application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

eruption mechanism as inferred from geomagnetic changes with special attention to the 1989 1990 activity of aso volcano abstract geomagnetic changes associated with the volcanic activity of aso volcano were detected with a dense network of continuously recording proton precession magnetometers during the period from june 1989 to june 1990 magnetic date clearly indicate that changes in the magnetization within the volcano are most probably caused by temperature changes this activity can be divided into five stages which are characterized by magnetization and demagnetization of the volcano these magnetic changes with durations of a few months are definitely correlated with some typical volcanic events at the crater as well as the volcanic tremor activity the demagnetization stage appears when the vent is covered by a water pool or the volcanic activity is enhanced the magnetization stage follows the opening of a vent and several large explosions which make the vent permeable the source of magnetic changes lies at a depth of about 200 m below the crater rim in the southwestern part of the active crater magnetic moments responsible for observed magnetic changes at stages 1 2 and 4 are 3 4 5 2 and 2 2 wbm respectively the corresponding source volume is estimated as a single sphere of radius 40 50 m or a spherical shell of 100 m or so an effective mechanism of rapid heating cooling exists which is ascribed to the interaction of groundwater and superheated vapor i e a shallow hydrothermal system this hydrothermal system driven by the surface cap of the vent controls every feature of the eruptions at the final outlet of aso volcano

shallow s wave attenuation and actively degassing magma beneath taal volcano philippines taal volcano philippines is one of the world s most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas a real time broadband seismic network was recently deployed and has detected volcano tectonic events beneath taal our source location analysis of these volcano tectonic events using onset arrival times and high frequency seismic amplitudes points to the existence of a region of strong attenuation near the ground surface beneath the east flank of volcano island in taal lake this region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation and it coincides with a region of high electrical conductivity the high attenuation region matches that inferred from an active seismic survey conducted at taal in 1993 these features strongly suggest that the high attenuation region represents an actively degassing magma body near the surface that has existed for more than 20 years

hydrothermal circulation beneath mount pelee inferred by self potential surveying structural and tectonic implications abstract self potential sp surveys were made on mount pelee volcano martinique island french west indies in 1991 and 1992 in order to recognize its hydrothermal system the associated groundwater channeling and the main superficial structures of the massif almost 70 km of profiles were carried out with an average sample spacing of 50 m measurements essentially reveal negative sp anomalies down to 1700 mv with high gradients 1 83 mv m due to the infiltration of meteoric water into the massif rims of summit calderas morne macouba and etang sec present sharp negative sp anomalies on the western northern and eastern flanks negative sp anomalies indicate no upward water flow beneath mount pelee summit on the southwestern volcano flank a 3 5 6 km horseshoe shaped structure corresponding to a southwest flank collapse event older than 25 000 years bp is clearly identified by the sp mapping high gradients border the inner southern rim from morne calebasse to st pierre town and the caribbean sea along the northern rim of the horseshoe shaped structure the negative sp anomalies give place to a positive sp anomaly up to 200 mv of sw ne trend this zone covers the area of two active hot springs sources chaudes and puits chaud 40 65 c marine magnetic surveys and bathymetry show that the horseshoe shaped structure spreads into the caribbean sea up to about 10 km from the coast buried structural discontinuities are evidenced inside the flank collapse structure the upper one deviates the groundwater flow coming from the summit toward the south flank where the flow finds an indentation to expand again downwards this discontinuity is either an old hypothetical caldera rim partly destroyed by the collapse of the south southwestern flank and covered by recent pyroclastic deposits or more probably the trace of a bulge landslide a circulation model of the hydrothermal waters is proposed rainfall 5 6 m year is partly drained inside the summital calderas and the flank collapse zone through pyroclastic flows down to an impermeable basement there the groundwater constitutes perched aquifers at the contact of the bulge landslide or of the hypothetical old caldera rim along the inner northern border of the flank collapse structure the phreatic water is reheated warm groundwater flows along the northern avalanche structure rim and discharges near the coast in ground and marine outcrops of medium temperature finally the main part of the meteoric water is channeled along the old caldera rim or along the bulge landslide towards the south flank of mount pelee where some gaps in the rim exist there the groundwater finds again a subhorizontal gravitational circulation along mount pelee slopes into the caribbean sea

