controlling factors on earthquake swarms associated with magmatic intrusions constraints from iceland abstract the currently two most important surveying tools in volcano monitoring are observations of seismicity and surface deformation magma migration within the earth s crust is frequently associated with seismic activity often occurring as distinct earthquake swarms understanding the exact nature and significance of these swarms is important when evaluating volcanic crisis situations there seems however to be no general correlation between the amount of seismic energy release and the rate and volume of magma on the move which may complicate an immediate risk evaluation it has previously been shown that stressing rate appears as the controlling factor on the occurrence of seismicity during intrusion however in this paper we emphasize that this is only true under specific circumstances other factors influence the evolution and resulting seismic energy release and each intrusion scenario needs to be evaluated separately three icelandic cases where seismic swarms have been confirmed through deformation measurements to be related to magmatic movements were selected we show how the relationship between volume change and resulting seismicity varies greatly between cases and suggest that in a general approach the most important factor governing the level of seismic energy release is the background stress state tectonic setting regional stresses and tectonic history are therefore all of great importance when evaluating a magmatically induced seismic crisis the stressing rate only plays the dominant role when either a stress in the intruded area is close to the yield strength before intrusion or possibly b when the intrusion is extraordinarily voluminous and rapid

processes dominating macro fabric generation in periglacial colluvium abstract mass wasting processes in a periglacial environment are considered to result from a combination of frost creep and gelifluction the relative importance of these processes is often difficult to determine but appears to be related to factors such as slope angle soil moisture content soil texture and vegetation cover further the importance of any one of these factors can vary from year to year thereby making long term predictions of slope stability or reconstructions of behaviour history difficult this study uses two dimensional macro fabric analysis as a recorder of the dominant mode of mass wasting on a slope clast trend and plunge data were collected from 68 sites at eagle summit alaska and examined in two separate dimensions the plane of the slope to represent the stress field driven by gravity and in a vertical plane trending down the slope to represent the stress field created by frost heaving pressures circular correlation tests indicate the importance of the downslope stress field on clast position in the plane of the slope in the vertical plane clast plunge varies according to slope on gentle slopes clasts tend to be steeply dipping on moderate slopes they are parallel to the plane of the slope and on steep slopes they are imbricated these observations correspond to modeled experiments of slope deformation under periglacial conditions and suggest that at the scale of the slope mass wasting processes are influenced by varying intensities of frost heave and gravity transfer that are conditioned by slope angle

satellite radar interferometry 1993 1999 suggests deep accumulation of magma near the crust mantle boundary at the krafla volcanic system iceland 1 deep magma accumulation near the crust mantle boundary 21 km depth at the krafla volcanic system is suggested from insar observations a best fit model derived from four interferograms covering 1993 1999 comprises an opening dike representing plate spreading and post rifting deformation and two mogi sources a mogi source deflating at a rate of 0 3 106 m3 yr coincides with the shallow krafla magma chamber while a deeper inflating mogi source further north at 21 km depth inflates at a rate of 26 106 m3 yr the inflating source is at or near the crust mantle boundary as identified by seismic studies and is interpreted as accumulating magma

geometrical aspects of sorted patterned ground in recurrently frozen soil a model for sorted patterned ground shows that some types arise from density driven rayleigh free convection that occurs during thawing of water saturated recurrently frozen soils the regularly spaced convection cells result in an uneven melting of the underlying ice front frost action causes stones to be upthrusted and to form in a pattern on the ground surface that mirrors the corrugation in the underlying ice front the implications of the water circulation direction in the cells on the sorting process are considered

slowness anomalies from two dense seismic arrays at deception island volcano antarctica in this article we analyze the data collected by two short period seismic arrays deployed at deception volcano southern shetland islands antarctica the field survey was conducted during the 1998 1999 austral summer and was aimed at a quantitative assessment of the complex wave fields associated with the magmatic and hydrothermal activity of the volcano the two arrays had apertures of 320 m and 240 m and were separated by a distance of about 3 km during the experiment the arrays recorded several regional earthquakes related to the dynamics of the brans field strait and adjoining areas and local volcano tectonic earthquakes seismograms of earthquakes recorded at regional distances reveal a marked difference in the ap parent velocities measured at the two array sites we investigate the causes and implications of these anomalies by first comparing the effectiveness of estimating the horizontal slowness vector using three different techniques the multiple signal classification music approach the zero lag cross correlation zlc method and plane wave fitting to p wave arrival times while each technique provides the same horizontal slowness vector as the most likely estimates the plane wave fitting is associated with the most robust definition of measurement uncertainties we then investigate the dispersive properties of rayleigh waves in the 1 8 hz frequency band at both arrays and invert the two dispersion curves for a shallow velocity structure the results indicate a marked difference in the seismic velocities for the shallower 200 m beneath the two sites this may be reconciled with the observed wave vector anomalies by assuming the existence of a sharp lateral velocity heterogeneity the effect of which would be to bend downward rays impinging at the northernmost array the reliability of this hypothesis is verified by computing finite difference wave fronts in a 2d heterogeneous medium based on the morpho structural char acteristics of the volcano the inferred velocity discontinuity maybe associated with the ring fracture system bordering the collapsed caldera structure that extends over the inner part of the island

influence of clast axial ratio on macrofabric strength in periglacial colluvium samples of fabric data collected from periglacial solifluction lobes in central alaska show a systematic positive relation between clast axial ratio and fabric strength samples composed of clasts with low a b axial ratios have relatively low fabric strength restricting sampling to clasts with axial ratios of 1 5 1 or higher increases fabric strength and decreases its variability to enhance comparability between fabric studies and the utility of fabric interpretation sampling should be restricted to clasts with relatively large 1 5 1 axial ratios

magmatic inflation at a dormant stratovolcano 1996 1998 activity at mount peulik volcano alaska revealed by satellite radar interferometry 1 a series of ers radar interferograms that collectively span the time interval from july 1992 to august 2000 reveal that a presumed magma body located 6 6 0 5 km beneath the southwest flank of the mount peulik volcano inflated 0 051 0 005 km3 between october 1996 and september 1998 peulik has been active only twice during historical time in 1814 and 1852 and the volcano was otherwise quiescent during the 1990s the inflation episode spanned at least several months because separate interferograms show that the associated ground deformation was progressive the average inflation rate of the magma body was 0 003 km3 month from october 1996 to september 1997 peaked at 0 005 km3 month from 26 june to 9 october 1997 and dropped to 0 001 km3 month from october 1997 to september 1998 an intense earthquake swarm including three ml 4 8 5 2 events began on 8 may 1998 near becharof lake 30 km northwest of peulik more than 400 earthquakes with a cumulative moment of 7 15 1017 n m were recorded in the area through 19 october 1998 although the inflation and earthquake swarm occurred at about the same time the static stress changes that we calculated in the epicentral area due to inflation beneath peulik appear too small to provide a causal link the 1996 1998 inflation episode at peulik confirms that satellite radar interferometry can be used to detect magma accumulation beneath dormant volcanoes at least several months before other signs of unrest are apparent this application represents a first step toward understanding the eruption cycle at peulik and other stratovolcanoes with characteristically long repose periods

seismic tomography model reveals mantle magma sources of recent volcanic activity at el hierro island canary islands spain summary we present a 3 d model of p and s velocities beneath el hierro island constructed using the traveltime data of more than 13 000 local earthquakes recorded by the instituto geogr afico nacional ign spain in the period from 2011 july to 2012 september the velocity models were performed using the lotos code for iterative passive source tomography the results of inversion were thoroughly verified using different resolution and robustness tests the results reveal that the majority of the onshore area of el hierro is associated with a high velocity anomaly observed down to 10 12 km depth this anomaly is interpreted as the accumulation of solid igneous rocks erupted during the last 1 myr and intrusive magmatic bodies below this high velocity pattern we observe a low velocity anomaly interpreted as a batch of magma coming from the mantle located beneath el hierro the boundary between the low and highvelocityanomaliesismarkedbyaprominentseismicitycluster thoughttorepresentanomalous stresses due to the interaction of the batch of magma with crust material the areas of recent eruptions orchilla and la restinga are associated with low velocity anomalies surrounding the main high velocity block these eruptions took place around the island where the crust is much weaker than the onshore area and where the melted material cannot penetrate these results put constraints on the geological model that could explain the origin of the volcanism in oceanic islands such as in the canaries which is not yet clearly understood

