The remote island of Barren Island is located east of India in the Andaman Islands. Eruptions date back to 1787, with activity consisting of ash plumes, Strombolian explosions, and lava flows. The most recent eruption began in September 2018, with activity that included ash emissions and thermal anomalies (BGVN 46:12). This report covers similar activity during September 2021 through May 2022 using various satellite data as a primary source of information. Apparent eruptive activity continued until the end of January 2022, after which there was ongoing heat detected from the upper flanks of the central cone for a few months and a stronger thermal anomaly in the crater on 15 May.

The Suomi NPP/VIIRS sensor data showed 11 thermal anomalies over eight days on 14 and 19 October, 29-31 December 2021, and 1, 2, and 6 January 2022. Two MODVOLC thermal alerts were issued on 16 January 2022. Some of this thermal activity was visible in Sentinel-2 infrared satellite imagery on clear weather days on 6, 11, 21, and 31 December 2021, and 5, 25, and 30 January 2022 (figure 55).

Figure 55. Weak thermal anomalies were visible at the summit crater of Barren Island on 6 and 31 December 2021 (top left and right) and 25 and 30 January 2022 (bottom left and right). The anomalies were stronger on 31 December and 25 January. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

A continuous ash emission was reported during 1700-2200 on 8 January 2022 that rose to 1.2 km altitude and drifted WNW, according to visible and RGB satellite images from HIMAWARI-8. Ash plumes were also visible during 1200-1700 on 9 January, rising to 1.2 km altitude and drifting W to SW, based on data from the HIMAWARI-8 satellite, according to the Darwin VAAC.

The MIROVA thermal anomaly data from September 2021 through May 2022 showed intermittent low- to moderate-levels of thermal activity, with the greatest number of anomalies (12) occurring in March 2022 (figure 56). By May, only two were detected. After January 2022 no thermal anomalies were detected in Sentinel-2 infrared images, Suomi NPP/VIIRS sensor data, or MODVOLC thermal data until 15 May, when a weak thermal hotspot was visible in infrared satellite data at the summit crater (figure 57).

Figure 56. The MIROVA thermal anomaly data (Log Radiative Power) from September 2021 through May 2022 showed intermittent low to moderate levels of thermal activity beginning in early October. The number of anomalies increased slightly during March through May 2022. Three low-power anomalies were recorded in October, two in November, four in December 2021, six in January 2022, five in February, twelve in March nine in April, and two in May. Courtesy of MIROVA.

Figure 57. A single weak thermal anomaly was detected at the summit of Barren Island on 15 May 2022 in Sentinel-2 satellite imagery, accompanied by weak gas-and-steam emissions moving NE. Image using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: 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/); 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); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).

Bezymianny is located on the Kamchatka Peninsula as part of the Klyuchevskoy volcano group. Historical eruptions dating back to 1955 were characterized by dome growth, explosions, pyroclastic flows, ash plumes, and ashfall. The current eruption period began in May 2010, with recent activity consisting of frequent gas-and-steam emissions and weak thermal anomalies at the summit crater (BGVN 46:09). This report covers a strong explosion during 15-16 March 2022, which included ash plumes, block-and-ash avalanches, pyroclastic flows, and dome incandescence. In addition, similar low activity of gas-and-steam emissions and a frequent weak thermal anomaly at the summit crater occurred during September 2021 through April 2022 based on weekly and daily reports from the Kamchatka Volcano Eruptions Response Team (KVERT) and satellite data.

Activity during this reporting period prior to 15 March 2022 was relatively low, and according to KVERT, primarily consisted of persistent gas-and-steam emissions and weak thermal anomalies in the summit from the growing lava dome, though they were often obscured by clouds. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system based on the analysis of MODIS data showed intermittent low-power thermal anomalies during mid-September through March 2022 (figure 47). Some of these weak anomalies were visible in infrared satellite imagery on clear weather days; on 19 September the anomalies were accompanied by a gas-and-steam plume that drifted NE (figure 48). Two anomalies were observed during late October and three during mid-December. A brief spike in activity was recorded in mid-March in MIROVA data and the frequency and strength of the anomalies remained higher than the previous months through April.

Figure 47. Low-strength thermal anomalies were detected during September 2021 through March 2022 at Bezymianny, according to this MIROVA graph (Log Radiative Power). Only two anomalies were observed during late October and three during mid-December. A large spike in thermal activity was briefly recorded during mid-March and the frequency remained higher than the previous months through April. Courtesy of MIROVA.

Figure 48. Sentinel-2 infrared satellite image showing a weak thermal anomaly at the summit crater of Bezymianny on 19 September 2021. A gas-and-steam plume was also captured drifting NE. Image with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

During March 2022, activity increased slightly. On 15 March an ash plume was visible in satellite images at 0310 that rose to 4.9 km altitude and drifted 90 km W, indicating renewed explosive activity. By 0600 ash plumes rose to 6.1 km altitude and drifted S. Ash continued to be reported throughout the day; at 1322 they rose to 8.2 km and drifted SW. Satellite images showed block-and-ash flows descending the SE flank to the base, generating dark brown ash plumes. Thermal anomalies were visible at the summit and at the end of the flow. As a result, KVERT raised the Aviation Color Code (ACC) to Orange (the second highest level on a four-color scale). Activity intensified at 0053 on 16 March; ash plumes rose to roughly 12 km altitude and drifted more than 1,300 km NW and then NE. Activity during this time was also characterized by pyroclastic flows that descended the S, W, and N flanks. A large thermal anomaly was visible through 18 March, indicating continuing lava dome growth. On 23 March the ACC was lowered to Yellow. Dome collapses were detected on 25 and 31 March and ash clouds rose to 4 km altitude that drifted 40 km E and 20 km SW, respectively. Strong fumarolic activity, an incandescent lava dome, and avalanches were reported daily through April.

Geologic Background. The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); 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).

Great Sitkin, in the Aleutian island arc, has had only a single ash explosion since 1974, on 25 May 2021. During mid-July 2021, a lava dome began to grow in the summit crater, accompanied by elevated surface temperatures (BGVN 46:08). The volcano is monitored by the Alaska Volcano Observatory (AVO) using local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks. The current report summarizes activity during August 2021-April 2022, during which time the lava dome continued to grow and discharge lava.

AVO reported that unrest continued during the reporting period. During the first week of August 2021, the circular lava dome had grown to 180 m in diameter, based on measurements taken using a 3 August satellite image, and had an approximate volume of 1 million cubic meters. During the morning of 5 August observers on Adak Island, 30 km SW, reported possible low-level lava fountaining from the active vent (figure 14). Throughout August, the lava dome remained active, growing in diameter from 250 m on 6 August, to 380 m three days later, 700 m by 16 August, 850-860 m by 21 August, and 1,090 m by 29 August (figure 15). The growing dome fueled lava discharges, numerous small earthquakes, and weak explosions. In addition, steam-and-gas plumes and emissions were periodically observed (figure 3). Based on satellite images, the crater’s surface temperature remained elevated throughout the reporting period. Cloudy conditions often prevented webcam and satellite views.

Figure 14. Photo of an active lava fountain at Great Sitkin at 0714 on 5 August 2021 as seen looking N from Adak Island. Photo by Peggy Kruse (AVO image 175201).

Figure 15. Lava dome growing on Great Sitkin on 6 August 2021, in a short-wave infrared (SWIR) false-color WorldView-3 satellite image. A lava tube breakout ~100 m long is visible through steam on the SSW margin. Courtesy of AVO (AVO image 175371).

Figure 16. Photo showing a steam plume rising from the dome at Great Sitkin at 0720 on 10 August 2021. Photo by Peggy Kruse (AVO image 175491).

During September, seismicity remained elevated and was characterized by small earthquakes consistent with lava effusion. By mid-September, the edges of the dome touched the S and W rims of the crater, and lava began to advance though a gap in the S rim of the summit crater. By 24 September the dome had overtopped the S and W crater rims and lava flowed 305 m down the S flank and 195 m down the W flank. The dome was about 25 m thick and had grown to 1,170 m E to W and 925 m N to S in dimension.

By 3 October the dome had grown to 1,200 m E-W and 1,000 m N-S. Lava flows continued to advance down the S and SW flanks and were about 300-350 m long (figure 17). The SW lobe was descending two drainages and produced hot avalanches that traveled 450 m downslope on top of a snow field. Satellite images acquired on 11 October showed that lava filled more than half of the summit crater, flowing onto the S and W flanks, and had recently reached the N crater rim. Lava had traveled 330 m down the S flank, 350 m down the W flank, descended small valleys, and in some areas, advanced over snow and ice. Blocks that had detached from the end of the W flow descended 450 m. Analysis of satellite imagery on 25 October showed that the lava dome covered an area greater than 1 km² and had overflowed the crater rim to the N, W, and S (figure 18). Elevated surface temperatures identified in satellite images during 25-26 October clearly showed the vent location (figure 19). By 30 October the lava had advanced about 680 m down the W flank, 560 m down the S flank, and 90 m down the N flank. During the latter part of October, seismicity remained slightly elevated and no explosions were recorded.

Figure 17. A pansharpened near-infrared WorldView-3 satellite image of Great Sitkin on 2 October 2021, showing lava flows and a small steam plume. Courtesy of AVO (AVO image 178461).

Figure 18. A visible WorldView-2 satellite image of Great Sitkin on 25 October 2021 shows the growing lava dome in the summit crater. At this point the dome covered an area greater than 1 km2 and had overflowed the crater rim to the N, W, and S. A steam plume can be seen extendings from the active vent region to the S. Courtesy of AVO (AVO image 178581).

