magma reservoir response to transient recharge events the case of santorini volcano greece igneous bodies are built incrementally by episodic magma injection events that vary in rate and duration such recharge events can either grow an upper crustal magma reservoir or trigger an eruption this bifurcation in behavior remains poorly constrained but is essential to volcanic hazard assessment here we use a numerical model that couples the thermal and mechanical processes in a magma reservoir to study the evolution of the santorini magmatic system greece over the past 20 k y our results constrain the recharge rate and duration that are necessary to trigger an eruption for the known long term average inflow rate of 10 3 km3 yr the size of the chamber and its exsolved volatile content are dominant controls on the critical recharge rate and duration that will trigger an eruption our model successfully reproduces the main features of the minoan eruption and nea kameni activity providing volume estimates for the active part of the current subvolcanic reservoir as well as information regarding the presence of exsolved volatiles thermomechanical models offer a new framework to integrate the historic eruption record with geodetic measurements and provide a context to understand the past present and future of active volcanic centers

an analysis of the cross shore beach morphodynamics of a sandy and a composite gravel beach in this paper beach profile surveys acquired over more than a decade at a sandy beach narrabeen beach new south wales australia and a composite sand gravel beach milford on sea christchurch bay uk are analysed to compare and contrast cross shore morphodynamics of the two beach types the different behavioural characteristics of the two beach types at decadal inter annual and intra annual time scales are investigated comparisons of beach profiles with dean s equilibrium profile and vellinga s erosion profile show that the dean s profile satisfactorily represents the time mean profiles of both beach types statistical and empirical orthogonal function eof analyses confirm the generally accepted model that the inter tidal zone is the most morphodynamically active region on a sandy beach whereas the swash zone is the most dynamic region on a mixed sand gravel beach the results also imply that during storms composite sand gravel beaches may become unstable due to cutback of the upper beach while sandy beaches are more likely to be unstable as a result of beach lowering due to sediment transport from the inter tidal zone to the sub tidal zone during storms eof results also show that milford on sea beach is in a state of steady recession while the narrabeen beach shows a cyclic erosion accretion variability a multivariate technique canonical correlation analysis cca shows that on the composite beach a strong correlation exists between incident wave steepness and profile response which could be attributed to the unsaturated surf zone whereas on the sandy beach any correlation is much less evident

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

evidence that coupling to magma chambers controls the volume history and velocity of laterally propagating intrusions 1 in this paper i present a simple analytical solution for the unsolved problem of a propagating dike coupled to a magma chamber as recognized by segall et al 2001 the flow of the magma from a chamber to a dike is described by an ordinary differential equation for the unknown pressures of chamber and dike the most intuitive assumption on magma exchange is that the volume gained by the intrusion equals the volume lost by the chamber this constraint however implies a chamber so large that its pressure does not drop during the feeding process and an incompressible magma that does not expand or vesiculate as it intrudes models assuming constant driving pressure fail to explain observations here mass conservation constrains pressure as magma flows from the chamber to the dike and the compressibilities of magma and sources control volume changes these assumptions allow me to decouple the equations and solve the system analytically the model predicts that chamber and dike volume change exponentially with time as v t v 1 exp t the asymptotic volume v and the timescale are found to be functions of rock magma chamber and dike parameters and of the initial pressure conditions assuming that the intrusion is shaped as an elongating cuboid its velocity is found to change as v v0exp t where v0 is the initial dike velocity the model is successfully tested against the best observations available for lateral dike propagation events the volume history of chamber and dike during the 2000 miyakejima intrusion japan and dike velocity during the 1978 krafla event iceland and during some intrusions following the 2005 event in afar ethiopia this paper confirms and extends the results of a previous study by rivalta and segall 2008 who found the final ratio between dike volume and the volume withdrawn from the chamber to be rv 1 4 m 3 1 where is the host rock rigidity and m is the magma compressibility here i demonstrate that the formula for rv holds at any time during the intrusion not just at the end this model confirms that some magma chambers behave as stiff magma tanks able to inflate large dikes as balloons and demonstrates that high volume ratios are unlikely if the chamber has a pure sill shape fitting observations with the model allows us to estimate several dike chamber magma and rock parameters

