thermal monitoring of north pacific volcanoes from space long term thermal modeling of volcanoes using satellite imagery provides an effective tool for monitoring remote yet dangerous volcanoes in the north pacific this region includes volcanoes in alaska the aleutian islands and the kamchatkan peninsula thermal infrared data collected multiple times per day from weather satellites show distinct signatures for three different types of volcanic activity at different volcanic centers near real time automated techniques are being developed to monitor relative changes in radiant temperature at volcanoes in this region radiant temperature values as a function of time are extracted and compared to background values for a series of active volcanoes by establishing a long term thermal record for these volcanoes significant deviations indicative of an impending eruption can be detected this tool is used to search for precursors to explosive eruptions in order to increase warning times and hazard mitigation for these potentially catastrophic events a six year archive of satellite imagery has been compiled for this active region and is available for study

rheologic and structural controls on the deformation of okmok volcano alaska fems insar and ambient noise tomography 1 interferometric synthetic aperture radar insar data indicate that the caldera of okmok volcano alaska subsided more than a meter during its eruption in 1997 the large deformation suggests a relatively shallow magma reservoir beneath okmok seismic tomography using ambient ocean noise reveals two low velocity zones lvzs the shallow lvz corresponds to a region of weak fluid saturated materials within the caldera and extends from the caldera surface to a depth of 2 km the deep lvz clearly indicates the presence of the magma reservoir beneath okmok that is significantly deeper 4 km depth compared to previous geodetic based estimates 3 km depth the deep lvz associated with the magma reservoir suggests magma remains in a molten state between eruptions we construct finite element models fems to simulate deformation caused by mass extraction from a magma reservoir that is surrounded by a viscoelastic rind of country rock embedded in an elastic domain that is partitioned to account for the weak caldera materials observed with tomography this configuration allows us to reduce the estimated magma reservoir depressurization to within lithostatic constraints while simultaneously maintaining the magnitude of deformation required to predict the insar data more precisely the insar data are best predicted by an fem simulating a rind viscosity of 7 5 1016 pa s and a mass flux of 4 2 109 kg d from the magma reservoir the shallow weak layer within the caldera provides a coeruption stress regime and neutral buoyancy horizon that support lateral magma propagation from the central magma reservoir to extrusion near the rim of the caldera

segmented lateral dyke growth in a rifting event at barðarbunga volcanic system iceland crust at many divergent plate boundaries forms primarily by the injection of vertical sheet like dykes some tens of kilometres long1 previous models of rifting events indicate either lateral dyke growth away from a feeding source with propagation rates decreasing as the dyke lengthens2 3 4 or magma flowing vertically into dykes from an underlying source5 6 with the role of topography on the evolution of lateral dykes not clear here we show how a recent segmented dyke intrusion in the bar arbunga volcanic system grew laterally for more than 45 kilometres at a variable rate with topography influencing the direction of propagation barriers at the ends of each segment were overcome by the build up of pressure in the dyke end then a new segment formed and dyke lengthening temporarily peaked the dyke evolution which occurred primarily over 14 days was revealed by propagating seismicity ground deformation mapped by global positioning system gps interferometric analysis of satellite radar images insar and graben formation the strike of the dyke segments varies from an initially radial direction away from the bar arbunga caldera towards alignment with that expected from regional stress at the distal end a model minimizing the combined strain and gravitational potential energy explains the propagation path dyke opening and seismicity focused at the most distal segment at any given time and were simultaneous with magma source deflation and slow collapse at the bar arbunga caldera accompanied by a series of magnitude m 5 earthquakes dyke growth was slowed down by an effusive fissure eruption near the end of the dyke lateral dyke growth with segment barrier breaking by pressure build up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries

effects of tidal stresses on volcanic activity at mount etna italy 1 here we model quantitatively the stress and strain induced by tidal forces as possible triggers of mount etna eruptions during 1989 2000 and 2001 by means of 2d numerical analysis by finite difference method applied to the volcano edifice spectral and vectorial analysis of tidal acceleration indicates that the quasi diurnal semi diurnal and ter diurnal constituents may have induced decompressions up to some kpa in the shallow i e 1 500 m gas saturated magma reservoir which controlled magma vesiculation and the timing of lava fountain activity from the south east crater sec we consider the geological heterogeneities in the volcanic edifice i e rock geometries and properties feeder conduit and vent systems volcanic landforms the magma properties i e bulk modulus volatile content and the ongoing volcano tectonic stresses i e volcano flank deformations which strongly influence the response of eruptive activity to tidal forces indeed the tidal factor may act on flank deformation concomitant to shallow magma inflation the implications of our model may help understand the eruptive behaviour and the disequilibrium state of the volcano and may be useful for hazard assessment at mount etna

low cost volcano surveillance from space case studies from etna krafla cerro negro fogo lascar and erebus satellite data offer a means of supplementing ground based monitoring during volcanic eruptions especially at times or locations where ground based monitoring is difficult being directly and freely available several times a day data from the advanced very high resolution radiometer avhrr offers great potential for near real time monitoring of all volcanoes across large 3000 3000 km areas herein we describe techniques to detect and locate activity estimate lava area thermal flux effusion rates and cumulative volume and distinguish types of activity application is demonstrated using data for active lavas at krafla etna fogo cerro negro and erebus a pyroclastic flow at lascar and open vent systems at etna and stromboli automated near real time analysis of avhrr data could be achieved at existing or cheap to install receiving stations offering a supplement to conventional monitoring methods

the dynamics of a long lasting effusive eruption modulated by earth tides abstract deciphering eruptive dynamics in near real time is essential when dealing with hazard assessment and population evacuation recognition of specific patterns in time series measured during volcanic activity may help decipher distinctive behavior at active volcanoes providing insights into the underlying driving mechanisms multi parameter data sets usually agree on the overall trend characterizing the temporal evolution of an eruption providing insights into the first order eruptive dynamics however second order variations detected in different data sets remain often poorly understood the 2014 2015 holuhraun eruption iceland offers an excellent opportunity to investigate the dynamics of a long lasting effusive eruption we analyze the seismic tremor and the volcanic radiated power emitted by the lava field during the 6 months of the eruption using singular spectrum analysis ssa in both geophysical time series we identify periods from 5 to 32 days coinciding with periods of earth tides here we show that 50 of both signals are composed of tidal periods suggesting that magma movements follow frequencies imposed by lunisolar forces within the crust and at earth s surface

