accumulation beneath a mostly impermeable lava lake surface incorporation of so 2 camera data into a multi parameter dataset gives credence to the likelihood of shallow gas accumulation as the cause of these high stand events with accumulated gas release upon lake level drop compensating for the gas deficit reached during accumulation

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

experimental analysis of bubble driven magma motion in the conduit for persistently active open vent volcanoes this study uses analog experiments to understand the role of bubbles in inducing conduit convection for persistently degassing lava lake systems to do so air was fluxed through an initially stagnant column of liquid and the resulting return flow was measured the dynamics suggested by the experimental results is compared with that of quiescent persistently active volcanoes with a focus on eight volcanoes that exhibit summit lava lakes we find that magma flux is a function of combined gas flux conduit size and magma rheology experiments with high gas fluxes through low viscosity liquid took on turbulent characteristics which correspond to a high degree of return flow whereas lower gas fluxes through high viscosity liquids yielded slug flow which corresponded to less return flow we model the magma flux due to bubble ascent and find that gas driven liquid flow can yield faster flow rates than other mechanisms at work in volcanic conduits this can explain the discrepancy between previous estimates of magma flow in conduits and relatively fast lava lake surface velocity observations we show how bubble driven convective flow can work alongside density driven convection and discuss the depths in the conduit where each are likely to dominate the system

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

radiative temperature measurements at kupaianaha lava lake kilauea volcano hawaii field spectroradiometer data in the wavelength range of 0 4 2 5 m and spectral resolution of 1 5 nm have been used to compute the radiative temperature of the surface of kupaianaha lava lake kilauea volcano hawaii two sets of observations a total of 120 spectra were made on october 12 1987 and january 23 1988 when the lava lake was in a period of active overturning the area of the surface for which temperatures were measured was 0 23 0 55 m2 two numerical models of two and three components have been used to match the measured radiant flux ratios and to describe the surface of the lava pond in terms of radiant area and temperature three stages of activity on the lake surface are identified stage 1 characterized by magma fountaining and overturning events exhibited the hottest crustal temperatures 180 572 c and the largest fractional hot areas 10 3 stage 1 average flux densities were 2 2 104 w m2 the highest recorded for the three stages of activity on either day the largest radiative area of fresh magma was 29 at 1100 c while cooling from magmatic temperatures to newly formed crust at 790 c took place in a matter of seconds stage 2 marked by rifting events between plates of crust exhibited crustal temperatures between 100 and 340 c with fractional hot areas at least an order of magnitude lower than those found for stage 1 average flux densities calculated for three examples of stage 2 activity were 5 3 103 w m2 stage 3 which was quiescent periods when the lake was covered by a thick crust dominated the activity of the lake both temporally and spatially over 90 of the time the characteristic crustal temperature of stage 3 was 80 345 c with most solutions near 200 300 c and fractional hot areas of 10 5 of the viewing area average flux densities for stage 3 were 4 9 103 w m2 for many stage 3 examples a two component model was sufficient to describe the spectral data however for almost all of the stage 1 and 2 examples and the remainder of the stage 3 examples a three component model was required these determinations of lava temperature and radiant area have relevance for satellite and airborne measurements of the thermal characteristics of active volcanoes and indicate that temporal variability of the thermal output of lava lakes occurs on the time scale of seconds to minutes

a frozen record of density driven crustal overturn in lava lakes the example of kīlauea iki 1959 lava lakes are found at basaltic volcanoes on earth and other planetary bodies density driven crustal foundering leading to surface renewal occurs repeatedly throughout the life of a lava lake this process has been observed and described in a qualitative sense but due to dangerous conditions no data has been acquired to evaluate the densities of the units involved k lauea iki pit crater in hawai i houses a lava lake erupted during a 2 month period in 1959 part of the surface of the k lauea iki lake now preserves the frozen record of a final incomplete crustal overturn cycle we mapped this region and sampled portions of the foundering crust as well as overriding and underlying lava to constrain the density of the units involved in the overturn process overturn is driven by the advance of a flow front of fresh low density lava over an older higher density surface crust the advance of the front causes the older crust to break up founder and dive downwards into the lake to expose new hot low density lava we find density differences of 200 to 740 kg m3 between the foundering crust and over riding and under lying lava respectively in this case crustal overturn is driven by large density differences between the foundering and resurfacing units these differences lead inevitably to frequent crustal renewal simple density differences between the surface crust and underlying lake lava make the upper layers of the lake highly unstable

