G. G. Salerno

Effusive to explosive transition during the 2003 eruption of Stromboli volcano

The persistent explosive activity of Stromboli volcano (Italy) ceased in December 2002 and correlated with the onset of a seven-month-long effusive eruption on the volcano flank from new vents that opened just below the summit craters. We intensively monitored this effusive event, collecting and interpreting, in real time, an extensive multiparametric geophysical data set. The resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical Strombolian activity. We present a direct link between gas flux, magma volume flux, and seismicity, supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity. This insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity.

Sulphur dioxide fluxes from Mount Etna, Vulcano, and Stromboli measured with an automated scanning ultraviolet spectrometer

We report here SO 2 flux measurements for the southern Italian volcanoes: Mount Etna, Vulcano, and Stromboli made in July 2002 from fixed positions, using an automated plume scanning technique. Spectral data were collected using a miniature ultraviolet spectrometer, and SO 2 column amounts were derived with a differential optical absorption spectroscopy evaluation routine. Scanning through the plume was enabled by a 45° turning mirror affixed to the shaft of a computer controlled stepper motor, so that scattered skylight from incremental angles within the horizon-to-horizon scans was reflected into the field of view of the spectrometer. Each scan lasted ∼5 min and, by combining these data with wind speeds, average fluxes of 940, 14, and 280 Mg d - 1 were obtained for Etna, Vulcano, and Stromboli, respectively. For comparative purposes, conventional road and airborne traverses were also made using this spectrometer, yielding fluxes of 850, 17, and 210 Mg d - 1 . The automated scanning technique has the advantage of obviating the need for time-consuming traverses underneath the plume and is well suited for longer-term telemetered deployments to provide sustained high time resolution flux data.

A total volatile inventory for Masaya Volcano, Nicaragua

NERC project “Magma dynamics at persistently degassing basaltic volcanoes: A novel approach to linking volcanic gases and magmatic volatiles within a physical model” (NE/F004222/1 and NE/F005342/1).

Crater Gas Emissions and the Magma Feeding System of Stromboli Volcano

Quiescent and explosive magma degassing at Stromboli volcano sustains high-temperature crater gas venting and a permanent volcanic plume which constitute key sources of information on the magma supply and dynamics, the physical processes controlling the explosive activity and, more broadly, the volcano feeding system. The chemical composition and the mass output of these crater emissions (gases, trace metals, radioactive isotopes) were measured using different methodologies: within-plume airborne measurements, ground-based plume filtering, and/or in situ analysis, remote UV and open-path Fourier transform infrared absorption spectroscopy. The results obtained, summarized in this paper, demonstrate a primary control of the magmatic gas phase on the eruptive regime and the budget of the volcano. The large excess gas discharge, compared with the lava extrusion rate, and the source depth of slug-driven Strombolian explosions evidence extensive separate gas transfer across the volcano conduits, promoted by the high gas content (vesicularity) and then permeability of the shallow basaltic magma. Combined with data for volatiles dissolved in olivine-hosted melt inclusions, the results provide updated constraints for the magma supply rate (similar to 0.3 m(3) s(-1) average), the ratio of intrusive versus extrusive magma degassing (similar to 15), and the amount of unerupted degassed magma that should be convectively cycled back in conduits and accumulated beneath the volcano over time (similar to 0.25 km(3) in the last three decades). The results also provide insight into the possible triggering mechanism of intermittent paroxysmal explosions and the geochemical signals that might allow forecasting these events in the future.

