regional retrograde metamorphism of a high grade terrain the willyama complex broken hill australia abstract retrograde metamorphism has been a major influence in the development of the presently observed lithologies of the willyama complex broken hill two broad types of retrogression are distinguished pseudomorphous and kinematic retrogression the former type of retrogression involves replacement of prograde phases without complete loss of the high grade fabric hence the prograde assemblage can frequently be inferred kinematic retrogression involves the development of a new schistose fabric and like pseudomorphous retrogression is commonly related to f3 deformation retrogression was initiated during the waning stage of prograde metamorphism and was accompanied by an influx of aqueous fluid at similar pressure but lower temperature conditions than prograde metamorphism the source of the water is believed to be the crystallization of cooling partial melts the regional nature of this willyama style of retrogression is attributed to the metasediment rich nature of the sequence the high geothermal gradient and the considerable amount of in situ partial melting

strength and anisotropy of foliated rocks with varied mica contents abstract we have shortened 15 schists and gneisses with varying compositions 15 75 mica by volume at angles of 45 and 90 to foliation s to investigate the influence of micas on the strength and anisotropy of foliated rocks at the conditions tested t 25 c p c 200 mpa and e 10 5 s 1 compressive strengths vary by a factor 4 in the 45 and 90 orientations and individual rock types exhibit directional responses ranging from isotropic to strongly anisotropic trends of decreasing strength decreasing anisotropy and increasing ductility are observed with increasing mica content strains in all samples were localized within inclined shear zones accommodated by dislocation slip and grain scale microkinking in micas and microcracking in all other silicates stress strain response and grain scale deformation microstructures both indicate that mechanical behavior is strongly influenced by the concentration and spatial arrangement of micas shear zone formation is associated either with discrete brittle fracture transitional strain softening or steady strength ductile shear in both brittle and transitional samples extensive microcracking of strong quartzo feldspathic bridges occurs and stress drop magnitudes decrease with decreasing spacing and increasing overlap of adjacent critically oriented micas steady strength ductile shear zones develop in samples containing domains of interconnected micas and isotropic mechanical response is observed in those in which micas are contiguous in nearly all directions

controls on metamorphic equilibration the importance of intergranular solubilities mediated by fluid composition a dramatic demonstration of the role of intergranular solubility in promoting chemical equilibration during metamorphism is found in the unusual zoning of garnet in pelitic schist exposed at harpswell neck maine usa many garnet crystals have irregular patchy distributions of mn cr fe and mg in their inclusion rich interiors transitioning to smooth concentric zoning in their inclusion poor outer rims in contrast zoning of ca and y is comparatively smooth and concentric throughout we re assess the disputed origin of these zoning features by examining garnet growth in the context of the thermal and structural history of the rocks and by evaluating the record of fluid rock interaction revealed in outcrop scale veining and fluid inclusion assemblages the transition in the character of garnet zoning correlates with the onset of a synkinematic simple shear dominated phase of garnet growth and with a shift in the composition of the intergranular fluid from co2 rich to h2o rich compositional variations in garnet are therefore best explained by a two stage growth history in which intergranular diffusive fluxes reflect differences in the concentration of dissolved species in these two contrasting fluids interiors of garnet crystals grew in the presence of a co2 rich fluid in which limited solubility for mn and cr and perhaps fe and mg produced patchy disequilibrium overprint zoning while appreciable solubility for ca and y permitted their rock wide equilibration rims grew in the presence of an h2o rich fluid in which high intergranular concentrations for all elements except cr enabled diffusion over length scales sufficient for rock wide equilibration this striking example of partial chemical equilibrium during reaction and porphyroblast growth implies that thermal effects may commonly be subsidiary in importance to solubilities in the intergranular medium as determinants of length scales for metamorphic equilibration

a quaternary solution model for white micas based on natural coexisting phengite paragonite pairs a thermodynamic model for the quaternary white mica solid solution with end members muscovite mg celadonite paragonite feceladonite ms mgcel pg fecel is presented the interaction energies for the mgcel pg join the fecel pg join and the ternary interactions were obtained from natural coexisting phengite paragonite pairs phengite paragonite pairs were selected based on the criteria that their chemical compositions may be represented as a linear combination of the model end member compositions and that the respective formation conditions 350 650 c 4 21kbar are accurately known previously published excess free energy expressions were used for the ms pg ms mgcel and ms fecel binaries the suggested mixing model was tested by calculating multicomponent equilibrium phase diagrams this proved to be particularly well suited to reproduce compositional variations of white micas from amphibolite facies metapelites

retrieval of p t t d paths in a syn metamorphic shear zone implications for p t calculations and the permian triassic orogeny on the korean peninsula abstract crustal scale shear zones developed on the boundaries of the precambrian gyeonggi massif gm can play key role on understanding collisional orogeny during the late paleozoic to early mesozoic in the korean peninsula garnet schist formed on the boundary between the gm and okcheon metamorphic belt omb experienced contractional dn and extensional dn 1 shearing combined with a clockwise pressure temperature deformation p t d path two distinct mineral assemblages were found in the schists 1 garnet pre and or syn dn staurolite syn dn and or inter dn and dn 1 and syn dn 1 andalusite syn dn 1 bearing and 2 garnet pre and or syn dn epidote bearing assemblages depending on bulk rock compositions various compositions an10 40 in the former assemblage and an45 70 in the latter one and texture of plagioclase resulted from bulk rock compositions heterogeneous strain and dissolution and precipitation during the multiple shearing the p t conditions estimated for the early contractional shearing top to the north reverse shear are 560 c 600 c and 5 5 7 0 kbar based on the intersections between compositional isopleths for pre and or syn dn garnet and plagioclase an30 40 an45 55 calculated in the mno na2o cao k2o feo mgo al2o3 sio2 h2o and mno na2o cao k2o feo mgo al2o3 sio2 h2o tio2 fe2o3 systems subsequent extensional shearing top to the south normal shear was characterized by recrystallization of fine grained syn dn 1 staurolite with growth of syn dn 1 andalusite porphyroblasts during cooling and decompression to 560 c and 3 5 kbar the contractional and extensional shearing probably occurred at the permian and the late triassic to early jurassic respectively based on the previous geochronological data consequently inferred p t t d paths on the gm omb boundary probably suggest not only crustal thickening followed by thinning but also multiple amalgamations of several terranes

microstructures mineral chemistry and geochronology of white micas along a retrograde evolution an example from the aar massif central alps switzerland abstract this study investigates gneissic tectonites of different mechanical origins and aims at unravelling the link between microstructures white mica chemistry and k ar data the highest temperature mylonitic deformation which is investigated is dominated by dislocation creep in monomineralic quartz and viscous granular flow in polymineralic domains these mylonites show homogenous mineral chemistry resulting in robust and consistent k ar age data the lowest temperature deformation investigated is that of a retrograde brittle deformation producing cohesionless fault gouges within the cohesionless fault gouges frictional granular flow is considered as the main deformation mechanism the k bearing phases inside the fault gouges record no chemical resetting during this brittle overprint but contain mechanically fragmented k bearing micas and significant amounts of newly produced smectite this yields k ar ages inside of a gouge that are in the range of adjacent mylonite ages and may not represent the timing of gouge formation in an effort to understand these uncertainties in k ar ages detailed observations of the microstructural context of k bearing white mica were made microstructural criteria in combination with quantitative element mapping allowed for the discrimination of five important mica related processes 1 fracturing recrystallization of white mica 2 re precipitation of new fine grained white mica inside the deforming rock matrix 3 pseudomorphic replacement of precursor minerals by white mica and chlorite 4 pseudomorphic replacement of pre existing white mica without grain size reduction and 5 remnant grains the combination of these different processes led to a high variability in mineral chemistry and isotope data for tectonites which relates directly to variations in the size of the equilibrium volumes despite the samples being highly deformed in the presence of fluids inherited sheet silicates may survive if inherited sheet silicates are present they contribute to an increase in both the chemical heterogeneity and the apparent k ar ages of a sample

fluid rock reaction weakening of fault zones the presence of weak phyllosilicates may explain the low shear strengths of fault zones if they define well developed fabrics the growth of phyllosilicates is favored in meteoric water dominated granitic fault systems where mineral aqueous fluid equilibria predict that modal phyllosilicate will increase via feldspar replacement reactions in deeper more alkaline rock dominated regimes the reactions reverse and feldspars tend to replace phyllosilicates in mg rich mafic rocks however phyllosilicates chlorite biotite can replace stronger framework and chain silicates in both shallower approximately 10 km meteoric h sub 2 o dominated and in deeper alkaline rock dominated regimes where these phyllosilicates precipitate in active fault zones they contribute directly to reaction softening because low temperature deformation of phyllosilicates is not governed by frictional processes alone but can occur by pressure independent dislocation glide the strength of phyllosilicate rich fault rocks can be low at all depths low strain rate creep during interseismic periods can align phyllosilicate grains in foliated gouge and phyllonites where preferred orientations are strong and contiguity of phyllosilicates is large strengths of rocks within fault zones may approach minimum strengths defined by single phyllosilicate crystals fault zones containing localized high concentrations of phyllosilicates with strong preferred orientations in well defined folia can exhibit aseismic slip especially where mafic mg rich rocksmore occur along the fault like parts of the san andreas fault 104 refs 6 figs 1 tab less

oblique photogrammetry with visible and thermal images of active lava flows digital images from hand held cameras are increasingly being acquired for scientific purposes particularly where non contact measurement is required however they frequently consist of oblique views with significant camera to object depth variations and occlusions that complicate quantitative analyses here we report the use of oblique photogrammetric techniques to determine ground based thermal camera orientations position and pointing direction and to generate scene information for lava flows at mount etna sicily multiple images from a consumer grade digital slr camera are used to construct a topographic model and reference associated ground based thermal imagery we present data collected during the 2004 2005 eruption and use the derived surface model to apply viewing distance corrections to account for atmospheric attenuation to the thermal images on a pixel by pixel basis for viewing distances of 100 to 400 m the corrections result in systematic changes in emissive power of up to 3 with respect to values calculated assuming a uniform average viewing distance across an image

