Logo link to homepage

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/).

Search Bulletin Archive by Publication Date

Select a month and year from the drop-downs and click "Show Issue" to have that issue displayed in this tab.

   

The default month and year is the latest issue available.

Bulletin of the Global Volcanism Network - Volume 42, Number 05 (May 2017)

Managing Editor: Edward Venzke

Ambrym (Vanuatu)

Occasional low-level ash emissions; lava lakes in Benbow and Marum craters active into April 2017

Asosan (Japan)

Lengthy eruptive episode 25 November 2014-May 2015; major explosions on 14 September 2015 and 8 October 2016

Etna (Italy)

Major eruptions with lava fountains, ash plumes, and lava flows during January-February, May, and December 2015

Fuego (Guatemala)

Strombolian activity, lava and pyroclastic flows, lahars, and ash plumes, June 2014-December 2015

Ibu (Indonesia)

Dome growth and ash plumes continue during December 2015-March 2017

Pacaya (Guatemala)

Steady growth of intra-crater cone during 2016 fills MacKenney Crater

Sabancaya (Peru)

Eruption with continuing ash plumes began on 6 November 2016

Semeru (Indonesia)

Activity diminishes 2009-2013, active lava dome growth 2014-2016

Tungurahua (Ecuador)

Nine ash plumes over 10 km altitude 2011-2014; lava flow in April 2014

White Island (New Zealand)

Ongoing unrest, with phreatic activity on 27 April and 13 September 2016



Ambrym (Vanuatu) — May 2017 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


Occasional low-level ash emissions; lava lakes in Benbow and Marum craters active into April 2017

Ambrym, a volcanic island in the archipelago of Vanuatu with a large caldera (figure 35) is frequently active. Since at least 2001 the caldera has been the site of two lava lakes (BGVN 29:06, 32:05, and 40:06). The Vanuatu Geohazards Observatory (VGO) is responsible for monitoring the volcano, and the Wellington Volcanic Ash Advisory Center (VAAC) tracks ash plumes to provide aviation warnings.

Figure (see Caption) Figure 35. Map of the Ambrym caldera showing features and lava flows through 1989. The insert shows an outline of the island with a fracture zone passing through an outline of the circular caldera in the center of the triangular island. Courtesy of Stromboli Online; original source unknown.

On 21 February 2015 the VGO issued a notice reminding the public that a minor eruption was occurring from a new vent inside the caldera. The Alert Level was raised from 2 to 3 (on a new scale of 0-5; see figure 30 in BGVN 40:06). Hazardous areas were near and around the active vents (Benbow, Maben-Mbwelesu, Niri-Mbwelesu and Mbwelesu), and downwind areas prone to ashfall. VGO reported both on 2 March 2015 and 27 May 2016 that activity at Ambrym had slightly decreased but remained elevated. The Alert Level was lowered to 2. Areas deemed hazardous were near and around the active vents, and in downwind areas prone to ashfall.

The Wellington VAAC reported that low-level ash emissions from Ambrym were identified in satellite images on 12 July 2016, 11-13 October 2016, and 3 April 2017. MODIS satellite thermal sensors have measured nearly continuous thermal anomalies over the past year ending in mid-April 2017, evident in both MIROVA (figure 36) and MODVOLC data (figure 37); similar levels of thermal anomalies are present in MODVOLC records since 2009.

Figure (see Caption) Figure 36. Plot of MODIS thermal infrared data analyzed by MIROVA showing log radiative power for Ambrym for the year ending 18 April 2017. Courtesy of MIROVA.
Figure (see Caption) Figure 37. MODVOLC thermal alerts measured during mid-January to mid-April 2017, as an example of similar densities of thermal alerts since about 2009. More than approximately 160 thermal alert pixels (red/orange squares) for this 3-month period are centered over the Marum and Benbow craters. Courtesy of (HIGP), MODVOLC Thermal Alerts System.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: Vanuatu Geohazards Observatory (VGO), Geo-Hazards office, Vanuatu Meteorology and Geo-Hazards Department (URL: http://www.vmgd.gov.vu/vmgd/); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://vaac.metservice.com/); 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/); Stromboli Online (URL: http://www.swisseduc.ch/stromboli/perm/van/links-en.html).


Asosan (Japan) — May 2017 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Lengthy eruptive episode 25 November 2014-May 2015; major explosions on 14 September 2015 and 8 October 2016

Japan's 24-km-wide Asosan caldera on the island of Kyushu has been active throughout the Holocene. Nakadake has been the most active of 17 central cones within the caldera for 2,000 years. Historical eruptions have been primarily basaltic to basaltic-andesitic ash eruptions, with periodic Strombolian activity. Minor ash emissions during May-June 2011, January-February 2014, and August-September 2014 preceded a major eruptive episode which began in late November 2014 and continued through 1 May 2016. Another eruption, with the largest ash plume in 20 years, occurred on 8 October 2016. The Japan Meteorological Agency (JMA) provides regular reports of activity; the Tokyo Volcanic Ash Advisory Center (VAAC) issues aviation alerts reporting on possible ash plumes. This report covers the period from the beginning of the late 2014 episode through March 2017.

Minor ash eruptions occurred at Asosan during 13 January-19 February 2014 and 30 August-6 September 2014. Trace ashfall was reported on 24 October 2014. A new large eruptive episode began in late November with ash plumes and Strombolian activity that continued from 25 November 2014 through late May 2015. Ash explosions also occurred on 28 June, 8 August, and 3 and 10-11 September 2015. A large explosion with pyroclastic flows occurred on 14 September. This was followed by intermittent ash plumes until 23 October 2015. Minor ash explosions took place on 7 and 25 December 2015. More explosions with ash were recorded on 17-18 February, 4 March, 16 and 30 April, and 1 May 2016. Nakadake crater was then quiet until a large explosion with an 11.9-km-high ash plume on 8 October 2016, after which no further explosive activity was reported through March 2017.

Activity during January-October 2014. After no activity during 2012 and 2013, increased seismicity in December 2013 preceded a series of minor ash eruptions between 13 January and 19 February 2014 (BGVN 40:02). The largest, on 29 January, rose 2.7 km and drifted NW. The next episode began on 30 August and lasted for only a week until 6 September 2014. The ash plumes were continuous during most of this brief time, but only rose as high as 2.1 km, and drifted N and NE. Other than a small amount of ashfall reported on 24 October, only steam plumes issued from Nakadake between early September and 25 November, the beginning of a lengthy eruptive episode.

Activity during November 2014-May 2015. The details of the beginning of this episode have been covered in a previous Bulletin report (BGVN 40:02). Ashfall was reported from ash plumes in several directions (NE, WSW, SW) as far as 38 km away, although plume heights were seldom above 2.4 km altitude (figure 36). Incandescence was observed at night from the webcams. Strombolian activity occurred from two active vents at Nakadake, producing frequent explosions of incandescent material onto the crater rim (figure 37). Blocks up to 10 cm wide were observed by JMA scientists within 1.2 km SW of the crater in mid-December 2014.

Figure (see Caption) Figure 36. Ash plume from Asosan on 26 November 2014. Image taken from Kumamoto University webcam located about 1 km SW of Nakadake crater. Courtesy of Volcano Discovery.
Figure (see Caption) Figure 37. Strombolian activity at the Nakadake crater at Asosan on 27 December 2014. Image taken from the Kyoto University webcam located at Nakadake crater which was destroyed during a subsequent eruption. Courtesy of Volcano Discovery.

Ash plumes and Strombolian activity continued from 25 November 2014 through late May 2015. The Tokyo VAAC issued near-daily reports through early May, when they became more intermittent until a month-long break beginning on 26 May. Plume heights were rarely higher than 1.5 km above the rim (3 km altitude). Field surveys noted intermittent ejecta from the Strombolian activity as high as 300 m above the crater rim. Ashfall was reported in the surrounding Kumamoto (W), Oita (NE), and Miyazaki (SE) prefectures (figure 38).

Figure (see Caption) Figure 38. A dense ash plume drifting S from Asosan on 13 January 2015. The ash plume is visible for at least 30 km. Upper image is the inset box of lower image. Courtesy of NASA Earth Observatory.

The JMA report for February 2015 noted that observations conducted by Kumamoto University indicated that as much as 1,500,000 tons of ash fell from the start of the eruption on 25 November 2014 through 2 February 2015. The results of GNSS (Global Navigation Satellite Systems) measurements suggested a slight inflation across Kusasenri, another cone located W of Nakadake, during February. In late April, ashfall was reported in areas to the SE and NE. A large-amplitude tremor that lasted for 5 minutes was recorded on 3 May. During a field survey on 5 May, JMA scientists observed that the S side of one of the pits (named the 141st pit) in the Nakadake crater had collapsed. On 26 May, an ash plume at 2.1 km altitude was reported 37 km NE of Kumamoto airport (about 25 km W of Asosan). This was the last ash plume reported until 28 June.

Activity during June-October 2015. A field survey by JMA personnel on 10 June noted a lake in part of the 141st pit. Thermal infrared measurements indicated temperatures of up to 80°C in the lake, which had not been observed since 8 July 2014; the lake had disappeared by 29 June. An ash plume was reported by the Tokyo VAAC drifting SW at 1.5 km altitude on 28 June.

Tremor amplitude began decreasing by mid-July, but the number of isolated tremors remained large. Steam plumes and a crater lake were again observed at the 141st pit in late July and August, and temperatures remained high (80-90°C) at the lake. A high-temperature fumarole (around 600°C) was observed SW of the 141st pit on 31 July and again during August. A small eruption was reported on 8 August by JMA with grayish plumes rising 600 m above the crater rim and minor ashfall reported on the S side of the crater. The Tokyo VAAC reported minor ash plumes on 3 and 10-11 September.

A series of new larger explosions began early on 14 September 2015 local time. JMA raised the Alert level from 2 (Do not approach the crater) to 3 (Do not approach the volcano) (on a scale of 1-5) the same day. The ash plumes were reported by JMA at 2,000 m above the crater rim drifting NW. A pyroclastic flow and ejecta impacted the immediate area around the crater. Aerial observation later that day noted discoloration extending 1.3 km SE and 1 km NE from the Nakadake crater as a result of the pyroclastic flow. Ashfall was also observed in areas to the W of the crater from northern Kumamoto Prefecture (including Tamana (50 km NW), Kumamoto City (40 km W), and Yamaga (40 km NW)) to Fukuoka Prefecture (more than 30 k NW). According to a news article in The Japan Times, about 30 tourists in the immediate area were evacuated, and some flights were either canceled or re-routed from Kumamoto Airport, 20 km W. Areas within 4 km of the craters were closed. The Tokyo VAAC reported the plume from the 14 September explosion at 3.7 km altitude drifting NW. During an overflight the following week, scientists observed evidence for pyroclastic flows as far as 3 km SE from the crater. Scientists from Kumamoto University estimated that about 40,000 tons of ash were ejected on 14 September.

Ash plumes were reported daily by the Tokyo VAAC until 23 October 2015, when several small explosions sent plumes up to 1.6 km above the crater rim. A field survey that day noted bombs scattered over the W and NW flank of the crater. After this, only steam plumes to 300 m above the rim were reported from Nakadake during November, leading JMA to lower the Alert level to 2 on 24 November.

Activity during December 2015-May 2016. A small explosion occurred on 7 December 2015. A field survey later that day revealed minor ashfall on the SW side of Nakadake crater. Visual confirmation of emissions associated with a relatively large-amplitude tremor on 25 December was obscured by clouds. During a 7 January 2016 survey, staff from JMA and the Aso Volcanological Laboratory observed fresh ejecta up to 0.5 m in diameter as far as 100 m SW of the crater rim, inferring that it resulted from the 25 December explosion.

The next reported ash eruptions took place on 17-18 February 2016. A field survey on 17 February revealed ashfall in Takamori (7 km SSE). Another survey on 18 February noted lapilli along the SW crater wall from the 17 February explosion. After the 18 February explosion, lapilli were observed 400 m NW of the crater and ashfall was noted in Aso City (10 km NE). Two MODVOLC thermal alerts on 28 February were located about 2 km NE of the active crater and likely unrelated to volcanic activity.

An explosion early in the morning on 4 March 2016 sent a milky-white plume to 1 km above the crater rim. A field survey later in the day confirmed slight ashfall on the E side of the crater. Small explosions were reported by JMA on 16 and 30 April. The Tokyo VAAC issued advisories, but ash was not detected in satellite imagery. The Tokyo VAAC issued no further advisories until 7 October 2016, although JMA noted a small explosion on 1 May with gray-white 'smoke' rising to 300 m above the crater. This was the last reported explosion by JMA until 7 October 2016. Seismic tremor amplitudes decreased after 15 May. During July through September, JMA noted that most of the crater floor was filled with hot water, and seismicity was low and intermittent.

Activity during October 2016-March 2017. After an explosion late in the day on 7 October 2016 and another one in the early hours of 8 October, JMA raised the Alert Level to 3. The Tokyo VAAC reported a large ash plume rising to 11.9 km altitude early on 8 October, and drifting NE. During an overflight on 8 October and a field survey on 12 October, significant ash deposits were observed (figures 39 and 40). They extended as far as 1.6 km on the NW flank and 1 km on the SE flank; ash was also abundant on the NE flank.

Figure (see Caption) Figure 39. View to the N of ash deposits around the Nakadake crater at Asosan after a large explosion on 8 October 2016. Photo by Kyodo/via Reuters.
Figure (see Caption) Figure 40. Area on the SW side of Asosan's Nakadake crater covered with ash by the explosion on 8 Oct 2016. Note the six bunkers on the left side of the crater in figure 39. They correspond to the bunkers in this image. Photo: JMA. Courtesy of Volcano Discovery.

Ashfall 3 cm thick was reported at the Aso City police station 6 km NE of Nakadake crater in Kumamoto Prefecture (figure 41). Ashfall was also confirmed in Oita (50 km NE), Ehime (across the Inland Sea, 150 km NE), and Kagawa (300 km NE) prefectures. According to news articles (Reuters), ashfall was reported as far away as 320 km. Kyoto University Volcano Research Center estimated the amount of ash ejected on 8 October to be around 50-60,000 tons. Samples analyzed by the National Institute of Advanced Industrial Science and Technology (AIST) and the National Research Institute for Earth Science and Disaster Prevention (NIED) revealed a 10% juvenile magma component, and that the explosions were possibly phreatomagmatic. Inflation was recorded near the crater up until 8 October, after which it remained steady.

Figure (see Caption) Figure 41. Cars are covered with volcanic ash from Asosan in Aso City, about 10 km NE of Nakadake crater in Kumamoto prefecture on 8 October 2016. Photo credit: Kyodo/via REUTERS.

On 12 November 2016, JMA observed incandescence at night at Nakadake crater for the first time since 26 April 2015. While SO2 emissions were reported as continuous after the 8 October explosion, the volcano was otherwise quiet and JMA lowered the Alert Level to 2 on 20 December 2016. There was no change of activity during January 2017, and thus the Alert Level was lowered to 1 on 7 February 2017. Field surveys during February noted that 80% of the bottom of Nakadake was filled with hot water. JMA reported no further activity through the end of March 2017.

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); The Japan Times (URL: http://www.japantimes.co.jp/news/2015/09/14/national/mount-aso-erupts-belching-black-plume/#.WRBxXlXyuJD); Reuters (URL: http://www.reuters.com/article/us-japan-volcano-idUSKCN12804E?il=0).


Etna (Italy) — May 2017 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Major eruptions with lava fountains, ash plumes, and lava flows during January-February, May, and December 2015

Italy's Mount Etna on the island of Sicily has recorded eruptions for the past 3,500 years. Lava flows, and explosive eruptions with ash plumes and lava fountains, commonly occur from its four major summit crater areas, the North East Crater, the Voragine-Bocca Nuova complex, the South East Crater (formed in 1978), and the newest, the New South East Crater (formed in 2011). The Etna Observatory, 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 brief summary of the major events during 2011-2014, and a detailed summary of events between January 2015 and March 2016. Major eruptions took place during 28 December 2014-2 January 2015, 31 January-2 February 2015, 11-16 May 2015, and 3-7 December 2015.

Summary of 2011-2014 activity. Most of the 44 eruptive episodes at Etna reported by INGV between 12 January 2011 and 2 December 2013 occurred at the New South Crater (NSEC) (figure 154) at the SE edge of the summit crater area. These eruptive events generally lasted for less than an hour and were characterized by sustained lava fountains accompanied by dense ash emissions and ejected pyroclastic material. Eruptive episodes occurred at Bocca Nuova (BN) in July 2011, July-August and October 2012, and January-February 2013. In addition, two weeks of intense Strombolian activity took place at Voragine (VOR) between late February and mid-March 2013. After an episode on 27 April 2013, Etna was quiet for six months until a large explosion on 26 October 2013 sent pyroclastic material several kilometers above the summit and caused a brief closure at the Catania airport. Two other episodes at NSEC during the middle and end of December 2013 were characterized by strong Strombolian activity, but without sustained lava fountains and fewer ash emissions.

Figure (see Caption) Figure 154. DEM (Digital Elevation Model) of the summit crater area at Etna, August 2007, updated with GPS measurements at NSEC in January 2014, and annotated by INGV. The white hatched lines outline the crater rims. BN = Bocca Nuova; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 6 January 2015, No. 2).

During 2014, major activity was characterized by four events: 1) modest Strombolian activity and lava flows from the NSEC between 21 January and around 7 April; 2) intense Strombolian activity at NSEC accompanied by a lava flow to the SE during 14-18 June; 3) strong Strombolian explosions and lava flows from several vents between NSEC and the E flank of the North East Crater (NEC) between 5 July and 10 August; and 4) intense Strombolian activity at NSEC accompanied by a lava flow during 10-15 August. Weak explosive activity was also reported from NSEC during the second week of October.

