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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.

Recently Published Bulletin Reports

Ibu (Indonesia) Daily ash explosions continue, along with thermal anomalies in the crater, October 2022-May 2023

Dukono (Indonesia) Continuing ash emissions, SO2 plumes, and thermal signals during October 2022-May 2023

Sabancaya (Peru) Explosions, gas-and-ash plumes, and thermal activity persist during November 2022-April 2023

Sheveluch (Russia) Significant explosions destroyed part of the lava-dome complex during April 2023

Bezymianny (Russia) Explosions, ash plumes, lava flows, and avalanches during November 2022-April 2023

Chikurachki (Russia) New explosive eruption during late January-early February 2023

Marapi (Indonesia) New explosive eruption with ash emissions during January-March 2023

Kikai (Japan) Intermittent white gas-and-steam plumes, discolored water, and seismicity during May 2021-April 2023

Lewotolok (Indonesia) Strombolian eruption continues through April 2023 with intermittent ash plumes

Barren Island (India) Thermal activity during December 2022-March 2023

Villarrica (Chile) Nighttime crater incandescence, ash emissions, and seismicity during October 2022-March 2023

Fuego (Guatemala) Daily explosions, gas-and-ash plumes, avalanches, and ashfall during December 2022-March 2023



Ibu (Indonesia) — June 2023 Citation iconCite this Report

Ibu

Indonesia

1.488°N, 127.63°E; summit elev. 1325 m

All times are local (unless otherwise noted)


Daily ash explosions continue, along with thermal anomalies in the crater, October 2022-May 2023

Persistent eruptive activity since April 2008 at Ibu, a stratovolcano on Indonesian’s Halmahera Island, has consisted of daily explosive ash emissions and plumes, along with observations of thermal anomalies (BGVN 47:04). The current eruption continued during October 2022-May 2023, described below, based on advisories issued by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), daily reports by MAGMA Indonesia (a PVMBG platform), and the Darwin Volcanic Ash Advisory Centre (VAAC), and various satellite data. The Alert Level during the reporting period remained at 2 (on a scale of 1-4), except raised briefly to 3 on 27 May, and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side of the volcano.

According to MAGMA Indonesia, during October 2022-May 2023, daily gray-and-white ash plumes of variable densities rose 200-1,000 m above the summit and drifted in multiple directions. On 30 October and 11 November, plumes rose a maximum of 2 km and 1.5 km above the summit, respectively (figures 42 and 43). According to the Darwin VAAC, discrete ash emissions on 13 November rose to 2.1 km altitude, or 800 m above the summit, and drifted W, and multiple ash emissions on 15 November rose 1.4 km above the summit and drifted NE. Occasional larger ash explosions through May 2023 prompted PVMBG to issue Volcano Observatory Notice for Aviation (VONA) alerts (table 6); the Aviation Color Code remained at Orange throughout this period.

Figure (see Caption) Figure 42. Larger explosion from Ibu’s summit crater on 30 October 2022 that generated a plume that rose 2 km above the summit. Photo has been color corrected. Courtesy of MAGMA Indonesia.
Figure (see Caption) Figure 43. Larger explosion from Ibu’s summit crater on 11 November 2022 that generated a plume that rose 1.5 km above the summit. Courtesy of MAGMA Indonesia.

Table 6. Volcano Observatory Notice for Aviation (VONA) ash plume alerts for Ibu issued by PVMBG during October 2022-May 2023. Maximum height above the summit was estimated by a ground observer. VONAs in January-May 2023 all described the ash plumes as dense.

Date Time (local) Max height above summit Direction
17 Oct 2022 0858 800 m SW
18 Oct 2022 1425 800 m S
19 Oct 2022 2017 600 m SW
21 Oct 2022 0916 800 m NW
16 Jan 2023 1959 600 m NE
22 Jan 2023 0942 1,000 m E
29 Jan 2023 2138 1,000 m E
10 May 2023 0940 800 m NW
10 May 2023 2035 600 m E
21 May 2023 2021 600 m W
21 May 2023 2140 1,000 m W
29 May 2023 1342 800 m N
31 May 2023 1011 1,000 m SW

Sentinel-2 L1C satellite images throughout the reporting period show two, sometimes three persistent thermal anomalies in the summit crater, with the most prominent hotspot from the top of a cone within the crater. Clear views were more common during March-April 2023, when a vent and lava flows on the NE flank of the intra-crater cone could be distinguished (figure 44). White-to-grayish emissions were also observed during brief periods when weather clouds allowed clear views.

Figure (see Caption) Figure 44. Sentinel-2 L2A satellite images of Ibu on 10 April 2023. The central cone within the summit crater (1.3 km diameter) and lava flows (gray) can be seen in the true color image (left, bands 4, 3, 2). Thermal anomalies from the small crater of the intra-crater cone, a NE-flank vent, and the end of the lava flow are apparent in the infrared image (right, bands 12, 11, 8A). Courtesy of Copernicus Browser.

The MIROVA space-based volcano hotspot detection system recorded almost daily thermal anomalies throughout the reporting period, though cloud cover often interfered with detections. Data from imaging spectroradiometers aboard NASA’s Aqua and Terra satellites and processed using the MODVOLC algorithm (MODIS-MODVOLC) recorded hotspots on one day during October 2022 and December 2022, two days in April 2023, three days in November 2022 and May 2023, and four days in March 2023.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

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 (Multiplatform Application for Geohazard Mitigation and Assessment in Indonesia), Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); 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/).


Dukono (Indonesia) — June 2023 Citation iconCite this Report

Dukono

Indonesia

1.6992°N, 127.8783°E; summit elev. 1273 m

All times are local (unless otherwise noted)


Continuing ash emissions, SO2 plumes, and thermal signals during October 2022-May 2023

Dukono, a remote volcano on Indonesia’s Halmahera Island, has been erupting continuously since 1933, with frequent ash explosions and sulfur dioxide plumes (BGVN 46:11, 47:10). This activity continued during October 2022 through May 2023, based on reports from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG; also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and satellite data. During this period, the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to remain outside of the 2-km exclusion zone. The highest reported plume of the period reached 9.4 km above the summit on 14 November 2022.

According to MAGMA Indonesia (a platform developed by PVMBG), white, gray, or dark plumes of variable densities were observed almost every day during the reporting period, except when fog obscured the volcano (figure 33). Plumes generally rose 25-450 m above the summit, but rose as high as 700-800 m on several days, somewhat lower than the maximum heights reached earlier in 2022 when plumes reached as high as 1 km. However, the Darwin VAAC reported that on 14 November 2022, a discrete ash plume rose 9.4 km above the summit (10.7 km altitude), accompanied by a strong hotspot and a sulfur dioxide signal observed in satellite imagery; a continuous ash plume that day and through the 15th rose to 2.1-2.4 km altitude and drifted NE.

Figure (see Caption) Figure 33. Webcam photo of a gas-and-steam plume rising from Dukono on the morning of 28 January 2023. Courtesy of MAGMA Indonesia.

Sentinel-2 images were obscured by weather clouds almost every viewing day during the reporting period. However, the few reasonably clear images showed a hotspot and white or gray emissions and plumes. Strong SO2 plumes from Dukono were present on many days during October 2022-May 2023, as detected using the TROPOMI instrument on the Sentinel-5P satellite (figure 34).

Figure (see Caption) Figure 34. A strong SO2 signal from Dukono on 23 April 2023 was the most extensive plume detected during the reporting period. Courtesy of the NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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 (Multiplatform Application for Geohazard Mitigation and Assessment in Indonesia), Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sabancaya (Peru) — May 2023 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Explosions, gas-and-ash plumes, and thermal activity persist during November 2022-April 2023

Sabancaya is located in Peru, NE of Ampato and SE of Hualca Hualca. Eruptions date back to 1750 and have been characterized by explosions, phreatic activity, ash plumes, and ashfall. The current eruption period began in November 2016 and has more recently consisted of daily explosions, gas-and-ash plumes, and thermal activity (BGVN 47:11). This report updates activity during November 2022 through April 2023 using information from Instituto Geophysico del Peru (IGP) that use weekly activity reports and various satellite data.

Intermittent low-to-moderate power thermal anomalies were reported by the MIROVA project during November 2022 through April 2023 (figure 119). There were few short gaps in thermal activity during mid-December 2022, late December-to-early January 2023, late January to mid-February, and late February. According to data recorded by the MODVOLC thermal algorithm, there were a total of eight thermal hotspots: three in November 2022, three in February 2023, one in March, and one in April. On clear weather days, some of this thermal anomaly was visible in infrared satellite imagery showing the active lava dome in the summit crater (figure 120). Almost daily moderate-to-strong sulfur dioxide plumes were recorded during the reporting period by the TROPOMI instrument on the Sentinel-5P satellite (figure 121). Many of these plumes exceeded 2 Dobson Units (DU) and drifted in multiple directions.

Figure (see Caption) Figure 119. Intermittent low-to-moderate thermal anomalies were detected during November 2022 through April 2023 at Sabancaya, as shown in this MIROVA graph (Log Radiative Power). There were brief gaps in thermal activity during mid-December 2022, late December-to-early January 2023, late January to mid-February, and late February. Courtesy of MIROVA.
Figure (see Caption) Figure 120. Infrared (bands 12, 11, 8A) satellite images showed a constant thermal anomaly in the summit crater of Sabancaya on 14 January 2023 (top left), 28 February 2023 (top right), 5 March 2023 (bottom left), and 19 April 2023 (bottom right), represented by the active lava dome. Sometimes gas-and-steam and ash emissions also accompanied this activity. Courtesy of Copernicus Browser.
Figure (see Caption) Figure 121. Moderate-to-strong sulfur dioxide plumes were detected almost every day, rising from Sabancaya by the TROPOMI instrument on the Sentinel-5P satellite throughout the reporting period; the DU (Dobson Unit) density values were often greater than 2. Plumes from 23 November 2022 (top left), 26 December 2022 (top middle), 10 January 2023 (top right), 15 February 2023 (bottom left), 13 March 2023 (bottom middle), and 21 April 2023 (bottom right) that drifted SW, SW, W, SE, W, and SW, respectively. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

IGP reported that moderate activity during November and December 2022 continued; during November, an average number of explosions were reported each week: 30, 33, 36, and 35, and during December, it was 32, 40, 47, 52, and 67. Gas-and-ash plumes in November rose 3-3.5 km above the summit and drifted E, NE, SE, S, N, W, and SW. During December the gas-and-ash plumes rose 2-4 km above the summit and drifted in different directions. There were 1,259 volcanic earthquakes recorded during November and 1,693 during December. Seismicity also included volcano-tectonic-type events that indicate rock fracturing events. Slight inflation was observed in the N part of the volcano near Hualca Hualca (4 km N). Thermal activity was frequently reported in the crater at the active lava dome (figure 120).

Explosive activity continued during January and February 2023. The average number of explosions were reported each week during January (51, 50, 60, and 59) and February (43, 54, 51, and 50). Gas-and-ash plumes rose 1.6-2.9 km above the summit and drifted NW, SW, and W during January and rose 1.4-2.8 above the summit and drifted W, SW, E, SE, N, S, NW, and NE during February. IGP also detected 1,881 volcanic earthquakes during January and 1,661 during February. VT-type earthquakes were also reported. Minor inflation persisted near Hualca Hualca. Satellite imagery showed continuous thermal activity in the crater at the lava dome (figure 120).

During March, the average number of explosions each week was 46, 48, 31, 35, and 22 and during April, it was 29, 41, 31, and 27. Accompanying gas-and-ash plumes rose 1.7-2.6 km above the summit crater and drifted W, SW, NW, S, and SE during March. According to a Buenos Aires Volcano Ash Advisory Center (VAAC) notice, on 22 March at 1800 through 23 March an ash plume rose to 7 km altitude and drifted NW. By 0430 an ash plume rose to 7.6 km altitude and drifted W. On 24 and 26 March continuous ash emissions rose to 7.3 km altitude and drifted SW and on 28 March ash emissions rose to 7.6 km altitude. During April, gas-and-ash plumes rose 1.6-2.5 km above the summit and drifted W, SW, S, NW, NE, and E. Frequent volcanic earthquakes were recorded, with 1,828 in March and 1,077 in April, in addition to VT-type events. Thermal activity continued to be reported in the summit crater at the lava dome (figure 120).

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: Instituto Geofisico del Peru (IGP), Centro Vulcanológico Nacional (CENVUL), 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Sheveluch (Russia) — May 2023 Citation iconCite this Report

Sheveluch

Russia

56.653°N, 161.36°E; summit elev. 3283 m

All times are local (unless otherwise noted)


Significant explosions destroyed part of the lava-dome complex during April 2023

Sheveluch (also spelled Shiveluch) in Kamchatka, has had at least 60 large eruptions during the last 10,000 years. The summit is truncated by a broad 9-km-wide caldera that is breached to the S, and many lava domes occur on the outer flanks. The lava dome complex was constructed within the large open caldera. Frequent collapses of the dome complex have produced debris avalanches; the resulting deposits cover much of the caldera floor. A major south-flank collapse during a 1964 Plinian explosion produced a scarp in which a “Young Sheveluch” dome began to form in 1980. Repeated episodes of dome formation and destruction since then have produced major and minor ash plumes, pyroclastic flows, block-and-ash flows, and “whaleback domes” of spine-like extrusions in 1993 and 2020 (BGVN 45:11). The current eruption period began in August 1999 and has more recently consisted of lava dome growth, explosions, ash plumes, and avalanches (BGVN 48:01). This report covers a significant explosive eruption during early-to-mid-April 2023 that generated a 20 km altitude ash plume, produced a strong sulfur dioxide plume, and destroyed part of the lava-dome complex; activity described during January through April 2023 use information primarily from the Kamchatka Volcanic Eruptions Response Team (KVERT) and various satellite data.

