separation of ash and sulfur dioxide during the 2011 grimsvotn eruption modeling the transport of volcanic ash and gases released during volcanic eruptions is crucially dependent on knowledge of the source term of the eruption that is the source strength as a function of altitude and time for the first time an inversion method is used to estimate the source terms of both volcanic sulfur dioxide so2 and ash it was applied to the explosive volcanic eruption of grimsvotn iceland in may 2011 the method uses input from the particle dispersion model flexpart flexible particle dispersion model a priori source estimates and satellite observations of so2 or ash total columns from infrared atmospheric sounding interferometer to separately obtain the source terms for volcanic so2 and fine ash the estimated source terms show that so2 was emitted mostly to high altitudes 5 to 13 km during about 18 h 22 may 00 18 utc while fine ash was emitted mostly to low altitudes below 4 km during roughly 24 h 22 may 06 utc to 23 may 06 utc flexpart simulations using the estimated source terms show a clear separation of so2 transported mostly northwestward and the fine ash transported mostly southeastward this corresponds well with independent satellite observations and measured aerosol mass concentrations and lidar measurements at surface stations in scandinavia aircraft measurements above iceland and germany confirmed that the ash was located in the lower atmosphere this demonstrates that the inversion method in this case is able to distinguish between emission heights of so2 and ash and can capture resulting differences in transport patterns key points ash and so2 source terms estimated using inverse techniques and satellite data the transport and separation of ash and so2 are modeled model simulations correspond well with a range of independent observations 2014 the authors

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

pathways of high latitude dust in the north atlantic abstract the contribution of mineral dust from high latitude sources has remained an under examined feature of the global dust cycle dust events originating at high latitudes can provide inputs of aeolian sediment to regions lying well outside the subtropical dust belt constraining the seasonal variability and preferential pathways of dust from high latitude sources is important for understanding the potential impacts that the dust may have on wider environmental systems such as nearby marine or cryospheric domains this study quantifies dust pathways from two areas exhibiting different emission dynamics in the north and south of iceland which is a prominent northern hemisphere dust source the analysis uses air parcel trajectory modelling and for the first time for high latitude sources explicitly links all trajectory simulations to time specific meteorological observations of suspended dust this approach maximises the potential for trajectories to represent dust and illustrates that trajectory climatologies not limited to dust can grossly overestimate the potential for dust transport preferential pathways emerge that demonstrate the role of iceland in supplying dust to the northern atlantic and sub arctic oceans for dust emitted from northern sources a dominant route exists to the northeast into the norwegian greenland and barents seas although there is also potential for delivery to the north atlantic in summer months from the southern sources the primary pathway extends into the north atlantic with a high density of trajectories extending as far south as 50 n particularly in spring and summer common to both southern and northern sources is a pathway to the west southwest of iceland into the denmark strait and towards greenland for trajectories simulated at 500 m the vertical development of dust plumes from iceland is limited likely due to the stable air masses of the region suppressing the potential for vertical motion trajectories rarely ascend high enough to reach the central portions of the greenland ice sheet the overall distribution of trajectories suggests that contributions of icelandic dust are relatively more important for neighbouring marine environments than the cryosphere

evaluation of the physical and chemical properties of eyjafjallajokull volcanic plume using a cloud resolving model the eyjafjallajokull volcanic eruption which occurred on april 14 2010 caused many environmental air traffic and health problems an attempt has been made to demonstrate for the first time that certain improvements could be made in the quantitative prediction of the volcanic ash parameters and in the accounting of the processes in the immediate vicinity of the volcano using a cloud resolving model this type of explicit modeling by treatment of volcanic ash and sulfate chemistry parameterization with input of a number parameters describing the volcanic source is the way forward for understanding the complex processes in plumes and in the future plume dispersion modeling results imply that the most significant microphysical processes are those related to accretion of cloud water cloud ice and rainwater by snow and accretion of rain and snow by hail the dominant chemical conversion rates that give a great contribution to the sulfate budget are nucleation and dynamic scavenging and oxidation processes a three dimensional numerical experiment has shown a very realistic simulation of volcanic ash and other chemical compounds evolution with a sloping structure strongly influenced by the meteorological conditions in cloud oxidation by h2o2 is the dominant pathway for so2 oxidation and allows sulfate to be produced within the so2 source region the averaged cloud water ph of about 5 8 and rainwater ph of 4 5 over simulation time show quantitatively how the oxidation may strongly influence the sulfate budget and acidity of volcanic cloud compared to observations model results are close in many aspects information on the near field volcanic plume behavior is essential for early preparedness and evacuation this approach demonstrates a potential improvement in quantitative predictions regarding the volcanic plume distribution at different altitudes it could be a useful tool for modeling volcanic plumes for better emergency measures planning

