spectral and dynamical hints on the time scale of preparation of the 5 april 2003 explosion at stromboli volcano stromboli volcano is well known for its continuous strombolian activity moreover the volcano occasionally shows effusive phases the latest in 1985 1986 on 28 december 2002 stromboli entered a new effusive phase accompanied by different paroxysmal events that led to considerable hazards for inhabitants and tourists on the island of stromboli on 30 december 2002 a major sector collapse affected the sciara del fuoco slope and initiated a tsunami on 5 april 2003 a powerful explosion which can be compared in size with the most recent explosion in 1930 covered a large part of the normally tourist accessible summit area with bombs as this explosion was not forecasted although the island was by then effectively monitored by a dense deployment of instruments in this paper we tackle the problem of highlighting the time scale of preparation of this event and conduct a search for possible precursors for this purpose we analyze the seismic data preceding the paroxysm with spectral and dynamical methods

real time seismic amplitude measurement rsam a volcano monitoring and prediction tool seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions although several real time earthquake detection and data acquisition systems exist few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent analog seismic records provide a quick visual overview of activity however continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders at the cascades volcano observatory an inexpensive 8 bit analog to digital system controlled by a laptop computer is used to provide 1 min average amplitude information from eight telemetered seismic stations the absolute voltage level for each station is digitized averaged and appended in near real time to a data file on a multiuser computer system raw realtime seismic amplitude measurement rsam data or transformed rsam data are then plotted on a common time base with other available volcano monitoring information such as tilt changes in earthquake activity associated with dome building episodes weather and instrumental difficulties are recognized as distinct patterns in the rsam data set rsam data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion mount st helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations weather related noise shows up as low level long term disturbances on all seismic stations regardless of distance from the volcano implemented in mid 1985 the rsam system has proved valuable in providing up to date information on seismic activity for three mount st helens eruptive episodes from 1985 to 1986 may 1985 may 1986 and october 1986 tiltmeter data the only other telemetered geophysical information that was available for the three dome building episodes is compared to rsam data to show that the increase in rsam data was related to the transport of magma to the surface thus if tiltmeter data is not available rsam data can be used to predict future magmatic eruptions at mount st helens we also recognize the limitations of rsam data two examples of rsam data associated with phreatic or shallow phreatomagmatic explosions were not preceded by the same increases in rsam data or changes in tilt associated with the three dome building eruptions

lead isotopic compositions of the western dharwar craton southern india evidence for distinct middle archean terranes in a late archean craton abstract lead and sr isotopic compositions of whole rocks and feldspar separates from several fielddefined suites of rocks from the western dharwar craton of southern india elucidate a complex history of the area the evolution of the craton earlier than 3 0 ga is difficult to determine because of thermal and metasomatic overprinting at 3 0 ga many whole rocks were completely reset then but feldspar separates preserve some of the earlier history apparently a series of terranes evolved from the mantle over the period 3 4 to 3 0 ga to form the western dharwar craton in each case metamorphism and anatexis of older terranes accompanied extraction of juvenile material from the mantle the oldest gneisses 3 4 ga had radiogenic pb and sr isotopic compositions when they formed and were derived from older crustal protoliths that were plausibly accreted to the crust at or even before 3 8 ga the old gneisses were greatly depleted in rb probably at 3 4 ga when the protoliths of younger magmatic rocks may have separated from the mantle younger gneisses apparently formed from these mafic intermediate protoliths in the age range of 3 2 to 3 0ga the 3 0 ga event in the central part of the craton was accompanied by intrusion of small diapiric trondhjemites formed by melting of older crust and penecontemporaneous metasomatism of country rocks by hydrous fluids carrying u and other lithophilic elements the resultant deep crust was greatly depleted in heat producing elements and the craton has been inactive since 3 0 ga except for production of minor granites from depleted source regions at 2 5 2 6 ga the lack of activity at 2 5 ga contrasts strongly with extensive magmatism and metamorphism in surrounding areas that had not undergone depletion at 3 0 ga lower crustal depletion also has caused present day reduced heat flow to be very low

correlations between so2 flux seismicity and outgassing activity at the open vent of villarrica volcano chile 1 the characteristics of the open vent activity of villarrica volcano chile were studied in detail by integrating visual observations of the lava lake analysis of the seismic tremor and measurements of so2 flux the outgassing activity comprises a persistent gas plume emission from the bottom of the crater as well as frequent explosive events three main styles of bubble bursting were identified at the surface of the active lava lake seething magma small short lived lava fountains and strombolian explosions seething magma consists of continual burst of relatively small bubbles a few meters in diameter with varying strength over the entire surface of the lava lake small lava fountains seen as a vigorous extension of seething magma commonly have durations of 20 120 s and reach 10 40 m high above the lava lake correlations between seismicity and visual observations indicate that the seismic tremor is mostly caused by the explosive outgassing activity furthermore for different periods between 2000 and 2006 during which the activity remained comparable the real time seismic amplitude measurement system rsam and so2 emission rates show a very good correlation higher so2 emissions appeared to be related to higher levels of the lava lake stronger bubble bursting activity and changes in the morphology and texture of the crater floor background low levels of activity correspond to a lava lake located 80 m below the crater rim small and or blocky morphology of the roof seismic amplitude rsam lower than 25 units few volcano tectonic earthquakes and daily averages of so2 emissions lower than 600 mg d

models of tremor and low frequency earthquake swarms on montserrat recent observations from soufriere hills volcano in montserrat reveal a wide variety of low frequency seismic signals we discuss similarities and differences between hybrid earthquakes and long period events and their role in explosions and rockfall events these events occur usually in swarms and occasionally merge into tremor an observation that can shed further light on the generation and composition of harmonic tremor we use a 2d finite difference method to model major features of low frequency seismic signatures and compare them with the observations a depth dependent velocity model for a fluid filled conduit is introduced which accounts for the varying gas content in the magma and the impact on the seismic signals is discussed we carefully analyse episodes of tremor that show shifting spectral lines and model those in terms of changes in the gas content of the magma as well as in terms of a time dependent triggering mechanism of low frequency resonances in this way we explain the simultaneous occurrence of low frequency events and tremor with a spectral content comprising integer harmonics

classification of seismic signals at villarrica volcano chile using neural networks and genetic algorithms each volcano has its own unique seismic activity the aim of this work is to construct a system able to classify seismic signals for the villarrica volcano one of the most active volcanoes in south america since seismic signals are the result of particular processes inside the volcano s structure they can be used to forecast volcanic activity this paper describes the different kinds of seismic signals recorded at the villarrica volcano and their significance three kind of signals were considered as most representative of this volcano s activity the long period the tremor and the energetic tremor signals a classifier is implemented to read the seismic registers at 30 second intervals extract the most relevant features of each interval and classify them into one of the three kinds of signals considered as most representative of this particular volcano to do so 1033 different kinds of 30 s signals were extracted and classified by a human expert a feature extraction process was applied to obtain the main characteristics of each of them this process was developed using criteria which have been shown by others to effectively classify seismic signals based on the experience of a human expert the classifier was implemented with a multi layer perceptron mlp artificial neural network whose architecture and training process were optimized by means of a genetic algorithm this technique searched for the most adequate mlp configuration to improve the classification performance optimizing the number of hidden neurons the transfer functions of the neurons and the training algorithm the optimization process also performed a feature selection to reduce the number of signal features optimizing the number of network inputs the results show that the optimized classifier reaches more than 93 exactitude identifying the signals of each kind the amplitude of the signals is the most important feature for its classification followed by its frequency content the described methodology can be used to classify more seismic signals to improve the study of the activity of this volcano or to extend the study to other active volcanoes of the region

