Tephrostratigraphy of the last 2 ka activity of Etna volcano

Stratigraphic and facies analysis, conducted in the 90’s, on the pyroclastic successions blanking the Etna volcano flanks permitted the reconstruction of the last 100 ka tephrostratigraphic record of the volcano explosive activity. During the Holocene, several strong explosive events occurred, including a basaltic plinian eruption in 122 BC. However, the historical period lacks of detailed investigation on the Etna pyroclastic succession, therefore, we focused our research on this period. We started with an accurate field work aimed to the description of the pyroclastic deposits cropping out prevalently on the NE flank of the volcano. This tephra succession is characterized by alternations of ash layers, scoriaceous lapilli rich horizons and varicoloured tuffs attributed to a phreatomagmatic activity. Several yellowish volcanoclastic horizons, sometimes rich in charcoal, separate the tephra layers, indicating non-eruptive periods between the eruptions. We compiled 7 tephrostratigraphic sections having as common base the marker bed “FG” of the 122 BC plinian eruption and we collected 62 tephra samples and 7 charcoals for laboratories analysis. In particular, grainsize, component, chemical and petrographic analysis were carried out on tephra samples, whereas the charcoals were sent to Beta Analytics, Miami, for 14C radiometric analysis. The whole data set permitted us to correlate the tephra layers and to recognised 16 tephrostratigraphic units. The integration of the radiometric data with historical chronicles regarding the past activity of Etna, allow us to attribute some tephrostratigraphic units to 7 Etna historic eruptions whose distal deposit had never been found before. These eruptions could be considered as belonging to class B of Branca and Del Carlo (2005), characterised by prevalent intense explosive activity producing copious tephra fallouts, as happened during the 2001 and 2002-2003 eruptive events

Probability hazard map for future vent opening at Etna volcano (Sicily, Italy).

We evaluate a probability hazard map for future vent opening at Etna volcano using a data set of flank vents spanning last 4.0 ka

Monitoring Etna volcanic plumes using a scanning LiDAR

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Lidar depolarization measurement of fresh volcanic ash from Mt. Etna, Italy

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A multi-sensor approach for volcanic ash cloud retrieval and eruption characterization: the 23 November 2013 Etna lava fountain

Volcanic activity is observed worldwide with a variety of ground and space-based remote sensing instruments, each with advantages and drawbacks. No single system can give a comprehensive description of eruptive activity, and so, a multi-sensor approach is required. This work integrates infrared and microwave volcanic ash retrievals obtained from the geostationary Meteosat Second Generation (MSG)-Spinning Enhanced Visible and Infrared Imager (SEVIRI), the polar-orbiting Aqua-MODIS and ground-based weather radar. The expected outcomes are improvements in satellite volcanic ash cloud retrieval (altitude, mass, aerosol optical depth and effective radius), the generation of new satellite products (ash concentration and particle number density in the thermal infrared) and better characterization of volcanic eruptions (plume altitude, total ash mass erupted and particle number density from thermal infrared to microwave). This approach is the core of the multi-platform volcanic ash cloud estimation procedure being developed within the European FP7-APhoRISM project. The Mt. Etna (Sicily, Italy) volcano lava fountaining event of 23 November 2013 was considered as a test case. The results of the integration show the presence of two volcanic cloud layers at different altitudes. The improvement of the volcanic ash cloud altitude leads to a mean difference between the SEVIRI ash mass estimations, before and after the integration, of about the 30%. Moreover, the percentage of the airborne “fine” ash retrieved from the satellite is estimated to be about 1%–2% of the total ash emitted during the eruption. Finally, all of the estimated parameters (volcanic ash cloud altitude, thickness and total mass) were also validated with ground-based visible camera measurements, HYSPLIT forward trajectories, Infrared Atmospheric Sounding Interferometer (IASI) satellite data and tephra deposits

Interplay between Tectonics and Mount Etna’s Volcanism: Insights into the Geometry of the Plumbing System

