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Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

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

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

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

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

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

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

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

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

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

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

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

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



Ibu (Indonesia) — June 2023 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia (Multiplatform Application for Geohazard Mitigation and Assessment in Indonesia), Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Dukono (Indonesia) — June 2023 Citation iconCite this Report

Dukono

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia (Multiplatform Application for Geohazard Mitigation and Assessment in Indonesia), Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sabancaya (Peru) — May 2023 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

Information Contacts: Instituto Geofisico del Peru (IGP), Centro Vulcanológico Nacional (CENVUL), Calle Badajoz N° 169 Urb. Mayorazgo IV Etapa, Ate, Lima 15012, Perú (URL: https://www.igp.gob.pe/servicios/centro-vulcanologico-nacional/inicio); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Sheveluch (Russia) — May 2023 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Kamchatka Volcanological Station, Kamchatka Branch of Geophysical Survey, (KB GS RAS), Klyuchi, Kamchatka Krai, Russia (URL: http://volkstat.ru/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); Kam 24 News Agency, 683032, Kamchatka Territory, Petropavlovsk-Kamchatsky, Vysotnaya St., 2A (URL: https://kam24.ru/news/main/20230411/96657.html#.Cj5Jrky6.dpuf); Simon Carn, Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA (URL: http://www.volcarno.com/, Twitter: @simoncarn).


Bezymianny (Russia) — May 2023 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


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

Bezymianny is located on the Kamchatka Peninsula of Russia as part of the Klyuchevskoy volcano group. Historic eruptions began in 1955 and have been characterized by dome growth, explosions, pyroclastic flows, ash plumes, and ashfall. During the 1955-56 eruption a large open crater was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater. The current eruption period began in December 2016 and more recent activity has consisted of strong explosions, ash plumes, and thermal activity (BGVN 47:11). This report covers activity during November 2022 through April 2023, based on weekly and daily reports from the Kamchatka Volcano Eruptions Response Team (KVERT) and satellite data.

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

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

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

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

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

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

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Kamchatka Volcanological Station, Kamchatka Branch of Geophysical Survey, (KB GS RAS), Klyuchi, Kamchatka Krai, Russia (URL: http://volkstat.ru/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Chikurachki (Russia) — May 2023 Citation iconCite this Report

Chikurachki

Russia

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

All times are local (unless otherwise noted)


New explosive eruption during late January-early February 2023

Chikurachki, located on Paramushir Island in the northern Kuriles, has had Plinian eruptions during the Holocene. Lava flows have reached the sea and formed capes on the NW coast; several young lava flows are also present on the E flank beneath a scoria deposit. Reported eruptions date back to 1690, with the most recent eruption period occurring during January through October 2022, characterized by occasional explosions, ash plumes, and thermal activity (BGVN 47:11). This report covers a new eruptive period during January through February 2023 that consisted of ash explosions and ash plumes, based on information from the Kamchatka Volcanic Eruptions Response Team (KVERT) and satellite data.

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

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

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

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Marapi (Indonesia) — May 2023 Citation iconCite this Report

Marapi

Indonesia

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

All times are local (unless otherwise noted)


New explosive eruption with ash emissions during January-March 2023

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1).


Kikai (Japan) — May 2023 Citation iconCite this Report

Kikai

Japan

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Lewotolok (Indonesia) — May 2023 Citation iconCite this Report

Lewotolok

Indonesia

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

All times are local (unless otherwise noted)


Strombolian eruption continues through April 2023 with intermittent ash plumes

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

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

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

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

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


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

Barren Island

India

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

All times are local (unless otherwise noted)


Thermal activity during December 2022-March 2023

Barren Island is part of a N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic flow and surge deposits. Eruptions dating back to 1787, have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast. Previous activity was detected during mid-May 2022, consisting of intermittent thermal activity. This report covers June 2022 through March 2023, which included strong thermal activity beginning in late December 2022, based on various satellite data.

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

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

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

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

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

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

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Villarrica (Chile) — April 2023 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Fuego (Guatemala) — April 2023 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


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

Fuego, one of three large stratovolcanoes overlooking the city of Antigua, Guatemala, has been vigorously erupting since January 2002, with recorded eruptions dating back to 1531 CE. Eruptive activity has included major ashfalls, pyroclastic flows, lava flows, and lahars. Frequent explosions with ash emissions, block avalanches, and lava flows have persisted since 2018. More recently, activity remained relatively consistent with daily explosions, ash plumes, ashfall, avalanches, and lahars (BGVN 48:03). This report covers similar activity during December 2022 through March 2023, based on information from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH) daily reports, Coordinadora Nacional para la Reducción de Desastres (CONRED) newsletters, and various satellite data.

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

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

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

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

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

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

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

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

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

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

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Bulletin of the Global Volcanism Network - Volume 33, Number 01 (January 2008)

Managing Editor: Richard Wunderman

Etna (Italy)

Tall sustained lava fountains, lava flows, and tephra blanket on 22-24 November 2007

Heard (Australia)

Rare thermal anomalies through March 2008 suggest eruptions

Huila, Nevado del (Colombia)

Eruptions in February, April, and May 2007; lahars take out bridges

Krakatau (Indonesia)

Repeated minor eruptions during October-November 2007

Llaima (Chile)

Ash plumes observed in May and August 2007; new eruption beginning 1 January 2008

Sheveluch (Russia)

Lava-dome growth and block-and-ash flows continue April-December 2007

Turrialba (Costa Rica)

Fumarolic increases during August 2007-January 2008

Ubinas (Peru)

Continuing ashfall during 2006-2007



Etna (Italy) — January 2008 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Tall sustained lava fountains, lava flows, and tephra blanket on 22-24 November 2007

After the 10-hour-long episode of sustained lava fountaining from the Southeast Crater (SEC) on 4-5 September 2007 (BGVN 32:09), Etna remained quiescent for about three weeks. Ash emissions then resumed from the vent on the eastern flank of the SEC cone, which had been the main focus of activity since mid-August 2007. During October, ash emissions occurred intermittently, at times with minor incandescent ejections. This activity persisted until mid-November, after which there was a week-long pause until the early morning of 22 November. That day around 0500, weak Strombolian activity and ash emission started from the vent on the E flank of the SEC and continued with increasing strength for the following 36 hours.

A series of explosions occurred at the Bocca Nuova between 1658 and 1705 on 23 November, ejecting dark gray ash plumes, and producing strong seismic signals on nearby stations. During the following hours, Strombolian explosions occurred from the SEC vent, ejecting incandescent bombs to several tens of meters high.

After 2020, the vigor increased, with bursts of bombs rising to 100 m high, accompanied by a sharp rise in tremor amplitude. By 2130, a broad, pulsating lava fountain rose from the vent. Then, 15 min later, observers saw sustained fountaining up to 600 m high. The fountains discharged from what appeared to be two closely spaced sources within the depression, often making a V-shape.

Lava spilled over the vent's rim in at least three locations (figure 129), feeding three narrow branches of lava that ran E and coalesced, before spreading down the steep W slope of the Valle del Bove. A fourth lava flow started from an area ~ 150 m NE of the active vent, where fountain-fed spatter rapidly accumulated and ultimately began to flow. This flow joined the main lava flow toward the Valle del Bove at about 2,500 m elevation.

Figure (see Caption) Figure 129. Preliminary map of the lava flows emitted during Etna's lava-fountaining episodes of and 4-5 September 2007 and 23-24 November 2007. Both sets of flows discharged from the active vent on the E flanks of Southeast Crater (SEC). Courtesy of INGV-Catania.