changes in the diffuse co2 emission and relation to seismic activity in and around el hierro canary islands significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at el hierro canary islands before the occurrence of several seismic events during 2004 two precursory co2 efflux increases started thirteen and nine days before two seismic events of magnitude 2 3 and 1 7 which took place near el hierro island canary islands on march 23 and april 15 reaching a maximun value of 51 1 and 46 2 g m 2 d 1 respectively five and eight days before the two seismic events other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1 3 and 1 5 which took place on october 15 and 21 respectively reaching the maximum values four and one day before the earthquakes these changes were not related to variations in atmospheric or soil parameters the material failure forecast method ffm which analyzes the rate of precursory phenomena was successfully applied to forecast the first seismic event that took place in el hierro island in 2004

precursory subsurface 222rn and 220rn degassing signatures of the 2004 seismic crisis at tenerife canary islands precursory geochemical signatures of radon degassing in the subsurface of the tenerife island were observed several months prior to the recent 2004 seismic volcanic crisis these premonitory signatures were detected by means of a continuous monitoring of 222rn and 220rn activity from a bubbling co2 rich gas spot located at 2 850 m depth inside a horizontal gallery for groundwater exploitation at tenerife multivariate regression analysis mra on time series of the radon activity was applied to eliminate the radon activity fluctuation due to external variables such as barometric pressure temperature and relative humidity as well as power supply material failure forecast method ffm was successfully applied to forecast the anomalous seismicity registered in tenerife island in 2004 the changes in the 222rn 220rn ratio observed after the period of anomalous seismicity might suggest a higher gas flow rate and or changes in the vertical permeability induced by seismic activity

varying seismic acoustic properties of the fluctuating lava lake at villarrica volcano chile villarrica volcano outgasses through an open lava lake with bubbles ranging in size from submillimeter to several meters the largest of which produce strombolian bursting events that are visible from the crater rim thousands of shallow strombolian events identified through seismic waveform cross correlation were found to produce discrete and repetitive long period seismic and infrasonic signals we identified variations of up to 0 7 s in seismic acoustic arrival delay times between april and july 2010 at a station 750 m from the vent which we interpret as due to fluctuations in the level of lava lake during time periods interpreted as having high lava lake levels based on reduced time delays interevent times were also reduced and average seismic amplitude measurements seismic and acoustic event energies and volcano acoustic seismic ratios were all high as compared to times when the lava lake was lower the crater is also a source of nearly continuous monotonic infrasonic tremor we found that the peak frequency of this infrasonic tremor typically around 0 5 1 0 hz was inversely correlated with seismic acoustic delay times and therefore an indicator of lava lake level we use this correlation to propose a new model for infrasonic tremor generation namely using crater geometry to approximate a bessel horn we interpret the two clearest cycles of elevated seismicity and lava lake level as due to an increase in exsolved gas resulting from an injection of volatile rich magma or an overturn in a deeper magma reservoir

late archaean 2550 2520 ma juvenile magmatism in the eastern dharwar craton southern india constraints from geochronology nd sr isotopes and whole rock geochemistry the results of field geochronologic geochemical and isotopic studies are presented for the granitoids that occur east of the closepet batholith up to the kolar schist belt ksb field data such as common foliation strong shear deformation occasionally leading to mylonitization together with petrographic data including reduction in grain size with corroded borders show characteristics of the syn kinematic emplacement of the granitoids single zircon evaporation ages define a minimum age of 3127 ma for the tonalitic trondhjemitic granodioritic ttg basement and 2552 2534 ma plateau ages for the emplacement of the granitoids which slightly predate 20 30 ma the emplacement of the 2518 ma closepet batholith major and trace element data together with isotopic data suggest at least four magmatic suites from closepet batholith to the east which have independent magmatic evolution histories the observed data are compatible with magma mixing for the closepet batholith melting of ttg and assimilation fractional crystallization processes for bangalore granites either melting of heterogeneous source or different degree of melting of the same source for the granitoids of hoskote kolar and fractional crystallization for the western margin of the ksb isotopic nd sr and geochemical data lree and lil elements suggest highly enriched mantle and ancient ttg crust for the closepet batholith enriched mantle and ttg crust for the bangalore granites c a chondritic mantle source for the granitoids of hoskote kolar and the quartz monzonites of the western margin of the ksb and slightly depleted mantle for granodiorites of the eastern margin of the ksb we interpret all these geochronologic geochemical and isotopic characteristics of granitoids from the closepet batholith to the east up to the ksb in terms of a plume model the centre of the plume would be an enriched hot spot in the mantle that lies below the present exposure level of the closepet batholith melting of such an enriched mantle hot spot produces high temperature magmas closepet that penetrate overlying ancient crust where they strongly interact and induce partial melting of the surrounding crust these magmas cool very slowly as the hot spot maintains high temperatures for a long time thus they appear younger 2518 ma on the contrary to the east the plume induces melting of c a chondritic or slightly depleted mantle that produces relatively colder and less enriched magmas which show less or no interactions with the surrounding crust and cool rapidly and appear slightly older 2552 2534 ma this plume model can also account for late archaean geodynamic evolution including juvenile magmatism heat source for reworking inverse diapirism and granulite metamorphism in the dharwar craton

shrimp and electron microprobe chronology of uht metamorphism in the napier complex east antarctica implications for zircon growth at 1 000 c zircons in ultra high temperature uht metamorphosed paragneisses from mt riiser larsen in the napier complex east antarctica were dated by using ion microprobe shrimp and electron microprobe emp both shrimp and emp analyses yield consistent 2520 2460 ma age populations for garnet orthopyroxene bearing paragneiss and leucosomes enclosed within the peak uht event was dated at 2480 ma by shrimp analyses on metamorphic zircons from the garnet orthopyroxene paragneiss and those on magmatic zircons from the leucosomes which are interpreted to be formed at syn uht as obtained by shrimp the uht metamorphic event was terminated no later than 2460 ma minor 2520 ma shrimp age suggests either the onset of prograde metamorphism or another high grade metamorphic event unrelated to the uht emp analyses on metamorphic zircons from sapphirine quartz and osumilite bearing magnesian paragneisses give c 2500 2450 ma ages inherited igneous zircon cores of the magnesian paragneisses yield relatively scattered emp ages ranging over c 3000 2650 ma suggesting that igneous materials of these ages sourced the protoliths of the paragneisses and that they were deposited during the interval c 2650 2520 ma

does an inter flaw length control the accuracy of rupture forecasting in geological materials multi scale failure of porous materials is an important phenomenon in nature and in material physics from controlled laboratory tests to rockbursts landslides volcanic eruptions and earthquakes a key unsolved research question is how to accurately forecast the time of system sized catastrophic failure based on observations of precursory events such as acoustic emissions ae in laboratory samples or on a larger scale small earthquakes until now the length scale associated with precursory events has not been well quantified resulting in forecasting tools that are often unreliable here we test the hypothesis that the accuracy of the forecast failure time depends on the inter flaw distance in the starting material we use new experimental datasets for the deformation of porous materials to infer the critical crack length at failure from a static damage mechanics model the style of acceleration of ae rate prior to failure and the accuracy of forecast failure time both depend on whether the cracks can span the inter flaw length or not a smooth inverse power law acceleration of ae rate to failure and an accurate forecast occurs when the cracks are sufficiently long to bridge pore spaces when this is not the case the predicted failure time is much less accurate and failure is preceded by an exponential ae rate trend finally we provide a quantitative and pragmatic correction for the systematic error in the forecast failure time valid for structurally isotropic porous materials which could be tested against larger scale natural failure events with suitable scaling for the relevant inter flaw distances