Mt. Etna lies in front of the southeast-verging Apennine-Maghrebian fold-and-thrust belt, where the NNW-trending Malta Escarpment separates the Sicilian continental crust from the Ionian Mesozoic oceanic basin, presently subducting beneath the Calabrian arc (Selvaggi and Chiarabba, 1995). Seismic tomographic studies indicate the presence of a mantle plume beneath the volcano with a Moho transition at depth less than 20 km (Nicolich et al.,2000; Barberi et al., 2006). Geophysical and geological evidences suggest that the Mt. Etna magma ascent mechanism is related to the major NNW-trending lithospheric fault (Doglioni et al., 2001). However, the reason for the Mt. Etna mantle plume draining and channeling the magma from the upper mantle source to the surface is not yet clear. All models proposed in literature (Rittmann, 1973; Tanguy et al., 1997; Monaco et al.; 1997; Gvirtzman and Nur, 1999; Doglioni et al., 2001) do not explain why such a mantle plume has originated in this anomalous external position with respect to the arc magmatism and back-arc spreading zones associated with the Apennines subduction. Some ideas on the subduction rollback must be better developed through the comparison with new regional tomographic studies that are being released. Moreover, tomographic studies reveal a complex and large plumbing system below the volcano from -2 to -7 km a.s.l., wide up to 60 km2 that reduces itself in size down to -18 km of depth close to the apex of the mantle plume. Chiocci et al. (2011) found a large bulge on the underwater continental margin facing Mt. Etna, and suggested that the huge crystallized magma body intruded in the middle and upper continental crust was able to trigger an instability process involving the Sicilian continental margin during the last 0.1 Ma. This phenomenon induces the sliding of the volcano eastern flank observed since the 90s (Borgia et al, 1992; Lo Giudice and Rasà, 1992) because the effects of the bulge collapse are propagating upslope, and the continuous decompression at the volcano summit favors the ascent of basic magma without lengthy storage in the upper crust, as one might expect in a compressive tectonic regime. Taken together, these new evidences (tomographic, tectonic, volcanic) are concerned with the exceptional nature of Mt. Etna and raise the need to explain the origin of the mantle plume that supplies its volcanism. The lower crust and the uppermost mantle need to be better resolved in future experiments and studies. The use of regional and teleseismic events for tomography and receiver function analyses is required to explore a volume that has only marginally been investigated to date. The relation between the magma source in the mantle and the upper parts of the system, as well as the hypothesis above reported on the relation between tectonics and volcanism and the role of lithospheric faults, could be resolved only by applying seismological techniques able to better constrain broader and deeper models. Finally, although the recent tomographic inversions have progressively improved our knowledge of Etna’s shallow structure, highlighting a complex pattern of magma chambers and conduits with variable dimensions, the geometry of the conduits and the dimensions and shapes of small magmatic bodies still require greater investigation. Their precise definition is crucial to delineate a working model of this volcano in order to understand its behaviour and evolution. For this purpose, at least within the volcanic edifice, the precise locations of the seismo-volcanic signals can be considered a useful tool to constrain both the area and the depth range of magma degassing and the geometry of the shallow conduits. In this work, we furnish evidences that the tremor and LP locations allowed to track magma migration during the initial phase of the 2008-2009 eruption and in particular the initial northward dike intrusion, also confirmed by other geophysical, structural and volcanological observations (Aloisi et al., 2009; Bonaccorso et al., 2011), and the following fissure opening east of the summit area at the base of SEC. All these evidences, obtained by the marked improvement in the monitoring system together with the development of new processing techniques, allowed us to constrain both the area and the depth range of magma degassing, highlighting the geometry of the magmatic system feeding the 2008-2009 eruption

Challenges in UV camera-based real-time SO2 flux monitoring: insights from 5 years of continuous observations at Etna ad Stromboli

The advent of UV cameras has recently paved the way to volcanic SO2 flux observations of much improved temporal and spatial resolution, and has thus contributed to expanding use and utility of SO2 fluxes in volcano monitoring. Recently, the first examples of permanent UV camera systems have appeared that are now opening the way to routine fully automated monitoring of the volcanic SO2 flux at high-rate, and continuously (daily hours only). In 2014, using funding from the FP7-ERC project “Bridge” (http://www.bridge.unipa.it/), we deployed a network of 4 permanent UV cameras at Etna and Stromboli volcanoes (Sicily) that has been operating regularly since then. Using a suite of custom-built codes, data streamed by the UV camera are automatically processed and telemetered, allowing nearly real-time visualization and analysis of SO2 fluxes. Here, we summarise the key results obtained during the last 5 years of continuous observations (2014-2018) to demonstrate potentials and challenges in real-time continuous SO2 flux monitoring with UV cameras. We show that the spatially resolved SO2 flux time-series delivered by the UV camera allow effectively tracking migration in volcanic activity from the Central to New South-East Crater (Etna), and shifts in degassing activity along the crater terrace (Stromboli). At both volcanoes, the high temporal of UV cameras allows capturing the escalation in active (strombolian) SO2 degassing that typically precedes onset of paroxysmal (Etna in 2014-2016) or effusive (Stromboli in 2014) activity, and to quantify for the first time the syn- explosive SO2 budget for larger-scale explosions, including 2 paroxysmal lava fountains (Etna) and 1 major explosion (Stromboli). We finally demonstrate the ability of our automatic camera systems to capture temporal changes in SO2 flux regime, and thus to “live” monitoring degassing and eruptive behaviors at active volcanoes.PublishedNapoli6V. Pericolosità vulcanica e contributi alla stima del rischi