chemical and isotopical characterisation of fluid manifestations of ischia island italy abstract between 1994 and 1995 gas samples from fumaroles and thermal waters were collected on ischia island the chemical composition of the shallow and deep natural hydrothermal fluids discharged is related to the main hydrological and lithological characteristics of the rock formations present in the reservoir a biphase reservoir liquid gas is identified where the dominant liquid has a temperature of about 280 c on the basis of 13ctdc values it was possible to hypothesize a deep source characterised by carbon isotopic values varying from 0 to 3 these values are noticeably more positive with respect to those attributed to magmatic co2 13 c co 2 ranging from 5 to 8 thus suggesting a magmatic source modified by crustal contamination this hypothesis is supported by the carbon isotopic composition of co2 in sampled gases which varied from 0 to 5 the inferred isotopic value of carbon of magmatic co2 would then be about 2 the observed differences in c isotopic composition between fumarolic and magmatic gases would be caused by kinetic and or equilibrium fractionation processes these processes would cause a fractionation of 13c of deep co2 towards more negative values down to 5 actually co2 removal or addition processes caused by the interaction between deep gases and shallow hydrothermal waters are likely to be responsible for the different chemical and isotopic compositions of gaseous emissions for these reasons and on the basis of the homogeneity of geothermometric values the existence of a single large reservoir that feeds all of the fluids discharged at ischia island can be hypothesised based on acquired data a new geochemical model of the geothermal system of ischia island is proposed

hydrothermal alteration environments and recent dynamics of the ischia volcanic island southern italy insights from repeated field mineralogical and geochemical surveys before and after the 2017 casamicciola earthquake abstract this study presents the results of repeated surveys conducted in hydrothermally altered areas on the active volcanic island of ischia in the gulf of naples southern italy data were obtained from field work in situ temperature measurements x ray diffraction optical and scanning electron microscopy eds sem micro analysis infrared spectroscopy and whole rock geochemistry analyses on samples collected in october 2016 september 2017 march 2018 and november 2018 both prior to and following the damaging seismic event that occurred in august 2017 at casamicciola mineralogical results point to the evolution of acid sulfate zones along the northern and western flanks of a resurgent block located in the central part of the island in strict relation with endogenous fluid outgassing indicated in the literature mineralogy and whole rock geochemistry of these acid sulfate zones reveal magmatic hydrothermal environments in association with major structures that enable fluid circulation it is interpreted that rare coarser alunites within dominant steam heated and supergene alteration mineral assemblages are associated with environments that are no longer active but which are supplied by magmatic vapours in addition collected data indicate slow endogenous degassing from hydrothermal reservoirs data from september 2017 show variations in the sulfate assemblage within the acidic sulfate zone located near the earthquake s epicentre and acidification and the transitory appearance of alum k is apparent under a nearly unchanged endogenous supply meteorological conditions of late summer could in principle justify the appearance of alum k but its coexistence with alunogen and soil temperatures refute this possibility alum k is interpreted to be the product of alunite decomposition at a local temperature of ca 100 c assuming a correct space time relationship between the appearance of alum k and the earthquake it is thus inferred that mechanical activation by tectonic stress is the possible cause of alunite decomposition

fumarolic and diffuse soil degassing west of mount epomeo ischia italy abstract fumarolic fluid compositions and diffuse soil emissions of hydrothermal fluids of the donna rachele area 0 86 km 2 western flank of mt epomeo ischia island have been studied in order to develop a conceptual geochemical model of the hydrothermal system the degassing area was mapped and the total release of hydrothermal gas and heat associated with the diffuse emission of hydrothermal fluids was estimated a mesostructural study was carried out in order to investigate the relations between the brittle structures and the main pathways of the uprising vapor the fumarolic compositions are typical of hydrothermal fluids and water 99 represents the major component all gas species in the h 2 o h 2 co ch 4 co 2 h 2 s system are close to equilibrium concentrations at temperatures of 300 c and at redox conditions slightly more oxidizing than expected the compositions of the donna rachele fumarolic gas approach the pure liquid equilibrium composition this indicates a high fraction of separated vapor and suggests the presence of a highly energetic hydrothermal system at depth the pure liquid equilibrium compositions of the donna rachele fumaroles along with the historical records of shallow seismicity the explosion of a well in 1995 the occurrence of intense acoustic phenomena and of shallow wells discharging vapor indicate that the internal pressure of the hydrothermal system is occasionally larger than the hydrostatic pressure to quantify the energy dissipated in the donna rachele area by the emission of fumarolic fluids the hydrothermal diffuse degassing was studied by means of 336 soil co 2 flux measurements the highest co 2 fluxes were measured in hydrothermally altered areas along the faults that border mt epomeo structural data indicate that the vapor rises up along nw se striking normal faults related to gravity induced stresses and affecting highly fractured lavas the older faults which are related to the mt epomeo resurgence act as a permeability barrier and bound the donna rachele diffuse degassing structure the total hydrothermal co 2 output was estimated to be 9 t d 1 assuming that the h 2 o co 2 ratio of the fluids that feed the diffuse degassing is the same as that of fumarolic effluents the calculated heat flux is 40 mw this value which represents an important energy release is only a part of the total thermal energy release of ischia where other fumarolic areas occur the results obtained at ischia indicate the importance of thermal energy released by diffuse degassing structures in the energy balance of quiescent volcanoes values of the thermal energy release from the ischia hydrothermal system are comparable with those estimated on other quiescent volcanoes

solute provenance transport and denudation in a high arctic glacierized catchment recent understanding of chemical weathering in glacierized catchments has been focused on mid latitude alpine catchments comparable studies from the high latitudes are currently lacking this paper attempts to address this deficiency by examining solute provenance transport and denudation in a glacierized catchment at 78 n in the svalbard high arctic archipelago representative samples of snow glacier ice winter proglacial icing and glacier meltwater were obtained from the catchment during spring and summer 1993 and analysed for major ion chemistry seasonal variations in the composition of glacier meltwater occur and are influenced by proglacial solute acquisition from the icing at the very start of the melt season and subsequently by a period of discharge of concentrated snowmelt caused by snowpack elution weathering within the ice marginal channels that drain the glacier particularly carbonation reactions continues to furnish solute to meltwater when suspended sediment concentrations increase later in the melt season partitioning the solute flux into its various components sea salt crustal aerosol and atmospheric sources shows that c 25 of the total flux is sea salt derived consistent with the maritime location of the glacier and c 71 is crustally derived estimated chemical denudation 160 meq m 2 a 1 sea salt corrected cation equivalent weathering rate is somewhat low compared with other studied glacierized catchments estimates in the range 450 1000 meq m 2 a 1 which is probably attributable to the relatively short melt season and low specific runoff in the high arctic a positive relationship was identified between discharge and co 2 drawdown owing to carbonation reactions in turbid meltwater

mantle and crustal processes in the magmatism of the campania region inferences from mineralogy geochemistry and sr nd o isotopes of young hybrid volcanics of the ischia island south italy ischia one active volcano of the phlegraean volcanic district prone to very high risk is dominated by a caldera formed 55 ka bp followed by resurgence of the collapsed area over the past 3 ka the activity extruded evolved potassic magmas only a few low energy explosive events were fed by less evolved magmas a geochemical and sr nd o isotope investigation has been performed on minerals and glass from products of three of such eruptions molara vateliero and cava nocelle 2 6 ka bp data document strong mineralogical geochemical and isotopic heterogeneities likely resulting from mingling mixing processes among mafic and felsic magmas that already fed the ischia volcanism in the past detailed study on the most mafic magma has permitted to investigate its origin the mantle sector below ischia underwent subduction processes that modified its pristine chemical isotopic and redox conditions by addition of 1 of sediment fluids melts similar processes occurred from southeast to northwest along the apennine compressive margin with addition of up to 2 5 of sediment derived material this is shown by volcanics with poorly variable typical 18o mantle values and 87sr 86sr progressively increasing toward typical continental crust values multiple partial melting of this modified mantle generated distinct primary magmas that occasionally assimilated continental crust acquiring more 18o than 87sr at ischia 7 of hercynian granodiorite assimilation produced isotopically distinct k basaltic to latitic magmas a sw ne regional tectonic structure gave these magmas coming from large depth the opportunity to mingle mix with felsic magmas stagnating in shallower reservoirs eventually triggering explosive eruptions

gravitational slope deformation of a resurgent caldera new insights from the mechanical behaviour of mt nuovo tuffs ischia island italy abstract ischia island italy is an impressive example of the rare phenomenon of caldera resurgence the emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m concentrated in the western portion of mt epomeo 789 m a s l as a consequence of this uplift the island has experienced several slope instabilities at different scales since the holocene from shallow mass movements to large rock and debris avalanches these mass wasting events which mobilised large volumes of greenish alkali trachytic tuff the mt epomeo green tuff megt were strictly related to volcano tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island deep seated gravitational slope deformation dsgsd at mt nuovo located adjacent to densely populated coastal villages is an ongoing process that covers an area of 1 6 km 2 the mt nuovo dsgsd involves a rock mass volume of 190 mm 3 and is accommodated by a main shear zone and a series of sub vertical fault zones associated with high angle joint sets to improve our understanding of this gravity induced process we performed a physical porosity and permeability and mechanical uniaxial and triaxial deformation experiments characterisation of two ignimbrite deposits both from the megt that form a significant component of the nw sector of mt epomeo the main conclusions drawn from our experiments are twofold first the presence of water dramatically reduces the strength of the tuffs suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability second the transition from brittle dilatant to ductile compactant behaviour in the tuffs of the megt occurs at a very low effective pressure analogous to a depth of a couple of hundred metres and that this transition is likely moved closer to the surface in the presence of water we hypothesise that compactant porosity decreasing behaviour at the base of the layer could therefore facilitate slope instability although our results show that transient exposure to 300 c does not influence the short term strength of the tuff we speculate that the high in situ temperature could increase the efficiency of brittle and compactant creep and therefore increase the rate of slope deformation taken together our experimental data highlight a potentially important role for the hydrothermal system that reaches a minimum depth of 1 km in dictating the dsgsd at mt nuovo an understanding of this deformation process is not only important for the proximal coastal villages at risk of engulfment by a large debris avalanche but also for the towns and cities along the coast of the gulf of naples that are at risk to a secondary consequence of such an avalanche a tsunami wave

water geochemistry and soil gas survey at ungaran geothermal field central java indonesia abstract a soil gas survey for radon rn thoron tn co 2 and mercury hg and the chemical analysis of hot spring waters were undertaken in the ungaran geothermal field central java indonesia the results of soil gas surveys indicate fault systems trending nne ssw and wnw ese particularly high co 2 concentrations 20 and high hg concentrations were detected in vicinity of the fumaroles emanometries of rn tn and co 2 also conclusively identified the presence of a fracture zone for the migration of geothermal fluid the hg results infer that the up flow zone of high temperature geothermal fluids maybe located in the north of fumaroles in the gedongsongo area near the collapse wall chemistry of thermal springs in the up flow zone are acid ph 4 and show a ca mg so 4 composition the thermal waters are mainly ca mg hco 3 and ca na so 4 hco 3 types near the fumarolic area and are mixed na ca cl hco 3 waters in the south east of gedongsongo the 18 o between 5 3 and 8 2 and between 39 and 52 indicate that the waters are essentially meteoric in origin a conceptual hydro geochemical model of the gedongsongo thermal waters based on the soil gas isotope and chemical analytical results was constructed

