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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

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

Santa Maria (Guatemala) Active lava flows, explosions, ash plumes, and ashfall during December 2022-March 2023

Reventador (Ecuador) Daily explosions, gas-and-ash emissions, crater incandescence, and block avalanches during December 2022-March 2023



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).


Santa Maria (Guatemala) — April 2023 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Active lava flows, explosions, ash plumes, and ashfall during December 2022-March 2023

The Santiaguito lava-dome complex of Guatemala's Santa María volcano has been actively erupting since 1922. The lava dome-complex formed within a large crater on the SW flank of Santa Maria that formed during the 1902 eruption. Ash explosions, pyroclastic flows, and lava flows have emerged from Caliente, the youngest of the four vents in the complex, for more than 40 years. The Caliente vent has an elevation of about 2.5 km, and the summit of Santa Maria is at about 3.7 km elevation. A lava dome that appeared within the summit crater of Caliente in October 2016 has continued to grow, producing frequent block avalanches down the flanks. Recent activity has included frequent explosions, ash plumes, and ashfall (BGVN 48:03) has persisted for this reporting period of December 2022 through March 2023, using information from Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and satellite data.

Activity during December 2022 consisted of weak-to-moderate explosions and white-to-gray and blue gas-and-steam emissions that rose 200-800 m above the crater and drifted up to 15 km SW, NW, S, W, SSW, E, SE, and N. Explosions generated ash plumes that drifted as far as 6 km W and SW. Nighttime crater incandescence was often visible above the Caliente dome, accompanied by active lava flows that mainly traveled down the W, SW, and WSW flanks each day during December, also affecting the San Isidro (W) and El Tambor (SW) drainages. Frequent block-and-ash avalanches were detected on the W, WSW, S, and SE flanks, which sometimes resulted in ash plumes that drifted up to 10 km downwind. Ashfall was reported in Finca la Mosqueta and Santa Marta (5-6 km SW) on 2 December and in Las Marías (10 km S), Viejo Palmar, and the Palajunoj area on 9 December. On 11 December the active lava flow in the San Isidro and El Tambor drainages generated some block collapses, which resulted in ash clouds that rose several hundred meters high and drifted toward the Zanjón Seco drainage (SW flank). On 13, 18, 27, and 31 December block collapses from the lava flow generated ash clouds that rose several hundred meters high and drifted toward the San Isidro drainage. The smell of sulfur was reported on 13 December to the SE of the Caliente dome and on 14 December in the Las Marías area. Ashfall was recorded in Lotación Las Marías, Santa Marta, La Florida (6 km S), and El Faro (7 km S) on 22 December, which was accompanied by the smell of sulfur. Explosions on 27 and 31 December resulted in weak ashfall in El Faro, La Florida, Santa Marta, El Viejo (11 km S), El Palmar (12 km SSW), and Lotación Las Marías.

Daily white-to-gray gas-and-steam emissions continued during January 2023, rising 300-900 m above the crater, and drifting 3.5-8 km SW, W, S, SE, and E. Weak-to-moderate explosions persisted throughout the month, generating ash plumes that rose up to 900 m and drifted E, NE, and SW. Crater incandescence in the Caliente dome, on the S flank, and at the front of the lava flow on the W and SW flanks was visible. Lava flows were often observed on the W, SW, and WSW flanks in the San Isidro and El Tambor drainages; on 19 and 23 January the active lava flow was noted in the Zanjón Seco and San Isidro drainages and the longest part of the lava flow was 4.4 km on 15 January. Weak-to-moderate block collapses and block-and-ash avalanches were recorded at the middle and front of the lava flow on the W, SW, and WSW flanks of the Caliente dome, and on the S and SE flanks, which sometimes caused ash to rise as high as 1 km altitude and disperse 3 km to the W and S (figure 135). On 7 January explosions generated ash plumes that rose to 3 km altitude and drifted SW. On 9 January ashfall was recorded over Las Marías and El Viejo Palmar. The active lava flow in the San Isidro and El Tambor drainages generated some block collapses on 11 January, which produced ash plumes that rose several hundred meters high and caused weak ashfall in El Faro, La Florida, Santa Marta, El Viejo Palmar, and Las Marías. Ashfall was recorded at Monte Carlo on 13 January, weak ashfall was reported in El Faro, La Florida, Santa Marta, El Viejo Palmar, and Las Marías on 19 January, and weak ashfall was again reported on 23 January in Monte Claro, El Faro, La Florida, Santa Marta, and El Viejo Palmar.

Figure (see Caption) Figure 135. Image of gas-and-steam emissions rising above the Caliente dome at Santa María on 13 January 2023, accompanied by block avalanches descending the flanks. Photo has been color corrected. Courtesy of INSIVUMEH (BOLETÍN VULCANOLÓGICO ESPECIAL BESAN #001-2023, Guatemala 15 de enero de 2023, 18:30 horas (Hora Local)).

Similar activity persisted during February with frequent explosions that produced white gas-and-steam and ash emissions that rose 200-700 m above the crater and drifted SW, W, SE, E, and NW. During the night and early morning, constant crater incandescence at Caliente dome was observed, in addition to incandescence from the active lava flow on the W, SW, and WSW flanks. Weak-and-moderate avalanches were visible on the S, SW, W, SE, WSW, and E flanks and in the middle and front of the lava flow, sometimes generating ash clouds that rose several hundred meters high. Explosions on 3 February expelled gas-and-ash plumes that rose to 3.2 km altitude and drifted W. On 4 February explosions were accompanied by audible rumbles heard in El Palmar; gas-and-ash plumes rose several hundred meters above the lava dome and incandescent avalanches traveled W, S, and SE on the flanks. That same day, the lava flow was reported in the Zanjón Seco and San Isidro drainages; block collapses generated ash clouds that rose several hundred meters high. Weak ashfall was reported in Monte Claro, El Faro, La Florida, Santa Marta, and El Viejo Palmar. Seismic stations registered weak-to-moderate explosions that produced gray plumes that rose to 3.3 km altitude on 8, 11, and 19 February, which generally drifted W and SW. On 9 February ash plumes that rose 800 m above the crater and extended E. Explosions and block collapses on 12 February caused ashfall in Monte Claro, El Faro, La Florida, Santa Marta, and El Viejo Palmar. During the early morning of 15 February, four explosions were detected that generated gray plumes that rose to 2.9 km altitude. Nine explosions were recorded on 16 February, which produced gray plumes and generated weak avalanches on all flanks. On 20 February weak ashfalls from explosions and block collapses were reported in Monte Claro, El Faro, La Florida, Santa Marta, and El Viejo Palmar. Measurements taken on 23 February showed that the length of the lava flow was 4.3 km long.

During March, degassing 400-800 m above the crater dispersed W, SW, S, and SE, and nighttime crater and lava flow incandescence to the WSW continued. Weak-to-moderate avalanches were reported on the S, W, SE, E, and N flanks and from the middle and front of the lava flow. The lava flow remained active on the SW, W, and WSW flanks and in the Zanjón Seco and San Isidro drainages, occasionally accompanied by block collapses that generated ash clouds up to several hundreds of meters high. Weak-to-moderate explosions persisted throughout the month, producing gas-and-ash emissions rising 500-1,000 m above the crater and drifting SW. On 19 March a gas-and-ash plume rose to 3.2 km altitude and drifted S and SE; the lava flow remained at 4.3 km long on the SW flank, according to INSIVUMEH. Additionally, strong rains in the upper part of the volcanic complex caused a lahar to descend the Cabello de Ángel drainage on the SE flank, consisting of a cement-like mixture of volcanic material and transporting tree branches of varying sizes. Small pyroclastic flows were reported during 22-23 March. Explosions on 23 March generated an ash plume that rose to 3.5 km altitude and drifted W and on 24 March ash plumes rose to 4.3 km altitude and drifted W. On 31 March explosions produced ash plumes that rose to 3.5 km altitude and drifted W, accompanied by constant avalanches on the S, SW, E, and N flanks of the Caliente dome and small pyroclastic flows.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) graph showed moderate-power thermal anomalies during the reporting period; the intensity gradually increased over January through March, and the frequency remained relatively high (figure 136). A total of 75 MODVOLC thermal alerts were issued on 40 days during December-March. Incandescent avalanches and active lava flows were also occasionally visible over the Caliente dome in Sentinel-2 infrared satellite imagery on clear weather days (figure 137).