The November lava flowed mostly on top of, or immediately adjacent to, the lava emitted during the eruption of early September 2007 (figure 129). At the base of the Valle del Bove slope, the November eruption's lava fanned out to form several minor lobes, the longest of which advanced to 1,670 m elevation, 4.2 km from the vent (figure 130; Burton and Neri, 2007).

Figure (see Caption) Figure 130. Aerial view, taken on 25 November 2007 from a helicopter of the Italian Civil Protection, of the lava flows erupted at Etna during 23-24 November 2007. View is from SE across the Valle del Bove (foreground). From Burton and Neri (2007), courtesy of INGV-Catania.

The explosive activity fed a dense tephra plume. It blew NE and caused ash and lapilli falls as far as 80 km away in southern Calabria, (Andronico and Cristaldi, 2007). At Piano Provenzana (~ 6.5 km NNE of the summit), the deposit was about 3 cm thick. Coarse scoriae, up to 5 cm across, fell ~ 10 km NNE from the SEC (in Linguaglossa) during the first hour of the eruption. During the following hours, finer ash fell in areas adjacent Etna and to the W.

Shortly after 0300 on 24 November, the eruptive activity and volcanic tremor amplitude began to diminish gradually, and during the next 20 min the fountain height dropped from ~ 600 m to under 200 m. Subsequently, the fountaining gave way to a series of powerful explosions, which showered the entire SEC cone with meter-sized bombs. The last of these explosions occurred at 0338, and for another 45 min after this, only minor explosive ejections occurred from the vent.

During the following hours, material continued to crumble and collapse on the steep slopes around the vent, exposing incandescent rock in countless spots. By 0600, the tremor amplitude had dropped to background levels, and no further eruptive activity was noted at the vent.

For several days after the eruption, gravitational instability of the new pyroclastic deposit, which had accumulated to thicknesses of several tens of meters, especially on the N side of the vent, caused occasional slides of material, exposing the still-incandescent interior of the deposit. A particularly large collapse from the overhanging W rim of the vent at 1713 on 27 November may have been accompanied by minor explosive activity, with incandescent material rolling to the base of the SEC cone (Calvari, 2007).

Ash emissions from the same vent occurred on 10 January 2008 and again on 1-3 February (figure 131). In mid-February such emissions became more frequent; some produced plumes several hundreds of meters high.

Figure (see Caption) Figure 131. Ash plume rising about 1 km high above the active vent on the eastern slope of Etna's Southeast Crater cone, on the morning of 10 January 2008. View is from Trecastagni, ~ 16 km SSE of the active vent. Courtesy of INGV-Catania.

References. Andronico, D. and Cristaldi, A., 2007, Il parossismo del 23-24 novembre 2007 al Cratere di SE: caratteristiche del deposito di caduta. Report published on-line at: http://www.ct.ingv.it/Report/RPTVETCEN20071123.pdf

Burton, M. and Neri, M., 2007, Stato attuale e osservazione dell'Etna 25 novembre 2007. Report published on-line at: http://www.ct.ingv.it/Report/WKRVGREP20071125.pdf

Calvari, S., 2007, Rapporto sull'attivit? dell'Etna del 27 novembre 2007. Report published on-line at: http://www.ct.ingv.it/Report/WKRVGREP20071127.pdf

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

Information Contacts: Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.


Heard (Australia) — January 2008 Citation iconCite this Report

Heard

Australia

53.106°S, 73.513°E; summit elev. 2745 m

All times are local (unless otherwise noted)


Rare thermal anomalies through March 2008 suggest eruptions

Due to its isolated location in the S Indian Ocean on the Kerguelen Plateau, Heard Island is rarely visited, and satellite imagery provides the only regular information on eruptive activity. The Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System MODVOLC provides an analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) satellite thermal anomaly data, with 1-2 daily observations. That system remains the best source of evidence at isolated, glacier-covered volcanoes like Heard, though it is difficult to determine how often meteorological clouds may obscure thermal anomalies.

The last report summarized activity beginning in March 2000 (BGVN 32:06), describing three eruptive episodes (based on thermal anomalies). The last thermal anomaly mentioned was on 6 April 2007. As seen on table 5, the MODVOLC system recorded the next thermal anomaly on 24 July 2007. For the rest of 2007, there were anomalies recorded on two days in August and two days in November. During 2008 as late as 2 March, anomalies occurred in February and March.

Table 5. Thermal anomalies measured by MODIS/MODVOLC over Heard Island during 7 April 2007 through 2 March 2008. Courtesy of HIGP Thermal Anomalies Team.

Date Time (UTC) Pixels Satellite
24 Jul 2007 1750 1 Aqua
12 Aug 2007 1820 1 Terra
30 Aug 2007 1955 1 Aqua
11 Nov 2007 1800 1 Terra
11 Nov 2007 1945 2 Aqua
22 Feb 2008 1955 3 Aqua
02 Mar 2008 1950 1 Aqua

Geologic Background. Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben because of its extensive ice cover. The active Mawson Peak forms the island's high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported at this isolated volcano, but observations are infrequent and additional activity may have occurred.

Information Contacts: 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/).


Nevado del Huila (Colombia) — January 2008 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Eruptions in February, April, and May 2007; lahars take out bridges

Nevado del Huila was the scene of elevated seismicity during February and May 2000 (BGVN 25:05). In 1994, the M 6.4 Paéz earthquake triggered avalanches and lahars along the Paéz river, which took many lives (BGVN 19:05, 19:07). A more recent abstract summarized the losses from the Paéz earthquake as 271 reported deaths, 1,700 people missing, and more than 32,000 people evacuated during the crisis (Schuster, 1996). Correa and Pulgarín (2002a, b) wrote reviews of the volcano's geology, hazards, and related topics.

This report discusses the onset of eruptions during February 2007 and repeated eruptions during April and May 2007. During the most active intervals during February and April there were substantial ash plumes, lahars, earthquake swarms (and some individual earthquakes up to M ~ 3), and the growth of fissures, crevasses, and new fumaroles on the volcano's upper, glacier-covered slopes. During the April eruption thousands of residents evacuated. This report draws heavily on material issued by the Instituto Colombiano de Geología y Minería (INGEOMINAS), Observatory Vulcanológico and Sismológico de Popayán.

The andesitic-dacitic edifice (figure 6) is large and elongate (with a footprint of ~ 170 km2 ). Located in the Central Cordillera (figure 7), it forms Colombia's highest peak. This area only 3 degrees from the equator experiences periods of high precipitation. In 1995 its alpine glaciers covered ~ 13.4 km2 with an approximate volume of 800 x 106 m3 (Pulgarín and others, 2005).

Figure (see Caption) Figure 6. An aerial photo showing the upper slopes of Nevado del Huila from the W. The photo was taken at unknown date prior to 2002 when the volcano was in a non-eruptive state. From N to S the four main peaks consist of Pico Norte ("N"), Pico la Cresta ("LC"), Pico Central ("C"), and Pico Sur ("S"). Heavy cloud banks such as those in the foreground are common, adding to the difficulty of monitoring this remote, high stratovolcano. Taken from Correa and Pulgarín (2002a).
Figure (see Caption) Figure 7. A sketch map showing the three distinct ranges (cordillera) of the Andes in Colombia, with Nevado del Huila indicated. Between the Western and Central cordillera, the valley contains the Cauca river (not shown). It flows N and ultimately joins the Magdalena river (not shown), traveling ~ 1,350 km beyond its starting point to reach Northern Colombia. Between the Central and Eastern cordillera, the valley contains the Magdalena river (not shown). It flows N and travels ~ 1,500 km before entering the Caribbean sea at Barranquilla. After a digital elevation map prepared by the USGS; courtesy of the International Charter "Space and Major Disasters."

