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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

Fuego (Guatemala) Ongoing ash plume explosions and block avalanches, April-September 2019

Erta Ale (Ethiopia) Continued summit activity and lava flow outbreaks during April-October 2019

Karymsky (Russia) Moderate explosive activity with ash plumes through 24 September 2019

Shishaldin (United States) Active lava lake and spattering on 23 July 2019; minor explosions and lava fountaining on 17 August

Klyuchevskoy (Russia) Ongoing weak thermal anomalies during July-September 2019, but no ash plumes after 1 August

Heard (Australia) Ongoing thermal anomalies at the summit crater during April-September 2019

Dukono (Indonesia) Eruption with frequent ash plumes continues through September 2019

Poas (Costa Rica) Occasional phreatic explosions continue through September 2019

Etna (Italy) Five lava flows and numerous ash plumes and Strombolian explosions, April-September 2019

Ubinas (Peru) Intermittent ash explosions in June-August 2019

Santa Maria (Guatemala) Persistent explosions with local ashfall, March-August 2019; frequent lahars during June; increased explosions in early July

Stromboli (Italy) Major explosions on 3 July and 28 August 2019; hiker killed by ejecta



Fuego (Guatemala) — September 2019 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Ongoing ash plume explosions and block avalanches, April-September 2019

Guatemala's Volcán de Fuego was continuously active through September 2019; it has been erupting vigorously since 2002 with historical observations of eruptions dating back to 1531. These eruptions have resulted in major ashfalls, pyroclastic flows, lava flows, and damaging lahars. Large explosions with hundreds of fatalities occurred during 3-5 June 2018; after a brief pause, significant activity resumed and continued during April-September 2019, the period covered in this report. Reports are provided by the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH) and the National Office of Disaster Management (CONRED); aviation alerts of ash plumes are issued by the Washington Volcanic Ash Advisory Center (VAAC). Satellite data from NASA and other sources provide valuable information about heat flow and gas emissions.

Daily activity continued at a high level throughout April-September 2019 (table 19) with multiple ash explosions every hour, incandescent ejecta reaching hundreds of meters above the summit sending block avalanches down multiple ravines, and ash falling on communities on the SW flank and beyond. During April and part of May a lava flow was also active in the Seca ravine. Although explosive activity remained at a high level throughout the period, thermal activity began a decline in May that continued through September, noticeable in both the MIROVA radiative power data (figure 117), and monthly images of MODVOLC thermal alerts (figure 118).

Table 19. Activity summary by month for Fuego with information compiled from INSIVUMEH daily reports.

Month Fumarole Color, Height (m), Direction Ash Explosions per hour Ash Plume Heights (km) Ash Plume Distance (km) and Direction Incandescent Ejecta Height (m) Ravines affected by avalanche blocks Sounds and Vibrations Villages Reporting ashfall Lava Flow activity
Apr 2019 Gray and White, 4,100-4,500, W-SW 10-25 4.3-5.0 10-25, W-SW-E-N 100-450 Seca, Taniluyá, Ceniza, Trinidad, Las Lajas and Honda Weak to moderate rumbles, shock waves rattled roofs, train engine noises every 5-20 minutes Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Los Yucales, Finca Palo Verde, Sangre de Cristo, San Pedro Yepocapa, La Rochela, Ceilán, El Rodeo, Alotenango, Ciudad Vieja, Osuna Active flow in Seca ravine, 200-800 m long
May 2019 Gray and White, 4,200-4,500, W-SW-S 12-26 4.5-4.9 10-30, W-SW-S-SE 200-450 Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas and Honda Weak to moderate rumbles, shock waves rattled roofs, train engine noises at regular intervals Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Los Yucales, Finca Palo Verde, Sangre de Cristo, San Pedro Yepocapa, Ceilán, La Rochela Active flow in Seca ravine, 300-1,000 m
Jun 2019 White, 4,100-4,500, E-SE-N-W-SW 10-24 4.4-4.8 10-30, W-SW-NW-N-E-SE 200-450 Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas and Honda Weak to moderate rumbles, shock waves rattled roofs, train engine noises every 5-10 minutes Sangre de Cristo, Yepocapa, Morelia, Santa Sofía, Panimache I and II, El Porvenir, Finca Palo Verde, La Rochela, Ceilán, Alotenango, San Miguel Dueñas --
Jul 2019 White, 4,100-4,500, W-SW 8-25 4.3-4.8 10-25, W-SW 150-450 Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas and Honda Weak to moderate rumbles, shock waves rattled roofs, train engine noises every 5-15 minutes Morelia, Santa Sofía, El Porvenir, Finca Palo Verde, San Pedro Yepocapa, Panimaché I y II, Sangre de Cristo, La Rochela, Ceilán --
Aug 2019 White, 4,100-4,500, W-SW 10-23 4.4-4.8 10-25 W-SW 200-400 Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas y Honda Weak to moderate rumbles, shock waves rattle windows; train engine noises every 3-13 minutes Morelia, Santa Sofía, El Porvenir, Finca Palo Verde, San Pedro Yepocapa, Panimaché I y II, Sangre de Cristo, and others Flow in Seca ravine, 13 Aug 75-100 m
Sep 2019 White, 4,100-4,400, W-SW 5-22 4.4-4.8 10-20 W-SW 200-400 Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas and Honda Weak to moderate rumbles, shock waves rattled roofs, train engine noises every 3-10 minutes Panimaché I, Panimache II villages,Morelia, Santa Sofía, Palo Verde estate, San Pedro Yepocapa, Sangre de Cristo, El Porvenir, La Rochela villages and Ceylon --
Figure (see Caption) Figure 117. Thermal activity at Fuego increased steadily from January through April 2019, and then began a gradual decline through September as seen in this MIROVA graph of Radiative Power. The active lava flow in the Seca Ravine in April and early May likely contributed to the higher heat values during that time. Courtesy of MIROVA.
Figure (see Caption) Figure 118. A steady decline in thermal activity at Fuego is apparent in the MODVOLC thermal alert images for April-September 2019. During April and early May a lava flow was active in the Seca ravine that extended as far as 1,000 m from the summit. Courtesy of MODVOLC.

Activity increased at the very end of March 2019. The rate of explosions increased to 14-32 events per hour by 31 March; ash plumes rose to 5 km altitude and resulted in ashfall in numerous nearby communities. An early morning lava flow that day reached 800 m down the Seca ravine. Continuous white and gray fumarolic plumes reached 4.1 to 4.4 km altitude during April 2019 and drifted generally W and SW. There were about 15-20 ash-bearing explosions per hour; the highest rate of 25 per hour occurred on 10 April. Plume altitudes were below 4.8 km for most of the month; on 28 and 29 April they rose to 5.0 and 4.9 km. For most of the month they drifted W and SW; the wind direction changed to the E during 10-16 April. Most days of the month ashfall was reported in the communities of Panimaché I y II, Morelia, Santa Sofía, Finca Palo Verde, San Pedro Yepocapa, Sangre de Cristo and El Porvenir on the W and SW flank. During 10-13 April when the wind direction changed to easterly, communities to the NE, E and SE of Alotenango, Ciudad Vieja, La Reunión, La Rochela, El Rodeo, Osuna, Ceilán and others on the N and E flanks were affected by ashfall. The Washington VAAC issued multiple daily advisories on 18 days in April, identifying short-lived ash plumes drifting with the prevailing winds.

Incandescent ejecta rose 200-300 m above the summit on most days (figure 119). During 23-25 April, ejecta rose 300-450 m above the summit. Six ravines were affected by the incandescent avalanche blocks nearly every day: the Seca, Taniluyá, Ceniza, Trinidad, Las Lajas, and Honda. The explosions caused rumbles, shock waves that rattled roofs, and sounds similar to a train locomotive at intervals of 5-20 minutes in nearby communities throughout the month. A lava flow was present in the Seca (Santa Teresa) ravine for most of the month; its length varied from 200 to 800 m. Special reports of lahars were issued seven times during April. On 4 April a moderate lahar descended the Seca ravine carrying centimeter- to meter-sized blocks, tree trunks and branches. During 9-11 April nine lahars were recorded in the Las Lajas, El Jute, Seca, Rio Mineral, Taniluya, and Ceniza ravines. The largest flows were 20 m wide and 3 m deep carrying blocks and debris up to 3 m in diameter; they were warm and thick with a strong sulfurous odor. Two more lahars were reported on 18 April in the Taniluya and Ceniza ravines carrying 1-2 m sized blocks in a warm, sulfurous flow.

Figure (see Caption) Figure 119. Incandescent ejecta rose several hundred meters above the summit of Fuego on 30 April 2019 and sent large blocks down multiple ravines, typical activity for the entire month. Courtesy of CONRED (Boletín Informativo No. 1242019, martes, 30 de abril 2019, VOLCÁN DE FUEGO BAJO CONSTANTE MONITOREO).

During May 2019, primarily white fumaroles rose to 4.2-4.5 km altitude and drifted W, SW, and S; gray fumaroles were reported only during the first few days of the month. Generally, 15-20 ash explosions per hour occurred; the maximum was 26 on 17 May. Ash plume heights ranged from 4.5-4.8 km altitude nearly every day, drifting 10-25 km primarily W, SW, and S throughout the month, except for 6-8 May when plumes drifted NW and 18-19 May when wind directions changed and sent ash S and SE. Plumes drifted 25-30 km SE, S, and SW on 19 May. Ashfall was reported daily from communities on the W flank including Panimaché I and II, Morelia, Santa Sofía, El Porvenir, Los Yucales, Finca Palo Verde, Sangre de Cristo, and San Pedro Yepocapa, among others, and also from the E side including Ceilán and La Rochela when the wind direction changed. The Washington VAAC issued multiple daily ash advisories on 19 days during May.

Incandescent Strombolian activity continued sending ejecta 200-300 m above the summit during the first half of the month and 300-450 m high during the latter half (figure 120). Seven major ravines, the Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas, and Honda were affected by block avalanches throughout the month. Intermittent explosions caused rumbles, shock waves that rattled roofs, and sounds similar to a train locomotive at frequent intervals on most days. The lava flow in the Seca ravine advanced from 300 m length on 2 May to 1,000 m long on 9 May. It was reported as being 500 m long on 18 May but was not active after that date. Numerous lahars descended multiple ravines in May. INSIVUMEH issued nine special reports of lahar activity on 3, 14, 16, 20, 23, and 27-29 May. They affected the Las Lajas, Ceniza, El Jute, El Mineral, and Seca ravines. The thick, pasty flows contained blocks of various sizes up to 3 m in diameter along with tree trunks and branches. Several were warm with a sulfurous smell (figure 121). SO2 emissions remained low throughout April-September with only minor emissions recorded in satellite data on 1 April and 9 May 2019 (figure 122).

Figure (see Caption) Figure 120. Incandescent ejecta at Fuego was captured on 27 May 2019 under a starry night sky by photographer Diego Rizzo in a 25-second exposure. Block avalanches are seen descending several ravines. NASA used the photo as an Astronomy Photo of the day and noted that the central plane of the Milky Way galaxy runs diagonally from the upper left, with a fleeting meteor just below, and the trail of a satellite to the upper right. The planet Jupiter also appears toward the upper left, with the bright star Antares just to its right. Much of the land and the sky were captured together in a single 25-second exposure taken in mid-April from the side of Acatenango volcano; the meteor was captured in a similar frame taken about 30 minutes earlier and added to this image digitally. Courtesy of NASA Astronomy Picture of the Day, copyright by Diego Rizzo.
Figure (see Caption) Figure 121. Lahars were reported at Fuego nine separate times during May 2019. A steaming lahar descends a ravine at Fuego on 11 May 2019 (top). The Santa Teresa Canyon was clogged with debris from numerous past lahars on 22 May 2019. INSIVUMEH monitors the ravines continuously during the rainy season. Courtesy of CONRED (Boletín Informativo No. 1382019, sábado, 11 de mayo 2019, LLUVIAS GENERAN DESCENSO DE LAHARES EN EL VOLCÁN DE FUEGO and Boletín Informativo No. 1562019, miércoles, 22 de mayo 2019, SE REGISTRA DESCENSO DE LAHARES MODERADOS EN EL VOLCÁN DE FUEGO).
Figure (see Caption) Figure 122. Weak SO2 emissions were recorded from Fuego on 1 April and 9 May 2019 by the TROPOMI instrument on the Sentinel 5P satellite. Courtesy of NASA Goddard Space Flight Center.

The fumarolic plumes were only white during June 2019, rising to 4.1-4.5 km altitude daily, drifting W or SW except during the first days of the month when variable winds sent the steam N, E, and SE. Explosions with ash took place 15-20 times per hour on most days with plumes rising to 4.5-4.8 km altitude and drifting primarily W or SW except for the first days of the month (figure 123). On most days, ash plumes drifted 15-20 km W and SW, except during 2-7 June when winds sent ash E, SE, N, and NW. Ashfall was reported virtually every day in Sangre de Cristo, Yepocapa, Morelia, Santa Sofía, and Panimache I and II. In addition, the communities of El Porvenir, Los Yucales, and Finca Palo Verde reported ashfall several days each week. During 2, 4, and 7 June, the N and SE winds caused ash to fall in Alotenango and San Miguel Dueñas. The Washington VAAC issued ash advisories on 15 days during June.

Figure (see Caption) Figure 123. Emissions of both steam and ash rose from Fuego on 11 June 2019. Courtesy of Paul A. Wallace, University of Liverpool.

The height of the Strombolian ejecta varied from 200-300 m above the summit on many days in June , but also was sometimes stronger, rising 300-450 m. While block avalanches were reported in all seven barrancas (ravines) more than once (Seca, Taniluyá, Ceniza, Trinidad, El Jute, Las Lajas and Honda), on all days they were reported in the Seca, Taniluya, Ceniza, and Trinidad. Weak to moderate rumbles and shock waves rattled roofs every day, and train engine noises were heard every 5-10 minutes. Seven special reports of lahars were issued on days 2, 11, 21-23, and 30. They affected the Las Lajas, El Jute, Seca, El Mineral, and Ceniza ravines with thick, pasty flows containing blocks 1-3 m in size, shaking the ground as they flowed downstream.

During July 2019, white steam plumes rose daily from the summit of Fuego to an altitude of 4.1-4.3 km and drifted W and SW; higher plumes on 30 and 31 July rose to 4.5 km altitude. Fifteen to twenty ash explosions per hour were typical throughout the month and produced ash plumes that rose to 4.3-4.8 km altitude and drifted SW and W for 10-25 km before dissipating (figure 124). Near-daily ashfall was reported in Morelia, Santa Sofía, El Porvenir, Finca Palo Verde, San Pedro Yepocapa, Panimaché I y II, and Sangre de Cristo; La Rochela and Ceilán also reported ash on 4 and 6 July. Incandescent ejecta height varied from 150-450 m above the summit from day to day, sending block avalanches down all seven ravines on many days. Weak to moderate rumbles and shock waves rattled roofs every day, and train engine noises were heard every 5-15 minutes. On 19 July noises and vibrations were heard and felt 25 km away. Only one lahar was reported on 12 July in the Las Lajas ravine. It was warm, with a sulfurous odor, and carried volcanic ash, sand, and blocks 1-3 m in diameter that shook the ground as they flowed downstream. The Washington VAAC issued ash advisories on 13 days during July.

Figure (see Caption) Figure 124. Steam-and-ash plumes rose from Fuego on 12 July 2019 in this image taken at dawn from Villa Flores San Miguel Petapa. Courtesy of Alex Cruz (cropped and color adjusted from original).

White steam plumes continued during August 2019, rising to an altitude of 4.1-4.5 km and drifting W and SW daily. Ash-bearing explosions continued also at a rate of about 15-20 per hour throughout the month, rising most days to between 4.5 and 4.7 km altitude. They drifted 15-20 km W or SW nearly every day before dissipating. Every day during the month, ashfall was reported in Morelia, Santa Sofía, El Porvenir, Finca Palo Verde, San Pedro Yepocapa, Panimaché I y II, Sangre de Cristo, and other communities on the SW flank. The Washington VAAC reported ash plumes at Fuego on 15 days during August (figure 125).

Figure (see Caption) Figure 125. An ash emission at Fuego was recorded on 22 August 2019. Courtesy of William Chigna.

Incandescent ejecta also rose every day during August 2019 to 200-300 m above the summit, a few days were reported to 350-400 m. Every day, block avalanches descended the Seca, Taniluyá, Ceniza, and Trinidad ravines; most days blocks also traveled down the Las Lajas and Honda ravines, and many days they were also reported in the El Jute ravine (figure 126). Every 5-10 minutes, every day, weak and moderate rumbles sounding like a train engine shook buildings and rattled roofs in the nearby villages. On 13 August a small lava flow, 75-100 m long, was reported in the Seca ravine. Six lahars were reported on 3 August. They occurred in the Santa Teresa, Mineral, Ceniza, El Jute, and Las Lajas ravines. The thick pasty flows carried blocks 1-2 m in diameter, tree trunks and branches, and disrupted the roads between Siquinala and San Andres Osuna and El rodeo and El Zapote. The next day two more occurred in the Seca and Mineral drainages. From 17-20 August, six more lahars occurred, most in the Las Lajas drainage, but also in the Seca, Mineral and Ceniza ravines.

Figure (see Caption) Figure 126. Incandescent blocks traveled down several ravines at Fuego on 2 August 2019. Courtesy of Publinews Guatamala.

There were no changes in the steam fumaroles during September 2019; plumes seldom rose over 4.3 km altitude and continued drifting W and SW. The ash explosion rate decreased somewhat and rates of 5-10 per hour were typical on many days. Ash plume heights remained constant around 4.5-4.7 km altitude most days, also drifting W and SW 15-20 km before dissipating (figure 127). While ashfall was reported daily in Panimaché I, Morelia, Santa Sofía, Porvenir, Palo Verde, Yepocapa and other communities on the SW flank for the first half of the month, it grew more intermittent during the second half of September. South-directed winds deposited ash on La Rochela villages and Ceylon on 25 September. The Washington VAAC issued aviation ash advisories on 11 days during the month. Strombolian ejecta mostly rose 200-300 m above the summit; occasionally it reached 300-400 m. On most days, block avalanches descended the Seca, Taniluyá, Ceniza, Trinidad, and Las Lajas ravines; occasionally they were reported in the El Jute and Honda ravines as well. Every day, rumbles and shock waves shook roofs in nearby villages every 5-10 minutes. Lahars were reported twice, on 2 ad 9 September, in the Seca and Rio Mineral drainages both days, dragging branches, tree trunks and blocks up to 2 m in diameter.

Figure (see Caption) Figure 127. An ash plume drifts from the summit of Fuego on 16 September 2019, seen from the La Reunion webcam. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán de Fuego (1402-09), Semana del 14 al 20 de septiembre de 2,019).

Geologic Background. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); 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); NASA Astronomy Picture of the day (URL: https://apod.nasa.gov/apod/ap190527.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/); Paul A. Wallace, Lecturer in Geology, University of Liverpool, Liverpool England (URL: https://www.liverpool.ac.uk/environmental-sciences/staff/paul-wallace/, Twitter: @Paul_A_Wallace, URL: https://twitter.com/Paul_A_Wallace/status/1138527752963993600); Alex Cruz, Photojournalist, Guatemala (Twitter: @ACruz_elP, URL: https://twitter.com/ACruz_elP/status/1149690904023691264/photo/1); William Chigna, Guatemala (Twitter: @William_Chigna, URL: https://twitter.com/William_Chigna/status/1164575009966370816); Publinews Guatemala, (Twitter: @PublinewsGT, URL: https://twitter.com/PublinewsGT/status/1157288917365903360).


Erta Ale (Ethiopia) — November 2019 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Continued summit activity and lava flow outbreaks during April-October 2019

Erta Ale, located in Ethiopia, contains multiple active pit craters both within the summit and the southeast calderas. On 17 January 2017 the active lava lake displayed intense spattering, fountaining, and rim overflows with lava flows that traveled as far as 1 km, forming a lava flow field. During April 2018 through March 2019 minor activity continued in both the summit and southeast calderas, and along the active lava flow to the E (BGVN 44:04). This report updates volcanism from April through October 2019. Information primarily comes from infrared satellite images and MODIS data.

Continued lava flow breakouts occurred from April through October 2019. On 4 May 2019 a lava flow outbreak was observed in satellite imagery NE of the summit caldera (figure 92). This outbreak continued to appear in clear-weather thermal satellite images through 13 June when it was seen south of its original location (figure 93). Faint incandescence is observed at the summit caldera between June and October 2019, though it is more pronounced in the months of August through October. On 28 June a second smaller lava flow outbreak occurred within 3.8 km of the summit location. The two lava flow outbreaks remained active at least through 18 June. The distal NE lava flow does not appear in very similar images from 17 August or 16 September 2019, but three proximal thermal anomalies are seen in the southeastern caldera within 4 km of the summit. The thermal anomalies remained within 5 km through October 2019.

Figure (see Caption) Figure 92. Sentinel-2 thermal satellite imagery of Erta Ale volcanism on 4 May 2019 with thermal anomalies observed to the northeast of the summit caldera (bright orange). White plumes are seen rising from the summit with faint incandescence. Sentinel-2 satellite images with "False Color (Urban)" (bands 12, 11, 4) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 93. Sentinel-2 thermal satellite imagery of Erta Ale volcanism between 8 June and 21 October 2019. Lava flow outbreaks initially occur in the distal NE part of the lava flow, which then migrates slightly south. A second lava flow outbreak is seen less than 5 km of the summit caldera. Faint incandescence is seen at the summit caldera in each of these images. Sentinel-2 satellite images with "False Color (Urban)" (bands 12, 11, 4) rendering; courtesy of Sentinel Hub Playground.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed consistently high-power thermal anomalies during this reporting period (figure 94). Through July 2019 these thermal anomalies were detected at distances greater than 5 km from the summit. In early August 2019 there was an abrupt decrease in the distance that continued through late October 2019 (figure 94); this likely indicates when the distal NE outbreak ended and lava emissions from the closer SE locations increased (see satellite images in figure 93). The distance changes of MODIS thermal anomalies from the summit seen in MIROVA are corroborated by MODVOLC data, which show no distal NE thermal alert pixels after July 2019 (figure 95).

Figure (see Caption) Figure 94. Two time-series plots of thermal anomalies from Erta Ale for the year ending on 24 October 2019 as recorded by the MIROVA system. The top plot (A) shows that the thermal anomalies were consistently strong (measured in log radiative power) and occurred frequently. The lower plot (B) shows these anomalies as function of distance from the summit, including a sudden decrease in the distance (measured in kilometers) in early August 2019 that reflects a change in lava flow outbreak location. Courtesy of MIROVA.
Figure (see Caption) Figure 95. Locations of the thermal alerts at Erta Ale during November 2018-July 2019 (top) and August-October 2019 (bottom) identified by the MODVOLC system. A majority of the proximal (less than 5 km from the summit) thermal anomalies are found within the southeastern calderas while the distal (beyond 5 km) anomalies are northeast of the summit. Note that the distal NE anomalies are not present after July 2019. Two thermal alerts mark the location of the summit caldera (bottom map). Data courtesy of HIGP-MODVOLC Thermal Alerts System.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: 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/); 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/).


Karymsky (Russia) — November 2019 Citation iconCite this Report

Karymsky

Russia

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

All times are local (unless otherwise noted)


Moderate explosive activity with ash plumes through 24 September 2019

Eruptive activity at Karymsky has been frequent since 1996, with moderate ash explosions, gas-and-steam emissions, and thermal anomalies. The latest eruptive period began in mid-February 2019 (BGVN 44:05) when explosions resumed after more than four months of quiet, producing an ash plume that extended 55 km downwind. Intermittent explosive activity continued until 24 September 2019. The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT).

Ash plumes were reported during the second half of February and the first half of March 2019 (BGVN 44:05). During May-September 2019 similar activity continued, with ash plumes being generated at least every few days (table 12). Though not included in the weekly KVERT report as notable events, obvious ash plumes were also seen in Sentinel-2 imagery on 22 July and photographed from an aircraft on 23 July. Volcanologists doing fieldwork on 14 August observed an ash plume rising to 5 km altitude (figure 44). A week later, during 20-22 August, explosions generated ash plumes as high as 6 km altitude that were visible in satellite imagery (figure 45). Although not noted in KVERT reports, a photo from 9 September showed a plume blowing downwind directly from the summit crater (figure 46). No significant ash plumes were reported by KVERT after 24 August, but the last ash explosion was recorded on 24 September.

Table 12. Notable ash plumes reported from Karymsky during May-October 2019. All dates are in UTC. Courtesy of KVERT.

Date Observations
06-07 May 2019 Gas-and-steam plume containing ash rose to 2-2.2 km in altitude and drifted 105 km SE and SW.
21 May 2019 Ash plume drifted 9 km SW.
24 May 2019 Ash plume identified in satellite images drifted 45 km NE.
13-17 Jul 2019 Ash plumes drifted 60 km in multiple directions.
25 Jul 2019 Ash plume drifted 134 km SE.
26 Jul 2019 Ash plume drifted 60 km SE.
03-05 Aug 2019 Ash plumes drifted 180 km SE and NW.
06 Aug 2019 Ash plume rose 2-2.5 km in altitude and drifted about 17 km NW.
14 Aug 2019 Volcanologists observed explosions and ash plumes that rose to 5 km altitude. Satellite images showed ash plumes drifting E and SSE that same day.
20-22 Aug 2019 Ash plumes visible in satellite images drifted 500 km SW. Explosions on 21 August produced ash plumes to 6 km altitude.
23-24 Aug 2019 Ash plumes drifted 51 km SE.
Figure (see Caption) Figure 44. Aerial photo showing an ash plume rising to 5 km altitude from Karymsky 14 August 2019. Photo by D. Melnikov; courtesy of IVS FEB RAS, KVERT.
Figure (see Caption) Figure 45. Satellite image from Sentinel-2 (natural color) of an ash plume at Karymsky on 21 August 2019. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 46. Photo showing explosive activity at Karymsky at 1920 UTC on 9 September 2019. Photo by A. Manevich; courtesy of IVS FEB RAS, KVERT.

During May-October 2019, thermal anomalies were detected with the MODIS satellite instruments analyzed using the MODVOLC algorithm only on 25 July (2 pixels) and 21 August (10 pixels). Consistent with both observations, KVERT noted ash explosions on those dates. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots in May, none in June, 3 in July, 5 in August, and none in September or October. KVERT reported that a thermal anomaly was visible in satellite images on most, if not all, days when not obscured by clouds.

The Aviation Color Code remained at Orange (the second highest level on a four-color scale) until 3 October, when KVERT reduced it to Yellow, after which moderate gas-and-steam activity continued.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); 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).


