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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

Masaya (Nicaragua) Lava lake persists with decreased thermal output, November 2018-February 2019

Santa Maria (Guatemala) Daily explosions cause steam-and-ash plumes and block avalanches, November 2018-February 2019

Reventador (Ecuador) Multiple daily explosions with ash plumes and incandescent blocks rolling down the flanks, October 2018-January 2019

Kuchinoerabujima (Japan) Weak explosions and ash plumes beginning 21 October 2018

Kerinci (Indonesia) A persistent gas-and-steam plume and intermittent ash plumes occurred from July 2018 through January 2019

Yasur (Vanuatu) Eruption continues with ongoing explosions and multiple active crater vents, August 2018-January 2019

Ambae (Vanuatu) Ash plumes and lahars in July 2018 cause evacuation of the island; intermittent gas-and-steam and ash plumes through January 2019

Agung (Indonesia) Ongoing intermittent ash plumes and frequent gas-and-steam plumes during August 2018-January 2019

Erebus (Antarctica) Lava lakes persist through 2017 and 2018

Villarrica (Chile) Intermittent Strombolian activity ejects incandescent bombs around crater rim, September 2018-February 2019

Popocatepetl (Mexico) Explosions with ash plumes and incandescent ejecta continue during September 2018-February 2019

Pacaya (Guatemala) Continuous activity from the cone in Mackenney crater; daily lava flows on the NW flank during October 2018-January 2019



Masaya (Nicaragua) — March 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 persists with decreased thermal output, November 2018-February 2019

Nicaragua's Volcan Masaya has an intermittent lava lake that has attracted visitors since the time of the Spanish Conquistadores; tephrochronology has dated eruptions back several thousand years. The unusual basaltic caldera has had historical explosive eruptions in addition to lava flows and an actively circulating lava lake. An explosion in 2012 ejected ash to several hundred meters above the volcano, bombs as large as 60 cm fell around the crater, and ash fell to a thickness of 2 mm in some areas of the park. The reemergence of the lava lake inside Santiago crater was reported in December 2015. By late March 2016 the lava lake had grown and intensified enough to generate a significant thermal anomaly signature which has varied in strength but continued at a moderate level into early 2019. Information for this report, which covers the period from November 2018 through February 2019, is provided by the Instituto Nicareguense de Estudios Territoriales (INETER) and satellite -based imagery and thermal data.

The lava lake in Santiago Crater remained visible and active throughout November 2018 to February 2019 with little change from the previous few months (figure 70). Seismic amplitude RSAM values remained steady, oscillating between 10 and 40 RSAM units during the period.

Figure (see Caption) Figure 70. A small area of the lava lake inside Santiago Crater at Masaya was visible from the rim on 25 November 2018 (left) and 17 January 2019 (right). Left image courtesy of INETER webcam; right image courtesy of Alun Ebenezer.

Every few months INETER carries out SO2 measurements by making a transect using a mobile DOAS spectrometer that samples for gases downwind of the volcano. Transects were done on 9-10 October 2018, 21-24 January 2019, and 18-21 February 2019 (figure 71). Average values during the October transect were 1,454 tons per day, in January they were 1,007 tons per day, and in February they averaged 1,318 tons per day, all within a typical range of values for the last several months.

Figure (see Caption) Figure 71. INETER carries out periodic transects to measure SO2 from Masaya with a mobile DOAS spectrometer. Transects taken along the Ticuantepe-La Concepcion highway on 9-10 October 2018 (left) and 21-24 January 2019 (right) showed modest levels of SO2 emissions downwind of the summit. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Octubre 2018 and Enero 2019).

During a visit by INETER technicians in early November 2018, the lens of the Mirador 1 webcam, that had water inside it and had been damaged by gases, was cleaned and repaired. During 21-24 January 2019 INETER made a site visit with scientists from the University of Johannes Gutenberg in Mainz, Germany, to measure halogen species in gas plumes, and to test different sampling techniques for volcanic gases, including through spectroscopic observations with DOAS equipment, in-situ gas sampling (MultiGAS, denuders, alkaline traps), and using a Quadcopter UAV (drone) sampling system.

Periodic measurements of CO2 from the El Comalito crater have been taken by INETER for many years. The most recent observations on 19 February 2019 indicated an emission rate of 46 +/- 3 tons per day of CO2, only slightly higher than the average value over 16 measurements between 2008 and 2019 (figure 72).

Figure (see Caption) Figure 72. CO2 measurements taken at Masaya on 19 February 2019 were very close to the average value measured during 2008-2019. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua, Febrero 2019).

Satellite imagery (figure 73) and in-situ thermal measurements during November 2018-February 2019 indicated constant activity at the lava lake and no significant changes during the period. On 14 January 2019 temperatures were measured with the FLIR SC620 thermal camera, along with visual observations of the crater; abundant gas was noted, and no explosions from the lake were heard. The temperature at the lava lake was measured at 107°C, much cooler than the 340°C measured in September 2018 (figure 74).

Figure (see Caption) Figure 73. Sentinel-2 satellite imagery (geology, bands 12, 4, and 2) clearly indicated the presence of the active lava lake inside Santiago crater at Masaya during November 2018-February 2019. North is to the top, and the Santigo crater is just under 1 km in diameter for scale. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 74. Thermal measurements were made at Masaya on 14 January 2019 with a FLIR SC620 thermal camera that indicated temperatures over 200°C cooler than similar measurements made in September 2018.

Thermal anomaly data from satellite instruments also confirmed moderate levels of ongoing thermal activity. The MIROVA project plot indicated activity throughout the period (figure 75), and a plot of the number of MODVOLC thermal alerts by month since the lava lake first appeared in December 2015 suggests constant activity at a reduced thermal output level from the higher values in early 2017 (figure 76).

Figure (see Caption) Figure 75. Thermal anomalies remained constant at Masaya during November 2018-February 2019 as recorded by the MIROVA project. Courtesy of MIROVA.
Figure (see Caption) Figure 76. The number of MODVOLC thermal alerts each month at Masaya since the lava lake first reappeared in late 2015 reached its peak in early 2017 and declined to low but persistent levels by early 2018 where they have remained for a year. Data courtesy of MODVOLC.

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); Alun Ebenezer (Twitter: @AlunEbenezer, URL: https://twitter.com/AlunEbenezer).


Santa Maria (Guatemala) — March 2019 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Daily explosions cause steam-and-ash plumes and block avalanches, November 2018-February 2019

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing and actively erupting since 1922. The youngest of the four vents in the complex, Caliente, has been erupting with ash explosions, pyroclastic, and lava flows for more than 40 years. A lava dome that appeared within the summit crater of Caliente in October 2016 has continued to grow, producing frequent block avalanches down the flanks. Daily explosions of steam and ash also continued during November 2018-February 2019, the period covered in this report, with information primarily from Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center).

Activity at Santa Maria continued with little variation from previous months during November 2018-February 2019. Plumes of steam with minor magmatic gases rose continuously from the Caliente crater 100-500 m above the summit, generally drifting SW or SE before dissipating. In addition, daily explosions with varying amounts of ash rose to altitudes of around 2.8-3.5 km and usually extended 20-30 km before dissipating. Most of the plumes drifted SW or SE; minor ashfall occurred in the adjacent hills almost daily and was reported at the fincas located within 15 km in those directions several times each month. Continued growth of the Caliente lava dome resulted in daily block avalanches descending its flanks. The MIROVA plot of thermal energy during this time shows a consistent level of heat flow with minor variations throughout the period (figure 89).

Figure (see Caption) Figure 89. Persistent thermal activity was recorded at Santa Maria from 6 June 2018 through February 2019 as seen in the MIROVA plot of thermal energy derived from satellite thermal data. Daily explosions produced ash plumes and block avalanches that were responsible for the continued heat flow at the volcano. Courtesy of MIROVA.

During November 2018 steam plumes rose to altitudes of 2.8-3.2 km from Caliente summit, usually drifting SW, sometimes SE. Several ash-bearing explosions were reported daily, rising to 3-3.2 km altitude and also drifting SW or SE. The highest plume reported by INSIVUMEH rose to 3.4 km on 25 November and drifted SW. The Washington VAAC reported an ash emission on 9 November that rose to 4.3 km altitude and drifted W; it dissipated within a few hours about 35 km from the summit. On 11 November another plume rose to 4.9 km altitude and drifted NW. INSIVUMEH issued a special report on 2 November noting an increase in block avalanches on the S and SE flanks, many of which traveled from the crater dome to the base of the volcano. Nearly constant avalanche blocks descended the SE flank of the dome and occasionally traveled down the other flanks as well throughout the month. They reached the bottom of the cone again on 29 November. Ashfall was reported around the flanks more than once every week and at Finca Florida on 12 November. Finca San Jose reported ashfall on 11, 13, and 23 November, and Parcelamiento Monte Claro reported ashfall on 15, 24, 25, and 27 November.

Constant degassing from the Caliente dome during December 2018 formed white plumes of mostly steam that rose to 2.6-3.0 km altitude during the month. Weak explosions averaging 9-13 per day produced gray ash plumes that rose to 2.8-3.4 km altitude. The Washington VAAC reported an ash emission on 4 December that extended 25 km SW of the summit at 3.0 km altitude and dissipated quickly. Small ash plumes were visible in satellite imagery a few kilometers WNW on 8, 12, 30, and 31 December at 4.3 km altitude; they each dissipated within a few hours. Ashfall was reported in Finca Monte Claro on 1 and 4 December, and in San Marcos Palajunoj on 26 and 30 December along with Loma Linda. On 28 December ashfall on the E flank affected the communities of Las Marías, Calahuache, and El Nuevo Palmar. Block avalanches occurred daily, sending large blocks to the base of the volcano that often stirred up small plumes of ash in the vicinity (figure 90).

Figure (see Caption) Figure 90. Activity during December 2018 at Santa Maria included constant degassing of steam plumes, weak explosions with ash plumes, and block avalanches rolling down the flanks to the base of the cone. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Diciembre 2018).

Multiple explosions daily during January 2019 produced steam-and-ash plumes (figure 91). Constant degassing rising 10-500 m emerged from the SSE part of the Caliente dome, and ashfall, mainly on the W and SW rim of the cone, was a daily feature. Seismic station STG-3 detected 10-18 explosions per day that produced ash plumes, which rose to between 2.7 and 3.5 km altitude. The Washington VAAC noted a faint ash emission in satellite imagery on 1 January that was about 25 km W of the summit at 4.3 km altitude. A new emission appeared at the same altitude on 4 January about 15 km NW of the summit. A low-density emission around midday on 5 January produced an ash plume that drifted NNE at 4.6 km altitude. Ash plumes drifted W at 4.3 km altitude on 11 and 14 January for short periods of time before dissipating.

Figure (see Caption) Figure 91. Explosions during January produced numerous steam-and-ash plumes at the Santiaguito complex of Santa Maria. A moderate explosion on 31 January 2019 produced an ash plume that rose to about 3.1 km altitude (top). A thermal image and seismograph show another moderate explosion on 18 January 2019 that also rose nearly vertically from the summit of Caliente. Courtesy of INSIVUMEH (Informe mensual de actividad Volcanica enero 2019, Volcan Santiaguito).

Ash drifted mainly towards the W, SW, and S, causing ashfall in the villages of San Marcos Palajunoj, Loma Linda, Monte Bello, El Patrocinio, La Florida, El Faro, Patzulín and a few others several times during the month. The main places where daily ashfall was reported were near the complex, in the hilly crop areas of the El Faro and San José Patzulín farms (figure 92). Blocks up to 3 m in diameter reached the base of the complex, stirring up ash plumes that settled on the immediate flanks. Juvenile material continued to appear at the summit of the dome during January; the dome had risen above the edge of the crater created by the explosions of 2016. Changes in the size and shape of the dome between 23 November 2018 and 13 January 2019 showed the addition of material on the E and SE side of the dome, as well as a new effusive flow that travelled 200-300 m down the E flank (figure 93).

Figure (see Caption) Figure 92. Near-daily ashfall affected the coffee plants at the El Faro and San José Patzulín farms (left) at Santiaguito during January 2019. Large avalanche blocks descending the flanks, seen here on 23 January 2018, often stirred up smaller ash plumes that settled out next to the cone. Courtesy of INSIVUMEH (Informe mensual de actividad Volcanica enero 2019, Volcan Santiaguito).
Figure (see Caption) Figure 93. A comparison of the growth at the Caliente dome of the Santiaguito complex at Santa Maria between 23 November 2018 (top) and 13 January 2019 (bottom) shows the emergence of juvenile material and a 200-300 m long effusive flow that has moved slowly down the E flank. Courtesy of INSIVUMEH (Informe mensual de actividad Volcanica enero 2019, Volcan Santiaguito).

Persistent steam rising 50-150 m above the crater was typical during February 2019 and accompanied weak and moderate explosions that averaged 12 per day throughout the month. White and gray ash plumes from the explosions rose to 2.8-3.3 km altitude; daily block avalanches usually reached the base of the dome (figure 94). Ashfall occurred around the complex, mainly on the W, SW, and NE flanks on a daily basis, but communities farther away were affected as well. The Washington VAAC reported an ash plume on 7 February in visible satellite imagery moving SW from the summit at 4.9 km altitude. The next day a new ash plume was located about 20 km W of the summit, dissipating rapidly, at 4.3 km altitude. Ashfall drifting SW affected Palajuno Monte Claro on 5, 9, 15, and 16 February. Ash drifting E and SE affected Calaguache, Las Marías and surrounding farms on 14 and 17 February, and fine-grained ash drifting SE was reported at finca San José on 21 February.

Figure (see Caption) Figure 94. Activity at the Caliente dome of the Santiaguito complex at Santa Maria included daily ash-and-steam explosions and block avalanches descending the sides of the dome in February 2019. A typical explosion on 2 February 2019 produced an ash plume that rose to about 3 km altitude and drifted SW (left). A block avalanche on 14 February descended the SE flank and stirred up small plumes of ash in the vicinity (right, top); the avalanche lasted for 88 seconds and registered with seismic frequencies between 3.46 and 7.64 Hz (right bottom). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 01 al 08 de febrero de 2019).

