Etna update, 20/01/2023

Last week, lava emission at the north-eastern base of Mt Etna's New Southeast Crater temporarily decreased. As a result, a new lava flow developed, which is now heading directly towards Valle del Bove.

On 14 January, the fronts of the lava tongues fed by the effusive vent at the northeastern base of New Southeast Crater stagnated at about 2200 - 2300 m altitude. During the evening, the associated thermal anomalies recorded by the Monte Cagliato thermal imaging camera weakened more and more. On 15 January, the lava flow was only active in the upper section, within the Valle del Leone. On 16 January, new small lava tongues were again working their way down the steep western slope of the Valle del Bove, but were no longer as well fed as in the previous weeks. On 17 January, only very small thermal anomalies were visible and it looked as if the lava emission had stopped completely. On the morning of 18 January, a new thermal anomaly appeared near the effusive vent. A new lava flow was now moving in an easterly direction, leaving the previously created lava field. By the evening of 19 January, the lava flow had continued on its easterly course, but progressed slowly despite the steepening terrain. This morning, its front stagnated at a roughly estimated altitude of about 2400 metres. Later, clouds moved in and hindered further observation.
Meanwhile, the summit craters continued their usual gas emissions during last week. They were strongest at Bocca Nuova and often pulsed. At New Southeast Crater, some gas was persistently emitted from the summit area. At Voragine and Bocca Nuova no gas emission was visible.

As INGV reports, the front of the most advanced lava flow was observed on 14 January at 2250 m elevation. By 14 January, a lava field with an area of 700,000 m2 had developed. The volume was calculated at 3.5 - 4.5 million m3 [1].

The analysis of the data from the GPS stations showed no significant changes for the period between 09 and 15 January [1].
The clinometric data did not show any significant changes in the Inclinations of the volcano between 09 and 15 January [1].

The measurement of infrasound activity at the summit craters was frequently disturbed by strong winds during the period 09 - 15 January. During the calm phases, activity similar to that of the previous week was recorded [1].

Sulphur dioxide emissions at the summit craters remained at the lower-medium level during the period 09-15 January.
Ground carbon dioxide emissions (station ETNAGAS) remained at a medium level between 09 and 15 January and were subject to only minor fluctuations.
The concentration of helium isotopes (3He/4He - ratio) in the Etna area, which was last determined on 09 January, was with a value of 0.63 similar to the last measurement in December. The value was thus still at a high level [1].

On the online seismograms of the ECNE station, weak explosion signals as well as individual long-period signals were regularly visible during the past week. From 18 January, there were also repeated phases of stronger noise that lasted only 1 - 3 minutes [2].
The tremor fluctuated between low and medium levels during the past week. The strongest decrease occurred on 17 January. Subsequently, the tremor increased again somewhat [2].
The source of the tremor was located between 09 and 15 January in the area below the central crater at an altitude between 1000 m and 2800 m [1].

My interpretation of the data and speculations about the further development:
The tremor was subject to some fluctuations in the last few days and the rate of lava production temporarily decreased significantly on 17 January. This could indicate that the supply of fresh magma to the effusive vent is gradually stalling. Presumably, not enough magma is rising at the moment or it has sought another path in the mountain along which it is migrating. Sulphur dioxide emissions from the summit craters have also been declining in recent weeks and there has been slight deflation of the volcanic edifice.
This suggests, in my opinion, that the current eruption may be slowly coming to an end. However, the still high Helium-3 concentration shows that fresh magma continues to rise under the mountain, which will be erupted sooner or later, at least in part. So it remains difficult to make a prognosis.

1 - INGV-Sezione di Catania. 2023. Etna - BOLLETTINO SETTIMANALE - SETTIMANA DI RIFERIMENTO 09/01/2023 - 15/01/2023
2 - INGV-Sezione di Catania. 2023. Home. TREMORE VULCANICO. ECNE

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