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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 33, Number 05 (May 2008)

Managing Editor: Richard Wunderman

Azul, Cerro (Ecuador)

Eruption (29 May-11 June 2008) of lava in caldera and from fissures on SE side

Chaiten (Chile)

Widespread rhyolitic ash; a dome then a tephra cone; destructive lahars

Etna (Italy)

6-km-long lava flow; ash emissions; 13 May 2008 opening of a new eruptive fissure

Home Reef (Tonga)

Pumice found on southeastern Papua New Guinea beaches

Kerinci (Indonesia)

Occasional steam plumes in 2007-2008; ash emission on 9 September 2007

Veniaminof (United States)

Minor ash bursts during February 2008



Cerro Azul (Ecuador) — May 2008 Citation iconCite this Report

Cerro Azul

Ecuador

0.92°S, 91.408°W; summit elev. 1640 m

All times are local (unless otherwise noted)


Eruption (29 May-11 June 2008) of lava in caldera and from fissures on SE side

Equador's Instituto Geofísico (IG) reported that Cerro Azul began to erupt late on the night of 29 May 2008. The report was based on satellite data, network seismic data, and eye-witness reports. In repose for 10 years (BGVN 23:08), this shield volcano forms the extreme SW end of the elongate island (figure 2). Cerro Azul contains a 4 x 5 km summit crater. The eruption from the SE flank (figure 3) prevailed during 29 May to 11 June and with few exceptions emitted lava flows with `a`a textured surfaces. The flows reached 2-3 km wide and up to 10 km long. Some lava also emerged from a vent in the NE wall of the caldera. Eruptions appeared to have ceased during 2 June, breaking the time line into two eruptive phases.

Figure (see Caption) Figure 2. Satellite radar interferometry (InSAR) maps showing line-of-sight (LOS) ground displacements in centimeters for Fernandina and Isabela islands. For Cerro Azul (and the volcanoes Darwin, Alcedo, and Sierra Negra) the InSAR data covered 6.4 years, 1992-1998. To produce the interferograms, the phase difference between radar echoes from two satellite passes is calculated. Index map shows the Galapágos islands (~ 1,000 km W of mainland Ecuador). Maps are from Amelung and others (2000).
Figure (see Caption) Figure 3. Annotated satellite image of Cerro Azul showing first-order estimates of fissure vents, the approximate margins of frequently complex flow fields, as well as eruption dates. The base image is from before the 2008 eruption. The 2008 flows generally followed similar routes as those during the SE-flank eruptions of 1978 and 1998. N is towards the top right; for scale, the distance from the crater rim to the sea directly W is ~ 8 km. Background image, Image Science and Analysis Laboratory, NASA-Johnson Space Center. Annotations and fieldwork by Andrés Gorki Ruiz, Patricio Ramón, and Nathalie Vigoroux.

The first eruptive phase involved a rapid emission of lava during 29 May-1 June. Outside the caldera, the eruptive fissures were oriented in directions either tangential (circumferential) or radial to the volcano's symmetry. During this first phase, on 30 May, lava also extruded inside the summit caldera (figure 3).

The second eruptive phase emitted lavas over nine days (3-11 June). The lavas escaped from a separate fissure at a lower elevation than the first and oriented radially ("fissura 3" on figure 3). The flatter terrain near fissure 3 led to lavas forming an equant flow field. This contrasted with the first-phase lavas, which erupted on higher, steeper ground where they developed elongate distribution patterns.

A seismic station in the Galapagos (PAYG) suggested that activity began at 2143 hours on 29 May (local time). Signal amplitude emerged slowly at first (figure 4). Starting about an hour after that and for the next 7 hours the station registered 40 earthquakes near Cerro Azul.

Figure (see Caption) Figure 4. Seismic data portraying Cerro Azul's earthquakes and eruption. The left panel shows a map of the islands and station PAYG to the E, where the large dot (left) represents an epicenter near the caldera. The right panel shows the seismic traces associated with the initial signals associated with the eruption (upper is orthogonal horizontal and the lower, vertical). The vertical line at left represents 03:43:12 local time on 30 May. Courtesy of IG.

The largest, M ~ 3.7, took place at 0051 on 30 May (local time), centered in the N caldera at shallow depth. Satellite thermal anomalies measured by MODIS/ MODVOLC showed a hot spot on the S flank at 2300 (local time). At the same time a red glow was observed in the direction of the volcano from Puerto Villamil, the capitol of Isabela Island ~ 50 km E.

According to IG, a satellite image from a Volcanic Ash Advisory Center (VAAC) showed an emission column at 0715 on 30 May 2008, probably with a low ash content, extending 140 km NW from the volcano. On the morning of 31 May, a white plume ~ 2 km high, with no visible ash, could be seen rising above the cloud cover from a point on the coast SE of the eruption site. Cloud cover then prevented further observation of the plume.

Vent areas. Aerial images taken by scientists of the Galápagos National Park on 30 May 2008 between 1400 and 1600 revealed an absence of radial fissures at that time. Lava from the higher elevation circumferential vents covered the area located at ~ 1 km elevation. Fissures 1 and 2 were therefore thought to have formed sometime between the afternoon of 30 May and morning of 1 June.

IG reports indicated that in late May into early June field visits were made by Gorki Ruiz, Oscar Carvajal, Freddy Mosquera, and Nathalie Vigouroux (and possibly others). According to Dennis Geist, they encountered sometimes foggy conditions. They inspected the area of initial eruption from Cinco Cerros, and made some key observations (figure 3) and photographs (figures 5 and 6).

Figure (see Caption) Figure 5. Lava spewing from part of the uppermost fissure of Cerro Azul on 1 June 2008. Photo by IG.
Figure (see Caption) Figure 6. A view at Cerro Azul on 2 June 2008 looking W from 980 m elevation, showing the complexity of some of the flow fields in the vicinity. The foreground captures the rough-textured `a`a surface. Courtesy of Ruiz, IG.

Fissure 1 emitted multiple lava flows; some of these reached 15 m thick. Fissure 2 lay farther out on the SE flank in an area of lower slope.

