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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 24, Number 10 (October 1999)

Managing Editor: Richard Wunderman

Campi Flegrei (Italy)

Variable sulfate concentration; rising temperatures and other increases

Damavand (Iran)

Morphology and brief description of summit from visiting excursion

Guagua Pichincha (Ecuador)

A growing dome, high seismicity, and wind-assessment challenges

Kolbeinsey Ridge (Iceland)

Submarine eruption or dike intrusion south of the Spar Fracture Zone

Langila (Papua New Guinea)

Some strong ash emissions in September-October

Manam (Papua New Guinea)

Inflationary trend continues; seismic peak in mid-August

Moyorodake [Medvezhia] (Japan - administered by Russia)

Small phreatic eruption from the Kudriavy summit forms a new crater

Rabaul (Papua New Guinea)

Ash eruptions continue; new vent generates ash emissions for eight days

Taftan (Iran)

Visitors note mineral springs and fumaroles

Tanga (Papua New Guinea)

Possible uplift or growth of Lif Island over two decades

Tungurahua (Ecuador)

Crisis continues with few earthquakes, abundant tremor, high SO2, and explosions

Ulawun (Papua New Guinea)

Explosions in mid-October-the first in 6.5 years

Vesuvius (Italy)

9 October seismic swarm includes an M ~ 3.5 event, the largest in 50 years

Vulcano (Italy)

H2S, SO2, HF, HCl, and other gases tending to increase during 1998-99



Campi Flegrei (Italy) — October 1999 Citation iconCite this Report

Campi Flegrei

Italy

40.827°N, 14.139°E; summit elev. 458 m

All times are local (unless otherwise noted)


Variable sulfate concentration; rising temperatures and other increases

Regular geochemical surveys of Campi Flegrei's fumarolic gases, crater lakes, and thermal springs (figure 21) have led to the following conclusions. First, the temperature of Bocca Grande continued the increase noted in 1997. Second, the sulfate concentration increase noted in 1997 for crater lakes and thermal springs was a "transitory event" caused by the unstable underlying geothermal system. Third, there have been shifts in the f (phi) function, an empirical relationship related to fumarolic gas chemistry (Martini, 1996). The f function acted as an empirical indicator of ground upheaval during the events of 1982-85. Since 1996 the f function has steadily increased to levels not observed since 1982-85 (figure 21).

Figure (see Caption) Figure 21. Campi Flegrei hydrothermal data plotted for 1980-late 1999. Courtesy of Marino Martini.

Reference. Martini, M., 1996, Chemical character of the gaseous phase in different stages of volcanism: precursors and volcanic activity, in Scarpa and Tilling (eds.) Monitoring and mitigation of volcano hazards: Springer, Berlin, p. 199-219.

Geologic Background. Campi Flegrei is a 13-km-wide caldera that encompasses part of Naples and extends to the south beneath the Gulf of Pozzuoli. Episodes of significant uplift and subsidence within the dominantly trachytic caldera have occurred since Roman times. The earliest known eruptive products are dated 47,000 years BP. The caldera formed following two large explosive eruptions, the massive Campanian ignimbrite about 36,000 BP, and the over 40 km3 Neapolitan Yellow Tuff (NYT) about 15,000 BP. Following eruption of the NYT a large number of eruptions originated from widely scattered subaerial and submarine vents. Most activity occurred during three intervals: 15,000-9,500, 8,600-8,200, and 4,800-3,800 BP. The latest eruption were in 1158 CE at Solfatara and activity in 1538 CE that formed the Monte Nuovo cinder cone.

Information Contacts: Marino Martini, Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, 50125, Firenze, Italy.


Damavand (Iran) — October 1999 Citation iconCite this Report

Damavand

Iran

35.951°N, 52.109°E; summit elev. 5670 m

All times are local (unless otherwise noted)


Morphology and brief description of summit from visiting excursion

On 1 August 1999, a group from the Societe de Volcanologie Geneve ascended the ice- and rock-covered summit. On the way up the N flank they saw vertical coal deposits below 2,450 m elevation, reaching thicknesses of tens of meters. Above 4,000 m elevation huge blocks were seen that appeared to have traveled from ~1 km above. Just below the summit were large sulfur-bearing blocks that appear to be mixed with a clay- like material. Within 100 m of the N rim of the summit chunks of pure sulfur were observed. The circular summit crater was ~150 m in diameter. In the center of the crater lay a small frozen lake approximately 40 m across. From the N rim of the summit, an active fumarole could be seen to the south.

Geologic Background. The Damavand stratovolcano is located 70 km NE of Iran's capital city of Tehran and 70 km S of the Caspian Sea. A younger cone has been constructed during the past 600,000 years over an older edifice, remnants of which were previously interpreted as a caldera wall. Flank vents are rare, and activity at the dominantly trachyandesite volcano has been concentrated at the summit vent, which has produced a series of radial lava flows. Lava effusion has dominated, pyroclastic activity has been limited, and the only major explosive event produced a welded ignimbrite about 280,000 years ago. The youngest activity, from the summit vent, produced a series of lava flows that cover the W side of the volcano. The youngest dated lava flows were emplaced about 7,000 years ago. No recorded eruptions are known, but hot springs are located on the flanks, and fumaroles are found at the summit crater.

Information Contacts: D. Zurcher and R. Haubrichs, Societe de Volcanologie Geneve (SVG), C.P. 6423, CH-1211, Geneve 6, Switzerland (Bulletin de la SVG, October 1999, p. 6 (in French)).


Guagua Pichincha (Ecuador) — October 1999 Citation iconCite this Report

Guagua Pichincha

Ecuador

0.171°S, 78.598°W; summit elev. 4784 m

All times are local (unless otherwise noted)


A growing dome, high seismicity, and wind-assessment challenges

This report covers 20 October through 21 November 1999, an interval when the new, still-emerging dome exceeded half the height of the adjacent 1660 dome, and in addition extruded a 75-m-tall spine. Seismic records through 31 October illustrated that September and October had a striking abundance of both earthquakes and phreatic explosions (figures 18 and 19). In contrast to September and the first two-thirds of October (BGVN 24:09), during this interval explosions were comparatively rare (table 6).

