A thermal anomaly at Nishinoshima was identified in satellite images on 5 December, prompting JMA to expand the marine exclusion zone around the island to 1.5 km. The Japan Coast Guard (JCG) conducted an overflight the next day and observed Strombolian explosions ejecting blocks as high as 200 m above a crater on the E side of the central pyroclastic cone. Lava flows had traveled to within 200 m of the coastline. Light gray eruption plumes drifted E. During an overflight on 7 December observers confirmed continuing Strombolian activity and saw lava entering the sea.

Sources: Japan Meteorological Agency (JMA), Japan Coast Guard

Strong tremor at Semisopochnoi was recorded by local seismic and regional infrasound networks beginning at 0026 on 7 December, heralding the start of an eruption and prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. The meteorological cloud deck over the volcano was at around 3 km (10,000 ft) a.s.l.; no ash signals were detected above this altitude. A period of intermittent explosions was detected, and afterwards seismicity remained elevated at least through 9 December.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

A deadly and short-lived (1-2 minutes) eruption at White Island began around 1411 on 9 December, prompting GeoNet to raise the Alert Level to 4 and the Aviation Color Code to Orange. The eruption originated from the crater floor and generated an ash plume that rose 3.7 km (12,000 ft) above the vent. Ashfall was confined to the island and covered the crater floor based on webcam views. Activity waned after the event and within a few hours the Alert Level was lowered to 3. An exclusion zone extending just under 10 km around the island was emplaced for all (non-police) vessels.

The New Zealand Police stated that 47 local and international people in a tour group were on the island at the time of the eruption. A majority of the people in the group were seriously injured and taken to area hospitals; six were confirmed dead. On 10 December the police concluded that there likely were no additional survivors after several reconnaissance flights conducted post-eruption; nine people remained missing and assumed to be on the island.

On 10 December GeoNet reported that although seismic activity had dropped to low levels after the eruption, localized steaming and mud jetting continued from the active vents. Tremor significantly increased starting around 0400 on 11 December. Results from an overflight to collect gas emission data, along with other monitoring data collected over time, suggested that a shallow magma source was driving the tremor, gas emissions, and jetting activity.

Sources: GeoNet, New Zealand Police

JMA reported that incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 2-9 December. There were 15 explosions and four non-explosive eruptive events detected by the seismic network. Ash plumes rose 2.3-2.6 km above the crater rim and blocks were ejected as far as 1.7 km away. The Alert Level remained at 3 (on a 5-level scale).

Source: Japan Meteorological Agency (JMA)

Based on satellite and wind model data, and information from PVMBG, the Darwin VAAC reported that during 4-9 December ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC)

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 30 November and 1-2 and 5 December that sent ash plumes up to 3 km (10,000 ft) a.s.l. Ash plumes drifted NE and E. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

PVMBG reported that during 2-8 December lava continued to effuse from Karangetang’s Main Crater (S), traveling as far as 1.8 km down the Nanitu, Pangi, and Sense drainages on the SW and W flanks. Sometimes dense white plumes rose to 200 m above the summit. Incandescence from both summit craters was visible at night. The Alert Level remained at 2 (on a scale of 1-4).

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

KVERT reported that Strombolian activity at Klyuchevskoy was visible on 29 November and 1 December, the same days a weak thermal anomaly was identified in satellite images. The Aviation Color Code remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

IG reported that during 4-10 December seismic data from Reventador’s network indicated a high level of seismic activity, including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions. Weather sometimes prevented views of the summit area, although during clear conditions ash, gas, and steam plumes were visible rising sometimes higher than 1 km above the crater rim and drifting N, NW, W, and SW. Crater incandescence was periodically observed at night. Blocks rolled 500-700 m down the flanks in multiple directions during 7-10 December.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)

IG reported that the eruption at Sangay that began on 7 May was continuing as of 4 December without a notable increase or decrease in activity levels. Activity was concentrated at two eruptive centers: the Central Crater and the Ñuñurcu dome (located 190 m SSE of Central Crater). Sporadic explosions at Central Crater produced ash plumes that rose as high as 2 km above the crater rim and drifted mainly NE during the previous month. Minor ashfall was recorded in the towns of Alao (20 km NW), Cebadas (35 km WNW), and Guaguallá (Chimborazo province), in Macas (42 km SSE, Morona-Santiago province), and in the Azuay province. Almost continuous lava effusion from the Ñuñurcu dome fed lava flows that traveled down the SE flank.

Collapses along the margins of the lava flows generated small pyroclastic flows and small rockfalls that reached the upper channel of the Río Volcán. These deposits created dams which were remobilized by rainfall into lahars, which in turn partially dammed parts of the river at the confluence of the Río Upano. Parque Nacional Sangay and IG-EPN staff measured deposits at the confluence that were more than 2 m thick on 27 November; similar deposits were observed along a 16-km stretch upsteam. Sulfur dioxide emissions up to 640 tons/day were detected by satellite in recent weeks, and a strong sulfur odor was noted around 1 km above the crater rim during a 3 December overflight.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)

The Darwin VAAC reported that during 4-5 and 7-9 December discrete ash emissions from Sangeang Api rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted NW, W, and SW. A thermal anomaly was visible on 27 November. The Alert Level remained at 2 (on a scale of 1-4).

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 29 November-6 December. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

AVO reported that elevated surface temperatures at Shishaldin were identified in satellite images during 3-4 December consistent with lava effusion, and a pilot confirmed active lava flows on the flank. Continuous tremor was recorded by the seismic network during 4-5 December. Seismicity, including Strombolian explosion signals, continued to increase until 2100 on 5 December and then afterwards was characterized by episodic tremor bursts and occasional Strombolian activity. Intermittent, very minor, and low-level ash or steam emissions near the summit and along the N flank were visible in clear webcam views on 5 December. A new lava flow had traveled 1.4 km down the NW flank. The eruption either slowed or paused during 6-7 December as evidenced by decreased seismicity and slightly elevated surface temperatures in satellite data. Temperatures again increased and were slightly elevated during 7-9 December, likely signifying renewed lava effusion. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Source: US Geological Survey Alaska Volcano Observatory (AVO)