evolution of santorini volcano dominated by episodic and rapid fluxes of melt from depth santorini volcano in greece was thought to be continually charged by small injections of magma measurements of surface deformation show that magma equivalent to 10 50 of that emitted in previous small eruptions has been injected beneath santorini since january 2011 implying that the volcano is instead charged by rapid episodic fluxes of melt

constraints on dike propagation from continuous gps measurements the january 1997 east rift zone eruption on kilauea volcano hawaii occurred within a network of continuous global positioning system gps receivers the gps measurements reveal the temporal history of deformation during dike intrusion beginning 8 hours prior to the onset of the eruption the dike volume as a function of time estimated from the gps data using elastic green s functions for a homogeneous half space shows that only two thirds of the final dike volume accumulated prior to the eruption and the rate of volume change decreased with time these observations are inconsistent with simple models of dike propagation which predict accelerating dike volume up to the time of the eruption and little or no change thereafter deflationary tilt changes at kilauea summit mirror the inferred dike volume history suggesting that the rate of dike propagation is limited by flow of magma into the dike a simple lumped parameter model of a coupled dike magma chamber system shows that the tendency for a dike to end in an eruption rather than intrusion is favored by high initial dike pressures compressional stress states large compressible magma reservoirs and highly conductive conduits linking the dike and source reservoirs comparison of model predictions to the observed dike volume history the ratio of erupted to intruded magma and the deflationary history of the summit magma chamber suggest that most of the magma supplied to the growing dike came from sources near to the eruption through highly conductive conduits interpretation is complicated by the presence of multiple source reservoirs magma vesiculation and cooling as well as spatial variations in dike normal stress reinflation of the summit magma chamber following the eruption was measured by gps and accompanied a rise in the level of the pu u o o lava lake for a spheroidal chamber these data imply a summit magma chamber volume of 20 km3 consistent with recent estimates from seismic tomography continuous deformation measurements can be used to image the spatiotemporal evolution of propagating dikes and to reveal quantitative information about the volcanic plumbing systems

catastrophic caldera forming eruptions thermomechanics and implications for eruption triggering and maximum caldera dimensions on earth abstract approximately every 100 000 years the earth experiences catastrophic caldera forming supereruptions that are considered to be one of the most hazardous natural events on earth utilizing new temperature dependent viscoelastic numerical models that incorporate a mohr coulomb failure criterion we find that eruptive failure of the largest magma chambers is a function of the geometry of the overlying roof and the location of the brittle ductile transition in particular the ductile halo created around the hot magma chamber buffers increasing overpressures and prevents pressure relief via magmatic injection from the magma chamber the numerical results indicate that as chamber volume increases the higher temperatures in the host rock and the decrease in the roof aspect ratio cause a shift from reservoir triggered eruption to an external roof triggered mechanism specifically as overpressure increases within the largest magma chambers extensive uplift in the overlying roof promotes the development of through going faults that may trigger eruption and caldera collapse from above we find that for magma chamber volumes 103 km3 and roof aspect ratios depth width

clast mobility within boulder beaches over two winters in galicia northwestern spain abstract a micro drone was used to make low altitude flights over boulder beaches at laxe brava and oia in galicia northwestern spain flights were made in july 2012 may 2013 and spring 2014 high resolution digital terrain models and orthophotographs combined with gis mapping were used to monitor changes in the position of thousands of boulders maximum storm wave height was higher in the winter of 2013 2014 than in winter 2012 2013 and this was reflected in an increase in the proportion of the boulders that moved in the two winters from 17 to almost 48 at laxe brava and from 53 to almost 88 at oia the greater mobility of the boulders at oia can be attributed in part to their generally smaller size although there was considerable overlap between the size of boulders that moved and those that did not move within and between the two beaches there were mobile boulders in areas up to several metres above the high tidal level on both beaches and boulder transport in the shore normal and alongshore directions triggered some changes in the beach profiles particularly in the middle to upper parts of the beaches estimates of threshold transport conditions scaled to boulder mass breaker height and other variables suggested that all but the very largest boulders on the two beaches should have been mobile even during the summer months when the waves were much lower than in winter model over prediction can be attributed to a number of factors including constraints on movement imposed by surrounding boulders differences in boulder size and their effect on pivoting angles and on the degree to which boulders are exposed or sheltered from wave impact and difficulties in assigning appropriate values to model coefficients