Multiparametric study of the February-April 2013 paroxysmal phase of Mt. Etna New South-East crater

European FP7 MED-SUV (MEditerranean SUpersite Volcanoes). Grant Number: 308665 European Research Council European FP7 (FP/2007-2013)/ERC. Grant Number: 279802 SIGMA (Sistema Integrato di sensori in ambiente cloud per la Gestione Multirischio Avanzata)

A comprehensive interpretative model of slow slip events on Mt. Etna's eastern flank

Starting off from a review of previous literature on kinematic models of the unstable eastern flank of Mt. Etna, we propose a new model. The model is based on our analysis of a large quantity of multidisciplinary data deriving from an extensive and diverse network of INGV monitoring devices deployed along the slopes of the volcano. Our analysis had a twofold objective: first, investigating the origin of the recently observed slow-slip events on the eastern flank of Mt. Etna; and second, defining a general kinematic model for the instability of this area of the volcano. To this end, we investigated the 2008–2013 period using data collected from different geochemical, geodetic, and seismic networks, integrated with the tectonic and geologic features of the volcano and including the volcanic activity during the observation period. The complex correlations between the large quantities of multidisciplinary data have given us the opportunity to infer, as outlined in this work, that the fluids of volcanic origin and their interrelationship with aquifers, tectonic and morphological features play a dominant role in the large scale instability of the eastern flank of Mt. Etna. Furthermore, we suggest that changes in the strain distribution due to volcanic inflation/deflation cycles are closely connected to changes in shallow depth fluid circulation. Finally, we propose a general framework for both the short and long term modeling of the large flank displacements observed.

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.

“Failed” eruptions revealed by pattern classification analysis of gas emission and volcanic tremor data at Mt. Etna, Italy

Abstract During the spring of 2007, paroxysmal activity occurred at the Southeast Crater of Mt. Etna, always associated with sharp rises in the amplitude of the volcanic tremor. Activity ranged from strong Strombolian explosions to lava fountains coupled with copious emission of lava flows and tephra. During inter-eruptive periods, recurrent seismic unrest episodes were observed in the form of temporary enhancements of the volcanic tremor amplitude, but they did not culminate in eruptive activity. Here, we present the results of an analysis of these inter-eruptive periods by integrating seismic volcanic tremor, in-soil radon, plume SO2 flux, and thermal data. SO2 flux and thermal radiation are envisaged as the “smoking gun,” and certifying that changes in seismic or radon data can be considered as volcanogenic. Short-term changes were investigated by pattern classification based on Kohonen maps and fuzzy clustering on volcanic tremor, radon, and ambient parameters (pressure and temperature). Our results unveil “failed” eruptions between February and April 2007 that are explained as ascending magma batches, which triggered repeated episodes of gas pulses and rock fracturing, but that failed to reach the surface.

Dome-like behaviour at Mt. Etna: The case of the 28 December 2014 South East Crater paroxysm

On the 28 December 2014, a violent and short paroxysmal eruption occurred at the South East Crater (SEC) of Mount Etna that led to the formation of huge niches on the SW and NE flanks of the SEC edifice from which a volume of ~3 × 106 m3 of lava was erupted. Two basaltic lava flows discharged at a rate of ~370 m3/s, reaching a maximum distance of ~5 km. The seismicity during the event was scarce and the eruption was not preceded by any notable ground deformation, which instead was dramatic during and immediately after the event. The SO2 flux associated with the eruption was relatively low and even decreased few days before. Observations suggest that the paroxysm was not related to the ascent of volatile-rich fresh magma from a deep reservoir (dyke intrusion), but instead to a collapse of a portion of SEC, similar to what happens on exogenous andesitic domes. The sudden and fast discharge eventually triggered a depressurization in the shallow volcano plumbing system that drew up fresh magma from depth. Integration of data and observations has allowed to formulate a novel interpretation of mechanism leading volcanic activity at Mt. Etna and on basaltic volcanoes worldwide.

Heat and SO2 Emission Rates at Active Volcanoes - The Case Study of Masaya, Nicaragua

The necessity of understanding volcanic phenomena so as to assist hazard assessment and risk management, has led to development of a number of techniques for the tracking of volcanic events so as to support forecasting efforts. Since 1980s scientific community has progressively drifted research and surveillance at active volcanoes by integrated approach. Nowadays, volcano observatories over the world record and integrate real or near-real time data for monitoring and understanding volcano behaviour. Among the geophysical, geochemical, and volcanological parameters, the tracking of temperature changes at several volcanic features (e.g. open-vent systems, eruptive vents, fumaroles) and variations in sulphur dioxide flux and concentration at volcanic plumes are key factors for studying and monitoring active volcanoes.