surface cooling advection and the development of different surface textures on active lavas on kilauea hawai i the validity of lava flow cooling models were investigated using data from a high resolution high frame rate thermal imaging camera on kilauea hawai i during august 2004 once the surface temperature data for small lava flow and lobes were corrected for emissivity viewing distance humidity and viewing angle it was clear that their upper surfaces were thermally stratified on eruption the interior of a stationary lava lobe was exposed by removing the crust and its cooling rate was measured at 30 hz for this flow the measured cooling trend was successfully modelled using a finite difference cooling model however modelled and measured cooling rates of a pahoehoe lobe and a small channelised lava flow were only in agreement until the crust began to deform the departure from the modelled trend at this point is attributed to two factors one is the complex cooling regime of a highly deformed ropy crust in which exposed lava at the crests of the ropes radiates in all directions compared with lava in the troughs where radiative cooling is less effective the second and more important reason for the difference is the reduced flow rate of the crust once it begins to be compressed the underlying visco elastic zone beneath the crust flows more rapidly than the crust and consequently advective heat flow significantly reduces cooling rates variations in heat loss from different flow textures and the incorporation of different advective heat components is clearly important in future flow models one of the critical parameters in such models is the temperature at which different surface textures develop temperature profiles along lobes and flows also revealed that rope textures developed on pahoehoe lavas when temperatures were in the range of 700 800 c brittle deformation of pahoehoe crust occurred when temperature dropped below 700 c and small pahoehoe lobes stopped advancing at temperatures of 600 650 c it is important to recognise that the flow front temperatures at which these flows stop advancing will be significantly greater than for larger flows on similar gradients the higher internal and basal shear stresses of large lava flows will allow the flow to advance until the visco elastic layer at the front of a front is significantly cooler than the temperatures recorded on these small flows on kilauea

sulfur speciation oxidation state and sulfur concentration in backarc magmas we have determined the fe3 fe2 ratio s content and the so2 4s2 ratio by sk x ray peak shift for a suite of twelve mid ocean ridge and backarc basin glasses these samples range in oxidation state from two orders of magnitude below to 1 5 orders of magnitude above the ni nio oxygen buffer sulfur speciation in the glasses is strongly dependent on magmatic oxidation state we propose that the solubility mechanism for s in basaltic melts changes over the o2 range which characterizes convergent margin magmas in low o2 sulfide saturated basaltic melts such as most morbs s is present largely as s2 and its concentration is controlled by sulfide melt silicate melt equilibrium and varies positively with o2 at higher o2 s where sulfide melt becomes unstable s concentration is controlled by melt vapor equilibrium and decreases with increasing o2 for the range of o2 s in the back arc basin basalts in this study nno 1 to nno 1 5 s is dissolved in the silicate in both oxidized and reduced forms for the lower o2 end of this range s2 dominates and equilibria involving reduced s species control s melt concentration at higher o2 s the proportion of oxidized s increases and melt vapor equilibria involving these species become more important because s partitions strongly into the vapor phase over the o2 range investigated magmatic degassing may be effective at stripping s from the melt the low s concentrations in island arc and backarc lavas do not necessarily reflect a low s source but rather result from higher o2 in the convergent margin environment

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

determining ages of multiple muscovite bearing foliations in phyllonites using the 40ar 39ar step heating method applications to the alleghanian orogeny in central new england

mantle convection with longest wavelength thermal heterogeneity in a 3 d spherical model degree one or two 1 the formation of longest wavelength mantle convection in the sluggish lid regime is investigated using a three dimensional spherical model the bottom rayleigh number is fixed at 107 considering temperature dependent rheology degree one dominant thermal convection occurs for both purely basal heating and mixed i e basal and internal heating modes for the purely basal heating mode degree one convection occurs when the viscosity contrast due to temperature dependent rheology is 103 104 in both boussinesq and extended boussinesq fluids however with extended boussinesq fluid degree one convection may only occur in the basal heating mode in the mixed heating mode degree one convection shifts to one with high degree modes presumably because of enhanced viscous dissipation in the highly viscous lid over up downwelling plumes the geophysically relevant degree two convection with sheet like downwellings is not observed in this study the inclusion of visco plastic rheology in the top part of the mantle breaks down degree one convection

multiple generation folding and non coaxial strain of lava crusts viscoelastic strain in lava flows is commonly expressed as gravity driven buckling of the lava crust this surface folding process creates the well known ropy p hoehoe texture of basaltic lavas and the ogives and surface ridges of more compositionally evolved lava flows previous work has shown that surface fold wavelengths are proportional to the viscosity contrast between the lava crust and core and to the thickness of the crust thus fold analysis can be an important tool for understanding lava flow rheology we analyze fold wavelength patterns of solidified natural lava flows from the myvatn lava fields iceland piton de la fournaise la reunion and experimental lava flows from the syracuse university lava project in each case lava flows exhibited two dominant wavelengths consistent with multiple generations of coaxial folding the ratio of the two dominant wavelengths for basalt iceland la reunion is 5 1 whereas the wavelength ratio for basaltic andesite syracuse is 3 1 suggesting a compositional control on deformation as proposed by previous studies video analysis of incrementally folded syracuse lava crusts reveals significant non coaxial strain which violates the assumptions of plane strain used in crustal buckling models these results show that interpreting lava rheology from finite strain requires careful consideration of complex three dimensional strain fields despite these complexities the correlation between fold wavelength ratios and lava flow composition persists and may provide important insight into flow characterization

metamorphic thermal and tectonic evolution of central new england mountain skitchewaug and big staurolite nappes reactivation of a new detailed tectonic model is presented for the acadian orogenic this fabric during thrusting is recorded in some rocks of the big belt of central new england vermont and new hampshire that staurolite nappe by rotated garnets that grew during near isothermal accounts for a wide range of petrological and structural observations loading only the sillimanite isograd crosses the fall mountain three belts are considered the eastern vermont merrimack and skitchewaug nappe boundary metamorphic breaks across the skitintervening bronson hill belts specific observations in eastern chewaug big staurolite nappe boundary at the base of the big vermont that are accounted for in the model include the following staurolite nappe and at the margin of the keene and alstead domes p t paths are clockwise with maximum pressures near the athens require post metamorphic thrusting when p t conditions were in chester and strafford domes of 8 11 kbar but with maximum the greenschist facies these observations can be explained by a pressures decreasing to 3 5 kbar at the boundary with the bronson relatively simple model involving in sequence thrusting from east to hill belt differential exhumation of the vermont domes relative to west commencing in central new hampshire at 400 410 ma the rocks in easternmost vermont is required by the recorded differences preservation of the low grade belt along the vermont new hampin maximum pressure 5 6 kbar 15 20 km and the present day shire border requires that crustal thickening in vermont was not geographical separation 7 10 km specific observations in new caused by emplacement of new hampshire nappes onto eastern hampshire that are explained include the following p t paths in vermont and that the nappes of western new hampshire had time the merrimack belt are counter clockwise with maximum pressures to cool before final juxtaposition against the low grade belt cooling of 4 5 kbar and are related to high regional heat flow and heat ages constrain this final juxtaposition to have occurred in the transfer by early acadian plutons p t paths in the bronson hill carboniferous suggesting that the acadian was a prolonged event belt are intimately associated with structural position an early spanning as much as 100 myr contact metamorphism is evidenced in the skitchewaug and fall mountain nappes near contacts with the early acadian bethlehem gneiss 400 410 ma peak metamorphic temperature rises upwards in the nappe sequence an inverted metamorphic sequence

the volume and shape of the 1991 1993 lava flow field at mount etna sicily the 1991 1993 lava flow is the most voluminous flow erupted at mount etna sicily in over 300 years estimates of the volume obtained by various methods range from 205 106 m3 tanguy 1996 to over 500 106 m3 barberi et al 1993 this paper describes the results of an electronic distance measurement edm based field survey of the upper surface of the 1991 1993 flow field undertaken in 1995 the results were digitised interpolated and converted into a digital elevation model and then compared with a pre eruption digital elevation model constructed from a 1 25 000 contour map of the area based on 1989 aerial photographs our measurements are the most accurate to date and show that the 1991 1993 lava flow occupies a volume of 231 29 106 m3

modeling lava lake heat loss rheology and convection 1 measurements at erta ale s lava lake and theoretical equations for lake rheology density driven convection and thermally driven plume ascent allow the constraint of lake dynamics cooling and crystallization expected from surface heat losses imply a viscosity increase from 150 pa s to 300 1800 pa s for cooled surface layers convection is expected to proceed vigorously under low viscosity conditions driving rapid 0 1 0 4 m s 1 surface motions and sluggishly under moderate to high viscosity conditions to drive slower motions 0 08 m s 1 convection is likely driven by small 6 kg m 3 density differences where surface cooling can influence lake rheology and explain variable rates of surface convective motion

evidence for syntectonic crystallization for the mudstone to slate transition at lehigh gap pennsylvania u s a data primarily for phyllosilicates have been obtained for the continuous transitional sequence from mudstone to slate with well developed slaty cleavage at lehigh gap pennsylvania and for slates from quarries in the same area samples were studied by optical microscopy powder x ray diffraction and electron microprobe analysis with emphasis on transmission and analytical electron microscopy mineral grains are virtually free of deformation induced strain concomitant with the gradual development of cleavage normal to bedding the following changes are observed or confirmed 1 the orientation of phyllosilicate grains changes discontinuously from being preferentially parallel to bedding to being parallel to cleavage 2 crystal imperfections as expressed in layer terminations low angle grain boundary like features and other defects decrease in density 3 complex mixed layering is replaced by homogeneous packets of layers of single phases and 4 illite transforms to muscovite with increase in k a1 and change from a lmd to 2m polytype slaty cleavage apparently develops due in part to pressure solution of phyllosilicates oriented parallel to bedding mass transport of components and crystallization to form new grains parallel to cleavage it reflects transitions from imperfect metastable phases toward ordered stable phases in a low temperature 225 c metamorphic environment