seafloor geomorphology of the sw barents sea and its glaci dynamic implications abstract three dimensional 3d reflection seismic imaging techniques provide a unique means of identifying large scale submarine geomorphic features produced by former ice sheets we have used such techniques to image the geomorphology of the sw barents sea but using a dense grid of 2d seismic covering a 240 000 2 km large study area supplemented with 3d seismic from selected areas the study area is located at the convergence of ice flow from the former fennoscandian barents sea and svalbard ice sheets the morphology of the major cross shelf troughs is characterized by elongated ridge groove features interpreted to be glacial bedforms produced by fast flowing grounded glaciers mega scale glacial lineations have been grouped into distinct flow sets related to three specific ice flow events these events document the last glacial maximum lgm and two readvances during deglaciation of specific interest is a detailed and well preserved set of seafloor imprints in the bjornoyrenna trough which acted as the main pathway for ice streams draining the surrounding ice sheets the geomorphic features indicate that bjornoyrenna hosted six separate ice stream lobes that diverged fan like at their margins but were not all active simultaneously an end moraine zone 68 km wide up to 85 m high and 300 km long filled the whole width of this major glacial trough as a result of high sediment flux within sub ice stream deformable beds the imprint of this ice stream system can be followed on our seabed images for 500 km however detailed geomorphologic elements demonstrate that these imprints reflect time transgressive behaviour and do not indicate the length or width of single ice streams the seismic derived seafloor geomorphology demonstrates that the barents sea ice behaved in a much more dynamic way during the last glaciation than previously assumed with major shifts between ice originating from the fennoscandian spitsbergen and barents sea ice sheets

the geochemical characteristics of the hydrate bound gases from the nyegga pockmark field norwegian sea the nyegga pockmark field located south east of the voring plateau norwegian sea was investigated on the uob cruises gs07 148 2007 and gs08 155 2008 remotely operated vehicle rov monitoring and successful recovery of gas hydrate give insights to the origin of the hydrocarbon gases in the complex pockmark feature named g11 isotope values of methane 13c ranging from 72 4 to 66 2 and d from 202 0 to 198 0 in the hydrate bound gas suggest that the methane is microbially produced and originates from co2 reduction it is proposed that the ethane from the gas hydrate has mixed thermogenic and microbial contributions which is supported by the fact that the gas hydrate also contains propane and isobutane the composition of the hydrate bound gas thus leads to small inclusions of structure ii sii in the hydrate while the major part is structure i si the isotope data and gas composition together with the geological setting suggest that the hydrate bound gas originated predominantly from a free gas system located beneath the gas hydrate stability zone and accumulated under glaciated debris formations the free gas system is mainly microbial methane from in situ production however a contribution of thermogenic gas from deeper polygonal faults to the free gas system seems evident from the composition of the gas the rov monitoring strengthens previous suggestions that the fauna in the complex pockmark g11 are supported by ongoing micro seepage

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

constraints on the dynamics of pockmarks in the sw barents sea evidence from gravity coring and high resolution shallow seismic profiles abstract newly acquired sediment cores and high resolution seismic lines were studied in order to constrain the timing and mechanism of pockmark formation in the loppa high area in the southwestern barents sea the evolution of the pockmarks after their formation was also investigated together with the possibility that they are currently active features the cores retrieved within the pockmarks lack a layer of ice rafted debris and an overlying sequence of laminated glaciomarine sediments that were deposited on the undisturbed seafloor at the inception of the bolling interstadial 15 cal kyr bp the pockmarks are suggested to have formed in that period probably due to climate change induced destabilisation of methane hydrates and the subsequent release of free gas the depressions deepened as a result of reduced sedimentation above active seeps the pockmark cores contain a series of gravel rich layers which are attributed to the winnowing of sediment during episodic fluid venting activity the seismic images reveal little disturbance of the most ancient sediments underneath the pockmarks indicating that the pockmark chimneys are localised features and were not imaged the holocene marine sediment cover in the pockmarks is thinner than on the surrounding seafloor indicating relatively low sedimentation rates inside the depressions the gas seepage may thus have been active until the recent past although no indications of present day methane flux were found

