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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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Bulletin of the Global Volcanism Network - Volume 28, Number 04 (April 2003)

Managing Editor: Edward Venzke

Aira (Japan)

Ash plume observed in July 2002; plume photo from 17 April 2003

Anatahan (United States)

Eruption on 10 May is the first historical activity

Asamayama (Japan)

Four minor ash eruptions during February-April 2003

Chikurachki (Russia)

New eruption on 18 April generates long plumes and ashfall

Cosiguina (Nicaragua)

Earthquake swarm in September 2002

Erta Ale (Ethiopia)

Frequent changes in the active crater morphology and lava lake level

Guntur (Indonesia)

Increased seismicity since December 2002

Kikai (Japan)

Eruption plumes and ashfall during 24 May-5 June 2002

Miyakejima (Japan)

Small explosion in November 2002; continued high SO2 flux through April 2003

Niuafo'ou (Tonga)

Fumarolic and hot spring activity in the caldera during October 2002

Semeru (Indonesia)

Continued ash explosions, with frequent lava avalanches and pyroclastic flows

Soufriere Hills (United Kingdom)

Continued dome growth, rockfalls, and pyroclastic flows

Stromboli (Italy)

Strong explosion on 5 April covers much of the summit in pyroclastic deposits

Suwanosejima (Japan)

Ash explosions in September and December 2002, and activity in January 2003



Aira (Japan) — April 2003 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Ash plume observed in July 2002; plume photo from 17 April 2003

An observer at Kagoshima Airport reported seeing an ash cloud from Sakura-jima at 0900 on 22 July 2002 that rose to 2.1-2.4 km altitude. An ash plume was visible on satellite imagery at 1052 (0152 UTC) that day extending to the SW.

A photograph taken by the webcam at ttp://yumemaru.com/s/ shows a plume of undetermined composition originating from the island on 17 April 2003 (figure 22). This type of event is common at Sakura-jima.

Figure (see Caption) Figure 22. Photograph of Sakura-jima taken on 17 April 2003 showing a plume originating from the island. Courtesy of Yunemaru.

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: Charles Holliday, U.S. Air Force Weather Agency, 106 Peacekeeper Drive, Ste 2NE, Offut AFB, NE 68113-4039, USA (URL: http://www.557weatherwing.af.mil/); Yunemaru (URL: http://yumemaru.com/).


Anatahan (United States) — April 2003 Citation iconCite this Report

Anatahan

United States

16.35°N, 145.67°E; summit elev. 790 m

All times are local (unless otherwise noted)


Eruption on 10 May is the first historical activity

An explosive eruption on 10 May at Anatahan marked the first report of activity at the volcano since an earthquake swarm on 29 May 1993 that led to the evacuation of the island (BGVN 18:05 and 18:08). No eruptions had previously been documented in historical time from this small volcanic island in the Commonwealth of the Northern Mariana Islands (CNMI) (figure 2).

Figure (see Caption) Figure 2. Map of the Mariana Islands and outline of the adjacent Mariana Trench. The Commonwealth of the Northern Mariana Islands extends from Rota in the south to Farallon de Pajaros in the north. The island of Anatahan is approximately 9 km long and 4 km wide. Courtesy of CNMI Emergency Management Office.

A group of scientists was near Anatahan on 10 May deploying seismographs for the Margins Mariana Subduction Factory Imaging Project, which is comprised of members from Washington University, St. Louis; Scripps Inst. of Oceanography; and CNMI Emergency Management Office. They passed Anatahan as the eruption was occurring. The island was uninhabited at the time. According to members of the research group who viewed the eruption from about 10 km away, the eruption began on 10 May around 1700. The CNMI Emergency Management Office (EMO) reported that the ash cloud produced from the eruption eventually rose to an altitude of ~12 km (figure 3). During an observational helicopter flight, EMO personnel discovered that the eruption was emanating from the eastern crater (figure 4). They noted that only ash was being emitted, no lava flows were seen, and no explosions were seen or heard. The scientists had visited the island on 6 May and saw no signs of any unusual activity.

Figure (see Caption) Figure 3. Photograph taken on 10 May 2003 of an ash cloud produced from the eruption of Anatahan that began that day. The cloud top is at ~ 4.6 km and emanates from the eastern crater. The view is toward the SW. Courtesy of CNMI Emergency Management Office.
Figure (see Caption) Figure 4. Map of Anatahan showing the deep pit on the eastern side of the summit, which is referred to as the East Crater, and is the source of the eruption that began on 10 May 2003. Courtesy of Scott Rowland, University of Hawaii Manoa.

The Washington Volcanic Ash Advisory Center (VAAC) issued an advisory about the Anatahan eruption stating that an ash cloud was visible on satellite imagery on 10 May at 2232 at an estimated altitude of 10.5 km. One layer of the ash cloud drifted south at a speed of ~65 km/hour, and a lower level at an altitude of ~4.5 km drifted W at ~28 km/hr. By 0655 the next day ash was seen in satellite imagery drifting in three different directions: WNW at an altitude around 5.5 km, SW around 8.5 km, and two separate and smaller ash plumes were drifting SE at altitudes around 13.4 km. At this time, a hotspot was visible on GOES-9 imagery.

On 11 May the CNMI Emergency Management Office, Office of the Director issued a special advisory stating, "Due to this active volcano eruption with high level clouds and [an] ash plume, the general public especially fishermen, tour operators and commercial pilots are advise[d] to stay away from the island of Anatahan until further notice from the Office of Emergency Management." The eruption continued through at least 14 May, when the Washington VAAC issued an ash advisory stating that ash was visible on satellite imagery drifting W of Anatahan at an altitude of ~4.9 km.

Geologic Background. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of a large stratovolcano with a 2.3 x 5 km compound summit caldera. The larger western portion of the caldera is 2.3 x 3 km wide, and its western rim forms the island's high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern portion of the caldera contained a steep-walled inner crater whose floor prior to the 2003 eruption was only 68 m above sea level. A submarine cone, named NE Anatahan, rises to within 460 m of the sea surface on the NE flank, and numerous other submarine vents are found on the NE-to-SE flanks. Sparseness of vegetation on the most recent lava flows had indicated that they were of Holocene age, but the first historical eruption did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera.

