numerical modeling of liquefaction and comparison with centrifuge tests the prediction of liquefaction and resulting displacements is a major concern for earth structures located in regions of moderate to high seismicity conventional procedures used to assess liquefac

volcanic conduit controls on effusive explosive transitions and the 2010 eruption of merapi volcano indonesia abstract individual volcanoes can produce both effusive and explosive eruptions a transition between these two eruption styles dramatically changes the hazards and can occur either between distinct eruption events or within one eruption episode the causes of these transitions are difficult to determine due to the number of system parameters that can influence whether or not magma fragments in a runaway process we apply a numerical model of magma ascent in a volcanic conduit to isolate and test the effects of key parameters related to magma rheology and system geometry we find that for a given volcanic system parameters that control magma viscosity such as initial water mass fraction initial crystal volume fraction and temperature have the greatest influence on whether or not magma fragments during ascent and erupts explosively we also define a critical condition for the full set of initial parameters under which a transition in eruption style from effusive to explosive or the reverse is more likely to occur under these conditions small heterogeneities in the water or crystal content of the magma or small perturbations to the conduit pressure gradient due to magma chamber overpressure or dome growth or collapse can disrupt the magmatic conditions and cause a transition in eruption style the 2010 vei 4 eruption of merapi volcano included both effusive and explosive phases and was larger by an order of magnitude than its eruptions during the previous century we constrain our model for the merapi system using published literature values and show that between the previous eruption in 2006 and the 2010 eruption the shallow magmatic system at merapi reached critical conditions due to the ascent from depth of a large hotter more volatile rich magma under these critical conditions and according to our model results small changes in the volatile content of the magma small dome collapses subtle changes in degassing rate or the addition of co2 to the magma through decarbonation of the bedrock are all feasible mechanisms for triggering rapid transitions between effusive and explosive activity during the 2010 eruption period

magmatic processes revealed by textural and compositional trends in merapi dome lavas syn eruptive degassing of volcanoes may lead to syn eruptive crystallization of groundmass phases we have investigated this process using textural and compositional analysis of dome material from merapi volcano central java indonesia samples included dome lavas from the 1986 88 1992 93 1994 and 1995 effusive periods as well as pyroclastic material deposited by the november 1994 dome collapse with total crystallinities commonly in excess of 70 phenocrysts 1 microlites the liquids present in merapi andesites are highly evolved rhyolitic at the time of eruption feldspar microlites in dome rocks consist of plagioclase cores ab63an29or8 surrounded by alkali feldspar rims ab53an5or42 compositional pairs which are not in equilibrium a change in the phase relations of the ternary feldspar system caused by degassing best explains the observed transition in feldspar composition a small proportion of highly vesicular airfall tephra grains from the 1994 collapse have less evolved glass compositions than typical dome material and contain rimless plagioclase microlites suggesting that the 1994 collapse event incorporated less degassed partially liquid magma in addition to fully solidified dome rock as decompression drives volatile exsolution rates of degassing and resultant microlite crystallization may be governed by magma ascent rate microlite crystallinity is nearly identical among the 1995 dome samples an indication that similar microlite growth conditions ph2 o and temperature were achieved throughout this extrusive period however microlite number density varied by more than a factor of four in these samples and generally increased with distance from the vent low vent ward microlite number densities and greater microlite concentrations down flow probably reflect progressively decreasing rates of undercooling at the time of crystal nucleation during extrusion of the 1995 dome comparison between dome extrusion episodes indicates a correlation between lava effusion rate and microlite number density suggesting that extrusion slowed during 1995 crystal textures and compositions in the 1992 93 and 1994 domes share the range exhibited by the 1995 dome suggesting that transitions in crystallization conditions i e rates of undercooling determined by effusion rate are cyclic q 2000 elsevier science b v all rights reserved

transitions between explosive and effusive eruptions of silicic magmas water rich silicic magmas may erupt explosively giving rise to massive columns of fragmented ash1 5 or effusively as viscous bubbly lavas to form lava domes6 8 complex cycles of explosive and effusive eruptions are often observed8 12 although these two eruption mechanisms have been modelled independently1 8 the conditions under which a volcano exhibits a particular style of eruption are not known and the transitions between eruption styles are poorly understood by modelling the ascent of magma along a permeable conduit we show here that for small magma chamber overpressures the style of eruption explosive or effusive is dependent on the magma flow rate we also identify a critical overpressure above which only explosive eruptions occur complex eruption sequences follow naturally for example if a shallow magmatic system is supplied with magma at an intermediate flow rate the eruption will be slow and effusive until the chamber over pressure becomes too large an explosive eruption then relieves the overpressure and an effusive eruption style resumes we suggest that monitoring of temporal variations in chamber overpressure for example by measuring ground deformation can be used to assess whether a passively effusing volcano has the potential to erupt explosively

petrologic constraints on the decompression history of magma prior to vulcanian explosions at the soufriere hills volcano montserrat abstract a series of 88 vulcanian explosions occurred at the soufriere hills volcano montserrat between august and october 1997 conduit conditions conducive to creating these and other vulcanian explosions were explored via analysis of eruptive products and one dimensional numerical modeling of magma ascent through a cylindrical conduit the number densities and textures of plagioclase microlites were documented for twenty three samples from the events the natural samples all show very high number densities of microlites and 50 by number of microlites have areas 2 pre explosion conduit conditions and decompression history have been inferred from these data by comparison with experimental decompressions of similar groundmass compositions our comparisons suggest quench pressures 13 75 mpa each during ascent from chamber to surface values are consistent with field studies of the same events and statistical analysis of explosion time series data the microlite volume number density trend with depth reveals an apparent transition from growth dominated crystallization to nucleation dominated crystallization at pressures of 7 mpa and lower a concurrent sharp increase in bulk density marks the onset of significant open system degassing apparently due to a large increase in system permeability above 70 vesicularity this open system degassing results in a dense plug which eventually seals the conduit and forms conditions favorable to vulcanian explosions the corresponding inferred depth of overpressure at 250 700 m near the base of the dense plug is consistent with depth to center of pressure estimated from deformation measurements here we also illustrate that one dimensional models representing ascent of a degassing crystal rich magma are broadly consistent with conduit profiles constructed via our petrologic analysis the comparison between models and petrologic data suggests that the dense conduit plug forms as a result of high overpressure and open system degassing through conduit walls