precursory diffuse co2 and h2s emission signatures of the 2011 2012 el hierro submarine eruption canary islands 1 on october 12 2011 a submarine eruption began 2 km off the coast of la restinga south of el hierro island co2 and h2s soil efflux were continuously measured during the period of volcanic unrest by using the accumulation chamber method at two different geochemical stations hie01 and hie07 recorded co2 and h2s effluxes showed precursory signals that preceded the submarine eruption beginning in late august the co2 efflux time series started increasing at a relatively constant rate over one month reaching a maximum of 19 gm 2d 1 one week before the onset of the submarine volcanic eruption the h2s efflux time series at hie07 showed a pulse in h2s emission just one day before the initiation of the submarine eruption reaching peak values of 42 mg m 2 d 1 10 times the average h2s efflux recorded during the observation period since co2 and h2s effluxes are strongly influenced by external factors we applied a multiple regression analysis to remove their contribution a statistical analysis showed that the long term trend of the filtered data is well correlated with the seismic energy we find that these geochemical stations are important monitoring sites for evaluating the volcanic activity of el hierro and that they demonstrate the potential of applying continuous monitoring of soil co2 and h2s efflux to improve and optimize the detection of early warning signals of future volcanic unrest episodes at el hierro continuous diffuse degassing studies would likely prove useful for monitoring other volcanoes during unrest episodes

seismic hydraulic fracture migration originated by successive deep magma pulses the 2011 2013 seismic series associated to the volcanic activity of el hierro island in this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of el hierro canary islands during 2011 2013 we estimated temporal variations of the gutenberg richter b value throughout the period of analysis and performed high precision relocations of the preeruptive and syneruptive seismicity using a realistic 3 d velocity model our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust these magma pulses occurred within a small and well defined volume resulting in the emplacement of fresh magma along the crust mantle boundary underneath el hierro we analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust our results suggest that very high earthquake rates underneath el hierro represent the response of a stable lower crust to stress perturbations with pulsatory character linked to the injection of magma from the mantle magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms the absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity had diffusive character we conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the moho we suggest within this framework that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement

leakage of magmatic hydrothermal volatiles from a crater bottom formed by a submarine eruption in 1989 at teishi knoll japan abstract a submarine eruption occurred off the izu peninsula of japan on 13 july 1989 forming teishi knoll which has a diameter of 450 m and a height of ca 10 m above the surrounding 90 100 m deep seafloor immediately after the eruption intense gas release was observed from two vents in the crater the gas bubbling gradually decreased and apparently ceased in 1990 given that no survey has been undertaken to examine volatile release from the crater of teishi knoll we collected seawater samples at three different sites from just above the crater bottom on 17 july 2012 in order to detect signs of magmatic volatile release seawater samples from the crater bottom have dissolved ch 4 contents and 13 c values higher than those of shallower 50 100 m deep seawater samples total inorganic carbon contents from the bottom seawater samples are also higher and 13 c and 14 c values lower than those of shallower seawater samples these data indicate the addition of minor ch 4 and co 2 of hydrothermal or magmatic origin to the bottom seawater from the crater 3 he 4 he ratios and total organic carbon data are also consistent with the leakage of magmatic fluids the most prominent ch 4 and co 2 anomalies were observed at the site located closest to one of the bubbling gas sites of the 1989 eruption as such volcanic gas emissions still continue today at extremely low levels 23 years after eruption of this monogenetic volcano the monitoring of ultra trace amounts of chemical components in seawater is a prospective method to monitor temporal changes in magmatic activity at such submarine volcanoes

glacial and periglacial geomorphology and its paleoclimatological significance in three north ethiopian mountains including a detailed geomorphological map abstract geomorphological investigations and detailed mapping of past and present peri glacial landforms are required in order to understand the impact of climatic anomalies the ethiopian highlands show a great variety in past and contemporary climate and therefore in the occurrence of glacial and periglacial landforms however only a few mountain areas have been studied and detailed geomorphological understanding is lacking in order to allow a fine reconstruction of the impact of the past glacial cycle on the geomorphology vegetation complexes and temperature anomalies a detailed geomorphological map of three mountain areas mt ferrah amba 12 51 n 39 29 e mt lib amba 12 04 n 39 22 and mt abuna yosef 12 08 n 39 11 e was produced in all three study areas inactive solifluction lobes presumably from the last glacial maximum lgm were found in the highest study area of abuna yosef three sites were discovered bearing morainic material from small late pleistocene glaciers these marginal glaciers occurred below the modeled snowline and existed because of local topo climatic conditions evidence of such pleistocene avalanche fed glaciers in ethiopia and africa has not been produced earlier current frost action is limited to frost cracks and small scale patterned ground phenomena the depression of the altitudinal belts of periglacial and glacial processes during the last cold period was assessed through periglacial and glacial landform mapping and comparisons with data from other mountain areas taking latitude into account the depression of glacial and periglacial belts of approximately 600 m implies a temperature drop around 6 c in the last cold period this cooling is in line with temperature depressions elsewhere in east africa during the lgm this study serves as a case study for all the intermediate mountains 3500 4200 m of the north ethiopian highlands

a double seismic antenna experiment at teide volcano existence of local seismicity and lack of evidences of volcanic tremor data analyzed in the present work correspond to a 40 days field experiment carried out in teide volcano canary islands spain with two short period small aperture dense seismic antennas in 1994 the objective of this experiment was to detect analyze and locate the local seismicity we analyzed also the background seismic noise to investigate the possible presence of volcanic tremor from a set of 76 events we selected 21 of them in base of their good signal to noise ratio and their possibility to locate their seismic source by using the seismic antennas a visual classification based on the s p time and seismogram shape has permitted to establish three groups of events local seismicity s p time between 3 and 5 s very local earthquakes s p time smaller than 3 s and artificial explosions these earthquakes have been located by applying the zero lag crosscorrelation technique and the inverse ray tracing procedure those earthquakes that were recorded simultaneously by both seismic antennas were also located by intersecting both back azimuths the analysis of the seismicity has revealed that the amount of seismicity in teide volcano is moderate this seismicity could be distributed in three main areas inside the caldera edifice below the teide pico viejo complex in the eastern border of the caldera edifice and offshore of the island at present this activity is the only indicator of the volcano dynamics the analysis of the back ground seismic noise has revealed that at frequencies lower than 2 hz the oceanic load signal is predominant over other signals even over local earthquakes with a magnitude of 2 0 due to this although if in the teide area were present a weak volcanic tremor or other volcanic signals with predominant peaks below 2 hz to observe them would be a very difficult task q 2000 elsevier science b v all rights reserved

the abundance and relative volatility of refractory trace elements in allende ca al rich inclusions implications for chemical and physical processes in the solar nebula abstract we have determined the relative volatility of lithophile refractory trace elements lrte in the solar nebula by first calculating 50 condensation temperatures for 26 lrte oxides assuming ideal solid solution in perovskite and where appropriate in hibonite and melilite the measured abundances of 25 lrte and six siderophile refractory trace elements in 97 group i 11 111 and v allende ca al rich inclusions cai s and in ultra refractory inclusions then are used to empirically modify lrte and refractory siderophile volatility sequences that are based on condensation temperatures alone sc is significantly less depleted in group ii allende cai s than are other lrte e g zr hf y that also have very high oxide condensation temperatures ba sr and eu three moderately volatile lrte are significantly more enriched in ca rich group ii and group iii allende cai s than they are in spinel rich varieties of these inclusions we explain these observations and several others by invoking dust fractionation s and crystal chemical and diffusion effects during the formation of allende cai s that overprinted volatility based on solid gas reactions alone for example we show that hibonite probably was not the carrier of the super refractory lithophile component that is missing from group ii allende inclusions anomalous hf depletions relative to zr and y that are common in group i iii and v allende cai s can be partly explained if anders and ebihara 38 overestimated the cosmic abundance of hf by approximately 10