al zoning in orthopyroxene in a sapphirine quartzite evidence for 1120 c uht metamorphism in the napier complex antarctica and implications for the entropy of sapphirine a unique sapphirine orthopyroxene quartz granulite from mt riiser larsen in the tula mountains of enderby land east antarctica preserves two generations of coarse and texturally equilibrated orthopyroxene and sapphirine coexisting with quartz initial subhedral orthopyroxene porphyroblasts retain core compositions enriched in al2o3 12 2 0 5 wt compared with their rims and finer orthopyroxene 9 6 0 5 wt al2o3 that forms granoblastic textures with sapphirine sapphirine and quartz also form symplectites on and along cleavage planes within orthopyroxene these compositional and textural features are consistent with the reaction 2mgal2sio6 mg2al4 sio10 sio2 leading to the formation of sapphirine quartz at the expense of aluminous orthopyroxene calculations in the mas and fmas systems and theoretical considerations involving the phases enstatite sapphirine sillimanite quartz and cordierite indicate that the reaction above progresses from left to right with decreasing temperature in the orthopyroxene sapphirine quartz field at pressures of ca 8 10 kbar the temperature difference required to account for the ca 2 5 3 wt decrease in al2o3 in orthopyroxene is at least 60 80 c and implies peak temperatures for the initial assemblage of at least 1120 c if the second granoblastic assemblage equilibrated at 1040 c the p t conditions required by the sapphirine quartz association and other p t sensitive assemblage indicators in the napier complex it is not possible to distinguish whether the two assemblages are simply related by cooling and re equilibration or reflect a polyphase evolution involving the superposition of a second uht event on an earlier even higher temperature uht metamorphism preliminary thermodynamic modelling of the reaction above incorporating the observed range in orthopyroxene al2o3 zoning indicates that present estimates for the entropy of high temperature sapphirine are potentially too high by 15 18 compared with sapphirine entropy estimates that are consistent with mas system experiments the mt riiser larsen sapphirine quartz rocks preserve the first definitive record of regional metamorphic temperatures in excess of 1120 c in the napier complex or indeed any uht granulite terrain worldwide similarly high peak temperatures may be retrieved from detailed studies of sapphirine quartz granulites from other regions further expanding the thermal realm of crustal metamorphism but progress will critically depend on the experimental acquisition of new entropy data for sapphirine

seismological aspects of the 1988 1989 lonquimay chile volcanic eruption abstract more than 1600 earthquakes were recorded in a four month period on portable seismographic stations installed in the lonquimay area immediately after the initiation of the volcanic eruption of december 25 1988 hypocentral parameters were calculated on a subset of 150 events showing clear p and s arrivals seismic activity was restricted to a north south elongated region that included the main crater of the lonquimay volcano the new navidad crater lies along the eastern margin of the area of seismicity most of the hypocenters are located at depths shallower than 6 km and none have depths exceeding 10 km the largest earthquakes of the sequence took place on dec 28 m 4 7 jan 12 13 m 4 8 and 5 0 and feb 24 m 5 3 the number of events per day varied it peaked on dec 27 with more than 260 events and more than 200 events were recorded on jan 13 both of which corresponded to the days of large earthquakes the relation of large to small events given by the b value of the magnitude frequency distribution log n a bm is typical of volcanic sequences b 1 7 and much larger than the equivalent for tectonic environments the rate of decay of the number of aftershocks of each large earthquake is proportional to t p with p increasing from 0 63 to 1 08 as the eruption progressed in time initial low values of p indicate a slow stress release in the region larger absolute values of p are comparable with tectonic environments and might be indicators of the last stages of the eruption process the total seismic energy release is 9 6 10 19 ergs about five orders of magnitude less than the estimated thermal energy the spatial distribution of earthquakes suggests that the sources of stress change associated with the eruption are located under and possibly to the south of the main crater of the lonquimay volcano and that the evacuation channels of magma occupied a zone of weakness in the region of the new crater

feldspar thermometry in ultrahigh temperature metamorphic rocks evidence of crustal metamorphism attaining 1100 c in the archean napier complex east antarctica ultrahigh metamorphic temperatures attained in the mid to lower crust have been assessed by examining the mineral chemistry of ternary feldspars with relatively coarse exsolution lamellae from the archean napier complex east antarctica chemical compositions of re integrated perthitic mesoperthitic and antiperthitic feldspars are calculated from the modal proportions and the chemical analyses of host and lamellar domains formed through exsolution based on ternary feldspar solvus models re integrated compositions of feldspars from a variety of rock types yield the minimum equilibrium temperatures ranging from 1000 to 1110 c 0 8 gpa these data confirm the suggestion that the regional thermal conditions of the napier complex reached or exceeded 1100 c as feldspar is one of the common constituents of the crustal rocks this approach could be applicable to a wide variety of rocks in which feldspar represents exsolution textures

smnd ages of archaean metavolcanics of the dharwar craton south india abstract well constrained sm nd arrays of whole rocks are reported for the first time from three important stratigraphic units of the dharwar volcano sedimentary sequence of south india if interpreted as isochrons these arrays will correspond to the following ages and initial nd ratios relative to chur 2 911 0 049 ga and 0 20 0 40 for the kalasapura mafic basal metavolcanics of the bababudan greenstone belt 2 848 0 070 ga and 0 88 0 82 for the santaveri formation comprising mafic to felsic metavolcanics overlying the kalasapura rocks and 2 747 0 015 ga and 1 72 0 10 for the ingaldhal mafic felsic metavolcanic suite of the chitradurga greenstone belt the possibility that these sm nd arrays are mixing lines between unrelated components depleted and enriched respectively in light rare earth elements has been discussed leading to the conclusion that the ages closely correspond to their time of eruption the older suites from the bababudan belt from a mantle source of chur like composition the younger suite from the chitradurga belt from one with a prior history of lree depletion

characteristics of seismic waves composing hawaiian volcanic tremor and gas piston events observed by a near source array a correlation method specifically designed for describing the characteristics of a complex wave field is applied to volcanic tremor and gas piston events recorded by a semicircular array of geos instruments set at the foot of the puu oo crater on the east rift of kilauea volcano hawaii the spatial patterns of correlation coefficients obtained as functions of frequency for the three components of motion over the entire array are similar for gas piston events and tremor and clearly depict dispersive waves propagating across the array from the direction of puu oo the wave fields are composed of comparable amounts of rayleigh and love waves propagating with similar and extremely slow phase velocities ranging from 700 m s at 2 hz to 300 m s at 8 hz the highly cracked solidified lava flow on which the array was deployed and subjacent structure of alternating lava and ash layers formed during repeated eruptions of puu oo since 1983 appear to be responsible for the low velocities observed the results from puu oo stand in sharp contrast to those obtained in an experiment conducted in 1976 on the partially solidified lava lake of kilauea iki rayleigh waves were not observed in kilauea iki but well developed trains of love waves were seen to propagate there with velocities twice as high as those observed near puu oo these differences in the propagation characteristics of surface waves at the two sites may be attributed to the presence of a soft horizontal layer of molten rock in kilauea iki which may have lowered the phase velocity of rayleigh waves more drastically than that of love waves resulting in severe scattering of the rayleigh wave mode on the other hand the thin superficial pahoehoe flow under our array at puu oo may have favored the development of vertical columnar joints more extensively at this location than at kilauea iki which may have reduced the shear moduli controlling the love wave mode the average phase velocities in the frequency band from 2 to 5 hz found at puu oo are roughly similar to those determined for tremor at klyuchevskoy volcano kamchatka but the frequency dependence appears much stronger at puu oo