sulfur bearing magmatic accessory minerals almost all magmas contain sulfide or sulfate bearing phases in most natural samples the sulfur bearing phase is a sulfide which typically is pyrrhotite fe1 x s or pyrite fes2 although chalcopyrite cufes2 pentlandite fe ni 9s8 sphalerite zns or molybdenite mos2 may be present as well sulfate minerals are rare at magmatic conditions and anhydrite caso4 is the most common other magmatic so4 bearing minerals include the sodalite group minerals hauyne simplified formula na ca 4 8 al6si6 o s 24 so4 cl 1 2 scapolite minerals silvialite ca na 4al6si6o24 so4 co3 and s bearing apatite ca5 po4 3 f cl oh barite baso4 has been mentioned in rare cases marchev 1991 sulfur bearing minerals usually constitute a negligible fraction of the mineral assemblage in magmatic rocks and thus can be classified as accessory minerals the crystallization of sulfide sulfate and s bearing minerals strongly depends on melt composition temperature and pressure and the s speciation in melt which in turn is strongly dependent on the prevailing oxygen fugacity baker and moretti 2011 this volume wilke et al 2011 this volume irrespectively of the low abundance of s bearing minerals the evolution of sulfur in magmas may be evaluated from the occurrence of sulfides and sulfates these minerals are critical for estimating the activity of various sulfur bearing species in magmas and can be used to constrain the oxygen fugacity and the s concentration in the melt e g pre eruptive sulfur concentration in melts the presence of either sulfide or sulfate in silicate melt indicates that the predominant dissolved sulfur species in the melt are s2 or s6 respectively typically one of these species is dominant but there are conditions where s2

the effect of dislocation density on the aqueous solubility of quartz and some geologic implications a theoretical approach the internal energy associated with dislocations is calculated in quartz as a function of dislocation density these calculations show that at dislocation densities of 109 1010 1011 and 1012 cm dislocation cm3 the energy stored per mole of quartz is 2 2 19 7 170 and 1426 j respectively the density of free dislocations in natural quartz rarely exceeds 109 line cm cm3 and the resulting increase in free energy is probably too small to affect any geochemical processes significantly this applies to the overwhelming volume of rocks in the earth s crust the density of dislocations in tangles may exceed 1011 line cm 2 which is significant but the volume of quartz containing tangles is a very small fraction of most quartz grains nevertheless where fluid rock ratios are low the aqueous activity of sio2 may be significantly increased by the dissolution of quartz containing dislocation tangles such dissolution could be geologically significant in active greenschist facies fault zones and mylonites where repeated cold working would produce a sustained source and large population of dislocation tangles in such a setting the locally high internal energies of quartz containing dislocation tangles would lead to strain solution the resulting high activity of aqueous silica would enhance the stability of feldspars and would establish chemical potential gradients of sio2 which would drive the diffusive mass transfer of sio2 out of the fault zone

evidence for deformation induced k feldspar replacement by myrmekite several examples of deformation induced myrmekite have been found in two amphibolite facies mylonites derived from granitic protoliths namely a muscovite poor s c mylonite and a single foliation muscovite poor mylonitic gneiss back scattered sem and conventional optical microscopy show that in both rock types syntectonic myrmekitic intergrowths of oligoclase and quartz formed on the two sides of k feldspar grains that faced the local inferred incremental shortening direction for the mylonite myrmekite does not occur on the two ends of the grain that faced the incremental stretching direction the replacement of k feldspar by plagioclase and quartz results in a volume decrease and is favoured on high normal stress sites around the grains we suggest that the ambient temperature pressure and chemical activities were such that the replacement reaction was favoured but the addition of extra strain energy along the high pressure sides of the grains localized the reaction at these sites this energy could arise from elastic strain or strain associated with tangled dislocations or twin boundaries the relative roles of stress and strain energy concentrations in driving the replacement reaction are not known but both were probably important

conclusion recommendations and findings of the red seed working group red seed stands for risk evaluation detection and simulation during effusive eruption disasters and combines stakeholders from the remote sensing modelling and response communities with experience in tracking volcanic effusive events the group first met during a three day long workshop held in clermont ferrand france between 28 and 30 may 2013 during each day presentations were given reviewing the state of the art in terms of a volcano hot spot detection and parameterization b operational satellite based hot spot detection systems c lava flow modelling and d response protocols during effusive crises at the end of each presentation set the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors modellers and responders during an effusive crisis the results of collating the final reports and follow up discussions that have been on going since the workshop are given here we can reduce our discussions to four main findings 1 hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min 2 spectral radiance metrics can also be provided with high degrees of confidence however if we are to achieve a truly global system more local receiving stations need to be installed with hot spot detection and data processing modules running on site and in real time 3 models are operational but need real time input of reliable time averaged discharge rate data and regular updates of digital elevation models if they are to be effective the latter can be provided by the radar photogrammetry community 4 information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities all of this requires a sophisticated and centralized data collection distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust while the next chapter carries out an exercise to explore the viability of the last point the detailed recommendations behind these findings are detailed here

lava effusion rates from hand held thermal infrared imagery an example from the june 2003 effusive activity at stromboli a safe easy and rapid method to calculate lava effusion rates using hand held thermal image data was developed during june 2003 at stromboli volcano italy we used a forward looking infrared radiometer flir to obtain images of the active lava flow field on a daily basis between may 31 and june 16 2003 during this time the flow field geometry and size where flows typically a few hundred meters long were emplaced on a steep slope meant that near vertical images of the whole flow field could be captured in a single image obtained from a helicopter hovering at an altitude of 750 m and 1 km off shore we used these images to adapt a thermally based effusion rate method previously applied to low and high spatial resolution satellite data to allow automated extraction of effusion rates from the hand held thermal infrared imagery a comparison between a thermally derived 0 23 0 87 m3 s 1 and dimensionally derived effusion rate 0 56 m3 s 1 showed that the thermally derived range was centered on the expected value over the measurement period the mean effusion rate was 0 38 0 25 m3 s 1 which is similar to that obtained during the 1985 86 effusive eruption and the time averaged supply rate calculated for normal non effusive strombolian activity a short effusive pulse reaching a peak of 1 2 m3 s 1 was recorded on june 3 2003 one explanation of such a peak would be an increase in driving pressure due to an increase in the height of the magma contained in the central column we estimate that this pulse would require the magma column to attain a height of 190 m above the effusive vent which is approximately the elevation difference between the vent and the floor of the ne crater our approach gives an easy to apply method that has the potential to provide effusion rate time series with a high temporal resolution

reaction localization and softening of texturally hardened mylonites in a reactivated fault zone central argentina the tres arboles ductile fault zone in the eastern sierras pampeanas central argentina experienced multiple ductile deformation and faulting events that involved a variety of textural and reaction hardening and softening processes much of the fault zone is characterized by a d2 ultramylonite composed of fine grained biotite plagioclase that lacks a well defined preferred orientation the d2 fabric consists of a strong network of intergrown and interlocking grains that show little textural evidence for dislocation or dissolution creep these ultramylonites contain gneissic rock fragments and porphyroclasts of plagioclase sillimanite and garnet inherited from the gneissic and migmatitic protolith d1 of the hangingwall the assemblage of garnet sillimanite biotite suggests that d1 related fabrics developed under upper amphibolite facies conditions and the persistence of biotite garnet sillimanite plagioclase suggests that the ultramylonite of d2 developed under middle amphibolite facies conditions greenschist facies mylonitic shear bands d3 locally overprint d2 ultramylonites fine grained folia of muscovite chlorite biotite truncate earlier biotite plagioclase textures and coarser grained muscovite partially replaces relic sillimanite grains anorthite content of shear band d3 plagioclase is c an30 distinct from d1 and d2 plagioclase c an35 the anorthite content of d3 plagioclase is consistent with a pervasive grain boundary fluid that facilitated partial replacement of plagioclase by muscovite biotite is partially replaced by muscovite and or chlorite particularly in areas of inferred high strain quartz precipitated in porphyroclast pressure shadows and ribbons that help define the mylonitic fabric all d3 reactions require the introduction of h and or h2o indicating an open system and typically result in a volume decrease syntectonic d3 muscovite quartz chlorite preferentially grew in an orientation favourable for strain localization which produced a strong textural softening strain localization occurred only where reactions progressed with the infiltration of aqueous fluids on a scale of hundreds of micrometre local fracturing and microseismicity may have induced reactivation of the fault zone and the initial introduction of fluids however the predominant greenschist facies deformation d3 along discrete shear bands was primarily a consequence of the localization of replacement reactions in a partially open system

40ar 39ar dating of white micas from an alpine high pressure metamorphic belt on naxos greece the resetting of the argon isotopic system overprinting of white micas from high pressure low to medium temperature m1 metamorphic assemblages in pelitic schists on naxos during subsequent thermal dome m2 metamorphism ranges from minor in the southeast of the island to complete recrystallization in the amphibolite facies rocks near the migmatites in the centre of the dome the original m1 minerals are phengites si4 6 7 7 0 and the overprinting minerals are muscovites si4 6 0 6 45 40ar 39ar step heating analyses of white mica separates from rocks in the area where phengite and muscovite occur together yield complex age spectra characterized by low apparent ages in the first and the last stages of gas release and high apparent ages in between these upward convex age spectra are shown to be caused by mixing of two generations of micas each of which has a different age spectrum and argon release pattern seemingly good plateaus in some age spectra from white micas of the area must be interpreted as providing meaningless intermediate ages further the upward convex age spectra have been used to trace the isotopic signature of phengites toward increasing m2 metamorphic grade and suggest that as long as phengites can be observed in the rocks upward convex age spectra occur on naxos crystallization of muscovite at the expense of phengite appears to be the main mechanism of resetting argon isotopic ages in white micas however there is also good evidence for argon loss by volume diffusion from phengites simple diffusion calculations suggest that the m2 metamorphism was caused by a shortlived heat source

