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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 23, Number 02 (February 1998)

Managing Editor: Richard Wunderman

Aira (Japan)

Several explosions during January-February

Axial Seamount (Undersea Features)

Hydrothermal plumes detected on research cruise suggest lava extrusion

Bezymianny (Russia)

Fumarolic plumes present on most days

Cameroon (Cameroon)

1997 seismicity remains low with one earthquake swarm

Fournaise, Piton de la (France)

First eruption in over 5 years begins 9 March

Heard (Australia)

No evidence of recent activity in March

Huila, Nevado del (Colombia)

Significant increase in seismicity in December 1997

Karymsky (Russia)

Ongoing gas-and-ash explosions

Kilauea (United States)

Steady, low activity during February

Klyuchevskoy (Russia)

Earthquakes, tremor, and gas-and-steam plumes throughout February

Langila (Papua New Guinea)

Intermittent eruptive activity at Crater 2

Manam (Papua New Guinea)

Low-level vapor emission and nighttime summit-crater glow in February

McDonald Islands (Australia)

The eruption of 1996-97 and its inferred lavas and tephra

Popocatepetl (Mexico)

Cyclical dome extrusions that by late 1997 filled one-third of crater capacity

Rabaul (Papua New Guinea)

January activity presages February eruption

Sheveluch (Russia)

Frequent gas-and-steam plumes

Soufriere Hills (United Kingdom)

Dome growth continues; discussion of the 26 December dome collapse



Aira (Japan) — February 1998 Citation iconCite this Report

Aira

Japan

31.5772°N, 130.6589°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Several explosions during January-February

Sakura-jima produced frequent explosions in December 1997-January 1998 (BGVN 23:01). A 20 January volcanic ash advisory reported an eruption at 1227. An 8 February advisory reported an eruption at 0420; the volcanic ash cloud reached ~2.1 km altitude and drifted SE. A notice later in the day reported another eruption at 0508 with an ash cloud at ~2.1 km altitude extending SE. A 16 February advisory reported an eruption on 15 February that sent a plume to the E at ~18 km altitude. Observers in Kagoshima Airport saw a volcanic ash cloud to the SE and S at 0600 on 16 February. Satellite images did not show a plume due to the presence of low weather clouds. A 24 February ash advisory noted an eruption at 0705; volcanic ash extended E at ~18 km altitude.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Information Contacts: Sakurajima Volcanological Observatory (SVO), Disaster Prevention Research Institute (DPRI), Kyoto University, Sakurajima, Kagoshima, 891-14, Japan; Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.


Axial Seamount (Undersea Features) — February 1998 Citation iconCite this Report

Axial Seamount

Undersea Features

45.95°N, 130°W; summit elev. -1410 m

All times are local (unless otherwise noted)


Hydrothermal plumes detected on research cruise suggest lava extrusion

An episode of intense seismicity occurred at Axial Seamount during 25 January-early February (see map, BGVN 23:01). In response, a team of scientists sailed aboard Oregon State University's research vessel Wecoma during 9-16 February. The following report summarizes the preliminary findings of the Axial Response Team (ART). Although the team found evidence of extensive new venting at Axial Volcano, vigorous event plumes were absent.

Despite wind gusts and high seas, the team deployed 8 ocean bottom hydrophones on 10 February around the intersection of Axial's S rift zone and summit caldera. In addition, the team made measurements of water conductivity, temperature, depth, and light attenuation at 16 sites (figure 4). The light- attenuation measurements were used to estimate particle loading in the hydrothermal plumes.

Figure (see Caption) Figure 4. Deployment of a water-sampling instrument package during the ART cruise. Ron Greene of Oregon State University is on the right. Courtesy of R. Embley.

Some instruments had been previously deployed and were in place on the sea floor before and during the event, including two volcanic system monitors and an array of three temperature sensor/current-meter moorings along the rectangular caldera's SE corner at the center of the summit epicenter locations. Earlier pre-event data on plume distribution and chemistry were gathered during a research cruise in the summer of 1997, a time when very weak plumes were present close to the sea floor.

Hydrothermal discharge from Axial seamount's summit was roughly an order of magnitude greater than before the eruption. The caldera's S end was filled with plumes that had temperature anomalies approaching 0.2°C and intense light-attenuation coefficients (~0.2/m); these plumes rose at least 200 m above the ocean bottom. The temperature anomalies were about twice as great as those seen after the 1993 CoAxial eruption (BGVN18:07). The plume was tracked ~20 km SW, where it remained as strong as in the caldera. The areal pattern of integrated relative light-attenuation (figure 5) indicated that the plume drifted steadily SW, in agreement with past current-meter readings. Both methane and hydrogen gas concentrations were higher during the cruise than in previous measurements, reaching concentrations as high as 600 nM and 200 nM, respectively. Background concentrations for methane are typically <1 nM.

Figure (see Caption) Figure 5. Plan view showing contours of relative light-attenuation that has been integrated over depths of 1.1-1.5 km. Dots indicate water sampling stations; the heavy line indicates the transect shown in figure 6. Increased suspended particles cause greater light-attenuation. Courtesy of NOAA/PMEL.

Vertical profiles gathered at the water sampling stations revealed hydrothermal signal maxima occurring at shallow (1.2-1.4 km) and/or deep (1.4-1.5 km) locations. A very strong plume at the S end of the caldera at a depth of ~1.4-1.5 km was detected on 12 February. The plume's peak (~1.47 km depth) had a light- attenuation coefficient >0.440/m, a value significantly greater and found at shallower water depths than previously detected over Axial Caldera. Increased mass concentration of particles suspended in the water column causes greater light-attenuation values. Water samples collected from the plume had very high levels of methane (~600 nM); hydrogen gas concentration measured ~4 nM. The profile taken over the vent field (at station 6) revealed a very strong plume with considerable vertical structure that extended ~1.2 km to the sea floor. The plume showed light attenuation (figure 6) and temperature anomalies with maxima occurring at both 1375- and 1425-m depth.

No event plumes were detected directly above the caldera. The team may have arrived after any event plumes had drifted away from the site. The few wispy plumes ~50-80 m thick found almost 600 m above the caldera were possible event plume remnants. No sign of venting was detected along the length of the S rift zone; a dike intrusion was thought to have occurred there during the seismic swarm of late January 1998. The lack of plumes differed from the 1993 CoAxial eruption, where the intrusion was associated with long plumes.

A small but distinct hydrothermal signal at 1.2-1.3 km depth was detected on 15 February ~18 km S of the caldera, within the central seismic cluster. The signal was interpreted as a plume remnant. Water sampling revealed methane concentrations of 5-20 nM but no elevated H2 concentrations. This indicated either that the original hydrothermal source was low in H2 or that the H2 had been lost to microbial oxidation.

A NE-SW transect of relative light attenuation (figure 6) suggested that the plume thickened and shallowed downstream from the caldera. The changes in intensity along the transect may have arisen from one or more causes, including fluctuations in water speed, temporal changes in the intensity of venting, and initial venting of more buoyant fluids.

