flowgo a kinematic thermo rheological model for lava flowing in a channel we present a kinematic self adaptive numerical model to describe the down flow thermal and rheological evolution of channel contained lava as our control volume of lava advances down a channel it cools and crystallizes an increasingly thick and extensive surface crust grows and its heat budget and rheology evolve by estimating down flow heat and velocity loss our model calculates the point at which the control volume becomes stationary giving the maximum distance lava flowing in the channel can extend modeled effusion rates velocities widths surface crust parameters heat budget cooling temperature crystallinity viscosity and yield strength all compare well with field data collected during eruptions at mauna loa k lauea and etna modeled lengths of 25 27 2 5 5 7 and 0 59 0 83 km compare with measured lengths of 25 27 4 and 0 75 km for the three flows respectively over proximal flow portions we calculate cooling crystallization viscosity and yield strength of 1 10 c km 1 0 001 0 01 volume fraction km 1 103 104 pa s and 10 3 102 pa respectively at the flow front cooling crystallization viscosity and yield strength increase to 100 c km 1 0 1 volume fraction km 1 106 107 pa s and 103 104 pa respectively all of which combine to cause the lava to stop flowing our model presents a means of a analyzing lava flow thermo rheological relationships b identifying important factors in determining how far a channel fed flow can extend c assessing lava flow hazard and d reconstructing flow regimes at prehistoric unobserved or remote flows

trace element degassing and enrichment in the eruptive plume of the 2000 eruption of hekla volcano iceland during its last eruption in february 2000 hekla volcano iceland emitted a sub plinian plume that was condensed and scavenged down to the ground by heavy snowstorms offering the unique opportunity to study the chemistry of the gaseous plume released during highly explosive eruptions in this paper we present results on trace element and minor volatile species sulfates chlorides and fluorides concentrations in snow samples collected shortly after the beginning of the eruption the goal of this study is to better constrain the degassing and mobility of trace elements in gaseous emissions trace element volatility at hekla is quantified by means of enrichment factors ef relative to be well known volatile trace elements e g transition metals heavy metals and metalloids are considerably enriched in the volcanic plume of hekla their abundances are governed by the primary magmatic degassing of sulfate and or halide compounds which are gaseous at magmatic temperature their volatility is however slightly lower than in basaltic systems most likely because of the lower magma temperature and higher magma viscosity at hekla more surprisingly refractory elements e g ree th ba and y are also significantly enriched in the eruptive plume of hekla where their apparent volatility is two orders of magnitude higher than in mafic systems in addition ree patterns normalized to the hekla 2000 lava composition show a significant enrichment of hree over lree suggesting the presence of ree fluorides in the volcanic plume such enrichments in the most refractory elements and ree fractionation are difficult to reconcile with primary degassing processes since ree fluorides are not gaseous at magma temperature ree enrichments at hekla could be attributed to incongruent dissolution of tephra grains at low temperature by f rich volcanic gases and aerosols within the eruptive plume this view is supported by both leaching experiments performed on hekla tephra and thermodynamic considerations on ree mobility in hydrothermal fluids and modeling of glass dissolution in f rich aqueous solutions tephra dissolution may also explain the observed enrichments in other refractory elements e g th y and ba and could contribute to the degassing mass balance of some volatile trace elements provided they are mobile in f rich fluids it thus appears that both primary magmatic degassing and secondary tephra dissolution processes govern the chemistry of eruptive plumes released during explosive eruptions

