plume tracker interactive mapping of volcanic sulfur dioxide emissions with high performance radiative transfer modeling abstract we describe the development of plume tracker an interactive toolkit for the analysis of multispectral thermal infrared observations of volcanic plumes and clouds plume tracker is the successor to map so2 and together these flexible and comprehensive tools have enabled investigators to map sulfur dioxide so 2 emissions from a number of volcanoes with tir data from a variety of airborne and satellite instruments our objective for the development of plume tracker was to improve the computational performance of the retrieval procedures while retaining the accuracy of the retrievals we have achieved a 300 improvement in the benchmark performance of the retrieval procedures through the introduction of innovative data binning and signal reconstruction strategies and improved the accuracy of the retrievals with a new method for evaluating the misfit between model and observed radiance spectra we evaluated the accuracy of plume tracker retrievals with case studies based on modis and airs data acquired over sarychev peak volcano and aster data acquired over kilauea and turrialba volcanoes in the sarychev peak study the airs based estimate of total so 2 mass was 40 lower than the modis based estimate this result was consistent with a 45 reduction in the airs based estimate of plume area relative to the corresponding modis based estimate in addition we found that our airs based estimate agreed with an independent estimate based on a competing retrieval technique within a margin of 20 in the kilauea study the aster based concentration estimates from 21 may 2012 were within 50 of concurrent ground level concentration measurements in the turrialba study the aster based concentration estimates on 21 january 2012 were in exact agreement with so 2 concentrations measured at plume altitude on 1 february 2012

surging accelerating surface lowering and volume reduction of the malaspina glacier system alaska usa and yukon canada from 1972 to 2006 near concurrent surges and multi decadal surface elevation changes on the malaspina glacier system alaska usa and yukon canada were investigated using digital elevation models and laser altimetry from airborne and space borne sensors surface elevation changes on seward lobe in two time periods support a hypothesis of moraine folding by a mechanism of sequential surges alternating from southeast to south southwest the near concurrent surges of agassiz lower seward and marvine glaciers support a hypothesis of englacial water storage being a critical factor of surging acceleration of area average surface lowering on the piedmont glaciers occurred from 1 5 0 1 m a 1 between 1972 and 1999 to 2 3 0 3 m a 1 between 1999 and 2002 on the western half of upper seward glacier above 1600 m acceleration of surface lowering occurred from 2000 to 2003 relative to that from 1976 to 2000 indicating an effect from the surge of lower seward glacier from 2003 to 2006 the rate of surface lowering on upper seward glacier has moderated back to the pre 2000 rate indicating a recovery of surface elevation following the surge from 1972 to 2002 the malaspina glacier system lost 156 19 km 3 ice equivalent on an area of 3661 km 2

quantifying tropospheric volcanic emissions with airs the 2002 eruption of mt etna italy 1 the atmospheric infrared sounder airs is a hyperspectral ir spectrometer orbiting on the eos aqua spacecraft since may 2002 in late october 2002 airs detected lower tropospheric sulfur dioxide and ash emitted by an eruption of mt etna italy in plumes which could be tracked over 1000 km from the volcano into north africa we report retrievals of so2 and ash column amounts and ash particle size in the etna plumes airs total so2 compares favorably with contemporaneous ground based correlation spectrometry cospec measurements retrieval of ash cloud parameters in the eruption plumes permits quantitative studies of distal ash fallout the etna data demonstrate the potential of airs to improve measurements of volcanic so2 and ash loading in the troposphere and to refine our understanding of volcanic cloud composition structure and evolution

