validation of the ice 3g model of wurm wisconsin deglaciation using a global data base of relative sea level histories a global data base consisting of radiocarbon controlled relative sea level rsl histories from 392 different geographic locations has been compiled for use in analyses of the glacial isostatic adjustment process these data may be employed to constrain both the spatiotemporal characteristics of the last deglaciation event of the current ice age and the rheological structure of the planetary interior in a previous paper in this series tushingham and peltier 1991 we employed the rsl data in this set from sites that were once ice covered to refine the apriori model of deglaciation that had been delivered by past research in the area of pleistocene geomorphology peltier and andrews 1976 wu and peltier 1983 to produce a new global model of this event that we have called ice 3g in the present paper following a description of the full data base and of the methods used to compile it we employ data from the sites that were not ice covered 200 time series to verify the plausibility of this refined model of deglaciation and to test the extent to which the totality of the observations constrain the radial viscoelastic structure of the planet the analysis of solutions to the forward problem presented here reinforce previous inferences of a preference for a thick lithosphere by rsl data from sites along the u s east coast and a preference by data from most near field sites for an increase in viscosity across the 670 km discontinuity in the mantle by a factor of approximately 2 when the viscosity of the upper mantle is fixed to the value of 1021 pa s originally deduced by haskel 1935 on the basis of his analysis of the data from fennoscandia

volcanic ash hazard to aviation during the 2003 2004 eruptive activity of anatahan volcano commonwealth of the northern mariana islands abstract within the commonwealth of the northern mariana islands cnmi anatahan is one of nine active subaerial volcanoes that pose hazards to major air traffic routes from airborne volcanic ash the 2003 2004 eruptive activity of anatahan volcano affected the region s aviation operations for 3 days in may 2003 on the first day of the eruption 10 may 2003 two international flights from saipan to japan were cancelled and several flights implemented ash avoidance procedures on 13 may 2003 a high altitude flight through volcanic gas was reported with no perceptible damage to the aircraft toms and modis analysis of satellite data strongly suggests that no significant ash and only minor amounts of so 2 were involved in the incident consistent with crew observations on 23 may 2003 airport operations were disrupted when tropical cyclone winds dispersed ash to the south dusting saipan with light ashfall and causing flight cancellations there and at guam 320 km south of the volcano operational near real time monitoring of ash clouds produced by anatahan has been conducted since the first day of the eruption on 10 may 2003 by the washington volcanic ash advisory center vaac the vaac was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of anatahan after being contacted about an unusual cloud by national weather service forecasters in guam at 1235 utc on 10 may 2003 the vaac analyzed goes 9 images confirming anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 utc the vaac issued its first volcanic ash advisory for anatahan at 1300 utc on 10 may 2003 more than 5 h after the start of the eruption the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real time geophysical monitoring the initial eruption plume reached 10 7 13 4 km 35 000 44 000 ft well into jet cruise altitudes thereafter the maximum plume height decreased and during the rest of the eruption usually did not exceed 5 km 17 000 ft which lessened the potential hazard to aircraft at higher cruise altitudes drifting ash clouds commonly extended hundreds of kilometers from the volcano occasionally as far west as the philippines over the course of the eruptive activity in 2003 2004 the vaac issued 323 advisories 168 with graphical depictions of ash clouds for anatahan serving as a reliable source of ash cloud information for aviation related meteorological offices and air carriers with a record of frequent eruptions in the cnmi continued satellite and in situ real time geophysical monitoring is needed at anatahan and other marianas volcanoes so that potential hazards to aviation from any future eruptive activity can be quickly and correctly assessed

the 2011 2012 summit activity of mount etna birth growth and products of the new se crater abstract between january 2011 and april 2012 the southeast crater sec on mount etna was the site of 25 episodes of lava fountaining which led to the construction of a new pyroclastic cone on the eastern flank of the sec during these episodes lava overflows reached 4 3 km in length with an area of 3 19 km 2 and a volume of 28 10 6 m 3 the new cone informally called new southeast crater nsec grew over a pre existing subsidence depression pit crater which had been formed in 2007 2009 the evolution of the nsec cone was documented from its start by repeated gps surveys carried out both from a distance and on the cone itself and by the acquisition of comparison photographs these surveys reveal that after the cessation of the lava fountains in april 2012 the highest point of the nsec stood 190 m above the pre cone surface while the cone volume was about 19 10 6 m 3 representing 38 of the total bulk volume of the volcanic products including pyroclastic fallout erupted in 2011 2012 which is 50 10 6 m 3 about 33 10 6 m 3 dense rock equivalent growth of the new cone took place exclusively during the paroxysmal phases of the lava fountaining episodes which were nearly always rather brief on the average 2 h overall the paroxysmal phases of all 25 episodes represent 51 h of lava fountaining activity the time needed to build the cone this is the fastest documented growth of a newborn volcanic cone both in terms of volume and height mean effusion rates during the lava fountaining episodes on 20 august 2011 e11 as well as 12 and 24 april 2012 e24 and e25 exceeded 500 m 3 s with maximum rates of 980 m 3 s during e11 and thus they are among the highest effusion rates ever recorded at etna the composition of the erupted products varies in time reflecting different rates of magma supply into the shallow feeding system but without notable effects on the eruptive phenomenology this implies that the dynamics leading to the episodic lava fountaining was largely though not entirely controlled by the repeated formation and collapse of a foam layer in the uppermost portion of the magmatic reservoir of the nsec

modelling tephra dispersal and ash aggregation the 26th april 1979 eruption la soufriere st vincent abstract on the 26th april 1979 la soufriere st vincent volcano west indies erupted producing a tephra fallout that blanketed the main island and the neighboring bequia island located southwards using deposit measurements and the available observations reported in brazier et al 1982 we estimated the optimal eruption source parameters such as the mass eruption rate mer the total erupted mass tem and the total grain size distribution tgsd by means of a computational inversion method tephra transport and deposition were simulated using the 3d eulerian model fall3d the field based tgsd reconstructed by brazier et al 1982 shows a bi modal pattern having a coarse and a fine population with modes around 0 5 and 0 06 mm respectively a significant amount of aggregates was observed during the eruption to quantify the relevance of aggregation processes on the bulk tephra deposit we performed a comparative study in which we accounted for aggregation using three different schemes computing ash aggregation within the plume under wet conditions i e considering both the effects of air moisture and magmatic water consistently with the eruptive phreatomagmatic eruption features the sensitivity to the driving meteorological model wrf arw was also investigated by considering two different spatial resolutions 5 and 1 km and model output frequencies results show that for such short lived explosive eruptions high resolution meteorological data are critical optimal results best fitting all available observations indicate a column height of 12 km above the vent a mer of 7 8 10 6 kg s which for an eruption duration of 370 s gives a tem of 2 8 10 9 kg the optimal aggregate mean diameter obtained is 1 5 with a density of 350 kg m 3 contributing to 22 of the deposit mass

quantitative assessment of volcanic ash hazards for health and infrastructure at mt etna italy by numerical simulation abstract we performed a quantitative hazard assessment to determine the potential impacts of volcanic tephra fall on human health and infrastructure in the vicinity of mt etna italy using the numerical model vol calpuff we explored the dynamics of long lasting weak plume eruptions and their effects on the surrounding region input data are based on credible estimates of the main parameters characterising the expected events as derived from the historically observed and reconstructed explosive record of mt etna monte carlo techniques are used to capture the effects on estimates of finer ash concentration and total ground deposition due to volcanological uncertainties and meteorological variability numerical simulations compute the likelihoods of experiencing critical 10 m volcanic particle vp 10 concentrations in ambient air and tephra ground deposition at various populated locations around the volcano including the city of catania and at key infrastructure such as airports and main roads results show how the towns and infrastructure on the east side of the volcano are significantly more exposed to ash related hazards than those on the west side in accordance with wind statistics simulation outcomes also illustrate how at the sites analysed the amount of deposited particulate matter is proportional to the intensity i e mass flow rate of the event whereas predicted values of vp 10 concentrations are significantly larger for smaller events due to the reduced dispersal of low altitude plumes the use of a simple re mobilization model highlights the fact that particle re suspension needs to be considered in the estimation of vp 10 values our findings can be used to inform civil protection agencies responsible for mitigating tephra fall impacts to human health road transport and aviation safety

