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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

Nevados de Chillan (Chile) Explosions and pyroclastic flows continue; new dome emerges from Nicanor crater in June 2020

Bagana (Papua New Guinea) Ash plumes during 29 February-2 March and 1 May 2020

Kerinci (Indonesia) Intermittent ash emissions during January-early May 2020

Tinakula (Solomon Islands) Intermittent small thermal anomalies and gas-and-steam plumes during January-June 2020

Ibu (Indonesia) Frequent ash emissions and summit incandescence; Strombolian explosions in March 2020

Suwanosejima (Japan) Frequent explosions, ash plumes, and summit incandescence in January-June 2020

Kadovar (Papua New Guinea) Intermittent ash plumes and persistent summit thermal anomalies, January-June 2020

Sangay (Ecuador) Daily ash plumes and frequent pyroclastic flows produce ashfall and lahars, January-June 2020

Karangetang (Indonesia) Incandescent block avalanches through mid-January 2020; crater anomalies through May

Shishaldin (United States) Intermittent thermal activity and a possible new cone at the summit crater during February-May 2020

Masaya (Nicaragua) Lava lake level drops but remains active through May 2020; weak gas plumes

Krakatau (Indonesia) Strombolian explosions, ash plumes, and crater incandescence during April 2020



Nevados de Chillan (Chile) — May 2020 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)


Explosions and pyroclastic flows continue; new dome emerges from Nicanor crater in June 2020

Nevados de Chillán is a complex of late-Pleistocene to Holocene stratovolcanoes in the Chilean Central Andes. An eruption started with a phreatic explosion and ash emission on 8 January 2016 from a new crater (Nicanor) on the E flank of the Nuevo crater, itself on the NW flank of the large Volcán Viejo stratovolcano. Strombolian explosions and ash emissions continued throughout 2016 and 2017; a lava dome within the Nicanor crater was confirmed in early January 2018. Explosions and pyroclastic flows continued during 2018 and 2019, with several lava flows appearing in late 2019. This report covers continuing activity from January-June 2020 when ongoing explosive events produced ash plumes, pyroclastic flows, and the growth of new dome inside the crater. Information for this report is provided primarily by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN)-Observatorio Volcanológico de Los Andes del Sur (OVDAS), and by the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Explosions with ash plumes rising up to three kilometers above the summit area were intermittent from late January through early June 2020. Some of the larger explosions produced pyroclastic flows that traveled down multiple flanks. Thermal anomalies within the Nicanor crater were recorded in satellite data several times each month from February through June. A reduction in overall activity led SERNAGEOMIN to lower the Alert Level from Orange to Yellow (on a 4-level, Green-Yellow-Orange-Red scale) during the first week of March, although tens of explosions with ash plumes were still recorded during March and April. Explosive activity diminished in early June and SERNAGEOMIN reported the growth of a new dome inside the Nicanor crater. By the end of June, a new flow had extended about 100 m down the N flank. Thermal activity recorded by the MIROVA project showed a drop in thermal energy in mid-December 2019 after the lava flows of September-November stopped advancing. A decrease in activity in January and February 2020 was followed by an increase in thermal and explosive activity in March and April. Renewed thermal activity from the growth of a new dome inside the Nicanor crater was recorded beginning in mid-June (figure 52).

Figure (see Caption) Figure 52. MIROVA thermal anomaly data for Nevados de Chillan from 8 September 2019 through June 2020 showed a drop in thermal activity in mid-December 2019 after the lava flows of September-November stopped advancing. A decrease in activity in January and February 2020 was followed by an increase in explosive activity in March and April. Renewed thermal activity from the growth of a new dome inside the Nicanor crater was recorded beginning in mid-June. Courtesy of MIROVA.

Weak gas emissions were reported daily during January 2020 until a series of explosions began on the 21st. The first explosion rose 100 m above the active crater; the following day, the highest explosion rose 1.6 km above the crater. The Buenos Aires VAAC reported pulse emissions visible in satellite imagery on 21 and 24 January that rose to 3.9-4.3 km altitude and drifted SE and NE, respectively. Intermittent explosions continued through 26 January. Incandescent ejecta was observed during the night of 28-29 January. The VAAC reported an isolated emission on 29 January that rose to 5.2 km altitude and drifted E. A larger explosion on 30 January produced an ash plume that SERNAGEOMIN reported at 3.4 km above the crater (figure 53). It produced pyroclastic flows that traveled down ravines on the NNE and SE flanks. The Washington VAAC reported on behalf of the Buenos Aires VAAC that an emission was observed in satellite imagery on 30 January that rose to 4.9 km altitude and was moving rapidly E, reaching 15 km from the summit at midday. The altitude of the ash plume was revised two hours later to 7.3 km, drifting NNE and rapidly dissipating. Satellite images identified two areas of thermal anomalies within the Nicanor crater that day. One was the same emission center (CE4) identified in November 2019, and the second was a new emission center (CE5) located 60 m NW.

Figure (see Caption) Figure 53. A significant explosion and ash plume from the Nicanor crater at Nevados de Chillan on 30 January 2020 produced an ash plume reported at 7.3 km altitude. The left image was taken within one minute of the initial explosion. Images posted by Twitter accounts #EmergenciasÑuble (left) and T13 (right); original photographers unknown.

When the weather permitted, low-altitude mostly white degassing was seen during February 2020, often with traces of fine-grained particulate material. Incandescence at the crater was observed overnight during 4-5 February. The Buenos Aires VAAC reported an emission on 14 February visible in the webcam. The next day, an emission was visible in satellite imagery at 3.9 km altitude that drifted E. Episodes of pulsating white and gray plumes were first observed by SERNAGEOMIN beginning on 18 February and continued through 25 February (figure 54). The Buenos Aires VAAC reported pulses of ash emissions moving SE on 18 February at 4.3 km altitude. Ash drifted E the next day at 3.9 km altitude and a faint plume was briefly observed on 20 February drifting N at 3.7 km altitude before dissipating. Sporadic pulses of ash moved SE from the volcano on 22 February at 4.3 km altitude, briefly observed in satellite imagery before dissipating. Thermal anomalies were visible from the Nicanor crater in Sentinel-2 satellite imagery on 23 and 28 February.

Figure (see Caption) Figure 54. An ash emission at Nevados de Chillan on 18 February 2020 was captured in Sentinel-2 satellite imagery drifting SE (left). Thermal anomalies within the Nicanor crater were measured on 23 (right) and 28 February. Images use Atmospheric penetration rendering (bands 12, 11, 8a); courtesy of Sentinel Hub Playground.

Only low-altitude degassing of mostly steam was reported for the first half of March 2020. When SERNAGEOMIN lowered the Alert Level from Orange to Yellow on 5 March, they reduced the affected area from 5 km NE and 3 km SW of the crater to a radius of 2 km around the active crater. Thermal anomalies were recorded at the Nicanor crater in Sentinel-2 imagery on 4, 9, 11, 16, and 19 March (figure 55). A new series of explosions began on 19 March; 44 events were recorded during the second half of the month (figure 56). Webcams captured multiple explosions with dense ash plumes; on 25 and 30 March the plumes rose more than 2 km above the crater. Fine-grained ashfall occurred in Las Trancas (10 km SW) on 25 March. Pyroclastic flows on 25 and 30 March traveled 300 m NE, SE, and SW from the crater. Incandescence was observed at night multiple times after 20 March. The Buenos Aires VAAC reported several discrete pulses of ash that rose to 4.3 km altitude and drifted SE on 20 and 21 March, SW on 25 March, and SE on 29 and 30 March. Another ash emission rose to 5.5 km altitude later on 30 March and drifted SE.

Figure (see Caption) Figure 55. Sentinel-2 Satellite imagery of Nevados de Chillan during March 2020 showed thermal anomalies on five different dates at the Nicanor crater, including on 9, 11, and 16 March. A second thermal anomaly of unknown origin was also visible on 11 March about 2 km SW of the crater (center). Images use Atmospheric penetration rendering (bands 12, 11, 8a); courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 56. Forty-four explosive events were recorded at Nevados de Chillan during the second half of March 2020 including on 19 March. Courtesy of SERNAGEOMIN webcams and chillanonlinenoticia.

In their semi-monthly reports for April 2020, SERNAGEOMIN reported 94 explosive events during the first half of the month and 49 during the second half; many produced dense ash plumes. The Buenos Aires VAAC reported frequent intermittent ash emissions during 1-13 April reaching altitudes of 3.7-4.3 km (figure 57). They reported the plume on 8 April visible in satellite imagery at 7.3 km altitude drifting SE. An emission on 13 April was also visible in satellite imagery at 6.1 km altitude drifting NE.

Figure (see Caption) Figure 57. Sentinel-2 satellite imagery captured a strong thermal anomaly and an ash plume drifting SE from Nevados de Chillan on 10 April 2020. Image uses Atmospheric penetration rendering (bands 12, 11, 8a); courtesy of Sentinel Hub Playground.

During the second half of April 2020, SERNAGEOMIN reported that only one plume exceeded 2 km in height; on 21 April, it rose to 2.4 km above the crater (figure 58). The Buenos Aires VAAC reported isolated pulses of ash on 18, 26, 28, and 30 April. During the second half of April SERNAGEOMIN also reported that a pyroclastic flow traveled about 1,200 m from the crater rim down the SE flank. The ash from the pyroclastic flow drifted SE and S as far as 3.5 km. Satellite images showed continued activity from multiple emission centers around the crater. Pronounced scarps were noted on the internal walls of the crater, attributed to the deepening of the crater from explosive activity.

Figure (see Caption) Figure 58. Tens of explosions were reported at Nevados de Chillan during the second half of April 2020 that produced dense ash plumes. The plume on 21 April rose 2.4 km above the Nicanor crater. Photo by Josefa Carrasco Acuña from San Fabián de Alico; posted by Noticias Valpo Express.

Intermittent explosive activity continued during May 2020. The plumes contained abundant particulate material and were accompanied by periodic pyroclastic flows and incandescent ejecta around the active crater, especially visible at night. The Buenos Aires VAAC reported several sporadic weak ash emissions during the first week of May that rose to 3.7-5.2 km altitude and drifted NE. SERNAGEOMIN reported that only one explosion produced an ash emission that rose more than two km above the crater during the first two weeks of the month; on 6 May it rose to 2.5 km above the crater and drifted NE. They also observed pyroclastic flows on the E and SE flanks that day. Additional pyroclastic flows traveled 450 m down the S flank during the first half of the month, and similar deposits were observed to the N and NE. Satellite observations showed various emission points along the NW-trending lineament at the summit and multiple erosion scarps. Major erosion was noted at the NE rim of the crater along with an increase in degassing around the rim.

During the second half of May 2020 most of the ash plumes rose less than 2 km above the crater; a plume from one explosion on 22 May rose 2.2 km above the crater; the Buenos Aires VAAC reported the plume at 5.5 km altitude drifting NW (figure 59). Continuing pyroclastic emissions deposited material as far as 1.5 km from the crater rim on the NNW flank. There were also multiple pyroclastic deposits up to 500 m from the crater directed N and NE during the period. SERNAGEOMIN reported an increase in steam degassing between Nuevo-Nicanor and Nicanor-Arrau craters.

Figure (see Caption) Figure 59. Explosions produced dense ash plumes and pyroclastic flows at Nevados de Chillan multiple times during May 2020 including on 22 May. Courtesy of SERNAGEOMIN.

Webcam images during the first two weeks of June 2020 indicated multiple incandescent explosions. On 3 and 4 June plumes from explosions reached heights of over 1.25 km above the crater; the Buenos Aires VAAC reported them drifting NW at 3.9 km altitude. Incandescent ejecta on 6 June rose 760 m above the vent and drifted NE. In addition, pyroclastic flows were distributed on the N, NW, E and SE flanks. Significant daytime and nighttime incandescence was reported on 6, 9, and 10 June (figure 60). The VAAC reported emission pulses on 6 and 9 June drifting E and SE at 4.3 km altitude.

Figure (see Caption) Figure 60. Multiple ash plumes with incandescence were reported at Nevados de Chillan during the first ten days of June 2020 including on 6 June, after which explosive activity decreased significantly. Courtesy of SERNAGEOMIIN and Sismo Alerta Mexicana.

SERNAGEOMIN reported that beginning on the afternoon of 9 June 2020 a tremor-type seismic signal was first recorded, associated with continuous emission of gas and dark gray ash that drifted SE (figure 61). A little over an hour later another tremor signal began that lasted for about four hours, followed by smaller discrete explosions. A hybrid-type earthquake in the early morning of 10 June was followed by a series of explosions that ejected gas and particulate matter from the active crater. The vent where the emissions occurred was located within the Nicanor crater close to the Arrau crater; it had been degassing since 30 May.

Figure (see Caption) Figure 61. A tremor-type seismic signal was first recorded on the afternoon of 9 June 2020 at Nevados de Chillan. It was associated with the continuous emission of gas and dark gray ash that drifted SE, and incandescent ejecta visible after dark. View is to the S, courtesy of SERNAGEOMIN webcam, posted by Volcanology Chile.

After the explosions on the afternoon of 9 June, a number of other nearby vents became active. In particular, the vent located between the Nuevo and Nicanor craters began emitting material for the first time during this eruptive cycle. The explosion also generated pyroclastic flows that traveled less than 50 m in multiple directions away from the vent. Abundant incandescent material was reported during the explosion early on 10 June. Deformation measurements showed inflation over the previous 12 days.

SERNAGEOMIN identified a surface feature in satellite imagery on 11 June 2020 that they interpreted as a new effusive lava dome. It was elliptical with dimensions of about 85 x 120 m. In addition to a thermal anomaly attributed to the dome, they noted three other thermal anomalies between the Nuevo, Arrau, and Nicanor craters. They reported that within four days the base of the active crater was filled with effusive material. Seismometers recorded tremor activity after 11 June that was interpreted as associated with lava effusion. Incandescent emissions were visible at night around the active crater. Sentinel-2 satellite imagery recorded a bright thermal anomaly inside the Nicanor crater on 14 June (figure 62).

Figure (see Caption) Figure 62. A bright thermal anomaly was recorded inside the Nicanor crater at Nevados de Chillan on 14 June 2020. SERNAGEOMIN scientists attributed it to the growth of a new lava dome within the crater. Image uses Atmospheric penetration rendering (bands 12, 11, 8a); courtesy of Sentinel Hub Playground.

A special report from SERNAGEOMIN on 24 June 2020 noted that vertical inflation had increased during the previous few weeks. After 20 June the inflation rate reached 2.49 cm/month, which was considered high. The accumulated inflation measured since July 2019 was 22.5 cm. Satellite imagery continued to show the growth of the dome, and SERNAGEOMIN scientists estimated that it reached the E edge of the Nicanor crater on 23 June. Based on these images, they estimated an eruptive rate of 0.1-0.3 m3/s, about two orders of magnitude faster than the Gil-Cruz dome that emerged between December 2018 and early 2019.

Webcams revealed continued low-level explosive activity and incandescence visible both during the day and at night. By the end of June, webcams recorded a lava flow that extended 94 m down the N flank from the Nicanor crater and continued to advance. Small explosions with abundant pyroclastic debris produced recurring incandescence at night. Satellite infrared imagery indicated thermal radiance from effusive material that covered an area of 37,000 m2, largely filling the crater. DEM analysis suggested that the size of the crater had tripled in volume since December 2019 due largely to erosion from explosive activity since May 2020. Sentinel-2 satellite imagery showed a bright thermal anomaly inside the crater on 27 June.

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/, https://twitter.com/Sernageomin); 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/); 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); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); #EmergenciasÑuble (URL: https://twitter.com/urgenciasnuble/status/1222943399185207296); T13, Channel 13 Press Department (URL: https://twitter.com/T13/status/1222951071443771394); Chillanonlinenoticia (URL: https://twitter.com/ChillanOnline/status/1240754211932995595); Noticias Valpo Express (URL: https://twitter.com/NoticiasValpoEx/status/1252715033131388928); Sismo Alerta Mexicana (URL: https://twitter.com/Sismoalertamex/status/1269351579095691265); Volcanology Chile (URL: https://twitter.com/volcanologiachl/status/1270548008191643651).


Bagana (Papua New Guinea) — July 2020 Citation iconCite this Report

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


Ash plumes during 29 February-2 March and 1 May 2020

Bagana lies in a nearly inaccessible mountainous tropical rainforest area of Bougainville Island in Papua New Guinea and is primarily monitored by satellite imagery of ash plumes and thermal anomalies. After a state of elevated activity that lasted through December 2018 (BGVN 43:05, 44:06, 44:12), the volcano entered a quieter period that persisted through at least May 2020. This report focuses on activity between December 2019 and May 2020.

Atmospheric clouds often obscured satellite views of the volcano during the reporting period. When the volcano could be observed, light-colored gas plumes were often observed (figure 43). Based on satellite and wind model data, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that during 29 February-2 March ash plumes rose to an altitude of 1.8-2.1 km and drifted SW and N. On 1 May an ash plume rose to an altitude of 3 km and drifted NW and W. According to both Darwin VAAC volcanic ash advisories, the Aviation Color Code was Orange (second highest of four hazard levels).

