cooling mechanisms and an approximate thermal budget for the 1991 1993 mount etna lava flow the 1991 1993 eruption of mount etna sicily built a 7 2 km aa lava flow field within the valle del bove this letter provides estimates of the power losses associated with various cooling mechanisms operating during the development of the flow field derived from time series analysis of nighttime satellite remote sensing data unlike sensors used in many previous remote sensing studies of active lava the ers 1 along track scanning radiometer atsr provides unsaturated measurements of spectral radiance from even very hot surfaces this allows for more accurate solution of the lava flow endmember thermal components we find that radiative and conductive processes dominated with our model suggesting energy losses of similar magnitude radiative losses peaked about one month into the eruption when lava flowed in open channels conductive losses peaked after two months with a marked decline caused by a significant decrease in the horizontal spreading rate of lava by the end of the eruption the 235 106 m of erupted lava is estimated to have lost only 28 of its initial thermal energy a further 6 5 1017 j must be lost before the lava reaches ambient temperature

resolving mass flux at high spatial and temporal resolution using grace intersatellite measurements 1 the grace mission is designed to monitor mass flux on the earth s surface at one month and high spatial resolution through the estimation of monthly gravity fields although this approach has been largely successful information at submonthly time scales can be lost or even aliased through the estimation of static monthly parameters through an analysis of the grace data residuals we show that the fundamental temporal and spatial resolution of the grace data is 10 days and 400 km we present an approach similar in concept to altimetric methods that recovers submonthly mass flux at a high spatial resolution using 4 4 blocks at 10 day intervals we estimate the mass of surplus or deficit water over a 52 60 grid centered on the amazon basin for july 2003 we demonstrate that the recovered signals are coherent and correlate well with the expected hydrological signal

stronger or longer discriminating between hawaiian and strombolian eruption styles the weakest explosive volcanic eruptions globally strombolian explosions and hawaiian fountaining are also the most common yet despite over a hundred years of observations no classifications have offered a convincing quantitative way of demarcating these two styles new observations show that the two styles are distinct in their eruptive time scale with the duration of hawaiian fountaining exceeding strombolian explosions by 300 10 000 s this reflects the underlying process of whether shallow exsolved gas remains trapped in the erupting magma or is decoupled from it we propose here a classification scheme based on the duration of events brief explosions versus prolonged fountains with a cutoff at 300 s that separates transient strombolian explosions from sustained hawaiian fountains

spatter and welded air fall deposits generated by fire fountaining eruptions cooling of pyroclasts during transport and deposition abstract according to the physico mathematical model presented here juvenile ballistic fragments can travel through the atmosphere during fire fountaining eruptions preserving enough heat to agglutinate or to weld on impact with the ground s surface even a few kilometres from the source area the range is mostly related to exit velocity and ejection angle as well as to such typical properties of the transported particles as size density and shape the selective nature of the transport system can give rise to inverse lateral size density grading the most important interdependent factors that control the degree of final agglutination or welding are accumulation rate grain size and duration of deposition in the investigated grain size range an accumulation rate of 0 2 m h appears as a minimum value to promote welding this value cannot be considered as an absolute threshold because it can be significantly lowered by increasing the grain size duration of deposition appears as another critical factor because it controls the maximum temperature of the whole deposit and its final thickness and therefore the cooling rate of its main portion after the end of deposition in the case of high accumulation rates of coarse particles but during a short period of time primary agglutination may be the dominant factor in controlling the final sintering of particles conversely high accumulation rates of coarse particles during a long period of time give rise to both primary agglutination and welding

observations of the antarctic circumpolar current and deep boundary current in the southwest atlantic fourteen month velocity and temperature records from an array of 14 moorings north and west of the falkland plateau and supporting hydrographic and tracer data reveal a narrow boundary current that carries dense antarctic waters the current flows west along the northern flank of the falkland plateau with mean speeds of more than 10 cm s 1 at 5000 m and more than 30 cm s 1 at 2500 m the westward flow extends from the bottom to at least 1000 m but the upper portion of the current is a branch of the antarctic circumpolar current acc following the only deepwater route between the scotia sea and the argentine basin waters colder than 0 2 c are too cold to be associated with the acc at drake passage and must ultimately derive from the weddell sea as part of the deep thermohaline circulation the westward transport of water colder than 0 2 c is 8 2 106 m3 s 1 in the mean the bottom boundary current is similar to that predicted by the stommel arons model but considerable variability is introduced by the meandering of the overlying acc chlorofluorocarbon data suggest that new antarctic water from the georgia basin enters the argentine basin via the deep boundary current which passes beneath the acc some new water is also advected east after being entrained in the acc most of the water in the deep boundary current is recirculated water that has been in residence in the argentine basin for some time water colder than 0 2 c is relatively new to the basin and comprises about 2 5 106 m3 s 1 of the westward flow of the boundary current

modal variability in the southeast pacific basin energetics of the 2009 event abstract we study the barotropic variability in the southeast pacific basin in particular focusing on the extreme event during the fourth quarter of 2009 a 3 year integration of a barotropic shallow water model forced with wind stress anomalies generates localized variability that is similar in spatial extent and amplitude as the observed anomalous event an eigenmode analysis of the same model shows the presence of several free modes in the southeast pacific but projection of the modal patterns on the model output shows that their amplitudes are low instead the mode is interpreted as an almost free mode the modal excitation accounts for a considerable fraction 23 on average of the kinetic energy input by the wind stress in the southeast pacific basin increasing to 38 for the anomalous event in 2009 surprisingly a similar but weaker event during the third quarter of 2008 appears to have been more significant from an energetics point of view with almost 50 of the energy being input into the mode key areas of energetic dissipation appear to be the eltanin fracture zone the crest of the east pacific rise and the chile rise east pacific rise intersection

stochastic variability of oceanic flows above topography anomalies 1 we describe a stochastic variability mechanism which is genuinely internal to the ocean i e not due to fluctuations in atmospheric forcing the key ingredient is the existence of closed contours of bottom topography surrounded by a stirring region of enhanced eddy activity this configuration leads to the formation of a robust but highly variable vortex above the topography anomaly the vortex dynamics integrates the white noise forcing of oceanic eddies into a red noise signal for the large scale volume transport of the vortex the strong interannual fluctuations of the transport of the zapiola anticyclone 100 sv in the argentine basin are argued to be partly due to such eddy driven stochastic variability on the basis of a 310 years long simulation of a comprehensive global ocean model run driven by a repeated year forcing

the 7 september 2008 vulcanian explosion at stromboli volcano multiparametric characterization of the event and quantification of the ejecta this paper was partially supported by a research project project ingv dpc paroxysm v2 03 2007 2009 funded by istituto nazionale di geofisica e vulcanologia and by the italian civil protection

volcanic plume and bomb field masses from thermal infrared camera imagery masses erupted during normal explosions at stromboli volcano italy are notoriously difficult to measure we present a method that uses thermal infrared video for cooling bomb fields to obtain the total power emitted by all hot particles emitted during an explosion a given mass of magma m will emit a finite amount of thermal power defined by m cp te t0 cp and te being magma specific heat capacity and temperature and t0 being ambient temperature we use this relation to convert the total power emitted by the bomb field to the mass required to generate that power to do this we extract power flux curves for the field and integrate this through time to obtain total power e this is used to estimate mass q in q e cp te t0 when applied to individual bombs we obtain masses of between 1 and 9 kg per bomb or a volume of 970 and 6500 cm3 these volumes equate to spheres with diameters 12 and 27 cm for the entire bomb field we obtain volumes of 7 28 m3 we calculate masses for 32 eruptions and obtain typical bomb masses of between 103 and 104 kg per eruption in addition we estimate that between 102 and 103 kg of gas and ash are emitted as part of a mixed plume of bombs gas and ash we identify two types of eruption on the basis of the erupted bomb masses and the ratio of the plume s gas and ash component to the bomb component the first type is bomb dominated is characterized by bomb masses of 104 kg and has ash gas bomb ratios of 0 02 the second type is ash and gas dominated is characterized by erupted bomb masses of 103 kg and has ash gas bomb ratios of around one and as high as two there is no correlation between the quantity of bombs and quantity of gas ash erupted in addition while source pressure for each explosion correlates with the quantity of gas and ash erupted the mass of bombs emitted varies independently of pressure

