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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

Pacaya (Guatemala) Lava flows and Strombolian explosions continued during February-July 2019

Colima (Mexico) Renewed volcanism after two years of quiet; explosion on 11 May 2019

Masaya (Nicaragua) Lava lake activity declined during March-July 2019

Rincon de la Vieja (Costa Rica) Occasional weak phreatic explosions during March-July 2019

Aira (Japan) Explosions with ejecta and ash plumes continue weekly during January-June 2019

Agung (Indonesia) Continued explosions with ash plumes and incandescent ejecta, February-May 2019

Kerinci (Indonesia) Intermittent explosions with ash plumes, February-May 2019

Suwanosejima (Japan) Small ash plumes continued during January through June 2019

Great Sitkin (United States) Small steam explosions in early June 2019

Ibu (Indonesia) Frequent ash plumes and small lava flows active in the crater through June 2019

Ebeko (Russia) Continuing frequent moderate explosions though May 2019; ashfall in Severo-Kurilsk

Klyuchevskoy (Russia) Weak thermal anomalies and moderate Strombolian-type eruptions in September 2018-June 2019



Pacaya (Guatemala) — August 2019 Citation iconCite this Report

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


Lava flows and Strombolian explosions continued during February-July 2019

Pacaya is one of the most active volcanoes in Guatemala, with activity largely consisting of frequent lava flows and Strombolian activity at the Mackenney crater. This report summarizes continued activity during February through July 2019 based on reports by Guatemala's Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and Sistema de la Coordinadora Nacional para la Reducción de Desastres (CONRED), visiting scientists, and satellite data.

At the beginning of February activity included Strombolian explosions ejecting material up to 5 to 30 m above the Mackenney crater and a degassing plume up to 300 m. Multiple lava flows were observed throughout the month on the N, NW, and W flanks, reaching 350 m from the crater and resulting in avalanches from the flow fronts. Strombolian activity continued with sporadic to continuous explosions ejecting material 5-75 m above the Mackenney crater. Degassing produced plumes up to 300 m above the crater, and incandescence from the crater and lava flows were seen at night. Daniel Sturgess of Bristol University observed activity on the 24th, noting a 70-m-long lava flow with individual blocks from the front of the flow rolling down the flanks (figure 108). He reported that mild Strombolian explosions occurred every 10-20 minutes and ejected blocks, up to approximately 4 m in diameter, as high as 5-30 m above the crater and towards the northern flank.

Figure (see Caption) Figure 108. An active lava flow on the NW flank of Pacaya on 24 February 2019 with incandescence visible in lower light conditions. Courtesy of Daniel Sturgess, University of Bristol.

Similar activity continued through March with multiple lava flows reaching a maximum of 200 m N and NW, and avalanches descending from the flow fronts. Ongoing Strombolian explosions expelled material up to 75 m above the Mackenney crater. Degassing produced a white-blue plume to a maximum of 900 m above the crater (figure 109) and incandescence was noted some nights.

Figure (see Caption) Figure 109. A degassing plume at Pacaya reaching 350 m above the crater and dispersing to the S on 19 March 2019. Courtesy of CONRED.

During April lava flows continued on the N and NW flanks, reaching a maximum length of 300 m, with avalanches forming from the flow fronts. Degassing formed plumes up to 600 m above the crater that dispersed with various wind directions. Strombolian activity continued with explosions ejecting material up to 40 m above the crater. On the 2nd and 3rd weak rumbles were heard at distances of 4-5 km. Similar activity continued through May with lava flows reaching 300 m to the N, degassing producing plumes up to 600 m above the crater, and Strombolian explosions ejecting material up to 15 m above the crater.

Lava flows continued out to 300 m in length to the N and NW during June (figures 110 and 111). Strombolian activity ejected material up to 30 m above the crater and degassing resulted in plumes that reached 300 m. During July there were multiple active lava flows that reached a maximum of 300 m in length on the N and NW flanks (figure 112). Avalanches generated by the collapse of material at the front of the lava flows were accompanied by explosions ejecting material up to 30 m above the crater.

Figure (see Caption) Figure 110. An active lava flow on Pacaya on 9 June 2019 with incandescent blocks rolling down the flank from the flow front. Courtesy of Paul Wallace, University of Liverpool.
Figure (see Caption) Figure 111. Activity at Pacaya on 22 June 2019 with a degassing plume dispersed to the W and a 300-m-long lava flow. Photos by Miguel Morales, courtesy of CONRED.
Figure (see Caption) Figure 112. Two lava flows were active to the N and NW at Pacaya on 20 July 2019. Photos courtesy of CONRED.

During February through July multiple lava flows and crater activity were detected in Sentinel-2 satellite thermal images (figures 113 and 114) and relatively constant thermal energy was detected by the MIROVA system with a slight decrease in the energy and frequency of anomalies during June (figure 115). The thermal anomalies detected by the MODVOLC system for each month from February through July spanned 6-30, with six during June and 30 during April.

Figure (see Caption) Figure 113. Sentinel-2 thermal satellite images of Pacaya show lava flows to the N and NW during February through April 2019. There was a reduction in visible activity in early March. False color (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 114. Sentinel-2 thermal satellite images of Pacaya showing lava flow and hot avalanche activity during June and July 2019. False color (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 115. MIROVA log radiative power plot of MODIS thermal infrared at Pacaya during October 2018 through July 2019. Detected thermal energy is relatively stable with a decrease through June and subsequent increase during July. Courtesy of MIROVA.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

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/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.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/); Daniel Sturgess, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom (URL: http://www.bristol.ac.uk/earthsciences/); Paul Wallace, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, 4 Brownlow Street, Liverpool L69 3GP, United Kingdom (URL: https://www.liverpool.ac.uk/environmental-sciences/staff/paul-wallace/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Colima (Mexico) — August 2019 Citation iconCite this Report

Colima

Mexico

19.514°N, 103.62°W; summit elev. 3850 m

All times are local (unless otherwise noted)


Renewed volcanism after two years of quiet; explosion on 11 May 2019

Frequent historical eruptions at Volcán de Colima date back to the 16th century and include explosive activity, lava flows, and large debris avalanches. The most recent eruptive episode began in January 2013 and continued through March 2017. Previous reports have covered activity involving ash plumes with extensive ashfall, lava flows, lahars, and pyroclastic flows (BGVN 41:01 and 42:08). In late April 2019, increased seismicity related to volcanic activity began again. This report covers activity through July 2019. The primary source of information was the Centro Universitario de Estudios e Investigaciones de Vulcanologia, Universidad de Colima (CUEIV-UdC).

On 11 May 2019, CUEIV-UdC reported an explosion that was recorded by several monitoring stations. A thermal camera located south of Colima captured thermal anomalies associated with the explosion as well as intermittent degassing, which mainly consisted of water vapor (figure 131). A report from the Unidad Estatal de Protección Civil de Colima (UEPCC), and seismic and infrasound network data from CUEIV-UdC, recorded about 60 high-frequency events, 16 landslides, and 14 low-magnitude explosions occurring on the NE side of the crater during 11-24 May. Drone imagery showed fumarolic activity occurring on the inner wall of this crater on 22 May (figure 132).

Figure (see Caption) Figure 131. Gas emissions from Colima during the 11 May 2019 eruption as seen from the Naranjal station. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 17 mayo 2019 no 121).
Figure (see Caption) Figure 132. A drone photo showing fumarolic activity occurring within the NE wall of the crater at Colima on 22 May 2019. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 24 mayo 2019 no 122).

Small explosions and gas-and-steam emissions continued intermittently through mid-July 2019 concentrated on the NE side of the crater. An overflight on 9 July 2019 revealed that subsidence from the consistent activity slightly increased the diameter of the vent; other areas within the crater also showed evidence of subsidence and some collapsed material on the outer W wall (figure 133). During the weeks of 19 and 26 July 2019, monitoring cameras and seismic data recorded eight lahars.

Figure (see Caption) Figure 133. A drone photo of the crater at Colima on 8 July 2019 shows continuing fumarolic activity and evidence of a collapsed wall on the W exterior side. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 12 julio 2019 no 129).

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: Centro Universitario de Estudios e Investigaciones de Vulcanologia, Universidad de Colima (CUEIV-UdC), Colima, Col. 28045, Mexico; Centro Universitario de Estudios Vulcanologicos y Facultad de Ciencias de la Universidad de Colima, Avenida Universidad 333, Colima, Col. 28045, Mexico (URL: http://portal.ucol.mx/cueiv/); Unidad Estatal de Protección Civil, Colima, Roberto Esperón No. 1170 Col. de los Trabajadores, C.P. 28020, Mexico (URL: http://www.proteccioncivil.col.gob.mx/).


Masaya (Nicaragua) — August 2019 Citation iconCite this Report

Masaya

Nicaragua

11.984°N, 86.161°W; summit elev. 635 m

All times are local (unless otherwise noted)


Lava lake activity declined during March-July 2019

Masaya, in Nicaragua, contains a lava lake found in the Santiago Crater which has remained active since its return in December 2015 (BGVN 41:08). In addition to this lava lake, previous volcanism included explosive eruptions, lava flows, and gas emissions. Activity generally decreased during March-July 2019, including the number and frequency of thermal anomalies, lava lake levels, and gas emissions. The primary source of information for this report comes from the Instituto Nicareguense de Estudios Territoriales (INETER).

On 21 July 2019 a small explosion in the Santiago Crater resulted in some gas emissions and an ash cloud drifting WNW. In addition to the active lava lake (figure 77), monthly reports from INETER noted that thermal activity and gas emissions (figure 78) were decreasing.

Figure (see Caption) Figure 77. Active lava lake visible in the Santiago Crater at Masaya on 27 June 2019. Photo by Sheila DeForest (Creative Commons BY-SA license).
Figure (see Caption) Figure 78. Gas emissions coming from the Santiago Crater at Masaya on 29 June 2019. Photo by Sheila DeForest (Creative Commons BY-SA license).

On 15 May and 22 July 2019, INETER scientists used a FLIR SC620 thermal infrared camera to measure temperatures of fumaroles on the Santiago Crater. In May 2019 the temperature of fumaroles had decreased by 48°C since the previous month. Between May and July 2019 fumarole temperatures continued to decline; temperatures ranged from 90° to 136°C (figure 79). Compared to May 2019 these temperatures are 3°C lower. INETER reports that the level of the lava lake has been slowly dropping during this reporting period.

Figure (see Caption) Figure 79. FLIR (forward-looking infrared) and visible images of the Santiago Crater at Masaya showing fumarole temperatures ranging from 90° to 136°C. The scale in the center shows the range of temperatures in the FLIR image. Courtesy of INETER (March 2019 report).

According to MIROVA (Middle InfraRed Observation of Volcanic Activity) data from MODIS satellite instruments, frequent thermal anomalies were recorded from mid-March through early May 2019, with little to no activity from mid-May to July 2019 (figure 80). Sentinel-2 thermal images show high temperatures in the active lava lake on 10 March 2019 (figure 81). Thermal energy detected by the MODVOLC algorithm showed 14 hotspot pixels with the most number of hotspots (7) occurring in March 2019.

Figure (see Caption) Figure 80. Thermal anomalies were relatively constant at Masaya from early September 2018 through early May 2019 and then abruptly decreased until mid-June 2019 as recorded by MIROVA. Courtesy of MIROVA.
Figure (see Caption) Figure 81. Sentinel-2 thermal satellite image showing a detected heat signature from the active lava lake at Masaya on 10 March 2019. The lava lake is visible (bright yellow-orange). Approximate diameter of the crater containing the lava lake is 500 m. Thermal (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is 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 twin volcanoes of Nindirí and Masaya, the source of historical 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 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); 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); Sheila DeForest (URL: https://www.facebook.com/sheila.deforest).


Rincon de la Vieja (Costa Rica) — August 2019 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)


Occasional weak phreatic explosions during March-July 2019

The acid lake of Rincón de la Vieja's active crater has generated intermittent weak phreatic explosions regularly since 2011, continuing during the past year through at least August 2019. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), and the information below comes from its weekly bulletins between 4 March and 2 September 2019. Clouds often prevented webcam and satellite views. The current report describes activity from March through July 2019.

OVSICORI-UNA reported that weak events occurred on 19 March at 1851 and on 29 March 2019 at 2043. A two-minute-long phreatic explosion on 1 April at 0802 produced a plume that rose 600 m above the crater rim. Continuous emissions were visible during 3-4 April, rising 200 m above the crater rim. On 3 April, at 1437, a small explosion was detected. An explosion on 10 April at 0617 produced a gas-and-steam plume that rose 1 km above the crater rim and drifted SE. On 12 April at 0643, a plume rose 500 m. Another event took place at 0700 on 13 April, although poor weather conditions prevented visual observations. On 14 April, OVSICORI-UNA noted that aerial photographs showed a milky-gray acid lake at a relatively low water level with convection cells of several tens meters of diameter in the center and eastern parts of the lake.

According to an OVSICORI-UNA bulletin, a small phreatic explosion occurred on 1 May. Another explosion on 11 May at 0720 produced a white gas-and-steam plume that rose 600 m above the crater rim. Phreatic explosions were recorded on 14 May at 1703 and on 17 May at 0357, though dense fog prevented visual confirmation of both events with webcams. On 15 May a local observer noted a diffuse plume of steam and gas, material rising from the crater, and photographed milky-gray deposits on the N part of the crater rim ejected from the event the day before. A major explosion occurred on 24 May.

OVSICORI-UNA recorded a significant phreatic 10-minute-long explosion that began on 11 June at 0343, but plumes were not visible due to weather conditions. No further phreatic events were reported in July.

Seismic activity was very low during the reporting period, and there was no significant deformation. Short tremors were frequent toward the end of April, but were only periodic in May and June; tremor almost disappeared in July. A few long-period earthquakes were recorded, and volcano-tectonic earthquakes were even less frequent.

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 that was 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 1916-m-high 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 3500 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: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/, https://www.facebook.com/OVSICORI/).


Aira (Japan) — July 2019 Citation iconCite this Report

Aira

Japan

31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Explosions with ejecta and ash plumes continue weekly during January-June 2019

Sakurajima rises from Kagoshima Bay, which fills the Aira Caldera near the southern tip of Japan's Kyushu Island. Frequent explosive and occasional effusive activity has been ongoing for centuries. The Minamidake summit cone has been the location of persistent activity since 1955; the Showa crater on its E flank has also been intermittently active since 2006. Numerous explosions and ash-bearing emissions have been occurring each month at either Minamidake or Showa crater since the latest eruptive episode began in late March 2017. This report covers ongoing activity from January through June 2019; the Japan Meteorological Agency (JMA) provides regular reports on activity, and the Tokyo VAAC (Volcanic Ash Advisory Center) issues tens of reports each month about the frequent ash plumes.

From January to June 2019, ash plumes and explosions were usually reported multiple times each week. The quietest month was June with only five eruptive events; the most active was March with 29 (table 21). Ash plumes rose from a few hundred meters to 3,500 m above the summit during the period. Large blocks of incandescent ejecta traveled as far as 1,700 m from the Minamidake crater during explosions in February and April. All the activity originated in the Minamidake crater; the adjacent Showa crater only had a mild thermal anomaly and fumarole throughout the period. Satellite imagery identified thermal anomalies inside the Minamidake crater several times each month.

Table 21. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in Aira caldera, January-June 2019. The number of events that were explosive in nature are in parentheses. No events were recorded at the Showa crater during this time. Data courtesy of JMA (January to June 2019 monthly reports).

