Volcanos

Roundup of Global Volcanic Activity – Ongoing Activity for the Week 29 September – 5 October 2021

Aira – Kyushu (Japan) : JMA reported that incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 27 September-4 October. The trend of inflation that was first detected on 13 September continued. The sulfur dioxide emission rate was 1,500 tons per day on 28 September. A very small eruptive event occurred on 3 October.

Great Sitkin – Andreanof Islands (USA) : AVO reported that lava effusion continued at Great Sitkin during 29 September-5 October. Seismicity remained elevated and was characterized by small earthquakes consistent with lava effusion. Elevated surface temperatures were detected in satellite images. By 3 October the dome had grown to 1,200 m E-W and 1,000 m N-S. Lava flows that continued to advance down the S and SW flanks were about 300-350 m long. The SW lobe was descending two drainages and produced hot avalanches that traveled 450 m downslope on top of a snow field.

Karymsky – Eastern Kamchatka (Russia) : KVERT reported that a thermal anomaly over Karymsky was identified in satellite images during 24-28 September. Ash plumes rose as high as 4.6 km (15,100 ft) a.s.l. and drifted 100 km E, SE, and SW during 24-26 September.

Katmai – United States : AVO reported that beginning at 0400 on 2 October strong winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes blew unconsolidated ash SE towards Kodiak Island at an altitude up to 1.8 km (6,000 ft) a.s.l. The ash was originally deposited during the Novarupta eruption in 1912.

Klyuchevskoy – Central Kamchatka (Russia) : On 29 September strong winds resuspended unconsolidated ash from Klyuchevskoy’s flanks.

Krysuvik-Trolladyngja – Iceland : The Institute of Earth Sciences reported that lava effusion at Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, likely ceased during the evening of 18 September. The area of the flow field was about 4.85 square kilometers, and the total volume erupted was 150 million cubic meters, based on 30 September measurements. Parts of lava flows thickened in areas to the S of Geldingadalur and in Nàtthagi valley, and deflated in areas N of Geldingadalur. Points of incandescence were visible at night, at least through 4 October, likely from lava flows that continued to advance downslope. A seismic swarm in an area SW of Keilir (about 10 km NE of the fifth vent), at the N end of the dike intrusion, began on 27 September. According to news reports, over 6,000 earthquakes at depths of 5-6 km had been recorded by 4 October with at least 12 of them over M 3; the largest event was a M 3.8. Some of the larger events were felt in the capital. The seismicity was similar to patterns recorded before the beginning of the eruption to the SW. IMO stated that more data was needed to characterize the data as either indicative of magma movement or due to tectonic stress. IMO warned of the potential for lapilli and scoria fallout within a 650 m radius of the active vent. Authorities also warned of gas emission hazards.

Langila – New Britain (Papua New Guinea) : The Darwin VAAC reported that a discrete ash plume from Langila rose to 1.8 km (6,000 ft) a.s.l. on 3 October and drifted S. A thermal anomaly was visible afterward. On 4 October an ash plume again rose to 1.8 km a.s.l. and drifted S.

Lewotolok – Lembata Island (Indonesia) : PVMBG reported that the eruption at Lewotolok continued during 28 September-4 October. White-and-gray plumes rose as high as 800 m above the summit and drifted NW, W, and SW. Rumbling sounds were reported almost daily. During 30 September-1 October and 3-4 October incandescent material was ejected as far as 700 m away from the vent in multiple directions.

Merapi – Central Java (Indonesia) : BPPTKG reported minor morphological changes to Merapi’s SW lava dome, located just below the SW rim and in the summit crater, and no changes to the summit crater dome during 24-30 September. The SW dome grew 1 m taller and had an estimated volume of 1.63 million cubic meters; the summit lava dome had an estimated volume of 2.85 million cubic meters. As many as 67 lava avalanches traveled a maximum of 1.8 km SW.

