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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.

Recently Published Bulletin Reports

Sabancaya (Peru) Strong, sporadic explosions with ash plumes throughout December 2017-May 2018

Masaya (Nicaragua) Lava lake persists during July 2017-April 2018

Chillan, Nevados de (Chile) Hundreds of ash-bearing explosions; dome appears in crater in mid-December 2017

Marapi (Indonesia) Two explosions during April-May 2018 cause ashfall to the southeast

Nyiragongo (DR Congo) Thermal anomalies show that lava lake remains active through May 2018

Ebeko (Russia) Ash explosions remained frequent through May 2018, with plumes typically rising more than 1 km

Langila (Papua New Guinea) Gradual decline in activity after July 2017, but continuing through May 2018

Pacaya (Guatemala) Pyroclastic cone fills MacKenney crater; lava flows emerge from fissures around the crater rim

Reventador (Ecuador) Near-daily explosions produce 1-km-high ash plumes and incandescent blocks on all flanks, October 2017-March 2018.

Santa Maria (Guatemala) Daily explosions with minor ash and block avalanches at Caliente, November 2017-April 2018

Sheveluch (Russia) Intermittent thermal anomalies along with gas and steam emissions continue through April 2018

Kikai (Japan) Elevated thermal activity during February-April 2018; one earthquake swarm in March



Sabancaya (Peru) — June 2018 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


Strong, sporadic explosions with ash plumes throughout December 2017-May 2018

Although tephrochronology has dated activity at Sabancaya back several thousand years, renewed activity that began in 1986 was the first recorded in over 200 years. Intermittent activity since then has produced significant ashfall deposits, seismic unrest, and fumarolic emissions. A renewed period of explosive activity began in early November 2016 and continued through 2017. It was characterized by continuing pulses of ash emissions with plume heights exceeding 10 km altitude, thermal anomalies, and numerous significant SO2 plumes (BGVN 42:12). Details of the continuing eruptive activity from December 2017 to May 2018 in this report come 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 notices come from the Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data is reported from several sources.

Sabancaya continued with its explosive eruption that began on 6 November 2016 during December 2017-May 2018. Around 100 aviation notices were issued each month by the Buenos Aires VAAC; tens of daily explosions were reported, fluctuating from highs in the 60s per day in December 2017 to lows in the teens per day during February-April 2018. Ash plumes heights varied at 3-5 km above the summit; altitudes mentioned in the VAAC reports were between 7.3 and 8.5 km altitude most days, although plume heights over 9.1 km were observed a number of times. MIROVA thermal anomalies were recorded every week; MODVOLC thermal alerts occurred every month. A significant number of SO2 anomalies greater than two Dobson Units were measured by NASA's Goddard Space Flight Center each month (table 2).

Table 2. Eruptive Activity at Sabancaya, December 2017-May 2018. Compiled using data from IGP-OVS, OVI-INGEMMET, Buenos Aires VAAC, HIGP - MODVOLC Thermal Alerts System, and NASA Goddard Space Flight Center.

Month VAAC Reports Avg Daily Explosions by week Max Plume Heights (m above crater) Plume Drift MODVOLC Alerts Min Days with SO2 over 2 DU
Dec 2017 120 69, 63, 55, 67, 42 2,500-3,300 40-50 km, SW, NE, NW, W, N 2 7
Jan 2018 101 41, 57, 57, 33 2,500-3,300 50 km, SW, W, NW, N 2 13
Feb 2018 94 22, 18, 19, 17 2,500-4,500 30-50 km, SE, S, SW, NW 1 12
Mar 2018 115 12, 10, 17, 17, 18 2,000-5,350 30-50 km, S, SW, W, NW, N 3 13
Apr 2018 114 15, 15, 19, 22 2,000-3,200 30-40 km, All 3 12
May 2018 132 25, 27, 30, 35, 28 1,900-4,300 30-40 km, NW, N, NE, E, SE, S 4 7

Activity during December 2017-February 2018. The Buenos Aires VAAC issued 120 aviation alerts during December 2017; webcam and satellite imagery revealed continuous emissions of water vapor and gas, accompanied by sporadic puffs of ash, throughout the month. When visible in satellite imagery, plumes rose to 7.3-8.2 km altitude (figure 46); a few plumes were reported to 9.1 km altitude. According to OVI-INGEMMET, about 1,800 explosions took place in December. During the third week, ashfall was reported in Huambo (28 km WNW). There were two MODVOLC thermal alerts issued, on 3 and 10 December.

Figure (see Caption) Figure 46. Webcam photo of an ash plume at Sabancaya on 16 December 2017. The Buenos Aires VAAC reported a plume that day to 8.2 km altitude. Courtesy of OVI-INGEMMET (RSSAB-51-2017/OVI-INGEMMET & IGP Semana del 11 al 17 de diciembre de 2017).

The number of explosions reported by OVI-INGEMMET dropped slightly to about 1,400 during January 2018. The number of VAAC reports was similar to December; when weather clouds prevented observations of emissions, seismic activity showed intermittent peaks that suggested puffs of ash. Plume descriptions by the Buenos Aires VAAC ranged from intermittent plumes that rose to 7.0-7.6 km altitude early in the month to persistent puffs of ash that rose to 7.9-8.2 km altitude during the last two weeks of January. The prevailing winds were directed SW and NW, and ash plumes often drifted as far as 50 km. NASA Goddard Space Flight Center recorded at least 13 days with SO2 emissions greater than two Dobson Units (DU) (figure 47). HIGP issued two MODVOLC thermal alerts on 4 and 20 January.

Figure (see Caption) Figure 47. SO2 emissions at Sabancaya were significant throughout the report period. Most months, NASA-GSFC measured 10 or more days where the Dobson Unit (DU) values exceeded two. Dobson Units are a measure of the molecular density of SO2 in the atmosphere. The larger plumes shown here are from 6 January 2018 (top left), 23 February 2018 (top right), 18 March 2018 (bottom left), and 28 April 2018 (bottom right). Courtesy of NASA Goddard Space Flight Center.

OVI-INGEMMET reported ash plume heights during February 2018 at 2,500-4,500 m above the summit. They also noted that deflation was measured during the middle two weeks of the month. The number of daily explosions decreased significantly from the previous few months, with about 500 total explosions recorded in February. The Buenos Aires VAAC noted that the webcam showed continuous emissions of gases with sporadic puffs of ash every day that the summit was visible. Ash plumes were only visible in satellite imagery a few times during the month; during 8-10 February, intermittent emissions were seen moving SE between 7.9 and 8.5 km altitude. During 17-24 February, weak, thin ash plumes drifted several different directions at 7.3-7.9 km altitude (figure 48), and on 28 February a plume was visible drifting NW at 7.6 km altitude. Only a single MODVOLC thermal alert was issued on 18 February.

Figure (see Caption) Figure 48. A strong pulse of ash rose from the summit of Sabancaya early in the morning of 21 February 2018. Courtesy of OVI-INGEMMET (RSSAB-08-2018/OVI-INGEMMET & IGP Semana del 19 al 25 de febrero de 2018).

Activity during March-May 2018. Three MODVOLC thermal alerts were issued in March 2018, two on 14 March and one on 27 March. Sporadic ash explosions continued, but with the lowest number per day of the reporting period. About 450 explosions were recorded during March. In spite of the smaller number of explosions, some of the tallest ash plumes of the period occurred this month. The Buenos Aires VAAC reported a diffuse ash plume drifting NW in satellite imagery on 2 March at 8.8 km altitude. The following week, several ash plumes were spotted in satellite imagery at altitudes of 7.3-8.2 km drifting either SW or NW. On 11 March, cloudy weather prevented visual satellite imagery observations, but multispectral imagery and the webcam revealed intermittent pulses of ash moving SW at 7.6 km altitude. The following day sporadic strong pulses of ash were observed in the webcam, and there was a pilot report of an ash plume at 9.1 km altitude. During the second half of March, ash plumes were noted in satellite imagery most days at altitudes of 6.4-8.2 km; a few pulses produced short-lived ash plumes that rose over 9.1 km, including on 14, 22, 24, and during 27-30 March (figure 49). The highest plume was observed in visible imagery drifting E on 28 March at 10.1 km altitude. A lahar was also reported on 28 March descending the SE flank, towards the Sallalli River; no damage was reported.

Figure (see Caption) Figure 49. An ash plume at Sabancaya on 30 March 2018 can be seen rising from the summit and above the meteorological cloud in this webcam image. The Buenos Aires VAAC reported ash plumes on 30 March that rose to 9.1 and 9.5 km and drifted NE. Courtesy of OVI-INGEMMET (RSSAB-13-2018/OVI-INGEMMET & IGP Semana del 26 de marzo al 01 de abril de 2018).

The number of explosions during April 2018 increased slightly from March to about 540. The maximum plume heights ranged from 2,000 to 3,200 m above the summit according to OVI-INGEMMET. The webcam showed continuous emissions of water vapor and gas and sporadic pulses of ash throughout the month. Ashfall was reported during the first week in Achoma (23 km NE), Chivay (33 km NE), and Huanca. During the second week, the prevailing winds brought ashfall to the W and NW to Huambo (28 km W) and Cabanaconde (22 km NW). The Buenos Aires VAAC reported faint ash plumes visible in satellite imagery nearly every day; plume heights consistently ranged from 7.0 to 8.2 km altitude. Three MODVOLC thermal alerts were issued during the month, one on 13 April and two on 17 April.

Activity increased in many ways during May 2018. The Buenos Aires VAAC issued 132 aviation alerts, the most of any month during the period. The numbers of daily explosions increased compared to April, resulting in a monthly total of around 900. OVI-INGEMMET reported plume heights up to 4,300 m above the summit. MODVOLC thermal alerts were issued on 8, 19, 24, and 26 May. In addition to ash plumes visible in satellite imagery every day at altitudes of 7.3-8.2 km altitude (figure 50), a significant number of ash plumes were reported to altitudes greater than 9.1 km during the month, resulting in more VONA's (Volcanic Observatory Notice to Aviation) issued than in previous months. Sporadic strong puffs of ash were observed in the webcam on the days that satellite imagery measurements of ash plume heights exceeded 9.1 km including on 4, 5, 10, 14, 19, 21, 22, 25, 28, and 31 May. The highest plumes reached 10.4 km altitude on 19 May and 10.1 km altitude on 25 May. Hotspots were also reported on 20, 24, and 27 May. As in previous months, the webcam showed constant emissions of steam and gas, with intermittent pulses of volcanic ash throughout the month.

Figure (see Caption) Figure 50. An IGP webcam at Sabancaya recorded the plume height above the summit at 2,800 m on 27 May 2018. Courtesy of OVI-INGEMMET (RSSAB-22-2018/OVI-INGEMMET & IGP Semana del 28 de mayo al 3 de junio del 2018).

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, Peru (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/); 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); 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, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Masaya (Nicaragua) — June 2018 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Lava lake persists during July 2017-April 2018

Nicaragua's Volcan Masaya has an intermittent lava lake that has attracted visitors since the time of the Spanish Conquistadores; tephrochronology has dated eruptions back several thousand years. The unusual basaltic caldera has had historical explosive eruptions in addition to lava flows and actively circulating magma at the lava lake. An explosion in 2012 ejected ash to several hundred meters above the volcano, bombs as large as 60 cm fell around the crater, and ash fell to a thickness of 2 mm in some areas of the park. Brief incandescence and thermal anomalies of uncertain origin in April 2013 were followed by very little activity until the reemergence of the lava lake inside Santiago crater was reported in December 2015. By late March 2016 the lava lake had grown and intensified enough to generate a significant thermal anomaly signature (BGVN 41:08, figure 49) which persisted at a constant power level through April 2017 (BGVN 42:09, figure 53) with an increase in the number of thermal anomalies from November 2016 through April 2017. Although the MIROVA thermal anomaly signal decreased slightly in intensity during May 2017, INETER scientists reported continued strong convection at the lava lake. Similar activity continued throughout July 2017-April 2018 and is covered in this report with information provided by the Instituto Nicareguense de Estudios Territoriales (INETER) and satellite thermal data.

A persistent thermal signature in the MIROVA data during July 2017-April 2018 supported the visual observations of the active lava lake at the summit throughout this period (figure 58). MODVOLC thermal alerts were also issued every month, with the number of alerts ranging from a high of 17 in November 2017 to a low of six in April 2018.

Figure (see Caption) Figure 58. MIROVA thermal data for Masaya for the year ending on 11 May 2018 showed a persistent and steady level of heat flow consistent with the observations of the active lava lake inside Santiago crater. Courtesy of MIROVA.

INETER made regular visits to the summit most months in coordination with specialists from several universities to gather SO2 data; CO2, H2S and gravity measurements were also taken during specific site visits. Thermal measurements around the lava lake inside Santiago crater taken on 24 February 2018 indicated temperatures ranging from 210-389°C. Seismicity remained very low throughout the period. The lava lake was actively convecting each time it was visited, and Pele's hair was abundant around the summit area (figures 59-64).

Figure (see Caption) Figure 59. The lava lake at Masaya was actively convecting on 22 August 2017 when observed by INETER scientists. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Agosto, 2017).
Figure (see Caption) Figure 60. Pele's hair near the summit of Masaya on 22 August 2017. Scale is likely a few tens of centimeters. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Agosto, 2017).
Figure (see Caption) Figure 61. The summit crater (Santiago) of Masaya with an active lava lake and fumarole plume (white circle) during 8-16 January 2018. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Enero, 2018).
Figure (see Caption) Figure 62. Thermal measurements of the lava lake inside Santiago crater at the summit of Masaya on 24 February 2018 indicated temperatures in the 210-389°C range. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Febrero, 2018).
Figure (see Caption) Figure 63. Nindiri plateau, the broad, flat area inside the summit crater of Masaya, was covered with Pele's hair and basaltic tephra on 6 March 2018. Courtesy of Carsten ten Brink.
Figure (see Caption) Figure 64. The lava lake inside Santiago crater at Masaya was actively convecting on 1 April 2018. Courtesy of Alexander Schimmeck.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Alexander Schimmeck, flickr (URL: https://www.flickr.com/photos/alschim/), photo used under Creative Commons license Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) (URL: https://creativecommons.org/licenses/by-nc-nd/2.0/); Carsten ten Brink, flickr (URL: https://www.flickr.com/photos/carsten_tb/), photo used under Creative Commons license Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) (URL: https://creativecommons.org/licenses/by-nc-nd/2.0/).


Nevados de Chillan (Chile) — June 2018 Citation iconCite this Report

Nevados de Chillan

Chile

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

All times are local (unless otherwise noted)


Hundreds of ash-bearing explosions; dome appears in crater in mid-December 2017

Nevados de Chillán is a complex of late-Pleistocene to Holocene stratovolcanoes constructed in the Chilean Central Andes. The Nuevo and Arrau craters are adjacent vents on the NW flank of the cone of the large stratovolcano referred to as Volcán Viejo. An eruption started with a phreatic explosion and ash emission on 8 January 2016 from a new crater on the E flank of Nuevo. Explosions continued through September 2017 with ash plumes rising several kilometers and Strombolian activity sending ejecta hundreds of meters (BGVN 42:10). This report covers continuing activity from September 2017-May 2018. Information for this report is provided by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN)-Observatorio Volcanológico de Los Andes del Sur (OVDAS), Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI), and by the Buenos Aires Volcanic Ash Advisory Center (VAAC).

About 150 ash-bearing explosions were recorded during September and October 2017, with plumes rising almost 2 km above the summit. Activity decreased during the second half of October, and no ash plumes were recorded during November. A significant increase in activity in early December led to over 200 explosions with ash emissions. An overflight on 21 December 2017 produced images of a fissure at the bottom of the new crater. The presence of a growing lava dome in the crater was confirmed in early January 2018. Frequent Strombolian explosions produced nighttime incandescence at the summit and down the flanks. Hundreds of ash-bearing explosions occurred during February 2018; the largest plume rose 2.5 km above the summit, and many smaller pulses produced ash and steam that rose 1.5 km. Sporadic incandescence at night and continued explosions of magmatic gases were typical during March 2018. A large explosion on 31 March coincided with the first appearance of a low-level MODIS thermal anomaly in the MIROVA data, and incandescence from explosions at night indicated that the dome continued to grow during April and May. SERNAGEOMIN reported that the top of the lava dome was visible from the E flank for the first time at the end of May 2018.

Activity during September-December 2017. SERNAGEOMIN reported 117 ash-bearing explosions between 16 and 30 September 2017 (figure 17). The one that released the most energy occurred on 19 September. The plumes of steam and ash rose up to 1,800 m above the crater. The Buenos Aires VAAC observed a narrow plume of ash in satellite imagery moving N at 3.9 km altitude and dissipating rapidly on 15 September, and a similar plume moving SE near the summit on 26 September 2017.

Figure (see Caption) Figure 17. Over 100 ash-bearing explosions were reported at Nevados de Chillán during late September 2017, including ones on 15 September (upper left), 20 September (upper right), 23 September (lower left) and 24 September (lower right). Courtesy of SERNAGEOMIN.

During the first two weeks of October 2017 there were 30 ash-bearing explosions recorded. The Buenos Aires VAAC reported small sporadic puffs of ash on 6 October 2017 that were visible in the webcam (figure 18), but not in satellite data, and a similar dense but short-lived plume on 14 October. SERNAGEOMIN reported a series of pulsating low-energy explosions visible in the webcam that drifted SW on 11 and 12 October 2017, and rose no more than 1 km above the summit.. Only two ash-bearing explosions were recorded during the second half of the month. The volcano was much quieter during November; plumes of steam were observed rising only 100 m above the summit throughout the month, with no ash-bearing plumes reported.

Figure (see Caption) Figure 18. Ash plumes at Nevados de Chillán on 6 (left) and 11 (right) October 2017 were two of the 30 plumes recorded during the first half of October. Courtesy of SERNAGEOMIN.