geotechnical condition of slopes at a proposed pipeline crossing great bear river valley northwest territories an in situ analysis of naturally occurring creep has been carried out in ice rich permafrost soils underlying a slope at the proposed canadian arctic gas pipeline crossing of great bear river in th

tracing the origin of thermogenic hydrocarbon signals in pockmarks from the southwestern barents sea abstract the glacially influenced southwestern barents sea is a promising area for petroleum exploration the present study area which is located in the loppa high region exhibits extensive pockmark fields covering an area of several square kilometers and containing thousands of pockmarks in high density to investigate whether the pockmark formation was driven by petroleum leakage to the surface acting thus as indicators for an active petroleum system gravity cores from selected pockmark and reference sites were investigated using an organic geochemical approach various biomarkers indicative of thermogenic hydrocarbons such as short chain n alkanes with a low carbon preference index alkylcyclohexanes hopanes steranes and diasteranes mixed with biomarkers representing immature organic matter were detected in the pockmark but also in reference cores outside of the pockmark and even from a non pockmark area the abundance and level of thermal maturity of the thermogenic hydrocarbons are comparable between the pockmark and reference sites additionally their distribution with depth is quite similar to those of the immature biomarkers these observations support the conclusion that the thermogenic hydrocarbon signal in the pockmarks is the result of reworked eroded mature material mixed with immature organic matter distributed across the entire area rather than the result of seepage events of thermogenic hydrocarbons through the pockmark system the data show that in the loppa high region the pure presence of petroleum derived hydrocarbons in pockmark areas cannot be used to indicate the presence or leakage of deeper petroleum systems

geochemistry of historical age silicic tephras in iceland the major element chemistry of nine silicic tephras of historical age from iceland is assessed as a key step in the development of the recent tephrochronology of the north atlantic region the tephras include the largest such layers produced by each of the five central volcanoes hekla o raefajokull eyjafjallajokull torfajokull and askja since the ninth century ad h 1104 o1362 e 1821 landnam tephra c 870 a 1875 and four other tephras h 1158 h 1510 h 1947 o1727 the determination of grain discrete major element chemistry of the glass fraction is a fundamental stage in the identification and correlation of tephra and allows links to be made between icelandic source areas with precise dating evidence and distal deposits elsewhere in the north atlantic region although major element data can be used to discriminate between tephra layers produced by the different central volcanoes on its own it cannot be used to identify all the holocene layers produc

high levels of particulate matter in iceland due to direct ash emissions by the eyjafjallajokull eruption and resuspension of deposited ash 1 the dangers to people living near a volcano due to lava and pyroclastic flows and on glacier or snow covered volcanoes jokulhlaups are well known the level of risk to human health due to high concentrations of ash from direct emission and resuspension from the ground is however not as well known the eruption at eyjafjallajokull 14 april to 20 may 2010 produced abundant particulate matter due to its explosive eruption style even after the volcanic activity ceased high particulate matter pm concentrations were still measured on several occasions due to resuspended ash the 24 hour mean concentration of pm10 in the small town of vik 38 km se of the volcano reached 1230 g m 3 which is about 25 times the health limit on 7 may 2010 with 10 min average values over 13 000 g m 3 even after the eruption ceased values as high as 8000 g m 3 10 min and 900 g m 3 24 h were measured because of resuspension of freshly deposited fine ash in reykjavik 125 km wnw of the volcano the pm10 concentration reached over 2000 g m 3 10 min during an ash storm on 4 june 2010 which should have warranted airport closure summarizing our study reveals the importance of ash resuspension compared to direct volcanic ash emissions this likely has implications for air quality but could also have detrimental effects on the quality of ash dispersion model predictions which so far generally do not include this secondary source of volcanic ash