Figure (see Caption) Figure 43. Sentinel-2 image of Bagana, showing a gas plume drifting SE on 13 March 2020, during a period when the Darwin VAAC had not reported any ash explosions (Natural Color rendering, bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

During the reporting period, the MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system recorded only intermittent thermal anomalies, all of which were of low radiative power. Sulfur dioxide emissions detected by satellite-based instruments over this reporting period were at low levels.

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

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Kerinci (Indonesia) — July 2020 Citation iconCite this Report

Kerinci

Indonesia

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

All times are local (unless otherwise noted)


Intermittent ash emissions during January-early May 2020

Kerinci is a stratovolcano located in Sumatra, Indonesia that has been characterized by explosive eruptions with ash plumes and gas-and-steam emissions. The most recent eruptive episode began in April 2018 which has included intermittent explosions and ash plumes. The previous report (BGVN 44:12) described more recent activity consisting of intermittent gas-and-steam and ash plumes which occurred during June through early November 2019. This volcanism continued through May 2020, though little to no activity was reported during December 2019. The primary source of information for this report comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

Activity during December 2019 consisted of white gas-and-steam emissions rising 100-500 m above the summit. White and brown emissions continued intermittently through May 2020, rising to a maximum altitude of 1 km above the summit on 14 April. During 3-6 and 8-9 January 2020, the Darwin VAAC and PVMBG issued notices reporting brown volcanic ash rising 150-600 m above the summit drifting S and ESE (figure 19). PVMBG published a VONA notice on 24 January at 0828 reporting ash rising 400 m above the summit. Brown emissions continued intermittently throughout the reporting period. On 1 February, volcanic ash was observed rising 300-960 m above the summit and drifting NE; PVMBG reported continuing brown emissions during 1-3 February. During 16-17 February, two VONA notices reported that brown ash plumes rose 150-400 m above the summit and drifted SW accompanied by consistent white gas-and-steam emissions (figure 20).

Figure (see Caption) Figure 19. Brown ash plume rose 500-600 m above Kerinci on 4 January 2020. Courtesy of MAGMA Indonesia via Øystein Lund Andersen.
Figure (see Caption) Figure 20. White gas-and-steam emissions rose 400 m above Kerinci on 19 February 2020. Courtesy of MAGMA Indonesia via Øystein Lund Andersen.

During 1-16 and 25-26 March 2020 brown ash emissions were frequently observed rising 100-500 m above the summit drifting in multiple directions. During 6-8 and 10-15, April brown ash emissions were reported 50-1,000 m above the summit. The most recent Darwin VAAC and VONA notices were published on 14 April, reporting volcanic ash rising 400 and 600 m above the summit, respectively; however, PVMBG reported brown emissions rising up to 1,000 m. By 25-27 April brown ash emissions rose 50-300 m above the summit. Intermittent white gas-and-steam emissions continued through May. The last brown emissions seen in May were reported on the 7th rising 50-100 m above the summit.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); 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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com, images at https://twitter.com/OysteinLAnderse/status/1213658331564269569/photo/1 and https://twitter.com/OysteinLAnderse/status/1230419965209018369/photo/1).


Tinakula (Solomon Islands) — July 2020 Citation iconCite this Report

Tinakula

Solomon Islands

10.386°S, 165.804°E; summit elev. 796 m

All times are local (unless otherwise noted)


Intermittent small thermal anomalies and gas-and-steam plumes during January-June 2020

Tinakula is a remote stratovolcano located 100 km NE of the Solomon Trench at the N end of the Santa Cruz. In 1971, an eruption with lava flows and ash explosions caused the small population to evacuate the island. Volcanism has previously been characterized by an ash explosion in October 2017 and the most recent eruptive period that began in December 2018 with renewed thermal activity. Activity since then has consisted of intermittent thermal activity and dense gas-and-steam plumes (BGVN 45:01), which continues into the current reporting period. This report updates information from January-June 2020 using primary source information from various satellite data, as ground observations are rarely available.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed weak, intermittent, but ongoing thermal activity during January-June 2020 (figure 41). A small cluster of slightly stronger thermal signatures was detected in late February to early March, which is correlated to MODVOLC thermal alert data; four thermal hotspots were recorded on 20, 27, and 29 February and 1 March. However, observations using Sentinel-2 satellite imagery were often obscured by clouds. In addition to the weak thermal signatures, dense gas-and-steam plumes were observed in Sentinel-2 satellite imagery rising from the summit during this reporting period (figure 42).

Figure (see Caption) Figure 41. Weak thermal anomalies at Tinakula from 26 June 2019 through June 2020 as recorded by the MIROVA system (Log Radiative Power) were intermittent and clustered more strongly in late February to early March.
Figure (see Caption) Figure 42. Sentinel-2 satellite imagery shows ongoing gas-and-steam plumes rising from Tinakula during January through May 2020. Images with atmospheric penetration (bands 12, 11, 8a) rendering; courtesy of Sentinel Hub Playground.

Three distinct thermal anomalies were observed in Sentinel-2 thermal satellite imagery on 22 January, 11 April, and 6 May 2020, accompanied by some gas-and-steam emissions (figure 43). The hotspot on 22 January was slightly weaker than the other two days, and was seen on the W flank, compared to the other two that were observed in the summit crater. According to MODVOLC thermal alerts, a hotspot was recorded on 6 May, which corresponded to a Sentinel-2 thermal satellite image with a notable anomaly in the summit crater (figure 43). On 10 June no thermal anomaly was seen in Sentinel-2 satellite imagery due to the presence of clouds; however, what appeared to be a dense gas-and-steam plume was extending W from the summit.

Figure (see Caption) Figure 43. Sentinel-2 thermal satellite images showing a weak thermal activity (bright yellow-orange) on 22 January 2020 on the W flank of Tinakula (top) and slightly stronger thermal hotspots on 11 April (middle) and 6 May (bottom) in at the summit, which are accompanied by gas-and-steam emissions. Images with atmospheric penetration (bands 12, 11, 8a) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. Similar to Stromboli, it has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The satellitic cone of Mendana is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Frequent historical eruptions have originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Ibu (Indonesia) — July 2020 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


Frequent ash emissions and summit incandescence; Strombolian explosions in March 2020

Ibu is an active stratovolcano located along the NW coast of Halmahera Island in Indonesia. Volcanism has recently been characterized by frequent ash explosions, ash plumes, and small lava flows within the crater throughout 2019 (BGVN 45:01). Activity continues, consisting of frequent white-and-gray emissions, ash explosions, ash plumes, and lava flows. This report updates activity through June 2020, using data from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellites.

Volcanism during the entire reporting period dominantly consisted of white-and-gray emissions that rose 200-800 m above the summit drifting in multiple directions. The ash plume with the maximum altitude of 13.7 km altitude occurred on 16 May 2020. Sentinel-2 thermal satellite imagery detected multiple smaller hotspots within the crater throughout the reporting period.

Continuous ash emissions were reported on 6 February rising to 2.1 km altitude drifting E, accompanied by a hotspot visible in infrared satellite imagery. On 16 February, a ground observer reported an eruption that produced an ash plume rising 800 m above the summit drifting W, according to a Darwin VAAC notice. Ash plumes continued through the month, drifting in multiple directions and rising up to 2.1 km altitude. During 8-10 March, video footage captured multiple Strombolian explosions that ejected incandescent material and produced ash plumes from the summit (figures 21 and 22). Occasionally volcanic lightning was observed within the ash column, as recorded in video footage by Martin Rietze. This event was also documented by a Darwin VAAC notice, which stated that multiple ash emissions rose 2.1 km altitude drifting SE. PVMBG published a VONA notice on 10 March at 1044 reporting ash plumes rising 400 m above the summit. PVMBG and Darwin VAAC notices described intermittent eruptions on 26, 28, and 29 March, all of which produced ash plumes rising 300-800 m above the summit.

Figure (see Caption) Figure 21. Strombolian explosions recorded at the crater summit of Ibu during 8-10 March 2020 ejected incandescent ejecta and a dense ash plume. Video footage copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 22. Strombolian explosions recorded at the crater summit of Ibu during 8-10 March 2020 ejected incandescent ejecta and ash. Frequent volcanic lightning was also observed. Video footage copyright by Martin Rietze, used with permission.

A majority of days in April included white-and-gray emissions rising up to 800 m above the summit. A ground observer reported an eruption on 9 April, according to a Darwin VAAC report, and a hotspot was observed in HIMAWARI-8 satellite imagery. Minor eruptions were reported intermittently during mid-April and early to mid-May. On 12 May at 1052 a VONA from PVMBG reported an ash plume 800-1,100 m above the summit. A large short-lived eruption on 16 May produced an ash plume that rose to a maximum of 13.7 km altitude and drifted S, according to the Darwin VAAC report. By June, volcanism consisted predominantly of white-and-gray emissions rising 800 m above the summit, with an ash eruption on 15 June. This eruptive event resulted in an ash plume that rose 1.8 km altitude drifting WNW and was accompanied by a hotspot detected in HIMAWARI-8 satellite imagery, according to a Darwin VAAC notice.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected frequent hotspots during July 2019 through June 2020 (figure 23). In comparison, the MODVOLC thermal alerts recorded a total of 24 thermal signatures over the course of 19 different days between January and June. Many thermal signatures were captured as small thermal hotspots in Sentinel-2 thermal satellite imagery within the crater (figure 24).

Figure (see Caption) Figure 23. Thermal anomalies recorded at Ibu from 2 July 2019 through June 2020 as recorded by the MIROVA system (Log Radiative Power) were frequent and consistent in power. Courtesy of MIROVA.
Figure (see Caption) Figure 24. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) showed occasional thermal hotspots (bright orange) in the Ibu summit crater during January through June 2020. Courtesy of Sentinel Hub Playground.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Martin Rietze, Taubenstr. 1, D-82223 Eichenau, Germany (URL: https://mrietze.com/, https://www.youtube.com/channel/UC5LzAA_nyNWEUfpcUFOCpJw/videos, video at https://www.youtube.com/watch?v=qMkfT1e4HQQ).


Suwanosejima (Japan) — July 2020 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Frequent explosions, ash plumes, and summit incandescence in January-June 2020

Suwanosejima is an active stratovolcano located in the northern Ryukyu Islands. Volcanism has previously been characterized by Strombolian explosions, ash plumes, and summit incandescence (BGVN 45:01), which continues to occur intermittently. A majority of this activity originates from vents within the large Otake summit crater. This report updates information during January through June 2020 using monthly reports from the Japan Meteorological Agency (JMA), the Tokyo Volcanic Ash Advisory Center (VAAC), and various satellite data.

During 3-10 January 2020, 13 explosions were detected from the Otake crater rising to 1.4 km altitude; material was ejected as far as 600 m away and ashfall was reported in areas 4 km SSW, according to JMA. Occasional small eruptive events continued during 12-17 January, which resulted in ash plumes that rose 1 km above the crater rim and ashfall was again reported 4 km SSW. Crater incandescence was visible nightly during 17-24 January, while white plumes rose as high as 700 m above the crater rim.

Nightly incandescence during 7-29 February, and 1-6 March, was accompanied by intermittent explosions that produced ash plumes rising up to 1.2 km above the crater rim (figure 44); activity during early February resulted in ashfall 4 km SSW. On 19 February an eruption produced a gray-white ash plume that rose 1.6 km above the crater (figure 45), resulting in ashfall in Toshima village (4 km SSW), according to JMA. Explosive events during 23-24 February ejected blocks onto the flanks. Two explosions were recorded during 1-6 March, which sent ash plumes as high as 900-1,000 m above the crater rim and ejected large blocks 300 m from the crater.

Figure (see Caption) Figure 44. Surveillance camera images of summit incandescence at Suwanosejima on 29 January (top left), 21 (middle left) and 23 (top right) February, and 25 March (bottom left and right) 2020. Courtesy of JMA (Monthly bulletin reports 511, January, February, and March 2020).
Figure (see Caption) Figure 45. Surveillance camera images of which and white-and-gray gas-and-steam emissions rising from Suwanosejima on 5 January (top), 19 February (middle), and 24 March 2020 (bottom). Courtesy of JMA (Monthly bulletin reports 511, January, February, and March 2020).

Nightly incandescence continued to be visible during 13-31 March, 1-10 and 17-24 April, 1-8, 15-31 May, 1-5 and 12-30 June 2020; activity during the latter part of March was relatively low and consisted of few explosive events. In contrast, incandescence was frequently accompanied by explosions in April and May. On 28 April at 0432 an eruption produced an ash plume that rose 1.6 km above the crater rim and drifted SE and E, and ejected blocks as far as 800 m from the crater. The MODVOLC thermal alerts algorithm also detected four thermal signatures during this eruption within the summit crater. An explosion at 1214 on 29 April caused glass in windows to vibrate up to 4 km SSW away while ash emissions continued to be observed following the explosion the previous day, according to the Tokyo VAAC.

During 1-8 May explosions occurred twice a day, producing ash plumes that rose as high as 1 km above the crater rim and ejecting material 400 m from the crater. An explosion on 29 May at 0210 produced an off-white plume that rose as high as 500 m above the crater rim and ejected large blocks up to 200 m above the rim. On 5 June an explosion produced gray-white plumes rising 1 km above the crater. Small eruptive events continued in late June, producing ash plumes that rose as high as 900 m above the crater rim.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed relatively stronger thermal anomalies in late February and late April 2020 with an additional six weaker thermal anomalies detected in early January (2), early February (1), mid-April (2), and mid-May (1) (figure 46). Sentinel-2 thermal satellite imagery in late January through mid-April showed two distinct thermal hotspots within the summit crater (figure 47).

Figure (see Caption) Figure 46. Prominent thermal anomalies at Suwanosejima during July-June 2020 as recorded by the MIROVA system (Log Radiative Power) occurred in late February and late April. Courtesy of MIROVA.
Figure (see Caption) Figure 47. Sentinel-2 thermal satellite images showing small thermal anomalies (bright yellow-orange) from two locations within the Otake summit crater at Suwanosejima. Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Kadovar (Papua New Guinea) — July 2020 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


Intermittent ash plumes and persistent summit thermal anomalies, January-June 2020

The steeply sloped 1.4-km-diameter Kadovar Island is located in the Bismark Sea offshore from the mainland of Papua New Guinea about 25 km NNE from the mouth of the Sepik River. Its first confirmed observed eruption began in early January 2018, with ash plumes and lava extrusion resulting in the evacuation of around 600 residents from the N side of the island (BGVN 43:03). A dome appeared at the base of the E flank during March-May 2018 (Planka et al., 2019); by November activity had migrated to a new dome growing near the summit on the E flank. Pulsating steam plumes, thermal anomalies, and periodic ash emissions continued throughout 2019 (BGVN 44:05, 45:01), and from January-June 2020, the period covered in this report. Information was provided by the Rabaul Volcano Observatory (RVO), the Darwin Volcanic Ash Advisory Center (VAAC), satellite sources, and photographs from visitors.

Activity during January-June 2020. Intermittent ash plumes, pulsating gas and steam plumes, and thermal anomalies continued at Kadovar during January-June 2020. MIROVA thermal data suggested persistent low-level anomalies throughout the period (figure 45). Sentinel-2 satellite data confirmed thermal anomalies at the summit on 5 and 25 January 2020, and an ash emission on 20 January (figure 46). Persistent pulsating steam plumes were visible whenever the skies were clear enough to see the volcano.

Figure (see Caption) Figure 45. Persistent low-level thermal activity at Kadovar was recorded in the MIROVA graph of radiative power from 2 July 2019 through June 2020. The island location is mislocated in the MIROVA system by about 5.5 km SE due to older mis-registered imagery; the anomalies are all on the island. Courtesy of MIROVA.
Figure (see Caption) Figure 46. Sentinel-2 satellite data confirmed thermal anomalies at the summit of Kadovar on 5 (left) and 25 January 2020, and an ash emission and steam plume that drifted SE on 20 January (center). Pulsating steam-and-gas emissions left a trail in the atmosphere drifting SE for several kilometers on 25 January (right). Left image uses Atmospheric penetration rendering (bands 12, 11, 8a), center and right images use Natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

On 2 February 2020 the Darwin VAAC reported a minor eruption plume that rose to 1.5 km altitude and drifted ESE for a few hours. Another plume was clearly discernible in satellite imagery on 5 February at 2.1 km altitude moving SE. RVO issued an information bulletin on 7 February reporting that, since the beginning of January, the eruption had continued with frequent Vulcanian explosions from the Main Vent with a recurrence interval of hours to days. Rocks and ash were ejected 300-400 m above the vent. Rumbling could be heard from Blupblup (Rubrub) island, 15 km E, and residents there also observed incandescence at night. On clear days the plume was sometimes visible from Wewak, on the mainland 100 km W. Additional vents produced variable amounts of steam. The Darwin VAAC reported continuous volcanic ash rising to 1.5 km on 22 February that extended ESE until it was obscured by a meteoric cloud; it dissipated early the next day. A small double ash plume and two strong thermal anomalies at the summit were visible in satellite imagery on 24 February (figure 47).