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); 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/).


Reventador (Ecuador) — March 2019 Citation iconCite this Report

Reventador

Ecuador

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

All times are local (unless otherwise noted)


Multiple daily explosions with ash plumes and incandescent blocks rolling down the flanks, October 2018-January 2019

The andesitic Volcán El Reventador lies well east of the main volcanic axis of the Cordillera Real in Ecuador and has historical eruptions with numerous lava flows and explosive events going back to the 16th century. The eruption in November 2002 generated a 17-km-high eruption cloud, pyroclastic flows that traveled 8 km, and several lava flows. Eruptive activity has been continuous since 2008. Daily explosions with ash emissions and ejecta of incandescent blocks rolling hundreds of meters down the flanks have been typical for many years. Activity continued during October 2018-January 2019, the period covered in this report, with information provided by Ecuador's Instituto Geofisico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and infrared satellite data.

Multiple daily reports were issued from the Washington VAAC throughout the entire October 2018-January 2019 period. Plumes of ash and gas usually rose to altitudes of 4.3-6.1 km and drifted about 20 km in prevailing wind directions before either dissipating or being obscured by meteoric clouds. The average number of daily explosions reported by IG-EPN for the second half of 2018 was more than 20 per day (figure 104). The many explosions during the period originated from multiple vents within a large scarp that formed on the W flank in mid-April (BGVN 43:11, figure 95) (figure 105). Incandescent blocks were observed often in the IG webcams; they traveled 400-1,000 m down the flanks.

Figure (see Caption) Figure 104. The number of daily seismic events at El Reventador for 2018 indicated high activity during the first and last thirds of the year; more than 20 explosions per day were recorded many times during October-December 2018, the period covered in this report. LP seismic events are shown in orange, seismic tremor in pink, and seismic explosions with ash are shown in green. Courtesy of IG-EPN (Informe Anual del Volcán El Reventador – 2018, Quito, 29 de marzo del 2019).
Figure (see Caption) Figure 105. Images from IG's REBECA thermal camera showed the thermal activity from multiple different vents at different times during the year (see BGVN 43:11, figure 95 for vent locations). Courtesy if IG (Informe Anual del Volcán El Reventador – 2018, Quito, 29 de marzo del 2019).

Activity during October 2018-January 2019. During most days of October 2018 plumes of gas, steam, and ash rose over 1,000 m above the summit of Reventador, and most commonly drifted W or NW. Incandescence was observed on all nights that were not cloudy; incandescent blocks rolled 400-800 m down the flanks during half of the nights. During episodes of increased activity, ash plumes rose over 1,200 m (8, 10-11, 18-19 October) and incandescent blocks rolled down multiple flanks (figure 106).

Figure (see Caption) Figure 106. Ash emissions rose over 1,000 m above the summit of Reventador numerous times during October 2018, and large incandescent blocks traveled hundreds of meters down multiple flanks. The IG-EPN COPETE webcam that captured these images is located on the S caldera rim. Courtesy of IG Daily Reports (Informe diario del estado del Volcan Reventador, numbers 2018-282, 292, 295, 297).

Similar activity continued during November. IG reported 17 days of the month with steam, gas, and ash emissions rising more than 1,000 m above the summit. The other days were either cloudy or had emissions rising between 500 and 1,000 m. Incandescent blocks were usually observed on the S or SE flanks, generally travelling 400-600 m down the flanks. The Washington VAAC reported a discrete ash plume at 6.1 km altitude drifting WNW about 35 km from the summit on 15 November. The next day, intermittent puffs were noted moving W, and a bright hotspot at the summit was visible in satellite imagery. During the most intense activity of the month, incandescent blocks traveled 800 m down all the flanks (17-19 November) and ash plumes rose over 1,200 m (23 November) (figure 107).

Figure (see Caption) Figure 107. Ash plumes rose over 1,000 m above the summit on 17 days during November 2018 at Reventador, and incandescent blocks traveled 400-800 m down the flanks on many nights. Courtesy of IG Daily Reports (Informe diario del estado del Volcan Reventador, numbers 2018-306, 314, 318, 324).

Steam, gas, and ash plumes rose over 1,200 m above the summit on 1 December. The next day, there were reports of ashfall in San Rafael and Hosteria El Hotelito, where they reported an ash layer about 1 mm thick was deposited on vehicles during the night. Ash emissions exceeded 1,200 m above the summit on 5 and 6 December as well. Incandescent blocks traveled 800 m down all the flanks on 11, 22, 24, and 26 December, and reached 900 m on 21 December. Ash emissions rising 500 to over 1,000 m above the summit were a daily occurrence, and incandescent blocks descended 500 m or more down the flanks most days during the second half of the month (figure 108).

Figure (see Caption) Figure 108. Ash plumes that rose 500 to over 1,000 m were a daily occurrence at Reventador during December 2018. Incandescent blocks traveled as far as 900 m down the flanks as well. Courtesy of IG Daily Reports (Informe diario del estado del Volcan Reventador, numbers 2018-340, 351, 353, 354, 358, 359).

During the first few days of January 2019 the ash and steam plumes did not rise over 800 m, and incandescent blocks were noted 300-500 m down the S flank. An increase in activity on 6 January sent ash-and-gas plumes over 1,000 m, drifting W, and incandescent blocks 1,000 m down many flanks. For multiple days in the middle of the month the volcano was completely obscured by clouds; only occasional observations of plumes of ash and steam were made, incandescence seen at night through the clouds confirmed ongoing activity. The Washington VAAC reported continuous ash emissions moving SE extending more than 100 km on 12 January. A significant explosion late on 20 January sent incandescent blocks 800 m down the S flank; although it was mostly cloudy for much of the second half of January, brief glimpses of ash plumes rising over 1,000 m and incandescent blocks traveling up to 800 m down numerous flanks were made almost daily (figure 109).

Figure (see Caption) Figure 109. Even during the numerous cloudy days of January 2019, evidence of ash emissions and significant explosions at Reventador was captured in the Copete webcam located on the S rim of the caldera. Courtesy of IG Daily Reports (Informe diario del estado del Volcan Reventador, number 2019-6, 21, 26, 27).

Visual evidence from the webcams supports significant thermal activity at Reventador. Atmospheric conditions are often cloudy and thus the thermal signature recorded by satellite instruments is frequently diminished. In spite of this, the MODVOLC thermal alert system recorded seven thermal alerts on three days in October, four alerts on two days in November, six alerts on two days in December and three alerts on three days in January 2019. In addition, the MIROVA system measured moderate levels of radiative power intermittently throughout the period; the most intense anomalies of 2018 were recorded on 15 October and 6 December (figure 110).

Figure (see Caption) Figure 110. Persistent thermal activity at Reventador was recorded by satellite instruments for the MIROVA system from 5 April 2018 through January 2019 in spite of frequent cloud cover over the volcano. The most intense anomalies of 2018 were recorded on 15 October and 6 December. Courtesy of MIROVA.

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: Instituto Geofísico (IG-EPN), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); 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/).


Kuchinoerabujima (Japan) — March 2019 Citation iconCite this Report

Kuchinoerabujima

Japan

30.443°N, 130.217°E; summit elev. 657 m

All times are local (unless otherwise noted)


Weak explosions and ash plumes beginning 21 October 2018

Activity at Kuchinoerabujima is exemplified by interim explosions and periods of high seismicity. A weak explosion occurred on 3 August 2014, the first since 1980, and was followed by several others during 29 May-19 June 2015 (BGVN 42:03). This report describes events through February 2019. Information is based on monthly and annual reports from the Japan Meteorological Agency (JMA) and advisories from the Tokyo Volcanic Ash Advisory Center (VAAC). Activity has been limited to Kuchinoerabujima's Shindake Crater.

Activity during 2016-2018. According to JMA, between July 2016 and August 2018, the volcano was relatively quiet. Deflation had occurred since January 2016. On 18 April 2018 the Alert Level was lowered from 3 to 2 (on a scale of 1-5). A low-temperature thermal anomaly persisted near the W fracture in Shindake crater. During January-March 2018, both the number of volcanic earthquakes (generally numerous and typically shallow) and sulfur dioxide flux remained slightly above baselines levels in August 2014 (60-500 tons/day compared tp generally less than 100 tons/day in August 2014).

JMA reported that on 15 August 2018 a swarm of deep volcanic earthquakes was recorded, prompting an increase in the Alert Level to 4. The earthquake hypocenters were about 5 km deep, below the SW flanks of Shindake, and the maximum magnitude was 1.9. They occurred at about the same place as the swarm that occurred just before the May 2015 eruption. Sulfur dioxide emissions had increased since the beginning of August; they were 1,600, 1,000, and 1,200 tons/day on 11, 13, and 17 August, respectively. No surficial changes in gas emissions or thermal areas were observed during 16-20 August. On 29 August, JMA downgraded the Alert Level to 3, after no further SO2 flux increase had occurred in recent days and GNSS measurements had not changed.

A very weak explosion was recorded at 1831 on 21 October, with additional activity between 2110 on 21 October and 1350 on 22 October; plumes rose 200 m above the crater rim. During an overflight on 22 October, observers noted ash in the emissions, though no morphological changes to the crater nor ash deposits were seen. Based on satellite images and information from JMA, the Tokyo VAAC reported that during 24-28 October ash plumes rose to altitudes of 0.9-1.5 km and drifted in multiple directions. During a field observation on 28 October, JMA scientists did not observe any changes in the thermal anomalies at the crater.

JMA reported that during 31 October-5 November 2018, very small events released plumes that rose 500-1,200 m above the crater rim. On 6 November, crater incandescence began to be periodically visible. During 12-19 November, ash plumes rose as high as 1.2 km above the crater rim and, according to the Tokyo VAAC, drifted in multiple directions. Observers doing fieldwork on 14 and 15 November noted that thermal measurements in the crater had not changed. Intermittent explosions during 22-26 November generated plumes that rose as high as 2.1 km above the crater rim. During 28 November-3 December the plumes rose as high as 1.5 km above the rim.

JMA reported that at 1637 on 18 December an explosion produced an ash plume that rose 2 km and then disappeared into a weather cloud. The event ejected material that fell in the crater area, and generated a pyroclastic flow that traveled 1 km W and 500 m E of the crater. Another weak explosion occurred on 28 December, scattering large cinders up to 500 m from the crater.

The Tokyo VAAC did not issue any ash advisories for aviation until 21 October 2018, when it issued at least one report every day through 13 December. It also issued advisories on 18-20 and 28 December.

Activity during January-early February 2019. JMA reported that at 0919 local time on 17 January 2019 an explosion generated a pyroclastic flow that reached about 1.9 km NW and 1 km E of the crater. It was the strongest explosion since October 2018. In addition, "large cinders" fell about 1-1.8 km from the crater.

Tokyo VAAC ash advisories were issued on 1, 17, 20, and 29 January 2018. An explosion at 1713-1915 on 29 January produced an ash plume that rose 4 km above the crater rim and drifted E, along with a pyroclastic flow. Ash fell in parts of Yakushima. During 30 January-1 February and 3-5 February, white plumes rose as high as 600 m. On 2 February, an explosion at 1141-1300 generated a plume that rose 600 m. No additional activity during February was reported by JMA. The Alert Level remained at 3.

Geologic Background. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km west of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. The youngest cone, centrally-located Shintake, formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Kerinci (Indonesia) — February 2019 Citation iconCite this Report

Kerinci

Indonesia

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

All times are local (unless otherwise noted)


A persistent gas-and-steam plume and intermittent ash plumes occurred from July 2018 through January 2019

Kerinci is a frequently active volcano in Sumatra, Indonesia. Recent activity has consisted of intermittent explosions, ash, and gas-and-steam plumes. The volcano alert has been at Level II since 9 September 2007. This report summarizes activity during July 2018-January 2019 based on reports by The Indonesia 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.

Throughout this period dilute gas-and-steam plumes rising about 300 m above the summit were frequently observed and seismicity continued (figure 6). During July through January ash plumes were observed by the Darwin VAAC up to 4.3 km altitude and dispersed in multiple directions (table 7 and figure 7).

Figure (see Caption) Figure 6. Graph showing seismic activity at Kerinci from November 2018 through February 2019. Courtesy of MAGMA Indonesia.

Table 7. Summary of ash plumes (altitude and drift direction) for Kerinci during July 2018 through January 2019. The summit is at 3.5 km altitude. Data courtesy of the Darwin Volcanic Ash Advisory Center (VAAC) and MAGMA Indonesia.

Date Ash plume altitude (km) Ash plume drift direction
22 Jul 2018 4.3 SW
28-30 Sep 2018 4.3 SW, W
02 Oct 2018 4.3 SW, W
18-22 Oct 2018 4.3 N, W, WSW, SW
19 Jan 2019 4 E to SE
Figure (see Caption) Figure 7. Dilute ash plumes at Kerinci during July 2018-January 2019. Sentinel-2 natural color (bands 4, 3, 2) satellite images courtesy of Sentinel Hub Playground.

Based on satellite data, a Darwin VAAC advisory reported an ash plume to 4.3 km altitude on 22 July that drifted to the SW and S. Only one day with elevated thermal emission was noted in Sentinel-2 satellite data for the entire reporting period, on 13 September 2018 (figure 8). No thermal signatures were detected by MODVOLC. On 28-29 September there was an ash plume observed to 500-600 m above the peak that dispersed to the W. Several VAAC reports on 2 and 18-22 October detected ash plumes that rose to 4.3 km altitude and drifted in different directions. On 19 January from 0734 to 1000 an ash plume rose to 200 m above the crater and dispersed to the E and SE (figure 9).

Figure (see Caption) Figure 8. Small thermal anomaly at Kerinci volcano on 13 September 2018. False color (urban) image (band 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 9. Small ash plume at Kerinci on 19 January 2018 that reached 200 m above the crater and traveled west. Courtesy of MAGMA Indonesia.

