GNGTS 2021 - Atti del 39° Convegno Nazionale

125 GNGTS 2021 S essione 1.2 shallow pressure (lower than 40 MPa), which fed a steady-state Strombolian and effusive activity at the summit for several months. Diffusion timescales for the period November-December 2019 evidence short-term processes of crystal re-equilibration at low pressure that refer to recharge episodes that started 10-14 days before crystals were erupted ( Fig. 2 ). Such persistent activity changed to more intense Strombolian explosions in January 2020 in response of the migration of deeper, more basic magma toward the shallow reservoir. Volcanic tremor and infrasonic events also correlate well with petrological data and volcanological observations. Volcanic activity at VOR was preceded by a gradual volcanic tremor amplitude increase starting from mid-August and from resumption of activity at NEC ( Fig. 2 ). In mid-September 2019, source locations of vol- canic tremor and infrasound events shifted from the NSEC toward the NEC and VOR. As VOR began erupting, the tremor amplitude rapidly increased, while its centroid altitude remained constant at very shallow depth (> 2.5 km a.s.l). A deepening of the volcanic tremor source cen- troid was observed starting from mid-December 2019, in accordance with the evidence of mafic replenishments from deeper environments resulting from the analysis of crystal zoning and dif- fusion profiles. Conclusion The changes in the state of volcanic activity observed during the 2019-2020 period agree with the evidence of continuous magma replenishment affecting the plumbing system since the post- 2016 paroxysmal activity at VOR. In this framework, the renewal of the activity at NSEC on May 2019 may be viewed as the response of a pressure imbalance between the intermediate and the shallowest part of the volcano feeding system that promote the drainage of magmas toward shal- low reservoirs, leading to the eruption. The NSEC reactivation allowed re-establishing a mecha- nism of steady-state recharge/discharge of plumbing system, powered by continuous magmatic intrusion, which seems to be recurrent in the post-2016 volcanic record (Currenti and Bonaccorso 2019; Viccaro et al., 2019). Repeated intrusions from depth pushed out the magma stored in the shallow storage zones, leading to the persistent activity observed at VOR throughout the last months of 2019. Since April 2020, the persistent Strombolian activity shifted at NSEC, suggesting that magma replenishment continued through the entire 2020. References Currenti, G., Bonaccorso, A., 2019. Cyclic magma recharge pulses detected by high-precision strainmeter data: the case of 2017 inter-eruptive activity at Etna volcano . Sci. Rep. 9, 7553. Viccaro, M., Giuffrida, M., Zuccarello, F., Scandura, M., Palano, M., Gresta, S., 2019. Violent paroxysmal activity drives self‐feeding magma replenishment at Mt. Etna . Sci. Rep. 9, 6717