a multidisciplinary effort to assign realistic source parameters to models of volcanic ash cloud transport and dispersion during eruptions during volcanic eruptions volcanic ash transport and dispersion models vatds are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind those models use input parameters called eruption source parameters such as plume height h mass eruption rate duration d and the mass fraction m63 of erupted debris finer than about 4 or 63 m which can remain in the cloud for many hours or days observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected moreover observed plume height may change during an eruption requiring rapid assignment of new parameters this paper reports on a group effort to improve the accuracy of source parameters used by vatds in the early hours of an eruption we do so by first compiling a list of eruptions for which these parameters are well constrained and then using these data to review and update previously studied parameter relationships we find that the existing scatter in plots of h versus yields an uncertainty within the 50 confidence interval of plus or minus a factor of four in eruption rate for a given plume height this scatter is not clearly attributable to biases in measurement techniques or to well recognized processes such as elutriation from pyroclastic flows sparse data on total grain size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions 0 01 and large silicic ones 0 5 we classify eleven eruption types four types each for different sizes of silicic and mafic eruptions submarine eruptions brief or vulcanian eruptions and eruptions that generate co ignimbrite or co pyroclastic flow plumes for each eruption type we assign source parameters we then assign a characteristic eruption type to each of the world s 1500 holocene volcanoes these eruption types and associated parameters can be used for ash cloud modeling in the event of an eruption when no observational constraints on these parameters are available

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

a parametric and comparative study of different tephra fallout models abstract we perform a parametric and comparative study on three different tephra dispersal models fall3d hazmap and tephra applied to two different scenarios expected for etna volcano these scenarios are similar to the recent 2002 03 and 1990 etna eruptions and correspond respectively to a weak and to a strong plume eruption for each model and scenario we perform a parametric study on several inputs in order to quantify how a variation on a given input parameter i e an uncertainty on the model input affects the results of the model the study considers topographic effects different description for the eruption column column height influence different fits for terminal velocities of particles the effect of particle shape and finally the variation of the modal grain size model differences are quantified by means of a normalized distance that indicates how close in average the results from two different simulations are we also compare predictions from different models to determine under which circumstances the use of a more elaborated model is justified results from our parametric study show that output of the models can be strongly sensitive to the uncertainties and assumptions on input parameters such as mainly mass eruption rate column height distribution of the mass along the column bulk grain size distribution this highlights that for optimal forecasts is urgent to improve the description of these parameters and of some important physical processes like fragmentation and eruption column dynamics further differences between models are often lower than those due to the uncertainties of input parameters although they become more high in simulating weak plumes thus the choice of the model mainly depends on the kind of application such as the need to simulate the evolution of volcanic clouds in the atmosphere finally the use of both a semi analytical hazmap and a fully computational fall3d model for inverting field data of the 2001 etna eruption showed that the best fit parameters are similar for both models and are consistent with values obtained using independent techniques

eruption dynamics and tephra dispersal from the 24 november 2006 paroxysm at south east crater mt etna italy abstract between 30 august and 15 december 2006 mt etna italy underwent both effusive and explosive activity which took place from the south east crater one of its summit craters several paroxysmal episodes followed in succession separated by a few days of minor activity and characterised by dissimilar explosive style and intensity here we report one of the most studied and powerful episodes which started early in the morning on 24 november 2006 and lasted about 13 h excellent weather conditions enabled reconstructing in detail the onset and evolution of the eruptive phenomena both by live camera recordings and direct observations the explosive activity consisted of powerful strombolian activity alternating with short periods of lava fountains a weak volcanic plume rose up to 2 km above the volcanic vent followed by tephra fallout which covered the se and s flanks of etna campaigns allowed collecting about 40 tephra samples and mapping the fallout deposit the clockwise shifting of the volcanic plume during the eruption caused the different timing of the fallout on the ground thus widening the dispersal area voronoi s method was used to evaluate i the total grain size distribution indicating that the fallout deposit peaked at 1 and for the first time at etna ii the total componentry distribution finding that most of the particles were lithics with a low proportion of juvenile vs lithics 34 65 the total erupted mass was estimated 1 9 108 kg corresponding to a mass eruption rate of 5 103 kg s 1 physical parameters and textural features of the erupted products suggest that the 24 november 2006 explosive event may be classified as small sized in the recent history of etna and that the eruptive dynamic was mainly governed by magma gas decoupling which produced relatively fine grained fallout deposits containing unusual elongated sideromelane ash particles

an analysis of anisotropic mantle viscosity and its possible effects on post glacial rebound abstract this paper presents a preliminary analysis of the possibility of using post glacial rebound observations to place constraints on the anisotropy of upper mantle viscosity we extend existing analyses by considering a visco elastic spherical self gravitating earth we show that three independent viscosity parameters are required to describe a maxwell solid with transversely isotropic viscosity and isotropic elasticity we develop a theoretical formalism for including the effects of transversely isotropic visco elasticity in post glacial rebound models using this formalism to describe anisotropy in the upper mantle we model the free air gravity anomaly relative sea level changes and present day horizontal motion caused by the rebound to assess their dependence on the upper mantle viscosity parameters we find that as long as those parameters are no larger than the lower mantle isotropic viscosity the results for the gravity and sea level changes are notably sensitive to only one of the three viscosity parameters this suggests at least for the case where the lower mantle viscosity is significantly larger than the upper mantle viscosity that post glacial rebound studies of gravity and sea level will be hard pressed to usefully constrain viscous anisotropy we do find that the horizontal motion is relatively sensitive to transverse isotropy and so might be used in principle to constrain the anisotropy in practice though it is likely that the strong dependence of horizontal motion on details of the ice model coupled with the uncertainties in existing ice models would make such attempts impractical

eruption dynamics of the 23 february 2013 event at mt etna abstract volcanic activity at mt etna in the last decade has mostly been manifested by sequences of short paroxysmal episodes characterised by powerful lava fountains and high eruption columns on the 23 february 2013 an exceptionally intense episode occurred at the new south east crater producing a fountain 800 m high among the highest ever recorded at etna and a 9 km eruption column that dispersed ash 400 km from the vent textural and petrographic analyses of lapilli revealed that magma erupted during the high intensity phase is characterised by low microlite contents

a three dimensional eulerian model for transport and deposition of volcanic ashes abstract volcanic ash fallout represents a serious threat to people living near active volcanoes because it can produce several undesirable effects such as collapse of roofs by ash loading respiratory sickness air traffic disruption or damage to agriculture the assessment of such volcanic risk is therefore an issue of vital importance for public safety and its mitigation often requires to evaluate the temporal evolution of the phenomenon through reliable computational models we develop an eulerian model named fall3d for the transport and deposition of volcanic ashes the model is based on the advection diffusion sedimentation equation with a turbulent diffusion given by the gradient transport theory a wind field obtained from a meteorological limited area model lam and the source term derived from by buoyant plume theory it can be used to forecast either ash concentration in the atmosphere or ash loading on the ground model inputs are topography meteorological data given by a lam mass eruption rate and a particle settling velocity distribution a test application to the july 2001 etna eruption is presented

modelling postglacial sea levels with power law rheology and a realistic ice model in the absence of ambient tectonic stress previous studies of postglacial rebound with power law rheology and simple ice models over laurentia have found that sea level data in the transition zone e g boston cannot be easily explained unless non linear rheology is restricted to lie within a thin layer between the lithosphere and the upper mantle the reason is the existence of a viscously stationary zone which is characteristic of non linear mantles in this study the simple ice model is replaced by a realistic ice history adapted from the ice 3g model which takes into account important effects such as retreating ice margins and eustatic ocean loading a 3 d finite element model is used to calculate the deformation and the relative sea levels in eastern canada and along the us east coast the purpose is to investigate whether the realistic load model allows sea level data near the centre of rebound and along the atlantic east coast of canada and the usa to be explained by non linear rheology simultaneously the assumptions made are that 1 postglacial rebound sees the steady state creep and not the transient creep 2 either ambient tectonic stresses do not interact with rebound stress or the ambient stress level is low 3 lateral heterogeneity of rock properties and anisotropic flow can be neglected results indicate that the retreating ice margin does make it easier for non linear rheology in the mantle to explain the sea level data in the transition zone around boston however reconciling all the sea level data near the centre of rebound and along the atlantic east coast simultaneously is still difficult for a non linear rheology so far two types of models with non linear rheology have been found to be able to explain the sea level data inside and outside laurentia simultaneously they are 1 earth models with a thin 270 km non linear zone overlying a 1021 pa s lower mantle 2 earth models with a linear upper mantle with an average viscosity of 1021 pa s overlying a non linear lower mantle with a 3 10 35 pa 3 s 1 and n 3