Figure (see Caption) Figure 18. The number of monthly earthquakes at Guagua Pichincha during July 1998-October 1999. Earthquakes are reported in three categories (shown left-to-right for each month): medium-period (hybrid), long-period, and volcano-tectonic. For July 1998, registered events in these categories were 0, 8, and 45, respectively. Hybrid earthquakes generally dominated the record until September 1998 when the long-period earthquakes became most common. Hybrid earthquakes, typically found at less than 3 km depth below the caldera, are here defined as having noteworthy spectral energy at both 1.8-2 Hz and 3-6 Hz, with the higher frequency particularly conspicuous in the early arrival portion of the record. Volcano-tectonic earthquakes only appear for September and October 1999 at this scale. Courtesy of the Geophysical Institute.
Figure (see Caption) Figure 19. The number of monthly explosions at Guagua Pichincha, July 1998-October 1999. Courtesy of the Geophysical Institute.

Table 6. A summary of 20 October-21 November events at Guagua Pichincha as conveyed in the Geophysical Institute's daily reports. Unless noted otherwise, the stated plume and column heights (e.g. "1.5 km plume") refer to the distance from the plume's base to its top. Courtesy of the Geophysical Institute.

Date Explosions Estimated plume heights and other comments
20 Oct 1999 0 --
21 Oct 1999 0 An overflight took place and surficial evidence of dome building was noted
22 Oct 1999 0 Strong fumarolic activity seen and heard, steam rising to ~1.5-2 km
23 Oct 1999 0 2-km steam plume
24 Oct 1999 0 1.5-km steam plume
25 Oct 1999 0 1.6-km steam plume
26 Oct 1999 0 2.5-km steam plume; aerial observers found evidence of continued venting of tephra
27 Oct 1999 0 1.5-km steam plume
28 Oct 1999 0 Red tephra covering caldera; slight growth and plentiful fractures noted in dome area; COSPEC measurements failed to show important variations (values unreported)
29 Oct 1999 0 1.2-km high plumes bearing wind-blown ash; low fumarolic activity
30 Oct 1999 0 Ongoing dome growth; limited fumarolic activity
31 Oct 1999 0 Rockfalls in the dome area; limited fumarolic activity
01 Nov 1999 0 Plume to 1.3 km; some plumes appeared tinted blue or red
02 Nov 1999 0 Plume to under 1 km; an infrared camera indicated a source of high heat flux in the dome area.
03 Nov 1999 0 Steam plume to under 1 km; low fumarolic emission rates
04 Nov 1999 0 Reddish gray fumarolic plume to 1.2-1.3 km; rocks sliding off dome's carapace to W
05 Nov 1999 0 --
06 Nov 1999 0 Cloudy, but an observer heard noises attributed to avalanches
07 Nov 1999 0 New growth recognized on the active dome, which rose ~ 10 m above the middle of the 1660 dome.
08 Nov 1999 0 --
09 Nov 1999 0 Degassing vapor appeared gray and occasionally earth-toned in color as it rose ~ 800 m. The dome extrusion included a 75-m-tall spine.
10 Nov 1999 1 Small explosion; fumarolic plumes rose to ~1.5 km
11 Nov 1999 0 --
12 Nov 1999 -- Not posted
13 Nov 1999 -- The depression hosting the new dome had increased in diameter; materials detached from both the new dome and its spine.
14 Nov 1999 0 Low fumarolic activity
15 Nov 1999 0 Rapid dome growth continued; 2 km tall column incorporating dust from an intracrater landslide
16 Nov 1999 0 --
17 Nov 1999 16 Explosion signals. The most important explosion signals had reduced displacements of 13 and 26 cm2. The weather was cloudy, with abundant airborne ash; the official press release noted that during the afternoon a light gray ash column attained an altitude of 5 km, but the text stated the column only contained a minor ash component.
18 Nov 1999 1 This eruption took place at 2126 and had a reduced displacement of 18 cm2. The resulting plume rose to an altitude of 9 km.
19 Nov 1999 0 1.2-km-high fumarolic plume
20 Nov 1999 0 Cloudy
21 Nov 1999 0 Cloudy

Reports and observations of dome growth were sporadic, interrupted by bad weather and the difficulty of monitoring the intracrater area. On 21 October dome material extruded at a spot W of the 1660 dome. Mid-November reports repeatedly noted rapid dome growth, although this was occasionally offset by intervals with abundant mass-wasting. The daily report on 4 November noted that the cumulative energy from long-period earthquakes was larger than that seen prior to the 5 October eruption. Substantial, though not necessarily larger, outbursts occured after 21 November.

Data from the Geophysical Institute indicated that robust seismicity continued through much of November. There were more total earthquakes in November than in either September or October. The biggest differences occurred in long-period and medium-period (hybrid) earthquakes, both of which rose substantially in November and dominated the number of earthquakes registered in September-October (figure 1). Four November days had long-period earthquake peaks equivalent to or larger than the daily number seen in October. The number of hybrid earthquakes fell in the last week of October, but considerable numbers continued through about 10 November. Volcano-tectonic earthquakes peaked in October. Rockfalls also peaked in October but a second, broader peak occurred into November.

Winds aloft. The morphology of the volcano, its proximity to Quito, and deposits from previous eruptive episodes suggest airborne ash as a key hazard. To forecast when ash will fall in Quito requires knowing the local winds from the altitude of the volcano to the top of the ash column.

According to John Ewert, historical wind data were obtained from reports by the Civil Aviation Agency (Direccion De Aviacion Civil, DAC), which were summarized in Barberi and others (1992). Useful as background for planning purposes, these historical records are less relevant than actual wind velocity data at the time of the eruption. Daily wind directions are reported by NOAA, derived in part from automated routines that track cloud and water vapor drift on Geostationary Operational Environmental Satellite (GOES) images. Such data are fairly accurate for the troposphere, but at least one of the larger eruptions in early October penetrated through the troposphere and entered the stratosphere at ~11 km. But, obtaining stratospheric wind data has proven difficult.

Some relevant wind field observations can come from aviators in aircraft equipped with suitable navigation instruments. Accordingly, scientists suggested this to the Ecuadorian Civil Aviation agency, who requested that pilots in the area call in their GPS-derived cockpit wind measurements. Although this has been helpful for understanding the local tropospheric winds, it still left the higher altitudes winds uncharted.

