converted phases analysis of the campi flegrei caldera using active seismic data abstract we applied a type of depth migration for converted seismic phases to active and passive seismic data sets from the campi flegrei volcanic region in southern italy the migration method is based on the diffraction summation migration technique travel times to grid points in a volume were calculated in smooth p and s velocity models and trace energy near the calculated converted phase time was stacked over multiple sources at one receiver weighting factors based on snell s law at an arbitrarily oriented local interface were applied to better focus trace energy pp reflection images from the active data set provide increased detail to images of the caldera rim from other studies the migrated images also show features near 2 3 km in depth beneath pozzuoli city which may be associated with an over pressured gas volume as suggested by other geophysical investigations possible deeper features near 4 km depth may be related to the presence of the carbonate basement or may image a previously undetected feature such as a small body of strongly thermometamorphosed volcanic rock the current passive earthquake data set from the 1984 ground uplift episode was not well suited to the converted phases analysis due to narrow p s windows and high noise levels in the traces however two stations provide confirmation and extension of imaged features in the active data

in situ observation of the percolation threshold in multiphase magma analogues magmas vesiculate during ascent producing complex interconnected pore networks which can act as outgassing pathways and then deflate or compact to volcanic plugs similarly in conduit fragmentation events during dome forming eruptions create open systems transiently before welding causes pore sealing the percolation threshold is the first order transition between closed and open system degassing dynamics here we use time resolved synchrotron source x ray tomography to image synthetic magmas that go through cycles of opening and closing to constrain the percolation threshold c at a range of melt crystallinity viscosity and overpressure pertinent to shallow magma ascent during vesiculation we observed different percolative regimes for the same initial bulk crystallinity depending on melt viscosity and gas overpressure at high viscosity 106 pa s and high overpressure 1 4 mpa we found that a brittle viscous regime dominates in which brittle rupture allows system spanning coalescence at a low percolation threshold c 0 17 via the formation of fracture like bubble chains percolation was followed by outgassing and bubble collapse causing densification and isolation of the bubble network resulting in a hysteresis in the evolution of connectivity with porosity at low melt viscosity and overpressure we observed a viscous regime with much higher percolation threshold c 0 37 due to spherical bubble growth and lower degree of crystal connection finally our results also show that sintering of crystal free and crystal bearing magma analogues is characterised by low percolation thresholds c 0 04 0 10 we conclude that the presence of crystals lowers the percolation threshold during vesiculation and may promote outgassing in shallow crystal rich magma at initial stages of vulcanian and strombolian eruptions

the 25 september 2007 eruption of mount ruapehu new zealand directed ballistics surtseyan jets and ice slurry lahars abstract at 20 26 nzdt on 25 september 2007 a moderate gas driven eruption beneath the summit crater lake of mt ruapehu new zealand generated a directed ballistic fallout apron and surtseyan jet that impacted an area of c 2 5 km2 to the north of the vent two climbers were caught in the blast at a hut 600 m from the vent primary ice slurry lahars were generated in two catchments draining the summit region including a flow that entered a commercial ski field the ejecta consists of blocks of andesitic lava and scoria erupted during previous volcanic episodes a variety of mineral cemented lake floor sediments vent fill debris and rare glassy material interpreted to be derived from a fresh batch of magma a minority of clasts contain formerly molten elemental sulphur indicating that vent temperatures at the base of the lake were in excess of 119 c the ballistic deposit is confined to a c 40 wide swath directed northwards that extends up to 2 km from the inferred vent location beneath crater lake the strong directionality of the jetted deposits and ballistic free shadow zones sheltered by intervening topography all point to a relatively low angle directed blast previous similar eruptions at ruapehu also show preferred deposit orientations that are here correlated with an inclined and off centre vent beneath crater lake the 25 september 2007 eruption appears to have resulted from failure of a relatively shallow hydrothermal seal composed of elemental sulphur and other mineral precipitates developed in the vent breccia which breached following overpressurization by a pulse of magmatic gases released from deeper in the conduit this event highlights the potential hazard from relatively minor gas driven eruptions at ruapehu that can occur with little or no warning improved understanding of the eruption mechanism for this style of eruption will inform future risk assessments for ruapehu and other similar volcanoes worldwide

estimation of magma depth for resurgent domes an experimental approach post collapse resurgence is a phenomenon affecting many calderas attributed to a renewed magma rise the process is still poorly understood and the associated source parameters remain poorly constrained a set of experiments has been conducted to gain insight into the structural evolution of caldera resurgent domes a sand plaster mixture was chosen as an analogue for the brittle pile of volcanic rocks and silicone putty simulates the ductile behavior of the intruding magma resurgence is driven by the vertical uplift of the silicone with variable shape and depth similarity conditions are achieved through eight dimensionless numbers which are of the same order of magnitude in both nature and experiments results show that extension due to doming is in many cases accommodated by one axial graben opposite master faults of this graben intersect at depth at the junction with the rising viscous silicone the simplicity of the geometry of the whole analogue system provides equations which allow the estimation of the silicone depth from surface parameters these equations are then used in some field examples to assess the magma depth beneath natural resurgent domes

conductivity distribution beneath lascar volcano northern chile and the puna inferred from magnetotelluric data abstract during two field campaigns in 2007 and 2010 long period and broadband magnetotelluric measurements were conducted in the central andes of northern chile and northwestern argentina at a latitude of 23 7 s the study area spans from the precordillera over the active volcanic arc of the western cordillera until the western part of the puna a special focus was on lascar a subduction related stratovolcano with an historical activity characterized by fumarolic emissions and occasional sub plinian eruptions like the one occurred on 1993 the broadband instruments covering a period range between t 0 005 s and 1000 s were installed in the proximities of lascar volcano while the long period devices t 10 s 10 000 s were installed on a profile slightly south of lascar crossing the salar de atacama basin the volcanic arc and reaching the western border of the puna remote reference and robust techniques were used for data processing induction vectors phase tensor ellipses and strike direction of the conductivity distribution were calculated showing some 3 d behavior for the lascar sites at shallower depths with induction vectors close to the edifice influenced partially by the topography 3 d modeling and inversion revealed conductive anomalies beneath lascar volcano but also beneath the puntas negras volcanic chain for the long period transect the behavior is closer to a 2 d case with more stable strike direction coherent with induction vectors and phase tensor ellipses the major result of 2 d inversion is a vast high conductivity zone in the backarc crust which seems to be the southern extension of a large highly conductive anomaly observed in prior studies beneath the altiplano

a review on phreatic eruptions and their precursors abstract an analysis of the reported information on 132 historical phreatic events indicates that most of these 115 were not followed by a magmatic or phreatomagmatic eruption only in 18 cases precursory phenomena are reportedly lacking whereas they are recognized for the majority 72 of the considered cases these precursors have been analyzed as a function of the kind of phreatic event and of its possible triggering mechanism unfortunately the quality of the available information is poor however data suggest that anomalous seismicity ground deformation changes in the output chemistry and temperature of fumaroles and thermal springs are potential mid term precursors whereas seismic tremor is a common short term precursor

maximum warning times for imminent volcanic eruptions accelerations in seismicity are important precursors to eruptions at volcanoes reawakening after extended repose intervals these have previously been quantified for subduction zone settings in terms of the linkage of crustal faults by shearing introducing a damage mechanics criterion for the weakening of rock between major fractures the model is here modified for failure in tension consistent with conditions in crust surrounding a pressurized magma reservoir the results indicate that final accelerations develop over similar to 2 3 weeks at tensile strains of 4 5 3 2 x10 3 since a week or more is required to identify an accelerating trend seismic forecasts of eruptions after long repose are unlikely to be reliable more than days in advance improvements will require the integration of additional precursors or extension of the model to earlier stages of fracture growth in stressed crust