volcanic activity influenced by tectonic earthquakes static and dynamic stress triggering at mt merapi 1 mt merapi is one of the most dangerous volcanoes in indonesia located within the tectonically active region of south central java this study investigates how mt merapi affected and was affected by nearby tectonic earthquakes in 2001 a mw6 3 earthquake occurred in conjunction with an increase in fumarole temperature at mt merapi in 2006 another mw6 3 earthquake took place concomitant with an increase of magma extrusion and pyroclastic flows here we develop theoretical models to study the amount of stress transfer between the earthquakes and the volcano showing that dynamic rather than static stress changes are likely responsible for the temporal and spatial proximity of these events our examination of the 2001 and 2006 events implies that volcanic activity at mt merapi is influenced by stress changes related to remote tectonic earthquakes a finding that is important for volcano hazard assessment in this densely inhabited area

heat and mass transport in sublacustrine vents in yellowstone lake wyoming in situ chemical and temperature data documenting a dynamic hydrothermal system abstract recent advances in the development of in situ chemical and temperature sensors have shown great promise as a means to investigate time series changes in marine and terrestrial hydrothermal systems here we apply this technology to assess chemical and physical controls on sublacustrine vent fluids in yellowstone lake wy autonomous sensor systems were deployed in august 2017 using rov assets to position instruments at two sites in the deep hole region of the lake off shore from stevenson island earlier studies have documented that fissure related depressions 120 m water depth in this region host numerous vents issuing high enthalpy co2 saturated and h2s bearing vapor at temperatures in excess of 150 c the ysz ceramic based in situ chemical sensors deployed here were designed to measure ph and redox at 60 s intervals for up to one year two titanium sheathed thermocouples one coupled directly to the electrochemical sensor and another independently powered and positioned slightly deeper in vents at deployment sites provided insight on maximum temperature in the near surface region in addition to in situ chemical and temperature data vent fluid samples were acquired at the outset and during recovery with a novel isobaric system that maintains lake bottom pressure precluding fluid sample de gassing at the same time push cores of vents and in the near vent region were also acquired the mineralized cores provide evidence of long term mass transfer processes while also facilitating insertion and stabilization of the sensor units on the lake floor recovery of the sensors documented similar chemical controls at both sites suggesting compositionally invariant vapor influx characterized by moderately low ph 4 5 and reducing conditions buffered by co2 and h2s respectively accordingly the diatomaceous sediment was extensively altered to kaolinite and pyrite temperature variability at the two sites was especially significant one site site b situated on the slope of what might be a hydrothermal domal structure demonstrated noteworthy cooling and heating episodes that may be associated with hydrothermally or seismically triggered sediment slumping events upon instrument recovery in 2018 the vent site was largely sediment covered and the sensor insert showed evidence of dis location and melting by conductive heating under the hot sediment overburden the initially active and high temperature vent fluid 148 c had largely ceased and replaced by diffuse flow venting at the margin of the previous up flow zone the time series in situ chemical and physical data obtained in the course of the study document the existence of a dynamic hydrothermal system in time and space while underscoring the challenges of research of this type in such environments

the 2006 lava dome eruption of merapi volcano indonesia detailed analysis using modis tir abstract merapi is one of indonesia s most active and dangerous volcanoes prior to the 2010 vei 4 eruption activity at merapi during the 20th century was characterized by the growth and collapse of a series of lava domes periods of very slow growth were punctuated by short episodes of increased eruption rates characterized by dome collapse generated pyroclastic density currents pdcs an eruptive event of this type occurred in may june 2006 for effusive eruptions such as this detailed extrusion rate records are important for understanding the processes driving the eruption and the hazards presented by the eruption we use thermal infrared tir images from the moderate resolution imaging spectrometer modis instrument on nasa s aqua and terra satellites to estimate extrusion rates at merapi volcano during the 2006 eruption using the method of harris and ripepe 2007 we compile a set of 75 nighttime modis images of the eruptive period to produce a detailed time series of thermal radiance and extrusion rate that reveal multiple phases of the 2006 eruption these data closely correspond to the published ground based observational record and improve observation density and detail during the eruption sequence furthermore additional analysis of radiance values for thermal anomalies in band 21 3 959 m of modis images results in a new framework for detecting different styles of activity we successfully discriminate among slow dome growth rapid dome growth and pdc producing dome collapse we also demonstrate a positive correlation between pdc frequency and extrusion rate and provide evidence that extrusion rate can increase in response to external events such as dome collapses or tectonic earthquakes this study represents a new method of documenting volcanic activity that can be applied to other similar volcanic systems

the sequence of sediment behaviour during wave induced liquefaction this paper presents the results of an experimental investigation of the complete sequence of sediment behaviour beneath progressive waves the sediment was silty with d50 0 060 mm two kinds of measurements were carried out pore water pressure measurements across the sediment depth and water surface elevation measurements the process of liquefaction compaction was videotaped from the side simultaneously with the pressure and water surface elevation measurements the video records were then analysed to measure i the time development of the mudline ii the time development of liquefaction and compaction fronts in the sediment and iii the characteristics of the orbital motion of the liquefied sediment including the motion of the interface between the water body and the sediment the ranges of the various quantities in the tests were wave height h 9 17 cm wave period t 1 6 sec water depth 42 cm and the shields parameter 0 34 0 59 the experiments reveal that with the introduction of waves excess pore pressure builds up which is followed by liquefaction during which internal waves are experienced at the interface of the water body and the liquefied sediment the sequence of processes known from a previous investigation this sequence of processes is followed by dissipation of the accumulated excess pore pressure and compaction of the sediment which is followed by the formation of bed ripples the present results regarding the dissipation and compaction appear to be in agreement with recent centrifuge wave tank experiments as for the final stage of the sequence of processes formation of ripples the ripple steepness normalized with the angle of repose for sediment with liquefaction history is found to be the same as that in sediment with no liquefaction history

rheology of crystal bearing silicate melts an experimental study at high viscosities the viscosity of partially crystallized mg3al2si3o12 melts has been measured under uniaxial compression in the interval 1010 1013 poise as a function of the volume fraction of crystals these inclusions are well rounded spherulites of aluminous enstatite having the same composition as the melt and whose growth rate is negligible at the temperature of the measurements the viscosity increases by less than 1 order of magnitude for crystal fractions of 40 vol and remains newtonian up to the maximum stress exerted namely 1 kbar the einstein roscoe equation 0 1 m n provides very good fits to the measurements only if either the m or n parameter is allowed to depend on temperature for modeling of magmatic processes however the widely recommended constant values m 0 6 and n 2 5 should be adequate the rheology changes abruptly when the clustered spherulites begin to oppose shear deformation at a crystal fraction of about 40 vol the viscosity becomes non newtonian with yield strengths of a few tens of bars at temperatures at which the viscosity of the melt is higher than 1010 poise as long as the crystal fraction remains lower than 70 vol the deformation proceeds in an irregular manner with a nonuniform distribution of crystals and melt the deformation becomes again regular at low stresses with lower melt fractions but samples undergo extensive fracturation along the direction of uniaxial stress similar rheology changes have been observed during the isothermal crystallization of li2si2o5 melts which produces small ellipsoidal inclusions these results suggest that the influence of solid suspensions on the rheology of magmas is primarily determined by the crystal fraction even though additional measurements would be useful to determine the possible influence of other factors such as the size distribution or the shape of the inclusions