precursory seismicity of the 1994 eruption of popocatepetl volcano central mexico popocatepetl volcano is located in the central mexican volcanic belt within a densely populated region inhabited by over 20 million people the eruptive history of this volcano indicates that it is capable of producing a wide range of eruptions including plinian events after nearly 70 years of quiescence popocatepetl reawakened in december 21 1994 the eruptive activity has continued up until the date of this submission and has been characterized by a succession of lava dome growth and destruction episodes similar to events that have apparently been typical for popocatepetl since the fourteenth century in this regime the episodes of effusive and moderately explosive activity alternate with long periods of almost total quiescence in this paper we analyze five years of volcano tectonic seismicity preceding the initial eruption of the current episode the evolution of the v t seismicity shows four distinct stages which we interpret in terms of the internal processes which precede an eruption after a long period of quiescence the thermal effects of a magma intrusion at depth the fracturing related to the slow development of magma related fluid pathways the concentration of stress causing a protracted acceleration of this process and a final relaxation or redistribution of the stress shortly before the initial eruption are reflected in the rates of v t seismic energy release a hindsight analysis of this activity shows that the acceleration of the seismicity in the third stage asymptotically forecast the time of the eruption the total seismic energy release needed to produce an eruption after a long period of quiescence is related to the volume of rock that must be fractured so imposing a characteristic threshold limit for polygenetic volcanoes limit that was reached by popocatepetl before the eruption

f rich phlogopite stability in ultra high temperature metapelites from the napier complex east antarctica fluorine rich phlogopite f content up to 8 wt f f oh 0 9 in ultra high temperature metapelitic granulites from the napier complex east antarctica is associated with aluminous orthopyroxene osumilite sapphirine garnet and quartz textural relationships imply that some of the phlogopite is of primary origin and stable under ultra high temperature conditions this is in accord with recent experimental evidence on the stability of f rich phlogopite because the f rich phlogopite also occurs as rounded inclusions in aluminous orthopyroxene al 2 o 3 up to 12 8 wt sapphirine osumilite and garnet it is inferred that the ultra high temperature mineral assemblages which includes these minerals formed during prograde partial melting reactions at the expense of phlogopite at a depth of less than 30 km thus the coarse grained peak metamorphic assemblages formed below 9 kbar and there is no evidence the rocks underwent any significant degree of decompression during or soon after peak metamorphic conditions the phlogopite breakdown reactions we suggest on the basis of textural arguments differ from those postulated from experiments on f free systems

first seismic record for intra arc strike slip tectonics along the liquine ofqui fault zone at the obliquely convergent plate margin of the southern andes a temporal seismic network recorded local seismicity along a 130 km long segment of the transpressional dextral strike slip liquine ofqui fault zone lofz in southern chile seventy five shallow crustal events with magnitudes up to m tief w 3 8 and depths shallower than 25 km were observed in an 11 month period mainly occurring in different clusters those clusters are spatially related to the lofz to the volcanoes chaiten michinmahuida and corcovado and to active faulting on secondary faults further activity along the lofz is indicated by individual events located in direct vicinity of the surface expression of the lofz focal mechanisms were calculated using deviatoric moment tensor inversion of body wave amplitude spectra which mostly yield strike slip mechanisms indicating a ne sw direction of the p axis for the lofz at this latitude the seismic activity reveals the present day activity of the fault zone the recent m tief w 6 2 event near puerto aysen southern chile at 45 4 s on april 21 2007 shows that the lofz is also capable of producing large magnitude earthquakes and therefore imposing significant seismic hazard to this region

features of volcanic tremors on mt etna sicily during the march august 1983 eruption the seismic analysis of the volcanic tremors preceding and accompanying the etnean eruption of march august 1983 has shown a significant variation in the spectral content before the beginning of the eruption the tremor peaks at 1 4 and 1 6 hz which might be associated with the feeding pipes of the ne crater schicket al 1982a being the dominant feature of the spectra

synchronous degassing patterns of the neighbouring volcanoes llaima and villarrica in south central chile the influence of tidal forces the neighbouring volcanoes villarrica and llaima are two of the most active volcanoes in chile and both currently degas continuously we present a semi continuous time series of so2 fluxes for villarrica and llaima volcanoes the time series was obtained using five scanning mini differential optical absorption spectrometers mini doas uv spectrometers over 6 months 13 february to 31 july 2010 and is based on 6 829 scans for villarrica and 7 165 scans for llaima statistical analyses of the so2 flux time series reveal a periodicity of degassing maxima about every 7 days and further a conspicuous synchronicity of the degassing maxima and minima between the two volcanoes intra day variations in so2 fluxes also show a striking correlation between villarrica and llaima all these patterns correlate well with the trend of the modelled solid earth tide curves where the 7 day degassing maxima correspond with both the fortnightly tidal maxima and minima the intra day degassing peaks mostly correlate well with the periods of maximum deformation rates during the diurnal tidal cycle and further with semidiurnal minima in atmospheric pressure a phenomenon we refer to as the tidal pump as there is little time lag between the tidal action and the changes in degassing rates we infer that degassing at both volcanoes is controlled by conduit convection involving physical separation between gas and magma at comparatively shallow levels variations in daily degassing rates were up to a factor of ca 12 and 10 for villarrica and llaima respectively without any noticeable changes in the periodicity we thus suggest that the described cyclic variations must be taken into account for all comparable volcanoes when using gas monitoring as a tool for volcanic hazard mitigation

seismic hazard of volcanic activity abstract seismic activity is a common feature of volcanic eruptions the majority of volcanic earthquakes are small their magnitudes do not exceed 2 or 3 at the same time significant moderate size and large volcanic earthquakes may also occur the study of 28 significant m w 4 5 earthquakes associated with volcanic eruptions of 20th century allowed us to formulate the following results about seismic hazard of volcanic activity 1 during the 20th century only three large m w 7 0 earthquakes directly associated with volcanic eruptions in the world were recorded 2 the maximum magnitude m w was estimated to be 5 4 for earthquakes related to central eruptions 7 0 for caldera collapse 5 9 for central eruptions accompanied by flank and or fissure eruptions 7 1 for flank and or fissure eruptions without central eruptions and 5 9 for submarine eruptions for seismicity just before the eruption the maximum magnitude of earthquakes was estimated to be m w 7 1 for seismicity at the initial stage of eruption m w 7 0 for paroxysmal stage of eruption m w 5 6 and for final stage of eruption m w 6 1 3 it was shown that the recurrence time of eruptions of the same type of volcano associated with significant m w 4 5 earthquakes was more than 100 years for 86 of events studied

source mechanism of volcanic earthquakes a description and classification of seismic sources found in active zones of volcanism are given the main sources of seismic wave energy are caldera collapse shear fractures with comparatively low spectral corner frequencies shallow gas explosions hydraulic pressure transients and non stationary magma flew

age of younger tonalitic magmatism and granulitic metamorphism in the south indian transition zone krishnagiri area comparison with older peninsular gneisses from the gorur hassan area abstract a major episode of continental crust formation associated with granulite facies metamorphism occurred at 2 55 2 51 ga and was related to accretional processes of juvenile crust dating of tonalitic trondhjemitic granitic gneisses and charnockites from the krishnagiri area of south india indicates that magmatic protoliths are 2550 2530 5 ma as shown by both u pb and 207pb 206pb single zircon methods monazite ages indicate high temperatures of cooling corresponding to conditions close to granulite facies metamorphism at 2510 10 ma these data provide precise time constraints and sr nd isotopes confirm the existence of late tonalitic granodioritic juvenile gneisses at 2550 ma pb single zircon ages from the older peninsular gneisses gorur hassan area are in agreement with some previous sr ages and range between 3200 20 and 3328 10 ma these gneisses were derived from a 3 3 3 5 ga mantle source as indicated from nd isotopes they did not participate significantly in the genesis of the 2 55 ga juvenile magmas all these data together with previous work suggest that the 2 51 ga granulite facies metamorphism occurred near the contact of the ancient peninsular gneisses and the 2 55 2 52 ga juvenile tonalitic trondhjemitic terranes during synaccretional processes subduction mantle plume rb sr biotite ages between 2060 and 2340 ma indicate late cooling probably related to the dextral major east west shearing which displaced the 2 5 ga juvenile terranes toward the west

