INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 19-25 December. The active flow field consisted of overlapping lava flows that expanded into the Valle del Leone and the Valle del Bove. By 25 December the most active lava flow had descended to 2,150 m elevation. Gas emissions rose from the summit craters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

After JMA first reported new activity around the Kaitoku Seamount in August, discolored water continued to be periodically visible in Sentinel satellite images through 27 December. Though weather clouds sometimes prevented views of the vent area, and on occasion no activity was visible in clear images, plumes of discolored water drifting away from the vent area appeared to become more frequent in October. Images from 18 October, and 22 and 27 November possibly captured material at the surface or an eruption plume rising above the water. The Japan Coast Guard posted pictures of disturbed water around the vent in November. Recent Sentinel images on 17 and 27 December captured plumes of discolored water drifting as far as 10 km from the vent area.

Sources: Sentinel Hub, Japan Coast Guard

Unrest continued to be detected at Ahyi Seamount during 21-27 December. Wake Island hydrophone sensors detected daily signals that possibly indicated explosions. An underwater plume was visible in satellite images during 26-27 December. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Source: US Geological Survey

JMA reported ongoing eruptive activity at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 19-26 December. Crater incandescence was visible nightly. Sulfur dioxide emissions were slightly high at 1,500 tons per day on 19 December. An explosion at 0449 on 22 December ejected blocks 600-900 m from the vent. An explosion at 1954 on 24 December produced an ash plume that rose 1.2 km above the crater rim and ejected large blocks as far as 1.1 km from the vent. 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)

KVERT reported that a thermal anomaly over Alaid was identified in satellite images on 17 and 22 December; weather clouds obscured observations on the other days during 16-21 December. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

On 23 December IG issued a special report about increased activity at Cotopaxi. A total of 27 ash emissions had been recorded since the eruption began on 21 October; one ash emission was recorded in October, four were recorded in November, and 22 were recorded by 23 December. Based on Washington VAAC notices, ash clouds drifted the farthest, 60 km NNW, on 26 November and 20 December after rising 2.2 km (the maximum recorded height) and 1.5 km above the crater rim, respectively. Ashfall on those two days was reported in the Mejía, Rumiñahui, and Quito regions. Ash samples from 21 October and 26 November revealed a slight increase in the total percentage of juvenile material; an analysis of 20 December ash was in progress. Increases in sulfur dioxide emissions were measured both by satellite and ground-based Differential Optical Absorption Spectroscopy (DOAS) instruments. Gas measurements taken during periodic overflights showed increases in the ratio of sulfur dioxide to hydrogen sulfide. Based on these and other monitoring data, IG reiterated that the activity was caused by magma in the volcano’s conduit, though not from new magma entering the system after the 2015 eruption.

Daily emissions with ash continued to be observed in webcam images and reported by the Washington VAAC during 23-27 December; weather clouds obscured views on 26 December. Gas-and-steam plumes with low ash content rose as high as 1.5 km above the crater rim and drifted in various directions. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)

PVMBG reported that almost daily white-and-gray plumes of variable densities rose from Dukono as high as 400 m above the summit and drifted N and E during 23-27 December. Inclement weather conditions sometimes prevented visual observations. 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.

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

KVERT reported that moderate activity at Ebeko was ongoing during 15-22 December. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions on 18 December generated ash plumes that rose to 2.5 km (8,200 ft) a.s.l. and drifted NE. A thermal anomaly was identified in satellite images that same day; the volcano was obscured by weather clouds on the other days of the week. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

AVO reported that satellite data acquired on 22 December confirmed that the lava flow field at Great Sitkin was advancing E. Slow lava effusion likely continued during 23-27 December, though nothing significant was visible in sometimes cloudy satellite images or detected in seismic data. Elevated surface temperatures were identified in satellite images during 21-23 and 25-27 December. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

