an integrated carbon isotope record of an end permian crater lake above a phreatomagmatic pipe of the siberian traps abstract the largest mass extinction in earth history occurred at the end permian 252 million years ago and is marked by a global negative carbon isotope excursion and the onset of siberian trap volcanism prompting diverse hypotheses on the link between flood basalt volcanism carbon cycle perturbations and mass extinction phreatomagmatic pipes associated with siberian trap volcanism have been proposed as conduits for the release of 12c enriched carbon gases from thermogenic and or magmatic sources to the end permian atmosphere some of the pipes have preserved crater lake sediments of volcaniclastic origin this study examined the preserved evidence for 12c enriched carbon release into the western oktyabrsk crater in east siberia from the underlying volcanic basin we find that the 13c 12c ratio of the carbonate cement organic matter and long chain n alkanes in the lacustrine crater sediments support the hypothesis that 12c enriched carbon infiltrated the basal crater sediments and lake water immediately after crater formation the values and trends of 13ccarb 13ctoc and 13cn alkanes in the crater sediments are consistent with 12c enriched carbon with isotopic values similar to that of carbon sourced from thermogenic and or 12c enriched magmatic sources this implies that carbon release through the pipes in the tunguska basin may explain the source of the global negative carbon isotope perturbations and their coincidence with siberian trap volcanism at the end permian

geostatistical characterization of snow depth structures on sea ice near point barrow alaska a contribution to the amsr ice03 field validation campaign the objective of this paper is to characterize spatial properties of snow depth structures and their role as indicators of sea ice properties and sea ice morphogenetic processes and to provide quantitative measures of sea ice properties that may be utilized in analyses of passive microwave data snow depth data collected near point barrow alaska as part of the amsrice03 field validation campaign for advanced microwave scanning radiometer amsr e sea ice products from nasa earth observing systems satellite aqua are analyzed and compared to p 3 polarimetric scanning radiometer psr data a proxy for amsr e brightness temperatures the approach taken in the analysis is geostatistical characterization various functions of first and second order are calculated for the snow depth profiles then geostatistical classification parameters are extracted and combined into feature vectors on which the characterization is based the complexity of sea ice requires a generalization of the method by introduction of the hyperparameter concept results include a quantitative characterization of sea ice provinces from field transects in the beaufort sea chukchi sea and elson lagoon which represent a good subset of arctic sea ice types an internal segmentation of the longer profiles and a derivation of surface roughness length and of sea ice type complexity psr data reflect complexity of spatial snow depth structures as captured in multidimensional feature vectors and less directly snow depth and surface roughness length these results indicate that passive microwave data in general may be affected by spatial snow depth and surface roughness with a dependence on scale and quantified by geostatistical classification

formation of si al mg ca rich zoned magnetite in an end permian phreatomagmatic pipe in the tunguska basin east siberia magma sediment interactions in the evaporite rich tunguska basin resulted in the formation of numerous phreatomagmatic pipes during emplacement of the siberian traps the pipes contain magnetite apatite deposits with copper and celestine mineralization we have performed a detailed petrographic and geochemical study of magnetite from long cores drilled through three pipe breccia structures near bratsk east siberia the magnetite samples are zoned and rich in si 5 3 wt sio2 ca al and mg they exhibit four textural types 1 massive ore in veins 2 coating on breccia clasts 3 replacement ore and 4 reworked ore at the crater base the textural types have different chemical characteristics breccia coating magnetite has relatively low mg content relative to si as compared to the other groups and appears to have formed at lower oxygen fugacity time series analyses of mgo variations in microprobe transects across si bearing magnetite in massive ore indicate that oscillatory zoning in the massive ore was controlled by an internal self organized process we suggest that hydrothermal fe rich brines were supplied from basalt sediment interaction zones in the evaporite rich sedimentary basin leading to magnetite ore deposition in the pipes hydrothermal fluid composition appears to be controlled by proximity to dolerite fragments temperature and oxygen fugacity magnetite from the pipes has attributes of iron oxide apatite deposits e g textures oscillatory zoning association with apatite and high si content but has higher mg and ca content and different mineral assemblages these features are similar to magnetite found in skarn deposits we conclude that the siberian traps related pipe magnetite deposit gives insight into the metamorphic and hydrothermal effects following magma emplacement in a sedimentary basin

documenting surface magmatic activity at mount etna using atsr remote sensing analysis of thermally generated night time volcanic radiances recorded with a 1 km pixel size at 1 6 and 11 m during 1991 1993 and 1996 1999 for mount etna shows that lava flows extending beyond the summit craters can be distinguished from vent activity the two phenomena plot in different regions of feature space when the mean volcanic radiance per anomalous pixel at 11 m is plotted against the mean volcanic radiance at 1 6 m the distinct feature space characteristics of lava flow fields are apparent within 1 2 days of the onset of each effusive event such a plot also enables lava flow fields being fed by open channels to be distinguished from tube fed flow fields rank order analysis of the total 1 6 m volcanic radiance series shows that vent activity and lava flows belong to different populations and offers further scope for remotely identifying changes in eruptive state

the 2010 ash emissions at the summit craters of mt etna relationship with seismo acoustic signals 1 mt etna volcano italy typically generates lava fountains and strombolian eruptions from the summit craters producing significant emissions of tephra which may cause moderate to high impact both in the atmosphere and on the ground however we have also witnessed a number of minor ash emissions that although far less powerful may pose considerable volcanic hazards in this paper we deal with three ash emissions occurring in 2010 8 april at southeast crater 25 august at bocca nuova and 14 15 november at northeast crater correlating their volcanological features with the associated seismo acoustic signals we provide details regarding the chronology eruption column dispersal of the deposit and texture grain size componentry and morphology of the emitted ash each eruptive episode has also been characterized by means of seismo acoustic analyses evaluating the volcanic acoustic seismic ratio vasr furthermore the source of volcanic tremor recorded from march to december 2010 was localized the joint volcanological and seismo acoustic analyses allowed distinguishing two main kinds of ash emissions types a 8 april and 25 august and b 14 15 november regarding the former the accumulation of gas below a dense cap rock obstructing the conduit vent giving rise with the uncorking to impulsive explosivity was hypothesized the latter type instead is characterized by a longer lasting and less explosivity likely due to the existence of open conduit conditions therefore type b ash emissions are less hazardous than type a this simple model regarding minor explosive activity may constitute a starting point to assess the volcanic risk from unexpected explosions

organic inclusions in salt part 3 oil and gas inclusions in cambrian evaporite deposit from east siberia a contribution to the understanding of nitrogen generation in evaporites abstract halite in cambrian kcl deposits from the southern part of the siberian platform which have been thermally overprinted by dolerite intrusions commonly contains inclusions dominantly composed of co2 and less commonly host inclusions composed of hydrocarbons four types of hydrocarbon inclusions have been identified in samples taken from locations devoid of dolerite intrusions these are 1 monophase gaseous inclusions i e n2 ch4 or n2 ch4 2 aliphatic oil inclusions 3 two phase l1 l2 hydrocarbon brine inclusions and 4 n2 hydrocarbon inclusions the area where the n2 rich inclusions occur is associated with ammonium free k chlorides by comparing different types of k salt environments the origin of the nitrogen could be identified first ammonium ions are produced by deamination of organic matter and stored in k chlorides and thereafter n2 is released from nh4 k minerals by oxidation in zones rich in iron oxides and or by 40k radiolysis

magma supply path beneath mt asama volcano japan 1 obtaining a sharp image of magma supply path through dense geophysical observations is important for forecasting time and magnitude of hazardous future eruptions here we reveal a clear magma plumbing system using dense seismic and geodetic networks around mt asama central japan magma intrusions occurred several times beneath the western flank of mt asama forming a wnw ese directed zone with 1 km below sea level the eastern end of this zone connects a narrow vertical pathway extending right under the summit crater which erupted in 2004 monitoring magmatic activity with a well designed observational network is vital to mitigate future volcano hazards

mobilizing salt magma salt interactions salt sequences form an integral part of many sedimentary basins worldwide many of these basins have experienced igneous activity either syn or post deposition of the salt sequences despite this little work has so far been undertaken to understand magma salt interactions within the subsurface and how aspects such as salt halokinesis may be influenced by igneous activity within this paper we detail the first direct description of relationships and textures that are developed during intrusive igneous salt interaction we show that salt composition appears to play a dominant role in controlling where igneous intrusions invade laterally through salt sequences in a sedimentary basin in particular we illustrate that hydrous salts such as carnallite act as preferential horizons for lateral magma intrusion this lithological control appears primarily related to the heating and subsequent dehydration reaction of carnallite which causes the carnallite to behave as viscous fluidal horizons resulting in the non brittle emplacement of magma and spectacular peperitic salt magma mingling textures we suggest that heating and transformation of carnallite and other hydrous salts into viscous fluidal horizons during igneous intrusion within a regional salt sequence may act as a possible trigger for contemporaneous halokinesis by creating fluid like viscous detachment layers over longer time scales however a solidified rigid boxwork of dikes and sills may create zones of increased mechanical strength that will locally inhibit further salt flow

snow dunes a controlling factor of melt pond distribution on arctic sea ice 1 the location of snow dunes over the course of the ice growth season 2007 08 was mapped on level landfast first year sea ice near barrow alaska landfast ice formed in mid december and exhibited essentially homogeneous snow depths of 4 6 cm in mid january by early february distinct snow dunes were observed despite additional snowfall and wind redistribution throughout the season the location of the dunes was fixed by march and these locations were highly correlated with the distribution of meltwater ponds at the beginning of june our observations including ground based light detection and ranging system lidar measurements show that melt ponds initially form in the interstices between snow dunes and that the outline of the melt ponds is controlled by snow depth contours the resulting preferential surface ablation of ponded ice creates the surface topography that later determines the melt pond evolution

