18o exchange between steam and carbon dioxide in volcanic and hydrothermal gases implications for the source of water abstract the oxygen isotopic compositions of h 2 o and co 2 from 31 fumaroles from different volcanoes vesuvio campi flegrei vulcano and etna in italy soufriere of guadeloupe in lesser antilles prove that 18 o exchange between co 2 and steam is fast enough in natural gas phases to allow rapid isotopic reequilibration within a wide temperature range 100 1000 c the isotopic composition of h 2 o discharged by volcanic hydrothermal fumaroles is affected by isotopic reequilibration along with cooling of the gas phase and this secondary process must be taken into account when interpreting the origin of the water from isotopic data the use of corrected 18 o values computed considering the overall oxygen isotopic composition of the h 2 o co 2 system is therefore compulsory to overcome interpretative biases as an example we apply this method to 100 600 c fumaroles at vulcano crater whose isotopic composition is reinterpreted considering the effects of 18 o exchange between co 2 and h 2 o in contrast to most previous interpretations the corrected isotopic values for h 2 o clearly show that the vulcano system is fed by a two component mixture of magmatic water with a typical andesitic composition and either 18 o shifted seawater or magmatic steam partly condensed within the volcanic ground with minor contribution of local meteoric water the possible additional effects of isotopic reequilibration involving other o and h bearing gas species in volcanic fluids such as so 2 h 2 s hcl hf and h 2 have been also considered the influence of so 2 upon the isotopic composition of h 2 o is subordinate with respect to that of co 2 whereas significant shifts in deuterium composition are expected from hydrogen isotopic exchanges in the h 2 o h 2 s hcl hf h 2 gas system

genesis of fumarolic emissions as inferred by isotope mass balances co2 and water at vulcano island italy we have developed a quantitative model of co2 and h2o isotopic mixing between magmatic and hydrothermal gases for the fumarolic emissions of the la fossa crater vulcano island italy on the basis of isotope balance equations the model takes into account the isotope equilibrium between h2o and co2 and extends the recent model of chemical and energy two end member mixing by nuccio et al 1999 as a result the h2o and co2 content and the d 18o and 13c isotope compositions for both magmatic and hydrothermal end members have been assessed low contributions of meteoric steam added at a shallow depth have been also recognized and quantified in the fumaroles throughout the period from 1988 to 1998 nonequilibrium oxygen isotope exchange also seems to be occurring between ascending gases and wall rocks along some fumarolic conduits the 13cco2 of the magmatic gases varies around 3 to 1 vs peedee belemnite pdb following a perfect synchronism with the variations of the co2 concentration in the magmatic gases this suggests a process of isotope fractionation because of vapor exsolution caused by magma depressurization the hydrogen isotopes in the magmatic gases 1 to vs standard mean ocean water smow as well as the above 13cco2 value are coherent with a convergent tectonic setting of magma generation where the local mantle is widely contaminated by fluids released from the subducted slab magma contamination in the crust probably amplifies this effect the computed isotope composition of carbon and hydrogen in the hydrothermal vapors has been used to calculate the d and 13c of the entire hydrothermal system including mixed h2o co2 vapor liquid water and dissolved carbon we have computed values of about 10 vs smow for water and 2 to 6 5 vs pdb for co2 on these grounds we think that mediterranean marine water dh2o 10 feeds the hydrothermal system it infiltrates at depth throughout the local rocks reaching oxygen isotope equilibrium at high temperatures interaction processes between magmatic gases and the evolving seawater also seem to occur causing the dissolution of isotopically fractionated aqueous co2 and providing the source for hydrothermal carbon these results have important implications concerning fluid circulation beneath vulcano and address the more convenient routine of geochemical surveillance

thermal expansion contraction and slope instability of a fumarole field inferred from geodetic measurements at vulcano between 1987 and 1993 fumarole temperatures at the fossa crater of vulcano italy were characterized by the highest values since the 1920 s increasing from about 300 c in 1987 to 690 c in may 1993 before decreasing to 400 c by 1996 1997 during 1990 vulcano s electronic distance measurement edm network was expanded to provide more detailed coverage of the northern sector of the fossa crater and in particular to monitor the movement of the northern flank the fossa cone measurements carried out between 1990 and 1994 showed shortening by about 6 to 7 cm along baselines measured to a small section of the northern rim over the following four years these baselines showed a slow extension by about 3 cm to gradually recover part of the previous deformation we believe that the shortening and lengthening of the edm baselines was respectively due to the increasing and decreasing temperature of the rock body lying close to the deforming area this caused thermal expansion followed by contraction the positive movement of the rim was not completely matched by a negative recovery suggesting that a non recoverable sliding movement was also responsible for some of the shortening of the baselines we verified our hypothesis by calculating the expected dilatation of a rock body as a function of the volume of rock heated and its thermal expansion coefficient and compared the expected deformation to that observed the geodetic investigation showed that the unstable portion affects a small length of the rim about 100 m long and involves a volume of about 0 8 106 m3 however this zone lies directly above a particularly unstable portion of the flank as well as the main village and port on the island

late quaternary earthquake related soft sediment deformation along the belgian portion of the feldbiss fault lower rhine graben system abstract trench investigations along the bree fault scarp in belgium in the framework of a first paleoseismological experience in the area of the lower rhine graben system have not only demonstrated the existence of seismogenic faults almost extending to the present ground surface but also exposed several types of soft sediment deformation affecting sandy sediments and soils of inferred late weichselian to holocene age the observed features include asymmetric folding small scale normal faulting possible sand intrusions and small water escape or load structures establishing a seismic origin for the individual features is not always possible based on their sedimentary characteristics only particularly due to the potential confusion with periglacial phenomena but their abundance the close association of different deformational styles and their vicinity to a known active fault all seem to be compatible with an earthquake induced scenario the features are to some extent comparable to those generated during the recent ms 5 3 roermond earthquake at the opposite side of the roer valley graben stratigraphical and mutual geometrical relationships suggest the occurrence of at least three distinct deformational events since probably 30 000 years and one event before that time since nothing is yet known about their regional distribution however estimating the associated paleomagnitudes from these soft sediment deformations is premature

active faulting and paleoseismology along the bree fault lower rhine graben belgium paleoseismic analysis of the 10 km long bree fault scarp in the lower rhine graben yields numerous lines of evidence of earthquake activity in the holocene and late pleistocene this active normal fault a part of the feldbiss fault system dips 70 ne and is expressed at the surface by a prominent nw se trending 7 to 20 m high scarp formed since the deposition of the maas river main terrace 700 kyr b p trenches and geophysical prospecting show that the fault which is known to have 100 m of vertical offset since the late pliocene breaks late pleistocene and holocene deposits ground penetrating radar seismic refraction and electric tomography suggest that at shallow depth the amount of displacement is larger than the youngest vertical offset visible in the trenches and corresponds to cumulative fault displacements the analysis of 36 leveling profiles across the scarp indicates that its height can be classified into three groups likely corresponding to different events a morphologic dating gives approximate ages of 2 1 5 kyr b p 14 5 kyr b p and 41 6 kyr b p for the past three surface faulting earthquakes analysis of faulted stratigraphy and earthquake induced deformation structures exposed in trenches suggests the occurrence of three large earthquakes during the past 45 l03 years and yields 0 07 mm yr of relative vertical deformation rate the most recent seismic event occurred between a d 610 and 890 the first identification of an active fault with surface ruptures in the lower rhine graben area emphasizes that large earthquake sources exist within intraplate europe and that at least some of these events are preserved in the geologic record

tornillos at vulcano clues to the dynamics of the hydrothermal system abstract the number of tornillo events has recently increased at the vulcano island italy while only 15 tornillos were recorded during 2004 2006 584 events occurred in 2007 2008 they were located just below la fossa crater at depths ranging between 0 1 and 1 km b s l during two intervals in 2007 2008 increases in the number of tornillos took place at the same time as temperature and geochemical anomalies were observed the spectral content of the tornillos generally characterized by one two dominant spectral peaks near 6 and 10 hz varied over time with changes also noted in the quality factors the simplest source mechanism proposed for tornillos is the free eigenvibration of a fluid volume within a crack or a conduit based on this model we propose a causal relationship between the temperature and geochemical anomalies and the increases in numbers of tornillos as the amount of hydrothermal fluids increases during the anomalies the upward flux of fluids grows the consequent changes in the pressure temperature and dynamics of the system of cracks and conduits result in the generation of tornillos based on the fluid filled crack conduit model the shallow depths of the sources and the values of the quality factors the fluid within the resonant crack conduit was inferred to be an ash gas or water droplet gas mixture moreover the observed variations in the wavefield can be caused by small changes in the location of the source in the source mechanism or in the medium in between the source and the seismic station finally another peculiar feature of tornillos is the amplitude modulation that can be explained as a result of a beating phenomenon