post emplacement cooling and contraction of lava flows insar observations and a thermal model for lava fields at hekla volcano iceland lava flows contract as they cool causing progressive subsidence of the flow surface here we study this process by measuring and modelling the deformation of emplaced lava flows and the surrounding substrate the temporal trend of vertical lava movements was investigated using interferometric analysis of synthetic aperture radar insar images from the 1991 and 2000 hekla eruptions covering periods of 23 and 12 years respectively data from six tracks from three satellites including both ascending and descending passes were used to create 99 interferograms from which trends of accumulated subsidence and subsidence velocities were derived subsidence rates are similar for both lava flows and decay approximately exponentially from about 20 mm year five years after emplacement to about 2 mm year 15 years after emplacement a one dimensional semi analytical model was fitted to the observed subsidence rates with subsidence due to phase change calculated analytically and subsidence due to thermal contraction calculated numerically using dilatometic constraints obtained experimentally the initial thicknesses of the 1991 and 2000 lava fields d1991 and d2000 scaled thermal expansivity and thermal diffusivity are the crucial parameters influencing lava subsidence and subsidence rate inversion for these parameters reveal linear correlations between them best fitting results of inversions for d1991 range from 10 m to 27 m for d2000 from 10 m to 30 m 9 24 10 6k 1 and 1 7 10 7m2s 1

recent advances in sar interferometry time series analysis for measuring crustal deformation abstract synthetic aperture radar sar interferometry is a technique that permits remote detection of deformation at the earth s surface and has been used extensively to measure displacements associated with earthquakes volcanic activity and many other crustal deformation phenomena analysis of a time series of sar images extends the area where interferometry can be successfully applied and also allows detection of smaller displacements through the reduction of error sources here we review recent advances in time series sar interferometry methods that further improve accuracy this is particularly important when constraining displacements due to processes with low strain rates such as interseismic deformation we include examples of improved algorithms applied to image deformation associated with the 2010 eruption of eyjafjallajokull volcano in iceland slow slip on the guerrero subduction zone in mexico and tectonic deformation in western anatolia turkey

post eruptive deformation associated with the 1986 87 and 1989 lava flows of etna detected by radar interferometry we analysed 92 interferograms produced using ers1 sar images taken on etna between may 1992 and october 1993 nineteen show a local subsidence in the eastern flank of the volcano correlated with the location of the 30 october 1986 1 march 1987 and 27 september 9 october 1989 lava flows using fringe unwrapping and data gridding techniques and assuming that over the sampled time window deformation was a linear function of time we derive a map of along range rate of motion the correlation between the deformation field and the area covered by recent lavas suggests that compaction of the lava flows continues several years after the eruptions the area of maximum subsidence 47 mm yr is localised at the narrowing of the 1989 flow between 1500 and 1700 m a s l we observe that subsidence extends outside the lava flows accounting for at least 12 mm yr assuming a relaxation process of the substrate in response to loading produced by recent lavas a simple 1d maxwell visco elastic model predicts a maximum subsidence rate of 25 mm yr and a relaxation time of about 3 5 years the relaxation time agrees with those derived from post eruptive displacements observed by levelling on etna and piton de la fournaise after several eruptions we conclude that at the time of our measurements 25 to 50 of the deformation was related to relaxation of the substrate and the other part due to compaction of the lava flows

plate boundary deformation and man made subsidence around geothermal fields on the reykjanes peninsula iceland abstract we present interferometric synthetic aperture radar insar data from 1992 1999 and 2003 2008 as well as gps data from 2000 2009 for the active plate boundary on the reykjanes peninsula southwest iceland the geodetic data reveal deformation mainly due to plate spreading anthropogenic subsidence caused by geothermal fluid extraction and possibly increasing pressure in a geothermal system subsidence of around 10 cm is observed during the first 2 years of production at the reykjanes geothermal power plant which started operating in may 2006 we model the surface subsidence around the new power plant using point and ellipsoidal pressure sources in an elastic halfspace short lived swarms of micro earthquakes as well as aseismic fault movement are observed near the geothermal field following the start of production possibly triggered by the stresses induced by geothermal fluid extraction

pressure sources versus surface loads analyzing volcano deformation signal composition with an application to hekla volcano iceland the load of lava emplaced over periods of decades to centuries induces a gradual viscous response of the earth resulting in measurable deformation this effect should be considered in source model inversions for volcanic areas with large lava production and flow emplacement in small centralized regions if deformation data remain uncorrected constructive load and pressure source interference may result in an overestimate of depth and volume of a magma reservoir whereas destructive signal interference may cause these values to be underestimated in both cases the source geometry preference could be biased the ratio of horizontal and vertical displacements aids the identification of composite signals we provide a method to quantify and remove the lava load deformation signals using deformation at hekla volcano iceland as an example