eruption chronologies plume heights and eruption styles at tungurahua volcano integrating remote sensing techniques and infrasound article i nfo satellite remote sensing allows volcanic ash plumes to be detected and tracked and routinely aids in hazard mitigation especially to the aviation community although satellite imagery provides valuable information about volcanic plume processes i e plume heights plume composition and plume transport it has its limitations in addition to the observational gaps produced by meteorological clouds as well as temporal and spatial resolution restrictions large volcanic clouds often obscure the vent during an eruption therefore some key information about eruption dynamics and processes are impossible to obtain from satellite images in this paper we investigate four eruptions at tungurahua volcano ecuador during the 2006 2008 time period we integrate satellite derived eruption chronologies plume heights and plume aspect ratios with infrasound data primarily acoustic power and hand held thermal imagery when available integrating these datasets allows us to identify accurate eruption onsets durations and cessations as well as define different types of eruption styles ranging from plinian to weak vulcanian transitions between the different eruption styles were also documented results show that there is a positive correlation between plume height and acoustic power we conclude that combining the two datasets allows better constraints on eruption processes and source parameters using these methods in real time monitoring will allow more accurate eruption monitoring and ash hazard mitigation

earth tides and etnean volcanic eruptions an attempt at correlation of the two phenomena during the 1983 1985 and 1986 eruptions abstract an attempt has been made to correlate volcanic events on mt etna and moon sun attraction during the eruptions of 28 march 6 august 1983 12 march 13 july 1985 and 30 october 1986 the possibility of a trigger effect has been supposed for eruptive phenomena that originate by small and continuous external forces under particular stress conditions on the volcanic structure the parameters compared for the two phenomena are the hourly mean tremor amplitude recorded at serra la nave station and the hourly value of the vertical and of the two partial horizontal north south and east west components of the tidal acceleration induced by the moon sun system the relationship between two series of values the former for the tremor amplitude and the latter for one of the tidal acceleration components were then tested by statistical methods based on the information theoretic measure of interdependence between any pair of signal sequences the results show an effect of the horizontal tidal components on well known tectonic structures which may be widened or closed in contrast there is little evidence that the uprise of magma masses might depend on the vertical tidal attraction

infrared image analysis of volcanic thermal features lascar volcano chile 1984 1992 fifteen landsat thematic mapper tm images of lascar volcano chile recorded between december 1984 and april 1992 document the evolution of a lava dome within the summit crater four of the scenes were acquired at night in every image the two short wavelength infrared bands 5 and 7 have detected thermal radiation from the volcano as a consequence of the planck distribution function the relative response of these two channels depends on the proportions of very hot 600 c surfaces occupying tiny pixel areas and broader regions at moderate temperatures 280 c intercomparison of bands 5 and 7 thereby provides a means for interpreting tm thermal anomalies even in the absence of ground observations pronounced changes in the configuration and intensity of the lascar anomaly suggest that the volcano has experienced at least two cycles of lava dome activity since 1984 the first of these progressed through a cooling period possibly reflecting a reduced flux of magmatic volatiles at the surface and culminated in an explosive eruption on september 16 1986 which appears to have completely destroyed the inferred lava dome the tm data indicate that a new dome had been emplaced by november 1987 more than 15 months before it was first discovered by local observers lascar s style of cyclical effusive and explosive activity is typical of many volcanoes and the remote sensing techniques presented herein could be applied elsewhere

mayon volcano philippines some insights into stress balance abstract mayon volcano is part of the bicol volcanic chain a peninsula in the south east of luzon island mayon s eruptive history during this century is fairly periodic with eruptions nearly every 10 years during the last two eruptions indications for tidal triggering of activities were found from statistical analyses hints for such a correlation exist for a number of volcanoes the statistical analysis of the seismicity points to a tidal triggering at mayon volcano in order to verify these indications the pressure balance between internal and external forces was computed the computations show that an interrelation between volcanic activities and tides especially ocean loading is probable for this purpose a global ocean model is improved by a regional model and a model of the local areas in order to consider the tidal distribution and the complicated geometry of the coasts the method of farrell w e 1972 deformation of the earth by surface loads rev geophys space physics 10 761 797 is used to calculate the ocean tidal loading the pressure increase in the vent due to vesiculation was tentatively modelled assumed a temperature decrease of 2 c per year the resulting stress is compared to the stress produced by the tidal forces body tides and ocean tidal loading it turns out that during a period of several days the small tidal forces may affect the stress balance considerably if the volcano is already in a critical state using fe modelling we estimate by neglecting all external forces how fast pressure can build up in the vent and to which extent the different physical parameters influence the pressure increase the maximum pressure resulting from the crystallization of the melt is compared with the maximum pressure yielding when in addition tidal forces are acting

remote infrared detection of the cessation of volcanic eruptions when an effusive eruption ends lava surfaces initially cool rapidly so that within minutes temperatures across the hottest zones have dropped by 600 c this means that eruption cessation is simple to detect using satellite infrared data where a sudden irrecoverable decline in thermal radiance occurring over a period of hours is characteristic of termination avhrr data acquired during and after 5 eruptions at krafla iceland illustrate this in all cases the 3 9 m spectral radiance in the first image following the known time of eruption cessation is markedly reduced compared to that recorded during the eruption and subsequently remains at persistently low levels

