physical models of volcanic eruptions abstract our present understanding of the dynamics of volcanic eruptions is summarized a few important facts about volcanic eruptions are reviewed and outstanding problems are identified current research efforts are aimed at explaining why an eruption may alternate between and pass through different dynamical regimes the basic physics of eruptions are explained from a dynamical point of view with emphasis on the processes acting to fix the gas content of the erupted material the coupling between flow processes and pressure release leads to large changes of decompression rate during ascent in a volcanic conduit the decompression rate may reach very high values which suggests that the kinetics of degassing play an important role accurate values of the solubility of the major magmatic volatile species are required at pressures of

steep sided domes on venus characteristics geologic setting and eruption conditions from magellan data a survey of more than 95 percent of the venus surface reveals 145 steep sided domes which can be subdivided into a variety of morphologic forms the most common being shaped like inverted bowls or flat topped domes results of a preliminary analysis of the distribution and geologic setting of the domes are presented the relation of the domes to analogous terrestrial features is examined and possible models for their mode of emplacement are outlined

shapes of venusian pancake domes imply episodic emplacement and silicic composition the main evidence available for constraining the composition of the large circular pancake domes on venus is their gross morphology laboratory simulations using polyethylene glycol show that the height to diameter aspect ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic with more episodes leading to greater cooling and taller domes thus without observations of their emplacement the compositions of venusian domes cannot be uniquely constrained by their morphology however by considering a population of 51 venusian domes to represent a sampling of many stages during the growth of domes with comparable histories and by plotting aspect ratio versus total volume we find that the shapes of the domes are most consistent with episodic emplacement on earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition strengthening earlier inferences about the presence of evolved magmas on venus

modelling the lava dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part i dome shape and internal structure lava domes comprise core carapace and clastic talus components they can grow endogenously by inflation of a core and or exogenously with the extrusion of shear bounded lobes and whaleback lobes at the surface internal structure is paramount in determining the extent to which lava dome growth evolves stably or conversely the propensity for collapse the more core lava that exists within a dome in both relative and absolute terms the more explosive energy is available both for large pyroclastic flows following collapse and in particular for lateral blast events following very rapid removal of lateral support to the dome knowledge of the location of the core lava within the dome is also relevant for hazard assessment purposes a spreading toe or lobe of core lava over a talus substrate may be both relatively unstable and likely to accelerate to more violent activity during the early phases of a retrogressive collapse soufriere hills volcano montserrat has been erupting since 1995 and has produced numerous lava domes that have undergone repeated collapse events we consider one continuous dome growth period from august 2005 to may 2006 that resulted in a dome collapse event on 20th may 2006 the collapse event lasted 3 h removing the whole dome plus dome remnants from a previous growth period in an unusually violent and rapid collapse event we use an axisymmetrical computational finite element method model for the growth and evolution of a lava dome our model comprises evolving core carapace and talus components based on axisymmetrical endogenous dome growth which permits us to model the interface between talus and core despite explicitly only modelling axisymmetrical endogenous dome growth our core talus model simulates many of the observed growth characteristics of the 2005 2006 shv lava dome well further it is possible for our simulations to replicate large scale exogenous characteristics when a considerable volume of talus has accumulated around the lower flanks of the dome model results suggest that dome core can override talus within a growing dome potentially generating a region of significant weakness and a potential locus for collapse initiation

viscosity of the dome of mount st helens abstract a sample of dacite from the dome of mt st helens has been studied experimentally and found to have a viscosity that declines from about 10 15 at 800 c to 10 3 poise at 1500 c its yield strength declines from about 2 10 6 dynes cm 2 at 800 c to less than the precision of our measurements 10 4 dynes cm 2 above 1050 c the geometrical form of the dome is approximately consistent with these properties if the internal temperature of the dome is between 900 and 1000 c the melting behavior of the crystalline dacite has been determined between 1000 and 1225 c data on the composition of the liquid fraction and sizes and proportion of crystals have been used to derive a set of equations for predicting the effective viscosity of crystal bearing magmas below their liquidus temperatures although of the bulk composition of the magma has changed little the increasing crystallinity and viscosity appear to have influenced eruptive behavior of the volcano during its most recent periods of activity

solid state ice volcanism on the satellites of uranus voyager images of the uranian satellites ariel and miranda show flow features with morphologies indicating that ice has been extruded to the satellites9 surfaces in the solid state these images provide the first observational evidence for solid state ice volcanism in the solar system topographic profiles have been measured across a number of flow features on ariel with a simple model of extrusion spreading and cooling of a viscous flow the initial viscosity of the flow material is found to have been no more than about 10 16 poise far lower than expected for h 2 o ice at the ambient surface temperatures in the uranian system sharply reduced viscosities may have resulted from incorporation of ices like nh 3 or ch 4 in the uranian satellites

the formation of perched lava ponds on basaltic volcanoes the influence of flow geometry on cooling limited lava flow lengths analysis of the formation of morphologically distinctive perched lava ponds produced in effusive basaltic eruptions focusses attention on the ways in which cooling and fluid dynamics interact to limit the distance a lava flow can travel if a previously channelised flow spreads laterally on encountering a sudden decrease in the slope of the substrate or some other abrupt change in topography its speed and thickness decrease progressively in a way dictated by the requirements of mass and energy conservation there is a consequent dramatic increase in heat loss from the lava as it thins where a flow spreads approximately radially in this way it may form a perched lava pond the high heat loss limits the size of any such pond to be at most a few hundred meters under almost all circumstances pond size depends much more strongly on lava volume flux than on any other physical parameter involved in the system and the formation of these features provides a means of estimating eruption rates in paleo eruptive episodes