Month Ash emissions (explosive) Max. plume height above crater Max. ejecta distance from crater
Jan 2019 8 (6) 2.1 km 1.1 km
Feb 2019 15 (11) 2.3 km 1.7 km
Mar 2019 29 (12) 3.5 km 1.3 km
Apr 2019 10 (5) 2.2 km 1.7 km
May 2019 15 (9) 2.9 km 1.3 km
Jun 2019 5 (2) 2.2 km 1.3 km

There were eight eruptive events reported by JMA during January 2019 at the Minamidake summit crater of Sakurajima. They occurred on 3, 6, 7, 9, 17, and 19 January (figure 76). Ash plume heights ranged from 600 to 2,100 m above the summit. The largest explosion, on 9 January, generated an ash plume that rose 2,100 m above the summit crater and drifted E. In addition, incandescent ejecta was sent 800-1,100 m from the summit. Incandescence was visible at the summit on most clear nights. During an overflight on 18 January no significant changes were noted at the crater (figure 77). Infrared thermal imaging done on 29 January indicated a weak thermal anomaly in the vicinity of the Showa crater on the SE side of Minamidake crater. The Kagoshima Regional Meteorological Observatory (KRMO) (11 km WSW) recorded ashfall there during four days of the month. Satellite imagery indicated thermal anomalies inside Minamidake on 7 and 27 January (figure 77).

Figure (see Caption) Figure 76. Incandescent ejecta and ash emissions characterized activity from Sakurajima volcano at Aira during January 2019. Left: A webcam image showed incandescent ejecta on the flanks on 9 January 2019, courtesy of JMA (Explanation of volcanic activity in Sakurajima, January 2019). Right: An ash plume rose hundreds of meters above the summit, likely also on 9 January, posted on 10 January 2019, courtesy of Mike Day.
Figure (see Caption) Figure 77. The summit of Sakurajima consists of the larger Minamidake crater and the smaller Showa crater on the E flank. Left: The Minamidake crater at the summit of Sakurajima volcano at Aira on 18 January 2019 seen in an overflight courtesy of JMA (Explanation of volcanic activity in Sakurajima, March 2019). Right: Two areas of thermal anomaly were visible in Sentinel-2 satellite imagery on 27 January 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

Activity increased during February 2019, with 15 eruptive events reported on days 1, 3, 7, 8, 10, 13, 14, 17, 22, 24, and 27. Ash plume heights ranged from 600-2,300 m above the summit, and ejecta was reported 300 to 1,700 m from the crater in various events (figure 78). KRMO reported two days of ashfall during February. Satellite imagery identified thermal anomalies at the crater on 6 and 26 February, and ash plumes on 21 and 26 February (figure 79).

Figure (see Caption) Figure 78. An explosion from Sakurajima at Aira on 7 February 2019 sent ejecta up to 1,700 m from the Minamidake summit crater. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, February 2019).
Figure (see Caption) Figure 79. Thermal anomalies and ash emissions were captured in Sentinel-2 satellite imagery on 6, 21, and 26 February 2019 originating from Sakurajima volcano at Aira. Top: Thermal anomalies within the summit crater were visible underneath steam and ash plumes on 6 and 26 February (closeup of bottom right photo). Bottom: Ash emissions on 21 and 26 February drifted SE from the volcano. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

The number of eruptive events continued to increase during March 2019; there were 29 events reported on numerous days (figures 80 and 81). An explosion on 14 March produced an ash plume that rose 3,500 m above the summit and drifted E. It also produced ejecta that landed 800-1,100 m from the crater. During an overflight on 26 March a fumarole was the only activity in Showa crater. KRMO reported 14 days of ashfall during the month. Satellite imagery identified an ash plume on 13 March and a thermal anomaly on 18 March (figure 82).

Figure (see Caption) Figure 80. A large ash emission from Sakurajima volcano at Aira was photographed by a tourist on the W flank and posted on 1 March 2019. Courtesy of Kratü.
Figure (see Caption) Figure 81. An ash plume from Sakurajima volcano at Aira on 18 March 2019 produced enough ashfall to disrupt the trains in the nearby city of Kagoshima according to the photographer. Image taken from about 20 km away. Courtesy of Tim Board.
Figure (see Caption) Figure 82. An ash plume drifted SE from the summit of Sakurajima volcano at Aira on 13 March (left) and a thermal anomaly was visible inside the Minamidake crater on 18 March 2019 (right). "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

A decline in activity to only ten eruptive events on days 7, 13, 17, 22, and 25 was reported by JMA for April 2019. An explosion on 7 April sent ejecta up to 1,700 m from the crater. Another explosion on 13 April produced an ash plume that rose 2,200 m above the summit. Most of the eruptive events at Sakurajima last for less than 30 minutes; on 22 April two events lasted for almost an hour each producing ash plumes that rose 1,400 m above the summit. Ashfall at KRMO was reported during seven days in April. Two distinct thermal anomalies were visible inside the Minamidake crater on both 12 and 27 April (figure 83).

Figure (see Caption) Figure 83. Two thermal anomalies were present inside Minamidake crater at the summit of Sakurajima volcano at Aira on 12 (left) and 27 (right) April 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

There were 15 eruptive events during May 2019. An event that lasted for two hours on 12 May produced an ash plume that rose 2,900 m from the summit and drifted NE (figure 84). The Meteorological Observatory reported 14 days with ashfall during the month. Two thermal anomalies were present in satellite imagery in the Minamidake crater on both 17 and 22 May.

Figure (see Caption) Figure 84. An ash plume rose 2,900 m above the summit of Sakurajima at Aira on 12 May 2019 (left); incandescent ejecta went 1,300 m from the summit crater on 13 May. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, May 2019).

During June 2019 five eruptive events were reported, on 11, 13, and 24 June; the event on 11 June lasted for almost two hours, sent ash 2,200 m above the summit, and produced ejecta that landed up to 1,100 m from the crater (figure 85). Five days of ashfall were reported by KRMO.

Figure (see Caption) Figure 85. A large ash plume on 11 June 2019 rose 2,200 m above the summit of Sakurajima volcano at Aira. Courtesy of Aone Wakatsuki.

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 Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

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); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Mike Day, Minnesota, Twitter (URL: https://twitter.com/MikeDaySMM, photo at https://twitter.com/MikeDaySMM/status/1083489400451989505/photo/1); Kratü, Twitter (URL: https://twitter.com/TalesOfKratue, photo at https://twitter.com/TalesOfKratue/status/1101469595414589441/photo/1); Tim Board, Japan, Twitter (URL: https://twitter.com/Hawkworld_, photo at https://twitter.com/Hawkworld_/status/1107789108754038789); Aone Wakatsuke, Twitter (URL: https://twitter.com/AoneWakatsuki, photo at https://twitter.com/AoneWakatsuki/status/1138420031258210305/photo/3).


Agung (Indonesia) — June 2019 Citation iconCite this Report

Agung

Indonesia

8.343°S, 115.508°E; summit elev. 2997 m

All times are local (unless otherwise noted)


Continued explosions with ash plumes and incandescent ejecta, February-May 2019

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Lava emerged into the summit crater at the end of November and intermittent ash plumes rose as high as 3 km above the summit through the end of the year. Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater (BGVN 43:08, 44:02). Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from February through May 2019.

Intermittent but increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity at Agung during February through May 2019. During February, explosions were reported three times; events on seven days in March were documented with ash plumes and ashfall in surrounding villages. Five significant events occurred during April; two involved incandescent ejecta that traveled several kilometers from the summit, and ashfall tens of kilometers from the volcano. Most of the five significant events reported in May involved incandescent ejecta and ashfall in adjacent villages; air traffic was disrupted during the 24 May event. Ash plumes in May reached altitudes over 7 km multiple times. Thermal activity increased steadily during the period, according to both the MIROVA project (figure 44) and MODVOLC thermal alert data. MAGMA Indonesia reported at the end of May 2019 that the volume of lava within the summit crater remained at about 25 million m3; satellite information indicated continued thermal activity within the crater. Alert Level III (of four levels) remained in effect throughout the period with a 4 km exclusion radius around the volcano.

Figure (see Caption) Figure 44. Thermal activity at Agung from 4 September 2018 through May 2019 was variable. The increasing frequency and intensity of thermal events was apparent from February-May. Courtesy of MIROVA.

Steam plumes rose 30-300 m high daily during February 2019. The Agung Volcano Observatory (AVO) and PVMBG issued a VONA on 7 February (UTC) reporting an ash plume, although it was not visible due to meteoric cloud cover. Incandescence, however, was observed at the summit from webcams in both Rendang and Karangasem City (16 km SE). The seismic event associated with the explosion lasted for 97 seconds. A similar event on 13 February was also obscured by clouds but produced a seismic event that lasted for 3 minutes and 40 seconds, and ashfall was reported in the village of Bugbug, about 20 km SE. On 22 February a gray ash plume rose 700 m from the summit during a seismic event that lasted for 6 minutes and 20 seconds (figure 45). The Darwin VAAC reported the plume visible in satellite imagery moving W at 4.3 km altitude. It dissipated after a few hours, but a hotspot remained visible about 10 hours later.

Figure (see Caption) Figure 45. An ash plume rose from the summit of Agung on 22 February 2019, viewed from the Besakih temple, 7 km SW of the summit. Courtesy of PunapiBali.

Persistent steam plumes rose 50-500 m from the summit during March 2019. An explosion on 4 March was recorded for just under three minutes and produced ashfall in Besakih (7 km SW); no ash plume was observed due to fog. A short-lived ash plume rose to 3.7 km altitude and drifted SE on 8 March (UTC) 2019. The seismic event lasted for just under 4 minutes. Ash emissions were reported on 15 and 17 March to 4.3 and 3.7 km altitude, respectively, drifting W (figure 46). Ashfall from the 15 March event spread NNW and was reported in the villages of Kubu (6 km N), Tianyar (14 km NNW), Ban, Kadundung, and Sukadana. MAGMA Indonesia noted that two explosions on the morning of 17 March (local time) produced gray plumes; the first sent a plume to 500 m above the summit drifting E and lasted for about 40 seconds, while the second plume a few hours later rose 600 m above the crater and lasted for 1 minute and 16 seconds. On 18 March an ash plume rose 1 km and drifted W and NW. An event on 20 March was measured only seismically by PVMBG because fog prevented observations. An eruption on 28 March produced an ash plume 2 km high that drifted W and NW. The seismic signal for this event lasted for about two and a half minutes. The Darwin VAAC reported the ash plume at 5.5 km altitude, dissipating quickly to the NW. No ash was visible four hours later, but a thermal anomaly remained at the summit (figure 47). Ashfall was reported in nearby villages.

Figure (see Caption) Figure 46. Ash plumes from Agung on 15 (left) and 17 (right) March 2019 resulted in ashfall in communities 10-20 km from the volcano. Courtesy of PVMBG and MAGMA Indonesia (Information on G. Agung Eruption, 15 March 2019 and Gunung Agung Eruption Press Release March 17, 2019).
Figure (see Caption) Figure 47. A thermal anomaly was visible through thick cloud cover at the summit of Agung on 29 March 2019 less than 24 hours after a gray ash plume was reported 2,000 m above the summit. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

The first explosion of April 2019 occurred on the 3rd (UTC); PVMBG reported the dense gray ash plume 2 km above the summit drifting W. A few hours later the Darwin VAAC raised the altitude to 6.1 km based on infrared temperatures in satellite imagery. The seismic signal lasted for three and a half minutes and the explosion was heard at the PGA Post in Rendang (12 km SW). Incandescent material fell within a radius of 2-3 km, mainly on the S flank (figure 48). Ashfall was reported in the villages of Telungbuana, Badeg, Besakih, Pempatan, Teges, and Puregai on the W and S flanks (figure 49). An explosion on 11 April also produced a dense gray ash plume that rose 2 km above the summit and drifted W. A hotspot remained about six hours later after the ash dissipated.

Figure (see Caption) Figure 48. Incandescent ejecta appeared on the flanks of Agung after an eruption on 4 April 2019 (local time) as viewed from the observation post in Rendang (8 km SW). Courtesy of Jamie Sincioco.
Figure (see Caption) Figure 49. Ashfall in a nearby town dusted mustard plants on 4 April 2019 from an explosion at Agung the previous day. Courtesy of Pantau.com (Photo: Antara / Nyoman Hendra).

PVMBG reported an eruption visible in the webcam early on 21 April (local time) that rose to 5.5 km altitude and drifted SW. The ash spread W and S and ash fell around Besakih (7 km SW), Rendang (8 km SW), Klungkung (25 km S), Gianyar (20 km WSW), Bangli (17 km WNW), Tabanan (50 km WSW), and at the Ngurah Rai-Denpasar Airport (60 km SW). About 15 hours later a new explosion produced a dense gray ash plume that rose to 3 km above the summit and produced incandescent ejecta in all directions as far as 3 km away (figure 50). The ash spread to the S and ashfall was reported in Besakih, Rendang, Sebudi (6 km SW), and Selat (12 km SSW). Both of the explosions were heard in Rendang and Batulompeh. The incandescent ejecta from the explosions remained within the 4-km exclusion zone. A satellite image on 23 April showed multiple thermal anomalies within the summit crater (figure 51). A dense gray plume drifted E from Agung on 29 April (30 April local time) at 4.6 km altitude. It was initially reported by ground observers, but was also visible in multispectral satellite imagery for about six hours before dissipating.

Figure (see Caption) Figure 50. An explosion at Agung on 21 April 2019 sent incandescent eject 3,000 m from the summit. Courtesy of MAGMA Indonesia (Gunung Agung Eruption Press Release April 21, 2019).
Figure (see Caption) Figure 51. Multiple thermal anomalies were still present within the summit crater of Agung on 23 April 2019 after two substantial explosions produced ash and incandescent ejecta around the summit two days earlier. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG reported an eruption on 3 May 2019 that was recorded on a seismogram with a signal that lasted for about a minute. Satellite imagery reported by the Darwin VAAC showed a growing hotspot and possible ash near the summit at 4.3 km altitude moving NE. A few days later, on 6 May, a gray ash plume rose to 5.2 km altitude and drifted slowly W before dissipating; it was accompanied by a seismic signal that lasted for about two minutes. Explosions on 12 and 18 May produced significant amounts of incandescent ejecta (figure 52). The seismic signal for the 12 May event lasted for about two minutes; no plume was observed due to fog, but incandescent ejecta was visible on the flanks and the explosion was heard at Rendang. The Darwin VAAC reported an ash plume from the explosion on 17 May (18 May local time) at 6.1 km altitude in satellite imagery moving E. They revised the altitude a short while later to 7.6 km based on IR temperature and movement; the plume drifted N, NE, and E in light and variable winds. A few hours after that it was moving NE at 7.6 km altitude and SE at 5.5 km altitude; this lasted for about 12 hours until it dissipated. Ashfall was reported in villages downwind including Cutcut, Tongtongan, Bonyoh (20 km WNW), and Temakung.

Figure (see Caption) Figure 52. Explosions on 12 (left) and 18 (right) May (local time) 2019 produced substantial ejecta on the flanks of Agung visible from a distance of 10 km or more in PVMBG webcams. The ash plume from the 18 May event resulted in ashfall in numerous communities downwind. Courtesy of PVMBG (Information Eruption G. Agung, May 13, 2019, Information Eruption G. Agung, May 18, 2019).

The initial explosion on 18 May was captured by a webcam at a nearby resort and sent incandescent ejecta hundreds of meters down the NE flank within 20 seconds (figure 53). Satellite imagery on 3, 8, 13, and 18 May indicated multiple thermal anomalies growing stronger at the summit. All of the images were captured within 24 hours of an explosive event reported by PVMBG (figure 54).

Figure (see Caption) Figure 53. The 18 May 2019 explosion at Agung produced an ash plume that rose to over 7 km altitude and large bombs of incandescent material that traveled hundreds of meters down the NE flank within the first 20 seconds of the explosion. Images taken from a private webcam located 12 km NE. Courtesy of Volcanoverse, used with permission.
Figure (see Caption) Figure 54. Satellite images from 3, 8, 13, and 18 May 2019 at Agung showed persistent and increasing thermal anomalies within the summit crater. All images were captured within 24 hours of explosions reported by PVMBG. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG issued a VONA on 24 May 2019 reporting a new ash emission. They indicated that incandescent fragments were ejected 2.5-3 km in all directions from the summit, and the seismic signal lasted for four and a half minutes (figure 55). A dense gray ash plume was observed from Tulamben on the NE flank rising 2 km above the summit. Satellite imagery indicated that the plume drifted SW and ashfall was reported in the villages of Besakih, Pempatan, Menanga, Sebudi, Muncan, Amerta Bhuana, Nongan, Rendang, and at the Ngurah Rai Airport in Denpassar. Additionally, ashfall was reported in the districts of Tembuku, Bangli, and Susut (20 km SW). The Darwin VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude along with a thermal anomaly and incandescent lava visible in webcam imagery. The remains of the ash plume were about 170 km S of the airport in Denpasar (60 km SW) and had nearly dissipated 18 hours after the event. According to a news article several flights to and from Australia were cancelled or diverted, though the International Gusti Ngurah Rai (IGNR) airport was not closed. On 31 May another large explosion produced the largest ash plume of the report period, rising more than 2 km above the summit (figure 56). The Darwin VAAC reported its altitude as 8.2 km drifting ESE visible in satellite data. It split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours.