Satellite data. Activity during the majority of this reporting period was characterized by continued lava dome growth, strong fumarole activity, explosions, and hot avalanches. According to the MODVOLC Thermal Alerts System, 140 hotspots were detected through the reporting period, with 33 recorded in January 2023, 29 in February, 44 in March, and 34 in April. Frequent strong thermal activity was recorded during January 2023 through April, according to the MIROVA (Middle InfraRed Observation of Volcanic Activity) graph and resulted from the continuously growing lava dome (figure 94). A slightly stronger pulse in thermal activity was detected in early-to-mid-April, which represented the significant eruption that destroyed part of the lava-dome complex. Thermal anomalies were also visible in infrared satellite imagery at the summit crater (figure 95).

Figure (see Caption) Figure 94. Strong and frequent thermal activity was detected at Sheveluch during January through April 2023, according to this MIROVA graph (Log Radiative Power). These thermal anomalies represented the continuously growing lava dome and frequent hot avalanches that affected the flanks. During early-to-mid-April a slightly stronger pulse represented the notable explosive eruption. Courtesy of MIROVA.
Figure (see Caption) Figure 95. Infrared (bands B12, B11, B4) satellite imagery showed persistent thermal anomalies at the lava dome of Sheveluch on 14 January 2023 (top left), 26 February 2023 (top right), and 15 March 2023 (bottom left). The true color image on 12 April 2023 (bottom right) showed a strong ash plume that drifted SW; this activity was a result of the strong explosive eruption during 11-12 April 2023. Courtesy of Copernicus Browser.

During January 2023 KVERT reported continued growth of the lava dome, accompanied by strong fumarolic activity, incandescence from the lava dome, explosions, ash plumes, and avalanches. Satellite data showed a daily thermal anomaly over the volcano. Video data showed ash plumes associated with collapses at the dome that generated avalanches that in turn produced ash plumes rising to 3.5 km altitude and drifting 40 km W on 4 January and rising to 7-7.5 km altitude and drifting 15 km SW on 5 January. A gas-and-steam plume containing some ash that was associated with avalanches rose to 5-6 km altitude and extended 52-92 km W on 7 January. Explosions that same day produced ash plumes that rose to 7-7.5 km altitude and drifted 10 km W. According to a Volcano Observatory Notice for Aviation (VONA) issued at 1344 on 19 January, explosions produced an ash cloud that was 15 x 25 km in size and rose to 9.6-10 km altitude, drifting 21-25 km W; as a result, the Aviation Color Code (ACC) was raised to Red (the highest level on a four-color scale). Another VONA issued at 1635 reported that no more ash plumes were observed, and the ACC was lowered to Orange (the second highest level on a four-color scale). On 22 January an ash plume from collapses and avalanches rose to 5 km altitude and drifted 25 km NE and SW; ash plumes associated with collapses extended 70 km NE on 27 and 31 January.

Lava dome growth, fumarolic activity, dome incandescence, and occasional explosions and avalanches continued during February and March. A daily thermal anomaly was visible in satellite data. Explosions on 1 February generated ash plumes that rose to 6.3-6.5 km altitude and extended 15 km NE. Video data showed an ash cloud from avalanches rising to 5.5 km altitude and drifting 5 km SE on 2 February. Satellite data showed gas-and-steam plumes containing some ash rose to 5-5.5 km altitude and drifted 68-110 km ENE and NE on 6 February, to 4.5-5 km altitude and drifted 35 km WNW on 22 February, and to 3.7-4 km altitude and drifted 47 km NE on 28 February. Scientists from the Kamchatka Volcanological Station (KVS) went on a field excursion on 25 February to document the growing lava dome, and although it was cloudy most of the day, nighttime incandescence was visible. Satellite data showed an ash plume extending up to 118 km E during 4-5 March. Video data from 1150 showed an ash cloud from avalanches rose to 3.7-5.5 km altitude and drifted 5-10 km ENE and E on 5 March. On 11 March an ash plume drifted 62 km E. On 27 March ash plumes rose to 3.5 km altitude and drifted 100 km E. Avalanches and constant incandescence at the lava dome was focused on the E and NE slopes on 28 March. A gas-and-steam plume containing some ash rose to 3.5 km altitude and moved 40 km E on 29 March. Ash plumes on 30 March rose to 3.5-3.7 km altitude and drifted 70 km NE.

Similar activity continued during April, with lava dome growth, strong fumarolic activity, incandescence in the dome, occasional explosions, and avalanches. A thermal anomaly persisted throughout the month. During 1-4 April weak ash plumes rose to 2.5-3 km altitude and extended 13-65 km SE and E.

Activity during 11 April 2023. The Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS) reported a significant increase in seismicity around 0054 on 11 April, as reported by strong explosions detected on 11 April beginning at 0110 that sent ash plumes up to 7-10 km altitude and extended 100-435 km W, WNW, NNW, WSW, and SW. According to a Tokyo VAAC report the ash plume rose to 15.8 km altitude. By 0158 the plume extended over a 75 x 100 km area. According to an IVS FEB RAS report, the eruptive column was not vertical: the initial plume at 0120 on 11 April deviated to the NNE, at 0000 on 12 April, it drifted NW, and by 1900 it drifted SW. KVS reported that significant pulses of activity occurred at around 0200, 0320, and then a stronger phase around 0600. Levin Dmitry took a video from near Békés (3 km away) at around 0600 showing a rising plume; he also reported that a pyroclastic flow traveled across the road behind him as he left the area. According to IVS FEB RAS, the pyroclastic flow traveled several kilometers SSE, stopping a few hundred meters from a bridge on the road between Klyuchi and Petropavlovsk-Kamchatsky.

Ashfall was first observed in Klyuchi (45 km SW) at 0630, and a large, black ash plume blocked light by 0700. At 0729 KVERT issued a Volcano Observatory Notice for Aviation (VONA) raising the Aviation Color Code to Red (the highest level on a four-color scale). It also stated that a large ash plume had risen to 10 km altitude and drifted 100 km W. Near-constant lightning strikes were reported in the plume and sounds like thunderclaps were heard until about 1000. According to IVS FEB RAS the cloud was 200 km long and 76 km wide by 0830, and was spreading W at altitudes of 6-12 km. In the Klyuchi Village, the layer of both ash and snow reached 8.5 cm (figure 96); ashfall was also reported in Kozyrevsk (112 km SW) at 0930, Mayskoye, Anavgay, Atlasovo, Lazo, and Esso. Residents in Klyuchi reported continued darkness and ashfall at 1100. In some areas, ashfall was 6 cm deep and some residents reported dirty water coming from their plumbing. According to IVS FEB RAS, an ash cloud at 1150 rose to 5-20 km altitude and was 400 km long and 250 km wide, extending W. A VONA issued at 1155 reported that ash had risen to 10 km and drifted 340 km NNW and 240 km WSW. According to Simon Carn (Michigan Technological University), about 0.2 Tg of sulfur dioxide in the plume was measured in a satellite image from the TROPOMI instrument on the Sentinel-5P satellite acquired at 1343 that covered an area of about 189,000 km2 (figure 97). Satellite data at 1748 showed an ash plume that rose to 8 km altitude and drifted 430 km WSW and S, according to a VONA.

Figure (see Caption) Figure 96. Photo of ash deposited in Klyuchi village on 11 April 2023 by the eruption of Sheveluch. About 8.5 cm of ash was measured. Courtesy of Kam 24 News Agency.
Figure (see Caption) Figure 97. A strong sulfur dioxide plume from the 11 April 2023 eruption at Sheveluch was visible in satellite data from the TROPOMI instrument on the Sentinel-5P satellite. Courtesy of Simon Carn, MTU.

Activity during 12-15 April 2023. On 12 April at 0730 satellite images showed ash plumes rose to 7-8 km altitude and extended 600 km SW, 1,050 km ESE, and 1,300-3,000 km E. By 1710 that day, the explosions weakened. According to news sources, the ash-and-gas plumes drifted E toward the Aleutian Islands and reached the Gulf of Alaska by 13 April, causing flight disruptions. More than 100 flights involving Alaska airspace were cancelled due to the plume. Satellite data showed ash plumes rising to 4-5.5 km altitude and drifted 400-415 km SE and ESE on 13 April. KVS volcanologists observed the pyroclastic flow deposits and noted that steam rose from downed, smoldering trees. They also noted that the deposits were thin with very few large fragments, which differed from previous flows. The ash clouds traveled across the Pacific Ocean. Flight cancellations were also reported in NW Canada (British Columbia) during 13-14 April. During 14-15 April ash plumes rose to 6 km altitude and drifted 700 km NW.

Alaskan flight schedules were mostly back to normal by 15 April, with only minor delays and far less cancellations; a few cancellations continued to be reported in Canada. Clear weather on 15 April showed that most of the previous lava-dome complex was gone and a new crater roughly 1 km in diameter was observed (figure 98); gas-and-steam emissions were rising from this crater. Evidence suggested that there had been a directed blast to the SE, and pyroclastic flows traveled more than 20 km. An ash plume rose to 4.5-5.2 km altitude and drifted 93-870 km NW on 15 April.

Figure (see Caption) Figure 98. A comparison of the crater at Sheveluch showing the previous lava dome (top) taken on 29 November 2022 and a large crater in place of the dome (bottom) due to strong explosions during 10-13 April 2023, accompanied by gas-and-ash plumes. The bottom photo was taken on 15 April 2023. Photos has been color corrected. Both photos are courtesy of Yu. Demyanchuk, IVS FEB RAS, KVERT.

Activity during 16-30 April 2023. Resuspended ash was lifted by the wind from the slopes and rose to 4 km altitude and drifted 224 km NW on 17 April. KVERT reported a plume of resuspended ash from the activity during 10-13 April on 19 April that rose to 3.5-4 km altitude and drifted 146-204 km WNW. During 21-22 April a plume stretched over the Scandinavian Peninsula. A gas-and-steam plume containing some ash rose to 3-3.5 km altitude and drifted 60 km SE on 30 April. A possible new lava dome was visible on the W slope of the volcano on 29-30 April (figure 99); satellite data showed two thermal anomalies, a bright one over the existing lava dome and a weaker one over the possible new one.

Figure (see Caption) Figure 99. Photo showing new lava dome growth at Sheveluch after a previous explosion destroyed much of the complex, accompanied by a white gas-and-steam plume. Photo has been color corrected. Courtesy of Yu. Demyanchuk, IVS FEB RAS, KVERT.

References. Girina, O., Loupian, E., Horvath, A., Melnikov, D., Manevich, A., Nuzhdaev, A., Bril, A., Ozerov, A., Kramareva, L., Sorokin, A., 2023, Analysis of the development of the paroxysmal eruption of Sheveluch volcano on April 10–13, 2023, based on data from various satellite systems, ??????????? ???????? ??? ?? ???????, 20(2).

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka's largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

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/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Kamchatka Volcanological Station, Kamchatka Branch of Geophysical Survey, (KB GS RAS), Klyuchi, Kamchatka Krai, Russia (URL: http://volkstat.ru/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); Kam 24 News Agency, 683032, Kamchatka Territory, Petropavlovsk-Kamchatsky, Vysotnaya St., 2A (URL: https://kam24.ru/news/main/20230411/96657.html#.Cj5Jrky6.dpuf); Simon Carn, Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA (URL: http://www.volcarno.com/, Twitter: @simoncarn).


Bezymianny (Russia) — May 2023 Citation iconCite this Report

Bezymianny

Russia

55.972°N, 160.595°E; summit elev. 2882 m

All times are local (unless otherwise noted)


Explosions, ash plumes, lava flows, and avalanches during November 2022-April 2023

Bezymianny is located on the Kamchatka Peninsula of Russia as part of the Klyuchevskoy volcano group. Historic eruptions began in 1955 and have been characterized by dome growth, explosions, pyroclastic flows, ash plumes, and ashfall. During the 1955-56 eruption a large open crater 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. The current eruption period began in December 2016 and more recent activity has consisted of strong explosions, ash plumes, and thermal activity (BGVN 47:11). This report covers activity during November 2022 through April 2023, based on weekly and daily reports from the Kamchatka Volcano Eruptions Response Team (KVERT) and satellite data.

Activity during November and March 2023 was relatively low and mostly consisted of gas-and-steam emissions, occasional small collapses that generated avalanches along the lava dome slopes, and a persistent thermal anomaly over the volcano that was observed in satellite data on clear weather days. According to the Tokyo VAAC and KVERT, an explosion produced an ash plume that rose to 6 km altitude and drifted 25 km NE at 1825 on 29 March.

Gas-and-steam emissions, collapses generating avalanches, and thermal activity continued during April. According to two Volcano Observatory Notice for Aviation (VONA) issued on 2 and 6 April (local time) ash plumes rose to 3 km and 3.5-3.8 km altitude and drifted 35 km E and 140 km E, respectively. Satellite data from KVERT showed weak ash plumes extending up to 550 km E on 2 and 5-6 April.