Summary of December 2014-March 2016 activity. Activity from NSEC during 28-29 December 2014 created two major lava flows and an ash plume. During 31 January-2 February 2015 NSEC produced a new lava flow and several ash plumes. A minor ash emission from the BN crater took place on 12 April 2015. A large Strombolian eruption began at NSEC during the night of 11-12 May 2015, followed by a lava flow down the E flank on 13 May. Activity continued until 16 May. Minor ash emissions were reported from the NEC on 20 May, and again during 16, 18, and 19 July 2015.

The VOR crater released minor ash emissions on 20 and 24 August 2015, and again on 18 September. Small amounts of ash were also observed in a plume from NEC on 4 October. This was followed the next week by sporadic ash emissions from VOR which grew into persistent Strombolian explosions by the end of October and continued into mid-November. Strombolian activity at a new crater on the E flank of NSEC began on 25 November; ash emissions began there on 2 December 2015.

A major lava fountaining event from VOR began on 3 December 2015 which generated an ash plume that dispersed ash 70 km NE. This was followed by a 7-km-high (over 10 km altitude) ash plume the next day that sent ash to the E. Three more lava-fountain episodes took place at VOR over the next two days. After this the activity decreased at VOR but increased at NSEC with a 3.5-km-long lava flow on 6 December, followed by ash emissions and Strombolian activity. Sporadic ash emissions continued from VOR, NSEC, and NEC during December 2015-March 2016.

Activity during December 2014-February 2015. After four and a half months of relative quiet, with only minor ash emissions during 7-16 October 2014, the NSEC began a new eruptive episode on 28 December 2014 (BGVN 40:02). This was the 45th major episode at Etna since January 2011, according to INGV, and was characterized by lava fountains, lava flows in two different directions from a NE-SW trending fissure that crossed the NSEC (see figure 152, BGVN 40:02), and a tephra plume that drifted to the E. INGV calculated a volume of lava from the 28-29 December event, based on a lava thickness of 1.5-2 m, of about 3 x 106 m3. Coarse ash and lapilli as large as 4-5 cm were reported in Fornazzo (9 km E), and mostly coarse ash and fine lapilli were deposited in Giarre (15 km E). Fine ash was also reported in Linguaglossa 17 km NE.

Explosive activity at NSEC resumed on 2 January 2015 with dense continuous ash emissions lasting until the next day that dispersed SW (figure 155). During the night of 1-2 January, INGV also observed new Strombolian activity from VOR for the first time in two years. During the next week, incandescent pyroclastic material rose up to 150 m above the crater rim and occasionally fell outside the crater onto the W and SW flanks; this was accompanied by minor ash emissions rising a few hundred meters. MODVOLC thermal alerts were issued nine times between 5 and 10 January. Strombolian and ash plume activity resumed at the NEC on 14 January for a few days (figure 156), but clouds obscured the summit area for most of the rest of the month. Intense degassing and minor ash was seen during clear weather through 31 January.

Figure (see Caption) Figure 155. Dense ash cloud from the New Southeast Crater (NSEC) at Etna that dispersed to the SW on 2 January 2015. A) taken from the webcam at La Montagnola (EMOV) 3 km S of the summit, and B) from the town of Tremestieri Etneo, 20 km S of Etna. Photo by Boris Behncke; courtesy of INGV (Il Parossismo dell'Etna del 28 Dicembre 2014 e la Susseguente Attivita al Crateri Sommitale, INGV).
Figure (see Caption) Figure 156. The summit area of Etna on 14 January 2015, observed from a Coast Guard AW139 helicopter. Minor gray ash was emitting from the Northeast Crater (NEC) and the Voragine (VOR). Dense steam plumes are visible coming from Bocca Nuova (BN) and the fumarolic vents at Southeast (SEC) and NSEC. Photo by Marco Neri; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 20 January 2015, No. 4).

A sudden increase in volcanic tremor amplitude in the early morning of 31 January 2015 indicated a new ash emission from the summit which was obscured from view by clouds. Later in the morning, fine ash fell over the snow in Rifugio Citelle (6 km NE). Strombolian activity was observed, along with a new lava flow moving to the SW, from the NSEC the next day. Sixteen MODVOLC thermal alerts were issued during 1-2 February while the lava flow was active. A field survey on 2 February determined that the lava front had stopped at 1,950 m elevation near the Monte Scavo area on the SW flank (figure 157). An ash emission occurred at NSEC in the early morning of 2 February; only persistent degassing was observed from the summit craters for the remainder of February.

Figure (see Caption) Figure 157. The 1 February 2015 lava flow at Etna observed on 2 February from the base of the S flank of the New Southeast Crater (NSEC). BN = Bocca Nuova, SEC = South East Crater. The NSEC is at the top right of photo. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 10 February 2015, No. 7).

Activity during March-September 2015. Degassing continued from the summit craters through March 2015 as viewed during limited clear weather. A high-temperature fumarole was observed in an infrared camera image on the E edge of NSEC on 29 March. The next ash emission occurred on 12 April from Bocca Nuova; it produced a plume a few tens of meters high that drifted SE, leaving fallout of fine reddish ash on the snow covering the western wall of the Bove Valley above 2,000 m elevation. A second smaller emission later in the day quickly dissipated.

A visit to the summit on 29 April 2015 confirmed persistent degassing from the craters. INGV scientists noted that the narrow septum separating the BN and VOR craters was much lower in height and broken through at the base, compared with earlier visits (figure 158). A small brownish-red ash plume on 1 May rose from BN; it likely resulted from a collapse inside the NW crater wall.

Figure (see Caption) Figure 158. A view from the SE rim looking into the Bocca Nuova (BN) crater at Etna on 29 April 2015. In the foreground (a) is the SE pit crater which is blocked with debris, and in the background (b), the NW pit crater is degassing. The red arrow indicates the portion of the septum (setto) between Bocca Nuova (BN) and Voragine (VOR) that has collapsed. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 5 May 2015, No. 19).

A Strombolian eruption began during the night of 11-12 May 2015 from the central part of NSEC. By midnight, the activity was strong enough to send tephra out of the crater and onto the flanks. A new lava flow appeared from a fracture just below the rim on the NE side early on 13 May; it generally followed the path of the 28 December 2014 flow to the NE. This was followed by increased ash emissions later in the day. The lava flow continued to advance NE during 14 May, into the Valle del Leone, and crossed near Monte Rittmann, flowing rapidly down the steep slope connecting the Valle del Leone with the Valle del Bove, headed towards Monte Simone (figure 159). By the end of the day it had traveled 3.5 km and was at 2,000 m elevation.

Figure (see Caption) Figure 159. Early morning on 14 May 2015 reveals the lava flow on the NE flank of Etna from a fissure on the E flank. Photo by Emanuela/Volcano Discovery Italia; courtesy of Volcano Discovery.

Intense Strombolian activity continued the next day at NSEC along with intermittent ash emissions. The lava flow split and flowed down the central part of the Valle del Bove, travelling 4.5 km to just below 1,800 m elevation. During the morning of 15 May a series of strong ash emissions lasting 2-3 minutes each continued from BN for about two hours. By the evening, the lava flow had traveled about 5 km and was at 1,700 m elevation (figure 160). Between 12 and 16 May, MODVOLC issued 103 thermal alerts for Etna.

Figure (see Caption) Figure 160. Images from the Monte Cagliato thermal camera (8.3 km ESE) taken on 14, 15, and 16 May 2015 at Etna show the summit from the E. The 13-16 May lava flow is seen progressively expanding into Valle del Bove until reaching the vicinity of Rocca Musarra and Serracozzo. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 19 May 2015, No. 21).

By the morning of 16 May, volcanic tremor had diminished and Strombolian activity had ceased, but magma was still feeding the lava flow until the afternoon, when it tapered off. During the morning of 20 May there were sporadic brown ash emissions from the NEC. After this, variable amounts of degassing continued at the summit craters for a few months, with the NEC being the most active. This period of relative quiet permitted INGV scientists to make several surveys of the summit during July to document the effects of the recent eruptions on the craters (figures 161 and 162).

Figure (see Caption) Figure 161. The vent at the bottom of the Northeast Crater (NEC) at Etna is viewed with both visible (top) and thermal (bottom) images on 2 July 2015. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 7 July 2015, No. 28).
Figure (see Caption) Figure 162. Views of the multiple vents at Etna's New Southeast Crater (NSEC) on 8 July 2015 showing changes caused by the 2014 and 2015 activity. Top: Vent on the S side of NSEC formed during the 31 January-2 February 2015 episode, looking SW. Bottom: The NSEC, looking SE at the main crater formed during the 28 December 2014 episode. Inside of this are several vents that were active during the 11-16 May 2015 episode. Photo by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 14 July 2015, No. 29).

During a field visit on 16 July 2015, INGV scientists witnessed intense pulsating gas emissions and loud noises at NEC; the gas often contained small amounts of reddish fine-grained ash. Increased gas emissions on 18 and 19 July rose a few hundred meters above the summit and occasionally released appreciable amounts of reddish ash that covered the W flank of the crater. Small puffs with minor ash were intermittent for the next several days. Only degassing from the summit craters was observed until 20 August when minor ash emissions were noted from VOR. The next day increased seismicity was recorded at the summit area, but there were no visible surface effects. Frequent gas emissions that included minor ash were observed at the summit during a visit on 24 August (figures 163 and 164).

Figure (see Caption) Figure 163. Emissions from Etna's summit crater on 24 August 2015. Steam emissions from the Northeast Crater (NEC) viewed from the N edge of the crater (top) and a weak ash emission from the Voragine (bottom), seen from the NW edge of the crater. Photos by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 1 September 2015, No. 36).
Figure (see Caption) Figure 164. Activity at the summit craters at Etna on 24 August 2015. Top: The Bocca Nuova seen from its E rim, with vapor emitting from the cone (conetto) that formed during 2011-2013 activity, and darker emissions of gas and small amounts of fine-grained ash from the pit located in the center of the crater floor (pozzo centrale). Bottom: fumarolic activity at the Southeast Crater (SEC) and New Southeast Crater (NSEC), viewed from the E edge of the Voragine. Photos by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 1 September 2015, No. 36).

Degassing continued at the summit craters during September. The Montagnola webcam captured a minor ash emission from VOR on 18 September 2015. A glowing fumarole was observed inside the NSEC during a summit visit on 23 September 2015 (figure 165).

Figure (see Caption) Figure 165. A glowing fumarole inside Etna's New Southeast Crater (NSEC) observed on 23 September 2015. Photo by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 29 September 2015, No. 40).

Activity during October-November 2015. Small but appreciable amounts of reddish ash which quickly dissipated were contained in a gas plume from NEC on 4 October 2015. Activity the following week (12-18 October) was characterized by sporadic, minor ash emissions from VOR; they were brownish-red, and were ejected during pulsating events that lasted for a few tens of seconds, repeating for as long as a few hours. Explosive activity was witnessed by a field crew at the bottom of VOR on 19 October. Lithic fragments and ashes were ejected in the immediate area of the crater. Activity increased at VOR during the end of October. During an inspection on 27 October, Strombolian explosions every 5-10 minutes sent incandescent pyroclastic material around the crater and produced minor ash emissions. A few bombs fell along the NW crater rim (figure 166).

Figure (see Caption) Figure 166. Activity at Etna's Voragine Crater on 27 October 2015. a) DEM of the summit crater area at Etna (DEM 2012, Aerogeophysical Laboratory - Section 2). The red circle indicates the position of the vent inside Voragine. BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. b) The vent on the N side of the Voragine; c) detail of a Strombolian explosion from the vent. Photo by B. Ragonese (Group Guide Etna Nord, 27 October 2015); courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 3 November 2015, No. 45).

On the morning of 2 November, after stormy weather conditions had blocked views of the summit for several days, volcanic ash was observed on the camera lens of the Montagnola (EMOV) webcam that was later washed away by rain. During a 4 November field survey, an ash deposit was discovered within layers of snow that fell between 31 October and 2 November on the upper part of the S flank (figure 167). The source of the ash remains unknown.

Figure (see Caption) Figure 167. Ash deposit at Etna interlayered in the snow that fell between 31 October and 2 November 2015, exposed along the track leading from the cable car station at Torre del Filosofo, at an elevation of approximately 2,800 m. Photo taken on 4 November 2015. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 10 November 2015, No. 46).

Modest Strombolian activity continued from the bottom of VOR during November 2015. A single small explosion occurred at the NSEC in the early hours of 8 November. During a 14 November field visit, INGV scientists observed intracrater explosive activity continuing at VOR which included several explosions with abundant ash emissions, interspersed with periods of strong spattering. On the E rim of the crater, several fresh, large (40 cm) clasts of volcanic debris had fallen as far as 12 m from the edge of the rim (figure 168).

Figure (see Caption) Figure 168. Explosive activity at the Voragine crater (VOR) at Etna on 14 November 2015. a and b) volcanic ash explosions; c) an episode of strong spattering of ejecta without ash emissions; d) a recent bomb from the eastern edge of the pit inside the crater. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 17 November 2015, No. 47).

By the third week in November 2015, ash emissions from VOR were more frequent and reached high enough levels to be visible from the webcams on the S slope. Lapilli and bombs rising more than 10 m above the northern edge of VOR were observed on a site visit on 19 November. During 20 and 21 November, a slow and gradual increase in the magnitude of volcanic tremor was noted, but there was no visible change at the summit. Weak Strombolian activity began at NSEC on 25 November and was observed in the Montagnola webcam. This led to the formation of a new "pit crater" located a few tens of meters below the E edge of the NSEC, with a diameter of 15-20 m.

Eruption of 2-8 December 2015. While on a site visit to VOR on 2 December 2015, INGV observed continuing Strombolian explosions with material ejected tens of meters above the crater rim; the cone at the bottom of the crater had continued to grow from the previous week. An explosion at the NSEC pit crater in the afternoon generated minor ash emissions, and Strombolian activity at VOR increased in the evening. A progressive increase in explosive activity began at VOR on 3 December. In the early morning, a lava fountain reached heights well over 1 km (figure 169) above the crater rim.

Figure (see Caption) Figure 169. Eruption from the Voragine crater (VOR) at Etna during the early morning of 3 December 2015. Witnesses reported the lava fountain as over 1 km in height. Photo by Marco Restivo/Demotix/Corbis; courtesy of Erik Klemetti.

An ash plume from this eruption initially drifted NE; ashfall was reported in Linguaglossa (17 km NE), Francavilla di Sicilia (20 km NE), Milazzo, Messina (70 km NE) and Reggio Calabria (70 km NE) (figure 170). Weak and sporadic ash emissions also occurred from the NSEC pit crater. INGV reported this as one of the most intense and among the largest eruptions from Etna in the last twenty years, similar to events on 22 July 1998 and 4 September 1999. After about one hour, activity diminished and returned to less intense Strombolian activity.

Figure (see Caption) Figure 170. The OLI instrument on Landsat 8 collected this natural-color view of the ash plume from Etna on 3 December 2015 drifting SE after initially drifting NE. The close-up image (bottom) reveals abundant fresh ashfall on the NE quadrant of the volcano. Courtesy of NASA Earth Observatory.

The explosive activity at VOR intensified again around 0900 UTC on 4 December, with renewed lava fountains and an ash plume that rose 7-8 km above the summit (10-11 km altitude); this episode lasted until about 1025 UTC (figure 171). Ash emissions continued throughout the day from the NSEC as well. Bombs and lapilli were deposited high on the SW slope above 2,000 m elevation. Ashfall was reported in the Giarre-Zafferana area 17 km E. Strombolian activity continued for much of the day at VOR until 2000 UTC, when the third lava fountain (since 3 December) erupted that lasted for about 90 minutes before subsiding again to less intense Strombolian activity.

Figure (see Caption) Figure 171. Eruption at Etna from the Voragine crater (VOR) in the morning of 4 December 2015, viewed from Cesaro, province of Messina (27 km NW). Copyrighted photo by Giuseppe Famiani, used with permission.

A fourth episode of lava fountaining from VOR took place mid-afternoon on 5 December 2015 and lasted for about 60 minutes. After this, activity decreased (both ash emissions and Strombolian explosions) from VOR, but increased at the NSEC pit crater, which grew due to continuous activity. In the early morning the following day two pyroclastic flows descended a few hundred meters toward the Valle del Bove. Around 1700 UTC, INGV personnel observed two lava flows, fed from the NSEC, headed toward Valle del Bove; one headed E for 3.5 km and reached 2,100 m elevation, and the other advanced ENE a few hundred meters to 2,600-2,700 m elevation. The easternmost vent at NSEC began emitting dark ash plumes on 7 December along with Strombolian activity that evening (figure 172). Activity at NSEC lasted for about 48 hours, ending in the morning of 8 December.

Figure (see Caption) Figure 172. Lava flows and Strombolian activity at Etna on the evening of 7 December 2015 from the new vent on the E side of the New Southeast Crater (NSEC) that formed in late November. Photo by B. Behncke, taken from Piano del Vescovo, on the SE flank. Courtesy of INGV (Etna Update, 8 December 2015).

Activity during December 2015-March 2016. Ash plumes accompanied by sporadic Strombolian activity were ejected from the NEC beginning on 7 December, and lasting intermittently through 14 December. Renewed explosions on 13 December at NSEC produced ash emissions, minor incandescence, and thermal anomalies. MODVOLC reported 84 thermal anomalies at Etna between 2 and 9 December.

