the anaerobic oxidation of methane and sulfate reduction in sediments from gulf of mexico cold seeps we determined the geochemical characteristics of sediments and measured rates of the anaerobic oxidation of methane aom and sulfate reduction sr in samples collected near thermogenic structure ii gas hydrate mounds and in areas lacking hydrates along the continental slope in the gulf of mexico we used radiotracer c 14 and s 35 techniques to determine rates of aom and sr over depth in sediment cores abundant mats of white and orange beggiatoa spp were common in areas of active seepage and these sediments were enriched in hydrogen sulfide and methane in cores collected from areas without beggiatoa or hydrate concentrations of redox metabolites showed little variation over depth and these sites were inferred to be areas of low seepage integrated aom rates were low in beggiatoa free cores 0 05 mmol m 2 day 1 and averaged 2 8 4 6 mmol m 2 day 1 in seep cores that contained beggiatoa or gas hydrate integrated sr rates were also low in beggiatoa free cores 1 mmol m 2 day 1 and averaged 54 94 mmol m 2 day 1 in cores with beggiatoa or hydrate rates of sr generally exceeded rates of aom and the two processes were loosely coupled suggesting that the majority of sr at gulf of mexico hydrocarbon seep sites is likely fueled by the oxidation of other organic matter possibly other hydrocarbons and oil rather than by aom

modis and aster synergy for characterizing thermal volcanic activity abstract volcanic activity is diverse in its manifestations and spans wide temporal and spatial scales monitoring volcanoes with any single sensor system can only provide a limited perspective on the nature of such activity because of trade offs between spatial temporal and spectral resolution spaceborne observations of volcanoes are thus optimized by utilizing data from different and complementary remote sensing instruments this study examines the combined use of the moderate resolution imaging spectroradiometer modis and the advanced spaceborne thermal emission and reflection radiometer aster for analyzing thermal anomalies from four separate volcanoes erta ale ethiopia k lauea hawai i lascar chile and kliuchevskoi russia modis provides a high temporal resolution daily but low spatial resolution 1 km dataset and is used to measure volcanic thermal radiance aster provides relatively high spatial resolution 90 m image data and is used to define the size of thermal features albeit at a poorer temporal frequency erta ale and k lauea have been erupting continuously over the 11 year study period and their thermal emission signatures reveal a persistent baseline on which occasional increases in thermal output associated with more profuse effusions of lava are superimposed kliuchevskoi also displays occasional peaks in thermal activity due to the eruption of lava however intervening periods are characterized by weak or absent thermal anomalies lascar on the other hand provides an example of volcanic activity that is difficult for modis type sensors to detect it is characterized by fumarolic activity that is too low in temperature and too spatially limited to be readily detectable with its coarser instantaneous field of view i e pixel size however high resolution data from aster can be used to supplement and complement the modis dataset beyond characterizing the size of thermal anomalies aster can also provide constraints on their shape location and orientation and is capable of detecting relatively subtle thermal anomalies given its high spatial resolution thermal infrared wavebands these qualities permitted the identification of a thermal precursor to lava flows at kliuchevskoi the precursor which was associated with a rising lava lake is characterized as an increase in the size and intensity of aster detected thermal anomalies situated in the active crater wavelet analysis of the modis dataset was also carried out this revealed the time scales over which radiant output waxed and waned during individual eruptive episodes as well as the repose time between episodes such information might be useful in forecasting the likely duration and onset of future eruptions

the volcanic signal in surface temperature observations abstract climate records of the past 140 years are examined for the impact of major volcanic eruptions on surface temperature after the low frequency variations and el nino southern oscillation signal are removed it is shown that for 2 years following great volcanic eruptions the surface cools significantly by 0 1 0 2 c in the global mean in each hemisphere and in the summer in the latitude bands 0 30 s and 0 30 n and by 0 3 c in the summer in the latitude band 30 30 60 n by contrast in the first winter after major tropical eruptions and in the second winter after major high latitude eruptions north america and eurasia warm by several degrees while northern africa and southwestern asia cool by more than 0 5 c because several large eruptions occurred at the same time as enso events the warming produced by the enso masked the volcanic cooling during the first year after the eruption the timescale of the enso response is only 1 year while the volcanic response timescale is 2 years so the coo

evidence of episodic fluid gas and sediment venting on the northern gulf of mexico continental slope surficial sediments and sea floor features of the northern gulf of mexico continental slope record dramatic episodic venting and slower seepage of formation fluids brines crude oil gases and fine grained sediments faults activated by massive sediment input during periods of plio pleistocene falling to low sea levels accompanied by compensating salt movement provide avenues of vertical transport to the continental slope surface many of these faults cut thick sedimentary sequences that frequently contain geopressured zones which provide the driving force for fluid and gas expulsion flux rate and fluid characteristics are interpreted as important determinants of modern sea floor geology and biology qualitatively under conditions of rapid flux of sediment rich fluids mud volcanoes up to 1 km wide and 50 m high and extensive sheets of extruded mud result these sediments contain old and displaced microfaunas muds are frequently extruded with large volumes of crude oil and gas both biogenic and thermogenic in water depths greater than approximately 500 m rapid to moderate vertical flux of hydrocarbon gases and fluids results in the construction of relief features composed of gas hydrates ejected mud and authigenic carbonates areas with near surface hydrates frequently support complex chemosynthetic communities with associated hardgrounds containing calcareous remains of mussels clams and associated gastropods slow flux seeps promotes the formation of 13 c depleted carbonate hardgrounds stacked carbonate slabs and moundlike carbonate buildups frequently 20 m relief barite along with carbonate has been found in areas where rapid flux of sediment carrying fluids has waned in the recent past and mineral rich brines are now being ejected crests chimneys and cones of these minerals are found in such settings both recent numerical simulations of fluid release from geopressured zones and direct observations at the sea floor support a pattern of episodic venting short term episodes of venting are probably regulated by fault movement perhaps controlled by local salt adjustment destabilization of gas hydrates by oceanographic processes also causes short term episodic gas expulsion these events occur with interannual to intra annual frequencies longer gas hydrate stabilization destabilization cycles in continental margin settings are forced by hydrostatic loading and unloading at the frequency of sea level change radiometric dating suggests that other long term episodes of venting and major venting expulsion events are also probably modulated by sea level change time scales of thousands of years in response to low stand sedimentary loading results of this summary of vent seep related phenomena suggest that sediment input from the shelf margin associated with cyclic plio pleistocene falling to low sea level periods followed by major listic fault and salt adjustments to a new sediment load have activated venting seepage throughout this period and perhaps longer

anaerobic oxidation of methane and sulfate reduction along the chilean continental margin anaerobic oxidation of methane aom and sulfate reduction sr were investigated in sediments of the chilean upwelling region at three stations between 800 and 3000 m water depth major goals of this study were to quantify and evaluate rates of aom and sr in a coastal marine upwelling system with high organic input to analyze the impact of aom on the methane budget and to determine the contribution of aom to sr within the sulfate methane transition zone smt furthermore we investigated the formation of authigenic carbonates correlated with aom we determined the vertical distribution of aom and sr activity methane sulfate sulfide ph total chlorins and a variety of other geochemical parameters depth integrated rates of aom within the smt were between 7 and 1124 mmol m 2 a 1 effectively removing methane below the sediment water interface single measurements revealed aom peaks of 2 to 51 nmol cm 3 d 1 with highest rates at the shallowest station 800 m the methane turnover was higher than in other diffusive systems of similar ocean depth this higher turnover was most likely due to elevated organic matter input in this upwelling region offering significant amounts of substrates for methanogenesis sr within the smt was mostly fuelled by methane aom led to the formation of isotopically light dic 13c 24 6 vpdb and of distinct layers of authigenic carbonates 13c 14 6 vpdb

three dimensional volcanic aerosol dispersal a comparison between multiangle imaging spectroradiometer misr data and numerical simulations 1 the three dimensional reconstruction of volcanic plumes is a central goal to enhance our understanding on dispersal processes in this paper we use data from the multiangle imaging spectroradiometer misr on board nasa s terra spacecraft combined with a stereo matching retrieval procedure we show the potential of misr in capturing important features of volcanic plumes like column height optical depth type and shape of the finest particles of two highly explosive eruptions occurring on mount etna in 2001 and 2002 this work tests how tephra dispersal models reconstruct the 3 d shape of volcanic clouds we compare misr data with fall3d an eulerian model for the transport and deposition of volcanic ash and aerosols coupled with the weather research and forecasting mesoscale meteorological model agreement between simulations and misr data is good regarding both events although it could be improved by increasing the accuracy of the meteorological data a better constraint on volcanological input parameters like the height of the eruptive column and improving our understanding of processes such as aggregation phenomena and volcanic cloud microphysics