chemical and isotopic assessment in volcanic thermal waters cases of ischia italy and sao miguel azores portugal isotopic fractionation of 10b 11b provides a sound tool for identifying hydrogeochemical processes in complex areas owing to its ability to discriminate between various scenarios in addition the occurrence of boron as a minor element in areas of active volcanism allows its use in comparison with concentrations of other conservative or non conservative ions this allows the detection of water mixtures of diverse origin and temperature deep or shallow including fresh water seawater and even brines this tool was applied in studies of the volcanic islands of ischia and sao miguel across widely differing geographical and climatic contexts five groups of waters have been identified in ischia island marine transition hot carbonated cold carbonated and fresh waters for sao miguel island the identified groups are cold carbonic hot carbonic boiling and acidic boiling waters copyright 2008 john wiley sons ltd

temporal distribution of suspended sediment transport in a mediterranean basin the lower tordera ne spain abstract suspended sediment dynamics are still imperfectly understood especially in areas of mediterranean climate with strong seasonal contrasts where few studies have been conducted the aim of this study is to analyze the variability in the suspended sediment load at different temporal scales within flood variability monthly seasonal and annual in the tordera river 894 km 2 located in northeastern spain suspended sediment samples were obtained during base flows q 3 5 m 3 s 1 and flood events q 3 5 m 3 s 1 the analysis of the variability in the suspended sediment is structured in two consecutive steps i the construction of statistical relations between suspended sediment concentrations c and discharge q and ii the application of those relations to assess the suspended sediment yield the results show that in a single event the sediment peak generally precedes the peak discharge following a clockwise hysteretic loop furthermore it was observed that the reduction in the suspended sediment concentrations in a sequence of events can be mainly associated with a phenomenon of sediment exhaustion the total amount of suspended sediment transported during a single flood is thus related to its duration and time during the year as well as to its magnitude at a seasonal scale the export of suspended sediment takes place in two phases i sediment preparation and ii sediment transfer and exhaustion during the latter phase the exhaustion of the sediment load is primarily related to the sequence of flood events at the annual scale the results show high inter annual variability according to the number of floods recorded yearly since almost all the suspended load is transported during those events

the 100 ka and rapid sea level changes recorded by prograding shelf sand bodies in the gulf of lions western mediterranean sea thick forced regressive units on the wide continental shelf of the gulf of lions western mediterranean recorded the composite effect of sea level changes during the quaternary they are mostly composed of coastal siliciclastic and bioclastic wedges showing clinoform geometry these deposits have been intensively explored through high resolution seismic investigations but only recently it was possible to ground truth seismic interpretations based on a long 100 m borehole that crossed the succession and recovered a large part of the mainly sandy deposits similar to 84 recovery a multiproxy analysis of the sedimentary succession shows that 1 the stratal architecture of the shelf margin is defined by major bounding surfaces that are polygenic erosion surfaces associated with coarse grained material incorporating abundant and diverse shells including cold water fauna presently absent from the mediterranean sea between each surface coarsening upward units with steep up to 5 degrees foresets are made of massive more than 20 m thick sands with possible swaley and hummocky cross stratification passing seaward to sands with muddy intervals and further offshore alternating highly boiturbated sands and silts each prograding wedge corresponds to a forced regressive shoreface or delta front prodelta deposited during the overall sea level falls occurring at relatively slow interglacial glacial transition and therefore represents the record of 100 ka cyclicity higher frequency milankovitch cyclicities are also probably represented by distinct shoreface delta front wedges 2 detailed examination of the architecture and chronostratigraphy of the most recent sequence shows that minor bounding surfaces corresponding to abrupt shallowing of sedimentary facies separate downward stepping parasequences within the last 100 ka sequence

interaction between fumarolic gases and thermal groundwaters at vulcano island italy evidences from chemical composition of dissolved gases in waters abstract the chemical composition of some gaseous species dissolved in thermal groundwaters from vulcano island was determined directly in the field the determinations were made using a methodology based on the equilibrium partitioning of gases between a liquid and a gaseous phase the analyses were performed with a portable gas chromatograph using a simple analytical procedure lasting 70 s he and co 2 partial pressures are notably higher than those of waters in equilibrium with the atmosphere confirming an interaction between volcanic gases and groundwaters the highest co 2 values were recorded in wells located in areas of anomalous co 2 and he exhalations related to the active volcano tectonic structures on the island the temporal variations in co 2 concentrations both in the crater fumarolic gases and in the dissolved gases of some wells showed a very similar pattern lastly the lowering of the he contents in the dissolved gases that occurred in 1996 1997 was probably due to a decreased interaction between the main degassing system crater fumaroles and the thermal groundwaters

chemical features and isotopic composition of gaseous manifestations on vulcano island aeolian islands italy an interpretative model of fluid circulation abstract between 1987 and 1995 gases were sampled from various manifestations on vulcano island including various fumaroles at la fossa crater and baia di levante and diffuse soil gas emissions in several areas which are characterized by high c02 fluxes since the end of 1987 volcanic activity has increased considerably showing a marked rise in temperature 300 c in 1987 to 670 c in december 1992 and in output of steam from crater fumaroles in addition variations have been observed in the chemical and isotopic compositions of gases and thermal waters which can be attributed to an increased inflow of deeper fluids the isotopic composition of fumarolec steam seems to be the result of mixing processes between a positive endmember of deep origin d 10 15 18o 6 8 and two endmembers of meteoric origin with different oxygen shifts variations observed in the c02 isotopic composition suggest that all sampled manifestations are fed by a single deep source which may be magmatic such a source would be characterized by the 613cco2 values of high temperature fumaroles 13cco2 0 these values are noticeably more positive than those generally attributed to magmatic gases 13cco2 5 8 implying crustal contamination processes of the magma the observed decrease in 18oco2 values of the crater fumaroles from 20 in 1978 to between 12 and 15 in 1993 1994 was probably caused by two different processes the first is a reduction of the enrichment factor between c02 and h2o which is related to the increased temperature of the gases and the second is a mixing with more negative waters of meteoric origin finally c02 addition or removal processes caused by interactions between deep gases and shallow hydrothermal waters are likely to be responsible for the different chemical and isotopic compositions of gaseous emissions in the vulcano porto area and the crater fumaroles

particle size characteristics of suspended sediment transported in meltwater from the gangotri glacier central himalaya an indicator of subglacial sediment evacuation abstract proglacial meltwater streams draining out of the himalayan glaciers carry considerable amounts of suspended sediment with a variety of particle sizes because of the supraglacial englacial and subglacial debris as well as formation of sediments from erosion by the movement of the ice this paper examines particle size transported in the proglacial meltwater stream of gangotri glacier for seven consecutive melt seasons may october 2000 2006 in order to provide information on i temporal variations in the particle size distribution ii texture and mineralogy of the sediments and iii origin and evacuation pattern of the sediments our results indicate dominance of silt size 0 002 0 06 mm particles 71 followed by sand size 0 06 0 6 mm particles 24 and clay size

simple shearing block resurgence in caldera depressions a model from pantelleria and ischia abstract similar resurgent blocks occur in caldera depressions at the islands of pantelleria and ischia the two blocks which are tilted show similar deformation patterns and similar distributions of volcanic vents related to resurgence the remaining parts of the floors of the two calderas are not deformed similarities between the two features are so striking that the resurgence mechanism must have been alike a dynamic model for resurgence is presented and called simple shearing block resurgence the triggering mechanism is an increase of the magmatic pressure in the upper part of a shallow magma chamber which results in a vertical direction of the maximum stress applied on the roof rocks the block is first defined by high angle inland dipping marginal detachments and then deformed through a simple shearing mechanism reverse faults on its mostly uplifted side determine an horizontal shortening of the block which is balanced on the opposite side by normal faults oblique movements take place along the other two sides due to this distribution of the stress around the block magmas can reach the surface only through the extensional faults on the less uplifted side

shear wave velocity and attenuation structure of ischia island using broad band seismic noise records abstract in volcanic areas accurate localization of earthquakes requires detailed velocity and possibly attenuation models taking into account wide lithological variability and high geothermal gradients ischia island campania region italy is a seismically active volcano recently affected by a mw 3 9 event casamicciola august 21 2017 1 km depth due to the lack of a specific velocity model the earthquakes occurred on the island were localized using the one developed for the nearby campi flegrei caldera the aim of this work is the definition of a mean representative 1d shear wave velocity vs and attenuation q model of the shallower crust up to 2 km depth of ischia seismic noise array and spectral ratios techniques were applied to broad band seismic signals recorded by temporary and permanent networks updated after the august 2017 earthquake the values of both shear wave velocity vs and quality factor q are realistic with q values comparable with those obtained for campi flegrei and stromboli volcanic areas by taking into account stratigraphic information from deep wells and ultrasonic measurements of velocity on granite and trachytic lava samples a geological interpretation of the resulting velocity model is provided such a model can have significant implications for understanding the dynamics of a volcano mainly those leading to seismic activity

rare earth elements geochemistry in springs from taftan geothermal area se iran abstract concentrations of rare earth elements rees were determined in springs and andesitic dacitic rocks of taftan geothermal field hydrochemical results of major ions indicate that thermal springs are na so 4 cl and ca so 4 cl types concentrations of rees are in ranges of 10 4 to 1 2 and 49 to 62 times of chondrite for springwater and rock samples respectively the thermal sts and tts and the cold aps springs with low ph values exhibit a very high ree contents 0 64 to 3 15 mg l saturation index indicates that fe and al phases can control dissolved ree concentration in fts and pf cold springs the speciation of ree complexes indicates dominant presence of lnso 4 and free ion in the taftan thermal springs in aps cold spring with ph 4 fluoride complexes are dominate over the free ion and sulfate species while in pf and fts cold springs with ph 6 4 and 7 respectively carbonate complexes lnco 3 are predominant species chondrite normalized pattern for the low ph waters show very distinctive gull wing patterns characteristic feature of acid sulfate geothermal systems and are similar to those of the host rocks chemical characteristics of rare earth elements in spring and volcanic rock samples indicate that rees are originated from the andesitic dacitic host rocks whole rock normalized ree patterns and petrographic evidences show that rare earth elements leached mainly from marginal alteration of minerals and matrix decomposition in volcanic rocks in chondrite normalized ree patterns significant negative eu anomaly in the cold springs compare to the thermal and acidic springs indicates that alteration of plagioclase is more intense in the later corresponding to increasing in temperature and acidic state of reactant water

helium isotopes and tectonics in southern italy geodynamic evolution of southern italy can be understood within the framework of the mediterranean alpine system subduction of a plate along the sicily calabrian forearc under the tyrrhenian sea has been suggested by many geophysicists although it is not yet confirmed and remains somewhat controversial helium isotope ratios provide useful information on the geotectonic structure of the region the authors report here the sup 3 h sup 4 he ratios of terrestrial gas samples from southern italy the observed sup 3 he sup 4 he ratios are relatively high in the eolian volcanic arc region and low in the other areas dichotomous explanations are presented firstly volcanic arc forearc hypothesis suggests the subduction along the sicily calabrian forearc secondly horizontal transport hypothesis is described based on the relationship between the ratios and radial distance from the recent spreading basin in southern tyrrhenian sea

event based suspended sediment dynamics in a central new york watershed abstract using discharge and sediment data collected from 23 events between 2008 and 2010 in a 311 km2 watershed of central new york we investigated event sediment dynamics of the studied watershed after showing the statistical difference of the data in different seasons we examined the detailed hysteresis patterns of all events spring events had figure eight with anticlockwise figure 8 ac clockwise c anticlockwise ac and complicated patterns summer events had c ac figure 8 ac figure 8 c and complicated patterns fall and winter events had the same patterns as those in summer as well as a weak loop pattern the diversity of patterns within and between seasons suggests that detailed processes of sediment transport were not only complicated during one event but also varied from season to season although hysteresis analysis failed to identify these detailed processes and the associated sediment sources in such a relatively large watershed it successfully revealed a common feature dominating the transport processes event sediment transport was generally supply limited further analysis on the correlation between event sediment yield ssye and event peak discharge qpeak indicated that i events with clockwise patterns tended to have more ssye than those with other patterns for the same qpeak and ii data from all events may be statistically well described by a single ssye qpeak equation regardless of hysteresis patterns this equation i reveals that complicated event transport processes may be lumped into a simple process over events and ii reflects the general supply limited nature identified by hysteresis analysis using this equation and the magnitude frequency analysis we further discovered that in the past 21 years sediment was mainly transported by more frequent but relatively small discharges with the recurrence interval no more than 0 5 year

extreme sediment delivery events recorded in the contemporary sediment record of a montane lake southern coast mountains british columbia the extreme sediment delivery regime of a montane catchment was examined through the analysis of recent lacustrine varve deposits recovered from a high density sampling program years of anomalously high sediment yield from the green lake watershed were identified over a 70 year period 1930 2000 based on whole lake varve deposit volumes intra annual sediment delivery events were categorized and described for those anomalous years using historical hydroclimatic data and the stratigraphic record observed within inflow proximal sediment cores extreme sediment delivery coincided with high discharge conditions and elevated sediment availability resulting from 1 rapid glacier recession of the early twentieth century 2 late summer and autumn rainstorm generated floods and 3 freshet floods caused by unusual snowmelt conditions the thickness and physical characteristics of varves vary among years that experienced different types of moderate and extreme sediment delivery events in relation to the defin

the potential failure of monte nuovo at ischia island southern italy numerical assessment of a likely induced tsunami and its effects on a densely inhabited area ischia is the emergent top of a large volcanic complex that rises more than 1 000 m above the sea floor at the north western end of the gulf of naples caldera resurgence in the central part of the island has resulted in the formation of differentially displaced blocks among which mt epomeo 787 m a s l is the most uplifted deformation and slope instability have been recognised as common features induced by a block resurgence mechanism that causes uplift and favours gravitational loading and flank failure the monte nuovo block a topographic high on the north western flank of mt epomeo has recently been interpreted as a block affected by deep seated gravitational slope deformation this block may undergo a catastrophic failure in the case of renewal of magmatic activity this paper investigates the potential failure of the monte nuovo block as a rockslide debris avalanche the consequent tsunami generation and wave propagation and discusses the catastrophic effects of such an event mobilization prone volume has been estimated at about 160 106 m3 and would move from a maximum elevation of 400 m a s l the landslide itself would sweep away a densely populated territory as large as 3 5 km2 the highest waves generated by the tsunami on which this paper is mainly focussed would hit the northern and western shores of ischia however the high coast would prevent inundation and limit devastation to beaches harbours and surrounding areas most of the tsunami energy would head towards the north east hitting the campania coast severe inundation would affect an area of up to 20 km2 around the mouth of the volturno river including the urban area of castel volturno in contrast less energy would travel towards the south and the gulf of naples would be perturbed by long persisting waves of limited damaging potential

assessment of different colour parameters for discriminating potential suspended sediment sources and provenance a multi scale study in luxembourg abstract sediment colour has recently been used successfully to estimate suspended sediment sources in small catchments using the fingerprinting approach the methodology offers opportunity for further research since it provides a rapid and cheap means for investigating sediment sources however the colour based fingerprinting approach has not yet been tested in medium and large catchments this paper aims to test whether colour parameters are capable of discriminating sediment sources in a nested system of seven sub catchments ranging from 0 7 to 247 km 2 of the attert river catchment nw luxembourg time integrated suspended sediment samples and samples of potential sediment sources land use types and channel banks were collected in all catchments sediment colour was then computed from diffuse reflectance spectrometry measurements asd fieldspec ii spectrometer 0 4 2 5 m taken over the visible wavelength range twenty four colour parameters were derived from several colour space models cie xyy cie xyz rgb munsell hvc helmholtz chromaticity cieluv and cielab and their ability to discriminate potential suspended sediment sources and provenance was evaluated and compared results demonstrated that time integrated suspended sediment samples collected in the study catchments had statistically different colour values moreover these values always represented a mixture of the colour values measured on potential suspended sediment sources in the catchment inter source colour contrasts land use types and channel banks were observed in all catchments kruskal wallis h test however although colour is able to distinguish potential sediment sources in small catchments the level of source discrimination decreases as the catchment size increases probably due to heterogeneous geology and pedology intra source variability and to source overlap nevertheless in the studied medium sized catchments ranging from 19 4 to 247 km 2 colour could differentiate between topsoil and sub surface i e channel bank material and or up to three sources types no single colour model had discrimination power across catchments instead in each catchment a different combination of colour parameters gathered from different colour space models produced optimal discrimination of potential sediment sources furthermore a colour based fingerprinting approach did not possess potential for integrating spatial provenance and source type information because colour parameters could not discriminate between contrasting geological sub areas in summary although colour parameters were not capable of discriminating the range of land use type and channel banks as potential suspended sediment sources in medium sized catchments they afford substantial information and could be integrated into the classical fingerprinting approach together with other constituents e g geochemistry radionuclides and or organic compounds

cyclical slope instability and volcanism related to volcano tectonism in resurgent calderas the ischia island italy case study abstract the results of a detailed stratigraphic study carried out in the areas located to the east and south west of mt epomeo at ischia are presented and compared with those of previous geological archaeological and historical investigations to show the relationships among caldera resurgence volcanism and slope instability in the past 5 5 ka resurgence at ischia began at about 30 ka b p and occurred through intermittent uplifting and tectonic quietness phases during the past 5 5 ka reactivation of faults and related volcanic activity was accompanied by emplacement of deposits generated by surface gravitational movements these deposits were generated in four main phases dated between 5 5 and 2 9 ka around 2 9 ka between 2 6 and 2 3 ka and between 2 3 and 1 9 ka respectively deposits formed by gravitational movements preceded and followed the emplacement of volcanic rocks testifying that slope instability was induced by vertical movements which also activated and or reactivated faults and fractures that fed volcanism the results of this study therefore suggest that although slope failure can occur as a consequence of a variety of factors resurgence has to be considered a factor inducing a particularly intense slope instability resurgence is accompanied by activation of faults and renewal of volcanism causing oversteepening of the slopes and generating seismicity that could trigger surface gravitational movements furthermore the availability of large amount of loose material rapidly accumulated along the slopes during eruptions favors landslide generation

isotopic study of the origin of sulfur and carbon in solfatara fumaroles campi flegrei caldera abstract isotopic study of the origin of sulfur and carbon in the hottest solfatara fumaroles of campi flegrei caldera southern italy was carried out on gas samples collected between 1983 and 1988 i e during and after the 1982 1984 seismo volcanic crisis the results for sulfur h2s the first ever reported on these gases indicate a mean 34 s of 0 3 0 3 range 0 7 to 0 1 versus canyon diablo troilite standard consistent with an igneous derivation of this element from either active magma degassing or and leaching of reduced sulfur bearing minerals in the volcanic layers the lack of peculiar 34s variation during and after the crisis suggests that the chemical variation of h2s and s c ratio in the fumaroles increase and then decrease by a factor 3 were not due to a changing origin of sulfur the mean 13c of carbon co2 over the period of survey 1 6 0 2 range 1 9 to 1 3 versus pdb standard is similar to the values obtained before the crisis since 1970 such an isotopic constancy requires a large and stable source of carbon feeding the fumaroles the measured 13c values are much higher than those typical of primary mantle magmatic carbon 6 2 and plot within the 13c range for marine carbonates 0 2 such high values may reflect either a 13c fractionation during degassing of co2 from the underlying 5 km depth magma chamber or b the contribution of heavy co2 of sedimentary origin derived from either thermometamorphism of mesozoic limestone series embedding the magma chamber or possibly past contamination of the local mantle by subducted sediments various arguments among which volcanological evidence of an isolated and cooling magma reservoir which would have been extensively degassed and so depleted in 13c along with time the low 3he 4he ratios and the broad 13c enrichment of volcanic fluids in the region and geochemical evidence of crust magma fluid interactions suggest that a considerable fraction 60 of co2 in solfatara fumaroles derives from carbonate sediments in the basement the contribution of magma derived co2 may be higher within the central part of the caldera including solfatara crater than toward its western margin where fumarolic and geothermal well gases exhibit lower 3he 4he ratios and still higher 13c values such a geochemical pattern is consistent with the central distribution of ground deformation and seismicity during the 1982 1984 crisis and with the idea of a residual magma body confined beneath the central part of the structure alternatively higher 13c and lower 3he 4he ratios toward the western margin may result from dilution of solfatara type gas during progressively deeper water boiling finally accepting that solfatara co2 derives from simple crustal mixing between magmatic and sedimentary carbon its constant isotopic composition together with the constant he isotope ratio would restrict the possibility of magma intrusion and or higher magmatic gas input as mechanisms responsible for the 1982 1984 events however this conclusion would no more hold true if the magma itself or even its mantle source were previously contaminated by crustal carbon

variation in the total dissolved carbon isotope composition of thermal waters of the island of ischia italy and its implications for volcanic surveillance abstract during surveys conducted in 1997 30 thermal waters for a total of 39 analysis were collected from shallow wells utilised for resort spas on the island of ischia well temperatures ranged from 25 to 82 c and their depths from 30 to 150 m pools with temperatures of 26 to 67 c were also sampled on the northern flank of the mt epomeo the samples were analysed for bulk chemical composition as well as h o and c isotope composition isotopic analyses of water samples showed wide variations in both deuterium and oxygen 18 which ranged from 37 4 to 8 1 and 6 8 to 1 1 respectively overall 13 c in total dissolved carbon tdc ranged from 11 5 to 2 3 and computed 13 c of co 2 g results ranged from 18 5 to 1 72 water samples with co 2 content of up to about 1 bar partial pressure exhibited 13 c co 2 ranging from 4 to 1 water samples varied chemically from low salinity hco 3 well waters 1 4 g l of essentially meteoric origin to high salinity cl waters up to 40 g l mixing processes from local groundwater seawater and evaporated waters have also been identified models for the chemical and isotopic data on the thermal manifestations have been developed for low and high pressure conditions in order to assess the isotopic composition of deep co 2 assuming that this component is continuously added to the solutions until degassing occurs at shallow depths or at the surface constraints due to the reaction of water with volcanic glass have been taken into account for in the computations in addition to those relative to the carbon components participating in the carbonate equilibria results from such simulations indicate that deep co 2 added to the shallow waters probably has a carbon isotope composition 2 which most likely stems from a mixed magmatic sedimentary origin

suspended sediment load during floods in a small stream of the dolomites northeastern italy abstract suspended sediment load was analyzed in a small high gradient stream of the eastern italian alps which was instrumented to measure discharge and sediment transport the ratio of suspended to total sediment yield and the relations between sediment concentration and water discharge were analyzed for seven floods which occurred from 1991 to 1996 in summer and autumn from june to october different patterns of hysteresis in the relation between suspended sediment and discharge were related to types and locations of active sediment sources the within storm variation of particle size of suspended sediment during a major flood indicates a coarsening of transported material for increasing discharge an analysis of grain size has shown that erosion areas on hillslopes were the main sources of suspended load

isotope geochemistry of pantelleria volcanic fluids sicily channel rift a mantle volatile end member for volcanism in southern europe chemical and isotopic ratio he c h and o analysis of hydrothermal manifestations on pantelleria island the southernmost active volcano in italy provides us with the first data upon mantle degassing through the sicily channel rift zone south of the african european collision plate boundary we find that pantelleria fluids contain a co2 he rich gas component of mantle magmatic derivation which at shallow depth variably interacts with a main thermal 100 c aquifer of mixed marine meteoric water the measured 3he 4he ratios and 13c of both the free gases 4 5 7 3 ra and 5 8 to 4 2 respectively and dissolved helium and carbon in waters 1 0 6 3 ra and 7 1 to 0 9 together with their covariation with the he co2 ratio constrain a 3he 4he ratio of 7 3 0 1 ra and a 13c of ca 4 for the magmatic end member these latter are best preserved in fluids emanating inside the active caldera of pantelleria in agreement with a higher heat flow across this structure and other indications of an underlying crustal magma reservoir outside the caldera the magmatic component is more affected by air dilution and at a few sites by mixing with either organic carbon and or radiogenic 4he leached from the u th rich trachytic host rocks of the aquifer pantelleria magmatic end member is richer in 3he and has a lower closer to morb 13c than all fluids yet analyzed in volcanic regions of italy and southern europe including mt etna in sicily 6 9 0 2 ra 13c 3 1 this observation is consistent with a south to north increasing imprint of subducted crustal material in the products of italian volcanoes whose he and c but also o and sr isotopic ratios gradually evolve towards crustal values northward of the african eurasian plate collision boundary our results for pantelleria extend this regional isotopic pattern further south and suggest the presence of a slightly most pristine or less contaminated 3he richer mantle source beneath the sicily channel rift zone the lower than morb 3he 4he ratio but higher than morb co2 3he ratio of pantelleria volatile end member are compatible with petro geochemical evidence that this mantle source includes an upwelling himu em1 type asthenospheric plume component whose origin according to recent seismic data may be in the lower mantle

drivers of erosion and suspended sediment transport in three headwater catchments of the mexican central highlands quantifying suspended sediment exports from catchments and understanding suspended sediment dynamics within river networks is important especially in areas draining erodible material that contributes to the siltation of downstream reservoirs and to the degradation of water quality a one year continuous monitoring study of water and sediment fluxes was conducted in three upland subcatchments 3 0 9 3 and 12 0 km2 located within the cointzio basin in the central volcanic highlands of mexico michoacan state two subcatchments generated high sediment exports i e huertitas 900 1500 t km 2 y 1 and potrerillos 600 800 t km 2 y 1 whereas the third subcatchment was characterized by a much lower sediment yield i e la cortina 30 t km 2 y 1 such disparities in subcatchment behaviours were associated with the presence of severely gullied areas in huertitas and potrerillos rather than with rainfall erosivity indices an adapted classification of hysteretic patterns between suspended sediment concentration ssc and discharge was proposed because 42 of flood events contributing to 70 of sediment export were not discriminated by the classical clockwise anticlockwise typology this new classification allowed the identification of relationships in the hydrosedimentary responses of successive floods a stream transport capacity limit was also detected during hydrograph recession phases overall hydrosedimentary processes proved to be seasonally dependent sediment export was repeatedly limited by the stream transport capacity during the first part of the rainy season whereas a channel minimum erosivity threshold was frequently reached at the end of the season

geothermal assessment of the island of ischia southern italy from isotopic and chemical composition of the delivered fluids abstract the ischia geothermal system is hosted by silicic rocks of the quaternary potassic roman province in southern italy exploration drilling down to 1156 m depth in the mid 1950s provided information on boiling profiles up to 250 c and on the depth and permeability of the potential reservoirs discharge fluid samples were collected and analyzed to define the inflow of surrounding seawater c1 ranges from 2 5 to 20 g kg into the system analyses of samples from surface manifestations and shallow wells collected during 1983 and 1988 point to the existence of three distinct mixing regimes involving three water components a dishomogeneous body of diluted water cl less than 2 5 g kg that occurs at depths 700 m and reequilibrates at 240 c at least is overlain by an aquifer of groundwater variably mixed with variably seawater cl from 4 to 10 g kg which tends to reequilibrate at 160 c steam heated waters locally develop and act as dilutants of the rising geothermal fluids dilution mixing and evaporation of the ascending chloride fluids are supported by oxygen and hydrogen isotopic data the thermal waters being enriched in 18 o and d with respect to local meteoric water by up to 7 and 30 respectively the relative composition of the major cations in thermal solutions was used to discriminate the two main groups of thermal waters the reservoir temperatures of which are estimated from the na k gethermometer k mg geothermometer indicates reequilibration in near surface conditions the isotopic composition of the fumarolic steam varies from 7 to 12 in 8 o and from 35 to 70 in d in agreement with a deep mixed fluid that boils adiabatically from 240 to 80 c the deuterium content of the h 2 o h 2 pair gives enrichment factor of about 830 corresponding to equilibrium temperature conditions slightly higher than the surface boiling temperatures the 13 c of co 2 is almost constant at 4 5 1 0 4 suggesting an important magmatic contribution and the 18 o values of co 2 appears to in equilibrium with accompanying steam at the measured temperatures the co 2 ar and h 2 ar chemical ratios have been used to derive aquifer temperatures the values obtained being consistent with those of solute geothermometers

suspended sediment from the gangotri glacier quantification variability and associations with discharge and air temperature abstract to understand the sediment delivery variation for a himalayan glacier gangotri glacier garhwal himalayas and to determine its relationship with discharge and air temperature suspended sediment samples and discharge data were collected near the glacier snout 4000 m for four melt seasons during the period 2000 2003 these data were used to estimate suspended sediment concentration ssc suspended sediment load ssl sediment yield and erosion rate in the glacier melt stream bhagirathi the monthly distribution of suspended sediment and its variability from year to year have been examined mean monthly ssc for may june july august september and october were found to be 1942 2063 3658 2551 734 and 136 mg l 1 respectively maximum ssc in meltwater was observed in july followed by august it was found that the cumulative percentage delivery of ssc precedes discharge throughout the melt season mean monthly total ssl for may june july august september and october during the study period was found to be 149 423 1220 746 143 and 5 10 3 ton respectively the strong variability is found in ssl c v 1 1 than ssc c v 0 8 because computation of ssl includes both discharge c v 0 6 and ssc delivery response of ssl in terms of percentage of total load is less in the early part of the melt season than in the later stage in comparison to that of discharge this may be due to the fact that in the beginning of the melt season low melt rate conditions prevails and thus the low discharge velocity could not flush out stored glacial sediment it has been observed that 59 64 of the sediment passed through the channel by the time 50 of the total discharge passed the average suspended sediment yield for the whole melt season from the study area was estimated to be about 4834 ton km 2 and corresponding erosion rate was 1 8 mm the relationship between mean monthly ssc and discharge r 2 0 99 is much better than the daily ssc and discharge r 2 0 40 because variability of both parameters is averaged out on monthly scale mean monthly ssc and mean monthly ssl provide a good exponential relationship with mean monthly air temperature these results are relevant for planning and management of water resources in the high altitude areas and for designing hydropower projects

effect of seasonal snow cover on suspended sediment runoff in a mountainous catchment summary the effect of snow cover and snowmelt on suspended sediment ss runoff at a mountainous catchment in the temperate zone was investigated the observation was carried out from march 1999 to may 2002 3 years at an experimental catchment with the area of 0 347 km 2 ranging from 280 m to 618 m above mean sea level with average stream gradient of 1 4 it was concluded that the snow accumulation and ablation process in the catchment had a significant impact on ss runoff characteristics especially during the snow melting period it was estimated that more than 60 of the annual ss load flowed out during the snow melting period because of the enhanced water discharge the daily average ss flux during the snow melting period was calculated to be 2 54 g s 1 km 2 corresponding to a 6 7 times greater ss flux than that during other periods the c q relation analysis in each runoff event revealed a dynamic change in the ss runoff mechanism during the snow melting period strong clockwise hysteresis in c q relation in the early stage of the snow melting period may be explained by consumption of the bed load by the first flush followed by quick depletion of the material on the stream bed due to suppression of further ss supply by thick snow cover counterclockwise hysteresis in c q relation was observed only in the late stage of the snow melting period ss production at steep slopes beside the stream by avalanches and surface soil slides induced by an abundance of meltwater was considered to be one of the main causes of the counterclockwise loops it would be hypothesized that exposure of other steep slopes or bluffs in the catchment apart from the stream and stream bank failure by repeating surges of the stream water stage could also be other possible ss sources causing counterclockwise hysteresis in the late snow melting period

determining the sources of suspended sediment in a forested catchment in southeastern australia 1 knowledge is scarce regarding the relative contributions from harvested areas and unsealed roads to sediments in forested catchments we investigate the source composition of suspended sediment using sediment tracers and an improved multivariate mixing model sediment samples were collected during six rainfall events geochemical and radiometric tracer properties were corrected for particle size and organic content as well as conservativeness during erosion and sediment delivery the mixing model incorporates variability of the tracer properties using a monte carlo simulation technique mean sediment contribution from the undisturbed forest was 50 70 harvested areas gravel surfaced roads and ungravelled roads contributed 5 15 6 14 and 12 25 respectively the unsealed roads contribute 20 to 60 times more sediment than the undisturbed forest and about 10 times more sediment than the harvested areas on a per unit area basis harvested areas contribute 1 to 5 times greater sediment than the undisturbed forest these results support other studies that identify unsealed roads as important sediment sources in forested catchments

age and geochemistry of tephra layers from ischia italy constraints from proximal distal correlations with lago grande di monticchio unraveling the eruptive history of the island of ischia southern italy is problematic due to its burial caldera collapse resurgent uplift and erosion here we present new major and trace element glass data for 39 75 ka proximal tephra deposits including those of the caldera forming monte epomeo green tuff megt eruption correlations with the distal tephra archive preserved at lago grande di monticchio lgdm are used to constrain the timing of as yet undated eruptive events out of 13 lgdm tephras analysed from the 39 104 ka time window glass geochemical data show that all are compositionally consistent with the explosive volcanic eruptions of ischia whilst 5 of them can be correlated with specific proximal deposits pre megt pyroclastic sequences comprise three compositional groups these groups occur repeatedly in sucessive eruptions proximal distal correlations indicate that the porticello eruption occurred at 59 2 ka and the tisichiello eruption probably occurred at 76 3 ka the megt eruption is correlated with lgdm tm 19 which has been directly dated at 55 2 ka post megt tephras form compositional groups that overlap with the pre megt but are displaced to lower feo and tio2 and lower incompatible element contents proximal distal correlations indicate that the schiappone and pietre rosse eruptions occurred at 50 6 2 0 ka and 45 6 ka respectively tephra from the megt eruption span a wide compositional range broadly overlapping the three pre megt compositional groups but are displaced to higher nd and y and contain an additional less evolved glass population glass geochemistry is used to recognise and confirm distal equivalents of the megt at lgdm tm 19 and in the ionian y 7 adriatic prad 1870 and tyrrhenian c 18 md 28 seas distal occurences of megt tephra define a dispersal axis to the south southeast and are found as far as 540 km from ischia making the megt one of the most widely dispersed late quaternary pyroclastic deposit erupted in the campanian region we estimate a volume of approximately 40 km3 for the fallout portion of the megt pyroclastic sequence on the basis of proximal and distal deposit thicknesses

sediment concentration versus water discharge during single hydrologic events in rivers relations between sediment concentration c and water discharge q for a hydrologic event such as a flood are studied qualitatively by analyzing smoothed temporal graphs discharge and concentration vs time in terms of mode spread and skewness comparing cq ratios at a given discharge on the rising and falling limbs of the discharge hydrograph provides a consistent reliable method for categorizing c q relations five common classes of such relations are single valued straight or curved clockwise loop counterclockwise loop single valued plus a loop and figure eight temporal graph mode and skewness influence the type of relation whereas temporal graph spread affects the details of the particular c q relation its graphical breadth shape orientation and plotted location field examples of the various types of relations are given including varieties that heretofore have received little attention such as the figure eight explanations for each type of c q relation are discussed

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

chemical and isotopic investigations of fumarolic gases from ischia island southern italy evidences of magmatic and crustal contribution abstract chemical and isotopic investigations have been carried out on subaerial and submarine fumarolic fluids on the island of ischia gulf of napoli southern italy chemical analyses of gases from the hottest fumarole 117 c located on mount epomeo show a typical geothermal composition thermodynamic computations indicate a feeding source temperature of mt epomeo ranging from 300 to 500 c isotopic compositions suggest that the island is divided into two parts east and west fumarole gases on the west side of the island indicate a magmatic source with small crustal contamination and are characterized by carbon isotopic data similar to morb 13 c ranging from 3 5 to 5 11 with about 50 of the helium having a magmatic origin 3 6 3 7 r r a fumaroles located on the east side of the island have carbon isotopic data ranging from 0 45 to 0 76 and a lower helium isotopic ratio from 2 09 to 2 89 r r a the east fumaroles seem to be fed by fluids deriving from a reservoir located in or close to a carbonatic source in the crust

interdecadal patterns of total sediment yield from a montane catchment southern coast mountains british columbia canada article i nfo we reconstruct sediment yield for a mountain watershed of western canada since the mid twentieth century from studies of annually laminated lake sediments delta progradation and solute transfer total yield averaged 320 40 mg km 2 a 1 and comprised 35 suspended load 50 bedload and 15 dissolved load ratios between the individual yield components varied approximately threefold at interannual timescales because of significant variability in the suspended and bedload fractions asynchronous flux in suspended and bedload fractions through time arise from differences in sediment availability and transitory sediment storage in the channel periods of elevated yield coincide with rapid glacier recession an extreme rainstorm and a landslide our results indicate that in montane environments extrapolation from even decade long monitoring programs may lead to biased projections of long term yield and delivery mode proportions if variations in sediment supply and catchment response to hydroclimatic and geomorphic controls are not considered

establishing fine grained sediment budgets for the pang and lambourn locar catchments uk summary an integrated approach to data collection combining the use of 137cs measurements sediment source fingerprinting bed sediment surveys and conventional river monitoring has been successfully employed to establish the fine grained sediment budgets of two lowland groundwater fed catchments in the uk gross surface erosion is higher on cultivated land pang 55 263 t yr 1 or 507 t km 2 yr 1 lambourn 79 997 t yr 1 or 437 t km 2 yr 1 than on pasture pang 1960 t yr 1 or 140 t km 2 yr 1 lambourn 1425 t yr 1 or 95 t km 2 yr 1 in both study areas and a substantial proportion of the mobilized sediment is sequestered within the fields pang 28 058 t yr 1 or 228 t km 2 yr 1 lambourn 55 575 t yr 1 or 281 t km 2 yr 1 and between the individual fields and the river channel network pang 28 672 t yr 1 or 233 t km 2 yr 1 lambourn 24 782 t yr 1 or 125 t km 2 yr 1 the sediment contribution from banks and subsurface sources is relatively low and typically ca 5 t yr 1 in the pang and ca 11 t yr 1 in the lambourn representing only about 1 of the suspended sediment output from each study catchment the mean level of fine grained sediment storage in the main channel system is equivalent to 38 pang and 21 lambourn of the respective mean annual suspended sediment yields of the two catchments the estimated sediment delivery ratio for both study catchments is ca 1

geochemical monitoring of the 2002 2003 eruption at stromboli volcano italy precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters significant changes in the helium and carbon isotopic composition of shallow thermal waters vs gas and a crater fumarolic gas have been recorded at stromboli prior and during the 2002 2003 eruption the3he 4he ratios corrected for air contamination rc ra and 13c of fumarolic gases gradually increased from may to november 2002 before the eruption onset these variations imply early degassing of a gas rich magma at depth that likely fed both the intense strombolian activity and small lava overflows recorded during that period the lava effusion of late december 2002 was shortly preceded by a marked rc ra decrease both in water and fumarolic gases comparison of he co2 and ch4 co2 ratios in dissolved gas and with rm delta 13 rm c rm co 2 values rules out the rc ra decrease due to an increasing input of radiogenic4he the rc ra decrease is attributed to the he isotope fractionation during rapid magma ascent and degassing a new uprising of 3he rich magma probably occurred in january to february 2003 when rc ra ratios displayed the highest values in dissolved gases ever measured before 4 56 rc ra the increase in he co2 and ch4 co2 ratios and decrease in 13c of dissolved co2 was recorded after the 5 april 2003 explosive paroxysm likely caused by enhanced gas water interaction inducing co2 dissolution no anomalous rc ra values were recorded in the same period when usual strombolian activity gradually resumed

modern erosion rates in the high himalayas of nepal abstract current theories regarding the connections and feedbacks between surface and tectonic processes are predicated on the assumption that higher rainfall causes more rapid erosion to test this assumption in a tectonically active landscape a network of 10 river monitoring stations was established in the high himalayas of central nepal across a steep rainfall gradient suspended sediment flux was calculated from sampled suspended sediment concentrations and discharge rating curves accounting for solute and bedload contributions the suspended sediment fluxes were used to calculate watershed scale erosion rates that were then compared to monsoon precipitation and specific discharge we find that in individual watersheds annual erosion rates increase with runoff in addition our data suggest average erosion rate increases with discharge and precipitation across the entire field site such that the wetter southern watersheds are eroding faster than the drier northern watersheds the spatially non uniform contemporary erosion rates documented here are at odds with other studies that have found spatially uniform long term rates 10 5 10 6 yr across the pronounced rainfall gradient observed in the region the discrepancy between the modern rates measured here and the long term rates may be reconciled by considering the high erosional efficiency of glaciers the northern catchments were much more extensively glacierized during the pleistocene and therefore they likely experienced erosion rates that were significantly higher than the modern rates we propose that in the northern watersheds the high rates of erosion during periods of glaciation compensate for the low rates during interglacials to produce a time averaged rate comparable to the landslide dominated southern catchments

quantitative models of hydrothermal fluid mineral reaction the ischia case abstract the intricate pathways of fluid mineral reactions occurring underneath active hydrothermal systems are explored in this study by applying reaction path modelling to the ischia case study ischia island in southern italy hosts a well developed and structurally complex hydrothermal system which because of its heterogeneity in chemical and physical properties is an ideal test sites for evaluating potentialities limitations of quantitative geochemical models of hydrothermal reactions we used the eq3 6 software package version 7 2b to model reaction of infiltrating waters mixtures of meteoric water and seawater in variable proportions with ischia s reservoir rocks the mount epomeo green tuff units megt the mineral assemblage and composition of such megt units were initially characterised by ad hoc designed optical microscopy and electron microprobe analysis showing that phenocrysts dominantly alkali feldspars and plagioclase are set in a pervasively altered with abundant clay minerals and zeolites groundmass reaction of infiltrating waters with megt minerals was simulated over a range of realistic for ischia temperatures 95 260 c and co 2 fugacities 10 0 2 to 10 0 5 bar during the model runs a set of secondary minerals selected based on independent information from alteration minerals studies was allowed to precipitate from model solutions when saturation was achieved the compositional evolution of model solutions obtained in the 95 260 c runs were finally compared with compositions of ischia s thermal groundwaters demonstrating an overall agreement our simulations in particular well reproduce the mg depleting maturation path of hydrothermal solutions and have end of run model solutions whose na k mg compositions well reflect attainment of full equilibrium conditions at run temperature high temperature 180 260 c model runs are those best matching the na k mg compositions of ischia s most chemically mature water samples supporting quenching of deep reservoir conditions for these surface manifestations whilst fe sio 2 and to a lesser extent so 4 contents of natural samples are better reproduced in low temperature 95 c runs suggesting that these species reflect conditions of water rock interaction in the shallow hydrothermal environment the ability of model runs to reproduce the compositional features of ischia s thermal manifestations demonstrated here adds supplementary confidence on reaction path modelling as a realistic and insightful representation of mineral fluid hydrothermal reactions our results in particular demonstrate the significant impact of host rock minerals assemblage in governing the paths and trends of hydrothermal fluids maturation

temporal variation of suspended sediment transport in the koga catchment north western ethiopia and environmental implications event sediment transport and yield were studied for 45 events in the upstream part of the 260 km2 agricultural koga catchment that drains to an irrigation reservoir discharge and turbidity data were collected over a period of more than a year accompanied by grab sampling turbidity was very well correlated with the sediment concentrations from the samples r 0 99 which allowed us to estimate the temporal patterns of sediment concentrations within events the hysteresis patterns between discharge and sediment concentrations were analysed to provide insight into the different sediment sources anticlockwise patterns are the dominant hysteresis patterns in the area suggesting smaller contributions of suspended sediment from the river channels than from the hillslopes and agricultural areas complicated types of hysteresis patterns were mostly observed for long events with multiple peaks for a given discharge sediment yields in august and september when the catchment was almost completely covered with vegetation were much smaller than during the rest of the rainy season the hysteresis patterns and timing suggest that the sediment availability from the agricultural areas and hillslopes affects sediment yields more strongly than does peak discharge two distinct types of sediment rating curves were observed for the season when the agricultural land was covered with vegetation and when it was not indicating the dominating contribution of land use cover to sediment yields in the catchment the rate of suspended sediment transport in the area was estimated as 25 6 t year 1 ha 1 copyright 2013 john wiley sons ltd

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

the structure of a hydrothermal system from an integrated geochemical geophysical and geological approach the ischia island case study the complexity of volcano hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work we use here an integrated multidisciplinary approach combining geological investigations with hydrogeochemical and soil degassing prospecting and resistivity surveys to provide a comprehensive characterization of the shallow structure of the southwestern ischia s hydrothermal system we show that the investigated area is characterized by a structural setting that although very complex can be schematized in three sectors namely the extra caldera sector ecs caldera floor sector cfs and resurgent caldera sector rcs this contrasted structural setting governs fluid circulation geochemical prospecting shows in fact that the caldera floor sector a structural and topographic low is the area where co2 rich 40 cm3 l hydrothermally mature log mg na ratios 150 g m 2 d 1 is clearly captured by electrical resistivity tomography ert and transient electromagnetic tem surveys as a highly conductive resistivity 10 000 mg l and poorly conductive meteoric derived tds 4 000 mg l waters are observed respectively we finally integrate our observations to build a general model for fluid circulation in the shallowest 0 5 km part of ischia s hydrothermal system

excess helium and argon of radiogenic origin in mediterranean brine basins extraordinary helium and argon signatures were observed in a recently discovered brine lake district in the eastern mediterranean sea at water depths of 3500 m in the urania basin 4he concentrations are enriched by a factor of up to 32000 compared to normal seawater low 3he 4he ratios of 1 10 7 and high 40ar 36ar ratios of up to 470 indicate a radiogenic source these data represent by far the highest radiogenic supersaturations ever observed in an oceanic environment we propose a new conceptional model assuming that the urania basin is fed by advective transport from a deep fluid reservoir below the messinian evaporite sequence the evaporite seal provides the unique condition for accumulating the extraordinary high amounts of radiogenic helium from deep sedimentary strata injection of radiogenic helium from brine pools like the urania basin may contribute significantly to the inventory of terrigenic helium in the deep waters of the eastern mediterranean

magma degassing as a source of long term seismicity at volcanoes the ischia island italy case transient seismicity at active volcanoes poses a significant risk in addition to eruptive activity this risk is powered by the common belief that volcanic seismicity cannot be forecast even on a long term here we investigate the nature of volcanic seismicity to try to improve our forecasting capacity to this aim we consider ischia volcano italy which suffered similar earthquakes along its uplifted resurgent block we show that this seismicity marks an acceleration of decades long subsidence of the resurgent block driven by degassing of magma that previously produced the uplift a process not observed at other volcanoes degassing will continue for hundreds to thousands of years causing protracted seismicity and will likely be accompanied by moderate and damaging earthquakes the possibility to constrain the future duration of seismicity at ischia indicates that our capacity to forecast earthquakes might be enhanced when seismic activity results from long term magmatic processes such as degassing

tracing and quantifying magmatic carbon discharge in cold groundwaters lessons learned from mammoth mountain usa abstract a major campaign to quantify the magmatic carbon discharge in cold groundwaters around mammoth mountain volcano in eastern california was carried out from 1996 to 1999 the total water flow from all sampled cold springs was 1 8 10 7 m 3 yr draining an area that receives an estimated 2 5 10 7 m 3 yr of recharge suggesting that sample coverage of the groundwater system was essentially complete some of the waters contain magmatic helium with 3 he 4 he ratios as high as 4 5 times the atmospheric ratio and a magmatic component in the dissolved inorganic carbon dic can be identified in virtually every feature sampled many waters have a 14 c of 0 5 pmc a 13 c near 5 and contain high concentrations 20 50 mmol l of co 2 aq but are otherwise dilute specific conductance 100 300 s cm with low ph values between 5 and 6 such waters have previously escaped notice at mammoth mountain and possibly at many other volcanoes because co 2 is rapidly lost to the air as the water flows away from the springs leaving neutral ph waters containing only 1 3 mmol l hco 3 the total discharge of magmatic carbon in the cold groundwater system at mammoth mountain is 20 000 t yr as co 2 ranging seasonally from about 30 to 90 t day several types of evidence show that this high discharge of magmatic dic arose in part because of shallow dike intrusion in 1989 but also demonstrate that a long term discharge possibly half this magnitude 10 000 t yr predated that intrusion to sustain a 10 000 t yr dic discharge would require a magma intrusion rate of 0 057 km 3 per century assuming complete degassing of magma with 0 65 wt co 2 and a density of 2 7 t m 3 the geochemical data also identify a small

a model for ischia hydrothermal system evidences from the chemistry of thermal groundwaters abstract ischia volcano in central italy has long been known for its copious surface hydrothermal manifestations signs of a pervasive circulation of hot fluids in the subsurface because of the significant chemical heterogeneity of fumarolic gas discharges and hot spring discharges evidences of a complex hydrothermal setting a definite model of fluid circulation at depth is currently unavailable in spite of the several previous efforts here we report on the chemical and isotopic composition of 120 groundwater samples collected during several sampling surveys from 2002 to 2007 the acquired data suggest that the composition of surface manifestations reflect contributions from meteoric water sea water and thermal fluids rising from two distinct hydrothermal reservoir with equilibrium temperatures of respectively 150 c and 270 c and depths of 150 300 m and 300 m but possibly 1000 m we also make use of an isotopic characterization of the dissolved gas phase in thermal waters to demonstrate that the ischia hydrothermal system is currently supplied by a deep rising gas component dgc characterized by co2 97 7 1 2 vol on a water free basis 13cco2 3 51 0 9 and helium isotopic ratio of about 3 5 ra 3he 4he ratio normalized to the air ratio ra likely magmatic in origin an assessment of the thermal budget for ischia hydrothermal system is also presented in the attempt to derive a first estimate of the size and rate of degassing of the magmatic reservoir feeding the gas emissions we calculate that a heat flow of about 153 222 mw presently drives hydrothermal circulation on the island which we suggest is supplied in convective form e g by the ascent of a high t magmatic vapour phase by complete degassing of 2 2 3 3 107 m3 yr 1 of trachytic magma with 2 1 wt dissolved h2o content if extrapolated to entire period of quiescence lasting since the arso eruption in 1302 a d this volume corresponds to 1 6 2 3 1010 m3 of magma degassed in about 700 years of quiescent activity

diffuse emission of co2 from the fossa crater vulcano island italy numerous measurements of co2 degassing from the soil carried out with the accumulation chamber method indicate that in the period april july 1995 the upper part of the fossa cone released a total output of 200 t d 1 of co2 which corresponds to approximately 1000 t d 1 of steam these large amounts of fluids are of the same order of magnitude as those released by the high temperature fumarolic field located inside the crater the spatial distribution of soil gas fluxes shows that the main structures releasing co2 are the inner slopes of the crater and a nw se line located ne of the crater rim which correspond to the main direction of vulcano island active faults the comparison of the co2 maps with the soil temperature distribution derived from both direct measurements and airborne infrared images indicates the occurrence of extensive condensation of fumarolic steam within the upper part of the fossa cone whose total amount is comparable to the rainfall budget part of the condensate which originates from this process contributes to the recharge of the phreatic aquifer of porto plain modifying the chemical and isotopic composition of the groundwater

structural seismic and hydrothermal features at the border of an active intermittent resurgent block ischia island italy resurgent blocks are uplifted parts of volcanoes where most of the deformation uplift is accommodated along peripheral faults the island of ischia italy has an active resurgent block uplifted 1000 m in the last 30 ka which allows us to investigate the deformation associated with a strong uplift in volcanic areas air photo interpretation was matched with field work 1 5000 scale mapping and structural analysis throughout the resurgent block these results have been matched with a review of the seismic and hydrothermal activity at ischia the results show that the block has a polygonal shape in map view and is characterized by a trapdoor uplift which results in a 15 tilt towards the se the northern most uplifted part is bordered by e w and ne sw trending faults arranged in parallel segments over an area 1 5 km wide i0 5 mcs degree shallow 1 1 6 km depth earthquakes focused in correspondence with the outermost set of faults on the northernmost part of the block here variations in the hydrothermal activity have been observed during seismic events previously performed analogue models show that resurgent blocks are bordered by inward dipping high angle reverse faults outermost fault system and outward dipping normal faults innermost fault system we propose a model of trapdoor uplift of a block which induces reverse faulting responsible for seismicity and hydrothermal variations along the most uplifted part outward dipping normal faults in the innermost part form as a consequence of the gravitational sliding of the volumes bordered by the reverse faults the further reactivation of the outermost reverse faults triggers a new cycle of intermittent trapdoor uplift of the block

helium strontium isotope constraints on mantle evolution beneath the roman comagmatic province italy european social fund scottish universities carnegie trust for the universities of scotland

the uppermost crust structure of ischia southern italy from ambient noise rayleigh waves abstract ambient noise measurements were performed at the island of ischia southern italy along alignments of 2 4 7 km by using two three component seismic stations synchronous noise recordings of 2 20 h were cross correlated over 20 30 s windows stacked and iteratively band pass filtered to enhance the dispersive wave trains frequency time analysis was performed on the vertical and radial components of cross correlations and the fundamental mode rayleigh wave group velocity was obtained validation of the dispersion data was possible with those obtained from an earthquake recording along a close path the non linear inversion of average rayleigh wave group velocity dispersion curves along 13 paths receiver inter distances allowed the definition of shear wave velocity models in the uppermost 1 2 km of the crust the correlation of vs profiles vs depth and drilling stratigraphy allowed to attribute vs lower than 1 km s to tuffs and vs of 1 41 km s to very fractured lavas higher vs are found in the central area of the island in correspondence of the resurgent area the top of the trachytic lava basement with vs of 2 2 2 4 km s and density of 2 3 g cm3 is about 0 6 0 7 km deep b s l in the centre of ischia below altered very fractured lava or thermally altered tuff

slope instability induced by volcano tectonics as an additional source of hazard in active volcanic areas the case of ischia island italy ischia is an active volcanic island in the gulf of naples whose history has been dominated by a caldera forming eruption ca 55 ka and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka the results of new geomorphological stratigraphical and textural investigations of the products of gravitational movements triggered by volcano tectonic events have been combined with the information arising from a reinterpretation of historical chronicles on natural phenomena such as earthquakes ground deformation gravitational movements and volcanic eruptions the combined interpretation of all these data shows that gravitational movements coeval to volcanic activity and uplift events related to the long lasting resurgence have affected the highly fractured marginal portions of the most uplifted mt epomeo blocks such movements mostly occurring since 3 ka include debris avalanches large debris flows lahars smaller mass movements rock falls slumps debris and rock slides and small debris flows and deep seated gravitational slope deformation the occurrence of submarine deposits linked with subaerial deposits of the most voluminous mass movements clearly shows that the debris avalanches impacted on the sea the obtained results corroborate the hypothesis that the behaviour of the ischia volcano is based on an intimate interplay among magmatism resurgence dynamics fault generation seismicity slope oversteepening and instability and eruptions they also highlight that volcano tectonically triggered mass movements are a potentially hazardous phenomena that have to be taken into account in any attempt to assess volcanic and related hazards at ischia furthermore the largest mass movements could also flow into the sea generating tsunami waves that could impact on the island s coast as well as on the neighbouring and densely inhabited coast of the neapolitan area