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

using the goes sounder to monitor upper level so2 from volcanic eruptions 1 this study explores the sensitivity of the geostationary operational environmental satellite goes sounder observations to atmospheric loadings of so 2 from volcanic eruptions the goes sounder offers a more rapid refresh rate than similar instruments on board polar orbiting satellites such as the high resolution infrared radiation sounder hirs carried on the noaa and metop spacecraft one of the goes sounder s 19 channels is in an so 2 absorption band simulations demonstrate that this channel centered at approximately 7 4 mm when combined with other channels can detect the presence of large amounts of so 2 e g greater than 50 du in the upper atmosphere e g above 8 km the goes sounder can also provide upper limits of the amount of upper level so 2 provided the atmospheric altitude of the so 2 is known the sensitivity is demonstrated on two volcanic eruptions of the soufriere hills volcano on the island of montserrat through use of the goes sounder measurements the advection and rapid spreading of the plume are easily observed efforts to fully characterize the plume size and transport are hampered by the limited spatial coverage of the current goes sounder

transport of volcanic aerosol in the troposphere the case study of the 2002 etna plume 1 the transport of aerosol in the troposphere during the 2002 eruption of mount etna was investigated integrating lidar observations and numerical simulations the case study concentrates on the period 30 october to 2 november the lidar observations performed in potenza italy reveal the presence of aerosol layers made up of young sulfate particles and a low soot content characteristic of the volcano s emission downward large scale motion was measured with a velocity larger than that due to gravitational sedimentation forward trajectories from the volcano simulated from 27 october to 4 november show that particles released at the beginning of the period reached potenza after traveling over the southern and western mediterranean basin partially including the sahara region direct northward transport occurred on 31 october and 1 november the main result of this study is to highlight how the integrated use of observations and model simulations leads to understanding the main features of transport in this case study furthermore some specific points are outlined there is fair agreement between the simulated and observed presence of particles over potenza the vertical structure of the aerosol layers and the downward motion are also well evidenced time variations of the particle concentration deduced from measurements and approximately estimated from the numerical simulations also show qualitative agreement

performance of aster and srtm dems and their potential for assessing glacial lakes in the lunana region bhutan himalaya to assess the potential volume of a glacial lake outburst flood glof more precisely than in previous studies we analyze ground survey data and remote sensing digital elevation models dems around glacial lakes in the lunana region bhutan based on a dem generated from differential gps ground surveys we first evaluate the relative accuracies of dems produced by the advanced spaceborne thermal emission and reflection radiometer aster and the shuttle radar topography mission srtm root mean square errors of the altitudinal difference between these dems and ground survey data were 11 0 m for aster and 11 3 m for srtm these errors are similar to those of previous studies we show that a topographical classification allows a better estimate of elevation on lakes ponds riverbeds and glaciers due to their flat surfaces while the relative accuracy is worse over moraines and hill slopes due to their narrow ridges and steep slopes using the optical satellite images and the ground survey data we re evaluate the glof volume in 1994 as 17 2 5 3 10 6 m 3 we show glof related information such as distance altitudinal difference and gradient at possible outburst points where the lake level is higher than the neighboring riverbed and or glacial lake

multi decadal satellite measurements of global volcanic degassing abstract satellite instruments have been providing measurements of global volcanic emissions of sulfur dioxide so 2 since 1978 based on observations in the ultraviolet uv infrared ir and microwave spectral bands we review recent advances in satellite remote sensing of volcanic gases focusing on increased instrument sensitivity to tropospheric so 2 emissions and techniques to determine volcanic plume altitude a synthesis of 36 years of global uv ir and microwave satellite measurements yields an updated assessment of the volcanic so 2 flux to the upper troposphere and lower stratosphere utls between 1978 and 2014 1 2 tg yr the present availability of multiple uv and ir satellite so 2 products provides increased confidence in calculated so 2 loadings for many eruptions we examine the temporal and latitudinal distribution of volcanic so 2 emissions and reassess the relationship between eruptive so 2 discharge and eruption magnitude finding a first order correlation between so 2 emission and volcanic explosivity index vei but with significant scatter based on the observed so 2 vei relation we estimate the fraction of eruptive so 2 emissions released by the smallest eruptions 0 48 tg yr which is not recorded by satellite observations a detailed breakdown of the sources of measured so 2 emissions reveals intuitively expected correlations between eruption frequency so 2 loading and volcanic degassing style we discuss new constraints on e folding times for so 2 removal in volcanic plumes and highlight recent measurements of volcanic hydrogen chloride hcl injections into the utls an analysis of passive volcanic emissions of so 2 detected in ozone monitoring instrument omi so 2 data since 2004 provides new insight into the location and stability of the dominant sources of volcanic so 2 over the past decade since volcanic so 2 emissions constitute a random highly variable perturbation to the atmosphere climate system continued monitoring of volcanic so 2 emissions from space by multiple uv and ir instruments to extend the current multi decadal record is essential and near global geostationary measurements of so 2 may be available by the end of the current decade

