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Zanon, Vittorio
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Zanon, Vittorio
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- PublicationRestrictedThe exceptional activity and growth of the Southeast Crater, Mount Etna (Italy), between 1996 and 2001(2006)
; ; ; ; ;Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Pecora, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Zanon, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; Between 1971 and 2001, the Southeast Crater was the most productive of the four summit craters of Mount Etna, with activity that can be compared, on a global scale, to the opening phases of the Pu‘u ‘Ō‘ō-Kūpaianaha eruption of Kīlauea volcano, Hawai‘i. The period of highest eruptive rate was between 1996 and 2001, when near-continuous activity occurred in five phases. These were characterized by a wide range of eruptive styles and intensities from quiet, non-explosive lava emission to brief, violent lava-fountaining episodes. Much of the cone growth occurred during these fountaining episodes, totaling 105 events. Many showed complex dynamics such as different eruptive styles at multiple vents, and resulted in the growth of minor edifices on the flanks of the Southeast Crater cone. Small pyroclastic flows were produced during some of the eruptive episodes, when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae. Fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry (including the growth of a shallow magma reservoir under the Southeast Crater), magma supply rates, and flank instability. During this period, volume calculations were made with the aid of GIS and image analysis of video footage obtained by a monitoring telecamera. Between 1996 and 2001, the bulk volume of the cone increased by ~36×106 m3, giving a total (1971– 2001) volume of ~72×106 m3. At the same time, the cone gained ~105 m in height, reaching an elevation of about 3,300 m. The total DRE volume of the 1996–2001 products was ~90×106m3. This mostly comprised lava flows (72×106 m3) erupted at the summit and onto the flanks of the cone. These values indicate that the productivity of the Southeast Crater increased fourfold during 1996–2001 with respect to the previous 25 years, coinciding with a general increase in the eruptive output rates and eruption intensity at Etna. This phase of intense summit activity has been followed, since the summer of 2001, by a period of increased structural instability of the volcano, marked by a series of important flank eruptions.283 41 - PublicationOpen AccessDynamics of low energy explosive activity at Stromboli volcano (Aeolian Islands, Italy)(2007-07-02)
; ; ; ;Zanon, V.; University of the Azores; University of the Azores, Ponta Delgada ;Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Pecora, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; Twenty low-energy (0.0077 0.625 kgs-1) explosions from the Northeast Crater of Stromboli Volcano, recorded by a thermal camera, were studied in detail to better understand their dynamics. Each single burst consists of three different jets of different material which come one after another: at first, cold vapour flashes above the crater, expands and then disappears within 0.6 s after the onset of the explosion, at a velocity of 40-113 ms-1. This air shock wave is immediately followed by the expansion of a jet of hot magmatic gas, at a velocity of 35-75 ms-1. Colder coarse tephra (bombs and scoriae) appear about 1.6-2 s after the onset of explosion, moving at a reduced velocity (28-60 ms-1). Further on, some of these data were utilized to calibrate a set of flow simulation in a 220-260-m-long conduit, which validates the model of slug flow for these kinds of eruptions. Finally, coupling all the collected data with the stratigraphy of the volcano, we hypothesized that a physical barrier might be responsible for the formation of slugs of gas and their ascent toward the surface at regular intervals. This barrier acts as a siphon and seems to be generated by the displacement of the upper conduit due to summit instability. This model justifies the ~constant interval between explosions, the insensitivity of this behavior to the occurrence of effusive episodes and highly explosive events, as well as the generation of fairly constant petrochemical characteristics of the magma which is commonly erupted, with time.127 149 - PublicationOpen AccessGeochemical processes in the roots of the Azores magmatic systems(2024)