On their website, the Geophysical Institute has posted wind data derived from atmospheric wind measurements by radiosondes ("weather balloons") launched from the critical region of interest and penetrating well into the stratosphere (to altitudes over ~30 km)-but these were unavailable in early October. At the Instituto's request, the U.S. Office of Federal Disaster Assistance provided funding for a U.S. Air Force meteorological team to travel to Ecuador to work with the Ecuadoran Meteorological Institute (INAMHI) and the Civil Aviation Agency to better define the local wind fields. The Air Force team repeatedly conducted the highly desirable radiosonde measurements. Ewert said the Air Force team returned to the U.S., so he was not sure how long such radiosondes probes would continue.

In early October, Ewert tried to obtain realistic models of plume drift to understand the dispersal of potential large ash columns at Pichincha. He did so using the Volcanic Ash Forecast Transport And Dispersion (VAFTAD) model that was developed by NOAA's Air Resources Laboratory (Heffter and Stunder, 1993) to support the Washington and Anchorage Volcanic Ash Advisory Centers (VAACs). Ewert gained access to the model using the NOAA web site. The site contains VAFTAD model output issued by NOAA in response to individual eruptions.

VAFTAD uses output from the NOAA global meteorological model. Grid dimensions vary with latitude; near the equator the horizontal grid is ~100 km to a side (farther towards the poles at 60 degrees latitude, ~190 km to a side). The concentration grid dimensions are set to half the size of the horizontal grid (i.e. ~50 km to a side near the equator). Given these dimensions, its not surprising that Ewert found VAFTAD only marginally effective for comprehension of ash dispersal in areas immediately adjacent Pichincha (and Tungurahua). What is needed is a more local-scale modeling capability for Pichincha based on an understanding of the local-scale 3-D meteorology. According to atmospheric modeler J. L. Heffter, serious modeling challenges in South America also include the effects of terrain, local air flow patterns, and a broad scarcity of meteorological data. In the absence of such models, Ewert concluded that the local radiosonde data was the best practical solution for gauging the velocity of winds aloft. Atmospheric modeler Barbara Stunder of NOAA also concluded that local radiosonde data extrapolated out a few hours may give a sufficient forecast of transport velocity.

On their Real-time Environmental Applications and Display sYstem (READY) website, NOAA displays regular VAFTAD forecasts for hypothetical eruptions for planning purposes. These include dispersal models for Pichincha, and 10 other recently active volcanoes (Augustine, Colima, Fuego, Kliuchevskoi, Pacaya, Pavlof, Popocatépetl, Shishaldin, Soufriere Hills, and Tungurahua). These models are run automatically once a day and the resulting plume forecasts appear on charts. In addition, from this same website, users can run the VAFTAD model for volcanic eruptions at any location.

As a historical note, during the Cook Inlet eruptions, NOAA's forecast wind field data were accessed using a personal computer to print out projected trajectories. In the case of the 24 February 1990 eruption of Redoubt, which reached ~8.5 km altitude, the actual ground deposit was surprisingly close to the relevant projected trajectories (Murray and others, 1994). Currently, the Canadian Volcanic Ash Advisory Center (VAAC) provides a web-accessible, real-time trajectory modeling routine for selected volcanoes on North America and elsewhere.

References. Barberi, F., Ghigliotti, M., Macedonio, G., Orellana H., Pareschi M.T., and Rosi, M., 1992, Volcanic hazard assessment of Guagua Pichincha (Ecuador) based on past behavior and numerical models: Journal of Volcanology and Geothermal Research, v. 49, no. 1-2, p. 53-68.

Heffter, J.L., and Stunder, B.J.B, 1993, Volcanic Ash Forecast Transport And Dispersion (VAFTAD) model: Weather Forecasting, v. 8, p. 534-541.

Murray, T.L., Bauer, C.I., and Paskievitch, J.F., 1994, Using a personal computer to obtain predicted plume trajectories during the 1989-90 eruption of Redoubt Volcano, Alaska: in USGS Bulletin 2047-Volcanic Ash and Aviation Safety, p. 253-256.

Geologic Background. Guagua Pichincha and the older Pleistocene Rucu Pichincha stratovolcanoes form a broad volcanic massif that rises immediately W of Ecuador's capital city, Quito. A lava dome grew at the head of a 6-km-wide scarp formed during a late-Pleistocene slope failure ~50,000 years ago. Subsequent late-Pleistocene and Holocene eruptions from the central vent consisted of explosive activity with pyroclastic flows accompanied by periodic growth and destruction of the lava dome. Many minor eruptions have been recorded since the mid-1500's; the largest took place in 1660, when ash fell over a 1,000 km radius and accumulated to 30 cm depth in Quito. Pyroclastic flows and surges also occurred, primarily to then W, and affected agricultural activity.

Information Contacts: Geophysical Institute (Instituto Geofísico), Escuela Politécnica Nacional, Apartado 17-01-2759, Quito, Ecuador; John Ewert, Volcano Disaster Assistance Team (VDAP), United States Geologic Survey (USGS), Cascades Volcano Observatory, 5400 MacArthur Blvd., Vancouver, WA 98661 USA (URL: https://volcanoes.usgs.gov/observatories/cvo/); Barbara Stunder, NOAA Air Resources Laboratory (ARL), 3rd Floor, 1315 East-West Highway, Silver Spring, MD 20910 USA (URL: http://www.arl.noaa.gov/); NOAA/NESDIS Operational Significant Event Imagery Support Team, E/SP22, 5200 Auth Road, Camp Springs, MD 20746-4304 USA (URL: https://www.nnvl.noaa.gov/); Montreal Volcanic Ash Advisory Centre, Operations Branch, Canadian Meteorological Centre, 2121 Voie de Service Nord, Route Transcanadienne, Dorval, Québec H9P 1J3, Canada (URL: http://www.cmc.ec.gc.ca/cmc/cmoe/vaac/A-vaac.html).


Kolbeinsey Ridge (Iceland) — October 1999 Citation iconCite this Report

Kolbeinsey Ridge

Iceland

66.67°N, 18.5°W; summit elev. 5 m

All times are local (unless otherwise noted)


Submarine eruption or dike intrusion south of the Spar Fracture Zone

A submarine eruption or dike intrusion on 30 August 1999 was identified by seismic events from the Icelandic Seismological Network (SIL) at the Vedurstofa Islands. The swarm was centered ~180 km N of Grimsey and 100 km N of Kolbeinsey Island near 68.15°N, 17.75°W along the Southern Kolbeinsey Ridge south of the Spar Fracture Zone (figures 1 and 2). Although the swarm started at 0456 (UTC), most of the 143 earthquakes registered occurred between 0830 and 1100, with events continuing until after 2300 (figure 3). Seismic activity on the southern segment of Kolbeinsey Ridge had been registered since 1 July 1999.

