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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 36, Number 05 (May 2011)

Managing Editor: Richard Wunderman

Ambae (Vanuatu)

Increased degassing starting December 2009

Ambrym (Vanuatu)

Ongoing plumes, some bearing ash and to over 6 km altitude

Cleveland (United States)

Thermal anomalies and possible plumes through mid-September 2010

Etna (Italy)

Ongoing effusive fissure eruption that began on 13 May 2008 ends on 4 July 2009

Galeras (Colombia)

Eruption on 25 August 2010; gas emissions in early 2011

Gaua (Vanuatu)

Drops in both tremor and caustic effects on vegetation after mid-2010

Merapi (Indonesia)

Recovery; intermittent activity; damaging lahars

Ulawun (Papua New Guinea)

Seismicity ongoing with plumes during May 2010-May 2011

Yasur (Vanuatu)

Explosion induced ash falls, strong degassing during late May-early June 2011



Ambae (Vanuatu) — May 2011 Citation iconCite this Report

Ambae

Vanuatu

15.389°S, 167.835°E; summit elev. 1496 m

All times are local (unless otherwise noted)


Increased degassing starting December 2009

Our last Bulletin report (BGVN 31:12) on Aoba (Ambae) described the destruction of vegetation by acidic gas emissions and the breach of the islet lake during 2006. This report discusses comparative quiescence into late 2009 when degassing escalated (substantial gas plumes were seen) and the hazard status rose. The volcano has remained quiet into mid-2011.

The Vanuatu region lies ~2,200 km N off the New Zealand coast and ~2,100 km NE off the coast of Australia (figure 31). A 1999 census suggested ~9,400 people resided on Ambae. Cronin and others (2004) describe the residents as "dispersed amongst more than 276 small extended family settlements and villages (Wallez 2000). Settlements are mostly restricted to the lower island slopes within 4 km of the coast. The highest population densities occur at the NE and SE ends of the island."

Figure (see Caption) Figure 31. (A) Major islands of the Republic of Vanuatu. (B) Aoba (Ambae) Island, showing locations of settlements, main stream channels and roads. Cronin and others (2004) discuss the communities of Lolovange and Lolowai (ellipses). Taken from Cronin and others (2004) after work by Wallez (2000).

The Vanuatu Geohazards Observatory (VGO) noted increases in activity from Aoba (Ambae) starting in December 2009.This began when local villagers near the volcano reported seeing a plume over the island. In December 2009 the Vanuatu Volcanic Alert Level (VVAL) was raised to Level 1. The scale ranges from 0 to 4: 0 represents normal low-level activity and 4 represents a large eruption and island wide danger. The reported source of activity is a recent cone located in the crater lake, Voui (BGVN 30:11 and 30:12).

The VGO went on to note that "An expatriate pilot based on Gaua, also witnessed a plume on Ambae on Tuesday 6th April on his way back to Gaua from Santo. Aerial pictures that were taken by two Geohazards staff on 11 April 2010 also confirmed gas emissions that were more concentrated than normal... [which] reaffirms the [Ozone Monitoring Instrument or OMI] satellite image of gas emissions above. Another observation made on Ambae is the presence of sulphur-hydromagmatic activity on the SE part of the second crater of Ambae enclosing Manaro Lakua indicated by what seemed like two fumarolic zones.... There was also some discoloration of the water in Manaro Lakua near the 'fumaroles' with some areas near the shore [colored] brown, and some areas [colored] pale blue—a sign of the incorporation of sulphur dioxide. It was also reported that while flying above the area, strong sulphur dioxide gas could be smelt even at 5,000 feet [~1.5 km altitude] on 11 April."

The VGO also noted that the OMI satellite pictures depicted fluctuating gas emissions during this period. The image for 11 April 2010 indicated elevated SO2 and gave the integrated concentration-pathlength as 15 kilotons. On this day, VGO had noted SO2 fluxes over 3,000 tons/day.

References. Cronin, SJ, Gaylord, DR, Charley, D., Alloway, BV, Wallez, S, and Esau, JW, 2004, Participatory methods of incorporating scientific with traditional knowledge for volcanic hazard management on Ambae Island, Vanuatu, Bulletin of Volcanology, v. 66, pp.652-668, Springer-Verlag.

Wallez S, 2000, Socio-economic survey of the impact of the volcanic hazards for Ambae Island: geo-hazards mitigation program section. Department of Geology, Mines and Water Resources, Port Vila, Vanuatu. p 39.

Geologic Background. The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone with numerous scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Information Contacts: Vanuatu Geohazards Observatory (VGO) (URL: http://www.vmgd.gov.vu/vmgd/); Ozone Monitoring Instrument (OMI), Sulfur Dioxide Group), 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/).


Ambrym (Vanuatu) — May 2011 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


Ongoing plumes, some bearing ash and to over 6 km altitude

In our last report on Ambrym (BGVN: 3411), we described the frequent thermal anomalies from the volcano's active lava lakes during October 2008-September 2009. Satellite imagery in 2009 and 2010 suggested ongoing visible plumes and thermal alerts consistent with active lava lakes. Several satellite images of Vanuatu appear below (figures 21-22).

Figure (see Caption) Figure 21. A hazy layer of vog (volcanic fog) overlies Malekula and a few other islands of the Vanuatu archipelago in this natural-color satellite image from 6 October 2009. The source of the vog is Ambrym, a volcano (and island of the same name) in the SE (lower right) corner of this scene. The haze extends over the Coral Sea several hundred kilometers to the NW. Ambrym emits SO2, the gas responsible for the formation of vog, intermittently. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite acquired this natural-color image. NASA image by Jeff Schmaltz, MODIS Rapid Response, NASA Goddard Space Flight Center (the Rapid Response Team provides twice-daily images of this region). Caption by Robert Simmon.
Figure (see Caption) Figure 22. Diffuse plumes rise from Gaua volcano (top) and Ambrym volcano (bottom) in the Vanuatu archipelago. Both Gaua and Ambrym are located in the New Hebrides island arc, where the Pacific plate is subducting beneath the Australian plate. This natural-color image was acquired on 2 August 2010, by the Moderate Resolution Imaging Spectrometer (MODIS) aboard NASA's Terra satellite. NASA image by Jeff Schmaltz ; caption by Robert Simmon. Courtesy of NASA Earth Observatory.

Based on observations by aircraft pilots, analyses of satellite imagery, and information from the Vanuatu Geohazards Observatory (VGO), the Wellington Volcanic Ash Advisory Center (VAAC) reported that on 8 and 10 August 2010 ash and steam plumes from Ambrym volcano rose to an altitude 6.1 km and drifted W and NW.

Ambrym is a major source of SO2 in the Vanuatu Republic. The VGO web site shows daily Vanuatu volcanic sulfur dioxide (SO2) fluxes through a partnership with GNS Science Institute (Taupo, New Zealand) using OMI satellite images.

Figure 23 shows a 22 May 2011 satellite image of Ambrym. Similar images were acquired by NASA satellites on 28 March 2011 and on 7 June 2011. On figure 23, a blue-tinged volcanic plume emissions extends from Ambrym to the W. The plume contains vog, a mix of gases and aerosols that is formed when SO2 and other volcanic gases react with sunlight, oxygen, and moisture.