a review of tephra transport and dispersal models evolution current status and future perspectives abstract tephra transport models try to predict atmospheric dispersion and sedimentation of tephra depending on meteorology particle properties and eruption characteristics defined by eruption column height mass eruption rate and vertical distribution of mass models are used for different purposes from operational forecast of volcanic ash clouds to hazard assessment of tephra dispersion and fallout the size of the erupted particles a key parameter controlling the dynamics of particle sedimentation in the atmosphere varies within a wide range largest centimetric to millimetric particles fallout at proximal to medial distances from the volcano and sediment by gravitational settling on the other extreme smallest micrometric to sub micrometric particles can be transported at continental or even at global scales and are affected by other deposition and aggregation mechanisms different scientific communities had traditionally modeled the dispersion of these two end members volcanologists developed families of models suitable for lapilli and coarse ash and aimed at computing fallout deposits and for hazard assessment in contrast meteorologists and atmospheric scientists have traditionally used other atmospheric transport models dealing with finer particles for tracking motion of volcanic ash clouds and eventually for computing airborne ash concentrations during the last decade the increasing demand for model accuracy and forecast reliability has pushed on two fronts first the original gap between these different families of models has been filled with the emergence of multi scale and multi purpose models second new modeling strategies including for example ensemble and probabilistic forecast or model data assimilation are being investigated for future implementation in models and or modeling strategies this paper reviews the evolution of tephra transport and dispersal models during the last two decades presents the status and limitations of the current modeling strategies and discusses some emergent perspectives expected to be implemented at operational level during the next few years improvements in both real time forecasting and long term hazard assessment are necessary to loss prevention programs on a local regional national and international level

the continuing story of etna s new southeast crater 2012 2014 evolution and volume calculations based on field surveys and aerophotogrammetry abstract during the years 2013 2014 the new southeast crater nsec at the summit of mount etna produced frequent episodes of lava fountaining paroxysms and its cone continued to grow at unprecedented rates many of the episodes were of rather brief duration and violently explosive producing mostly pyroclastic material and minor volumes of lava other episodes especially those since mid december 2013 were characterized by violent strombolian activity without producing sustained lava fountains and significant amounts of tephra but emitting more voluminous lava flows one episode of intense strombolian and effusive activity that was possibly fed from the nsec conduit occurred from vents located approximately 1 km north of the crater on the east flank of the northeast crater in july august 2014 the evolution of the nsec cone between 2012 and 2014 was documented by repeated gps surveys carried out both from a distance and on the cone itself by the acquisition of comparison photographs and by two aerophotogrammetric surveys from these surveys the highest point of the nsec results to have grown from 190 m may 2012 to 215 m october 2014 above the pre cone surface reaching an elevation of 3290 m and its volume more than doubled to 50 0 6 5 10 6 m 3 representing the 40 of the total bulk volume of the volcanic products including pyroclastic fallout erupted in 2011 2014 which is 147 2 10 6 m 3 101 3 10 6 m 3 dense rock equivalent the whole of the 2011 2014 nsec activity marks an unusually high frequency of rather explosive tephra rich eruptive episodes compared to etna s activity in past decades and centuries although the average magma production rate in this interval is close to the supposed long term output rate of the volcano the latest eruptive episodes show a tendency of the nsec coalescing with the old southeast crater cone which therefore represents a miniature example of a growing compound volcano at the summit of etna

the dynamics of volcanic jets temporal evolution of particles exit velocity from shock tube experiments pyroclast ejection during explosive volcanic eruptions occurs under highly dynamic conditions involving great variations in flux particle sizes and velocities this variability must be a direct consequence of complex interactions between physical and chemical parameters inside the volcanic plumbing system the boundary conditions of such phenomena cannot be fully characterized via field observation and indirect measurements alone in order to understand better eruptive processes we conducted scaled and controlled laboratory experiments by performing shock tube experiments at known conditions we defined the influence of physical boundary conditions on the dynamics of pyroclast ejection if applied to nature we are focusing in the near vent processes where independently of fragmentation mechanism impulsively released gas pyroclast mixtures can be observed these conditions can be met during e g strombolian or vulcanian eruptions parts of plinian eruptions or phreatomagmatic explosions the following parameters were varied 1 tube length 2 vent geometry 3 particle load 4 temperature and 5 particle size distribution gas and particles in the experiments are not coupled st 1 the initial overpressure with respect to atmosphere was always at 15mpa we found a positive correlation of pyroclast ejection velocity with 1 particle load 2 diverging vent walls and 3 temperature as well as a negative correlation with 1 tube length and 2 particle size additionally we found that particle load strongly affects the temporal evolution of particle ejection velocity these findings stress the importance of scaled and repeatable laboratory experiments for a better understanding of volcanic phenomena and therefore volcanic hazard assessment

retrieval of microphysical and morphological properties of volcanic ash plumes from satellite data application to mt ruapehu new zealand a quantitative analysis of the properties of several mt ruapehu new zealand ash plumes has been performed using multispectral satellite data from the avhrr 2 and atsr 2 instruments the analysis includes identification of the plume from background clouds using the reverse absorption effect in the thermal channels modelling and retrieval of particle sizes determination of the plume height from cloud shadows stereoscopy and meteorological data and estimates of the mass of fine particles radii less than 10 m a new spectral technique for identifying opaque silica rich ash clouds is demonstrated by utilizing the near infrared 1 6 m and visible 0 67 m channels of the atsr 2 and the optical properties of a simple volcanic cloud are presented for use in radiative transfer studies it is found that the ruapehu eruption cloud contained silica rich ash particles with radii generally less than a few micrometres the distribution of fine particles is monomodal with a dominant mode peak of about 3 m radius mass loadings of fine particles are found to be in the range 1 to 7 mg m 3 and are consistent with estimates of mass loadings of volcanic clouds from eruptions of other volcanoes the height of the plume top derived from radiosonde data and plume top temperatures in the opaque regions was found to be between 7 5 and 8 5 km while the plume thickness was estimated to be between 1 5 and 3 km cloud height derived from atsr 2 stereoscopy on a different plume gave heights in the range 5 to 8 km the results of this study provide important information on the optical properties of nascent volcanic eruption plumes this information may prove useful in determining the potential effects of volcanic clouds on local climate and in assessing any hazard to aviation

physical characterization of explosive volcanic eruptions based on tephra deposits propagation of uncertainties and sensitivity analysis abstract regardless of the recent advances in geophysical monitoring and real time quantitative observations of explosive volcanic eruptions the characterization of tephra deposits remains one of the largest sources of information on eruption source parameters esps i e plume height erupted volume mass mass eruption rate mer eruption duration total grain size distribution tgsd esps are crucial for the characterization of volcanic systems and for the compilation of comprehensive hazard scenarios but are naturally associated with various degrees of uncertainties that are traditionally not well quantified recent studies have highlighted the uncertainties associated with the estimation of esps mostly related to i the intrinsic variability of the natural system ii the observational error and iii the strategies used to determine physical parameters here we review recent studies focused on the characterization of these uncertainties and we present a sensitivity analysis for the determination of esps and a systematic investigation to quantify the propagation of uncertainty applied to two case studies in particular we highlight the dependence of esps on specific observations used as input parameters i e diameter of the largest clasts thickness measurements area of isopach contours deposit density downwind and crosswind range of isopleth maps and empirical constants and wind speed for the determination of mer the highest uncertainty is associated to the estimation of mer and eruption duration and is related to the determination of crosswind range of isopleth maps and the empirical constants used in the empirical parameterization relating mer and plume height given the exponential nature of the relation between mer and plume height the propagation of uncertainty is not symmetrical and both an underestimation of the empirical constant and an overestimation of plume height have the highest impact on the final outcome a 20 uncertainty on thickness measurements area of isopach contours integration limit for the power law fit and deposit density result in esp uncertainties 20 for plume height and erupted volume mass finally a third case study has also been used to explore the sensitivity of the voronoi tessellation strategy for the determination of tgsd and the inversion on both mass area and grain size data for the determination of erupted mass and plume height results confirm the validity of the methods but also the strong dependence on the distribution and number of observations