ion microprobe studies of efremovka cais i magnesium isotope composition five coarse grained ca al rich refractory inclusions cais from the efremovka cv3 chondrite are analysed for their magnesium isotopic composition using an ion microprobe the analysed inclusions represent the three common cai types a b1 and b2 data for magnesium isotopic composition of the major mineral phases melilite spinel fassaite and anorthite in these inclusions are used to determine intrinsic magnesium isotopic fractionations and to identify nonlinear effect in 26mg due to the decay of extinct 26al the magnesium isotopic mass fractionation f mg generally favours the heavier isotopes as is expected in the case of coarse grained cais the f mg data for two of the inclusions however show contrasting trends sympathetic behaviour found in both isotopic and petrographic data in one type b1 inclusion suggests that the parent melt of this inclusion experienced a short duration volatilization event prior to crystallization the isotopic data also suggest possible presence of relict spinel in this inclusion that constrains the cooling rate of the parent melt to 70 c h during crystallization hot and dense nebular settings that allow for such fast cooling can only be localized in nature the pristine nature of the efremovka cais as evident from the lack of secondary alteration products in them is well supported by the isotopic data three of the five inclusions yield well behaved mg al isochrons with 26al27al 0 close to the canonical value of 5 10 5 the anorthite data for another inclusion suggest minor disturbance in the isotopic systematics and yield a nearly well behaved isochron with a slightly lower value of 26al27al 0 data for melilite and anorthite in the fifth inclusion define apparent isochrons that suggest partial re equilibration and exchange of magnesium isotopes between these two phases the efremovka data are suggestive of a relatively homogeneous distribution of 26al in the solar nebula

efremovka 101 1 a cai with ultrarefractory ree patterns and enormous enrichments of sc zr and y in fassaite and perovskite inclusion 101 1 from the cv3 carbonaceous chondrite efremovka is a compact type a ca al rich inclusion cai highly enriched in ultrarefractory ur oxides it is the first complete cai with a ur rare earth element ree pattern found in a cv3 chondrite the inclusion is petrographically complex and was formed in a multistage process it consists of several lithologically unrelated units the core contains abundant y and zr perovskite sc and zr rich fassaite and metallic feni enclosed in melilite all mineral species except spinel in all lithological units exhibit the same basic ur ree pattern four different populations of perovskites are distinguished by different y zr ratios a few of the perovskites have y zr ratios similar to those obtained from crystal liquid fractionation experiments perovskites from the other three populations have either chondritic lower than chondritic y zr ratios or extremely low zr contents ca isotopic ratios differ among three perovskites from different populations demonstrating a variety of sources and formational processes most fassaites crystallized in situ through reaction between the cai liquid and preexisting perovskites this process induced redistribution of zr y sc and v between perovskite and fassaite thus overprinting the original abundances in perovskite fassaite reaction rims around feni metals are also encountered they are enriched in v which was gained from the metal through oxidation of v in metal during fassaite crystallization the relative abundances of zr y and sc in perovskites are complementary to the abundances of these elements in sc and zr fassaite indicating subsolidus partitioning of these elements between the two phases perovskites are enriched in y and depleted in sc and zr in comparison to fassaites the core contains two complete captured cais several sinuous fragments and fine grained polygonal refractory fragments an assemblage of andradite wollastonite hedenbergite and pure metallic iron is encoun tered as enclaves in the interior of some sinuous fragments metallic fe and wollastonite formed by reduction of preexisting andradite and hedenbergite nebular alteration products upon inclusion in the highly reduced cai melt numerous spinel clusters and framboids with varying v2o3 and cr2o3 concentrations are enclosed in individual melilite crystals in the host cai and captured cais the rim sequence of the host consists of six layers from the inside outward a feo poor spinel b sc bearing fassaite c al diopside d al and ca bearing olivine e pure diopside and f ca poor olivine like the constituents of the cai core all mineral layers of the rim sequence except spinel have the same ur ree pattern however the total ree abundances decrease systematically by 1 order of magnitude from layer 2 to layer 6 this feature strongly suggests formation of the rim sequence by successive condensation from a unique reservoir enriched in ur elements and excludes formation by flash heating petrography mineral chemistry ree refractory lithophile element abundances and ca isotopic compositions demonstrate the complex multistage formation history of a cai that on the surface looks like a regular type a inclusion copyright 2002 elsevier science ltd

on the interpretation of subglacial till fabric abstract the modal distribution of stone long axis fabrics and their respective eigenvalues can be used to infer the genesis of subglacial till in this paper we offer a two axis diagram that compares fabric modality to fabric isotropy s3 s1 and addresses the problem of eigenvectors falling between the modes of some well developed till fabrics with low eigenvalues our simple five fold scheme of modality categories includes 1 unimodal clusters 2 spread unimodal 3 bimodal clusters 4 spread bimodal and 5 polymodal to girdle like fabrics and requires the analyst to study equal area lower hemisphere schmidt plots of the fabric data after assigning the fabric to a morality category isotropy is calculated and both results are plotted on the graph whic helps to separate two main fields of subglacial till 1 lodgement and subglacial meltout tills and 2 deformation fill on the basis of selected published fabrics from tills at modern glaciers as well as our own pleistocene till data lodgement and subglacial meltout tills tend to have unimodal or bimodal fabrics in contrast deformation tills and tills that experienced multiple processes tend to have polymodal to girdle like fabrics some overlap occurs between fields be cause of the complex nature of till formation i e because pure end member till facies are rare and most tills are hybrids we strongly recommend that schmidt plots be visually analyzed and used in conjunction with eigenvalues when studying till however fabric data alone is not enough multiple criteria including structural lithologic and stone morphologic data from the till must also be considered before drawing conclusions on till genesis furthermore if eigenvectors fall between fabric modes then they cannot be used to indicate former ice movement directions finally our new modality isotropy diagram may have wider applications

construction of an oceanic island insights from the el hierro canary islands 2011 2012 submarine volcanic eruption eight consecutive swath bathymetry data sets were obtained to monitor the submarine eruption that occurred from 10 october 2011 to 5 march 2012 south of el hierro island in the canary islands an increase in seismic activity since july 2011 preceded the onset of the eruption which was marked by seismic tremor and stained waters the first bathymetry 15 d after the eruption started depicts a cone topping at 205 m depth growing on a preexisting valley recurrent mapping shows changes in the morphology and depth of the cone allowing us to identify collapses and calculate eruptive volumes and rates which peaked at 12 7 10 6 m 3 d 1 of non dense rock equivalent ndre on 29 30 october the final cone consists of at least four vents along a north northwest south southeast lineation with the shallowest summit at 89 m depth the total accumulated volume was 329 10 6 ndre m 3 of which one third formed the cone similar cones have been identified on the submerged flanks of the island with volumes ranging from 6 to 1000 10 6 ndre m 3 as in many other volcanic islands large scale landslides play an important role in the evolution of el hierro a giant flank landslide el golfo 13 134 ka 150 180 km 3 mobilized in a single event a volume equivalent to 450 550 eruptions of the size of the reported one showing striking differences in the construction and destruction rates of the island this study is relevant for future monitoring programs and geohazard assessment of new submarine eruptions