A significant increase in activity in early December 2017 resulted in 245 explosions associated with ash emissions during the first two weeks, some rising as high as 3,000 m above the summit. The Buenos Aires VAAC reported a puff of ash on 1 December that rose to 3.7 km altitude and drifted S, dissipating rapidly. The next day another plume rose slightly higher, to 4.3 km. A dense emission on 4 December rose to 4.9 km and drifted SE before dissipating in a few hours and was not visible in satellite data. On 11 and 14 December, short-lived emissions rose to 4.3 km (figure 19). A yellow cloud of sulfur formed on 11 December within 300 m of the active crater. The webcams also recorded sporadic nighttime incandescence during increased explosions in the early morning of 14 December. Continuous steam emissions with pulses of minor ash were first noted on 16 December; they were visible in satellite imagery the next day at 3.9-4.3 km altitude drifting NE, and by 18 December, consisted only of water vapor.

Figure (see Caption) Figure 19. An increase in explosive activity at Nevados de Chillán in December 2017 resulted in numerous explosions with ash plumes including on 1 December (upper left), 2 December (upper right), 4 December (lower left), and 11 December (lower right). Courtesy of SERNAGEOMIN.

In a special report released on 19 December, OVDAS-SERNAGEOMIN reported an increase in surface activity over the previous three days, recording minor explosions averaging four per hour, and seismic pulses lasting 5-10 minutes; they also noted harmonic tremor with the increase in explosion frequency. A detailed review of images taken during an overflight on 21 December revealed a fissure 30-40 m long trending NW at the bottom of the crater. Incandescence at night was regularly observed after 20 December (figure 20), and ash emissions rose to 3,000 m above the summit during the second half of the month.

Figure (see Caption) Figure 20. Phreatic explosions with steam and minor ash were common at Nevados de Chillán during the last two weeks of December 2017. Ash emissions and pyroclastic flows (top image) were noted during 12-19 December, and numerous incandescent blocks accompanied the explosions on 28 December (bottom image). Courtesy of SERNAGEOMIN.

Activity during January-April 2018. SERNAGEOMIN volcanologists identified a growing lava dome within the new crater during two overflights on 9 and 12 January 2018 (figures 21); it was emerging from the fissure first identified on 21 December. During the first two weeks of January SERNAGEOMIN reported 1,027 pulsating explosions associated primarily with magmatic gases, and very little ash that rose up to 1,000 m above the summit. Confirmed ash emissions were reported on 11 January at 4.3 km altitude faintly visible moving SE in satellite imagery, according to the Buenos Aires VAAC. Nighttime incandescence from the growing dome was periodically observed (figure 22). Based on the overflight data and satellite imagery, they calculated a growth rate for the dome of 1,360 m3 per day. They estimated the size at 37,000 m3 by mid-month.

Figure (see Caption) Figure 21. During an overflight at Nevados de Chillán on 9 January 2018, SERNAGEOMIN scientists observed the growing dome within the crater. Courtesy of SERNAGEOMIN.
Figure (see Caption) Figure 22. Incandescence at night increased from the growing dome at Nevados de Chillán on 13 January 2018. Courtesy of SERNAGEOMIN.

Overflights on 23 and 31 January measured temperatures of 305-480°C over the surface of the dome, with the highest values at the fissure. The growth rate calculated after these overflights was 2,540 m3 per day. The webcam revealed emissions of ash and water vapor during the second half of the month that rose less than 1,000 m above the summit crater.

An explosion on 2 February 2018 sent an ash plume to 2,500 m above the summit (figure 23). Vibrations from the explosion were reported in Las Trancas (10 km) and at the Gran Hotel Termas de Chillan (5 km). SERNAGEOMIN began referring to the active crater as Nicanor, and the dome was named Gil-Cruz. During the first two weeks of February, 840 explosions associated with plumes of magmatic gases were reported. The plumes generally rose as high as 1,500 m above the summit and were often accompanied by incandescence at night. Two overflights on 7 and 14 February recorded temperatures of 500 and 550°C. SERNAGEOMIN determined a dome growth rate of 1,389 m3 per day, and a total volume of 82,500 m3 by mid-month. At least four explosions on 14 February were characterized by two simultaneous plumes, one of white steam and the other darker with a higher ash content according to SERNAGEOMIN. The highest plume that day reached 1,200 m above the summit crater. The Buenos Aires VAAC also reported a small pulse of ash on 14 February that rose to 4.6 km altitude and drifted SE. The dome continued to grow slowly during the rest of February, with a small increase in size noted during a 22 February flyover. Plumes of mostly water vapor with minor ash rose a maximum of 1,080 m above the summit during the hundreds of small explosions that took place.

Figure (see Caption) Figure 23. A substantial explosion on 2 February 2018 at Nevados de Chillán sent an ash plume 2,500 m above the summit and generated vibrations that were felt 10 km from the summit. Courtesy of SERNAGEOMIN.

Sporadic incandescence at night and continued explosions of magmatic gases were typical during March 2018, with plume heights reaching 2,000 m over the Nicanor crater. During an overflight on 11 March, a temperature of 330°C was measured around the Gil-Cruz dome, which had grown to a volume of about 100,000 m3 but still remained below the crater rim. Morphological changes in the still-slowly growing dome included fracture lines and unstable large vertical blocks. A significant decrease in seismic energy was noted beginning on 24 March that ended when two larger explosions occurred on 30 and 31 March (figure 24).

Figure (see Caption) Figure 24. A substantial explosion on 31 March 2018 at Nevados de Chillán generated distinct ash and steam plumes (top) and sent several large blocks down the flanks (bottom). Courtesy of SERNAGEOMIN.

During an overflight on 3 April 2018, scientists observed energetic pulses of steam and minor ash from the central NW-SE trending fissure inside the crater. They noted that lapilli from explosions had been ejected as far as 1 km from the fissure, and that the Gil-Cruz dome had increased in volume since 11 March; they also observed an area of subsidence on the top of the growing dome (figure 25). The dome was expanding toward the E side of the crater, and the top of the dome rose above the crater rim. They measured a maximum temperature of 670°C on the surface of the dome. The decrease in daily seismicity, the larger explosions of the previous days, and the increased size of the dome with greater risk of collapse, pyroclastic flows, and lahars, all led SERNAGEOMIN to raise the alert level at Chillan to Orange on 5 April 2018.

Figure (see Caption) Figure 25. The growing lava dome at Nevados de Chillán, referred to as Gil-Cruz, had an active steam plume at the center when photographed by SERNAGEOMIN during an overflight on 3 April 2018. Courtesy of SERNAGEOMIN.

The Buenos Aires VAAC reported continuous emissions of steam and gas with minor ash along with a small pulse of ash on 2 April 2018. Low-altitude plumes of mostly water vapor were common throughout April 2018. Incandescence from explosions was visible on clear nights during the month, and ejecta rose as high as 250 m above the crater and was scattered around the crater rim. Seismicity remained constant at moderate levels related to the repeated explosions and the growth of the dome. A faint ash plume could be seen in visible satellite imagery on 18 April at 3.7 km altitude drifting E.

Observations reported on 1 May 2018 from the previous flyover indicated that the rate of growth of the dome had slowed to about 690 m3 per day, and the estimated volume had grown to about 150,000 m3. Activity remained at similar levels throughout May 2018. Seismic instruments recorded long-period seismicity and tremor episodes similar to previous months that corresponded with surface explosions and the extrusion of the lava dome. Seismic energy levels were moderate but fluctuated at times. Plumes of predominantly water vapor with minor gas rose a few hundred meters above the summit drifting generally S or SE before dissipating. Incandescence was often observed on clear nights, accompanied by ejection of incandescent blocks that were observed generally 100 to 150 m above the active crater. A larger explosive event took place on 7 May. Occasional plumes with minor ash were reported on 11 May. SERNAGEOMIN reported on 24 May 2018 that the top of the lava dome was visible from the E flank.

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

Information Contacts: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637/1671, Santiago, Chile (URL: http://www.onemi.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Marapi (Indonesia) — June 2018 Citation iconCite this Report

Marapi

Indonesia

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

All times are local (unless otherwise noted)


Two explosions during April-May 2018 cause ashfall to the southeast

The Marapi volcano on Sumatra (not to be confused with the better known Merapi volcano on Java) previously erupted on 4 June 2017, generating dense ash-and-steam plumes that rose as high as 700 m above the crater and caused minor ashfall in a nearby district (BGVN 42:10). The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

On 27 April 2018, a phreatic explosion produced an ash plume that rose 300 m above the crater rim (figure 8); a thin ash deposit was reported in the Cubadak area (Tanah Datar Regency), about 12 km SE. Another explosion at 0703 on 2 May 2018 (figure 9) produced a voluminous dense gray ash plume that rose 4 km above the crater rim and drifted SE; seismic data recorded by PVMBG indicated that the event lasted just over 8 minutes (485 seconds).

The Alert Level has remained at 2 (on a scale of 1-4), where it has been since August 2011. Residents and visitors have been advised not to enter an area within 3 km of the summit.

Figure (see Caption) Figure 8. Ash plume from a phreatic explosion at Marapi on 27 April 2018. Courtesy of Sutopo Purwo Nugroho (BNPB).
Figure (see Caption) Figure 9. An explosion from Marapi on 2 May 2018 sent an ash plume to a height of 4 km. Courtesy of PVMBG.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/).


Nyiragongo (DR Congo) — June 2018 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Thermal anomalies show that lava lake remains active through May 2018

As has been the case since at least 1971, the active lava lake in the summit crater of Nyiragongo was present during a tourist visit in June 2017, and seismicity was recorded in the crater in October 2017 (BGVN 42:11). Thermal data from satellite-based instruments shows that an open lava lake remained through 23 May 2018. MIROVA analysis of MODIS satellite thermal data (figure 64) shows nearly daily strong thermal anomalies. Similarly, MODVOLC alerts for the same time period shows a consistently frequent number of anomalies (figure 65).

Figure (see Caption) Figure 64. Thermal anomaly MIROVA plot of log radiative power at Nyiragongo for the year ending 23 May 2018. Courtesy of MIROVA.
Figure (see Caption) Figure 65. Map showing MODVOLC alert pixels at Nyiragongo, reflecting MODIS satellite thermal data, for the year ending 23 May 2018. Each pixel shows a thermal alert for a ground area of about 1.5 km2. Nyiragongo (many pixels) is in the center of the map, and Nyamuragira volcano (fewer pixels) is about 13 km to the NNW. Courtesy of HIGP - MODVOLC Thermal Alerts System.

Geologic Background. One of Africa's most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, 3470-m-high Nyiragongo displays the steep slopes of a stratovolcano. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); 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/).


Ebeko (Russia) — June 2018 Citation iconCite this Report

Ebeko

Russia

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

All times are local (unless otherwise noted)


Ash explosions remained frequent through May 2018, with plumes typically rising more than 1 km

The most recent eruption at Ebeko, a remote volcano in the Kuril Islands, began in October 2016 (BGVN 42:08) with explosive eruptions accompanied by ashfall. Frequent ash explosions were observed through November 2017 and the eruption remained ongoing at that time (BGVN 43:03). Activity consisting of explosive eruptions, ash plumes, and ashfalls continued during December 2017 through May 2018 (table 6). Eruptions were observed by residents in Severo-Kurilsk (about 7 km E), by volcanologists, and based on satellite imagery. The Kamchatkan Volcanic Eruption Response Team (KVERT) is responsible for monitoring Ebeko, and is the primary source of information. The Aviation Color Code (ACC) remained at Orange throughout this reporting period. This color is the second highest level of the four color scale.

Table 6. Summary of activity at Ebeko volcano from December 2017 to May 2018. Aviation Color Code (ACC) is a 4-color scale. Data courtesy of KVERT

Date Plume Altitude Plume Distance Plume Direction Other observations
1-4 and 7 Dec 2017 2 km -- -- ACC at Orange. Ashfall reported in Severo-Kurilisk. Explosions on 2-4 and 7 Dec.
8, 9, 11 Dec 2017 2.3 km -- -- Explosions.
16, 18-19, and 21-22 Dec 2017 3.5 km 16 km SSW Explosions. Ash plume and weak thermal anomaly on 16 Dec.
25 Dec 2017 1.5 km -- -- Explosion.
01-05 Jan 2018 -- -- -- No activity noted.
08-10 Jan 2018 2.5 km -- -- Explosions.
11-12, 14-16, and 18 Jan 2018 3.1 km -- -- Explosion. Minor ashfall reported in Severo-Kurilsk on 15,16, and 18 Jan.
22-23 Jan 2018 2 km -- -- Explosions.
26-27 and 29-31 Jan 2018 2.5 km -- -- Explosions. Ashfall reported in Severo-Kurilsk on 29 Jan.
05-08 Feb 2018 2.4 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 8 Feb.
09-10 and 14 Feb 2018 2.2 km -- -- Explosions.
17-18 and 20-21 Feb 2018 2.4 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 17-18 Feb.
23-25 and 27-28 Feb 2018 3.3 km -- -- Explosions.
06 Mar 2018 1.7 km -- -- Explosions.
12-13 Mar 2018 2.7 km -- -- Explosions.
18 and 21-22 Mar 2018 1.8 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 17 and 21 Mar.
23-25 and 28-29 Mar 2018 2.3 km -- -- Explosions.
31 Mar-06 Apr 2018 2.7 km -- -- Explosions.
07 and 11-12 Apr 2018 1.8 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 6 Apr.
15 and 17-19 Apr 2018 2.6 km -- -- Explosions.
21 and 25 Apr 2018 2.5 km -- -- Explosions.
01-03 May 2018 2.8 km -- -- Explosions.
04 and 06-10 May 2018 2.4 km -- -- Explosions.
12-14 May 2018 2.8 km 21 km SW Explosions. Ash plume drifted SW on 13 May.

Minor ash explosions were reported throughout the period from December 2017 through May 2018 (figure 17). Minor amounts of ash fell in Severo-Kurilisk at the end of 2017 and into 2018. Ash was reported on 2-4, and 7 December 2017; 15, 16, 18, and 29 January 2018; 8, 17, and18 February; 17 and 21 March; and 6 April. Ash plume altitudes during this reporting period ranged from 1.5 to 3.5 km (table 6); the summit is at 1.1 km.

Figure (see Caption) Figure 17. Explosions from Ebeko sent ash up to an altitude of 1.5 km, or about 400 m above the summit, on 6 February 2018. Courtesy of T. Kotenko (IVS FEB RAS).

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

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


Langila (Papua New Guinea) — June 2018 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Gradual decline in activity after July 2017, but continuing through May 2018

Langila, one of the most active volcanoes of New Britain (figure 7), has been intermittently ejecting ash since April 2016 (BGVN 42:09). Volcanic ash warnings continue to be issued by the Darwin Volcanic Ash Advisory Centre (VAAC). Recent ash plume altitudes (table 5) are in the range of 1.5-2.5 km, but several in mid-April to mid-May 2018 reached up to twice that level. Thermal anomaly data acquired by satellite-based MODIS instruments showed a gradual decrease in power level and occurrence through mid- to late-2017, followed by significantly fewer alerts and anomalies in the first half of 2018. Rabaul Volcano Observatory (RVO) data indicates the activity during 2017 was primarily located in Crater 2 (northern-most crater).

Figure (see Caption) Figure 7. Satellite imagery showing Langila volcano at the far NW end of New Britain island. The brown color of recent lava flows and other volcanic deposits are easily noticeable compared to green vegetated areas. The volcano is about 9 km due south of the community labeled Poini. Imagery in this view is from sources listed on the image; courtesy of Google Earth.

Table 5. Reported data by Darwin Volcanic Ash Advisory Centre (VAAC) on ash plume altitude and drift from Langila based on analyses of satellite imagery and wind model data between 21 June 2017 and 28 May 2018.

Dates Ash Plume Altitude (km) Ash Plume Drift Other Observations
07 Aug 2017 2.1 55 km NW --
09 Aug 2017 1.8 N --
16 Aug 2017 2.1 NW --
01-02 Sep 2017 1.8 N, NW --
07-08, 10-12 Sep 2017 1.8-2.4 NNW, NW, SW --
22-23 Sep 2017 2.1 NNW --
04 Oct 2017 1.8 N Minor ash emission
11, 15-16 Oct 2017 1.8-2.1 NE, NNW, NW --
17-18, 20 Oct 2017 1.5-1.8 NE, NNW, NW --
05 Nov 2017 3.7 SE, ESE --
15-16 Nov 2017 1.8-2.7 S, SW --
15 Apr 2018 3.7 S --
24 Apr 2018 4 SW Ash dissipated in 6 hours
13 May 2018 5.5 W At 0709; ash dissipated in 6 hours
17-18, 21-22 May 2018 2.1-2.4 WSW, W, WNW --
23, 26-28 May 2018 2.4-3 WSW, W, NW --

MIROVA analysis of thermal anomalies measured by MODIS satellite sensors show a gradual decline of radiative power from early June 2017 to the end of the year (figure 8). Sporadic low-power anomalies occurred in January, April, and May 2018.

Figure (see Caption) Figure 8. Thermal anomalies from MODIS data analyzed by MIROVA, plotted as log radiative power vs time for the year ending 6 June 2018. Courtesy of MIROVA.

Thermal alerts from MODVOLC analyses were concentrated between early June 2017 and late September 2017 (figure 9), with only one pixel being measured in 2018 through early June, that alert being on 5 January 2018.

Figure (see Caption) Figure 9. Map showing thermal anomalies from MODIS data analyzed by MODVOLC for the year ending 6 June 2018. Courtesy of HIGP - MODVOLC Thermal Alerts System.

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: 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/); Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea.