structural changes of volcanic tremor at stromboli volcano abstract the occurrence of a tectonic event sufficiently close to a volcano and or sufficiently energetic can trigger a change in its eruptive activity examples include ambrym vanuatu teide spain tungurahua ecuador and villarrica chile of course the possibility that an earthquake can even trigger a new eruption has serious implications in terms of hazard however no serious attempt has been carried out so far to formalize the identification of these structural changes with a statistical approach in this work a statistical approach is applied to identify structural changes in volcanic tremor recorded at stromboli from april to july 2006 we considered different fluctuation type tests using the open source package strucchange written in r language zeileis a leisch f hornik k kleiber c 2002 strucchange an r package for testing for structural change in linear regression models j stat softw 7 2 1 38 stromboli is a particularly interesting case study whilst previous work falsaperla s alparone s spampinato s 2003 seismic features of the june 1999 tectonic swarms in the stromboli volcano region italy j volcanol geotherm res 125 1 2 121 136 had suggested that tectonic events have no influence on volcanic activity most recent results carniel r tarraga m 2006 can tectonic events change volcanic tremor at stromboli geophys res lett 33 l20321 doi 10 1029 2006gl027690 suggest otherwise the aim of this work is to confirm by use of a statistical method the presence of changes in the recorded tremor related to the occurrence of volcano tectonic events on stromboli as pointed out by carniel and tarraga carniel r tarraga m 2006 can tectonic events change volcanic tremor at stromboli geophys res lett 33 l20321 doi 10 1029 2006gl027690 we found that there was at least one variation in the time series associated to every earthquake even in the cases for which previous analyses could not recognize any variation carniel r tarraga m 2006 can tectonic events change volcanic tremor at stromboli geophys res lett 33 l20321 doi 10 1029 2006gl027690

differences of precursory seismic energy release for the 2007 effusive dome forming and 2014 plinian eruptions at kelud volcano indonesia abstract early warnings of the timing style and size of volcanic eruptions made on the basis of seismic monitoring are important for mitigation of the hazards associated with volcanic eruptions we calculated the rates of seismic energy release at kelud volcano indonesia preceding both the 2007 effusive lava dome eruption and the 2014 plinian eruption for the 2007 eruption there was first a step wise increase in the rate of release of seismic energy followed by a gradual decrease until the eruption for the 2014 eruption the rate of energy release was almost constant until 10 days before the eruption then gradually increased until there was a dramatic acceleration during the last day before the eruption the total seismic energy released by the 2007 and 2014 eruptions were 3 10 8 j and 2 2 10 9 j respectively the relative difference between the ejected volumes of the 2007 and 2014 eruptions is roughly equivalent to that of the total seismic energy released preceding the eruptions we conducted several trials of the material failure forecast method ffm applying it to the square root of the rate of seismic energy released to assess its usefulness for predicting the timing of eruptions the predicted onset of the 2007 eruption was one day earlier than the actual eruption and the seismic energy release preceding the actual eruption did not increase dramatically as suggested by the ffm model several trials of ffm for the 2014 eruption predicted the onset of the eruption to be three days to two weeks later than the actual eruption even as the end time of the ffm time window approaches several hours to 10 min before the actual eruption onset the predicted eruption onset is still 3 h later than the actual onset thus the results of our ffm modeling did not show the method to be useful for predicting eruption times for kelud volcano the differences of the ffm modeling results for the 2007 and 2014 eruptions likely reflect the differences in the rate of energy release immediately before the two eruptions a deceleration before the 2007 eruption and an acceleration before the 2014 eruption these differences may reflect differences in precursory processes for effusive lava dome and plinian eruptions

monochromatic infrasonic tremor driven by persistent degassing and convection at villarrica volcano chile 1 infrasonic data collected at villarrica volcano chile in march 2009 show a sustained continuous infrasonic oscillation tremor with a monochromatic low frequency content at 0 75 hz this tremor is extremely stable in time both at the summit and at a distal 4 km small aperture array infrasonic tremor is characterized by discrete high amplitude bursts with a cyclic recurrence time of 40 s and is well correlated 0 93 with seismic tremor these new data are compared with previous datasets collected in 2002 and 2004 during different levels of activity all data show the same persistent infrasonic tremor and have the same strong correlation with seismic tremor the stability and correlation of infrasonic and seismic tremor indicate the existence of a sustained and continuous process which we suggest is related to the gravity driven bubble column dynamics responsible for conduit convection

a late holocene explosive mafic eruption of villarrica volcano southern andes the chaimilla deposit abstract villarrica chile is one of the most active volcanoes in south america having erupted about 60 times in the last 460 years although its historical eruptive activity has been mainly effusive and weakly explosive it had strong explosive behaviour in postglacial times chaimilla

geochemical variations in andean basaltic and silicic lavas from the villarrica lanin volcanic chain 39 5 s an evaluation of source heterogeneity fractional crystallization and crustal assimilation at 39 5 s in the southern volcanic zone of the andes three pleistocene recent stratovolcanoes villarrica quetrupillan and lanin form a trend perpendicular to the strike of the andes 275 to 325 km from the peru chile trench basalts from villarrica and lanin are geochemically distinct the latter have higher incompatible element abundances and la sm but lower ba la and alkali metal la ratios these differences are consistent with our previously proposed models involving a a west to east decrease in an alkali metal rich high ba la slab derived component which causes an across strike decrease in degree of melting or b a west to east increase in the contamination of subduction related magma by enriched subcontinental lithospheric mantle silicic and mafic lavas from the stratovolcanoes have overlapping sr nd and o isotopic ratios silicic lavas also have geochemical differences that parallel those of their associated basalts e g rhyolite from villarrica has lower la sm and incompatible element contents than high sio2 andesite from lanin at each volcano the most silicic lavas can be modelled by closed system fractional crystallization while andesites are best explained by magma mixing apparently crustal contamination was not an important process in deriving the evolved lavas basaltic flows from small scoria cones 20 35 km from villarrica volcano have high incompatible element contents and low ba la like lanin basalts but trend to higher k rb 356 855 and lower 87sr 86sr 0 70361 0 70400 than basalts from either stratovolcano however all basalts have similar nd pb and o isotope ratios the best explanation for the unique features of the cones is that the sources of svz magmas e g slab derived fluids or melts of the subcontinental lithospheric mantle have varying alkali metal and radiogenic sr contents these heterogeneities are not manifested in stratovolcano basalts because of extensive subcrustal pooling and mixing this model is preferable to one involving crustal contamination because it can account for variable sr isotope ratios and uniform nd and pb isotope ratios among the basalts and the divergence of the cones from across strike geochemical trends defined by the stratovolcanoes

analysis of the unrest of active volcanoes using variations of the base level noise seismic spectrum we present an easy to use robust tool for monitoring the unrest of active volcanoes the base level noise seismic spectrum blnss the volcano s base level activity can easily be determined by continuous monitoring of the minimum amplitude of all spectral components and thus indicates the volcanic activity which is always present on fixed segment waveforms the selection of comparative time intervals also eliminates transitory signals related to weather environmental conditions thus avoiding the misinterpretations in terms of predominant frequencies found in short term analysis the application to data recorded at the soufriere hills llaima and villarrica volcanoes demonstrates the methodology s ability to clearly distinguish volcanic background activity from signs of re activation and provides information related to the behavior and dynamics of volcanic unrest