age and setting of the bronson hill magmatic arc a re evaluation based on u pb zircon ages in southern new england new u pb zircon ages of selected rocks from the bronson hill anticlinorium in southern new england are as follows microcline gneiss of the dry hill gneiss in the pelham dome believed to be metamorphosed alkali rhyolite is confirmed as late proterozoic yielding an age of 613 3 ma another sample shows strong evidence of zircon inheritance with a minimum mean age of 1402 ma plagioclase rich gneisses with associated amphibolites swanzey pauchaug monson and fourmile gneisses now believed to represent metamorphosed intrusive igneous rocks yield ages from 454 to 442 3 2 ma thus ranging from early late through latest ordovician consistent with other absolute ages of the oliverian plutonic series in the region quartz phyric rhyolite from the upper member of the ammonoosuc volcanics and rhyolite tuff from the partridge formation are dated at 453 2 ma and 449 3 2 ma respectively indicating that eruption of felsic lavas in the overlying volcanic section spanned an interval of approximately 4 m y additional zircon ages are reported from a crosscutting but deformed tonalite dike in the swanzey gneiss 381 3 ma and a coarse grained gabbro from the prescott intrusive complex 407 3 2 ma intrusive into the partridge formation metamorphic overprinting of the region during both the acadian and alleghanian orogenies is indicated by u pb titanite ages of 357 5 ma and 292 5 ma from a tonalite gneiss on prescott peninsula and the dry hill gneiss respectively the above ages and other zircon ages as well as petrography and geochemistry of the fourmile monson swanzey pauchaug and other plagioclase rich gneisses of the bronson hill anticlinorium suggest that they represent the plutonic root of a calc alkaline magmatic arc at least 250 km long that was produced partly or entirely on a continental margin in late ordovician time ca 454 442 ma the physically overlying cover sequence of chemically different tholeiitic arc volcanic and sedimentary rocks of the ammonoosuc volcanics and partridge formation previously thought to rest unconformably on the plagioclase rich plutonic gneisses is now shown to have had a magmatic history overlapping with them the zircon ages in the plutonic gneisses and the cover sequence indicate that both are the same age or slightly younger than the late ordovician caradocian emplacement of the giddings brook slice of the taconian allochthons and too young to have formed above an early and medial ordovician subduction zone

porphyroblast nucleation growth and dissolution in regional metamorphic rocks as a function of deformation partitioning during foliation development in regional metamorphic rocks the partitioning of deformation into progressive shearing and progressive shortening components results in strain and strain rate gradients across the boundaries between the partitioned zones these generate dislocation density gradients and hence chemical potential gradients that drive dissolution and solution transfer phyllosilicates and graphite are well adapted to accommodating progressive shearing without necessarily building up large dislocation density gradients within a grain because of their uniquely layered crystal structure however most silicates and oxides cannot accommodate strain transitions within grains without associated dislocation density gradients and hence are susceptible to dissolution and solution transfer as a consequence zones of progressive shearing become zones of dissolution of most minerals and of concentration of phyllosilicates and graphite exceptions are mylonites where strain rates are commonly high enough for plastic deformation to dominate over diffusion rates and therefore over dissolution and solution transfer porphyroblastic minerals cannot nucleate and grow in zones of active progressive shearing as they would be dissolved by the effects of shearing strain on their boundaries however they can nucleate and grow in zones of progressive shortening and this is aided by the propensity for microfracturing in these zones which allows rapid access of fluids carrying the material presumed to be necessary for nucleation and growth zones of progessive shortening also have a number of characteristics that help to lower the activation energy barrier for nucleation this includes a build up of stored strain energy relative to zones of progressive shearing in which dissolution is occuring porphyroblast growth is generally syndeformational and previously accepted criteria for static growth are not valid when the role of deformation partitioning is taken into account porphyroblasts in a contact aureole do not grow statically either as microfracturing associated with emplacement allows access of fluids in a fashion that is similar to microfracturing in zones of progressive shortening the criteria used for porphyroblast timing can be readily accommodated in terms of deformation partitioning reactivation of deforming foliations and a general lack of rotation of porphyroblasts with the spectacular exception of genuinely spiralling garnet porphyroblasts

monazite geochronology in central new england evidence for a fundamental terrane boundary monazite crystallization ages have been measured in situ using sims and emp analysis of samples from the bronson hill anticlinorium in central new england in west central new hampshire each major tectonic unit nappe displays a distinctive p t path and metamorphic history that requires significant post metamorphic faulting to place them in their current juxtaposition and monazite ages were determined to constrain the timing of metamorphism and nappe assembly monazite ages from the low pressure high temperature fall mountain nappe range from c 455 to 355 ma and y zoning indicates that these ages comprise three to four distinct age domains similar to that found in the overlying chesham pond nappe the underlying skitchewaug nappe contains monazite ages that range from c 417 to 307 ma 40 ar 39 ar ages indicate rapid cooling of the chesham pond and fall mountain nappes after 350 ma which is believed to represent the time of emplacement of the high level chesham pond and fall mountain nappes onto rocks of the underlying skitchewaug nappe garnet zone rocks from western new hampshire contain monazite that display a range of ages c 430 340 ma both the metamorphic style and monazite ages suggest that the low grade belt in western new hampshire is continuous with the vermont sequence to the west rocks of the big staurolite nappe in western new hampshire contain monazite that crystallized between c 370 and 290 ma and the same unit along strike in northern new hampshire and central connecticut records ages of c 257 300 ma conspicuously absent from this nappe are the older age populations that are found in both the overlying nappes and underlying garnet zone rocks these monazite ages confirm that the metamorphism observed in the big staurolite nappe occurred significantly later than that in the units structurally above and below these data support the hypothesis that the big staurolite nappe represents a major tectonic boundary along which rocks of the new hampshire metamorphic series were juxtaposed against rocks of the vermont series during the alleghanian

scales of equilibrium and disequilibrium during cleavage formation in chlorite and biotite grade phyllites se vermont detailed electron microprobe analyses of phyllosilicates in crenulated phyllites from south eastern vermont show that grain scale zoning is common and sympathetic zoning in adjacent minerals is nearly universal we interpret this to reflect a pressure solution mechanism for cleavage development where precipitation from a very small fluid reservoir fractionated that fluid multiple analyses along single muscovite biotite and chlorite grains 30 200 m in length show zoning patterns indicating tschermakitic substitutions in muscovite and both tschermakitic and di trioctahedral substitutions in biotite and chlorite using cross cutting relationships and mineral chemistry it is shown that these patterns persist in cleavages produced at metamorphic conditions of chlorite grade chlorite grade overprinted by biotite grade and biotite grade zoning patterns are comparable in all three settings requiring a similar cleavage forming mechanism independent of metamorphic grade moreover the use of 40ar 39ar geochronology demonstrates this is true regardless of age furthermore samples with chlorite grade cleavages overprinted by biotite porphyroblasts suggest the closure temperatures for the diffusion of al si mg and fe ions are greater than the temperature of the biotite isograd 400 c parallel and smoothly fanning tie lines produced by coexisting muscovite chlorite and muscovite biotite pairs on compositional diagrams demonstrate effectively instantaneous chemical equilibrium and probably indicate simultaneous crystallization these results do not support theories suggesting cleavages form in fluid dominated systems if crenulation cleavages formed in systems in which the chemical potentials of all major components are fixed by an external reservoir then the compositions of individual grains defining these cleavages would be uniform on the contrary the fine scale chemical zoning observed probably reflects a grain scale process consistent with a pressure solution mechanism in which the aqueous activities of major components are defined by local dissolution and precipitation thus the role of fluids was probably limited to one of catalysing pressure solution and fluids apparently did not drive cleavage development

modeling the solubility of sulfur in magmas a 50 year old geochemical challenge there are myriad reasons why we wish to understand the behavior of sulfur in magmatic systems reasons that vary from pure intellectual curiosity to possible impacts on society and its resources since ancient times sulfur has been associated with volcanic activity and the role of sulfur in the formation of ore deposits has long been recognized because of the necessity of metal ores for our modern life style e g barnes 1979 naldrett 1989 simon and ripley 2011 this volume recently the mechanisms and quantities of sulfur freed from natural magmas have become an important environmental issue due to their potential effects on global climate change for example the average annual volcanic so2 emission rate of 7 5 to 10 5 teragrams tg per year halmer et al 2002 may contribute 10 of the global atmospheric sulfur input halmer et al 2002 smith et al 2004 and individual eruptive episodes can rapidly contribute gigantic sulfur loads to the atmosphere 100 s to 1000 s of tg depending on the scale of the eruption self 2006 such sulfur emissions can produce potentially catastrophic local and global changes e g fedele et al 2003 ward 2009 courtillot and rennes 2003 correlated the timing of flood basalts with extinction events in earth s history and hypothesized a causal relation part of the kill mechanism responsible for extinction may be volcanically derived sulfur creating anoxic oceans and another part of the mechanism may be climatic changes brought about by sulfur injection into the atmosphere ward 2009 indeed erwin 2006 advocates that sulfur released from the eruption of the siberian flood basalts played a role in the end permian extinction in light of the evidence that volcanic degassing is a significant source of sulfur to the atmosphere stoiber et al 1987 symonds et al 1994 andres

spatial heterogeneity of the mantle wedge structure and interplate coupling in the ne japan forearc region 1 we performed 3 d seismic tomography in the forearc region of the northeastern japan subduction zone using both onshore and offshore seismic station data we obtained the vp vs and vp vs structures around the plate boundary with high spatial resolution the position of the plate boundary as defined by relocated hypocenters coincides with the sharp velocity boundary between the oceanic crust and the mantle wedge the mantle wedge above the coseismic slip area of the 1978 and 2005 off miyagi interplate earthquakes m 7 is characterized by high vp and vs but low vp vs off fukushima however where large earthquakes rarely occur we found a high vp vs anomaly at the tip of the mantle wedge the spatial distribution of serpentinized mantle wedge limits the spatial extent of the strongly coupled area on the plate boundary and thus can explain the difference in seismic activity between the off miyagi and off fukushima regions