Figure (see Caption) Figure 136. Moderate-power thermal anomalies were frequently detected at Santa María during 20 November 2022 through March 2023, as shown on this MIROVA graph (Log Radiative Power). Anomalies gradually increased in intensity beginning in January through March. Courtesy of MIROVA.
Figure (see Caption) Figure 137. Sentinel-2 infrared satellite imagery showing strong thermal activity at the Caliente dome of Santa María and incandescent avalanches and lava flows primarily on the SW and W flanks on 23 December 2022 (top left), 27 January 2023 (top right), 11 February 2023 (bottom left), and 3 March 2023 (bottom right). Clouds often covered the summit. Images rendered using bands 12, 11, 8a. Courtesy of Copernicus Browser.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).


Reventador (Ecuador) — April 2023 Citation iconCite this Report

Reventador

Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

All times are local (unless otherwise noted)


Daily explosions, gas-and-ash emissions, crater incandescence, and block avalanches during December 2022-March 2023

Volcán El Reventador, located in Ecuador, includes a 4-km-wide avalanche scarp open to the E. Recorded eruptions date back to the 16th century and have been characterized by explosive events, lava flows, ash plumes, and lahars. Frequent lahars in this region of heavy rainfall have built deposits on the scarp slope. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents. The current eruption began in July 2008 and more recently has consisted of daily explosions, ash plumes, lava flows, and block avalanches (BGVN 48:02). This report covers similar activity during December 2022 through March 2023 using daily reports from Ecuador's Instituto Geofisico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and satellite data.

During December 2022 through March 2023, IG-EPN reported daily explosions, gas-and-steam and ash plumes rising as high as 1,100 m above the crater, and frequent crater incandescence, often accompanied by incandescent block avalanches and lava flows that traveled down each of the flanks and lava flows that generally affected the NE and E flanks. On average, there were more daily explosions detected during December 2022 compared to January through March 2023, with 57 per day (table 17).

Table 17. Monthly summary of explosions and plume heights recorded at Reventador from December 2022 through March 2023. Data courtesy of IG-EPN (December 2022-March 2023 daily reports).

Month Average number of explosions per day Max plume height above the crater rim (m)
Dec 2022 57 1,000
Jan 2023 43 1,000
Feb 2023 30 1,000
Mar 2023 33 1,100

Activity during December 2022 consisted of daily explosions, ash plumes, crater incandescence, a lava flow, and occasional block avalanches, though cloudy weather often obscured clear views of the summit. There were 0-114 explosions recorded each day, in addition to long-period (LP) events and tremor emissions (TREMI). The Washington VAAC reported ash emissions that rose as high as 1.9 km above the crater during 5-6 and 12-13 December and drifted in different directions. IG-EPN also noted that gas-and-ash emissions rose 400-1,000 m above the summit and drifted S, W, NW, W, N, SW (figure 169). A lava flow was observed on the NE flank during 2-6 December and on the E flank during 9-11 December. There were six volcano-tectonic (VT) events detected during 7-8 December. Block avalanches frequently affected one, or multiple flanks, traveling 400-700 m below the crater. During 11-12 December a lava flow was reported on the NE flank.

Figure (see Caption) Figure 169. Webcam image of an ash plume rising 800 m above the crater of Reventador on 17 December 2022, accompanied by block avalanches on the flanks. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2022-351, 17 de diciembre de 2022).

Daily explosions and ash plumes continued during January 2023, with 12-96 explosions recorded each day. LP and TREMI-type events and crater incandescence were also frequently recorded on clear weather days, cloudy weather often obscured views of the summit. Gas-and-ash emissions rose 500-1,000 m above the crater and drifted W, NW, SW, N, and S. According to the Washington VAAC, ash emissions rose 688-3,750 m above the crater and drifted in multiple directions. During 31 December 2022 through 1 January 2023 nighttime crater incandescence was accompanied by block avalanches 500 m below the crater on all flanks. The lava flow continued to be observed on the NE flank during 31 December 2022 as well as during 1, 5-6, 7-9, 10-11, 16-17, 18-20, and 23-26 January. Block avalanches traveled 500-700 m from the crater throughout the month, affecting one or multiple flanks (figure 170). An ash plume was reported on 15 January that drifted S. A pyroclastic flow occurred during the morning of 29 January on the N flank.

Figure (see Caption) Figure 170. Thermal camera image showing the incandescent block avalanches (bright yellow) descending multiple flanks of Reventador on 22 January 2023. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2023-022, 22 de enero de 2023).

During February there were 12-100 daily explosions detected, along with LP and TREMI-type events. Crater incandescence persisted, in addition to block avalanches. Gas-and-ash emissions rose 200-1,000 m above the crater and drifted W, NW, NE, and N (figure 171). The Washington VAAC reported that ash emissions rose 400-2,200 m above the crater and drifted NE, NW, W, SW, SE, and N. During 1-6, 13-17, and 21-26 February incandescent block avalanches descended all the flanks 600-900 m below the crater. An active lava flow continued down the NE flank during 8-10, 14-15, 18-19, and 20-21 February. Block avalanches descended the E flank 900 m below the crater during 10-11 February. There were three VT-type events that were detected on 24 February.

Figure (see Caption) Figure 171. Webcam image of a gas-and-ash plume rising 1,000 m above the crater of Reventador on 25 February 2023. Photo has been color corrected. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2023-056, 25 de febrero de 2023).

Daily explosions, LP and TREMI-type events, crater incandescence, and block avalanches continued during March. There were 20-52 daily explosions recorded during the month. Cloudy weather often prevented clear views of the summit. Gas-and-ash emissions rose 600-1,100 m above the crater and drifted NW, W, N, NE, E, S, and SE. According to the Washington VAAC, ash emissions rose 688-1,300 m above the crater and drifted NW, W, NE, E, and SE. Block avalanches traveled down all the flanks 400-700 m below the crater during 2-3, 5-6, 8-12, 14-17, 23-24, and 30-31 March. During 6-7 March block avalanches descended all the flanks as far as 900 m below the crater, accompanied by ash emissions that rose 1,000 m above the summit that drifted W. IG-EPN reported that a lahar was detected on 6 March. During the nights of 12 and 15 March incandescent blocks moved down the S flank 400-500 m below the crater. During 20-21 March ash emissions rose 1 km above the crater and drifted S and SE (figure 172); reports from the Secretaría de Gestión de Riesgos (SGR) reported that light ashfall was observed in San Carlos and San Luis.

Figure (see Caption) Figure 172. Webcam image of a gas-and-ash plume rising Reventador on 20 March 2023. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2023-079, 20 de marzo de 2023).

Additional satellite data. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent thermal anomalies of moderate power during December 2022 through mid-January 2023, followed by a break in detected activity through late February (figure 173). During March, eight anomalies were detected intermittently throughout the month. The MODVOLC system identified a total of two thermal hotspots on 6 December 2022 and 20 March 2023. Although the summit was often obscured by weather clouds, Sentinel-2 infrared satellite images sometimes showed thermal activity at the summit crater (figure 174).

Figure (see Caption) Figure 173. Thermal activity at Reventador was more frequent during December 2022 through mid-January 2023, based on this MIROVA graph (Log Radiative Power). There was a short pause in detected activity during mid-January through late February. There were three anomalies detected during late February and eight during March. Courtesy of MIROVA.
Figure (see Caption) Figure 174. Sentinel-2 infrared satellite images of Reventador showed small thermal anomalies at the summit crater on 2 December 2022 (top left), 27 December 2022 (top right), 31 January 2023 (bottom left), and 25 February 2023 (bottom right). Though weather clouds often prevented clear views of the summit, gray ash emissions were sometimes visible above the clouds, as shown on 27 December and 25 February. Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. Volcán El Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have left extensive deposits on the scarp slope. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); 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 18, Number 03 (March 1993)

Managing Editor: Edward Venzke

Aira (Japan)

40-hour-long earthquake swarm

Arenal (Costa Rica)

Strombolian activity increases; new lava flow

Asosan (Japan)

Activity decreases; crater lake forms

Concepcion (Nicaragua)

Detailed description of crater

Deception Island (Antarctica)

Activity declines from last year's levels

Etna (Italy)

1991-93 eruption ends

Galeras (Colombia)

Three small explosions; ashfall to 65 km

Irazu (Costa Rica)

Fumarolic activity declines

Kilauea (United States)

Lava continues to flow into ocean; phreatic explosion kills one

Kozushima (Japan)

Earthquake swarm on 25 March; no surface anomalies

Langila (Papua New Guinea)