; ; ; ; ; The Azores archipelago, situated east of the Mid-Atlantic Ridge, comprises volcanic islands arranged along sub-parallel spreading systems and rests on a thick oceanic crust. Magma is supplied directly from the roots of the volcanic systems. Located at or nearby the boundary between the crust and the mantle, they consist of mafic cumulates and mafic mush layers. This work focuses on tephra samples and a submarine lava younger than 40.000 years, collected from both central volcanoes and fissure zones. Our report details a new dataset of major, trace, and volatile elements analysed in glassy melt inclusions trapped in olivine (Fo75.8–85.6) which are extracted from cumulative bodies at the vicinity of the crust-mantle boundary. Their compositions cover a range from subalkaline to mildly alkaline basalt, and trachybasalt, which match those of Azores lavas. They registered a chemical evolution through fractional crystallisation of olivine alone, as well as olivine and clinopyroxene, as both the FeOt/MgO (1.4–3.1) and CaO/Al2O3 (0.4–1.0) ratios of the melt decrease. Incompatible element ratios of Zr (40–352 ppm), Ba (135–612 ppm), and Rb (5–77 ppm), as compared to Nb (5–82 ppm), exhibit variability within a limited but significant range of values. The ranges in the Nb/Zr, Ba/Nb and Rb/Nb ratios recorded by melt inclusions possibly reveal distinct geochemical sources (at least two), and mixing between partial melts as they move upward. The halogen signature is characteristic of the shallow mantle. The majority of melt inclusions show Cl/K ratio (0.06) similar to E-MORB, although some of them are comparable to N-MORB (Cl/K = 0.03). Their F/Nd ratio may achieve a rather high value (27.8).94 8 - PublicationRestrictedActive faults on the eastern flank of Etna volcano (Italy) monitored through soil radon measurements(European Geosciences Union, 2012-04)
; ; ; ; ; ;Neri, Marco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Giammanco, Salvatore; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ferrera, Elisabetta; Università degli Studi di Catania, Dip. Scienze della Terra ;Patanè, Giuseppe; Università degli Studi di Catania, Dip. Scienze della Terra ;Zanon, Vittorio; Centro de Vulcanologia e Avaliação de Riscos Geológicos - Universidade dos Açores; ; ; ; This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the unstable 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. In particular, the highest anomalies were found at the intersection between WNW-ESE and NW-SE -running faults. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. These maps revealed a progressive deepening of hypocenters from NW to SE, with the exception of a narrow zone in the central part of the area, with a roughly WNW-ESE direction. Also, the highest values of seismic energy were released during events in the southern and northwestern sectors of the area. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10 km 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 earthquake depth and intensity can give some hints on the source of gas and/or on fault dynamics. Lastly, an important spin-off of this study is the recognition of some areas where radon activity was so high (>50000 Bq/m3) that it may represent a potential hazard to the local population. In fact, radon is the leading cause of lung cancer after cigarette smoke for long exposures and, due to its molecular weight, it accumulates in underground rooms or in low ground, particularly where air circulation is low or absent. In the investigated area this risk is real, as it is inhabited by thousands of people who reside there all year long. Therefore, this study serves as a starting point for the assessment of radon hazard in the Mt. Etna area, considering both spatial and temporal changes in soil radon emissions depending on the presence of faults and/or the occurrence of seismic activity.189 14 - PublicationRestrictedSoil radon measurements as a potential tracer of tectonic and volcanic activity(2016-04-15)
; ; ; ; ; ; ; ;Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ferrera, E.; Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania ;Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Currenti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Cirrincione, R.; Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania ;Patanè, G.; Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania ;Zanon, V.; Centro de Vulcanologia e Avaliação de Riscos Geológicos, Universidade dos Açores, Ponta Delgada, Portugal; ; ; ; ; ; In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.705 6 - PublicationRestrictedHg and CO2 emissions from soil diffuse degassing and fumaroles at Furnas Volcano (São Miguel Island, Azores): Gas flux and thermal energy output(2018)