Information Contacts: Doug Wiens, Washington University, St. Louis, McDonnell Hall 403 Box 1169, St. Louis, MO 63130; Allan Sauter, Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla CA, 92093-0225; Juan Camacho, Commonwealth of the Northern Mariana Islands Emergency Management Office, P.O. Box 10007, Saipan, MP 96950 (URL: http://www.cnmihsem.gov.mp/); Washington VAAC, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/); Scott Rowland, University of Hawai'i at Manoa, Hawai'i Institute of Geophysics and Planetology, 1680 East-West Road, POST 602, Honolulu, HI 96822; Frank Trusdell, Hawaiian Volcano Observatory, PO Box 51, Hawaii National Park, HI, 96718-0051.


Asamayama (Japan) — April 2003 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Four minor ash eruptions during February-April 2003

Asama, located near the resort town of Karuizawa ~150 km W of Tokyo, has been seismically active since 18 September 2000. Heightened seismicity occurred in June 2002, when the daily number of volcanic earthquakes exceeded 300 (BGVN 27:06). The Asama Volcano Observatory (ERI, University of Tokyo) and JMA reported that a new episode of elevated seismicity started around 0620 on 18 September 2002. A relatively large amount of volcanic gas trailed from the summit. The seismicity increased after 0800, 18 September, such that 243 volcanic earthquakes took place on 18 September and another 128 on the 19th, after which the seismic activity decreased. However, the temperature of the crater bottom remained at the elevated levels observed since May 2002. No change was observed in ground deformation.

According to the Japan Meteorological Agency (JMA), seismicity had been at background levels for several months, and the temperature of the crater had been rather low prior to four minor eruptions between 6 February and 18 April 2003. The first eruption occurred at about noon on 6 February as an ash cloud was seen rising to 300 m above the summit crater, with minor ashfall around the summit. Seismic tremor related to the emission started at around 1201 and lasted about 40 seconds. On 30 March at 0154 hours, a gray ash cloud rose 300 m, with minor ashfall around the summit. Then, on 7 April at 0924, an ash cloud rose 200 m. On 18 April at 0732 the volcano spewed a mixture of black smoke and pale ash ~300 m high. There were no reports of injuries or damage from these eruptions, and the JMA reported that more such activity is expected. All of the eruptions were brief, none having durations of more than 10 minutes. No unusual precursory seismic activity preceded these events, but plume activity has increased since the beginning of February.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asamayama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has observed activity dating back at least to the 11th century CE. Maekake has had several major Plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: Hitoshi Yamasato and Tomoyuki Kanno, Japan Meteorological Agency (JMA), Volcanological Division, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: http://www.jma.go.jp/jma/index.html); Hidefumi Watanabe and Setysuya Nakada, Volcano Research Center-Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo, Tokyo, 113-0032 Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html).


Chikurachki (Russia) — April 2003 Citation iconCite this Report

Chikurachki

Russia

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

All times are local (unless otherwise noted)


New eruption on 18 April generates long plumes and ashfall

A new eruption that began at Chikurachki on 18 April 2003 was reported by the Kamchatka Volcanic Eruptions Response Team (KVERT) and the Alaska Volcano Observatory (AVO). The most recent previous eruption occurred in early 2002 (BGVN 27:01 and 27:04). Ash explosions were seen by observers on Paramushir Island, and at 1500 and 2000 ashfall was observed in Podgorny town and Cape Vasiliev. The Aviation Meteorological Center at Yelizovo Airport reported that on 19 April ash plumes rose 2,000 m above the crater. According to satellite data from the USA, distinct volcanic events were detected at approximately 2300 on 19 April, 0200 on 20 April, and 0430 on 20 April (1200, 1500, and 1730 UTC, 19 April), with the ash moving towards the SE. Interpretation of satellite imagery revealed plumes extending more than 50 km SE and SSE during 18-19 April, with the longest reaching more than 250 km at 1501 on the 19th.

Visual data from Vasiliev Cape and Paramushir Island on 22 April showed a white gas-and-steam plume that rose 500 m above the crater. According to satellite data from the USA and Russia, ash plumes less than 100 km long were moving SE and E during 22-25 April. Longer plumes on 25 April were directed NNE. Observers from Vasiliev Cape noted a white plume rising ~500 m above the crater on 27 April. On 28 April residents in Severo-Kurilsk observed a very fine layer of gray ash (less than 1 mm thick) near the city, 3 km S of the volcano. The longest plume seen in satellite imagery during April was more then 300 km long when observed at 2028 on 29 April.

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: Olga Girina, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry (IVGG), Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Cosiguina (Nicaragua) — April 2003 Citation iconCite this Report

Cosiguina

Nicaragua

12.98°N, 87.57°W; summit elev. 872 m

All times are local (unless otherwise noted)


Earthquake swarm in September 2002

In September 2002 an earthquake swarm was registered near Cosigüina. This swarm was the first to be recognized at that volcano in the 27 years of the existence of Nicaragua's seismic network. The historical seismic record contains no evidence of the type of cluster that occurred in September 2002, although there was seismic activity in 1951 that could have been of local origin (see below).

The seismicity began on 4 September, with M 2.4-3.6 events. The main earthquake occurred on 9 September with a magnitude of 3.9. The last event occurred on 16 September with a magnitude of 3.7. A total of 34 earthquakes occurred to the N of Cosigüina volcano. Unfortunately, the seismic station at the volcano failed to function due to radio signal transmission problems. Seismic readings were also obtained from the National System of Territorial Studies of El Salvador (SNET) for 31 earthquakes. Epicenters of the earthquakes, located with the readings obtained by the seismic networks of the Instituto Nicaragüense de Estudios Territoriales (INETER) and SNET, were concentrated in a zone approximately 4-5 km N and W of the crater (figure 1). The distribution, along a SW-NE axis, might be simply a product of the geometry of the configuration of seismic stations with which the events were located.

Figure (see Caption) Figure 1. Epicentral map of the earthquakes located N of Cosigüina volcano. September 2002. Black triangle indicates approximate summit location. Courtesy of INETER.

Randy White (USGS) indicated to INETER that the seismicity seems to have been of the volcano-tectonic type, caused by an intrusion of magma, based on several observations: 1) the two stages of the cluster on 4-6 and 9 September showed a release of similar seismic energy; 2) In the two stages there were many similarly sized events; 17 with a magnitude of 3.0 or less, but none greater than 3.9; 3) The maximum magnitude increased several times; and 4) The distribution of energy was highly unusual for tectonic seismicity. Apparently there were several groups of one or a few events in intervals of 5-7 hours. Regular pulsations are typical for volcanic earthquake swarms that last more than several hours.