Pacaya (Guatemala) — May 2018 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Pyroclastic cone fills MacKenney crater; lava flows emerge from fissures around the crater rim

Extensive lava flows, bomb-laden Strombolian explosions, and ash plumes emerging from MacKenney crater have characterized persistent activity at Pacaya since 1961. The latest eruptive episode began with intermittent ash plumes and incandescence in June 2015; the growth of a new pyroclastic cone inside the summit crater was confirmed in mid-December 2015. Strombolian activity from the cone continued during 2016 and it grew sporadically through September 2017 (BGVN 42:12). Lava flows first emerged from fissures around the summit during January-April 2017. Explosions from the cone summit caused growth and destruction of the top of the cone; by the end of September it was about 10 m above the elevation of the crater rim. This report describes the continued growth of the pyroclastic cone and the increasing emergence of lava flows around the summit during October 2017-March 2018. Information was provided primarily by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and satellite thermal data.

Thermal activity was relatively quiet at Pacaya during October and November 2017. The pyroclastic cone inside MacKenney crater continued to grow as material from Strombolian explosions sent ejecta a few tens of meters above the cone and onto its flanks, slowly filling the area within the crater. In late November, small lava flows began to emerge from the crater. Material flowed from the 2010 fissure on the NW side of the crater, and also appeared from new lateral fissures on the W and SW flanks. Multiple small short-lived lava flows traveled a few hundred meters down the flanks with increasing frequency during January through March 2018. Strombolian activity from the summit of the cone occasionally reached over 100 m; by the end of March, the summit of the cone remained about 25 m above the crater rim, and much of the crater was filled with ejecta (figure 84).

Figure (see Caption) Figure 84. A satellite image of Pacaya dated 7 March 2018 shows MacKenney crater at the summit nearly full of ejecta from the growing pyroclastic cone, and at least two small steam plumes on the SW flank from fissures that show dark traces of recent fresh lava. Courtesy of DigitalGlobe and Google Earth.

Activity during October-December 2017. Activity during October 2017 consisted primarily of degassing with small plumes of steam and gas rising 100 m above the summit, and weak Strombolian explosions. . By the end of the month, the cone inside MacKenney crater rose about 10 m above the crater rim. At night, incandescent ejecta could be seen 25-100 m above the summit of the cone. During the last week of October strong winds dispersed the plumes SW and SE, and ashfall was reported 2 km from the crater in El Rodeo.

Steam and gas plumes generally rose no more than 25 m above the summit for the first 20 days of November 2017. Beginning on 21 November, more substantial steam and gas plumes, rising 500 m, were observed in the webcam (figure 85). An increase in tremor activity on 28 November coincided with an increase in explosive activity, a gray ash plume, and the appearance of a small lava flow on the NW flank that extended about 30 m. By the end of the month the cone had reached about 25 m above the rim of MacKenney crater and continued to grow from the accumulation of tephra fragments ranging in size from one millimeter to 50 cm that were ejected 25-100 m above the summit (figure 86). Explosions could be heard up to 1 km from the cone.

Figure (see Caption) Figure 85. A steam plumes rises about 500 m above the summit of Pacaya on 21 November 2017. Courtesy of Michigan Technological University and INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, novembre 2017).
Figure (see Caption) Figure 86. The pyroclastic cone at Pacaya had nearly filled MacKenney Crater by 17 November 2017 (upper photo). An explosion from the summit of the cone with ash and ejecta was captured by the thermal camera on 17 November (lower image). Courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, novembre 2017).

Strombolian explosions rising to 25 m continued in early December. On 10 December 2017, INSIVUMEH noted that there were two lava flows, one flowing on the SE flank with a length of 50-75 m and a second flowing NW towards Cerro Chino for 75-100 m. Strombolian explosions were reported 100 m above the summit of the cone on 15 December, and 25-50 m high on 25 December. The flow on the NW flank was about 100 m long on 26 December.

Activity during January-March 2018. Weak Strombolian activity continued from the cone during January 2018 with ejecta reaching 50 m above the summit. Small lava flows on the NW flank, generally only a few tens of meters long, were visible as incandescence at night (figure 87). While the height of the cone inside MacKenney crater remained about 25 m above the crater rim, material from the continuing low-level explosions had filled a large area of the crater by the end of the month. Blocks up to 1 m in diameter were also dislodged by the tremors and flow activity on the SW flank of MacKenney crater (figure 88). An increase in explosive activity beginning on 20 January resulted in audible explosions heard 2 km from the cone and fine ash deposited on the flanks. A new, larger flow also emerged from the crater early on 20 January and descended about 400 m down the SW flank, with material spalling off the front as it cooled. The following day, low-level Strombolian activity continued, and the flow remained active 200 m down the SW flank. During the last few days of January, the flow rate decreased, and the active flow was only 25 m long (figure 89).

Figure (see Caption) Figure 87. Incandescence from the summit of Pacaya on 8 January 2018, viewed from the SW flank, was caused by Strombolian activity and lava flows. Photo by Instagram user @cesiasocoy, courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, enero 2018).
Figure (see Caption) Figure 88. Low-level Strombolian activity sent ejecta up to 50 m above the summit of the cone at MacKenney crater on Pacaya during most of January 2018. The top of the cone inside the crater was just visible above the crater rim at the summit in this view from the NW flank taken on 17 January 2018. White blocks at the base of the SW slope on the right of the image are recently dislodged, 1-m-diameter blocks. Courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, enero 2018).
Figure (see Caption) Figure 89. Lava flows on the SW flank of Pacaya on 25 January 2018, photographed by Instagram user @Carolinegod1. Courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, enero 2018).

Low-level steam and occasional gas plumes rising up to 300 m above the summit were typical during February 2018 (figure 90). In addition, intermittent lava flows continued to travel tens to a few hundred meters down the S, SW, and W flanks. A 25-m-long flow was observed on the SW flank on 2 February. On 8 February, a 150-m-long flow was noted, also on the SW flank. INSIVUMEH reported a 300-m-long lava flow from the NW area of crater on 9 February in the region of the 2010 fissure; it traveled NW towards Cerro Chino crater. A flow 75-100 m long was observed on the SW flank on 10 February; the next day 150-m-long flows were visible on both the SW and W flanks. Flows on both flanks were 100 m long on 12 February. A 30-m-long flow appeared on the SW flank on 13 February. The flow on the NW flank that began on 9 February was 20-m-wide and only 50 m long during the afternoon of 14 February. A flow was also visible on 14 February extending 250 m down the SW flank (figure 91).

Figure (see Caption) Figure 90. A vigorous steam plume rose 300 m from the summit of the pyroclastic cone inside MacKenney crater at Pacaya during February 2018. The top of the cone was just visible above the crater rim in this view from the NW. Courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, febrero 2018).
Figure (see Caption) Figure 91. Steaming lava flowed on the SW flank of Pacaya on 14 February 2018 and dislodged loose debris on the slope. Courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, febrero 2018).

Multiple lava flows on the SW flank ranged from 50-200 m long during 15-20 February. A flow on the W flank grew from 25 to 150 m during 17-23 February (figure 92). A flow reached 500 m down the SW flank on 25 February and after flow-front collapses was still 300 m long by the end of the month. A new surge of lava on 27 February emerged from the fissure on the NW flank of MacKenney crater and traveled 150 m towards Cerro Chino crater. Explosive activity remained constant; weak explosions, generally 3-5 times per hour, scattered ejecta on the flanks of the cone and created incandescence at night that often reached 15-35 m above the cone. The explosions also generated weak avalanches that sent material up to 1 m in diameter down the S and SW flanks to an area frequented by park visitors. Explosions were sometimes heard up to 3 km from the crater. Strombolian explosions increased in height towards the end of the month; they were reported at 150 m above the summit on 26 February.

Figure (see Caption) Figure 92. A lava flow emerged from a fissure on the W flank of Pacaya on 18 February 2018 and was imaged with a thermal camera as it traveled 150 m down the flank. Courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, febrero 2018).

Strombolian activity and persistent lava flows throughout March 2018 resulted in continued growth of the pyroclastic cone within the MacKenney crater. Low-level steam and gas plumes generally rose a few tens of meters above the summit; occasional plumes rose as high as 500 m. Small lateral fissures near the crater rim produced repeated small lava flows that generally flowed less than 250 m SW and W. Weak explosions averaging 3-5 per hour sent ejecta 10-50 m above the pyroclastic cone.

During the first week of March, flows on the SW flank were active as far as 500 m down the flank. A flow on 4 March was 65 m long, and one on 5 March ranged from 50-200 m long (figure 93). During the second week, two flows were active to 300 m down the W flank, and two others on the SW flank were 150-200 m long. A flow was reported 200 m down the E flank on 16 March. Multiple lava flows were visible during 17-23 March; one traveled 250 m down the SW flank, two others went 150 m down the W flank and remained active through the end of the month.

Figure (see Caption) Figure 93. Landsat satellite imagery from 5 March 2018 shows a thermal anomaly from a SW-directed lava flow at Pacaya, about 250 m long. Landsat 8 image processed by Rudiger Escobar (Michigan Technological University), courtesy of INSIVUMEH (Departamento de Investigación y servicios Geofísicos, Informe mensual de la actividad volcánica, marzo 2018).

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/); Google Earth (URL: https://www.google.com/earth/).


Reventador (Ecuador) — May 2018 Citation iconCite this Report

Reventador

Ecuador

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

All times are local (unless otherwise noted)


Near-daily explosions produce 1-km-high ash plumes and incandescent blocks on all flanks, October 2017-March 2018.

Historical records of eruptions at Ecuador's Volcán El Reventador date back to 1541 and include numerous lava flows and explosive events (figure 74). The largest historical eruption took place in November 2002 and generated a 17-km-high eruption cloud, pyroclastic flows that traveled 8 km, and several lava flows. Eruptive activity has been continuous since 2008. Persistent ash emissions and incandescent block avalanches characterized activity during January-September 2017 with large pyroclastic and lava flows during June and August (BGVN 43:01). Explosions that produced ash plumes and incandescent blocks continued throughout October 2017-March 2018. Information is provided primarily by the Instituto Geofisico-Escuela Politecnicia Nacional (IG-EPN) of Ecuador, the Washington Volcanic Ash Advisory Center (VAAC), and also from satellite-based MODIS infrared data.

Figure (see Caption) Figure 74. Aerial image of Reventador's inner caldera with its pyroclastic cone emitting a plume of steam and ash. View is looking to the W. Photograph taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.

Persistent, near-daily ash emissions were typical for Reventador during October 2017-March 2018 (figure 75). In general, the plumes drifted W and NW over sparsely populated nearby areas, but occasional wind-direction changes resulted in ashfall in larger communities within 30 km to the S and SW. The plume heights were commonly 1,000 m above the summit, with the highest plume rising 5 km (to 8.5 km altitude) in October. Most days that the summit and slopes were not obscured by weather clouds, there were observations of incandescent blocks falling at least 300-500 m down the flanks. Larger explosions generated Strombolian fountains and incandescent blocks that traveled 800 m down the flanks every week, even farther on occasion (figure 76). Heavy rains caused one lahar in late November; no damage was reported. Small pyroclastic flows on the flanks were observed once or twice each month (figure 77). The lava flows of June and August 2017 continued to cool on the flanks (figure 78). Thermal activity was somewhat higher during October 2017 with 19 MODVOLC thermal alerts issued, but it remained constant throughout the rest of the period with 8-11 alerts each month. The MIROVA radiative power data showed a similar pattern of moderate, ongoing activity during this time.

Figure (see Caption) Figure 75. A dense ash plume rose from Reventador during the first week of December 2017, viewed from a shelter 3.5 km E of the summit. Photograph taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.
Figure (see Caption) Figure 76. Incandescent blocks rolled hundreds of meters down the flanks of Reventador during the first week of December 2017. Photograph taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.
Figure (see Caption) Figure 77. A small pyroclastic flow traveled down the flank of Reventador during the first week of December 2017 while an ash plume rose about 1 km above the summit. Photograph taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.
Figure (see Caption) Figure 78. The lava flows from June and August 2017 were still cooling on the flanks of Reventador during the first week of December 2017. Photograph taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.

Activity during October-December 2017. The Washington VAAC issued ash advisories every day but one during October 2017. IGEPN reported near-daily emissions of ash, with plumes rising over 1,000 m many days of the month and rising to 500-800 m the other days. Plume drift directions were generally W or NW. Incandescence at the summit crater was visible on most nights, and incandescent block avalanches were seen rolling 400-800 m down the flanks during 15 nights of the month. Explosive activity intensified for several days near the end of the month (figure 79). A possible pyroclastic flow traveled down the SE flank in the morning of 24 October.

Figure (see Caption) Figure 79. Strombolian explosions from two vents at the summit and incandescence on the SE flank of Reventador were captured on 24 October 2017 by B. Bernard. Photo taken from the Hosteria Reventador, 7.2 km SE from the summit. Courtesy of IGEPN (Informe Especial del Volcán El Reventador – 2017 – No. 5, Actualización de la actividad del volcán, 30 de octubre del 2017).

IGEPN scientists in the field during 23-25 October 2017 noted a high level of explosive activity with loud noises and vibrations felt in the vicinity of Hostería Reventador, about 7.2 km SE of the volcano. Thermal imaging data gathered during their trip indicated that the maximum temperatures of the explosions were over 500°C and that the lava flows of June and August were much cooler with temperatures ranging between 100 and 150°C (figure 80). A dense ash plume rose to more than 2,800 m above the summit and drifted N and E on 25 October (figure 81).

Figure (see Caption) Figure 80. Thermal imaging at Reventador on 24 October 2017 indicated that the temperatures of explosions were over 500°C, and that the lava flows of June and August 2017 were much cooler, around 100-150°C. Image taken by M. Almeida from the Hosteria Reventador, 7.2 km SE from the summit. Courtesy of IGEPN (Informe Especial del Volcán El Reventador – 2017 – No. 5, Actualización de la actividad del volcán, 30 de octubre del 2017).
Figure (see Caption) Figure 81. A dense ash plume rose at least 2,800 m above the summit of Reventador on 25 October 2017 and drifted NE. Photo by B Bernard, courtesy of IGEPN (Informe Especial del Volcán El Reventador – 2017 – No. 5, Actualización de la actividad del volcán, 30 de octubre del 2017).

The Washington VAAC reported numerous ash emissions during 24-26 October 2017 at altitudes of 5.8-6.1 km, drifting N and NE from the summit about 35 km. IGEPN reported continuing ash emissions beginning on 27 October that lasted for several days, including observations that day of a plume that rose to 4,900 m above the summit. The Washington VAAC reported the plume at 8.5 km altitude, the highest for the period of this report. During the last few days of October, the wind changed to the S, resulting in reports of moderate ashfall in Napo province in the towns of San Luis, San Carlos (9 km S), El Salado (14 km S), El Chaco (33 km SW), and Gonzalo Díaz de Pineda (El Bombón, 26 km SW).

Persistent ash emissions continued during November 2017 along with observations of incandescence at the summit crater. Plumes of steam, gas, and ash were reported over 600 m above the summit throughout the month; the Washington VAAC issued multiple daily aviation alerts with plume heights averaging 4.3-4.9 km altitude, usually drifting W. Higher altitude plumes over 6.0 km were reported a few times with the highest during 11-12 November rising to 6.7 km. There were reports in the morning of 1 November of ashfall in Borja and San Louis (SE) and on 4 November of minor ashfall in the communities adjacent to the volcano. Incandescent blocks were seen rolling 300 m down the flanks during 7-9 November. Heavy rains on 20 November resulted in a lahar on the E flank. During 22-27 November blocks rolled as far as 800 m down all the flanks, with many on the S and SE flanks (figure 82).

Figure (see Caption) Figure 82. Steam, gas, and ash plumes, and incandescent blocks rolling down the flanks were common occurrences at Reventador throughout November 2017. Top: An ash and steam plume on 22 November 2017 rose over 600 m and drifted W. Bottom: Incandescent blocks rolled as far as 800 m down the flanks on 23 November 2017, mostly on the S and SE flanks. Courtesy of IGEPN webcam (Informe Diario del Estado del Volcán Reventador Nos. 2017-326, and 2017-327).

Although multiple daily aviation alerts continued throughout December 2017 from the Washington VAAC, weather clouds often prevented satellite observations of the ash plumes. When visible, plume heights were generally 4-5 km altitude, drifting W or NW; the highest plume on 17 December reached 5.5 km and drifted WNW before dissipating. IGEPN noted incandescence at the summit on almost all nights it was visible; incandescent blocks traveled as far as 900 m down all the flanks on 11 December, and 400-800 m most nights. They also reported ash plumes rising more than 600 m above the summit 24 days of the month. A video of typical activity at Reventador was taken by Martin Rietze during 1-7 December 2017, along with numerous excellent photographs (figures 83-85).

Figure (see Caption) Figure 83. Strombolian explosions at Reventador during the first week of December 2017 sent showers of incandescent debris skyward (upper photo) before sending larger incandescent blocks hundreds of meters down the flanks of the cone (lower photo) while a dense ash plume rose from the summit area. Photographs taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.
Figure (see Caption) Figure 84. Lightning strikes were photographed within the dense ash plumes that rose from the summit of Reventador during the first week of December 2017. Photograph copyright by Martin Rietze and used with permission.
Figure (see Caption) Figure 85. Explosions at Reventador during the first week of December 2017 produced dense ash plumes and small pyroclastic flows down multiple flanks. The flanks were bare at the beginning of the ash emission event (upper photo) but small pyroclastic flows can be seen descending the flanks a few moments later (lower photo). Photograph taken during 1-7 December 2017, copyright by Martin Rietze and used with permission.

Activity during January-March 2018. Except for several cloudy days during the third week of January 2018 when no observations were possible, IGEPN reported recurring emissions of steam, gas, and ash rising over 600 m and drifting mostly W or NW throughout the month. During 11-12 January ash plumes briefly drifted E. Incandescent block avalanches were reported most often traveling 200-400 m down the S and SE flanks; a few times they travelled up to 800 m down all the flanks. Other than the cloudy days of 20-24 January, the Washington VAAC issued multiple daily aviation alerts. When ash plumes were visible in satellite imagery, plume altitudes ranged from 4.3-4.9 km, except for 30-31 January when they were reported at 5.2 km (figure 86).