effects of compressibility on the flow of lava lava contains gas bubbles and hence is a compressible liquid whose density increases as a function of pressure after eruption at the earth s surface it spreads at a rate which is a function of its thickness and it is compressed under its own weight therefore both thickness and spreading rate are determined by a balance between viscous and compressible effects theoretical equations are derived for the shape and velocity of a compressible liquid spreading on a horizontal surface solutions are obtained for a fixed eruption rate q the radial extent of the flow increases proportional to t1 2 a dimensionless number c is defined which characterizes the importance of flow compression c rho 0 beta g left frac mu q rho 0 2 g right 1 mathord left vphantom 1 4 right kern nulldelimiterspace 4 where 0 is bubbly lava density at atmospheric pressure compressibility viscosity and g the acceleration of gravity c can be thought of as the ratio of two characteristic length scales one for compression effects and one for viscous effects the larger c is the more important compressibility effects are as c is increased the flow becomes thinner because the liquid is compressed more and more efficiently compressibility acts to smooth out variations of flow thickness which provide the driving force thus all else being equal a compressible liquid flows less rapidly than an incompressible one when trying to infer the effective viscosity of a flow from its spreading rate the neglect of compressibility leads to an overestimate the various factors which act to determine the distribution of gas bubbles in lava flows are reviewed and discussed quantitatively comparison with data from obsidian dome eastern california shows that disequilibrium effects are important and that bubble resorption during burial in a thick flow is not a pervasive phenomenon the analysis is applied to the 1979 dome of soufriere de saint vincent w i an effective value of compressibility for this 100 m thick dome is 1 5x10 6 pa 1 this implies that all else being equal the viscosity of this lava may be overestimated by a factor of 5 if no account is taken of the compressible nature of the flow

tephra fountaining rheomorphism and spatter flow during emplacement of the pitigliano tuffs latera caldera italy abstract toward the end of the main ash flow phase ca 156 ka of the latera caldera central italy explosive eruptions near the nw caldera rim produced coarse grained tephra exposed in 35 m high faces of the toscapomice casa collina quarry the pyroclastic sequence fills a narrow sw ne paleovalley and records the near continuous eruption of a compositionally zoned magma batch white phonolitic pumice clasts abruptly grade upward to and partly intrude black spatter like pumice fragments also of phonolite composition this sequence in turn is overlain by densely welded tuff that grades upward to tephriphonolitic scoriae and ash the upper welded part of this sequence referred to as the vulcanite complessa di pitigliano has long been among the more enigmatic deposits in the latera area this sequence displays evidence for both fall and flow emplacement and is here interpreted as an ash fountain fed deposit that locally welded as spatter yet became sufficiently fluidized in distal parts to behave as a spatter rich pyroclastic flow this mechanism requires that the eruption underwent abrupt transition from a vigorously convecting column to a weakly convecting ash fountain and that this period of explosive activity culminated with unusually high accumulation rates the rapidly emplaced tephra retained sufficient heat to weld by compaction and undergo rheomorphism close to the vent yet contained high enough proportions of fluidized dust to have flowed outward along the northern caldera rim and eventually to have welded by vapor phase sintering

morphological evolution of a new volcanic islet sustained by compound lava flows we investigated the creation of a volcanic islet and emplacement of lava flows in the sea by analyzing data from the island forming eruption at nishinoshima japan that has been continuing since november 2013 aerial observations and satellite images were used to perform a quantitative analysis of the eruption processes the most intriguing characteristic of the lava flows is the development of lobes and tubes from breakouts and bifurcations of andesitic a type lava flows internal pathways that fed lava to the active flow front were eventually developed by crust solidification and dominated the lava transport the average discharge was 2 10 5 m 3 day and the total volume of erupted material reached 0 1 km 3 at the end of february 2015 fractal analysis of the lava flow margins suggests that the growth pattern is self similar with a fractal dimension d of 1 08 1 18 which is within the range of subaerial basaltic lava flows the morphological evolution of nishinoshima is controlled primarily by effusion of lava with an apparent viscosity of 10 4 10 6 pa s average discharge of 2 3 m 3 s and eruption duration lasting 2 yr our data and analyses suggest that the effect of lava coming in contact with seawater as well as the variations in the lava discharge rate on local and overall scales are important factors affecting the development of crust and the lava transport system

methods of determining the rheological properties of magmas at sub liquidus temperatures non vesicular basaltic melts behave as newtonian fluids at temperatures above their liquidus and their viscosities can be calculated using a method developed by shaw 1972 and bottinga and weill 1972 because many igneous processes involve the flow of silicates at sub liquidus temperatures numerous attempts have been made to calculate the interactive effects of the crystal phase however current methods are appropriate only for relatively low crystal concentrations and they assume newtonian behaviour we argue that this assumption is invalid when bubble or crystal concentrations exceed 30 at higher concentrations factors other than concentration become increasingly important these include particle shape and size distribution a method which takes these factors into account is tested on a range of suspensions including magmas at sub liquidus temperatures and rheological properties calculated using this method agree closely with the measured values we also demonstrate that an equation which was introduced to explain large differences in measured apparent viscosities during the cooling and crystallisation of mount st helens dacite murase et al 1985 and which is currently used to calculate the rheological properties of crystallising lavas generates viscosities which may be in error by several orders of magnitude this difference is argued to be caused by a combination of factors including the ten orders of magnitude range in the strain rates utilised during the mount st helens measurements causing orders of magnitude difference in the resulting apparent viscosities rheological data on crystallising silicic melts are reinterpreted taking into account the non newtonian rheology of the magmas and changes in activation energy of flow during crystallisation

a low cost method applicable worldwide for remotely mapping lava dome growth abstract lava dome growth and collapse represents both a significant hazard as it can trigger pyroclastic density currents and a monitoring challenge limiting monitoring to a few known active volcanoes here i propose a new differencing technique based on synthetic aperture radar sar amplitude images to quantify the extent of lava dome growth this differencing technique which is both low cost and can be utilized worldwide is applied to sar amplitude images at mount st helens and validated using 2004 2008 aerial photography observations difference of amplitude images accurately characterize the dome growth location the low ground resolution of the 2004 2008 sar data leads to underestimation by 10 to 15 of the dome extent but the accuracy of this method will increase with the improved resolution of current and future sar missions amplitude images are a low level sar product available from all sar satellites mostly freely making the proposed method ideal for systematic low cost monitoring of lava dome growth worldwide with minimum processing required

