At Etna, the activity between August 24 and August 30 concerned all the craters.
The New Southeast Crater (NSEC) was characterized by explosive intracrateric activity, significantly variable in frequency and intensity, with ejection during the most energetic phases of coarse pyroclastic material on the crater rim. This activity produced the progressive widening of the mouth of the "saddle cone".
The activity was also characterized by discontinuous emissions of volcanic ash with the formation of generally dilute eruptive clouds which were rapidly dispersed in the atmosphere. Between the afternoon of August 25 and the early morning hours of August 26, the ash emission increased in intensity producing a volcanic cloud 4.5 km above sea level which dispersed towards the south-south-east. A further increase in explosive activity also occurred on the morning of August 29. The volcanic cloud generated during this activity was approximately 4.5 km high.
Intracrateric strombolian activity of the Nord-east crater (NEC) was produced by at least two explosive vents.
The Voragine Crater (VOR) is characterized by outgassing activity with occasional explosions from the main slag cone which produces the launch of coarse materials and modest ash emissions which quickly disperse into the atmosphere.
The crater of Bocca Nuova (BN) was the site of degassing of the pit crater, which continues to be affected by slow and gradual enlargement, and by fumarole systems along the internal walls.
Sources: INGV OE and Gio Giusa
On Java, the Raung, in activity level 2 / waspada, presents this August 2 a white plume of moderate intensity, about 200 meters above the summit.
Seismicity is expressed in
- 10 blast earthquakes, with an amplitude of 1 to 6 mm and a direction of 11 to 70 seconds,
- 7 episodes of non-harmonic tremor
- 3 distant tectonic earthquakes.
Source: Magma Indonesia
At Piton de La Fournaise, since the July 3 intrusion, seismic activity has remained low and inflation stopped around July 13. No eruptive activity was observed during the month of August 2020.
In August 2020, the OVPF recorded in the Piton de la Fournaise massif in total:
- 20 superficial volcano-tectonic earthquakes (0 to 2.5 km deep) under the summit craters
- 1 deep earthquake (2.5 to 5 km deep);
- 192 collapses (in the Crater Dolomieu and at the ramparts of the Enclos Fouqué and the Rivière de l'Est.
The seismicity under the Piton de la Fournaise during the month of August 2020 remained low with on average less than one superficial volcano-tectonic earthquake per day.
Piton de la Fournaise - average east-west travel speeds, deduced from InSAR data between October 31, 2019 and August 3, 2020. - Doc. OVPF
Following the cessation of inflation (swelling) of the building around July 13, no significant deformation was observed at the level of the terminal cone in August 2020 except for a very slight deflation at the level of the summit area.
On the other hand, the acceleration of movements observed on the upper part of the eastern flank since the eruption of October 2019 continues. Ten months after the start of this acceleration, the subsidence and the eastward movement recorded at the GPSG station, located at an altitude of 1005 m on the eastern flank, reached 18 and 14 cm respectively.
Interferometric satellite data show that this movement extends over an area of approximately 6-8 km² in the upper part of large slopes ... These deformations can have several origins, including
- persistent fluid movements at depth towards this flank which has undergone magmatic intrusions on numerous occasions in 2019-2020;
- the closure / contraction of the dykes / sills which fed the eruptions of 2019-2020;
- a destabilization of this flank.
A helicopter reconnaissance carried out with the assistance of SAG and PGHM on August 12, 2020, however, showed no new visible fracturing zone on the surface on the eastern flank of the volcano.
Source: OVPF Monthly Bulletin - full article : http://www.ipgp.fr/sites/default/files/ovpf_20200901_bullmensufinal.pdf