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

sea ice roughness from airborne lidar profiles light detection and ranging lidar data acquired during the amsr ice03 arctic flights are used to observe and characterize the spectral behavior of sea ice roughness height distributions and roughness spectral densities are derived from surface profiles measured over a variety of sea ice types the spectral densities are fit to lorentzian curves to obtain the correlation length and root mean square height of roughness within the sampling bandpass of the lidar profiler the utilization of these spectral parameters outside of their bandpass is also discussed

riphean basins of the central and western siberian platform abstract the siberian platform is unique by its volume of meso neoproterozoic sedimentary deposits for about one billion years 1650 650 ma several sedimentary basins were developed here resulting in the formation of several kilometers thickness of sedimentary cover the riphean mesoproterozoic lower neoproterozoic rocks are exposed mainly along platform peripheries the most complete sections are represented by several megacycles each megacycle contains terrigenous series at the base and carbonate formations in the upper part several isolated and anisochronous basins were created during the riphean on the territory of east siberia some of them were intracratonic others were developed on passive margins neoproterozoic orogeny along the platform boundaries resulted in re organization of the siberian basins with extensive faulting uplifting and erosion of the territories in eastern siberia riphean series contain large hydrocarbon accumulations the reservoirs were formed mainly due to fracturing and leaching of carbonate strata e g vugular carbonates of the pre vendian weathering crust the upper proterozoic deposits are overlain by thick clayey carbonate and saliferous carbonate series of the upper vendian and cambrian isolating them from the upper sedimentary cover the riphean basins contained thick organic rich clayey and clayey carbonate in some of them a hydrocarbon generation maximum took place at the end of the riphean the pre vendian erosion has removed a significant volume of riphean sediments during this time a majority of already formed hydrocarbon accumulations have been lost or degraded remaining riphean series have generated hydrocarbons during the paleozoic despite its complex history the riphean is still considered highly prospective with source rocks developing at multiple levels and reservoirs occurring in both carbonate and clastic rocks discoveries of new oil and gas fields in east siberia are likely but will depend on integration of detailed seismic data and a large volume of core data for the correct prognosis of riphean reservoir distribution

snow depth and ice thickness measurements from the beaufort and chukchi seas collected during the amsr ice03 campaign in march 2003 a field validation campaign was conducted on the sea ice near barrow ak the goal of this campaign was to produce an extensive dataset of sea ice thickness and snow properties depth and stratigraphy against which remote sensing products collected by aircraft and satellite could be compared chief among these were products from the polarimetric scanning radiometer psr flown aboard a nasa p 3b aircraft and the aqua advanced microwave scanning radiometer for the earth observing system amsr e the data were collected in four field areas three on the coastal sea ice near barrow ak and the fourth out on the open ice pack 175 km northeast of barrow the snow depth ranged from 9 4 20 8 cm in coastal areas n 9881 for three areas with the thinnest snow on ice that had formed late in the winter out in the main pack ice the snow was 20 6 cm deep n 1906 the ice in all four areas ranged from 138 219 cm thick n 1952 with the lower value again where the ice had formed late in the winter snow layer and grain characteristics observed in 118 snow pits indicated that 44 of observed snow layers were depth hoar 46 were wind slab snow and ice measurements were keyed to photomosaics produced from low altitude vertical aerial photographs using these and a distinctive three way relationship between ice roughness snow surface characteristics and snow depth strip maps of snow depth each about 2 km wide were produced bracketing the traverse lines these maps contain an unprecedented level of snow depth detail against which to compare remote sensing products the maps are used in other papers in this special issue to examine the retrieval of snow properties from the psr and amsr e sensors

recent seismicity and tomographic modeling of the mount etna plumbing system the monitoring of seismic activity in eastern sicily southern italy has been recently improved in the framework of the poseidon project to investigate both tectonics and volcanic processes of mount etna this effort has produced a homogeneous and complete data set which we use to image the deep structure of the volcano and to define the space and time distribution of the recent seismicity encompassing the 1995 eruption diffuse eruptions between 1995 and 1997 a further magma intrusion started in 1997 and an increase of volcanic activity in july 1998 we inverted p wave arrival times from 307 selected local earthquakes to obtain a three dimensional velocity model of the volcano with a simultaneous inversion for hypocenters and velocity parameters the new tomographic images permit us to define the structure beneath the volcano from the surface down to 18 km depth the main structural feature revealed by our inversion is a high velocity body located beneath the central craters whose lateral extent increases from 6 km between 18 and 9 km depth to 12 km between 9 and 3 km depth near the surface the fast anomaly branches in two separate high vp regions which are located below the summit craters and the eastern flank valle del bove respectively the high velocity features are interpreted as high density cumulates of solidified magma that intruded the shallow crust we hypothesize that magma ascends the crust within the relatively small high velocity conduit below 9 km depth and is stored at depth shallower than 9 km within the broad high velocity region as also suggested by petrological data a sharp increase of seismicity in 1997 with earthquakes occurring at the border of the high velocity body suggests that mount etna sustained recent episodes of intrusions which possibly herald future eruptions no large low velocity anomaly interpretable as a melted magma chamber is imaged in the upper 18 km of the crust while a broad low velocity anomaly in the uppermost mantle revealed by regional seismic data possibly indicates the magma source region at depth earthquake occurrence from the deep source to the shallow intrusive area helps to trace the magma migration and the feeding of the volcanic system

a first assessment of icebridge snow and ice thickness data over arctic sea ice we present a first assessment of airborne laser and radar altimeter data over snow covered sea ice gathered during the national aeronautics and space administration operation icebridge mission we describe a new technique designed to process radar echograms from the university of kansas snow radar to estimate snow depth we combine icebridge laser altimetry with radar derived snow depths to determine sea ice thickness results are validated through comparison with direct measurements of snow and ice thickness collected in situ at the danish greenarc 2009 sea ice camp located on fast ice north of greenland the icebridge instrument suite provides accurate measurements of snow and ice thickness particularly over level ice mean icebridge snow and ice thickness agree with in situ measurements to within 0 01 and 0 05 m respectively while modal snow and ice thickness estimates agree to within 0 02 and 0 10 m respectively icebridge snow depths were correlated with in situ measurements r 0 7 for an averaging length of 55 m the uncertainty associated with the derived icebridge sea ice thickness estimates is 0 40 m the results demonstrate the retrieval of both first year and multiyear ice thickness from icebridge data the airborne data were however compromised in heavily ridged ice where snow depth and hence ice thickness could not be measured techniques developed as part of this study will be used for routine processing of icebridge retrievals over arctic sea ice the limitations of the greenarc study are discussed and recommendations for future validation of airborne measurements via field activities are provided

seismic source mechanism of degassing bursts at kilauea volcano hawaii results from waveform inversion in the 10 50 s band the current march 2008 to february 2009 summit eruptive activity at kilauea volcano is characterized by explosive degassing bursts accompanied by very long period vlp seismic signals we model the source mechanisms of vlp signals in the 10 50 s band using data recorded for 15 bursts with a 10 station broadband network deployed in the summit caldera to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account the vlp signals associated with the bursts originate in a source region 1 km below the eastern perimeter of halemaumau pit crater the observed waveforms are well explained by the combination of a volumetric component and a vertical single force component for the volumetric component several source geometries are obtained which equally explain the observed waveforms these geometries include 1 a pipe dipping 64 to the northeast 2 two intersecting cracks including an east striking crack dike dipping 80 to the north intersecting a north striking crack another dike dipping 65 to the east 3 a pipe dipping 58 to the northeast intersecting a crack dipping 48 to the west southwest and 4 a pipe dipping 57 to the northeast intersecting a pipe dipping 58 to the west southwest using the dual crack model as reference the largest volume change obtained among the 15 bursts is 24 400 m3 and the maximum amplitude peak to peak of the force is 20 gn each burst is marked by a similar sequence of deflation and inflation trailed by decaying oscillations of the volumetric source the vertical force is initially upward synchronous with source deflation then downward synchronous with source reinflation followed by oscillations with polarity opposite to the volumetric oscillations this combination of force and volume change is attributed to pressure and momentum changes induced during a fluid dynamic source mechanism involving the ascent expansion and burst of a large slug of gas within the upper 150 m of the magma conduit as the slug expands upon approach to the surface and more liquid becomes wall supported by viscous shear forces the pressure below the slug decreases inducing conduit deflation and an upward force on the earth the final rapid slug expansion and burst stimulate vlp and lp oscillations of the conduit system which slowly decay due to viscous dissipation and elastic radiation consideration of the fluid dynamic arguments leads us to prefer the dual crack vlp source model as it is the only candidate model capable of producing plausible values of length scales and pressure changes the magnitudes of the vertical forces observed in the 15 bursts appear consistent with slug masses of 104 to 106 kg

potential for airborne offbeam lidar measurements of snow and sea ice thickness 1 this article discusses the capabilities and limitations of a new approach to airborne measurements of snow and sea ice thickness such measurements can help better understand snow and sea ice processes and can also contribute to the validation of satellite measurements the approach discussed here determines physical snow and sea ice thickness by observing the horizontal spread of lidar pulses the bright halo observed around an illuminated spot extends farther out in thicker layers because photons can travel longer without escaping through the bottom since earlier studies suggested the possibility of such sea ice retrievals this article presents a theoretical analysis of additional uncertainties that arise in airborne observations of snow and sea ice snow and sea ice retrievals pose somewhat different challenges because while sea ice is usually much thicker snow contains a much higher concentration of scatterers as a result sea ice halos are larger but snow halos are brighter the results indicate that airborne sea ice retrievals are possible at night and that snow retrievals are possible during both night and day for snow thicknesses less than about 50 cm observational issues such as calibration uncertainty can cause retrieval uncertainties on the order of 10 in 1 km resolution retrievals for moderate snow and sea ice thicknesses 30 cm and 3 m respectively these issues cause similar 10 uncertainties in sea ice thickness retrievals as well these results indicate that offbeam lidars have the potential to become an important component of future snow and sea ice observing systems

abrupt warming in the latest permian detected using high resolution in situ oxygen isotopes of conodont apatite from abadeh central iran abstract climate warming probably as a result of massive degassing of greenhouse gases from the siberian traps magmatism has often been acclaimed as a major cause of the end permian mass extinction indeed several studies have documented a sudden rise in seawater temperatures during the latest permian earliest triassic as evidenced by oxygen isotopic records measured on conodont apatite however whether such a rapid increase in seawater temperatures occurred before during or after the mass extinction remains controversial moreover the pattern of this rise in seawater temperatures and its timing relative to the latest permian earliest triassic carbon cycle disruption mass extinction as well as the siberian traps magmatism still need to be rigorously examined in various regions in this study we present high resolution oxygen isotopic records of conodont apatite 18oapatite from the upper permian lowermost triassic interval at the abadeh section central iran that are analyzed with in situ secondary ion mass spectrometry sims method the 18oapatite results from abadeh demonstrate a clear pattern consisting of three phases 1 from the lower wuchiapingian clarkina dukouensis zone to the end permian mass extinction horizon 18oapatite values are relatively stable fluctuating in the range of 18 28 20 15 with an average of 19 44 2 18oapatite value remains high as 19 26 at the mass extinction horizon above this horizon a sudden decrease occurs in the clarkina hauschkei zone and reaches a low value of 17 05 close to the permian triassic boundary 3 in the lowermost triassic 18oapatite values maintain a low baseline in the range of 16 92 17 39 with an average of 17 11 overall the most dramatic change in 18oapatite values i e a decrease of 2 converting into an abrupt warming of 10 c occurred above the mass extinction horizon and below the permian triassic boundary at abadeh the abadeh 18oapatite record is consistent with previous results documented in south china iran and armenia in terms of the timing and magnitude of a substantial warming and therefore represents a global signature if applying the high precision temporal framework established in the well dated meishan gssp section to abadeh the abrupt warming of 10 c took only a maximum duration of 37 kyr thousand years by projecting the carbon cycle change temperature rise mass extinction at the abadeh and meishan sections and the temporal evolution of the siberian traps magmatism onto a unified timescale the temporal correlation strongly suggests that the switch from dominantly extrusive eruptions to widespread sill intrusions is probably the most annihilating phase of the siberian traps magmatism and is temporally consistent with the end permian mass extinction