precise determination of the relative wave propagation parameters of similar events using a small aperture seismic array 1 we propose a method to determine accurately the relative wave propagation parameters apparent slowness and propagation azimuth of a cluster of seismic events with similar waveforms recorded on a seismic array this relative slowness estimate relse method is based on precise measurements of the delays among arrivals of different earthquakes to each of the array receivers delays are determined using interpolations of the cross correlation functions of the earthquake waveforms accurate relative slowness vectors are estimated using a least squares fit of the observed delays to the delays corresponding to the arrivals of plane wave fronts we tested the method using both synthetics and real data in order to understand its resolution capabilities in presence of seismic noise and to assess the uncertainty regions associated with the slowness vector estimates from these analyses we establish a procedure to determine the 90 uncertainty regions associated with the estimates of relative slowness vectors as an example of application of the relse method we analyzed a multiplet composed of 16 similar earthquakes recorded during the 1999 seismic crisis at deception island volcano antarctica using a conventional slowness estimate method produces virtually the same result for every earthquake because of the large uncertainties alternatively using the relse method reduces the uncertainties of the estimates and allows to resolve the detailed distribution of relative apparent slowness vectors our results show that the slowness vectors are aligned within a narrow north south trending band which represents a clue toward the features of the source region and or source distribution we repeated the procedure using different earthquakes as master events the estimated distribution of slowness vectors is similar in every case which demonstrates that our results are independent of the choice of reference event index terms 7299 seismology general or miscellaneous 7203 seismology body wave propagation 7215 seismology earthquake parameters 7230 seismology seismicity and seismotectonics 7280 seismology volcano seismology 8419 keywords seismic arrays slowness vectors multiplet analysis deception island volcano

array analysis using circular wave front geometry an application to locate the nearby seismo volcanic source summary the zero lag cross correlation technique used for array analysis in the hypothesis of plane waves has been modified to allow the wave front to be circular synthetic tests have been performed to check the capability of the method which returns the input test data when the source array distances are not greater than two or three times the array aperture for this distance range the method furnishes an estimate of the apparent velocity and the epicentral coordinates of the source for more distant sources the method becomes equivalent to that based on the planar wave approximation which gives an estimate of the backazimuth to the source and the apparent velocity the method has been applied to seismic data recorded at the active volcano located at deception island antarctica 35 volcanic long period events occurring in a small swarm were selected results show that the epicentres are close to the array between 0 4 and 2 km and aligned in a sw direction in agreement with one of the main directions of the fracture system of deception volcano

seismovolcanic signals at deception island volcano antarctica wave field analysis and source modeling the seismovolcanic signals associated with the volcanic activity of deception island antarctica recorded during three antarctic summers 1994 1995 1995 1996 and 1996 1997 are analyzed using a dense small aperture 500 m seismic array the visual and spectral classification of the seismic events shows the existence of long period and hybrid isolated seismic events and of low frequency quasi monochromatic and spasmodic continuous tremors all spectra have the highest amplitudes in the frequency band between 1 and 4 hz while hybrids and spasmodic tremors have also significant amplitudes in the high frequency band 4 10 hz the array analysis indicates that almost all the well correlated low frequency signals share similar array parameters slowness and back azimuth and have the same source area close to the array site the polarization analysis shows that phases at high frequency are mostly composed of p waves and those phases dominated by low frequencies can be interpreted as surface waves no clear shear waves are evidenced from the energy evaluation we have found that the reduced displacement values for surface and body waves are confined in a narrow interval volcano tectonic seismicity is located close to the array at a depth shallower than 1 km the wave field properties of the seismovolcanic signals allow us to assume a unique source model a shallow resonating fluid filled crack system at a depth of some hundreds of meters all of the seismic activity is interpreted as the response of a reasonably stable stationary geothermal process the differences observed in the back azimuth between low and high frequencies are a near field effect a few episodes of the degassification process in an open conduit were observed and modeled with a simple organ pipe

hibonite bearing microspherules a new type of refractory inclusions with large isotopic anomalies reported are petrographic descriptions major and trace element chemistry and mg ca and ti isotopic compositions of a new class of refractory inclusions that consist of spherules composed of hibonite and a silicate glass the distinctive features of these inclusions are excesses in 48ca and 50ti in both glass and hibonite and 26mg depletions relative to terrestrial isotopic compositions three spherules have been examined and analyzed one from the lance co3 meteorite and two from the murchison cm2 meteorite lance 3413 1 31 la3413 1 31 and murchison 7 228 mur7 228 have euhedral to subhedral hibonite crystals enclosed within glass murchison 7 753 mur7 753 has a rounded hibonite core with several small inclusions of perovskite a small fragment of glass is attached to the hibonite and an fe silicate rim is imperfectly preserved around the grain la3413 1 31 has a group ii ree pattern mur7 228 a refractory pattern with depletions in the relatively volatile elements sr ba nb v and eu and mur7 753 a pattern characterized by the prior removal of an ultrarefractory component and overall fractionation of all rees the partitioning of the lrees between hibonite and glass in mur7 228 is consistent with equilibrium hibonite liquid partition coefficients previously determined la3413 1 31 shows much less partitioning while mur7 753 shows no evidence for partitioning and preserves an unequilibrated refractory component highly enriched in gd all spherules have initial magnesium depleted in 26mg by around 3 relative to terrestrial mg but only mur7 228 shows evidence for in situ decay of 26al with an initial 26al27al of 1 7 0 7 10 5 both hibonite and glass in all three spherules show excesses of 48ca and 50ti ranging up to 40 and 20 respectively relative to terrestrial ca and ti spherules such as these are rare and the only other occurrence is in the unique chondrite alh85085 the hibonite in the spherules shows similarities to isotopically anomalous hibonite crystal fragments placs but it is unlikely that the spherules formed by remelting of placs the precursors include isotopically anomalous ca ti carriers but also isotopically normal refractory components that probably formed as condensates the spherules formed by melting of these precursors under disequilibrium conditions and rapid cooling after hibonite crystallization these inclusions must have formed early prior to the dilution of isotopic anomalies by mixing processes and in an area characterized by excesses of 48ca and 50ti depletions of 26mg and lack of 26al

seismicity patterns prior to the 2011 el hierro eruption abstract the first fully monitored volcanic eruption in the canary islands started on 10 october 2011 2 km south of the island of el hierro this submarine eruption was preceded by various precursory signals the most evident of which were the seismic series that started in july 2011 consisting of almost 10 000 low magnitude earthquakes located by manual picking this seismicity revealed a 20 km horizontal migration from the north of the island to the south at depths of between 10 and 17 km the deeper events occurring further south we applied a relative location algorithm hypodd to improve hypocentral locations the resulting distribution is more compact slightly shallower and reveals a clearer difference in depths from north to south tests performed to check the reliability of the results gave maximum uncertainties of 400 m in the relocations furthermore new features were found including the origin of the seismicity in the center of the island and the presence of two alternating seismogenic zones in the north of the island during the first month of activity online material figures of waveforms from cross correlation data statistics stereogram of ray parameters ray tracing tests and table of hypodd relocations

spatial and temporal variations of diffuse co2 degassing at el hierro volcanic system relation to the 2011 2012 submarine eruption we report herein the results of extensive diffuse co2 emission surveys performed on el hierro island in the period 1998 2012 more than 17 000 measurements of the diffuse co2 efflux were carried out most of them during the volcanic unrest period that started in july 2011 two significant precursory signals based on geochemical and geodetical studies suggest that a magma intrusion processes might have started before 2011 in el hierro island during the preeruptive and eruptive periods the time series of the diffuse co2 emission released by the whole island experienced two significant increases the first started almost 2 weeks before the onset of the submarine eruption reflecting a clear geochemical anomaly in co2 emission most likely due to increasing release of deep seated magmatic gases to the surface the second one between 24 october and 27 november 2011 started before the most energetic seismic events of the volcanic seismic unrest the data presented here demonstrate that combined continuous monitoring studies and discrete surveys of diffuse co2 emission provide important information to optimize the early warning system in volcano monitoring programs and to monitor the evolution of an ongoing volcanic eruption even though it is a submarine eruption