pockmark formation and evolution in deep water nigeria rapid hydrate growth versus slow hydrate dissolution in previous works it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water nigeria it was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics new results obtained by drilling into gas hydrate bearing sediments with the mebo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indicate that pockmark formation and evolution in the study area are mainly controlled by rapid hydrate growth opposed to slow hydrate dissolution on one hand positive temperature anomalies free gas trapped in shallow microfractures near the seafloor and coexistence of free gas and gas hydrate indicate rapid hydrate growth on the other hand slow hydrate dissolution is evident by low methane concentrations and almost constant sulfate values 2 m above the gas hydrate occurrence zone

the 2005 eruption of kliuchevskoi volcano chronology and processes derived from aster spaceborne and field based data abstract kliuchevskoi volcano located on the kamchatka peninsula of eastern russia is one of the largest and most active volcanoes in the world its location and diversity of eruption styles make satellite based monitoring and characterization of its eruptive activity essential in 2005 the kamchatka volcano emergency response team kvert first reported that seismic activity of kliuchevskoi increased above background levels on 12 january kamchatka volcanic eruption response team kvert report 2005 kliuchevskoi volcano 14 january through 13 may 2005 http www avo alaska edu activity avoreport php view kam info id month january year 2005 cited january 2007 by 15 january kliuchevskoi entered an explosive effusive phase which lasted for five months and produced basaltic lava flows lahar deposits and phreatic explosions along its northwestern flank we present a comparison between field observations and multispectral satellite image data acquired by the advanced spaceborne thermal emission and reflection radiometer aster instrument in order to characterize the eruptive behavior the aster instrument was targeted in an automated urgent request mode throughout the eruption timeline in order to collect data at the highest observation frequency possible brightness temperatures were calculated in all three aster wavelength regions during lava flow emplacement the maximum lava flow brightness temperatures calculated from the 15 m pixel visible near infrared vnir data were in excess of 800 c the shortwave infrared swir data were radiometrically and geometrically corrected normalized to the same gain settings and used to estimate an eruptive volume of 2 35 10 2 km 3 at the summit these data were also used to better constrain errors arising in the thermal infrared tir data due to sub pixel thermal heterogeneities based on all the aster data the eruption was separated into three phases an initial explosive phase 20 january 31 january an explosive effusive phase 1 february 8 march and a subsequent cooling phase decorrelation stretch dcs images of the tir data also suggested the presence of silicate ash so 2 and water vapor plumes that extended up to 300 km from the summit the aster rapid response program provided important multispectral moderate spatial resolution information that was used to detect and monitor the eruptive activity of this remote volcano which can be applied to other eruptions worldwide

time integrated variation of sources of fluids and seepage dynamics archived in authigenic carbonates from gulf of mexico gas hydrate seafloor observatory article i nfo authigenic carbonate rocks recovered from the gulf of mexico gas hydrate seafloor observatory in mississippi canyon block 118 mc118 at approximately 900 m water depth were studied using mineralogical bulk geochemical and lipid biomarker analyses carbonate rocks occurred as fractured blocks and nodular masses incorporated in carbonate breccias the carbonates were comprised mainly of high mg calcite and aragonite the stable carbon isotope composition

control of sulfate pore water profiles by sedimentary events and the significance of anaerobic oxidation of methane for the burial of sulfur in marine sediments abstract gravity driven mass flow deposits proven by sedimentary and digital echosounder data are indicative for prevailing dynamic sedimentary conditions along the continental margin of the western argentine basin in this study we present geochemical data from a total of 23 gravity cores pore water so 4 is generally depleted within a few meters below the sediment surface by anaerobic oxidation of methane aom the different shapes of so 4 profiles concave kink and s type can be consistently explained by sedimentary slides possibly in combination with changes in the ch 4 flux from below thus mostly representing transient pore water conditions since slides may keep their original sedimentary signature a combined analysis and numerical modeling of geochemical physical properties and hydro acoustic data could be applied in order to reconstruct the sedimentary history we present first order estimates of the dating of sedimentary events for an area where conventional stratigraphic methods failed to this day the results of the investigated sites suggest that present day conditions are the result of events that occurred decades to thousands of years ago and promote a persisting mass transport from the shelf into the deep sea depositing high amounts of reactive compounds the high abundance of reactive iron phases in this region maintains low hydrogen sulfide levels in the sediments by a nearly quantitative precipitation of all reduced sulfate by aom for the total region we estimate a so 4 or ch 4 flux of 6 6 10 10 moles per year into the zone of aom projected to the global continental slope and rise area this may sum up to about 2 6 10 12 moles per year provided that the sulfur is completely fixed in the sediments it is about twice the global value of the recent global sulfur burial in marine sediments of 1 2 10 12 moles per year as previously estimated thus aom obviously contributes very significantly to the regulation of global sulfur reservoirs which is hitherto not sufficiently recognized this finding may have implications for global geochemical models as sulfur burial is an important control factor in the development of atmospheric oxygen levels over time

using picosatellites for 4 d imaging of volcanic clouds proof of concept using iss photography of the 2009 sarychev peak eruption abstract volcanic ash clouds can present an aviation hazard over distances of thousands of kilometres and to help to mitigate this hazard advanced numerical models are used to forecast ash dispersion in the atmosphere however forecast accuracy is usually limited by uncertainties in initial conditions such as the eruption rate and the vertical distribution of ash injected above the volcano here we demonstrate the potential of the telematics earth observation mission tom picosatellite formation due for launch in 2020 to provide valuable information for constraining ash cloud dispersion models through simultaneous image acquisition from three satellites tom will carry commercial frame cameras using photogrammetric simulations we show that such data should enable ash cloud heights to be determined with a precision 30 140 m depending on configuration comparable to the vertical resolution of lidar observations 30 180 m depending on the cloud height to support these estimates we processed photographs taken from the international space station of the 2009 sarychev peak eruption as a proxy for tom imagery structure from motion photogrammetric software successfully reconstructed the 3 d form of the ascending ash cloud as well as surrounding cloud layers direct estimates of the precision of the ash cloud height measurements as well as comparisons between independently processed image sets indicate that a vertical measurement precision of 200 m was achieved image sets acquired at different times captured the plume dynamics and enabled a mean ascent velocity of 14 m s 1 to be estimated for regions above 7 km in contrast the uppermost regions of the column at a measured cloud top height of 11 km were not ascending significantly enabling us to constrain a 1 d plume ascent model from which estimates for the vent size 50 m and eruption mass flux 2 6 106 kg s 1 could be made thus we demonstrate that nanosatellite imagery has the potential for substantially reducing uncertainties in ash dispersion models by providing valuable information on eruptive conditions

chemosynthetic mussels at a brine filled pockmark in the northern gulf of mexico a large 540 square meters bed of bathymodiolus n sp mytilidae bivalvia rings a pool of hypersaline 121 35 practical salinity units brine at a water depth of 650 meters on the continental slope south of louisiana the anoxic brine dissolved oxygen 0 17 milliliters per liter contains high concentrations of methane which nourishes methanotrophic symbionts in the mussels the brine which originates from a salt cored diapir that penetrates to within 500 meters ofthe sea floor fills a depression that was evidently excavated by escaping gas the spatial continuity of the mussel bed indicates that the brine level has remained fairly constant however demographic differences between the inner and outer parts of the bed record small fluctuations

dynamic fluid flow and chemical fluxes associated with a seafloor gas hydrate deposit on the northern gulf of mexico slope abstract gas hydrates outcrop on the seafloor at the bush hill hydrocarbon seep site in the northern gulf of mexico four newly designed fluid flux meters chemical samplers called the mosquito were deployed for 430 days at bush hill to determine how dynamic subsurface fluid flow influences gas hydrate stability and to quantify the associated methane fluxes into the ocean three of the flux meters were deployed adjacent to an outcropping gas hydrate mound while the fourth monitored background conditions the flux meter measurements reveal that the subsurface hydrology in the vicinity of the mound is complex and variable with frequent changes from downward to upward flow ranging from 161 to 273 cm yr and with temporal variations in the horizontal component of flow the continuous record of fluid chemistry indicates that gas hydrate actively formed in the sediments we propose that long periods of downward flow of seawater adjacent to gas vents up to 4 months are driven by local sub pressure resulting from gas ebullition through faults and fractures due to overpressure at depth high frequency variations in flow rates days to weeks are likely due to temporal changes in sediment permeability and the 3 d fluid flow field as a result of active gas hydrate and authigenic carbonate precipitation as well as the presence of free gas gas hydrate formation occurred as a result of long term emanation of ch 4 at focused gas vents followed by a more diffuse intergranular methane flux the estimated ch 4 flux to the water column from focused gas vents across the bush hill seep is 5 10 6 mol yr this significant flux suggests that bush hill and similar hydrocarbon seeps in the northwestern gulf of mexico may be important natural sources of methane to the ocean and possibly the atmosphere