interannual bottom pressure signals in the australian antarctic and bellingshausen basins abstractanalyses of large scale 750 km ocean bottom pressure pb fields derived from the gravity recovery and climate experiment grace and from an estimating the circulation climate of the ocean ecco state estimate reveal enhanced interannual variability partially connected to the antarctic oscillation in regions of the australian antarctic basin and the bellingshausen basin with pb magnitudes comparable to those of sea level and good correlation between the grace and ecco pb series consistent with the theory of gill and niiler the patterns of stronger pb variability are partly related to enhanced local wind curl forcing and weakened gradients in h f where h is ocean depth and f is the coriolis parameter despite weaker h f gradients motions against them are sufficiently strong to play a role in balancing the local wind input topographic effects are as or more important than changes in f additionally and contrary to the dominance of barotropic processes at subannual time scales barocl

petrophysical model of deep electrical conductors graphite lining as a source and its disconnection due to uplift petrophysical information including stress release data recently made available for low porosity 0 1 0 4 crystalline rocks has been used to develop a broken conductor model that may explain the origin of enhanced electrical conductivity of the intermediate to lower continental crusts of shields and its disappearance when the rocks are uplifted average pore size and pore density of their fluid flow paths are 0 1 0 4 m and 1 400 m respectively the model assumes that these paths are filled or lined with interconnected electrical conducting minerals such as graphite resulting in the rocks having resistivities as low as 40 to 800 m in situ graphite film thicknesses required to produce these resistivities are 5 20 nm 50 200 a the model also assumes that electrical conducting paths break up during uplift due to stress release resulting in a poorly conducting rock petrophysical data of granites and observations from deep drill holes suggest a porosity increase of the order of 3 from an uplift of 10 km or more however the newly formed pore space would fill with deposits or intruded material so that surface rock porosities would not be much larger than at depth electrical resistivities of rock samples containing disconnected grain boundary graphite presently exposed by the kapuskasing uplift of the canadian shield are in the range of 3000 12000 m for the direction of foliation these values are 10 100 times larger than the estimates for similar rocks containing interconnected graphite but are 10 100 times smaller than usually observed in the canadian shield for similar rocks absent of grain boundary graphite these observations are in good agreement with the results predicted by the broken conductor model for an uplift of 10 km or more if a gross linear relationship is assumed between crack porosity and uplift for the upper 10 km of the crust

analogue experiments on the rise of large bubbles through a solids rich suspension a weak plug model for strombolian eruptions abstract physical interactions between bubbles and crystals affect gas migration and may play a major role in eruption dynamics of crystal rich magmas strombolian eruptions represent an end member for bubble crystal interactions in which large bubbles significantly larger than the crystal size rise through a crystal rich near surface magma indeed volcanoes that produce strombolian eruptions often generate ejecta with 30 vol often 45 vol average crystallinity at stromboli volcano italy average crystallinity can reach 55 vol which is approaching the eruptibility limit for magmas at such high crystallinities the solids interact mechanically with each other and with bubbles this complex rheology complicates the two phase liquid gas slug flow model often applied to strombolian eruptions to examine the effect of crystals on bubble rise we performed analogue experiments in which large bubbles rise in a vertical tube filled with silicone oil and polypropylene particles the particles have a slightly lower density than the oil and therefore form a layer of oil particles at the upper surface we varied surface pressure particle volume fraction length of the particle bearing cap and bubble size to examine the ways in which these parameters influence strombolian type eruptions we show that in experiments suspended solids begin to affect bubble rise dynamics at particle volume fractions as low as 30 vol or when divided by the random close packing value a normalized particle fraction 0 64 bubbles in experiments with higher particle contents deform as they rise and burst through a small aperture generating surface fountains that begin abruptly and decay slowly and longer lasting acoustic signals of lower amplitude than in particle poor experiments particle fractions 38 vol 0 80 generated strong deformations on fast expanding bubbles that applied a high stress on the cap but they trapped bubbles that were less overpressured qualitatively the gas release behavior observed in particle rich experiments is consistent with observations of strombolian eruptions moreover we estimate that the observed crystallinity of pyroclasts at stromboli volcano represents 0 8 from this we suggest a weak plug model for strombolian eruptions that evolves towards a low viscosity equivalent of vulcanian style plug failure with a more crystalline stronger and less permeable plug importantly this model allows the rise of several bubbles in the conduit at the same time and suggests that longer lasting more pulsatory and complex eruptions may reveal an increase in near surface crystallinity shedding some light on changing conduit conditions that could help determine the different gas rise regimes involved in passive degassing puffing and different expressions of strombolian explosions

classification landing distribution and associated flight parameters for a bomb field emplaced during a single major explosion at stromboli italy we propose a novel approach to studying a ballistic bomb deposit favorable circumstances a unique dispersal axis an operational thermal video camera and application of an innovative methodology allowed estimates of volume and mass erupted and definition of mass partitioning between bombs of various sizes this allowed the creation of a multidisciplinary database for a single major explosion at stromboli volcano italy the type locality of strombolian eruptions the dispersion and direction of the deposit were consistent with a major explosion on 21 january 2010 field data comprised 780 mapped bomb locations and sizes and were organized into a gis with a lidar derived digital elevation model as its base this allowed us to define the landing distribution and flight parameters for erupted bombs the data defined discontinuous deposition to build a cluster dominated bomb field with a total deposit volume of 10 m3 a mass of 2 104 kg and a grain size dominated by large bombs 1 m in diameter the parameters defined here for a major eruption at stromboli show that the strombolian style of volcanism and its deposits need to be treated carefully and a different approach is needed in the future to truly characterize and classify such small but globally common explosive eruptions the recognition that sedimentation from such eruptions will be uneven leads to the important conclusion that isopachs and isopleths cannot be used to estimate eruption volumes for such explosions

gas mass derived by infrasound and uv cameras implications for mass flow rate abstract mass flow rate is one of the most crucial eruption source parameter used to define magnitude of eruption and to quantify the ash dispersal in the atmosphere however this parameter is in general difficult to be derived and no valid technique has been developed yet to measure it in real time with sufficient accuracy linear acoustics has been applied to infrasonic pressure waves generated by explosive eruptions to indirectly estimate the gas mass erupted and then the mass flow rate here we test on stromboli volcano italy the performance of such methodology by comparing the acoustic derived results with independent gas mass estimates obtained with uv cameras and constraining the acoustic source by thermal imagery we show that different acoustic methods give comparable total gas masses in the 2 to 1425 kg range which are fully consistent with the gas masses derived by uv cameras and previous direct so 2 measurements we show that total erupted gas mass estimated by infrasound is not simply a function of the initial pressure but rather the full infrasonic waveform should be considered thermal imagery provides evidence that infrasound is generated during the entire gas thrust phase we provide examples to show how total gas masses derived by infrasonic signals can be affected by large uncertainties if duration of the signal is neglected only when duration of infrasound is included the best correlation 0 8 with uv cameras and the 1 1 direct linear proportionality is obtained our results open new perspective for remotely derived gas mass and mass flow rates from acoustic signals

