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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

Tinakula (Solomon Islands) Thermal anomalies in satellite data December 2018-June 2019; ship visit January 2019

Piton de la Fournaise (France) Eruptive episodes in February-March and June 2019; multiple fissures and lava flows

Semeru (Indonesia) Decreased activity after October 2018

Heard (Australia) Thermal hotspots continue during October 2018-March 2019 at the summit and on the upper flanks

Dukono (Indonesia) Numerous ash explosions from October 2018 through March 2019

Rincon de la Vieja (Costa Rica) Occasional weak phreatic explosions continue through February 2019

Turrialba (Costa Rica) Frequent passive ash emissions continue through February 2019

San Cristobal (Nicaragua) Weak ash explosions in January and March 2019

Semisopochnoi (United States) Minor ash explosions during September and October 2018

Asosan (Japan) Multiple brief ash emission events during April and May 2019; minor ashfall in adjacent villages

Nyamuragira (DR Congo) Lava lake reappears in central crater in April 2018; activity tapers off during April 2019

Tengger Caldera (Indonesia) New explosions with ash plumes from Bromo Cone mid-February-April 2019



Tinakula (Solomon Islands) — July 2019 Citation iconCite this Report

Tinakula

Solomon Islands

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

All times are local (unless otherwise noted)


Thermal anomalies in satellite data December 2018-June 2019; ship visit January 2019

Remote Tinakula lies 100 km NE of the Solomon Trench at the N end of the Santa Cruz Islands, which are part of the country of the Solomon Islands located 400 km to the W. It has been uninhabited since an eruption with lava flows and ash explosions in 1971 when the small population was evacuated (CSLP 87-71). The nearest communities live on Te Motu (Trevanion) Island (about 30 km S), Nupani (40 km N), and the Reef Islands (60 km E); residents occasionally report noises from explosions at Tinakula. Ashfall from larger explosions has historically reached these islands. The most recent eruptive episode was a large ash explosion and substantial SO2 plume during 21-26 October 2017; satellite imagery suggested that a flow of some type traveled down the scarp on the W flank. Renewed thermal activity that was recognized in satellite imagery beginning in December 2018 continued intermittently through June 2019 and is covered in this report. Satellite imagery and thermal data are the primary sources of information for this volcano. It is occasionally visited by members of the National Disaster Management Office (NDMO) of the Solomon Islands Government, tourists, and research vessels who are able to capture ground-based information.

Satellite images from December 2018 to February 2019 show thermal anomalies at the summit vent. Excellent ship-based photographs of the island on 24-25 January 2019 provided by a crewmember from the R/V Petrel identify numerous volcanic features and show a steam-and-gas plume at the vent. Satellite images from April and May 2019 show thermal anomalies at both the summit vent and along the W flank scarp suggesting flow activity during that time.

A stream of incandescence on the NW flank of Tinakula in a Sentinel 2 satellite image on 24 October 2017 confirmed that some type of high-temperature flow accompanied the explosions and eruptive activity of 21-25 October 2017 (BGVN 43:02). Satellite imagery during most of 2018 recorded steam plumes drifting in several directions from the summit, but no thermal activity (figure 24). There was no further evidence of activity in satellite visible or thermal data until almost exactly one year later when the MIROVA project recorded two thermal alerts in the third week of October 2018 (figure 25). Satellite images from that week were cloudy and did not confirm any surface activity.

Figure (see Caption) Figure 24. Sentinel-2 satellite imagery of Tinakula provides valuable information about activity at this remote volcano in the South Pacific. A large explosion with ash plumes and flows occurred during 21-26 October 2017. Top left: a strong E-W linear thermal anomaly suggesting a flow event from the summit was evident on the NW flank on 24 October 2017. Top right: a small steam plume rose from the summit vent on a cloudless 11 February 2018. Bottom left: a dense steam plume drifted SE from the summit vent on 4 September 2018. Bottom right: clouds and dense steam obscure the summit on 24 October 2018, about the same time that MIROVA reported a thermal anomaly. Top left image uses bands 12, 11, 8A, others use 12, 4, 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 25. The MIROVA project recorded the first thermal anomaly in a year from Tinakula during the third week of October 2018. Courtesy of MIROVA.

The first satellite imagery confirming renewed thermal activity appeared on 8 December 2018, around the same time as a small MIROVA anomaly. After that, several images during January and February 2019 confirmed moderately strong thermal activity at the summit (figure 26). Whether the anomalies were the result of active lava effusion or strong incandescent gases from the summit vent is uncertain.