magma storage and migration associated with the 2011 2012 el hierro eruption implications for crustal magmatic systems at oceanic island volcanoes 1 starting in july 2011 anomalous seismicity was observed at el hierro island a young oceanic island volcano on 12 october 2011 the process led to the beginning of a submarine nw se fissural eruption at 15 km from the initial earthquake loci indicative of significant lateral magma migration here we conduct a multifrequency multisensor interferometric analysis of spaceborne radar images acquired using three different satellite systems radarsat 2 envisat and cosmo skymed constellation of small satellites for mediterranean basin observation the data fully captures both the pre eruptive and coeruptive phases elastic modeling of the ground deformation is employed to constrain the dynamics associated with the magmatic activity this study represents the first geodetically constrained active magmatic plumbing system model for any of the canary islands volcanoes and one of the few examples of submarine volcanic activity to date geodetic results reveal two spatially distinct shallow crustal magma reservoirs a deeper central source 9 5 4 0 km and a shallower magma reservoir at the flank of the southern rift 4 5 2 0 km the deeper source was recharged explaining the relatively long basaltic eruption contributing to the observed island wide uplift processes and validating proposed active magma underplating the shallowest source may be an incipient reservoir that facilitates fractional crystallization as observed at other canary islands data from this eruption supports a relationship between the depth of the shallow crustal magmatic systems and the long term magma supply rate and oceanic lithospheric age such a relationship implies that a factor controlling the existence depth of shallow crustal magmatic systems in oceanic island volcanoes is the lithosphere thermomechanical behavior

a calcium aluminum rich inclusion from the essebi cm2 chondrite evidence for captured spinel hibonite spherules and for an ultra refractory rimming sequence abstract an unusual refractory inclusion was discovered in the essebi cm2 chondrite the inclusion has high concentrations of refractory lithophile and siderophile elements with strong enrichments of the most refractory elements lu sc hf in one part of the inclusion the inclusion consists of a melilite rich core partially surrounded by a very refractory rim which in turn is covered by a mantle enriched in si al fe mn cl and s melilite compositions vary from ak 10 26 in the core to ak 0 12 in the rim the core contains several complex framboids consisting of spinel fassaite or spinel hibonite these framboids are probably spherules of the types reported from murchison and were possibly captured by the molten inclusion before it solidified these findings may indicate a genetic link between framboids in cai s and the spinel rich spherules in murchison the rim sequence consists of the following five layers from inside to outside 1 1 hibonite spinel melilite 2 2 hibonite perovskite spinel melilite melilite in this layer is altered to sodalite nepheline calcite 3 3 a hibonite corundum solid solution 4 4 a spinel corundum solid solution as much as 0 1 mole fraction al 2 67 o 4 5 5 sc rich fassaite as much as 6 2 wt sc 2 o 3 spinel al 2 o 3 solid solution al rich diopside pt rich metal crystals occur only in the rim some of these metal crystals contain minor amounts of zr and hf indicating that they formed under reducing conditions the bulk mineral chemistry and texture of the essebi inclusion indicates a complex history involving capture of solid spinel and spinel hibonite spherules similar to the murchison type by a refractory melt droplet solidification of the droplet without obliteration of the spherule textures transportation of the composite object to hotter regions of the solar nebula where the very refractory rim condensed alteration of melilite to sodalite nepheline minor calcite and finally burial in the essebi parent body the cl s bearing mantle probably formed by reactions between the inclusion and liquid and gaseous phases in the parent body

evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of el hierro canary islands spain we report precursory geophysical geodetic and geochemical signatures of a new submarine volcanic activity observed off the western coast of el hierro canary islands submarine manifestation of this activity has been revealed through acoustic imaging of submarine plumes detected on the 20 khz chirp parasound subbottom profiler topas ps18 mounted aboard the spanish rv hesperides on june 28 2012 five distinct filament shaped acoustic plumes emanating from the flanks of mounds have been recognized at water depth between 64 and 88 m on a submarine platform located nw el hierro these plumes were well imaged on topas profiles as flares of high acoustic contrast of impedance within the water column moreover visible plumes composed of white rafts floating on the sea surface and sourcing from the location of the submarine plumes were reported by aerial photographs on july 3 2012 5 days after acoustic plumes were recorded in addition several geophysical and geochemical data support the fact that these submarine vents were preceded by several precursory signatures i a sharp increase of the seismic energy release and the number of daily earthquakes of magnitude 2 5 on june 25 2012 ii significant vertical and horizontal displacements observed at the canary islands gps network nagoya university iter grafcan with uplifts up to 3 cm from june 25 to 26 2012 iii an anomalous increase of the soil gas radon activity from the end of april until the beginning of june reaching peak values of 2 7 kbq m3 on june 3 2012 and iv observed positive peak in the air corrected value of 3he 4he ratio monitored in ground waters 8 5 atmospheric 3he 4he ratio ra at the northwestern el hierro on june 16 2012 combining these submarine and subaerial information we suggest these plumes are the consequence of submarine vents exhaling volcanic gas mixed with fine ash as consequence of an event of rapid rise of volatile rich magma beneath the nw submarine ridge of el hierro these precursory signals have revealed important to improve and optimize the detection of early warning signals of volcanic unrest episodes at el hierro

crystal chemical effects on the partitioning of trace elements between mineral and melt an experimental study of melilite with applications to refractory inclusions from carbonaceous chondrites the partitioning behavior of the trace elements be sc ba la ce and tm between melilite and liquid has been determined using stepwise integration of a rayleigh fractionation equation for ion microprobe analyses of synthetic zoned melilite crystals distribution coefficients between melilite and liquid d mel l i were determined over the entire range of melilite spinel crystallization for one bulk composition corresponding to that of an average type b inclusion from the allende c3v carbonaceous chondrite beryllium is incompatible in gehlenitic meliliters e g d mel l b e 0 5 for x ak 0 3 but compatible in akermanitic melilites e g d mel l b e 1 9 for x ak 0 75 barium d mel l b a 0 04 0 05 sc d mel l s c 0 01 0 02 la d mel l l 0 07 0 29 ce d mel l c e 0 05 0 21 and tm d mel l t m 0 03 0 14 are all incompatible in melilites in the range ak25 ak75 variations in d mel l i as a function of x ak are explicable in terms of a simple thermodynamic treatment of trace element partitioning based on crystal chemical considerations characteristic trace element zoning patterns are predicted for early crystallizing melilite from meliliterich type b inclusions for example concentrations of the rees in melilite should continually decrease with increasing degrees of crystallization opposite the behavior normally expected of an incompatible element concentrations of be should rise with increasing degrees of crystallization even when the element is compatible again opposite the behavior normally expected of compatible elements in general zoning patterns of trace elements in melilite from type b inclusions are consistent with those predicted for fractional crystallization from a melt in a closed system trace element zoning patterns in meteoritic melilite crystals constrain the origin and thermal histories of ca al rich inclusions from carbonaceous chondrites

monitoring the volcanic unrest of el hierro canary islands before the onset of the 2011 2012 submarine eruption 1 on 10 october 2011 a submarine volcanic eruption started 2 km south from el hierro island spain since july 2011 a dense multiparametric monitoring network was deployed all over the island by instituto geografico nacional ign by the time the eruption started almost 10000 earthquakes had been located and the deformation analyses showed a maximum deformation of more than 5 cm earthquake migration from the north to the south of the island and acceleration of seismicity are in good correlation with changes in the deformation pattern as well as with some anomalies in geochemical and geomagnetic parameters an earthquake of local magnitude 4 3 at 12 km depth 8 october 2011 and shallower seismicity a day after preceded the onset of the eruption this is the first time that a volcanic eruption is fully monitored in the canary islands data recorded during this unrest episode at el hierro will contribute to understand reawakening of volcanic activity in this region and others of similar characteristics