Shishaldin (United States) — October 2019 Citation iconCite this Report

Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


Active lava lake and spattering on 23 July 2019; minor explosions and lava fountaining on 17 August

Recent activity at Shishaldin, located on Unimak Island within the Aleutian Islands, has included a lava eruption in the summit crater, thermal anomalies, elevated seismicity, and gas-and-steam and ash plumes (BGVN 41:11). This report describes minor gas-and-steam emissions, increased seismicity, thermal anomalies, lava fountaining accompanied by minor explosive activity, and a spatter cone. The primary source of information is the Alaska Volcano Observatory (AVO). This report updates activity through September 2019.

Volcanism was relatively low between March 2016 and early July 2019; increased seismicity and steam emissions were detected in December 2017, but the activity declined in February 2018. Elevated seismicity and some thermal anomalies accompanied by incandescence observed in satellite imagery (when not obscured by clouds) returned in mid-July 2019 (figure 12).

Figure (see Caption) Figure 12. Summary graphic of MODVOLC thermal alerts measured over Shishaldin during July-September 2019. Courtesy of HIGP - MODVOLC Thermal Alerts System.

Elevated surface temperatures and low-level seismic tremors remained elevated through September 2019 (figure 13). Field crews reported an active lava lake and minor spattering within the summit crater on 23 July 2019 (figures 14 and 15). Satellite imagery showed the presence of a small spatter cone and some lava flows within the summit crater on 28 July. A small steam plume was observed in satellite imagery and webcam images on 29 July, 20 August, and 30 September.

Figure (see Caption) Figure 13. Sentinel-2 satellite imagery of Shishaldin showing detected thermal anomalies between the months of July and September 2019. Top left: Satellite image on 19 July showing a gas-and-steam plume. Top center: On 29 July a thermal anomaly is detected in the summit crater. Top right: On 28 August, the thermal anomaly is still present. Bottom left: On 7 September, the thermal anomaly continues. Bottom right: On 24 September, the power of the thermal anomaly significantly decreases. Atmospheric penetration satellite image (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 14. Photo of surface lava within the summit crater at Shishaldin taken on 23 July 2019. Photo by David Fee (color corrected); courtesy of Alaska Volcano Observatory (AVO).
Figure (see Caption) Figure 15. Photo of lava and a slightly growing spatter cone within the summit crater at Shishaldin taken on 23 July 2019. Photo by Dane Ketner (color corrected); courtesy of Alaska Volcano Observatory (AVO).

On 17 August 2019, a video taken by NOAA during an overflight showed repetitive minor explosive activity and low-level lava fountaining within the summit crater. This activity may have continued through 24 September, according to AVO. The spatter cone grew slightly in August and September, partially filling the summit crater. Accompanying lava flows also grew slightly during this time.

Satellite data from 3 September showed SO2 emissions and elevated surface temperatures. Satellite imagery and tiltmeter data recorded a collapse and slumping of the summit crater floor, which may have occurred on 19 September. In the last few weeks of September, seismicity and surface temperatures decreased to slightly above background levels.

According to MIROVA (Middle InfraRed Observation of Volcanic Activity) data from MODIS satellite instruments, more frequent thermal anomalies were detected in mid-July 2019 and remained elevated through early September (figure 16).

Figure (see Caption) Figure 16. Thermal anomalies increased at Shishaldin from mid-July 2019 through early September and then abruptly stopped as recorded by MIROVA (log radiative power). Courtesy of MIROVA.

Geologic Background. The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

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


Klyuchevskoy (Russia) — October 2019 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Ongoing weak thermal anomalies during July-September 2019, but no ash plumes after 1 August

During September 2018 through June 2019, activity at Klyuchevskoy was characterized by weak thermal anomalies and moderate Strombolian-type explosions. Ash emissions were only reported on 1-2 July and 1 August during the period of July-September 2019. The volcano is monitored by the Kamchatkan Volcanic Eruption Response Team (KVERT) and is the primary source of information.

According to KVERT, moderate activity continued from July through at least the middle of September, with gas-and-steam emissions. At the beginning of July, KVERT reported incandescence in the crater. During 1-2 July, ash plumes drifted as far as 85 km E and SE. Ash plumes were visible blowing E in Sentinel-2 images on 17 and 19 July (figure 32); steam plumes were evident on some other days. KVERT reported that an ash emission was seen in webcam images on 1 August.

Figure (see Caption) Figure 32. An ash plume can be seen blowing E from the summit crater of Klyuchevskoy in this Sentinel-2 natural color (bands 4, 3, 2) satellite image from 17 July 2019. Courtesy of Sentinel Hub Playground.

No thermal anomalies were detected with the MODIS satellite instruments analyzed using the MODVOLC algorithm. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected no thermal anomalies in June, four scattered ones in July, and only one in August, all low power. According to KVERT, a weak thermal anomaly was detected throughout the reporting period, at least through mid-September, except for the numerous days when the volcano was obscured by clouds; the temperature of the anomalies had steadily decreased with time.

Instruments aboard NASA satellites detected high levels of sulfur dioxide near or directly above the volcano every day during the first week of July and on 12 July, but not on other days during the reporting period. However, the origin for the high levels may, at least in part, have been due to other active volcanoes in the area.

At the beginning of July, the Aviation Color Code (ACC) remained at Orange (the second highest level on a four-color scale). Because of decreased activity, KVERT lowered the ACC to Yellow on 30 August and to Green (the lowest on the scale) on 24 September.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); 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/); 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/); 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/).


Heard (Australia) — October 2019 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Ongoing thermal anomalies at the summit crater during April-September 2019

Heard Island, in the Southern Indian Ocean, is about 4,000 km from its closest point to Australia and about 1,500 km from the closest point in Antarctica. Because of the island's remoteness, monitoring is primarily accomplished by satellites. The Big Ben volcano has been active intermittently since 1910, if not before (BGVN 42:10), and thermal anomalies have been observed every month since June 2018 (BGVN 43:10, 44:04). The current reporting period is from April to September 2019.

During April-September 2019, only one thermal anomaly was detected with the MODIS satellite instruments analyzed using the MODVOLC algorithm, and that was on 10 June (2 pixels). The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected a few scattered thermal alerts in late May-early June and three in September; most were between 1-2 km of the summit and of low to moderate power.

The island is usually covered by heavy clouds, obscuring satellite views. However, Sentinel-2 satellite imagery detected cloud-obscured thermal anomalies during the reporting period, most likely due to a persistent lava lake and possibly lava flows (BGVN 41:08).

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

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


Dukono (Indonesia) — October 2019 Citation iconCite this Report

Dukono

Indonesia

1.693°N, 127.894°E; summit elev. 1229 m

All times are local (unless otherwise noted)


Eruption with frequent ash plumes continues through September 2019

The eruption at Dukono, ongoing since 1933, is typified by frequent ash explosions and ash plumes (BGVN 43:04). This activity continued through at least September 2019. The data below were primarily provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Center for Volcanology and Geological Hazard Mitigation (CVGHM), and the Darwin Volcanic Ash Advisory Centre (VAAC).

According to PVMBG, during April-September 2019 the volcano continued to generate ash plumes almost every day that rose to altitudes of 1.5-3 km (table 20, figure 12). Ashfall was reported on 8 August at the Galela Airport, Maluku Utara, 17 km NW. The Alert Level remained at 2 (on a scale of 1-4), and the 2-km exclusion zone remained in effect.

Table 20. Monthly summary of reported ash plumes from Dukono for April-September 2019. The direction of drift for the ash plume through each month was highly variable, but did not extend for any notable distances during this reporting period. Data courtesy of the Darwin VAAC and PVMBG.

Month Plume Altitude (km) Notable Plume Drift
Apr 2019 1.5-2.4 --
May 2019 1.5-3 --
Jun 2019 1.8-2.4 --
Jul 2019 1.5-2.1 --
Aug 2019 1.8-2.1 --
Sep 2019 1.5-2.1 --
Figure (see Caption) Figure 12. Satellite image from Sentinel-2 (natural color) of an ash plume at Dukono on 4 August 2019, with the plume blowing almost straight up. Courtesy of Sentinel Hub Playground.

Instruments aboard NASA satellites detected high levels of sulfur dioxide near or directly above the volcano on 11, 20-22 April; 17, 22, and 27 May; 15-18 August; and 23-24 and 29 September. However, the cause of the high levels may, at least in part, have been due to other active volcanoes in the area.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); 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/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Poas (Costa Rica) — October 2019 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Occasional phreatic explosions continue through September 2019

Activity at Poás is characterized by weak phreatic explosions and gas-and-ash-emissions, with a hot acid lake that occasionally disappears (BGVN 44:05). During the current reporting period of May-September 2019, this weak activity continued. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), and most of the material below comes from their weekly bulletins (Boletin Semanal Vulcanologia).

According to OVSICORI-UNA, a period of continuous emissions occurred during 30 April-1 May with plumes rising 300 m above the crater rim and drifting SW. Ash emissions were visible for a few hours on 30 April, and incandescence was visible at night. OVSICORI-UNA did not report any additional phreatic explosions in May until daily phreatic, geyser-type explosions were observed between 29 May and 1 June, which reached approximately 100 m above the vent. A phreatic explosion on 10 June reached approximately 20-30 m in height, and frequent small phreatic explosions (heights below 20 m) were reported through 16 June.

OVSICORI-UNA reported that on 12 June small geyser-like explosions ejected material less than 50 m high at a rate of about once per hour. At 0604 on 18 June an explosion that lasted about six minutes produced a plume of unknown height. Residents reportedly heard several loud noises during 0610-0615 and observed a plume rising from the crater. Ash fell in Cajón (12 km SW), San Luis de Grecia (11 km SW), Los Ángeles, San Miguel de Grecia (11 km SW), San Isidro (28 km SE), and San Roque (23 km SSE). Whitish ash deposits surrounding the crater, especially on the W and S sectors, were visible in webcam images. On 21 June frequent small phreatic explosions from vent A (Boca Roja) were visible during good viewing conditions ejecting material less than 10 m high.

No additional phreatic activity was reported by OVSICORI-UNA during rest of June or July. The small crater lake was still present on 5 July when visible in satellite imagery and as seen by visitors (figure 130), During the first part of August geyser-like explosions occurred on several days, and reached a maximum height of 50 m. This activity culminated on 17 August with about 30 explosions/day from the vent (Boca Roja). At least one event at 0650 on that day generated a 1-km-high plume of steam, gas, and fine particles. By 26 August, the geyser-type activity had ceased. Geyser-type phreatic explosions resumed on 12 September, reaching a maximum height of 30 m. The number of explosions increased up to 10-15 events/hour and then became continuous for a short time. A phreatic explosion occurred on 22 September at 2059 that generated a plume that rose 3 km above the crater rim and drifted NE. During 22-23 September explosions generated plumes that rose 1 km.

Figure (see Caption) Figure 130. View of the Poás crater on 5 July 2019. The volcano is surrounded by cloud-cover, and there is some steam rising from the crater lake. Photo by Sheila DeForest (Creative Commons BY-SA license).

According to OVSICORI-UNA, during 16-26 September sulfur dioxide emissions drifted W and NE, causing a sulfur odor in Alajuela, Heredia, San José, and Cartago. Acidic rain was recorded at an official's house in the Poás Volcano National Park (PNVP) on 23 September and at the Universidad Nacional Costa Rica (UNA) in Heredia (23 km SE) on 26 September. On 30 September, at 0540, a 5-minute long phreatic explosion ejected sediment, and produced a plume that rose 2 km above the crater rim and drifted SW. Ashfall and a sulfur odor was reported in Trojas de Sarchi (10 km SW) and Grecia (16 km SSW). Officials closed the PNVP because of the eruption and ongoing elevated seismicity; the park remained closed the next day.

During the first week of August, strong evaporation had reduced the intracrater lake significantly, and by mid-September, the lake had disappeared. At the end of September, however, some water had begun to accumulate again.

General monitoring data. During April and May, OVSICORI-UNA took few gas measurements due to an unfavorable wind direction. An SO2 measurement during the first part of June was between 100 and 200 t/d. Flux remained low through July, with low SO2/CO2 ratios, and high H2S/SO2 ratios, which OVSICORI-UNA stated were consistent with water infiltration. At the end of July, SO2 concentrations significantly increased to 300-800 t/d, with H2S disappearing and the CO2/SO2 ratio declining, with some fluctuations. Levels remained high through most of August, but had decreased to about 300 t/d by the end of the month. They rose again in September, with fluctuations, and on 29 September were measured at about 1,000 t/d before falling to between 300-400 t/d.

According to OVSICORI-UNA weekly reports, seismicity was relatively low during the reporting period, with a few VTs and LPs and normal background tremor. No significant deformation occurred, except for some deflation in June and July.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Sheila DeForest (URL: https://www.facebook.com/sheila.deforest).


Etna (Italy) — October 2019 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Five lava flows and numerous ash plumes and Strombolian explosions, April-September 2019

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years and has been erupting continuously since September 2013 through at least September 2019. Lava flows, explosive eruptions with ash plumes, and Strombolian lava fountains commonly occur from its summit areas that include the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. Varying activity that included several lava flows, Strombolian activity, and numerous ash plumes from most of the active summit vents and several flank fissures occurred during April-September 2019, the period covered in this report, with information provided primarily by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Degassing of variable intensity was typical activity from all the vents at Etna during much of April 2019. Intermittent ash emission and Strombolian activity occurred at Bocca Nuova, especially during the last week. Minor ash emissions were reported from NEC and NSEC the last week as well. Most of the activity at the summit during May 2019 was focused around the New South East Crater (NSEC); repeated Strombolian activity was witnessed from the E vent near the summit throughout the month. Beginning on 30 May, two fissures opened on the N and SE flanks of NSEC and produced lava flows that traveled E and SE across the W wall of the Valle del Bove. The flows ceased during the first week of June; activity for the rest of that month consisted of intermittent explosions with small ash plumes from Voragine and Bocca Nuova. Discontinuous Strombolian explosions and isolated ash emissions from NEC, NSEC, and Bocca Nuova characterized activity during the first half of July 2019; the explosions intensified at NSEC later in the month. A lava flow emerged from the lower NE flank of NSEC on 18 July that lasted for several days. Explosions produced substantial ash plumes from the NSEC summit crater, causing ashfall nearby, and a new flow emerged from a fissure on the S flank of NSEC on 27 July.

Explosions with intermittent ash emissions during August 2019 were focused primarily on the North East Crater (NEC), with occasional ash emissions from Bocca Nuova. These continued into early September. Activity increased to include Strombolian explosions with the ash emissions at NEC, Bocca Nuova, and Voragine where a scoria cone formed deep within the crater from continued Strombolian activity. A lava flow emerged from the base of the scoria cone on 18 September and was active for about four days, sending branches of lava into multiple areas of the adjacent Bocca Nuova crater. Ash emissions at NEC continued during the end of the month. The multiple episodes of varying activity during the period were reflected in the MIROVA thermal energy data; spikes of thermal activity that corresponded to periods of lava effusion were apparent late May-early June, multiple times in July, and during the second half of September (figure 260).

Figure (see Caption) Figure 260. The multiple episodes of varying activity at Etna from 11 December 2018 through September 2019 were reflected in the MIROVA thermal energy data; spikes of thermal activity were apparent in late April, late May-early June, multiple times in July, and during the second half of September. The largest energy spikes correlated with lava flows. Courtesy of MIROVA.

Activity during April-May 2019. During a site visit to the summit on 1 April scientists from INGV noted weak degassing from both pit craters, BN-1 and BN-2, within Bocca Nuova (BN); the Voragine (VOR) and North East Crater (NEC) were emitting abundant steam and gas emissions. The New Southeast Crater (NSEC) also had significant fumarolic activity concentrated primarily on the crater rim along with gas plumes visible from both the E vent and the 24 December 2018 flank fissure (figure 261). A brief episode of ash emission was observed from BN on the morning of 8 April. Persistent pulsating flashes of incandescence were noted at the E vent of NSEC during the second week. A new vent was observed in the inner wall of the Voragine crater during an inspection on 19 April, located immediately below the vent which formed on 12 January 2019 (figure 262). During the last week of April there were ten episodes of ash emission from BN, two from NEC, and one produced by the E vent at NSEC. Strombolian activity was observed on the morning of 28 April at BN-1, and persistent incandescence was visible from the E vent of NSEC. Early on 30 April both BN-1 and BN-2 were producing explosions every few seconds. Coarse ejecta (lapilli and bombs) rose higher than the crater rim; most fell back within the crater, but some material was observed on the rim the following day.

Figure (see Caption) Figure 261. During a site visit to the summit of Etna on 1 April 2019 scientists from INGV noted weak degassing from both pit craters, BN-1 and BN-2, within Bocca Nuova (BN); Voragine (VOR) and North East Crater (NEC) were emitting abundant steam and gas emissions, and the New Southeast Crater (NSEC) also had significant fumarolic activity concentrated primarily on the crater rim along with gas plumes visible from both the E vent (bocca orientale) and the 24 December 2018 flank fissure. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 15/2019, ETNA, Bollettino Settimanale, 01/04/2019 - 07/04/2019, data emissione 09/04/2019).
Figure (see Caption) Figure 262. A new vent was observed at the W rim of Etna's Voragine crater on 19 April 2019. INGV scientists concluded that it likely formed during 17-18 April. It was located immediately below a pit crater that opened on 12 January 2019. Inset shows thermal image of the vents. Courtesy of INGV (Report 17/2019, ETNA, Bollettino Settimanale, 15/04/2019 - 21/04/2019, data emissione 24/04/2019).

Activity at the summit during May 2019 was focused around the New South East Crater (NSEC). Discontinuous Strombolian activity was observed at the E vent of NSEC early on 2 May accompanied by ash emissions from the summit vent that rose about 1,000 m (figure 263). Explosion frequency increased beginning on 5 May with weak and discontinuous ash emissions reported from the NSEC summit for the next several days; ash emissions were also observed from the Saddle vent and the NSEC E vent during 6-8 May. In addition to ash emissions and Strombolian activity continuing from both the summit and E vents at NSEC during the third and fourth weeks, overnight on 17-18 May several larger Strombolian explosions sent pyroclastic ejecta tens of meters above the crater rim (figure 264). The explosion intervals ranged from a few minutes to a few hours. The new vent that had formed at Voragine in mid-April coalesced with the 12 January vent during the second week of May; dilute ash was observed from the BN-1 vent on 23 May.

Figure (see Caption) Figure 263. Strombolian activity at the E vent of NSEC at Etna was accompanied by ash emission on 2 May 2019. Left image is from the thermal camera at La Montagnola and the right image is from Tremestieri Etneo, taken by B. Behncke. Coutesy of INGV (Report 19/2019, ETNA, Bollettino Settimanale, 29/04/2019 - 05/05/2019, data emissione 07/05/2019).
Figure (see Caption) Figure 264. Strombolian activity sent ejecta from a vent at Etna's NSEC crater on 14 May 2019 (a) and was captured by the Monte Cagliato thermal camera. Ash emission from the same vent was also visible that day (b) and on 17 May (c). Strombolian explosions from the E Vent of NSEC on 17 May (d) were captured by the EMOH (Montagnola) webcam. Courtesy of INGV (Report 21/2019, ETNA, Bollettino Settimanale, 13/05/2019 - 19/05/2019, data emissione 21/05/2019).

A fissure opened at the base of the N flank of NSEC shortly after midnight on 30 May 2019 at an elevation of about 3,150 m (figure 265). It produced mild explosive activity and a lava flow that spread towards the W wall of the Valle del Bove. By 0800 UTC the flow had reached an elevation of 2,050 m. A second fissure opened at 0335 the same morning at the base of the SE flank of NSEC at an elevation of 3,050 m. The lava flowed along the W wall of the Valle del Bove towards Serra Giannicola Grande and had reached an elevation of 2,260 m by 0815. Strong winds dispersed ash emissions from the fissures to the NE for much of the day; ashfall occurred in Linguaglossa (figure 266). The Toulouse VAAC reported an ash plume drifting ENE at 3.9 km altitude on 30 May. Samples of the ash that were collected and analyzed were shown to be about 70% lithic clasts, 25% crystals, and about 5% juvenile material. It became clear the next day that two vents along the SE-flank fissure initially produced separate flows that coalesced into a single flow which expanded along the W wall of Valle del Bove. By 0830 on 31 May that flow had reached an elevation of 1,700 m at the base of Serra Giannicola Grande. The fissure at the base of the N flank continued to propagate along the W wall of Valle del Bove also, and had reached an elevation of 2,050 near Monte Simone by 1030 on 31 May (figure 267). When the new eruptive activity began on 29 May, inclinometers measured slight but prolonged deflation of the volcano.

Figure (see Caption) Figure 265. Two fissures opened at Etna during the early morning of 30 May 2019. One started from the base of the N flank of the NSEC/SEC complex and flowed E towards the Valle del Bove, and a second fissure with two vents opened on the SE flank of NSEC and flowed SE towards Serra Giannicola Grande. Mapping of the lava flows were done with drones, using the Sentinel 2 satellite images of 30 May and thermal images from 2 June taken at the Schiena dell'Asino. Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019, data emissione 04/06/2019).
Figure (see Caption) Figure 266. Lava flows broke out at Etna on both the N and SE flanks of NSEC on 30 May 2019. Ash emissions were also produced from the fissures. The northern flank fissure is seen from the (a) Monte Cagliato thermal camera (EMCT) and (b) the Montagnola high definition camera (EMOH). The fissure on the SE flank was seen from the Montagnola thermal (c) and high definition (d) (EMOH) webcams. Ash emissions and lava flows were visible on the flank (e) and ashfall was recorded in Linguaglossa (f). Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019, data emissione 04/06/2019).
Figure (see Caption) Figure 267. Images of the active lava flows at Etna on 31 May 2019 indicated the extent of the flow activity. Lava was flowing from two vents along a fissure on the SE flank (a and b, drone images courtesy of the FlyEye Team OE). The thermal image of the flow (c) is from Schiena dell'Asi, the visible photo (d) is also taken from Schiena dell'Asi by L. Lodato. The thermal (e) and visual (f) images of the active lava fields were taken from the Monte Cagliato (EMCT) thermal webcam and the Monte Cagliato (EMCH) high definition webcam. Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019, data emissione 04/06/2019).

Activity during June-July 2019. The flow from the N flank of NSEC ceased advancing on 1 June 2019, but the active spattering continued from the fissure on the SE flank for a few more days. The SE-flank flow had reached 1,700 m elevation in the Valle del Bove by the afternoon of 2 June (figure 268). The intensity and frequency of the explosions decreased over the next few days, with the active flow front receding back towards the vent until it stopped moving on 6 June. The NE rim of the summit cone at NSEC appeared lowered by several meters after the eruption ceased. The lava flows and explosions of 30 May-2 June produced persistent SO2 emissions that drifted E and N for over 800 km (figure 269).

Figure (see Caption) Figure 268. During the morning of 1 June 2019 Strombolian and effusive activity at Etna continued from the fissure on the SE flank of NSEC (a and b, photos by M. Neri). By the evening of 1 June there was only one remaining arm of the flow that was active (c) as seen in the Monte Cagliato (EMCT) thermal webcam. The following evening, 2 June, another thermal image(d, photo by S. Scollo) showed the remaining active arm. Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019).
Figure (see Caption) Figure 269. Active lava flows and Strombolian activity at Etna during 30 May-2 June 2019 contributed to significant SO2 plumes that drifted E and NE from the volcano during this time, extending as far as 800 km from the source. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Goddard Space Flight Center.

Activity for the rest of June 2019 moved to the other craters, mainly Voragine, after the flows ceased at NSEC. On the morning of 6 June there were sporadic ash emissions from NEC that quickly dissipated. A small ash plume appeared from Bocca Nuova (BN) on 11 June. An explosive sequence that began on 13 June from the crater floor of Voragine continued intermittently through the third week of the month (figure 270) and produced several small ash plumes. A new vent opened on the crater floor and produced a small ash plume; ejecta also landed on the crater rim several times. On 22 June small, discontinuous ash emissions were produced from BN-1; they dispersed rapidly, but intermittent explosions continued during the following week. By the end of the month, only BN was exhibiting activity other than degassing; incandescence from the crater was seen during the night of 24 June and three isolated ash emissions were seen in the webcams on 26 June.

Figure (see Caption) Figure 270. An ash plume at Etna rose from the Voragine crater on 15 June 2019 during a series of intermittent explosions. Image taken from the Torre del Filosofo by M. Coltelli. Courtesy of INGV (Report 25/2019, ETNA, Bollettino Settimanale, 10/06/2019 - 16/06/2019, data emissione 18/06/2019).

Discontinuous Strombolian explosions and isolated ash emissions characterized activity during the first half of July 2019. Pulsating degassing from NEC produced ash emissions on 2 and 3 July (figure 271), and incandescence on 4 and 5 July. Intense degassing was observed at NSEC during 1-5 July, this turned into isolated ash emissions and Strombolian activity on 5 and 6 July from the E vent with explosions occurring every 1-5 minutes; the ejecta landed on the upper E flank. Dilute ash emissions were observed from Bocca Nuova on 6 July. NEC produced two major ash emissions on the evening of 8 July and the late morning of 13 July. The ash plumes quickly dispersed in the summit area. Strombolian activity at the E vent of NSEC was witnessed on 14 July. Explosive activity at Bocca Nuova remained deep within the crater during mid-July. Steam produced by the 13 June 2019 vent on the floor of Voragine occasionally contained dilute ash. During 15-17 July sporadic explosions were observed at NSEC accompanied by small puffs of ash that rapidly dispersed.

Figure (see Caption) Figure 271. Surveillance cameras at Etna captured images of explosions with ash emissions from NEC on 2 (top) and 3 (bottom) July 2019. The left images are from Montagnola and the right images are from Monte Cagliato. Courtesy of INGV (Report 28/2019, ETNA, Bollettino Settimanale, 01/07/2019 - 07/07/2019, data emissione 09/07/2019).

Beginning early on 18 July, Strombolian activity increased at NSEC from an explosion every 1-2 minutes to multiple explosions per minute in the following hours. Continuous activity during the evening decreased sharply around 2200. About an hour later visual and thermal surveillance cameras on Monte Cagliato recorded the opening of a vent on the lower NE flank of NSEC; lava slowly advanced from the vent towards Valle del Leone (figures 272 and 273). Explosive activity resumed at the NSEC summit a few hours later, accompanied by occasional ash emissions from NEC and Bocca Nuova. Explosions tapered off briefly by noon on 19 July, but a sudden increase in explosive activity during the afternoon of 19 July produced Strombolian activity and sporadic ash emissions from three vents inside the NSEC crater. Ashfall was reported that evening in communities on the S flank of Etna. The Toulouse VAAC reported significant ash above the summit at 3.7 km altitude. Activity declined again later that evening at NSEC, but abundant ash emission began at NEC that lasted until the morning of 20 July. A new phase of explosive activity began at NSEC around 0700 on 20 July with an ash plume and an increase in lava emission from the vent on the NE flank (figure 274). By the evening of 20 July only a small amount of material was feeding the lava flow; the farthest advanced fronts were at an elevation around 2,150 m, above Monte Simone. A few small ash emissions were observed at Bocca Nuova on 21 July.