Figure (see Caption) Figure 1. Bathymetric relief map showing Iceland, the Kolbeinsey Ridge, and the earthquake swarm of 30 August 1999. Courtesy of the Icelandic Meteorological Office.
Figure (see Caption) Figure 2. Bathymetric map showing the 30 August 1999 earthquake swarm along the Southern Kolbeinsey Ridge south of the Spar Fracture Zone. Courtesy of the Icelandic Meteorological Office.
Figure (see Caption) Figure 3. Earthquakes from the Kolbeinsey Ridge swarm on 30 August 1999 plotted by time and magnitude. Courtesy of the Icelandic Meteorological Office.

Kolbeinsey Ridge is divided from Iceland by an oblique running transform fault, the Tjörnes Fracture Zone (TFZ). It is a slow-spreading ridge with an estimated asymmetric spreading of 10 mm/year. The ridge crest is nearly bare of sediments, although the bathymetry is very shallow. Kolbeinsey Ridge is cut by two major transform faults, the Spar Fracture Zone and the 70.8° Fracture Zone, and is thus divided into three segments, the Southern Kolbeinsey Ridge (SKR), the Northern Kolbeinsey Ridge (NKR), and the Central Kolbeinsey Ridge (CKR). The most active part of the ridge is the CKR north of the Spar Fracture Zone. Individual submarine volcanoes have not been named so far because the SIL registers events in detail only up to 300 km N of the Tjörnes Peninsula, covering just the southernmost segment of Kolbeinsey Ridge. Seismic events cluster along three lineaments in the region where the Tjörnes Fracture Zone cuts Kolbeinsey Ridge: the Grimsey lineament (east of Grimsey and N of the actual TFZ), the Husavik-Flatey fault (the actual TFZ), and the Dalvik lineament (cutting the Eyrarfjördur in half subparallel to the actual TFZ). This area is known for its hydrothermal fields made of anhydrite chimneys 200-400 m beneath sea level, which are detected along the seismic lineaments.

A submarine eruption was reported in 1372 on the Kolbeinsey Ridge NW of Grimsey Island at about 66.67°N, but the location is uncertain. Other reports of submarine eruptions N of Iceland have an even more uncertain location (1755) or have been discredited (1783 and 1838).

Further References. Kodaira, S., Mjelde, R., Gunnarsson, K., Shiobara, I., and Shimamura, H., 1997, Crustal structure of the Kolbeinsey Ridge, North Atlantic, obtained by use of ocean bottom, seismographs: JGR, v. 102, B2.

Rögnvaldsson, S.T., Gudmundsson, A., and Slunga, R., 1998, Seismotectonic analysis of the Tjörnes Fracture Zone, an active transform fault in north Iceland: JGR, v. 103, B12.

Geologic Background. A submarine eruption was reported in 1372 CE near the Kolbeinsey Ridge NW of Grimsey Island. Kolbeinsey Island, the only subaerial expression of this portion of the Mid-Atlantic Ridge, is a small, rapidly eroding island that formed during the late Pleistocene or Holocene. Dredged glass shards indicate submarine eruptive activity during the late-Pleistocene until at least 11,800 radiocarbon years ago. The island was 700 m long in 1616 CE, but had shrunk to 42 m long and 5 m high by 1985. The Kolbeinsey Hydrothermal Field lies south of the island. Thorarinsson (1965) roughly plotted the location of the 1372 eruption at about 66°40'N. Reidel et al. (2003) note that the location is uncertain, but could lie between the Kolbeinsey Ridge and Hóll Seamount. Other reports of submarine eruptions north of Iceland have an even more uncertain location (1755) or have been discredited (1783 and 1838).

Information Contacts: Carsten Riedel, Christian-Albrechts-Universität, Kiel, Germany (URL: http://www.ifg.uni-kiel.de/); Icelandic Meteorological Office, Bustadavegur 9, 150 Reykjavík, Iceland (URL: http://www.vedur.is/).


Langila (Papua New Guinea) — October 1999 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Some strong ash emissions in September-October

No noise or night glow was reported from any vent during August and activity was very low in September and October. Throughout this period varying amounts of white vapor were observed from Craters 2 and 3. A blue component was observed in the vapors emitted from Crater 2 on the mornings of 4 and 5 August, whereas light to moderate ash emissions occurred on 6 and 7 August. On the morning of the 10th, ash was forcibly ejected 500-1,000 m above the crater rim. Only white vapor was emitted until the end of the month except on 25, 29, and 31 August when a light ash component was reported. On 21 and 30 September forceful emissions of thick brown ash were observed rising ~2 km above the summit from Crater 2. Such occasional forceful emissions continued into the first few days of October. The ash clouds rose 500-1,000 m above the summit and were later blown N. After that the emissions reduced to thin to thick white vapor.

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower E flank of the extinct Talawe volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: Ima Itikarai, Kila Mulina, and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Manam (Papua New Guinea) — October 1999 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Inflationary trend continues; seismic peak in mid-August

Throughout August-October, both Main and Southern Crater emitted varying amounts of white vapor. No noise or night glow was reported in either month. Prior to 13 August, a gray component to the plume was occasionally observed at Main Crater. The summit area was clear during 1-21 September, but was cloud-covered through the end of the month and sporadically during October.

Daily seismicity was at its lowest level in late July, but seismic amplitudes built up slightly until mid-August. Activity decreased subsequently, except one individual peak on 13 August with the highest daily energy level since November 1998. Seismic activity was stable at a low level in September and October.

The seismic peak on 13 August may have been related to an upward tilt toward the summit that built up until 10 August, at which stage it reached a level that has commonly led to increased eruptive activity. However, no significant activity occurred and a gradual down-tilting took place throughout the remainder of August. In September the water-tube tiltmeter 4 km SW of the summit registered ~5 µrad of inflation. The overall inflationary trend continued, with a total of ~20 µrad of inflation recorded between July and the end of October.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical basaltic-andesitic stratovolcano to its lower flanks. These valleys channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Ima Itikarai, Kila Mulina, and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Moyorodake [Medvezhia] (Japan - administered by Russia) — October 1999 Citation iconCite this Report

Moyorodake [Medvezhia]

Japan - administered by Russia

45.389°N, 148.838°E; summit elev. 1124 m

All times are local (unless otherwise noted)


Small phreatic eruption from the Kudriavy summit forms a new crater

Changes in activity at the Kudriavy cone (figure 2) were detected in mid-September 1999, preceding an eruption on 7 October. Since 1989 the temperatures of sediments in the dry lakes within the crater (lakes temporarily exist after snow melting and strong rains) at a depth of 0.75 m have consistently fallen in the range of 48-82°C, with fluctuations of 3-5°C. In contrast, September 1999 measurements at the control points in the Hot Lake area showed increasing temperatures of 60-102°C. [These temperature measurements have been made 1-3 times each year.]