improved space borne detection of volcanic ash for real time monitoring using 3 band method abstract for over 25 years thermal infrared data supplied by satellite based sensors are used to detect and characterize volcanic ash clouds using a commonly accepted method the 2 band reverse absorption technique this method is based on a two channel difference model using the opposite extinction features of water ice and ash particles at 11 and 12 m wavelengths although quite efficient with the supervision of a user this method shows however some limitations for reliable automated detection of volcanic ash in a real time fashion here we explore a method dedicated to the operational monitoring of volcanic ash that combines the 11 12 m brightness temperature difference btd11 12 with a second brightness temperature difference between channels 8 7 m and 11 m btd8 7 11 we first achieve a detailed microphysics analysis of different atmospheric aerosols volcanic ash water ice sulfuric acid mineral dust using optical properties e g extinction efficiency single scattering albedo and asymmetry parameter calculated by mie theory and showing that btd8 7 11 can be particularly efficient to remove most of artifacts then we tested this method for eight different eruptions between 2005 and 2011 from six different volcanoes mount etna piton de la fournaise karthala soufriere hills eyjafjallajokull and grimsvotn using data from the spinning enhanced visible and infrared imager seviri on board meteosat second generation msg geostationary satellite we show that between 95 6 and 99 9 of ash contaminated pixels erroneously identified by the btd11 12 method i e artifacts were detected and removed by the 3 band method for all eruptions the 3 band method shows a high and constant reliability having a false alarm rate in the range 0 002 0 08 hence allowing operational implementation for automated detection in case of a volcanic crisis

total grain size distribution of an intense hawaiian fountaining event case study of the 1959 kīlauea iki eruption the 1959 eruption of k lauea iki on the island of hawai i is a principal example of powerful hawaiian fountaining over 36 days including repose periods 16 fountaining episodes created a small cone a downwind tephra blanket of approximately 0 003 km3 and a lava lake of about 0 04 km3 volume during the explosive activity the maximum fountain heights reached 600 m based on a dataset of more than 450 tephra grain size samples we present both a total grain size distribution tgsd of the entire downwind tephra deposit and also tgsds for two eruptive subunits the opening and the closing stages the opening stage was characterized by persistent fountaining over a period of 8 days with fountain heights averaging 100 m in contrast the closing stage was characterized by two short hours long but powerful fountaining episodes up to 600 m the significantly different fountaining intensities are reflected in the characteristics of the tgsds for the closing stages we link bimodality of tgsds to periods of simultaneous deposition of ballistics and fallout from the convective cloud both of which are a function of the maximum fountain height the 1959 k lauea iki case study presents a well constrained set of tgsd data linked with hawaiian style fountaining of two contrasting intensities and can be used as a valuable reference point for eruption source parameters in future modeling of pyroclast dispersal during hawaiian fountaining eruptions

fine ash content of explosive eruptions abstract in explosive eruptions the mass proportion of ash that is aerodynamically fine enough to cause problems with jet aircraft or human lungs 50

a traversing system to measure bottom boundary layer hydraulic properties this study describes a new convenient and robust system developed to measure benthic boundary layer properties with emphasis placed on the determination of bed shear stress and roughness height distribution within estuarine systems by using velocity measurements this system consisted of a remotely operated motorised traverser that allowed a single adv to collect data between 0 and 1 m above the bed as a case study we applied the proposed traversing system to investigate bottom boundary layer bbl hydraulic properties within coombabah creek queensland australia four commonly employed techniques 1 log profile lp 2 reynolds stress rs 3 turbulent kinetic energy tke and 4 inertial dissipation id used to estimate bed shear stresses from velocity measurements were compared bed shear stresses estimated with these four methods agreed reasonably well of these the lp method was found to be most useful and reliable additionally the lp method permits the calculation of roughness height which the other three methods do not an average value of bed shear stress of 0 46 n m2 roughness height of 4 3 mm and drag coefficient of 0 0054 were observed within coombabah creek results are consistent with that reported for several other silty bed estuaries

melt inclusion record of the conditions of ascent degassing and extrusion of volatile rich alkali basalt during the powerful 2002 flank eruption of mount etna italy 1 two unusual highly explosive flank eruptions succeeded on mount etna in july august 2001 and in october 2002 to january 2003 raising the possibility of changing magmatic conditions here we decipher the origin and mechanisms of the second eruption from the composition and volatile h2o co2 s cl content of olivine hosted melt inclusions in explosive products from its south flank vents our results demonstrate that powerful lava fountains and ash columns at the eruption onset were sustained by closed system ascent of a batch of primitive volatile rich 4 wt basaltic magma that rose from 10 km depth below sea level bsl and suddenly extruded through 2001 fractures maintained opened by eastward flank spreading this magma the most primitive for 240 years probably represents the alkali rich parental end member responsible for etna lavas evolution since the early 1970s few of it was directly extruded at the eruption onset but its input likely pressurized the shallow plumbing system several weeks before the eruption this latter was subsequently fed by the extrusion and degassing of larger amounts of the same but slightly more evolved magma that were ponding at 6 4 km bsl in agreement with seismic data and with the lack of preeruptive so2 accumulation above the initial depth of sulphur exsolution 3 km bsl we find that while ponding this magma was flushed and dehydrated by a co2 rich gas phase of deeper derivation a process that may commonly affect the plumbing system of etna and other alkali basaltic volcanoes

low pressure crystallization paths of h2o saturated basaltic hawaiitic melts from mt etna implications for open system degassing of basaltic volcanoes melt inclusions indicate that the basaltic hawaiitic magmas from mt etna sicily contained up to 2 3 wt h2o dissolved in the melt prior to eruption the effect of h2o degassing during magma ascent has been experimentally constrained between 1135 and 1009 c for ph2o ptotal varying from 800 to 270 bars the starting material was a primitive hawaiitic lava sample mgo 7 1 wt representative of the less evolved lava emitted at mt etna experiments were conducted in tzm pressure vessels with ag70pd30 capsules in order to minimize the feo loss at temperatures of 1135 1090 c ph2o 800 bars with ninio and fmq buffers olivine fo83 80 is the liquidus phase in equilibrium with a residual hawaiitic melt mg 0 60 0 57 cao al2o3 0 82 salitic pyroxene begins to crystallize at 1075 c plagioclase at 1025 c and at 1009 c the magma is 33 5 crystallized with olivine ca rich pyroxene and plagioclase 16 60 24 at ph2o 270 bars fmq buffer olivine fo79 3 80 and salitic pyroxene are the main liquidus phases between 1100 and 1090 c they are in equilibrium with hawaiitic melts mg 0 51 cao al2o3 0 73 at 1070 c the experimental charges are highly crystallized 51 5 with olivine fo70 salite and plagioclase an78 4 76 3 in 14 44 42 relative proportions increasing the water content of hawaiitic basaltic magmas expands the stability field of the olivine relative to the other phases lowers the crystallization temperatures of pyroxene and plagioclase and results in the development of a more an rich plagioclase when compared to the natural samples these results support a model of early and moderate crystallization of olivine from etnean primitive hawaiitic magmas containing close to 2 5 wt h2o with nno oxygen buffering conditions at low pressure ph2o ptotal we propose a model of crystallization driven by decompression and water degassing during the emplacement of magma in the volcanic pile itself and possibly concomitant with the opening of fractures

effect of wind on the rise height of volcanic plumes a theoretical model of a volcanic plume based on applying the equations of motion in a plume centered coordinate system suggests that the interaction between a volcanic plume and wind causes enhanced entrainment of air and horizontal momentum plume bending and a decrease in plume rise height at constant eruption rate because of rapid dilution in the high windspeeds of the polar jet plumes that vary over more than one order of magnitude in mass eruption rate 106 to 107 108 kg s if injected into the polar jet may all attain rise heights only slightly different from that of the core of the jet 10 km as opposed to 17 33 km in a still atmosphere

monitoring etna volcanic plumes using a scanning lidar in this paper we use data obtained from lidar measurements during an ash emission event on 15 november 2010 at mt etna in italy in order to evaluate the spatial distribution of volcanic ash in the atmosphere a scanning lidar system located at 7 km distance from the summit craters was directed toward the volcanic vents and moved in azimuth and elevation to analyse different volcanic plume sections during the measurements ash emission from the north east crater and high degassing from the bocca nuova crater were clearly visible from our analysis we were able to 1 evaluate the region affected by the volcanic plume presence 2 distinguish volcanic plumes containing spherical aerosols from those having non spherical ones and 3 estimate the frequency of volcanic ash emissions moreover the spatial distribution of ash mass concentration was evaluated with an uncertainty of about 50 we found that even during ash emission episodes characterised by low intensity like the 15 november 2010 event the region in proximity of the summit craters should be avoided by air traffic operations the ash concentration being greater than 4 10 3 g m3 the use of a scanning permanent lidar station may usefully monitor the volcanic activity and help to drastically reduce the risks to aviation operations during the frequent etna eruptions

density driven transport in the umbrella region of volcanic clouds implications for tephra dispersion models this work has benefited from funding provided by the italian presidenza del consiglio dei ministri dipartimento della protezione civile dpc agreement ingv dpc 2012 2013 this paper does not necessarily represent dpc official opinion and policies a f acknowledges funding by the spanish project atmost cgl2009 10244