INETER volcanologist Pedro Perez investigated the volcano on 12 September, but saw nothing anomalous. He also conducted interviews with local residents, went to the summit crater, and took measurements of thermal waters at the foot of the volcano. Within the crater walls, landslides were observed in the E, S, and W portions. Residents in the Marañonal, Potosí, Punta Ñata, and Apascali sectors did not feel the earthquakes.

Seismicity in August 1951. The following description is based on news reports compiled by INETER (The News, 1951 Ago. 07; The Press, 1951 Ago. 04, 05, 07, 09, 18).

In August 1951 there was strong seismic activity in western Nicaragua and southwestern Honduras. On 2 August one of a series of strong events produced a 200-m-long crack near Cosigüina that spewed large amounts of water, flooding the region. The seismic shocks also demolished three houses in Chinandega. These earthquakes were felt more strongly to the W and diminished to the N and in the direction of Managua. The population in these areas slept outside their homes for many days. The people of these sectors, mainly the western population, felt continuous and violent seismic shocks until 8 August. On 17 August a strong tremor shook the western region and Managua. Apparently, this seismic activity produced more than 100 events, not all of which were felt by all residents.

Geologic Background. Cosigüina (also spelled Cosegüina) is a low basaltic-to-andesitic composite volcano that is isolated from other eruptive centers in the Nicaraguan volcanic chain. The stratovolcano forms a large peninsula extending into the Gulf of Fonseca at the western tip of the country. It has a pronounced somma rim on the northern side; a young summit cone rises 300 m above the northern somma rim and buries the rim on other sides. The younger cone is truncated by a large elliptical prehistorical summit caldera, 2 x 2.4 km in diameter and 500 m deep, with a lake at its bottom. Lava flows predominate in the caldera walls, although lahar and pyroclastic-flow deposits surround the volcano. A brief but powerful explosive eruption in 1835 is Nicaragua's largest during historical time. Ash fell as far away as México, Costa Rica, and Jamaica, and pyroclastic flows reached the Gulf of Fonseca.

Information Contacts: Virginia Tenorio and Wilfried Strauch, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado 1761, Managua, Nicaragua (URL: http://www.ineter.gob.ni/).


Erta Ale (Ethiopia) — April 2003 Citation iconCite this Report

Erta Ale

Ethiopia

13.601°N, 40.666°E; summit elev. 585 m

All times are local (unless otherwise noted)


Frequent changes in the active crater morphology and lava lake level

Over the last few years the Afar National Regional State has allowed a program of visitation to Erta Ale volcano by natural science field workers. As a result, numerous expeditions have visited the volcano since November 2000 and January-February 2001 (BGVN 26:12). The following brief reports are a result of some of these visits during January, February, and April 2002, November-December 2002, and January 2003. Typical lava lake activity was commonly reported, but some changes, such as a significant changes of the lake level, were also noted.

Activity during January 2002. Members of the Société de Volcanologie Genève (SVG) visited Erta Ale at the end January 2002. The lava lake remained elliptical with a N-S axis of ~130-133 m and an E-W axis of ~104-111 m; the width had increased ~10 m as a result of crumbling of the terrace along the lake edge. The size of the pit-crater was the same, with an E-W diameter of ~170 m, while the height of the vertical E wall was 46 m. Attempts to measure CO2 and SO2 concentrations inside the crater on 27 January 2002 were unsuccessful because the gas concentrations were below the detection limits of the Dräger tubes (10 ppm SO2 and 0.5% CO2).

Activity during February 2002. During a 14-19 February 2002 stay on Erta Ale by a team that included Roberto Carniel and Jürg Alean (Stromboli Online), the lava lake was active and produced spectacular fountains of lava. The lake level oscillated by several meters during their observation period. Seismic measurements were conducted along with thermal and video recordings of the lake.

Activity during April 2002. During 12-21 April 2002 a group from SVG led by Franck Pothé and Evelyne Pradal visited the volcano and reported significant changes in the morphology and activity of the lava lake since January 2002. The level of the lake had risen ~15 m and its surface area had decreased by ~33%. Over a 36-hour period the level varied intermittently by 1-2 m, the variation sometimes occurring within several minutes. Activity on the lake was intense, with continuous degassing and small lava fountains ~15 m high.

Activity during November-December 2002. A German group from Volcano Expeditions International visited the volcano during November-December 2002. They reported that the S crater was ellipsoidal with dimensions of ~130 m N-S and ~160 m E-W (figure 10). The lava lake occupied about half of the crater, and the lake surface was ~90 m below the W rim of the S pit. The remaining area in the E was covered by basalt that had a terrace ~45 m below the crater rim (figure 10). Previous observations had located the terrace at ~70 m below the rim. It was widely covered with talus; hence, the lava lake must had risen up to the present terrace level between spring 2002 and this visit. Almost no talus was found on the terrace, indicating that the lava cover was not old. Lava fountaining up to 20 m high occurred mainly in the W, S, and center areas of the crater lake. GPS measurements were used to accurately map part of the caldera rim and locate some key points (figure 11).

Figure (see Caption) Figure 10. A sketch map (top) and E-W cross-section (bottom) of the active S crater at Erta Ale on 4 December 2002.Courtesy of C. Weber.
Figure (see Caption) Figure 11. Partial survey of the Erta Ale caldera measured using a 12-channel GPS receiver. GPS reception was excellent due to the exposed nature of Erta Ale, where signals are shaded only when the receiver is close to the caldera wall inside the caldera. The GPS point HAK is the climbing location at 13.60402°N, 40.66401°E, and elevation 563.0 m. The highest point was a hornito on the N caldera rim, location HNN, at 13.60829°N, 40.66222°E, elevation 594.9 m. Courtesy of Lothar Fritsch.

Several earthquakes were felt during the visit. No seismic equipment was present, but five events were felt on 4 and 5 December 2002. No significant change in the lava lake was noticed during these events. Strong fumarolic activity was observed inside and outside the NW crater as well as on the outside of the caldera rim. The surface near the crater rim was broken by cracks in concentric circles, and the crater walls were formed of very unstable material. On 6 December three large rockfalls from crater wall collapses occurred along ~50 m of the crater wall circumference within a few minutes. About 40 m of the wall height collapsed with an estimated average thickness of 10 m, thus ~20,000 m3 of material slid into the lake, creating a large cloud of orange-brown dust that filled the pit and generated large amounts of Pélé's Hair.

