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Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

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

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

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

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

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

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

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

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

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

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

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

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



Ibu (Indonesia) — June 2023 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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


Dukono (Indonesia) — June 2023 Citation iconCite this Report

Dukono

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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


Sabancaya (Peru) — May 2023 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Sheveluch (Russia) — May 2023 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Bezymianny (Russia) — May 2023 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


Chikurachki (Russia) — May 2023 Citation iconCite this Report

Chikurachki

Russia

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

All times are local (unless otherwise noted)


New explosive eruption during late January-early February 2023

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

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

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

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

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

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


Marapi (Indonesia) — May 2023 Citation iconCite this Report

Marapi

Indonesia

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

All times are local (unless otherwise noted)


New explosive eruption with ash emissions during January-March 2023

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

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

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

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

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

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

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


Kikai (Japan) — May 2023 Citation iconCite this Report

Kikai

Japan

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Lewotolok (Indonesia) — May 2023 Citation iconCite this Report

Lewotolok

Indonesia

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

All times are local (unless otherwise noted)


Strombolian eruption continues through April 2023 with intermittent ash plumes

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

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

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

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

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

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

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

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

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

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

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


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

Barren Island

India

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

All times are local (unless otherwise noted)


Thermal activity during December 2022-March 2023

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

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

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

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

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

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

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

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


Villarrica (Chile) — April 2023 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Fuego (Guatemala) — April 2023 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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Bulletin of the Global Volcanism Network - Volume 36, Number 09 (September 2011)

Managing Editor: Richard Wunderman

Additional Reports (Unknown)

Tonga: Photo from space on 13 April 2011 raises questions about drifting pumice rafts

Asosan (Japan)

Small ash-bearing eruptions during May and to lesser extent in June 2011

Erebus (Antarctica)

Lava lake convects and spews spatter and gases in December 2010

Mayon (Philippines)

Brief seismic crisis in May 2011, low activity follows

Nabro (Eritrea)

First historically observed eruption began 13 June 2011

Santa Maria (Guatemala)

Eruption on 26 April 2010; ongoing activity through September 2011

Stromboli (Italy)

Recent activity; plumbing insights; new water vapor flux technique; hydrogeology

Tofua (Tonga)

Elaborative comments on April 2010 observations

Turrialba (Costa Rica)

Frequent degassing and occasional ashfall, March 2010-June 2011



Additional Reports (Unknown) — September 2011 Citation iconCite this Report

Additional Reports

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Tonga: Photo from space on 13 April 2011 raises questions about drifting pumice rafts

This report presents a serendipitous observation near Tofua, possibly indicative of volcanism elsewhere (not on Tofua). A photo of Tofua and vicinity from space taken on 13 April 2011 displays significant material on the sea surface - the possible relict of an eruption at some unknown center.

A photo taken from space by Astronaut Paulo Nespoli (figure 1) could suggest an eruption in the Southern Pacific region at an unknown volcano. Nespoli took the photo from the International Space Station on 13 April 2011 (Nespoli, 2011). It shows occasional white clouds over the island's high points, and a thin gray-blue plume indicative of Tofua's volcanic emissions wafting to the SE.

see figure caption Figure 1. Photo taken 13 April 2011 from the International Space Station with hand-held camera showing Tofua and debris on the sea surface suggestive of pumice. The composition and source of the debris is unknown; however, the shape, distribution, and color of areas of debris are consistent with zones of floating pumice. Image (239B2033) courtesy of Astronaut Paolo Nespoli (European Space Agency and the International Space Station); labels and dashed lines added.

The elongate and sinuous bands of debris seen in the photo are suggestive of floating pumice seen before in the region (eg., see Home Reef, BGVN 31:09; 31:10; 31:12; 32:04; 33:05; 33:12; Metis Shoal, BGVN 20:06). If this is pumice in elongate strands such as seen from Home Reef's 2006 eruption, it could also be derived from deposits of an older eruption. Debris floating in strands are most conspicuous at upper left of figure 1, where they form a curve cut by the photograph's left edge. Faintly linked to that area is a thinner strand of sinuous debris. Other strands of similar width appear elsewhere.

Reference. Nespoli, P., 2011, Tofua Island, Tonga: Flickr (uploaded 18 April 2011) (URL: http://www.flickr.com/photos/magisstra/5618223635/).

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

Information Contacts:


Asosan (Japan) — September 2011 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Small ash-bearing eruptions during May and to lesser extent in June 2011

After small ash-bearing eruptions, the Alert Level on Aso was raised from 1 to 2 (on a scale of 1-5) on 17 May 2011. Aso, the largest volcano in SW Japan, consists of a large, 24-km-diameter caldera located on the Japanese island of Kyushu (figure 26). Under normal conditions the area within the caldera is restricted and, with the raising of the Alert Level, authorities restricted entry within 1 km of Naka-dake cone, containing one of the active craters that comprise the Aso volcanic complex.

Figure (see Caption) Figure 26. Map of the main islands of Japan; Mt. Aso is on the Island of Kyushu. Map from Wordtravels.com.

Fumarole temperature from hydrogen isotopic ratios. The temperature of fumarole gas is a primary observation used at many volcanoes. Tsunogai and others (2011) describe a method of using hydrogen isotope ratios to determine fumarolic temperature. Because the isotopes can be collected at a distance from the vent and without entering the crater, this method offers several advantages. Aso was one of the volcanoes where this technique was applied because it has a deep crater that makes direct sampling and at-vent measurements impractical. Direct sampling of gases is potentially far more hazardous. Infrared measurements may suffer bias when cooled, outgassed material, such as ash, obstructs the hotter portions of the plume. Such measurements could understate the emission's radiant heat and thus its temperature.

We previously published a topographic map depicting the Aso caldera and the location of Naka-dake within the caldera (BGVN 19:09 ), one of 17 central cones. Of these, Naka-dake is the most active. Naka-dake has a crater lake at its summit that contributes to its tendency towards phreatic and mud eruptions.

Aso resides in a National Park of the same name. Naka-dake is easily accessible by public transport and is a popular tourist destination. The rims of the active crater area contain parking and viewpoints accessible by toll road or the Arcosan Ropeway (steel-cabled aerial tramway). At the rim, massive concrete structures offer some protection from falling ballistics in the case of sudden explosions. Another attraction in the area is the Aso Volcano Museum, which features a webcam and photos of phreatic eruptions at Aso.

Aso has been highly active in recent years, but rarely to an extent where it has become dangerous to people. Aso erupted from 10 June 2003 to 14 Jan 2004 (BGVN 29:01). During that time Aso mainly erupted mud, associated with volcanic tremors, and a small amount of ash. A rise in thermal activity in the area may have been a contributing factor in the eruption (Volcano Research Center, University Tokyo). On 14 April 2005, the volcano erupted again, forcing five tourists to be evacuated after hundreds of small earthquakes were detected in the prior two weeks.