magmatic degassing of multicomponent vapors and assessment of magma depth application to vulcano island italy degassing of magmatic h2o co2 and rare gases plays a major role in understanding large scale earth processes and in the assessment of volcanic activity here we describe a quantitative model for magmatic degassing of h2o co2 noble gas n2 mixtures our modeling takes into account non ideal behaviors by adopting recently developed approaches for the solubility of h2o co2 mixtures in silicate liquids and for noble gas partitioning in h2o co2 bearing magmas this new approach allows quantitative treatment of inert gas fractionation throughout the degassing of any h2o co2 bearing natural magma in a wide range of thermo baric conditions magma degassing simulations performed by our model have clearly displayed that dissolved h2o and co2 in the melt strongly affect inert gas degassing due to their modest solubility differences in h2o rich magmas all the inert gases are strongly partitioned into vapor at early degassing extents after the quick exhaustion of co2 in contrast co2 rich melts retain dissolved helium longer because co2 has firstly to be released from magma whereas nitrogen and heavy noble gases undergo a similar or higher exsolution than co2 at early magma degassing extents we have successfully applied the degassing model to the active volcanic system of vulcano island italy where several geochemical parameters have been monitored over the last decade by quantitatively assessing magma pressure over time the model has allowed us to reconstruct the rise of magma towards the surface the results clearly show that the magma has reached low pressure and depth beneath vulcano thus interaction with the hydrothermal system as well catastrophic magma rises may result in hazardous future scenarios

correlated increase in co2 fumarolic content and diffuse emission from la fossa crater vulcano italy evidence of volcanic unrest or increasing gas release from a stationary deep magma body 1 the peculiarity of the quiescent la fossa volcano is the occurrence of crises characterized by strong increases of fumarole t and output and by chemical changes indicative of an increasing input of magmatic fluids several surveys carried out during a new crisis began in november 2004 indicate that the total diffuse co2 emission for the crater area increases by one order of magnitude during crises up to 1600 ton d 1 in december 2005 concern exists on the possibility that these crises be related to an unrest process leading to eruption the repetition along decades of the same gas compositional variations during crises their temporal coincidence with increases of the local shallow seismicity and the lack of any significant ground motion rather suggest that they correspond to moments of increasing volatile release from a stationary magma system

fumarolic activity of avachinsky and koryaksky volcanoes kamchatka from 1993 to 1994 volcanic gas and condensate samples were collected in 1993 1994 from fumaroles of koryaksky and avachinsky basaltic andesite volcanoes on the kamchatka peninsula near petropavlovsk kamchatsky the highest temperature fumarolic discharges 220 c at koryaksky and 473 c at avachinsky are water rich 940 985 mmol mol of h2o and have chemical and isotopic characteristics typical of kamchatka kurile high and medium temperature volcanic gases the temperature and chemical and water isotopic compositions of the koryaksky gases have not changed during the past 11 years they represent an approximate 2 1 mixture of magmatic and meteoric end members low temperature near boiling point discharges of avachinsky volcano are water poor 880 mmol mol their compositions have not changed since the 1991 eruption and are suggested to be derived from partially condensed magmatic gases at shallow depth based on a simple model involving mixing and single step steam separation low water and high co2 contents as well as the observed cl concentration and water isotopic composition in low temperature discharges are the result of near surface boiling of a brine composed of the almost pure condensed magmatic gas high methane content in low temperature avachinsky gases and the 220 c koryaksky fumarole low c isotopic ratio in co2 at koryaksky 11 8 and water isotope data suggest that the meteoric end member contains considerable amounts of the regional methane rich thermal water discovered in the vicinity of both volcanoes

dynamics of shallow hydrothermal eruptions new insights from vulcano s breccia di commenda eruption understanding the dynamics and effects of hydrothermal eruptions is crucial to the hazard assessment in both volcanic and geothermal areas eruptions from hydrothermal centres may occur associated with magmatic phases but also as isolated events without magmatic input with the most recent examples being those of te maari tongariro new zealand in 2012 and ontake japan in 2014 the most recent caldera of the island of vulcano southern italy hosts in its centre the la fossa cone active since 5 5 ka and now characterised by continuous fumarolic degassing in historical times la fossa cone has experienced several hydrothermal eruptions with the most violent event being the breccia di commenda eruption that occurred during the thirteenth century ad based on analysis of 170 stratigraphic logs we show that the breccia di commenda eruption occurred in three main phases after an opening low intensity ash emission phase phase 1 the eruption energy climaxed during phase 2 when a series of violent explosions produced an asymmetric shower of ballistic blocks and the contemporaneous emplacement of highly dispersed lithic rich blast like pyroclastic density currents pdcs the tephra units emplaced during phase 2 ranging in volume from 0 2 to 2 7 105 m3 were covered in turn by thin ash fall deposits phase 3 the dynamics of the most violent and intense stage of the eruption phase 2 was investigated by numerical simulations a three dimensional numerical model was applied describing the eruptive mixture as a eulerian eulerian two phase non equilibrium gas particle fluid plus a one way coupled lagrangian ballistic block fraction at the initial simulation time a mass of about 109 kg with initial overpressure above 10 mpa and a temperature of 250 c was suddenly ejected from a 200 m long eastward inclined nne ssw trending fissure the mass release formed blast like pdcs on both sides of the fissure and launched ballistic blocks eastwards field investigations and numerical simulations confirm that hydrothermal explosions at la fossa cone include intense ballistic fallout of blocks emission of pdcs potentially travelling beyond the la fossa caldera and significant ash fallout the hazard associated with both ballistic impact and pdc ingress as associated with hydrothermal eruption is significantly larger with respect to that associated with vulcanian type events of la fossa

evidence of early cretaceous transpression in the sulu orogenic belt eastern china abstract recent studies have documented marine turbidites with syn sedimentary deformation features in the central sulu orogenic belt of eastern china these units preserve essential information on the late mesozoic evolution of the sulu orogenic belt referred to as the baxiandun formation the turbidites exhibit similar lithologic characteristics to nearby units such as the lingshandao formation that have been well studied even though precise geochronologic constraints are lacking for a more precise correlation this study reports detrital zircon u pb age data that correlate the baxiandun formation turbidites of the central sulu orogenic belt to the early cretaceous lingshandao formation we also report al in hornblende emplacement depth estimates for granitic intrusions of the sulu orogenic belt s laoshan mountain a sharp contact between the laoshan granites and the marine baxiandun formation indicates that the baxiandun basin rapidly subsided to the emplacement depth of the laoshan plutons lateral correlation among the marine turbidites the lingshandao and baxiandun formations combined with information established by previous studies indicates initiation of transpressional tectonics at 122 121 ma transpression ceased with the emplacement of the laoshan granites whose a1 type composition indicates a return to extensional tectonics at ca 111 ma

slow deformation and lower seismic hazard at the new madrid seismic zone global positioning system gps measurements across the new madrid seismic zone nmsz in the central united states show little if any motion these data are consistent with platewide continuous gps data away from the nmsz which show no motion within uncertainties both these data and the frequency magnitude relation for seismicity imply that had the largest shocks in the series of earthquakes that occurred in 1811 and 1812 been magnitude 8 their recurrence interval should well exceed 2500 years longer than has been assumed alternatively the largest 1811 and 1812 earthquakes and those in the paleoseismic record may have been much smaller than typically assumed hence the hazard posed by great earthquakes in the nmsz appears to be overestimated