combined electromagnetic geochemical and thermal surveys of taal volcano philippines during the period 2005 2006 since 1572 33 phreatic to phreatomagmatic eruptions have occurred on taal volcano philippines some of them causing several hundred casualties considering the time delay between two consecutive eruptions there is an 88 probability that taal volcano should have already erupted since 1992 several phases of seismic activity have been recorded accompanied by ground deformation opening of fissures and surface activity the volcanic activity of taal appears to be controlled by dike injections and magma supply buffered by a hydrothermal system that releases fluids and heat through boiling and subsequent steaming in early 2005 a multidisciplinary project was launched for studying the hydrothermal activity to map the hydrothermal system combined surveys were carried out to investigate self potential total magnetic field ground temperature and carbon dioxide soil degassing along with satellite thermal imaging of the main crater lake the elevated temperatures and high concentrations of carbon dioxide as well as electromagnetic anomalies indicate large scale hydrothermal degassing this process is enhanced along the tectonic features e g crater rim and faults of the volcano while active fissures opened along the e w northern flank during the 1992 1994 seismic activity heat and fluids from the hydrothermal system are essentially released in the northern part of the crater which is bounded to the south by a suspected nw se fault along which seismicity seems to take place and dikes are thought to be intruded during the january 2005 surveys a new seismic crisis started and the felt earthquakes prompted spontaneous evacuation of hundreds of inhabitants living on the volcano repeated surveys show changes of self potential total magnetic field and ground temperature with time without any noticeable spatial enlargement these observations suggest that the northern flank located between the crater rim and the 1992 1994 fissures is connected with a deep thermal source in main crater and is reactivated during seismic crises this sector could be subjected to flank failure

volcanomagnetic effects observed on piton de la fournaise volcano reunion island 1985 1987 a permanent network of four to six telemetered magnetic stations has been installed on piton de la fournaise volcano in october 1985 and 1986 eight eruptive sequences have occurred since then some of which affected only the summit whereas others affected the whole massif volcanomagnetic variations are observed with each of these volcanic events the geomagnetic field intensity is measured simultaneously every minute at each station with a precision of 0 25 nt nanotesla the main results are the following volcanomagnetic variations observed with eruptions have amplitudes of several nanoteslas to more than 10 nt with characteristic time durations ranging from l min or less to several months a good correlation between the magnetic variations recorded at the different stations is observed spatial and temporal properties of the volcanomagnetic field appear to be controlled by the features of the eruptions several days before the beginning of the december 1985 march july november december 1986 and january 1987 eruptions changes in the intensity differences are observed with amplitudes of a few nanoteslas up to 5 nt at stations located close to the active part of the rift zone variations are also observed in the most remote stations for larger eruptions in march 1986 november december 1986 and january 1987 correlations between magnetic variations ground deformations and seismic activity have been observed for the december 1985 march 1986 november december 1986 and january 1987 events three main mechanisms could account for the observed volcanomagnetic variations piezomagnetic effects electrokinetic effects and electrical resistivity changes since variations in the stress field in the surroundings can modify the induced and natural magnetizations of magnetized rocks the circulation of water through the interconnected pore network microcracks faults aquifers and also the electrical resistivity of geological structures through the modification of the properties of the pore network

geochemical evidence for a magmatic co2 degassing event at mammoth mountain california september december 1997 recent time series soil co2 concentration data from monitoring stations in the vicinity of mammoth mountain california reveal strong evidence for a magmatic degassing event during the fall of 1997 lasting more than 2 months two sensors at horseshoe lake first recorded the episode on september 23 1997 followed 10 days later by a sensor on the north flank of mammoth mountain direct degassing from shallow intruding magma seems an implausible cause of the degassing event since the gas released at horseshoe lake continued to be cold and barren of other magmatic gases except for he we suggest that an increase in compressional strain on the area south of mammoth mountain driven by movement of major fault blocks in long valley caldera may have triggered an episode of increased degassing by squeezing additional accumulated co2 from a shallow gas reservoir to the surface along faults and other structures where it could be detected by the co2 monitoring network recharge of the gas reservoir by co2 emanating from the deep intrusions that probably triggered deep long period earthquakes may also have contributed to the degassing event the nature of co2 discharge at the soil air interface is influenced by the porous character of high sierra soils and by meteorological processes solar insolation is the primary source of energy for the earth atmosphere and plays a significant role in most diurnal processes at the earth surface data from this study suggest that external forcing due largely to local orographic winds influences the fine structure of the recorded co2 signals

