Tommaso Caltabiano

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.

SO2 flux measurements at Mount Etna (Sicily)

Since 1987, over 220 measurements of the SO2 flux at Mount Etna have been carried out using a correlation spectrometer (COSPEC) with different measuring techniques (mainly with COSPEC mounted on a ground-based vehicle). This paper reports and analyzes the data obtained between October 1987 and December 1991. During this period, three distinct time intervals characterized by particular SO2 emission patterns were identified. The first interval (A) showed a mean SO2 flux of 5500 t/d associated with relatively quiet summit crater eruptive activity. The second interval (B) included two eruptive periods, September–October 1989 and January–February 1990, associated with high fluxes reaching 10,000–25,000 t/d. The third interval (C) started in concert with a regional earthquake (December 13, 1990) and showed first a decrease and then an increase of SO2 emissions before the onset of the major 1991–1993 flank eruption. Analysis of the data reveals a cyclic pattern to the SO2 emissions over prolonged periods; a nearly constant supply of SO2 from the volcanos main feeder system, especially evident in the long term; a two- to fivefold increase above mean flux values (from 10,000 to 25,000 t/d) when occurring with paroxysmal eruptive activity; and minimal flux values (∼1000 t/d) about 1 month prior to important eruptive events.

Deformation and eruptions at Mt. Etna (Italy): A lesson from 15 years of observations

This work was partly funded by INGV and the Italian DPC and was supported by ASI, the Preview Project and CRdC-AMRA. DPC-INGV Flank project providing the funds for the publication fees.

SO2∶HCl ratios in the plumes from Mt. Etna and Vulcano determined by Fourier Transform Spectroscopy

Volcanic gases have important climatic and environmental effects, and provide insights into magmatic processes. Direct sampling of volcanic gases is inherently difficult and often hazardous. Here, the authors report the results of long path measurements of SO{sub 2} and HCl from Mt. Etna and Vulcano (Italy) obtained by active mode Fourier Transform InfraRed (FTIR) spectroscopy. Spectra recorded in September 1994 over path lengths of up to 2 km indicate SO{sub 2}:HCl ratios of 3-5:1 for Etna, and 0.7-1.4:1 for Vulcano, consistent with their different styles of activity. Combined with contemporaneous Correlation Spectrometer (COSPEC) SO{sub 2} flux measurements, these ratios indicate an HCl flux for Etna of about 1700 t/d (about 16% of the present global anthropogenic flux) and for Vulcano of about 13 t/d. They also report the first remote spectroscopic detection of volcanic SiF{sub 4}. 17 refs., 3 figs., 1 tab.

Volcanic gas emissions from the summit craters and flanks of Mt. Etna, 1987-2000

In the last 13 years gas emissions from both the summit and the flanks of Mount Etna volcano have been monitored using remote sensing techniques (COSPEC, and FTIR since 2000) and on-site monitoring devices. The SO 2 flux variations (600 to 25,000 Mg/day) indicated: (i) low values coinciding with deep seismicity prior to eruptions or/and preceding increases in summit volcanic activity; (ii) increasing trends tracking the ascent of fresh magma within the shallow feeding system and whose rate seems proportional to the speed of magma rise; (iii) decreasing trends related to progressive degassing of magma batches; (iv) an imbalance between the amount of magma erupted and that which contributed the SO 2 emission (∼ 13 % of the degassing magma having been erupted during the studied period), implying that magma degassing is dominantly intrusive; (v) a seasonal component, probably due to variations in solar zenith angle, meteorological parameters and, possibly, tidal forces.FTIR monitoring allowed to recognize significant variations of SO 2 /HCl and SO 2 /HF ratios in the volcanic plume which, combined with COSPEC data, provided new insight into the dynamics of ascent and degassing of discrete magma bodies. Strong variations in CO 2 -rich soil degassing are interpreted as markers of gradual magma ascent from great depth (>10 km) to the upper (<5 km) feeding system of Mt. Etna. These changes appear to precede increases in SO 2 plume flux at the craters and, so, provide additional constraints upon the interpretation of COSPEC data and the modeling of magma rise at that volcano.

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.

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.