geochemical modeling of mixing between magmatic and hydrothermal gases the case of vulcano island italy abstract in this study we present a geochemical approach to model the mixing of magmatic and hydrothermal gases our model is based on a rigorous formulation of a perfectly dimensioned system of mass and energy balance equations inputs of the equation set are the h2o and co2 content and gas emission temperature at the surface together with some constraints gained from the chemical physical features of the hydrothermal system the output data give the composition of magmatic gas mixing fractions and temperatures of gas mixtures in the mixing zone the comparison of the emission temperature of fumarolic gases with their calculated mixing temperatures provides valuable indications on the expansion process that gases undergo during their ascent towards the surface our mixing model is exemplified by the fumarolic system of vulcano island italy we calculate the thermodynamic parameters of the hydrothermal system by means of an h2o co2 nacl equation of state while the thermo baric conditions of the magma have been assessed by previous geophysical and petrologic investigations the obtained results show that during volcanic crises at vulcano island and in agreement with magma degassing processes both the co2 and the he contents of magmatic gas display peaks with a progressively declining amplitude suggesting a progressive magmatic impoverishment of volatiles strongly partitioned in the gas phase mixing fractions of various fumaroles are normally variable while they display almost homogeneous values during periods of increased volcanic activity on the basis of results gained some implications regarding the hazard of phreato magmatic explosions are also discussed the high temperature reached by fumarolic gases strongly constrains their probable expansion process during the ascent towards the surface a comparison between the temperature of the fumarolic gas and the calculated mixing temperature at depth indicates that the expansion process can be reasonably described as almost iso enthalpic although field evidences suggest that the fumarolic emission temperature could be affected by the sharp permeability changes in the last few hundred meters therefore our results and field evidences clearly indicate that variations in gas emission temperature cannot be considered a good indicator of volcanic activity as it is strongly dependent on expansion process and ultimately on rock permeability changes the model greatly improves the knowledge of the volcanic system of vulcano island and provides an important tool for the interpretation and evaluation of volcanic activity moreover a similar approach can be considered for other volcanic systems having analogous characteristics

quantification and propagation of errors when converting vertebrate biomineral oxygen isotope data to temperature for palaeoclimate reconstruction oxygen isotope analysis of bioapatite in vertebrate remains bones and teeth is commonly used to address questions on palaeoclimate from the eocene to the recent past researchers currently use a range of methods to calibrate their data enabling the isotopic composition of precipitation and the air temperature to be estimated in some situations the regression method used can significantly affect the resulting palaeoclimatic interpretations furthermore to understand the uncertainties in the results it is necessary to quantify the errors involved in calibration in some situations the regression method used can significantly affect the resulting palaeoclimatic interpretations while quantification of the errors involved in calibration is necessary to understand the uncertainties in the results studies in which isotopic data are converted rarely address these points and a better understanding of the calibration process is needed this paper compares regression methods employed in recent publications to calibrate isotopic data for palaeoclimatic interpretation and determines that least squares regression inverted to is the most appropriate method to use for calibrating causal isotopic relationships we also identify the main sources of error introduced at each conversion stage and investigate ways to minimise this error we demonstrate that larger sample sizes substantially reduce the uncertainties inherent within the calibration process typical uncertainty in temperature inferred from a single sample is at least 4oc which multiple samples can reduce to 1 2oc moreover the gain even from one to four samples is greater than the gain from any further increases we also show that when converting 18oprecipitation to temperature use of annually averaged data can give significantly less uncertainty in inferred temperatures than use of monthly rainfall data equations and an online spreadsheet for the quantification of errors are provided for general use and could be extended to contexts beyond the specific application of this paper palaeotemperature estimation from isotopic data can be highly informative for our understanding of past climates and their impact on humans and animals however for such estimates to be useful there must be confidence in their accuracy and this includes an assessment of calibration error we give a series of recommendations for assessing uncertainty when making calibrations of 18obioapatite 18oprecipitation temperature use of these guidelines will provide a more solid foundation for palaeoclimate inferences made from vertebrate isotopic data

liquefaction related ground failure a case study in the new madrid seismic zone central united states large curvilinear sand blows resulting from earthquake induced liquefaction commonly occur along the margins of fine grained channel fill deposits in the st francis basin of the new madrid seismic zone one such example identified on aerial photographs and satellite images was studied in detail by examining relations of sedimentary deposits and liquefaction features in the field and by compiling borehole data previously collected by the army corps of engineers ground failure in this example included liquefaction of subsurface sandy deposits development of en echelon fissures in the overlying channel fill deposit forceful venting of sandbearing water to the ground surface resulting in the formation of sand dikes and sand blows and differential ground subsidence across the sand dikes a combination of mechanisms including the development of a water rich zone below the clayey surficial deposits may have contributed to the failure at the study site located in southeastern missouri the near surface sedimentary geology can be described as a two layered system with a sandy channel deposit below and a less permeable clayey overbank deposit above the contact between the two layers is roughly horizontal except where embedded by a channel fill deposit the basal contact of the channel fill deposit is inclined along its margin and extends below the base of the overbank deposits sand blows are abundant in the overbank deposits which are about 6 m thick in contrast sand blows rarely occur within the 18 m thick channel fill deposit except along its margin here feeder dikes of the sand blows are concentrated within 15 m of and arranged in an en echelon pattern subparallel to the margins of the channel fill deposit on the side of the feeder dikes toward the edge of the channel fill deposit the ground surface is displaced downward as much as 1 2 m large ground displacements often pose the greatest threat to the integrity of engineered structures as demonstrated in this case study the spatial relations of sedimentary deposits as well as their permeability and thickness appear to influence both the location and mode of ground failure a better understanding of factors contributing to liquefaction related ground failures can help to identify sites that may be prone to large ground displacements and thus to mitigate the hazard posed by earthquakes in this region

origin of the fumarolic fluids of vulcano island italy and implications for volcanic surveillance variations in d and 18o values with h2o contents and outlet temperatures indicate that the fumaroles of la fossa crater have discharged mixtures of magmatic water and marine hydrothermal water since 1979 the contribution of meteoric water was low in the period 1979 1982 and very low afterwards the 18o values of the marine hydrothermal component of 5 to 7 2 are due to isotopic exchange with the 18o rich silicates of the rocks under high temperature and low permeability conditions the 18o value of the magmatic end member is generally 3 5 to 4 3 although values as high as 5 5 to 6 5 were reached in the summer of 1988 when magma degassing appears to have extended into the core of the magma body the d values of the end member were close to 20 typical of andesitic waters both the isotopic values and chemical data strongly support a dry model consisting of a central magmatic gas column and a surrounding hydrothermal envelope in which marine hydrothermal brines move along limited fracture zones to undergo total evaporation on approaching the conduits of magmatic fluids the vents at the eastern and western boundaries of the fumarolic field are fed by fluids whose pressure is governed by the coexistence of vapor liquid and halite giving rise to a high risk of phreato magmatic explosions should magma penetrate into these wet environments most la fossa eruptions were triggered by an initial hydrothermal blast and continued with a series of phreatomagmatic explosions the fluids discharged by the forgia vecchia fumaroles are mixed with meteoric water which is largely evaporated although subordinate loss of condensed steam may be responsible for scrubbing most of the acidic gas species the temperatures and pressures and the risk of a sudden pressure increase are low a boiling hydrothermal aquifer at 230 c is present underneath the baia di levante beach this area has a minor risk of hydrothermal explosions

sediment deformation in miocene and post miocene strata northeastern brazil evidence for paleoseismicity in a passive margin abstract stratigraphic intervals characterized by varied and complex styles of soft sediment deformation structures are well preserved in miocene and late pleistocene to holocene deposits of a sedimentary basin located in northeastern brazil the miocene strata represented by the barreiras formation record only brittle structures including numerous faults and fractures with straight and high angle dipping planes that are often filled with sands derived from overlying beds folds consisting of broad anticlines and synclines are also present in this unit the late pleistocene to holocene deposits named post barreiras sediments contain an indurated sandy package with a large variety of ductile and brittle deformation structures i e massive sandstones with isolated sand fragments and breccias undulatory strata sand dykes and diapirs sinks and bowls pebbly pockets plunged sediment mixtures fitted sand masses cone shaped cracks fault grading and sedimentary enclaves these features confined to sharp based stratigraphic horizons that progressively grade downward into undisturbed deposits are related to seismic shocks of high surface wave magnitude i e ms 5 or 6 amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic wave propagation seismic waves caused by activity along one or most likely several tectonic structures would have propagated throughout the depositional environment producing laterally extensive seismites the close proximity to earthquake epicenters would have promoted pervasive re sedimentation due to pore overpressure resulting high volumes of massive sandstones and breccia the similarity between deposits with correlatable strata from many other areas along the brazilian coast allows raise the hypothesis that the seismic episodes might have affected sedimentation patterns in a large i e extension of several hundreds of kilometers geographic area thus the modern seismicity recorded along northeastern brazil was recurrent during the quaternary and perhaps also in the pliocene the estimated high magnitude of the seismic events and the great regional extent of the affected area demonstrate that the brazilian coast experienced tectonic stress through the last geological episodes of its evolution which would have favored sediment accumulation and penecontemporaneous re sedimentation this geological context is unexpected in a passive margin inducing to revisit the debate on how active is a passive margin