satellite thermal observations of the bezymianny lava dome 1993 2008 precursory activity large explosions and dome growth 1 fifteen years worth of advanced very high resolution radiometer avhrr data is presented and used to quantitatively assess processes occurring at bezymianny this andesitic volcano is one of kamchatka s most dangerous volcanoes with 16 eruptions in the last decade that have dispersed ash into north pacific air routes all known episodes of increased activity for which data were available were detected in band 3 3 53 3 93 m avhrr thermal data twenty three peaks can be seen in the data nineteen peaks correspond to known explosions while the remaining three peaks correspond to known phases of dome growth that were not believed to have been accompanied by explosive activity start and end dates of extrusive phases defined by the thermal data are presented repose times between phases of extrusion vary from four months to just over two and half years with an average of just less than a year using rank order statistics a maximum time interval between consecutive explosions of 1288 170 days is determined this could serve as a cut off time for declaring the current dome growth activity over the calculated cumulative erupted volume 0 28 km3 and time averaged extrusion rate 0 6 m3 s 1 from 1993 to 2008 corresponds to values found at bezymianny from 1956 to 1976 showing that the satellite based methodology provides a good way of quantitatively assessing dome growth three different types of precursors to explosive behavior have been identified at bezymianny 1 values that cluster around the mode of the data set prior to explosion potentially due to endogenous dome growth 2 upward trends that commence 15 20 days prior to explosion and reach sensor saturation levels are due to significant extrusion and 3 a gradual upward trend that starts 5 days prior to explosion probably due to ramping up of extrusion this work shows that retrospectively analyzing and modeling of a volcano s thermal signal provides increased insight into its characteristic behavior the methods used in this paper can be used at other dome building volcanoes around the world the insights presented here can be used to improve monitoring capabilities to aid in providing early warnings to large explosions at bezymianny

hydrocarbon gas hydrates in sediments of the mississippi canyon area northern gulf of mexico the gulf of mexico hydrates research consortium has begun installing a seafloor observatory to monitor gas hydrate outcrops and the hydrate stability zone in mississippi canyon area lease block 118 relevant background information concerning the mississippi canyon area and gas hydrate occurrences in the northern gulf of mexico is presented microbial influences and possible scenarios of hydrate accumulation are considered the design of the observatory was based on field data recorded in the mississippi canyon area principally lease block 118 mc118 and the vicinity of lease block 798 mc798 swath bathymetry by autonomous underwater vehicle played a large part as did seismic imaging within the hydrate stability zone and core sampling these data and the results of their analyses are discussed in detail discussion and interim conclusions are presented in an effort to expand the information base on how natural gas hydrates form in sediments and how they affect seafloor stability the university of mississippi organized the gulf of mexico hydrates research consortium in 1999 its principal goal is to develop and install a seafloor observatory capable of monitoring a hydrate outcrop and its environment more or less continuously for a period of 5 10 years in 2006 the consortium included researchers from more than 30 universities and corporations a board of scientific advisers oversees project management site selection geochemical aspects microbial aspects seismoacoustic aspects data quality control and data archiving a summary of project history an overview of observatory design and a list of organizations that participate in the scientific board is given by mcgee 2006 a number of possible sites for the observatory were considered by the site selection committee data presented here were collected in the vicinity of two sites of known hydrate occurrence in the mississippi canyon area sites lease block 118 mc118 and lease block 798 mc798 a lease block in the northern gulf of mexico comprises a square of sides 3 statute miles 5 km consortium members voted in october 2004 to select a prominent seafloor mound located in mc118 as the observatory site the minerals management service mms of the us department of interior reserved the vicinity of the mound exclusively for consortium activities pre installation studies began in january 2005 and the first monitoring components were installed during may of the same year additional components were scheduled for deployment during the following september but the aftermath of hurricane katrina forced a delay until june 2006 in addition to information on regional contexts this contribution includes early results and tentative conclusions produced by consortium activities prior to the resumption of the installation quaternary geology of the mississippi

characterization and interpretation of volcanic activity at karymsky volcano kamchatka russia using observations of infrasound volcanic emissions and thermal imagery 2 a multiparameter data set including measurements of infrasound volcanic emissions and thermal imagery is used to characterize and interpret diverse volcanic activity observed during field campaigns in august 2011 and july 2012 at karymsky volcano kamchatka russia four activity types are visually identified and characterized according to so2 emission rate ash mass event duration peak temperature thermal radiation energy infrasound onset and frequency reduced infrasonic pressure and acoustic energy these activity types include 1 ash explosions 2 pulsatory degassing 3 gas jetting and 4 explosive eruption unique infrasound signals are associated with all four activity types suggesting that infrasound can be used to help remotely and continuously detect and characterize volcanic activity at karymsky and other similar volcanoes our observations suggest that so2 is emitted continuously though in varying abundance while ash is emitted discontinuously and is only associated with certain types of activity our data set supports previous models that attribute variations in surface activity to changes in conduit permeability at karymsky volcano evidence for a decrease in conduit permeability as a trigger for ash explosions and explosive eruption activity types is supported by weakened but still detectable so2 emission rates prior to eruption along with the highly impulsive infrasonic onset and large reduced infrasound pressure indicating high pressure at the vent we speculate that changes in conduit permeability at karymsky volcano result from changes in magma supply from the shallow crustal storage region though additional measurements are required to validate this hypothesis

a natural hydrate dissolution experiment on complex multi component hydrates on the sea floor abstract dissolution of natural hydrate cores was measured using time lapse photography on the seafloor at barkley canyon 850 m depth and 4 17 c two types of hydrate fabrics in close contact with one another were studied a yellow hydrate stained with condensate oil and a white hydrate from thermogenic origins both fabrics contained methane as well as heavier hydrocarbons these multi component hydrates were calculated to be well within p t stability conditions 2 s while the white hydrate dissolved faster at 0 25 0 02 mmol gas m 2 s to determine the controlling mechanism for the observed changes in the hydrate cores experimental results were compared with an engineering correlation for convective mass transfer using water velocity as a fitting parameter the correlation agreed well with results from a previous dissolution experiment on well characterized synthetic hydrates even with a number of other unknowns when applied to the natural hydrate the mass transfer correlation predicted the dissolution rate within 20 this seafloor based experiment along with visual observations of seafloor hydrate dissolution over a 3 day period were used to further understand the fate of natural seafloor hydrates exposed on the seafloor by showing that mass transfer is the rate controlling mechanism for dissolution of these natural hydrate outcrops proper hydrodynamic calculations can be employed to give a refined estimate on hydrate dissolution rates

a method for estimating edge length from flake dimensions use and implications for technological change in the southern african msa abstract this paper presents a method for estimating edge length from flake dimensions comparison of estimated values with data from measured flake edges demonstrates the robusticity of the method building on the work of braun braun d r 2005 examining flake production strategies examples from the middle paleolithic of southwest asia lithic technology 30 107 125 braun d r harris j w k 2003 technological developments in the oldowan of koobi fora innovative techniques of artifact analysis and new interpretations of oldowan behavior in mora r de la torre i eds oldowan rather more than smashing stones treballs d arqueologia 9 pp 132 144 this estimate is used to generate an edge length to mass value for complete flakes taken to be a proxy for flaking efficiency it is shown that this value is useful in tracking the onset variability and decline of a well known technological phase the howiesons poort of south africa the results suggest that the howiesons poort was a time in which flaking efficiency was emphasised furthermore comparison of upper limits of edge to mass values for different raw materials may provide an insight into changes in raw material selection

a multi sensor satellite assessment of so 2 emissions from the 2012 13 eruption of plosky tolbachik volcano kamchatka abstract prolonged basaltic effusive eruptions at high latitudes can have significant atmospheric and environmental impacts but can be challenging to observe in winter conditions here we use multi sensor satellite data to assess sulfur dioxide so2 emissions from the 2012 2013 eruption of plosky tolbachik volcano kamchatka which lasted 9 10 months and erupted 0 55 km3 dre observations from the ozone monitoring instrument omi the ozone mapping and profiler suite omps the atmospheric infrared sounder airs and the moderate resolution imaging spectroradiometer modis are used to evaluate volcanic activity so2 emissions and heat flux associated with the effusion of lava flows gaps in the primary omi so2 time series dataset occurred due to instrument limitations and adverse meteorological conditions four methods were tested to assess how efficiently they could fill these data gaps and improve estimates of total so2 emissions when available using data from other so2 observing instruments was the most comprehensive way to address these data gaps satellite measurements yield a total so2 loading of 200 kt so2 during the 10 month plosky tolbachik eruption although actual so2 emissions may have been greater based on the satellite so2 measurements the fast fourier transform fft multi taper method mtm was used to analyze cyclical behavior in the complete data series and a 55 day cycle potentially attributable to the eruptive behavior of plosky tolbachik during the 2012 2013 eruption was identified