fabric variability associated with periglacial mass wasting at eagle summit alaska fabric analysis is a frequently applied technique and when used in concert with other tools aids the interpretation of glacigenic and colluvial depositional environments the research presented here focuses on its application to periglacial colluvium using a stratified systematic unaligned sampling framework in order to assess the variation of fabrics generated the range of possible variation in fabric is necessary information for its application to periglacial paleoenvironmental interpretation fabric strength and shape from 68 samples of 50 stones each on a range of microgeomorphic settings across terrain influenced by periglacial mass wasting in central alaska were analyzed in relation to local slope orientation clast characteristics organic mat thickness stone density distance downslope from the divide soil texture and soil moisture principal components analysis pca was used to reduce stone characteristics to three factors multiple regression analyses of the three factors and environmental variables with the fabric strength parameters as dependent variables indicate that stone characteristics particularly size and platyness are the most significant factors determining fabric strength no distinct fabric strength or shape was associated with specific landforms these results raise serious doubts as to the time cost effectiveness of the application of fabric analysis as a paleoenvironmental tool to identify periglacial landforms from their deposits

magma emission rates from shallow submarine eruptions using airborne thermal imaging abstract the effusion rate is the most important parameter to gather when a volcanic eruption occurs because it controls the way in which a lava body grows extends and expands influencing its dimensional properties calculation of lava flow volume from thermal images collected by helicopter surveys has been largely used during the last decade for monitoring subaerial effusive eruptions however due to the depths where volcanic activity occurs monitoring submarine volcanic eruptions is a very difficult task the 2011 2012 submarine volcanic eruption at el hierro canary islands has provided a unique and excellent opportunity to monitor eruptive processes occurring on the seabed the use of a hand held thermal camera during daily helicopter flights allowed us to estimate for the first time the daily and total erupted magma volumes from a submarine eruption the volume of magma emitted during this eruption has been estimated at 300 mm3 giving an average effusion rate of 25 m3 s 1 thermal imagery by helicopter proved to be a fast inexpensive safe and reliable technique of monitoring volcanic eruptions when they occur on the shallow seabed

experimental studies of trace element partitioning in ca al rich compositions anorthite and perovskite using electron probe and ion probe techniques experimental crystal liquid partition coefficients d have been measured in meteoritic ca al rich inclusion cai compositions for mg zr y and rees in anorthite and perovskite partitioning data for ti in anorthite and al in perovskite are also reported where cross comparisons are possible between electron and ion probe data agreement is good concentration variations in anorthite for many elements are beyond what can be explained by fractional crystallization but show well defined interelement correlations which could reflect the temperature dependence of the d values or could result from liquid boundary layers for anorthite our d values for rees are lower and they decrease more rapidly with decreasing ionic radius than most in the literature most of the older ree d patterns for plagioclase in the literature are too flat because of insufficient purity of mineral separates or because of analytical problems new ion probe data for minor and trace elements in anorthite from type b cais permit detailed comparisons with fractional crystallization models based on the measured d values for most comparisons models and observations do not agree for amounts of crystallization less than 90 it is possible that anorthite does not appear until after 95 crystallization compared to about 40 which would be expected from isothermal equilibrium crystallization experiments the lrees are highly compatible elements in perovskite but d values drop sharply for the hrees y and zr d values for rees increase strongly from air to highly reducing conditions as coupled ree ti 3 substitutions become possible model calculations show that ree patterns in igneous perovskites from cais will reflect the d pattern and the models can explain some ree patterns from compact type a cais however there are other sets of trace element data for perovskite in cais that cannot easily be explained by igneous processes

reply to comment from blanco et al 2015 on evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of el hierro canary islands spain by perez et al bull volcanol 2014 76 882 896

pebble orientation on large experimental debris flow deposits abstract replicable pronounced orientation of discoid pebbles 8 mm embedded on surfaces of large 10 m3 experimental debris flow deposits reveals that strongly aligned imbricate fabric can develop rapidly over short distances in mass flows pebble long axes aligned subparallel to deposit margins as well as subparallel to margins of surge waves arrested within the deposits pebble alignment exhibited modes both parallel to a p the primary flow direction intermediate axes dipped preferentially inward from surge wave margins b i orientation repetitive development of margin parallel imbricate fabric distributed across deposit surfaces provides compelling evidence that deposits formed dominantly through progressive incremental accretion rather than through simple en masse emplacement pronounced fabric along deposit and arrested surge wave margins reflects significant grain interaction along flow margins this sedimentological evidence for significant marginal grain interaction complements theoretical analyses iverson 1997 and other experimental data major 1996 iverson 1997 that indicate that resistance along flow margins is an important factor affecting debris flow deposition the fabric on the experimental deposits demonstrates that debris flows can develop strongly imbricate particle orientation that mimics fabric developed during fluvial deposition particle shape and local stress fields appear to have more control over fabric development than does general depositional process other criteria in addition to particle orientation are needed to discriminate mass flow from fluvial gravel deposits and to unravel depositional history

does clast size influence fabric strength abstract clast fabric strength is commonly used as a quantitative tool to determine the depositional history of subglacial tills this paper emphasizes the variance in fabric strength relative to clast size data on 46 clast fabric analyses were sampled from two basal till localities in southeast denmark and another eleven analyses from a basal till locality beyond a glacier in south iceland it is demonstrated that clasts longer than 2 3 cm show a stronger preference for parallel orientation than do shorter clasts this implies that two operators sampling fabric data a few meters apart within the same till unit but selecting clasts longer or shorter than 20 mm may classify the till as two different types of basal till because of differences in clast size alone additionally this study demonstrates considerable variations in fabric strength over short lateral distances within the same basal till bed it is concluded that caution should be exercised in using eigenvalues to infer depositional processes and strain histories in subglacial environments sedimentological criteria other than clast fabric must also be considered before drawing final conclusions on subglacial deposition

ocean noise triggering of rhythmic long period events at deception island volcano 1 we report on swarms of repeating long period lp events with remarkably periodic occurrence at deception island volcano antarctica the lp events show dominant frequencies near 2 hz and characteristic inter event times that range from 10 s to 20 s for individual swarms we observe that lp inter event times are approximate integer multiples of the dominant periods of the oceanic microseism indicating a synchronization of lp activity with the phase of ocean noise we attribute lp periodicity to the coincidence of sustained lp activity in an unstable hydrothermal system and external forcing by ocean noise that introduces periodic pressure variations in volcano fluids we estimate the volumetric strain change generated by the oceanic microseism at the source location and conclude that strain of order 10 7 is sufficient to introduce clear periodicity in the lp sequences and that periodicity increases with increasing strain

diffusive helium emissions as a precursory sign of volcanic unrest significant increases in helium emissions from the soil and 3 he 4 he ratios in groundwater on el hierro island canary islands spain were observed prior to the 2011 2012 submarine eruption off the coast of the island the changes of diffusive helium emissions rate were observed one month prior to the submarine eruption onset 12 october 2011 and the major increase preceded increases in seismic energy release during the volcanic unrest measured 3 he 4 he ratios in groundwaters from a well in el hierro island increased from 2 3 r a to 7 2 r a r a 3 he 4 he ratio in air 1 month prior to the eruption onset and reached a peak of 8 2 r a indicating a dominant magmatic contribution to the dissolved gases in ground waters 3 he 4 he values and diffusive helium emission studies have been extremely important for forecasting the onset of the volcanic unrest and subsequent volcanic eruption an aseismic exsolution of magmatic gases from magma bodies beneath el hierro island through fractures and vertical permeability structures increased the diffusive helium emission rate prior to episodes of seismic energy release associated with the volcanic unrest

self organization of sorted patterned ground striking circular labyrinthine polygonal and striped patterns of stones and soil self organize in many polar and high alpine environments these forms emerge because freeze thaw cycles drive an interplay between two feedback mechanisms first formation of ice lenses in freezing soil sorts stones and soil by displacing soil toward soil rich domains and stones toward stone rich domains second stones are transported along the axis of elongate stone domains which are squeezed and confined as freezing soil domains expand in a numerical model implementing these feedbacks circles labyrinths and islands form when sorting dominates polygonal networks form when stone domain squeezing and confinement dominate and stripes form as hillslope gradient is increased