geochemistry and geochronology of proterozoic tholeiite dykes of east antarctica evidence for mantle metasomatism two episodes of tholeiite dyke emplacement have been identified in archaean high grade metamorphics of the napier complex in enderby land middle proterozoic amundsen dykes are typical continental tholeiites and most of the chemical variation in individual suites can be explained in terms of different degrees of partial melting and low pressure crystal fractionation group i amundsen tholeiites were derived from a relatively homogeneous source region 1 190 200 m y ago whereas that of the group ii amundsen tholeiites was chemically and isotopically heterogeneous group ii dykes have various degrees of enrichment in incompatible elements and commonly show normalised trace element abundance patterns with negative nb anomalies these features imply variable metasomatism of the source region by a volatile rich fluid phase rather than a melt of any observed igneous composition enriched in k rb ba th and possibly la and ce early proterozoic 2 350 48 m y tholeiites were emplaced at considerable depths in the crust during the waning stages of granulite facies metamorphism and include a high mg suite of possible komatiitic affinity ranging in composition from hypersthene rich tholeiite norite to quartz rich tholeiite they tend to have higher ratios of highly to moderately incompatible elements e g k zr k ce and larger nb anomalies i e higher k nb compared with middle proterozoic tholeiites suggesting derivation from more enriched source regions isotopic data are not compatible with significant crustal contamination but constrain source metasomatism to a time immediately before emplacement metasomatism of the source region of the much younger group i tholeiites may have been contemporaneous with that of the high mg suite

the fault nature of the ms 5 4 volcanic earthquake preceding the 1996 subglacial eruption of grimsvotn volcano iceland abstract the seismic activity preceding and accompanying the september 30 1996 subglacial eruption of the grimsvotn volcano iceland developed in three stages 1 the first stage first 19 h included the main shock of magnitude m s 5 4 and its aftershocks along the northern slope of the bardarbunga volcano situated about 20 km nw from grimsvotn 2 seismic foci during the next 17 h marked a line connecting two volcanoes bardarbunga and grimsvotn this stage culminated in the opening of a fissure and the beginning of eruption 3 the third stage was observed during the eruption midnight of september 30 october 7 and included continuous seismic activity along the northern slope of the bardarbunga volcano as well as more western distributed epicenters which together had clustered the ring fault epicentral zone a finite fault broadband teleseismic p waveform inversion was applied to the main shock of september 29 the inversion showed that the rupture had developed downdip from the hypocenter in about 3 s and the main asperity was ruptured at depths between 4 and 6 km a comparison with the deep distribution of aftershocks showed that their hypocenters were situated above the destroyed asperities at the depths between 0 and 4 km these space time seismic patterns and the results of the finite fault inversion may be interpreted in the following way there was a magma chamber under bardarbunga volcano covered by the strong rocks or asperities the main shock of september 29 broke the asperity and formed a path for magma transport then a fissure was formed connecting the opened magma chamber with the feeding structures of grimsvotn volcano and magma was injected laterally to the site of eruption the continuous seismic activity during the third period was related to the collapse of rocks around the released parts of the magma chamber the role of the m s 5 4 earthquake in this sequence was decisive

response of zircon u pb isotopes and whole rock geochemistry to co2 fluid induced granulite facies metamorphism kabbaldurga karnataka south india the arrested prograde amphibolite to granulite facies transition at kabbaldurga south india overprints archacan amphibolite facies nebulitic gneisses and the late archaean closepet granite previous studies have shown that this facies transition was controlled by a channelled influx of a dehydrating fluid assumed to be co2 at 750 c and 5 5 kbar confining pressure the effect of this type of prograde transition on zircon u pb isotopic systematics and whole rock geochemistry has been studied using 1 kg amphibolite facies transitional and granulite facies domains from a single block of gneiss the zircon populations from all three domains have essentially similar morphology and u pb systematics this similarity shows that at the conditions under which the prograde granulite facies transition took place via fluid influx the zircon u pb systematics were not disturbed by the process using the pooled data from all three domains it is concluded that the protolith of the gneiss formed at 2965 4 ma 2 and that zircons also grew during an anatectic event common to all domains at 2528 5 ma the granulite facies metamorphism has not been dated directly due to the lack of response to the zircon u pb isotopic systematies to it however field and petrographic criteria dictate that its maximum age is 2528 5 ma the age of the anatectic event common to each domain in the gneiss block which was overprinted during the granulite facies event for most major and trace elements consistent enrichment or depletion trends associated with the transition to granulite facies cannot be identified with confidence however the granulite facies portion is lree light rare earth element enriched and h heavy ree depleted compared with the amphibolite facies domain and the transitional domain is at intermediate values the isotopic and geochemical evidence presented supports the conclusion that the granulite facies charnockitic rocks at kabbaldurga were not formed by removal of an anatectic melt but that they formed later by simple metamorphic overprint of amphibolite facies rocks

volcanic tremors and shocks associated with eruptions at etna sicily september 1980 abstract three strong ash eruptions superimposed on an otherwise rather quiet state of volcanic activity took place from the northeast crater of etna during september 1980 the eruptions lasted only a few hours and were associated with an increase in the amplitudes of volcanic tremors by a factor of 10 compared with the mean value of the preceding months special emphasis in the tremor analysis was given to the eruption of september 26 1980 the time function of the amplitude envelope of the tremors follows a mathematical function which resembles the behaviour of a mechanical oscillator with a resonant period of about 300 s a detailed spectral analysis of the tremors before during and after the eruption reveals factors which seem to be associated with the ascent and descent of the tremor sources in the magma columns the turbulent eruptive magma flow apparently is concentrated in a few dykes and pipes their eigenvibrations during an eruption are observed as spectral peaks of small bandwidth superimposed on the smoother spectrum without a volcanic eruption an analysis of seismicity shows a maximum in august with epicenters clustering along a nw se direction

chemical th u total pb dating by electron microprobe analysis of monazite xenotime and zircon from the archean napier complex east antarctica evidence for ultra high temperature metamorphism at 2400 ma abstract the chemical th u total pb isochron method chime of dating was carried out on monazite xenotime zircon and polycrase in six samples of ultra high temperature uht granulites and one of pegmatite from five localities in the napier complex enderby land east antarctica despite the chronological heterogeneity in many grains the chime ages overall show strong evidence for a major event near 2420 ma analyzed monazite and xenotime grains except monazite from mt riiser larsen have a narrow range of chime ages 2412 42 ma from beaver island and 2429 36 2421 18 and 2431 22 ma from reference peak these ages are indistinguishable from chime ages on zircon 2436 17 and 2420 20 ma and on central older domains of monazite 2404 54 ma from mt riiser larsen and on a zircon rim 2430 15 ma from mt cronus we conclude that the ca 2420 ma ages relate to the uht metamorphism but we do not exclude the possibility that lead loss has lowered the ages by some 50 ma this interpretation is consistent with a preponderance of ages obtained by other methods on the napier complex particularly the ca 2475 25 ma age for a generation of pegmatites coeval with the uht event and containing the uht mineral assemblage beryllian sapphirine khmaralite quartz events prior to 2500 ma and after 2420 ma have also left their imprint on the chime ages for example a 3646 ma chime age suggests that a zircon core is inherited whereas ca 2200 and 2000 ma chime ages in zoned monazite could be due to further lead loss during post uht activity the much younger chime age of 1094 67 ma for monazite from a pegmatite at zircon point casey bay confirms 1000 1100 ma lead loss ages reported for this region and could result from fluid activity in an outlier of rayner activity near the boundary between the rayner and napier complexes approximately 2500 ma ages have been reported from granulite facies but not uht rocks in the madras and nilgiri blocks in south india these blocks and the napier complex could have constituted a single structural unit by late archean time