Figure (see Caption) Figure 6. Cross-section showing relative light attenuation in and adjacent to Axial's caldera. Water-sampling sites (eg., 10, 11, etc.) are labeled along the top axis. The line of the cross section appears on figure 5. Courtesy of NOAA/PMEL.

Particles in water samples from stations 11 and 1 (figure 5) were studied by scanning electron microscope (SEM). Samples from station 11 contained many angular glass shards up to 95 micrometers in diameter. Many of the shards had precipitated halite particles attached to them; precipitation of halite coatings on altered glass surfaces was consistent with heating seawater to >400°C at 1.5 km depth. Similar coatings were found on basaltic particles from the 1993 CoAxial eruption.

Many small particles with high iron concentrations were also observed. Although these particles were of similar size to iron oxides from past eruptive sites, their shapes were more angular than the typically rounded, globular shapes seen in the past. Chemical analysis showed that these particles also contained halides and a higher than usual ratio of phosphorus to iron. Analysis of particles from station 1 showed abundant elemental sulfur. These observations were taken to suggest a lava eruption on the SE caldera floor.

Axial Volcano rises 700 m above the mean level of the ridge crest and is the most magmatically robust and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset. The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km, figure 5) that lies between the two rift zones. The caldera is defined on three sides by a boundary fault of up to 150 m relief. Organisms have colonized the hydrothermal vents near the caldera faults and the rift zones. Following the initial discovery of venting N of the caldera in 1983, a concentrated mapping and sampling effort was made in the mid-late 1980s.

Geologic Background. Axial Seamount rises 700 m above the mean level of the central Juan de Fuca Ridge crest about 480 km W of Cannon Beach, Oregon, to within about 1,400 m of the ocean surface. It is the most magmatically and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset. The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km) that lies between two rift zones and is estimated to have formed about 31,000 years ago. The caldera is breached to the SE and is defined on three sides by boundary faults of up to 150 m relief. Hydrothermal vents with biological communities are located near the caldera fault and along the rift zones. Hydrothermal venting was discovered north of the caldera in 1983. Detailed mapping and sampling efforts have identified more than 50 lava flows emplaced since about 410 CE (Clague et al., 2013). Eruptions producing fissure-fed lava flows that buried previously installed seafloor instrumentation were detected seismically and geodetically in 1998 and 2011, and confirmed shortly after each eruption during submersible dives.

Information Contacts: Jim Cowen, Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawai'i at Manoa, 1000 Pope Road, Honolulu, HI USA 96822; Ed Baker, NOAA Pacific Marine Environmental Laboratory (PMEL), 7600 Sand Point Way N.E., Seattle, WA USA 98115; Bob Embley, NOAA Pacific Marine Environmental Laboratory (PMEL), 2115 SE OSU Drive, Newport, OR 97365 USA (URL: http://www.pmel.noaa.gov/).


Bezymianny (Russia) — February 1998 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


Fumarolic plumes present on most days

Fumarolic plumes rose 50-800 m above the volcano on 27 January, 3-5, 9, 12-14, 17-18, 20-22, 23-25, and 28 February. A steam plume rose 50 m on 30 January. Plumes on 17-18, 23-25, and 28 February traveled SE. No seismicity registered under the volcano during 23 February-1 March.

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: Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Cameroon (Cameroon) — February 1998 Citation iconCite this Report

Cameroon

Cameroon

4.203°N, 9.17°E; summit elev. 4095 m

All times are local (unless otherwise noted)


1997 seismicity remains low with one earthquake swarm

Local seismicity in the Mt. Cameroon region has remained consistently low from 1995 through 1997 at an average of 15 events/month (figure 2). An earthquake swarm recorded in January 1996 consisted of 33 events (modified from BGVN 22:02). Another swarm, of 30 earthquakes, occurred in August 1997. All of the recorded signals were A-type volcanic earthquakes under M 3. Many seismic stations remain out of order and in need of repair, so there is the possibility that other data were lost. However, no events were felt by local residents.

Figure (see Caption) Figure 2. Monthly seismicity in the Mt. Cameroon region, 1993-97. Note that the number of seismic stations functioning varied over the interval shown. Courtesy of IRGM/ARGV.

Geologic Background. Mount Cameroon, one of Africa's largest volcanoes, rises above the coast of west Cameroon. The massive steep-sided volcano of dominantly basaltic-to-trachybasaltic composition forms a volcanic horst constructed above a basement of Precambrian metamorphic rocks covered with Cretaceous to Quaternary sediments. More than 100 small cinder cones, often fissure-controlled parallel to the long axis of the 1400 km3 edifice, occur on the flanks and surrounding lowlands. A large satellitic peak, Etinde (also known as Little Cameroon), is located on the S flank near the coast. Historical activity was first observed in the 5th century BCE by the Carthaginian navigator Hannon. During historical time, moderate explosive and effusive eruptions have occurred from both summit and flank vents. A 1922 SW-flank eruption produced a lava flow that reached the Atlantic coast, and a lava flow from a 1999 south-flank eruption stopped only 200 m from the sea. Explosive activity from two vents on the upper SE flank was reported in May 2000.

Information Contacts: Ateba Bekoa and Ntepe Nfomou, IRGM Antenne de Recherches Geophysiques et Volcanologiques (ARGV), P.O. Box 370, Buea, Cameroon; G.E. Ekodek and J.M. Nnange, Institut de Recherches Geologiques et Minieres (IRGM), P.O. Box 4110, Yaounde, Cameroon; J.D. Fairhead, Dept. of Earth Sciences, The University of Leeds, Leeds, LS2 9JT, United Kingdom.


Piton de la Fournaise (France) — February 1998 Citation iconCite this Report

Piton de la Fournaise

France

21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)


First eruption in over 5 years begins 9 March

Piton de la Fournaise began erupting 9 March at 1500 preceded by a number of earthquakes and strong deformations. The volcano had been quiet since the last fissure eruption on 27 August 1992. The Volcanological Observatory of Piton de la Fournaise (OVPDLF) was able to give authorities two days warning of the impending crisis. Thomas Staudacher, director of OVPDLF, deployed additional seismic and deformation monitoring equipment in the early stages of the event.

Eruptions first started from a fissure at 2,450 m on the N flank of the terminal Dolomieu crater, a spot in the interior of l'Enclos Fouqu' caldera (figure 40). Venting quickly migrated northward to lower altitudes (1,950 m). The activity was focused at two fissures near the very bottom of the slope of Dolomieu and cones were forming at the place where lava fountains were most active.

Figure (see Caption) Figure 40. Sketch map of Piton de la Fournaise and vicinity. Notice that the topographic contour intervals are uneven. Courtesy of OVPDLF.

The lava fountains, some reaching 50 m in height, fed a voluminous flow that progressed N and E towards the Indian Ocean. Lava issued in a sustained flow rate estimated at 20 m3/s; the total volume since the start of the eruption was estimated on 10 March at 7 x 106 m3. The zone where the lava was flowing, to the NE along Osmondes plain in the direction of the sea, is wholly uninhabited. By 10 March activity appeared to be weakening, the front of the flow moving more slowly towards Grandes Pentes. Mist and haze over the Osmondes plain on 11 March prevented observation of the advance of the flow.