A VONA issued at 0843 on 7 April described an ash plume that rose to 4.5-5 km altitude and drifted 250 km ESE. Later that day at 1326 satellite data showed an ash plume that rose to 5.5-6 km altitude and drifted 150 km ESE. A satellite image from 1600 showed an ash plume extending as far as 230 km ESE; KVERT noted that ash emissions were intensifying, likely due to avalanches from the growing lava dome. The Aviation Color Code (ACC) was raised to Red (the highest level on a four-color scale). At 1520 satellite data showed an ash plume rising to 5-5.5 km altitude and drifting 230 km ESE. That same day, Kamchatka Volcanological Station (KVS) volcanologists traveled to Ambon to collect ash; they reported that a notable eruption began at 1730, and within 20 minutes a large ash plume rose to 10 km altitude and drifted NW. KVERT reported that the strong explosive phase began at 1738. Video and satellite data taken at 1738 showed an ash plume that rose to 10-12 km altitude and drifted up to 2,800 km SE and E. Explosions were clearly audible 20 km away for 90 minutes, according to KVS. Significant amounts of ash fell at the Apakhonchich station, which turned the snow gray; ash continued to fall until the morning of 8 April. In a VONA issued at 0906 on 8 April, KVERT stated that the explosive eruption had ended; ash plumes had drifted 2,000 km E. The ACC was lowered to Orange (the third highest level on a four-color scale). The KVS team saw a lava flow on the active dome once the conditions were clear that same day (figure 53). On 20 April lava dome extrusion was reported; lava flows were noted on the flanks of the dome, and according to KVERT satellite data, a thermal anomaly was observed in the area. The ACC was lowered to Yellow (the second lowest on a four-color scale).

Figure (see Caption) Figure 53. Photo showing an active lava flow descending the SE flank of Bezymianny from the lava dome on 8 April 2023. Courtesy of Yu. Demyanchuk, IVS FEB RAS, KVERT.

Satellite data showed an increase in thermal activity beginning in early April 2023. A total of 31 thermal hotspots were detected by the MODVOLC thermal algorithm on 4, 5, 7, and 12 April 2023. The elevated thermal activity resulted from an increase in explosive activity and the start of an active lava flow. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system based on the analysis of MODIS data also showed a pulse in thermal activity during the same time (figure 54). Infrared satellite imagery captured a continuous thermal anomaly at the summit crater, often accompanied by white gas-and-steam emissions (figure 55). On 4 April 2023 an active lava flow was observed descending the SE flank.

Figure (see Caption) Figure 54. Intermittent and low-power thermal anomalies were detected at Bezymianny during December 2022 through mid-March 2023, according to this MIROVA graph (Log Radiative Power). In early April 2023, an increase in explosive activity and eruption of a lava flow resulted in a marked increase in thermal activity. Courtesy of MIROVA.
Figure (see Caption) Figure 55. Infrared satellite images of Bezymianny showed a persistent thermal anomaly over the lava dome on 18 November 2022 (top left), 28 December 2022 (top right), 15 March 2023 (bottom left), and 4 April 2023 (bottom right), often accompanied by white gas-and-steam plumes. On 4 April a lava flow was active and descending the SE flank. Images using infrared (bands 12, 11, 8a). Courtesy of Copernicus Browser.

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 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/); Kamchatka Volcanological Station, Kamchatka Branch of Geophysical Survey, (KB GS RAS), Klyuchi, Kamchatka Krai, Russia (URL: http://volkstat.ru/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Chikurachki (Russia) — May 2023 Citation iconCite this Report

Chikurachki

Russia

50.324°N, 155.461°E; summit elev. 1781 m

All times are local (unless otherwise noted)


New explosive eruption during late January-early February 2023

Chikurachki, located on Paramushir Island in the northern Kuriles, has had Plinian eruptions 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. Reported eruptions date back to 1690, with the most recent eruption period occurring during January through October 2022, characterized by occasional explosions, ash plumes, and thermal activity (BGVN 47:11). This report covers a new eruptive period during January through February 2023 that consisted of ash explosions and ash plumes, based on information from the Kamchatka Volcanic Eruptions Response Team (KVERT) and satellite data.

According to reports from KVERT, an explosive eruption began around 0630 on 29 January. Explosions generated ash plumes that rose to 3-3.5 km altitude and drifted 6-75 km SE and E, based on satellite data. As a result, the Aviation Color Code (ACC) was raised to Orange (the second highest level on a four-color scale). At 1406 and 1720 ash plumes were identified in satellite images that rose to 4.3 km altitude and extended 70 km E. By 2320 the ash plume had dissipated. A thermal anomaly was visible at the volcano on 31 January, according to a satellite image, and an ash plume was observed drifting 66 km NE.

Occasional explosions and ash plumes continued during early February. At 0850 on 1 February an ash plume rose to 3.5 km altitude and drifted 35 km NE. Satellite data showed an ash plume that rose to 3.2-3.5 km altitude and drifted 50 km NE at 1222 later that day (figure 22). A thermal anomaly was detected over the volcano during 5-6 February and ash plumes drifted as far as 125 km SE, E, and NE. Explosive events were reported at 0330 on 6 February that produced ash plumes rising to 4-4.5 km altitude and drifting 72-90 km N, NE, and ENE. KVERT noted that the last gas-and steam plume that contained some ash was observed on 8 February and drifted 55 km NE before the explosive eruption ended. The ACC was lowered to Yellow and then Green (the lowest level on a four-color scale) on 18 February.

Figure (see Caption) Figure 22. Satellite image showing a true color view of a strong ash plume rising above Chikurachki on 1 February 2023. The plume drifted NE and ash deposits (dark brown-to-gray) are visible on the NE flank due to explosive activity. Courtesy of Copernicus Browser.

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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Marapi (Indonesia) — May 2023 Citation iconCite this Report

Marapi

Indonesia

0.38°S, 100.474°E; summit elev. 2885 m

All times are local (unless otherwise noted)


New explosive eruption with ash emissions during January-March 2023

Marapi in Sumatra, Indonesia, is a massive stratovolcano that rises 2 km above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera and trending ENE-WSW, with volcanism migrating to the west. Since the end of the 18th century, more than 50 eruptions, typically characterized by small-to-moderate explosive activity, have been recorded. The previous eruption consisted of two explosions during April-May 2018, which caused ashfall to the SE (BGVN 43:06). This report covers a new eruption during January-March 2023, which included explosive events and ash emissions, as reported by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) and MAGMA Indonesia.

According to a press release issued by PVMBG and MAGMA Indonesia on 26 December, primary volcanic activity at Marapi consisted of white gas-and-steam puffs that rose 500-100 m above the summit during April-December 2022. On 25 December 2022 there was an increase in the number of deep volcanic earthquakes and summit inflation. White gas-and-steam emissions rose 80-158 m above the summit on 5 January. An explosive eruption began at 0611 on 7 January 2023, which generated white gas-and-steam emissions and gray ash emissions mixed with ejecta that rose 300 m above the summit and drifted SE (figure 10). According to ground observations, white-to-gray ash clouds during 0944-1034 rose 200-250 m above the summit and drifted SE and around 1451 emissions rose 200 m above the summit. Seismic signals indicated that eruptive events also occurred at 1135, 1144, 1230, 1715, and 1821, but no ash emissions were visually observed. On 8 January white-and-gray emissions rose 150-250 m above the summit that drifted E and SE. Seismic signals indicated eruptive events at 0447, 1038, and 1145, but again no ash emissions were visually observed on 8 January. White-to-gray ash plumes continued to be observed on clear weather days during 9-15, 18-21, 25, and 29-30 January, rising 100-1,000 m above the summit and drifted generally NE, SE, N, and E, based on ground observations (figure 11).

Figure (see Caption) Figure 10. Webcam image of the start of the explosive eruption at Marapi at 0651 on 7 January 2023. White gas-and-steam emissions are visible to the left and gray ash emissions are visible on the right, drifting SE. Distinct ejecta was also visible mixed within the ash cloud. Courtesy of PVMBG and MAGMA Indonesia.
Figure (see Caption) Figure 11. Webcam image showing thick, gray ash emissions rising 500 m above the summit of Marapi and drifting N and NE at 0953 on 11 January 2023. Courtesy of PVMBG and MAGMA Indonesia.

White-and-gray and brown emissions persisted in February, rising 50-500 m above the summit and drifting E, S, SW, N, NE, and W, though weather sometimes prevented clear views of the summit. An eruption at 1827 on 10 February produced a black ash plume that rose 400 m above the summit and drifted NE and E (figure 12). Similar activity was reported on clear weather days, with white gas-and-steam emissions rising 50 m above the summit on 9, 11-12, 20, and 27 March and drifted E, SE, SW, NE, E, and N. On 17 March white-and-gray emissions rose 400 m above the summit and drifted N and E.

Figure (see Caption) Figure 12. Webcam image showing an eruptive event at 1829 on 10 February 2023 with an ash plume rising 400 m above the summit and drifting NE and E. Courtesy of PVMBG and MAGMA Indonesia.

Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

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).


Kikai (Japan) — May 2023 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Intermittent white gas-and-steam plumes, discolored water, and seismicity during May 2021-April 2023

Kikai, located just S of the Ryukyu islands of Japan, contains a 19-km-wide mostly submarine caldera. The island of Satsuma Iwo Jima (also known as Satsuma-Iwo Jima and Tokara Iojima) is located at the NW caldera rim, as well as the island’s highest peak, Iodake. Its previous eruption period occurred on 6 October 2020 and was characterized by an explosion and thermal anomalies in the crater (BGVN 45:11). More recent activity has consisted of intermittent thermal activity and gas-and-steam plumes (BGVN 46:06). This report covers similar low-level activity including white gas-and-steam plumes, nighttime incandescence, seismicity, and discolored water during May 2021 through April 2023, using information from the Japan Meteorological Agency (JMA) and various satellite data. During this time, the Alert Level remained at a 2 (on a 5-level scale), according to JMA.

Activity was relatively low throughout the reporting period and has consisted of intermittent white gas-and-steam emissions that rose 200-1,400 m above the Iodake crater and nighttime incandescence was observed at the Iodake crater using a high-sensitivity surveillance camera. Each month, frequent volcanic earthquakes were detected, and sulfur dioxide masses were measured by the University of Tokyo Graduate School of Science, Kyoto University Disaster Prevention Research Institute, Mishima Village, and JMA (table 6).

Table 6. Summary of gas-and-steam plume heights, number of volcanic earthquakes detected, and amount of sulfur dioxide emissions in tons per day (t/d). Courtesy of JMA monthly reports.

Month Max plume height (m) Volcanic earthquakes Sulfur dioxide emissions (t/d)
May 2021 400 162 900-1,300
Jun 2021 800 117 500
Jul 2021 1,400 324 800-1,500
Aug 2021 1,000 235 700-1,000
Sep 2021 800 194 500-1,100
Oct 2021 800 223 600-800
Nov 2021 900 200 400-900
Dec 2021 1,000 161 500-1,800
Jan 2022 1,000 164 600-1,100
Feb 2022 1,000 146 500-1,600
Mar 2022 1,200 171 500-1,200
Apr 2022 1,000 144 600-1,000
May 2022 1,200 126 300-500
Jun 2022 1,000 154 400
Jul 2022 1,300 153 600-1,100
Aug 2022 1,100 109 600-1,500
Sep 2022 1,000 170 900
Oct 2022 800 249 700-1,200
Nov 2022 800 198 800-1,200
Dec 2022 700 116 600-1,500
Jan 2023 800 146 500-1,400
Feb 2023 800 135 600-800
Mar 2023 1,100 94 500-600
Apr 2023 800 82 500-700

Sentinel-2 satellite images show weak thermal anomalies at the Iodake crater on clear weather days, accompanied by white gas-and-steam emissions and occasional discolored water (figure 24). On 17 January 2022 JMA conducted an aerial overflight in cooperation with the Japan Maritime Self-Defense Force’s 1st Air Group, which confirmed a white gas-and-steam plume rising from the Iodake crater (figure 25). They also observed plumes from fumaroles rising from around the crater and on the E, SW, and N slopes. In addition, discolored water was reported near the coast around Iodake, which JMA stated was likely related to volcanic activity (figure 25). Similarly, an overflight taken on 11 January 2023 showed white gas-and-steam emissions rising from the Iodake crater, as well as discolored water that spread E from the coast around the island. On 14 February 2023 white fumaroles and discolored water were also captured during an overflight (figure 26).

Figure (see Caption) Figure 24. Sentinel-2 satellite images of Satsuma Iwo Jima (Kikai) showing sets of visual (true color) and infrared (bands 12, 11, 8a) views on 7 December 2021 (top), 23 October 2022 (middle), and 11 January 2023 (bottom). Courtesy of Copernicus Browser.
Figure (see Caption) Figure 25. Aerial image of Satsuma Iwo Jima (Kikai) showing a white gas-and-steam plume rising above the Iodake crater at 1119 on 17 January 2022. There was also green-yellow discolored water surrounding the coast of Mt. Iodake. Courtesy of JMSDF via JMA.
Figure (see Caption) Figure 26. Aerial image of Satsuma Iwo Jima (Kikai) showing white gas-and-steam plumes rising above the Iodake crater on 14 February 2023. Green-yellow discolored water surrounded Mt. Iodake. Courtesy of JCG.