the evolution of a dynamic geological system the support of a gis for geochemical measurements at the fumarole field of vulcano italy abstract the island of vulcano aeolian arc southern italy has displayed several periods of volcanic unrest since the end of the last eruption 1890 we report here results obtained from a long term survey concerning variations of both the steam output and the exhaling surface area at the summit crater fumarolic field of la fossa the field measurements analysed in a geographical information system gis show a highly dynamic volcanic system in which deep variations in the geochemistry and the temperature of the released fluids were accompanied by fluctuations in the mass output of steam and the topography of the crater field the use of a gis facilitated digitized reconstructions of maps of the crater field in addition to analysis of the steam flux data the fumarolic field expanded its surface area from 50 m 2 in 1983 to more than 2400 m 2 in 1995 accompanied by an increase in steam output from 152 to about 1400 tonnes per day the possibility that the observed phenomena are related to volcano tectonic activity and to magma uprising is taken into consideration

modeling the formation of advanced argillic lithocaps volcanic vapor condensation above porphyry intrusions hypogene advanced argillic alteration typically quartz alunite with halos of kaolinite dickite and roots of pyrophyllite diaspore forms in the epithermal environment from condensates of magmatic vapor that contain so2 and hcl which exsolved from an underlying intrusive source the most aggressive nearly isochemical leaching of the host rock by the most acidic condensate commonly ph 1 leaves residual silica that recrystallizes to quartz within the flow channel at a high condensate rock ratio forming the core of alteration the alteration characteristically flares upward along feeder structures and if a permeable lithologic unit is intersected the alteration zones mushroom to form a subhorizontal blanket due to lateral flow where subsequently mineralized the residual quartz commonly with a vuggy texture that reflects the texture of the original lithology has higher au and cu grades than the quartz alunite halo tonnage in these high sulfidation systems may develop within the subhorizontal lithocap although the highest grades are typically confined to the structurally controlled feeders we modeled a typical volcanic vapor condensate starting with the measured composition of 877 c fumaroles from satsuma iwojima rhyolite dome japan as it cooled and reacted with a host rhyolite the predicted hydrothermal mineralogy reproduces the alteration pattern observed in lithocaps that host high sulfidation deposits the modeling confirms that aluminum rich minerals pyrophyllite diaspore locally andalusite are stable at higher temperature at depth whereas at lower temperature and shallower depth na and k alunite become stable at the lowest temperature 10 1 and where so2 h2s in the original volcanic vapor this so2 dominant composition is typical of andesitic to rhyolitic volcanoes the reason for this mineral transition and the upward flare widening of the alteration zone along structures is related to the dissociation and increased reactivity of h2so4 and hcl as the temperature decreases below 200 c only quartz pyrite native s and anhydrite are stable hence the formation of the dominant quartz from the silica residue a further check on our modeling is the observation that the calculated composition of the condensate after reaction with fresh satsuma iwojima rhyolite and alteration minerals and cooling to 100 c is similar within a factor of two to that of acidic springs with ph 1 that discharge around satsuma iwojima and other active volcanoes the most extensive lithocap alteration residual quartz and or quartz alunite is commonly offset from the surface projection of the causative intrusion this observation can be explained by a combination of two factors hydrology and temperature due to hydraulic gradients at shallow depths in a volcanic edifice the acidic condensate tends to flow along permeable lithologic units away from the locus of the high temperature vapor plume which rises directly over the intrusion where lateral flow occurs the most intense leaching and widespread advanced argillic alteration which develops largely at temperatures of 200 to 250 c based on our modeling will form away from the near surface projection of the intrusion which is the area of highest surface temperature due to ascent of the vapor plume this potential for lithocap alteration to form on the shoulder of the underlying causative intrusion must be assessed when exploring for high sulfidation ore the highest ore grades are commonly related to structures that are proximal to the parent intrusion but they are unlikely to lie directly over the intrusion in addition identifying the most likely location of the source intrusion will help the explorer to efficiently assess any potential for deeper porphyry style mineralization

rapid intraplate strain accumulation in the new madrid seismic zone remeasurement of a triangulation network in the southern part of the new madrid seismic zone with the global positioning system has revealed rapid crustal strain accumulation since the 1950s this area experienced three large moment magnitudes 8 earthquakes in 1811 to 1812 the orientation and sense of shear is consistent with right lateral strike slip motion along a northeast trending fault zone as indicated by current seismicity detection of crustal strain accumulation may be a useful discriminant for identifying areas where potentially damaging intraplate earthquakes may occur despite the absence of large earthquakes during historic time

the episodic and abrupt geochemical changes at la fossa fumaroles vulcano island italy and related constraints on the dynamics structure and compositions of the magmatic system abstract herein we report on the chemical and isotopic c h o and he compositions of the fluids from la fossa crater fumaroles of vulcano from 1999 to 2010 consistent with records obtained since the end of the 1980s our data show that the geochemical features of the fumarole system have experienced several episodes of remarkable change each lasting no more than a few months typical signatures of these short term anomalies are large increments in co 2 n 2 and he concentrations coupled to increased 13 c 12 c isotopic ratios but their meaning remains widely debated within a model of fumarolic fluids based on mixing between hydrothermal and magmatic endmembers we have developed a novel approach to constrain chemical he co 2 and n 2 he and isotopic 13 c 12 c d h and 3 he 4 he ratios of the magmatic endmember during the short term anomalies although much of the geochemical variability in fumaroles results from changes in mixing proportions the magmatic fluid unquestionably shows significant variations in time the magmatic he co 2 n 2 he 13 c 12 c and 3 he 4 he values throughout 1988 1996 differed from those feeding the anomaly at the end of 2004 early clues of the new magmatic fluid appeared in 1998 1999 far from any short term anomaly whereas new and old magmatic fluids coexisted after 2004 we quantitatively prove that the detected geochemical changes are consistent with the degassing path of a magma having a latitic composition and suggest the presence of two magma ponding levels at slightly different pressures where bubble melt decoupling can occur the different he isotope compositions at these levels suggest low hydraulic connectivity typical of a complex reservoir with dike and sill structures in this framework the short term geochemical anomalies are probably due to gas accumulation at the top of magma bodies followed by massive escape or activation of new degassing levels in the reservoir for which the stress field almost certainly plays a key role such a scenario explains the observed increases in both fumarole output and shallow high frequency seismicity due to increased pore pressure during the anomalies while being consistent with the concomitant absence of any deep seismicity or ground deformation eventually related to magma movement

review of the evolution of geochemical monitoring networks and methodologies applied to the volcanoes of the aeolian arc italy abstract fluids discharged from volcanic systems are the direct surface manifestation of magma degassing at depth and provide primary insights for evaluating the state of volcanic activity we review the geochemical best practice in volcanic surveillance based to a huge amount of monitoring data collected at different active volcanoes using both continuous and discontinuous approaches the targeted volcanoes belong to the aeolian arc located in the tyrrhenian sea italy and they have exhibited different activity states during the monitoring activities reported here la fossa cone on vulcano island has been in an uninterrupted quiescent stage characterized by variable solfataric activity in contrast stromboli island has shown a persistent mild explosive activity episodically interrupted by effusive eruptions in 1985 2002 2007 and 2014 panarea island which is the summit of a seamount rising from the seafloor of the southern tyrrhenian sea showed only undersea fluid release the only observable clues of active volcanism at panarea island have been impulsive changes in the undersea fluid release with the last submarine gas burst event being observed in november 2002 the geochemical monitoring and observations at each of these volcanoes has directly involved the volcanic plume and or the fumarole vents thermal waters and diffuse soil degassing depending on the type of manifestations and the level of activity encountered through direct access to the magmatic samples when possible and the collection of as much observable data related to the fluid release as possible the aim has been i to verify the thermodynamic equilibrium condition ii to discern among the possible hydrothermal magmatic marine and meteoric sources in the fluid mixtures iii to develop models of the fluid circulation supported by data iv to follow the evolution of these natural systems by long term monitoring and v to support surveillance actions related to defining the volcanic risk and the evaluation and possible mitigation of related hazards the examples provided in this review article show the close relationships among data analysis interpretation and modeling we particularly focus on describing the fieldwork procedures since any theoretical approach must always be verified and supported by field data rather than just by experiments controlled in laboratory indeed the natural systems involve many variables producing effects that cannot be neglected the monitored volcanic systems have been regarded as natural laboratories and all of the activities have focused on both volcanological research and surveillance purposes in order to ensure that these two goals have overlapped an appendix is also included that explains the scientific approach to the systematic activities regarding geochemical monitoring of volcanic activity

