G. Giudice

Forecasting Etna eruptions by real-time observation of volcanic gas composition

It is generally accepted, but not experimentally proven, that a quantitative prediction of volcanic eruptions is possible from the evaluation of volcanic gas data. By discussing the results of two years of real-time observation of H2O, CO2, and SO2 in volcanic gases from Mount Etna volcano, we unambiguously demonstrate that increasing CO2/SO2 ratios can allow detection of the pre-eruptive degassing of rising magmas. Quantitative modeling by the use of a saturation model allows us to relate the pre-eruptive increases of the CO2/SO2 ratio to the refilling of Etnas shallow conduits with CO2-rich deep-reservoir magmas, leading to pressurization and triggering of eruption. The advent of real-time observations of H2O, CO2, and SO2, combined with well-constrained models of degassing, represents a step forward in eruption forecasting.

Unmanned aerial vehicle measurements of volcanic carbon dioxide fluxes

[i] We report the first measurements of volcanic gases with an unmanned aerial vehicle (UAV). The data were collected at La Fossa crater, Vulcano, Italy, during April 2007, with a helicopter UAV of 3 kg payload, carrying an ultraviolet spectrometer for remotely sensing the SO 2 flux (8.5 Mg d- 1 ), and an infrared spectrometer, and electrochemical sensor assembly for measuring the plume CO 2 /SO 2 ratio; by multiplying these data we compute a CO 2 flux of 170 Mg d -1 . Given the deeper exsolution of carbon dioxide from magma, and its lower solubility in hydro-thermal systems, relative to SO 2 , the ability to remotely measure CO 2 fluxes is significant, with promise to provide more profound geochemical insights, and earlier eruption forecasts, than possible with SO 2 fluxes alone: the most ubiquitous current source of remotely sensed volcanic gas data.

Excess volatiles supplied by mingling of mafic magma at an andesite arc volcano

We present the results of a study of volcanic gases at Soufriere Hills Volcano, Montserrat, which includes the first spectroscopic measurements of the major gas species CO2 and H2S at this volcano using a Multisensor Gas Analyzer System (MultiGAS) sensor. The fluxes of CO2 and H2S were 640.2750 t/d and 84.266 t/d, respectively, during July 2008, during a prolonged eruptive pause. The flux of CO2 is similar to estimates for the entire arc from previous geochemical studies, while the measured H2S flux significantly alters our interpretation of the sulphur budget for this volcano. The fluxes of both sulphur and carbon show considerable excesses over that which can be supplied by degassing of erupted magma. We demonstrate, using thermodynamic models and published constraints on preeruptive volatile concentrations, that the gas composition and fluxes are best modeled by mixing between (1) gases derived from isobaric quenching of mafic magma against cooler andesite magma at depth and (2) gases derived from shallower rhyolitic interstitial melt within the porpyritic andesite. The escape of deep-derived gases requires pervasive permeability or vapor advection extending to several kilometers depth in the conduit and magma storage system. These results provide more compelling evidence for both the contribution of unerupted mafic magma to the volatile budget of this andesitic arc volcano and the importance of the intruding mafic magma in sustaining the eruption. From a broader perspective, this study illustrates the importance and role of underplating mafic magmas in arc settings. These magmas play an important role in triggering and sustaining eruptions and contribute in a highly significant way to the volatile budget of arc volcanoes. Copyright

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring

Abstract Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur‐rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8–10 km deep, whereas the shallow magmatic gas source is at ~3–5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high‐temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

An Overview of the Volcan Project: An UAS for Exploration of Volcanic Environments

This paper presents an overview of the Volcan Project, whose goal is the realization of an autonomous aerial system able to perform aerial surveillance of volcanic areas and to analyze the composition of gases inside volcanic plumes. There are increasing experimental evidences that measuring the chemical composition of volcanic gases can contribute to forecast volcanic eruptions. However, in situ gas sampling is a difficult operation and often exposes scientists to significant risks. At this aim, an Unmanned Aircraft System equipped with remote sensing technologies, able to sense the plume in the proximity of the crater, has been developed. In this paper, the aerial platform will be presented, together with the problems related to the flight in a hard scenario like the volcanic one and the tests performed with the aim of finding the right configuration for the vehicle. The developed autonomous navigation system and the sensors unit for gas analysis will be introduced; at the end, several experimental results will be described.

