Etna update, 09.12.22:
Effusive activity at the northeastern base of New Southeast Crater continued last week. While the tremor remained elevated, seismic activity increased slightly.
Effusive activity continued at the northeast base of New Southeast Crater last week. The released lava flow, which remained relatively narrow, continued to move into the Valle del Leone, reaching a length of about 600 m on 08 December. Meanwhile, some gas was persistently emitted in the summit area of the New Southeast Crater. I could not observe any explosive activity. Light sensitive webcams sometimes showed faint glow on the upper northern flank of the cone, where an explosive vent was active in May/June.
Bocca Nuova continued to release gas in pulses during the last week. At Voragine and Northeast Crater there was only minor gas emission.
The INGV reports that the effusive vent, which opened on 30 November, is located at an altitude of 2900 metres. The lava flow released by the vent moved parallel to the lava flow emitted from 27 November and had a length of 450 m on 30 November. Its front moved on 2700 m high terrain .
The analysis of the data from the GPS stations showed the continuation of the inflation of the volcanic edifice in November .
The clinometric data showed a rapid change in the slope in the summit area of one microradian on 15 September .
Infrasound activity at the summit craters was moderate in November and the amplitudes of the events were low. The source of the activity was Bocca Nuova .
Sulphur dioxide emissions at the summit craters increased somewhat in November. The mean emission rate reached average levels.
Ground carbon dioxide emissions (ETNAGAS station) were at average levels in November.
The concentration of helium isotopes (3He/4He ratio) in the Etna area, which was last determined on 24 November, was lower than in the previous month with a value of 0.57 and was at an average level .
The online seismograms of the ECNE station were characterised by slight noise during the past week due to the increased tremor. Weak long-period signals were frequently observed.
The tremor was at a medium level last week and was subject to only slight fluctuations .
On 02.12. and 03.12. two weak quakes occurred near Sant'Alfio (eastern flank), the strongest having a magnitude of 1.6. On 07.12. two quakes occurred east of Sant'Alfio, with magnitudes of 2.5 and 1.4. On 08.12. an earthquake of magnitude 2.5 was registered south of Paternò (southern flank). On 08.12. an earthquake with a magnitude of 1.5 occurred near Mangano (eastern flank) .
My interpretation of the data and speculation about further developments:
The slight increase in seismic activity, which had recently been particularly concentrated on the eastern flank of Etna, as well as the continuation of the inflation of the volcanic edifice indicate, in my opinion, that magma continues to be stored in the mountain. The relatively weak effusive activity that has continued over the past week is unlikely to provide much relief in this regard.
Most of the gas from the rising magma is likely to escape via Bocca Nuova. As long as there is not a large amount of fresh magma rising, I do not expect explosive activity at the South East Crater complex.
Therefore, I think it is most likely that the purely effusive activity at the New South East Crater will continue. However, new vents could open further north or east at any time. A reduction of the effusive activity or a slow cessation of the eruption is also possible.
1 - INGV-Sezione di Catania. 2022. Etna - BOLLETTINO MENSILE MESE DI RIFERIMENTO NOVEMBRE 2022
2 - INGV-Sezione di Catania. 2022. Home. TREMORE VULCANICO. ECNE
3 - INGV. Osservatorio Etneo. Sorveglianza e Monitoraggio. DATABASE TERREMOTI. Localizzazioni di sala operativa. 2022.
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