Pavlof – United States : AVO reported that seismicity at Pavlof remained elevated during 29 September-5 October. No explosions were recorded most days by the seismic and infrasound networks, and no eruptive activity was observed in mostly cloudy webcam and satellite images. On 3 October webcam images showed that recent ash deposits on the flanks had been covered by fresh snow; later that night either new ash deposits were visible in webcam images or older deposits were revealed due to snowmelt. Weakly elevated surface temperatures were identified in satellite images. At least two minor explosions were recorded during 4-5 October and minor emissions likely comprised of steam and sulfur dioxide were visible in morning webcam images on 5 October.

Reventador – Ecuador : IG reported that a high level of activity continued to be recorded at Reventador during 29 September-3 October; cloudy weather conditions sometimes prevented webcam and satellite views. Gas-and-ash plumes, often observed multiple times a day with the webcam or reported by the Washington VAAC, rose as high as 1 km above the summit crater and drifted mainly W and NW. Crater incandescence was often observed at night along with incandescent blocks that rolled as far as 800 m down the flanks.

Sangay – Ecuador : IG reported a high level of activity at Sangay during 28 September-5 October. Weather clouds and rain sometimes prevented visual and webcam observations of the volcano. Ash plumes were identified in satellite images by the Washington VAAC or in webcam views during 30 September-1 October and 3 and 5 October; plumes rose 500-1,200 m above the volcano and drifted W and SW. Thermal anomalies over the volcano were often visible in satellite data. .

Semisopochnoi – Aleutian Islands (USA) : AVO reported that eruptive activity at Semisopochnoi’s North Cerberus crater continued during 29 September-5 October. Seismicity remained elevated with intermittent explosion signals or bursts of activity likely from explosions. A few explosions were also detected in regional infrasound data during 2-5 October. Small ash clouds were observed almost daily in either webcam or satellite images rising to altitudes below 3 km (10,000 ft) a.s.l.; plumes drifted ENE on 2 October, then N and NW on 3 October. Sulfur dioxide plumes were possibly observed on a few days, though definitely on 3 October. Webcams located 5-6 km from the active vent recorded ashfall during 4-5 October.

Sheveluch – Central Kamchatka (Russia) ; KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 24 September-1 October.

Suwanosejima – Ryukyu Islands (Japan) : JMA reported that 129 explosions at Suwanosejima’s Ontake Crater produced eruption plumes that rose as high as 3 km above the crater rim during 27 September-4 October. Large volcanic bombs were ejected as far as1 km from the crater. Crater incandescence was visible nightly.

Taal – Luzon (Philippines) : PHIVOLCS reported that sulfur dioxide emissions at Taal averaged 8,854 tonnes/day beginning on 27 September, and peaked on 5 October at 25,456 tonnes/day which was the highest ever sulfur dioxide gas flux recorded at the volcano. On 27 September the number of daily volcanic earthquakes significantly decreased. During 27 September-5 October upwelling of hot volcanic fluids in the lake was visible and gas-and-steam plumes rose as high as 3 km above the lake. The report noted that a sudden increase in inflation below Taal Volcano Island was recorded in August. The Volcano Alert Level remained at a 2 (on a scale of 0-5). PHIVOLCS reminded the public that the entire Taal Volcano Island is a Permanent Danger Zone (PDZ) and that boating on Taal Lake was prohibited.

Telica – Nicaragua : INETER reported that on 4 September a diffuse ash plume from Telica rose 1.2 km (4,000 ft) a.s.l. and drifted less than 10 km WSW, based on satellite images and model data.

Yasur – Vanuatu : On 30 September the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that seismic data and recent visual observations at Yasur confirmed ongoing explosions and gas-and-ash emissions. A few earthquakes were recorded on 28 September. The Alert Level remained at 2 (on a scale of 0-4). VMGD reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 600-m-radius exclusion zone, and that volcanic ash and gas could reach areas impacted by trade winds.

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