May-June 2011 unrest. The latest series of eruptions began on 6 May 2011 with mud erupting about 5-10 m from the hot caldera lake. On 13 May the temperature of fumarolic emissions in the caldera had increased. The Japan Meteorological Agency noted that "A small volcanic flame [glow?] has been observed at nights at the crater pits in the center of Naka-dake." On 15 May, Naka-dake erupted a small amount of ash, with the plume rising to an altitude of 2.1 km. One approach to measuring areas of elevated temperature involves infrared photographs. Visible and infrared photos of Naka-dake crater documented temperature increases in the crater from 21 April to 15 May (figure 27). The temperature of fumarolic emissions in the crater reached around 370°C (the temperature measurement method was not disclosed).

Figure (see Caption) Figure 27. Visible (left) and infrared (right) images on two different days (contact JMA for temperature scales). a) 21 April 2011 and b) 15 May 2011. Courtesy of JMA.

On 16 May, an eruption sent one plume to an altitude of 1.8-2.1 km and another ash plume to 2.4 km, according to the Tokyo Volcanic Ash Advisory Center. A video depicting the plume that day can be found on Youtube (Asahi.com, 2011). The video shows aerial footage of the plume, which is bent downwind. The emission is constant but not vigorous.

Rocks ejected from Naka-dake on 17 May landed in restricted areas, and ash plumes rose to an altitude of 1.8 km. Ash plumes continued rising to similar altitudes through the end of May, and small scale eruptions continued through 10 June, accompanied by low level seismicity. No additional plumes were reported through mid-October. The website of the Mt. Aso Ropeway noted that entry restrictions ended on 20 June 2011, allowing them to carry passengers.

References. Asahi.com, 2011, Naka Erupting, YouTube (URL: http://www.youtube.com/watch?v=uBKJnM2JIZs), posted 16 May 2011.

Tsunogai, U., Kamimura, K., Anzai, S., Nakagawa, F., and Komatsu, K., 2011, Hydrogen isotopes in volcanic plumes: Tracers for remote temperature sensing of fumaroles, Geochimica et Cosmochimica Acta, v. 75, no. 16, p. 4531-4546.

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

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Volcano Research Center, VRC-ERI, Univ. Tokyo (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Wordtravels (URL: http://www.wordtravels.com/Travelguide/Countries/Japan/Map).


Erebus (Antarctica) — September 2011 Citation iconCite this Report

Erebus

Antarctica

77.53°S, 167.17°E; summit elev. 3794 m

All times are local (unless otherwise noted)


Lava lake convects and spews spatter and gases in December 2010

This report includes first-hand observations of Erebus's crater, which includes the persistent Ray lava lake, a body that remained molten, though considerably crusted over, in December 2010. Several recent studies on Erebus presented maps and gas emissions measured by open-path FTIR spectroscopy in December 2004. Our last report on Erebus covered ongoing lava lake activity through October 2007 (BGVN 33:03). MODVOLC thermal alerts occurred during 2007 and continued at least into late 2011. Mt. Erebus is located on the western half of Ross Island (figure 11).

Figure (see Caption) Figure 11. Shaded relief map of Ross Island showing Erebus, created from a digital elevation map. Taken from Csatho and others (2008).

December 2010 observations. Csatho and others (2008) used laser scanning (LIDAR) acquired from aircraft in 2001 to study the morphology of the Erebus summit area (figure 12). The crater contains the persistent and convecting Ray lava lake. A second lava lake is occasionally active in the Werner vent (Werner lava lake). The authors noted the elevation of the surfaces of the inner crater's two lava lakes, both at ~3,515 m, was about the same as another active vent in the crater. Ray lava lake (~750 m2), which was discovered in 1972, sits in the inner crater's NE sector, and is larger than Werner lava lake (~166 m2).

Figure (see Caption) Figure 12. Morphology of the summit crater of Erebus compiled from laser imagery (ALS-LIDAR) acquired 30 December 2001. Taken from Csatho and others (2008).

Kayla Iacovino posted a blog on 15 December 2010 about then-recent conditions on the summit of Erebus (Iacovino, 2011). She noted that the weather for the past few days was unusually clear (figure 13). In addition, she presented a shot of a churning lava lake (by Clive Oppenheimer) which was somewhat obscured by steam over the lake. Iacovino noted that during her 2010 visit, only Ray lava lake was active. It had shrunk in size (some of it had crusted over) since December 2009. She commented that "There were a lot of bursts of activity in the lake, including some bomb-throwing eruptions (although no bombs made it out of the crater) and a couple of very active fumaroles on the lava lake's perimeter. The plume was essentially constant."

Figure (see Caption) Figure 13. A December 2010 photo composite showing the inner crater at Erebus. The Ray lava lake lies to the left side of the crater floor. Courtesy of Laura Jones (New Mexico Tech; posted online at Iacovino, 2010).

Oppenheimer provided two other views during the same December 2010 field season. One shows the crater, and the other, the active lava lake, large portions of which were covered by crust (figures 14 and 15).

Figure (see Caption) Figure 14. An aerial photo of Erebus taken from a helicopter looking at the main crater and its inner crater from an oblique angle. Courtesy of Clive Oppenheimer.
Figure (see Caption) Figure 15. A photo of the floor and portions of the confining walls of the Ray lava lake, which contained a bright orange-red circular area with exposed molten material at the surface. As seen here, the exposed molten material discharged ample spatter and gases. Note the network of glowing cracks bounding and crossing the chilled darker portions of the lava lake. Courtesy of Clive Oppenheimer.

2004 gas measurements. A study of the gas emissions conducted in December 2004 (Oppenheimer and Kyle, 2008) concluded with the statements below.

"We measured the emissions of seven gas species from Werner and Ray lava lakes at Erebus volcano by open-path FTIR spectroscopy. The results are among the few available for a highly alkalic magmatic system. Compared to typical subduction zone related volcanoes, Erebus gas is CO2-rich (consistent with abundant CO2 in olivine hosted melt inclusions sampled from Erebus basanite), and the CO2/CO ratio is lower (and perfectly consistent with the oxygen fugacity of Erebus phonolite estimated from the composition of component minerals). Combination of the measured gas proportions with the estimated SO2 flux carried by the plume provides estimates of the fluxes of all the other species. This yields the first measurements of the fluxes of H2O (~860 Mg per day) and carbonyl sulfide (~0.5 Mg per day). By mass, CO2 is the major component of the plume, and the estimated CO2 flux is ~1,300 Mg per day....

"The H2O/CO2 ratio and HF content of the individual plumes emitted by the two lava lakes are distinct, and point to a more 'evolved' gas released from Werner lake. This could indicate that the Werner lake is fed by a shallow offshoot of the conduit that supplies the Ray lake, or that magma feeding Werner lake is more comprehensively degassed due to a higher degree of crystallization....

References. Oppenheimer, C., Kyle, P.R., 2008, Probing the magma plumbing of Erebus volcano, Antarctica, by open-path FTIR spectroscopy of gas emissions, Journal of Volcanology and Geothermal Research, v. 177, p. 743-754.