insights into pāhoehoe lava emplacement using visible and thermal structure from motion photogrammetry we present the evolution over 3 months of a 2016 2017 p hoehoe flow at k lauea as it changed from a narrow sheet flow into a compound lava field fed by a stable system of tubes the portion of the flow located on k lauea s coastal plain was characterized using helicopter based visible and thermal structure from motion photogrammetry to construct a series of georeferenced digital surface models and thermal maps on eight different days results reveal key influences on the emplacement and evolution of such long lived p hoehoe flows this region of the flow grew by 12 10 6 m 3 with a near constant time average discharge rate of 1 2 2 7 m 3 s the development of two tube systems is captured and shows an initial nascent tube enhanced by a narrow topographic confinement which later inflated and created a topographic inversion that modulated the emplacement of a second flow lobe with its own tube system the analysis of breakouts at various stages of the field s life suggests that the evolution of the thermal and morphological properties of the flow surface reflect its maturity thermal properties of breakouts were used to expand the empirical relationship of breakout cooling to longer timescales this study contributes to the long term development and validation of more accurate predictive models for p hoehoe required during the management of long lasting lava flow crises in hawai i and elsewhere

dating polygenetic metamorphic assemblages along a transect across the western alps multichronometric analyses were performed on samples from a transect in the french italian western alps crossing nappes derived from the brianconnais terrane and the piemonte liguria ocean in an endeavour to date both high pressure hp metamorphism and retrogression history twelve samples of white mica were analysed by 39ar 40ar stepwise heating complemented by two samples from the monte rosa nappe 100 km to the ne and also attributed to the brianconnais terrane one sm nd and three lu hf garnet ages from eclogites were also obtained white mica ages decrease from c 300ma in the westernmost samples zone houille re reaching c 3008c during alpine metamorphism to 548ma in the internal units to the east which reached c 5008c during the alpine orogeny the spatial pattern of eocene k ar ages demonstrates that si rich hp white mica records the age of crystallization at 47 48ma and retains ar at temperatures of around 5008c paleocene early eocene lu hf and sm nd ages recording prograde garnet growth before the hp peak confirm eclogitization in eocene times petrological and microstructural features reveal important mineralogical differences along the transect all samples contain mixtures of detrital syn d1 and syn d2 mica and retrogression phases d3 in greatly varying proportions according to local variations in the evolution of pressure temperature fluid activity deformation p t a d conditions samples from the zone houille re mostly contain detrital mica the abundance of white mica with si46 45 atoms per formula unit increases eastward across the whole traverse phengitic mica grown during hp metamorphism defines the d1 foliation syn d2 mica is more si poor and associated with nappe stacking exhumation and hydrous retrogression under greenschist facies conditions syn d1 phengite is very often corroded overgrown by or intergrown with syn d2 muscovite most importantly syn d2 recrystallization is not limited to s2 schistosity domains micrometrescale chemical fingerprinting reveals muscovite pseudomorphs after phengite crystals which could be mistaken for syn d1 mica based on microstructural arguments alone the cl k ratio in white mica is a useful discriminator as d2 retrogression was associated with a less saline fluid than eclogitization as petrology exerts the main control on the isotope record constraining the petrological and microstructural framework is necessary to correctly interpret the geochronological data described in both the present study and the literature our approach which ties geochronology to detailed geochemical petrological and microstructural investigations identifies 47 48ma as the age of hp formation of syn d1 mica along the studied transect and in the monte rosa area cretaceous apparent mica ages which were proposed to date eclogitization by earlier studies based on conventional thermochronology are due to ar inheritance in incompletely recrystallized detrital mica grains the inferred age of the probably locally diachronous greenschist facies low si syn d2 mica ranges from 39 to 43ma coexistence of d1 and d2 ages and the constancy of non reset d1 ages along the entire transect provides strong evidence that the d1 white mica ages closely approximate formation ages volume diffusion of ar in white mica activation energy e 250 kj mol 1 pressure adjusted diffusion coefficient d 050 03 cm2 s 1 has a subordinate effect on mineral ages compared with both prograde and retrograde recrystallization in most samples

40ar 39ar analyses of artificially mixed micas and the treatment of complex age spectra from samples with multiple mica populations abstract artificial mixtures of two age populations of muscovite and of biotite were prepared at relative weight percents of 3 1 1 1 and 1 3 and analyzed by the 40ar 39ar vacuum furnace step heating method the original micas are late jurassic and late cretaceous samples that yield flat age spectra with plateau ages defined by 97 100 of the gas release and no evidence for excess argon the age spectra from mica mixtures yield patterns that systematically decrease with decreasing jurassic mica content and increasing cretaceous component however the mixed muscovite spectra are relatively flat consistent with the two original samples showing similar degassing patterns during vacuum furnace heating in contrast the mixed biotite spectra are highly discordant with an overall decrease in age during the step heat analysis this is consistent with the degassing patterns of the original mica samples which indicate the jurassic biotite high fe mg outgases at lower temperatures and the cretaceous biotite low fe mg remains retentive until the higher temperature steps the individual degassing patterns and compositions show consistencies with known compositional controls on argon diffusivity indicating that micas may maintain argon retention characteristics rooted in crystal chemistry during vacuum furnace heating all but one of the mixed samples failed to yield ages reflecting the age of the original micas these results imply that complex age spectra obtained for multiply deformed rocks with multiple mica populations may define geologically meaningless ages as a result of simultaneous degassing i e mixing of sample reservoirs during heating comparison of laboratory degassing rates and crystal chemistry indicates compositional controls on argon retention are likely preserved during vacuum furnace step heating and micas may degas retain argon in a predictable manner these conclusions support assertions that recovery of fossil age gradients in slowly cooled samples may be possible using furnace step heating

the exceptional activity and growth of the southeast crater mount etna italy between 1996 and 2001 between 1971 and 2001 the southeast crater was the most productive of the four summit craters of mount etna with activity that can be compared on a global scale to the opening phases of the pu u k paianaha eruption of k lauea volcano hawai i the period of highest eruptive rate was between 1996 and 2001 when near continuous activity occurred in five phases these were characterized by a wide range of eruptive styles and intensities from quiet non explosive lava emission to brief violent lava fountaining episodes much of the cone growth occurred during these fountaining episodes totaling 105 events many showed complex dynamics such as different eruptive styles at multiple vents and resulted in the growth of minor edifices on the flanks of the southeast crater cone small pyroclastic flows were produced during some of the eruptive episodes when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry including the growth of a shallow magma reservoir under the southeast crater magma supply rates and flank instability during this period volume calculations were made with the aid of gis and image analysis of video footage obtained by a monitoring telecamera between 1996 and 2001 the bulk volume of the cone increased by 36 106 m3 giving a total 1971 2001 volume of 72 106 m3 at the same time the cone gained 105 m in height reaching an elevation of about 3 300 m the total dre volume of the 1996 2001 products was 90 106m3 this mostly comprised lava flows 72 106 m3 erupted at the summit and onto the flanks of the cone these values indicate that the productivity of the southeast crater increased fourfold during 1996 2001 with respect to the previous 25 years coinciding with a general increase in the eruptive output rates and eruption intensity at etna this phase of intense summit activity has been followed since the summer of 2001 by a period of increased structural instability of the volcano marked by a series of important flank eruptions

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

the changing morphology of an open lava channel on mt etna an open channel lava flow on mt etna sicily was observed during may 30 31 2001 data collected using a forward looking infrared flir thermal camera and a minolta land cyclops 300 thermal infrared thermometer showed that the bulk volume flux of lava flowing in the channel varied greatly over time cyclic changes in the channel s volumetric flow rate occurred over several hours with cycle durations of 113 190 min and discharges peaking at 0 7 m3 s 1 and waning to 0 1 m3 s 1 each cycle was characterized by a relatively short high volume flux phase during which a pulse of lava with a well defined flow front would propagate down channel followed by a period of waning flow during which volume flux lowered pulses involved lava moving at relatively high velocities up to 0 29 m s 1 and were related to some change in the flow conditions occurring up channel possibly at the vent they implied either a change in the dense rock effusion rate at the source vent and or cyclic variation in the vesicle content of the lava changing its bulk volume flux pulses would generally overspill the channel to emplace p hoehoe overflows during periods of waning flow velocities fell to 0 05 m s 1 blockages forming during such phases caused lava to back up occasionally backup resulted in overflows of slow moving a that would advance a few tens of meters down the levee flank compound levees were thus a symptom of unsteady flow where overflow levees were emplaced as relatively fast moving p hoehoe sheets during pulses and as slow moving a units during backup small localized fluctuations in channel volume flux also occurred on timescales of minutes volumes of lava backed up behind blockages that formed at constrictions in the channel blockage collapse and or enhanced flow under around the blockage would then feed short lived wave like down channel surges real fluctuations in channel volume flux due to pulses and surges can lead to significant errors in effusion rate calculations

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

probing the depths of oliverian magmas implications for paleozoic tectonics in the northeastern united states oliverian magma series gneisses 442 454 ma in the cores of domes in southwestern new hampshire have an igneous mineralogy that crystallized at pressures p of 9 11 kbar and temperatures t of 650 775 c whereas the cover ammonoosuc volcanics has the same formation age 453 2 ma yet is clearly extrusive a significant crustal section 30 km thick must have originally separated the two units a recognition that demands tectonic reinterpretation of this classic orogen acadian age ca 400 ma metamorphism at p 4 6 kbar t 625 c is well documented in the cover but the absence of expected diffusional reequilibration in oliverian garnets indicates that they never exceeded 550 c after formation juxtaposition of the oliverian magma series gneisses and their cover must have occurred after the cover had cooled below 550 c and was likely via either neo acadian or alleghanian thrusting

topographic and stochastic influences on pahoehoe lava lobe emplacement a detailed understanding of p hoehoe emplacement is necessary for developing accurate models of flow field development assessing hazards and interpreting the significance of lava morphology on earth and other planetary surfaces active p hoehoe lobes on k lauea volcano hawai i were examined on 21 26 february 2006 using oblique time series stereo photogrammetry and differential global positioning system measurements during this time the local discharge rate for peripheral lava lobes was generally constant at 0 0061 0 0019 m3 s but the areal coverage rate of the lobes exhibited a periodic increase every 4 13 0 64 min this periodicity is attributed to the time required for the pressure within the liquid lava core to exceed the cooling induced strength of its margins the p hoehoe flow advanced through a series of down slope and cross slope breakouts which began as 0 2 m thick units i e toes that coalesced and inflated to become approximately meter thick lobes the lobes were thickest above the lowest points of the initial topography and above shallow to reverse facing slopes defined relative to the local flow direction the flow path was typically controlled by high standing topography with the zone directly adjacent to the final lobe margin having an average relief that was a few centimeters higher than the lava inundated region this suggests that toe scale topography can at least temporarily exert strong controls on p hoehoe flow paths by impeding the lateral spreading of the lobe observed cycles of enhanced areal spreading and inflated lobe morphology are also explored using a model that considers the statistical likelihood of sequential breakouts from active flow margins and the effects of topographic barriers