Figure (see Caption) Figure 26. Thermal anomalies at the summit vent of Tinakula were recorded six times between early December 2018 and early February 2019 with Sentinel-2 satellite images. Top row: 8 December 2018 and 2 January 2019. Middle row: 12 (anomaly is just below date) and 27 January 2019. Bottom row: 1 and 6 February 2019. All images are bands 12, 4, 2. Courtesy of Sentinel Hub Playground.

Visual confirmation of activity at Tinakula is rare, but the research vessel R/V Petrel sailed past the volcano on 24 and 25 January 2019 and a crewmember provided detailed images of the W flank and vent area. The summit vent is located at the top of a W facing scarp, and steam is frequently observed rising from the vent (figures 27). Recent flows and volcaniclastic deposits were visible in the ravine on the W flank (figures 28 and 29). Fresh-looking lava was also visible near the summit vent on top of older deposits (figure 30). Eroded volcaniclastic deposits near the base of the scarp on the W flank were visible on top of older veined and layered volcanic rocks (figure 31). Crewmembers on the vessel R/V Petrel could clearly see an incandescent glow from the summit crater at night (figure 32).

Figure (see Caption) Figure 27. A view from the SW of the W flank of Tinakula on 24-25 January 2019. The summit vent is at the top of a W facing scarp, the steam plume drifted E. Used with permission from Paul G Allen's Vulcan Inc.
Figure (see Caption) Figure 28. The W flank of Tinakula as seen from the W on 24-25 January 2019. The steam plume drifted E. Recent flows and volcaniclastic deposits appeared dark in the steep ravine on the W face (left side). Used with permission from Paul G Allen's Vulcan Inc.
Figure (see Caption) Figure 29. Steam and gas rose from the summit vent at Tinakula on 24-25 January 2019. Recent lava deposits are visible in front of the plume and in the ravine on the left (the W flank). Used with permission from Paul G Allen's Vulcan Inc.
Figure (see Caption) Figure 30. The edge of the summit vent of Tinakula on 24-25 January 2019 had recent lava on older deposits; steam and gas is rising from the vent in the background. Used with permission from Paul G Allen's Vulcan Inc.
Figure (see Caption) Figure 31. The W flank of Tinakula on 24-25 January 2019. Eroded volcaniclastic deposits overlie older veined and layered volcanic rocks. Used with permission from Paul G Allen's Vulcan Inc.
Figure (see Caption) Figure 32. Incandescence was clearly visible from the summit vent at Tinakula on 24-25 January 2019. Used with permission from Paul G Allen's Vulcan Inc.

During April and May 2019, both the MIROVA project and MODVOLC measured a number of thermal anomalies (figure 33) using MODIS satellite data. MODVOLC alerts were issued on 4 and 20 April, and 11, 18, and 27 May. Sentinel-2 satellite images during the period confirmed that a flow on the W flank was a likely source of the thermal energy in addition to the summit vent (figure 34). Thermal anomalies appeared again at the end of June in MIROVA data, but no satellite images showed anomalies at that time.

Figure (see Caption) Figure 33. The number and intensity of MIROVA thermal anomalies increased at Tinakula during April and May 2019. After a short pause, they returned at the end of June. Courtesy of MIROVA.
Figure (see Caption) Figure 34. Sentinel-2 satellite images captured thermal anomalies at the summit and on the W flank of Tinakula during April and May 2019 suggesting the presence of an incandescent flow down the W scarp. Top row: 7 and 22 April 2019 (bands 12, 8, 4). Bottom row: 27 April and 12 May 2019 (bands 12, 11, 8A). 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); Vulcan Inc. (URL: https://www.vulcan.com/), additional details about the R/V Petrel (URL: https://www.paulallen.com/).


Piton de la Fournaise (France) — July 2019 Citation iconCite this Report

Piton de la Fournaise

France

21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)


Eruptive episodes in February-March and June 2019; multiple fissures and lava flows

Short pulses of intermittent eruptive activity have characterized Piton de la Fournaise, the large basaltic shield volcano on La Réunion Island in the western Indian Ocean, for several thousand years. For the last 20 years, frequent effusive basaltic eruptions have occurred on average twice per year. The activity is characterized by lava fountains and lava flows, and occasional explosive eruptions that shower blocks over the summit area and produce ash plumes. Almost all of the recent activity has occurred within the Enclos Fouqué caldera, although past eruptions in 1977, 1986, and 1998 have occurred at vents outside of the caldera. Four separate eruptive episodes were reported during 2018; from 3-4 April, 27 April-1 June, 13 July, and 15 September-1 November (BGVN 43:12, 43:09). Two episodes from 2019 during February-March and June are covered in this report, with information provided primarily by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) as well as satellite instruments.