The circumferential fissure emitted six separate lava flows, some up to 5 m thick. These descended rapidly down the SE flank. Scientists were able to visit the new lava flows at an elevation of ~ 1,100 m on 2 June 2008. One of the lava flows was thin (under 1 m) with variable plagioclase and minor amounts of olivine (or pyroxene) crystals. At ~ 1,000-m elevation the flows from the circumferential fissure were overlain by tephra and lava from the upper radial fissure (fissure 1). At this location, the slope of the terrain lessened and the morphology changed to more blocky `a`a. There, the flows piled up behind the flow front.

The size of the cones built up by lava fountaining on the upper radial fissure decreased with distance from the summit. The lowest cone, at ~ 800 m elevation, was under 5 m high and emitted a small pahoehoe flow that extended a few ten's of meters downslope, but with little to no tephra.

The onset of the second eruptive phase was reported in various ways. MODVOLC alerts and related thermal images showed new hot spots at the SE end of the volcano on 3 June. They later increased in intensity and migrated E. On the night of 4 June, observers at Cinco Cerros saw a red glow. Observers on a 4 June flight spotted fissure 3. As shown below, on 5 June a huge increase in MODIS thermal anomalies occurred.

When seen on 4 and 5 June, fissure 3 emitted a lava curtain hundreds of meters long. Aerial observations suggested the height of lava fountaining was ~ 60 m with large blocks also thrown that high. The venting fed a SE-directed lava flow. Owing to the relatively flat terrain found in the saddle between Cerro Azul and Sierra Negra volcanoes, the lava flow appeared to be progressing very slowly. Part of the new flow spread over portions of the 1998 flow. A plume ~ 50 km long moving N was visible from the airplane, as well as in satellite images.

Sulfur-dioxide fluxes. Simon Carn provided satellite information on sulfur dioxide (SO2) burdens measured from the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite (figures 7 and 8). The SO2 fluxes were measured once per day from 29 May to 8 June 2008. The map shown is for 31 May (UTC), the day with highest flux, ~ 35,000 tons/day. In general, the plumes blew SW from the source. The histogram (figure 7) indicates the daily SO2 fluxes emitted during this eruption period, with the highest flux on 31 May. Low fluxes occurred during 2-4 June, corresponding with the eruptive lull of 2 June.

Figure (see Caption) Figure 7. One of several available maps of sulfur dioxide (SO2) plumes measured from Aura/OMI satellite images. Data acquisition for this map occurred during 1930-2110 on 31 May UTC. Gray areas indicate regions where meteorological clouds may be obscuring the satellite view of the lower atmosphere. Courtesy of Simon Carn.
Figure (see Caption) Figure 8. Histogram showing daily sulfur dioxide (SO2) burdens measured by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite between 29 May and 8 June 2008 UTC. These burdens were calculated based on an assumed SO2 altitude of 3 km and should be considered preliminary estimates. Courtesy of Simon Carn.

Satellite thermal anomalies. The most recent previous eruption of the volcano took place in September 1998 (BGVN 23:08 and 23:09). In accord with the 10-year quiet period, thermal anomalies at Cerro Azul were absent at least as far back as 1 January 2000 and onward through 29 May 2008. The current eruption's anomalies appeared during 30 May-17 June 2008 (table 1) and were distributed broadly around lavas associated with fissure 3. There was a 90-pixel anomaly at 0420 on 5 June 2008; later that day there were only 5 pixels.

Table 1. MODVOLC thermal anomalies measured by MODIS instruments at Cerro Azul from 30 May through 17 June 2008. All anomalies were located E of the crater, with the farthest seen ~ 28 km due E. Courtesy of the Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System.

Date (UTC) Time (UTC) Number of pixels Satellite
30 May 2008 0500 6 Terra
30 May 2008 0755 12 Aqua
31 May 2008 0405 14 Terra
31 May 2008 0700 4 Aqua
31 May 2008 1625 5 Terra
01 Jun 2008 0445 9 Terra
01 Jun 2008 0745 14 Aqua
03 Jun 2008 0435 7 Terra
04 Jun 2008 0815 25 Aqua
04 Jun 2008 1600 8 Terra
05 Jun 2008 0420 90 Terra
05 Jun 2008 0720 41 Aqua
05 Jun 2008 1645 14 Terra
05 Jun 2008 1940 5 Aqua
06 Jun 2008 0505 1 Terra
07 Jun 2008 0410 3 Terra
09 Jun 2008 0355 2 Terra
09 Jun 2008 1620 2 Terra
10 Jun 2008 0440 17 Terra
10 Jun 2008 0735 5 Aqua
10 Jun 2008 1700 2 Terra
12 Jun 2008 0430 3 Terra
12 Jun 2008 0725 4 Aqua
14 Jun 2008 0415 1 Terra
14 Jun 2008 1935 1 Aqua
16 Jun 2008 0405 1 Terra
17 Jun 2008 0445 1 Terra
17 Jun 2008 0745 5 Aqua

Environmental concerns and a bathymetric map. According to Galapagos National Park officials on 3 June 2008 (as reported by Agence France-Presse, AFP) the lava did not affect the islands' famed giant tortoises. Isabela, the largest island in the archipelago, is home to rare and unique flora and fauna, including the Galapagos giant tortoise, which can reach more than 230 kg in mass and live more than 100 years. The Galapagos archipelago, which consists of about 30 islands, islets, and standing rocks, is a UNESCO World Heritage Site. In 2007, UNESCO declared the archipelago's environment in danger due to the increase of tourism and the introduction of invasive species. The archipelago has a population of ~ 40,000.

William Chadwick has merged all available datasets (as of 1994) for bathymetry in the Galápagos region. Cerro Azul sits adjacent a steep drop-off to the W, with water adjacent the shore reaching ~ 3.5 km depth. In contrast, much of the island cluster is on a broad shallow platform. Chadwick offers this compiled map on his website (see Information Contacts).

Reference. Amelung, F., Jónsson1, S., Zebker, H., and Segall, P., 2007, Widespread uplift and 'trapdoor' faulting on Galápagos volcanoes observed with radar interferometry: Nature, v. 407, p. 993-996 (26 October 2000).