volcanic tremors at etna a model for hydraulic origin spectral analysis of volcanic tremors at etna reveals 2 characteristic features 1 the escaping vapor and gas streams drive the magma in random turbulent motion generating a seismic wave emission according toa f n exp m f k wherea amplitude f frequency n m k parameters 2 sudden transients in the boundary conditions of the piping system generate hydraulic pressure pulses which in the seismogram appear as wave packages their monochromatic frequency content suggests that their origin is associated with strong resonance phenomena it is conclusive that volcanic eruptions may be distinguished and classified according to different eigenfrequencies of the fissure and pipe network involved in the volcanic activity furthermore positions of active dykes may be traced following the amplitude distributions associated with pronounced spectral lines in the tremor spectra

seismic triggering by rectified diffusion in geothermal systems widespread seismicity was triggered by the june 28 1992 landers california earthquake at a rate which was maximum immediately after passage of the exciting seismic waves rectified diffusion of vapor from hydrothermal liquids and magma into bubbles oscillating in an earthquake can increase the local pore pressure to seismically significant levels within the duration of the earthquake in a hydrothermal system modeled as a two component h 2o co 2 fluid in porous rock the pressure initially increases linearly with time the rate of pressure buildup depends sensitively on the mean bubble radius and is large for small bubbles the diffusion induced pressure is relaxed by percolation and resorption of vapor into the liquid solution the induced seismicity itself also relieves stress values of parameters used in the present calculations give results consistent with observations of triggered seismicity at long valley caldera after the landers earthquake for one representative condition at 250 c and 5 6 km depth oscillating strain acting on 10 m diameter bubbles increases pore pressure at the rate of 151 pa s resulting in a pressure increase of 12 kpa in the 80 s duration of the landers earthquake the elevated pressure induced by a single 26 m diameter cloud of bubbles in saturated rock relaxes by percolation through soil of 0 2 mdarcy permeability in 53 6 hours observations of earthquake swarms at other locations suggest that self induced buildup of pore pressure by rectified diffusion can provide a positive feedback mechanism for amplifying seismicity

mid to late archaean 3 3 2 5 ga tonalitic crustal formation and high grade metamorphism at mt riiser larsen napier complex east antarctica abstract the archaean napier complex consists of felsic orthogneiss mafic granulite and a variety of paragneisses metamorphosed in the granulite facies in part at ultrahigh temperature uht 900 c orthopyroxene bearing felsic orthogneiss of tonalitic granodioritic composition the highly recrystallized archaean tonalite trondhjemite granodiorite ttg crust is a major constituent of the complex especially at mt riiser larsen which is located within the uht region sensitive high resolution ion microprobe shrimp u pb analyses of zircon grains from three different layers of orthopyroxene bearing felsic orthogneiss were carried out two of the analyzed orthogneiss samples yield 3270 12 ma and 3267 5 ma concordia ages from igneous zircon cores another sample shows slightly scattered and discordant ages 3350 ma with a concordia age of 3073 12 ma these data suggest that the initial ttg crust of the mt riiser larsen was formed at 3270 ma and perhaps at 3070 ma these ages are considerably younger than the formation of tonalitic crust at mt sones gage ridge and at fyfe hills 3840 3770 ma but older than that at proclamation island 2980 ma and several other areas at 2840 ma two of the orthogneiss samples yield subordinate 2850 2790 ma zircon concordia ages that are considered to result from a high grade metamorphic event which may also relate to 2830 ma granitic magmatism recorded in the area zircon grains from the three analyzed orthogneiss samples yield an intense 2520 2450 ma age cluster that probably reflect the uht metamorphic event in the area the ca 3300 ma age for ttg magmatism and ca 2500 ma age for high grade metamorphism are comparable to the events in south india which is thought by some authors to have been continuous with the napier complex from the mid proterozoic until gondwana break up

volcanology 2020 how will thermal remote sensing of volcanic surface activity evolve over the next decade abstract volcanological remote sensing spans numerous techniques wavelength regions data collection strategies targets and applications attempting to foresee and predict the growth vectors in this broad and rapidly developing field is therefore exceedingly difficult however we attempted to make such predictions at both the american geophysical union agu meeting session entitled volcanology 2010 how will the science and practice of volcanology change in the coming decade held in december 2000 and the follow up session 10 years later looking backward and forward volcanology in 2010 and 2020 in this summary paper we assess how well we did with our predictions for specific facets of volcano remote sensing in 2000 the advances made over the most recent decade and attempt a new look ahead to the next decade in completing this review we only consider the subset of the field focused on thermal infrared remote sensing of surface activity using ground based and space based technology and the subsequent research results this review keeps to the original scope of both agu presentations and therefore does not address the entire field of volcanological remote sensing which uses technologies in other wavelength regions e g ultraviolet radar etc or the study of volcanic processes other than the those associated with surface mostly effusive activity therefore we do not consider remote sensing of ash gas plumes for example in 2000 we had looked forward to a golden age in volcanological remote sensing with a variety of new orbital missions both planned and recently launched in addition exciting field based sensors such as hand held thermal cameras were also becoming available and being quickly adopted by volcanologists for both monitoring and research applications all of our predictions in 2000 came true but at a pace far quicker than we predicted relative to the 2000 2010 timeframe the coming decade will see far fewer new orbital instruments with direct applications to volcanology however ground based technologies and applications will continue to proliferate and unforeseen technology promises many exciting possibilities that will advance volcano thermal monitoring and science far beyond what we can currently envision

a model to describe precursory material failure phenomena applications to short term forecasting at colima volcano mexico some volcanoes exhibit at times accelerating strain and seismicity before eruptions different authors have used this behavior to predict eruptions and to develop materials science models here a linear kelvin voigt viscoelastic model is proposed to describe the observed behavior this model also has applications to other failure phenomena such as landslides the strain rate of a variety of materials under constant stress after an instantaneous elastic response is found to be well described by a general relaxation law dot varepsilon left t right b over 1 st where b and s are parameters depending on the material and its creep state whether the creep regime is primary or tertiary depends upon the sign of s s 0 corresponds to pseudoviscous flow the creep behavior of the viscoelastic body is analyzed for different load histories it is found that the body has an exponential distribution of retardation frequencies that may or may not converge depending on the sign of s according to the model tertiary creep implies material degradation and a critical weakening of the medium leading to a runaway growth of the strain and seismic energy release rates if tertiary creep is detected time of failure predictions may be done from field data through determination of two model parameters for varying loads the model response compare well with reported examples of pre eruptive volcano behavior and with reported results of landslide experiments the model is tested with the july 1994 in hindsight and november 1998 in foresight colima volcano eruptions although this method provides some guidance in estimating the time over which accelerating volcanic precursors may end in an eruption it is emphasized that eruptions may fail to occur at the estimated time or may not occur at all on the other hand eruptions may not be preceded by such a behavior

four zircon ages from one rock the history of a 3930 ma old granulite from mount sones enderby land antarctica ion microprobe u th pb analyses of zircons from a granulite grade orthogneiss from mount sones enderby land antarctica record the ages of four principal events in the history of the gneiss three of which already have been recognized through previous isotopic dating of other samples the structure of the zircons indicates at least four different stages of growth the several zircon ages were obtained by grouping the analyses according to the stage they represented in the observed stratigraphic succession of growth and thereby defining separate u pb discordance patterns for each stage the stratigraphically oldest zircon rare discrete cores is indistinguishable in age from the most common euhedrally zoned zircon both crystallized when the tonalitic precursor of the orthogneiss was emplaced into the crust 3927 10 ma ago making the orthogneiss currently the oldest known terrestrial rock the outer parts of most grains and some whole grains recrystallized at 2948 31 17 ma during or immediately after possibly 100 ma of high granulite grade metamorphism the recrystallized zircon was isotopically disturbed by tectonism associated with reactivation of the southern margin of the napier complex at 1000 ma in the intervening time at 2479 23 ma the cores and zoned zircon suffered a major isotopic disturbance involving movement of radiogenic pb which left most of the crystals with radiogenic pb deficiencies but produced local radiogenic pb excesses in others a new generation of zircon characterized by very high th u and low u grew at that time that event deformation and possibly a minor rise in temperature produced widespread perturbations of other isotopic systems throughout the napier complex