overview of the 2006 eruption of mt merapi abstract in the last part of the 20th century and the beginning of the 21st century mt merapi in central java indonesia erupted about every 2 5 years most of the eruptions were low in explosivity with vei 3 or less eruptions usually involve the formation of a lava dome either in the beginning or in the end of the eruptive episode for the 2006 eruption the precursory signal was first observed in the middle of the year 2005 with a decrease in edm slope distances to points on the rim an increase of seismicity and a possible increase of so 2 emissions those early events marked the beginning of a more continuous period of inflation which led to the eruption in total the pre eruption displacement of the southern rim reached at least 2 4 m toward the measuring station in kaliurang kal from late april until june 2006 a lava dome grew on the summit with a volume that gradually increased until it reached about 4 1 million m 3 in 38 days the total of erupted magma was about 5 3 million m 3 dense rock equivalent dre the dome subsequently collapsed in three steps from june 4 to june 14 leaving an open scar on its southeast side in this paper we detail the changes of dome morphology that were monitored by taking successive photographs from similar positions the eruption in 2006 marked a significant change in summit morphology from west southwestward opening during the 20th century to the currently southeast orientation also an mw 6 4 earthquake occurred on 26 may midway through the eruption which adds interesting questions about the relationship of the eruption and the earthquake edm data from 2006 and previous eruptions show that the summit remains inflated after each eruption i e no significant deflation occurs following eruptions the lack of post eruption deflation suggests that magma remains in the shallow parts of the edifice after the eruption as a result the complex of summit lava domes and their intrusive roots grow with time and merapi s rim and summit become progressively more unstable and prone to collapse

hydrothermal and tectonic activity in northern yellowstone lake wyoming yellowstone national park is the site of one of the world9s largest calderas the abundance of geothermal and tectonic activity in and around the caldera including historic uplift and subsidence makes it necessary to understand active geologic processes and their associated hazards to that end we here use an extensive grid of high resolution seismic reflection profiles 450 km to document hydrothermal and tectonic features and deposits in northern yellowstone lake sublacustrine geothermal features in northern yellowstone lake include two of the largest known hydrothermal explosion craters mary bay and elliott9s mary bay explosion breccia is distributed uniformly around the crater whereas elliott9s crater breccia has an asymmetric distribution and forms a distinctive 2 km long hummocky lobe on the lake floor hydrothermal vents and low relief domes are abundant on the lake floor their greatest abundance is in and near explosion craters and along linear fissures domed areas on the lake floor that are relatively unbreached by vents are considered the most likely sites of future large hydrothermal explosions four submerged shoreline terraces along the margins of northern yellowstone lake add to the holocene record of postglacial lake level fluctuations attributed to heavy breathing of the yellowstone magma reservoir and associated geothermal system the lake hotel fault cuts through northwestern yellowstone lake and represents part of a 25 km long distributed extensional deformation zone three postglacial ruptures indicate a slip rate of 0 27 to 0 34 mm yr the largest 3 0 m slip and most recent event occurred in the past 2100 yr although high heat flow in the crust limits the rupture area of this fault zone future earthquakes of magnitude 5 3 to 6 5 are possible earthquakes and hydrothermal explosions have probably triggered landslides common features around the lake margins few high resolution seismic reflection surveys have been conducted in lakes in active volcanic areas our data reveal active geothermal features with unprecedented resolution and provide important analogues for recognition of comparable features and potential hazards in other subaqueous geothermal environments

effects of conduit geometry on magma ascent dynamics in dome forming eruptions abstract we develop a steady state two phase flow model of magma ascent through an axisymmetric conduit of variable radius r and length l in order to quantify relationships between conduit geometry and magma ascent dynamics holding boundary conditions and chamber magma properties constant we vary conduit geometry systematically and independently such that the upper conduit radius increases or decreases by a factor of r t r b radius ratio 0 4 r t r b 2 5 above a change initiation height h 0 1 h l 0 7 and over length l e l e l 0 2 where r t and r b are conduit radius above t and below b the radius change and h is the height above the top of the magma chamber conduit widening causes a drop in overpressure and corresponding increase in gas volume fraction and magma acceleration over the whole length of the conduit with all changes increasing in magnitude with increasing radius ratio magma ascent rate increases roughly as r 2 and volumetric flow rate subsequently increases as r 4 when r t r b r both increasing r t for a fixed r b increasing radius ratio and increasing r b for a fixed r t decreasing radius ratio increase volume flow and magma ascent rates compared to changes in geometry small changes in chamber pressure

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

uplift of immersed tunnel in liquefiable seabed under wave and current propagation abstract in ocean environments wave usually propagates in association with a current the paper presents a cyclic characterization framework for elastoplastic consolidating behavior of liquefiable seabed around the immersed tunnel under combined wave and current loading based on the biot dynamic consolidation theory special attention is placed on modeling the nonlinear wave current interaction the cyclic plasticity behavior of marine deposits and the soil structure contact effect the paper extends an existing masing model to large strain regime in the order of 10 2 in the framework of cyclic plasticity for capturing the liquefaction induced nonlinear behavior of marine deposits then the proposed cyclic plasticity model is implanted into an explicit time matching finite difference analysis platform permitting a comprehensive simulation of the intensive response of the immersed tunnel in the seabed experiencing the excess pore pressure accumulation and residual liquefaction retrospective simulation of a well documented centrifuge test by the proposed framework indicates satisfactory agreement validating the reliability for capturing the excess pore pressure accumulation and residual liquefaction during wave propagation finally the influences of current on the wave induced liquefaction in the vicinity of an immersed tunnel are investigated by a numerical example the results indicate that the ocean current significantly changes the original characteristics of wave induced liquefaction as well as the induced uplift of the immersed tunnel especially with consideration of the cyclic plasticity behavior of marine deposits the mechanisms of seabed liquefaction and the induced uplift of the immersed tunnel under wave and current actions are also interpreted

earthquake induced variations in extrusion rate a numerical modeling approach to the 2006 eruption of merapi volcano indonesia abstract extrusion rates during lava dome building eruptions are variable and eruption sequences at these volcanoes generally have multiple phases merapi volcano java indonesia exemplifies this common style of activity merapi is one of indonesia s most active volcanoes and during the 20th and early 21st centuries effusive activity has been characterized by long periods of very slow