The April 2007 activity impacted not only the immediate vicinity of the volcano, but also ten's of kilometers to the S, where rivers carried debris. In order to assess the impact of the lahars, INGEOMINAS compared calibrated Landsat images from before and after the 19 February eruption. They found clear visual evidence that the lahars had discolored the Betania Reservoir, ~ 150 km downstream.

The Símbola joins the Paéz river ~ 28 km (straight-line distance) S of Pico Central (figure 8). Adjacent that intersection sits the town of Belacázar (figure 9). Another ~ 15 km downstream, the Paéz merges into the Magdalena river, the 6th largest river the world in terms of sediment yield (~ 690 t / (km2 ? yr); Restrepo and others, 2005). A straight-line distance of ~ 50 km downslope from the intersection of the Paéz and Magdalena rivers, the Magdalena enters the Betania Reservoir.

Figure (see Caption) Figure 8. A false-color Landsat TM5 mosaic image showing the Magdalena river and some of its headwaters (eg. the Paéz and Símbola rivers) that feed from Nevado del Huila (upper left corner). Images are Landsat-5, 30-m resolution. Left image acquired 7 August 1989. Right image acquired 2 January 1988. The annotations include the epicenter for the Paéz earthquake (star) and the Betania Reservoir. On the colored version, snow is shown by the elongate magenta region around Huila.Created March 2007 by INGEOMINAS; courtesy of the International Charter "Space and Major Disasters."
Figure (see Caption) Figure 9. Map indicating the topography and naming conventions on the Huila edifice and some surrounding regions. The inset shows the volcano's location at the triangle labeled CVNH. Note epicenter for the Paéz earthquake. This was modified from a larger map in Correa and Pulgarín (2002a).

Beyond the reservoir, the Magdalena flows NNE; it ultimately reaches the Carribean Sea at a large delta in N Colombia by the large city of Barranquilla (figure 7). According to Restrepo and Kjerfve (2000), "the Magdalena is the largest river discharging directly into the Caribbean sea [228 km3 water annually], and it has the highest sediment yield of any medium-sized or large river along the entire E coast of South America."

Unrest and 19 February eruption. Since 1994 the volcano has been monitored by multiple telemetered seismometers with data sent to the city of Popayán (~ 100 km SSW). Mumucué (2007) pointed out that people living around the volcano saw the appearance of fumaroles in October 2006.

From 22 November 2006, INGEOMINAS assigned an elevated hazard of Level II ('Eruption probable in the coming days or weeks'). Some fracture-related earthquakes took place at depths of 2 km below the summit. Some of these earthquakes reached MR 1.6-1.9.

A 13 February flight mainly found steam escaping both secondary craters and fumarole fields on the main crater's margin. The previous day, observers W of the volcano in Consacá saw steam emissions outside the crater.

A seismometer recorded an earthquake swarm during 1030-1259 on 18 February. The seismometer, located 2 km S of Pico Central (at station 'Cerro Negro') measured 108 earthquakes interpreted as rock fracture events in the upper part of the volcano. An M 3 earthquake followed, and at 0137 on 19 February a new swarm of 53 earthquakes occurred. In this swarm fracture earthquakes were accompanied by those of longer period; the amplitude and number of events increased into the next morning.

Seismic records also contained some long-period earthquakes called tornillos (events with long, gradually decreasing codas or tails, so that their seismic trace resembles the tapering profile of a wood screw; tornillo is Spanish for screw). During March 2006-February 2007, instruments had recorded 105 tornillos (an average of 9 per month). In contrast, during 1-19 February 2007, instruments recorded 20 tornillos, more than double the number usually seen during a full month.

INGEOMINAS reported two earthquakes on 19 February 2007, at 0830 and 0853, with probable explosive character. Aviation authorities reported ash-bearing columns over the edifice reaching ~ 0.6-0.7 km above the summit.

A later INGEOMINAS summary of events stated that the eruption began at 0856 on 19 February, manifested as a ~ 1.5 km tall eruption column blowing mainly W. Ashfall was noted by inhabitants of Toribio, Silvia, and Páez (in the Department of Cauca). Small mudflows came down the Bellavista and Azufrada rivers feeding into the Paéz river, but airborne observers found significant fresh deposits at higher elevations. Authorities advised inhabitants to move to higher ground. Inhabitants noticed the rise of the Paéz river at 1150 on 19 February.

A 20 February flight detected significant fresh ash, abundant crevasses in the ice, and a steaming fissure near the summit (figure 10). The fissure extended ~ 2 km between Pico Central and Pico la Cresta to the N. Observers noted that the fissure continually emitted gases along its entire length. The flight was a collaboration between INGEOMINAS and IGEFA (Inspección General de la Fuerza Aérea).

Figure (see Caption) Figure 10. (a-f) Six aerial photos of Nevado del Huila taken from multiple angles and distances on 20 February 2007. A) A view with the Paéz river basin in the foreground and with Nevado del Huila steaming in the background. B) A close up of the SE flank looking NW, showing dark snow on the W side of the volcano and a thinner coating on the E side. C) Contrasting ash-free and thickly ash-covered ice at the N-central side of the summit (Pico Central to the right), with the elongate fissure emitting steam near the ridgeline. D) Pico Central seen at comparatively close range from the E side of the mountain, where a thin coating of ash is apparent over many of the upper slopes. E) A view looking S across Pico la Cresta slightly off the trend of the ridge axis, highlighting steam emissions from the fissure, areas of ash-covered snow, and abundant fresh crevasses in the upslope ice. F) A photo looking NW at the gray ash deposits on glacial ice of Pico Central and again illustrating venting steam. Courtesy of the Colombian Air Force and INGEOMINAS.

A VAAC report noted an eruption at about 1400 UTC on the 19th to approximately FL 200 (~ 6.1 km altitude) moving W and dissipating quickly. No ash was seen in satellite imagery the next day at either 0045 or 1100 UTC, however, around this latter time, a pilot observed an ash cloud. In addition, a local aircraft reported ash to ~ 6.1 km at 0500 UTC on the 21st.

During 30 March-16 April 2007 INGEOMINAS observers reported the initiation of noteworthy seismicity indicating rock fractures and movement of fluids. The fracture events were located at depths of 4-8 km E and SW from the central peak and at magnitudes of less than 1.0. Low gas columns were again seen on 11 April, moving W.

Seismicity further increased on 17 April, leading up to an eruption on the 18th. Early on 18 April, a cluster of 25 rock-fracture earthquakes occurred, M 0.5 to 1.5. These were located at a depth less than 2 km. Seismicity again increased later that morning.

April 2007 eruption. A brief summary of the 18 April eruption appeared on the website hosted by the International Charter "Space and Major Disasters" on 20 April). It stated, "The Nevado del Huila volcano erupted at 02:57 local time 18 April, causing avalanches and floods [lahars] which affected the villages of La Plata, Paicol, Tesalia, Natagá, [and] Belalcázar. About 5,000 people were evacuated." (That same website hosted more than 10 (Landsat, Radarsat, and Envisat) images shedding light on this remote volcano's behavior, hazards, and impacts).