strong correlation of major earthquakes with solid earth tides in part of the eastern united states east of the eastern american continental divide and south of fat 42 5 n moderate to large historic earthquakes correlate strongly with times of high and low solid earth tides this effect is most pronounced when solar declination lies between 17 n and 17 s significant correlations also exist between major earthquakes time of day lunar declinations and lunar phase

volcano alert level systems managing the challenges of effective volcanic crisis communication over the last four decades volcano observatories have adopted a number of different communication strategies for the dissemination of information on changes in volcanic behaviour and potential hazards to a wide range of user groups these commonly include a standardised volcano alert level system vals used in conjunction with other uni valent communication techniques such as information statements reports and maps and multi directional techniques such as meetings and telephone calls this research based on interviews and observation conducted 2007 2009 at the five us geological survey usgs volcano observatories and including some of the key users of the vals argues for the importance of understanding how communicating volcanic hazard information takes place as an everyday social practice focusing on the challenges of working across the boundaries between the scientific and decision making communities it is now widely accepted that the effective use value and deployment of information across science policy interfaces of this kind depend on three criteria the scientific credibility of the information its relevance to the needs of stakeholders and the legitimacy of both the information and the processes that produced it translation and two way communication are required to ensure that all involved understand what information is credible and relevant findings indicate that whilst vals play a role in raising awareness of an unfolding situation supplementary communication techniques are crucial in facilitating situational understanding of that situation and the uncertainties inherent to its scientific assessment as well as in facilitating specific responses in consequence best practice recommendations eschew further standardisation and focus on the in situ cultivation of dialogue between scientists and stakeholders as a means of ensuring that information and the processes through which it is produced are perceived to be legitimate by all involved

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

three dimensional deformation analysis global vector spherical harmonic and local finite element representation abstract deformation elements which have global support such as tidal induced displacements are represented in terms of vector spherical harmonics in contrast local strain and local rotation are represented in terms of irregularly shaped three dimensional finite elements these geodetic finite elements reflect the structure of a geodetic network which is arbitrarily shaped various continuity classes are discussed numerical examples are presented

synthesizing multi sensor multi satellite multi decadal datasets for global volcano monitoring abstract owing to practical limitations less than half of earth s 1400 subaerial volcanoes have no ground monitoring and few are monitored consistently earth observing satellite missions provide global and frequent measurements of volcanic activity that are closing these gaps in coverage we compare databases of global satellite detections of ground deformation 1992 2016 so2 emissions 1978 2016 and thermal features 2000 2016 that together include 306 volcanoes each database has limitations in terms of spatial and temporal resolution but each technique contributed 45 86 unique detections of activity that were not detected by other techniques integration of these three databases shows that satellites detected 102 volcanic activities per year before the year 2000 and 103 activities per year after the year 2000 we find that most of the 54 erupting volcanoes without satellite detections are associated with low volcano explosivity index eruptions and note that many of these eruptions 71 97 135 occurred in the earliest decades of remote sensing pre 2000 when detection thresholds were high from 1978 to 2016 we conduct a preliminary analysis of the timing between the onset of satellite detections of deformation n 154 episodes n 71 volcanoes thermal features n 16 544 episodes n 99 volcanoes and so2 emissions n 1495 episodes n 116 volcanoes to eruption start dates we analyze these data in two ways first including all satellite detected volcanic activities associated with an eruption and second by considering only the first satellite detected activity related to eruption in both scenarios we find that deformation is dominantly pre eruptive 47 and 57 whereas available databases of thermal features and so2 emissions utilizing mainly low resolution sensors are dominantly co eruptive 88 and 76 for thermal features 97 and 96 for so2 emissions

characterising unrest during the reawakening of the central volcanic complex on tenerife canary islands 2004 2005 and implications for assessing hazards and risk mitigation abstract increased onshore seismic activity in april 2004 marked the first documented renewal of tectonic unrest on tenerife canary islands spain since the island s last volcanic eruption in 1909 events included tremors felt earthquakes and the occasional emission of a visible gas plume from the central 3718 m high teide volcano and an increased diffuse emission of co 2 here we evaluate results from seismic and microgravimetric observations in addition to other available data obtained between april 2004 and july 2005 in order to shed light on the source of these events we discuss the information to assess whether collectively the phenomena qualify to be termed volcanic unrest and the socio economic implications of the phenomena and critically examine the ensuing scientific response we also evaluate the potential volcanic eruption precursory character of the data suggestions for the establishment of improved volcano monitoring programmes early warning systems and civil response protocols for volcanic crises on tenerife are proposed

modeling and detecting interactions between earth tides and earthquakes with application to an aftershock sequence in the pyrenees abstract assuming that earthquakes are governed by solid friction and that the fault plane solutions are known a simplified model of correlation between the seismicity and a specified component of the tidal stress is proposed in the case of an earthquake sequence with a uniform time distribution and with a prevailing focal mechanism a test of statistical significance is derived from a binomial probability distribution this interaction model is checked over the aftershock sequence of a magnitude 5 earthquake which occurred within a seismic array in the pyrenees on 29 february 1980 the tidal stress field including the ocean tide effect is computed for this area the global time decrease of the seismicity is taken into account by a time transformation in order to deal with the time and space complexity of the stress field a moving window analysis is used it is shown that during one 7 day period out of a total of 30 days a positive correlation appears between earth tides and seismicity in agreement with the proposed model

volcano tectonic seismicity at unzen volcano japan 1985 1999 abstract the eruption of unzen volcano in southwestern japan began on november 17 1990 and an extrusion of a dacite lava dome lasted from may 20 1991 until early february 1995 the seismic network operated by the shimabara earthquake and volcano observatory of kyushu university sevo located about 4000 volcano tectonic earthquakes during the period from 1985 to 1999 the seismicity was greatest in the period between one year before the eruption and the start of the lava dome extrusion the hypocenters were mostly distributed within a 12 20 km area on the western side of the volcano an inclined seismic aseismic boundary shallows eastward to the summit probably reflecting the thermal structure beneath the volcano within 4 km west from the summit however the seismicity is very low it was suggested that the high temperature ductile and low q bodies exist there we obtained focal mechanism solutions for about 90 earthquakes among them orientations of p axes for the earthquakes occurring on the upper side of the inclined seismic aseismic boundary suggest a pressure source located below this boundary although most of the focal mechanisms have t axes nearly horizontal in the n s direction consistent with the n s extensional tectonic stress several earthquakes whose focal mechanisms are inconsistent with the tectonic stress were observed within a horizontal distance of 5 km from the summit this is because the pressurization of volcanic gas or magma beneath the summit produced a strong local stress in the summit surroundings