simulation of inflated pahoehoe lava flows a new stochastic model simulates late stage pahoehoe lobes where random processes dominate emplacement the model prescribes probabilistic rules for determining where and when parcels of lava move within the lobe unlike a classical brownian motion random walk the model allows individual parcels to remain dormant but fluid for multiple time steps the randomness of parcel volume transfers within the lobe interior as well as at the margins qualitatively reflects inflation processes observed in the field the fraction of inflated volume to total volume increases with the total volume with greater than 75 of the lobe volume contributed through inflation for typical lobes the influence on planform shape and topographic cross sectional profiles of total volume source area and shape topographic confinement and sequential breakouts at the lobe margins are all explored with the stochastic model each of these factors influences the overall lobe thickness and width the model provides a means for assessing the relative importance of these processes through comparisons with field data for the first time gaussian and parabolic functions are quantitatively fit to field measurements of pahoehoe lobes both functional forms provide adequate description of the cross sectional flow shapes when comparing simulated lobes to field data sequential breakouts at the lobe margins are found to be an important process controlling the final topographic distribution of observed pahoehoe lobes

thermal mapping of a pāhoehoe lava flow kīlauea volcano abstract p hoehoe lava flows are a major component of hawaiian eruptive activity and an important part of basaltic volcanism worldwide in recent years p hoehoe lava has destroyed homes and threatened parts of hawai i with inundation and disruption in this study we use oblique helicopter borne thermal images to create high spatial resolution 1 m georeferenced thermal maps of the active p hoehoe flow on k lauea volcano s east rift zone thermal maps were created on 27 days during 2014 2016 in the course of operational monitoring encompassing a phase of activity that threatened the town of p hoa our results illustrate and reinforce how p hoehoe flows are multicomponent systems consisting of the vent master tube distributary tubes and surface breakouts the thermal maps accurately depict the distribution and character of p hoehoe breakouts through time and also delineate the subsurface lava tube surface breakouts were distributed widely across the p hoehoe flow with significant portions concurrently active well upslope of the flow front often concentrated in clusters of activity that evolved through time gradual changes to surface breakout distribution and migration relate to intrinsic processes in the flow including the slow evolution of the distributary tube system abrupt disruptions to this system and the creation of new breakouts and associated hazards were triggered by extrinsic forcing namely fluctuations in lava supply rate at the vent which disrupted the master lava tube although the total area of a p hoehoe flow has been suggested to relate to effusion rate our results show that changes in the proportion of expansion vs overplating can complicate this relationship by modifying existing techniques we estimate time averaged discharge rates for the flow during 2014 2016 generally in the range of 1 2 m 3 s 1 mean 1 3 0 4 m 3 s 1 less than half of k lauea s typical eruption rate on the east rift zone and suggestive of a weak eruptive regime during 2014 2016 we caution however that this discharge rate approach requires further independent corroboration the thermal maps provide the first synoptic characterization of p hoehoe flow activity at high spatial resolution essential both for operational hazard assessment and fundamental understanding of p hoehoe behavior

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

factors affecting the accuracy of thermal imaging cameras in volcanology volcano observatories and researchers are recognizing the potential usefulness of thermal imaging cameras both before and during volcanic eruptions obvious applications include measurements of the surface temperatures of active lava domes and lava flows to determine the location of the most active parts of these potentially hazardous features if appropriate precautions are taken the new generation of thermal imaging cameras can be used to extract quantitative as well as qualitative information on volcanic activity for example they can be used to measure the temperature of lava on eruption and to reveal how the crust cools during flow emplacement this is important for the validation of lava flow models to ensure that meaningful temperatures are collected thermal imaging data must be corrected for instrumental errors emissivity of the surface being imaged atmospheric attenuation viewing angle and surface roughness controlled laboratory experiments have been undertaken to determine the emissivity of smooth and rough samples and the effects of viewing angle and to quantify the errors measured emissivities range from 0 973 0 002 for smooth samples of basalt and 0 984 0 004 for rough samples errors in emissivity corrected temperatures are within 15 c for lava at 1100 c variations from individual sensor receptors which provide individual pixel temperature data were found to be 0 6 and instrumental errors of the cameras used were 0 1 apparent temperatures were found to vary by less than the instrumental error for viewing angles up to 30 degrees from normal to lava and thereafter increased by 1 c per degree by increasing the apparent viewing distance of a small vent on mount etna from 1 5 to 30 m the maximum temperature is shown to decrease by 53 c due to integrated averaging of radiance over increased pixel areas at a viewing distance of 250 m the maximum temperature decreased by 200 c with a further 75 c decrease due to atmospheric attenuation for a relative humidity of 50 however errors in relative humidity measurements can lead to atmospheric attenuation correction inaccuracies up to 200 c at viewing distances of 1 km we show how temperatures measured using thermal imaging cameras can be corrected to give improved estimates of temperature distributions on the surface of active lava flows

replacement reactions and deformation by dissolution and precipitation processes in amphibolites the deformation of the middle to lower crust in collisional settings occurs via deformation mechanisms that vary with rock composition fluid content pressure and temperature these mechanisms are responsible for the accommodation of large tectonic transport distances during nappe stacking and exhumation here we show that fracturing and fluid flow triggered coupled dissolution precipitation and dissolution precipitation creep processes which were responsible for the formation of a mylonitic microstructure in amphibolites this fabric is developed over a crustal thickness of 500 m in the lower seve nappe scandinavian caledonides amphibolites display a mylonitic foliation that wraps around albite porphyroclasts appearing dark in panchromatic cathodoluminescence the albite porphyroclasts were dissected and fragmented by fractures preferentially developed along the 001 cleavage planes and display lobate edges with embayments and peninsular features two albite oligoclase generations bright in cathodoluminescence resorbed and overgrew the porphyroclasts sealing the fractures electron backscattered diffraction shows that the two albite oligoclase generations grew both pseudomorphically and topotaxially at the expense of the albite porphyroclasts and epitaxially around them these two albite oligoclase generations also grew as neoblasts elongated parallel to the mylonitic foliation the amphibole crystals experienced a similar microstructural evolution as evidenced by corroded ferrohornblende cores surrounded by ferrotschermakite rims that preserve the same crystallographic orientation of the cores misorientation maps highlight how misorientations in amphibole are related to displacement along fractures perpendicular to its c axis no crystal plasticity is observed in either mineral species plagioclase and amphibole display a crystallographic preferred orientation that is the result of topotaxial growth on parental grains and nucleation of new grains with a similar crystallographic orientation amphibole and plagioclase thermobarometry constrains the mylonitic foliation development to the epidote amphibolite facies 600 c 0 75 0 97 gpa our results demonstrate that at middle to lower crustal levels the presence of h2o rich fluid at grain boundaries facilitates replacement reactions by coupled dissolution precipitation and favours deformation by dissolution precipitation creep over dislocation creep in plagioclase and amphibole

dating slate belts using 40 ar 39 ar geochronology and zircon ages from crosscutting plutons a case study from east central maine usa abstract we report the ages of cleavage development in a normally intractable lower greenschist facies slate belt the central maine aroostook matapedia belt in east central maine we have attacked this problem by identifying the minimum ages of muscovite in a regional acadian cleavage s 1 and in a local ductile fault zone cleavage s 2 using 40 ar 39 ar geochronology and the ages of crosscutting plutons our success stems from the regional low grade metamorphism of the rocks in which each crystallization event preserves a 40 ar 39 ar crystallization age and not a cooling age evidence for recrystallization via a pressure solution mechanism comes from truncations of detrital authigenic and in some rocks s 1 muscovite and chlorite grains by new cleavage forming muscovite and chlorite grains low blank furnace age spectra from meta arkosic and slaty rocks climb from moderate temperature devonian age steps dominated by cleavage forming muscovite to ordovician age steps dominated by a detrital muscovite component s 1 and s 2 cleaved rocks were hornfelsed by granitoids of 407 and 377 ma respectively the combination of these minimum ages with the maximum metamorphic crystallization ages establishes narrow constraints on the timing of these two cleavage forming events 410 ma s 1 and 380 ma s 2 these two events coincide in time with a change in the plate convergence kinematics from the arrival of the avalon terrane acadian orogeny to a right lateral transpression arrival of the meguma terrane in the neoacadian orogeny

contrasting tectonothermal domains and faulting in the potomac terrane virginia maryland discrimination by 40ar 39ar and fission track thermochronology new 4 0 ar 3 9 ar data reveal ages and thermal discontinuities that identify mapped and unmapped fault boundaries in the potomac terrane in northern virginia thus confirming previous interpretations that it is a composite terrane the rocks of the potomac terrane were examined along the potomac river where it has been previously subdivided into three units the mather gorge sykesville and laurel formations in the mather gorge formation at least two metamorphic thermal domains were identified the blockhouse point and bear island domains separated by a fault active in the late devonian early ordovician ca 475 ma cooling ages of amphibole in the bear island domain reflect cooling from taconic metamorphism whereas the blockhouse point domain was first metamorphosed in the devonian the 4 0 ar 3 9 ar data from muscovites in a third eastern domain within the mather gorge formation the stubblefield falls domain record thrusting of the sykesville formation over the mather gorge formation on the plummers island fault in the devonian the existence of two distinctly different thermal domains separated by a tectonic boundary within the mather gorge argues against its status as a formation hornblende cooling ages in the sykesville formation are early devonian ca 400 ma reflecting cooling from taconic and acadian metamorphism the ages of retrograde and overprinting muscovite in phyllonites from domain bounding faults are late devonian acadian and late pennsylvanian alleghanian marking the time of assembly of these domains and subsequent movement on the plummers island fault our data indicate that net vertical motion between the bear island domain of the mather gorge complex and the sykesville formation across the plummers island fault is east side up zircon fission track cooling ages demonstrate thermal equilibrium across the potomac terrane in the early permian and apatite fission track cooling ages record tilting of the potomac terrane in the cretaceous or later with the west side up at least 1 km

