Salvatore Giammanco

Continuous soil radon monitoring during the July 2006 Etna eruption

[1] Continuous soil radon monitoring was carried out near the Southeast Crater (SEC) of Mt. Etna during the 10-day July 2006 Strombolian-effusive eruption. This signal was compared with simultaneously acquired volcanic tremor and thermal radiance data. The onset of explosive activity and a lava fountaining episode were preceded by some hours with increases in radon soil emission by 4–5 orders of magnitude, which we interpret as precursors. Minor changes in eruptive behavior did not produce significant variations in the monitored parameters. The remarkably high radon concentrations we observed are unprecedented in the literature. We interpret peaks in radon activity as due primarily to microfracturing of uranium-bearing rock. These observations suggest that radon measurements in the summit area of Etna are strongly controlled by the state of stress within the volcano and demonstrate the usefulness of radon data acquisition before and during eruptions. Citation: Neri, M., B. Behncke, M. Burton, G. Galli, S. Giammanco, E. Pecora, E. Privitera, and D. Reitano (2006), Continuous soil radon monitoring during the July 2006 Etna eruption, Geophys. Res. Lett., 33, L24316, doi:10.1029/ 2006GL028394.

Degassing of SO2 and CO2 at Mount Etna (Sicily) as an indicator of pre-eruptive ascent and shallow emplacement of magma

Abstract We studied soil CO 2 emissions together with crater SO 2 fluxes from Mt Etna during the period July 1997 to March 1999. This period was characterized by high levels of volcanic activity, and ended with the onset of a 10xa0month-long sub-terminal eruption on February 4, 1999. Soil CO 2 degassing was measured at two sites (P39 on the lower SW flank of Etna and P78 on the E flank) known for being connected to deep faults that allow the escape of magmatic gas. Site P39 is inferred to drain gas from a deep (>15xa0km) magma reservoir, whereas site P78 is connected to a shallower (5–10xa0km) reservoir. Based on the temporal variations of measured soil CO 2 and crater SO 2 data, five intervals of anomalous degassing were recognized. Each of them is interpreted as due to massive gas release from a magma batch that is moving toward the surface. The time lag between the occurrence of degassing anomalies of CO 2 and those of SO 2 agrees well with the different depth of exsolution of the two gases. Our data also indicate a step-like migration of magma to the surface, which bears on the existence of at least three different temporary storage levels within Etnas feeder system. Lastly, the observed anomalies preceded by months to weeks increases in the summit activity of Mt Etna, including the February 4, 1999 eruption. Comparison between the amounts of degassing magma during each interval of anomalous degassing, based on SO 2 fluxes, and erupted volumes of lava during the same periods, seems to indicate that the 1999 eruption was largely fed by magma that started entering the upper feeder system of Etna about 1xa0year earlier.

Measurements of 220Rn and 222Rn and CO2 emissions in soil and fumarole gases on Mt. Etna volcano (Italy): Implications for gas transport and shallow ground fracture

This work was funded by the Istituto Nazionale di nGeofisica e Vulcanologia (S.G., M.N.) and by the Dipartimento nper la Protezione Civile (Italy), projects V3_6/28-Etna n(M.N.) and V5/08-Diffuse degassing in Italy (S.G.), and NSF nEAR 063824101 (K.W.W.S.).

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.

Paroxysmal summit activity at Mt. Etna (Italy) monitored through continuous soil radon measurements

[1]xa0Soil radon emissions have been proved as a useful tool for predicting earthquakes and volcanic eruptions and furthermore aided in determining the location of active faults. Continuous radon monitoring was carried out near Southeast Crater of Mt. Etna in September–November 1998, during a period of frequent eruptive episodes at that crater. Radon anomalies were detected when eruptive episodes and the accompanying volcanic tremor became increasingly intense: no anomalies in radon activity were observed during the first five, and weaker, eruptive episodes, whereas significant spikes in radon activity preceded the latter five episodes by ≥46 hours. This probably reflects increased gas leakage through fractures intersecting the shallow plumbing system, as gas pressure in the Southeast Crater conduit became higher with time. Radon monitoring thus might serve to better understand eruptive mechanisms and possible precursors, making further studies in this field a promising perspective.