Activity during January 2003. French teams from Terra Incognita visited the summit on 4 and 13-14 January 2003. The ~120 m long by 80 m wide lava lake was still in the W portion of the S pit crater; its surface was ~100 m below the crater rim (figure 12). The new platform, located ~50 m below the rim, was in the E part of the crater and covered ~25% of the crater floor. Gas emissions were abundant, and were assumed to be rich in SO2 based on their blue color and strong odor. The lava lake exhibited convection and lava fountains.

Figure (see Caption) Figure 12. Sketch map and cross-section of the Erta Ale lava lake, January 2003. Courtesy of Jacques-Marie Bardintzeff and Franck Pothé.

Geologic Background. The Erta Ale basaltic shield volcano in Ethiopia has a 50-km-wide edifice that rises more than 600 m from below sea level in the Danakil depression. The volcano includes a 0.7 x 1.6 km summit crater hosting steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera usually also holds at least one long-term lava lake that has been active since at least 1967, and possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: P. Vetsch, Marc Caillet, Steven Haefeli, and Pierre-Yves Burgi, Société de Volcanologie Genève (SVG), PO Box 6423, CH-1211 Geneva 6, Switzerland (URL: http://www.volcan.ch/); Jürg Alean, Stromboli Online, Rheinstrasse 6, CH-8193 Eglisau, Switzerland (URL: http://www.swisseduc.ch/stromboli/); Christoph Weber and Lothar Fritsch, Volcano Expeditions International (VEI), Muehlweg 11, 74199 Untergruppenbach, Germany; Jacques-Marie Bardintzeff, Université Paris-Sud, F-91405 Orsay, France; Franck Pothé, Terra Incognita, CP 701, 36 quai Arloing 69256 Lyon Cédex, France.


Guntur (Indonesia) — April 2003 Citation iconCite this Report

Guntur

Indonesia

7.143°S, 107.841°E; summit elev. 2251 m

All times are local (unless otherwise noted)


Increased seismicity since December 2002

During December 2002, the Volcanological Survey of Indonesia (VSI) reported that activity at Guntur was higher than normal. As a result, the Alert Level was raised to 2 (on a scale of 1-4). No plume was observed, but deep and shallow volcanic earthquakes were registered, as well as tectonic earthquakes, through at least mid-May 2003. Tremor was also reported occasionally (table 1). On 28 December a "white ash plume around Guntur crater and Kabuyutan crater reached 3 m high." No ashfall was reported. The temperature at Guntur crater was 79.7°C and at Kabuyutan was 92.7°C. EDM deformation measurements taken on 22 November, 14 December, and 28 December 2002 revealed 11 cm of inflation. On 13 January 2003, an earthquake (MM 2-3) was felt in surrounding areas. Elevated tremor was noted during the first week of April 2003. Guntur remained at Alert Level 2 throughout mid-May.

Table 1. Seismicity at Guntur during 1 December 2002-18 May 2003. Courtesy of VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Tectonic
01 Dec-08 Dec 2002 8 8 19
09 Dec-15 Dec 2002 5 12 23
16 Dec-22 Dec 2002 2 6 16
23 Dec-29 Dec 2002 -- 5 14
30 Dec-05 Jan 2003 8 24 15
06 Jan-12 Jan 2003 3 6 12
13 Jan-19 Jan 2003 2 11 12
20 Jan-26 Jan 2003 3 23 20
27 Jan-02 Feb 2003 5 5 22
03 Feb-09 Feb 2003 5 4 11
10 Feb-16 Feb 2003 4 5 22
17 Feb-23 Feb 2003 3 11 17
24 Feb-02 Mar 2003 6 4 19
03 Mar-09 Mar 2003 3 10 30
10 Mar-16 Mar 2003 4 5 20
17 Mar-23 Mar 2003 1 3 28
24 Mar-30 Mar 2003 4 4 24
31 Mar-06 Apr 2003 13 6 23
07 Apr-13 Apr 2003 5 2 17
14 Apr-20 Apr 2003 3 3 22
21 Apr-27 Apr 2003 6 3 31
28 Apr-04 May 2003 4 2 18
05 May-11 May 2003 2 -- 24
12 May-18 May 2003 3 1 19

Geologic Background. Guntur is a complex of several overlapping stratovolcanoes about 10 km NW of the city of Garut in western Java. Young lava flows, the most recent of which was erupted in 1840, are visible on the flanks of the erosionally unmodified Gunung Guntur, which rises about 1550 m above the plain of Garut. It is one of a group of younger cones constructed to the SW of an older eroded group of volcanoes at the NE end of the complex. Guntur, whose name means "thunder," is the only center with recorded activity, with eruptions since the late-17th century. Although it produced frequent explosive eruptions in the 19th century, it has not erupted since.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Kikai (Japan) — April 2003 Citation iconCite this Report

Kikai

Japan

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

All times are local (unless otherwise noted)


Eruption plumes and ashfall during 24 May-5 June 2002

According to a Japanese Meteorological Agency (JMA) report on 6 June 2002, discolored plumes associated with volcanic tremor had intermittently issued from Kikai since 11 May 2002. The U.S. Air Force Weather Agency reported that plumes emanating from Satsuma-Iwo-jima (an island forming part of the NW caldera rim of Kikai) were visible on satellite imagery during 24-28 May and 1-4 June 2002. The thin plumes drifted to the S, SE, and E during May, and were estimated to be lower than 3 km altitude. Ash was seen from the island of Yaku-shima on the afternoon of 26 May. JMA noted that the number of small volcanic earthquakes increased after 29 May. The JMA report also stated that discolored plumes were observed from Mishima village in the Ryukyu Islands, and that ash fell on residential areas, during 3-5 June 2002.

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: Naokuni Uchida, Japan Meteorological Agency (JMA), Fukuoka, Japan (URL: http://www.jma.go.jp/); Volcano Research Center, Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Charles Holliday, U.S. Air Force Weather Agency, 106 Peacekeeper Drive, Ste 2NE, Offut AFB, NE 68113-4039, USA (URL: http://www.557weatherwing.af.mil/).