According to an 18 April 2007 report from the Washington Volcanic Ash Advisory Center (VAAC), a pilot in Colombia saw an ash cloud. Two ash plumes were evident on GOES-10 (split window) satellite imagery for an eruption starting at 0815 UTC on 18 April. They rose to poorly constrained altitudes of ~ 9 and 11 km and drifted E at 9 km/hour. The lower ash cloud was ~ 37 km across and moved SW at 9-18 km/hour. The higher ash cloud was ~ 19 km across and moved E at 0-9 km/hour. These clouds had dissipated by 1034 UTC.

The 18 April eruption sent an a torrent of brown water and rocks down the volcano's sides and into the Paéz and Símbola rivers (figures 11 and 12), causing them to flood, destroying several kilometers of highway and endangering or sweeping away what some government reports stated were 15 bridges (although it is uncertain how many of those were footbridges, and new reports tended to indicate a slightly higher numbers). In an evaluation the lahars of 18 April, INGEOMINAS staff found them quite similar, though smaller, than those of the earthquake and disaster of 1994.

Figure (see Caption) Figure 11. Photo from hillside overlooking the confluence of the Paéz and Símbola rivers, viewed upstream towards Nevado del Huila. One of the battered and partly lahar-covered bridges lies in the left-foreground. Photo was taken 25 April 2007 and came from Mumucué (2007).
Figure (see Caption) Figure 12. An aerial photo of part of the Huila lahar shot in sub-vertical orientation on 22 April 2007. Name and location of this settlement is uncertain. Lahars were apparently insufficiently thick to overrun established settlements. Courtesy of INGEOMINAS.

Videos. At least three videos taken chiefly from Colombian military or national guard helicopters were posted on the web during April-May 2007 (see Videos, under References). They featured either the volcano or the powerful lahars or both, as follows.

Video 1("Avalancha . . ."; posted 18 April 2007) contains lahar footage from a television newscast, much of it taken from a helicopter. The shots include several bridges destroyed or impacted by lahars and the dialog mentioned nineteen bridges affected. Segments also show closeups of sediments and considerable flooding. Few if any flooded or damaged buildings were shown. Footage shows segments of the river with various gradients; the dark water carrying considerable debris. In one scene of a threatened bridge taken from shore, the turbulent river races by and among the passing logs seemingly floats a large farm animal.

Video 2 ("Sobrevuelo . . ." [Overflight . . .]) was taken by INGEOMINAS on 3 March 2007. It shows the volcano in modest eruption. A dense, dark plume emerges from the complex ice-bound summit area. Somewhat surprisingly, the plume immediately descends one flank of the volcano.

Video 3 (Erupcion . . . 18 Abril) shows vigorous white plumes escaping from multiple vents and forming a dense white plume. The text says that the footage was taken hours after the eruption on 18 April 2007. The base of the volcano is shrouded in weather clouds. The footage credits "Ejercito Nacional-INGEOMINAS-FAC."

Further observations and assessments. Seismicity escalated during 19-20 April but decreased on the 21st. Two larger earthquakes soon took place, on the 22nd and 27th. Their respective seismic signals appeared to come from rock fracturing at shallow depths; they had epicenters at Pico Central, and they were M 3.0 and M 3.2. On 23 April instruments detected continuous low-frequency tremor, interpreted as continuing instability and possible eruptions.

On 22 April, the Colombian Air Force flew INGEOMINAS staff past the volcano. They observed the N-trending fissure seen in February and found it had extended to reach a length of 2.3 km and a width of ~ 200 m. It emitted a white, sulfurous smelling gas column to 5 km altitude. The 22 April observers also saw a second new fissure ~ 2 km long across the same region. Strong fumaroles also discharged. Some lahars remained active down both E and W flank drainages.

Associated with the eruptions and as recent as 28 April 2007, there had been a total of 5,708 seismic events. Of those, 2,861 had signals suggesting rock fracture and 2,847 had signals suggesting movement of fluids.

During late April and early May 2007 the seismicity generally decreased (except for a 6 May, M 3.2 earthquake). On 5 May, INGEOMINAS staff, using a land-based correlation spectrometer, measured an SO2 flux from the volcano at 3,000 tons per day.

Early on 14 May, INGEOMINAS recorded a cluster of 54 low magnitude earthquake events, possibly triggering or associated with an ash emission. Based on satellite imagery of 14 May, the Washington VAAC reported an ash plume 8 km wide in an area 45 km W; it drifted SW and dissipated.

Based on seismic interpretation, INGEOMINAS inferred ash emissions during 27 May. Aerial observations later that day confirmed the emissions. Tremor recorded on 28 May possibly indicated another pulse of ash emissions. The SO2 flux measured on 1 June continued at 3,000 metric tons per day and on 2 June increased to ~ 6,900 metric tons per day. Flights on 3, 6, and 10 June indicated no changes in the existing fissures nor changes in the fumarolic field. Seismicity was relatively quiet during June 2007.

Humanitarian concerns. Luz Amanda Pulido, director of the national disaster office said that there were no reports of deaths or injuries. According to a 22 May report of the UN Office for the Coordination of Human Affairs (OHCA), by 26 April authorities resolved to evacuate 2,307 families affected by the crisis.

A government document issued May 2007 discussed the displaced residents. According to that report (Mumucué, 2007) the number of indigenous inhabitants living around the volcano and affected by lahars or emissions or both totaled 26,949 people. The affected territory he discussed (the Municipio de Páez, which has Belacazar as the main urban center) had an area of ~ 161,000 hectares. The inhabitants losses included cultivated areas and farm animals, including horses and smaller livestock. Photos showed displaced families living in temporary camps with outdoor cooking facilities. Another photo showed workers installing a footbridge where a vehicle bridge was lost to the torrent. That photo, taken ~5 days after the 18 April lahars began showed that by this time the river had greatly receded. The report was also a plea for supplies, including children's clothing and two-way radios with solar panels. Total days of community work devoted to reconstruction after the disaster and as late as May 2007 amounted to 4,264 (Mumucué, 2007).

References. Correa, A.M., and Pulgarín, B.A, 2002a, Revisión histórica de los estudios geológicos y otros aspectos, sobre el volcán Nevado del Huila y su área de influenza, Instituto Colombiano de Geologia y Mineria, INGEOMINAS; Observatorio Vulcanológico y Sismológico, Popayán; Junio de 2002, 51 p.

Correa, A., and Pulgarín, B., 2002b, Morfología, estratigrafía y petrografía general del Complejo Volcánico Nevado del Huila (énfasis en el flanco occidental): INGEOMINAS, Centro Operativo, Popayán, Informe Interno, 104 p.

Mumucué, J.A., May 2007, Analisis de los diversos eventos de erupción volcánica en la región de Tierradentro Páez Cauca hasta el momento: Republica de Colombia, Departamento del Cauca - Region de Tierradentro, Asociación de Cabildos Nasa ?xh??xha.

Pulagarín, B.A., Jordan, E., and Linder, W., 2005, Aspectos geológicos y cambio glaciar del volcán Nevado del Huila entre 1961 y 1995: Proceedings I Conferencia Cambio Climático, Bogotá 2005, 17 p.

Restrepoa, J.D., Kjerfveb, B., Hermelina, M., and Restrepoa, J.C., 2005, Factors controlling sediment yield in a major South American drainage basin: the Magdalena River, Colombia: Journal of Hydrology, v. 316, nos. 1-4, 10 January 2006, p. 213-232.

Restrepoa, J.D., and Kjerfve, B., 2000, Magdalena river: interannual variability (1975-1995) and revised water discharge and sediment load estimates: Journal of Hydrology, v. 235, nos. 1-2, 22 August 2000, p. 137-149, Elsevier.