Figure (see Caption) Figure 55. A large explosion at Agung on 24 May 2019 produced incandescent ejecta that covered all the flanks and dispersed ash to many communities to the SW. Courtesy of PVMBG (Gunung Agung Eruption Press Release 24 May 2019 20:38 WIB, Kasbani, Ir., M.Sc.).
Figure (see Caption) Figure 56. An explosion at Agung on 31 May 2019 sent an ash plume to 8.2 km altitude, the highest for the report period. Courtesy of Sutopo Purwo Nugroho, BNPB.

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

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.vsi.esdm.go.id/); 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); The Jakarta Post, Mount Agung eruption disrupts Australian flights, (URL: https://www.thejakartapost.com/news/2019/05/25/mount-agung-eruption-disrupts-australian-flights.html); PunapiBali (URL: http://punapibali.com/, Twitter: https://twitter.com/punapibali, image at https://twitter.com/punapibali/status/1098869352588288000/photo/1); Jamie S. Sincioco, Phillipines (URL: Twitter: https://twitter.com/jaimessincioco. Image at https://twitter.com/jaimessincioco/status/1113765842557104130/photo/1); Pantau.com (URL: https://www.pantau.com/berita/erupsi-gunung-agung-sebagian-wilayah-bali-terpapar-hujan-abu?utm_source=dlvr.it&utm_medium=twitter); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN ).


Kerinci (Indonesia) — June 2019 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Intermittent explosions with ash plumes, February-May 2019

Frequently active, Indonesia's Mount Kerinci on Sumatra has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838. Intermittent explosions with ash plumes, usually multiple times per month, have characterized activity since April 2018. Similar activity continued during February-May 2019, the period covered in this report with information provided primarily by the Indonesian volcano monitoring agency, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), MAGMA Indonesia, notices from the Darwin Volcano Ash Advisory Center (Darwin VAAC), and satellite data. PVMBG has maintained an Alert Level II (of 4) at Kerinci for several years.

On 13 February 2019 the Kerinci Volcano Observatory (KVO), part of PVMBG, noted a brownish-white ash emission that was drifting NE about 400 m above the summit. The seismicity during the event was dominated by continuous volcanic tremor. A brown ash emission was reported on 7 March 2019 that rose to 3.9 km altitude and drifted NE. Ash also drifted 1,300 m down the SE flank. Another ash plume the next morning drifted W at 4.5 km altitude, according to KVO. On 10, 11, and 13 March KVO reported brown ash plumes drifting NE from the summit at about 4.0-4.3 km altitude. The Darwin VAAC observed continuous ash emissions in satellite imagery on 15 March drifting W at 4.3 m altitude that dissipated after about 3 hours (figure 10). A gray ash emission was reported on 19 March about 600 m above the summit drifting NE; local news media noted that residents of Kayo Aro reported emissions on both 18 and 19 March (figure 11). An ash emission appeared in satellite imagery on 25 March (figure 10). On 30 March the observatory reported two ash plumes; a brown emission at 0351 UTC and a gray emission at 0746 UTC that both drifted NE at about 4.4 km altitude and dissipated within a few hours. PVMBG reported another gray ash plume the following day at a similar altitude.

Figure (see Caption) Figure 10. Sentinel-2 satellite imagery of Kerinci from 15 (left) and 25 (right) March 2019 showed evidence of ash plumes rising from the summit. Kerinci's summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 11. Dense ash plumes from Kerinci were reported by local news media on 18 and 19 March 2019. Courtesy of Nusana Jambi.

Activity continued during April with a brown ash emission reported on 3 April by several different agencies; the Darwin VAAC and PVMBG daily reports noted that the plume was about 500 m above the summit (4.3 km altitude) drifting NE. KVO observed two brown ash emissions on 13 April (UTC) that rose to 4.2 km altitude and drifted NE. Satellite imagery showed minor ash emissions from the summit on 14 April; steam plumes 100-500 m above the summit characterized activity for the remainder of April (figure 12).

Figure (see Caption) Figure 12. A dilute ash emission rose from the summit of Kerinci on 14 April 2019 (left); only steam emissions were present on a clear 29 April in Sentinel-2 imagery (right). "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.

Ashfall on the NE and S flanks within 7 km of the volcano was reported on 2 May 2019. According to a news article, at least five villages were affected late on 2 May, including Tanjung Bungo, Sangir, Sangir Tengah, Sungai Rumpun, and Bendung Air (figures 13 and 14). The smell of sulfur was apparent in the villages. Brown ash emissions were observed on 3 and 4 May that rose to 4.6 and 4.1 km altitude and drifted SE. The Darwin VAAC reported an emission on 5 May, based on a pilot report, that rose to 6.7 km altitude and drifted NE for about an hour before dissipating. A brown ash emission on 10 May rose 700 m above the summit and drifted SE. Satellite imagery captured ash emissions from the summit on 14 and 24 May (figure 15). For the remainder of the month, 300-700-m-high dense steam plumes were noted daily until PVMBG reported white and brown plumes on 26 and 27 May rising 500-1,000 m above the summit. Although thermal anomalies were not reported during the period, persistent weak SO2 emissions were identified in TROPOMI instrument satellite data multiple times per month (figure 16).

Figure (see Caption) Figure 13. Ashfall was reported from five villages on the flanks of Kerinci on 2 May 2019. Courtesy of Uzone.
Figure (see Caption) Figure 14. An ash plume at Kerinci rose hundreds of meters on 2 May 2019; ashfall was reported in several nearby villages. Courtesy of Kerinci Time.
Figure (see Caption) Figure 15. Ash emissions from Kerinci were captured in Sentinel-2 satellite imagery on 14 (left) and 24 (right) May 2019. The summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 16. Weak SO2 anomalies from Kerinci emissions were captured by the TROPOMI instrument on the Sentinel-5P satellite multiple times each month from February to May 2019. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

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.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nuansa Jambi, Informasi Utama Jambi: (URL: https://nuansajambi.com/2019/03/20/gunung-kerinci-semburkan-asap-tebal/); Kerinci Time (URL: https://kerincitime.co.id/gunung-kerinci-semburkan-abu-vulkanik.html); Uzone.id (URL: https://news.uzone.id/gunung-kerinci-erupsi-5-desa-tertutup-abu-tebal).


Suwanosejima (Japan) — July 2019 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Small ash plumes continued during January through June 2019

Suwanosejima is an active volcanic island south of Japan in the Ryuku islands with recent activity centered at Otake crater. The current eruption began in October 2004 and activity has mostly consisted of small ash plumes, ballistic ejecta, and visible incandescence at night. This report summarizes activity during January through June 2019 and is based on reports by the Japan Meteorological Agency (JMA), and various satellite data.

Thermal activity recorded by the MIROVA system was low through January and February after a decline in November (figure 36), shown in Sentined-2 thermal infrared imagery as originating at a vent in the Otake crater (figure 37). During January an explosive event was observed at 1727 on the 3rd, producing a gray plume that rose 600 m above the crater. A white gas-and-steam plume rose to 1.5 km above the crater and nighttime incandescence was observed throughout the month. Reduced activity continued through February with no reported explosive eruptions and light gray plumes up to 900 m above the crater. Incandescence continued to be recorded at night using a sensitive surveillance camera.

Figure (see Caption) Figure 36. MIROVA log radiative power plot of MODIS thermal infrared data at Suwanosejima during September 2018 through June 2019. There was reduced activity in 2019 with periods of more frequent anomalies during March and June. Courtesy of MIROVA.
Figure (see Caption) Figure 37. A Sentinel-2 thermal satellite image shows Suwanosejima with the active Otake crater in the center with elevated temperatures shown as bright orange/yellow. There is a light area next to the vent that may be a gas plume. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

There was an increase in thermal energy detected by the MIROVA system in mid-March and there was a MODVOLC thermal alert on the 15th. Occasional small explosions occurred but no larger explosive events were recorded. A white plume was noted on the 27th rising to 900 m above the crater and an event at 1048 on the 30th produced a light-gray plume that rose to 800 m. Incandescence was only observed using a sensitive camera at night (figure 38).

Figure (see Caption) Figure 38. Incandescence from the Suwanosejima Otake crater reflecting in clouds above the volcano. Courtesy of JMA (Volcanic activity of Suwanosejima March 2019).

No explosive events were observed through April. A white gas-and-steam plume rose to 1,200 m above the crater on the 19th and incandescence continued intermittently. Minor explosions were recorded on 5, 30, and 31 May, but no larger explosive events were observed during the month. The event on the 30th produced ash plume that reached 1.1 km above the crater. Similar activity continued through June with one explosive event occurring on the 2nd. Overall, there was a reduction in the number of ash plumes erupted during this period compared to previous months (figure 39).

Figure (see Caption) Figure 39. Observed activity at Suwanosejima for the year ending in July 2019. The black vertical bars represent steam, gas, or ash plume heights (scale in meters on the left axis), yellow diamonds represent incandescence observed in webcams, gray volcano symbols along the top are explosions accompanied by ash plumes, red volcano symbols represent large explosions with ash plumes. Courtesy of JMA (Volcanic activity of Suwanosejima June 2019).

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed 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 the horseshoe-shaped Sakuchi caldera, which extends 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: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Great Sitkin (United States) — July 2019 Citation iconCite this Report

Great Sitkin

United States

52.076°N, 176.13°W; summit elev. 1740 m

All times are local (unless otherwise noted)


Small steam explosions in early June 2019

The Great Sitkin volcano is located about 40 km NE of Adak Island in the Aleutian Islands and has had a few short-lived eruptions over the past 100 years. Prior to the latest activity in early June 2019 described below, small phreatic explosions occurred in June and August 2018 (BGVN 43:09). An eruption in 1974 produced a lava dome in the center of the crater. The Alaska Volcano Observatory (AVO) is the primary source of information for this September 2018-June 2019 reporting period.

Low-level unrest occurred from September 2018 through February 2019 with slightly elevated seismic activity (figure 6). Small explosions were seismically detected by AVO on 30 October, 5 and 16 November, and 11 December 2018, but they were not seen in regional infrasound data and satellite data did not show an ash cloud.

On 1, 7, and 9 June 2019, AVO reported small steam explosions as well as slightly elevated seismic activity. Steam plumes and surficial evidence of an explosion were not observed during these events. On 18 June 2019 weakly elevated surface temperatures were recorded, field crews working on Adak observed some steam emissions, and a gas flight was conducted. Elevated concentrations of carbon dioxide detected above the lava dome were likely associated with the steam explosions earlier in the month (figures 7 and 8). From 23 June through the end of the month seismicity began to decline back to background levels.

Figure (see Caption) Figure 6. A steam plume was seen at the summit of Great Sitkin on 7 December 2018. Photo by Andy Lewis and Bob Boyd; courtesy of AVO/USGS.
Figure (see Caption) Figure 7. Some degassing was observed on the southern flank of the Great Sitkin during an overflight on 18 June 2019. Photo by Laura Clor; image courtesy of AVO/USGS.
Figure (see Caption) Figure 8. View of Great Sitkin with white plumes rising from the summit on 20 June 2019. Photo by Laura Clor, courtesy of AVO/USGS.

Geologic Background. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/).


Ibu (Indonesia) — July 2019 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


Frequent ash plumes and small lava flows active in the crater through June 2019

Ibu volcano on Halmahera island in Indonesia began the current eruption episode on 5 April 2008. Since then, activity has largely consisted of small ash plumes with less frequent lava flows, lava dome growth, avalanches, and larger ash plumes up to 5.5 km above the crater. This report summarizes activity during December 2018 through June 2019 and is based on Volcano Observatory Notice for Aviation (VONA) reports by MAGMA Indonesia, reports by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and Badan Nasional Penanggulangan Bencana (BNPB), and various satellite data.

During December PVMBG reported ash plumes ranging from 200 to 800 m above the crater. There were 11 MODVOLC thermal alerts that registered during 1-12 December. An explosion on 12 January 2019 produced an ash plume that reached 800 m above the crater and dispersed to the S (figure 15). A report released for this event by Sutopo at BNPB said that Ibu had erupted almost every day over the past three months; an example given was of activity on 10 January consisting of 80 explosions. There were four MODVOLC thermal alerts through the month.

Figure (see Caption) Figure 15. An eruption at Ibu at 1712 on 21 January 2019 produced an ash plume that rose to 800 m above the crater. Courtesy of BNPB (color adjusted).

Throughout February explosions frequently produced ash plumes as high as 800 m above the crater, and nine MODVOLC thermal alerts were issued. Daily reports showed variable plume heights of 200-800 m most days throughout the month. Wind directions varied and dispersed the plumes in all directions. A VONA released at 1850 on 6 February reported an ash plume that rose to 1,925 m altitude (around 600 m above the summit) and dispersed S. Activity continued through March with the Darwin VAAC and PVMBG reporting explosions producing ash plumes to heights of 200-800 m above the crater and dispersing in various directions. There were ten MODVOLC alerts through the month.

Similar activity continued through April, May, and June, with ash plumes reaching 200-800 m above the crater. There were 12, 6, and 15 MODVOLC Alerts in April, May, and June, respectively.

Planet Scope satellite images show activity at a two vents near the center of the crater that were producing small lava flows from February through June (figure 16). Thermal anomalies were frequent during December 2018 through June 2019 across MODVOLC, MIROVA, and Sentinel-2 infrared data (figures 17 and 18). Sentinel-2 data showed minor variation in the location of thermal anomalies within the crater, possibly indicating lava flow activity, and MIROVA data showed relatively constant activity with a few reductions in thermal activity during January and February.

Figure (see Caption) Figure 16. Planet Scope natural color satellite images showing activity in the Ibu crater during January through June 2019, with white arrows indicating sites of activity. One vent is visible in the 21 February image, and a 330-m-long (from the far side of the vent) lava flow with flow ridges had developed by 24 March. A second vent was active by 12 May with a new lava flow reaching a maximum length of 520 m. Activity was centered back at the previous vent by 23-27 June. Natural color Planet Scope Imagery, copyright 2019 Planet Labs, Inc.
Figure (see Caption) Figure 17. Examples of thermal activity in the Ibu crater during January through May 2019. These Sentinel-2 satellite images show variations in hot areas in the crater due to a vent producing a small lava flow. Sentinel-2 false color (urban) images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 18. MIROVA log radiative power plot of MODIS thermal infrared at Ibu from September 2018 through June 2019. The registered energy was relatively stable through December, with breaks in January and February. Regular thermal anomalies continued with slight variation through to the end of June. Courtesy of MIROVA.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

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/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/).


Ebeko (Russia) — July 2019 Citation iconCite this Report

Ebeko

Russia

50.686°N, 156.014°E; summit elev. 1103 m

All times are local (unless otherwise noted)


Continuing frequent moderate explosions though May 2019; ashfall in Severo-Kurilsk

The Ebeko volcano, located on the northern end of the Paramushir Island in the Kuril Islands, consists of many craters, lakes, and thermal features and has been frequently erupting since late February 2017. Typical activity includes ash plumes, explosive eruptions, and gas-and-steam activity. The previous report through November 2018 (BGVN 43:12) described frequent ash explosions that sometimes caused ashfall in Severo-Kurilsk (7 km E). The primary source of information is the Kamchatka Volcanic Eruptions Response Team (KVERT). This report updates the volcanic activity at Ebeko for December 2018 through May 2019.