Csatho, B., Schenk, T., Kyle, P., Wilson, T. and Krabill, W. B., 2008, Airborne laser swath mapping of the summit of Erebus volcano, Antarctica: Applications to geological mapping of a volcano, Journal of Volcanology and Geothermal Research, v. 177, no. 3, 531-548.

Iacovino, K., 2010, A view from the top: great weather on Erebus, Science Friday, posted 15 December 2010; accessed 24 October 2011.(URL: http://www.sciencefriday.com/blog/2010/12/a-view-from-the-top-great-weather-on-erebus/

Geologic Background. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. It is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater; other lava lakes are sometimes present. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: Kayla Iacovino and Clive Oppenheimer, Cambridge University, Department of Geography, Downing Place, Cambridge, CB2 3EN, UK; Laura K. Jones, Department of Earth and Environmental Science, New Mexico Tech, Socorro, NM 87801, USA; 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/).


Mayon (Philippines) — September 2011 Citation iconCite this Report

Mayon

Philippines

13.257°N, 123.685°E; summit elev. 2462 m

All times are local (unless otherwise noted)


Brief seismic crisis in May 2011, low activity follows

Mayon volcano (figure 19) underwent an eruptive crisis in late 2009 into early 2010 and a seismic crisis in May 2011. This report provides some final remarks on the late 2009 to early 2010 eruptive crisis, and summarizes activity through 23 September 2011. Our previous report summarized the heightened activity in December 2009, which culminated in the evacuation of 47,000 people from their homes (BGVN 34:12). The eruption waned following the evacuation, and, accordingly, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) lowered the Alert Level from a high of 4 to 3 (on a scale from 0 to 5) on 2 January 2010. At that point, ~2,000 evacuees were still unable to return to their homes. On 13 January, the Alert Level was lowered from 3 to 2, and, according to Sophia Dedace (GMANews), enabled the remaining evacuees to return to their homes. Dedace reported that Governor Joey Salceda estimated the damage to agriculture and infrastructure from Mayon's 2009-2010 eruption at 26.2 million Philippine pesos (~$600,000 USD).

Figure (see Caption) Figure 19. Maps showing geographic location (star on index map) and shaded relief map of Mayon volcano. Index map courtesy of Ginkgo Maps; shaded relief map courtesy of United Nations Institute for Training and Research's (UNITAR's) Operational Satellite Applications Programme (UNOSAT).

On 2 March 2010, amid continually declining activity at Mayon, PHIVOLCS lowered the Alert Level from 2 to 1. As of 23 September 2011, the Alert Level remained unchanged, indicating, as stated by PHIVOLCS, "low level unrest" and that "no eruption [is] imminent." At Alert Level 1 (and all higher levels), access is prohibited within the 6-km-radius Permanent Danger Zone.

With the exception of May 2011, seismicity (figure 20) typically consisted of no more than a few volcanic earthquakes and rockfall events per day (i.e. less than 50 of either type per month) and relatively low SO2 flux (averaged per month on figure 20). Mayon typically vented ash-free steam at weak-to-moderate intensities, and crater glow persisted, observable by residents at night.

Figure (see Caption) Figure 20. Reported volcanic earthquakes and seismically detected rockfall events per month (dark and light gray bars, respectively, left axis) and SO2 flux (open triangles and dashed line) averaged per month (right axis) at Mayon from 1 January 2010 to July 2011. Background colors indicate the Alert Level corresponding to the scale to the right of the figure. Little if any data are available from March through December 2010, presumably due to low activity during this interval. Data courtesy of Philippine Institute of Volcanology and Seismology (PHIVOLCS).

During May 2011 there was a significant increase in seismicity, reaching a daily maximum of 38 volcanic earthquakes on 25 May. This increase coincided with a slight increase in the SO2 flux (averaged per month, figure 20). The increase in both seismicity and SO2 flux was short-lived, and activity declined to relatively low levels by June 2011.

Geologic Background. Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); GMANews.TV, 6/F GMA Network Center, EDSA corner Timog Avenue, Diliman, Quezon City, 1101, PHILIPPINES (URL: http://www.gmanews.tv/index.html); United Nations Institute for Training and Research's (UNITAR's) Operational Satellite Applications Programme (UNOSAT), Palais des Nations, CH-1211 Geneva 10, Switzerland (URL: http://www.unitar.org/unosat/); Ginkgo Maps (URL: http://www.ginkgomaps.com/).


Nabro (Eritrea) — September 2011 Citation iconCite this Report

Nabro

Eritrea

13.37°N, 41.7°E; summit elev. 2218 m

All times are local (unless otherwise noted)


First historically observed eruption began 13 June 2011

The first documented historical eruption at Nabro began on 13 June 2011. Nabro lies in a belt of active volcanoes that follows the Red Sea and lies in the Afar Triangle in Southern Eritrea near the border with Ethiopia (figure 1). An earthquake swarm began on 12 June 2011. The swarm included an M 5.1 earthquake in the vicinity of Nabro and early the next day, satellite remote sensing revealed a large ash plume. Tensions remain in the war-ravaged border region of Eritrea and Ethopia; despite an official cease fire, access to the region remains limited. Nabro's eruption delivered large and concentrated SO2 plumes, dropped ash over extensive areas, forced thousands of evacuations, and, according to the Eritrean government, led to fatalities.

Figure (see Caption) Figure 1. Nabro's location in Eritrea and with respect to neighboring countries in East Africa. (Inset) The location of Eritrea in Northeastern Africa along the Red Sea.

Nabro lies in the midst of a chain of volcanoes (figure 2; dashed lines indicate trends of volcanic ranges). Each of the three main volcanoes on figure 2 contains a prominent summit crater or caldera (figures 3 and 4).

Figure (see Caption) Figure 2. A regional map showing Nabro in the volcanic range of the same name (Nabro Volcanic Range, NVR). According to the map's authors (Wiart and Oppenheimer, 2005), the NVR trends with a bearing of N26°E and extends 110 km from the SE margin of the Afar depression at Bara' Ale to islands in the Red Sea. Nabro marks the highest point in the NVR (which the map authors state as 2,248 m, some 30 m higher than the value given in our header, above). Taken from Wiart and Oppenheimer (2005).
Figure (see Caption) Figure 3. Satellite image of the Nabro region taken in February 2000 processed to form a shaded-relief map. When viewed in color, the lower elevations are in green, grading through yellow to red to blue at the highest elevations on the rims of the various nested calderas. Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the NASA Space Shuttle Endeavour. The scale is inexact, and the Eritrean-Ethiopian border is approximate. Courtesy of NASA Jet Propulsion Laboratory.
Figure (see Caption) Figure 4. Astronauts on the NASA International Space Station took this photograph of Nabro on 30 January 2011, showing the pre-eruption morphology of Nabro and some smaller volcanic centers to the S. Nabro's outer crater is ~8 km across and opens to the SSW. Centered within that larger caldera lie two much smaller craters, one inside the other. The inner wall of the caldera has steep sides, some as high as 400 m. Courtesy of NASA Earth Observatory.