Schuster, R. L., 1996, Recent earthquake-induced catastrophic landslides in the Andes of Ecuador and Colombia; Abstract, Colorado Scientific Society (URL: http://www.coloscisoc.org/abstracts).

Video References. (1) "Avalancha del Volcan Nevado del Huila" [A newscast from a Colombian television station, www.youtube.com/watch?v=k6nW1DP5mqg

(2) INGEOMINAS, 3 March 2007, Sobrevuelo Ingeominas Nevado Huila pocos dias despues de la erupción" (posted 8 May 2007) [Overflight of summit area] http://www.youtube.com/watch?v=UPP0vzBzZ38 (00:39)

(3) INGEOMINAS, 2007, Erupcion Nevado del Huila Colombia 18 Abril; Video stamped with "Ejercito Nacional-INGEOMINAS-FAC"; http://www.youtube.com/watch?v=xUnYOALOCWg; (00:56) (Posted 8 May 2007)

Geologic Background. Nevado del Huila, the highest peak in the Colombian Andes, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. The high point of the complex is Pico Central. Two glacier-free lava domes lie at the southern end of the volcanic complex. The first historical activity was an explosive eruption in the mid-16th century. Long-term, persistent steam columns had risen from Pico Central prior to the next eruption in 2007, when explosive activity was accompanied by damaging mudflows.

Information Contacts: Instituto Colombiano de Geología y Minería (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Popayán, Popayán, Colombia; Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Jorge Castilla Echenique, Salud para desplazados, Programa de Emergencias y Desastres OPS/OMS, PWR Colombia; Jorge E. Victoria R., Salud en Desastres y Emergencias Complejas, Organización Panamericana De La Salud, Oficina de Neiva, Carrera 10 No. 4-72, Huila, Colombia; International Charter-Space and Major Disasters (URL: http://www.disasterscharter.org/).


Krakatau (Indonesia) — January 2008 Citation iconCite this Report

Krakatau

Indonesia

6.1009°S, 105.4233°E; summit elev. 285 m

All times are local (unless otherwise noted)


Repeated minor eruptions during October-November 2007

During 23-26 October 2007, minor eruptions occurred at Anak Krakatau (BGVN 32:09), an island and active vent on the rim of the famous larger caldera whose name often is misspelled as "Krakatoa." This report continues coverage from late October through November 2007. The Center of Volcanology and Geological Hazard Mitigation (CVGHM) raised the Alert Level to 3 (on a scale of 1-4) for Krakatau on 26 October because of the presence of multiple gray plumes from the volcano and an increase in seismicity. Plumes rose to an altitude of ~ 1 km during 23-26 and 30 October. Villagers and tourists were advised not go within 3 km of the summit.

According to an Associated Press news article, "red-hot lava flares" from Anak Krakatau rose 500-700 m above the S crater on 6 November. Multiple ash clouds were also observed. On 9 November, CVGHM officials in Bandung, West Java, conducted seismic and visual monitoring. Officials said, that on that day there were 182 eruptions coupled with 11 volcanic earthquakes, 54 shallow volcanic shocks, eight deep volcanic tremors and 44 shallower tremors. The volcano spewed "smoke" 29 times. On 13-14 November, as reported by CVGHM, lava flows and incandescent rocks traveled 400 m down the flanks.

As reported by VolcanoDiscovery's Tom Pfeiffer, who visited there from 21-26 November, emissions were relatively constant. He noted that all activity occurred from the newly formed crater on the upper S flank just below the old summit crater (figure 18). On 21 November, the new crater had an oval shape, approximately 50 x 70 m. Dense, dark brown, billowing ash clouds escaped in pulses from the crater at near-constant intervals of about 2 minutes, rising typically 100-200 m above the crater and drifting E. A few blocks were ejected along with the ash clouds (figure 19).

Figure (see Caption) Figure 18. A sudden explosion ejecting rocks and ash on the S flank of the old Anak Krakatau crater on 22 November, 2007. Courtesy Tom Pfeiffer of Volcano Discovery.
Figure (see Caption) Figure 19. Ballistic blocks land all over the cone of Anak Krakatau where the impacts stir up dust on 22 November 2007. A few also flew as far as the sea. Courtesy Tom Pfeiffer of Volcano Discovery.

Pfeiffer also reported that at more irregular intervals, about 10-30 min apart, more violent, small vulcanian explosions interrupted the weaker ash venting events. The more violent explosions consisted of a sudden spray of mostly solid rocks and few incandescent scoria, followed by more powerful and turbulent ash plumes that rose up to 1 km above the crater (figure 20). Generally, these vulcanian explosions occurred after a slightly longer quiet period and, in most cases, the length of the quiet period correlated with the force of the explosion.

Figure (see Caption) Figure 20. Eruption plume at Anak Krakatau rising to ~ 1 km on 23 November 2007. Courtesy Tom Pfeiffer of Volcano Discovery.

Pfeiffer noted that several more powerful explosions occurred at intervals of approximately 16-24 hours. The strongest, on 21-22 November, showered the whole island with incandescent blocks, ignited bush fires, and produced a very loud cannon-shot noise that rattled windows on the W coast of Java, 40 km away (figure 21).

Figure (see Caption) Figure 21. On the evening of 21 November 2007, a powerful blast throws bombs and blocks all over the old cone of Anak Krakatau. Courtesy Tom Pfeiffer of Volcano Discovery.

Other, unusually large blasts occurred at around 0200 on 21 November and at around 0900 and 1320 on 23 November (figure 22). Early on 23 November, activity became more ash-rich and the vigor of the individual events increased slightly over the next two days. The pace of single explosions stayed at near-constant intervals of about 2 minutes. During 24-25 November, ash plumes typically rose to over 1 km above the crater and were easily visible from the W coast of Java. Based on a pilot report, on 24 November, the Darwin Volcanic Ash Advisory Center noted that an ash plume rose to an altitude of 3 km and drifted NE.

Figure (see Caption) Figure 22. Another very powerful blast occurs at around 0300 on 24 November 2007. Incandescent blocks reach the lower western flanks of the island. Courtesy Tom Pfeiffer of Volcano Discovery.

Based on the University of Hawaii's Institute of Geophysics and Planetology (HIGP) Thermal Alerts System MODVOLC analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) satellite thermal anomaly data, occasional hot spots were identified by Terra or Aqua satellites. The thermal alerts occurred on twelve occasions between 27 October and 9 December 2007. Seven of these took place between 16 and 26 November 2007.

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

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Center, Bureau of Meteorology, Australia (URL: http://www.bom.gov.au/info/vac); Tom Pfeiffer, Volcano Discovery (URL: http://www.decadevolcano.net/, http://www.volcanodiscovery.com/volcano-tours/krakatau/photos.html); Associated Press (URL: http://www.ap.org/).


Llaima (Chile) — January 2008 Citation iconCite this Report

Llaima

Chile

38.692°S, 71.729°W; summit elev. 3125 m

All times are local (unless otherwise noted)


Ash plumes observed in May and August 2007; new eruption beginning 1 January 2008

From January 2002 through April 2003 (BGVN 29:02) there were increases in seismicity and fumarolic activity, along with minor eruptions, pronounced glacial melting, and substantial ash and gas plumes. Renewed activity consisting of minor eruptions was reported in May and possibly August 2007, but a larger eruption began on 1 January 2008. The source for most of the following is the Observatorio Volcanológico de los Andes del Sur (OVDAS)-SERNAGEOMIN (Volcano Observatory of the Southern Andes-Chile National Service of Geology and Mining).