2001 flank eruption of the alkali and volatile rich primitive basalt responsible for mount etna s evolution in the last three decades abstract since the early 1970s enhanced eruptive activity of mount etna has been accompanied by selective geochemical changes in erupted lavas among which a gradual increase of alkalis whose origin is still debated here we provide further insight into the origin of this recent evolution based on a detailed study of the chemistry and dissolved volatile content of melt inclusions trapped in olivine crystals of unusual plagioclase poor primitive basalt that was extruded during a highly explosive flank eruption in july august 2001 two types of lava were erupted simultaneously along a n s fracture system trachybasalts from the upper vents 2950 2700 m were simply drained out by fracturing of the central volcanic conduit they are identical to summit crater lavas and contain mg poor olivines fo 70 72 with evolved and volatile poor melt inclusions that represent late stage crystallisation during shallow open conduit degassing in contrast plagioclase poor basalt 80 of total extruded through the lower vents 2550 2100 m derived from lateral dyke intrusion of a more primitive and volatile rich magma across the sedimentary basement this primitive melt is best preserved in rare fo 82 4 80 5 skeletal olivines present in lapilli deposits from the most powerful activities at the 2550 m vent its high dissolved contents of h 2 o 3 4 wt co 2 0 11 to 0 41 wt s 0 32 wt cl 0 16 wt and f 0 094 wt point to its closed system ascent from 400 to 250 mpa 12 to 6 5 km depth b s l however the predominance of euhedral olivine phenocrysts with common reverse zoning cores fo 76 78 and rims fo 78 80 and decrepited inclusions shows that most of the erupted basalt derived from a slightly more evolved crystallizing body of the same magma that was invaded by the uprising primitive melt prior to erupting the few preserved inclusions in these olivines indicate pre eruptive storage of that magma body at about 5 km depth b s l in coherence with seismic data we propose that the 2001 flank eruption resulted from gradual overpressuring of etna s shallow plumbing system due to the influx of volatile rich primitive basalt that may have begun several months in advance we find that this basalt is much richer in alkalis 2 0 wt k 2 o and has higher s cl 2 0 but lower cl k and cl f ratios than all pre 1970s etnean lavas 1 4 wt k 2 o s cl 1 5 as further exemplified by melt inclusions in entrained olivine xenocrysts combining these new observations with previously published data we argue that the 2001 basalt represents a new alkali rich basic end member feeding mt etna only few amount of which had previously been extruded during a 1974 peripheral eruption and more recently during brief paroxysmal summit events over the last three decades this new magma has progressively mixed with and replaced the former k poorer trachybasalts filling the plumbing system leading to extrusion of gradually more primitive and alkali richer lavas its geochemical singularities cannot result from shallow crustal contaminations instead they suggest the involvement of an alkali richer but cl poorer arc type component during recent magma genesis beneath etna

effects of wind on entrainment efficiency in volcanic plumes the entrainment of air by turbulent mixing plays a central role in the dynamics of volcanic eruption clouds as the amount of entrained air controls the height of the plume in one dimensional models of volcanic plumes the efficiency of entrainment under a wind field is parameterized using two empirical constants the first is the coefficient associated with the entrainment caused by the shear between the volcanic plume and the ambient air i e the radial entrainment coefficient and the other is associated with the entrainment caused by wind i e the wind entrainment coefficient in this study we used three dimensional numerical simulations of volcanic plumes to determine the effective values of these empirical constants from the relationship between eruption conditions and plume heights these simulations suggest that the value of the radial entrainment coefficient is 0 05 0 06 which is slightly smaller than that of pure jets or plumes seen in laboratory experiments 0 07 0 15 the value of the wind entrainment coefficient was estimated to be 0 1 0 3 which is significantly smaller than those estimated from laboratory experiments 0 3 1 0 the entrainment coefficients derived from these simulations successfully explain the observations made during the 2011 shinmoe dake eruptions in which the volcanic plumes were significantly distorted by the wind

glacial isostatic adjustment and earth rotation refined constraints on the viscosity of the deepest mantle we explore the extent to which two properties of earth s present day rotational state may be applied to constrain the viscosity of the lower regions of the lower mantle the analysis builds upon recent advances in understanding the radial resolving power of the relative sea level data of postglacial rebound which have demonstrated anew that no significant increase of viscosity across the 660 km seismic discontinuity appears to be allowed by these data such observations do not constrain the viscosity of the mantle below about 1400 km depth however and here we estimate the average viscosity in this deepest region by invoking observations of the present day rate and direction of polar wander and the present day magnitude of the nontidal acceleration of the rate of planetary rotation since the rotational response to the glaciation cycle depends only upon the degree 2 spherical harmonic components of the induced deformation this response is expected to provide the most specific sampling possible of deep mantle properties our analysis is based upon the use of glacial excitation functions calculated from complete gravitationally self consistent solutions of the sea level equation for the most recent refinement of the history of ice sheet thickness variations across the last glacial interglacial transition namely the ice 4g model this analysis shows that when earth rotation observations are combined with relative sea level constraints the viscosity of the deepest mantle is required to be 1 order of magnitude higher than the viscosity of the upper part of the lower mantle such significant elevation of viscosity in the lowermost region of the lower mantle is also in accord with recent inferences based upon analysis of the nonhydrostatic geoid the analyses presented herein therefore suffice to effect a reconciliation between the requirements of these distinct geophysical observations

near source doppler radar monitoring of tephra plumes at etna over the last twenty years mount etna has produced more than one hundred explosive events ranging from light ash emissions to violent sub plinian eruptions significant hazards arise from tephra plumes which directly threaten air traffic and generate fallout affecting surrounding towns and infrastructures we describe the first radar system named voldorad 2b fully integrated into a volcano instrumental network dedicated to the continuous near source monitoring of tephra emissions from etna s summit craters this 23 5 cm wavelength pulsed doppler radar is operated in collaboration between the observatoire de physique du globe de clermont ferrand opgc and the istituto nazionale di geofisica e vulcanologia osservatorio etneo ingv oe since 2009 probed volumes inside the fixed northward pointing conical beam total about 1 5 km in length covering the summit craters which produced all recent tephra plumes the backscattered power related to the amount of particles crossing the beam and particle along beam velocities are recorded every 0 23 s providing a proxy for the tephra mass eruption rate radar raw data are transmitted in real time to the volcano monitoring center of ingv oe in catania and are used to automatically release alerts at onset and end of eruptive events processed radar parameters are also made available from the voldorad database online http voldorad opgc fr in addition to eruptive crater discrimination by range gating relative variations of eruption intensity can be tracked including through overcast weather when other optical or infrared methods may fail to provide information short lived dense ash emissions can be detected as illustrated for weak ash plumes from the bocca nuova and new south east craters in 2010 the comparison with thermal images suggests that the front mushroom of individual ash plumes holds the largest particles coarse ash and small lapilli and concentrations at least within the first hundred meters for these short lived ash plumes the highest particle mass flux seems to occur typically within the first 10 s we also analyze data from the first lava fountain generating an ash and lapilli plume on 12 january 2011 that initiated a series of 25 paroxysmal episodes of the new south east crater until april 2012 we illustrate the pulsating behavior of the lava fountain and show that vertical velocities reached 250 m s 1 with brief peaks exceeding 300 m s 1 leading to mean and maximum tephra fluxes dre of 185 and 318 m3 s 1 with peaks exceeding 380 m3 s 1 respectively and a total volume of pyroclasts emitted during the lava fountain phase of 1 3 106 m3 finally we discuss capacities and limits of the instrument along with future work aimed at providing source term inputs to tephra dispersal models in order to improve hazard assessment and risk mitigation at etna

