1,721,118 research outputs found
CHEMICAL AND ISOTOPIC GAS EMISSIONS AT CAMPI-FLEGREI - EVIDENCE FOR AN ABORTED PERIOD OF UNREST
No full textThe hydrothermal system beneath Campi Flegrei is quantified by analyzing gas samples. At the Bocca Grande fumarole in Solfatara Crater large variations were measured in the amount of water vapor, hydrogen sulfide, nitrogen and hydrogen gases, methane, and hydrogen chloride. Some variations could be controlled partly by a change in heat flux from a deep source to a surficial hydrothermal system. The changes in gas chemistry since 1985 could be evidence of an aborted period of unrest, which was characterized as a change in gas emissions but did not progress far enough to produce uplift or earthquake swarms. -from Autho
Special issue MinWat2020, third international multidisciplinary conference on mineral and thermal waters
No full textFLUID GEOCHEMISTRY AT VULCANO ISLAND - A CHANGE IN THE VOLCANIC REGIME OR CONTINUOUS FLUCTUATIONS IN THE MIXING OF DIFFERENT SYSTEMS
No full textIncreasing fumarolic activity and the rise of outlet fumarole temperatures has occurred at Vulcano island (southern Italy) since September 1987. Regular sampling and analysis have been conducted on the well-known F5 fumarole and later on F5HT and FA fumaroles on the Fossa crater plus other gas emanations from different sites on the island. Significant chemical and isotopical oscillations have been recorded over the period 1987-1991. Several mechanisms are considered for explaining the chemical and isotopic data, in relation to the recent increase in activity. The high CO content of the high temperature (650°C) FA fumarole, located at the interior of the crater, along with helium and carbon isotopic ratios similar to other fumaroles is probably due to an easier ascent of these fluids to the surface. Apparent equilibrium temperatures, close to the fumarolic outlet temperature, indicate isothermal expansion of the gas from a shallow equilibration zone for both high- and lower-temperature gases. High 3He/4He ratios for the beach fluids, similar to those of the crater fluids, suggest a large magmatic reservoir at depth, feeding both the crater and the beach intermediate reservoirs. -from Autho
Systematic variations of 3He/4He ratios and carbon in fumarolic fluids from active volcanic areas in Italy: Evidence for radiogenic 4He and crustal carbon addition by the subducting African Plate?
No full textThe determination of deep temperatures by means of the CO-CO2-H2-H2O geothermometer: an example using fumaroles in the Campi Flegrei, Italy
No full textChromatographic analyses of fumarolic gases, collected in sampling bottles containing an alkaline solution, have been carried out using a thermal conductivity detector and a flame ionization detector, after catalytic conversion of CO and CH4. The latter method enables the concentration of carbon monoxide to be measured with sufficient accuracy for use in a CO-CO2-H2-H2O geothermometer. Application of this geothermometer to fumaroles in the crater of Solfatara in the Campi Flegrei, Italy, indicates that they are fed from a steam reservoir at 250±15 °C and at 10-36±2atm of oxygen. On the other hand, the CH4-CO2-H2-H2O geothermobarometer seems to re-equilibrate at superficial temperatures and cannot be used for infering thermodynamic conditions at depth. Regular sampling of these fumaroles together with a geothermometric interpretation of the gas analyses provides a means of monitoring, with comparative accuracy, the chemical and thermal evolution of the hydrothermal reservoir below the Solfatara crater. Such monitoring would probably detect an increase in temperature at depth and the injection of magmatic gas into the reservoir. © 1987 Springer-Verlag
1995 Nyiragongo and Nyamulagira activity in the Virunga National Park: A volcanic crisis
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Methane production and consumption in an active volcanic environment of Southern Italy
No full textMethane fluxes were measured, using closed chambers, in the Crater of Solfatara volcano, Campi Flegrei (Southern Italy), along eight transects covering areas of the crater presenting different landscape physiognomies. These included open bare areas, presenting high geothermal fluxes, and areas covered by vegetation, which developed along a gradient from the central open area outwards, in the form of maquis, grassland and woodland. Methane fluxes decreased logarithmically (from 150 to -4.5 mg CH 4 m -2 day -1) going from the central part of the crater (fangaia) to the forested edges, similarly to the CO 2 fluxes (from 1500 g CO 2 m -2 day -1in the centre of the crater to almost zero flux in the woodlands). In areas characterized by high emissions, soil presented elevated temperature (up to 70°C at 0-10 cm depth) and extremely low pH (down to 1.8). Conversely, in woodland areas pH was higher (between 3.7 and 5.1) and soil temperature close to air values. Soil (0-10 cm) was sampled, in two different occasions, along the eight transects, and was tested for methane oxidation capacity in laboratory. Areas covered by vegetation mostly consumed CH 4 in the following order woodland > macchia > grassland. Methanotrophic activity was also measured in soil from the open bare area. Oxidation rates were comparable to those measured in the plant covered areas and were significantly correlated with field CH 4 emissions. The biological mechanism of uptake was demonstrated by the absence of activity in autoclaved replicates. Thus results suggest the existence of a population of micro-organisms adapted to this extreme environment, which are able to oxidize CH 4 and whose activity could be stimulated and supported by elevated concentrations of CH 4. © 2004 Elsevier Ltd. All rights reserved
One year after the Nyiragongo volcanic alert: evolution of the communication between Goma inhabitants, scientists and local authorities
No full textRadiogenic 4He, 21Ne and 40Ar in fumaroles gases:implication for the subducted african continental plate beneath Italy and mixing between mantle and crustal fluids. The case of Vulcano island
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