anomalous earthquakes associated with nyiragongo volcano observations and potential mechanisms abstract a series of five unusual earthquakes 4 6 m 5 3 has been recently located near nyiragongo volcano d r congo in the western rift valley of the east african rift despite their moderate size these earthquakes do not appear in global seismicity catalogs but were located using long period surface waves primarily recorded on the global seismographic network three of the events occurred in the week following the january 2002 eruption of nyiragongo while the final two occurred in 2003 and 2005 respectively and are not linked to a major eruption at nyiragongo or its neighboring volcano nyamuragira several common techniques were used to investigate the characteristics of these seismic sources in the context of the volcanic activity of the region the frequency content of the five anomalous earthquakes was compared to that from local events found in global catalogs and the newly detected earthquakes were shown to be slow events being greatly depleted in frequencies above 0 1 hz each of the newly detected earthquakes was modeled by a series of forces and by a centroid moment tensor a deviatoric moment tensor was shown to provide a better fit to the data the newly detected earthquakes are highly non double couple in nature each having a large compensated linear vector dipole component of the moment tensor drawing on models based on similar observations from other active volcanoes we propose that the earthquakes are caused by slip on non planar faults beneath the volcano we suggest a mechanism in which these newly detected earthquakes are generated by the collapse of the roof of a shallow magma chamber along an inward dipping cone shaped ring fault diking events which result in magma evacuation from shallow magma chambers could trigger such earthquakes our results provide new constraints on the dynamics of the poorly understood magma system beneath nyiragongo an active volcano that is a significant threat to life and property

tidal triggering of intermediate and deep focus earthquakes tidal stress changes within the earth due to the gravitational attraction of the sun and moon can exceed 20 mbar h whereas tectonic stress rates are of the order of 0 2 mbar h although the absolute magnitude of tidal stresses is less than 1 of the typical stress drops observed in earthquakes a correlation between the tidal stress history on a fault plane and the time of failure should exist if 1 tidal and tectonic stresses are combined in a simple manner 2 the tectonic stress buildup over time is smooth and 3 failure occurs immediately upon attainment of some critical stress to search for possible tidal triggering of intermediate and deep focus earthquakes 7359 events were selected from a global catalog and subdivided into 30 regions each event was assigned a tidal phase relative to both the semidiurnal and biweekly tidal stress curves at the time of occurrence all tidal phase distributions were checked for a preferred phase orientation using the rayleigh test and for nonrandomness using the chi square test results of this analysis for the semidiurnal earth tide show that three regions have a preferred phase direction and four regions display nonrandomness significant at the 90 confidence level which would be expected for this number of random data sets the biweekly tide when normalized for the unequal distribution of biweekly phase over time after correction for clustering of events in some of the data sets shows only three non random data sets at the 95 level as defined by the chi square test thus intermediate and deep focus earthquakes in most subduction zones occur independently of both the semidiurnal and biweekly tidal stress cycles and we may conclude that failure below 70 km does not occur at the instant a stress curve the simple sum of tectonic and tidal stresses reaches the yield strength of subcrustal rocks this implies that either tectonic stress rates prior to failure are not smooth and are unaffected by predictable sources of stress or that failure does not necessarily occur when a certain critical stress is reached these may in turn be due to some time delay characteristic of deep failure to the stress history of the material to the diffusion of fluids or to the mode of failure itself at present a unique and unexplained phenomenon at such high temperatures and pressures

distribution of the lunisolar tidal elastic stress tensor components within the earth s mantle a set of second order spheroidal love shida numbers h r k r l r and their radial derivatives were determined for the case of a symmetric non rotating elastic isotropic snrei earth with a liquid core by these means the stress tensor components from the surface to the core mantle boundary cmb were calculated for the case of zonal tesseral and sectorial tides the possible dependence of geophysical phenomena on the lunisolar effect is discussed for the three different kinds of tides the case of tidal triggering of earthquakes is discussed in more detail since the tidal potential and its derivatives are coordinate dependent and the zonal tesseral and sectorial tides have different distributions on and within the earth the lunisolar stress cannot influence the break out of every seismological event in the same degree a correlation between earthquake energy release and the lunisolar effect can exist in some cases where the seismic area is well determined and has either one seismic source or severe similar ones particularly in volcanic areas where the seismic activity is connected to the volcano s activity or in the case of some aftershock swarms significant correlation was found by different authors

a new perspective in identifying the precursory patterns of eruptions the complexity of the processes responsible for volcanic eruptions makes a theoretical approach to forecasting the evolution of volcanic unrest rather difficult a feasible strategy for this purpose appears to be the identification of possible repetitive schemes patterns in the pre eruptive unrest of volcanoes nevertheless the limited availability and the heterogeneity of pre eruptive data and the objective difficulty in quantitatively recognizing complex pre eruptive patterns make this task very difficult in this work we address this issue by using a pattern recognition approach applied to the seismicity recorded during 217 volcanic episodes of unrest around the world in particular we use two non parametric algorithms that have proven to give satisfactory results in dealing with a small amount of data even if not normally distributed and or characterized by discrete or categorical values the results show evidence of a longer period of instability in the unrest preceding an eruption compared to isolated unrest this might indicate even if not necessarily a difference in the energy of processes responsible for the two types of unrest however if the unrest is followed by an eruption it seems that the seismic energy released during the unrest parameterized by the duration of the swarm and the maximum magnitude recorded is not indicative of the magnitude of the impending eruption we also found that in general unrest followed by the largest explosive eruptions have a longer repose time than those related to moderate eruptions this evidence supports the fact that the occurrence of a large eruption needs a sufficient amount of time after the last event in order to re charge the feeding system and to achieve a closed conduit regime so that a sufficiently large amount of gas can be accumulated

evidences of volcanic unrest on high temperature fumaroles by satellite thermal monitoring the case of santa ana volcano el salvador on october 1st 2005 santa ana volcano el salvador underwent a vei 3 phreatomagmatic eruption after approximately one century of rest casualties and damages to some of the local infrastructures and surrounding plantations were followed by the evacuation of the nearby communities the analysis of modis moderate resolution imaging spectroradiometer infrared data reveals that the main explosion was preceded by a one year long thermal unrest associated to the development of a fumaroles field located at the western rim of the summit crater lake by combining space based thermal flux and ground based measurements seismicity sulfur emissions and lake temperatures we suggest that the activity observed at santa ana between 2004 and 2005 was driven by the gradual intrusion of an undegassed magma body at a very shallow depth magma injection induced thermal anomalies associated with sustained degassing from the fumaroles field and promoted the interaction between the magmatic hydrothermal system and the overlying water table this process culminated into the vei 3 phreatomagmatic eruption of october 2005 that strongly modified the shallow structure of the crater area the subsequent three years long activity resulted from self sealing of the fracture system and by the opening of a new fracture network directly connecting the deeper hydrothermal system with the crater lake our results show that satellite based thermal data allow us to detect the expansion of the high temperature fumarolic field this may precede an explosive eruption and or a lava dome extrusion in particular we show that thermal records can be analyzed with other geochemical i e so2 emissions and geophysical seismicity data to track a shallow magmatic intrusion interacting with the surrounding hydrothermal system this provides a remarkable support for volcano monitoring and eruption forecasting particularly in remote areas where permanent ground data acquisition is hazardous expensive and difficult

soil formation in phobjikha valley central bhutan with special regard to the redistribution of loessic sediments abstract soil development and landscape evolution were studied in the basin shaped phobjikha valley at 2900 3200 m a s l to the west of the black mountain range west central bhutan the local environmental setting with strong along valley winds frequent freeze thaw cycles extensive dry periods and sparse vegetation cover seems to encourage the generation and short distance transport of silt sized particles the effects of this process are evidenced in the smooth valley morphology and in the nature of the examined pedons their involvement in continuing redistribution of local sediments is reflected by a homogeneous silty clayey and stone free texture varying profile depths buried topsoils and weakly developed recent a horizons in protected locations in situ weathering of metamorphic parent materials results in alu andic features with bulk densities 2 and phosphate retention 95 dominance by al hydroxy interlayered clay minerals and large amounts of well crystallised iron oxides indicate an advanced stage of weathering in areas of preferred eolian deposition argic and ferralic features emerge with clay contents of up to 60 and surface areas of 50 m2 g 1 under forest umbric horizons can develop ceceff is below 10 cmolc kg 1 at all sites cluster and factor analyses of soil chemical and physical parameters confirm the redistribution of local sediments as a dominant factor behind the measured variables no clear indication of glacial activities in the area was found whereas the massive silty sediments in the lower parts of most profiles the presence of debris slopes and the asymmetric cross sections of the side valleys suggest periglacial conditions buried topsoils dated at about 2000 conventional 14c years bp indicate a weakening or absence of sediment influx under wetter conditions towards the end of the holocene climate optimum charcoal on top of paleosols suggests that human activities of deforestation grazing and arable agriculture may have contributed to the reactivation of local sediment redistribution until today