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

eruptive history of la poruna scoria cone central andes northern chile new stratigraphic lithological and petrographic analyses of la poruna scoria cone 21 53 s 68 30 w central andes northern chile allow the reconstruction of the eruptive sequence of this monogenetic cone petrographic and lithological characteristics allow us to identify three main lithostratigraphic units at la poruna scoria cone the first unit consists of agglutinated lapilli spatter beds and clastogenic lavas that are related to the construction of the cone the other two units are associated with a lava flow field and consist of flow of andesitic composition which differ both in their degree of weathering and in their development of channel surface and internal structures e g levees ogives and joints with these lithostratigraphic analyses we interpret that the construction of la poruna occurred during four main eruption phases involving strombolian hawaiian and transitional eruptive styles furthermore differences in the degree of erosion alteration and weathering of the lithostratigraphic units in the lava field of la poruna suggest that this flow field was formed during two eruptive events the excellent outcrop conditions and preservation state of the volcanic products of la poruna allow new stratigraphic insights that advance the wider and more general understanding and the dynamics of this important type of volcanism and the potential hazards of a scoria cone eruption the polycyclic style of the eruption needs to be included in the hazards assessment of these centers type especially when the cone is associated with structures that can be reactivated this process could correspond to a second phase of activity involving ash fall bomb and lava emission

explosive volcanic eruptions ix the transition between hawaiian style lava fountaining and strombolian explosive activity the commonest eruption styles of basaltic volcanoes involve hawaiian lava fountaining or intermittent strombolian explosions we investigate the ways in which magma rise speed at depth magma volatile content and magma viscosity control which of these eruption styles takes place we develop a model of the degree of coalescence between gas bubbles in the magma which allows us to simulate the transition between the two extreme styles of activity we find that magma rise speed is the most important factor causing the transition with gas content and viscosity also influencing the rise speed at which the transition occurs counter to intuitive expectations a decrease in gas content does not cause a transition from hawaiian to strombolian activity but instead causes a transition to passive effusion of vesicular lava rather a change from hawaiian to strombolian style requires a significant reduction in magma rise speed

a window on the deep ocean the special value of ocean bottom pressure for monitoring the large scale deep ocean circulation we show how by focusing on bottom pressure measurements particularly on the global continental slope it is possible to avoid the fog of mesoscale variability which dominates most observables in the deep ocean this makes it possible to monitor those aspects of the ocean circulation which are most important for global scale ocean variability and climate we therefore argue that such measurements should be considered an important future component of the global ocean observing system to complement the present open ocean and coastal elements our conclusions are founded on both theoretical arguments and diagnostics from a fine resolution ocean model that has realistic amplitudes and spectra of mesoscale variability these show that boundary pressure variations are coherent over along slope distances of tens of thousands of kilometres for several vertical modes we illustrate the value of this in the model atlantic by determining the time for boundary and equatorial waves to complete a circuit of the northern basin 115 and 205 days for the first and second vertical modes showing how the boundary features compare with basin scale theoretical models and demonstrating the ability to monitor the meridional overturning circulation using these boundary measurements finally we discuss applicability to the real ocean and make recommendations on how to make such measurements without contamination from instrumental drift

the gas content and buoyancy of strombolian ash plumes plinian plumes erupt with a bulk density greater than that of air and depend upon air entrainment during their gas thrust phase to become buoyant if entrainment is insufficient the column collapses into a potentially deadly pyroclastic flow this study shows that strombolian ash plumes can be erupted in an initially buoyant state due to their extremely high initial gas content and in such cases are thus impervious to column collapse the high gas content is a consequence of decoupled gas rise in the conduit in which particles are ultimately incidental the relations between conduit gas flow eruption style and plume density are explored here for strombolian scenarios and contrasted with conventional wisdom derived from plinian eruptions considering the inherent relation between gas content and initial plume density together with detailed measurements of plume velocities can help unravel ambiguities surrounding conduit processes eruption styles and hazards at poorly understood volcanoes analysis of plume dynamics at santiaguito volcano guatemala adds further support for a model involving decoupled gas rise in the conduit

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

an ocean resonance in the southeast pacific 1 satellite altimeter observations of sea surface height show an extensive region of high variability in the southeastern pacific which previous studies have suggested is a rossby wave trapped by topography here we investigate the feature using results from a high resolution global ocean model we calculate the empirical orthogonal modes and find that 29 of the ssh variability is due to a single mode we correlate the time series of the mode with the local ekman pumping and find that the correlation is largest when the wind curl is averaged over a region roughly the size of the mode we calculate the response function relating the two time series and find that it is dominated by a resonance at zero frequency with a decay time of about two days we conclude that the feature is a highly damped geostrophic mode of the ocean

magma budgets and steady state activity of vulcano and stromboli we present three models for magma budget during steady state volcanic activity by which non erupted magma is emplaced as dykes or cumulates or crystallises in place using gas and thermal data we apply our models at vulcano to calculate degassing cooling and crystallisation of magma at a rate of 40 375 kg s 1 within a magma body with an upper surface at a 2 km depth at stromboli we calculate a steady magma supply of 300 1300 kg s 1 to shallow 1 km depths

frequency based detection and monitoring of small scale explosive activity by comparing satellite and ground based infrared observations at stromboli volcano italy abstract thermal activity is a common precursor to explosive volcanic activity the ability to use these thermal precursors to monitor the volcano and obtain early warning about upcoming activity is beneficial for both human safety and infrastructure security by using a very reliably active volcano stromboli volcano in italy a method has been developed and tested to look at changes in the frequency of small scale explosive activity and how this activity changes prior to larger ash producing explosive events thermal camera footage was used to designate parameters for typical explosions at stromboli size of spatter field cooling rate frequency of explosions and this information was applied to characterize explosions in satellite imagery satellite data from the national aeronautics and space administration s moderate resolution imaging spectroradiometer modis and us japan designed advanced spaceborne thermal emission and reflection radiometer aster for numerous periods in 2002 to 2009 were analyzed for thermal features which were used to calculate an estimate of the level of activity during the given time period the results at stromboli showed a high level of small scale explosions which stop completely prior to large paroxysmal eruptive episodes this activity also corresponds well to seismic and infrasonic records at stromboli indicating that this thermal infrared monitoring method may be used in conjunction with other detection methods where available and also indicates that it may be a useful method for volcano monitoring when other methods e g seismic instrumentation infrasound arrays etc are not available

explosive volcanic eruptions vii the ranges of pyroclasts ejected in transient volcanic explosions an earlier treatment of the motions of pyroclasts produced in discrete volcanic explosions assumed that clasts were ejected into a stationary atmosphere we argue here that the air in the vicinity of an explosion site will itself be moving radially away from the source with a speed comparable to that of the clasts especially at early times after the start of the motion as a result the initial relative velocity of clasts and air will be small in the earlier treatment this relative velocity was inevitably large leading to an overestimate of the atmospheric drag force at early times and a consequent underestimate of the final clast range we set up a simple model of the explosion process which allows us to link the initial clast and air velocities and to find an approximation to the subsequent air flow field integration of the equations of motion for clasts with a wide range of sizes densities initial speeds and initial elevation angles allows the ranges of these clasts to be found clast range data from three documented explosive eruptions are re analysed to yield initial velocities and the implications of these velocities for pre explosion pressure conditions are discussed

