Multiparametric exploration of active magma degassing at Mt. Etna in 2023

Active magma degassing is the release of slightly over-pressurized gas pockets from volcanic vents. This activity can shed light on the geometry of the shallow plumbing system of volcanoes and its internal dynamics. During a summer 2023 field campaign, we conducted comprehensive recordings, including thermal infrared, high-speed, and high-resolution video, as well as broadband microphone signals, capturing ten consecutive days of active degassing events at the Bocca Nuova crater of Mt. Etna. Two distinct vents exhibited notable degassing activity. The first, henceforth referred to as 'Sboffer,' was a crater characterized by the emission of loud, low-frequency sounds accompanying each degassing event (hence the name). The second vent, smaller than the first one and designated as 'Ringer,' took the form of a circular pit on the Bocca Nuova crater floor, emitting volcanic vortex rings—reminiscent of smoke rings (hence the name)—during events. We focused our analysis on the thermal data, characterizing emissions from both vents by examining brightness temperature anomalies along horizontal measurement lines in the thermal video recordings. Both vents exhibited a bimodal distribution in the intensity and duration of events. Specifically, Sboffer produced larger events with a mean amplitude of 100-160°C and a recurrence time of approximately 500 seconds, along with smaller events with amplitudes of 20-24°C occurring every 200-400 seconds. Ringer, on the other hand, featured larger events with amplitudes of 70-100°C and smaller events with amplitudes of 20-23°C, occurring at much higher frequencies of every 4 and 1.5 seconds, respectively. The maximum temperature recorded during the larger events reached nearly 600°C for Ringer and 500°C for Sboffer. The exit velocities for large events were measured at 15 m/s for Sboffer and 10 m/s for Ringer. Remarkably, all parameters at both vents remained consistently stable throughout the ten-day observation period. Preliminary investigations were conducted to explore potential correlations between the acoustic signal and thermal data. The aim was to ascertain the depth of the explosive events and examine potential correlations with temperature variations and the intensity of the explosions.