Seismic precursors. According to an article in the Ethiopian Journal issued on 13 June 2011, a series of moderate earthquakes struck the Eritrea-Ethiopia border region on the evening of 12 June 2011. The U.S. Geological Survey (USGS) reported a total of 14 light-to-moderate earthquakes in the border area, the two strongest being M 5.7, both centered in Eritrea. The series began at 1837 hours when an M 5.1 earthquake struck ~128 km WNW of Assab, a port city in the southern Red Sea region of Eritrea. It occurred at ~10 km depth and was followed by seven smaller ones, between M 4.5 and M 4.8, during the next 2.5 hours. Those were then followed by earthquakes of M 4.7, 4.8, and 5.0. Soon after, at 2332 hours, the first M 5.7 earthquake struck about 123 km WNW of Assab at a depth of 10 km. It was quickly followed by the second M 5.7 earthquake and other smaller earthquakes.

Eruption. The Toulouse Volcanic Ash Advisory Center (VAAC) reported that an eruption from Nabro (originally attributed to Dubbi, ~25 km NNE of Nabro) started between 0300 and 0500 on 13 June 2011. The eruption plume initially rose to altitudes of 9.1-13.7 km; it was detected at altitudes of 6.1-10.7 km during 13-14 June.

According to the Eritrean Ministry of Information, ashfall covered hundreds of square kilometers, and the government evacuated area residents. Eye witnesses first observed the eruption at about 2100 on 13 June. Satellite images that same day showed the plume drifting more than 1,000 km NW, over parts of Sudan. On 14 June 2011 news articles reported that a detached ash cloud was detected over southern Israel. Throughout the eruption, satellite images were nearly the only source of new information about activity.

The Addis Fortune website reported that, although the major eruption took place in Nabro, large quantities of dust from the earthquake occurred in the town of Afambo (~26.5 km N of Nabro). It also reported that the Eritrean government announced that inhabitants had moved to safe areas. The well-known Afdera salt accumulation site in the depression was covered in volcanic ash. The salt, extracted for human and other consumption, had thus become inedible. The ash clouds also caused the cancellation of some domestic and international flights in Eritrea and Ethiopia.

During the week of 15-21 June 2011, Nabro continued to produce plumes. Based on analyses of satellite imagery during that period, the Toulouse VAAC reported that plumes comprised mostly of water and SO2 rose to altitudes of 6.1-7.9 km (figure 5). Ash was occasionally detected near the volcano. Satellite imagery posted on the MODIS/MODVOLC website showed a dark brown ash plume fanning out to the SW on 19 June. By 19 June, the altitude of Nabro's ash plume dropped from a maximum of 14 km to 7.6 km. The ash halted flights in eastern Africa for a time. The eruption killed seven people, according to the Eritrean government, although later reports appeared to discount that. Other reports indicated that thousands were affected in both Eritrea and Ethiopia, though news was sparse.

Figure (see Caption) Figure 5. This large and intense SO2 gas cloud emitted from Nabro was captured by the OMI satellite's spectrometer during the time interval between 1017 and 1159 UTC on 19 June 2011. The SO2 traveled to the S and the W during the period, and some portions of intense gas clearly extended off this image in those directions. The scale at right is in Dobson Units (DU, a unit common in atmospheric research and widely described in text books). The mass of SO2 depicted on this image was ~103 kilotons (kt); the area of cloud was ~591,000 km2; the maximum SO2 values on the image occurred at the location 40.87°N and 13.14°E and reached 68 DU. Courtesy of Simon Carn, and NASA Global Sulfur Dioxide Monitoring Aura/OMI website.

A thermal satellite image acquired at night on 19 June revealed a 15-km-long lava flow that had traveled NW (figure 6). A high-altitude plume, likely rich in water vapor, rose from erupting vents; a diffuse ash-rich plume drifted SW. The more restricted plume on 19 June enabled images to reveal a NW-trending lava flow that extended ~15 km from the summit area, although the area of venting remained obscured by a water-rich plume.

Figure (see Caption) Figure 6. A thermal infrared, false-color image of Nabro on 19 June 2011 taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Hot areas are bright with new lava flows shown in white, and cold areas are dark. Thermal infrared data were combined with a shaded relief image to show the terrain. Courtesy of NASA Earth Observatory.

On 22 June a report from the Eritrea Ministry of Energy and Mines stated that the ash and lava covered hundreds of square meters. A satellite image acquired that day showed a gas-and-ash plume rising from the caldera and drifting W. An image from 24 June showed the erupting vent, plumes and emissions, and lava flows (figure 7).

Figure (see Caption) Figure 7. A false-color image of Nabro, acquired by the Advanced Land Imager (ALI) aboard the Earth Observing-1 (EO-1) satellite on 24 June 2011, highlighted hot areas throughout the lava flow and flow front, as well as above the vent in the center of the caldera. The bright red portions indicate hot surfaces. To the W, portions of an active lava flow (particularly the flow-front) are also hot. The speckled pattern on upstream portions of the flow is likely due to hardened crust splitting and exposing fluid lava. An ash plume rose from the vent, and at higher altitudes a plume composed of water vapor and SO2 drifted W and obscured the active lava flow. Black ash deposits covered the landscape to the S and W. Courtesy of NASA Earth Observatory.

During 22-26 June large amounts of SO2 in the region continued to be detected by satellite images. Based on analyses of satellite imagery, the Toulouse VAAC reported that during 26-27 June plumes reached altitudes of up to 6.1 km.

An annotated satellite image acquired on 29 June (figure 8) showed a clear view of the eruption. NASA Earth Observatory analysts labeled what they inferred to be the vent, an area in the main caldera's center and likely engulfing both the two inner craters with either very hot lava or with fresh tephra that probably formed cones or other features whose surface cooled quickly. An ash plume rose from the vent and drifted S. Based on analyses of satellite imagery, the Toulouse VAAC reported that on 16 July an ash plume from Nabro rose to altitudes below 5.5 km. A weak eruption detected on 17 July decreased through the day then appeared to stop.

Figure (see Caption) Figure 8. A visible and infrared image of Nabro from the Advanced Land Imager (ALI) on the Earth Observing-1 (EO-1) satellite, taken 29 June 2011. The image shows the still-hot lava flow, fresh ash over the lower half of the photo (dark landscape, accentuated by slanting lines or dashes in the lower portion of the image). A diffuse ash plume rose from the vent. The hottest lava is indicated by orange-red, with cooler zones fading to black. The ~15 km long flow on the W side of the volcano is mottled with black, indicating areas with cooler surfaces. The lava to the E and S of the vent appears to be newer, since little of it has cooled. Image and interpretation of NASA Earth Observatory (with lines and additional labels added).

According to an article by the South Africa Weather and Disaster Information Service (SAWDIS) dated 30 June 2011, a press release from the Eritrean Government disclosed that, though the advancing lava in the nearby village of Sireru had slowed down, a large area of land covered by vegetation was destroyed and river beds were covered within 24 hours.