25 day period large scale oscillations in the argentine basin revealed by the topex poseidon altimeter the measurement of the global sea surface height made by the topex poseidon satellite has provided the first synoptic view of large scale oceanic variability at intraseasonal scales from weeks to months areas of significant intraseasonal variability were found primarily in the tropics and the high latitude oceans the southern ocean in particular the focus of the paper is the finding of large scale oscillations at a period of 25 days in the argentine basin of the south atlantic ocean these oscillations exhibit a dipole pattern of counterclockwise rotational propagation centered at 458s 3178e over the zapiola rise the scale of the dipole is about 1000 km the peak to trough amplitude is on the order of 10 cm the amplitude of these oscillations has large seasonalto interannual variations these oscillations are shown to be associated with a free barotropic mode of the basin as a solution to a linearized barotropic vorticity equation closed f h contours provide a mechanism for the confinement of the waves to the topographic feature of the zapiola rise results from a numerical model simulation reproduced the patterns of the observed oscillations the resultant mass transport variability is on the order of 50 sv sv 106 m3 s21 deep current meters in the argentine basin reveal signals consistent with the altimetry observations

thermal seismic and infrasonic evidences of variable degassing rates at stromboli volcano abstract during june 1999 we measured the amplitude and rate number of events per second at which gas exited the vent at stromboli volcano as discrete gas bursts or puffs this allowed us to identify two styles of gas burst puffing activity the first is characterized by frequent rapidly rising puffs the second by less frequent slowly rising puffs each style persisted over 5 40 min long durations and was associated with a high and low number of strombolian explosions per hour respectively each period was also associated with characteristic delay times between the arrival of the infrasonic and thermal signals during strombolian explosions the delays were longer during vigorous puffing periods to explain our observations we propose a model in which the degassing process cycles between vigorous and weak degassing phases during vigorous degassing phases bubble layers ascend the conduit at a frequency of 0 5 1 0 s 1 this high degassing level reflects a gas rich magma column and leads to an increased rate in the formation of shallow foams and hence an increase in puffing and explosive activity as well as a higher free surface level and or gas jet velocity during weak phases bubble layers ascend the conduit at a reduced frequency of 0 2 0 3 s 1 during such times the magma column is poor in gas this leads to a decreased rate of foam layer formation and hence a reduction in puffing and explosive activity as well as a lower free surface level and or gas jet velocity variations in puffing activity can thus be used to track changes in the rate at which the shallow system is supplied by fresh gas rich magma our observations indicate that the two degassing styles last from 5 to 40 min and that the switch from one to the other occurs over a matter of minutes

a case history of paroxysmal explosion at stromboli timing and dynamics of the april 5 2003 event abstract on april 5 2003 stromboli volcano italy produced the most violent explosion of the past 50 years the event was exceptionally well documented thanks to the presence on the island of several scientists and a large number of instruments deployed over the preceding months to monitor the effusive eruption that began in december 2002 integration of visual documentation deposit features and geophysical data allowed an accurate reconstruction of the explosive event and its dynamics the eruption consisted of a 8 min long explosive event which evolved through four phases whose timing was precisely recorded by an infrared thermometer located about 450 m from the summit crater phases 2 and 3 lasted 39 and 42 s respectively both had an impulsive character were responsible for ejecting almost the entire mass of the pyroclastic products phases 1 and 4 represented respectively a short lived precursory event and a waning tale during phase 2 meter sized ballistic blocks were launched with velocities of 170 m s to altitudes of up to 1400 m above the craters these fell on the volcano flanks and on the village of ginostra about 2 km distant from the vent a vertical jet rose above the craters which developed to feed a convective plume that reached a height of up to 4 km the calculated mass of the phase 2 fallout deposit and mass discharge rate were 1 1 1 4 108 kg and 2 8 3 6 106 kg s respectively during phase 3 a scoria flow deposit with an estimated volume of 0 9 1 1 104 m3 was erupted from the same vent that fed the ongoing sustained lava flow the average mass discharge rate for this phase was 2 5 3 1 105 kg s products emitted during phases 2 and 3 consisted of lithic and fresh magmatic material in similar proportions the juvenile fraction consisted of a deep originated almost aphyric highly vesicular pumice mingled with a shallow derived crystal rich moderately vesicular scoria similarities with the eruption dynamics of other historical paroxysms at stromboli makes the april 5 2003 explosion representative of these highly energetic events that constitute the most hazardous volcanic phenomena at stromboli volcano

bottom currents derived from a shipborne adcp on woce cruise a11 in the south atlantic abstract this paper is divided into two parts the first describing an enhancement of the shipborne adcp system and the second describing information about bottom currents that have been obtained therefrom on woce cruise a11 in the south atlantic punta arenas to cape town rrs discovery has been fitted with a gps3df receiver and an array of antennas about its bridge which determine the instantaneous attitude of the ship the heading record from this instrument has been compared with the ship s gyrocompass throughout the 40 day cruise differences have been calculated and examined according to heading speed and movements underway differences are found insensitive to heading except in a southerly sector but on station differences exhibit a sinusoidal dependence on heading with range 3 steaming from a station led to transient behavior with recognizable effects for 1 hour the results are generally consistent with earlier reports and are attributed to gyro error an improved heading measurement has a

ocean dynamics associated with rapid j2 fluctuations importance of circumpolar modes and identification of a coherent arctic mode 1 fluctuations of the earth s dynamic oblateness j2 are a measure of global redistributions of mass between equatorial and polar regions sensitive to the component which is symmetric about the equator cox and chao recently published a time series of monthly values of j2 based on satellite orbit determination which showed rapid fluctuations from month to month as well as a large change in j2 in 1997 1998 we here investigate the ocean dynamics associated with these rapid fluctuations using a barotropic ocean model forced by atmospheric wind stress and pressure we find that the model has significant skill in reproducing the observations though not the change in 1997 1998 much of the model variability is related to coherent circumpolar fluctuations in arctic and antarctic bottom pressure which despite their apparent symmetry are forced by quite different mechanisms the antarctic mode is forced by circumpolar winds whereas the arctic mode is forced by northward winds over the entrances to the polar sea comparison with in situ observations shows that the model has skill in reproducing the polar modes arctic tide gauge records confirm the presence of a coherent mode at short periods and at long periods over at least the eurasian arctic shelf if barotropic and representative of the whole arctic this would be large enough to make a major contribution to measured j2 fluctuations but does not account for the 1997 1998 event

multiple oscillatory modes of the argentine basin part ii the spectral origin of basin modes in this paper the spectrum of barotropic basin modes of the argentine basin is shown to be connected to the classical rossby basin modes of a flat bottom constant depth rectangular basin first the spectrum of basin modes is calculated for the argentine basin by performing a normal mode analysis of the barotropic shallow water equations then a homotopy transformation is performed that gradually morphs the full bathymetry geometry through a flat bottom configuration into a rectangular basin following the eigenmodes through this transition establishes a connection between most of the basin modes and the classical rossby basin modes of a rectangular geometry in particular the 20 day mode of the argentine basin is identified with the lowest order mode of classical theory sensitivity studies show that the decay rate of each mode is controlled by bottom friction but that it is insensitive to lateral friction lateral friction strongly impacts the oscillation frequency in addition the modes are found to be only slightly sensitive to the presence of a background flow

precise comparisons of bottom pressure and altimetric ocean tides 1 a new set of pelagic tide determinations is constructed from seafloor pressure measurements obtained at 151 sites in the deep ocean to maximize precision of estimated tides only stations with long time series are used median time series length is 567 days geographical coverage is considerably improved by use of the international tsunami network but coverage in the indian ocean and south pacific is still weak as a tool for assessing global ocean tide models the data set is considerably more reliable than older data sets the root mean square difference with a recent altimetric tide model is approximately 5 mm for the m2 constituent precision is sufficiently high to allow secondary effects in altimetric and bottom pressure tide differences to be studied the atmospheric tide in bottom pressure is clearly detected at the s1 s2 and t2 frequencies the altimetric tide model is improved if satellite altimetry is corrected for crustal loading by the atmospheric tide models of the solid body tide can also be constrained the free core nutation effect in the k1 love number is easily detected but the overall estimates are not as accurate as a recent determination with very long baseline interferometry