physics based models of ground deformation and extrusion rate at effusively erupting volcanoes 1 we present a model of effusive silicic volcanic eruptions which relates magma chamber and conduit physics to time dependent data sets including ground deformation and extrusion rate the model involves a deflating chamber which supplies newtonian magma through a cylindrical conduit solidification is approximated as occurring at fixed depth producing a solid plug that slips along its margins with rate dependent friction changes in tractions acting on the chamber and conduit walls are used to compute surface deformations given appropriate material properties and initial conditions the model predicts the full evolution of an eruption allowing us to examine the dependence of observables on initial chamber volume overpressure and volatile content employing multiple data sets in combination with a physics based model allows for better constraints on these parameters than is possible using kinematic idealizations modeling posteruptive deformation provides an improved constraint on the rate of influx into the magma chamber from deeper sources we compare numerical results to analytical approximations and to data from the 2004 2008 eruption of mount st helens for nominal parameters the balance between magma chamber pressure and frictional resistance of the solid plug controls the evolution of the eruption with little contribution from the fluid magma below the idealized crystallization depth while rate dependent plug friction influences the time dependent evolution of the eruption it has no control on the final chamber pressure or extruded volume

an initial evaluation of drone based monitoring of boulder beaches in galicia north western spain low altitude flights by a micro drone were made in 2012 and 2013 over two boulder beaches in north western spain geographical information system software was used to map the data boulder outlines from the first flight were recorded on 4796 clasts at laxe brava and 2508 clasts at oia changes in location were identified by overlaying these outlines on the 2013 images about 17 5 of the boulders mean surface area 0 32 m2 moved at laxe brava and about 53 mean surface area 0 23 m2 at oia most movement on both beaches was between the mid tide to about 2 m above the high tidal level the location and elevation of the highest points were also recorded on the 2012 images on 4093 boulders at laxe brava and 3324 boulders at oia these elevations were compared with the elevations at the same locations in 2013 the occurrence and scale of the elevational changes were generally consistent with changes in the boulder outlines the study confirmed that boulder beaches can be cheaply and effectively monitored using high resolution micro drone technology copyright 2014 john wiley sons ltd

storm driven cyclic beach morphodynamics of a mixed sand and gravel beach along the mid atlantic coast usa abstract the morphodynamics of a mixed sand and gravel beach in delaware were investigated based on 18 almost monthly beach profile surveys at 46 locations from 2009 to 2011 60 sediment cores and 550 surface sediment samples collected at various alongshore and cross shore transects three different atmospheric disturbances occurred within a 3 month window during the study period 1 a distal hurricane 2 an energetic winter storm and 3 nor ida a long lasting and extremely energetic event resulting from the collision of a hurricane and winter storm the storm induced beach changes and post storm recovery following each of the three storms are evaluated a distinctive beach cycle was identified consisting of a built up berm profile and depleted nearly planar storm profile the time scale of the beach cycle relates to the frequency and intensity of storm impact and duration of inter storm recovery instead of simple seasonality the initiation of post storm recovery occurs during the subsiding phase of the storm attributable to the reduction in wave height and steepness transitioning to accretionary swells the sediment characteristics of the storm deposit associated with nor ida demonstrated substantial cross shore variation ranging from sandy gravel and gravelly sand within the storm swash zone near the pre storm dune edge to well sorted medium to coarse sand seaward of the storm swash zone storm deposits along mixed sand and gravel beaches demonstrate a variety of sedimentological characteristics in addition the studied beaches lacked a sandbar under all wave conditions a new beach cycle model is proposed for the non barred mixed sand and gravel beach