NASA's Earth Observatory noted that images from 28 September showed heat from the vent in the central crater and from an area 1.3 km S of the vent that indicated an active lava flow. A small and diffuse plume rose from the vent. A region of seemingly thicker black ash (that completely covered the sparse vegetation) was noted S of the crater and thinner layers of ash (with some areas of visible vegetation) flanked either side of the region.

MODVOLC Thermal Alerts. Prior to 12 June 2011 the MODVOLC website indicated that no thermal alerts were measured over at least the past 5 years. The onset of thermal alerts was a 3-pixel area detected at 0115 on 13 June 2011 (2215 on 12 June UTC), followed by nearly daily measurements through 1 September 2011. Since that date, several alerts per week have been measured for Nabro up to 5 November 2011.

Some individual satellite passes measured high numbers of alerts. A 9-pixel alert occurred on 8 September, and as many as 95 pixels were measured for a single satellite pass at 2245 on 17 June. Other single orbital passes during June-August measured alerts of 50 to more than 70 pixels.

Reference. Wiart, P., and Oppenheimer, C., 2005, Large magnitude silicic volcanism in north Afar: the Nabro Volcanic Range and Ma'alalta volcano, Bulletin of Volcanology, v. 67, no. 2, pp. 99-115.

Geologic Background. The Nabro stratovolcano is the highest volcano in the Danakil depression of northern Ethiopia and Eritrea, at the SE end of the Danakil Alps. Nabro, along with Mallahle, Asavyo, and Sork Ale volcanoes, collectively comprise the Bidu volcanic complex SW of Dubbi volcano. This complex stratovolcano constructed primarily of trachytic lava flows and pyroclastics, is truncated by nested calderas 8 and 5 km in diameter. The larger caldera is widely breached to the SW. Rhyolitic obsidian domes and basaltic lava flows were erupted inside the caldera and on its flanks. Some very recent lava flows were erupted from NNW-trending fissures transverse to the trend of the volcanic range.

Information Contacts: NASA Earth Observatory (URL: http://earthobservatory.nasa.gov); MODIS/MODVOLC, 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 (URL: http://modis.higp.hawaii.edu/); Toulouse Volcanic Ash Advisory Centre (VAAC) (URL: http://www.meteo.fr/vaac/); NASA Global Sulfur Dioxide Monitoring (URL: http://so2.gsfc.nasa.gov/index.php); Jet Propulsion Laboratory (URL: http://photojournal.jpl.nasa.gov); S.A. Weather and Disaster Information Service. (SAWDIS) (URL: http://saweatherobserver.blogspot.com); Ethiopian Journal (URL: http://www.ethjournal.com); Addis Fortune (URL: http://www.addisfortune.com); Simon Carn, Dept of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA (URL: https://so2.gsfc.nasa.gov/).


Santa Maria (Guatemala) — September 2011 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Eruption on 26 April 2010; ongoing activity through September 2011

The following report provides information from May 2010 through mid-October 2011 on Santa Maria volcano and its active dome complex, Santiaguito. The last report (BGVN 35:03) covered activity form 2008 to April 2010. The sources for this report are Guatemala's Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH) and Washington Volcanic Ash Advisory Center (VAAC). Santa Maria's eruptive history from the Global Volcanism Program database identifies the current eruption as beginning 22 June 1922 and continuing to mid-October 2011. The database's criteria for an eruption ending requires at least a 3-month pause in volcanic emissions (Siebert and others, 2010).

A recent report concerned the eruption of 26 April 2010, an event mentioned at the end of our last report (BGVN 35:03). A table summarizes some significant activity during the current reporting period. It is notable that during about nine months of 2011 (up to early October), MODVOLC measured thermal alerts several times each month (in each instance covering an area of 1 to 3 pixels). In comparison, during 2009, seven thermal alerts were measured and, during 2010, three alerts were measured.

More details on the 26 April 2010 eruption. Chigna (2010) noted the 26 April 2010 eruption of Santiaguito was associated with four large seismic events (M 3.9 at 0624, M 4.92 at 0648, M 5.89 at 0723, and M 5.72 at 0758). The seismic network recently established at the volcano permitted first-time recognition of some seismic signals known as tornillos ['screws' in Spanish; defined by Morrissey and Mastin (2000) as monochromatic, long period seismic events lasting a few minutes, with long codas of progressively decreasing amplitude that may be eruption precursors] (figure 34a). Pyroclastic flows were generated within the gullies on the S flank. An ash column rose to an altitude of 15 km, drifting to the W, NW, N, NE, and E, causing closure of village schools SW of Santiaguito and in the Quetzaltenango area. The ashfall was reported out to 7.3 km from the volcano; civil aeronautics alerted air traffic to avoid the plume within a radius of 80 km.

Figure (see Caption) Figure 34. Examples of seismic records at Santa Maria. (a) Tornillo (screw) event. (b) Pyroclastic flow due to dome collapse; arrows indicate the onset of the primary events. Both seismic records taken from Chigna (2010).

Activity from May 2010 to early-October 2011. Tables 3 and 4, summarizing activity from May 2010 through early-October 2011, document nearly continuous explosions, plumes, and pyroclastic flows. Various mass wasting processes were common, particularly block avalanches and lahars, often set into motion by precipitation.

Table 3. Summary of available information on explosions, plumes, and other volcanic emissions of Santa Maria volcano reported during May-December 2010. "--" is 'not reported' in original VAAC reports. Courtesy of INSIVUMEH, Washington VAAC, and MODVOLC.

Date Explosions noted Plume color and composition Plume Height Drift Direction Other Activity
07 May 2010 17 weak to moderate Gray 2.9-3.4 km SW --
10 May 2010 -- White 75 m -- --
19 May 2010 Yes Ash 2.9-3.4 km SW Hot lahars carried blocks
20 May 2010 Yes -- 3.3 km E Pyroclastic flow to SW
04 Jun 2010 -- -- -- -- Lahar carried blocks
19-20 Jul 2010 24 in 48-hour period Ash 300-900 m SE, W --
05-06 Aug 2010 -- Steam -- SW Lahars carried trees, blocks
01 Sep 2010 -- Ash 100 m SE Pyroclastic flow to SW
02 Sep 2010 Yes Ash 500-1,000 m W, SW Block avalanches on W flank
06 Sep 2010 Yes Ash 500-1,000 m W, SW --
11 Sep 2010 Yes Ash 1 km E, SE Pyroclastic flows (2) to 3 km SW
13 Sep 2010 -- White 100 m S --
22 Oct 2010 Yes Ash 300 m SW Block avalanches on S and SW flanks
26 Oct 2010 -- Steam 150 m -- --
29 Oct 2010 Yes Ash 900 m SW Pyroclastic flow down SW flank to 5 km S
31 Oct 2010 -- Ash -- W --
17, 22 Nov Yes Ash 0.7-1 km E, SE --
19 Nov 2010 -- -- -- -- Ashfall to the S
08 Dec 2010 Yes Ash 700 m SE Block avalanches; ashfall to SE
10 Dec 2010 -- Ash -- 21 km W --
13-14 Dec 2010 Yes Ash 300-700 m SE Block avalanches; pyroclastic flows
29-30 Dec 2010 Yes Ash 300-600 m S, SE Ashfall

Table 4. Summary of available information on explosions, plumes, and other volcanic emissions of Santa Maria volcano reported during January through early-October 2011. "--" is 'not reported' in original VAAC reports. Courtesy of INSIVUMEH, Washington VAAC, and MODVOLC.