Dynamics of a lava fountain revealed by geophysical, geochemical and thermal satellite measurements: The case of the 10 April 2011 Mt Etna eruption

[1]xa0Geophysical (tilt, seismic tremor and gravity signals), geochemical (crater SO2flux) and infrared satellite measurements are presented and discussed to track the temporal evolution of the lava fountain episode occurring at Mt Etna volcano on 10 April 2011. The multi-disciplinary approach provides insight into a gas-rich magma source trapped in a shallow storage zone inside the volcano edifice. This generated the fast ascending gas-magma dispersed flow feeding the lava fountain and causing the depressurization of a deeper magma storage. Satellite thermal data allowed estimation of the amount of erupted lava, which, summed to the tephra volume, yielded a total volume of erupted products of about 1 × 106 m3. Thanks to the daylight occurrence of this eruptive episode, the SO2 emission rate was also estimated, showing a degassing cycle reaching a peak of 15,000 Mg d−1 with a mean daily value of ∼5,700 Mg d−1. The SO2 data from the previous fountain episode on 17–18 February to 10 April 2011, yielded a cumulative degassed magma volume of about ∼10.5 × 106 m3, indicating a ratio of roughly 10:1 between degassed and erupted volumes. This volumetric balance, differently from those previously estimated during different styles of volcanic activities with long-term (years) recharging periods and middle-term (weeks to months) effusive eruptions, points toward the predominant role played by the gas phase in generating and driving this lava fountain episode.

Magmatic Gas Leakage at Mount Etna (Sicily, Italy): Relationships with the Volcano‐Tectonic Structures, the Hydrological Pattern and the Eruptive Activity.

In this paper we provide a review of chemical and isotopic data gathered over the last three decades on Etna volcanos fluid emissions and we present a synthetic framework of their spatial and temporal relationships with the volcano-tectonic structures, groundwater circulation and eruptive activity. We show that the chemistry, intensity and spatial distribution of gas exhalations are strongly controlled by the main volcano-tectonic fault systems. The emission of mantle-derived magmatic volatiles, supplied by deep to shallow degassing of alkali-hawaiitic basalts, persistently occurs through the central conduits, producing a huge volcanic plume. The magmatic derivation of the hot gases is verified by their He, C and S isotopic ratios. Colder but widespread emanations of magma-derived CO 2 and He also occur through the flanks of the volcano and through aquifers, mainly concentrated within two sectors of the south-southwest (Paterno-Belpasso) and eastern (Zafferana) flanks. In these two peripheral areas, characterized by intense local seismicity and gravity highs, magma-derived CO 2 and helium are variably diluted by shallower crustal-derived fluids (organically-derived carbon, radiogenic helium). Thermal and geochemical anomalies recorded in groundwaters and soil gases within these two areas prior to the 1991-1993 eruption are consistent with an input of hot fluids released by ascending magma. Magmatic fluids interacted with the shallow aquifers, modifying their physico-chemical conditions, and led to strong variations of the soil CO 2 flux. In combination with routine survey of the crater plume emissions, geochemical monitoring of remote soil gases and groundwaters thus contributes to forecasting Etnas eruptions.

New evidence for the form and extent of the Pernicana Fault System (Mt. Etna) from structural and soil–gas surveying

A multidisciplinary study based on structural and soil–gas surveys was carried out in order to investigate the relationship between soil CO2 degassing and the tectonic setting of the lower northeastern flank of Mt. Etna volcano. The results show that anomalous soil CO2 emissions occur mainly along faults trending WNW–ESE and also where these faults intersect the other main fault set (trending NE–SW) that displaces the study area. In particular, anomalies in CO2 degassing were revealed both along the Pernicana Fault and along another fault (Fiumefreddo Fault) which may represent the prolongation of the former towards the Ionian Sea coast. In the areas where these structures show evident surface faulting, they are all characterised by left-lateral displacements and aseismic creep behaviour. Furthermore, the geochemical survey revealed that these faults join in an area devoid of geological evidence of surface faulting and continue underneath an apparently unfaulted alluvial cover near the coastline. In the light of these findings, we suggest that the Pernicana and Fiumefreddo Faults are discrete segments of a near continuous left-lateral shear zone affecting the whole north-eastern flank of Mt. Etna as far as the Ionian coast.

Spatial distribution of soil radon as a tool to recognize active faulting on an active volcano: The example of Mt. Etna (Italy)

This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the eastern flank of Mt. Etna, in a zone characterized by the presence of numerous seismogenic and aseismic faults. The statistical treatment of the geochemical data allowed recognizing anomaly thresholds for both parameters and producing distribution maps that highlighted a significant spatial correlation between soil gas anomalies and tectonic lineaments. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10xa0km depth) seismic activity, while less evident correlation was found between soil gas anomalies and the released seismic energy. This study confirms that mapping the distribution of radon and thoron in soil gas can reveal hidden faults buried by recent soil cover or faults that are not clearly visible at the surface. The correlation between soil gas data and earthquakes depth and intensity can give some hints on the source of gas and/or on fault dynamics.

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.