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

ducks low cost thermal monitoring units for near vent deployment abstract during 1999 we designed and tested a thermal monitoring system to provide a cheap robust modular real time system capable of surviving the hostile conditions encountered proximal to active volcanic vents in november 2000 the first system was deployed at pu u o o kilauea hawai i to target persistently active vents aside from some minor problems such as sensor damage due to tampering this system remained operational until january 2004 the success of the prototype system led us to use the blueprint for a second installation at stromboli aeolian islands italy this was deployed dug into a bomb proof bunker during may 2002 and survived the april 2003 paroxysmal eruption despite being located just 250 m from the vent in both cases careful waterproofing of connectors and selection of suitable protection has prevented water damage and corrosion in the harsh atmosphere encountered at the crater rim the pu u o o system cost us 10 000 and comprises four modules sensors transmission and power hub repeater station and reception site the sensor component consists of three thermal infrared thermometers housed in pelican cases fitted with germanium arsenide selenium windows two 1 field of view fov sensors allow specific vents to be targeted and a 60 fov sensor provides a crater floor overview a hard wire connection links to a pelican case housed microprocessor modem and power module from here data are transmitted via a repeater site to a dedicated pc at the hawaiian volcano observatory here data are displayed with a delay of 3 s between acquisition and display the modular design allows for great flexibility at stromboli 1 and 15 fov sensor modules can be switched depending changes in activity style and crater geometry in addition a direct line of site to the stromboli reception center negates the repeater site requirement reducing the cost to us 5500 for a single sensor system we have also constructed self contained units with internal data loggers for us 1500 unit these have been tested at kilauea stromboli etna masaya santiaguito fuego pacaya poas soufriere hills villarrica and erta ale these instruments have proved capable of detecting thermal signals associated with 1 gas emission 2 gas jetting events 3 crater floor collapse 4 lava effusion 5 lava flow in tubes 6 lava lake activity 7 lava dome activity and 8 crater lake skin temperature

identification of variable convective regimes at erta ale lava lake abstract during february 17 19 2002 we collected a combined thermal and seismic data set for persistent lava lake activity at erta ale volcano ethiopia these data indicate that the lake cycled between periods characterized by low 0 01 0 08 m s 1 and high 0 1 0 4 m s 1 surface velocities typically lasting tens to hundreds of minutes these periods of high and low velocity motion define periods of vigorous and sluggish convection respectively spectral analysis revealed that vigorous convection periods were characterized by high frequencies and energies in the thermal data and an increased presence of high frequency energy in the seismic data the data show that vigorous periods were characterized by formation of hot short lived plastic crusts and sluggish periods by cooler longer lived brittle crusts here the higher transit velocity across the lake surface from upwelling zones of crust formation to downwelling zones of crust destruction during the vigorous periods decreases the crust lifetime this in turn decreases the total cooling and thickening experienced by a plate of crust moving across the lake surface two scenarios can be envisaged to explain such convection cycles the first relates variable convection rates to changes in the volume flux and rheology of magma entering the lake in the second cyclic convection is set up by the generation of convective instabilities within the lake in this case cooling of a surface layer generates a slow moving viscous increasingly dense convection layer at the lake surface which is consumed and replaced during overturn

multiparametric approach in investigating volcano hydrothermal systems the case study of vulcano aeolian islands italy seismic activity ground deformation and soil and fumarole temperatures acquired during 2004 2007 at vulcano aeolian islands are analysed and the time relations among the different time series are discussed changes in temperature of fumarolic gases took place during four anomalous periods november 2004 march 2005 october 2005 february 2006 august october 2006 july december 2007 at the same time as an increasing number of volcano seismic events in particular the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440 c and from 20 to 90 c respectively the maximum daily number of volcano seismic events was 57 reached during the second anomalous period this seismicity characterised by focal depth generally lower than 1 km below sea level b s l and composed of different kinds of events associated to both resonance and shear failure processes is related to the shallow dynamics of the hydrothermal system during the analysed period very few volcano tectonic earthquakes took place and tilt recordings showed no sharp or important changes in light of such observations the increases in both temperature and volcano seismic events number were associated to increases in the release of gas from a deep and stable magma body without magma intrusions within the shallow hydrothermal system indeed a greater release of gas from depth leads to increased fluid circulation that can promote increases in volcano seismic events number by both fracturing processes and resonance and vibration in cracks and conduits the different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body finally all the observed variations together with the changing temporal distribution of the different seismic event kinds suggest that the hydrothermal system at vulcano can be considered unsteady and dynamic