Figure (see Caption) Figure 23. A natural-color image showing Ambrym and its W-blowing plume. The image was acquired by MODIS (the Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite) on the morning of 22 May 2011. NASA image by Jeff Schmaltz, MODIS Rapid Response Team, NASA-GSFC. Courtesy of NASA Earth Observatory.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides Arc. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: Vanuatu Geohazards Observatory, Department of Geology, Mines and Water Resources of Vanuatu (URL: http://www.vmgd.gov.vu/vmgd/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); MODIS/MODVOLC Thermal Alerts System, Hawai'i Institute of Geophysics and Planetology (HIGP), 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/); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac/, URL: http://vaac.metservice.com/).


Cleveland (United States) — May 2011 Citation iconCite this Report

Cleveland

United States

52.825°N, 169.944°W; summit elev. 1730 m

All times are local (unless otherwise noted)


Thermal anomalies and possible plumes through mid-September 2010

Occasional small ash eruptions occurred at Cleveland during 2009 through early June 2010 (BGVN 35:06). Mild restless behavior continued at least into mid-September 2010 but it was uncertain whether ash had been emitted.

Table 3 compiles key observations and alerts for Cleveland volcano during mid-June through 31 March 2011. The Alaska Volcano Observatory (AVO) reported that thermal anomalies were sometimes visible and sometimes absent on satellite imagery. One or two ash plumes may have also been emitted. Accordingly, these observations caused authorities to raise and lower the Volcano Alert Level and Aviation Color Code (table 3). Volcano seismicity was absent because Cleveland lacks a real-time seismic network. The thermal anomalies and possible plumes could both could stem from steam emissions (see AVO statement at bottom of this report).

Table 3. Reports of activity at Cleveland based on satellite imagery during 10 June 2010 through 31 March 2011. Also shown are Volcano Alert Level and Aviation Color Code fluctuations based on that activity. Courtesy AVO.

Date Observation based on satellite imagery Volcano Alert Level Aviation Color Code
10 Jun 2010 -- Advisory Yellow
11 Jun 2010 -- Unassigned Unassigned
16 Aug-1 Sep 2010 Thermal anomalies visible on most days -- --
26 Aug 2010 -- Advisory Yellow
07-08 Sep 2010 Clear-weather views showed no thermal anomalies or recent deposits on the flanks -- --
08 Sep 2010 -- Unassigned Unassigned
11 Sep 2010 Thermal anomaly visible -- --
12 Sep 2010 Possible ash plume rose to ~7.6-km altitude and drifted E -- --
12 Sep 2010 -- Advisory Yellow
13-15 Sep 2010 Thermal anomalies visible -- --
16-24 Sep 2010 Cloud cover prevented views -- --
25-26 Sep 2010 Weak thermal anomaly visible -- --
27-28 Sep 2010 Cloud cover prevented views -- --
31 Mar 2011 -- Unassigned Unassigned

On 12 September 2010, a possible ash plume was visible in satellite imagery; it rose to an estimated altitude of 7.6 km and drifted E. A 14 September image showed a dense white plume issuing from Cleveland (figure 9).

Figure (see Caption) Figure 9. Image of a small, dense, compact white plume issuing from Cleveland at 1431 on 14 Sept 2010, captured by the GeoEye IKONOS satellite. In color versions of the image, red highlights areas of vegetation detected by the near-infrared channel. Photographed/created by Rick Wessels. Image processed by AVO/USGS; copyright 2010 by GeoEye. Courtesy AVO.

On 31 March 2011, AVO lowered the Volcano Alert Level and the Aviation Color Code to Unassigned, noting that no eruptive activity had been confirmed during the previous few months. No significant thermal anomalies or ash deposits on snow were observed in satellite imagery.

In its 31 March 2011 report, AVO stated that "Cleveland experiences frequent episodes of low-level unrest; the summit crater at Cleveland often emits visible plumes of water vapor and possibly small quantities of volcanic gas. Heat associated with this process can produce occasional weak thermal anomalies detected by satellite; however, these do not always indicate eruptive activity has occurred or is imminent."

AVO also stated, in an earlier report, that low-level ash emissions at Cleveland occur frequently and also do not necessarily mean that a larger eruption is imminent.

Geologic Background. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 it produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

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/).


Etna (Italy) — May 2011 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Ongoing effusive fissure eruption that began on 13 May 2008 ends on 4 July 2009

A new eruptive fissure opened on W flank at ~2,800 m elevation on 13 May 2008 (BGVN 33:05)). Effusive eruptions there continued until 4 July 2009. There was some degassing at some of the summit craters degassed, while others were quiet. Figure 137 presents a map made in 2009 showing summit craters and the eruptive fissure. The following account was compiled from reports of the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania (INGV-CT) surrounding events from 16 July 2008 through 10 November 2009.

Figure (see Caption) Figure 137. Schematic map of the eruptive fissure at Etna that opened on 13 May 2008, as updated on 22 May 2009, showing the lava field that emanated from it. In colored versions of this Bulletin, the fissure is a thin blue line, the lava field appears in yellow, and red arrows show some of the near-source flow directions. Summit crater abbreviations (SEC, NEC, and BN) defined in text. From the 25-31 May 2009 report by INGV-CT's Marco Neri (with reference to report WKRVG20090526).

2008. On 15 July 2008 INGV-CT scientists inspected the summit craters at 2,800 m and found degassing from the Northeast Crater (NEC) and to a lesser degree from the Bocca Nuova (BN) crater BN-1. Eruptions issued from Vent 2 of the active NW-trending fissure located E of the summit craters. The activity consisted mainly of weak Strombolian and diffuse ash emissions.

During 15 and 17 July lava flows occurred in the Valle del Bove. During 11-17 August, there was less intense activity and reduced emissions. During 18-24 August NEC and, to lesser degree, one of two craters at the BN degassed. The other summit craters, many obstructed with eroded debris, degassed from the walls and fumaroles along fissures. Although the Southeast Crater (SEC) appeared obstructed with debris, it emitted both diffuse and occasionally intense fumarolic emissions from its walls and crater floor. During 25-31 August the eruptive activity at the fissure at 2,800 m elevation showed little change, with only weak degassing.

A lull in activity ended in mid-October. On 13-20 October, observers saw increased degassing on the NW flanks, including at NEC and BN-1. During 27 October-2 November, the NEC continued with intense degassing. The other summit craters, all obstructed by detritus, showed degassing diffused from the walls and localized fumarolic fields along fissures. The SEC showed diffused and occasionally intense fumarolic activity from its walls and the crater floor.

During 17-23 November, the fissure at 2,800 m continued to show modest effusive activity, producing a small lava flow along the high part of the western wall of the Valle del Bove. On 19 November the lava flow front had reached the elevation of ~2,500-2,600 m.

During 1-7 December the degassing at summit craters was particularly intense at NEC, while at SEC, fumarolic degassing was observed along the flanks of the cone and the crater rim. Observations on 5 December showed small sporadic ash emissions at the upper portion of the eruptive fissure at 2,800 m. Images recorded on 5 December near Mt. Zoccolaro revealed two lava flows trending parallel to the eruptive fissure to the W of the Valle del Bove. Between 29 December 2008 and 19 January 2009 weak degassing continued.

2009. During 19-25 January lava flows from the fissure at 2,800 m fanned out at elevations between ~2,600 m and ~2,450 m. During the same week, the SO2 flux increased. During 26 January-2 February effusive activity at the eruptive vents along the W rim of the Valle del Bove continued in the lava field that has been active since May 2008. During 16-22 March eruptive activity continued along the high flanks of the volcano. At times observers saw intense degassing at the NEC and BN (figure 137).