investigating the use of the saharan dust index as a tool for the detection of volcanic ash in seviri imagery abstract despite the similar spectral signatures of ash and desert dust relatively little has been done to explore the application of dust detection techniques to the problem of volcanic ash detection the saharan dust index sdi is routinely implemented for dust monitoring at some centres and could be utilised for volcanic ash detection with little computational expense thereby providing a product that forecasters already have some familiarity with to complement the suite of existing ash detection tools we illustrate one way in which the index could be implemented for the purpose of ash detection by applying it to three scenes containing volcanic ash from the 2010 eyjafjallajokull eruption iceland and the 2011 eruption of puyehue chile it was also applied to an image acquired over etna in january 2011 where a volcanic plume is clearly visible but is unlikely to contain any ash these examples demonstrate the potential of the sdi as a tool for ash monitoring under different environmental and atmospheric conditions in addition to presenting a valuable qualitative product to aid monitoring this work includes a quantitative assessment of the detection skill using a manually constructed expert ash mask the optimum implementation of any technique is likely to be dependent on both atmospheric conditions and on the properties of the imaged ash which is often unknown in a real time situation here we take advantage of access to a truth rarely available in a real time situation and calculate an ash mask based on the optimum threshold for the specific scene which is then used to demonstrate the potential of the sdi the sdi mask is compared to masks calculated from a simplistic implementation of the more traditional split window method again exploiting our access to the truth to set the most appropriate threshold for each scene and to a probabilistic method that is implemented without reference to the truth and which provides useful insights into the likely cloud ash contamination of each pixel since the sensitivity of the sdi and split window methods to the tailored thresholds was not tested such tailoring is unlikely to be possible in a real situation this study presents the maximum anticipated skill for the sdi in the context of the maximum skill anticipated for the split window method although both are likely to be lower in a real time situation the results for the sdi are comparable to those of the other methods with a true skill score of 80 02 for the eyjafjallajokull night time scene compared to 88 81 and 46 63 for the split window and probabilistic method respectively and 90 06 for the eyjafjallajokull day time scene compared to 97 61 and 56 96 for the puyehue image the sdi resulted in a true skill score of 74 85 while the split window approach achieved 99 62 these results imply that the sdi which is already implemented operationally at some centres for dust detection could be a useful complement to existing ash monitoring techniques

spatio temporal variability in elevation changes of two high arctic valley glaciers uncertainties in estimates of glacier and ice cap contribution to sea level rise exist in part due to poor quantification of mass balance errors particularly those resulting from extrapolation of sparse measurements centre line data are often assumed to be representative of the glacier as a whole with little attention paid to extrapolation errors or their effect on mass balance estimates here we present detailed digital elevation model dem measurements of glacier wide elevation changes over the last 40 years at two glaciers on svalbard norwegian arctic austre broggerbreen and midtre lovenbreen are shown to have lost 27 54 0 98 and 9 65 0 76 10 7 m 3 of ice respectively between 1966 and 2005 findings that we relate to trends in average summer air temperatures and winter accumulation these volume losses correspond to geodetic balances of 0 58 0 03 and 0 41 0 03 m w e a 1 respectively our analysis revealed high spatial complexity in patterns of elevation change varying between glaciers between measurement intervals and within and between elevation bins balances from extrapolated centre line geodetic data were the same within errors as those from full coverage dem differencing in the majority of comparisons yet significantly underestimated balance in three instances additionally field mass balance from centre line ablation stake data underestimated balances from full coverage geodetic measurements during three of six measurement periods these findings may support the hypothesis that field measurements under estimate svalbard glacier mass loss at least partly as a result of the failure of centre line measurements to account for glacier wide variations in ablation our results demonstrate the importance of deriving accurate interpolation functions and constraining extrapolation errors from sparse measurements