Date Explosions noted Plume color and composition Plume Height Drift Direction Other Activity
01 Jan 2011 -- -- -- W Satellite thermal anomalies
03-04 Jan 2011 Yes Ash 700 m SW Avalanches to W flank
05-06 Jan 2011 Yes Ash 400-500 m SW --
08 Jan 2011 -- Ash? -- 30 km SSW --
10-11 Jan 2011 Yes Ash 600 m SW, W Avalanches on S and E flanks
20-21 Jan 2011 -- Ash 4.3-5.2 km SW Avalanches; rockfalls
23-24 Jan 2011 -- Ash 300 m N --
02-03 Feb 2011 Yes Ash 300 m --

References. Chigna, G., 2010, Eruption of Santiaguito (1402-03) 26 April 2010. INSIVUMEH (URL: http://www.insivumeh.gob.gt/).

Morrissey, M., and Mastin, L., 2000, Vulcanian eruptions, p. 463-475, in Sigurdsson, H. (ed), Encyclopedia of Volcanoes, Academic Press, San Diego.

Siebert, L., Simkin, T., and Kimberly, P., 2010, Volcanoes of the World, 3rd ed., Berkeley: University of California Press, 568 p.

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

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/inicio.html); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20748, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); MODVOLC-HIGP, 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/).


Stromboli (Italy) — September 2011 Citation iconCite this Report

Stromboli

Italy

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

All times are local (unless otherwise noted)


Recent activity; plumbing insights; new water vapor flux technique; hydrogeology

Activity at Stromboli (figure 76), since February 2010 (BGVN 35:03) through 11 October 2011 was generally of medium to low intensity, with minor fluctuations typical for Stromboli. Istituto Nazionale di Geofisica e Vulcanologia (INGV) reported occasional episodes of increased activity; note that the dates provided below are illustrative and by no means all-inclusive. This generally occurred as either more intense explosions or increased spattering (figure 77). More intense explosions often generated coarse pyroclastics and/or expelled erupted products farther than during typical activity, sometimes to the summit platform (Pizzo sopra la Fossa) overlooking the active craters, and beyond. For example, some specific pronounced events took place on 19 December 2010, 5 August, and 5 September 2011.

Figure (see Caption) Figure 76. Index map (inset) and aerial photograph of Stromboli, showing the active vents and Sciara del Fuoco, a Pleistocene landslide scarp. Underlined names indicate coastal towns. Index map courtesy of Ginkgo Maps; aerial photograph courtesy of the Italian Air Force.
Figure (see Caption) Figure 77. Photograph of an eruption at Stromboli at approximately 1930 on 15 July 2011 showing spattering behavior. Courtesy of Tom Pfeiffer, Volcano Discovery.

On 30 June 2010, incandescent material thrown from the vent caused small fires on the upper flanks of the volcano. Increased spattering activity often resulted in intra- and, less frequently, extra-crater lava flows (figure 78a and b, respectively) such as those seen during 18-23 October 2010, 1-2 August, and 7 September 2011. The extra-crater lava flows of 1-2 August from the northernmost vent were the first observed since December 2010; they extended only a few hundred meters downslope (figure 78a). Extra-crater lava flows were often accompanied by land- or rock-slides down Sciara del Fuoco, fed by material that broke free from lava flow fronts and rolled down slope (e.g. 1 August 2011).

Figure (see Caption) Figure 78. Intra-crater (a) and extra-crater (b) lava flows at Stromboli. (a) Spatter fed lava flow emitted from a small cone on the SW rim of the crater terrace; a small group of glowing vents can be seen at bottom left (circled). Photographed during the night of 11-12 August 2011 by Gijs de Reijke. (b) Aerial view of the summit area of Stromboli, highlighting extra-crater lava flows onto Sciara del Fuoco. The northern (N) and southern (S) vent areas are labeled in red; lava flows were emitted during 11-12 December 2010 (1, yellow), 1-2 August 2011 (2, pink), and on 18 August 2011 (3, red). Photo by Mauro Coltelli; courtesy of Istituto Nazionale di Geofisica e Vulcanologia (INGV).

Some of the parameters reported by INGV during February 2010 to October 2011 included seismic, deformation, visual observation, and gas flux. The flux of CO2 and SO2, and particularly the CO2/SO2 ratio measured in the plumes, provided insight into the provenance of the generally discreet gas discharges ("gas slugs") that regularly burst upon reaching Stromboli's vent. INGV reported that a coupled increase in the CO2/SO2 ratio and decrease of SO2 flux (seen, for example, during the weeks of 5-12 and 19-26 September 2011) indicated an increased contribution of volatiles from deeper portions of the magmatic system.

Recent insight into magma generation. A study of erupted ash textures and compositions by D'Oriano and others (2011) yielded results comparable with the implications of the CO2/SO2 ratio reported by INGV. The authors use the commonly accepted terms for two separate populations of magma at Stromboli; these terms are presented and used herein.

"LP magmas" are those with low porphyricity (similar sized phenocrysts) that are considered to have relatively deeper origins and simple cooling histories. "HP magmas" are those with high porphyricity (multiple size populations of phenocrysts) that are considered to reside in a shallow reservoir in the crust and have more complex, multiple stage cooling histories.

D'Oriano and others (2011) found that there is a coupled, possibly persistent ascent of deep-derived CO2 and small amounts of LP magma. They concluded that the coupled ascent of LP magma and CO2 is transient and does not disturb the HP magma that resides in the shallow reservoir. See figure 79 for a schematic of the plumbing and magma storage zones of Stromboli.

Figure (see Caption) Figure 79. Schematic cross-section of Stromboli showing the crustal plumbing system and highlighting HP and LP magma storage zones. From Aiuppa and others (2010), based upon earlier works.

New technique for measuring plume water vapor concentration. LIDAR (Light Detection and Ranging) has been used for the first time to measure water vapor flux of a volcanic plume. Fiorani and others (2011) used a CO2 laser-based LIDAR system called ATLAS (Agile Tuned Lidar for Atmospheric Sensing) at Stromboli to measure both wind speed and water vapor concentration of the erupted plume. When combined, the measurements yielded water vapor flux of the plume. Their measurements agreed with measurements obtained from traditional methods, and were the first such measurements at an active volcano.