a year of lava fountaining at etna volumes from seviri 1 we present a new method that uses cooling curves apparent in high temporal resolution thermal data acquired by geostationary sensors to estimate erupted volumes and mean output rates during short lava fountaining events the 15 minute temporal resolution of the data allows phases of waxing and peak activity to be identified during short 150 to 810 minute long events cooling curves which decay over 8 to 21 hour periods following the fountaining event can also be identified application to 19 fountaining events recorded at etna by msg s seviri sensor between 10 january 2011 and 9 january 2012 yields a total erupted dense rock lava volume of 28 106 m3 with a maximum intensity of 227 m3 s 1being obtained for the 12 august 2011 event the time averaged output over the year was 0 9 m3 s 1 this being the same as the rate that has characterized etna s effusive activity for the last 40 years

transient explosions at open vent volcanoes the case of stromboli italy stromboli is a persistently active open vent basaltic volcano whose activity is controlled by the balance between magma supply outgassing and eruptive rates and is characterized by low intensity regular strombolian explosions however two types of large transient violent explosive eruptions suddenly occur with no clear precursory activity these explosions called major and paroxysmal depending on size cover a large variability in intensity and mag nitude but are all marked by short duration paroxysms have significantly larger intensities 106 kg s than major explosions 104 kg s and fundamental differences in the characteris tics composition crystallinity vesicularity of the erupted tephra suggesting that different sources feed these two eruption types paroxysms are generated by the explosive fragmen tation of low porphyricity lp magma mingled with high porphyricity resident magma in the shallow reservoir whereas major eruptions are likely associated with destabilization of the lower portion of the shallow magmatic system continuously hybridized by the arrival of lp magma in general the intensity of these explosions is related to the amount of the lp magma erupted 107 kg in paroxysms and 104 105 kg in major explosions suggesting that the magma plays a major role in the fragmentation mechanism despite its primary impor tance in the hazards of stromboli the total amount of magma erupted in these events in the past 10 years is less than 1 of the total mass erupted by the volcano

interaction of mesoscale variability with large scale waves in the argentine basin abstract the argentine basin of the south atlantic ocean is a region of complicated ocean dynamics involving a wide range of spatial and temporal scales previous studies reported the existence of a basin mode of topographic barotropic rossby waves with a period close to 25 days in the region using observations of sea level anomalies from satellite altimeter measurements the present study provides evidence of interaction between the large scale 25 day waves and the energetic mesoscale variability of the region the amplitude of the 25 day waves is highly intermittent with dominant periods in the range of 110 150 days within this period band the wave amplitude is coherent with the energy level of the mesoscale variability when the mesoscale energy level goes down the wave amplitude goes up and vice versa suggesting an exchange of energy between the two scales this coherence is linked to the first three empirical orthogonal functions eofs of the sea level anomalies the spatial patterns of these

an algorithm for the detection and characterisation of volcanic plumes using thermal camera imagery volcanic plumes are turbulent mixtures of particles and gas which are injected into the atmosphere during a volcanic eruption depending on the intensity of the eruption plumes can rise from a few tens of metres up to many tens of kilometres above the vent and thus present a major hazard for the surrounding population currently however few if any algorithms are available for automated plume tracking and assessment here we present a new image processing algorithm for segmentation tracking and parameters extraction of convective plume recorded with thermal cameras we used thermal video of two volcanic eruptions and two plumes simulated in laboratory to develop and test an efficient technique for analysis of volcanic plumes we validated our method by two different approaches first we compare our segmentation method to previously published algorithms next we computed plume parameters such as height width and spreading angle at regular intervals of time these parameters allowed us to calculate an entrainment coefficient and obtain information about the entrainment efficiency in strombolian eruptions our proposed algorithm is rapid automated while producing better visual outlines compared to the other segmentation algorithms and provides output that is at least as accurate as manual measurements of plumes

a summary of electromagnetic studies on the abitibi grenville transect electromagnetic surveys on the abitibi grenville lithoprobe transect have elucidated a number of conductivity signatures that can be genetically linked to precambrian tectonic processes some major fault zones are moderately conductive possibly signalling graphite deposition from a mantle co2 flux along crust penetrating fault systems however conductive graphitic metasedimentary rocks characteristic of foreland basins are apparently absent from the transect area a weak inverse correlation between metamorphic grade and electrical conductivity was observed by following rock units across the grenville front into high grade equivalents within the parautochthonous belt a uniformly conductive mid crustal layer extends across the grenville front apparently without change in character the existence of this ubiquitous mid crustal conductor has been interpreted to mean that electrical conductivity is controlled by the present day pressure temperature and fluid saturation of the lower crust independent o

strombolian explosions 2 eruption dynamics determined from acoustic measurements strombolian activity consists of a series of explosions due to the breaking of a large overpressurized bubble at the surface of the magma column acoustic pressure due to sound waves has been measured and analyzed at stromboli for more than 50 explosions three parts can be distinguished in the acoustic pressure waveform which are related to the behavior of the bubble before during and after its bursting before the sharp rise in acoustic pressure the signal is dominated by waves with a frequency of 2 hz which develop on the nose of the bubble they produce sound in air by imposing a rapid motion to the interface and one could detect a bubble travelling in the uppermost 30 m of the magma column when the bubble reaches the air magma interface its strong vibration driven by a large overpressure inside the gas generates the main event with a frequency around 9 hz after the bubble has burst kinematic waves of frequency around 4 5 hz are the main source of sound they develop at the surface of the magma left on the conduit side the three types of motion although determined independently give consistent results furthermore combining the results obtained for the two types of kinematic waves the magma viscosity is estimated to be of 300 65 pa s which is in good agreement with petrological constraints and corroborates the validity of our analysis this suggests that acoustic measurements constitute a powerful tool in the understanding of eruption dynamics

lava discharge during etna s january 2011 fire fountain tracked using msg seviri etna s january 2011 eruption provided an excellent opportunity to test the ability of meteosat second generation satellite s spinning enhanced visible and infrared imager seviri sensor to track a short lived effusive event the presence of lava fountaining the rapid expansion of lava flows and the complexity of the resulting flow field make such events difficult to track from the ground during the etna s january 2011 eruption we were able to use thermal data collected by seviri every 15 min to generate a time series of the syn eruptive heat flux lava discharge waxed over a 1 h period to reach a peak that was first masked from the satellite view by a cold tephra plume and then was of sufficient intensity to saturate the 3 9 m channel both problems made it impossible to estimate time averaged lava discharge rates using the syn eruptive heat flux curve therefore through integration of data obtained by ground based doppler radar and thermal cameras as well as ancillary satellite data from moderate resolution imaging spectrometer and advanced very high resolution radiometer we developed a method that allowed us to identify the point at which effusion stagnated to allow definition of a lava cooling curve this allowed retrieval of a lava volume of 1 2 106 m3 which if emitted for 5 h was erupted at a mean output rate of 70 m3 s 1 the lava volume estimated using the cooling curve method is found to be similar to the values inferred from field measurements