Frequent moderate explosive activity continued after November 2018. Volcanologists in Severo-Kurilsk observed explosions sending up ash, which drifted N, NE, and E, resulting in ash falls on Severo-Kurilsk on 28 different days between December 2018 and March 2019. On 25 December 2018 an explosion sent ash up to a maximum altitude of 4.5 km and then drifted N for about 5 km. Explosions occurring on 8-10 March 2019 sent ash up to an altitude of 4 km, resulting in ashfall on Severo-Kurilsk on 9-10 March 2019. An ash plume from these explosions rose to a height of 2.5 km and drifted to a maximum distance of 30 km ENE.

Satellite data analyzed by KVERT registered 12 thermal anomalies from December 2018 through May 2019. According to satellite data analyzed by MIROVA (Middle InfraRed Observation of Volcanic Activity), only one thermal anomaly was recorded from December 2018-May 2019, and no hotspot pixels were recognized using satellite thermal data from the MODVOLC algorithm.

Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

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/); 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/).


Klyuchevskoy (Russia) — July 2019 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Weak thermal anomalies and moderate Strombolian-type eruptions in September 2018-June 2019

Klyuchevskoy has had alternating eruptive and less active periods since August 2015. Activity has included lava flows, a growing cinder cone, thermal anomalies, gas-and-steam plumes, and ash explosions. Though some eruptions occur near the summit crater, major explosive and effusive eruptions have also occurred from flank craters (BGVN 42:04 and 43:05). Intermittent moderate gas-and-steam and ash emissions were previously reported from mid-February to mid-August 2018. The Kamchatka Volcanic Eruptions Response Team (KVERT) is the primary source of information for this September 2018-June 2019 reporting period.

KVERT reported that moderate gas-and-steam activity, some of which contained a small amount of ash, and weak thermal anomalies occurred intermittently from the beginning of September 2018 through mid-April 2019. On 21-22 April 2019 webcam data showed a gas-and-steam plume extending about 160 km SE (figure 31). Moderate Strombolian-type volcanism began late April 2019 and continued intermittently through June 2019. On 11-12 June webcam data showed explosions that sent ash up to a maximum altitude of 6 km, with the resulting ash plume extending about 200 km WNW.

Figure (see Caption) Figure 31. Gas-and-steam plume containing some amount of ash rising from the summit of Klyuchevskoy on 22 April 2019. Photo by A. Klimova, courtesy of Institute of Volcanology and Seismology (IVS FEB RAS).

Thermal anomalies were noted by KVERT during two days in September 2018, six days in April 2019, eleven days in May 2019, and six days in June 2019. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed infrequent weak thermal anomalies December 2018 through early May 2019.

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

Information Contacts: 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/); 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/).

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Bulletin of the Global Volcanism Network - Volume 20, Number 04 (April 1995)

Managing Editor: Richard Wunderman

Arenal (Costa Rica)

Gas analysis; high tremor and a large explosion

Asamayama (Japan)

First month with over 1,000 earthquakes since 1991

Atmospheric Effects (1995-2001) (Unknown)

Lidar data from Cuba

Barren Island (India)

Ash plumes from three vents; fire fountaining and lava flows

Deception Island (Antarctica)

Report from a 1994-95 austral summer survey

Fogo (Cape Verde)

Fire fountains continue but lava extrusion rate declines

Galeras (Colombia)

Earthquake swarm continues; higher pressure gas emissions

Irazu (Costa Rica)

Rainfall-induced mass wasting and three seismic events

Kanaga (United States)

Occasional mild steam plumes

Kilauea (United States)

Lava flows, breakouts, tremor, and more

Langila (Papua New Guinea)

Ash clouds to several hundred meters above the crater

Manam (Papua New Guinea)

Both seismicity and tilt low; gently steaming

Momotombo (Nicaragua)

Fumarole chemistry and temperature data for 1983 and 1995

Poas (Costa Rica)

Two new hot springs; moderate number of earthquakes and tremor

Popocatepetl (Mexico)

Located seismic events and summit crater observations

Rabaul (Papua New Guinea)

Tavurvur explosions stop on 16 April

Rincon de la Vieja (Costa Rica)

Description of the crater lake and fumaroles

Ruapehu (New Zealand)

Crater lake temperature drops 10°C from 13-year high

Stromboli (Italy)

Explosion on 5 March and tremor; crater observations

Unzendake (Japan)

No lava dome growth, small rockfalls, rare tremors

Veniaminof (United States)

Small plumes seen; warm spots identified from satellite images

Villarrica (Chile)

Tremor, mild explosions, and a new pyroclastic cone

Vulcano (Italy)

Fumaroles at Fossa Grande and Forgia Vecchia craters

White Island (New Zealand)

Currently non-eruptive but 2-year-long inflation continues



Arenal (Costa Rica) — April 1995 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Gas analysis; high tremor and a large explosion

During April, Crater C continued its ongoing emission of gas, lava flows, and small Strombolian eruptions. The lava flow that started in October 1994, reached 1,100 m elevation along the W arm and at 850 m elevation along the NW arm. On Arenal's NW, W, and SW flanks the tips and borders of tree leaves showed signs of scalding by acidic rain; some species were merely discolored, others were dying.

During April, a total of 484 low-frequency seismic events took place (figure 72); the majority of these events correlated with Strombolian eruptions; some events were registered as far away as 30 km SW of the active crater (station JTS). In terms of total (broad-band) seismicity, the most seismically active single day was 30 April, with 53 events registered.

Figure (see Caption) Figure 72. Arenal low-frequency seismicity for 1994 and January-April 1995. Data courtesy of OVSICORI-UNA.

According to OVSICORI-UNA, tremor prevailed during April for a total of 326 hours, 160% larger than any month (with data) in 1994 and thus far in 1995 (figure 72). At station JTS the tremor's dominant frequency fell between 2.0 and 3.2 Hz, its amplitude was as large as 101 mm.

ICE reported that average daily ashfall near the vent fluctuated significantly in the past few collection intervals (table 10). In three of the four collection intervals, the percentage of material above and below a quarter of a millimeter (250 µm) typically broke down in a roughly 40:60 ratio (coarse to fine).

Table 10. Ash collected 1.8 km W of Arenal's active vent, 19 October 1994 through 21 April 1995. Courtesy of ICE.

Collection Interval Avg daily ashfall (grams/m2) Ash % 300+µ Ash % less than 300µ
19 Oct-23 Jan 1995 7.6 38.0 62.0
23 Jan-03 Mar 1995 8.2 54.7 45.3
03 Mar-30 Mar 1995 22.7 42.2 57.8
30 Mar-21 Apr 1995 16.3 39.5 60.5

On 9 May at 2003, one of the biggest explosions in the last year and a half took place--sufficiently large to capture the attention of local newspapers. The amplitude of the accompanying seismic signal recorded 23 km W of Arenal reached ~20x larger than a "normal explosion"; the signal took ~0.3 seconds to grow to maximum amplitude. The elevated signal from the 9 May seismic event lasted >1.2 minutes; in contrast, at this same station the elevated signal from a normal explosion lasts perhaps 0.1 minute.

Robust, monochromatic, 2.5 Hz tremor took place at least 40 minutes prior to the 9 May event. After the event, the tremor became spasmodic, and although the bulk of the energy remained at 2.5 Hz, there was also some centered around 2.0 and 3.2 Hz.

Glyn Williams-Jones and John Stix sent the following. "During the period from 20 February to 20 April 1995, CO2 and Rn soil gas samples and correlation spectrometer SO2 fluxes were measured on Arenal. Four lines of 19 soil gas stations consisting of meter-long, 7.6-cm-diameter PVC tubes and 1-cm-diameter metal tubes, buried to approximately 75 cm in the ground, were installed on the N, S, W, and E flanks of the volcano.

"Radon values are extremely low, ranging from 2values show a similar pattern, with proximal stations starting at 0.01% to a maximum of ~8% for the more distal stations. The more developed organic-rich soils appear to show higher values of CO2 and Rn, implying a possible organic or soil influence.

"The SO2 flux in the volcanic plume was measured using a Plume Tracker instrument, similar to a COSPEC correlation spectrometer. The instrument was mounted 'looking up' on a moving motor vehicle passing under the plume. Eleven days of SO2 data were collected, resulting in more than 100 measurements. The flux appears to be small but highly variable, with the highest measured value at 370 metric tons/day (t/d). The highest values were associated with explosive eruptions. Following eruptions, SO2 flux dropped to background levels of about 60 +- 10 t/d. Less apparent from the data is a possible gradual increase in SO2 output prior to an eruption.

"The values that we measured are comparable to those measured by Casadevall and others (1984) in 1 February 1982 (210 +- 30 t/d) and by Stoiber and others (SEAN 07:11) in November 1982 (~50 t/d). It is likely that these variations are related to changes in the volcano's activity."

Arenal's first chronicled eruption, in 1968, began an unbroken sequence of Strombolian explosions, and basaltic andesite discharges from multiple vents (see map in BGVN 18:08). The volcano lies adjacent to Lake Arenal, a dammed reservoir for generating hydroelectric power.

References. Casadevall, T.J., Rose, W.I., Fuller, W.H., Hunt, W.H., Hart, M.A., Moyers, J.L., Woods, D.C., Chuan, R.L., and Friend, J.P., 1984, Sulfur dioxide and particles in quiescent volcanic plumes from Póas, Arenal, and Colima volcanoes, Costa Rica and Mexico: J. Geophys. Res., v. 89, p. 9633-9641.

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: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; G.E. Alvarado, Waldo Taylor, and Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles: OSIVAM; Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica; Glyn Williams-Jones and John Stix, Departement de Geologie, Universite de Montreal, Quebec, Canada, H3C 3J7.


Asamayama (Japan) — April 1995 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


First month with over 1,000 earthquakes since 1991

Last reported on in 1991 (BGVN 16:04), but one of Japan's most active volcanoes, Asama had an increase in seismicity during mid-April. On 17 April the seismic system at station B, 2 km S of the summit, recorded 107 earthquakes. After that, the daily number of earthquakes dropped to between about 10 and 80. The total number of April earthquakes at station B was 1031; the last month with over 1,000 detected earthquakes was April 1991 (1,051).

Asama has had over 100 explosive eruptions since ~350 AD. The vast majority of these eruptions have been assigned Volcanic Explosivity Index (VEI) values of 2-3, but several had VEI values of 4 or 5.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Atmospheric Effects (1995-2001) (Unknown) — April 1995 Citation iconCite this Report

Atmospheric Effects (1995-2001)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Lidar data from Cuba

At Camaguey, Cuba, a volcanic aerosol layer was detected at 19-23 km altitude from 18 November through 28 December 1994 (table 2). Backscatter ratios (0.53 µm) were in the 1.26-1.40 range, with integrated backscatter values of 0.18-0.29 x 10-3. These data are similar to those acquired in Cuba during July-October 1994 (Bulletin v. 19, v. 10).

Table 2. Lidar data from Cuba showing altitudes of aerosol layers (bases only). Backscattering ratios are for the Nd-YAG wavelength of 0.53 µm. The integrated value shows total backscatter, expressed in steradians^-1, integrated over 300-m intervals from 16-33 km.

DATE LAYER ALTITUDE (km) (peak) BACKSCATTERING RATIO BACKSCATTERING INTEGRATED
Camaguey, Cuba (21.2°N, 77.5°W)
05 Nov 1994 18.1 (23.2) 1.38 0.22 x 10-3
09 Nov 1994 16.3 (25.0) 1.41 0.28 x 10-3
18 Nov 1994 18.4 (23.8) 1.40 0.25 x 10-3
24 Nov 1994 18.1 (22.6) 1.40 0.29 x 10-3
29 Nov 1994 17.5 (21.6) 1.42 0.29 x 10-3
03 Dec 1994 18.1 (22.0) 1.33 0.23 x 10-3
07 Dec 1994 18.4 (22.0) 1.33 0.18 x 10-3
17 Dec 1994 18.4 (22.6) 1.26 0.19 x 10-3
24 Dec 1994 17.8 (21.1) 1.39 0.22 x 10-3
28 Dec 1994 17.8 (19.0) 1.28 0.20 x 10-3

Information Contacts: Juan Carlos Antuna, Centro Meteorologico de Camaguey, Apartado 134, Camaguey 70100, Cuba.


Barren Island (India) — April 1995 Citation iconCite this Report

Barren Island

India

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

All times are local (unless otherwise noted)


Ash plumes from three vents; fire fountaining and lava flows

The GSI made an aerial survey on 2 March and a land survey on 8 March 1995 to monitor the ongoing eruption . . . . Surveys in late January revealed mainly Strombolian emissions from two vents near the S crater wall (figure 3; vents A and B). Lava flows had reached the sea by the end of January.

Figure (see Caption) Figure 3. Geologic sketch map of Barren Island showing lava flows and distribution of volcanic products from the 1995 and 1991 eruptions. Modified from Haldar and others (1992); courtesy of the GSI.

The GSI Photogeology and Remote Sensing Division analyzed seven Landsat TM IRS images . . . from November 1994 through February 1995. No signs of eruption were seen on 6 November or 8 December, but conspicuous activity was present on 29 December 1994. Vigorous activity was noted on 9 January. An image from 20 January showed decreasing emissions, but on 25 January the eruption was increasing again. Billowing smoke could be seen through gaps in the cloud cover on 11 February. The lava surface temperature was estimated to be well above 1,000°C on 9 and 25 January, based on preliminary analysis of a few thermally radiant pixels.

On 2 March aerial observers noted thick columns of dark to yellowish gray gas followed by white fumes gushing vigorously from the two vents active in late January. The gas column was rising ~1 km, and the eruption was confined to the S side of the summit crater. Denser air containing volcanic aerosols was encountered ~90 km WSW of the volcano at an altitude of ~2,100 m. Very dense air was noticed ~35 km W, and a very thick gas and smoke cloud was encountered ~15 km W at a height of ~1,500 m.

On 8 March the eruption was largely characterized by phreatomagmatic explosions. In addition to the two previously mentioned vents, the pre-existing conduit in the center of the 1991 crater (figure 3; vent C) was vigorously active. Huge billowing dark emissions from all three summit vents were followed by thick jets of white fumes at intervals of 30-60 seconds, with deep thundering explosions. The combined eruption column rose ~1.5 km before being blown SW by the wind into a horizontal plume. Space Shuttle astronauts observed this plume blowing generally W on 9 and 14 March (20:02).

A fourth vent had also opened at the S foot of the existing volcanic cone by 8 March (figure 3; vent D). It had constructed a small spatter cone from which thick lava was pouring out and a fire fountain was rising ~30 m. Ground temperature ~100-300 m from the foot of the cone was 62-83°C. Hot lava was cascading into the sea along the NW shore, ~200 m S of the landing site, causing the seawater to boil profusely. The lava front thickness had increased from ~6 m on 24 January to ~10 m on 8 March. Ejecta ranged in size up to 10 x 18 x 25 cm. Extensive ashfalls covered the S and W parts of the island, and ash was seen falling as far as 10 km S of the island. Marine life has not been seriously affected; fish were observed ~500 m from shore. Birds were also seen flying over the N part of the island.

Reference. Haldar, D., Laskar, T., Bandyopadhyay, P.C., Sarkar, N.K., and Biswas, J.K., 1992, Volcanic eruption of the Barren Island volcano, Andaman Sea: Journal of the Geological Society of India, v. 39, p. 411-419.

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: Director General, GSI; Deputy Director General, GSI Eastern Region.


Deception Island (Antarctica) — April 1995 Citation iconCite this Report

Deception Island

Antarctica

63.001°S, 60.652°W; summit elev. 602 m

All times are local (unless otherwise noted)


Report from a 1994-95 austral summer survey

Deception has been monitored every austral summer since 1986; its flooded caldera forms a 5 x 9 km bay breached to the SW, giving Deception Island a ring shape. This report describes the 1994-95 summer survey, which included geophysical, geochemical, and volcanological work.

