The remote Bagana volcano on central Bougainville Island, Papua New Guinea, has been erupting almost continuously since February 2000 and consists of frequent non-explosive lava flows, gas and sulfur dioxide emissions, occasional emissions of ash, and thermal anomalies. Infrequently, explosions producing pyroclastic flows occur (BGVN 46:09, 47:09). The current report describes activity during September 2022-March 2023 using information from the Darwin Volcanic Ash Advisory Center (VAAC) and satellite data.

Eruptive activity continued throughout the reporting period, with persistent thermal activity as seen in satellite images. When visibility allowed, Sentinel-2 images revealed persistent thermal activity in the NE part of the summit crater, with weaker thermal signals on the SE flank, just below the summit (figure 1). Strong activity on 18 November (figure 45) included what appear to be lava flows in the crater and extending down the NW flank, and on the lower SE flank. Gas-and-steam emissions were also visible in most Sentinel-2 images, usually drifting NE.

Figure 45. Sentinel-2 infrared satellite image of Bagana showing a strong thermal signal in the NE part of the summit crater and extending down the NW flank, with weaker hotspots on the lower SE flank. Images use “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Consistent with the Sentinel-2 images, the MIROVA thermal detection system showed a persistent low to moderate power anomaly in both MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible Infrared Imaging Radiometer Suite) data, with more frequent and stronger activity during October-November 2022 (figure 46). Hotspots were only detected on three days by the MODIS-MODVOLC system (23 October, 13 November, and 20 November).

Figure 46. Graphs showing thermal anomalies near the crater summit at Bagana during September 2022-March 2023, as recorded by the MIROVA system (Log Radiative Power) using MODIS (top) and VIIRS (bottom) data. Nearly persistent low-to-moderate hotspots were recorded during September through the first part of January, with more persistent and higher power signals during October and November 2022. Courtesy of MIROVA.

A few strong SO₂ plumes were observed by the TROPOMI instrument aboard the Sentinel-5P satellite, mostly during November. They were most prominent during 28 October-5 November 2022, consistent with ash plumes reported by the Darwin VAAC that rose to an altitude of 2.1-2.7 km (or 200-600 m above the summit) during 31 October-2 November.

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

Frequent weak-to-moderate ash explosions and lava flows have been recorded since the 19th century from three active craters at the summit of Langila, located on Papua New Guinea’s New Britain Island. The current eruption period began in October 2015; recent activity has included low-level thermal activity, ash emissions, and SO₂ plumes (BGVN 47:10). Similar low-level activity continued during October 2022-March 2023 based on information from the Darwin Volcanic Ash Advisory Center (VAAC) and satellite images.

The only completely clear Sentinel-2 image during the reporting period showed a single bright hotspot at the SE crater on 20 October, and thermal anomalies were visible on 4 and 7 November in two craters (figure 31). Persistent clouds prevented observations until another anomaly in one crater was visible starting on 28 January and on other clear days through March 2023. Gas-and-steam emissions rising from the crater were also sometimes present. The MIROVA hotspot detection system also recorded only a few scattered thermal anomalies during October 2022-March 2023 (figure 32), which cloud cover was common. The MODIS-MODVOLC thermal detection system did not record any hotspots during this time.

Figure 31. Sentinel-2 infrared satellite images of Langila showed a persistent hotspot in the SE crater and occasional wispy gas-and-steam emissions during October 2022-March 2023. A thermal anomaly is seen here from one crater on 20 October (top) and two craters on 4 November 2022 (bottom). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Figure 32. The MIROVA hotspot detection system (Middle InfraRed Observation of Volcanic Activity) graph showed intermittent low-power MODIS thermal anomalies at Langila into mid-November 2022, one in early January 2023, and then more frequent detections in the second half of March 2023. Courtesy of MIROVA.

A single strong SO₂ plume was observed by the TROPOMI instrument aboard the Sentinel-5P satellite during the reporting period, on 26 October 2022. According to the Darwin VAAC, an ash plume rose 2.7 km in altitude, or 1.4 km above the summit, on 20 October and drifted NW. The plume dissipated within five hours.

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower E flank of the extinct Talawe volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km². It contains the 1-km-wide, 240-m-deep Arenas summit crater. Eruptions have been documented since 1570 CE. The current eruption period has been ongoing since November 2014 and more recently has consisted of intermittent ash emissions, thermal activity, and lava dome growth (BGVN 47:08). This report updates activity including gas-and-ash emissions, dome growth, and seismicity during August 2022 through January 2023 using information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various satellite data.

Intermittent thermal anomalies were recorded during August 2022 through January 2023, with three peaks of strong and frequent hotspots detected during late October, mid-December, and late January, according to the MIROVA graph (Log Radiative Power) (figure 140). Some of this thermal activity was also visible in Sentinel-2 infrared satellite imagery, occasionally accompanied by white gas-and-steam emissions (figure 141). According to data from the TROPOMI instrument on the Sentinel-5P satellite, sulfur dioxide plumes were also detected throughout the reporting period, many of which had a maximum mass that exceeded 2 Dobson Units (DU) and drifted in different directions (figure 142).

Figure 140. Intermittent thermal anomalies were detected at Nevado del Ruiz during August 2022 through January 2023, according to this MIROVA graph (Log Radiative Power). Slightly stronger and more frequent anomalies were detected during late October, mid-December, and late January. Two gradual declines in both power and frequency were observed during November and late-December. Courtesy of MIROVA.

Figure 141. Sentinel-2 infrared satellite images showed an occasional thermal anomaly at the summit crater of Nevado del Ruiz, seen here on 25 September 2022 (top left), 30 October 2022 (top right), 29 December 2022 (bottom left), and 28 January 2023 (bottom right). Sometimes white gas-and-steam emissions accompanied the thermal activity, as shown on 25 September, 30 October, and 29 December. Images use “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Figure 142. Sulfur dioxide emissions from Nevado del Ruiz were often recorded during August 2022 through January 2023 with the TROPOMI instrument on the Sentinel-5P satellite. Plumes drifted in different directions and often exceeded 2 Dobson Units (DU) on 29 August 2022 (top left), 8 September 2022 (top middle), 20 October 2022 (top right), 29 November 2022 (bottom left), 14 December 2022 (bottom middle), and 17 January 2023 (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during August and September remained relatively low, consisting of seismicity and gas-and-ash emissions and continued lava dome growth in the Arenas crater. Seismic events included volcanic tremor, tremor pulses, and very long period earthquakes. Gas-and-ash emissions were associated with some of these seismic signals. Additionally, occasional drumbeat-type seismicity, associated with rock fracturing and the evolution of the growing lava dome, was reported. Gas-and-ash emissions rose to 2 km above the summit during 4-5 August and drifted NW, W, and SW. As a result, ash fell in the nearby towns of Santa Rosa de Cabal (33 km W), Pereira (40 km WSW), Villamaría (28 km NW), and Manizales (25 km N). On 12, 18, and 25 August gas-and-steam plumes rose 2-3.2 km above the summit and drifted NW, W, and SW; a gas-and-ash emission was reported at 1751 on 18 August and rose 3.2 km above the summit and drifted WNW. During the week of 23-30 August gas-and-ash emissions resulted in ashfall in Villamaría and Manizales. Gas-and-steam emissions rose 2.3-2.5 km above the summit on 10, 13, 26, and 28 September and drifted NW, W, SW, WNW, N, and NE.

During October and November similar low levels of seismicity, dome growth, and plumes of gas-and-steam plumes (mostly sulfur dioxide) with some ash, persisted. Gas-and-steam emissions rose 1.8-2.9 km above the summit on 5, 13, 22, and 31 October and drifted in various directions. SGC reported that there was an increase in sulfur dioxide degassing values on 20 October, with the maximum recorded mass value of approximately 5,000 tons. Gas-and-steam emissions rose 1.8-2.2 km above the summit on 4, 8, 16, and 25 November and drifted NW, SW, SE, ESE, and NE. According to data from the Washington VAAC, ash plumes rose to 6.4-7.3 km altitude and drifted S and SE on 11 November based on satellite and webcam images. During 13-14 November ash plumes rose to 6.7 km altitude and drifted NE.

Seismicity and gas-and-steam emissions continued during December and January 2023. Pulses of gas-and-ash emissions associated with seismic signals were also reported. Additionally, people in the municipalities of Tolima and Manizales (Caldas) reported sightings of continuous ash emissions during 2-13 December. Gas-and-steam emissions rose 1.7-2.9 km above the summit on 2, 13, 21, and 31 December and drifted SW, SE, SSE, NE, W, and NW. On 7 December gas-and-steam and ash emissions rose 2 km above the summit and drifted W. Ashfall was detected in Dosquebradas (40 km WSW), Santa Rosa de Cabal (34 km W), and Pereira (40 km WSW in Risaralda), Manizales (27 km NW) and Villamaría (26 km NW in Caldas), and in the Los Nevados National Natural Park sector on 14 December and to the N near Tolima during 3-9 January as ash emissions continued intermittently for several hours at a time. Gas-and-steam emissions rose 1.3-2.9 km above the summit and drifted in different directions on 6, 14, 22, 25 January. An ash cloud was observed at 0706 on 6 January that caused ashfall in Villahermosa (27 km NE). On 23 January ashfall was reported in Manizales and on 29 January ash was remobilized and caused ashfall in Eje Cafetero.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Kaitoku Seamount is a three-peaked submarine volcano located about 1 km S of Tokyo, Japan. The base of the seamount has a diameter of 40 km and a height of 2.5 km above the ocean floor. The two peaks in the south are called Tokai Tokuba and Nishi Tokuba (figure 2). The most recent previous confirmed eruption was in 1984, when discolored water, gas-and-steam plumes, and floating pumice was reported (SEAN 09:10). Water discoloration was observed in December 1984 and June 1986, and the Japan Coast Guard (JCG) described activity in July 2001 which mainly consisted of bubbles. This report covers a new eruption that was characterized by strongly discolored water during August 2022 through January 2023 based on information from the Japan Meteorological Agency (JMA), Japan Coast Guard (JCG), and satellite data.