Figure (see Caption) Figure 47. Ash emissions and thermal anomalies continued at Kadovar during February 2020. Two small plumes of ash or dense steam rose from the summit on 24 February 2020, seen in this Natural color rendering (bands 4, 3, 2) on the left. The same image rendered in Atmospheric penetration (bands 12, 11, 8a) on the right shows two thermal anomalies in the same locations as the ash plumes. Courtesy of Sentinel Hub Playground.

The Darwin VAAC reported continuous ash emissions beginning on 13 March 2020 that rose to 1.5 km altitude and drifted SE. The plume was visible intermittently in satellite imagery for about 36 hours before dissipating. During April, pulsating steam plumes rose from two vents at the summit, and thermal anomalies appeared at both vents in satellite data (figure 48). Small but distinct SO2 anomalies were visible in satellite data on 15 and 16 April (figure 49).

Figure (see Caption) Figure 48. Steam plumes and thermal anomalies continued at Kadovar during April 2020. Top: A thermal anomaly at the summit accompanied pulsating steam plumes that drifted several kilometers SE before dissipating on 4 April 2020. Bottom left: Two gas-and-steam plumes drifted E from the summit on 9 April. Bottom right: Two adjacent thermal anomalies were present near the summit on 19 April. Top and bottom right images use Atmospheric penetration rendering (bands 12, 11, 8a), bottom left image uses Natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 49. Small but distinct SO2 anomalies were detected at Kadovar on 15 and 16 April 2020 with the TROPOMI instrument on the Sentinel-5P satellite. Nearby Manam often produces larger SO2 plumes that obscure evidence of activity at Kadovar. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Two summit vents remained active throughout May and June 2020, producing pulsating steam plumes that were visible for tens of kilometers and thermal anomalies visible in satellite data (figure 50). A strong thermal anomaly was visible beneath meteoric clouds on 8 June.

Figure (see Caption) Figure 50. During May and June 2020 thermal and plume activity continued at Kadovar. Top: Gas-and-steam plumes drifted NW from two sources at the summit of Kadovar on 19 May 2020. Bottom left: Two thermal anomalies marked the E rim of the summit crater on 28 June 2020. Bottom right: A zoomed out view of the same 28 June image shows pulsating steam plumes drifting 10 km NW from Kadovar. Top image is Natural color rendering (bands 4, 3, 2). Bottom images are Atmospheric penetration rendering (bands 12, 11, 8a) of Sentinel-2 images. Courtesy of Sentinel Hub Playground.

Visitor observations on 21 October 2019. Claudio Jung visited Kadovar on 21 October 2019. Shortly before arriving on the island an ash plume rose tens of meters above the summit and drifted W (figure 51). From the NW side of the summit crater rim, Jung saw the actively growing dome on the side of a larger dome, and steam and gas issuing from the growing dome (figure 52). The crater rim was covered with dead vegetation, ash, and large bombs from recent explosions (figure 53). The summit dome had minor fumarolic activity around the summit area and dead vegetation halfway up the flank (figure 54) while the fresh blocky lava of the actively growing dome on the E side of the summit produced significant steam and gas emissions. The growing dome produced periodic pulses of dense steam during his visit (figure 55).

Figure (see Caption) Figure 51. Views looking S show the shoreline dome at the base of the E flank of Kadovar that was active during March-May 2018 (left), and an ash plume drifting W from the summit dome located on the E side of the summit crater (right) on 21 October 2019. Copyrighted photos courtesy of Claudio Jung, used with permission.
Figure (see Caption) Figure 52. A panorama looking SE from the crater rim of Kadovar on 21 October 2019 shows the actively growing dome on the far left with a narrow plume of steam and gas being emitted. A large dome fills the summit crater; the crater rim is visible on the right. Copyrighted photo courtesy of Claudio Jung, used with permission.
Figure (see Caption) Figure 53. The crater rim of Kadovar on 21 October 2019 was covered with dead vegetation, ash, and large bombs from recent explosions. Person is sitting on a large bomb; weak fumarolic activity is visible along the rim. Copyrighted photo courtesy of Claudio Jung, used with permission.
Figure (see Caption) Figure 54. The summit dome of Kadovar on 21 October 2019 had minor fumarolic activity around most of its summit and dead vegetation half-way up the flank (left). The dead tree stumps suggest that vegetation covered the lower half of the dome prior to the eruption that began in January 2018. The fresh blocky lava of the actively growing dome on the E side of the summit dome produced significant steam and gas emissions (right). Copyrighted photos courtesy of Claudio Jung, used with permission.
Figure (see Caption) Figure 55. Dense steam from the growing dome on the E side of the summit drifted W from Kadovar on 21 October 2019. Copyrighted photo courtesy of Claudio Jung, used with permission.

Reference: Planka S, Walter T R, Martinis S, Cescab S, 2019, Growth and collapse of a littoral lava dome during the 2018/19 eruption of Kadovar Volcano, Papua New Guinea, analyzed by multi-sensor satellite imagery, Journal of Volcanology and Geothermal Research, v. 388, 15 December 2019, 106704, https://doi.org/10.1016/j.jvolgeores.2019.106704.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Information Contacts: 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; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Claudio Jung (URL: https://www.instagram.com/jung.claudio/).


Sangay (Ecuador) — July 2020 Citation iconCite this Report

Sangay

Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

All times are local (unless otherwise noted)


Daily ash plumes and frequent pyroclastic flows produce ashfall and lahars, January-June 2020

Frequent activity at Ecuador's Sangay has included pyroclastic flows, lava flows, ash plumes, and lahars reported since 1628. Its remoteness on the east side of the Andean crest make ground observations difficult; remote cameras and satellites provide important information on activity. The current eruption began in March 2019 and continued through December 2019 with activity focused on the Cráter Central and the Ñuñurco (southeast) vent; they produced explosions with ash plumes, lava flows, and pyroclastic flows and block avalanches. In addition, volcanic debris was remobilized in the Volcan river causing significant damming downstream. This report covers ongoing similar activity from January through June 2020. Information is provided by Ecuador's Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), and a number of sources of remote data including the Washington Volcanic Ash Advisory Center (VAAC), the Italian MIROVA Volcano HotSpot Detection System, and Sentinel-2 satellite imagery. Visitors also provided excellent ground and drone-based images and information.

Throughout January-June 2020, multiple daily reports from the Washington Volcanic Ash Advisory Center (VAAC) indicated ash plumes rising from the summit, generally 500-1,100 m. Each month one or more plumes rose over 2,000 m. The plumes usually drifted SW or W, and ashfall was reported in communities 25-90 km away several times during January-March and again in June. In addition to explosions with ash plumes, pyroclastic flows and incandescent blocks frequently descended a large, deep ravine on the SE flank. Ash from the pyroclastic flows rose a few hundred meters and drifted away from the volcano. Incandescence was visible on clear nights at the summit and in the ravine. The MIROVA log radiative power graph showed continued moderate and high levels of thermal energy throughout the period (figure 57). Sangay also had small but persistent daily SO2 signatures during January-June 2020 with larger pulses one or more days each month (figure 58). IG-EPN published data in June 2020 about the overall activity since May 2019, indicating increases throughout the period in seismic event frequency, SO2 emissions, ash plume frequency, and thermal energy (figure 59).

Figure (see Caption) Figure 57. This graph of log radiative power at Sangay for 18 Aug 2018 through June 2020 shows the moderate levels of thermal energy through the end of the previous eruption in late 2018 and the beginning of the current one in early 2019. Data is from Sentinel-2, courtesy of MIROVA.
Figure (see Caption) Figure 58. Small but persistent daily SO2 signatures were typical of Sangay during January-June 2020. A few times each month the plume was the same or larger than the plume from Columbia’s Nevado del Ruiz, located over 800 km NE. Image dates are shown in the header over each image. Courtesy of NASA’s Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 59. A multi-parameter graph of activity at Sangay from May 2019 to 12 June 2020 showed increases in many types of activity. a) seismic activity (number of events per day) detected at the PUYO station (source: IG-EPN). b) SO2 emissions (tons per day) detected by the Sentinel-5P satellite sensor (TROPOMI: red squares; source: MOUNTS) and by the IG-EPN (DOAS: green bars). c) height of the ash plumes (meters above crater) detected by the GOES-16 satellite sensor (source: Washington VAAC). d) thermal emission power (megawatt) detected by the MODIS satellite sensor (source: MODVOLC) and estimate of the accumulated lava volume (million M3, thin lines represent the error range). Courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2020 - N°3, “Actualización de la actividad eruptiva”, Quito, 12 de junio del 2020).

Activity during January-March 2020. IG-EPN and the Washington VAAC reported multiple daily ash emissions throughout January 2020. Gas and ash emissions generally rose 500-1,500 m above the summit, most often drifting W or SW. Ashfall was reported on 8 January in the communities of Sevilla (90 km SSW), Pumallacta and Achupallas (60 km SW) and Cebadas (35 km WNW). On 16 January ash fell in the Chimborazo province in the communities of Atillo, Ichobamba, and Palmira (45 km W). Ash on 28 January drifted NW, with minor ashfall reported in Púngala (25 km NW) and other nearby communities. The town of Alao (20 km NW) reported on 30 January that all of the vegetation in the region was covered with fine white ash; Cebadas and Palmira also noted minor ashfall (figure 60).

Figure (see Caption) Figure 60. Daily ash plumes and repeated ashfall were reported from Sangay during January 2020. Top left: 1 January 2020 (INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-2, JUEVES, 2 ENERO 2020). Top right: 20 January 2020 (INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-21, MARTES, 21 ENERO 2020). Bottom left: 26 January-1 February 2020 expedition (Martes, 18 Febrero 2020 12:21, EXPEDICIÓN AL VOLCÁN SANGAY). Bottom right: 30 January 2020, minor ashfall was reported in the Province of Chimborazo (#IGAlInstante Informativo VOLCÁN SANGAY No. 006, JUEVES, 30 ENERO 2020). Courtesy of IG-EPN.

A major ravine on the SE flank has been the site of ongoing block avalanches and pyroclastic flows since the latest eruption began in March 2019. The pyroclastic flows down the ravine appeared incandescent at night; during the day they created ash clouds that drifted SW. Satellite imagery recorded incandescence and dense ash from pyroclastic flows in the ravine on 7 January (figure 61). They were also reported by IG on the 9th, 13th, 26th, and 28th. Incandescent blocks were reported in the ravine several times during the month. The webcam captured images on 31 January of large incandescent blocks descending the entire length of the ravine to the base of the mountain (figure 62). Large amounts of ash and debris were remobilized as lahars during heavy rains on the 25th and 28th.

Figure (see Caption) Figure 61. Sentinel-2 satellite imagery of Sangay from 7 January 2020 clearly showed a dense ash plume drifting W and ash and incandescent material from pyroclastic flows descending the SE-flank ravine. Left image uses natural color (bands 4, 3, 2) rendering and right images uses atmospheric penetration (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 62. Pyroclastic flows at Sangay produced large trails of ash down the SE ravine many times during January 2020 that rose and drifted SW. Top left: 9 January (INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-9, JUEVES, 9 ENERO 2020). Top right: 13 January (INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-14, MARTES, 14 ENERO 2020). On clear nights, incandescent blocks of lava and pyroclastic flows were visible in the ravine. Bottom left: 16 January (INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-17, VIERNES, 17 ENERO 2020). Bottom right: 31 January (#IGAlInstante Informativo VOLCÁN SANGAY No. 007, VIERNES, 31 ENERO 2020). Courtesy of IG-EPN.

Observations by visitors to the volcano during 9-17 January 2020 included pyroclastic flows, ash emissions, and incandescent debris descending the SE flank ravine during the brief periods when skies were not completely overcast (figure 63 and 64). More often there was ash-filled rain and explosions heard as far as 16 km from the volcano, along with the sounds of lahars generated from the frequent rainfall mobilizing debris from the pyroclastic flows. The confluence of the Rio Upano and Rio Volcan is 23 km SE of the summit and debris from the lahars has created a natural dam on the Rio Upano that periodically backs up water and inundates the adjacent forest (figure 65). A different expedition to Sangay during 26 January-1 February 2020 by IG personnel to repair and maintain the remote monitoring station and collect samples was successful, after which the station was once again transmitting data to IG-EPN in Quito (figure 66).

Figure (see Caption) Figure 63. Hikers near Sangay during 9-17 January 2020 witnessed pyroclastic flows and incandescent explosions and debris descending the SE ravine. Left: The view from 40 km SE near Macas showed ash rising from pyroclastic flows in the SE ravine. Right: Even though the summit was shrouded with a cap cloud, incandescence from the summit crater and from pyroclastic flows on the SE flank were visible on clear nights. Courtesy of Arnold Binas, used with permission.
Figure (see Caption) Figure 64. The steep ravine on the SE flank of Sangay was hundreds of meters deep in January 2020 when these drone images were taken by members of a hiking trip during 9-17 January 2020 (left). Pyroclastic flows descended the ravine often (right), coating the sides of the ravine with fine, white ash and sending ash billowing up from the surface of the flow which resulted in ashfall in adjacent communities several times. Courtesy of Arnold Binas, used with permission.
Figure (see Caption) Figure 65. Debris from pyroclastic flows that descended the SE Ravine at Sangay was carried down the Volcan River (left) during frequent rains and caused repeated damming at the confluence with the Rio Upano (right), located 23 km SE of the summit. These images show the conditions along the riverbeds during 9-17 January 2020. Courtesy of Arnold Binas, used with permission.
Figure (see Caption) Figure 66. An expedition by scientists from IG-EPN to one of the remote monitoring stations at Sangay during 26 January-1 February 2020 was successful in restoring communication to Quito. The remote location and constant volcanic activity makes access and maintenance a challenge. Courtesy of IG-EPN (Martes, 18 Febrero 2020 12:21, EXPEDICIÓN AL VOLCÁN SANGAY).

During February 2020, multiple daily VAAC reports of ash emissions continued (figure 67). Plumes generally rose 500-1,100 m above the summit and drifted W, although on 26 February emissions were reported to 1,770 m. Ashfall was reported in Macas (40 km SE) on 1 February, and in the communities of Pistishi (65 km SW), Chunchi (70 km SW), Pumallacta (60 k. SW), Alausí (60 km SW), Guamote (40 km WNW) and adjacent areas of the Chimborazo province on 5 February. The Ecuadorian Red Cross reported ash from Sangay in the provinces of Cañar and Azuay (60-100 km SW) on 25 February. Cebadas and Guamote reported moderate ashfall the following day. The communities of Cacha (50 km NW) and Punín (45 km NW) reported trace amounts of ashfall on 29 February. Incandescent blocks were seen on the SE flank multiples times throughout the month. A pyroclastic flow was recorded on the SE flank early on 6 February; additional pyroclastic flows were observed later that day on the SW flank. On 23 February a seismic station on the flank recorded a high-frequency signal typical of lahars.

Figure (see Caption) Figure 67. Steam and ash could be seen drifting SW from the summit of Sangay on 11 February 2020 even though the summit was hidden by a large cap cloud. Ash was also visible in the ravine on the SE flank. Courtesy of Sentinel Hub Playground, natural color (bands 4, 3, 2) rendering.

A significant ash emission on 1 March 2020 was reported about 2 km above the summit, drifting SW. Multiple ash emissions continued daily during the month, generally rising 570-1,170 m high. An emission on 12 March also rose 2 km above the summit. Trace ashfall was reported in Cebadas (35 km WNW) on 12 March. The community of Huamboya, located 40 km ENE of Sangay in the province of Morona-Santiago reported ashfall on 17 March. On 19 and 21 March ashfall was seen on the surface of cars in Macas to the SE. (figure 68). Ash was also reported on the 21st in de Santa María De Tunants (Sinaí) located E of Sangay. Ash fell again in Macas on 23 March and was also reported in General Proaño (40 km SE). The wind changed direction the next day and caused ashfall on 24 March to the SW in Cuenca and Azogues (100 km SW).

Figure (see Caption) Figure 68. Ashfall from Sangay was reported on cars in Huamboya on 17 March 2020 (left) and in Macas on 19 March (right). Courtesy IG-EPN, (#IGAlInstante Informativo VOLCÁN SANGAY No. 024, MARTES, 17 MARZO 2020 and #IGAlInstante Informativo VOLCÁN SANGAY No. 025, JUEVES, 19 MARZO 2020).

Incandescence from the dome at the crater and on the SE flank was noted by IG on 3, 4, and 13 March. Remobilized ash from a pyroclastic flow was reported drifting SW on 13 March. The incandescent path of the flow was still visible that evening. Numerous lahars were recorded seismically during the month, including on days 5, 6, 8, 11, 15, 30 and 31. Images from the Rio Upano on 11 March confirmed an increase from the normal flow rate (figure 69) inferred to be from volcanic debris. Morona-Santiago province officials reported on 14 March that a new dam had formed at the confluence of the Upano and Volcano rivers that decreased the flow downstream; by 16 March it had given way and flow had returned to normal levels.