till fabric patterns and significance particle response to subglacial stress abstract the analysis of particle arrangements within glacial sediments fabric has long been considered to reflect the behaviour of the ice that transported and deposited or deformed the sediment particles can develop specific fabric arrangements as a response to bulk sediment strain driven by effective stress at the bed of a glacier as such fabric analysis has been used to try and understand the complex relationship between glacier and ice sheet dynamics and the geological evidence of former glaciation developments have focused on the use of stereonet patterns and statistical measures vector and eigenvector analysis of clast fabric to infer the process of sediment deposition deformation and consequent ice flow directions and dynamics however as this study identifies fundamental processes of particle orientation march jeffery and taylor rotation mechanisms would suggest more complex explanations than have been previously reported this study reports the results of a detailed field and laboratory investigation of macro scale clast and microfabrics from a till sequence in central scotland the results suggest a systematic behaviour of different particle size fractions which may be interpreted in terms of the strain response of sediment three fabric patterns are identified that illustrate consistent progressively shifting and more complex particle behaviour it is suggested these orientation patterns indicate the degree to which subglacial sediment has undergone strain and the nature of the deforming bed erosional or accretionary it is concluded that this approach may yield fundamental information about the strain conditions underlying different ice masses providing critical data linking glaciological modelling with the sedimentary evidence of glaciation

an ultra refractory inclusion from the ornans carbonaceous chondrite a small refractory inclusion 1 g was found in the ornans carbonaceous chondrite the inclusion is extremely enriched in the most refractory ree lu er ho the more volatile light ree having more than two orders of magnitude lower concentrations refractory metals are fractionated in a similar way high abundances of the most refractory metals os re low content of more volatile metals such as ru and pt gas solid equilibrium at high temperatures can easily account for the observed relative abundances of refractory elements independent temperature estimates from ree abundances and refractory metal contents suggest an equilibrium temperature of about 1670 k at 10 3 atm the trace element pattern of the inclusion is complementary to the pattern of fine grained allende inclusions the inclusion may either represent a first condensate from a cooling gas of approximately solar composition or the very last residue from an evaporation process only the low contents of w and mo do not fit the pattern of refractory elements predicted from condensation calculations both elements however readily form volatile oxides therefore this depletion could be taken as indication of an evaporative origin of the inclusion the metal phase consists of small os rich grains in a comparatively os poor matrix grains and matrix appear to be a mechanical mixture this textural evidence cannot be easily reconciled with an evaporative origin a condensation origin of the inclusion would require that w and mo were lost at a later time in a more oxidising environment without affecting the metallic ta found in some of the metal grains

geochemical investigations of submarine volcanic exhalations to the east of panarea aeolian islands italy abstract results are presented on scubadiving investigations carried out on thermal manifestations in the area of panarea aeolian islands the area investigated falls inside a caldera which extends from the main island to the group of islets located to the northeast the distribution of the gaseous manifestations is regulated by the ne sw nw se and n s regional tectonic directrices through which the more recent basic magma intruded giving rise to dikes and pillow lavas f o 2 temperature relation of the gases sampled in the investigated area was calculated to be log f o 2 11 24 593 t which indicates that a buffering mechanism acted on the gases as they cooled down during their ascent the high 3 he 4 he ratio 6 10 6 and the 13 c 3 2 pdb suggest the presence of a magmatic component in the gas feeding the investigated manifestations the above relations and the almost constant high he n 2 ratio suggest that all the fumaroles are fed by the same deep hot fluids on the basis of both the chemical characters of the fluids and the geothermo barometric data a deep geothermal body having a temperature of about 240 c is recognized two other shallower thermal aquifers with a temperature of 170 210 c are identified a circulation pattern of the geothermal fluids is also proposed on the basis of calculations regarding the convective energy released by the geothermal system of panarea and the magmatic mass responsible for the positive gravimetric anomaly of the area it was estimated that the last volcanic activity took place less then 10 000 years ago

solifluction rates processes and landforms a global review abstract field data on the rates of solifluction and associated parameters are compiled from the literature in an attempt to evaluate factors controlling the spatial variability in solifluction processes and landforms with special attention on the climate solifluction relationship the analyzed data originate from 46 sites over a wide range of periglacial environments from antarctic nunataks to tropical high mountains solifluction broadly defined as slow mass wasting resulting from freeze thaw action in fine textured soils involves several components needle ice creep and diurnal frost creep originating from diurnal freeze thaw action annual frost creep gelifluction and plug like flow originating from annual freeze thaw action and retrograde movement caused by soil cohesion the depth and thickness of ice lenses and freeze thaw frequency are the major controls on the spatial variation in solifluction processes near the warm margin of the solifluction affected environment diurnal freeze thaw action induces shallow but relatively rapid movement of a superficial layer 5 10 cm thick on average often creating the thin stone banked lobes typically seen on tropical high mountains in addition to diurnal movement annual frost creep and gelifluction may occur on slopes with soil climates of seasonal frost to warm permafrost dislocating a soil layer shallower than 60 cm at a rate of centimeters per year and eventually producing medium size solifluction lobes in high arctic cold permafrost regions two sided freezing can induce plug like flow of a soil mass 60 cm or thicker the correlation between process and landform suggests that the riser height of lobes is indicative of the maximum depth of movement and prevailing freeze thaw type climate change may result in new different ground freezing conditions thereby influencing the surface velocity and maximum depth of soil movement soil moisture and topography also control solifluction high moisture availability in the seasonal freezing period enhances diurnal freeze thaw action and subsequent seasonal frost heaving the latter contributes to raising the moisture content of the thawed layer and promotes gelifluction during the thawing period the slope angle defines the upper limit of the surface velocity of solifluction a diagram correlating the potential frost creep with the actual surface velocity permits an inter site comparison of the relative magnitude of solifluction components physically based modelling of periglacial slope evolution requires synthetic and more detailed field monitoring and laboratory simulations of solifluction processes

soil gas radon emissions and volcanic activity at el hierro canary islands the 2011 2012 submarine eruption 1 soil gas radon 222rn and thoron 220rn activities have been continuously measured during the period of the recent volcanic unrest that occurred at el hierro canary islands at two different monitoring stations namely hie02 and hie03 significant increases in soil 222rn activity and 222rn 220rn ratio from the soil were observed at both stations prior to the 2011 2012 submarine eruption off the coast of el hierro showing the highest increases before the eruption onset and before the occurrence of the strongest seismic event m 4 6 statistical analysis showed that the long term temporal trend of filtered radon data matched closely that of seismic energy release during the volcanic unrest the observed increases of 222rn are related to the rock fracturing processes seismic activity and the magmatic co2 outflow increase as observed in hie03 station

insights into the 2011 2012 submarine eruption off the coast of el hierro canary islands spain from statistical analyses of earthquake activity summary the purpose of this work is to gain insights into the 2011 2012 eruption of el hierro canary islands by mapping the evolution of the seismic b value the el hierro seismic sequence offers a rather unique opportunity to investigate the process of reawakening of an oceanic intraplate volcano after a long period of repose the 2011 2012 eruption is a submarine volcanic event that took place about 2 km off of the southern coast of el hierro the eruption was accompanied by an intense seismic swarm and surface manifestations of activity the earthquake catalogue during the period of unrest includes over 12 000 events the largest with magnitude 4 6 the seismic sequence can be grouped into three distinct phases which correspond to well separated spatial clusters and distinct earthquake regimes the estimated b value is of 1 18 0 03 and a magnitude of completeness of 1 3 for the entire catalogue b is very close to 1 0 which indicates completeness of the earthquake catalogue with only minor departures from the linearity of gutenberg richter frequency magnitude distribution the most straightforward interpretation of this result is that the seismic swarm reached its final stages and no additional large magnitude events should be anticipated similarly to what one would expect for non volcanic earthquake sequences the results dividing the activity in different phases illustrate remarkable differences in the estimate of b value during the early and late stages of the eruption the early pre eruptive activity was characterized by a b value of 2 25 in contrast the b value was 1 25 during the eruptive phase based on our analyses and the results of other studies we propose a scenario that may account for the observations reported in this work we infer that the earthquakes that occurred in the first phase reflect magma migration from the upper mantle to crustal depths the area where magma initially intruded into the crust because of its transitional nature is characterized by high fracturing thus favours anomalously high b values the larger magnitude earthquakes recorded in the second phase may reflect relaxation around the magma reservoir that had fed the eruption and thus lower b values