improving volcanic ash cloud detection by a robust satellite technique abstract automated and reliable satellite based techniques are strongly required for volcanic ash cloud detection and tracking in fact volcanic ash clouds pose a serious hazard for air traffic and the synoptic and possibly frequent coverage offered by satellites can provide exciting opportunities for monitoring activities as well as for risk mitigation purposes a new avhrr based technique for improved automatic detection of volcanic clouds by means of multi temporal analysis of historical long term satellite records has been recently proposed the technique basically rests on the robust avhrr techniques rat approach which is an innovative strategy of satellite data analysis devoted to a former characterisation of the measured signal in terms of expected value and natural variability and a further recognition of signal anomalies by an automatic unsupervised change detection step in this work an extension of this method to nighttime observations is presented by using thermal infrared information coming from avhrr bands centred approximately at 3 5 11 0 and 12 0 m results achieved for two recent eruptive events of mount etna occurred in may 2000 and in july 2001 seem to be encouraging showing clear improvements in terms of ash detection sensitivity as well as in terms of false alarms reduction the technique performance is also evaluated by comparison with the traditional split window brightness temperature difference method this exercise revealed a general improvement obtained by the proposed approach even though some common problems still remain unsolved the main merits of such an approach are its intrinsic self adaptability to different environmental natural observational conditions and its natural exportability also to different satellite sensors the results here presented show the benefits of such a technique especially when different observational conditions time of pass seasonal period atmospheric moisture solar illumination volcanic cloud composition satellite angles of view etc are considered the future prospects also in terms of possible operational scenarios coming from the implementation of such an approach on the new generation of satellite sensors like for example seviri aboard meteosat second generation platform are also discussed

aster and field observations of the 24 december 2006 eruption of bezymianny volcano russia abstract an explosive eruption occurred at bezymianny volcano kamchatka peninsula russia on 24 december 2006 at 09 17 utc seismicity increased three weeks prior to the large eruption which produced a 12 15 km above sea level asl ash column we present field observations from 27 december 2006 and 2 march 2007 combined with satellite data collected from 8 october 2006 to 11 april 2007 by the advanced spaceborne thermal emission and reflection radiometer aster as part of the instrument s rapid response program to volcanic eruptions pixel integrated brightness temperatures were calculated from both aster 90 m pixel thermal infrared tir data as well as 30 m pixel short wave infrared swir data four days prior to the eruption the maximum tir temperature was 45 c above the average background temperature 33 c at the dome which we interpret was a precursory signal and had dropped to 8 c above background by 18 march 2007 on 20 december 2006 there was also a clear thermal signal in the swir data of 128 c using aster band 7 2 26 m the maximum swir temperature was 181 c on the lava dome on 4 january 2007 decreasing below the detection limit of the swir data by 11 april 2007 on 4 january 2007 a hot linear feature was observed at the dome in the swir data which produced a maximum temperature of 700 c for the hot fraction of the pixel using the dual band technique this suggests that magmatic temperatures were present at the dome at this time consistent with the emplacement of a new lava lobe following the eruption the eruption also produced a large 6 5 km long by up to 425 m wide pyroclastic flow pf deposit that was channelled into a valley to the south southeast the pf deposit cooled over the following three months but remained elevated above the average background temperature a second field investigation in march 2007 revealed a still warm pf deposit that contained fumaroles it was also observed that the upper dome morphology had changed in the past year with a new lava lobe having in filled the crater that formed following the 9 may 2006 eruption these data provide further information on effusive and explosive activity at bezymianny using quantitative remote sensing data and reinforced by field observations to assist in pre eruption detection as well as post eruption monitoring

misr observations of etna volcanic plumes 1 in the last twelve years mt etna located in eastern sicily has produced a great number of explosive eruptions volcanic plumes have risen to several km above sea level and created problems for aviation and the communities living near the volcano a reduction of hazards may be accomplished using remote sensing techniques to evaluate important features of volcanic plumes since 2000 the multiangle imaging spectroradiometer misr on board nasa s terra spacecraft has been extensively used to study aerosol dispersal and to extract the three dimensional structure of plumes coming from anthropogenic or natural sources including volcanoes in the present work misr data from several explosive events occurring at etna are analyzed using a program named minx misr interactive explorer minx uses stereo matching techniques to evaluate the height of the volcanic aerosol with a precision of a few hundred meters and extracts aerosol properties from the misr standard products we analyzed twenty volcanic plumes produced during the 2000 2001 2002 03 2006 and 2008 etna eruptions finding that volcanic aerosol dispersal and column height obtained by this analysis is in good agreement with ground based observations misr aerosol type retrievals 1 clearly distinguish volcanic plumes that are sulphate and or water vapor dominated from ash dominated ones 2 detect even low concentrations of volcanic ash in the atmosphere 3 demonstrate that sulphate and or water vapor dominated plumes consist of smaller sized particles compared to ash plumes this work highlights the potential of misr to detect important volcanic plume characteristics that can be used to constrain the eruption source parameters in volcanic ash dispersion models further the possibility of discriminating sulphate and or water vapor dominated plumes from ash dominated ones is important to better understand the atmospheric impact of these plumes

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

oceanic gas hydrate instability and dissociation under climate change scenarios 1 global oceanic deposits of methane gas hydrate clathrate have been implicated as the main culprit for a repeated remarkably rapid sequence of global warming effects that occurred during the late quaternary period however the behavior of contemporary oceanic methane hydrate deposits subjected to rapid temperature changes like those predicted under future climate change scenarios is poorly understood and existing studies focus on deep hydrate deposits under equilibrium conditions in this study we simulate the dynamic response of several types of oceanic gas hydrate accumulations to temperature changes at the seafloor and assess the potential for methane release into the ecosystem the results suggest that while many deep hydrate deposits are indeed stable under the influence of rapid seafloor temperature variations shallow deposits such as those found in arctic regions or in the gulf of mexico can undergo rapid dissociation and produce significant carbon fluxes over a period of decades

satellite thermal infrared data of shiveluch kliuchevskoi and karymsky 1993 2008 effusion explosions and the potential to forecast ash plumes this paper presents an analysis of advanced very high resolution radiometer avhrr thermal data from shiveluch kliuchevskoi and karymsky kamchatka russia from 1993 to 2008 these different volcanoes show contrasting and variable patterns in their thermal data and lack reliable precursory thermal trends prior to large explosions pixel integrated temperatures pirt at shiveluch were above background during three phases 1 1993 1995 2 2001 2005 and 3 2006 time of writing each of which was associated with growth of an andesitic dome punctuated by explosions the coarse spatial resolution of the avhrr may have prevented observation of precursory thermal patterns at this volcano kliuchevskoi showed five phases these show a rapid days or gradual weeks to months increase in temperature followed by rapid drop offs suggesting these basaltic eruptions start explosively followed by lava effusion or vice versa fast magma ascent rates probably prevent the generation of thermal precursors at karymsky elevated pirt values cluster into seven phases showing three trends 1 persistently high pirt 2 a gradual increase and decrease and 3 gradual increase followed by steep drop offs these trends are due to the extrusion of viscous andesitic dacitic lava not to strombolian vulcanian activity and show no consistent pattern prior to large explosions pirt values at karymsky lake reflect the dyke intrusion that started the 1996 eruptive cycle at karymsky the values obtained here provide a baseline against which to monitor these volcanoes and karymsky lake in the future

a multi sensor plume height analysis of the 2009 redoubt eruption abstract during an explosive volcanic eruption accurately determining the height of a volcanic plume or cloud is essential to accurately forecast its motion because volcanic ash transport and dispersion models require the initial plume height as an input parameter the direct use of satellite infrared temperatures for height determination one of the most commonly employed methods at the alaska volcano observatory often does not yield unique solutions for height this result is documented here for the 2009 eruption of redoubt volcano satellite temperature heights consistently underestimated the height of ash plumes in comparison to other methods such as ground based radar and multi angle imaging spectroradiometer misr stereo heights for ash plumes below the tropopause increasing transparency of a plume begins to affect the accuracy of simple temperature height retrievals soon after eruption with decreasing opacity plume temperature heights become increasingly inaccurate comparison with dispersion models and aircraft gas flight data confirms that radar and misr stereo heights are more accurate than basic satellite temperature heights even in the cases in which satellite temperature results appeared to be relatively accurate e g for plumes below the tropopause a mixed signal of plume and ground radiation still presented an issue for almost every event studied this was true regardless of the fact that a band differencing method was used to remove presumably translucent pixels the data presented here make a strong case for the use of data fusion in volcano monitoring as there is a need to confirm satellite temperature heights with other height data if only basic satellite temperature heights are available for a given eruption then these heights must be considered with a significant margin of error