Geologic Background. Multiple eruption centers have exhibited recent activity at Kikai, a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake (or Iwo-dake) lava dome and Inamuradake scoria cone, as well as submarine lava domes. Recorded eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Satsuma-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Satsuma-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: https://www1.kaiho.mlit.go.jp/kaiikiDB/kaiyo30-2.htm); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Lewotolok (Indonesia) — May 2023 Citation iconCite this Report

Lewotolok

Indonesia

8.274°S, 123.508°E; summit elev. 1431 m

All times are local (unless otherwise noted)


Strombolian eruption continues through April 2023 with intermittent ash plumes

The current eruption at Lewotolok, in Indonesian’s Lesser Sunda Islands, began in late November 2020 and has included Strombolian explosions, occasional ash plumes, incandescent ejecta, intermittent thermal anomalies, and persistent white and white-and-gray emissions (BGVN 47:10). Similar activity continued during October 2022-April 2023, as described in this report based on information provided by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), MAGMA Indonesia, the Darwin Volcanic Ash Advisory Centre (VAAC), and satellite data.

During most days in October 2022 white and white-gray emissions rose as high as 200-600 m above the summit. Webcam images often showed incandescence above the crater rim. At 0351 on 14 October, an explosion produced a dense ash plume that rose about 1.2 km above the summit and drifted SW (figure 43). After this event, activity subsided and remained low through the rest of the year, but with almost daily white emissions.

Figure (see Caption) Figure 43. Webcam image of Lewotolok on 14 October 2022 showing a dense ash plume and incandescence above the crater. Courtesy of MAGMA Indonesia.

After more than two months of relative quiet, PVMBG reported that explosions at 0747 on 14 January 2023 and at 2055 on 16 January produced white-and-gray ash plumes that rose around 400 m above the summit and drifted E and SE (figure 44). During the latter half of January through April, almost daily white or white-and-gray emissions were observed rising 25-800 m above the summit, and nighttime webcam images often showed incandescent material being ejected above the summit crater. Strombolian activity was visible in webcam images at 2140 on 11 February, 0210 on 18 February, and during 22-28 March. Frequent hotspots were recorded by the MIROVA detection system starting in approximately the second week of March 2023 that progressively increased into April (figure 45).

Figure (see Caption) Figure 44. Webcam image of an explosion at Lewotolok on 14 January 2023 ejecting a small ash plume along with white emissions. Courtesy of MAGMA Indonesia.
Figure (see Caption) Figure 45. MIROVA Log Radiative Power graph of thermal anomalies detected by the VIIRS satellite instrument at Lewotolok’s summit crater for the year beginning 24 July 2022. Clusters of mostly low-power hotspots occurred during August-October 2022, followed by a gap of more than four months before persistent and progressively stronger anomalies began in early March 2023. Courtesy of MIROVA.

Explosions that produced dense ash plumes as high as 750 m above the summit were described in Volcano Observatory Notices for Aviation (VONA) at 0517, 1623, and 2016 on 22 March, at 1744 on 24 March, at 0103 on 26 March, at 0845 and 1604 on 27 March (figure 46), and at 0538 on 28 March. According to the Darwin VAAC, on 6 April another ash plume rose to 1.8 km altitude (about 370 m above the summit) and drifted N.

Figure (see Caption) Figure 46. Webcam image of Lewotolok at 0847 on 27 March 2023 showing a dense ash plume from an explosion along with clouds and white emissions. Courtesy of MAGMA-Indonesia.

Sentinel-2 images over the previous year recorded thermal anomalies as well as the development of a lava flow that descended the NE flank beginning in June 2022 (figure 47). The volcano was often obscured by weather clouds, which also often hampered ground observations. Ash emissions were reported in March 2022 (BGVN 47:10), and clear imagery from 4 March 2022 showed recent lava flows confined to the crater, two thermal anomaly spots in the eastern part of the crater, and mainly white emissions from the SE. Thermal anomalies became stronger and more frequent in mid-May 2022, followed by strong Strombolian activity through June and July (BGVN 47:10); Sentinel-2 images on 2 June 2022 showed active lava flows within the crater and overflowing onto the NE flank. Clear images from 23 April 2023 (figure 47) show the extent of the cooled NE-flank lava flow, more extensive intra-crater flows, and two hotspots in slightly different locations compared to the previous March.

Figure (see Caption) Figure 47. Sentinel-2 satellite images of Lewotolok showing sets of visual (true color) and infrared (bands 12, 11, 8a) views on 4 March 2022, 2 June 2022, and 23 April 2023. Courtesy of Copernicus Browser.

Geologic Background. The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Barren Island (India) — April 2023 Citation iconCite this Report

Barren Island

India

12.278°N, 93.858°E; summit elev. 354 m

All times are local (unless otherwise noted)


Thermal activity during December 2022-March 2023

Barren Island is part of a N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). 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. Eruptions dating back to 1787, 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. Previous activity was detected during mid-May 2022, consisting of intermittent thermal activity. This report covers June 2022 through March 2023, which included strong thermal activity beginning in late December 2022, based on various satellite data.

Activity was relatively quiet during June through late December 2022 and mostly consisted of low-power thermal anomalies, based on the MIROVA (Middle InfraRed Observation of Volcanic Activity) graph. During late December, a spike in both power and frequency of thermal anomalies was detected (figure 58). There was another pulse in thermal activity in mid-March, which consisted of more frequent and relatively strong anomalies.

Figure (see Caption) Figure 58. Occasional thermal anomalies were detected during June through late December 2022 at Barren Island, but by late December through early January 2023, there was a marked increase in thermal activity, both in power and frequency, according to this MIROVA graph (Log Radiative Power). After this spike in activity, anomalies occurred at a more frequent rate. In late March, another pulse in activity was detected, although the power was not as strong as that initial spike during December-January. Courtesy of MIROVA.

The Suomi NPP/VIIRS sensor data showed five thermal alerts on 29 December 2022. The number of alerts increased to 19 on 30 December. According to the Darwin VAAC, ash plumes identified in satellite images captured at 2340 on 30 December and at 0050 on 31 December rose to 1.5 km altitude and drifted SW. The ash emissions dissipated by 0940. On 31 December, a large thermal anomaly was detected; based on a Sentinel-2 infrared satellite image, the anomaly was relatively strong and extended to the N (figure 59).

Figure (see Caption) Figure 59. Thermal anomalies of varying intensities were visible in the crater of Barren Island on 31 December 2022 (top left), 15 January 2023 (top right), 24 February 2023 (bottom left), and 31 March 2023 (bottom right), as seen in these Sentinel-2 infrared satellite images. The anomalies on 31 December and 31 March were notably strong and extended to the N and N-S, respectively. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Thermal activity continued during January through March. Sentinel-2 infrared satellite data showed some thermal anomalies of varying intensity on clear weather days on 5, 10, 15, 20, and 30 January 2023, 9, 14, 19, and 24 February 2023, and 21, 26, and 31 March (figure 59). According to Suomi NPP/VIIRS sensor data, a total of 30 thermal anomalies were detected over 18 days on 2-3, 7, 9-14, 16-17, 20, 23, 25, and 28-31 January. The sensor data showed a total of six hotspots detected over six days on 1, 4-5, and 10-12 February. During March, a total of 33 hotspots were visible over 11 days on 20-31 March. Four MODVOLC thermal alerts were issued on 25, 27, and 29 March.

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/).


Villarrica (Chile) — April 2023 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Nighttime crater incandescence, ash emissions, and seismicity during October 2022-March 2023

Villarrica, located in central Chile, consists of a 2-km-wide caldera that formed about 3,500 years ago, located at the base of the presently active cone. Historical eruptions date back to 1558 and have been characterized by mild-to-moderate explosive activity with occasional lava effusions. The current eruption period began in December 2014 and has recently consisted of ongoing seismicity, gas-and-steam emissions, and thermal activity (BGVN 47:10). This report covers activity during October 2022 through March 2023 and describes Strombolian explosions, ash emissions, and crater incandescence. Information for this report primarily comes from the Southern Andes Volcano Observatory (Observatorio Volcanológico de Los Andes del Sur, OVDAS), part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN) and satellite data.

Seismicity during October consisted of discrete long-period (LP)-type events, tremor (TR), and volcano-tectonic (VT)-type events. Webcam images showed eruption plumes rising as high as 460 m above the crater rim; plumes deposited tephra on the E, S, and SW flanks within 500 m of the crater on 2, 18, 23, and 31 October. White gas-and-steam emissions rose 80-300 m above the crater accompanied by crater incandescence during 2-3 October. There was a total of 5 VT-type events, 10,625 LP-type events, and 2,232 TR-type events detected throughout the month. Sulfur dioxide data was obtained by the Differential Absorption Optical Spectroscopy Equipment (DOAS) installed 6 km in an ESE direction. The average value of the sulfur dioxide emissions was 535 ± 115 tons per day (t/d); the highest daily maximum was 1,273 t/d on 13 October. These values were within normal levels and were lower compared to September. During the night of 3-4 October Strombolian activity ejected blocks as far as 40 m toward the NW flank. Small, gray-brown ash pulses rose 60 m above the crater accompanied white gas-and-steam emissions that rose 40-300 m high during 4-5 October. In addition, crater incandescence and Strombolian explosions that ejected blocks were reported during 4-5 and 9-11 October. Based on satellite images from 12 October, ballistic ejecta traveled as far as 400 m and the resulting ash was deposited 3.2 km to the E and SE and 900 m to the NW.

Satellite images from 14 October showed an active lava lake that covered an area of 36 square meters in the E part of the crater floor. There was also evidence of a partial collapse (less than 300 square meters) at the inner SSW crater rim. POVI posted an 18 October photo that showed incandescence above the crater rim, noting that crater incandescence was visible during clear weather nights. In addition, webcam images at 1917 showed lava fountaining and Strombolian explosions; tourists also described seeing splashes of lava ejected from a depth of 80 m and hearing loud degassing sounds. Tephra deposits were visible around the crater rim and on the upper flanks on 24 October. On 25 October SERNAGEOMIN reported that both the number and amplitude of LP earthquakes had increased, and continuous tremor also increased; intense crater incandescence was visible in satellite images. On 31 October Strombolian explosions intensified and ejected material onto the upper flanks.

Activity during November consisted of above-baseline seismicity, including intensifying continuous tremor and an increase in the number of LP earthquakes. On 1 November a lava fountain was visible rising above the crater rim. Nighttime crater incandescence was captured in webcam images on clear weather days. Strombolian explosions ejected incandescent material on the NW and SW flanks during 1, 2, and 6-7 November. POVI reported that the width of the lava fountains that rose above the crater rim on 2 November suggested that the vent on the crater floor was roughly 6 m in diameter. Based on reports from observers and analyses of satellite imagery, material that was deposited on the upper flanks, primarily to the NW, consisted of clasts up to 20 cm in diameter. During an overflight on 19 November SERNAGEOMIN scientists observed a cone on the crater floor with an incandescent vent at its center that contained a lava lake. Deposits of ejecta were also visible on the flanks. That same day a 75-minute-long series of volcano-tectonic earthquakes was detected at 1940; a total of 21 events occurred 7.8 km ESE of the crater. Another overflight on 25 November showed the small cone on the crater floor with an incandescent lava lake at the center; the temperature of the lava lake was 1,043 °C, based data gathered during the overflight.

Similar seismicity, crater incandescence, and gas-and-steam emissions continued during December. On 1 December incandescent material was ejected 80-220 m above the crater rim. During an overflight on 6 December, intense gas-and-steam emissions from the lava lake was reported, in addition to tephra deposits on the S and SE flanks as far as 500 m from the crater. During 7-12 December seismicity increased slightly and white, low-altitude gas-and-steam emissions and crater incandescence were occasionally visible. On 24 December at 0845 SERNAGEOMIN reported an increase in Strombolian activity; explosions ejected material that generally rose 100 m above the crater, although one explosion ejected incandescent tephra as far as 400 m from the crater onto the SW flank. According to POVI, 11 explosions ejected incandescent material that affected the upper SW flank between 2225 on 25 December to 0519 on 26 December. POVI recorded 21 Strombolian explosions that ejected incandescent material onto the upper SW flank from 2200 on 28 December to 0540 on 29 December. More than 100 Strombolian explosions ejected material onto the upper W and NW flanks during 30-31 December. On 30 December at 2250 an explosion was detected that generated an eruptive column rising 120 m above the crater and ejecting incandescent material 300 m on the NW flank (figure 120). Explosions detected at 2356 on 31 December ejected material 480 m from the crater rim onto the NW flank and at 0219 material was deposited on the same flank as far as 150 m. Both explosions ejected material as high as 120 m above the crater rim.

Figure (see Caption) Figure 120. Webcam image of a Strombolian explosion at Villarrica on 30 December 2022 (local time) that ejected incandescent material 300 m onto the NW flank, accompanied by emissions and crater incandescence. Courtesy of SERNAGEOMIN (Reporte Especial de Actividad Volcanica (REAV), Region De La Araucania y Los Rios, Volcan Villarrica, 30 de diciembre de 2022, 23:55 Hora local).

During January 2023, Strombolian explosions and lava fountaining continued mainly in the crater, ejecting material 100 m above the crater. Gas-and-steam emissions rose 40-260 m above the crater and drifted in different directions, and LP-type events continued. Emissions during the night of 11 January including some ash rose 80 m above the crater and as far as 250 m NE flank. POVI scientists reported about 70 lava fountaining events from 2130 on 14 January to 0600 on 15 January. At 2211 on 15 January there was an increase in frequency of Strombolian explosions that ejected incandescent material 60-150 m above the crater. Some ashfall was detected around the crater. POVI noted that on 19 January lava was ejected as high as 140 m above the crater rim and onto the W and SW flanks. Explosion noises were heard on 19 and 22 January in areas within a radius of 10 km. During 22-23 January Strombolian explosions ejected incandescent material 60-100 m above the crater that drifted SE. A seismic event at 1204 on 27 January was accompanied by an ash plume that rose 220 m above the crater and drifted E (figure 121); later that same day at 2102 an ash plume rose 180 m above the crater and drifted E.

