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Bridging the gap between Gas Emissions and geophysical observations at active volcanoes

Final Report Summary - BRIDGE (Bridging the gap between Gas Emissions and geophysical observations at active volcanoes)

The ERC-funded BRIDGE project has aimed at achieving a major state-of-the-art progress in field of volcanic gas studies. This 48 month-long project, started in October 2012 and terminated in September 2016, has successfully completed a novel interpretative scheme of shallow crustal volcanic processes, funded upon the combined analysis of co-acquired volcanic gas and geophysical (seismic, infrasonic, geodetic, thermal) signals. The ambition of the project has been to prompt a real major scientific and technical advance in Volcanology, by bridging together the too often disconnected volcanic gas and geophysical observations.
A prerequisite for such joint analysis was filling the existing technological gap between geochemical and geophysical observations at volcanoes. To this aim, initial efforts of the BRIDGE science team have been focused on technological innovation. This activity has led us to designing, building-up, testing (in laboratory and then in the field), and finally field deploying a new generation of volcanic gas sensing instruments. BRIDGE results have ultimately contributed a significant step ahead in our ability to real-time measure volcanic gases at high-rate, thus rendering the temporal resolution of gas measurements more comparable to that of geophysical observations.
Within BRIDGE, we have successfully realised the first networks of fully automated UV cameras at Etna and Stromboli volcanoes in Italy. Use of these new UV-cameras systems has also been field validated in a series of field expeditions, that have allowed us to characterise with unprecedented detail the degassing features, mechanisms and rates at a series of volcanic targets worldwide (especially in Central and Southern America, and in Indonesia). UV cameras have allowed us to obtain continuous, unattended long-term imaging of SO2 flux emissions from active volcanoes with high temporal (0.5-25 Hz) and spatial resolution. These new observational systems have paved the way to improved understanding of the dynamics of volcanic degassing, and of what controls the switch from passive (quiescent) degassing to eruption. Using the much improved spatial/temporal resolution and temporal continuity of our SO2 flux records, we have fully captured, at both Etna and Stromboli, the volcanic degassing signatures typical of the transition from regular, quiescent degassing toward either effusive (Stromboli) or paroxysmal explosive activity (Etna). In tandem-analysis of volcanic gas and co-acquired geophysical signals has contributed better understanding and modelling of the volcanic processes that govern such transitions. We have found that, at open-vent basaltic volcanoes, the strombolian-to-effusive transition, and/or the onset of paroxysmal explosive activity (e.g. lava fountaining), can be tracked real-time, and ultimately forecasted, using UV camera records. We have found, in particular, that such passive vs. eruptive activity switches can be resolved and detected in UV camera time-series from temporal increases in SO2 transients. These transients, or rapid pulses of SO2 flux increase, have been interpreted as due to bursting of individual over-pressured SO2-rich gas pockets, becoming more frequent and voluminous as eruption is approached. We have real-time characterised (via UV imaging) the onset, duration and degassing regime of several thousands of such SO2 transients, and compared their sin-explosive gas eruption rates/masses with the magnitude, shape and duration of the thermal, seismic and acoustic signals they irradiate. This has brought to significant advances in our understanding of the interplay between chemical and physical signals, and of the source mechanisms that produce seismicity and infrasound at open-vent volcanoes. These multi-disciplinary results have finally led us to initialise improved models of volcanic degassing processes, and to better constrain the processes that trigger basaltic explosive volcanic eruptions.
BRIDGE has also spent major efforts to improve our ability to measure the volcanic CO2 flux. This gas, although being the second in order of abundance in volcanic gases, has been impossible to measure with remote sensing techniques, hitherto. To this aim, we have fully succeeded in the challenging task of developing the first DIAL-Lidar for volcanic CO2 sensing. To our knowledge, this is the first example of a Lidar specifically designed to probe degassing of volcanic CO2, and represents a major step ahead in our ability to remotely sense volcanic emissions. By conducting fieldwork experiments at Etna and Stromboli volcanoes, we have demonstrated for the first time that Lidars can remotely detected the volcanic CO2 flux from up to 4 km distance. Our novel CO2 flux observations are now opening novel horizons to quantification of global volcanic CO2 budgets, and are contributing a better comprehension of the mechanisms that drive “deeply” sourced paroxysmal explosions at basaltic volcanoes. At quiescent, hydrothermal volcanoes (e.g. Campi Flegrei), our novel Lidar-Based CO2 flux time-series have allowed us to infer a “deep” magmatic gas trigger for deformation (uplift) unrests that periodically interrupt their long-lasting repose periods.
Overall, cica 60 papers on indicixed journals have been published on BRIDGE-related science, and BRIDGE results have been disseminated at a variety of international meetings, schools and congresses.