Explosions send incandescent material 80 m above summit

Las Pilas-El Hoyo Complex (Nicaragua)

Weak fumarolic activity

Manam (Papua New Guinea)

Activity continues at very low level

Masaya (Nicaragua)

Crater walls stabilizing

Mayon (Philippines)

Strombolian eruption; activity wanes

Momotombo (Nicaragua)

Small gas plume

Negro, Cerro (Nicaragua)

No fumarolic activity; vegetation recovers from 1992 eruption

Niijima (Japan)

Earthquake swarm on 23 March; no surface anomalies

Pagan (United States)

Banded tremor; increased ash eruptions

Poas (Costa Rica)

Gas columns to 500 m; gradual deflation

Rabaul (Papua New Guinea)

Seismic activity increases; no significant surface deformation

Raoul Island (New Zealand)

Tectonic earthquake swarm; strongest swarm since 1964

Rincon de la Vieja (Costa Rica)

Hour-long earthquake swarm

San Cristobal (Nicaragua)

Gas plume; little evidence of acid rain

Sheveluch (Russia)

Activity increasing; steam and ash explosions

Suwanosejima (Japan)

Sporadic, weak ash eruptions

Telica (Nicaragua)

No observed activity

Ulawun (Papua New Guinea)

Activity continues at low level

Unzendake (Japan)

Dome 11 extruded; endogenous dome growth deforms old crater rim



Aira (Japan) — March 1993 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


40-hour-long earthquake swarm

Explosions continued . . . in March (19 total) . . . . A 40-hour-long swarm of B-type earthquakes occurred on 8-10 March. The highest ash plume of the month, 4,000 m above the crater, resulted from an explosion at 1004 on 5 March.

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: JMA.


Arenal (Costa Rica) — March 1993 Citation iconCite this Report

Arenal

Costa Rica

10.463°N, 84.703°W; summit elev. 1670 m

All times are local (unless otherwise noted)


Strombolian activity increases; new lava flow

Gas emission and lava flows continued from Crater C. Both the number and magnitude of Strombolian eruptions increased from January and February levels. Some eruptions caused vibration of windows at the Macadamia Biological Observatory (2.7 km S) and ballistic bombs reached the 1,000-m elevation on the flanks.

The more-SW lava flow that was active last month advanced over a grassy field and stopped at 760 m elevation. A new flow descended SW, following the same route as the December 1992 flow. At 1,350 m elevation it divided; one lobe went W, reaching 1,100 m elevation, while the other traveled SW to 1,200 m elevation. Another lava flow moved down the SSW flank to 1,450 m elevation. At 0920 on 31 March, gravitational failure of this flow produced numerous small avalanches falling to 750-850 m elevation. On 23 March at 1930 a pyroclastic flow descended SE to 1,100 m elevation.

Seismic activity remained normal. An average of 40 earthquakes/day were recorded by ICE (figure 53), a slight increase from last month. A seismometer operated by UNA, 2.7 km NE of the main crater, registered a total of 465 explosions and 226.5 hours of tremor during 13-31 March (figure 54. The dominant frequencies of these events were 1.5-2.3 Hz. During 28-30 March the tremor increased, becoming continuous for a 24-hour period. The highest daily total of explosions for the month occurred on 16 March, the fewest on 30 March. Fumaroles near the summit continued to emit sulfur gases and water vapor. Explosions were accompanied by decreased gas emission.

Figure (see Caption) Figure 53. Earthquakes/day recorded at Arenal during March 1993. Courtesy of ICE.
Figure (see Caption) Figure 54. Hours of tremor/day (top) and events/day (bottom) recorded 2.7 km NE of the summit of Arenal during 13-31 March 1993. Courtesy of OVSICORI.

The slight inflationary trend seen at most of the dry-tilt stations stopped. Occasional slight deflation occurred at dry-tilt sites Ferreto (3 km SW of summit) and Cedeño (4 km NW of summit). EDM lines on the S and W contracted in March.

Geologic Background. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. An eruptive period that began with a major explosive eruption in 1968 ended in December 2010; continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows characterized the eruption from vents at the summit and on the upper western flank.

Information Contacts: G. Soto and R. Barquero, ICE; E. Fernández, J. Barquero, V. Barboza, T. Marino, R. Van Der Laat, F. de Obaldía, and R. Sáenz, OVSICORI.


Asosan (Japan) — March 1993 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Activity decreases; crater lake forms

Activity in March and early April was lower than in previous months. Rain created a small lake in part of Crater 1. On roughly half of the March visits, mud and blocks were seen being ejected a few meters above the lake. A white steam plume continually rose 200-500 m; it contained a minor amount of ash on 7 March. Seismic activity was low.

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

Information Contacts: JMA.


Concepcion (Nicaragua) — March 1993 Citation iconCite this Report

Concepcion

Nicaragua

11.538°N, 85.622°W; summit elev. 1700 m

All times are local (unless otherwise noted)


Detailed description of crater

"On 10 January geologists climbed Concepción in unusually clear conditions, allowing a survey of the summit crater (figure 2). The crater is almost circular, 300 m in diameter and about 250 m deep. The upper part has a funnel shape, which descends into a pit crater. The N and E sides have a break in slope half way down; the SW side is a vertical cliff. This cliff is the head scarp of a landslide that fell into the crater in December 1992, forming a 100-m-wide scree slope infilling part of the pit crater. A 30-m-wide elliptical area plastered with yellow sulfur and containing two small sulfur mounds is at the lowest point.

Figure (see Caption) Figure 2. Map of the crater area of Concepción volcano made from observations 10 January 1993. Contours are approximate and represent height below the summit (about 1,700 m above sea level). The white area within the older crater rim contains pyroclastic deposits. Courtesy of B. van Wyk de Vries.

"The summit morphology and crater shape have changed considerably since the pre-1957 eruption topographic map, which shows a broad 600-m-wide summit plateau with a 200-m-diameter crater. Now the summit is marked by a steep cone with a slope of 30-40°, and a knife-edged crater rim. Altered red lava below 1957 pyroclastics in the deep gullies to the W probably represent the pre-1957 surface and indicate that the present summit is 50-100 m higher than the spot height of 1,610 m surveyed before the 1957 eruption. If this interpretation is correct, Concepción could be the highest volcano in Nicaragua.

"Lava flows exposed in the crater walls and on the W flank are associated with copious semi-welded and welded pyroclastics and breccia. A prominent thick dyke on the NE side of the crater has the same strike as one of the historical lava flows, which it appears to have fed. Fractures running at 20°N cut the crater bottom near the sulfur mounds and on the N and SW walls. The strike is similar to fractures observed on the SW flank of the volcano, which are responsible for the formation of the deep SW gully. Other fractures in the crater are N-oriented (figure 2), some extending as far as the N flank of the cone, where they have fumarolic activity. These fumaroles are visible from the base of the volcano and have been periodically observed since 1986. Fumarolic areas with yellow-grey sulfur are also found around the crater walls. The most active fumaroles, however, are at the base of the pit crater, either on the sulfur mounds or along the 20°N-oriented fissures. Two moderate fumarolic areas with yellow-gray sulfur are on the S and W walls. No glow was observed from the crater rim, suggesting that no large high-temperature fumaroles were present.

"A local fireman reported ashfall on Alta Gracia (about 5.5 km NE of the summit) in December 1992, and a plume was reported during the same month. These phenomena were probably caused by the crater landslide. Vegetation, almost exclusively 'Sombrilla del Pobre' (Nostoc Gunnera) has begun to re-colonize the upper 200 m of the cone, which was bare in 1990, thus gas and ash emissions have been considerably lower than in the 1980's. However, analyses by Warren Spring Laboratory, UK, of SO2 diffusion tubes placed in the garden of a house in Esquipulas, 8 km E of the volcano, recorded an average SO2 concentration of 60 g/m3, indicating that gas emissions from the crater were sufficient to cause mild fumigation of populated areas downwind.

"Lahars continue to form during rainstorms, with the main loci of activity being the SW gully and the N flank. The road N of the volcano was cut by a lahar in late 1992. Erosion remains rapid on higher slopes, where some gullies had widened by 2-5 m since 1990. The 1957/74 pyroclastic deposits are especially vulnerable to erosion and gully headwalls have almost intersected the crater rim to the N, W, and SW in the last two years. Rapid erosion of these deposits probably constitutes much of the source for the laharic material to the N and W of the cone. The towns of San Jose del Sur (6.2 km SSW), San Marcos (5.6 km NNW), and La Flor (5.3 km NW) are in a particularly dangerous situation because they are in the paths of lahars descending these gullies. The fracture system in the crater walls could be a potential conduit for a future lava eruption that would flow toward the town of San Jose del Sur."