Piton de la Fournaise experienced two eruptions during November 2018-June 2019. The first lasted from 18 February to 10 March 2019, and the second episode was 11-13 June. The episode in February-March started consisted of multiple fissures opening on the E flank of the Dolomieu crater on 18 February with lava flows that traveled several hundred meters. After a brief pause, one new fissure opened nearby on 19 February and produced up to 3 million m3 of lava in a little over four days. Although the flow rate then declined, the eruption continued until 10 March. During the last three days, 7-10 March, two new fissures opened nearby and produced large volumes of lava, bringing the total eruptive volume to about 14.5 million m3. After little activity during April and May, a small eruption occurred on the SSE outer slope of Dolomieu crater that lasted for about 48 hours on 11-13 June; multiple small flows traveled about 1,000 m down the steep flank before ceasing. The MIROVA thermal anomaly graph of log radiative power clearly showed the abruptness of the beginning and ends of the last three eruptive episodes at Piton de la Fournaise from August 2018 through June 2019 (figure 165).

Figure (see Caption) Figure 165. The MIROVA graph of thermal energy from Piton de la Fournaise from 30 July 2018 through June 2019 shows the last three eruptive episodes at the volcano. From 15 September through 1 November 2018 fissures and flows were active on the SW flank of Dolomieu crater near Rivals crater (BGVN 43:12). Fissures opened on the E flank of the crater on 18 February 2019, and after a brief pause resumed on 19 February at the foot of Piton Madoré. Lava flows remained active until 10 March 2019. A short episode of lava effusion occurred on 11-12 June 2019 on the SSE outer slope of Dolomieu crater. Courtesy of MIROVA.

Activity during November 2018-March 2019. Following the end of the 15 September-1 November 2018 eruption, seismic activity immediately below the summit remained low (with only 20 shallow and two deep earthquakes during November). The inflationary signal recorded since the beginning of September stopped, and the OVPF deformation networks did not record any significant deformation. There were 35 shallow earthquakes (0-2 km depth) below the summit crater during December, and one deep earthquake. Only 12 shallow earthquakes and one deep earthquake (greater than 2 km below the surface) were reported in January.

OVPF reported an increase in CO2 concentrations beginning in December 2018, and noted the beginning of inflation on 13 February 2019. A seismic swarm of 379 earthquakes accompanied by minor but rapid deformation (less than 1 cm) was reported on 16 February 2019. A new seismic swarm of 208 earthquakes began early on 18 February with a much larger ground deformation (10 cm of elongation of the summit zone). A volcanic tremor indicative of the arrival of magma near the surface began at 0948 that morning. Webcams indicated that eruptive fissures had opened in the NE part of the Enclos Fouqué caldera. The onset of the eruption was marked by a sudden drop in CO2 flux which then stabilized. The eruptive sites were confirmed visually around 1130. Three fissures with actively flowing lava opened on the E flank of Dolomieu Crater; the fountains of lava were less than 30 m high. The front of the longest flow had reached 1,900 m elevation after one hour. The eruption lasted a little over 12 hours and was over by 2200 that evening; it covered about 150-200 m of the hiking trail to the summit.

Seismicity remained high after the event ended, and at 1500 on 19 February 2019 another seismic swarm of 511 deep earthquakes located under the E flank at about 2.5 km depth occurred. It was not accompanied by a significant amount of deformation. At 1710 tremor signals appeared on the observatory seismographs and the first gas plumes and lava ejection were observed at 1750 and 1912, respectively. During an overflight the next day (20 February), OVPF team members observed the new eruptive site at an elevation of 1,800 m at the foot of Piton Madoré. One fissure and one fountain were active at 0620 on 20 February and the flow front was at 1,300 m elevation (figure 166). During the night of 20-21 February the flow front crossed over the "Grandes Pentes" area in the eastern half of the Enclos Fouque (figure 167).

Figure (see Caption) Figure 166. The eruption which began on 19 February 2019 on the E flank of Dolomieu crater at Piton de la Fournaise produced a lava fountain and flow which traveled down at least 500 m of elevation by the next morning when this photo was taken at 0620 local time. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 20 février 2019 à 11h00, Heure locale).
Figure (see Caption) Figure 167. The active fissure at Piton de la Fournaise was producing lava fountains and an active flow during the evening of 20 February 2019. Overnight the flow crossed over the "Grandes Pentes" area of the caldera. Photo courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du jeudi 21 février 2019 à 14H00, Heure locale).