a large self potential anomaly on unzen volcano shimabara peninsula kyushu island japan self potential sp observation was carried out in the summit area of unzen one of the active volcanoes in kyushu island japan we found a positive sp anomaly in the vicinity of the newly extruded lava dome the potential difference across the anomaly exceeds 1000mv per 500m streaming potentials associated with subsurface hydrothermal convection seem to be the most reasonable mechanism for the positive anomaly in association with the first emergence of the lava dome a sharp increase of sp was detected which is considered to be a result of the growth of the hydro thermal system

runoff control of soil degassing at an active volcano the case of piton de la fournaise reunion island abstract airborne atmospheric and in situ soil gas analyses demonstrate that distal gas leaks are non existent at piton de la fournaise pf despite frequent eruptions airborne traverses made at a constant altitude indicated that no detectable large scale co 2 degassing occurs from the volcano in situ soil gas traverses co 2 4 he 222 rn across the active rift zones the summit crater and the caldera rims show both a lack of positive anomalies and evidence of strong depleted concentrations for he and co 2 with respect to air depletions in soil he is explained by intense rain water infiltration a more unexpected result lies in the very low co 2 concentrations down to 92 ppm in bare soils in the summit region such a depletion was not previously reported and is attributed to considerable basalt weathering operating as the result of huge runoff a model has enabled both the runoff and the co 2 consumption occurring within the basaltic layers to be calculated data obtained are consistent with values expected from large scale erosion models and with the local calculated diffusive flux of co 2 in soils the huge runoff together with the basaltic lithology of the volcano are found to be the main factor controlling the soil gas signatures at pf

coherent modes in multiscale variability of streamflow over the united states motivated by the need to understand large scale hydrologic response significant research has been directed toward the identification of coherent regions using characteristics of streamflow variability typically these regions are delineated using principal component analysis on streamflow this method does not account for differences in temporal scales of fluctuations embedded in the time series to capture this we use wavelet spectral analysis wavelet spectra from the specific streamflow series are obtained for outflow binned at 3 length segments along the border of the conterminous united states rotated principal component analysis is performed on the wavelet spectra to obtain clusters of segments that exhibit similar distribution of variability across scales three physically distinct modes explain over 89 of the variability two of the modes identified are associated with high variability at seasonal scales and the third is associated with high variability at small timescales the runoff generation mechanisms underlying the observed modes of multiscale variability of various regions are also discussed each of these coherent modes of multiscale variability indicate the existence of regions with similar scales of fluctuations that are located geographically apart as well as regions located geographically close with dissimilar scales of fluctuations

fracturing associated with the 1977 1978 eruption of usu volcano north japan as revealed by geophysical measurements abstract none of the ground temperature measurements inside the somma caldera of usu volcano in southwestern hokkaido japan show patterns that correlate with the development of surface faults and the hypocenter distribution of earthquake swarms observed during the 1977 1978 eruptions audiomagnetotelluric a m t soundings on the surface of the somma caldera display well defined high resistivity zones h r z within the low resistivity edifice h r z are explained as being due to rising dry steam and low resistivity zones are attributed to ionized water in the volcanic edifice inversion of data shows that elongated h r z have a shallow roof and are some hundred meters wide steam rising along narrow vertical fractures generates widely distributed vapor dominated geothermal systems because rising steam condenses near the surface the condensed steam creates a water filled zone which inhibits the free escape of succeeding steam distribution of elongated h r z correlates well with the high ground temperature zones a self potential survey reveals a positive anomaly developed over the usu edifice about 350 mv in magnitude electrokinetic coupling effect due to intensive hydrothermal convection is a probable interpretation of the anomaly because the high potential zone is closely related to a high ground temperature zone hydraulic fracturing of the upper crust at the time of eruption allowed release of elastic strain energy due to magma pressure at depths with the spectacular consequence that one side of the major fracture was uplifted about 180 m the geometry of such a process may be drawn from seismological results the roof of the edifice is pushed up by expanding magma accompanying intensive seismic activities we suggest that earthquake free zones are proof of magma filled fractures and that eruption took place when one of these fractures opened to the surface