hydrocarbon seepage and its sources at mud volcanoes of the kumano forearc basin nankai trough subduction zone twelve submarine mud volcanoes mv in the kumano forearc basin within the nankai trough subduction zone were investigated for hydrocarbon origins and fluid dynamics gas hydrates diagnostic for methane concentrations exceeding solubilities were recovered from mvs 2 4 5 and 10 molecular ratios c1 c2 40 v pdb indicate that hydrate bound hydrocarbons hcs at mvs 2 4 and 10 are derived from thermal cracking of organic matter considering thermal gradients at the nearby iodp sites c0009 and c0002 the likely formation depth of such hcs ranges between 2300 and 4300 m below seafloor mbsf with respect to basin sediment thickness and the minimum distance to the top of the plate boundary thrust we propose that the majority of hcs fueling the mvs is derived from sediments of the cretaceous to tertiary shimanto belt below pliocene pleistocene to recent basin sediments considering their sizes and appearances hydrates are suggested to be relicts of higher mv activity in the past although the sporadic presence of vesicomyid clams at mv 2 showed that fluid migration is sufficient to nourish chemosynthesis based organisms in places distributions of dissolved methane at mvs 3 4 5 and 8 pointed at fluid supply through one or few mv conduits and effective methane oxidation in the immediate subsurface the aged nature of the hydrates suggests that the major portion of methane immediately below the top of the methane containing sediment interval is fueled by current hydrate dissolution rather than active migration from greater depth

thermal and visual time series at a seafloor gas hydrate deposit on the gulf of mexico slope ambient temperature is a critical factor determining the stability of gas hydrate deposits on continental margins to study this process directly under varying conditions a monitoring array comprising a time lapse camera and in situ temperature probes was deployed at a hydrocarbon seep known as bush hill where gas hydrates deposits are exposed at the seafloor in a water depth of 570 m for intervals of 91 days and 30 days the digital camera recorded several daily images of a prominent gas hydrate mound consisting of structure ii gas hydrate the temperature probes were constructed with one autonomous thermistor at each end of a 50 cm pvc wand and recorded temperatures with precision of better than 0 1 8c at 30 min intervals over 327 days one probe was implanted with a tight seal into a drill hole about 7 cm deep in the top of the gas hydrate mound the second was inserted about 50 cm deep into the adjacent sediments for each probe the top thermistor recorded the ambient water temperature while the bottom thermistor synoptically recorded the internal temperature of the hydrate or sediment the bottom water temperatures ranged from 6 64 to 9 73 8c with a mean of 7 90 8c and standard deviation of 0 437 photographic results showed no dramatic changes in the size shape or gas venting from the mound by comparing the temperatures recorded at the tips of the probes with the synoptic water temperature we estimate that thermal diffusivity for the gas hydrate deposit was 7 14d 10 8 to 8 33d 10 8 m 2 s 1 and was 1 77d 10 7 to 3 01d 10 7 m 2 s 1 for the sediments at the sites where temperatures were recorded the diffusivity measured in gas hydrate was lower than that measured under laboratory conditions stability of gas hydrate in this setting is not likely to be affected by short term changes in bottom water temperature within the range observed d 2005 elsevier b v all rights reserved

deep sulfate reduction completely mediated by anaerobic methane oxidation in sediments of the upwelling area off namibia abstract porewater concentrations of sulfate methane and other relevant constituents were determined on four sediment cores from the high productivity upwelling area off namibia which were recovered from the continental slope at water depths of 1300 and 2000 m at all four stations a distinct sulfate methane transition zone was observed several meters below the seafloor in which both sulfate and methane are consumed nutrient porewater concentration profiles do not show gradient slope changes at the depths of the transition zones flux calculations carried out on the basis of the determined porewater profiles revealed that anaerobic methane oxidation accounts for 100 of deep sulfate reduction within the sulfate methane transition zone and consumes the total net diffusive sulfate flux a significant contribution of organic carbon oxidation to the reduction of sulfate at these depths could therefore be excluded we state that porewater profiles of sulfate with constant gradients above the transition zones are indicative for anaerobic methane oxidation controlling sulfate reduction

gas hydrate destabilization enhanced dewatering benthic material turnover and large methane plumes at the cascadia convergent margin mixed methane sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the cascadia convergent margin vent fields from which methane charged low salinity fluids containing sulfide ammonia 4he and isotopically light co2 escape are associated with these exposures they characterize a newly recognized mechanism of dewatering at convergent margins where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward this process augments the convergence generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths the enhanced turnover results from the oxidation of methane hydrogen sulfide and ammonia by vent biota the injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide a large fraction of the methane is oxidized within the water column and generates 13c anomalies of the dissolved inorganic carbon pool

ocean circulation promotes methane release from gas hydrate outcrops at the neptune canada barkley canyon node 1 the neptune canada cabled observatory network enables non destructive controlled experiments and time series observations with mobile robots on gas hydrates and benthic community structure on a small plateau of about 1 km2 at a water depth of 870 m in barkley canyon about 100 km offshore vancouver island british columbia a mobile internet operated vehicle was used as an instrument platform to monitor and study up to 2000 m2of sediment surface in real time in 2010 the first mission of the robot was to investigate the importance of oscillatory deep ocean currents on methane release at continental margins previously other experimental studies have indicated that methane release from gas hydrate outcrops is diffusion controlled and should be much higher than seepage from buried hydrate in semipermeable sediments our results show that periods of enhanced bottom currents associated with diurnal shelf waves internal semidiurnal tides and also wind generated near inertial motions can modulate methane seepage flow dependent destruction of gas hydrates within the hydrate stability field is possible from enhanced bottom currents when hydrates are not covered by either seafloor biota or sediments the calculated seepage varied between 40 400 mol ch4 m 2 s 1 this is 1 3 orders of magnitude higher than dissolution rates of buried hydrates through permeable sediments and well within the experimentally derived range for exposed gas hydrates under different hydrodynamic boundary conditions we conclude that submarine canyons which display high hydrodynamic activity can become key areas of enhanced seepage as a result of emerging weather patterns due to climate change

initiation of gas hydrate pockmark in deep water nigeria geo mechanical analysis and modelling abstract a review of recent literature shows that two geomorphologically different types of pockmarks contribute to gas seepage at the seafloor type 1 pockmarks are defined as seafloor craters associated to fluid seepage and are the most classical type referred to as pockmarks in the literature in contrast type 2 pockmarks reveal a complex seafloor morphology that may result from the formation decomposition of gas hydrates in underlying sedimentary layers interpretation of very high resolution seismic data sedimentological analyses and geotechnical measurements acquired from the eastern niger submarine delta reveal that type 2 pockmarks are associated to the presence at depth of a conical body of massive gas hydrates based on acquired data theoretical analysis and numerical modelling it was possible to propose a novel geo mechanical mechanism controlling the irregular seafloor deformations associated to type 2 pockmark and to show that pockmark shapes and sizes are directly linked to the initial growth and distribution of sub seafloor gas hydrates the study illustrates the role of gas hydrates formation in the fracturation deformation of the subsurface sediment and the formation of type 2 pockmarks

hydrocarbon migration pathway and methane budget for a gulf of mexico natural seep site green canyon 600 abstract hydrocarbon seeps occur worldwide along continental margins and act as conduits for fluid discharge from the lithosphere to the overlying hydrosphere atmosphere the dynamics and rates of hydrocarbon release at cold seeps remain poorly constrained seepage enables a variety of processes that alter the seafloor morphology and affect the geochemistry of substrata supporting diverse and important chemosynthetic communities here we merge complementary geochemical oil fingerprinting geophysical deep seismic subbottom backscatter multibeam and video imaging video time lapse camera dsv alvin video rov video auv photo surveys data sets to constrain the pathways and magnitudes of methane fluxes from the source reservoir to the seafloor at a well studied prolific seep site green canyon gc 600 in the northern gulf of mexico oil samples from the reservoir an active vent and the sea surface showed compositional similarities consistent with the plumbing system structure identified in seismic data spatial distribution of seep indicators such as bacterial mats microbial communities methane derived carbonates and hydrate outcrops were then used to quantify the total magnitude of methane potentially sequestered in the study domain using a systems approach we combined published values for methane fluxes with data we collected across various scales and resolutions to compile a methane budget for gc600 the system considered for the methane budget is defined as the movement of methane from the salt ridge to the seafloor water interface for each seep domain birthday candles and mega plume total estimated input of methane was 2 8 10 8 2 2 10 9 mol yr in the birthday candles domain and 2 7 10 8 2 3 10 9 in the mega plume domain the combined total output of the system ranged from 3 2 10 5 8 2 10 5 and 3 2 10 6 5 2 10 6 mol yr respectively for birthday candles and mega plume domains leaving a potential surplus input minus output of 2 6 10 8 2 3 10 9 mol yr processes that could balance this budget include accumulation of gas hydrate and sediment free gas and the underestimated potential of biological sinks such as methane oxidation