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/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Yasur (Vanuatu) — February 2019 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Eruption continues with ongoing explosions and multiple active crater vents, August 2018-January 2019

According to the Vanuatu Meteorology and Geo-Hazards Department (VMGD), which monitors Yasur, the volcano has been in essentially continuous Strombolian activity since Captain Cook observed ash eruptions in 1774, and undoubtedly before that time. VMGD reported that, based on visual observations and seismic data, activity continued through January 2019, with ongoing, sometimes strong, explosions. The Alert Level remained at 2 (on a scale of 0-4). VMGD reminded residents and tourists to remain outside the 395-m-radius permanent exclusion zone and warned that volcanic ash and gas could reach areas influenced by trade winds.

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were recorded 6-15 days per month during the reporting period, sometimes with multiple pixels. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month. Active crater vents were also frequently visible in Sentinel-2 satellite imagery (figure 50).

Figure (see Caption) Figure 50. Sentinel-2 satellite color infrared image (bands 8, 4, 3) of Yasur on 17 November 2018 showing at least three distinct heat sources in the crater. Courtesy of Sentinel Hub Playground.

Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department, Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory); 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).


Ambae (Vanuatu) — February 2019 Citation iconCite this Report

Ambae

Vanuatu

15.389°S, 167.835°E; summit elev. 1496 m

All times are local (unless otherwise noted)


Ash plumes and lahars in July 2018 cause evacuation of the island; intermittent gas-and-steam and ash plumes through January 2019

Ambae is one of the active volcanoes of Vanuatu in the New Hebrides archipelago. Recent eruptions have resulted in multiple evacuations of the local population due to ashfall. The current eruption began in September 2017, with the initial episode ending in November that year. The second episode was from late December 2017 to early February 2018, and the third was during February-April 2018. The Alert Level was raised to 3 in March, then lowered to Level 2 again on 2 June 2018. Eruptive activity began again on 1 July and produced thick ash deposits that significantly impacted the population, resulting in the full evacuation of the Island of Ambae. This report summarizes activity from July 2018 through January 2019 and is based on reports by the Vanuatu Meteorology and Geo-hazards Department (VMGD), The Vanuatu Red Cross, posts on social media, and various satellite data.

On 1 July Ambae entered a new eruption phase, marked by an ash plume that resulted in ashfall on communities in the W to NW parts of Ambae Island and the NE part of Santo Island (figure 78). On 9-10 July VMGD reported that a small eruption continued with activity consisting of ongoing gas-and-steam emissions. An observation flight on 13 July confirmed that the eruption was centered at Lake Voui and consisted of explosions that ejected hot blocks with ongoing gas-and-steam and ash emissions. Populations on Ambae and a neighboring island could hear the eruption, smell the volcanic gases, and see incandescence at night.

Figure (see Caption) Figure 78. Ash plume at Ambae on 1 July 2018 that resulted in ashfall on the W to NW parts of the island, and on the NE part of Santo Island. Courtesy of VMGD.

On 16 July the Darwin VAAC reported an ash plume to 9.1 km that drifted to the NE. During 16-24 July daily ash plumes from the Lake Voui vent rose to altitudes of 2.3-9.1 km and drifted N, NE, E, and SE (figure 79 and 80). Radio New Zealand reported that on the 16th significant ash emission blocked out sunlight, making the underlying area dark at around 1600 local time. Much of E and N Ambae Island experienced heavy ashfall and the eruption could be heard over 30 km away. The Vanuatu Red Cross Society reported worsening conditions in the south on 24 July with ashfall resulting in trees falling and very poor visibility of less than 2 m (figures 81, 82, and 83). The Daily Post reported that by 19 July lahars had washed away two roads and other roads were blocked to western Ambae. Volcanologists who made their way to the area reported widespread damage (figure 84). The Alert Level was raised from level 2 to 3 (on a scale of 0-5) on 21 July due to an increase in ash emission and more sustained plumes, similar to March 2018 activity.

Figure (see Caption) Figure 79. Ash plumes produced by the Ambae eruption in July 2018 as seen in Terra/MODIS visible satellite images. Images courtesy of NASA Worldview.
Figure (see Caption) Figure 80. Sentinel-2 satellite image of an ash plume from Ambae in Vanuatu on 23 July 2018 with the inset showing the ash plume at the vent. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 81. Ashfall at Ambae, posted on 25 July 2018. Courtesy of the Vanuatu Red Cross Society.
Figure (see Caption) Figure 82. An ash plume at Ambae in July during a day and a half of constant ashfall, looking towards the volcano. Courtesy of Michael Rowe.
Figure (see Caption) Figure 83. Ashfall from the eruption at Ambae blocked out the sun near the volcano on 24 July 2018. Courtesy of the Vanuatu Red Cross Society.
Figure (see Caption) Figure 84. Impacts of ashfall near Ambae in July 2018. Photos by Nicholson Naki, courtesy of the Vanuatu Red Cross (posted on 22 July 2018).

At 2100 on 26 July the ongoing explosions produced an ash plume that rose to 12 km and spread NE, E, SE. A state of emergency was announced by the Government of Vanuatu with a call for mandatory evacuations of the island. Ash emissions continued through the next day (figure 85 and 86) with two episodes producing volcanic lightning at 1100-1237 and 1522-2029 on 27 July (figure 87). The Darwin VAAC reported ash plumes up to 2.4-6.4 km, drifting SE and NW, and pilots reported heavy ashfall in Fiji. Large SO2 plumes were detected accompanying the eruptions and moving towards the E (figure 88).

Figure (see Caption) Figure 85. Ash plumes at Ambae at 0830 and 1129 local time on 27 July 2018. The ash plume is significantly larger in the later image. Webcam images from Saratamata courtesy of VMGD.
Figure (see Caption) Figure 86. Two ash plumes from Ambae at 1200 on 27 July 2018 as seen in a Himawari-8 satellite image. Courtesy of Himawari-8 Real-time Web.
Figure (see Caption) Figure 87. Lightning strokes detected at Ambae on 27 July 2018. There were two eruption pulses, 1100-1237 (blue) and 1522-2029 local time (red) that produced 185 and 87 lightning strokes, respectively. Courtesy of William A. Brook, Ronald L. Holle, and Chris Vagasky, Vaisala Inc.
Figure (see Caption) Figure 88. Aura/OMI data showing the large SO2 plumes produced by Ambae in Vanuatu during 22-31 July 2018. Courtesy of NASA Goddard Space Flight Center.

Video footage showed a lahar blocking a road around 2 August. The government of Vanuatu told reporters that the island had been completely evacuated by 14 August. A VMGD bulletin on 22 August reported that activity continued with ongoing gas-and-steam and sometimes ash emissions; residents on neighboring islands could hear the eruption, smell volcanic gases, and see the plumes.

On 1 September at 2015 an explosion sent an ash plume to 4-11 km altitude, drifting E. Later observations in September showed a decrease in activity with no further explosions and plumes limited to white gas-and-steam plumes. On 21 September VMGD reported that the Lake Voui eruption had ceased and the Alert Level was lowered to 2.

Observed activity through October and November dominantly consisted of white gas-and-steam plumes. An explosion on 30 October at 1832 produced an ash plume that rose to 4-5 km and drifted E and SE. Satellite images acquired during July-November show the changing crater area and crater lake water color (figure 89). VMGD volcano alert bulletins on 6, 7, and 21 January 2019 reported that activity continued with gas-and-steam emissions (figure 90). Thermal energy continued to be detected by the MIROVA system through January (figure 91).

Figure (see Caption) Figure 89. The changing lakes of Ambae during volcanic activity in 2018. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 90. A steam plume at Ambae on 21 January 2019. Courtesy of VMGD.
Figure (see Caption) Figure 91. Log radiative power MIROVA plot of MODIS infrared data at Ambae for April 2018 through January 2019 showing the increased thermal energy during the July 2018 eruption and continued activity. Courtesy of MIROVA.

Geologic Background. The island of Ambae, also known as Aoba, is a massive 2500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac/, http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html); 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/); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/); Himawari-8 Real-time Web, developed by the NICT Science Cloud project in NICT (National Institute of Information and Communications Technology), Japan, in collaboration with JMA (Japan Meteorological Agency) and CEReS (Center of Environmental Remote Sensing, Chiba University) (URL: https://himawari8.nict.go.jp/); Vanuatu Red Cross Society (URL: https://www.facebook.com/VanuatuRedCross); William A. Brooks and Ronald L. Holle, Vaisala Inc., Tucson, Arizona, and Chris Vagasky, Vaisala Inc., Louisville, Colorado (URL: https://www.vaisala.com/); Michael Rowe, The University of Auckland, 23 Symonds Street, Auckland, 1010, New Zealand (URL: https://unidirectory.auckland.ac.nz/profile/michael-rowe); Radio New Zealand, 155 The Terrace, Wellington 6011, New Zealand (URL: https://www.radionz.co.nz/international/pacific-news/359231/vanuatu-provincial-capital-moves-due-to-volcano); Vanuatu Daily Post (URL: http://dailypost.vu/).


Agung (Indonesia) — February 2019 Citation iconCite this Report

Agung

Indonesia

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

All times are local (unless otherwise noted)


Ongoing intermittent ash plumes and frequent gas-and-steam plumes during August 2018-January 2019

Agung is an active volcano in Bali, Indonesia, that began its current eruptive episode in September 2017. During this time activity has included ash plumes, gas-and-steam plumes, explosions ejecting ballistic blocks onto the flanks, and lava extrusion within the crater.

This report summarizes activity from August 2018 through January 2019 based on information from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), MAGMA Indonesia, the National Board for Disaster Management - Badan Nasional Penanggulangan Bencana (BNPB), the Darwin Volcanic Ash Advisory Center (VAAC), and satellite data.

During August 2018 through January 2019 observed activity was largely gas-and steam plumes up to 700 m above the crater (figures 39 and 40). In late December and January there were several explosions that produced ash plumes up to 5.5 km altitude, and ejected ballistic blocks.

Figure (see Caption) Figure 39. Graph showing the observed white gas-and-steam plumes and gray ash plumes at Agung during August 2018 through January 2019. The dates showing no data points coincided with cloudy days where the summit was not visible. Data courtesy of PVMBG.
Figure (see Caption) Figure 40. A white gas-and-steam plume at Agung on 21 December 2018. Courtesy of MAGMA Indonesia.

The Darwin VAAC reported an ash plume on 8-9 August based on satellite data, webcam footage, and ground report information. The ash plume rose to 4.3 km and drifted to the W. They also reported a diffuse ash plume to 3.3 km altitude on 16-17 August based on satellite and webcam data. During September through November there were no ash plumes observed at Agung; activity consisted of white gas-and-steam plumes ranging from 10-500 m above the crater.

Throughout December, when observations could be made, activity mostly consisted of white gas-and-steam plumes up to 400 m above the crater. An explosion occurred at 0409 on 30 December that lasted 3 minutes 8 seconds produced an ash plume rose to an altitude of 5.5 km and moved to the SE and associated incandescence was observed at the crater. Light Ashfall was reported in the Karangasem regency to the NE, including Amlapura City and several villages such as in Seraya Barat Village, Seraya Tengah Village, and Tenggalinggah Village (figure 41).

Figure (see Caption) Figure 41. A webcam image of an explosion at Agung that began at 0409 on 30 December 2018. Light Ashfall was reported in the Karangasem regency. Courtesy of PVMBG.

White gas-and-steam plumes continued through January 2019 rising as much as 600 m above the crater. Several Volcano Observatory Notices for Aviation (VONAs) were issued during 18-22 January. An explosion was recorded at 0245 on 19 January that produced an ash plume to 700 m above the crater and ejected incandescent blocks out to 1 km from the crater. On 21 January another ash plume rose to an estimated plume altitude of 5.1 km. The next morning, at 0342 on the 22nd, an ash plume to an altitude of 2 km that dispersed to the E and SE.

Satellite data shows continued low-level thermal activity in the crater throughout this period. MIROVA thermal data showed activity declining after a peak in July, and a further decline in energy in September (figure 42). Low-level thermal activity continued through December. Sentinel-2 thermal data showed elevated temperatures within the ponded lava in the crater (figure 43).

Figure (see Caption) Figure 42. Log radiative power MIROVA plot of MODIS infrared data for May 2018 through January 2019 showing thermal anomalies at Agung. The black data lines indicate anomalies more than 10 km from the crater, which are likely due to fires. Courtesy of MIROVA.
Figure (see Caption) Figure 43. Sentinel-2 thermal satellite images showing areas of elevated temperatures within the lava ponded in the Agung crater during August 2018 through January 2019. Courtesy of Sentinel Hub Playground.

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/); 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/); 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).


Erebus (Antarctica) — January 2019 Citation iconCite this Report

Erebus

Antarctica

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

All times are local (unless otherwise noted)


Lava lakes persist through 2017 and 2018

Between the early 1980's through 2016, activity at Erebus was monitored by the Mount Erebus Volcano Observatory (MEVO), using seismometers, infrasonic recordings to measure eruption frequency, and annual scientific site visits. MEVO recorded occasional explosions propelling ash up to 2 km above the summit of this Antarctic volcano and the presence of two, sometimes three, lava lakes (figure 26). However, MEVO closed in 2016 (BGVN 42:06).

Activity at the lava lakes in the summit crater can be detected using MODIS infrared detectors aboard the Aqua and Terra satellites and analyzed using the MODVOLC algorithm. A compilation of thermal alert pixels during 2017-2018 (table 4, a continuation of data in the previous report) shows a wide range of detected activity, with a high of 182 alert pixels in April 2018. Although no MODVOLC anomalies were recorded in January 2017, detectors on the Sentinel-2 satellite imaged two active lava lakes on 25 January.

Table 4. Number of MODVOLC thermal alert pixels recorded per month from 1 January 2017 to 31 December 2018 for Erebus by the University of Hawaii's thermal alert system. Table compiled by GVP from data provided by MODVOLC.