sediment transport by sea ice in the chukchi and beaufort seas increasing importance due to changing ice conditions abstract sediment laden sea ice is widespread over the shallow wide siberian arctic shelves with off shelf export from the laptev and east siberian seas contributing substantially to the arctic ocean s sediment budget by contrast the north american shelves owing to their narrow width and greater water depths have not been deemed as important for basin wide sediment transport by sea ice observations over the chukchi and beaufort shelves in 2001 02 revealed the widespread occurrence of sediment laden ice over an area of more than 100 000 km2 between 68 and 74 n and 155 and 170 w ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed multiple layers of rafted nilas indicative of a flaw lead environment adjacent to the landfast ice of the chukchi and beaufort seas this is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern chukchi sea in february of 2002 as well as formation of sediment laden ice along the beaufort sea coast as far eastward as the mackenzie shelf moored upward looking sonar on the mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment analysis of radarsat synthetic aperture sar imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment 20 m for the chukchi sea sediment loads averaged at 128 t km 2 with sediment occurring in layers of roughly 0 5 m thickness mostly in the lower ice layers the total amount of sediment transported by sea ice mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment is at minimum 4 106 t in the sampling area and is estimated at 5 8 106 t over the entire chukchi and beaufort shelves in 2001 02 representing a significant term in the sediment budget of the western arctic ocean recent changes in the chukchi and beaufort sea ice regimes reduced summer minimum ice extent ice thinning reduction in multi year ice extent altered drift paths and mid winter landfast ice break out events have likely resulted in an increase of sediment laden ice in the area apart from contributing substantially to along and across shelf particulate flow an increase in the amount of dirty ice significantly impacts sub ice algal production and may enhance the dispersal of pollutants

imaging the multi level magma reservoir at mt etna volcano italy 1 the continuous gps network operating on mt etna with its 36 stations is currently one of the largest worldwide the aim of this network is the evaluation of volcanic hazard and the modelling of the active sources in this paper we propose an in depth analysis and modelling of continuous gps data collected at mt etna from may 2008 to december 2010 the analyzed period has been divided into four different coherent phases 1 14 may 2008 02 august 2008 deflation of the entire gps network 2 02 august 2008 14 june 2009 deflation of the summit area and inflation at lower heights 3 14 june 2009 21 may 2010 inflation of the entire gps network 4 21 may 2010 31 december 2010 inflation at medium and low heights and end of the inflation in the summit area analytical models indicate a non uniform deformation style revealing spaced sources acting at different time on different segments of a multi level magma reservoir the etnean plumbing system imaged here is depicted as an elongated magma reservoir that extends from the volcano body downwards to about 6 5 km below sea level b s l sloping slightly towards the north west with storage volumes located at about 6 5 2 0 and 0 0 km b s l the changes in position of the modelled pressure sources during the analyzed time intervals indicate that throughout the 2008 eruptive period the deformation field was mostly driven by the upward migration of magma on the other hand the pattern of deformation recorded after the end of the eruption strongly suggests a significant contribution of the magma overpressure generated by the gas boiling thus outlining the importance of volatiles content in magma

new constraints on the age geochemistry and environmental impact of high arctic large igneous province magmatism tracing the extension of the alpha ridge onto ellesmere island canada

the riphean sedimentary basins of the eastern siberia province and their petroleum potential abstract from their location in the regional pattern of the eastern siberia province their style and their evolutionary history the riphean sedimentary basins are divided into two groups marginal cratonic and intracratonic the first group includes basins of pericratonic troughs fore deeps and marginal transverse aulacogens they are characterized by a definite division into structural stages according to both characteristics of the individual formations and interbedding of rocks with different lithology within sequences there is a complex combination of formations such as black shale and flyschlike volcanoclastic terrigenous carbonate and others the second group incorporates aulacogenic and platform intracratonic sedimentary basins the main features of aulacogen type sedimentary basin structure are due to their rift origin and style of subsequent development the early stages are marked by an alternation of volcanoclastic terrigenous and volcanoclastic carbonate rocks there is rythmic interbedding of terrigenous and terrigenous carbonate rocks up section depositional environments in sedimentary basins of platform depression have been controlled to a large extent by the structural dynamic setting of the final stages in the formation of adjacent pericratonic troughs and intracratonic aulacogens the succession consists mainly of terrigenous carbonate and carbonate terrigenous units i e products of erosion and re deposition of early riphean complexes and ancient basement distribution of particulate organic matter and its catagenetic transformation indicate rather high petroleum generating potential for the riphean regional development of high quality seals upper vendian argillaceous evaporite carbonate units and lower cambrian salts greatly favors preservation of hydrocarbon accumulation three groups of hydrocarbon reservoirs are differentiated based on structural tectonic lithologic formational and geochemical features hydrocarbon fields of considerable commercial importance have been discovered for the first time in world exploration practice in the riphean of the east siberian province these should lead to the re evaluation of the hydrocarbon potential of late proterozoic basins on other continents

spherical and ellipsoidal volcanic sources at long valley caldera california using a genetic algorithm inversion technique abstract we model the second inflation period at long valley caldera california using a genetic algorithm technique and high quality geodetic measurements of elevation changes and baseline extensions we compare two source inversions for both spherical mogi point sources and the finite prolate ellipsoid of yang and davis a sensitivity analysis for the genetic algorithm is performed based upon synthetic data set inversions on similar sources in order to better constrain the areal location orientation and volume of the potential sources the spherical sources are well constrained the larger located at 9 9 km beneath the resurgent dome with a volume of 0 036 km 3 while the second at only 0 008 km 3 is located at a depth of 7 3 km beneath the south moat the depths to the ellipsoidal sources are switched with the larger source at a depth of 9 6 km and the smaller at 11 8 km with volumes of 0 037 and 0 002 km 3 respectively

a comparison of pyrolysis products with models for natural gas generation abstract hydrous pyrolysis using progressive heating from 150 to 365 c is used to study the generation and isotopic composition of hydrocarbon gases and carbon dioxide different source rocks from the draupne heather dunlin and brent formations in the north sea a miocene brown coal from germany a coal from the middle jurassic ness formation in the northern north sea and a rich marine type source from the late jurassic kimmeridge clay formation onshore uk are studied the experimental results are related to vitrinite reflectance as a maturity reference parameter and to existing models for natural gas generation hydrous pyrolysis simulates the observed isotopic composition of natural systems fairly closely the largest deviations are found for methane which is most sensitive to fractionation effects the obtained results mainly reflect variations in source rock type and initial isotopic composition different maturity dependent trends are found between coal derived and marine type ii derived gases trends in the experimental data fit well with basic assumptions of existing models for natural gas generation

performance of the radial semblance method for the location of very long period volcanic signals we investigate the performance of a source location method that com bines multichannel semblance and particle motions and is being increasingly used to obtain estimates of the source locations of very long period vlp seismic signals recorded on volcanoes the method makes use of the radial particle motions and large wavelengths that characterize the vlp events to assess the capabilities of this radial semblance method and to better understand its limitations we quantify the effects of window length noise contents of the signal inaccurate velocity models receiver coverage and orientation errors in the horizontal components of the receiv ers our results show that the semblance method performs best when 1 the noise level is low enough to allow a good characterization of the waveforms 2 the sources are located at distances between one half of the average receiver spacing and about two times the network aperture and 3 the orientations of the horizontal components of the seismometers are known with relative accuracy when these requirements are met the radial semblance method constitutes an adequate tool to obtain preliminary locations of vlp volcanic signals recorded by broadband networks moreover we provide a formula to determine the radial semblance level that should be used to define error regions associated to the estimated source locations

an accurate and efficient method for including the effects of topography in three dimensional elastic models of ground deformation with applications to radar interferometry topography has a large effect on the results predicted by elastic surface deformation models in regions of significant relief in some cases topography may have more influence on the predicted deformation field than do model source parameters we have developed an approximate analytical technique for including topographic effects that retains most of the computational simplicity of elastic half space models while providing an accurate representation of topographic effects we use a series expansion of the elastic half space solution with a small slope approximation yielding a set of higher order corrections the integrated effect of these corrections is evaluated using fourier methods we investigate the effectiveness of our method by comparing predicted results for a tilted triaxial ellipsoid with those predicted by finite element models the resulting displacements and displacement gradients are in good agreement with finite element results both for relatively smooth topography synthetically generated and for the greater relief in the vicinity of mount etna volcano we then compare the results of our method with those predicted by traditional elastic half space models using different reference elevations and with a previously proposed method of estimating topographic effects our new method provides a significantly better fit to the finite element results than do the other methods our method is able to accurately portray both the number and the horizontal pattern of fringes in a synthetic interferogram when compared with finite element results in particular the method accurately represents the broadening of fringes that is observed in regions of high relief as well as reproducing the location of the fringe center and the topographically induced deviation of the fringes from a regular pattern elastic half space models typically show a fringe center that is displaced with respect to the finite element results indicating that parameter inversions based on such a model would provide incorrect estimates of the horizontal source position the lack of topographically generated fringe distortions in elastic half space results would also likely lead to inaccuracies in the predicted magnitude and orientation of proposed deformation sources our new technique over comes these limitations and should be useful when evaluating either traditional geodetic results or the greater areal coverage provided by interferometric observations

the basalt pipes of the tunguska basin siberia russia high temperature processes and volatile degassing into the end permian atmosphere abstract a number of mechanisms have been proposed to explain the end permian crisis many of them explore the link between this catastrophe and the siberian traps we test the hypothesis that eruption of thermogenic gas generated in contact aureoles around igneous sills intruded into evaporite sequences of the tunguska basin triggered the crisis in particular we test the idea that the aspect that breccia pipes represent conduits for voluminous gas migration from the deep basins to the atmosphere this contribution sheds new light on the pipe formation based on new field and borehole observations and electron microscopy analyses of more than three hundred mapped magnetite bearing basalt pipes 43 are classified as diatremes the diatremes are usually circular or elliptical with multiple zones of brecciation reaching the surface sometimes with preserved in filled crater lakes the pipe diameter on the surface varies from a few tens of meters for small single diatremes to about a kilometer the largest crater lake area is 2 7 km 2 we have conducted a detailed study of the breccias in the sholokhovsk basalt pipe located within the nepa potash deposit in the tunguska basin siberia russia about n 59 and e 107 and find that the breccias are cemented by carbonate matrix calcite dolomite and halite breccia clasts are altered at various temperatures evidenced by growth of albite and garnet from basaltic glass and diopside garnet magnetite and chlorine bearing amphibole up to 1 8 cl in altered magmatic clasts these mineral assemblages suggest high temperature interactions with evaporites within the pipe conduits the large number of pipes support that degassing of halogen rich volatiles was a widespread and violent process with implications for the end permian crisis