appearance and preservation of natural gas hydrate from hydrate ridge sampled during odp leg 204 drilling abstract the state of preservation of natural gas hydrate samples recovered from 6 sites drilled during odp leg 204 at southern summit of hydrate ridge oregon margin has been investigated by x ray diffraction xrd and cryo scanning electron microscopy cryo sem techniques a detailed characterization of the state of decomposition of gas hydrates is necessary since no pressurized autoclave tools were used for sampling and partial dissociation must have occurred during recovery prior to the quench and storage in liquid nitrogen samples from 16 distinct horizons have been investigated by synchrotron x ray diffraction measurements at hasylab hamburg a full profile fitting analysis rietveld method of synchrotron xrd data provides quantitative phase determinations of the major sample constituents such as gas hydrate structure i si hexagonal ice ih and quartz the ice content ih in each sample is related to frozen water composed of both original existing pore water and the water from decomposed hydrates hydrate contents as measured by diffraction vary between 0 and 68 wt in the samples we measured samples with low hydrate content usually show micro structural features in cryo sem ascribed to extensive decomposition comparing the appearance of hydrates at different scales the grade of preservation seems to be primarily correlated with the contiguous volume of the original existing hydrate the dissociation front appears to be indicated by micrometer sized pores in a dense ice matrix

methane under saturated fluids in deep sea sediments implications for gas hydrate stability and rates of dissolution abstract deep sea sediments contain earth s largest reservoir of methane ch 4 3000 gtons c trapped within ice like crystals known as gas hydrates understanding the controls on gas hydrate stability is critical because methane released from hydrate destabilization is hypothesized to be a powerful agent of past and potentially future climate change hydrates are stable under high pressure low temperature moderate salinity and saturated gas conditions yet the degree of gas saturation is rarely known in nature because in situ dissolved pore water ch 4 concentrations are rarely measured here we report measurements of these concentrations in sediments immediately surrounding deep sea gas hydrate deposits and show that pore fluids are greatly under saturated with respect to expected values for equilibrium with methane gas hydrate this indicates that the hydrates are dissolving even though they are found within the appropriate pressure and temperature stability field however dissolution rates calculated from the in situ ch 4 data are significantly less than dissolution rates predicted for methane under saturated pore water in direct contact with pure methane gas hydrate if equilibrium ch 4 concentrations exist immediately adjacent to the hydrate surface diffusion retarding factors found naturally in ocean sediments such as oil coatings or biofilms appear to enhance stability in outcropping hydrate deposits the in situ seafloor evidence provided herein leads us to hypothesize that the stability of the worldwide hydrate deposits may be much greater than predicted from diffusion kinetics because biological microbial excretion of slime or surfactants and or physical processes oil coatings effectively armor and stabilize exposed hydrate surfaces substantially retarding their dissolution

reducing discrepancies in ground and satellite observed eruption heights abstract the plume height represents a crucial piece of evidence about an eruption feeding later assessment of its size character and potential impact and feeding real time warnings for aviation and ground based populations there have been many observed discrepancies between different observations of maximum plume height for the same eruption a comparison of maximum daily height estimates of volcanic clouds over indonesia and papua new guinea during 1982 2005 shows marked differences between ground and satellite estimates and a general tendency towards lower height estimates from the ground without improvements in the quality of these estimates reconciled among all available methods warning systems will be less effective than they should be and the world s record of global volcanism will remain hard to quantify examination of particular cases suggests many possible reasons for the discrepancies consideration of the satellite and radar cloud observations for the 1991 pinatubo eruptions shows that marked differences can exist even with apparently good observations the problem can be understood largely as a sampling issue as the most widely reported parameter the maximum cloud height is highly sensitive to the frequency of observation satellite and radar cloud heights also show a pronounced clumping near the height of the tropopause and relative lack of eruptions reaching only the mid troposphere reinforcing the importance of the tropopause in determining the eruption height in convectively unstable environments to reduce the discrepancies between ground and satellite estimates a number of formal collaboration measures between vulcanological meteorological and aviation agencies are suggested

assessing the altitude and dispersion of volcanic plumes using misr multi angle imaging from space sixteen years of volcanic activity in the kamchatka peninsula russia abstract volcanic eruptions represent a significant source of atmospheric aerosols and can display local regional and global effects impacting earth systems and human populations in order to assess the relative impacts of these events accurate plume injection altitude measurements are needed in this work volcanic plumes generated from seven kamchatka peninsula volcanoes shiveluch kliuchevskoi bezymianny tolbachik kizimen karymsky and zhupanovsky were identified using over 16 years of multi angle imaging spectroradiometer misr measurements eighty eight volcanic plumes were observed by misr capturing 3 25 of reported events at individual volcanoes retrievals were most successful where eruptive events persisted over a period of weeks to months compared with existing ground and airborne observations and alternative satellite based reports compiled by the global volcanism program gvp misr plume height retrievals show general consistency the comparison reports appear to be skewed towards the region of highest concentration observed in misr constrained plume vertical extent the report observations display less discrepancy with misr toward the end of the analysis period 2013 2016 with improvements in the suborbital data likely the result of the deployment of new instrumentation conversely the general consistency of misr plume heights with conventionally reported observations supports the use of misr in the ongoing assessment of volcanic activity globally especially where ground based observations are unavailable differences between the northern shiveluch kliuchevskoi bezymianny and tolbachik and southern kizimen karymsky and zhupanovsky volcanoes broadly corresponding to the central kamchatka depression ckd and eastern volcanic front evf geological sub regions of kamchatka respectively are distinguished by varying magma composition for example by comparison with reanalysis model simulations of local meteorological conditions ckd plumes were generally less constrained by mid tropospheric

characterising volcanic cycles at soufriere hills volcano montserrat time series analysis of multi parameter satellite data abstract the identification of cyclic volcanic activity can elucidate underlying eruption dynamics and aid volcanic hazard mitigation whilst satellite datasets are often analysed individually here we exploit the multi platform nasa a train satellite constellation to cross correlate cyclical signals identified using complementary measurement techniques at soufriere hills volcano shv montserrat in this paper we present a multi taper mtm fast fourier transform fft analysis of coincident so 2 and thermal infrared tir satellite measurements at shv facilitating the identification of cyclical volcanic behaviour these measurements were collected by the ozone monitoring instrument omi and moderate resolution imaging spectroradiometer modis respectively in the a train we identify a correlating cycle in both the omi and modis data 54 58 days with this multi week feature attributable to episodes of dome growth the 50 day cycles were also identified in ground based so 2 data at shv confirming the validity of our analysis and further corroborating the presence of this cycle at the volcano in addition a 12 day cycle was identified in the omi data previously attributed to variable lava effusion rates on shorter timescales omi data also display a one week 7 8 days cycle attributable to cyclical variations in viewing angle resulting from the orbital characteristics of the aura satellite longer period cycles possibly relating to magma intrusion were identified in the omi record 102 121 and 159 days in addition to a 238 day cycle identified in the modis data corresponding to periodic destabilisation of the lava dome through the analysis of reconstructions generated from cycles identified in the omi and modis data periods of unrest were identified including the major dome collapse of 20th may 2006 and significant explosive event of 3rd january 2009 our analysis confirms the potential for identification of cyclical volcanic activity through combined analysis of satellite data which would be of particular value at poorly monitored volcanic systems

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

methane sources and production in the northern cascadia margin gas hydrate system abstract the oceanographic and tectonic conditions of accretionary margins are well suited for several potential processes governing methane generation storage and release to identify the relevant methane evolution pathways in the northern cascadia accretionary margin a four site transect was drilled during integrated ocean drilling program expedition 311 the 13c values of methane range from a minimum value of 82 2 on an uplifted ridge of accreted sediment near the deformation front site u1326 1829 mbsl meters below sea level to a maximum value of 39 5 at the most landward location within an area of steep canyons near the shelf edge site u1329 946 mbsl an interpretation based solely on methane isotope values might conclude the 13c enrichment of methane indicates a transition from microbially to thermogenically sourced methane however the co existing co2 exhibits a similar trend of 13c enrichment along the transect with values ranging from 22 5 to 25 7 the magnitude of the carbon isotope separation between methane and co2 ec 63 8 5 8 is consistent with isotope fractionation during microbially mediated carbonate reduction these results in conjunction with a transect wide gaseous hydrocarbon content composed of 99 8 by volume methane and uniform dch4 values 172 8 that are distinct from thermogenic methane at a seep located 60 km from the expedition 311 transect suggest microbial co2 reduction is the predominant methane source at all investigated sites the magnitude of the intra site downhole 13c enrichment of co2 within the accreted ridge site u1326 and a slope basin nearest the deformation front site u1325 2195 mbsl is 5 at the mid slope site site u1327 1304 mbsl the downhole 13c enrichment of the co2 is 25 and increases to 40 at the near shelf edge site u1329 this isotope fractionation pattern is indicative of more extensive diagenetic alteration at sites with greater 13c enrichment the magnitude of the 13c enrichment of co2 correlates with decreasing sedimentation rates and a diminishing occurrence of stratigraphic gas hydrate we suggest the decreasing sedimentation rates increase the exposure time of sedimentary organic matter to aerobic and anaerobic degradation during burial thereby reducing the availability of metabolizable organic matter available for methane production this process is reflected in the occurrence and distribution of gas hydrate within the northern cascadia margin accretionary prism our observations are relevant for evaluating methane production and the occurrence of stratigraphic gas hydrate within other convergent margins