Figure 19. A short-wave infrared WorldView-3 satellite image of Great Sitkin on 25 October 2021. Red-orange areas represent high-temperature lava, purple is snow, light blue is vegetation, and browns to blacks are rock. Courtesy of AVO (AVO image 178481).

By mid-November the lava flows on the N and W flanks had not progressed, but the S-flank flow had advanced to 650 m. According to AVO, satellite images acquired on 23 November showed that slow lava effusion continued. Lava continued to fill the summit crater and the flows on the flanks advanced short distances. During 24-30 November seismicity remained slightly above background levels. Elevated surface temperatures were periodically detected. Steam emissions were sometimes visible in webcam images. Slow lava effusion continued during December, and seismicity was very low, but persistent. A radar image acquired during 14-15 December showed a growing flow field with lava lobes advancing down the N, W, and S flanks. Crater surface temperatures remained elevated.

Based on AVO reports, activity continued to decrease during January-April 2022. Slow lava effusion continued during this period, along with very low but persistent seismicity (figure 20). Crater surface temperatures remained slightly elevated, and occasional steam emissions were observed. Lava flows continued to advance, and by mid-February lava flows had reached 1,050 m, 930 m, and 220 m down the S, W, and N flanks, respectively. Lava flows were also active on the SSW flank. An AVO report in March indicated that snow covered most of the flow except for the advancing fronts of the lava lobes and around the vent area. During the first week of April lava flows on the S, W, and N flanks advanced up to 10 m; elevated surface temperatures identified in satellite images during 8-10 April indicated continuing effusion. Steaming from the vent and flow field was occasionally seen in satellite images.

Figure 20. Photo of Great Sitkin taken from Adak Island on 14 January 2022 showing steam rising lava flows advancing through snow on the flanks. Photo by Steve Skeehan (AVO image 181451).

Geologic Background. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.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/); 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/).

Sabancaya is located NE of Ampato and SE of Hualca Hualca volcanoes. Holocene activity has consisted of Plinian eruptions, followed by lava flow effusions, which have formed an extensive apron around the volcano on all sides except the south. Records of eruptions date back to 1750, with the most recent eruption beginning in November 2016, which has been characterized by daily explosions, ash emissions, thermal activity, and high levels of sulfur dioxide (BGVN 46:10). This activity continues during this reporting period of October 2021 through March 2022. The Observatorio Vulcanologico INGEMMET (OVI) reported daily on numbers of explosions, ash plume heights and directions of drift, seismicity, ashfall, and other activity; IGP (Instituto Geophysico del Peru) issued weekly reports of activity.

Activity during October 2021 through March 2022 consisted of tens of daily explosions, gas-and-steam plumes, strong sulfur dioxide emissions, and frequent thermal anomalies from the dome in the summit crater. Ash plumes rose 800-4,000 m above the summit and drifted in different directions. Daily sulfur dioxide measurements ranged from 400 and 5,600 tons/day, the largest of which took place on 5 January 2022. Some light ashfall was reported around the volcano during October and March. The Buenos Aires Volcanic Ash Advisory Center (VAAC) issued frequent reports of ash emissions that rose to 5.5-9.5 km altitude. Minor inflation continued to be detected near Hualca Hualca (4 km N).

Moderate levels of thermal activity were reported by the MIROVA project during October 2021 through March 2022; the intensity increased gradually during October, followed by a gradual decrease in November and continuing through mid-January 2022 (figure 111). Short breaks in activity occurred in late January through February, though the levels of these anomalies were relatively consistent. A total of 10 thermal alerts were detected by the MODVOLC system on 1, 17, and 19 November 2021, 4 January 2022, 5, 7, 12, and 21 February, and 13 and 25 March. Thermal anomalies were visible in Sentinel-2 infrared satellite images on clear weather days (figure 112). Moderate to strong sulfur dioxide plumes were recorded almost daily during the reporting period by the TROPOMI instrument on the Sentinel-5P satellite (figure 113). A majority of these plumes exceeded 2 Dobson Units (DU) and drifted in different directions.

Figure 111. Frequent low-to-moderate strength thermal anomalies with some fluctuations occurred during October 2021 through March 2022 at Sabancaya, as shown in this MIROVA graph (Log Radiative Power). The strength of the anomalies increased gradually during October, then they were on a declining trend through mid-January 2022. Short breaks in activity occurred in late January through February, and the strength of the anomalies remained relatively consistent. Courtesy of MIROVA.

Figure 112. Sentinel-2 infrared satellite images of Sabancaya showed thermal anomalies in the summit crater on clear weather days on 26 October 2021 (top left), 30 November 2021 (top right), 25 December 2021 (bottom left), and 25 March 2022 (bottom right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Figure 113. Strong sulfur dioxide plumes from Sabancaya were recorded by the TROPOMI instrument on the Sentinel-5P satellite during October 2021 through February 2022; the DU (Dobson Unit) density values were frequently greater than 2. Plumes from 12 October 2021 (top left), 8 November 2021 (top middle), 4 December 2021 (top right), 16 January 2022 (bottom left), 13 February 2022 (bottom middle), and 20 March 2022 (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

An average of 35 daily explosions were reported by IGP during October, generating gas-and-ash plumes 2-3.5 km above the summit that drifted in various directions (figure 114). A total of 4,486 volcanic earthquakes were detected during the month, which included volcanic-tremor (VT) events. Frequent sulfur dioxide measurements ranged from 1,900 and 4,000 tons/day. Intermittent light ashfall was reported in towns to the SW and NE, including Lluta, Taya, Mocca, Cuñirca, Achoma, Ichupampa, and Yanque. During November, an average of 70 daily explosions were detected, which produced gas-and-ash plumes to 2-2.5 km altitude above the summit. There were 2,846 volcanic earthquakes recorded during the month, which included VT-type events.

Figure 114. Photo of a gray ash plume rising from Sabancaya at 0619 on 31 October 2021. Courtesy of INGEMMET.

During December 2021 and January 2022, IGP reported an average of 53 and 39 daily low energy explosions, respectively. These explosions generated ash-and-gas plumes that rose 1-4 km above the summit and drifted in different directions. About 2,777 volcanic earthquakes were recorded during December and 1,280 during January. Sulfur dioxide measurements ranged from 700 and 5,600 tons/day, the highest of which took place on 5 January. On 5 January an ash-and-gas plume rose 2 km above the summit and drifted SW, accompanied by incandescent ejecta (figure 115).

Figure 115. Photos of gray ash plumes rising from Sabancaya on 5 January 2022 (left) and 24 February 2022 (right). The plume on the left rose 2 km above the summit and drifted SW, while the one on the right rose 2.4 km above the summit and drifted SE. Courtesy of INGEMMET.

Similar activity of ash-and-gas plumes and low energy explosions persisted during February and March; an average of 25 and 26 daily explosions were detected, respectively. Ash-and-gas plumes rose 800-3,000 m above the summit and drifted in multiple directions, especially NE and SE. On 24 February an ash-and-gas plume rose 2.4 km above the summit and drifted SE (figure 115). Some light ashfall was intermittently reported in villages surrounding the volcano on 4, 7-11, and 14-16 March; on 4 March, for example, it affected Pinchollo to the NE. About 662 volcanic earthquakes were detected during February and 756 during March. Sulfur dioxide measurements ranged from 400 and 5,000 tons/day, the highest of which was taken on 24 February.

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru (IGP), Calle Badajoz N° 169 Urb. Mayorazgo IV Etapa, Ate, Lima 15012, Perú (URL: https://www.igp.gob.pe/servicios/centro-vulcanologico-nacional/inicio); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); 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/); 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).

Fuego has been vigorously erupting since January 2002 with recorded eruptions dating back to 1531. Eruption activity has included major ashfalls, pyroclastic flows, lava flows, and lahars. Frequent explosions with ash emissions, block avalanches, and lava flows have persisted since 2018. This report covers similar activity during December 2021 through March 2022 based on daily reports from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH) and various satellite data.

The frequent explosions that occurred during December 2021 through March 2022 generated shock waves and vibrations that rattled roofs and windows in communities near the volcano. Ash plumes rose to 4.2-5.2 km altitude each day and drifted in different directions, though dominantly W and SW. The explosions also produced incandescent block avalanches that descended several flank drainages (barrancas), with some of the blocks reaching the edge of vegetation near the bottom. The Ceniza and Trinidad drainages were primarily affected by strong block avalanches throughout the reporting period, though all drainages were affected, including Las Lajas, El Jute, Santa Teresa, Taniluyá, Honda, and Seca. Nighttime incandescence and ejecta could often be seen rising 50-400 m above the summit. Ashfall was frequently reported in nearby communities (table 25). Active lava flows were reported in the Ceniza each month and Ceniza and Santa Teresa drainages during March. The MIROVA graph showed that frequent and moderate thermal activity was consistent throughout the reporting period, with a pulse in activity during February-March (figure 158). A total of 90 MODVOLC thermal alerts were issued. Sentinel-2 infrared satellite data showed thermal anomalies inside the summit crater, as well as the incandescent block avalanches descending primarily the S and SW flanks five to six times each month (figure 159).

Table 25. Activity at Fuego during December 2021-March 2022 included multiple explosions every hour that produced ash emissions that rose as high as 5.2 km altitude and drifted generally W and SW as far as 50 km from the volcano. Incandescent pulses often sent ejecta hundreds of meters high, and ashfall was reported in many communities around the volcano. Data from INSIVUMEH daily reports.

