The Japan Coast Guard conducted an overflight on 14 December of Ioto (Iwo-jima) to inspect the new island formed by an eruption from a submarine vent about 1 km off the SE coast at Okinahama. No eruptive activity was detected, but the shape of the island had notably changed due to erosion and wave action. During the previous 10 days deposits at the N part of the “J” shaped island had separated and migrated N, connecting to the Okinahama coast, and the curved part of the “J” had eroded into two smaller islands.

Sources: Japan Coast Guard, Copernicus Browser

AVO reported that a small explosion at Kanaga was detected in local infrasound and seismic data at 2231 on 18 December, and was followed by elevated seismicity. No ash emissions were detected in partly cloudy satellite images. The next day the Volcano Alert Level was raised to Advisory (the second level on a four-level scale) and the Aviation Color Code was raised to Yellow (the second color on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

On 17 December seismicity at Lewotobi increased significantly, prompting PVMBG to raise the Alert Level to 2 (on a scale of 1-4). Seismicity had been increasing during the previous week and was characterized by greater numbers of both deep and shallow volcanic earthquakes, and the emergence of tornillo-type earthquakes which indicated fluid movement. The public was warned to stay 2 km away from the craters at each summit.

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

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 13-19 December, though foggy and raining weather conditions often prevented visual observations of the summit. White-and-gray ash plumes that were sometimes dense rose 400-600 m and drifted S, SW, NW, and NE during 13-15 and 18 December. The Alert Level remained at 2 (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)

PVMBG reported that during 1-17 December the maximum height of steam-and-gas plumes at Raung was 500 m above the summit. An M 2.6 local tectonic earthquake was detected on 18 December and afterwards plumes rose as high as 1 km. Seismicity during December indicated that fluid movement was concentrated at shallow depths; signals indicating emissions significantly increased on 18 December. Deformation data indicated a trend of deflation. On 18 December PVMBG raised the Alert Level to 2 (on a scale of 1-4) noting that the visual observations and seismic data indicated unstable conditions. The pubic was warned to stay 3 km away from the summit crater.

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

IMO reported that a new eruption on the Reykjanes peninsula began at 2217 on 18 December from fissures that opened in a location close to the older Sundhnúkagígar crater row, about 3 km NE of the town of Grindavík. A magmatic dike began intruding beneath the area in late October based on seismic and deformation data; magma continued to flow into the dike causing ground cracking in areas along its axis. The eruption was immediately preceded by an earthquake swarm that began at 2100 on 18 December and the opening of the fissure was accompanied by significant ground deformation.

Increased seismicity and a burst of incandescence indicating the start of the eruption was seen in webcam images. IMO raised the Aviation Color Code to Red (the highest level on a four-color scale) until the situation was able to be evaluated and in case ash was present in any emissions. After the first fissure opened, it propagated S in a series of four additional segments, slightly offset from each other but aligned with the previous dike intrusion. The total length of the fissure was estimated to be 4 km, with the north end just E of the Stóra-Skógfell cones and the south end E of the Sundhnúk cone. Large lava fountains possibly rose hundreds of meters high along the fissures, feeding lava flows in multiple directions. The rate of lava discharge during the first two hours of the eruption was about 100-200 cubic meters per second. The tallest lava fountains were located on the N end of the fissure. The largest earthquake, a M 4.1, was recorded at 2325. The Aviation Color Code was lowered to Orange. By midnight seismicity had declined and the eruption was less intense.

During a second overflight with the Iceland Coast Guard at around 0400 on 19 December scientists noted that the fissure had stopped extending and that most of the activity was concentrated in the central portion. There was minor activity at the S end, near the Hagafell cone, and most of the lava was advancing E towards Fagradalsfjall. Two branches traveled W, remaining N of Stóra-Skógfell. Gas plumes drifted W and NW. Residents of Grindavík, evacuated in November due to ground cracking and unsafe conditions, had recently been allowed to return and allowed to stay until 2100, but not overnight; they again fully evacuated the town due to the eruption. The recently reopened Blue Lagoon resort closed again. Some area roads were also temporarily closed.

Eruptive activity concentrated at five vents during the early part of 19 December. By 1430 the lava discharge rate was about one-fourth the rate measured at the beginning of the eruption and about one-third of the fissure was active. Lava fountains were lower, rising as high as about 30 m. The eruption intensity continued to decline and by 1830 only three vents were erupting. About 5 cm of deflation was detected in Svartsengi; a total of 35 cm of uplift had been recorded there since the beginning of the dike intrusion in November. The power plant in Svartsengi, W of the fissure, was not threatened by the current lava flows, though construction of an earthen barrier around it and the Blue Lagoon continued.

