Volcanos

Roundup of Global Volcanic Activity – Ongoing Activity for the Week 28 July – 3 August 2021

Dieng Volcanic Complex – Central Java (Indonesia) : PVMBG reported that on 30 July a burst of mud originated from the Siglagah thermal feature (Dieng Volcanic Complex), located on a steep hill, about 1 km NE of the center of Pagerkandang cone. The event caused an audible banging noise and sent a mudflow, 1-3 m thick, 10 m N. Observers that had visited the site in July saw gas emissions rising 10-30 m high and occasionally heard “bursting” noises up to 100 m away. The event was not accompanied by an increase in seismicity.

Great Sitkin – Andreanof Islands (USA) : AVO reported that unrest continued at Great Sitkin during 28 July-3 August. Seismicity remained elevated and a small swarm was recorded during 1-2 August. Elevated surface temperatures and a north-drifting steam plume were identified in satellite images during 27-28 July. Minor steam emissions were visible during 31 July-3 August. The circular lava dome in the crater had grown to 180 m in diameter based on measurements taken using a 3 August satellite image.

Nyiragongo – DR Congo : Goma Volcano Observatory (GVO) reported that a small area of incandescence from the floor of Nyiragongo’s collapsed crater was visible in a 26 July satellite image.

Pagan – Mariana Islands (USA) : Residents reported felt earthquakes and observed minor emissions at Pagan at around 1430 on 29 July.

Savo – Solomon Islands : According to a news source, residents on Savo in the Solomon Islands reported increased seismicity to authorities on 28 July. Two days later a team from the Geological Survey Division (GSD) and the National Disaster Management Office (NDMO) investigated the volcano. They saw steam-and-gas emissions rising from an area in the crater, possibly indicating an active fissure.

Semisopochnoi – Aleutian Islands (USA) : AVO reported that seismicity at Semisopochnoi had increased in recent days. A notable increase at 0200 on 31 July prompted AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch a few hours later. Additionally, increased infrasound recorded by local stations suggested low-level emissions. Weather clouds obscured satellite views, though a possible sulfur dioxide plume was detected. Steaming was visible in webcam images. Increased seismicity and elevated activity in infrasound data were recorded during 31 July-1 August, and multiple, discrete, energetic explosions were detected during 1-3 August. Weather clouds again obscured satellite views; steaming was visible in webcam views. Beginning at 1015 on 2 August the local networks recorded an explosion and an intense burst of seismic and acoustic tremor that lasted for about 15 minutes. A small ash cloud was visible in satellite images drifting 60 km N at altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. Ash emissions from the active vent in North Crater were visible in webcam views on the morning of 3 August.

Ulawun – New Britain (Papua New Guinea) : According to the Darwin VAAC, pilots observed ash plumes from Ulawun on 29 July and 3 August rising 3-3.4 km (10,000-11,000 ft) a.s.l. and drifting E and SSE, respectively. Weather clouds prevented satellite confirmation of the emissions.

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