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec SUM
2017 0 21 9 0 0 1 11 61 76 52 0 3 234
2018 0 21 58 182 55 17 137 172 103 29 0 0 774
SUM 0 42 67 182 55 18 148 233 179 81 0 3 1008
Figure (see Caption) Figure 26. Sentinel-2 images of the summit crater area of Erebus on 25 January 2017. Top: Natural color filter (bands 4, 3, 2). Bottom: Atmospheric penetration filter (bands 12, 11, 8A) in which two distinct lava lakes can be observed. The main crater is 500 x 600 m wide. Courtesy of Sentinel Hub Playground.

Geologic Background. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. The 3794-m-high Erebus is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: 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).


Villarrica (Chile) — March 2019 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Intermittent Strombolian activity ejects incandescent bombs around crater rim, September 2018-February 2019

Historical eruptions at Chile's Villarrica, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. An intermittently active lava lake at the summit has been the source of explosive activity, incandescence, and thermal anomalies for several decades. Sporadic Strombolian activity at the lava lake and small ash emissions have continued since the last large explosion on 3 March 2015. Similar continuing activity during September 2018-February 2019 is covered in this report, with information provided primarily by the Southern Andes Volcano Observatory (Observatorio Volcanológico de Los Andes del Sur, OVDAS), part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), and Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile, a research group that studies volcanoes across Chile.

After ash emissions during July 2018 and an increase in of thermal activity from late July through early September 2018 (BGVN 43:10), Villarrica was much quieter through February 2019. Steam plumes rose no more than a few hundred meters above the summit and the number of thermal alerts decreased steadily. Intermittent Strombolian activity sent ejecta a few tens of meters above the summit crater, with larger bombs landing outside the crater rim. A small pyroclastic cone appeared at the surface of the lava lake, about 70 m below the rim, in November. The largest lava fountain rose 35 m above the crater rim in late January 2019.

Steam plumes rose no more than 300 m above the crater during September 2018 and were less than 150 m high in October; incandescence at the summit was visible during clear nights, although a gradual decrease in activity suggested a lowering of the lake level to SERNAGEOMIN. SERNAGEOMIN attributed an increase in LP seismic events from 1,503 in September to 5,279 in October to dynamics of the lava lake inside the summit crater; counts decreased gradually in the following months.

POVI reported webcam evidence of Strombolian activity with ejecta around the crater several times during November 2018. On 5 November the webcam captured an image of an incandescent bomb, more than a meter in diameter, that landed on the NW flank. The next day, explosions sent ejecta 50 m above the edge of the crater, and pyroclastic debris landed around the perimeter. Significant Strombolian explosions on 16 November sent incandescent bombs toward the W rim of the crater (figure 71). The POVI webcam in Pucón captured incandescent ejecta landing on the crater rim on 23 November. POVI scientists observed a small pyroclastic cone, about 10-12 m in diameter, at the bottom of the summit crater on 19 November (figure 72); it was still visible on 25 November.

Figure (see Caption) Figure 71. Strombolian activity at the summit of Villarrica was captured several times in the POVI webcam located in Pucón. An explosion on 5 November 2018 ejected a meter-sized bomb onto the NW flank (left). On 16 November, incandescent bombs were thrown outside the W rim of the crater (right). Courtesy of POVI (Volcán Villarrica, Resumen Gráfico del Comportamiento, November 2017 a Febrero 2019).
Figure (see Caption) Figure 72. A small pyroclastic cone was visible at the bottom of the summit crater at Villarrica (about 70 m deep) on 19 November 2018 (left); it was still visible on 25 November (right). Courtesy of POVI (Volcán Villarrica, Resumen Gráfico del Comportamiento, November 2017 a Febrero 2019).

During December 2018 webcam images showed steam plumes rising less than 350 m above the crater. Infrasound instruments identified two small explosions related to lava lake surface activity. SERNAGEOMIN noted a minor variation in the baseline of the inclinometers; continued monitoring indicated the variation was seasonal. A compilation by POVI of images of the summit crater during 2018 showed the evolution of the lava lake level during the year. It had dropped out of sight early in the year, rose to its highest level in July, and then lowered slightly, remaining stable for the last several months of the year (figure 73).

Figure (see Caption) Figure 73. Evolution of the lava pit at Villarrica during 2018. During July the lava lake level increased and for November and December no significant changes were observed. Courtesy of POVI (Volcán Villarrica, Resumen Gráfico del Comportamiento, November 2017 a Febrero 2019).

Between 25 December 2018 and 15 January 2019, financed with funds contributed by the Fundación Volcanes de Chile, POVI was able to install new HD webcams with continuous daily image recording, greatly improving the level of detail data available of the activity at the summit. POVI reported that after a five-week break, Strombolian explosions resumed on 3 January 2019; the lava fountains rose 20 m above the crater rim, and pyroclastic ejecta fell to the E. On 24 January the Strombolian explosions ejected ash, lapilli, and bombs up to 15 cm in diameter; the lava fountain was about 35 m high.

An explosion on 7 February reached about 29 m above the crater's edge; on 9 February a lava fountain three meters in diameter rose 17 m above the crater rim. Sporadic explosions were imaged on 12 February as well (figure 74). During a reconnaissance overflight on 24 February 2019, POVI scientists observed part of the lava pit at the bottom of the crater (figure 75). As of 28 February they noted a slight but sustained increase in the energy of the explosions. SERNAGEOMIN noted that steam plumes rose 400 m in January and 150 m during February, and incandescence was visible on clear nights during both months.

Figure (see Caption) Figure 74. Strombolian activity at Villarrica in January and February 2019 was imaged with a new HD webcam on several occasions. On 24 January 2019 explosions ejected ash, lapilli, and bombs up to 15 cm in diameter; the lava fountain was about 35 m high (left); on 12 February 2019 explosions rose about 19 m above the crater rim (right). Courtesy of POVI (Volcán Villarrica, Resumen Gráfico del Comportamiento, November 2017 a Febrero 2019).
Figure (see Caption) Figure 75. During a reconnaissance overflight on 24 February 2019, POVI scientists observed part of the lava pit at the bottom of the crater at Villarrica; gas and steam emissions and incandescence from small explosions were noted. Courtesy of POVI (Volcán Villarrica, Resumen Gráfico del Comportamiento, November 2017 a Febrero 2019).

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: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/).


Popocatepetl (Mexico) — March 2019 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Explosions with ash plumes and incandescent ejecta continue during September 2018-February 2019

Frequent historical eruptions have been reported from Mexico's Popocatépetl going back to the 14th century. Activity increased in the mid-1990s after about 50 years of quiescence, and the current eruption, ongoing since January 2005, has included numerous episodes of lava-dome growth and destruction within the 500-m-wide summit caldera. Multiple emissions of steam and gas occur daily, rising generally 1-3 km above the 5.4-km-elevation summit; many contain small amounts of ash. Larger, more explosive events with ash plumes and incandescent ejecta landing on the flanks usually occur several times every week.

Activity through August 2018 was typical of the ongoing eruption with near-constant emissions of water vapor, gas, and minor ash, as well as multiple explosions every week with ash-plumes and incandescent blocks scattered on the flanks (BGVN 43:11). This report covers similar activity from September 2018 through February 2019. Information about Popocatépetl comes from daily reports provided by México's Centro Nacional de Prevención de Desastres (CENAPRED); ash emissions are also reported by the Washington Volcanic Ash Advisory Center (VAAC). Satellite visible and thermal imagery and SO2 data also provide helpful observations of activity.

Near-constant emissions of steam and gas, often with minor ash content, were typical activity throughout September 2018-February 2019. Intermittent larger explosions with plumes of moderate ash content that generated ashfall in nearby communities were reported each month except November. Periods with increased explosive activity that consisted of multiple daily explosions included all of September into early October, early December 2018, and the second half of February 2019 (figure 116). Increased observations of incandescence at the summit generally coincided with increases in explosive activity. Increases in thermal anomalies measured by the MIROVA project during this time also correlated with times of increased explosive activity as reported by CENAPRED (figure 117).

Figure (see Caption) Figure 116. The numbers of low intensity emissions of steam and gas, often with minor amounts of ash ranged from a few tens to several hundred per day throughout September 2018-February 2019 (blue, left axis). Increases in the daily numbers of larger ash-bearing explosions occurred during September-early October 2018, early December, and the second half of February 2019 (orange, right axis). Data courtesy of CENEPRED.
Figure (see Caption) Figure 117. Thermal anomalies registered by the MIROVA project from 5 April 2018 through February 2019 had periods of increased frequency and intensity during September-early October, early December 2018, and in the second half of February 2019. Courtesy of MIROVA.

Activity during September 2018. Multiple explosions with ash plumes were reported nearly every day in September (figure 118). The Washington VAAC reported an ash plume visible in satellite imagery 15 km NW of the summit at 7.6 km altitude on 4 September. Most plumes reported by the VAAC during the month rose to 6.1-7.6 km and drifted up to 40 km in multiple directions. Two small episodes of ash emissions with tremor on 16 September were followed the next day by a series of emissions, explosions, and tremor that lasted for over six hours; incandescent blocks were visible on the flanks in the early morning. An increase in activity late on 18 September produced Strombolian eruptions that lasted for nearly eight hours along with ash emissions and incandescent blocks on the flanks. A plume on 19 September still had detectable ash 150 km NE of the summit; a smaller plume drifting E was responsible for ashfall reported in Tlaxcala.

Figure (see Caption) Figure 118. Multiple explosions with ash plumes were reported nearly every day in September at Popocatépetl, generating ash plumes that rose from 1.5-3 km above the crater and drifted in multiple directions. The CENAPRED webcams captured images of ash plumes on 8, 11, and 19 September, and the Sentinel-2 satellite (rendering is Atmospheric penetration, based on bands 12, 11 and 8A) imaged ash plumes from two of seven reported explosions on 24 September 2018. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 9, 11, y 20 de septiembre de 2018) and Sentinel Hub Playground (lower image).

Discrete puffs of ash were observed by the Washington VAAC on 20 September moving WSW extending around 200 km from the summit. Three explosions on 21 September ejected incandescent blocks onto the NE flank. During an overflight on 21 September, CENAPRED observed dome number 80, partly destroyed by the recent explosions (figure 119). The Washington VAAC reported an ash plume at 8.8 km altitude on 21 September 30 km WSW from the summit. Ashfall was reported by CENACOM (Mexican National Communications Center) on 29 September in Atlautla, Tehuixtitlan, and Cuecuecuautitla in the State of Mexico, and in the Tláhuac Delegation, Iztapalapa, and Xochimilco in Mexico City.

Figure (see Caption) Figure 119. During an overflight on 21 September 2018, CENAPRED observed dome number 80 at Popocatépetl, partly destroyed by the recent explosions. Courtesy of CENAPRED (Sobrevuelo al volcán Popocatépetl hoy 21 de septiembre de 2018).

Activity during October and November 2018. The Washington VAAC reported an ash plume at 7 km altitude on 2 October, 35 km W of the summit. Numerous smaller plumes were reported by the VAAC during both months at about 6 km altitude drifting in multiple directions. Two larger explosions on 8 October produced ash plumes that rose to 3.5 and 2.4 km, respectively, above the summit, and drifted NE (figure 120). As a result, ashfall was reported at the Puebla airport. On 10 and 12 October, extended periods of LP tremor were accompanied by gas emissions, but otherwise lower levels of activity were noted for much of the month. An ash plume extended over 80 km NE at 7.6 km altitude on 10 November. An explosion on 13 November produced incandescent fragments on the flanks. During 19-21 November episodes of LP seismicity and tremors produced gas and ash emissions; some of the episodes lasted for as long as 13 hours; incandescent fragments were observed on the upper slopes during the more intense periods. On 22 November scientists on an overflight by CENAPRED observed dome 81 with a diameter of 175 m and an estimated depth of 30 m (figure 121).

Figure (see Caption) Figure 120. A large explosion early on 8 October 2018 at Popocatépetl sent an ash plume to 3.5 km above the summit crater that drifted NE. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 9 de Octubre de 2018).
Figure (see Caption) Figure 121. On 22 November 2018 scientists on an overflight by CENAPRED observed dome 81 at Popocatépetl with a diameter of 175 m and an estimated depth of 30 m. Courtesy of CENAPRED (Sobrevuelos, herramienta útil para el monitoreo volcánico del Popocatépetl, jueves, 22 de noviembre de 2018).

Activity during December 2018. Increased ash emissions were reported in early December 2018, producing ash plumes that rose at least 1 km above the crater and drifted mostly E; incandescent blocks ejected on 5 December fell mostly back into the crater. Multiple explosions on 6 and 7 December produced ash plumes that rose as high as 2.5 km above the crater and resulted in ashfall in Amecameca and Tlalmanalco; they also produced incandescent blocks that traveled as far at 2.5 km from the crater, according to CENAPRED. An explosion on 9 December produced a 2-km-high ash plume that drifted NE (figure 122). Satellite images captured during clear skies on 18 December showed incandescence at the dome inside the summit crater, and dark ash and ejecta covering much of the upper flanks (figure 123). An ash plume was centered about 100 km NE of the summit on 24 December at 7.6 km altitude, and dissipating rapidly, according to the Washington VAAC. Incandescent blocks were ejected onto the flanks on 26 December during an evening explosion.

Figure (see Caption) Figure 122. An explosion on 9 December 2018 produced a 2-km-high ash plume at Popocatépetl that drifted NE. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 9 de diciembre de 2018).
Figure (see Caption) Figure 123. Clear skies on 18 December 2018 resulted in a Sentinel-2 satellite image of Popocatépetl that showed incandescence on the dome inside the summit crater, and dark tephra surrounding all the upper flanks. Rendering is Atmospheric penetration, based on bands 12, 11 and 8A. Courtesy of Sentinel Hub Playground.