Figure (see Caption) Figure 69. Images from the Rio Upano on 11 March 2020 (left) confirmed an increase from the normal flow rate related to lahars from Sangay descending the Rio Volcan. By 16 March (right), the flow rate had returned to normal, although the large blocks in the river were evidence of substantial activity in the past. Courtesy of IG (#IGAlInstante Informativo VOLCÁN SANGAY No. 018, MIÉRCOLES, 11 MARZO 2020 and #IGAlInstante Informativo VOLCÁN SANGAY No. 023, LUNES, 16 MARZO 2020).

Activity during April-June 2020. Lahar activity continued during April 2020; they were reported seven times on 2, 5, 7, 11, 12, 19, and 30 April. A significant reduction in the flow of the Upano River at the entrance bridge to the city of Macas was reported 9 April, likely due to a new dam on the river upstream from where the Volcan river joins it caused by lahars related to ash emissions and pyroclastic flows (figure 70). The flow rate returned to normal the following day. Ash emissions were reported most days of the month, commonly rising 500-1,100 m above the summit and drifting W. Incandescent blocks or flows were visible on the SE flank on 4, 10, 12, 15-16, and 20-23 April (figure 71).

Figure (see Caption) Figure 70. A significant reduction in the flow of the Upano River at the entrance bridge to the city of Macas was reported on 9 April 2020, likely due to a new dam upstream from lahars related to ash emissions and pyroclastic flows from Sangay. Courtesy of IG-EPN (#IGAlInstante Informativo VOLCÁN SANGAY No. 032, JUEVES, 9 ABRIL 2020).
Figure (see Caption) Figure 71. Incandescent blocks rolled down the SE ravine at Sangay multiple times during April 2020, including on 4 April (left). Pyroclastic flows left two continuous incandescent trails in the ravine on 23 April (right). Courtesy of IG-EPN (INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-95, SÁBADO, 4 ABRIL 2020 and INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-114, JUEVES, 23 ABRIL 2020).

Activity during May 2020 included multiple daily ash emissions that drifted W and numerous lahars from plentiful rain carrying ash and debris downstream. Although there were only a few visible observations of ash plumes due to clouds, the Washington VAAC reported plumes visible in satellite imagery throughout the month. Plumes rose 570-1,170 m above the summit most days; the highest reported rose to 2,000 m above the summit on 14 May. Two lahars occurred in the early morning on 1 May and one the next day. A lahar signal lasted for three hours on 4 May. Two lahar signals were recorded on the 7th, and three on the 9th. Lahars were also recorded on 16-17, 20-22, 26-27, and 30 May. Incandescence on the SE flank was only noted three times, but it was cloudy nearly every day.

An increase in thermal and overall eruptive activity was reported during June 2020. On 1 and 2 June the webcam captured lava flows and remobilization of the deposits on the SE flank in the early morning and late at night. Incandescence was visible multiple days each week. Lahars were reported on 4 and 5 June. The frequent daily ash emissions during June generally rose to 570-1,200 m above the summit and drifted usually SW or W. The number of explosions and ash emissions increased during the evening of 7 June. IG interpreted the seismic signals from the explosions as an indication of the rise of a new pulse of magma (figure 72). The infrasound sensor log from 8 June also recorded longer duration tremor signals that were interpreted as resulting from the descent of pyroclastic flows in the SE ravine.

Figure (see Caption) Figure 72. Seismic and infrasound signals indicated increased explosive and pyroclastic flow activity at Sangay on 7-8 June 2020. Left: SAGA station (seismic component) of 7 and 8 June. The signals correspond to explosions without VT or tremor signals, suggesting the rise of a new magma pulse. Right: SAGA station infrasound sensor log from 8 June. The sharp explosion signals are followed a few minutes later (examples highlighted in red) by emergent signals of longer duration, possibly associated with the descent of pyroclastic material in the SE flank ravine. Courtesy if IG-EPN (Informe Especial del Volcán Sangay - 2020 - N°3, “Actualización de la actividad eruptiva”, Quito, 12 de junio del 2020).

On the evening of 8 June ashfall was reported in the parish of Cebadas and in the Alausí Canton to the W and SW of Sangay. There were several reports of gas and ash emissions to 1,770 m above the summit the next morning on 9 June, followed by reports of ashfall in the provinces of Guayas, Santa Elena, Los Ríos, Morona Santiago, and Chimborazo. Ashfall continued in the afternoon and was reported in Alausí, Chunchi, Guamote, and Chillanes. That night, which was clear, the webcam captured images of pyroclastic flows down the SE-flank ravine; IG attributed the increase in activity to the collapse of one or more lava fronts. On the evening of 10 June additional ashfall was reported in the towns of Alausí, Chunchi, and Guamote (figure 73); satellite imagery indicated an ash plume drifting W and incandescence from pyroclastic flows in the SE-flank ravine the same day (figure 74).

Figure (see Caption) Figure 73. Ashfall from Sangay was reported in Alausí (top left), Chunchi (top right) and Guamote (bottom) on 10 June 2020. Courtesy of IG-EPN (#IGAlInstante Informativo VOLCÁN SANGAY No. 049, MIÉRCOLES, 10 JUNIO 2020).
Figure (see Caption) Figure 74. Incandescent pyroclastic flows (left) and ash plumes that drifted W (right) were recorded on 10 June 2020 at Sangay in Sentinel-2 satellite imagery. Courtesy of Sentinel Hub Playground.

Ashfall continued on 11 June and was reported in Guayaquil, Guamote, Chunchi, Riobamba, Guaranda, Chimbo, Echandía, and Chillanes. The highest ash plume of the report period rose to 2,800 m above the summit that day and drifted SW. That evening the SNGRE (Servicio Nacional de Gestion de Riesgos y Emergencias) reported ash fall in the Alausí canton. IG noted the increase in intensity of activity and reported that the ash plume of 11 June drifted more than 600 km W (figure 75). Ash emissions on 12 and 13 June drifted SW and NW and resulted in ashfall in the provinces of Chimborazo, Cotopaxi, Tungurahua, and Bolívar. On 14 June, the accumulation of ash interfered with the transmission of information from the seismic station. Lahars were reported each day during 15-17 and 19-21 June. Trace amounts of ashfall were reported in Macas to the SE on 25 June.

Figure (see Caption) Figure 75. The ash plume at Sangay reported on 11 June 2020 rose 2.8 km above the summit and drifted W according to the Washington VAAC and IG (left). Explosions and high levels of incandescence on the SE flank were captured by the Don Bosco webcam (right). Courtesy of IG-EPN (#IGAlInstante Informativo VOLCÁN SANGAY No. 055, JUEVES, 11 JUNIO 2020 and INFORME DIARIO DEL ESTADO DEL VOLCÁN SANGAY No. 2020-164, VIERNES, 12 JUNIO 2020).

During an overflight of Sangay on 24 June IG personnel observed that activity was characterized by small explosions from the summit vent and pyroclastic flows down the SE-flank ravine. The explosions produced small gas plumes with a high ash content that did not rise more than 500 m above the summit and drifted W (figure 76). The pyroclastic flows were restricted to the ravine on the SE flank, although the ash from the flows rose rapidly and reached about 200 m above the surface of the ravine and also drifted W (figure 77).

Figure (see Caption) Figure 76. A dense ash plume rose 500 m from the summit of Sangay on 24 June 2020 and drifted W during an overflight by IG-EPN personnel. The aerial photograph is taken from the SE; snow-covered Chimborazo is visible behind and to the right of Sangay. Photo by M Almeida, courtesy of IG EPN (Jueves, 02 Julio 2020 10:29, INFORME DEL SOBREVUELO AL VOLCÁN SANGAY EL 24 DE JUNIO DE 2020).
Figure (see Caption) Figure 77. Pyroclastic flows descended the SE flank ravine at Sangay during an overflight by IG-EPN personnel on 24 June 2020. Ash from the pyroclastic flow rose 200 m and drifted W, and infrared imagery identified the thermal signature of the pyroclastic flow in the ravine. Photo by M Almeida, IR Image by S Vallejo, courtesy of IG EPN (Jueves, 25 Junio 2020 12:24, SOBREVUELO AL VOLCÁN SANGAY).

Infrared imagery taken during the overflight on 24 June identified three significant thermal anomalies in the large ravine on the SE flank (figure 78). Analysis by IG scientists suggested that the upper anomaly 1 (125°C) was associated with explosive activity that was observed during the flight. Anomaly 2 (147°C), a short distance below Anomaly 1, was possibly related to effusive activity of a small flow, and Anomaly 3 (165°C) near the base of the ravine that was associated with pyroclastic flow deposits. The extent of the changes at the summit of Sangay and along the SE flank since the beginning of the eruption that started in March 2019 were clearly visible when images from May 2019 were compared with images from the 24 June 2020 overflight (figure 79). The upper part of the ravine was nearly 400 m wide by the end of June.

Figure (see Caption) Figure 78. A thermal image of the SE flank of Sangay taken on 24 June 2020 indicated three thermal anomalies. Anomaly 1 was associated with explosive activity, Anomaly 2 was associated with effusive activity, and Anomaly 3 was related to pyroclastic-flow deposits. Image prepared by S Vallejo Vargas, courtesy of IG EPN (Jueves, 02 Julio 2020 10:29, INFORME DEL SOBREVUELO AL VOLCÁN SANGAY EL 24 DE JUNIO DE 2020).
Figure (see Caption) Figure 79. Aerial and thermal photographs of the southern flank of the Sangay volcano on 17 May 2019 (left: visible image) and 24 June 2020 (middle: visible image, right: visible-thermal overlay) show the morphological changes on the SE flank, associated with the formation of a deep ravine and the modification of the summit. Photos and thermal image by M Almeida, courtesy of IG EPN (Jueves, 02 Julio 2020 10:29, INFORME DEL SOBREVUELO AL VOLCÁN SANGAY EL 24 DE JUNIO DE 2020).

Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Arnold Binas (URL: https://www.doroadventures.com).


Karangetang (Indonesia) — June 2020 Citation iconCite this Report

Karangetang

Indonesia

2.781°N, 125.407°E; summit elev. 1797 m

All times are local (unless otherwise noted)


Incandescent block avalanches through mid-January 2020; crater anomalies through May

The Karangetang andesitic-basaltic stratovolcano (also referred to as Api Siau) at the northern end of the island of Siau, north of Sulawesi, Indonesia, has had more than 50 observed eruptions since 1675. Frequent explosive activity is accompanied by pyroclastic flows and lahars, and lava-dome growth has created two active summit craters (Main to the S and Second Crater to the N). Rock avalanches, observed incandescence, and satellite thermal anomalies at the summit confirmed continuing volcanic activity since the latest eruption started in November 2018 (BGVN 44:05). This report covers activity from December 2019 through May 2020. Activity is monitored by Indonesia's Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), and ash plumes are monitored by the Darwin VAAC (Volcanic Ash Advisory Center). Information is also available from MODIS thermal anomaly satellite data through both the University of Hawaii's MODVOLC system and the Italian MIROVA project.

Increased activity that included daily incandescent avalanche blocks traveling down the W and NW flanks lasted from mid-July 2019 (BGVN 44:12) through mid-January 2020 according to multiple sources. The MIROVA data showed increased number and intensity of thermal anomalies during this period, with a sharp drop during the second half of January (figure 40). The MODVOLC thermal alert data reported 29 alerts in December and ten alerts in January, ending on 14 January, with no further alerts through May 2020. During December and the first half of January incandescent blocks traveled 1,000-1,500 m down multiple drainages on the W and NW flanks (figure 41). After this, thermal anomalies were still present at the summit craters, but no additional activity down the flanks was identified in remote satellite data or direct daily observations from PVMBG.

Figure (see Caption) Figure 40. An episode of increased activity at Karangetang from mid-July 2019 through mid-January 2020 included incandescent avalanche blocks traveling down multiple flanks of the volcano. This was reflected in increased thermal activity seen during that interval in the MIROVA graph covering 5 June 2019 through May 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 41. An episode of increased activity at Karangetang from mid-July 2019 through mid-January 2020 included incandescent avalanche blocks traveling up to 1,500 m down drainages on the W and NW flanks of the volcano. Top left: large thermal anomalies trend NW from Main Crater on 5 December 2019; about 500 m N a thermal anomaly glows from Second Crater. Top center: on 15 December plumes of steam and gas drifted W and SW from both summit craters as seen in Natural Color rendering (bands 4,3,2). Top right: the same image as at top center with Atmospheric penetration rendering (bands 12, 11, 8a) shows hot zones extending WNW from Main Crater and a thermal anomaly at Second Crater. Bottom left: thermal activity seen on 14 January 2020 extended about 800 m WNW from Main Crater along with an anomaly at Second Crater and a hot spot about 1 km W. Bottom center: by 19 January the anomaly from Second Crater appeared slightly stronger than at Main Crater, and only small anomalies appeared on the NW flank. Bottom right: an image from 14 March shows only thermal anomalies at the two summit craters. Courtesy of Sentinel Hub Playground.

A single VAAC report in early April noted a short-lived ash plume that drifted SW. Intermittent low-level activity continued through May 2020. Small SO2 plumes appeared in satellite data multiple times in December 2019 and January 2020; they decreased in size and frequency after that but were still intermittently recorded into May 2020 (figure 42).

Figure (see Caption) Figure 42. Small plumes of sulfur dioxide were measured at Karangetang with the TROPOMI instrument on the Sentinel-5P satellite multiple times during December 2019 (top row). They were less frequent but still appeared during January-May 2020 (bottom row). Larger plumes were also detected from Dukono, located 300 km ESE at the N end of North Maluku. Courtesy of Global Sulfur Dioxide Monitoring Page.

PVMBG reported in their daily summaries that steam plumes rose 50-150 m above the Main Crater and 25-50 m above Second Crater on most days in December. The incandescent avalanche activity that began in mid-July 2019 also continued throughout December 2019 and January 2020 (figure 43). Incandescent blocks from the Main Crater descended river drainages (Kali) on the W and NW flanks throughout December. They were reported nearly every day in the Nanitu, Sense, and Pangi drainages, traveling 1,000-1,500 m. Incandescence from both craters was visible 10-25 m above the crater rim most nights.

Figure (see Caption) Figure 43. Incandescent block avalanches descended the NW flank of Karangetang as far as 1,500 m frequently during December 2019 and January 2020. Left image taken 13 December 2019, right image taken 6 January 2020 by PVMBG webcam. Courtesy of PVMBG, Oystein Anderson, and Bobyson Lamanepa.

A few blocks were noted traveling 800 m down Kali Beha Barat on 1 December. Incandescence above the Main crater reached 50-75 m during 4-6 December. During 4-7 December incandescent blocks appeared in Kali Sesepe, traveling 1,000-1,500 m down from the summit. They were also reported in Kali Batang and Beha Barat during 4-14 December, usually moving 800-1,000 m downslope. Between 5 and 14 December, gray and white plumes from Second Crater reached 300 m multiple times. During 12-15 December steam plumes rose 300-500 m above the Main crater. Activity decreased during 18-26 December but increased again during the last few days of the month. On 28 December, incandescent blocks were reported 1,500 m down Kali Pangi and Nanitu, and 1,750 m down Kali Sense.

Incandescent blocks were reported in Kali Sesepi during 4-6 January and in Kali Batang and Beha Barat during 4-8 and 12-15 January (figure 44); they often traveled 800-1,200 m downslope. Activity tapered off in those drainages and incandescent blocks were last reported in Kali Beha Barat on 15 January traveling 800 m from the summit. Incandescent blocks were also reported traveling usually 1,000-1,500 m down the Nanitu, Sense, and Pangi drainages during 4-19 January. Blocks continued to occasionally descend up to 1,000 m down Kali Nanitu through 24 January. Pulses of activity occurred at the summit of Second Crater a few times in January. Steam plumes rose 25-50 m during 8-9 January and again during 16-31 January, with plumes rising 300-400 m on 20, 29, and 31 January. Incandescence was noted 10-25 m above the summit of Second Crater during 27-30 January.

Figure (see Caption) Figure 44. Incandescent material descends the Beha Barat, Sense, Nanitu, and Pangi drainages on the NW flank of Karangetang in early January 2020. Courtesy of Bobyson Lamanepa; posted on Twitter on 6 January 2020.

Activity diminished significantly after mid-January 2020. Steam plumes at the Main Crater rose 50-100 m on the few days where the summit was not obscured by fog during February. Faint incandescence occurred at the Main Crater on 7 February, and steam plumes rising 25-50 m from Second Crater that day were the only events reported there in February. During March, steam plumes persisted from the Main Crater, with heights of over 100 m during short periods from 8-16 March and 25-30 March. Weak incandescence was reported from the Main Crater only once, on 25 March. Very little activity occurred at Second Crater during March, with only steam plumes reported rising 25-300 m from the 22nd to the 28th (figure 45).