Figure (see Caption) Figure 86. Ash plumes and incandescent blocks were reported numerous times at Reventador during January 2018. Top left: Steam, gas, and ash were reported rising over 600 m and drifting NW and E on 2 January. Top right: on 3 January, the drift directions of the steam, gas, and ash plumes were W and NE. Lower left: Incandescent blocks were reported travelling 800 m down all the flanks on 12 January. Lower right: Ash plumes on 30 January were reported by the Washington VAAC at 5.2 km altitude, the highest during the month; they drifted N and W. Courtesy of IGEPN (Informe Diario del Estado del Volcán Reventador, Nos. 2018-2, 2018-3, 2018-12, and 2018-30).

Multiple daily aviation alerts continued from the Washington VAAC throughout February 2018. While daily plume heights mostly averaged 4.3-4.9 km altitude, there were a greater number of higher-altitude ash plumes than during recent months. A plume on 5 February was reported at 6.1 km drifting 15 km N and a plume the following day drifted 30 km ENE at 7.6 km altitude. A plume on 16 February rose to 5.5 km and drifted 55 km NW; one on 22 February rose to 7.0 km and drifted almost 100 km SE before dissipating. The next day, a plume rose to 5.5 km and drifted 35 km SE. Two separate plumes were observed in satellite imagery drifting NE on 25 February, the first rose to 5.5 km and drifted 110 km and the second rose to 6.4 km and drifted 45 km before dissipating. IGEPN reported a plume of steam, gas, and ash on 27 February that rose over 1,000 m above the summit and drifted NE. Although IGEPN only reported incandescent avalanche blocks on 11 days in February, more likely occurred because the view was obscured by weather clouds for 14 days of the month.

Minor ashfall in the vicinity of the volcano was reported by IGEPN on 1 March 2018. They also noted steam and gas plumes containing moderate amounts of ash that rose over 2,000 m above the summit and drifted SW and S that day (figure 87). IGEPN reported ash emissions around 600 m or higher above the summit on 21 days during the month. In addition to persistent incandescent activity at the summit, avalanche blocks rolled down all the flanks 800 m numerous times. A pyroclastic flow was reported 400 m down the S flank on 13 March (figure 88). Incandescent blocks rolled 1,000 m down all the flanks on 22 March. Other than a plume reported in satellite imagery at 5.8 km moving E on 26 March, all of the ash plumes reported by the Washington VAAC during March ranged from 3.9-4.9 km altitude and generally drifted NW or W.

Figure (see Caption) Figure 87. A plume of steam, gas, and ash rose from Reventador on 1 March 2018; IGEPN reported it as rising over 2,000 m above the summit and drifting SW and S. A small pyroclastic flow also appeared to descend the flank. Courtesy of IGEPN (Informe Diario del Estado del Volcán Reventador, No. 2018-60).
Figure (see Caption) Figure 88. Continued explosions at Reventador during March 2018 produced abundant incandescent avalanche blocks, ash plumes, and a few pyroclastic flows. Top: Abundant incandescent blocks rolled 800 m down all the flanks on 6 March 2018. Bottom: An ash plume rose over 600 m above the summit and drifted NW while a pyroclastic flow traveled 400 m down the S flank on 13 March 2018. Courtesy of IGEPN (Informe Diario del Estado del Volcán Reventador, Nos. 2018-65 and 2018-72).

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

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IGEPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); 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/); Martin Rietze (URL: http://mrietze.com/web16/Ecuador17.htm).


Santa Maria (Guatemala) — May 2018 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Daily explosions with minor ash and block avalanches at Caliente, November 2017-April 2018

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing since 1922. The youngest of the four vents in the complex, Caliente, has been actively erupting with ash explosions, pyroclastic, and lava flows for more than 40 years. During January-October 2017 (BGVN 42:12), daily weak ash emissions sent ash plumes to altitudes around 3.3 km, and ashfall was frequent in villages and farms within 12 km S and SW. The lava dome that appeared within the summit crater of Caliente in October 2016 continued to grow, increasing the frequency of block avalanches moving down the flanks. Several lahars affected the major drainages during May-October. Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center) provided regular updates on the continuing activity during the time period of this report from November 2017-April 2018.

Activity at Santa Maria was very consistent with little variation during November 2017-April 2018. Plumes of steam with minor magmatic gases rose continuously from the Caliente crater 300-500 m above the summit, drifting SW or SE before dissipating. In addition, tens of daily explosions with varying amounts of ash rose to altitudes of around 3.5-4.0 km and usually traveled short distances of 20-30 km before dissipating. The longest-lived plume, on 22 March 2018 drifted 100 km before dispersing. Almost all of the plumes drifted SW or SE; minor ashfall occurred in the mountains and was reported at the fincas up to 15 km away in those directions several times each month. Continued growth of the lava dome at Caliente resulted in block avalanches descending its flanks every day. The MIROVA plot of thermal energy during this time shows a consistent level of heat flow with minor variations. The spike of strongest heat flow in late March 2018 corresponds with the largest ash plume reported (figure 70) for the period.

Figure (see Caption) Figure 70. MIROVA plot of thermal energy from Santa Maria for the year ending 12 July 2018 shows persistent low levels of heat flow. The spike at the end of March 2018 corresponds to the largest reported ash plume for the period. Courtesy of MIROVA.

Activity during November 2017-January 2018. During November 2017, persistent steam plumes rose 100-500 m above the summit crater at Caliente, and generally drifted SE. Tens of weak explosions daily created ash plumes that rose to about 3.2 km altitude and drifted usually SE. These resulted in ashfall reported near Finca San José on 9, 26, and 28 November, and in the mountains around Finca la Florida on 27 November. The Washington VAAC reported an ash emission seen in satellite imagery on 18 November drifting S about 15 km from the summit at 4.3 km altitude. Block avalanches were reported daily, they usually extended down the SE flank, occasionally making it to the base of the dome.

Characteristic steam plumes rising 100-500 m continued daily throughout December 2017. Numerous daily weak to moderate explosions generated ash plumes that rose to around 3.0-3.3 km altitude and drifted most often to the SW. Weak to moderate, and occasionally strong block avalanches descended the SE flank of the dome most days.

The Caliente dome maintained constant degassing with mostly steam plumes and occasional magmatic gas throughout January 2018 (figure 71). The plumes rose 50-300 m above the dome; most plumes came from the crater, but a few rose from fissures on the flanks. Explosions with ash plumes rose to 2.8-3.5 km altitude and generally drifted W or SW (figure 72). The seismic station registered 15-21 weak to moderate explosions per day. Ash generally drifted to the E or SE and caused ashfall in the regions around the fincas of San José, Patzulin, La Quina and others. Finca San José reported ashfall in the vicinity on 6, 7, and 9 January, and El Faro noted nearby ashfall on 9 January. A small plume with minor ash content was noted in satellite imagery by the Washington VAAC on 10 January drifting E at 4.3 km altitude. Ash emissions extended about 35 km SW before dissipating on 12 January, also at 4.3 km. Weak and moderate-size block avalanches occurred daily with blocks generally descending the SE or E flank of the dome.

Figure (see Caption) Figure 71. A typical plume of steam and magmatic gas rose from the Caliente vent at Santa Maria on 8 January 2018. Courtesy of INSIVUMEH (Informe mensual de actividad volcánica enero 2018, Volcán Santiaguito, 1402-03).
Figure (see Caption) Figure 72. An explosion at the Caliente dome of Santa Maria on 7 January 2018 sent ash a few hundred meters above the summit crater. Courtesy of INSIVUMEH (Informe mensual de actividad volcánica enero 2018, Volcán Santiaguito, 1402-03).

Activity during February-April 2018. Plumes of steam and gas continued rising daily to a few hundred meters above Caliente during February 2018. Weak and moderate explosions with steam and ash rose to 2.6-3.2 km altitude and drifted variably S, SE, W, or SW during the month (figure 73). Explosions averaged about 14 per day. Ashfall was reported in the fincas to the E and SE during the first week, including at Finca San José on 5 February, and la Florida on 10 February; they occurred in the mountainous areas W and SW during the rest of the month. Ashfall was also reported around the perimeter of the volcano several times during the last week of the month. The Washington VAAC reported an ash plume at 4.6 km altitude on 12 February drifting rapidly W, and a thin veil of gas and minor ash on 28 February extending about 15 km SW from the summit at 4.3 km altitude. Observations of repeated block avalanches down the SE flank throughout the month concurred with thermal measurements on 28 February that showed the hottest areas of the dome at the summit and on the SE flank (figure 74).

Figure (see Caption) Figure 73. An explosion of steam and ash rose from Caliente at Santa Maria on 18 February 2018. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 17 al 23 de febrero de 2018).
Figure (see Caption) Figure 74. Material inside the summit crater of Caliente at Santa Maria measured about 140°C on 28 February 2018, and showed the warmest region on the SE flank where most of the block avalanches occurred. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo:, Volcán Santiaguito (1402-03), Semana del 24 de febrero al 02 de marzo de 2018).

Block avalanches down the SE and S flanks of Caliente from the growing summit dome persisted at weak to moderate levels throughout March 2018 (figure 75). Ten to twenty daily ash-bearing explosions usually rose to about 3.2 km altitude and drifted SW or SE causing ashfall around the perimeter. Ashfall was reported in the mountains around Finca San José on 4-6, 9, 20, and 23 March, and in the Palajunoj area on 11 March. Steam plumes rising from the summit of Caliente to 2.9-3.1 km altitude drifting SE or SW were a daily feature of activity (figure 76). The Washington VAAC reported an ash plume on 5 March that rose to 4.6 km altitude and drifted SW before dissipating within 15 km of the summit. On 21 March, an emission was observed in satellite imagery that extended about 35 km SW from the summit at 4.6 km altitude. Another ash plume the following day also rose to 4.6 km altitude and extended almost 100 km SW before dissipating. That same day, 22 March, MODVOLC issued four thermal alerts for Santiaguito, and the MIROVA system showed a spike in thermal activity as well (figure 70).

Figure (see Caption) Figure 75. Block avalanches descended the SE flank of Caliente at Santa Maria on 6 March 2018. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo:, Volcán Santiaguito (1402-03), Semana del 03 al 09 de marzo de 2018).
Figure (see Caption) Figure 76. A typical steam plume rose from Caliente summit during the last week of March 2018. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 17 al 23 de marzo de 2018).

Multiple daily explosions with ash rose up to 3.2 km altitude during April 2018. The plumes drifted SW or SE, spreading fine-grained ash over the nearby hills. Finca San José reported ashfall on 2 April and the Palajunoj area reported ashfall on 10, 13, 15, and 17 April. Abundant degassing of mostly steam plumes at the Caliente crater continued throughout the month, as did the constant descent of block avalanches down the SE flank.

Geologic Background. Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); 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/); 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).


Sheveluch (Russia) — May 2018 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Intermittent thermal anomalies along with gas and steam emissions continue through April 2018

An eruption at Sheveluch has been ongoing since 1999, and volcanic activity was previously described through January 2018 (BGVN 43:02). Ongoing activity has consisted of pyroclastic flows, explosions, and lava dome growth with a viscous lava flow in the N. According to the Kamchatka Volcanic Eruption Response Team (KVERT), moderate emissions of gas-and-steam have continued, and ash explosions up to 10-15 km in altitude could occur at any time. The Aviation Color Code remained at Orange (the second highest level on a four-color scale) throughout this reporting period from February through April 2018.

KVERT reported continuous moderate gas-and-steam plumes from Sheveluch during February-April 2018 (figure 49). Satellite imagery interpreted by KVERT showed a thermal anomaly over the volcano on 13 days during February, 21 days in March, and 15 days in April. Cloud cover obscured satellite imagery the remainder of the time during this reporting period.

Figure (see Caption) Figure 49. Photo of the lava dome at Sheveluch on 25 March 2018. Courtesy of Yu. Demyanchuk (IVS FEB RAS, KVERT).

The MIROVA system detected intermittent low-power thermal anomalies from February through April 2018. Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were not detected during this period.

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, 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/).


Kikai (Japan) — May 2018 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Elevated thermal activity during February-April 2018; one earthquake swarm in March

Heightened activity at Kikai (also known as Satsuma Iwojima) was reported during January 2013-July 2014 (BGVN 3907), which included one eruption with intermittent explosions, occasional ash and steam plumes, and sporadic weak seismic tremor. Subsequently, seismicity remained at background levels, and plume activity was low. A short-lived period of heightened activity occurred in March 2018, with increased daily plume heights, sulfur dioxide output, and seismicity. Activity returned to background levels by 26 April. This report is based on information supplied by the Japanese Meteorological Agency (JMA).

JMA reported that one small-amplitude short-duration volcanic tremor was detected on 16 March 2018. The number of volcanic earthquakes increased on 19 March, with 93 occurrences, prompting JMA to raise the Alert Level from 1 (active volcano) to 2 (restricted area around the crater), on a 5-level scale. The report noted increased thermal activity since February, with occasional visual observations of incandescence. Plume heights and volcanic earthquakes briefly increased during 22-23 March (figure 8, plot 4).

Figure (see Caption) Figure 8. Plots showing multi-year records of measured plume heights (1 and 4) and volcanic earthquakes (2 and 5) during January 1998-April 2018 from Kikai. Explosive events are indicated by the small volcano icons along the top of plot 1. Plot 3 indicates measured sulfur dioxide in tons/day since 2012. The orange diamonds on plot 4 indicate observations of incandescence. Plume heights are measured in meters above the crater. This record is from a seismic station located less than 1 km from the summit. Courtesy of Japan Meteorological Agency (JMA).

The number of volcanic earthquakes was low during 27 March-2 April. A white plume at the Iwo-dake summit crater rose to 1,800 m above the crater rim in late March (figure 8, plot 4), the highest seen in many years. At the same crater a highly sensitive surveillance camera revealed incandescence at night on 27 and 28 March due to increased thermal activity. No incandescence was observed after 12 April (figure 8, plot 4).

In its report for 20-26 April, JMA noted a white plume at the Iwo-dake summit crater that rose to 700 m above the rim. A field survey conducted on 25 and 26 April confirmed the slight expansion of a thermal anomaly area when compared to 24 and 25 March, but the release amount of sulfur dioxide was slightly less than 300 tons per day (compared with 600 tons on March 24) (figure 8, plot 3).

On 27 April 2018, with volcanic earthquakes being small in number and no observed volcanic tremor, JMA determined that activity had decreased and reduced the warning level from 2 to 1.

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. Kikai was the source of one of the world's largest Holocene eruptions about 6300 years ago. Rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred in the 20th century at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km east of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).

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Bulletin of the Global Volcanism Network - Volume 38, Number 01 (January 2013)

Managing Editor: Richard Wunderman

Akita-Komagatake (Japan)

Short lived plume rising to 50 m observed on 14 December 2011

Dona Juana (Colombia)

Seismic swarm in 2010 and monitoring efforts

Heard (Australia)

Satellite imagery reveals lava flows in December 2012

Huila, Nevado del (Colombia)

Dome growth and displaced glacier in 2009; decreasing activity during 2010-2012

Izu-Oshima (Japan)

Non-eruptive May 2010 surface deformation from inferred deep instrusion

Kikai (Japan)

Steam plumes rose to 800 m duing latter half of 2012

Kuchinoerabujima (Japan)

Increased seismicity, 11 December 2011-5 January 2012

San Cristobal (Nicaragua)

Ash eruption during 25-28 December 2012



Akita-Komagatake (Japan) — January 2013 Citation iconCite this Report

Akita-Komagatake

Japan

39.761°N, 140.799°E; summit elev. 1637 m

All times are local (unless otherwise noted)


Short lived plume rising to 50 m observed on 14 December 2011

The Japanese Meterological Agency (JMA) reported that a short-lived plume rose to 50 m above Akita-Komaga-take on 14 December 2011 and was recorded by a camera located to the N of Me-dake's summit.

Aerial observations were conducted in cooperation with the Japan Ground Self Defense Force on 13 December. Areas of snow melt corresponded to geothermal areas that had been previously identified. No new geothermal areas were found.

An M 2.6 earthquake on 27 December at 1234 local time occurred ~2 km W of Me-dake, with a maximum JMA Seismic Intensity of 1 in Senboku-city, Akita Prefecture. The JMA Seismic Intensity scale, used in Japan and Taiwan is classified into 10 categories; 0 to 4, 5 weak, 5 strong, 6 weak, 6 strong, and 7. The seismicity around the area had temporarily increased, but then returned to baseline levels. No volcanic activity related to this seismicity was observed.

JMA reported no activity at Akita-Komaga-take in 2012.

Geologic Background. Two calderas partially filled by basaltic cones cut the summit of Akita-Komagatake volcano. The larger southern caldera is 1.5 x 3 km wide and has a shallow sloping floor that is drained through a narrow gap cutting the SW caldera rim. On its northern side the southern caldera borders a smaller more circular 1.2-km-wide caldera, whose rim is breached widely to the NE. The two calderas were formed following explosive eruptions at the end of the Pleistocene, between about 13,500 and 11,600 years ago. Two cones, Medake and Kodake, occupy the NE corner of the southern caldera, whose long axis trends NE-SW. The 1637-m-high Komagatake (also known as Onamedake) cone within the northern caldera is highest point, and has produced lava flows to the north and east; it has a 100-m-wide summit crater. Small-scale historical eruptions have occurred from cones and fissure vents inside the southern caldera. The temperatures of geothermal areas increased beginning in 2005, and some fumarolic plumes were observed in 2011-12.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/en).