circumpolar transport of a volcanic cloud from hekla iceland 1 hekla volcano iceland erupted on 17 august 1980 and emplaced a sulfur dioxide so2 cloud into the north polar stratosphere at a maximum altitude of 15 km the so2 is tracked using satellite data from the ultraviolet uv nimbus 7 total ozone mapping spectrometer n7 toms and the infrared ir high resolution infrared radiation sounder hirs 2 on the noaa tiros operational vertical sounder tovs platform the eruption emitted 0 5 0 7 tg of so2 which later split into three distinct clouds one of which circled the north pole at the perimeter of an atypically persistent arctic cyclone for six days impacting airspace on three continents separate clouds drifted across eastern russia alaska and canada maximum so2 columns derived from toms and hirs 2 accurately define the volcanic cloud s path and fit trajectories produced by the noaa hybrid single particle lagrangian integrated trajectory hysplit model providing confidence in the model when combined with the so2 measurements trajectory altitudes derived from hysplit provide robust estimates of the altitudes of the so2 clouds 8 15 km which would be elusive using either the satellite data or the trajectory model in isolation near coincident spectrally discrete uv and ir retrievals are compared in the volcanic cloud and indicate good agreement between toms and hirs 2 so2 columns for pixels with similar viewing geometry hekla eruptions which follow a pattern of early explosive venting of volcanic gases with significant stratospheric injection could play a role in promoting arctic ozone loss depending on the phase of the north atlantic oscillation during the eruption

evaluation of redoubt volcano s sulfur dioxide emissions by the ozone monitoring instrument abstract the 2009 eruption of redoubt volcano alaska provided a rare opportunity to compare satellite measurements of sulfur dioxide so2 by the ozone monitoring instrument omi with airborne so2 measurements by the alaska volcano observatory avo herein we 1 compare omi and airborne so2 column density values for redoubt s tropospheric plume 2 calculate daily so2 masses from mount redoubt for the first three months of the eruption 3 develop simple methods to convert daily measured so2 masses into emission rates to allow satellite data to be directly integrated with the airborne so2 emissions dataset 4 calculate cumulative so2 emissions from the eruption and 5 evaluate omi as a monitoring tool for high latitude degassing volcanoes a linear correlation r2 0 75 is observed between omi and airborne so2 column densities omi daily so2 masses for the sample period ranged from 60 1 kt on 24 march to below detection limit with an average daily so2 mass of 6 7 kt the highest so2 emissions were observed during the initial part of the explosive phase and the emissions exhibited an overall decreasing trend with time omi so2 emission rates were derived using three methods and compared to airborne measurements this comparison yields a linear correlation r2 0 82 with omi derived emission rates consistently lower than airborne measurements the comparison results suggest that omi s detection limit for high latitude springtime conditions varies from 2000 to 4000 t d cumulative so2 masses calculated from daily omi data for the sample period are estimated to range from 542 to 615 kt with approximately half of this so2 produced during the explosive phase of the eruption these cumulative masses are similar in magnitude to those estimated for the 1989 90 redoubt eruption strong correlations between daily omi so2 mass and both tephra mass and acoustic energy during the explosive phase of the eruption suggest that omi data may be used to infer relative eruption size and explosivity further when used in conjunction with complementary datasets omi daily so2 masses may be used to help distinguish explosive from effusive activity and identify changes in lava extrusion rates the results of this study suggest that omi is a useful volcano monitoring tool to complement airborne measurements capture explosive so2 emissions and provide high temporal resolution so2 emissions data that can be used with interdisciplinary datasets to illuminate volcanic processes

the hydrothermal transformation rate of kaolinite to muscovite illite batch reactor experiments were performed to measure the rate of the reaction 1 5 kaolinite k muscovite h 1 5 water at temperatures ranging from 250 to 307 c in these experiments the rate of kaolinite conversion to muscovite illite was monitored as the rate of production of h runs were performed in small volume 50 ml titanium hydrothermal reactors charged with well crystallized georgia kaolinite indian ruby muscovite and 25 ml of kcl solution 0 5 2 0 m both solids and solutions were monitored at specific intervals throughout each experiment the determined rate law is dmh dt dmk dt amm k mk k mh where mk and mh are the concentrations of potassium ion and hydrogen ion k and k are the forward and reverse rate constants in kg m 2 sec 1 am is the total surface area of the muscovite in m2 and m is the mass of the solution in kg the initial rate method was used to find k and k was found by fitting data to an integrated rate equation temperature functions for the rate constants are in k 12 90 1 87 104 t r2 0 98 and in k 6 03 1 21 104 t r2 0 95 the activation energies ea for the forward and reverse reaction are 155 15 kj mol 1 and 101 10 kj mol 1 respectively

