Rapid provision of maps and volcanological parameters: quantification of the 2021 Etna volcano lava flows through the integration of multiple remote sensing techniques

In 2021, more than 50 paroxysmal episodes occurred at the South-East Crater (SEC) of Mt Etna, Italy. The 23–24 March lava fountain was one of the longest episodes and began with weak Strombolian explosions, gradually transitioning to lava fountaining. The eruption intensity then dropped more slowly than in previous episodes, resulting in pulsating Strombolian explosions dominated by ash emission. Thirty-four tephra samples were used to reconstruct the fallout dispersal and estimate the total erupted mass. Grain size, textural, petrological and geochemical analyses indicate different features and were compared with the gas phase (SO2 and HCl) in the volcanic plume. By applying stochastic global optimization to simulations of the temporal evolution of the eruption column height and tephra dispersal and deposition, the total erupted mass retrieved (6.76 × 108 kg) matches well the total erupted mass estimation by the ground-based deposit (8.03 ± 2.38 × 108 kg), reducing the column height throughout the episode from 6.44 to 4.5 km above sea level and resulting in a mass eruption rate ranging from 1.96 × 105 to 8.18 × 103 kg/s. The unusual duration of the March episode and the characteristics of the erupted products point to the change in explosive style and magma fragmentation from fountaining to ash emission phases, associated with a slower magma supply inducing a change in magma rheology and a final, prolonged ash generation. Furthermore, this study showed that using observational data and the variation in eruption source parameters for numerical simulations can improve the accuracy of predicting the dispersal plume, thus mitigating the potential impact of longer paroxysmal episodes.

The 23–24 March 2021 lava fountain at Mt Etna, Italy

Andronico,

D’Oriano,

Pardini

et al. 2024

The 2020–2022 paroxysmal episodes of the South-East Crater (Mt. Etna): insights into high-frequency eruptive activity from petrological monitoring

Corsaro,

Miraglia,

Arienzo

et al. 2024

Over the last 20 years, the South-East Crater (SEC) of Etna has produced high-intensity explosive activity including Strombolian explosions and lava fountains associated with lava effusion. In the 2020–2022 period, SEC volcanic activity was characterized by two paroxysmal sequences from 13 December 2020 to 1 Apr 2021 (SEQ1) and from 19 May to 23 October 2021 (SEQ2); another two paroxysms occurred on 10 and 21 February 2022. The 2020–2022 eruptive activity was monitored by the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) with instrumental networks, field surveys, and laboratory analyses. A detailed record of the chemical variations of glass was acquired in the framework of the syn-eruptive petrological monitoring; chemical (major and trace elements) and isotopic (Sr and Nd) compositions of bulk rocks completed the study. The findings of the petrological monitoring, coupled with volcanological parameters and literature data, allowed magma evolution to be tracked and the subsurface magmatic processes responsible for the observed compositional variations to be inferred. Changes in magma supply rates and mixing between an evolved magma stored in the shallow reservoir and a more primitive magma ascending from intermediate depths controlled magma evolution during the 2020–2022 paroxysmal activity. We discuss magmatic processes in the plumbing system before and during the eruption and the relationship between rate of magma supply and the eruptive dynamics. Finally, the 2020–2022 paroxysmal activity of SEC tested the INGV-OE procedures of petrological monitoring, in the framework of monitoring best practices.

An unobserved lava fountain deciphered in real-time by high-precision borehole strainmeter and contribution to hazard evaluation: the Etna 21 May 2023 eruption

Bonaccorso,

Carleo,

Currenti

et al. 2024

A powerful lava fountain took place on 21 May 2023 at Mt. Etna after a year of repose, preceded a few days earlier by a shallow seismic swarm. The main critical issue with the eruption was the difficulty to track this eruptive event with conventional remote sensing devices, such as webcams and satellite instruments, due to the bad weather conditions and especially the dense cloud cover. Despite the sophisticated monitoring available at the volcano, the eruption effectively remained “hidden”. It was here that the borehole dilatometers excelled: as with all recent lava fountains at Etna, these high-precision instruments detected significant strain changes and proved a valuable contribution to real-time monitoring of the event. Through recently implemented approaches, the analysis of the strain data allowed us to decipher the eruption: namely identify the timing of the events, evaluate the “size” of the fountain (i.e. its eruptive intensity), and also estimate the erupted volumes in near real-time. This provided a useful support during the Civil Protection emergency meeting at the Prefecture of Catania, where these results were presented and jointly discussed. Overall, the 21 May 2023 lava fountain was an important showcase, demonstrating the strategic contribution that real-time high-precision strain signals may have in defining and assessing the hazard associated with an eruptive event even in adverse weather conditions, when remote sensing systems may be unable to furnish direct information on the ongoing phenomenon.