Etna update, 06/01/2023:
During the past week, lava production continued at the northeast base of Mt Etna's New Southeast Crater. The lava continued to move in the form of several partial flows through the Valle del Leone to the edge of the Valle del Bove. On the steepening terrain, new tongues developed again and again. Sometimes a more southern and sometimes a more northern tongue was fed. As a result, the fronts of the tongues did not advance far and stagnated at about 2200 m high terrain in the area southwest to west of Monte Simone.
During 03 January, the intensity of the thermal anomalies visible from the active lava tongues in the Monte Cagliato thermal imager photos weakened considerably. By the evening, only the upper section of the lava field was active. In the afternoon of 04 January, the thermal anomalies in the area of the effusive vent intensified and some time later the lava tongues at the edge of the Valle del Bove became active again. Until the morning of 05 January, they again moved down the steep terrain, but initially did not advance further than about 2300 - 2200 m altitude.
By the evening of 05 January, the lava flow intensified and, especially in the southern section of the lava field, a lava tongue became more and more intense. In the early morning of 06 January, its front reached the valley floor of the Valle del Bove at about 2000 m altitude. At the same time, a little further north, another tongue made better progress than in previous weeks and moved towards the valley floor.
On the evening of 02 January, light sensitive webcams showed pulsating glow over Bocca Nuova. However, I could not observe any thermal anomalies. Probably deep-seated strombolian explosions started in one of the vents of Bocca Nuova. Also during the following nights, faint glow was visible above Bocca Nuova. On the evening of 05 January, the gas clouds above the summit crater were only sporadically illuminated, but in the early morning of 06 January, the glow became more frequent again.
The analysis of the data from the GPS stations showed no significant changes between 26 December and 01 January. However, a reversal of the trend towards inflation was observed during the past month and measurements between the Pizzi Deneri (EPDN), Cratere del Piano (ECPN) and Punta Lucia (EPLU) stations revealed a slight deflation of the volcanic edifice [1].
Clinometric data showed no significant changes between 26 December and 01 January [1].
Infrasound activity at the summit craters remained low during the period from 26 Dec to 01 Jan, but measurements were affected by wind. The source of the activity was Bocca Nuova [1].
Sulphur dioxide emissions at the summit craters hardly changed in the period between 26 December and 01 January compared to the previous week and remained at medium levels.
Ground carbon dioxide emissions (ETNAGAS station) remained at a medium level between 26 December and 01 January [1].
The online seismograms of station ECNE were initially still overlaid by noise caused by the persistently increased tremor. After the tremor decreased, weak explosion signals were occasionally visible from 05 January onwards [2].
In the past week, the tremor was initially still at a medium level and was subject to only minor fluctuations. From 05 January, it decreased significantly and reached a low level [2].
Between 26 December and 01 January, the source of the tremor was in the area of the Southeast Crater at an altitude between 2700 and 2900 m [1].
On 01.01., two earthquakes occurred in the area north of Ragalna (southern flank), reaching magnitudes of 2.0 and 2.8 [3].
My interpretation of the data and speculations about the further development:
It was interesting in the past few days that sporadic glow appeared again over Bocca Nuova after a long time. This was last the case in September last year. Presumably, deep-seated strombolian explosions are occurring there again now. It is also interesting that the tremor decreased significantly on 05 January, but this did not affect the lava production at the effusive vent. On the contrary, as the fronts of the lava eruptions have advanced today as never before during the current eruption, the production rate has apparently increased.
Since weak deflation has been measured at the volcanic edifice in recent weeks, more lava is probably currently being produced than is rising from under the mountain. If this continues, the end of the eruption could soon be in sight. However, there still seems to be plenty of fresh magma acummulating under the mountain, because the ratio of helium isotopes had reached high levels again in the last measurement in mid-December. Thus, it remains difficult to predict how the current eruption will continue.
1 - INGV-Sezione di Catania. 2023. Etna - BOLLETTINO SETTIMANALE - SETTIMANA DI RIFERIMENTO 26/12/2022 - 01/01/2023
2 -INGV-Sezione di Catania. 2023. Home. TREMORE VULCANICO. ECNE
3 - INGV. Osservatorio Etneo. Sorveglianza e Monitoraggio. DATABASE TERREMOTI. Localizzazioni di sala operativa. 2023.
