Le Fumarole di Vulcano

In tempi storici l’Isola di Vulcano è stata interessata da numerose eruzioni. Come già detto l’ultima attività vulcanica è avvenuta fra il 1888 e il 1890. Da allora l’attività del vulcano è caratterizzata dalla presenza di numerose aree fumarolizzate..

SnO₂ nanoparticles in silica: nanosized tools for femtosecond-laser machining of refractive index patterns

We show that SnO2 nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10–2, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology

Carbon Dioxide Diffuse Emission from the Soil at Vesuvio and Campi Flegrei (Pozzuoli): Ten Years of Observations

Carbon dioxide flux from the soil is regularly monitored in selected areas of Vesuvio and Solfatara (Campi Flegrei, Pozzuoli) with the main aim of investigating if the surface phenomena could provide information about the processes occurring at depth. Surveyed areas include 15 fixed points around the rim of Vesuvio and 71 fixed points in the floor of Solfatara crater, where soil CO2 flux is measured since 1998, at least once a month. In addition, two automatic permanent stations, located at Vesuvio and Solfatara, continually measure the CO2 flux and some environmental parameters that can potentially influence the CO2 diffuse degassing. We analysed, with statistical procedures, the feature of the acquired signals, evaluating the spatial and temporal variations of the CO2 degassing process. Series acquired by continuous stations are characterized by an annual periodicity that is related to the typical periodicities of some meteorological parameters (e.g., air temperature, air humidity, etc.). Such a kind of signal permits to define the “reference” level of the CO2 degassing process that diffusely affects the flanks and the base of the volcanoes. Conversely, series of CO2 flux data arising from periodic measurements over the arrays of Vesuvio and Solfatara, are less dependent on external factors such as meteorological parameters, local soil properties (porosity, hydraulic conductivity) and topographic effects (high or low ground). Therefore we argue that the longterm trend of this signal contains the “best” possible representation of the endogenous signal related to the upflow of deep hydrothermal fluids. At Vesuvio and Solfatara, the variations of these series have shown some correspondence with other physical changes of the volcanic systems

VOLCANIC CO2 FLUX MEASUREMENTS BY TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY

Introduction In the last decades, the use of near-infrared room-temperature diode lasers for gas sensing has grown significantly. The use of these devices, for instance in combination with optical fibers, is particularly convenient for volcanic monitoring applications [1,2]. Here, we report on the first results of the application of an open-path infrared tunable laser-based at Campi Flegrei (Southern Italy). Such Diode-laser-based measurements were performed, during two field campaigns (october 2012, and january 2013), in the attempt to obtain novel information on the current degassing unrest of Solfatara and Pisciarelli fumarolic fields. Results and Discussion At each site, we used an ad-hoc designed measurement geometry, using a TDLS (a Gas Finder unit) and several differently positioned retroreflectors (mirrors), to scan the fumaroles’ plume from different angles and distances. From post-processing of the data (acquired at 1 hz), we derived tomographic maps of CO2 concentrations in the plume and, by integration and combination with plume transport speed (from video cameras), we inferred the CO2 flux directly. The so-calculated fluxes, the first ever obtained at Campi Flegrei, average of 500 tons/day, and support a significant contribution of fumaroles to the total CO2 budget. The cumulative (fumarole [this study] +soil [3]) CO2 output from Campi Flegrei is finally evaluated at 1600 tons/day. [1] Gianfrani L. et al. (2000). Appl. Phys. B-Rapid Common. 70, 467-470. [2] Richter D. et al (2002), Optics and Lasers in Engineering, Volume 37, Issues 2–3, Pages 171-186. [3] Chiodini G. et al. (2010), Journal of Geophysical Research, Volume 115, B03205, doi:10.1029/2008JB006258

On the Unruh effect in de Sitter space

We give an interpretation of the temperature in de Sitter universe in terms of a dynamical Unruh effect associated with the Hubble sphere. As with the quantum noise perceived by a uniformly accelerated observer in static space-times, observers endowed with a proper motion can in principle detect the effect. In particular, we study a "Kodama observer" as a two-field Unruh detector for which we show the effect is approximately thermal. We also estimate the back-reaction of the emitted radiation and find trajectories associated with the Kodama vector fields are stable.Comment: 8 pages; corrected typos; sections structure revise

Role of non-mantle CO2 in the dynamics of volcano degassing: The Mount Vesuvius example

International audienceMount Vesuvius, Italy, quiescent since A. D. 1944, is a dangerous volcano currently characterized by elevated CO2 emissions of debated origin. We show that such emissions are most likely the surface manifestation of the deep intrusion of alkalic-basaltic magma into the sedimentary carbonate basement, accompanied by sidewall assimilation and CO2 volatilization. During the last eruptive period (1631-1944), the carbonate-sourced CO2 made up 4.7-5.3 wt% of the vented magma. On a yearly basis, the resulting CO2 production rate is comparable to CO2 emissions currently measured in the volcanic area. The chemical and isotopic composition of the fumaroles supports the predominance of this crust-derived CO2 in volatile emissions at Mount Vesuvius

Campi Flegrei volcanic surveillance by thermal IR continuous monitoring

Solfatara and Pisciarelli areas are the most impressive example of hydrothermal activity at Campi Flegrei caldera (Southern Italy). In these areas INGV-Osservatorio Vesuviano has been handling since 2004 a surveillance network for continuous, long-term volcanological monitoring of fumaroles fields by using thermal IR acquisition stations. In this paper different methodologies of analysis applied to time series of IR scenes are introduced and discussed. In spite of substantially different approaches to data analysis, the results of these methodologies agree with ground deformation data of the same area and likely are a useful tool for volcano monitoring and long-term risk definition