scales of columnar jointing in igneous rocks field measurements and controlling factors columnar jointing is a common feature of solidified lavas sills and dikes but the factors controlling the characteristic stoutness of columns remain debated and quantitative field observations are few in number in this paper we provide quantitative measurements on sizing of columnar joint sets and our assessment of the principal factors controlling it we focus on 1 chemistry as it is the major determinant of the physical mechanical and thermal properties of the lava and 2 geology as it influences the style of emplacement and lava geometry setting boundary conditions for the cooling process and the rate of heat loss in our analysis we cover lavas with a broad range of chemical compositions from basanite to phonolite for six of which we provide new geochemical analyses and of geological settings our field measurements cover 50 columnar jointing sites in three countries we provide reliable manually digitized data on the size of individual columns and focus the mathematical analysis on their geometry 23 889 data on side length of which 17 312 are from full column sections and 3 033 data on cross sectional area and order of polygonality the geometrical observations show that the variation in characteristic size of columns between different sites exceeds one order of magnitude side length ranging from 8 to 338 cm and that the column bounding polygons average order is less than 6 the network of fractures is found to be longer than required by a minimum energy hexagonal configuration indicating a non equilibrium geologically quick process in terms of the development and characteristic sizing of columnar joint sets our observations suggest that columns are the result of an interplay between the geological setting of emplacement and magma chemistry when the geological setting constrains the geometry of the emplaced body it exerts a stronger control on characteristic column stoutness at unconstrained geometries e g unconfined lava flows chemistry plays the major role resulting in stouter columns in felsic lavas and slenderer columns in mafic lavas

the liquid composition and crystallization history of the 1979 soufriere magma st vincent w i abstract electron microprobe analyses of glassy melt inclusions in phenocrysts of tephra lava and scoria samples of the basaltic andesite 1979 eruption of the soufriere volcano st vincent reveal that the magma is the product of fractional crystallization of alkalic high alumina olivine basalt magma using differentiation trends defined by melt inclusion matrix glass analyses we have constructed a quantitative model of the crystallization history of the 1979 magma sulfur analyses of melt inclusions in selected phenocrysts and estimates of volatile contents by difference suggest that the soufriere volcanic system was not closed with respect to volatiles before the 1979 eruption the volatile content of rare primitive melt inclusions in olivine phenocrysts ranges from two to eight weight percent the sulfur content of these inclusions ranges from 320 to 560 ppm and generally decreases with increasing silica content the volatile content of common melt inclusions in plagioclase orthopyroxene and clinopyroxene airfall phenocrysts on the other hand is probably less than two weight percent and sulfur contents are below the detection limit of 50 ppm these melt inclusions contain appreciably lower volatile content than the most primitive olivine melt inclusions suggesting that they may be samples of largely degassed magma the low volatile content of most soufriere 1979 eruption products inferred from microprobe data is consistent with the vulcanian style and small magnitude of the 1979 eruption which probably involved mainly phreatomagmatic disruption of magma rising and cooling beneath the 1971 lava island rhyodacitic glass of rare banded pumices is observed to be the product of fusion of crustal xenoliths

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

non explosive magma water interaction in a continental setting miocene examples from the eastern cordillera central andes nw argentina the middle upper miocene las burras almagro el toro bat igneous complex within the eastern cordillera of the central andes 24 s nw argentina has revealed evidence of non explosive interaction of andesitic magma with water or wet clastic sediments in a continental setting including peperite generation we describe and interpret lithofacies and emplacement mechanisms in three case studies the las cuevas member 11 8 ma comprises facies related to i andesite extruded in a subaqueous setting and generating lobe hyaloclastite lava and ii marginal parts of subaerial andesite lava dome s in contact with surface water comprising fluidal lava lobes hyaloclastite and juvenile clasts with glassy rims the lampazar member 7 8 ma is represented by a syn volcanic andesite intrusion and related peperite that formed within unconsolidated water saturated coarse grained volcaniclastic conglomerate and breccia the andesite intrusion is finger shaped and grades into intrusive pillows pillows are up to 2 m wide tightly packed near the intrusion fingers and gradually become dispersed in the host sediment 50 m from the parent intrusion the almagro a member 7 2 ma shows evidence of mingling between water saturated coarse grained volcaniclastic alluvial breccia and intruding andesite magma the resulting intrusive pillows are characterized by ellipsoidal and tubular shape and concentric structure the high level penetration of magma in this coarse sediment was unconfined and irregular magma was detached in apophyses and lobes with sharp contacts and fluidal shapes and without quench fragmentation and formation of a hyaloclastite envelope the presence of peperite and magma water contact facies in the bat volcanic sequence indicates the possible availability of water in the system between 11 7 ma and suggests a depositional setting in this part of the foreland basin of the central andes characterized by an overall topographically low coastal floodplain that included extensive wetlands

mechanism of the 1979 explosive eruption of soufriere volcano st vincent abstract the vulcanian explosive phase of the soufriere of st vincent in 1979 occurred when magma penetrated the water logged 1971 1972 lava island in the center of the crater lake the 13 day period of explosive and volcanoseismic activity ceased when the crater lake had dried up and subsequent activity was restricted to quiet lava extrusion the explosive phase produced 15 5 105m3 dense rock equivalent d r e of new magma and 22 106m3 d r e of lithic material from the 1971 1972 island whereas the following extrusive phase produced a dome of volume 47 106m6 considerations of the energetics of the explosive eruption indicate that the available heat content of the new magma 5 8 1016j was not sufficient to account for the observed phenomena including evaporation of the 25 106m3 crater lake and that additional 8 1016 j of heat remaining in the 1971 1972 lava mass are required to drive the eruption plumes field relations the high proportion of lithic material and the energy relations of the eruption are consistent with a phreato magmatic eruption mechanism involving a three way interaction of the 1971 1972 lava mass crater lake water and magma as a consequence of net veining and thermally induced hydraulic fracturing of the water logged 1971 1972 lava island by new magma in 1979

comparison of the shapes and sizes of seafloor volcanoes on earth and pancake domes on venus the fact that flat topped pancake domes observed on venus resemble flat topped volcanoes on earth s seafloor suggests that volcanic processes on the seafloor and on venus may operate to construct volcanic forms with similar characteristics to test this the shapes and size distributions of terrestrial submarine volcanoes seamounts from several magmatic and tectonic provinces are quantitatively compared with those of venusian pancake domes seamount heights and diameters are highly correlated suggesting that there may be a universal mechanism for their growth the 2014 point sample mean of the height to diameter ratio is d 0 10 0 04 in contrast heights and diameters of 52 pancake domes exhibit no obvious trend and values of d are as much as three orders of magnitude smaller with a 52 point sample mean of d 0 02 0 03 seamounts with basal diameters db 10 km have flatness values ratio of top to bottom diameter that span the entire range between 0 pointed cone and 1 truncated cone larger sized seamounts tend to have small values of flatness and more pointed tops this is not true for pancake domes which show large flatnesses at all sizes additionally seamounts have distinctive profiles with their flank slopes increasing in gradient toward the summit flank slopes of pancake domes however commonly increase in gradient toward the base with respect to sizes the diameter distributions of the different seamount populations are consistent with a model in which the number of seamounts decreases exponentially with increasing diameter the diameter distribution of 126 pancake domes by contrast is more uniform its mean is db 22 13 km this size is at least an order of magnitude larger than the estimated characteristic diameters of the seamount populations based on the above results i conclude that seamounts have significantly different shapes and size distributions than venusian pancake domes that have been identified and measured to date this suggests that one or more of the variables e g magma composition crystallinity magma volume effusion rate cooling rate pre existing topography governing their formation differs in terms of shapes and size distributions the small db 20 km volcanic edifices first identified from venera data are good morphologic matches to seamounts and should be the focus of future work investigating the formation of comparable volcanic features in these two different planetary environments