earthquake swarms to the west of mt ruapehu preceding its 1995 eruption abstract some months prior to the 1995 eruption of mt ruapehu new zealand a series of shallow earthquake swarms occurred about 15 20 km west of the summit of ruapehu several earthquakes in these swarms were felt and the largest event was m l 4 8 crustal earthquakes of m l 3 0 within 20 km of the summit of ruapehu have been rather uncommon in recent years furthermore the two periods of strongest activity were both just before times when the temperature of crater lake showed rapid increases the second of these rapid heating phases was immediately followed by increases in the mg 2 ion concentration in crater lake indicating that chemical interactions were occurring between fresh magmatic material and the lake water the coincidence between seismicity and lake changes suggested a link with the following eruption a 1 d simultaneous inversion to locate the earthquakes more accurately showed that most of the earthquakes fell into three spatial clusters each cluster having a small horizontal cross section the predominant depth was about 10 16 km the b value of this swarm was 0 74 quite compatible with ordinary tectonic earthquakes each cluster of earthquakes lies close to the normal raurimu fault which runs predominantly north south to the west of ruapehu with an east trending branch splaying off near its northern end see fig 1 b composite focal mechanisms of events in the two more southern clusters are oblique normal while the other cluster to the north has an oblique reverse mechanism the two oblique normal mechanisms suggest that extension has occurred on part of the fault this stress pattern was also observed in the focal mechanism solutions of events that occurred after the eruption when a denser network of portable seismographs covered the region although we cannot definitely connect the occurrence of these swarms to the eruptions later in 1995 there is a strong suggestion that the seismicity was connected to the process of magma movement which temperature and chemical changes in crater lake suggest was occurring during the first half of 1995

first observations of the fumarolic gas output from a restless caldera implications for the current period of unrest 2005 2013 at campi flegrei 1 the fumarolic gas output has not been quantified for any of the currently deforming calderas worldwide due to the lack of suitable gas flux sensing techniques in view of resumption of ground uplift since 2005 and the associated variations in gas chemistry campi flegrei in southern italy is one of the restless calderas where gas flux observations are especially necessary here we report the first ever obtained estimate of the campi flegrei fumarolic gas output based on a set of multigas surveys performed in 2012 and 2013 with an ad hoc designed measurement setup we estimate that the current campi flegrei fumarolic sulphur s flux is low on the order of 1 5 2 2 tons day suggesting substantial scrubbing of magmatic s by the hydrothermal system however the fumarolic carbon dioxide co2 output is 460 160 tons day mean sd which is surprisingly high for a dormant volcano in the hydrothermal stage of activity and results in a combined fumaroles soil co2 output of 1560 tons day assuming magma to be the predominant source we propose that the current co2 output can be supplied by either i a large 0 6 4 6 km3 deeply stored 7 km magmatic source with low co2 contents 0 05 0 1 wt or ii by a small to medium sized 0 01 0 1 km3 but co2 rich 2 wt magma possibly stored at pressures of 100 to 120 mpa independent geophysical evidence e g inferred from geodetic and gravity data is needed to distinguish between these two possibilities

standardisation of the usgs volcano alert level system vals analysis and ramifications the standardisation of volcano early warning systems vews and volcano alert level systems vals is becoming increasingly common at both the national and international level most notably following un endorsement of the development of globally comprehensive early warning systems yet the impact on its effectiveness of standardising an early warning system ews in particular for volcanic hazards remains largely unknown and little studied this paper examines this and related issues through evaluation of the emergence and implementation in 2006 of a standardised united states geological survey usgs vals under this upper management directive all locally developed alert level systems or practices at individual volcano observatories were replaced with a common standard research conducted at five usgs managed volcano observatories in alaska cascades hawaii long valley and yellowstone explores the benefits and limitations this standardisation has brought to each observatory the study concludes 1 that the process of standardisation was predominantly triggered and shaped by social political and economic factors rather than in response to scientific needs specific to each volcanic region and 2 that standardisation is difficult to implement for three main reasons first the diversity and uncertain nature of volcanic hazards at different temporal and spatial scales require specific vews to be developed to address this and to accommodate associated stakeholder needs second the plural social contexts within which each vals is embedded present challenges in relation to its applicability and responsiveness to local knowledge and context third the contingencies of local institutional dynamics may hamper the ability of a standardised vals to effectively communicate a warning notwithstanding these caveats the concept of vals standardisation clearly has continuing support as a consequence rather than advocating further commonality of a standardised vals we recommend adoption of a less prescriptive vals that is scalable and sufficiently flexible for use by local stakeholders via standardised communication products designed to accommodate local contingency while also adhering to national policy

pacific basin tsunami hazards associated with mass flows in the aleutian arc of alaska abstract we analyze mass flow tsunami generation for selected areas within the aleutian arc of alaska using results from numerical simulation of hypothetical but plausible mass flow sources such as submarine landslides and volcanic debris avalanches the aleutian arc consists of a chain of volcanic mountains volcanic islands and submarine canyons surrounded by a low relief continental shelf above about 1000 2000 m water depth parts of the arc are fragmented into a series of fault bounded blocks tens to hundreds of kilometers in length and separated from one another by distinctive fault controlled canyons that are roughly normal to the arc axis the canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes the volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large scale sector collapse into the sea large scale mass flow deposits have not been mapped on the seafloor south of the aleutian islands in part because most of the area has never been examined at the resolution required to identify such features and in part because of the complex nature of erosional and depositional processes extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the aleutian islands because the aleutian arc is surrounded by deep open ocean mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources to test this hypothesis we present a series of numerical simulations of submarine mass flow initiated tsunamis from eight different source areas we consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope the flows have lengths that range from 40 to 80 km maximum thicknesses of 400 800 m and maximum widths of 10 40 km we also evaluate tsunami generation by volcanic debris avalanches associated with flank collapse at four locations makushin cleveland seguam and yunaska sw volcanoes which represent large to moderate sized events in this region we calculate tsunami sources using the numerical model topics and simulate wave propagation across the pacific using a spherical boussinesq model which is a modified version of the public domain code funwave our numerical simulations indicate that geologically plausible mass flows originating in the north pacific near the aleutian islands can indeed generate large local tsunamis as well as large transoceanic tsunamis these waves may be several meters in elevation at distal locations such as japan hawaii and along the north and south american coastlines where they would constitute significant hazards

thermal survey of mount etna volcano from space surveys of ground thermal anomalies and the monitoring of their evolution are of great importance in the study of volcanoes thermal monitoring techniques could be used in conjunction with classical monitoring tools i e seismological and deformation networks to give better predictions of the onset of a volcanic event in order to detect and emphasize small anomalies in the surface temperature of the ground we have developed a new method based on the joint use of two satellite radiometers the noaa advanced very high resolution radiometer avhrr for the quality of its thermal band calibration and the landsat thematic mapper tm for its high spatial resolution this method is applied to the mount etna volcano sicily and reveals several thermal anomalies one anomaly is already known and is associated with the permanently active craters of the summit zone the second is a larger area where an eruption occurred one week after the data acquisition 10 23 86 the general trend of the thermal anomalies leads to recognition of a large semi circular intrusive zone corresponding to the borders of the well known valle del bove