Figure 158. Frequent moderate-to-strong levels of thermal activity at Fuego were shown in the MIROVA graph (Log Radiative Power) during April 2021 through March 2022. Both the frequency and intensity of these anomalies increased during February-March 2022, which sharply declined in power through March 2022. Courtesy of MIROVA.

Figure 159. Frequent incandescent block avalanches descended multiple drainages at Fuego during December 2021 through March 2022, as shown in these Sentinel-2 infrared satellite images on 5 December 2021 (top left), 14 January 2022 (top right), 18 February 2022 (bottom left), and 10 March 2022 (bottom right). Ash emissions also occurred daily and are seen on 14 January and 10 March. Avalanches dominantly affected the S and SW flanks. The ash plume visible in the image on 10 March drifted generally W. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

During December 2021 explosions occurred at a rate of 3-13 per hour, producing ash plumes that rose to 4.2-5.2 km altitude, and drifted in multiple directions. Ash was reported extending as far as 40 km from the volcano on 11 and 16 December. Shock waves frequently rattled windows and roofs around the volcano. Pulses of incandescent ejecta rose 100-300 m high. A total of 22 MODVOLC thermal alerts were recorded on 11 days during the month: 1, 2, 6, 7, 10, 18, 23, 26, 27, 29, and 30 December. Ashfall was reported on 15 days during the month, dominantly affecting Panimaché I and II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), San Pedro Yepocapa (8 km NW), Palo Verde, and Sangre de Cristo. Ashfall was detected in Yucales on 17 December, in San Andrés Osuna and La Rochela on 21 December, in San Andrés Osuna, La Rochela, and Ceylán on 23-24 December, and in Quisache, El Campamento, La Soledad, and Acatenango on 29 December. Moderate block avalanches constantly descended the Ceniza (SSW) drainage, sometimes reaching the edge of vegetation. Avalanches also affected the Taniluyá (SW), Trinidad (S), Santa Teresa, Las Lajas (SE), El Jute, Seca (W), and Honda drainages.

Daily explosions ranged between 5 and 13 per hour during January 2022, which generated ash plumes that rose to 4.3-4.8 km altitude and drifted dominantly W and SW. Ash extended as far as 50 km W on 6 January. Intermittent pulses of incandescent ejecta rose 100-400 m high. A total of 17 MODVOLC thermal alerts were recorded on 11 days during the month: 12, 15, 19, 21, 23, 24, 26, 28, 29, 30, and 31 January. Ashfall was reported on 20 days, primarily affecting Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Palo Verde, Sangre de Cristo. Ashfall was detected in Yucales on 2 and 7 January, La Rochela on 10, 15, and 20 January, San Pedro Yepocapa on 12 January, Alotenango, Ciudad Vieja, and Antigua Guatemala on 16 January, Ceilán and San Andrés Osuna on 18 January, Alotenago and Reunión on 22 January, and La Rochela, Ceilán, and San Andrés Osuna on 31 January. Frequent block avalanches descended the Ceniza, Taniluyá, and Trinidad, and Seca drainages more frequently, and weaker down the Santa Teresa, Las Lajas, and Honda drainages throughout the month. Sometimes the avalanches reached vegetation. On 26 January a 50-m-long lava flow was observed descending the Ceniza drainage, which remained active through the end of the month, growing as long as 150 m; it was no longer observed by 1 February. Constant avalanches were detected at the front of the flow, which traveled down the Trinidad drainage.

High levels of activity persisted in February. Daily explosions ranged between 2 and 14 per hour, which produced ash plumes that rose to 4.3-4.8 km altitude and drifted in different directions, though dominantly W and SW. Ash plumes drifted as far as 30 km S and SW on 16 February. Pulses of incandescent ejecta rose as high as 300 m. There were 29 MODVOLC thermal alerts reported on 15 days during the month: 2-6, 9, 11-14, 18, 20, 21, 23, and 28 February. Ashfall was reported on 17 days, affecting Panimaché I and II, Morelia, Santa Sofía, El Porvenir, San Pedro Yepocapa, Sangre de Cristo, Finca Palo Verde, La Rochela, Ceilán, San Andrés Osuna, Alotenango, Ciudad Vieja, San Miguel Dueñas, Antigua Guatemala, Yucales, and possibly Siquinala on 6 February. Block avalanches continued to descend dominantly the Ceniza and Trinidad drainages, as well as the Taniluyá, Santa Teresa, and Las Lajas drainages, sometimes reaching vegetation. A lava flow originating from the crater began on 5 February and traveled down the Ceniza drainage, which grew as long as 300 m on 22 February. The flow continued through 23 February down the Ceniza drainage, causing near-continuous block avalanches and landslides along the front of it. On 27 February the block avalanches caused some fires in vegetated areas.

During March, daily explosions ranged between 1 and 11 per hour, which generated ash plumes that rose to 4.3-5 km altitude and drifted in multiple directions, as far as 40 km W on 5 March. Nighttime crater incandescence and ejecta rose 100-400 m high. MODVOLC detected 22 thermal alerts on eight days during the month: 4-8 and 10-12 March. Ashfall was reported on 22 days, affecting primarily Panimaché I and II, Morelia, Santa Sofía, El Porvenir, La Rochela, Ceilán, San Andrés Osuna, and Palo Verde (figure 160). Possible ashfall in San Pedro Yepocapa and San Miguel Pochuta was reported on 5 March. On 5 March a lava flow measured 200 m long and contains incandescent blocks that broke off the front of the flow and traveled down the flank, reaching vegetation. By 7 March there were two lava flows in the Ceniza and Santa Teresa drainage, measuring 250-400 m and 100-200 m long, respectively. Pyroclastic flows were observed descending multiple drainages on the SW, S, and SE flanks and affecting areas as far as 7 km away on 9 March, according to CONRED. An ash plumes on 14 March rose to 4.5-5 km altitude and drifted 15-20 km W and SW (figure 161). On 24 March weak ashfall was reported in La Soledad, San Antonio, Nejapa, Acatenango, and Patzicía and on 27 March, it was reported in Santa Maria de Jesus, Alotenango, and Ciudad Vieja. Strong block avalanches descended the Ceniza and Trinidad drainages, sometimes reaching the edge of vegetation at the bottom. The avalanches were also occasionally observed down the Las Lajas, Santa Teresa, Taniluyá, Honda, and Seca drainages.

Figure 160. Photo of ashfall on leaf in Panimaché I taken in early March 2022. Courtesy of Amilcar Calderas, INSIVUMEH.

Figure 161. Photo of an ash plume rising from Fuego on 14 March 2022. Courtesy of Beth Bartel, Michigan Technological University.

Geologic Background. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.php); 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); Amilcar Calderas, Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: https://www.facebook.com/amilcar.calderas); Beth Bartel, Michigan Technological University, 1400 Townsend Drive, Houghton, Michigan 49931-1295 (URL: https://twitter.com/EatTheCrust).

Copahue is located along the Chile-Argentina border and contains an eastern summit crater with an acidic 300-m-wide crater lake that has exhibited fumarolic activity. The current eruption period began in July 2021 and has been characterized by ash plumes, frequent sulfur dioxide emissions, seismicity, and gas-and-steam emissions (BGVN 46:11). Weak thermal anomalies were also detected. This report covers activity from November 2021 through April 2022, which describes the end of the last eruption period with two thermal anomalies in early November. Information primarily comes from the Servicio Nacional de Geología y Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) and various satellite data.

Activity was relatively low during November 2021 and consisted of 19 volcano-tectonic (VT) type events and two long-period (LP) events. Gas-and-steam emissions rose less than 1.2 km above the summit. Two weak thermal anomalies were detected in the summit crater on 1 and 6 November 2021, according to Sentinel-2 infrared satellite images (figure 68). No further thermal activity was detected after 6 November through April 2022. Sulfur dioxide data obtained using Differential Absorption Optical Spectroscopy (DOAS) showed an average value of 486 ± 68 tons/day (t/d) and a maximum value of 1,850 t/d on 4 November.

Figure 68. Sentinel-2 infrared satellite images showed a small thermal anomaly in the Copahue summit crater on 1 (left) and 6 (right) November 2021. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

During December 2021 through April 2022, seismic activity consisted of 136 VT-type, seven LP-type, and one tremor type (TR) events. Gas-and-steam emissions rose 300-320 m high. Thermal anomalies were no longer observed in satellite imagery. Sulfur dioxide emissions ranged from 213-415 t/d, with a daily maximum value of 1,634 t/d on 28 March.

Geologic Background. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/, https://twitter.com/Sernageomin); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Chikurachki is a relatively small cone located on Paramushir Island in the northern Kurile Islands. Reported eruptions date back to 1690 with the most recent previous activity during July-August 2016. Activity has consisted of moderate explosive eruptions, ash plumes, sulfur dioxide emissions, and some ashfall (BGVN 41:11). This report updates information from August 2016 through April 2022, which includes a new eruption during 31 January through 2 February 2022 characterized by ash explosions. Information primarily comes from the Kamchatka Volcanic Eruptions Response Team (KVERT), the Tokyo Volcanic Ash Advisory Center (VAAC), and satellite information.

The July-August 2016 eruption began on 27 July when an ash plume rose to an altitude of 4-5 km and drifted 176 km NE (BGVN 41:11). Notable activity continued on 18 August when an ash plume rose over 2.7 km above the crater and drifted 280 km NE. Based on satellite observations, KVERT reported that a gas-and-ash plume rose to 2.5 km altitude on 29 August and drifted 35 km SE.

