On 9 September IMO raised the Aviation Color Code for Askja to Yellow, noting that inflation that began in early August was ongoing and notably rapid. The uplift was centered at the W edge of Oskjuvatn caldera, which rose a total of 7 cm. The data suggested that magma was accumulating at 2-3.5 km depth.

Source: Icelandic Meteorological Office (IMO)

The Japan Coast Guard reported that during a 12 September overflight of Fukutoku-Oka-no-Ba, observers noted that the W island was unchanged while the E side had been completely eroded and submerged. Yellow-green to yellow-brown discolored water extended from the vent area to the SW, S, and SE, suggesting continuing eruptive activity. Another area of discolored water had an approximate diameter of 2 km and was about 2 km ENE of the volcano. The discolored water prompted JMA to issue a navigation warning to nearby vessels.

Source: Japan Coast Guard

Instituto Geográfico Nacional (IGN) and Instituto Volcanológico de Canarias (INVOLCAN) reported that a seismic swarm beneath Cumbre Vieja at the S part of La Palma began at 1618 on 11 September and was likely associated with a magmatic intrusion. The swarm intensified in number of events and magnitude, and by 1600 on 12 September a total of 315 earthquakes had been recorded and ranged 8-13 km in depth. The largest event was a M 2.8 (on the Mb_lg scale). On 13 September a scientific committee comprised of representatives from multiple agencies and institutions raised the Alert Level to Yellow (the second lowest level on a four-color scale) for the municipalities of El Paso, Los Llanos de Aridane, Mazo, and Fuencaliente de la Palma. By 0800 on 14 September 2,935 earthquakes had been detected. Larger events were felt by residents during 13-14 September; the largest earthquake was a M 3.9, recorded at 0600 on 14 September. Overall, the events were becoming shallower (8-10 km) and hypocenters migrated slightly to the W. GPS and tiltmeter networks showed deformation totaling 1.5 cm centered over the clusters of epicenters.

A total of 10 seismic swarms have been detected at La Palma since 2017; one in 2017, one in 2018, five in 2020, and three in 2021. The earthquakes in the previous swarms were deeper, between 20 and 30 km, and were less intense than the current swarm.

Sources: Instituto Volcanológico de Canarias (INVOLCAN), Gobierno de Canarias, Instituto Geográfico Nacional (IGN)

The U.S. Geological Survey reported that emissions of ash and sulfur dioxide from Pagan were last detected on 6 September, though robust steam plumes occasionally continued to be visible at least through 14 September. The Aviation Color Code and the Volcano Alert Level were lowered to Yellow and Advisory, respectively, on 10 September.

Source: US Geological Survey

On 14 September GeoNet reported that intermittent ash emissions at Whakaari/White Island continued to be visible during the previous week. Vigorous fumarolic plumes from the active vent area sometimes carried minor amounts of ash downwind at low altitudes and occasionally deposited ash on the island. Periods where ash was visible in the emissions did not correspond to explosive seismic or acoustic signals, suggesting that the ash was produced by weak wall fragments falling into the gas stream through the active vents and not from eruptive activity. Seismicity was characterized by low levels of volcanic tremor and occasional volcanic earthquakes. The Volcanic Alert Level remained at 2 and the Aviation Color Code remained at Yellow.

Source: GeoNet

JMA reported that incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 6-10 September. Deformation data showed inflation beginning at around 0300 on 13 September. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.

Source: Japan Meteorological Agency (JMA)

SERNAGEOMIN lowered the Alert Level for Cerro Hudson to Green (the lowest level on a four-color scale) on 7 September, based on decreased activity. Neither morphological changes nor thermal anomalies were visible in satellite images or webcam views during 16-31 August. Seismicity remained low and sulfur dioxide emissions were not recorded.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)

According to volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, explosions during 4 and 6-8 September produced ash plumes that rose as high as 2 km (6,600 ft) a.s.l. and drifted N, S, and E. Ash fell in Severo-Kurilsk on 6 and 8 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

The fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, had paused for several days. The Institute of Earth Sciences reported that based on aerial photography acquired on 9 September, during the pause, the area of the flow field had grown to 4.6 square kilometers, and the total volume erupted was 143 million cubic meters. The crater floor was visible and was at least 70 m deep, with a deeper cavity or drainage sometimes visible.

Lava visibly returned on 11 September; RSAM values increased and low lava fountains emerged from a few areas on the flow field to the W of the main crater. Lava also returned to the main vent. Lava fountains from the main crater were visible for periods of 5-10 minutes on 13 September and lava advanced in multiple directions. Lava flowed N on 14 September. By 15 September lava quickly advanced S, flowing past the earthen barriers constructed at the S end of Geldingadalur valley, and turning E into the Nàtthagi valley. The Aviation Color Code remained at Orange due to the lack of ash and tephra emissions, though 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.

Sources: Icelandic Meteorological Office (IMO), Institute of Earth Sciences, Icelandic National Broadcasting Service (RUV), Oliver Lamb (University of North Carolina), Icelandic National Broadcasting Service (RUV), Benjamin Hennig (University of Iceland)

AVO reported that lava effusion continued at Great Sitkin during 7-14 September, though weather clouds often prevented webcam and satellite views. Seismicity remained elevated and was characterized by small earthquakes consistent with lava effusion. A radar image from 9 September indicated that the lava dome had grown to 1,100 m E to W and 860 m N to S, and was 25-30 m thick. Lava began to advance though a gap in the S rim of the summit crater. Elevated surface temperatures were visible in satellite data on 14 September. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

Icelandic Meteorological Office (IMO) reported that the jökulhlaup from the [eastern and western Skaftá cauldrons, NW of Grímsvötn] that began on 1 September had decreased during 8-10 September. IMO warned of continuing flood conditions in the downstream parts of the Skaftá river.