Hydrogeology of Stromboli. A detailed geophysical survey of Stromboli revealed some hydrogeological features of the volcano (figure 80). Revil and others (2011) conducted a survey measuring electrical resistivity, soil CO2 concentrations, soil temperature, and self-potential along two profiles (a and b, figures 80 and 81). Their survey focused on the Pizzo crater (near the active vents), and the Rina Grande sector collapse on the E side of the island. They published a detailed schematic interpretation of fluid-flow pathways along the two profiles (figure 81).

Figure (see Caption) Figure 80. Geologic map of Stromboli. Red dots denote geophysical profiles of Revil and others (2011); (a) profile across Pizzo crater, near the active vents, and (b) profile down the length of the Rino Grande sector collapse, on the E flank of Stromboli. The two profiles are coincident to the W of Neo-Stromboli crater. Modified from Revil and others (2011).
Figure (see Caption) Figure 81. Interpretive hydrogeology diagram of Revil and others (2011) at Stromboli highlighting fluid flow pathways along two profiles; (a) profile across Pizzo crater, and (b) profile down the length of the Rino Grande sector collapse. See legend at right; areas in gray indicate the inferred extent of the hydrothermal system; orange lines and arrows indicate hot water flow; gray arrows indicate gas discharge; black solid and dashed lines indicate faults. See Revil and others (2011) for further details.

The authors identified an unconfined aquifer above the villages of Scari and San Vincenzo. They stated that the Rina Grande sector collapse is the "most important structural control for magmatic and hydrothermal fluids" in the upper part of the Stromboli edifice, and that it hosts the two main diffuse degassing areas of the edifice. They further concluded that the hydrothermal system reaches shallow levels in the lower part of the Rina Grande collapse (profile b, figures 80 and 81). This fact, they wrote, "raises questions about the mechanical stability of this [E] flank of the edifice".

References. Aiuppa, A., Bertagnini, A., Métrich, N., Moretti, R., Di Muro, A., Liuzzo, M., Tamburello, G., 2010, A model of degassing for Stromboli volcano, Earth and Planetary Science Letters, v. 295, no. 1-2, p. 195-204 (DOI: 10.1016/j.epsl.2010.03.040).

D'Oriano, C., Bertagnini, A., and Pompilio, M., 2011, Ash erupted during normal activity at Stromboli (Aeolian Islands, Italy) raises questions on how the feeding system works, Bulletin of Volcanology, v. 73, no. 5, p. 471-477 (DOI:10.1007/s00445-010-0425-0).

Fiorani, L., Colao, F., Palucci, A., Poreh, D., Aiuppa, A., and Giudice, G., 2011, First-time lidar measurement of water vapor flux in a volcanic plume, Optics Communications, v. 284, no. 5, p. 1295-1298 (DOI:10.1016/j.optcom.2010.10.082).

Revil, A., Finizola, A., Ricci, T., Delcher, E., Peltier, A., Barde-Cabusson, S., Avard, G., Bailly, T., Bennati, L., Byrdina, S., Colonge, J., Di Gangi, F., Douillet, G., Lupi, M., Letort, J., and Tsang Hin Sun, E., 2011, Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements, Geophysical Journal International, v. 186, no. 3, p. 1078-1094 (DOI:10.1111/j.1365-246X.2011.05112.x).

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

Information Contacts: Boris Behncke and Mauro Coltelli, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, 95125 Catania (URL: http://www.ct.ingv.it/); Ginkgo Maps (URL: http://www.ginkgomaps.com/); Italian Air Force (URL: http://www.aeronautica.difesa.it/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Gijs de Reijke, Arnhem High School, Nijmegen, Netherlands.


Tofua (Tonga) — September 2011 Citation iconCite this Report

Tofua

Tonga

19.75°S, 175.07°W; summit elev. 515 m

All times are local (unless otherwise noted)


Elaborative comments on April 2010 observations

This report on Tofua elaborates on observations in our previous report (BGVN 36:07).

Several maps show Tofua (figure 7) with respect to other geographic features, and also areas of responsibility of Volcanic Ash Advisory Centers in the region. A map of islands in the main part of the Archipelago appeared in BGVN 34:02.

Figure (see Caption) Figure 7. (inset at lower right) Tofua shown in geographic context. Tofua is a part of the Kingdom of Tonga. (main map) Various areas of responsibility of Volcanic Ash Advisory Centers (VAACs) in the region; responsibility for Tonga resides with the Wellington Volcanic Ash Advisory Centre. Courtesy of ESRI Corporation (modified).

Mark Belvedere (Kalia Foundation) sent additional comments regarding his visit to Tofua on 24 April 2010 (see BGVN 36:07). Belvedere noted that at night as they approached the island the glow from the active crater flickered and was visible ~50 km from the volcano. The glow was absent during the day but a plume was conspicuous. In describing his approach to the crater he stated that "As I was walking up towards [it] the area was littered with lava stone from the sizes of golf balls to beach balls." The observation of those ejecta made him nervous. To him, the crater "looked like an air-breathing red hot lava tube ready to shoot out lava stones at any moment but NO I didn't stay to physically see it shooting out the lava nor the lava stones."

Upon reaching the summit the visitors were surprised at how unstable the rim looked. Belvedere had to have his companions hold his feet in order to lean out over the crater to get the photo shown in our previous report (BGVN 36:07). He guessed the distance to the sloping crater floor was on the order of 50 m. The low-level eruptions accompanied larger ash plumes. The plumes were quite reflective at night. A sulfurous odor prevailed.

Stuart Kershaw's attempts to create a video with narration on the scene proved difficult because the eruptions were broken with pauses of about 8-15 minutes, and each pulse behaved differently in terms of how much sound they generated.

Geologic Background. The low, forested Tofua Island in the central part of the Tonga Islands group is the emergent summit of a large stratovolcano that was seen in eruption by Captain Cook in 1774. The summit contains a 5-km-wide caldera whose walls drop steeply about 500 m. Three post-caldera cones were constructed at the northern end of a cold fresh-water caldera lake, whose surface lies only 30 m above sea level. The easternmost cone has three craters and produced young basaltic-andesite lava flows, some of which traveled into the caldera lake. The largest and northernmost of the cones, Lofia, has a steep-sided crater that is 70 m wide and 120 m deep and has been the source of historical eruptions, first reported in the 18th century. The fumarolically active crater of Lofia has a flat floor formed by a ponded lava flow.

Information Contacts: Mark Belvedere, Kalia Foundation USA, 4515 SW Natchez Ct., Tualatin, OR 97062, USA (www.kaliafoundation.org); Treasure Island Eueiki Eco Resort, Vava'u, Kingdom of Tonga (www.tongaislandresort.com); Stuart Kershaw, In the Dark Productions (URL: http://inthedarkproductions.co.uk/); Sakopo Lolohea, Tongan Visitor Bureau, Ministry of Tourism. Vuna Rd., Nuku'alofa, Tonga (URL: http://www.tonga.holiday.com/).