Figure 2. Submarine bathymetry map of Kaitoku Seamount. The island on the left is Nishi Tokuba (at a depth of 100 m) and the island on the right is Tokai Tokuba (depth of 97 m). The image date was not provided. Courtesy of JCG.

The JCG received a report on 19 August that discolored water was observed near the volcano on 18 and 19 August. This was also visible in a Sentinel-2 satellite image (figure 3). According to aerial observations by the JCG on 23 and 28 August, both discolored water and floating material were observed. The discolored water was yellow-white, approximately 100 m in diameter, and located near the Tokai Tokuba peak. On 28 August multiple zones of white discolored water were observed directly above the volcano and floating material covered an area approximately 200-m-wide and 6-km-long to the SE (figure 4).

Figure 3. Sentinel-2 satellite image showing a small amount of discolored water (bright blue-white) above Kaitoku Seamount on 19 August 2022. Image with “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Figure 4. Multiple zones of white discolored water above Kaitoku Seamount were visible during aerial observations on 28 August 2022. The floating material (yellow dotted circle) was identified to the SE in an area approximately 200 m wide and 6 km long. Courtesy of JMA (monthly report of activity at Kaitoku Seamount, August 2022).

Discolored water observations continued during September and October, which was interpreted as ongoing volcanic activity. Sentinel-2 satellite images showed small blue-white discolored plumes on 3, 8, 23, and 28 September that drifted SE, S, SW, and N from a single point. On 16 September an aerial observation conducted by JCG showed blue-white discolored water approximately 20 m wide and 30 m long (figure 5). Strong yellow-blue discolored water was visible on 28 September that mainly occurred around a single point, but a faint plume extended to the N. Though weather clouds sometimes prevented clear views of the vent area, discolored water plumes appeared more frequently in October. On 12 October there was a zone of dense yellow-white discolored water approximately 200 m in diameter; no floating material was observed (figure 6). Sentinel-2 satellite images captured discolored plumes on 3, 8, 13, 18, and 23 October, that mainly encompassed a single area. Part of the plumes extended SW, NW, E, and NE (figure 7).

Figure 5. Blue-white discolored water was observed during an aerial overflight of Kaitoku Seamount that was approximately 20 m wide and 30 m long at 1422 on 16 September 2022. Photo has been color corrected. Courtesy of JMA (monthly report of activity at Kaitoku Seamount, September 2022).

Figure 6. Aerial observation showing blue-white to green-yellow discolored water approximately 200 m in diameter at Kaitoku Seamount on 12 October 2022. Photo has been color corrected. Courtesy of JMA (monthly report of activity at Kaitoku Seamount, October 2022).

Figure 7. Bright blue-white to green-yellow discolored plumes at Kaitoku Seamount were visible in Sentinel-2 satellite images on 18 (left) and 23 (right) October 2022 that both drifted E and NE, respectively. The image taken on 18 October possibly captured material at the surface (darker circle). The white-and-gray irregular circles are atmospheric clouds, mostly seen in the 23 October image. Images with “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

During November 2022 through January 2023 occasional strongly discolored plumes persisted. Sentinel-2 satellite images captured green-yellow discolored plumes on 22 and 27 November that drifted several kilometers SW and SE (figure 8). An aerial observation conducted by JCG on 25 November showed a yellow-white circular shape of discolored water approximately 300 m in diameter (figure 9). Additionally, blue-white discolored water was observed extending 1 km SW from the volcano and was about 10 km in length. Strong green-yellow discolored plumes were visible in Sentinel-2 satellite images on 17 and 27 December that drifted SE and S as far as 10 km from the vent area (figure 10). Frequent strongly discolored plumes were captured in satellite imagery on 1, 6, 11, 16, and 26 January 2023 that drifted in different directions for several kilometers. On 1 and 16 January white bubbles were also visible around the vent area (figure 11).

Figure 8. Sentinel-2 satellite images showing two strong green-yellow discolored plumes at Kaitoku Seamount on 22 (left) and 27 (right) November 2022. Some darker material may have also been captured at the sea surface accompanying the discoloration. The plume on 22 November drifted several kilometers SW and on 27 November a strong plume drifted SE for several tens of kilometers. Images with “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Figure 9. A bright plume of yellow-white discolored water approximately 300 m in diameter at Kaitoku Seamount at 1357 on 25 November 2022 was observed during an aerial overflight. Photo has been color corrected. Courtesy of JMA (monthly report of activity at Kaitoku Seamount, November 2022).

Figure 10. Green-yellow discolored water plumes captured in Sentinel-2 satellite images at Kaitoku Seamount on 17 (left) and 27 (right) December 2022 drifted SE and S, and extended as far as 10 km from the vent area. Images with “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Figure 11. Sentinel-2 satellite imagery showing green-yellow discolored water plumes drifting W and S from the vent area of Kaitoku Seamount on 1 (left) and 16 (right) January 2023. White bubbles were also visible above the vent area on both days. Images with “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Geologic Background. A submarine eruption was observed in 1984 from Kaitoku Seamount (Kaitoku Kaizan), a three-peaked submarine volcano 130 km NNW of Kita-Iojima. A submarine eruption had previously been reported in 1543 from a point about 40 km SW, which the Japan Meteorological Agency attributes to Kaitoku.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: https://www1.kaiho.mlit.go.jp/kaiikiDB/kaiyo20-2.htm); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Volcán El Reventador, located in Ecuador, includes a 4-km-wide avalanche scarp open to the E. Recorded eruptions date back to the 16th century and have been characterized by explosive events, lava flows, ash plumes, and lahars. Frequent lahars in this region of heavy rainfall have built deposits on the scarp slope. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents. The current eruption began in July 2008 and more recently has consisted of frequent explosions, ash plumes, lava flows, and incandescent block avalanches (BGVN 47:09). This report covers similar activity of daily explosions, ash plumes, and incandescent block avalanches during August through November 2022 using daily reports from Ecuador's Instituto Geofisico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and satellite data.

During August through November 2022, IG-EPN reported daily explosions, gas-and-steam and ash plumes rising 300-1,500 m above the crater, and frequent crater incandescence, often accompanied by incandescent block avalanches and lava flows that traveled down the NE, E, and SE flanks. On average, there were more explosions detected during August through September compared to October through November.

Table 16. Monthly summary of explosions and plume heights recorded at Reventador from February through November 2022. Data courtesy of IG-EPN (August-November 2022 daily reports).

Activity during August consisted of explosions, ash plumes, crater incandescence, and avalanches of material, though cloudy weather sometimes obscured views of the summit. There were 16-65 daily explosive events, which generated ash emissions that rose 400-1,200 m above the summit and drifted NW, W, WSW, SW, and N (figure 163). The Washington VAAC reported that ash plumes rose 688-2,800 m above the summit and drifted W, NW, and SW. Frequent nighttime crater incandescence was observed at the summit. There were 20-87 long period (LP) earthquakes and 1-30 emission tremors (signals indicating steam) detected. A continuing active lava flow moving NE was reported during 2-4 August. During 3-4 and 6-8 August incandescent block avalanches descended 500-700 m from the crater. During the nights of 11-13 August incandescent block avalanches rolled as far as 400 m from the crater on all flanks. Incandescent avalanches traveled 600 m on the NW flank during 15-16 August. Incandescent material was observed on all flanks during the morning of 22 August as far as 500 m from the crater. During the night and early morning of 24-25 August crater incandescence was accompanied by a block avalanche along the NE flank extending 500 m from the crater. On 25 August an ash plume rose 300 m above the crater and drifted NW. During 28-29 August crater incandescence and an incandescent avalanche was observed moving 600 m from the crater on all flanks.

Figure 163. Webcam image of a strong ash plume rising 1 km above the crater of Reventador on 27 August 2022 at 1745. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2022-240, 28 de agosto de 2022).

Similar activity was reported during September, with 18-79 daily explosions producing gas-and-ash plumes 600-1,500 m above the crater that drifted W, NW, N, SW, and NE. Nighttime crater incandescence was often observed. There were 17-92 LP earthquakes and 1-22 emission tremors detected during the month. During 31 August-2 September incandescent blocks rolled 500-600 m from the crater; during 2-3 September the blocks moved down the NE flank. According to the Washington VAAC, ash plumes rose 688-1,700 m above the crater and drifted W, NW, N, NE, and SW. Incandescent block avalanches were reported on all flanks during 4-5, 14-15, 17-19, 21-23, and 25-28 September moving 400-800 m from the crater. During 7-8 September incandescent block avalanches on the S flank rolled as far as 500 m from the crater. On 19 September an incandescent block avalanche descended 600 m on the NE flank and on 20 September an incandescent block avalanche descended 800 m on the E and ESE flank. During 22-25 September IG-EPN reported that the active lava flow on the NE flank persisted (figure 164). An incandescent block avalanche on the SE flank reached 600 m from the crater during 29-30 September.

Figure 164. Thermal camera image showing the active lava flow (bright yellow) at Reventador descending the NE flank at 0636 on 25 September 2022. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2022-268, 25 de septiembre de 2022).