linking variable explosion style and magma textures during 2002 at stromboli volcano italy microtextural characteristics of fresh ejecta from stromboli volcano were examined from three periods of differing eruption style and intensity in 2002 activity shifted from relatively weak and infrequent ash charged explosions during january through may into two broad cycles of waxing activity in june through late september and late september through december followed by the onset on 28 december of the 2002 2003 effusive eruption analyzed sets of lapilli from may september october and 28 december show contrasts in the physical properties of magma resident in the shallow conduit during this range of activity three distinct textures are observed among the analyzed pyroclasts low density ld with an abundance of subspherical bubbles the presence of large irregularly shaped bubbles and a light to transparent glass matrix transitional texture tt with an intermediate number of subspherical bubbles a high frequency of large irregularly shaped bubbles and a honey colored glass matrix and high density hd with sparse relatively small bubbles conspicuous large irregular bubbles and a dark glass matrix observational and quantitative data density vesicle size indicate that these textures are linked through variable residence time in stromboli s shallow conduit with an ongoing evolution from ld to hd magma calculations suggest that residual ld magma will evolve to hd texture in a period of hours to days contrasting amounts of the ld tt and hd magmas are present in each sample with the most tt in may the most ld in september october and the most hd in december this implies that the shallow magma had a different rheology at each collection period the viscosity of ld and hd magmas are calculated to be in the range of 2 000 to 2 600 and 3 000 to 5 000 pa s respectively which with their changing proportions must have implications for rates of bubble slug ascent and processes of fragmentation this study suggests that an increasing maturity of magma in stromboli s shallow conduit with resultant increase in viscosity feeds back to reduce the intensity of explosions whereas a steady flux of ld magma favors more powerful explosions

volumetric characteristics of lava flows from interferometric radar and multispectral satellite data the 1995 fernandina and 1998 cerro azul eruptions in the western galapagos we have used a suite of remotely sensed data numerical lava flow modeling and field observations to determine quantitative characteristics of the 1995 fernandina and 1998 cerro azul eruptions in the western galapagos islands flank lava flow areas volumes instantaneous effusion rates and average effusion rates were all determined for these two eruptions for which only limited syn eruptive field observations are available using data from spot topsar ers 1 and ers 2 we determined that the 1995 fernandina flow covers a subaerial area of 6 5 106 m2 and has a subaerial dense rock equivalent dre volume of 42 106 m3 field observations atsr satellite data and the flowgo numerical model allow us to determine that the effusion rate declined exponentially from a high of 60 200 m3 s 1 during the first few hours to 5 m3 s 1 prior to ceasing after 73 days with a mean effusion rate of 4 16 m3 s 1 integrating the atsr derived exponentially declining effusion rate over the eruption duration produces a total subaerial submarine dre volume of between 27 and 100 106 m3 the range in values being due to differing assumptions about heat loss characteristics only values in the higher part of this range are consistent with the independently derived subaerial volume using spot topsar ers 1 and ers 2 data we determine that the 1998 cerro azul flow is 16 km long covers 16 km2 and has a dre volume of 54 106 m3 flowgo produces at vent velocity and effusion rate values of 11 m s 1 and 600 m3 s 1 respectively the velocity value agrees well with the 12 m s 1 estimated in the field the mean effusion rate total dre volume duration was 7 47 m3 s 1 dike dimensions fissure lengths and pressure gradients along the conduit based on magma chamber depth estimates of 3 5 km produce mean effusion rates for the two eruptions that range over nearly four orders of magnitude the range being due to uncertainty in the magma viscosity dike dimensions and pressure gradient between magma chamber and vent although somewhat consistent with mean effusion rates from other techniques their wide range makes them less useful the exponentially declining effusion rates during both eruptions are consistent with release of elastic strain being the driving mechanism of the eruptions our results provide independent input parameters for previously published theoretical relationships between magma chamber pressurization and eruption rates that constrain chamber volumes and increases in volume prior to eruption as well as time constants of exponential decay during the eruption the results and theoretical relationships combine to indicate that at both volcanoes probably 25 30 of the volumetric increase in the magma chamber erupted as lava onto the surface in both eruptions the lava flow volumes are less than 1 of the magma chamber volume

machine learning as a detection method of strombolian eruptions in infrared images from mount erebus antarctica abstract mount erebus antarctica has a persistent lava lake with strombolian eruptions volcanic eruptions can be automatically detected with multiple methods such as cross correlation of seismic recordings and identifying anomalies in gas emissions we demonstrate a new method of detecting strombolian eruptions by training a convolutional neural network to automatically categorize eruptions in infrared images obtained from the rim of the crater above the ray lava lake atop mount erebus over 9 million images were obtained from previous research peters et al 2014a the infrared images were shot during a span of over 2 years one image every 2 s when weather conditions did not hinder the electrical supply training was performed with infrared images of the eruptions detected through seismic cross correlation with a stacked waveform eruptions detected using machine learning on infrared images from december 2013 through december 2014 correctly categorized 84 of the detections as eruptions the remaining 16 were caused by effects from the plume confounding the neural network nearly all of the eruptions detected utilizing seismic cross correlation were also categorized correctly by the neural network during periods for which image data was available we concluded machine learning is an effective method for classifying the characteristics of strombolian eruptions which further improves the ability to study their origins while assessing the hazards posed by volcanic eruptions

dynamically balanced absolute sea level of the global ocean derived from near surface velocity observations 1 the 1992 2002 time mean absolute sea level distribution of the global ocean is computed for the first time from observations of near surface velocity for this computation we use the near surface horizontal momentum balance the velocity observed by drifters is used to compute the coriolis force and the force due to acceleration of water parcels the anomaly of horizontal pressure gradient is derived from satellite altimetry and corrects the temporal bias in drifter data distribution ncep reanalysis winds are used to compute the force due to ekman currents the mean sea level gradient force which closes the momentum balance is integrated for mean sea level we find that our computation agrees within uncertainties with the sea level computed from the geostrophic hydrostatic momentum balance using historical mean density except in the antarctic circumpolar current a consistent horizontally and vertically dynamically balanced near surface global pressure field has now been derived from observations

pāhoehoe flow cooling discharge and coverage rates from thermal image chronometry 1 theoretically and empirically derived cooling rates for active p hoehoe lava flows show that surface cooling is controlled by conductive heat loss through a crust that is thickening with the square root of time the model is based on a linear relationship that links log time with surface cooling this predictable cooling behavior can be used assess the age of recently emplaced sheet flows from their surface temperatures using a single thermal image or image mosaic this allows quantification of the variation in areal coverage rates and lava discharge rates over 48 hour periods prior to image capture for p hoehoe sheet flow at k lauea hawai i this gives coverage rates of 1 5 m2 min at discharge rates of 0 01 0 05 m3 s increasing to 40 m2 min at 0 4 0 5 m3 s our thermal chronometry approach represents a quick and easy method of tracking flow advance over a three day period using a single thermal snap shot

volcanic plume characteristics determined using an infrared imaging camera abstract measurements of volcanic emissions ash and so2 from small sized eruptions at three geographically dispersed volcanoes are presented from a novel multichannel uncooled imaging infrared camera infrared instruments and cameras have been used previously at volcanoes to study lava bodies and to assess plume dynamics using high temperature sources here we use spectrally resolved narrowband 0 5 1 m bandwidth imagery to retrieve so2 and ash slant column densities g m 2 and emission rates or fluxes from infrared thermal imagery at close to ambient atmospheric temperatures the relatively fast sampling 0 1 0 5 hz of the multispectral imagery and the fast sampling 1 hz of single channel temperature data permit analysis of some aspects of plume dynamics estimations of so2 and ash mass fluxes and total slant column densities of so2 and fine ash in individual small explosions from stromboli italy and karymsky russia and total so2 slant column densities and fluxes from lascar chile volcanoes are provided we evaluate the temporal evolution of fine ash particle sizes in ash rich explosions at stromboli and karymsky and use these observations to infer the presence of at least two distinct fine ash modes with mean radii of 10 m the camera and techniques detailed here provide a tool to quickly and remotely estimate fluxes of fine ash and so2 gas and characterize eruption size