morphology and growth style of a miocene submarine dacite lava dome at atsumi northeast japan abstract a miocene submarine lava dome at tate iwa atsumi yamagata japan displays well preserved primary morphological features the dome currently rises above a wave cut coastal platform and is 55 m high and 90 180 m across it comprises a massive core and a lava lobe hyaloclastite rim both of which are composed of compositionally uniform feldspar phyric dacite sio2 64 wt the boundary between these two zones is distinct but gradational the massive core consists of homogeneous coherent dacite and is characterized by flow banding along the margin and by columnar joints radiating from the centre to the margin the lava lobe hyaloclastite rim encircles the massive core and consists of a complex of 80 90 dacitic lava lobes and 10 20 hyaloclastite the lava lobes are 1 6 m thick 3 12 m wide and more than 5 m long each lobe consists of a radially columnar jointed core and a glassy rim 10 30 cm thick the hyaloclastite comprises polyhedral dacite clasts 5 100 cm across in a matrix of dacite fragments up to 5 mm across the lava lobes and hyaloclastite have gradational contacts in places paleobathymetric studies based on foraminifera in sediment beneath the dome and the k ar age of the dome suggest that it was extruded in a middle bathyal environment 1500 2000 m below sea level at 12 9 0 6 ma the internal structures of the dome suggest that it formed by a combination of exogenous growth involving extrusions of small dacite lobes and endogenous growth involving a continuous magma supply and simple expansion from the interior the presence of small lava lobes along the rim suggests that the magma had relatively low viscosity at the time of extrusion in spite of its high silica content magma temperatures calculated by two pyroxene and fe ti oxide geothermometers were 999 1042 and 957 1005 c respectively the inferred low viscosity may be attributed to the high temperature of the magma and or a high confining pressure resulting from the deep sea environment

geological mapping of the ac 10 rongo quadrangle of ceres abstract the dawn spacecraft arrived at dwarf planet ceres in spring 2015 and imaged its surface from four successively lower polar orbits at ground sampling dimensions between 1 3 km px and 35 m px to understand the geological history of ceres a mapping campaign was initiated to produce a set of 15 quadrangle based geological maps using the highest resolution framing camera imagery here we present the geological map of the ac 10 rongo quadrangle which is located at the equator encompassing the region from 22 n to 22 s and 288 to 360 e the total relief within the quadrangle is 11 1 km with altitudes ranging from about 7 3 km to 3 8 km we identified nine geological units based on surface morphology and surface textural characteristics the dominant and most widespread unit is the cratered terrain crt representing ancient reworked crustal material its consistent formation age across the quadrangle is 1 8 ga two edifices unit th ahuna mons and an unnamed tholus within begbalel crater are interpreted to be of cryo volcanic origin the southwest portion of the quadrangle is dominated by ejecta material ye emplaced during the formation of the 260 km diameter yalode impact basin at about 580 ma rayed crater ejecta material cr is dominant in the eastern part of the quadrangle but also occurs in isolated patches up to a distance of 455 km from the 34 km diameter source crater haulani the remaining five geological units also represent impact crater materials degraded rim crdeg bright crater cb hummocky floor cfh talus ta and crater c materials widespread yalode and haulani ejecta materials can potentially be utilised as stratigraphic markers therefore it is essential to consistently map their full areal extent and to date their formations using impact crater statistics

laboratory measurements of the strontium distribution coefficient kdsr for sediments from a shallow sand aquifer a batch method has been modified and improved for measuring strontium distribution coefficients kdsr for sediments from the shallow aquifer at chalk river an average measured kdsr value of 10 ml g for whole aquifer sediments compares favorably both with a field value of 7 ml g determined using the retardation equation and with an average kdsr of 10 ml g based on analytical results for aquifer sediments and coexisting groundwaters from a portion of the flow system that is contaminated with 90sr measurements of kdsr for mineralogically pure segregates indicate that vermiculite an alteration product of biotite is the most effective adsorbent phase kdsr results for grain size fractions suggest that the distribution of minerals with respect to grain size may strongly influence the kdsr of the whole sediment relationships between kdsr and exchangeable calcium on the sediments and competing cation concentration in the test solution indicate that electrostatic forces primarily control the sorption of strontium

imaging the 2013 explosive crater excavation and new dome formation at volcan de colima with terrasar x time lapse cameras and modelling abstract the summit region of steep volcanoes hosting lava domes often displays rapid geomorphologic and structural changes which are important for monitoring the source region of hazards explosive crater excavation is often followed by new lava dome growth which is one of the most dynamic morphometric changes that may occur at volcanoes however details of these crater formations and the ensuing new dome growth remain poorly studied a common problem is the lack of observational data due to hazardous field access and the limited resolution of satellite remote sensing techniques this paper describes the destructive constructive crater activity at volcan de colima mexico which occurred between january and march 2013 the crater geometry and early dome formation were observed through a combination of high resolution terrasar x spotmode satellite radar images and permanently installed monitoring cameras this combined time lapse imagery was used to identify ring shaped gas emissions prior to the explosion and to distinguish between the sequential explosion and crater excavation stages which were followed by dome growth by means of particle image velocimetry the digital flow field is computed from consecutive camera images showing that vertical dome growth is dominant at the beginning the upward growth is found to grade into spreading and a lateral growth domain after approximately two months of gradually filling the excavated craters with new magma the dome overflows the western margin of the crater and develops into a flow that produces block and ash flow hazards we discuss and compare the observations to discrete element models allowing us to mimic the vertical and lateral growth history of the dome and to estimate the maximum strength of the bulk rock mass moreover our results allow a discussion on the controls of a critical dome height that may be reached prior to its gravitational spreading