Seismicity had increased since the beginning of 1998. Volcanic tremor accompanied venting, including an almost continuous seismic swarm (30 earthquakes per hour in the hours preceding the eruption) beneath the summit's Bory crater in the SW. In the hour before magma venting, inclinometers in the summit area indicated the injection of a dyke and then the opening of a surface fissure. Tremors and swarm were accompanied by intermittent earthquakes, discrete events not usually seen in Piton's past eruptions.

By 1600 on 11 March, cones of scoria had attained heights of 10 m on Piton's upper slopes and 30 m on its lower slopes and were being fed by lava fountains nearly 30 m high. On 12 March at about 0245, a new but much less productive eruptive fissure opened on the opposite (SW) side of the terminal cone at 2,250 m elevation.

A "level one" volcano alert was issued 9 March at 0500 by island prefect Robert Pommies following heavy seismic activity during the weekend. The alert was reduced to "level two" after it was seen that the lava eruption was centered on the N of the volcano. Agence France Presse reported that there was no threat to the village of Sainte-Rose, which had to be evacuated in 1978.

A 14-16 March report stated that eruptive activity at both fissures (N and SW of the central cone) continued uninterrupted through 12 March. Emissions at the N fissures focused on the central vents and built cones ~50 m high. The output rate was ~15-30 m3/s and the lava flow front was stationary (4 km E at ~1,100 m elevation) with a maximum lava temperature of 1,167°C. Also, venting on the SW fissure centered on a limited stretch and built a spatter rampart ~70 m long. The output rate was ~5-10 m3/s with a maximum temperature of ~1,135°C. The latter activity gave rise to a 1.5 km flow. The discrete seismic events that were observed over the continuous tremor had ceased since 12 March but a single event was observed in the night of 13-14 March.

Geologic Background. Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three scarps formed at about 250,000, 65,000, and less than 5,000 years ago by progressive eastward slumping, leaving caldera-sized embayments open to the E and SE. Numerous pyroclastic cones are present on the floor of the scarps and their outer flanks. Most recorded eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest scarp, which is about 9 km wide and about 13 km from the western wall to the ocean on the E side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures outside the scarps.

Information Contacts: Thomas Staudacher, Director, Observatoire Volcanologique du Piton de la Fournaise (OVPDLF), 14 RN3, le 27Km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.jussieu.fr/); Agence France Presse, Paris, France.


Heard (Australia) — February 1998 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


No evidence of recent activity in March

During 18-21 March geologists sampled Holocene lava flows on Heard Island. On beaches of the N Laurens Peninsula, they found fresh pumice ranging in size up to about 20 x 20 cm . The pumice was concentrated among other storm- transported debris a little distance above the normal surf zone and appeared to have been deposited by wave action. Light creamy green to pale gray in color, the pumice had angular, ovoid or flattened shapes and contained predominantly microphenocrysts and occasional phenocrysts visible to the naked eye. Lithic fragments were not observed.

On Heard Island, Big Ben's summit was usually obscured by clouds. The summit was visible on 20 March, however, and at this time no evidence of recent volcanic activity was observed at Mawson Peak, Big Ben's recently active crater (figure 3). Similarly no plume was seen coming from Heard when McDonald vented steam in early April. In accord with these observations, scientists inferred that the December 1996-January 1997 volcanic activity attributed to Heard actually denoted activity at McDonald.

Figure (see Caption) Figure 3. Map of Heard Island showing principal volcanic centers on both the Laurens and Azorella Peninsulas (see shaded boxes) and on Big Ben (the massif comprising the bulk of the SE part of the island). The beached pumice samples were collected at the N end of the Laurens Peninsula. Courtesy of K. Collerson.

References. LeMasurier, W.E., and Thompson, J.W., primary eds., 1990, Volcanoes of the Antarctic Plate and Southern Oceans, Antarctic Research Series: American Geophysical Union, Washington, D. C. (ISBN 0066-4634).

Collerson, K. D., 1997, Field studies at Heard and McDonald Island in March 1997: unpublished Australian National Antarctic Research Expedition (ANARE) report.

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

Information Contacts: Kenneth Collerson, Department of Earth Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; Kevin Kiernan, Department of Geography and Environmental Sciences, University of Newcastle, Newcastle, New South Wales 2300, Australia; Richard Williams, Australian Antarctic Division, Channel Highway, Hobart, Tasmania, Australia; Andrew Tupper, Northern Territory Regional Forecasting Centre, Bureau of Meteorology, P. O. Box 735, Darwin, Northern Territory 0801, Australia.


Nevado del Huila (Colombia) — February 1998 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Significant increase in seismicity in December 1997

The Observatorio Vulcanológico y Sismológico de Popayán (OVSP) reported increased seismicity at the Nevado del Huila volcanic complex. The complex is studied using three seismic stations in SW Colombia. One substantial seismic increase occurred during 20-25 December 1997. About 108 volcano-tectonic earthquakes in three swarms were located in a small area 3 km east of Pico Norte (figure 2). Seismic activity has not previously been known in this area. The swarms were 6-8.5 km in depth (figure 3) with magnitudes ranging from 0.93 to 2.98 (Richter scale).

Figure (see Caption) Figure 2. Epicenter map showing volcano-tectonic seismicity at the Nevado del Huila complex during January to December 1997. Courtesy OVSP.
Figure (see Caption) Figure 3. Depths of volcano-tectonic seismicity at Nevado del Huila during January to December 1997. Courtesy OVSP

A second increase, energy released by volcano-tectonic earthquakes, has grown over the last two years. The period with the largest recorded energy was associated with the swarms of late December 1997, which totaled 1.20 x 108 ergs (figure 4).

Figure (see Caption) Figure 4. Seismic energy from volcano-tectonic and long-period (LP) earthquakes recorded at stations monitoring Nevado del Huila, 1993-1998. Courtesy OVSP.

The Nevado del Huila volcanic complex is comprised of three main peaks aligned N-S; these are named Pico Norte, Pico Central and Pico Sur. Pico Central is the highest summit in the Cordillera Central, is composed of interbedded tephra and steep-sided lava flows located inside an old caldera. The sole known eruption recorded in historical time was an explosion in the 16th century. Two persistent steam columns rise from the southern peak and hot springs surround the volcano. The volcano has 13.4 km2 of glacial cover.

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

Information Contacts: Fabiola Patricia Rodríguez and Juan Carlos Diago, Observatorio Vulcanológico y Sismológico de Popayán, Calle 5B 2-14, Popayán, Colombia.


Karymsky (Russia) — February 1998 Citation iconCite this Report

Karymsky

Russia

54.049°N, 159.443°E; summit elev. 1513 m

All times are local (unless otherwise noted)


Ongoing gas-and-ash explosions

Seismicity remained above background level and low-level Strombolian activity sent ash and steam 300-400 m above the crater during 27 January-1 March. During 27 January-8 February, gas-and-ash explosions occurred every 30-40 minutes. During 9 February-1 March, 70-100 gas-and-ash explosions occurred per day. On 9 February, 11 tectonic earthquakes were recorded ~10 km S of Karymsky.