dynamic characteristics of a sandy seabed under storm wave loading considering the effect of principal stress rotation abstract this paper aims to investigate the cyclic characteristics of soil under storm waves with the typical irregular character in which a generalized plasticity model considering the effect of principal stress rotation psr was adopted to model soil behavior in the present model the plastic strain generated by principal stress rotation was considered to be an additional item in the constitutive relationship of soil and the normalized loading and plastic flow directions were determined based on the stress tensor invariants comparisons between the present model previous hollow cylinder apparatus hca tests and geotechnical centrifugal wave tests all show good agreement numerical results indicate that the moveable and random characteristics of the storm wave result in similar and irregular dynamic responses in sandy deposits along the extension direction of the seabed moreover the severest wave loading in a real storm will significantly magnify both the speed and extent of liquefaction of the sandy seabed numerical results also demonstrate that ignoring the psr involved in the storm wave seabed interaction will significantly underestimate the build up of pore water pressure additionally when considering the impact of psr the sandy seabed exhibits higher liquefaction resistance when subjected to the random wave compared to the representative regular wave however since the sharply weakening liquefaction resistance of soil under the severest wave condition cannot be captured with the regular wave it is suggested that the random wave be adopted to further investigate the storm wave seabed interaction parametric studies show that soil properties e g permeability and saturation significantly affect the liquefaction characteristics of soil under storm waves

generation and evolution of hydrothermal fluids at yellowstone insights from the heart lake geyser basin 1 we sampled fumaroles and hot springs from the heart lake geyser basin hlgb measured water and gas discharge and estimated heat and mass flux from this geothermal area in 2009 the combined data set reveals that diverse fluids share an origin by mixing of deep solute rich parent water with dilute heated meteoric water accompanied by subsequent boiling a variety of chemical and isotopic geothermometers are consistent with a parent water that equilibrates with rocks at 205 c 10 c and then undergoes 21 2 adiabatic boiling measured diffuse co2 flux and fumarole compositions are consistent with an initial dissolved co2 concentration of 21 7 mmol upon arrival at the caldera boundary and prior to southeast flow boiling and discharge along the witch creek drainage the calculated advective flow from the basin is 78 16 l s 1of parent thermal water corresponding to 68 14 mw or 1 of the estimated thermal flux from yellowstone helium and carbon isotopes reveal minor addition of locally derived crustal biogenic and meteoric gases as this fluid boils and degasses reducing the he isotope ratio rc ra from 2 91 to 1 09 the hlgb is one of the few thermal areas at yellowstone that approaches a closed system where a series of progressively boiled waters can be sampled along with related steam and noncondensable gas at other yellowstone locations steam and gas are found without associated neutral cl waters e g hot spring basin or cl rich waters emerge without significant associated steam and gas upper geyser basin

geodynamics of the yellowstone hotspot and mantle plume seismic and gps imaging kinematics and mantle flow abstract integration of geophysical and geological data show that the yellowstone hotspot resulted from a mantle plume interacting with the overriding north america plate a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16 17 ma 700 km long yellowstone snake river plain ysrp silicic volcanic system accessibility of the ysrp allowed large scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements seismic tomography reveals a crustal magma reservoir of 8 to 15 melt 6 km to 16 km deep beneath the yellowstone caldera an upper mantle low p wave velocity body extends vertically from 80 km to 250 km beneath yellowstone but the anomalous body tilts 60 wnw and extends to 660 km depth into the mantle transition zone we interpret this conduit shaped low velocity body as a plume of up to 3 5 vp and 5 5 vs perturbation that corresponds to a 1 2 partial melt models of whole mantle convection reveal eastward upper mantle flow beneath yellowstone at relatively high rates of 5 cm yr that deflects the ascending plume into its west tilted geometry a geodynamic model of the yellowstone plume constrained by vp and vs velocities and attenuation parameters suggests low excess temperatures of up to 120 k corresponding to a maximum 2 5 melt and a small buoyancy flux of 0 25 mg s i e properties of a cool weak plume the buoyancy flux is many times smaller than for oceanic plumes nonetheless plume buoyancy has produced a 400 km wide 500 m high topographic swell centered on the yellowstone plateau contemporary deformation derived from gps measurements reveals sw extension of 2 3 mm yr across the yellowstone plateau one fourth of the total basin range opening rate which we consider to be part of basin range intraplate extension locally decadal episodes of subsidence and uplift averaging 2 cm yr characterize the 80 year yellowstone caldera monitored history and are modeled as hydrothermal magmatic sources moreover a recent episode 2004 2009 of accelerated uplift of the yellowstone caldera at rates up to 7 cm yr has been modeled as resulting from magmatic recharge of a 10 km deep sill at the top of the crustal magma reservoir regionally gravitational potential energy of the yellowstone swell drives the lithosphere southwest and downhill from the yellowstone plateau 400 km where it coalesces with basin range province wide westward extension based on the geometry and its assumed 660 km depth we extrapolate the plume source southwest to its original location at 17 ma and 600 km southwest and 200 km north of the ysrp importantly this location is beneath the southern part of the columbia plateau flood basalt field of the same age and implies that the yellowstone mantle plume may be the common source for both of these large volcanic fields our time progression model suggests that the original plume head rose vertically behind the juan de fuca plate but at 12 ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler thicker continental lithosphere becoming entrained in eastward upper mantle flow these results reveal that yellowstone plume plate processes have had a profound effect on late cenozoic geologic evolution and topography of a large part of the western u s

magma eruption rates of merapi volcano central java indonesia during one century 1890 1992 the magma eruption rates of merapi volcano form 1890 to 1992 are re examined chronologically for this volcano movements of extruded lavas and domes as well as their extrusions are important because they control the modes of the subsequent activities and cause nuees ardentes and lahars the monthly eruption rates varied widely but the cumulative volume of lavas has increased linearly and is expressed as 0 1x106 m3 month the magma production rate of this volcano may have been constant for these 100 years recurrent excessive effusion of lavas is tentatively interpreted by assuming a magma reservoir the averaged eruption rate is small in comparison with other volcanoes such as nyramuragia kilauea and vesuvio however it is remarkable that the activity has been continuous for these 100 years and the total amount of lava discharged during this period reached more than 108 m3 a simple model for the formation of the 1992 lava dome is presented the viscosity of the lavas is probably between 106 and 107 p and the length of the magma conduit is probably less than 10 km