mechanisms of activity and unrest at large calderas large caldera collapses represent catastrophic natural events second only to large meteoritic impacts in addition some calderas are densely populated making the risk extreme even for moderate eruptions understanding caldera mechanisms unrest and the danger of eruption is therefore a crucial challenge for earth sciences several key features of caldera behaviour have yet to be fully understood through a combination of case studies and theoretical modelling the following topics are addressed in this volume the conditions required to produce and to release large volumes of magma erupted during caldera formation how magmatic feeding systems evolve before and after a caldera has formed the processes that limit the behaviour of precursors to eruptions how pre emptive precursors can be distinguished from those that drive unrest without an eruption and given that post collapse eruptions may occur across a wide area the optimum procedures for designing hazard maps and mitigation strategies

the lower jurassic hanson formation of the transantarctic mountains implications for the antarctic sector of the gondwana plate margin the hanson formation antarctica consists of interbedded sandstones and tuffaceous rocks of early jurassic age the sandstones pebbly to medium grained range between quartzo feldspathic and volcaniclastic with some of the former being coarse grained arkoses that imply proximal sources geochronology of detrital zircons provides evidence for source rock ages whereas sandstone petrology demonstrates a mixed provenance tuffaceous strata are reworked fine to very fine grained tuffs resulting from distal plinian eruptions dated tuffs provide time constraints on the duration of volcanism the sandstones and tuffs accumulated in a rift environment geochemically the tuffs are rhyolitic in composition and the sr and nd isotope data together with the patterns on multi element diagrams suggest they were derived from a volcanic arc which is interpreted to have been located along the west antarctic gondwana margin the silicic volcanism extends the distribution and timing of magmatism in the early jurassic along that margin the early jurassic extensional regime was delimited by the plate margin region and the east antarctic craton the rift valley system along the east antarctic craton margin in which the hanson strata accumulated was the focus for subsequent emplacement of the intrusive and extrusive rocks of the lower jurassic ferrar large igneous province the early jurassic extensional rifts may have been reactivated during cretaceous cenozoic development of the west antarctic rift system

hydrological and geochemical change related to volcanic activity of usu volcano japan abstract mt usu is a stratovolcano located on the southern side of the toya caldera in hokkaido japan in historical times it emitted dacitic products associated to remarkable crustal deformations usu volcano erupted on march 31st 2000 after 23 yr of dormancy and this eruption was the fourth in the 20th century secular variations in water levels temperature and chemical compositions of thermal water have been observed around usu volcano the water levels decreased since october 1999 6 months prior to the eruption the decrease in water levels is a precursory change and is probably due to leakage of thermal water from the shallow aquifer hosting it no variations in temperature and chemical composition of thermal water were evident prior to the eruption however in a few wells the temperature of the thermal water increased by up to 15 c with respect to the pre eruptive values moreover the concentration of some solutes na k cl and so4 became higher after the eruption these thermal and chemical changes are ascribable to increased input of a deep hydrothermal liquid into the shallow groundwater aquifer

3d density model of the central andes abstract we developed a 3d density model of the continental crust the subducted plate and the upper mantle of the central andes between 20 29 s and 74 61 w through the forward modelling of bouguer anomaly the goal of this contribution is to gain insight on the lithospheric structure integrating the available information geophysical geologic petrologic and geochemical in a single model the geometry of our model is defined and constrained by hypocentre location reflection and refraction on and offshore seismic lines travel time and attenuation tomography receiver function analysis magnetotelluric studies thermal models and balanced structural cross sections the densities allocated to the different bodies are calculated considering petrologic and geochemical data and pressure and temperature conditions the model consists of 31 parallel e w vertical planes where the continental crust comprises distinct bodies which represent the different morphotectonic units of the central andes we include a partial melting zone at midcrustal depths under the altiplano puna low velocity zone and consider the presence of a rheologically strong block beneath the salar de atacama basin according to recent seismic studies contour maps of the depth of the continental moho the thickness of the lower crust and the depth to the bottom of the lithosphere below south america are produced the possible percentage of partial melt in the central andes low velocity zone is estimated the residual anomaly is calculated by subtracting from the bouguer anomaly the gravimetric effect of the modelled subducted slab and of the modelled moho isostatic anomalies are calculated from regional and local isostatic mohos calculated with and without internal loads derived from our gravity model which are then compared to the modelled continental moho this study contributes to a more detailed knowledge of the lithospheric structure of this region of the andes and provides an integrated 3d density model which may be used by the geoscientific community as a tool that can help to understand and interpret the geodynamic features and processes acting along the central andes

volcanoes on borders a scientific and geo political challenge while the scientific community readily collaborates across international borders the boundaries of administrative units particularly the nation state can be critical in defining the availability of scientific resources the management of crises and the use of land managing border eruptions can be particularly challenging when international relations between the relevant nation states are strained or complex or when political agendas become involved given that over 700 volcanoes lie within 100 km of an international border and over 1300 are within 250 km the potential for cross border eruption impacts is significant this paper aims to provide an overview of the topic it presents results from a global study of volcanoes on or near borders and uses five case studies to highlight key issues that arise in the management of risk at such volcanoes while volcano monitoring provides critical support for hazard assessment and decision making its availability depends on the policies of particular governments and institutions furthermore the complexity and diversity of volcanic hazards activity and impacts can exacerbate existing cross border inequalities in vulnerabilities in scientific resources in disaster management and mitigation capacity and indeed public awareness we suggest that pre crisis planning and communication resource sharing and international agreements can help to mitigate the challenges of cross border eruptions

a catalogue of caldera unrest at taupo volcanic centre new zealand using the volcanic unrest index vui caldera unrest occurs frequently at taupo volcanic centre tvc new zealand occasionally resulting in deleterious socio economic impacts this large silicic volcano most recently erupted in 232 ad in an explosive caldera forming rhyolitic eruption devastating the central north island eruptions are preceded by volcanic unrest often consisting of seismicity deformation degassing and or geothermal system changes these phenomena may also occur due to non magmatic processes complicating eruption forecasting as volcanic unrest may or may not lead to an eruption it needs to be characterised to provide effective warnings this is best achieved by understanding past unrest in this research a catalogue of caldera unrest at tvc is developed using an historical chronology methodology spanning from 1872 to december 2011 the volcanic unrest index vui which is introduced by potter et al 2015 is estimated for the catalogue demonstrating its use and providing a characterisation of unrest at tvc sixteen episodes of unrest are identified 4 are classified as moderate unrest vui 3 and 12 are classified as minor unrest vui 2 there has been median interval of approximately 3 years between unrest episodes and a median unrest episode duration of just under 5 months this research provides context for future caldera unrest crises at tvc and contributes to the global caldera unrest dataset