Figure (see Caption) Figure 121. Webcam image of an ash plume at Villarrica on 27 January rising 220 m above the crater and drifting E. Courtesy of SERNAGEOMIN (Reporte Especial de Actividad Volcanica (REAV), Region De La Araucania y Los Rios, Volcan Villarrica, 27 de enero de 2023, 12:35 Hora local).

Seismicity, primarily characterized by LP-type events, and Strombolian explosions persisted during February and March. POVI reported that three explosions were heard during 1940-1942 on 6 February, and spatter was seen rising 30 m above the crater rim hours later. On 9 February lava fountains were visible rising 50 m above the crater rim. On 17 February Strombolian explosions ejected material 100 m above the crater rim and onto the upper SW flank. Webcam images from 20 February showed two separate fountains of incandescent material, which suggested that a second vent had opened to the E of the first vent. Spatter was ejected as high as 80 m above the crater rim and onto the upper NE flank. A sequence of Strombolian explosions was visible from 2030 on 20 February to 0630 on 21 February. Material was ejected as high as 80 m above the crater rim and onto the upper E flank. LP-type earthquakes recorded 1056 and at 1301 on 27 February were associated with ash plumes that rose 300 m above the crater and drifted NE (figure 122). Crater incandescence above the crater rim was observed in webcam images on 13 March, which indicated Strombolian activity. POVI posted a webcam image from 2227 on 18 March showing Strombolian explosions that ejected material as high as 100 m above the crater rim. Explosions were heard up to 8 km away. On 19 March at 1921 an ash emission rose 340 m above the crater and drifted NE. On 21 and 26 March Strombolian explosions ejected material 100 and 110 m above the crater rim, respectively. On 21 March Strombolian explosions ejected material 100 m above the crater rim. Low-intensity nighttime crater incandescence was detected by surveillance cameras on 24 March.

Figure (see Caption) Figure 122. Photo of an ash plume rising 300 m above the crater of Villarrica and drifting NE on 27 February 2023. Courtesy of SERNAGEOMIN (Reporte Especial de Actividad Volcanica (REAV), Region De La Araucania y Los Rios, Volcan Villarrica, 27 de febrero de 2023, 11:10 Hora local).

Infrared MODIS satellite data processed by MIROVA (Middle InfraRed Observation of Volcanic Activity) detected an increase in thermal activity during mid-November, which corresponds to sustained Strombolian explosions, lava fountaining, and crater incandescence (figure 123). This activity was also consistently captured on clear weather days throughout the reporting period in Sentinel-2 infrared satellite images (figure 124).

Figure (see Caption) Figure 123. Low-power thermal anomalies were detected during August through October 2022 at Villarrica, based on this MIROVA graph (Log Radiative Power). During mid-November, the power and frequency of the anomalies increased and remained at a consistent level through March 2023. Thermal activity consisted of Strombolian explosions, lava fountains, and crater incandescence. Courtesy of MIROVA.
Figure (see Caption) Figure 124. Consistent bright thermal anomalies were visible at the summit crater of Villarrica in Sentinel-2 infrared satellite images throughout the reporting period, as shown here on 19 December 2022 (left) and 9 February 2023 (right). Occasional gas-and-steam emissions also accompanied the thermal activity. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. The glacier-covered Villarrica stratovolcano, in the northern Lakes District of central Chile, is ~15 km south of the city of Pucon. A 2-km-wide caldera that formed about 3,500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesite cone at the NW margin of a 6-km-wide Pleistocene caldera. More than 30 scoria cones and fissure vents are present on the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Eruptions documented since 1558 CE have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

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/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); 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).


Fuego (Guatemala) — April 2023 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Daily explosions, gas-and-ash plumes, avalanches, and ashfall during December 2022-March 2023

Fuego, one of three large stratovolcanoes overlooking the city of Antigua, Guatemala, has been vigorously erupting since January 2002, with recorded eruptions dating back to 1531 CE. Eruptive 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. More recently, activity remained relatively consistent with daily explosions, ash plumes, ashfall, avalanches, and lahars (BGVN 48:03). This report covers similar activity during December 2022 through March 2023, based on information from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH) daily reports, Coordinadora Nacional para la Reducción de Desastres (CONRED) newsletters, and various satellite data.

Daily explosions reported throughout December 2022-March 2023 generated ash plumes to 6 km altitude that drifted as far as 60 km in multiple directions. The explosions also caused rumbling sounds of varying intensities, with shock waves that vibrated the roofs and windows of homes near the volcano. Incandescent pulses of material rose 100-500 m above the crater, which caused block avalanches around the crater and toward the Santa Teresa, Taniluyá (SW), Ceniza (SSW), El Jute, Honda, Las Lajas (SE), Seca (W), and Trinidad (S) drainages. Fine ashfall was also frequently reported in nearby communities (table 27). MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent, moderate thermal activity throughout the reporting period; however, there was a brief decline in both power and frequency during late-to-mid-January 2023 (figure 166). A total of 79 MODVOLC thermal alerts were issued: 16 during December 2022, 17 during January 2023, 23 during February, and 23 during March. Some of these thermal evets were also visible in Sentinel-2 infrared satellite imagery at the summit crater, which also showed occasional incandescent block avalanches descending the S, W, and NW flanks, and accompanying ash plumes that drifted W (figure 167).

Table 27. Activity at Fuego during December 2022 through March 2023 included multiple explosions every hour. Ash emissions rose as high as 6 km altitude and drifted generally W and SW as far as 60 km, causing ashfall in many communities around the volcano. Data from daily INSIVUMEH reports and CONRED newsletters.

Month Explosions per hour Ash plume altitude (max) Ash plume distance (km) and direction Drainages affected by block avalanches Communities reporting ashfall
Dec 2022 1-12 6 km WSW, W, SW, NW, S, SE, NE, and E, 10-30 km Santa Teresa, Taniluyá, Ceniza, El Jute, Honda, Las Lajas, Seca, and Trinidad Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Finca Palo Verde, Yepocapa, Yucales, Sangre de Cristo, La Rochela, Ceilán, San Andrés Osuna, and Aldea La Cruz
Jan 2023 1-12 5 km W, SW, NW, S, N, NE, E, and SE, 7-60 km Ceniza, Las Lajas, Santa Teresa, Taniluyá, Trinidad, Seca, Honda, and El Jute Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Palo Verde, Yucales, Yepocapa, Sangre de Cristo, La Rochela, Ceylon, Alotenango, and San Andrés Osuna
Feb 2023 1-12 4.9 km SW, W, NW, and N, 10-30 km Santa Teresa, Taniluyá, Ceniza, Las Lajas, Seca, Trinidad, El Jute, and Honda Panimaché I and II, Morelia, Santa Sofía, Palo Verde, San Pedro Yepocapa, El Porvenir, Sangre de Cristo, La Soledad, Acatenango, El Campamento, and La Asunción
Mar 2023 3-11 5 km W, SW, NW, NE, N, S, SE, and E, 10-30 km Seca, Ceniza, Taniluyá, Las Lajas, Honda, Trinidad, El Jute, and Santa Teresa Yepocapa, Sangre de Cristo, Panimaché I and II, Morelia, Santa Sofía, El Porvenir, La Asunción, Palo Verde, La Rochela, San Andrés Osuna, Ceilán, and Aldeas
Figure (see Caption) Figure 166. Thermal activity at Fuego shown in the MIROVA graph (Log Radiative Power) was at moderate levels during a majority of December 2022 through March 2023, with a brief decline in both power and frequency during late-to-mid-January 2023. Courtesy of MIROVA.
Figure (see Caption) Figure 167. Frequent incandescent block avalanches descended multiple drainages at Fuego during December 2022 through March 2023, as shown in these Sentinel-2 infrared satellite images on 10 December 2022 (top left), 4 January 2023 (top right), 18 February 2023 (bottom left), and 30 March 2023 (bottom right). Gray ash plumes were also occasionally visible rising above the summit crater and drifting W, as seen on 4 January and 30 March. Avalanches affected the NW and S flanks on 10 December, the SW and W flanks on 18 February, and the NW, W, and SW flanks on 30 March. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Daily explosions ranged between 1 and 12 per hour during December 2022, generating ash plumes that rose to 4.5-6 km altitude and drifted 10-30 km in multiple directions. These explosions created rumbling sounds with a shock wave that vibrated the roofs and windows of homes near the volcano. Frequent white gas-and-steam plumes rose to 4.6 km altitude. Strombolian activity resulted in incandescent pulses that generally rose 100-500 m above the crater, which generated weak-to-moderate avalanches around the crater and toward the Santa Teresa, Taniluyá, Ceniza, El Jute, Honda, Las Lajas, Seca, and Trinidad drainages, where material sometimes reached vegetation. Fine ashfall was recorded in Panimaché I and II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Finca Palo Verde, Yepocapa (8 km NW), Yucales (12 km SW), Sangre de Cristo (8 km WSW), La Rochela, Ceilán, San Andrés Osuna, and Aldea La Cruz. INSIVUMEH reported that on 10 December a lava flow formed in the Ceniza drainage and measured 800 m long; it remained active at least through 12 December and block avalanches were reported at the front of the flow. A pyroclastic flow was reported at 1100 on 10 December, descending the Las Lajas drainage for several kilometers and reaching the base of the volcano. Pyroclastic flows were also observed in the Ceniza drainage for several kilometers, reaching the base of the volcano on 11 December. Ash plumes rose as high as 6 km altitude, according to a special bulletin from INSIVUMEH. On 31 December explosions produced incandescent pulses that rose 300 m above the crater, which covered the upper part of the cone.

Activity during January 2023 consisted of 1-12 daily explosions, which produced ash plumes that rose to 4.2-5 km altitude and drifted 7-60 km in multiple directions (figure 168). Incandescent pulses of material were observed 100-350 m above the crater, which generated avalanches around the crater and down the Ceniza, Las Lajas, Santa Teresa, Taniluyá, Trinidad, Seca, Honda, and El Jute drainages. Sometimes, the avalanches resuspended older fine material 100-500 m above the surface that drifted W and SW. Ashfall was recorded in Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Palo Verde, Yucales, Yepocapa, Sangre de Cristo, La Rochela, Ceylon, Alotenango, and San Andrés Osuna. Intermittent white gas-and-steam plumes rose to 4.5 km altitude and drifted W and NW.

Figure (see Caption) Figure 168. Webcam image showing an ash plume rising above Fuego on 15 January 2023. Courtesy of INSIVUMEH.

There were 1-12 daily explosions recorded through February, which generated ash plumes that rose to 4.2-4.9 km altitude and drifted 10-30 km SW, W, NW, and N. Intermittent white gas-and-steam emissions rose 4.5 km altitude and drifted W and SW. During the nights and early mornings, incandescent pulses were observed 100-400 m above the crater. Weak-to-moderate avalanches were also observed down the Santa Teresa, Taniluyá, Ceniza, Las Lajas, Seca, Trinidad, El Jute, and Honda drainages, sometimes reaching the edge of vegetated areas. Occasional ashfall was reported in Panimaché I and II, Morelia, Santa Sofía, Palo Verde, San Pedro Yepocapa, El Porvenir, Sangre de Cristo, La Soledad, Acatenango, El Campamento, and La Asunción. On 18 February strong winds resuspended previous ash deposits as high as 1 km above the surface that blew 12 km SW and S.

During March, daily explosions ranged from 3-11 per hour, producing ash plumes that rose to 4-5 km altitude and drifted 10-30 km W, SW, NW, NE, N, S, SE, and E. During the night and early morning, crater incandescence (figure 169) and incandescent pulses of material were observed 50-400 m above the crater. Weak-to-moderate avalanches affected the Seca, Ceniza, Taniluyá, Las Lajas, Honda, Trinidad, El Jute, and Santa Teresa drainages, sometimes reaching the edge of vegetation. Frequent ashfall was detected in Yepocapa, Sangre de Cristo, Panimaché I and II, Morelia, Santa Sofía, El Porvenir, La Asunción, Palo Verde, La Rochela, San Andrés Osuna, Ceilán, and Aldeas. Weak ashfall was recorded in San Andrés Osuna, La Rochela, Ceylon during 8-9 March. A lahar was reported in the Ceniza drainage on 15 March, carrying fine, hot volcanic material, tree branches, trunks, and blocks from 30 cm to 1.5 m in diameter. On 18 March lahars were observed in the Las Lajas and El Jute drainages, carrying fine volcanic material, tree branches and trunks, and blocks from 30 cm to 1.5 m in diameter. As a result, there was also damage to the road infrastructure between El Rodeo and El Zapote.

Figure (see Caption) Figure 169. Sentinel-2 infrared satellite image showing Fuego’s crater incandescence accompanied by a gas-and-ash plume that drifted SW on 25 March 2023. Images use bands 12, 11, 5. Courtesy of INSIVUMEH.

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/ ); 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).