Geologic Background. Located at the SW tip of the J-shaped Isabela Island, Cerro Azul contains a steep-walled 4 x 5 km nested summit caldera complex that is one of the smallest diameter, but at 650 m one of the deepest in the Galápagos Islands. The shield volcano is the second highest of the archipelago. A conspicuous bench occupies the SW and west sides of the caldera, which formed during several episodes of collapse. Youthful lava flows cover much of the caldera floor, which has also contained ephemeral lakes. A prominent tuff cone located at the ENE side of the caldera is evidence of episodic hydrovolcanism. Numerous spatter cones dot the western flanks. Fresh-looking lava flows, many erupted from circumferential fissures, descend the NE and NW flanks. Historical eruptions date back only to 1932, but Cerro Azul has been one of the most active Galápagos volcanoes since that time. Solfataric activity continues within the caldera.

Information Contacts: Andres "Gorki" Ruiz, Freddy Mosquera, and Patricio Ramón, Instituto Geofísico, Escuela Politécnica Nacional(IG), AP 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Nathalie Vigouroux, Department of Earth Sciences, Simon Fraser University, Burnaby, Canada; Oscar Carvajal, The Galápagos National Park Service, Isla Santa Cruz, Galápagos, Ecuador; Dennis Geist and Gorki Ruiz, Geological Sciences, Box 3022, University of Idaho, Moscow ID 83844; Simon Carn, Joint Center for Earth Systems Technology, University of Maryland Baltimore Campus (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250 (URL: http://so2.umbc.edu/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), 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/); William Chadwick, CIMRS, Oregon State University, NOAA/PMEL VENTS Program, Hatfield Marine Science Center, 2115 S.E. OSU Dr., Newport, OR 97365 (URL for map: https://www.pmel.noaa.gov/eoi/staff/chadwick/galapagos.html).


Chaiten (Chile) — May 2008 Citation iconCite this Report

Chaiten

Chile

42.8349°S, 72.6514°W; summit elev. 1122 m

All times are local (unless otherwise noted)


Widespread rhyolitic ash; a dome then a tephra cone; destructive lahars

[Chaitén began erupting] on the morning of 2 May 2008 (BGVN 33:04). This report discusses events through 30 May, in particular, summarizing reports ("Noticias") issued by Servicio Nacional de Geología y Minería (SERNAGEOMIN). News and other reports have variously stated 8,000-12,000 people evacuated.

Impacts of ashfall in Argentina also spurred a local government report (Anonymous, 2008) noting that the Argentine Atomic Energy Commission analyzed tephra (pumice and ash) from ashfalls in Argentina. Results established the tephra as a low-silica rhyolite (table 1).

Table 1. Major element analyses (ranges for four samples) from Chaitén's ash. The samples were all from Argentina, at or near the settlements of Corovado (120 km SE of the volcano), Trevelin and Esquel (~100 km E), and Epuyén (~120 km NE). The values presented are weight percent (with total Fe shown as Fe2O3). In general, low silica rhyolites are typically about 69-74% SiO2; high-silica rhyolites, about 75-84%SiO2. Values here were measured by Laboratorio de Geoquímica de la Comisión Nacional de Energía Atómica, Regional Cuyo (Anonymous, 2008).

Oxide Range (wt. %)
SiO2 71.80-73.30
Al2O3 13.50-14.35
Total Fe as Fe2O3 1.43- 1.85
CaO 1.00- 2.50
MgO 0.30- 0.60
Na2O 4.40- 4.60
K2O 3.15- 3.30
MnO 0.04
Total 99.33-99.92

News reports during May (and later) stated that ash in and over Argentina closed airports. Many flights were also cancelled.

Chaitén volcano is in southern Chile, at the S end of Patagonia's Lakes district (figure 3). The evacuated town of Chaitén (figure 4) served as the provincial capital of Palena. The town was home to about 4,000 people, but lahars have buried at least portions of it. That town was also the main jumping-off point for Pumalin Park, a new nature sanctuary funded by philanthropist Douglas Tompkins.

Figure (see Caption) Figure 3. Map showing Chaitén volcano and other Southern Volcanic Zone volcanoes in Chile. The large island to the west is Chiloé Island. The passage at the N end of Chiloé island is called the Chacao strait; and the body of water it leads to is the Ancud gulf; farther S it becomes the Corcovado gulf. The city of Puerto Montt and major roads emphasize that the town of Chaitén lacks road access to the N. The town has an airport, but most residents evacuated by boat. Courtesy of Google Earth.
Figure (see Caption) Figure 4. A pre-eruption photograph taken in 2003 looking downward and approximately SW from the International Space Station. Chaitén volcano sits in the lower right, with the larger snow-covered Minchinmavida at lower left. The Blanco river leads from the 3-km-diameter caldera towards the sea and passes through the town of Chaitén (top right), 10 km from the volcano. Photo ISS006E42130; courtesy of NASA.

To the W of Chaitén town lies both the large (190 km long) Chiloé island and the much smaller Talcán island. Talcán island sits ~ 30 km from the town of Chaitén; it served as a staging area for monitoring efforts. Many of the larger rivers along the coast in the region reach the sea at fjords, and Chaitén town sits at the head of a fjord of the same name.

Synopsis of key events. Events during May included the month-long persistence of ash plumes; impressive electrical discharges coincident with some ash plumes; an ash blanket spanning cross-continent; some variable (and difficult to forecast) plume-dispersal patterns; small pyroclastic flows on multiple days; and lahars that progressively engulfed the town of Chaitén.

Some other highlights include the following. By 6 May, two explosion craters on the dome's N flank had united to form one large crater. By 21 May, aerial viewers saw a new dome had extruded in the N-central sector of the older rhyolite dome (figure 5). That new dome continued to grow through May, sprouting on the older dome, and later in the month, forming a large tephra cone. On 24 May, observers saw a vigorous eruption venting from an explosion crater on the old dome. They also noted that the new dome had grown taller than the old one. On 26 May, reports declared that the eruption had entered a less energetic phase (subplinean) with ash plumes rising 3-5 km in altitude.