Dona Juana (Colombia) — January 2013 Citation iconCite this Report

Dona Juana

Colombia

1.5°N, 76.936°W; summit elev. 4137 m

All times are local (unless otherwise noted)


Seismic swarm in 2010 and monitoring efforts

Doña Juana, a volcano in repose, is located ~50 km NE of Pasto, the provincial capital where the local Instituto Colombiano de Geología y Minería (INGEOMINAS) volcanic and seismic observatory is based (figure 1). In this report we discuss monitoring efforts that began as early as 2004, highlight elevated seismicity detected in mid-2010, and describe the relatively new national park which encompasses Doña Juana and two other volcanic centers (Petacas and Ánimas). Petacas is ~19 km NE of Doña Juana and Ánimas, 12.5 km NE. Ánimas lacks a clear Holocene age; however, Ánimas is an important landmark in this report because the recent seismicity is often found proximal to this volcano. Listed as a Quaternary volcanic center, Ánimas can be found in the "Preliminary List of Pleistocene Volcanoes" section of the Volcanoes of the World 3rd edition (Siebert and others, 2010).

Figure (see Caption) Figure 1. This map of instrumentation from 2012 shows the monitoring network for Doña Juana with telemetered locations for the observatory in Pasto (red circle). Triangles are short period seismic stations (red triangles correspond to INGEOMINAS stations and the pink triangle is part of the National Seismic Network of Colombia (RSNC)), the orange hexagon is a broadband seismic station, green circles are electronic tiltmeters, and green squares are repeater stations for telemetry. The volcanic centers of Doña Juana and Galeras are labeled with yellow text. Courtesy of INGEOMINAS.

Aerial observations and field investigations. Aerial observations had been collected since 2004 in collaboration with the Colombian Air Force (FAC). Overflights during clear conditions provided views of the lava domes and exposures of bare rock where high elevation and frequent rockfalls limit vegetation (figure 2). Remote sensing images of the region also captured the variations in vegetation and distribution of scree slopes (figure 3).

Figure (see Caption) Figure 2. This SE looking photo of Doña Juana was taken during aerial surveys on 12 March 2007. The town of La Cruz appears in the foreground, ~13 km W of the volcanic edifice (on the skyline). Courtesy of INGEOMINAS.
Figure (see Caption) Figure 3. This false-color ASTER image of Doña Juana from 9 September 2010 provided a clear view of the sharp boundaries between heavy vegetated outer flanks (red) and the scrub-covered dome complex (green). Within the central dome area a pale region is attributed to scree from rockfalls. The lowlands, where agriculture dominates the topography, can be distinguished by the pale pink to white regions. Courtesy of NASA.

During 13-21 September 2006, INGEOMINAS led field investigations around Doña Juana. Four scientists focused on the area's stratigraphy and composition of volcanic deposits for development of a future hazard map as well as enhancing the knowledge of the volcano's eruptive history.

Monitoring stations. Three seismic stations were online in 2008: Lava, Florida, and Páramo (figure 4). The Páramo tiltmeter was also online in 2008. In 2009 two additional stations were online; La Cruz seismic station was installed in April and La Florida electronic tiltmeter was installed in June. In 2011, geochemical monitoring began at hot springs within 7 km of the edifice.

Figure (see Caption) Figure 4. The telemetered monitoring network for Doña Juana in 2012 included seismic and electronic tiltmeter instruments. Regular monitoring efforts also included measurements at hot springs (see text). Names of the two volcanic centers Doña Juana and Ánimas and the local communities are highlighted in green. The largest nearby community is the town of La Cruz, ~13 km NNW of the volcanic edifice. Volcán Ánimas is the nearest volcanic center to Doña Juana (~12.5 km NE); however, there has been no documented Holocene volcanism from this site. Courtesy of INGEOMINAS.

As of December 2012, the monitoring network consisted of four seismic stations, with radio repeaters linked to the Pasto network, and two electronic tiltmeters.

Hot spring investigations. INGEOMINAS routinely monitored six thermal springs located ~7 km N and SW from the summit (figure 4). There were three visits during 2011 (August, October, and December) and a visit in April 2012. Temperature and pH monitoring as well as geochemical analysis were the main goals for these investigations.

In their online April 2012 technical bulletin, INGEOMINAS noted that bicarbonate (HCO3) concentrations varied at all monitoring sites, and highest values were consistent between the Tajumbina (1,276-1,436 mg/L) and Ánimas II (1,159-1,229 mg/L) sites. Of all sites, Ánimas I showed an increase since August 2011 in both temperature (41.2°C to 55.3°C) and pH (6.5 to 6.83).

In April 2012, INGEOMINAS discovered a new hot spring location, Ánimas III. This site was within 1 km of Ánimas I, and at the time of sampling, had a neutral pH (7.02) and a lower temperature (56.6°C) compared to the neighboring Ánimas I and Ánimas II sites.

Seismicity. INGEOMINAS reported trends in local seismicity during 2009-2012 in technical bulletins available online. Limited seismicity was detected in 2009 and an abrupt change appeared in early 2010 (figure 5). Combined seismicity (volcano-tectonic, tremor, long period, hybrid, and a category noted as "VOL") tallied for 2010 produced an average of 241 events per month. INGEOMINAS assigned earthquakes to the "VOL" category if they did not meet the criteria of other earthquake types but could be distinguished by fracturing signals proximal to the volcanic edifice. Volcano-tectonic (VT) earthquakes occurred more frequently than other types, occurring on average 107 times per month.

Figure (see Caption) Figure 5. Monthly earthquakes detected with the Doña Juana seismic network during 2009-2012. The number of earthquakes represents a sum of volcano-tectonic, tremor, long period, hybrid, and 'VOL' (see text) events per month. Bar color alternates from red to blue to distinguish years. Courtesy of INGEOMINAS.

Seismicity peaked in August 2010 owing to three VT swarms. That month the various earthquakes totaled more than 675 events. These were low-magnitude earthquakes (M 0-2.7) with relatively shallow depths (7-10 km below the summit).

The calculated locations of earthquakes were available for events during 2010-2012 (table 1). During this time period, epicenters were frequently dispersed between Doña Juana and Ánimas except for the mid-2010 activity and during January-February 2011. This record of information highlights the significance of August 2010 when VT earthquakes were clustered ~7 km NE of Doña Juana, slightly closer to the older volcanic edifice Ánimas (figure 6).

Table 1. During June 2010-December 2012, earthquake detection was sufficient for calculating magnitudes and locations. During several months (January-May 2010, June and October 2011, and September and November 2012) no locations were determined. "Notes" refer to epicenter characteristics such as clustering locations; "dispersed" events are those that occurred at various depths and distances from the volcanic centers. Courtesy of INGEOMINAS.

Month Total Located Magnitude Depth (km below summit) Notes
Jun 2010 68 0.1-2.6 5-10 ~5 km SW of Ánimas
Jul 2010 14 0.2-1.5 6-10 ~5 km SW of Ánimas
Aug 2010 130 0-2.7 7-10 ~5 km SW of Ánimas
Sep 2010 34 0.2-2.1 1-11 ~5 km SW of Ánimas
Oct 2010 10 0.6-2.7 ~7 dispersed
Nov 2010 5 1.1-2.3 3-6 dispersed
Dec 2010 7 0.2-1.8 4-10 dispersed
Jan 2011 59 0.1-3.1 3-14; 6-8 ~8 km SW of Ánimas; many earthquakes clustered at 6-8 km depth
Feb 2011 1 1.2 7 2 km SW of Ánimas
Mar 2011 7 0.5-2.1 15-50 between Doña Juana and Ánimas
Apr 2011 2 <0.2 5.7-6.5 between Doña Juana and Ánimas
May 2011 2 0.4, 1.7 8, 11 dispersed
Jun 2011 -- -- -- --
Jul 2011 9 0.3-1.1 6-12 some clustering near Ánimas
Aug 2011 7 <2 4-15 between Doña Juana and Ánimas
Sep 2011 1 0.7 4 between Doña Juana and Ánimas
Oct 2011 -- -- -- --
Nov 2011 9 0.3-1.5 3-8 between Doña Juana and Ánimas
Dec 2011 2 0.9, 1.7 4-6 between Doña Juana and Ánimas
Jan 2012 16 0.3-1.5 1-19 between Doña Juana and Ánimas
Feb 2012 5 0.9-1.7 2-8 between Doña Juana and Ánimas
Mar 2012 2 0.8, 1.3 7 between Doña Juana and Ánimas
Apr 2012 5 0.4-1.3 0-18 dispersed
May 2012 7 0.5-1.4 3-9.5 dispersed
Jun 2012 20 0-2.3 1-14 dispersed
Jul 2012 13 0.7-1.9 1-14 dispersed
Aug 2012 6 0.2-1.9 0-14.5 SW of Doña Juana
Sep 2012 -- -- -- --
Oct 2012 4 0.7-1.3 0-20 SW of Doña Juana
Nov 2012 -- -- -- --
Dec 2012 2 1.1, 0.7 2, 20 ~10 km S of Doña Juana
Figure (see Caption) Figure 6. Volcano-tectonic seismicity during August 2010 was characterized by a swarm located between Doña Juana and Ánimas volcano; ~8 km NE of Doña Juana. Courtesy of INGEOMINAS.

Colombia's 52nd Natural National Park. In 2007, the Doña Juana-Cascabel Volcanic Complex Natural National Park was created both by the Ministry of Environmental, Housing and Territorial Development and the Colombian Natural National Parks (figure 7). This included Doña Juana, Ánimas, and Petacas volcano (located ~19 km NE of Doña Juana) within the 65,858 hectares of preserved land. Within this densely forested region, a series of streams and waterfalls was locally known as El Cascabel. The park was developed to protect diverse flora and fauna, including numerous endangered species such as the Andean condor, the Moor tapir, the spectacled bear, and puma; approximately 11% of the park includes alpine terrain.

Figure (see Caption) Figure 7. This map of biomes includes the Doña Juana-Cascabel Volcanic Complex Natural National Park and surrounding region. Doña Juana is located in the SW portion of the park. Shaded areas indicate low-elevation Amazon through high-elevation Andean environments. The park boundary is indicated by a heavy black line; populated areas are shaded light pink, road systems are represented by gray lines, and major towns are labeled. This map appears in the 2008-2013 Management Plan of PNN CVDJ-C (2008).

References. Department of the Environment, Housing and Territorial Development Special Administration Unit of the system of Natural National Parks (UAESPNN), 2008, Doña Juana-Cascabel Volcanic Complex Natural National Park (PNN CVDJ-C) Management Plan 2008-2013, Popayán, Colombia, July 2008.

Siebert L., Simkin T., and Kimberly P., 2010, Volcanoes of the World, 3rd edition, University of California Press, Berkeley, 558 p.

Geologic Background. The forested Doña Juana stratovolcano contains two calderas, breached to the NE and SW. The summit of the andesitic-dacitic volcano is comprised of a series of post-caldera lava domes. The older caldera, open to the NE, formed during the mid-Holocene, accompanied by voluminous pyroclastic flows. The younger caldera contains the active central cone. The only historical activity took place during a long-term eruption from 1897-1906, when growth of a summit lava dome was accompanied by major pyroclastic flows.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Pasto, Pasto, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); WWF Colombia (URL: http://www.wwf.org.co/?109882/Nuevo-Parque-Nacional-Natural-en-el-piedemonte-Andino-Amazonico-colombiano); Doña Juana-Cascabel Volcanic Complex National Natural Park (URL: http://www.parquesnacionales.gov.co/).


Heard (Australia) — January 2013 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Satellite imagery reveals lava flows in December 2012

We received an informal report from Matt Patrick (Hawaiian Volcano Observatory) on a new eruptive episode at Big Ben volcano, Heard Island (figure 16). He noted that MODVOLC thermal alerts reappeared at Heard in September 2012 after a four year hiatus (the last eruptive episode ended on 2 March 2008; BGVN 33:01), suggesting the start of a new eruptive episode at the volcano. Since Heard Island is unsettled and extremely isolated, monitoring of the volcano is possibly primarily through satellite imagery (Patrick, 2013).

Figure (see Caption) Figure 16. A contour map (interval = 200 m) showing the partly ice-covered Heard Island. At the time of map preparation, the brown areas were ice free. Produced and issued in January 2000 by the Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia.

EO-1 Advanced Land Imager images collected through late 2012 and early 2013 confirm that eruptive activity resumed around September 2012, in the form of a low-level effusive style eruption similar to its other recent eruptions (figures 17 and 18). Patrick noted that the vent crater had enlarged significantly over the four years following the end of the last eruptive phase, March 2006-March 2008.

Figure (see Caption) Figure 17. A series of images documenting the summit crater and subsequent lava advances at Mawson Peak, Heard Island from 3 July 2012 to 5 January 2013. The Earth Observing-1 (EO-1) satellite's Advanced Land Imager (ALI) Band 1 (panchromatic) images (10-m-pixel size) acquired several clear images on 3 July, 9 September, 13 October, 15 and 28 December 2012, and 5 January 2013. North is to the top of the photos. In the first three images the 200-m diameter crater at the summit of Mawson Peak is easily visible, and there is no evidence of activity outside of the crater. Courtesy of Matt Patrick.
Figure (see Caption) Figure 18. EO-1 ALI Band 10-3-2 RGB composites (30-m-pixel size) of the same series of images as in figure 17 (3 July 2012 to 5 January 2013). North is to the top of the photos. The red is the shortwave infrared band (Band 10, 2 microns); red pixels indicate high temperatures suggesting hot lava surfaces. As in figure 17, the 3 July 2012 image shows that the summit crater was cold, with no evidence of lava inside. However, the 9 September 2012 image clearly shows that elevated temperatures (and presumably lava) had appeared in the crater, consistent with the appearance of MODVOLC thermal alerts later that month. Therefore, this eruptive episode appears to have started around September. Courtesy of Matt Patrick.

The 15 December 2012 image in figure 17 shows that a short lava flow from the summit was emplaced on the SW flank. The flow was ~420 m long and had two lobes. By 28 December, a flow consisting of two lobes (presumably the same flow as in the 15 December image) had reached 770 m SW of the summit crater. In the 5 January 2013 image this flow was 780 m long and had changed little over the previous week.

Figure 18 shows that the 9 September and 13 October 2012 images suggested active lava contained with the summit crater. The 15 and 28 December 2012 images showed elevated temperatures on the lava flow SW of the summit, suggesting it was active over this interval, which was consistent with the observed elongation of the flow in the visible images. Fewer high-temperature pixels in the 5 January 2013 image and the meager advancement observed in the visible images, suggested that the flow had stalled by this point.

Overall, the activity as of mid-March 2013 had consisted of lava within the crater and a lava flow of at least 770 m long emplaced SW of the crater. This low-level effusive activity is consistent with the previous three eruptive episodes observed in satellite images at Heard Island (Patrick and Smellie, in review). These three episodes, May 2000-November 2001 (BGVN 25:11, 26:02, 26:03, and 28:01), June 2003-July 2004 (BGVN 29:12), and March 2006-March 2008 (BGVN 31:05, 31:11, 32:03, 32:06, 33:01, and 35:09), each lasted 1-2 years. On this basis, Patrick suggested that this new eruptive episode may persist for a similar duration. MODVOLC thermal alerts were measured nearly continuously from 21 September 2012 through 24 February 2013.

References. Patrick, M., 2013, A new eruptive episode at Big Ben Volcano, Heard Island, informal communication to BGVN, 23 February 2013.

Patrick, M.R., and Smellie, J.L., in review, A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-2010, Antarctic Science, in review in 2013.

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 volcano lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben volcano because of its extensive ice cover. The historically active Mawson Peak forms the island's 2745-m 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 in historical time at this isolated volcano, but observations are infrequent and additional activity may have occurred.

Information Contacts: Matt Patrick, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia (URL: https://data.aad.gov.au/database/mapcat/heard/heard_island.gif); MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP) 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/).


Nevado del Huila (Colombia) — January 2013 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Dome growth and displaced glacier in 2009; decreasing activity during 2010-2012

Lava dome emplacement occurred at Nevado del Huila's Pico Central (central peak) in late 2008, and was accompanied by seismic unrest and significant sulfur dioxide (SO2) emissions (BGVN 37:10). Extrusion continued between November 2008 and November 2009. Ash plumes were frequently observed by webcameras during late 2008 to December 2009, and satellite imagery reviewed by the Washington Volcanic Ash Advisory Center (VAAC) detected intermittent ash emissions between October 2009 and April 2011. From January 2009 to December 2012, the Instituto Colombiano de Geología y Minería (INGEOMINAS) reported persistent emissions from the lava dome and dramatic changes to the perched glacier as the lava dome expanded across the E and W flanks. Activity generally decreased in November 2010 through 2012.

In this report, we focus on the time period of December 2008-December 2012 and also discuss monitoring efforts overseen by INGEOMINAS with collaborators such as the Colombian Air Force (FAC), the Washington VAAC, and the Sulfur Dioxide Group's Ozone Monitoring Instrument (OMI). The following subsections review webcamera and aerial observations, thermal-camera imaging, satellite images of volcanic plumes, seismicity, SO2 measurements (DOAS, Flyspec, and OMI), acoustic flow monitoring, and new tilt data. The local monitoring network was expanded during this reporting period, adding two infrasound monitoring stations in 2009 and 2012, two webcameras in 2010 and 2012, and instrumentation at the Caloto site that included a broadband seismometer and an electronic tilt station in 2012.

Web-camera observations. From December 2008 to December 2009, the Tafxnú web-camera (located ~15 km S of the volcanic edifice) frequently recorded gas-and-ash plumes rising higher than 2,000 m above the active dome (figure 26). In 2009, plumes (frequently ash-and-gas, but in some cases gas without ash) rose to maximum heights above the dome as follows: 1,000-2,000 m in June; 1,000-2,500 m in November; and 2,000-5,000 m in December.