deep magma storage at hekla volcano iceland revealed by insar time series analysis 1 hekla volcano is one of the most active volcanoes in iceland the most recent eruption occurred from 26 february to 8 march 2000 when about 0 19 km3 of magma was erupted we present deformation data from multitemporal analyses of synthetic aperture radar sar images acquired between 1993 and 2008 focusing on pixels with low phase variance using persistent scatterer and small baseline approaches prior to and after the 2000 eruption we find a broad area of inflation around the volcano radius about 20 km with satellite line of sight los shortening of up to 5 mm yr we interpret this signal as the result of pressure increase in a deep seated magma chamber which we model as a spherical source at 14 20 km depth increasing in volume by 0 003 0 02 km3 yr within a 6 km radius of the summit of the volcano a los lengthening is superimposed on the broad inflation signal which correlates partly with recent lava flows we interpret this signal as the result of thermally contracting lava flows combined with viscoelastic yielding due to the load of the volcano and its lavas coeruptive deflation during the 2000 eruption was similar to the cumulative inflation from 1993 to 2000 and is consistent with a spherical magma chamber at 14 18 km depth that decreases in volume by 0 04 0 08 km3 interferograms spanning the 2000 eruption show a local coeruptive deformation signal near the eruptive fissure this is consistent with a dike opening from the surface to depths up to 5 8 km with a volume of 0 005 0 006 km3

calculated effect of vesicles on the thermal properties of cooling basaltic lava flows abstract this paper investigates the effects of porosity in the form of vesicles and bubbles on the transfer of heat within basaltic lava this study was undertaken to provide input for realistic cooling models of basaltic lava flows and to help explain some recent field measurements by jones 1992 1993 these field observations indicate that the surfaces of vesicular pahoehoe flows cool significantly more rapidly than that of dense flows it has been suggested that thermal radiation across vesicles is responsible for this enhanced cooling rate it is shown here that for vesicles in typical pahoehoe flows radiation across vesicles may enhance the effective thermal conductivity and thermal diffusivity but only at high temperatures t 800 c and high vesicularities 40 it is also found that convection of the gas phase within bubbles will not occur unless the cavities are larger than about 1 cm furthermore previous work has demonstrated that porosity greatly reduces the thermal conductivity and thermal inertia of cold lava it is shown here that this should also be true at high temperatures examining only radiation across vesicles severely understates the effect of porosity on the cooling of the surface of lava flows thermal inertia developed to describe diurnal surface temperature variations is the most appropriate thermal parameter in this case thermal inertia is a measure of how quickly surface temperature responds to heating or cooling with low thermal inertia materials responding more quickly it is shown here that porosity greatly reduces thermal inertia at all temperatures and that this provides a more general explanation for the field observation

interferometric synthetic aperture radar study of okmok volcano alaska 1992 2003 magma supply dynamics and postemplacement lava flow deformation 1 okmok volcano located in the central aleutian arc alaska is a dominantly basaltic complex topped with a 10 km wide caldera that formed circa 2 05 ka okmok erupted several times during the 20th century most recently in 1997 eruptions in 1945 1958 and 1997 produced lava flows within the caldera we used 80 interferometric synthetic aperture radar insar images interferograms to study transient deformation of the volcano before during and after the 1997 eruption point source models suggest that a magma reservoir at a depth of 3 2 km below sea level located beneath the center of the caldera and about 5 km northeast of the 1997 vent is responsible for observed volcano wide deformation the preeruption uplift rate decreased from about 10 cm yr 1 during 1992 1993 to 2 3 cm yr 1 during 1993 1995 and then to about 1 2 cm yr 1 during 1995 1996 the posteruption inflation rate generally decreased with time during 1997 2001 but increased significantly during 2001 2003 by the summer of 2003 30 60 of the magma volume lost from the reservoir in the 1997 eruption had been replenished interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows most likely due to thermal contraction interferograms for periods after the eruption suggest at least four distinct deformation processes 1 volcano wide inflation due to replenishment of the shallow magma reservoir 2 subsidence of the 1997 lava flows most likely due to thermal contraction 3 deformation of the 1958 lava flows due to loading by the 1997 flows and 4 continuing subsidence of 1958 lava flows buried beneath 1997 flows our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes

the hekla eruption 1980 1981 the sixteenth eruption of hekla since 1104 began on august 17th 1980 after the shortest repose period on record only ten years the eruption started with a plinian phase and simultaneously lava issued at high rate from a fissure that runs along the hekla volcanic ridge the production rate declined rapidly after the first day and the eruption stopped on august 20th a total of 120 million m3 of lava and about 60 million m3 of airborne tephra were produced during this phase of the activity in the following seven months steam emissions were observed on the volcano activity was renewed on april 9th 1981 and during the following week additional 30 million m3 of lava flowed from a summit crater and crater rows on the north slope

the generation and expulsion of gases in ya131 gas field south china sea implication of laboratory pyrolysis results abstract laboratory pyrolysis methods were used to determine the source and thermal maturity of the gas accumulation in the ya131 gas field south china sea the mudstone source rock samples used in the pyrolysis experiments were selected from the yacheng and meishan formations in the ying qiong basin the total amount of gases generated and expelled from the yacheng formation mudstone is larger than that from the meishan formation mudstone suggesting that the gas generation potential of the yacheng formation is higher than that of the meishan formation the similarity between the gases from the ya131 field and the gases produced at the higher pyrolysis temperatures used in the maturation study in terms of wetness the amounts of c 1 c 2 c 3 and the percentages of c 1 c 2 c 4 and c 5 c 7 implies that the gases of the ya131 field are high maturity gases however there are distinct differences between the normalised molecular compositions of the c 6 and c 7 species of the gases from the ya131 field and those of the pyrolysis gases produced in the laboratory comparison of the stable carbon isotope composition of the n alkanes pristane pr and phytane ph in the saturated hydrocarbon fraction of the condensate from the ya131 field with that of rock extracts from the yacheng meishan ying huang formations indicates no definite correlation between the condensate and the extracts these observations suggest that there may be additional source rocks for the ya131 field existing within the deeper part of the basin

tracking lava flow emplacement on the east rift zone of kīlauea hawai i with synthetic aperture radar coherence 1 lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior although maps are traditionally created through field surveys remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location synthetic aperture radar sar imagery in particular can detect changes in a flow field by comparing two images collected at different times with sar coherence new lava flows radically alter the scattering properties of the surface making the radar signal decorrelated in sar coherence images we describe a new technique sar coherence mapping scm to map lava flows automatically from coherence images independent of look angle or satellite path we use this approach to map lava flow emplacement during the pu u kupaianaha eruption at k lauea hawai i the resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows as well as the locations of active flow paths however the scm technique is only moderately successful at mapping flows that enter vegetation which is also often decorrelated between successive sar images along with measurements of planform morphology we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness finally we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post emplacement flow subsidence

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

ground surface deformation patterns magma supply and magma storage at okmok volcano alaska from insar analysis 1 intereruption deformation 1997 2008 eruption magma storage had increased by 3 7 5 2 1 0 7 m 3 or 85 100 of the 1997 eruption volume we propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region eventuallytheeffectsofcontinuingmagmasupplyandvesiculationofstoredmagmacaused acriticalpressurethresholdtobeexceeded triggeringthe2008eruption asimilarpatternof initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption in both cases withdrawal of magma during the eruptions depressurized the shallow storage zone causing significant volcano wide subsidence and initiating a new intereruption deformation cycle