During 6-12 April the level of activity remained constant and unchanged from the preceding time period.

During 18-31 May and 29 June-5 July 2009 the level of activity remained substantially unchanged, although in the earlier interval there were at least three lava flows, the foremost of which reached ~2,400 m elevation. The SO2 fluxes increased and on 27 and 28 May became particularly elevated, to 8,000 and 6,000 metric tons per day (t/d), respectively. For the later interval, the SO2 fluxes often remained more modest, ~2,900 t/d, with a maximum of ~3,500 t/d recorded 30 June. On 1, 3 and 5 July instruments measured higher peaks, to 7,000 t/d.

Although the explosive eruptive phases ceased in early July, ongoing degassing continued. Throughout August, the activity level remained unchanged, although roaring sounds emerged at SEC. Activity during 28 September-4 October showed little variance, but elevated SO2 fluxes became elevated, with average values ranging between 1,500 and 4,500 t/d, with a peak on 4 October 2009 at 8,000 t/d.

A 10 November message from INGV's Sonia Calvari explained that the effusive fissure eruption that began on 13 May 2008 ended 4 July 2009. There was thereafter an absence of significant explosive activity at the summit craters for a few months before deep explosive activity resumed once again at SEC on 6 November. The INGV monitoring web cameras detected pulsating red glowing from SEC's eastern floor, venting within the depression that cuts its E flank. However, as late as 10 November, no ejecta were found on the summit's snow cover.

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: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania (INGV-CT), Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).


Galeras (Colombia) — May 2011 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Eruption on 25 August 2010; gas emissions in early 2011

Our previous report (BGVN 34:12) covered explosive eruptions at Galeras on 30 September 2009, 20 November 2009, and 2 January 2010 (included in table 11). This report discusses the recent eruption in August 2010 and intense degassing and seismic events between January 2011 and May 2011.

Figure (see Caption) Table 11. Minimum volumes of erupted material from Galeras calculated for events from August 2004 to August 2010. Number of eruptions, Date, Local Time (hour and minute), and Calculated Minimum Volume in cubic meters. Adapted from INGEOMINAS (2010a).

The Instituto Colombiano de Geología y Minería (INGEOMINAS) use an alert scale from I-IV, a Level I being the highest. They declared a Level I alert during an eruption in August 2010 and a Level II during unrest in late January 2011. To date, Level III status has been maintained since 8 February 2011.

Eruption of 25 August 2010. On 20 August 2010, after several days of increased gas emissions, an earthquake swarm began. According to INGEOMINAS, seismicity remained high during 21-22 August. Five volcano-tectonic earthquakes were felt by local residents and caused windows to vibrate. The events were located within a 300-900 m radius of the crater, at depths of less than 2 km. The largest event was M 4.3.

On 23 August a M 4.6 earthquake struck E of Galeras at a depth of 2 km. The Alert Level was raised to II (Orange; "probable eruption in terms of days or weeks"). SO2 emissions peaked at 304 tons/day on 23-24 August (table 12).

Figure (see Caption) Table 12. Emissions of SO2 (metric tons/day) from Galeras during August 2010 measured by ScanDOAS and MovilDOAS (supported by Proyecto NOVAC). Low (under 500); Moderate (500-1,000); High (1,000-3,000); Very High (over 3,000). Courtesy of INGEOMINAS (2010a).

An eruption began at 0400 on 25 August, prompting INGEOMINAS to raise the Alert Level to I (Red; "imminent eruption or in progress"). Meteorological cloud cover initially prevented visual observations of the summit, although an eruption plume was seen among the clouds and thermal anomalies were detected by an infrared camera. At ~0700, an overflight of the flanks was videorecorded which documented a low-altitude gray plume distinctive from the atmospheric clouds (INGEOMINAS, 2010c). With a thermal camera, the Colombian Air Force documented that hot material fell from the secondary crater, El Paisita (INGEOMINAS, 2010b). Ashfall was reported to the NW, as far away as 30 km and quantified as over 37,033 m3 of material (table 11). Ash was reported in Samaniego, Linares, Ancuya, Sandoná, and Consacá. Observers in Pasto (~ 10 km E) reported that gas-and-ash plumes rose 300 m above the crater.

Seismicity associated with the 25 August eruption continued for a period of about 12 hours and gradually declined in the afternoon. INGEOMINAS lowered the Alert Level to II. According to news articles, at least 7,000 residents were ordered by government officials to evacuate, although few left their homes. During 26-31 August, at least 12 earthquakes, M 2-4, struck within a 2 km radius from the crater, at depths not more than 3 km. Gas plumes drifted NW, then S.

Seismic and thermal activity in 2011 through May. Overflights conducted by INGEOMINAS on 7 January 2011 collected multiple infrared and visible photopairs, one set of which appears as figure 113. The maximum temperature of the central crater reached 287.2°C. Temperatures of the rim and flank fumaroles were also recorded. A calculation was made for an area of three fumaroles close to the rim yielding a maximum temperature of 31.2°C.

Figure (see Caption) Figure 113. A set of visible (left) and infrared (right) photo of both the crater and some flank fumaroles at Galeras taken during an INGEOMINAS overflight on 7 January 2011. The flank location is not disclosed. Taken from INGEOMINAS (2011b).

According to INGEOMINAS, on 25 January an emerging seismic pattern from Galeras, characterized by "tornillo-type" earthquakes, was similar to patterns detected before past eruptions. Tornillos are "monochromatic [narrow range of frequencies] long-period seismic events of a few minutes duration with long codas of constantly decreasing amplitude" (Morrissey and Mastin, 2000). The waveform of a tornillo is illustrated and described in more depth in BGVN27:05. The staff noted a strong sulfur gas odor and observed emissions that drifted N from various areas of the crater. Based on changes in seismicity and observed gas emissions, INGEOMINAS raised the Alert Level to II.

On 27 January 2011, scientists again observed emissions from various areas of the crater during an overflight (figure 114) and there was a slight increase in the number of vents. Gas plumes drifted NW and thermal imagery showed clearly-defined fumaroles. Imagery measured the maximum temperature of the central vent around 300°C (reported as 294.7°C).

Figure (see Caption) Figure 114. A stillshot from video footage of degassing at Galeras taken during an INGEOMINAS overflight on 27 January 2011. Gas from the crater and fumaroles was blown in a diffuse plume moving approximately W. Look direction is W. Taken from INGEOMINAS (2011b).

On the morning of 30 January, tornillos ceased.

In early February 2011, seismic levels continued to fluctuate. On 6 February an overflight revealed that gas emissions had increased in comparison to the previous week, forming plumes that drifted NW; however INGEOMINAS lowered the Alert Level to III.

INGEOMINAS reported gas-and-steam emissions on 31 March and 1 April with low ash content. On 1 April, a M 2.3 earthquake occurred 3 km E of the crater at a depth of 6 km and was felt by nearby residents. During an overflight on 2 April, scientists noted a sulfur gas odor and observed that gas emissions rose from multiple areas of the active cone. During 30 March-5 April, SO2 gas values were between 50 and 2,000 tons per day, the latter value considered high for Galeras.