Sources: Icelandic Meteorological Office (IMO), Icelandic National Broadcasting Service (RUV)

PVMBG reported increased activity at Tengger Caldera’s Bromo cone in a 13 December press release. Emissions that day were white, gray, and brown, had variable densities, and rose as high as 900 m above the summit. The plumes drifted in multiple directions. The report noted that tremor was continuous and accompanied in December by three volcanic earthquakes. Deformation data indicated inflation in December. Daily white emissions that rose as high as 700 m above the summit and drifted in multiple directions were visible through 18 December. The Alert Level remained at 2 (on a scale of 1-4), and visitors were warned to stay outside of a 1-km radius of the crater.

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

JMA reported ongoing activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 11-18 December, with incandescence at the crater observed nightly. Small eruptive events were occasionally recorded through the week. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.

Source: Japan Meteorological Agency (JMA)

KVERT reported that moderate explosive activity was ongoing at Ebeko during 7-14 December. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 7 and 11-12 December generated ash plumes that rose as high as 2.5 km (8,200 ft) a.s.l and drifted NE. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are UTC; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

AVO reported that an 11 December radar image of Great Sitkin showed continuing growth of a thick flow in the summit crater; effusion likely continued during 12-19 December. Weather clouds often obscured views of the volcano, though no notable activity was visible in a few clear webcam images on 15 December. Seismicity was low. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

PVMBG reported that Ibu continued to erupt during 13-19 December. Daily white-and-gray ash emissions that were sometimes dense rose 200-1,300 m above the summit and drifted in multiple directions during 13-16 December. The Alert Level remained at a 2 (the second highest level on a four-level scale), with the public advised to stay outside of the 2 km hazard zone and 3.5 km away from the N area of the active crater.

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

PVMBG reported that the eruption at Krakatau continued during 13-19 December. White-and-gray ash plumes that were sometimes dense rose as high as 1 km above the summit and drifted NE and N during 13-16 December. Some webcam images posted with the daily reports showed incandescence at the vent. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 km away from the crater.

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

PVMBG reported that the eruption at Lewotolok continued during 13-19 December. White-and-gray ash plumes rose 100 m on 13 December and drifted E. White steam-and-gas plumes rose 100-200 m above the summit on the other days and drifted E, NE, and NW. Incandescence lava was ejected 200 m from the vent on 15 and 18 December and summit incandescence was visible in webcam images on 16 and 19 December. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the summit crater.

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

PHIVOLCS characterized activity at Mayon as “decreased unrest” during 12-19 December. The seismic network recorded 1-4 daily volcanic earthquakes and 1-2 rockfall events during 12-15 December. The summit was occasionally obscured by weather conditions, though on most days emissions were visible drifting in multiple directions. The Tokyo VAAC reported that at 1447 on 17 December an ash emission was identified in a satellite image rising to 2.4 km (8,000 ft) a.s.l. and drifting WSW based on satellite data and information from PHIVOLCS. The Alert Level remained at 2 (on a 0-5 scale). Residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

BPPTKG reported that the eruption at Merapi (on Java) continued during 8-14 December. A series of pyroclastic flows traveled 3.8 km SW down the Bebeng and Krasak drainages on 8 December. Minor amounts of ash fell in the districts of Dukun, Sawangan, Magelang, and Selo. During the week the SW lava dome produced a total of 243 lava avalanches; 22 traveled as far as 2 km down the Boyong drainage and 221 traveled as far as 1.9 km down the Bebeng drainage. Minor morphological changes to the SW lava dome were identified in webcam images due to continuing lava effusion and collapses of material. Both the number and intensity of shallow volcanic earthquakes and hybrid events significantly decreased during the week. 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)

OVSICORI-UNA reported that at 0646 on 16 December a small phreatic eruption at Poás ejected material 20 m above the lake’s surface and produced a steam plume that rose 200 m. Additionally, two small eruptions were recorded at 1436 on 17 December and 0022 on 18 December.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

CENAPRED reported that eruptive activity continued at Popocatépetl during 11-19 December. Long-period events totaling 34-280 per day were accompanied by steam-and-gas plumes that occasionally contained minor amounts of ash. The plumes mainly drifted ENE. The seismic network recorded 1.5-15.5 daily hours of tremor, as well as two volcano-tectonic earthquakes during 14-15 December and one M 1.9 volcano-tectonic earthquake on 16 December. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale) and the public was warned to stay 12 km away from the crater.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)