periodic outgassing as a result of unsteady convection in ray lava lake mount erebus antarctica abstract persistently active lava lakes show continuous outgassing and open convection over years to decades ray lake the lava lake at mount erebus ross island antarctica maintains long term near steady state behavior in temperature heat flux gas flux lake level and composition this activity is superposed by periodic small pulses of gas and hot magma every 5 18 min and disrupted by sporadic strombolian eruptions the periodic pulses have been attributed to a variety of potential processes including unstable bidirectional flow in the conduit feeding the lake in contrast to hypotheses invoking a conduit source for the observed periodicity we test the hypothesis that the behavior could be the result of dynamics within the lake itself independent of periodic influx from the conduit we perform numerical simulations of convection in ray lake driven by both constant and periodic inflow of gas rich magma from the conduit to identify whether the two cases have different observational signatures at the surface our simulations show dripping diapirs or pulsing plumes leading to observable surface behavior with periodicities in the range of 5 20 min we conclude that a convective speed faster than the inflow speed can result in periodic behavior without requiring periodicity in conduit dynamics this finding suggests that the surface behavior of lava lakes might be less indicative of volcanic conduit processes in persistently outgassing volcanoes than previously thought and that dynamics within the lava lake itself may modify or overprint patterns emerging from the conduit beyond its importance for erebus this result highlights the need to understand periodic processes emerging at all levels of the volcanic plumbing system in order to interpret surface observations

backward tracking of gas chemistry measurements at erebus volcano erebus volcano in antarctica offers an exceptional opportunity to probe the dynamics of degassing its behavior is characterized by an active lava lake through which sporadic strombolian eruptions occur here we develop a framework for interpreting contrasting degassing signatures measured at high temporal resolution which integrates physical scenarios of gas melt separation into a thermodynamic model that includes new volatile solubility data for erebus phonolite in this widely applicable framework the measured gas compositions are backtracked from surface to depth according to physical templates involving various degrees of separation of gas and melt during ascent overall explosive signatures can be explained by large bubbles gas slugs rising slowly in equilibrium from at least 20 bars but at most a few hundred bars in a magmatic column closer to the stagnant end member than the convecting end member the span of explosive signatures can be due to various departure depths and or slug acceleration below a few tens of bars results also reveal that explosive gases last equilibrated at temperatures up to 300 degrees c colder than the lake due to rapid gas expansion just prior to bursting this picture individual rise of gas and melt batches from a single potentially very shallow phonolitic source offers an alternative to the conclusions of previous work based on a similar data set at erebus according to which differences between quiescent and explosive gas signatures are due to the decompression of two deep volatile saturated sources that mixed to various degrees phonolite at 1 3 kbar and basanite at 5 8 kbar

physico chemical controls on ore deposition in the arapucandere pb zn cu precious metal deposit biga peninsula nw turkey abstract arapucandere is one of a number of similar cu zn pb au ag epithermal deposits in the biga peninsula which are mineralogically and tectonically similar fluid inclusions have very low salinities between 1 7 and 0 wt nacl and a wide range of temperatures from 360 to 160 c there was extensive boiling and flashing of the hydrothermal fluids which initiated mineral deposition the range of temperatures is consistent with emplacement of the veins at 700 m depth with the pressure decreasing from near lithostatic to near hydrostatic and a decrease in temperature to 250 c due to adiabatic expansion of the fluids there is evidence of a limited amount of boiling but the temperature and pressure decrease was close to the liquid vapour curve flashing of the fluids was caused by sudden drops to sub hydrostatic pressures and even lower temperatures mineralization was caused by these pressure related temperature decreases as there is no evidence of cooling and dilution of the ore fluids 34 s values of sulphides indicate a magmatic source but the more negative than usual values also suggest boiling affected isotopes d and 18 o of the fluids indicate a mixing between meteoric waters and magmatic fluids with the large range of d due to boiling la icp ms analyses of fluid inclusions reveal high cu zn pb concentrations in the fluids despite their low salinity transported as chloride complexes exceptional pressure and temperature decrease causing the fluids to flash was likely to have been in response to earthquakes