Figure (see Caption) Figure 5. The dome-filled caldera of Chaitén volcano is seen in an aerial view from the S taken prior to the 2008 eruption. The elliptical 2.5 x 4 km wide summit caldera was formed during an eruption about 9,400 years ago. A rhyolitic, 962-m-high obsidian lava dome occupies much of the caldera floor. Photo by Eric Manríquez T. (Instituto Geográfico Militar).

SERNAGEOMIN began to author reports on Chaitén starting the day the eruption began (2 May 2008, BGVN 32:04). Ten reports discussed May events. In addition, although little discussed in this report, the advent of digital and internet technology enabled eruption observers to share unprecedented numbers of photographs and videos. Satellite data on the eruption was also impressive (eg., NASA's Earth Observatory website featured 14 reports on Chaitén's May impacts).

Activity during 4-31 May. Amid reports of tall plumes on 3-6 May (BGVN 33:04), Andes del Sur (OVDAS) of SERNAGEOMIN installed three non-telemetered seismic stations around the volcano. These stations were later moved to more accessible places to enable more frequent data inspection. Improved seismic stations were installed later in the month (see below).

The 5 May eruptive vigor is partly revealed by an astronaut photo (NASA-ISS, 2008). Taken from a height of 344 km, it showed a plume punching through weather clouds and manifesting powerful vertical transport. It also highlights how weather clouds then would have thwarted ground observers from seeing, and thus assessing, the height of the plume top in those conditions.

Satellite imagery acquired on 5 May and discussed by NASA's Earth Observatory website that day revealed the Chaitén plume and a fresh blanket of ash. The ash blanket stretched from the high Andes to the Atlantic coast, and the ash plume continued E beyond it. Areas of the land surface along the Andes and to the Pacific were obscured by weather clouds.

The 6 May report noted that the eruption intensified at 0820 that day, leading to vigorous explosions of rhythmic character and high sustained energy. An ash column rose to ~ 30 km altitude. At this point in time, the column was taller and wider than those seen in the earlier, initial eruptive phase.

A helicopter flight at 1000 on the 6th indicated that two explosion craters on the dome's N flank had united to form one crater ~ 800 m in diameter. The column height had decreased. Consistent with mobile ash on the ground, the amount of ash in rivers in the region had increased.

After large explosions on 6 and 7 May, earthquakes occurred that were thought to denote moving fluid associated with a magma chamber beneath the volcano. Hypocenter calculations suggested the magma chamber was at less than 5 km depth. The ambient seismicity near the volcano around that time was ~ 35 volcano-tectonic earthquakes per day.

During 8 May, despite frequent low-hanging clouds, viewers glimpsed areas E of Chaitén. Along a N-trending valley there, thin gray spirals of cloud descended into the Rayas river, and ultimately the Rayas itself also began to emit clouds. SERNAGEOMIN's 9 May report explained these phenomena as the result of small pyroclastic flows inferred to have heated the river waters, thus yielding vapor that subsequently condensed to form the spirals of cloud.

The atmosphere, which on 8 May was cloudy during the hours 0715 to 1515, cleared somewhat during 1500-1630. At 1600 viewers saw both the volcano and a NE-blowing mushroom-shaped cloud that reached 14 km altitude. Photographic evidence (not included) showed that to the W side of the column there appeared a smaller cloud that looked denser and medium to dark gray. That smaller cloud was thought to have been associated with a new vent located at the foot of the dome's W side.

At 1300 on 12 May observers on Talcán island saw the upper portion of an ash column, which rose to 8.0 km altitude. Helicopter flights found strong SW winds aloft, blowing 80-100 km/hour to the NE. Despite the wind, during the flight about four explosions rose to similar (8 km) altitudes, thus sustaining the plume.

Aerial inspection of the caldera and dome at 1430 on 12 May revealed that small pyroclastic flows had burned multiple hectares of native forest in the headwaters of the Rayas river on the caldera's N flank and as far as the Austral highway. Similar processes had also devastated vegetation both everywhere within the caldera and on parts of the outer NE flanks. A wide, vertically oriented ash column originated from a vent extending from a crater on the older dome's N flank to its summit.

A photo of the caldera provided in the 13 May report showed a powerful billowing eruption. Incandescent areas spread along the dome's upper SE side, and a blanket of fresh fragmental deposits covered much of the upper dome.

On 12 May a helicopter crew found Chaitén town flooded by lahars traveling down the Blanco river. Based on the two photos in the report, the lahars at that point had covered roughly the lower half of single-story structures closest to the river and as far back as perhaps 3-5 buildings from those closest to the river's former margin. Some buildings closest the river were dislodged, a few had only their uppermost walls and roofs exposed. Significant portions of the town farther from the river still stood above the level of inundation.

Subsequent to 12 May, the river rose yet farther, and lahars took out a bridge. The lahars stretched ~ 200 m farther into the town reaching ~ 40 homes and numerous vehicles. Scenes of the town of Chaitén became the subject of many news reports and some videos posted on the web.

NASA's Earth Observatory posted an image acquired on 12 May (figure 6). Ash was again visible across the entire continent, spreading in a band trending ENE of the volcano. The ash is more visible in this image as the plume is blowing well S of the ash blanket.

Figure (see Caption) Figure 6. Chaitén's plume crosses the bottom of this Terra satellite image from 12 May 2008, becoming more diffuse before reaching the Atlantic coast. The ashfall blanket in an E-W cross-continent band. Courtesy of NASA Earth Observatory by Jeff Schmaltz and Michon Scott (their 12 May report).

The 16 May report noted that the eruption was clearly plinean in nature and the source of continuous plumes. But, in the past two days, the plumes had not risen above 5 km altitude. Seismicity during 14-16 May included swarms of hybrid earthquakes.

At 0730 on 15 May observers saw the upper part of an ash plume reach 4 km altitude. The plume was swept NE in 140 km/hr winds. That day, a helicopter took observers over the town of Chaitén and the Amarillo and Michinmahuida rivers. Wide areas of the region were covered by white tephra. Lahars continued, apparent both to Chaitén's S and along the Blanco river to the coast. Lahars covered the Chaitén airfield and invaded the dock areas, as well as its main plaza, swamping government buildings. The lahars continued rising as the river bed and flood plains filled with sediments. Discolored water was seen widely (including N of Chaitén town in Pumalín bay,). Some elongate pumice rafts were floating in the Corcovado gulf.