Figure (see Caption) Figure 2. Photograph of fumarolic plumes rising from the crater of the Kudriavy cone at Medvezhia, September-October 1999. Courtesy of G.S. Steinberg.

The weather in August, September, and October was unusually dry for the region, with rain only during 24-25 September and 2-3 October. A temperature survey of two lakes was made in September. Usually, lakes exist 1-2 days after rains, but the water in Hot Lake still covered more than half the area on 4 October. Temperatures in the dry part of the lake had increased by 14-22°C. The lake water close to the hot dome was boiling and seething due to gas emissions. [The hot dome is 150-170 m in diameter, rising 60-70 m above the bottom of Hot Lake to the W and 30-40 m above the bottom of the dry lake to the S.] On 5 October the diameter of the lake was 15 m. That day two channels were excavated to allow the water to drain so that sediment temperatures could be measured. The temperature increase in this newly drained area was more than 30°C. Fumarole gas compositions during the second part of September showed increased hydrogen, oxygen, and fluorine. Sulfur ignition was seen in some locations. The number of earthquakes also increased, and although the one-channel seismic station deployed was insufficient to determine any hypocenters, the elevated seismicity was obvious. District and province authorities were warned three days before the start of the 7 October eruption that Kudriavy was unstable and could erupt soon. [On the evening of 4 October the Governor of Sakhalin and the Mayor of Kurilsk were notified that activity at Kudriavy had rapidly increased and that an eruption was expected to begin during the week of 8-15 October, with possible stronger activity later in the month.]

From the base camp, 3.5 km W from the volcano, black and gray clouds of gas and ash were observed rising above the usual fumarolic plumes at 1735 on 7 October and then extending ~10 km NW. Ejections of gas and ash occurred at intervals of 1-2 minutes. Because of the strong winds, maximum altitude of ejections was 1,100 m. The upper camp was at 940 m elevation, 30-40 m from the crater edge and 300 m from Hot Lake (figure 3). Because of strong winds, bad visibility, and the low-intensity start of the eruption, volcanic tremor and gas-and-ash ejections were not noticed in the upper camp until 10 minutes after observers in the base camp saw the plume. Night observations showed that intense ejections stopped at 0200 on 8 October. Observations through the clouds of the N part of the crater revealed "slight reddish lights - reflected light of the hot rocks and blue lights - light of the burning sulfur" that marked the edges of a crater.

Figure (see Caption) Figure 3. Aerial photograph of the N part of the Kudriavy crater at Medvezhia showing the locations of the upper camp and the new explosion crater W of the hot lava dome during 7-8 October 1999. North is to the left. Courtesy of G.S. Steinberg.

No juvenile ash was identified, so the eruption was determined to be phreatic. This eruption was similar to a geyser eruption: periodic vertical ejection of the gas, ash, and steam. Ejecta didn't fall more than 30-40 m from the new crater. The surface of Hot Lake was covered by rocks with diameters of 20-30 cm, and ashfall deposits were concentrated to the NW. The volume of erupted material was nearly 40,000-45,000 m3. Areas with rhenium mineralization (see BGVN 20:10) located on the dome were not involved in the eruption or covered by eruption products. The first phase of the eruption was over on 13 October.

The eruption created a new crater in the Hot Lake area and removed part of the dome (figure 4). The crater was elliptical with dimensions of 30 x 40 m and a depth 35-40 m from the bottom of the lake and 80-110 m from the flat part of the dome (figure 5). The walls of the crater were vertical. In the lower part of the S crater wall was a 6 x 8 m cave of incandescent rocks. Based on the light intensity, the temperature was estimated to be higher than 1,000-1,100°C. Hot gas rose from this area and condensed 40-60 m above the edge of the crater. Small fiery areas and fragments with burning sulfur were seen on the S, W, and N walls. [Minor explosions continued from the cave until 13 October. Activity then declined, consisting of gas emissions with some small rock fragments that didn't reach the crater rim. No significant changes were noted through 2 November, when observations ended.]

Figure (see Caption) Figure 4. Photograph of the hot dome and dry lake area in the N part of the Kudriavy crater at Medvezhia prior to the 7-8 October 1999 eruption. Courtesy of G.S. Steinberg.
Figure (see Caption) Figure 5. Photograph of the 7-8 October 1999 crater adjacent to the hot dome in the N part of the Kudriavy crater at Medvezhia, October 1999. Courtesy of G.S. Steinberg.

Geologic Background. The Moyorodake volcanic complex (also known as Medvezhia) occupies the NE end of Iturup (Etorofu) Island. Two overlapping calderas, 14 x 18 and 10 x 12 km in diameter, were formed during the Pleistocene. The caldera floor contains several lava domes, cinder cones and associated lava fields, and a small lake. Four small closely spaced stratovolcanoes were constructed along an E-W line on the eastern side of the complex. The easternmost and highest, Medvezhii, lies outside the western caldera, along the Pacific coast. Srednii, Tukap, and Kudriavy (Moyorodake) volcanoes lie immediately to the west. Historically active Moyorodake is younger than 2000 years; it and Tukap remain fumarolically active. The westernmost of the post-caldera cones, Menshoi Brat, is a large lava dome with flank scoria cones, one of which has produced a series of young lava flows up to 4.5 km long that reached Slavnoe Lake. Eruptions have been documented since the 18th century, although lava flows from cinder cones on the flanks of Menshoi Brat were also probably erupted within the past few centuries.

Information Contacts: Genrikh S. Steinberg, Institute of Volcanology and Geodynamics, Russian Academy of Natural Science, Box 18, Yuzhno-Sakhalinsk 693008, Russia.