Low activity was reported from September 2016 through mid-March 2021, after which occasional dark brown to black ash deposits were visible in Sentinel-2 satellite imagery. On 21 March 2021 brown deposits were seen on the SE flank, where light ashfall was also visible on 5 and 7 April. Ash covered much of the summit area on 30 April, accompanied by an ash plume that drifted SW. An ash plume deposited ash on the SE flank on 5 May. Strong ashfall surrounded the perimeter of the summit on 12 May, which was also noted on 15-25 May; an ash plume that drifted W was visible on 15 May (figure 13). Ashfall was visible on multiple flanks on 4, 6, 11, 16, 19, 24, and 29 June, and 1, 4, 6, 9, 11, 16, and 21 July. A light brown ash plume drifted SE on 5 August. On 10 August a gray ash plume drifted S, and on 23 and 25 August a brown ash plume drifted W (figure 13).

Figure 13. Sentinel-2 satellite images showing brown-to-gray plumes rising from Chikurachki on 15 May (top left), 10 August (top right), 23 August (bottom left), and 25 August (bottom right) 2021. Plumes drifted in different directions. Ash deposits were visible on the SE and NW flanks of the volcano on 15 May 2021. Images use “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Thin ash deposits were visible on the SW flank on 17 January 2022 in a Sentinel-2 satellite image, accompanied by a white gas-and-steam emission. An explosive eruption began at 0300 on 31 January 2022 according to KVERT. Strong gas-and-steam emissions were first visible at 1200 on 31 January and possibly contained some ash. The plume rose as high as 5 km altitude and drifted 80 km SW. A thermal anomaly was also noted in the crater area on 31 January and KVERT raised the ACC to Orange. Ash plumes rose as high as 3 km altitude and drifted 104 km WSW on 1 February, based on a satellite image. On 2 February explosions produced ash plumes that rose to 5 km altitude and drifted 255 km S and SE. Ash explosions were no longer detected by 3 February and as a result, the ACC was lowered to Yellow. On 5, 12, and 22 April, some fresh ash deposits were visible in satellite images surrounding the summit crater (figure 14).

Figure 14. Sentinel-2 satellite images showing fresh black ash deposits surrounding the summit crater and to the E of Chikurachki on 12 (left) and 22 (right) April 2022. Images use “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Geologic Background. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is a relatively small cone constructed on a high Pleistocene edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic Plinian eruptions have occurred during the Holocene. Lava flows have reached the sea and formed capes on the NW coast; several young lava flows are also present on the E flank beneath a scoria deposit. The Tatarinov group of six volcanic centers is located immediately to the south, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov centers are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of an eruption around 1690 CE from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/); Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The first known observed eruption in the Galapagos occurred at Volcán Wolf on Isabela Island in August of 1797. Basaltic lava flows have occurred within the summit crater and on the flanks a few times each century since then. The most recent eruptions in 1982 (SEAN 07:08) and 2015 (BGVN 41:10) produced lava fountains and flows within the crater and on the flanks. A new eruption beginning on 7 January 2022 produced a large SO₂ plume, a small amount of ash, and lava flows on the SE flank that lasted through April 2022. Details of the 2022 eruption are provided with information primarily from the Geophysical Institute of the National Polytechnic School (IG-EPN) in Quito, Ecuador. IG maintains a broadband seismic network and a DOAS (Differential Optical Absorption Spectrometer) SO₂ monitoring station on the islands that transmits data to the mainland. The Washington Volcanic Ash Advisory Center (VAAC) is responsible for aviation warnings, and satellite data provide valuable remote thermal and SO₂ information.

Summary of January-April 2022 eruption. The 6 January through 14 April 2022 eruption lasted longer than the eruptions in 1982 and 2015. The eruption began with a very large SO₂ plume, a moderate-size ash plume, and multiple vents that produced lava flows. IG-EPN officials noted that the lava flows originated from an 8-km-long SE-flank radial fissure with at least five vents. The flows reached a maximum distance of about 18.5 km; they stopped 150-200 m from the coastline, covering an area of more than 30 km².

Description of January-April 2022 eruption. After seven years of no activity, a new eruption at Wolf was first reported shortly late on 6 January 2022, Galápagos time. Within the hour, a plume of gas and ash had reached 3.8 km altitude and drifted NE while a second plume drifted W at 1.9 km altitude. Lava flows were observed descending the SE flank. Seismicity had been detected at the FER1 station on Fernandina Island a few hours earlier that likely signaled the start of the eruption. Twenty-nine MODVOLC thermal alerts appeared on 7 January on the SE flank, confirming a significant thermal event from the lava flow. Rangers from Parque Nacional Galápagos reported that a fissure on the S flank was the source of the flow. They witnessed the flow descending the SE flank and burning vegetation (figures 12 and 13).

Figure 12. A new lava flow at Wolf descends the SE slope on 7 January 2022 burning adjacent vegetation and creating white smoke. Courtesy of Parque Nacional Galápagos.

Figure 13. Lava flows descended the SE flank of Wolf on 7 January 2022, burning shrubs and grasses in their path. Courtesy of Parque Nacional Galápagos.

The Washington VAAC issued its first report of ash emissions on 7 January 2022; plumes initially rose to two altitudes: 3.7 km drifting W, and 5.6 km altitude drifting NE. Later the plumes dropped to 2.4 km drifting W and 4.6 km drifting NE. The plume drifting to the W extended over 80 km. The VAAC noted reports of a large SO₂ plume later in the day reaching approximately 185 km W of the summit before dissipating. By the next day, they reported that emissions were primarily gas, drifting W at 1.3 km altitude. During 8-9 January gas emissions drifted SW at 700 m altitude. By 9 January, only an SO₂ plume was reported moving SW from the summit, and no further ash advisories were issued. Sulfur dioxide degassing decreased substantially from 60 million tons measured on 7 January to 8 million tons measured on 12 January (figure 14).

Figure 14. A large SO2 plume with a mass over 60 kilotons emerged from Wolf on 7 January 2022 at the beginning of the eruption as recorded by the TROPOMI instrument on the Sentinel-5P satellite. The mass decreased each subsequent day but remained very large for several days and measurable each day until early February 2022. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

During a flyover on 11 January 2022, the Park Minister noted continuing volcanic activity, and that the flow had traveled about 15 km from its source on the SE flank. IG-EPN reported that the lava flow was emerging from at least three fissures. The initial fissure from 7 January was at 1,290 m elevation and the subsequent fissures were located at 1,090 m elevation. By 11 January the flow was about 3 km from the coast (figure 15). IG-EPN produced the first map of the 7.4 km² flow on 12 January 2022 based on satellite data from 7 and 11 January (figure 16). The maximum length of the flow was estimated at 16.5 km from the initial vent, and 15 km from the two subsequent active fissures. The numbers of daily thermal alerts decreased steadily between 7 and 13 January, interpreted by IG-EPN as a decrease in the lava flow rate.

Figure 15. A Sentinel satellite image annotated by IG-EPN from 11 January 2022 showing gas emissions and the active lava flow at Wolf. Courtesy of IG-EPN, Informe Volcánico Especial – GALÁPAGOS – 2022 No. 02, Actualización de la actividad del volcán Wolf – Isla Isabela, Archipiélago de Galápagos, Quito, 13 de enero de 2022.

Figure 16. A preliminary map of the lava flow at Volcán Wolf on Isabela Island in the Galápagos as of 11 January 2022. The map was created from Sentinel-2 and PlanetScope satellite images. The flow covered an area of approximately 7.4 km2 and reached a maximum length of about 16.5 km. Courtesy of IG-EPN, Informe Volcánico Especial – GALÁPAGOS – 2022 – No. 02, Actualización de la actividad del volcán Wolf – Isla Isabela, Archipiélago de Galápagos, Quito, 13 de enero de 2022.

By 17 January the lava flow had advanced to slightly more than 2 km from the ocean. By early February the active vent was downslope from the original vents, and IG-EPN was able to map multiple flow fronts on the S and SE flanks (figure 17). Multiple near-daily MODVOLC thermal alerts continued throughout February, with pulses of lava flow activity producing tens of alerts on some days. The lava flows remained active on the SE flank, slowly advancing towards the coast; satellite imagery helped IG-EPN scientists to map the track of the lava flow (figure 18).

Figure 17. A map of the lava flow at Volcán Wolf as of 8 February 2022 shows the active flow fronts as of various dates (yellow dots, red arrows). The original, inactive vents are shown with a green triangle and the active vent as of that date is shown in orange. Courtesy of IG-EPN, INFORME DIARIO DEL VOLCAN WOLF No. 2022-034, Quito, miércoles 09 de febrero de 2022.

Figure 18. Sentinel-2 satellite imagery of Volcán Wolf from 11 and 16 January (top), and 15 and 25 February (bottom), show the active area of the lava flow changing over the first seven weeks of the eruption. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Lava flows remained active on the SE flank throughout March 2022; IG-EPN scientists used the location of the FIRMS thermal anomalies to map the active areas of the flow over time (figure 19). By the end of March, the number of daily thermal alerts had diminished significantly, suggesting a further decrease in the flow rate. Parque Nacional Galápagos personnel reported at the end of March that lava flow activity continued on the SE flank but had not reached the ocean. Multiple hot spots in satellite images suggested that lava was flowing through tubes that were visible to the park rangers patrolling the coast.

Figure 19. Maps of the advance of the lava flows at Volcán Wolf from 9 and 15 March 2022 show the progress of the different branches over time. Data is based on thermal anomalies reported by FIRMS. Courtesy of IG-EPN, INFORME DIARIO DEL VOLCAN WOLF No. 2022-062 and 2022-068, Quito, miércoles 09 y 15 de marzo de 2022.