glacigenic clast fabrics genetic fingerprint or wishful thinking the interpretation of glacigenic diamictons is a subjective process for which quantitative support is frequently sought from parameters such as clast shape and fabric it has been widely suggested that different glacigenic diamicton facies possess distinct clast fabric signatures this paper examines this concept using a data set of 111 clast fabrics and a synthesis of published results eigenvalues are calculated and compared for a variety sedimentary facies it is concluded that clast fabric alone is not able to discriminate between different glacigenic facies and it is argued that clast fabric offers little quantitative support in the interpretation of glacigenic sediments it is suggested therefore that although clast fabric may continue to have a role as an indicator of relative strain at specific sites its use in the discrimination of glacigenic facies is limited consequently we should be much more selective in undertaking such analyses in the future copyright 1999 john wiley sons ltd

characterization of fracture systems using precise array locations of earthquake multiplets an example at deception island volcano antarctica 1 volcano tectonic earthquakes are common seismic events in active volcanic areas the stress produced by volcanic processes is released through fracturing of the shallow crust very often these earthquakes occur in multiplets with similar waveforms a fact which indicates common source characteristics in this work we introduce a method that uses array techniques to calculate precise relative locations of earthquake multiplets we use the relative slowness estimate method to determine accurately the apparent slownesses and propagation azimuths of the earthquakes relative to a selected master event we also obtain precise estimates of the s p delays this information is used to calculate precise relative locations by ray tracing in an earth model we applied this method to determine the characteristics of the fractures activated during the 1999 seismic series at the deception island volcano antarctica we selected a set of 17 earthquake multiplets initially located in a small 4 4 km region a few km ne of the array site we estimated precise locations for 14 of the clusters in most cases hypocenters were distributed in well defined planar geometries we found the best fitting planes which we interpreted as fractures in the medium for two clusters the method spatially separated the earthquakes into two subgroups thus we obtained two planes for each of these clusters resulting in a total of 16 fracture planes this is the first time that the orientations of fracture planes related to a seismic series have been obtained using a seismic array we performed several tests to check various aspects in relation to the stability of the method and concluded that the results were robust the dip angles indicate that the planes are mostly subvertical while the strike angles clearly show a nw se trend for most of the planes and a few planes with ne sw trends the geometry and position of these planes suggest that the 1999 seismic series was influenced by regional tectonics although the origin of the destabilization of the system may be related to the reactivation of a shallow magma chamber

a unique ultrarefractory inclusion from the murchison meteorite through freeze thaw disaggregation of the murchison meteorite we have recovered a refractory inclusion hib 11 that is unique in terms of its texture mineral compositions and bulk composition it consists of anhedral y rich 1 6 wt y2o3 perovskite and lathlike spinel grains enclosed in a matrix of fine grained sc rich 10 5 wt sc2o3 avg ti rich 12 6 wt tio2 avg reporting all ti as tio2 clinopyroxene the chondrite normalized rare earth element ree pattern is complex with light ree lree at 10 c1 abundances increasing from gd through ho the latter at 104 c1 decreasing through yb at 200 c1 and lu at 400 c1 the pattern reflects several stages of high temperature volatility fractionation removal of lu and er from the source gas in the first condensation event was followed by partial to complete removal of the somewhat less refractory heavy ree gd through ho in the hib 11 precursors by condensation from the fractionated residual gas in a second event both of these events probably reflect condensation of ree into zro2 or a mixed zr sc ti y oxide at temperatures too high for hibonite stability a second lower temperature component which was subsequently added had fractionated nd poor ce rich lree abundances that resulted from condensation from a gas that had undergone prior removal of the more refractory lree resulting in enrichment in ce and the most volatile ree eu and yb the aggregate was then melted and quickly cooled forming a fine grained spherule this is the first reported inclusion in which the two most refractory ree lu and er are strongly fractionated from the other ree an absence of mass fractionation among the ti isotopes indicates that hib 11 is not an evaporative residue implying that volatility fractionation of trace elements took place during condensation the fact that the two most refractory heavy ree could be separated from the other only slightly less refractory heavy ree suggests that a wide variety of ree patterns is possible and that ultrarefractory inclusions with other unusual ree patterns important recorders of nebular condensation may yet be discovered

deformation induced microstructures in soils affected by mass movements the soil deformation produced by mass movements gives rise to specific microscopic features the study of some markers of deformation such as the orientation of rigid clasts and the morphology of fine grained intercalations indicates that in most cases mass movements can be related to simple shear the development of these features varies according mainly to the type of mass movement solifluction debris flow or earth slide different factors play a significant role in their formation intrinsic soil characteristics such as the grain size of the matrix water content and matrix element viscosity ratios and external factors such as the intensity and homogeneity of deformation a careful study of the microscopic features leads to a better understanding of the dynamics of mass deposits

three armed rifts or masked radial pattern of eruptive fissures the intriguing case of el hierro volcano canary islands abstract using new surface structural data as well as subsurface structural data obtained from seventeen water galleries we provide a comprehensive model of the volcano tectonic evolution of el hierro canary islands we have identified measured and analysed more than 1700 volcano structural elements including vents eruptive fissures dykes and faults the new data provide important information on the main structural patterns of the island and on its stress and strain fields all of which are crucial for reliable hazard assessments we conducted temporal and spatial analyses of the main structural elements focusing on their relative age and association with the three main cycles in the construction of the island the tinor edifice the el golfo las playas edifice and the rift volcanism a radial strike distribution which can be related to constructive episodes is observed in the on land structures a similar strike distribution is seen in the submarine eruptive fissures which are radial with respect to the centre of the island however the volcano structural elements identified onshore and reflecting the entire volcano tectonic evolution of the island also show a predominant ne sw strike which coincides with the main regional trend of the canary archipelago as a whole two other dominant directions of structural elements n s and wnw ese are evident from the establishment of the el golfo las playas edifice during the second constructive cycle we suggest that the radial striking structures reflect comparatively uniform stress fields during the constructive episodes mainly conditioned by the combination of overburden pressure gravitational spreading and magma induced stresses in each of the volcanic edifices by contrast in the shallower parts of the edifice the ne sw n s and wnw ese striking structures reflect local stress fields related to the formation of mega landslides and masking the general and regional radial patterns

effect of mechanical interactions on the development of shape preferred orientations a two dimensional experimental approach abstract modifications in the development of preferred orientations of rigid particles due to mechanical interactions between particles are studied experimentally in two dimensions experiments in both pure shear and simple shear were performed and the results analysed using an easy and fast new automatic method for increased concentration of rigid particles the rotation of individual particles may be slowed down or even stopped due to collisions or disturbance of the flow in the matrix caused by neighbours in coaxial flow the fabric intensity is consequently reduced in simple shear flow the fabric evolution is no longer cyclic the intensity is on average weaker and the fabric axis rotates asymptotically toward the shear plane in the case of preferred orientations of particles having a low aspect ratio 2 5 the fabric rotates through the shear plane then undergoes a reverse rotation and rotates toward the shear plane again in the light of these experimental results we emphasize that quantification of finite strain based on such fabrics may lead to significant underestimates and calculated values should be taken as minimum estimates the kinematic significance of concentrated rigid particle preferred orientations in rocks is modified by interactions between particles techniques for qualitative or quantitative kinematic analysis may become unreliable for simple shear flows the concentrated population fabrics show an angular behaviour close to that of passive markers they tend to align parallel to the shear plane in simple shear flow