As of 7 April 2011 there was a decrease in transient seismic signals. Within the first week of the month there were three tornillo events with oscillations around 7.5 Hz. After 7 April tornillos were no longer recorded and seismicity was dominated by an increase of events interpreted as the result of fluid motion within the volcanic system and gas emissions. The April 2011 INGEOMINAS monthly report concluded that hypocenters of earthquakes clustered in three distinct zones (figure 115).

Figure (see Caption) Figure 115. A map and cross sections plotting 206 epicenters and hypocenters of volcano-tectonic and hybrid earthquakes that occurred during 1-30 April 2011 at Galeras. In the N-S section (right) and the E-W section (bottom), each line represents 1.7 km of depth with respect to the summit (elevation, ~4,200 m). Magnitudes of seismic events are indicated by circle size. Colors indicate depths, which ranged from under 1 km to over 10 km. Courtesy of INGEOMINAS (2011c).

One zone was a shallow (under1 km) area focused on the crater in the SE sector. A second source was located to the W of the crater with depths up to 2.5 km (with respect to the summit) and a deeper source was identified between 5 and 7.5 km to the E of the crater. The most distant events (up to 8 km) were dispersed with depths around 11 km. The largest of these, M 2.4, occurred at 0454 on 1 April.

Between 13 April-17 May 2011, steam rose up to 1.2 km in altitude and the values of SO2 ranged from low to high with emission values reaching up to 1,600 tons per day. Residents in the city of San Juan de Pasto, just to the E, reported the foul odor of sulfur gases, mainly H2S. On 18 April, an onsite INGEOMINAS team noted a strong odor of sulfur gases and emission from both the main crater and secondary craters and fumarolic fields. That same day a M 1.9 earthquake occurred 6 km SW of Galeras at a depth of ~7 km.

According to INGEOMINAS, favorable weather conditions during 11, 15-10, and 22 May allowed observers to note plumes with heights up to 700 m. On 15-16 May, heavy rains produced lahars that swept down Galeras'slopes carrying rocks, soil, and plant material into and down drainages.

With support from the Colombian Air Force, overflights of Galeras were conducted on 18, 20 and 22 May. Various rates of gas emissions were observed, mostly from vents, secondary craters, and cracks on the slopes of the active cone. Thermal anomalies were detected in various areas, with an average value of 170°C at the bottom of the main crater and 205°C in the secondary crater "The Paisita" N of the active cone.

References. INGEOMINAS, Instituto Colombiano de Geología y Minería, 2010a, Pasto Observatory Work Group: Monthly Report on Galeras and the Volcanoes of Doña Juana, Cumbal, and Azufral, August 2010 (URL: http://intranet.ingeominas.gov.co/pasto/images/1/1e/Boletin_mensual_de_actividad_de_los_volcanes_del_sur_agosto_2010.pdf).

INGEOMINAS, Instituto Colombiano de Geología y Minería, 2010b, Review of Activity from Galeras 24 Aug.-30 Aug., 2010, (URL: http://intranet.ingeominas.gov.co/pasto/Imagen:Resumen_actividad_galeras_ago_24_ago_30_2010.pdf).

INGEOMINAS, Instituto Colombiano de Geología y Minería, 2010c, Sobrevuelo volcán Galeras 8/25/2010, (URL: http://intranet.ingeominas.gov.co/pasto/Videos_2010).

INGEOMINAS, Instituto Colombiano de Geología y Minería, 2011a, Thermal Images 2011, 1/7/2011,

(URL: http://intranet.ingeominas.gov.co/pasto/Imágenes_térmicas_2011).

INGEOMINAS, Instituto Colombiano de Geología y Minería, 2011b, Sobrevuelo volcán Galeras 1/27/2011, (URL: http://intranet.ingeominas.gov.co/pasto/Videos_2011).

INGEOMINAS, Instituto Colombiano de Geología y Minería, 2011c, Pasto Observatory Work Group: Monthly Report on Galeras and the Volcanoes of Doña Juana, Cumbal, and Azufral, April 2011 (URL: http://intranet.ingeominas.gov.co/pasto/images/8/8b/Boletin_mensual_de_actividad_de_los_volcanes_del_sur_abril_2011.pdf).

Morrissey, M.M., and Mastin, L.G., 2000, Vulcanian Eruptions, in Sigurdsson, H., ed., Encyclopedia of Volcanoes: San Diego, California, Academic Press, p. 463-475.

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large open caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate eruptions since the time of the Spanish conquistadors.

Information Contacts: Instituto Colombiano de Geología y Minería (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Popayán, Popayán, Colombia.


Gaua (Vanuatu) — May 2011 Citation iconCite this Report

Gaua

Vanuatu

14.281°S, 167.514°E; summit elev. 729 m

All times are local (unless otherwise noted)


Drops in both tremor and caustic effects on vegetation after mid-2010

The Vanuatu Geohazards Observatory (VGO) report of December 2010 noted seismicity activity and gas emissions during the period from September 2010 through 21 December 2010. This follows the more substantial emissions reported through 19 June 2010. The Ambrym report figure in BGVN 36:05 showing a 2 August 2010 satellite image of the region, includes a plume from Gaua visible for at least 80 km.

The geologic map of Vanuatu (figure 19), formerly called the New Hebrides islands, is centered ~2,200 km N off the New Zealand coast and ~2,100 km NE off the coast of Australia (figure 19). Gaua is sometimes referred to as residing on the island of Santa Maria. This island is also sometimes labeled Gaua, and volcano's topographic high is sometimes called Mont-Geret. The map locates the archepelago's major islands, volcanoes, igneous and metamorphic rocks. Most of the Pliocene and Quaternary islands have been formed by volcanic growth, with uplift in a few cases. Those islands containing older Tertiary rocks resulted from differential elevation of fault bounded blocks (Mitchel and Warden, 1971). Map revised from one on the VGO web site.

Figure (see Caption) Figure 19. Geologic map of Vanuatu. Gaua island is labeled with its alternate name, Santa Maria (Gaua volcano is also called Mont-Geret). The volcano Ambae is situated on Aoba island; the volcano Ambrym, on Ambrym island; and the volcano Yasur, on Tanna island. The key shows basic igneous and metamorphic rock units. Those islands containing older Tertiary rocks have resulted from differential elevation of fault bounded blocks (Mitchel and Warden, 1971). Map revised from one on the VGO web site.

Based on VGO information, the Wellington VAAC reported that on 7 and 16-19 June 2010 an ash plume from Gaua rose to an altitude of ~3 km. On 19 June the plume drifted more than 90 km W but later plume dispersal and emissions were obscured on satellite imagery.

Late 2010 observations on Gaua indicated renewed growth of the vegetation near the volcano's vent and on the island's leeward W side. That area had suffered damage during April-May 2010 due to gas emissions (BGVN 35:05). These observations suggested diminished emissions from the volcano.

Since September 2010, seismic monitoring showed decreasing numbers of counts of volcano-related earthquakes (figure 20). The Alert Level of Gaua volcano was lowered to Level 1 in December 2010. No satellite thermal alerts were measured by MODVOLC during 6 April 2010 through late July 2011.

Figure (see Caption) Figure 20. Gaua volcanic tremor counts recorded for the year 2010. REG adjacent to large pulse traces identify regional earthquakes and/or earthquakes close to Gaua unrelated to volcanic activity. Our previous report (BGVN 35:05) presented a similar plot through 22 April 2010. Courtesy of VGO.