resistivity and self potential changes associated with volcanic activity the july 8 2000 miyake jima eruption japan abstract the miyake jima volcano abruptly erupted on july 8 2000 after 17 years of quiet and gave birth to a crater 1 km in diameter and 250 m deep this expected unrest was monitored during the years 1995 2000 by electromagnetic methods including dc resistivity measurements and self potential sp surveys beneath the 2500 yr old hatcho taira summit caldera audio magnetotelluric soundings made in 1997 98 identified a conductive medium 200 500 m thick within the 50 m isoline located at a few hundred metres depth it was associated with the active steady state hydrothermal system centred close to the 1940 cone and extending southward a dc resistivity meter set in a schlumberger array with 600 1000 and 1400 m long injection lines evidenced strong resistivity changes between september 1999 and july 3 2000 in the vicinity of the newly formed crater the apparent resistivity has reached about three times its initial values on the 1400 m long line and has lowered to about 20 on the 600 m line just prior to the july 8 2000 eruption sp mapping made inside the summit hatcho taira caldera revealed negative anomalies where positive ones had occurred during the previous tens of years the largest negative anomaly 225 mv in amplitude mainly took place above the 1940 cone which collapsed in the crater formation a permanent 1 km long sp line across the caldera suggests accelerating changes during the 3 months preceding the eruption on a larger scale the comparison between 1995 and 2000 surveys has shown a global increase of the hydrothermal activity beneath the volcano its source could have been 250 m to the south of the crater these observations suggest that the hydrothermal system was slowly disturbed in the months preceding the eruption while drastic changes have occurred during the 2 weeks before the summit collapse when tectonic and volcanic swarms have appeared

self potential variations associated with ultra long period seismic signals at merapi volcano 1 we report about self potential sp anomalies registered 150 m from the active lava dome of merapi volcano which are associated with ultra long period ulp seismic signals periods 100 s during a 5 month period of simultaneous sp and seismological measurements 50 ulp events were detected seismologically if sp time series corresponding to ulp events are aligned to the onset times of ulp events and stacked the resulting traces show anomalous sp with an amplitude of 5 20 mv km and 40 60 min duration in contrast the anomalous signals were not present in ground temperature data nor in sp data recorded 1 km from the summit sp anomalies associated with ulp seismicity might be caused by electro kinetic effect of fluid flow in subsurface this result is consistent with the ulp generation model based on seismological observations and adds new information towards the understanding of ulp seismicity

dynamics of active magmatic and hydrothermal systems at taal volcano philippines from continuous gps measurements 1 a dense network of continuous single and dual frequency gps receivers at taal volcano philippines reveals four major stages of volcanogenic deformation deflation from installation in june 1998 to december 1998 inflation from january to march 1999 deflation from april 1999 to february 2000 and inflation from february to november 2000 the largest displacements occurred during the february november 2000 period of inflation which was characterized by 120 mm of uplift of the center of volcano island relative to the northern caldera rim at average rates up to 216 mm yr deformation sources were modeled using a constrained least squares inversion algorithm the source of 1999 deflation and inflation in 2000 were modeled as contractional and dilatational mogi point sources centered at 4 2 and 5 2 km depth respectively beneath volcano island the locations of the inflationary and deflationary sources are indistinguishable within the 95 confidence estimates modeling using a running 4 month time window from june 1999 to march 2001 reveals little evidence for source migration we suggest that the two periods of inflation observed at taal result from episodic intrusions of magma into a shallow reservoir centered beneath volcano island subsequent deflation may result from exsolution of magmatic fluids and or gases into an overlying unconfined hydrothermal system