OVPF reported on 22 February 2019 that 22 shallow earthquakes had been reported since the eruption began on 19 February. Surface flow rates estimated from satellite data, via the HOTVOLC system (OPGC - University of Auvergne), were between 2.5 and 15 m3/s. The quantity of lava emitted between 19 and 22 February was between 1 and 3 million m3. OVPF observed the growth of an eruptive cone that was filled with a small lava lake producing ejecta during a morning overflight on 22 February. A channelized flow moved downstream from the cone and split into two lobes about 1 km from (and 200 m below) the cone (figure 168). The split in the flow occurred near the Guyanin crater. The N flowing lobe, about 50 m wide, had an actively flowing front located at 1,320 m elevation; the incandescent flow was travelling over a recent flow (likely from the previous night). The S-flowing lobe spread to 200 m wide and split into two tongues 300 m SE of Guyanin crater.

Figure (see Caption) Figure 168. During an overflight on the morning of 22 February 2019 scientists from OVPF observed a growing spatter cone with a small lava lake at Piton de la Fournaise. A channelized flow moved downstream from the fissure and split into two flows. Photo courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du vendredi 22 février 2019 à 13h30, Heure locale).

Incandescent ejecta from the cone was captured in a webcam image overnight on 22-23 February 2019 (figure 169). The rate of advance of the flow slowed significantly by 24 February, but the intensity of the eruptive tremor remained relatively constant. Mapping of the lava flow on 28 February carried out by the OI2 platform (OPGC - University Clermont Auvergne) from satellite data confirmed the slow progress of the flow after 24 February (300 m in 5 days) (figure 170). The flow front was located at 1,200 m elevation, and only the N arm was active; the lava had traveled about 2.2 km from the vent by 28 February.

Figure (see Caption) Figure 169. Incandescent ejecta from the eruptive cone at Piton de la Fournaise was captured in the webcam in the early hours of 23 February 2019. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 23 février 2019 à 13h30, Heure locale).
Figure (see Caption) Figure 170. Contours of the lava flows at Piton de la Fournaise from 18-28 February 2019 were determined from satellite data by the OI2 platform (Université Clermont Auvergne), dated 18 (red) and 19 (blue) February (top image); 20 (green), 21 (red), 22 (blue), 27 (turquoise), and 28 (pink) February (bottom image). Courtesy of and copyright by OVPF/IPGP. Top: Bulletin d'activité du vendredi 22 février 2019 à 13h30 (Heure locale); bottom: Bulletin d'activité du jeudi 28 février 2019 à 16h30 (Heure locale).

Between 28 February and 1 March 2019 a third lobe of lava appeared flowing NE from the vent on the N side of the new flow area; it split into two lobes sometime on 1 March. Very little new lava was recorded on the other lobes. By 4 March the flow rate estimated by satellite data was about 7.5 m3/s. During a site visit on the morning of 5 March OVPF scientists sampled the N lobe of the flow and bombs and tephra near the cone, and acquired infrared and visible images. They noted the continued growth of the cone which still had an open vent at the summit and a base 100 m in diameter. It was 25 m high with a 50-m-wide eruptive vent at the top (figure 171). High-temperature gas emissions and strong Strombolian activity issued from the vent. Steam emissions were present around the base of the cone, suggesting the presence of lava tunnels. A single lobe of lava flowed N from the cone.

Figure (see Caption) Figure 171. The eruptive cone at Piton de la Fournaise on 5 March 2019 had a 100-m-diameter base, 25 m of vertical height, and 50-m-wide vent at the summit. Courtesy of and copyright by OVPF/IPGP, (Bulletin d'activité du mardi 5 mars 2019 à 17h30, Heure locale).

A new fissure that opened about 150 m from the main vent on the NW flank of Piton Madoré was first observed on the morning of 6 March (figure 172); OVPF concluded that it had opened late on 5 March. A small cone was forming and a new flow traveled N from the main eruptive site. At least six new emission points were noted the following morning (7 March) around the Piton Madoré. Poor weather prevented confirmation by aerial reconnaissance that day, but in a site visit on 8 March OVPF scientists determined that the new fissure from 5 March remained active; a small cone about 10 m high had two flow lobes on the W and N sides (figure 173). A fissure that opened on 7 March was located 300 m S of the 19 February vent and oriented E-W. It was very active on the morning of 8 March with two 50-m-high lava fountains (figure 174). Samples collected by OVPF indicated that the vents of 5 and 7 March produced lava of different compositions.