Figure (see Caption) Figure 272. Map of the summit craters of Etna showing the active vents and the lava flow of 19-21 July 2019. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 30/2019, ETNA, Bollettino Settimanale, 15/07/2019 - 21/07/2019, data emissione 23/07/2019).
Figure (see Caption) Figure 273. Activity at Etna on 18 and 19 July 2019 included a new lava flow from a vent on the NE flank of NSEC and Strombolian activity at the NSEC summit vent. (a) Start of the flow from a vent on the NE flank of NSEC seen from the high-resolution camera at Monte Cagliato (EMCH) at 2307 UTC on 18 July. (b) Strombolian activity at the NSEC and glow of the new lava flow on the right seen from Tremestieri Etneo, 2347 that evening. (c) A new advancing lava flow and brown ash emission from NEC seen from the EMCH camera, 0338 on 19 July; (d) lava flow seen from the thermal camera at Monte Cagliato, 0700 on 19 July. Courtesy of INGV (Report 30/2019, ETNA, Bollettino Settimanale, 15/07/2019 - 21/07/2019, data emissione 23/07/2019).
Figure (see Caption) Figure 274. Activity at Etna on 20 July 2019 included (a) ash emission from both NSEC and NEC craters at 0402 seen from Tremestieri Etneo, (b) ash from NSEC and the active flow on the SE flank at 0608 seen from the Monte Cagliato high-resolution camera, (c) ash emission from NSEC at 0700 seen by Tremesteieri Etneo, and (d) explosive activity at NSEC and the lava flow on the W wall of the Valle del Bove at 0700 seen from the Monte Cagliato thermal camera. Courtesy of INGV (Report 30/2019, ETNA, Bollettino Settimanale, 15/07/2019 - 21/07/2019, data emissione 23/07/2019).

Visible and thermal images taken on 24 July 2019 indicated only degassing at BN-1 and BN-2, and limited degassing from low-temperature fumaroles from the multiple vents at VOR (figure 275). After a few days of quiet, NSEC resumed discontinuous ash emissions on 25 July. A sudden increase in the amplitude of volcanic tremor was noted early on 27 July, which was followed a few hours later by the opening of a new eruptive fissure on the S flank of NSEC (figure 276). Explosive activity intensified and produced a dense ash-rich plume that dispersed to the E at an estimated altitude of 4.5-5 km. A thin layer of ash was reported in Giarre, Riposto, and Torre Archirafi. A lava flow emerged from the S portion of the fissure and expanded SW and S. By 1135 the most advanced front had reached and passed the N side of the base of the Barbagallo Mountians at an elevation of about 2,850 m. It continued to spread down into the area between Monte Frumento Supino and the pyroclastic cones of 2002-2003 (figure 277). A series of particularly strong explosions occurred from NSEC around midday, producing an ash plume that rose to 7.5 km altitude. By this time the most advanced lava fronts were located at an elevation of about 2,600 m, but they were rapidly advancing SSW towards Monte Nero, surrounding Monte Frumento Supino from the W. Explosive activity decreased significantly early in the morning on 28 July; flow activity also slowed around the same time. Occasional puffs of reddish-brown ash were noted from NEC during the morning as well. The explosions and the lava effusion ceased on the evening of 28 July. An isolated ash emission from Bocca Nuova in the early hours of 31 July was the last activity reported in July. A substantial SO2 plume (6.59 DU) from the explosions on 27 July had drifted to the E coast of the Adriatic Sea by midday on 28 July and was detected in satellite instruments.

Figure (see Caption) Figure 275. Degassing was the only activity occurring at the multiple vents at Etna's Voragine crater on 24 July 2019. The joined pit crater from the 12 January and 18 April 2019 vents is at the upper left; the newest vent formed 16 June 2019 is at lower left and appears cool in the thermal image inset a. Photo and annotations by S. Branca. Courtesy of INGV (Rep. N° 31/2019, ETNA, Bollettino Settimanale, 22/07/2019 - 28/07/2019, data emissione 30/07/2019).
Figure (see Caption) Figure 276. A new eruptive fissure at Etna opened on the S flank of NSEC on 27 July 2019 (line of red circles). The base map is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Black hatch marks indicate the crater rims: BN=Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 31/2019, ETNA, Bollettino Settimanale, 22/07/2019 - 28/07/2019, data emissione 30/07/2019).
Figure (see Caption) Figure 277. Lava flows and substantial ash emissions were reported at Etna on 27 July 2019. The lava flow at 1216 was located at about 2,600 m elevation (a). A thermal image of the S flank of NSEC showed the extent of the flow activity (b). A large ash plume formed after several explosions at NSEC at 1221 (c). Thermal images of the emissions were captured by the Montagnola (EMOT) webcam and by an INGV operator (d, e). Photos by S. Branca (a), B. Behncke (c), and E. Pecora (b, e). Courtesy of INGV (Report 31/2019, ETNA, Bollettino Settimanale, 22/07/2019 - 28/07/2019, data emissione 30/07/2019).

Activity during August-September 2019. Activity during August 2019 was focused primarily on the North East Crater (NEC), with occasional ash emissions from Bocca Nuova. The plumes were occasionally dense and dark brown from NEC. Weak emissions of dilute ash from NEC quickly dispersed on the morning of 4 August, followed by more intermittent ash emissions during 6-10 August; a few had significant concentrations of ash that drifted SE. Part of the N rim of NEC collapsed during the explosions of early August (figure 278). During a site inspection to the summit by INGV personnel on 16 August, continuous degassing at Bocca Nuova was interrupted every 10-15 minutes by explosions, but no ejecta was noted. Discontinuous emissions from NEC formed small ash plumes that rose a few hundred meters and remained in the summit area (figure 279). Thermal surveys that day indicated high temperatures of about 800°C along a 10-m-fracture zone on the northern rim of VOR. Ash emissions from NEC were persistent through 20 August when they decreased significantly; a few explosions had dilute ash emissions from Bocca Nuova that day and the next (figure 280). Sulfur dioxide emissions were notable during 19-22 August, drifting S and W hundreds of kilometers before dissipating. Isolated and dilute ash from NEC early on 28 August was interpreted by INGV as resulting from collapses along the inner crater walls. During site inspections on 27, 28, and 30 August, deep explosions from Bocca Nuova were heard, and degassing was observed at all of the summit vents.

Figure (see Caption) Figure 278. Part of the N rim of the NEC crater at Etna collapsed during explosions in early August 2019. In this image from 10 August 2019 the collapsed N wall is shown by white arrows, the old crater rim is the dashed yellow line, and the new rim is the solid yellow line. Photo by Michele Mammino, courtesy of INGV (Report 33/2019, ETNA, Bollettino Settimanale, 05/08/2019 - 11/08/2019, data emissione 13/08/2019).
Figure (see Caption) Figure 279. Discontinuous emissions at Etna on 16 August 2019 from the NEC crater formed small ash plumes that rose a few hundred meters and remained in the summit area (a). Smaller ash plumes remained within the crater (b and c). Courtesy of INGV (Report 34/2019, ETNA, Bollettino Settimanale, 12/08/2019 - 18/08/2019, data emissione 20/08/2019).
Figure (see Caption) Figure 280. In the foreground weak degassing occurs on 21 August 2019 at Etna's BN-2 vent inside Bocca Nuova while a small ash plume in the background rises from NEC. Photo by F. Ciancitto, courtesy of INGV (Report 35/2019, ETNA, Bollettino Settimanale, 19/08/2019 - 25/08/2019, data emissione 27/08/2019).

Activity during September 2019 began with discontinuous and dilute ash emissions from NEC and Bocca Nuova, as well as episodes of Strombolian activity at both vents. This was followed by increased Strombolian activity, ash emissions, and a lava flow at Voragine. Isolated ash emissions occurred at NEC and VOR on 4 and 5 September. Sporadic deep explosions were heard from BN-1 during a site inspection on 7 September. Overnight during 7-8 September the visual webcams recorded incandescence at NEC and pyroclastic ejecta observed outside the crater rim that coincided with increased tremor activity. A more intense episode of Strombolian activity began the following evening at NEC. Activity was continuous from 1800 on 9 September to 0500 on 10 September, and produced dilute ash emissions that quickly dispersed (figure 281). Slight ashfall was reported in Piedimonte Etneo, Giarre-Riposto, and Rifugio Citelli. Continuous puffs of dilute ash were observed beginning at dawn on 11 September with sporadic ejecta again landing outside the crater rim. Significant SO2 plumes were measured by satellite instruments on 10 and 11 September (figure 282).

Figure (see Caption) Figure 281. Activity at Etna overnight during 9-10 September 2019 included Strombolian activity and dilute ash emissions from NEC that were observed from webcams on the S, W, and E flanks. Courtesy of INGV (Report 38/2019, ETNA, Bollettino Settimanale, 09/09/2019 - 15/09/2019, data emissione 17/09/2019).
Figure (see Caption) Figure 282. Significant SO2 plumes from Etna were detected on 10 and 11 September 2019. Increased Strombolian activity was reported by INGV from the NEC crater during 9-11 September. Courtesy of NASA Goddard Space Center.

In addition to the Strombolian activity at NEC on 12 September, ash emissions began that morning at VOR. They increased in frequency and then transitioned to near-continuous Strombolian activity that produced ejecta which landed in the base of the adjacent Bocca Nuova crater. The explosions from the Strombolian activity were felt in Zafferana Etnea, Aci S. Antonio, Pedara, and neighboring areas. On 13 September the webcams observed multiple periods of continuous ash emissions from NEC and short, intense pulses of ash from VOR that accompanied Strombolian activity; coarse ejecta rose 20 m above and landed outside of the crater rim, producing impact craters on the W side of the summit between VOR and BN. The vent that sourced the Strombolian activity was located in the deepest part of the Voragine crater. By 15 September, continued ejecta had formed a scoria cone around the vent inside VOR (figure 283).

Figure (see Caption) Figure 283. On 13 September 2019 Strombolian activity at Etna's NEC and VOR craters increased (a). INGV personnel observed an ash emission from NEC (b), a Strombolian explosion with ejecta from VOR (c), and impact craters from the ejecta around the rim (d). The continued activity at VOR produced a scoria cone inside the crater that grew noticeably between 13 (e) and 15 (f) September. Photos (a) and (e) courtesy of L. D'Agata, photo (f) by B. Behncke. Courtesy of INGV (Report 38/2019, ETNA, Bollettino Settimanale, 09/09/2019 - 15/09/2019, data emissione 17/09/2019).

Explosive activity inside VOR increased on the afternoon of 18 September 2019. Pyroclastic ejecta and ash erupted from several vents and reached heights of several tens of meters. A lava flow emerged from the W base of the scoria cone and headed S, advancing several hundred meters (figure 284). It then flowed over the saddle that divides VOR and BN, split into two branches, and entered Bocca Nuova. One stream poured into BN-1, and another stopped near the edge of the BN-2 pit crater. By 22 September the flow was cooling, but strong Strombolian activity continued inside Voragine. NEC was characterized by large-scale ash emissions during the end of September, including one in the morning of 27 September that sent a plume over the S flank of Etna before dissipating (figure 285). Strombolian activity continued within Bocca Nuova during the last week of the month.

Figure (see Caption) Figure 284. Significant Strombolian and lava flow activity at Etna affected the Voragine crater on 18 and 19 September 2019. Visible and thermal images of the scoria cone (cono scorie) and lava flow (colata) inside Etna's large Voragine crater on 19 September 2019 (top) were taken from the southern edge of BN. Photo by F. Ciancitto. The bottom images were taken from the SW rim of BN on 18 September (left) by M. Tomasello and (right) 19 September by INGV personnel. Courtesy of INGV (Report 39/2019, ETNA, Bollettino Settimanale, 16/09/2019 - 22/09/2019, data emissione 24/09/2019).
Figure (see Caption) Figure 285. An ash emission from Etna's NEC crater early on 27 September 2019 sent a plume drifting S before dissipating. It was captured by both the high-definition webcam of Bronte (EBVH, left) and the Milo (EMV) webcam. Courtesy of INGV (Report 40/2019, ETNA, Bollettino Settimanale, 23/09/2019 - 29/09/2019, data emissione 01/10/2019).

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: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); 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/); 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/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/info/vaac/).


Ubinas (Peru) — September 2019 Citation iconCite this Report

Ubinas

Peru

16.355°S, 70.903°W; summit elev. 5672 m

All times are local (unless otherwise noted)


Intermittent ash explosions in June-August 2019

Prior to renewed activity in June 2019, the most recent eruptive episode at Ubinas occurred between 13 September 2016 and 2 March 2017, with ash explosions that generated plumes that rose up to 1.5-2 km above the summit crater (BGVN 42:10). The volcano remained relatively quiet between April 2017 and May 2019. This report discusses an eruption that began in June 2019 and continued through at least August 2019. Most of the Information was provided by the Instituto Geofísico del Perú (IGP), Observatoria Vulcanologico del Sur (IGP-OVS), the Observatorio Volcanológico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET), and the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Activity during June 2019. According to IGP, seismic activity increased suddenly on 18 June 2019 with signals indicating rock fracturing. During 21-24 June, signals indicating fluid movement emerged and, beginning at 0700 on 24 June, webcams recorded ash, gas, and steam plumes rising from the crater. Plumes were visible in satellite images rising to an altitude of 6.1 km and drifting N, NE, and E.

IGP and INGEMMET reported that seismic activity remained elevated during 24-30 June; volcano-tectonic (VT) events averaged 200 per day and signals indicating fluid movement averaged 38 events per day. Emissions of gas, water vapor, and ash rose from the crater and drifted N and NE, based on webcam views and corroborated with satellite data. According to a news article, a plume rose 400 m above the crater rim and drifted 10 km NE. Weather clouds often obscured views of the volcano, but an ash plume was visible in satellite imagery on 24 June 2019 (figure 49). On 27 June the Alert Level was raised to Yellow (second lowest on a 4-level scale).

Figure (see Caption) Figure 49. Sentinel-2 satellite image in natural color showing an ash plume blowing north from Ubinas on 24 June 2019. Courtesy of Sentinel Hub Playground.

Activity during July 2019. IGP reported that seismic activity remained elevated during 1-15 July; VT events averaged 279 per day and long-period (LP) events (indicating fluid movement) averaged 116 events per day. Minor bluish emissions (magmatic gas) rose from the crater. Infrared imagery obtained by Sentinel-2 first showed a hotspot in the summit crater on 4 July.

According to IGP, during 17-19 July, gas-and-ash emissions occasionally rose from Ubinas's summit crater and drifted N, E, and SE. Beginning at 0227 on 19 July, as many as three explosions (two were recorded at 0227 and 0235) generated ash plumes that rose to 5.8 km above the crater rim. The Buenos Aires VAAC reported that, based on satellite images, ash plumes rose to an altitude as high as 12 km. The Alert Level was raised to Orange and the public were warned to stay beyond a 15-km radius. Ash plumes drifted as far as 250 km E and SE, reaching Bolivia. Ashfall was reported in areas downwind, including the towns of Ubinas (6.5 km SSE), Escacha, Anascapa (11 km SE), Tonohaya (7 km SSE), Sacohaya, San Miguel (10 km SE), Huarina, and Matalaque, causing some families to evacuate. The Buenos Aires VAAC reported that during 20-23 July ash plumes rose to an altitude of 7.3-9.5 km and drifted E, ESE, and SE.

IGP reported that activity remained elevated after the 19 July explosions. A total of 1,522 earthquakes, all with magnitudes under 2.2, were recorded during 20-24 July. Explosions were detected at 0718 and 2325 on 22 July, the last ones until 3 September. The Buenos Aires VAAC reported that an ash plume rising to an altitude of 9.4 km. and drifting SE was identified in satellite data at 0040 on 22 July (figure 50). Continuous steam-and-gas emissions with sporadic pulses of ash were visible in webcam views during the rest of the day. Ash emissions near the summit crater were periodically visible on 24 July though often partially hidden by weather clouds. Ash plumes were visible in satellite images rising to an altitude of 7 km. Diffuse ash emissions near the crater were visible on 25 July, and a thermal anomaly was identified in satellite images. During 26-28 July, there were 503 people evacuated from areas affected by ashfall.

Figure (see Caption) Figure 50. Image of ash streaming from the summit of Ubinas on 22 July 2019 captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. Courtesy of NASA's Earth Observatory (Joshua Stevens and Kathryn Hansen).

Activity during August 2019. IGP reported that during 13-19 August blue-colored gas plumes rose to heights of less than 1.5 km above the base of the crater. The number of seismic events was 1,716 (all under M 2.4), a decrease from the total recorded the previous week.

According to IGP, blue-colored gas plumes rose above the crater and eight thermal anomalies were recorded by the MIROVA system during 20-26 August. The number of seismic events was 1,736 (all under M 2.4), and there was an increase in the magnitude and number of hybrid and LP events. Around 1030 on 26 August an ash emission rose less than 2 km above the crater rim. Continuous ash emissions on 27 August were recorded by satellite and webcam images drifting S and SW.

IGP reported that during the week of 27 August, gas-and-water-vapor plumes rose to heights less than 1 km above the summit. The number of seismic events was 2,828 (all under M 2.3), with VT signals being the most numerous. There was a slight increase in the number of LP, hybrid, and VT events compared to the previous week. The Alert Level remained at Orange.

Thermal anomalies. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected a large concentration of anomalies between 19 July until almost the end of August 2019, all of which were of low radiative power (figure 51). Infrared satellite imagery (figure 52) also showed the strong thermal anomaly associated with the explosive activity on 19 July and then the continuing hot spot inside the crater through the end of August.

Figure (see Caption) Figure 51. Log radiative power MIROVA plot of MODIS thermal anomalies at Ubinas for the year ending on 4 October 2019. Thermal activity began in the second half of July. Courtesy of MIROVA.
Figure (see Caption) Figure 52. Sentinel-2 satellite images (Atmospheric penetration rendering, bands 12, 11, 8A) showing thermal anomalies during the eruption on 19 July (left) and inside the summit crater on 29 July 2019 (right). A hot spot inside the crater persisted through the end of August. Courtesy of Sentinel Hub Playground.

Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Information Contacts: Instituto Geofisico del Peru (IGP), Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa (URL: http://ovi.ingemmet.gob.pe); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php?lang=es); 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); Instituto Nacional de Defensa Civil Perú (INDECI) (URL: https://www.indeci.gob.pe/); Gobierno Regional de Moquegua (URL: http://www.regionmoquegua.gob.pe/web13/); La Republica (URL: https://larepublica.pe/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/).


Santa Maria (Guatemala) — September 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)


Persistent explosions with local ashfall, March-August 2019; frequent lahars during June; increased explosions in early July

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 March-August 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 March-August 2019, except for a short-lived increase in the frequency and intensity of explosions during early July that produced minor pyroclastic flows. Plumes of steam with minor magmatic gases rose continuously from both the S rim of the Caliente crater and from the summit of the growing dome throughout the period. They usually rose 100-700 m above the summit, generally drifting W or SW, and occasionally 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 no more than 25 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 10 km in those directions several times each month. Continued growth of the Caliente lava dome resulted in daily block avalanches descending its flanks to the base of the dome. The MIROVA plot of thermal energy during this time shows a consistent level of heat from early December 2018 through April 2019, very little activity during May and June, and a short-lived spike in activity from late June through early July that coincides with the increase in explosion rate and intensity. Activity decreased later in July and into August (figure 95).

Figure (see Caption) Figure 95. Thermal activity at Santa Maria from 8 December 2018 through August 2019 was similar to previous months. A noticeable decrease in activity occurred during May and early June 2019 with a short-lived spike during late June and early July that corresponded to an increase in explosion rate and intensity during that brief interval. Courtesy of MIROVA.

Explosive activity increased slightly during March 2019 to 474 events from 409 events during February, averaging about 15 per day; the majority of explosions were weak to moderate in strength. The moderate explosions generated small block avalanches daily that sent debris 300 m down the flanks of Caliente dome; the explosions contained low levels of ash and large quantities of steam. Daily activity consisted mostly of degassing around the southern rim of the crater and within the central dome, with plumes rising about 100 m from the S rim, and pulsating between 100-400 m above the central dome, usually white and sometimes blue with gases; steam plumes drifted as far as 10 km. The weak ash emissions resulted in ashfall close to the volcano, primarily to the W and SW in the mountainous areas of El Faro, Patzulín, La Florida, and Monte Bello farms. During mid-March, residents of the villages of Las Marías and El Viejo Palmar, located S of the dome, reported the smell of sulfur. The seismic station STG3 registered 8-23 explosions daily that produced ash plumes which rose to altitudes between 2.7 and 3.3 km altitude. Explosions from the S rim were usually steam rich, while reddish oxidized ash was more common from the NE edge of the growing dome in the summit crater (figure 96). The constant block avalanches were generated by viscous lava slowly emerging from the growing summit dome, and also from the explosive activity. On the steep S flank of Santa Maria, blocks up to 3 m in diameter often produce small plumes of ash and debris as they fall.

Figure (see Caption) Figure 96. Mostly steam rose from the S rim of the Caliente dome at Santa Maria throughout March-August 2019. On 1 March 2019, oxidized reddish ash from the growing dome was also part of the emissions (left). The dome continued to grow, essentially filling the inside of the summit crater of Caliente. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA MARZO 2019, VOLCÁN SANTIAGUITO).

Late on 4 March 2019 an explosion was heard 10 km away that generated incandescence 100 m above the crater and block avalanches that descended to the base of the Caliente dome; it also resulted in ashfall around the perimeter of the volcano. Powerful block avalanches were reported in Santa María creek on 8 March. Ashfall was reported in the villages of San Marcos and Loma Linda Palajunoj on 14 March. Ash plumes on 18 March drifted W and caused ashfall in the villages of Santa María de Jesús and Calaguache. A small amount of ashfall was reported on 26 March around San Marcos Palajunoj. The Washington VAAC reported volcanic ash drifting W from the summit on 8 March at 4.6 km altitude. A small ash plume was visible in satellite imagery moving WSW on 11 March at 4.6 km altitude. On 20 March a plume was detected drifting SW at 3.9 km altitude for a short time before dissipating.

Explosion rates of 10-14 per day were typical for April 2019. Ash plumes rose to 2.7-3.2 km altitude. Block avalanches reached the base of the Caliente dome each day. Steam and gas plumes pulsated 100-400 m above the S rim of the crater (figure 97). Ashfall in the immediate vicinity of the volcano, generally on the W and SW flanks was also a daily feature. The Washington VAAC reported multiple small ash emissions on 2 April moving W and dissipating quickly at 4.9 km altitude. An ash plume from two emissions drifted WSW at 4.3 km altitude on 10 April, and on 22 April two small discrete emissions were observed in satellite images moving SE at 4.6 km altitude. Ashfall was reported on 13 and 14 April in the nearby mountains and areas around Finca San José to the SE. On 15 and 23 April, ash plumes drifted W and ashfall was reported in the area of San Marcos and Loma Lina Palajunoj.

Figure (see Caption) Figure 97. Degassing from the Caliente dome at Santa Maria on 3 April (left, infrared image) and 13 April 2019 (right) produced steam-rich plumes with minor quantities of ash. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo:, Volcán Santiaguito, Semana del 30 de marzo al 05 de abril de 2019).

Constant degassing continued from the S rim of the crater during May 2019 while pulses of steam and gas rose 100-500 m from the dome at the center of the summit crater. Weak to moderate explosions continued at a rate of 8-12 per day. White and gray plumes of steam and ash rose 300-700 m above the crater daily. A moderate-size lahar on 16 May descended the Rio San Isisdro; it was 20 m wide and carried blocks 2 m in diameter. Ashfall was reported on the W flank around the area of San Marcos and Loma Lina Palajunoj on 21 and 24 May. INSIVIUMEH reported on 29 and 30 May that seismic station STG8 recorded moderate lahars descending the Rio San Isidro (a drainage to the Rio Tambor). The thick, pasty lahars transported blocks 1-3 m in diameter, branches, and tree trunks. They were 20 m wide and 1.5-2 m deep.

Weak to moderate explosions continued during June 2019 at a rate of 9-12 per day, producing plumes of ash and steam that rose 300-700 m above the Caliente crater. On 1 June explosions produced ashfall to the E over the areas of Calaguache, Las Marías and other nearby communities. Ash plumes commonly reached 3.0-3.3 km altitude and drifted W and SW, and block avalanches constantly descended the E and SE flanks from the dome at the top of Caliente. Ashfall was reported at the Santa María de Jesús community on 7 June. Ashfall to the W in San Marcos and Loma Linda Palajunoj was reported on 10, 15, 18, 20, and 22 June. Ashfall to the SE in Fincas Monte Claro and El Patrocinio was reported on 26 June. A few of the explosions on 28 June were heard up to 10 km away. On 29 June ash dispersed to the W again over the farms of San Marcos, Monte Claro, and El Patrocinio in the area of Palajunoj; the next day, ash was reported in Loma Linda and finca Monte Bello to the SW. The Washington VAAC reported ash emissions on 29 June that rose to 4.3 km and drifted W; two ash clouds were observed, one was 35 km from Santa Maria and the second drifted 55 km before dissipating.

With the onset of the rainy season, eight lahars were reported during June. The Rio Cabello de Ángel, a tributary of Río Nimá I (which flows into Rio Samalá) on the SE flank experienced lahars on 3, 5, 11, 12, 21, and 30 June (figure 98). The lahars were 15-20 m wide, 1-2 m deep, and carried branches, tree trunks and blocks 1-3 m in diameter. On 12 and 15 June, lahars descended the Río San Isidro on the SW flank. They were 1.5 m deep, 15-20 m wide and carried tree trunks and blocks up to 2 m in diameter.

Figure (see Caption) Figure 98. Activity at Santa Maria on 12 June 2019 included explosions with abundant ash and lahars. This lahar is in the Rio Nimá I, and started in the Rio Cabello de Ángel. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito, Semana del 08 al 14 de junio de 2019).

An increase in the frequency and intensity of seismic events was noted beginning on 28 June that lasted through 6 July 2019. Explosions occurred at a rate of 5-6 per hour, reaching 40-45 events per day instead of the 12-15 typical of previous months. Ash plumes rose to 3.5-3.8 km altitude and drifted W, SW, and S as far as 10 km, and ashfall was reported in San Marcos Palajunoj, Loma Linda villages, Monte Bello farms, El Faro, La Mosqueta, La Florida, and Monte Claro. Activity decreased after 7 July back to similar levels of the previous months. As a result of the increased activity during the first week of July, several small pyroclastic flows (also known as pyroclastic density currents or PDC's) were generated that traveled up to 1 km down the S, SE, and E flanks during 2-5 and 13 July, in addition to the constant block avalanches from the dome extrusion and explosions (figure 99). As activity levels decreased after 6 July, the ash plume heights lowered to 3.3 km altitude, while pulsating degassing continued from the summit dome, rising 100-500 m.