During October, there were 7-66 daily explosions detected, generating gas-and-ash plumes that rose 300-1,200 m above the crater and drifted N, W, NW, SW, NE (figure 165). There were 2-157 LP earthquakes and 3-25 emission tremors detected throughout the month. Nighttime crater incandescence was often visible throughout the month. The Washington VAAC reported that ash plumes rose 988-2,500 m above the crater and drifted in multiple different directions. Based on data from a thermal camera, IG-EPN reported on 1-6, 10-11, 13-18, 22-27 October that the lava flow on the NE flank remained active. During 8-9 October a lava flow was observed along the E flank. Incandescent block avalanches were observed during 15-17 October that rolled 400-700 m below the crater on all flanks.

Figure 165. Webcam image showing an ash plume rising 1 km above the crater at Reventador on 6 October 2022 at 0715. Some incandescent material was also visible on the right flank of the volcano. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2022-279, 06 de octubre de 2022).

Activity continued during November, with 18-60 daily explosions producing gas-and-ash plumes that rose 500-1,500 m above the crater (figure 166) and drifted in several directions, though cloudy weather often obscured clear views. Overall, there were 22-87 LP earthquakes and 2-19 emission tremors detected during the month. Crater incandescence was often visible during nights and early mornings. According to notices from the Washington VAAC, ash plumes rose 688-2,200 m above the crater and drifted in different directions. The lava flow on the NE flank remained active during 1-2, 8-10, 15, 18-20 November. During 6-7 November crater incandescence was accompanied by incandescent block avalanches descending all the flanks and an active lava flow on the SE flank. On 9 November an incandescence avalanche was reported on the N flank. On 10 and 17 November incandescent material was reported on all flanks moving as far as 500-800 m from the crater.

Figure 166. Webcam image of an ash plume rising 1 km above the summit crater of Reventador on 28 November 2022 at 0653. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2022-332, 28 de noviembre de 2022).

Additional satellite data. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent moderate thermal anomalies throughout the reporting period (figure 167), which was most likely caused by the frequent incandescent block avalanches and lava flows that were visible on multiple flanks. Additionally, the MODVOLC system identified a total of 20 thermal hotspots on 14, 16, 24, and 28 August, 23, 24, and 28 September, 2, 9, and 10 October, and 5, 6, and 22 November. Although the summit was often obscured by clouds, Sentinel-2 infrared satellite images also showed some thermal activity in the crater (figure 168). Using Sentinel-5P TROPOMI data processed by the MOUNTS (Monitoring Unrest From Space) system, and the DOAS (Differential Optical Absorption Spectroscopy) network, IG-EPN noted that the greatest volume of sulfur dioxide emissions was measured on 19 November, with 2,033 tons. Other sulfur dioxide measurements ranged from 0.1 to 824 tons.

Figure 167. Intermittent moderate thermal activity was detected at Reventador during July through November 2022, based on this MIROVA graph (Log Radiative Power). There was a short pause in activity during mid-to-late October. Courtesy of MIROVA.

Figure 168. Sentinel-2 infrared satellite images of Reventador showing a small thermal anomaly at the summit crater on 14 August 2022 (top left), 18 September 2022 (top right), and 27 November 2022 (bottom right). Weather clouds often prevented clear views of the summit. On 13 October 2022 (bottom left), a faint gray plume was also visible in natural color satellite imagery. Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering and “Natural Color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Geologic Background. Volcán El Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor about 1,300 m to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the scarp. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MOUNTS Project (Monitoring Unrest From Space), an operational monitoring system for volcanoes using Sentinel satellite data from ESA's Copernicus, Open Access Hub, hosted at UNAM and CT TU-Berlin (URL: http://www.mounts-project.com/home).

Stromboli, located in Italy, has exhibited nearly constant lava fountains for the past 2,000 years; recorded eruptions date back to 300 BCE. Eruptive activity occurs at the summit from multiple vents, which include a north crater area (N area) and a central-southern crater (CS area) on a terrace known as the ‘terrazza craterica’ at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano-island. Activity typically consists of Strombolian explosions, incandescent ejecta, lava flows, and pyroclastic flows. Thermal and visual monitoring cameras are located on the nearby Pizzo Sopra La Fossa, above the terrazza craterica, and at multiple flank locations. The current eruption period has been ongoing since 1934 and recent activity has consisted of Strombolian explosions and incandescent ejecta (BGVN 47:07). Activity described here includes daily explosions, incandescent ejecta, spatter activity, and lava flows during July through December 2022 using reports from Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) and various satellite data.

Frequent explosive activity continued throughout the reporting period, generally in the low-to-medium range, based on the number of hourly explosions in the summit crater (figure 242, table 15). Intermittent thermal activity was recorded by the MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data (figure 243). There was a gradual increase in thermal power and frequency from September through October and again during early-to-mid November. The strongest thermal activity was detected during early December and continued at a high level through the end of the month. These thermal activity increases likely reflected the period in which active lava flows were reported in the Sciara del Fuoco that preceded intense spattering activity. Sentinel-2 infrared satellite imagery captured relatively strong thermal hotspots at the two active summit craters on clear weather days, showing an especially strong event on 6 October, where a lava flow covered much of the NW flank (figure 244).

Figure 242. Explosive activity persisted at Stromboli during July through December 2022, with low to medium numbers of daily explosions at the summit crater. The average number of daily explosions (y-axis) during July-December (x-axis) are broken out by area and as a total, with red for the N area, blue for the CS area, and black for the combined total. The data are smoothed as daily (thin lines) and weekly (thick lines) averages. The black squares along the top represent days with no observations due to poor visibility (Visib. Scarsa). The right axis indicates the qualitative activity levels from low (basso) to highest (altissimo) with the green highlighted band indicating the most common level. Courtesy of INGV (Report 01/2023, Stromboli, Bollettino Settimanale, 26/12/2022 - 01/01/2023).

Table 15. Summary of type, frequency, and intensity of explosive activity at Stromboli by month during July-December 2022; information from webcam observations. Courtesy of INGV weekly reports.

Figure 243. Intermittent thermal activity at Stromboli occurred during July through December 2022 with increases in power and frequency during early October, mid-November, and December, as shown in this MIROVA graph (Log Radiative Power). The strongest thermal activity was detected during early and late December. Courtesy of MIROVA.

Figure 244. A persistent thermal anomaly was detected at the two major crater areas (N and CS) from the active vents of Stromboli during clear weather days on 31 July 2022 (top left), 25 August 2022 (top right), 24 September 2022 (middle left), 4 October 2022 (middle right), 9 October 2022 (bottom left), and 13 November 2022 (bottom right). During 4 and 9 October the thermal anomaly intensified and by 9 October there was a strong lava flow field that covered much of the NW flank. On 13 November degassing rings were also visible above the summit. Images use “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Activity during July-August 2022. Variable low-to-medium Strombolian explosions were reported in both the N and CS crater areas also accompanied by spattering activity (figure 245). The N1 and S2 craters, both of which have two emission points, generated low to medium intensity explosions that ejected fine to coarse material 30-150 m above the crater. Explosions at the N1 crater ejected coarse, partially reworked material mixed with fine ash, which remained suspended a few tens of meters above the crater and dispersed as a light-colored plume, eventually falling in the innermost vent area. Explosive activity at the S2 crater was sporadic and mainly consisted of mainly reworked fine ash and light brown ash plumes. Craters N2 (in the N area), and C and S1 (in the CS area) exhibited frequent degassing and were less explosive. INGV reported that crater incandescence from the degassing craters was visible during the day and night (figure 246). Explosions on 18 July were higher energy and consisted of mainly juvenile material. An explosive sequence at N2 on 25 July was characterized by continuous, diffuse degassing. Explosions affected both the N and CS crater areas; at 0256 an explosion of coarse mixed with fine material was detected at the S2 crater; at 0256 a more intense explosion was detected in the N2 crater, ejecting material 300 m above the crater, and falling along the Sciara del Fuoco. This stronger explosion lasted about two minutes and was accompanied by a lava fountain that gradually decreased in intensity and became spattering after about six minutes. At 0257 a pyroclastic flow originating from the deposits of the previous explosion extended toward the coastline for a few hundred meters. A low intensity explosion with fine material was detected at 0258. The overall duration of the explosive sequence lasted about eight minutes.

Figure 245. Shaded terrain model showing the location of the active craters at Stromboli updated on 17 July 2022. The red circles indicate explosive activity, and the yellow circles indicate intense continuous degassing. Courtesy of INGV (Report 29/2022, Stromboli, Bollettino Settimanale, 11/07/2022 - 17/07/2022).

Figure 246. Aerial images of the N2 crater at Stromboli taken on 15 July 2022 showing crater incandescence. Intense degassing was observed on the outer flank of the N2 crater on the Sciara side. Courtesy of INGV (Report 29/2022, Stromboli, Bollettino Settimanale, 11/07/2022 - 17/07/2022).

On 27 July a lava overflow was reported in the N2 crater area. After the explosive sequence on 25 July, spatter activity was reported in the N2 crater area which, by 1708, had turned into a lava flow (figure 247). Two branches reached the central part of the Sciara at an elevation of 600 m. By 2000 the flow had stopped. During 8-14 August the N2 crater showed sporadic explosions consisting of low intensity coarse material and weak spattering. Some observational data was lost from webcams at 400 m elevation during the latter half of August due to bad weather damaging an optical fiber link on 12 August.