reference data set of volcanic ash physicochemical and optical properties uncertainty in the physicochemical and optical properties of volcanic ash particles creates errors in the detection and modeling of volcanic ash clouds and in quantification of their potential impacts in this study we provide a dataset that describes the physicochemical and optical properties of a representative selection of volcanic ash samples from nine different volcanic eruptions covering a wide range of silica contents 50 80 wt sio2 we measured and calculated parameters describing the physical size distribution complex shape and dense rock equivalent mass density chemical bulk and surface composition and optical complex refractive index from ultra violet to near infrared wavelengths properties of the volcanic ash and classified the samples according to their sio2 and total alkali contents into the common igneous rock types basalt to rhyolite we found that the mass density ranges between 2 49 and 2 98 g cm3 for rhyolitic to basaltic ash types and that the particle shape varies with changing particle size d 100 m the complex refractive indices in the wavelength range between 300 nm and 1500 nm depends systematically on the composition of the samples the real part values vary from n 1 38 to 1 66 depending on ash type and wavelength and the imaginary part values from k 0 00027 to 0 00268 we place our results into the context of existing data and thus provide a comprehensive dataset that can be used for future and historic eruptions when only basic information about the magma type producing the ash is known

stratospheric volcanic ash emissions from the 13 february 2014 kelut eruption mount kelut indonesia erupted explosively around 15 50 ut on 13 february 2014 sending ash and gases into the stratosphere satellite ash retrievals and dispersion transport modeling are combined within an inversion framework to estimate the volcanic ash source term and to study ash transport the estimated source term suggests that most of the ash was injected to altitudes of 16 17 km in agreement with space based lidar data modeled ash concentrations along the flight track of a commercial aircraft that encountered the ash cloud indicate that it flew under the main ash cloud and encountered maximum ash concentrations of 9 3 mg m 3 mean concentrations of 2 1 mg m 3over a period of 10 11 min of the flight giving a dosage of 1 2 0 3 g s m 3 satellite data could not be used directly to observe the ash cloud encountered by the aircraft whereas inverse modeling revealed its presence

soluble iron inputs to the southern ocean through recent andesitic to rhyolitic volcanic ash eruptions from the patagonian andes patagonia due to its geographic position and the dominance of westerly winds is a key area that contributes to the supply of nutrients to the southern ocean both through mineral dust and through the periodic deposits of volcanic ash here we evaluate the characteristics of fe dissolved into soluble and colloidal species from volcanic ash for three recent southern andes volcanic eruptions having contrasting features and chemical compositions contact between cloud waters wet deposition and end members of andesitic hudson volcano and rhyolitic chaiten volcano materials was simulated results indicate higher fe release and faster liberation rates in the andesitic material fe release during particle seawater interaction dry deposition has higher rates in rhyolitic type ashes rhyolitic ashes under acidic conditions release fe in higher amounts and at a slower rate while in those samples containing mostly glass shards fe release was lower and faster the 2011 puyehue eruption was observed by a dust monitoring station puyehue type eruptions can contribute soluble fe to the ocean via dry or wet deposition nearly reaching the limit required for phytoplankton growth in contrast the input of fe after processing by an acidic eruption plume could raise the amount of dissolved fe in surface ocean waters several times above the threshold required to initiate phytoplankton blooms a single eruption like the puyehue one represents more than half of the yearly fe flux contributed by dust

ash mists and brown snow remobilization of volcanic ash from recent icelandic eruptions recent eruptions in iceland and chile have demonstrated that volcanic ash problems persist long after an eruption for this reason ash dispersion models are being extended to include ash remobilization critical to these models is knowledge of the ash source and the particle sizes that can be mobilized under different wind and moisture conditions here we characterize the physical and chemical characteristics of ash deposited on new snow in reykjavik iceland following a blizzard on 6 march 2013 morphological textural and compositional analyses indicate resuspension from multiple eruptive deposits including both grimsvotn 2011 and eyjafjallajokull 2010 eruptions grain size measurements show a mode of 32 63 m with particles as large as 177 m there is little mass in the very fine fraction 10 m pm10 we compare our observations to predictions using the lagrangian particle dispersion model name uk met office the model output is consistent with observations in that it forecasts resuspension from both eyjafjallajokull and grimsvotn source regions and shows ash deposition coincident with the timing of observed deposition in reykjavik the modeled deposit in reykjavik predicts however a substantially lower proportion of grimsvotn ash than observed this discrepancy has highlighted the need to reassess the assumptions used in the simulations particularly regarding the source area and precipitation thresholds furthermore we suggest that modification of ash deposits in the form of erosion redeposition compaction or cementation may influence the dynamics of resuspension over time thus influencing the ability of model simulations to accurately forecast remobilization events