time series analysis of high temperature fumaroles monitored on the island of vulcano aeolian archipelago italy abstract the exhalation activity at the la fossa cone vulcano island aeolian archipelago italy has been ongoing for more than 1 century many of the monitored geochemical and geophysical parameters have showed transient variations of energy release the time series analyses of fumarole temperatures presented in this paper enabled the sequence of observations to be defined and information from different monitoring stations to be integrated the motion of fluids feeding the fumaroles of the la fossa cone is driven by the thermal and kinetic energies that balance the seismic and volcanic forces active in the region and the temperatures of the fumaroles reflect the local response of the hydrothermal system to these forces during a 14 year period of observation from 1998 to 2012 fumarole temperatures showed various trends but also cyclic variations characterized by sharp increases the repetition of these variations during periods with different trends indicates that no physical variation occurred from the hydrothermal source to the surface during the analyzed period and after each periodic geochemical crisis the previous thermal conditions were restored although the continuous monitoring of high temperature fumaroles was limited to only a few sites the observed trends characterized the most important fumaroles in the area of vulcano island an evaluation of thermal energy release based on these spatially discrete measurements would be a speculative exercise in thermodynamics but the analyses of the recorded data represent a step forward in interpreting the signals from ongoing volcanic activity and in assessing the seismic risk

changes in heat released by hydrothermal circulation monitored during an eruptive cycle at mt etna italy the shallow vertical temperature profile has been measured in the proximity of an eruptive fissure far about 4 km north northeast from mt etna central craters the monitoring site was a steam heated soil lying between a group of flank fractures on the upper northeast flank of mt etna italy i e on the northeast rift we chose this area because it was close to an eruptive fissure that opened in 2002 and extended from about 2500 to about 1500 m a s l with our aim being to determine a connection between this fracture system and the ongoing volcanic activity heat flux anomalies from the ground from september 2009 to september 2012 were evaluated changes in the hydrothermal release which can be related to variations in volcanic activity are discussed and compared to the published geophysical data the heat flux ranges varied during the pre eruptive from about 7 to 38 w m 2 syn eruptive from about 3 to 49 w m 2 and post eruptive phases with the heat released being lowest at the latter phase from about 1 to 20 w m 2 moreover the heat flux time variation was strongly correlated with the eruption rate from the new southeast crater between january 2011 and april 2012 the migration of magma through active conduits acts as a changing heating source for steam heated soils located above the active fractures our findings suggest that tracking the heat flux above active fractures constitutes a useful investigation field for low cost thermal monitoring of volcanic activity time variations in their emissions could highlight the relationship between a hydrothermal circuit and the local network of fractures possibly indicating variation in the structural weakness of a volcanic edifice continuous monitoring of heat flux combined with a realistic model would contribute to multidisciplinary investigations aimed at evaluating changes in volcano dynamics

double origin of hydrothermal convective flux variations in the fossa of vulcano italy soil temperature measurements can provide information on the distribution of degassing fissures their relationship to the internal structure of the volcano and the temporal evolution of the system at vulcano island italy heat flux from a 3 km deep magma body drives a hydrothermal system which extends across the main fossa crater this heat flux is also associated with variable magmatic gas flow a high density map of soil temperatures was made in 1996 at a constant depth of 30 cm on the central and southern inner flanks of the fossa crater these measurements extended over an area covering about 0 04 km2 across which the heat flux is predominantly associated with a shallow boiling aquifer the map shows that hot zones relate to structures of higher permeability mainly associated with a fissure system dating from the last eruptive cycle 1888 1890 from 1996 to january 2005 we studied the evolution of the heat flux for the high temperature part of the map both by repeating our measurements as part of 14 visits during which temperatures were measured at a constant depth and using data from permanent stations which allowed soil temperatures to be continuously measured for selected vertical profiles these data allowed us to calculate the heat flux and its variation with good precision for values lower than about 100 w m 2 which is generally the case in the study area above 100 w m 2 although the heat flux value is underestimated its variations are recorded with an error less than 10 during the period 1996 2004 two increases in the thermal flux were recorded the first one was related to the seismic crisis of november 1998 which opened existing or new fissures the second in november 2004 was probably due to magma migration and was associated with minor seismic activity

hydrothermal processes governing the geochemistry of the crater fumaroles at mount etna volcano italy article i nfo we investigated the geochemistry of the fumaroles at the summit area of mt etna including sulfur speciation and the content of acidic gases the carbon isotope composition of the etnean plume was also measured in order to compare it to that of fumaroles two types of fumaroles were identified i low temperature fumaroles which are dominated by co2 with minor amounts of so2 and h2s and negligible chlorine contents and ii high temperature fumaroles which are strongly air contaminated and characterized by appreciable amounts of volcanogenic carbon sulfur and chlorine as recognized by martelli et al 2008 both groups of fumaroles are fed by the degassing of an underlying magma nevertheless compositional data clearly show that secondary processes affect the composition of the fluids once they leave the magma body here a model of cooling and condensation of fluids is proposed to explore such postmagmatic processes the model which uses etnean plume geochemistry as starting composition of fluids exsolved from magma shows that so2 and h2s control the redox conditions of the gas mixture during the cooling until the reactions involving co co2 and h2 h2o ratios are fully quenched at temperatures around 350 450 c the dissolution of gases in water subsequent to condensation must occur at thermobaric conditions over 50 bar and 260 c which allows a total removal of hcl b partial removal of sulfur species while preserving the so2 h2s ratio and c the c s ratio to increase by almost 10 fold relative to that in the plume the observed ch4 co2 ratios are higher than those calculated for the etnean magmatic gas and hence they provide evidence of modest contributions from peripheral hydrothermal fluids during the migration of magmatic gases toward the surface in both low and high temperature fumaroles due to the peculiar thermodynamic conditions the model predicts that carbon isotopes do not experience any postmagmatic fractionation and hence the isotopic composition of the fumaroles is representative of magmatic carbon measurements of the carbon isotope composition of the plume corroborate these findings

did two massive earthquakes in the holocene induce widespread landsliding and near surface deformation in part of the ottawa valley canada recent evidence based on ages of large landslides and the existence of severely disturbed terrain in champlain sea sediments to the east of ottawa suggests that this area may have been the site of two of the most geologically destructive earthquakes in eastern canada the walls of several paleochannels downcut into sensitive marine clayey silts are scarred by numerous large earthflows of sizes unequaled in historical time while radiocarbon ages of 15 landslides as much as 35 km apart range from ca 1870 to 5130 yr b p the majority of events cluster at ca 4550 yr b p the coincidence of numerous large failures in different paleovalleys occurring concurrently long after channel abandonment and at a time of drier climate suggests that the widespread landsliding was triggered by a strong earthquake close to the landslide area areas of very disturbed terrain in a flat erosional plain show severely deformed bedding and irregular ground subsidence and are attributed to a large earthquake ca 7060 yr b p that strongly shook a thick sequence of sensitive material filling deep steep sided bedrock basins

archeological and pedological evidence for large prehistoric earthquakes in the new madrid seismic zone central united states prehistoric liquefaction features have been identified by careful observation of their structural and stratigraphic relations to native american occupation horizons and their subtle soil characteristics the ages of these liquefaction features have been estimated from radiocarbon dating of wood associated with the features and native american artifacts found within bounding occupation horizons at three sites near blytheville arkansas in the central part of the new madrid seismic zone one sand blow crater formed between a d 800 and 1400 two sand blow deposits formed between a d 800 and 1670 and three possibly four sand dikes formed since 4035 b c where not found in association with native american occupation horizons and artifacts prehistoric liquefaction features can be difficult to distinguish from features that formed during the great new madrid earthquakes of a d 1811 and 1812 this raises the possibility that prehistoric liquefaction features may have been misinterpreted during previous studies in the area nevertheless a paleoearthquake chronology is beginning to emerge for the new madrid seismic zone our findings are consistent with paleoseismological studies in the northern part of the seismic zone and suggest a recurrence interval of hundreds of years for earthquakes large enough to induce liquefaction in this region m 6 4 by mapping the age distribution of liquefaction features a more accurate assessment of the long term earthquake potential of the region will be possible