shallow soil co2 flow along the san andreas and calaveras faults california 1 we evaluate a comprehensive soil co2 survey along the san andreas fault saf in parkfield and the calaveras fault cf in hollister california in the context of spatial and temporal variability origin and transport of co2 in fractured terrain co2 efflux was measured within grids with portable instrumentation and continuously with meteorological parameters at a fixed station in both faulted and unfaulted areas spatial and temporal variability of surface co2 effluxes was observed to be higher at faulted saf and cf sites relative to comparable background areas however 13c 23 3 to 16 4 and 14c 75 5 to 94 4 values of soil co2 in both faulted and unfaulted areas are indicative of biogenic co2 even though co2 effluxes in faulted areas reached values as high as 428 g m 2 d 1 profiles of soil co2 concentration as a function of depth were measured at multiple sites within saf and cf grids and repeatedly at two locations at the saf grid many of these profiles suggest a surprisingly high component of advective co2 flow spectral and correlation analysis of saf co2 efflux and meteorological parameter time series indicates that effects of wind speed variations on atmospheric air flow though fractures modulate surface efflux of biogenic co2 the resulting areal patterns in co2 effluxes could be erroneously attributed to a deep gas source in the absence of isotopic data a problem that must be addressed in fault zone soil gas studies

identification of a hidden thermal fissure in a volcanic terrain using a combination of hydrothermal convection indicators and soil atmosphere analysis abstract mapping and characterizing fracturing in a volcanic terrain is facilitated by the analysis of physical and chemical properties of soils the parameters analyzed include the temperature at shallow depth the spontaneous potential sp and the 4 he 44 co 2 and 222 rn contents of soil gases as measured in situ by mass spectrometry and counter this analysis allowed a distinction of deep fissures not accompanied by thermal loss characterized by a negative sp anomaly and high he levels and of a hidden fissure with thermal loss characterized by a positive sp anomaly and high he rn and co 2 levels this fissure has no visible surface manifestations this method of analysing the convective thermal transfer is useful when analysing fracturing in volcanic structures to estimate their eruptive potential

mapping and surveillance of active fissure zones on a volcano by the self potential method etna sicily abstract the self potential s p method often employed in base metal exploration has successfully been applied to volcanological problems test surveys on the site of mount etna sicily have revealed some positive anomalies as high as a few hundred millivolts over recent and old eruptive fissures the s p technique allows one to determine the precise location of the fissures the interpretation of the geophysical results including s p taking into account the structure of mount etna has shown two important zones upon which several s p investigations have been carried out studies of the causes of these s p anomalies have shown the importance of the streaming potential as the principal source mechanism

geochemical and isotopic evidence for seawater contamination of the hydrothermal system of taal volcano luzon the philippines the hydrologic structure of taal volcano has favored development of an extensive hydrothermal system whose prominent feature is the acidic main crater lake ph 3500 mg kg and low so4 cl ratios 0 3 the br cl ratio of most samples suggests incorporation of seawater into the hydrothermal system water and dissolved sulfate isotopic compositions reveal that the main crater lake and spring discharges are derived from a deep parent fluid t approximate to 300 degrees c which is a mixture of seawater volcanic water and lake taal water the volcanic end member is probably produced in the magmatic hydrothermal environment during absorption of high temperature gases into groundwater boiling and mixing of the parent water give rise to the range of chemical and isotopic characteristics observed in the thermal discharges incursion of seawater from the coastal region to the central part of the volcano is supported by the low water levels of the lakes and by the fact that lake taal was directly connected to the china sea until the sixteenth century the depth to the seawater meteoric water interface is calculated to be 80 and 160 m for the main crater lake and lake taal respectively additional data are required to infer the hydrologic structure of taal geochemical surveillance of the main crater lake using the so4 cl na k or mg cl ratio cannot be applied straightforwardly due to the presence of seawater in the hydrothermal system

magnetic and electric field observations during the 2000 activity of miyake jima volcano central japan magnetic and electric field variations associated with the 2000 eruption of miyake jima volcano are summarized for about 1 week prior to the july 8 phreatic explosion significant changes in the total intensity were observed at a few stations which indicated uprising of a demagnetized area from a depth of 2 km towards the summit this nonmagnetic source can be regarded as a vacant space itself electric and magnetic field variations were observed simultaneously associated with the tilt step event which was the abrupt v50 s inflation at a few km depth within the volcano followed by gradual recovery vseveral hours the electric field is ascribed to the electrokinetic effect most probably due to forced injection of fluids from the source while the magnetic field to the piezomagnetic effect due to increased pressure large magnetic variations amounting to a few tens of nt were observed at several stations since july 8 and they turned almost flat after the august 18 largest eruption magnetic changes are explained mostly by the vanishing of magnetic mass in the summit and additionally by the thermal demagnetization at a rather shallow depth a large increase in the self potential by 130 mv was also observed near the summit caldera associated with the august 18 eruption which suggests that the hydrothermal circulation system sustained within the volcano for the past more than 10 years was destroyed by this eruption 9 2002 published by elsevier science b v