Figure (see Caption) Figure 45. Steam plumes at Karangetang rose over 100 m above both summit craters multiple times during March, including on 26 March 2020. Courtesy of PVMBG and Oystein Anderson.

The Darwin VAAC reported a continuous ash emission on 4 April 2020 that rose to 2.1 km altitude and drifted SW for a few hours before dissipating. Incandescence visible 25 m above both craters on 13 April was the only April activity reported by PVMBG other than steam plumes from the Main Crater that rose 50-500 m on most days. Steam plumes of 50-100 m were reported from Second Crater during 11-13 April. Activity remained sporadic throughout May 2020. Steam plumes from the Main Crater rose 50-300 m each day. Satellite imagery identified steam plumes and incandescence from both summit craters on 3 May (figure 46). Faint incandescence was observed at the Main Crater on 12 and 27 May. Steam plumes rose 25-50 m from Second Crater on a few days; a 200-m-high plume was reported on 27 May. Bluish emissions were observed on the S and SW flanks on 28 May.

Figure (see Caption) Figure 46. Dense steam plumes and thermal anomalies were present at both summit craters of Karangetang on 3 May 2020. Sentinel 2 satellite image with Natural Color (bands 4, 3, 2) (left) and Atmospheric Penetration rendering (bands 12, 11, 8a) (right); courtesy of Sentinel Hub Playground.

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

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/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); 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/); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com); Bobyson Lamanepa, Yogyakarta, Indonesia, (URL: https://twitter.com/BobyLamanepa/status/1214165637028728832).


Shishaldin (United States) — June 2020 Citation iconCite this Report

Shishaldin

United States

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

All times are local (unless otherwise noted)


Intermittent thermal activity and a possible new cone at the summit crater during February-May 2020

Shishaldin is located near the center of Unimak Island in Alaska, with the current eruption phase beginning in July 2019 and characterized by ash plumes, lava flows, lava fountaining, pyroclastic flows, and lahars. More recently, in late 2019 and into January 2020, activity consisted of multiple lava flows, pyroclastic flows, lahars, and ashfall events (BGVN 45:02). This report summarizes activity from February through May 2020, including gas-and-steam emissions, brief thermal activity in mid-March, and a possible new cone within the summit crater. The primary source of information comes from the Alaska Volcano Observatory (AVO) reports and various satellite data.

Volcanism during February 2020 was relatively low, consisting of weakly to moderately elevated surface temperatures during 1-4 February and occasional small gas-and-steam plumes (figure 37). By 6 February both seismicity and surface temperatures had decreased. Seismicity and surface temperatures increased slightly again on 8 March and remained elevated through the rest of the reporting period. Intermittent gas-and-steam emissions were also visible from mid-March (figure 38) through May. Minor ash deposits visible on the upper SE flank may have been due to ash resuspension or a small collapse event at the summit, according to AVO.

Figure (see Caption) Figure 37. Photo of a gas-and-steam plume rising from the summit crater at Shishaldin on 22 February 2020. Photo courtesy of Ben David Jacob via AVO.
Figure (see Caption) Figure 38. A Worldview-2 panchromatic satellite image on 11 March 2020 showing a gas-and-steam plume rising from the summit of Shishaldin and minor ash deposits on the SE flank (left). Aerial photo showing minor gas-and-steam emissions rising from the summit crater on 11 March (right). Some erosion of the snow and ice on the upper flanks is a result of the lava flows from the activity in late 2019 and early 2020. Photo courtesy of Matt Loewen (left) and Ed Fischer (right) via AVO.

On 14 March, lava and a possible new cone were visible in the summit crater using satellite imagery, accompanied by small explosion signals. Strong thermal signatures due to the lava were also seen in Sentinel-2 satellite data and continued strongly through the month (figure 39). The lava reported by AVO in the summit crater was also reflected in satellite-based MODIS thermal anomalies recorded by the MIROVA system (figure 40). Seismic and infrasound data identified small explosions signals within the summit crater during 14-19 March.

Figure (see Caption) Figure 39. Sentinel-2 thermal satellite images (bands 12, 11, 8A) show a bright hotspot (yellow-orange) at the summit crater of Shishaldin during mid-March 2020 that decreases in intensity by late March. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 40. MIROVA thermal data showing a brief increase in thermal anomalies during late March 2020 and on two days in late April between periods of little to no activity. Courtesy of MIROVA.

AVO released a Volcano Observatory Notice for Aviation (VONA) stating that seismicity had decreased by 16 April and that satellite data no longer showed lava or additional changes in the crater since the start of April. Sentinel-2 thermal satellite imagery continued to show a weak hotspot in the crater summit through May (figure 41), which was also detected by the MIROVA system on two days. A daily report on 6 May reported a visible ash deposit extending a short distance SE from the summit, which had likely been present since 29 April. AVO noted that the timing of the deposit corresponds to an increase in the summit crater diameter and depth, further supporting a possible small collapse. Small gas-and-steam emissions continued intermittently and were accompanied by weak tremors and occasional low-frequency earthquakes through May (figure 42). Minor amounts of sulfur dioxide were detected in the gas-and-steam emissions during 20 and 29 April, and 2, 16, and 28 May.

Figure (see Caption) Figure 41. Sentinel-2 thermal satellite images (bands 12, 11, 8A) show occasional gas-and-steam emissions rising from Shishaldin on 26 February (top left) and 24 April 2020 (bottom left) and a weak hotspot (yellow-orange) persisting at the summit crater during April and early May 2020. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 42. A Worldview-1 panchromatic satellite image showing gas-and-steam emissions rising from the summit of Shishaldin on 1 May 2020 (local time) (left). Aerial photo of the N flank of Shishaldin with minor gas-and-steam emissions rising from the summit on 8 May (right). Photo courtesy of Matt Loewen (left) and Levi Musselwhite (right) via AVO.

Geologic Background. The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Masaya (Nicaragua) — June 2020 Citation iconCite this Report

Masaya

Nicaragua

11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)


Lava lake level drops but remains active through May 2020; weak gas plumes

Masaya, which is about 20 km NW of the Nicaragua’s capital of Managua, is one of the most active volcanoes in that country and has a caldera that contains a number of craters (BGVN 43:11). The Santiago crater is the one most currently active and it contains a small lava lake that emits weak gas plumes (figure 85). This report summarizes activity during February through May 2020 and is based on Instituto Nicaragüense de Estudios Territoriales (INETER) monthly reports and satellite data. During the reporting period, the volcano was relatively calm, with only weak gas plumes.

Figure (see Caption) Figure 85. Satellite images of Masaya from Sentinel-2 on 18 April 2020, showing and a small gas plume drifting SW (top, natural color bands 4, 3, 2) and the lava lake (bottom, false color bands 12, 11, 4). Courtesy of Sentinel Hub Playground.

According to INETER, thermal images of the lava lake and temperature data in the fumaroles were taken using an Omega infrared gun and a forward-looking infrared (FLIR) SC620 thermal camera. The temperatures above the lava lake have decreased since November 2019, when the temperature was 287°C, dropping to 96°C when measured on 14 May 2020. INETER attributed this decrease to subsidence in the level of the lava lake by 5 m which obstructed part of the lake and concentrated the gas emissions in the weak plume. Convection continued in the lava lake, which in May had decreased to a diameter of 3 m. Many landslides had occurred in the E, NE, and S walls of the crater rim due to rock fracturing caused by the high heat and acidity of the emissions.

During the reporting period, the MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system recorded numerous thermal anomalies from the lava lake based on MODIS data (figure 86). Infrared satellite images from Sentinel-2 regularly showed a strong signature from the lava lake through 18 May, after which the volcano was covered by clouds.

Figure (see Caption) Figure 86. Thermal anomalies at Masaya during February through May 2020. The larger anomalies with black lines are more distant and not related to the volcano. Courtesy of MIROVA.

Measurements of sulfur dioxide (SO2) made by INETER in the section of the Ticuantepe - La Concepción highway (just W of the volcano) with a mobile DOAS system varied between a low of just over 1,000 metric tons/day in mid-November 2019 to a high of almost 2,500 tons/day in late May. Temperatures of fumaroles in the Cerro El Comalito area, just ENE of Santiago crater, ranged from 58 to 76°C during February-May 2020, with most values in the 69-72°C range.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself 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 Nindirí and Masaya cones, 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 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. 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 have caused 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Krakatau (Indonesia) — June 2020 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Strombolian explosions, ash plumes, and crater incandescence during April 2020

Krakatau, located in the Sunda Strait between Indonesia’s Java and Sumatra Islands, experienced a major caldera collapse around 535 CE, forming a 7-km-wide caldera ringed by three islands. On 22 December 2018, a large explosion and flank collapse destroyed most of the 338-m-high island of Anak Krakatau (Child of Krakatau) and generated a deadly tsunami (BGVN 44:03). The near-sea level crater lake inside the remnant of Anak Krakatau was the site of numerous small steam and tephra explosions. A larger explosion in December 2019 produced the beginnings of a new cone above the surface of crater lake (BGVN 45:02). Recently, volcanism has been characterized by occasional Strombolian explosions, dense ash plumes, and crater incandescence. This report covers activity from February through May 2020 using information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), the Darwin Volcanic Ash Advisory Center (VAAC), and various satellite data.

Activity during February 2020 consisted of dominantly white gas-and-steam emissions rising 300 m above the crater, according to PVMBG. According to the Darwin VAAC, a ground observer reported an eruption on 7 and 8 February, but no volcanic ash was observed. During 10-11 February, a short-lived eruption was detected by seismograms which produced an ash plume up to 1 km above the crater drifting E. MAGMA Indonesia reported two eruptions on 18 March, both of which rose to 300 m above the crater. White gas-and-steam emissions were observed for the rest of the month and early April.

On 10 April PVMBG reported two eruptions, at 2158 and 2235, both of which produced dark ash plumes rising 2 km above the crater followed by Strombolian explosions ejecting incandescent material that landed on the crater floor (figures 108 and 109). The Darwin VAAC issued a notice at 0145 on 11 April reporting an ash plume to 14.3 km altitude drifting WNW, however this was noted with low confidence due to the possible mixing of clouds. During the same day, an intense thermal hotspot was detected in the HIMAWARI thermal satellite imagery and the NASA Global Sulfur Dioxide page showed a strong SO2 plume at 11.3 km altitude drifting W (figure 110). The CCTV Lava93 webcam showed new lava flows and lava fountaining from the 10-11 April eruptions. This activity was evident in the MIROVA (Middle InfraRed Observation of Volcanic Activity) graph of MODIS thermal anomaly data (figure 111).

Figure (see Caption) Figure 108. Webcam (Lava93) images of Krakatau on 10 April 2020 showing Strombolian explosions, strong incandescence, and ash plumes rising from the crater. Courtesy of PVMBG and MAGMA Indonesia.
Figure (see Caption) Figure 109. Webcam image of incandescent Strombolian explosions at Krakatau on 10 April 2020. Courtesy of PVMBG and MAGMA Indonesia.
Figure (see Caption) Figure 110. Strong sulfur dioxide emissions rising from Krakatau and drifting W were detected using the TROPOMI instrument on the Sentinel-5P satellite on 11 April 2020 (top row). Smaller volumes of SO2 were visible in Sentinel-5P/TROPOMI maps on 13 (bottom left) and 19 April (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 111. Thermal activity at Anak Krakatau from 29 June-May 2020 shown on a MIROVA Log Radiative Power graph. The power and frequency of the thermal anomalies sharply increased in mid-April. After the larger eruptive event in mid-April the thermal anomalies declined slightly in strength but continued to be detected intermittently through May. Courtesy of MIROVA.

Strombolian activity rising up to 500 m continued into 12 April and was accompanied by SO2 emissions that rose 3 km altitude, drifting NW according to a VAAC notice. PVMBG reported an eruption on 13 April at 2054 that resulted in incandescence as high as 25 m above the crater. Volcanic ash, accompanied by white gas-and-steam emissions, continued intermittently through 18 April, many of which were observed by the CCTV webcam. After 18 April only gas-and-steam plumes were reported, rising up to 100 m above the crater; Sentinel-2 satellite imagery showed faint thermal anomalies in the crater (figure 112). SO2 emissions continued intermittently throughout April, though at lower volumes and altitudes compared to the 11th. MODIS satellite data seen in MIROVA showed intermittent thermal anomalies through May.

Figure (see Caption) Figure 112. Sentinel-2 thermal satellite images showing the cool crater lake on 20 March (top left) followed by minor heating of the crater during April and May 2020. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

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Bulletin of the Global Volcanism Network - Volume 31, Number 09 (September 2006)

Managing Editor: Richard Wunderman

Bamus (Papua New Guinea)

Forceful vapor emission seen on 12 July 2006

Barren Island (India)

Ongoing emissions, including lava, but late-September news reports of slowing pace

Bulusan (Philippines)

Ten explosions recorded seismically between 21 March and 28 June 2006

Cleveland (United States)

Short duration explosions during August-October 2006

Fourpeaked (United States)

Eruption on 17 September, followed by emissions until at least early November

Home Reef (Tonga)

Extensive pumice rafts between Tonga and Fiji during August-October

Montagu Island (United Kingdom)

Five years of nearly persistent eruptive activity

Rabaul (Papua New Guinea)

Strong eruption at Tavurvur ejected ash and large plumes to the troposphere

San Cristobal (Nicaragua)

Multi-year update: 13 June 2004, local ash fall; early 2006, small eruptions

Soufriere Hills (United Kingdom)

Extrusive dome dynamics during May-September 2006

Sulu Range (Papua New Guinea)

Volcano seismicity declines in September and October 2006



Bamus (Papua New Guinea) — September 2006 Citation iconCite this Report

Bamus

Papua New Guinea

5.2°S, 151.23°E; summit elev. 2248 m

All times are local (unless otherwise noted)


Forceful vapor emission seen on 12 July 2006

According to the Papua New Guinea Department of Mining (DOM), reports coming from Bialla Local Level Government (LLG) indicated that Bamus showed signs of unusual activity. At 1010 on 12 July 2006 observers saw white vapor coming out at the summit. The emission was forceful at about 1110 that day, with a tint of gray color in the emission. The vapor-rich plume blew inland to the SSE. No ashfall was reported.

Officials from Bialla LLG together with a DOM observer witnessed the activity, as did Max Benjamin from Walindi Resort (~ 40-50 km away). Benjamin called the Rabaul Volcano Observatory to report the activity. No satellite-detected thermal anomalies at the volcano were reported by the MODIS website for this time frame.

Geologic Background. Symmetrical 2248-m-high Bamus volcano, also referred to locally as the South Son, is located SW of Ulawun volcano, known as the Father. These two volcanoes are the highest in the 1000-km-long Bismarck volcanic arc. The andesitic stratovolcano is draped by rainforest and contains a breached summit crater filled with a lava dome. A satellitic cone is located on the southern flank, and a prominent 1.5-km-wide crater with two small adjacent cones is situated halfway up the SE flank. Young pyroclastic-flow deposits are found on the volcano's flanks, and villagers describe an eruption that took place during the late 19th century.

Information Contacts: Steve Saunders and Herman Patia, Rabaul Volcanological Observatory (RVO), Department of Mining, Private Mail Bag, Port Moresby Post Office, National Capitol District, Papua, New Guinea.


Barren Island (India) — September 2006 Citation iconCite this Report

Barren Island

India

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

All times are local (unless otherwise noted)


Ongoing emissions, including lava, but late-September news reports of slowing pace

Our last report on Barren Island discussed events through much of January 2006 (BGVN 31:01); since that time we have only found sporadic reports of activity.

According to a news article by The Indo-Asian News Service, a team of scientists that visited Barren Island around 12 March 2006 found that the volcano was still very active. The height of the volcanic cone had increased by 50 m since eruptive activity began in May 2005. In addition, lava flows covered the NW side of the island.

Since March 2006 there have been only a few satellite images and pilot reports of continued activity. Based on a pilot report and satellite imagery, the Darwin VAAC reported that an ash plume was emitted during 5-6 April that did not rise higher than 4.6 km altitude. On 19 April a low-level plume extending W was visible on satellite imagery.

On 2 May satellite imagery detected a plume from Barren Island near 3.7 km altitude. The following day low-level ash plumes extended N. Based on a pilot report, the Darwin VAAC reported an ash plume at 1230 on 26 May that remained below 3 km altitude and drifted N.

On 23 September a news report in The Hindu stated that Indian Coast Guard officials indicated that the continuing eruption at Barren Island was decreasing in intensity. The news piece cited a surveillance report statement that there was less lava but more "smoke" from the volcano.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: The Hindu (URL: http://www.hinduonline.com); Indo-Asian News Service (IANS) (URL: http://www.eians.com/); Geological Survey of India, 27 Jawaharlal Nehru road, Kolkata 700 016, India (URL: https://www.gsi.gov.in/); Indian Coast Guard, National Stadium Complex, New Delhi 110 001, India (URL: http://indiancoastguard.nic.in/indiancoastguard/); Darwin Volcanic Ash Advisory Center, Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).