analysis of wave induced liquefaction of sand beds this paper describes finite element analyses of wave induced liquefaction of sand beds the authors were motivated by previous experimental results in which a series of centrifuge wave tank tests were performed on loosely packed fresh deposits of sand with viscous scaling introduced the principal finding was that the resistance to liquefaction under progressive waves was considerably smaller than the resistance exhibited under standing waves an important factor for this marked difference was suggested to be the rotation of the principal stress axes that occurs under progressive wave loading the present study extends an existing cyclic plasticity constitutive model to account for the effect of stress axis rotation of sands this model was incorporated into a finite element analysis procedure which was applied to soil responses to progressive wave and standing wave loading the predicted results compare well with observed soil behaviour the predicted effective stress paths and associated stress strain

cyclic characterization of wave induced oscillatory and residual response of liquefiable seabed the paper presents a robust modeling method for a fully coupled effective stress analysis of the wave induced liquefaction scenarios based on the biot consolidation theory in this context emphasis is placed on the implementation of a well calibrated cyclic soil model and an empirical shear volume coupling equation which links the increment of volumetric strain per cycle of wave with the shear strain occurring during that particular cycle unlike most of the previous investigations using the amplitude of shear stress over the wave period or the phase resolved oscillatory shear stresses as the source term for calculating the residual pore pressure in this study the source term is related to the rate of plastic volumetric deformation and implemented into the biot consolidation equation to consider both generation and partial dissipation of excess pore pressure during wave propagation then the proposed modeling method is incorporated into a dynamic finite difference analysis procedure model calibrations are carried out in terms of individual soil element behavior and seabed response under progressive waves respectively overall good agreement demonstrates the reliability of the modeling method for the prediction of wave induced seabed response finally the paper highlights the potentials of proposed modeling framework to simulate the basic features of wave induced seabed response i e the coupling of progressive buildup of pore pressure and cyclic softening of soil skeleton by means of numerical examples the obtained results show that the cyclic behavior of liquefiable seabed under wave actions can be well captured by the proposed model

extrusion cycles during dome building eruptions abstract we identify and quantify controls on the timescales and magnitudes of cyclic periodic volcanic eruptions using the numerical model domeflow de michieli vitturi et al 2010 which was developed by the authors for magma systems of intermediate composition domeflow treats the magma mixture as a liquid continuum with dispersed gas bubbles and crystals in thermodynamic equilibrium with the melt and assumes a modified poiseuille form of the viscous term for fully developed laminar flow in a conduit of cylindrical cross section during ascent magma pressure decreases and water vapor exsolves and partially degasses from the melt as the melt simultaneously crystallizes causing changes in mixture density and viscosity two mechanisms previously proposed to cause periodic eruption behavior have been implemented in the model and their corresponding timescales explored the first applies a stick slip model in which motion of a shallow solid plug is resisted by static dynamic friction as described in iverson et al 2006 for a constant magma supply rate at depth this mechanism yields cyclic extrusion with timescales of seconds to tens of seconds with values generally depending on assumed friction coefficients the second mechanism does not consider friction but treats the plug as a high viscosity newtonian fluid during viscous resistance pressure beneath the degassed plug can increase sufficiently to overcome dome overburden plug weight and viscous forces and ultimately drive the plug from the conduit in this second model cycle periods are on the order of hours and decrease with increasing magma supply rate until a threshold is reached at which point periodicity disappears and extrusion rate becomes steady vanishingly short periods magma volatile content for fixed chamber pressure has little effect on cycle timescales but increasing volatile content increases mass flow rate and cycle magnitude as defined by the difference between maximum and minimum extrusion rates increasing mass flow rate also increases the magnitude of predicted deformation cycles both models have been applied to dome building eruptions using conditions appropriate for the soufriere hills volcano montserrat results suggest that the modeled stick slip mechanism cannot explain the cycles of extrusion and explosion well documented at montserrat timescales of hours however a subset of the simulations for the viscous plug model are consistent with the montserrat data and therefore demonstrate the feasibility of this second formulation

viscosity of high crystal content melts dependence on solid fraction 1 the rheological properties of suspensions containing high solid fractions are investigated attention is focused on viscosity of silicate and magmatic melt systems a general empirical equation which describes the relative viscosity of suspensions as a function of suspended solid fraction is proposed in the limit of very dilute solid concentrations it reduces to the einstein equation the proposed relationship is satisfactorily applied to reproduce available experimental data relative to silicate melts moreover the extrapolation of the model to very high concentrations is compared with experimental observations on partially melted granite

textural and micro petrological variations in the eruptive products of the 2006 dome forming eruption of merapi volcano indonesia implications for sub surface processes the interplay between magma ascent degassing and changing magmatic properties are widely recognized as critical factors controlling the style of silicic volcanic eruptions microlite textures in samples from the prolonged dome forming eruption of merapi in 2006 provide a record of changing magmatic ascent conditions and shallow conduit processes throughout the eruption analysis of microlite textural parameters including measurements of areal number density na mean microlite size crystal aspect ratio and groundmass crystallinity combined with the monitoring record and field observations indicate that magma ascent paths change between continuous ascent at varying rates from a deeper magma storage region to ascent being temporarily stalled at shallow depths in the latter stages of the eruption supporting the idea of an ephemeral shallow magma storage region at merapi plagioclase microlite compositions show evidence of decompression induced degassing often displaying rims of anorthoclase and more k rich alkali feldspar sanidine anorthite contents also support the textural data of later erupted magma being temporarily stalled at shallow depths crystal size distributions csds are interpreted to show that both growth dominated and nucleation dominated crystallisation regimes existed during the 2006 eruption resulting from changing conditions of undercooling t during variable magma ascent paths by contrast microlite textural analysis and feldspar microlite compositions of samples from the fast growing lava dome of the second phase of the 2010 eruption prior to the cataclysmic events on 5 november indicate faster ascent rates a crystallisation regime more strongly dominated by nucleation due to high t and interaction of the 2010 magma with more hotter magma from depth

textural and mineral chemistry constraints on evolution of merapi volcano indonesia abstract we analyze and compare the textures of merapi lavas basalts and basaltic andesites ranging in age from proto merapi through modern activity with the goal of gaining insights on the temporal evolution of merapi s magmatic system analysis of textural parameters such as phenocryst and microphenocryst crystallinity coupled with crystal size distribution theory provides information about the storage and transport of magmas we combine textural analyses with geochemical investigations for a comprehensive comparison of erupted lavas over time the chemical analyses identify crystal growth processes in magma chambers and underline differences between sample groups our work suggests the occurrence of two distinct histories presumably associated with at least two generally distinct types of rheological behaviors and storage transport systems these behaviors are associated with different plagioclase growth patterns with both groups influenced by late stage shallow decompression degassing induced microlite crystallization both groups contain amphibole crystals that indicate an early period of mid crustal to deep crustal storage of water rich magmas dome lavas from the 20th century eruptive activity indicate quasi steady state nucleation and growth evolution interspersed with episodes of reheating and textural coarsening suggesting residence in magma storage at multiple depths both 10 km and