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Scientific Event Alert Network Bulletin - Volume 13, Number 10 (October 1988)

Managing Editor: Lindsay McClelland

Additional Reports (Unknown)

Azores-Gibraltar Fracture Zone: 850 events; tremor near submarine volcano

Aira (Japan)

Continued explosions, tephra emission, and seismicity

Akan (Japan)

Increased seismicity but no change in surface activity

Asosan (Japan)

Glow on crater floor; crater closed to tourists

Atmospheric Effects (1980-1989) (Unknown)

No new volcanic aerosols

Bagana (Papua New Guinea)

Seismic data indicate continued lava extrusion

Fernandina (Ecuador)

Caldera wall collapsed; crater lake moved; lava flows, phreatic eruptions observed

Fukutoku-Oka-no-Ba (Japan)

Discolored water

Kie Besi (Indonesia)

Satellite data on July plumes

Kilauea (United States)

Repeated collapse of new coastal lava benches

Kusatsu-Shiranesan (Japan)

Seismicity during September-October 1988; tremor in January 1989 associated with phreatic emissions

Langila (Papua New Guinea)

Two Vulcanian explosions; glow

Liamuiga (Saint Kitts and Nevis)

Earthquake swarm

Manam (Papua New Guinea)

Low-level activity continues

Medicine Lake (United States)

Occasional seismicity; caldera subsides

Pagan (United States)

Moderate ash emission; plume altitude corrected

Poas (Costa Rica)

Crater lake activity continues

Rabaul (Papua New Guinea)

Seismicity increases slightly; minor inflation

Ruiz, Nevado del (Colombia)

Minor ash emission and continued vigorous seismicity

Suwanosejima (Japan)

Plume seen from aircraft

Tolima, Nevado del (Colombia)

Occasional seismicity; minor fumarolic activity

Tupungatito (Chile-Argentina)

Volcano-seismic trigger for 1987 debris flow disputed

Ulawun (Papua New Guinea)

Earthquakes and tremor; vapor emission

Villarrica (Chile)

Lava lake activity

Whakaari/White Island (New Zealand)

Ash emission; earthquake swarms



Additional Reports (Unknown) — October 1988 Citation iconCite this Report

Additional Reports

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Azores-Gibraltar Fracture Zone: 850 events; tremor near submarine volcano

A seismic swarm began 16 October about 30 km S of Sao Miguel Island. [Several older houses were damaged in Vila Franca do Campo and Povoacao on the S coast of Sao Miguel Island. Most of the epicenters were located along a branch of the Azores-Gibraltar fracture zone. [The strongest shock recorded by the WWSSN was an mb 5.1 event at 0615 on 16 October (37.58°N, 25.37°W, 10 km depth)]. In mid-November, the swarm was ending after 850 events had been recorded by the Azores Univ seismic array.

Since early November, tremor has been registered at the Sao Miguel and Terceira Islands stations of the Univ seismic network [but see 14:3]. This tremor appeared to originate from Don Joao de Castro Bank (38.23°N, 26.63°W, 14 m depth), a shallow submarine volcano that erupted in December 1720. Several earthquakes centered near the volcano reached MM V at Terceira, 80 km away.

Geologic Background. Reports of floating pumice from an unknown source, hydroacoustic signals, or possible eruption plumes seen in satellite imagery.

Information Contacts: V. Forjaz, Univ of the Azores; NEIC; Lisbon International Service.


Aira (Japan) — October 1988 Citation iconCite this Report

Aira

Japan

31.5772°N, 130.6589°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Continued explosions, tephra emission, and seismicity

In September, three explosions . . . were recorded. Two of the September explosions were followed by air shocks. Ash emission without explosion sounds occurred throughout the month. On 9 September at 0713, an explosion preceded emission of the month's highest plume (2,800 m). At the observatory, 523 g/m2 of ash accumulated during 13 days of ashfall in September. A total of 1,833 volcanic earthquakes were detected at the B station and earthquake swarms were recorded on five days (2, 3, 8, 9, and 29 September).

Activity was low during the first half of October but increased later in the month. Eight explosions were recorded, bringing the year's total to 150. Ashfall at [KLMO] dropped to 393 g/m2 in October. On 23 October, an ash plume reached 2,000 m altitude.

Satellite data showed a plume on 30 August that reached an estimated altitude of 3,600 m and extended ~110 km SE. On 27 September at 2329, a plume extended 40-50 km SE of the volcano, and on 13 October at 2137, a 3,000-m plume extended ~40 km ENE.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Information Contacts: JMA; W. Gould, NOAA.


Akan (Japan) — October 1988 Citation iconCite this Report

Akan

Japan

43.384°N, 144.013°E; summit elev. 1499 m

All times are local (unless otherwise noted)


Increased seismicity but no change in surface activity

The number of volcanic earthquakes increased sharply on 18 October. A seismograph . . . registered ~300 events on the 18th and 150 the next day. The month's total of 800 events was the highest since observations began in 1973. No change in vapor emission was evident. A small white plume continued to rise 100-150 m from Me-Akan-dake's crater.

Geologic Background. Akan is a 13 x 24 km caldera located immediately SW of Kussharo caldera. The elongated, irregular outline of the caldera rim reflects its incremental formation during major explosive eruptions from the early to mid-Pleistocene. Growth of four post-caldera stratovolcanoes, three at the SW end of the caldera and the other at the NE side, has restricted the size of the caldera lake. Conical Oakandake was frequently active during the Holocene. The 1-km-wide Nakamachineshiri crater of Meakandake was formed during a major pumice-and-scoria eruption about 13,500 years ago. Within the Akan volcanic complex, only the Meakandake group, east of Lake Akan, has been historically active, producing mild phreatic eruptions since the beginning of the 19th century. Meakandake is composed of nine overlapping cones. The main cone of Meakandake proper has a triple crater at its summit. Historical eruptions at Meakandake have consisted of minor phreatic explosions, but four major magmatic eruptions including pyroclastic flows have occurred during the Holocene.

Information Contacts: JMA.


Asosan (Japan) — October 1988 Citation iconCite this Report

Asosan

Japan

32.8849°N, 131.085°E; summit elev. 1592 m

All times are local (unless otherwise noted)


Glow on crater floor; crater closed to tourists

On the night of 16 October, JMA geologists noted irregular areas of red glow in a 30 x 10 m area on Naka-dake's crater floor, the first glow seen there since June 1985. The local government prohibited access within 1 km of the crater 17-27 October. Steam emission was observed from Crater No. 1 and its small crater lake shrank. The lake temperature was 71°C on 1 October. Seismicity and tilt showed no significant changes.

Geologic Background. The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Information Contacts: JMA.


Atmospheric Effects (1980-1989) (Unknown) — October 1988 Citation iconCite this Report

Atmospheric Effects (1980-1989)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


No new volcanic aerosols

No large new volcanic layers appear to have been injected since the November 1985 eruption of Ruiz. Lidar data in September and October showed few remaining stratospheric volcanic aerosols. Satellite data suggest that eruption clouds ejected on 9 May at Banda Api and 29 July at Makian, both in Indonesia, may have penetrated the stratosphere. Small new layers were detected by lidar after the Banda Api eruption, but neither eruption appears to have had a significant long-term effect on the stratosphere.

Geologic Background. The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found here.

Information Contacts: Thomas DeFoor, Mauna Loa Observatory, P.O. Box 275, Hilo, HI 96720 USA; Horst Jäger, Fraunhofer-Institut für Atmosphärische Umweltforschung, Kreuzeckbahnstrasse 19, D-8100 Garmisch-Partenkirchen, West Germany.


Bagana (Papua New Guinea) — October 1988 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Seismic data indicate continued lava extrusion

"Bagana's level of activity in October was steady. From the number of explosive earthquakes (1-12/day) and rockfall-related tremor (90-300 events/day), it is believed that the volcano is still extruding lava from its summit crater at a slow steady rate."

Geologic Background. Bagana volcano, in a remote portion of central Bougainville Island, is frequently active. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although occasional explosive activity produces pyroclastic flows. Lava flows with tongue-shaped lobes up to 50 m thick and prominent levees descend the flanks on all sides.

Information Contacts: D. Lolok, B. Talai, and P. Lowenstein, RVO.


Fernandina (Ecuador) — October 1988 Citation iconCite this Report

Fernandina

Ecuador

0.37°S, 91.55°W; summit elev. 1476 m

All times are local (unless otherwise noted)


Caldera wall collapsed; crater lake moved; lava flows, phreatic eruptions observed

The 14 September eruption led to the caldera's most dramatic changes since its floor dropped 350 m in 1968. The following account is based mainly on reports from Tui De Roy and Alfredo Carrasco, and photographs by Carrasco. Quoted material is from De Roy.

The E wall of the caldera, oversteepened since the 1968 collapse, failed, and the resulting debris avalanche covered the caldera floor, burying a 110-m-high tuff cone that had survived the 350 m drop in 1968. The caldera lake had been ~2 km in diameter, with a maximum depth in 1970 of 75 m at the SE end of the caldera. The avalanche drove it to the W and NW as a tsunami, and when it was first viewed from the rim (18-21 September) the lake had been raised by as much as 150 m, displaced to the NW, and greatly reduced in volume. The lake level dropped rapidly during those 3 days, as water percolated into the avalanche deposit below, and it was expected to disappear soon.

The eruption that apparently triggered the avalanche deposited up to 1.5 m of scoria on the caldera's ESE rim, ignited several fires in the dry brush vegetation, and destroyed the principal nesting area for Fernandina's large population of land iguanas. De Roy recognized that "fire storm" winds must have been strong, for wood on the side away from the caldera had been severely abraded by scoria and no branches thinner than a finger survived. She also measured a temperature of 45°C at 20 cm below the surface of the scoria, noting that "near the margins of the scoria field, where ground vegetation was not fully smothered, smoldering soil fires were running under the scoria, with occasional flare-ups spreading through the dry scrub." Pelé's hair was liberally distributed on the S rim ("wind-drifted heaps 5 cm thick around clumps of grass") and W flank, and reticulite was found floating 20 km S of Fernandina (and already colonized by larval crabs) 3 days after the eruption's start.

Lava flows continued after the avalanche, principally from a vent area ~ 100 m N and E of the 1973 vents, at an elevation ~ 750 m on the inner E wall. Flows coated the lower slopes and were filling in low spots on the caldera floor 18-21 September. De Roy described the hummocky avalanche deposits as "large heaps of rubble, including substantial rocks similar to the landslide accumulations along the caldera walls. [They are] scattered at random over the floor, some at least 20-30 m high, as though dumped by giant truck loads." Carrasco's photographs show low flows advancing to the W, near the former W lakeshore, to the NW between rubble masses, and to the NNW into the steaming lake remnant. These flows were moving during the 18-21 September observations, and "showed various glow points during the nights," but seemed to De Roy to be the redistribution of still-molten lava on the floor rather than continued feeding from vents.

Several phreatic explosions were witnessed from the rim, and small secondary explosion craters pockmarked many parts of the caldera floor. The largest explosion was at 1022 on 17 September as De Roy and others were ascending the NW flank of the volcano. A rumble and explosion were heard and "a billowing cloud rose rapidly over the caldera, then drifted SW, trailing black curtains of scoria or ash as well as a plume of brownish dust." Other explosions, mostly from the lava flow margins, were timed by David Day at 2330 on 17 September, 0415, 0658, and 0708 on the 18th, and 1005 on the 19th.

The E rim of the caldera, at an elevation of 1,350-1,450 m, was little changed by the 1968 collapse, but inner slopes averaged nearly 45° and were the caldera's most common sites of rock avalanches throughout the last 20 years. The lake lay at an elevation of ~ 430 m along the foot of this wall. De Roy estimates that a width "possibly as much as - but no more than - 250 m" was removed in the [main] avalanche and smaller avalanches that were continuing while the group was on the rim. A zone of nearly 3 km along the E wall has been affected. At 1403 on 19 September, David Day was on a cone ~ 200 m from the E rim "when a huge landslide removed a slice of rim perhaps 10 m thick by 40 m or so wide. This was followed immediately by a violent E-W jolt which he described as a rebound sensation. This jolt was not felt by the rest of the team on the S rim, nor were any other tremors felt during our stay." Fissures were observed in the new scoria within 50 m of the rim "sagging like glacier crevasses under snow." Landslides were common ("sometimes going on uninterrupted for an hour or more") during the group's 3 days on the rim, and the caldera was obscured by rockfall dust during much of 20-21 September.

The Nimbus-7 satellite that passes Galápagos around local noon every day has provided some interesting (and puzzling) information on SO2 distribution. Its orbit on the day of the eruption was far to the east of Fernandina and in the worst position of its 6-day cycle for measuring the eruption. It registered no SO2 on 14 September, less than an hour after the eruptive cloud was first sighted in Galápagos, but its orbit improved in the following days and so did the volcano's production of gas. On 15 September a broad SO2 plume extended from about 300 km NW of Fernandina to about 250 km SW, but no SO2 was detected as far as 400 km W. On the 16th there was a transmission problem that lost all data in a roughly E-W band 0-300 km S of Fernandina, but a weak SO2 anomaly was clear from 400 to 700 km SW. Coverage to the N and NW was good on the 16th, but no anomaly was seen in that quadrant. On the 17th there was a weak SO2 anomaly for ~200 km SW of Fernandina, and a considerably stronger one from 700-800 km SW. This was the plume's greatest distance from the volcano, but the weak local plume suggests that the source (Fernandina) was no longer supplying much volcanic gas. On the 18th there was no anomaly at all within 300 km of Fernandina, but a strong SO2 concentration (in fact the strongest of the eruption at 35 m-atm cm) 500-600 km to the SW. It is not clear why the strongest concentration of the eruption was that far (in time as well as space) from the eruption. On the 19th it had completely dispersed and no SO2 anomaly appeared on the image.

Geologic Background. Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Information Contacts: T. De Roy and D. Day, Isla Santa Cruz; A. Carrasco and G. Reck, Charles Darwin Research Station; A. Krueger, GSFC.