gravity magnetic and seismic surveys of the caldera complex lake taupo north island new zealand abstract the taupo volcanic centre lies at the southern end of the taupo volcanic zone in the central north island of new zealand major rhyolitic eruptions of 400 and 35 km 3 dense rock equivalent occurred from this centre 26 5 and 1 8 thousand years ago respectively as a result of these eruptions much of the volcanic centre has collapsed and now lies beneath the waters of lake taupo gravity data measured on lake taupo show that the most intense negative bouguer anomaly to occur anywhere within the taupo volcanic zone lies over the northern part of the lake this anomaly is interpreted to outline the area of caldera collapse caused by the 26 5 ka eruption which has been subsequently modified by the 1 8 ka eruption and filled by approximately 3 km of low density uncompacted volcaniclastic material a thick laminated sequence of seismic reflectors forming a distinct unit in the seismic sections can be recognized over most of the lake area and lies beneath material interpreted to have been erupted in the 1 8 ka eruption this sequence of reflectors is interpreted to be the result of the lacustrine deposition of unconsolidated material immediately following the 26 5 ka eruption a prominent magnetic anomaly within the western part of the collapse structure is interpreted to be caused by a body of more highly magnetised material lying at or near the base of the low density caldera fill the laminated sequence of reflectors tilts and thickens towards this magnetic anomaly suggesting that the magnetised material occurs in the deepest part of the 26 5 ka collapse structure the southern margin of the intense low gravity anomaly is marked by a zone of faulting observed in the seismic reflection data magnetic and seismic data in the southern part of the lake are interpreted as a welded ignimbrite sheet overlain in places by rhyolite lavas similar to the pre 26 5 ka surface exposed west of the lake this surface appears to have been down faulted by approximately 500 m and is covered by more recent low density volcaniclastic material the thickness of the volcaniclastic material increases northward as the pre 26 5 ka surface is tilted downwards towards the area of major collapse the northward tilt of this surface suggests that subsidence in the southern part of the lake may also be a response to the 26 5 ka eruption

precipitation and dissolution of gibbsite during weathering of andesitic boulders in humid tropical west java indonesia abstract several weathered andesite boulders sampled in typic humitropepts from the cigudeg area west java indonesia were studied using micromorphological mineralogical xrd tg dta sem edxra and chemical techniques because all data of the boulders are similar only the results of the largest boulder are presented in this paper three zones are distinguished the rim of the boulder core a transition layer and outer layers in the rim of the core weathering attacks the glass matrix and the anorthite rich parts of the plagioclases even before sufficient iron is liberated from pyroxenes goethite is deposited in their cracks as a first step to the formation of a boxwork in the transition layer mono and divalent cations have been lost but al shows an absolute accumulation as gibbsite in plagioclase pseudomorphs and pores it is presumed that the al originates from the more internal parts of the core towards the outer layer gibbsite gets completely removed supposedly as the result of a lowering of ph and the plagioclase pseudomorphs become filled with illuvial kaolinitic clay illuviation of clay and the import of iron from the surrounding soil material put limits to the use of isovolumetric calculations the goethite boxworks after pyroxenes reflect the original pattern of fractures rather than cleavage patterns

native sulfur sulfates and sulfides from the active campi flegrei volcano southern italy genetic environments and degassing dynamics revealed by mineralogy and isotope geochemistry abstract we investigated sulfur bearing minerals from the campi flegrei caldera southern italy in relation to the increase of hydrothermal activity phenomena since 2006 aimed at providing insights into the volcanic system dynamics mineral encrustations and muds were sampled between 2013 and 2015 at the long standing degassing crater of the solfatara tuff cone and its recently restless north eastern pisciarelli slope deep seated sulfides were further separated from two drill cores agip s mofete boreholes 1500 m and 2695 m depth the mineral assemblage and texture of sampled encrustations were determined by x ray diffraction optical and scanning electron microscopy and x ray microanalysis by energy dispersive spectrometry native sulfur and alunite dominate among the newly formed mineral phases other minerals are mostly alunogen and locally pickeringite potassium alum hematite and pyrite mereiterite and amarillite sporadically occur the mud pools are rich in gypsum potassium alum and pyrite quartz and argillic phases locally with analcime are dispersed in the outcropping rocks 34 s values were determined for shallow subsurface native sulfur 5 5 to 0 0 and alunite 1 7 to 0 2 as well as for the deep seated pyrite 3 3 to 7 4 in the depth range 1500 2695 m 18 o values were measured for shallow native alunite 4 2 to 7 0 pisciarelli alunite was finally analyzed for its 87 sr 86 sr ratio and 143 nd 144 nd ratios 0 707517 6 and 0 512459 6 respectively textural and isotopic data constrain the genesis of alunite at the expense of k feldspars through rock alteration by hydrothermal fluids we suggest that the caldera is a low sulfidation system hosting acid sulfate deposits in its active degassing area the acid sulfate environment developed on an argillitic facies that thins outwards and is characteristic for steam heated and magmatic steam environments these environments developed in relation to the fractured settings that facilitates the gas emissions from deeper levels and the meteoric infiltration from surface to depth newly determined 34 s data are lower than previously published values suggesting a progressive decrease in the sulfur isotopic composition through time at least since 1956 the isotopic variation is associated with a lowering of the so 2 h 2 s ratio and the widening of the surface of co 2 degassing in the absence of significant changes in the average co 2 flux values and in the carbon and helium isotope compositions native sulfur and sulfates move from sulfur isotope equilibrium to disequilibrium we ascribe this transition to enhanced so 2 scrubbing due to a high rock permeability that facilitates a faster gas ascent rate in the shallow crust

predicting eruptions from precursory activity using remote sensing data hybridization abstract many volcanoes produce some level of precursory activity prior to an eruption this activity may or may not be detected depending on the available monitoring technology in certain cases precursors such as thermal output can be interpreted to make forecasts about the time and magnitude of the impending eruption kamchatka russia provides an ideal natural laboratory to study a wide variety of eruption styles and precursory activity prior to an eruption at bezymianny volcano for example a clear increase in thermal activity commonly occurs before an eruption which has allowed predictions to be made months ahead of time conversely the eruption of tolbachik volcano in 2012 produced no discernable thermal precursors before the large scale effusive eruption however most volcanoes fall between the extremes of consistently behaved and completely undetectable which is the case with neighboring kliuchevskoi volcano this study tests the effectiveness of using thermal infrared tir remote sensing to track volcanic thermal precursors using data from both the advanced spaceborne thermal emission and reflection radiometer aster and advanced very high resolution radiometer avhrr sensors it focuses on three large eruptions that produced different levels and durations of effusive and explosive behavior at kliuchevskoi before each of these eruptions tir spaceborne sensors detected thermal anomalies i e pixels with brightness temperatures 2 c above the background temperature high temporal low spatial resolution i e hours and 1 km avhrr data are ideal for detecting large thermal events occurring over shorter time scales such as the hot material ejected following strombolian eruptions in contrast high spatial low temporal resolution i e days to weeks and 90 m aster data enables the detection of much lower thermal activity however activity with a shorter duration will commonly be missed aster and avhrr data are combined to track low level anomalies months prior to an eruption and higher energy events prior to large eruptions to develop a monitoring approach for this eruption style results show that strombolian eruptions produce enough energy in the pre eruptive phase to trigger an avhrr detection paired with aster data the results can be extended back in time to develop a precursory timeline which captures subtle changes in volcanic activity that would commonly go unnoticed in a single data set although these precursors may be volcano and eruption specific the now sixteen year old database from aster allows this methodology to be repeatable at other volcanoes to establish a quantitative precursory baseline which would be an improvement over current eruption classifications