Figure (see Caption) Figure 26. On 6 and 9 November 2009, summit activity from Nevado del Huila was observed by INGEOMINAS' N-looking Tafxnú web-camera. Accelerated dome growth was noted by INGEOMINAS that month (discussed in text below), and they annotated this image to circle the location of incandescence and summit activity. Note that these images have been altered from the originals; GVP staff increased the brightness and contrast in order to better distinguish the peaks of the Huila complex. (Top images) Incandescence on 6 November was absent at 0331 (left image) but appeared at 0333 within the green circled region (right image). INGEOMINAS suggested this incandescence resulted from dome collapse events exposing hot rock. The darker peak centered in the foreground is Pico Sur, while the active Pico Central is located higher and to the right of that peak in these images. (Bottom images) Plumes of ash and gas drifting NW from Pico Central were observed on 9 November at 0652 (left image) and 0653 (right image). The green circled region in the left-hand image corresponds to the same location circled in the image from 0333 on 6 November. Two water droplets on the camera lens created the local circular distortions. Courtesy of INGEOMINAS.

An additional camera was brought online in July 2010, located in the town of Maravillas (~10 km SE). A third camera, located at the Caloto site (~4 km SSW of the active dome) came online in July 2012 (figures 27 and 28).

Figure (see Caption) Figure 27. This composite image shows, at left, a map view of the three Nevado del Huila webcamera locations and the extent of their viewsheds. Photos at right show camera installation sites. The newest monitoring station (Caloto) was installed on 19 May 2012 on the SW flank. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 28. A map of monitoring stations for Nevado del Huila from June 2012 included locations of webcameras and seismic, geochemical, and geophysical instruments. The summit of Pico Central is located approximately beneath the text BUCB. Note that yellow and black lines represent major and minor roads, respectively, and blue lines represent rivers. Courtesy of INGEOMINAS.

Observations of dome growth and summit activity during 2009-2010. With support from the Colombian Air Force (FAC) during 2009-2012, INGEOMINAS monitored dome growth and geomorphological changes at Huila by conducting aerial observations with helicopters.

During February 2009 and June-December 2009, INGEOMINAS reported numerous episodes of tremor that were likely associated with ash emissions, but cloud cover and nightfall sometimes precluded direct observations. Notable ash plumes were observed on 11 February, 23 July, 3 August, 16-23 October, and 3, 9, 12, 13 and 15 November; ashfall was noted by observers on all days except 11 February. A crack that had formed along the N face of Pico Central in 2007 continued to steam during this time period.

During three overflights conducted in January 2009, INGEOMINAS determined that the Pico Central lava dome had grown since November 2008. With repeat aerial photography, scientists calculated a total dome volume of 52 x 106 m3 with dimensions of 1,000 m N-S and 250 m E-W. The fresh dome rock continuously degassed (figure 29). Tafxnú webcamera images also showed that gas emissions frequently rising above Pico Central were often blue-colored. Due to continued unrest at Nevado del Huila (note that this name is shortened to 'Huila' during the remainder of this report), especially seismicity and active dome growth at Pico Central, INGEOMINAS maintained Orange Alert (Alert Level II; the second highest Alert Level on a 4-color scale from Green/IV-Yellow/III-Orange/II-Red/I) during January-February 2009.

Figure (see Caption) Figure 29. On 28 January 2009, the FAC facilitated observations of Nevado del Huila's growing lava-dome. In this view, the SW flank (centered) emitted a small gas column. This image highlights the zone of active lava dome growth (outlined in yellow) and the perimeter of the crater (outlined in orange). Courtesy of FAC and INGEOMINAS.

On 11 February 2009, a small pulse of tremor was accompanied by an ash plume discharged at Pico Central which was captured by the Taxfnú webcamera during 0745-0751. During that time period, INGEOMINAS noted a small pulse of tremor. On 23 February, an INGEOMINAS passenger on a commercial aircraft saw diffuse gas escaping from both the crater that hosts the dome and from the N-flank crack. During March, the webcamera frequently showed degassing from the crater and the lava dome. Clear conditions enabled observers on commercial flights to observe a white plume rising from Pico Central in the morning of 10 March. INGEOMINAS noted that both seismicity and remote observations of dome growth indicated decreased activity since February. Accordingly, on 31 March 2009, INGEOMINAS reduced the Alert Level to Yellow (II).

Aerial observations in April highlighted the presence of ash covering the S glacier, confirming the ongoing eruption. Elevated temperatures were concentrated at the extreme high and low points of the dome and degassing continued from the higher-elevation portion of the crater (figure 30).

Figure (see Caption) Figure 30. Photos taken on 19 April 2009 showed Nevado del Huila's active dome and the adjacent ash-covered and locally disturbed glacier. (top) In this visible-light view, the active lava dome has extended down the SW flank of Pico Central (yellow line). Cloud cover obscures the upper peaks of Pico Central (left) and Pico Sur (right). The glacier around Pico Central is difficult to distinguish due to ash cover and cracking attributed to dome emplacement. (bottom) This image is a close-up of the lava dome's SW flank with a forward-looking infrared (FLIR) camera which disclosed higher thermal flux from the dome's upper and lower regions. Gas emissions had been more concentrated from the higher region of the dome, however, the bright glow in this image may also be due to the reflective cloud-cover seen in the visible-spectrum image (top). Courtesy of FAC and INGEOMINAS.

During May and June 2009, the dome's surface continued to produce thermal anomalies, and dome growth was inferred based on the observable fragmentation of dome rock and a wider distribution of fresh material. INGEOMINAS noted that the color of the extruded material in the higher region of the dome had changed to a red-brown color (earlier dome rock was distinctively gray).

On 23 July ashfall was reported at the local military base in Santo Domingo and José Jair Cuspian (Caloto). They reported ashfall in the NW sector of the volcanic edifice. INGEOMINAS reported that this ash event coincided with a pulse of tremor registered that day at 0442.

On 3 August there was a pulse of tremor at 0036 and INGEOMINAS received reports of ashfall in the municipalities of Toribío and Santander de Quilichao (~30 km and ~50 km W of the edifice, respectively). Aerial observations on 16 August established that the crater had grown wider.

During September 2009 there were no major changes observed via webcam. On 16 and 23 October, reports of widespread ashfall came from various municipalities of N Cauca, Valle del Cauca, and in the foothills around the volcano (departments of Cauca, Valle, Tolima, and Huila) (figure 31). There were also reports of sulfur odors from the most proximal communities.

Figure (see Caption) Figure 31. An ash plume from Nevado del Huila's newly-formed crater and fumarolic sites was observed from aircraft on 23 October 2009. (top) A dark curtain of ash ("Cortina de cenizas") drifted SE from Pico Central that day; the plume height was ~1,000 m above the crater. The Washington VAAC reported ash in satellite images at 1015 that day, and noted that the ash plume rose to 6 km altitude, was ~46 km long, and drifting SE at 5 m/s. (bottom) A closer view of the W flank highlights gas-and-ash plumes rising from the upper crater (orange outline) while isolated sites released white plumes, including the site on the N flank of Pico Central (at left) where steam from a fissure had been observed consistently since November 2007. The accumulation of newly erupted material was typically observed from the upper region of the dome (circled in blue); the extent of the dome is outlined with yellow. Ashfall had covered the snow and glaciers of Huila; however, cracks in the glacier remained visible as jagged black and white lines, particularly on Pico Sur (right-hand edge of photo). Courtesy of FAC and INGEOMINAS.

At 0541 on 16 October 2009, the webcamera captured images of an ash plume rising in pulses from Pico Central and drifting E. Accordingly, the Alert Level was raised from Yellow (III) to Orange (II), where it stayed until 5 January 2010. An overflight on 23 October provided views of both intense fumarolic activity from the dome and a column of ash that reached up to 1,000 m above the crater. The summit and glaciers were covered by ashfall, lava extrusion was continuing from the upper region of the crater, and there were thermal anomalies where gas emissions were concentrated. An 11-minute-long episode of tremor that began at 0200 on 28 October was thought to signify dome rock extrusion.

Based on observations during overflights on 30 October and 2 November, INGEOMINAS calculated that the dome volume had increased by ~9 x 106 m3 since the previous estimate in January 2009. Aerial observers saw ash emitted in pulses.

Rapid dome growth occurred in November as witnessed during five aerial investigations (2, 4, 6, 10, and 25 November). On 3 November, an explosion was heard and ashfall was reported by the communities of Inzá, Mosoco, Jambaló y Belalcázar, and other communities SW of the volcano. New layers of ash had accumulated around the summits of Huila, often appearing brown-red as opposed to the gray material deposited in previous months (figure 32). A weekly INGEOMINAS report announced that by 10 November 2009, the dome volume had increased by ~16 x 106 m3 since the previous estimate, more than doubling the amount of growth that had occurred during January-October 2009.

Figure (see Caption) Figure 32. Aerial photos from November 2009 documented rapid changes on Nevado del Huila's Pico Central. (top) On 4 November INGEOMINAS observed additional ejecta surrounding the lava dome and elevated ash emissions. In this photo of the S face of Pico Central, steam and ash rise from the crater, and brown-red ash and blocks cover the glacier that surrounds the active dome. Dome rock extends from the center of Pico Central to lower elevations on the W flank. (bottom) This view of Nevado del Huila's SE flank on 25 November 2009 reveals the increased size of the lava dome which towers above Pico Sur, the rugged-looking peak centered in this view. Ash covered snow and glacial ice surrounds the immediate region of the dome while plumes of gas drift westerly. The dark gray, rounded peak to the lower left is Cerro Negro, the location of a seismic station that remained offline during this reporting period. Courtesy of FAC and INGEOMINAS.

Gas emissions were observed by the webcamera at Tafxnú and during four overflights in December 2009; however, fumarolic activity dropped during the first week of December. Aerial observations determined that 2008 dome rock was being covered by 2009 lava that contained fewer large blocks; the 2008 dome material was distinctively more gray and blocky. During an overflight on 29 December, clear weather allowed INGEOMINAS scientists to observe minor dome collapse events, new cracks in the glacier along the lower E dome contact, and additional dome rock extending down the E flank.

In January 2010, dome growth continued and notably expanded the dome E by ~50 m, further displacing portions of the Pico Central glacier. Gray ash continued to be deposited in the area, covering the glacier surfaces. White plumes were observed this month during overflights and from the webcamera. On 5 January, INGEOMINAS reduced the Alert Level from Orange (II) to Yellow (III); this status was maintained until 15 June 2010.

On 22 February 2010, scientists on board an FAC helicopter noted displaced glacial ice, some steaming along the dome edge, and the surface textures of the 2008 and 2009 lava domes persisted (blocky vs. smaller clast sizes, respectively; figure 33). Based on aerial observations, INGEOMINAS calculated a total dome volume of at least 70 x 106 m3.

Figure (see Caption) Figure 33. During an overflight on 22 February 2010, Nevado del Huila's active dome, displaced ice, and gas emissions were visible. Fresh volcanic material clearly began to extend W and E, divided by the long axis of the Huila complex. (Top) An aerial view of Pico Central's S-facing peak where the active dome was shedding material to the W and E. (Middle) Degassing dome rock is visible along the W flank. The blocky gray rock centered in this region was attributed to 2008 lava extrusion. (Bottom) New dome rock is in contact with the fragmented glacial ice on the E flank, and dome steaming is visible along the margin. Courtesy of FAC and INGEOMINAS.

INGEOMINAS reported that on 12 April additional ash had accumulated on the glacier and lava extrusion was continuing. Columns of gas continued to be emitted from the surface of the new dome, at the contact of 2008 and 2009 lava, and from the crack that had formed in 2007 on the N flank of Pico Central.

No overflights were conducted in June, however the Alert Level was raised to Orange (II) due to increased seismicity, primarily hybrid earthquakes and SO2 emissions (see seismic and SO2 discussion below). INGEOMINAS suggested that the marked increase in hybrid earthquakes may have been linked with the ascent of new magmatic material within the volcanic edifice.

In July, degassing continued and intermittent, small ash emissions were observed toward the end of the month by the ground-based cameras Tafxnú and Maravillas. By 16 July, INGEOMINAS reduced the Alert Level to Yellow (III), due to the reduction in seismicity and SO2 flux, where it remained through August. The Washington VAAC reported possible ash plumes drifting from Huila during 28-30 of July but an absence of such plumes during August.

A 19 August flight revealed that snow had accumulated on the dome. INGEOMINAS noted that some episodes of tremor were likely related to the process of lava dome extrusion and these conditions did not show wide variations in August. Minor ash emissions were reported toward the end of the month. The Maravillas camera detected incandescence on 26 and 29 August, possibly from hot rockfalls from the lava dome.

A pulse of tremor on 30 August at 0635 coincided with ash emissions also observed by the Tafxnú camera. In the afternoon that day, people in the town of Toribío (~30 km W) noted an ash plume. There was also a report that the Símbola River changed color due to the presence of ash. The VAAC noted a hotspot at the summit in satellite images on 31 August.

During September, webcameras imaged plumes of gas as well as gray and reddish-colored emissions attributed to volcanic ash. These plumes were not visible in satellite imagery; however, the Washington VAAC released two notices on 9 September in response to reports from INGEOMINAS that ground-based observations included continuous emissions of gases and some ash.

During the first week of September, the Maravillas webcamera and local populations observed incandescence from the active dome; INGEOMINAS attributed the activity to hot rockfalls on the dome. On 9 September, INGEOMINAS raised the Alert Level to Orange (II); seismicity (particularly energetic tremor) and frequent incandescence were considerations for this announcement. On 9 September, both webcameras captured images of ash and incandescence. On 10 September, drumbeat earthquakes (earthquake signatures related to dome extrusion) had appeared in the seismic records. The last time that drumbeat earthquakes had been detected from Huila was in November 2008 (BGVN 37:10). By 21 September, INGEOMINAS announced that 1,799 drumbeat earthquakes had been detected over the past 13 days.

An overflight on 15 September determined that conditions at the dome were continuing to change; extrusion continued from the highest part of the dome (near the contact with the crater wall). They also observed a debris flow containing rocks and ice that had originated from the edge of the dome and had traveled ~1.5 km down the E flank (figure 34). By the end of the month, gas emissions continued and incandescence was observed by the webcameras.

Figure (see Caption) Figure 34. On 15 September 2010 INGEOMINAS observed debris flows along the E flank of Nevado del Huila. (top) Snow had visibly collected on the active dome that continued to degass and displace the glacier. Near the dome, the glacier was notably fragmented and discolored due to overlying debris and ash. (bottom) This view is a closeup of the area below the fragmented glacier on Huila's E flank. The extent of the debris flow is visible as a 1.5 km long trace of gray material that had incorporated blocks of ice and rocks. Courtesy of FAC and INGEOMINAS.

Aerial observations on 29 September, 1 October, and 4 November confirmed ongoing dome growth. On 1 October, the VAAC reported ash drifting from the summit. On 12 October, INGEOMINAS reduced the Alert Level to Yellow (III); they stated that conditions appeared to have stabilized, in particular local seismicity and gas-and-ash emissions. The webcameras continued to capture images of white gas emissions during the second week of October. White plumes and some incandescence were visible in October. Thermal images from 4 November found that the W-central dome's temperature was 250°C. On 11 November the Washington VAAC reported ash drifting from the summit.

Observations during January-December 2011. The webcameras continued to record images of white plumes rising from the Pico Central dome throughout 2011. Aerial observations during the year noted frequent gas emissions and infrequent ash plumes. During an overflight on 25 January, a FLIR camera detected temperatures up to 90°C from various locations on the dome (figure 35). During an overflight on 29 March, observers noted degassing and odors of sulfur.

Figure (see Caption) Figure 35. In these photo pairs taken during an overflight on 25 January 2011, INGEOMINAS measured surface temperatures of Nevado del Huila's lava dome. (top) These photos are centered on the E flank of Huila. The thermal image is zoomed in on the brown-colored lava dome that continued to steam and degass, forming a small plume rising above Pico Central. For the dome, the minimum ("BAJA") and maximum ("ALTA") temperatures were less than 30 and 68.3°C, respectively. (bottom) These photos are viewing the S-facing Pico Central with the lava dome (centered). Gas emissions were rising from the highest region of the dome and the minimum and maximum temperatures were less than 30 and 80.6°C, respectively. Courtesy of FAC and INGEOMINAS.

On 19 April, the Washington VAAC reported that an ash plume was detected in enhanced multispectral imagery at 0315. The plume was drifting NNW from Huila. The announcement included a note that the ash plume did not appear to be the result of an explosive event. Later that day, after sunrise, INGEOMINAS confirmed that low seismicity was detected, a white plume was visible, but ash emissions were absent.

Aerial observations on 26 April included intense degassing from the NW side of the lava dome; the emissions were gray. A thermal camera detected temperatures of the dome in the range of 78-83°C. The glacier also appeared to have further deformed since the last aerial observations in March.

In May, degassing was observed with the webcameras on days where weather conditions permitted clear views. On 6 and 20 June, scientists confirmed that degassing continued during an overflight; they also observed the accumulation of snow on the lava dome as well as on the surrounding glacier. On 20 June, notable rockfalls were visible from the lava dome that contributed to scree along the dome's lower edges.

Degassing continued to appear in clear webcamera views and during overflights in June-July and September-December. Aerial observers on 22 October saw snow avalanches on the Pico Norte glacier and intense steaming from the upper regions of the dome.

Observations during January-December 2012. Throughout 2012, INGEOMINAS recorded observations of the dome based primarily on webcamera images. No major changes were noted in the weekly and monthly online reports; pervasive steaming and white plumes were frequently observed throughout the year by the two webcameras (Tafxnú and Maravillas). INGEOMINAS maintained Yellow Alert (III) during 2012.

One overflight was conducted by INGEOMINAS in 2012. On 14 January 2012, scientists observed the usual degassing and noted that snow had collected on the dome and glacier. That day's clear viewing conditions allowed detailed observations of the lava dome texture and INGEOMINAS attributed the spiny texture of the dome to late-stage extrusion (figure 36).