INGV scientists observed on a 12 December visit that the BN and VOR craters were essentially joined into a larger, single crater after the early December explosions, similar to the former Central Crater at Etna. VOR was covered with tens of meters of pyroclastic debris. The debris also covered much of the rest of the summit area, including the lava flows from the previous winter. The parking lot of the visitor area, located 0.5-1 km W and NW of VOR, was marked with numerous impact craters several meters in diameter.

Two minor ash emissions occurred at VOR on 19 December. After that, only steam emissions were observed at the summit until 28 December when a new series of ash emissions with minor incandescence were ejected from the vent on the E flank of NSEC. They were sporadic over the next several days and had ceased by 8 January 2016. Trace amounts of ash were again reported from the E flank vent during the last days of January 2016 and on 6 February. During this time, emissions from NEC often contained trace amounts of ash. Modest amounts of brown ash were observed from the NEC in the morning of 9 February.

An explosive event at NEC on 23 February created an ash plume tens of meters high which drifted N and rapidly dissipated. Lightning was observed in the ash cloud. Ashfall was reported in Linguaglossa, Gaggi, and Santa Teresa Riva (40 km NE) from this event. A new emission on 25 February consisted of several pulses of medium-low intensity that produced a very dilute ash plume a few meters above the crater. During March 2016, sporadic ash emissions at NEC accompanied persistent degassing, but there were no reports of ashfall other than in the immediate area of the crater.

Sulfur dioxide data. Numerous images of SO2 emissions from Etna during this period were captured by the Aura instrument on NASA's OMI satellite. Emissions during the four major eruptive events discussed in this report (28-29 December 2014, 31 January-2 February 2015, 11-16 May 2015, and 2-7 December 2015) were the largest (figure 173).

Figure (see Caption) Figure 173. Sulfur dioxide plume data for Etna during the four major eruptive episodes covered in this report. Clockwise from top left: 29 December 2014, SO2 plume drifts E; 1 February 2015, SO2 plume drifts ENE; 15 May 2015 SO2 plume drifts SW, E and NE; the largest, from 6 December 2015, shows a detached plume drifting NNE and another plume moving NW that is truncated by the row-anomaly shadow. Courtesy of NASA/GSFC.

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/); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Erik Klemetti Eruptions Blog, Wired (URL: https://www.wired.com/author/erikvolc/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).


Fuego (Guatemala) — May 2017 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


Strombolian activity, lava and pyroclastic flows, lahars, and ash plumes, June 2014-December 2015

Volcán de Fuego, one of three active volcanos in Guatemala, 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. A major explosion on 13 September 2012 that caused significant ashfall to the S and SW (figure 30) was described by the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH) as the largest event in the prior 13 years. From September 2012 through June 2014 continuing explosions with ash plumes and ashfall, pyroclastic flows, lahars, and lava flows have impacted much of the region within 20 km of the volcano (BGVN 39:04). This report covers the ongoing activity from June 2014 through mid-December 2015. In addition to regular reports from INSIVUMEH, information comes from the Coordinadora Nacional para la Reducción de Desastres (CONRED), and aviation alerts are provided by the Washington Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 30. Guatemala's Volcán de Fuego (Volcano of Fire) erupted on the morning of 13 September 2012. According to the Coordinadora Nacional para la Reducción de Desastres (CONRED), the eruption included ash emissions to the W and a 500-m-long lava flow. This natural-color image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite. Courtesy of NASA-Earth Observatory.

Fuego was continuously active from June 2014 through December 2015. Ash plumes generally rose to heights of less than 1 km above the summit (4.8 km altitude) and dispersed ash over villages located 10-15 km S, SW, and W virtually every week, and occasionally to the NE and E. The highest plumes rose to 5.75 km in October 2014, 5.8 km in January 2015, and at least 6.1 km in February 2015. The most significant ash eruptions were in February 2015 when air traffic was disrupted in Guatemala City and in November 2015 when ashfall was reported up to 90 km SW. Incandescent ejecta rose 100-300 m above the crater rim on a regular basis, but the strongest events sent tephra and lava fountains as high as 500 m in July 2014, 800 m in August 2014, and 500 m in December 2015. Pyroclastic flows descended several drainages during larger explosive events in February, July, September, and November 2015. Numerous lava flows affected at least five different drainages around Fuego. They were reported during June, July, and August 2014, and February-April, June, and September-November 2015. Lahars during June and September 2014 and June 2015 damaged roadways and filled ravines with meter-sized debris. Table 12 shows the towns and drainages mentioned in the report and their distances and directions from the summit of Fuego, and is posted at the end of this report.

Activity during June-December 2014. Activity at Fuego during June 2014 was dominated by explosions that produced ash plumes which rose between 100 and 800 m above the summit (3.9-4.6 km altitude), and drifted most often generally westward. Minor amounts of ash were reported from explosions on 18-19 June in towns within 15 km of the summit, mainly El Porvenir (8 km ENE), Los Yucales (12 km SW), Santa Sofía (12 km SW), Morelia (10 km SW), Sangre de Cristo (10 km SW), and Panimaché (I and II, ~8 km SW). The Washington VAAC issued three reports of minor volcanic ash from explosions on 18, 20, and 23 June, which dissipated within a few hours.

Numerous lahars impacted drainages in June. Las Lajas (SE), Honda (E), and Seca (W) drainages were affected on 1 June, and Las Lajas and El Jute (SE) were impacted the next day. Honda, El Jute, Ceniza (SSW), and Santa Teresa (S) drainages had 1.5-m-diameter blocks in lahars on 5 June, and there were more lahars in Las Lajas and El Jute drainages on 9 June. Incandescent ejecta rose 100-200 m above the crater rim several times, and was responsible for avalanches descending the Taniluyá (SW), Trinidad (S), and Ceniza drainages. A new lava flow reported on 29 June descended the Taniluyá drainage for 150 m and caused avalanches in the nearby Ceniza drainage.

Surges of lava and incandescent avalanches traveled down six drainages (Santa Teresa, Taniluya, Ceniza, Trinidad, Las Lajas, and Honda) during the first half of July 2014, the farthest going 400 m down the Ceniza. MODVOLC thermal alerts possibly related to the lava flows and incandescent material were captured on 1, 2, and 11 July. Pulses of incandescent material rose to 100 m above the rim in early July, but increased to heights up to 500 m above the crater for the second half of the month, causing block avalanches down the flanks. Weak-to-moderate ash-bearing explosions early in the month increased to moderate-to-strong explosions by month's end that sent dark gray ash 400-600 m above the crater. The Washington VAAC reported ash plumes on 8, 11, 18, and 31 July. While no emissions were reported on 11 July, strong winds scattered recent ash as high as 5.5 km altitude (1.8 km above the crater). Ashfall was reported most days in nearby areas, including the Santa Teresa, Taniluya, Ceniza, and Trinidad drainages, and at the Observatory, Morelia, Santa Sophia, Ingenio los Tarros (15 km SW), Panimaché, Yepocapa (9 km NW), and Finca La Conchita.

During August 2014, explosions with incandescent blocks rose 50-400 m above the crater, but explosions as high as 800 m occurred several times. Block avalanches traveled down the flanks into Taniluya, Ceniza, Las Lajas, Trinidad, Honda, and Santa Teresa canyons. Ash plumes rose 300-900 m above the crater and drifted in various directions as far as 15 km before dissipating, numerous times during the month. The Washington VAAC reported a number of discrete ash emissions during 5-8 August, although most were not visible in satellite imagery, and again on 18 August when the highest plume of the month was reported at 5.5 km, or 1.7 km above the crater moving NW. Ashfall was reported in the villages of Yepocapa, Finca La Conchita, Sangre de Cristo, Morelia, and Panimaché I and II, Santa Sofia, Alotenango (8 km ENE), Antigua (18 km NE), San Miguel Dueñas (10 km NE), and around the Observatory. On 30-31 August lava flowed again towards Ceniza Canyon.

On 2 September 2014, INSIVUMEH seismically detected a lahar flowing through the Taniluyá drainage which was measured at a width of 75 m and a height of 2.5 m. The flow cut the road between Santa Lucia Cotzulmaguapa and the communities of Morelia, Santa Sofía, and Panimaché I and II. Lahars were also detected within Río Ceniza and Santa Teresa drainages. Incandescent blocks rose 75-100 m above the crater and weak avalanches were channeled into the Ceniza, Trinidad, Taniluyá, Santa Teresa, Las Lajas, and Honda drainages. Ash plumes rose 500-1,000 m above the summit crater and drifted a few tens of kilometers before dissipating. Fine gray ashfall was reported in communities within 10 km SW and ENE. A lava flow in Ceniza Canyon was 100 m long by 13 September. During 16 September, ashfall was reported in the communities of Alotenango, Antigua, and Ciudad Vieja (13.5 km NE), up to around 20 km NE. Another lahar was detected on 22 September, flowing down the El Jute and Las Lajas drainages on the SE flank carrying volcanic debris, lava blocks, branches, and tree trunks.

This moderate activity continued into early October 2014. Ash plumes that rose to 1,950 m above the summit (5.75 km altitude) were reported by INSIVUMEH during 11-12 October, and plumes to 5.5 km were reported by the Washington VAAC on 28 October. MODVOLC thermal alerts were issued during 5-6-7 October and 23-24 October.

Activity increased again in November 2014. Larger explosions generated block avalanches that descended the drainages on the SE and SW flanks, and ashfall was reported numerous times in the villages within 15 km SW. The Washington VAAC issued 5 series of alerts during 10-11 (drifting NE at 5.2 km), 13 (drifting S), and 17, 23, and 28-29 November (drifting 25 km W at 4.6 to 4.9 km altitude). MODVOLC thermal alerts were also issued on 7 days, including 3 pixels on 25 November.

Heightened activity continued into December 2014 with Special Bulletins issued by INSIVUMEH on 1 and 10 December noting more frequent and intense explosions (as many as 6-8 per hour), and dense gray ash plumes drifting 20 km W and SW depositing fine ash. Lava fountaining was reported on 10 December rising 100-150 m above the crater. The Washington VAAC reported ash plumes on 1-2, 5, 12-15 (S, SE), 27 (NW), and 29-30 (W) December based largely on reports from INSIVUMEH. The plume heights ranged from 4.1 to 4.9 km altitude (300-1,100 m above the crater). There were also MODVOLC thermal alerts on 9 days during December, including three pixels on 6 December.

Activity during 2015. Similar activity continued into January 2015. Ashfall was reported 10-15 km SW from plumes rising 550-950 m above the crater. Incandescent blocks traveled down the SW and SE drainages, generating small fires in vegetated areas. MODVOLC thermal alerts were issued on eight different days during January. The Washington VAAC only issued reports on 9 and 12 January. The 12 January plume was reported as discrete volcanic ash emissions seen in visible satellite imagery fanning out about 16 km W of the summit. The altitude of the plume was noted as 5.8 km, or 2 km above the summit.

A significant Strombolian eruption began on 7 February 2015 that lasted for about 22 hours; pyroclastic flows also descended multiple drainages (figure 31). CONRED reported that ash fell in Guatemala City (about 40 km ENE) and flights were diverted to El Salvador. The communities that reported ashfall from the event are shown in figure 32. The Washington VAAC reported an ash plume visible at about 6.1 km altitude (2.3 km above) and 45 km E of the summit. The next day, the plume was still visible at 5.8 km altitude about 100 km E.

Figure (see Caption) Figure 31. An ash cloud from a pyroclastic flow at Fuego on 7 February 2015 fills the horizon. Courtesy of INSIVUMEH and CONRED.
Figure (see Caption) Figure 32. Communities (in red) that reported ashfall from Fuego on 7 February 2015. Courtesy of CONRED.

On 8 February, although activity had decreased, the seismic network detected 30 explosions per minute. The explosions generated shock waves detected in areas 15 km S and SW. Lava flows up to 2 km long were observed in the El Jute and Trinidad drainages on the SE flanks, reaching vegetated areas and causing fires. Sixteen MODVOLC thermal alert pixels were recorded on 8 February; they continued on 9, 11-13 and 17 February before a 10 day break. INSIVUMEH noted that by 9 February activity levels had subsided with weak to moderate explosions producing ash plumes that rose 550 m above the summit and drifted 8-10 km NW (figure 33).

Figure (see Caption) Figure 33. Ash plumes and incandescence at Fuego on 9 February 2015. Courtesy of twitter user JL@parachico, (https://twitter.com/search?q=Volcan Fuego 2015&src=typd)

More intense activity returned on 16 February with 4-6 ash-bearing explosions per hour. The Washington VAAC reported the plumes at 4.9 km altitude, although INSIVUMEH noted pilot reports of ash at 7-9 km altitude. Ash fell in many villages to the NW, W, S, and SE more than 15 km from the summit. By 19 February, the ash plumes extended up to 150 km S of the summit. Intermittent emissions with dense ash plumes continued to rise from Fuego and disperse through 22 February.

A new effusive episode began on 28 February 2015 when lava fountains rose 300-400 m above the summit. A strong MODVOLC thermal alert signal persisted with multiple pixels through 3 March; afterwards MODVOLC pixels only appeared on six additional days during the month. One lava flow traveled 1.6 km S down the Trinidad drainage and another traveled 600 m W down the Santa Teresa drainage. Ash plumes also rose up to 1.25 km above the crater and drifted 35 km W generating ashfall in communities to the SW. Numerous ash plumes continued intermittently; VAAC reports were issued on 16 days during the month, through 24 March.

Hot spots appeared in satellite data numerous times during April 2015. Incandescent tephra was ejected 150-200 m above the crater. Block avalanches continued from the end of a new 300-m-long lava flow in the Trinidad drainage on 17 April. MODVOLC thermal alert pixels appeared on 12 days through 26 April, with large multi-pixel alerts on 17 and 18 April. According to INSIVUMEH, ash plumes continued rising 650-850 m above the crater and drifting 8-11 km S, SW, and W, but VAAC reports of ash only appeared on 17 and 18 April.

Far fewer MODVOLC thermal alerts were issued during only five different days spanning 5-31 May 2015. The Washington VAAC issued reports of ash plumes on 13, 15, 17, and 18 May. INSIVUMEH noted an increased number and intensity of explosions briefly during 14-15 May; ash plumes rose 450-750 m above the crater and drifted 10-12 km W and SW. They also reported a S-flank lava flow on 18 May. Ashfall was reported in the communities within 10 km SW of the summit. Incandescent material was ejected 150-200 m above the crater, causing block avalanches in drainages on the S and SW.

Strombolian activity again increased during June 2015, ejecting material 300 m above the crater for 30 hours during 4-6 June. Ash plumes rose to around 1 km above the summit and drifted 10-15 km S and SW. During this episode, lava flows traveled 600 and 1,200 m down the Santa Teresa and Trinidad drainages. Two cinder cones within the crater were reported on 6 June. A lahar was detected on 12 June that was 25 m wide and 2-3 m deep, travelling S down the Trinidad drainage carrying abundant volcanic material and blocks 1-2 m in diameter. MODVOLC thermal alerts were captured on 16 days during June. The Washington VAAC reported ash plumes from explosions on 5, 6, and 28 June with altitudes below 4.8 km and ashfall within 10 km in many areas, including La Soledad (11 km N) and Acatenango (12 km NW). During 29-30 June a 300-m-long lava flow was visible in the Las Lajas drainage on the SE flank.

Based on INSIVUMEH notices, CONRED reported that for a 30-hour period during 30 June-1 July 2015 activity at Fuego was at a high level, characterized by explosions, high-temperature pyroclastic flows (that began on 1 July), and ashfall. Ash plumes rose 4.8 km above the crater and drifted 25 km W and NW, producing ashfall in 22 local communities. An SO2 plume drifting NW was captured by the OMI instrument on the Aura satellite on 1 July (figure 34). The majority of material deposited by pyroclastic flows was located in the Las Lajas drainage where the flow reached 4-5 km in length. People in the La Reunion area near the river bed were evacuated. Nine MODVOLC thermal alert pixels were captured on 1 July, and 10 on 2 July, corroborating the high-temperature pyroclastic flows reported by CONRED. Only single thermal alert pixels were captured after that on 14, 25, and 29 July. The Washington VAAC reports issued on 1, 2, 6, and 14 July included reports of ash emissions to 4.9 km extending up to 55 km SW.

Figure (see Caption) Figure 34. An SO2 plume drifting W from Fuego on 1 July 2015 during a phase of high eruptive activity. Courtesy of NASA GSFC.

Although there were no VAAC reports issued between 14 July and 1 September 2015, the number of MODVOLC thermal alerts increased substantially during August from the previous month, with an especially large multi-pixel signature from 5 through 10 August. INSIVUMEH reported ash plumes rising to 4.2-4.6 m dispersing ash around 12 km in various directions several times during the month, as well as incandescent material rising to 200 m above the crater and sending block avalanches down the drainages on the S and W flanks.

Lava fountains, explosions, pyroclastic flows, and ashfall in surrounding areas picked up again beginning with a strong MODVOLC thermal alert signal on 30 August and lasted through 2 September. By the time activity decreased that day, the remnants of three lava flows were visible in the Santa Teresa, Trinidad and Las Lajas drainages on the S and SE flanks. There were no MODVOLC thermal alerts between 2 and 27 September, and no Washington VAAC reports between 2 and 29 September. During this time, INSIVUMEH reported moderate levels of explosions with ash-bearing plumes rising to 4.5 km altitude and drifting 10-12 km from the summit, dispersing minor amounts of ash to the villages within that radius.