Miyakejima (Japan) — April 2003 Citation iconCite this Report

Miyakejima

Japan

34.094°N, 139.526°E; summit elev. 775 m

All times are local (unless otherwise noted)


Small explosion in November 2002; continued high SO2 flux through April 2003

Miyake-jima has remained restless since the eruption that began in June 2000 (BGVN 25:05-25:07, 25:09, 26:02, 27:03, and 27:11). Small explosions with minor ash emission have been common (see BGVN 27:11). The most recent event reported by the Japan Meteorological Agency was at about 1320 on 24 November 2002, with the plume rising to an unknown height. The SO2 gas output remained high, ~4,000-9,000 tons/day, as of March 2003 (figure 19). Robust degassing was ongoing through the week of 16-22 April 2003. All residents on Miyake-jima island have been evacuated since September 2000, after which time SO2 fluxes reached extremely high values (over 80,000 tons/day in October 2000).

Figure (see Caption) Figure 19. SO2 flux at Miyake-jima during August 2000-March 2003. Triangles along the timeline indicate explosions. Courtesy of the Geological Survey of Japan and the Japan Meteorological Agency.

Geologic Background. The circular, 8-km-wide island of Miyakejima forms a low-angle stratovolcano that rises about 1,100 m from the sea floor in the northern Izu Islands about 200 km SSW of Tokyo. The basaltic volcano is truncated by small summit calderas, one of which, 3.5 km wide, was formed during a major eruption about 2,500 years ago. Numerous craters and vents, including maars near the coast and radially oriented fissure vents, are present on the flanks. Frequent eruptions have been recorded since 1085 CE at vents ranging from the summit to below sea level, causing much damage on this small populated island. After a three-century-long hiatus ending in 1469 CE, activity has been dominated by flank fissure eruptions sometimes accompanied by minor summit eruptions. A 1.6-km-wide summit crater was slowly formed by subsidence during an eruption in 2000.

Information Contacts: Akihiko Tomiya, Geological Survey of Japan, AIST, 1-1 Higashi, 1-Chome Tsukuba, Ibaraki 305-8567, Japan (URL: http://staff.aist.go.jp/a.tomiya/tomiyae.html); Japan Meteorological Agency (JMA), Fukuoka, Japan (URL: http://www.jma.go.jp/).


Niuafo'ou (Tonga) — April 2003 Citation iconCite this Report

Niuafo'ou

Tonga

15.6°S, 175.63°W; summit elev. 260 m

All times are local (unless otherwise noted)


Fumarolic and hot spring activity in the caldera during October 2002

Niuafo'ou is Tonga's most active volcano with at least 10 periods of activity, both explosive and effusive, since the early 1800s. The most recent period of activity in 1946 (Taylor 1999) resulted in the complete evacuation of the island. This volcanic center, ~450 km N of Tongatapu, is an isolated volcanic island located in the N-central Lau Basin (figure 4). In May 1999 a vent was producing hot water and H2S, and dead fish were observed near the vent (BGVN 26:05). Paul W. Taylor visited the volcano in October 2002 and noted fumarolic activity in two areas of the central caldera. On 20 October fumarolic and hot spring activity was noted in the NE part of the caldera.

Figure (see Caption) Figure 4. Locality map of the Lau Basin region, showing the location of Niuafo'ou. The symbols indicate centers with recorded eruptions (circles with stars); centers with no recorded activity (black stars); and probable submarine centers (white stars). Bathymetric contours are in kilometers. Courtesy of Paul Taylor.

Form and structure. Niuafo'ou is a subaerial shield volcano formed by submarine explosive and effusive activity during the Holocene. The island is approximately 8 km in diameter with a central caldera ~4 km in diameter with two lakes, Vai Lahi and Vai Si'i (figures 5 and 6). Periods of explosive activity have formed several small cinder cone complexes within the caldera. A detailed description of the geological features of Niuafo'ou is provided in Taylor (1991). Niuafo'ou rises to a height of 213 m above sea level at a point on the N rim of the caldera, a point known to the Niuafo'ouans as Piu Ofahifa.

Figure (see Caption) Figure 5. Geological map of Niuafo'ou (after Taylor, 1991) showing the major features of the island. Courtesy of Paul Taylor.
Figure (see Caption) Figure 6. Photograph of Niuafo'ou looking approximately W across the caldera. Both caldera lakes, Vai Lahi (background) and Vai Si'i (foreground) are visible. Courtesy of Paul Taylor.

Activity during October 2002. During a visit to Niuafo'ou in October 2002 to conduct a series of community workshops, it was noted that fumarolic activity was occurring in two areas of the central caldera. On 14 October Cecile Quesada (a French anthropologist) and Chris Simard visited the Vai Kona and Vai Sulfa areas along the S edge of the caldera (figure 6) and observed continued activity at the site. On 20 October, Taylor, Alejandra Meija-restrepo, Quesada, and Simard visited the Vai Si'i area in the NE part of the caldera and observed continued fumarolic and hot spring activity.

Vai Kona/Vai Sulfa Area. The Vai Kona/Vai Sulfa area of Niuafo'ou has been the site of persistent fumarolic and hot spring activity for many years. Activity was reported in 1958 (Richard, 1962) and again during 1982-83 and 1984 (Taylor, 1991). The level of Vai Kona fluctuates periodically. When Quesada and Simard visited the site on 14 October 2002, areas of persistent activity were observed.

Activity at Vai Kona was concentrated along the S shores of the lake (figure 7). Quesada and Simard observed numerous active vents on the floor of the lake, with large quantities of bubbles reaching the surface. The water temperature was estimated to be 25-30°C. Thick dark mud was present on the bottom of the lake and the temperature of the mud around the vents was estimated to be 35-40°C. Several active hot springs were also observed along the W shore of Vai Kona. These observations suggest that activity at the site has intensified since observed in 1958 and 1983.

Figure (see Caption) Figure 7. Niuafo'ou Island showing the location of fumarolic activity observed during October 2002. Courtesy of Paul Taylor.

Vai Sulfa occupies a small depression W of the southern end of Vai Kona (figure 7). The entire feature covers an area of about 30 m2 and consists of two sections. The W part of the depression is occupied by a small lake, while the E section is dry. At the center of this dry area is a vent ~40 cm across and 20-30 cm deep filled with mud and leaves. When leaves were removed from the hole during the visit it began to fill with water, and a boiling sound was heard. Extensive deposits of sulfur existed around the entire depression, and a strong smell of sulfur was present. Similar activity was also occurring when Quesada and Simard visited the area during July and September 2001. However, activity was less intense at those times.