exsolution enthalpy of water from silicate liquids abstract because water dissolves in silicate melts as at least two species h2o molecules and oh groups the exsolution evaporation enthalpy of the h2o component from a silicate melt depends on species proportions which in turn depends on h2o pressure in this short communication a formal analysis of the exsolution enthalpy of water from a silicate melt is presented taking into account of the role of speciation the exsolution enthalpy from a rhyolitic melt at 850 c is found to increase with pressure at 100 bar and this increase is mostly caused by the speciation reaction sahagian and proussevitch sahagian d l proussevitch a a 1996 thermal effects of magma degassing j volcanol geotherm res 74 19 38 also found an increase of the exsolution enthalpy with pressure up to 20 bar for an albitic melt however the rate of increase determined from this work is an order of magnitude less than that determined by sahagian and proussevitch it is concluded that the strong pressure dependence of the exsolution enthalpy at low pressures they inferred is probably an artifact of their treatment the method presented here is general and can be applied to other multi species components

swash zone sediment transport step dynamics and morphological response on a gravel beach abstract state of the art morphodynamic field data were collected from slapton sands uk a fine gravel beach d50 2 10 mm over a 10 day period under a range of wave tide conditions comprising a mixture of southerly swell and easterly wind waves hs 0 5 1 m ts 4 8 s tide range 3 4 m over the field period the upper beach experienced accretion and berm formation during tides with low steepness swell dominated wave conditions h l 0 01 surprisingly the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves and suggests that upper beach morphological change can be decoupled from the overall sediment budget a submerged accretionary feature the beach step grew and migrated onshore on the rising tide typically reaching a maximum relief of around 0 5 m then gradually decreased in prominence while migrating offshore as the tide fell resulting in little net morphological change the step was better developed during the falling tide than the rising tide and through its control on the swash hydro and sediment dynamics the step had a significant effect on the development of the berm swash flow velocities under the conditions measured were often in excess of 2 m s 1 for both the uprush and the backwash onshore mean flows occurred in the upper swash region 40 inundation was characterised by offshore mean flows swash infiltration losses in the swash zone increased from 40 in the lower swash region to 100 in the upper swash region the most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone 90 100 inundation

getting granite dikes out of the source region whether a dike can propagate far from a magma reservoir depends upon the competition between the rate at which propagation widens the dike and the rate at which freezing constricts the aperture available for magma flow various formulations are developed for a viscous fluid at temperature t sub m intruding a growing crack in an elastic solid the initial solid temperature equals t sub m at the source and decreases linearly with distance from the source if t sub m is the unique freezing temperature of the fluid dike growth is initially self similar and an essentially exact solution is obtained if t sub m is above the solidus temperature the solution is approximate but is designed to overestimate the distance the dike may propagate the ability of a dike to survive thermally depends primarily upon a single parameter that is a measure of the ratio of the dike frozen margin thickness to elastic thickness perhaps more intuitively one may define a minimum distance from the essentially solid reservoir wall to the point at which the host rock temperature drops below the solidus necessary for dikes to propagate far into subsolidus rock it is concluded that for reasonable material properties and source conditions most basalt dikes will have little difficulty leaving the source region but most rhyolite dikes will be halted by freezing soon after the magma encounters rock at temperatures below the magma solidus while these results can explain why granitic dikes are common near granitic plutons but rare elsewhere the potentially large variation in magmatic systems makes it premature to rule out the possibility that most granites are transported through the crust in dikes nonetheless these results highlight difficulties with such proposals and suggest that it may also be premature to rule out the possibility that most granite plutons ascend as more equidimensional bodies