In response to the crisis at Chaitén, during mid-May, the United States gave Chile several radio-telemetered seismic stations. Three members of the US Geological Survey (USGS) also joined SERNAGEOMIN and other agencies in Chile to install two stations. The visiting team, there during mid-May to early June, also discussed instrument operations, maintenance, and data interpretation.

The diagram in figure 7 indicates the key components of the portable seismic station initially used (without telemetry) and the new seismic stations installed (with digital instrumentation, telemetry, and linkage to the Internet). Both of the new seismic stations were installed on the mainland, broadcasting to a site on Chiloé island. Photographs of the area were taken during fieldwork (figures 8-10).

Figure (see Caption) Figure 7. Diagrams comparing seismic stations and related components. At Chaitén, the portable stations were replaced by telemetered seismic stations during mid-May 2008. The A/D converter changes continuouos (Analog) signals to a stream of discrete (Digital) numbers. A "wideband" (broadband) seismic sensor can detect ground motions over wide frequency ranges compared to the narrower ranges typical of older instruments. These instruments also have a more uniform response across these varied frequencies, easing data interpretation. Courtesy of SERNAGEOMIN (from their 20 May report).
Figure (see Caption) Figure 8. Chaitén eruption plume seen looking E across the gulf on 19 May 2008. The snow-covered flanks of Michimahuida volcano appear in the background. Courtesy of J.N. Marso (USGS).
Figure (see Caption) Figure 9. Native forest destroyed by pyroclastic surges on the flanks of Chaitén during mid-May to early June 2008. Note the singed band located between the zone of total destruction (bottom) and unaffected forest (top). A road is visible across much of the photo. Photo by A.B. Lockhart, USGS.
Figure (see Caption) Figure 10. (top) Town of Chaitén overrun by lahars during mid-May to early June 2008. Lahars had began to accumulate as a delta at the river mouth. Owing to sedimentation, the river (seen in background) had changed course and was then flowing through the town. The airport is on photo's right side between the town and the steep hill in background. (bottom) This closer view illustrates variable amounts of lahar damage affecting Chaitén town. This town was completely evacuated within several days of the eruption's onset. Photos by A.B. Lockhart, USGS.

At midday on 15 May, the authors described a cold wind that carried fine ash W. Ash fell on the ship Aquiles and on Talcán island, reaching 0.5-1.0 mm thick. In the same time frame, ash fell at the Blanco and Rayas rivers at least as far W as the Chaitén fjord's mouth.

Favorable weather, including strong wind, enabled scientists to assess the caldera on 21 May (figure 11). They found a new dome had emerged, already of significant size. It extruded from an area in the old dome. The eruption at the time was vigorous, though marked by sporadic explosions.

Figure (see Caption) Figure 11. (top) An annotated photo from a helicopter on 21 May 2008 looking S into the erupting Chaitén caldera documenting the emergence of a new dome on the N side of the old one. The old dome (dark color, lower right) emitted a white plume; the new one (pale rose in colored versions of this photo, center) emitted a pale rose plume. Small block-and-ash flows descended the new dome's N side. The dark material in the background is the far (S) caldera wall. The venting ash column delivered considerable ashfall downwind. (bottom) A schematic (plan view) of the caldera seen that day (composed 23 May 2008 by H. Moreno). Both courtesy of SERNAGEOMIN.

An overflight on 24 May revealed the new dome had slightly higher elevation than the old dome. Airborne observers saw the cone's 200-m-diameter crater vigorously expelling gas and ash. This vent was on the higher parts of the old dome in an area just to the S of the active dome.

The eruption, although unceasing, was described in the 26 May report as having decreased to subplinean. It remained in this lower energy state through at least month's end. On 25 May, ash columns reached ~ 3.5 km in altitude, with occasional explosions prompting plumes up to 5 km. Plumes often blew NE.

The 22 May report mentioned a swarm of hybrid earthquakes, in this case with considerable 3 Hz content. Volcano-tectonic earthquakes diminished progressively during 22-26 May, both in number and magnitude. These accompanied a reduction in volcanism.

A substantial tephra cone had developed on top of the new and old domes by 26 May (figure 12). The new dome, pink in color, was still present but lay directly behind the collar of tephra composing the new tephra cone. A summit crater vented plumes of different color. Although a dome had emerged, vigorous ash plume emission continued.

Figure (see Caption) Figure 12. Chaitén seen from a helicopter on 26 May with the camera aimed NE. A tephra cone stood atop the new and old dome complex. The cone's steep upper walls discharged a broad plume from an unusually ample summit crater. The plume was two-toned, with distinctively shaded material on its left and right sides. Lumpy areas on the middle to lower cone correspond to the obsidian on the now buried older dome. Some burned vegetation exists in the bottom center of the photo along the outflowing Blanco river. Photo by J.N. Marso (USGS).

A 26 May Terra image showed some areas of ashfall, but also several unusual features attributed to the eruption. These were described in the 26 May Earth Observatory report. First, rivers and lakes around the volcano were a distinct blue-green color, and this discoloration persisted into the Corcovado gulf, presumably from the waters' high suspended loads.

Second, although views of ridges (topographic highs) were clear and unobstructed in the image, a dendritic pattern of clouds, fog or mist hugged the valleys (topographic lows) for at least 200-300 km N and NE of the volcano. These white, opaque clouds originated from Chaitén.

On 28 May the ash column rose to 3.5-4 km altitude, blowing N to NW. It affected localities hundreds of kilometers away. Chilean airports closed in Puerto Montt, Osorno, Valdivia, and as far as 300 km N in Temuco. Lower altitude winds blew ash farther W, affecting coastal areas between the town of Chaitén and Chumildén, including Talcán island. In these areas, suspended ash appeared as a dense mist, grounding aircraft, including those used for vol;cano inspections.

During the last few days May, the number and magnitude of volcano-tectonic earthquakes diminished, and both low-frequency and hybrid earthquakes were absent. These changes coincided with a drop in the altitudes of eruption columns over the course of about a week.