Rabaul (Papua New Guinea) — October 1999 Citation iconCite this Report

Rabaul

Papua New Guinea

4.2459°S, 152.1937°E; summit elev. 688 m

All times are local (unless otherwise noted)


Ash eruptions continue; new vent generates ash emissions for eight days

During all of August and until 17 September the mild activity that has occurred at Tavurvur cone since November 1998 continued, consisting only of weak, pale gray ash emissions. These emissions, usually several hours apart, had slightly increased frequency and ash/vapor volume for two periods around 11 August and at the very end of that month. During the reporting interval the volume of ash was small and the ash plumes rose only a few hundred meters above the summit. Three mild explosions occurred on 5, 13, and 15 September and sent dark gray ash clouds to ~1,000 m before they were blown to the NW.

However, between 0915 and 1015 on 17 September, a vent that presumably last erupted in 1941 opened. For about eight consecutive days the new vent produced continuous emissions of dark gray ash clouds, sometimes in puffs. Associated with the ash emissions was the strong odor of sulfur gas. Night observations on 17-18 September showed weak red glow at the mouth of the vent, seemingly associated with the puffs, and weak deep roaring noises were heard. Subsequent to the eight days, the emissions changed to pale gray in color and occasionally to white vapor for short intervals. Three mild explosions occurred on 20, 26, and 28 September; the resulting ash columns rose ~1,500 m and caused significant ashfall on Rabaul Town.

Fluctuating volumes of continuous emissions took place in October from the old 1941 vent that re-opened on 17 September 1999. The emissions fluctuated from very thin white to thick white-gray vapor, and occasionally dark gray ash clouds. The ash clouds rose several hundred meters above the summit and were later blown to the N, NW, and W between 1 and 17 October by variable winds, and primarily to the S and SE after 18 October. Two moderate dark gray ash clouds on 28 and 31 October were released forcefully and rose about 1,500 m above the summit before they were blown NW, resulting in light ashfalls.

The vent that produced the lava flows in 1996 and 1997 (South Vent) showed declining vapor/ash emissions during October. Early in October the vent produced about 4-5 distinct daily ash emissions, but almost none during the last 2-3 weeks. Three mild explosions of dark gray ash columns on 7, 11, and 18 October rose ~1,000 m above the summit before they were blown to the N and NW, causing fine ashfalls. The odor of sulfur was at a very reduced level compared to that during the second half of September, and by 16 October was almost unnoticeable.

The number of low-frequency earthquakes increased to 235 in September over the 165 in August, exceeding the numbers in May (159), June (35), and July (89). A total of 40 high-frequency events were recorded in August, the highest for any month this year, whereas only four occurred in September, and only two of which had epicenters NE of the caldera. Twelve explosions were detected seismically in August compared with three each in June and July. There were a total of 617 low-frequency events, a further increase, in October. All these events originated from the summit of Tavurvur. The bigger events were associated with summit emissions, as observed in the past. Only four high-frequency events were recorded. None of them were big enough to be located, but from the sequence of arrivals from stations that recorded them, they appeared to originate from the NE, outside of the caldera.

Measured deformation of the ground surface within the caldera remained slight as it has since February, although ~5 µrad of tilt accumulated at the water-tube tiltmeter at Sulphur Creek, before the two periods of increased activity in August. Overall, ground deformation remained low with indications of very low levels of long-term caldera resurgence.

Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the asymmetrical shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1,400 years ago. An earlier caldera-forming eruption about 7,100 years ago is thought to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the N and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and W caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Information Contacts: Ima Itikarai, Kila Mulina, and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Taftan (Iran) — October 1999 Citation iconCite this Report

Taftan

Iran

28.6°N, 61.13°E; summit elev. 3940 m

All times are local (unless otherwise noted)


Visitors note mineral springs and fumaroles

In response to reported fumarolic activity near the summit, a group from the Societe de Volcanologie Geneve ascended the summit on 27 July 1999. The activity focused at a solfatara 1.5 x 5 m in size with several openings emitting SO2-rich vapor plumes. The surrounding area resembled a snowcap despite consisting entirely of sulfur and clay.

During the ascent clear water was seen at 3,220 m elevation almost 800 m below the summit. At about the 3,240 m elevation, a spring was discovered pouring from the flank of the volcano. The water in the spring reached a temperature of nearly 30°C and a pH of 1. The spring water created a white-yellowish deposit which darkened as it dried. The dried deposits were colored sharp yellow to dark orange. Despite their color, these deposits were not formed from sulfur, but rather from iron chlorides. When redissolved back in water, a colorless solution resulted.

Geologic Background. Taftan is a strongly eroded andesitic stratovolcano with two prominent summits. The volcano was constructed along the Makran-Chagai Arc in SE Iran. The higher SE summit cone has been the source of lava flows, as well as of highly active, sulfur-encrusted fumaroles. In January 1902 the volcano was reported to be smoking heavily for several days, with occasional strong night-time glow. A lava flow was reported in 1993, but may have been a mistaken observation of a molten sulfur flow. Despite these reports there is no clear evidence for Holocene activity. The youngest date obtained by Pang et al. (2014), using U-Pb on a zircon, was about 800 ka. Biabangard and Moradian (2008) obtained K-Ar dates around 700 ka.

Information Contacts: D. Zurcher and R. Haubrichs, Societe de Volcanologie Geneve (SVG), C.P. 6423, CH-1211, Geneve 6, Switzerland (Bulletin de la SVG, October 1999, p. 6 (in French)).


Tanga (Papua New Guinea) — October 1999 Citation iconCite this Report

Tanga

Papua New Guinea

3.5°S, 153.22°E; summit elev. 472 m

All times are local (unless otherwise noted)


Possible uplift or growth of Lif Island over two decades

During 1999 concerned local residents reported two decades of 'unusual growth' of Lif Island, the western island on the rim of the partially submerged ~5-km-diameter caldera of Tanga volcano. An inspection by scientists from the Rabaul Volcano Observatory showed no obvious signs of uplift, but apical spits of raised reef estimated as being up to 1 m above sea level in Wallace and others (1983), were estimated to be more than 2 m high when visited (although it is not certain the same features are being described). Numerous coastal warm springs are present on all three islands marking the submerged caldera rim. A GPS network has been installed to monitor the caldera.