numerical modeling of lava flow cooling applied to the 1997 okmok eruption approach and analysis 1 throughout february and march of 1997 okmok volcano in the eastern aleutian islands of alaska erupted a 6 km long lava flow of basaltic a a within its caldera a numerical model for lava flow cooling was developed and applied to the flow to better understand the nature of its cooling radiation and convection from the surface as well as conduction to the ground were used to transport the flow s heat to its surroundings in the model internally a conduction only approach moved heat from the interior outward vesiculation latent heat generation and thermal conductivity changes with temperature are among the other factors that were dynamically accounted for results indicate that ambient temperature fluctuations on the scale of days to weeks must be taken into account to create an accurate short term prediction of lava surface temperature daily data of rainfall and ambient temperature as opposed to yearly averages greatly increased the accuracy of the model furthermore convective cooling of the lava surface was observed to be a dominant heat loss process during the first 200 days indicating the convective heat transfer coefficient is a prime determinant of the accuracy of the model for predicting surface temperatures over a longer cooling period 2 years thermal conductivity and porosity proved to be among the dominating factors for heat loss because of the limiting role of conductive heat flow in the interior the model s flexibility allows application to flows other than the 1997 okmok eruption

calculation of lava effusion rates from landsat tm data we present a thermal model to calculate the total thermal flux for lava flowing in tubes on the surface or under shallow water once defined we use the total thermal flux to estimate effusion rates for active flows at kilauea hawaii on two dates input parameters were derived from landsat thematic mapper tm field and laboratory measurements using these parameters we obtain effusion rates of 1 76 0 57 and 0 78 0 27 m3 s 1 on 23 july and 11 october 1991 respectively these rates are corroborated by field measurements of 1 36 0 14 and 0 89 0 09 m3 s 1 for the same dates kauahikaua et al 1996 using weather satellite avhrr data of lower spatial resolution we obtain similar effusion rates for an additional 26 dates between the two tm derived measurements we assume that although total effusion rates at the source declined over the period the shut down of the ocean entry meant that effusion rates for the surface flows alone remained stable such synergetic use of remotely sensed data provides measurements that can a contribute to monitoring flow field evolution and b provide reliable numerical data for input into rheological and thermal models we look forward to being able to produce estimates for effusion rates using data from high spatial resolution sensors in the earth observing system eos era such as landsat 7 the hyperspectral imager the advanced spaceborne thermal emission spectrometer and the advanced land imager

integrated satellite observations of the 2001 eruption of mt cleveland alaska abstract satellite data were the primary source of information for the eruption of mt cleveland alaska on 19 february and 11 and 19 march 2001 multiple data sets were used pre syn and post eruption to mitigate the hazard and determine an eruption chronology the 19 february eruption was the largest of the three resulting in a volcanic cloud that formed an arc over 1000 km long moved to the ne across alaska and was tracked using satellite data over more than a 50 h period the volcanic cloud was concurrently detected on the goes avhrr and modis data at various times and their respective signals compared all three sensors detected a cloud that had a very similar shape and position but there were differences in their areal extent and internal structural detail goes data showed the largest volcanic cloud in terms of area probably due to its oblique geometry modis bands 31 and 32 which are comparable to goes and avhrr thermal infrared wavelengths were the least effective single channels at detecting the volcanic cloud of those investigated modis bands 28 29 31 and 32 modis bands 28 and 29 detected the largest volcanic clouds that could easily be distinguished from weather clouds of the split window data modis bands 29 minus band 32 detected the largest cloud but the band 31 minus band 32 data showed the volcanic cloud with the most internal structural detail the puff tracking model accurately tracked the movement and predicted the extent and shape of this complex cloud even into areas beyond satellite detection numerous thermal anomalies were also observed during the eruption on the twice daily avhrr data and the high spatial resolution landsat data the high resolution radarsat data showed that the avhrr thermal anomalies were due to lava and debris flow features and a newly formed fan along the west coast of the island field observations and images from a hand held forward looking infrared radiometer flir showed that the flow features were a a lava debris flows and a warm debris fan along the west coast real time satellite data were the primary tool used to monitor the eruption track changes and to mitigate hazards high resolution data even though coverage is infrequent were critical in helping to identify volcanic processes and to compile an eruption chronology

radon surveys and real time monitoring at stromboli volcano influence of soil temperature atmospheric pressure and tidal forces on 222rn degassing abstract we used a network of stations to perform systematic radon surveys at stromboli volcano the time series of periodic measurements show that monthly average 222rn emissions reflect changes in volcanic activity and exhibit increasing trends prior and during the last major eruptive cycles maps of radon emissions indicate that diffuse degassing is operative at stromboli volcano concentrated degassing essentially occurs in the summit area and within a sector proximal to the two major ne trending faults these sites were chosen for deploying the two real time stations that are currently operating at stromboli in these devices the 222rn electronic dosimeters are connected to a radiomodem for wireless data transfer to a receiving station at the volcano observatory radon activity soil temperature and atmospheric pressure data are sampled and instantaneously transferred via web so that they can be checked remotely collected time series reveal an overall inverse correlation between radon emissions and seasonal temperature variations radon emissions in sectors of diffuse degassing are modulated by tidal forces as well radon activities recorded at the summit station located along the fracture zone where the gas flux is concentrated are positively correlated with changes in atmospheric pressure and confirm the occurrence of the atmospheric stack effect we finally emphasize that real time radon monitoring is an innovative technique that may be systematically applied in volcano surveillance