Figure 247. Webcam images of the lava flow development at Stromboli during the evening of 27 July 2022 taken by the SCT infrared camera. The lava flow appears light yellow-green in the infrared images. Courtesy of INGV (Report 31/2022, Stromboli, Bollettino Settimanale, 25/07/2022 - 31/07/2022).

Activity during September-October 2022. Hourly Strombolian explosions were variably low-to-moderate in intensity. Ejected material rose between 80 to more than 150 m above the crater and generally consisted of coarse material mixed with fine ash. In the northern crater area, N1 crater generally showed little degassing activity, but there were episodic ash emissions observed on 9 September. The N2 crater showed intense gas-and-steam emissions and few explosions consisting of lava fragments. Gas-and-steam emissions were relatively low in the CS area. Weak infrequent ash emissions consisting of some coarse material mixed with fine ash were sometimes observed from at least two vents near the S2 crater. Near the central crater (C) gas-and-steam emissions were almost absent.

On 25 September a strong explosion from a vent in the N2 crater was accompanied by intense spattering. Shortly afterwards a lava overflow was reported in the N crater area along the central and summit of the Sciara del Fuoco, lasting around four hours (figure 248). A strong explosion was observed in the N2 crater area on 29 September (figure 249). The first pulse was the most energetic, lasting about eight seconds and ejecting fine material 300 m above the crater that fell along the Sciara del Fuoco. This activity was followed by at least four low-intensity explosive events that ejected material less than 100 m above the crater. The N2 crater showed continuous spattering after the 29 September explosion.

Figure 248. Webcam images of the effusive event at the N crater area of Stromboli on 25 September 2022. A strong explosion was captured at 0229 UTC accompanied by strong spattering activity. By 0247 a lava flow had developed. Courtesy of INGV (Report 39/2022, Stromboli, Bollettino Settimanale, 19/09/2022 - 25/09/2022).

Figure 249. Infrared webcam images showing the explosive event at Stromboli that occurred at 1324 UTC on 29 September 2022. The explosion ejected material as high as 300 m above the crater that was deposited along the Sciara del Fuoco. Courtesy of INGV (Report 40/2022, Stromboli, Bollettino Settimanale, 26/09/2022 - 02/10/2022).

On 3 and 4 October two lava flows were observed at the N crater area. The first flow originated from a fissure on the external cone in the N2 crater area in the Sciara del Fuoco on 3 October. As the lava flow grew in volume, a lava channel formed along the Sciara del Fuoco up to the coast. By 1600 UTC the lava flow had begun to cool. On 4 October a new lava flow from the N crater area overlapped the previous flow and loose material moved along the Sciara del Fuoco. Another lava flow was observed from the N2 crater area beginning on 0721 UTC on 9 October. At 0722 UTC a pyroclastic flow began due to a collapse on the edge of the N2 crater that faced the Sciara del Fuoco (figure 250). The pyroclastic flow moved rapidly and reached the coastline by 0723 UTC, spreading out over the sea a few hundred meters. The pyroclastic flow was then followed by a strong lava flow that developed into two branches and reached the sea in a few minutes.

Figure 250. A sequence of webcam photos showing the evolution of the pyroclastic flow that originated from the N2 crater area at 0721 on 9 October 2022 (a-h). In addition, a lava flow was also seen in an infrared webcam image and during field observations (i and l). Courtesy of INGV (Report 41/2022, Stromboli, Bollettino Settimanale, 03/10/2022 - 09/10/2022).

The effusive activity that began on 9 October developed a lava flow field that consisted of numerous overlapping minor flows. Frequent collapses of material occurred from the lava channel that was formed during 3-4 October, rolling along the Sciara del Fuoco, and reaching the coast, forming a delta. As the hot material interacted with the sea, lobes formed, which generated gas-and-ash emissions that rose to 1 km altitude. Low-level intense spattering activity was variable and contained within the N2 crater with occasional phases of lava fountaining. By 14 October the eruptive activity markedly decreased. INGV reported that by 15 October, according to surveillance cameras and field observations, the flow along the Sciara del Fuoco had stopped. On 16 October the spattering activity in the N2 crater had stopped. After the spattering ended there were numerous series of low-intensity ash events in the N2 crater. Observations from a drone overflight on 16 October revealed new fractures with thermal anomalies between N1 and N2. During 21-22 October two emission points showed low-intensity explosive activity with coarse material and intense spattering activity in the N2 crater area.

Activity during November-December 2022. Explosive activity persisted in both the N and CS crater areas consisting of coarse-to-fine material; spattering activity mainly occurred in the N crater area. The N1 crater contained two emission points that produced explosions of low-to-medium intensity that ejected coarse material up to 120 m above the crater. The N2 crater also contained two emission points that generated low-to-high intense explosions where material sometimes reached more than 150 m above the crater. The S2 crater generated explosions that ejected fine material mixed with coarse material 150-250 m above the crater. No explosive activity was noted in the S1 and C craters. Continuous spattering was reported on 2 November and became more intense during 6 and 8-9 November. A lava flow was observed on 16 November beginning at 0705 UTC, based on seismic data. Due to bad weather conditions during the latter half of the month, visual observations of the summit craters could not be made.

During December, only one explosion was noted in the CS crater area; explosions and spattering mostly occurred in the N crater area. On 4 December at 1410 UTC a lava flow was observed during the afternoon in the upper part of the Sciara del Fuoco, followed by a small flow starting around 1428 UTC that traveled along the central part of the Sciara del Fuoco (figure 251). The two lava flows were 50 m and 80 m below the crater rim of the N crater, respectively, and reached the coast around 1600 UTC. Pyroclastic flows were detected at 1431 and 1518 UTC, the latter of which originated from a fracture on the NW flank of the N crater area within the Sciara del Fuoco and reached the coast in a few seconds. They traveled along the Sciara del Fuoco and then several hundreds of meters into the sea. Accompanying gas-and-ash plumes rose to 1 km altitude. Intense spattering activity was reported hours after the lava and pyroclastic flows began.

Figure 251. Map of the active (red) and cooling (yellow) lava flow moving NW from the N crater area at Stromboli on 7 December 2022. The background image is the shaded relief model of the Sciara del Fuoco and crater area obtained by processing images acquired during several drone overflights. Courtesy of INGV (Report 50/2022, Stromboli, Bollettino Settimanale, 05/12/2022 - 11/12/2022).

The effusive activity from 4 December was observed at least through 8 December, based on webcam images. Both explosive and effusive activity was observed in the N crater area from three vents within the Sciara del Fuoco after 4 December. Additionally, intense spattering activity accompanied the lava flow. No explosive activity was observed in the CS area. Activity that occurred during 4-9 December generated a collapse of material on the N area of the crater terrace, and to a lesser extent, in the CS terrace.

On 16 December at 1208 UTC, after intense spattering activity in the N crater area near N2, a lava flow began to flow in the central area of the Sciara del Fuoco. The flow gradually decreased in volume after a few hours before stopping. Similarly, at 0842 on 19 and 1447 on 21 December (UTC), two lava flows were observed from the vents in the N crater area that spread along the central area of the Sciara del Fuoco after intense spattering activity near the N2 vent. The only explosive activity that was detected in the CS crater area occurred on 22 December, when fine material mixed with coarse material was ejected higher than 150 m above the crater. A lava flow during 26-28 December traveled to 400 m elevation and, similar to previous lava flow events, was preceded by intense spattering activity from the N1 vent that gradually intensified (figure 252). The lava flow began at 2013 UTC on 26 December and had ended by 0830 on 28 December. The flow was mainly fed by the N1 vent and to a lesser extent, by the N2 vent during 0505-0712 UTC.

Figure 252. Webcam images showing the evolution of the lava flow activity (bright yellow-red) from the N1 vent in the N crater area of Stromboli during 26-28 December 2022 taken by the INGE-OE surveillance camera. In images E and F, the N2 vent also partly fed the flow. Courtesy of INGV (Report 01/2023, Stromboli, Bollettino Settimanale, 26/12/2022 - 01/01/2023).

Geologic Background. Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the "Lighthouse of the Mediterranean" in the NE Aeolian Islands. This volcano has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy, (URL: http://www.ct.ingv.it/en/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Saunders Island consists of a large central volcanic edifice intersected by two seamount chains in the remote South Sandwich Volcanic Arc in the South Atlantic. The young Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th. The current eruption period began in November 2014 and more recently has been characterized by intermittent thermal anomalies and gas-and-steam emissions (BGVN 47:03). Visits are infrequent because of the remote location, and views are often obscured by cloudy weather. This report covers activity from February 2022 through January 2023 primarily using satellite data.

Activity at the Mount Michael summit crater consisted of intermittent thermal activity during the reporting period. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed a total of 15 low-power thermal anomalies detected near the summit crater (figure 46). One anomaly was recorded in late May, four in early June, two in late July, two in late September, one in early October, two in late November, one in mid-December 2022, and two in January 2023. Some of this thermal activity was also visible in Sentinel-2 infrared satellite imagery at the summit crater (figure 47). A strong gas-and-steam plume drifted NE on 6 February, based on a satellite image. On 24 September and 16 November two hotspots of similar size and intensity were detected at the summit crater. Weak sulfur dioxide emissions were recorded on 6, 11, 26, and 27 February, 2 and 3 March, 5, 6, and 8 October, 16 and 25 November, and 9 December as detected by the TROPOMI instrument on the Sentinel-5P satellite that drifted in different directions (figure 48).

Figure 46. A total of 15 thermal anomalies were detected near the Mount Michael summit crater at Saunders during 17 April 2022 through January 2023. One anomaly occurred during late May, four during early June, two during late July, two during late September, one during early October, two during late November, one in mid-December 2022, and two during January 2023. Courtesy of MIROVA.