Reference. Mitchel, AH and Warden, AJ, 1971, Geological evolution of the New Hebrides island arc, Journal of Geological Soc. of London, October 1971, 127, p. 501-529 (DOI: 10.1144/gsjgs.127.5.0501)

Geologic Background. The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km summit caldera. Small vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; littoral cones were formed where these lava flows reached the ocean. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. The active Mount Garet (or Garat) cone in the SW part of the caldera has three pit craters across the summit area. Construction of Garet and other small cinder cones has left a crescent-shaped lake. The onset of eruptive activity from a vent high on the SE flank in 1962 ended a long period of dormancy.

Information Contacts: Vanuatu Geohazards Observatory (VGO), Department of Geology, Mines and Water Resources (DGMWR), Vanuatu (URL: http://www.vmgd.gov.vu/vmgd/); MODIS/MODVOLC thermal alerts satellite system, 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/).


Merapi (Indonesia) — May 2011 Citation iconCite this Report

Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


Recovery; intermittent activity; damaging lahars

A VEI 4 (Volcanic Explosivity Index) eruption began at Merapi volcano on 26 October 2010. Within the last 100 years, this volcano had not produced such large-magnitude explosions (Surono and others, in review; Andreastuti and others, 2011). The eruption and secondary events affected areas in all directions around the volcano; pyroclastic flows reached 4 km to the N, 11.5 km to the W, 7 km to the E, and ~15 km to the S, and explosive bombs reached 4 km from the summit in all directions (Jousset, 2010). These events included explosive central vent eruptions that caused significant changes in the summit morphology (figure 48) and according to Act Forum Indonesia, triggered evacuations of communities within a 20 km radius of the summit. In BGVN 36:1/2 we reported on preliminary damage assessments that included significant fatalities and damaged infrastructure.

Figure (see Caption) Figure 48. A photo comparison of Merapi's morphological changes on 23 March 2010 and 16 March 2011. Viewed from the S flank, these photos focus on the summit dome. Non-juvenile material was excavated during two episodes of explosive activity. During 26-29 October ~1.4 x 106 m3 was excavated from the crater and from 4-5 November ~10 x 106 m3 was removed (Surono and others, in review). Photo courtesy of the Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPK") from their report covering 14-20 March 2011.

The explosive events of 2010 represent a break in Merapi's iconic style of activity (Surono and others, in review). "Merapian" is a term often assigned to volcanic events characterized by hot pyroclastic block flows generated during the collapse of growing viscous lava domes (Schmincke, 2004). Standard eruptive activity at Merapi includes "continuous degassing and extrusion of andesitic lava domes whose collapses generate block avalanches and gravitational pyroclastic flows" (Allard and others, 2011).

At least 17 VEI = 2 events have occurred since the catastrophic 15 April 1872 eruption (Siebert and others, 2010). While explosive activity is characteristic of past behavior, assessments of data from 2010 confirm that the 26 October eruptive sequence did not begin with lava extrusion (typical of past eruptions). Instead, intense explosions initiated activity that lasted for ~5 weeks (Surono and others, in review).

During the Merapi special session at the EGU General Assembly held in April 2011, Andreastuti and others (2011) concluded that "the rate of magma extrusion [during the peak of Merapi's 2010 activity] was as much as 17-to 21-times higher [than] the 2006 eruption and the distance of pyroclastic flows in the same drainage (Gendol River) reached 15 km in 2010 and only 7 km in 2006."

This assessment and others (e.g. Alder and others, 2011) linked the highly explosive eruptions of October-November 2010 to elevated and variable gas emissions.

On 4 December 2010, after 40 days of maintaining the highest alert, the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) downgraded the hazard Alert Level from 4 to 3 ("Awas," Red Alert to "Siaga," Watch). The Alert Level was reduced again on 19 January 2011 from 3 to 2 (to "Waspada," Advisory). The Alert Level remained at Level 2 into June 2011.

In this report we review the recovery efforts, Merapi's intermittent activity, and the long-term lahar crisis from March to June 2011. We also include a review of intervals of gas geochemistry data recorded prior to the 26 October 2010 disaster that recently became available.

Recovery efforts. Since October 2010, of the ~300,000 people evacuated, 11,000 were still displaced as of January 2011 (Jakarta Post and IRIN). Authorities had set up nine camps within the city of Yogyakarta and ~70 camps were located farther away within Central Java. On 2 May 2011 the head of Badan Nasional Penanggulangan Bencana (BNPB), Indonesia's National Disaster Management Agency, reported: "With almost all the displaced having moved to temporary shelters, our focus now is how to rebuild communities affected by the disaster" (IRIN, 2011).

In May 2011 the Indonesian government sought international aid (including the International Red Cross and United Nations) and international non-governmental organizations were working in Indonesia for relief efforts. The Jakarta Post reported on 12 May 2011 that Australia had agreed to help Indonesia establish a Disaster Relief Center for disaster management training; the location will be in Sentul, West Java and will serve members of the Association of Southeast Asian Nations (ten countries currently belong to ASEAN). BNPB had called upon the World Bank to begin a Risk Transfer scheme, allowing the local government to focus aid specifically on reconstruction programs.

According to reports from the Jakarta Globe in April 2011, the recent disaster and long history of volcanism at Merapi prompted the Indonesian government to implement an extensive recovery plan for the Yogyakarta province. They prioritized the development of spatial planning maps, expansion of the Merapi National Park, large-scale reforestation (approximately 1,300 hectares), and allocation of 1.35 trillion Rupiah ($155 million) to improve housing, infrastructure, social efforts, and economic stimulation plans. New mapping in the province will reassign land-use and designate relocation sites for former residents. In general, residential areas lying within 10 km of the summit will remain off limits (Sayudi and others, 2010). The Jakarta Post noted these maps also highlight where reforestation will occur. Impacts were substantial to Merapi National Park which lost up to 2,800 hectares out of 6,410 hectares of forest due to the recent eruptions. The Volcano Technical Research Center (BPPTK) reassessed zones in the Sleman region, the area hardest hit by volcanic activity, and will release a map indicating hazard zones. "[These maps] will show which areas are safe, unsafe and suitable for habitation," stated Sleman administration spokeswoman Endah Sri Widiastuti (Jakarta Post).

A controversial location within the 10 km exclusion zone is the village of Kinahrejo, the former home of spiritual leader Mbah Maridjan, called the guardian of Merapi. Working with a team of 17 respected community members, he preserved traditional ceremonies and local culture for Merapi residents. Pyroclastic flows covered the village on 26 October 2010, taking the life of the guardian and other inhabitants who did not evacuate.

The new guardian is Mbah Maridjian's son, Asihono (his new name: Mas Lurah Suraksosihono). During Merapi's disastrous eruptions of October and November, Asihono cooperated with the local government and agencies including the Volcanology and Geological Disaster Mitigation Agency (PVMBG) and BPPTK. On 4 April 2011 Sultan Hamengku Buwono X elected Asihono from a group of eight candidates. In an interview with Jakarta Globe on 5 April 2011, the new guardian explained: "I'm not just going to take a cultural approach based on the dreams or guidance from the spirits, but I will also coordinate with the authorities to protect human life and the environment on Mount Merapi and anticipate the fall of victims to future eruptions."

New dome growth. Seismicity was variable and intermittent explosions were observed at Merapi at least every month through June 2011 since the main eruptive events of October and November 2010. This activity kept local residents vigilant and caused some alarm when incandescence suddenly appeared on Merapi's summit on 25 March and 13 April (figure 49). On these two occasions, a bright glow on the crater's E side was recorded on closed circuit television (CCTV).