eruption mechanisms and short duration of large rhyolitic lava flows of yellowstone abstract large volume effusive rhyolite lava flows are a common but poorly understood occurrence from silicic volcanic centers we integrate characterization of lava flow topographic morphology and petrographic textures and zoning of crystals with physical models of viscous fluid flow in order to interpret the eruption durations and discharge rates for the most recent effusive volcanic eruptions from yellowstone these large volume 10 70 km3 crystal poor rhyolite lavas erupted within the yellowstone caldera as 100 200 m thick flows and have a cumulative erupted volume of 650 km3 that is similar to less frequent caldera forming events but occur as individual eruptions spread over 100 ka most of this work is focused on the axisymmetric 124 ka 50 km3 summit lake flow we examined crystallinity major and trace element concentrations oxygen and hydrogen isotopic values and quartz morphology and zoning in samples from the center to margin of this flow water contents down to 0 1 wt and d values of 110 are low and require closed system degassing until near surface lithostatic pressure while major elements are consistent with water undersaturated pre eruptive storage and crystallization at 4 8 km depth we found some evidence for subtle km scale zoning within the lavas but describe significant microscopic scale compositional diversity including sharp boundaries between high ti cores and 200 m thick rims on quartz phenocrysts embayed quartz external morphology and rim growth may be the result of undercooling during coalescence of magma bodies during shallow transport between dikes and sills modeling the emplacement of the lava flow as a simple viscous fluid suggests that emplacement of rhyolite lava at 800 c occurred over 2 to 5 yrs with high discharge rates 100 m3 s such high magma discharge rates are accommodated through 6 km long fissures that allow for slower magma ascent velocities of 10 yr flow durations and significant cooling of the flow front that should result in a more complex compound flow morphology than observed higher temperatures require unrealistically wide 50 m dike widths to accommodate large discharge rates petrographic and isotopic evidence from crystals suggests recharge and merger of individual magma batches occurs on a similar timescale to the eruption duration and may directly cause overpressure and emplacement of these rhyolite lava flows from a shallow ephemeral magma chamber large volume rhyolitic lavas are able to erupt effusively through elongate fissures that utilize preexisting zones of crustal weaknesses such as ring fractures less common explosive eruptions at yellowstone may result when ascending magmas are forced through narrower conduits or when recharge rates are especially high the results of this study provide a unique top down constraint on effusive eruption rates make new interpretations of common petrographic textures and presents a comprehensive model for eruption control

drill core based facies reconstruction of a deep marine felsic volcano hosting an active hydrothermal system pual ridge papau new guinea odp leg 193 abstract pual ridge is a deep marine felsic volcanic edifice in the eastern manus back arc basin papua new guinea with an estimated volume of 6 to 9 km 3 it is 1 1 5 km wide 20 km long and rises 500 600 m above the surrounding ocean floor the active pacmanus hydrothermal field on the crest of pual ridge at 1640 1690 m below sea level was the target of ocean drilling program leg 193 variably altered dacite lavas have been recovered from the subsurface of a low t discharge site snowcap and a high t black smoker site roman ruins reaching a maximum depth of 380 m below seafloor mbsf volcanic facies interpretation of these cores is difficult due to incomplete recovery and widespread pseudoclastic textures generated by fracturing and multi phase incomplete fluid dacite interaction however distinction of genuine volcaniclastic facies and facies with alteration related clastic appearance is important in order to define paleo seafloor positions within the volcanic stratigraphy that may be prospective for massive sulfide mineralization this has been accomplished using remnant primary characteristics indicative of transportation such as polymictic composition grading or textural evidence for differential movement of individual clasts three phases of volcanic activity can be distinguished and a proximal facies association dominated by coherent facies of dacite lavas exists below snowcap at roman ruins a medial facies association consists of lava flows with about equal proportions of coherent and volcaniclastic facies endogenous growth was an important process during lava flow emplacement and groundmass textures such as perlite flow banding and spherulites indicate that cooling rates were variable locally allowing for high temperature devitrification a tube pumice breccia unit is interpreted as the resedimented facies of a quench fragmented highly vesicular dacite lava carapace sulfide accumulations in the subsurface are restricted to roman ruins suggesting that the abundance of volcaniclastic facies favored ascent of metal bearing fluids due to the inherent high permeability evidence for mineralization at paleo seafloor positions at 110 and 195 mbsf indicate a complex interrelationship between volcanic and hydrothermal activity a facies model has been developed which may help to locate subaqueous felsic lava dominated volcanic centers and associated sulfide deposits in ancient volcano sedimentary successions

an experimental study of the surface thermal signature of hot subaerial isoviscous gravity currents implications for thermal monitoring of lava flows and domes received 22 july 2011 revised 23 november 2011 accepted 23 november 2011 published 7 february 2012 1 management of eruptions requires a knowledge of lava effusion rates for which a safe thermal proxy is often used however this thermal proxy does not take into account the flow dynamics and is basically time independent in order to establish a more robust framework that can link eruption rates and surface thermal signals of lavas measured remotely we investigate the spreading of a hot isoviscous axisymmetric subaerial gravity current injected at constant rate from a point source onto a horizontal substrate we performed laboratory experiments and found that the surface thermal structure became steady after an initial transient we develop a theoretical model for a spreading fluid cooled by radiation and convection at its surface that also predicts a steady thermal regime we show that despite the model s simplicity relative to lava flows it yields the correct order of magnitude for the effusion rate required to produce the radiant flux measured on natural lava flows for typical thermal lava properties and an effusion rate between 0 1 and 10 m 3 s 1 the model predicts a steady radiated heat flux ranging from 10 8 to 10 10 w the assessed effusion rate varies quasi linearly with the steady heat flux with much weaker dependence on the flow viscosity this relationship is valid only after a transient time which scales as the diffusive time ranging from a few days for small basaltic flows to several years for lava domes the thermal proxy appears thus less reliable to follow sharp variations of the effusion rate during an eruption