sedimentation of long lasting wind affected volcanic plumes the example of the 2011 rhyolitic cordon caulle eruption chile sedimentation processes and fragmentation mechanisms during explosive volcanic eruptions can be constrained based on detailed analysis of grain size variations of tephra deposits with distance from vent and total grain size distribution tgsd grain size studies strongly rely on deposit exposure and in case of long lasting eruptions can be complicated by the intricate interplay between eruptive style atmospheric conditions particle accumulation and deposit erosion the 2011 cordon caulle eruption chile represents an ideals laboratory for the study of long lasting eruptions thanks to the good deposit accessibility in medial to distal area all layers analyzed are mostly characterized by bimodal grain size distributions with both the modes and the fraction of the coarse subpopulation decreasing rapidly with distance from vent and those of the fine subpopulation being mostly stable due to gradually changing wind direction the two subpopulations characterizing the deposit of the first 2 days of the eruption are asymmetrically distributed with respect to the dispersal axis the tgsd of the climactic phase is also bimodal with the coarse subpopulation representing 90 wt of the whole distribution polymodality of individual samples is related to size selective sedimentation processes while polymodality of the tgsd is mostly related to the complex internal texture e g size and shape of vesicles of the most abundant juvenile clasts the most representative tgsd could be derived based on a combination of the voronoi tessellation with a detailed analysis of the thinning trend of individual size categories finally preferential breakage of coarse pumices on ground impact was inferred from the study of particle terminal velocity

resuspension of ash after the 2014 phreatic eruption at ontake volcano japan abstract we determined the resuspension process of an ash deposit after the phreatic eruption of september 27th 2014 at ontake volcano japan by analyzing the time series data of particle concentrations obtained using an optical particle counter and the characteristics of an ash sample the time series of particle concentration was obtained by an optical particle counter installed 11 km from the volcano from september 21st to october 19th 2014 the time series contains counts of dust particles ash and soil pollen and water drops and was corrected to calculate the concentration of dust particles based on a polarization factor reflecting the optical anisotropy of particles the dust concentration was compared with the time series of wind velocity the dust concentration was high and the correlation coefficient with wind velocity was positive from september 28th to october 2nd grain size analysis of an ash sample confirmed that the ash deposit contains abundant very fine particles

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

sources of uncertainty in the mazama isopachs and the implications for interpreting distal tephra deposits from large magnitude eruptions estimating the area of tephra fallout and volume of large magnitude eruptions is fundamental to interpretations of the hazards posed by eruptions of this scale this study uses the tephra from the caldera forming eruption of mount mazama crater lake or usa to demonstrate the challenges faced when working with large prehistoric tephra deposits and outlines the methodologies required to determine eruption volume and magnitude we combine 250 mazama tephra occurrences reported by a range of disciplines including archaeology paleoclimatology and volcanology with new field studies to better understand the extent of the distal tephra we find that the mazama tephra has been remobilised to varying degrees over the past 7000 years so each tephra locality was appraised for the likelihood that it records primary tephra fallout we designated 45 of the distal 100 km from source tephra sites as suitable for use in the production of isopachs using a spline fitting method the new distal isopachs were then integrated with proximal fallout data and estimates of the ignimbrite volume from previous studies to revise the estimated bulk erupted volume from the climactic mazama eruption to 176 km3 61 km3 dense rock equivalent dre this study demonstrates the importance of collating tephra localities from a range of disciplines and that even remobilised deposits provide valuable information about the extent of the deposit interpreting remobilised deposits can provide insight into post eruptive processes that could potentially pose secondary hazards following large magnitude eruptions we also show that in some circumstances remobilised deposits preserve important physical properties such as grain size