Bulusan (Philippines) — September 2006 Citation iconCite this Report

Bulusan

Philippines

12.769°N, 124.056°E; summit elev. 1535 m

All times are local (unless otherwise noted)


Ten explosions recorded seismically between 21 March and 28 June 2006

On 19 March 2006, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the status of Bulusan from Zero Alert (no alert) to Alert Level 1 to reflect elevated seismic, fumarolic, and other unrest (BGVN 31:05). From that date until an ash explosion on 28 June 2006, 10 explosions were recorded (see table 3).

Table 3. Summary of significant events through late July 2006 at Bulusan . Numbering of explosion-type (E-type) quakes began 21 March 2006. Courtesy of Philippine Institute of Volcanology and Seismology (PHIVOLCS).

Date Local Time Plume Altitude Drift Direction Comments
19 Mar 2006 -- -- -- Seismic swarm which lasted until 21 Mar; Alert Level raised to 1.
21 Mar 2006 2258 1.5 km N, W, SW 1st explosion-type (E-type) earthquake lasted 20 min; total of 4 E-type earthquakes recorded.
08 Apr 2006 2000 -- -- Lahar at Cogon spillway.
09 Apr 2006 1036-1058 -- -- Lahar at Cogon spillway.
29 Apr 2006 1044 1.5 km WSW, NW 2nd E-type earthquake; total of three E-type earthquakes recorded.
25 May 2006 2117-2130 -- -- 3rd E-type earthquake; ash deposits, trace to 2 mm thick in Juban, Irosin. Cloud-covered summit.
31 May 2006 1617 1.5 W, WNW 4th E-type earthquake.
07 Jun 2006 2017-2030 2.0 N, W, SW 5th E-type earthquake; smaller E-type earthquake at 0225 on 8 Jun; Alert Level raised to 2.
10 Jun 2006 1218 1.0 NE, E 6th E-type earthquake, lasting 25 min.
13 Jun 2006 1904 1.5 NW 7th E-type earthquake, lasting 13 min.
18 Jun 2006 1556 1.5 W 8th E-type earthquake.
20 Jun 2006 2013 -- -- 9th E-type earthquake ? mild; event not observed; seismic signal recorded for 17 min; rains generated some lahars. Cloud-covered summit.
24 Jun 2006 2300 -- -- Lahar at Cogon spillway.
28 Jun 2006 0206 -- -- 10th E-type earthquake; the associated volcanic event was not observed but seismic signal recorded as E-type earthquake lasted 4 min. Cloud-covered summit.
29 Jun 2006 0800 -- -- Continuous decline in activity; Alert Level lowered to 1.

After the ash explosion of 28 June 2006, Bulusan's monitored parameters gradually decreased to near baseline levels. The daily count of volcanic earthquakes was very low, and SO2 emission rates and ground-deformation data revealed the volcano's deflated condition, indicating the absence of active magma ascent. Ash emission stopped and steaming from the active vents and fissures gradually returned to normal levels. Due to the decline in activity, on 29 July PHIVOLCS lowered the status of Bulusan from Alert Level 2 to 1.

On 10 October 2006 at 1256 UTC, the Tokyo Volcanic Ash Advisory Center announced that an eruption plume from Bulusan was visible on satellite imagery reaching altitudes of 3 km and drifting SW and SSE.

Unlike nearby Mayon volcano (~ 70 km NW) (see BGVN 31:08), no thermal anomalies were detected at Bulusan by satellite or recorded by the Hawai'i Institute of Geophysics and Planetology (HIGP) MODIS/ MODVOLC web site from the beginning of 2006 to 10 October 2006.

Geologic Background. Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph); Tokyo Volcanic Ash Advisory Center (VAAC) (URL: http://www.jma.go.jp/jma/jma-eng/jma-center/vaac/index/html); HIGP MODIS Thermal Alert System, Hawai'i Institute of Geophysics and Planetology (HIGP), University of Hawaii at Manoa, 168 East-West Road, Post 602, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Cleveland (United States) — September 2006 Citation iconCite this Report

Cleveland

United States

52.825°N, 169.944°W; summit elev. 1730 m

All times are local (unless otherwise noted)


Short duration explosions during August-October 2006

Cleveland's commonly observed activity consisting of short duration explosions, such as those seen earlier in the year on 6 February 2006 (BGVN 31:01) and on 23 May 2006 (BGVN 31:07), continued during August and October 2006. This report will cover the 24 August and 28 October eruptions.

At 1955 on 24 August a brief eruption was seen by mariners on a passing ship. The eruption was unconfirmed by satellite data. Video footage sent to the Alaska Volcano Observatory (AVO) on 28 August showed that an ash cloud rose to an approximate altitude of 3 km and produced minor ashfall. Shortly after the eruption, minor steaming was observed from the vent on additional footage. In response to the eruption, the AVO raised the level of Concern Color Code from 'unassigned' to 'Yellow' on 7 September. A weak thermal anomaly in the summit crater was present in subsequent satellite images.

Clouds obstructed visibility through most of September and October.

A pilot reported that a minor eruption started at 1345 on 28 October. Satellite data confirmed the presence of an ash cloud drifting ENE of the volcano. The height of the cloud was estimated at an altitude of 6 km using the satellite imagery. One pilot reported the plume top at an altitude of 9 km. The AVO raised the alert level to 'Orange' during 28-29 October. On 30 October the AVO lowered the level to 'Yellow' because of no further evidence of activity.

Geologic Background. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 it produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

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


Fourpeaked (United States) — September 2006 Citation iconCite this Report

Fourpeaked

United States

58.77°N, 153.672°W; summit elev. 2105 m

All times are local (unless otherwise noted)


Eruption on 17 September, followed by emissions until at least early November

Until the eruption of Fourpeaked on 17 September, evidence for eruptive activity in the past 10,000 years was uncertain. The volcano is largely glacier covered with only isolated outcrops (figure 1). This report discusses the initial observation of plumes and subsequent activity until the end of October 2006. Fourpeaked is in S Alaska ~ 320 km SW of Anchorage. It is SW of the mouth of Cook Inlet and within NE Katmai National Park (figure 2).

Figure (see Caption) Figure 1. Fourpeaked volcano, the glacier-covered peak at the upper left is one of a group of poorly known volcanoes NE of Katmai National Park. In the foreground of this photo is Kaguyak caldera, which hosts a 2.5-km- wide lake. Pre-eruption photo at uncertain date taken by Chris Nye (Alaska Division of Geological and Geophysical Surveys, Alaska Volcano Observatory.
Figure (see Caption) Figure 2. A map showing the location of Fourpeaked and Douglas volcanoes, Cook Inlet, and adjacent settlements including the city of Homer on the SW Kenai Peninsula. Created by Seth Snedigar and Janet Schaafer, AVO-ADGGS.

On the evening of 17 September, AVO received several reports of two discrete plumes rising from the Cape Douglas area. The plumes were photographed at an unstated time on 17 September from the town of Homer (figure 3). At this stage, neither Douglas nor Fourpeaked had devoted seismic instruments.

Figure (see Caption) Figure 3. A photograph of the eruption of Fourpeaked on 17 September 2006. The photo was taken from Main Street in Homer at an unstated time. Copyrighted photograph by Lanny Simpson, Alaska High Mountain Images (shown on AVO's website).

Retrospective analysis of data from the NEXRAD Doppler radar in King Salmon showed an unusual cloud starting at 1200 on 17 September. The maximum cloud height determined by radar during the first hour of the event was 6 km altitude. The radar return from the cloud continued until at least 2145 (figure 4).

Figure (see Caption) Figure 4. Image from the King Salmon NEXRAD weather radar showing the volcanic cloud at Fourpeaked on 17 September 2006 at 1240 (2040 UTC). In color the radar reflectivity ranges from light blue (low) to dark green (moderate), which corresponds to greater numbers and/or sizes of particles. It cannot be determined whether the signal is due to large water droplets, ice particles, coarse-grained ash, or a mixture. Image created by Dave Schneider, AVO/USGS, using data and software from the NOAA National Climatic Data Center.

A cloud of sulfur dioxide gas was observed by colleagues at the Volcanic Emissions Group at the University of Maryland Baltimore. They used data collected at 1500 by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite (figure 5).

Figure (see Caption) Figure 5. Image showing the total amount of sulfur dioxide over Fourpeaked on 17 September 2006 as measured by the Ozone Monitoring Instrument on NASA's Aura satellite. Sulfur dioxide is displayed in Dobson Units (DU, a measure of the number of molecules in a unit area of the atmospheric column). Image created by the Volcanic Emissions Group at the University of Maryland Baltimore County.

On the basis of the suite of visual, radar, and satellite observations, all the 17 September clouds were inferred volcanic in origin. Although satellite data did not detect ash during this event, AVO received reports of a trace of ashfall at Nonvianuk Lake outlet (110 km WNW) and near Homer (150 km NE). Field observers saw deep scouring of a glacier flowing W from the summit, indicating flooding, probably from the 17 September event.In the caption to a 20 September AVO photo by K.L. Wallace there was noted a "continuous layer of discolored snow and ice above [~1 km elevation,]~3,000 feet asl on the NE flank of Fourpeaked volcano (S of Douglas volcano). Could possibly be ash from the 9/17/06 event."

Both fixed-wing and helicopter overflights in the Cape Douglas area on 20 September confirmed the source of volcanic activity to be Fourpeaked volcano. AVO raised the Level of Concern Color Code from "Not Assigned" to YELLOW on 20 September.

A 23 September observation flight conducted in relatively good weather permitted the first look at the summit since the event of 17 September. Observers saw a linear series of vents running N from the summit for about 1 km. Most of these vents vigorously emitted steam and other volcanic gases. Gas measurements indicated abundant quantities of sulfur dioxide, hydrogen sulfide, and carbon dioxide. Thermal measurements of up to 75°C were recorded at the vents, although steam was likely obscuring hotter areas. Adjacent glacial ice had been disrupted and showed signs of subsidence. Airborne gas measurements taken on 23, 24, and 30 September again documented high emission rates of sulfur dioxide, hydrogen sulfide, and carbon dioxide, and a distinct sulfur smell was evident up to 50 km from the summit. An AVO status report on 3 October noted that cloudy conditions had prevented visual or satellite observations, but limited seismic data being received did not indicate significant volcanic activity.

The AVO reported that volcanic unrest continued at Fourpeaked during 30 September-24 October. A seismometer installed on 25 September indicated ongoing low-level seismicity. Due to the limited number of seismometers, earthquake epicenters were not located. Emission rates of sulfur dioxide were high during 4-10 October and on 27 October. Observations were hindered due to cloud cover, but on 12 October AVO staff reported that two prominent vents were emitting steam and gas. Figure 6 shows several shots illustrating the enlarged opening in the ice on 15 October.

Figure (see Caption) Figure 6. Photographs of the steaming vent area at Fourpeaked volcano on 15 October 2006. Courtesy of Kate Bull (AVO-ADGGS).

On 20 October, field crews installed a web camera located 16 km (10 miles) N of Fourpeaked. Steam plumes originating from vents along the summit were visible via the web camera on 27 and 30 October. Steaming continued through at least 4 November (figure 7).

Figure (see Caption) Figure 7. A 4 November 2006 photograph documenting steaming on the uppermost section of the northern flank of Fourpeaked volcano. Courtesy of Jennifer Adleman (AVO/USGS).

Geologic Background. Poorly known Fourpeaked volcano in NE Katmai National Park consists of isolated outcrops surrounded by the Fourpeaked Glacier, which descends eastward almost to the Shelikof Strait. The orientation of andesitic lava flows and extensive hydrothermal alteration of rocks near the present summit suggest that it probably marks the vent area. Eruptive activity during the Holocene had not been confirmed prior to the first historical eruption in September 2006. A N-trending fissure extending 1 km from the summit produced minor ashfall.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA; Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA; and Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.avo.alaska.edu/); S.A. Carn, N.A. Krotkov, A.J. Krueger, and K. Yang, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA.


Home Reef (Tonga) — September 2006 Citation iconCite this Report

Home Reef

Tonga

18.992°S, 174.775°W; summit elev. -10 m

All times are local (unless otherwise noted)


Extensive pumice rafts between Tonga and Fiji during August-October

Pumice rafts drifting from Tonga to Fiji occurred during August-October 2006. The source of these pumice rafts was Home Reef, which was first observed to be in eruption on 9 August and was clearly building an island by 12 August (figure 2). A compilation of report sightings through mid-October 2006, plotted using Google Earth, shows the timing and distribution of the pumice rafts that are discussed in this report (figure 3). As is our convention, and as available, a list of contributors (and their vessels) is noted in last section of this report.

Pumice traveled both N and S around Fiji's Lau Group. To the N, pumice reached Taveuni through the Nanuku passage and entered the Koro sea, washing onto southern Vanua Levu, before moving into the Bligh Waters N of Viti Levu by 20 September. To the S, extensive pumice was seen N of Vatoa Island on 16 September, and on Kadavu Island by the end of the month. Pumice was also encountered by the Encore II W of Viti Levu on 30 September while enroute to New Caledonia.

Figure (see Caption) Figure 2. Photograph of the new island being built by the eruption at Home Reef as seen on 12 August 2006. The island was ~1.5 km in diameter. View is towards the W from about 2.8 km away. Courtesy of Fredrik Fransson of the Maiken.
Figure (see Caption) Figure 3. Map of Tonga (right) and Fiji (upper left) showing dates and locations where observers saw pumice rafts (placemarks with dots) or where mariners crossing between Tonga and Fiji failed to see rafts (placemarks with crosses). Some locations are approximate; see text for additional details and sources of each observation. The base map is from Google Earth with points plotted by Bulletin editors.

Early observations of the eruption. The news service Matangi Tonga Online quoted Allan Bowe, the owner of the Mounu Island Resort in southern Vava'u, regarding volcanic activity in the direction of Home Reef during 9-11 August. Bowe heard ". . . what sounded like continuous thunder rumbling to the S and there was a huge plume of smoke and cloud rising up into the sky." In another Matangi news article, Siaosi Fenukitau, a captain of one of the fishing boats of the Maritime Projects Co. (Tonga) Ltd., reported that around mid-September they sighted a new volcanic island near Home Reef that was larger than Fotuha'a, a small island in Ha'apai with a population of about 134 people.

The yacht Maiken left Neiafu on 11 August, passing the N side of Late Island. After about 9 km the crew noticed brown, somewhat grainy streaks in the water. The streaks became larger and more frequent as they continued SW "until the whole horizon was a solid line to what looked like a desert." The brownish pumice fragments the size of a fist were floating in water that was strangely green. They motored into the vast (many miles wide) belt of densely packed pumice, and within seconds Maiken slowed down from seven to one knot. Initially the thin layer on the surface was pushed away by the bow wave, but when they entered the solid field it started to pile up and "behaved like wet concrete" and "looked like rolling sand dunes as far as the eye could see." After retreating from the pumice with only minor paint abrasion along the waterline, and then cleaning their intake filters, they decided to anchor in Vaiutukakau bay outside Vava'u for the night. The next morning, 12 August, they received radio confirmation of an eruption, but the vent and extent were uncertain. They decided to go S to avoid the pumice rafts floating NW, heading SSW until they encountered the pumice, then sailing alongside until the rafts were broken up enough to safely travel through.

As they approached Home Reef it became clear that one of the clouds on the horizon was a volcanic plume. Observations from a closer vantage point revealed that an intermittent "massive black pillar shot upwards toward the sky" and particles were raining down. Since the wind was pushing the plume NW, the Maiken motored up to within 2.8 km of the island (to 18°59.5'S, 174°46.3'W) while the sun was going down. Multiple peaks forming a crater open to the sea on one side were visible, and it looked like it was "made of black coal." Not wanting to encounter more pumice rafts after dark, they continued SSW towards the southern part of the Lau Group.

Pumice sightings between Tonga and Fiji. Boats that later noted seeing pumice in Fiji did not report any activity or rafts near Tonga during 27-29 August. The Soren Larsen sailed through "a sea of floating pumice" one evening that "sounded like we were sailing through ice" just before reaching Fiji. This encounter was probably on 30 August when their online tracker located the ship just W of the central Lau islands after departing Neiafu on the 28th. No eruptive activity or pumice was noted in the online log of the Soren Larsen for 14-15 and 23-24 August when they transited to northern Tonga to the E of Home Reef.

While the Encore II crew was visiting the Mounu Island Resort on 2 September there were "grapefruit-sized" pumice pieces on the beach. A few days later, while listening to the "Rag of the Air" net broadcast out of Fiji, the Encore II crew learned of pumice rafts along their expected route. The operator of this broadcast, Jim Bandy, provides weather reports for boats going between Tonga and Fiji. One report was of a mass of pumice about 11 km long and at least a meter ("many feet") deep. The Encore II departed from Neiafu on 8 September on a course around a set of Fijian islands and reefs called the Lau Group. The crew believed that this route, going NW around the Lau Group, helped them avoid most of the pumice.