Vai Si'i Area. A new site of fumarolic activity was first reported during May 1999 and observed during June 1999 (BGVN 26:05). When the site was visited on 20 October the focus of activity had moved to an area along the E shore of Vai Si'i. Numerous vents were present on the floor of the lake along the shoreline. The affected area stretched along the shoreline for ~25-30 m from where the vents were concentrated (figure 7). Active vents were aligned along the shoreline. Although the temperature of the lake water was an estimated 30°C (the prevailing air temperature), the temperature just below the surface of the sediment around the vents had increased to an estimated 65-75°C.

The vents were producing gas that was bubbling to the surface. A strong sulfur smell was noted, and large deposits of sulfur were present in the mud that comprised the floor of the lake around the vents. The deposits formed three elongated lobes that stretched S from the vents. The lobe-like distribution was probably the result of wind-induced currents. Vegetation along the shoreline was dead and encrusted with white sulfur (?). The observations suggests a net increase in activity at the Vai Si'i site since June 1999.

Conclusions. The observed fumarolic activity on Niuafo'ou indicates that the volcanic system is still active. Although not widespread, the fumarolic manifestations observed during 1999-2002 probably represent a net increase in the activity of the system since the last eruption in 1946. At this stage the level of activity is not of concern, but it should be monitored for signs of increase.

References. Richard, J.J., 1962, Kermadec, Tonga and Samoa: Catalogue of Active Volcanoes of the World, part 13.

Taylor, P.W., 1991, The Geology and Petrology of Niuafo'ou Island, Tonga: Subaerial Volcanism in an Active Back-arc Basin: Unpublished MSc thesis, Macquarie University, AVI Occasional Report, No. 91/01.

Taylor, P.W., 1999, The 1946 Eruption of Niuafo'ou: AVI Occasional Report, No. 99/03.

Geologic Background. Niuafo'ou ("Tin Can Island") is a low 8-km-wide island that forms the summit of a largely submerged basaltic shield volcano in the north central Lau Basin about 170 km W of the northern end of the Tofua volcanic arc. The circular island encloses a 5-km-wide caldera that is mostly filled by a lake whose bottom extends to below sea level. The inner walls of the caldera drop sharply to the lake, named Big Lake (or Vai Lahi), which contains several small islands and pyroclastic cones on its NE shore. Eruptions recorded since 1814, mostly from circumferential fissures on the west-to-south side of the island, have often damaged villages. A major eruption in 1946 forced evacuation of most of its 1,200 inhabitants.

Information Contacts: Paul W. Taylor, Australian Volcanological Investigations, PO Box 291, Pymble, NSW 2073 Australia.


Semeru (Indonesia) — April 2003 Citation iconCite this Report

Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Continued ash explosions, with frequent lava avalanches and pyroclastic flows

At Semeru, the end of December 2002 was characterized by high numbers of explosions and pyroclastic flows (BGVN 27:12). The 29 December pyroclastic flow at Besuk Bang (figures 11 and 12) traveled ~9 km from the summit. During January through 23 March 2003, the Volcanological Survey of Indonesia (VSI) reported that seismicity was dominated by explosions and avalanches (table 11). A "white-gray ash" column rose 300-700 m above the summit. Activity was especially high during 1-12 January, when tens of ash explosions were visually observed per week (figures 13 and 14). Continuous tremor occurred on 8 January, with an amplitude of 11-12 mm. The Alert level remained at 2.

Figure (see Caption) Figure 11. The edge of 29 December 2002 Semeru pyroclastic-flow deposit at Besuk Bang in January 2003. This pyroclastic flow extended ~ 9 km from the summit. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).
Figure (see Caption) Figure 12. Boulders from the Semeru pyroclastic-flow deposit at Besuk Bang around December 2002-January 2003. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).

Table 11. Summary of weekly seismicity at Semeru during 1 January-23 March 2003. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Explosions Avalanches Tremor earthquakes Pyroclastic flows
01 Jan-05 Jan 2003 -- 4 354 89 7 0
06 Jan-12 Jan 2003 -- -- 382 84 38 1
13 Jan-19 Jan 2003 -- 1 554 89 7 0
20 Jan-26 Jan 2003 1 2 641 50 15 0
27 Jan-02 Feb 2003 18 -- 739 84 9 3
03 Feb-09 Feb 2003 2 -- 777 58 9 14
10 Feb-16 Feb 2003 3 4 641 53 13 5
17 Feb-23 Feb 2003 4 9 700 105 10 9
24 Feb-02 Mar 2003 6 -- 629 33 8 10
03 Mar-09 Mar 2003 -- 4 794 18 4 0
10 Mar-16 Mar 2003 2 -- 550 89 20 21
17 Mar-23 Mar 2003 -- -- 563 57 9 13
Figure (see Caption) Figure 13. View toward the summit of Semeru looking NW from G. Sawur (observatory post) around December 2002-January 2003. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).
Figure (see Caption) Figure 14. Eruptive plumes rise from two different vents at the summit of Semeru around December 2002-January 2003. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).

Lava avalanches in January 2003 extended up to 750 m from the crater rim and sometimes entered the Besuk Kembar river. One pyroclastic flow traveled 1,500 m and also entered Besuk Kembar. Pyroclastic flows were more numerous in February, travelling between 2.5 and 4 km from the summit into the Besuk Bang drainage. Lava avalanches were continuous during 17-23 February towards Besuk Kambar. Several pyroclastic flows in March moved toward Besuk Bang (up to 4 km long) and Besuk Kembar (up to 2 km long).

Infrared satellite data, January 2001-March 2003. Between January 2001 and March 2003, MODIS detected quasi-continuous thermal alerts at Semeru (figure 15). During January 2001-March 2002, the anomalies were characterized by 1-2 alert-pixels with a maximum alert ratio of -0.567 (4 May 2001). The Darwin VAAC reported ash plumes and clouds on several occasions throughout this period, and VSI reported numerous seismic events representing explosions and other phenomena (BGVN 26:08).

Figure (see Caption) Figure 15. MODIS thermal alerts on Semeru during January 2001-March 2003. Thermal alerts collated by Diego Coppola and David Rothery; data courtesy of the Hawaii Institute of Geophysics and Planetology's MODIS Thermal Alert Team.