Figure 47. Sentinel-2 infrared satellite images showed an intermittent thermal anomaly (bright yellow-orange) within the Mount Michael summit crater at Saunders on 6 February 2022 (top left), 3 August 2022 (top right), 24 September 2022 (bottom left), and 16 November 2022 (bottom right). Strong gas-and-steam plumes were visible on 6 February. Two visible hotspots of similar size and brightness were visible in the images taken on 24 September and 16 November. Images use “Atmospheric penetration” rendering (bands 12, 11, 8a) rendering. Courtesy of Sentinel Hub Playground.

Figure 48. Small sulfur dioxide plumes rising from Saunders were detected by the TROPOMI instrument on the Sentinel-5P satellite on 6 February 2022 (left) and 8 October 2022 (right) that drifted NW and SE, respectively. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Saunders Island consists of a large central volcanic edifice intersected by two seamount chains, as shown by bathymetric mapping (Leat et al., 2013). The young Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater and a remnant of a somma rim to the SE. Tephra layers visible in ice cliffs surrounding the island are evidence of recent eruptions. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th century. A low ice-free lava platform, Blackstone Plain, is located on the north coast, surrounding a group of former sea stacks. A cluster of parasitic cones on the SE flank, the Ashen Hills, appear to have been modified since 1820 (LeMasurier and Thomson, 1990). Analysis of satellite imagery available since 1989 (Gray et al., 2019; MODVOLC) suggests frequent eruptive activity (when weather conditions allow), volcanic clouds, steam plumes, and thermal anomalies indicative of a persistent, or at least frequently active, lava lake in the summit crater. Due to this observational bias, there has been a presumption when defining eruptive periods that activity has been ongoing unless there is no evidence for at least 10 months.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Kerinci, a stratovolcano in central Sumatra, Indonesia, has had numerous moderate explosive eruptions since 1838. The previous eruption lasted from April 2018 until June 2021 and included intermittent gas-and-steam and ash plumes (BGVN 43:07, 46:07). This report covers activity during July 2021-February 2023, and is based on data from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and satellites.

A new eruption began on 15 October 2022, when observers reported plumes with brown, gray, or black ash that drifted downwind a short distance above the crater, with the highest rising 1.2 km on 12 January 2023; the last reported ash plume was on 27 February 2023. Weather clouds obscured the volcano on most days, allowing only infrequent good webcam photos or satellite images. Although ash plumes were often seen, white steam-and-gas plumes were also visible on many days. There were no thermal anomalies detected over the course of this activity in Sentinel-2 or MODIS data. Though infrequently observed by the TROPOMI instrument aboard the Sentinel-5P satellite, the sulfur dioxide plumes that were detected were localized above the volcano.

According to PVMBG’s MAGMA-Indonesia daily reports from July 2021 through early October 2022, no explosions or ash emissions were observed; white emissions were observed most days when weather permitted. The Darwin VAAC issued an advisory for a plume on 14 October 2021 that reached as high as 750 m, but no ash was identified in satellite data and PVMBG only observed a white steam-and-gas plume. During 15-16 October a new eruption began with a steam-and-ash plumes that rose about 50-350 m above the summit (figure 25) and drifted NE. According to PVMBG and the Darwin VAAC, on 19 October, at 0620 and 0815, ash plumes rose 500-700 m above the summit. On most subsequent days in October ash emissions were visible rising 300-750 m above the summit and drifting primarily NE and NW.

Figure 25. Webcam photo of Kerinci on 16 October 2022 showing a gray ash plume rising from the summit crater. Courtesy of MAGMA Indonesia.

In November, ash plumes rose 150-400 m and drifted in various directions. At 0830 on 27 November an ash plume rose 400 m and drifted E. During 29-30 November, white steam-and-gas plumes rose 300 m. During December, frequent ash plumes and white steam-and-gas plumes rose 100-300 m almost daily, except for an ash plume at 0822 on 6 December which rose 700 m and drifted SW. According to PVMBG, the amplitude of continuous tremor increased during 28-29 December.

The eruption was ongoing during 4-8 January with brown, brown-to-gray, or white-and-brown ash plumes rising as high as 200 m above the crater rim and drifting NE and E. During 10-14 January daily ash plumes that were brown or gray rose generally 400-900 m above the summit and drifted N, NE, and W. At 1810 on 12 January a dense gray ash plume rose 1.2 km above the summit and drifted NW.

An eruptive event was recorded at 0230 on 3 February but not visually confirmed; white-and-gray ash plumes were visible later that day rising 100 m above the summit and drifting NE and E. Plumes with brown or gray ash were visible when conditions were clear, typically in the early morning hours, during 4-10 and 14 February, with small plumes only reaching 150-200 m above the summit and drifting in easterly directions. At 1207 on 15 February a dense brown ash plume rose 200 m and drifted E (figure 26). Dense brown ash plumes rose 150-250 m and drifted E and SE at 0908 and 1937 on 16 February. Plumes with gray or brown ash rose 50-150 m above the crater rim on 26 and 27 February.

Figure 26. Webcam photo of Kerinci showing a brown ash plume rising from the summit crater on 15 February 2023. Courtesy of MAGMA Indonesia.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

Aira caldera is located in the northern half of Kagoshima Bay and contains the active post-caldera Sakurajima volcano near the southern tip of Japan’s Kyushu Island. Frequent historical eruptions have been recorded since the 8th century and have deposited ash on Kagoshima, one of Kyushu’s largest cities, 10 km W from the summit. The largest recorded eruption took place during 1471-76. The current eruption period began during late March 2017 and has more recently consisted of explosive events, eruption plumes, minor ashfall, and crater incandescence (BGVN 47:07). This report updates information from July through December 2022 using monthly activity from the Japan Meteorological Agency (JMA) and satellite data.

Thermal activity remained at low levels during the reporting period; only two anomalies were detected each month during late July and early August, and there was a brief period of no registered thermal data during mid-August through most of September (figure 132). After late October, the frequency of thermal anomalies increased slightly and up to two anomalies were observed in the Minamidake crater in Sentinel-2 infrared satellite imagery during the latter part of the year (figure 133).

Table 28. Number of monthly explosive events, days of ashfall, area of ash covered, and sulfur dioxide emissions from Sakurajima’s Minamidake crater at Aira during July-December 2022. Note that smaller ash events are not listed. Ashfall days were measured at Kagoshima Local Meteorological Observatory, and ashfall amounts represent material covering all the Kagoshima Prefecture. Data courtesy of JMA monthly reports.

Figure 132. Thermal activity at Sakurajima in the Aira caldera was relatively low during late July through December 2022, according to this MIROVA graph (Log Radiative Power). Two thermal anomalies were recorded during each month of late July and early August. No thermal activity was detected for a brief period during mid-August through most of September. The number of anomalies increased after mid-October and continued through the end of the year. Courtesy of MIROVA.

Figure 133. Sentinel-2 infrared satellite imagery showed small thermal anomalies in the Minamidake crater at Aira’s Sakurajima volcano on 28 September 2022 (top left), 18 October 2022 (top right), and 27 November 2022 (bottom left). Vent A is located to the left and Vent B is to the right of Vent A; both vents are part of the Minamidake crater. Clouds covered Vent B on 28 September. A gas-and-steam emission covered the crater on 12 December 2022 (bottom right). Images use “Atmospheric penetration” rendering (bands 12, 11, and 8a). Courtesy of Sentinel Hub Playground.

JMA reported that during July there were 37 eruption events detected, 12 of which were explosion events. Accompanying eruption plumes rose 2.8 km above the crater rim. Nighttime incandescence was observed in the Minamidake crater using a high-sensitivity surveillance camera. No eruptions in the Showa crater were reported. Seismicity consisted of 146 volcanic earthquakes, which had increased compared to 57 earthquakes in June. According to field surveys, daily sulfur dioxide emissions ranged 1,400-3,200 tons/day (t/d). The Kagoshima Local Meteorological Observatory reported a total of 28 g/m² of ashfall was observed during 6 days. On 17 July an explosion at 1852 generated an eruption plume that rose 2.8 km above the crater rim and large volcanic blocks were ejected 800-1,100 m above the crater rim (figure 134).

Figure 134. Webcam image of the explosions at the Minamidake summit crater of Aira’s Sakurajima at 1855 on 17 July 2022. Courtesy of JMA monthly report (Sakurajima volcanic activity explanatory material, July 2022).

JMA reported an inflation event was first detected around 0900 on 18 July and warned residents that an inflation event suggested a magmatic intrusion was occurring. A field visit reported that sulfur dioxide emissions were at 1,900 t/d. Four eruptive events were recorded between 23 July and 1500 on 24 July that produced plumes that rose 1.2 km above the crater rim. A larger explosion at 2005 on 24 July ejected large volcanic blocks 2.4-2.5 km E. The accompanying volcanic plume rose 300 m above the crater rim and mixed with meteoric clouds. The last time an explosion ejected material more than 2 km from the crater was on 4 June 2020, according to JMA. The Volcano Alert Level (VAL) was briefly raised from 3 to 5 (on a 5-level scale) at 2050, signaling that the residents should evacuate. Ashfall was reported in Kagoshima City (10 km W). JMA noted that inflation stopped after this event. A field survey was conducted by the Japan Meteorological Agency Mobile Survey Team (JMA-MOT) on 25 July and confirmed that material was deposited more than 2.4 km from the vent, and they observed ashfall in an area from Shirahamacho (42 km NW) to Kurokamicho (5 km SE). Ash was deposited on the E flank of the Minamidake crater, based on data from infrared thermal imaging equipment and visual observations (figure 135). During 25-26 July a few small explosions and eruptive events generated plumes that rose as high as 2.2 km above the crater rim and disappeared into meteoric clouds. After 26 July, JMA noted that material had not been ejected more than 2 km from the crater, so the VAL was lowered back to 3.

