Report for Etna
INGV reported that Strombolian activity at Etna’s SE Crater (SEC) was periodically visible during 20-26 November; weather clouds often prevented visual observations. The frequency of the eruptive activity was on the scale of hours, and explosions were most intense during 25-26 November. The explosions ejected material that fell within the crater or nearby on the flanks and produced ash emissions that rapidly dispersed near the summit. Lava overflowed the crater starting at 1810 on 24 November and produced a slow-moving lava flow that descended the S flank to the base of the cone. The lava flowed down the same ravine as one of the three flows emplaced on 12 November and was no longer being fed by 0450 on 25 November. During periods of more intense Strombolian activity on 26 November ejected lava that accumulated on the upper S flank and was visible in thermal webcam images. Activity at Bocca Nuova Crater was characterized by pulsating gas emissions and flashes of incandescence generated by the hot gases.
Report for Krakatau
PVMBG issued four Volcano Observatory Notices for Aviation (VONAs) on 26 November describing ash plumes from Krakatau rising as high as 1 km above the summit and drifting NW and NE. Webcam images showed incandescent material being ejected above the vent. There were 12 VONAs issued on 27 November; white-and-gray ash plumes that were sometimes dense rose as high as 1.5 km and drifted NE and NW. Webcam images continued to show incandescence at the vent and material being ejected from the vent. At least nine VONAs on 28 November described ash plumes rising as high as 2 km and drifting NE, N, and NW. 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.
Report for Merapi
BPPTKG reported that the eruption at Merapi (on Java) continued during 17-23 November. The SW lava dome produced a total of 91 lava avalanches that descended the flanks; three traveled as far as 1.3 km down the upper part of the Boyong drainage and 88 traveled as far as 1.8 km down the upper Bebeng drainage. Minor morphological changes to the SW lava dome were identified in webcam images due to continuing lava effusion and collapses of material. 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.
Report for Bagana
The Darwin VAAC reported that an ash plume from Bagana was identified in satellite images rising to 3 km (10,000 ft) a.s.l. and drifting SW at 1300 on 24 November. The plume was continuously emitted for several hours. The plume had dissipated by 0710 on 25 November.
Report for Mayon
PHIVOLCS reported that slow lava effusion at Mayon’s summit crater continued during 22-28 November. The lengths of the lava flows in the Mi-Isi (S), Bonga (SE), and Basud (E) drainages remained at 2.8 km, 3.4 km, and 1.1 km, respectively. Collapses at the lava dome produced rockfalls and occasional pyroclastic density currents (PDCs, or pyroclastic flows) that descended the flanks as far as 4 km. Seismic stations recorded 7-111 daily rockfall events and 0-7 daily volcanic earthquakes. Two earthquakes indicated Strombolian explosions during 26-27 November. A total of three PDC events were recorded during the week. Sulfur dioxide emissions averaged 857-1,992 tonnes per day. Lahars descended the Buyoan-Padang and Mi-Isi drainages during 25-26 November. The Alert Level remained at 3 (on a 0-5 scale) and residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ). PHIVOLCS recommended that civil aviation authorities advise pilots to avoid flying close to the summit.
Report for Great Sitkin
AVO reported that slow lava effusion continued at Great Sitkin during 22-28 November characterized by a thick flow in the summit crater that mainly expanded E. Seismicity was low. Weakly elevated surface temperatures were identified in satellite imagery during 24-25 November. 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).
Report for Bogoslof
AVO reported that seismicity at Bogoslof had declined during the previous three weeks to background levels and the last moderate earthquake, a M 2.7, was recorded on 9 November. No other signs of unrest were detected. Both the Volcano Alert Level and the Aviation Color Code were changed to Unassigned on 24 November. A seismic swarm had started around 22 October and was characterized by 5-10 events per hour and a total of around 1,100 earthquakes per week at the peak. The volcano was monitored by a single local seismic station, distant seismic and infrasound instruments, satellite data, and lightning networks.
Report for Shishaldin
AVO reported that unrest continued at Shishaldin during 22-28 November. Seismicity began to decrease on 21 November, though remained elevated with ongoing seismic tremor and small, low-frequency earthquakes recorded during the week. Elevated surface temperatures were identified in satellite images during 22 and 25-26 November. Robust steam emissions rising from the summit vent as well as from a scarp on the upper NE flank, near the summit were visible in satellite and webcam images drifting 50 km SSE during 25-26 November. During 27-28 November steam plumes were visible in webcam images and small explosions were observed in seismic and local infrasound data. Weather clouds often prevented views of the volcano. 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).
