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Italy is the land of iconic volcanoes, whose activity has been witnessed, described and portrayed for centuries. This legacy has greatly contributed to shaping the public perception of volcanoes and their impact, well beyond the national borders. Stories about famous eruptions overlap and nowadays easily mix up with the impressive footage that is readily available from ongoing eruptions worldwide. As a result, the public discourse may flatten the wide spectrum of possible phenomena into an oversimplified sketch of volcanic eruptions and their impact, where all events seem equally probable and look alike. Actual volcanoes differ in size, eruption magnitude, state of activity, eruptive style, geographical position, and each is located within a specific social and cultural context. All these elements combine in defining the consequences of volcanic activity as well as in determining the severity of the damage and the size of the impacted area. How can we convey such a complexity to the general public? Can social media contribute to raise awareness and build a more resilient society? An effective hazard communication should propose a comprehensible yet realistic description of volcanic settings and provide adequate tools to recognize and understand the specific features of each phenomenon and volcanic area. As we write, two Italian volcanoes display persistent eruptive activity, while other two are going through unrest phases that started in 2012, at Campi Flegrei, and in late summer of 2021, at Vulcano Island. Other active volcanoes (Vesuvius, Ischia, Colli Albani, Lipari, and Pantelleria) have been dormant for tens, hundreds, or thousands of years. Communication in these different contexts also require different approaches that take into account the specific needs of local communities. Social media may provide a unique opportunity to quickly share relevant news and information. Yet, this type of communication has its challenges and volcano observatories can rarely rely on expert social media managers. Sharing experiences and lessons learned is a key to ensure the growth of the volcanological community and improve its ability to connect and engage local residents. Here we discuss the online communication strategies implemented by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) since 2018 to inform Internet and social media users about volcanoes, volcanology, and ongoing volcanic activity, both in Italy and abroad. We describe the internal procedures that we developed and practiced and the experience gathered so far, during both quiet periods and a few volcanic crises. Our experience confirms previous indications about the importance of a steady online presence and suggests that public interest is not always easily predictable.

Understanding the dynamics of mild explosive activity is a fundamental tool for hazard assessment at open conduit volcanoes. This is a particularly critical task for Etna volcano. Etna is in fact characterized by frequent, mild explosive activity, punctuated by lava flows and paroxysmal events (‘lava fountains’), which, because of their greater impact, have been the main target for hazard studies, whereas more frequent Strombolian activity has been overlooked. As a result, their impact and associated hazards have been never quantified, despite the extensive monitoring and surveillance activities carried out on this volcano. In this paper, we analyze video recordings of a sequence of Strombolian explosions occurring at the summit craters of Mt. Etna, in Italy, in February 2020. Data were also integrated with a petrographic analysis of collected samples, and drone surveys were performed at the same time as the video recordings. We estimate the frequency of explosions (20–12 per min); particle exit speeds (1–50 m/s), and erupted mass (100–102 kg) of those explosions. A very regular, small-scale activity (marked by a single burst of gas breaking the magma free surface into bombs and lapilli fragments) was occasionally punctuated by larger explosions, (at least one every 5 min), with a longer duration, fed by larger magma volumes, and consisting of two to three distinct pulses followed by a stationary phase. We found that the repose times between explosions follows a log logistic distribution, which is in agreement with the behavior of open vent explosive activity. The four largest explosions of the sequence were analyzed in detail: they emitted particles with median diameters (Mdphi) ranging from −10.1 to −8.8 phi, with bimodal distributions.

Determining the volume of the various types of products of a highly frequent active volcano can be very difficult, especially if most of them are deposited on a growing volcanic cone. The New South-East Crater (NSEC) of Mt Etna, Italy, may be considered one of the best case studies because of tens of paroxysmal episodes which it produced in the last few years. On 25-26 October 2013, a lava fountain at the NSEC produced magma jets up to 500 m high, a maximum ~8 km high column, a multilobate lava flow field 1.3–1.5 km long, and almost 30 m of growth in height of the NSEC cone. Mapping of explosive and effusive deposits allowed us to calculate the total volume of erupted products, including lava flows, proximal, and distal tephra fallout, and the amount of coarse pyroclastics on the cone. The estimation of the latter products was also confirmed subtracting digital elevation models (DEMs) obtained at different stages of the NSEC growth. Results show that the volume of tephra fallout away from the cone was only

Mount Etna produces frequent eruptions from its summit craters and from fissures on its flanks. The flank fissures trend approximately radially to the summit, and are mainly concentrated in three rift zones that are located on the NE, S and W flanks. Many flank eruptions result from lateral magma transfer from the central conduit into fractures intersecting the flanks, although some eruptions are fed through newly formed conduits that are not directly linked to the central conduit. We analyzed the structural features of eruptions from 1900 to the present, one of the most active periods in the documented eruptive history of Etna, which comprised 35 summit and 33 flank events. Except for a small eruption on the W flank in 1974, all of the flank eruptions in this interval occurred on or near the NE and S rifts. Eruptions in the NE sector were generally shorter, but their fissure systems developed more rapidly and were longer than those in the S sector. In contrast, summit eruptions had longer mean durations, but generally lower effusion rates (excluding paroxysmal events characterized by very high effusion rates that lasted only a few hours). This database was examined considering the main parameters (frequency and strike) of the eruptive fissures that were active over the last ~2 ka. The distribution in time and space of summit and flank eruptions appears to be closely linked to the dynamics of the unstable E to S flank sector of Etna, which is undergoing periodic displacements induced by subvolcanic magma accumulation and gravitational pull. In this framework, magma accumulation below Etna exerts pressure against the unbuttressed E and S flanks, which have moved away from the rest of the volcano. This has caused an extension to the detachment zones, and has facilitated magma transfer from the central conduit into the flanks.

The individuation of areas that are more likely to be affected by new events in volcanic regions is of fundamental relevance for the mitigation of the possible consequences, both in terms of loss of human life and material properties. Here, we describe a methodology for defining flexible high-detail lava-hazard maps and a technique for the validation of the results obtained. The methodology relies on: (i) an accurate analysis of the past behavior of the volcano; (ii) a new version of the SCIARA model for lava-flow simulation (based on the macroscopic cellular automata paradigm); and (iii) high-performance parallel computing for increasing computational efficiency. The new release of the SCIARA model introduces a Bingham-like rheology as part of the minimization algorithm of the differences for the determination of outflows from a generic cell, and an improved approach to lava cooling. The method is here applied to Mount Etna, the most active volcano in Europe, and applications to land-use planning and hazard mitigation are presented.