implications of longeval lava lakes for geomorphological and plutonic processes at erta ale volcano afar erta ale volcano sited within the afar triangle of ethiopia is one of the least visited of perennially active subaerial volcanoes satellite images recorded over the past thirty years illustrate the sustained activity of the volcano and complement the few brief periods of field observation we consider that erta ale s lava lakes have probably persisted for 90 years placing them among the longest lived yet recorded despite sustained surface heat fluxes of 100 400 mw the net surface growth rate integrated over the interval 1968 1995 was only 10 kg s 1 we speculate that this minimal lava discharge cannot be used to infer a low magma supply rate to the volcano since heat losses from die lava lakes inhibit eruption by increasing magma density this implies growth of the underlying crust by formation of dikes and sills containing cumulates accommodated and possibly promoted by regional extension and intrusion loading open vent degassing and rift kinematics are clearly reflected in erta ale s morphology which is characterised by very gentle 3 slopes and a summit caldera

radiative heat power at stromboli volcano during 2000 2011 twelve years of modis observations abstract twelve years of night time modis moderate resolution imaging spectroradiometer observations has been analysed to detect and quantify the radiative heat power emitted by stromboli volcano from march 2000 to september 2011 using an accurate background subtraction of the modis signal at 4 m we were able to discriminate two main regimes of thermal radiation related to different levels of volcanic activity effusive eruptions occurred on december 28 2002 and february 27 2007 radiated at an average of 186 mw with a frequency of alert detection of 50 95 conversely during the typical strombolian activity an average of 9 mw is radiated with a frequency of alert detection of 0 45 although during the effusive eruptions the radiative power is basically controlled by the lava discharge rate our results suggest that during non effusive periods strombolian regime both the intensity and the frequency of modis alerts are controlled by the height of the magmatic column feeding the activity at the surface in particular we found that a radiative power of 50 mw corresponds to a high magma column which is exposed in the vent area at the same rate in which the deeper gas rich magma is typically supplied within the feeding system of stromboli 0 3 m3 s 1 in this condition the magmatic system approaches steady state regimes above this threshold a transition from strombolian to effusive regimes may occur as shown by the detection of 50 mw 8 10 days before the onset of both the last two major flank eruptions these values were reached after 1 2 months of gradual increase of the radiative power which was likely associated the rising of the magma column within the shallowest portion of the conduit in addition our data suggest that over the years 2000 2011 several cycles of rise and fall of the magma column have occurred which however did not culminate into an effusive eruption but only into recurrent episodes of sustained spattering or fountaining and summit overflows these fluctuations has substantially increased in frequency and intensity after the 2007 eruption thus suggesting that this event has perturbed in some way the shallow plumbing system of stromboli we stress that the detection of a radiative power higher than 50 mw is a clear evidence of a very high magma column which may prelude the onset of an effusive eruption and or periods of sustained vent activity in conclusion we suggest that systematic analysis of modis data can be used to detect variations in the intensity of strombolian activity and may considerably improve volcano surveillance at stromboli as well as at other open system volcanoes

extraterrestrial lava lakes abstract active lava lakes are rare on earth with only ten documented examples all formed by lavas of basaltic composition and housed inside summit craters or calderas the existence of lava lakes on other planetary bodies may imply similarities in either composition or volcano tectonic settings and so has important implications for understanding the link between melt production and volcanism we review lava lakes on earth and other planets particularly active caldera like features interpreted to be currently containing active lava lakes on jupiter s moon io and features interpreted as remnants of lava lakes on venus and mars mercury and the moon do not boast the major calderas or shield volcanoes of their larger rocky neighbors partly due to a horizontally compressive tectonic regime arising from global contraction that makes it difficult to move melts through the upper crust we discuss the evidence for active lava lakes on io and show how modeling based on terrestrial lava lakes can reveal how these phenomena differ on both bodies the superficial similarities do not necessarily imply that the plumbing is similar observations of the largest lava lake on io loki patera provide insight into the nature of ionian lava lakes in general which may be more similar to eruptive episodes on the east pacific rise on earth which lead to temporary lava lakes although temporal data for io s lava lake activity are scarce studies of temporal variability of lava lakes on earth are useful for providing ground truth for comparisons future studies of earth by remote sensing and field observations and of io by both ground based observations and future missions are needed to answer many questions including why lava lakes rare on earth appear to be common on io