Fukutoku-Oka-no-Ba (Japan) — October 1988 Citation iconCite this Report

Fukutoku-Oka-no-Ba

Japan

24.285°N, 141.481°E; summit elev. -29 m

All times are local (unless otherwise noted)


Discolored water

JMSA observed sea discolorations on 12 August in an area of 0.09 x 0.9 km and on 15 September in a zone of 0.05 km (N-S) by 1.8 km (E-W).

Geologic Background. Fukutoku-Oka-no-ba is a submarine volcano located 5 km NE of the island of Minami-Ioto. Water discoloration is frequently observed, and several ephemeral islands have formed in the 20th century. The first of these formed Shin-Ioto ("New Sulfur Island") in 1904, and the most recent island was formed in 1986. The volcano is part of an elongated edifice with two major topographic highs trending NNW-SSE, and is a trachyandesitic volcano geochemically similar to Ioto.

Information Contacts: Y. Sawada, JMA; D. Shackelford, Fullerton, CA.


Kie Besi (Indonesia) — October 1988 Citation iconCite this Report

Kie Besi

Indonesia

0.32°N, 127.4°E; summit elev. 1357 m

All times are local (unless otherwise noted)


Satellite data on July plumes

New data from Japan's GMS satellite.... An image at 1200 on 29 July (figure 1) shows a dense plume with a surface temperature of -70°C (figure 2), suggesting an altitude of 15.2 km (table 1).

Table 1. Analysis of GMS satellite data by Yosihiro Sawada, with parameters of the 29 July Makian plume and possible eruption clouds on 31 July 1988.

Date Local time Attached to volcano? Width (km) Length (km) Direction Surface Temp. Height (km)
29 Jul 1988 1200 yes 60 110 SW -70°C 15.2
29 Jul 1988 1500 no 90 310 SW-W -61°C 13.5
29 Jul 1988 1800 no 80 430 SW-W -50°C 12.1
29 Jul 1988 2100 no 90 450 SW-W -- --
31 Jul 1988 0300 no 30 130 SW-W -49°C 11.9
31 Jul 1988 0600 no 20 60 SW -20°C 7.6
31 Jul 1988 0900 yes 50 210 SW -14°C 6.8
31 Jul 1988 1200 yes 40 130 W-SW -73°C 15.6

By the time of the next image, three hours later, the plume was detached from the volcano and was noticeably more diffuse. Possible volcanic plumes were also detected on GMS imagery returned 31 July (figures 1 and 3), but no ground reports of large eruption clouds are known at those times.

Figure (see Caption) Figure 3. Temperature gradients in the clouds shown in figure 1. Makian is marked by a solid triangle. Courtesy of Y. Sawada.

Geologic Background. Kie Besi volcano, forming the 10-km-wide Makian island off the west coast of Halmahera, has been the source of infrequent, but strong eruptions that have devastated villages on the island. The large 1.5-km-wide summit crater, containing a small lake on the NE side, gives the peak a flat-topped profile. Two prominent valleys extend to the coast from the summit crater on the north and east sides. Four cones are found on the western flanks. Eruption have been recorded since about 1550; major eruptions in 1646, 1760-61, 1861-62, 1890, and 1988 caused extensive damage and many fatalities.

Information Contacts: Y. Sawada, JMA.


Kilauea (United States) — October 1988 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Repeated collapse of new coastal lava benches

. . . lava continued to flow into the ocean from the tube system near Kupapau Point through October. Some minor surface activity occurred 2-4 October when lava broke out from the tube system between 300 and 180 m elevation.

The coastal lava bench growth and collapse sequences continued. A major collapse on the 13th removed ~2/3 of the 220 x 30-40 m bench, and there were minor collapses on 20 and 29 October and 5 November. Benches collapsed suddenly, without warning, making viewing the coastal area very hazardous. Small littoral cones formed periodically, the largest 10 m high. They were soon stranded behind the growing shoreline, then destroyed as the benches collapsed. Pyroclastic material consisting of fine shards and Pele's hair was ejected by littoral explosions, forming a tephra blanket several centimeters thick > 250 m downwind.

The lava pond at Kupaianaha remained 15-28 m below the rim. A 5-m-diameter "island" was visible 15-24 October ~20 m from the pond's edge, probably a piece that had collapsed from the rim. Activity increased in Pu`u `O`o crater on 26-27 October, with lava covering ~25% of the crater floor. Lava appeared to well up through one of the two active vents on the crater floor, and drain back down the other.

Low-level tremor continued . . . near Pu`u `O`o, Kupaianaha, and the Wahaula station near the coastal lava flows. East-rift tremor showed steady amplitude until the 27th, then changed to a pattern of varying amplitude that produced a banded pattern on the revolving drum seismic recorders. High-amplitude tremor lasting < 1 hour typically alternated with several hours of low-amplitude tremor. The fluctuating tremor continued until 4 November, then resumed its typical steady pattern. Bursts of deep tremor . . . increased from last month. The number of microearthquakes was about average in the summit region and East rift zone. There were 12 earthquakes of M 2.6-4.1, mostly centered beneath Kīlauea and Mauna Loa.

Geologic Background. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Information Contacts: C. Heliker and R. Koyanagi, HVO.


Kusatsu-Shiranesan (Japan) — October 1988

Kusatsu-Shiranesan

Japan

36.618°N, 138.528°E; summit elev. 2165 m

All times are local (unless otherwise noted)


Seismicity during September-October 1988; tremor in January 1989 associated with phreatic emissions

[Ida and others (1989) report that swarm-like seismicity began at the end of September 1988 and continued through October, with most located events centered SE of Mizugama crater. Hypocenters remained in the same area during the following period, but focal depths shallowed and episodic volcanic tremor became more frequent. Continuous volcanic tremor began suddenly on 6 January 1989 and lasted for almost 24 hours. The tremor was associated with emission of steam or water from the NW part of Yugama Crater, which distributed a small amount of ash over the crater lake.]

Reference. Ida, Y., Osada, N., Sawada, M., Koyama, E., and Kagiyama, T., 1989, Seismological Study Based on Recently Installed Permanent Stations and a Small Eruptive Event on January 6, 1989 at Kusatsu-Shirane Volcano: Bulletin of the Earthquake Research Institute, University of Tokyo, v. 64, p. 325-345 (in Japanese with English abstract and figure captions).

Geologic Background. The Kusatsu-Shiranesan complex, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid-Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the E, S, and SW flanks. The latest eruptive stage began about 14,000 years ago. Historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries.

Information Contacts:


Langila (Papua New Guinea) — October 1988 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Two Vulcanian explosions; glow

"Activity increased slightly in October. Weak to moderate white with occasional grey emission continued from Crater 2 throughout the month. Steady weak glow was observed for about a week (5-11 October) at Crater 2. Two loud Vulcanian explosions occurred on the 27th and 30th. Crater 3 remained relatively inactive with only weak white and grey emissions on 1, 5, 8, 9, and 17 October."

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

Information Contacts: D. Lolok, B. Talai, and P. Lowenstein, RVO.


Liamuiga (Saint Kitts and Nevis) — October 1988 Citation iconCite this Report

Liamuiga

Saint Kitts and Nevis

17.37°N, 62.8°W; summit elev. 1156 m

All times are local (unless otherwise noted)


Earthquake swarm

An earthquake swarm in the vicinity of Mt. Liamuiga began on 24 October and had declined by early November.

"The volcano is monitored by a single short-period seismograph station 8 km SE of the crater (SKI, figure 1). A second station (NEV) is 35 km to the SE and there are four other stations within 80 km of the volcano. The stations have been operating since 1952/53 and since 1980 have been linked by radio telemetry to the Seismic Research Unit, 700 km to the S. Data transmission is by standard analog techniques but data are recorded digitally using IBM PC-AT microcomputers. Since SKI was installed in 1953 it has recorded occasional microearthquakes with S-P intervals <2 seconds. These earthquakes show impulsive arrivals and clear P and S phases. They may possibly be small tectonic earthquakes but it is more likely that they are A-type volcanic earthquakes associated with Mt. Liamuiga. Normally, one or two are recorded each month.

Figure (see Caption) Figure 1. Epicenters of the two largest earthquakes (6-pointed stars) and 10 smaller events (open circles) at Liamuiga, 24 October-3 November 1988. Location uncertainties are ~5 km. Seismic stations are shown by solid triangles. Stations off the map are indicated by arrows, labeled with approximate distances from Mt. Liamuiga. Courtesy of UWI.

"On 24 October, a swarm of these events began and built up rapidly, peaking on 26 October when 186 earthquakes were recorded (figure 2). Many of the earthquakes were felt on St. Kitts and they caused great alarm. John Shepherd carried out an intensity survey on the morning of 27 October. At least five earthquakes were felt by all on St. Kitts. The most severe earthquakes up to that time were at 1201 and 1824 GMT on 26 October, with estimated magnitudes (mb) of 4.3 and 4.5. Both were felt throughout St. Kitts at up to MM VI and caused minor damage to weak masonry. They were also felt on the neighbouring islands of Nevis, Saba, Antigua, and Saint Maarten. Other earthquakes have been reported felt, mainly in the settlements on the flanks of Mt. Liamuiga. A party of tourists was visiting the crater of Mt. Liamuiga at the time of the second large earthquake. They reported that it was difficult to stand and that numerous small landslides were generated on the inner and outer walls of the crater.

Figure (see Caption) Figure 2. Daily numbers of earthquakes near Mt. Liamuiga (S-P intervals <3 seconds) recorded by station SKI beginning 24 October 1988. Courtesy of UWI.

"Figure 1 shows epicenters of the two biggest earthquakes and 10 others that were sufficiently well recorded for estimates to be made. Focal depths of all events were in the 10-20 km range (mean 15 km). Clearly, the number and distribution of the stations in operation when the earthquakes began were not ideal for the location of the smaller events, so these epicenters are subject to uncertainties of the order of 5 km. To reduce these uncertainties, Lloyd Lynch added three extra stations to the network (BSK, SKDB, and SENA) on 29-30 October. Data from these stations are now being analyzed.

"It is too early to say whether this earthquake swarm has any direct connection with Mt. Liamuiga. It is still possible that they are of tectonic origin. However, the characteristics of the swarm are similar to those of previous volcanic earthquake swarms in other islands of the Lesser Antilles. Many of these swarms have occurred, particularly in the islands of Nevis, Montserrat, Dominica, Guadeloupe, and St. Vincent. Only a small proportion of these swarms have culminated in volcanic eruptions, but on the other hand, almost all eruptions have been preceded by earthquake swarms. This is the first known swarm in St. Kitts and the situation will be carefully monitored."

Geologic Background. Mount Liamuiga volcano, comprising the NW end of St. Kitts Island, contains a steep-walled, 1-km-wide summit crater, which contained a shallow lake until 1959. Two lava domes are located on the upper W flank, and intrusion of a 3rd dome, Brimstone Hill, on the lower SW flank uplifted a Pleistocene limestone block. Liamuiga, sometimes referred to as Mount Misery, is the youngest of three NW-migrating volcanic centers on St. Kitts. Its most recent major eruptions less than 2,000 years ago produced pyroclastic flows and mudflows whose deposits underlie populated coastal areas. Reports of possible eruptions in 1692 and 1843 are considered uncertain. An earthquake swarm from late 1988 to early 1989 caused small landslides in the summit crater; another earthquake swarm took place in 1999-2000. Active fumaroles are found in the summit crater.

Information Contacts: J. Shepherd, L. Lynch, and K. Rowley, UWI.


Manam (Papua New Guinea) — October 1988 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Low-level activity continues

"Low-level activity continued in October. Weak to moderate white vapour [emissions continued] from the two summit craters. Occasional small amounts of ash were ejected from Southern Crater and blue vapour from Main Crater."

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical basaltic-andesitic stratovolcano to its lower flanks. These valleys channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: D. Lolok, B. Talai, and P. Lowenstein, RVO.


Medicine Lake (United States) — October 1988 Citation iconCite this Report

Medicine Lake

United States

41.611°N, 121.554°W; summit elev. 2412 m

All times are local (unless otherwise noted)


Occasional seismicity; caldera subsides

"Seismicity... continued sporadically throughout October. As of 15 November, seismicity had declined to several locatable events/week. Most were of M less than 1 with the exception of a M 2 event on 29 October. The installation of a tightly spaced seismic network on 22 October permits even small events to be located. Three well-constrained earthquakes have been located since 29 October in the E, central, and S portions of Medicine Lake glass flow in the NW part of the caldera (figure 1). Depths of recent events are shallow, between 0.5 and 1.5 km. The locations of the recent events show a northward shift from those of the late September swarm. Seismologists are uncertain whether this shift is real or the result of improved locations from the new network."

A levelling line (~16 benchmarks spaced 1.5-2.25 km apart along the main caldera access road through the W, center, and SE portions of the caldera) was reoccupied on three occasions. Relative to a 1954 National Geodetic Survey, August 1988 measurements showed 175 ± 11 mm of central caldera subsidence with respect to the W and S rims, although subsidence extended outside the caldera. An October 1988 survey indicated 8 ± 5 mm of additional subsidence which is within 2-3 standard errors of noise levels. However, the shapes of the long- and short-term deformation curves are similar, with maximum subsidence occurring at the central caldera benchmark, suggesting to geologists that the deformation is real. The line will be relevelled in the spring when snow conditions permit.