lunar intrusive domes morphometric analysis and laccolith modelling abstract this study examines a set of lunar domes with very low flank slopes which differ in several respects from the frequently occurring lunar effusive domes some of these domes are exceptionally large and most of them are associated with faults or linear rilles of presumably tensional origin accordingly they might be interpreted as surface manifestations of laccolithic intrusions formed by flexure induced vertical uplift of the lunar crust or alternatively as low effusive edifices due to lava mantling of highland terrain or kipukas or structural features all of them are situated near the borders of mare regions or in regions characterised by extensive effusive volcanic activity clementine multispectral uvvis imagery indicates that they do not preferentially occur in specific types of mare basalt our determination of their morphometric properties involving a combined photoclinometry and shape from shading technique applied to telescopic ccd images acquired at oblique illumination reveals large dome diameters between 10 and more than 30 km flank slopes below 0 9 and volumes ranging from 0 5 to 50 km 3 we establish three morphometric classes the first class in1 comprises large domes with diameters above 25 km and flank slopes of 0 2 0 6 class in2 is made up by smaller and slightly steeper domes with diameters of 10 15 km and flank slopes between 0 4 and 0 9 and domes of class in3 have diameters of 13 20 km and flank slopes below 0 3 while the morphometric properties of several candidate intrusive domes overlap with those of some classes of effusive domes we show that a possible distinction criterion are the characteristic elongated outlines of the candidate intrusive domes we examine how they differ from typical effusive domes of classes 5 and 6 defined by head and gifford head j w gifford a 1980 lunar mare domes classification and modes of origin moon planets 22 235 257 and show that they are likely no highland kipukas due to the absence of spectral contrast to their surrounding these considerations serve as a motivation for an analysis of the candidate intrusive domes in terms of the laccolith model by kerr and pollard kerr a d pollard d d 1998 toward more realistic formulations for the analysis of laccoliths j struct geol 20 12 1783 1793 to estimate the geophysical parameters especially the intrusion depth and the magma pressure which would result from the observed morphometric properties accordingly domes of class in1 are characterised by intrusion depths of 2 3 3 5 km and magma pressures between 18 and 29 mpa for the smaller and steeper domes of class in2 the magma intruded to shallow depths between 0 4 and 1 0 km while the inferred magma pressures range from 3 to 8 mpa class in3 domes are similar to those of class in1 with intrusion depths of 1 8 2 7 km and magma pressures of 15 23 mpa as an extraordinary feature we describe in some detail the concentric crater archytas g associated with the intrusive dome ar1 and discuss possible modes of origin in comparison to the candidate intrusive domes terrestrial laccoliths tend to be smaller but it remains unclear if this observation is merely a selection effect due to the limited resolution of our telescopic ccd images an elongated outline is common to many terrestrial laccoliths and the putative lunar laccoliths while the thickness values measured for terrestrial laccoliths are typically higher than those inferred for lunar laccoliths but the typical intrusion depths are comparable

soil altitudinal sequence on base poor parent material in a montane cloud forest in sierra juarez southern mexico the soils of montane cloud forests mcf are still insufficiently studied a number of researchers report podzols to be the main soil group for mcf ecosystems however a great deal of contradictory data exists we studied an altitudinal sequence of soils formed on ferrous chlorite shale under natural mcf vegetation in sierra juarez southern mexico from 1500 to 2500 m asl the soils of the upper part of the toposequence were folic stagnic podzols with inclusions of folic stagnosols in local depressions while the soils of the lower part of the toposequence were folic cambisols humic hyperdystric all the soils in the toposequence were extremely acid and had thick organic surface horizon mineral horizons of all soils were poor both in exchangeable and total reserves of bases the bases were concentrated mainly in organic topsoil with decreasing altitude both the thickness of albic horizons the depth of the maximum acid oxalate extractable fe and al concentrations and the difference in clay content between the eluvial and illuvial horizons decreased in the upper part of the toposequence the composition of soil clays was similar to that of parent material chlorite and mica with some mixed layered 2 1 minerals however gibbsite and kaolinite were also present in the soils of the other site within the same upper mcf belt the phenomenon was ascribed to parent material heterogenity in the medium and lower parts of the toposequence gibbsite and kaolinite were the dominant minerals we consider that the main pedogenic processes in the study area are raw humus accumulation weathering in situ podzolization and iron reduction due to water stagnation in mineral topsoil the intensity of weathering decreases while the extent of water stagnation increases with altitude to a great extent the genesis and altitudinal distribution of the soils in the mcf depends on parent material

recent geodetic unrest at santorini caldera greece 1 after approximately 60 years of seismic quiescence within santorini caldera in january 2011 the volcano reawakened with a significant seismic swarm and rapidly expanding radial deformation the deformation is imaged by a dense network of 19 survey and 5 continuous gps stations showing that as of 21 january 2012 the volcano has extended laterally from a point inside the northern segment of the caldera by about 140 mm and is expanding at 180 mm yr a series of spherical source models show the source is not migrating significantly but remains about 4 km depth and has expanded by 14 million m3since inflation began a distributed sill model is also tested which shows a possible n s elongation of the volumetric source while observations of the current deformation sequence are unprecedented at santorini it is not certain that an eruption is imminent as other similar calderas have experienced comparable activity without eruption

effects of slope orientation on pedogenesis of altimontane soils from the brazilian semi arid region baturite massif ceara given the importance of climate conditions for the development of soils studies on climosequences are a valuable tool to predict the influence of climate change on weathering rates and on soil formation processes the baturite massif a humid enclave located in the brazilian semi arid region has unique characteristics that cause a disproportional distribution of rainfall the eastern and northern slopes receive more than 1 600 mm year of rainfall whereas the southern and western slopes have semi arid characteristics with rainfall of less than 600 mm year eight soil profiles were selected to investigate the influence of these distinct climates on soil formation to achieve this physical chemical morphological mineralogical and micromorphological data were determined and analyzed in the humid slope predominate soil processes include melanization brunification intense leaching acidification and alitization with intensified weathering in higher altitudes in contrast the environment in the dry slope favored the occurrence of soils with a higher base status high activity clays low al saturation and bisialitization processes coexisting with monosialitization mainly in the soils located at lower altitudes micromorphological data indicate that clay illuviation is not the main process responsible for the enrichment of clay in the subsurface horizons the contrasting environmental conditions with different mineralogical composition seem to be an important indicator of weathering intensity and pedoenvironmental conditions

magma and volatile supply to post collapse volcanism and block resurgence in siwi caldera tanna island vanuatu arc v24c 04 allen s r 2005 complex spatterand pumice rich pyroclastic deposits from an andesitic caldera forming eruption the siwi pyroclastic sequence tanna vanuatu bulletin of volcanology 67

factors and processes of gibbsite formation in northern thailand abstract gibbsite is usually considered as end product of weathering in tropical environments with potentially high leaching rates however there are also hints towards gibbsite formation in initial stages of weathering in different climates this study reports on a systematic approach based on soil forming factors in order to research the conditions of gibbsite formation in northern thailand highlands therefore three major study sites were chosen which differ with respect to parent rock relief climate and vegetation the results show that gibbsite is common in soils of the area reasons for its occurrence in soils are manifold it can be a heritage of the parent rock a result of initial weathering under free draining conditions or an accumulation under intense chemical weathering caused by high rainfall especially the investigation in granite and gneiss areas with a high share of primary minerals indicates that gibbsite can be an early and direct transformation without intermediates from micas and feldspars if free drainage is assured with progressing soil genesis clay formation reduces drainage and favours kaolinite formation only sites with extremely high rainfall and low evaporation high elevations in northern thailand show again a dominance of gibbsite in the clay fraction throughout the whole soil profile