Activity during January 2019. An explosion in the early morning of 16 January 2019 produced incandescent blocks that traveled 1.5 km down the slopes. It also produced an ash emission that lasted for 25 minutes; the seismic signal associated with the event was a mixture of harmonic tremor and high-frequency low-amplitude earthquakes. In the first minutes the height of the column reached 1,000 m above the crater, later it decreased to 500 m; ash was dispersed ENE. Late on 22 January a large explosion produced an ash plume that rose 3.5 km above the crater and numerous incandescent blocks that were observed as far as 2 km from the summit (figure 124); ashfall was reported in Santa Isabel Cholula, Santa Ana Xalmimilulco, Domingo Arenas, San Martin Texmelucan, Tlalancaleca, San Salvador el Verde, San Andres Calpan, San Nicolás de los Ranchos, and Huejotzingo, all in the state of Puebla. A large discrete ash plume was observed in satellite imagery by the Washington VAAC on 24 January at 6.7 km altitude moving NE to about 35 km distance before dissipating. In an overflight on 27 January CENAPRED noted that the internal crater remained about 300 m wide and 150 m deep, and no dome was visible (figure 125).

Figure (see Caption) Figure 124. Late on 22 January 2019 a large explosion at Popocatépetl produced an ash plume that rose 3.5 km above the crater and produced numerous incandescent blocks that were observed as far as 2 km from the summit. Courtesy of CENAPRED (Actualización de Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 22 de enero de 2019).
Figure (see Caption) Figure 125. During an overflight of Popocatépetl on 27 January 2019 observers from CENAPRED noted that the internal crater remained about 300 m wide and 150 m deep, and no dome was visible. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 27 de enero de 2019).

Activity during February 2019. Several days of increased activity of harmonic tremor and explosions were reported during 14-19 February 2019 (figure 126). Incandescent blocks from Strombolian activity appeared on the flanks late on 14 February traveling as far as 1.5 km, along with a continuous stream of ash and gas that drifted SW for seven hours. The initial ash plume rose 800 m, but by early the next day had risen to 2 km. Ashfall was reported in the communities of Hueyapan, Tetela del Volcán, Zacualpan, Temoac, Jantetelco, Cuautla, Ocuituco, and Yecapixtla, in the state of Morelos, and in Tochimilco, Puebla, on 15 February.

Figure (see Caption) Figure 126. Several days of increased activity at Popocatépetl, including harmonic tremor and explosions, were reported during 14-19 February 2019. Incandescent blocks from Strombolian activity appeared on the flanks late on 14 February traveling as far as 1.5 km, along with a continuous stream of ash and gas that drifted SW for seven hours (left). Steam and gas streamed continuously from the summit for many hours on 17 February (right); the plume drifted NNE at 1-1.5 km altitude. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 14 y 18 de febrero de 2019).

A new episode of Strombolian activity early on 16 February lasted for six hours and produced 2-km-high ash plumes that drifted SE. Later that afternoon, a new harmonic tremor episode, again lasting about six hours, was accompanied by water vapor and gas emissions that drifted NE and incandescent blocks ejected 400 m down the flanks. A Sentinel-2 satellite image that day recorded a significant thermal signature from the summit dome (figure 127).

Figure (see Caption) Figure 127. A Sentinel-2 satellite image on a clear 16 February 2019 recorded a significant thermal signature from the summit dome of Popocatépetl. Rendering is Atmospheric penetration (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Satellite instruments recorded a strong SO2 signature from the volcano during 15-18 February (figure 128). Multi-hour periods of harmonic tremor were recorded during 17-19 February, accompanied by gas-and-ash emissions. Ash plume heights were between 1 and 2 km above the crater, and minor ashfall was reported in Tlaxco and Xalostoc in Nativitas, and Hueyotlipan, Amaxac de Guerrero, Tepetitla de Lardizábal, and Texoloc in Tlaxcala, on 18 February. Two overflights on 18 and 19 February confirmed the formation of dome 82 inside the summit crater, estimated to be 200 m in diameter (figure 129).

Figure (see Caption) Figure 128. Significant SO2 plumes were measured by the TROPOMI instrument on the Sentinel-5P satellite during 15-18 February 2019 at Popocatépetl. The plume initially drifted SW (top left, 15 February); changes in the wind direction carried the plume to the N (top right, 16 February), then to the NE (bottom left, 17 February), and back to the N on 18 February (bottom right). Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 129. An overflight on 19 February by CENAPRED confirmed the formation of dome 82 inside the summit crater at Popocatépetl, estimated to be 200 m in diameter. Courtesy of CENAPRED (Actualización del reporte del monitoreo de CENAPRED al volcán Popocatépetl, 19 de febrero de 2019).

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: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: http://www.cenapred.unam.mx/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); 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); 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/).


Pacaya (Guatemala) — March 2019 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Continuous activity from the cone in Mackenney crater; daily lava flows on the NW flank during October 2018-January 2019

Extensive lava flows, bomb-laden Strombolian explosions, and ash plumes emerging from MacKenney crater have characterized the persistent activity at Pacaya since 1961. The latest eruptive episode began with intermittent ash plumes and incandescence in June 2015; the growth of a new pyroclastic cone inside the summit crater was confirmed in mid-December 2015. The pyroclastic cone has continued to grow, rising above the crater rim in late 2017 and sending numerous flows down the flanks of the crater throughout 2018 (BGVN 43:11). Similar activity continued during October 2018-January 2019, covered in this report, with information provided primarily by Guatemala's Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH).

There were few variations in the eruptive activity at Pacaya during October 2018-January 2019. Virtually constant Strombolian activity from the summit of the pyroclastic cone within Mackenney crater produced ejecta that rose 5-30 m daily. Periods of increased activity occasionally increased the height of the ejecta to 50 m. Lava flows descended the NW flank of Mackenney cone towards Cerro Chino crater, usually one or two a day, sometimes three or four. They travelled 50-300 m down the flank; the longest reached 600 m in mid-October and 500 m at the end of January. Steam and gas plumes persisted from the summit; a single VAAC report mentioned dilute ash in mid-October. Plumes generally rose a few hundred meters above the summit, occasionally reaching 700-800 m. Incandescent avalanche blocks at the heads of the flows were sometimes as large as a meter in diameter and traveled far down the flanks.

Constant Strombolian activity during October 2018 from the pyroclastic cone within Mackenney crater was ejected up to 30 m above the summit of the cone throughout the month, with occasional more intense episodes rising 50 m. Lava flows were reported daily by INSIVUMEH on the NW flank from 50 to 300 m long. White and blue gas-and-steam emissions generally rose a few hundred meters from the summit of the pyroclastic cone and usually drifted S or N. The highest rose 800 m on 26 and 27 October. In a special report issued late on 12 October INSIVUMEH noted that seismicity had increased during the day; Strombolian explosions also increased and ejected material 25-50 m above the summit, producing block avalanches in the vicinity of the flows (figure 103). The cone within Mackenney crater continued to grow, reaching 75 m above the rim and nearly filling the crater at its base. According to the Washington VAAC, on 14 October a pilot reported minor ash emissions moving W at an estimated 650 m above the summit. Multi-spectral imagery showed a faint ash plume moving W at 3.4 km altitude, and a well-defined hotspot was seen in short-wave infrared imagery.

Figure (see Caption) Figure 103. Strombolian activity sent ejecta 25-50 m above the summit of Pacaya on 12 October 2018, and lava flows traveled 600 m down the NW flank towards Cerro Chino, as seen from the community of Escuintla located about 20 km W. Courtesy of Carlos Barrios and INSIVUMEH.

Similar activity persisted throughout November 2018 (figures 104 and 105). The Strombolian activity usually rose 5-30 m high; on 24 November INSIVUMEH reported ejecta 75 m high and the presence of four lava flows on the NW flank that traveled distances ranging from 50 to 200 m. Steam-and-gas emissions rose no more than 500 m above the summit. On 24 and 28 November incandescent avalanche blocks were observed at the fronts of the lava flows.

Figure (see Caption) Figure 104. Constant Strombolian activity rising 25-50 m above the summit of Pacaya was reported on 12 November 2018. In addition, a lava flow 150 m long traveled down the NW flank towards Cerro Chino, as seen in this image with incandescent blocks below the flow. A diffuse plume of mostly gas and steam rose 350 m above the crater. Courtesy of CONRED.
Figure (see Caption) Figure 105. Continuous lava flows up to 300 m long were observed during the last week of November 2018 at Pacaya. They traveled down the NW flank and often had large incandescent blocks that descended the flank beneath the flow. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Pacaya (1402-11), Semana del 24 al 30 de noviembre de 2018).

During December 2018, continuous Strombolian activity was observed 25 m high. Incandescent avalanche blocks were noted at the fronts of the lava flows more frequently than in previous months. One to three lava flows extending 50-300 m down the NW flank towards Cerro Chino were reported every day that the flanks were visible (figure 106). Late on 13 December INSIVUMEH released a special bulletin noting that explosions were heard as far as 8 km from Mackenney crater, and Strombolian activity rose 25-50 m. Constant tremor activity had been produced from the ongoing lava flows descending the flank; the incandescent avalanche blocks up to 1 m in diameter were falling from the front of the flows. By the end of December, the growing pyroclastic cone had filled the inside of Mackenney crater, reaching 75-100 m above the crater rim. In a special information report on 28 December, INSIVUMEH noted that changes in the eruptive patterns included an increase in seismic tremor along with more persistent and higher energy Strombolian activity from the active cone, which frequently sent material outside of the crater onto the flanks.

Figure (see Caption) Figure 106. Lava flows traveled down the NW flank of Pacaya on 7 December 2018. Courtesy of INSIVUMEH (Informe mensual de la actividad volcanica, diciembre 2018, Volcan de Pacaya).

There were no significant changes in activity during January 2019. Constant Strombolian activity rose 5-30 m above the summit; INSIVUMEH reported the height at 50 m on 7 January. Large incandescent avalanche blocks were noted at the front of the lava flows several times; one or two flows daily reached lengths of 100-300 m. The flow reported on 29 January reached 500 m, traveling down the NW flank towards Cerro Chino. Steam plumes, sometimes with bluish gas, rose generally to around 100 m above the summit, occasionally higher. Growth and destruction of the pyroclastic cone inside Mackenney crater continued as it had for the previous several months. The persistent Strombolian and lava flow activity was responsible for a strong thermal signature recorded in satellite data and plotted by the MIROVA project during the period (figure 107).

Figure (see Caption) Figure 107. A MIROVA graph of thermal radiative power at Pacaya from 5 April 2018 through January 2019 showed little change during the period from October 2018-January 2019 covered in this report. 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/); Carlos Barrios (Twitter: @shekano, URL: https://twitter.com/shekano).

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Scientific Event Alert Network Bulletin - Volume 14, Number 12 (December 1989)

Managing Editor: Lindsay McClelland

Aira (Japan)

1989 activity summarized

Asosan (Japan)

Ash emission and seismicity decline

Bagana (Papua New Guinea)

Lava overflows crater; rockfalls

Etna (Italy)

Southeast Crater explosive activity drops tephra on nearby towns

Etorofu-Yakeyama [Grozny Group] (Japan - administered by Russia)

Small explosions form new fumaroles; mudflows

Kilauea (United States)

Two ocean entries remain active; littoral explosions

Langila (Papua New Guinea)

Moderate seismicity; weak glow

Lascar (Chile)

Strong steam plumes

Long Valley (United States)

Seismicity increases in caldera's S moat

Lonquimay (Chile)

Continued ash emission and lava production; strong SO2

Manam (Papua New Guinea)

Weak gas emissions; glow

Michoacan-Guanajuato (Mexico)

Fumarole temperatures decrease

Rabaul (Papua New Guinea)

Increase in seismicity; inflation

Redoubt (United States)

Lava dome destroyed by explosions; major mudflow; smaller explosions followed by renewed lava extrusion

Ruiz, Nevado del (Colombia)

Small ash ejections; seismicity remains stable

Sorikmarapi (Indonesia)

Phreatic explosion ejects mud

St. Helens (United States)

Small ash emission; ashfalls to 80 km distance

Supply Reef (United States)

Renewed activity at September site

Ulawun (Papua New Guinea)

Gas emissions and seismicity remain at background

White Island (New Zealand)

Mild explosions; new crater enlarged



Aira (Japan) — December 1989 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


1989 activity summarized

A total of 13 explosions were recorded in December; the largest, at 1155 on the 13th, ejected ash to 3,000 m above the crater. Monthly ash accumulation at [KLMO] was 13 g/m2. The explosions caused no damage.

A total of 44 explosions from the summit crater of Minami-dake were recorded in 1989, a decrease from 155 recorded in 1988. Yearly ash accumulation at KLMO was 2,352 g/m2. A seismometer (2.3 km NW of the crater) registered 18,296 earthquakes in 1989.

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: JMA.


Asosan (Japan) — December 1989 Citation iconCite this Report

Asosan

Japan

32.884°N, 131.104°E; summit elev. 1592 m

All times are local (unless otherwise noted)


Ash emission and seismicity decline

Activity was less vigorous in December than in November, with only three recorded explosions (see table 4), bringing the year's total to 39. Minor ash emission was observed almost daily. A total of 755 g/m2 of ash was deposited at AWS. The number of isolated tremor episodes recorded by a seismometer at AWS decreased in late December (figure 16). The amplitude of continuous tremor declined to a level similar to that of early September (figures 16 and 17). Rumbling was slightly audible at AWS during the month.

Figure (see Caption) Figure 16. Daily number of isolated volcanic tremor episodes (top) and daily maximum and mean amplitudes of continuous tremor (bottom) at Aso, April-December 1989. Courtesy of JMA.
Figure (see Caption) Figure 17. Monthly mean amplitude of continuous tremor at Aso, 1966-1989. Courtesy of JMA.

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

Information Contacts: JMA.


Bagana (Papua New Guinea) — December 1989 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Lava overflows crater; rockfalls

"Mild, sustained, eruptive activity continued throughout December. Numerous rockfalls or avalanches occurred from the unstable blocky flows that slowly spilled over all sides of the summit crater, producing short-lived, red incandescence at night. The seismicity continued to be dominated by rockfall events (several tens/day), with only a few B-type events and occasional swarms of discontinuous tremor (1/2 hour on the 18th and 3 hours on the 21st)."

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: P. de Saint-Ours, RVO.