MODVOLC thermal alerts were issued on 13 days during April 2022, with the number of daily alerts significantly fewer than previous months since January. Thermal anomalies continued to be present in satellite imagery through 21 April, and then briefly on 29 and 30 April (figure 20). IG-EPN scientists plotted the advance of the flow as the location of thermal alerts on a satellite image base several times during April; no advance was detectible after 14 April (figure 21). No surface activity was observed after 21 April. An updated map of the lava flow was published on 20 April 2022 (figure 22). Single MODVOLC thermal alerts were issued on 3 and 7 May, and two alerts on 16 May were the last recorded for the eruption.

Figure 20. Thermal anomalies in Sentinel-2 satellite imagery of Volcán Wolf on 17 March, 27 March, 6 April and 16 April 2022 show the slow advance and decrease in thermal energy from the flow. Images use Atmospheric penetration rendering (12, 11, 8a). The summit crater in the upper left is about 4 km across. Courtesy of Sentinel Hub Playground.

Figure 21. Maps from Volcán Wolf plot the advance of the thermal alerts through 8 April (left) and 14 April 2022 (right) on a satellite image base, indicating the decrease in flow. No further advances were mapped after 14 April. Courtesy of IG-EPN, INFORME DIARIO DEL VOLCAN WOLF No. 2022-092 and 2022-098, Quito, viernes 08 y 14 de abril de 2022.

Figure 22. The preliminary map from 20 April 2022 of the lava flows emitted during the eruption of Volcán Wolf that began in January. The map was made based on satellite images from PlanetScope. The lava flows covered more than 30 km2, and the maximum length covered was approximately 18.5 km from the highest vent; the flow did not reach the coast. Courtesy of IG-EPN and F.J. Vasconez, INFORME ESPECIAL VOLCÁN WOLF No. 2022-003 APARENTE FINAL DEL PERIODO ERUPTIVO Quito, 05 de mayo de 2022.

Eruption review using satellite data. Sulfur dioxide emissions that were initially as high as 60 kilotons, gradually tapered off during January and none were recorded in satellite data after early February (figure 23); they decreased steadily throughout the period and ended in early April (figure 24). Hundreds of thermal alerts from satellite data created rough maps of the 2015 and 2022 flow areas showing the difference in their relative locations. The 2015 flow started on the crater rim and flowed both into the crater and down the E flank and into the ocean, while the 2022 flow started about 1.5 km down the SE flank from the caldera rim and stopped a few hundred meters from the coastline (figure 25).

Figure 23. Sulfur dioxide emissions at Volcán Wolf decreased significantly after 15 January 2022, the last day where the mass of the SO2 plume exceeded 10 kilotons. Only very faint emissions were recorded by satellite instruments after early February. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 24. Sulfur dioxide emissions in tons per day for Volcán Wolf from 6 January through 2 April 2022. Data from Mounts and NASA (F.J. Vasconez). Courtesy of IG-EPN, INFORME ESPECIAL VOLCÁN WOLF No. 2022-003 APARENTE FINAL DEL PERIODO ERUPTIVO Quito, 05 de mayo de 2022.

Figure 25. The MODVOLC thermal alerts plotted on a Google Earth base from eruptions at Wolf during 2015 (left) and 2022 (right) show how the thermal alerts roughly outline the area affected by lava flows. Lava during the 2015 eruption effused from the crater rim and flowed into crater and down the E flank into the ocean. The 2022 flow started about 1.5 km down the SE flank from the caldera rim and traveled about 18.5 km before stopping a few hundred meters from the coastline. Courtesy of MODVOLC.

The MIROVA Log Radiative Power graph of MODIS data shows the onset of the eruption in early January 2022 with high levels of heat initially, followed by a period with more fluctuations, and then a period of gradual decrease through mid-April 2022 before dropping off quickly to low levels (figure 26). The MIROVA distance graph based on the central caldera location shows how the lava flow initially quickly extended 10 km beyond SE-flank vent location, was then restricted to higher on the flank, and then gradually moved farther away over time.

Figure 26. The MIROVA data shows both the intensity of the Radiative Power (left) and the distance from the summit of the volcano (right). The graph of Log Radiative Power from December 2021 through May 2022 shows the onset of the eruption in early January 2022 followed by an overall decrease in heat emissions. The Distance graph of the eruption shows the onset of activity more than 10 km from the caldera center, then activity higher up the flank and gradually moving farther away as the eruption continued. Courtesy of MIROVA.

IG-EPN scientists plotted the hundreds of daily thermal alerts recorded by different satellite sensors such as MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible Infrared Imaging Radiometer Suite), which are processed by different platforms (e.g., MIROVA , FIRMS, WORLDVIEW). The plot indicated a decreasing trend in thermal alerts, in both quantity and intensity from the beginning of the eruption in early January 2022 through the end of April (figure 27). This decrease reflected the decline in the rate of lava emission, as well as the progressive cooling of the lava flows.

Figure 27. A time series plot of thermal alerts from several different instruments for Volcán Wolf from January through April 2022 has a moving average of 7 days plotted as a black line over the primary data. After an initial peak at the start of the eruption, the activity gradually decreases through the end of April (F.J. Vasconez). Courtesy of IG-EPN, INFORME ESPECIAL VOLCÁN WOLF No. 2022-003, APARENTE FINAL DEL PERIODO ERUPTIVO Quito, 05 de mayo de 2022.

Geologic Background. Wolf, the highest volcano of the Galápagos Islands, straddles the equator at the north end of the archipelago's largest island, Isabela. The 1710-m-high edifice has steeper slopes than most other Isabela volcanoes, reaching angles up to 35 degrees. A 6 x 7 km caldera, at 700 m one of the deepest of the Galápagos Islands, is located at the summit. A prominent bench on the west side of the caldera rises 450 above the caldera floor, much of which is covered by a lava flow erupted in 1982. Radial fissures concentrated along diffuse rift zones extend down the north, NW, and SE flanks, and submarine vents lie beyond the north and NW fissures. Similar unvegetated flows originating from a circumferential chain of spatter and scoria cones on the eastern caldera rim drape the forested flanks to the sea. The proportion of aa lava flows at Volcán Wolf exceeds that of other Galápagos volcanoes. An eruption in in 1797 was the first documented historical eruption in the Galápagos Islands.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Parque Nacional Galápagos (URL: https://galapagos.gob.ec/noticias/, https://www.facebook.com/parquegalapagos/posts/290645263104217); 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/); 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); 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/); 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).

Krakatau volcano in the Sunda Strait between Java and Sumatra, Indonesia, had a major caldera collapse around 535 CE; this event formed a 7-km-wide caldera ringed by the three islands of Verlaten, Lang, and Rakata. A new island grew that was then destroyed in the 1883 caldera-forming eruption. Anak Krakatau (Child of Krakatau), constructed beginning in late 1927 (BGVN 44:03, figure 56), was the site of over 40 smaller eruptions until 22 December 2018 when a large explosion destroyed most of the 338-m-high edifice and generated a deadly tsunami (BGVN 44:03). Intermittent ash-bearing explosions from the sea-level crater since May 2021 have contributed to the growth of a new pyroclastic cone to about 150 m elevation. Activity from December 2021 to April 2022, including a new lava flow in April 2022, is covered in this report with information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, referred to as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), the Darwin Volcanic Ash Advisory Center (VAAC), and several sources of satellite data. Additional information not previously reported of eruptive activity during 2011 and 2013 is also provided.

Anak Krakatau was quiet from 7 November 2021 until a series of explosions during 3-6 February 2022. Steam and ash plumes rose 2 km above the summit and drifted in multiple directions. Multiple explosions during 24-30 March 2022 produced plumes of dense gray and black ash that also rose 2 km above the summit. Renewed explosions during 15-23 April 2022 rose 500-2,000 m above the summit and drifted in multiple directions. Activity increased significantly on 23 April, causing PVMBG to raise the Alert Level from II to III. A lava flow emerged from the summit onto the W flank and reached the sea. Continuous ash emissions rose to 6 km altitude until 25 April when activity tapered off before ceasing by 27 April 2022 (figure 119). Thermal activity remained low throughout the period until increased explosive and effusive activity began in late April (figure 120).

Figure 119. Explosions resumed at Krakatau after three months of quiet on 3 February 2022 (top left) with steam and ash plumes that rose 2 km above the summit and drifted S. A series of explosions that began on 15 April produced ash and steam on 19 April (top right) that drifted SE. Activity intensified on 23 April and a lava flow emerged and traveled down the SW flank of the cone, producing a strong thermal anomaly and dense steam emissions on 24 April (bottom left). Remnants of the cooling flow were still visible as thermal anomalies on the SW flank on 27 April 2022 (bottom right). Courtesy of Sentinel Hub Playground.

Figure 120. Thermal activity remained low at Anak Krakatau until late April 2022 when explosions and a lava flow caused a spike in the thermal signature recorded in the MIROVA project graph of log radiative power from 1 June 2021 through April 2022. Courtesy of MIROVA.

Activity during December 2021-April 2022. Anak Krakatau was quiet during December 2021 and January 2022, with only diffuse steam plumes 25-100 m high reported on many days. Low levels of seismicity consisted of continuous tremor, harmonic tremor, and seismicity from fumarolic degassing on most days, with infrequent deeper low-magnitude earthquakes.