Figure (see Caption) Figure 99. An increase in explosive activity at Santa Maria during the first week of July 2019 resulted in several small pyroclastic flows descending the flanks, including one on 3 July 2019 (left). An ash emission on 19 July 2019 rose above the nearby summit of Santa Maria (right). Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA JULIO 2019, VOLCÁN SANTIAGUITO).

The Washington VAAC reported an ash plume on 2 July from a series of emissions that rose to 3.9 km altitude and drifted W. Satellite imagery on 4 July showed a puff of ash moving W from the summit at 4.3 km altitude. The next day an ash emission was observed in satellite imagery moving W at 4.9 km altitude. A plume on 11 July drifted W at 4.3 km for several hours before dissipating. Ashfall was reported on 2 July at the San Marcos farm and in the villages of Monte Claro and El Patrocinio in the Palajunoj area. On 4 and 6 July ash fell to the SW and W in San Marcos and Loma Linda Palajunoj. On 5 July there were reports of ashfall in Monte Claro and areas around San Marcos Palajunoj and some explosions were heard 5 km away. In Monte Claro to the SW ash fell on 7 July and sounds were heard 5 km away every three minutes. Incandescence was observed in the early morning on the SE and NE flanks of the dome. During 8 and 9 July, four to eight weak explosions per hour were noted and ash dispersed SW, especially over Monte Claro; pulsating degassing noises were heard every two minutes. Monte Bello and Loma Linda reported ashfall on 12, 16, 17, 19, and 20 July. On 15, 22, 26, and 29 July ash was reported in San Marcos and Loma Linda Palajunoj; 33 explosions occurred on 25 July. Two lahars were reported on 8 July. A strong one in the Rio San Isidro was more than 2 m deep, and 20-25 m wide with blocks as large as 3 m in diameter. A more moderate lahar affected Rio Cabello de Angel and was also 2 m deep. It was 15-20 m wide and had blocks 1-2 m in diameter.

Activity declined further during August 2019. Constant degassing continued from the S rim of the crater, but only occasional pulses of steam and gas rose from the central dome. Weak to moderate explosions occurred at a rate of 15-20 per day. White and gray plumes with small amounts of ash rose 300-800 m above the summit daily. Block avalanches descended to the base of the dome and sent fine ash particles down the SE and S flanks. Ashfall was common within 5 km of the summit, generally on the SW flank, near Monte Bello farm, Loma Linda village and San Marcos Palajunoj. Explosions rates decreased to 10-11 per day during the last week of the month. Degassing and ash plumes rose to 2.9-3.2 km altitude throughout the month.

On 1 August ash plumes drifted 10-15 km SW, causing ashfall in that direction. On 3 and 27 August ashfall occurred at Monte Claro and El Patrocinio in the Palajunoj area to the SW. On 7 and 31 August ashfall was reported in Monte Claro. San Marcos and Loma Linda Palajunoj reported ash on 11, 16, 19, and 23 August. On 21 August ashfall was reported to the SE around Finca San José. The Washington VAAC reported an ash plume visible in satellite imagery on 10 August 2019 drifting W at 4.3 km altitude a few kilometers from the summit which dissipated quickly. On 27 August a plume was observed 25 km W of the summit at 3.9 km altitude, dissipating rapidly. On 3 August a moderate lahar descended the Rio Cabello de Ángel that was 1 m deep, 15 m wide and carried blocks up to 1 m in diameter along with branches and tree trunks. A large lahar on 20 August descended Río Cabello de Ángel; it was 2-3 m high, 15 m wide and carried blocks 1-2 m diameter, causing erosion along the flanks of the drainage (figure 100).

Figure (see Caption) Figure 100. A substantial lahar at Santa Maria on 20 August 2019 sent debris down the Río Cabello de Ángel in the vicinity of El Viejo Palmar (left), the spectrogram of the seismic signal lasted for 2 hours and 16 minutes (top right), and the seismograph was saturated with the lahar signal in red (bottom right). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito, Semana del 17 al 23 de agosto de 2019).

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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).


Stromboli (Italy) — September 2019 Citation iconCite this Report

Stromboli

Italy

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

All times are local (unless otherwise noted)


Major explosions on 3 July and 28 August 2019; hiker killed by ejecta

Near-constant fountains of lava at Stromboli have served as a natural beacon in the Tyrrhenian Sea for at least 2,000 years. Eruptive activity at the summit consistently occurs from multiple vents at both a north crater area (N area) and a southern crater group (CS area) on the Terrazza Craterica at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano-island. Periodic lava flows emerge from the vents and flow down the scarp, sometimes reaching the sea; occasional large explosions produce ash plumes and pyroclastic flows. Thermal and visual cameras that monitor activity at the vents are located on the nearby Pizzo Sopra La Fossa, above the Terrazza Craterica, and at multiple locations on the flanks of the volcano. Detailed information for Stromboli is provided by Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) as well as other satellite sources of data; March-August 2019 is covered in this report.

Typical eruptive activity recorded at Stromboli by INGV during March-June 2019 was similar to activity of the past few years (table 6); two major explosions occurred in July and August with a fatality during the 3 July event. In the north crater area, both vents N1 and N2 emitted fine (ash) ejecta, occasionally mixed with coarser lapilli and bombs; most explosions rose less than 80 m above the vents, some reached 150 m. Average explosion rates ranged from 1 to 12 per hour. In the CS crater area continuous degassing and occasional intense spattering were typical at vent C, vent S1 was a low-intensity incandescent jet throughout the period. Explosions from vent S2 produced 80-150 m high ejecta of ash, lapilli, and bombs at average rates of 2-17 per hour.

After a high-energy explosion and lava flow on 25 June, a major explosion with an ash plume and pyroclastic flow occurred on 3 July 2019; ejecta was responsible for the death of a hiker lower down on the flank and destroyed monitoring equipment near the summit. After the explosion on 3 July, coarse ejecta and multiple lava flows and spatter cones emerged from the N area, and explosion rates increased to 4-19 per hour. At the CS area, lava flows emerged from all the vents and spatter cones formed. Explosion intensity ranged from low to very high with the finer ash ejecta rising over 250 m from the vents and causing ashfall in multiple places on the island. This was followed by about 7 weeks of heightened unrest and lava flows from multiple vents. A second major explosion with an ash plume and pyroclastic flow on 28 August reshaped the summit area yet again and scattered pyroclastic debris over the communities on the SW flank near the ocean.

Table 6. Summary of activity levels at Stromboli, March-August 2019. Low-intensity activity indicates ejecta rising less than 80 m, medium-intensity is ejecta rising less than 150 m, and high-intensity is ejecta rising over 200 m above the vent. Data courtesy of INGV.

Month North (N) Area Activity Central-South (CS) Area Activity
Mar 2019 Low- to medium-intensity explosions at both N1 and N2. Coarse-grained ejecta (lapilli and bombs) from N1, fine-grained ash mixed with coarse material from N2. Explosion rates of 3-12 per hour. Medium-intensity explosions from both S area vents, lapilli and bombs mixed with ash, 2-9 explosions per hour.
Apr 2019 Low- to medium-intensity explosions at both N1 and N2. Coarse-grained ejecta (lapilli and bombs) from N1, fine-grained ash from N2. Explosion rates of 5-12 per hour. Continuous degassing from C, low-intensity incandescent jets form S1, up to 4 emission points from S2, mostly fine-grained ejecta, 4-15 explosions per hour.
May 2019 Low- to medium-intensity explosions at both N1 and N2. Mostly fine-grained ejecta, occasionally mixed with coarser material. Explosion rates of 2-8 per hour. Continuous degassing from C, low-intensity incandescent jets form S1, low- to medium-intensity explosions from C, S1, and S2. Mostly fine-grained ejecta, occasionally mixed with coarser material. Explosion rates of 5-16 per hour.
June 2019 Low- to medium-intensity explosions at both N1 and N2. Mostly fine-grained ejecta, occasionally mixed with coarser material. Explosion rates of 1-12 per hour. Continuous degassing at C and sporadic short duration spattering events, low- to medium-intensity incandescent jets at S1, multiple emission points from S2. Ejecta of larger lapilli and bombs mixed with ash. Explosion rates of 2-17 per hour. High-energy explosion on 25 June.
Jul 2019 Low- to medium-intensity explosions at both N1 and N2. Coarse ejecta after major explosion on 3 July. Intermittent intense spattering. Explosions rates of 4-19 per hour. Lava flows from all vents. Major explosion and pyroclastic flow, 3 July, with fatality from falling ejecta. Lava flows from all vents. Continuous degassing and variable intensity explosions from low to very high (over 200 m). Coarse ejecta until 20 July; followed by mostly ash.
Aug 2019 Low- to medium-intensity explosions from the N area, coarse ejecta and occasional intense spattering. Explosion rates of 7-17 per hour. Lava flows. Low- to high-intensity explosions; ash ejecta over 200 m; ashfall during week 1 in S. Bartolo area, Scari, and Piscità. Major explosion on 28 August, with 4-km-high ash plume and pyroclastic flow; lava flows. Explosion rates of 4-16 per hour.

Thermal activity was low from March through early June 2019 as recorded in the MIROVA Log Radiative Power data from MODIS infrared satellite information. A sharp increase in thermal energy coincided with a large explosion and the emergence of numerous lava flows from the summit beginning in late June (figure 144). High heat-flow continued through the end of August and dropped back down at the beginning of September 2019 after the major 28 August explosion.

Figure (see Caption) Figure 144. Thermal activity at Stromboli was low and intermittent from 12 November 2018 through early June 2019, based on this MIROVA plot of thermal activity through August 2019. A spike in thermal energy in late June coincided with a major explosion on 3 July and the emergence of lava from the summit area. Heightened activity continued from 3 July through 28 August with multiple lava flows emerging from both crater areas. Courtesy of MIROVA.

Activity during March-June 2019. Activity was low during March 2019. Low- to medium-intensity explosions occurred at both vents N1 and N2 in the north area. Ejecta was mostly coarse grained (lapilli and bombs) from N1 and fine-grained ash mixed with some coarse material from N2. Intense spattering activity was reported from N2 on 29 March. Explosion rates were reported at 5-12 per hour. At the CS area, medium-intensity explosions from both south area vents produced lapilli and bombs mixed with ash at a rate of 2-9 explosions per hour.

During a visit to the Terrazza Craterica on 2 April 2019, degassing was visible from vents N1, N2, C, and S2; activity continued at similar levels to March throughout the month. Low- and medium-intensity explosions with coarse ejecta, averaging 3-12 per hour, were typical at vent N1 while low-intensity explosions with fine-grained (ash) ejecta occurred at a similar rate from N2. Continuous degassing was observed at the C vent, and low-intensity incandescent jets were present at S1 throughout the month. Multiple emission points from S2 (as many as 4) produced low- to medium-intensity explosions at rates of 4-14 explosions per hour; the ejecta was mostly fine-grained mixed with some coarse material. Frequent explosions on 19 April produced abundant pyroclastic material in the summit area.

Low to medium levels of explosive activity at all of the vents continued during May 2019. Emissions consisted mostly of ash occasionally mixed with coarser material (lapilli and bombs). Rates of explosion were 2-8 per hour in the north area, and 5-16 per hour in the CS Area. Explosions of low-intensity continued from all the vents during the first part of June at rates averaging 2-12 per hour, although brief periods of high-frequency explosions (more than 21 events per hour) were reported during the week of 10 June. Strong degassing was observed from crater C during an inspection on 12 June (figure 145); by the third week, continuous degassing was interrupted at C by sporadic short-duration spattering events.

Figure (see Caption) Figure 145. The Terrazza Craterica as seen from the Pizzo sopra la Fossa (above, near the summit) at Stromboli on 12 June 2019. In red are the two craters (N1 and N2) of the N crater area, in green is the CS crater area with 2 vents (C1 and C2) in the central crater and S2, the largest and deepest crater in the CS area, also with at least two vents. S1 is hidden by the degassing of crater C. Photograph by Giuseppe Salerno, courtesy of INGV (Report 25/2019, Stromboli, Bollettino Settimanale, 10/06/2019-16/06/2019).

Late on 25 June 2019, a high-energy explosion that lasted for 28 seconds affected vent C in the CS area. The ejecta covered a large part of the Terrazza Craterica, with abundant material landing in the Valle della Luna. An ash plume rose over 250 m after the explosion and drifted S. After that, explosion frequency varied from medium-high (17/hour) on 25 June to high (25/hour) on 28 June. On 29 June researchers inspected the summit and noted changes from the explosive events. Thermal imagery indicated that the magma level at N1 was almost at the crater rim. The magma level at N2 was lower and explosive activity was less intense. At vent C, near-constant Strombolian activity with sporadic, more intense explosions produced black ash around the enlarged vent. At vent S2, a pyroclastic cone at the center of the crater produced vertical jets of gas, lapilli, and bombs that exceeded 100 m in height (figure 146).

Figure (see Caption) Figure 146. A high-energy explosion at Stromboli late on 25 June 2019 affected vent C in the CS Area (top row). The ejecta covered a large part of the Terrazza Craterica. An ash plume rose over 250 m after the explosion and drifted S. On 29 June (bottom row) thermal imagery indicated that the magma level at N1 was almost at the crater rim. At vent C, near-constant Strombolian activity was interrupted with sporadic, more intense explosions. At vent S2, a pyroclastic cone at the center of the crater produced vertical jets of gas, lapilli, and bombs that exceeded 100 m in height. Photo 2f by L. Lodato, courtesy of INGV (Rep 27/2019, Stromboli, Bollettino Settimanale, 24/06/2019-30/06/2019).

Activity during July 2019. A large explosion accompanied by lava and pyroclastic flows affected the summit and western flank of Stromboli on 3 July 2019. Around 1400 local time an explosion from the CS area generated a lava flow that spilled onto the upper part of the Sciara del Fuoco. Just under an hour later several events took place: lava flows emerged from the C vent and headed E, from the N1 and N2 vents and flowed N towards Bastimento, and from vent S2 (figure 147). The emergence of the flows was followed a minute later by two lateral blasts from the CS area, and a major explosion that involved the entire Terrazza Craterica lasted for about one minute (figure 148). Within seconds, the pyroclastic debris had engulfed and destroyed the thermal camera located above the Terrazza Craterica on the Pizzo Sopra La Fossa and sent a plume of debris across the W flank of the island (figure 149). Two seismic stations were also destroyed in the event. The Toulouse VAAC reported a plume composed mostly of SO2 at 9.1 km altitude shortly after the explosion. They noted that ash was present in the vicinity of the volcano, but no significant ashfall was expected. INGV scientists observed the ash plume at 4 km above the summit.

Figure (see Caption) Figure 147. A major eruptive event at Stromboli on 3 July 2019 began with an explosion from the CS area that generated a lava flow at 1359 (left). About 45 minutes later (at 1443:40), lava flows emerged from all of the summit vents (right), followed closely by a major explosion. Courtesy of INGV (Eruzione Stromboli. Comunicato straordinario del 4 luglio 2019).
Figure (see Caption) Figure 148. A major explosion at Stromboli beginning at 1445 on 3 July 2019 was preceded by lava flows from all the summit vents in the previous 60 seconds (top row). This thermal camera (SPT) and other monitoring equipment on the Pizzo Sopra La Fossa above the vents were destroyed in the explosion (bottom row). Courtesy of INGV (Il parossismo dello Stromboli del 3 luglio 2019 e l'attività nei giorni successivi: il punto della situazione al 13 luglio 2019).
Figure (see Caption) Figure 149. The monitoring equipment at Stromboli on the Pizzo Sopra La Fossa above the summit was destroyed in the major explosion of 3 July 2019 (left, photo by F. Ciancitto). Most of the W half of the island was affected by pyroclastic debris after the explosion, including the town of Ginostra (right). Courtesy of INGV (Report 28/2019, Stromboli, Bollettino Settimanale, 01/07/2019 - 07/07/2019).

Two pyroclastic flows were produced as a result of the explosions; they traveled down the Sciara and across the water for about 1 km before collapsing into the sea (figure 150). A hiker from Sicily was killed in the eruption and a Brazilian friend who was with him was badly injured, according to a Sicilian news source, ANSA, and the New York Post. They were hit by flying ejecta while hiking in the Punta dei Corvi area, due W of the summit and slightly N of Ginostra, about 100 m above sea level according to INGV. Most of the ejecta from the explosion dispersed to the WSW of the summit. Fallout also ignited vegetation on the slopes which narrowly missed destroying structures in the town. Ejecta blocks and bombs tens of centimeters to meters in diameter were scattered over a large area around the Pizzo Sopra La Fossa and the Valle della Luna in the direction of Ginostra. Smaller material landed in Ginostra and was composed largely of blonde pumice, that floated in the bay (figure 151). The breccia front of the lava flows produced incandescent blocks that reached the coastline. High on the SE flank, the abundant spatter of hot pyroclastic ejecta coalesced into a flow that moved 200-300 m down the flank before cooling, crossing the path normally used by visitors to the summit (figure 152).

Figure (see Caption) Figure 150. At the time of the major explosion of Stromboli on 3 July 2019 people on a German ship located about 2 km off the northern coast captured several images of the event. (a) Two pyroclastic flows traveled down the Sciara del Fuoco and spread over the sea up to about 1 km from the coast. (b) The eruption column was observed rising several kilometers above the summit as debris descended the Sciara del Fuoco. (c) Fires on the NW flank were started by incandescent pyroclastic debris. The photos were taken by Egon Karcher and used with permission of the author by INGV. Courtesy of INGV (Il parossismo dello Stromboli del 3 luglio 2019 e l'attività nei giorni successivi: il punto della situazione al 13 luglio 2019).
Figure (see Caption) Figure 151. Pumice filled the harbor on 4 July 2019 (left) and was still on roofs (right) on 7 July 2019 in the small port of Ginostra on the SW flank of Stromboli after the large explosion on 3 July 2019. Photos by Gianfilippo De Astis, courtesy of INGV (Il parossismo dello Stromboli del 3 luglio 2019 e l'attività nei giorni successivi: il punto della situazione al 13 luglio 2019).
Figure (see Caption) Figure 152. A small lava flow high on the SE flank of Stromboli formed during the 3 July 2019 event from abundant spatter of hot pyroclastic ejecta that coalesced into a flow and moved 200-300 m down the flank before cooling, crossing the path normally used by visitors to the summit. Photo by Boris Behncke taken on 9 July 2019, courtesy of INGV (Il parossismo dello Stromboli del 3 luglio 2019 e l'attività nei giorni successivi: il punto della situazione al 13 luglio 2019).

INGV scientists inspected the summit on 4 and 5 July 2019 and noted that the rim of the Terrazza Craterica facing the Sciara del Fuoco in both the S and N areas had been destroyed, but the crater edge near the central area was not affected. In addition, the N area appeared significantly enlarged and deepened, forming a single crater where the former N1 and N2 vents had been located; an incandescent jet was active in the CS area (figure 153). Explosive activity declined significantly after the major explosions, although moderate overflows of lava continued from multiple vents, especially the CS area where the flows traveled about halfway down the southern part of the Sciara del Fuoco; lava also flowed E towards Rina Grande (about 0.5 km E of the summit). The main lava flows active between 3 and 4 July produced a small lava field along the Sciara del Fuoco which flowed down to an elevation of 210 m in four flows along the S edge of the scarp (figure 154). Additional block avalanches rolled to the coastline.

Figure (see Caption) Figure 153. The summit craters of Stromboli were significantly altered during the explosive event of 3 July 2019. The rim of the Terrazza Craterica facing the Sciara del Fuoco in both the CS and N areas was destroyed, but the crater edge near the CS area was not affected. In addition, the N area was significantly enlarged and deepened, forming a single crater where the former N1 and N2 vents had been located; an incandescent jet was active in the CS area. Courtesy of INGV (Report 28/2019, Stromboli, Bollettino Settimanale, 01/07/2019 - 07/07/2019).
Figure (see Caption) Figure 154. The main lava flows active between 3 and 4 July at Stromboli after the major explosion on 3 July 2019 produced a small lava field along the Sciara del Fuoco. Left: Aerial photo taken by Stefano Branca (INGV-OE) on 5 July; the yellow arrow shows a small overflow from the N crater area, the red arrow shows the largest overflow from the CS crater area. Right: Flows from the CS area traveled down to an elevation of 210 m in four flows along the S edge of the scarp. Additional block avalanches rolled to the coastline. Right photo by Francesco Ciancitto taken on 5 July 2019. Courtesy of INGV (Il parossismo dello Stromboli del 3 luglio 2019 e l'attività nei giorni successivi: il punto della situazione al 13 luglio 2019).

During the second week of July lava flows continued; on 8 July volcanologists reported two small lava flows from the CS area flowing towards the Sciara del Fuoco. A third flow was noted the following day. The farthest flow front was at about 500 m elevation on 10 July, and the flow at the center of the Sciara del Fuoco was at about 680 m. An overflow from the N area during the evening of 12 July produced two small flows that remained high on the N side of the scarp; lava continued flowing from the CS area into the next day. A new flow from the N area late on 14 July traveled down the N part of the scarp (figure 155).

Figure (see Caption) Figure 155. During the second week of July 2019 lava flows at Stromboli continued from both crater areas. Top left: Lava flows from the CS area flowed down the Sciara on 9 July while Strombolian activity continued at the summit, photo by P. Anghemo, mountain guide. Bottom left: A lava flow from the CS area at Stromboli is viewed from Punta dei Corvi during the night of 12-13 July 2019. Photo by Francesco Ciancitto. Right: The active flows on 10 July (in red) were much closer to the summit crater than they had been during 3-4 July (in yellow). Courtesy of INGV, top left and right photos published in Report 29/2019, Stromboli, Bollettino Settimanale, 08/07/2019 - 14/07/2019; bottom left photo published in 'Il parossismo dello Stromboli del 3 luglio 2019 e l'attività nei giorni successivi: il punto della situazione al 13 luglio 2019'.

A new video station with a thermal camera was installed at Punta dei Corvi, a short distance N of Ginostra on the SW coast, during 17-20 July 2019. During the third week of July lava continued to flow from the CS crater area onto the southern part of the Sciara del Fuoco, but the active flow area remained on the upper part of the scarp; block avalanches continuously rolled down to the coastline (figure 156). During visits to the summit area on 26 July and 1 August activity at the Terrazza Craterica was observed by INGV scientists. There were at least six active vents in the N area, including a scoria cone and an intensely spattering hornito; the other vents were ejecting coarse material in jets of Strombolian activity. In the CS area, a large scoria cone was clearly visible from the Pizzo, with two active vents generating medium- to high-intensity explosions rich in volcanic ash mixed with coarse ejecta (figures 157 and 158). Some of the finer-grained material in the jets reached 200 m above the vents. A second smaller cone in the CS area faced the southernmost part of the Sciara del Fuoco and produced sporadic low-intensity "bubble explosions." Effusive activity decreased during the last week of July; the active lava front was located at about 600 m elevation. Blocks continued to roll down the scarp, mostly from the explosive activity, and were visible from Punta dei Corvi.

Figure (see Caption) Figure 156. Lava continued to flow from the CS area at Stromboli during the third week of July 2019, although the active flow area remained near the top of the scarp. Block avalanches continued to travel down the scarp. Image taken by di Francesco Ciancitto from Punta dei Corvi on 19 July 2019. Courtesy of INGV (Report 30/2019, Stromboli, Bollettino Settimanale, 15/07/2019 - 21/07/2019).
Figure (see Caption) Figure 157. Thermal and visible images of Terrazza Craterica at the summit of Stromboli from the Pizzo Sopra La Fossa on 1 August 2019 showed significant changes since the major explosion on 3 July 2019. A large scoria cone was present in the CS area (left) and at least six vents from multiple cones were active in the N area (right). The active lava flow 'Trabocco Lavico' emerged from the southernmost part of the CS area (far left). Courtesy if INGV (Report 32/2019, Stromboli, Bollettino Settimanale, 29/07/2019 - 04/08/2019.
Figure (see Caption) Figure 158. At the summit of Stromboli on 1 August 2019 two active vents inside a large cone in the CS area generated medium- to high-intensity explosions rich in volcanic ash mixed with coarse ejecta (left). There were at least six active vents in the N area (right), including a scoria cone and an intensely spattering hornito; the other vents were ejecting coarse material in jets of Strombolian activity. Courtesy of INGV (Report 32/2019, Stromboli, Bollettino Settimanale, 29/07/2019 - 04/08/2019).

Activity during August 2019. A small overflow of lava on 4 August 2019 from the N area lasted for about 20 minutes and formed a flow that went a few hundred meters down the Sciara del Fuoco. Observations made at the summit on 7 and 8 August 2019 indicated that nine vents were active in the N crater area, three of which had scoria cones built around them (figure 159). They all produced low- to medium-intensity Strombolian activity. In the CS area, a large scoria cone was visible from the summit that generated medium- to high-intensity explosions rich in volcanic ash, which sometimes rose more than 200 m above the vent. Lava overflowing from the CS area on 8 August was confined to the upper part of the Sciara del Fuoco, at an elevation between 500 and 600 m (figure 160). Occasional block avalanches from the active lava fronts traveled down the scarp. Ashfall was reported in the S. Bartolo area, Scari, and Piscità during the first week of August.

Figure (see Caption) Figure 159. Nine vents were active in the N crater area of Stromboli on 7 August 2019, three of which had scoria cones built around them. They all produced low- to medium-intensity Strombolian activity (top). In the CS area (bottom), a large scoria cone was visible from the summit that generated medium- to high-intensity explosions rich in volcanic ash, which sometimes rose more than 200 m above the vent. Visible images taken by S. Consoli, thermal images taken by S. Branca. Courtesy of INGV (Report 33/2019, Stromboli, Bollettino Settimanale, 05/08/2019 - 11/08/2019).
Figure (see Caption) Figure 160. Multiple Lava flows were still active on the Sciara del Fuoco at Stromboli on 7 August 2019. Top images by INGV personnel S Branca and S. Consoli, lower images by A. Di Pietro volcanological guide. Courtesy of INGV (Report 33/2019, Stromboli, Bollettino Settimanale, 05/08/2019 - 11/08/2019).

Drone surveys on 13 and 14 August 2019 confirmed that sustained Strombolian activity continued both in the N area and the CS area. Lava flows continued from two vents in the CS area; they ceased briefly on 16 and 17 August but resumed on the 18th, with the lava fronts reaching 500-600 m elevation (figure 161). A fracture field located in the southern part of the Sciara del Fuoco was first identified in drone imagery on 9 July. Repeated surveys through mid-August indicated that about ten fractures were identifiable trending approximately N-S and ranged in length from 2.5 to 21 m; they did not change significantly during the period. An overflight on 23 August identified the main areas of activity at the summit. A NE-SW alignment of 13 vents within the N area was located along the crater edge that overlooks the Sciara del Fuoco. At the CS area, the large scoria cone had two active vents, there was a pit crater, and two smaller scoria cones. A 50-m-long lava tube emerged from one of the smaller lava cones and fed two small flows that emerged at the top of the Sciara del Fuoco (figure 162).