geoscience impact a synthesis of studies of the sudbury structure geophysical probing results are synthesized into a three dimensional framework necessary for understanding the genesis of the sudbury structure based primarily on seismic reflection results centred on the sudbury igneous complex remnants of crustal melting from a catastrophic meteorite impact are superimposed on the juxtaposition of mid crustal rocks exhumed during the archean against deformed paleoproterozoic sedimentary rocks sedimentation metamorphism deformation and metasomatic overprints are all part of the post impact history of sudbury and tend to dominate the geophysical response of the structure pre impact deformation although certainly preserved in some aspects of sudbury geology is not clearly expressed in the geophysical data nor are any elements of impact induced deformation geophysical views of the sudbury igneous complex are thus somewhat biased in representing mostly the post impact but pre grenvillian history of the region with the exception of igneous events establishing th

on the dynamics of the zapiola anticyclone recent observations obtained in the south atlantic suggest the existence of a strong anticyclonic flow positioned over a major bottom topographic feature known as the zapiola drift here a numerical simulation of the south atlantic is described in which this anticyclone is reproduced and the model is used to diagnose the dynamics maintaining this flow with a mean barotropic transport of 140 sv and bottom velocities of 10 cm s 1 the simulated zapiola anticyclone compares well with in situ observations furthermore the model surface eddy kinetic energy shows a local minimum over the drift in agreement with observations from topex poseidon numerical experiments show that the circulation feature is sensitive to the intensity of the eddy field and to the particular value of the bottom friction both of these tendencies are in agreement with a theoretical explanation of the zapiola anticyclone that has recently appeared elsewhere thus we argue that the anticyclone is maintained by eddy driven potential vorticity fluxes accelerating flow within topographically closed ambient potential vorticity contours as far as we know this is the first south atlantic simulation to reproduce the zapiola anticyclone in a realistic fashion the quantitative success of this experiment is attributed to the use of a topography following sigma coordinate in a spatially well resolved model

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

implications of laboratory electrical measurements on interpretation of em surveys and origin of the sudbury structure electrical resistivity and effective porosity have been measured for 52 drillcore samples representing major sedimentary and igneous lithologies exposed in the sudbury structure ss the purpose was to constrain interpretation of high conductivity anomalies observed by surface electromagnetic em surveys conducted across the ss and to provide information on its origin while zones of low resistivity are known to exist in the upper sedimentary formations rocks at depth are generally characterized by high resistivities 104 7 104 m leaving the source of the deep em anomaly unexplained however samples with low resistivities 7 20 m have been unexpectedly found in the cores from lower sections of the ss depths possibly corresponding to that of the em anomaly these samples are characterized by low porosities 0 3 0 6 normal bulk densities 2 78 2 81 and a porphyritic texture with a blackish matrix suggesting carbon as the likely cause of the low resistivities

on deep current and hydrographic observations from a mudwave region and elsewhere in the argentine basin near bottom current measurements from both sides of a mudwave in an extensive mudwave region of the mid argentine basin are examined for evidence of lee waves such waves appear to exist when the across crest flow exceeds a critical value predicted by flood 1988 deep sea research 35 973 983 of about 9 cm s 1 the observations agree with the predictions of blumsack and weatherly 1989 deep sea research 36 155 172 in three of four cases however if it is assumed that the flow perturbations induced by lee waves are shifted slightly downcurrent from that predicted by the blumsack and weatherly model then there is agreement in all four cases the mudwave region is characterized as having a strong 10 cm s 1 steady eddy kinetic energy mean kinetic energy current the westward flow is consistent with the anticyclonic abyssal gyre centered about the zapiola drift inferred by flood and shor 1987 deep sea research 35 973 983 near bottom flow measurements made further to the west in the region of confluence of the brazil and malvinas current extensions reveal relatively energetic fluctuations and equatorward flowing deep western boundary currents along the continental slope along the continental rise a poleward flow is observed consistent with that inferred by reid 1989 progress in oceanography 23 149 244 too cold bottom layers were found to be common only on the lower continental slope 4000 m depth and at the mid basin mudwave site

the 25 day period large scale oscillations in the argentine basin revisited abstract from sea surface height measurements made by the ocean topography experiment topex poseidon satellite fu et al found and described large scale oscillations at the period of 25 days in the argentine basin of the south atlantic ocean these oscillations were previously hinted at by in situ observations only the extensive space time sampling capability of topex poseidon however was able to give a complete description of the phenomenon as a counterclockwise rotating dipole centered at 45 s 317 e over the zapiola rise fu et al also undertook theoretical and numerical studies to suggest that the phenomenon is a resonantly excited barotropic normal mode of the locally closed f h contour in a simulation study however they also found that the space time smoothing scheme employed would probably lower the amplitude of the estimated phenomenon by 30 40 by reprocessing the data using a different method and showing the amplitude to be almost 2 times as large in this note it is confirmed that t

variations of the argentine gyre observed in the grace time variable gravity and ocean altimetry measurements this work is supported by taiwan ministry of science and technology grants 105 2811 m 001 031 and 106 2116 m 001 013 and by national nature science foundation of china grants 41474019 41504014 and 41704012

high frame rate thermal imagery of strombolian explosions implications for explosive and infrasonic source dynamics 1 explosive activity at stromboli volcano is analyzed using a high frame rate 50 hz thermal camera and differential pressure transducers we develop a thermal image based decomposition method to derive vertical and horizontal exit velocities of the explosive cloud peak vertical velocity ranges between 23 and 203 m s slightly higher than previous estimates and rapidly decreasing to a constant value of 30 50 m s within the first 0 1 s plume velocities are consistent with an elongated cloud expanding much faster vertically than horizontally and indicating the interaction with the conduit wall considering a vent radius of 2 m we estimate a volumetric flux of 200 600 m3 s which converts to total volumes of gas particles of 103 104 m3 for a single eruption these volumes are proportional to the thermal energy recorded by the camera providing a means to convert thermal radiance to volumes comparing the thermal onset of the explosions with the arrival time of the acoustic pressure we demonstrate that infrasound is propagating 0 14 1 7 s ahead of the explosive front the time difference between thermal and acoustic onsets constrains the infrasonic source within the conduit at 15 35 m below the crater rim peak amplitudes of acoustic pressure show a power law relationship p u2 with the exit vertical velocities consistent with the energy balance of a two phase flow rapidly accelerated in the conduit by gas decompression our results support monopole isotropic acoustic radiation of a source embedded within the conduit walls and indicate that explosive dynamics undergo strong accelerations of 103 104 m s2

types and mechanisms of strombolian explosions characterization of a gas dominated explosion at stromboli textural and chemical analyses of bombs quenched directly from a normal explosion at stromboli volcano italy were integrated with coincident seismic acoustic and thermal data the data set defines a new gas dominated type of strombolian eruption named type 0 these events are characterized by high velocity emission 150 250 m s 1 of a few relatively small juvenile particles with entrained non juvenile clasts that previously fell back into the vent to be re erupted for the studied event the explosion depth was more than 250 m deep and the particles showed little residence time in the shallow system slug ascent velocities over the final 20 35 m of magma filled conduit and the low viscosity of the resident magma are all consistent with simple bubble burst in a clean conduit this conduit type and eruption style likely fit popular slug ascent and burst models used to explain strombolian eruptions in contrast the ballistic dominated type of explosions type 1 are associated with larger proportions of stagnant material in the shallow system magma mix we argue that the additional volume of this stagnant material pushes the free surface upward because of the larger volume of material available for entrainment into a type 1 slug burst which has to fragment through a thick cap of degassed material type 1 events tend to be rich in particles in contrast the less spectacular gas rich type 0 events have little material to entrain thus being poor in lapilli and bombs