Near the Spanish Antarctic station "Gabriel de Castilla" a 500 x 600 m seismic array was deployed. Composed of three, 16-bit digital acquisition systems, the seismic array incorporated the following: 1) a Marck L15B with flat response between 1-48 Hz (12 vertical geophones and 4 horizontal geophones), 2) a Marck L4C with flat response between 0.1-48 Hz (two vertical geophones and four horizontal geophones), and 3) a broad-band, three-component Guralp CMG-3ESP with response between 0.033 and 48 Hz.

Figure 10 shows the acquired seismic data, which were collected from 7 December 1994 through 23 February 1995. The seismic data were subdivided into several groups on the basis of their time-domain and frequency-domain appearance. The resulting groups consisted of 262 volcanic tremors, 145 hybrid events, 300 low-frequency events, and 18 high-frequency (local) events (S - P time under 4 seconds). Applying classical array techniques, the preliminary locations for these events suggested that many came from two areas near 'Vapour Hill' (presumably located on the W side of the island at a spot previously designated 'Steaming Hill' on the map in BGVN 19:09).

Figure (see Caption) Figure 10. Deception Island seismicity, December 1994-February 1995. Courtesy of Alicia Garcia.

A summary of seismic events detected during previous surveys appears in table 2. Although seismic parameters were not always clearly delineated in previous BGVN reports, the seismic events registered in 1991 and 1992 were thought to have been less energetic than in 1994-95. Although the occurrence of earthquake activity was distributed throughout December, January, and February, the team observed at least 10 days with a notable increase in seismicity, days when volcanic swarms had average durations of ~3-6 hours. Given the absence of volcanic activity the researchers suggested that some of the seismicity may be contributed by thermally driven seasonal change.

Table 2. A summary of detected seismic events at Deception Island during austral summer surveys. "--" = not reported.

Season Duration (months) Total events recorded Magnitude SEAN/BGVN (Vol:No)
1987 2 -- ~0.5 mb 13:02
1988 2 -- ~0.5 mb 13:02
1988-89 3 more than 2,000 -- 14:03
1989-90 3 1,000 0.5-2.1 mb 15:03
1989-90 3 -- M 3.2 16:05
1991-92 3 766 0.8-2 (4 of M greater than 3) 17:04
1992-93 3 (?) 135 0.3-0.9 18:03
1993-94 3 "a few" 1.5-2 19:09
1994-95 3 725 -- 20:04

Although no data were presented, in addition to reoccupying the local gravimetric net, the magnetic field intensity was continuously recorded using three proton precession magnetometers.

Temperatures of fumaroles and hot soils remained stable with respect to those measured in the last survey. The anhydrous component of gases were mainly CO2 (96-99%) and H2S (0.2- 3.9%); SO2 was not detected.

Geologic Background. Ring-shaped Deception Island, one of Antarctica's most well known volcanoes, contains a 7-km-wide caldera flooded by the sea. Deception Island is located at the SW end of the Shetland Islands, NE of Graham Land Peninsula, and was constructed along the axis of the Bransfield Rift spreading center. A narrow passageway named Neptunes Bellows provides entrance to a natural harbor that was utilized as an Antarctic whaling station. Numerous vents located along ring fractures circling the low, 14-km-wide island have been active during historical time. Maars line the shores of 190-m-deep Port Foster, the caldera bay. Among the largest of these maars is 1-km-wide Whalers Bay, at the entrance to the harbor. Eruptions from Deception Island during the past 8700 years have been dated from ash layers in lake sediments on the Antarctic Peninsula and neighboring islands.

Information Contacts: J.M. Ibanez and J. Morales; Instituto Andaluz de Geofísica, Apartado 2145, Univ. Granada, Granada, Spain; A. Garcia and R. Ortiz, Dpto. Volcanologia. Museo Nac. Ciencias Naturales, C.S.I.C., Jose Gutierrez Abascal no. 2, 28006-Madrid, Spain; E. del Pezzo, Dpto. Fisica, Univ. Salerno, Salerno, Italy; C. Risso, Instituto Antartico Argentino, Cerrito 1248, Buenas Aires, Argentina.


Fogo (Cape Verde) — April 1995 Citation iconCite this Report

Fogo

Cape Verde

14.95°N, 24.35°W; summit elev. 2829 m

All times are local (unless otherwise noted)


Fire fountains continue but lava extrusion rate declines

On 2-3 April a fissure eruption began on Fogo Island from the SW flank of Pico cone (Fogo Peak) within the 8-km-diameter Cha Caldera (BGVN 20:03). During the initial stage of the eruption there was a burst or jetting of gas, followed by ejection of large blocks and fire fountaining. A lava flow cut off the main road to local villages by the morning of 3 April, and ash fell on the island. Approximately 1,300 residents in the caldera were evacuated.

Volcanologists from the United States, Portugal, and France were requested by the Cape Verdean government to help monitor and evaluate the activity. João Gaspar (Universidade dos Açores) and colleagues observed the activity until 11 April. U.S. Geological Survey (USGS) volcanologists, assisted by Cape Verdean geologists, installed a seismic station and monitored the eruption during 10-25 April. Additional information about the vent activity during 14-19 April was provided by Henry Gaudru and members of the Société Volcanologique Européenne who visited the volcano. François Le Guern (CNRS France) monitored the volcano on 25-27 April.

Summary of activity, 3-16 April. Detailed activity reports through 16 April have already been published (BGVN 20:03). Seven vents were active on the first day of the eruption, with fire-fountains feeding pahoehoe lava flows, ejection of volcanic bombs, and a gas-and-ash plume 2,000 m high. A scoria cone was soon built, from which lava flows were directed SW before turning NW towards the caldera wall. As the main aa flow approached the caldera scarp it turned N, covering the settlement of Boca de Fonte by 9 April and approaching Portela and Bangaeira (see map in BGVN 20:03). Less vigorous fire fountaining continued on 12-16 April, and fed new lava flows on top of the previous aa flow. There were occasional periods of Strombolian spatter ejections. By late on 16 April the remobilized flow-front was ~4 km from the source vent and only a little more than 500 m from the nearest house in Portela.

Activity during 17-25 April. Except where noted otherwise, the following observations are from the USGS team and their Cape Verdean colleagues. Activity continued on 17 April with little change at the vent. Spatter fountains rose 100-150 m, and the cone was ~150 m high. Volcanic tremor amplitude remained moderate to strong. The N end of the aa flow advanced ~150 m during 16-17 April, to ~420 m SW of the nearest house in Portela, and the E side of the flow moved 20-50 m ENE. The W side of the flow advanced >100 m and by 1430 had crushed half of the winery at Boca de Fonte. After these breakouts blocked the access road a new road was created through agricultural fields, forcing residents rescuing belongings to walk an additional 500 m. Flow movement was barely perceptible after 1430 and largely restricted to short spiny pahoehoe and aa oozes at flow margins, although lava output at the vent was unchanged.

Between 1630 and 2030 on 17 April, Gaudru noted that Strombolian explosions were less vigorous and that the main lava channel had widened from 2-3 m to 5-6 m because of lava-block obstructions. The W flank of the cone was also covered by cinders. Explosive activity increased at 1900, sending incandescent ejecta 150-200 m above the rim of the cone. A flame visible behind the E part of the cone was apparently coming from a small vent on the upper E flank. At 2000 explosions began ejecting material >300 m W instead of vertically.

Tremor amplitude began to increase around 0650 on 18 April, and at 0740 became continuous at about twice the previous amplitude. Eruptive style changed from fire fountaining to Strombolian activity, with spatter discharged by loud gas bursts every 3-8 seconds. Lava production increased during the morning; by noon the lava was largely pahoehoe in the upper 300 m of the channel. Estimated channel dimensions and the speed of lava in it yielded production rates of 4-8.5 x 106 m3/day. Microearthquakes were intermittent, with three larger events (all M <1) at 1314 and 1803 on 18 April, and at 0426 on 19 April.

Seismograph records showed that activity during 0110-0320 and 0426-0610 on 19 April was characterized by strong explosive bursts, which were interpreted to be vent clearing episodes after pieces of the cone and newly erupted spatter closed the conduit. After 0610 the seismicity indicated a return to fire-fountaining. A favorable wind direction permitted a close approach to the vent and lava channel to verify the volume estimate, but the lava appeared somewhat more viscous/sluggish. There was no measureable movement at the edges of the aa flow on 19 April after <3 m of movement the day before, however, lava continued ponding in its channel near the middle of the flow.

Observations made by Gaudru from 1230 on 18 April until 1230 on 19 April indicated that activity remained strong with incandescent fragments rising >200 m and loud detonations. Explosions every 1-2 seconds, accompanied by earthquakes, ejected particles ranging in size up to >1 m3. Gas outbursts were more intense, and black plumes hovered over the active cone. Partial obstruction of the crater caused a larger explosion at 1745 on 18 April that sent gas and cinders 500-600 m high. After several seconds of quiet, stronger explosive activity began again with sounds that shook the ground. The upper E flank crater sent an intermittent orange-red flame 10-15 m high for several hours during this period, higher than previous days. Eruptive activity observed by the Gaudru group became more regular at 0100 on 19 April, when an intense episode began that sent lava fountains >300 m high for several hours. Explosive activity began again at dawn that lasted throughout the morning of 19 April.

Tremor amplitude on 19 April changed from moderate-strong to moderate around 1500, when Strombolian activity reverted back to fire fountains. Fire fountain heights diminished somewhat on 20 April, rising generally 20-50 m above the vent. Intermittent Strombolian activity continued with more energetic bursts that sent viscous lava clots >160 m high. A full lava channel 200 m W of the vent appeared much like it did the day before. A new aa lobe was moving sluggishly on top of the earlier flow, and by 1700 its distal end was ~600 m from the N end of the flow, nearest to Portela.

Strong Strombolian activity on 21 April produced loud bursts of viscous spatter 50-150 m high. A levee formed on top of the spillway adjacent to the vent behind which fountains rose 10-20 m, often interrupted by explosions. Lava exited through a hole in the bottom of the levee into a W-flank channel roofed over in two places. At the bottom of the spillway the lava entered a sinuous channel, moving W and NW on top of the previously emplaced flow; this channel remained full all day. The volume of lava erupted was similar to values for the past several days, 4-8 x 106 m3/day. The 160-m-high cinder cone was no longer increasing significantly in height, but impact craters as large as 5 m wide and 1 m deep, created by fall of spatter bombs 0.5-2 m across, littered its flanks and parts of the cinder-mantled caldera floor up to 200 from the vent. As is common during eruptions of viscous mafic lava, the inner walls of the cone collapsed into the conduit, resulting in explosive vent-clearing episodes. The overriding aa flow on the E side of the N flow moved another 6 m N during 21 April.

Volcanic tremor on 21-22 April continued at moderate to strong levels, punctuated by frequent sonic bursts. Noisy Strombolian bursts sent clots of spatter over the top of the cone and onto its flanks. The volume of lava flowing into the channel was similar to that of 21 April. At noon, lava from a new crack on the N flank of the cone flowed 150 m N and soon stagnated. The aa flow advanced 2 m W near the new end of the road (150 m S of Boca de Fonte), and ~3 m NE on the E side of the N flow. Most of the volume of lava was concentrated in an aa lobe that was very slowly overriding the earlier flow. This lobe locally was at least 15 m thick and covered an estimated 75% of the existing flow field.

Activity on 23 April was spectacular. Deafening explosions from four discrete vents rocked the caldera all day; at times the ground was in continuous motion from concussion waves. The overriding aa lobe only moved ~4 m N on the E side of the main aa flow. However, early in the afternoon a new vent opened at the NW base of the cone. By 1700 lava was flowing W from this vent, and by 1807 spatter ejected to heights of 10-15 m was visible. Pahoehoe lava flowed on top of older aa and soon joined the large stagnating aa channel 500-700 m from the main cone. For the preceding 4 days the seismograph had recorded sonic bursts and microseisms. It was believed that shock waves associated with the bursts caused several fractures on the cone. One of these cracks provided a new pathway for lava to exit the cone, thus robbing the main channel of most of its lava. Strong volcanic tremor was interrupted by frequent sonic bursts.

Moderate to strong tremor continued on 24 April. At the main cone in the morning, Strombolian bursts every few seconds sent spatter fragments onto the cone's flanks. In the afternoon, the intense sonic bursts and Strombolian activity that had characterized the past few days were absent. A gray-black plume, laden with fine-grained (<1 mm) juvenile particles and volcanic gases, rose to heights approaching 1.5 km above the caldera floor. Lava in relatively low volumes continued to erupt from the NW base of the cone, moving horizontally from the cone into a tear-shaped cavity. Once the lava reached the surface, degassing occurred, at times intensely enough to drive low-level Strombolian activity. The amount of visible degassing rivaled the plume from the main vent. The depression and lava chute were 25-35 m long and 1-2 m wide. Lava moving at 1 m/s then spilled out of the chute and entered a channel, which was 3-5 m wide, with a speed of 6 m/minute. The flow in the chute and lava channel was initially pahoehoe, changing to aa with increasing distance. The new lava channel joined the former channel, now stagnant in its upper part, 500-700 m below the cone. This new channel caused the hydraulic head within the main cone to be lowered, resulting in decreased Strombolian activity.

By 25 April the lava extrusion rate slowed to ~250,000 m3/day, and tremor amplitude was somewhat diminished. Spatter generally was not visible within the cone and only rarely did isolated fragments clear its top. However, lava that had ponded in the aa channel advanced on the S side of the earlier large flow. This advance, which probably began late on 24 April, moved as much as 0.5 m/minute during the afternoon. Most of the new lobe was aa, with minor pahoehoe. The thermocouple temperature was 1,065°C (steady for several minutes) in the pahoehoe. At about 1500-1700 loud explosions at vents within the main cone increased in frequency, although spatter output did not change.

Activity in late April-early May. At the request of the Cape Verde government, the French Embassy in Praia and the Ministere de l' Environnement in Paris arranged for François Le Guern (CNRS) to observe the activity during 25-27 April. Incandescent scoria fountains rose 50 m over the crater 5-10 times/day followed by quiet periods. Sometimes explosions with black ash or transparent brown or blue haze lasted a few tens of minutes. Lava output was estimated to be 1 x 106 m3/day on 26 April with a lava front 300 m long, decreasing by 10-15% on the following days. On 27 April lava advanced <0.5 m/hour.

From late April through 2 May a team from the International Federation of Red Cross and Red Crescent Societies reported that lava continued to flow from the crater, though at a much reduced rate, and had already covered 5 km2 of cultivated land including five houses and a winery that was a major source of income for the displaced. At that time the flow was contained inside the existing banks of lava. News reports indicated that after a period of non-explosive emissions and weak lava flow production, the eruption strengthened slightly on 7 May with greater lava output. On 8 May the United Nations coordinator in Praia reported decreased activity with some explosions and moderate to strong tremor. The lava emission rate was relatively low, coming from vents at the NW base of the cone.

Displaced persons and future plans. Apart from the destruction to outlying buildings, the villages themselves remained intact but largely deserted in early May. During the day there was regular foot traffic as people removed items of use to the camps, including livestock. The Red Cross of Cape Verde has volunteers in four camps containing 157 families. The camps are: Sao Filipe, population 534 (including 313 children); Patim, population 88 (53 children); Achada Furna, population 156 (90 children); and Mosteiros, population 90 (55 children). Adding the ~150 people living with friends and relatives, the total number of displaced person comes to 1,014. These numbers fluctuate as people return to the area and re-evacuate following felt earthquakes.

With emergency needs met, government officials believe that the focus should be on the resettlement of displaced persons. The United Nations DHA-Disaster Mitigation Branch was focusing on civil protection preparedness planning for future volcanic eruptions and other natural disasters.

On 10 May, at the request of the Cape Verde government, a team of four geologists and two students from the Universidade dos Açores went to Fogo to study the eruption. Their objectives are to monitor the progress of the eruption and to begin research related to gas release and the risks of contamination of public water supplies.