eruptive history geochronology and magmatic evolution of the puyehue cordon caulle volcanic complex chile forty three 40 ar 39 ar age determinations of lava flows domes ignimbrites and dikes plus 14 c dates from seven distal tephra layers combined with stratigraphy geochemistry and sr and th isotope data establish an eruptive chronology for the puyehue cordon caulle volcanic complex at 40 5 s in the andean southern volcanic zone svz the complex preserves 131 km 3 of lava and tephra that erupted from numerous vents widely separated in time and space approximately 80 of the total volume consists of basaltic to andesitic lava that formed two broad shield volcanoes between 314 and 70 ka the modern puyehue stratovolcano was built on the southerly shield during the past 69 k y following a hiatus of 25 k y puyehue has erupted 15 km 3 of basaltic to rhyolitic magma that spans the entire compositional range found in the southern svz and evolved via at least six phases including 1 basaltic andesitic to dacitic lavas between 69 and 32 ka 2 a shift to bimodal magma compositions that is first expressed by a rhyodacite mingled with inclusions of mgo rich basaltic andesite at 34 ka 3 dacitic to rhyolitic flows and domes from 19 to 12 ka 4 basaltic to basaltic andesitic flows between 15 and 12 ka 5 subsequent rhyolitic dome growth in several effusive and explosive stages between 7 and 5 ka followed by 6 a powerful series of phreatomagmatic and sub plinian eruptions at ca 1 1 ka that obliterated the preceding rhyolite domes and formed the present 2 5 km diameter 280 m deep summit crater along the cordon caulle fissure zone 5 km 3 of rhyodacitic to rhyolitic lavas domes and cones have formed during the past 16 5 k y including explosive and effusive eruptions in 1921 1922 and 1960 eruptive rates were nonuniform over time with background growth at 0 04 km 3 k y or less punctuated by spurts at up to 0 90 km 3 k y the time averaged rate 0 42 km 3 k y is nearly double that at the tatara san pedro complex 500 km to the north during the past 300 k y these findings indicate that within a single arc the magmatic and eruptive fluxes at individual frontal volcanoes can be highly variable the last three stratocone building events on puyehue began during periods of deglaciation suggesting a relationship between unloading of ice and ease of magma ascent puyehue basalt exhibits subtle changes in 238 u 230 th 87 sr 86 sr and trace element composition over time that signal shifts in the composition and degree of melting of the mantle wedge or the extent to which basalt was modified by assimilation of heterogeneous crustal melts the complex has become exceptionally bimodal and more explosive over time with recent rhyolites evolving by extreme crystal fractionation of mafic magma and lesser volumes of andesite and dacite created via mixing of rhyolite and basalt despite the high flux of basalt during the past 300 k y no large silicic magma reservoir formed in the upper crust instead 238 u 230 th data favor rapid ascent of several small bodies of basaltic and silicic magma from the lower crust promoted perhaps by conduits that reflect strike slip faulting beneath the complex

from fine sand to boulders examining the relationship between beach face slope and sediment size abstract it is a long standing maxim that coarser sediment sizes are associated with steeper beach face slopes but because most work has focused on sandy beaches few data are available for the pebble cobble or boulder size ranges little is known therefore about how beach morphology and grain size relate at the coarser size grades we compiled data from the literature 2144 measurements of beach face slope with associated grain sizes covering the range from very fine sand to boulders this meta analysis shows that beach faces do tend to steepen as average grain size increases at least up to the cobble size range but the trend is not simple although previous studies suggested a simple power law relationship between grain size and beach face slope in fact the data distribution is best fit by a curve that is steep at the finer grain sizes but is much more gentle as grain size coarsens and may trend downward for boulders fine and medium sands have the greatest range of reported slopes and the data support the importance of effective weight modification and boundary layer dynamics as primary controls on beach face steepness at these fine size grades around the very coarse sand size grade a plateau marks a shift in beach dynamics as hydraulic conductivity increases beaches switch to being infiltration dominated the trend toward steeper slopes continues but at a lower and steady rate from granules through cobbles there appears to be a falloff in slope for the coarsest boulder deposits but we note that this is based on very few locations so should be considered preliminary the overall data distribution is described by a power law function tan a d 50 0 125 b c the broadness of each transition zone also shows that a range of factors other than grain size governs where that tipping point occurs in the cobble and boulder size ranges there are two deposit categories boulder beaches and supratidal boulder ridges although not commonly thought of as beaches boulder ridges record long term storm deposition and reworking on the highest energy coasts supratidal ridges and boulder beaches seem to show different slope grain size relationships with the steepest slopes occurring in boulder ridges and with boulder beaches showing more gentle gradients than other coarse clastic beaches but our data set reveals how little quantitative information exists about the coarsest end of the beach spectrum and invites further work to investigate the sedimentology of cobble and boulder dominated systems