stability of an immersed tunnel in offshore conditions under deep water wave impact abstract one of the special design requirements for the immersed tunnel of the busan geoje fixed link in south korea has been the stability of the tunnel under wave impact with up to 9 2 m significant wave height a large part of the tunnel is placed in a trench and is founded on soft marine clay which is reinforced by cement deep mixing cdm columns to limit and control the settlements caused by the weight of the tunnel and its protection material being beyond the scope of any design standard the problem of the tunnel stability under wave impact has been investigated and verified by a combination of physical model tests and numerical modelling this paper provides a detailed description of the methodology applied to solve this particular problem and a discussion of the results and consequences for the design of the tunnel

an overview of the seismicity of merapi volcano java indonesia 1983 1994 abstract from 1982 to 1995 merapi volcano java indonesia experienced two main eruptive cycles from 1984 to 1986 and from 1992 to 1994 each cycle had a duration slightly larger than 2 years four major eruptive events occurred in 1984 1986 1992 and 1994 these eruptions were monitored by a telemetered seismic network we present an overview of the seismicity observed between 1983 and 1995 from seismological observations several types of characteristic events are recognised volcanotectonic earthquakes are standard microearthquakes either shallow an aseismic zone is situated between two seismic zones at a depth between 1 5 and 2 5 km below the summit we postulate that it is a small shallow magma reservoir where magma injected from below can be stored temporarily we try to relate seismic observations during both eruptive cycles to the initial injection of deep magma to the superficial magma system the first eruption in each case seems to involve magma enriched in gas that extrudes the content of the conduit and explodes the old dome a regular outflow of magma follows the initial explosion and gradually a dome is building up then it stops and a period of repose is observed later a second episode of dome growth occurs the height of the dome reaches a maximum corresponding to a state of lithostatic equilibrium the time delay of more than 2 years between the beginning and the end of a cycle may result from crystallisation in a volatile rich magma and from the building up of pressure in the superficial magma pocket some important events like the collapse of the dome on 22 november 1994 are not preceded by any seismic precursor when it reaches a large volume the dome is not stable and is likely to collapse by gravity for instance after the sudden influx of matter or gas or after a heavy rain on merapi tremors are observed but do not always precede a dangerous event

emplacement temperatures of the november 22 1994 nuee ardente deposits merapi volcano java abstract a study of emplacement temperatures was carried out for the largest of the 22 november 1994 nuee ardente deposits at merapi volcano based mainly on the response of plastic and woody materials subjected to the hot pyroclastic current and the deposits and to some extent on eyewitness observations the study emphasizes the turgo kaliurang area in the distal part of the area affected by the nuee ardente where nearly 100 casualties occurred the term nuee ardente as used here includes channeled block and ash flows and associated ash clouds of surge and fallout origins the emplacement temperature of the 8 m thick channeled block and ash deposit was relatively high 550 c based mainly on eyewitness reports of visual thermal radiance emplacement temperatures for ash cloud deposits a few cm thick were deduced from polymer objects collected at turgo and kaliurang most polymers do not display a sharp melting range but polyethylene terephthalate used in water bottles melts between 245 and 265 c and parts of the bottles that had been deformed during fabrication molding turn a milky color at 200 c the experimental evidence suggests that deposits in the turgo area briefly achieved a maximum temperature near 300 c whereas those near kaliurang were

field observations and surface characteristics of pristine block and ash flow deposits from the 2006 eruption of merapi volcano java indonesia abstract a series of pristine block and ash flow deposits from the may june 2006 eruption of merapi represent an exceptional record of small volume pyroclastic flows generated by gravitational lava dome collapses over a period of about two months the deposits form nine overlapping lobes reaching 7 km from the summit in the gendol river valley on the volcano s southern flank which were produced by successive flows generated during and after the major dome collapse event on june 14 both single pulse post june 14 events and multiple pulse pyroclastic flows generated by sustained dome collapses on june 14 are recognised and three types of deposits spread over an area of 4 7 km are distinguished totalling 13 3 10 6 m 3 1 valley confined basal avalanche deposits 11 7 10 6 m 3 in the gendol river valley 2 overbank pyroclastic flow and associated surge deposits 1 4 10 6 m 3 where parts of the basal avalanche spread laterally onto interfluves and were subsequently channeled into the surrounding river valleys and 3 dilute ash cloud surge deposits 0 2 10 6 m 3 along valley margins variations in the distribution surface morphology and lithology of the deposits are related to the source materials involved in individual pyroclastic flow forming events and varying modes of transport and deposition of the different flows inferred flow velocities of the largest block and ash flows generated on june 14 vary from 43 8 13 5 m s for the basal avalanche and from 62 6 24 2 m s for the ash cloud surge the minimum temperatures range from 400 c for the basal avalanche to 165 c for the overlying ash cloud due to the potential of being re channeled into adjacent river valleys and flowing laterally away from the main river channel the overbank pyroclastic flows are considered the most hazardous part of the block and ash flow system the conditions that lead to their development during flow transport and deposition must be taken into account when assessing future pyroclastic flow hazards at merapi and similar volcanoes elsewhere

geochemical heterogeneity of sublacustrine hydrothermal vents in yellowstone lake wyoming abstract rov based submersible operations in yellowstone lake yellowstone national park wyoming usa have identified two locations with chemically and mineralogically distinct sublacustrine hydrothermal fluids and deposits the deep hole east of stevenson island si deep hole and the se west thumb deep vent field se wt field the si deep hole is the deepest part of yellowstone lake 120 m and hosts up to 174 c fluids heated by steam that condenses on contact with cold lake water the resulting hot fluids exit through a clay alteration cap that largely consists of kaolinite the si deep hole hydrothermal vents are analogous to steam heated hot springs elsewhere in yellowstone national park ynp e g the mud volcano area which are typified by fumaroles and acid sulfate fluids these deep sublacustrine vent fluids are more aptly termed carbonic acid sulfide owing to a lack substantial sulfate from h2s oxidation and acidity attributed to dissolved co2 at 53 m depth vent fluids at the se wt field achieve temperatures of up to 141 c these neutral chloride fluids are largely similar to those that produce siliceous deposits in many subaerial ynp geyser basins geothermometry calculations and binary mixing relationships indicate the se wt field fluids equilibrated at 207 to 224 c following mixing between oxygenated dilute cold groundwater and a fluid with t 345 to 364 c cl 400 ppm and d 149 vsmow broadly similar to the putative deep parent fluid that supplies most geyser basins in ynp the d values of se wt field fluids cannot be derived from lake water implying km scale lateral hydrothermal fluid flow from outside the boundary of yellowstone lake the fluid compositions and hydrothermal processes operating in the two sublacustrine vent systems are distinct but the overarching influence of magmatic heating complex degassing and alteration mineralization effects are broadly comparable to those that affect their subaerial counterparts the high temperatures and hydrostatic pressures of the sublacustrine vents however provide a window into the evolution of fluid chemistry in more deeply seated and less accessible regions of the subsurface ynp and similar volcanically active hydrothermal systems elsewhere