Geologic Background. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Information Contacts: Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry; Tom Miller, Alaska Volcano Observatory.


Kilauea (United States) — February 1998 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Steady, low activity during February

During 4 February-5 March, the Pu`u `O`o eruption returned to steady-state activity after a brief magma surge and two seismic swarms in January (BGVN 22:12 and 23:01). Seismicity was low and little inflation or deflation was detected at Kīlauea's summit. Magma moved through shallow conduits towards the E rift zone without disturbing the ground surface.

The Pu`u `O`o vent area remained relatively unchanged in appearance during February. Fumes issued from cracks in the cone and surrounding area. Profuse fumes from new cracks near the N rim obscured the views of remote surveillance cameras and observers on helicopter overflights.

Lava continued to travel in tubes from the Pu`u `O`o vents to the ocean; however, during 4-24 February surface lava flows were sparse. Every 4-5 days a small flow issued from the lava tubes across the coastal plain. Most of the surface flows were near the Waha`ula ocean entry. At Kamokuna, lava continued to form a low shelf or bench at the foot of a 10-15 m cliff bordering the ocean. A bench collapse at the Kamokuna coastal entry occurred between 16 and 19 February. The collapse destroyed 4 hectares of land that had formed since the most recent collapse on 15 January (BGVN 22:12). The lava supply to the coastal tube system was interrupted briefly on 21 February, causing the steam plumes at the sea entry to dwindle for most of the day.

Kīlauea is one of five coalescing volcanoes that comprise the island of Hawaii. Historically its eruptions originated primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the summit caldera to the sea. This latest Kīlauea eruption began in January 1983 along the E rift zone. The eruption's early phases, or episodes, occurred along a portion of the rift zone that extends from Napau Crater on the uprift end to ~8 km E on the downrift end. Activity eventually centered on what was later named Pu`u `O`o. More than 223 hectares of new land have been added to the island and local communities have suffered more than $100 million in damages since the beginning of the eruption.

Geologic Background. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii Volcanoes National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Ken Rubin and Mike Garcia, Hawaii Center for Volcanology, University of Hawaii, Dept. of Geology & Geophysics, 2525 Correa Rd., Honolulu, HI 96822 USA (URL: http://www.soest.hawaii.edu/GG/hcv.html).


Klyuchevskoy (Russia) — February 1998 Citation iconCite this Report

Klyuchevskoy

Russia

56.056°N, 160.642°E; summit elev. 4754 m

All times are local (unless otherwise noted)


Earthquakes, tremor, and gas-and-steam plumes throughout February

Beginning at 0616 on 28 January and continuing until 1 March, seismicity at Kliuchevskoi was above background level. During 28 January-8 February, earthquakes registered at depths of 25-30 km under the volcano and were accompanied by volcanic tremor. Surface earthquakes accompanied by volcanic tremor were recorded during 9-22 February, and deep earthquakes were detected during 23 February-1 March.

Fumarolic plumes rose 1-3 km above the volcano on 27 January, 3 February, and 17 February. Gas-and-steam plumes rose 50-2000 m on 30 January, 4-5, 9, 11-15, 18-22, 24-28 February, and 1 March. The plumes drifted 1-10 km with prevailing winds.

Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Langila (Papua New Guinea) — February 1998 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)


Intermittent eruptive activity at Crater 2

Throughout February, there was intermittent weak eruptive activity at Langila's Crater 2 while Crater 3 remained quiet. On the 3rd, two loud explosions were heard that produced thick dark ash clouds rising 2,500 m above the crater. A similar explosion occurred on 5 February. During 6-14 and 24-26 February, Crater 2 discharged small- to moderate-sized gray ash clouds. Low roaring and rumbling sounds were heard on the 20th, 22nd, and 24th. Crater 3 was restricted to weak fumarolic emissions the entire month. Both seismographs remained inoperative.

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: Ben Talai, RVO.


Manam (Papua New Guinea) — February 1998 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)


Low-level vapor emission and nighttime summit-crater glow in February

Activity at both summit craters of Manam was low throughout February. Both craters emitted continuous weak white vapor. Glow was observed at Southern crater on the nights of 3, 5-9, 14-18, and 25-27 February, but there were no sounds.

Seismic activity showed no significant change: 1,100-1,300 low-frequency earthquakes of very low magnitude were recorded daily. Following a deflation of ~1.5 µrad in January, radial tilt as measured at Tabele stabilized for February.

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: Ben Talai, RVO.


McDonald Islands (Australia) — February 1998 Citation iconCite this Report

McDonald Islands

Australia

53.03°S, 72.6°E; summit elev. 230 m

All times are local (unless otherwise noted)


The eruption of 1996-97 and its inferred lavas and tephra

This report discusses field and geochemical observations that indicates activity at McDonald Island. The activity is inferred to have began in December 1996; it continued through early 1997.

Visual observations. During mid-December 1996, a pilot reported a vapor plume in the vicinity of Heard Island (figure 1). Initially, the report was thought to indicate an eruption of Big Ben, an intermittently active volcano on Heard Island that last erupted in 1993 (BGVN 17:12). Another report discussed a possible volcanic plume near Heard Island on 5 January 1997 (BGVN 22:01). A 15 January 1997 satellite image showed an extensive high-altitude linear cloud formation drifting E from near Heard Island; this activity was also assumed to be associated with Big Ben.

Figure (see Caption) Figure 1. Location of Heard and McDonald Islands on the Kerguelen Plateau in the S Indian Ocean. "SWIR" refers to the Southwest Indian Ridge, "SEIR" to the Southeast Indian Ridge. Gaussberg is an isolated conical mountain of volcanic origin on the coast of Antarctica. Courtesy of K. Collerson.

On 18 March 1997, the "RSV Aurora Australis," a ship en route to Heard Island, sailed within 7.4 km of McDonald Island. Observers on board reported seeing steam plumes emitted at high velocity from several point sources and from the fissure system on the island's steep N face between the topographic features known as The Needle, Samarang Hill, and Macaroni Hill (figure 2). They also saw a low, diffuse, white vapor plume extending SE from the island's N summit. Steam vented from a rubble-covered slope that possibly indicated a lava flow or pyroclastic deposit. Ken Collerson documented these observations on video tape (Collerson, 1997; Collerson and others, 1998).

Figure (see Caption) Figure 2. Sketch map of McDonald Island showing the new lavas in the vicinity of Samarang Hill. Courtesy of K. Collerson.

On 2 April, observers on the vessel "FV Austral Leader" saw vapor rising from the island's summit. The ship came within 2.6-4.6 km of McDonald Island for closer observation and confirmed steam venting similar to that observed on 18 March. Observations included "smoke" clouds rising from the summit and flanks of the N and middle parts of the island, possible lava flows traveling down gullies, and a yellow- green deposit (possibly sulfur) close to the source of the steam emissions. In addition, a diffuse white vapor plume from the N summit of the island was drifting N to NE. An early April photograph of steam venting appears on figure 3.