a review of controls on lava lake level insights from halema uma u crater kīlauea volcano the height of the lava column is a fundamental measure of open vent volcanic activity but little continuous long term data exist to understand this parameter the recent 2008 2018 lava lake activity at the summit of k lauea volcano provides an opportunity to track and understand the processes that control lava level over timescales ranging from minutes to years we review recently published data as well as analyze the long term record of lava level at k lauea s summit during 2009 2017 longer timescale fluctuations over days to months have a strong positive linear correlation with ground deformation suggesting they reflect pressure changes in the summit magma reservoir shorter timescale fluctuations over minutes to hours have an inverse relationship with spattering i e outgassing intensity at the lake surface increased outgassing lowers the lake level and vice versa our analysis of the long term lava level data thus confirms that lava level at halema uma u is controlled by these two types of processes 1 those related to magma reservoir pressure changes such as magma supply rate and 2 shallow outgassing fluctuations such as gas pistoning frequency filtering can isolate pressure and outgassing driven components of lava level change time series analysis indicates that there was no large persistent periodicity in the lava level a minor fortnightly oscillation might be related to earth tides but was not continuously present the correlation between lava level and deformation of the summit indicates that the lava lake acts as a reliable piezometer tracking lava level over time may thus provide an indication of flank eruptive potential we show that long term interdisciplinary monitoring is necessary to discriminate the processes that control lava level

detecting and mapping buried buildings with ground penetrating radar at an ancient village in northwestern argentina abstract we describe an archaeo geophysical investigation performed near the palo blanco archaeological site catamarca argentina a large area beyond the northern limit of the site was explored with the ground penetrating radar gpr method in order to detect new buildings the exploration showed signals of mud walls in a sector that was located relatively far from the previously known buildings a detailed survey was performed in this sector and the results showed that the walls belonged to a large dwelling with several rooms the discovery of this dwelling has considerably extended the size of the site showing that the dwellings occupied at least twice the originally assumed area high density gpr surveys were acquired at different parts of the discovered building in order to resolve complex structures interpreted maps of the building were obtained different characteristics of the walls were satisfactory determined in spite of the low contrast of the dielectric constant at their interfaces and the noticeable spatial fluctuations of the signals due to wall collapses systematic excavations confirmed the gpr maps providing further relevant information about the characteristics of the walls and the occupational floor as well as material for radiocarbon analyses these analyses indicated that the discovered building was occupied until about ad 880 this fact extends 180 years the previously known period for the village and also for the settlements in the region formerly ad 200 to ad 700 the performed investigations moreover confirmed different architectural characteristics assumed for palo blanco related to the internal and external layouts interconnection between the rooms without intermediary courtyards seems to indicate a better use of the internal spaces and a more integrated spatial conception in palo blanco than in other villages of the region

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

constraints on determining the eruption style and composition of terrestrial lavas from space the surface temperatures of active lavas relate to cooling rates chemistry and eruption style we analyzed 61 hyperspectral satellite images acquired by the national aeronautics and space administration s earth observing 1 eo 1 hyperion imaging spectrometer to document the surface temperature distributions of active lavas erupted at 13 volcanoes images were selected to encompass the range of common lava eruption styles specifi cally lava fountains fl ows lakes and domes our results reveal temperature distributions for terrestrial lavas that correlate with composition i e a statistically signifi cant difference in the highest temperatures retrieved for mafi c lavas and intermediate and felsic lavas and eruption style maximum temperatures observed for mafi c lavas are 200 c higher than for intermediate and felsic lavas all eruption styles exhibit a low temperature mode at 300 c lava fountains and a a flows also exhibit a higher temperature mode at 700 c the observed differences between the temperatures are consistent with the contrasting rates at which the lava surfaces are thermally renewed eruption styles that allow persistent and pervasive thermal renewal of the lava surface e g fractured crusts on channel fed a a flows exhibit a bimodal temperature distribution eruption styles that do not e g the continuous skin of pahoehoe lavas exhibit a single mode we conclude that insights into composition and eruption style can only be gained remotely by analyzing a large spatio temporal sample of data this has implications for determining composition and erup tion style at the jovian moon io for which no in situ validation is available