Geologic Background. Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the N flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.


Deception Island (Antarctica) — March 1993 Citation iconCite this Report

Deception Island

Antarctica

62.9567°S, 60.6367°W; summit elev. 602 m

All times are local (unless otherwise noted)


Activity declines from last year's levels

Activity has declined from the more vigorous behavior seen during the 1991-92 survey to levels recorded during earlier surveys. Only 135 seismic events (M 0.3-0.9) were recorded compared to the 766 events detected during the 1991-92 survey. Episodes of tremor in the NW sector of the island were recorded on 1 January, 2 February, and 16 February 1993. Five deep (55-85 km) earthquakes, M 1.6-2.4, were detected.

Fumaroles emitted mainly CO2 (87-98%) and H2S (1.8-13%); no SO2 was detected. Dry-tilt measurements of 600 µrads uplift at Fumarole Bay indicated a slight elevation of the entire fumarolic area. Temperature measurements made by the Spanish Oceanographic Ship "Hespérides" showed a decrease in the intensity of the submarine emissions in Port Foster Bay since the 1990-91 survey.

Geologic Background. Ring-shaped Deception Island, at the SW end of the South Shetland Islands, NE of Graham Land Peninsula, was constructed along the axis of the Bransfield Rift spreading center. A narrow passageway named Neptunes Bellows provides an entrance to a natural harbor within the 8.5 x 10 km caldera that was utilized as an Antarctic whaling station. Numerous vents along ring fractures circling the low 14-km-wide island have been reported active for more than 200 years. Maars line the shores of 190-m-deep Port Foster caldera bay. Among the largest of these maars is 1-km-wide Whalers Bay, at the entrance to the harbor. Eruptions during the past 8,700 years have been dated from ash layers in lake sediments on the Antarctic Peninsula and neighboring islands.

Information Contacts: R. Ortiz, Museo Nacional de Ciencias Naturales, Spain; C. Risso, Instituto Antártico Argentino.


Etna (Italy) — March 1993 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


1991-93 eruption ends

The following, based on the report of the IIV, describes activity in March.

The 1991-93 eruption ended on March 30 after 473 days of continuous lava flows. Lava stopped flowing to the S side of the flow field in mid-February, but continued to flow from several vents at 1,700-1,650 m elevation on the N side of the field, covering previous flows from the current eruption. Shortly after 8 March, an overflight revealed a thin flow that had traveled 0.5 km from an ephemeral vent at 2,020 m elevation. On 11 March a large lava flow moved toward the Valle del Bove over an area not yet covered during this eruption. Flowing 1.5 km from a large ephemeral vent at the end of a tube at 1,550 m elevation, lava spread down some gullies, stopping after 3 days at 1,390 m elevation, 5 km from the eruptive fissure (figure 59).

Figure (see Caption) Figure 59. Topographic sketch map of the active portion of the 1991-93 lava flow field; 1. Flow field formed after 27 May 1992 through March 1993; 2. Flow field before 27 May 1992; 3. Limit of active flows through February 1993 ; 4. Directions of the main active lava flows in March 1993; 5. Lava tube. Courtesy of IIV.

Lava flows declined in the second half of March. On 21 March a vigorous flow emerged from a vent at 1,850 m elevation and traveled several hundred meters NE in a few hours before slowing and finally stopping within two days. The remaining ephemeral vents gradually disappeared and the last small lava flow was observed on the morning of 30 March. In the following days, fieldwork at the eruptive fissure and along the upper lava tube revealed that no molten lava remained in the tube and that the delivery system was cooling.

Steady degassing continued through March at the summit craters. The floor of Northeast crater dropped another several meters. Seismicity remained low, especially from 1-10 March. For the month, 65 long-period events and 8 volcano-tectonic events (maximum M 2.4) were recorded. The only notable swarm occurred on 28 March when 10 events were recorded in two minutes. There were no significant variations in the volcanic tremor amplitude. Four of the 9 bore-hole tiltmeters recorded a sharp deformation event of moderate amplitude at the beginning of March.

The 1991-93 eruption began on 15 December 1991 and lasted 473 days. It was probably the largest eruption at Etna in the last 300 years, covering ~ 7 km2 with >250 million m3 of lava.

The following information compiled by volcanologists at the IIV, Univ di Catania, and OV complements the official IIV report above.

The lava flow that had reached 1,400 m elevation on 14 March (18:02) stopped on 17 March. At about 1700 on 21 March a modest lava flow escaped through a skylight on the main lava tube just below 2,000 m elevation. It was accompanied by intense degassing from the upper part of the eruptive fissure. Through 25 March lava was observed flowing inside the main vent at 2,205 m and small, short-lived flows issued from ephemeral vents in the N part of the lava field at ~ 1,900 m elevation. Poor weather prevented detailed observation of the last days of the eruption.

Degassing (vapor and gas) from the upper part of the eruptive fissure declined. By 20 March it was difficult to observe from a distance. Degassing increased at the summit craters (especially from the central crater) during the final phase of the eruption. Through 9 April, the NE crater, where recent rockfalls had occurred, continued to be obstructed and weak fumarolic activity was present along the walls. COSPEC measurements of SO2 flux revealed a sharp increase during the last half of March (>16 x 103 t/d on 23 March). Measurements in April indicated the flux was returning to a normal level of 6-8 x 103 t/d.

From 16 March to 19 April, 337 seismic events were recorded. They ranged from M 1.0-3.0 and showed characteristic frequencies of 1-6 Hz. All were located in the summit crater region except a M 2.7 at 0649 on 14 April that was located low on the E flank. Volcanic tremor was totally absent.

During the 1991-93 eruption an estimated 300 x 106 m3 of lava flowed from the fissure on the W wall of Valle del Bove at an average rate of 7.3 m3/s.

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

Information Contacts: The first section is from the official report of theIIV. The second section is fromR. Romano, T. Caltabiano, M. Grasso, and M. Porto, IIV; P. Carveni and C. Monaco, Univ di Catania; G. Luongo, OV.


Galeras (Colombia) — March 1993 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Three small explosions; ashfall to 65 km

Small eruptions occurred on 23 March, 4 April, and 13 April. The seismic signal associated with the pyroclastic eruption at 2239 on 23 March (VEI 1) lasted 12 minutes, saturating the seismic network for 90 seconds. The eruption produced a column calculated to have been 8 km high, and ejected >8.35 x 105 m3 of material. About 6.35 x 105 m3 of ejecta went W and ashfall was noted 65 km from the volcano. Approximately 2 x 105 m3 of projectiles, some as large as 90 cm in diameter, fell within a 2 km radius of the vent and destroyed the communications station on the caldera rim, approximately 700 m from the active crater. Two policemen in the station at the time of the event were not injured. Incandescent ballistics and lightning were seen from Pasto and a loud roar was heard, but no shock wave was felt. During the 10 hours following the eruption, 445 seismic events, both long-period and tremor, were recorded. The mechanical characteristics of the eruption appeared to be the same as those for the July 1992 eruption; obstruction of the conduit at depth and subsequent explosion because of overpressurization.

Overflights of the crater after the eruption revealed a reactivation of circular and radial fractures associated with collapses on the border of the active crater. New craters and associated fumarolic activity were also noted. In the weeks prior to the eruption, SO2 flux was low, 37-81 t/d. Following the eruption, the SO2 flux rose to 800 t/d on 24 March, but then declined to 581 t/d on 26 March and to 132 t/d by 29 March.

Forty-two screw-type seismic events were recorded in March. They were located slightly W of the active crater at depths between 0.2 and 1.0 km. The dominant frequency for individual events ranged from 2.35 to 4.00 Hz, and the durations were between 22 and 185 seconds. The event lasting 185 seconds occurred on 12 March and had a dominant frequency of a 2.9 Hz.

An eruption at 1603 on 4 April produced a 5-km high ash column. The eruption was smaller than others this year and no ballistics fell outside the active crater. The seismic network recorded the eruption as a long-period event lasting 123 seconds, saturating the network for only 17 seconds. There were no precursors. After the eruption, SO2 flux was ~200 t/d, but fell to 100 t/d by the next day. Through 7 April, SO2 flux remained low and the amplitude and duration of long-period events declined.