Figure (see Caption) Figure 3. Photo of McDonald Island taken early April 1997 portraying steam venting at Samarang Hill (in the foreground). In the background resides glacier-draped Heard Island (44 km E of McDonald Island, with a summit elevation of 2,750 m). Copyrighted photo taken by Richard Williams and used with permission of the Australian Antarctic Division.

Although observers never went ashore on McDonald Island during or after the eruption, Collerson estimated the extent of the lavas and fumarolic activity from visual observations, digital video images, and 35 mm photographs. A preliminary sketch map of new lavas appears on figure 2.

During 18-21 March geologists sampled Holocene lava flows on Heard Island. On beaches of the N Laurens Peninsula, they found fresh pumice ranging in size up to about 20 x 20 cm . The pumice was concentrated among other storm- transported debris a little distance above the normal surf zone and appeared to have been deposited by wave action. Light creamy green to pale gray in color, the pumice had angular, ovoid or flattened shapes and contained predominantly microphenocrysts and occasional phenocrysts visible to the naked eye. Lithic fragments were not observed.

On Heard Island, Big Ben's summit was usually obscured by clouds. The summit was visible on 20 March, however, and at this time no evidence of recent volcanic activity was observed at Mawson Peak, Big Ben's recently active crater (figure 4). Similarly no plume was seen coming from Heard when McDonald vented steam in early April (figure 3). In accord with these observations, scientists inferred that the December 1996-January 1997 volcanic activity attributed to Heard actually denoted activity at McDonald.

Figure (see Caption) Figure 4. Map of Heard Island showing principal volcanic centers on both the Laurens and Azorella Peninsulas (see shaded boxes) and on Big Ben (the massif comprising the bulk of the SE part of the island). The beached pumice samples were collected at the N end of the Laurens Peninsula. Courtesy of K. Collerson.

Satellite observations. Satellite images showing plumes similar to volcanic ash clouds extending E from the Heard Island area were reported to Australia's Bureau of Meteorology during the summers of 1996-97. Standard detection techniques did not confirm that the clouds were volcanic; however, several volcanologists and meteorologists studied the plumes and concluded that the clouds were probably not volcanic.

Meteorologists from the Tasmanian and Antarctic office of the Bureau of Meteorology suggested that the plumes were probably banner clouds, a type of cloud that often forms behind mountain peaks at high latitudes.

The ~600-km-long plumes seen repeatedly on the satellite images were not consistent with the prior activity of Heard Island; Heard Island was unlikely to produce large-scale eruptions and high-level ash clouds. However, McDonald Island was not ruled out as a possible source of volcanic plumes.

Geochemical studies. Researchers conducted major element and inductively coupled plasma mass spectrometer trace element analyses on the fresh pumice collected from Heard Island. The pumices were strongly alkaline with elevated incompatible element abundances. Although the results were similar to previous studies of McDonald Island phonolites, the pumices were generally more evolved, suggesting that they were derived from an extremely fractionated magma chamber. This conclusion was also supported by high- precision Th isotopic data. Extreme Na2O values for two samples, coupled with very high volatile contents and carbonatite-like HFSE and LILE abundances, suggested that some of the pumices contained an exsolved sodium- rich carbonate phase.

Sr, Nd, and Pb isotopic compositions of six samples of the fresh pumice collected on Heard Island were within the error of values reported for McDonald Island phonolites. The Sr, Nd, and Pb isotopic data for the pumices differed from other potential young volcanic sources in the southern hemisphere such as South Sandwich Islands, Marion Island, Iles Crozet, and the Ross Sea Igneous Province, and were thus interpreted as derived from McDonald Island.

References. LeMasurier, W.E., and Thompson, J.W., primary eds., 1990, Volcanoes of the Antarctic Plate and Southern Oceans, Antarctic Research Series: American Geophysical Union, Washington, D. C. (ISBN 0066-4634).

Collerson, K. D., Regelous, M., Frankland, R., Wendt, J. I., Kiernan, K., and Wheller, G., 1998, 1997 eruption of McDonald Island (southern Indian Ocean): new trace element and Th-Sr-Pb-Nd isotopic constraints on Heard-McDonald Island magmatism. Abstr. 14th Aust. Geol. Convention, Townsville, July 1998.

Collerson, K. D., Regelous, M., Wendt, J. I., and Wheller, G., 1998, 1997 eruption of McDonald Island (Southern Indian Ocean): new trace element and Th-Sr-Pb-Nd isotopic constraints on Heard-McDonald Island magmatism: Earth Planet Sci. Lett (in prep.)

Collerson, K. D., 1997, Field studies at Heard and McDonald Island in March 1997: unpublished Australian National Antarctic Research Expedition (ANARE) report.

Geologic Background. Historical eruptions have greatly modified the morphology of the McDonald Islands, located on the Kerguelen Plateau about 75 km W of Heard Island. The largest island, McDonald, is composed of a layered phonolitic tuff plateau cut by phonolitic dikes and lava domes. A possible nearby active submarine center was inferred from phonolitic pumice that washed up on Heard Island in 1992. Volcanic plumes were observed in December 1996 and January 1997 from McDonald Island. During March 1997 the crew of a vessel that sailed near the island noted vigorous steaming from a vent on the N side of the island along with possible pyroclastic deposits and lava flows. A satellite image taken in November 2001 showed the island to have more than doubled in area since previous reported observations in November 2000. The high point of the island group had shifted to the McDonald's N end, which had merged with Flat Island.

Information Contacts: Kenneth Collerson, Department of Earth Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; Kevin Kiernan, Department of Geography and Environmental Sciences, University of Newcastle, Newcastle, New South Wales 2300, Australia; Richard Williams, Australian Antarctic Division, Channel Highway, Hobart, Tasmania, Australia; Andrew Tupper, Northern Territory Regional Forecasting Centre, Bureau of Meteorology, P. O. Box 735, Darwin, Northern Territory 0801, Australia.


Popocatepetl (Mexico) — February 1998 Citation iconCite this Report

Popocatepetl

Mexico

19.023°N, 98.622°W; summit elev. 5393 m

All times are local (unless otherwise noted)


Cyclical dome extrusions that by late 1997 filled one-third of crater capacity

The following report on Popocatépetl incorporates both background descriptive information, some of which had previously remained unreported, and a more detailed discussion of ongoing dome growth based on aerial photographs and flight observations. The volcano was last discussed in BGVN 23:01. By late 1997 the growing dome occupied 30-38% of the crater's capacity.

During 1996-98, Popocatépetl extruded six named domes in the summit crater (A through F, table 10 and figure 24). Elliptical in shape, the summit crater measures 820 x 650 m, with the longer axis trending approximately E-W. The lowest point of the crater rim occurs along the NE side and lies at 5,180 m elevation; the average elevation of the irregular floor was estimated at 5,030 m (De la Cruz-Reyna et al., in review). The crater's deepest point, at 4,963 m elevation, lay at the bottom of the ~160-m-diameter craterlet formed during the 1922 eruption (BGVN 21:03). Based on the observed shapes and dimensions, the crater could potentially contain a volume of ~35 x 106 m3 before additional material would spill out the low point on the crater rim.