Figure (see Caption) Figure 49. Bright incandescence visible on the E side of Merapi's crater was observed at 1940 on 25 March 2011. Courtesy of Volcano Technical Research Center (BPPTK Activity Report 21-27 March 2011).

The point of incandescence was a location of concentrated degassing. In the aftermath of the eruption in 2010, fumaroles became well established and BPPTK intends to resume gas monitoring. They reported that a new dome was growing in the crater: "The final phase is usually marked by eruption of lava dome growth. However, we won't lower the [alert] status as long as the condition of Merapi is still volatile," reported Subandriyo of BPPTK on 11 April 2011 (Kompas News). Since 19 January 2011, the Alert Level was at 2, Advisory.

Gas monitoring. From ultraviolet correlation spectrometer (COSPEC) measurements, BPPTK reported continuous SO2 emissions for both 1992 through early 2009 (BPPTK, 2011b) and January 2005-January 2010 (figure 50). Other data resulted from sampling with Giggenbach bottles; a method of condensate retrieval requiring evacuated alkaline-solution-filled bottles (Williams-Jones and Rymer, 2000). Gas species such as CO2, SO2, H2S, and HCL were analyzed during June 2003-June 2010 (figure 51).

Figure (see Caption) Figure 50. Merapi SO2 fluxes measured from January 2005 to roughly April 2009 using COSPEC (sulfur dioxide in metric tons per day). The curve shown displays an undisclosed averaging function on the data. Modified from BPPTK, 2011a.
Figure (see Caption) Figure 51. Gas sampling at Merapi's Woro Crater (a location map is posted in BGVN 32:02) conducted during June 2003-January 2011. Results from Giggenbach bottle collection and lab analysis for gas species are plotted on log scales. Right-hand vertical axis corresponds to upper (blue) data and trendlines. Left-hand vertical axis corresponds to the lower (black) data trendlines and data. Original concentration units were undisclosed (but Bulletin editors hope to clarify these units in later discussions on Merapi). Modified from BPPTK, 2011a.

SO2 ranged from ~75 metric tons/day (t/d) to ~285 t/d and appeared to peak mid-year in 2005 and 2006 (figure 50). A sudden decrease of 50 t/d in January 2007 preceded an increasing trend that ended in mid-2008. These fluxes also had fewer sustained peaks around March 2008 and declined until the available record ends around March 2009.

The SO2 peak of ~200 t/d generally correlated with the 2005 mid-year episode of elevated seismicity that prompted the BPPTK (at that time called the Directorate of Volcanology and Geological Hazard Mitigation, "DVGHM") to raise the Alert Level from Normal to Advisory (from 1 to 2). However, there were no additional reports of plumes or increased dome activity then (BGVN 32:02).

In 2006, the Alert Level was raised to the highest level on 13 May due to intense dome growth and earthquake activity (BGVN 31:05), a time when SO2 reached ~225 t/d.

According to information recorded in Bulletin reports, the abrupt decrease of SO2 in late 2006-early 2007 did not appear to correlate with significant volcanism in that time interval. The gradual increasing-and-decreasing trend in SO2 flux from 2007 until the end of the record was marked by rare ash plumes (e.g. 19 March 2007, 9 Aug 2007, and 19 May 2008), and modest dome growth (BGVN 32:02). Bulletin reports also noted incandescence and ashfall had continued during 23 May-29 May 2007. MODVOLC thermal anomalies became rare after 5 September 2006 (BGVN 33:10).

Intermittent activity during 18 April-1 May 2011. Unrest at Merapi since the 2010 crisis was characterized by intermittent increases in seismicity as observed from 18 to 24 April 2011 (figure 52). Over the course of that week, rockfall signals doubled from the previous observation period and 39 multiphase events were recorded.

Figure (see Caption) Figure 52. Histograms from September 2010 to June 2011 summarize the number of seismic events from four categories is summarized for Merapi. Events shown are rockfalls; MP, multiphase (shallow source, dominant frequency ~1.5 Hz); VA, deep volcano-tectonic earthquakes, 2.5-5 km below the summit; VB, shallow volcano-tectonic earthquakes, less than ~1.5 km below the summit. Tremor episodes were infrequent and thus excluded. Courtesy of BPPTK (Activity Report 6-12 June 2011). (A figure in BGVN 36:1/2 presented representative samples of these various waveforms.)

BPPTK also reported that ground deformation was variable throughout this time period as EDM (Electronic Distance Meter) measurements were recorded across the summit. Measurements made on 18 April 2011 compared with those recorded on 25 April 2011 from the monitoring post of Selo showed the following changes: a difference in distance amounting to +8 mm (R1) and a change in movement amounting to 0.1 mm per day.

Measurements carried out on 18 April 2011 compared to those of 24 April 2011 from Jrakah monitoring post indicated the following changes: a difference in distance amounting to -4 mm (R1) with a change in movement amounting to 0.5 mm per day, and a difference in distance of +6 mm (R2) with a movement of 0.7 mm per day.

Plumes of ash and gas reached an altitude of ~800 m on 24 and 25 April. Communities near Merapi's flanks reported ashfall on 29 April, 30 April, and 1 May 2011. (BPPTK Activity Report 25 April-1 May 2011).

Ongoing hazards. The recent weekly report by BPPTK (20 March to 12 June 2011), described plumes of gas and ash that occurred regularly. As measured from above the summit, the average height of these plumes was ~500 m; a maximum height of 900 m was recorded on 20 April. The tallest plume was accompanied by a ramping up of earthquakes and the regular occurrence of lahars, some hot enough to steam while racing through river drainages (figure 53).

Figure (see Caption) Figure 53. On 21 March 2011 and 14 April 2011 steaming lahars descended Merapi's flanks. This photo was taken on 14 April 2011from a CCTV camera installed in Pencar village, less than 20 km S of Merapi in the Desa Bimomartani region. Note Merapi volcano in upper right-hand area of the photo. Courtesy of BPPTK (Activity Report discussing 11-17 April 2011).

A large amount of volcanic ash fell from Merapi's explosive eruptions in 2010; this has aggravated slope stability and led to increased lahar hazards. In an interview on 11 April 2011 for Kompas News, Subandriyo, the Head of the BPPTK explained that "only about 30 percent" of the material that fell on Merapi's flanks has been remobilized by erosion. "Therefore, the threat of [lahars] will occur two to three years ahead."

As of June 2011, 15 major lahars had occurred since November 2010. The worst occurred on 23 January 2011 along the eroded banks of the Putih river. The major highway between Magelang and Yogyakarta was cut off when a 60 m wide section of blacktop was torn away by torrential mudflows. As a result, hundreds of homes within 12 different villages near the river were inundated forcing 5,000 people to flee. There were three fatalities.

Major infrastructure was also affected; 52 levees were damaged and 14 bridges were destroyed. Intense lahar damage was also reported along the SE rivers: Blongkeng, Batang, Progo, Code, and Gendol.

References. Allard, P., Métrich, N., and Sabroux, J.-C., 2011, Volatile and magma supply to standard eruptive 549 activity at Merapi volcano, Indonesia. EGU General Assembly 2011, Geophysical 550 Research Abstracts 13, EGU 2011-13522 (2011).