On 26 May 2007, the Buenos Aires Volcanic Ash Advisory Center (VAAC) reported that ash plumes from Llaima rose to altitudes of 3-4.3 km and were visible on satellite imagery drifting E. A pilot reported another ash plume on 28 May that rose to an altitude of 5.5-6.7 km and drifted E. On 29 May, an ash plume rose to an altitude of 3 km and drifted E. No further activity was reported until 8 August, when pilots observed a plume to an altitude of 5.2 km drifting E. Ash was not identified on satellite imagery for this date.

Eruption during January 2008. Based on pilot reports and observations of satellite imagery, the Buenos Aires VAAC reported that on 1 January 2008 an ash plume rose to an altitude of 12.5 km and drifted E and ESE. The eruption began at 1820 hours, according to the Chile National Emergency Office. Lava was reported to be visible on the E flank and fumaroles at the summit were noted. The strong explosive activity prompted authorities to raise the Alert level to Yellow. According to news media reports, around 700 people were evacuated from local communities following the initial eruption, including about 200 tourists and National Forest Service employees from the Conguillo National Park. Most of the residents returned the following day when activity declined.

SERNAGEOMIN reported that tremor coincided with the onset of the gas and pyroclastic emissions on 1 January. Lava and incandescent material initially emitted were confined to the crater, but within a few hours, a Strombolian phase began. Soon, brightly glowing material covered much of the previously ice-covered summit (figure 14). Around the time of the eruption, an increase in volume of the Captrén river on the N flank was observed; this was likely a response to the glacial melting.

Figure (see Caption) Figure 14. Llaima as seen in eruption on 1 January 2008. Photo taken from W of the volcano between Temuco and Vilcun, Chile. Photo by Antonio Vergara via the flikr website (Creative Commons license).

On the following day, observers on an overflight saw small emissions of ash and gas (mainly steam) and three small lahars on the N and W flanks. Tremor decreased, though explosions continued. Based on pilot reports and satellite imagery, the Buenos Aires VAAC reported that an ash plume rose to an altitude of 12.5 km and drifted E (figure 15). A later overflight revealed that the explosion on 2 January occurred at an area high on the E flank, outside the summit crater. A lava flow on the E flank was also noted. On 3 January an ash plume was visible on satellite imagery at an altitude of 3.7 km drifting NE. Airborne observers noted small sporadic gas-and-ash emissions.

Figure (see Caption) Figure 15. A GOES-12 visual image of Llaima plume, captured at 1039 UTC on 2 January 2008. North is toward the top of the image, and the plume blew to the ESE. Courtesy of Charles Holliday, U.S. Air Force Weather Agency.

In addition to ash, Llaima's eruption released considerable sulfur dioxide (SO2), identified by satellite instruments in the days following the 1 January eruption (figure 16). The initially intense SO2 plume dispersed as it moved E. On 4 January, the plume passed over Tristan da Cunha, a remote archipelago in the South Atlantic Ocean (figure 16). According to Charles Holliday, Simon Carn, and Michon Scott, the SO2 dissipated after 6 January 2008.

Figure (see Caption) Figure 16. An image acquired by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite showing the progress of the SO2 plume from Llaima during 2-4 January 2008. The island of Tristan de Cunha is shown along in the southern Atlantic Ocean. (In the colored version of this image, red indicates the greatest concentration-pathlength of SO2 and lavender-pink indicates the lowest concentration-pathlength.) OMI measures the total atmospheric column amount of SO2 in Dobson Units (a common unit used in atmospheric research). NASA image courtesy Simon Carn; text modified from that by Simon Carn and Michon Scott.

Between 1835 and 1915 on 6 January 2008 a helicopter overflight was conducted, coordinated by Jaime Pinto, Director of the Araucania Region Emergency Office (OREMI). Observers noted that main crater vent was clogged with lava (figure 17), which, after the eruption, dropped a few dozen meters inside the crater. During the eruption, lava diverged into two areas in the main crater, draining flows to the W and NE and melting the ice. The melted ice produced three lahars toward the W flank, which merged into one that entered the Calbuco River. To the NE, the melted ice generated a single channel lahar that flowed into the Captrén River, cutting the road in several locations. A small lahar also traveled to the E. The dispersion of ash and gases was mainly to the E, although initially they went ESE. There were abundant cracks seen in the glaciers in the SW and SE of the main crater, particularly in the SE.

Figure (see Caption) Figure 17. Topographic map showing Llaima and features observed during a helicopter overflight on 6 January 2008. The features include lahars (shaded in green), the Calbuco and Captren rivers, detached areas of lava blocks and ashes, fallen pyroclastics, fumaroles, and limit of falling ash (highlighted dashed lines). Courtesy of SERNAGEOMIN.

SERNAGEOMIN reported that during 10-14 January 2008 seismicity decreased in terms of energy, but increased in the number of events. Based on seismic interpretation, weak explosions produced plumes of gas and ash that drifted NE. On 11 January, the upper surface of lava flows on the W flank that were observed during an overflight were cooled and snow-covered near the crater, but snow-free, and therefore still hot, about 500 m farther downslope. Blocks of incandescent material rolled ~ 1.5 km downslope and caused steam emissions where they contacted the glacier. Abundant cracks in glaciers to the SW of the crater were noted. Based on observations of satellite imagery and pilot reports, the Buenos Aires VAAC reported that ash plumes rose to an altitude of 5.5-6.7 km and drifted NE on 11 January and SW on 13 January.

Eruptive activity continued during the second half of January from the main crater and from two craters and a fissure on the E flank. The main crater contained three active pyroclastic cones. On 16 January one of the craters, ~ 15 m in diameter, produced ash plumes that rose to an altitude of ~ 3.6 km. Glaciers on the NE slope and W flank were fractured and dislocated. Ash plumes rising from the E flank attained an altitude of 4.1 km. Ash emissions vented from a NE-trending fissure ~ 80 m long and ~ 10 m wide. On 16-17 January glowing rocks were emitted from the fissure's NE end; ash plumes caused by rolling rocks rose from multiple areas.

At 0732 on 18 January, an explosion from the E flank sent an ash plume to an altitude of 9.1 km that quickly dispersed NE. People later saw a small lateral explosion from the same area, ash-and-gas emissions from several points, and a new fissure.

On 19 January, an explosion produced an ash plume that rose to an altitude of 4.1 km. An overflight revealed Strombolian activity in the main crater from a new pyroclastic cone that was 120 m in diameter and 100 m high; the cone was absent during a 17 January overflight. A second crater to the SW emitted gas. Sporadic ash emissions were noted from the E sector and an explosion produced a pyroclastic flow and an ash plume that quickly dissipated. On 20 January, another explosion produced an ash plume that rose to an altitude of 4.1 km. Gas and ash emissions were again noted from multiple areas. On 21 January, cloud cover prevented visual observations, but one small ash emission was seen at the end of the day.

On 23 January, a brown ash plume rose to an altitude of 3.5 km and drifted W. Observers on an overflight later that day saw Strombolian eruptions from the pyroclastic cone in the main crater accompanied by emissions of brown ash. A small hornito emitting bluish gas and a lava field were noted between the pyroclastic cone and the inner margins of the crater. Explosions from the E flank were detected on 24 January, and on 26 January steam plumes were observed. Strombolian eruptions in the main crater accompanied by gas and ash emissions continued during through 27 January. Ash plumes rose to altitudes of 3.3-4.1 km and drifted NW, E, SE, and S.