the magnitude and impact of the 431 ce tierra blanca joven eruption of ilopango el salvador the tierra blanca joven tbj eruption from ilopango volcano deposited thick ash over much of el salvador when it was inhabited by the maya and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption nonetheless the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained in this multifaceted study we have resolved the date of the eruption to 431 2 ce by identifying the ash layer in a well dated high resolution greenland ice core record that is 7 000 km from ilopango and calculated that between 37 and 82 km3 of magma was dispersed from an eruption coignimbrite column that rose to 45 km by modeling the deposit thickness using state of the art tephra dispersal methods sulfate records from an array of ice cores suggest stratospheric injection of 14 2 tg s associated with the tbj eruption exceeding those of the historic eruption of pinatubo in 1991 based on these estimates it is likely that the tbj eruption produced a cooling of around 0 5 c for a few years after the eruption the modeled dispersal and higher sulfate concentrations recorded in antarctic ice cores imply that the cooling would have been more pronounced in the southern hemisphere the new date confirms the eruption occurred within the early classic phase when maya expanded across central america

estimating the volume of tephra deposits a new simple strategy volume determination of tephra deposits is necessary for the assessment of the dynamics and hazards of explosive volcanoes several methods have been proposed during the past 40 years that include the analysis of crystal concentration of large pumices integrations of various thinning relationships and the inversion of field observations using analytical and computational models regardless of their strong dependence on tephra deposit exposure and distribution of isomass isopach contours empirical integrations of deposit thinning trends still represent the most widely adopted strategy due to their practical and fast application the most recent methods involve the best fitting of thinning data using various exponential segments or a power law curve on semilog plots of thickness or mass area versus square root of isopach area the exponential method is mainly sensitive to the number and the choice of straight segments whereas the power law method can better reproduce the natural thinning of tephra deposits but is strongly sensitive to the proximal or distal extreme of integration we analyze a large data set of tephra deposits and propose a new empirical method for the determination of tephra deposit volumes that is based on the integration of the weibull function the new method shows a better agreement with observed data reconciling the debate on the use of the exponential versus power law method in fact the weibull best fitting only depends on three free parameters can well reproduce the gradual thinning of tephra deposits and does not depend on the choice of arbitrary segments or of arbitrary extremes of integration

reconstructing eruptive source parameters from tephra deposit a numerical study of medium sized explosive eruptions at etna volcano since the 1970s multiple reconstruction techniques have been proposed and are currently used to extrapolate and quantify eruptive parameters from sampled tephra fall deposit datasets atmospheric transport and deposition processes strongly control the spatial distribution of tephra deposit therefore a large uncertainty affects mass derived estimations especially for fall layer that are not well exposed this paper has two main aims the first is to analyse the sensitivity to the deposit sampling strategy of reconstruction techniques the second is to assess whether there are differences between the modelled values for emitted mass and grainsize versus values estimated from the deposits we find significant differences and propose a new correction strategy a numerical approach is demonstrated by simulating with a dispersal code a mild explosive event occurring at mt etna on 24 november 2006 eruptive parameters are reconstructed by an inversion information collected after the eruption a full synthetic deposit is created by integrating the deposited mass computed by the model over the computational domain i e an area of 7 5 104 km 2 a statistical analysis based on 2000 sampling tests of 50 sampling points shows a large variability up to 50 for all the reconstruction techniques moreover for some test examples power law errors are larger than estimated uncertainty a similar analysis on simulated grain size classes shows how spatial sampling limitations strongly reduce the utility of available information on the total grain size distribution for example information on particles coarser than 4 is completely lost when sampling at 1 5 km from the vent for all columns with heights less than 2000 m above the vent to correct for this effect an optimal sampling strategy and a new reconstruction method are presented a sensitivity study shows that our method can be extended to a wide range of eruptive scenarios including those in which aggregation processes are important the new correction method allows an estimate of the deficiency for each simulated class in calculated mass deposited providing reliable estimation of uncertainties in the reconstructed total whole deposit grainsize distribution

a model for wet aggregation of ash particles in volcanic plumes and clouds 2 model application 1 the occurrence of particle aggregation has a dramatic effect on the transport and sedimentation of volcanic ash the aggregation process is complex and can occur under different conditions and in multiple regions of the plume and in the ash cloud in the companion paper costa et al develop an aggregation model based on a fractal relationship to describe the rate particles are incorporated into ash aggregates the model includes the effects of both magmatic and atmospheric water present in the volcanic cloud and demonstrates that the rate of aggregation depends on the characteristics of the initial particle size distribution the aggregation model includes two parameters the fractal exponent df which describes the efficiency of the aggregation process and the aggregate settling velocity correction factor e which influences the distance at which distal mass deposition maxima form both parameters are adjusted using features of the observed deposits here this aggregation model is implemented in the fall3d volcanic ash transport model and applied to the 18 may 1980 mount st helens and the 17 18 september 1992 crater peak eruptions for both eruptions the optimized values for df 2 96 3 00 and e 0 27 0 33 indicate that the ash aggregates had a bulk density of 700 800 kg m 3 the model provides a higher degree of agreement than previous fully empirical aggregation models and successfully reproduces the depositional characteristics of the deposits investigated over a large range of scales including the position and thickness of the secondary maxima

quantifying volcanic ash dispersal and impact of the campanian ignimbrite super eruption 1 we apply a novel computational approach to assess for the first time volcanic ash dispersal during the campanian ignimbrite italy super eruption providing insights into eruption dynamics and the impact of this gigantic event the method uses a 3d time dependent computational ash dispersion model a set of wind fields and more than 100 thickness measurements of the ci tephra deposit results reveal that the ci eruption dispersed 250 300 km 3 of ash over 3 7 million km 2 the injection of such a large quantity of ash and volatiles into the atmosphere would have caused a volcanic winter during the heinrich event 4 the coldest and driest climatic episode of the last glacial period fluorine bearing leachate from the volcanic ash and acid rain would have further affected food sources and severely impacted late middle early upper paleolithic groups in southern and eastern europe citation costa a a folch g macedonio b giaccio r isaia and v c smith 2012 quantifying volcanic ash dispersal and impact of the campanian ignimbrite super eruption geophys res lett 39 l10310 doi 10 1029 2012gl051605

total grain size distribution and volume of tephra fall deposits on 17 june 1996 ruapehu volcano new zealand produced a sustained andesitic sub plinian eruption which generated a narrow tephra fall deposit extending more than 200 km from the volcano the extremely detailed data set from this eruption allowed methods for the determination of total grain size distribution and volume of tephra fall deposits to be critically investigated calculated total grain size distributions of tephra fall deposits depend strongly on the method used and on the availability of data across the entire dispersal area the voronoi tessellation method was tested for the ruapehu deposit and gave the best results when applied to a data set extending out to isomass values of 1 g m 2 the total grain size distribution of a deposit is also strongly influenced by the very proximal samples and this can be shown by artificially constructing subsets from the ruapehu database unless the available data set is large all existing techniques for calculations of total grain size distribution give only apparent distributions the tephra fall deposit from ruapehu does not show a simple exponential thinning but can be approximated well by at least three straight line segments or by a power law fit on semi log plots of thickness vs area 1 2 integrations of both fits give similar volumes of about 4 106 m3 integration of at least three exponential segments and of a power law fit with at least ten isopach contours available can be considered as a good estimate of the actual volume of tephra fall integrations of smaller data sets are more problematic

using data insertion with the name model to simulate the 8 may 2010 eyjafjallajokull volcanic ash cloud a data insertion method where a dispersion model is initialized from ash properties derived from a series of satellite observations is used to model the 8 may 2010 eyjafjallajokull volcanic ash cloud which extended from iceland to northern spain we also briefly discuss the application of this method to the april 2010 phase of the eyjafjallajokull eruption and the may 2011 grimsvotn eruption an advantage of this method is that very little knowledge about the eruption itself is required because some of the usual eruption source parameters are not used the method may therefore be useful for remote volcanoes where good satellite observations of the erupted material are available but little is known about the properties of the actual eruption it does however have a number of limitations related to the quality and availability of the observations we demonstrate that using certain configurations the data insertion method is able to capture the structure of a thin filament of ash extending over northern spain that is not fully captured by other modeling methods it also verifies well against the satellite observations according to the quantitative object based quality metric sal structure amplitude location and the spatial coverage metric figure of merit in space