introducing the volcanic unrest index vui a tool to quantify and communicate the intensity of volcanic unrest accurately observing and interpreting volcanic unrest phenomena contributes towards better forecasting of volcanic eruptions thus potentially saving lives volcanic unrest is recorded by volcano observatories and may include seismic geodetic degassing and or geothermal phenomena the multivariate datasets are often complex and can contain a large amount of data in a variety of formats low levels of unrest are frequently recorded causing the distinction between background activity and unrest to be blurred despite the widespread usage of these terms in unrest literature including probabilistic eruption forecasting models and in volcanic alert level val systems frequencies and intensities of unrest episodes are not easily comparable over time or between volcanoes complex unrest information is difficult to communicate simply to civil defence personnel and other non scientists the volcanic unrest index vui is presented here to address these issues the purpose of the vui is to provide a semi quantitative rating of unrest intensity relative to each volcano s past level of unrest and to that of analogous volcanoes the vui is calculated using a worksheet of observed phenomena ranges for each phenomenon within the worksheet can be customised for individual volcanoes as demonstrated in the companion paper for taupo volcanic centre new zealand potter et al 2015 the vui can be determined retrospectively for historical episodes of unrest based on qualitative observations as well as for recent episodes with state of the art monitoring this enables a long time series of unrest occurrence and intensity to be constructed and easily communicated to end users the vui can also assist with val decision making we present and discuss two approaches to the concept of unrest

the toba caldera complex abstract the toba caldera in indonesia is one of the most remarkable volcanic features formed during quaternary geologic time its rich history of research for over a century has yielded important information on the physical volcanology of silicic calderas and super eruptions geochemical evolution of silicic magma bodies and geophysical imaging of active sub volcanic systems during the past 1 3 my the toba area has erupted intermediate composition lavas followed by intermediate pyroclastics three quartz bearing silicic tuffs and most recently intermediate to silicic lavas this pattern represents the incremental assembly and periodic eruption of a crustal magma body of batholithic proportions the apparent migration of activity to the west may have implications for the next toba super eruption

seismic precursors to the mount st helens eruptions in 1981 and 1982 six categories of seismic events are recognized on the seismograms from stations in the vicinity of mount st helens two types of high frequency earthquakes occur near the volcano and under the volcano at depths of more than 4 kilometers medium and low frequency earthquakes occur at shallow depths less than 3 kilometers within the volcano and increase in number and size before eruptions temporal changes in the energy release of the low frequency earthquakes have been used in predicting all the eruptions since october 1980 during and after eruptions two types of low frequency emergent surface events occur including rockfalls and steam or gas bursts from the lava dome

tidal coulomb failure stresses in the northern andean intermediate depth seismic clusters implications for a possible correlation between tides and seismicity abstract a recent statistical analysis of the relationship between tides and seismic activity in colombia has suggested the existence of correlation anomalies for the case of intermediate depth events in the bucaramanga nest and the cauca cluster moncayo et al 2019 in this work we explore in detail the hypothesis that tides may be triggering seismic activity in these regions and extend the analysis to two other seismic clusters in northern central south america specifically in the areas of el puyo ecuador and pucallpa peru for this purpose we use the available focal mechanism information for seismic events at these locations and calculate for each event the tidal coulomb failure stress tcfs as obtained from estimations of the tidal strain tensor tidal strains are computed considering the earth body tides and the effect of the ocean tidal loading since our purpose is to elucidate the role of tides in earthquake nucleation calculations of the tcfs are conducted not only for the time of earthquake but also for the time of the closest maximum strain within a window of a few hours before the events our results tend to support the hypothesis that tidal stresses are contributing to earthquake generation in all the studied areas this trend is especially stronger when tcfs are calculated at pre earthquake times the physical explanation for the positive contribution of tides to earthquake triggering in intermediate depth clusters may lie in the fact that a wide diversity of fault plane orientations is possible within a relatively small volume of subducted lithosphere so making the tides more likely to help loosening up the blocks at the fault plane to promote slip

influence of tidal forces on the triggering of seismic events tidal stresses are generated in any three dimensional body influenced by an external inhomogeneous gravity field of rotating planets or moons in this paper as a special case stresses caused within the solid earth by the body tides are discussed from viewpoint of their influence on seismic activity the earthquake triggering effects of the moon and sun are usually investigated by statistical comparison of tidal variations and temporal distribution of earthquake activity or with the use of mathematical or experimental modelling of physical processes in earthquake prone structures in this study the magnitude of the lunisolar stress tensor in terms of its components along the latitude of the spherical surface of the earth as well as inside the earth up to the core mantle boundary were calculated for the prem dziewonski and anderson in phys earth planet inter 25 4 297 356 1981 results of calculations prove that stress increases as a function of depth reaching a value around some kpa at the depth of 900 1500 km well below the zone of deep earthquakes at the depth of the overwhelming part of seismic energy accumulation around 50 km the stresses of lunisolar origin are only 0 0 1 0 103 pa despite the fact that these values are much smaller than the earthquake stress drops 1 30 mpa kanamori in annu rev earth planet sci 22 207 237 1994 this does not exclude the possibility of an impact of tidal forces on outbreak of seismic events since the tidal potential and its derivatives are coordinate dependent and the zonal tesseral and sectorial tides have different distributions from the surface down to the cmb the lunisolar stress cannot influence the break out of every seismological event in the same degree the influencing lunisolar effect of the solid earth tides on earthquake occurrences is connected first of all with stress components acting parallel to the surface of the earth the influence of load tides is limited to the loaded area and its immediate vicinity

the fortnightly tide and the tidal triggering of earthquakes in this paper we test the southern california network earthquake catalog and the world wide earthquake catalog for a fortnightly tidal periodicity and find none in studies that test the hypothesis of tidal triggering of earthquakes it is usually necessary to resolve the tidal shear stress onto the plane of the fault and in the direction of the slip vector to determine if the stress is compatible with the fault motion heaton 1975 1982 this analysis requires accurate focal mechanisms and knowledge of the focal plane on which slip occurred for as many earthquakes as possible to improve the statistical sampling of the data set however if we consider the fortnightly tide which is a simple amplitude modulation focal mechanism information is not required our analysis assumes that we have a large data base of earthquakes with varying mechanisms the alignment of the slip vector with the tidal shear stress will vary from earthquake to earthquake however if tidal triggering of earthquakes does occur more earthquakes should be triggered out of the total population when the tidal stress is large than when it is small if the largest semi diurnal tide is normalized to an amplitude of 1 0 the fortnightly tide would have an amplitude of 0 17 on this scale and a period of about 2 weeks munk and macdonald 1960 therefore the effect on the occurrence of earthquakes by the tidal shear stress will be modulated with a 2 week period considering the fortnightly tide allows us to utilize entire catalogs of data to test the tidal triggering hypothesis without knowledge of the focal mechanisms

kaolinite dating from acrisol and ferralsol a new key to understanding the landscape evolution in nw amazonia brazil abstract ferralsols and acrisols are major types of soils of the amazon basin observed on various landform units comprising plateau surfaces incised hills at their edges and slopes the present study focuses on an acrisol developed on plateaus surfaces from northwest amazonia and a ferralsol from the convex hills of the incised plateau edges local geomorphologic models of weathering covers suggest that ferralsols are younger than plateau acrisols but the absolute chronology of their formation is still lacking this type of information is however critical to understand the evolution of northwest amazon basin landscapes and to identify its link with major climatic and geomorphologic events in this article kaolinite rich samples from soils and saprolites belonging to a transect in the sao gabriel da cachoeira region amazon state brasil are investigated based on their crystal chemical characters several types of kaolinites are identified using a previously developed methodology based on electron paramagnetic resonance epr spectroscopy crystallization ages are proposed for these different kaolinites saprolite kaolinites are dated from 6 to 3 6 ma in the acrisol profile and display significantly more recent ages