; ; ; ; ; ; ; ; ; ; ;Gaseous elemental mercury (Hg0 g or GEM) and CO2 are emitted from active hydrothermal systems in volcanic areas mostly through diffuse degassing. Here, data from about 400 simultaneous measurements of soil GEM and CO2 flux performed within the caldera of Furnas Volcano, São Miguel Island (Azores) are discussed for the first time. This survey aimed at providing a new insight into the origin and magnitude of GEM in the investigated hydrothermal/volcanic environment and its relation with CO2 release. The distribution of GEM and CO2 emissions over an area of about 0.04km2 are correlated with soil temperature, and measurements have provided total CO2 and GEM output of 39td−1 and 1.8×10−6td−1, respectively. These results are similar to the emission from currently active volcanic/hydrothermal areas elsewhere, as well as from important non-volcanic areas, such as Sulphur Bank Mercury Mine (California, USA) and Idrija Mercury Mine (Slovenia, EU), pointing out the relevance of diffuse degassing processes at Furnas Volcano. Atmospheric spot measurements in the most vigorous fumarole vents of the geothermal field have shown that the fumarolic GEM contribution (9.2 ×10−7td−1) represents a minor fraction of the total (fumarolic+diffusive) GEM output (2.7 ×10−6td−1) for the study area of this volcano. Basing upon the integration of the hydrothermal CO2 released and the H2O/CO2 ratio in the fumarolic gas, we have also estimated the thermal energy release associated with diffuse degassing at Furnas Volcano. Our estimates are ∼7.8MW and 9.8MW, respectively for Furnas Lake and Furnas Village fumaroles.42 1 - PublicationOpen AccessThe fumarolic CO2 output from Pico do Fogo volcano (Cape Verde)(2020-10)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Pico do Fogo volcano, in the Cape Verde Archipelago off the western coasts of Africa, has been the most active volcano in the Macaronesia region in the Central Atlantic, with at least 27 eruptions during the last 500 years. Between eruptions fumarolic activity has been persisting in its summit crater, but limited information exists for the chemistry and output of these gas emissions. Here, we use the results acquired during a field survey in February 2019 to quantify the quiescent summit fumaroles’ volatile output for the first time. By combining measurements of the fumarole compositions (using both a portable Multi-GAS and direct sampling of the hottest fumarole) and of the SO2 flux (using near-vent UV Camera recording), we quantify a daily output of 1060±340 tons CO2, 780±320 tons H2O, 6.2±2.4 tons H2S, 1.4±0.4 tons SO2 and 0.05±0.022 tons H2. We show that the fumarolic CO2 output from Pico do Fogo exceeds (i) the time-averaged CO2 release during 2015-type recurrent eruptions and (ii) is larger than current diffuse soil degassing of CO2 on Fogo Island. When compared to worldwide volcanoes in quiescent hydrothermal-stage, Pico do Fogo is found to rank among the strongest CO2 emitters. Its substantial CO2 discharge implies a continuous deep supply of magmatic gas from the volcano’s plumbing system (verified by the low but measurable SO2 flux), that becomes partially affected by water condensation and sulphur scrubbing in fumarolic conduits prior to gas exit. Variable removal of magmatic H2O and S accounts for both spatial chemical heterogeneities in the fumarolic field and its CO2-enriched mean composition, that we infer at 64.1±9.2 mol. % H2O, 35.6±9.1 mol. % CO2, 0.26±0.14 mol. % total Sulfur (St), and 0.04±0.02 mol. % H2.924 99 - PublicationOpen AccessGround displacement assessment on Pico Volcano, Azores, by multitemporal InSAR dataInterpreting the signal deriving from interferometric synthetic aperture radar (InSAR) analyses in volcanic islands, characterized by strong regional deformations and recurrent seismicity, is a complex and challenging issue. In these zones, the secondary effects connected to the SAR acquisition system cannot be neglected, and it is important to consider that delay phenomena of the electromagnetic waves, due to the propagation in the tropospheric layer and loss of SAR coherence because of dense vegetation, could affect the interferometric phase. This work focuses on Pico, the second largest and the youngest island of the Azores Archipelago (North Atlantic Ocean). This island consists of a central volcano and a fissure zone. These systems are inactive but recurrent microseismicity occurs in a rock volume host- ing a partially crystallized magma storage system, which fed the recent activity of the central volcano. In the same area affected by microseismicity, the main volcanic edifice shows flank instability. All these elements support the hypothesis of possible reactivation of the shallow magmatic system. Aiming to check potential active ground displacements and to define their source, we collected two datasets of C-band Sentinel-1 SAR data, both in descending and ascending acquisition geometry, from January, 2017, to December, 2020. The application of the small baseline subset method of differential InSAR allowed drawing the mean ground velocity maps over the island and the displacement time series, useful to understand the defor- mation evolution. InSAR data only evidence areas affected by small-scale subsidence at the cinder cones of the fissure zone and along the southeastern slope of Pico volcano, where local debris flows activate during rainy periods.