Source: Icelandic Meteorological Office (IMO)

PVMBG reported that during 7-12 September gray-and-white ash plumes from Ibu rose 200-800 m above the summit and drifted N and W. The Alert Level remained at a 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

KVERT reported that a thermal anomaly over Karymsky was identified in satellite images during 3-10 September. Ash plumes rose 4 km (13,100 ft) a.s.l. and drifted 165 km E during 2-6 and 9 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Based on analyses of satellite imagery and wind model data, the Darwin VAAC reported that during 11-12 September ash plumes from Langila rose to 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted W. A thermal anomaly at the summit was identified in satellite data.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

PVMBG reported that the eruption at Lewotolok continued during 7-14 September. White-and-gray plumes rose as high as 700 m above the summit and drifted NWW, SW, and S. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

BPPTKG reported that both of Merapi’s two lava domes, situated just below the SW rim and in the summit crater, continued to grow during 3-9 September. The SW dome grew 5 m taller and had an estimated volume of 1.55 million cubic meters and the summit lava dome grew 1 m wider and had an estimated volume of 2.85 million cubic meters. One pyroclastic flow traveled 2 km down the SW flank and as many as 129 lava avalanches traveled a maximum of 2 km SW. According to the Darwin VAAC ash plumes rose 3 km (10,000 ft) a.s.l. and drifted E on 9 September, based on satellite and webcam views. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-5 km away from the summit based on location.

Sources: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Darwin Volcanic Ash Advisory Centre (VAAC)

SERNAGEOMIN reported continuing explosive and effusive activity at Nevados de Chillán’s Nicanor Crater during 16-31 August, though weather conditions often prevented visual confirmation. Explosions generated ash plumes that rose as high as 1.1 km above the crater rim and were denser towards the end of August. Crater incandescence was sometimes visible at night, and though not intense, it brightened during explosive periods. The L5 and L6 lava flows continued to advance, though at a very low rate, averaging 1 m/h for L5. The L5 lava flow was 1,380 m long and L6 was 850 m long based on satellite images, measured from the rim of Nicanor Crater to the distal end of the flows. A decrease in thermal anomalies over the flows identified in satellite images suggested that the flows were cooling. The average temperature was 73 degrees Celsius with a maximum of 100 degrees for L5 and an average of 79 degrees Celsius with a maximum of 100 degrees for L6. Temperatures at the vents at Nicanor Crater averaged 115 degrees Celsius and were as high as 252 degrees during explosive phases. Sulfur dioxide emissions measured from local DOAS stations abruptly decreased and remained low. There was a total of five thermal anomalies, all with low radiance values. On 29 August pyroclastic flows traveled 560 m NE and collapses of L5’s middle and distal parts of the flow were observed. The Alert Level remained at Yellow, the second lowest level on a four-color scale. ONEMI stated that Alert Level Yellow (the middle level on a three-color scale) remained in place for the communities of Pinto and Coihueco, noting that the public should stay at least 2 km away from the crater.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI)

AVO reported that seismicity at Pavlof continued at low levels during 7-14 September and was interspersed with periods of more energetic tremor. Although weather clouds often obscured views, a series of four very minor ash emissions were visible in webcam images for a period of five hours on 10 September. The explosions produced minor and diffuse ash emissions that rose from a vent on the E flank and dissipated within minutes. A small explosion was recorded on 12 September and on 13 September, though cloud cover prevented visual confirmation of both events. The Volcano Alert Level and Aviation Color Code remained at Watch and Orange, respectively.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

AVO reported that eruptive activity at Semisopochnoi's North Cerberus crater continued during 7-14 September. Seismicity was elevated and characterized by periods of continuous tremor. Short-lived explosions lasting several minutes were detected daily in infrasound data. Small ash clouds from the explosions rose 3-4.6 km (10,000-15,000 ft) and dissipated within two hours. Sulfur dioxide emissions were detected in satellite images at altitudes less than 3 km (10,000 ft) a.s.l., sometimes extending downwind for hundreds of kilometers. During 7-9 September periods of lower-altitude ash emissions interspersed with voluminous steam plumes were observed in web camera images moving horizontally by the wind and rising no higher than 1.5 km (5,000 ft) a.s.l. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

KVERT reported that a bright thermal anomaly over Sheveluch was identified in satellite images during 3-10 September. The Kamchatka Branch of Geophysical Services (KBGS; Russian Academy of Sciences) Kamchatka volcano station reported that tourists visiting the volcano on 8 September experienced ashfall; weather conditions prevented views of summit. The next day they saw a small pyroclastic flow and that night saw crater incandescence and small incandescent avalanches traveling SE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Institute of Volcanology and Geodynamics, Russian Academy of Natural Science

JMA reported that four explosions at Suwanosejima's Ontake Crater produced eruption plumes that rose as high as 3.3 km above the crater rim during 3-10 September. Large volcanic bombs were ejected 500 m from the crater. Crater incandescence was visible nightly. The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.

Source: Japan Meteorological Agency (JMA)

PHIVOLCS reported that gas-and-steam plumes from Taal rose as high as 2.5 km above the lake during 8-14 September and drifted NE, SE, S, and SW. Sulfur dioxide emissions were 5,246-11,840 tonnes/day during 9-10 and 12-13 September. 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.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)