Geologic Background. The island of Fogo consists of a single massive stratovolcano that is the most prominent of the Cape Verde Islands. The roughly circular 25-km-wide island is truncated by a large 9-km-wide caldera that is breached to the east and has a headwall 1 km high. The caldera is located asymmetrically NE of the center of the island and was formed as a result of massive lateral collapse of the ancestral Monte Armarelo edifice. A very youthful steep-sided central cone, Pico, rises more than 1 km above the caldera floor to about 100 m above the caldera rim, forming the 2829 m high point of the island. Pico, which is capped by a 500-m-wide, 150-m-deep summit crater, was apparently in almost continuous activity from the time of Portuguese settlement in 1500 CE until around 1760. Later historical lava flows, some from vents on the caldera floor, reached the eastern coast below the breached caldera.

Information Contacts: R. Moore, U.S. Geological Survey, Mail Stop 903, Federal Center Box 25046, Denver, CO 80225 USA; Frank Trusdell, U.S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, HI 96718, USA; Veronica Carvalho Martins, U.S. Embassy, Rua Hoji Ya Henda 81, C.P. 201, Praia, Cape Verde; Arrigo Querido and Helena Tatiana Osorio, INGRH Servicos Estudos Hidrologicos, C.P. 367, Praia, Cape Verde; François LeGuern, CNRS Centre des Faibles Radioactivités, 91190 Gif-sur-Yvette, France; João Gaspar and Nicolau Wallenstein, Departamento Geociências, Universidad dos Açores, rue da Mae de Deus 58, 9500 Ponta Delgada, Açores, Portugal; Henry Gaudru, Christine Pittet, Patrick Barois, and Marc Sagot, Société Volcanologique Européenne (SVE), C.P. 1, 1211 Geneva 17, Switzerland; United Nations Department of Humanitarian Affairs, Palais des Nations, 1211 Geneva 10, Switzerland; International Federation of Red Cross and Red Crescent Societies, C.P. 372, 1211 Geneva 19, Switzerland.


Galeras (Colombia) — April 1995 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Earthquake swarm continues; higher pressure gas emissions

Volcanic activity was relatively low in April. During approximately 1-20 April there was an increase in the pressure of gas emissions. Heavy rains on 12 and 18 April caused mudflows along the W-flank Azufral river that reached heights of 5 and 15 m, respectively, above the usual water level in narrow sections of the canyon. These two events were detected by the seismic network at Galeras.

A high-frequency earthquake swarm (magnitudes up to 2.3) on 14 April associated with rock fracturing (15 events within 100 minutes) was located at depths of 1.5-4 km below the summit. Ten other high-frequency events had dispersed epicenters at depths of <5 km. Four nearly monochromatic long-duration earthquakes with slowly decaying codas (screw-type events) occurred during 19-20 April. Screws were not detected after increased gas emissions on 22 April sent a plume ~2 km high that was seen from Pasto (~9 km E).

The earthquake swarm NNE of the active crater that began in March continued in April, but with fewer and lower-magnitude events. However, there were two events felt in Pasto and in the towns of Jenoy and Narino on 3 and 27 April. By the end of April there had been 1,967 events from this source since 4 March, of which 67 were felt in small towns near the epicenter.

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 horseshoe-shaped 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 historical eruptions since the time of the Spanish conquistadors.

Information Contacts: INGEOMINAS-Observatorio Vulcanologico y Sismologico de Pasto (OVP), Apartado Aereo 1795, San Juan de Pasto (Narino), Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).


Irazu (Costa Rica) — April 1995 Citation iconCite this Report

Irazu

Costa Rica

9.979°N, 83.852°W; summit elev. 3432 m

All times are local (unless otherwise noted)


Rainfall-induced mass wasting and three seismic events

OVSICORI-UNA reported that, with respect to January, the lake level in April dropped 50 cm. The greenish yellow lake constantly bubbled on its N, NE, W, and SW shores. Small landslides took place along the crater's N, E, and SW walls.

On the NW flank, where there had been a small phreatic eruption vented from a well-established fumarole in December 1994, fumaroles remained active at both the eruption site and on the adjacent crater's N wall. Rainfall caused new mass wasting that sent debris into the Rio Sucio.

ICE reported that Mauricio Mora recorded three seismic events in the vicinity of the volcano. These appeared similar to tectonic earthquakes; their hypocenters fell within about 10 km of Irazú's main crater.

Geologic Background. Irazú, one of Costa Rica's most active volcanoes, rises immediately E of the capital city of San José. The massive volcano covers an area of 500 km2 and is vegetated to within a few hundred meters of its broad flat-topped summit crater complex. At least 10 satellitic cones are located on its S flank. No lava flows have been identified since the eruption of the massive 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 historically active crater, which contains a small lake of variable size and color. Although eruptions may have occurred around the time of the Spanish conquest, the first well-documented historical 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.

Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles (OSIVAM), Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San Jose, Costa Rica; Mauricio Mora, Escuela Centroamericana de Geologia, Universidad de Costa Rica.


Kanaga (United States) — April 1995 Citation iconCite this Report

Kanaga

United States

51.923°N, 177.168°W; summit elev. 1307 m

All times are local (unless otherwise noted)


Occasional mild steam plumes

As of 31 March, observers in Adak (33 km E) continued to report occasional mild steam plumes above the summit. Through 31 March no thermal anomaly had been detected since 13 October 1994 when eruptive activity that began in December 1993 apparently ceased (BGVN 18:12 and 19:11). That eruption was characterized by intermittent, low-level steam and ash emissions producing plumes rarely rising over 3,000-4,500 m altitude and drifting a few tens of kilometers downwind. There are no seismometers on Kanaga, located 965 km WSW of the tip of the Alaska Peninsula on Kanaga Island, and monitoring is done through a combination of satellite image analysis and observations by pilots and residents of Adak.

Geologic Background. Symmetrical Kanaga stratovolcano is situated within the Kanaton caldera at the northern tip of Kanaga Island. The caldera rim forms a 760-m-high arcuate ridge south and east of Kanaga; a lake occupies part of the SE caldera floor. The volume of subaerial dacitic tuff is smaller than would typically be associated with caldera collapse, and deposits of a massive submarine debris avalanche associated with edifice collapse extend nearly 30 km to the NNW. Several fresh lava flows from historical or late prehistorical time descend the flanks of Kanaga, in some cases to the sea. Historical eruptions, most of which are poorly documented, have been recorded since 1763. Kanaga is also noted petrologically for ultramafic inclusions within an outcrop of alkaline basalt SW of the volcano. Fumarolic activity occurs in a circular, 200-m-wide, 60-m-deep summit crater and produces vapor plumes sometimes seen on clear days from Adak, 50 km to the east.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA, b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Kilauea (United States) — April 1995 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 flows, breakouts, tremor, and more

The 12-year-long eruption on Kilauea's E rift zone continued in March-April, with vents on the SW flank of the Pu`u `O`o cone feeding directly into lava tubes. Recent heights of the lava lake are at the bottom of table 4 and a map showing recent flows appears on figure 97 (for comparison, the previous map appeared in BGVN 20:02).

Table 4. Summary of Kilauea seismic data, lava flux rate, and lava pond heights for stated dates or intervals in 1995. Courtesy of HVO.

Date/Interval Observation Type Comment
Late Feb-03 Mar 1995 Earthquakes Intermediate depth activity remained high, slowly decaying to background levels.
Late Feb-10 Mar 1995 East Rift Zone Tremor Tremor with stable amplitudes ~3-4x background.
03 Mar 1995 Pu`u `O`o lava pond 79 m below rim.
10 Mar 1995 East Rift Zone Tremor Tremor dropped to 2x background with intermittent bursts of higher amplitude (similar to banded tremor) at 1900.
14 Mar-15 Mar 1995 Earthquakes In a 37-hour period beginning at 0900 on 14 March there were 134 intermediate-depth events.
14 Mar-27 Mar 1995 East Rift Zone Tremor Tremor continued.
19 Mar 1995 Earthquakes M 4.3 earthquake at ~50 km depth, W of the Island of Hawaii.
21 Mar 1995 Pu`u `O`o lava pond 75 m below rim.
27 Mar 1995 Earthquakes M 4.1 earthquake at 25 km depth beneath the upper E rift zone.
28 Mar-10 Apr 1995 East Rift Zone Tremor Tremor fairly constant at 2-3x background.
28 Mar-10 Apr 1995 Pu`u `O`o lava pond 75-81 m below rim.
11 Apr-24 Apr 1995 Earthquakes Shallow, long-period microearthquake counts were slightly above average. The number of short-period events was low.
11 Apr-24 Apr 1995 East Rift Zone Tremor Tremor continued, amplitudes were low, ~1.5-2x background. Shallow, long-period microearthquake counts were slightly above average.
11 Apr-24 Apr 1995 Pu`u `O`o lava pond 90-86 m below rim. Continued lava circulation from W to E in the pond.
03 May 1995 Earthquakes Swarm of 13 located earthquakes, the largest M 3.9; they were interpreted as shallow crustal adjustments beneath Hilina Pali.
10-30 Apr 1995 Lava flux rate ~400,000 m3/day (Volcano Watch, 1995).
Figure (see Caption) Figure 97. Kilauea lava flows grouped into three time intervals: 1983 to 1992; 1992 to April 1995; and 11-20 April 1995. Heavy dashed line indicates lava tubes, and the contour interval is 500 m. Courtesy of USGS.

During 28 February-13 March fluid pahoehoe breakouts spread W and covered more of the Chain of Craters road. The eruption slowed during 14-16 March. Flows became more viscous and the amount of lava entering the ocean dwindled. On 16 March, cooler temperatures were measured on a thermocouple hanging through an opening in the roof of an active lava tube. By the morning of 17 March all flows entering the sea had temporarily stopped, but temperatures rose to normal values in the active tube and by early afternoon lava began escaping the tube system at three elevations; one reached within 500 m of the highway by 27 March.

In the 24 March-10 April interval, two tubes diverging toward the E and W sides of the flow field, the Kamoamoa and the Lae'apuki tubes, respectively, continued to feed flows on the coastal plain. The Highcastle lava flow escaped from the E tube (figure 97), advancing toward the ocean as a sheet flow, covering the lower part of another recent flow (the Jason flow), and reaching the ocean on 29 March. By 6 April, the Highcastle flows had built a 500-m-wide lava bench 20-30 m oceanward. On 7 April, a large breakout from the 104-m elevation on Paliuli headed towards the ocean on top of previously emplaced flows. By 8 April, flows on the coastal plain had stilled and the amount of lava entering the ocean decreased. The east rift zone eruption paused briefly on 11 April and flows on the coastal plain stagnated.

When the eruption later resumed, lava broke out of the tube system on Pulama pali, feeding numerous aa and pahoehoe flows. Two lava flows entered the ocean on about 18-20 April. Pahoehoe lava engulfed an older cone that had been created by littoral explosions in July 1994, leaving only a remnant of the cone visible on 20 April. The following day, a seismic station in the coastal area recorded a bench collapse-littoral explosion and at the same time observers saw the steam plume abruptly increase in size.

On the topic of a public policy issue relevant to volcanologists and public access to volcanoes, in 1992 US and local government personnel rescued a movie cameraman trapped on a ledge above Pu`u O`o lava lake. Although rescue workers were cited for valor, an Associated Press news report (Miller, 1995) also mentions how local authorities made subsequent attempts to gain partial reimbursement for $75,000 in rescue expenses. These latter efforts were unsuccessful. According to the news story, in the United States two strategies appear to have emerged for dealing with rescue and related costs: 1) stiff fees paid by park users (eg. $150 for a climbing permit in Denali National Park, Alaska), and 2) rules or laws that specifically dictate that fees be billed to those rescued.

References. Miller, Angela S., 1995, When Risk Leads to Rescue, Who Pays the Cost?: Associated Press, 10 February 1995.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Tari Mattox and Paul Okubo, USGS Hawaiian Volcano Observatory, Hawaii Volcanoes National Park, HI 96718, USA.


Langila (Papua New Guinea) — April 1995 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)


Ash clouds to several hundred meters above the crater

Monitoring of Langila resumed on 3 April following a lapse from 18 March to 2 April. Up to that time, activity at Crater 3 remained low and activity at Crater 2 continued at a moderate level. After the lapse in monitoring, Crater 2 continued to emit white vapors in low to moderate volumes. Gray ash clouds were occasionally emitted to several hundred meters above the crater. Occasional rumbling sounds and night time glows were normally associated with the ash emissions. Loud explosions were heard on 3 and 30 April. Ashfall NW of the volcano (in the Kilenge area) was reported on 11 April. Crater 3 released thin white vapor accompanied by wisps of blue vapor on 12, 14, 21, and 27 April. There were neither audible sounds nor night glows. Both seismographs remained inoperative during the month.

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 eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north 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 of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: David Lolok and Ben Talai, RVO.


Manam (Papua New Guinea) — April 1995 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)


Both seismicity and tilt low; gently steaming

Although activity at Manam remained low in April, throughout the month both Main and Southern Craters infrequently discharged white vapor. Southern Crater discharged wispy blue vapor on the 11th; faint rumbling sounds were heard on one occasion only (at 2330 on 23 April); weak night glow was seen mainly during the 2nd and 4th weeks of April, when then summit was clearly visible. Main Crater issued occasional, thin to thick white vapors. These emissions were gentle and were not accompanied by night glow or audible sounds. The seismicity fluctuated at a low level throughout the month. No significant change was shown by the water-tube tiltmeter located about 4 km SW from the summit.

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 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche 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 historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical 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: David Lolok and Ben Talai, RVO.


Momotombo (Nicaragua) — April 1995 Citation iconCite this Report

Momotombo

Nicaragua

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

All times are local (unless otherwise noted)


Fumarole chemistry and temperature data for 1983 and 1995

On 25 February 1995 Lucano Giannini and Orlando Vaselli (University of Florence) visited the crater of Momotombo to collect fumarolic gas samples. The chemical composition of the gases at the highest observed temperature is shown on table 4. Also shown for comparison are values obtained in 1983, when seismic activity, ground deformation, and subsurface basaltic magma emplacement took place. The temperature decrease and gas compositional changes were thought to mainly reflect the twelve years of cooling.

Table 4. Chemical analyses on Momotombo fumaroles, 1983 and 1995. Courtesy of Marino Martini, University of Florence.

Component 1983 1995
Temperature (°C) 835 660
H2O (volume %) 94.00 91.18
CO2 (dry gas %) 56.95 72.79
SO2 (dry gas %) 22.33 8.72
H2S (dry gas %) 5.00 3.87
HCl (dry gas %) 5.83 6.25
HF (dry gas %) 0.30 0.36
B (dry gas %) 0.081 0.018
Br (dry gas %) 0.0088 0.0073
NH4 (dry gas %) 0.0088 0.0038
H2 (dry gas %) 8.47 5.12
N2 (dry gas %) 0.78 2.73
CO (dry gas %) 0.25 0.12

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: Marino Martini, University of Florence, Italy.


Poas (Costa Rica) — April 1995 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Two new hot springs; moderate number of earthquakes and tremor

Fumarolic activity continued at Poás in the active, northern crater lake. OVSICORI-UNA reported the lake level rose 50 cm in April with respect to March. When observed in April, the lake appeared light green and had a temperature of 41°C. On small areas along the lake's NW and W shore, small bubbles escaped continually. A low (less than 50-m tall) steam cloud hovered over the lake.

On the lake's SW terrace there were two new intermittent springs (74°C and 64°C) that were light-gray in color, presumably caused by suspended sediment. On the S terrace, fumaroles continued to emit gases and on the SW side there appeared a new fumarole with a 74°C temperature. The pyroclastic cone gave off gas that had a 89°C temperature.

Low-frequency seismicity at Poás in April declined by about 15% compared to March (table 6). Tremor began on about 8 March and the monthly duration reached 11 hours, more than the past few months but significantly less than the tens or hundreds of hours recorded during the months of May-September 1994.

Geologic Background. The broad, well-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, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 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 the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA); Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles: OSIVAM; Instituto Costarricense de Electricidad (ICE); Mauricio Mora, Escuela Centroamericana de Geologia, Universidad de Costa Rica.