The next pulse of activity began with three MODVOLC thermal alert pixels on 27 September 2015. Lava flows were persistent during October, as reported by INSIVUMEH and evidenced by the number of MODVOLC thermal alert pixels. Multi-pixels days were common between 27 September and 14 October, and again from 23-28 October. INSIVUMEH first reported lava flows on 4 October that were 400 m long in the Santa Teresa drainage and 300 m long in the Trinidad canyon. By 8 October the Trinidad canyon flow was 1.5 km long; the Santa Teresa canyon flow reached 1 km from the crater by 13 October. These flows were fed by Strombolian activity that had increased on 10 October, sending incandescent material 200 m above the crater (figure 35). Lava fountains during 13-14 October produced another lava flow in the Santa Teresa canyon that was 500 m long by 20 October.

Figure (see Caption) Figure 35. Lava flows in the Santa Teresa drainage at Fuego fed by Strombolian activity from the summit vents, 10 October 2015. View is from Yepocapa, 8 km NW. Courtesy of INSIVUMEH (http://www.insivumeh.gob.gt/erupcion_volcan_fuego.html)

A new surge of activity beginning on 21 October through the end of the month generated 200-300 m-high lava fountains that advanced lava flows 1.5 km down the Santa Teresa, Trinidad, and Las Lajas drainages. Ash plumes during October reported by INSIVUMEH rose 450-1,200 m above the crater, dispersing ash to villages 10-12 km S and SW on several occasions; no ash plumes were observed by the Washington VAAC until 26 October when a plume rose to 5.2 km (1.4 km above the summit) and drifted SW.

On 1 November, the Washington VAAC reported discrete ash emissions at 5.2 km altitude drifting SW that dissipated within 50 km early in the day, and a second slightly higher plume later in the day that also dissipated quickly. Most of the rest of the ash plumes at the beginning of November were under 1 km in height above the summit and dispersed ash to communities within 12 km SW. Block avalanches from a 200-m-high fountain of incandescent ejecta traveled down Santa Teresa, Trinidad, and Las Lajas drainages early in the month.

New lava flows were reported in the Las Lajas and El Jute drainages beginning on 9 November 2015. A strong multipixel MODVOLC signal was captured during 7-11 November, including 12 pixels on 9 November. By 10 November the lava flows were 2.5 km long, and incandescent material was ejected 300 m high. Ashfall was reported in Panimache I and II, Morelia, Santa Sofia, El Porvenir, Sangre de Cristo and the municipality of San Pedro Yepocapa. Pyroclastic flows also descended the E flank on 10 November. The Washington VAAC reported an ash plume that morning below 5.2 km altitude drifting WSW at 15 knots. The plume was visible in satellite imagery extending for 110 km to the coast, and possibly out over the ocean to 185 km. By late in the day, ongoing lava flows and rockfalls were causing ash to rise to 6.1 km altitude and the winds were moving the ash out of the valleys around 140 km SW of Fuego. Ashfall was reported from communities as far as 90 km to the west including San Andrés Osuna (12 km SW), El Zapote (10 km S), Siquinala (20 km SW), Santa Lucia Cotzumalguapa (22 km SW), Mazatenango (87 km W), Patulul (30 km W), and Cocales (35 km W).

Strong multi-pixel MODVOLC signatures increased again between 25 November and 2 December and correlate with INSIVUMEH's reporting of large and strong explosions and new lava flows beginning on 29 November. The Washington VAAC reported ongoing emissions to 5.2 km altitude on 25 November which dissipated quickly. INSIVUMEH noted lava fountains rising to 500 m above the crater, feeding four lava flows that traveled 3 km down the Ceniza, Trinidad, Las Lajas, and Santa Teresa drainages on 29 November. A fifth lava flow was seen the next day along with small pyroclastic flows in the Honda drainage on the E flank. A new pulse of ash emissions to 5.5 km began on 30 November extending 45 km SW from the summit and continued through 1 December drifting more to the NW into S Mexico before dissipating.

Discrete ash emissions to 5.5 km altitude which quickly dissipated were observed in webcam imagery on 9 December 2015. Late the following day, another plume was spotted at the same elevation drifting 37 km NNE. Activity increased during the night of 14-15 December, characterized by an increased number of explosions (4-6 per hour). Ash plumes rose almost 1 km high and drifted 10-15 km NE, E, and SE. Two 800-m-long lava flows were active in the Trinidad and Santa Teresa drainages. Strong multi-pixel MODVOLC alerts appeared daily from 11-18 December. The Washington VAAC observed ongoing emissions on 16 December at 5.2 km altitude; they drifted as far as 280 km SW of Fuego. Lava flows remained active in the Las Lajas, Trinidad, and Santa Teresa drainages. Activity decreased toward the end of the month with modest ash emissions rising less than a kilometer above the summit, and incandescent material rising 150 m above the crater.

Table 12. Towns and drainages around Fuego and their distance and direction from the summit.

Towns Location
Acatenango 12 km NW
Alotenango 8 km ENE
Antigua 18 km NE
Chimaltenango 21 km NNE
Ciudad Vieja 13.5 km NE
Cocales 35 km W
El Porvenir 8 km ENE
El Zapote 10 km S
Ingenio los Tarros 15 km SW
La Soledad 11 km N
Los Yucales 12 km SW
Mazatenango 87 km W
Morelia 10 km SW
Panimaché (I and II) 8 km SW
Patulul 30 km W
San Andrés Osuna 12 km SW
San Miguel Duenas 10 km NE
Sangre de Cristo 10 km SW
Santa Lucia Cotzumalguapa 22 km SW
Santa Sofía 12 km SW
Siquinala 20 km SW
Yepocapa 9 km NW

Drainage / Ravine
Direction
Ceniza SSW
El Jute SE
Honda E
Las Lajas SE
Santa Teresa S
Seca W
Taniluya SW
Trinidad S

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/); 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); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).


Ibu (Indonesia) — May 2017 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


Dome growth and ash plumes continue during December 2015-March 2017

Previously reported activity at Ibu through November 2015 included shallow seismicity, lava dome growth on the N part of the crater, and occasional white-to-gray plumes rising as high as 500 m above the summit (BGVN 40:11). This report, describing activity through early March 2017, is based on information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Centre (VAAC).

During the reporting period (at least through 22 Aug 2016), the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side. Inclement weather often prevented visual observation.

According to PVMBG reports, similar activity to that previously described in 2013-2015 continued through at least 22 August 2016. Seismicity was dominated by signals indicating surface or near-surface activity, and the lava dome in the N part of the crater continued to grow. Occasional plumes (described variously as white-to-medium gray, gray-to-gray black, and ash) rose to altitudes of 1.5-2.4 km (200-1,100 m above the summit crater).

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed infrequently during the reporting period. Hotspots were observed on seven days in December 2015, but only 1-3 days per month for subsequent months through March 2017. No hotspots were recorded during December 2016 and February 2017. In contrast, the MIROVA detection system recorded numerous anomalies between April 2016 and March 2017 (figure 10), almost all of which were at least 1 km from the volcano and of low power output.

Figure (see Caption) Figure 10. Thermal anomalies recorded at Ibu by the MIROVA system using MODIS infrared satellite data for the year ending 10 March 2017. Courtesy of MIROVA.

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

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


Pacaya (Guatemala) — May 2017 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Steady growth of intra-crater cone during 2016 fills MacKenney Crater

Guatemala's Pacaya volcano has a 450-year record of frequent historical observations of activity, in addition to confirmed radiocarbon dating of eruptions over 1,500 years. Its location approximately 30 km S of the capital of Guatemala City makes it both a popular tourist attraction as a National Park, and a hazard to the several million people that live within 50 km. Activity during the last 50 years has been characterized by extensive lava flows, bomb-laden Strombolian explosions, and ash plumes that have dispersed ash to cities and towns across the region.

Major lava flows and Strombolian activity in January and early March 2014 were previously reported (BGVN 42:04). This report describes activity for the remainder of 2014 through 2016. Information was provided by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), the Coordinadora Nacional para la Reducción de Desastres (CONRED) of Guatemala, and the Washington Volcanic Ash Advisory Center (VAAC), which provides air traffic advisories. Satellite imagery and visitors to the volcano also provided evidence of activity.

Ash plumes were intermittent for the remainder of 2014 after the activity of January and March; they were reported on 10 April, 25 and 28 August, during 11-18 November, and on 22 December. Episodes of ash emissions in mid- and late January 2015 and up to 17 February marked the end of this episode. Renewed activity on 8 June 2015 included intermittent ash plumes and incandescence observed at the summit. Ash plumes were intermittent until 22 September but observations of incandescence grew more frequent and intense during the rest of the year. A small intra-crater cone was growing in mid-December 2015 at the center of MacKenney Crater. Strombolian activity from the cone continued throughout 2016. It was most active during June and July, depositing new ejecta on the N and W flanks of the volcano. Although it had quieted down by the end of the year, persistent degassing, steam plumes, and occasional incandescence were still observed. The intra-crater cone had filled much of MacKenney Crater by December 2016.

Activity during April-December 2014. Extensive lava flows in January and early March 2014 affected large areas on both the N and S flanks of Pacaya (BGVN 42:04). The volcano quieted down significantly after the first week in March. A plume with minor ash was observed rising to 2.6 km altitude and drifting approximately 1 km S and SW on 10 April. During the rest of April through late August 2014 only white and blueish-white plumes rose 50-150 m above the summit, and no thermal anomalies were reported.

INSIVUMEH reported on 25 and 28 August 2014 that small bursts of gray ash rose 200-700 m above the summit and drifted S and SW. Otherwise, only plumes of steam and magmatic gases were observed during August through early November. Small bursts with minor amounts of ash were reported again on 11, 16, and 18 November 2014 that rose a few hundred meters above the summit and drifted S and SW. Incandescence was observed at the summit crater on 9 December. Only steam and gas plumes were observed by INSIVUMEH for the rest of December 2014, but the Washington VAAC reported an emission of gases and possible minor ash to 3.4 km altitude (900 m above the summit) on 22 December drifting S for a few hours before dissipating.

Activity during 2015. Renewed seismic activity with numerous small ash emissions was reported in a special bulletin by INSIVUMEH on 14 January 2015. They noted that about 24 weak explosions with ash had occurred in recent days. In another special notice issued on 28 January, they reported that ash emissions originating from MacKenney Crater had drifted 4 km S and SW. They noted as many as 40 ash explosions within the previous 24 hours. Gas plumes were also observed from an area on the S flank.

Weak ash and steam emissions rising a few hundred meters above the summit were also reported on 1 February 2015. MODVOLC showed three thermal alert pixels on the SE flank on 10 February, but they were near an area of agricultural development and likely not be related to volcanism. Only steam emissions were reported by INSIVUMEH until 13 February when a new series of weak explosions sent dark gray ash plumes 500-700 m above the crater; the plumes were observed until 17 February. After this, INSIVUMEH reported only minor seismicity and steam-and-gas plumes through 5 June. Three MODVOLC pixels on 25 March, located on the E flank, were in agriculture areas similar to the February alerts.

Continuing ash explosions every three or four hours indicated renewed activity on 8 June 2015, as reported by INSIVUMEH. The seismic network detected signals consistent with collapse inside the crater along with ash emissions. Plumes with gas and minor ash were reported on 14, 16, and 18 June rising 50 m above the crater. Increased seismicity on 18 June led to noises that were audible 3 km away. For the rest of June and into the first week of July, ash was frequently dispersed around the crater from gas-and-ash plumes, and incandescence was visible on clear nights. Incandescence from MacKenny crater was reported again on 23 August. CONRED also reported that the low-frequency tremors that started in mid-June were continuing in mid-August.

Blue and white plumes, along with minor ash emissions, were observed drifting W of the summit crater on 1 September 2015, and the low-frequency tremors and incandescence continued on clear nights for the rest of the month. Two ash plumes, on 11 and 22 September, rose to 700 and 900 m above the crater. Although only a single MODVOLC thermal alert pixel appeared near the summit on 2 October, numerous observations of incandescence were made by INSIVUMEH during the month. Cloudy weather limited observations of incandescence during November to only the first and last weeks, but observations were nearly continuous during December.

A visit to the summit of Pacaya on 22 December 2015 by Volcano Discovery provided evidence of the activity responsible for the incandescence observed during the previous months (figure 71). During stronger intervals of activity, lava bombs were ejected 150-200 m above the crater rim, but generally fell back within the crater. A few fresh (days-to-weeks-old) bombs were seen near the eastern crater rim. Around the main vent at the bottom of the approximately 100-m-deep crater, a small cone, about 15 m tall, had formed. Bubbles of lava burst into fragments of spatter from the vent, building up the cone (figure 72). A small secondary vent at the eastern side of the cone also showed occasional spattering, mainly during phases of elevated activity at the main vent. Parts of the crater floor were covered by recent lava flows.

Figure (see Caption) Figure 71. A small cinder cone with a vent 2-3 m wide is active on the floor of MacKenney Crater at the summit of Pacaya on 22 December 2015. Courtesy of Volcano Discovery (photo by Tom Pfeiffer).
Figure (see Caption) Figure 72. Lava bubbles inside the cinder cone at Pacaya burst into thousands of glowing fragments on 22 December 2015, building the cinder cone. Courtesy of Volcano Discovery (photo by Tom Pfeiffer).

Activity during 2016. INSIVUMEH reported that during January 2016, Pacaya exhibited activity similar to 2015. Incandescence was visible at night during 20-27 January, and during this time a hot spot was captured at the summit in a Landsat image. A small collapse on the NW side of the inner crater generated a column of gray emissions that rose to 3 km altitude (500 m above the summit) on 20 January. A Landsat image on 12 February again showed incandescence and a steam plume rising 100 m above the crater. Incandescence reappeared on 20 February and persisted for the remainder of the month. Emissions from the main crater were primarily magmatic SO2 and steam; they generally rose 50-150 m above the crater and drifted N.

Incandescent activity at MacKenney Crater increased during March and April 2016. Landsat images showed incandescence aligned along a NW-SE trending fissure within the crater. MODVOLC thermal alert pixels appeared on 1, 19, and 26 March and again on 10 April; the 10 April thermal alert was readily visible as a hotspot in satellite imagery (figure 73). INSIVUMEH noted that the intra-crater cone continued to grow during March and April. The MIROVA Log Radiative Power data also registered a number of thermal anomalies during March and April (figure 74).

Figure (see Caption) Figure 73. Incandescence at the MacKenney Crater at Pacaya taken with the European Space Agency's Sentinel 2 satellite on 10 April 2016. Image courtesy INSIVUMEH and ESA (Reporte Mensual, Volcan Pacaya, April 2016).
Figure (see Caption) Figure 74. MIROVA Log Radiative Power data for Pacaya for the year ending 28 December 2016. Thermal anomalies within 5 km of the summit were reported a number of times during January-April, and again during June and July. Courtesy of MIROVA.

During May 2016 the intra-crater cone continued to grow, and minor Strombolian activity during the night was observed regularly by INSIVUMEH. Most of the activity occurred on the N flank, with some incandescence on the W flank at the end of the month. Seismicity continued at modest levels with occasional explosions resulting from minor collapses of the crater wall. Strombolian activity increased during June, although the degassing plume did not reach more than 400 m above the crater. The webcam recorded incandescent material accumulating on the NW flank.

Seismic activity during July 2016 remained constant, caused by degassing and Strombolian explosions which were observed during 7-10 July. Material was ejected 75 m above the crater during 23-24 July. Views of Pacaya from the NW and the S during July and August revealed minor fumarolic activity from the summit as well as evidence of the extensive January-March 2014 lava flows (figures 75 and 76). Incandescence continued to be observed at night and in satellite images during July and August, with debris from the Strombolian activity concentrated on the N and NW flanks.

Figure (see Caption) Figure 75. View of Pacaya on 18 July 2016 from La Meseta (the Mesa) on the NW flank showing lava flows from early 2014 and steam emissions from the summit. Courtesy of INSIVUMEH (Reporte Mensual, Volcan Pacaya, July 2016).
Figure (see Caption) Figure 76. View of Pacaya from Los Pocitos, 5 km S of the summit, on 17 August 2016 showing steam plume drifting SW and part of the extensive 2014 lava flow in the foreground. Courtesy of INSIVUMEH (Report Mensual, Volcan Pacaya, August 2016).

By October 2016, observations of incandescence at the summit were less frequent. INSIVUMEH noted that intermittent incandescence continued for the rest of 2016 with new material accumulating within MacKenney Crater. Visitors to the intra-crater cone in early December 2016 noted strong degassing of steam, magmatic gases, and possible ash, but no Strombolian activity. The intra-caldera cone was significantly larger than when observed a year earlier (figure 77).

Figure (see Caption) Figure 77. Intra-crater cone at Pacaya in early December 2016. Courtesy of Volcano Discovery (Image from Mynor Marroquin via @ClimaEnGuate / Twitter).

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.php); 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/); European Space Agency (ESA) (URL: http://www.esa.int/ESA); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).


Sabancaya (Peru) — May 2017 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Eruption with continuing ash plumes began on 6 November 2016

Although historical records of eruptive activity at Peru's Sabancaya volcano go back to 1750, there have only been a handful documented since the 1980s; activity that began in 1986 was the first recorded in over 200 years. During the last period of substantial ash eruptions between 1990 and 1998 ashfall deposits up to 4 cm thick were reported 8 km E of the volcano. Evidence for minor ash-emitting events was reported in 2000 and 2003. Intermittent seismic unrest and fumarolic emissions characterized activity from late 2012 through 2015. Seismically detected explosions during August 2014 led to releases of SO2 gases and steam plumes, some as high as 2 km, along with possible minor volcanic ash. Possible minor volcanic ash emissions were also mentioned by Peruvian authorities and pilot reports between September and December 2014 but there were no confirmed reports of ash emissions during this period. A crater inspection during 9-10 July 2015 found trace amounts of ash at the crater that contained crystals of plagioclase, biotite, and amphibole, along with fresh volcanic glass. These were interpreted by the volcanologists to represent minor ash emissions during recent weeks.