cyclic spattering seismic tremor and surface fluctuation within a perched lava channel kīlauea volcano in late 2007 a perched lava channel built up to 45 m above the preexisting surface developed during the ongoing eruption near pu u cone on k lauea volcano s east rift zone the lava channel was segmented into four pools extending over a total of 1 4 km from late october to mid december a cyclic behavior consisting of steady lava level rise terminated by vigorous spattering and an abrupt drop in lava level was commonly observed in pool 1 we use geologic observations video time lapse camera images and seismicity to characterize and understand this cyclic behavior spattering episodes occurred at intervals of 40 100 min during peak activity and involved small 5 10 m high fountains limited to the margins of the pool most spattering episodes had fountains which migrated downchannel each spattering episode was associated with a rapid lava level drop of about 1 m which was concurrent with a conspicuous cigar shaped tremor burst with peak frequencies of 4 5 hz we interpret this cyclic behavior to be gas pistoning and this is the first documented instance of gas pistoning in lava well away from the deeper conduit our observations and data indicate that the gas pistoning was driven by gas accumulation beneath the visco elastic component of the surface crust contrary to other studies which attribute similar behavior to the periodic rise of gas slugs the gas piston events typically had a gas mass of about 2 500 kg similar to the explosions at stromboli with gas accumulation and release rates of about 1 1 and 5 7 kg s 1 respectively the time averaged gas output rate of the gas pistoning events accounted for about 1 2 of the total gas output rate of the east rift zone eruption

ground penetrating radar survey of a prehistoric site in southern italy abstract in this paper we present and discuss the results of a ground penetrating radar gpr study carried out in an area of southern italy where a karst cave with prehistoric remains was found the aim of the study involved the imaging of the subsurface stratigraphy both inside and outside the cave in order to assist archaeologists in an excavation programme the survey grid comprised 18 intersecting gpr profiles problems associated with the use of the gpr within a cave environment are highlighted and the data processing sequence designed to extract useful geo archaeological signatures is described interpretation of the radar sections was controlled by the excavation of two trenches inside and outside the cave allowing detailed outlining the complex stratigraphy and the reconstruction of palaeolithic and neolithic subsurface horizons

integrated near surface geophysical survey of the cathedral of mallorca abstract this paper describes an integrated near surface geophysical study carried out in order to obtain high resolution images of the shallow subsurface under and around the cathedral of mallorca the study was a part of a global project focused on determining the state of the building structure and on evaluating the cathedral s dynamical behaviour natural frequencies and vibration modes ground penetrating radar gpr and the capacitively coupled resistivity method were used to obtain 2d images of the shallow subsurface refraction microtremor array measurements remi were also used to characterize the rock and soil properties and several invasive boreholes provided detailed and exact information on the stratigraphy the information from the geophysical data was used to determine a final model of the ground with indications of the most likely vulnerable zones as a part of this final model gpr profiles enabled us to delineate the superficial ground structure and to detect some archaeological features electrical resistivity imaging data were in good agreement with the gpr results and showed shallow major changes in the soil and rock under the filling materials the refraction microtremor array remi results indicate the existence of compacted soils in different areas probably corresponding to old filled zones in good correlation with gpr and resistivity profiles in the most superficial part of the ground

origins and implications of zigzag rift patterns on lava lakes abstract the distinctive rift patterns observed on newly formed lava lakes are very likely a product of interaction between heat transfer cooling of lava and deformation of the solid crust in response to applied stresses one common pattern consists of symmetric zigzag rifts separating spreading plates zigzags can be characterized by two measurable parameters an amplitude a and an angle between segments that make up the zigzags similar patterns are observed in analog wax experiments in which molten wax acts as cooling and solidifying lava we perform a series of these wax experiments to find the relationship between a and the cooling rate we develop a model to explain the observed relationships is determined by a balance of spreading and solidification speeds the amplitude a is limited by the thickness of the solid wax crust theoretical predictions agree well with experimental data this enables us to scale the model to basaltic lava lakes if zigzag rifts are observed on the surface of lava lakes and if physical properties of the lava crust can be measured or inferred by other means measurements of and a make it possible to calculate crust spreading velocity and crust thickness