Report for Reventador
IG-EPN reported that the eruption at Reventador was ongoing during 21-28 November. Seismicity was characterized by 31-60 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Several daily ash-and-gas plumes rose as high as 1.2 km above the crater rim and drifted in multiple directions. Daily crater incandescence was visible during both overnight and morning hours. Incandescent material was ejected 200 m above the crater rim during 21-23 November, and avalanches of incandescent material descended the flanks daily, traveling 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).
Report for Sangay
IG-EPN reported a high level of eruptive activity at Sangay during 21-28 November, with seismic stations recording 232-463 daily explosions. Ash-and-gas plumes visible in webcam and satellite images during 21, 23, and 27-28 November rose as high as 2 km above the crater rim and drifted N, NE, SE, and SW. Webcam images showed incandescent material at the summit vent and descending the SE flank as far as 1.8 km from the crater during 21-22 November. Weather clouds prevented observations during the rest of the week. Secretaría de Gestión de Riesgos maintained the Alert Level at Yellow (the second highest level on a four-color scale).
Report for Brava
According to the Cape Verde National Institute of Meteorology and Geophysics (INMG), seismicity at Brava increased on 30 October and remained elevated. A M 3.6 earthquake was recorded at 1819 on 30 October and was followed by eight more events of similar magnitudes that were felt by residents. A M 4.8 was recorded at 2100 and was followed by a 48-hour-long seismic swarm mostly consisting of low-magnitude events that were unable to be located. The Alert Level was raised to 2 (the second level on a five-level scale) on 30 October.
The rate of seismicity was variable, with two events every 1-10 minutes during 30 October-1 November. Most of the events were located at depths of 3-4 km; the hypocenters were initially located in the Praia de Águada area but then they migrated towards the center of the island. Continuous harmonic tremor emerged on 9 November and was interpreted as indicating the movement of magmatic gases. On 15 November seismicity increased and was characterized by more intense periods of volcanic tremor, long-period events, and “burst” events defined as identical events separated by a few seconds. In addition, residents began to feel earthquakes more often. The Alert Level was raised to 3. Three earthquakes all with magnitudes greater than three occurred during 18-19 November, and harmonic tremor again intensified on 19 November.
Report for Taal
PHIVOLCS reported that unrest at Taal continued during 22-28 November. Daily pronounced upwelling of gases and hot fluids in the lake generated steam-and-gas plumes that rose as high as 1.2 km above the crater and drifted SW. Sulfur dioxide emissions averaged 7,608 and 11,962 tonnes per day on 23 and 27 November, respectively. The seismic network recorded 6-66 daily periods of volcanic tremor each lasting 1-7 minutes long. The Alert Level remained at 1 (on a scale of 0-5), and PHIVOLCS reminded the public that the entire Taal Volcano Island was a Permanent Danger Zone (PDZ).
Report for Ruapehu
GeoNet reported that 40 small earthquakes at Ruapehu was recorded by the seismic network during 21-26 November. The earthquakes were 0.3-1.8 in magnitude and located at depths of 3-6 km, though most clustered at depths of 4-5 km. Volcanic tremor levels were low during 2023 and did not vary in response to the sequence. The temperature of the crater lake water was slowly rising, starting in mid-October. During an overflight on 22 November, scientists observed that the color of the lake had changed to blue-green instead of the typical gray color, consistent with less gas flux disturbing lake-bottom sediment. No upwelling was observed and sulfur slicks on the water’s surface were visible. Water was overflowing at the lake’s outlet. Overall, activity was low. The Volcanic Alert Level remained at 1 (on a scale from 0-5) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).
Report for Ioto
The Japan Coast Guard made observations during an overflight of Ioto (Iwo-jima) on 23 November. They posted video, photos, and infrared photos that showed explosions at the main vent producing dark, dense ash-and-steam plumes and ejecting large blocks that landed on the island and in the ocean.
Report for Lewotolok
PVMBG reported that the eruption at Lewotolok continued during 22-28 November. White steam-and-gas plumes rose 300-400 m above the summit and drifted W and NW during 22 and 24-26 November. White-and-gray ash plumes rose as high as 1.9 km during 23 and 27-28 November and drifted W and NW. Incandescence at the summit was visible on 22 and 26 November. 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.
Report for Semeru
PVMBG reported that eruptive activity continued at Semeru during 22-28 November. No emissions were observed on 22 November. White-and-gray ash plumes that were often dense rose 300-800 m above the summit and drifted in multiple directions during 23-28 November. 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.