sediment mapping and long term monitoring of currents and sediment fluxes in pockmarks in the oslofjord norway abstract pockmarks in the oslofjord norway show no evidence of recent expulsion of gas or water but have still experienced reduced sedimentation rates through the holocene they are therefore suitable model systems for studying the currents and sedimentation in pockmarks mapping of sediment in a single pockmark using a large number of precisely positioned cores shows thickening of an unconsolidated almost flocculent layer inside the pockmark x ray fluorescence logging of anthropogenic metals indicates higher sedimentation rates and mass accumulation rates inside the pockmark with respect to the surrounding seafloor furthermore the cores taken near the pockmark centre contained relatively coarser material than those from outside the depression sediment traps collected substantially more sediments inside than outside of the pockmark when positioned close to the seafloor this agrees with resuspension of sediments from the seafloor being enhanced inside the pockmark moreover the traps deployed in the pockmark intercepted relatively coarser sediments acoustic backscatter near the seabed varies in a diurnal cycle not related to the tide this is interpreted as a probable result of vertical migration of zooplankton or fish inside the pockmark there is also a diurnal cycle in current velocity with high values in the daytime possibly because of swimming fish the data indicate that pockmarks collect particles which may be largely due to deposition of sediments transported as bedload this process should be dominant for pockmarks found in proximity to fluvial coarse grained sediment input the suspended fine material however is kept in suspension by turbulence and possibly biological activity and can be transported away before settling whether an inactive pockmark will behave as a sediment depocentre or will be maintained by the action of currents is likely to depend on the relative importance of bedload versus suspended load transport

gas hydrate stability zone modelling in areas of salt tectonics and pockmarks of the barents sea suggests an active hydrocarbon venting system the barents sea seabed exhibits an area of major glacial erosion exposing parts of the old hydrocarbon basins in this region we modelled the gas hydrate stability field in a 3d perspective including the effects of higher order hydrocarbon gases we used 3d seismic data to analyse the linkage between fluid flow expressions and hydrate occurrences above old sedimentary basin systems and vertical faults pockmarks showed a relation to fault systems where some of them are directly connected to hydrocarbon bearing sedimentary formations the influence of bottom water temperature pore water salinity and geothermal gradient variation on gas hydrate stability zone ghsz thickness is critically analysed in relation to both geological formations and salt tectonics our analysis suggests a highly variable ghsz in the barents sea region controlled by local variations in the parameters of stability conditions recovery of gas hydrate sample from the region and presence of gas enhanced reflections below estimated bsr depths may indicate a prevalent gas hydrate stable condition

intrusion triggering of the 2010 eyjafjallajokull explosive eruption the ash cloud that brought chaos to european air traffic in april this year was the result of emissions from an icelandic volcano that had been intermittently active for about 18 years a combination of detailed space based geodetic measurements and seismic monitoring of the eyjafjallajkull volcano in the run up to the ash producing explosive summit eruption reveals an unusual deformation pattern that may be attributed to its off rift setting with relatively cool subsurface structure and limited magma at shallow depth as to the predictability of such a dramatic reawakening the immediate precursors to the initial eruption of the volcano in 2010 were subtle and difficult to detect but the clear signs of volcanic unrest during the weeks months and years preceding it may provide better clues to the catastrophic explosion

ash resuspension related to the 2011 2012 cordon caulle eruption chile in a rural community of patagonia argentina abstract the 2011 2012 cordon caulle eruption emitted about 1 km3 of rhyodacitic tephra dominant westerly winds in the region caused most of the primary tephra to deposit in neighboring argentina in addition to the impact of widespread dispersal and fallout of primary tephra during the eruption argentina was also significantly affected by remobilization of the primary ash even several years after the climactic phase of the eruption in this mixed methods study we combine aspects of natural and social sciences to characterize the ash resuspension events associated with the 2011 2012 cordon caulle deposits and assess the impacts on the argentinian farming community of ingeniero jacobacci in the patagonian steppe our findings show the primary importance of wind rainfall and ash availability in controlling the occurrence and persistence of ash resuspension events the role played by these variables was also reflected in the seasonal distribution of events observed regarding the impacts our results complement those of earlier studies and demonstrate that ash resuspension events can exacerbate the negative impact of primary tephra fallout events from the time of deposition to many years after the eruption only after five years has the environment and the farming community begun to show signs of recovery our findings also highlight the importance of assessing ash resuspension events in multi hazard scenarios involving volcanic and hydrometeorologic hazards