the 1991 eruption of hekla iceland the eruption that started in the hekla volcano in south iceland on 17 january 1991 and came to an end on 11 march produced mainly andesitic lava this lava covers 23 km2 and has an estimated volume of 0 15 km3 this is the third eruption in only 20 years whereas the average repose period since 1104 is 55 years earthquakes as well as a strain pulse recorded by borehole strainmeters occurred less than half an hour before the start of the eruption the initial plinian phase was very short lived producing a total of only 0 02 km3 of tephra the eruption cloud attained 11 5 km in height in only 10 min but it became detached from the volcano a few hours later several fissures were active during the first day of the eruption including a part of the summit fissure by the second day however the activity was already essentially limited to that segment of the principal fissure where the main crater subsequently formed the average effusion rate during the first two days of the eruption was about 800 m3 s 1 after this peak the effusion rate declined rapidly to 10 20 m3 s 1 then more slowly to 1 m3 s 1 and remained at 1 12 m3 s 1 until the end of the eruption site observations near the main crater suggest that the intensity of the volcanic tremor varied directly with the force of the eruption a notable rise in the fluorine concentration of riverwater in the vicinity of the eruptive fissures occurred on the 5th day of the eruption but it levelled off on the 6th day and then remained essentially constant the volume and initial silica content of the lava and tephra the explosivity and effusion rate during the earliest stage of the eruption as well as the magnitude attained by the associated earthquakes support earlier suggestions that these parameters are positively related to the length of the preceeding repose period the chemical difference between the eruptive material of hekla itself and the lavas erupted in its vicinity can be explained in terms of a density stratified magma reservoir located at the bottom of the crust we propose that the shape of this reservoir its location at the west margin of a propagating rift and its association with a crustal weakness all contribute to the high eruption frequency of hekla

the millennium eruption of hekla in february 2000 the 18th historic eruption of hekla started on 26 february 2000 it was a short lived but intense event emitting basaltic andesitic 55 5 wt sio2 pyroclastic fragments and lava during the course of the eruption monitoring was done by both instruments and direct observations together providing unique insight into the current activity of hekla during the 12 day eruption a total of 0 189 km3 dre of magma was emitted the eruptive fissure split into five segments the segments at the highest altitude were active during the first hours while the segments at lower altitude continued throughout the eruption the eruption started in a highly explosive manner giving rise to a subplinian eruptive column and consequent basaltic pyroclastic flows fed by column collapses after the explosive phase reached its maximum the eruption went through three more phases namely fire fountaining strombolian bursts and lava effusion in this paper we describe the course of events of the eruption of hekla and the origin of its magma and then show that the discharge rate can be linked to different style of eruptive activity which are controlled by fissure geometry we also show that the eruption phases observed at hekla can be linked with inferred magma chamber overpressure prior to the eruption

thermal mechanical modeling of cooling history and fracture development in inflationary basalt lava flows abstract thermal mechanical analyses of isotherms in low volume basalt flows having a range of aspect ratios agree with inferred isotherm patterns deduced from cooling fracture patterns in field examples on the eastern snake river plain idaho and highlight the caveats of analytical models of sheet flow cooling when considering low volume flows our field observations show that low volume lava flows have low aspect ratios width divided by thickness typically

surface movements of emplaced lava flows measured by synthetic aperture radar interferometry lava flows continue to move after they have been emplaced by flow mechanisms this movement is largely vertical and can be detected using differential synthetic aperture radar sar interferometry there are three main components to this motion 1 movement of surface scatterers resulting in radar phase decorrelation 2 measurable subsidence of the flow surface due to thermal contraction and clast repacking and 3 time dependent depression of the flow substrate these effects act in proportion to the thickness of the lava flow and decay with time although there is a time lag before the third component becomes significant we explore these effects using sar data from the ers satellites over the etna volcano sicily phase decorrelation on young thick a a lava flows persists for a few years and probably results from surface block rotations during flow contraction maximum measured subsidence rates of the 1991 1993 lava flow over a period of 70 days are about 0 7 mm day 1 but are potentially greater in areas of data decorrelation these rates fall to 2 7 10 2 mm day 1 after about 20 years in flows about 50 m thick sooner for thinner flows comparison with measured subsidence rates on kilauean lava lakes suggests that thermal contraction only accounts for about one third of the observed subsidence the remaining motion is thought to come from surface clast repacking during cooling and from creep mechanisms in the flow substrate measurements of postemplacement surface movement provide new constraints on the thermomechanical properties of lava flows and have cautionary implications for the interpretation of interferometric sar data of volcanoes 2001 american geophysical union