Volcanos

Roundup of Global Volcanic Activity – New Activity for the Week 19 May – 25 May 2021

Great Sitkin – Andreanof Islands (USA) : An increase in local earthquake activity at Great Sitkin during 24-25 May prompted AVO to raise the Aviation colour Code to Orange and the Volcano Alert Level to Watch on 25 May. An explosive eruption began later that day at 2104; the Aviation colour Code and the Volcano Alert Level were raised to Red/Warning, respectively. The explosions lasted for 1-2 minutes and produced an ash plume rising to 4.6 km (15,000 ft) a.s.l. that was observed by local mariners. Witnesses 42 km away heard “a very loud explosion.” After the explosive period seismicity decreased and satellite image images showed a detached plume drifting E. Around mid-morning on 26 May AVO lowered the Aviation colour Code and the Volcano Alert Level to Orange/ Watch, respectively.

Manam – Papua New Guinea : The Darwin VAAC reported that during 20-21 May ash plumes from Manam rose to 2.1 km (7,000 ft) a.s.l. and drifted NW.

Nyiragongo – DR Congo : At around 1815 on 22 May seismicity at Nyiragongo spiked, around the same time observers reported at least two fissures opening on the lower S flanks, NW of Kibati (8 km SSE) and Rukoko (10 km S). Lava from the first fissure, originating near the Shaheru crater, flowed E over a major road (N2) and then S. The second fissure produced lava flows that traveled S, overtaking and setting fire to many houses and structures in communities north of Goma, just W of Monigi (12 km S). Video posted on social media showed lava fountaining from the fissures, a glowing red sky, and residents running through the streets. About 1,000 homes and buildings were destroyed and about 25,000 people were displaced. The lava cut off electricity and water supplies to some areas. The flow may have been as wide as 1 km and stopped 1.25 km from the Goma International Airport, in the SE part of the city, during 22-23 May. According to the Toulouse VAAC ash plumes may have initially rose to 13.7 km (45,000 ft) a.s.l., though subsequent estimates put the ash plumes mostly at 6.1-9.1 km (20,000-30,000 ft) a.s.l. during 22-23 May. Satellite images and local scientists indicated that the summit lava lake had drained before the flank fissures had opened, but began refilling afterward; collapses in the summit crater were the likely cause of the ash plumes.

Initial reports indicated that about 32 people had died: about 12 from lava and gas asphyxiation while crossing lava flows, and most of the rest from accidents while fleeing. Several people, including many children, remained missing, though families were continuing to be reunited.

Seismic data during 22-24 May showed events seemingly propagating from the summit area to the S into Lake Kivu. Several strong earthquakes shook buildings in Goma, causing some to collapse and injure people; a news article noted that tremor was felt about every 30 minutes beginning around noon on 23 May. Both airports in Goma closed for security reasons. A M 5.1 earthquake with a hypocenter beneath Lake Kivu was recorded at 1037 on 24 May. The VAAC noted that ashfall around the volcano and in surrounding towns was visible in satellite data. Cracks a few 10s of centimeters wide opened in different parts of the city on 25 May. The cracks stretched for several hundred meters from the northern city limit down to the lake, and were nearly 100 m long near the airport. Some cracks were hot and emitting gasses, and some were flaming. Ash plumes rose to 6.1 km (20,000 ft) a.s.l. and drifted S; ground-based reports indicated ash in the atmosphere above Goma. Seismicity remained intense on 25 May with more than 130 earthquakes between M 2 and 5 recorded in a 24-hour period. News reports indicated hundreds of damaged buildings in neighboring Rwanda.

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