Andreastuti, S., Costa, F., Pallister, J.,Sumarti., S., Subandini, S., Heriwaseso, A., Kurniadi, Y. , Petrology and pre-eruptive conditions of the 2010 Merapi magma. EGU General Assembly 2011, Geophysical 550 Research Abstracts 13, EGU2011-5150 (2011).

BPPTK, Volcano Technical Research Center, 2011a, Geochemistry of Merapi. (URL: http://www.merapi.bgl.esdm.go.id/aktivitas_merapi.php?page=aktivitas-merapi&subpage=geokimia)BPPTK, Volcano Technical Research Center, 2011b, Monitoring of Geochemical and Temperature of Merapi. (URL: http://www.merapi.bgl.esdm.go.id/pages.php?page=geokimia-dan-suhu)

Schmincke, H.-U, 2004, Volcanism, Berlin:Springer, 324 pp.

Jousset, P., 12/6/10, Centennial Eruption at Merapi volcano: October/November 2010, MIAVITA, European Commission. (URL: http://miavita.brgm.fr/Documents/MIAVITA-Merapi-eruption.pdf)

Sayudi, D.S., Nurnaning, A., Juliani, DJ., Muzani, M.; 2010, "Peta Kawasan Rawan Bencana Gunungapi Merapi, Jawa Tengah Dan Daerah Istimewa Yogyakarta 2010," (The map of the Rawan Bencana Gunungapi Merapi Region, Central Java: Yogyakarta Special District 2010), Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK"). (URL: http://www.merapi.bgl.esdm.go.id/peta/2011/04/KRBGMerapi2010FINALcopyright_78a74b.jpg)

Siebert L., Simkin T., and Kimberly P., 2010, Volcanoes of the World, 3rd edition, University of California Press, Berkeley, 558 p.

Surono, Jousset, P., Pallister, J., Boichu, M., Buongiorno, M.F., Budisantoso, A., Costa, F., Andreastuti, S., Prata, F., Schneider, D., Clarisse, L., Humaida, H., Sumarti, S., Bignami, C., Griswold, J., Carn, S., Oppenheimer, C., (in review), 100-year explosive eruption of Java's Merapi volcano, Journal of Volcanology and Geothermal Research.

Williams-Jones, G. and Rymer, H., 2000, Hazards of Volcanic Gases, in Sigurdsson, H., ed., Encyclopedia of Volcanoes: San Diego, California, Academic Press, p. 997-1004.

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Information Contacts: Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK") (URL: http://www.merapi.bgl.esdm.go.id/index.php); Badan Nasional Penanggulangan Bencana (BNPB- Indonesian National Disaster Management Agency) (URL: http://dibi.bnpb.go.id); Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); IRIN News (URL: http://www.IRINnews.org); Jakarta Globe (URL: http://www.thejakartaglobe.com); The Jakarta Post (URL: http://www.thejakartapost.com); KompasNews, Jakarta, Indonesia (URL: http://www.Kompas.com); Mitigate and Assess risk from Volcanic Impact on Terrain and human Activities project (MIAVITA) (URL: http://miavita.brgm.fr/default.aspx); Act Forum Indonesia (URL: http://www.actalliance.org/); Relief Web (URL: https://reliefweb.int/).


Ulawun (Papua New Guinea) — May 2011 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Seismicity ongoing with plumes during May 2010-May 2011

This report discusses Ulawun's ongoing mild seismicity, variably colored, though often white plumes, and other observations during May 2010 to late May 2011. The bulk of the reporting came from the Rabaul Volcano Observatory (RVO) with some information on plumes from the Darwin Volcanic Ash Advisory Center (VAAC) and others. Seismicity at Ulawun has generally been low since 2007, with occasional modest increases and steam emission (BGVN 33:03, 34:10, and 35:02).

Activity during 2010. RVO reported that, according to Real-time Seismic Amplitude Measurements (RSAM), seismic activity increased on 18 May 2010. According to RVO, white vapor emitted during 1-20 May 2010 became thicker during 22-28 May. On 22 and 25 May, some plumes were partially gray. According to the Darwin VAAC, plumes on 22-28 May reached an altitude of 3 km and extended as far as 70 NM in variable directions.

People on the S and SE sides of the island heard "low jetting" noises during 24-25 May 2010. Weak and fluctuating incandescence was seen from the S at night during 28-29 May. Emissions became gray in color during 29-31 May, and on 30 May very fine ashfall was reported in areas to the SSW, S, and SSE. On 1 and 2 June only white vapor emissions were noted. RVO recommended a Stage 1 Alert as a result of increasing seismicity and occasional gray plumes, incandescence, and audible noises. According to a news report (Radio Australia), up to 10,000 residents live adjacent to Ulawun.

According to RVO, during 2-12, 16-19, and 23-25 June 2010 residents heard occasional low roaring or rumbling noises daily on the ESE, SE, S, and NW flanks. During 2-19 and 23-26 June, white to gray-brown plumes rose to ~3 km altitude (figure 15). The Darwin VAAC noted that between 3-6 June, the plumes extended up to 315 km W. On 16-17 and 19-20 June, white and gray plumes rose 1 km above the summit. Very fine ash particles fell in Ulamona (~10 km NW) on 3 and 8 June, and then fell daily during 9-19 and 23-25 June on the NW, W, and SW flanks. Throughout June, fluctuating incandescence from the summit crater was seen at night from the S, SW, N, and SE flanks. RVO reported that on 18 and 19 June, seismicity increased to a high level and was dominated by volcanic tremor. Seismicity declined to moderate levels on 20 June and, based on RSAM values, declined further on 26 June 2010.

Figure (see Caption) Figure 15. Natural-color image of a small white plume venting from Ulawun's summit crater and blowing W on 10 June 2010. Image was taken by the Advanced Land Imager on NASA's Earth Observing-1 (EO-1) satellite. Green vegetation predominates outboard of 1-2 km from the summit. On the upper slopes, bare (unvegetated) volcanic rocks prevail, appearing as charcoal-brown streaks. The plume's pale color suggests that, of the visible components in the plume, steam rather than ash predominates. NASA Earth Observatory image created by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 team and the United States Geological Survey. Original (but now slightly revised) caption crafted by Michon Scott.

According to RVO, white-to-gray plumes rose less than 500 m from Ulawun during 27 June-9 July 2010, and fine ash fell in areas to the SW, W, and NW. The Darwin VAAC reported that during 1-5 July, ash plumes drifted 55-195 km at an altitude of 3 km. On 28 June and during 5-6 July the volcano omitted occasional roaring noises. A slight increase in seismicity (above moderate levels) took place during 5-8 July.

RVO reported diffuse gray plumes that rose 200-500 m above Ulawun during 16-21 July 2010. Plumes were white to light-brown during 21-29 July. During 6-24 August, white and gray-to-brown plumes rose no more than 300 m above Ulawun, and fine ash fell on the NW and W flanks. Tremor continued, but overall seismicity declined slightly. RSAM values remained at a moderate level.

Based on analyses of satellite imagery and information from RVO, the Darwin VAAC reported that on 26 November 2010 an ash plume from Ulawun rose to an altitude of 3.7 km and drifted 55 km NE.

Several videos of Ulawun's plumes as posted on the web in 2010 showed them as white in color (Sabretoothed69, 2010). Other brief video by the same author take viewers to the Ulawun seismic station and its drum recorder, and to witness aspects of local culture such as villagers dancing.