Figure (see Caption) Figure 36. On 14 January 2012, clear conditions provided aerial views of Nevado del Huila's lava dome texture. (top) This view of the dome's SE face is centered on the part of the lava dome that had started to accumulate snow cover. Steaming was visible from some regions of the dome but a strong plume was not visible during this overflight. (bottom) INGEOMINAS noted that the higher region of the dome had distinguishable spines that may have formed recently. Courtesy of FAC and INGEOMINAS.

Declining seismicity during January-August 2009. During 2009, four seismometers (two broadband and two short-period stations) were maintained by INGEOMINAS. Ash emissions in October 2009 temporarily disabled the short-period Verdún 2 station, located ~5 km N of the active dome. The Cerro Negro short-period station, closest to the active dome, was not operating during this reporting period (2009-2012). In general, three to four seismic stations were operating during 2009-2012.

In 2009, a total of nine earthquakes were large enough for people nearby to feel shaking; these events had magnitudes between 2.8 and 4.8 with focal depths between 6.2 and 12 km. The epicenters were 3-25 km away from the closest seismic station, CENE, which was located ~3 km S of Pico Central. INGEOMINAS highlighted these earthquakes in their monthly technical bulletins.

From January to September 2009, INGEOMINAS reported a decreasing trend in seismicity. In particular, volcano-tectonic (VT) and long period (LP) earthquakes were becoming less frequent on a monthly basis (figure 37). INGEOMINAS described VT earthquakes as resulting from rock-fracturing events, and LP earthquakes from fluid transport processes within the volcanic edifice. Large daily counts of LP earthquakes generally became less frequent over time. Low levels of tremor, hybrid events, and superficial activity (rockfalls and explosions) were detected throughout this time interval.

Figure (see Caption) Figure 37. Nevado del Huila's seismicity, in particular VT, LP, and tremor earthquakes, decreased overall during January-August 2009. In this plot, the number of events were tallied per day and plotted over time. The legend in the upper right-hand corner lists terminology in Spanish that relates to these conventions: VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Explosions were detected mainly in June and July; see previous subsection "Observations of dome growth and summit activity during 2009-2010" for descriptions of explosive activity. Courtesy of INGEOMINAS.

Clustered epicenters in 2009. Beginning in January 2009, INGEOMINAS described a clustering of seismicity notable in distinct regions of the volcanic edifice. These consisted of three regions, the SW sector, the SE sector, and beneath the central edifice (Pico Central). This pattern was particularly clear in June, October, and December. The June 2009 map of seismicity appears in figure 38. The deepest earthquakes (8-12 km) tended to occur S of the edifice while shallow events were distributed throughout the area. Several deep and distal earthquakes occurred each month with depths between 10-20 km and epicenters up to 25 km from the edifice; these events have been attributed to regional faults.

Figure (see Caption) Figure 38. A map with cross-sections plotting epicenters and hypocenters of volcano-tectonic and hybrid earthquakes during June 2009 at Nevado del Huila. Three zones of clustered activity took place beneath the volcanic edifice (dashes lines). Note the yellow bar for scale (10 km) and the yellow text labeling five seismic stations (marked with blue squares). Four stations were operating; Cerro Negro (CENE) was offline during this reporting period. The active summit area of Pico Central is ~3 km N of the CENE station. Courtesy of INGEOMINAS.

Peaks in seismicity and ash emissions between October 2009 and May 2010. INGEOMINAS reported an abrupt increase in seismicity in October 2009. The occurrence of VT, LP, hybrid, and tremor events had more than doubled since September. On 12 October, a swarm of VT events was detected (figure 39). During the onset of elevated seismicity, INGEOMINAS reported ash emissions during 17-21 October and the Washington VAAC released reports of ash observations from satellite imagery on 16 October.

Figure (see Caption) Figure 39. Seismicity from January 2009 through May 2010 detected from Nevado del Huila included notable peaks in LP earthquakes. In their May 2010 report, INGEOMINAS noted that tremor had been recorded continuously throughout January-May. The legend in the upper left-hand corner lists VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Courtesy of INGEOMINAS.

The appearance of volcanic ash in satellite images was periodically reported by the Washington VAAC from October through mid-November 2009. Aided by the web-camera Tafxnú, INGEOMINAS reported observations of ash plumes frequently occurring through November.

The Washington VAAC reported that, after 15 November 2009, volcanic ash was no longer visible in satellite images. In their monthly technical report, INGEOMINAS noted seismic signals suggesting ash emissions in December 2009, and visual observations of white plumes from the summit that were inferred to be gas-rich. As seen on figure 39, LP events peaked dramatically during 9-10 December when signals characterized as drumbeats were detected (see BGVN 37:10 for additional descriptions of drumbeat earthquakes). INGEOMINAS suggested the onset of drumbeat earthquakes was associated with the extrusion of new material to the surface and growth of the lava dome.

INGEOMINAS reported an average of 995 LP earthquakes per month during January-March 2010. VT events tallied on a monthly basis averaged 239 during that same time interval, suggesting an absence of discernible major changes in the volcanic system since the drumbeat earthquake swarm in December 2009. Tremor was detected more frequently over time and from February to May an average increase of 37 events per month was recorded.

As seen at the right on figure 39, during April-May 2010, very high LP seismicity returned. LP earthquakes peaked in May, with a total of 5,141 events. During April-May, the Washington VAAC released advisories in response to possible ash plumes from Huila, however, they did not detect ash due to frequent cloud cover, and because numerous reports indicated eruptions at night, when satellite instruments offer fewer means of detecting ash.

An ML 3.8 earthquake shook the towns of Toéz and Tálaga (15 km SSW and 22 km S respectively) at 0708 on 23 May. These towns are located SW of Pico Central. The earthquake was located 8.13 km SW of Pico Central and was 7.2 km deep (relative to the elevation of the active crater).

Seismicity and ash observations during June-December 2010. In June, direct observations of ash plumes were rare due to weather conditions; however, the Washington VAAC reported ash visible in satellite imagery on 2 June 2010. While LP seismicity remained low in early June 2010, hybrid seismicity emerged from background levels (figure 40). During January-May, typically 3-34 hybrid earthquakes were detected per month. By 14 June, more than 200 hybrid events were occurring per day; however, by 24 June, hybrid earthquakes had decreased to less than 50 events per day. Hybrid earthquakes, events INGEOMINAS attributes to the combined mechanisms of fluid transport and rock fractures, rarely dominate Huila's seismic records.

Figure (see Caption) Figure 40. Seismicity from Nevado del Huila during 2010 included peaks of LP, VT, and tremor episodes. The legend in the upper left-hand corner lists VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Courtesy of INGEOMINAS.

As seen on figure 40, during August-November 2010, elevated tremor persisted (630-2,576 episodes per month). LP seismicity peaked in May and then twice between September and December. For the tallest peak (September 2010), counts reached more than 1,000 events per day.

On 3 December at 2054 a felt M 3.4 earthquake within the Páez River drainage centered 6.2 km S of Pico Central had a relatively shallow focal depth of 5.2 km (as measured beneath the crater). Another felt earthquake was reported by residents in the Belalcázar-Cauca area on 29 December. This ML 2.9 event occurred at 2106 with a focal depth of 8 km, located 8.5 km SW of Pico Central. This earthquake lacked any noticeable effect on the stability of the volcanic system.

Seismicity in 2011. In 2011, INGEOMINAS noted that both LP earthquakes and tremor were decreasing over time (figure 41). Tremor persisted at low levels. In June VT and LP earthquakes notably increased to 434 and 623 events, respectively, but returned to background levels during the following month.

Figure (see Caption) Figure 41. This plot of Nevado del Huila's seismicity during January-December 2011 shows a general decline in seismicity. This plot excludes VT earthquakes, highlighting instead the daily count of LP, hybrid, and tremor events. Courtesy of INGEOMINAS.

In November 2011, several moderate earthquakes (M≤4) struck near Huila. In particular, three events had magnitudes 2.8, 3.2, and 4.0. For example, on 26 November, inhabitants of Mesa de Toéz felt an M 4.0 event whose epicenter was 8.5 km SW of Pico Central with a depth of 7.4 km (as measured below the crater). VT epicenters in November were widely distributed throughout the edifice and local region (figure 42). Depths of these earthquakes were within the range of past VT earthquakes (0-12 km). Persistent seismicity SW of Huila also continued in November.

Figure (see Caption) Figure 42. A map and cross-sections showing Nevado del Huila's VT epicenters during November 2011. The active dome is ~3 km N of CENE. INGEOMINAS noted four areas where seismicity was clustered (yellow shaded ovals). Note that the largest highlighted region has been an area of persistent seismicity throughout the year (for example, see figure 38). Seismic stations are marked with blue squares and labels (DIAB, VER2, CENE, BUCO, and MARA). Courtesy of INGEOMINAS.

Seismicity in 2012. The low-level seismicity observed in the last months of 2011 continued through 2012. In a comparison with 2011, the average number of events per year was remarkably reduced in 2012 (VT, LP, and tremor); hybrid earthquakes, however, were the exceptions. The average for hybrid earthquakes per month was slightly higher in 2012 (table 4). Hybrid earthquakes were quite variable in number during 2011, ranging from 0 to 60 per month.

Table 4. Monthly counts for volcanic-tectonic, long period, tremor, and hybrid events detected at Nevado del Huila during 2011-2012. More event types and data appear in INGEOMINAS online reports. Courtesy of INGEOMINAS.

Month Volcanic-tectonic Long-period Tremor Hybrid
Jan 2011 284 388 220 2
Feb 2011 217 1,064 154 15
Mar 2011 217 876 168 13
Apr 2011 168 634 152 0
May 2011 136 729 220 0
Jun 2011 434 623 128 60
Jul 2011 165 416 77 25
Aug 2011 143 491 51 32
Sep 2011 137 304 27 8
Oct 2011 110 371 50 13
Nov 2011 176 219 32 2
Dec 2011 164 195 32 34
2011 Avg: 196 526 109 17
 
Jan 2012 155 245 27 28
Feb 2012 111 159 12 18
Mar 2012 145 200 27 21
Apr 2012 154 244 19 21
May 2012 87 200 34 13
Jun 2012 121 183 11 18
Jul 2012 109 208 14 16
Aug 2012 118 178 15 30
Sep 2012 93 172 5 14
Oct 2012 168 257 18 23
Nov 2012 171 205 9 14
Dec 2012 158 227 26 32
2012 Avg: 133 207 18 21

The wide distribution of epicenters noted in November and December 2011 persisted during January-February 2012, but fewer earthquakes were detected during these months. From March through December, significant clustering was absent, although, in October some events appeared concentrated along Huila's N-S axis.

The largest earthquake in 2012 occurred in March; a 3.8 earthquake shook the town of Toribio (in Cauca) at 0248 on 15 March. The epicenter was 1.8 km E of Pico Central with a focal depth of approximately 3.2 km. Seismicity that month was slightly higher than February (table 4). Throughout the year, VT earthquakes were typically less than M 2.6.

Infrasound monitoring 2009-2012. Augmenting seismic monitoring efforts, an infrasound station installed at the Diablo monitoring site (located ~5 km NNW of the active dome) became operational in July 2009. An additional acoustic monitoring system was installed at the Caloto station (located ~3.7 km from the active dome) in May 2012. Data collected with infrasonic microphones complements seismic instrumentation and can be analyzed with similar techniques. The method has also detected distant explosions from volcanoes such as Sakura-jima, Japan (BGVN 20:08), Fuego, Guatemala (BGVN 36:06), and Stromboli, Italy (BGVN 26:07).

Sulfur dioxide emissions during 2009-2012. INGEOMINAS conducted routine sulfur dioxide (SO2) gas monitoring with differential optical absorption spectroscopy (DOAS) equipment from January 2009 through December 2012. With this mobile scanner, INGEOMINAS conducted traverses along the Pan-American Highway between the cities of Calí and Popayán (figure 43).

Figure (see Caption) Figure 43. On 14 and 24 August 2010, INGEOMINAS technicians traversed routes along the Pan-American Highway with mobile DOAS equipment to measure Nevado del Huila's SO2 gas fluxes. These images include color-coded line segments that correspond to high and low concentrations (red and blue, respectively). The approximate locations of the plume have been shaded to correspond with the locations of high SO2 flux. The plots shows the wavelength on the x-axis and concentration-pathlength (ppm-m) on the y-axis. (Top) This image includes the mapped route between the towns of Santander de Quilichao and Villarrica where the gas plume was scanned on 14 August. The wind speed was 10.8 m/s, wind direction was 294°, and SO2 flux was 28.2 kg/s (1,441 t/d). (Bottom) This image includes the results from 24 August when field technicians traversed routes between Pescador and Villarrica. SO2 flux was 23.3 kg/s (2,020 t/d); wind speed and direction were not reported. Courtesy of INGEOMINAS.

Scanning DOAS systems at fixed locations were operating during 2009-2012. During October 2009, elevated SO2 emissions were detected by the Calí and Santander de Quilichao stations (figure 44). In September 2009, a station was operating in Manantial (~53 km W of Huila).

Figure (see Caption) Figure 44. During 7 January 2009-27 November 2012, INGEOMINAS measured the SO2 flux from Nevado del Huila in a series of numbered campaigns (x-axis). A total of 137 values were reported from three detection methods, scan DOAS stations (corresponding to numbers 33 and 35 dating from October 2009, and 55-57 dating from June 2010), FLYSPEC (numbers 118-122 dating from May 2012, and 128 and 129 dating from August 2012), and mobile DOAS (all other values). Red and blue highlighting distinguishes the datasets from each year. SO2 detection was conducted several times each month and the maximum value from each measurement was reported. Courtesy of INGEOMINAS.

Wind velocity has a strong bearing on the computed SO2 flux. In their December 2011 technical bulletin, INGEOMINAS discussed the variability in windspeed and direction, including the Weather Research and Forecasting (WRF) modeling system used for calculations during 2011 (figure 45). The WRF was public domain software available online and was developed in order to provide atmospheric simulations based on numerical modeling.

Figure (see Caption) Figure 45. INGEOMINAS released the source of their windspeed data used for SO2 flux calculations in their December 2011 technical report. (top) This plot shows the datapoints used throughout 2011 for windspeed values determined by the WRF Model. (bottom) These images show a map of the expected aerial extent of the gas plume, a series of photos showing plume conditions during the SO2 surveys, and a table of the measurements from three surveys in December. Courtesy of INGEOMINAS.

In May and August 2012, INGEOMINAS reported the results from FLYSPEC (a portable UV spectrometer) surveys and discussed the variations observed in SO2 flux. They emphasized that SO2 fluxes were low, a finding consistent with previous measurements during this post-crisis period (dome growth had ceased by November 2009). They also mentioned that seismicity had been low in May 2012, particularly in those events related to fluid motion (LP earthquakes, for example).

Flux calculations required wind speed data from the WRF models and daily forecasts from the Institute of Hydrology, Meteorology, and Environmental Studies (IDEAM), Colombia. Wind speeds in the range of 6-12 m/s during 8-29 May 2012 were applied to SO2 flux calculations.

Elevated SO2 emissions from Huila were detected almost daily by the OMI spectrometer during 2009-2012. The AURA satellite maps SO2 in the atmospheric column using ultraviolet solar backscatter. A flux can be estimated for the OMI spectrometer data by looking at the total mass of SO2 measured and the time it took to accumulate. On this basis, INGEOMINAS compared peaks in SO2 flux detected during traverses with DOAS (mobile and scanning) with OMI data for October 2009 (figure 46).

Figure (see Caption) Figure 46. In October 2009, elevated SO2 flux was detected from Nevado del Huila by three remote sensing techniques. (Top) The plotted values show combined datasets from mobile DOAS, OMI, and scan DOAS. (Bottom) The OMI spectrometer on the AURA satellite detected 9.95 kt of SO2 on 20 October 2009 (left) during its pass at 2414-2417 local time (coverage area of 368,974 km2, recording a maximum value of 43.3 Dobson Units (DU)). On 26 October 2009 (right) it detected 7.79 kt of SO2 during its pass at 2337-2340 local time (coverage area of 314,303 km2, recording a maximum value of 31.12 DU). Courtesy of INGEOMINAS and Simon Carn, Michigan Technological University and Joint Center for Earth Systems Technology, University of Maryland Baltimore County.

Lahar investigations. INGEOMINAS maintained seven early warning systems to warn of downstream flooding in vulnerable municipalities such as Belalcázar. At sites within the drainages of the Páez and Símbola rivers, flow monitoring with geophones has continued since October 2006, employing equipment installed by the INGEOMINAS Popayan Observatory in collaboration with the Nasa Kiwe Corporation (CNK). CNK is a relief group that has been active in this area of Colombia since the 1994 earthquake and resultant landslides that devastated the Cauca and Huila regions, including communities along the Páez river (BGVN 19:05). Those events also damaged the Tierradentro archaeological sites, a UNESCO World Heritage Site since 1995.

Following Huila's 2007 lahars (BGVN 33:01), Worni and others (2012) conducted fieldwork and reconstructed events in order to model future lahars for mitigation purposes. The researchers argued that large-volume lahars (tens to hundreds of millions of cubic meters) require targeted studies. The authors noted that "in 1994, 2007, and 2008, Huila volcano produced lahars with volumes of up to 320 million m3." To constrain the dimensions of simulated flows, they used inundation depths, travel duration, and observations of flow deposits from the April 2007 events and applied the two programs LAHARZ and FLO-2D for lahar modeling.

LAHARZ was developed by USGS scientists in order to provide a deterministic inundation forecasting tool; this program was designed to run in a Geographic Information System (GIS) environment (Schilling, 1998; Iverson and others, 1998). "For user-selected drainages and user-specified lahar volumes, LAHARZ can delineate a set of nested lahar-inundation zones that depict gradations in hazard in a manner that is rapid, objective, and reproducible" (Schilling, 1998). Worni and others (2012) presented results from the semi-empirical LAHARZ models along with physically-based results from FLO-2D (FLO-2D Software I, 2009) in order to forecast future inundation areas with specified flow volumes (figure 47). The authors concluded that, despite local deviations, the two models produced reasonable inundation depths (differing by only 10%) and encouraged future investigations that could address sources of uncertainty such as the effects of sediment entrainment that would cause dynamic changes in lahar volumes.