the intrusion of fluid mechanics into geology during the last few years a number of fluid dynamicists often in collaboration with geologists have been investigating problems suggested by geology and creating the new field of geological fluid mechanics the research has uncovered many new fluid mechanical phenomena and the studies have ranged widely over theoretical contributions laboratory experiments and confirmatory field observations this paper presents an overview of part of the field with a strong emphasis on the novel fluid mechanical concepts the presentation includes discussion of some of the effects of cooling and crystallization and the resulting convective motions the flow of gravity currents at both high and low reynolds number and the erosion of solid retaining walls by hot turbulent flows

extended cooling and viscous flow of large hot rhyolite lavas implications of numerical modeling results abstract a common misconception about rhyolite lava flows is that they cannot advance far from their vents and are constrained to be small due to their high viscosities although a high viscosity lava will indeed flow quite slowly it may advance a great distance if the lava efficiently retains heat and thus mobility and if the available magma supply is large to evaluate this possibility a finite difference numerical model was used to determine the rate of heat loss from units interpreted to be large rhyolite lavas cooling of such 100 300 m thick units is very slow and is further retarded by a vesicular carapace and by evolution of latent heat thermal history alone suggests that large thick lava flows could remain active for several decades to constrain the duration of flow advance of these units their inferred apparent viscosities are compared with those of active lava flows mean flow velocity of some large rhyolites in southwestern idaho usa was estimated based on the observation that the units must still have been advancing by viscous flow at the start of spherulite crystallization indicating perhaps a 10 to 18 year flow duration based on studies of obsidian dome california mean flow velocities would have been roughly 0 59 to 2 5 km yr and calculated average apparent viscosities of the flows ranged from 1 8 to 3 6 orders of magnitude greater than the viscosity of the lava itself this relationship also holds for active andesite and basaltic andesite block lava flows which have apparent viscosities 2 7 to 4 orders of magnitude greater than lava viscosities this implies that large rhyolites may indeed have been emplaced in the same manner as less silicic block lavas and that long distance viscous flow is not unrealistic for rhyolite lavas a good example of a large volume lava is the 15 km 3 rhyolite of the badlands sw idaho where vent relations show that lava effused from a fissure and advanced up to 9 km more extensive rhyolites could also be emplaced solely by effusion extended flow of these lavas may lead to the remelting and removal of basal crumble breccias and to the formation of welded shard textures in their margins both processes tending to obscure the lava flow origin of the units the great dimensions of lava like rhyolitic units with volumes of 10 to at least 200 km 3 are not a sufficient reason to assume they erupted as ignimbrites

microshear zones in a miocene submarine dacite dome of southwest japan microscopic shear zones have been found in the groundmass of glassy rocks of a miocene submarine dacite dome in southwest japan similar textures have been reported previously but only in dykes these textures give a valuable insight into the deformation of the dome during its emplacement by recording the orientations of the principal strains detailed textural analysis indicates that the microshear zones formed as a result of flattening and stretching of the magma simultaneously with quenching measured stretching directions are near parallel suggesting the magma flowed in one dominant direction rather than in a radial pattern the strain is believed to also be influenced by high magma pressure inside the dome being imposed on the high viscosity outer part of the dome

lava flows as kinematic waves a recently proposed model for the emplacement of lava flows is reinterpreted as a kinematic wave theory for the depth of the flow with this interpretation the longitudinal profile of an advancing flow is considered to be a propagating waveform with its length limited continuously by the amount of lava extruded the application of kinematic wave formalism provides new insights into the effects of time dependent source behavior on the shape and extent of the wave eruption behavior with a period of increasing flow depth at the source is shown to produce so called breaking points in the depth profile where the kinematic wave model itself could be invalid two models of such eruption behavior are investigated and this is shown not to be the case specifically when the conservation of lava volume is imposed the breaking points always reside beyond the front of the wave in general it is found that source behavior propagates downstream faster than the flow advances thus only a fraction of the source time dependence is reflected in the shape of the kinematic wave the remainder of the time dependent source effects must be deposited in the flow front lateral margins or solidifying crust or be dissipated irretrievably by processes not included in the model the fraction of eruption history contained in the advancing waveform depends crucially on the nature of the flow rate flow depth relation for the lava distal surface waves budding at the nose of the flow distal levee collapse and other volcanological observations may be manifestations of time dependent source behavior that advanced beyond the kinematic wave front

volcanic constructs on ganymede and enceladus topographic evidence from stereo images and photoclinometry paul m schenklunar and planetary institute houston texasjeffrey m moorespace sciences division and the seti institute nasa ames research center moffett field californiaabstract the morphology of volcanic features on ganymede differs significantly from that onthe terrestrial planets few if any major volcanic landforms such as thick flows or shieldvolcanoes have been identified to date using new stereo voyager images we have searchedganymede for relief generating volcanic constructs we observed seven major types of volcanicstructures including several not previously recognized the oldest are broad flat topped domespartially filling many older craters in dark terrain similar domes occur on enceladus togetherwith smooth dark deposits these domes indicate that the volcanic history of the dark terrain iscomplex bright terrain covers vast areas although the style of emplacement remains unclear smooth bright materials embay and flood older terrains and may have been emplaced as low viscosity fluids associated with smooth bright material are a number of scalloped shaped semi enclosed scarps that cut into preexisting terrain in planform these structures resemble terrestrialcalderas the youngest volcanic materials identified are a series of small flows that may haveflooded the floor of the multiring impact structure gilgamesh forming a broad dome theidentification of volcanic constructs up to 1 km thick is the first evidence for extrusion ofmoderate to high viscosity material on ganymede viscosity and yield strength estimates for thesematerials span several orders of magnitude indicating that volcanic materials on ganymede have arange of compositions and or were extruded under a wide range of conditions and or eruptive styles introductionthe voyager survey of the outer solar system has revealedan astonishing variety of endogenic landforms on the surfacesof icy satellites despite extensive endogenic resurfacing ofsomc satellites for example ganymede enceladus andtriton volcanism on these surfaces has little topographicexpression we do not see massive volcanic edifices similarto olympus mons or mauna kea even the best putativeexamples of volcanic landforms seen on ariel miranda triton and enceladus exhibit rarely more than 1 2 km ofrelief jankowski and squyres 1988 pozio and kargel 1989 schenk 1991a croft et al 1995 this may berelated to the soft theology of ice see poirier 1982 durham et al 1983 and kirby et al 1987 or torheology and volcanic styles peculiar to icy petrologicsystems e g kargel 1991 kargel et al 1991 well over half of the surface of ganymede radius 2634 kin has been covered by endogenic effusions it is now consideredlikely that ganymede experienced one or more episodes ofchaotic orbital behavior malhotra 1991 possiblyresulting in tidal heating volcanic resurfacing constitutes arecord of ganymede s compositional and thermal evolution andmay record some of these putative tidal heating events yetthis satellite has been the subject of morphological study for15 years without the unambiguous detection of relief copyright 1995 by the american geophysical union paper number 95je01854 0148 0227 95 95je 01854505 00generating volcanic constructions on its landscape the styleof emplacement and composition of those volcanic depositsthat have been identified remains unclear on any planetary surface volcanic and other nonimpactconstructs can be difficult to recognize in spacecraft images particularly those obtained under high sun conditions e g malin 1978 topography is especially low on the galileansatellites and imaging resolution is at best 500 m pixel major local albedo variations on ganymede further complicategeologic and topographic mapping with these problems inmind we have undertaken the production of stereo pairs ofvoyager images where coverage permits to aid in the searchfor and characterization of volcanic landforms on ganymede ssurface in addition to an examination of previously identifiedvolcanic materials we report the discovery of severalpreviously unrecognized volcanic landforms and at least twotypes with substantial relief and describe their morphologyand geologic setting morphology of volcanic depositsindicates that ganymede extrusions probably had a range oftheologies and may be compositionally variable we concludewith speculations and predictions regarding their mode ofemplacement and the implications of volcanic landforms forthe geologic evolution of ganymede stereo imaging with voyagerthis study was motivated by the recognition that asignificant fraction of the surfaces of most of the outer planetsatellites were imaged by voyager in stereo e g croft andsoderblom 1991 schenk and moore 1993 we can usestereo imaging to detect subtle topographic features that were19 009