Unrest with steam plumes and variable seismicity continued during 2016 until 6 November when continuous ash-bearing explosions began. Activity during 2016 through February 2017 is covered in this report with information from the two Peruvian observatories that monitor the volcano: Instituto Geofisico del Peru - Observatoria Vulcanologico del Sur (IGP-OVS), and Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET). Aviation reports and notices come from the Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data is reported from several sources.

Sabancaya maintained a level of seismic and fumarolic unrest through most of 2016, similar to levels recorded in 2014 and 2015, with almost constant water-vapor and SO2 plumes rising from the crater. Additionally, tectonic (not volcanic) seismicity caused damage and fatalities in nearby villages. An explosion on 27 August 2016 did not produce ash, but new areas of fumarolic activity on the N flank were observed around this time. Hybrid seismic events related to the movement of magma, and SO2 emissions, increased noticeably during September and October 2016. An explosive eruption with numerous ash plumes began on 6 November 2016. Continuous ash emissions with plume heights exceeding 10 km altitude were recorded several times through February 2017. Thermal anomalies were first measured in satellite data in early November, along with numerous significant SO2 plumes.

Activity during January-October 2016. Heights of plumes consisting of water vapor and minor magmatic gases generally decreased during January 2016, from 1,800 m to less than 1,200 m by the month's end. Seismic activity was generally low in terms of both numbers of events and magnitude. The daily number of events ranged from 8 to 20, and the largest event, a M 4.0, was registered on 29 January.

Plume heights continued declining in February, from 1,000 m during the first week to 400-800 m by the end of the month. During March, April, and May the heights of steam and SO2 plumes ranged from 200 to 1,300 m above the crater, and values of SO2 flux ranged from 600 to 1,500 metric tons per day (t/d). These values increased only slightly in July and August; plumes rose 2,000 m above the crater rim and SO2 emissions were as high as 2,600 t/d.

Seismicity continued at low levels through late August. Three significant tectonic earthquakes in mid-August were not related to volcanic activity, but the earthquake 25 km NE of Sabancaya on the Ichupampa fault on 14 August caused at least four fatalities, and numerous aftershocks were recorded in the region. A spike in SO2 emissions at the volcano to 4,030 t/d occurred shortly after the earthquake.

On 27 August 2016 there was a hybrid-type seismic event that IGP-OVS interpreted as an explosion of 72 MJ (Megajoules) of energy. An official statement from the Scientific and Technical Committee for Risk Management (IGP-OVS, OVI-INGEMMET, and others) issued on 6 September noted that "dense gray gases reached 1,000 m above the crater and drifted E." However, no VAAC reports were issued, and ash was not mentioned in the OVI INGEMMET weekly report.

During the last two weeks of August, two large zones of new fumarolic activity were detected in satellite imagery. OVI visited the site on 25 August, and IGP-OVS visited on 1 September 2016. The scientists observed areas of increased fumarolic emissions outside of the crater on the NE and NW flanks of the volcano (figure 19). The first zone was located on the NW flank and extended from the vicinity of the crater down to 5,700 m elevation, while the second area was located on the NE flank at about 5,600 m. Both areas follow a NW-SE trend. The flux of SO2 increased to values greater than 4,000 t/d at the end of August.

Figure (see Caption) Figure 19. New areas of fumarolic activity at Sabancaya, August 2016. Top: Two large fumarolic areas photographed on 1 September 2016 that appeared on the flanks during late August. The main zone was located on the NW flank and extended from the vicinity of the crater down to 5,700 m elevation, while the second area was located on the NE flank at about 5,600 m. Courtesy of IGP-OVS (Sabancaya Report 27, 1 September 2016) Bottom: Google Earth image showing location of fumarolic fields. A, B, C, and D are part of the NW flank field and E is the NE flank field. Courtesy of OVI-INGEMMET (Special Report, 1 September 2016).

OVI-INGEMMET reported an increase in the total number of seismic events during September 2016, especially hybrid-type events, along with generally lower plume heights, but increased emissions of SO2. IGP-OVS noted a swarm of hybrid-type seismic events on 27 September distinct from the distal tectonic-related events of the previous month, and indicative of an increase in volcanic activity. IGP-OVS returned to Sabancaya on 28 September 2016 to gather temperature measurements at the new fumarole areas. A NW-SE trending belt on the NE side of the volcano had temperature readings between 71° and 91°C.

At the beginning of October, water vapor and SO2 gas plumes rose as high as 2,000 m above the crater, and the SO2 flux was over 3,000 t/d. Volcanic seismicity increased from 220 earthquakes per day during the first week to 470 during the second week. SO2 emissions continued to increase and by 22 October were at 7,173 t/d.

From 9 January through 3 November 2016 the Buenos Aires VAAC issued 52 reports with pilot observations of ash. The VAAC was unable to confirm the presence of ash in emissions and instead described only water vapor or magmatic gases recorded via the web camera. There were no MODIS thermal anomalies shown by the MODVOLC or MIROVA systems from January 2014 through October 2016.

Activity during November 2016-February 2017. OVI-INGEMMET reported an eruption beginning at 2040 local time on 6 November 2016 (0140 on 7 November UTC) that started with an explosion and was followed by the continuous emission of low volume ash that rose up to 1,500 m above the crater rim (about 7,500 m altitude) (figure 20).

Figure (see Caption) Figure 20. The beginning of the eruption at Sabancaya, in the province of Caylloma in Arequipa, on 6 November 2016. Courtesy OVI-INGEMMET (Sabancaya 2016 Weekly Report 45).

Several types of volcanic-related seismic events continued to increase in number and intensity during November and December. The eruption exhibited an average of 39 daily explosive events with ash plumes (figures 21, 22, and 23) between 7 November and 15 December. There were 63 explosions on 30 November, and between 5 and 11 December there were 328 explosions.

Figure (see Caption) Figure 21. Ash plume rising over 4,000 m above the summit (5, 967 m elevation) at Sabancaya, 24 November 2016. Courtesy OVI-OVS (2016 Sabancaya Joint OVI-OVS Weekly Report 2, 21-27 November).
Figure (see Caption) Figure 22. Plume heights and compositions at Sabancaya from 28 October through 27 November 2016. Ash emissions began on 6 November, and continued to increase in density and plume height throughout the month. White circles represent water vapor, light gray are ash, dark gray are abundant ash, blue are SO2 gas, and yellow are sulfur aerosols. Courtesy OVI-OVS (2016 Sabancaya Joint OVI-OVS Weekly Report 2, 21-27 November).
Figure (see Caption) Figure 23. NASA Earth Observatory images of ash plumes from Sabancaya on 16 and 19 November 2016. The bright area to the SW in the 16 November image is snow near the peak of Mount Ampato, which is covered with ash in the 19 November image. The 16 November image was acquired by a multispectral imager on the European Space Agency's Sentinel 2 spacecraft. The Operational Land Imager (OLI) on Landsat 8 captured the November 19 image. Courtesy of NASA Earth Observatory.

Ash emissions were continuous from the beginning of the eruption through mid-December, with heights up to 4.5 km (10.5 km altitude) above the crater, according to the Scientific-Technical Committee of government scientists monitoring the eruption. Ashfall several millimeters thick was recorded in areas as far as 40 km away. During the first weeks of the eruption ash fell mainly to the E and NE on the villages of Maca, Achoma, Yanque and Chivay (18-30 km NE). Later in December, ashfall was reported W and NW in the villages of Huambo (28 km W), Cabanaconde (22 km NW), and Pinchollo (18 km N). On 26 December, ashfall was again reported in the villages of Cabanaconde, Pinchollo, and Tapay (25 km NW) to the NW and N, and Lari and Madrigal (20 km NE), Maca, and areas of Achoma to the NE. The seismic energy released from tremors and explosive events continued to increase throughout November into December (figures 24 and 25).

Figure (see Caption) Figure 24. Seismic energy and types of seismic events at Sabancaya, 6 November-8 December 2016. HIB are hybrid-type seismic events, TRE are tremors, EXP are explosions. Black line represents cumulative energy in Megajoules (MJ). Y axis is daily seismic energy on the left and cumulative energy on the right. Stars represent the period of continuous explosions. Courtesy of OVI-OVS (2016 Sabancaya Joint OVI-OVS Weekly Report 4, 5-11 December).
Figure (see Caption) Figure 25. Web camera image of ash-and-steam plume at Sabancaya, 9 December 2016. Courtesy of OVI-OVS (2016 Sabancaya Joint OVI-OVS Weekly Report 4, 5-11 December).

Beginning on 21 December there was a notable increase in seismicity (mainly of hybrid events), in the number (up to 52 per day) and height of plumes, and ash emissions. These changes led the Scientific-Technical Committee to raise the Volcanic Warning Level from Yellow to Orange (2 to 3 on a 4-level scale) on 28 December, warning people to remain more than 12 km from the crater (figures 26 and 27). A small lahar affected the area of Pinchollo (18 km N) on 3 January 2017.

Figure (see Caption) Figure 26. Dense ash cloud at Sabancaya, 26 December 2016. Increasing intensity of seismicity and number of explosions led to an increase in the Volcano Warning Level on 28 December. Courtesy of OVI-OVS (Informe Especial No. 01-2017).
Figure (see Caption) Figure 27. Seismic energy released by Sabancaya between 5 December 2016 and 4 January 2017. Note increasing energy of the explosions in early January. Courtesy of OVI-OVS (Informe Especial No. 01-2017).

Seismicity remained high during January with long-period (LP), tremor, and hybrid-type events all continuing, and an average of 70-76 daily explosions. During the second week in January explosions peaked at an average of 84 per day. This number decreased during early February to around 20 per day but then rose back to over 40 by the end of the month. A significant number of hybrid seismic events occurred during the last week of February.

Gas-and-ash plumes rose to 4.5 km above the crater in early January, dropping back to 2-3 km for the rest of the month, before rising again to 3-4 km (9-10 km altitude) during February. In their Special Report in January 2017, the joint Scientific-Technical committee presented a map showing that ash dispersal had affected communities in nearly every direction 40 km from the summit (figure 28).

Figure (see Caption) Figure 28. Area affected by ashfall (in pink) from Sabancaya as of mid-January 2017. Courtesy of OVI-OVS (Informe Especial No. 01-2017).

Buenos Aires VAAC Reports, November 2016-February 2017. The Buenos Aires VAAC first noted minor amounts of volcanic ash in emissions visible from the volcano webcam on 7 November 2016 (UTC). Ash was not identified in satellite imagery until midday 8 November when it was reported at 7.6 km altitude (about 1.7 km above the summit). Observations of continuous emissions of steam and ash were reported daily, when not obscured by weather, from then through the end of February 2017. Plume heights were commonly 7.6-8.2 km altitude, about 1.7-2.3 km above the summit. Higher plumes were also recorded a number of times during this period, including 10.3 km altitude on 17 and 23 November. The plume was clearly visible in satellite imagery on 24 November, drifting SE at 10.9 km. Plumes on 3 December rose 10 km and drifted SW; they were partially hidden by weather clouds. Pulses of volcanic ash drifting over 35 km SE at 10.6 km altitude were visible on 11 and 12 December. For most of January 2017 the plumes were obscured by weather clouds, but were visible on 6 January at 9.1 km altitude. Higher plumes were more often recorded in February; they rose continuously over 10 km from 4 to 7 February. The highest plume during the period was on 26 February, at 11.9 km, drifting SW.

Thermal anomalies in satellite data. The MIROVA thermal anomaly plot of MODIS data provided independent satellite confirmation of the beginning of the eruption. The first thermal anomaly appeared on 2 November 2016, and values increased in frequency and intensity in the subsequent weeks. Energy values reached moderate levels in early February 2017 (figure 29). The first MODVOLC thermal alert pixel for Sabancaya appeared on 6 January 2017. There were seven MODVOLC alert pixels in January and six in February, suggesting a persistent source of heat during this time.

Figure (see Caption) Figure 29. Log Radiative Power values for Sabancaya between 13 March 2016 and 13 March 2017. The first MIROVA-identified thermal anomaly was on 2 November 2016, and values increased in frequency and intensity after that. Courtesy of MIROVA.

Sulfur dioxide data. Sulfur dioxide plumes from Sabancaya were captured numerous times by the OMI satellite instrument from NASA's Global Sulfur Dioxide Monitoring system between November 2016 and February 2017. They revealed significant SO2 plumes travelling in all directions away from the summit for distances up to 200 km (figure 30).

Figure (see Caption) Figure 30. SO2 plumes drifting in different directions up to 200 km from Sabancaya captured by the OMI instrument on the Aura satellite. Clockwise from top left: 7 November 2016, first day of ash eruption, plume drifting SW and S towards Arequipa; 16 November 2016, plume drifting NE toward Lake Titicaca; 25 December 2016, plume drifting WSW over the Pacific Ocean; 27 February 2017, large plume drifting S and W, corresponding to an 11.9-km-altitude ash plume reported by Buenos Aires VAAC on 26 February. Courtesy of NASA GSFC.

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa (URL: http://ovi.ingemmet.gob.pe); 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/); 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/); 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 Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Semeru (Indonesia) — May 2017 Citation iconCite this Report

Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Activity diminishes 2009-2013, active lava dome growth 2014-2016

With hundreds of eruptive events in the 19th and early 20th centuries, and nearly continuous activity since 1967, Indonesia's Semeru is one of the world's most active volcanos. This activity has included lava flows, Vulcanian and Strombolian explosions, nuées ardentes, lava domes, and mudflows; fatalities and serious injuries occurred in 1981, 1994, 1997, and 2000.

Activity at the volcano is tracked by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, (CVGHM), the Darwin Volcanic Ash Advisor Center (VAAC), and remote sensing satellite data that provides visible imagery and thermal anomaly data. In this report, imagery and data from 2000-2009 is reviewed, along with details of activity from 2009 through March 2017.

Overview of activity since 2000. Strong evidence for continuous eruption at Semeru was gathered by satellite instruments from March 2000 through 2 January 2009. PVMBG reported ash explosions and an active lava dome in the Jonggring Seloko summit crater during early March 2009; after an ash plume on 15 March the gas and ash "gradually disappeared." A single MODVOLC thermal alert pixel was captured on 8 August 2009. PVMBG noted in their March 2010 report that the character of eruptive activity changed in April 2009 from ash-dominated explosions to emissions associated with dome growth. Only intermittent minor emissions were reported until incandescence appeared at the summit on 5 January 2010; strong thermal alert signals indicated continued lava-dome growth through November 2010. After 29 November 2010, there were no reports of unrest until small ash plumes were observed on 13 May 2011. These were followed by reports of pyroclastic flows in June, observations of the growing lava dome in September, and a new lava flow in December 2011.

Pyroclastic flows in January and February 2012 accompanied observations of incandescence and thermal alerts detected by satellite through mid-May. Small ash plumes from the summit area and incandescence at the lava dome were observed on 19 July 2012, but no further activity was noted until June 2013 when thermal alerts reappeared for about a month. An ash plume was reported by the Darwin VAAC in October 2013 and a thermal alert pixel appeared on 29 November 2013. After this, another break in activity occurred until the following spring.

PVMBG reported 22 incidents of emissions that were white to gray during March 2014, and 21 during 1-27 April 2014. They also reported eight explosions during April with white to gray emissions. A new, longer-lasting eruptive episode began with ash plumes, an incandescent lava flow, and rock avalanches that descended from the summit lava dome on 26 April 2014.

Thermal alert pixels reappeared on 5 June 2014 and remained abundant through 30 July 2016. During this time, the lava dome was actively growing and a lava flow slowly advanced down the S-flank Kembar ravine. Ash plume eruptions increased in frequency during 2015, and during 2016 they became large enough to produce aviation advisories from the Darwin VAAC several times. An image of the incandescent lava flow on the S flank in September 2016 and a thermal alert pixel in November 2016 suggested continuing dome growth through the end of the year. An ash plume reported by the Darwin VAAC on 9 January 2017 indicated continuing activity.

Satellite data from 2000-2009. From March 2000 through 2 January 2009, the University of Hawai'i's MODVOLC system recorded numerous thermally elevated pixels captured by the MODIS satellite instrument every single month except for February 2002. Explosive activity, lava avalanches, and pyroclastic flows were the sources of these abundant alerts (see previous BGVN reports). A NASA image from 14 June 2004 available in Google Earth clearly shows an ash plume erupting from Semeru and abundant ash deposited around its flanks (figure 20).

Figure (see Caption) Figure 20. An ash plume rising from Semeru on 14 June 2004. Abundant recent ash deposits surround the summit, and steep ravines that carry pyroclastic flows and lahars are clearly visible. The ash plume is directly over the summit crater, and remnants of an earlier plume have drifted NW to the upper left edge of the image. Courtesy of Google Earth.

Imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite also captured images in 2006 and 2007 that demonstrate the characteristics of ash explosions from Semeru. They commonly occur as discrete puffs at regular intervals and can maintain their integrity for tens of kilometers from the volcano (figure 21).

Figure (see Caption) Figure 21. Two NASA-EO satellite images from MODIS on 15 June 2006 and 3 May 2007 show the often pulsing nature of ash emissions from Semeru. The discrete puffs can maintain their integrity for tens of kilometers from the volcano. Prevailing winds most commonly send ash to the W. Courtesy of NASA-EO.