Popocatepetl (Mexico) — April 1995 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Located seismic events and summit crater observations

"We report on Popocatepetl seismic activity during the interval 21 December 1994 to 2 May 1995. Activity was monitored using seven seismic stations located around to the volcano above 2,600 m elevation (figure 9). These stations are part of the Popocatepetl Seismic Network. Beginning 21 December, the volcano changed dramatically in its seismic and fumarolic activity. Several explosions emitted ash that fell on Puebla City, an area located about 50 km away. About 22 hours after this activity, seismic tremor was observed for the first time at several stations.

Figure (see Caption) Figure 9. Stations of the Popocatepetl Seismic Network (triangles) and epicenters for located events detected 21 December to 2 May 1995 (dots). Courtesy of Instituto de Geofisica, UNAM.

"In the 21 December-2 May interval we located 75 seismic events in the vicinity of the volcano (figure 9). We used arrival times from digital records from at least three stations and located the events using Hypocenter software. The average standard location errors in the horizontal and vertical directions do not exceed 1 km with a standard deviation of 0.14 km (figure 10). Earthquake magnitudes (calculated using a coda length magnitude for tectonic events in Mexico) ranged between 1.4 and 3.4 (as represented by different sized dots on figure 10). The E-W cross section of the hypocenters (figure 10) shows a concentration of seismic events in a circle of 3.0 km diameter and in a conduit that connects to the overlying crater. These results crudely suggest a magma chamber located below sea level and connected to the volcano crater. A N-S cross section suggests the same findings.

Figure (see Caption) Figure 10. An E-W cross section of the hypocenters beneath Popocatepetl for the interval 21 December 1994 to 2 May 1995. Earthquake magnitudes are shown by dot sizes; the size of error bars are discussed in the text. Courtesy of Instituto de Geofisica, UNAM.

"During the first four days (21-24 December) seismic tremor was continuous and of high amplitude. During the following 20 days (25 December-13 January) tremor was also continuous, but the amplitude diminished five-fold compared to the first four days. After that, in the next 45 days (14 January-28 February), tremor turned sporadic with durations of about 10 minutes and with amplitudes comparable to those in the first four days. During the last 60 days, tremor became more sporadic with smaller durations, but it still had amplitudes similar to, and in some cases exceeding, those of the first four days.

"On 12 March an expedition lead by Enrique Chaves-Popuard reached the volcano's summit. The meteorological conditions allowed the team to videotape the interior of the crater. The following observations were made: a) the crater lake disappeared, b) three new craters appeared at the foot of the main crater's E wall, c) most of the fumarolic emissions came from these new craters, d) the number of small fumarolic vents has increased in the older inner crater, and e) several fumarolic vents were observed in the S and E walls of the main crater."

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

Information Contacts: Carlos Valdes-Gonzalez, Guillermo Gonzalez-Pomposo, and A. Arciniega-Ceballos, Departamento de Sismologia y Volcanologia, Instituto de Geofisica, UNAM, Ciudad Universitaria 04510 D.F., Mexico.


Rabaul (Papua New Guinea) — April 1995 Citation iconCite this Report

Rabaul

Papua New Guinea

4.271°S, 152.203°E; summit elev. 688 m

All times are local (unless otherwise noted)


Tavurvur explosions stop on 16 April

Two strong explosions took place at the intra-caldera cone Tavurvur on 30 March; after that, the repose intervals between explosions at Tavurvur lengthened, lasting from several hours to more than 24 hours. Tavurvur discharged several noteworthy explosions on 13-15 April; explosions ceased on 16 April.

During the first half of April, explosions sent ash clouds 1-2 km above the crater, but they were typically spasmodic and relatively mild. Ash predominantly fell to the SE (mainly over Talwatt and occasionally at Kokopo, with smaller amounts in Rabaul on a few days). Accompanying the normally gray ash emissions were weak roaring sounds heard late on the 3rd, low rumbling sounds on the 9th, and lightning seen in and around the billowing ash column on the 11th.

At 1206 on 13 April an impressive explosion occurred. It began with fast-rising, spear-headed jets of dark ash, which fed a billowing ash cloud that rose to about 2 km above the crater. Some ballistic blocks landed in the bay immediately W and NW of Tavurvur. On 14 April, moderate-to-strong explosions started at about 0920, with the most intense activity occurring between 1030 and 1040. Resulting eruption clouds were dark gray and quite dense; fallout was heavy at Tavurvur and immediately downwind (SE). In and around the eruption column, lightning was noted. The activity declined slowly through the day and stopped at about 2320.

Strong explosions resumed at about 1320 on 15 April. During a roughly 1 hour period, several large eruption clouds rose to about 2 km. These ash clouds remained intact as they drifted to the SE. Prolonged moderate ash emission also took place from early to mid-afternoon. During the early hours of 16 April, mild explosive activity took place; it stopped at about 0600. From that time onward activity chiefly consisted of weak white vapor emissions. Following a period of heavy rainfall on the 24th, however, these emissions again became more voluminous, but by the next day they returned to a very low level.

Seismicity in the first half of April, until the 16th, partly consisted of low-frequency earthquakes associated with Tavurvur's explosions. Explosion sizes appeared to correspond to earthquake amplitudes. Six high-frequency earthquakes also occurred (compared to 5 in March and 4 in February). These earthquakes all had epicenters outside the caldera--five to the N-NE and one to the SW.

During April, electronically measured tilt in the interior of the caldera at Matupit Island continued to show a trend of very slow deflation. Other ground deformation measurements failed to show significant trends.

An aerial inspection, on 8 April, revealed that Tavurvur's surface was covered with fresh black ash. Numerous gray blocks had also landed, mainly on the S flank and inside the old crater. The fumarole previously emitting blue-vapor (located about 1/3 of the way down the 1994 lava flow) was inactive. One white-vapor fumarole was noted where the lava had advanced over the crater rim. The crater displayed variably colored sublimate deposits and small erosional gullies. A step-like structural form was seen on the crater's E side, and a smooth, bowl shape was seen on its W side. Inside the crater there were neither visible vents nor a lava mound.

Vulcan continued weak white vapor emissions, coming mainly from the crater of the 1994 cone. Fumaroles at the base of the 1994 crater had been mostly buried by mud leaving only one on the W side of the crater. The upper one of the two pit craters on the N flank of the 1994 cone had caved in. Temperature of hot springs along the N shore were consistent with previous months' readings at ~100°C.

The State of Emergency in Rabaul was lifted on 10 April, making way for the Gazelle Restoration Authority to promote the rehabilitation process.

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 688-m-high asymmetrical pyroclastic 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 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western 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: David Lolok and Ben Talai, RVO


Rincon de la Vieja (Costa Rica) — April 1995 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)


Description of the crater lake and fumaroles

The remote Rincón de la Vieja volcanic complex continues to display unsettled seismic and fumarolic activity. OVSICORI-UNA reported that during April fumarolic venting continued from the W wall, creating noise audible from the crater's rim. Escaping gases stung the skin. Radial fractures encircled the crater on its NE, N, and NW sides.

G. Soto (ICE), Jean-Philippe Rancon, and Gorges Boudon climbed the volcano on 1 May and reported that the lake contained a scum of floating sulfur and was pale turquoise in color. No lake temperature measurements were made but the entire surface steamed slightly. In contrast to a previous visit in March 1994, the lake level seemed significantly higher, although the amount has yet to be quantified from photographic records; zones of bubbling (previously several meters across) were absent.

Fumaroles on the crater's inner SE wall were quite active and fumed noiselessly. Gas plumes, clearly visible from the volcano's N flank, rose up to 100 m above the crater before being blown by the wind. Small, steam-rich fumaroles adjacent to concentric fractures surrounded the crater, typically near the 1,640 m contour. These fumaroles were also active last year.

At least two other noteworthy fumaroles, expelling steam and sulfurous gases, sit on the N flank (along the valley called Quebrada Azumicrorada at around 1,200- and 1,300-m elevation). In clear weather, these fumaroles are visible from local villages and residents stated that they had been active for the past several years.

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 that was 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 1916-m-high 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 3500 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: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles: OSIVAM; Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica; Jean-Philippe Rancon, BRGM, Orleans, France (presently at USGS Cascades Volcano Observatory, 5400 MacArthur Blvd., Vancouver, WA 98661-7095 USA); Georges Boudon, Observatoires Volcanologiques, Institut de Physique du Globe de Paris, 4 Place Jussieu, 75252 Paris 05, France.


Ruapehu (New Zealand) — April 1995 Citation iconCite this Report

Ruapehu

New Zealand

39.28°S, 175.57°E; summit elev. 2797 m

All times are local (unless otherwise noted)


Crater lake temperature drops 10°C from 13-year high

The following was extracted from the IGNS Ruapehu Immediate Report (RUA 95/02). Peaks on the crater lake temperature versus time curve have often correlated to small vent-clearing eruptions (see figure 16).

"Crater Lake has been in a heating phase since late November, reaching the highest temperature (55°C) in 13 years by 12 February, but a 10°C decline since then and a reduction in volume suggest this phase has peaked. Minor phreatic eruptions have been occurring since early January but appear to have become infrequent, or may have even ceased, during February. Despite the relatively high heat output, the recent activity has so far followed the cycle of heating and cooling typical of Ruapehu since at least 1985."

There were several reports of steam clouds and other phenomena after 20 January. A hiker on 24 January described the crater lake seen through the clouds as "a seething surface" that made "roaring sounds" lasting 1 to 2 minutes.

Two or more observers on 29 January described the crater lake, which was visible for almost 2 hours, as "pale gray, almost white" and two, 1.5 m (or smaller) upwelling and splashing episodes were seen. The report also mentioned "pure yellow styrofoam-sulfur" littering the Outlet area. The water temperature, measured with two calibrated thermometers, was 51.4°C.

Hikers in cloudy weather on 30 January witnessed a "small hydrothermal eruption up to 10-20 m." Hikers in cloudy weather on 5 February heard sloshing noises from the crater lake followed by two "loud explosions." On 15 February observers saw a 3 km tall, stationary steam plume over the crater lake; on 25 and 27 February observers also saw steam clouds. These clouds were undoubtedly steam, but they may have arisen from "atmospheric enhancement" due to a rise in relative humidity rather than from definite eruptions. Their interpretation thus remains ambiguous. A ground inspection on 2 March failed to confirm any significant surging took place around the shore of Lake Wade.

In the interval 31 January-early March there were few discrete earthquakes and mainly background tremor was detected on the volcano's Dome seismograph. On the other hand, there were short intervals of strong, high frequency tremor, an unusual occurrence for Ruapehu.

Although in the latest crater visit on 2 March all deformation survey stations were accessible and clear of snow, most of the length changes seen since 13 January were insignificant (<= 5 mm). Station I (see map, BGVN 19:12) appeared to have moved 18 mm ENE relative to all other stations since May 1994--a motion consistent with moderate deflation seen in the past 10 months, but also possibly due to displacement by local snow loading or other factors.

Mg and Cl analyses of lake water were made on 18 and 29 January, and on 2 March, but showed relatively change. The Mg/Cl ratio changed only about 4% (shifting downward from an 18 January value of 0.036 to a 2 March value of 0.035). The Mg/Cl ratios were interpreted to indicate that the heating event was driven by convective flow of lake water through the upper portion of the vent. Thus, the heating event was regarded as mainly due to fluid flow rather than heat input from magmatic sources within the edifice.

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The 110 km3 dominantly andesitic volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: P.M. Otway, Institute of Geological and Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand.


Stromboli (Italy) — April 1995 Citation iconCite this Report

Stromboli

Italy

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

All times are local (unless otherwise noted)


Explosion on 5 March and tremor; crater observations

Due to funding problems, the power supply to the 3-component summit seismic station maintained by the University of Udine was interrupted from 10 December 1994 until 13 January 1995. The previous report (BGVN 20:01) described seismic activity through 9 December. This station has been operating since 1989, but may be permanently shut down in June if funding is not continued.

Stromboli island was visited by Giada Giuntoli and Boris Behncke on 19-24 April. Generally, the volcano showed much less activity than during a previous visit in August 1994, but an increase was evident on 23 April, resulting in the resumption of eruptions from Crater 1, which had been inactive for several weeks. Behncke also provided a review of crater morphology changes since 1989.

Seismicity, early 1995. Throughout 13 January-4 April the daily number of shocks remained roughly constant at 200-400 (figure 39). On 26 February tremor intensity began to decrease, and for a few days its average value remained stable below 3 Volts x seconds (Vs). However, the number of major shocks remained high. On 5 March a large explosion accompanied the return of tremor intensity to more usual values of around 5 Vs. The explosion threw pyroclastic material towards Forgia Vecchia and Fossetta, a depression SW of the crater area. The ejecta rose high enough to be clearly seen from the village of Stromboli, where the explosion was strongly felt. Tremor level continued to increase following the explosion; after a short decrease it quickly increased again to a peak of 10.8 Vs on 30 March. The number of major shocks decreased after 13 March. The increase in tremor intensity after the 5 March event did not match the behavior recorded after the explosions of 10 February 1993 and 16 October 1993 (BGVN 18:01, 18:02, and 18:09). On those occasions a remarkable decrease of all seismicity, and of the tremor level in particular, was noted immediately afterwards.

Figure (see Caption) Figure 39. Seismicity recorded at Stromboli, 13 January-4 April 1995. Open bars show the number of recorded events/day, the solid bars those with ground velocities >100 micron/s (instrument saturation level). The line shows daily tremor energy computed by averaging hourly 60-second samples. The seismic station is located 300 m from the craters at 800 m elevation. Courtesy of Roberto Carniel.

Activity on 20 April 1995. During a summit visit on 20 April between 0000 and 1500, activity was low compared to previous visits (September 1989, March and November 1990, August 1991, and March and August 1994); only three vents were erupting, in contrast to 10 in August. A detailed record of the eruptions was made for ~4 hours (table 2). The most notable change was the almost complete inactivity of Crater 1 (figures 40 and 41), which had contained at least six erupting vents in August 1994. Only vent 1/3 displayed some brief weak explosions, mostly of burning gas carrying a few incandescent fragments from the conduit walls. Crater 2 was not erupting, as in March and August 1994, but was the site of loud gas emissions.

Table 2. Eruptive activity at Stromboli observed between 0800 and 1210 on 20 April 1995, from Pizzo sopra la Fossa. Courtesy of Boris Behncke.

Time Crater-Vent Description
0800 1-3 Brief (1 sec) gas explosion.
0810 1-3 Explosion (2 sec) with dark fumes.
0811 3-2 Very small explosion, no bombs visible.
0811 3-1 Strong bomb ejection to ~30 m.
0813 3-2 Lava fountain (15 sec) with some ash, to ~60 m above crater terrace.
0816 1-3 Brief thud with gas puff.
0825 3-2 Small, low fountain inside crater (5 sec).
0830 2-? Loud gas emission, no solid ejections (2-3 sec).
0845 3-2 Small ash explosion (10 sec) to 30 m.
0857 3-2 Small ash explosion (5 sec).
0859 3-2 Large bomb and ash fountain to 80 m (10 sec).
0902 3-2 Small bomb fountain with no ash to 30 m (5 sec).
0906 3-2 Very small explosion (mainly gas) inside crater (4 sec).
0908 3-2 Large bomb and ash fountain to 50 m, ash plume to 250 m (10 sec).
0912 1-3 Small gas explosion (2 sec).
0937 3-1 Single burst of large bombs to 30 m.
0944 3-1 Bomb ejection to ~20 m.
0952 1-3 Brief (1 sec) gas burst.
0954 3-1 Large bomb ejection with very large (up to 5 m) clots to ~30 m.
1010 3-2 Ash fountain to 150 m.
1043 3-2 Vigorous bomb and ash fountain; bombs to 80 m; dense ash column to >200 m (~30 sec).
1045 1-3 Small gas explosion (1 sec).
1110 3-2 Large bomb and ash fountain similar to that of 1043.
1124 1-3 Small gas explosion (1 sec).
1132 1-3 Small gas explosion (1 sec).
1136 3-2 Bomb and ash fountain, ash to >200 m.
1148 3-1 Abundant very large bombs to ~25 m; "whooshing" sound.
1152 3-1 Similar to 1148 but with less bombs.
1155 3-1 Similar to 1148 but with less bombs.
1207 1-3 Small gas explosion (1 sec).
1208 3-2 Bomb fountain to

The most active vents were in Crater 3. Vent 3/1 activity consisted of almost continuous low spattering from a small lava pond with occasional bursts to ~60 m above the vent; similar activity was seen in March 1994 (BGVN 19:03). Rare bursts of large incandescent lava clots (up to 5 m in diameter) were accompanied by faint "whooshing" noises. Only twice were bombs ejected beyond the pit of 3/1, onto the NE wall of Crater 3. Eruptions from vent 3/2 occurred at intervals ranging from 2 minutes to >1 hour (see table 1), with periods of more frequent eruptions alternating with periods of very low activity. For example, six eruptions occurred during a 25-minute period (0845-0910), while from 0910 until 1210 there were only five more. Some of these eruptions consisted of loud gas emissions with very low spatter fountains, but most produced incandescent fountains 80-100 m high. Between sunrise on 20 April (at about 0700) and noon, the eruptions produced ash plumes up to 250 m high. Most of the ejected material fell back into the pit, but sometimes the entire NW rim of Crater 3 was covered with pyroclastics, and bombs rolled down the Sciara del Fuoco.