controls on conduit magma flow dynamics during lava dome building eruptions 1 lava dome eruptions commonly display fairly regular alternations between periods of high and low or no activity with timescales typically of weeks to years and sudden transitions between effusive and explosive activity we develop a transient model of the magma flow in a volcanic conduit from an open system magma chamber with continuous replenishment the model incorporates gas exsolution bubble growth gas escape through the magma and decompression induced crystallization and considers variations in magma temperature water content conduit diameter phenocryst size chamber volume and magma rheology calculations show the presence of periodic variations in discharge rate due to the transition from a stable regime when discharge rate is low and crystals grow efficiently leading to high magma viscosity to another stable state when discharge rate is high and crystallization is negligible the difference in discharge rates between these regimes can be several orders of magnitude periods are similar to the observed timescales and mainly depend on the chamber volume the system shows strongly nonlinear responses to the variation of governing parameters if magma has a bingham rheology pauses in discharge rate occur between peaks of discharge and the peaks are much higher than for the case of newtonian rheology large changes in discharge rate and eruptive behavior can occur as the consequence of small changes in magma temperature water content phenocryst size distribution or conduit diameter the system can fluctuate between low and high discharge rates with transitions to explosive activity

waves coastal boulder deposits and the importance of the pre transport setting the pre transport environment of a coastal boulder along with its shape size and density determines the height of wave required for it to be transported different forces act on sub aerial boulders as opposed to submerged boulders when struck by a wave boulders derived from joint bounded blocks on shore platforms predominantly experience lift force and require a wave of greater height to be transported than boulders in other environments no one equation is applicable to determine the height of palaeo waves responsible for depositing a field or ridge of imbricated coastal boulders a range of equations and their derivation is presented here which can be applied to the respective pre transport environment of a boulder such an approach is necessary when attempting to reconstruct the frequency and magnitude of past coastal wave hazards and for differentiating between tsunami and storm wave deposited boulder fields

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

locating magma reservoirs using insar and petrology before and during the 2011 2012 cordon caulle silicic eruption abstract we combine petrological and insar observations to probe the origin of deformation of cordon caulle volcano in southern chile before and during the 2011 2012 eruption the erupted rhyodacite is crystal poor and was stored at about 900 c with ca 4 wt h2o and 220 ppm co2 in the melt corresponding to a storage depth of about 6 7 km in addition to a previously documented 2007 2008 deformation episode we find three pre eruptive deformation episodes the first between 2008 and 2009 that covers 400 km2 with a maximum uplift of 18 5 cm the second between february and march 2010 that covers 20 km2 with a maximum uplift of 10 cm and the third between march and may 2011 that covers 40 km2 with a maximum uplift of 6 cm modeling of the 2008 2009 deformation episode suggests source depths of about 5 9 km consistent with the petrologically determined magma storage depth the sum of modeled source volume changes from 2007 to 2009 is about 12 times smaller than the observed erupted volume our calculation of magma compressibility shows that there must have been a significant volume of pre existing magma in the reservoir to account for this difference co eruptive subsidence shows evidence for three distinct magma sources and pre eruptive inflation is seen at two of the three sources modeled deformation sources are located 2 10 km from the 2011 2012 eruptive vent and coincide with the vents from previous historical eruptions 1921 22 1960 and with the neighboring puyehue volcano this implies the existence of an interconnected magma plumbing system that allows for pressure transfer and which covers an area of at least 20 km2 thus the deformation and geochemical characteristics of cordon caulle resemble those of a large silicic caldera system the presence of a mafic crystal clot demonstrates the existence of basaltic melts in the silicic reservoir but we find that the mafic magmas reached the reservoir at least several hundred years before eruption therefore if the pre eruptive deformation was caused by replenishment to a shallow reservoir the new magma was silicic and similar to the pre existing magma and or there was no interaction between the two we find that pre eruptive deformation can occur in pulses and reach its peak years before eruption and thus lack of deformation does not necessarily imply that eruption is not imminent