gas burst vs gas rich magma recharge a multidisciplinary study to reveal factors controlling triggering of the recent paroxysmal eruptions at mt etna abstract since january 2011 mt etna volcano has been affected by more than forty paroxysmal eruptions at the summit new south east crater nsec on the basis of their very variable duration seven eruptions have been selected among the twenty five of 2011 2012 in order to decipher potential differences in their triggering mechanism paroxysms have been investigated through a multidisciplinary approach that integrates data from volcanic tremor and petrology textures and micro analysis on plagioclase crystals our results lead to the conclusion that close relationships exist between the duration of the eruptions and the temporal evolution of the volcanic tremor amplitude especially during the strombolian phase preceding the paroxysmal activity in this regard we distinguished 1 paroxysms preceded by long lasting initial strombolian phases characterized by low rate of volcanic tremor amplitude increase and 2 eruptions preceded by short initial strombolian phases showing high rate of volcanic tremor amplitude increase based on the pattern of volcanic tremor amplitude increase the former mainly showed a ramp shaped morphology while the latter a bell shaped trend location of the volcanic tremor centroid during the quiescent intervals between the paroxysmal eruptions has highlighted the presence of a magmatic volume at 1 2 km a s l beneath the north east crater nec during the syn eruptive strombolian and lava fountaining phases the centroid of volcanic tremor migrates below the nsec this leads to the consideration that the magma batch residing beneath nec played an important role in the volcanic activity at nsec during the considered period also the textures and compositional zoning anorthite and iron variations in selected plagioclase crystals of the analyzed lavas suggest relations between duration of the paroxysms and dynamics of pre eruptive magmatic processes at depth particularly two mechanisms have been accounted for triggering of eruptions at the nsec on the basis of the concordant or discordant behavior of anorthite and iron in plagioclase coupled with disequilibrium textures at the rim concordant anorthite and iron increases in plagioclase crystals with sieve textured rims indicate recharge by more mafic gas rich magma this textural compositional behavior has been related to long lasting eruptions whose volcanic tremor amplitude evolution produced ramp shaped increase of the volcanic tremor amplitude before the paroxysmal phase on the contrary crystals with sieve textures at the rim characterized by increasing iron at rather constant or decreasing anorthite suggest the prominent role of gas injections into the residing system in this instance the compositional behavior has been linked with short lasting eruptions whose volcanic tremor amplitude evolution led to a sudden increase of the seismic amplitude before the climax of the eruption thus our work put forward the idea that the evolution and duration of the strombolian phase preceding the paroxysmal eruptions of 2011 2012 at mt etna are strongly controlled by the eruption triggering mechanism which can be either gas burst or gas rich magma recharge

multiparametric study of the february april 2013 paroxysmal phase of mt etna new south east crater european fp7 med suv mediterranean supersite volcanoes grant number 308665 european research council european fp7 fp 2007 2013 erc grant number 279802 sigma sistema integrato di sensori in ambiente cloud per la gestione multirischio avanzata

gas slug ascent through changes in conduit diameter laboratory insights into a volcano seismic source process in low viscosity magmas seismic signals generated during the flow and degassing of low viscosity magmas include long period lp and very long period vlp events whose sources are often attributed to dynamic fluid processes within the conduit we present the results of laboratory experiments designed to investigate whether the passage of a gas slug through regions of changing conduit diameter could act as a suitable source mechanism a vertical liquid filled glass tube featuring a concentric diameter change was used to provide canonical insights into potentially deep or shallow seismic sources as gas slugs ascend the tube we observe systematic pressure changes varying with slug size liquid depth tube diameter and liquid viscosity gas slugs undergoing an abrupt flow pattern change upon entering a section of significantly increased tube diameter induce a transient pressure decrease in and above the flare and an associated pressure increase below it which stimulates acoustic and inertial resonant oscillations when the liquid flow is not dominantly controlled by viscosity net vertical forces on the apparatus are also detected the net force is a function of the magnitude of the pressure transients generated and the tube geometry which dictates where and hence when the traveling pressure pulses can couple into the tube in contrast to interpretations of related volcano seismic data where a single downward force is assumed to result from an upward acceleration of the center of mass in the conduit our experiments suggest that significant downward forces can result from the rapid deceleration of relatively small volumes of downward moving liquid

an investigation into shallow borehole tiltmeters shallow borehole tiltmeters are frequently used for ground deformation monitoring in volcanic areas where they are usually installed within a few meters of the surface a major problem concerns the noise affecting the installation at shallow depth where large tilt and strain are caused by temperature effects the long term stability of these instruments and the best shallow depth of installation in terms of best cost benefit are the crucial points we conducted an experiment in order to compare the signals of three shallow borehole electronic tiltmeters installed in the same place at different depths we verified the signal reliability in revealing the long term slow deformation and looked into the reduction of the temperature effects with depth we present three years of data and discuss the limits and the advantages of the different installation depths

spatial variability of barrow area shore fast sea ice and its relationships to passive microwave emissivity aircraft acquired passive microwave data laser radar height observations radarsat synthetic aperture radar imagery and in situ measurements obtained during the amsr ice03 experiment are used to investigate relationships between microwave emission and ice characteristics over several space scales the data fusion allows delineation of the shore fast ice and pack ice in the barrow area ak into several ice classes results show good agreement between observed and polarimetric scanning radiometer psr derived snow depths over relatively smooth ice with larger differences over ridged and rubbled ice the psr results are consistent with the effects on snow depth of the spatial distribution and nature of ice roughness ridging and other factors such as ice age apparent relationships exist between ice roughness and the degree of depolarization of emission at 10 19 and 37 ghz this depolarization would yield overestimates of total ice concentration using polarization based algorithms with indications of this seen when the nt 2 algorithm is applied to the psr data other characteristics of the microwave data such as effects of grounding of sea ice and large contrast between sea ice and adjacent land are also apparent in the psr data overall the results further demonstrate the importance of macroscale ice roughness conditions such as ridging and rubbling on snow depth and microwave emissivity

long term dynamics of piton de la fournaise volcano from 13 years of seismic velocity change measurements and gps observations we study the piton de la fournaise pdf volcano dynamics through the observation of continuous seismic velocity changes from 2000 to 2013 we compute the cross correlations of ambient seismic noise recorded at more than 30 short period and broadband stations of the undervolc temporary seismic experiment and of the pdf volcano observatory network the velocity changes are estimated from the travel time delay measured on the cross correlations computed between pairs of stations we average the relative velocity changes for all pairs of stations and obtain a time series of the velocity change of piton de la fournaise volcano over 13 years from the period 0 5 to 4 s the depth sensitivity of the velocity change is ranging from approximately 100 m to 2500 m a slow decrease of velocity is measured from 2000 and ends with a major eruption that occurred in april 2007 this eruptive episode is followed by an increase of the velocity these long term changes are compared to the deformation of the piton de la fournaise edifice estimated from geodetic measurements an analysis of baseline change between gps stations indicates an inflation of the volcanic edifice prior to april 2007 followed by a deflation since then this deflation predominantly affects the terminal cone seismic velocity changes and deformation have similar long term trends with velocity decrease observed during inflation and velocity increase during deflation however the velocity change magnitude is about 2 orders of magnitude greater than the deformation this suggests nonlinear relation between velocity changes and deformation

contact metamorphism and thermogenic gas generation in the voring and more basins offshore norway during the paleocene eocene thermal maximum voluminous volcanic intrusive activity took place in the voring and more basins at the paleocene eocene boundary at about 56 ma this event caused thermal maturation of cretaceous sedimentary rocks in the basins we have estimated the resulting thermogenic gas generation potential from contact metamorphism using numerical simulations calibrated using borehole data the borehole 6607 5 2 from the utgard sill complex in the voring basin contains two c 100 m thick sills and is used as a case study we present both new and compiled data showing that 1 the bulk organic content is reduced towards the sill intrusions 2 a c 1 km thick stratigraphic interval is thermally affected based on vitrinite reflectance data 3 relative emplacement timing can affect the gas yield by up to 25 and 4 some of the thermogenic methane is still present in the aureoles the numerical model is calibrated using data from 11 wells we estimate that the total gas generation potential for the two utgard sills equals that of the troll field c 10 gt ch 4 the largest producing gas field offshore norway we show that in the voring and more basins the total gas generation potential is up to 1500 gt ch 4 c 1100 gt c even from the relatively organic poor cretaceous source rocks with c 1 wt organic carbon with implications for the carbon cycle at the paleocene eocene boundary

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

a new high resolution stratigraphic and palaeoenvironmental record spanning the end permian mass extinction and its aftermath in central spitsbergen svalbard abstract research on the permian triassic boundary ptb along the northern margins of pangaea exposed today in the arctic region has been heavily reliant on field observations where data resolution was consequently determined by outcrop condition and accessibility core drilling in central spitsbergen allowed for a near complete recovery of two 90 m cores through the ptb analyses of the core and nearby outcrops include stratigraphic logging and sampling xrf scanning petrography biostratigraphy isotope geochemistry and geochronology the first appearance datum fad of h parvus in svalbard places the base of the triassic ca 4 m above the base of the vikinghogda formation and ca 2 50 m above the end permian mass extinction epme and its associated sharp negative 13c the ptb therefore falls within the reduviasporonites chalastus assemblage zone in svalbard precise u pb tims dating of two zircon crystals in a tephra layer just above the first documented hindeodus parvus in svalbard gives an age of 252 13 0 62 ma high resolution palaeoenvironmental proxies including si kcps kilo counts per second zr rb k ti fe k and v cr indicate a transition towards a more arid climate in the earliest triassic contemporaneous with prolonged bottom water dysoxic anoxic conditions following an increase in volcanic activity in the late permian statistical analysis of zr rb k ti and v cr elemental ratios suggests that the system was impacted by long eccentricity 400 kyr cyclicity the 13c excursion in organic carbon 13corg record signals a large negative carbon isotope excursion cie associated with the mass extinction event but also records a second smaller negative cie ca 22 m above this interval this younger 13corg excursion correlates to similar cies in the dienerian late induan records of other sections notably in the tethys ocean which have been interpreted as recording a small biotic crisis during the post extinction recovery evidence of this negative cie in spitsbergen suggests that the dienerian crisis may have been global in extent the negative 13corg values are associated with evidence for dysoxia or anoxia in the core and the occurrence of tephra layers in the same interval suggests a possible connection between the dienerian crisis and a discrete episode of volcanic activity

how contact metamorphism can trigger global climate changes modeling gas generation around igneous sills in sedimentary basins abstract large volumes of greenhouse gases such as ch4 and co2 form by contact metamorphism of organic rich sediments in aureoles around sill intrusions in sedimentary basins thermogenic gas generation and dehydration reactions in shale are treated numerically in order to quantify basin scale devolatilization we show that aureole thicknesses defined as the zone of elevated metamorphism relative to the background level vary within 30 250 of the sill thickness depending on the temperature of the host rock and intrusion besides the sill thickness in shales with total organic carbon content of 5 wt ch4 is the dominant volatile 85 135 kg m3 generated through organic cracking relative to h2o generation from dehydration reactions 30 110 kg m3 even using conservative estimates of melt volumes extrapolation of our results to the scale of sill complexes in a sedimentary basin indicates that devolatilization can have generated 2700 16200 gt ch4 in the karoo basin south africa and 600 3500 gt ch4 in the voring and more basins offshore norway the generation of volatiles is occurring on a time scale of 10 1000 years within an aureole of a single sill which makes the rate of sill emplacement the time constraining factor on a basin scale this study demonstrates that thousands of gigatons of potent greenhouse gases like methane can be generated during emplacement of large igneous provinces in sedimentary basins