the 1997 eruption of okmok volcano alaska a synthesis of remotely sensed imagery abstract okmok volcano in the eastern aleutian islands erupted in february and march of 1997 producing a 6 km long lava flow and low level ash plumes this caldera is one of the most active in the aleutian arc and is now the focus of international multidisciplinary studies a synthesis of remotely sensed data airsar derived dems landsat mss and etm data avhrr ers jers radarsat has given a sequence of events for the virtually unobserved 1997 eruption elevation data from the airsar sensor acquired in october 2000 over okmok were used to create a 5 m resolution dem mosaic of okmok volcano avhrr nighttime imagery has been analyzed between february 13 and april 11 1997 landsat imagery and sar data recorded prior to and after the eruption allowed us to accurately determine the extent of the new flow the flow was first observed on february 13 without precursory thermal anomalies at this time the flow was a large single lobe flowing north according to avhrr band 3 and 4 radiance data and ground observations the first lobe continued growing until mid to late march while a second smaller lobe began to form sometime between march 11 and 12 this is based on a jump in the thermal and volumetric flux determined from the imagery and the physical size of the thermal anomalies total radiance values waned after march 26 indicating lava effusion had ended and a cooling crust was growing the total area 8 9 km 2 thickness up to 50 m and volume 1 54 10 8 m 3 of the new lava flow were determined by combining observations from sar landsat etm and airsar dem data while the first lobe of the flow ponded in a pre eruption depression our data suggest the second lobe was volume limited remote sensing has become an integral part of the alaska volcano observatory s monitoring and hazard mitigation efforts studies like this allow access to remote volcanoes and provide methods to monitor potentially dangerous ones

conclusion recommendations and findings of the red seed working group red seed stands for risk evaluation detection and simulation during effusive eruption disasters and combines stakeholders from the remote sensing modelling and response communities with experience in tracking volcanic effusive events the group first met during a three day long workshop held in clermont ferrand france between 28 and 30 may 2013 during each day presentations were given reviewing the state of the art in terms of a volcano hot spot detection and parameterization b operational satellite based hot spot detection systems c lava flow modelling and d response protocols during effusive crises at the end of each presentation set the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors modellers and responders during an effusive crisis the results of collating the final reports and follow up discussions that have been on going since the workshop are given here we can reduce our discussions to four main findings 1 hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min 2 spectral radiance metrics can also be provided with high degrees of confidence however if we are to achieve a truly global system more local receiving stations need to be installed with hot spot detection and data processing modules running on site and in real time 3 models are operational but need real time input of reliable time averaged discharge rate data and regular updates of digital elevation models if they are to be effective the latter can be provided by the radar photogrammetry community 4 information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities all of this requires a sophisticated and centralized data collection distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust while the next chapter carries out an exercise to explore the viability of the last point the detailed recommendations behind these findings are detailed here

numerical modeling of lava flow cooling applied to the 1997 okmok eruption comparison with advanced very high resolution radiometer thermal imagery 1 throughout february and march 1997 okmok volcano in the eastern aleutian islands of alaska erupted a 6 km long lava flow of basaltic a a within its caldera in the first part of the study a numerical model for lava flow cooling was developed by patrick et al and applied to the flow to better understand the nature of its cooling in this second part of the study the model predictions for lava surface temperature over a 200 day cooling period were compared to advanced very high resolution radiometer avhrr thermal imagery various methods were used to extract the subpixel lava temperature from the avhrr pixel integrated values including the dual band method and pixel merging inherent to these approaches is the multicomponent modeling of the lava surface temperature whereas active flows have been shown to have several thermal components so too do flows undergoing extended cooling because of the dependence of the methods on the avhrr instantaneous field of view ifov the scan dependent ifov dimensions and overlap values were considered results from patrick et al indicate that convective heat loss from the surface largely controls surface temperature during extended cooling but the functions governing this heat loss mechanism are poorly understood avhrr derived temperatures from this part of the study suggest that values for the convective heat transfer coefficient for this flow were most commonly between 50 and 100 w m 2 k 1 and generally above 25 w m 2 k 1 these results are in agreement with previously measured values from the field but are significantly higher than those assumed in other remote sensing studies of cooling lava also the avhrr data corroborate the modeled prediction of seasonal warming of the lava surface

effusion rate trends at etna and krafla and their implications for eruptive mechanisms abstract using effusion rates obtained from ground and satellite based data we build a data set of 381 effusion rate measurements during effusive activity at etna and krafla between 1980 and 1999 this allows us to construct detailed effusion rate curves for six fissure fed eruptions at etna and krafla and four summit fed eruptions at etna these define two trends type i and ii type i trends have effusion rates that rise rapidly to an initial peak before declining more slowly resulting in an exponential decrease in eruption rate and declining growth in cumulative volume type ii trends are characterised by steady effusion and eruption rates and hence a linear increase in cumulative volume the former is typical of fissure eruptions and can be explained by tapping of an enclosed pressurised system the latter are typical of persistent etnean summit eruptions plus one persistent effusive eruption at stromboli 1985 1986 examined here and can be explained by overflow of the time averaged magma supply we use our effusion rate data to assess the magma balance at etna 1980 1995 and krafla 1975 1984 between 1980 and 1995 etna was supplied at a time averaged rate of 6 8 2 3 m 3 s 1 of which 13 was erupted at krafla 817 30 10 6 m 3 was erupted and intruded during 1975 1984 and the ratio of erupted to intruded volume was 0 3 at etna there is evidence for intrusion of the unerupted magma within and beneath the edifice as well as storage in the central magma column at krafla unerupted magma was intruded into a rift zone but an increasing proportion of the supply was erupted from 1980 onwards a result of the rift zone capacity being reached magma intruded prior to an eruptive event may also be entrained and or pushed out during eruption to contribute to the initial high effusion rate phases of type i events the detail in our effusion rate curves was only possible using a thermal approach which estimates effusion rates using satellite data we look forward to analysing satellite derived effusion rate trends in real time using data from current and soon to be launched sensors