the origin of thermogenic gas hydrates on the northern cascadia margin as inferred from isotopic 13c 12c and d h and molecular composition of hydrate and vent gas the isotopic 13c and d and hydrocarbon compositions of hydrate bound and vent gas collected from the seafloor of barkley canyon northern cascadia margin offshore vancouver island canada were evaluated to characterize the gas and infer the type and maturity of the source rock kerogen the hydrate gas contained methane having 13c values from 43 4 to 42 6 d values from 143 to 138 and a large percentage 14 9 to 31 9 of c2 to c5 hydrocarbons these data are consistent with a thermogenic gas source the data from barkley canyon are interpreted within the context of similar data from the gulf of mexico and caspian sea thermogenic hydrates which occur in regions where the petroleum systems supporting gas and oil generation are better understood a stable carbon isotope based natural gas plot model and d h data from the hydrate gas indicate that the source rock for the barkley canyon hydrate and vent gas had primarily type iii kerogen mixed with a small fraction of type ii kerogen oil from a seep having a pristane phytane ratio of 3 2 was identified as a gas condensate which supports the conclusions drawn from the gas data a mechanism for explaining how fluids are conducted from the deep petroleum reservoir to the seafloor of barkley canyon is proposed

life at the edge of methane ice microbial cycling of carbon and sulfur in gulf of mexico gas hydrates the processes of methane oxidation and sulfate reduction were examined in subsamples of gas hydrate associated materials collected along the gulf of mexico continental slope standard radiotracer techniques were used to determine rates of microbial activity in different layers of the hydrate environment including outer sediment os interface sediment is worm burrow sediment wb interior hydrate in and a mixture of hydrate and sediment mix the anaerobic oxidation of methane aom and sulfate reduction sr were observed in all hydrate samples examined and the rates of these processes showed similar spatial trends between different hydrate layers highest rates of both aom and sr were observed at interface between the sediment and hydrate aom rates were about 3 11 nmol cm 3 day 1 in worm burrow and interface sediments as compared to 1 nmol cm 3 day 1 in other hydrate material types rates of sr ranged from 59 to 490 nmol cm 3 day 1 in worm burrow and interface sediments while rates in interior hydrate samples were an order of magnitude lower these rates observed in hydrate materials are lower than rates from nearby methane rich sediments at ambient temperatures nevertheless our data show that active microbial populations inhabit all layers of the hydrate environment and suggest their activity may impact biogeochemical methane and sulfur cycling in this unique niche d 2004 elsevier b v all rights reserved

dynamics of the gas flux from shallow gas hydrate deposits interaction between oily hydrate bubbles and the oceanic environment decomposition of methane hydrates on the continental margins is a potentially significant source of atmospheric methane but the input depends upon the poorly understood fate of the hydrocarbon bubbles rising from the sea floor during a field trip to the gulf of mexico three different seepages were imaged and analyzed three different imaging techniques were tried side front and back illumination of which back illumination produced the best results the images were analyzed and the size dependent bubble distribution mass flux and rise speeds determined the total observed gas flux was 62 3 10 3 mol s 1 primarily methane of which a single vent produced seven times the next largest vent of this major vent 50 of the bubble mass was contained in the largest bubbles r 5500 m the vertical velocities demonstrated that these bubbles were heavily contaminated with oil which was also corroborated by bubble shape and oscillation observations

subsurface methane sources and migration pathways within a gas hydrate mound system gulf of mexico 1 geochemical profiles were coupled with seismic information to examine subsurface hydrocarbon source migration and fate at a gulf of mexico carbonate gas hydrate mound woolsey mound three seafloor features were investigated in detail 1 major faults resulting from a rising salt body 2 an acoustic backscatter anomaly and 3 a pockmark associated with a major fault we analyzed sulfate chloride dissolved inorganic carbon and hydrocarbon concentrations and carbon isotopes in pore water extracted from 20 m piston cores to characterize gas source and calculate methane flux dissolved biogenic methane dominated the off fault sites while the contribution of thermogenic methane increased near a major fault where thermogenic gas hydrates were recovered within the pockmark methane concentrations were low and isotopes indicated a biogenic source since pockmarks are typically formed from expulsive fluid flow this suggests that either the pockmark is the legacy of a conduit that has become plugged or that the expulsed fluid is confined within the fault walls at the acoustic anomaly nonsteady state sulfate profiles suggested temporal variability in methane flux estimates from 75 gravity cores collected across woolsey mound since 2002 were mapped to display the spatial variability in methane flux relative to the faults methane flux to the seafloor was generally low but increased several fold near the faults suggesting that the faults may provide conduits for hydrocarbons to bypass the microbial biofilter and cross the sediment water interface

pre eruption deformation caused by dike intrusion beneath kizimen volcano kamchatka russia observed by insar abstract interferometric synthetic aperture radar insar images reveal a pre eruption deformation signal at kizimen volcano kamchatka russia where an ongoing eruption began in mid november 2010 the previous eruption of this basaltic andesite to dacite stratovolcano occurred in 1927 1928 insar images from both ascending and descending orbital passes of envisat and alos palsar satellites show as much as 6 cm of line of sight shortening from september 2008 to september 2010 in a broad area centered at kizimen about 20 cm of opening of a nearly vertical dike provides an adequate fit to the surface deformation pattern the model dike is approximately 14 km long 10 km high centered 13 km beneath kizimen and strikes ne sw time series analysis of multi temporal interferograms indicates that 1 intrusion started sometime between late 2008 and july 2009 2 continued at a nearly constant rate and 3 resulted in a volume expansion of 3 2 107 m3 by september 2010 i e about two months before the onset of the 2010 eruption earthquakes located above the tip of the dike accompanied the intrusion eventually magma pressure in the dike exceeded the confining strength of the host rock triggering the 2010 eruption our results provide insight into the intrusion process that preceded an explosive eruption at a pacific rim stratovolcano following nearly a century of quiescence and therefore have implications for monitoring and hazards assessment at similar volcanoes elsewhere

automated volcanic eruption detection using modis abstract the moderate resolution imaging spectroradiometer modis flown on board nasa s first earth observing system eos platform terra offers complete global data coverage every 1 2 days at spatial resolutions of 250 500 and 1000 m its ability to detect emitted radiation in the short 4 m and long 12 m wave infrared regions of the electromagnetic spectrum combined with the excellent geolocation of the image pixels 200 m makes it an ideal source of data for automatically detecting and monitoring high temperature volcanic thermal anomalies this paper describes the underlying principles of and results obtained from just such a system our algorithm interrogates the modis level 1b data stream for evidence of high temperature volcanic features once a hotspot has been identified its details location emitted spectral radiance satellite observational parameters are written to an ascii text file and transferred via file transfer protocol ftp to the hawaii institute of geophysics and planetology higp where the results are posted on the internet http modis higp hawaii edu the global distribution of volcanic hotspots can be examined visually at a variety of scales using this website which also allows easy access to the quantitative data contained in the ascii files themselves we outline how the algorithm has proven robust as a hotspot detection tool for a wide range of eruptive styles at both permanently and sporadically active volcanoes including soufriere hills montserrat popocatepetl mexico bezymianny russia and merapi java amongst others we also present case studies of how the system has allowed the onset development and cessation of discrete eruptive events to be monitored at nyamuragira congo piton de la fournaise reunion island and shiveluch russia

measurements of the fate of gas hydrates during transit through the ocean water column 1 we report on controlled experiments to document the fate of naturally occurring methane hydrate released from the sea floor 780 m 4 3 c by remotely operated vehicle rov disturbance images of buoyant sediment coated solids rising 0 24 m s from the debris cloud soon revealed clear crystals of methane hydrate as surficial material sloughed off decomposition and visible degassing began close to the predicted phase boundary yet pieces initially of 0 10 m size easily survived transit to the surface ocean smaller pieces dissolved or dissociated before reaching the surface ocean yet effectively transferred gas to depths where atmospheric ventilation times are short relative to methane oxidation rates

kinetics of convective crystal dissolution and melting with applications to methane hydrate dissolution and dissociation in seawater abstract large quantities of methane hydrate are present in marine sediment when methane hydrate is exposed or released to seawater it dissolves in seawater or dissociates into methane gas and water there was some confusion in the literature about the kinetics of these processes it is critical to realize that dissolution and dissociation are two different processes dissolution is due to instability in the presence of seawater similar to dissolution of nacl in water and is controlled by mass transfer dissociation is due to inherent instability similar to melting of ice with or without water although presence of warm water may increase the dissociation rate dissociation of methane hydrate into gas and water is similar to ice melting and is controlled by heat transfer hence dissolution is relatively slow and dissociation is rapid in this work we extend previous theory on convective crystal dissolution and melting to greater reynolds numbers we carry out laboratory experiments on the dissolution and descent of nacl kcl nabr and kbr in water to verify the applicability of our theory we then apply our models as well as previous ones to estimate methane hydrate dissolution and dissociation rates for several cases including dissolution of exposed methane hydrate floor dissolution and dissociation of hydrate as it rises through seawater the results show i convective dissolution rate of exposed hydrate floor is of the order 0 07 m yr ii convective dissolution rate of a rising hydrate crystal is 0 2 0 3 m s and a crystal of 5 mm radius is able to survive the rise through an 1800 m seawater column and iii convective dissociation rate is high and depends on the difference between the ambient water temperature and the equilibrium dissociation temperature of hydrate starting from a depth when hydrate just reaches dissociation instability a hydrate sphere of 5 mm radius would survive only a 47 m water column because hydrate is unstable in the surface ocean and would undergo rapid dissociation only very large hydrate chunks greater than about 0 09 m radius would be able to survive a 530 m surface water column