sulfur abundance and its speciation in oxidized alkaline melts abstract the sulfur concentrations and the relative proportions of s2 and s6 were measured by electron microprobe in a series of melt inclusions trapped in phenocrysts from different subduction related and within plate volcanoes the melt inclusions correspond to potassic and shoshonitic primary melts to tholeiitic and hawaiitic primitive melts in the tholeiitic and the transitional basaltic melt inclusions sulfur is mainly present as s2 s 6 s total 0 03 to 0 08 and varies from 0 13 to 0 18 wt the occurrence of immiscible sulfides attests to their saturation in shoshonitic and potassic primary melts sulfur s 0 12 to 0 32 wt is dissolved as both s2 and s6 s 6 s total 0 3 to 0 7 their oxygen fugacity estimated from the s 6 s total ratios ranges from ninio to ninio 1 log unit hawaiitic melts may also dissolve up to 0 3 wt sulfur possibly because of their oxidation state close to ninio as illustrated by samples from mt etna italy variations of sulfur at constant s 6 s total ratio and temperature in both the potassic and shoshonitic primary melts indicate that these melts are undersaturated with respect to a s rich condensed phase in agreement with their relatively high oxidation state it strongly suggests that sulfur behavior in relatively oxidized primary alkaline melts is controlled by the mantle source melting conditions

geochronologic studies in central new england i evidence for pre acadian metamorphism in eastern vermont sup 40 ar sup 39 ar geochronology on hornblendes from central new england reveals a grenvillian cooling age 1026 plus minus 12 ma along the eastern margin of the green mountain massif acadian ages in east central vermont 350 397 ma and along the bronson hill anticlinorium in new hampshire and massachusetts 407 280 ma and late ordovician to silurian ages 440 451 ma along a belt in eastern vermont and central massachusetts these ages indicate a minimal acadian overprint in eastern vermont the highest degree of acadian overprint being located along the axis of the domes in the connecticut valley synclinorium these data suggest that the formation of the domes occurred in the acadian moreover the late ordovician to silurian cooling ages in eastern vermont suggest that much of the metamorphic mineralogy and fabric observed in the connecticut valley synclinorium may be pre silurian in age

rapid exhumation of cretaceous arc rocks along the blue mountains restraining bend of the enriquillo plantain garden fault jamaica using thermochronometry from multiple closure systems abstract the effect of rapid erosion on kinematic partitioning along transpressional plate margins is not well understood particularly in highly erosive climates the blue mountains restraining bend bmrb of eastern jamaica bound to the south by the left lateral enriquillo plantain garden fault epgf offers an opportunity to test the effects of highly erosive climatic conditions on a 30 km wide restraining bend system no previous thermochronometric data exists in jamaica to describe the spatial or temporal pattern of rock uplift and how oblique 20 plate motion is partitioned into vertical strain to define the exhumation history we measured apatite n 10 and zircon n 6 u th he ages 40ar 39ar n 2 amphibole and k spar ages and u pb zircon n 2 crystallization ages late cretaceous u pb and 40ar 39ar ages 74 68 ma indicate rapid cooling following shallow emplacement of plutons during north south subduction along the great caribbean arc early to middle miocene zircon helium ages 19 14 ma along a vertical transect suggest exhumation and island emergence at 0 2 mm yr older zircon ages 10 15 km to the north 44 35 ma imply less rock uplift apatite helium ages are young 6 1 ma across the entire orogen suggesting rapid exhumation of the bmrb since the late miocene these constraints are consistent with previous reports of restraining bend formation and early emergence of eastern jamaica an age elevation relationship from a vertical transect implies an exhumation rate of 0 8 mm yr while calculated closure depths and thermal modeling suggests exhumation as rapid as 2 mm yr the rapid rock uplift rates in jamaica are comparable to the most intense transpressive zones worldwide despite the relatively slow 5 7 mm yr strike slip rate we hypothesize highly erosive conditions in jamaica enable a higher fraction of plate motion to be accommodated by vertical deformation thus strike slip restraining bends may evolve differently depending on erosivity and local climate

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

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

inverting multispectral thermal time series images of volcanic eruptions for lava emplacement models we present a novel method for interpreting time series of multispectral observations of volcanic eruptions we show how existing models relating to radiance and area emplacement can be generalized into an integration convolution of a net area emplacement nae function and a coolingfunction assumingallsurfacesfollowthesamecoolingcurve thenaedescribesthevari ation in the rate of emplacement of hot material with time and temperature while the cooling func tion describes the cooling of a hot surface with time discretizing the integration convolution equation yields an underdetermined matrix equation that we solve using second order tikhonov regularization to stabilize the solution we test the inversion by modelling plausible nae surfaces calculating the radiances adding noise and inverting for the original surface three or more spec tralbands are requiredtocapture theoverallshapeofthenae andrecovering specificquantitiesis difficult single wavebands that yield flat kernels recover the total area emplacement curve rate of increase of hot area the integral of the nae with respect to temperature surprisingly well due to their property of conserving nae suggesting novel methods for calculating area emplacement rates and effusion rates from time series of satellite images and radiometer measurements gold open access this article is published under the terms of the cc by 3 0 license

phase relations and chemical composition of phengite and paragonite in pelitic schists during decompression a case study from the monte rosa nappe and camughera moncucco unit western alps the metamorphic evolution of metapelites from the eastern part of the monte rosa nappe and the camughera moncucco unit both situated in the upper penninic units sw of the simplon line were investigated using microstructural relationships and equilibrium phase diagrams the units under consideration experienced prealpine amphibolite facies conditions and underwent a complex metamorphic evolution during the alpine orogeny peak pressures during an early alpine high pressure stage of 12 5 16 kbar were similar in the monte rosa nappe and camughera moncucco unit a pronounced thermal gradient is indicated during decompression leading to an amphibolite facies overprint as the decompression paths went through the chlorite biotite and plagioclase stability fields in most of the monte rosa nappe through the staurolite field in the easternmost monte rosa nappe and in the camughera moncucco unit and through the sillimanite field in the easternmost camughera moncucco unit in high al metapelites the initial formation of staurolite is related to continuous paragonite breakdown and associated formation of biotite in the course of this reaction phengite becomes successively sodium enriched in low al metapelites in contrast the initial staurolite formation occurs via the continuous breakdown of sodium rich phengite in both low and high al metapelites the largest volume of staurolite is formed during the continuous breakdown of sodium rich phengite below p t conditions of about 9 5 kbar at 600 650 c during this reaction phengite becomes successively potassium enriched as sodium from phengite is used to form the albite component in plagioclase for normal pelitic chemistries phengite becomes na enriched during decompression through the breakdown of paragonite along a nearisothermal decompression path the na content in phengite reaches its maximum when paragonite is entirely consumed during further decompression the paragonite component in phengite decreases again because na is preferentially incorporated into the albite component of plagioclase

high resolution compositional mapping of matrix phases implications for mass transfer during crenulation cleavage development in the moretown formation western massachusetts abstract high resolution compositional maps provide a new tool for investigating mass transfer during cleavage formation the moretown formation of western massachusetts contains a well developed crenulation cleavage with alternating mica rich crenulation limbs and mica poor crenulation hinges compositional mapping shows two generations of plagioclase the second of which was synchronous with the crenulation cleavage a significant amount of the syn crenulation plagioclase 10 20 modally grew in hinge domains a small amount of syn crenulation plagioclase 1 and a large amount of phengitic muscovite grew in limb domains the maps also show that uncrenulated domains experienced mass transfer and reactivation of older cleavages and thus cannot be used as undeformed reference domains for comparison with crenulated regions compositional mapping facilitates a new degree of integration between petrologic and structural analysis knowledge of the structural context of compositional domains allows better selection of phases and compositions for interpreting metamorphic reactions and linking metamorphism to deformational stages knowledge of syntectonic reactions provides new insights into mass transfer and volume change during deformation in the moretown formation plagioclase and phengite producing reactions play a large role in controlling the nature and magnitude of mass transfer but microstructures control the location of reactants and products within the evolving fabric

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

the initial cooling of pahoehoe flow lobes in this paper we describe a new thermal model for the initial cooling of pahoehoe lava flows the accurate modeling of this initial cooling is important for understanding the formation of the distinctive surface textures on pahoehoe lava flows as well as being the first step in modeling such key pahoehoe emplacement processes as lava flow inflation and lava tube formation this model is constructed from the physical phenomena observed to control the initial cooling of pahoehoe flows and is not an empirical fit to field data we find that the only significant processes are a heat loss by thermal radiation b heat loss by atmospheric convection c heat transport within the flow by conduction with temperature and porosity dependent thermal properties and d the release of latent heat during crystallization the numerical model is better able to reproduce field measurements made in hawai i between 1989 and 1993 than other published thermal models by adjusting one parameter at a time the effect of each of the input parameters on the cooling rate was determined we show that a the surfaces of porous flows cool more quickly than the surfaces of dense flows b the surface cooling is very sensitive to the efficiency of atmospheric convective cooling and c changes in the glass forming tendency of the lava may have observable petrographic and thermal signatures these model results provide a quantitative explanation for the recently observed relationship between the surface cooling rate of pahoehoe lobes and the porosity of those lobes jones 1992 1993 the predicted sensitivity of cooling to atmospheric convection suggests a simple field experiment for verification and the model provides a tool to begin studies of the dynamic crystallization of real lavas future versions of the model can also be made applicable to extraterrestrial submarine silicic and pyroclastic flows