assessing tephra total grain size distribution insights from field data analysis abstract the total grain size distribution tgsd of tephra deposits is crucial for hazard assessment and provides fundamental insights into eruption dynamics it controls both the mass distribution within the eruptive plume and the sedimentation processes and can provide essential information on the fragmentation mechanisms tgsd is typically calculated by integrating deposit grain size at different locations the result of such integration is affected not only by the number but also by the spatial distribution and distance from the vent of the sampling sites in order to evaluate the reliability of tgsds we assessed representative sampling distances for pyroclasts of different sizes through dedicated numerical simulations of tephra dispersal results reveal that depending on wind conditions a representative grain size distribution of tephra deposits down to 100 m can be obtained by integrating samples collected at distances from less than one tenth up to a few tens of the column height the statistical properties of tgsds representative of a range of eruption styles were calculated by fitting the data with a few general distributions given by the sum of two log normal distributions bi gaussian in units the sum of two weibull distributions and a generalized log logistic distribution for the cumulative number distributions the main parameters of the bi lognormal fitting correlate with height of the eruptive columns and magma viscosity allowing general relationships to be used for estimating tgsd generated in a variety of eruptive styles and for different magma compositions fitting results of the cumulative number distribution show two different power law trends for coarse and fine fractions of tephra particles respectively our results shed light on the complex processes that control the size of particles being injected into the atmosphere during volcanic explosive eruptions and represent the first attempt to assess tgsd on the basis of pivotal physical quantities such as magma viscosity and plume height our empirical method can be used to assess the main features of tgsd necessary for numerical simulations aimed to real time forecasting and long term hazard assessment when more accurate field derived tgsds are not available

evaluating the structure and magnitude of the ash plume during the initial phase of the 2010 eyjafjallajokull eruption using lidar observations and name simulations 1 the eyjafjallajokull volcano in iceland erupted explosively on 14 april 2010 emitting a plume of ash into the atmosphere the ash was transported from iceland toward europe where mostly cloud free skies allowed ground based lidars at chilbolton in england and leipzig in germany to estimate the mass concentration in the ash cloud as it passed overhead the uk met office s numerical atmospheric dispersion modeling environment name has been used to simulate the evolution of the ash cloud from the eyjafjallajokull volcano during the initial phase of the ash emissions 14 16 april 2010 name captures the timing and sloped structure of the ash layer observed over leipzig close to the central axis of the ash cloud relatively small errors in the ash cloud position probably caused by the cumulative effect of errors in the driving meteorology en route result in a timing error at distances far from the central axis of the ash cloud taking the timing error into account name is able to capture the sloped ash layer over the uk comparison of the lidar observations and name simulations has allowed an estimation of the plume height time series to be made it is necessary to include in the model input the large variations in plume height in order to accurately predict the ash cloud structure at long range quantitative comparison with the mass concentrations at leipzig and chilbolton suggest that around 3 of the total emitted mass is transported as far as these sites by small 100 m diameter ash particles

can observations of postglacial rebound tell whether the rheology of the mantle is linear or nonlinear it has been argued that since a power law mantle may appear to the postglacial rebound process as linear if the rebound stress is less than the ambient tectonic stress therefore observations of rebound cannot be used to determine whether the flow law in the mantle is linear or nonlinear the purpose of this paper is to show that this may not be completely true if the rebound process sees the steady state creep it will be demonstrated that for sites near the centre of rebound the relative sea level rsl observations cannot distinguish a newtonian mantle from a power law mantle with large ambient stress however for sites outside the ice margin the rsl signature for a power law mantle is clearly distinguishable from that due to deep flow in a newtonian mantle this characteristic of power law medium is independent of the ambient stress level and is unlikely to change with more complicated rebound models if these results remain valid in future work then rsl data near the ice margin can be used to argue against a steady state power law mantle

an example of enhanced tephra deposition driven by topographically induced atmospheric turbulence spatial variations in the thickness and grain size characteristics of tephra fall deposits imply that tephra depositional processes cannot be fully captured by models of single particle sedimentation from the base of the eruption plume here we document a secondary thickness maximum in a 9 75 ka tephra fall deposit from chaiten volcano chile cha1 eruption this secondary thickness maximum is notably coarser grained than documented historical examples being dominated by medium grained ash and an origin via particle aggregation is therefore unlikely in the region of secondary thickening we propose that high levels of atmospheric turbulence accelerated particles held within the mid to lower troposphere 0 to 6 km towards the ground surface we suggest that this enhancement in vertical atmospheric mixing was driven by the breaking of lee waves generated by winds passing over elevated topography beneath the eruption plume lower atmospheric circulation patterns may exert a significant control on the dispersal and deposition of tephra from eruption plumes across all spatial scales particularly in areas of complex topography

thermal infrared remote sensing of volcanic emissions using the moderate resolution imaging spectroradiometer the volcanological community has a powerful new tool in the spaceborne moderate resolution imaging spectroradiometer modis which from its synoptic perspective provides satellite imagery of every volcano on earth every 2 days modis has the spectral characteristics to be able to utilise previously developed retrievals that quantify volcanic ash ice sulfates and sulfur dioxide using their thermal infrared 8 12 am transmission signature in this paper we present a detailed description of the methodologies based within the thermal infrared region that are being applied to modis data modis data for two eruptions hekla iceland and cleveland alaska are presented to show results from the ice ash and so2 retrieval schemes we look at current problems with the retrievals used to quantify volcanic emissions detail recent developments within the field that can be applied to modis data and suggest areas where improvements need to be made in the future published by elsevier b v

simultaneous retrieval of volcanic ash and so2 using msg seviri measurements 1 volcanic ash and sulphur dioxide masses from the november 2005 eruption of karthala volcano comoros islands are simultaneously retrieved using rapid scan multispectral infrared measurements from the spin enhanced visible and infrared imager on board the meteosat second generation geosynchronous satellite retrievals are made every 15 min which show that the ash and so2 separate in the vertically sheared atmosphere producing a fast moving upper level 12 km so2 cloud a slower moving middle level 8 km ash cloud and a boundary layer 3 km so2 plume the total mass of fine ash is 0 1 0 05 tg sio2 the upper level so2 mass is 0 19 0 01 tg s while the boundary layer so2 mass is 0 009 0 01 tg s these are the first simultaneous satellite measurements of ash and so2 from an erupting volcano and confirm previous ideas about vertical separation we suggest care must be exercised when using so2 as a tracer for volcanic ash in aviation hazard warning systems

representivity of incompletely sampled fall deposits in estimating eruption source parameters a test using the 12 13 january 2011 lava fountain deposit from mt etna volcano italy the southeast crater sec of mt etna italy is renowned for its high activity mainly long lived eruptions consisting of sequences of individual paroxysmal episodes which have produced more than 150 eruptive events since 1998 each episode typically forms eruption columns followed by tephra fallout over distances of up to about 100 km from the vent one of the last sequences consisted of 25 lava fountaining events which took place between january 2011 and april 2012 from a pit vent on the eastern flank of the sec and built a new scoria cone renamed new southeast crater the first episode on 12 13 january 2011 produced tephra fallout which was unusually dispersed toward to the south extending out over the mediterranean sea the southerly deposition of tephra permitted an extensive survey at distances between 1 and 100 km providing an excellent characterization of the tephra deposit here we document the stratigraphy of the 12 13 january fallout deposit draw its dispersal and reconstruct its isopleth map these data are then used to estimate the main eruption source parameters the total erupted mass tem was calculated by using four different methodologies which give a mean value of 1 5 0 4 108 kg the mass eruption rate mer is 2 5 0 7 104 kg s using eruption duration of 100 min the total grain size tgs distribution peaked at 3 phi ranges between 5 and 5 phi and has a median value of 1 4 phi further for the eruption column height we obtained respective values of 6 8 13 8 km by using the method of carey and sparks 1986 and 3 4 0 3 km by using the methods of wilson and walker 1987 mastin et al 2009 and pistolesi et al 2011 and considering the mean value of mer from the deposit we also evaluated the uncertainty and reliability of tem and tgs for scenarios where the proximal and distal samples are not obtainable this is achieved by only using a sector spanning the downwind distances between 6 and 23 km this scenario is typical for etna when the tephra plume is dispersed eastward i e in the prevailing wind direction our results show that if the analyzed deposit has poorer sample coverage than presented in this study the tem 3 4 107 kg is 22 than the tem obtained from the whole deposit the lack of the proximal 6 km deposit may cause more significant differences in the tgs estimations

corrigendum to assessing tephra total grain size distribution insights from field data analysis earth planet sci lett 443 2016 90 107