Activity during January 2009-July 2012. The style of activity changed during 2009. MODVOLC recorded only a single thermal alert pixel on 2 January 2009, and nothing after that until August 2009. PVMBG maintains a four-level Volcano Alert system; Level 1 (Normal) is the lowest, followed by Level II (Alert), Level III (Standby), and Level IV (Beware). They reported that typical activity during Alert Level II ("Alert") conditions were ash eruptions at 20-30 minute intervals with plumes rising 100-400 m from the summit. They noted a loud explosion on 8 February 2009, and another on 6 March that was accompanied by lightning. The 6 March event led PVMBG to increase the Alert Level to III (Standby) in their 6 March 2009 report. This activity was followed a few days later by an ash eruption, reported by the Darwin VAAC, with a plume that rose to 4.6 km altitude. After another ash emission on 15 March that rose 600 m above the crater, ash emissions "gradually disappeared" and seismicity decreased, according to a 17 July 2009 report from PVMBG; the Alert Level was then lowered back to II.

A single MODVOLC thermal alert pixel was recorded on the NW flank on 8 August 2009. In their next report in March 2010, PVMBG noted that from November 2009 through February 2010 visibility was generally poor due to weather, but there were occasional undescribed emissions that rose 50-500 m above the summit. They reported that the pattern of activity between April 2009 and 1 March 2010 changed from being dominated by ash eruptions to regular low-level emissions.

Incandescence from the summit on 5 January 2010 was followed by a MODVOLC thermal alert on 21 January. PVMBG reported a new lava flow on 25 February, which by 28 February had traveled 750 m. Rock avalanches from lava flows were reported during February (BGVN 35:08), September, and November 2010 (BGVN 37:04). Thermal alerts increased in number during April and May, before tapering off and ending on 28 November 2010. In their 4 November report PVMBG kept the Alert Level at II but noted an increase in lava-dome growth at the summit. Ash plumes were also observed by the Darwin VAAC rising to 4.6 km and drifting 75-110 km N and NW during 18-19 November.

No activity was reported between 29 November 2010 and 13 May 2011. Evidence for activity beginning again in May comes from a report by Volcano Discovery of 2-3 small ash eruptions per day during 13- 17 May (figure 22). MODVOLC thermal alert pixels reappeared on 2 June and were also noted on 15 June and 1 July. PVMBG reported eruptions of pyroclastic material on 9, 14, and 17 June. Volcano Discovery reported a growing lava dome on 1 September with 3-4 ash explosions per day during the first two weeks of September. MODVOLC thermal alerts were recorded on 5 and 7 October. PVMBG noted that seismicity had increased beginning on 29 December 2011, which was accompanied by dense white-and-gray plumes rising to 600 m above the Jonggring Seloko crater; a 300-m-long lava flow was also observed that day.

Figure (see Caption) Figure 22. A view to the south of Semeru on the morning of 13 May 2011 from the Bromo-Tennger volcanic complex located 18 km N. The Bromo cone to the left is also producing an emission; Batok is in the middle foreground. Courtesy of Andi Rosati/Volcano Discovery.

Dense gray-white plumes rose 600 m and preceded an explosion on 6 January 2012; the explosion was followed by summit incandescence. Repeated observations of incandescent material flowing up to 400 m SE toward the Besuk Kembar drainage were made during the rest of January. On 2 February, just after midnight, a pyroclastic flow traveled 300 m from the Jongring Seloko crater, and by mid-morning it had traveled farther, to 2.5 km from the crater. This led PVMBG to raise the Alert Level to III that day, prohibiting people from an area on the SE slopes within 4 km of the crater (BGVN 37:04).

Numerous MODVOLC thermal alert pixels were recorded between 30 January and 21 April 2012, and a final pixel recorded on 9 May 2012. PVMBG noted that several pyroclastic flows had occurred during February, and incandescence at the summit was common through the end of March. During April, white plumes rose 500 m above the summit, seismicity decreased, and no incandescence was observed. Based on this, PVMBG lowered the Alert Level to II on 2 May 2012. A Google Earth image of the volcano taken a few weeks later on 21 May 2012 shows a clear view of the summit crater with the lava dome visible (figure 23). Volcano Discovery reported that on an expedition during 18-19 July they observed slow lava dome growth, with an incandescent area at the SW part of the dome producing small to moderate ash explosions. There were no reports of ash plumes from the Darwin VAAC during 2012.

Figure (see Caption) Figure 23. DigitalGlobe satellite image of Semeru captured on 21 May 2012 with a clear view of the lava dome inside the Jonggring Seloko summit crater. Slow moving lava flows from the dome traveled down the ravine on the S flank. Courtesy of Google Earth.

Activity during June 2013-December 2015. After the 19 July 2012 update from Volcano Discovery, there was no evidence for activity at Semeru until a MODVOLC thermal alert pixel appeared on 4 June 2013, followed by four more in June and one on 7 July. No reports were issued by PVMBG during 2013. The Darwin VAAC issued a report on 18 October 2013 that a low-level ash plume had been observed, but was not visible on satellite imagery. A single MODVOLC pixel was recorded on 29 November.

The volcano was quiet again from 29 November 2013 until April 2014. PVMBG reported white-and-gray plumes drifting W from the summit 22 times during March 2014, and 21 times during April, at heights between 100 and 400 m from the summit. They also reported eight explosions during April with gray-to-white emissions rising 300-500 m and drifting W. Incandescent material was reported on 26 and 27 April, with rock avalanches sliding 300 m S from the summit. Strong multi-pixel MODVOLC alerts were recorded beginning on 5 June 2014 and continued for the rest of the year, although there were no further reports from PVMBG or the Darwin VAAC. The thermal anomalies were likely due to the growth of the lava dome. Volcano Discovery reported a lava flow from the dome in July 2014, noting that it extended a few hundred meters down Kembar ravine on the S flank in early September, when they also observed Strombolian activity in the summit crater (figure 24). They reported in November 2014 that the lava dome had a diameter of 100-200 m, and Strombolian activity ejected bombs up to 100 m above the vent (figure 25).

Figure (see Caption) Figure 24. Strombolian activity in the summit crater at Semeru in mid-September 2014. Courtesy of Andi/Volcano Discovery.
Figure (see Caption) Figure 25. The active lava dome at Semeru in late November 2014. Courtesy of Andi/Volcano Discovery.

Multiple MODVOLC thermal alert pixels were recorded every month during 2015. Although the volcano was very active during January-March 2015, PVMBG did not raise the Alert Level. Steam plumes rising 200-300 m above the crater were reported almost daily; explosions with gray-white plumes rising to heights of 200-500 m happened several times a week. In January, incandescent material traveled as far as 300 m down the Kembar ravine. In early March a trace amount of ash was deposited at a monitoring post near the summit after one explosion. During April 2015, ash plumes rose 200-600 m above the crater 68 times according to PVMBG; minor ashfall was reported on the flanks, and explosions were heard 30 times.

Activity increased further in May 2015, with ash plumes reported 122 times, rising 200-500 m above the summit and drifting W, NW, and SW. Incandescent rock avalanches descended as far as 1 km in the Kembar ravine. During June and July, ash emissions continued at the rate of a few per day, rising to 500 m above the summit (figure 26).

Figure (see Caption) Figure 26. Ash emission at Semeru on 11 June 2015. Courtesy of Aris Yanto and Volcano Discovery.

During August 2015 ash events were reported 47 times, with plumes rising 100-600 m above the summit and drifting S. Rock avalanches were reported twice travelling 500 m down the S flank. By September, explosions with white-and-gray plumes had decreased to 45 for the month. They caused the plumes to rise 100-500 m above the summit and drift W and N. Thirty-two explosions occurred during October producing gray-to-white plumes that rose 200-500 m and drifted W. Incandescent material was observed nine times in November and traveled as far as 500 m down the S flank. Also in November, Volcano Discovery reported continuous degassing and minor explosions from the lava dome (figure 27). Strombolian activity was observed five times in December by PVMBG. Dense gray-to-white ash plumes occurred eight times during November and 20 times in December, rising 100-500 m and drifting W.

Figure (see Caption) Figure 27. Active vent on the lava dome inside Semeru's summit crater in early November 2015. Courtesy of Andi/ Volcano Discovery.

Activity during 2016-March 2017. Twenty-one ash explosions were reported in January 2016, with low-level plumes rising to 500 m and drifting E, N, and W. Although activity during 2016 began similarly to 2015, the character of the eruption changed during February. Beginning in mid-February, larger ash plumes triggered a series of VAAC reports, the first in many years. Multiple MODVOLC thermal alert pixels were also captured through the end of July 2016, with another one on 24 August and 19 November, suggesting continued growth of the lava dome and intermittent lava.

The Darwin VAAC reported ash plumes five times in 2016, on 13 February, 17 April (UTC), 25 and 27 May, and 10 June. The 13 February plume rose 7.9 km (4.3 km above the summit) and drifted 45 km NE. A local news source, Tempo Nasional, also reported a pyroclastic flow the same day that traveled 4-5 km down the S and SE flanks (figure 28).

Figure (see Caption) Figure 28. Pyroclastic flow from Semeru on 13 February 2016. Courtesy of David P, Tempo Nasional.

The 18 April 2016 ash plume rose to 4.3 km altitude and drifted 40 km NE. Plumes on 25 and 27 May also rose to 4.3 km but drifted 25-40 km SW. On 10 June another plume rose 3.7 km and drifted 25 km SW. Volcano Discovery observed mild Strombolian activity from the crater on 26 July, and noted that the lava flow in the southern ravine was inactive. On another visit in late September the lava flow was incandescent 1,500 m down the ravine (figure 29). The MODVOLC thermal alert pixel from 19 November suggested that the lava dome remained active.

Figure (see Caption) Figure 29. The incandescent lava flow in the ravine on the S slope of Semeru on 25 September 2016. View looking north. Courtesy of Aravind P./VolcanoDiscovery.

A report from the Darwin VAAC on 9 January 2017 noted that an ash plume rose 3.9 km altitude that drifted N. A decrease in thermal activity is clear in the MIROVA thermal anomaly data for late March 2016 through late March 2017. Volcanic Radiative Power (VRP) values during April through June 2016 were in the Moderate range; they decreased in intensity (and frequency) to the Low range between July and December, and decreased again in both intensity and frequency after December 2016 (figure 30).

Figure (see Caption) Figure 30. MIROVA thermal anomaly data for Semeru between 22 March 2016 and 22 March 2017. Volcanic Radiative Power (VRP) values during April through June 2016 were abundant and in the Moderate intensity range of 107-108 Watts; they decreased in intensity (and frequency) to slightly below 107 W between July and December, and decreased again in both intensity and frequency after December 2016. Courtesy of MIROVA.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

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/); 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/); Volcano Discovery, https://www.volcanodiscovery.com; 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/); Tempo Nasional, https://nasional.tempo.co, https://nasional.tempo.co/read/news/2016/02/14/058744712/ini-yang-jadi-penyebab-guguran-awan-panas-di-gunung-semeru.


Tungurahua (Ecuador) — May 2017 Citation iconCite this Report

Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


Nine ash plumes over 10 km altitude 2011-2014; lava flow in April 2014

Abundant ash emissions, Strombolian activity, pyroclastic flows, lahars, and a few lava flows have all been documented at Tungurahua, which lies in the center of Ecuador. Historic observations are recorded back to 1557, and radiocarbon dates are as old as 7750 BCE. Prior to renewed activity in 1999, the last major eruption had occurred during 1916-1918. Since 1999, there have been numerous eruptive episodes, but only a few with breaks in activity longer than three months. Our last bulletin report (BGVN 40:03) covered the first part of the eruption that began on 22 November 2010. This report details activity from November 2011 through December of 2014. Tungurahua is monitored by the Observatorio del Volcán Tungurahua (OVT) of the Instituto Geofísico (IG) of Ecuador, and aviation alerts are reported by the Washington Volcanic Ash Advisory Center (VAAC).

Summary of November 2010-December 2014 activity. After a period of quiescence from 29 July through 21 November 2010, a new eruption began with a series of ash explosions and Strombolian activity on 22 November. Explosions continued through 25 December 2010 (BGVN 40:03), and emissions containing ash continued through 2 January 2011. A new eruption with tremor and ash emissions began on 20 April 2011; explosions with substantial ash plumes occurred on 22 April. Strombolian activity was frequent, and ashfall affected numerous communities within 10 km for the next five weeks. This episode ended with explosions and ash plumes on 21 May (BGVN 40:03), followed by ashfall reported to the SW through 26 May 2011. After damaging lahars at the end of May, Tungurahua was quiet until November 2011.

Volcanic activity between November 2011 and December 2014 occurred in eight discrete episodes (table 19). The length of these episodes ranged from 3 weeks to 9 months, and the lengths of the breaks between them lasted from 4 weeks to 3 months. Ash plumes rising several kilometers above the 5-km-high summit and ashfall in communities tens of kilometers from the volcano characterized each episode. Strombolian activity also sent incandescent blocks down the flanks hundreds of meters, pyroclastic flows traveled several kilometers down the ravines, and lahars during the wet seasons flooded drainages and frequently damaged roadways. A lava flow several hundred meters long descended the upper W flank in April 2014.

Table 19. Episodes of activity at Tungurahua, November 2011 through December 2014. These episodes are based on reported activity as described in this report, and may not correspond to current or previous "Eruptive Episodes" identified by IG.

Episode Start Episode Stop Approx. Duration Following Interval of Repose
27 Nov 2011 4 Sep 2012 40 weeks 12 weeks
14 Dec 2012 24 Jan 2013 7 weeks 5 weeks
01 Mar 2013 24 Mar 2013 3 weeks 4 weeks
24 Apr 2013 15 May 2013 3 weeks 8 weeks
13 Jul 2013 23 Aug 2013 6 weeks 6 weeks
06 Oct 2013 12 Nov 2013 5 weeks 11 weeks
30 Jan 2014 11 May 2014 14 weeks 11 weeks
17 Jul 2014 15 Dec 2014 20 weeks --

Hundreds of ash plumes were emitted over this time period. Nine times, the ash plumes were recorded at altitudes over 10 km (more than 5 km above the summit) (table 20), with the highest on 4 April 2014 rising to 15.2 km altitude (50,000 ft).

Table 20. Ash plumes over 10 km altitude recorded at Tungurahua between November 2011 and December 2014.

Date (local) Altitude (km) Drift direction(s) Distance (km)
27 Nov 2011 10.7 WNW 100
03 Dec 2011 11.0 SW 110
22 Dec 2011 12.2 NE --
04 Feb 2012 12.2 NE 250
11 Apr 2012 10.7 NE, W, SE 170
16 Dec 2012 12.2 NW, NE 140
14 Jul 2013 13.7 NNE, WNW 370
01 Feb 2014 13.7 S, SW --
04 Apr 2014 15.2 NW, N, NE 300

Activity during May 2011-September 2012. After loud explosions and ash emissions on 21 May 2011, constant rains at the end of May caused lahars and muddy water to descend the ravines of Tungurahua (BGVN 40:03). Ashfall was reported on 26 May, although cloud cover prevented observations of plumes. No further ash emissions or thermal anomalies were confirmed for six months. The Washington VAAC issued a volcanic ash advisory on 7 October based on a report from IG, and two additional reports on 24 October and 9 November from pilot reports. They noted that no ash was visible in satellite imagery at the time of those reports; on 9 November a revised statement from IG stated that no ash emissions had occurred since June.

A new eruption began on 27 November 2011, when three large explosions generated pyroclastic flows and caused ashfall within 10 km in several communities. Ashfall was reported in El Manzano (8 km SW), Bilbao (8 km W), Pailitas (8 km W), Cotaló (8 km NW), and Cusúa (8 km NW) (figure 62). The first Washington VAAC reports after these explosions noted an ash plume at 10.7 km altitude (5.7 km above the summit crater) drifting WNW and extending about 100 km from the summit.

Figure (see Caption) Figure 62. Isopach map of ashfall accumulation around Tungurahua on 27 November 2011. Courtesy of IG (Resumen Mensual, Actividad del Volcan Tungurahua, November 2011).

During the next three weeks, nearly constant ash emissions with plumes as high as 11 km altitude (3 December) deposited ashfall in numerous communities. In addition to those communities mentioned above, Choglontús (13 WSW), Chacauco (17 km NW), Cahuají 8 km SW), Baños (9 km N), and Vazcún also received ashfall during this period. Many residents in Cusúa, Juive (8 km NNW), Palitahua (6 km SSW), and El Manzano evacuated voluntarily. Strombolian activity sent large incandescent blocks 500 m above the crater and 1,000 m down the flanks (figure 63), and pyroclastic flows traveled as far as 2 km down the flanks (BGVN 40:03). MODVOLC thermal alerts were issued on 1 and 4 December. Substantial plumes of SO2 were recorded by NASA's Global Sulfur Dioxide Monitoring system between 28 November and 8 December (figure 64).

Figure (see Caption) Figure 63. Strombolian activity at Tungurahua sometime between 27 and 30 November 2011. Incandescent blocks reached 500 m above the crater, and traveled up to 1,000 m down the flanks. Courtesy of IG; photo by J. Bustillos, IG-EPN (Resumen Mensual, Actividad del Volcan Tungurahua, November 2011).
Figure (see Caption) Figure 64. Plumes of SO2 at Tungurahua between 28 November and 5 December 2011. The plumes dispersed in multiple directions and were detected as far as 300 km from the volcano. Clockwise from top left: 28 November, 1 December, 3 December, and 5 December. Gas plumes were detected through 8 December 2011. Courtesy of NASA GSFC (Goddard Space Flight Center).