Report for Sabancaya
Instituto Geofísico del Perú (IGP) reported that the eruption at Sabancaya continued at moderate levels during 20-26 November with a daily average of 31 explosions. Gas-and-ash plumes rose as high as 2.9 km above the summit and drifted NE and SW. 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.
Report for Suwanosejima
JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 20-27 November and crater incandescence was visible nightly. No explosions were detected, though ash plumes rose as high as 1.2 km above the crater rim and drifted mainly SE and W during 20-21 and 25 November. 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.
Report for Nevado del Ruiz
Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued at low-to-moderate levels during 21-27 November. Seismic events indicating the movement of fluids increased in number and intensity compared to the previous week, especially with respect to the signals indicating emissions. The number of signals indicating rock fracturing decreased in both number an intensity. These events were located in areas up to 6 km in various directions from Arenas Crater, at depths of 1-8 km. The largest earthquake, a M 2, was recorded at 1949 on 25 November. Thermal anomalies on the crater floor were identified in satellite images. Ash-and-gas plumes rose as high as 1.3 km above the summit on 21 November and up to 1.7 km on 27 November. The plumes drifted WSW and SW. Sulfur dioxide emissions increased through the week. The Alert Level remained at Yellow, Level III (the second level on a four-level scale).
Report for Purace
Observatorio Vulcanológico y Sismológico de Popayán, Servicio Geologico Colombiano (SGC) reported that at 1929 on 16 November the seismic network recorded a signal at Puracé associated with an ash-and-gas emission. Ash deposits on the N flank were confirmed by an observer the next day. SGC noted that localized deformation between Puracé and Curiquinga volcanoes continued to be recorded. Sulfur dioxide gas emissions had stable values, but carbon dioxide concentrations were high compared to values recorded so far in 2023. The Alert Level remained at Yellow (the second lowest on a four-color scale).
Report for Dukono
PVMBG reported that the eruption at Dukono was ongoing during 15-21 November. Although seismicity had returned to normal eruptive levels the previous week, ash-and-gas plumes continued to rise to higher-than-normal heights. Daily dense white-and-gray or gray-to-black ash plumes rose as high as 2.5 km above the summit and drifted NW, W, and S. The Alert Level remained at Level 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.
Report for Ulawun
Rabaul Volcano Observatory (RVO) reported that white steam plumes and occasional puffs of ash rose from Ulawun’s summit crater during 22-24 November, though weather clouds hindered views during 23-24 November. Lava continued to flow from a new fissure vent that had opened on the SW flank, near the vent that had formed in 2019. The intensity of the incandescence from the flow decreased during 23-24 November, suggesting that effusion may have slowed. Seismicity remained at background levels. The Alert Level remained at Stage 2 (on the four-level scale).
Report for Aira
JMA reported ongoing activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 20-27 November, with incandescence at the crater observed nightly. Explosions at 1905 on 20 November and 0226 on 21 November produced ash plumes that rose 1.2 km above the crater rim and drifted SW. Eruptive events on 22 November produced emissions that rose 1 km and drifted N and E. During an overflight of the crater on 24 November plumes obscured views of Minamidake Crater, though observers noted no changes at the geothermal area at Showa Crater. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.
Report for Reykjanes
On 22 November the Icelandic Meteorological Office (IMO) lowered the Aviation Color Code for Reykjanes to Yellow (the second level on a four-color scale), noting that seismicity associated with the magmatic dike intrusion had decreased during the previous week. Although inflation continued to be detected at Svartsengi, they determined that the likelihood of an eruption had decreased. During 22-27 November seismic activity was relatively stable at a rate of about 500 earthquakes per day, with most events concentrated near Sýlingarfell and Hagafell. Sometimes around midnight on 27 November an hour-long seismic swarm occurred in the vicinity of Sýlingarfell. A total of 170 earthquakes were recorded and located at depths of 3-5 km; the largest event was an M 3. Seismicity slowly decreased during 28-29 November and most of the events were small, below M 1. The rate of deformation also declined, though uplift at Svartsengi continued at around 1 cm per day. The seismic and deformation data suggested that magma continued to flow into the middle portion of the dike.
Report for Sheveluch
KVERT reported that the eruption at Sheveluch continued during 16-23 November. A daily thermal anomaly was identified in satellite images. On 17 November plumes of resuspended ash drifted about 116 km E. 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.