thinking about lips a brief history of ideas in large igneous province research abstract large igneous provinces lips are extraordinary igneous and tectonic events that have influenced the planet in profound ways including the major turnovers in the history of life the lip concept definitions and terminology first nucleated in a 1990 workshop jointly arranged by joint oceanographic institutions and u s science support program subsequently presented in a series of seminal papers by millard f coffin and olav eldholm in the early 1990 s they combined existing data and information from continental flood basalts with the emerging geophysical understanding of oceanic plateaus and rifted continental margins the new terminology had major implications within the geosciences and beyond however when investigating how geoscientists described and interpreted these vast provinces prior to the 1990 s we are left with a series of questions who first realized that lips represent extraordinary events in the history of the earth what terminology was used and why were geologists interested in this type of events here we discuss some of the key developments in lip research including mapping projects expeditions international programs correlations across continents and the history of the terminology we focus our discussion on four cases the karoo lip the siberian traps the north atlantic igneous province and the ontong java plateau comprising key examples of lips with long histories of study and exploration we conclude that the past 150 years of lip related research and endeavor was largely driven by a need to understand fundamental aspects of earth evolution including continental drift plate tectonic reconstructions the origin of basalt mantle processes and plumes and the role of volcanism in driving mass extinctions and climatic changes

reconstruction of subgrid scale topographic variability and its effect upon the spatial structure of three dimensional river flow a new approach to describing the associated topography at different scales in computational fluid dynamic applications to gravel bed rivers was developed surveyed topographic data were interpolated using geostatistical methods into different spatial discretizations and grain size data were used with fractal methods to reconstruct the microtopography at scales finer than the measurement subgrid scale the combination of both scales of topography was then used to construct the spatial discretization of a three dimensional finite volume computational fluid dynamics cfd scheme where the topography was included using a mass flux scaling approach the method was applied and tested on a 15 m stretch of solfatara creek wyoming united states using spatially distributed elevation and grain size data model runs were undertaken for each topography using a steady state solution this paper evaluates the impact of the model spatial discretization and additional reconstructed variability upon the spatial structure of predicted three dimensional flow the paper shows how microtopography modifies the spatial structure of predicted flow at scales finer than measurement scale in terms of variability whereas the characteristic scale of predicted flow is determined by the cfd scale changes in microtopography modify the predicted mean velocity value by 3 6 for a mesh resolution of 5 cm whereas a change in the computational scale modifies model results by 60 the paper also points out how the spatial variability of predicted velocities is determined by the topographic complexity at different scales of the input topographic model

volcanic processes detected by tiltmeters a review of experience on sicilian volcanoes abstract a review of the experience gained in the use of tiltmeters on mt etna stromboli and vulcano during the last 30 years is reported here tilt data represent a fundamental contribution towards understanding volcanic processes such as dike intrusions fracture propagation lava fountains and volume changes in magmatic or hydrothermal systems causing a deflation inflation of the edifice intrusive processes preceding lateral eruptions show large variations up to over 100 microradians while minor variations not exceeding 2 5 microradians are linked to lava fountains that form ash plumes and lead to fallout deposits that cause severe hazards to aviation high precision tilt also allows detecting the slight ground deformation linked to strombolian activity 0 01 0 2 microradians as well as co seismic variations 0 1 1 5 microradians and tidal effects 0 1 0 2 microradians that may have a role in the evolution of a volcanic system time amplitude tilt ranges linked to each process are generally different allowing to discriminate in real time between a signal associated to one process and another one this fact is important in terms of early warning particularly during the first phases of dikes propagation that precede a lateral eruption by hours days

continuous monitoring of soil co2 flux on mt etna the 2004 2005 eruption and the role of regional tectonics and volcano tectonics 1 the soil co2 flux on mt etna as recorded by the etnagas network an automatic system for measuring soil co2 flux and meteorological parameters started to increase strongly about 5 months prior to the onset of the 2004 2005 eruption and decreased a few months before the end of the eruption time delays in the occurrences of anomalies in soil co2 flux at different sites in the geochemical network constrain the relationship between soil co2 flux distributions and the tectonic framework of etna volcano the anomalies observed before the 2004 2005 eruption support the intrusion of new undegassed magma into the upper feeding system of the volcano 20 km below sea level magma subsequently rose slowly in the volcano conduits thereby triggering the onset of the 2004 2005 eruption the time delays in the occurrences of anomalies in combination with spectral analysis indicate the importance of tectonic and volcanotectonic structures in driving the ascent of deep gases within the crust moreover greatest amplitude pulsations of the low frequency components of the co2 flux signals were correlated with the paroxystic activities of the 2004 2005 eruption this study confirms that co2 flux variation is a useful indicator for volcanic activity in the surveillance of the mt etna and similar basaltic volcanoes

winter snow cover on the sea ice of the arctic ocean at the surface heat budget of the arctic ocean sheba temporal evolution and spatial variability 1 the evolution and spatial distribution of the snow cover on the sea ice of the arctic ocean was observed during the surface heat budget of the arctic ocean sheba project the snow cover built up in october and november reached near maximum depth by mid december then remained relatively unchanged until snowmelt ten layers were deposited the result of a similar number of weather events two basic types of snow were present depth hoar and wind slab the depth hoar 37 of the pack was produced by the extreme temperature gradients imposed on the snow the wind slabs 42 of the snowpack were the result of two storms in which there was simultaneous snow and high winds 10 m s 1 the slabs impacted virtually all bulk snow properties emphasizing the importance of episodic events in snowpack development the mean snow depth n 21 169 was 33 7 cm with a bulk density of 0 34 g cm 3 n 357 r2 of 0 987 giving an average snow water equivalent of 11 6 cm 25 higher than the amount record by precipitation gauge both depth and stratigraphy varied significantly with ice type the greatest depth and the greatest variability in depth occurring on deformed ice ridges and rubble fields across all ice types a persistent structural length in depth variations of 20 m was found this appears to be the result of drift features at the snow surface interacting with small scale ice surface structures a number of simple ways of representing the complex temporal and spatial variations of the snow cover in ice ocean atmosphere models are suggested

contact metamorphic devolatilization of shales in the karoo basin south africa and the effects of multiple sill intrusions abstract quantification of fluid generation during contact metamorphism of shale is important for the understanding of metamorphic processes fluid flow in sedimentary basins and perturbations of the global carbon cycle in this study we provide geochemical and numerical analyses from the organic rich ecca group in the karoo basin south africa which was affected by contact metamorphism from multiple sill intrusions in the early jurassic organic matter was efficiently converted to hydrocarbons during contact metamorphism and complete loss of organic carbon in the innermost aureole is common mineral dehydration reactions are evident from the occurrence of metamorphic minerals like biotite and loss of the clay fraction towards the intrusive contact we have developed a numerical model in order to quantify fluid production from both inorganic and organic reactions during contact metamorphism the modelling results are constrained by data from two case studies in the karoo basin in order to obtain reliable estimates of the carbon loss from metamorphism of shale we show that single thin 15 m thick sills have a gas production potential of several gigatons of methane ch4 if emplaced over a 1000 km2 area furthermore the vertical spacing between simultaneously emplaced sills has an important influence on the gas generation potential when two sills are emplaced with a vertical spacing of 7 times the intrusion thickness the total ch4 generation is up to 35 more than for two separate sills data and modelling from five sills emplaced within the ecca group show hydrocarbon generation throughout the organic rich section with total carbon loss next to the sills this has implications for the fluid production and metamorphism in volcanic basins where multiple sills are common

early cambrian seawater chemistry from fluid inclusions in halite from siberian evaporites abstract thirty nine samples of lower cambrian marine sedimentary halite with zoned primary fluid inclusions were analyzed using the umca method introduced by petrichenko 1973 petrichenko o i 1973 metody doslidzhennya u mineralakh galogennykh porid naukova dumka kyiv 91 pp in order to determine the contents of k mg 2 so 4 2 and ca 2 ions and to interpret the composition of parent seawater the analyzed samples were from the giant salt basin of eastern siberia where five major phases of salt deposition can be distinguished in the late vendian danilovo and early cambrian usolye belsk angara and litvintsevo basins our samples are all from early cambrian basins although the largest data set comes from the angara basin the results indicate that early cambrian parent seawater was similar in all studied basins and was characterized by lower mg 2 and so 4 2 and higher ca 2 concentrations relative to modern seawater the concentration of k in early cambrian seawater was similar to that of modern seawater accordingly the seawater in the entire early cambrian was ca 2 rich and so 4 2 poor the change of composition of seawater from so 4 2 rich ca 2 poor in the latest neoproterozoic to ca 2 rich so 4 2 poor recorded throughout the early cambrian probably occurred within a relatively short time span during the earliest cambrian nemakit daldynian time and caused a rise in ca 2 concentrations in the shelf seas leading to the onset of biocalcification and then the cambrian explosion

correlation of nearshore ice movement with seabed ice gouges near barrow alaska nearshore patterns of ice motion near barrow alaska were monitored between 1973 and 1979 with a sea ice radar system side scan sonar surveys of the seafloor were made at the same location during the summers of 1977 and 1978 the two data sets provide information on ice motion ice gouging and the rate and character of seabed deformation by ice four ice stages open water freeze up winter and breakup can be defined on the basis of the frequency and patterns of ice motion and ice cover processes as recorded by the radar system in all four ice stages the dominant ice motion was nearly parallel to the coast side scan sonar surveys show that the principal ice gouge directions nearshore were at a high angle to the coast and to the predominant direction of ice drift in both years gouge density was greatest in a narrow zone centered about the 10 m isobath which reflects the distribution of deep ice keels and the pattern of reworking of the seafloor by waves and currents we believe the majority of observed gouges were formed by keels of multiyear ice floes during an event that occurred in july 1975 2 years before the first seabed survey persistence of the gouge pattern from 1975 until 1977 is attributed to persistence of the ice cover and limited reworking by waves and currents or additional gouging the observed decrease in gouge density between 1977 and 1978 is attributed to 1 seafloor reworking and gouge infilling by storms and 2 the absence of ice conditions that were conducive to creating fresh gouges

global temperature response to century scale degassing from the siberian traps large igneous province abstract the siberian traps large igneous province was a key player in the end permian extinction and climatic change due to degassing from lavas and heated sedimentary rocks although the specific degassing scenarios from the province are debated this implies that gas release on a timescale tuned to the cooling of lava flows and subvolcanic intrusions i e decades to centuries must have been sufficient to affect the atmospheric chemistry here we test this assumption by using simple box model calculations to constrain century scale degassing of co2 and ch4 from high end volumes of individual lava flows and sills from the siberian traps the model includes gas fluxes of ch4 and co2 their atmospheric lifetimes and radiative forcing as well as the climate sensitivity in a global average climate system calibrated to end permian time the fluxes are estimated based on lava degassing and contact aureole volumes and devolatilization during the first 100 years following emplacement we test the sensitivity to extreme emissions of up to 25 gtc yr ch4 fractions from 0 to 100 wide ranges of climate sensitivities 1 5 6 0 c for co2 doubling pre event concentrations and atmospheric lifetimes we find that the global annual mean temperature perturbation is 7 0 c in our baseline case using a 10 gtc yr emission and a 60 ch4 fraction assuming 4 5 c as the climate sensitivity even for low emission scenarios 0 7 1 2 gtc yr the temperature response is 1 5 c we conclude that sporadic individual large scale volcanic events in large igneous provinces have the potential to cause a strong global warming on very short timescales in addition to the emission strength the ch4 fraction and the climate sensitivity have the strongest impact on the century scale temperature perturbation