MODVOLC Thermal Alerts. Numerous MODIS thermal anomalies were measured almost daily throughout the month of January 2008 (table 2). As shown by the number of pixels for various observing time, the anomalies covered a particularly large area on 2 January (24 pixels). In contrast, anomalies were absent during the previous intervals of 1 January 2002 through 26 April 2007, and 16 June 2007 through 1 January 2008.

Table 2. Thermal anomalies measured by MODIS/MODVOLC over Llaima from 27 April 2007 through 30 January 2008. No anomalies were detected from 2002 through 26 April 2007, or 16 June 2007 through 1 January 2008. Courtesy of HIGP Thermal Anomalies Team.

Date Time (UTC) Pixels Satellite
27 Apr 2007 1910 3 Aqua
14 Jun 2007 1455 5 Terra
15 Jun 2007 0515 1 Aqua
02 Jan 2008 0250 2 Terra
02 Jan 2008 0430 9 Terra
02 Jan 2008 0605 24 Aqua
02 Jan 2008 1355 2 Terra
02 Jan 2008 1535 3 Terra
02 Jan 2008 1810 2 Aqua
03 Jan 2008 0335 4 Terra
03 Jan 2008 0510 2 Aqua
03 Jan 2008 1440 1 Terra
03 Jan 2008 1850 1 Aqua
04 Jan 2008 0555 3 Aqua
05 Jan 2008 0320 1 Terra
06 Jan 2008 0545 1 Aqua
11 Jan 2008 0425 1 Terra
11 Jan 2008 0600 2 Aqua
12 Jan 2008 0330 1 Terra
14 Jan 2008 0630 1 Aqua
15 Jan 2008 0400 1 Terra
15 Jan 2008 0535 1 Aqua
16 Jan 2008 0620 2 Aqua
17 Jan 2008 0345 1 Terra
17 Jan 2008 0525 3 Aqua
17 Jan 2008 1450 2 Terra
18 Jan 2008 0605 1 Aqua
20 Jan 2008 0555 1 Aqua
22 Jan 2008 0405 1 Terra
22 Jan 2008 0545 2 Aqua
23 Jan 2008 0625 1 Aqua
24 Jan 2008 0530 3 Aqua
24 Jan 2008 1455 1 Terra
25 Jan 2008 0255 3 Terra
25 Jan 2008 0615 4 Aqua
26 Jan 2008 0340 2 Terra
26 Jan 2008 0520 2 Aqua
26 Jan 2008 1445 1 Aqua
27 Jan 2008 0425 2 Terra
27 Jan 2008 0600 2 Aqua
27 Jan 2008 1525 1 Terra
28 Jan 2008 0330 4 Terra
28 Jan 2008 0505 4 Aqua
28 Jan 2008 1845 1 Aqua
29 Jan 2008 0410 4 Terra
29 Jan 2008 0550 2 Aqua
30 Jan 2008 0315 2 Terra
30 Jan 2008 0630 4 Aqua
30 Jan 2008 1420 5 Terra
31 Jan 2008 0400 6 Terra
31 Jan 2008 0535 3 Aqua
31 Jan 2008 1915 3 Aqua

Geologic Background. Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other, Pichillaima, to the SE. The massive, dominantly basaltic-to-andesitic, stratovolcano has a volume of 400 km3. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following the eruption of the 24 km3 Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7200 years ago, construction of the present edifice began, characterized by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century.

Information Contacts: Servico Nacional de Geologia y Mineria (SERNAGEOMIN), Avda Sta María N° 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); 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/productos.php); Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC); Charles Holliday, U.S. Air Force Weather Agency (AFWA)/XOGM, Offutt Air Force Base, NE 68113, USA; 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/); Associated Press (URL: http://www.ap.org/); United Nations Office for the Coordination of Humanitarian Affairs (OCHA) (URL: https://reliefweb.int/); Antonio Vergara, Temuco, Chile (URL: http://www.flickr.com/people/odiofotolog/).


Sheveluch (Russia) — January 2008 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Lava-dome growth and block-and-ash flows continue April-December 2007

Shiveluch (also spelled Sheveluch), the scene of lava-dome growth, is one of the most active volcanoes on Kamchatka. It was last reported here discussing events through early April 2007 (BGVN 32:03). The following report covering the interval early April-December 2007 came from multiple sources.

Shiveluch's eruptions are of an explosive nature and the volcano has been in a state of heightened activity since 5 December 2006. Vigorous activity continued to the time of this report (March 2008). Small lava-dome collapse events produced ash plumes and short block-and-ash flows, which in turn generated mudflows when snow was present. This activity was recorded in shallow volcanic earthquakes and tremor and a large, ever-present thermal anomaly on satellite imagery.

The Level of Concern Color Code remained at Orange throughout this report period (early April through December 2007). The Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS) is monitoring the volcano and believes that it poses little danger for nearby populated localities.

During April 2007 growth of the lava dome continued, and hot lava extruded at the top of the dome. Hot avalanches from the top of the dome occurred daily. Ash and ash-and-steam plumes rose to altitudes of ~ 4.6-6.5 km. Some plumes were seen on satellite imagery drifting E, SE, and S. According to satellite data, ash plumes extended ~ 60 km on 28-29 April, mainly to the S and SW, and ~ 50 km to the E on 5 and 7 May. During 27-28 May, plumes were seen on satellite imagery drifting SW.

A large thermal anomaly was conspicious during the last week of April 2007, and hot avalanches originating from the dome were noted on 30 April, 4 May, and 6-7 May. Gas-steam emissions occurred repeatedly. On 7 May a mudflow traveled down Shiveluch's slope, reaching ~ 20 km beyond the lava dome and blocking ~ 30 m of a road, isolating the district center Ust-Kamchatsk on the E of the peninsula. There were no vehicles on this portion of the road when the mudflow descended, and no casualties occurred. Figure 12 contrasts the dome in 2006 and 2007.

Figure (see Caption) Figure 12. The dome at Shiveluch as seen from the SW at two points in time, July 2006 and July 2007. The dome grew to substantially fill the active crater. The most active lava dome growth took place along in the dome's E sector. Photo by Natasha Gorbach (from Gorbach, 2007).

During July, gas-steam plumes frequently reached 4.0-6.1 km altitude. Ash was not always identified on satellite imagery because clouds obscured visibility; however, on 16 July satellite imagery detected gas-steam and ash plumes that extended for about 7-40 km to the S and SW of the volcano. Seismic data suggested that gas-and-ash emissions were concurrent with hot avalanches (figure 13).

Figure (see Caption) Figure 13. The lava dome of Shiveluch volcano as seen from the SW on 11 July 2007. The dark dome contrasts with glowing zones where hot avalanches descended. Photo by Y. Demyanchuk.

On 25 September 2007, video observations indicated ash plumes rising to 6 km altitude and drifting E. According to video for 27 September and 2 October 2007, gas-steam plumes rose up to 4.5 and 3.5 km altitude, respectively. Weak fumarolic activity was noted on both 1 and 8 October. KB GS RAS noted that there was no significant variation in the previous ongoing activity through December 2007 that might indicate any impending activity of greater significance. Frequent MODIS thermal alerts continued throughout 2007 into 2008.

Reference. Gorbach, N., 31 July 2007, Bulletin of activity at Sheveluch volcano, issued 31 July 2007 [title approximate (translated from Russian); available in Russian at URL: http://www.kscnet.ru/ivs/volcanoes/inform_messages/2007/Sheveluch_072007/Sheveluch_072007.html).