Etna (Italy) — December 1989 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3295 m

All times are local (unless otherwise noted)


Southeast Crater explosive activity drops tephra on nearby towns

Summit activity. (S. Calvari, M. Coltelli, O. Consoli, M. Pompilio, V. Scribano.) After only fumarolic emissions from Southeast Crater in November (14:11), renewed activity began on 16 December with continuous ejection of reddish cinders. The activity continued for the following two days, becoming weaker on the 18th. A new vent on the crater bottom, observed 21 December from the rim, exhibited strong explosive activity, but without visible tephra ejection. The activity became somewhat more intense during the following days. Only very small cinders (probably juvenile) reached the crater rim. Strong, deep, explosive activity was noted at Bocca Nuova, but there was no evidence of new tephra on the crater rim. La Voragine was obstructed and characterized by weak fumarolic emissions from the crater bottom. Gas emission from a vent on the floor of Northeast crater continued as before, but reddish cinders and gas were emitted on the 16th.

Seismic activity. (S. Privitera, C. Cardaci, O. Cocina, V. Longo, A. Montalto, D. Patane, A. Pellegrino, S. Spampinato.) Seismic activity in December returned to levels similar to those preceding the July-October seismic and eruptive activity (14:7-11). Five events with M>2 were recorded at 5-10 km depths on the Valle del Bove and the volcano's W sector. The most energetic event (M 2.8) occurred 9 December on the E part of the Valle del Bove at 9 km depth. The number and energy of low-frequency events increased, with maximum activity recorded on 16 December. Tremor amplitude also increased and was characterized by energy fluctuations, especially on the 18th and 19th.

Ground deformation. (A. Bonaccorso, O. Campisi, B. and G. Puglisi, R. Velardita.) Preliminary interpretation of the signal at the SPC borehole tilt station on the S flank showed no significant variation during December. Deformation measured on the NE trilateration network was characterized by shear, with almost equal moduli of the main strain axes. Distance measurements across the fracture on the volcano's S side indicate general stability relative to 7 October and 11 November surveys.

Summit crater SO2 flux. (T. Caltabiano, R. Romano.) Samples collected 7, 20, and 29 December revealed that SO2 flux had stabilized below the mean value of 4,000 t/d. A relatively low value (2,000 t/d) was recorded in late November. December 1989 SO2 flux was slightly higher than the December 1988 trend, probably related to a longer-period flux component.

Early January activity. A seismic phase characterized by fluctuations in the mean amplitude of volcanic tremor began on 4 January at 1950 and was recorded at the ESP station of the permanent Mt. Etna seismic network. Iseismicity;amplitude By 5 January at 0120, the amplitude had stabilized at medium-high values. The most energetic phase was recorded between 0730 and 0922 on several seismic stations. During the following hours, tremor amplitude decreased, but sporadic 1-minute fluctuations brought the tremor amplitude to normal levels. The seismic phase was probably accompanied by lava fountaining at Southeast Crater, but bad weather prevented direct observation. The activity deposited lapilli and small scoria (up to 4 cm) on the NW side of the volcano in the Bronte-Randazzo area, with a dispersion axis oriented toward the town of Maletto (15 km NW of the summit crater). Scoria 13 km from the summit crater was 2-3 cm in diameter. Fieldwork in the following days revealed that a small amount of lava had poured over Southeast Crater's rim, probably due to lava fountaining. The 300-m lava flow, ~ 50 m wide and 1-2 m thick, reached the lowermost 1971 crater. As of 10 January, Southeast Crater showed no explosive activity.

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

Information Contacts: R. Santacroce, IIV.


Etorofu-Yakeyama [Grozny Group] (Japan - administered by Russia) — December 1989 Citation iconCite this Report

Etorofu-Yakeyama [Grozny Group]

Japan - administered by Russia

45.012°N, 147.871°E; summit elev. 1158 m

All times are local (unless otherwise noted)


Small explosions form new fumaroles; mudflows

After an increase in fumarolic emissions and weak ash explosions in May, fumarolic activity remained vigorous. An eruption on 19 June at 2230, accompanied by 2-3 minutes of weak rumbling, sent ash and gas to ~2 km. An early August explosion formed new fumarolic vents on the dome's N flank, ~70-100 m from the summit (figure 1).

Figure (see Caption) Figure 1. September 1989 photograph by A. Samoluk, looking W at the new fumaroles formed by an August explosion on the dome's N side.

On a 16 September ascent of the dome, geologists G. Steinberg and S Tkachenko observed vigorous gas emission from several sulfur-encrusted fissures, and deep narrow craters ~2-3 m in diameter. Two mud flows (4-6 m wide) that extended 1.5-2 km down the dome's N side had destroyed areas of thick vegetation (bushes and bamboo). One flow reached Lake Lopastnye (figure 2). No juvenile material was found in the flows. A small mudflow deposit on the S side of the dome, and another on the W (previously seen 18 and 20 May; reported as E slope in 14:5) were also observed.

Figure (see Caption) Figure 2. September 1989 photograph by A. Samoluk, looking S at two mudflows on the dome's N side. Lake Lopastnye is in the foreground.

Geologic Background. Etorofu-Yakeyama (Ivan Grozny), is located in the center of Iturup Island. It has a 3-3.5 km diameter caldera that is open to the south, where the large extrusive andesitic dome was emplaced. Several other lava domes of Holocene age were constructed to the NE; extrusion of these domes has constricted a former lake in the northern side of the caldera to an extremely sinuous shoreline. Historical eruptions, the first of which took place in 1968, have been restricted to Etorofu-Yakeyama.

Information Contacts: G. Steinberg and R. Bulgakov, Yuzhno-Sakhalinsk.


Kilauea (United States) — December 1989 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Two ocean entries remain active; littoral explosions

Throughout December, lava from Kupaianaha pond continued to flow into the ocean . . . (figure 64). Most of the lava (75-95%) entered the water at the Poupou entry, the rest at the October entry on the Kailiili delta, now designated the W Kailiili entry (figure 65). The output at W Kailiili had diminished to a trickle by the end of December.

The Poupou lava tube branched near the coastline and, during most of the month, terminated in two streams of lava, 25-50 m apart at the waterline. Intermittent littoral explosions added spatter and limu to the large 2-3-m littoral cone atop the sea cliff. Two smaller cones formed in early December ~20 m to the E. They were nearly buried at mid-month by a surface flow that emerged from the tube near the ocean and cascaded over the sea cliff to form a 30 x 10 m bench. This flow stagnated within a few days. As the surface flow emerged, an inflated area ~3 m high by 15-20 m in diameter formed behind the large cone.

Breakouts from the lava tube system at 550-480 m elevation (1,850-1,600 ft) produced small pahoehoe flows that encroached on the kipukas along the W flow margin. At the 180 m (600 ft) level, breakouts fed small flows that terminated 300-400 m upslope of the Royal Gardens kipuka through the 18th. Surface breakouts in Royal Gardens were first reported on 11 December. On 6 December, a thin flow encroached on the S half of the Wahaula Heiau (temple) grounds. One lobe of the flow stagnated ~10 m N of the ruins, but most lava flowed farther E and cascaded over the sea cliff onto the new black sand beach below. Activity of the Wahaula flow ceased after 8 December.

The level of Kupaianaha lava pond, which had dropped to ~30 m below the rim in November, remained low and stable in December. Glowing vents at the bottom of Pu`u `O`o were reported on the 3rd and 11th, but no active lava was present.

Low-level tremor continued . . . near Pu`u `O`o and Kupaianaha. Above the background of continuous tremor, high-frequency microshocks associated with minor crustal fracturing around Kupaianaha were detected by the Kalalua seismometer, ~1 km away. The number of shallow (<5 km) microearthquakes was about average in the summit region and the East rift zone. Intermediate-depth (5-15 km) long-period events continued, reaching several hundred/day. A widely felt earthquake (preliminary M 5.1) struck the S flank of Kilauea at 2313 on 27 December at 9 km depth.

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: C. Heliker and R. Koyanagi, HVO.


Langila (Papua New Guinea) — December 1989 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)


Moderate seismicity; weak glow

"Although a weak red glow was observed over Crater 2 on most nights of the month, activity at Langila remained at a moderate level throughout December. Vapours were emitted in small to moderate amounts, and deep rumbling noises were occasionally heard. The seismicity consisted of a few tens to several hundreds of small-amplitude B-type events/day."

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: P. de Saint-Ours, RVO.


Lascar (Chile) — December 1989 Citation iconCite this Report

Lascar

Chile

23.37°S, 67.73°W; summit elev. 5592 m

All times are local (unless otherwise noted)


Strong steam plumes

Strong steam eruptions were observed by Stephen Foot on 17 December between 0915 and 0930, and on 21 December at 1130. In each instance, fumarolic activity changed from the normal emission of a small diffuse plume to ejection of a very dense white cloud that rose ~2 km above the crater for ~15 minutes. The clouds were opaque and produced a heavy shadow. The plumes then diminished in height, remaining near the volcano for about an hour, then moved N on the 17th and NE on the 21st. No recent precipitation had occurred in the area.

Geologic Background. Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Information Contacts: S. Foot, MINSAL Ltda., Santiago; M. Gardeweg, SERNAGEOMIN, Santiago.


Long Valley (United States) — December 1989 Citation iconCite this Report

Long Valley

United States

37.7°N, 118.87°W; summit elev. 3390 m

All times are local (unless otherwise noted)


Seismicity increases in caldera's S moat

The seismic swarm ... declined significantly from October through December. Meanwhile, a few earthquakes began in October around the S margin of the resurgent dome, which has been relatively inactive for several years. A distinct increase in seismicity began there in November. A burst of 40 events was recorded 5 January in the S moat area, followed by fluctuating activity; some days were seismically quiet. Seismicity appeared similar in many ways to that of the early 1980's, although more of the current activity occurred on the W side of the resurgent dome than previously. Focal depths, generally ~6-10 km, also resembled those of the early 1980's, with the deeper events on the E side of the epicentral zone. Some shocks on the W side of the resurgent dome were <4 km deep. The rate of extension across the resurgent dome began to increase in mid-1989, reaching ~5 microstrain/year by December. This is ~5 times the rate seen in recent years.

Geologic Background. The large 17 x 32 km Long Valley caldera east of the central Sierra Nevada Range formed as a result of the voluminous Bishop Tuff eruption about 760,000 years ago. Resurgent doming in the central part of the caldera occurred shortly afterwards, followed by rhyolitic eruptions from the caldera moat and the eruption of rhyodacite from outer ring fracture vents, ending about 50,000 years ago. During early resurgent doming the caldera was filled with a large lake that left strandlines on the caldera walls and the resurgent dome island; the lake eventually drained through the Owens River Gorge. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation, seismicity, and other unrest in recent years. The late-Pleistocene to Holocene Inyo Craters cut the NW topographic rim of the caldera, and along with Mammoth Mountain on the SW topographic rim, are west of the structural caldera and are chemically and tectonically distinct from the Long Valley magmatic system.

Information Contacts: D. Hill, USGS Menlo Park.


Lonquimay (Chile) — December 1989 Citation iconCite this Report

Lonquimay

Chile

38.379°S, 71.586°W; summit elev. 2832 m

All times are local (unless otherwise noted)


Continued ash emission and lava production; strong SO2

Ash emission and lava production, generally relatively weak, continued at Lonquimay. Stronger activity occurred on 27 and 28 November, when a dense cauliflower-shaped ash column rose 2,000-2,500 m above the vent and was carried SE (Lonquimay district). The press reported renewed stronger activity about 24 December, on the eve of the eruption's first anniversary, when gas and tephra were ejected to ~2,000 m height, and debris fell ~500 m away. Strong felt earthquakes and underground noise were associated with the activity.

For the first time since the eruption began almost 11 months earlier, geologists were able to reach the summit of Navidad cone during several days of fieldwork that began 19 November. Direct measurements indicated that the S, W, and E flanks were 150, 100, and 190 m high respectively. The inner walls of the main cone showed annular fractures denoting small (<5 m) partial collapses of the nested airfall deposits. Fumarolic activity occurred through the fractures; a temperature of 264°C was measured on the inner W wall. The air was saturated with acid gases 15 m below the main crater rim. Nested within the formerly horseshoe-shaped main crater, 400-450 m in diameter, was a funnel-shaped crater 50 m across. The more intense explosions (including bomb ejection) and steam jets emerged from vents in the wall and deeper parts of this crater. Tephra in the 500-m-high column consisted primarily of bombs and ash. Lapilli were very scarce, and most tephra were dense, fine, angular lithics, indicating Vulcanian-type behavior. Winds carried the plume SE.

William Rose reports that "COSPEC measurements 19 and 21 November under the plume at Portezuelo, 1.3 km SE of Navidad cone, revealed highly variable SO2 fluxes ranging from 300 to > 14,000 t/d. These are much higher than the 80-300 t/d measured by Kyle on 13 July. The November SO2 emission rates are in the lower part of the range of other measurements at actively erupting volcanoes. When compared with estimates of the lava effusion rate, the November SO2 fluxes suggest that Lonquimay lavas contain a high sulfur content and/or intrusive (unerupted) magma may be contributing sulfur to the Navidad plume."

Lava continued to emerge from a 3-m-wide vent at the NE foot of the cone. The lava surface had a black aa-like crust and moved at ~50-55 m/hour. On 21 November, the level of the top of the flow dropped substantially between observations at the vent at 1200 and 1830, leaving former hot levees perched as much as 3 m above the flow surface, although flow velocity seemed unchanged. These fluctuations precluded an accurate effusion rate estimate, but it probably exceeded 15 x 103 m3/day. Lava temperature measured by thermocouple 500 m from the vent was 934°C. The flow front was ~10.7 km from Navidad cone along the Lolco river (figure 15). Front thickness varied between 45 and 50 m. Since 17 September, the lava had covered an additional area of ~0.16 km2, representing lava production of ~7.2 x 106 m3 in 60 days, for a mean of 120 x 103 m3/day.

Figure (see Caption) Figure 15. Map showing the lava flow front and two lava-impounded lakes as of 22 November. Courtesy of H. Moreno.

Two small lakes were impounded behind the lava flow, near the former channel of the Lolco river and in the La Holandesa valley, but the other three lakes observed on 17 September (14:9) had disappeared. Lolco river water emerged from under the flow front at 70°C, with a pH of 6.5.