Elderly residents also graphically described the sudden appearance of two islands in the middle of the caldera about 60 years ago (pre-World War II), which they claimed have subsequently grown in size. These islands consist of Bitlik, 300 m in diameter and 35 m high, and Bitbok, 600 m long and 90 m high; both are made up of well-jointed Q-trachyte (Johnson and others, 1976) with dates of 1.08-1.14 m.y. (Wallace and others, 1983). The initial uplift was said to have been accompanied by "big white smoke" and "a big wave people had to run from." Although a British Admiralty Chart of 1886 (no. 2766) shows that the two islands were then in existence and of a similar size, these stories, of the local oral history, may relate to an earlier event. The RVO staff extends their thanks to Deborah Hall (The British Library, Map Library, London) and Brian D. Thynne (National Maritime Museum, London) for their assistance.

References. Johnson, R.W., Wallace, D.A., and Ellis, D.J., 1976, Feldspathoid-bearing potassic rocks and associated types from volcanic islands off the coast of New Ireland, Papua New Guinea: a preliminary account of geology and petrology, in Johnson, R.W. (editor): Volcanism in Australasia, 297-316.

Licence, P.S., Terrill, J.E., and Fergusson, L.J., 1987, Epithermal gold mineralisation, Ambitle Island, Papua New Guinea: Proceedings of the Conference, Pacific Rim Congress 87.

Wallace, D.A., Johnson, R.W., Chappell, B.W., Arculus, R.J., Perfit, M.R., and Crick, I.H., 1983, Cainozoic volcanism of the Tabar, Lihir, Tanga, and Feni Islands, Papua New Guinea: geology, whole-rock analysis, and rock-forming mineral compositions: B.M.R., Aust. Report 243.

Geologic Background. Malendok, Lif and Tefa islands are remnants of the summit of a mostly submerged stratovolcano. In the center of the caldera, the small islands of Bitlik and Bitbok mark remnants of early Pleistocene post-caldera lava domes marking the volcano's latest activity. A small hot spring on Malendok Islands marks the only current thermal activity.

Information Contacts: Ima Itikarai and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Tungurahua (Ecuador) — October 1999 Citation iconCite this Report

Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


Crisis continues with few earthquakes, abundant tremor, high SO2, and explosions

This report briefly summarizes Tungurahua's activity during the period 6-29 October 1999. During this period there was increasing seismicity, particularly tremor, which began in September. Relatively continuous gas emissions also prevailed, with most plumes rising to altitudes of 1-5 km above the summit and extending in various directions as far as 16 km from the volcano.

On 15 October, electronic distance measurements and inclinometer data on the cone's W side indicated an anomalous deformation on the W-NW flanks. That evening a strong collapse of incandescent rocks took place over the higher side of the volcano. A magmatic body was soon seen or inferred very close to the surface below the area of fallen rock. Due to the rapid change in the cone, the Geophysical Institute recommended a change of status from yellow to orange for the most vulnerable zones on the W and SW sides of the volcano. This change was implemented at 0900 on 16 October and prevailed throughout the remainder of the reporting period. That same day pilots were warned of a plume to ~5 km extending to 16 km towards the W. Light ash fell. A flight the next day, 17 October, disclosed an enlarged crater that had expanded by unspecified amounts on its E and SE sides.

On 17 October light ash fell from a plume reaching 3-5 km high. In the afternoon observers saw incandescent rocks on volcano's W side. On 18-24 October plumes were seen by pilots rising to 7-8 km in altitude. Along the highway between the cities of Penipe and Baños recent deposits of two mudflows were found in the Chontapamba and Rea valleys. On 24 October more incandescent rock was seen on the volcano's N side.

Tremor remained at a constantly high level throughout the reporting period but other kinds of seismicity remained relatively low. The most frequently occurring earthquakes, those of long period, typically occurred fewer than 20 times a day. Volcano-tectonic earthquakes and hybrid earthquakes took place less than half as often.

In addition, gas plumes appeared to rise to higher altitudes beginning in mid-October, and incandescent rocks reached distances of 1 km below the volcano summit. Tremor amplitudes grew, saturating seismic stations near the crater and thwarting the ability to recognize local events. This tremor accompanied numerous explosions, 45 being recorded during the last few days of the period.

SO2 fluxes were estimated by either daily COSPEC readings, weather permitting, or sulfuric anhydride measurements, or both. The indicated values ranged from as low as 3,100 to as much as 10,800 tons/day with wide variability (table 1). These high values were taken as indicating elevated magmatic gas, in accord with the observed emissions.

Table 1. Daily values of SO2 flux (metric tons/day) at Tungurahua, 6-27 October 1999. These estimates were based on COSPEC or sulfur anhydrite measurement or both. Plumes on additional days were not measured quantitatively. Courtesy of the Geophysical Institute.

Date SO2 flux (metric tons/day)
06 Oct 1999 5,600
07 Oct 1999 5,600; 6,400
08 Oct 1999 5,700; 9,300
09 Oct 1999 8,900; 3,300
10 Oct 1999 9,700; 10,800; 5,300; 3,100
14 Oct 1999 4,786
15 Oct 1999 5,000
23 Oct 1999 7,800
27 Oct 1999 7,580

Geologic Background. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II collapsed about 3,000 years ago and produced a large debris-avalanche deposit to the west. The modern glacier-capped stratovolcano (Tungurahua III) was constructed within the landslide scarp. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Information Contacts: Geophysical Institute (Instituto Geofísico), Escuela Politécnica Nacional, Apartado 17-01-2759, Quito, Ecuador.


Ulawun (Papua New Guinea) — October 1999 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Explosions in mid-October-the first in 6.5 years

During the past 6.5 years, through September 1999, summit activity at Ulawun consisted of variable amounts of emissions that ranged from very thin white vapor to moderate volumes of thick white vapor. Seismic activity was generally low. Low frequency earthquakes were recorded. Their occurrence was very variable and the amplitudes of the events fluctuated, but remained near background levels. In June 1998 a number of high-frequency earthquakes began occurring, but have been very sporadic since.

After this period of very low activity, Ulawun produced moderate explosions at 2015 and 2049 (UT) on 19 October. The first explosion produced a thick dark ash column, visible in the moonlight, that rose several hundred meters above the summit before it was blown to the N and NW, causing ashfall on the flanks. The second explosion was smaller but also produced a dark ash column. People on Lolobau Island, ~18 km NW of Ulawun, observed very weak, dull glow on the summit. The partially working seismograph picked up tremor activity during the time of the explosions. The following morning, 20 October, summit activity consisted of thick volumes of white and occasionally gray vapor. This tapered off to moderate volumes of white vapor by the end of the month. Seismic activity also decreased to normal background levels.