3d gravity inversion and thermodynamic modelling reveal properties of shallow silicic magma reservoir beneath laguna del maule chile abstract active large volume silicic magma systems are potentially the most hazardous form of volcanism on earth knowledge of the location size and physical properties of silicic magma reservoirs is therefore important for providing context in which to accurately interpret monitoring data and make informed hazard assessments accordingly we present the first geophysical image of the laguna del maule volcanic field magmatic system using a novel 3d inversion of gravity data constrained by thermodynamic modelling the joint analysis of gravity and thermodynamic data allows for a rich interpretation of the magma system and highlights the importance of considering the full thermodynamic effects on melt density when interpreting gravity models of active magmatic systems we image a 30 km 3 low density volatile rich magma reservoir at around 2 km depth containing at least 85 melt hosted within a broader 115 km 3 body interpreted as wholly or partially crystallised 70 crystal cumulate mush our model suggests a magmatic system with shallow crystal poor magma overlying deeper crystal rich magma even though a large density contrast 600 kg m 3 with the surrounding crust exists the lithostatic load is 50 greater than the magma buoyancy force suggesting buoyancy alone is insufficient to trigger an eruption the reservoir is adjacent to the inferred extension of the troncoso fault and overlies the location of an intruding sill driving present day deformation the reservoir is in close proximity to the 2 0 km 3 nieblas rln eruption at 2 3 ka which we calculate tapped approximately 7 of the magma reservoir however we suggest that the present day magma system is not large enough to have fed all post glacial eruptions and that the location or size of the system may have migrated or varied over time with each eruption tapping only a small aliquot of the available magma the presence of a shallow reservoir of volatile rich near liquidus magma in close proximity to regional scale faulting has important implications for volcano monitoring and hazard mitigation

the role of volatiles in magma chamber dynamics many andesitic volcanoes exhibit effusive eruption activity1 with magma volumes as large as 107 109 m3 erupted at rates of 1 10 m3 s 1 over periods of years or decades during such eruptions many complex cycles in eruption rates have been observed with periods ranging from hours to years2 3 4 5 6 7 longer term trends have also been observed and are thought to be associated with the continuing recharge of magma from deep in the crust and with waning of overpressure in the magma reservoir here we present a model which incorporates effects due to compressibility of gas in magma we show that the eruption duration and volume of erupted magma may increase by up to two orders of magnitude if the stored internal energy associated with dissolved volatiles can be released into the magma chamber this mechanism would be favoured in shallow chambers or volatile rich magmas and the cooling of magma by country rock may enhance this release of energy leading to substantial increases in eruption rate and duration

magma compressibility and the missing source for some dike intrusions 1 dike intrusions are often accompanied by localized deflation interpreted as depressurizing magma chambers feeding the dike in some cases the inferred volume decrease is a factor of 4 or 5 less than the volume increase of the dike here we explore whether this discrepancy can be explained by compressibility of the magma combined with the fact that cracks are much more compliant than equidimensional magma chambers if pressure changes are small the magma compressibility m is constant and the dike ends up in hydrostatic equilibrium with an ellipsoidal magma chamber at the same depth the ratio rv of the volume of the crack to the volume lost by the chamber is rv 1 4 m 3 1 where is the host rock rigidity for gas poor magmas m 0 6 2 10 10 pa 1 and 3 25 gpa we find 1 2 rv 7 7 large changes in magma compressibility due to gas exsolution increase rv

boulder accumulations related to storms on the south coast of the reykjanes peninsula iceland coastal boulder accumulations are often mentioned in the literature even though their interpretation remains difficult especially along rock coasts affected both by storms and tsunamis studies on the geomorphic impact of such high energy events are actually of great interest since their intensity and frequency are key issues for the future evolution of coasts in the framework of the global change the southwest coast of iceland faces the powerful storms of the north atlantic ocean with wave heights of more than 15 m the probability for past and present tsunamis to hit this coast is very low in this paper we describe boulder accumulations along the volcanic rock coast of reykjanes southwest iceland they consist of cliff top boulders clusters and ridges beaches and boulder fields large boulders up to 70 t in weight have been transported and deposited up to 65 m inland 6 masl the maximum limit of boulder deposition and driftwood was found respectively 210 m and 550 m inland storms appear to be a predominant factor in the geomorphic evolution of reykjanes coasts our observations also give new insight for the interpretation of coastal boulder accumulations processes of erosion and deposition by tsunamis are a rising topic in the literature and the effects of recurrent and powerful storms are neglected