Figure 135. Photo of ashfall in Kurokamicho taken on 25 July 2022 after the explosion at Aira’s Sakurajima on 24 July 2022. Courtesy of JMA monthly report (Sakurajima volcanic activity explanatory material, July 2022).

There were 71 eruptions reported during August, 16 of which were explosions. Volcanic plumes rose 2.8 km above the crater rim. Nighttime crater incandescence was observed at the Minamidake crater. There were 207 volcanic earthquakes detected during the month. According to a field survey the amount of sulfur dioxide emissions released ranged between 1,500-2,500 t/d. Ashfall was not observed. On 2 August at 0055 a volcanic plume rose 2.8 km above the crater. On 15 August at 0009 an explosion produced an eruption plume that rose 2 km above the crater rim and ejected large blocks 1.3-1.7 km above the summit.

During September there were 36 eruption events and 23 of which were explosions. Volcanic plumes rose 2.8 km above the crater rim and nighttime crater incandescence persisted. There were 319 volcanic earthquakes detected during the month. Sulfur dioxide emissions ranged between 1,900-2,400 t/d. According to the Kagoshima Local Meteorological Observatory, a total of 53 g/m² ashfall was observed over 14 days. On 23 September at 1335 a volcanic plume rose 1.7 km above the crater rim and continued until 1600. Some ashfall was observed on the SE flank. On 30 September at 1144 an explosion rose 2.8 km above the crater rim and drifted down-flank to the SE until 1600. A large amount of ash was deposited on the SE flank. Around 0000 volcanic blocks were ejected 1.3-1.7 km from the Minamidake crater.

Eruptive activity continued during October, with 39 events reported, which included 12 explosions. Volcanic plumes rose 2.4 km above the crater rim. Nighttime crater incandescence continued. Seismicity consisted of 145 volcanic earthquakes. According to a field survey, the amount of sulfur dioxide released during the month ranged from 1,900 t/d to 4,000 t/d, the latter of which was measured on 14 October. JMA noted that the amount of volcanic gas released has been generally high since July. Ashfall measurements showed that a total of 24 g/m² fell over 18 days at the Kagoshima Local Meteorological Observatory. An explosion was detected at 1932 on 10 October that ejected material 1.3-1.7 km from the Minamidake summit crater. A field survey conducted on 11 October confirmed weak incandescence was visible in the Minamidake crater and a geothermal area was observed on the SE flank of Minamidake, part of the inner Showa crater wall. At 1424 on 18 October an eruption plume rose 2.4 km above the crater (figure 136). Smaller eruptive events were occasionally recorded during 28-31 October.

Figure 136. Webcam image showing an eruption plume rising 2.4 km above Aira’s Sakurajima at 1429 on 18 October 2022. Photo has been color corrected. Courtesy of JMA monthly report (Sakurajima volcanic activity explanatory material, October 2022).

JMA reported 17 eruptive events occurred during November, which included 5 explosions. Volcanic plumes rose 2.2 km above the crater rim. Nighttime crater incandescence was reported in the Minamidake crater. There were 135 volcanic earthquakes detected throughout the month. The amount of sulfur dioxide emissions ranged from 700 t/d to 1,900 t/d and a total amount of 9 g/m² of ashfall was observed at the Kagoshima Local Meteorological Observatory over 10 days. Explosions were detected at 0515 on 4 November and 1954 on 20 November and ejected volcanic blocks 600-900 m. An explosion at 2010 on 15 November generated a volcanic plume that rose 600 m above the crater rim and drifted SE. An explosion at 1334 on 21 November generated an eruption plume that rose 2.2 km above the crater rim and ejected large blocks as far as 500 m from the vent (figure 137). Small eruptive events were also detected during 25-28 November.

Figure 137. Webcam image of an explosion at Aira’s Sakurajima on 1336 on 21 November 2022. The accompanying volcanic plume rose 2.2 km above the crater rim. Photo has been color corrected. Courtesy of JMA monthly report (Sakurajima volcanic activity explanatory material, November 2022).

During December, JMA reported that there were 20 eruptions, 11 of which were explosions. Volcanic plumes rose as high as 3.2 km above the crater rim. Nighttime crater incandescence remained visible at the Minamidake crater. There were 78 volcanic earthquakes detected during the month. According to a field survey the amount of sulfur dioxide emissions released was 1,400-2,800 t/d. During the month, 12 g/m² of ash fell over 8 days during the month, as observed at the Kagoshima Local Meteorological Observatory. At 0340 on 2 December a volcanic plume rose 3.2 km above the crater rim and ejected blocks as far as 1.1 km from the vent (figure 138). A second explosions was detected at 1929 on 3 December that produced an eruption plume that rose 3 km above the crater rim and ejected volcanic blocks 1-1.3 km from the crater. Webcam video of the event showed incandescent material ejected above the crater and lightning in the ash plume. Two explosions were recorded on 14 December that generated eruption plumes rising 1.7 km above the crater rim and disappearing into the meteoric clouds. Ejected blocks traveled as far as 700 m from the vent. An explosion at 0805 on 17 December produced a plume that rose 700 m above the crater rim and interacted with meteoric clouds. Ejected blocks traveled 900 m from the vent. At 0449 on 22 December ejected blocks traveled 600-900 m from the vent. On 24 December at 1954 an explosion produced an eruption plume that rose 1.2 km above the crater rim and ejected large blocks as far as 1.1 km from the vent. Two explosions on 27 and 29 December generated volcanic plumes 1.7 km above the crater rim and ejected blocks as far as 900 m from the vent.

Figure 138. Webcam image showing the explosion in the Minamidake summit crater at Aira’s Sakurajima at 0344 on 2 December 2022. The plume rose 3.2 km above the crater rim. Photo has been color corrected. Courtesy of JMA monthly report (Sakurajima volcanic activity explanatory material, December 2022).

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Karangetang (also known as Api Siau), at the northern end of the island of Siau, Indonesia, contains five summit craters along a N-S line. More than 40 eruptions have been recorded since 1675; twentieth-century eruptions have included frequent explosive activity, sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters and collapses of lava flow fronts have produced pyroclastic flows. The two active summit craters are Kawah Dua (the N crater) and Kawah Utama (the S crater, also referred to as the “Main Crater”). The most recent eruption began in late November 2018 and has more recently consisted of intermittent white-and-gray gas-and-steam plumes and summit crater incandescence (BGVN 47:07). This report covers activity during July through December 2022, characterized by crater incandescence and near daily white gas-and-steam emissions, based on reports from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), MAGMA Indonesia, and satellite data.

Relatively low activity during the reporting period was mainly characterized by almost daily white, and less frequently gray, gas-and-steam emissions that rose 25-200 m above the summit (figure 57). Incandescence from the S crater on 9 November and from both the N and S craters on 14 November was visible in satellite images. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed weak-to-moderate power thermal anomalies during August through mid-December 2022 (figure 58). There was only one small anomaly detected during early July. By later August, thermal activity began to increase in both frequency and power, which peaked during late September and then began to decline. Anomalies were then lower in power and less frequent during October through mid-December. A thermal anomaly was visible in Sentinel-2 infrared satellite imagery in the N summit crater throughout the reporting period, occasionally accompanied by gas-and-steam emissions (figure 59). A weaker anomaly was visible in the S summit crater at least on 17 July, 31 August, 15 September, 15 October, and 4 December.

Figure 57. Webcam images of Karangetang showing white-to-gray plumes rising above both summit craters on 31 August 2022 (top left), 22 September 2022 (top right), 20 October 2022 (bottom left), and 2 December 2022 (bottom right). Courtesy of MAGMA Indonesia.

Figure 58. Weak-to-moderate power thermal anomalies were detected in the summit area of Karangetang during August through mid-December 2022 as recorded by this MIROVA graph (Log Radiative Power). Only a single low-power anomaly was detected during early July. There was a gradual increase in both power and frequency of anomalies during September, which then had declined by the end of the month. Courtesy of MIROVA.

Figure 59. A small thermal anomaly (yellow-orange) was visible at the N summit crater at Karangetang on 17 July 2022 (top left), 31 August 2022 (top right), 15 September 2022 (middle left), 15 October 2022 (middle right), 29 November 2022 (bottom left), and 4 December 2022 (bottom right). A weaker anomaly was also detected in the S summit crater during these dates, except on 29 November due to cloud cover. Gas-and-steam emissions were occasionally observed from both summit craters. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Semeru in East Java, Indonesia contains the active Jonggring-Seloko vent at the Mahameru summit. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. The most recent eruption began in June 2017 and more recently has consisted of pyroclastic flows, ash plumes, and an active lava flow (BGVN 47:07). This report covers activity from July through December 2022, dominantly characterized by ash plumes, gas-and-steam plumes, and incandescent avalanches using daily, VONA, and special reports from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), MAGMA Indonesia, and various satellite data.

Activity during July through October mainly consisted of intermittent ash plumes and white gas-and-steam plumes, though weather often obscured clear views of the summit. During July, the ash plumes rose to 3.9-4.6 km altitude and drifted mainly SW; the plume that rose to 4.6 km altitude occurred on 4 and 5 July and drifted N at 0803 and 0534, respectively. In August, the ash plumes rose to 4-4.3 km altitude and drifted SW, W, N, and S. During September, ash plumes rose 300-700 m above the summit and drifted mainly N, SW, and W. Ash plumes during October rose to 3.9-4.1 km altitude and drifted SW, N, W, and S. Intermittent white-to-gray gas-and-steam plumes rose 50-500 m above the summit during October.