Chapter 16 Pre-eruptive vapour and its role in controlling eruption style and longevity at Soufrière Hills Volcano

Abstract We use volatiles in melt inclusions and nominally anhydrous phenocrysts, with volcanic gas flux and composition, and textural analysis of mafic inclusions to estimate the mass of exsolved vapour prior to eruption at Soufrière Hills Volcano (SHV). Pre-eruptive andesite coexists with exsolved vapour comprising 1.6–2.4 wt% of the bulk magma. The water content of orthopyroxenes indicates a zone of magma storage at pressures of approximately 200–300 MPa, whereas melt inclusions have equilibrated at shallower pressures. Inclusions containing >3 wt% H2O are enriched in CO2, suggesting flushing with CO2-rich gases. Intruding mafic magma contains >8 wt% H2O at 200–300 MPa. Rapid quenching is accompanied by crystallization and vesiculation. Upon entrainment into the andesite, mafic inclusions may undergo disaggregation, where expansion of volatiles in the interior overcomes the strength of the crystal frameworks, thereby recharging the vapour content of the andesite. Exsolved vapour may amount to 4.3–8.2 vol% at 300 MPa, with implications for eruption longevity and volume; we estimate the magma reservoir volume to be 60–200 km3. Exsolved vapour may account for the small volume change at depth during eruptions from geodetic models, and has implications for magma flow: exsolution is likely to be in equilibrium during rapid magma ascent, with little nucleation of new bubbles.

Architecture of a UAV for volcanic gas sampling

This paper describes the architecture of a UAV designed to study the composition of gas inside volcanic plumes. The main aim of the system is that of flying inside the plume (volcanic cloud) to directly analyze the concentration of the main components of the fumes. The system must be capable of flying autonomously at up to 4000m altitude with a payload of 5Kg using electric motors, to avoid contaminations with the gas sampling system, at a cruise speed of 40km/h. The complete architecture is presented together with the HMI: this can be used both for path planning and for navigation

New evidence of CO2 soil degassing anomalies on Piton de la Fournaise volcano and the link with volcano tectonic structures

INSU (CNRS) and La Reunion Prefecture (Projet pour la quantification de l’alea volcanique a La Reunion)

“Hardware in the Loop” Tuning for a Volcanic Gas Sampling UAV

Significant advances have been made in recent years in volcanic eruption forecasting and in understanding the behaviour of volcanoes. A major requirement is improvement in the collection of field data using innovative methodologies and sensors. Collected data are typically used as input for computer simulations of volcanic activity, to improve forecasts for longlived volcanic phenomena, such as lava flow eruptions and sand-rain.

Emission of gas and atmospheric dispersion of SO2 during the December 2013 eruption at San Miguel volcano (El Salvador, Central America)

San Miguel volcano, El Salvador, erupted on 29 December 2013, after a 46year period characterized by weak activity. Prior to the eruption a trend of increasing SO2 emission rate was observed, with all values measured after mid-November greater than the average value of the previous year (similar to 310td(-1)). During the eruption, SO2 emissions increased from the level of similar to 330td(-1) to 2200td(-1), dropping after the eruption to an average level of 680td(-1). Wind measurements and SO2 emission rates during the preeruptive, syneruptive, and posteruptive stages were used to model SO2 dispersion around the volcano. Atmospheric SO2 concentration exceeded the dangerous threshold of 5 ppm in the crater region and in some sectors with medium elevation of the highly visited volcanic cone. Combining the SO2 emission rate with measured CO2/SO2, HCl/SO2, and HF/SO2 plume gas ratios, we estimate the CO2, HCl, and HF outputs for the first time on this volcano.