Reference. Anonymous, 2008, Análisis químicos realizados en la contingencia del Volcán Chaitén: Municpalidad de Lago Puelo, 4 p. Accessed July 2008 (URL: http://www.lagopuelo.gov.ar/extras/riesgos/Analisis_quimicos_realizados_contingencia_Volcan_Chaiten[1].pdf).

Naranjo, J.A., and Stern, C.R., 2004, Holocene tephrochronology of the southernmost part (42°30'-45°S) of the Andean Southern Volcanic Zone: Revista Geológica de Chile, v. 31, no. 2, p. 225-240.

NASA-ISS, 2008, Astronaut photo from the International Space Station taken at 2027 on 5 May 2008 UTC. (Frame 6214, Mission ISS 017; file name, ISS017-E-6214.JPG). Image Science and Analysis Laboratory, NASA-Johnson Space Center (URL: http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS017&roll=E&frame=6214>

Geologic Background. Chaitén is a small caldera (~3 km in diameter) located 10 km NE of the town of Chaitén on the Gulf of Corcovado. Multiple explosive eruptions throughout the Holocene have been identified. A rhyolitic obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of artifacts from archaeological sites along the Pacific coast as far as 400 km from the volcano to the N and S. The caldera is breached on the SW side by a river that drains to the bay of Chaitén. The first recorded eruption, beginning in 2008, produced major rhyolitic explosive activity and building a new dome and tephra cone on the older rhyolite dome.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Avenida Santa María 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637 / 1671, Santiago, Chile (URL: http://www.onemi.cl/); José Antonio Naranjo, Departamento de Geología Aplicada, SERNAGEOMIN, Avenida Santa María 0104, Santiago, Chile; NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); John Pallaster, Andy B. Lockhart, Jeff N. Marso, and John Ewert, US Geological Survey (USGS), Volcano Disaster Assistance Program (VDAP), 1300 SE Cardinal Court, Bldg. 10, Suite 100, Vancouver, WA 98683, USA; Image Science and Analysis Laboratory, NASA-Johnson Space Center, The Gateway to Astronaut Photography of Earth (URL: http://eol.jsc.nasa.gov/).


Etna (Italy) — May 2008 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3357 m

All times are local (unless otherwise noted)


6-km-long lava flow; ash emissions; 13 May 2008 opening of a new eruptive fissure

After several months of eruptive activity at the summit craters, on 13 May a new eruptive fissure opened between 3,050 and 2,650 m elevation on Etna's upper E side, feeding lava flows into the Valle del Bove (figure 132). This took place without threatening inhabited areas. It was preceded by several months of sporadic ash emissions, a brief period of Strombolian activity, and a powerful eruptive phase from Southeast Crater (SEC) on 10 May. As of 20 June, modest Strombolian activity continued from two vents along the fissure at approximately 2,800 m elevation, accompanied by lava emission from a third vent, with lava advancing ~ 5 km to the E.

Figure (see Caption) Figure 132. Map showing extent of lava flows from Mount Etna, 2006-2008, including the lava flow field of the 2008 flank eruption as of 21 June 2008. Summit craters are Northeast Crater (NEC), Voragine (VOR), Bocca Nuova (BN), and Southeast Crater (SEC), whose recently active vent on the E flank is labelled SEC-E. The upper E flank fissure system is distinguished by two segments: one (A) active on 13 May morning; and the other (B) starting on the afternoon of 13 May and continuing through June. Courtesy of INGV-CT.

This report was compiled from contributions by the staff of the Istituto Nazionale di Geofisica e Vulcanologia, sezione di Catania (INGV-CT), which are available as pdf files on the Institute's website (see Information Contacts).

Activity during January-April 2008. During this time interval, periodic emissions of ash occurred from a vent located on the E flank of the SEC cone (hereafter named SEC-E), which had been the site of two strong eruptive episodes on 4-5 September and 23-24 November 2007 (see BGVN 32:08, 32:09 and 33:01). This activity apparently ejected mostly lithic ash, and no incandescence was seen through mid-April. A period of weak Strombolian activity occurred between 23 and 28 April (figure 133), when explosions ejected incandescent bombs up to 100 m above the vent, and some material fell to the base of the SEC cone. The area was quiet between 29 April and 10 May.

Figure (see Caption) Figure 133. Thermal camera image of a Strombolian explosion from the active eastern vent of the Southeast Crater (SEC-E) on 23 April 2008. Courtesy of INGV-CT.

Event of 10 May 2008. A sharp increase in the volcanic tremor amplitude at 1400 UTC on 10 May announced the onset of a new paroxysmal eruptive episode at the SEC. Observation was difficult, due to inclement weather conditions. During the first stages of activity, eyewitnesses in the summit area observed explosive activity at several locations within and around SEC-E, and lava overflows feeding several branches of lava toward the Valle del Bove (figure 134). While lava descended very rapidly into the Valle del Bove, explosive interaction with patches of remaining snow repeatedly occurred along the path of the lava flows. The lava advanced across the Valle del Bove floor toward Monte Calanna down to an elevation of ~ 1,370 m, reaching a total length of 6.4 km from its source. This is one of the longest lava flows fed by a summit eruption of Etna in recorded history. A preliminary estimate of the lava volume yields ~ 4.5 x 106 m3, which was emitted at peak rates exceeding 300 m3/s (in comparison, peak eruption rates calculated for the violent fire-fountaining episodes at the SEC in 2000 were consistently below 200 m3/s; Behncke et al. 2006). Tephra fallout occurred mostly to the N and later to the NE (Andronico et al. 2008). The activity came to an abrupt halt at about 1800, after which no appreciable activity occurred for the following 2.5 days. Figure 134 is an aerial view of the SEC with its SEC-E vent, taken during a period of complete quiescence on 28 May.

Figure (see Caption) Figure 134. Oblique aerial view of the Southeast Crater and its E flank vent (SEC-E, in the foreground) in a state of total quiescence, taken from a helicopter of the Italian Civil Protection Department on 28 May 2008. Courtesy of INGV-CT.