Table 10. Approximate dates when the first extruded material was seen for Popocatépetl's domes A through F. Courtesy of CENAPRED.

Dome Extrusion date Comment
A late Mar 1996 --
B 21 May 1996 --
C 21 Jan 1997 Higher viscosity lavas than domes A or B.
D 04 Jul 1997 Followed the unusually large 30 June 1997 explosion that left a large crater in dome C.
E 19 Aug 1997 --
F 07 Dec 1997 --
Figure (see Caption) Figure 24. Schematic plan views showing the main crater at the summit of Popocatépetl and the sequence of named domes (A-F) found during 26 May 1996 through 7 December 1997. Courtesy of CENAPRED.

In late March 1996, observers saw dome A growing at the bottom of Popocatépetl crater and slowly covering the 1922 craterlet (BGVN 21:03). By 21 May 1996, two elliptical lava bodies were observed in the main crater of Popocat'petl, completely covering the older dome and craterlet (BGVN 21:04). As shown on figure 24, domes A and B grew along the SE and NW sectors of the principal crater's floor (BGVN 22:10). By 26 May 1996 the highest point on dome B reached 5,109 m elevation. Then, after July 1996 dome B's moderate growth slowly declined and subsequent circular fractures on the central dome indicated subsidence. By September 1996 the growth rate could not be measured and ash emissions became smaller. After September 1996, explosive emissions became less frequent, but more intense (e.g. those on 28 and 31 October 1996, BGVN 22:10).

By 21 November 1996, dome B had covered most of dome A and it crept radially out towards the crater's walls. Apparently, explosive activity around that time caused enhanced central subsidence as concentric fractures returned to the dome's surface and the elevation of its central part fell to 5,090 m. More explosions were recorded on 27, 28, and 29 November, on 2, 5, 7, and 29 December, and on 5, 12, 17, and 19 January, 1997. The January explosions were noted as large. By 21 January observers reported that dome B's previously irregular surface appeared smooth due to a cover of fresh tephra. More surprisingly, the central depression within dome B increased in depth, creating what looked like a new crater.

More explosions soon followed (on 23 and 29 January, and on 4, 5, 8, and 25 February; BGVN 22:03). Next, new lava extruded at the center of the depression constructing a new, smaller dome (C). The lavas comprising dome C appeared to have a greater viscosity than those of either A or B.

Explosions on 19 and 20 March 1997 (BGVN 22:04) failed to remove significant proportions of dome C; by 23 April dome C's central part reached 5,060 m elevation (figure 24). As previously reported (BGVN 22:04 and 22:07), subsequent explosions (24 and 29 April, 11, 14, 15, 24, and 27 May, and 3 and 11 June 1997) partially destroyed dome C leaving it covered by explosive clasts of very different sizes. Moreover, the central part of dome C had subsided, leaving its lowest point at 5,049 m elevation. More explosions on 14, 19, 21, and 30 June and on 2 July thwarted observations of the crater's interior. The 30 June 1997 explosion, the largest since the eruption began in 1994, quickly dispatched an ash column to 13 km altitude (BGVN 22:07). When observers looked into the crater on 4 July 1997, dome C had been partially destroyed and contained a large crater.

Within that crater there lay a dish-shaped zone of fresh ropy-lava given the name dome D. In addition, tongues of material radiated from the crater over the volcano's S and SE flanks; these were interpreted as granular flows deposited by the 30 June eruption (BGVN 22:07). Although not previously reported, on 10 August subsidence and radial fracturing became more evident on dome D. Later, by 19 August, dome D sprouted additional lava thus forming what was termed dome E (BGVN 22:10).

Dome E, initially an elliptical lobe that was 50-m long, 36-m wide, and 6-m high, had a very rough surface texture. Dome E later attained a circular shape, and by 10 September it had almost filled the hosting craterlet within the surrounding dome's body. Apart from some radial fractures, the surface appearance was rather regular with a slight inner depression and a region emitting gases in the center. This circular center had a height of 5,105 m elevation. From then on, E extruded in a piston-like manner and when seen on 22 October, E retained an almost cylindrical shape: Its height had grown about 15 m without significant change in its horizontal extent. When viewed on 29 November E's surface appeared smoother except for the presence of some minor explosion craterlets.

Starting on 25 November, significant seismic changes indicated subcrater magmatism and on 2 December observers noted both mild ash emissions and night-time incandescence. On 7 December observers recognized yet another new, large lava body in the crater (BGVN 22:11).

Dome F was composed of a lower-viscosity, black, ropy lava; it subsequently grew to a maximum diameter of 380 m and exceeded by 20 m the height of dome E as measured on 22 October. Relative quiet during 7-24 December ended on the latter day with a 30-minute-long series of explosions and moderate ash emissions. Volcano-tectonic seismicity took place during the final days of 1997, leading up to a large 1 January explosion. Aerial observers on 6 January saw that dome F had been partially destroyed and covered by volcanic debris (BGVN 22:12). The negative values on table 11 correspond to the 1 January 1998 explosion, which left a crater at dome F's center. This crater was 250 m in diameter and 60 m in depth with a shape similar to the 1922 dome and craterlet. Dense, degassed lava blocks with diameters of 0.6-0.8 m were thrown 2 km from the crater; they produced impact craters about 3 m in diameter.

Table 11. Estimates of Popocatépetl dome volumes for the stated dates. Volumes are "actual" and not adjusted as dense rock equivalents. The maximum crater capacity is estimated at ~ 35 x 106 m3. The negative emitted volume shown for 1 January 1998 appears because explosions removed material from the dome, although some uncertain amount of these broken dome fragments remained within the crater (see text). Courtesy of CENAPRED.

Date Emitted volume (m3) Cumulative volume (m3) Percent of crater capacity
Mar 1996-Oct 1997 9,500,000 9,500,000 27%
Nov 1997 1,500,000 11,000,000 31%
Dec 1997 2,500,000 13,500,000 38%
01 Jan 1998 -1,000,000 12,500,000 35%

Afterwards, until early February 1998, the volcano remained relatively quiet. On 14 March 1998, new precursory seismicity was detected. In behavior reminiscent of December 1997 and January 1998, two explosions occurred on 21 March at 0511 and 1559. The first, a moderately explosive exhalation, produced light ashfalls on towns in the state of Puebla. The second, a more intense explosion, produced a 3-km-tall plume and threw blocks 2-4 km about the crater. A 23 March exhalation appeared very similar to the one at 0511 on 21 March, resulting in a low-altitude plume that the wind dispersed NW. No damage or casualties were reported.

Reference. De la Cruz-Reyna, S., Macias, J.L., and Castillo-Alanis, F., (manuscript submitted late February 1998), Dome growth and associated activity during the current eruptive episode of Popocatepetl volcano, central Mexico: Earth and Planetary Sciences Letters.