cause of the rupture and distribution of broken submarine carbonate chimneys in the gulf of cadiz southwestern spain abstract during the 2000 and 2001 r v cornide de saavedra cruises a vast field of hydrocarbon derived carbonate chimneys was discovered and sampled along the cadiz contourite channel and guadalquivir diapiric ridge photographs taken on board using an underwater camera revealed a spectacularly high density of pipe like chimneys lying on the sea floor though some of them were also found protruding from muddy sediment the major axes of the fallen chimneys which can be as long as 1 m exhibit a regular spatial distribution showing a conspicuous nw se trend furthermore their basal morphology shows a characteristic angular breakage associated to a flexo traction process both the uniform distribution of the major axis and the basal morphology of the chimneys imply that the cause of the rupture could be related either to strong bottom sea currents or to inertia forces associated with oscillatory ground motion due to seismic shaking the preferential orientation of the broken chimneys their mechanical properties the geological and topographical conditions of the area in relation to seismic ground motion amplification and the flow speed of the mediterranean outflow water mow along the cadiz contourite channel suggest that the most probable cause of the chimneys rupture was an earthquake the minimum magnitude of this seismic event is estimated to be more than 7 0 the causative fault being located directly under the chimney field or as far as 30 60 km away the chimneys rupture took place between ca 5 ka to present

on the modified mercalli intensities and magnitudes of the 1811 1812 new madrid earthquakes we reexamine original felt reports from the 1811 1812 new madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks in many cases we interpret lower values than those assigned by earlier studies in some cases the revisions result from an interpretation of original felt reports with an appreciation for site response issues additionally earlier studies had assigned modified mercalli intensity mmi values of v vii to a substantial number of reports that we conclude do not describe damage commensurate with intensities this high we investigate several approaches to contouring the mmi values using both analytical and subjective methods for the first mainshock on 02 15 lt december 16 1811 our preferred contouring yields m 7 2 7 3 using the area moment regressions of johnston 1996 for the 08 00 lt on january 23 1812 and 03 45 lt on february 7 1812 mainshocks we obtain m 7 0 and m 7 4 7 5 respectively our magnitude for the february mainshock is consistent with the established geometry of the reelfoot fault which all evidence suggests to have been the causative structure for this event we note that the inference of lower magnitudes for the new madrid events implies that site response plays a significant role in controlling seismic hazard at alluvial sites in the central and eastern united states we also note that our results suggest that thrusting may have been the dominant mechanism of faulting associated with the 1811 1812 sequence

the record of seismically induced liquefaction on late quaternary terraces in northwestern tennessee between december 1811 and february 1812 the four largest historical earthquakes mb 7 0 in eastern north america occurred in the new madrid missouri seismic zone nmsz although this area has been the focus of considerable seismological and geological research estimates of the repeat time of large magnitude seismic events remain poorly constrained the available estimates are based primarily on earthquake frequency statistics and limited paleoseismology studies johnston and nava 1985 analyzed about 180 yr of historical seismicity data and 10 yr of instrumental data and concluded that the repeat time for largemagnitude events m b 7 0 is between 550 and 1100 yr this estimate assumes that the data set is representative of the seismicity in the nmsz and that the slope of the line relating earthquake frequency to magnitude b value is constant from smallto large magnitude earthquakes johnston and nava 1985 however pacheco et al 1992 reported that b values may not be constant in earthquake frequency magnitude distributions and thus the estimated recurrence interval of johnston and nava 1985 must be considered tentative two geological studies suggest that the recurrence interval of large magnitude earthquakes in the nmsz is on the order of 450 to 600 yr two exploratory trenches across the reelfoot scarp in northwestern tennessee fig 1 revealed the only unequivocal example of holocene surface faulting in the upper mississippi embayment russ et al 1978 russ 1979 kelson et al 1993 stratigraphic relations across the northern part of the scarp indicate at least two episodes of faulting had occurred after about 2250 yr b p and before the 1811 to 1812 seismic events russ 1979 based on these two prehistoric earthquakes the dating error limits and the 1811 to 1812 events russ 1979 estimated an average recurrence interval of 600 yr or less for large magnitude earthquakes in the nmsz this estimated average recurrence interval is corroborated by a radiocarbon age estimate of a d 1310 to 1540 for fault scarp colluvium along the central reelfoot scarp kelson et al 1993 however inasmuch as russ 1979 found no evidence that offset occurred on the reelfoot scarp during the 1811 to 1812 earthquakes the relation between surface ruptures on the reelfoot scarp and large paleo earthquakes in the nmsz is not clear the widespread development of liquefaction features during the 1811 to 1812 earthquake series obermeier 1989 obermeier et al 1990 and the probable development of similar features during previous large magnitude seismic events m b 6 2 nuttli 1982 has been the basis for several efforts to identify paleoliquefaction features saucier 1991 estimated an average recurrence

estimation of intraplate strain accumulation in the new madrid seismic zone from repeat gps surveys the new madrid seismic zone nmsz a region within the eastern portion of the north american plate where great earthquakes occurred in 1811 1812 provides a type example of large earthquakes within a relatively stable continental interior assessing the scale and causes of deformation in such regions as well estimation of the recurrence interval for the large earthquakes within them has long been recognized as an important but challenging issue for which the advent of space based geodesy provides an important new tool here we report initial results from two global positioning system gps surveys of a geodetic network spanning the new madrid seismic zone because the expected strain signal is small the data were analyzed in three different ways first site velocities were estimated and analyzed for spatial gradients parallel and perpendicular to the trend of the major strike slip faults inferred from seismicity this analysis suggests but does not require a few millimeters per year of right lateral shear across the southern portion of the seismic zone consistent with the earthquake focal mechanisms second we divided the network into near field subnetworks and found possibly significant shear associated with approximately e w shortening within the southern nmsz and possible n s shortening across the left step connecting the presumed strike slip faults third we compared the strain observed along individual baselines to that predicted from the results of earlier near field surveys which combined gps and triangulation data in the southern part of the seismic zone we found general agreement with the earlier study although our data suggest lower strain rates hence after only 2 years of measurements the gps data suggest but do not yet require detectable strain accumulation however given that great earthquakes occur in the area and that our results are reasonably consistent with the results of other geodetic studies using different data and with earthquake mechanisms it seems likely that we are seeing strain accumulation in the southern nmsz a simple interpretation of the data as showing about 3 to 5 mm yr 1 of right lateral fault parallel motion implies a 1000 to 3300 year recurrence for great earthquakes with 5 to 10 m slip assuming all the accumulating strain is released seismically this recurrence interval may be an underestimate if the observed strains are largely postseismic effects of the 1811 1812 earthquakes a possibility suggested by the observation that plate wide data show less motion across the nmsz future surveys should resolve this issue as the longer measurement spans yield more precise velocity estimates

rapid response of a hydrologic system to volcanic activity masaya volcano nicaragua hydrologic systems change in response to volcanic activity and in turn may be sensitive indicators of volcanic activity here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of masaya volcano nicaragua one of the most active volcanoes in central america the soil temperatures were measured in a low temperature fumarole field located 3 5 km down the flanks of the volcano analysis of these time series reveals that they respond extremely rapidly on a time scale of minutes to changes in volcanic activity also manifested at the summit vent these rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism the soil temperature response 5 c is repetitive and complex with as many as 13 pulses during a single volcanic episode analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity they are thus easily distinguished from seasonal trends diurnal variations or individual rainfall events which triggered rapid transient increases in temperature during 5 of events we suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism a response that can be enhanced by meteoric water infiltration monitoring of distal fumaroles can therefore provide insight into coupled volcanic hydrologic meteorologic systems and has potential as an inexpensive monitoring tool

multiparametric approach in investigating volcano hydrothermal systems the case study of vulcano aeolian islands italy seismic activity ground deformation and soil and fumarole temperatures acquired during 2004 2007 at vulcano aeolian islands are analysed and the time relations among the different time series are discussed changes in temperature of fumarolic gases took place during four anomalous periods november 2004 march 2005 october 2005 february 2006 august october 2006 july december 2007 at the same time as an increasing number of volcano seismic events in particular the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440 c and from 20 to 90 c respectively the maximum daily number of volcano seismic events was 57 reached during the second anomalous period this seismicity characterised by focal depth generally lower than 1 km below sea level b s l and composed of different kinds of events associated to both resonance and shear failure processes is related to the shallow dynamics of the hydrothermal system during the analysed period very few volcano tectonic earthquakes took place and tilt recordings showed no sharp or important changes in light of such observations the increases in both temperature and volcano seismic events number were associated to increases in the release of gas from a deep and stable magma body without magma intrusions within the shallow hydrothermal system indeed a greater release of gas from depth leads to increased fluid circulation that can promote increases in volcano seismic events number by both fracturing processes and resonance and vibration in cracks and conduits the different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body finally all the observed variations together with the changing temporal distribution of the different seismic event kinds suggest that the hydrothermal system at vulcano can be considered unsteady and dynamic