hydrothermal venting of greenhouse gases triggering early jurassic global warming abstract the climate change in the toarcian early jurassic was characterized by a major perturbation of the global carbon cycle the event lasted for approximately 200 000 years and was manifested by a global warming of 6 c anoxic conditions in the oceans and extinction of marine species the triggering mechanisms for the perturbation and environmental change are however strongly debated here we present evidence for a rapid formation and transport of greenhouse gases from the deep sedimentary reservoirs in the karoo basin south africa magmatic sills were emplaced during the initial stages of formation of the early jurassic karoo large igneous province and had a profound influence on the fate of light elements in the organic rich sedimentary host rocks total organic carbon contents and vitrinite reflectivity data from contact aureoles around the sills show that organic carbon was lost from the country rocks during heating we present data from a new type of geological structures termed breccia pipes rooted in the aureoles within the shale of the western karoo basin the breccia pipes are cylindrical structures up to 150 meters in diameter and are mainly comprised of brecciated and baked black shale thousands of breccia pipes were formed due to gas pressure build up during metamorphism of the shales resulting in venting of greenhouse gases to the toarcian atmosphere mass balance calculations constrained by new aureole data show that up to 1800 gt of co2 was formed from organic material in the western karoo basin about 15 times this amount of co2 27 400 gt may have formed in the entire basin during the intrusive event u pb dating of zircons from a sill related to many of the pipes demonstrates that the magma was emplaced 182 5 0 4 million years ago this supports a causal relationship between the intrusive volcanism the gas venting and the toarcian global warming

an automated strategy for calculation of phase diagram sections and retrieval of rock properties as a function of physical conditions we formulate an algorithm for the calculation of stable phase relations of a system with constrained bulk composition as a function of its environmental variables the basis of this algorithm is the approximate representation of the free energy composition surfaces of solution phases by inscribed polyhedra this representation leads to discretization of high variance phase fields into a continuous mesh of smaller polygonal fields within which the composition and physical properties of the phases are uniquely determined the resulting phase diagram sections are useful for understanding the phase relations of complex metamorphic systems and for applications in which it is necessary to establish the variations in rock properties such as density seismic velocities and volatile content through a metamorphic cycle the algorithm has been implemented within a computer program that is general with respect to both the choice of variables and the number of components and phases possible in a system and is independent of the structure of the equations of state used to describe the phases of the system

the effects of large igneous provinces on the global carbon and sulphur cycles abstract the correlation between large igneous provinces lips extinction events and rapid climate change suggests that volcanism can have a detrimental impact on earth surface conditions changes in atmospheric and ocean chemistry particularly the climate sensitive carbon and sulphur cycles are among the most probable processes for inducing global environmental stress however the interactions and feedbacks between volcanism and these cycles are numerous and complex making the characterisation of the response to a lip challenging here we summarise the sources and sinks of carbon and sulphur from large scale volcanism and magmatism using information from modern and ancient systems for the sources we review the current understanding of volcanic emissions and explore the relative contributions and importance of magma derived degassing versus volatile release from sediments affected by igneous intrusions and lava in addition we explore the various ways in which lips can reduce atmospheric concentrations of these same elements the relative influences of each source and sink are in part determined by the mode of lip emplacement and eruption style along with the subsequent timescales of such effects we focus on a few key examples including the siberian traps the parana etendeka and the central atlantic magmatic province camp to demonstrate how the environmental impact can vary considerably with differing modes of emplacement lip duration and eruption styles in particular we show that the host rocks can have a dominant role as a source or sink of emissions depending on the lithologies affected by the lip emplacement

insights into explosive activity at closely spaced eruptive vents using infrasound signals example of mt etna 2008 eruption abstract on 13 may 2008 an eruptive fissure opened on mount etna s eastern flank feeding both explosive activity and lava effusion from multiple vents for about 14 months during the investigated may september 2008 eruptive period infrasound recordings from a 4 station sparse network allowed tracking of the explosive activity in terms of location and dynamics in order to focus on activity from the eruptive fissure the infrasonic events generated by the summit craters were selected by using both spectral features and time delays between pairs of stations and excluded from our analysis then to accurately locate events from the fissure we used a composite method based on the semblance and brightness functions this enabled the study of the co existence of more than one infrasound source and or its migration along the eruptive fissure hence results permitted us to discriminate the number of active vents and their location along the fissure even when due to poor weather conditions it was not possible to access the vents or carry out direct observations the eruptive activity was characterised by variations in the number of active vents according to the overall intensity of the eruptive event variability of the infrasound waveforms highlighted either that distinct vents produced signals with different waveforms or that single vents generated different events during distinct periods of time or finally both the previous phenomena we applied the strombolian bubble vibration model to model waveform differences and attributed the signal variations to bubble radius changes

monitoring seismo volcanic and infrasonic signals at volcanoes mt etna case study volcanoes generate a broad range of seismo volcanic and infrasonic signals whose features and variations are often closely related to volcanic activity the study of these signals is hence very useful in the monitoring and investigation of volcano dynamics the analysis of seismo volcanic and infrasonic signals requires specifically developed techniques due to their unique characteristics which are generally quite distinct compared with tectonic and volcano tectonic earthquakes in this work we describe analysis methods used to detect and locate seismo volcanic and infrasonic signals at mt etna volcanic tremor sources are located using a method based on spatial seismic amplitude distribution assuming propagation in a homogeneous medium the tremor source is found by calculating the goodness of the linear regression fit r 2 of the log linearized equation of the seismic amplitude decay with distance the location method for long period events is based on the joint computation of semblance and r 2 values and the location method of very long period events is based on the application of radial semblance infrasonic events and tremor are located by semblance brightness and semblance based methods respectively the techniques described here can also be applied to other volcanoes and do not require particular network geometries such as arrays but rather simple sparse networks using the source locations of all the considered signals we were able to reconstruct the shallow plumbing system above sea level during 2011

time space variation of volcano seismic events at la fossa vulcano aeolian islands italy new insights into seismic sources in a hydrothermal system we investigated the relationship between volcano seismic events recorded at la fossa crater of vulcano aeolian islands italy during 2004 2006 and the dynamics of the hydrothermal system during the period of study three episodes of increasing numbers of volcano seismic events took place at the same time as geothermal and geochemical anomalies were observed these geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the hydrothermal fluids three classes of seismic events long period high frequency and monochromatic events characterised by different spectral content and various similarity of the waveforms have been recognised these events clustered mainly below la fossa crater area at depths of 0 5 1 1 km b s l were space distributed according to the classes based on their features we can infer that such events at vulcano are related to two different source mechanisms 1 fracturing processes of rocks and 2 resonance of cracks or conduits filled with hydrothermal fluid in the light of these source mechanisms the increase in the number of events at the same time as geochemical and geothermal anomalies were observed was interpreted as the result of an increasing magmatic component of the hydrothermal fluids implying an increase of their flux indeed such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending fluids increased pore pressures gave rise to fracturing processes while the increased fluid flux favoured resonance and vibration processes in cracks and conduits finally a gradual temporal variation of the waveform of the hybrid events one of the subclasses of long period events was observed likely caused by heating and drying of the hydrothermal system

volcanic tremor location during the 2004 mount etna lava effusion 1 a lava emission started at mt etna italy on 7 september 2004 neither earthquake seismicity heralded or accompanied the opening of the fracture field from which the lava poured out nor volcanic tremor changed in amplitude and frequency content at the onset of the effusive activity to highlight long term changes we propose a method for the location of the tremor source based on a 3d grid search using the amplitude decay of the seismic signal from january to november 2004 we find the centroid of the tremor source within a zone close to and partially overlapped with the summit craters pre effusive phase which extended up to 2 km south of them effusive phase the depths are of between 1698 and 2387 m a s l we hypothesize the lava effusion stemmed from a degassed magma body although we find evidence of temporary magma overpressure conditions such as those documented on 25 september

precursory swarms of long period events at redoubt volcano 1989 1990 alaska their origin and use as a forecasting tool abstract during the eruption of redoubt volcano from december 1989 through april 1990 the alaska volcano observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long period lp seismic events dominant period of about 0 5 s the initial eruption on december 14 occurred after 23 years of quiescence and was heralded by a 23 hour swarm of lp events that ended abruptly with the eruption after a series of vent clearing explosions over the next few days dome growth began on december 21 another swarm with lp events similar to those of the first began on the 26th and ended in a major tephra eruption on january 2 eruptions continued over the next two weeks and then ceased until february 15 when a large eruption initiated a long phase of repetitive dome building and dome destroying episodes that continued into april warnings were issued before the major events on december 14 and january 2 but as the eruptive sequence continued after january 2 the energy of the swarms decreased and forecasting became more difficult a significant but less intense swarm preceded the february 15 eruption which was not forecast this eruption destroyed the only seismograph on the volcanic edifice and stymied forecasting until march 4 when the first of three new stations was installed within 3 km of the active vent from march 4 to the end of the sequence on april 21 there were eight eruptions six of which were preceded by detectable swarms of lp events although weak these swarms provided the basis for warnings issued before the eruptions on march 23 and april 6 the initial swarm on december 13 had the following features 1 short duration 23 hours 2 a rapidly accelerating rate of seismic energy release over the first 18 hours of the swarm followed by a decline of activity during the 5 hours preceding the eruption 3 a magnitude range from 0 4 to 1 6 4 nearly identical lp signatures with a dominant period near 0 5 s 5 dilatational first motions everywhere and 6 a stationary source location at a depth of 1 4 km beneath the crater this occurrence of long period events suggests a model involving the interaction of magma with groundwater in which magmatic gases steam and water drive a fixed conduit at a stationary point throughout the swarm the initiation of that sequence of events is analogous to the failure of a pressure relief valve connecting a lower supercharged magma dominated reservoir to a shallow hydrothermal system a three dimensional model of a vibrating fluid filled crack recently developed by chouet is found to be compatible with the seismic data and yields the following parameters for the lp source crack length 280 380 m crack width 140 190 m crack thickness 0 05 0 20 m crack stiffness 100 200 sound speed of fluid 0 8 1 3 km s compressional wave speed of rock 5 1 km s density ratio of fluid to rock 0 4 and ratio of bulk modulus of fluid to rigidity of rock 0 03 0 07 the fluid filled crack is excited intermittently by an impulsive pressure drop that varies in magnitude within the range of 0 4 to 40 bar such disturbance appears to be consistent with a triggering mechanism associated with choked flow conditions in the crack

seismoacoustic investigations of paroxysmal activity at mt etna volcano new insights into the 16 november 2006 eruption 1 on 16 november 2006 a 1 day long paroxysmal eruption occurred at the summit craters of mt etna volcano a multiparametric approach consisting of analyzing infrasonic seismic and video camera recordings was carried out to follow its evolution volcanological and geophysical observations identified three eruptive phases in the first phase infrasonic and seismic characteristics reflected the highly explosive nature of the activity waveform characterization of infrasound events confirmed the activity of the several explosive vents at the summit of southeast crater sec during the second phase results highlighted the decoupling between seismic and infrasonic sources which was due to the decrease in explosive activity and the reactivation of effusive vents located south of bocca nuova and on the saddle between bocca nuova and sec the third phase was the most intense and was characterized by various volcanic phenomena pyroclastic flows jets of dark ash and white steam the very high radiated infrasonic energy together with infrasound event features led us to infer a gas enrichment of the shallow magma column preceding by a few minutes and likely related to the pyroclastic flows in the sec area after the eruption at sec variations in infrasound events related to the activity of northeast crater nec were found the observed spectral changes and the source mechanism modeling of the nec infrasound events suggest the existence of a link in the plumbing system feeding the two craters