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Servando de la Cruz-Reyna1,2, Roberto Meli1, Jose Luis Macias1,2, Francisco Castillo Alanis1, and Bulamaro Cabrera3; 1Instituto de Geofisica, UNAM, Coyoac n 04510, México D.F., México; 2CENAPRED, Delfin Madrigal 665, Col. Pedregal de Santo Domingo, Coyoacan, 04360, México D.F., México; 3SCT, Aldadena 23, 6o piso, Col. N poles, 03810, México D.F., México.


Rabaul (Papua New Guinea) — February 1998 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)


January activity presages February eruption

A continuous glow was visible at nights throughout January 1998 at Tavurvur crater, and there was also a slow but steady inflation of the volcano during the month. An expected eruption began at Tavurvur on 3 February 1998.

The eruption began with emissions of pale to dark gray ash clouds typically 5-20 minutes apart. There was no noise associated with the emissions although small, low-frequency seismic events did accompany each event. Over the next few days roaring and rumbling could be heard down-wind (to the SE) of Tavurvur and seismic events became generally larger. Loud explosions were recorded once to 5 times daily. The explosions usually were accompanied by forceful emissions of dense gray to dark ash clouds that rose to 2000-3500 m above the crater. These were followed by moderate to small ash-cloud emissions lasting ~30 minutes. During the explosions lava fragments were ejected to heights of 200-300 m, showering the slopes 200-500 m from the base of the cone. Some small ash flows were also generated during explosions. During strong ash emissions at night, successive 5-minute projections of glowing lava fragments were observed. This pattern of eruptive activity lasted until the end of February.

Ash rose to 300 m above the crater (600 m a.s.l.) and was usually distributed to the SE, with occasional drifts to the N and W. Each ash emission produced light ash fall at Talwat village SE of Tavurvur near the base of the cone. There was also very light ash fall recorded elsewhere on New Britain, including at Tokua airport 20 km from Tavurvur.

Seismic activity was generally low. A slight increase in the frequency of volcanic earthquakes in early February reflected the increase in activity at the summit of Tavurvur. The increase was indicated on the 1- minute RSAM data as background values of 20 RSAM units increased to 100. Between 10 and 48 earthquakes were recorded daily. The average number per day was 27, but after 22 February they dropped to 9. Two high-frequency earthquakes recorded during February were located 20-30 km ESE of the caldera.

During the current phase of eruptive activity there has been no significant change in ground deformation compared to the inflationary trend prior to the eruption. A water-tube tiltmeter located 3.5 km NW of Tavurvur showed a slow yet steady rate of inflation: total accumulated tilt for February was 4 µrad. Real-time GPS measurement taken from a remote station on Matupit Island 2 km W of Tavurvur showed no significant change.

Although COSPEC SO2 measurements lacked precursory signatures suggesting an eruption, a slightly higher SO2 flux of ~350 metric tons/day was measured when the eruption started. After several days the flux decreased to a low level of ~190 tons/day. The low flux values attained during the month were partly due to a change in wind direction away from the fixed observation post.

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: Ben Talai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Sheveluch (Russia) — February 1998 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Frequent gas-and-steam plumes

During February seismicity remained near or slightly above background level. No volcanic activity was observed during 27 January-1 February. Gas-and-steam plumes rose 50-1,000 m above the volcano on 3, 4, 8, 11-12, 12-14, 17-18, 20, 24, 28 February, and 1 March.

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: Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Soufriere Hills (United Kingdom) — February 1998 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Dome growth continues; discussion of the 26 December dome collapse

The following summarizes a scientific report of the Montserrat Volcano Observatory (MVO) for 18 January-1 February, a time period when seismic and volcanic activity were low but dome growth continued. In addition, this report condenses MVO's Special Report 6 on the 26 December 1997 dome collapse, perhaps the most intense outburst yet recorded during the current crisis.

Visual observations. Few views of the dome complex were obtained due to poor visibility until the end of January, when observers saw active growth in the crater left by the 26 December 1997 dome collapse in the volcano's SW sector (BGVN 22:12). Also reported were occasional rockfalls, ash venting, steaming, and a dilute steam-and-ash plume that drifted WNW. Ash venting and rockfall activity became slightly more vigorous at the end of January, when a shift in prevailing winds sent light ashfall to the N part of the island.

Seismicity. Rockfall signals dominated seismicity; most coincided with a seismic-amplitude cycle with a periodicity of ~12 hours. This regular, slight increase in seismicity despite any major events has continued since the 26 December collapse and has been interpreted to indicate cyclical degassing as the dome grew.

Ground deformation. Displacement vectors for the interval April/May 1997 to January 1998 for sites around the volcano (table 25) revealed that areas NE, E, and SE of the volcano had been significantly displaced. The sector between Whites, Hermitage, and Roches Yard had moved ~6 cm NNE. Similar measurements at Long Ground, Tar River, and Perches suggested that these sites were displaced as a homogenous unit with little deformation. The Hermitage site showed considerably more movement than the others. Because of its proximity to the dome, it may have been more strongly influenced by local pressure or loading effects. Distant sites on the volcano's W and N flanks (Dagenham, Old Towne and Windy Hill) showed less displacement.

Table 25. Displacement vectors during April 1997-January 1998 for sites around Soufriere Hills. The site at Harris is the baseline. The Tar River vector reflects readings beginning in March 1997; the Roches Yard vector, beginning in October 1996. Courtesy of MVO.

Site Displacement (mm) Vector (degrees from grid north)
Whites 25 353
Long Ground 66 033
Hermitage 100 026
Tar River 57 030
Perches 59 049
Roches Yard 66 342
Windy Hill 15 283
Dagenham 16 077
Old Towne (M27) 19 084

New GPS sites were established on the summit of Gages Mountain and in the N part of the island at Drummond's and Blakes. A triple-prism EDM reflector was installed on the remnant of Peak B, a piece of the crater wall between Tuitt's and Mosquito Ghauts. The reflector was installed less than 100 m from the dome's N limit and, along with the new GPS sites, will monitor the N flanks.

Environmental monitoring. Results from diffusion tubes revealed slightly elevated SO2 levels (11.5 ppb) at St. George's Hill. On 24 January new tubes were placed at various sites on the W side of island. Geochemical sampling showed that all samples had3) at the CPS site (~7 km NNW of the volcano), presumably due to human activity in this area.

Report on the 26 December dome collapse. The collapse occurred early on 26 December 1997 after the very rapid dome growth that followed the explosive phase of September-22 October 1997 (BGVN 22:09-22:11). Dome growth within the explosion crater and large lobes extruding N and S formed a large dome over the Galway's Wall attaining a summit elevation of 1,020 m (figure 38), the greatest dome height since the eruption began. Seismic activity was generally low but a hybrid swarm beginning at 1430 on 24 December merged to continuous tremor a few hours before the collapse.