IG-EPN reported that the eruption at Reventador was ongoing during 12-19 December. Seismicity was characterized by 23-51 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions; data reception was interrupted during 13-14 December. Several daily ash-and-gas plumes rose as high as 1 km above the crater rim and drifted in multiple directions, though cloudy conditions prevented views at times during 18-19 December. Crater incandescence was often visible during both overnight and morning hours, and avalanches of incandescent material frequently descended the flanks to distances as far as 800 m from the summit. Weather conditions sometimes prevented views of the volcano. Secretaría de Gestión de Riesgos maintained the Alert Level at Orange (the second highest level on a four-color scale).

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

Instituto Geofísico del Perú (IGP) reported that the eruption at Sabancaya continued at moderate levels during 11-17 December with a daily average of 55 explosions. Gas-and-ash plumes rose as high as 3.5 km above the summit and drifted E and SE. Thermal anomalies over the lava dome in the summit crater were identified in satellite data. Minor inflation was detected near the Hualca Hualca sector (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12 km radius.

Source: Instituto Geofísico del Perú (IGP)

IG-EPN reported a high level of eruptive activity at Sangay during 12-19 December, with seismic stations recording 109-613 daily explosions. Daily ash-and-gas plumes were visible in webcam and satellite images, rising as high as 2 km above the crater rim and drifting SW, W, and NW; ash plumes rose as high as 3 km during 18-19 December. Webcam images showed incandescence at the summit vent and incandescent material descending the SE flank as far as 1.8 km from the crater. Weather clouds often prevented observations of the summit area. Secretaría de Gestión de Riesgos maintained the Alert Level at Yellow (the second highest 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 eruptive activity continued at Semeru during 13-19 December. White-and-gray ash plumes that were sometimes dense rose 500-700 m above the summit and drifted in multiple directions during 13 and 15-18 December. The Alert Level remained at 3 (third highest on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

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

KVERT reported that the eruption at Sheveluch continued during 7-14 December. A daily thermal anomaly was identified in satellite images. The Aviation Color Code remained at Orange (the third 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 unrest continued at Shishaldin during 12-19 December. Seismicity remained low and was characterized by small low-frequency earthquakes recorded daily and tremor recorded during 15-19 December. Barely elevated surface temperatures identified in satellite images during 13-14 December were likely associated with cooling deposits on the upper flanks. Minor steaming at the summit was visible in webcam images on 15 December. Infrasound signals indicating weak explosions were detected during 17-18 December but did not produce ash emissions; only minor steaming at the summit was visible in clear webcam images. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 11-18 December and crater incandescence was visible nightly. No explosions were detected, though eruption plumes rose as high as 800 m above the crater rim and large blocks were ejected as far as 200 m from the vent. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 1 km away from the crater.

Source: Japan Meteorological Agency (JMA)

Instituto Geofísico del Perú (IGP) reported that activity at Ubinas was at low levels during 1-15 December. Seismicity was low with daily averages of 143 volcano-tectonic earthquakes indicating rock fracturing and 23 earthquakes signifying the movement of gas and magma. Additionally, there was a total of more than 16 hours of seismic signals associated with ash emissions. During 10-15 December webcam images recorded emissions of gas, steam, and ash that rose as high as 2.5 km above the summit and drifted NW and W. The Alert Level remained at Yellow (the second level on a four-color scale) and the public was warned to stay 2 km away from the crater.

Source: Instituto Geofísico del Perú (IGP)

On 19 December GeoNet reported that activity at Whakaari/White Island remained low based on gas and observation flights conducted over the previous two months. Minor steam-and-gas emissions rose from a cluster of fumarolic vents located on the W shore of the lake; there has been no evidence of ash in the emissions. The discharge rates of the emissions during the year were characterized by low-to-moderate levels which were typical. Temperatures at the larger vents generally declined. The level of the lake had dropped, isolating a small pool from the main body of the lake. The Volcanic Alert Level remained at 2 (on a scale of 0-5) and the Aviation Color Code remained at Yellow (the second level on a four-color scale). GeoNet noted that Alert Levels reflect the level of unrest at the volcano but also consider the greater level of uncertainty due to the current lack of consistent and useful real-time data.

Source: GeoNet