monitoring and modelling hydrothermal fluid emission at la solfatara phlegrean fields italy an interdisciplinary approach to the study of diffuse degassing discharge of hydrothermal fluids at la solfatara is one of the many pieces of evidence testifying to the level of activity and the potential danger characterizing the volcanic complex of the phlegrean fields recent measurements of diffuse degassing shed light on the unexpected magnitude of this process and prompted further research to improve our understanding of the hydrothermal system feeding the surface phenomenon at la solfatara in this work we first present new data on co2 diffuse degassing that were collected during a campaign in july 2000 and confirm previous measurements of the degassing rate these data together with other information on subsurface structures and conditions provided the necessary constraints to perform physical modelling of the hydrothermal fluid circulation at la solfatara numerical simulations describe the ascent and evolution of a hot multi phase and multi component fluid composed of water and carbon dioxide through a homogeneous porous medium when certain system properties and conditions are used this model reproduces some of the main features which characterize the natural system including the energy budget associated with the ascent and condensation of hot fluids and the development of a single phase gas region whose existence was inferred from independent chemical data further simulations investigated the effects associated with changes in rock properties and fluid injection rates results showed that an increase in the permeability at shallow depth may have an important influence on the system conditions and fluid discharge they imply that surface phenomena accompanied by very high temperatures at shallow depths may survive long after deep feeding has ceased

carbon dioxide degassing by advective flow from usu volcano japan magmatic carbon dioxide co2 degassing has been documented before the 31 march 2000 eruption of usu volcano hokkaido japan six months before the eruption an increase in co2 flux was detected on the summit caldera from 120 september 1998 to 340 metric tons per day september 1999 followed by a sudden decrease to 39 metric tons per day in june 2000 3 months after the eruption the change in co2 flux and seismic observations suggests that before the eruption advective processes controlled gas migration toward the surface the decrease in flux after the eruption at the summit caldera could be due to a rapid release of co2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera

a large hydrothermal reservoir beneath taal volcano philippines revealed by magnetotelluric resistivity survey 2d resistivity modeling taal volcano located in the southwestern part of luzon island philippines has frequently experienced catastrophic eruptions from both the main crater on volcano island and flank eruptions these eruptions have been magmatic phreatomagmatic and hydrothermal with the latter implying the existence of a large scale hydrothermal system beneath the volcano we conducted an electrical resistivity survey using the magnetotelluric method in order to identify the location and geometry of the hydrothermal reservoir and sealing cap rock two dimensional inversion using the observed data indicates four similar resistivity sections the structure at shallow depths corresponds to volcanic deposits and an aquifer below 1 km the structure features a relatively resistive zone beneath the main crater surrounded by a conductive shell we interpreted these to be a large hydrothermal reservoir with an impermeable cap rock sealing it recent ground deformation detected by gps measurements suggests that the hydrothermal reservoir is active the interpreted cap rock thins just beneath the main crater and could easily be destroyed by an imbalance in the hydrothermal system we conclude that this hydrothermal reservoir plays a significant role in driving catastrophic eruptions that begin with a hydrothermal explosion at the main crater

rapid fluid disruption a source for self potential anomalies on volcanoes self potential sp anomalies observed above suspected magma reservoirs dikes etc on various volcanoes kilauea hawaii mount unzen japan piton de la fournaise reunion island miyake jima japan result from transient surface electric fields of tens of millivolts per kilometer and generally have a positive polarity these sp anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained we propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization disruption as liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions both charge generation and local increase in electrical resistivity by removal of fluids should occur we report laboratory observations of electric fields in hot rock samples generated by pulses of fluid water through the rock at atmospheric pressure these indicate the relative amplitudes of rapid fluid disruption rfd potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign above vaporization temperatures rfd effects of positive sign in the direction of gas flow dominate whereas below these temperatures effects of negative sign dominate this suggests that the primary contribution to observed self potential anomalies arises from gas related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport at lower temperatures the primary contribution is from electrokinetic effects modulated perhaps by changing electrical resistivity and rfd effects from high pressure but low temperature co 2 and so 2 gas flow ripping water molecules from saturated crustal rocks if charge generation is continuous as could well occur above a newly emplaced dike positive static potentials will be set up that could be sustained for many years and the simplest method for identifying these hot active regions would be to identify the sp anomalies they generate