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

a comparison of field and satellite derived thermal flux at piton de la fournaise implications for the calculation of lava discharge rate we present thermal measurements made by high spatial resolution ground based a hand held thermal camera and low spatial resolution space based modis instruments for a lava flow field active during the last phase of the may july 2003 eruption at piton de la fournaise la reunion multiple oblique ground based thermal images were merged to provide full coverage of the flow field these were then corrected for path length attenuation and orthorectified allowing the at surface radiance emitted by the flow field to be estimated comparison with the radiance recorded by the modis sensors during the eruption reveals that for clear sky conditions and moderate to low viewing angles satellite zenith 40 the satellite measurements represent 90 of the at surface radiance and thus represent valuable data for quantifying volcanic thermal anomalies nevertheless extreme viewing geometries and the presence of clouds strongly affect the radiance reaching the sensor and affected data from 94 of the overpasses ground based thermal data were used to investigate an empirical relationship between the radiant heat flux and lava discharge rate during the emplacement of pahoehoe flows while the average radiation temperature for flow surface that were 6 24 h old ranged between 500 k and 625 k the ratio between radiative heat flux and time averaged lava discharge rate tadr ranged between 1 5 108 j m 3 and 3 5 108 j m 3 this relationship was used to estimate tadr values from optimal modis data and produced results in line with those obtained from gps surveys coppola et al 2005 our results underscore the importance of ground based thermal analysis for the interpretation of satellite measurements particularly in terms of calculating discharge rate trends

stabilities of laurite rus2 and monosulfide liquid solution at magmatic temperature we have reversed the equilibria ru s2 rus2 and 2feo s2 2fes o2 under controlled temperature oxygen fugacity fo2 and sulfur fugacity fs2 at 1 atm to test if the platinum group mineral laurite rus2 has a stability field at magmatic temperature outside that of magmatic monosulfide liquid the fs2 in equilibrium with ru and rus2 is given by log fs2 6 9 12190 t 1173 to 1673 k whereas the fs2 at sulfide saturation of a basaltic melt may be approximated from log fs2 6 7 12800 t 2 log xfeo log fo2 1473 to 1673 k our experiments support the notion that the sulfide mineral laurite can crystallize directly out of a sulfur bearing sulfide undersaturated silicate melt as implied by laurite chromite intergrowth textures in natural chromite ore

a simple explanation for the space based calculation of lava eruption rates abstract knowing how lava effusion rates vary during basaltic eruptions can be of great significance when trying to provide preliminary forecasts regarding how far lava will flow however problems exist in accurately determining effusion rates using conventional field based techniques to ameliorate this problem harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 j volcanol geotherm res 102 2000 237 269 developed a method for determining effusion rates using infrared satellite data and showed how the method could be used to provide realistic estimates of effusion rates repeatedly during several eruptions at kilauea hawai i krafla iceland etna and stromboli italy harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 indicate that their method allows instantaneous lava effusion rates to be determined thermodynamically by equating the amount of heat lost by an active lava flow derived from the satellite data to the amount of heat liberated by the cooling mass of lava the purpose of this paper is to provide a simpler alternative explanation we find that rather than being used to calculate heat loss harris et al j geophys res 102 1997 7985 8003 bull volcanol 59 1997 49 64 j volcanol geotherm res 102 2000 237 269 actually use the satellite data to estimate the area of active lava present within the satellite s field of view at the movement of data acquisition thus changes in the effusion rates they present can only be proportional to changes in this area the active flow areas were then multiplied by a constant the value of which is obtained from a crude approximation of the lava flows heat balance crucially the absolute value of this term falls within the range of an empirically derived parameter that was found by pieri and baloga j volcanol geotherm res 30 1986 29 45 to explain strong linear correlations between eruption rate i e the time averaged effusion rate and lava flow area for 34 historic hawaiian flows as a result we find that the method of harris et al j geophys res 102 1997 7985 8003 does not yield instantaneous effusion rates but instead provides a valid and useful way to estimate average effusion rates i e the eruption rate from measurements of flow area

reaction softening by dissolution precipitation creep in a retrograde greenschist facies ductile shear zone new hampshire usa we describe strain localization by a mixed process of reaction and microstructural softening in a lower greenschist facies ductile fault zone that transposes and replaces middle to upper amphibolite facies fabrics and mineral assemblages in the host littleton schist near claremont new hampshire here na poor muscovite and chlorite progressively replace first staurolite then garnet and finally biotite porphyroblasts as the core of the fault zone in approached across the transect higher grade fabric forming na rich muscovite is also progressively replaced by fabric forming na poor muscovite the mineralogy of the new phyllonitic fault rock produced is dominated by na poor muscovite and chlorite together with late albite porphyroblasts the replacement of the amphibolite facies porphyroblasts by muscovite and chlorite is pseudomorphic in some samples and shows that the chemical metastability of the porphyroblasts is sufficient to drive replacement in contrast element mapping shows that fabric forming na rich muscovite is selectively replaced at high strain microstructural sites indicating that strain energy played an important role in activating the dissolution of the compositionally metastable muscovite the replacement of strong high grade porphyroblasts by weaker na poor muscovite and chlorite constitutes reaction softening the crystallization of parallel and contiguous mica in the retrograde foliation at the expense of the earlier and locally crenulated na rich muscovite defined foliation destroys not only the metastable high grade mineralogy but also its stronger geometry this process constitutes both reaction and microstructural softening the deformation mechanism here was thus one of dissolution precipitation creep activated at considerably lower stresses than might be predicted in quartzo feldspathic rocks at the same lower greenschist facies conditions this article is protected by copyright all rights reserved

time dependent profiles of lava flows this work investigates the combined effects of a time dependent effusion rate and a spatially varying viscosity on the thickness profile of a flowing lava we formulate relatively simple governing equations as a primitive dynamical model for these two influences on lava flow morphology free boundary solutions for the profile of the flow and its extent are presented and analyzed for different boundary conditions at the source of the flow and several models for the spatial dependence of the viscosity the results presented here suggest that time dependence in the flow depth at the source and the form of the viscosity variation are significant influences on the morphology and dimensions of lava flows moreover this analysis implies that time dependent source conditions may contribute to the scatter in plots of eruption rate versus flow length and disparities between field and laboratory estimates of lava viscosity

eruptive behavior of the marum mbwelesu lava lake vanuatu and comparisons with lava lakes on earth and io abstract observations from field remote sensing of the morphology kinematics and temperature of the marum mbwelesu lava lake in the vanuatu archipelago in 2014 reveal a highly active vigorously erupting lava lake active degassing and fountaining observed at the 50 m lava lake led to large areas of fully exposed lavas and rapid 5 m s movement of lava from the centers of upwelling outwards to the lake margins these rapid lava speeds precluded the formation of thick crust there was never more than 30 non translucent crust the lava lake was observed with several portable handheld low cost near infrared imagers all of which measured temperatures near 1000 c and one as high as 1022 c consistent with basaltic temperatures fine scale structure in the lava fountains and cooled crust was visible in the near infrared at 5 cm pixel from 300 m above the lake surface the temperature distribution across the lake surface is much broader than at more quiescent lava lakes peaking 850 c and is attributed to the highly exposed nature of the rapidly circulating lake this lava lake has many characteristics in common with other active lava lakes such as erta ale in ethiopia being confined persistent and high temperature however it was much more active than is typical for erta ale which often has 90 crust furthermore it is a good analogue for the persistent high temperature lava lakes contained within volcanic depressions on jupiter s moon io such as pele also believed from spacecraft and ground based observations to exhibit similar behavior of gas emission rapid overturn and fountaining

field thermal monitoring during the august 2003 eruption at piton de la fournaise la reunion 1 a detailed set of thermal images collected during the last day of the august 2003 eruption of piton de la fournaise la reunion clearly revealed several dynamic processes associated with a spatter cone containing a lava pond and feeding a channelized lava flow periods of steady effusion were interrupted by brief pulses of lava effusion that closely coincide with peaks in seismic tremor amplitude the thermal measurements show that roofing of a lava channel during steady effusion and cooling of surface flows decrease thermal radiance in two different ways here we show that the decrease in thermal radiance because of channel roofing is not related to a decrease in volcanic activity as might be interpreted from satellite data in addition we introduce a new method of representing thermal data hereby named radiative thermogramme that successfully describes thermal patterns produced by distinct eruptive processes within the same span of time this graphic solution can be directly correlated with volcanic field processes and provides a useful tool for interpreting a high number of thermal data in a wide range of volcanic activities

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

image based measurement of flux variation in distal regions of active lava flows 1 understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes here we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active a flows in order to investigate distal flow processes at mount etna sicily photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow fronts velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava significant variations of the magma flux were observed and pulses of increased flux arrived within the flow front region on timescales of several hours the pulses are believed to be the distal result of more frequent flux changes observed in the vent region hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short period variations in effusion rate in considering advance processes for the individual flow fronts it must be assumed that they were fed by a highly unsteady flux which was volumetrically at least an order of magnitude lower than that observed near the vent

rheological control on the radiant density of active lava flows and domes abstract during an effusive extrusive eruption the capability of an active lava body flow or dome to radiate thermal energy depends on how the lava discharge rate is accommodated by the expansion of the magma body and by the cooling of its surface this feature can be described by a single empirical parameter defined radiant density c rad in j m 3 that for a given discharge rate expresses the efficiency of the lava body to change its area and or to insulate its inner core thus modulating the heat radiated from the active surface by comparing the volcanic radiative energy vre in j detected by modis during 28 eruptions at 18 active volcanoes with their erupted lava volumes vol in m 3 we show that the radiant density c rad vre vol is inversely proportional to the silica content of the erupted lava basic lavas 45 52 wt sio 2 have the highest observed radiant density 1 to 4 10 8 j m 3 while intermediate 52 63 wt sio 2 and acidic 63 wt sio 2 lavas show a gradually lower radiant densities 1 5 to 9 10 7 j m 3 and 0 2 to 1 10 7 j m 3 for intermediate and acidic composition respectively we regard this correlation as the result of the control that the rheology of lavas exerts on cooling and spreading processes of related bodies in particular we found that for any given compositional group the radiant density is essentially related to a characteristic thickness of active lavas at the time of a satellite acquisition we suggest that the radiant density of effusive extrusive lava bodies can be predicted 50 by means of an empirical relationship based on the sio 2 content of the erupted lava this makes this parameter very useful in observing volcanic activity especially in remote regions where access may not be possible by measuring the energy radiated during an eruption and by assuming a lava composition based on the tectonic setting or magmatic province we suggest that the radiant density can be used to estimate lava discharge rates and erupted volumes for volcanoes characterised by effusive or extrusive activity