Figure (see Caption) Figure 47. Results are shown from two modeling programs to understand lahar hazards from Nevado del Huila, FLO-2D (top three images) and LAHARZ (bottom three images), for the specified flow volumes. Note the modeled effects on the Belalcázar region (located ~20 km S of Huila). Three scenarios are presented based on lahar flow volumes of 3 x 108, 6 x 108, and 10 x 108 m3. Image from Worni and others (2012).

Deformation monitoring during 2009-2012. An electronic tilt station was operating in July 2009, located at the Diablo monitoring site ~6.26 km NW of Pico Central (4.1 km above sea level). Telemetered data from a new electronic tilt station became available in May 2012; the station was located in the town of Caloto, located ~4 km SSW of Pico Central (4.2 km above sea level). Data from Diablo and Caloto was presented in the monthly technical bulletins posted online by INGEOMINAS.

After seven months of calibrations, INGEOMINAS developed an initial baseline for the new tilt data. The N and E components of Caloto recorded minor fluctuations during this time period. The trend of the E component was generally stable while the N component detected a gradual excursion during 17 June-25 September 2012.

References. FLO-2D Software I, 2009, FLO-2D User's Manual. Available at: www.flo-2d.com.

Iverson, R.M., Schilling, S.R, and Vallance, J.W., 1998, Objective delineation of areas at risk from inundation by lahars, Geological Society of America Bulletin, v. 110, no. 8, pg. 972-984.

Schilling, S.P, 1998, LAHARZ: GIS programs for automated mapping of lahar-inundation hazard zones, U.S. Geological Survey Open-File Report 98-638, 80 p.

Worni, R., Huggle, C., Stoffel, M., and Pulgarín, B., 2012, Challenges of modeling current very large lahars at Nevado del Huila Volcano, Colombia, Bulletin of Volcanology, 74: 309-324.

Geologic Background. Nevado del Huila, the highest peak in the Colombian Andes, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. The high point of the complex is Pico Central. Two glacier-free lava domes lie at the southern end of the volcanic complex. The first historical activity was an explosive eruption in the mid-16th century. Long-term, persistent steam columns had risen from Pico Central prior to the next eruption in 2007, when explosive activity was accompanied by damaging mudflows.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Popayán, Popayán, Colombia; Washington Volcanic Ash Advisory Center (VAAC), NOAA Science Center Room 401, 5200 Auth road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Ozone Monitoring Instrument (OMI), Sulfur Dioxide Group, Joint Center for Earth Systems Technology, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA (URL: https://so2.gsfc.nasa.gov/); Nasa Kiwe Corporation (CNK) (URL: http://www.nasakiwe.gov.co/index.php); Weather Research Forecasting (WRF) (URL: http://www.wrf-model.org/index.php).


Izu-Oshima (Japan) — January 2013 Citation iconCite this Report

Izu-Oshima

Japan

34.724°N, 139.394°E; summit elev. 758 m

All times are local (unless otherwise noted)


Non-eruptive May 2010 surface deformation from inferred deep instrusion

Oshima is an active volcano located on the northern tip of the Izu-Bonin volcanic arc. Our last report of activity at Oshima (BGVN 21:08) enumerated a flurry of shallow low-frequency earthquakes beneath the top and W flank of the volcano that started on 5 August 1996.

Since those relatively benign events, the Japan Meteorological Agency (JMA) had not observed any subsequent events worthy of note until May 2010 when land surface inflation was detected. The inflation was registered by a strainmeter, a Global Positioning System (GPS) network (run by the Geospatial Information Authority of Japan, GSI), and a tiltmeter network (run by the National Research Institute for Earth Science and Disaster Prevention, NIED).

In July 2010 seismicity in the shallow parts of and around Oshima began to increase. (High seismicity synchronous with inflation of the edifice was seen earlier, including in 2004 and 2007). These events were considered to be due to magma intrusion into the deeper part of the volcano. There were no remarkable changes in surface phenomenon. In September, the inflation that was detected in May began declining. Seismicity in the shallow parts of and around Oshima continued at a low level with some small earthquakes which temporally increased in the western offshore areas of Oshima on 22 December 2010.

The earthquakes increased in frequency again on 9 February 2011. GPS and strainmeter measurements indicated contraction since January, but the trend reversed to show inflation in October 2011. Seismicity remained at a low level. Very low level gas emissions were sometimes observed by a camera positioned on the NW summit. Based on a field survey on 28 October, no remarkable change in surface phenomena was observed.

No remarkable activity has been noted since October 2011. Throughout the noted activity, JMA held the Alert Level at 1.

Geologic Background. Izu-Oshima volcano in Sagami Bay, east of the Izu Peninsula, is the northernmost of the Izu Islands. The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Miharayama, that has been the site of numerous historical eruptions. More than 40 parasitic cones are located within the caldera and along two parallel rift zones trending NNW-SSE. Although it is a dominantly basaltic volcano, strong explosive activity has occurred at intervals of 100-150 years throughout the past few thousand years. Historical activity dates back to the 7th century CE. A major eruption in 1986 produced spectacular lava fountains up to 1600 m height and a 16-km-high subplinian eruption column; more than 12,000 people were evacuated from the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).


Kikai (Japan) — January 2013 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Steam plumes rose to 800 m duing latter half of 2012

Kikai is a 17 x 20 km mostly submarine caldera as close as ~40 km from the S margin of the island of Kyushu (see figure 1 in BGVN 37:07; also see Shinohara and others, 2002, for 16 journal articles devoted to this volcano. Maeno, 2008, offers an online overview). A few areas on the caldera rim lie above water (figure 2). Mild-to-moderate emissions have often occurred at the dome called Iwo-dake (alternately spelled Iodake, figure 2). Table 4 summarizes the seismicity and steam plume observations for July-December 2012, an interval of calm, absence of tremor, and low hazard status.

Figure (see Caption) Figure 2. A shaded-relief, contour map of Kikai caldera that labels three islands on the N caldera rim, Satsuma Iwo-jima, Showa Iwo-jima, and Take-shima. Satsuma Iwo-jima contains the highest point of the complex (704 m elevation). On that island, the cones Iwo-dake (a rhyolitic volcano) and Inamura-dake (a basaltic volcano) both reflect post-caldera volcanism focused along or just inside the caldera's wall (the shaded, scalloped line trending NE across the island). The island Showa Iwo-jima emerged during the caldera's last major eruptions, during 1934-1935, starting with floating pumices and including late-stage lava emissions that helped armor the island and allowed it to erode only modestly during the subsequent decades of breaking waves. The caldera floor chiefly resides 300-500 m below sea level but it also contains some post-eruptive cones. From Fukashi Maeno (2008).

Table 4. Monthly summary of seismicity and plume observations at Kikai during July-December 2012. All reported plumes were described as white. Data courtesy of JMA.

Month Earthquakes per month Maximum steam plume height (m above Iwo-dake crater rim)
Jul 2012 238 800
Aug 2012 187 300
Sep 2012 193 500
Oct 2012 219 700
Nov 2012 168 400
Dec 2012 -- --

We last reported on Kikai activity through mid-2012 (BGVN 37:07) covering generally small steam plumes and monthly seismicity of up to ~200 earthquakes per month through June 2012. This report is a compilation of subsequent monthly reports of volcanic activity through December 2012 from Japan Meteorological Agency (JMA) monthly reports. The Alert Level remained constant at Level 2 (on a scale of 1-5: 2 = "Do not approach the crater"), before being downgraded to Level 1 in December 2012.

Between July and September 2012, plume emissions at the Iwo-dake summit crater continued (table 4). Weak incandescence was recorded at night with a high-sensitivity camera on 22 July, 28 August, 6 November and 22-24 November. Seismic activity remained at low levels. No unusual ground deformation was observed in GPS data through December 2012.

An aerial observation conducted by the Japan Maritime Self-Defense Force (JMSDF) on 11 September 2012 revealed white plumes rising from Iwo-dake's summit crater and flanks.

The results of a field survey conducted from 17-20 November 2012 showed no remarkable change in white fumes from Iwo-dake. Infrared images also found that the temperature distribution had remained essentially unchanged. Aerial monitoring conducted by the Japan Coast Guard (JCG) on 25 November 2012 revealed the presence of brown and green discolored water around the eastern coast (similar findings as a previous survey) as well as patterns of steaming similar to those observed during the field survey. SO2 emissions during 17-20 November 2012 were measured to be ~400 tons/day; a previous survey conducted in July 2012 yielded an estimated flux of ~500 tons/day.

References. Shinohara, H., Iguchi, M., Hedenquist, J.W., and Koyaguchi, T., 2002, Preface to special volume, Earth, Planets and Space 54 (3), pp. 173-174.

Maeno, F, 2008, Geology and eruptive history of Kikai Caldera, Earthquake Research Institute, University of Tokyo (URL: http://www.eri.u-tokyo.ac.jp/fmaeno/kikai/kikaicaldera.html); accessed 23 February 2013.

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. Kikai was the source of one of the world's largest Holocene eruptions about 6300 years ago. Rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred in the 20th century at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km east of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Kuchinoerabujima (Japan) — January 2013 Citation iconCite this Report

Kuchinoerabujima

Japan

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

All times are local (unless otherwise noted)


Increased seismicity, 11 December 2011-5 January 2012

Since a small eruption in 1980, Kuchinoerabu-jima experienced numerous periods of elevated seismicity, with volcanic earthquakes and tremor detected at least through December 2009 (BGVN 35:11). The volcano is located in the Ryukyu Island arc, off Japan's SW coast (figure 4).

Figure (see Caption) Figure 4. A map of the major volcanoes of Japan. Kuchinoerabu-jima is at the lower left. Courtesy of USGS/CVO.

Recent monthly reports of volcanic activity from the Japan Meteorological Agency (JMA) translated into English resumed in October 2010. The only recent English-translated JMA report on Kuchinoerabu-jima available online through December 2012 was in January 2012. We know of no other recent report on this volcano's seismic activity; therefore, this report summarizes seismicity between December 2011 and January 2012.

According to JMA, seismicity increased to a relatively high level immediately after 11 December 2011, but then decreased on 5 January 2012. On 20 January 2012, the Alert Level was lowered from 2 to 1; JMA noted that the possibility of an eruption was minimal.

During the December 2011-January 2012 period, no significant change in plume activity was observed, and plume heights remained below 100 m above the crater. According to a field survey on 11 January, infrared images (compared to images obtained in December 2011) showed no significant change in temperature distribution either at the summit or on the W slope of Shin-dake (also refered to as Shin-take), the youngest and most active cone.

Field surveys found that sulfur dioxide levels were 50 and 100 metric tons/day on 12 and 13 January 2012, respectively, which were lower than those recorded in December 2011 (200 metric tons/day on 9 December 2011).

According to JMA, continuous GPS measurements have established a baseline across Shin-dake, collecting data since September 2010. Shin-dake's rate of change in surface deformation at the stations has been slowing since September 2011.

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).


San Cristobal (Nicaragua) — January 2013 Citation iconCite this Report

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Ash eruption during 25-28 December 2012

Our last report highlighted monitoring efforts at San Cristóbal and the explosive eruption that began on 8 September 2012 (BGVN 37:08). By 16 September 2012, seismicity and emissions had decreased; however, the Instituto Nicaragüense de Estudios Territoriales (INETER) announced in late December 2012 that volcanic activity had re-started. In this report, we cover the time period of 25-31 December when seismicity, explosions, and gas-and-ash emissions were reported.

At 2000 on 25 December 2012, observers noted a series of gas-and-ash explosions from the summit. The wind carried the fine- to sand-sized ash SW. Several hours prior to this activity, INETER had reported that seismicity was elevated but sulfur dioxide emissions (SO2) were relatively low compared to measurements from previous days.

During the early hours of the morning on 26 December, winds dispersed fine ash NW, W, and SW. Sand-size ash was fell on the W and SW flanks (figure 28). Civil Defense authorities from the municipality of Chinandega reported an ash plume up to 500 m above the summit and described the event as a "moderate eruption" similar to the 8 September 2012 event.

Figure (see Caption) Figure 28. A view S toward San Cristóbal with an ash plume drifting westerly on 26 December 2012. The lower hills to the right are part of El Chonco, an older volcanic edifice. Photograph by Hector Retamal, AFP, Getty Images.

On 26 December, government officials reported to Reuters that local inhabitants were evacuating. Rosario Murillo, a government spokeswoman, called on residents within a 3 km radius of the volcano to leave the area; some families had already self-evacuated.

By 1000 that day, INETER reported that seismicity had increased, and that they had received reports from Civil Defense stating that an eruption of fine ash rose to ~2,500 m above the crater. By the early afternoon, four major seismic events were detected and interpreted as explosions at the summit. Ashfall from these events primarily affected an area within a 5-6 km radius of the summit: El Viejo, Las Rojas, Banderas, Abraham Rugama, and those communities north of Chinandega's urban limit Grecia (particularly two communities called ##1 and ##4; see figure 19 in BGVN 36:12 for major town locations).

In their second communication on 26 December, INETER suggested that local inhabitants protect their water sources from ashfall, particularly those communities W, SW, and S of the volcano. They also announced that grazing lands would be closed in those regions due to the quantity of ash that had fallen. Research at Raupehu, New Zealand, and elsewhere has found that grazing animals can suffer damage to their teeth and poisoning due to elevated sulfur and fluorine if they consume ash-covered plants (Cronin and others, 2003). Precautions were also recommended for young children who could be adversely affected by inhaling fine ash. INETER noted that aviation traffic had been alerted to the presence of ash in the region.

The Washington Volcanic Ash Advisory Center (VAAC) detected ash from San Cristóbal during 26-28 December. Emissions were ongoing during that time period; plumes rose 2.4-4.3 km a.s.l. and drifted approximately W over the Pacific Ocean as far as 670 km WNW from the summit (figure 29).

Figure (see Caption) Figure 29. The aerial extent of observed volcanic ash from San Cristóbal was concentrated in three discrete regions mainly offshore of Central America at 0430 on 28 December 2012. The red polygons were developed by the VAAC as geospatial files (KML) for display in Google Earth. Courtesy of Washington VAAC and Google Earth.

INETER reported to local news agencies that 7 of the 13 municipalities of Chinandega were affected by ashfall by 27 December. Visibility was greatly reduced within the urban city of Chinandega. Emissions continued from the summit and reached 200 m above the crater rim in the morning. At the time of their second online notice, a plume of fine ash was visible rising up to 500 m above the crater, and small-to-moderate sized explosions of gas and ash continued.

On 28 December, the minister of Agriculture and Forestry told the local news agency, La Jornada, that while 2 millimeters of ash had fallen in some areas around the volcanic edifice, the farming areas should not be adversely affected since most of the crops had already been harvested. The public utility company, ENACAL, conducted investigations into water quality for the region.

News agencies reported that up to 20 km of highway was affected by ashfall along the Pan-American Highway between Honduras and Nicaragua. Vehicles opted to use headlights due to reduced visibility. La Jornada reported that a total of 268 people had left the area of San Cristóbal by 28 December and 68 were evacuated by the national humanitarian agency (Nicaraguan Humanitarian Rescue Unit, UHR).

INETER reported that small to moderate sized explosions had occurred in the morning of 28 December and a significant increase in SO2 flux was detected. This announcement included warnings regarding eye, skin, and respiratory irritation due to volcanic gases. There were also recommendations regarding ash removal from roofs and structures. Ash was distributed NW, W, and SW from the volcano and satellite images detected ash extending across the Pacific Ocean following the regional airstream offshore of El Salvador.

After an explosion of ash and gas at 1100 on 28 December, emissions throughout the day were ash-poor. Seismicity also decreased that day and, by 29 December, explosions had ceased and diffuse gas emissions continued. In their online bulletin, INETER reported that, as of 31 December, no ash explosions had been detected over the past two days. Gas emissions continued from the summit but SO2 levels had returned to normal.

Volcanic hazards map for San Cristóbal. A map of volcanic hazards was available on the INETER website for the region of San Cristóbal (figure 30). Volcanic ballistics, lahars, landslides, lava flows, and tephrafall were assessed and likely impacted areas were delineated. The tephrafall region corresponded to the prevailing winds and correlated well with ash-effected regions during the December 2012 events.

Figure (see Caption) Figure 30. Volcanic hazards from San Cristóbal include ejecta, lahars, landslides, and lava flows. This map was released in April 2006 and developed to show the aerial extent of potential events. Densely populated regions are yellow, road systems are black, and rivers are blue; additional color regions correspond to hazards listed in the key (in Spanish). The brown circle has a radius of 5 km and encompasses the main volcanic edifice indicating the maximum expected extent of ballistics (volcanic bombs for example); the two tan regions indicate the extent of possible tephra fall (where lighter shading indicates a medium-level risk zone and darker is higher-level risk); red regions follow major drainages where lahars and landslides could occur; the region shaded pink encompasses the areas most likely effected by future lava flows. Courtesy of INETER.

Reference. Cronin, S.J., Neall, V.E., Lecointre, J.A., Hedley, M.J., and Loganathan, P., 2003, Environmental hazards of fluoride in volcanic ash: a case study from Ruapehu volcano, New Zealand, Journal of Volcanology and Geothermal Research, 121, 271-291.

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); La Jornada (URL: http://www.lajornadanet.com/diario/archivo/2012/diciembre/28/1.php); La Prensa de Nicaragua (URL: http://www.laprensa.com.ni/2012/12/27/ambito/128746/imprimir); Reuters.

Atmospheric Effects

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

View Atmospheric Effects Reports

Special Announcements

Special announcements of various kinds and obituaries.

View Special Announcements Reports

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (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/).