An ash eruption at 0321 on 13 April lasted 140 seconds and saturated the seismic network for 33 seconds. An increase in gas emissions was noted later that morning during an overflight. Recorded in the preceding week were two small episodes of tremor, occasional screw-type events and a swarm of small, strongly impulsive seismic events.

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

Information Contacts: M. Calvache, INGEOMINAS, Pasto; T. Fischer and D. Lescinsky, Arizona State Univ; J. Ewert and A. Lockhart, USGS.


Irazu (Costa Rica) — March 1993 Citation iconCite this Report

Irazu

Costa Rica

9.979°N, 83.852°W; summit elev. 3436 m

All times are local (unless otherwise noted)


Fumarolic activity declines

Fumarolic activity in the N and NW portions of the crater decreased and the lake remained green. Lake temperature varied depending on the sampling site. ICE volcanologists measured 14°C at the surface, 17°C near the bottom, and 24°C near subaqueous fumaroles. UNA volcanologists measured 40°C near fumaroles and 24°C near the center of the lake. Lake level fluctuated 10-15 cm depending on rainfall, with smaller daily variations. Collapses continued from the E and SE crater walls.

Major fumaroles in the NW portion of the crater had temperatures of 91-92°C. No change was evident in the acidity or temperature of springs around the volcano. Dry-tilt measurements at the summit continued to indicate deflation through March. Areal dilatation has continued to decline, with decreases similar to those since September.

Geologic Background. The massive Irazú volcano in Costa Rica, immediately E of the capital city of San José, covers an area of 500 km2 and is vegetated to within a few hundred meters of its broad summit crater complex. At least 10 satellitic cones are located on its S flank. No lava effusion is known since the eruption of the Cervantes lava flows from S-flank vents about 14,000 years ago, and all known Holocene eruptions have been explosive. The focus of eruptions at the summit crater complex has migrated to the W towards the main crater, which contains a small lake. The first well-documented eruption occurred in 1723, and frequent explosive eruptions have occurred since. Ashfall from the last major eruption during 1963-65 caused significant disruption to San José and surrounding areas. Phreatic activity reported in 1994 may have been a landslide event from the fumarolic area on the NW summit (Fallas et al., 2018).

Information Contacts: G. Soto and R. Barquero, ICE; E. Fernández, J. Barquero, V. Barboza, T. Marino, R. Van Der Laat, F. de Obaldía, and R. Sáenz, OVSICORI.


Kilauea (United States) — March 1993 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Lava continues to flow into ocean; phreatic explosion kills one

The . . . eruption continued as lava from E-51 and 53 vents fed several channelized flows that descended from Pulama Pali. Flows on the Kamoamoa delta entered the ocean on 2 March while a flow near Laeapuki (~750 m W of the Kamoamoa delta) stagnated within 30 m of the Chain of Craters Road. Breakouts on 5 March began covering new land E of the delta, including nearly 200 m of the Chain of Craters Road. By 15 March, much of the Kamoamoa delta had been resurfaced by new flows and lava was entering the ocean on the E and W sides of the delta. More flows cascaded over Paliuli on 13 March and advanced towards Chain of Craters Road N of Laeapuki. On 28 March, the Laeapuki flow cascaded over Paliuli W of the Kamoamoa flows, crossed Chain of Craters Road and entered the ocean (figure 88). The Laeapuki flow inflated rapidly creating a hummocky, tumuli-covered surface. Lava continued to enter the ocean at Laeapuki and on the E and W sides of the Kamoamoa delta through 12 April. Small blocks of Laeapuki bench collapsed into the ocean on 11 April.

A new collapse pit, containing lava, formed in late February halfway up Pu`u `O`o cone from the E-51 vent (figure 89). In the first half of March the spatter cone at the E-53 vent collapsed to half its original height. On 18 March, a vigorous flow broke out of the E-51 lava tube between the 51 and 53 vents, filling most of the 52 collapse area before it stopped.

Figure (see Caption) Figure 89. Map of the active vent area on the East rift zone of Kīlauea, March 1993. Courtesy of HVO.

On 26 February the crater floor of Pu`u `O`o was 59 m below the crater rim. In late March, the floor was 4 m lower and the lava pond fluctuated 1-14 m below that. During early April the lava pond fluctuated from 73-77 m below the rim.

The summit of Kīlauea continued to deflate until 5 March, when it reached the low recorded during last February's earthquake swarm . . . . From 5 to 15 March, the summit water-tube tiltmeter recorded ~7 µrad WNW inflation. This trend continued until about 20 March. During 20-27 March, the tiltmeter recorded almost 20 µrad deflation, surpassing the low of 5 March. After some reinflation, no significant changes occurred 30 March-12 April.

Tremor amplitudes recorded by a station near Pu`u `O`o were 2-3x background. Microearthquake activity continued at low rates beneath the summit and at low-to-average rates along the East rift.

At approximately 2100 on 19 April, a group of as many as 20 people ventured into a restricted area near Laeapuki to observe lava flowing into the ocean. A lava bench on which they were standing collapsed, causing the group to flee. The collapse was followed by three distinct earthquake-like events and the sudden explosion of a lava tube that had filled with ocean water. The explosion threw 35-cm-diameter rocks as far as 170 m inland. One man did not attempt to leave the initial collapse area and was last seen falling into the ocean. This is the first known death attributable to explosive volcanic activity at Kīlauea since 1924. Others in the group sustained 3rd-degree burns and serious abrasions caused by falling incandescent rock and hot ocean water. No one was seriously hurt by the large bombs.

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: T. Mattox and D. Clague, HVO; Hawaii Volcanoes National Park.


Kozushima (Japan) — March 1993 Citation iconCite this Report

Kozushima

Japan

34.219°N, 139.153°E; summit elev. 572 m

All times are local (unless otherwise noted)


Earthquake swarm on 25 March; no surface anomalies

. . . On 25 March, a swarm occurred at Kozu-shima island, ~20 km SW of Nii-jima. The largest event was M 3.9. No surface anomalies, onshore or offshore, were observed . . . .

Geologic Background. A cluster of rhyolitic lava domes and associated pyroclastic deposits form the 4 x 6 km island of Kozushima in the northern Izu Islands. The island is the exposed summit of a larger submarine edifice more than 20 km long that lies along the Zenisu Ridge, one of several en-echelon ridges oriented NE-SW, transverse to the trend of the northern Izu arc. The youngest and largest of the 18 lava domes, Tenjosan, occupies the central portion of the island. Most of the older domes, some of which are Holocene in age, flank Tenjosan to the north, although late-Pleistocene domes are also found at the southern end of the island. A lava flow may have reached the sea during an eruption in 832 CE. The Tenjosan dome was formed during a major eruption in 838 CE that also produced pyroclastic flows and surges. Earthquake swarms took place during the 20th century.

Information Contacts: JMA.


Langila (Papua New Guinea) — March 1993 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)


Explosions send incandescent material 80 m above summit

"Eruptive activity . . . remained at a moderate-to-strong level during March. Crater 2 continued to release white-grey ash-laden vapour at a moderate-to-strong rate and occasional thick dark grey-to-brown ash clouds. These emissions were accompanied by weak-to-loud explosion noises. From the 23rd until the end of the month, continuous dark grey ash clouds rose several hundred meters above the summit. Fine ashfall was reported downwind (SE). These emissions were accompanied by weak explosions and rumbling noises. The summit area was cloud-covered on most nights during the first half of the month. However, incandescent Strombolian projections were visible on the 4th and 5th. On 15, 19-20, and after 23 March until the end of the month, steady weak to occasional bright fluctuating glow was visible. Incandescent Strombolian projections up to 80 m above the summit were seen on the 27th and 29th.

"Activity at Crater 3 was mild during the month, with weak-to-moderate emissions of white and blue vapour accompanied by the occasional forceful ejection of moderate-to-thick dark grey ash clouds rising several hundred meters above the summit. During the last 3 weeks of the month the emissions were accompanied by occasional weak explosion noises. Night glow and incandescent projections were seen on 15, 16, and 19 March. "A slight increase in seismicity during the month was recorded by the seismograph 9 km N of the volcano. About 200 Vulcanian explosion earthquakes were recorded during the month with the highest daily total of 24 events on both the 23rd and 24th."

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: H. Patia, R. Stewart, and C. McKee, RVO.