Figure (see Caption) Figure 161. Detail of a vent at Stromboli on 14 August 2019 located in the SW part of the Sciara del Fuoco at an elevation of 730 m. Flow is tens of meters long. Courtesy of INGV (COMUNICATO DI DETTAGLIO STROMBOLI del 20190816 ORE 17:05 LT).
Figure (see Caption) Figure 162. Thermal and visual imagery of the summit of Stromboli on 23 August 2019 revealed a NE-SW alignment of 13 vents within the N area located along the crater edge that overlooks the Sciara del Fuoco. At the CS area, the large scoria cone had two active vents (1 and 2), there was a pit crater (3), and two smaller scoria cones (4). A 50-m-long lava tube formed from one of the smaller lava cones (5) and fed two small flows that emerged at the top of the Sciara del Fuoco. Photos by L. Lodato and S. Branca, courtesy of INGV (Report 35/2019, Stromboli, Bollettino Settimanale, 19/08/2019 - 25/08/2019).

INGV reported a strong explosion from the CS area at 1217 (local time) on 28 August 2019. Ejecta covered the Terrazza Craterica and sent debris rolling down the Sciara del Fuoco to the coastline. A strong seismic signal was recorded, and a large ash plume rose more than 2 km above the summit (figure 163). The Toulouse VAAC reported the ash plume at 3.7-4.6 km altitude, moving E and rapidly dissipating, shortly after the event. Once again, a pyroclastic flow traveled down the Sciara and several hundred meters out to sea (figures 164). The entire summit was covered with debris. The complex of small scoria cones within the N area that had formed since the 3 July explosion was destroyed; part of the N area crater rim was also destroyed allowing lava to flow down the Sciara where it reached the coastline by early evening.

Figure (see Caption) Figure 163. A major explosion at Stromboli on 28 August 2019 produced a high ash plume and a pyroclastic flow. The seismic trace from the STR4 station (top left) indicated a major event. The ash plume from the explosion was reported to be more than 2 km high (right). The thermal camera located at Stromboli's Punta dei Corvi on the southern edge of the Sciara del Fuoco captured both the pyroclastic flow and the ash plume produced in the explosion (bottom left). Seismogram and thermal image courtesy of INGV (INGVvulcani blog, 30 AGOSTO 2019INGVVULCANI, Nuovo parossismo a Stromboli, 28 agosto 2019). Photo by Teresa Grillo (University of Rome) Courtesy of AIV - Associazione Italiana di Vulcanologia.
Figure (see Caption) Figure 164. A pyroclastic flow at Stromboli traveled across the sea off the W flank for several hundred meters on 28 August 2019 after a major explosion at the summit. Photo by Alberto Lunardi, courtesy of INGV (5 SETTEMBRE 2019INGVVULCANI, Quando un flusso piroclastico scorre sul mare: esempi a Stromboli e altri vulcani).

At 1923 UTC on 29 August a lava flow was reported emerging from the N area onto the upper part of the Sciara del Fuoco; it stopped at mid-elevation on the slope. About 90 minutes later, an explosive sequence from the CS area resulted in the fallout of pyroclastic debris around Ginostra. Shortly after midnight, a lava flow from the CS area traveled down the scarp and reached the coast by dawn, but the lava entry into the sea only lasted for a short time (figure 165).

Figure (see Caption) Figure 165. Lava flows continued for a few days after the major explosion of 28 August 2019 at Stromboli. Left: A lava flow emerged from the N crater area on 29 August 2019 and traveled a short distance down the Sciara del Fuoco. Incandescent blocks from the flow front reached the ocean. Photo by A. DiPietro. Right: A lava flow that emerged from the CS crater area around midnight on 30 August 2019 made it to the ocean around dawn, as seen from the N ridge of the Sciara del Fuoco at an altitude of 400 m. Photo by Alessandro La Spina. Both courtesy of INGV. Left image from 'COMUNICATO DI ATTIVITA' VULCANICA del 2019-08-29 22:20:06(UTC) – STROMBOLI', right image from INGVvulcani blog, 30 AGOSTO 2019 INGVVULCANI, 'Nuovo parossismo a Stromboli, 28 agosto 2019'.

An overflight on 30 August 2019 revealed that after the explosions of 28-29 August the N area had collapsed and now contained an explosive vent producing Strombolian activity and two smaller vents with low-intensity explosive activity. In the CS area, Strombolian activity occurred at a single large crater (figure 166). INGV reported an explosion frequency of about 32 events per hour during 31 August-1 September. The TROPOMI instrument on the Sentinel-5P satellite captured small but distinct SO2 plumes from Stromboli during 28 August-1 September, even though they were challenging to distinguish from the larger signal originating at Etna (figure 167).

Figure (see Caption) Figure 166. A 30 August 2019 overflight of Stromboli revealed that after the explosions of 28-29 August the N area had collapsed and now contained a single explosive vent producing Strombolian activity and two smaller vents with low intensity explosive activity. In the CS area, a single large crater remained with moderate Strombolian activity. No new lava flows appeared on the Sciara del Fuoco, only cooling from the existing flows was evident. Courtesy of INGV (Report 35.6/2019, Stromboli, Daily Bulletin of 08/31/2019).
Figure (see Caption) Figure 167. Small but distinct SO2 signals were recorded from Stromboli during 28 August through 1 September 2019; they were sometimes difficult to discern from the larger signal originating at nearby Etna. Courtesy of NASA Goddard Space Flight Center.

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

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy, (URL: http://www.ct.ingv.it/en/); 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/); 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/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/info/vaac/); AIV, Associazione Italiana di Vulcanologia (URL: https://www.facebook.com/aivulc/photos/a.459897477519939/1267357436773935; ANSA.it, (URL: http://www.ansa.it/sicilia/notizie/2019/07/03/-stromboli-esplosioni-da-cratere-turisti-in-mare); The New York Post, (URL: https://nypost.com/2019/07/03/dozens-of-people-dive-into-sea-to-escape-stromboli-volcano-eruption-in-italy/).

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Bulletin of the Global Volcanism Network - Volume 42, Number 10 (October 2017)

Managing Editor: Edward Venzke

Chillan, Nevados de (Chile)

Intermittent ash emissions from new craters along the E flanks of Volcáns Nuevo and Arrau persist through September 2017

Dieng Volcanic Complex (Indonesia)

Three phreatic eruptions at Sileri Crater; deaths due to helicopter crash involved in evacuations

Etna (Italy)

Extensive lava flows during February-May 2017; new summit crater emerges

Fuego (Guatemala)

Six eruptive episodes with Strombolian fountains, lava flows, ash plumes, and pyroclastic flows during July-December 2016

Heard (Australia)

Expedition visit in March-April 2016, intermittent eruptive activity through September 2017

Ibu (Indonesia)

Occasional weak ash explosions and thermal anomalies during April-August 2017

Marapi (Indonesia)

Four short ash explosions on 4 June 2017

Tolbachik (Russia)

Eruption that started in late November 2012 ends by mid-September 2013

Ubinas (Peru)

Intermittent ash explosions during September 2016-February 2017

Wrangell (United States)

Occasional steam plumes and wind-blown ash, but no recent eruptive activity



Nevados de Chillan (Chile) — October 2017 Citation iconCite this Report

Nevados de Chillan

Chile

36.868°S, 71.378°W; summit elev. 3180 m

All times are local (unless otherwise noted)


Intermittent ash emissions from new craters along the E flanks of Volcáns Nuevo and Arrau persist through September 2017

Nevados de Chillán, in the Chilean Central Andes, is a complex of late-Pleistocene to Holocene stratovolcanoes constructed along a NNW-SSE trend (figure 5). The Nuevo and Arrau craters, active during 1906-1945 and 1973-1986, respectively, are adjacent vents on the NW cone of a large stratovolcano complex 5 km SE of Cerro Blanco; the summit 1 km SE of Arrau is named Volcán Viejo (figure 6). A short eruption during August-September 2003 created a new fissure vent between the Nuevo and Arrau craters (BGVN 29:03, figure 3). Increased seismicity and fumarolic activity were recorded during December 2015, and a new eruption started with a phreatic explosion and ash emission on 8 January 2016 from a new crater on the E flank of Nuevo cones (BGVN 41:06). This report adds information about the beginning of the event and continues with activity through September 2017. Information for this report is provided by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN) - Observatorio Volcanológico de Los Andes del Sur (OVDAS), Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Corporación Ciudadana Red Nacional de Emergencia (RNE), and by the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 5. This photograph, taken by an astronaut aboard the International Space Station on 11 June 2013, shows three of the largest features of the Nevados de Chillán volcanic complex: Cerro Blanco, Volcán Nuevo, and Volcán Viejo. North is to the lower right. New eruptive activity began in January 2016 from craters located in between Volcán Nuevo and Volcán Viejo.
Figure (see Caption) Figure 6. Detailed location map identifying features of the Nevados de Chillán complex, and the warning zones around the volcano. The colors represent High (maroon), Medium (orange-red), and Low (gold) probabilities of pyroclastic material accumulation of more than one centimeter during a VEI 6 event. Circles with hatch marks inside represent craters. Stars are "Centro de emission,", blue ovals are hot springs. Diagonal cross-hatch is the area most susceptible to pyroclastic material greater than 6.4 cm in diameter in a radius of about 4 km around the active vents. The blue grid lines are spaced four km apart. Courtesy of SERNAGEOMIN, excerpted from Orozco et al. (2016).

Ash emissions at Nevados de Chillán began on 8 January 2016, and were intermittent through September 2017. Four new craters emerged in a NNE trend along the flanks of Volcán Nuevo and Volcán Arrau; two eventually merged into a single 100-m-diameter crater. Most plumes were brief pulses of steam and ash that rose 200-300 m above the craters. Larger events sent a few plumes as high as 2.2 km above the summit (to 5.4 km altitude). Strong prevailing winds quickly dissipated most ash plumes. Periods of multiple small explosions lasted for 1-2 weeks, separated by periods of relative quiet characterized by only steam-and-gas emissions from the active craters and nearby fumarolic centers. The first observable incandescence at the craters was noted in early March 2016. Incandescent bombs were thrown 300 m above the craters during July and September 2016, and 500 m high during March-May 2017 when blocks also fell with 500 m of the craters.

Activity during 2016. After the first explosion with ash emissions on 8 January 2016, nine more pulses of ash were emitted the next day, and small sporadic emissions were reported in the following days (figure 7). OVDAS researchers flew over the volcano on 9 January and concluded that the explosions came from a new crater on the E slope of Volcán Nuevo, about 40 m from the edge of the crater. Researchers from the University of Cambridge who visited the site on 13 January observed continuous degassing at the new 20-m-wide crater. The Buenos Aires VAAC noted puffs of steam and gas dissipating a few hundred meters above the summit (at 3.7 km altitude) in satellite imagery on 16 January 2016. ONEMI reported an ash emission on 29 January that originated from the Arrau crater (see figure 6). During an overflight on 30 January, OVDAS researchers saw occasional explosions from the new crater at Nuevo, as well as activity at a new 30-m-diameter crater about 50 m from the Arrau crater on its NE flank (figure 8). Several fumaroles were also identified on the E flank of Arrau crater.

Figure (see Caption) Figure 7. Ash emission at Nevados de Chillán on 9 January 2016 from the edifice that contains the Nuevo and Arrau craters. The peak to the right is Volcán Viejo. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Advierten nuevo pulso volcánico en el Nevados de Chillán, 9 January 2016).
Figure (see Caption) Figure 8. Photograph showing the Arrau crater at Nevados de Chillán observed during a flyover on 30 January 2016. Ash emissions from a new crater on the NE flank (at right) were reported on 29 January. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Otro cráter más se formó en Nevados de Chillán, 31 January 2016).

During the first two weeks of February 2016, there were 175 episodes of discrete tremor; webcams recorded explosions that ejected material from both craters. The Buenos Aires VAAC reported a brief ash emission on 3 February that dissipated quickly near the summit. During an overflight on 11 February coordinated with ONEMI, scientists identified a third crater, which created a 150-m-long NNE trend with the other two active craters identified during January. During the second half of February, emissions consisted mostly of steam plumes rising no more than 300 m above the crater.

Activity during March 2016 was characterized by steam plumes rising from the active craters; on 3 March, however, a small ash emission was observed. Incandescence was observed in the crater area on the night of 9 March. SERNAGEOMIN reported the beginning of an episode of long-period (LP) seismicity on 18 March, with a pulsating pattern of 3-4 events per minute. During the second half of March, LP and tremor activity was associated with ash emissions. Notably, a low-energy tremor on 30 March lasted for several hours, and concurrently a dense ash plume rose 200 m.

Ash emissions were observed on 7, 8, 9, 18, and 19 April 2016. Plumes were reported rising 400 m on 8 April, and 200 m on 18 and 19 April. Incandescence was observed along with the ash on 18 April. A significant explosion on 9 May 2016 generated an ash plume that rose 1,700 m above the summit (figure 9). The Buenos Aires VAAC reported the ash plume at 3.9 km altitude (700 m above the summit) drifting SE. An overflight by OVDAS on 9 May confirmed the presence of three active craters on the active summit, with the central one having enlarged by 50% since the previous overflight on 11 February. Only pulsating steam emissions were observed in the webcam during the remainder of May and June 2016.

Figure (see Caption) Figure 9. An ash plume rises 1,700 m above the active crater area at Nevados de Chillán after an explosion in the early morning of 9 May 2016. Courtesy of SERNAGEOMIN.

Only steam emissions were reported during the first half of July 2016, but on 21 July an ash-laden emission sent incandescent bombs 300 m above the crater. The Buenos Aires VAAC reported that the webcam showed an ash emission to 3.4 km altitude (200 m above the craters) that day. Webcam Images obtained on 25 July showed debris from an explosion scattered 300 m down the NE flank. During the next few days, ash emissions were inferred from the seismic tremors, but weather conditions prevented direct observations.

During the first two weeks of August 2016, 14 explosions were recorded from the new craters on the E flanks of Nuevo and Arrau. The largest explosion, on 8 August, sent an ash plume 2 km above the crater, according to SERNAGEOMIN (figure 10). The Buenos Aires VAAC reported brief ash emissions on 1, 4, 8, and 9 August at altitudes of 3.7, 3.4, 4.3, and 3.7 km altitude, respectively. Fresh ashfall was visible on the flanks during a flyover on 12 August (figure 11). On the few days when the weather permitted observation of the summit during the remainder of the month, only steam plumes were observed rising no more than 400 m above the crater.

Figure (see Caption) Figure 10. An ash emission at Nevados de Chillán rises 2 km above the active craters on 8 August 2016. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Volcán Nevados de Chillán presenta nuevo pulso eruptive, 8 August 2016).
Figure (see Caption) Figure 11. Fresh ashfall coats the flanks of the active summit at Nevados de Chillán on 12 August 2016, after a large explosion on 8 August. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Registro aéreo muestra actual pulso eruptivo de volcán Nevados de Chillán, 12 August 2016).

Pulsating steam plumes, interrupted by periodic ash emissions, were typical during September 2016. During the first two weeks of the month, 37 recorded explosions were characterized by a high concentration of particulate material. The largest explosion, during the evening of 1 September, generated incandescent bombs for 20 minutes. Incandescence was observed during nighttime explosions a number of times. The Buenos Aires VAAC noted a pilot report of an ash cloud moving SW at 5.2 km altitude on 2 September. They also reported a weak emission of steam and gas with possible diffuse ash visible in the webcam that day. Another pilot report on 6 September indicated an ash cloud moving NE at 6.4 km altitude from a brief but intense emission event around 1420 UTC (figure 12). SERNAGEOMIN noted in their late September report that there had been six explosive episodes since January 2016, with the latest one that occurred during 1-10 September being the strongest.

Figure (see Caption) Figure 12. An ash plume rises from Nevados de Chillán on 6 September 2016. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Volcán Nevados de Chillán registró nuevo pulso eruptive, 6 September 2016).

Explosive activity was recorded on 3, 7, and 8 October 2016 by SERNAGEOMIN; The events were low-energy episodes that emitted small quantities of ash. The Buenos Aires VAAC noted a pilot report on 3 October of an ash cloud moving SE near the summit. It was visible in the webcam but not in satellite imagery, and dissipated quickly. The tallest emission of those days rose to 300 m above the crater on 7 October. During an overflight on 22 October, the continued presence of the three craters along the E flanks of Nueva and Arrau reported previously was confirmed. In addition, the existence of a fourth crater was noted along the same trend as the others. The Buenos Aires VAAC noted ash emissions on 26 and 28 October rising to between 3.7 and 4.3 km altitude and dissipating quickly near the summit.

Seismic activity during the first half of November 2016 included 17 explosions from the active craters. An explosion on 18 November generated an ash plume that rose 1.2 km (figure 13). The Buenos Aires VAAC noted a pilot report of possible ash emissions between 4.6 and 6.1 km altitude on 17 and 27 November, although neither were identified in satellite data.

Figure (see Caption) Figure 13. An ash emission rises 1.2 km above the active crater area at Nevados de Chillán on 18 November 2016. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Sernageomin emite reporte especial por actividad volcánica del complejo Nevados de Chillán, 18 November 2016).

Explosions associated with LP and tremor seismicity continued into December 2016. There were 14 explosive seismic events during the second half of the month, reported by SERNAGEOMIN. The largest occurred on 28 December. The Buenos Aires VAAC noted pilot reports of ash emissions that dissipated near the summit on 13, 28, and 29 December.

Activity during January-September 2017. Explosions related to LP and tremor seismicity increased again on 5 January 2017. The Buenos Aires VAAC reported a dark fumarolic plume drifting E at 4.5 km altitude on 6 January that was observed by a pilot and in the webcam. On 11 and 13 January, the webcam showed sporadic puffs of ash that dissipated very quickly. The largest event occurred on 15 January; the Buenos Aires VAAC reported a narrow plume of ash in satellite imagery at 3.9 km altitude moving W. The webcam also showed sporadic and small puffs that dissipated quickly. An event on 16 January produced an emission that rose 700 m above the crater according to SERNAGEOMIN. This was the last LP-associated explosion of the month. Scientists on a 20 January overflight noted low-intensity steam plumes from the Nuevo and Arrau craters, and from the Chudcún crater which formed in 2003 between them (see figure 6). Yellow and ocher-colored areas, indicating the presence of precipitated sulfur, were visible around the fumaroles and craters.

Low-level degassing rising less than 200 m above the crater was the only surface activity observed during February 2017. A new stage of explosive activity began on 7 March 2017 with emissions that rose as high as 300 m above the crater. The Buenos Aires VAAC noted a pilot report of an ash plume at 3.7 km altitude, and a short-lived puff of ash seen in the webcam. On 11 March, eight explosions sent incandescent blocks up to 0.5 km from the active craters, and emissions rose to 500 m above the crater. Another series of eight explosions on 14 March produced incandescent material and sent an ash plume 1.5 km above the craters. The Buenos Aires VAAC reported intermittent emissions rising up to 4.9 km altitude that day, followed by continuing steam emissions. The following day they noted a small plume near the volcano at 3.9 km altitude visible in satellite data.

During a flyover on 15 March, OVDAS scientists noted that two of the craters (craters 3 and 4) had merged into a single crater 100 m in diameter (figure 14). They also observed five explosions within the space of an hour, the highest resulting plume rose 900 m above the active crater. Webcam images during 16-17 March showed ash emissions rising to 2 km above the crater. The Buenos Aires VAAC reported an ash emission visible in satellite imagery at 5.5 km altitude moving SW on 16 March. For the remainder of the month, only weak degassing under 200 m above the crater was observed. Beginning on 24 March, low-level incandescence at night was reported for the rest of the month.

Figure (see Caption) Figure 14. OVDAS scientists photographed two merged craters (3+4) at Nevados de Chillán on 15 March 2017. They also witnessed five explosions from one crater within an hour (yellow arrow). Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Complejo Volcánico Nevados de Chillán tiene cráter de 100 metros de diámetro, 24 March 2017).

Between 1 and 12 April 2017, there were 56 intermittent explosions marking a new phase of activity according to SERNAGEOMIN. The webcams around the complex imaged emissions up to 3 km above the crater throughout the month. The Buenos Aires VAAC reported sporadic emissions of ash visible in the webcam on 3 and 6-8 April. A faint emission at 3.7 km altitude was spotted in satellite imagery on 10 April. From 16 to 30 April, there were 79 intermittent explosions recorded. During dusk and dawn, incandescent material was observed traveling 600 m down the flanks, with some episodes lasting for 60 minutes. The Buenos Aires VAAC reported a brief ash emission and incandescent material visible in the webcam on 17 April, and sporadic ash emissions that rose to 3.9 km altitude on 21, 29, and 30 April (figure 15).

Figure (see Caption) Figure 15. An ash emission on 30 April 2017 at Nevados de Chillán rose to 3.9 km altitude (700 m above the craters), and was photographed by a twitter user near the volcano. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Nuevo pulso eruptivo de volcán Nevados de Chillán preocupa en la región del Bío Bío, 30 April 2017).

Nine intermittent explosions occurred between 1 and 11 May 2017. The webcams showed emissions from the explosions rising generally 300 m above the craters according to SERNAGEOMIN. Intermittent explosions increased again during 27-31 May. Emissions rose to 1.5 km above the craters and incandescent blocks could be seen traveling 600 m down the flank. Periods of constant incandescence lasted for 30 minutes.

This explosive episode continued into June 2017, with 23 intermittent explosions between 1 and 5 June. The largest emission event on 5 June sent a plume 2.2 km above the craters (figure 16). The Buenos Aires VAAC observed the ash plume at 4.6 km altitude in satellite imagery. During 6-15 June, only steam emissions rising to 300 m were reported. Intermittent explosions on 20, 22, 25, and 26 June produced plumes that rose only 200 m above the craters; cloudy weather prevented observation from the webcams during these events.

Figure (see Caption) Figure 16. Twitter users in Chile shared this image of an ash plume rising from the active craters at Nevados de Chillán with regional authorities on 5 June 2017. The Buenos Aires VAAC reported the plume rising to 4.6 km altitude. Courtesy of Corporación Ciudadana Red Nacional de Emergencia (RNE) (Volcán Nevados de Chillán emite nuevo pulso eruptive, 5 June 2017).

No explosive events were observed in the webcams during the first half of July 2017; only steam plumes rising 200 m were reported. A single low-energy explosion was recorded on 31 July; the emission rose to only 100 m above the crater. During August 2017, there were 83 intermittent explosions associated with ash emissions recorded by SERNAGEOMIN. The emissions rose to about 300 m above the active craters; a few larger emissions rose 1,000 m. The Buenos Aires VAAC noted a pilot report of ash emissions on 17 August; the webcam captured a brief emission that dissipated rapidly.

About 150 intermittent explosions were reported during September 2017. The highest plumes, generally composed of steam and ash, rose 2,000 m above the craters. The Buenos Aires VAAC observed a narrow plume of ash in satellite imagery moving N at 3.9 km altitude and dissipating rapidly on 15 September, and a similar plume moving SE near the summit on 26 September 2017.

Reference: Orozco, G.; Jara, G.; Bertin, D. 2016. Peligros del Complejo Volcánico Nevados de Chillán, Región del Biobío. Servicio Nacional de Geología y Minería, Carta Geológica de Chile, Serie Geología Ambiental 28: 34 p., 1 mapa escala 1:75.000. Santiago.

Geologic Background. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

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/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637/1671, Santiago, Chile (URL: http://www.onemi.cl/); Corporación Ciudadana Red Nacional de Emergencia (RNE, Citizen Corporation National Emergency Network), Avda. Vicuña Mackenna Nº3125, San Joaquín, Santiago de Chile, Chile (URL: http://www.reddeemergencia.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php?lang=es).


Dieng Volcanic Complex (Indonesia) — October 2017 Citation iconCite this Report

Dieng Volcanic Complex

Indonesia

7.2°S, 109.879°E; summit elev. 2565 m

All times are local (unless otherwise noted)


Three phreatic eruptions at Sileri Crater; deaths due to helicopter crash involved in evacuations

Located on an elevated plateau in central Java NW of Yogyakarta (figure 4), multiple craters within the Dieng Volcanic Complex (figure 5) have been intermittently active over the past 200 years. Brief phreatic eruptions took place at Sibanteng crater on 15 January 2009 (BGVN 34:04) and at Sileri crater on 26 September later that year (BGVN 34:08). Increased unrest during March-April 2013 (BGVN 38:08) consisted of elevated volcanic gas emissions from Timbang Crater that resulted in an increase in the Alert Level to as high as 3 on 27 March, then back to Level 2 on 8 May. There was a precautionary evacuation of local villages, but no eruption took place. Regular monitoring is done by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

Figure (see Caption) Figure 4. Topographic terrain map of central Java showing the Dieng Volcanic Province to the NW of Gunung Sumbing and Gunung Sindoro volcanoes. The volcano indicated by a red symbol N of Yogyakarta is Merapi. Courtesy of Peakery.
Figure (see Caption) Figure 5. Topographic terrain map of the Dieng Volcanic Province on the Dieng plateau of central Java. The notable cone at bottom center is Bisma; the crater with a lake at center is Merdada, adjoining Kawah Sikidang to the SE. The frequently active Sileri area is immediately W of the more noticeable Pagerkandang crater N of Merdada. Courtesy of Peakery.

The alert status remained at Level 2 for about 15 months following the hazardous gas emissions in 2013. On 11 August 2014 the PVMBG noted that, due to decreased activity and no observable flow of gas in high concentrations from the crater, the Alert Level was lowered to 1 (on a scale of 1-4). No further activity was reported until late April 2017.

A phreatic event from Sileri Crater at 1303 on 30 April 2017 ejected material 10 m high and 1 m past the crater edge, forming a 1-2 mm thick deposit. Another emission at 0941 on 24 May consisted of gas and black "smoke" that rose 20 m.

The Disaster Management Authority, Badan Nacional Penanggulangan Bencana (BNPB), reported that there had been another phreatic eruption from the Sileri Crater lake at 1154 on 2 July 2017, ejecting mud and material 150 m high, and 50 m to the N and S. The event injured 11 of 18 tourists that were near the crater. According to a news article a helicopter on the way to assist with evacuations after the event crashed, killing all eight people (four crewmen and four rescuers) on board. PVMBG scientists visited the next day and observed weak white emissions rising 60 m.