As the Encore II approached their turning point about two thirds of the way to Fiji, on 10 September, they encountered "rivers of pumice" floating roughly parallel to their NW course due to the SE winds (figure 4). Some pumice fragments that they collected were about 5-10 cm in diameter, although most were about the size of pea gravel. The parallel streams of pumice, only a single layer in depth, were sometimes up to 90 m wide and 400 m long. The crew later heard reports from several boats that had taken a more westerly route through the Lau Group to Fiji and encountered much larger areas of pumice. The crew on the Norwegian sailboat Stormsvalen went through larger and thicker areas of pumice, leaving a track in the pumice as they went through (figures 5 and 6). They noted that boats traveling through the pumice during higher winds and seas encountered a problem of airborne pumice pelting the crews and their boats. One crew reported pumice covering their deck.

0 Figure 4. Photograph showing small areas of floating pumice just NE of the Lau Group of islands, Fiji, around 10 September 2006. Courtesy of the Encore II crew.
Figure (see Caption) Figure 5. Photograph showing a large pumice raft near the Lau Group of islands, Fiji, on an unknown date in early to mid-September 2006. Courtesy of the Stormsvalen crew via the Encore II.
Figure (see Caption) Figure 6. View of a large pumice raft after the passage of a sailing vessel near the Lau Group of islands, Fiji, on an unknown date in early to mid-September 2006. Courtesy of the Stormsvalen crew via the Encore II.

A sailboat blog entry by Sara Berman and Jean Philippe Chabot noted a "strong sulfur odor" in the direction of the volcano upon leaving Tongan waters around 20 September. As they progressed SW towards Fiji they passed through streams of pumice containing pieces ranging from very small pebbles to larger pieces the size of a baseball. Every time a wave crashed on deck they heard the pumice making its way onto the boat and into the cockpit.On 30 September the Windbird log noted that ". . . cruisers are still having to avoid the huge pumice field that is floating about between Tonga and Fiji."

Bob McDavitt's "Weathergram" for 15 October noted that reports from yachts sailing between Tonga and Fiji indicated an absence of pumice. These observations suggest that the bulk of material produced by the eruption, or series of eruptions, had crossed to Fiji by mid-October.

Pumice rafts in northern Fiji. The earliest known direct observations of the floating pumice in Fiji come from a boat with callsign KB1LSY, the crew of which noted that "thick pumice" slowed them to 2 knots for 30 minutes during the early morning hours of 28 August. This occurred as they approached the northern islands of the Lau Group in Fiji, about 500 km NW of Home Reef.

According to Roberta Davis, the pumice arrived at Taveuni, Fiji, on 14 September. There were several rafts ~300 m from shore with other rafts scattered farther out. Local mariners noted that pieces in the top layer were approximately the size of pea gravel. Suspended below the surface were pieces almost as large as footballs. The beaches on the northern shores of Taveuni were covered in what appeared to be black popcorn. The pumice was present at Taveuni for up to 6 days.

On 19 September David Forsythe reported that large rafts of pumice were passing through the northern Lau group in Fiji (figure 7). He noted gooseneck barnacles up to 10 mm long on the largest pieces. Bulletin editors found compiled growth rates for various stalked barnacles ( Thiel and Gutow, 2005), which indicated 17-29 days of growth.

Figure (see Caption) Figure 7. Panoramic view of Indigo Swan Beach filled with pumice, Naitauba Island, Fiji, as seen in September 2006. Courtesy of David Forsythe.

The Encore II crew observed pumice along the S side of Vanua Levu, W of the Lau Group, around 16 September. They noted pumice at Fawn Harbour that obscured the channel into the harbor and it made a boat at anchor appear to be aground on an island. They also observed streams of pumice near the Makogai Channel on 20 September. The Fiji Times Online reported on 20 September that villagers living along the coastal areas of Saqani in Cakaudrove (Vanua Levu) were battling to clear their pumice-covered seashores and rivers. Villagers saw the pumice floating in the sea near their homes on 18 September, and by the next day the pumice covered the river and villagers could not fish or travel by boats and bamboo rafts to their plantations.

While diving at the "Bligh Triangle" of Fiji at sites NW of Viti Levu, the crew aboard the Nai'a encountered floating pumice during 20 September-7 October. The pumice was "surrounding the Nai'a and the skiffs with occasional big carpets of floating rock." Roman Leslie, an Australian volcanologist who was fishing in Koro (Lomaiviti Group), also observed the pumice in late September.Scientists aboard the research vessel Yokosuka observed pumice settling to the shore of Viti Levu on 6 October. The rafts were in bands up to 70-80 m wide and several hundred meters long. The pumice fragments were fully abraded, and dominantly less than 1 cm in diameter with occasional large blocks up to 15-20 cm in diameter. The pumice seemed to be quite phenocryst-rich. The sound of the moving, abrading rafts was described as "sizzling."

Pumice rafts in southern Fiji. A biologist aboard the National Geographic motor vessel Endeavour reported that on the morning of 16 September they observed an extensive region of floating pumice "... in long, wind-driven rows, approximately 1-5 m wide and up to several hundred meters long." Pieces of pumice averaged 0.5-8 cm in longest dimension. The largest piece observed was approximately 15 cm in longest dimension. The observations continued over the next 90 km, for 3.5 hours, with little interruption, until they made landfall at Vatoa Island in the Lau Group. Moderate windrows of pumice, up to several inches deep, were observed on the beaches of Vatoa.

Roger Matthews arrived in Kadavu, Fiji, on 30 September and reported that pumice had been coming ashore for about a week. On the southern coast of the island near the airport, the layer of pumice on 30 September was 10-15 cm thick floating on top of ~1 m of water (figure 8). Farther NE, pumice that began coming ashore at the Matava Resort on 3 October carried goose barnacle shells that measured about 2-3 mm on the bigger clasts. By 7 October barnacle size on arriving pumice had increased to around 4-6 mm. While scuba diving, Matthews noted neutrally buoyant bits of pumice, generally in the 3-10 mm size range, down to at least 40 m water depth. The pumice did not appear to have an even size distribution (figure 9). There were a number of big clasts, 2-3 cm, with a large amount of material in the 8-15 mm range. In the shore deposits there appeared to be a large volume of fines in the sub-2 mm size. The material was clean with no algae, just the occasional barnacles. The clasts contained phenocrysts up to 2 mm long. The raft drifted in and out depending on wind conditions, at times extending 75-100 m from shore, and invaded streams at high tide. On shore there were 20-cm-thick deposits, some of which was used as fill behind the sea walls (figure 10).

Figure (see Caption) Figure 8. Pumice found floating in North Bay along the southern coast of Kadavu, Fiji, on 30 September 2006. Courtesy of Roger Matthews.
Figure (see Caption) Figure 9. A close up view of pumice seen near Matava Resort on the S shore of Kadavu, Fiji, 3 October 2006. Courtesy of Roger Matthews.
Figure (see Caption) Figure 10. Pumice deposits seen at ebb tide near Matava Resort on the S shore of Kadavu, Fiji, 8 October 2006. Some of the pumice has been used as fill behind the sea wall. Deposits can be seen on the steps into the water, and waves propagating through the pumice could still break. Courtesy of Roger Matthews.

A 31 October story in the Fiji Times described transportation difficulties between Daviqele Village, on the W end of Kadavu, and other parts of the island due to pumice that a resident said had "covered [Naluvea Bay] for over two months now." Similar problems were reported by Adrian Watt at Matava Resort on the S shore of Kadavu. In an email relayed by Roberta Davis, Watt noted that by 2 November the pumice had mostly stopped coming in, with "... just a few strands of small pieces being blown along wind lines here and there." The pieces were generally 5-10 mm in diameter, but several were bigger, and one was larger than 30 cm across. Large bays on Kadavu's SE side were pumice choked, hampering boat travel, and clogged cooling systems damaged or destroyed many outboard engines.

Reference. Thiel, M., and Gutow, L., 2005, The ecology of rafting in the marine environment. II. The rafting organisms and community: Oceanography and Marine Biology: An Annual Review, 2005, v. 43, p. 279-418.

Geologic Background. Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, copious amounts of floating pumice, and an ephemeral island 500 x 1500 m wide, with cliffs 30-50 m high that enclosed a water-filled crater. Another island-forming eruption in 2006 produced widespread dacitic pumice rafts that reached as far as Australia.

Information Contacts: Fredrik Fransson and Håkan Larsson, Yacht Maiken, 32 Macrossan St., Unit 70, Brisbane 4000, Australia (URL: http://yacht-maiken.blogspot.com/); Paul and Nancy Horst, Encore II (URL: http://www.encorevoyages.com/); KB1LSY Crew (URL: http://www.pangolin.co.nz/yotreps/tracker.php?ident=KB1LSY); Matangi Tonga Online, Vava'u Press Ltd., PO Box 958, Nuku'alofa, Tonga (URL: http://www.matangitonga.to/); Roger Matthews, Private Bag 93500, Takapuna, North Shore City 1332, New Zealand; Ken Tani, R/V Yokosuka; David Forsythe, Naitauba Island, Fiji; David Cothran, 1211 Colestin Rd., Ashland, OR 97520, USA; Bob McDavitt's Weathergram (URL: http://www.pangolin.co.nz/yotreps/list_manager.php##Bob McDavitt's Pacific Weathergrams); Nick Sambrook, Tall Ship Soren Larsen, P.O.Box 60-660 Titirangi Auckland 0642, New Zealand (URL: http://www.sorenlarsen.co.nz/2006/V237_Tonga-Fiji/V237_Tonga-Fiji_Nick.htm, http://www.sorenlarsen.co.nz/Voylog_Track.htm); Windbird Crew (URL: http://handleysail.com/logs/?cat=1&paged=2); NAI'A Liveaboard Scuba Diving, Lautoka, Fiji (URL: http://www.naia.com.fj/); Roberta Davis, Makaira by the Sea, Taveuni, Fiji (URL: http://www.fijibeachfrontatmakaira.com/); Adrian Watt, Matava Resort, Kadavu, Fiji (URL: http://www.matava.com/); Sara Berman and Jean Philippe Chabot (URL: http://zayasail.blogspot.com/2006/09/east.html).


Montagu Island (United Kingdom) — September 2006 Citation iconCite this Report

Montagu Island

United Kingdom

58.445°S, 26.374°W; summit elev. 1370 m

All times are local (unless otherwise noted)


Five years of nearly persistent eruptive activity

Matthew Patrick reported that the month of October represents the 5-year anniversary of the start of the still-ongoing eruption at Mount Belinda on Montagu Island. The first satellite thermal alert for the volcano occurred on 20 October 2001, and was the first definitive record of historical volcanic activity on the island (BGVN 28:02) (Patrick and others, 2005). The MODVOLC monitoring system uses MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data processed at the University of Hawai'i-Manoa. Current MODVOLC results, shown in figure 16A, indicate more-or-less persistent activity throughout the 5-year period, with radiant heat flux apparently peaking in late 2005 and early 2006.

Figure (see Caption) Figure 16. Plots of MODVOLC data at Belinda volcano on Montagu Island from 2001 to October 2006. (A) Chronological graph of radiant heat output from Mount Belinda measured from satellite sensors. (B) Chronological plot showing the distance of satellite-measured thermal anomaly pixels from the Mount Belinda vent. Courtesy of HIGP Thermal Alerts Team.

Landsat and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) imagery has shown that the eruption consisted of central vent activity producing lava flows. Small-scale explosive activity has also commonly blanketed the E side of the island. Three effusive events have been observed in ASTER/Landsat imagery, with the most recent (September-October 2005) producing a lava flow that traveled 3.5 km and reached the sea to build a 500-m-wide delta of lava (BGVN 30:09 and 30:11).

Figure 16B shows relative location (distance from the vent) comparing Mount Belinda's vent with the locations of MODVOLC alert pixels. This plot clearly shows longer flows during the September 2005 effusive event. Following this period, there were several other long-distance events. It is unclear if these reflect additional effusive events.

In addition, the first two effusive events observed in the ASTER/Landsat images do not appear on the MODVOLC plot (figure 16B), due either to cloud cover or their short flow lengths. Since the beginning of 2006, no cloud-free ASTER images have been available.

Geographic terminology. The nomenclature of volcanic features on Montagu Island, particularly in regard to Mount Belinda, has been quite variable. Although the name Montagu has been applied to the major volcanic edifice forming the island (LeMasurier and Thomson, 1990), the name Mount Belinda has been variously applied to the entire volcano, the currently active young cone on the northern side of the island, the 6-km-wide summit caldera, and a peak on the southern caldera rim that is the island's high point. In consultation with John Smellie of the British Antarctic Survey, we have used Montagu to refer to the volcano forming the island and Mount Belinda for the currently active cone.

References. LeMasurier, W.E., and Thomson, J.W. (eds.), 1990, Volcanoes of the Antarctic Plate and Southern Oceans: Washington, D C: American Geophysical Union, 487 p.

Patrick, M.R., Smellie, J.L., Harris, A.J.L., Wright, R., Dean, K., Izbekov, P., Garbeil, H., and Pilger, E., 2005, First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands, Bulletin of Volcanology, v. 67, no. 5, p. 415-422.

Geologic Background. The largest of the South Sandwich Islands, Montagu consists of a massive shield volcano cut by a 6-km-wide ice-filled summit caldera. The summit of the 10 x 12 km wide island rises about 3000 m from the sea floor between Bristol and Saunders Islands. Around 90% of the island is ice-covered; glaciers extending to the sea typically form vertical ice cliffs. The name Mount Belinda has been applied both to the high point at the southern end of the summit caldera and to the young central cone. Mount Oceanite, an isolated 900-m-high peak with a 270-m-wide summit crater, lies at the SE tip of the island and was the source of lava flows exposed at Mathias Point and Allen Point. There was no record of Holocene or historical eruptive activity until MODIS satellite data, beginning in late 2001, revealed thermal anomalies consistent with lava lake activity that has been persistent since then. Apparent plumes and single anomalous pixels were observed intermittently on AVHRR images during the period March 1995 to February 1998, possibly indicating earlier unconfirmed and more sporadic volcanic activity.

Information Contacts: Matthew Patrick, Dept. of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA; HIGP MODIS Thermal Alert System, Hawai'i Institute of Geophysics and Planetology (HIGP), University of Hawaii at Manoa, 168 East-West Road, Post 602, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); John Smellie, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingly Road, Cambridge CB3 0ET, United Kingdom (URL: https://www.bas.ac.uk/).


Rabaul (Papua New Guinea) — September 2006 Citation iconCite this Report

Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


Strong eruption at Tavurvur ejected ash and large plumes to the troposphere

A 7 October Rabaul eruption obscured visibility in and around the caldera, which sits at the NE end of New Britain Island (figure 42). The eruption took place at the intra-caldera cone Tavurvur, and emissions included lava flows. Intermittent eruptions had occurred at Tavurvur since 1994, the last of which took place on 15 January 2006 (BGVN 31:02). Photos by pilots shortly after the eruption documented a dramatic umbrella-shaped plume, which rose to the tropopause and created an SO2 cloud that later divided into two parts, one moving NW, the other SE.

Figure (see Caption) Figure 42. (Top) Index maps indicating the location and geography around Rabaul caldera. (Bottom) A map of Rabaul derived from work by Almond and McKee and prepared by Lyn Topinka (US Geological Survey). For other maps see previous Bulletin reports on Rabaul (most recently, BGVN 28:01).

Rabaul Volcano Observatory (RVO) observations. The RVO announced that a sustained eruption from Tavurvur did not appear to have been any immediate precursors apart from a small deflation. The sub-Plinian eruption began at about 0845 on 7 October 2006 and continued into the early afternoon. Semi-continuous to rhythmic air blasts were obvious in Rabaul town, with doors slamming and windows rattling. Rabaul received moderately heavy ashfall; heavy lapilli of ~ 1 mm diameter fell, and a few lithics up to 3 cm across fell around the S and SW parts of the caldera. According to Herman Patia at RVO, a small pumice raft accumulated in Greet Harbor and pumice was still drifting about several weeks later.

Ashfall affected the whole of the Gazelle peninsula (the name given to the bulbous, 50-km-diameter NE end of New Britain island). About 1 cm of ash was deposited on the SW side of the caldera in the Blue Lagoon-Vulcan sector. Ashfall occurred ~ 7 km SE of Rabaul caldera's center point in Kokopo and -20 km S of the center point in Warangoi. The density of ashfall was such that Tavurvur was obscured from all directions. In the town of Rabaul the experience was very similar to the October 1996 and January 1997 Strombolian eruptions.

At 1200 on 7 October 2006 the RSAM was about 1900 units and its rate appeared to be decreasing. (The Real-time Seismic Amplitude is an often-used tool to summarize seismic activity during volcanic crises by presenting a measure of the average amplitude of ground shaking over successive 10-min intervals.)

Thick ash clouds rose to a height of about 18 km. The cloud subsequently dispersed over a broad western swath (N to W to S).