Geologic Background. Medicine Lake is a large Pleistocene-to-Holocene, basaltic-to-rhyolitic shield volcano east of the main axis of the Cascade Range. Volcanism, similar in style to that of Newberry volcano in Oregon, began less than one million years ago. A roughly 7 x 12 km caldera truncating the summit contains a lake that gives the volcano its name. A series of young eruptions lasting a few hundred years began about 10,500 years before present (BP) and produced 5 km3 of basaltic lava. Nine Holocene eruptions clustered during three eruptive episodes at about 5000, 3000, and 1000 years ago produced a chemically varied group of basaltic lava flows from flank vents and silicic obsidian flows from vents within the caldera and on the upper flanks. The last eruption produced the massive Glass Mountain obsidian flow on the E flank about 900 years BP. Lava Beds National Monument on the N flank of Medicine Lake shield volcano contains hundreds of lava-tube caves displaying a variety of spectacular lava-flow features, most of which are found in the voluminous Mammoth Crater lava flow, which extends in several lobes up to 24 km from the vent.

Information Contacts: S. Walter, USGS Menlo Park; D. Dzurisin, CVO.


Pagan (United States) — October 1988 Citation iconCite this Report

Pagan

United States

18.13°N, 145.8°E; summit elev. 570 m

All times are local (unless otherwise noted)


Moderate ash emission; plume altitude corrected

On 12 October at 1050, a U.S. Air Force pilot noted a plume that extended 1.5-7.5 km at <1 km altitude. The plume was not evident on satellite images.

Geologic Background. Pagan Island, the largest and one of the most active of the Mariana Islands volcanoes, consists of two stratovolcanoes connected by a narrow isthmus. Both North and South Pagan stratovolcanoes were constructed within calderas, 7 and 4 km in diameter, respectively. North Pagan at the NE end of the island rises above the flat floor of the northern caldera, which may have formed less than 1,000 years ago. South Pagan is a stratovolcano with an elongated summit containing four distinct craters. Almost all of the recorded eruptions, which date back to the 17th century, have originated from North Pagan. The largest eruption during historical time took place in 1981 and prompted the evacuation of the sparsely populated island.

Information Contacts: M. Matson, NOAA.


Poas (Costa Rica) — October 1988 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2697 m

All times are local (unless otherwise noted)


Crater lake activity continues

Geologists visited Poás on 2 November and observed activity similar to that of previous months. Mud plumes rose 2-3 m from three sites near the center of the crater lake. Intense convective bubbling occurred at multiple points in the lake. No explosions were observed. Since September, the level of the lake had dropped ~1 m and its diameter had decreased, leaving a growing sedimentary terrace. Fumarolic activity continued on the summit and N edge of of the 1953-55 [dome]. Several tens of volcanic earthquakes were recorded daily, predominantly B-type events.

Acid vapor produced by the activity was blown W by strong dry-season trade winds, away from the overlook area. Plants inside the crater, around the overlook, and SE toward Lake Botos sprouted leaves without acid burns, in contrast to earlier leaves that had burned edges. The pH of drinking water in the Visitors Center, supplied from Lake Botos, had risen since September to 5.0-5.5, indicating lower ambient acidity.

Park guards have experienced coughing, sneezing, itching of eyes and skin, and stomach problems because of the acid. The effects are transitory and have not caused them permanent damage (Dra. Y. Soto, personal communication). According to the park guards, birds that had been absent from the summit area in recent months have returned and can be heard singing, demonstrating a decrease in ambient acidity. Dead birds had been seen in the crater near the 1953-55 [dome] in January.

Geologic Background. The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: G. Soto, Univ de Costa Rica (UCR), San José.


Rabaul (Papua New Guinea) — October 1988 Citation iconCite this Report

Rabaul

Papua New Guinea

4.2459°S, 152.1937°E; summit elev. 688 m

All times are local (unless otherwise noted)


Seismicity increases slightly; minor inflation

"Seismicity increased slightly in October with a total of 402 earthquakes recorded. Events averaged 13/day with the highest count reaching 60 on the 3rd. One weakly felt earthquake of M 2.6 occurred on the 30th and was centered in the Blanche Bay area. Most of 14 locatable events were situated in the NW caldera ring fault between Vulcan and Matupit Island. Smaller concentrations also occurred on the NE portion near Tavurvur and SW of Karavia Bay.

"Tilt measurements [and EDM results] showed no significant changes during the month. . . . Between 20 September and 4 November, levelling measurements showed a slight (12 mm) . . . uplift at the S part of Matupit Island."

Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the asymmetrical shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1,400 years ago. An earlier caldera-forming eruption about 7,100 years ago is thought to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the N and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and W caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Information Contacts: D. Lolok, B. Talai, and P. Lowenstein, RVO.


Nevado del Ruiz (Colombia) — October 1988 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Minor ash emission and continued vigorous seismicity

The number of earthquakes and seismic energy release remained at high levels during October, continuing the pattern of vigorous seismicity that began to build in late 1987. Tremor amplitude declined slightly. Fluctuations in tremor amplitude were associated with small explosions that briefly emitted ash. A swarm of 212 high-frequency events was recorded 1 October from 1,410 to 1,450. The month's two strongest shocks (M 2.3) occurred on the 9th and 12th. Several of the locatable events were scattered SE of the volcano, while others were centered near the crater at depths of 1-4 km (figure 20). No significant deformation was recorded.

Figure (see Caption) Figure 20. Epicenters of 49 seismic events at Ruiz, October 1988. Courtesy of the Observatorio Vulcanológico de Colombia.

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

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


Suwanosejima (Japan) — October 1988 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Plume seen from aircraft

A jetliner crew observed a 2.0-km-high plume . . . on 9 August at 1630.

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

Information Contacts: Y. Sawada, JMA; D. Shackelford, Fullerton, CA.


Nevado del Tolima (Colombia) — October 1988 Citation iconCite this Report

Nevado del Tolima

Colombia

4.658°N, 75.33°W; summit elev. 5215 m

All times are local (unless otherwise noted)


Occasional seismicity; minor fumarolic activity

Seismicity at Tolima was recorded in December 1987 and September-October 1988 by a telemetric station 2 km SE of the summit (figure 1). During October, as many as seven high-frequency events/day were recorded and minor fumarolic activity was observed. A 50-m-thick ice cap with an area of ~2 km2 covers the summit.

Figure (see Caption) Figure 1. Number of earthquakes/day recorded by a seismic station 2 km SE of the summit, December 1987-October 1988. Courtesy of the Observatorio Vulcanológico de Colombia.

Geologic Background. The steep-sided, glacier-covered Nevado del Tolima volcano contrasts with the broad profile of Nevado del Ruiz to the north. The andesitic-dacitic younger Tolima formed during the past 40,000 years, rising above and largely obscuring a 3-km-wide late-Pleistocene caldera. The summit consists of a cluster of late-Pleistocene to Holocene lava domes associated with thick block-lava flows on the N and E flanks, and extensive pyroclastic-flow deposits. The summit contains a funnel-shaped crater 200-300 m deep. Holocene activity has included explosive eruptions ranging in size from moderate to Plinian, and the last major eruption took place about 3,600 years ago. Lava dome growth has produced block-and-ash flows that traveled primarily to the NE and SE. Minor explosive eruptions have been recorded in the 19th and 20th centuries.

Information Contacts: C. Carvajal and F. Muñoz, INGEOMINAS, Manizales.


Tupungatito (Chile-Argentina) — October 1988 Citation iconCite this Report

Tupungatito

Chile-Argentina

33.425°S, 69.797°W; summit elev. 5660 m

All times are local (unless otherwise noted)


Volcano-seismic trigger for 1987 debris flow disputed

The following is from Alfredo Eisenberg and M. Pardo. "González-Ferrán (13:6) attributed the 29 November 1987 debris flow to an increase in local shallow volcano-seismic activity that he said can be observed on our seismograms of 28, 29, and 30 November. The seismic network in central Chile did not record any activity of this kind during those days, nor the previous ones. It is also important to note that only one station is located within 40 km of Tupungatito volcano's main crater (figure 3 and table 1). Stations on the Argentine side of the Andes did not register any volcano-seismic activity either. We did record the debris fall, however, at 1033 on 29 November, with an equivalent local magnitude of 4.5. This event, as far as we can see from the records, was not preceded by a triggering earthquake."

see figure caption Figure 3. Seismicity in central Chile, 27-30 November 1987. Circles mark epicenters of located earthquakes (table 1), squares the position of seismological stations. The source of the debris flow is marked by a circled cross, and Tupungatito volcano by a star.

Table 1. Seismicity recorded in central Chile, 27-30 November 1987, by Univ of Chile seismograph stations. Magnitude mt corresponds to an estimation of mb from the total duration of the PEL station record.

Date Time Latitude Longitude Depth (km) Magnitude (mt)
27 Nov 1987 1038 33°31'S 72°14'W 50 4.3
27 Nov 1987 1130 33°07'S 71°39'W 18 4.1
28 Nov 1987 0916 33°44'S 72°32'W 10 4.1
28 Nov 1987 2153 33°18'S 70°30'W 75 3.7
29 Nov 1987 0214 34°12'S 70°14'W 00 3.7
29 Nov 1987 0332 33°53'S 72°02'W 20 4.5
29 Nov 1987 0807 33°06'S 71°53'W 27 4.4
30 Nov 1987 0010 32°43'S 71°24'W 5 4.0
30 Nov 1987 0637 33°18'S 71°34'W 23 4.2
30 Nov 1987 1055 34°53'S 70°46'W 109 4.3
30 Nov 1987 1325 32°00'S 71°30'W 28 4.1
30 Nov 1987 1510 32°12'S 71°42'W 28 4.1

Geologic Background. Tupungatito volcano, the northernmost historically active volcano of the central Chilean Andes, is located along the Chile-Argentina border about 90 km E of Santiago and immediately SW of the Pleistocene Tupungato volcano. Tupungatito consists of a group of 12 Holocene andesitic and basaltic andesite craters and a pyroclastic cone at the NW end of the 4-km-wide, Pleistocene dacitic Nevado Sin Nombre caldera, which is filled by glaciers at its southern end and is breached to the NW. Lava flows from the northernmost vent have traveled down the NW flank breach. Tupungatito has produced frequent mild explosive eruptions during the 19th and 20th centuries.

Information Contacts: A. Eisenberg and M. Pardo, Univ of Chile.


Ulawun (Papua New Guinea) — October 1988 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Earthquakes and tremor; vapor emission

"During most days the summit crater remained under cloud cover. When visible, the summit released mostly white vapour in weak to moderate and occasionally large amounts. Recorded seismicity was at a low level during the first four days of October (3-13 small B-type events/day), but a sudden upsurge in the number of seismic events occurred on the 5th with a total of 575 recorded. From the 6th to the 25th, daily totals of events fluctuated between 2 and 415. The average amplitude from the 1st to the 25th remained constant. On the 26th, a sudden change in seismic activity occurred and continued to the end of the month. [This] seismicity was characterized by bands of low-frequency harmonic tremor recorded for long periods (1-2 hours) with a further increase in size and number of accompanying B-type events. These events sometimes occurred in groups (1-3 events/minute) with average amplitude 8 times higher than normal. A steady increase in the number of B-type events occurred from the 26th with the highest number (820) recorded on the 31st."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: D. Lolok, B. Talai, and P. Lowenstein, RVO.


Villarrica (Chile) — October 1988

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Lava lake activity

Boris Behncke reports that lava lake activity was observed at Villarrica in October 1988, by a student from Rühr Univ, Bochum. The summit crater, ~ 150 m deep, included a small cone that contained a vigorously bubbling lava pool roughly 50 m in diameter. Spatter was occasionally ejected above the crater rim. The lava lake activity had apparently been continuing since the end of the more vigorous 1984-85 eruptive activity.

Geologic Background. The glacier-covered Villarrica stratovolcano, in the northern Lakes District of central Chile, is ~15 km south of the city of Pucon. A 2-km-wide caldera that formed about 3,500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesite cone at the NW margin of a 6-km-wide Pleistocene caldera. More than 30 scoria cones and fissure vents are present on the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Eruptions documented since 1558 CE have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: Boris Behncke, Rühr Univ, Bochum, Germany.


Whakaari/White Island (New Zealand) — October 1988 Citation iconCite this Report

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


Ash emission; earthquake swarms

Since geologists last visited ... on 14 August, no eruptions have been reported although numerous E-type (explosion) earthquakes have occurred. During fieldwork on 14 October, a continuous expanded gas plume containing fine pink ash rose from Hitchhiker vent. Brick-red ash covered the island's E half and small impact craters were scattered ESE of the vent. Tephra ejected after 1 August was 70 mm thick at Congress Crater's rim and included altered lithic fragments, abraded crystals, and a few % fresh, light brown, highly vesicular scoria fragments. High pressure/temperature gas was emitted from fumaroles roughly 200 m E of Hitchhiker vent, including two new vents. Gas vents were surrounded by aprons of material ranging from anhydrite-cemented ash to lithic blocks.

Since early August, an average of seven B-type and fewer than five high-frequency A-type seismic events have been recorded/day. Earthquake swarms were detected 24-25 August (62 events), 7-8 September (38 events), and 23-24 September (57 events followed by E-type earthquakes). Of 20 E-type events recorded in August, 16 occurred 12-24 August. Four E-type events were recorded in September and one on 2 October, before ash accumulation on solar panels suspended operation of seismic instruments on 4 October.

Geologic Background. The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: I. Nairn and B. Scott, NZGS Rotorua.

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements  Obituaries

Misc Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subject.

Additional Reports  False Reports