Activity of Etna, Pacaya, Semisopochnoi and Merapi.

At Etna on March 19, 2021, two strong explosions at 6:15 a.m. and 6:29 a.m. were heard at the Southeast Crater, which announced its 15th paroxysmal episode in the sequence that began on February 16, 2021.

The amplitude of the tremor increased, reaching the high level threshold. The sources of the signal are located under the southeast crater at a depth of about 2,500 m. asl. Infrasound activity is currently increasing with 1 to 2 events per minute.
Explosive activity at the southeast crater continues. The forecast model indicates the dispersion of the eruptive cloud in the ENE direction.

The INGV reports at 08:15 UTC an increase in Strombolian activity at the Southeast Crater with ash emissions. The forecast model indicates the dispersion of the eruptive cloud in the direction of the ENE.

The magnitude of the tremor is steadily increasing to high levels.

The sources fall within the area of ​​the SE crater at a depth of 2500 m. asl.

The GNSS network data does not show significant variations, while the clinometric network exhibits modest variations (less than 0.1 microradians) in association with the current activity.

At 08:31 UTC, Strombolian activity in the southeast crater turned into a lava fountain.
The tremor continues to increase, and it reaches the second alarm level.

At 10:36 UTC, the lava fountain activity at the Southeast Crater is over. However, Strombolian activity continues.

INGV staff present in the field reported a relapse of centimetric products in the locality of Vena and ashes in Milo and Piedimonte. Due to the cloud cover, the observation of the current activity is very limited and discontinuous. The eruptive cloud dispersed in the ENE direction.
The amplitude of the tremor decreases while remaining at high values. The sources are located near the southeast crater at a depth of 2800 s.l.m. Infrasound activity is in decline.
Analysis of the clinometric data of the paroxysmal event showed variations at different stations, with maximum cumulative values ​​(less than 3.0 microradians) recorded at the Cratere del Piano (ECP) station. GNSS (HF) network data over the past few hours has not shown any significant changes.

Source: INGV OE

Photos of EtnaWalk by clicking on this link.

In Pacaya, the explosive and effusive activity remains at a high level on March 18, 2021.

Explosions continue at Mackenney Crater, accompanied by ash plumes at 3,000 - 3,500 meters asl., with a south-southwest dispersion over 25-30 km. (according to VAAC Washington, ash travels about 100 km southeast at 4.30 p.m. - notice valid for 6 hours) and causes ash fallout on El Rodeo, Patronicio, Los Pocitos and others Expulsion of ballistic material is observed at 300 m. above the crater and their deposit over 400 m. distance.

Two new flows are reported: the first, with a length of 500m., With a part overflowing the meseta to the south-east; the second, 400 meters long, to the east, with a new crack, causes fires in the vegetation.

The pre-existing lava flow on the southern flank is now 500 meters long.

A typical sign of a strong volcanic tremor rise indicates rapid flow of magma through volcanic conduits to the surface and increasing the rate of lava flow effusion.

Sources: Insivumeh and VAAC Washington

Regional infrasound sensors detected a small explosion from the Semisopochnoi volcano on March 19 at 11:50 UTC (03:50 AKDT), indicating an increase in eruptive activity.

As a result, AVO is increasing the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH. Cloudy weather conditions obscure satellite views of the volcano. It is not known whether the explosion produced a low level ash cloud or a local ash deposit.

Small eruptions producing small deposits of ash near the volcano are typical of activity during the unrest in Semisopochnoi since September 2018. Local seismic stations have been offline since November 11, 2020. New explosions could occur at any time without warning.

Source: AVO

In Merapi, on Java, following the activity of the avalanches and the growth of the dome, the morphology of the summit area has changed.

The volume of the lava dome in the southwest sector is 840,000 m³ with a growth rate of 12,900 m³ / day.
Morphological analysis of the peak area based on photos of the southeast sector from March 18 to March 11, 2021 shows that the height of the central dome is 65 m, and the estimated volume of the dome is 950,000 m³ with a rate growth since January 4, 2021 of 12,800 m³ / day.

Between March 12 and March 18, 2021, pyroclastic avalanche flows occurred 3 times, with a maximum sliding distance of 1,000 m towards the southwest and were recorded on a seismogram with a maximum amplitude of 40 mm and with a duration of 102 seconds on March 12, 2021 at 07:00 WIB.
Boulder falls have been observed 211 times, with an estimated maximum gliding distance of 1,200 meters to the southwest, and 4 times in the crater.

The deformation of Mount Merapi which was monitored using EDM and GPS this week showed no significant changes.

Seismic activity this week is still dominated by surface earthquakes.

Source: BPPTKG