Start of flank eruption, 13 May 2008. The intrusion of a dike into the upper portions of the Etna's edifice was marked by a seismic swarm starting at 0840 UTC (Unit? Funzionale Sismologia, 2008). Eruptive activity started from a fissure segment ("A" in figures 132 and 136 and shown close-up in figure 135) located roughly at 3,000 m elevation at the E base of the Northeast Crater (NEC) cone, where fire-fountaining produced a thick scoria deposit and generated sheet flows 2.5 km E toward Monte Simone. This activity probably lasted only a few hours and was followed by the propagation of new fissures to the SE ("B" in figures 132 and 136), down to an elevation of ~ 2,650 m, into the Valle del Leone, in the opposite direction of the initial dike intrusion, which apparently came to a halt during the early afternoon.

Figure (see Caption) Figure 135. Close-up aerial view of fissure segment "A," formed on the morning of 13 May 2008, and its rheomorphic lavas, taken from a helicopter of the Italian Civil Protection Department on 15 May 2008. Lava fountaining from this fissure segment lasted only for a few hours at the start of the eruption, but weak ash emissions continued for several days. Note fracture pattern created by the dragging along of freshly fallen tephra deposits along the margins of moving lava flows. Courtesy of INGV-CT.
Figure (see Caption) Figure 136. Photomosaic composed of about 10 frames taken from a helicopter of the Italian Civil Protection Department on 15 May 2008, showing eastern sector of Etna with the active eruptive fissure just below the summit craters at right, and extent of active lava flows in the Valle del Bove, in the center and at left. Courtesy of INGV-CT.

Visual observations were severely hampered by poor weather conditions, but heavy scoria falls were noted on the N flank during the early afternoon, and satellite imagery showed a narrow plume extending NNE (Coltelli et al. 2008). INGV staff visiting the summit area later that day stated that explosive activity occurred from multiple vents along an eruptive fracture to the E of the summit, and lava was flowing toward the Valle del Bove. Fieldwork carried out during the following days revealed that an extensive fracture field had formed around the NEC and beyond toward the upper N flank of Etna (Neri, 2008).

Continuing activity, 14 May to present. Improved weather conditions on 14 and 15 May permitted the first overviews of the eruption area (figure 136), and revealed that lava flows from the still active fissure segment at ~ 2,700-2,800 m elevation had descended approximately 6 km to 1,300 m elevation, but movement of the lava flow fronts had slowed significantly. Intense Strombolian activity occurred from a number of vents, and lava issued from at least two main locations. The uppermost fissure segment, first active on the morning of 13 May, showed little activity except for degassing and occasional emissions of dilute ash plumes. Ash was also emitted periodically from SEC-E.

On 16 and 17 June, ash emissions from that vent became more vigorous, and ash was also emitted from several vents in the upper portion of the still-active fissure segment on the upper E flank. The active lava flows, however, showed a significant reduction in their length compared to the first few days of eruption. During the following days, the ash emissions at the SEC stopped, and activity at the E flank fissure showed a marked diminution. Throughout late May and into early June, Strombolian activity was confined to one or two vents at about 2,800 m elevation, and lava emission from a single vent located a few tens of meters downslope fed small flow lobes that advanced to ever decreasing distances, reaching a minimum of ~ 0.4 km on 4 June.

A gradual but clear increase in the volcanic tremor amplitude and changes in the gas geochemistry heralded a revival of both the explosive and effusive activity on 8 June, which created a fresh surge of lava into the Valle del Bove. On 18 June, little more than one month after the start of the flank eruption, the lava fronts reached an elevation of about 1,350 m between Rocca Musarra and Rocca Capra (figure 132) and a distance of 5 km from the vents. Mild Strombolian activity continued from two vents located at ~ 2,800 m elevation.

After extending 5 km down through the Valle del Bove in mid-June, lava flows remained much shorter until the last few days of the month, when a new lobe advanced 4.8 km E, somewhat southward of the mid-June lava lobe. The late-June lobe was seen stagnant on 1 July. On the afternoon of 4 July, ash emissions from a point of the eruptive fissure upslope from the recently active vents (at 2,800 m elevation) marked the reactivation of a vent that had been inactive since mid-May. Vigorous Strombolian activity occurred from this vent during the following days, alternating with periods of ash emission. As of 6 July, lava was traveling further S, extending less than 4 km from the vents.

References. Andronico, D., Coltelli, M., Cristaldi, A., Lo Castro, D., and Scollo, S., 2008, Il parossismo del 10 maggio 2008 al Cratere di SE: caratteristiche del deposito di caduta (URL: http://www.ct.ingv.it/Report/RPTVETCEN20080510.pdf).

Behncke, B., Neri, M., Pecora, E., and Zanon, V., 2006, The exceptional activity and growth of the Southeast Crater, Mount Etna (Italy), between 1996 and 2001: Bulletin of Volcanology, v. 69, p. 149-173.

Budetta, G., Ciraudo, A., Currenti, G., Del Negro, C., Ganci, G., Greco, F., Herault, A., Napoli, R., Scandura, D., Sicali, A., and Vicari, A., 2008, Aggiornamento dello stato di attivit? dell'Etna: Osservazioni gravimetriche e magnetiche, (URL: http://www.ct.ingv.it/Report/UFGMET20080513.pdf ).

Coltelli, M., Prestifilippo, M., Scollo, S., and Spata, G., 2008, Rapporto tecnico del 13 Maggio 2008 ? Osservazione da satellite e simulazione dell'emissione di cenere (URL: http://www.ct.ingv.it/Report/Rapporto_UPNV_CT_ 20080513.pdf )

Neri, M., 2008, Eruzione dell'Etna: Fratture non eruttive sul fianco settentrionale del Cratere di Nord-Est; Aggiornamento al 28 Maggio 2008 (URL: http://www.ct.ingv.it/Report/RPTVGSTR20080528.pdf ).

Puglisi, G., Gambino, S., Mattia, M., and Aloisi, M., 2008, Monitoraggio Geodetico delle Deformazioni del suolo all'Etna: Aggiornamento 14 maggio 2008 ? 09:00 (URL: http://www.ct.ingv.it/Report/UFDG-RA_2008-08.pdf ).