Turrialba (Costa Rica) — September 2011 Citation iconCite this Report

Turrialba

Costa Rica

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

All times are local (unless otherwise noted)


Frequent degassing and occasional ashfall, March 2010-June 2011

During 5-6 January 2010, Turrialba discharged a phreatic eruption that resulted in a new vent and ashfall up to 30 km from the crater (BGVN 35:02). This report discusses activity from February 2010 through October 2011. Portions of this report were initially synthesized and edited by Shereena Dyer, as part of a graduate student writing assignment in a volcanology class at Oregon State University under the guidance of professor Shan de Silva.

Since the January eruption, Turrialba (figure 23) has continued to eject gas and ash intermittently, maintained elevated fumarolic output and temperatures, and produced strong SO2-bearing plumes from the vent. This activity continued over much of the reporting interval. The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) annual report highlighted the 5-6 January eruption as the key event during 2010. According to OVSICORI-UNA, field observations on 6 January found that two small vents had opened and joined together on the SE inner wall of the SW crater. Current monitoring includes a web camera 600 m from the active crater that takes an image every 10 seconds.

Figure (see Caption) Figure 23. View of Turrialba's SW crater (depression in foreground) and central crater (at distance). The photo documents the character of persistent ongoing fumarolic degassing on an unstated day in January 2011. The yellow zones on the hillsides represent sulfur-bearing deposits sublimated from the sulfur-rich gas emissions. Courtesy of OVSICORI-UNA.

After the 5-6 January eruptions, emission levels dropped. In late February 2010, scientists found a pool of molten sulfur at the base of the S crater wall with a temperature of 153°C.

OVSICORI-UNA reported that scientists visited Turrialba on 7 March 2010. A gas plume, common with this volcano, was observed that night rising 1.5 km above the crater and drifting NW. Noises from the crater were described as sounding like a jet engine and rumblings. The January 2010 vent emitted gas in March with surface temperatures between 300 and 320°C. Small blocks 3-12 cm in diameter and of different colors dominated the surface around the vent. Lithics ejected 30-50 m away from the vent measured 170°C. Incandescence seen at night originated from the vent that ejected reddish-colored tephra. Two SO2 measurements taken on or around 13 March from a ground-based spectrometer yielded 1,100 and 750 t/d, the former taken closer to the volcano.

According to OVSICORI-UNA, most of the gas emitted in April originated from the January 2010 vent; in April it produced plumes that rose 2 km above the crater rim. Gas also rose from other areas, including fissures SW of the W crater and from multiple vents and fissures in the main crater. Gas plumes mainly drifted NW, W, and SW, coinciding with areas where vegetation had suffered the greatest damage from the gases.

In April 2010, OVSICORI-UNA reported that multiple years of rain data had been collected at the station La Silvia on the W flank and was frequently found to be acidic (pH often well below 5). During 2007 though mid-2010, the rain had pH 2.8-5.7 and elevated specific conductivity (figure 24). Note that the lowest pH values on the plot were collected during 2009 and 2010.

Figure (see Caption) Figure 24. Specific conductivity (microS/cm) and pH of rainfall collected at La Silvia station associated with Turrialba during parts of the 1980s and then from 2007 through mid-2010. Note break in horizontal scale owing to absence of data. Courtesy of OVSICORI-UNA/CONARE.

In May scientists noted that on the NW, W, SW sides there were new effects of acid-rain-damaged leaves and vegetation up to 4 km from the main crater. During August, observers noted farms 18 km SW of Turrialba with burns on onions, chemical damage attributed to volcanic gases.

A farm 3 km NW of the summit appears in comparative photos from 2007 and 2011 (figure 25). The houses in the photos were abandoned for a few months after the seismic swarms in the middle of 2007. The residents returned during February-March 2008, only to permanently leave in the middle of 2008 due to harsh atmospheric conditions. This farm remained abandoned in November 2011. Many others were also abandoned in areas of intense impact.

Figure (see Caption) Figure 25. For Turrialba, comparative views from 2007 (top) and 2011 (bottom) of a farm below the crater and to the NW. These photographs show the effects of acidification on the vegetation and infrastructure. Courtesy of OVSICORI-UNA.

Based on web camera views, the Washington Volcanic Ash Advisory Center (VAAC) reported that on 24 July 2010 a plume of steam, gas, and ash drifted W. Over the next three hours, the plume became more diffuse and steam-rich. Another ash emission was observed on 15 August 2010; the plume drifted about 600 m E of the active crater. Satellite imagery showed an approximately 10-km-wide ash plume drifting 15 km W.

The volcano was relatively quiet during November and December. In January 2011, vegetation damage from acid rain could be observed on the SW, W, and NW flanks. Residents in the village of Silvia, 2.3 km SW of the crater, reported a strong stench of SO2 during the month. On 14 January, nearby residents reported minor ashfall and rumbling noises, and again, strong sulfurous odors. OVSICORI closed the Turrialba Volcano National Park temporarily, evacuated a few people as a precaution, and installed a surveillance base in the town of La Central (~4 km SW of the crater). OVSICORI-UNA noted that a blue-and-white gas plume rose from Turrialba the next day.

During a visit to the volcano in January 2011, OVSICORI-UNA found that a 2- to 5-cm-thick layer of freshly ejected material, with clasts ranging in size from a few millimeters to 5 cm, blanketed the W edge of the crater. Officials discovered two small landslides on the walls of the crater. The walls were considered unsafe due to the loose material. The cavity in the crater that formed in January 2010 had been widened as a result of falling material and the W part of the cavity was offset by about 4 m. A new cavity in the vent appeared to have formed from one of the explosions. Heavy rainfall created a large gully, incising the W edge of the crater at a depth of 0.4-1.5 m. Despite the intense rainfall, the crater was covered in sulfur-bearing deposits. An "eerie sound," which at times could be heard kilometers from the summit, was associated with the emission of gas. A gray plume had a temperature at the vent ranging from 480-498°C.

OVSICORI-UNA reported that on 9 June 2011 scientists conducting fieldwork at Turrialba observed a new lake in the SW crater. Since February, rock landslides along with abundant mud and clay had accumulated in the bottom of the crater, blocking the vent. Meteoric water from rains starting in May had formed a light-green-colored lake that was 70 m in diameter and ~1 m deep. Minor bubbling in the SW and NE shores was noted, and steam and sulfur dioxide gas emissions rose from many fumarolic vents around the crater.

OVSICORI-UNA reported on 12 October 2011 that degassing at Turrialba had affected the vegetation, soil, infrastructure, and economy (figure 25). Acidification of the soil had impaired, possibly permanently, vegetation growth; the economic effect on farms and livestock has yet to be determined. A school building near the volcano was still used by students and teachers, despite having been deemed unsafe. The extent of the effect of acidification on livestock and the economy had not yet been determined.

Reference. OVSICORI-UNA, 2010, Real-time webcamera of Turrialba volcano, Costa Rica (URL: http://www.ovsicori.una.ac.cr/vulcanologia/videoturri.html)

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: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).

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