Activity on 21 and 23 April 1995. When observed from Punta Labronzo, on the N side of the island, on the evening of 21 April activity consisted of frequent low lava fountains from vent 3/2 and fluctuating incandescence over vent 3/1. Small ash plumes produced by eruptions from 3/2 were driven down the Sciara del Fuoco by strong winds. A dramatic change was evident late on 23 April, when the volcano was again observed from Punta Labronzo. Crater glow was much more intense, though still intermittent, and a persistent glow was visible at a small spot in the gap on the NE rim of Crater 1 (formed by the 5 March explosion). Vent 3/2 erupted as during the preceding days with somewhat larger ash plumes. However, a vent in the N part of Crater 1 ended the period of unusual inactivity of this crater, erupting spectacularly at intervals of 10-25 minutes. These eruptions were very brief (< 5 seconds) and produced cannon-shot-like bangs. Narrow incandescent columns rose obliquely to at least 150 m above the vent before falling onto the Sciara del Fuoco, depositing abundant incandescent material on the steep slope. For 3-5 minutes, incandescent material would cascade down to about half of the Sciara's extension, with a few large blocks tumbling farther. None appeared to reach the sea during the 1-hour observation period.

Figure (see Caption) Figure 40. Sketch map of the summit area of Stromboli, April 1995, showing the three craters and locations of vents. Courtesy of Boris Behncke.

Morphologic changes occur almost continuously, with alternating constructive and destructive processes. Periods of spatter-cone growth and crater filling usually last from a few months to several years and are followed by either crater-floor subsidence or explosive disruption of the cones. Cone growth was continuous from at least 1989 (maybe 1986) until October 1993, interrupted only by small-scale cone collapse and minor explosions. At the same time, the craters were filled to their rims with tephra and minor lava flows (as in May 1993; BGVN 18:04). Two large explosions in October 1993 blew out all of the material from the craters, leaving deep (>60 m) and wide chasms with near-vertical walls, still present in March 1994 (BGVN 19:03). New spatter cones grew rapidly during unusually vigorous activity in the summer and autumn of 1994, reaching much larger dimensions than the 1989-93 cones. In March 1995, parts of these cones were again removed by powerful explosions similar to, but smaller than, the October 1993 explosions. Also during early 1995, subsidence in Crater 3 created two pits at least 50 m deep.

Crater 1 has been the site of the most pronounced spatter-cone growth during 1989-95. Very small cones rarely formed at vent 3/1 and within the one vent of Crater 2. Most of the filling of craters 2 and 3 was due to the accumulation of pyroclastics. Three large, steep-sided cones and several smaller ones grew within Crater 1 between March and August 1994, the largest at vent 1/2 in the central portion of the crater, reaching ~30 m above its base. A powerful explosion in March 1995 blew out a pit 60-70 m in diameter and some 40 m deep with vertical walls, removing half of the cone (figure 41), and exposing the now-inactive conduit. Some of the smaller 1994 cones were also destroyed during the March explosion. The "twin cones" above vents 1/4 and 1/5 had grown much larger since August 1994, reaching ~25 m above their bases. Crater 2 had changed little since the summer of 1994. The small (~5 m high) hornito in its center, first observed in October 1994 (BGVN 19:10) was still present.

Figure (see Caption) Figure 41. View of the crater terrace from Pizzo Sopra la Fossa, 20 April 1995. Courtesy of Boris Behncke.

Crater 3, which had been filled with pyroclastics in August 1994, had two major depressions at the sites of vents 3/1 and 3/2. These depressions differ from the explosion pit in Crater 1, lacking its vertical walls and sharp rim, and may have formed in response to the lowering of the magmatic column sometime during November 1994 when the period of high-level activity ended. Another major change since 1989 is the significant upward growth of the entire crater terrace, most notable on the NW side facing the Sciara del Fuoco. This change is also evident on the profile views of Crater 1 taken from an observation point ~400 m NW (figure 42). Since the early and mid-20th century, the crater terrace has grown upwards by 50-100 m, completely burying the formerly conspicuous Filo di Baraona (figure 40), a frequently cited reference point in older literature at the SW end of the crater terrace. The highest point of the crater terrace is the SW rim of Crater 3, lying at ~780-800 m elevation (some 40 m above its NE rim), at the site of the former Filo di Baraona. This is significantly higher than the ~725 m estimated by Hornig-Kjarsgaard and others (1993).

Figure (see Caption) Figure 42. Comparative profile views of Crater 1 from the NE, illustrating the repeated growth and destruction of spatter cones between September 1989 and April 1995. The June 1993 sketch is based on photographs taken by Jon Dehn (Geological Survey of Japan, Hokkaido) and shows two lava lobes (arrows) from the vigorous May 1993 activity extending downslope. Courtesy of Boris Behncke.

Reference. Hornig-Kjarsgaard, I., Keller, J., Koberski, K., Stadlbauer, E., Francalanci, L., and Lenhart, R., 1993, Geology, stratigraphy and volcanological evolution of the island of Stromboli, Aeolian arc, Italy: Acta Vulcanologica, v. 3, p. 21-68.

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

Information Contacts: Roberto Carniel, Dipartimento di Georisorse e Territorio, via Cotonificio 114, I-33100 Udine, Italy; Giada Giuntoli and Boris Behncke, GEOMAR Research Center, Dept. of Volcanology and Petrology, Christian-Albrechts-Universitat zu Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany.


Unzendake (Japan) — April 1995 Citation iconCite this Report

Unzendake

Japan

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

All times are local (unless otherwise noted)


No lava dome growth, small rockfalls, rare tremors

No lava dome growth was revealed by theodolite surveys, helicopter inspections, or fieldwork during March and April. Rare rockfalls in March, 1-2/week, traveled 5m3. However, little lava was supplied after mid-February (figure 79). Theodolite survey results indicated that the endogenous dome started to shrink a little (1-2 m maximum) in April, compared with the data from February.

Figure (see Caption) Figure 79. Daily eruption volume at Unzen, May 1991-April 1995, showing two distinct pulses of magma-supply. No effusion of lava has been observed since mid-February 1995. The total volume of magma erupted during this 4-year period was ~0.20 km3. Eruption volumes were estimated by Geological Party, Joint University Research Group (JURG), using photographs from daily helicopter inspections and theodolite surveys. Only aerial photographs were used by the Geographical Survey Institute (GSI), the Public Works Research Institute (PWRI), and the Geological Survey of Japan (GSJ) to calculate the volume changes. Courtesy of Setsuya Nakada.

Volcanic gas emission decreased in April, such that no fume was observed from distant sites. Scientists from the Shimabara Earthquake and Volcano Observatory (SEVO), Kyushu University, installed mirrors for EDM and GPS stations near the top of the endogenous dome during April fieldwork. A sample from the dike on the top of the endogenous dome, which extruded at the end of 1994 and is the latest juvenile material, had a composition similar to lobe-13 samples collected in August 1994 (~65 wt.% SiO2); the specific gravity was ~2.46.

Only 15 microearthquakes beneath the dome and 10 tremor events were detected in March at the Japan Meteorological Agency seismograph 3.6 km SW of the dome. The same station detected 29 earthquakes and 18 tremor events in April. No pyroclastic flows were detected in March or April, but tiltmeters recorded upward movement of the summit on 9 and 24 March. SEVO noted small tremors on 8 and 15 April that were associated with minor tiltmeter changes; epicenters were several hundred meters W of the dome.

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: Setsuya Nakada, Volcano Research Center - Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan; Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Veniaminof (United States) — April 1995 Citation iconCite this Report

Veniaminof

United States

56.17°N, 159.38°W; summit elev. 2507 m

All times are local (unless otherwise noted)


Small plumes seen; warm spots identified from satellite images

During the first quarter of 1995, thermal anomalies were detected on satellite images of Veniaminof intermittently through 13 March. However, because neither ground observers nor pilots reported eruptive activity, these anomalies were thought to be related to the cooling lava flow in the summit caldera. On 17 April an observer in Port Heiden (97 km NE) saw small, dark plumes from Veniaminof. Observers from Perryville (32 km S) reported on 21 April that there had been a small steam plume during the preceding several days. This activity coincided with warm spots near the active vent seen on satellite images from 14, 21, and 22 April.

Geologic Background. Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA, b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Villarrica (Chile) — April 1995 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Tremor, mild explosions, and a new pyroclastic cone

Gustavo Fuentealba contributed the following on 4 May. "Seismic activity has increased in the past few days compared to March. In mid-April explosions were visible to the level of the crater rim and these explosions coincided with seismicity registered on portable instruments 15 km from the crater. The seismic signals arrived at 90-second intervals.

"In agreement with mid-April explosions and seismic data, aerial observations and photos around that time (taken by members of the Corporacion Nacional Forestal) revealed the growth of a new pyroclastic cone. Starting on 28 April and 1 May, there were intervals of poor visibility, but a new increase in seismic activity included tremor at 30-second intervals. Seismic activity declined suddenly, starting about 1915 on 1 May, but it reappeared ~8 hours later with tremor at 60-second intervals. Although continued poor visibility thwarted direct observations, it was thought probable that the April pyroclastic cone had collapsed."

Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot 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. Historical eruptions, documented since 1558, 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: Gustavo Fuentealba1 and Paola Pena, Observatorio Volcanologico de los Andes del Sur. 1 Also at Universidad de la Frontera, Ciencias Fisicas, Avenida Francisco Salazar 01145, Casilla 54-D A 238, Temuco, Chile.


Vulcano (Italy) — April 1995 Citation iconCite this Report

Vulcano

Italy

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

All times are local (unless otherwise noted)


Fumaroles at Fossa Grande and Forgia Vecchia craters

During an 18 Apri visit by Boris Behncke to the Fossa Grande crater the most vigorous fumaroles were present on the N inner crater rim and near its bottom. The main focus of fumarolic activity had shifted notably from the crater rim towards its center since his March 1992 visit (BGVN 17:03). Some of the spectacular fissures on the outer N crater wall were inactive, but several large fumaroles had formed near the crater floor. Molten sulfur was present in many fumaroles on the crater rim. Fumarolic activity on the oversteepened S part of the 18th century Forgia Vecchia craters and on the upper SE slope of the cone has changed little since 1992. Fumaroles were also active at Gran Cratere in October 1994.

Geologic Background. The word volcano is derived from Vulcano stratovolcano in Italy's Aeolian Islands. Vulcano was constructed during six stages during the past 136,000 years. Two overlapping calderas, the 2.5-km-wide Caldera del Piano on the SE and the 4-km-wide Caldera della Fossa on the NW, were formed at about 100,000 and 24,000-15,000 years ago, respectively, and volcanism has migrated to the north over time. La Fossa cone, active throughout the Holocene and the location of most of the historical eruptions, occupies the 3-km-wide Caldera della Fossa at the NW end of the elongated 3 x 7 km island. The Vulcanello lava platform forms a low, roughly circular peninsula on the northern tip of Vulcano that was formed as an island beginning in 183 BCE and was connected to Vulcano in about 1550 CE. Vulcanello is capped by three pyroclastic cones and was active intermittently until the 16th century. The latest eruption from Vulcano consisted of explosive activity from the Fossa cone from 1898 to 1900.

Information Contacts: Giada Giuntoli and Boris Behncke, GEOMAR Research Center, Dept. of Volcanology and Petrology, Christian-Albrechts-Universitat zu Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany.


White Island (New Zealand) — April 1995 Citation iconCite this Report

White Island

New Zealand

37.52°S, 177.18°E; summit elev. 321 m

All times are local (unless otherwise noted)


Currently non-eruptive but 2-year-long inflation continues

No eruptive activity occurred during January-March 1995. Wade Crater's floor remained occupied by an aqua-blue lake; photographs taken on 11 November 1994 and 27 February 1995 disclosed a lake-level rise of ~15-20 m. The lake appeared free of convection, but did contain conspicuous orange-colored material floating on its surface. The lake surface in March was thus considerably above the floors of Wade and Princess craters.

Dominant locations of fumaroles in or adjacent to Wade Crater included those high on the W wall, on the W side of the May 1991 embayment (particularly large and conspicuous fumaroles), and NE of Wade Lake on the divide between Wade and TV1 craters.

A 4 March leveling survey had a low error of closure (<=1.5 mm). The survey detected continued uplift, apparent since at least early 1993 (figure 23), with a maximum rate of 4.8 mm/month (58 mm/year) centered about 250 m SE of the middle of Wade Crater (Peg N). An area of shorter-term relative subsidence, apparent since at least August 1994, persists in the TV1-Donald Duck Crater area.

Figure (see Caption) Figure 23. White Island deformation at leveling Peg C, ~750 m SE of the shore of Lake Wade, 1967-1995. Courtesy of IGNS.

The magnitudes of these upward and downward motions were as follows. For the interval 21 November 1994 to 4 March 1995 the motion was 15 mm (up at Peg N) and -1 to -16 mm (down near TV1). For the interval 19 January 1994 to 4 March 1995 the motion was about 64 mm (up at peg N) and 26 mm (up near TV1).

Continued uplift of the crater floor suggested a crater-wide inflation that has been in progress for more than 2 years (figure 23). This inflation bears a close resemblance to the 5-year inflation that led up to a noteworthy eruption beginning in December 1976. An early phase of the 1976 eruption "sprinkled mustard-green colored ash" up to 1 m or more thick, over the crater and lesser thickness over the E part of the Island (SEAN 02:01).

Geologic Background. Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.

Information Contacts: B.J. Scott, Institute of Geological and Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand.

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

Additional 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 subregion and subject.

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (BGVN 22:08) False Report of Mount Pinokis Eruption

False report of volcanism intended to exclude would-be gold miners

12/1997 (BGVN 22:12) False Report of Somalia Eruption

Press reports of Somalia's first historical eruption were likely in error

11/1999 (BGVN 24:11) False Report of Sea of Marmara Eruption

UFO adherent claims new volcano in Sea of Marmara

05/2003 (BGVN 28:05) Har-Togoo

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

False report of activity; confusion caused by burning dung in a lava tube



False Report of Mount Pinokis Eruption (Philippines) — August 1997

False Report of Mount Pinokis Eruption

Philippines

7.975°N, 123.23°E; summit elev. 1510 m

All times are local (unless otherwise noted)


False report of volcanism intended to exclude would-be gold miners

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


Press reports of Somalia's first historical eruption were likely in error

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.


False Report of Sea of Marmara Eruption (Turkey) — November 1999

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

48.831°N, 101.626°E; summit elev. 1675 m

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure (see Caption) Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure (see Caption) Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure (see Caption) Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.


Elgon (Uganda) — December 2005

Elgon

Uganda

1.136°N, 34.559°E; summit elev. 3885 m

All times are local (unless otherwise noted)


False report of activity; confusion caused by burning dung in a lava tube

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).