effusive eruption of viscous silicic magma triggered and driven by recharge a case study of the cerro chascon runtu jarita dome complex in southwest bolivia the cerro chascon runtu jarita complex is a group of ten late pleistocene 85 ka lava domes located in the andean central volcanic zone of bolivia these domes display considerable macroscopic and microscopic evidence of magma mixing two groups of domes are defined chemically and geographically a northern group the chascon consists of four lava bodies of dominantly rhyodacite composition these bodies contain 43 48 phenocrysts of plagioclase quartz sanidine biotite and amphibole in a microlite poor rhyolitic glass rare mafic enclaves and selvages are present mineral equilibria yield temperatures from 640 to 750 c and log o2 of 16 geochemical data indicate that the pre eruption magma chamber was zoned from a dominant volume of 68 to minor amounts of 76 sio2 this zonation is best explained by fractional crystallization and some mixing between rhyodacite and more evolved compositions the mafic enclaves represent magma that intruded but did not chemically interact much with the evolved magmas a southern group the runtu jarita is a linear chain of six small domes 1 km3 total volume that probably is the surface expression of a dike the five most northerly domes are composites of dacitic and rhyolitic compositions the southernmost dome is dominantly rhyolite with rare mafic enclaves the composite domes have lower flanks of porphyritic dacite with 35 vol phenocrysts of plagioclase orthopyroxene and hornblende in a microlite rich rhyodacitic glass sieve textured plagioclase mixed populations of disequilibrium plagioclase compositions xenocrystic quartz and sanidine with ternary composition reaction rims indicate that the dacite is a hybrid the central cores of the composite domes are rhyolitic and contain up to 48 vol phenocrysts of plagioclase quartz sanidine biotite and amphibole this is separated from the dacitic flanks by a banded zone of mingled lava macroscopic microscopic and petrologic evidence suggest scavenging of phenocrysts from the silicic lava mineral equilibria yield temperatures of 625 727 c and log o2 of 16 for the rhyolite and 926 1000 c and log o2 of 9 5 for the dacite the rhyolite is zoned from 73 to 76 sio2 and fractionation within the rhyolite composition produced this variation most of the 63 73 sio2 compositional range of the lava in this group is the result of mixing between the hybrid dacite and the rhyolite eruption of both groups of lavas apparently was triggered by mafic recharge a paucity of explosive activity suggests that volatile and thermal exchanges between reservoir and recharge magmas were less important than volume increase and the lubricating effects of recharge by mafic magmas for the runtu jarita group the eruption is best explained by intrusion of a dike of dacite into a chamber of crystal rich rhyolite close to its solidus the rhyolite was encapsulated and transported to the surface by the less viscous dacite magma which also acted as a lubricant simultaneous effusion of the lavas produced the composite domes and their zonation reflects the subsurface zonation the role of recharge by hotter more fluid mafic magma appears to be critical to the eruption of some highly viscous silicic magmas

on lava dome growth with application to the 1979 lava extrusion of the soufriere of st vincent abstract a theoretical analysis is presented for the spread of a viscous liquid flowing under its own hydrostatic pressure on a horizontal surface in order to model lava dome formation two situations are considered in detail the spreading of a constant volume of liquid and the case where the amount of liquid is continually increased experiments with silicone liquids show close agreement with theory the formation of a basaltic andesite lava extrusion in 1979 on the crater floor of the soufriere of st vincent west indies provided the motivation for and an application of the model the extrusion reached a diameter of 868 m and a height of 133 m over a period of 150 days over the first 90 days the growth relationships were consistent with those predicted by theory application of the theory to the soufriere dome suggests an effective viscosity of 2 x 10 12 poise for the basaltic andesite lava the large effective viscosity calculated for the lava may be attributed to the dominant influence of a high viscosity skin which forms at the margins of the flow as it cools after 70 days the rate of growth of the extrusion markedly decreased because a substantial collar of rubble accumulated at the flow front due to this collar the growth of the extrusion ceased after 150 days from approximately two weeks after the initiation of the extrusion the discharge rate of lava decreased approximately linearly with increasing dome height this observation suggests that the lava ascended under a decreasing hydrostatic driving pressure and that extrusion ceased when the lava column reached hydrostatic equilibrium