Las Pilas-El Hoyo Complex (Nicaragua) — March 1993 Citation iconCite this Report

Las Pilas-El Hoyo Complex

Nicaragua

12.4922°N, 86.6786°W; summit elev. 1088 m

All times are local (unless otherwise noted)


Weak fumarolic activity

El Hoyo's main fumarole was emitting vapor at usual levels on 6-7 January.

Geologic Background. Las Pilas-El Hoyo volcanic complex, overlooking Cerro Negro volcano to the NW, includes a diverse cluster of cones within about a 3-km-diameter area. A N-S-trending fracture system cutting across the edifice is marked by numerous flank vents, including maars, that are part of a 30-km-long volcanic massif. The Cerro Negro chain of cinder cones is listed separately in this compilation because of its extensive historical eruptions and possible distinct magmatic system. The lake-filled Asososca maar is located adjacent to the Cerro Asososca cone on the southern side of the fissure system, south of the axis of the Marrabios Range. Two small maars west of Lake Managua are located at the southern end of the fissure. Aside from a possible eruption in the 16th century, eruptions of Las Pilas took place in the 1950s from a fissure that cuts the eastern side of the 700-m-wide crater and extends down the N flank.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.


Manam (Papua New Guinea) — March 1993 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)


Activity continues at very low level

"Activity . . . continued at a very low level throughout March. During the month's first and last weeks, when the summit area was clear, emissions from both craters consisted of thin white vapours being released at a weak-to-moderate rate. No night glow was reported. There was a report of acid rainfall 12 March on the upper slopes SE of the summit. Seismicity throughout March consisted of discontinuous low-amplitude tremor and small low-frequency events. Tilt measurements showed no trends."

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: H. Patia, R. Stewart, and C. McKee, RVO.


Masaya (Nicaragua) — March 1993 Citation iconCite this Report

Masaya

Nicaragua

11.9844°N, 86.1688°W; summit elev. 594 m

All times are local (unless otherwise noted)


Crater walls stabilizing

"Masaya's Santiago crater, visited on 7 and 13-14 January, contains a few weak fumaroles on the rim of the 1989 vents and on the wall adjoining the Nindirí crater. The crater walls have stabilized since the 1989/90 collapses, and there is now little rockfall activity. Vegetation is beginning to colonize the crater walls."

Geologic Background. Masaya volcano in Nicaragua has erupted frequently since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold" until it was found to be basalt rock upon cooling. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of observed eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Recent lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.


Mayon (Philippines) — March 1993 Citation iconCite this Report

Mayon

Philippines

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

All times are local (unless otherwise noted)


Strombolian eruption; activity wanes

Lava fountaining began on 21 March after almost 2 months of intermittent precursors, including a small, but deadly, phreatomagmatic eruption on 2 February. Following the 2 February eruption, sluggish and intermittent production of lava continued until 19 March when its extrusion rate increased. Several tens of small collapse-type pyroclastic flows on both 19 and 20 March resulted from portions of the flow front detaching and rolling down the steep upper slopes of the volcano. On the night of 21 March, lava fountaining to heights of several hundred meters began, forming a small cone at the head of Bonga Gully where it descends from the summit crater. Most of the lava fell back into the crater and around the vent, but eventually flowed SSE down Bonga Gully. By 26 March the flow front was 4.5 km from the summit, and the estimated volume of lava extruded was 60 x 106 m3, more than half the volume of the 1984 flow. Ash-bearing steam clouds from the fountains rose 2-3.5 km above the crater and deposited a few millimeters of ash on nearby towns. This was less ash than resulted from the pyroclastic flows, which stopped when fountaining began.

The fountaining episodes typically lasted 20 minutes; the longest lasted 50 minutes. They were separated by repose periods lasting 30 minutes to 1 hour. Some episodes were followed by 10-20 minutes of intermittent 2-Hz tremor, the amplitude of which varied greatly suggesting that each tremor episode consisted of a series of tremor events. The tremor did not correlate with any visible steaming. Continuous, strong gas jets, glowing "like a blowtorch" and emitting a continuous "jet plane sound," were visible from Legazpi city, 14 km SE of the summit. They appeared to be in the summit crater, 100-200 m upslope from the vent.

COSPEC measurements of SO2 flux increased from 4,000 metric tons/day (t/d) on 1 March, to 5000 t/d on 24 March. On 26 March, the SO2 flux measured in the morning was 3,920 t/d rising to 7,600 and 8,800 t/d in the afternoon (two sets of measurements).

By 2 April, lava fountaining had ceased, and little or no new material was feeding the flow. Seismicity was low to moderate and dominated by small explosion-type earthquakes. Ash puffs were rare and weak. A single small pyroclastic flow occurred on 1 April, originating in the crater. The glow from the crater persisted, but was considerably dimmer and the gas jets burning in the crater had disappeared. However, SO2 emission remained high and variable, 3,000-8,000 t/d, and the volcano was not deflating.

The lava flow front, still about 5.4 km from the vent, was not expected to advance much farther, having moved only a few meters on 1 April. The flow was confined to Matanag Gully except for a small finger that reached the lower Bonga Channel. Lateral levees and pressure ridges were well defined.

On 9 April a dirty-white steam plume rose only 50 m above the crater rim. At night, a faint glow from the crater was visible. Small "explosion-type" earthquakes, continued; 57 were detected in the 24-hour period beginning at 1700 on 8 April. Most, however, were associated with incandescent materials detaching from the lava deposits in the Bonga Gully. The rate of SO2 emission was 2,272 t/d.

More than 45,000 people fled their homes during the early stages of the eruption, from 2 February to 19 March, filling 43 evacuation centers. An additional 12,000 evacuated their homes as the eruption entered its Strombolian phase on 19-21 March. Since the 2 February event, which killed 75 people, no deaths directly attributable to the eruption have been reported.

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

Information Contacts: PHIVOLCS; Chris Newhall, USGS; Reuters.


Momotombo (Nicaragua) — March 1993 Citation iconCite this Report

Momotombo

Nicaragua

12.423°N, 86.539°W; summit elev. 1270 m

All times are local (unless otherwise noted)


Small gas plume

A small gas plume was present on 6-7 January, with no apparent change from previous years.

Geologic Background. Momotombo is a young stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows extend down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms an island offshore in Lake Managua. Momotombo has a long record of Strombolian eruptions, punctuated by occasional stronger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after a 10 April 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the south flank.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Cambridge, England.


Cerro Negro (Nicaragua) — March 1993 Citation iconCite this Report

Cerro Negro

Nicaragua

12.506°N, 86.702°W; summit elev. 728 m

All times are local (unless otherwise noted)


No fumarolic activity; vegetation recovers from 1992 eruption

"No sign of fumarolic activity was seen when the base of Cerro Negro was visited on 6 January. Predictions that the farming area between Cerro Negro and the city of León (18 km WSW), would be devastated by the ashfall of April 1992 (about 4 cm of ashfall) had fortunately not been fulfilled. Fields >2 km from the volcano were cultivated again after the April 1992 event and farmers were expecting good harvests. Wild vegetation appeared healthy and had regrown to original levels. A few large trees close to the volcano appeared to have died after the eruption."

Geologic Background. Nicaragua's youngest volcano, Cerro Negro, was created following an eruption that began in April 1850 about 2 km NW of the summit of Las Pilas volcano. It is the largest, southernmost, and most recent of a group of four youthful cinder cones constructed along a NNW-SSE-trending line in the central Marrabios Range. Strombolian-to-subplinian eruptions at intervals of a few years to several decades have constructed a roughly 250-m-high basaltic cone and an associated lava field constrained by topography to extend primarily NE and SW. Cone and crater morphology have varied significantly during its short eruptive history. Although it lies in a relatively unpopulated area, occasional heavy ashfalls have damaged crops and buildings.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.


Niijima (Japan) — March 1993 Citation iconCite this Report

Niijima

Japan

34.397°N, 139.27°E; summit elev. 432 m

All times are local (unless otherwise noted)


Earthquake swarm on 23 March; no surface anomalies

A weak earthquake swarm occurred 23 March in the N part of Nii-jima island. The earthquakes, M 1.9 maximum, were located both onshore and offshore. . . . No surface anomalies, onshore or offshore, were observed . . . .

Geologic Background. The elongated island of Niijima, SSW of Oshima, is 11 km long and only 2.5 km wide. Eight low rhyolitic lava domes are clustered in two groups at the northern and southern ends of the island, separated by an area of flat-topped domes and a low isthmus of pyroclastic deposits. The Mukaiyama complex on the south and the Atchiyama lava dome on the north were formed during eruptions in the 9th century CE, the last known activity. Shikineyama and Zinaito domes form small islands immediately to the SW and W, respectively, during earlier stages of volcanism. Earthquake swarms occurred during the 20th century.