magma intrusion mechanisms and redistribution of seismogenic stress at mt etna volcano 1997 1998 terra nova 23 339 348 2011 abstract several volcanoes worldwide have shown changes in their stress state as a consequence of the deformation produced by the pressurization of a magmatic body this study investigated seismic swarms occurring on the western flank of mt etna in january 1997 january 1998 integrating seismic observations and geodetic data we constrained the seismogenic fault system and on the basis of stress tensor inversion and shmax analyses we inferred an inflating pressure source located at 5 5 km b s l beneath the west portion of summit area evaluation of coulomb failure stress related to the proposed model showed how a large part of the seismogenic fault underwent a significant coulomb failure stress increase 500 kpa we inferred the presence of a sub vertical faulted region potentially weak n50 e oriented beneath the western sector of mt etna this structure could be brought closer to failure thereby generating seismic swarms as the effect of elastic stress transfer induced by movement and or overpressure of magmatic masses within the upper crust under the volcano

pressurization and depressurization phases inside the plumbing system of mount etna volcano evidence from a multiparametric approach during 2013 mount etna volcano experienced intense eruptive activity at the summit craters foremost at the new southeast crater and to a minor degree at the voragine and bocca nuova bn which took place in two cycles february april and september december in this work we mainly focus on the period between these cycles applying a multiparametric approach the period from the end of april to 5 september showed a gradual increase in the amplitude of long period lp events and volcanic tremor a slight inflation testified by both tilt and gps data and a co2 flux increase such variations were interpreted as due to a gradual pressurization of the plumbing system from the shallowest part where lp and volcanic tremor are located down to about 3 9 km below sea level pressure source depths obtained by both geodetic and co2 data on 5 september at the same time as a large explosion at bn we observed an instantaneous variation of the aforementioned signals decrease in amplitude of lp events and volcanic tremor slight deflation and co2 flux decrease and the activation of a new infrasonic source located at bn in the light of it the bn explosion probably caused the instantaneous end of the pressurization and the opening of a new vent at bn that has become a new steady source of infrasonic events this apparently slight change in the plumbing system also led to the gradual resumption of activity at the new southeast crater culminating with the second lava fountain cycle of 2013

sills and gas generation in the siberian traps on its way to the surface the siberian traps magma created a complex sub volcanic plumbing system this resulted in a large scale sill emplacement within the tunguska basin and subsequent release of sediment derived volatiles during contact metamorphism the distribution of sills and the released sediment stored gas volume is however poorly constrained in this paper results from a study of nearly 300 deep boreholes intersecting sills are presented the results show that sills with thicknesses above 100 m are abundant throughout the upper part of the sedimentary succession a high proportion of the sills was emplaced within the cambrian evaporites with average thicknesses in the 115 130 m range and a maximum thickness of 428 m thermal modelling of the cooling of the sills shows that the contact metamorphic aureoles are capable of generating 52 80 tonnes of co2 m 2 with contributions from both marine and terrestrial carbon when up scaling these borehole results an area of 12 19 000 km2 is required to generate 1000 gt co2 this represents only 0 7 1 2 of the total area in the tunguska basin affected by sills emphasizing the importance of metamorphic gas generation in the siberian traps these results strengthen the hypothesis of a sub volcanic trigger and driver for the environmental perturbations during the end permian crisis this article is part of a discussion meeting issue hyperthermals rapid and extreme global warming in our geological past

modelling hydrothermal venting in volcanic sedimentary basins impact on hydrocarbon maturation and paleoclimate highlights numerical model of sill intrusions in sedimentary basins fracture and vent formation due to overpressure generation methane fluxes through a single vent with upscaling to basin scales additional regions in the naip required to correlate methane venting and the petm abstract vent structures are intimately associated with sill intrusions in sedimentary basins globally and are thought to have been formed contemporaneously due to overpressure generated by gas generation during thermogenic breakdown of kerogen or boiling of water methane and other gases generated during this process may have driven catastrophic climate change in the geological past in this study we present a 2d fem fvm model that accounts for explosive vent formation by fracturing of the host rock based on a case study in the harstad basin offshore norway overpressure generated by gas release during kerogen breakdown in the sill thermal aureole causes fracture formation fluid focusing and overpressure migration towards the sill tips results in vent formation after only few tens of years the size of the vent depends on the region of overpressure accessed by the sill tip overpressure migration occurs in self propagating waves before dissipating at the surface the amount of methane generated in the system depends on toc content and also on the type of kerogen present in the host rock generated methane moves with the fluids and vents at the surface through a single large vent structure at the main sill tip matching first order observations violent degassing takes place within the first couple of hundred years and occurs in bursts corresponding to the timing of overpressure waves the amount of methane vented through a single vent is only a fraction between 5 and 16 of the methane generated at depth upscaling to the voring and more basins which are a part of the north atlantic igneous province and using realistic host rock carbon content and kerogen values results in a smaller amount of methane vented than previously estimated for the petm our study therefore suggests that the negative carbon isotope excursion cie observed in the fossil record could not have been caused by intrusions within the voring and more basins alone and that a contribution from other regions in the naip is also required to drive catastrophic climate change

shallow magma pathway geometry at mt etna volcano 1 a fundamental goal of volcano seismology is to understand the dynamics of active magmatic systems in order to assess eruptive behavior and the associated hazard imaging of magma conduits quantification of magma transport and investigation of long period seismic sources together with their temporal variations are crucial for the comprehension of eruption triggering mechanisms at mt etna volcano several intense episodes of tremor activity were recorded during 2007 in association with strombolian activity and or intense fire fountaining episodes occurring from the south east crater sec the locations of the tremor sources and of the long period seismic events are used here to constrain both the area and the depth range of magma degassing highlighting the geometry of the shallow conduits feeding sec the imaged conduits consist of two connected resonating dike like bodies nnw sse and nw se oriented extending from sea level to the surface in addition we show how tremor long period lp and very long period vlp event locations and signatures reflect pressure fluctuations in the plumbing system associated with the ascent discharge of gas rich magma linked to the lava fountains the evidence here reported also corroborated by ground deformation variations can help develop a better prediction and early warning system for those eruptions effusive or explosive that apparently manifest no clear precursors

characterization of open and closed volcanic systems in indonesia and mexico using insar time series 1 we use 2007 2011 advanced land observing satellite alos data to perform an arc wide interferometric synthetic aperture radar insar time series survey of the trans mexican volcanic belt tmvb and to study time dependent ground deformation of four indonesian volcanoes selected following the 2007 2009 study of chaussard and amelung 2012 our objectives are to examine whether arc volcanoes exhibit long term edifice wide cyclic deformation patterns that can be used to characterize open and closed volcanic systems and to better constrain in which cases precursory inflation is expected we reveal deformation cycles at both regularly active and previously inactive indonesian volcanoes but we do not detect deformation in the tmvb reflecting a lower activity level we identify three types of relationships between deformation and activity inflation prior to eruption and associated with or followed by deflation kerinci and sinabung inflation without eruption and followed by slow deflation agung and eruption without precursory deformation merapi colima and popocatepetl at merapi no significant deformation is detected even during eruption the first two cases correspond to closed volcanic systems and suggest that the traditional model of magmatic systems and eruptive cycles do apply to andesitic volcanoes i e inflation and deflation episodes associated with magma accumulation or volatile exsolution in a crustal reservoir followed by eruptions or in situ cooling in contrast the last case corresponds to open volcanic systems where no significant pressurization of the magmatic reservoirs is taking place prior to eruptions and thus no long term edifice wide ground deformation can be detected we discuss these results in terms of insar s potential for forecasting volcanic unrest

characterizing winter landfast sea ice surface roughness in the canadian arctic archipelago using sentinel 1 synthetic aperture radar and the multi angle imaging spectroradiometer

mt etna 2001 eruption new insights into the magmatic feeding system and the mechanical response of the western flank from a detailed geodetic dataset abstract in the last decades the increasing availability of comprehensive geodetic datasets has allowed for more detailed constraints on subsurface magma storage and conduits at several active volcanoes worldwide here by using a large dataset of geodetic measurements collected between early january 2001 and august 2001 we identified at least six different deformation stages that allow us to quantify the surface deformation patterns before during and after the 2001 mt etna volcanic eruption our results are largely in agreement with previous works e g the presence of a deep inflating source and a shallow dike located beneath the north western and upper southern flanks of the volcano respectively however we provide 1 finer resolution of the temporal activity of these magmatic sources leading to 2 new evidence related to the evolution of the magmatic system and the mechanical response of the western flank in particular during the pre eruptive phase results and analysis show a clear change in the ground deformation pattern of the volcano in response to the 20 24 april 2001 seismic swarm that occurred beneath the western flank evolving from a volcano wide inflation to a slight deflation of the summit area we suggest that the source responsible for the volcano wide inflation beginning in the fall of 2000 experienced a drastic reduction in the inflation rate in response to this seismic swarm moreover we provide evidence for the presence of a new inflating source located beneath the upper southern flank at a depth of 7 0 km bsl that triggered both the occurrence of the 20 24 april 2001 seismic swarm and led to the rapid ascent of magma upward to the surface after 12 july the lower vents system was fed by fresh magma rising from this source the presence of this inflating source is inferred by 1 seismological and volcanological observations coming from the 2001 eruption and 2 seismological constraints coming from a previous similar episode that occurred at etna during the 1993 1998 period furthermore both shallow deflations observed after the 20 24 april 2001 seismic swarm and during the first day of the eruption also could be due to the deflation of two adjacent portions of the same shallow 2 km bsl reservoir such reservoirs would feed the activity that occurred at the south east crater after january 2001 and the activity of the upper vents system during the july august eruption in agreement with petrochemical observations through an updated revision of the available data we shed some light on the relevance of pre eruptive activity patterns an important element for an effective volcano monitoring

the onset of flood volcanism in the north western part of the siberian traps explosive volcanism versus effusive lava flows abstract the siberian traps large igneous province was formed during the end permian about 252 ma ago basaltic melt was injected into the organic and salt rich tunguska sedimentary basin forming interconnected sill complexes and associated hydrothermal vent complexes thick deposits of basaltic tuff and tephra covered the paleosurface before the onset of flood volcanism commonly taken as direct evidence for the explosive nature of the initial phase of volcanism the field work in this study revealed that tuffs are virtually absent along a 150 km long transect along the dyupkun lake and kureika river even though tuff is shown on available geological maps towards the south and west the transition between the end permian sediments and the flood basalts is either characterized by thin 2 5 m to no tephra deposits khantaika area hyaloclastites and associated lake deposited tephra kureika area or massive tephra deposits from local eruptive centers severnaya area the new results can be put into the context of other studies about volcanic tuff horizons in siberia and questions the notion of province scale explosive volcanism in siberia during the onset of flood volcanism moreover the main thicknesses of explosive tuff deposits up to 700 m are located in the central and southern parts of the province where the lip erupted through thick cambrian salt and carbonate sequences since numerous phreatomagmatic pipes are present in these areas we suggest a causal relationship between deep magma sediment interactions explosive eruptions and the resulting environmental stress that initiated the end permian mass extinction