36 12 - PublicationOpen AccessEvolution of the volcanic plumbing systemof Alicudi (Aeolian Islands - Italy): evidence from fluid and melt inclusionsin quartz xenoliths(2004)
; ; ; ; ;Bonelli, R.; Dipartimento di Scienze della Terra, Università degli Studi di Siena, Siena, Italy ;Frezzotti, M. L.; Istituto di Geologia Ambientale e Geoingegneria (IGAG) - CNR, Roma, Italy ;Zanon, V.; Dipartimento di Scienze della Terra, Università degli Studi di Perugia, Perugia, Italy ;Peccerillo, A.; Dipartimento di Scienze della Terra, Università degli Studi di Perugia, Perugia, Italy; ; ; Quartz-rich xenoliths in lavas (basalts to andesites; 90-30 ka) from Alicudi contain abundant melt and fluid inclusions. Two generations of CO2-rich fluid inclusions are present in quartz-rich xenolith grains: early (Type I) inclusions related to partial melting of the host xenoliths, and late Type II inclusions related to the fluid trapping during xenolith ascent. Homogenisation temperatures of fluid inclusions correspond to two density intervals: 0.93-0.68 g/cm3 (Type I) and 0.47-0.26 g/cm3 (Type II). Early Type I fluid inclusions indicate trapping pressures around 6 kbar, which are representative for the levels of partial melting of crustal rocks and xenolith formation. Late Type II fluid inclusions show lower trapping pressures, between 1.7 kbar and 0.2 kbar, indicative for shallow magma rest and accumulation during ascent to the surface. Data suggest the presence of two magma reservoirs: the first is located at lower crustal depths (about 24 km), site of fractional crystallization, mixing with source derived magma, and various degrees of crustal assimilation. The second magma reservoir is located at shallow crustal depths (about 6 km), the site where magma rested for a short time before erupting.154 333 - PublicationOpen AccessUn metodo per riconoscere faglie attive sepolte mediante misure areali di radon dal suolo(2014-04)
; ; ; ; ; ;Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ferrera, E.; Università degli Studi di Catania, Dipartimento di Scienze della Terra, Catania ;Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Patanè, G.; Università degli Studi di Catania, Dipartimento di Scienze della Terra, Catania ;Zanon, V.; Centro de Vulcanologia e Avaliação de Riscos Geológicos, Universidade dos Açores, Ponta Delgada, Portogallo; ; ; ; Lo studio riassume i risultati di una campagna di misure geochimiche e strutturali condotte nel 2004 (Neri et al., 2011) e riguarda la misurazione delle emissioni di gas radon e thoron dal suolo effettuate lungo il fianco orientale dell’Etna, in una zona caratterizzata dalla presenza di numerose faglie attive. Le elaborazioni statistiche effettuate hanno permesso di riconoscere soglie di anomalia dei dati geochimici, nonché la produzione di mappe di distribuzione che hanno evidenziato una significativa correlazione spaziale tra le anomalie riscontrate e i principali lineamenti tettonici. Entrambe le anomalie di radon e thoron si trovavano in aree interessate da sismicità relativamente profonda, in particolare in corrispondenza delle zone di intersezione tra faglie differentemente orientate. Questo studio conferma che la mappatura della distribuzione di gas radon e thoron dal suolo può rivelare la presenza di faglie nascoste da coperture recenti, o faglie che non sono chiaramente visibili in superficie.223 471
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