the influence of thermal and cyclic stressing on the strength of rocks from mount st helens washington stratovolcanoes and lava domes are particularly susceptible to sector collapse resulting from wholesale rock failure as a consequence of decreasing rock strength here we provide insights into the influence of thermal and cyclic stressing on the strength and mechanical properties of volcanic rocks specifically this laboratory study examines the properties of samples from mount st helens chosen because its strength and stability have played a key role in its history influencing the character of the infamous 1980 eruption we find that thermal stressing exerts different effects on the strengths of different volcanic units increasing the heterogeneity of rocks in situ increasing the uniaxial compressive stress generates cracking the timing and magnitude of which was monitored via acoustic emission ae output during our experiments aes accelerated in the approach to failure sometimes following the pattern predicted by the failure forecast method kilburn 2003 crack damage during the experiments was tracked using the evolving static young s modulus and poisson s ratio which represent the quasi static deformation in volcanic edifices more accurately than dynamic elastic moduli which are usually implemented in volcanic models cyclic loading of these rocks resulted in a lower failure strength confirming that volcanic rocks may be weakened by repeated inflation and deflation of the volcanic edifice additionally volcanic rocks in this study undergo significant elastic hysteresis in some instances a material may fail at a stress lower than the peak stress which has previously been endured thus a volcanic dome repeatedly inflated and deflated may progressively weaken possibly inducing failure without necessarily exceeding earlier conditions

thermal and gas dynamic investigations at lastarria volcano northern chile the influence of precipitation and atmospheric pressure on the fumarole temperature and the gas velocity abstract fumaroles are hydrothermal manifestations commonly associated with active volcanoes the dynamics of fumaroles are affected by interactions with internal and external factors however hazardous access and corrosive gases have so far limited successful case studies in this study we report and discuss the results of continuous thermal monitoring carried out on three high temperature 250 c fumaroles at the lastarria volcano chile together with simultaneously measured meteorological parameters from december 2013 to march 2016 in addition the dynamic pressure and the co2 concentration were recorded in a fourth vent the investigated sites are located in the largest and most dominant fumarole field which developed in a fracture system on the north west flank of the volcanic edifice we detect external factors controlling the fumarole temperature and the dynamic gas pressure for a better understanding of changes in these parameters and consequently to improve the evaluation of volcanic and hydrothermal activity selected fumaroles showed a continuous decrease in temperature or remained unbiased from this trend showing that the influence of external effects on outlet temperature is strongly site dependent but generally significant decreases in all vent temperatures can be observed in response to intensive precipitation diurnal variations occur only in the coolest fourth fumarole where gas temperature gas pressure and co2 concentration are inversely correlated with atmospheric pressure small barometric pressure reductions account for an increase in mass flow subsequently resulting in a higher temperature and co2 concentration the temperatures and thermodynamic properties of the fumarolic gas and infiltrated precipitation water were used to calculate the amount of discharging gas from the investigated field with about 67 106 m3 per day which is equivalent to 3545 tons

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 repeat time of the 1811 and 1812 new madrid earthquakes a geological perspective abstract the great new madrid earthquakes of 1811 and 1812 were accompanied by extensive liquefaction within the meizoseismal zone we examined tens of kilometers of freshly excavated ditch banks within the southern limb of the new madrid seismic zone for evidence of prehistoric liquefaction events radiocarbon dates indicate that the exposures studied provide a record of the last 5000 to 10 000 years analyses of the statistics of historical seismicity imply a relatively short 550 to 1100 yr repeat time for 1811 to 1812 type earthquakes in contrast our search did not reveal definitive evidence of widespread paleoliquefaction events and hence provides no independent support for the relatively short 550 to 1100 yr return time implied by statistics of historical seismicity

tornillo type seismic signals at galeras volcano colombia 1992 1993 abstract unusual low frequency seismic events called tornillos screws at the observatorio vulcanologico y sismologico de pasto ovsp have been observed at galeras volcano during 1992 1993 of six eruptions that occurred between july 1992 and june 1993 five were preceded by episodes of tornillo signals these signals are characterized by 1 a waveform having a homogeneous distribution of frequencies 2 a long coda lasting up to several minutes 3 a small amplitude compared to the duration and 4 a slow decay of the coda the tornillo signals have been grouped into thirteen principal forms the 1992 1993 tornillos showed four main periods of occurrence each of which was followed by an eruption episode i occurred from 11 to 16 july 1992 and consisted of nine events episode ii lasted from 23 december 1992 to 14 january 1993 with twenty events episode iii was observed from 13 february to 23 march 1993 with 74 events episode iv lasted from 10 april to 7 june 1993 with 109 events the seismic activity at galeras in april may 1993 was characterized mainly by the occurrence of tornillo signals the behavior of these signals was similar to that before previous episodes ending with eruptions these observations permitted us to forecast the 7 june 1993 eruption several days to weeks beforehand the occurrence of tornillos is the most important criterion for determining the probability of an eruption at galeras in the current period of reactivation the maximum daily number of tornillos and the longest duration of individual events occur near the end of each episode within an individual episode the durations of single events increase progressively near to the point of eruption a positive correlation is observed between the total number of pre eruptive tornillo signals during an episode and the volume of material ejected by the eruption these observations may suggest that the presence of tornillos is an indication of variations in the physical conditions between the fluid and the surrounding solid material within the volcano and they constitute an important tool for forecasting future eruptions at galeras

mapping fumarolic fields in volcanic areas a methodological approach based on the case study of la fossa cone vulcano island italy abstract changes in the activity state of a volcano can be inferred by monitoring the steam flux from fumarolic fields in terms of 4d x y z time variations in temperature and extension of the zone during the last decades several studies in this field have been conducted worldwide and at vulcano island italy in particular both direct and remotely sensed measurements have been used for identifying thermally anomalous areas but the possible role of the hydrothermal alteration of volcanic products producing a sealing effect that obscures the surface thermal evidence of fumarolic activity have never been explored the novelty of the present study carried out at la fossa cone vulcano island was the integration of direct and remotely sensed temperature measurements with the evaluation of soil permeability for the precise mapping of areas where shallow hydrothermal circulation could occur even in the absence of surface evidence the main results of this study concern the role of a coating found on rock surfaces and regolith in introducing mapping errors especially during diachronic temperature surveys based on remotely sensed measurements

long term monitoring on a closed conduit volcano a 25 year long time series of temperatures recorded at la fossa cone vulcano island italy ranging from 250 c to 520 c abstract the longest record of temperature data from an active volcano in southern italy is presented the dataset comes from continuous monitoring of fumarole temperatures from the la fossa cone of vulcano aeolian islands running from 1991 to 2016 the discussion includes an empirical approach based on a large number of direct measurements at vulcano island geochemical monitoring of the uprising fluids allows detection of the surface effects of perturbation in the state variables of the buried hydrothermal and magmatic systems the presented datasets show that fumaroles changing temperatures which are related to surface heat flow are useful indicators over the past 25 years the combined effects of runoff and chemo physical alterations were negligible on the output temperature of the earliest monitored fumaroles the maximum recorded variation was 298 c measured in the ground very close to the steaming vents at a depth of 0 5 m repetition of output temperature values occurred after 19 years in the same position the time variations suggest a cyclic characteristic although more years are needed to register the complete cyclic modulation a combination of minor cyclical variations has also been registered in the fumarole output the minor cycles appeared in this long series of data after 1995 and they can be interpreted as one of the surface effects of temporary departures from a stationary state assumed for the system feeding the la fossa area in this sector of the mediterranean area the steady state pressure field as well as the steady state temperature gradients can be perturbed either by magmatism or by seismo tectonic processes related to regional dynamics this long term monitoring allowed comparisons of many temperature subsets with other validated geochemical and geophysical data series and highlighted common source mechanisms accounting for endogenous processes changes in the magma source and or seismo tectonic activity have been the primary causes of the time variations the collected data show the effectiveness of the geochemical approach for following the heat flow changes that originated from a deep source in real time even though an estimation of magmatic and or hydrothermal energy release cannot be retrieved by surface temperature monitoring alone