Information Contacts: JMA.


Pagan (United States) — March 1993 Citation iconCite this Report

Pagan

United States

18.13°N, 145.8°E; summit elev. 570 m

All times are local (unless otherwise noted)


Banded tremor; increased ash eruptions

The number of reports of ash columns above North Pagan . . . has increased since the beginning of the year. A 168-km-deep Benioff-zone earthquake (Mb 5.7) occurred at 0118 GMT on 18 January with an epicentral location (18.38°N, 145.71°E) ~40 km N of Pagan. In January 1982, three earthquakes, 500-600 km deep, in the vicinity of Pagan preceded eruptive activity (8:2), and it is speculated that the January 1993 event affected the behavior of the volcano.

Columns rising to 2,000 m above the summit were observed in mid-January and on 17 March. It is thought that other, unobserved eruptive events have also occurred. A distinct change in seismic activity took place on about 13 February. Before then, the seismicity consisted of 12-24 long-period events/day, each lasting 30-60 seconds. The dominant frequency of the events was 2-5 Hz and their amplitude was 2-3x background. Occasional small ash columns to 30 m were observed. Since mid-February, there have been frequent reports of intermittent ash eruptions, and banded tremor has been recorded at 10x background levels. The tremor episodes last 30 minutes to an hour, and are separated by 1-2 hour intervals of relative quiet. Though battery problems at the solar-powered seismic station prevent recording of activity when there is insufficient sunlight, the banded tremor has been consistently recorded when the station was functioning. It is speculated that the frequent ash emissions are associated with the tremor episodes.

Geologic Background. Pagan Island, the largest and one of the most active of the Mariana Islands volcanoes, consists of two stratovolcanoes connected by a narrow isthmus. Both North and South Pagan stratovolcanoes were constructed within calderas, 7 and 4 km in diameter, respectively. North Pagan at the NE end of the island rises above the flat floor of the northern caldera, which may have formed less than 1,000 years ago. South Pagan is a stratovolcano with an elongated summit containing four distinct craters. Almost all of the recorded eruptions, which date back to the 17th century, have originated from North Pagan. The largest eruption during historical time took place in 1981 and prompted the evacuation of the sparsely populated island.

Information Contacts: R. Koyanagi, HVO; R. Chong, Disaster Control Office, Saipan; R. Moore, USGS.


Poas (Costa Rica) — March 1993 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2697 m

All times are local (unless otherwise noted)


Gas columns to 500 m; gradual deflation

Fumarolic activity in the N part of the crater lake continued as gas columns rose 500 m, one of them producing a jet-like noise that could be heard at the observation site, 1 km S of the active crater. The turquoise-green lake had a temperature of 67°C and contained floating patches of sulfur. Plumes to 1 m rose from sporadic phreatic eruptions in the central and SE portions of the lake.

During March, the seismic station 2.5 km SW of the main crater recorded 4,825 low-frequency events, an average of 156 events/day (figure 43). An earthquake of M 2.3, located 6 km SW of the main crater at 9 km depth, occurred on 25 March at 0813 GMT.

Figure (see Caption) Figure 43. Seismic events/day recorded 2.5 km SW of the main crater of Poás, March 1993. Courtesy of OVSICORI.

A precise level line running 1.8 km S down the main edifice from the observation site showed possible deflation since June 1992. Measurements at a dry-tilt site also indicated deflation. EDM measurements to the inner cone have not significantly changed since January 1991.

Geologic Background. The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: E. Fernández, J. Barquero, V. Barboza, T. Marino, R. Van der Laat, F. de Obaldía, and R. Sáenz, OVSICORI.


Rabaul (Papua New Guinea) — March 1993 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)


Seismic activity increases; no significant surface deformation

"There was a marked increase in seismic activity in March; 1,685 earthquakes were recorded . . . . This is the highest monthly total since April 1986 (1,769 earthquakes), and the second highest since the 1983-85 crisis period.

The earthquakes occurred both individually and in swarms. Large swarms, with >100 events, occurred 9, 15, 18, and 30 March. Only a few of the earthquakes were felt, the largest on the 15th, M 3.0-3.5. All of the 35 accurately located earthquakes were on the ring-fault system, and the majority were clustered near the recent eruptive centres of Vulcan (9) and Tavurvur/Rabalanakaia (16) (figure 12). Most of the events were located at depths <2 km. Nearly all of the Vulcan earthquakes occurred before 4 March, though the Tavurvur/Rabalanakaia events occurred throughout the month. Routine monthly leveling on the 23rd showed no significant changes from previous months. Wet and dry tilt measurements also showed no trends."

Figure (see Caption) Figure 12. Map of the Rabaul Caldera showing recently active volcanic vents and extinct composite cones (modified from Almond and McKee, 1982).

Reference. Almond, R. A., and McKee, C. O., 1982, Location of volcano-tectonic earthquakes within the Rabaul Caldera: Geological Survey of Papua New Guinea Report 82/19.

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: H. Patia, R. Stewart, and C. McKee, RVO.


Raoul Island (New Zealand) — March 1993 Citation iconCite this Report

Raoul Island

New Zealand

29.27°S, 177.92°W; summit elev. 516 m

All times are local (unless otherwise noted)


Tectonic earthquake swarm; strongest swarm since 1964

The strongest earthquake swarm since the 1964 eruption began at 0150 on 9 March. About 1 earthquake/minute was felt at the island's meteorological station, ~2 km N of Raoul Caldera and 3 km NW of Denham Bay. The larger events shook trees and caused small rockfalls. There were no apparent changes to the lakes in the caldera or to Denham Bay. On the afternoon of 9 March an overflight revealed no indications of volcanic activity. Though mechanical problems prevented the island's one seismograph from recording any earthquakes until that evening, seven earthquakes were detected in Wellington, ~1,600 km S. The strongest, M 4.3, occurred at 0734. Because the swarm may have been precursory to an eruption, the meteorological station staff of 4 men and 1 dog was evacuated by ship to a location 10 km from the island. They returned the following day and saw that the number of earthquakes had diminished considerably. Earthquakes continued to decline in number and intensity, and on 13 March, the ship departed the island, leaving the staff behind. Analysis of the seismicity indicated the swarm was of tectonic rather than volcanic origin.

No volcanic earthquakes or tremor, such as recorded in the 11 days prior to the 1964 eruption, were detected in this swarm, and the recent earthquakes were fewer and smaller than in 1964. There was no evidence of the increased heat flow to the surface that preceded the 1964 eruption. Though the level of one of the caldera lakes rose 38 cm on 12-25 March, this was minor compared to the rise of 600 cm in 11 days prior to the 1964 eruption.

Geologic Background. Anvil-shaped Raoul Island is the largest and northernmost of the Kermadec Islands. During the past several thousand years volcanism has been dominated by dacitic explosive eruptions. Two Holocene calderas exist, the older of which cuts the center the island and is about 2.5 x 3.5 km wide. Denham caldera, formed during a major dacitic explosive eruption about 2200 years ago, truncated the W side of the island and is 6.5 x 4 km wide. Its long axis is parallel to the tectonic fabric of the Havre Trough that lies W of the volcanic arc. Historical eruptions during the 19th and 20th centuries have sometimes occurred simultaneously from both calderas, and have consisted of small-to-moderate phreatic eruptions, some of which formed ephemeral islands in Denham caldera. An unnamed submarine cone, one of several located along a fissure on the lower NNE flank, has also erupted during historical time, and satellitic vents are concentrated along two parallel NNE-trending lineaments.

Information Contacts: I. Nairn and B. Scott, IGNS Wairakei; J. Latter, IGNS Wellington.


Rincon de la Vieja (Costa Rica) — March 1993 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

10.83°N, 85.324°W; summit elev. 1916 m

All times are local (unless otherwise noted)


Hour-long earthquake swarm

The seismic station 5 km SW of the main crater recorded an hour-long swarm of 10 volcano-tectonic earthquakes (M <1.9) on 26 March. Fumarolic activity continued inside the crater and in the crater lake.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: G. Soto and R. Barquero, ICE; E. Fernández, J. Barquero, V. Barboza, T. Marino, R. Van Der Laat, F. de Obaldía, and R. Sáenz, OVSICORI.