interferometric synthetic aperture radar study of okmok volcano alaska 1992 2003 magma supply dynamics and postemplacement lava flow deformation 1 okmok volcano located in the central aleutian arc alaska is a dominantly basaltic complex topped with a 10 km wide caldera that formed circa 2 05 ka okmok erupted several times during the 20th century most recently in 1997 eruptions in 1945 1958 and 1997 produced lava flows within the caldera we used 80 interferometric synthetic aperture radar insar images interferograms to study transient deformation of the volcano before during and after the 1997 eruption point source models suggest that a magma reservoir at a depth of 3 2 km below sea level located beneath the center of the caldera and about 5 km northeast of the 1997 vent is responsible for observed volcano wide deformation the preeruption uplift rate decreased from about 10 cm yr 1 during 1992 1993 to 2 3 cm yr 1 during 1993 1995 and then to about 1 2 cm yr 1 during 1995 1996 the posteruption inflation rate generally decreased with time during 1997 2001 but increased significantly during 2001 2003 by the summer of 2003 30 60 of the magma volume lost from the reservoir in the 1997 eruption had been replenished interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows most likely due to thermal contraction interferograms for periods after the eruption suggest at least four distinct deformation processes 1 volcano wide inflation due to replenishment of the shallow magma reservoir 2 subsidence of the 1997 lava flows most likely due to thermal contraction 3 deformation of the 1958 lava flows due to loading by the 1997 flows and 4 continuing subsidence of 1958 lava flows buried beneath 1997 flows our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes

the 2002 2003 eruption of stromboli italy evaluation of the volcanic activity by means of continuous monitoring of soil temperature co2 flux and meteorological parameters 1 from december 2002 to july 2003 stromboli volcano was characterized by a new effusive stage of eruption after a period of extraordinary strombolian activity signals recorded in two continuous monitoring stations during the eruption which have already been presented in very recent papers evidenced anomalies in the co2 flux just before the onset of the eruption a more detailed analysis carried out on the data subset acquired during the eruption integrated by daily field observations of the scientific personnel working at the volcanological observatory in stromboli showed that co2 flux and soil temperature are strictly related to volcanic events furthermore the relative minima and maxima of the two parameters showed a strong correlation with wind speed and direction this fact was especially true at the summit station whereas at the coastal sites seasonal and meteorological effects masked the volcanic signal the analysis of the wind data particularly the relationships between wind speed and direction air and soil temperature and local circulation of atmospheric air masses revealed that during the eruption in the summit area of stromboli air movements were not only related to atmospheric circulation but were also significantly affected and in certain cases caused by volcanic activity this conclusion was reached by observing several anomalies such as the discrepancies in the wind direction between the two stations higher air temperatures at the summit site and inversion of direction for wind before and after the reopening of the conduit in a major explosion on 5 april 2003 the relationships found between volcanic activity soil temperatures co2 fluxes and wind speed and direction indicate that soil temperature measurements in an open conduit volcano such as in this case could be used to monitor the level of volcanic activity along with co2 flux furthermore the possible volcanic origin of a peculiar type of air circulation identified in the summit area of stromboli suggests that the separation between volcanic and atmospheric signals might not be obvious requiring monitoring over a wide area rather than a single location

a review of algorithms for detecting volcanic hot spots in satellite infrared data since the 1980s application of thermal infrared satellite data for volcano monitoring has rapidly evolved to become a proven operational tool due to the large quantities of data provided by sensors in polar and geostationary orbits as well as the sheer number of active volcanoes on earth processing and managing such data sets requires an enormous amount of workforce a number of algorithms have been developed to facilitate detection location and tracking of hot spots of active volcanoes a collation and review of hot spot detection algorithms developed and applied by the volcanological community reveals three main types which have been applied to date contextual fixed threshold and temporal the founding algorithms for these three classes are vast modvolc and rst respectively through comparison with manually based detections the performance of each algorithm was tested for sustained lava flows etna and stromboli strombolian activity stromboli lava dome growth and collapse augustine and fumarole fields vulcano it is shown that as the number of correctly identified anomalies increases so too does the number of false positives although each of the algorithms operates well within the limits and criteria of their design requirements and application under current data restraints no algorithm can be expected to perform perfectly

relative scale and the strength and deformability of rock masses abstract the strength and deformation of rocks depend strongly on the degree of fracturing which can be assessed in the field and related systematically to these properties appropriate mohr envelopes obtained from the rock mass rating rmr classification system and the hoek brown criterion for outcrops and other large scale exposures of fractured rocks show that rock mass cohesive strength tensile strength and unconfined compressive strength can be reduced by as much as a factor often relative to values for the unfractured material the rock mass deformation modulus is also reduced relative to young s modulus a cook book example illustrates the use of rmr in field applications the smaller values of rock mass strength and deformability imply that there is a particular scale of observation whose identification is critical to applying laboratory measurements and associated failure criteria to geologic structures

long period tidal variations in the length of day a new model of long period tidal variations in length of day is developed the model comprises 80 spectral lines with periods between 18 6 years and 4 7 days and it consistently includes effects of mantle anelasticity and dynamic ocean tides for all lines the anelastic properties follow wahr and bergen experimental confirmation for their results now exists at the fortnightly period but there remains uncertainty when extrapolating to the longest periods the ocean modeling builds on recent work with the fortnightly constituent which suggests that oceanic tidal angular momentum can be reliably predicted at these periods without data assimilation this is a critical property when modeling most long period tides for which little observational data exist dynamic ocean effects are quite pronounced at shortest periods as out of phase rotation components become nearly as large as in phase components the model is tested against a 20 year time series of space geodetic measurements of length of day the current international standard model is shown to leave significant residual tidal energy and the new model is found to mostly eliminate that energy with especially large variance reduction for constituents sa ssa mf and mt

the 16 september 1986 eruption of lascar volcano north chile satellite investigations landsat thematic mapper tm images acquired in 1984 and 1985 revealed a pronounced thermal anomaly on lascar volcano north chile subsequent images showed that the anomaly was persistent but variable and that after a significant eruption on 16 september 1986 it was weaker and divided into several sources tm studies and other observations of lascar indicate that the persistent thermal anomaly may be due to high temperature fumaroles within the summit crater goes weather satellite images and field investigations confirm that the 16 september event was a short lived vulcanian type eruption which produced an ash column that reached 15 km altitude the ash cloud can be tracked on geos images to about 400 km downwind and covered an area 112 000 km2 transport occurred in the upper troposphere at speeds up to 180 km h ash fall from the plume was well sorted and moderately fine grained md 200 m formation and fallout of ash as aggregates was unimportant in the deposition of the ash layer although small the lascar 16 september eruption is significant because few historic eruptions have been recorded in the central andes little would have been known of the eruption in the absence of remote sensed data