transient effects of magma ascent dynamics along a geometrically variable dome feeding conduit abstract the transient dynamics of magma ascent during dome forming eruptions were investigated and the effects of magma chamber pressure perturbations on eruption rate are illustrated the numerical model domeflow developed by the authors for this work is applied to the problem domeflow is a transient 1 5d isothermal two phase flow model of magma ascent through an axisymmetric conduit of variable radius which accounts for gas exsolution bubble growth crystallization induced by degassing permeable gas loss through overlying magma and through conduit walls as well as viscosity changes due to crystallization and degassing for runs in which chamber pressure increases the time required to reach the new steady state transition time is a complex function of the pressure perturbation while for decreasing chamber pressure transition time is a monotonic function of the magnitude of the pressure perturbation the transition to the new steady state is mainly controlled by magma compressibility travel time time required for one parcel of magma to travel from chamber to surface and the time over which the pressure perturbation occurs results of many runs 300 were analyzed using dimensional analysis to reveal a general relationship which predicts the temporal evolution of magma effusion rate for a given sudden increase in chamber pressure the product of the change in steady state extrusion rate and the time required to reach the new steady state is linearly proportional to the normalized change in chamber pressure the volume of the conduit and the ratio of top and bottom conduit radii and inversely proportional to the cubic root of volatile fraction this relationship is used to interpret observed variations in two ongoing dome building eruptions the soufriere hills volcano montserrat and merapi volcano indonesia

effects of gas escape and crystallization on the complexity of conduit flow dynamics during lava dome eruptions 1 we investigated the coupled effects of gas escape and crystallization on the dynamics of lava dome eruptions using a one dimensional conduit flow model the relationship between chamber pressure pch and mass flow rate q for steady conduit flow commonly has a regime of negative differential resistance i e dpch dq 0 5 feedback 1 is the main mechanism that forms negative differential resistance in this case the transition from lava dome to explosive eruption occurs when the magma supply rate exceeds a fixed critical value for low phenocryst content magma volume fraction 0 5 feedback 2 plays a key role so that the transition is controlled by the permeability of the surrounding rocks the critical magma supply rate remarkably decreases with decreasing permeability transition due to feedback 2 is associated with a change in the chemical composition of volcanic gas a drastic increase in magma porosity from nearly 0 to greater than 0 8 and overpressure at a shallower level which can be detected from geochemical and geophysical field observations

causes and consequences of pressurisation in lava dome eruptions abstract high total and fluid pressures develop in the interior of high viscosity lava domes and in the uppermost parts of the feeding conduit system as a consequence of degassing two effects are recognised and are modelled quantitatively first large increases in magma viscosity result from degassing during magma ascent strong vertical gradients in viscosity result and large excess pressures and pressure gradients develop at the top of the conduit and in the dome calculations of conduit flow show that almost all the excess pressure drop from the chamber in an andesitic dome eruption occurs during the last several hundred metres of ascent second microlites grow in the melt phase as a consequence of undercooling caused by gas loss rapid microlite growth can cause large excess fluid pressures to develop at shallow levels theoretically closed system microlite crystallization can increase local pressure by a few tens of mpa although build up of pressure will be countered by gas loss through permeable flow and expansion by viscous flow microlite crystallization is most effective in causing excess gas pressures at depths of a few hundred metres in the uppermost parts of the conduit and dome interior some of the major phenomena of lava dome eruptions can be attributed to these pressurisation effects including spurts of growth cycles of dome growth and subsidence sudden onset of violent explosive activity and disintegration of lava during formation of pyroclastic flows the characteristic shallow level long period and hybrid seismicity characteristic of dome eruptions is attributed to the excess fluid pressures which are maintained close to the fracture strength of the dome and wallrock resulting in fluid movement during formation of tensile and shear fractures within the dome and upper conduit

insights into volcanic conduit flow from an open source numerical model 1 numerical models that calculate the fluid dynamics of explosive volcanic eruptions have been used with increasing frequency to understand volcanic processes and evaluate volcanic hazards yet those who develop such models rarely make them publicly available so that they can be verified used and possibly improved by other scientists in this paper i present a visual interactive open source numerical model that calculates steady state flow of magma and gas in vertical eruptive conduits and contains user friendly utilities for quickly determining physical thermodynamic and transport properties of silicate melts h2o gases and melt gas crystal mixtures the model represents an advance over previously published conduit models by incorporating a non arrhenian viscosity relation for hydrous silicate melts a relation between viscosity and volume fraction of gas that depends on capillary number and adiabatic temperature changes in the mixture using established thermodynamic relations for melts and h2o gas respectively volcanologists who have not had access to conduit models have frequently approximated conduit flow using an analytical equation for incompressible laminar newtonian pipe flow which predicts that the mass flux is proportional to the fourth power of conduit radius and inversely proportional to mixture viscosity the model presented here which is not much more difficult to use than a back of the envelope calculation shows that the pipe flow approximation significantly overestimates the sensitivity of mass flux to both conduit radius and mixture viscosity results from the model also show that viscous heating in the lower conduit which is not considered in most other models may increase the mass flux of large silicic eruptions by several percent and decrease the viscosity of the mixture at the fragmentation depth by a few tens of percent

