Etna volcano update: First paroxysm from summit craters in 2016
Wednesday May 18, 2016 | BY: T
The sequence of events at Etna's eruptions is often complex (for a detailed description, see the reports by INGV). Today's eruption was no exception, with some similarities to the last paroxysm of Voragine on 6 Dec 2015.
The strombolian activity from the NE crater increased during last night and began to produce dense ash plumes during this morning. Early in the morning of 18 May, relatively weak (possibly small strombolian-type) activity began at a vent on the eastern flank of the New SE cone, the same that had appeared on 25 Nov last year.
Around 1 pm, activity rapidly shifted to the Voragine summit crater where strong strombolian activity began and turned into a small paroxysym with pulsating lava fountaining and a lava flow from the summit crater. This activity lasted only a few hours before the current well-alimented lava flow from the New SE crater's flank vent appeared in the afternoon.
from INGV's update 18 May 13:45:
Since the evening of 17 May 2016, there has been an intense Strombolian activity at Etna's Northeast Crater (NEC), with ejection of incandescent bombs above the crater rim and fall of pyroclastics over the flanks of the cone.
This morning, 18 May, this activity was also accompanied by emission of volcanic ash forming a plume that was blown eastward by the wind and rapidly dispersed in the atmosphere.
There were also weak glows at the 25 November 2015 vent on the upper east flank of the New Southeast Crater (NSEC). The volcanic tremor amplitude remained elevated at values similar to those reached on the evening before. On the late forenoon, a clinometer installed at Punta Lucia, at nearly 3000 m elevation and about 1 km northwest of the NEC, recorded rapid inflation (swelling) of the summit area.
Shortly after 12:50 local time on 18 May 2016, the visual and thermal surveillance cameras of the INGV-OE recorded the onset of eruptive activity at the Voragine (VOR), which in just a few minutes evolved into a pulsating lava fountain. At the same time, the Strombolian activity at the NEC diminished and passed into emission of dark ash, and finally ended.
The image at lower left is a frame captured by the thermal monitoring camera at Bronte (EBT), about 45 minutes after the onset of the activity at the VOR. With the beginning of paroxysmal activity, the volcanic tremor amplitude showed a rapid increase, and its source migrated from a position below the NEC toward the VOR. From the Voragine an ash plume rose to 3000-3500 m above the summit and was blown by the wind to east-southeast. During the afternoon lava started to overflow from the western rim of the Voragine-Bocca Nuova depression, feeding a minor lava flow toward west, and limited to the summit area.
At the time this update is being published, lava fountaining is continuing at the VOR. The eruptive activity is monitored continuously by the systems of video and thermal cameras, seismic stations and ground deformation.
from INGV's update 17 May evening:
Since early April 2016, there has been a gradual resumption of summit eruptive activity at Etna, which initially consisted of increased gas emission mainly from the Northeast Crater (NEC) and from the vent that had opened on 25 November 2015 on the upper east flank of the New Southeast Crater (NSEC).
This was accompanied by rather discontinuous and small emissions of ash; during the first half of May, these emissions from the NSEC also produced small anomalies visible in the images of the thermal monitoring camera at Monte Cagliato (EMCT).
On 7 May, an increase in the volcanic tremor amplitude, whose source shifted toward the NSEC, was accompanied by the appearance of a source of infrasonic signals at the NSEC; however, the poor weather conditions allowed only to observe a modest emission of ash from the NSEC (25 November vent) and from the NEC.
During the night of 16 May, very weak and rare glows were observd at the 25 November vent of the NSEC, again accompanied by infrasound signals originating from the same vent. On the early morning of 17 May, the monitoring network of the INGV-Osservatorio Etneo (INGV-OE) recorded a gradual increase of the volcanic tremor amplitude, accompanied by infrasound signals coming from the NEC, and intense degassing with occasional, weak ash emissions from the same crater.
INGV-OE staff present in the area of the Grotta del Gelo (on the upper north-northwestern flank) reported hearing explosion sounds probably coming from the NEC.