PVMBG reported that during 8 July-14 September 2017 measurements indicated an increase in water temperature at Sileri Crater lake from 90.7 to 93.5°C. Soil temperatures also increased, from 58.6 to 69.4°C. At Timbang Crater temperatures in the lake increased from 57.3 to 62.7°C, and in the soil they decreased from 18.6 to 17.2°C. The report noted that conditions at Timbang Crater were normal.

Temperature increases at Sileri, along with tremor detected during 13-14 September, prompted PVMBG to raise the Alert Level to 2 (on a scale of 1-4). PVMBG warned the public to stay at least 1 km away from the crater rim, and for residents living within that radius to evacuate. However, after 20 September tremor and water temperatures both declined. The Alert Level was lowered back to 1 on 2 October, with a warning to stay at least 100 m from the crater rim.

Geologic Background. The Dieng plateau in the highlands of central Java is renowned both for the variety of its volcanic scenery and as a sacred area housing Java's oldest Hindu temples, dating back to the 9th century CE. The Dieng volcanic complex consists of two or more stratovolcanoes and more than 20 small craters and cones of Pleistocene-to-Holocene age over a 6 x 14 km area. Prahu stratovolcano was truncated by a large Pleistocene caldera, which was subsequently filled by a series of dissected to youthful cones, lava domes, and craters, many containing lakes. Lava flows cover much of the plateau, but have not occurred in historical time, when activity has been restricted to minor phreatic eruptions. Toxic gas emissions are a hazard at several craters and have caused fatalities. The abundant thermal features and high heat flow make Dieng a major geothermal prospect.

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/); Peakery (URL: https://peakery.com/).


Etna (Italy) — October 2017 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Extensive lava flows during February-May 2017; new summit crater emerges

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years. Lava flows, explosive eruptions with ash plumes, and lava fountains commonly occur from its major summit crater areas, the North East Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the South East Crater (SEC) (formed in 1978), and the New South East Crater (NSEC) (formed in 2011). A new crater, the SEC3 or "saddle cone" emerged during early 2017 from the saddle between SEC and NSEC.

After a major explosive event in December 2015 (BGVN 42:05), activity subsided for a few months before renewed Strombolian eruptions and lava flows affected all of the summit craters during late May 2016 (BGVN 42:09). These events were followed by a lengthy period of subsidence and intense fumarolic activity across the summit that lasted until a new eruptive episode began at the end of January 2017. The Osservatorio Etneo (OE), which provides weekly reports and special updates on activity, is run by the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV). This report uses information from INGV to provide a detailed summary of events between January and August 2017.

Summary of January-August 2017 Activity. Minor ash emissions began from a new vent in the saddle between NSEC and SEC on 20 January 2017, followed by Strombolian activity a few days later. Activity intensified at the end of February when the first of several lava flows emerged from this vent, and then from several other vents on the S flank of the new, rapidly growing cone during March and April. By mid-March 2017, Strombolian activity, ash emissions, and lava flows had created a cone higher than the adjacent NSEC and SEC cones. The last effusive episode at the end of April 2017 sent flows down both the N and S flanks of the new cone from multiple vents. Intermittent weak Strombolian activity at the new summit area was associated with abrupt tremor amplitude increases during May, but no additional flows were reported. During June-August, fumarolic activity persisted at several crater areas, and minor ash emissions were observed a few times, but no major eruptive activity took place. The sharp increase in heat flow resulting from the lava flows of March and April 2017 are clearly visible in the MIROVA thermal anomaly plot of log radiative power for the year ending on 12 October 2017 (figure 186).

Figure (see Caption) Figure 186. Thermal anomalies at Etna (log radiative power) identified by the MIROVA system for the year ending on 12 October 2017. Major effusive eruptive events with lava flows and Strombolian activity occurred from late February through April 2017. Courtesy of MIROVA.

Activity during January-February 2017. Sporadic incandescence continued from the 7 August 2016 vent on the E side of VOR during January 2017, and minor ash plumes rose from the NSEC "saddle" vent on 20 January. Modest Strombolian activity began at the saddle vent that on 23 January and continued into February (figure 187). Small bombs were ejected onto the flank of NSEC and minor ash plumes quickly dissipated in the high winds near the summit. Also during February, steady subsidence continued at BN, especially in the BN-1 area (see figure 185, BGVN 42:09), where active degassing with minor amounts of ash was observed on 1 February (figure 187). Debris deposits from Strombolian activity at the saddle vent covered the S side of the pyroclastic cone and travelled to its base during the end of February.

Figure (see Caption) Figure 187. Activity at Etna during the first week of February 2017. Left: Strombolian activity at the NSEC saddle vent; photo by B. Behncke. Right: degassing with minor ash emissions from the vent at the bottom of BN-1; photo by M. Ponte. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 30/01/2017-05/02/2017, No. 6/2017).

During the late afternoon of 27 February, the Strombolian activity that began on 20 January from the saddle vent between SEC and NSEC rapidly intensified, and lava emerged from the vent and flowed down the S flank of SEC (figure 188). It slowed after reaching the flat ground at the base of the cone, and expanded slowly SE toward the older cones of Monte Frumento Supino. Intense activity that evening sent shards and bombs 200 m above the vent while the flow continued. Ash from the Strombolian activity dispersed NE, with minor ashfall reported in Linguaglossa and Zafferana. A new cone of pyroclastic material that formed around the saddle vent quickly grew to about the same elevation as the NSEC and SEC crater rims, approximately 3,290 m (figure 189). The lava continued to flow until 2 March 2017, when it stopped at about 2,750 m elevation with an overall length of 2,180 m, covering an area of 306 x 103 m2, for a total volume of slightly less than 1 x 106 m3.

Figure (see Caption) Figure 188. An outline of the new lava flow at Etna that emerged from the saddle vent located between NSEC and SEC on 27 February 2017. It rapidly advanced down the steep S flank of SEC. Base map is a DEM image created by the INGV Cartography Laboratory. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 27/02/2017-05/03/2017, No. 10/2017).
Figure (see Caption) Figure 189. Strombolian activity, the 27 February lava flow, and ash and vapor emissions from the new NSEC/SEC saddle vent at Etna on 28 February 2017 around 1730 local time. Photo by F. Ciancitto; courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 27/02/2017-05/03/2017, No. 10/2017).

Activity during March 2017. Sporadic ash emissions continued from the new saddle vent during early March 2017, accompanied by weak Strombolian activity during the night of 12-13 March. Intense degassing continued from VOR during March as well, with incandescent bursts visible on many clear nights. On the morning of 15 March the Montagnola webcam recorded a lava overflow from the saddle vent down the S flank of NSEC, and an intensification of explosive activity that caused the flow to reach the base of the complex at about 3,000 m elevation. During the day, it advanced towards Monte Frumento Supino; it had reached elevation 2,800 m by the late evening, overlapping significantly with the earlier flow from 27 February. Strombolian eruptions were nearly constant until late afternoon, and continued intermittently, along with ash emissions, for several days.

Shortly before 2300 UTC on 15 March (0100 on 16 March local time), a second new flow emerged from a vent near the base of the S flank of the new NSEC/SEC cone (at about 3,200 m elevation) and travelled SE (figure 190), splitting into two lobes. INGV personnel in the summit area reported a series of phreato-magmatic explosions at 0043 (just after midnight) along the lava front at an elevation of approximately 2,700 m along the W edge of the Valle del Bove. The contact of the active flow with the underlying snow caused several explosions. An INGV volcanologist suffered minor injuries during one of the explosions. Increased emissions also caused minor ashfall in Adrano and Santa Maria di Licodia (both about 17 km SW).

Figure (see Caption) Figure 190. Explosions at Etna from a vent at the base of the new NSEC/SEC cone complex during the early morning of 16 March 2017 viewed from the Torre del Filosofo, 1 km S. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 13/03/2017-19/03/2017, No. 12/2017).

By the afternoon of 17 March 2017, the second flow had reached an elevation of about 2,600 m, near the base of the W slope of the Valle del Bove. INGV personnel at Monte Zoccolaro (1.5 km S) spotted a third flow on 18 March, located S of the other two (figure 191). The front had reached about 2,200 m elevation, and was responsible for some phreato-magmatic explosions during 18 and 19 March. Several avalanches of incandescent material reached the base of the slope at the edge of Valle del Bove as the flow fronts collapsed during 18 March. Two Landsat 8 Operational Land Imager images on 18 and 19 March captured evidence of the lava flows, an ash plume, and Strombolian activity during this episode (figure 192). By 19 March, the advance had slowed as the flows began to spread out over the valley floor. The flows into the Valle del Bove ceased on 20 March.

Figure (see Caption) Figure 191. Thermal image of the W wall of the Valle del Bove at Etna on 18 March 2017, viewed from Monte Zoccolaro showing the activity of the three lava flows. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 13/03/2017-19/03/2017, No. 12/2017).
Figure (see Caption) Figure 192. The eruption from Etna's NSEC/SEC cone on 18 and 19 March 2017 as captured from space. The upper image was taken on 18 March by the Operational Land Imager (OLI) on Landsat 8 as a natural-color image, and shows an ash plume and two columns of gas and steam drifting SE. The more northerly steam and gas plume and the ash plume are rising from the summit vent of the new NSEC/SEC cone, and the more southerly steam and gas plume is rising from the effusive vent at the base of the S flank of the NSEC/SEC cone. The lower image shows the thermal glow of active lava flows on the SE flank on 19 March 2017, and the Strombolian activity at the summit of the new cone (the yellow spot directly below the Mt. Etna label) surrounded by the city lights of Catania and the surrounding communities. An astronaut aboard the International Space Station took this image. Courtesy of NASA Earth Observatory.

Strombolian activity and ash emissions ceased at the summit vent of the NSEC/SEC cone between 20 and 22 March 2017 leaving a new pyroclastic cone that rose above the adjacent NSEC and SEC cones (figure 193). Once the Strombolian activity had ended, yet another lava flow emerged from the base of the cone at an elevation of about 3,010-3,030 m, and spread into several segments, one of which flowed W around Monti Barbagallo (near the former Torre del Filosofo) and then turned SW following the valley between Monti Barbagallo and Monte Frumento Supino. By 26 March the front of this flow segment had reached an elevation of 2,300 m and travelled about 2.5 km from the vent. A second segment of the flow travelled E of Monti Barbagallo, following the earlier flows that had been active along the W slope of the Valle del Bove; it slowed and broke into several additional segments, reaching 1.3 km from the vent on 26 March, and advancing through the first week of April.

Figure (see Caption) Figure 193. The new pyroclastic cone 'cono di scorie' between the SEC and NSEC rises above and between both older craters at Etna shortly after 22 March 2017. It first emerged during the eruption of 27 February to 1 March 2017, and then continued to increase in size until 22 March 2017 from extensive Strombolian activity. The dotted white line separates the South East Crater (SEC) from the New South East Crater (NSEC). "Bocca effusive" is the effusive vent that fed the lava flows beginning on 22 March, and the new lava is the dark material with fumarolic emissions in the foreground. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 20/03/2017-26/03/2017, No. 13/2017).

Activity during April 2017. The active lava flow continued WSW towards the cones of the 2002-2003 eruption from the vent at the base of the NSEC/SEC cone until it stopped advancing sometime during the night between 8 and 9 April (figure 194). Another new flow then emerged from the same vent on 10 April and was active for just over 24 hours. This flow travelled SE to the W edge of the Valle del Bove and moved a few hundred meters along the edge before stopping during the day of 12 April.

Figure (see Caption) Figure 194. The lava flow at Etna that emerged from the base of the NSEC/SEC cone complex on 22 March 2017 flows WSW towards the cones of the 2002-2003 eruption during the first week of April 2017. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 27/03/2017-02/04/2017, No. 14/2017).

During the evening of 13 April 2017, Strombolian activity at the summit crater of the NSEC/SEC cone accompanied the emergence of flows from three vents along the S flank at elevations of approximately 3,200 m, 3,150 m, and 3,010 m which headed S and SE. The upper flows were active for only a few hours, but the lower flow continued SE towards the Valle del Bove and had overlapped the 10-11 April flow by the next day. The active front of the flow was at an elevation of 2,400 m on the western slope of the Valle del Bove, just north of the Serra Giannicola Grande. A flyover on 14 April revealed the extent of the fracture system on the flank of the NSEC/SEC complex from which the numerous flows emerged (figure 195). The flow rate diminished during the day of 15 April, and the flow stopped sometime during the next night.

Figure (see Caption) Figure 195. Thermal images of the fracture system affecting the S flank of the NSEC/SEC cone at Etna on 14 April 2017 showing the pyroclastic cone 'Cono di scorie', a collapsed portion of the cone 'Porzione collassata', and the three eruptive vents 'Frattura eruttiva' that opened on 13 April (at 3,200 m, 3,150 m and 3,010 m elevation). Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 10/04/2017-16/04/2017, No 16/2017).

A thermal anomaly appeared at the S edge of the NSEC/SEC summit vent, which INGV began calling SEC3, on the morning of 19 April. Weak Strombolian activity from the vent was followed by the emergence of a lava flow from the S side of the crater rim that flowed down the S flank of the cone. Dense, brown ash emissions about an hour later accompanied the re-opening of three vents on the S flank from which new lava flows emerged (figure 196). Lava jets rose tens of meters above the crater rim for about an hour in the afternoon. The lava flows from the three vents formed into two branches moving down the S flank (figure 197), then turned E and spread over the W slope of the Valle del Bove; by 20 April they had reached an elevation of 1,950 m. Explosive activity ceased at SEC3 that afternoon, and the flows stopped advancing sometime during the night of 20-21 April. Observations of the summit of SEC3 on 22 April revealed a N-S trending graben formed in the S rim of the summit crater about 100 m long, 10 m wide, and several tens of meters deep.

Figure (see Caption) Figure 196. The new SEC3 cone at Etna lies in the former saddle between SEC and NSEC. The red circles indicate the positions of the three eruptive vents (V1, V2, and V3) that opened on 19 April 2017 on the S flank of the cone. Lava from the vents is flowing E toward the Valle del Bove in this N-looking photo taken by Mauro Coltelli on 20 April 2017. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 17/04/2017-23/04/2017, No. 17/2017).
Figure (see Caption) Figure 197. Lava flows from the summit crater of the new cone (SEC3) at Etna on 20 April 2017. Photo by Salvatore Allegra/Anadolu Agency/Getty Images/CFP, published in Globaltimes, 20 April 2017.

The next eruptive episode began late in the day on 26 April 2017, with a slow-moving lava flow that emerged from the summit vent of SEC3. The flow made it part way down the S flank before another flow from the same vent covered it and reached the base of the flank. Strombolian activity began at the summit vent during the late evening while the flow continued to spread SE toward the Valle del Bove (figure 198). Strombolian activity intensified during the early hours of 27 April and a new vent opened at the summit immediately N of the first one. At around 0220, two new eruptive fractures opened on the N flank of SEC3, from which lava flowed N toward the Valle del Leone (figure 199). At daybreak, an ash plume was visible about 1.5 km above the summit drifting E. Phreato-magmatic explosions were observed in the Valle del Leone when the northern lava flow encountered snow on the ground. Strombolian activity ceased around noon and the flows on both the N and S flanks had ceased by the following morning.

Figure (see Caption) Figure 198. Lava flows down the S flank of SEC3 at Etna during the early morning of 27 April 2017, heading SE towards the Valle del Bove. Strombolian activity occurred from both of the summit vents, and an ash plume rose from the summit. Photo taken from the roof of the INGV-Osservatorio Etneo located 27 km S of the volcano. Courtesy of INGV (Attivita' dell'Etna, 20 Aprile-14 Giugno 2017).
Figure (see Caption) Figure 199. Lava flows from both the N and S flanks of SEC3 at Etna on 27 April 2017. a) the two lava flows are clearly visible from the Monte Cagliato thermal camera (EMCT) in this view looking W. b) a phreato-magmatic explosion in the Valle del Leone from the lava flow encountering snow on the N side of SEC3. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 24/04/2017 - 30/04/2017, No. 18/2017).

Activity during May-August 2017. Intense degassing with incandescence at night continued from the vent at VOR throughout April and into May 2017. At NEC, degassing continued from the large fumarole field at the bottom of the summit crater. No further lava flows erupted during May 2017, however, there were several short, high-energy tremor episodes in the area around SEC3. During May, more than 35 episodes of transient increases in tremor amplitude were recorded by INGV seismic instruments (figure 200). During 15-18 May, there were 11 episodes of Strombolian activity from the northern SEC3 summit vent, repeated at regular intervals of about every 8-9 hours. Lava fragments were ejected outside the crater rim and rolled down the flanks (figure 201). Each episode was accompanied by a sharp increase in volcanic tremor amplitude. Eight additional episodes of weak and discontinuous Strombolian activity occurred between 25 and 28 May at intervals ranging from 3 to 14 hours, each lasting about an hour, and accompanied by increased tremor amplitude. A short sequence of dense ash emissions from BN-1 on the morning of 31 May was the only ash plume reported during May.

Figure (see Caption) Figure 200. During the month of May 2017, more than 35 episodes of transient increases in the amplitude of tremor were recorded by the seismic instruments at Etna. Some, but not all, of these episodes were accompanied by Strombolian activity at the N vent at the SEC3 summit. Courtesy of INGV (Attivita' dell'Etna, 20 Aprile-14 Giugno 2017).
Figure (see Caption) Figure 201. The summit of the new NSEC/SEC complex at Etna on 16 May 2017 as viewed from the NW. The blue arrow indicates the eruptive vent that produced discontinuous Strombolian activity during May. Photo by M. Cantarero; courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 15/05/2017-21/05/2017, No. 21/2017).

Weak and discontinuous Strombolian activity resumed at NSEC on 6 June 2017, along with a sudden increase in tremor. The activity lasted until 9 June and included four episodes of roughly one hour each. Very little material fell outside the crater rim during these events. Vigorous degassing and nighttime incandescence continued at the VOR vent during June. INGV-OE personnel inspected the summit on 23 and 29 June, and 2 July 2017. High temperatures (around 600°C) were recorded at the VOR vent on 23 June. The other fumarolic areas, especially in the fracture field between NEC and VOR, were around 250°C, cooler than when last measured on 31 August 2016. Occasional weak ash emissions began on 24 June from SEC3; they lasted for a few days and quickly dissipated near the top of the cone. They ceased late in the evening of 28 June.

In a survey by drone on 4 July 2017, INGV-OE personnel noted widespread degassing along the rim and E side of the SEC3 crater. The vent that had formed during 27 February-26 April appeared to be blocked (figure 202). During the late morning of 9 July, the vent that had formed during 26-27 April emitted a small amount of red-gray ash. The next day a small amount of ash emerged from the base of BN-1. Incandescence was frequently observed at night from the VOR vent and from the NSEC. Degassing was observed regularly throughout the month at the VOR vent, the bottom of BN-1, and NEC (figure 203).

Figure (see Caption) Figure 202. Detailed view of the summit of the new SEC3 cone at Etna on 4 July 2017 taken by an INGV-OE drone. 1) eruptive vent active during 27 February-26 April; 2) eruptive vents active during 26-27 April; a) closeup of the bottom of one of the 26-27 April vents, from which a small amount of reddish-gray ash emerged on 9 July. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 3/07/2017-9/07/2017, No. 28/2017).
Figure (see Caption) Figure 203. Panoramic photos of the summit craters of Etna on 27 July 2017. VOR, seen from the northwestern edge, continued with strong degassing from the 7 August 2016 vent on the E rim; the NEC, seen from the fracture that cuts the southern rim, had modest, diffuse degassing from the fracture zone within the crater; and BN, seen from the eastern edge, had moderate degassing occurring from the vent at the base of BN-1 throughout the month. Courtesy of INGV-OE (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 24/07/2017-30/07/2017, No. 31/2017).

Occasional weak, diffuse ash emissions continued during August 2017 from the bottom of BN-1. INGV-OE scientists attributed this to collapse at the base of the crater. Limited degassing was noted at NEC, but persistent degassing continued from the 7 August 2016 vent at VOR, and from a vent on the E side of NSEC in addition to a vent at the SEC3 summit (figures 204 and 205).

Figure (see Caption) Figure 204. Areas of persistent degassing and fumarolic activity at Etna during August 2017. The black hatch lines outline the crater rims: BN = Bocca Nuova, which contains the NW vent (BN-1) and the SE vent (BN-2); VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Yellow circles indicate the locations of the degassing mouths of VOR, BN, and both the "Cono della sella" (saddle cone, or SEC3) and the E vent at NSEC. The base map is from a 2014 DEM of the summit from INGV Aerogeophysics Laboratory - Section 2. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 31/07/2017-06/08/2017, No. 32/2017).
Figure (see Caption) Figure 205. Aerial photographs of the summit crater area of Etna taken on 16 August 2017. a) view from ENE; b) view from the SE. Weak fumarolic activity is visible from the E vent of the New South East Crater (NSEC). More intense and continuous degassing emerges from the Central Crater (VOR and BN). See figure 204 for additional label explanations. Photos by Piero Berti; courtesy of Butterfly Helicopter Services and INGV-OE (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 14/08/2017-20/08/2017, No. 34/2017).

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: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV-OE), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); 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/); Global Times, http://www.globaltimes.cn/galleries/774.html.


Fuego (Guatemala) — October 2017 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Six eruptive episodes with Strombolian fountains, lava flows, ash plumes, and pyroclastic flows during July-December 2016

Volcán de Fuego has been erupting continuously since 2002. Historical observations of eruptions date back to 1531, and radiocarbon dates are confirmed back to 1580 BCE. These eruptions have resulted in major ashfalls, pyroclastic flows, lava flows, and damaging lahars. Fuego was continuously active from January to June 2016. Daily explosions that generated ash plumes to within 1 km above the summit (less than 5 km altitude) were typical. In addition, there were ten eruptive episodes that included Strombolian activity, lava flows, pyroclastic flows, and ash plumes rising above 5 km altitude (BGVN 42:06). Every month, lahars flowed down several drainages. This report continues with a summary of similar activity during July-December 2016. In addition to regular reports from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH), the Washington Volcanic Ash Advisory Center (VAAC) provides aviation alerts. Locations of many towns and drainages are listed in table 12 (BGVN 42:05).

Activity during July-December 2016 was very similar to the previous six months. Background activity included daily explosions, and ash emissions that often generated minor ashfall in communities within 15 km, generally to the SW. Strombolian activity sent material 300 m above the crater, and block avalanches down the flanks. Six eruptive episodes occurred during the second half of 2016, with characteristics very similar to the ten that occurred during the first half of the year (table 13). The episodes usually lasted around 48 hours. During the eruptive episodes, the amplitude and frequency of explosions increased to several per hour, and ash emissions that rose 1-3 km above the summit crater (4.8-7.8 km altitude) distributed ash tens of kilometers away. Diffuse ash plumes were often visible in satellite imagery several hundred kilometers from the volcano. Each episode was also accompanied by Strombolian activity that sent incandescent material 200-500 m above the summit crater, creating lava flows that descended major drainages. Episodes 11 and 16, in July and December, also included pyroclastic flows. The thermal signature recorded in the University of Hawaii's MODVOLC thermal alert system closely correlated with the increased heat flow from the lava flows during the eruptive episodes. Numerous lahars descended major drainages after heavy rains during August, but no damage was reported. A modest lahar was reported near the end of September.

Table 13. Eruptive episodes at Fuego during 2016. Details of episodes 1-10 are described in BGVN 42:06, episodes 11-16 are discussed in this report. The eruptive episode number is just for 2016 and was assigned by the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH).

Dates Episode Max Ash Plume altitude Ash Plume drift Ash Plume max distance Ashfall report locations Lava Flow drainages Lava Flow lengths Incandescence above crater Pyroclastic Flow drainages
3-5 Jan 2016 1 6.0 km SW, SE, S 40 km 8-12 km SW and SE Las Lajas (SE), Trinidad (S), Santa Teresa (S) 2.5 km 400 m --
19-21 Jan 2016 2 6.7 km NE 90 km 8-18 km NE, 12 km NW Las Lajas (SE), Trinidad (S), Santa Teresa (S) 3 km 400-500 m Las Lajas (SE), El Jute (SE)
9-10 Feb 2016 3 5.2 km NNW 40 km 45 km N, NE Las Lajas (SE), Trinidad (S), Santa Teresa (S) 800 m-3 km 300-400 m Las Lajas (SE), El Jute (SE)
29 Feb-3 Mar 2016 4 7.3 km N 400 km 10 km SW, N, NW Las Lajas (SE), El Jute (SE) 2-3 km yes Las Lajas (SE), El Jute (SE)
26-27 Mar 2016 5 6.1 km W 150 km 9-12 km, SW, NW Las Lajas (SE), Santa Theresa (S), Trinidad (SE) 2.0, 1.3, 1.0 km 500 m --
12-14 Apr 2016 6 5.8 km SW 185 km 10 km SW Las Lajas (SE), Santa Theresa (S) 2.0, 1.0 km 100-300 m --
6-7 May 2016 7 5.5 km S, SW, SE 65 km 21 km SE Las Lajas (SE), Trinidad (SE) 3.0 km, 1.5 km 300 m --
18-19 May 2016 8 5.5 km SSW 90 km 30 km NW, S, SW, W -- -- -- Las Lajas (SE), Honda (E)
21-23 May 2016 9 5.5 km SW, W, S 75 km 8-12 km, SW, ENE Las Lajas (SE) 2 km 200-300 m --
24-26 Jun 2016 10 5.5 km S, SW, W 120 km 8-12 km NW, SW Las Lajas (SE), El Jute (SE), Taniluyá (SW) 2.5 km, 2.3 km, 600 m 300 m --
28-29 Jul 2016 11 5.5 km SW, W, NW 250 km 12 km SW, W, 27 km NW Santa Teresa, Las Lajas 1.5 km, 3 km 500 m Santa Teresa
6-8 Sep 2016 12 5.0 km W, SW 25 km SW, W Las Lajas, Taniluyá 1.2 km, 500 m 300 m --
27-28 Sep 2016 13 5.0 km W, SW 20 km -- Las Lajas, Santa Theresa 1.5 km, 1.8 km 300 m --
29-30 Oct 2016 14 7.0 km W, NW 110 km 10 km NW, SW Las Lajas, Santa Teresa, Taniluyá 2.0 km, 300 m, 500 m 400-500 m --
20-21 Nov 2016 15 5.0 km SSW 175 km 8-12 km SW Trinidad, Ceniza, Las Lajas 1.0 km, 2.0 km, 2.5 km 300 m --
20-21 Dec 2016 16 5.2 km W, SW 230 km 8-12 km SW Santa Teresa, Taniluyá, Trinidad, Las Lajas 2.5, 2.0, 600, 1.8 400 m 3.5 km Taniluyá

Activity during July 2016. Explosions of incandescent material from the summit crater of Fuego were constant during July 2016, according to INSIVUMEH. On 5 July, an increase in the number of explosions per hour led to an ash plume rising to 4.5 km altitude and drifting W and SW. Incandescent blocks reached the vegetation on the W flank a few hundred meters from the summit. Ashfall was reported in the villages of Morelia, Santa Sofia, Sangre de Cristo (all around 10-12 km SW), and San Pedro Yepocapa (9 km NW). Another increase in activity on 15 July resulted in eight weak-to-moderate explosions per hour, which generated ash plumes that rose to about 4.3-4.8 km altitude and drifted more than 15 km W and SW; ash fell on the flanks in those directions. The Washington VAAC reported ash emissions rising to 4.6-5.2 km altitude, and MODVOLC issued one thermal alert. On 17 July, the Washington VAAC reported an ash emission drifting about 18 km W at 4.9 km altitude. Another ash emission was observed in satellite imagery on 19 July, at 5.2 km altitude drifting NW. The Washington VAAC also reported that the webcam showed lava on the flank near the summit that day.