Figure (see Caption) Figure 172. A new fissure that opened about 150 m from the main vent on the NW flank of Piton Madoré at Piton de la Fournaise was first observed on the morning of 6 March 2019; OVPF concluded that it had opened late on 5 March. A small cone was forming on the flank of an old one and a new flow traveled N from the main eruptive site. Courtesy of OVPF/IPGP, copyright by Helicopter Coral (Bulletin d'activité du jeudi 7 mars 2019 à 15h00 Heure locale).
Figure (see Caption) Figure 173. The 5 March 2019 fissure at Piton de la Fournaise on the NW flank of Piton Madoré still had two active flow lobes emerging from it and heading N and W on 8 March 2019. Courtesy of and copyright by OVPF/IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, March 2019).
Figure (see Caption) Figure 174. A fissure that opened on 7 March 2019 at Piton de la Fournaise was located 300 m S of the 19 February vent and oriented E-W. It was very active on the morning of 8 March 2019 with two 50-m-high lava fountains. Courtesy of and copyright by OVPF/IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, March 2019).

There was a strong increase in the eruptive tremor intensity on 7 March, related to the opening of the two new fissures on 5 and 7 March (figure 175). As a result, the surface flow estimates made from satellite data increased significantly to high values greater than 50 m3/s, with the average values on 7-8 March of around 20-25 m3/s. The increased flow rates resulted in the flows traveling much greater distances. By the morning of 9 March the active flow had reached 650-700 m above sea level. The flow front had traveled about 1 km in 24 hours. Strong seismicity had been increasing under the summit zone for the previous 48 hours. After a phase of very strong surface activity observed overnight on 9-10 March that included lava fountains 50-100 m high (figure 176), surface activity ceased around 0630 on 10 March, and seismic activity decreased significantly. OVPF noted that sudden increases in seismicity and flow rates near the end of an eruption have occurred at about half of the eruptions at Piton de la Fournaise in recent years. Lava volumes emitted on the surface between 18 February and 10 March 2019 were estimated at about 14.5 million m3 (figure 177).

Figure (see Caption) Figure 175. An infrared view of the eruptive site on the E flank of Dolomieu crater at Piton de la Fournaise on 8 March 2019 clearly showed the original fissure from 19 February (bottom right of center), the fissure on Piton Madore that opened on 5 March (right) and the fissures that opened on 7 March (upper, right of center). The combined activity produced significant thermal and seismic activity at the volcano. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du vendredi 8 mars 2019 à 17h00, Heure locale).
Figure (see Caption) Figure 176. Lava fountains 50-100 m high were the result of very strong surface activity observed overnight on 9-10 March 2019 at Piton de la Fournaise. Surface activity ceased around 0630 on 10 March, and seismic activity decreased significantly. Photo taken on 9 March 2019 around midnight from the RN2. Courtesy of OVPF/IPGP, copyright by A. Finizola LGSR/IPGP (Bulletin d'activité du dimanche 10 mars 2019 à 19h30 Heure locale).
Figure (see Caption) Figure 177. A sudden increase in the flow rate at the end of the 18 February-10 March 2019 eruption at Piton de la Fournaise was recorded by researchers at the Université Clermont Auvergne. OVPF noted this was typical of about half of the eruptions at Piton de la Fournaise. Courtesy of OVPF/IPGP, copyright by HOTVOLC, Université Clermont Auvergne (OVPF Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, March 2019).

Significant SO2 plumes were captured by the TROPOMI instrument on the Sentinel 5-P satellite throughout the 18 February-10 March eruption (figure 178). After the surface eruption ceased, shallow seismicity continued at a lower rate of about 12 earthquakes per day. The end of the eruption (7-10 March) was accompanied by a marked deflation, interpreted by OVPF as the rapid emptying of the magma reservoir. Following the end of the eruption, inflation resumed for the rest of March but then ceased. Seismicity continued at a lower level during April with an average of six shallow earthquakes per day.