unsupported radiogenic pb in zircon a cause of anomalously high pb pb u pb and th pb ages ion microprobe u th pb isotopic analyses of zircons from a granodioritic orthogneiss from the napier complex mount sones enderby land antarctica have identified an unambiguous example of unsupported radiogenic pb in a 3 950 ma old crystal at one 40 m spot on the crystal an unusually large heterogeneity in pb content was found the concentration of radiogenic pb ranging from 5 to 50 percent higher than could have been generated in 3 950 ma by radioactive decay of the co existing u and th this relative excess of radiogenic pb is attributed to pb gain rather than to u and th loss because first the pb content varied by more than the u or th contents and secondly changes in the pb u pb th and pb isotopic composition correlated directly with changes in the pb concentration the individual 207pb 206pb apparent ages ranged from 4 000 ma to 4 145 ma all greater than the inferred age of the crystal a correlation between 207pb 206pb and pb u shows that the pb excess has not resulted from recent pb movement the spot apparently gained radiogenic pb about 2 500 ma ago at the same time as the majority of the other zircons in the rock suffered substantial pb loss the pb movement occurred in response to a discrete geologic event reverse discordance is a phenomenon that must be considered when interpreting zircon u pb ages especially 207pb 206pb ages of single crystals or portions of crystals

using a cross correlation technique to refine the accuracy of the failure forecast method application to soufriere hills volcano montserrat prior to many volcanic eruptions an acceleration in seismicity has been observed suggesting the potential for this as a forecasting tool the failure forecast method ffm relates an accelerating precursor to the timing of failure by an empirical power law with failure being defined in this context as the onset of an eruption previous applications of the ffm have used a wide variety of accelerating time series often generating questionable forecasts with large misfits between data and the forecast as well as the generation of a number of different forecasts from the same data series here we show an alternative approach applying the ffm in combination with a cross correlation technique which identifies seismicity from a single active source mechanism and location at depth isolating a single system at depth avoids additional uncertainties introduced by averaging data over a number of different accelerating phenomena and consequently reduces the misfit between the data and the forecast similar seismic waveforms were identified in the precursory accelerating seismicity to dome collapses at soufriere hills volcano montserrat in june 1997 july 2003 and february 2010 these events were specifically chosen since they represent a spectrum of collapse scenarios at this volcano the cross correlation technique generates a five fold increase in the number of seismic events which could be identified from continuous seismic data rather than using triggered data thus providing a more holistic understanding of the ongoing seismicity at the time the use of similar seismicity as a forecasting tool for collapses in 1997 and 2003 greatly improved the forecasted timing of the dome collapse as well as improving the confidence in the forecast thereby outperforming the classical application of the ffm we suggest that focusing on a single active seismic system at depth allows a more accurate forecast of some of the major dome collapses from the ongoing eruption at soufriere hills volcano and provides a simple addition to the well used methodology of the ffm

villarrica volcano chile characteristics of the volcanic tremor and forecasting of small explosions by means of a material failure method villarrica volcano chile 39 42 s 71 93 w is one of the most active volcanoes in the andes it shows persistent strombolian activity in a small lava lake situated at the bottom of the summit crater from september to december 2000 the volcano exhibited anomalous behaviour after a regional tectonic seismic event on 22 september the eruption of a small volume of lava apparently plugged the conduit this situation then lasted for ten days on 5 and 8 october a series of explosions reopened the system this eruption behaviour has allowed us to study the evolution of the characteristic tremor in the open and closed states of the conduit a shift in the peak frequency from 1 hz open to 2 hz closed the explosions related to the opening of the conduit were forecasted by means of a material failure method

u pb geochronology from tonagh island east antarctica implications for the timing of ultra high temperature metamorphism of the napier complex abstract ion microprobe u pb zircon geochronology of an orthopyroxene bearing felsic orthogneiss from central tonagh island enderby land east antarctica provides insight into the chronological metamorphic evolution of the archaean napier complex the details of which have been the source of debate for over two decades the orthogneiss crystallised at 2626 28 ma predating peak ultra high temperature uht metamorphism and development of an intense regional s1 gneissosity two subsequent episodes of zircon growth resetting can be identified a minor period of zircon growth occurred at 2546 13 ma the regional significance and geological nature of which is unclear this was followed by an episode of abundant zircon growth as mantles on 2626 ma cores and as anhedral grains partly characterised by high th u 1 2 at 2450 2480 ma this age coincides with both lower and upper concordia intercept ages from other u pb zircon studies and several rb sr and sm nd whole rock isochron ages from the napier complex we conclude that uht metamorphism occurred at 2450 2480 ma and find no compelling evidence that uht occurred much earlier as has been postulated the zircon u pb data from this study also indicates a lower intercept age of 500 ma which coincides with the emplacement of early palaeozoic pegmatite swarms and synchronous infiltration of aqueous fluids into the southwestern regions of the napier complex

using volcanic tremor for eruption forecasting at white island volcano whakaari new zealand abstract eruption forecasting is a challenging task because of the inherent complexity of volcanic systems despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions the material failure forecast method ffm is one of the very few techniques that can provide a forecast time for an eruption however the method requires testing and automation before being used as a real time eruption forecasting tool at a volcano we developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by real time seismic amplitude measurement rsam at one station and optimised this algorithm for the period august 2011 january 2014 which comprises the recent unrest period at white island volcano whakaari new zealand a detailed residual analysis was paramount to select the most appropriate model explaining the rsam time evolutions in a hindsight simulation four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0 21 which is 37 times higher than the probability of having an eruption on any day during the same period 0 0057 moreover the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view whereas the rsam time evolutions preceding these four eruptions have a similar goodness of fit with the ffm their spectral characteristics are different the duration amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions we propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes this hindsight exercise can be useful for future real time implementation of the ffm at white island a similar methodology could also be tested at other volcanoes even if only a limited network is available

multi chronometric dating of the huarong granitoids from the middle yangtze craton implications for the tectonic evolution of eastern china abstract the tectonic thermal history of the huarong granitoids is used to clarify the tectonic evolution of the middle yangtze craton and eastern china the huarong granitoids include the xiaomoshan and taohuashan plutons and form a northeast trending belt in the middle yangtze craton eastern china multi method geochronology reveals the thermal history of the huarong granitoids from their emplacement to near surface conditions la icp ms u pb zircon dating suggests granitoid emplacement at ca 117 ma a cluster of zircons at ca 127 ma is likely inherited from an earlier intrusion phase the granitoids formed in an extensional setting which was almost certainly associated with pacific plate subduction in the late early cretaceous biotite 40ar 39ar ages at ca 96 ma record regional post magmatic cooling apatite fission track aft and apatite u th sm he ahe thermochronology and thermal history modeling indicate cooling in three stages enhanced cooling at 96 60 ma is interpreted to reflect cooling from the late early cretaceous regional magmatism tertiary ca 60 20 ma very slow cooling stagnation or even re heating suggests insignificant exhumation and peneplanation this interval correlates with late cretaceous eocene red bed deposition and rifting throughout eastern china causes for speculative accelerated cooling after ca 20 ma may be a far field effect of the india asia collision or pacific plate subduction this study demonstrates that the middle yangtze craton was involved in the cretaceous extension widely occurring in the eastern china continent and suggests that the formation of the jianghan basin a major depocenter in the middle yangtze craton may have initiated at ca 120 ma