A VONA issued by the Anak Krakatau Volcano Observatory on 3 February 2022 indicated that gray ash emissions rose 200 m above the summit and drifted NE. The first explosion recorded in the early morning the following day produced a dense white and gray plume that rose 500 m above the summit and drifted SW; subsequent explosions produced plumes of dense, black ash that rose 600-1,000 m above the summit and drifted S and E (figure 121). Overnight on 4-5 February ash plumes rose to altitudes of 400-1,600 m. By midday local time on 5 February the plumes were rising 2,000 m above the summit and drifting slowly SE. Multiple explosions on 6 February sent ash plumes to 750-1,650 m altitude that drifted E before activity ceased by the end of the day. Multiple earthquakes from the explosions were recorded each day on 5 and 6 February. For the remainder of the month, white steam plumes rose 25-100 m and no further explosive activity was reported.

Figure 121. An eruption at Anak Krakatau during 3-6 February 2022 initially produced white and gray emissions that became dense black ash emissions to as high as 2 km above the summit (2,150 m altitude). Courtesy of MAGMA Indonesia.

Steam plumes rose 25-100 m above the crater during 1-23 March 2022. The background seismicity included continuous tremor, shallow and deep earthquakes, and multiple earthquakes from steam and gas venting on most days. A new series of explosions that began on 24 March produced white and gray steam and ash emissions that rose 25-1,000 m above the summit that day. Four eruption earthquakes were recorded. Multiple gray and black ash plumes also rose 1,000-2,000 m above the summit on 25 March and drifted E (figure 122), and 19 eruption earthquakes were recorded. Activity diminished on 26 and 27 March with gray plumes rising 400-600 m above the summit and drifting SE and NE; one eruption earthquake occurred on 26 March and two on 27 March. Gray and black ash emissions rose 1,000 m above the summit on 28 March and drifted E (figure 123). On 29 and 30 March gray and black ash emissions rose 500-700 m above the summit and drifted E and NE. One eruption earthquake was recorded on 28 March, three on 29 March, and four on the 30th.

Figure 122. Explosions at Anak Krakatau on 24 and 25 March 2022 produced gray and black ash plumes that rose as high as 2,000 m above the summit. Courtesy of MAGMA Indonesia.

Figure 123. Explosions continued at Anak Krakatau during 26-30 March 2022 with gray and black ash plumes reaching 1,000 m above the summit and drifting in multiple directions, shown here on 28 March. Courtesy of MAGMA Indonesia.

Explosions began again early on 15 April 2022 local time; three eruption earthquakes were recorded, and a white and black ash plume was reported at 1,000 m above the summit drifting SW, followed by plumes that rose 700-800 m above the 150-m-high peak (figure 124). Two eruption earthquakes on 17 April were recorded along with Strombolian activity. Multiple VONA’s were issued for dense gray and black ash plumes that rose 800 m and drifted SW. The Darwin VAAC reported continuous ash emissions drifting SW at 1.2-2 km altitude. Seven eruption earthquakes were recorded on 18 April. Three dense black ash plumes rose 700 m above the summit and drifted SW during the first half of the day (figure 124). This was followed in the afternoon by two larger gray and black plumes that rose 2,000 and 1,000 m above the summit. Continuous gray emissions rose 50-500 m during 19-21 April; the gray and black ash plume rose 800 m above the summit and drifted E.

Figure 124. During 15-18 April 2022 multiple gray and black ash plumes rose up to 1,000 m above the summit of Anak Krakatau and drifted mostly SW including this one on 18 April. Courtesy of MAGMA Indonesia.

Multiple explosions were observed on 22 April; dense, black ash plumes rose 500-1,500 m above the summit and drifted SW, rumbling sounds from the explosions were heard at the Observatory, and eight eruption earthquakes were recorded that day. Continuous high-amplitude tremor on 23 April accompanied ash emissions that rose 300-3,000 m above the summit and drifted SE and S. In a VONA released by the Observatory at 1434 local time they noted a lava flow on the W side of the crater that remained active the next day (figure 125). The Darwin VAAC reported continuous localized ash emissions to 4.6 km altitude extending SE, and plumes to 6.1 km later in the day. Explosions could be heard at the Pasauran PGA post on 24 April and they reported dense gray and black ash emissions rising to 3 km altitude, and drifting SE and S.

Figure 125. Bright incandescence from Anak Krakatau on 24 April 2022 was from a lava flow on the W flank, which produced steam as it entered the ocean. Courtesy of MAGMA Indonesia.

The sharp increases in seismic amplitude, eruption intensity, inflation and deflation patterns, and SO₂ emissions beginning on 23 April (figure 126) led PVMBG to raise the Alert Level from II to III the next day. The Darwin VAAC reported continuous ash emissions extending SW at 6.1 km altitude until early on 25 April when they dropped to 3 km altitude and drifted NE. Emissions were drifting E and SE at 1.5 km altitude on 26 and 27 April. During an overflight on 28 April BNPB officials observed a new lava flow on the SW flank that had emerged from the summit and entered the ocean (figure 127). Multiple MODVOLC thermal alerts were recorded during 20-29 April.

Figure 126. Large amounts of SO2 from Anak Krakatau were detected beginning on 23 April 2022 by the TROPOMI instrument on the Sentinel-5P satellite. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 127. An overflight of Anak Krakatau by BNPB officials on 28 April 2022 revealed a new lava flow on the SW flank of the pyroclastic cone that had reached the ocean. Courtesy of BNPB.

Eruptive activity during May-July 2011. An eruptive pause and decreased seismicity in March 2011 suggested that the eruption was over, though a possible weak ash plume was seen in satellite imagery on 31 July (BGVN 36:8). However, a MODVOLC thermal alert from 17 May 2011 suggested an earlier renewal of surface activity. Observations on 25 June 2011 from photographer Øystein Lund Andersen confirmed Strombolian activity, lava bombs, and lightning (figure 128), followed by another MODVOLC alert on 28 June. Multiple daily thermal alerts began on 18 July and were intermittent through the end of November 2011, and other reports of eruptive activity were more frequent during that time (BGVN 37:11 and 37:12).

Figure 128. Strombolian explosions, lava bombs, and lightning at Krakatau on 25 June 2011. Copyrighted photo courtesy of Øystein Lund Andersen, used with permission.

Eruptive activity during March and October 2013. According to Andersen, PVMBG reported an eruption on 11-12 March 2013, which they described as the first eruption since September 2012. During a visit on 23 March, Andersen found evidence of fresh eruptive activity on the E flank in the form of large clasts and fresh impacts (figure 129), observed gas emissions rising 300-400 m above the summit, and saw a small area of incandescent material near the SW corner of the crater rim. A field camera placed by Andersen on nearby Verlaten Island captured an explosion at 0856 local time on 28 March from the northern part of the crater, producing a pyroclastic flow down the N flank. A second eruption was recorded at 1716 local time, also on the N flank. A single MODVOLC thermal alert was issued that day. Photos taken of an hour-long eruption at midday on 29 March from the SSW area of the crater, a different location from the previous day (figure 130), showed a small pyroclastic flow traveling 100 m down the S flank. Incandescent gas emissions were noted during March-October 2013; the remote camera captured an ash emission on 31 October 2013, but the volcano remained quiet after that until 31 March 2014 (BGVN 40:08).

Figure 129. A fresh impact crater and a volcanic rock fragment at Anak Krakatau on 23 March 2011 supported the PVMBG report of an eruption on 11-12 March that damaged seismic equipment. Copyrighted image courtesy of Øystein Lund Andersen, used with permission.

Figure 130. Dark gray ash emissions and white steam emerged from Krakatau during a brief eruption on 28-29 March 2013. Copyrighted image courtesy of Øystein Lund Andersen, used with permission.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

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: https://www.bnpb.go.id/berita/tinjau-gunung-anak-krakatau-kepala-bnpb-imbau-masyarakat-tingkatkan-kesiapsiagaan); 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 MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Øystein Lund Andersen? (URL: https://www.oysteinlundandersen.com/, https://twitter.com/oysteinvolcano); 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/).

Turrialba, in Costa Rica, is a large stratovolcano that covers an area of 500 km². Three well-defined craters occur at the upper SW end of a broad 800 x 2,200 m summit depression that is breached to the NE. Five major explosive eruptions have occurred during the past 3,500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Minor eruptive activity has been frequent since 2010. The following report summarizes activity from September 2021-February 2022 and is based primarily on information from periodic reports published by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) and satellite data. During this period, activity continued at a low level, similar to that observed since the beginning of September 2020 (BGVN 46:09), with occasional weak ash explosions and ash emissions.

Based on OVSICORI-UNA’s 2021 annual report, activity continued to decrease in 2021, a trend that began in 2019. Frequent rim collapses into the bottom of the crater were evident. Sporadic ash emissions occurred between 13 June and 23 July 2021 (BGVN 46:09), and again beginning on 3 November continuing into late February 2022. Neither the seismic nor geodetic data suggested a new supply of magma, and petrological observations from ash samples revealed a large amount of lithic material and less than 12% of fresh magmatic material. These observations strongly suggested to OVSICORI-UNA that the explosions were phreatic (caused by the interaction between rainwater and a hot body or shallow magma).

A one-minute explosion from the West Crater at 0646 on 3 November produced a plume that rose 200 m above the crater rim and drifted W. Ash from the plume contained very few fragments of juvenile glassy material (less than 5%), and abundant porous and lithic material (~85%), indicating to OVSICORI-UNA that the explosion was mainly phreatic. Another small explosion was recorded on 7 November. On 11 November, a small area of incandescence was visible on the internal SW wall of the summit vent, which was vigorously degassing. An explosion at 0624 on 23 November lasted less than a minute and produced a plume that rose less than 500 m above the crater rim that drifted SW.