Eruptive episode 11 began on 28 July 2016 and lasted for about 48 hours. Moderate-to-strong explosions expelled ash plumes to 5.5 km altitude that eventually drifted more than 250 km SW, W, and NW. The INSIVUMEH webcam at Finca La Reunion (SE) captured an image of the ash plume accompanied by a pyroclastic flow which descended the Santa Teresa ravine (barranca) around midday on 29 July (figure 50). Incandescent material was ejected about 500 m above the crater and fed two lava flows; one traveled 1.5 km down the Santa Teresa ravine, and the other traveled 3 km down the Las Lajas ravine. Some of the villages that reported ashfall included Sangre de Cristo, San Pedro Yepocapa, and Patzún (27 km NW). The Washington VAAC observed the ash plume in the early morning of 29 July extending 30 km WNW from the summit at 5.8 km altitude. By late morning, the plume had risen to 6.7 km altitude and was visible 150 km NW. The plume altitude dropped later in the day to 5.2 km, and the drift direction changed more toward the W. The farthest edge of the plume was faintly visible over 250 km W before it dissipated that evening. Incandescent explosions continued into the night, but had subsided by the next morning. A MODVOLC thermal anomaly signal first appeared on 26 July and persisted through 31 July; there were 17 thermal alert pixels reported on 29 July.

Figure (see Caption) Figure 50. An ash plume rises from the summit of Fuego on 29 July 2016 while a small pyroclastic flow descends a drainage on the SE flank, as seen from the Finca la Reunion webcam. Eruptive episode 11 lasted from 28 to 30 July. Courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Julio 2016).

Activity during August 2016. Weak and moderate explosions that generated ash plumes characterized activity during August 2016. Although a few strong explosions were recorded, there were no distinct eruptive episodes documented by INSIVUMEH. Constant rains, however, led to several lahars descending the major ravines. Persistent steam plumes rose to 4.2 km and drifted W and SW. Weak-to-moderate explosions with ash reached 4.3 to 4.8 km altitude, and drifted more than 15 km SW and W before dissipating. Ashfall was reported primarily in the communities of Sangre de Cristo, Yepocapa, Morelia, Hagia Sophia, and Panimaché I and II. Incandescent material was ejected 300 m above the crater, and generated weak-to-moderate avalanches within the crater.

The Washington VAAC reported an ash plume visible in satellite imagery on 7 August at 4.9 km altitude extending about 10 km WNW from the summit. On 11 August, a narrow plume was spotted in both visible and multispectral imagery extending about 80 km W at the same altitude. A puff of volcanic ash appeared in clear satellite and webcam images drifting W at 4.9 km on 19 August. A series of ash emissions were spotted on 20 August in satellite imagery. The head of the plume was about 35 km W of the summit. The highest altitude plume reported by the Washington VAAC during August was at 5.8 km on 25 August, drifting 25 km W. A single MODVOLC thermal alert was also recorded that day. On 15 and 16 August moderate-to-large lahars descended the Las Lajas and El Jute ravines, carrying blocks as large as 3 m in diameter, tree trunks, branches, and other debris. Another lahar recorded on 28 August descended the Santa Teresa tributary of the Pantaleón River, where the residents noted the warm temperature of the debris.

Activity during September 2016. Two eruptive episodes took place during September 2016. Episode 12 began on 6 September and lasted about 48 hours. Moderate-to-strong explosions generated ash plumes that rose to 5 km altitude and drifted 25 km W and SW. Incandescent material rose to 300 m above the crater and fed two lava flows, one traveled 1.2 km down the Las Lajas ravine (figure 51), and the other travelled 500 m down the Taniluyá. The Washington VAAC reported an ash plume, identified in satellite imagery, on 7 September moving WSW at 4.9 km altitude. MODVOLC thermal alerts were issued during 4-8 September, with 10 alerts appearing on 8 September.

Figure (see Caption) Figure 51. On 7 September 2016, the Operational Land Imager (OLI) on Landsat 8 captured this image of lava flowing down the Las Lajas and Santa Teresa ravines at Fuego during eruptive episode 12. The image is a composite of natural color (OLI bands 4-3-2) and shortwave Infrared (OLI band 7). Shortwave infrared light (SWIR) is invisible to the naked eye, but strong SWIR signals indicate increased temperatures. Courtesy of NASA Earth Observatory.

A bright hotspot in satellite imagery was reported by the Washington VAAC on 25 September 2016. A modest lahar descended the Santa Teresa ravine on 26 September, carrying 50-cm-diameter blocks, branches, and tree trunks; it was 10 m wide and 1 m high. Eruptive episode 13 began the next day, 27 September 2016, with moderate-to-strong explosions, and an ash plume that rose to 5 km altitude and drifted more than 20 km W and SW (figure 52). Incandescent material rose 300 m above the crater, feeding two lava flows. Lava traveled 1.5 km down the Las Lajas ravine (figure 53) and 1.8 km down the Santa Teresa ravine. A fissure developed on the S flank of the crater rim, and new fumarolic activity was observed during the day. Constant rumbling noises were audible in the areas of Finca Palo Verde, Sangre de Cristo, and San Pedro Yepocapa on the W and SW flanks. The Washington VAAC reported an intense hotspot in shortwave imagery. Activity subsided on 28 September. A strong multi-pixel thermal alert signal appeared in the MODVOLC data from 24-29 September.

Figure (see Caption) Figure 52. An ash emission rises to 5 km altitude on 27 September 2016 at Fuego during eruptive episode 13. Courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Septiembre 2016).
Figure (see Caption) Figure 53. Lava flows down the Las Lajas barranca (ravine) at Fuego on 28 September 2016 during eruptive episode 13. Courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Septiembre 2016).

Activity during October 2016. Six to ten explosions per day were recorded at Fuego during October 2016. Some of them generated ashfall on the SW flank. Episode 14, which began at the end of the month, produced three lava flows and strong explosions with an ash plume that rose to 7 km altitude and drifted N and NW. The Washington VAAC reported multiple ash emissions at 5.2 km altitude on 3 October, with the furthest one extending 35 km S. The next day, ash emissions were observed at 4.9 km altitude and drifted 22 km SSE. Pyroclastic flows were seen in an INSIVUMEH webcam on 10 October. They also reported ashfall in nearby communities that day.

Incandescent material rose 150-200 m above the summit crater on 28 October, and lava traveled 500 m down the Las Lajas ravine. Episode 14 began the next day with a strong explosion that generated an ash plume to 7 km altitude that drifted 110 km W and NW. Constant loud rumbling was reported up to 15 km from the volcano, and ashfall was reported in San Pedro Yepocapa, Sangre de Cristo, and La Conchita. Three incandescent lava fountains were seen in the early hours of 30 October (figure 54). The first, 450 m above the crater, fed a 2-km-long flow in the Las Lajas ravine. The second fountain rose to 250 m and fed a flow that traveled 300 m down the Santa Teresa canyon. The third fountain rose 200 m and formed a flow that traveled down the Taniluyá drainage for 500 m. Activity declined during the night of 30 October, but weak and moderate avalanches of incandescent material continued into the first part of the next day.

Figure (see Caption) Figure 54. Three Strombolian fountains at Fuego feed three lava flows on 30 October 2016 during eruptive episode 14. Courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Octubre 2016).

The first ash emissions of episode 14 were visible in satellite imagery on 29 October, extending roughly 45 km NNW from the summit. By early the next day, the ash emissions were detected at 7.3 km altitude, based on a pilot report. They extended about 110 km NNW from the summit. Later in the day, the plume had lowered to 5 km altitude and drifted 15 km N and NW. A single MODVOLC thermal alert was reported on 13 October, but a lengthy series of multi-pixel alerts were generated during 24-31 October, including 19 pixels on 30 October at the peak of episode 14.

Activity during November 2016. Activity during November 2016 remained at background levels until the third week of the month; explosions increased in amplitude and frequency to as many as 15 per hour, leading to episode 15 which began on 20 November. The background levels of the second and third weeks included incandescent material rising to 300 m above the crater, causing avalanches down the flanks around the crater rim and continuous explosions of weak-to-moderate energy that generated ash plumes rising to altitudes between 4.3 and 4.7 km that drifted W and SW.

The Washington VAAC reported ash emissions in satellite imagery every day from 8 to15 November 2016. A plume was seen on 8 November rising to 4.6 km altitude and drifting 25 km SW. The next day, a plume at the same altitude drifted 45 km NW. On 10 November, a faint plume was seen in visible imagery, extending about 25 km NNW. A larger plume was visible in morning imagery on 11 November at 5.5 km altitude extending 35 km WSW. The next day, at the same altitude, a diffuse plume was visible 10 km W of the summit. Multiple emissions were spotted drifting W from the summit at 4.6-4.9 km altitude on 13 and 14 November. Two single MODVOLC thermal alerts were reported on 12 and 14 November. A hotspot was detected in satellite imagery on 15 November, along with continuing emissions to 4.6 km altitude that drifted within 10 km SW of the summit. On 17 November ashfall was reported in Morelia, Santa Sofia, and Panimache I and II. Emissions on 18 November rose to 4.7 km altitude and drifted 10 km SW, and on 20 November they rose to 4.9 km altitude and drifted 24 km from the summit (figure 55).

Figure (see Caption) Figure 55. Strombolian eruption and ash emission at Fuego, looking S from Acatenango summit on the early morning of 18 November 2016. Photo copyright by Martin Rietze, used with permission.

Eruptive episode 15 began on 20 November with strong explosions that caused ash plumes to rise to 5 km altitude and drift as far as 175 km SSW and W, generating ashfall again in Morelia, Santa Sofia, and Panimache I and II. Three lava flows emerged from the 300-m-high Strombolian ejections; one traveled 1 km down the Trinidad ravine, one descended 2 km down barranca Ceniza, and the third flowed 2.5 km down barranca Las Lajas (figure 56). Numerous clouds of volcanic ash rose from block avalanches in Las Ceniza ravine on 20 and 21 November.

Figure (see Caption) Figure 56. Eruptive episode 15 at Fuego occurred during 20-21 November 2016. An ash plume rose to 5 km altitude (top) before Strombolian activity 300 m high sent flows down three major ravines (bottom). These views from the rooftop of a hostel in Antigua (18 km NE) show the ravines in daylight during the afternoon of 20 November, and again around midnight that night as the incandescent material traveled downward. Photos copyright by Martin Rietze, used with permission.

The Washington VAAC reported an extremely large hotspot on 20 November 2016 (local time) in infrared imagery, along with ash emissions at 4.9 km altitude drifting SW to 65 km. Emissions at 3.8 km persisted into the night. By early morning on 21 November, they were visible extending 175 km W. A lengthy period of multi-pixel MODVOLC thermal alerts coincided with eruptive episode 15 during 17-23 November, and included 26 pixels on 21 November 2016. Eruptive activity decreased to background levels by 22 November, and only weak explosions and fumarolic activity were reported for the rest of the month.

Activity during December 2016. Weak-to-moderate explosions and ash plumes characterized background activity at Fuego during December 2016. Minor ashfall was regularly reported in communities located 8-12 km SW. Activity increased somewhat during 15-16 December, and eruptive episode 16 was recorded during 20-21 December. During episode 16, Strombolian activity created three lava flows that descended major ravines, and a large pyroclastic flow traveled 3.5 km from the summit, burning vegetation in its path.

The Washington VAAC reported an ash emission on 5 December at 5.8 km altitude drifting N. On 8 December, intermittent ash plumes were drifting W over the East Pacific Ocean at 6.1 km altitude. Remnants over 450 km W were seen in multispectral imagery by early on 9 December. Multiple new detached plumes continued moving WNW between 5.5 and 6.1 km altitude on 9 December. They were 80 km NW by late afternoon. New discrete emissions at 4.6 km altitude appeared in satellite imagery on 10 December, drifting W up to 130 km before dissipating.

During the afternoon of 20 December 2016, eruptive episode 16 began with moderate-to-strong ash emissions producing an ash plume that rose to 4.7 km altitude and drifted more than 15 km W and SW. Incandescent material rose 400 m above the crater, and bombs fell more than 300 m away. Block avalanches were concentrated in the Ceniza and Trinidad ravines. By the evening of 20 December, three lava flows had formed, in the Santa Teresa, the Taniluyá, and the Las Lajas ravines (figure 57). By the morning of 21 December, they were 2.5, 2.0, and 1.8 km long, respectively. During that day, strong explosions generated ash plumes that rose to 5.2 km altitude and drifted 18 km S, SW, W, and NW. Some of the communities that reported ash from this event included Panimaché, Morelia, Santa Sofia, Sangre de Cristo, San Pedro Yepocapa, and Palo Verde.

Figure (see Caption) Figure 57. Landsat image showing the locations of three lava flows at Fuego during eruptive episode 16 on 21 December 2016. Image courtesy of USGS/NASA, annotations courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Diciembre 2016).

Around 1000 on 21 December, pyroclastic flows that descended the Taniluyá ravine generated an ash plume that rose 2 km and drifted W and SW. The flows traveled 3.5 km and were estimated to be 300 m wide. They descended the ravine at high speed and high temperature, burning everything in their path (figure 58). These were the first pyroclastic flows in several months. By the end of eruptive episode 16, the lava flow in the Taniluyá ravine had reached 2.8 km in length (figure 59).

Figure (see Caption) Figure 58. A pyroclastic flow descends the Taniluyá ravine around 1000 local time on 21 December 2016 at Fuego during eruptive episode 2016. Courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Diciembre 2016).
Figure (see Caption) Figure 59. Both a pyroclastic flow (3.5 km long, yellow outline) and a lava flow (2.8 km long, red outline) descended the Taniluyá ravine at Fuego during eruptive episode 16, from 20 to 21 December 2016. The white arrows indicate the ravine. The orange outline indicates the area where vegetation was destroyed by the pyroclastic flows. Courtesy of INSIVUMEH (Informe Mensual De La Actividad Del Volcán Fuego, Diciembre 2016).

During episode 16, the Washington VAAC reported ash emissions rising to 5.2 km (about 1.4 km above the summit crater) altitude and drifting about 230 km SW. Continuing ash emissions on 23 December were visible in satellite imagery moving 45 km SW from the summit at 4.3 km altitude. Intermittent diffuse ash emissions extended up to 30 km WSW and NW from the summit during 28-31 December at 4.3-5.2 km altitude.

MODVOLC thermal alerts were intermittent throughout December. They were recorded on 8 (2), 11 (2), 12, 14 (2), 16 (3), and 18 (3) December prior to episode 16. The biggest interval of multi-pixel alerts was during episode 16 from 20-22 December, and included 14 alerts on 21 December 2016. Additional single alerts were recorded on 25 and 29 December.

Geologic Background. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); 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: http://www.ospo.noaa.gov/Products/atmosphere/vaac/, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Martin Rietze (URL: http://www.mrietze.com/index.htm).


Heard (Australia) — October 2017 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Expedition visit in March-April 2016, intermittent eruptive activity through September 2017

The remote island of Heard in the southern Indian Ocean is home to the Big Ben stratovolcano, which has had confirmed intermittent activity since 1910. The nearest continental landmass, Antarctica, lies over 1,000 km S. Visual confirmation of lava flows on Heard are rare; thermal anomalies detected by satellite-based instruments provide the most reliable information about eruptive activity. Thermal alerts reappeared in September 2012 after a four-year hiatus (BGVN 38:01), and have been intermittent since that time. Information comes primarily from MODVOLC and MIROVA thermal anomaly data, but Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) also provides reports from research expeditions. The independent March-April 2016 Cordell Expedition also provided recent ground-based observations mentioned in this report, which covers activity through September 2017.

Expeditions during January-April 2016. Scientists aboard the CSIRO Research Vessel Investigator observed an eruption of Big Ben on 31 January 2016. Vapor was seen emanating from the peak and lava flowed down the flank over a glacier (see figure 23, BGVN 41:08, and video link in Information Contacts). The research team, lead by the University of Tasmania's Institute for Marine and Antarctic Studies (IMAS), was conducting a study of the link between active volcanoes on the seafloor and the mobilization of iron by hydrothermal systems which enriches and supports life in the Southern Ocean.

During a private expedition from 22 March to 11 April 2016, scientists and engineers from the 2016 Cordell Expedition documented changes to the island and its life since a prior visit in 1997, and tested radio operations. On 23 March the team was able to photograph the usually cloud-covered Mawson Peak, the summit of Big Ben (figure 24). Steam was visible above the flat upper surface, possibly a crater rim or fissure. They estimated a height of about 45 m of an edifice rising above the adjacent slope. The ground at the site of the team campsite, near Atlas Cove on the NW side of the island, was covered with lava flows (figure 25). While the expedition had to cancel a planned expedition to the summit, rocks collected from the shoreline confirmed the diversity of volcanic rocks on the island (figure 26).

Figure (see Caption) Figure 24. Mawson Peak is the summit of Big Ben volcano on Heard Island in the southern Indian Ocean. This photograph, taken on 23 March 2016 from Altas Cove on the NW side of the island by the 2016 Cordell Expedition, shows steam from a possible crater or vent area at the summit, and lava flows covered with a dusting of snow around the otherwise glacier-covered peak. Courtesy of Robert W. Schmieder, 2016 Cordell Expedition, used with permission.
Figure (see Caption) Figure 25. Lava flows cover the ground near the 2016 Cordell Expedition campsite at Atlas Cove on the NW side of Heard Island in March 2016. Courtesy of Robert W. Schmieder, 2016 Cordell Expedition, used with permission.
Figure (see Caption) Figure 26. Rock samples collected at Heard by the 2016 Cordell Expedition during 23 March-11 April 2016 attest to the volcanic activity of the island. Top: A conglomerate sampled from the east shore of Stephenson Lagoon with mostly volcanic rock fragments, including vesicular basalt (dark brown, lower center) and clasts of volcanic breccia containing fragments of lava (large clast on right side). Sample is about 25 cm long. Bottom: A variety of textures was typical in the volcanic rocks collected on the islands. Courtesy of Robert W. Schmieder, 2016 Cordell Expedition, used with permission.

At the southern end of Sydney Cove, near Magnet Point on the northern tip of Laurens Peninsula (the NW side of the island), the team identified a small islet, with dimensions of about 40 x 120 m and nearly vertical sides about 100 m high. Columnar jointing in the volcanic rocks is well exposed at the base and on the nearly flat upper surface (figure 27).

Figure (see Caption) Figure 27. Distinctive columnar jointing in the volcanic rocks is visible around the base and on the top of a small islet in Sydney Cove off the NW end of Heard Island in this image taken during the 23 March-11 April 2016 Cordell Expedition. Courtesy of Robert W. Schmieder, 2016 Cordell Expedition, used with permission.

Satellite thermal and visual data, 2012-2017. The most consistent source of information about eruptive activity at Heard comes from satellite instruments in the form of visual and thermal imagery, and thermal anomaly detection. From the time that renewed activity was detected in MODVOLC data in late September 2012 through September 2017, either the MODVOLC or MIROVA systems have consistently detected thermal signals, with only a few short breaks. A four-month span from mid-July to mid-November 2014, and a two-month gap during February and March 2015 are the only periods longer than a month when no thermal signal was reported. Continuous MIROVA information from late January 2016 through September 2017 shows intermittent but persistent thermal anomalies throughout the period (figure 28).

Figure (see Caption) Figure 28. A continuous MIROVA signal from 27 January 2016 through 6 October 2017 shows persistent low-level thermal activity through the period with intervals of increased activity during late January 2016, July-August 2016, late September-November 2016, early February 2017, and September 2017. Courtesy of MIROVA.

The moderate signal at the very end of January 2016 coincides with the CSIRO expedition observing the lava flows on the flank of Big Ben. Low-level MIROVA anomalies were recorded in April and early May 2016. Activity picked up during June, and strengthened through July and August 2016. Late September through November 2016 was a period with heightened activity as well. From December 2016 through August 2017, intermittent low-to-moderate intensity anomalies were recorded every month. Activity appeared to increase briefly during early February and September 2017. On 4 February 2017, Landsat 8 captured a rare clear view that showed fresh lava and debris flows emanating from the summit on top of the snow (figure 29). The longest flow is estimated to be 1,300 m long. False-color infrared imagery of the same image of Mawson Peak also reveals two vents separated by about 250 m (figure 30). Subsequent imagery on 20 and 27 February also detected thermal anomalies at the summit. The visual imagery of the lava flows on 4 February 2017 corresponds to the early February spike in MIROVA thermal anomaly data.

Figure (see Caption) Figure 29. Lava and debris flows radiate away from Mawson Peak on Heard Island in this Landsat 8 OLI image captured on 4 February 2017. MIROVA thermal anomaly data show a spike in activity at the same time. Courtesy of NASA and Bill Mitchell (CC-BY).
Figure (see Caption) Figure 30. False-color infrared imagery of Mawson Peak, Heard Island, 4 February 2017. Two vents are visible in red-yellow, separated by about 250 m. Data source: Landsat 8 OLI/TIRS bands 7-6-5. Image courtesy of Bill Mitchell (CC-BY), data from NASA/USGS.

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

Information Contacts: Commonwealth Scientific and Industrial Research Organisation (CSIRO) (URL: http://www.csiro.au/); CSIROscope, CSIRO Blog, Big Ben Erupts: Australia's active volcano cluster blows its lid (URL: https://blog.csiro.au/big-ben-erupts/); Robert W. Schmieder, 2016 Cordell Expedition, 4295 Walnut Blvd., Walnut Creek, CA 94596, Post Expedition report to the Australian Antarctic Division (AAD) (URL: http://www.cordell.org/, http://www.heardisland.org/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Bill Mitchell, The Inquisitive Rockhopper, Big Ben eruption update 2017-02-27 (URL: https://inquisitiverockhopper.wordpress.com/2017/02/).


Ibu (Indonesia) — October 2017 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


Occasional weak ash explosions and thermal anomalies during April-August 2017

During March 2014-March 2017, activity at Ibu consisted of lava-dome growth, occasional weak emissions containing ash (figure 11), and frequent thermal anomalies (BGVN 40:11 and 42:05). Ongoing activity between April and August 2017 consisted primarily of intermittent ash explosions. Data come from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

Figure (see Caption) Figure 11. Photo of an ash explosion from Ibu's central vent in November 2014. Courtesy of Tom Pfeiffer, Volcano Discovery.

On 3 April 2017, at 0757 (local), an explosion produced an ash plume that rose to an altitude of 1.7 km and drifted S. Seismic signals indicated explosions and avalanches. During the rest of April through August, occasional explosions generated weak ash plumes that generally rose to altitudes of 1.5-1.8 km (0.2-0.5 km above the volcano) and drifted in various directions (table 2).

Table 2. Ash plume data for Ibu, April-August 2017. Courtesy of PVMBG and Darwin VAAC.

Date Maximum plume altitude (km) Plume drift direction
03 Apr 2017 1.7 S
07-08 Apr 2017 1.7 N
10-11 Apr 2017 1.5-1.6 S
12-13, 17 Apr 2017 1.5-1.8 S, SW
19-21 Apr 2017 1.5-1.8 E, N
26-27, 29-30 Apr 2017 1.5-1.8 E, NE, N
10-11 May 2017 1.8 E, SW
16 May 2017 1.5 --
19-20, 23 May 2017 1.5-1.8 E, NE, S
01, 05 Jun 2017 0.15-0.25 N, SE
09-12, 14 Jun 2017 1.5-1.8 N, W, SSW
14, 17-19 Jun 2017 1.5-1.8 S, SW, W, N
15 Aug 2017 1.8 N
24, 28 Aug 2017 1.5-1.8 W

Between April and August 2017, thermal anomalies (based on MODIS satellite instruments analyzed using the MODVOLC algorithm) were recorded 2-5 days per month, with no monthly trend. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots each month; all except one were within 3 km of the volcano, and all were of low or moderately-low power.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).


Marapi (Indonesia) — October 2017 Citation iconCite this Report

Marapi

Indonesia

0.38°S, 100.474°E; summit elev. 2885 m

All times are local (unless otherwise noted)


Four short ash explosions on 4 June 2017

Recent activity at the large Gunung Marapi stratovolcano on Sumatra has consisted of small ash plumes, with eruptions of a single day to periods of a few months. Ashfall around the active crater rim (figure 5) and thin layers of ash deposits seen in the crater wall (figure 6) provide evidence of both the recent and very long history of explosive activity. Since 2011 there have been eruptive episodes during August-October 2011, March-May 2012, 26 September 2012, February 2014, and 14 November 2015. As reported by the Indonesian Center of Volcanology and Geological Hazard Mitigation (PVMBG), another series of explosions took place on 4 June 2017.

Figure (see Caption) Figure 5. Photo taken at the rim of the active Verbeek Crater at Marapi on 17 April 2014. The most recent eruption prior to this photo was during 3-26 February 2014. Courtesy of Axel Drainville.
Figure (see Caption) Figure 6. Photo showing the rim and interior wall of the Verbeek Crater at Marapi on 17 April 2014. Courtesy of Axel Drainville.

Four explosions on 4 June lasted less than one minute each, and generated ash plumes above the summit (figure 7) and drifted E. The explosions occurred at 1001 local time (0301 UTC), 1011, 1256, and 1550. Dense ash-and-steam plumes from each explosion rose 300 m, at least 700 m, 200 m, and 250 m above the crater, respectively. The Darwin VAAC reported ash at about 3.6 km altitude extending 37 km ENE, based on satellite imagery. Ejected bombs were deposited around the crater, and minor ashfall was reported in the Pariangan District (8 km SSE), Tanah Datar Regency. Seismicity increased after the explosions. The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were advised not to enter an area within 3 km of the summit.

Figure (see Caption) Figure 7. Photos of ash plumes rising from Marapi on 4 June 2017. The upper right image appears to show a smaller white plume to the right. Photos by PVMBG, posted to Twitter by Sutopo Purwo Nugroho (BNPB).