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

ground surface deformation patterns magma supply and magma storage at okmok volcano alaska from insar analysis 1 intereruption deformation 1997 2008 eruption magma storage had increased by 3 7 5 2 1 0 7 m 3 or 85 100 of the 1997 eruption volume we propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region eventuallytheeffectsofcontinuingmagmasupplyandvesiculationofstoredmagmacaused acriticalpressurethresholdtobeexceeded triggeringthe2008eruption asimilarpatternof initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption in both cases withdrawal of magma during the eruptions depressurized the shallow storage zone causing significant volcano wide subsidence and initiating a new intereruption deformation cycle

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

late quaternary caldera forming eruptions in the eastern aleutian arc alaska late quaternary calderas have been identified at 12 of 40 volcanic centers in the eastern aleutian arc and sufficient radiocarbon dates and geologic information have now been obtained to either date or constrain the timing of the climactic caldera forming eruptions at least eight major caldera forming events each characterized by estimated eruption volumes of more than 10 km 3 occurred at seven different volcanic centers in the holocene and as many as six of these had estimated eruption volumes of more than 50 km 3 eruptions of similar magnitude formed two other calderas in wisconsin time the dating of these hitherto little known events adds significantly to the previously existing chronology of large prehistoric eruptions this refined chronology is important in understanding eruption induced climate changes in assessing volcanic hazards and in developing a tephrochronology for northwestern north america

apparent tidal influence on magmatic activity at oldoinyo lengai volcano tanzania as observed in moderate resolution imaging spectroradiometer modis data this paper investigates the relative timing of solid earth tides and thermal anomalies associated with volcanic activity at oldoinyo lengai ol tanzania from 2000 to 2008 the low viscosity of ol s carbonatite magmas may make it particularly susceptible to tidal stresses thermal data from the moderate resolution imaging spectroradiometer modis were filtered using the modlen algorithm and earth tides were modeled using tsoft application of the schuster and chi squared tests resulted in apparent correlations between times of thermal anomalies and the phase of the semi diurnal and biannual solid earth tides however for semi diurnal and biannual tides limited acquisition times of the modis data account for the apparent correlations re examining the data while accounting for the bias introduced by the limited acquisition times correlations are no longer found onset times of eruptive events and times of thermal anomalies show no statistically significant correlation with the fortnightly tide indicating this is not an influence on activity at ol tidal influences on magmatic activity if at all present cannot be observed in coarse resolution thermal data on semi diurnal and fortnightly time scales based on the available data correlations on biannual timescales cannot be ruled out

estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar the 1997 eruption of okmok volcano alaska interferometric synthetic aperture radar insar techniques are used to calculate the volume of extrusion at okmok volcano alaska by constructing precise digital elevation models dems that represent volcano topography before and after the 1997 eruption the posteruption dem is generated using airborne topographic synthetic aperture radar topsar data where a three dimensional affine transformation is used to account for the misalignments between different dem patches the preeruption dem is produced using repeat pass european remote sensing satellite data multiple interferograms are combined to reduce errors due to atmospheric variations and deformation rates are estimated independently and removed from the interferograms used for dem generation the extrusive flow volume associated with the 1997 eruption of okmok volcano is 0 154 spl plusmn 0 025 km sup 3 the thickest portion is approximately 50 m although field measurements of the flow margin s height do not exceed 20 m the in situ measurements at lava edges are not representative of the total thickness and precise dem data are absolutely essential to calculate eruption volume based on lava thickness estimations this study is an example that demonstrates how insar will play a significant role in studying volcanoes in remote areas

evolution of lava flow fields at mount etna 27 28 october 1999 observed by landsat 7 etm landsat 7 enhanced thematic mapper etm data are presented which document the thermal characteristics of a series of lava flows emplaced at mount etna volcano sicily during 27 28 october 1999 by examining the composition of the short wave infrared swir signal emitted from the flow surface we identified distinctive flow units the first unit appears to comprise recently active lava flows with relatively cool crusts which by virtue of the integrity of this crust as determined from the etm data we infer are stationary or barely moving the second unit is characterized by much higher levels of swir radiance consistent with a channel fed active flow unit analysis of the swir data confirm that this is fed by a lava channel the properties of which are consistent with vigorously active channels observed on kilauea hawaii model predictions of the maximum length that such flows could attain compare favorably with the actual flow lengths observed in the etm data indicating that the cooler flows had indeed stopped advancing and may have attained a cooling limited rather than volume limited maximum length our observations and modeling provide a physical corroboration for the supposition made by wadge 1978 in his analysis of the shape of lava flow fields on mount etna which in the cooling limited case principal flows are active one after the other and not at the same time

lava flow characterization at pisgah volcanic field california with multiparameter imaging radar multi incidence angle in the 25 to 55 range radar data acquired by the nasa jpl airborne synthetic aperture radar airsar at three wavelengths simultaneously and displayed at three polarizations are examined for their utility in characterizing lava flows at pisgah volcanic field california pisgah lava flows were erupted in three phases flow textures consist of hummocky pahoehoe smooth pahoehoe and aa with and without thin sedimentary cover of the eight airsar images used here four were calibrated to within an accuracy of 2 db with trihedral corner reflectors and data from these calibrations were used to process the additional images to a conservatively estimated 5 db level of accuracy calibrated radar backscatter data in db were plotted as a function of incidence angle at three wavelengths p band 68 cm l band 24 cm and c band 5 6 cm and three polarizations hh horizontal transmit horizontal receive hv horizontal transmit vertical receive and vv vertical transmit vertical receive for eight major units at pisgah for which multi incidence angle airsar data were available the eight units consist of near vent and distal aa flows near vent and distal hummocky pahoehoe flows a mantled hummocky pahoehoe flow a platform pahoehoe flow an alluvial fan and a playa analyses of these backscatter data show that major unmodified volcanic units at pisgah are readily distinguishable from each other and that they exhibit diffuse hh vv and or multiple hv scattering behavior typical of rough surfaces at these wavelengths these analyses show that discrimination of smooth lavas platform pahoehoe from mantled units with greater primary roughness hummocky pahoehoe is difficult and must rely on supporting observations such as evidence of localized weathering and or sediment deposition contrast with surrounding units and superposition of flow units l band backscatter and image data at hv polarization show the best discrimination of pisgah lava flows with optimal unit separation observed between 40 and 50 incidence angles backscatter data shown as a function of relative age of pisgah flows indicate that dating of lava flows on the basis of average radar backscatter may yield ambiguous results if primary flow textures and modification processes are not well understood

