Great Sitkin - photo taken from RV Tiglax by Lauren Flynn (USFWS) on 25.05.2021 after 9 a.m. - via AVO
A short-lived (1-2 minute) explosive eruption began at 9:04 p.m. AKDT (5:04 a.m. UTC May 26) at the Great Sitkin in the Aleutians, resulting in an ash cloud reaching 4,500 m. asl.
Since this explosion, the seismicity has decreased and satellite images show that the ash cloud has broken away from the vent and is moving east. Additional explosions are possible and the aviation color code has been changed to red from 25.05 at 9:30 p.m. to 26.05 at 8:31 a.m., before changing back to orange, and the volcanic alert level on Watch.
Great Sitkin is monitored with a local real-time seismic network, which will generally allow AVO to detect changes in disorders that can lead to an explosive eruption. Rapid detection of an ash-producing eruption would be achieved using a combination of seismic, infrasound, lightning and satellite data.
Infrasound signal from the Great Sitkin eruption on May 25, 2021. The top graph is the infrasound wave (low frequency sound) recorded on the GSMY station, approximately 6 kilometers from the vent. The eruption produced a single, loud explosion at ~ 05:04 UTC. The bottom graph is the spectrogram, showing the frequency content of infrasound over time - Doc. AVO
Between 17 and 23 May 2021, Sabancaya's activity remained at moderate levels, with an average of 78 explosions per day, accompanied by plumes reaching 3,200 meters above the summit.
During this period, I.G. Peru recorded 674 earthquakes of volcanic origin, associated with the circulation of magmatic fluids. Volcano-tectonic earthquakes, linked to the fragmentation of rocks, remain confined mainly to the north and northeast of the volcano.
The other parameters show no significant changes
The volcanic alert level remains orange, with an inaccessible area of 12 km in radius.
Source: I.G. Peru
Since the eruption on Saturday evening, MONUSCO has carried out eight helicopter reconnaissance flights and two drone flights over the Nyiragongo crater to monitor the volcano's activity, the mission said on Twitter, adding that a team civil and military engineers had been dispatched Tuesday to assess the damage.
As of May 26, 2021 at 10 p.m. UTC, 140 earthquakes have been recorded in the past 24 hours, ranging in magnitude from 2.1 to 4.8. The earthquakes caused the collapse of many buildings and cracks in the roads. Seismicity continues to migrate south.
A MONUSCO team descended on the field to study the possibility of reopening the Goma-Rutshuru-Butembo road, vital for the food supply in Goma.
Following the observations of May 25, and the emission of an ash plume, we can conclude that the crater collapsed three days after the emission of lava following an emptying of the lava lake, as in 2002.
Source: Monusco and georiska.africamuseum.be
In Kilauea, the eruption in Halema'uma'u crater has stopped. The lava lake has a depth of 229 m. and stagnates over its entire surface. No active lava was observed from the fissure; field teams saw no signs of activity in the lava lake.
Since the eruption began on December 20, 2020, more than 40 million cubic meters of lava have been emitted.
HVO will continue to monitor changes.