From April 2002 until the end of the year, MODIS thermal alerts for Semeru increased in frequency and magnitude. This period was characterized by continuous explosions, avalanches and pyroclastic flows, and is related to seismicity increases beginning in March 2002 that prompted VSI to raise the Alert Level to 2 (BGVN 27:06). Thermal alerts reached a maximum amplitude on 16 August (two alert pixels with a maximum alert ratio of -0.364) and 1 September (one alert pixel with alert ratio of -0.389). VSI reported that seismic activity was higher than normal during June-September 2002 (BGVN 27:09), and the explosions produced plumes that reached 300-500 m above the crater. Observers reported that lava avalanches traveled toward the Besuk Kembar river to distances of ~750 m from the crater rim, and an ash explosion ejected glowing material ~150 m toward the upper Besuk Kembar drainage. Center coordinates of alert pixels were concentrated in four adjacent pixels close to Semeru's summit, especially on the S side.

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

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Diego Coppola and David A. Rothery, Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK. Thermal alerts courtesy of the HIGP MODIS Thermal Alerts Team (URL: http://modis.higp.hawaii.edu/).


Soufriere Hills (United Kingdom) — April 2003 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Continued dome growth, rockfalls, and pyroclastic flows

During 1 March through 2 May 2003, the dome continued to grow, producing numerous rockfalls and moderate pyroclastic flows. Most activity was concentrated on the northern flanks, producing numerous pyroclastic flows in White's Ghaut, the Tar River Valley, and Tuitt's Ghaut. Pyroclastic flows and rockfalls traveled down all flanks of the dome at some time during the period. On 20 March, the greatest dome height recorded to date was measured, 1,098 m. A prominent extrusive lobe was established on the E and SE sides of the summit at the beginning of April. On 22 April, a large spine, inclined to the E, was observed on the summit, the top of which was at an elevation of 1,163 m.

The Washington VAAC issued notices daily to the aviation community regarding ash clouds emanating from the summit. Seismicity during the report period was dominated by rockfalls (table 44). Average daily SO2 emission rates varied throughout the report period (table 45) with a low of 31 tons/day on 25 March to a maximum of 1,550 tons/day on 1 May.

Table 44. Summary of weekly seismicity at Soufrière Hills during 28 February 2003-2 May 2003. Courtesy MVO.

Date Rockfall Hybrid Long-period Long-period / Rockfall Volcano-tectonic
28 Feb-07 Mar 2003 997 0 79 71 4
07 Mar-14 Mar 2003 1050 5 87 108 0
14 Mar-21 Mar 2003 1050 2 93 152 2
21 Mar-28 Mar 2003 1097 16 99 138 7
28 Mar-04 Apr 2003 754 7 74 101 2
04 Apr-11 Apr 2003 332 1 66 77 --
11 Apr-18 Apr 2003 393 7 72 56 --
18 Apr-25 Apr 2003 966 4 83 88 1
26 Apr-02 May 2003 813 4 168 121 1

Table 45. Average daily SO2 emission rates at Soufrière Hills during 28 February 2003-2 May 2003. Courtesy MVO.

Date SO2 emissions (tons/day)
28 Feb 2003 1020
28 Feb-07 Mar 2003 500-1020
07 Mar-14 Mar 2003 220-355
14 Mar-21 Mar 2003 285-380
21 Mar-28 Mar 2003 31-497
25 Mar 2003 31
28 Mar-04 Apr 2003 230-770
04 Apr-11 Apr 2003 151-780
06 Apr 2003 151
11 Apr-18 Apr 2003 220-550
18 Apr-25 Apr 2003 450-550
25 Apr-02 May 2003 390-1550
01 May 2003 1550

Throughout the period, access to all areas S of the Belham Valley, to Waterworks, Happy Hill, Lower Friths and Old Towne, and to Bramble airport and beyond was prohibited and a maritime exclusion zone around the S part of the island extended 3.7 km beyond the coastline from Trant's Bay in the E to Lime Kiln Bay on the W coast.

Activity during March 2003. Activity remained at levels similar to that of the previous few weeks (BGVN 28:02), with continued dome growth and moderate pyroclastic-flow activity. Lava extrusion was accompanied by rockfall activity and pyroclastic flows that were focused, during 1-7 March, on the NE and N slopes and valleys. Pyroclastic flows occurred most frequently in Tuitt's Ghaut with a few on Farrell's Plain with run-out distances up to 1 km.

During 8-14 March, rockfalls and pyroclastic flows occurred down all flanks. Dome growth continued and lava extruding into the center of the summit dome complex continued to increase the dome height. Dome glow at night was spectacular in the Tar River Valley and on the NW in Tuitt's Ghaut and the N talus slopes. Small rockfalls and pyroclastic flows occurred infrequently on the W flank and at the top of Gage's Valley. Ash venting was continuous in the summit area.

Lava extrusion during 15-21 March formed a series of spines and ridges. Theodolite measurements on 20 March indicated a dome height of 1,098 m, the highest recorded to date. Activity was dominated by rockfalls and pyroclastic flows mainly in the Tar River Valley, with several small pyroclastic flows in White's and Tuitt's Ghaut and one observed in the upper part of Tyre's Ghaut on 20 March. Ash venting continued.

Dome growth continued through the end of the month. Rockfalls and pyroclastic flows spilled off the active summit in a broad arc extending from the S around the E flanks to the NW. Most activity was towards the NE, with pyroclastic flows in the Tar River Valley and small flows on the N flanks of the dome in White's Ghaut, Tuitt's Ghaut, the upper reaches of Tyre's Ghaut and on Farrell's Plain. Most volcano-tectonic earthquakes (see table 44) occurred in a small swarm late in the evening of 25 March. On the same day, following a brief, intense rainstorm, a 4-5 hour period of increased pyroclastic-flow and rockfall activity occurred on the N and NW flanks of the dome. Observation flights on 27-28 March indicated that rockfalls and small pyroclastic flows were spilling onto the S flanks of the dome.

Activity during April 2003. A prominent extrusive lobe was established on the E and SE sides of the summit at the beginning of April and a large vertical spine, extruded at the back of this lobe on the night of 1-2 April, was the highest point on the dome. During 1-12 April, rockfalls and pyroclastic flows occurred mainly on the E side of the dome in the Tar River Valley. Rockfall activity also continued on the S side of the dome and some pyroclastic flows occurred on the NE flanks in White's Ghaut and Tuitt's Ghaut, and on the NW flank; several of the latter flowed into the upper reaches of Tyre's Ghaut. On 10 April torrential rainfall produced mudflows in the Belham River and triggered pyroclastic flows on the E, N, and NW flanks of the dome.