Another major explosion on 22 December sent ash plumes to 12.2 km (7.2 km above the summit), according to the Washington VAAC. Emissions continued through 28 December. Ashfall from explosions near the end of December accumulated to a depth of 2-4 mm in villages to the SW. After two weeks of quiet, with only steam plumes emitting from the summit, a series of explosions between 12 and 15 January 2012 caused ashfall in communities up to 10 km SW. Ash plumes reported by IG rose to 7 km altitude; weather clouds often prevented satellite observations. Three lahars occurred during this time; one descended the Achupashal drainage on the NW flank carrying blocks up to 1 m in diameter, and the other two descended the Juive and Pondoa drainiages farther N on the NW flank, carrying blocks 10-20 cm in diameter. Another lahar on 21 January traveled down the Pampas drainage.

A large explosion on 4 February 2012, with an ash plume reported by the Washington VAAC at 12.2 km altitude, caused lapilli and ash to fall in communities as far away as Cevallos (23 km NW). Ongoing emissions were reported five hours later; the ash cloud was observed 250 km NE near the Ecuador-Columbia border. A pyroclastic flow also descended the Achupashal drainage, and incandescent blocks traveled 1 km down the flanks. Ash plumes during 17-18 February were reported by IG to rise to 6 km altitude, although weather clouds obscured satellite images. From 23 February to 13 March, numerous ash plumes caused ashfall in most communities NW and SW of the volcano, as far as Choglontus (13 km WSW). The Washington VAAC and IG both reported plumes as high as 8.5 km altitude (3.5 km above the summit crater) drifting W and SW during this time. Strombolian activity ejected material 500 m above the crater and onto the W and NW flanks on 24 February, and another pyroclastic flow was observed in the Achupashal drainage on 4 March. Lahars descended the Chacauco (NW) and Mapayacu (SW) drainages on 11 March.

After a short break, explosions were again detected on 19 March 2012. During brief periods when the crater was visible, observers noted incandescence and a few blocks rolling 200 m down the flank. A single MODVOLC thermal alert pixel was recorded on 20 March. IG and the Washington VAAC reported numerous ash plumes between 20 and 29 March, although weather clouds and precipitation made observations difficult for much of the month. Ashfall was reported in the villages within 10 km in most directions. Heavy rain during 24-25 March generated lahars in the Pampas area to the S and caused flooding in the Puela (8 km SW), Palitahua, and Ulba (10 km NNE) sectors. Additional lahars on 1 April descended the Pingullo and Achupashal (NW) drainages, carrying material 30 cm in diameter and causing a temporary road closure.

Persistent ash emissions rising to 8 km altitude and higher began again on 9 April 2012, and occurred with few breaks until mid-June when they became more intermittent. Ashfall was commonly reported from villages within 10 km during this period. A large plume on 11 April was reported by the Washington VAAC at over 10 km altitude drifting NE and SE (figure 65); rice-sized tephra fell in Pillate (7 km W) on 22 April. Ashfall covered houses and pastures in Bilbao and Pillate on 6 May. Several plumes in early June (3, 5, 10, 11, 13) resulted in ashfall, with noise and vibrations noted, within 10 km. IG staff witnessed an ash emission on 4 June (during an overflight) that rose about 1 km above the crater and drifted E (figure 66). Numerous lahars descended drainages on the W and SW flanks in late April, and again down the W flank on 16 May. On 7 June a lahar caused a temporary closure of the Baños-Penipe highway. Smaller lahars were reported in the same area on 24 June.

Figure (see Caption) Figure 65. A large ash plume at Tungurahua that rose to 10.7 km altitude on 11 April 2012 was seen using the OVT webcam located near Guadalupe, 13 km N of the crater. Two block-and-ash flows are also visible, caused by the rolling of large blocks down the flank that disperse newly fallen ash as they descend the drainage. Courtesy of IG (Informe semanal No. 15-Volcan Tungurahua, 9-15 April 2012).
Figure (see Caption) Figure 66. Ash emissions and snow on the summit at Tungurahua on 4 June 2012 were observed during an IG overflight. The plume rose about 1 km and drifted E. Courtesy of IG; photo by P. Ramon OVT/IG (Informe semanal No. 23 – Volcan Tungurahua, 4-10 June 2012).

After an explosion on 27 June 2012 generated an ash plume that rose to 3 km above the crater, only small intermittent explosions with ash plumes occurred during July; steam-and-gas plumes rising up to 1 km above the summit were more common (figure 67). Incandescence at the summit and small explosions were noted on 25 July, and a few days later muddy waters carried blocks 50 cm in diameter down several S and W flank drainages. Surface and seismic activity increased noticeably during the last week of July.

Figure (see Caption) Figure 67. Fresh ash covers the snow on 7 July 2012 at Tungurahua, probably from an explosion on 5 July. View is to the south. Courtesy of OVT/IG; photo by P. Ramón OVT/IG, (Informe semanal No. 27 – Volcan Tungurahua, 2-8 July 2012).

Explosions on 5 August 2012 rattled windows in nearby areas and produced sounds resembling gunshots. A plume rose 3 km above the crater and drifted W. Several periods of continuous ash emissions occurred during the rest of the month; ashfall was reported in villages within 10 km many times. Incandescent blocks that were ejected 100 m above the crater fell 500 m down the flanks on 12-13 August. Activity significantly increased with strong explosions on 17 August. The next day, five small pyroclastic flows descended the NW and NE flanks, stopping 2.5 km from the crater. Numerous explosions continued on 19 and 20 August, with steam-and-ash plumes rising 1.5-2 km above the summit and drifting W and SW. Ash fell in communities farther to the NW than in previous months, including in Igualata (20 km W), El Santuario, Hualpamba, Cevallos (23 km NW), Quero (20 km NW), Mocha (25 km WNW), Santa Anita, and Tisaleo (29 km NW). IG scientists determined that an approximate volume of 400-500,000 cubic meters of ash was deposited within 15 km of the volcano between 10 and 20 August. The maximum deposit thicknesses were 3 mm in Yuibug, 2 mm in Pillate, 1.5 mm in Choglontús and Chontapamba, 1 mm in Cahuají, and 0.5 mm in Puela (figure 68).

Figure (see Caption) Figure 68. Isopach map of ashfall accumulation around Tungurahua during 10-20 August 2012. Courtesy of IG (Boletín Especial del Volcán Tungurahua No. 4, 25 Aug 2012).

An overflight on 20 August revealed an 80-m-wide inner crater. On 21 August, 16 large explosions caused windows to rattle. Strong "cannon shots" were heard in areas as far away as Ambato (31 km NW) and Riobamba (30 km S), although noises had decreased in intensity and duration compared to the previous few days. Ash plumes rose as high as 9.7 km altitude and drifted W, and a pyroclastic flow traveled 2.5 km down the NW flank that day. MODVOLC thermal alert pixels appeared during 16-23 August. Explosions and ash plumes rising up to 4 km above the crater continued for the rest of August, along with ejected incandescent tephra and ashfall in nearby communities. IG reported that the intensity of seismic tremor and emissions decreased beginning on 21 August.

NASA's Global Sulfur Dioxide Monitoring system captured SO2 plumes during 13-21 August, and again from 31 August to 3 September. An explosion on 3 September produced an ash plume that rose 300 m above the crater; two MODVOLC thermal alerts also appeared that day. A final ash plume was reported by IG on 4 September rising to 6.7 km altitude (1.7 km above the summit), but dense cloud cover prevented satellite observation. No more ash plumes were reported until 14 December 2012.

Activity during December 2012-January 2013. A major rainfall event on 1 December generated a large lahar that descended the Vazcún drainage on the N flank, causing an evacuation of people at the El Salado resort (8 km N) before the 6-m-deep lahar that carried 3-m-diameter blocks reached the area. An increase in seismicity beginning on 12 December preceded a large explosion on 14 December. The explosion created an ash plume, identified in satellite imagery by the Washington VAAC, that rose to 7.9 km altitude. The leading edge of the 10-km-wide, detached plume was 15 km SE of the summit. Pyroclastic flows traveled down the SW flank. A smaller ash plume the next day caused a trace of ashfall in Runtún (6 km NNE).

Three large explosions on 16 December 2012 ejected incandescent blocks and expelled an ash plume, containing lightning, that rose to 12.2 km altitude (7.2 km above the summit) (figure 69). The soundwaves from the explosion reportedly broke the windows of the church of Cusúa. The Washington VAAC identified the plume in satellite imagery extending up to 140 km NW, and 110 km NE at a lower altitude of 7.9 km. Ashfall was reported up to 31 km NW from Tungurahua, in Cotaló (8 km NW), Pondoa (8 km N), Runtún, and Pillate (8 km W). More specifically, coarse-grained ash fell in Baños (9 km N), Vascún, and Ulba (NNE), and medium-to-fine-grained ash fell in Palitahua (S), Choglontús (SW), El Manzano (8 km SW), Capil, Guadalupe Observatory (13 km N), Cevallos (23 km NW), Tisaleo (29 km NW), Ambato (31 km NW), Patate (NW), Píllaro, Pelileo (8 km N), Salcedo, and Pujilí, Latacunga, Rio Verde, Agoyán, and Palora.

Figure (see Caption) Figure 69. Ash plume and pyroclastic flows from explosions at Tungurahua at 0553 on 16 December 2012. View to the south from the OVT webcam, located near Guadalupe, about 13 km N of the crater. Courtesy of IG; photo by V. Valverde (IG-OVT) (Informe Especial del Volcán Tungurahua No. 10, 16 December 2012).

Explosions and ashfall continued on 17 December; a dense ash plume was observed drifting over 200 km NE at an altitude of 7 km. A seven-pixel MODVOLC thermal alert also appeared. Substantial SO2 plumes were recorded by the OMI satellite instrument between 16 and 29 December. Two pyroclastic flows traveled 3-4 km down the flanks and burned vegetation on 18 December. Explosions shook structures, were often heard by local residents, and generated ashfall in the neighboring communities for several days. The following week, ash plumes decreased in frequency and density, but explosions of incandescent blocks increased. During 21-24 December Strombolian explosions appeared at night; they peaked at over 500 m above the crater, sending blocks more than one kilometer down the W and NW flanks. On the night of 23 December, observers noted intermittent lava fountains rising to 500 m. Another MODVOLC thermal alert pixel was recorded on 24 December. After this, seismicity decreased significantly; the Washington VAAC last reported emissions on 30 December.

Trace amounts of ashfall were reported by IG on 6 and 10 January 2013 in Choglontús (SW) and El Manzano (8 km SW), after small explosions on those days. Explosions, but no ash, were recorded on 21 January; in the evening of 24 January, a column of steam and gas with very low ash content rose less than 1 km and drifted W and SW after reported explosions. The lookout at Palitahua reported black ashfall the following morning. After this, Tungurahua was quiet until the end of February 2013.

Activity during March 2013. IG reported increased seismicity on 28 February 2013. Explosions occurred, and ash emissions rose a few hundred meters above the crater the next day. Ashfall was reported in areas on the SW flank including Choglontús and El Manzano. Multiple VAAC reports were issued daily from 1 to 18 March. Ash plume heights were generally 1-1.5 km above the summit crater (6-6.5 km altitude), but were reported 4 km above the crater on 17 March. Several times during March, IG reported incandescent blocks rolling as far as 500 m down the flanks, and repeated ashfall in communities within 15 km (figure 70). Deformation measurements suggested that a small magma body was rising beneath the NW flank. An SO2 plume first appeared in the OMI satellite data on 2 March, and was visible daily until 12 March. From 10 to 15 March, MODVOLC recorded 15 thermal alert pixels. Pyroclastic flows occurred on 15 and 17 March; lava fountains rose 200-300 m above the crater on 17 March. A notable decline in seismicity began on 21 March, and a low-ash-content plume that rose 1 km above the crater on 24 March was the last ash emission until the end of April.

Figure (see Caption) Figure 70. Observations of volcanic activity at Tungurahua on 16 March 2013. Top: Detail of an ash column around 1800 local time. Bottom: Strombolian activity a short time later. Courtesy of IG; photos by P. Mothes OVT/IGEPN (Informe Especial del Volcán Tungurahua No.7, 16 March 2013).

Activity during April-May 2013. The webcam confirmed the minor emission of volcanic ash on 24 April 2013; the Washington VAAC reported an ash plume at 6.7 km altitude extending 50 km WNW from the summit on the same day. A series of large explosions began on 27 April. During the next week, these explosions sent steam-and-ash plumes up to 4.7 km above the summit (9.7 km altitude) which drifted at least 100 km SW and W. Ash plumes reported daily by the Washington VAAC rose 1-3 km above the summit until 15 May, and ash fell in communities across the region up to 30 km away in many directions. Lahars traveled down drainages on the S, N, and NW flanks on 4 May. A pyroclastic flow traveled 2 km down the NW flank on 5 May, and Strombolian activity was visible on most nights. During 9-10 May, lava fountains rose 700 m above the crater. MODVOLC thermal alert pixels appeared on 1, 10, 12, and 13 May. An SO2 plume was recorded in the OMI satellite data on 29 and 30 April, and again from 5 to 12 May. After a slight amount of ash was reported in Choglontus (SW) on 15 May, there were no more reports of ash plumes for two months.

Activity during July-August 2013. IG reported increased seismicity on 13 July 2012 in advance of two large explosions on the morning of 14 July; the first was heard in areas as far away as Guayaquil (about 180 km SW). The Washington VAAC reported the plume from these explosions at 13.7 km altitude (8.7 km above the summit) around midday. They noted that satellite imagery showed a dense ash plume expanding in all directions from the summit, but moving generally N and W. Significant amounts of tephra fell in areas near the volcano including Bilbao (4-cm-diameter), Chacauco (5-cm-diameter), Cotaló, Cahuají, Choglontus, El Manzano, Puela, and Penipe (15 km SW). Thinner deposits were reported in towns including Pelileo, Ambato, Cevallos, Colta (45 km SW), Guanujo (65 km WSW), and Guaranda (65 km WSW), and in the cantons of Guano (30 km SW), Valencia, Empalme, Buena Fé, and areas in the province of Manabi (180 km NW).

Several significant pyroclastic flows also descended drainages on the NW flanks, including the Achupashal and Juive Grande drainages, during the explosions of 14 July. The pyroclastic flows at Juive Grande reached a distance of 6.3 km and stopped a kilometer above the road (figure 71). The temperature measured in the deposit with a thermal camera the next day was 95°C. In the Achupashal stream, the pyroclastic flows reached 6.5 km and crossed the Chambo River. The temperature measured in this deposit was 65°C. According to USA Today, over 200 people were evacuated from Cusua, Chacauco, and Juive.

Figure (see Caption) Figure 71. Pyroclastic flow deposit from Tungurahua in the Juive Grande ravine, 14 July 2013. Courtesy of IG; photo by P. Mothes, IG-EPN (Informe Especial del Volcán Tungurahua No. 15, 16 July 2013).

Volcanic ash advisories were issued daily by the Washington VAAC until 1 August 2013. IG reported that on 19 July the geodetic monitoring system indicated an inflationary trend on the N flank and deflation SW of the volcano, a continuing indication of the presence of a magma body about 2 km below the crater. Ash fell in communities up to 30 km away several times during the period, including after large plumes that rose to 9.6 and 9.9 km altitude on 21 and 24 July. Minor amounts of ash were reported in the Guaranda, Salinas, and Guanujo (65 km WSW) areas after explosions on 26 July, one of which also generated a small pyroclastic flow. Strombolian activity occurred throughout the period, with activity including incandescent blocks rolling up to 500 m down the flanks several times. The OMI instrument captured SO2 plumes from 15 July through 2 August. MODVOLC thermal alerts were issued on 27 and 29 July. Seismic and explosive activity decreased during the first week in August. An ash plume on 8 August that rose 2 km above the summit and drifted W caused minor ashfall in Choglontus (SW). Trace ashfall was reported in Choglontús and El Manzano on 23 August.

Activity during October-November 2013. Activity resumed in early October 2013 with increased seismicity, Strombolian activity, ash plumes, and pyroclastic flows. A small explosion on 6 October produced ashfall in nearby areas. A larger high-level ash plume on 11 October was observed by the Washington VAAC rising to 8.5 km altitude; ashfall spread to nearby towns. Pyroclastic flows were reported on 14 October. Daily VAAC reports that began on 11 October continued through 30 October, followed by reports on 3, 7, and 9 November. The near-continuous ash emissions during this time generally rose 2-4 km above the crater, and deposited ash in communities within 30 km. Daily SO2 plumes were captured by OMI between 7 and 22 October, and eight MODVOLC thermal alerts appeared between 19 and 24 October. The last reports of ashfall during this episode were on 12 November when plumes rose 1.5 km from the summit and drifted W, with ashfall reported in El Manzano.

Activity during January-May 2014. The community of Pungal, 40 km SSW of Tungurahua, received ashfall on 30 January from a series of explosions that began after two and a half months of quiet. The Washington VAAC reported the ash plume visible at 8.2 km altitude extending 11 km ESE from the summit. A swarm of VT earthquakes on 1 February was followed by two explosions that generated ash plumes to 2-4 km above the summit, and pyroclastic flows that traveled 500 m down the NE and NW flanks. These explosions were followed a few minutes later by a larger explosion that produced an ash plume reported by IG that rose more than 8 km above the summit (figure 72).

Figure (see Caption) Figure 72. Two sequences of images from the OVT webcam, located near Guadalupe, about 13 km N of the crater, of the large explosions and ash emissions at Tungurahua that began at 2239 on 1 February 2014. Pyroclastic flows descended ravines on the NW and NE flanks. The images on the left record thermal activity during the explosions, while the images on the right record the visual activity. Courtesy of IG (Informe No. 728, Sintesis semanal del estado del Volcán Tungurahua, 28 Jan-4 Feb 2014).