Activity during 2011. According to RVO, the mild activity that began in May 2010 continued during 1 January-28 February 2011. The activity was characterized by brown-to-gray ash plumes that rose less than 500 m and produced fine ashfall to the SE. Sulfur-dioxide plumes drifted SE on 5 and 31 January. During 23-26 February, gray ash plumes occasionally drifted NE, SW, and NW.

RVO reported that during 1-9 May 2011, diffuse white plumes rose from Ulawun and low to modest RSAM values occurred (70-100 units). During 9-10 May, RSAM values distinctly increased, fluctuated, and peaked at 1,300 units before declining back to 100 units. During this time, local residents heard booming.

During 10, 13-14, 17, and 19-27 May, RVO reported gray-to-brown ash plumes rose above Ulawun's summit crater. On 17 May, emissions became briefly forceful and booming noises were reported. Light ashfall deposited between Ubili and Ulamona to the NW and Voluvolu to the NE, as well as on the NW and W flanks. Weak, fluctuating incandescence was observed on 22 May.

Reference. Sabretoothed69, 2010 (uploaded on 7 November 2010), YouTube (URL: http://www.youtube.com/watch?v=UnCSeky3Mes, uploaded by sabretoothed69)

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

Information Contacts: Rabaul Volcano Observatory (RVO), PO Box 386, Rabaul, Papua New Guinea; 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 Earth Observatory (URL: http://earthobservatory.nasa.gov/); Radio Australia (URL: http://www.radioAustralia.net.au/pacbeat/).


Yasur (Vanuatu) — May 2011 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Explosion induced ash falls, strong degassing during late May-early June 2011

On 12 May 2011, Yasur's crater (figure 42), which has undergone near-continuous eruption for over 200 (possibly 800) years, emitted persistent strong explosions that could be heard and felt by nearby residents. Satellite images (OMI and MODIS) and seismic data collected from the volcano's monitoring station also confirmed strong degassing and stronger than typical explosive activity since the beginning of May 2011. The volcano sits on Tanna Island in the island nation called the Republic of Vanuatu (formerly New Hebrides; ~2,200 km N off of New Zealand's coast and ~2,100 km NE off of Australia's coast). As seen on the map in the Gaua report in this issue (BGVN 36:05), Tanna island lies near the S end of the Republic. Figure 42 presents information about Vanuatu's tectonic setting and Yasur volcano's location and shape.

Figure (see Caption) Figure 42. (a) Map showing the Vanuatu arc in the SW Pacific, the position of the 6-7 km deep Vanuatu trench, convergence rates (indicated by arrows in cm/yr), and the location of Tanna volcanic island, which rises from a 1-km-deep plateau (redrawn from Pelletier and others, 1998 and Calmant and others, 2003). (b) Schematic map of Tanna island with the locations of the main volcanic centers (redrawn from Carney and MacFarlane, 1979). In its long dimension (N-S), Tanna island stretches ~40 km; its width is ~19 km. (c) Map of southeastern Tanna showing the Yasur crater and Yenkahe horst, bounded by the Siwi ring fracture (redrawn from Nairn and others, 1988 and Allen, 2005). From Métrich and others (2011).

An assessment conducted by the Vanuatu Geohazards Observatory (VGO) during 30 May-3 June 2011 found Yasur's crater in a state of high activity with strong explosions and bomb emissions from all of the three active vents. Fresh volcanic bombs fell around the crater rim, and some reached ~500 m S to the parking area, landing there about once per minute. Residents heard and viewed explosions from their villages.

Observations and assessments made by VGO during 11-12 June 2011 indicated a decrease in eruptive vigor and a return to more typical conditions. Explosions became both slightly weaker and less frequent. Constant Strombolian activity with occasional ejections of lava bombs still occured around the volcano.

On 7-8 July 2011 the VGO reported that Yasur volcano was at a high level of activity with strong degassing and ash emissions from all three active vents. The ash falls were mostly over the W part of the island. Fresh volcanic bombs had fallen around the crater rim. Some explosions could be heard and viewed from the villages, a pattern locals had noticed since the beginning of the year.

Hazard terminology and levels. The operative hazards scale for Yasur spans from 0 to 4, with larger values indicating greater hazards. It is called the VVAL (Vanuatu Volcano Alert Level).

Level 2 is defined as "Moderate eruptions, danger close to the volcano vent, within parts of Volcanic Hazards Map Red Zone" (see map in BGVN 35:04).

Level 3 is defined as "Large eruption, danger in specific areas within parts of Volcanic Hazards Map Red and Yellow Zones."

In the early phases of the upsurge in vigor, the VVAL for Yasur remained at Level 2 with the note that the risk area for volcanic projectiles remained in areas near the volcano crater and vicinity.

Associated with the assessed late-May to early June behavior, the VVAL stepped up to Level 3. A zone surrounding the summit became strictly prohibited (see visitor's map, BGVN 35:04).

Associated with the 11-12 June 2011 observations of decreasing vigor, the VVAL dropped to Level 2.

Background. Métrich and others (2011) point out that Siwi caldera is a volcanic complex containing both persistent eruptive activity of basaltic-trachyandesite composition (Yasur volcano) and rapid block resurgence (Yenkahe horst). They note that available data suggested that Yasur volcano releases, on average, over 134 x 103 tons/day of H2O and 680 tons/day of SO2. Measurements also indicated other gas fluxes: 840 tons/day of CO2, 165 tons/day of HCl, and 23 tons/day of HF.

References. Allen, S.R., 2005, Complex spatter- and pumice-rich pyroclastic deposits from an andesitic caldera forming eruption: The Siwi pyroclastic sequence, Tanna, Vanuatu, Bulletin of Volcanology, v. 67, pp. 27-41.

Calmant, S., Pelletier, B., Lebellegard, P., Bevis, M., Taylor, F.W., and Phillips, D.A., 2003, New insights on the tectonics along the New Hebrides subduction zone based on GPS results, Journal of Geophysical Research, v. 108, no. B6, pp. 2319-2339.

Carnay, JN., and MacFarlane, A, 1979, Geology of Tanna, Aneityum, Futuna and Aniva, New Hebrides Geological Survey Report 1979, pp. 5-29.

Métrich, N., Allard, P., Aiuppa, A., Bani, P., Bertagnini, A., Shinohara, H., Parello, F., Di Muro, A., Garaebiti, E., Belhadj, O., and Massare, D., 2011, Magma and Volatile Supply to Post-collapse Volcanism and Block Resurgence in Siwi Caldera (Tanna Island, Vanuatu Arc), Journal of Petrology, v. 52, no. 6, pp. 1077-1105; DOI: 10.1093/petrology/egr019.

Nairn, I.A., Scott, B.J., and Giggenbach, W.F., Yasur volcanic investigations, Vanuatu September 1988, New Zealand Geological Survey Report 1988, pp.1-74.

Pelletier, B., Calmant, S., and Pillet, R., 1998, Current tectonic of the Tonga-New Hebrides region, Earth and Planetary Science Letters, v. 164, pp. 263-276.

Geologic Background. Yasur has exhibited essentially continuous Strombolian and Vulcanian activity at least since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island in Vanuatu, this pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide open feature associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: Vanuatu Geohazards Observatory, Department of Geology, Mines and Water Resources of Vanuatu (URL: http://www.geohazards.gov.vu); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); MODIS/MODVOLC Thermal Alerts System, Hawai'i Institute of Geophysics and Planetology (HIGP), 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/); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac/, http://vaac.metservice.com/).

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