hydrothermal changes related to earthquake activity at mud volcano yellowstone national park wyoming the mud volcano hydrothermal area in yellowstone national park is near the intersection of a 20 km long zone of northeast trending normal faults with the eastern resurgent dome within the 600 000 year old yellowstone caldera recent crustal uplift along the northeast trending axis of the caldera is at a maximum 700 mm since 1923 near the mud volcano area from 1973 through april 1978 less than 10 earthquakes largest m 2 4 were located within 3 km of the mud volcano area in may 1978 earthquakes began occurring beneath the hydrothermal area at depths of 1 to 5 km the seismic activity continued until the end of november with intense swarms 100 events per hour occurring on october 23 and november 7 the largest event m 3 1 occurred on november 14 and at least 8 events were m 2 5 or larger in december 1978 heat flux in the mud volcano hydrothermal features began increasing along a 2 km long northeast trending zone existing mud cauldrons became more active new mud cauldrons and fumeroles were formed and vegetation primarily lodgepole pine was killed by increased soil temperature the increase in heat flux continued through july 1979 then gradually declined reaching the early 1978 level by june 1980 the spatial and temporal association of earthquakes and increased hydrothermal activity at mud volcano suggests that the seismic activity expanded preexisting fracture systems premitting increased fluid flow from depths of several kilometers

regional earthquake as a trigger for enhanced volcanic activity evidence from modis thermal data 1 the magnitude 6 4 earthquake that occurred in java on 26 may 2006 provided us with data capable of revealing an immediate eruptive response at two javanese volcanoes merapi and semeru the availability of pre processed thermal data for volcanic hot spots detected by the moderate resolution imaging spectrometer modis and provided on http hotspot higp hawaii edu allowed us to produce heat and volume flux time series for these two erupting volcanoes covering a 35 day period spanning the earthquake our results revealed a coupled response by the volcanoes to the earthquake both experiencing increases in heat and volume flux beginning 3 days after the earthquake with the response lasting 9 days the response was felt at both volcanoes as a factor of two to three increase in the rate of volumetric output after which output returned to the pre response rates this implies that the earthquake triggered enhanced output at two erupting volcanoes 50 and 300 km distant from the earthquake epicenter and separated from each other by 260 km

magmatic stoping during the caldera forming pomici di base eruption somma vesuvius italy as a fuel of eruption explosivity abstract magma carbonate interactions and the subsequent co2 release can occur before and during an eruption critically affecting magma storage and ascent processes however the mechanisms and timescales of those interactions are unclear particularly during the fast magma withdrawal that feeds high intensity eruptions in order to better understand magma carbonate interactions we selected the caldera forming pomici di base plinian eruption the oldest 22 ka and largest 4 4 km3 explosive event in the history of the somma vesuvius volcanic system as case study during this event the emission of trachytic and latitic shoshonitic 25 and 75 of the erupted magma volume respectively magmas generated a long lasting plinian column hypothetically driven by co2 liberation during magma carbonate interaction in this study we reconstruct in detail the evolution of the plumbing system during the pomici di base eruption combining geochemical major minor elements and radiogenic stable isotopes analyses of juvenile products with thermodynamic and kinetic calculations our results demonstrate that magmatic stoping i e the formation and transport of host rock pieces into a magma body during caldera collapse evolution can promote rapid magma assimilation of carbonate blocks and co2 rich fluids resulting from destabilization of the carbonate bedrock thus triggering co2 release and acting as a fuel for the eruption explosivity especially when residual hot mafic magmas are involved our findings suggest that the accurate knowledge of these processes and their influence on eruptive dynamics are critical for improving the hazard assessments of volcanoes with plumbing systems located in carbonate bedrocks

temperature evolution during magma ascent in basaltic effusive eruptions a numerical application to stromboli volcano the dynamics of magma ascent are controlled by the complex interdependent processes of crystallisation rheological evolution gas exsolution outgassing non ideal gas expansion and temperature evolution temperature changes within the conduit in particular play a key role on ascent dynamics since temperature strongly controls the crystallisation process which in turn has an impact on viscosity and thus on magma ascent rate the cooling produced by gas expansion is opposed by the heat produced by crystallisation and therefore the temperature profile within the conduit is quite complex this complexity means that unravelling the dynamics controlling magma ascent requires a numerical model unfortunately comprehensive integrated models with full thermodynamic treatment of multiple phases and rheological evolution are challenging to produce due to the numerical challenges involved until now models have tended to focus on aspects of the problem without a holistic approach in which petrological thermodynamic rheological and degassing processes and their interactions were all explicitly addressed and quantified here we present a new multiphase steady state model for magma ascent in which the main physical and chemical processes such as crystallisation degassing outgassing rheological evolution and temperature variations are quantitatively calculated basaltic magma s crystallisation and flow are sensitive to initial temperature and volatile content and therefore we investigate temperature variations during magma ascent in a basaltic system with a range of volatile contents as a test case we use one of the most well studied recent basaltic effusive eruptions the 2007 eruption of stromboli italy assuming equilibrium crystallisation and exsolution we compare the solutions obtained both with and without an isothermal constraint finding that temperature variations within the conduit have a significant influence on the ascent dynamics and therefore cannot be ignored when modelling basaltic volcanism furthermore we find good agreement between model results and volcanological observations when the non isothermal condition is assumed we investigate through a sensitivity analysis the role of magma chamber temperature on mass flow rate and crystal content we find that a temperature variation of 30 k at the base of the conduit has a bigger effect on mass discharge rate than an increase of 1 wt in water content finally we find that whilst variations in initial co2 concentration can affect the temperature pressure and viscosity profiles along the conduit they do not alter the macroscopic behaviour of the system c 2015 elsevier b v all rights reserved

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

high temperature hydrothermal vent fluids in yellowstone lake observations and insights from in situ ph and redox measurements abstract rov investigation of hydrothermal fluids issuing from vents on the floor of yellowstone lake revealed temperatures in excess of 170 c the highest temperature yet reported for vent fluids within yellowstone national park ynp the study site is east of stevenson island at depth of approximately 100 125 m in situ ph and redox measurements of vent fluids were made using solid state sensors designed to sustain the elevated temperatures and pressures ysz membrane electrode with ag ag 2 o internal element and internal pressure balanced ag agcl reference electrode were used to measure ph while a platinum electrode provided redox constraints lab verification of the ph sensor confirmed excellent agreement with nernst law predictions especially at temperatures in excess of 120 c in situ ph values of between 4 2 and 4 5 were measured for the vent fluids at temperatures of 120 to 150 c the slightly acidic vent fluids are likely caused by co 2 enrichment in association with magmatic degassing effects that occur throughout ynp this is consistent with results of simple model calculations and direct observation of co 2 bubbles in the immediate vicinity of the lake floor vents simultaneous redox measurements indicated moderate to highly reducing conditions 0 2 to 0 3 v as typical of measurements of this kind internal and external redox disequilibria likely preclude unambiguous determination of redox controlling reactions redox disequilibria however can be expected to drive microbial metabolism and diversity in the near vent environment thus the combination of in situ ph and redox sensor deployments may ultimately provide the requisite framework to better understand the microbiology of the newly discovered hot vents on yellowstone lake floor