stable carbon isotopic evidence for methane oxidation in plumes above hydrate ridge cascadia oregon margin 1 the transport and consumption of methane in the water column in the vicinity of the cold seeps of hydrate ridge on the cascadia oregon margin were characterized using measurements of the stable carbon isotope composition of methane the 13c ch4 values measured in the water column ranged from approximately 65 to 16 pdb the combination of measured methane concentration data and the stable carbon isotope values from the same depths support the hypothesis of biogenically produced methane which enters the water column from dissolving bubbles released from cold seepages likely as a consequence of destabilized methane hydrate 13c ch4 65 pdb kinetic fractionation factors associated with aerobic bacterial methane oxidation in the water column were calculated using a rayleigh distillation equation applied to a subset of the data fractionation factors ranged from 1 002 to 1 013 mean 1 008 and were in the lower end of the range of those reported in the literature a result likely due to the influence of temperature and mixing in plume waters the fraction of methane remaining after oxidation calculated using the same rayleigh model approach suggests that the aerobic oxidation of methane in the water column over hydrate ridge is nearly quantitative

monitoring of the volcanic rock compositions during the 2012 2013 fissure eruption at tolbachik volcano kamchatka abstract here we present the results from monitoring of the composition of rocks produced during the 2012 2013 fissure eruption at tolbachik volcano fte major and trace element concentrations in 75 samples are reported products of this eruption are represented by high alumina basaltic trachyandesites with higher alkalis and titanium contents than in all previously studied rocks of the tolbachik monogenetic volcanic field rocks erupted during the first three days 27 30 november from the northern also called menyailov group of vents are the most silica and alkali rich sio2 concentrations up to 55 35 wt and k2o up to 2 67 wt from december onwards when the eruptive activity switched from the menyailov vents to the southern naboko group of vents silica content dropped by 2 wt concentrations of mgo feo tio2 and mg increased and k2o and na2o concentrations and k2o mgo ratio decreased for the rest of the eruption the compositions of rocks remained constant and homogeneous no systematic compositional differences between lava bombs and scoria samples are evident trace element distributions in the rocks of the menyailov and naboko vent lavas are relatively uniform menyailov lavas have slightly higher th nb hf y and hree concentrations than the naboko vent lavas at more or less constant element ratios we explain the initial change in geochemistry by tapping of a slightly cooler and fractionated 3 mt and 8 cpx upper part of the magma storage zone before the main storage area began to feed the eruption thermodynamic constraints show that apparent liquidus temperatures varied from 1142 c to 1151 c and thermodynamic modeling shows that variations in compositions are consistent with a high degree of low pressure 100 300 mpa nominally anhydrous fractionation of a parent melt compositionally similar to the 1975 northern breakthrough high mg basalt geochemistry petrological observations and modeling are in agreement with the newly erupted material being derived from remnant high al magma from the 1975 76 southern breakthrough eruption with only slight amounts of cooling less than 1 c per year during the intervening 36 years

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

pyroclastic surges and flows from the 8 10 may 1997 explosive eruption of bezymianny volcano kamchatka russia the 8 10 may 1997 eruption of bezymianny volcano began with extrusion of a crystallized plug from the vent in the upper part of the dome progressive gravi tational collapses of the plug caused decompression of highly crystalline magma in the upper conduit leading at 13 12 local time on 9 may to a powerful vertical vulcanian explosion the dense pyroclastic mixture col lapsed in boil over style to generate a pyroclastic surge which was focused toward the southeast by the steep walled 1956 horseshoe shaped crater this surge with a temperature 30 km 2 with deposits as much as 30 cm thick and extending 7 km from the vent the surge deposits comprised mas sive to vaguely laminated gravelly sand md 1 2 to 3 7 sorting 1 2 to 3 of poorly vesiculated andesite mean density 1 82 g cm 3 vesicularity 30 vol sio2 content 58 0 wt the deposits with a volume of 5 15 106 m3 became finer grained and better sorted with distance the maximal diameter of juvenile clasts decreased from 46 to 4 cm the transport and deposition of the surge over a snowy landscape generated extensive lahars which traveled 30 km immediately following the surge semi vesiculated block and ash flows were emplaced as far as 4 7 km from the vent over time the juvenile lava in clasts of these flows became progres sively less crystallized apparently more silicic 59 0 to 59 9 wt sio 2 and more vesiculated density 1 64 to 1 12 g cm 3 vesicularity 37 to 57 vol at this stage the eruption showed transitional behavior with mass di vided between collapsing fountain and buoyant column the youngest pumice and ash flows were accompanied by a sustained sub plinian eruption column 14 km high from which platy fallout clasts were deposited 59 7 sio 2 density 1 09 g cm 3 vesicularity 58 vol the explosive activity lasted about 37 min and produced a to tal of 0 026 km 3 dense rock equivalent of magma with an average discharge of 1 2 104 m3 s 1 a lava flow 200 m long terminated the eruption the evolutionary succession of different eruptive styles during the explo sive eruption was caused by vertical gradients in crystal lization and volatile content of the conduit magma which produced significant changes in the properties of the erupting mixture

the 2001 2004 dome forming eruption of shiveluch volcano kamchatka observation petrological investigation and numerical modelling there have been three episodes of lava dome growth at shiveluch volcano kamchatka since the plinian explosive eruption in 1964 the episodes in 1980 1981 1993 1995 and 2001 2004 have discharged at least 0 27km 3 of silicic andesite magma a time averaged mean extrusion rate of 0 2m 3 s is thus estimated for the last 40years here the 2001 2004 activity is described and compared with the earlier episodes the recent activity involved three pulses in extrusion rate and a transition to ongoing lava extrusion estimated magma temperatures are in the range 830 to 900 c with 850 c as the best estimate using the plagioclase amphibole phenocryst assemblage and fe ti oxides melt inclusions in amphibole and plagioclase have maximum water contents of 5 1wt implying a minimum pressure of 155mpa for water saturated conditions the magma chamber depth is estimated to be about 5 6km or more a result consistent with geophysical data the thicknesses of opx mt amph reaction rims on olivine xenocrysts are used to estimate the residence time of olivine crystals in the shallow chamber in the range 2 months to 4 years suggesting replenishment of deeper magma into the shallow chamber contemporaneous with eruption the absence of decompression driven breakdown rims around amphiboles indicates ascent times of less than 7days volcanological observations of the start of the 2001 2004 episode suggest approximately 16 days for the ascent time and a conduit equivalent to a cylinder of diameter approximately 53 71m application of a conduit flow model indicates that the magma chamber was replenished during the 2001 2004 eruption consistent with the results of olivine reaction rims and that the chamber has an estimated volume of order 7km 3

dissolved methane in the beaufort sea and the arctic ocean 1992 2009 sources and atmospheric flux methane concentration and isotopic composition was measured in ice covered and ice free waters of the arctic ocean during 11 surveys spanning the years of 1992 1995 and 2009 during ice free periods methane flux from the beaufort shelf varies from 0 14 mg ch4 m 2 d 1 to 0 43 mg ch4 m 2 d 1 maximum fluxes from localized areas of high methane concentration are up to 1 52 mg ch4 m 2 d 1 seasonal buildup of methane under ice can produce short term fluxes of methane from the beaufort shelf that varies from 0 28 mg ch4 m 2 d 1 to 1 01 mg ch4 m 2 d 1 scaled up estimates of minimum methane flux from the beaufort sea and pan arctic shelf for both ice free and ice covered periods range from 0 02 tg ch4 yr 1 and 0 30 tg ch4 yr 1 respectively to maximum fluxes of 0 18 tg ch4 yr 1 and 2 2 tg ch4 yr 1 respectively a methane flux of 0 36 tg ch4 yr 1 from the deep arctic ocean was estimated using data from 1993 to 1994 the flux can be as much as 2 35 tg ch4 yr 1 estimated from maximum methane concentrations and wind speeds of 12 m s representing only 0 42 of the annual atmospheric methane budget of 560 tg ch4 yr 1 there were no significant changes in methane fluxes during the time period of this study microbial methane sources predominate with minor influxes from thermogenic methane offshore prudhoe bay and the mackenzie river delta and may include methane from gas hydrate methane oxidation is locally important on the shelf and is a methane sink in the deep arctic ocean