Figure (see Caption) Figure 178. Multiple days of high DU value SO2 plumes were recorded by the TROPOMI instrument on the Sentinel 5-P satellite during the 18 February-10 March 2019 eruption at Piton de la Fournaise. Top row: during 18, 21, and 22 February SO2 plumes drifted SE. Middle row: during 23, 24, and 25 February the wind direction changed from SE through S to SW and left a curling trail of SO2. Bottom row: 5, 7, and 8 March showed an increase in SO2 emissions that corresponded with increased seismicity and lava flow output before the eruption ceased.

Activity during May-June 2019. OVPF reported slight inflation near the summit beginning in early May, and an increase in CO2 concentration in the soil near Plaine des Cafres and Plaine des Palmistes. Strong shallow seismicity reappeared on 27 May 2019 and recurred on 30 and 31 May. Two small seismic swarms were measured on 31 May in the early morning. A new seismic swarm beginning at 0603 on 11 June accompanied by rapid deformation suggested a new eruption was imminent. A tremor near the summit area was first noted at 0635 local time; the webcams indicated a plume of gas, but poor visibility prevented evidence of fresh lava. Around 0930 that morning OVPF confirmed that five fissures had opened on the outer SSE slope of Dolomieu crater at elevations ranging from 2480 to 2025 m (figure 179). The flow fronts were not visible due to weather. Lava fountains under 30 m in height and lava flows were present in the three lowest fissures. The flows traveled rapidly down the steep flank of the crater (figure 180).

Figure (see Caption) Figure 179. Around 0930 on the morning of 11 June 2019 OVPF confirmed that five fissures had opened on the outer SSE slope of Dolomieu crater at Piton de la Fournaise at elevations ranging from 2480 to 2025 m. Courtesy of and copyright by OVPF-IPGP and Imazpress (Bulletin d'activité du mardi 11 juin 2019 à 11h00).
Figure (see Caption) Figure 180. Thermal imaging of the 11-12 June 2019 eruptive site at Piton de la Fournaise showed multiple streams of lava traveling rapidly down the steep flank from several fissures on 11 June 2019. Courtesy of and copyright by OVPF-IPGP (Bulletin d'activité du mardi 11 juin 2019 à 11h00).

The intensity of the eruptive tremor decreased throughout the day, and by 1530 only the lowest elevation fissure was still active (figure 181). The next afternoon (12 June) images in the OVPF webcam located in Piton des Cascades indicated the flow front was at about 1,200-1,300 m elevation. Seismographs indicated that the eruption stopped around 1200 on 13 June. Poor weather obscured visibility of the flow activity. Seismic activity decreased following the eruption, but appeared to increase again beginning on 21 June, with 10 events detected on 30 June. SO2 plumes were recorded in satellite data on 11 and 12 June 2019.

Figure (see Caption) Figure 181. The intensity of the eruptive activity at Piton de la Fournaise on 11 June 2019 decreased throughout the day, and by 1530 only the lowest elevation fissure was still active. Courtesy of and copyright by OVPF-IPGP (Bulletin d'activité du mardi 11 juin 2019 à 17h45 Heure locale).

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); 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/).


Semeru (Indonesia) — April 2019 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Decreased activity after October 2018

The ongoing eruption at Semeru has been characterized by numerous ash explosions and thermal anomalies, but activity apparently diminished in 2018 (BGVN 43:01 and 43:09); this decreased activity continued through at least February 2019. The current report summarizes activity from 24 August 2018 to 28 February 2019.

The Indonesian volcano monitoring agency, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), reported ongoing daily seismicity, dominated by explosion earthquakes and emission-related events from late November through February (figure 35). Ash plumes resulting in aviation advisories by the Darwin Volcanic Ash Advisory Centre (VAAC) were reported on 4, 6-7, and 19 September, and 12 October 2018. The next significant ash plume reported by the VAAC wasn't until 24 February 2019 (table 23).

Figure (see Caption) Figure 35. Seismicity recorded at Semeru during 28 November 2018-26 February 2019. Plot shows explosion earthquakes ('Letusan'), emission-related events ('Hembusan'), felt earthquakes ('Gempa Terasa'), local tectonic events ('Tektonic Lokal'), and distant tectonic events ('Tektonic Jauh'). Courtesy of PVMBG and MAGMA Indonesia.

Table 23. Summary of ash plumes at Semeru during 25 August 2018 through February 2019. The summit is at 3,657 m elevation. Data courtesy of Darwin VAAC.

Date Plume altitude (km) Plume drift Remarks
04 Sep 2018 4.3 W --
06-07 Sep 2018 4.3 SW --
19 Sep 2018 4 SSW Possible ash-and-steam plume.
12 Oct 2018 4.5 W Discrete eruption.
24 Feb 2019 4.3 W Discrete volcanic ash eruption.