morphology temperature and eruption dynamics at pele abstract the pele region of io has been the site of vigorous volcanic activity from the time of the first voyager i observations in 1979 up through the final galileo ones in 2001 there is high temperature thermal emission from a visibly dark area that is thought to be a rapidly overturning lava lake and is also the source of a large sulfur rich plume we present a new analysis of voyager i visible wavelength images and galileo solid state imager ssi and near infrared mapping spectrometer nims thermal emission observations which better define the morphology of the region and the intensity of the emission the observations show remarkable correlations between the locations of the emission and the features seen in the voyager images which provide insight into eruption mechanisms and constrain the longevity of the activity we also analyze an additional wavelength channel of nims data 1 87 m which paradoxically because of reduced sensitivity allows us to estimate temperatures at the peak locations of emission measurements of eruption temperatures on io are crucial because they provide our best clues to the composition of the magma high color temperatures indicative of ultramafic composition have been reported for the pillan hot spot and possibly for pele although recent work has called into question the requirement for magma temperatures above those expected for ordinary basalts our new analysis of the pele emission near the peak of the hot spot shows color temperatures near the upper end of the basalt range during the i27 and i32 encounters in order to analyze the observed color temperatures we also present an analytical model for the thermal emission from fire fountains which should prove generally useful for analyzing similar data this is a modification of the lava flow emission model presented in howell howell r r 1997 icarus 127 394 407 adapted to the fire fountain cooling curves first discussed in keszthelyi et al keszthelyi l jaeger w milazzo m radebaugh j davies a g mitchell k l 2007 icarus 192 491 502 when applied to the i32 observations we obtain a fire fountain mass eruption rate of 5 1 10 5 kg s 1 for the main vent area and 1 4 10 4 kg s 1 for each of two smaller vent regions to the west these fire fountain rates suggest a solution to the puzzling lack of extensive lava flows in the pele region much of the erupted lava may be ejected at high speed into the fire fountains and plumes creating dispersed pyroclastic deposits rather than flows we compare gas and silicate mass eruption rates and discuss briefly the dynamics of this ejection model and the observational evidence

using volcanic tremor for eruption forecasting at white island volcano whakaari new zealand abstract eruption forecasting is a challenging task because of the inherent complexity of volcanic systems despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions the material failure forecast method ffm is one of the very few techniques that can provide a forecast time for an eruption however the method requires testing and automation before being used as a real time eruption forecasting tool at a volcano we developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by real time seismic amplitude measurement rsam at one station and optimised this algorithm for the period august 2011 january 2014 which comprises the recent unrest period at white island volcano whakaari new zealand a detailed residual analysis was paramount to select the most appropriate model explaining the rsam time evolutions in a hindsight simulation four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0 21 which is 37 times higher than the probability of having an eruption on any day during the same period 0 0057 moreover the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view whereas the rsam time evolutions preceding these four eruptions have a similar goodness of fit with the ffm their spectral characteristics are different the duration amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions we propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes this hindsight exercise can be useful for future real time implementation of the ffm at white island a similar methodology could also be tested at other volcanoes even if only a limited network is available

contribution of the resistivity method to characterize mud walls in a very dry region and comparison with gpr abstract mud walls are frequent in many archaeological sites including sites located in semi desert regions in cases with buried walls the geophysical methods can be useful tools for their investigation since they provide maps of the subsoil in a non invasive way and in relatively short times this article deals with the characterization of mud walls in very dry soils through the resistivity method discussing a methodology to satisfactorily apply the method in this kind of adverse environment and how to interpret the results the case of the palo blanco archaeological site a pre incaic village located in the nw region of argentina is analyzed in very dry soils it is frequent that the electrical current cannot be injected due to the high values of electrical resistivity at the shallowest portions of soil which makes the resistivity method useless here we show how this problem can be systematically overcome by wetting a shallow thread between each pair of injection electrodes and the manner in which the resulting profiles can be analyzed we perform numerical simulations of the resistivity profiles considering 3d models of mud walls and wetted threads that reproduce experimental situations and compare them to 2d field data the resistivity profiles are analyzed for different orientations and distances between the wall and profile and fluctuations of the soil parameters the experimental profiles are interpreted from these simulations and compared to ground penetrating radar gpr profiles the resistivity methodology shows effective for characterizing the size and depth of the mud walls even in cases with collapsed or much eroded walls for which gpr often fails