natural to anthropogenic forcing in the holocene evolution of three coastal lagoons caldas da rainha valley western portugal in the coast of central portugal three lagoons were created by the holocene flooding of diapiric related depressions but experienced afterwards a significant sediment accumulation fast environmental and morphological changes after the middle holocene were clearly forced by anthropogenic activities since the middle ages and show a strong feedback on the human communities erosion in the studied watersheds depends on climatic and anthropic changes especially demographic rises increase agriculture and deforestation in the watersheds and sedimentation in the lagoons the region was successively occupied by ethnic groups since the neolithic including romans sueves visigoths and muslims but the main changes were largely due to anthropic forcing following the christian reconquest by the kingdom of portugal in fact during the middle ages and renaissance the area had intense nautical fishing and agricultural activities even if reduced during the 14th century crisis later due to severe sediment accumulation and shoaling sailing was drastically reduced and most of the area drowned in the maximum transgression was claimed to farming it is also noteworthy that the social evolution and sediment entrainment in the watersheds appear to be in tune with climatic trends deduced after regional and global data in synthesis we conclude that the human activities during the last millennium greatly accelerated the natural silting trend of the lagoons

the spreading of variable viscosity axisymmetric radial gravity currents applications to the emplacement of venusian pancake domes the magellan images of venus have revealed a number of intriguing volcanic features including the steep sided or pancake domes these volcanic domes or flows have morphologies that suggest formation by a single continuous emplacement of lava with a higher viscosity than that of the surrounding basaltic plains numerous investigators have suggested that such high viscosity is due to high silica content leading to the conclusion that the domes are evidence of evolved magmatic products on venus however viscosity depends on crystallinity as well as on silica content high viscosity could therefore also be due to a cooler and therefore higher crystal content lava models of dome emplacement which include both cooling and composition factors are thus necessary in order to determine the ranges of crystallinity and silica content which might lead to the observed gross dome morphologies accordingly in this study domes are modelled as radial viscous gravity currents with an assumed cooling induced viscosity increase to include both effects analytical and numerical results indicate that pancake dome formation is feasible with compositions ranging from basaltic to rhyolitic therefore observations of gross dome morphology alone are insufficient for determining composition and the domes do not necessarily represent strong evidence for evolved magmatism on venus

using the level set method to model endogenous lava dome growth modeling volcanic phenomena is complicated by free surfaces often supporting large rheological gradients analytical solutions and analogue models provide explanations for fundamental characteristics of lava flows but more sophisticated models are needed incorporating improved physics and rheology to capture realistic events to advance our understanding of the flow dynamics of highly viscous lava in peleean lava dome formation axi symmetrical finite element method fem models of generic endogenous dome growth have been developed we use a novel technique the level set method which tracks a moving interface leaving the mesh unaltered the model equations are formulated in an eulerian framework in this paper we test the quality of this technique in our numerical scheme by considering existing analytical and experimental models of lava dome growth which assume a constant newtonian viscosity we then compare our model against analytical solutions for real lava domes extruded on soufriere st vincent w i in 1979 and mount st helens usa in october 1980 using an effective viscosity the level set method is found to be computationally light and robust enough to model the free surface of a growing lava dome also by modeling the extruded lava with a constant pressure head this naturally results in a drop in extrusion rate with increasing dome height which can explain lava dome growth observables more appropriately than when using a fixed extrusion rate from the modeling point of view the level set method will ultimately provide an opportunity to capture more of the physics while benefiting from the numerical robustness of regular grids

a model for the spreading and compaction of two phase viscous gravity currents two phase viscous gravity current theory has numerous applications in the natural sciences from small scale lava sedimentary and glacial flows to large scale flows of partially molten mantle we develop the general equations for two phase viscous gravity currents composed of a high viscosity matrix and low viscosity fluid for both constant volume and constant flux conditions a loss of fluid phase is taken into account at the current s upper boundary and corresponds to the degassing of a lava flow or loss of water in sedimentary flows as the current spreads its surface increases and fluid loss is facilitated which modifies the mixture density and viscosity and thus the current s shape hence spreading of the flow affects fluid loss and vice versa our results show that two phase gravity currents retain and transport the fluid out to large distances but the fluid is almost entirely lost within a region of finite radius this loss radius depends on the flow s volume or flux fluid and matrix properties as well as on the size of fluid parcels or matrix permeability application to lava flows shows that degassing occurs over a large area which affects gas release and transport in the atmosphere

putative ice flows on europa geometric patterns and relation to topography collectively constrain material properties and effusion rates europa s surface exhibits numerous small dome like and lobate features some of which have been attributed to fluid emplacement of ice or slush on the surface we perform numerical simulations of non newtonian flows to assess the physical conditions required for these features to result from viscous flows our simulations indicate that the morphology of an ice flow on europa will be at least partially influenced by pre existing topography unless the thickness of the flow exceeds that of the underlying topography by at least an order of magnitude three classes of features can be identified on europa first some possibly most putative flow like features exhibit no influence from the pre existing topography such as ridges although their thicknesses are generally on the same order as those of ridges therefore flow processes probably cannot explain the formation of these features second some observed features show modest influence from the underlying topography these might be explained by ice flows with wide ranges of parameters ice temperatures 230 k effusion rates 10 7 m 3 year 1 and a wide range of grain sizes although surface uplift e g by diapirism and in situ disaggregation provide an equally compelling explanation third several observed features are completely confined by pre existing topographic structures on at least one side these are the best known candidates for flow features on europa if these features resulted from solid ice flows then temperatures 260 k and grain sizes 2 m are required such small grain sizes seem unlikely low viscosity flows such as ice slurries or brines provide a better explanation for these features our results provide theoretical support for the view that many of europa s lobate features have not resulted from solid ice flows

rapid dome growth at montagne pelee during the early stages of the 1902 1905 eruption a reconstruction from lacroix s data information obtained from various parts of the two books on montagne pelee by lacroix enables an estimate to be made of the size of l etang sec summit crater the volume of the 1902 1905 lava dome and its growth rate at various stages of development during the week preceding the 8 may nuee ardente dome growth was between 28 and 38 m3 s 1 leading to a volume of 17 23 106 m3 on the morning of the catastrophe considering that significant parts of the dome 1 3 were removed by the 8 and 20 may climactic eruptions a high magmatic flux could have continued until at least 27 may when the total remaining volume was estimated to 53 106 m3 after moderate activity in june july of order 10 m3 s 1 vigorous dome growth resumed dramatically leading to the third climactic eruption of 30 august a true calculation for this period being not feasible because of poor quality of the data from november 1902 to july 1903 most of the effusive activity was concentrated in the great spine erupted volume 15 106 m3 magma flux 1 2 m3 s 1 which was eventually destroyed by collapse and minor nuees ardentes the end of the eruption was characterized by a very low effusion rate 1 m3 s 1 in average from august 1903 to october 1905