The broad summit area with multiple craters is a popular destination for hiking expeditions. A video posted by YouTube user "SiGiTZ" documented the experience of one group during visits on 30 April 2016 and on 11 May 2017. The video provides excellent views from 2016 of the entire crater complex and of the Verbeek Crater, from which a steam-and-gas plume appears to be rising. A video posted by YouTube user "yogi antula" included a television broadcast from the Anak Borneo Channel of a video from climbers in the crater area during the 4 June explosions, taken from approximately 400-500 m away. In that video, a significant dark ash plume can be seen rising from Bungsu-Verbeek crater complex, along with a smaller white plume from a closer location. The news report was concerned with 16 hikers known to be on the mountain; there were no later reports of anyone being injured.

References: SiGiTZ, 1 August 2017, Expedisi puncak Gunung Marapi Bukittingi Sumbar Mei 2017 (URL: https://www.youtube.com/watch?v=pVxhWAbo2VA).

yogi antula, 5 June 2017, Video amatir pendakian saat Gunung Marapi Erupsi – 4 Juni 2017 (by Anak Borneo Channel) (URL: https://www.youtube.com/watch?v=8GAY6lsTLEE).

Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); 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/); Sutopo Purwo Nugroho, Badan Nasional Penanggulangan Bencana (BNPB) (URL: https://twitter.com/Sutopo_BNPB); Axel Drainville, Flickr.com, with Creative Commons license Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0, https://creativecommons.org/licenses/by-nc/2.0/) (URL: https://www.flickr.com/photos/axelrd/).


Tolbachik (Russia) — October 2017 Citation iconCite this Report

Tolbachik

Russia

55.832°N, 160.326°E; summit elev. 3611 m

All times are local (unless otherwise noted)


Eruption that started in late November 2012 ends by mid-September 2013

The most recent eruption began on 27 November 2012 along two fissures a few kilometers S of the main Tolbachik edifice, within the Tolbachinsky Dol lava plateau (BGVN 37:12). Monitoring is done by the Kamchatkan Volcanic Eruption Response Team (KVERT); they recorded an end date for this eruption as 15 September 2013.

Activity reported through February 2013 included Strombolian fire fountains (figure 14), voluminous lava flows on the surface (figure 15 and 16) and under the ice and snow cover (figure 17), ash explosions, and the building of cinder cones (BGVN 37:12). Satellite imagery in early June 2013 revealed both a lava pond at the active vent and a large lava flow lower down the flank, with multiple flow-front breakouts (figure 18). Cinder cones continued to grow along the S fissure through 16-22 August 2013, and lava flows remained active (figure 19), but then gas-and-ash plumes weakened and seismicity decreased during the last week of the month (BGVN 38:08).

Figure (see Caption) Figure 14. Lava fountain in the cinder cone at Tolbachik on 24 January 2013. Photo by Yu. Demyanchuk; courtesy of IVS FEB RAS and KVERT.
Figure (see Caption) Figure 15. Photo of lava flow at Tolbachik on 25 January 2013. Photo by Yu. Demyanchuk; courtesy of IVS FEB RAS and KVERT.
Figure (see Caption) Figure 16. Lava flows moving ESE at Tolbachik on 25 February 2013. Photo by Yu. Demyanchuk; courtesy of IVS FEB RAS and KVERT.
Figure (see Caption) Figure 17. Photo of a lava flow intruding under deep snow at Tolbachik on 25 February 2013. Photo by Yu. Demyanchuk; courtesy of IVS FEB RAS and KVERT.
Figure (see Caption) Figure 18. False-color image of Tolbachinsky in shortwave infrared and near-infrared light (combined with green light), taken on 6 June 2013 by the Advanced Land Imager on the Earth Observing-1 satellite. Hot surfaces glow in shortwave infrared wavelengths. The active vent and lava flow are bright red, along with scattered lava "breakouts"at the front of the flow. High temperature surfaces in the scene also glow in near infrared light, revealing a lava pond in the active vent and fluid lava in the center of the lava flow. Courtesy of NASA (image by Jesse Allen and Robert Simmon, caption by Robert Simmon).
Figure (see Caption) Figure 19. Photo of lava flow front adjacent to the Kruglenkaya slag cone at Tolbachik on 16 August 2013. Photo by D.V. Melnikov; courtesy of IVS FEB RAS and KVERT.

Seismicity continued to decrease during 22-24 August 2013, and KVERT noted on 27 August that no incandescence had been seen in recent days, and there were no current ash plumes. Satellite data did still show a large thermal anomaly in the northern area of Tolbachinsky Dol, which KVERT attributed to the lava flows remaining hot. The MODIS thermal anomaly data recorded in the MODVOLC system identified the latest hotspot on 27 August 2013. According to the Kamchatkan Volcanic Eruption Response Team (KVERT), the Aviation Color Code (ACC) was lowered from Orange to Yellow on 27 August 2013.

When the ACC was lowered to Green on 31 January 2014, KVERT reported that weak seismic activity and episodes of tremor continued, gas-and-steam activity was sometimes observed, and satellite data continued to show a weak thermal anomaly. However, they also stated that "probably its active phase was finishing in September 2013." The KVERT website recorded an end date of 15 September 2013. The new lava flows were still noticeable in visible satellite imagery more than a year after the eruption ended (figure 20).

Figure (see Caption) Figure 20. Satellite image from Landsat/Copernicus showing the final extent of new lava flows on the SSW flank of Tolbachik on 30 December 2014. The new lava flows extend across the center of the image, with the main edifice at top right. Color and contrast have been adjusted to enhance the contrast between fresh darker lava and faded older deposits. Courtesy of Google Earth.

Geologic Background. The massive Tolbachik basaltic volcano is located at the southern end of the dominantly andesitic Kliuchevskaya volcano group. The massif is composed of two overlapping, but morphologically dissimilar volcanoes. The flat-topped Plosky Tolbachik shield volcano with its nested Holocene Hawaiian-type calderas up to 3 km in diameter is located east of the older and higher sharp-topped Ostry Tolbachik stratovolcano. The summit caldera at Plosky Tolbachik was formed in association with major lava effusion about 6500 years ago and simultaneously with a major southward-directed sector collapse of Ostry Tolbachik volcano. Lengthy rift zones extending NE and SSW of the volcano have erupted voluminous basaltic lava flows during the Holocene, with activity during the past two thousand years being confined to the narrow axial zone of the rifts. The 1975-76 eruption originating from the SSW-flank fissure system and the summit was the largest historical basaltic eruption in Kamchatka.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Google Earth (URL: https://www.google.com/earth/).


Ubinas (Peru) — October 2017 Citation iconCite this Report

Ubinas

Peru

16.355°S, 70.903°W; summit elev. 5672 m

All times are local (unless otherwise noted)


Intermittent ash explosions during September 2016-February 2017

Ubinas is an active stratovolcano in southern Peru about 70 km E of the city of Arequipa. Holocene lava flows cover its flanks, and the historical record since the mid-1500's contains evidence of minor explosive eruptions, debris avalanches, tephra deposits, phreatic outbursts, and pyroclastic flows and lahars. An eruptive episode that began with phreatic explosions on 1 September 2013 lasted through 27 February 2016, producing numerous small ash emissions, several large explosions with ash plumes that rose above 10 km altitude, large SO2 anomalies, evacuations, and several millimeters of ashfall in surrounding villages. Significant MIROVA thermal anomalies first appeared in mid-June 2015 and persisted through January 2016. A smaller eruptive episode described below began on 13 September 2016 and continued with intermittent explosive activity through 2 March 2017. Information is provided by the Instituto Geofísico del Perú, Observatoria Vulcanologico del Sur (IGP-OVS), the Observatorio Volcanológico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET), and the Buenos Aires VAAC (Volcanic Ash Advisory Center).

After activity subsided at the end of February 2016, Ubinas remained quiet through August 2016, with only sporadic steam and gas emissions, and very low levels of seismicity. Seismicity increased again beginning on 9 September, and the first ash emission of a new episode was reported on 13 September 2016. An explosion on 3 October released a significant ash plume that rose 2 km above the 5,672-m-summit. Four additional explosions with minor ash emissions were reported in November, and one occurred on 6 December. Webcams captured images of sporadic low-density ash emissions throughout February 2017, with the last report of possible emissions on 2 March 2017. Emissions of steam and gas and seismicity decreased throughout April 2017, and IGP-OVS lowered the alert level to Green by the end of May. Ubinas remained quiet through September 2017.

Activity during April-December 2016. After the small ash emission of 27 February 2016, seismicity at Ubinas dropped to very low levels of a few events per day (BGVN 41:10, figure 40). Sporadic steam emissions with small quantities of bluish magmatic gases rose no more than a few hundred meters above the summit during March-August 2016; there were no reports of ash emissions. A small seismic swarm of about 100 earthquakes was recorded on 5 April. The first "tornillo" type earthquakes seen in several months appeared beginning on 4 June, indicating to IGP-OVS the beginning of a new eruptive cycle. The lagoon that had formed at the bottom of the summit crater due to rains earlier in the year began to disappear as the dry season approached (figure 41).

Figure (see Caption) Figure 41. A view down into the steep-sided summit crater at Ubinas shows remnants of a disappearing lake after the rainy season, during the second quarter of 2016. Photo by Melquiades Álvarez; courtesy of OVS (Reporte Annual Volcan Ubinas, 2016).

Beginning on 9 September 2016, both OVI and OVS noted an increase in seismic activity of LP, hybrid, and VT-type events (figure 42). On 13 September, OVS reported that steam plumes rose higher than 1,000 m above the summit for the first time in many months, and a minor ash emission was observed. OVI reported possible ash emissions in weekly reports on 12, 17, and 24 September. Emissions of bluish gas and steam were typical for the remainder of September (figure 43).

Figure (see Caption) Figure 42. An increase in several types of seismicity at Ubinas first appeared on 9 September 2016 after several months of quiet. This was followed by an ash emission on 13 September, and an explosion with ash on 3 October. Courtesy of IGP-OVS (Reporte N°31-2016, Actividad del volcán Ubinas, Resumen actualizado de la principal actividad observada del 01 al 18 de octubre).
Figure (see Caption) Figure 43. Bluish SO2-rich gas and steam emissions increased in frequency during the second half of September 2016 at Ubinas, as seen in this image taken from the village of Ubinas on 27 September 2016 by Melquiades Álvarez. Courtesy of IGP-OVS (Reporte Annual Volcan Ubinas, 2016).

Both OVI and OVS reported ash emissions from explosions on 3 October 2016 (figure 44). Seismic tremor, associated with ash emissions, lasted for nine and a half hours. The ash plume drifted NE, E, SE, and SW up to 2 km above the summit, according to OVS. Fumarolic activity then returned, with steam and bluish gases rising no more than 1,500 m above the crater rim for the remainder of October. The Buenos Aires VAAC noted the eruption reported by IGP, but was not able to identify volcanic ash from satellite data under clear skies. After peaking in early October at several hundred events per day, seismicity declined to below 50 events on 21 October, and then rose slightly to around 200 events per day for the rest of the month. Steam and gas emissions remained less than 500 m above the summit.

Figure (see Caption) Figure 44. An explosion at Ubinas on 3 October 2016 created a significant ash plume that rose 2,000 m above the crater rim, and drifted NE, E, SE, and SW. Photos by Melquiades Álvarez, courtesy of IGP-OVS (Reporte Annual Volcan Ubinas, 2016).

Three explosions with minor ash and gas (mostly SO2) were reported by IGP-OVS on 8 November (local time). NASA Goddard Space Flight Center reported a significant SO2 emission associated with this event. The ash plume rose to about 1,500 m above the crater rim (about 7.2 km altitude). Seismicity remained high, with 250-350 events per day for several days after the explosion before declining back to around 150 events per day by 15 November. Another explosion, with minor ash emissions that rose 500 m, was reported by both OVS and OVI on 17 November 2016. After a small spike in seismicity between 23 and 29 November, the number of seismic events dropped below 50 per day. OVS reported a small ash emission that rose 100 m above the summit and drifted NW on 6 December 2016. OVI noted a modest increase in seismicity between 6 and 15 December, but only sporadic emissions of water vapor and gas were detected for the remainder of the month.

Activity during January-September 2017. Gas and steam emissions remained below 500 m above the crater rim during January 2017. OVS reported an explosion at 0223 on 24 January, but could not confirm ash emissions due to darkness. Occasional emissions of steam and gas rose as high at 2 km above the summit crater, but they generally remained below 500 m. OVI observed five lahars during January, but no damage was reported. Seismicity remained below 60 events per day during the month, except for a few days during 8-12 January when the frequency increased to 100-150 events per day.

OVS reported sporadic low-density ash emissions throughout February 2017 (figure 45). They were accompanied, occasionally, by water vapor and bluish gas, and did not rise more than 1,500 m above the summit crater. Weather clouds obscured the summit for much of the month. OVI reported minor ash emissions on 4, 10, 14, and 18 February (figure 46). Seismicity fluctuated throughout the month from values as high as almost 70 events per day (8 February) to fewer than 10 events per day (10-19 February).

Figure (see Caption) Figure 45. Sporadic emissions of ash along with steam and magmatic gases were recorded in the IGP-OVS webcams at Ubinas on 4 and 9 February 2017. Courtesy of IGP-OVS (Reporte 03-2017 - Actividad del volcán Ubinas, Resumen actualizado de la principal actividad observada del 01 al 15 de febrero de 2017).
Figure (see Caption) Figure 46. The OVI webcam captured a clear image of the 4 February 2017 ash emission. Courtesy of OVI (Reporte Semanal de Monitoreo: Volcan Ubinas, Reporte 06, Semana del 30 de enero al 05 febrero de 2017).

OVS reported only magmatic gas and steam emissions (with no ash) during March 2017, with plumes rising to a maximum height of 300 m above the summit crater. OVI noted possible diffuse ash emissions on 1 and 2 March, but only steam and gas emissions for the remainder of the month. They reported variable seismicity with the frequency of daily events ranging from less than 10 per day to almost 70, averaging about 30 events per day.

Seismic energy decreased significantly during April 2017. Sporadic steam emissions reached maximum heights of only a few hundred meters above the crater. This relative quiet enabled OVS scientist Melquiades Álvarez to make a brief inspection of the summit crater on 14 April where he observed intermittent steam emissions rising from the base of the summit crater (figure 47). No ash emissions were reported during April. OVI reported that the number of seismic events dropped consistently during April from a high of 20 daily events on 1 April, to fewer than 5 events per day at the end of the month.

Figure (see Caption) Figure 47. A view into the summit crater at Ubinas on 14 April 2017 revealed only sporadic steam emissions. Photo by Melquiades Álvarez; courtesy of IGP-OVS (Reporte 07-2017-Actividad del volcán Ubinas, Resumen actualizado de la principal actividad observada del 01 al 15 de abril de 2017).

The reduction in activity continued during May 2017; steam and gas emissions became more sporadic and were rarely reported rising above 500 m over the summit crater. IGP-OVS reduced the alert level from Yellow to Green (2 to 1 on a 4-level scale) during the second half of the month. Seismicity reported by OVI fluctuated between 2 and 14 daily events. Ubinas remained quiet from June through September 2017, with only occasional minor fumarolic activity of steam or magmatic gas plumes that rose a few hundred meters above the summit crater (figure 48). Frequency of seismic events remained below 20 events per day through August and dropped to less than 10 per day in September.

Figure (see Caption) Figure 48. Virtually no emissions of any kind were reported from Ubinas after mid-July 2017, as seen in this image from the second half of August 2017. Courtesy of IGP-OVS (Reporte 16-2017-Actividad del volcán Ubinas, Resumen actualizado de la principal actividad observada del 16 al 31 de agosto de 2017).

Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Information Contacts: Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa (URL: http://ovi.ingemmet.gob.pe); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php?lang=es).


Wrangell (United States) — October 2017 Citation iconCite this Report

Wrangell

United States

62.006°N, 144.017°W; summit elev. 4278 m

All times are local (unless otherwise noted)


Occasional steam plumes and wind-blown ash, but no recent eruptive activity

A previous report on Wrangell noted that the heat flux from a crater on the N side of the summit rim had increased by an order of magnitude between 1964 and 1986 (SEAN 11:04). Wrangell has several active fumarolic areas in its summit caldera. These fumaroles frequently produce steam plumes that are mistaken for eruptive activity. The Alaska Volcano Observatory (AVO) receives several reports per year from pilots and local residents who observe larger than normal steam clouds over the summit. Although there have been some events possibly involving wind-blown ash, there have been no recent confirmed eruptions.

Activity during 1996-2000. According to Neal and McGimsey (1997), a pilot reported a suspicious cloud around 18 January 1996 rising about 1.5 km near Wrangell. The National Weather Service (NWS) confirmed that a robust steam plume had been visible over the volcano for several weeks.

McGimsey and Wallace (1999) reported that, on 3 June 1997, a pilot reported steam rising from the summit. On 24 June another report described a steam plume rising about 200 m above the summit. This sighting was not observed on satellite imagery.

McGimsey and others (2004) reported that on the morning of 14 May 1999, a NWS observer in Gulkana (about 75 km WNW) reported anomalous steam emissions containing a small amount of ash. During clear weather at approximately 0930 local time, a rapidly billowing grayish-white plume rose to about 900 m above the N summit crater. The observer stated that at this time of year, on clear days, a small, wispy, steam plume is usually visible above Wrangell in the early morning, and dissipates by early afternoon. On this day, the plume developed quickly, was abnormally voluminous, and had a grayish color.

A pilot had also observed the activity and noticed that more "dirt" surrounded the N crater than usual, and that on the upper part of the Chestnina Glacier high on the SW flank, blocks of ice were chaotically jumbled (higher relief between blocks) and that the glacier surface was much more crevassed than he had ever previously seen. He also observed that one of two known fumaroles at 3,350 m elevation on the S flank, which typically issue steam through ice holes, was surrounded by a sizeable patch of bare rock, a new development since his last recent flight over the area. The pilot further reported that he had observed no sign of flowage or melting events high on the flank, but that he had not flown over the lower reaches of the glacier. As of 1700 that day the NWS observer in Gulkana could still see a small steam plume and with binoculars could see that the snow around the summit area appeared to be light gray and that this was a definite color contrast and not an effect from shadows.

According to Neal and others (2004), a Trans Alaska Pipeline worker reported an unusually strong, white steam plume on 18 March 2000 between 0500 and 0600 local time. Later that day a National Park Service (NPS) employee in Kenny Lake reported robust steaming during the previous month from multiple sources on the SW flank between approximately 600-1,500 m below the summit. AVO found no anomalies in satellite imagery and concluded that no significant unrest had occurred.

Activity during 2002-2003. Neal and others (2005) reported that on 1 August 2002, AVO received several calls reporting a dark cloud drifting downwind from the general summit area and a dark deposit high on its snow-covered flank. AVO seismologists, however, checked data from the Wrangell seismic network and, based on a lack of correlative seismicity, concluded that no eruption or explosion had occurred. AVO also consulted with a local NPS geologist, who suggested that high winds had lofted fine-grained material exposed in the area near the summit fumaroles. On 4 August, an AVO geologist traveling in the area verified that a diffuse, light gray stripe extended a short distance down the flank of the volcano, emanating from the W caldera rim.

Subsequently, a local resident presented AVO with a video showing the waning portion of the event and his written observations. The witness described multiple dark billowing black ash puffs; the wind was from the E and the puffs were not rising over the summit. By the time he had returned to a good vantage point to film, about 10-12 minutes later, the billowing had stopped and the puffs had "turned a more grayish color."

According to the authors, the video showed discrete, light gray "puffs" that moved downwind and retained their individual integrity. There were no other weather clouds in the vicinity. A light gray, relatively motionless and irregular-shaped cloud sat near the caldera rim. A breeze could be observed at ground level (indicated by motion in the trees) but at altitude, clouds were not shearing rapidly. High on the snow-covered flank, a gray-colored swath extended from a high point at the W caldera rim near Wrangell's crater. The end of the video footage showed two distinct dark areas on the rim that were normally snow-covered. The resident's son reported a similar but more vigorous event on 2 August at about the same time of the day, but AVO received no further inquiries or reports.

AVO concluded that no volcanic process of significance had occurred. However, the authors stated "these observations remain enigmatic: lack of any seismicity would seem to preclude a phreatic or magmatic eruption and yet the pulsatory, 'puffing' nature of the dirty clouds is difficult to reconcile with a wind phenomenon."

McGimsey and others (2005) reported that NPS geologist Danny Rosenkrans contacted AVO with photographs taken by a local resident on 11 June 2003 showing an unusual towering cloud over the summit. Although the authors acknowledged that it could simply have been a common cumulus cloud, they noted that the absence of cumulus clouds in the area over nearby Mts. Drum and Sanford suggested that calm weather conditions permitted steam emissions from the known summit fumaroles to coalesce and form the plume-like cloud.

McGimsey and others (2005) also reported that on 18 September 2003 the Center Weather Service Unit called with a Pilot Weather Report of a steam plume 600-700 m over the volcano. The pilot reported no ash or sulfur smell. AVO scientists checked satellite imagery and seismograms and found nothing unusual.

Activity during 2007. McGimsey and others (2011) stated that an M 8.2 earthquake in the Kurile Islands on 13 January 2007 may have triggered seismicity at Wrangell and other nearby volcanoes. There were no reports of steaming immediately following this event; however, two weeks later, on 7 February, a relatively large local earthquake was recorded on the Wrangell network that was followed another two weeks later by steaming from the summit. According to the authors, this was the first report of Wrangell steaming in several years.

The authors also mentioned additional episodes of steaming in March 2007. On 25 March, a resident living about 80 km N of the summit reported a strong sulfur odor, an occurrence the resident stated was rare in his 15 years of living in the area. Earlier that day, the Wrangell network had recorded several multi-station seismic events. The authors note that several months later, local residents sent AVO photographs taken on 20 June of steaming from Wrangell and a deposit of ash extending from the W crater many hundreds of meters down the SW flank (figure 2). According to the authors, this ash was likely redistributed from the summit craters by strong winds. No anomalous seismic activity was observed.

Figure (see Caption) Figure 2. View of the northwest flank of Wrangell volcano on 20 Jun e2007 showing a dark stripe of probable redistributed ash extending from West Crater. The photo was taken at Mile 20 of the Tok Cutoff (Hwy 1), between Gakona and Slana. Strong north winds were reported. Note the steam plume rising from skyline saddle near North Crater (left). Photo by Norma Traw, courtesy of AVO.

Activity during 2010. A report by Neal and others (2014) noted that no significant eruptive activity or restlessness had occurred in 2010. However, the authors stated that AVO had received a report of possible vapor emission from the summit area. In May 2010, a single LIDAR swath taken during a summit overflight by glaciologists from the Geophysical Institute, University of Alaska-Fairbanks, depicted the topography of North Crater, a long-known fumarolic source on the NW rim of the ice-filled summit caldera. According to the authors, there are several secondary depressions, including a complex, kidney-bean shaped pit about 20 m deep and 200 m across, located in the center of North crater. This result is broadly consistent with previously recorded surveys of North Crater using photogrammetric techniques.

Neal and others (2014) reported that in early November 2010, a long-time local resident called AVO to report "more activity at the Mount Wrangell summit than he had ever seen before." He sent AVO several images of the volcano taken on 2 November and assured AVO that when the activity in question began, there had been no weather clouds in the area. He noted about ten "bursts" from the summit and said this was unusual compared to the typical steady emissions often seen. The authors stated that AVO reviewed available seismic and satellite data and, finding no evidence of volcanic signals, concluded that the phenomenon was most likely weather-related.

Activity during 2012. According to Herrick and others (2014), no eruptive activity or significant unrest had occurred in 2012, but as in previous years AVO received reports of fumarolic activity high on its flanks. The authors noted that, because of seismic station outages, AVO had removed Wrangell from its monitored list on 27 January 2012, where it remained for at least through the rest of the year. At the same time, the Aviation Color Code and Volcano Alert Level were downgraded from Green/Normal to Unassigned.

Herrick and others (2014) reported that on 11 March 2012, local observers noted "puffs of steam." AVO analysts using satellite images detected small plumes above known fumaroles. On 20 March 2012, a citizen noticed unusually rigorous steaming and described it as looking like "a pressure cooker shot through with nails." Steam rose from both the summit and a location on the SW flank at an elevation of about 3 km. Other calls to AVO registered concern about the significant plumes. Because no other evidence of significant volcanic unrest was detected, AVO concluded these events were likely generated by normal fumarolic activity.

References. Neal, C., and McGimsey, R. G., 1997, 1996 volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report OF 97-0433, 34 p.

McGimsey, R. G., and Wallace, K. L., 1999, 1997 volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report OF 99-0448, 42 p.

McGimsey, R. G., Neal, C. A., and Girina, O., 2004, 1999 Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report OF 2004-1033, 49 p.

McGimsey, R. G., Neal, C. A., Dixon, J. P., Malik, N., and Chibisova, M., 2011, 2007 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2010-5242, 110 p. Available online at http://pubs.usgs.gov/sir/2010/5242/.

Neal, C. A., McGimsey, R. G., and Chubarova, O., 2004, 2000 Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report OF 2004-1034, 37 p.

Neal, C. A., McGimsey, R. G., and Girina, O., 2005, 2002 Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report OF 2004-1058, 55 p., available online at http://pubs.usgs.gov/of/2004/1058/.

McGimsey, R. G., Neal, C. A., and Girina, O., 2005, 2003 volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report 2005-1310, 62 p., http://pubs.usgs.gov/of/2005/1310/.

McGimsey, R. G., Neal, C. A., Dixon, J. P., Malik, N., and Chibisova, M., 2011, 2007 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2010-5242, 110 p. Available online at http://pubs.usgs.gov/sir/2010/5242/.

Neal, C. A., Herrick, J., Girina, O. A., Chibisova, M., Rybin, A., McGimsey, R. G., and Dixon, J., 2014, 2010 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands - Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2014-5034, 76 p., http://dx.doi.org/10.3133/sir20145034/.

Herrick, J. A., Neal, C. A., Cameron, C. E., Dixon, J. P., and McGimsey, R. G., 2014, 2012 Volcanic activity in Alaska: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2014-5160, 82p., http://dx.doi.org/10.3133/sir20145160/.

Geologic Background. With a diameter of 30 km at 2000 m elevation, Mount Wrangell is one of the world's largest continental-margin volcanoes. The massive andesitic shield volcano has produced fluid lava flows as long as 58 km and contains an ice-filled caldera 4-6 km in diameter and 1 km deep, located within an ancestral 15-km-wide caldera. Most of the edifice was constructed during eruptions between about 600,000 and 200,000 years ago. Formation of the summit caldera followed sometime between about 200,000 and 50,000 years ago. Three post-caldera craters are located at the broad summit, along the northern and western caldera rim. A steep-sided flank cinder cone, Mount Zanetti, is located 6 km NW of the summit. The westernmost cone has been the source of infrequent historical eruptions beginning in the 18th century. Increased heat flux in recent years has melted large volumes of ice in the northern crater.

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

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subregion and subject.

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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