Figure (see Caption) Figure 38. Cross-section of the Galway's Wall area prior to and after the 26 December dome collapse. "A" is presented as a reference point on figure 39. "Before" information is based on survey data from 23 November and 8 December as well as from video and photographs. "After" is based on information from video and photographs. Courtesy of MVO.

The slope failure and dome collapse occurred at about 0300 and lasted ~15 minutes. Seismic evidence provided information on the duration of the event and the timing of specific phenomena, but reconstruction of the event has been done chiefly by evaluating deposits, changes in dome and flank morphology, and changes due to material transportation processes.

The event included a debris avalanche from the Galway's Wall and Galway's Soufriere areas and the consequent collapse of a destabilized portion of the lava dome (figures 38 and 39). The debris avalanche moved down the SW flank following the White River, leaving deposits through much of the valley; these deposits were later blanketed by pyroclastic-flow deposits. A portion of the material may have reached the ocean, generating a small tsunami (BGVN 22:12). The dome collapse produced pyroclastic flows and ash-cloud surges within the White River valley; a considerable volume of this material may have also reached the sea.

Figure (see Caption) Figure 39. Maps of the Galway's Wall area prior to and after the 26 December dome collapse. Both maps have the same scale and orientation. "A" is presented as a reference point on figure 37. "Before" information is based on survey data from 23 November and 8 December as well as video and photographs. "After" map is based on information from video and photographs. Courtesy of MVO.

Very intense pyroclastic surges occurred during the collapse, causing widespread devastation in the area S of Gingoes Ghaut. Some surges were associated with the main flows, but others may have been caused by explosions in the collapsing dome. A convective ash cloud generated by the pyroclastic flows and surges rose ~14.3 km and deposited fine ash over SW Montserrat.

Deposits. Five main depositional units from the 26 December event were identified (figure 40): debris-avalanche deposits, block-and-ash flow deposits, pyroclastic-surge deposits, co- ignimbrite fallout, and a possible blast deposit.

Figure (see Caption) Figure 40. Map of deposits from the 26 December dome collapse. Arrows indicate orientation of trees that were blown down. Courtesy of MVO.

A ~500 m wide, 25-70 m thick debris-avalanche deposit covered the central delta and lower reaches of the White River valley. The hummocky, orange-brown debris was poorly sorted, coarse, and blocky with an irregular bulbous ~25 m-high front. The deposit resulted from a slope failure of hydrothermally altered rocks in the Galway's Soufriere area, the lower outward flank of the Galway's Wall, and the overlying apron of fresh dome talus. Much of the material had a smoothed, heavily scoured upper surface with discontinuous remnants of pre- existing hydrothermally altered stratigraphy preserved within the deposit.

Block-and-ash deposits left by pyroclastic flows were similar to previous dome collapse flows at Soufriere Hills. They comprised dense to slightly vesicular (friable-textured) blocks in a poorly sorted, ash-rich matrix with little internal organization. The pyroclastic flows were largely confined to the White River valley, although some material spilled out at the river bend (~1.7 km from the coast) and traveled towards Morris'. The flows produced erosion features over the area between the White River valley and Morris' village. The block-and- ash deposits ponded behind and on top of the debris-avalanche deposits, filling the remainder of the White River valley to a maximum depth of 50-70 m. Block-and-ash deposits on the river delta were relatively thin (50-70 cm), broad, and flat-lying. They were poorly sorted with blocks reaching a maximum size of about 1 m (blocks >0.1 m formed ~10% of the surface).

Surge deposits associated with the collapse covered 9.1 km2 around the volcano's S flanks. Quite variable, some deposits differed markedly from previous surge deposits associated with pyroclastic-flow emplacement at Soufriere Hills. Conventional ash-cloud-surge deposits were found E of the White River valley on the delta and in the Trials area. These deposits were composed of a fine grained, ash-rich, and sandy layer (6-10 cm thick) with an underlying thin (0.5-2 cm) fines-depleted coarse sand layer. The surge deposits between the White River valley and German's Ghaut varied but the dominant facies was a 15-40 cm-thick, coarse sand/gravel fines- depleted unit. In some areas this deposit was overlain by a second fine-grained surge deposit. The coarse surge deposits largely comprised sub-angular dense dome rock and crystals with little pumiceous or friable component.

Small secondary pyroclastic-flow deposits with abundant charcoal occurred in the deep ghauts that drain the area covered by the surge deposits. One of these flows drained towards the E side of Soufriere Hills down Dry Ghaut. The thin, highly mobile flow was confined to the bottom of the ghaut (average width of 2-4 m) and extended to within 300 m of the sea. The deposit was poorly sorted and 50-70 cm thick, consisting predominantly of fine ash-rich sand.

A possible blast deposit was found on the volcano's SW flank between Gingoes Ghaut and the White River. The deposit comprised angular to sub-angular lithic clasts scattered on the surface, some up to 70 cm in diameter. The surface of the deposit was very subtly corrugated in the flow direction, suggesting a highly energetic emplacement mechanism.. This deposit was distinctly different from thinly spread 'normal' facies block- and-ash flows as it was locally only one clast thick and was completely fines depleted. Dense, fresh, angular dome rock made up most of the deposit, with small amounts of altered dome rock and sub-rounded, semi-vesicular, steely blue-gray dome rock. There was a marked lack of impact craters, bread crust-textured clast, or any ballistic blocks.

Co-ignimbrite ash covered most of the SW part of Montserrat and draped all the 26 December deposits, although heavy rains in early January altered the deposit. Near the coast in the Trials area the co- ignimbrite ash fell as accretionary lapilli, caused by incorporation of steam generated by hot material entering the ocean. The accretionary lapilli were up to 8 mm in diameter and formed a layer up to 4 cm thick. The fine-grained, crystal- rich ash was typical of ash generated from pyroclastic flows sourced from dome collapse. The co-ignimbrite ash plume reached an altitude of ~14 km and light ash fall was reported from Guadeloupe (60 km SSW), as well as St. Vincent and Bequia (both ~400 km SSW).

Temperatures determined from the various deposits several days after the eruption had values up to 293°C (table 26). The debris-avalanche deposit was mainly emplaced cold, although parts of the Galway's Soufriere and dome talus debris would have been warm at the time of incorporation into the avalanche.

Table 26. Temperature measurements for deposits from the 26 December collapse. 'PF' refers to pyroclastic flow; 'DAD', to the debris-avalanche deposit. Courtesy of MVO.

Deposit type Location Measurement depth (cm) Days after event Temp (°C)
Secondary PF Dry Ghaut 20 4 48
Secondary PF Dry Ghaut 25 4 138
Secondary PF Dry Ghaut 35 4 122
Surge White River delta 30 9 155
Surge White River delta 60 9 216
Surge White River delta 30 9 228
Surge White River delta 30 9 83
Surge White River delta 50 9 93
Fumarole White River delta 30 9 68
Surge/PF over DAD 20 13 157
Surge/PF over DAD 25 13 103
Surge/PF over DAD 60 13 293

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), c/o Chief Minister's Office, P. O. Box 292, Plymouth, Montserrat (URL: http://www.mvo.ms/).

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