Helicopter observations during 15 April indicated that the lobe extrusion continued on the ESE side of the dome summit above the Tar River Valley. Vigorous gas venting also was observed on the S side of the summit during this flight. Rockfall and pyroclastic-flow activity occurred throughout the week of 12-18 April on the E and SE sides of the dome with some rockfall activity on the N flanks. On 15 April a small pyroclastic flow occurred in the upper part of Tyre's Ghaut.

On 22 April a large spine was observed on the dome summit, positioned slightly S of the center and inclined at a high angle towards the E. The top of the spine was at an elevation of 1,163 m as compared to the ~1,090 m height of the general summit region of the dome. During 19-25 April, most of the rockfall and pyroclastic-flow activity occurred on the E and SE flank of the dome in the Tar River Valley. A few flows occurred to the NE in White's Ghaut and Tuitt's Ghaut, and to the N and NW onto Farrell's Plain and into the top of Tyre's Ghaut. Observations on 22 April indicated that rockfall debris was starting to spill S into the White River area. On 23 April several large rockfalls were observed on the W side of the dome in the Gages area.

During the last week of April, the prominent spine seen on the summit of the dome the previous week had partly disintegrated. Most of the rockfalls and pyroclastic flows into the Tar River Valley began along the face of the well-developed extrusion lobe present on the ESE side of the summit region. Rockfall debris spilled off the S side of the lobe into the upper reaches of White River, and some flows occurred towards the NE in White's Ghaut and Tuitt's Ghaut, and towards the N and NW on the top of Farrell's Plain and in the top of Tyre's Ghaut. Vigorous pulses of ash-venting occurred on the summit throughout this week.

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), Mongo Hill, Montserrat, West Indies (URL: http://www.mvo.ms/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/).


Stromboli (Italy) — April 2003 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Strong explosion on 5 April covers much of the summit in pyroclastic deposits

On the morning of 5 April, scientists from INGV-CT were conducting a daily helicopter flight with a portable thermal camera, surveying the active lava flow field on the upper sector of the Sciara del Fuoco, above a flat zone at the base of the 28 December 2002 eruptive fissure. Three vents along this surface were feeding small lava flows, and the summit craters were producing a very diluted gas cloud. A few minutes after the start of the survey, which began about 0900, the gas plume from the craters being blown W was suddenly crossed by a reddish ash emission, which was interpreted as resulting from further collapses within the craters. However, the red ash was soon replaced by darker juvenile material coming from Crater 1 (the NE crater) that formed a hot jet with a cauliflower shape rapidly growing above the crater. A few seconds later, Crater 3 also produced a hot jet of juvenile material. Data from the seismic network confirmed that the explosion began at 0912.

The eruptive process then evolved very rapidly, with jets from craters 1 and 3 joining together. A very powerful explosion pushed the helicopter away from the crater. A mushroom-shaped dark cloud rose from the craters, expanding vertically to an altitude of ~2 km, 1 km above the volcano's summit (figure 73). The eruptive cloud was surrounded at its base by a dark-gray cloud, while it was still expanding vertically and assuming the mushroom shape. Bombs, ash, and blocks fell on the NE flank above 400 m elevation, burning vegetation. Most of the ejecta drifted W, falling on Ginostra (~1.5 km from the summit) and destroying two houses; no people were injured.

Figure (see Caption) Figure 73. Photograph of the expanding eruption plume at Stromboli on 5 April 2003. Courtesy of INGV.

Continuing the helicopter survey after the eruption, observers saw that the lava-flow field on the upper Sciara del Fuoco was completely covered by a brown carpet of debris ejected from Crater 1 during the initial phase of the event. A thick steam cloud rose above the debris due to vaporization from the wet material by the underlying lava flows. Meanwhile, several alternating black and reddish pulses occurred, mainly from Crater 3. Several fingers of light-brown debris were expanding from the NW flank of Crater 1 along the mid-section of the Sciara del Fuoco. The upper part of the volcano above 700 m elevation was completely covered by pyroclastic products. Within a few minutes after the start of the eruption, the upper Sciara del Fuoco had active flows emerging from the layer of debris covering the lava-flow field. The explosive event caused abundant emission of pumice mixed with small brown scoria. The pumice contained small crystals and was very vesiculated. Lithic fragments of lava with light-gray groundmass and centimeter-sized crystals of pyroxene were common in the pumice.

A helicopter survey on 8 April showed four active vents pouring lava onto the upper Sciara del Fuoco at 590 m elevation. Two of the flows were expanding along the middle Sciara del Fuoco, causing detachment of blocks from the flow front and small rockfalls that reached the sea. Within the summit craters a thick layer of debris had accumulated following the event of 5 April.

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

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).


Suwanosejima (Japan) — April 2003 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Ash explosions in September and December 2002, and activity in January 2003

Though the volcano had been relatively quiet since 26 August 2002 (BGVN 27:07), the Japan Meteorological Agency reported that explosive eruptions became frequent on the morning of 12 September 2002. Rumbling was heard intermittently at a location ~4 km SSW of the summit, and light ashfall was observed on 12 September. Explosions occurred at 0816, 1246, 1746, and 1754 on 12 September, and at 0853, 1016, and 1027 on 13 September.

A pilot report contained in the Kagoshima Airport weather observation issued at 1000 on 5 December 2002 noted a plume estimated to be between 900 and 1,200 m altitude. The U.S. Air Force Weather Agency noted that the plume was also seen on DMSP (Defense Meteorological Satellite Program) imagery at 1034 and on NASA Terra MODIS imagery at 1055 on 5 December.

The REAL-Volc Project at the Volcano Research Center, Earthquake Research Institute, University of Tokyo, has detected several thermal anomalies on Suwanose-jima since they started an AVHRR monitoring system in 2001. Anomalies were seen on 11 October 2001, 20 November 2001, 30 December 2001, 20 April 2002, and 12 January 2003.

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: Naokuni Uchida, Japan Meteorological Agency (JMA-Fukuoka Center), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: http://www.jma.go.jp/); Takayuki Kaneko, Volcano Research Center, Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Charles Holliday, U.S. Air Force Weather Agency, 106 Peacekeeper Drive, Ste 2NE, Offut AFB, NE 68113-4039, USA (URL: http://www.557weatherwing.af.mil/).

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