Etna, new effusive vent in Valle del Bove and tremor at high values

At 06:09 UTC on August 17 the surveillance cameras of INGV-Osservatorio Etneo recorded the opening of a new effusive vent in Valle del Bove, at an altitude between 2,200 and 2,350 metres, producing a lava flow. The information is contained in the monitoring statement released by the institute and reported by AetnaNet, which also carries the wording used by the observatory to describe the ongoing phase: “Effusive activity continues from the vents at 2,750 and 1,990 metres altitude”.

The picture is therefore one of an eruption with multiple emission points active simultaneously. On August 16 INGV reported effusive activity from the two vents at 2,750 and 1,990 metres, with the most advanced lava front stalled at 1,395 metres altitude, between Rocca delle Palombe and Rocca Musarra. The opening of the new vent on August 17 adds to that system, it does not replace it.

Tremor and its source

The parameter observers watch to anticipate developments is the amplitude of volcanic tremor. According to the monitoring data, the value peaked around 17:40 UTC on August 16 and has since decreased slightly, though it remains at high levels. The source location is indicated in the area of the Voragine, at about 3,000 metres altitude.

At the same time, ash emission continues from the Voragine crater, dispersing toward the south-east. This is the explosive activity also described by ANSA on August 16, and it is what causes the most immediate practical consequences for eastern Sicily: not the lava, which flows in an uninhabited area, but the ash that enters the air column and falls on downwind towns.

The colour code for flights

The VONA advisory — the message through which volcanological observatories inform the aviation sector — issued by INGV has remained at orange level after being lowered from red on August 15, as reported by CataniaToday. Orange is the intermediate threshold: it signals an ongoing or probable eruption with limited ash emission, and does not in itself entail the closure of airspace.

The recent precedent, however, shows how quickly the situation can shift to the operational level: on August 7 the eruptive phase caused the suspension of incoming flights at Catania airport until 21:00. Between the colour code and the availability of an airport the relationship is not automatic — it depends on wind direction at altitude, the amount of ash and the decisions of the aviation authority — but it is the reason why the advisory is updated several times a day.

What is known and what is not

The available material contains no indications of evacuations, damage to infrastructure or people involved, and does not report the institute’s forecasts on the duration of the eruptive phase. The documented sequence concerns the parameters: tremor slightly decreasing but high, three active lava emission points, ash dispersing toward the south-east, orange aviation code.

The figure to watch in the coming hours is the altitude of the lava front, stalled at 1,395 metres in the August 16 reading: it is this that will show whether the flow is advancing to lower elevations or petering out within the broad amphitheatre of Valle del Bove.