Thermal anomalies using MODIS satellite instruments processed by the MODVOLC algorithm were only recorded on 26, 28, and 30 August 2018, and 22 and 31 October 2018. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots within 5 km of the volcano during August and early September, with a significant decrease in frequency through October (figure 36); only a few scattered hotspots were recorded from November 2018 through February 2019.

Figure (see Caption) Figure 36. MIROVA plot of thermal anomalies (Log Radiative Power) at Semeru during July 2018-February 2019. Courtesy of MIROVA.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/).


Heard (Australia) — April 2019 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Thermal hotspots continue during October 2018-March 2019 at the summit and on the upper flanks

Heard Island, in the Southern Indian Ocean, includes the large Big Ben stratovolcano and the smaller, apparently inactive, Mt. Dixon. Because of the island's remoteness, satellites are the primary monitoring tool. Big Ben has been active intermittently since 1910, and was active during October 2017-September 2018 (BGVN 43:10). Activity continued during October 2018-March 2019.

Satellite photos using Sentinel Hub showed hotspots every month between October 2018 and March 2019. Because the area was frequently covered by a heavy cloud layer, most of the hotspot signals were partially obscured. Though thermal anomalies are usually seen at summit vents, on 18 October 2018 an anomaly was present about 300 m down the E flank. Similarly, on 1 January 2019, a weak anomaly beginning about 200 m down the NW flank was about 300 m long (figure 40).

The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected three hotspots, two in October and one in early November 2018, all of low radiative power. There were no MODVOLC alert pixels during this period.

Figure (see Caption) Figure 40. Sentinel-2 L1C image of Heard Island's Big Ben volcano on 1 January 2019 one summit hotspot and an elongated thermal anomaly to the NW. Scale bar (bottom right) is 200 m. The photo was taken in atmospheric penetration view (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

Geologic Background. Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon volcano lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben volcano because of its extensive ice cover. The historically active Mawson Peak forms the island's 2745-m high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported in historical time at this isolated volcano, but observations are infrequent and additional activity may have occurred.

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


Dukono (Indonesia) — April 2019 Citation iconCite this Report

Dukono

Indonesia

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

All times are local (unless otherwise noted)


Numerous ash explosions from October 2018 through March 2019

The eruption at Dukono that began in 1933 has showered the area with ash from frequent explosions (BGVN 43:04, 43:12). The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Center for Volcanology and Geological Hazard Mitigation (CVGHM), is responsible for monitoring this volcano.

This long-term pattern of intermittent ash explosions continued during October 2018-March 2019, with ash plumes rising to between 1.5 and 2.7 km altitude, or about 300-1,500 m above the summit (table 19). Although meteorological clouds often obscured views, satellite imagery captured typical ash plumes on 28 September 2018 (figure 10) and 5 February 2019 (figure 11). Instruments aboard NASA satellites (TROPOMI and OMPS) detected high levels of sulfur dioxide near or directly above the volcano on multiple days during January-March 2019. The Alert Level remained at 2 (on a scale of 1-4), and visitors were warned to remain outside of the 2-km exclusion zone.

Table 19. Monthly summary of reported ash plumes from Dukono for October 2018-March 2019. The direction of drift for the ash plume through each month was highly variable. Data courtesy of the Darwin VAAC and PVMBG.

Month Plume Altitude (km) Notable Plume Drift
Oct 2018 1.5-2.1 --
Nov 2018 1.5-2.1 --
Dec 2018 1.5-2.4 --
Jan 2019 1.8-2.1 --
Feb 2019 1.8-2.7 --
Mar 2019 1.5-2.4 --
Figure (see Caption) Figure 10. Satellite image from Sentinel-2 (LC1 natural color) of an ash plume at Dukono on 28 September 2018 with the plume blowing towards the NE. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 11. Satellite image from Sentinel-2 (LC1 natural color) of an ash plume at Dukono on 5 February 2019, with the plume blowing SW. Courtesy of Sentinel Hub Playground.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Rincon de la Vieja (Costa Rica) — April 2019 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

10.83°N, 85.324°W; summit elev. 1916 m

All times are local (unless otherwise noted)


Occasional weak phreatic explosions continue through February 2019

Intermittent small phreatic explosions from the acid lake of Rincón de la Vieja's active crater has most recently occurred since 2011 (BGVN 42:08, 43:03, and 43:09). This activity continued through at least February 2019. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), and the information below comes from its weekly bulletins between 18 August 2018 and 28 February 2019. Weather conditions often prevented webcam views and estimates of plume heights. The volcano was in Activity Level 3 throughout the reporting period (volcano erupting, steady state).