geostatistical analysis of glacier roughness data in most glaciological and hydrological models surface roughness of snow and ice is an important parameter however roughness is generally used only as an estimated parameter for lack of available observations in this paper we present a method to collect and analyze ice surface roughness data using a specially designed instrument for survey and geostatistical methods for analysis the glacier roughness sensor grs built at the university of trier records variations in microtopography at 0 2 m 0 1 m resolution when pulled across an ice surface global positioning system data are used for location after several processing steps the data are analyzed using geostatistical methods the mathematical tool used to achieve a morphological characterization of ice surface types is the variogram grs data variograms and surface roughness analysis are ideal matches for morphological characterization because none of them requires or provides absolute elevation values morphology is described not by absolute elevation values but by the change of elevation in space which is the derivative of elevation surface roughness values the variogram is calculated from incremental values parameters extracted from variograms of grs data serve to distinguish lake surfaces wind structures ridge and vauey systems melting structures and blue ice areas examples are from jakobshavn isbrae drainage basin west greenland

patterns in the recent 2007 2008 activity of mount etna volcano investigated by integrated geophysical and geochemical observations 1 seismic deformation and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment in spite of their wide use there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques here we combine seismic volcanic tremor and long period seismicity deformation gps and geochemical volcanic gas plume co2 so2 ratios measurements in an attempt to interpret trends in the recent 2007 2008 activity of etna volcano we show that each eruptive episode occurring at the southeast crater sec was preceded by a cyclic phase of increase decrease of plume co2 so2 ratios and by inflation of the volcano s summit captured by the gps network these observations are interpreted as reflecting the persistent supply of co2 rich gas bubbles and eventually more primitive magmas to a shallow depth of 1 2 8 km asl magma storage zone below the volcano s central craters ccs overpressuring of the resident magma stored in the upper ccs conduit triggers further magma ascent and finally eruption at sec a process which we capture as an abrupt increase in tremor amplitude an upward 2800 m asl and eastward migration of the source location of seismic tremor and a rapid contraction of the volcano s summit resumption of volcanic activity at sec was also systematically anticipated by declining plume co2 so2 ratios consistent with magma degassing being diverted from the central conduit area toward sec

insights into mt etna s shallow plumbing system from the analysis of infrasound signals august 2007 december 2009 previous studies performed on mt etna on short and discontinuous time intervals indicate the north east crater nec as the most active source of infrasound the source mechanism of nec infrasound events was modeled as a double resonance this lead to infer the connection between the nec and both the southeast crater sec and the eruptive fissure ef that opened at the beginning of the 2008 2009 eruption nevertheless there are still several open questions that need to be addressed for instance the steadiness of nec event features should be studied as well as the orderliness of spectral changes of nec events time related to eruptive activity of other vents the investigation of such topics is strongly enhanced by the possibility of analysing infrasound signals during year long time periods with this aim about 40 000 infrasound events recorded at mt etna from august 2007 to december 2009 were analysed by using spectral and location techniques it was noted in particular that the nec events featured periods with very steady waveforms and spectral characteristics lasting from days to months with slow or sudden variations the most important eruptive episodes occurring at the sec or the ef were accompanied by significant spectral changes in nec events in light of such systematic behaviour the connection between the nec and the sec ef plumbing systems was not considered temporary but rather stable even during a relatively long time interval 2006 2009 moreover study of nec event spectral features and their changes over multiple years supports the double resonance source model such a model together with the inferred connections between nec and sec ef feeding systems implies that level fluctuations of a magma column inside the nec conduit correspond to magmastatic pressure decrease increase inside the main plumbing system these findings open up new and interesting possibilities for monitoring magma pressure changes inside the mt etna plumbing system

thermal effects of igneous intrusions on maturity of organic matter a possible mechanism of intrusion abstract this paper assesses thermal maturation of organic matter near a well dated intrusion in the dsdp 41 368 hole near cape verde rise eastern atlantic and near some other intrusions from the u k u s a and east greenland the traditional numerical model with instantaneous intrusion satisfactorily describes the thermal evolution and thermal maturity aureoles of igneous bodies only if the initial temperature of intrusion is close to or even lower than the solidus temperature calculations in this model with more real values of the intrusion temperature and with consideration of latent heat effects lead to considerable over estimation of thermal influence of the intrusion models which consider formation of the intrusive body over time as distinct from instantaneous intrusion and especially models of emplacement of an intrusive body in the shell of relatively cool magmatic rocks show better agreement between the computed and observed vitrinite reflectance profiles consideration of convective heat flow due to hydrothermal activity arising in the vicinity of the intrusion during its formation and cooling helps to explain the difference between maturation profiles above and below some sills

long period and very long period events at mt etna volcano characteristics variability and causality and implications for their sources abstract almost 50 000 long period lp events were recorded at mt etna from november 2003 to may 2006 we analysed these events as well as very long period vlp events which were associated with some of them during some intervals the spectral and wavefield features of lp events remained steady with significant changes occurring between the intervals based on the times of the changes we distinguish five different sub periods in particular during sub period iii june november 2005 the wavefield at the stations nearest to the summit area was composed of p waves locations for 150 lp events occurring in sub period iii determined using radial semblance changed at the same time as the events spectral features changed it was during this sub period that many of the lp events were associated with vlp events based on similarity of the waveforms we distinguished two families of vlp events with gradually evolving waveforms the two families are located in slightly different places but near the sources of the lp events the change between the families occurred at the same time as the spectra of the lp events changed finally the source of the vlp events was investigated by performing complete waveform moment tensor inversion of stacks of the two families synthetic green s functions for the full moment tensor were calculated for a homogeneous half space for both families the source region with the highest variance reduction lies approximately beneath the active craters at 500 m below the altitudes of the stations the solutions for both families are very similar with sources that are between 60 and 70 isotropic attempts to determine deviatoric moment tensors produced consistently poorer fits the remaining energy is poorly constrained and is likely to be noise in conclusion these results highlight changes in the lp and vlp events at mt etna over time and the causal relationship between them

siberian gas venting and the end permian environmental crisis abstract the end of the permian period is marked by global warming and the biggest known mass extinction on earth the crisis is commonly attributed to the formation of the siberian traps large igneous province although the causal mechanisms remain disputed we show that heating of tunguska basin sediments by the ascending magma played a key role in triggering the crisis our conclusions are based on extensive field work in siberia in 2004 and 2006 heating of organic rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated 100 000 gt co2 the gases were released to the end permian atmosphere partly through spectacular pipe structures with kilometre sized craters dating of a sill intrusion by the u pb method shows that the gas release occurred at 252 0 0 4 million years ago overlapping in time with the end permian global warming and mass extinction heating experiments to 275 c on petroleum bearing rock salt from siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases the results indicate that global warming and ozone depletion were the two main drivers for the end permian environmental crisis we demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a large igneous provinces causes an environmental crisis or not we propose that a similar mechanism could have been responsible for the triassic jurassic 200 ma global warming and mass extinction based on the presence of thick sill intrusions in the evaporite deposits of the amazon basin in brazil

formation and evolution of the end permian oktyabrsk volcanic crater in the tunguska basin eastern siberia abstract the siberian traps large igneous province comprises lava flows volcaniclastic and hyaloclastite deposits and a network of sills and dikes that were emplaced into the sediments beneath the volcanics spectacular examples of these intrusions are found in the tunguska basin sediments in eastern siberia hundreds of diatremes have been identified rooted above sill intrusions linking the contact metamorphic aureoles around the intrusive complexes in the tunguska basin with the paleo surface the diatremes in the southern part of the basin have been proposed as the main conduits for metamorphic gas release to the atmosphere and thus a trigger leading to the end permian terrestrial mass extinction the content of these diatremes has yet to be presented in detail in english language literature and fundamental questions remain regarding the content and formation history of these structures this study examines the geochemistry and petrography of crater sediments within the uppermost portion of the oktyabrsk diatreme complex in the southern tunguska basin eastern siberia we focus primarily on 505 m of lacustrine sediments within the western crater the sediments are tuffaceous silt and sandstones intercalated with conglomerates and cemented by calcite the major element composition of the bulk crater sediments indicates a mixture of basalt and carbonate the sedimentary mineral assemblages do not reflect primary basaltic rock but rather altered volcaniclastic material comprising clays zeolites calcite and pyrite with minor detrital magnetite fluorite apatite and garnets originating from hydrothermal diatreme deposits the western crater sediments contain no evidence of allochthonous sediment sources and were subjected to only low temperature diagenesis following burial making this deposit a prime locale for further investigations of in situ processes and biologic activity in siberia at the end permian the oktyabrsk complex formed via multiple episodes of mineral deposition and eruption events and the diatremes represent a likely source of the thick volcaniclastic deposits in the southern tunguska basin this system enables further investigation of the connection between the siberian traps magma sediment interaction and the end permian terrestrial environment

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

multidisciplinary investigation on a lava fountain preceding a flank eruption the 10 may 2008 etna case a multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of the erupted products to volcanic tremor long period events and tilt and gravity signals is used to investigate the source depth and magma dynamics of the 10 may 2008 lava fountain at southeast crater sec of mount etna the investigation was undertaken in the framework of the previous 2007 explosive activity as well as the subsequent effusive eruption beginning 13 may 2008 and lasting up to july 2009 all the data concur in indicating that the 10 may lava fountain was generated by the fragmentation of a foam layer trapped at the top of a shallow reservoir about 1500 1700 m below the summit of sec the shift from the episodic strombolian lava fountain activity occurring in 2007 at sec to the more powerful 10 may 2008 lava fountain is explained by the intrusion of a new more primitive magma into the shallow reservoir data also indicate that an attempted magma intrusion east of the summit area occurred during the 10 may fire fountain this event caused the fracturing and weakening of the surrounding rocks and created a preferential pathway for the penetration of the magma that only 3 days later started to feed the 2008 2009 effusive eruption

acid rain and ozone depletion from pulsed siberian traps magmatism the siberian traps flood basalts have been invoked as a trigger for the catastrophic end permian mass extinction widespread aberrant plant remains across the permian triassic boundary provide evidence that atmospheric stress contributed to the collapse in terrestrial diversity we used detailed estimates of magmatic degassing from the siberian traps to complete the first three dimensional global climate modeling of atmospheric chemistry during eruption of a large igneous province our results show that both strongly acidic rain and global ozone collapse are possible transient consequences of episodic pyroclastic volcanism and heating of volatile rich siberian country rocks we suggest that in conjunction with abrupt warming from greenhouse gas emissions these repeated rapidly applied atmospheric stresses directly linked siberian magmatism to end permian ecological failure on land our comprehensive modeling supplies the first picture of the global distribution and severity of acid rain and ozone depletion providing testable predictions for the geography of end permian environmental proxies

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago