fault controlled soil co2 degassing and shallow magma bodies summit and lower east rift of kilauea volcano hawaii 1997 soil co2 flux measurements were carried out along traverses across mapped faults and eruptive fissures on the summit and the lower east rift zone of kilauea volcano anomalous levels of soil degassing were found for 44 of the tectonic structures and 47 of the eruptive fissures intercepted by the surveyed profiles this result contrasts with what was recently observed on mt etna where most of the surveyed faults were associated with anomalous soil degassing the difference is probably related to the differences in the state of activity at the time when soil gas measurements were made kilauea was erupting whereas mt etna was quiescent although in a pre eruptive stage unlike mt etna flank degassing on kilauea is restricted to the tectonic and volcanic structures directly connected to the magma reservoir feeding the ongoing east rift eruption or in areas of the lower east rift where other shallow likely independent reservoirs are postulated anomalous soil degassing was also found in areas without surface evidence of faults thus suggesting the possibility of previously unknown structures

co2 diffuse emission from maar lake an example in changbai volcanic field ne china abstract numerous maars and monogenetic volcanic cones are distributed in northeast china which are related to westward deep subduction of the pacific ocean lithosphere comprising a significant part of the pacific ring of fire it is well known that diffuse co2 emissions from monogenetic volcanoes including wet e g maar lake and dry degassing systems e g soil diffuse emission fault degassing etc may contribute to budget of globally nature derived greenhouse gases however their relationship between wet e g maar lake and concomitant dry degassing systems e g soil diffuse emission fault degassing etc related to monogenetic volcanic field is poorly understood yuanchi maar one of the typical monogenetic volcanic systems is located on the eastern flank of tianchi caldera in changbai volcanic field of northeast china which displays all of three forms of co2 degassing including the maar lake soil micro seepage and fault degassing measurements of efflux of co2 diffusion from the yuanchi maar system yms indicate that the average values of co2 emissions from soil micro seepage fault degassing and water air interface diffusion are 24 3 23 3 g m 2 d 1 39 2 22 4 g m 2 d 1 and 2 4 1 1 g m 2 d 1 respectively the minimum output of co2 diffuse emission from the yms to the atmosphere is about 176 1 88 3 ton yr of which 80 4 results from the dry degassing system degassing from the fault contributes to the most of co2 emissions in all of the three forms of degassing in the yms contributions of mantle crust air and organic co2 to the soil gas are 0 01 0 10 10 20 32 36 and 48 54 respectively which are quantitatively constrained by a he c isotope coupling calculation model we propose that co2 exsolves from the upper mantle melting beneath the tianchi caldera which migrates to the crustal magma chamber and further transports to the surface of yms along the deep fault system during the transportation processes the emission of gas experiences crustal contamination influence of magma chamber beneath the yms sub surface processes and air dilution

the 2005 eruption of sierra negra volcano galapagos ecuador sierra negra volcano began erupting on 22 october 2005 after a repose of 26 years a plume of ash and steam more than 13 km high accompanied the initial phase of the eruption and was quickly followed by a 2 km long curtain of lava fountains the eruptive fissure opened inside the north rim of the caldera on the opposite side of the caldera from an active fault system that experienced an mb 4 6 earthquake and 84 cm of uplift on 16 april 2005 the main products of the eruption were an a a flow that ponded in the caldera and clastigenic lavas that flowed down the north flank the a a flow grew in an unusual way once it had established most of its aerial extent the interior of the flow was fed via a perched lava pond causing inflation of the a a this pressurized fluid interior then fed pahoehoe breakouts along the margins of the flow many of which were subsequently overridden by a a as the crust slowly spread from the center of the pond and tumbled over the pahoehoe the curtain of lava fountains coalesced with time and by day 4 only one vent was erupting the effusion rate slowed from day 7 until the eruption s end two days later on 30 october although the caldera floor had inflated by 5 m since 1992 and the rate of inflation had accelerated since 2003 there was no transient deformation in the hours or days before the eruption during the 8 days of the eruption gps and insar data show that the caldera floor deflated 5 m and the volcano contracted horizontally 6 m the total eruptive volume is estimated as being 150 106 m3 the opening phase tephra is more evolved than the eruptive products that followed the compositional variation of tephra and lava sampled over the course of the eruption is attributed to eruption from a zoned sill that lies 2 1 km beneath the caldera floor

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

diffuse emission of co2 from showa shinzan hokkaido japan a sign of volcanic dome degassing two soil co2 efflux surveys were carried out in september 1999 and june 2002 to study the spatial distribution of diffuse co2 degassing and estimate the total co2 output from showa shinzan volcanic dome japan seventy six and 81 measurements of co2 efflux were performed in 1999 and 2002 respectively covering most of showa shinzan volcano soil co2 efflux data showed a wide range of values up to 552 g m 2 d 1 carbon isotope signatures of the soil co2 ranged from 0 9 to 30 9 suggesting a mixing between different carbon reservoirs most of the study area showed co2 efflux background values during the 1999 and 2002 surveys b 8 2 and 4 4 g m 2 d 1 respectively the spatial distribution of co2 efflux anomalies for both surveys showed a good correlation with the soil temperature indicating a similar origin for the extensive soil degassing generated by condensation processes and fluids discharged by the fumarolic system of showa shinzan the total diffuse co2 output of showa shinzan was estimated to be about 14 0 15 6 t d 1 of co2 for an area of 0 53 km2

contrasting hydrothermal activity at sierra negra and alcedo volcanoes galapagos archipelago ecuador and approximately 85 so2 of the total sulfur gas relative amounts of he ar and n2 show a distinct hot spot signature the 13c co2 is approximately 3 6 and 34st is approximately 3 3 the d 18o of fumarole h2o indicates steam separation from local meteoric waters whose estimated minimum mean residence time from 3h analyses is 40 years fumarolic activity at alcedo is controlled by a caldera margin fault containing at least seven hydrothermal explosion craters and by an intracaldera rhyolite vent two explosion craters which formed in 1993 1994 produce approximately 15 m3 s of steam yet discharge temperatures are 97 c water content of the total gas is 95 97 mol noncondensible gas is 92 98 mol co2 and sulfur gas is dominated by h2s relative amounts of he ar and n2 show extensive mixing between hot spot and air or air saturated meteoric water components but the average the 13c co2 is approximately 3 5 and 34st is approximately 0 8 the d 18o of fumarole steam indicates separation from a homogeneous reservoir that is enriched 3 5 in 18o compared with local meteoric water 3h indicates that this reservoir water has a maximum mean residence time of approximately 400 years and empirical gas geothermometry indicates a reservoir temperature of 260 320 c the intracaldera hydrothermal reservoir in alcedo is probably capable of producing up to 150 mw however environmental concerns as well as lack of infrastructure and power users will limit the development of this resource

fumarole emissions at mount st helens volcano june 1980 to october 1981 degassing of a magma hydrothermal system abstract this study is an investigation of the chemical changes in the mount st helens fumarole gases up to october 1981 the sources of the fumarole gases and the stability of gas species in the shallow magma system these problems are investigated by calculations of element compositions thermodynamic equilibria and magmatic volatile hydrothermal steam mixing models the fumarole gases are treated as mixtures of magmatic volatiles and hydrothermal steam formed by magma degassing and boiling of local waters in a dryout zone near conduit and dome magma the magmatic volatile fraction is significant in fumaroles with temperatures in excess of the magma cracking temperature 700 c i e the temperature below which cracking is induced by thermal stresses during cooling and solidification linear composition changes of the fumarole gases over time appear to be the result of a steady decline in the magmatic volatile mixing fraction which may be due to the tapping of progressively volatile depleted magma the maximum proportion of hydrothermal steam in the fumaroles rose from about 25 35 in september 1980 to around 50 70 by october 1981 fractional degassing of magmatic co 2 and sulfur also contributed to the chemical changes in the fumarole gases the steady chemical changes indicate that replenishment of the magma system with undegassed magma was not significant between september 1980 and september 1981 extrapolations of chemical trends suggest that fumarole gases emitted at the time of formation of the first dome in mid june 1980 were more enriched in a magmatic volatile fraction and contained a minimum of 9 co 2 calculations show h 2 s is the predominant sulfur species in mount st helens magma below depths of 200 m rapid release of gases from magma below this depth is a plausible mechanism for producing the high h 2 s so 2 observed in mount st helens plumes during explosive eruptions this study suggests that dacite andesite volcanos may emit gases richer in co 2 during the earlier episodes of an eruptive cycle and burden the atmosphere with much more h 2 s than so 2 during explosive eruptions

diffuse carbon dioxide emissions from hidden subsurface structures at asama volcano japan we measured diffuse carbon dioxide co2 flux and soil temperature around the summit of asama volcano japan to assess the diffuse degassing structure around the summit area soil co2 flux was measured using an accumulation chamber method and the spatial distributions of co2 flux and soil temperature were derived from the mean of 100 sequential gaussian simulations results show that soil co2 flux was high on the eastern flank of kamayama cone and the eastern rim of maekake crater the outer cone these areas mostly correspond to high temperature anomalies the average emission rate of diffuse co2 was calculated to be 12 6 t day 1 12 2 14 6 t day 1 such diffuse emissions account for 12 of the total diffuse and plume co2 emissions from the summit area the diffuse co2 anomalies probably reflect permeable zones controlled by local topography and hidden fractures bordering maekake crater the permeable zones are connected to the low electrical resistivity zone inferred to indicate both a hydrothermal fluid layer and an upper sealed layer made of clay minerals magmatic gas from the main conduit ascends to the volcano surface through this fluid layer and the permeable zones these insights emphasize that the pathways and the connection between the pathways and the source of diffuse co2 combine to create the pattern of heterogeneous diffuse co2 emission seen at the surface only by using a combination of gas measurements and geophysical tools can we begin to understand the dynamics of this system as a whole

helium 3 emission in and around teide volcano tenerife canary islands spain air corrected he 4he ratios of fluid samples collected in and around teide volcano tenerife canary islands ranged from 5 97 to 8 06 ra helium 3 emission spatial distribution has a quite different pattern from other stratovolcanoes which show commonly a decreased trend for the he 4he ratio with respect to distance from the summit crater this finding might be related to the volcano tectonic setting differences between subduction type and oceanic island type statrovolcanoes radiogenic helium production is a significant process for the dilution of uprising derived mantle fluids in and around subduction type stratovolcanoes while it can be almost negligible for polygenetic volcanoes at oceanic islands

a volcano bursting at the seams inflation faulting and eruption at sierra negra volcano galapagos the results of geodetic monitoring since 2002 at sierra negra volcano in the galapagos islands show that the filling and pressurization of an 2 km deep sill eventually led to an eruption that began on 22 october 2005 continuous global positioning system cgps monitoring measured 2 m of accelerating inflation leading up to the eruption and contributed to nearly 5 m of total uplift since 1992 the largest precursory inflation ever recorded at a basaltic caldera this extraordinary uplift was accommodated in part by repeated trapdoor faulting and coseismic cgps data provide strong constraints for improved deformation models these results highlight the feedbacks between inflation faulting and eruption at a basaltic volcano and demonstrate that faulting above an intruding magma body can relieve accumulated strain and effectively postpone eruption

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

diffuse emission of carbon dioxide methane and helium 3 from teide volcano tenerife canary islands diffuse emission of co2 ch4 and he was investigated in the summit crater of teide volcano tenerife canary islands the results indicate that teide volcano releases abundant co2 not only from its active crater but also from its flanks as diffuse soil emanations the spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations our flux measurements indicate a total output of 380 ton day 1 of co2 and 1 6 on day 1 of ch4 by diffuse degassing from the he co2 ratios and the co2 flux we estimate a diffuse he flux of 0 052 mol year 1 isotopic analysis of carbon in soil gas samples from sites of high soil co2 flux indicates a magmatic origin for the co2 also reported by high he 4he ratios of 5 50 and 5 87 ra the origin of methane is more uncertain with low 13c values suggesting a biogenic contribution

the pattern of circumferential and radial eruptive fissures on the volcanoes of fernandina and isabela islands galapagos maps of the eruptive vents on the active shield volcanoes of fernandina and isabela islands galapagos made from aerial photographs display a distinctive pattern that consists of circumferential eruptive fissures around the summit calderas and radial fissures lower on the flanks on some volcano flanks either circumferential or radial eruptions have been dominant in recent time the location of circumferential vents outside the calderas is independent of caldera related normal faults the eruptive fissures are the surface expression of dike emplacement and the dike orientations are interpreted to be controlled by the state of stress in the volcano very few subaerial volcanoes display a pattern of fissures similar to that of the galapagos volcanoes some seamounts and shield volcanoes on mars morphologically resemble the galapagos volcanoes but more specific evidence is needed to determine if they also share common structure and eruptive style

scale effect on geomorphologic and kinematic dispersion geomorphologic dispersion relates to the fraction of the variance of residence time distributions that can be directly linked to the heterogeneity of the paths available to hydrologic runoff of a river basin in response to suitable rainfall pulses it thus defines the dispersive characters of geomorphological origin hillslope transport processes and systematic variations of advective processes in the channel network define a kinematic component of dispersion here we suggest that channel borne kinematic effects are likely to be clouded by hillslope dispersion in a surprisingly wide spectrum of basin scales we find that the signatures of hillslope transport on travel time distributions do not fade away rapidly with the size of the catchment i e when the basin scale becomes much greater than the mean hillslope size in particular because of their major impact on the skewness of the travel time distribution we suggest that an appropriate description of hillslope channel transitions entails a combination of geomorphic and kinematic effects which plays a decisive role in shaping the main characters of the hydrologic response in cases of practical interest

spatial distribution and temporal variation of 3 he 4 he in hot spring gas released from unzen volcanic area japan abstract following the first phreatic explosion on 17 november 1990 hot spring gases were collected periodically over the next 10 years for 3 he 4 he isotopic ratio and chemical analyses from three hot springs obanma unzen and shimabara located around unzen volcano japan the 3 he 4 he ratios although showing some scatter at each site show an increase from west to east obama 4 content the 3 he 4 he ratios at shimabara and unzen after 1990 were significantly higher than the single values for the 1983 sample marty et al 1989 possibly due to an additional supply of magmatic helium related to the recent post 1990 volcanic activity the 3 he 4 he ratio at shimabara hot spring increased slightly after november 1990 reaching a maximum value in july 1992 and decreasing later this suggests that magmatic helium with relatively high 3 he 4 he ratios took about one year to travel 5 km from beneath fugendake volcanic cone to shimabara hot spring site because the magma effusion rate and magma degassing rate reached a maximum in june 1991

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

continuous monitoring of distal gas emanations at vulcano southern italy the increasing activity of vulcano island italy since 1985 led to the initiation of continuous geochemical monitoring of the lateral soil gas emissions on the basis both of their relative geochemical characteristics and of local considerations three gaseous components were selected for monitoring namely co2 he and 222rn monitoring has been performed by means of specific analysers gases extracted from a water well located at the foot of the active cone were selected for monitoring on the basis of their geochemical and isotopic characters that indicate their genetic link with central high temperature fumarolic gases emitted at the crater very strong variations of gas composition can be observed within one day from 1 to about 94 for co2 some variations display a daily character and can be correlated with that of atmospheric pressure the three monitored gases are highly correlated suggesting very high kinetics of gas transfer in the system because of these considerable variations of chemical composition bulk concentrations obviously are not suitable for monitoring at vulcano however the evolution with time of ratios such as 222rn co2 and he co2 the latter being corrected for atmospheric contamination supplies numerical parameters that the expected to characterize the intensity of the degassing process a new input of magmatic gases that would lead to an increase in the 222rn co2 and he co2 ratios should therefore be detected by such a monitoring station

hydraulic causes for basin hydrograph skewness it has been suggested that hydrograph skewness depends on the relative dominance between hillslope and channel network transport processes where the former ones make the hydrograph positively skewed while the latter tends to make it negatively skewed more recently however the role of river hydraulics in shaping the hydrograph has been highlighted we present a set of numerical modelling experiments using a hydrodynamic model of river networks in which we investigate how channel hydraulics influence the shape of the hydrograph particularly its skewness we further investigate the influence of baseflow rainfall intensity cross section geometry and basin scale on unit hydrograph response we show that river hydraulics has a decisive role because positively skewed hydrographs may occur even when water inputs to the river network are negatively skewed and in catchments whose width function is also negatively skewed we show additional results related to the effect of the degree of non linearity in the relationship between celerity and discharge the effects of baseflow and rainfall intensity these further confirm that hydraulic factors may be decisive in determining hydrograph shape

carbon dioxide emissions from soils at hakkoda north japan 1 a soil gas and co2 efflux survey was carried out at hakkoda north japan to investigate the spatial distribution and origin of the gas which caused the accidental death of three japanese soldiers on 12 july 1997 in the study area no fumarolic and or thermal activity is observed chemical composition of the gas from areas with high co2 effluxes 5 000 g m 2 d 1 and high co2 contents 15 vol indicate a strong deep sourced contribution for co2 whereas air and or air saturated water is suggested for the rest of the discharged gases which are mainly released from a shallow aquifer isotopic analysis of soil gas and hot spring discharges suggests a combination of magmatic degassing and thermal decarbonation with magmatic degassing being the main contributior to the high co2 emission approximately 74 t d 1 of deep seated magmatic plus thermal decarbonation origin co2 were estimated to contribute to the total output of co2 from this area

diffuse co2 emission rate from pululahua and the lake filled cuicocha calderas ecuador abstract we report herein the first results of two soil co 2 efflux surveys carried out at cuicocha lake filled and pululahua caldera volcanic systems ecuador a total of 172 and 217 soil co 2 efflux measurements were taken at the surface environment of pululahua and cuicocha calderas respectively by means of the accumulation chamber method during the summer of 2006 to constrain the total co 2 output from the studied area soil co 2 efflux values ranged from non detectable up to 48 5 and 141 7 g m 2 d 1 for cuicocha and pululahua calderas respectively in addition probability graphs were used to distinguish the existence of different geochemical populations sequential gaussian simulation was used to construct an average map for 100 simulations and to compute the total co 2 emission at each studied area 106 and 270 t d 1 metric tons per day for cuicocha 13 3 km 2 and pululahua 27 6 km 2 volcanoes respectively

first estimates of fumarolic so2 fluxes from putana volcano chile using an ultraviolet imaging camera abstract putana is a stratovolcano in the central andes volcanic zone in northern chile on the border with bolivia fumarolic activiy has been visible at its summit crater at 5890 m altitude from long distances since the early 1800s however due to its remote location neither detailed geological studies have been made nor gas fluxes have been monitored and therefore its evolution remains unknown on november 28 2012 an ultraviolet uv imaging camera was transported to putana and for about 30 min images of the fumaroles were recorded at 12 hz these observations provide the first measurements of so2 fluxes from the fumarolic field of putana and demonstrate the applicability of the uv camera to detect such emissions the measurement series was used to assess whether the sampling rate of the data influences the estimate of the gas flux the results suggest that measurements made at 10 s and 1 min intervals capture the inherent turbulent variability in both the plume wind speed and so2 flux relatively high so2 fluxes varying between 0 3 kg s 1 and 1 4 kg s 1 which translates to 26 t day and 121 t day assuming constant degassing throughout the day were observed on november 28 2012 furthermore we demonstrate how an optical flow algorithm can be integrated with the so2 retrieval to calculate so2 fluxes at pixel level average values of 0 64 kg s 1 0 20 kg s 1 and 0 70 kg s 1 0 53 kg s 1 were retrieved from a classical transect method and the advanced optical flow based retrieval respectively assuming constant emissions throughout all times these values would results in an average annual so2 burden of 20 22 kt

accurately measuring volcanic plume velocity with multiple uv spectrometers a fundamental problem with all ground based remotely sensed measurements of volcanic gas flux is the difficulty in accurately measuring the velocity of the gas plume since a representative wind speed and direction are used as proxies for the actual plume velocity there can be considerable uncertainty in reported gas flux values here we present a method that uses at least two time synchronized simultaneously recording uv spectrometers flyspecs placed a known distance apart by analyzing the time varying structure of so2 concentration signals at each instrument the plume velocity can accurately be determined experiments were conducted on k lauea usa and masaya nicaragua volcanoes in march and august 2003 at plume velocities between 1 and 10 m s 1 concurrent ground based anemometer measurements differed from flyspec measured plume speeds by up to 320 this multi spectrometer method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic or industrial gas flux measurements

petrology of lavas from sierra negra volcano isabela island galapagos archipelago sierra negra volcano is a voluminous active basaltic shield situated in the western galapagos archipelago a hotspot related chain adjacent to the galapagos spreading center the volcano has erupted fe rich tholeiitic basalts of very limited compositional range comparison of lavas from each of five stratigraphic units covering the entire volcano indicates that the lavas are mineralogically similar and compositionally restricted 4 4 to 6 9 wt mgo the lavas are fe rich and hypersthene normative and plot in both the alkaline and tholeiite fields of the alkali silica diagram rare earth element ree patterns are steep and parallel the major and trace element data indicate a comagmatic relationship by fractional crystallization of the observed phenocryst phases projections into pseudoternary phase diagrams suggest that the magmas cooled and crystallized at pressures between 1 and 3 kbar calculated melt densities range from 2 73 to 2 77 g cm3 which are higher than those of typical mid ocean ridge basalt morb hawaiian tholeiite and other galapagos lavas the high calculated melt densities may be caused by fractionation at greater depths than is ordinary for the other basaltic magmas suppression of plagioclase and olivine crystallization in favor of augite may eliminate the minimum density window that has been proposed for morb fractionation sierra negra lavas have the most radiogenic lead and strontium isotopic ratios in the western galapagos indicating that the magmas have a relatively large contribution of plume material and have been minimally contaminated by entrainment of morb producing mantle magmatic 3he 4he isotopic ratios from sierra negra are approximately 15 times the atmospheric ratio although these ratios clearly indicate plume helium they are not the highest 3he 4he in the archipelago suggesting that helium is decoupled from the heavier isotopes high sm yb ratios light rare earth element lree enrichment and a steep ree slope are consistent with an origin by moderate extents 5 15 of partial melting of a garnet lherzolite source with ree characteristics that are between chondrite and depleted earth mantle sources sierra negra lavas are compositionally monotonous because homogeneous plume rich material has experienced long term exposure to a well regulated sublithospheric thermal environment with additional compositional restrictions imposed in the lithosphere by high magma flux

is hydrology kinematic a wide range of phenomena natural as well as man made in physical chemical and biological hydrology exhibit characteristics similar to those of kinematic waves the question we ask is can these phenomena be described using the theory of kinematic waves since the range of phenomena is wide another question we ask is how prevalent are kinematic waves if they are widely pervasive does that mean hydrology is kinematic or close to it this paper addresses these issues which are perceived to be fundamental to advancing the state of the art of water science and engineering copyright 2002 john wiley sons ltd

an in situ method for measuring co2 flux from volcanic hydrothermal fumaroles abstract the theory of an in situ method to measure co 2 flux from hydrothermal fumarolic vents using a tracer gas technique is established and applied to vents and wells at three sites izu oshima japan kirishima japan and teide canary islands spain volcanoes the method is done by releasing the tracer gas into the vent at known flux and by measuring co 2 to the tracer gas ratio in situ in izu oshima we carried out flux measurements at a low temperature steam well 90 c with three different tracer gas species h 2 ch 4 and sf 6 and three methods gc portable analyzers ftir to evaluate this method the calculated co 2 flux showed an average of 2 3 t day in the case of kirishima volcanic area the flux measurement was tested at two low temperature fumaroles on iwoyama cone 2 fluxes were 9 10 2 and 2 10 0 kg day respectively the total co 2 flux from the cone including both fumarolic and ground co 2 discharges was estimated to be less than several tons per day in teide volcano co 2 flux measurements were performed in the fumarolic system of the summit crater 85 c co 2 flux from one fumarole reached levels up to 30 2 kg day we estimated that the co 2 discharge from all fumaroles is roughly 30 t day or less at maximum these results imply that the total output of co 2 flux from teide s fumarolic activity is much lower than the observed levels of co 2 diffuse degassing from the summit crater

diffuse emission of carbon dioxide from cerro negro volcano nicaragua central america we report the first detailed soil co2 efflux survey carried out at cerro negro volcano nicaragua central america soil co2 efflux values ranged from 0 5 to 35 000 g m 2 d 1 spatial distribution of co2 efflux shows that volcanic gas is mainly released from the summit crater and the fissures opened during the august 1999 eruption the total co2 output of cerro negro is conservatively estimated to be 2 800 t d 1 based on a study area of 0 58 km contour maps of soil co2 efflux ground temperature and 13c co2 distributions support an important magmatic contribution for the total output of co2 at cerro negro volcano

daily monitoring of ecuadorian volcanic degassing from space we present daily measurements of sulfur dioxide so2 emissions from active volcanoes in ecuador and southern colombia between september 2004 and september 2006 derived from the ozone monitoring instrument omi on nasa s eos aura satellite omi is an ultraviolet visible spectrometer with an unprecedented combination of spatial and spectral resolution and global coverage that permits daily measurements of passive volcanic degassing from space we use non interactive processing methods to automatically extract daily so2 burdens and information on so2 sources from the omi datastream maps of monthly average so2 vertical columns retrieved by omi over ecuador and s colombia are also used to illustrate variations in regional so2 loading and to pinpoint sources the dense concentration of active volcanoes in ecuador provides a stringent test of omi s ability to distinguish so2 from multiple emitting sources our analysis reveals that tungurahua reventador and galeras were responsible for the bulk of the so2 emissions in the region in the timeframe of our study with no significant so2 discharge detected from sangay at galeras and reventador we conclude that omi can detect variations in so2 release related to cycles of conduit sealing and degassing which are a critical factor in hazard assessment the omi so2 data for reventador are the most extensive sequence of degassing measurements available for this remote volcano which dominated regional so2 production in june august 2005 at tungurahua the omi measurements span the waning stage of one eruptive cycle and the beginning of another and we observe increasing so2 burdens in the months prior to explosive eruptions of the volcano in july and august 2006 cumulative so2 loadings measured by omi yield a total of 1 16 tg so2 emitted by volcanoes on mainland ecuador s colombia between september 2004 and september 2006 as much as 95 of this so2 may originate from non eruptive degassing approximate apportionment of the total so2 loading indicates that 40 originated from tungurahua with 30 supplied by both reventador and galeras these measurements of volcanic so2 degassing in ecuador confirm omi s potential as an effective economical and risk free tool for daily monitoring of so2 emissions from hazardous volcanoes

river reach length and slope estimates for large scale hydrological models based on a relatively high resolution digital elevation model application of regular grid based distributed hydrological models requires information related to river drainage networks such as flow directions flow accumulated areas basin delineation and length and slope of river reaches for every grid cell most of those data may be extracted automatically from digital elevation models dem however when dealing with large basins available dems are usually in higher spatial resolution than the model grid upscaling procedures have therefore been developed to extract low resolution flow directions and flow accumulated areas from relatively high resolution dems this paper presents a new methodology which extends the upscaling method to automatically extract length and slope of river reaches for large scale grid based hydrological models the proposed method is new and is believed to be the first attempt to produce such information automatically from dems the methodology was applied to parts of the uruguay river basin in south america using the globally wide available dem produced by the shuttle radar topography mission srtm 90m quality of results was assessed by comparing calculated river lengths with distances measured over vectorized river networks which were assumed to be correct it was shown that the proposed methodology adequately assigns river lengths to every model cell while ensuring that the whole length of the streams is considered the effect of dem resolution on calculated river length errors was analyzed by resampling the srtm dem to three different cell sizes with best results obtained for the higher resolution dem the modification of the original high resolution dem through the process known as stream burning was also tested largely improving the quality of the results finally optimal distance transforms were used for the calculation of distance increments instead of euclidean local distances giving results that were generally better the quality of results for calculated slope values could not be assessed because no reliable data were available for comparison

monitoring quiescent volcanoes by diffuse co2 degassing case study of mt fuji japan since the 8th century more than seventeen eruptions have been recorded for the mt fuji volcano with the most recent eruption occurring in 1707 hoei eruption for the past 300 years the volcano has been in a quiescent stage and since the early 1960s has exhibited neither fumarolic nor thermal activity however the number of low frequency earthquakes with a hypocentral depth of 10 20 km increased significantly beneath the northeastern flank of mt fuji in 2000 2001 suggesting a possible resumption of magmatic activity in this study diffuse co2 efflux and thermal surveys were carried out in four areas of the volcano in 2001 2002 in order to detect possible signs of the upward movement of deep magma at all survey points the co2 efflux was below the detection limit with the exception of a few points with biological co2 emission and ground temperatures at a depth of 20 30 cm were below ambient indicating no surface manifestations of gas or heat emission should magma rise into the subsurface the diffuse co2 efflux would be expected to increase particularly along the tectonically weakened lineation on the mt fuji volcano allowing for the early detection of pre eruptive degassing

physical volcanology and structural development of sierra negra volcano isabela island galapagos archipelago sierra negra is the most voluminous of the western galapagos shields and exhibits many unusual morphologic features extensive lower flank apron steep upper flanks a broad summit plateau a large complex caldera ubiquitous occurrence of aa and radial and circumferential fissures a field based investigation of the volcano was conducted in order to establish the distribution and characteristics of eruptive zones and associated flow fields and to construct a volcano wide surface flow stratigraphy geochronologic data were used to determine the age of the units and combined with flow volume calculations to estimate both the historic and total volcano eruption rates ninety one kilometers of radial and circumferential fissures were mapped and grouped into four eruptive zones which form a volcano wide east northeast trending rift system that deflects around the caldera the eruptive zones are restricted spatially and temporally and document long term changes in the volcano s development long fluid lava flows are broadly distributed among five ages resulting in a subdued flank profile by the development of an extensive lower flank apron around the volcano ten historical eruptions have occurred with eruption rates of 44 to 248 m3 s and an average growth rate of 12 106 m3 yr age determinations of lava flows by 14c and cosmogenic 3he range from 400 to 6900 yr the total volcano growth rate is estimated to be 1 106 m3 yr these results confirm the young age of sierra negra lavas and the validity of the relative ages determined from stratigraphic study in total the volcano has undergone over 90 resurfacing in the past 4500 yr the summit of sierra negra is entirely occupied by a shallow elliptical 7 10 km caldera near vertical ring faults circumscribe the summit and expose 100 to 140 m of lava flows subparallel sets of caldera growth faults cut the western and southern caldera walls and are not associated with eruptive activity the inclination of remnant magnetism and the attitudes of the flows exposed in the caldera walls indicate that the lavas have not been appreciably deformed nor have they been intruded by dikes or sills the caldera interior is structurally complex and contains a 14 km long c shaped sinuous ridge composed of a complex set of normally faulted blocks with inward dipping 20 60 flow tops the sinuous ridge is interpreted to have formed gradually as the caldera floor pivoted in a trap door fashion jammed its western edge and then fractured in several places concomitant with the long term vertical and lateral growth of the volcano a regional tectonic stress field superimposed upon the galapagos platform appears to have exerted primary control on the location of sierra negra including the early development of the east northeast rift system intervolcano stresses have controlled the distribution of eruptive zones only where significant subaerial overlap of adjacent volcanoes occurs large volume high discharge rate eruptions from fissures along the east northeast rift system are responsible for the development of an extensive coastal apron flow stacking at mid flank elevations and generally subdued slopes in comparison to other western galapagos volcanoes the summit caldera and underlying magma chamber are subordinate in influencing the distribution of lower flank stress but dominate the development of the summit stress field and orientation of eruptive fissures the absence of summit deformation together with the ubiquitous occurrence of short stubby summit flows indicates that the steep upper flanks are constructional in origin

fumarole plume and diffuse co 2 emission from sierra negra caldera galapagos archipelago measurements of visible and diffuse gas emission were conducted in 2006 at the summit of sierra negra volcano galapagos with the aim to better characterize degassing after the 2005 eruption a total so2 emission of 11 2 t day 1 was derived from miniature differential optical absorption spectrometer mini doas ground based measurements of the plume emanating from the mini azufral fumarolic area the most important site of visible degassing at sierra negra volcano using a portable multigas system the h2s so2 co2 so2 and h2o so2 molar ratios in the mina azufral plume emissions were found to be 0 41 52 2 and 867 9 respectively the corresponding h2o co2 and h2s emission rates were 562 394 and 3 t day 1 respectively the total output of diffuse co2 emissions from the summit of sierra negra volcano was 990 85 t day 1 with 605 t day 1 being released by a deep source the diffuse to plume co2 emission ratio was about 1 5 mina azufral fumaroles released gasses containing 73 6 mol of h2o the main noncondensable components amounted to 97 4 mol co2 1 5 mol so2 0 6 mol h2s and 0 35 mol n2 the higher h2s so2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions 3he 4he ratios measured at mina azufral fumarolic discharges showed values of 17 88 0 25 ra indicating a mid ocean ridge basalts morb and a galapagos plume contribution of 53 and 47 respectively

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

secular variations of carbon and helium isotopes at izu oshima volcano japan abstract secular variations in 13c 12c ratios and chemical compositions of gas samples from october 1986 to july 1992 are reported from a 92 95 c steam well located about 3 km north of mt mihara an active volcano on izu oshima island japan the 13c value steeply increased from 2 97 relative to pdb carbonate in december 1986 to 1 15 in march 1988 and then gradually decreased to 1 75 in july 1992 over the same period the co 2 content changed similarly with time even though the experimental error is relatively large these variations are consistent with helium isotope changes initially rapid and then slow enhancements of 3he 4he ratio 13c value and co 2 content are invoked by violent eruptions of izu oshima volcano from 15 november to 18 december 1986 after the eruptive activity depletion of magmatic gas emission and subsequent mixing with crustal fluids in the hydrothermal system may produce the gradual decreases of 3he 4he ratio 13c value and co 2 content taking into account the rates of these decreases we suggest that helium and carbon isotope ratios will return to the situation of before the magmatic eruption within 15 years

the seismic signal strength of chemical explosions we have compared the seismic magnitude of a wide variety of chemical explosions of known yield to the magnitude expected for explosions set off in hard rock under conditions most favorable for generating strong seismic signals our results are based on numerous chemical explosions that include several different broad groups mostly taken from practical experience with explosions carded out on territory of the former soviet union to quantify these observations we define the deficit of an explosion as the expected signal strength if that charge size or yield were fired under the most favorable conditions in hard rock minus the actual strength we document the size of the deficit using two different measures of signal strength the energy class k and the seismic magnitude which may be the teleseismic mb or a regional magnitude in general for ripple fired chemical explosions carried out in the mining and con struction industries the magnitude deficit is around 1 5 to 2 the type of blasting that comes close to the maximum coupling efficiency zero deficit is now rare except for small yield single fired explosions that are specially designed to maximize signal strength such as explosions for seismic refraction surveys there are a small number of locations where the deficit is small 0 5 magnitude units for quite large chemical yields several hundred tons such explosions which appear to be uncommon and declining as blasting practices are modernized may require special attention in the context of verification of the comprehensive test ban treaty

on river floodplain interaction and hydrograph skewness understanding hydrological processes occurring within a basin by looking at its outlet hydrograph can improve and foster comprehension of ungauged regions in this context we present an extensive examination of the roles that floodplains play on driving hydrograph shapes observations of many river hydrographs with large floodplain influence are carried out and indicate that a negative skewness of the hydrographs is present among many of them through a series of numerical experiments and analytical reasoning we show how the relationship between flood wave celerity and discharge in such systems is responsible for determining the hydrograph shapes the more water inundates the floodplains upstream of the observed point the more negatively skewed is the observed hydrograph a case study is performed in the amazon river basin where major rivers with large floodplain attenuation e g purus madeira and jurua are identified with higher negative skewness in the respective hydrographs finally different wetland types could be distinguished by using this feature e g wetlands maintained by endogenous processes from wetlands governed by overbank flow along river floodplains a metric of hydrograph skewness was developed to quantify this effect based on the time derivative of discharge together with the skewness concept it may be used in other studies concerning the relevance of floodplain attenuation in large ungauged rivers where remote sensing data e g satellite altimetry can be very useful

widespread uplift and trapdoor faulting on galapagos volcanoes observed with radar interferometry volcanic uplift caused by the accumulation of magma in subsurface reservoirs is a common precursor to eruptions1 2 but for some volcanoes uplift of metres or more has not yet led to an eruption3 here we present displacement maps of volcanoes in the galapagos islands constructed using satellite radar interferometry that might help explain this dichotomy we show that all but one of the seven volcanoes on the islands of isabela and fernandina deformed during 1992 99 cerro azul and fernandina erupted4 5 6 during the observation period and show evidence of inflation co eruptive deflation and shallow dyke intrusion in contrast the largest volcano sierra negra has not erupted yet exhibits spatially and temporally variable deformation with a maximum uplift of 2 7 m between 1992 and 1999 which can be modelled by a shallow inflating sill inflation during 1997 98 however was accompanied by trapdoor faulting on a steeply dipping fracture system within the caldera repeated trapdoor faulting over geological time has formed an arcuate intra caldera ridge within sierra negra and may have acted to relax stresses above the magma chamber inhibiting summit eruptions similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes

geochemical precursors of the activity of an open conduit volcano the stromboli 2002 2003 eruptive events 1 marked increases of co2 h2 and he dissolved in thermal waters and changes in the dissolved carbon isotopic composition were observed at stromboli before the 28 december 2002 eruption and before a violent explosive paroxysm occurred on 5 april 2003 high anomalous co2 flux values were recorded at the crater rim since a week before the eruption onset the first anomalies in the thermal waters dissolved co2 amount appeared some months before the eruption when magma column rose at a very high level in the conduit high peaks of dissolved h2 and he were recorded a few days before the paroxysm carbon isotopic composition indicates a magmatic origin of the dissolved co2 whose increase together with those of h2 and he is attributed to an increasing output of deep gases likely produced by depressurization of a rising batch of a deep gas rich magma whose fragments have been emitted during the explosion

kinematic shock sensitivity analysis a series of numerical experiments is performed to determine the flow and channel characteristics that are most conducive to kinematic wave steepening and associated kinematic shock phenomena relevant flow and channel characteristics are identified at the outset and a program of 80 computer runs is completed varying the inflow hydrograph peak froude number time to peak and base to peak flow ratio and the channel cross sectional shape it is found that all have a definite effect on kinematic shock development the size of the wave is perhaps mostly responsible for the occurrence or nonoccurrence of the shock

constraints on magma chamber geometry at sierra negra volcano galapagos islands based on insar observations abstract we investigate the problem of estimating magma chamber geometry using insar observations of sierra negra volcano galapagos ascending and descending interferograms are combined to determine vertical and one horizontal component of displacement the ratio of maximum horizontal to vertical displacement suggests a sill like source spherical or stock like bodies are inconsistent with the data we estimate the geometry of the sill assuming a horizontal uniformly pressurized crack with unknown periphery and depth the sill is discretized into small elements that are either open and are subjected to the pressure boundary condition or remain closed we find the best fitting sill to be located beneath sierra negra s inner caldera at a depth of about 2 km using boundary element calculations we show that any magma chamber with a flat top coincident with the sill model fits the data equally well the data are insensitive to the sides and bottom of the magma chamber

a subgrid channel model for simulating river hydraulics and floodplain inundation over large and data sparse areas 1 this paper presents a new computationally efficient hydraulic model for simulating the spatially distributed dynamics of water surface elevation wave speed and inundation extent over large data sparse domains the numerical scheme is based on an extension of the hydraulic model lisflood fp to include a subgrid scale representation of channelized flows which allows river channels with any width below that of the grid resolution to be simulated the scheme is shown to be numerically stable and scalable before being applied to an 800 km reach of the river niger in mali the niger application focused on the performance of four different model structures a model without channels two dimensional 2 d model a model without a floodplain one dimensional 1 d model a model of the main channels and floodplain 1 d 2 d model and the subgrid approach developed here inclusion of both the channel network and the floodplain was shown to be essential meaning that large scale models of this region including routing models for land surface schemes will require a floodplain component including subgrid scale channels on the floodplain changed inundation dynamics over the delta significantly and increased simulation accuracy in terms of water level wave propagation speed and inundation extent furthermore only the subgrid model showed a consistent parameterization when calibrated against either gauge or icesat water level data suggesting that connectivity provided by small channels is a strong control on the hydraulics of the floodplain or at the very least that low resolution gridded hydraulic models require additional connectivity to represent the delta flow dynamics

variation in noble gas isotopic composition of gas samples from the aegean arc greece abstract in contrast to most other arcs with oceanic plate subduction the aegean arc is characterized by continent continent subduction noble gas abundances and isotopic compositions of 45 gas samples have been determined from 6 volcanoes along the arc 2 islands in the back arc region and 7 sites in the surrounding areas the 3he 4he ratios of the samples ranged from 0 027ra to 6 2ra ra denotes the atmospheric 3he 4he ratio of 1 4 10 6 demonstrating that even the maximum 3he 4he ratio in the region is significantly lower than the maximum ratios of most oceanic subduction systems which are equal to the morb value of 8 1 ra regional variations in the 3he 4he ratio were observed both along and across the arc the maximum 3he 4he ratio was obtained from nisyros volcano located in the eastern end of the arc and the ratio decreased westward possibly reflecting the difference in potential degree of crustal assimilation or the present magmatic activity in each volcano across the volcanic arc the 3he 4he ratio decreased with an increasing distance from the arc front reaching a low ratio of 0 063ra in macedonia which suggested a major contribution of radiogenic helium derived from the continental crust at nisyros a temporal increase in 3he 4he ratio due to ascending subsurface magma was observed after the seismic crisis of 1995 1998 and mantle neon was possibly detected the maximum 3he 4he ratio 6 2ra in the aegean region which is significantly lower than the morb value is not probably due to crustal assimilation at shallow depth or addition of slab derived helium to morb like mantle wedge but inherent characteristics of the subcontinental lithospheric mantle sclm beneath the aegean arc

soil efflux and total emission rates of magmatic co2 at the horseshoe lake tree kill mammoth mountain california 1995 1999 abstract we report the results of eight soil co 2 efflux surveys by the closed circulation chamber method at the horseshoe lake tree kill hltk the largest tree kill on mammoth mountain the surveys were undertaken from 1995 to 1999 to constrain total hltk co 2 emissions and to evaluate occasional efflux surveys as a surveillance tool for the tree kills hltk effluxes range from 1 to 10 000 g m 2 day 1 grams co 2 per square meter per day they are not normally distributed station efflux rates can vary by 7 35 during the course of the 8 to 16 h surveys disturbance of the upper 2 cm of ground surface causes effluxes to almost double semivariograms of efflux spatial covariance fit exponential or spherical models they lack nugget effects efflux contour maps and total co 2 emission rates based on exponential spherical and linear kriging models of survey data are nearly identical similar results are also obtained with triangulation models suggesting that the kriging models are not seriously distorted by the lack of normal efflux distributions in addition model estimates of total co 2 emission rates are relatively insensitive to the measurement precision of the efflux rates and to the efflux value used to separate magmatic from forest soil sources of co 2 surveys since 1997 indicate that contrary to earlier speculations a termination of elevated co 2 emissions at the hltk is unlikely anytime soon the hltk co 2 efflux anomaly fluctuated greatly in size and intensity throughout the 1995 1999 surveys but maintained a n s elongation presumably reflecting fault control of co 2 transport from depth total co 2 emission rates also fluctuated greatly ranging from 46 to 136 t day 1 metric tons co 2 per day and averaging 93 t day 1 the large inter survey variations are caused primarily by external meteorological processes operating on time scales of hours to days the externally caused variations can mask significant changes occurring at depth a striking example is the masking of a degassing event generated at depth and detected by a soil gas sensor network in september 1997 while an efflux survey was in progress thus occasional efflux surveys are not an altogether effective surveillance tool for the hltk and making them effective by greatly increasing their frequency may not be practical

on trapdoor faulting at sierra negra volcano galapagos abstract rapid uplift observed during 1992 1997 at sierra negra volcano western galapagos was followed by deformation that we have previously interpreted as trapdoor faulting on an intra caldera fracture system at that time no direct evidence for the trapdoor faulting was available to support this interpretation here we report field evidence of recent faulting at sierra negra and provide direct measurements of the faulting using pixel offsets between satellite radar amplitude backscatter images our field observations carried out in 2001 indicate that recent faulting occurred along the southern part of the intra caldera fault system with maximum offset of at least 0 5 1 m differences between two satellite radar amplitude images show 1 4 0 2 m range change across this fault system this suggests that 1 5 0 2 m of faulting occurred assuming vertical ground displacements consistent with our previous modeling results results of numerical modeling indicate that growing sills can cause faulting of the intrusion roof on outward dipping or nearly vertical faults this occurs at high excess magma pressure when the lateral extent half length of the sill becomes greater than its depth the derived 2 km deep sierra negra sill exhibits trapdoor faulting 3 km south of the center of the sill therefore these modeling results provide a plausible mechanical explanation for the trapdoor fault at sierra negra

results from new gps and gravity monitoring networks at fernandina and sierra negra volcanoes galapagos 2000 2002 gps and gravity networks were established on sierra negra and fernandina volcanoes in 2000 and remeasured in 2001 and 2002 after a decade in which the caldera inflated by over 2 5 m sierra negra s caldera began to subside between 2000 and 2002 at a rate of about 9 cm a neither inflation nor deflation was accompanied by eruption simple elastic modeling indicates that the deformation at sierra negra can be attributed to volumetric contraction of a 2 1 km deep sill beneath the caldera caused by either movement of magma out of the sill or loss of bubbles through degassing precise gravity measurements support but do not prove the former mechanism fernandina volcano is in a phase of slow refilling of the summit reservoir after the 1995 eruption causing lateral expansion of the caldera rim by about 3 cm a our estimate for the depth of the shallowest part of the fernandina magma chamber is 1 to 2 km neither volcano shows evidence of flank spreading

diffuse emission of co2 from miyakejima volcano japan abstract two soil gas surveys were carried out in may and september 1998 at miyakejima volcano in the izu mariana arc japan co 2 flux values for may and september surveys ranged from 0 1 to 18 150 g m 2 day 1 and from 0 1 to 9685 g m 2 day 1 respectively statistical graphical analysis showed three overlapping populations the spatial distribution of these emissions correlated quite closely with the geothermal and geological characteristics of the studied area the structure releasing higher co 2 is the summit cone oyama and surrounding areas where the most obvious geothermal features occur a total output about 100 150 t day 1 is estimated from this area a good correlation was observed between soil co 2 flux and soil temperature at the summit caldera indicating extensive condensation of fumarolic steam within the upper part of miyakejima carbon isotopic analysis of selected samples inside the summit caldera 13 c co 2 0 90 to 5 70 suggests a mixing of carbon derived from marine limestone and magmatic co 2 while a clear biogenic origin 13 c co 2 14 76 to 25 52 is observed for the diffuse degassing of co 2 outside summit caldera

summit co2 emission rates by the co2 so2 ratio method at kīlauea volcano hawaiʻi during a period of sustained inflation abstract the emission rate of carbon dioxide escaping from the summit of k lauea volcano hawai i proved highly variable averaging 4900 2000 metric tons per day t d in june july 2003 during a period of summit inflation these results were obtained by combining over 90 measurements of cospec derived so 2 emission rates with synchronous co 2 so 2 ratios of the volcanic gas plume along the summit cospec traverse the results are lower than the co 2 emission rate of 8500 300 t d measured by the same method in 1995 1999 during a period of long term summit deflation gerlach t m mcgee k a elias t sutton a j and doukas m p 2002 carbon dioxide emission rate of k lauea volcano implications for primary magma and the summit reservoir journal of geophysical research solid earth 107 b9 art no 2189 analysis of the data indicates that the emission rates of the present study likely reflect changes in the magma supply rate and residence time in the summit reservoir it is also likely that emission rates during the inflation period were heavily influenced by so 2 pulses emitted adjacent to the cospec traverse which biased co 2 so 2 ratios towards low values that may be unrepresentative of the global summit gas plume we conclude that the so 2 pulses are consequences of summit re inflation under way since 2003 and that co 2 emission rates remain comparable to but more variable than those measured prior to re inflation

4d gravity changes associated with the 2005 eruption of sierra negra volcano galapagos sierra negra volcano the most voluminous shield volcano in the galapagos archipelago and one of the largest basaltic calderas in the world erupted on october 22 2005 after more than 25 years of quiescence gps and satellite radar interferometryinsar monitoring of the deformation of the caldera floor in the months prior to the eruption documented extraordinary inflation rates 1c m day the total amount of uplift recorded since monitoring began in 1992 approached 5 m at the center of the caldera over the eight days of the eruption the caldera floor deflated a maximum of 5 m and subsquently renewed its inflation but at a decelerating rate to gain insight into the nature of the subsurface mass density changes associated with the deformation gravity measurements performed in 2005 2006 and 2007 are compared to previous measurements from 2001 2002 when the volcano underwent a period of minor deflation and magma withdrawal the residual gravity decrease between 2001 2002 and 2005 is among the largest ever recorded atan active volcano950 gal and suggests that inflation was accompanied by a relative density decrease in the magmatic system forward modeling of the residual gravity data in 4d from 2002 to 2005 gives an estimate of the amount of vesiculation in the shallow sill required to explain the observed gravity variations geochemical constraints from melt inclusion and satellite remote sensing data allow us to estimate the pre eruptive gas content of the magma and place constraints on the thickness of the gas rich sill necessary to produce the gravity anomalies observed results suggest that reasonable sill thicknesses 700 800 m and bubble contents 10 50 volume can explain the large decrease in residual gravity prior to eruption following the eruption 2006 and 2007 the deformation and gravity patterns suggest re equilibration of the pressure regime in the shallow magma system via a renewed influx of relatively gas poor magma into the shallow parts of the system

estimation of multiple inflows and effective channel by assimilation of multi satellite hydraulic signatures the ungauged anabranching negro river abstract with the upcoming swot satellite mission which should provide spatially dense river surface elevation width and slope observations globally comes the opportunity to assimilate such data into hydrodynamic models from the reach scale to the hydrographic network scale based on the hivdi hierarchical variational discharge inversion modeling strategy larnier et al 2020 this study tackles the forward and inverse modeling capabilities of distributed channel parameters and multiple inflows in the 1d saint venant model from multisatellite observations of river surface it is shown on synthetic cases that the estimation of both inflows and distributed channel parameters bathymetry friction is achievable with a minimum spatial observability between inflows as long as their hydraulic signature is sampled next a real case is studied 871 km of the negro river amazon basin including complex multichannel reaches 21 tributaries and backwater controls from major confluences an effective modeling approach is proposed using i ws elevations from envisat data and dense in situ gps flow lines moreira 2016 ii average river top widths from optical imagery pekel et al 2016 iii upstream and lateral flows from the mgb large scale hydrological model paiva et al 2013a the calibrated effective hydraulic model closely fits satellite altimetry observations and presents real like spatial variabilities flood wave propagation and water surface observation frequential features are analyzed with identifiability maps following brisset et al 2018 synthetic swot observations are generated from the simulated flowlines and allow to infer model parameters 436 effective bathymetry points 17 friction patches and 22 upstream and lateral hydrographs given hydraulically coherent prior parameter values inferences of channel parameters carried out on this fine hydraulic model applied at a large scale give satisfying results using noisy swot like data at reach scale inferences of spatially distributed temporal parameters lateral inflows give satisfying results as well with even relatively small scale hydrograph variations being inferred accurately on this long reach this study brings insights in i the hydraulic visibility of the signatures of multiple inflow hydrographs at a large scale with swot ii the simultaneous identifiability of spatially distributed channel parameters and inflows by assimilation of satellite altimetry data iii the need for prior information iv the need to further tailor and scale network hydrodynamic models and assimilation methods to improve the fusion of multisource information and potential information feedback to hydrological modules in integrated chains