Unit?Funzionale Sismologia (edited by D. Patanè), 2008, Quadro di sintesi e aggiornamento al 19 Maggio 2008 sullo stato di attivit?sismica dell'Etna (URL: http://www.ct.ingv.it/Report/REPUFS20080519.pdf ).

Geologic Background. Mount Etna, towering above Catania on the island of Sicily, has one of the world's longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

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


Home Reef (Tonga) — May 2008 Citation iconCite this Report

Home Reef

Tonga

18.992°S, 174.775°W; summit elev. -10 m

All times are local (unless otherwise noted)


Pumice found on southeastern Papua New Guinea beaches

Pumice from Home Reef has become one hypothesis for some mid-2007 observations on beaches in eastern Papua New Guinea, about 250-350 km NE of Milne Bay. The Rabaul Volcano Observatory (RVO) received a report about quantities of pumice on Woodlark Island beaches on 21 August 2007. The report was from the Deputy Administrator (DA) of Milne Bay Province who had been on election duty in a PNG Naval Patrol boat. The DA and the captain saw an echo sounder profile as they were sailing out of a lagoon at Budibudi Island (Lachland Islands) ~ 100 km ESE of Woodlark Island on the evening of 18 July 2007. They interpreted the profile as a possible submarine volcano. Later, they observed pumice clasts lying on the beaches of the Woodlark Islands. Recalling what they had seen on the echo sounder profile at Budibudi Island the previous day, the DA was very concerned that any activity the area would be a threat to the local population.

Additional information was gathered by RVO from the DA, government officers on Woodlark Island, and people from Budibudi Island. That investigation revealed no evidence of a pumice raft on Budibudi. Pumice clasts were only observed on Woodlark beaches, and images of pumice clasts showed that they were rounded and had incrustations. The lagoon at Budibudi also has no history of hydrothermal activity. There was also no evidence of continuous local earthquakes prior to or during July.

Simon Carn of the University of Maryland Baltimore County confirmed no evidence of anything unusual in the SO2 imagery. The UK Hydrographic Office provided scans of nautical charts of the remote islands, confirming that the site of the reported "eruption" was less than 35 m deep, so any activity would have been vigorous at the surface and obvious to Islanders.

It is assumed that the "submarine volcano" was a patch reef and the pumice was from the Home Reef eruption. Another alternative was that the pumice represented re-mobilized clasts from strand lines around the Solomon Sea, possibly a result of the 2 April Solomon Islands tsunami.

Geologic Background. Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, large amounts of floating pumice, and an ephemeral 500 x 1,500 m island, with cliffs 30-50 m high that enclosed a water-filled crater. In 2006 an island-forming eruption produced widespread dacitic pumice rafts that drifted as far as Australia. Another island was built during a September-October 2022 eruption.

Information Contacts: Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Simon Carn, Joint Center for Earth Systems Technology, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA (URL: https://so2.gsfc.nasa.gov/); Guy Hannaford, United Kingdom Hydrographic Office, Admiralty Way, Taunton, Somerset TA1 2DN, United Kingdom.


Kerinci (Indonesia) — May 2008 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Occasional steam plumes in 2007-2008; ash emission on 9 September 2007

Kerinci last erupted on 6 August 2004. Following that, the volcano was relatively quiet through January 2005 (BGVN 30:01). This report discusses events through 11 May 2008. Satellite thermal imaging has not shown any "hot-spots" for the past several years, but the behavior there has been characterized by emissions of billows of thin white smoke that rose to ~ 200 m above the crater.

On 8 September 2007, a number of minor seismic events occurred. On 9 September, vapor emissions increased, pulsing at ~ 5-minute intervals, and accompanied by inky black ash. The plume rose ~ 700-800 m above the crater rim and ash fell within ~ 8 km of the vent.

The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that the Alert Status was raised to 2 (on a scale of 1-4). Visitors and tourists were not permitted to approach the crater closer than 1 km.

Activity in the following months did not show any significantly abnormal behavior until 14-18 February 2008, when more voluminous thick white plumes rose ~ 500 m above the crater rim.

According to CVGHM, the seismicity increased during 17-24 March 2008. On 24 March, an ash-and-gas plume rose to an altitude of 4.3 km. Another increase in seismicity occurred during 10-11 May, when thick white plumes rose to altitudes of 4.3-4.5 km and drifted E. The Alert Status remained at 2.

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

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/).


Veniaminof (United States) — May 2008 Citation iconCite this Report

Veniaminof

United States

56.17°N, 159.38°W; summit elev. 2507 m

All times are local (unless otherwise noted)


Minor ash bursts during February 2008

Our previous report on Veniaminof (BGVN 31:08) noted the relative quiescence of the volcano through 15 September 2006, with the seismicity remaining low, but above earlier background levels. We received no subsequent reports of seismicity until 11 February 2008, when the Alaska Volcano Observatory (AVO) noted sporadic increases in seismic activity, including tremor episodes that lasted 1-2 minutes and occurred several times per hour.

On 22 February several minor ash bursts from Veniaminof were recorded by the seismic network and observed on web camera footage. The bursts rose to an altitude below 2.7 km; fallout was confined to the crater. Steam plumes emitted from the intra-caldera cone were seen on video footage during 23-25 February and seismic levels were elevated during 23-26 February.

On 27 February, web camera views showed steaming from the cone and occasional small ash bursts that rose to 200 m above the crater. The Aviation color code was raised to Yellow and the Alert Level was raised to Advisory. During 28 February-3 March, views were obscured by cloud cover. However, the elevated seismic activity continued to 4 March and low-level steaming was seen on 29 February during a break in the weather.

Subsequent to the February-March activity, the volcano returned to its quiescent state. AVO reported on 3 May that the Volcanic Alert Level for Veniaminof was lowered to Normal and the Aviation Color Code was lowered to Green due to the absence of ash emissions and elevated surface temperatures in satellite data and webcast imagery. Seismicity was still above past background levels, but the rate and intensity had declined over the previous several weeks.

Web camera imagery of Veniaminof volcano showed that occasional light steaming continued.

Geologic Background. Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

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

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