simultaneous retrieval of volcanic sulphur dioxide and plume height from hyperspectral data using artificial neural networks artificial neural networks anns are a valuable and well established inversion technique for the estimation of geophysical parameters from satellite images once trained they help generate very fast results furthermore 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 those natural hazards this paper describes an application of anns as an inverse model for the simultaneous estimation of columnar content and height of sulphur dioxide so2 plumes from volcanic eruptions using hyperspectral data from remote sensing in this study two anns were implemented in order to emulate a retrieval model and to estimate the so2 columnar content and plume height anns were trained using all infrared atmospheric sounding interferometer iasi channels between 1000 1200 and 1300 1410 cm 1 as inputs and the corresponding values of so2 content and height of plume obtained from the same iasi channels using the so2 retrieval scheme by carboni et al as target outputs the retrieval is demonstrated for the eruption of the eyjafjallajokull volcano iceland for the months of 2010 april and may and for the grimsvotn eruption during 2011 may both neural networks were trained with a time series consisting of 58 hyperspectral eruption images collected between 2010 april 14 and may 14 and 16 images from 2011 may 22 to 26 and were validated on three independent data sets of images of the eyjafjallajokull eruption one in april and the other two in may and on three independent data sets of the grimsvotn volcanic eruption that occurred in 2011 may the root mean square error rmse values between neural network outputs and targets were lower than 20 dobson units du for so2 total column and 200 millibar mb for plume height the rmse was lower than the standard deviation of targets for the grimsvotn eruption the neural network had a lower retrieval accuracy when the target value was outside the values used during the training phase the authors 2014 published by oxford university press on behalf of the royal astronomical society

validation of high resolution grace mascon estimates of glacier mass changes in the st elias mountains alaska usa using aircraft laser altimetry we acquired center line surface elevations from glaciers in the st elias mountains of alaska northwestern canada using aircraft laser altimetry during 2000 05 and compared these with repeat measurements acquired in 2007 the resulting elevation changes were used to estimate the mass balance of 32 900 km 2 of glaciers in the st elias mountains during september 2003 to august 2007 yielding a value of 21 2 3 8gta 1 equivalent to an area averaged mass balance of 0 64 0 12 m a 1 water equivalent w e high resolution 2 arc degrees spatial and 10 day temporal gravity recovery and climate experiment grace mass balance estimates during this time period were scaled to glaciers of the st elias mountains yielding a value of 20 6 3 0 gt a 1 or an area averaged mass balance of 0 63 0 09 m a 1 w e the difference in balance estimates altimetry minus grace was 0 6 4 8 gta 1 well within the estimated errors differences likely resulted from uncertainties in subgrid sampling of the grace mass concentration mascon solutions and from errors in assigning an appropriate near surface density in the altimetry estimates the good correspondence between grace and aircraft altimetry data suggests that high resolution grace mascon solutions can be used to accurately assess mass balance trends of mountain glacier regions that are undergoing large changes

phreatomagmatic ash from the ongoing eruption of etna reaching the greek island of cefalonia on october 26 2002 etna volcano sicily southern italy entered a new eruptive phase characterised by the usual effusive activity from fissure vents located both on the southern and on the northern sector of the summit area in addition explosive events of unusual intensity were recorded at the beginning of the eruption and produced a substantial plume rich in fine ash particles and steam on october 27 fine ash from the plume blown by the wind was reported falling on the island of cefalonia greece which is located approximately 500 km east of the volcano in this communication we report on the study of fine ash from the eruption as collected on cefalonia we elaborate on the nature of the peculiar type of explosion mechanism that led to such an unusual manifestation of etna which is phreatomagmatism this finding draws a new picture of the eruptive scenario of this active volcano and requires a careful evaluation of the hazard that similar events might pose in the future not just the surroundings of the volcano but also the aviation corridors of the southern mediterranean area could be potentially affected