transient two dimensional dynamics in the upper conduit of a rhyolitic eruption a comparison of closure models for the granular stress to elucidate the role of particle collisions in redistributing momentum after fragmentation a numerical study was performed comparing the behavior of an inviscid or collision less granular material with a granular material whose viscosity and pressure were modeled using kinetic theory the granular viscosity calculation is sensitive to particle size and three particle sizes were considered 0 0002 m 0 002 m and 0 02 m a critical volume fraction of gas 0 75 identifies the onset of fragmentation dividing the region of rhyolitic magma with dispersed bubbles from the region of turbulent gas with dispersed particles the transient simulations can be divided into two dynamic regimes an initial shock followed by a transition to steady state during the initial shock phase treatment of the granular pressure and viscosity led to greater particle velocities relative to the inviscid calculation due to the development of higher gas pressure at fragmentation however as steady state is approached the viscosity slows the particle phase relative to the inviscid counterpart for particles greater than a millimeter the modeled sub millimeter particle velocity was insensitive to the treatment of the granular pressure and viscosity centimeter scale particles have a much higher granular viscosity up to 10 1 pa s and the kinetic theory calculation is thus relevant in these conditions after reaching steady state the differential velocity between gas and particles at the conduit exit correlates with particle size for both the inviscid and granular viscosity calculations negligible differential velocity develops for sub millimeter particles but centimeter scale particles exit the conduit with 5 differential velocity between phases

morphodynamics of a boulder beach putuo island se china coast the role of storms and typhoon abstract in this paper we examine the sedimentological properties and morphodynamic evolution of a boulder beach at huayanpeng cape on putuo island off the southeast china coast focus is given to the formation of the boulder beach 256 2000 mm diameter and resulting morphology in relation to high energy storms and seasonal typhoon holocene sea level rise to the present position at ca 7000 6000 yrs bp provides a long term window for the formation of the beach the beach is primarily characterized from east to west by 1 the convex to concave beach morphology 2 reduced longest axis of the skeleton boulders 3 decreased flatness of the skeleton boulders and 4 greater sphericity of the skeleton boulders infilling cobbles pebbles in the beach demonstrate a bi modal distribution corresponding to dominant sizes of 100 250 mm and 50 100 mm in diameter on the eastern beach and western beach respectively this reflects changed intensity of storm waves alongshore multiple peaks of the distributions of infilling clasts for the western beach supratidal probably reflect storm and calm weather sedimentation statistically both the skeleton boulders and infilling clasts follow a distribution reflecting the high energy control of beach formation and the dominance of crushing in boulder size reduction a boulder transport model applied in the present study further reveals that boulders with an a axis length of 500 1000 mm the dominant component on the beach move under a wide range of wave conditions depending on wave height and wave period with a cluster of critical wave heights in the range 2 6 m and wave periods of 5 15 s

observations and modeling of steep beach grain size variability novel observations of surface grain size distributions are used in combination with intra wave modeling to examine the processes responsible for the sorting of sediment grains on a relatively steep beach slope 1 7 5 the field observations of the mean grain size collected with a digital camera system at consecutive low and high tides for a 2 week period show significant temporal and spatial variation this variation is reproduced by the modeling approach when the surf zone flow circulation is relatively weak showing coarse grain sizes at the location of the shore break and finer sediment onshore and offshore of the shore break the model results suggest that grain size sorting is dominated by the wave breaking related suspended sediment transport which removes finer sediment from the shore break and transports it both on shore and offshore the transport capacity of wave breaking related suspended sediment is controlled by the sediment response time scale in the advection diffusion equation where small large values promote onshore offshore transport comparisons with the observed beach profile evolution suggest a relatively short time scale for the suspended sediment response which could be explained by the vigorous breaking of the waves at the shore break