scale dependent location of hydrothermal vents stress field models and infrared field observations on the fossa cone vulcano island italy article i nfo hydrothermal venting occurs on numerous volcanoes of various age setting topographic and structural expression vent locations are commonly found not within volcanic craters only but predominantly at the crater margins and topographic highs a case example is vulcano island italy where the control on such vent locations along crater margins remained poorly understood however this paper describes numerical models combined with field observations and infrared imaging to explore the mechanisms that control the ascent paths of fluids in the fossa cone on vulcano using finite element modelling we calculate the gravitational stress in the volcanic edifice imposed by the topography results predict hydrofractures to be arranged in radial patterns at depth and in concentric patterns close to the surface furthermore low compressive stress values are found at the rims of the nested craters we compare the stress models to fumarole field data using a forward looking infrared camera we recorded images of the entire cone images were assembled to a mosaic and geocoded providing the first map of a remotely sensed temperature field in high resolution at la fossa the degassing and high temperature anomalies are found to be located mainly at the crests of the craters predominately in the northern and southern sector of the main crater therefore the stress distribution favours and indeed corresponds to the occurrence of fumaroles at la fossa the stress models also yield compression at the bottom of the crater where temperatures are cool thus we consider that the overall distribution of the fumaroles at the fossa cone is controlled by topography additional mechanisms contribute to the exact position of the degassing sites the influence of the lithological control seems to be strong in the southwestern part of the crater where the fumaroles are located 10 20 m below the inner crater rim in bedded strata in the northern part of the crater the exhalation sites can mainly be found at surface fractures and cracks emphasizing the structural control on the location of the fumaroles at this sector of the fossa cone using combined theoretical modelling and field observations this study helps to shed light into the processes directing fluids in volcanic edifices elsewhere and might contribute to the evaluation of upcoming hazard scenarios

vent temperature trends at the vulcano fossa fumarole field the role of permeability between 1994 and 2010 we completed 16 thermal surveys of vulcano s fossa fumarole field aeolian islands italy in each survey between 400 and 1 200 vent temperatures were collected using a thermal infrared thermometer from distances of 1 m the results show a general decrease in average vent temperature during 1994 2003 with the average for the entire field falling from 220 c in 1994 to 150 c by 2003 however between 2004 and 2010 we witnessed heating with the average increasing to 190 c by 2010 alongside these annual scale field wide trends we record a spatial re organisation of the fumarole field characterised by shut down of vent zones towards the crater floor matched by rejuvenation of zones located towards the crater rim heating may be expected to be associated with deflation because increased amounts of vaporisation will remove volume from the hydrothermal system gambino and guglielmino j geophys res 113 b07402 2008 however over the 2004 2010 heating period no ground deformation was observed instead the number of seismic events increased from a typical rate of 37 events per month during 1994 2000 to 195 events per month during 2004 2010 as part of this increase we noticed a much greater number of high frequency events associated with rock fracturing we thus suggest that the heating event of 2004 2010 was the result of changed permeability conditions rather than change in the heat supply from the deeper magmatic source within this scenario cooling causes shut down of lower sectors and re establishment of pathways located towards the crater rim causing fracturing increased seismicity and heat flow in these regions this is consistent with the zone of rejuvenation which lies towards and at the rim being the most favourable location for fracturing given the stress field of the fossa cone schopa et al j volcanol geotherm res 203 133 145 2011 it is also the most established zone having been active at least since the early twentieth century our data show the value of deploying multi disciplinary geophysical campaigns at degassing fumarolic hydrothermal systems this allows more complete and constrained understanding of the true heat loss dynamics of the system in the case study presented here it allows us to distinguish true heating from apparent heating phases while the former are triggered from the bottom up i e they are driven by increases in heat supply from the magmatic source the latter are triggered from the top down i e by changing permeability conditions in the uppermost portion of the system to allow more efficient heat flow over zones predisposed to fracturing

relationships between diffuse co2 emissions and volcanic activity on the island of vulcano aeolian islands italy during the period 1984 1994 measurements of co2 flux from the ground were periodically carried out on the island of vulcano aeolian islands italy between 1984 and 1994 three high flux areas were identified at the foot of the volcanic cone la fossa either inside or very close to the main village effect of the choice of the sampling grid was evaluated a different sampling grid resulted in similar distribution patterns but with different co2 fluxes therefore the absolute estimate of the total flux from the investigated area includes a large degree of uncertainty but repeated measurements with permanent sampling sites are accurate and can detect small changes no correlation of the flux with atmospheric parameters was found at sites with high fluxes some periods characterized by high co2 fluxes were observed and a close correlation was found between the gas emissions from the ground and other geochemical and geophysical parameters such as temperature chemical composition steam and so2 flux from fumaroles seismic energy release and ground deformations the results show that major temporal variations of diffuse co2 flux are related to variations in volcanic activity

continuous monitoring of high temperature fumaroles on an active lava dome volcan colima mexico evidence of mass flow variation in response to atmospheric forcing rapid multichannel monitoring of fumaroles on volcan colima mexico provides new insight into the time scales and magnitudes of fumarole temperature variation temperatures in five fumaroles all located along a single fracture cutting the summit lava dome of the volcano were monitored at 20 min intervals between may 1991 and may 1992 measurements were made using a programmable data logger deployed near the fumarole field and data were radiotelemetered to a nearby volcano observatory at regular intervals mean fumarole temperatures varied between 350 c and 550 c statistical analysis of these time series shows that significant diurnal variation occurs in each fumarole magnitudes of these daily fluctuations are generally between 25 c and 50 c although larger amplitude variations occur especially in cooler fumaroles simultaneous monitoring of atmospheric pressure at the fumaroles indicates that these variations in temperature are inversely correlated with barometric pressure these observations indicate that fumarole temperatures respond to atmospheric forcing a numerical model developed to explore the dependence of fumarole temperature on mass flow demonstrates that many aspects of observed temperature variation are accounted for by mass flow variation resulting from small changes in barometric pressure the relationship between mass flow and fumarole temperature is nonlinear the response of fumarole temperatures to a given change in mass flow is greatest in fumaroles with low mass flow and cool temperatures the nature of this dependence is little affected by fumarole geometry for the cases considered continuous measurement of fumarole temperatures may be an effective means of monitoring local mass flow on volcanoes at volcan colima average temperatures changed by less than 100 c during the 1 year sampling period during and immediately following effusive activity changes in degassing were abrupt and inconsistent along the length of the fracture following this period temperatures decreased gradually and there was a higher degree of correlation between fumaroles the method described here represents a substantial improvement over traditional fumarole monitoring techniques because subtle variation can be quickly identified using standard statistical techniques and the method provides regular information about thermal activity on a volcano minimizing the hazards normally associated with the collection of these data on a regular basis

practical evaluation of steady heat discharge from dormant active volcanoes case study of vulcarolo fissure mount etna italy abstract from a theoretical approach combined with experimental study i propose a method to compute both sensible and latent heat transfer in a thermally active volcanic area this method is applied to a fumarolic thermal fissure located on the south flank on mount etna italy the method involves four steps 1 mapping of self potential sp to quickly identify thermal anomalies 2 mapping of ground temperature t at constant depth in the area defined by sp mapping 3 measurement of vertical t profiles at selected representative stations including the coldest and hottest and 4 direct measurements of vapor flow where the convective heat flux reaches the surface when heat flux values vary in the range 10 300 w m 2 t measurements at a depth equal to about 1 m are sufficient to estimate the absolute flux value to within an absolute error less than 30 and 10 for the relative value ground temperature measurement is an easy and accurate method for estimating heat discharge on a limited surface to define the fissure system monitor time variations of heat flux or to calibrate remote sensing results on the ground

reconciling short recurrence intervals with minor deformation in the new madrid seismic zone at least three great earthquakes occurred in the new madrid seismic zone in 1811 and 1812 estimates of present day strain rates suggest that such events may have a repeat time of 1000 years or less paleoseismological data also indicate that earthquakes large enough to cause soil liquefaction have occurred several times in the past 5000 years however pervasive crustal deformation expected from such a high frequency of large earthquakes is not observed this suggests that the seismic zone is a young feature possibly as young as several tens of thousands of years old and no more than a few million years old

geoarchaeological evidence of strong prehistoric earthquakes in the new madrid missouri seismic zone sand blows and fissures that cover 10 500 km sup 2 in northeastern arkansas and southeastern missouri attest to the severity of the 1811 1812 earthquake series in the new madrid seismic zone however except for one occurence near new madrid missouri the region has been devoid of any evidence of other major shocks for at least 1 3 ka prior to 1811 and possibly for 9 ka stratigraphic relations and radiocarbon dating at a recently excavated archaeological site near east prairie missouri have revealed liquifaction phenomena attributable to a shock dated to within about 100 yr prior to a d 539 and a probable second one dated between about a d 539 and 991