a satellite chronology of the may june 2003 eruption of anatahan volcano abstract the first recorded eruption of anatahan began at approximately 17 00 local time on may 10 2003 here we present observations made by a suite of earth orbiting satellites of the heat ash and gas emitted from the volcano before during and after the eruption no thermal or sulphur dioxide emissions are apparent in modis moderate resolution imaging spectroradiometer airs atmospheric infrared sounder ep toms earth probe total ozone mapping spectrometer and aster advanced spaceborne thermal emission and reflection radiometer satellite images acquired prior to the eruption however within 24 h of eruption onset the university of hawaii s near real time satellite thermal monitoring system modvolc detected the eruption and confirmed anatahan s eastern caldera as the center of the activity although the eruption was initially phreatic it quickly transitioned into a magmatic phase that culminated in the emplacement of a dacitic lava dome the onset of the magmatic phase is recorded by modvolc as an order of magnitude increase in the heat flux from the volcano after may 16 indicative of fresh lava at the surface relative to low values 50 90 mw observed during the initial phreatic phase modvolc detected thermal emission from the volcano on a further 22 occasions during the next 2 weeks allowing us to quantitatively document temporal variations in thermal output during the eruption we use modis ep toms and airs data to document ash and sulphur dioxide emissions from anatahan covering the period may 10 june 13 2003 using daily satellite observations in conjunction with ground based estimates we arrive at a total so 2 discharge of 0 51 mt for the 1 month of activity of which 0 11 mt was emitted during activity on may 10 12 decreases in measured so 2 flux prior to the observation of a lava dome on june 4 indicate that the emerging dome may have blocked the upper conduit and inhibited degassing during this period a new episode of dome growth was detected by modvolc on april 12 2004 so far the level of thermal emission during the recent period of activity is substantially lower than that observed during the may june 2003 eruption

detailed fault structure highlighted by finely relocated aftershocks arthur s pass new zealand 1 more than 6000 aftershocks were recorded following the 1994 arthur s pass mw6 7 earthquake in south island new zealand here we relocate over 3500 of the aftershocks using double difference tomography to map detailed fault structures and obtain a 3 d model of p wave velocity and vp vs ratio in the volume around the aftershock region waveform cross correlation methods are used to calculate high quality differential times for event pairs two parallel clusters in particular are very well defined after the double difference relocation with a dip of 70 80 and n60e 10 strike a third nw dipping cluster aligns very closely with one of the preferred fault planes for the mainshock corroborating previous interpretations of the mainshock source mechanism results from the double difference tomography indicate p wave velocities and vp vs change markedly immediately above the upper bound of the seismicity with a vp of 4 5 to 5 5 km s and elevated vp vs found in the top 2 km

satellite and ground observations of the june 2009 eruption of sarychev peak volcano matua island central kuriles after 33 years of repose one of the most active volcanoes of the kurile island arc sarychev peak on matua island in the central kuriles erupted violently on june 11 2009 the eruption lasted 9 days and stands among the largest of recent historical eruptions in the kurile island chain satellite monitoring of the eruption using moderate resolution imaging spectroradiometer meteorological agency multifunctional transport satellite and advanced very high resolution radiometer data indicated at least 23 separate explosions between 11 and 16 june 2009 eruptive clouds reached altitudes of generally 8 16 km above sea level asl and in some cases up to 21 km asl clouds of volcanic ash and gas stretched to the north and northwest up to 1 500 km and to the southeast for more than 3 000 km for the first time in recorded history ash fall occurred on sakhalin island and in the northeast sector of the khabarovsky region russia based on satellite image analysis and reconnaissance field studies in the summer of 2009 the eruption produced explosive tephra deposits with an estimated bulk volume of 0 4 km3 the eruption is considered to have a volcanic explosivity index of 4 because the volcano is remote there was minimal risk to people or infrastructure on the ground aviation transport however was significantly disrupted because of the proximity of air routes to the volcano