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

modeling eruption source parameters by integrating field ground based and satellite based measurements the case of the 23 february 2013 etna paroxysm

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

mantle viscosity from the simultaneous inversion of multiple data sets pertaining to postglacial rebound we employ the formalism of bayesian inference to invert three distinct data sets related to the phenomenon of glacial isostatic adjustment these data consist respectively of the wavenumber spectrum of relaxation times for fennoscandian rebound inferred by mcconnell 1968 the characteristic relaxation times for a large collection of distinct 14c dated relative sea level curves from both canada and fennoscandia and two data related to the rotational response of the earth to the glaciation deglaciation cycle of the late pleistocene ice age our analyses show that the spherically symmetric viscosity structure objectively inferred on the basis of these data from the once glaciated regions of the northern hemisphere allows a fully satisfactory reconciliation of both us east coast relative sea level observations as well as providing a close fit to the requirements of aspherical geoid anomalies

a three dimensional numerical simulation of spreading umbrella clouds 1 during explosive volcanic eruptions an eruption column buoyantly rises as a turbulent plume and an umbrella cloud spreads laterally as a gravity current at the neutral buoyancy level the source conditions of explosive eruptions such as mass discharge rates of magma at vents have been estimated from the field observations e g satellite images on the height of the eruption columns and the spreading rate of umbrella clouds on the basis of the one dimensional 1 d plume model and the gravity current model however these simplified models contain empirical constants entrainment coefficient of turbulent plume k and froude number of gravity current that should be justified we developed a time dependent three dimensional 3 d numerical model of eruption clouds to independently determine the values of these constants the 3 d model is designed to calculate quantitative features of turbulent mixing between an eruption cloud and the ambient air without any a priori empirical constants by applying a sufficiently fine grid size with a third order accuracy scheme it has reproduced the fundamental features of eruption clouds including eruption columns pyroclastic flows coignimbrite ash clouds and umbrella clouds the altitudes of the spreading umbrella clouds in the 3 d simulations are consistent with those of the neutral buoyancy level of eruption columns estimated by the 1 d plume model with the entrainment coefficient k 0 1 the relationship between the volumetric flow rate and the spreading rate of the umbrella cloud in the 3 d simulations is explained by the axisymmetrical gravity current model with 0 2 for eruption clouds in the tropical atmosphere and 0 1 for those in the midlatitude atmosphere on the other hand the total column height in the 3 d simulations strongly oscillates even for a constant mass discharge rate and its time average tends to be substantially greater than the column height estimated by the 1 d plume model with k 0 1 particularly for large scale eruption clouds in the midlatitude atmosphere we recommend a method to estimate the mass discharge rate from the observation of the column height or the spreading rate of umbrella cloud the method and the accuracy of the 3 d simulations are tested on the basis of the field data e g the total height of the eruption column the altitude and the spreading rate of the umbrella cloud and the mass discharge rate of the pinatubo 1991 eruption

monitoring the december 2015 summit eruptions of mt etna italy implications on eruptive dynamics abstract a lengthy period of eruptive activity from the summit craters of mt etna started in january 2011 it culminated in early december 2015 with a spectacular sequence of intense eruptive events involving all four summit craters voragine bocca nuova new southeast crater and northeast crater the activity consisted of high eruption columns strombolian explosions lava flows and widespread ash falls that repeatedly interfered with air traffic the most powerful episode occurred on 3 december 2015 from the voragine after three further potent episodes from the voragine activity shifted to the new southeast crater on 6 december 2015 where strombolian activity and lava flow emission lasted for two days and were fed by the most primitive magma of the study period activity once more shifted to the northeast crater where ash emission and weak strombolian activity took place for several days sporadic ash emissions from all craters continued until 18 december when all activity ceased although resembling the summit eruptions of 1998 1999 which also involved all four summit craters this multifaceted eruptive sequence occurred in an exceptionally short time window of less than three days unprecedented in the recent activity of mt etna it also produced important morphostructural changes of the summit area with the coalescence of voragine and bocca nuova in a single large crater the central crater reproducing the morphological setting of the summit cone before the formation of bocca nuova in 1968 the december 2015 volcanic crisis was followed closely by the staff of the etna observatory to monitor the on going activity and forecast its evolution in accordance with protocols agreed with the italian civil protection department

the effect of etna volcanic ash clouds on the maltese islands abstract in this paper we have studied in depth the effect of etna volcanic ash clouds on the maltese islands research was carried out to gather information about etna s eruptions that impacted the maltese islands starting with historical eruptions dating back to the 14th century continuing to present day a statistical approach was utilized to provide tephra deposit load and ash concentration using puff a model which simulates the transport dispersion and sedimentation of volcanic ash three different eruptive scenarios that characterize etna s recent activity were considered the first scenario representing the 2001 eruption sc1 the second scenario representing the july 1998 eruption sc2 whilst the third scenario represents the recent activity in 2011 2012 sc3 we found that the time taken for the volcanic ash cloud to reach the maltese islands when the wind direction is toward the south west ranges from 4 to 6 h the probability that an etna volcanic cloud reaches malta during an eruption is about 15 per annum the now calibrated model may be now used to produce deposit load and cumulative columnar load i e summation from maximum height of volcanic cloud to ground of volcanic ash in atmosphere for the maltese area and help the aviation authorities and malta airport to make decisions during etna eruptions this will be of direct use to local communities and aviation

tephra sedimentation during the 2010 eyjafjallajokull eruption iceland from deposit radar and satellite observations the april may 2010 eruption of eyjafjallajokull volcano iceland was characterized by a nearly continuous injection of tephra in the atmosphere that affected various economic sectors in iceland and caused a global wide interruption of air traffic eruptive activity during 4 8 may 2010 was characterized based on short duration physical parameters in order to capture transient eruptive behavior of a long lasting eruption i e total grainsize distribution erupted mass and mass eruption rate averaged over 30 minute activity resulting 30 minute total grainsize distribution based on both ground and msg seviri satellite measurements is characterized by mdphi of about 2 phi and a fine ash content of about 30wt accumulation rate varied by two orders of magnitude with an exponential decay away from the vent whereas mdphi shows a linear increase until about 18 km from vent reaching a plateau of about 4 5 phi between 20 56 km associated mass eruption rate is in between 0 6 1 2 x 10 5 kg s 1 in situ sampling showed how fine ash mainly fell as aggregates of various typologies about 5 to 9 wt of the erupted mass remained in the cloud up to 1000 km from the vent suggesting that nearly half of the ash 7 phi settled as aggregates within the first 60 km particle sphericity and shape factor varied between 0 4 and 1 with no clear correlation with size and distance from vent our experiments also demonstrate how satellite retrievals and doppler radar grainsize detection can provide real time description of the source term but for a limited particle size range

the 4 5 september 2007 lava fountain at south east crater of mt etna italy abstract continuous monitoring of paroxysmal eruptions at mt etna italy is performed from the istituto nazionale di geofisica e vulcanologia sezione di catania in recent years this activity has allowed us to study fallout deposits and track the evolution of eruptive phases this communication reports on the paroxysm that occurred in the afternoon of 4 september 2007 when a powerful lava fountain started from south east crater at the summit of etna the fountaining formed a plume up to 2 km high for almost 12 h causing abundant tephra fallout in the eastern sector of the volcano and emplacement of a thick about 4 km long clastogenic lava flow extensive area collection of tephra samples from the fallout deposit was performed within a few hours after the end of the paroxysm we calculated a total erupted volume of 3 92 4 9 10 5 m 3 and a total grain size fitted by a gaussian distribution with the mode of 0 and equal to 1 3 the total volume of the clastogenic lava flow deposit that resulted was 2 4 10 6 m 3 the systematic study of paroxysms at etna helps to better investigate etnean type lava fountains and to improve the classification of explosive activity on basaltic volcanoes