In early August, a small flow of blocky lava had emerged from a vent midway down the cone's NE flank, aligned with the NE end of the fissure that has controlled the eruption. The flow, cold by November, was ~50 m long, 20 m wide, and 6 m thick.

Geologic Background. Lonquimay is a small, flat-topped, symmetrical stratovolcano of late-Pleistocene to dominantly Holocene age immediately SE of Tolguaca volcano. A glacier fills its summit crater and spills down the S flank. It is dominantly andesitic, but basalt and dacite are also found. There is an E-W fissure, although the prominent NE-SW Cordón Fissural Oriental fissure zone cuts across the entire volcano, that produced a series of NE-flank vents and cinder cones, some of which have been the source of voluminous lava flows, including those during 1887-90 and 1988-90 that traveled up to 10 km.

Information Contacts: J. Naranjo, SERNAGEOMIN, Santiago; H. Moreno, Univ de Chile; W. Rose and R. Andres, Michigan Technological Univ; Santiago Domestic Service, Chile.


Manam (Papua New Guinea) — December 1989 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)


Weak gas emissions; glow

"Activity remained at a low level in December. Weak emissions of white vapour occurred from both Southern and Main Craters throughout the month. A weak, dull, fluctuating glow was observed over Southern Crater on the night of the 25th. There was no significant tilt change".

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: P. de Saint-Ours, RVO.


Michoacan-Guanajuato (Mexico) — December 1989 Citation iconCite this Report

Michoacan-Guanajuato

Mexico

19.85°N, 101.75°W; summit elev. 3860 m

All times are local (unless otherwise noted)


Fumarole temperatures decrease

Geologists visited Ahuan fumarole on 23 November. The fumarole temperature was 305°C, a decrease from 336°C measured in May 1988.

Geologic Background. The widespread Michoacán-Guanajuato volcanic field contains over 1400 vents, including the historically active cinder cones of Parícutin and Jorullo, covering a 200 x 250 km wide area of Michoacán and Guanajuato states in west-central México. Cinder cones are the predominant volcanic form, but small shield volcanoes, lava domes, maars and tuff rings (many in the Valle de Santiago area), and coneless lava flows are also present. The shield volcanoes are mostly Pleistocene in age, and have morphologies similar to small Icelandic-type shield volcanoes, although the Michoacán-Guanajuato shields have higher slope angles and smaller basal diameters. Jorullo, which was constructed in the 18th century, and Parícutin, which grew above a former cornfield during 1943-52, are the two best known of the roughly 1000 small volcanic centers scattered throughout the volcanic field.

Information Contacts: Kurt Roggensack, Helen Mango, John Lucio, and Half Zantop, Dartmouth College.


Rabaul (Papua New Guinea) — December 1989 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)


Increase in seismicity; inflation

"December showed both a relative increase in seismicity and an accelerated rate of inflation in the central part of the caldera. The moderate rise in seismicity observed since October continued, with 886 caldera events (ML <=2.3) recorded in December. Background seismicity fluctuated between 10 and 40 events/day. Minor swarms occurred on 12 (52 events), 13 (121), 18 (45), and 24 (76) December, alternately from the NW (Beehives), N (Greet Harbour), and E (Blanche Bay) areas of the well-established annular seismic zone.

"Renewed inflation in the central part of the caldera was suggested by rise of the S tip of Matupit Island . . . of 3 mm/month from September to November. Uplift of 20 mm was recorded in December. Only six tilt stations around Greet Harbour and on the Vulcan Headland showed a significant inflationary trend (3-10 µrad/month since mid-October)."

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: P. de Saint-Ours, RVO.


Redoubt (United States) — December 1989 Citation iconCite this Report

Redoubt

United States

60.485°N, 152.742°W; summit elev. 3108 m

All times are local (unless otherwise noted)


Lava dome destroyed by explosions; major mudflow; smaller explosions followed by renewed lava extrusion

A series of explosions 14-19 December was followed by extrusion of lava into the active crater in late December. The lava dome was destroyed by strong explosions 2 January that triggered a major mudflow into the Drift River. Mud flowed against but did not penetrate the inner dikes protecting tanks at the Drift River oil facility. Vigorous explosions occurred again on 8 and 16 January, causing widespread light ashfalls, but associated mudflows were smaller. Lava extrusion had resumed on 18 January and seismic evidence suggested that it was continuing on 21 January.

Aerosols from the explosive activity have not yet been widely reported, but lidar instruments in Germany detected new material near the tropopause and aerosol layers were evident at sunrise over Colorado (see Atmospheric Effects in 14:12).

Petrography of 15 December tephra.Thin sections of a pumiceous juvenile lapillus and a lithic fragment, erupted 15 December, were examined at Michigan Technological Univ 60% of the pumiceous sample was vesicular colorless glass with refractive index

Avalanche and lahar deposits emplaced 14-19 December. Reconnaissance fieldwork on the N flank 26 December revealed thick deposits from a slush avalanche that appeared to have been triggered by pyroclastic flows, perhaps on 15 December. Scouring had occurred across the entire glacier where it was confined by valley walls, but only on the E half of its unconfined 3-km-wide lower portion. Water that apparently originated near the cloud-covered summit was flowing into the Drift River from a narrow channel eroded in the glacier. The avalanche deposit was roughly 10 m thick at a sampling site about 1 km beyond the nose of the glacier, which extends roughly 8 km from the vent. The deposit was very massive, with no grading or vertical sorting evident, although contacts could be seen between individual flow units (3 of which were evident from the helicopter). Breadcrust blocks that reached a maximum of about 1/2 m in diameter (in a very limited sample) were supported by a matrix of sand-sized ash, snow grains, and liquid water. After emplacement, water had drained from the upper portion of the deposit, leaving noticeable air space between ice grains, and saturated the snowpack below the avalanche, which refroze into a zone of horizontally banded ice. A sample from near the base of the avalanche had a bulk density of 1.09 g/cm3, with proportions by volume of 20% rock, 72% ice, and 8% pore space. Bulk densities of 2 samples from the porous upper portion of the deposit were only 0.85 and 0.72 g/cm3; one of the samples had volume proportions of 9% rock, 71% ice, and 20% pore space. Densities of the pyroclastic rock clasts ranged from 1.1 to 1.4. The avalanche had apparently been slushy during emplacement. Measurements of runup onto an older avalanche fan at a site 3.7 km below the nose of the glacier suggested a velocity of roughly 17 m/s.

Subsequent floodwaters eroded the distal portion of the slush avalanche and carried numerous large ice blocks as far as the mouth of the Drift River, forming levees that helped to confine later flows. Some of the stranded ice blocks, which reached many meters in diameter, were clear glacial ice, others were eroded pieces of the slush avalanche. The flood rafted ice blocks to 8 m above the riverbed and 1.3 m up the 4-m L-shaped outer levee at the Drift River oil facility.

Airphotos taken 16 December showed small lahars with lobate snouts that extended several kilometers down the SW side of the volcano. Most of the lahar deposition occurred below a 1/2-km-wide zone of roughly parallel erosional grooves that extended down the upper flank glaciers from the low point of the crater's S rim. However, patchy deposition occurred up to the crater rim, and the grooves were streaked with dark mud.

Summit lava dome. About 21 December, a change in the character of local earthquakes and a slight increase in the number of small shocks suggested to geologists that magma might be approaching the surface. Poor weather continued to obscure the vent area, although a vapor plume that reached 7.5 km altitude and sulfur odor at about 3.5 km altitude were detected from aircraft on 22 December. Seismic activity declined slightly on 24 December, but numerous small earthquakes continued to occur near the summit.

An overflight 26 December revealed a large elongate lava dome that emerged from a vent at the N edge of the 1.5-km-wide U-shaped breached crater, filled much of its N portion, and extended partway down the N flank. Many hot rock avalanches cascaded down the dome's steep N side, generating small billowing ash clouds that rose 300-600 m above the dome. The volcano continued to produce a vigorous vapor plume, primarily from the S side of the dome. Summit glow was visible at night roughly 80 km E of the volcano (on a low-light video camera at Kasilof). A slight increase in small earthquakes and rock avalanches near the summit during the next few days suggested an increased rate of lava extrusion. Ground and aerial surveys on 29 December confirmed significant additional growth of the dome, which was estimated from the air at roughly several hundred meters wide and twice as long. A vigorous gas plume that contained little ash rose 3.5-4.5 km. The dome had grown further by 1 January, and AVO estimated its volume at roughly 20-25 x 106 m3.

Strong explosions and mudflow, 2-3 January. Shallow microearthquakes associated with the lava dome and deeper events centered 7-10 km below the volcano began a rapid increase after a magnitude 1.9 earthquake, the largest of the eruption thus far, at 1934 on 1 January. By the next afternoon, seismic energy release had built to about the same level as immediately before the start of the eruption on 14 December. At 1600 on 2 January, AVO issued a statement noting the potential for partial collapse of the dome's unstable N flank, deposition of hot tephra onto the glacier with resulting flooding in the Drift River valley, and moderate to strong explosive activity. The Drift River facility was promptly evacuated.

Less than 2 hours later, a vigorous explosion at 1748 had the strongest seismic signal of the December-January eruption. Airplane pilots reported that the tephra column reached 13.5 km altitude; they saw apparent lava fountaining in the summit area, and noted incandescent material moving down the N flank into the upper Drift River valley. Residents of the Kenai Peninsula, across Cook Inlet from Redoubt, reported spectacular lightning. Ash moved NE in light wind, and minor ashfalls occurred at Anchorage. Satellite images (figure 3) showed a plume extending NE about 20-30 km at 1800, growing steadily to 430 km long and 620 km wide 6 1/2 hours later. Cloud top temperatures as cold as -53°C were measured from satellite data, yielding altitude estimates of roughly 8-8.5 km. The FAA issued warnings to aircraft, and most airlines cancelled flights to and from Anchorage. Another large explosive episode was recorded at 1927, and tephra was reported to 12 km altitude. Smaller explosive episodes were recorded at about 0130 and 0245 on 3 January.

Figure (see Caption) Figure 3. Thermal infrared image from a NOAA polar orbiting satellite on 2 January at 1915, about 90 minutes after the onset of the explosive episode. Cloud top temperature suggests the plume is at about 8.5 km altitude. Courtesy of Michael Matson.

During an AVO overflight between 1230 and 1300 on 3 January, a turbulent steam plume with only minor ash rose through weather clouds to 4-4.5 km. Clouds obscured the summit area on 3 January, but overflights during better weather 2 days later showed that the dome had been removed along with a substantial part of the upper Drift Glacier. Seismic activity had declined to the lowest level since the eruption began and there was no seismic indication of renewed lava extrusion.

Pyroclastic flows during the 2 January activity generated a major mudflow that covered the entire active flood plain of the Drift River to the head of its delta, inundated the delta, and reached Cook Inlet, 32 km from the vent. An area of about 60 km2 was affected. Peak discharge at a site about 18 km from the vent was estimated to be roughly equal to that of Ruiz volcano's November 1985 Río Azufrado lahar. The pyroclastic flows incorporated large amounts of ice and snow, and were transforming into lahars by the time they reached 700 m altitude, near the nose of the glacier. The flow transported high-density, high-temperature dome rocks to the coast and carried ice blocks several meters in diameter that did not rise to the flow surface, indicating that it remained a fully developed debris flow. Boulders, more visible from the air at the lower end of the deposit, reached 4 m in diameter; many were still hot and generating small steam plumes on 3 January. Water pushed aside by the debris flow inundated the area N of the main Drift River delta, forming a large lake. Ice jams formed at the mouths of small streams in that area, temporarily damming them. Heavy deposition in its main channel diverted the Drift River into a stream with considerably less capacity (Rust Slough) S of the oil facility, protected on that side by neither dikes nor topography. Water and debris were then able to flow around the 4-m outer dike, crossed the facility's landing strip, damaged support structures, and shut off electricity, but did not overflow the 2.5-m inner dikes protecting individual oil tanks. The tanks were not damaged and no oil was spilled. Crews returned during daylight on 3 January to begin cleanup. The flooding at the Drift River facility forced the shutdown of 10 of the 12 Cook Inlet oil production platforms.

Explosions and debris flows, 8-16 January. Strong explosive activity resumed 8 January with vigorous episodes at 1012 and 1048 (figure 4). No seismic precursor was noted, although the nearest seismic station, on the N flank, had been damaged in the 2 January eruption. Within 30 minutes, plumes reached 12-13.5 km altitude. The FAA issued an advisory to aircraft, and some flights were cancelled. Ash fell on the flanks and on a broad sector to the E, beginning about noon at Kenai (80 km E of Redoubt). Only a dusting of ash fell on Kenai, but Kasilof, about 25 km to the S, received more than 0.5 cm and was in "total darkness" at 1230. More than 1 cm accumulated at Soldotna, between Kenai and Kasilof. By 1430, satellite images showed that the plume, about 100 km long and 125 km wide, had detached from the volcano and extended nearly to Anchorage. Overflights later that day revealed no major changes to the summit area. A plume that was mainly vapor rose to about 5 km altitude [see also research aircraft data in 15:1].

Figure (see Caption) Figure 4. Thermal infrared image from the NOAA 10 polar orbiting satellite on 8 January at 1026, about 15 minutes after the explosion began. The eruption cloud is rising to about 12-13.5 km altitude. Courtesy of Michael Matson.

The 8 January pyroclastic flows triggered a debris flow much smaller than that of 2 January, but with a peak discharge comparable to that of the 18 May 1980 mudflow from Mt. St. Helens in the N fork of the Toutle River. One or perhaps 2 pyroclastic flows continued in a relatively dry state to below 500 m altitude on the glacier. Debris flow material was initially concentrated in a deep gully on the E side of Drift Glacier, then spilled NE across the floor of the Drift River valley (figure 5 from 15:01). The flow bifurcated around a small hill on the valley floor; the S lobe stopped abruptly, but the larger N lobe continued downvalley, transforming into a hyperconcentrated flow within 15 km of the vent. It spilled through a breach in the moraine that enters the valley from the Drift River lobe of Double Glacier, and continued for another 5.5 km. Ultimately the flow became sediment-laden before stopping above the head of the Drift River fan. There was no noticeable impact on the channels downstream. After the 8 January activity, the main debris flow channel was stripped of ice down to about 1250 m altitude, and ice was only intermittently evident for the next couple of hundred meters.