self potential soil co2 flux and temperature on masaya volcano nicaragua we investigate the spatial relationship between self potential sp soil co sub 2 flux and temperature and the mechanisms that produce sp anomalies on the flanks of masaya volcano nicaragua we measured sp soil co sub 2 fluxes 1 to 5 0 x 10 sup 4 g m sup 2 d sup 1 and temperatures 26 to 80 c within an area surrounding a normal fault adjacent to comalito cinder cone 2002 2003 these variables are well spatially correlated wavelengths of sp anomalies are le 100 m and high horizontal sp gradients flank the region of elevated flux and temperature carbon isotopic compositions of soil co sub 2 delta sup 13 c 3 3 to 1 1 per thousand indicate a deep gas origin given the presence of a deep water table 100 to 150 m high gas flow rates and subsurface temperatures above liquid boiling points we suggest that rapid fluid disruption is primarily responsible for positive sp anomalies here concurrent measurement of sp soil co sub 2 flux and temperature may be a useful tool to monitor intrusive activity

the volcanic activity of la soufriere of guadeloupe lesser antilles structural and tectonic implications abstract among observations made on la soufriere volcano guadeloupe to monitor its its activity are temperature measurements temperature of fumaroles hot springs ground surface and water inside two boreholes 80 and 90 m deep those measurements proved to be of prime importance in understanding mechanisms working in the volcano and governing its activity they lead with other observations such as self potential measurements and geochemical analysis of fumaroles and hot springs to a possible interpretation of phreatic activity rather different from the one retained earlier which was essentially based on seismic data in this model the magma reservoir is only in a stable state and in particular supplies heat at a constant rate to the overlying geological structures the cycle of volcanic activity and period of quiescence is interpreted as due to a cycle of clogging and reopening of the system of fractures transferring heat from a lower aquifer to an upper one and eventually to the atmosphere the model is discussed in regard of other geophysical observations in particular seismicity some inferences are made concerning a new phase of activity and suitable observations to predicit it

source process of long period seismic events at taal volcano philippines vapor transportation and condensation in a shallow hydrothermal fissure 1 we analyzed observations of a swarm of more than 40 000 long period lp seismic events at taal volcano philippines in 2010 2011 the event waveforms are strongly correlated to each other consistent with a fixed source location and begin with a dilatational first motion they have a peak frequency around 0 8 hz and a quality factor q of 6 waveform inversion of the events pointed to a tensile crack source dipping 30 60 at a shallow 100 200 m depth a simulation using a fluid filled crack model indicated that the complex frequencies of the waveforms are explained by the fundamental longitudinal mode resonance of a vapor filled crack 188 m long a satellite thermal infrared image acquired during the swarm period suggests that the lp events were not accompanied by surface gas releases we considered a vapor transportation model in which vapor exsolved from magma and rose in a fissure extending to the lp source this model yielded estimates that 105 107 m3 of magma was involved in the lp swarm and that the temperature of vapor in the lp source crack was around 600 k we modeled a triggering mechanism of the crack resonance based on sudden condensation of vapor at the crack tip in a cold aquifer this model explained observed characteristics of the events including the dilatational first motion the total volumetric change and the fixed source location

shape evolution and fabric in a boulder beach monument cove maine abstract unequal spacing of nearly vertical joints and sheeting in hornblende granite at monument cove maine forms large tabular blocks which accumulate as talus on the backbeach the blocks are subsequently rounded by wave action to form a pocket boulder and cobble beach measurements of the talus blocks and boulders indicate that the initial structurally controlled bladed and elongate habits are manifested in the boulders however as abrasion progresses more compact spherical and more platy discoidal boulders evolve the data suggest that the greatest change is toward compactness and that the ultimate clast shape at monument cove would be spherical the orientations of the l i planes and the l axes of the rounded clases were also measured the l i planes are well oriented dipping m inly offshore the l axes orientations form three main clusters one subparallel to the shoreline one down the dip of the beach and one oblique to the shoreline the latter two clusters lie within the modal dip of the l i planes