During November, white-to-gray gas-and-ash plumes generally rose 50-500 m above the summit. A strong eruptive event at 1550 on 9 November generated a white-to-gray ash plume that rose 1.5 km above the summit and drifted NE. A pyroclastic flow was also reported on 9 November that descended the SE flank as far as 4.5 km at 1550. During 11 and 16 November white gas-and-steam plumes rose 500-1,000 m above the summit and drifted NE, E, and S. A series of eruption events began on 21 November and continued through 28 November. Eruptive activity at 0608 on 21 November produced a white-to-gray ash plume that rose 400 m above the summit and drifted NE (figure 77). At 0503 on 22 November a white-to-gray ash plume rose 600 m above the summit and drifted S (figure 78). Another eruption later that day at 1541 generated a white-and-gray ash plume that rose 800 m above the summit and drifted N and NE. On 23 November at 0002 an eruption generated a gray ash plume that rose 700 m above the summit and drifted SE and S, accompanied by summit crater incandescence (figure 79). White gas-and-steam plumes throughout the 23rd rose 1-1.5 km above the summit and drifted S. On 24 November at 0540 an eruption produced a gray ash plume that rose 500 m above the summit and drifted N. At 0702 on 25 November a gray ash plume rose 500 m above the summit and drifted NE. On 26 November at 0444 a gray ash plume rose 700 m above the summit and drifted S. An eruption event on 28 November at 0556 generated a gray ash plume that rose 600 m above the summit and drifted N.

Figure 77. Webcam image of a gray ash plume rising 400 m above the summit of Semeru at 0621 on 21 November 2022. Courtesy of MAGMA Indonesia.

Figure 78. Webcam image of a dense, gray ash plume rising 600 m above the summit of Semeru at 0514 on 22 November 2022. Courtesy of MAGMA Indonesia.

Figure 79. Webcam image of summit crater incandescence at Semeru at 0015 on 23 November accompanied by a gray ash plume that rose 700 m above the summit. Courtesy of MAGMA Indonesia.

Frequent white-to-gray gas-and-ash plumes and occasional avalanches of material occurred during December. The ash plumes generally rose to 3.9-4.6 km altitude and drifted in different directions; avalanches were sometimes captured in webcam images. An eruption at 0550 on 2 December produced a white-to-gray ash plume that rose 500 m above the summit and drifted NE. On 3 December at 0520 a white-to-gray ash plume rose 500 m above the summit and drifted S. On 4 December at 0246 material collapsed on the SE flank, which produced a series of pyroclastic flows that mainly traveled 5-13 km SE and S, and as far as 19 km in those same directions (figure 80). Gray-to-brown ash plumes rose to 5.1 km altitude and drifted SE and S at 0411, and at 0918 similar plumes rose to 8.6 km altitude and drifted SW, W, and NW on 4 December. The ash plumes caused dark conditions and limited visibility, especially in Kajar Kuning (12 km SE) where residents reported dense ashfall and heavy rain. Ejected incandescent material was deposited as far as 8 km from the summit and ashfall was reported in areas 12 km SE. Pyroclastic flows were ongoing at least through 0951, traveling 5-7 km down the flanks. According to BNPB, there were 781 people across 21 evacuation shelters, and heavy ashfall prevented aid from easily reaching Pronojiwo Village.

Figure 80. Webcam image of a pyroclastic flow descending SE and S Semeru at 0458 on 4 December 2022. Courtesy of MAGMA Indonesia.

During 4-9 December, four pyroclastic flows moved as far as 6 km down the SE flank, and avalanches of material traveled 300-500 m SE. On 6 December an eruption at 0502 generated a white-to-gray ash plume that rose 400 m above the summit and drifted S and SW. A white-to-gray ash plume on 8 December rose 300 m above the summit and drifted N. On 9 December a dense, gray ash plume rose 500 m above the summit and drifted N at 0521. On 10 December a gray ash plume rose 700 m above the summit and drifted N. An eruption on 16 December at 0455 produced a white and gray-to-brown ash plume that rose 1 km above the summit and drifted N. At 0500 on 18 December a dense gray ash plume rose 300 m above the crater and drifted N and NE and at 0623 and at 0755 white-and-gray ash plumes rose 1 km and 700 m, respectively. On 19 December a gray-to-brown ash plume rose 1.5 km above the summit and drifted N and NE at 1558. On 20 December an ash plume rose 600 m and drifted N.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent, moderate-strength thermal anomalies during July through December (figure 81). There were two short gaps in thermal activity during November and mid-December. Based on data from the MODVOLC thermal algorithm, 48 thermal hotspots were detected: 14 in July, six in August, 11 in September, eight in October, four in November, and five in December. Thermal anomalies were visible on clear weather days at the summit crater in Sentinel-2 infrared satellite images throughout the reporting period. Occasional incandescent avalanches were captured in infrared satellite images on 9, 14, 19, 24, and 29 July, 3, 8, 13, and 23 August, 17 and 22 September, 1 and 6 November, and 11 and 21 December descending the SE flank (figure 82).

Figure 81. Frequent thermal activity was recorded in this MIROVA graph (Log Radiative Power) during July through December 2022. The power of these anomalies fluctuated slightly, but overall were moderately strong. There were two short gaps in thermal activity during November and mid-December. Courtesy of MIROVA.

Figure 82. A strong thermal anomaly (bright yellow-orange) in the summit crater of Semeru was visible in these infrared satellite images taken on 9 July 2022 (top left), 8 August 2022 (top right), 22 September 2022 (bottom left), and 11 December 2022 (bottom right). Each of these anomalies extended down the SE flank from the summit crater. On 8 August a small ash plume was also visible accompanying the thermal activity. Images use “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); National Public Radio (NPR) (URL: https://www.npr.org/2021/12/05/1061611299/indonesia-volcano-eruption-java-mount-semeru).

Suwanosejima, located in the northern Ryukyu Islands, Japan, is an 8-km-long island that consists of a stratovolcano and two historically active summit craters. Volcanism was intermittent for much of the 20th century, characterized by Strombolian explosions, ash plumes, and ashfall. The current eruption began in October 2004 and has recently consisted of frequent explosions, ash plumes, thermal activity, and ashfall (BGVN 47:04). This report updates similar activity of explosions, eruption plumes, ashfall, thermal activity, and seismicity during April-December 2022 based on information from the Japan Meteorological Agency (JMA) and satellite data.

Intermittent explosions were reported in the Otake crater, producing volcanic plumes that rose as high as 3.3 km above the crater rim, which occasionally resulted in ashfall in the nearby Toshima village (3.5 km SSW). Large volcanic blocks were ejected 900 m from the crater center and nighttime crater incandescence was frequently reported. Two thermal hotspots were detected by the MODVOLC thermal alerts system on the NW and NE flanks on 19 October 2022. The MIROVA (Middle InfraRed Observation of Volcanic Activity) Log Radiative Power graph of the MODIS thermal anomaly data showed three brief periods of thermal activity during early July, mid-August, and late September through October (figure 72). Sentinel-2 infrared satellite imagery showed three clear weather days with a thermal anomaly during the reporting period on 28 September, 8 October, and 27 November (figure 73).

Figure 72. Low thermal activity was detected at Suwanosejima briefly in early July, mid-August, and late September through October 2022, according to this MIROVA graph (Log Radiative Power). Courtesy of MIROVA.

Figure 73. Sentinel-2 infrared satellite images showed a gray ash emission rising above Suwanosejima on 16 April 2022 (top left), and a thermal anomaly was visible on 28 September (top right), 8 October (bottom left), and 27 November 2022 (bottom right). Images use “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Eruptive activity in the Otake crater continued during April; about 123 explosions were detected during the first half of the month. Crater incandescence was visible each night during 1-5 April. The sounds of rumbling and ashfall were occasionally reported in Toshima village, as well as sometimes in areas up to 5 km from the crater. Seismicity consisted of 491 volcanic earthquakes, not including explosion-related earthquakes. An explosion on 4 April at 2241 generated an eruption plume that rose 3.3 km above the crater rim. Large volcanic blocks were ejected as far as 900 m SE from the crater. No eruptive activity was reported during 9-11 and 15-18 April, although emissions rose 700-1,100 m above the crater rim. According to observations conducted by the University of Tokyo, Kyoto University, Toshima village, and JMA, the amount of sulfur dioxide released ranged from 300 to 1,600 tons per day (t/d), which was lower compared to March (3,400 t/d).

One explosion was detected during early May, followed by three more during 20-23 May; there were 33 explosions reported after 22 May through the end of the month. An explosion on 28 May at 0327 produced an eruption plume that rose 1.9 km above the crater rim. Large volcanic blocks were ejected about 500 m S from the crater. Nighttime incandescence was intermittently captured with a high-sensitivity surveillance camera. Rumbling sounds and ashfall were occasionally reported in Toshima village. A total of 417 volcanic earthquakes were detected during the month. Sulfur dioxide emissions had increased slightly compared to April, with 1,200-2,000 t/d emitted.