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: Yuri Demyanchuk, Natasha Gorbsch, and theKamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanology and Seismology, Far East Division, Russian Academy of Sciences, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/); Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS), Russia (URL: http://www.emsd.ru/); Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and the Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Turrialba (Costa Rica) — January 2008 Citation iconCite this Report

Turrialba

Costa Rica

10.025°N, 83.767°W; summit elev. 3340 m

All times are local (unless otherwise noted)


Fumarolic increases during August 2007-January 2008

Enhanced fumarolic activity accompanied by new fractures at the summit was noted during June-September 2007 (BGVN 32:08). The earlier report noted that the fumaroles had spread over a larger area and contained molten sulfur, a condensate previously not seen here in more than 25 years of continuous monitoring by the Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA). By mid-August 2007, acute chemical burning of important patches of natural forest had occurred. This report covers the period from October 2007 through January 2008.

During October, new sites of gas discharge, small landslides, and accelerated vegetation die-off were noted from various locations within and around the crater. Fumaroles were active and widespread across the central crater. Many exhibited sulfur deposits and those in the S, SE, and SW reached a temperature of 91°C.

Areas burned by acute acidification extended during November. Fieldwork conducted by OVSICORI-UNA confirmed an unusual output of gas from several fumaroles along the S outer wall of the volcano. Pastures turned yellowish near the upper areas, and native and exotic tree species were impacted as well as birch tree patches along most drainage basins.

During December, within the W crater, fumarole temperatures reached 280°C and significant sulfur deposits were noted. Local residents confirmed an unusual output of gas from several fumaroles along the S outer wall of the volcano. Areas burned by acute acidification extended during the month. On 5 December, members of the media and local communities observed a gas-and-steam plume from Turrialba that rose to an altitude greater than 5.3 km (figure 12).

Figure (see Caption) Figure 12. Column from Turrialba observed and photographed from Heredia City, located 40 km W of the volcano taken at 0540 on 5 December 2007. Courtesy OVSICORI-UNA.

On a team visit between 30 and 31 January 2008, OVSICORI staff documented the progression of fumarolic activity in the W crater, the external W crater walls, and distant areas towards the W, NW, and SW. Some of the fumaroles correspond with two fractures. One to the SW of the W crater, trending SW, was 100 m in length and 2 to 3 cm wide, and deposited sulfur. The second crack to the NW of the W crater, also trending SW , had temperatures of 72°C and discharged steam and gas affecting the adjacent vegetation. To the NW of the W crater, the team studied an area of about 20 x 50 m with constant gas emission and a temperature of 88°C.

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

Information Contacts: Eliécer Duarte, Erick Fernández, and Vilma Barboza, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apdo. 2346-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Tellez and Francois Robichaud, Université de Sherbrooke, 2500 boul. de l'Université, Sherbrooke, Québec J1K 2R1, Canada.


Ubinas (Peru) — January 2008 Citation iconCite this Report

Ubinas

Peru

16.345°S, 70.8972°W; summit elev. 5608 m

All times are local (unless otherwise noted)


Continuing ashfall during 2006-2007

Ubinas began erupting ash on 25 March 2006 (BGVN 31:03 and 31:05). As reported in BGVN 31:10, ash eruptions and steam emissions continued through 31 October 2006. This report discusses ongoing eruptions through December 2007 as drawn from Buenos Aires Volcanic Ash Advisory Center (VAAC) reports and the Instituto Geológical Minero y Metalúrgico (INGEMMET).

From November 2006 through December 2007, emissions of volcanic ash, rocks, and gases with water and steam were essentially continuous. INGEMMET authorities indicated that during March 2007 the volcano generated increased ashfall behavior that significantly affected people and the environment. At the beginning of the month, small explosions occurred every 6-8 days but the rate of activity increased toward the end. On 30 March 2007, nearby residents felt a strong explosion. A large ash plume vented from the volcano's summit and local communities were blanketed beneath falling ash. According to INGEMMET authorities, most of Querapi, a town ~ 4.5 km SE of the crater's active vent, was covered in volcanic ash, and the town of Anascapa, 6 km E, also experienced ashfall.

Volcanic ash clouds blown into the atmosphere also presented a hazard to aviation. As summarized in table 3, ash clouds were nearly continuously reported by the Buenos Aires VAAC and the INGEMMET. Plume heights reached as high as 9.1 km in May and again in November 2007. The aviation warning color code was generally Red through the period. The reports were based on satellite imagery and pilot reports. No thermal alerts were noted from the University of Hawaii's Institute of Geophysics and Planetology (HIGP) MODIS satellite-based thermal alert system during 2006 or 2007.

Table 3. Compilation of Volcanic Ash Advisories for aviation from Ubinas during November 2006 through December 2007. Courtesy of the Buenos Aires Volcanic Ash Advisory Center (VAAC) and the Instituto Geológical Minero y Metalúrgico (INGEMMET).

Date Altitude of Plume (km) Flight Level (thousands of feet) Direction of Plume
3-16 Nov 2006 5.5-7.3 190-260 SW, S, SW
25 Nov 2006 5.5 180 NE
2 Dec 2006 5.5 180 N
27-30 Dec 2006 4.9-8.5 160-280 E
28 Jan 2007 5.5-6.9 180-220 SE
2-5 Feb 2007 5.5 180 S, SW
18-21 Feb 2007 5.5-7.0 180-230 E, SW
11, 14 Mar 2007 5.5-6.4 180-210 N, SW
30 Mar 2007 5.5 180 E
5, 7-9, 10-11 Apr 2007 5.5-7.8 180-270 E, SE, S, SW, W
17-18, 22, 24 Apr 2007 5.5-7.2 180-280 NW, SW, SE
2-5 May 2007 5.5-9.1 180/300 N, S, SE, SW
12, 15-16 May 2007 5.5-8.2 180-270 SE, N, SW
17, 19-22 May 2007 5.5-9.1 180-300 E, SE
22-28 May 2007 5.5-7.3 180-240 NE, SE
30 May-6 Jun 2007 3.7-7.6 120-250 NE, SE
12-17 Jun 2007 5.5-6.7 180-230 NE, E, SW, W
27-28 Jun 2007 5.5-6.7 180-230 SW, NW, E
4 Jul 2007 5.5-6.1 180-200 S
23-25 Jul 2007 5.9-6.1 190-200 SE, S
9 Aug 2007 6.1 200 SE
11-14 Sep 2007 5.5-7.6 180-250 E, SE
20 Sep 2007 5.5-6.4 180-210 E
5-7 Oct 2007 5.5-6.4 180-210 N, S
11-13, 15 Oct 2007 5.5-7.6 180-250 N, SE
19-27 Oct 2007 5.5-8.5 180-280 NW, NE
1, 3-6 Nov 2007 5.5-7.6 180-250 NE, SE
11-12 Nov 2007 5.5-6.7 180-220 NE
16, 18, 20 Nov 2007 5.5-7.9 180-260 NE
24-27 Nov 2007 6.1-9.1 200-300 SE, E, SW
28-29 Nov 2007 6.7-7.6 220-250 SW, NE
4-7, 10 Dec 2007 5.5-8.5 180-280 NE
17 Dec 2007 5.5-6.7 180-220 N

Geologic Background. The truncated appearance of Ubinas, Perú's most active volcano, is a result of a 1.4-km-wide crater at the summit. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45°. The steep-walled, 150-m-deep summit crater contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one from about 1,000 years ago. Holocene lava flows are visible on the flanks, but activity documented since the 16th century has consisted of intermittent minor-to-moderate explosive eruptions.

Information Contacts: Instituto Geológical Minero y Metalúrgico (INGEMMET), Av. Canadá 1470, San Borja, Lima 41, Perú (URL: http://www.ingemmet.gob.pe/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/productos.php).

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