Figure (see Caption) Figure 5. Generalized map of Redoubt, showing the 1989-90 vent area and locations of seismic stations monitored by the Alaska Volcano Observatory. Reprinted from Alaska Volcano Observatory Staff, 1990.

A small explosive episode lasting roughly 15 minutes was recorded seismically on 11 January at 1001. No clear seismic precursor was detected, and poor weather prevented observations of the plume. Another brief eruption was reported at 1342, and a pilot estimated that the steam and ash cloud reached 12-13.5 km altitude. Multi-layered weather clouds made plume identification difficult on satellite images.

A 20-minute explosive episode that began at 2248 on 16 January produced widespread ashfalls. Pilots reported ash to 9 km altitude and satellite data indicated that the plume reached 11.5 km. By 0015, ash was falling in Skwentna, 170 km NE of Redoubt, where more than 1/2 cm accumulated. Ash mixed with snow fell in Cantwell, 370 km NE of Redoubt, and began at Eilson Air Force Base (near Fairbanks, 550 km from the volcano) at 1111. Ash then continued E toward Canada.

Data from debris flow detection devices indicated that a water and debris flow occurred in the upper Drift River within about 20 minutes of the eruption's start. One device, placed on the 8 January debris flow deposit, was triggered but not destroyed, suggesting that the 16 January flow was smaller. Considerable snow had accumulated on the Drift River flood plain since 8 January, and the flow continued to accumulate water as it continued downstream. Although the flow volume was not large in comparison with earlier episodes, it was sufficient to cause some of the water in the Drift River to return to its old channel. Personnel at the Drift River oil facility reported that no flooding occurred there.

Renewed lava extrusion, 18 January. Aerial observations on 18 January between 1330 and 1500 revealed that a small lava dome was again growing in the vent [see also 15:1]. A vigorous steam plume rose to about 5 km altitude. Seismicity the next day suggested that lava continued to be added to the new dome. Small seismic events on 19 January at 0522 and 0655, each lasting 15-20 minutes suggested vigorous venting that may have included some ash emission, but the activity was not witnessed.

Drift River oil facility. Concern about the potential for a major oil spill prompted the removal of most of the more than 900,000 barrels of oil that were stored in the Drift River facility's 7 tanks at the start of the eruption. Oil is transported by pipeline to the Drift River facility from 2 small coastal storage facilities (not accessible to tankers) that serve production platforms in Cook Inlet. Drainage of the Drift River tanks began about 10 January, and was expected to be completed about 20 January with the removal of a third tankerload of oil. To avoid prolonged shutdown of Cook Inlet oil production, officials tentatively planned to leave the Drift River facility empty until a tanker is ready to load, quickly fill the Drift River tanks from the small coastal holding facilities, then immediately pump the oil into the waiting tanker.

Reference. Riehle, J.R., 1985, A reconnaissance of the major Holocene tephra deposits in the Upper Cook Inlet region, Alaska: JVGR, v. 26, p. 37-74.

Geologic Background. Redoubt is a 3108-m-high glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. The volcano was constructed beginning about 890,000 years ago over Mesozoic granitic rocks of the Alaska-Aleutian Range batholith. Collapse of the summit of Redoubt 10,500-13,000 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.

Information Contacts: AVO Staff; R. Janda and T. Pierson, USGS CVO; SAB; M. Matson, NOAA/NESDIS; W.I. Rose and J. Vallance, Michigan Technological Univ; C. Newhall, USGS, Reston; N. Krull, FAA; AP; UPI; Reuters.


Nevado del Ruiz (Colombia) — December 1989 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Small ash ejections; seismicity remains stable

Seismicity dropped in late September, reaching the lowest level since early 1988 in October, and remained at low to moderate levels in November. Seismic activity remained relatively stable in December, with no significant changes in the daily number of high- or low-frequency earthquakes. The energy release of low-frequency events increased slightly toward the end of the month, while the energy released by high-frequency events decreased slightly. High-frequency events were centered in three zones; N of, beneath, and scattered around Arenas Crater at 1-6 km depth. Swarms of these events occurred on the 16th and 18th. Short pulses of low-energy tremor were associated with small ash emissions, one of which deposited a thin layer of ash over Manizales (30 km from Arenas crater) on the 27th. Dry and electronic tilt and short leveling vectors showed no significant variations. SO2 emissions measured by COSPEC were moderate, averaging 1,800 t/d.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


Sorikmarapi (Indonesia) — December 1989

Sorikmarapi

Indonesia

0.686°N, 99.539°E; summit elev. 2145 m

All times are local (unless otherwise noted)


Phreatic explosion ejects mud

[A single phreatic explosion rose 25 m above the Sibangor Tonga crater, spreading mud in a 5-m radius.]

Geologic Background. Sorikmarapi is a forested stratovolcano with a 600-m-wide summit crater containing a lake and substantial sulfur deposits. A smaller parasitic crater (Danau Merah) on the upper SE flank also contains a crater lake; these two craters and a series of smaller explosion pits occur along a NW-SE line. Several solfatara fields are located on the E flank. Phreatic eruptions have occurred from summit and flank vents during the 19th and 20th centuries.

Information Contacts: VSI.


St. Helens (United States) — December 1989 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


Small ash emission; ashfalls to 80 km distance

A brief explosive episode at 0537 on 6 January ejected ballistic tephra and a small amount of ash, and triggered rock avalanches. Strong winds carried the ash E, forming a very thin deposit along a narrow discontinuous band that extended 130 km (to the Toppenish area).

The 6 January vent was located at the apex of an arcuate fracture that climbs the dome's N flank to the vent position ~100 m above the crater floor, roughly one third of the way up the dome. The segment N of the fracture moved nearly 2 m outward and downward during the eruption. The ends of the fracture were ~400 m apart. The explosion had a northerly component, sending large ballistic tephra to the N base of the dome, where the Garden Rock seismometer was damaged. South of the vent, there were no new ballistics and only about a centimeter of fine ash had been deposited nearby. Deposition W of the dome was limited to ~1 mm of mud, and only dirty snow was found E of the dome. Rock-and-snow avalanches had originated from the fracture, leaving a scallop-shaped scar on the dome's N flank and forming two separate lobes at the base of the dome. One lobe was composed of dirty snow overlain by granular lithics. To its E, the larger avalanche lobe appeared to extend no more than 200 m from the base of the dome and contained mostly coarse rockfall material with a little snow. Some of its boulders had rolled in snow. Its maximum thickness was ~50 cm at a site roughly 100 m N of the base of the dome. The largest rock fragments beyond the base of the dome were ~30-40 cm in diameter, but 1-m boulders could be seen in the talus chute on the dome. Large ice crystals in the snow suggested that the avalanches had been warm at the time of emplacement, then had refrozen.

The 6 January tephra was dominated by lithic fragments from the dome, but dark, glassy, vesicular, dacitic material of unknown origin was also found in the ejecta. Although its mineralogy was the same as that of previous dome samples, proportions of mineral components were different, and its glass was pale brown in contrast to the clear glass that has characterized previously extruded dome rocks. The new material resembled hornblende-bearing andesites erupted by Mt. St. Helens between AD 1500 and 1800, but appeared very fresh and showed no signs of hydrothermal alteration.

Seismicity associated with the 6 January episode appeared suddenly, and saturated the station (YEL) ~1 km N of the dome for ~9 minutes (compared to 2 minutes for the [6] December seismicity). The signal was characterized by numerous minor shallow earthquakes and volcanic tremor, lasting a little more than 2.5 hours, with alternating periods of intense and low-level activity. Average tremor amplitudes were similar for the first 20 minutes of the [6] December and 6 January episodes, but the later [6] December tremor was stronger and continued for ~5 hours. Some rockfall signals occurred after both episodes. Seismicity following the 6 January episode was dominated by discrete earthquakes, with about a dozen recorded in the next few hours. After continuous tremor ended on 7 December, at least nine high-frequency, tremor-like, signals (cigar-shaped on the seismogram) lasting 2-20 minutes were recorded, accompanied by only two tiny earthquakes. Two of the cigar-shaped signals, each lasting ~2 minutes, were detected in the hours following the 6 January episode. Similar signals have been recorded during eruptions of Old Faithful Geyser at Yellowstone (Kieffer, 1984), and were thought to represent hydrothermal venting or near-surface movement of fluids at Ruiz volcano.

No pre-eruption deformation was detected, and the first sign of the activity on the tiltmeter nearest the vent was the loss of its signal. A second instrument showed a deflection of ~20 µrads during the eruptive episode. Outward movement of the dome's N flank apparently occurred during the eruption, with a maximum measured value of 1.8 m. No deformation was detected on the outer flanks of the edifice.

Reference: Kieffer, S.W., 1984, Seismicity at Old Faithful Geyser: An Isolated Source of Geothermal Noise and Possible Analogue to Volcanic Seismicity; Journal of Volcanology and Geothermal Research, v. 22, p. 59-86.

Geologic Background. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older St. Helens edifice, but few lava flows extended beyond the base of the volcano. The modern edifice was constructed during the last 2200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.

Information Contacts: D. Swanson and D. Dzurisin, CVO; C. Jonientz-Trisler, University of Washington.


Supply Reef (United States) — December 1989 Citation iconCite this Report

Supply Reef

United States

20.13°N, 145.1°E; summit elev. -8 m

All times are local (unless otherwise noted)


Renewed activity at September site

An ocean bottom seismometer off the Boso Peninsula, Japan, and hydrophones on Wake Island detected renewed episodes of apparent submarine volcanism on 22-24 and 26-27 December. Arrival directions and times were very similar to those from the 21-22 September activity, and probably originated from the same area.

Seismicity began to be recorded by the Boso Peninsula instrument on 22 December at about 0630, and events soon became frequent, although intervals between events were slightly longer than in September. Seismicity had nearly ended shortly before 0200 on 24 December, although one additional shock was recorded at 0245. T-phase signals resumed on 26 December at about 1600 and continued until about 2300 the next day, but occurred at significantly longer intervals than the two earlier episodes.

Using more precise sound velocities, Univ of Hawaii geophysicists refined the locations of the 21-22 September events to about 20.3°N, 144.9°E, roughly 30 km S of . . . Farallon de Pajaros (Uracas). The potential location error remains large, but is oriented along a NE-SW line oblique to the volcanic chain. The 21-22 September locations are very close to the site of the most recent documented activity near Farallon de Pajaros, a 3-km zone of discolored water that was observed in September 1985 near the 1969 eruption site.

Geologic Background. Supply Reef is a conical submarine volcano in the northern Mariana Islands that rises to within 8 m of the surface. The andesitic seamount lies about 10 km NW of the Maug Islands, the emergent summit of a submarine volcano that is joined to Supply Reef by a low saddle at a depth of about 1800 m. Supply Reef was mapped as Quaternary; living corals on the crater rim suggest that it is either dormant or extinct (Corwin, 1971). Several submarine eruptions have been detected by sonar signals originating from points very approximately located at distances of 15-25 km NW.

Information Contacts: Y. Sawada, JMA; C. McCreery and D. Walker, Univ of Hawaii.


Ulawun (Papua New Guinea) — December 1989 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Gas emissions and seismicity remain at background

"Activity continued at background level in December. White vapours were released in weak to moderate volume by the summit crater. Seismicity remained at background level, with only a few events/day of very small amplitude and occasional larger B-type shocks."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: P. de Saint-Ours, RVO.


White Island (New Zealand) — December 1989 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)


Mild explosions; new crater enlarged

Only mild eruptive activity has occurred since 11 October fieldwork revealed a possible new vent in Congress Crater. During a 4 November overflight, pilot R. Fleming witnessed ejection of tephra above 1978 Crater rim, and Bruce Christenson observed new blocks there on 9 November. No new tephra were found on the main crater floor during 12 and 18 November visits, but the new vent, named Corporate Crater, was clearly visible for the first time.

During 29 November fieldwork, geologists observed small amounts of new ash on the main crater floor, and 35 mm of new fine ash on 1978 Crater rim. Ash-covered lithic blocks (up to 0.2 m) had been ejected to 50 m from the E crater rim. Block distribution indicated a source in Corporate Crater (figure 12), now a deep vertical-walled pit that has grown to occupy the E half of Congress Crater. The remnant of Congress Crater's flat floor had been built up by ejecta and talus that infilled previously active Hitchhiker Vent. Scoriaceous bombs were found in the S part of the clast field, suggesting a source from R.F. Crater, which appeared unchanged since 11 October.

Figure (see Caption) Figure 12. Sketch map showing recently active features at White Island, late 1989. Courtesy NZGS.

Most gas emissions originated from R.F. Crater, with a small amount of steam rising from Corporate Crater. Donald Duck vent emitted voluminous white clouds from active crater floor vents that had migrated NW. Noisy Nellie vent discharged a large volume of high-pressure clear gas.

Medium-frequency (3-4 Hz) volcanic tremor and rare small A-type events were recorded 11-14 October. Small A-types were the only clear events recorded 14 October- 21 November. Since 21 November, fewer than 5 small A- and/or B-type events/day have been recorded.

The 29 November deformation survey showed minor but uniform uplift of most of the main crater, reversing the strong subsidence (centered over Donald Mound) in the 10 weeks prior to 11 October. The inflation was interpreted as evidence of renewed heating at depth beneath Donald Mound, possibly the precursor of future increased activity from 1978 Crater. Magnetic data generally showed only small changes, suggesting modest shallow cooling that may have been associated with heavy recent rainfall.

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: I. Nairn, NZGS Rotorua.

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.

View Atmospheric Effects Reports

Special Announcements

Special announcements of various kinds and obituaries.

View Special Announcements Reports

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 (SEAN 22:08) False Report of Mount Pinokis Eruption

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (SEAN 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/).