regional variations in the chemical and helium carbon isotope composition of geothermal fluids across tunisia abstract tunisia has numerous thermo mineral springs previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology however little work has been done so far to study the isotopic composition of volatiles associated with these geothermal manifestations here we report on the results of an extensive survey of both natural hot springs and production wells across tunisia aimed at investigating the spatial distribution of thermal fluids geochemical characteristics and he c isotopic composition the chemistry of the analyzed samples highlights the heterogeneity of the water mineralization processes in tunisia as a consequence of the complex geological and tectonic setting of the country in terms of chemical composition we are able to conclude however that dissolution of halite and gypsum plays a key control on groundwater chemistry helium and carbon isotope systematics confirm the prevalently crustal origin of the volatiles interacting with the aquifer systems consistent with the absence of any recent magmatism most samples are characterized by crustal type helium 3 he 4 he in the range 0 02 ra 0 4 ra associated with a co 2 predominantly metamorphic in origin with the exception of the saharan platform where the carbon content is low and mostly organically derived in eastern tunisia however a few samples have he c isotope compositions which suggest at least partial mantle derivation of the dissolved gas phase the 3 he 4 he ratio reaches 2 4 ra corresponding to 30 of mantle derived helium at the ain garci site a co 2 rich mineral spring located some 30 km south of the city of zaghouan this mantle signature is consistent with the fact that the pelagian block to which eastern tunisia belongs has been deeply affected by extensional and transtensional tectonics since the opening of the tethys a process which is still ongoing in the sicily channel pantelleria rift as a whole however our results show that the italian mantle gas anomaly only marginally extends to northwestern africa

contribution of glacier meltwater to streamflow in the wind river range wyoming inferred via a bayesian mixing model applied to isotopic measurements the wind river range wrr of wyoming has the largest concentration of alpine glaciers in the american rockies and contributes to several major river systems in the western united states declines in the areal extent and volume of these glaciers are well documented and eventual loss of alpine glaciers will reduce the amount of water available for agricultural and domestic use the contribution of glacial melt to streamflow remains largely unquantified in wyoming we used isotope measurements and bayesian modeling to estimate the fractional contribution of glacier meltwater to dinwoody creek dc in the wrr on bi weekly and seasonal spring summer and fall time scales over 2 years in 2007 and 2008 we made temporally intensive measurements of the stable isotope composition of water from the dc watershed samples of the primary sources of streamflow snowmelt glacier melt rain and baseflow were collected during field campaigns and automated collection of stream samples occurred over the melt season isotope data d and 18o were analyzed within a hierarchical bayesian framework that incorporated temporal and spatial correlations glacial melt contributed a significant proportion 53 59 to streamflow in a low flow year 2007 or when streamflow was low during a high flow year 2008 in 2008 a large and persistent snowpack contributed significantly 0 42 51 to streamflow in mid summer the large contribution of glacial melt to streamflow suggests that the loss of glaciers may impact riparian ecosystems and human water supplies in the late summer and in years with low snowpack copyright 2011 john wiley sons ltd

temporal dynamics of suspended sediment transport in a glacierized andean basin abstract suspended sediment transport can affect water quality and aquatic ecosystems and its quantification is of the highest importance for river and watershed management suspended sediment concentration ssc and discharge were measured at two locations in the estero morales a chilean andean stream draining a small basin 27 km2 hosting glacierized areas of about 1 8 km2 approximately half of the suspended sediment yield 470 t year 1 km 2 was transported during the snowmelt period and half during glacier melting the hysteresis patterns between discharge and ssc were calculated for each daily hydrograph and were analysed to shed light on the location and activity of different sediment sources at the basin scale during snowmelt an unlimited supply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be clockwise as the peaks in ssc precede the peak of discharge in daily hydrographs instead during glacier melting the source of fine sediments is the proglacial area producing counterclockwise hysteresis it is suggested that the analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and activity of sediment sources at the basin scale

thermal springs in italy their relation to recent tectonics the large scale circulation of thermal waters in italy is reviewed from both a chemical and an isotopic point of view two main areas are recognized one in the alpine region and the other in the central southern apennine region the alps are an area of very high hydraulic heads and low thermal gradients where hot deep seated waters of meteoric origin rapidly reach the surface along active boundary fault systems the apennines in contrast are characterized by lower hydraulic heads and higher thermal gradients all thermal springs in italy including those in active volcanic areas originate essentially from meteoric waters and most follow long pathways in mesozoic carbonate anhydritic aquifers before emerging as indicated by relations among present hydrothermal activity in central southern italy deep crustal structures and pco2 content in thermal waters

sediment load characteristics of a proglacial stream of siachen glacier and the erosion rate in nubra valley in the karakoram himalayas india abstract this paper discusses the results of studies on sediment transport and the erosion rate in the nubra river carried out in hydrological years from 1986 to 1991 discharge data of proglacial stream of the siachen glacier shows seasonal variation ranging from 0 26 10 6 m 3 d 1 in the beginning of the ablation season to about 23 10 6 m 3 d 1 in the peak ablation season suspended sediment mass in the nubra river varies from 0 01 kg m 3 s 1 in the beginning of the ablation season to about 2 3 kg m 3 s 1 at its peak a relationship is developed between daily suspended sediment transport and daily discharge the total sediment load calculated from the data varies from 296 to 1287 tons km 2 of the glacier basin area per year the erosion rate calculated from total sediment load which includes suspended sediment and bedload varies from 0 11 to 0 46 mm year 1 the erosion rates in the nubra basin are much lower than the hunza basin in western karakoram himalayas 1 8 mm year 1 which may be due to its geological setting consisting of highly erosion resistant rocks like diorites grano diorites granites and granite gniesses tectonic upliftment and high relief give rise to comparatively higher erosion rates in karakoram himalayas

source storage and mobilisation of fine sediment in a chalk stream system concern for sediment problems in the upper river piddle dorset including accumulation of fine sediment on the channel bed and elevated turbidity levels during periods of stable flow provided the stimulus for a detailed field investigation of the sediment dynamics of this chalk stream system undertaken during the period november 1991 to april 1993 two monitoring stations were established at south farm piddletrenthide and lawrence mede piddlehinton and estimates of suspended sediment load were obtained for these two sites in addition suspended sediment concentrations and bed sediment loadings were regularly sampled at several other sites sediment traps were deployed at ten representative sites along the river channel field observations of sediment sources and pathways were made during storm events and a sediment source fingerprinting study was undertaken estimates of annual suspended sediment yield provided values of 9 12 t km 2 year 1 which must be seen as low by uk standards elevated suspended sediment concentrations were not restricted to storm events but occurred throughout the monitoring period in response to remobilisation of sediment stored in the channel the evidence provided by the sediment loads recorded at the two monitoring stations by the sediment traps and by the measurements of bed sediment loading indicated that substantial amounts of sediment accumulated in the channel of the upper and middle reaches of the river during the winter months and that this slug of sediment was slowly transmitted downstream during the following summer fingerprinting of the transported sediment and of potential sources indicated that the dominant source of suspended sediment was likely to be surface soil from cultivated areas field reconnaissance surveys undertaken during storm events indicated that substantial inputs of surface runoff and suspended sediment entered the stream much of this sediment is however stored within the channel system and slowly transmitted downstream copyright 1999 john wiley sons ltd

the interaction between regional and local tectonics during resurgent doming the case of the island of ischia italy abstract the volcanic island of ischia is located on the tyrrhenian margin of central italy characterized by plio quaternary nw se and ne sw trending extensional fractures ischia displays a resurgent dome uplifted by at least 800 m in the last 33 ka remote sensing and field data have been collected to study the structural setting of the island the deformation pattern associated with resurgence and the superimposition of the regional and the resurgence induced stress fields nw se and ne sw extensional fracture systems predominate throughout the island and around the resurgent block suggesting a relationship with the regional extensional structures these systems were formed before resurgence and were partly reactivated during resurgence the reactivation of pre existing regional systems during resurgence confined the extent of the uplifted area n s and e w trending systems have been found exclusively at the borders of the dome and are interpreted as being induced by resurgence the topmost resurgent block shows an octagonal shape in map view and is tilted at an angle of 15 around a ne sw trending horizontal axis the block is partly bordered by high angle inward dipping regional faults more than 90 in volume of the volcanic products coeval with resurgence on ischia have been erupted outside the resurgent block area suggesting that the resurgence process locally replaced volcanic activity in the last 33 ka

history of the exploitation of thermo mineral resources in campi flegrei and ischia italy abstract thermo mineral springs are widely spread over the volcanic areas of campi flegrei and ischia and on the western side of the city of naples their use has since long been known by local inhabitants because they were one of the main curative therapies in the past the fortune and use of the thermal springs have been affected by the volcanic eruptions that occurred in different times in these areas the exploitation of geothermal springs in campi flegrei suffered a decisive decline after the eruption of monte nuovo in 1538 conversely after that eruption in ischia island there was a progressive increase of the use of thermal spring therapy the use of geothermal resources for electric generation has not been implemented in campi flegrei because of the difficulty in using hypersaline fluids whereas in ischia local authorities preferred only the development of touristic activity based on geothermal springs

14c geochronological constraints for the volcanic history of the island of ischia italy over the last 5000 years abstract the chronology of the most significant eruptions at the island of ischia in the last 5000 years has been studied by means of accelerator mass spectrometry to obtain 14 c data the results are in good agreement with stratigraphical and archeological constraints this allows interpretation of the measured dates as ages of the eruptions which produced the deposits overlying or incorporating the sampled paleosols and charcoal fragments respectively these ages define the timing of volcanism in the last 5000 years suggesting that the recent volcanic activity at ischia is characterized by periods of very intense volcanism alternating to periods of quiescence this timing of the volcanism is correlated with the behaviour of the magmatic system and dynamics of resurgence of the mt epomeo block

carbon and helium isotopes in thermal springs of la soufriere volcano guadeloupe lesser antilles implications for volcanological monitoring abstract la soufriere guadeloupe lesser antilles is one of the most active and dangerous volcanoes of the lesser antilles arc the renewal of the volcanic activity at la soufriere requires replenishment of the volatile poor andesitic stored magma with more primitive volatile rich basaltic magma this event will trigger early release of large quantities of highly volatile species like co 2 and helium in the hydrothermal system to use these precursors first their baseline abundances and their behaviour in the hydrothermal system must be known during the current phase of dormancy in this study we have combined a previous systematic investigation of noble gases with carbon data of hydrothermal fluids flowing out of la soufriere the results for dissolved gases reveal that an intense interaction between rising magmatic volatiles and groundwaters currently takes place at la soufriere we show that the pristine magmatic composition with a 13 c co2 value of 3 19 0 03 a 3 he 4 he ratio of 8 1 0 2 r a and a co 2 3 he ratio of 1 03 0 18 10 10 may vary during the ascent of magmatic fluids due to either fractionation or mixing processes with meteoric water and or an organic component here we provide a baseline for co 2 and helium isotopes at each monitored spring and describe the superficial processes affecting both elemental and isotopic ratios

the suspended sediment dynamics in the inner mongolia reaches of the upper yellow river article i nfo suspended sediment dynamics are still imperfectly understood especially in the upper yellow river where few studies on this issue have been conducted this study analyzed the variability in suspended sediment concentration at different temporal scales within flood monthly seasonal and annual using a dataset up to 49 years long 1954 2002 at toudaoguai station this paper provided insight into the characteristics of suspended sediment transport in the ningxia inner mongolia reaches of the upper yellow river the results show that in a single flood event changes in ssc are not simultaneous with changes in discharge resulting in counterclockwise hysteretic loops clockwise loops or figure eight loops the c q loops and sediment rating curves for different seasons had different characters the diversiform c q loops in the inner mongolia reaches of the upper yellow river may be mainly caused by the sediment inputs from tributaries the differ ent propagation velocity of sediment and water discharge spatial and temporal storage depletion processes of available sediment at annual scale the variations of annual mean discharge and ssc displayed a similar gradually deceasing trend and the relation between water discharge and ssc during 1954 2002 could be de scribed by a cubic polynomial function since the joint operation of liujiaxia and longyangxia reservoirs after 1986 the transport capacity of the upper yellow river has been much reduced

effect of sand supply on transport rates in a gravel bed channel in a series of flume experiments using constant discharge flow depth and gravel feed rate sand feed rates were varied from 0 16 to 6 1 times that of gravel the bed slope decreased with increasing sand supply indicating that the gravel could be transported at the same rate along with increasing amounts of sand at smaller shear stresses prediction of river response to an increase in sediment supply requires prediction of mutual changes in bed composition and transport and therefore a transport model defined in terms of the grain size of the bed surface a recent model provides satisfactory prediction of the experimental observations and indicates the general response of gravel beds to increased sand supply an increase in sand supply may increase the sand content of the river bed and the mobility of gravel fractions which can lead to bed degradation and preferential evacuation of these sediments from the river

mineral control of arsenic content in thermal waters from volcano hosted hydrothermal systems insights from island of ischia and phlegrean fields campanian volcanic province italy this paper documents arsenic concentrations in 157 groundwater samples from the island of ischia and the phlegrean fields two of the most active volcano hosted hydrothermal systems from the campanian volcanic province southern italy in an attempt to identify the environmental conditions and mineral solution reactions governing arsenic aqueous cycling on ischia and in the phlegrean fields groundwaters range in composition from nacl brines which we interpret as the surface discharge of deep reservoir fluids to shallow depth circulating fluids the latter ranging from acid sulphate steam heated to hypothermal cold bicarbonate groundwaters arsenic concentrations range from 1 6 to 6900 g l 1 and from 2 6 to 3800 g l 1 in the phlegrean fields and on ischia respectively they increase with increasing water temperature and chlorine contents and in the sequence bicarbonate groundwatersbsteam heated groundwatersbnacl brines according to thermochemical modeling we propose that high as concentrations in nacl brines form after prolonged water rock interactions at reservoir t fo2 and fh2s conditions and under the buffering action of an arsenopyrite pyrite pyrrhotite rock assemblage on their ascent toward the surface nacl brines become diluted by as depleted meteoric derived bicarbonate groundwaters giving rise to hybrid water types with intermediate to low as contents steam heated groundwaters give their intermediate to high as concentrations to extensive rock leaching promoted by interaction with as bearing hydrothermal steam 2005 elsevier b v all rights reserved

the whisper of the hydrothermal seismic noise at ischia island abstract this work is devoted to the study of the background seismic noise at ischia island we highlight two persistent independent signals with dominant frequency peaks in the range 1 2 hz and 3 4 hz respectively the first signal is the most energetic and persistent and its polarization properties are well defined revealing a shallow propagation likely controlled by both tectonic volcanic structures and morphological features this signal is well correlated at all the stations in the casamicciola area and its group velocity is estimated as 500 600 m s the second signal shows similar polarization properties but the temporal pattern of its amplitude is strongly affected by anthropogenic noise revealing a modulation on a diurnal scale on the investigated spatial scales any clearly correlated signal is not evidenced we interpret the 1 2 hz correlated wave packets as the persistent whisper of the shallow circulation of fluids which are a mixing of sea and meteoric water and thermal fluids of the hydrothermal reservoir in the conceptual scheme of the self sustained musical instruments we hypothesize that the solid structure of the shallow hydrothermal system of ischia is formed by a network of channels continuously excited by the circulating hydrothermal fluids which produce a whispered sound i e the seismic noise this mechanism is able to produce persistent self sustained oscillations that we observe as the 1 2 hz seismic signal and eventually higher modes

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

characterization of suspended sediment in meltwater from glaciers of garhwal himalaya glacierised basins are significant sources of sediments generated by glacial retreat estimation of suspended sediment transfer from glacierised basins is very important in reservoir planning for hydropower projects in himalaya the present study indicates that storage and release of sediment in proglacial streams may categorise the pattern of suspended sediment transfer from these basins assessment of suspended sediment concentration ssc suspended sediment load ssl and yield has been undertaken for dunagiri glacier basin located in garhwal himalaya 30o33 20 n 79o53 36 e and its results are compared with the gangotri and dokriani glaciers sharing close proximity out of the total drainage basin area about 14 3 of the area is glacierised data were collected for five ablation seasons 1984 1989 barring 1986 the mean daily sscs for july august and september were 333 9 286 0 and 147 15 mg l respectively indicating highest concentration of mean daily suspended sediment in july followed by august ssl trends were estimated to be 93 0 57 0 and 21 3 tonnes about 59 of the total ssl of the melt period was transported during the months of august and september sediment yield for the study basin was computed to be 296 3 t km 2 yr 1 it is observed that the cumulative proportion of ssc precedes the discharge throughout the melt season except in the year 1987 release of ssl in terms of total load is less in the early part of melt season than in the later stage as compared to that of discharge diurnal variations in ssc reach their maximum at 2400 h and therefore ssc was found to be high during night 2000 0400 h there was a good relationship between ssc and ssl with discharge for the ablation seasons 1988 and 1989 mean monthly ssc and mean monthly ssl provide a good exponentional relationship with mean monthly temperature copyright 2012 john wiley sons ltd

influence of volcanic activity on spring water chemistry at popocatepetl volcano mexico abstract the results of the 7 years 1994 2000 of monthly monitoring of spring water before and during eruptions show response to volcanic activity low salinity and temperature characterize most of the springs which are located on the flanks of popocatepetl volcano the ph ranges from 5 8 to 7 8 and temperature from 3 to 36 c oxygen and hydrogen isotopic data show that the water is of meteoric origin but so 4 2 cl f hco 3 b and so 4 2 cl variations precede main eruptive activity which is considered linked to influx of magmatic gases and acid fluids that react with sublimates and host rock and mix with the large water system na ca 2 sio 2 and mg 2 concentrations in the water also increased before eruptive activity the computed partial pressure of co 2 in equilibrium with spring waters shows values higher than air saturated water asw with the highest values up to 0 73 bar of pco 2 boron is detected in the water only preceding the larger eruptions when present boron concentration is normally under health standard limits but in two cases the concentration was slightly above other components are within health standard limits except for f in one spring

dissolved helium isotope ratios in ground waters a new technique based on gas water re equilibration and its application to stromboli volcanic system here a new technique for the determination of dissolved he isotope ratios in ground waters is presented this method is based on the extraction and subsequent equilibrium of dissolved gases in an added host gas phase ultra pure n2 is placed in glass flasks 250 cc containing water samples that were hermetically sealed after their collection after shaking in an ultrasonic bath for 10 min an aliquot of the separated gas phase was removed from the flask for ms analysis 3he 4he ratios are measured by using a modified double collector mass spectrometer vg 5400 tft helium and ne concentrations are calculated by comparing the partial pressures of masses 4 and 20 of the samples with those of the air standard measured by a quadrupole mass spectrometer qms vg quartz using he and ne equilibrium partitioning coefficients it is possible to calculate the amount of gas originally dissolved in the water the technique was tested on both air saturated waters asw and thermal waters from stromboli aeolian islands south italy the results of which confirmed good reproducibility 5 and accuracy 3 of the data the method was then applied to three thermal water samples collected from the same volcanic area and the results compared with those of a fumarolic and a soil gas the isotope ratios for dissolved he gave values of 4 06 4 23 ra which are significantly higher than those previously reported in the literature 3 0 3 5 and 2 9 ra and that measured at the fumarole 3 09 ra suggesting a newer and higher isotopic signature for the volcanic system the proposed method appears to be a useful tool in the determination of 3he 4he ratios in ground water systems especially when free gases are not available or are dangerous to collect

origins of methane discharging from volcanic hydrothermal geothermal and cold emissions in italy abstract we have addressed the origins of methane in fumarolic thermal and cold emissions discharging from a diversity of geological settings spread all over the italian peninsula and at panarea and pantelleria islands fluid discharges from the main geothermal systems of the peri tyrrhenian area including mt amiata larderello latera and manziana show 13c ch4 and d ch4 values 28 v pdb and 160 v smow respectively and c1 c2 concentration ratios 1000 these patterns suggest that ch4 discharged from these systems is primarily generated by abiogenic reduction of co2 and or co methane seems to have at least partially a different origin than the higher hydrocarbons that might be entirely related to the thermal decomposition of organic matter or alternatively to methane polymerization fumaroles from the volcanic systems of solfatara vesuvio panarea and pantelleria have c1 c2 concentration ratios in a wide range from 17 to 4300 but 13c ch4 and d ch4 values 21 v pdb and 120 v smow respectively such isotopic values are very similar to those reported for ch4 discharging from ultramafic hydrothermal systems in agreement with recent evidence provided for solfatara and pantelleria we therefore infer that the ch4 in the volcanic fumaroles is mainly abiogenic too the 13c ch4 from 21 6 to 36 9 v pdb and d ch4 from 113 to 164 v smow values as well as the c1 c2 concentration ratios from 19 to 2240 in the co2 rich fluid discharges located between the geothermal volcanic systems and the apennine sedimentary chain tend to decrease eastwards as the temperatures of the fluid reservoirs progressively diminish suggesting that the ch4 production is mainly related to thermogenic processes according to this general trend the ch4 dominated fluids from mud volcanoes located eastwards of the co2 rich emissions are fed by an almost pure thermogenic source the easternmost fluid discharges from the po valley and the adriatic coast where organic matter evolves at relatively shallow depths in the presence of a low geothermal gradient record the lowest 13c ch4 and d ch4 values i e as low as 69 v pdb and

mineral water occurrence and geochemistry in the azores volcanic archipelago portugal insight from an extended database on water chemistry the occurrence and geochemistry of mineral water discharges in the azores portugal have been studied due to the volcanic nature of the archipelago mineral water discharges occur in seven of the nine islands namely at sao miguel terceira sao jorge pico faial graciosa and flores both associated to perched water and basal aquifers and mainly corresponding to springs 72 4 the majority of the 116 discharges with water geochemistry data occurs in sao miguel island 73 3 water temperature ranges between 13 2 and 99 8 c average 37 1 c being 63 8 of the samples in the dataset classified as thermal waters are mainly acid to slightly alkaline with ph values ranging between 2 1 and 7 9 average 5 85 despite the wide range of electrical conductivity values 122 53 000 s cm the median value 876 s cm suggests that in general waters in the dataset are poorly mineralized being mainly from the na hco3 and na hco3 cl types besides a few samples are from na so4 and na so4 hco3 types instead waters abstracted in basal aquifers are mainly from the na cl type principal component analysis as well as a classic hydrogeochemistry approach suggests that mineral water chemistry evolves as function of several processes as silicate weathering enhanced by water temperature not excluding mixing mechanisms between cold and hot waters regarding the so4 rich thermal waters steam heating inputs are also to be considered dilution of volcanic co2 may also influence the chemical evolution of mineral waters the influence of seawater over the mineral water chemistry in basal aquifers is shown by the much higher conductivity and cl content