Based on reports from IG, satellite images, pilot observations, web-camera images, and the Guayaquil MWO, the Washington VAAC reported that the ash plume from the 1 February explosions rose to an estimated altitude of 13.7 km, and drifted S at high altitudes and SW at lower altitudes. IG noted that pyroclastic flows traveled 7-8 km, reaching the base of the volcano and crossing over the Achupashal Baños- Penipe highway. Continuous ash-and-gas emissions followed; ash fell in multiple areas and total darkness was reported in Chacauco (NW). Explosions continued every minute and vibrated structures in local towns. Pyroclastic flows descended the SW, W, NW, and NE flanks, but stopped short of towns and infrastructure. Ash emissions were sustained through the rest of the evening, and Strombolian explosions ejected incandescent blocks 800 m above the crater that fell and rolled 500 m down the flanks.

Numerous explosions and ashfall continued in subsequent days; on 3 February 2014 an ash plume rose 4 km above the summit and drifted N, reaching Quito (130 km N) as a mist of suspended very fine material that lingered most of the day. The Washington VAAC issued multiple daily reports of ash plumes from 30 January until 23 February. An eight-pixel thermal alert on 2 February was the beginning of a sequence of MODVOLC thermal alerts that included 10 more during February. SO2 plumes drifting W were captured by the OMI satellite instrument between 7 and 10 February. During 16-18 February, ash plumes again rose to altitudes between 9 and 10 km, dispersing ash to the W and NW. Strombolian activity and loud noises were common during this interval.

Fewer ash plumes were reported during March 2014, at generally lower heights of 1-3 km above the crater; ash fell in communities within 15 km. Only three MODVOLC thermal alerts were recorded: two on 6 March and one on 15 March. On 11 and 21 March rains caused major lahars in the Achupashal drainage which led to traffic disruption on the Baños- Penipe highway. Lahars on 31 March traveled down the Vascún (N) and Mapayacu (SW) drainages, carrying blocks up to 1 m in diameter in the latter drainage.

Explosions and substantial ash plumes increased in April 2014, with multiple daily VAAC reports issued between 2 and 25 April. The largest explosion, on 4 April, lasted five minutes, and generated pyroclastic flows that descended the NW and N flanks. It also caused an ash plume that rose over 10 km above the crater, reported at 15.2 km altitude (50,000 ft) by the Washington VAAC, the highest reported in many years (figure 73). Tephra up to 7 cm in diameter fell in Cusúa and Píllaro.

Figure (see Caption) Figure 73. A major explosion at Tungurahua on 4 April 2014. Top: The first phase of the explosion at the western edge of the crater, the ash plume reaches at least 8 km above the summit (13 km altitude); pyroclastic flows descend the Achupashal, La Pirámide, and Rea or Romero ravines. Middle: the beginning of the second phase, an explosion on the eastern edge of the crater, which produced a dense plume of ash that reached 10 km above the crater; pyroclastic flows descend the Vazcún and Juive ravines. Bottom: Emission column of at least 10 km above the crater (15 km altitude). Courtesy of IG; photos by F. Vásconez, OVT-IG (Informe No. 737, Sintesis semanal del estado de Volcán Tungurahua, 1-8 April 2014).

During 5-11 April, SO2 plumes drifting W were detected by the OMI satellite instrument. Large lahars descended the Achupashal (NW) and Confesionario drainages (WSW) on 8 April. On 9 April Strombolian activity caused incandescent blocks to roll 3 km down the flanks (figure 74). The next day a lava flow on the upper W flank, in the Mandur drainage, was estimated to be 2 km long, 100 m wide, and 15 m thick (figure 75). This was likely the cause of the six MODVOLC thermal alerts recorded on 11 April.

Figure (see Caption) Figure 74. At 2243 on 9 April 2014 a lava flow emerged from the crater at Tungurahua; the incandescent material covered the NW and W flanks. Courtesy of IG; photo by P. Ramón, OVT/IG (Sintesis semanal del estado de Volcán Tungurahua, 8-15 April 2014).
Figure (see Caption) Figure 75. The lava flow descending an area between Mandur and Hacienda ravines at Tungurahua. Upper image is from late in the day on 10 April 2014, lower image is a few hours later in the early morning of 11 April. Courtesy of IG; photo by P. Ramón, OVT/IG (Sintesis semanal del estado de Volcán Tungurahua, 8-15 April 2014).

A significant explosion on 14 April 2014 produced an infrasound signal that was detected at 150 decibels 5.5 km away. Unconfirmed reports indicated that windows in Chacauco and Cusúa shattered. The shock wave was also detected in other locations, including Ambato and Riobamba (30 km S). Although IG reported an ash plume rising to over 5 km above the crater (10 km altitude), the Washington VAAC only reported the plume to 8.5 km. A lahar in the Achupashal drainage on 15 April affected traffic on the main highway. Repeated ashfall was reported for the rest of the month in communities within 30 km; crater incandescence was often observed at night.

OVT reported a gas-and-ash emission to an estimated 9 km altitude on 8 May 2014. Three explosions on 10 May generated ash emissions that rose an estimated 5 km above the crater, with ashfall reported in the communities to the SW. There were no VAAC reports issued for the 10 May explosions. A small plume on 11 May had minor amounts of ash. After this, there were no further reports of ash until the end of July. Intense rains on 10 and 11 May caused lahars to flow down most drainages, and roads crossing the Chontapamba and Romero gorges were washed out (figure 76).

Figure (see Caption) Figure 76. Photos taken on 12 May of damage from lahars at Tungurahua from rains on 10 and 11 May 2014. Upper: Lahar that descended the Chontapamba ravine washed out the road and trapped a vehicle. Lower: A large lahar descended the Romero ravine and destroyed the highway in two places. Courtesy of IG; photos by P. Ramón, OVT/IG (Informe No. 742, Sintesis semanal del estado del Volcán Tungurahua, 6-13 May 2014).

The episodic nature of the activity at Tungurahua is demonstrated well by the plot of MIROVA thermal anomaly data captured between April 2013 and April 2014 (figure 77). While the whole duration of the episode is seldom recorded due to weather and other factors, each set of anomalies based on MODIS satellite data is within the boundaries of each episode listed in table 19.

Figure (see Caption) Figure 77. MIROVA thermal anomaly data from the year ending on 12 April 2014, showing the episodic nature of activity at Tungurahua. Courtesy of MIROVA, in IG weekly report (Sintesis semanal del estado de Volcán Tungurahua, 8-15 April 2014).

Activity during June-December 2014. Seasonal rains in June and July 2014 generated numerous lahars, some causing major damage to roads. Otherwise, the volcano was largely quiet with only 100-m-high steam plumes rising from the summit crater on clear days, until seismicity increased once again on 27 July. The seismicity was accompanied by a small ash plume that rose 1 km above the crater and drifted NW. This event was the beginning of a lengthy episode of explosions, ash plumes, Strombolian activity, pyroclastic flows, and lahars that lasted through most of December 2014.

Deformation data revealed additional information about the the activity at Tungurahua (figure 78). The inclinometer of the RETU station is located on the NNE flank at an elevation of 4,000 m. During a 14-month period from 1 June 2013 to 1 August 2014 the radial axis inflation and deflation correlated with four significant explosion events. Periods of gradual inflation were followed by sudden deflation that accompanied an explosion. A new series of explosions began shortly after 24 July 2014 when the last deflation on the graph was detected.

Figure (see Caption) Figure 78. Deformation record of the RETU station at Tungurahua. The inclinometer of the RETU station is located on the NNE flank at an elevation of 4,000 m. During a 14-month period from 1 June 2013 to 1 August 2014 the radial axis inflation and deflation correlated with four significant explosion events. Periods of gradual inflation were followed by sudden deflation and an explosion. A new series of explosions began shortly after 24 July 2014 when the last deflation on the graph began. Courtesy of IG-EPN Volcanology (Informe especial del Volcán Tungurahua No. 16, 28 July 2014).

Seismicity increased on 28 July 2014; a small explosion with an ash plume rose 1 km above the crater and drifted NW with ashfall reported in the Chontapamba area. The Washington VAAC issued multiple daily reports of ash plumes between 1 August and 11 September 2014. They were generally reported at 1-4 km above the summit, or to altitudes of 6-9 km. Ashfall was reported a number of times in communities within 30 km. Strombolian activity sent incandescent blocks as high as 1 km above the crater and up to 1.5 km down the flanks (figure 79). Incandescence appeared on most clear nights. Lahars occurred after rainy episodes during 8-9 and 13 August. On 30 and 31 August, near-constant explosions were detected, and pyroclastic flows traveled 1,500 m down the NW flank. The pyroclastic flows surrounded the lava flow from April 2014, in the La Hacienda, Achupashal, and Mandur drainages. Another pyroclastic flow reported on 3 September descended 500 m from the crater. During 10 August and 7 September, 12 MODVOLC thermal alerts were issued. SO2 plumes reappeared on the OMI satellite instrument on 2 August and were captured daily until 6 September.

Figure (see Caption) Figure 79. Incandescent blocks from Strombolian activity roll down the flank adjacent to snow near the summit of Tungurahua, 7 August 2014. Courtesy of IG; photo by P. Ramón, OVT/IG (Informe No. 755, Sintesis semanal sel estado del Volcán Tugurahua, 5-12 August 2014).

Activity decreased slightly toward the end of September 2014, although intermittent ash plumes were still reported as high as 2.5 km above the crater; ashfall was recorded in communities up to 25 km away, generally to the W. Rains on 12 and 14 September resulted in lahars within the NW drainages of Achupashal and La Pampa. LP seismic events increased slightly at the end of September along with several low-level ash plumes. The last reports of nighttime incandescence were on 27 September.

Emissions with low to moderate ash content were noted most days in early October. Ashfall was reported from a few communities within 30 km on 1, 3, and 6 October. Trace amounts of ashfall appeared on the SW flank the following week. OVT reported emissions with moderate ash content rising 2-3 km above the summit during 19 and 20 October. Plumes rising to 2 km with low ash content were observed on 25 October. During the end of October and the first few days of November, IG observed only water vapor emissions to 500 m above the crater.

Although quieter, Tungurahua was still active through November and December 2014. Trace amounts of ash in the emissions were observed from El Manzano on 3 November. On 7 and 8 November ash-bearing plumes rose less than 300 m and drifted WSW. For the rest of November, only steam plumes rose to 700 m above the crater. Incandescence was visible at the summit in the early morning hours of 21 November, and again on 4 December. Residents in Choglontus reported a steam-and-ash plume drifting S early on 6 December. A significant lahar on the NW flank washed out the Penipe-Banos road in the Achupashal gorge on 7 December. Low ash content was reported in plumes rising to 500 m above the crater each day from 9-15 December, and magmatic gases and steam emissions were persistent (figure 80). Slight incandescence was seen at night on 11 December. On 14 December, a column consisting of re-suspended ash was seen drifting E. For the remainder of December, weak water vapor plumes rose a few hundred meters above the crater; lahars were reported on 25 December.

Figure (see Caption) Figure 80. A minor plume of magmatic gases rose from the summit crater of Tungurahua on 11 December 2014, as seen from the NW. Courtesy of IG; photo by P. Ramón, OVT/IG (Informe No. 773, Sintesis semanal del estado del Volcan Tungurahua, 9-16 December 2014).

Geologic Background. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: 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/); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); USA Today (URL: http://www.usatoday.com/story/news/world/2013/07/14/ecuador-volcano-spews-ash/2516393/).


White Island (New Zealand) — May 2017 Citation iconCite this Report

White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


Ongoing unrest, with phreatic activity on 27 April and 13 September 2016

Following a period with frequent eruptions between 1995 and 2001, White Island (officially called Whakaari/White Island) was quiet until 2012, when plumes began rising from the crater lake on 5 August that included ash two days later (BGVN 37:06). Hydrothermal activity was vigorous, generating phreatic explosions and ash emissions through July 2013, followed by larger explosions in August and October (BGVN 39:02). No further eruptive activity was observed until 2016, when brief phreatic explosions took place on 27 April and 13 September. Monitoring by GNS Science is conducted under the GeoNet Project, the official source of geological hazard information in New Zealand. The following information comes from the GeoNet website.

GNS scientists visited in early February 2014 and measured the crater lake temperature of 57°C and that of fumarole F0, on the S part of the crater floor, at 147°C. The lake level was still rising, and had drowned one of the fumaroles on the southern lakeshore, causing occasional geysering in that area. A new Global Positioning System (GPS) station was installed on the crater floor to strengthen the deformation monitoring network. The average SO2 gas flux remained below 500 metric tons per day; this was lower than the previous few months and may have been partly due to the higher lake level. On 28 August 2014 the GeoNet seismic network detected a sequence of small earthquakes near White Island, the largest event was magnitude 3.3 and located within 5 km of the island. All the quakes were shallow (less than 10 km depth).

Monitoring by plane, ground instruments, and visual observation throughout 2015 indicated that minor volcanic unrest continued. In October 2015, GNS Science volcanologists measured such factors are ground deformation, CO2 soil gas, fumarole and crater lake temperature, lake level, and SO2 gas. Seismometers continued to monitor volcanic tremors, and airborne monitoring measured CO2, SO2, and H2S levels. Elevated amounts of CO2 emitted from one of the large accessible fumaroles was detected on 1 October; temperatures and SO2 emissions also increased. On 8 October volcanic tremor magnitude strengthened and became banded (the signal disappeared and reappeared every few hours), commonly noted during periods on unrest and eruptive periods.

Over two weeks in mid-April 2016 the lake level dropped by 2 m. Then, on the morning of 27 April, a brief eruption occurred (lasting about 90 minutes) accompanied by moderately elevated seismic activity. The eruption appears to have deposited material over the N side of the crater floor and up onto the N crater wall. The Volcanic Alert Level was raised to 3 (minor volcanic eruption) and the Aviation Colour Code (ACC) changed from Green to Orange. A subsequent lack of activity resulted in a lowering of the Volcanic Alert Level to 2 (moderate to heightened volcanic unrest) that evening. Observers who flew over the volcano the following day saw a dark-green ash covering at least 80% of the crater floor and up the sides of the crater wall on both N and S sides; the deposit was ~5 mm thick at a distance of 500 m from the eruption site (figure 66).

Figure (see Caption) Figure 66. Ash from the White Island eruption on 27 April 2016 covering the monitoring station. Courtesy of GeoNet (Volcanic Alert Bulletin WI 2016/02).

An aerial inspection two days after the eruption revealed a new crater and vent in the NE corner of the 1978/1990 crater complex. Analysis of the deposit showed the ash to be strongly hydrothermally altered old rock; no evidence of new, juvenile lava was found, suggesting that the eruption was likely driven by steam and gas, like the eruptions in 2012 and 2013. The eruption did produce very energetic blasts and surges that broke survey pegs at ground level. The eruption sequence, as reported by GNS, was that the area around Donald Duck Crater collapsed and exploded, then the former lake and sediments erupted, resulting in the blast and surge deposits. The lake floor dropped at least 13 m, and there was a collapse of the 1978/90 Crater walls.

Figure (see Caption) Figure 67. Collapsed area in Donald Duck Crater at White Island as a result of the 27 April 2016 eruption. Courtesy of GeoNet (Volcanic Alert Bulletin WI 2016/07).

By 2 May, observations indicated no change in volcanic activity. As a consequence, the ACC was lowered to Yellow, and by 9 May the Volcanic Alert Level was lowered to 1. Although the April activity was a moderate steam and gas eruption, it did result in a new vent and ash deposits.

GeoNet reported that in the morning of 13 September 2016 a vent on the 2012 lava dome had a minor passive ash emission. The Volcanic Alert Level was raised to 3 from 1, and the ACC was changed from Green to Orange. Observations from a visit on 14 September found that the ash emissions had ceased; the Volcanic Alert Level was lowered to 2 and the ACC lowered to Yellow. The Alert Level was lowered to 1 on 19 September. The crater lake water level began to drop on 24 September, and by 26 September the lake was gone.

GNS has been using Unmanned Aerial Vehicles (UAV's; also known as drones), to monitor the volcano. In December 2016 the drone was used to obtain images of the active crater area, resulting in a new Digital Terrain Model (DTM) of the area (figure 68).

Figure (see Caption) Figure 68. Digital Terrain Model of the White Island volcano crater floor as of December 2016. Courtesy of Geonet (Volcanic Alert Bulletin of December 2016).

According to a GeoNet report on 3 April 2017, visits to White Island over the previous 3-4 months confirmed that activity remained at low levels. Activity was confined to the gas-rich vents on the western side of the active crater. Hot, clear gas continued to be emitted. Some water had ponded on the floor of the active crater but no permanent lake had reformed. The seismic and acoustic activity generally remain low, and the SO2 gas flux was slowly declining (figures 69 and 70).

Figure (see Caption) Figure 69. View of the active crater area of White Island in early 2017. Note the gas vent (center-rear) and ponded rainwater. Courtesy of GeoNet (Volcanic Alert Bulletin WI-2017-01, 3 April 2017).
Figure (see Caption) Figure 70. Close up view of a gas vent in the active vent area of White Island in early 2017. Courtesy of GeoNet (Volcanic Alert Bulletin WI-2017-01, 3 April 2017).

Geologic Background. The uninhabited White Island, also known as Whakaari in the Maori language, is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of eruptions since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities.

Information Contacts: New Zealand GeoNet Project, a collaboration between the Earthquake Commission and GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.geonet.org.nz/).

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/).