According to JMA, the number of explosions had decreased after April; there were 21 explosions that were detected dominantly during 2-6 and 30 June. The explosions ejected large volcanic blocks as far as 600 m S from the crater. On 7 June ashfall was observed in Toshima village. During 10-13 June eruption plumes rose as high as 1.5 km above the crater rim and ejected material as far as 300 m from the vent. On 26 June at 1418 an explosion generated an eruption plume that rose 2 km above the crater rim. Nighttime crater incandescence continued. There were 314 volcanic earthquakes detected throughout the month. The amount of sulfur dioxide emissions ranged between 1,000 t/d and 3,700 t/d.

Since mid-April, eruptive activity continued to decrease and as a result, JMA lowered the Volcano Alert Level (VAL) to 2 (on a 5-level scale) on 11 July. The number and intensity of explosions had been variable since early April, but showed an overall decline, and material had not been ejected more than 1 km. Eruption plume heights occasionally exceeded 3 km above the crater rim since July 2021, but these heights had not been observed since mid-April 2022. The number of volcanic earthquakes temporarily increased on 17 May but were generally low. The number of recorded explosions during July was 34 and large volcanic blocks accompanied by explosions were ejected as far as 700 m SW from the crater. Nighttime crater incandescence persisted during both July and August. On 26 July at 2351 a volcanic plume rose more than 1.8 km above the crater rim. Resulting ashfall was reported in Toshima village. The number of volcanic earthquakes detected in the vicinity increased to 526 compared to the previous months. Sulfur dioxide measurements showed that 700-2,500 t/d were released during July and 600-2,200 t/d during August.

Beginning on 2 August, the number of explosions increased; there were 24 explosions detected during 2-7 August. On 11 and 28 August explosions at 0416 and 2151, respectively, ejected large blocks 800 m from the vent. Eruption plumes during 7-8 August rose 2 km above the crater and mixed with weather clouds (figure 74). During 28-29 August three explosions generated ash plumes that rose as high as 1.3 km above the crater rim. Intermittent explosions occurred during August (51 total) and the number of volcanic earthquakes increased to 615.

Figure 74. Webcam image showing an eruption plume rising 2 km above the crater rim of Suwanosejima at 2340 on 8 August 2022. Photo has been color corrected. Courtesy of JMA (Volcanic activity commentary for Suwanosejima, August 2022).

During September, 88 explosions were recorded; 25 occurred during 24-28 September. The frequency of explosions was greater in September than August. Thermal activity continued to be reported during the night, based on high-sensitivity surveillance cameras. Occasional rumbling sounds and ashfall were observed as well. On 24 September at 1819 an eruption plume rose more than 2 km above the crater rim. An aerial survey was conducted by the Japan Meteorological Agency Mobile Research Team (JMA-MOT) on 29 September in cooperation with the Kagoshima Prefecture reported that a gray-white plume was observed rising above the Mitake crater (figure 75). Additionally, observations made using an infrared thermal imaging device confirmed high temperature areas near the summit, which were interpreted to be the scattered ejecta around the crater. The VAL was raised to 3 (on a 5-level scale) on 28 September. On 30 September at 2141 an explosion ejected large volcanic blocks 900 m S from the crater. The number of volcanic earthquakes around the volcano increased significantly to 1,351 and sulfur dioxide emissions ranged between 500-1,600 t/d.

Figure 75. A gray-white plume was visible during an aerial survey of Suwanosejima at the Mitake crater at 1502 on 29 September 2022 (left). Higher temperature (red color is higher in temperature) areas based on an image from an infrared thermal imaging device was reported to be incandescent volcanic blocks (right). Photo on the left has been color corrected. Courtesy of JMA (Volcanic activity commentary for Suwanosejima, September 2022).

The number of detected explosions continued to increase during October, particularly with 119 detected during 17-19 October, and a total of 244 recorded through the month. An eruption at 1342 on 8 October produced a volcanic plume that rose 2.4 km above the crater rim. An aerial survey was conducted on 11 October in cooperation with the Kagoshima Prefecture and reported that gray-white plumes continued to rise above the Mitake crater. An explosion at 0513 on 20 October ejected large volcanic blocks to 800 m SW from the crater. Nighttime crater incandescence continued, in addition to occasional rumbling sounds and ashfall in Toshima village. There was an increase in the number of volcanic earthquakes during 25-31 October, with a total of 2,034 events detected. Sulfur dioxide emissions measured between 400 and 2,100 t/d; there were multiple days in which the amount of sulfur dioxide emissions exceeded 2,000 t/d, according to JMA.

Eruptive activity during November and December had notably decreased; 3 explosions were detected. Nighttime crater incandescence persisted, as well as occasional rumbling sounds and ashfall in Toshima village. There were 465 volcanic earthquakes detected during the month. On 4 November at 0137 a volcanic plume rose 2.4 km above the crater rim. An explosion was detected at 2238 on 11 November that generated an eruption plume that rose 1.6 km above the crater rim. An explosion at 0251 on 15 November produced volcanic plumes that rose 1-1.3 km above the crater rim and drifted SE; associated large volcanic blocks were ejected 500 m S from the crater. JMA reported that 700-2,000 t/d of sulfur dioxide emissions were measured during November. During December, activity remained relatively low compared to previous months; no explosions were observed during the month, though nighttime crater incandescence remained visible, according to JMA. Ashfall was occasionally reported in Toshima village. There were 184 volcanic earthquakes detected during the month. An eruption at 0421 on 2 December ejected material as far as 300 m E of the crater. An eruption plume on 3 December rose more than 1.8 km above the crater. Approximately 400-800 t/d sulfur dioxide emissions were measured, which was lower compared to November.

Geologic Background. The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. One of Japan's most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed, forming a large debris avalanche and creating the open Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The remote Bagana volcano on central Bougainville Island, Papua New Guinea, has been erupting almost continuously since February 2000 and consists of frequent non-explosive lava flows, gas and sulfur dioxide emissions, occasional emissions of ash, and thermal anomalies. Infrequently, explosions producing pyroclastic flows occur (BGVN 46:09, 47:09). The current report describes activity during September 2022-March 2023 using information from the Darwin Volcanic Ash Advisory Center (VAAC) and satellite data.

Eruptive activity continued throughout the reporting period, with persistent thermal activity as seen in satellite images. When visibility allowed, Sentinel-2 images revealed persistent thermal activity in the NE part of the summit crater, with weaker thermal signals on the SE flank, just below the summit (figure 1). Strong activity on 18 November (figure 45) included what appear to be lava flows in the crater and extending down the NW flank, and on the lower SE flank. Gas-and-steam emissions were also visible in most Sentinel-2 images, usually drifting NE.

Figure 45. Sentinel-2 infrared satellite image of Bagana showing a strong thermal signal in the NE part of the summit crater and extending down the NW flank, with weaker hotspots on the lower SE flank. Images use “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Consistent with the Sentinel-2 images, the MIROVA thermal detection system showed a persistent low to moderate power anomaly in both MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible Infrared Imaging Radiometer Suite) data, with more frequent and stronger activity during October-November 2022 (figure 46). Hotspots were only detected on three days by the MODIS-MODVOLC system (23 October, 13 November, and 20 November).

Figure 46. Graphs showing thermal anomalies near the crater summit at Bagana during September 2022-March 2023, as recorded by the MIROVA system (Log Radiative Power) using MODIS (top) and VIIRS (bottom) data. Nearly persistent low-to-moderate hotspots were recorded during September through the first part of January, with more persistent and higher power signals during October and November 2022. Courtesy of MIROVA.

A few strong SO₂ plumes were observed by the TROPOMI instrument aboard the Sentinel-5P satellite, mostly during November. They were most prominent during 28 October-5 November 2022, consistent with ash plumes reported by the Darwin VAAC that rose to an altitude of 2.1-2.7 km (or 200-600 m above the summit) during 31 October-2 November.

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

Frequent weak-to-moderate ash explosions and lava flows have been recorded since the 19th century from three active craters at the summit of Langila, located on Papua New Guinea’s New Britain Island. The current eruption period began in October 2015; recent activity has included low-level thermal activity, ash emissions, and SO₂ plumes (BGVN 47:10). Similar low-level activity continued during October 2022-March 2023 based on information from the Darwin Volcanic Ash Advisory Center (VAAC) and satellite images.

The only completely clear Sentinel-2 image during the reporting period showed a single bright hotspot at the SE crater on 20 October, and thermal anomalies were visible on 4 and 7 November in two craters (figure 31). Persistent clouds prevented observations until another anomaly in one crater was visible starting on 28 January and on other clear days through March 2023. Gas-and-steam emissions rising from the crater were also sometimes present. The MIROVA hotspot detection system also recorded only a few scattered thermal anomalies during October 2022-March 2023 (figure 32), which cloud cover was common. The MODIS-MODVOLC thermal detection system did not record any hotspots during this time.

Figure 31. Sentinel-2 infrared satellite images of Langila showed a persistent hotspot in the SE crater and occasional wispy gas-and-steam emissions during October 2022-March 2023. A thermal anomaly is seen here from one crater on 20 October (top) and two craters on 4 November 2022 (bottom). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Figure 32. The MIROVA hotspot detection system (Middle InfraRed Observation of Volcanic Activity) graph showed intermittent low-power MODIS thermal anomalies at Langila into mid-November 2022, one in early January 2023, and then more frequent detections in the second half of March 2023. Courtesy of MIROVA.

A single strong SO₂ plume was observed by the TROPOMI instrument aboard the Sentinel-5P satellite during the reporting period, on 26 October 2022. According to the Darwin VAAC, an ash plume rose 2.7 km in altitude, or 1.4 km above the summit, on 20 October and drifted NW. The plume dissipated within five hours.

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower E flank of the extinct Talawe volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).