characterization of microbial activity in pockmark fields of the sw barents sea abstract multibeam bathymetry revealed the occurrence of numerous craterlike depressions so called pockmarks on the sea floor of the hammerfest basin and the loppa high south western barents sea to investigate whether these pockmarks are related to ongoing gas seepage microbial processes associated with methane metabolism were analyzed using geochemical biogeochemical and microbiological techniques gravity cores were collected along transects crossing individual pockmarks allowing a direct comparison between different locations inside assumed activity center on the rim and outside of a pockmark reference sites concentrations of hydrocarbons in the sediment particularly methane were measured as headspace free gas and in the occluded and adsorbed gas fraction down to a depth of 2 6 m below sea floor mbsf sulfate reduction rates were quantified by radiotracer incubations concentrations of dissolved sulfate in the porewater were determined as well neither the sulfate profiles nor the gas measurements show any evidence of microbial activity or active fluid venting methane concentrations and sulfate reduction rates were extremely low or even below the detection limit the results show that the observed sediment structures are most likely paleo pockmarks their formation probably occurred during the last deglaciation

the respiratory health hazards of volcanic ash a review for volcanic risk mitigation studies of the respiratory health effects of different types of volcanic ash have been undertaken only in the last 40 years and mostly since the eruption of mt st helens in 1980 this review of all published clinical epidemiological and toxicological studies and other work known to the authors up to and including 2005 highlights the sparseness of studies on acute health effects after eruptions and the complexity of evaluating the long term health risk silicosis non specific pneumoconiosis and chronic obstructive pulmonary disease in populations from prolonged exposure to ash due to persistent eruptive activity the acute and chronic health effects of volcanic ash depend upon particle size particularly the proportion of respirable sized material mineralogical composition including the crystalline silica content and the physico chemical properties of the surfaces of the ash particles all of which vary between volcanoes and even eruptions of the same volcano but adequate information on these key characteristics is not reported for most eruptions the incidence of acute respiratory symptoms e g asthma bronchitis varies greatly after ashfalls from very few if any reported cases to population outbreaks of asthma the studies are inadequate for excluding increases in acute respiratory mortality after eruptions individuals with pre existing lung disease including asthma can be at increased risk of their symptoms being exacerbated after falls of fine ash a comprehensive risk assessment including toxicological studies to determine the long term risk of silicosis from chronic exposure to volcanic ash has been undertaken only in the eruptions of mt st helens 1980 usa and soufriere hills montserrat 1995 onwards in the soufriere hills eruption a long term silicosis hazard has been identified and sufficient exposure and toxicological information obtained to make a probabilistic risk assessment for the development of silicosis in outdoor workers and the general population a more systematic approach to multi disciplinary studies in future eruptions is recommended including establishing an archive of ash samples and a website containing health advice for the public together with scientific and medical study guidelines for volcanologists and health care workers

investigation of the complex dynamics and structure of the 2010 eyjafjallajokull volcanic ash cloud using multispectral images and numerical simulations 1 we investigated the structure and evolution of the 2010 eyjafjallajokull volcanic cloud and its dispersal over iceland and europe integrating satellite multispectral images and numerical simulations data acquired by medium resolution imaging spectrometer meris and advanced spaceborne thermal emission and reflection radiometer aster have been analyzed to quantify the cloud extent and composition the vol calpuff dispersal code was applied to reconstruct the transient and 3 d evolution of the cloud source parameters estimated on the base of available a posteriori volcanological data sets have been used quantitative comparisons between satellite retrievals and modeling results were performed for two selected instants of time during the first and third eruptive phases on a regional scale sensitivity of the model to initial volcanological conditions has been analyzed at continental scale several complex non intuitive features of cloud dynamics have been highlighted and strengths and limitations of the adopted methods identified the main findings are the level of quantitative agreement between satellite observations and numerical results depends on ash cloud composition particle sizes and concentration with better agreement for smaller particles and higher concentrations the agreement between observations and modeling outcomes also depends on the temporal stability of volcanological conditions and the complexity of the meteorological wind field the irregular dispersion of ash as reconstructed from satellite data and numerical modeling can be well explained by the different response of particle sizes to strong vertical wind shear and by resuspension processes acting at ground level eruptive source conditions are the main source of uncertainty in modeling especially during an ongoing crisis and at long range scales