Incandescence on the NW inner wall of the West Crater, which had been periodically visible since mid-November, was visible during 26-27 December, suggesting that fumarolic temperatures exceeded 300°C. OVSICORI-UNA reported three weak ash explosions on 28 December. The first, at 0644, was one minute long and produced an ash emission that rose 50 m above the crater rim and drifted W. Another, recorded at 1105 by the seismic and infrasound networks, was also heard by authorities in the Parque Nacional Volcán Turrialba. No data were reported for the third explosion.

An OVSICORI-UNA report on 14 January 2022 indicated that atmospheric SO₂ levels measured by the TROPOMI Sentinel-5P satellite showed an almost daily detection from the volcanic plume. However, detected values were relatively low (less than 50 tons) except for a few days, particularly on 29 December 2021 (~126 tons) and 7 January 2022 (84 tons).

Incandescence from the West Crater was visible overnight during 15-16 January 2022. Four explosions were recorded on 17 January, including one at 2126 and another at 2131. The second explosion was the strongest since June 2021 and generated an ash-rich plume that rose about 1 km above the summit and was accompanied by a pyroclastic flow that extended more than 400 m. Ashfall and a sulfur odor were reported by residents in Coronado, Tres Rios (30 km SW), Alajuela (50 km W), and Santa Ana (46 km WSW). The ash contained less than 3% juvenile material, indicating that the explosion was phreatic. Another explosion at 1115 on 18 January generated a plume that rose 300 m and drifted SW.

During 19-24 January, periodic explosions lasting 1-2 minutes each were recorded at the West Crater. At 0546 on 19 January an explosion produced an ash plume that rose 200 m above the summit and drifted W. In addition, a small explosion at 1052 generated a plume that rose 50 m and drifted NW. At 0706 on 24 January, an explosion generated a plume that rose 100 m and drifted SW. Two points of incandescence on the internal SW crater wall were also visible. Three areas of incandescence in the West Crater were visible during 26-27 January. A weak explosion was recorded on 30 January.

According to OVSICORI-UNA, on 6 February at 1259, a weak phreatic explosion at West Crater produced an ash plume that rose 100 m above the crater rim. Two incandescent points in the crater were visible in overnight webcam images during 7-8 February. Another explosion at the West Crater on 19 February at 0412 produced a small ash plume that rose 100 m above the summit and drifted W. Minor ashfall was reported by park rangers in Parque Nacional Volcán Irazú. A weaker explosion was recorded later that day at 1624, though weather clouds prevented visual confirmation.

A point of incandescence on the SW wall of the West Crater was visible on 23 February, coincident with the area of strongest gas emissions. An explosion at 1955 on 27 February produced a diffuse ash plume that rose 300 m above the summit and drifted NE. Rumbling sounds heard on 28 February were sometimes coincident with minor ash emissions.

Geologic Background. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr).

Short but frequent effusive eruptions have characterized activity at Piton de la Fournaise, the large basaltic shield volcano on Réunion Island in the western Indian Ocean, for several thousand years. Multiple fissure openings, normally within the Enclos Fouqué caldera, have defined recent eruptions, with associated lava fountaining, lava flows, and the development of cones and lava tubes (BGVN 44:11, 46:01). The most recent previous eruption occurred during 9 April-24 May 2021 (BGVN 46:07). This report details a new eruption that began on 22 December 2021 and ended in mid-January 2022. Information is provided by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and satellite instruments.

The beginning of a new eruption was signaled by a seismic event at 0105 on 22 December, accompanied by rapid deformation beneath the S flank. Volcanic tremor beneath the S part of the caldera began at 0330, signifying the arrival of magma at the surface. OVPF noted that the eruption was preceded by about one month of shallow seismicity, while edifice inflation had been continuous since the end of the previous eruption on 24 May 2021.

Webcam images showed that at least three fissures, then four, opened on the S flank, SE of Piton Kala Pélé and SW of Château Fort (see figure 110 in BGVN 43:03), producing lava fountains and lava flows. The lowest point of the eruption occurred at an elevation of 2,000-2,100 m, more than 500 m below the summit. By the evening, the eruption was focused at 2,030 m elevation where a cone was forming around the vent. The lava effusion rate during 22-23 December, based on satellite data, was an estimated 4-7 m/s, with peak rates of 22 m/s. The cone was 10 m high by 0930 on 23 December, and low lava fountains intermittently rose above the crater rim. Lava flowed from an opening at the base of the cone, though a lava tube was beginning to form; lava had descended 2.2 km SSE from the main vent (figure 215).

Figure 215. Photo showing Piton de la Fournaise’s active cone and lava flow on 23 December 2021 around 0900 local time. By the end of the previous day, activity had concentrated at a single point on the most downstream fissure at about 2,100 m elevation. Courtesy of OVPF.

During 24-25 December lava traveled from the base of the cone hundreds of meters through a tube before it emerged and advanced in a single channel (figure 216); the lava front had advanced slowly, only traveling an additional 300 m by 25 December (figure 217). During 25-26 December the lava tube broke open and lava was again visible emerging from the base of the cone (figure 218). The flow rate was between 2 and 27 m/s, averaging 5 m/s. A second vent at the base of the cone was visible during the morning of 27 December and lava was again flowing through a tube and emerging downstream. Lava fountaining continued with material occasionally ejected less than 15 m above the cone during 27-28 December. The effusion rate was an estimated 2-8 m/s, based on satellite data. Low lava fountaining, with material rarely rising just above the crater rim, was visible on 29 December. A small mound with a vent that had grown at the base of the main cone was producing gas emissions, and lava advanced through a tube.

Figure 216. Photo of the eruption at Piton de la Fournaise on 24 December 2021 around 1600 local time showing fountaining at the active cone and lava tunnels that extended more than 100 m before the flow emerged as a single channel downstream. Courtesy of OVPF.

Figure 217. Composite map-view image showing the lava flow at Piton de la Fournaise extending SE from the vent around 0830 local time on 24 December 2021. Flow location determined from aerial image processing using stereophotogrammetry on a satellite image base from Google Earth. Courtesy of OVPF.

Figure 218. Photo of the active vent at Piton de la Fournaise on 26 December 2021 at 1050 local time, showing lava emerging from the base of the cone after the lava tunnel had broken. Courtesy of OVPF.

Lava fountaining was slightly more intense during 30 December 2021 to 3 January 2022, with lava more frequently rising above the crater rim. Several breakouts of lava from the tube were noted downstream from the vent. The lava effusion rate was an estimated 2.3-9 m/s, with peak rates of 21 m/s. Activity at the main cone decreased during 3-4 January. Lava flows within the first 100 m from the cone were an estimated 15 m thick. The flow field continued to widen but had not significantly lengthened. During 6 and 8-9 January, the level of the lava lake periodically rose and overflowed the cone, sending lava flows down the flanks (figure 219). The lava effusion rate was an estimated 2-20 m/s. Several breakouts of lava from the tube were noted.

Figure 219. Webcam image of the active vent at Piton de la Fournaise on 8 January 2022, at 1645 local time, showing an occasional overflow from the lava lake in the cone. Courtesy of OVPF.

On 9 January a new lava flow slowly advanced along the S margin of the flow field, reaching 1,800 m elevation. Hikers on 10 January observed smoke from an area in the S part of the caldera, likely from vegetation that had been set on fire from lava flows. The flow field continued to widen but had not significantly lengthened, and during 10-13 January the flow on the S margin of the field slowly advanced to the S wall of Enclos Fouqué (figure 220).

Figure 220. Webcam image of the active vent at Piton de la Fournaise on 13 January 2022, at 0550 local time, showing several lava streams from the cone advancing slowly downslope toward the S wall of the Enclos Fouqué caldera. Courtesy of OVPF.

Activity decreased during 14-15 January, but then increased again during 15-16 January, though no overflows of the lake were recorded and lava was only periodically ejected above the rim. Some small vegetation fires were visible near the base of the caldera wall. Tremor decreased and the eruption stopped at 0210 on 17 January. On 21 January, OVPF lowered the Alert Level to Vigilance.

Numerous hotspots were identified in the MODVOLC system from 22 December through 30 January 2022. There were hotspots during eight days in December (10 pixels on 22 December) and 12 days in January (16 pixels on 14 January). Thermal anomalies recorded by the MIROVA system were also numerous during the eruption, with the Log Radiative Power extending into the high and very high range (figure 221).

Figure 221. Graph of thermal anomalies at Piton de la Fournaise during June 2021-January 2022, as recorded by the MIROVA system, showing numerous high and very high Log Radiative Power hotspots during the 22 December 2021-17 January 2022 eruption. Courtesy of MIROVA.

On 1 January 2022 infrared Sentinel-2 satellite images showed an extensive hotspot, presumably a lava flow, along the lower SSW flank, which continued through the middle of January. By 21 January and through the end of the month, images showed only one or two small bright spots of thermal activity.

The Sentinel-5P/TROPOMI satellite recorded high sulfur dioxide levels from 22 December 2021 through 10 January 2022 and a final discharge on 16 January. The most prominent and extensive pulses were on 22 December and 16 January (figure 222).

Figure 222. Images of high-level sulfur dioxide plumes recorded by the Sentinel-5P/TROPOMI instrument on 22 December 2021 and 16 January 2022 during the eruption at Piton de la Fournaise that began on 22 December 2021. Both plumes are tracking to the SW. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); 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/); 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/); 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).