measuring effusion rates of obsidian lava flows by means of satellite thermal data abstract space based thermal data are increasingly used for monitoring effusive eruptions especially for calculating lava discharge rates and forecasting hazards related to basaltic lava flows the application of this methodology to silicic more viscous lava bodies such as obsidian lava flows is much less frequent with only few examples documented in the last decades the 2011 2012 eruption of cordon caulle volcano chile produced a voluminous obsidian lava flow 0 6 km3 and offers an exceptional opportunity to analyze the relationship between heat and volumetric flux for such type of viscous lava bodies based on a retrospective analysis of modis infrared data mirova system we found that the energy radiated by the active lava flow is robustly correlated with the erupted lava volume measured independently we found that after a transient time of about 15 days the coefficient of proportionality between radiant and volumetric flux becomes almost steady and stabilizes around a value of 5 106 j m 3 this coefficient i e radiant density is much lower than those found for basalts 1 108 j m 3 and likely reflects the appropriate spreading and cooling properties of the highly insulated viscous flows the effusion rates trend inferred from modis data correlates well with the tremor amplitude and with the plume elevation recorded throughout the eruption thus suggesting a link between the effusive and the coeval explosive activity modelling of the eruptive trend indicates that the cordon caulle eruption occurred in two stages either incompletely draining a single magma reservoir or more probably tapping multiple interconnected magmatic compartments

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

remote sensing data types and techniques for lahar path detection a case study at mt ruapehu new zealand mt ruapehu is new zealand s most active onshore volcano in 2007 the volcano produced a large lahar following a break out from the summit crater lake here satellite and airborne remote sensing and image processing is used to extract the path of the lahar using aster and spot5 visible and near infra red imagery alos palsar l band synthetic aperture radar data and airborne lidar the results obtained from each of these datasets were compared to the lahar deposit manually digitized from aerial photography spot5 imagery produced the most accurate map of the lahar deposit 77 correct even though these data were acquired a year after the event this is attributed to the spatial resolution of the data the alos palsar coherence mapping calculated from images acquired 2 months before and nine months after the lahar was not as accurate as that obtained using the optical imagery 43 correct but this was still considered an important tool for acquiring data during cloudy periods lidar topographic data collected to constrain geomorphic changes caused by the lahar was the least accurate in terms of mapping the lahar path 28 correct no single technique was deemed to be the most accurate under all circumstances and a combination of data types would produce the best results by combining the satellite and lidar data it was possible to accurately classify 92 of the lahar path

a simple explanation for the space based calculation of lava eruption rates abstract knowing how lava effusion rates vary during basaltic eruptions can be of great significance when trying to provide preliminary forecasts regarding how far lava will flow however problems exist in accurately determining effusion rates using conventional field based techniques to ameliorate this problem harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 j volcanol geotherm res 102 2000 237 269 developed a method for determining effusion rates using infrared satellite data and showed how the method could be used to provide realistic estimates of effusion rates repeatedly during several eruptions at kilauea hawai i krafla iceland etna and stromboli italy harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 indicate that their method allows instantaneous lava effusion rates to be determined thermodynamically by equating the amount of heat lost by an active lava flow derived from the satellite data to the amount of heat liberated by the cooling mass of lava the purpose of this paper is to provide a simpler alternative explanation we find that rather than being used to calculate heat loss harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 j volcanol geotherm res 102 2000 237 269 actually use the satellite data to estimate the area of active lava present within the satellite s field of view at the movement of data acquisition thus changes in the effusion rates they present can only be proportional to changes in this area the active flow areas were then multiplied by a constant the value of which is obtained from a crude approximation of the lava flows heat balance crucially the absolute value of this term falls within the range of an empirically derived parameter that was found by pieri and baloga j volcanol geotherm res 30 1986 29 45 to explain strong linear correlations between eruption rate i e the time averaged effusion rate and lava flow area for 34 historic hawaiian flows as a result we find that the method of harris et al j geophys res 102 1997 7985 8003 does not yield instantaneous effusion rates but instead provides a valid and useful way to estimate average effusion rates i e the eruption rate from measurements of flow area

tidal modulation of eruptive activity at open vent volcanoes evidence from stromboli italy terra nova 24 233 237 2012 abstract the role of earth tides as a relevant controlling factor of a variety of geological processes including seismicity and volcanism is widely debated stromboli volcano italy is well known for its persistent explosive activity and represents an ideal setting to investigate tidal effects on the energy release and eruptive behaviour of volcanoes herein we report new evidence that tidal stresses may modulate the timing of eruptive activity at volcanoes in an open vent state we report statistically significant correlations of the peak eruption frequencies to fortnightly tidal maxima i e full and new moon during a 17 month long period of activity in 2010 2011 in fact the number of explosive events per hour increases by 85 during tidal maxima with respect to the average values we suggest that tidally induced cycles of compression decompression of country rocks controls fluctuating magma supply rate from the shallow plumbing system and thus eruption frequency