magnetic field changes on white island new zealand and the value of magnetic changes for eruption forecasting for about 15 years after their commencement in 1968 magnetic measurements in the crater of white island gave a good indication of the state of activity and the likelihood of an eruption episode commencing during this period magnetic thermal ground level and chemical measurements were all generally consistent with a model in which these surface changes were caused by increasing temperatures under the donald mound area in the central sub crater in more recent times there has not been such a relationship between the changes around the remnants of donald mound and the volcanic activity which has become localised in the west sub crater it appears that changes under the crater especially lowering of the ground surface and the water table at the west end of the crater have meant that eruptions are no longer preceded by heating under donald mound the west sub crater is not easily accessible for repeat surface surveys one way in which we might be able to monitor future volcanic activity at white island would be by repeated aeromagnetic surveys as the magnetic changes are so large that changes of hundreds of nanoteslas are likely to be observed at practical flying heights

genesis and evolution of unrest episodes at campi flegrei caldera the role of thermal fluid dynamical processes in the geothermal system we develop a model for describing water flow in a porous medium under the effect of thermal and pressure gradients the model simulates geothermal systems in calderas given the boundary conditions and the fluid dynamical properties of the medium the model allows computation in fluid dynamical stationary states of parameters characterizing the flow such as flow velocity and temperature and pressure distributions at depth the model is applied to investigate the effects of the local geothermal system on the unrest episodes at campi flegrei caldera using experimentally determined fluid dynamical parameters for the caldera rocks we show that changes of water flow in shallow aquifers under the effect of pressure and or temperature variations within the geothermal system can be very important in the genesis and evolution of unrest crises in particular they can strongly amplify the effect of pressure increase in the magma chamber on ground uplift they can also explain the timescales of evolution of ground movements in terms of transit times of the water front and of the connected temperature fronts due to advective transport on such grounds an integrated mechanic thermal fluid dynamical model was built allowing us to give a semiquantitative global explanation to the genesis and evolution of unrest phenomena results obtained here can be generalized to other similar calderas

soil gas emanations as precursory indicators of volcanic eruptions field measurements conducted on several active volcanoes in italy the lesser antilles and indonesia demonstrate the common occurrence of diffuse soil gas emanations from the volcanic piles at distances from active craters or fumarolic zones these emanations consist essentially of carbon dioxide and rare gases and their genetic link with crater fumaroles and or magma degassing at depth can be verified both chemically and isotopically we emphasize here the potential use of these fluids for continuous volcano monitoring and eruption forecasting

self potential and ground temperature at merapi volcano prior to its crisis in the rainy season of 2000 2001 abstract rainwater infiltration into the active lava dome of merapi volcano central java has often been suggested as a triggering mechanism for partial dome collapse and subsequent eruptive behavior however the phenomenon has not been systematically investigated we use a multi parametric approach to study the interaction of the hydrologic and magmatic system near the lava dome prior to its crisis in early 2001 we describe the hardware concept for a continuous monitoring system for self potentials u sp and ground temperature t installed in august 2000 at the solfatara woro only 150 m from the active lava dome relating the data from this station to measurements of rainfall air pressure solfatara temperature and seismicity several effects can be distinguished a a long term correlation is observed between electrode temperature difference and sp with estimated coupling coefficients of 2 1 0 5 mv c b after individual rainfall events u t signatures show a typical pattern of positive charge accumulation at the hot electrodes near the fumarolic vents c an exceptional anti correlation between u and t is observed in january 2001 during a period of rapid dome growth prior to the collapse and eruptive crisis d wavelet analysis of sp reveals the sporadic occurrence of periodic fluctuations with a clear 12 h s2 component because of their amplitude of up to 100 mv km and their periodicity s2 but not 24 h or lunar 12 h 25 min these fluctuations are unlikely to be caused by natural magnetic field variation or by earth tides instead they do seem correlated but not in phase with atmospheric pressure changes we discuss effects a d in the framework of source mechanisms related to water lava interactions