On 22 December KVERT lowered the Aviation Color Code for Klyuchevskoy to Green (the lowest level on a four-color scale), noting that the eruption had ended in November and the thermal anomaly that had been identified in satellite images had returned to background levels. Dates are based on UTC times; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

The Darwin VAAC reported that on 26 December an ash plume from Manam rose to 3 km (10,000 ft) a.s.l. and drifted S and SSE based on satellite images.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

BPPTKG reported that the eruption at Merapi continued during 16-22 December and seismicity remained at high levels. The SW lava dome produced three lava avalanches that traveled as far as 1.5 km down the SW flank (upstream in the Kali Bebeng drainage). Sounds of falling material were noted four times. No significant morphological changes to the central and SW lava domes were evident. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit based on location.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)

IG described the ongoing eruption at Reventador as moderate during 21-27 December. Daily seismicity was characterized by explosions, long-period earthquakes, periods of harmonic tremor, and signals that indicated emissions. Gas, steam, and ash plumes, observed daily with webcams or reported by the Washington VAAC, rose as high as 1.3 km above the summit and drifted in multiple directions. Weather clouds occasionally prevented webcam and satellite views of the volcano. Crater incandescence was visible nightly or during the early morning hours; incandescent blocks rolled down all flanks, descending as far as 700 m.

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

IG reported a high level of activity at Sangay during 20-27 December, which included daily explosions, volcanic tremor, and gas, steam, and ash emissions. The daily count of explosions ranged from 708-1,250, though seismic data transmission was sometimes interrupted. Almost daily ash-and-gas plumes were identified in IG webcam images and satellite images according to the Washington VAAC; weather clouds sometimes prevented observations of the summit. Gas, steam, and ash plumes rose as high as 1.2 km above the volcano and drifted mainly NW, W, SW, and S. Multiple daily thermal anomalies were identified in satellite images. Crater incandescence was visible some nights and early mornings. Incandescent material was observed rolling down the SE flank during 26-27 December.

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

KVERT reported that the ongoing eruption at Sheveluch during 15-22 December was generally characterized by explosions, hot avalanches, lava-dome extrusion, and strong fumarolic activity. A daily thermal anomaly was identified in satellite images, and ash plumes were visible drifting 110 km NNE on 16 December. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

INGV reported that both explosive and effusive activity at Stromboli were observed during 19-25 December at four vents in Area N, one N1 vent and three N2 vents; all were located in the upper portion of the Sciara del Fuoco. Explosions from the vents were variable in intensity and ejected coarse material (bombs and lapilli) 80-150 m high at a rate of 3-10 explosions per hour. Intense spattering from all four vents occurred during the week. Lava flows reached about halfway down the Sciara del Fuoco.

At 0942 on 19 December lava overflowed vents in the N2 area, after a period of intense spattering. The lava flowed part way down the Sciara del Fuoco, likely channeled in the ravine that had formed in October, out of view from webcams. The flow was well-fed for a couple of hours but then effusion slowed or stopped, and it began to cool. The same activity occurred again, with a lava overflow occurring at 1547 on 21 December and traveling about the same distance. On 22 December explosive activity at the Central-South area (CS) ejected fine-to-coarse material as high as 150 m above the vent.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 19-26 December. No explosions were recorded. Eruption plumes rose at least 1 km above the crater rim and disappeared into weather clouds, and blocks were ejected as far as 30 m from the vent. Ashfall was occasionally reported in Toshima village (3.5 km SSW) during 23-26 December. 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 reported that at 0845 on 24 December a volcano-tectonic earthquake at Villarrica was followed by increased Strombolian activity. Explosions ejected material generally to heights of less than 100 m, though one explosion ejected incandescent tephra as far as 400 m onto the SW flank. According to POVI, there were 11 ejections of incandescent ballistics that impacted the upper SW flank between 2225 on 25 December to 0519 on 26 December. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the public was warned that material could be ejected within 500 m of the crater. ONEMI maintained the Alert Level at Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI), Proyecto Observación Villarrica Internet (POVI)