thermal monitoring of lascar volcano chile using infrared data from the along track scanning radiometer a 1992 1995 time series lascar volcano 22 22 s 67 44 w is the most active volcano of the central andes of northern chile activity since 1984 has been characterised by periods of lava dome growth and decay within the active crater punctuated by explosive eruptions we present herein a technique for monitoring the high temperature activity within the active crater using frequent measurements of emitted shortwave infrared swir radiation made by the spaceborne along track scanning radiometer atsr the atsr is an instrument of low spatial resolution pixels 1 km across that shares certain characteristics with the modis instrument planned for use as a volcano monitoring tool in the nasa eos volcanology project we present a comprehensive time series of over 60 cloud and plume free nighttime atsr observations for 1992 1995 a period during which lascar experienced its largest historical eruption variations in short wavelength infrared flux relate directly to changes in high temperature surfaces within the active crater from these data interpretations can be made that supplement published field reports and that can document the presence and status of the lava dome during periods where direct ground based observations are lacking our data agree with less frequent information collected from sensors with high spatial resolution such as the landsat thematic mapper oppenheimer et al 1993 and are consistent with field observations and models that relate subsidence of the dome to subsequent explosive eruptions matthews et al 1997 most obviously lascar s major april 1993 eruption follows a period in which the magnitude of emitted shortwave infrared radiation fell by 90 at this time subsidence of the 1991 1992 lava dome was reported by field observers and this subsidence is believed to have impeded the escape of hot volatiles and ultimately triggered the eruption smithsonian institution 1993a extrapolating beyond the period for which field observations of the summit are available our data show that the vulcanian eruption of 20 july 1995 occurred after a period of gradual increase in short wavelength infrared flux throughout 1994 and a more rapid flux decline during 1995 we attribute this additional otherwise undocumented cycle of increasing and decreasing swir radiance as most likely representing variations in degassing through fumaroles contained within the summit crater alternatively it may reflect a cycle of dome growth and decay the explosive eruption of 17 december 1993 appears to have followed a similar but shorter variation in swir flux and we conclude that large explosive eruptions are more likely when the 1 6 m signal has fallen from a high to a low level the atsr instrument offers low cost data at high temporal resolution despite the low spatial detail of the measurements atsr type instruments can provide data that relate directly to the status of lascar s lava dome and other high temperature surfaces we suggest that such data can therefore assist with predictions of eruptive behaviour deduced from application of physical models of lava dome development at this and similar volcanoes

the topsar interferometric radar topographic mapping instrument the authors have augmented the nasa dc 8 airsar instrument with a pair of c band antennas displaced across track to form an interferometer sensitive to topographic variations of the earth s surface during the 1991 dc 8 flight campaign data were acquired over several sites in the us and europe and topographic maps were produced from several of these flight lines analysis of the results indicate that statistical errors are in the 2 4 m range while systematic effects due to aircraft motion are in the 10 20 m range the initial results from development of a second generation processor show that aircraft motion compensation algorithms reduce the systematic variations to 2 m while the statistical errors are reduced to 2 3 m

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

topographic analyses of k lauea volcano hawai i from interferometric airborne radar we analyze digital topographic data collected in september 1993 over a 500 km2 portion of k lauea volcano hawai i by the c band 5 6 cm wavelength topographic synthetic aperture radar topsar airborne interferometric radar field surveys covering an 1 km2 area of the summit caldera and the distal end of an 8 m thick a flow indicate that the 10 m spatial resolution topsar data have a vertical accuracy of 1 2 m over a variety of volcanic surfaces after conversion to a common datum topsar data agree favorably with a digital elevation model dem produced by the u s geological survey usgs with the important exception of the region of the ongoing eruption which postdates the usgs dem this dem comparison gives us confidence that subtracting the usgs data from topsar data will produce a reasonable estimate of the erupted volume as of september 1993 this subtraction produces dense rock equivalent dre volumes of 392 439 and 90 106 m3 for the pu u k pa ianah and episode 50 53 stages of the eruption respectively these are 124 89 and 94 of the volumes calculated by staff of the hawaiian volcano observatory hvo but do not include lava of k pa ianah and episodes 50 53 that flowed into the ocean and are thus invisible to topsar accounting for this lava increases the topsar volumes to 124 159 and 129 of the hvo volumes including the 2 m uncertainty derived from the field surveys produces topsar derived volumes for the eruption as a whole that range between 81 and 125 of the usgs derived values the vesicularity and ocean corrected topsar volumes yield volumetric eruption rates of 4 5 4 5 and 2 7 m3 s for the three stages of the eruption which compare with hvo derived values of 3 6 2 8 and 2 1 m3 s respectively our analysis shows that care must be taken when vertically registering the topsar and usgs dems to a common datum because c band topsar penetrates only partially into thick forest and therefore produces a dem within the tree canopy whereas the usgs dem is adjusted for vegetation

high effusion rates of the cordon caulle 2011 2012 eruption southern andes and their relation with the quasi harmonic tremor high effusion rates of intermediate to high silica lavas seem to be less uncommon than previously thought in particular during their initial eruptive stages in this study we report satellite based time averaged discharge rates for the 2011 2012 effusive phase at cordon caulle which are well correlated with the evolution of the quasi harmonic tremor the most significant seismic signal after the initial explosive stage such a correspondence could become a key method for detection of the onset of effusive phases especially in remote and or very cloudy areas supplying an additional tool for effective warnings and near real time hazards appraisal

analysis and evaluation of the nasa jpl topsar across track interferometric sar system we have evaluated the accuracy of digital elevation models dem s generated by the jpwnasa topsar synthetic aperture radar interferometer instrument by acquiring topographic radar data in the summer of 1992 over the national training center near ft irwin california and comparing the measurements to a very accurate digital elevation model derived for this area by the us army topographic engineering center tec fiducial corner reflectors were deployed in the area and their locations were determined to cm accuracy by the defense mapping agency dma dem s generated from the acquired radar data were rotated and translated to precisely overlay the reference dem allowing an analysis of the achieved height accuracy we present here a detailed description of horizontal and vertical errors and their characteristics the standard deviation measured over a 5 6 x 7 km area was approximately 2 m the corresponding figures for relatively flat areas were in the 1 2 meter range and for mountainous areas in the 2 3 meter range consistent with theoretical expectations we also discuss key factors that presently limit the system performance