an ocean resonance in the indian sector of the southern ocean 1 satellite altimeter observations of sea surface height show an extensive region of long wavelength fluctuations in the indian sector of the southern ocean a previous study showed that a similar feature found in the south pacific is due to a trapped geostrophic mode of the ocean here we investigate the feature in the indian sector and find that it is due to a similar mode with a decay time of approximately 3 5 days these previously unsuspected large scale modes of the ocean will have a significant effect locally on the satellite based gravity measurements currently underway

deep geometry of the sudbury structure from seismic reflection profiling seismic reflection data show the deep geometry of the sudbury structure to be markedly asymmetric the sudbury north range comprises shallowly south dipping sedimentary strata overlying a thick unit of heterolithic breccia and melt bodies layered rocks of the sudbury igneous complex and footwall gneiss reflections from the upper layers are interrupted by faults near the center of the sudbury basin whereas the basal mafic units and footwall gneiss continue dipping southward and appear to be tightly folded or truncated near the creighton fault in contrast the seismic image of the south range is dominated by a distinctive series of moderately south dipping reflections interpreted as thrust faults or shear zones on which severe telescoping and imbrication of lithological units and considerable northwest southeast shortening of the sudbury structure have occurred such shortening explains the noncircular shape of the structure and thus removes a critical objection to the sudbury impact crater hypothesis the new structural model is shown to be consistent with regional magnetic and gravity fields a large hidden ultramfic mafic mass is no longer required to explain the potential field data

on the transition from strombolian to fountaining activity a thermal energy based driver since 1999 mount etna s italy south east crater system has been characterised by episodic lava fountaining each episode is characterised by initial strombolian activity followed by transition to sustained fountaining to feed high effusion rate lava flow here we use thermal infrared data recorded by a permanent radiometer station to characterise the transition to sustained fountaining fed by the new south east crater that developed on the eastern flank of the south east crater starting from january 2011 we cover eight fountaining episodes that occurred between 2012 and 2013 we first developed a routine to characterise event waveforms apparent in the precursory strombolian phase this allowed extraction of a database for thermal energy and waveform shape for 1934 events we detected between 66 and 650 events per episode with event durations being between 4 and 55 s in total 1508 78 of the events had short waxing phases and dominant waning phases event frequency increased as climax was approached events had energies of between 3 0 106 and 5 8 109 j with rank order analysis indicating the highest possible event energy of 8 1 109 j to visualise the temporal evolution of retrieved parameters during the precursory phase we applied a dimensionality reduction technique results show that weaker events occur during an onset period that forms a low energy sink the transition towards fountaining occurs at 107 j where subsequent events have a temporal trend towards the highest energies and where sustained fountaining occurs when energies exceed 109 j such an energy based framework allows researchers to track the evolution of fountaining episodes and to predict the time at which sustained fountaining will begin

three forms of variability in argentine basin ocean bottom pressure ocean bottom pressure data are examined from a year long deployment of two bottom pressure recorders separated by 417 km in the argentine basin three forms of variability are found at high frequencies periods shorter than 2 hours the signal appears to be due to gravity wave propagation with the waves preferentially coming from the west at intermediate frequencies periods between 2 hours and 12 days the two records are highly coherent and in phase reflecting large scale coherent fluctuations which are well reproduced in a barotropic ocean model however the dominant mode is at a period of 20 days with a phase lag of about 90 100 degrees between the two records consistent with the a mode of variability previously inferred from satellite altimetry and current meters although the slightly shorter period is consistent with the suggestion that more than one mode contributes to the altimeter observations comparison with altimetry demonstrates that aliasing of higher frequency signals is not a significant source of error and confirms that a previously used altimetry mapping technique reduces the apparent amplitude of the mode the pressure records show a transport change of about 280 sv over one 12 day period and altimetry suggests that regions of higher variability exist the mode is only weakly excited in barotropic models but is strongly excited in a baroclinic model with a realistic eddy field suggesting that it is intrinsically linked to interactions between eddies mean flow and topography

wind forced intraseasonal sea level variability of the extratropical oceans abstract seven years worth of sea level observations from the topex poseidon altimeters and wind observations from the european remote sensing satellites ers 1 2 scatterometers were used to investigate the dynamics of large scale intraseasonal sea level variability at mid and high latitudes coherent patterns of sea level variability with spatial scales of 1000 km and timescales of 20 days to 1 year are identified in three particular regions the bellingshausen basin west of drake passage the australian antarctic basin and the central north pacific ocean 30 50 n near the date line significant coherence is found between wind stress curl and the sea level variability a simple barotropic vorticity equation in which the time rate of relative vorticity variation is balanced by the wind stress curl and a damping term is used to simulate the sea level anomalies with a significant degree of correlation with the observations although the coherence between the simulation and the observation is signifi

image processing of explosive activity at stromboli abstract a new way to study the dynamics of explosive behaviour at different vents of stromboli volcano is proposed the method is based on computer processing of images taken by an infrared film camera at a rate of 4 pictures per second each picture has been digitized by use of an image scanner with a 75 d p i dots per inch resolution and 256 levels of gray then processed and the total mass of the ejected material has been calculated for each photograph with this procedure the flux of ejected matter throughout every single explosive event has been reconstructed the analysis of trajectories made on adequate samples of ejecta has allowed us to evaluate the ejection velocity the mode of the mass flux distribution and the mean value of the velocities calculated for individual particles quantify the kinetic energy of an explosion vents nos 1 and 3 which remained active after the last effusive eruption of 1985 1986 show several explosive patterns the energy of which is measured the observed flux distributions have been checked both numerically and experimentally by modelling impulsive events the computer simulations of the mass distributions have allowed us to speculate on the possible explosive dynamisms two different models have been used a single impulse model confirms the behaviour actually shown by one of the two vents while the behaviour of the other is better depicted by a cumulative trend of successive impulses in rhythmic sequence moreover through the experimental approach we have had the opportunity to test the overall resolution of the method the observed matter flux distribution has then been associated to the seismic signals in order to correlate the dynamics involved in the explosions with the seismic source mechanisms

observations of the effect of wind on the cooling of active lava flows 1 we present the first direct observations of the cooling of active lava flows by the wind we confirm that atmospheric convective cooling processes i e the wind dominate heat loss over the lifetime of a typical pahoehoe lava flow in fact the heat extracted by convection is greater than predicted especially at wind speeds less than 5 m s and surface temperatures less than 400 c we currently estimate that the atmospheric heat transfer coefficient is about 45 50 w m 2 k 1 for a 10 m s wind and a surface temperature 500 c further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds

multiple oscillatory modes of the argentine basin part i statistical analysis observations of the sea surface height in the argentine basin indicate that strong variability occurs on a time scale of 2030 days the aim of this study is to determine the physical processes responsible for this variability first results are presented from two statistical techniques applied to a decade of altimetric data a complex empirical orthogonal function ceof analysis identifies the recently discovered dipole mode as the dominant mode of variability a principal oscillation pattern pop analysis confirms the existence of this mode which has a period of 25 days the second ceof displays a propagating pattern in the northern argentine basin plus a rotating dipole in the southwest corner the pop analysis identifies both patterns as individual modes with periods of 30 and 20 days respectively second the barotropic normal modes of the argentine basin are studied using a shallow water model capturing the full bathymetry of the basin coherences between the spatial patterns of these modes and altimeter data suggest that several of the basin modes are involved in the observed variability this analysis implies that the 20 day mode detected by recent bottom pressure measurements is a true barotropic mode however the 25 day variability as found in altimeter data cannot be directly attributed to the excitation of a free rossby basin mode this study indicates that the results of several apparently conflicting observations of the flow variability in the argentine basin can be reconciled by assuming that multiple basin modes are involved