The nature of the eruption changed to Strombolian at 1415 hours, with activity characterized by frequent explosions accompanied by shock waves. At 1730 hours, the Strombolian activity began to subside. A moderate to bright glow was visible during the evening of 7 October on Tavurvur's N rim, accompanied by occasional explosions and loud roaring noises throughout the night.

In the morning of 8 October, thick white and blue vapor accompanied occasional ash explosions drifted N and NW of Tavurvur. Inspection from Rapindik (2 km NNW from Tavurvur) revealed lava flows emplaced down the cone's W and N flanks. The W flank flow went into the harbor and caused small secondary explosions; visibility of the N flank was poor due to the white vapor emission. The RSAM level decreased to the background value of ~ 70 units.

Herman Patia reported that by 28 October 2006 the eruption had quieted down with only occasional ash emission accompanied by rare explosions. Seismic activity was at a low level and ground deformation was at a low rate. On 30 October mild eruptive activity continued at Tavurvur. The activity consisted of continuous emission of thick pale to dark gray ash clouds that drifted N to NW of the volcano. Fine ash fall occurred in the NE caldera at Namanula, and also in surrounding areas downwind and on the E side of Rabaul Town. There were no audible noises and no glow visible. The low-level eruptive activity consisted of occasional ash emissions similar to those that have occurred regularly since 1994.

Pilot observations. Figures 43 and 44 are pilot's photographs provided by Tony Gridley, Air Niugini, indicating the well-developed ash clouds visible 1-2 hours after the eruption. The photos are reminiscent of the 20 September 1994 photo of the eruption cloud taken from the orbiting Space Shuttle, an oblique, downward-looking perspective from the NE about 24 hours after the start of that eruption (BGVN 19:08).

Figure (see Caption) Figure 43. Aerial photo taken 1 or 2 hours after the eruption of 7 October 2006 at ~ 3.7 km (~ 12,000 ft) and ~ 90 km (~ 50 nautical miles) from Tokua airport (Rabaul's new airport, on the S side of the caldera) while flying at a heading of about 060° (i.e. looking ENE). The flight was "on the Hoskins-Tokua track." Courtesy of Tony Gridley, Air Niugini.
Figure (see Caption) Figure 44. Aerial photo taken 1 or 2 hours after the eruption of 7 October 2006 at ~ 3.7 km (~ 12,000 ft) and ~ 90 km from Tokua airport, heading about 060°. Courtesy of Tony Gridley, Air Niugini.

Satellite observations. According to Andrew Tupper, the 7 October eruption was clearly visible on infrared and visible imagery (to around tropopause altitudes). Figure 45 shows the ash cloud imaged from the MODIS satellite on 7 October 2006. Figure 46 depicts the sulfur dioxide (SO2) in Dobson Units (DU) from the Ozone Monitoring Instrument (OMI) for 7-9 October 2006. Further details appear in the figure caption. The SO2 concentration-pathlengths on the figure are shown using the logarithmic scale of Dobson Units. (As one explanation of this unit, if all SO2 in the air column the satellite observed was flattened into a thin layer at the surface of the Earth at a temperature of 0° C, then 1 Dobson Unit would make a layer of pure SO2 0.01 mm thick.)

Figure (see Caption) Figure 45. True-color (above) and false-color (below) images of a Rabaul eruption cloud created by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite, 7 October 2006. Volcanic emissions block the view of most of the island but Rabaul's approximate location is at the solid triangle. The brown or tan plume in the E clearly bears volcanic ash. The bright "cloud" to the immediate left of the brown ash represents a portion of the volcanic ash plume that reached a high enough altitude for the water content of that plume to turn to ice crystals that "white out" the ash content that would otherwise appear tan or brown. Courtesy of the NASA Earth Observatory.
Figure (see Caption) Figure 46. The Rabaul eruption injected SO2 into the atmosphere and measurements from satellite spectrometers led to creation of this series of images mapping the SO2 concentrations over the region during 7-9 October 2006. Data are from the Ozone Monitoring Instrument on NASA's Aura satellite. On 7 October, high SO2 concentrations lingered over New Britain. By 8 October, the original plume had split into two clouds, one spreading NW, the other, SE. On 9 October, the SO2 had diffused more, but a core of elevated concentration-pathlength values remained in the northern plume. Courtesy of NASA Earth Observatory and Simon Carn, University of Maryland Baltimore County.

Based on information from the RVO, the Darwin VAAC reported that a brief eruption of Rabaul on 11 October produced a plume that reached an altitude of 7.6 km altitude and dissipated NW. Continuous low-level emissions and vulcanian eruptions produced plumes to 1 km altitude during 12-17 October.

Moderate Resolution Infrared Spectroradiometry (MODIS) thermal anomalies. Table 4 shows the thermal anomalies as measured from the MODIS satellite during the eruption period. Note that there were no anomalies for several months before this period. The anomalies are in harmony with the observed lava flows.

Table 4. MODIS thermal anomalies for Rabaul volcano for 7-17 October 2006. Courtesy of Hawai'i Institute of Geophysics and Planetology.

Date Time (UTC) Pixels Satellite
07 Oct 2006 1140 4 Terra
08 Oct 2006 0000 2 Terra
08 Oct 2006 1220 6 Terra
08 Oct 2006 1520 4 Aqua
10 Oct 2006 1210 2 Terra
11 Oct 2006 0035 1 Terra
11 Oct 2006 1250 1 Terra
15 Oct 2006 1230 1 Terra
15 Oct 2006 1525 3 Aqua
17 Oct 2006 1215 1 Terra
22 Oct 2006 0015 2 Terra
22 Oct 2006 1535 1 Aqua
24 Oct 2006 1220 2 Terra

News releases. According to Reuters news service the 7 October blast shattered windows up to 12 km from the caldera. In 1994, a large eruption at Tavurvur and the nearby Vulcan peak destroyed much of Rabaul, covering the airport and much of the town with ash, and forcing the construction of a new capital, Kokopo, 20 km away. Ash was falling on Kokopo, causing power and phone cuts. There were no reports of death or injuries. In addition Reuters noted that "Rabaul Chamber of Commerce President and hotelier Bruce Alexander told Australian Associated Press that around 2,000 people?or 90 percent of the local population?had fled the town as Mt. Tavurvur erupted. All flights into Tokua airport across the harbor from Rabaul had been canceled due to ash falls."

According to The Sydney Morning Herald, with 90% of the residents absent and only essential personnel in Rabaul, local officials feared looters. Accordingly, extra police were called in, and armed police patrols were stepped up.

Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Information Contacts: Steve Saunders and Herman Patia, Rabaul Volcanological Observatory (RVO), Department of Mining, Private Mail Bag, Port Moresby Post Office, National Capitol District, Papua, New Guinea; Andrews Tupper, Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Darwin, Australia; Peter Webley, ARSC/UAF, 909 Koyukuk Drive, Fairbanks, Alaska; Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA; National Aeronautics and Space Administration Earth Observatory (URL: http://earthobservatory.nasa.gov/NaturalHazards); HIGP MODIS Thermal Alert System, Hawai'i Institute of Geophysics and Planetology (HIGP), University of Hawaii at Manoa, 168 East-West Road, Post 602, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


San Cristobal (Nicaragua) — September 2006 Citation iconCite this Report

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Multi-year update: 13 June 2004, local ash fall; early 2006, small eruptions

San Cristóbal was last reported on in BGVN 28:10, covering intermittent gas and ash emissions between August 2002 and September 2003. The Instituto Nicarag?ense de Estudios Territoriales (INETER) noted that low seismicity and minor gas and ash emissions characterized the period from October 2003 to June 2004.

On 7 June 2004 a lahar flowed more than 600 m. On 13 June 2004, an eruption caused ash to fall in the communities of Las Rojas, El Chonco, and El Viejo.

On 20 July 2004 at 1430, an M 4.3 earthquake occurred to the N of the volcano at a depth of less than four km. The earthquake was felt in the regions of Carlos Fonseca, Villa 15 de Julio, La Suiza, Las Rojas, Mocorón, San Jose del Obraje, Santa Carlota, San Antonio, Ranchería, and bordering regions. Some houses were damaged and the population was alarmed. The earthquake was felt in Matagalpa and Ocotal, and San Cristóbal emitted abundant gases for the following two days. During the rest of July, 95 aftershocks were registered; residents felt two more earthquakes, which occurred on 23 and 30 July.

During August to early December 2004, minor seismicity and ash and gas emissions were the norm. Ash explosions occurred on 3, 4, and 7 December. According to local people, ash fell in Chinandega and El Viejo.

The next available report discussed 16-22 November 2005. INETER detected an increase in seismicity beginning on 19 November. Increased tremor was interpreted as being related to gas and ash emissions. Ash fell W of the volcano and near the town of Chinandega, ~ 15 km SW of the volcano. The amount of tremor decreased later.

According to an Associated Press news report, explosions on 6 March 2006 produced columns of ash and gas that rose above the volcano. The activity ceased by 8 March and there were no evacuations.

INETER noted that phreatomagmatic eruptions began at San Cristóbal on 21 April 2006. Seismic tremor increased the same day around 1300. Small explosions produced gas-and-ash plumes during 21-23 April that deposited small amounts of ash in nearby towns.

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: Virginia Tenorio, Emilio Talavera, and Martha Navarro, Instituto Nicaraguense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Associated Press (URL: http://www.ap.org/).


Soufriere Hills (United Kingdom) — September 2006 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Extrusive dome dynamics during May-September 2006

Since the 20 May 2006 dome collapse, the lava dome at Soufrière Hills has continued to grow. Only weeks after the collapse, the alert level was raised to 4 as a result of increased seismic activity. At approximately 1300 on 30 June, the lava dome partially collapsed again, producing pyroclastic flows that traveled E. According to the Washington VAAC, a pilot reported an ash plume that reached ~ 3 km altitude and drifted NW. At 1830 on 30 June, Montserrat Volcano Observatory (MVO) indicated a second dome collapse that also generated ash plumes to an altitude of 3.0-3.5 km (figure 70). According to MVO, on 27 June (prior to the collapse on 30 June) the lava dome had an estimated volume of 27 million cubic meters.

Figure (see Caption) Figure 70. A photo taken on 30 June 2006 of Soufrière Hills as viewed from the Montserrat Volcano Observatory showing the first partial dome collapse of the day. The partial collapse began just before 1300 local time and lasted ~ 20 minutes, generating ash clouds to an altitude of ~ 3.5 km that drifted WNW. Pyroclastic flows (left side of picture) were confined to the Tar River valley and ultimately reached the sea. Most of the lava dome remained intact. Photo courtesy of MVO.

On 7 July, the alert level was lowered from 4 to 3. Increased rockfall activity and dome growth to the NE were observed on 21 July, and the post-collapse dome developed an asymmetric profile owing to a blocky spine on the NE. On 18 July the spine's summit stood at ~ 895 m elevation. As the dome continued to grow during July (figure 71), visual observations revealed that the still intact blocky spine began leaning E.

Figure (see Caption) Figure 71. A photo of Soufrière Hills taken on 25 July showing spines at the summit of the lava dome as viewed from the NE. Photo courtesy Greg Scott of Caribbean Helicopters.

During August the dome lost spines from its crest, giving it a more symmetrical profile as it continued to grow E. Heightened activity during the last week of August included an increase in seismicity and pyroclastic flows. On 29 August, pyroclastic flows reached the Tar River valley and generated a steam-and-ash cloud that reached an altitude of ~ 9 km. Heavy rainfall produced mudflows around the base of the volcano.

At 0300 on 31 August, two vigorous ash-and-steam vents opened on the W and N flanks of the dome (figure 72). The venting episode was audible at times from the town of Salem and the surrounding areas. MVO noted the continued dome growth and the opening of these vents when on 31 August they raised the alert level to 4.

Figure (see Caption) Figure 72. Photos showing activity at Soufrière Hills on 31 August 2006. (top) Emissions from the vigorous new vent inside Gages wall (Gages Mountain to the left of the vent and Chances Peak to the right). (bottom) N-looking photo showing the N crater wall, lava dome, and the new vigorous ash vent on the N side of the lava dome. Courtesy of MVO.

Heightened activity continued in September. The dome continued to develop substantially with a majority of growth on the W side. The vents that opened on 31 August remained active, with the vent above Gage's wall emitting a plume of hot gases and the N vent on the dome producing mainly ash-and-steam (figure 73). The opening of these vents coincided with high lava extrusion rates and consequent dome growth.

Figure (see Caption) Figure 73. A photo showing lava-dome glow viewed from the S at MVO at 2200 on 7 September 2006. Incandescent rocks can be seen tumbling down all flanks of the lava dome on this clear night. A faint glow is visible from the very hot and active gas vent just inside the Gages wall (just right of the dome in the picture). Photo courtesy of MVO.

At 0100 on 10 September, the vent above Gage's wall became more vigorous throughout the day, broadening the vent and generating a wide vertical ash column. By 1300 the venting there became violent and explosive with black jets of ash rising ~ 100 m. Pyroclastic flows traveled down the Gages valley for ~ 1 km (figure 74). The vent formed a crater in the Gages wall, reducing its height compared to that of Chances Peak by 30-50 m. By 11 September, pyroclastic flows from vent emissions had ceased, but vigorous ash venting continued. At 0830 an overhanging lava lobe that developed on the NE collapsed sending a pyroclastic flow almost to the sea at the end of the Tar River valley.

Figure (see Caption) Figure 74. A photo showing explosive ash venting from a spot above Gages valley at 1530 on 10 September. Pyroclastic flows can be seen advancing into Gages valley in the foreground. Photo courtesy of MVO.

Although volcanic tremor ended early on 16 September, an intense episode of volcanic tremor lasting just half an hour started at 1400 on 19 September. It was accompanied by intense rockfall activity giving rise to minor pyroclastic flows down the N and NE flanks of the lava dome. On 21 September the alert level was reduced to 3.

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), Fleming, Montserrat, West Indies (URL: http://www.mvo.ms/).


Sulu Range (Papua New Guinea) — September 2006 Citation iconCite this Report

Sulu Range

Papua New Guinea

5.5°S, 150.942°E; summit elev. 610 m

All times are local (unless otherwise noted)


Volcano seismicity declines in September and October 2006

On 31 October 2006 the Rabaul Volcanological Observatory (RVO) issued a followup report to the eruptive activity in the Sulu Range through much of October. Sulu Range was previously discussed in BGVN 31:07, but that report was ambiguous on the nature of the activity that had taken place during July 2006. This report and personal communications establishes that RVO staff are doubtful that the most energetic events were magmatic in character. Furthermore, RVO reported that in the weeks that followed, seismicity continued to decline.

The seismic unrest that began on 6 July declined from over 2,000 daily volcano-tectonic (VT) events to below 50 daily VT events during October (figure 2). The number fluctuated between 35 and 50 from late September to early October and between 5 and 25 during the third week of October.

Figure (see Caption) Figure 2. Sulu Range seismicity plot of daily VT earthquakes from 22 July 2006 to 24 October 2006 at the Kaiamu Seismic Station. The station did not operate on the days that lack earthquakes. Courtesy of RVO.

RVO noted that about two to three felt earthquakes with intensity 2 continued to be felt daily at irregular intervals within the Bialla area and that white steam emissions from the Silanga Hot Springs were still visible from Bialla. In addition, a moderately strong sulfur smell from the Silanga and Talopu hot springs continued to be reported.

An analysis by RVO scientists concluded that at no point did magma reach the surface. The declining trend in seismic activity from early to late October may indicate that the new magma that apparently intruded to shallow levels in July is beginning to stall.

A permanent seismic station will be installed at Kaiamu in December 2006 to provide continuous monitoring of activity from the Sulu Range and surrounding areas.

In an extension of elevated regional tectonic seismicity, a strong earthquake, M ~ 6.5, struck the S side of central New Britain on 17 October. The USGS computed the focal depth as ~ 60 km, with epicenter ~ 50 km S of the Sulu Range. According to a USGS machine-generated shaking and intensity map, the Sulu Range lies within the zone of highest computed intensity (VI).

Geologic Background. The Sulu Range consists of a cluster of partially overlapping small stratovolcanoes and lava domes in north-central New Britain off Bangula Bay. The 610-m Mount Malopu at the southern end forms the high point of the basaltic-to-rhyolitic complex. Kaiamu maar forms a peninsula with a small lake extending about 1 km into Bangula Bay at the NW side of the Sulu Range. The Walo hydrothermal area, consisting of solfataras and mud pots, lies on the coastal plain west of the SW base of the Sulu Range. No historical eruptions are known from the Sulu Range, although some of the cones display a relatively undissected morphology. A vigorous new fumarolic vent opened in 2006, preceded by vegetation die-off, seismicity, and dust-producing landslides.

Information Contacts: Steve Saunders and Herman Patia, Rabaul Volcanological Observatory (RVO), Department of Mining, Private Mail Bag, Port Moresby Post Office, National Capitol District, Papua, New Guinea; USGS Earthquakes Hazard Program (URL: http://earthquakes.usgs.gov/)

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements  Obituaries

Misc 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 subject.

Additional Reports  False Reports