Etna update, 27/01/2023

During past week, lava continued to be released at the northeast base of Mt Etna's New Southeast Crater, but the production rate was subject to strong fluctuations. Tremor and seismic activity remained inconspicuous.

After the mountain had been completely wrapped in clouds all day on 22 January, the Monte Cagliato thermal camera showed a significant weakening of the lava flow on 23 January. This had previously been released from the effusive vent at the northeast base of New Southeast Crater in an easterly direction. Only some spots of the flow, which had previously stagnated at the base of the steep western wall of Valle del Bove, were still hot. Then, on the morning of 24 January, a new powerful thermal anomaly appeared just below the effusive vent. It was caused by a new gush of lava that poured eastwards again over the meanwhile cooling flow of the previous days. The new lava flow progressed slowly and on the morning of 25 January its front stagnated at the edge of the Valle del Bove, above the escarpment. Later, clouds moved in again and hid the mountain until the morning of 26 January. Through gaps in the clouds it was visible that the flow continued to stagnate and had even weakened somewhat compared to the previous day. In the evening of 26 January, the thermal anomalies below the effusive vent intensified and again a surge of fresh lava started moving eastwards. During the previous night, this flow then moved down the steep western wall of the Valle del Bove and reached about 2300 m high terrain in the morning. As the day progressed, however, the front stagnated again and this evening the lava flow did not look quite as well fed as yesterday.
At the summit craters, Bocca Nuova again showed the most gas emission last week, which was still frequently intensified in a pulse-like manner. Voragine and Northeast Crater continued to release only few amounts of gas. At the New Southeast Crater, gas was persistently emitted from the summit area. In the morning of 26 January, some brownish ash clouds mixed with the gas clouds from about 11:30. Around 14:45 I could see an even stronger ash emission there, which was nevertheless comparatively weak. The point of emission was apparently the upper northern summit area, which also generated some weak glow at times during the nights of the last weeks.

The volume of lava released since 27 November is calculated by INGV to be 3.7 - 4.8 million m3.
In the meantime, a sample of the current material, taken on 20 December 2022, was chemically analysed. It showed that the lava, with a CaO/Al2O3 ratio of 0.46 and an FeOtot/MgO ratio of 3.3, was more evolved than the lava emitted in 2022 during the paroxysmal phases of the Southeast Crater complex or during the May eruption. According to the INGV, this means that hardly any material was produced from greater depths [1].

The evaluation of the data from the GPS stations showed no significant changes for the period between 16 and 22 January [1].
The clinometric data showed no significant changes between 16 and 22 January [1].

The measurement of infrasound activity at the summit craters was massively disturbed by strong winds during the period 16 - 22 January and thus no data could be provided [1].

Sulphur dioxide emissions at the summit craters remained unchanged in the period between 16 and 22 January compared to the previous week and remained in the lower-medium range.
Soil carbon dioxide emissions (ETNAGAS station) held at medium levels between 16 and 22 January and were subject to a slight downward trend [1].

On the online seismograms of station ECNE, weak long-period signals as well as weak explosion signals were occasionally visible during the past week [2].
The tremor initially hovered on the border between low and medium levels last week, but then increased slightly and remained at lower-medium levels [2].

On 22.01., a quake of magnitude 1.6 was registered southeast of Monte Fontane (eastern flank). On 25.01., a quake of magnitude 1.7 occurred in the area of the summit craters [3].

My interpretation of the data and speculation about further development:
The analysis of the lava released in December showed that it was more evolved than the lava from the May 2022 eruption and significantly higher than the material emitted from New Southeast Crater during the paroxysmal phases in February 2022. This is also not surprising, because it was already largely degassed magma that generated practically no explosive activity, but flowed out very quietly. This magma had been stored in the mountain for some time and had time to evolve.
Unfortunately, there is no analysis (yet) of the lava currently being released. It is quite possible that it is somewhat more primitive than the December lava. However, as there is still no significant explosive activity, the proportion of more highly evolved and degassed magma still seems to be high. However, this could change in the near future and fresher magma could reach the surface.
Yesterday there were some ash emissions in the summit area of New Southeast Crater. It is possible that these were caused by deep-seated explosions, but smaller collapse events are more likely. However, if more fresh magma rises, the gases could cause strombolian explosions in the New Southeast Crater. Perhaps the ash emissions yesterday were already a first indication? Interesting is also the currently strongly fluctuating emission rate; a behaviour that has prevailed since mid-January and always causes new lava spurts. This could also be an indication that another, more gas-rich magma is now beginning to rise. But it could also mean that sufficient pressure can no longer build up to produce lava on a sustained basis. The temporary sinking and rising of the magma column under the New Southeast Crater could then also generate collapse events.
Thus, in my opinion, two developments are conceivable in the near future: 1. onset of strombolian explosions in the summit area of New Southeast Crater, with lava emission at the effusive vent remaining intensified in a push-like manner. 2. weakening or even end of the eruption and collapse events in the summit area or along the northern flank of New Southeast Crater associated with ash emissions.
In any case, Etna remains exciting!

1 - INGV-Sezione di Catania. 2023. Etna - BOLLETTINO SETTIMANALE - SETTIMANA DI RIFERIMENTO 16/01/2023 - 22/01/2023
2 - INGV-Sezione di Catania. 2023. Home. TREMORE VULCANICO. ECNE
3 - INGV. Osservatorio Etneo. Sorveglianza e Monitoraggio. DATABASE TERREMOTI. Localizzazioni di sala operativa. 2023.

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