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

Information Contacts: Ima Itikarai, Kila Mulina, and Steve Saunders, RVO.


Vesuvius (Italy) — October 1999 Citation iconCite this Report

Vesuvius

Italy

40.821°N, 14.426°E; summit elev. 1281 m

All times are local (unless otherwise noted)


9 October seismic swarm includes an M ~ 3.5 event, the largest in 50 years

At the beginning of October a small cluster of seismic events was recorded by the permanent seismic network of the Osservatorio Vesuviano (figure 4). The most energetic event of the sequence occurred at 0741 on 9 October, with a duration magnitude (MD) of 3.6 and a Wood Anderson equivalent magnitude (MWA) of 3.4. This event was located in the crater area at a depth of about 3 km below sea level, with a preliminary stress-drop of 164 bar and a preliminary moment magnitude of 3.3. According to its MD value, this event was the most energetic of the last 50 years. Its fault plane solution showed a strike slip mechanism. All the events in this sequence were located below the crater area within the first 6 km of the upper crust, typical of seismicity at Vesuvius in recent years.

Figure (see Caption) Figure 4. Seismic activity at Vesuvius during 1 January-17 November 1999, showing the monthly number of events (histogram) and strain release (line). Courtesy of the Osservatorio Vesuviano.

During the swarm no changes were observed in the temperature or the composition of the fumaroles, in the CO2 flux from soil, or in ground deformation. Both the temperature and the level of the water-table sampled around the volcano appeared unchanged. As of mid-November seismicity seems to have returned to normal low background levels (both in terms of energy and in number of events) that have characterized Vesuvius for several years.

Geologic Background. One of the world's most noted volcanoes, Vesuvius (Vesuvio) forms a dramatic backdrop to the Bay of Naples. The active cone was constructed within a large caldera of the older Monte Somma edifice, thought to have formed incrementally beginning about 17,000 years ago. The Monte Somma caldera wall has channeled lava flows and pyroclastic flows primarily to the south and west. Eight major explosive eruptions have taken place in the last 17,000 years, often accompanied by large pyroclastic flows and surges, such as during the 79 CE Pompeii eruption. Intermittent eruptions since 79 CE were followed by a period of frequent long-term explosive and effusive eruptions between 1631 and 1944. The large 1631 eruption produced pyroclastic flows that reached as far as the coast and caused great destruction. Many towns are located on the flanks, and several million people live within areas that could be affected by eruptions.

Information Contacts: Lucia Civetta, Edoardo Del Pezzo, Francesca Bianco, Giuseppe Vilardo, and Mario Castellano, Osservatorio Vesuviano, Via Diocleziano 328, 80124 Napoli, Italy.


Vulcano (Italy) — October 1999 Citation iconCite this Report

Vulcano

Italy

38.404°N, 14.962°E; summit elev. 500 m

All times are local (unless otherwise noted)


H2S, SO2, HF, HCl, and other gases tending to increase during 1998-99

Periodic inspections of Vulcano have indicated that the total output from the fumarolic field at the crater "La Fossa" started to decrease in 1995. However, an analysis of the chemical compositions of the gaseous phases conducted as a part of an overall evaluation of the volcanic system provides important volcanological details. Different trends observed between the fumaroles located on the rim and those inside the crater (see BGVN 22:11) indicate that the Fossa cone is affected by deformation, possibly the result of increased vapor pressure at depth. The chemical data from samples collected at the same locations during 1998 and 1999 (table 6) indicate similar trends of increasing magmatic gases. This could imply widespread opening of the system, which could affect the stability of the edifice.

Table 6. Chemical data measured at Vulcano, 1998-99. Courtesy of Marino Martini.

Component Crater Rim 1997 Crater Rim 1998 Crater Rim 1999 Inside Crater 1997 Inside Crater 1998 Inside Crater 1999
Temperature 328°C 320°C 303°C 426°C 281°C 379°C
H2O (vol) 88.86 90.77 93.66 85.38 86.69 91.65
CO2 (dry) 92.37 90.57 86.91 97.13 96.54 91.95
H2S 3.10 3.41 6.54 0.40 0.26 1.25
SO2 2.11 2.30 2.78 0.99 1.55 3.90
HCl 1.26 1.47 1.77 0.78 0.43 0.85
HF 0.46 0.42 0.66 0.03 0.08 0.13
H2 0.12 0.18 0.22 0.05 0.18 0.08
CO 0.0005 0.0006 0.0002 0.0024 0.0114 0.0100

In addition to the data reported in table 6, temperature measurements taken along the N rim of Fossa crater some time during the period 2-16 July 1999 were reported by Claude Grandpey. The temperature in July was 340°C compared to ~410°C the previous April. Grandpey also reported stable temperatures (i.e., 95-100°C) at the fumaroles on the isthmus between Vulcano and Vulcanello.

Vulcano is located at the southern boundary of the Aeolian Islands, about 25 km from northern Sicily. It last erupted in 1888-90 when numerous meter-sized bombs and blocks fell in the area now occupied by the village of Vulcano Porto, which hosts thousands of tourists daily during the summer season. Vulcanello, the youngest part of Vulcano Island, began to form only ~2,100 years ago as an isolated island that later became connected with the main island. The latest activity at Vulcanello occurred in the 16th century when lava flows, now covered by large hotel complexes, were extruded.

Geologic Background. The word volcano is derived from Vulcano stratovolcano in Italy's Aeolian Islands. Vulcano was constructed during six stages over the past 136,000 years. Two overlapping calderas, the 2.5-km-wide Caldera del Piano on the SE and the 4-km-wide Caldera della Fossa on the NW, were formed at about 100,000 and 24,000-15,000 years ago, respectively, and volcanism has migrated north over time. La Fossa cone, active throughout the Holocene and the location of most historical eruptions, occupies the 3-km-wide Caldera della Fossa at the NW end of the elongated 3 x 7 km island. The Vulcanello lava platform is a low, roughly circular peninsula on the northern tip of Vulcano that was formed as an island beginning more than 2,000 years ago and was connected to the main island in about 1550 CE. Vulcanello is capped by three pyroclastic cones and was active intermittently until the 16th century. Explosive activity took place at the Fossa cone from 1898 to 1900.

Information Contacts: Marino Martini, Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, 50125, Firenze, Italy; Claude Grandpey, L'Association Volcanologique Europénne (LAVE), 7 rue de la Guadelopue, 75018 Paris, France.

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