Taal, located in the Philippines, is part of a caldera system in southern Luzon Island. Recorded eruptions date back to 3,580 BCE. The caldera is 15 x 20 km and contains Lake Taal, which has a depth of 160 m, and an island that also contains a lake within the Main Crater. Eruptive activity during 1-9 July 2021 was characterized by phreatomagmatic explosions, gas-and-steam emissions, including sulfur dioxide emissions, and seismicity (BGVN 46:10). This report describes activity during October 2021-March 2022 using reports from the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and satellite data. Prior to a notable eruption on 26 March, PHIVOLCS described “phreatomagmatic bursts” on 15 and 22 November 2021, 29-30 January, 2 and 10 February, and 25 March 2022; similar events occurred during 27-28 March.

Activity was relatively low during October through mid-November. Frequent volcanic earthquakes and low-level background tremor had persisted since the activity in early July. Gas-and-steam plumes rose as high as 3 km from the Main Crater on 18 November and drifted in different directions. Each day, an average sulfur dioxide flux was recorded and vog was commonly observed around the vicinity. During October, the SO₂ emissions ranged from 4,620 to 25,456 t/d, the latter of which was recorded on 5 October. On 30 October as many as 103 volcanic earthquakes and 21 volcanic tremor events were detected. In November, daily sulfur dioxide emissions ranged from 1,727-19,463 t/d, the highest flux occurring on 6 November. On 11 November there were 223 volcanic tremor events that were detected, in addition to 180 volcanic tremor events.

A short phreatomagmatic burst was recorded at 2339 on 15 November, followed by two more on 17 November at 0146 and 0254. The first event produced a plume that rose 2.4 km altitude and drifted SW while the next two events generated plumes 400-500 m high, based on thermal camera images. Three more short phreatomagmatic bursts were detected at 0811, 0817, and 0834 on 22 November each lasted 1-5 minutes; these events produced plumes 200-1,500 m high that drifted SW, according to thermal camera images.

Low-level activity continued during December 2021 and most of January 2022. Frequent volcanic earthquakes and low-level background tremor persisted; as many as 139 volcanic earthquakes and 114 volcanic tremor events were detected on 16 December. Intermittent gas-and-steam emissions rose as high as 3 km above the Main Crater, drifting in various directions. The sulfur dioxide daily flux ranged from 2,684-13,634 t/d throughout December, the highest value recorded on 24 December. Vog was also visible in the surrounding area. During 26 December through 29 January, the seismic network detected no more than one volcanic earthquake, though low-level background tremor continued. During January the sulfur dioxide daily flux ranged from 4,829 to 18,705 t/d; the largest was recorded on 27 January.

A series of nine weak phreatomagmatic bursts detected in the Main Crater between 1550 on 29 January and 0449 on 30 January produced gas-and-steam emissions that rose 400-900 m high, according to visual and thermal cameras. These events lasted between 10 seconds and two minutes and were accompanied by distinct infrasound signals.

During February through March, intermittent gas-and-steam emissions rose as high as 2.5 km and drifted in various directions. Sulfur dioxide emissions ranged from 2,456-10,270 t/d during February, the highest of which occurred on 12 February. As many as 169 volcanic tremor events were detected on 2 February. A phreatomagmatic burst recorded at 1555 on 2 February lasted two minutes and generated a plume that rose 300 m high and drifted SW. Another short phreatomagmatic burst was recorded on 10 February at 1616, based on seismic records and visual cameras, which produced a plume 300 m high and drifted SW within the Main Crater. Sulfur dioxide fluxes were in the 1,140-21,211 t/d range during March, the highest occurring on 16 March. On 22 March as many as 47 volcanic earthquakes and 25 volcanic tremor events were recorded. A phreatomagmatic burst was reported at 0226 on 25 March, according to seismic records and visual cameras; a plume rose 500 m above the Main Crater.

A phreatomagmatic eruption during 0722-0859 on 26 March consisted of as many as 66 explosions, prompting PHIVOLCS to raise the Volcano Alert Level (VAL) from 2 to 3 (on a scale of 0-5) at 0800 (figure 26). Eruption plumes rose as high as 3 km and wet ash that smelled of sulfur fell along the Calauit and Alas-as shorelines, and on the lakeshore of Banyaga, Agoncillo, Batangas. According to the National Disaster Risk Reducation and Management Council (NDRRMC), by 27 March about 2,961 people had been evacuated from Bilibinwang and Banyaga, Agoncillo and Boso-boso, Gulod and eastern Bugaan East, Laurel, Batangas Province.

Figure 26. Webcam image of the phreatomagmatic eruption at Taal’s Main Crater on 26 March 2022, recorded by the Main Crater Observation Station (VTMC). Courtesy of PHIVOLCS.

Two subsequent phreatomagmatic events the following day, at 0434 and 0504 on 27 March, produced plumes that rose 400-800 m above Main Crater. On 28 March three phreatomagmatic bursts from the Main Crater were detected at 0930, 0933, and 0946, generating 400-800 m plumes that drifted SW. On 27 March PHIVOLCS raised the Volcano Alert Level (VAL) from 2 to 3 (on a scale of 0-5). The VAL was then lowered from 3 to 2 on 9 April due to the decrease in gas-and-steam emissions and seismicity.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data detected frequent low- to-moderate thermal anomalies during mid-October 2021 through March 2022 (figure 27). A brief pause in thermal activity was visible during early October, and short periods of fewer anomalies occurred during mid- and late December. Some of these anomalies were also detected by MODVOLC using infrared satellite data on 22, 25, 26, 29, and 31 October, 5, 7, 9, 10, 17, 18, 21, 23, and 25 November, 14, 18, 22, and 23 December 2021, 3, 6, 15, 22, 23, 24, 29, and 31 January 2022, 5, 9, 11, 14, 15, 16, and 20 February, and 1, 11, 19, 22, 24, and 26 March. Frequent sulfur dioxide plumes of varying strength were detected in the Sentinel-5P satellite throughout the reporting period (figure 28).

Figure 27. Frequent thermal anomalies were detected near the summit of Taal during mid-October 2021 through March 2022, as shown by the MIROVA graph (Log Radiative Power). There was a brief break in thermal activity during early October and less anomalies occurred during mid- and late- December. Courtesy of MIROVA.

Figure 28. Strong sulfur dioxide plumes were detected at Taal on 2 October 2021 (top left), 19 November 2021 (top right), 11 January 2022 (bottom left), and 16 March 2022 (bottom right). Plumes drifted in different directions and those shown here exceeded 2 Dobson Units (DUs). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); The National Disaster Risk Reduction and Management Council (NDRRMC), NDRRMC Building, Camp General Emilio Aguinaldo, Quezon City, Philippines (URL: https://ndrrmc.gov.ph/index.php); Philippine News Agency (PNA), Philippine Information Agency Building, Visayas Avenue, Barangay Vasra, Quezon City, Philippines (URL: https://www.pna.gov.ph/); 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, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

The remote island of Barren Island is located east of India in the Andaman Islands. Eruptions date back to 1787, with activity consisting of ash plumes, Strombolian explosions, and lava flows. The most recent eruption began in September 2018, with activity that included ash emissions and thermal anomalies (BGVN 46:12). This report covers similar activity during September 2021 through May 2022 using various satellite data as a primary source of information. Apparent eruptive activity continued until the end of January 2022, after which there was ongoing heat detected from the upper flanks of the central cone for a few months and a stronger thermal anomaly in the crater on 15 May.

The Suomi NPP/VIIRS sensor data showed 11 thermal anomalies over eight days on 14 and 19 October, 29-31 December 2021, and 1, 2, and 6 January 2022. Two MODVOLC thermal alerts were issued on 16 January 2022. Some of this thermal activity was visible in Sentinel-2 infrared satellite imagery on clear weather days on 6, 11, 21, and 31 December 2021, and 5, 25, and 30 January 2022 (figure 55).

Figure 55. Weak thermal anomalies were visible at the summit crater of Barren Island on 6 and 31 December 2021 (top left and right) and 25 and 30 January 2022 (bottom left and right). The anomalies were stronger on 31 December and 25 January. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

A continuous ash emission was reported during 1700-2200 on 8 January 2022 that rose to 1.2 km altitude and drifted WNW, according to visible and RGB satellite images from HIMAWARI-8. Ash plumes were also visible during 1200-1700 on 9 January, rising to 1.2 km altitude and drifting W to SW, based on data from the HIMAWARI-8 satellite, according to the Darwin VAAC.

The MIROVA thermal anomaly data from September 2021 through May 2022 showed intermittent low- to moderate-levels of thermal activity, with the greatest number of anomalies (12) occurring in March 2022 (figure 56). By May, only two were detected. After January 2022 no thermal anomalies were detected in Sentinel-2 infrared images, Suomi NPP/VIIRS sensor data, or MODVOLC thermal data until 15 May, when a weak thermal hotspot was visible in infrared satellite data at the summit crater (figure 57).

Figure 56. The MIROVA thermal anomaly data (Log Radiative Power) from September 2021 through May 2022 showed intermittent low to moderate levels of thermal activity beginning in early October. The number of anomalies increased slightly during March through May 2022. Three low-power anomalies were recorded in October, two in November, four in December 2021, six in January 2022, five in February, twelve in March nine in April, and two in May. Courtesy of MIROVA.

Figure 57. A single weak thermal anomaly was detected at the summit of Barren Island on 15 May 2022 in Sentinel-2 satellite imagery, accompanied by weak gas-and-steam emissions moving NE. Image using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: 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/); 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); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).