San Cristobal (Nicaragua) — March 1993 Citation iconCite this Report

San Cristobal

Nicaragua

12.702°N, 87.004°W; summit elev. 1745 m

All times are local (unless otherwise noted)


Gas plume; little evidence of acid rain

"San Cristóbal was producing a gas plume in January 1993 at levels comparable to recent years. On 6 and 7 January a plume extended over Chinandega (~15 km SW) at about 1,000 m above sea level. No gas was smelled at farms at the base of the volcano. There was patchy evidence of acid rain on the leaves of a few coffee bushes and other plant species, but effects were mild and the coffee crops were not reported to be affected. Analyses of rainwater collected for drinking purposes at one farm revealed cation and anion concentrations expected of normal rainwater, as did a sample from the spring of a neighboring farm. The analyses were undertaken by the British Geological Survey."

Geologic Background. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.


Sheveluch (Russia) — March 1993 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Activity increasing; steam and ash explosions

Explosive activity at Shiveluch's active dome and increased seismicity prompted the KVERT to raise the Level of Concern Color Code from yellow to orange on 7 April, stating that an explosive eruption was possible within several hours or days with little warning. A major eruption occurred on 21 April that produced a column to an estimated altitude of 18 km. [But see 18:4.]

Explosive bursts began on 18 March. A gas and ash explosion at 0900 on 20 March sent an eruption cloud ~1 km above the summit. Another eruption cloud rose ~4 km at 2400 on 21 March, and spread to a diameter of 20 km in the absence of any wind. Explosions occurred every day 22-28 March and 3-4 April, with 2/day on 25, 27, and 28 March. Observers in early April saw no unusual activity in the crater, but the normal fumarolic emissions on the SE part of the active dome were continuing.

Shallow earthquake swarms were detected in early April by the seismic network of four stations that monitor Shiveluch. The nearest station is ~8 km from the summit on the slope of Shiveluch. Other stations are in Kliuchi, ~50 km SW of the summit, and on the Sredinny Ridge to the W, with the farthest station ~100 km from the summit. Earthquake counts increased above background (5 earthquakes/day) to 14 on 4 April, 30 in 4 hours on 5 April, and 42 in 20 hours on 6 April. The earthquakes had amplitudes >5 µm and durations of 2-2.5 minutes. There was a continuous swarm with 90 distinct earthquakes registered over constant weak background seismicity on 7 April. Seismicity beneath the active dome continued at similar levels 8-11 April.

A 400-m-high fumarolic plume was visible during clear weather on 11 April. At 1300 the next day, steam and gas explosions with a small amount of ash occurred at 5-minute intervals and produced columns that rose 1 km above the dome and extended 15 km SE. Small mudflows also traveled 1.5 km from the dome. Shallow seismicity beneath the dome decreased following the explosive activity. The number of earthquakes remained high, however, and their magnitudes increased during the period 12-15 April, with a maximum of 124 earthquakes 14 April.

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: V. Kirianov, IVGG.


Suwanosejima (Japan) — March 1993 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Sporadic, weak ash eruptions

Sporadic, weak ash eruptions [in March] resulted in slight ashfall on inhabited areas . . . .

Geologic Background. The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two active summit craters. The summit is truncated by a large breached crater extending to the sea on the E flank that was formed by edifice collapse. One of Japan's most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded eruption took place in 1813-14, when thick scoria deposits covered residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed, forming a large debris avalanche and creating an open collapse scarp extending to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: JMA.


Telica (Nicaragua) — March 1993 Citation iconCite this Report

Telica

Nicaragua

12.606°N, 86.84°W; summit elev. 1036 m

All times are local (unless otherwise noted)


No observed activity

There have been no reports of activity in the past year, and none was observed 6-7 January.

Geologic Background. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.


Ulawun (Papua New Guinea) — March 1993 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Activity continues at low level

"Activity . . . continued at the low levels reported for February. White vapour emissions usually varied from weak to moderate but were more forceful 26-27 March. Weak glow was reported on the 8th.

"Seismic activity was at a low level throughout the month; no distinct B-type earthquakes were recorded. Both RSAM and routine manual amplitude readings indicate a gradual decline in tremor levels since mid-February. However, the level of tremor is still higher than before January's brief flurry of activity."

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

Information Contacts: H. Patia, R. Stewart, and C. McKee, RVO.


Unzendake (Japan) — March 1993 Citation iconCite this Report

Unzendake

Japan

32.761°N, 130.299°E; summit elev. 1483 m

All times are local (unless otherwise noted)


Dome 11 extruded; endogenous dome growth deforms old crater rim

Dome 10 continued exogenous growth on the top of the dome complex until mid-March when its NE half began collapsing, generating relatively large pyroclastic flows that traveled 4 km E into Kitakamikoba, an evacuated area, (9 March) and 3.5 km E (12 and 16 March). A 17 March overflight revealed a new lava dome, number 11, growing on the resulting collapse-cliff on the E slope of dome 10 (figure 52). From late March through early April, endogenous growth of the dome complex and exogenous growth of dome 11 occurred simultaneously. Despite frequent collapses, dome 11 was 200 m long, 150 m wide, and 70 m thick by mid-April, and dome 10 reached 1,440 m elevation, 80 m above Mt. Fugen, Unzen's previous summit peak. The endogenous growth resulted in cracks radiating out from the epicentral location of the magma supply vent on dome 10. The estimated magma supply rate increased . . . to 1-3 x 105 m3/day during mid-March to mid-April.

Figure (see Caption) Figure 52. Sketch map of Unzen lava-dome complex on 2 April 1993. Note that N is to the right. Dome 11 began growing on a collapse-cliff of dome 10. EDM and GPS stations on the old crater wall NW of the dome complex (upper right) have moved as much as 2 m NW as a result of endogenous dome growth. Courtesy of S. Nakada.

A portion of the NW crater wall was moved out from the dome complex as a result of the endogenous growth (figures 52 and 53). EDM measurements by the GSJ and GPS measurements by SEVO showed up to 2 m of NW movement at a point roughly 150 m NW of the dome complex. The affected area of the crater wall had many small, steaming cracks trending towards dome 10, and small-scale pressure ridges had formed on its surface near the dome complex.

Figure (see Caption) Figure 53. Cartoon representing a SE-NW cross-section of the "pushed area" on the NW side of the dome complex at Unzen. Endogenous growth of the lava-dome complex has pushed out the prehistoric lava dome and talus that formed a portion of the old crater rim (indicated by the large arrow). Courtesy of Setsuya Nakada.

The frequency of pyroclastic flows generated by partial dome collapses gradually increased from 1 to 10/day in the first half of March. The frequency of flows had been low since mid-November, the longest lull of the current eruption (figure 54). The total of seismically recorded flows in March was 171, 4x that recorded in February. Collapses from domes 10 and 11 in late March to mid-April resulted in pyroclastic flows that typically traveled 1-3 km E and NE. The rate of pyroclastic flows remained at ~ 10/day.

Figure (see Caption) Figure 54. Daily count of earthquakes (top) and pyroclastic flows (bottom) at Unzen, 1 January 1991 to 15 April 1993. The 11 longer arrows at the top mark the onset of each of the domes; the short arrow indicates a phreatic eruption. Courtesy of JMA.

The low seismicity of the dome complex since early February continued until an earthquake swarm slowly developed on 9 March (figure 54). After reaching a peak of 492 events on 14 March, activity declined to background by 17 March. The number of recorded earthquakes rose . . . to 2,985 in March.

As in previous months, a steam plume, occasionally containing ash, continued to rise a few hundred meters above the dome complex.

Geologic Background. The massive Unzendake volcanic complex comprises much of the Shimabara Peninsula east of the city of Nagasaki. An E-W graben, 30-40 km long, extends across the peninsula. Three large stratovolcanoes with complex structures, Kinugasa on the north, Fugen-dake at the east-center, and Kusenbu on the south, form topographic highs on the broad peninsula. Fugendake and Mayuyama volcanoes in the east-central portion of the andesitic-to-dacitic volcanic complex have been active during the Holocene. The Mayuyama lava dome complex, located along the eastern coast west of Shimabara City, formed about 4000 years ago and was the source of a devastating 1792 CE debris avalanche and tsunami. Historical eruptive activity has been restricted to the summit and flanks of Fugendake. The latest activity during 1990-95 formed a lava dome at the summit, accompanied by pyroclastic flows that caused fatalities and damaged populated areas near Shimabara City.

Information Contacts: JMA; S. Nakada, Kyushu Univ.

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