According to OVSICORI-UNA, two distinct, 2-minute-long explosions occurred on 31 August 2018 beginning at 0434 and 1305. Several hours after the eruption tremor became continuous but low-frequency long-period (LP) earthquakes ceased. OVSICORI-UNA reported a gas emission late on 7 September. An unconfirmed small phreatic explosion occurred on 11 September at 0634, and another on 17 September at 1014. The seismic record showed continuous background tremor and very sporadic LP earthquakes.

Intermittent background tremor was recorded during the first half of October, along with a few emissions and phreatic explosions. Deformation measurements during October showed a contraction between the N and S of the volcano, with subsidence. On 17 October there was another phreatic explosion, and thereafter tremor disappeared and seismicity decreased. On 23 and 27 October seismic stations signaled additional possible phreatic explosions.

OVSICORI-UNA reported that a series of explosions began at 1945 on 4 November and consisted of at least three 2-minute-long episodes. The next day at 1511 a plume of water vapor and diffuse gas, recorded by a webcam and visible to residents to the N, rose about 100 m above the crater rim and drifted W. On 9 November a 2-minute-long explosion began at 1703. Another explosion on 27 November at 0237 produced a plume of water vapor and gas that rose 600 m above the crater rim and drifted SW. A short 1-minute explosion began at 1054 on 3 December.

Based on OVSICORI-UNA weekly bulletins, activity remained stable in January 2019 with small-amplitude phreatic explosions on 11, 12, and 14 January. More energetic phreatomagmatic explosions on 17 and 20 January produced lahars. Several small-amplitude explosions were detected at the end of the month. During January, a few LPs, no VTs, and intermittent tremor were recorded.

OVSICORI-UNA reported that two small-scale explosions occurred on 1 February, along with possible events at 1906 and 1950 on 5 February and at 0120 on 6 February. An event at 0000 on 6 February was also recorded; the report noted that poor weather conditions prevented visual observations of the crater. On 16 and 17 February strong degassing was observed. No LPs were recorded, but two significant VTs were detected on 17 and 22 February near or under the crater.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/).


Turrialba (Costa Rica) — April 2019 Citation iconCite this Report

Turrialba

Costa Rica

10.025°N, 83.767°W; summit elev. 3340 m

All times are local (unless otherwise noted)


Frequent passive ash emissions continue through February 2019

This report summarizes activity at Turrialba during September 2018-February 2019. During this period there was similar activity as described earlier in 2018 (BGVN 43:09), with occasional ash explosions and numerous, sometimes continuous, periods of gas-and-ash emissions (table 8). Data were provided by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA).

Table 8. Ash emissions at Turrialba, September 2018-February 2019. Cloudy weather sometimes obscured observations. Maximum plume height is above the crater rim. Information courtesy of OVSICORI-UNA.

Date Time Max plume height Plume drift Remarks
27 Aug-05 Sep 2018 -- 100 m SW, W Continuous gas-and-ash emissions.
06 Sep 2018 -- -- -- Mostly gas, punctuated by small sporadic ash plumes.
10 Sep 2018 1210 300 m NW --
01-13 Sep 2018 -- -- -- Continuous gas-and-ash emissions.
17-18 Sep 2018 -- 300 m SW, NW --
27 Sep 2018 0915 200 m NW --
30 Sep-01 Oct 2018 -- 500 m NW, NE --
03 Oct 2018 -- -- -- Incandescence.
08 Oct 2018 0800 500 m N --
10-16 Oct 2018 -- 1,000 m Various Intermittent emissions; some explosions, including an energetic one on 14 Oct at 1712. Clouds prevented estimate of plume height.
17-23 Oct 2018 -- 200-500 m E, NW, SW Periodic gas-and-ash emissions. Frequent Strombolian events since 5 Oct.
25-30 Oct 2018 -- -- -- Periodic ash emissions when weather conditions allowed observations.
26 Oct 2018 0134 500 m NE Ashfall in neighborhoods of Coronado (San José, 35 km WSW) and San Isidro de Heredia (Heredia, 38 km W).
29 Oct 2018 0231 500 m NW --
30 Oct 2018 1406 500 m W --
24 Oct-01 Nov 2018 -- 500 m -- Continuous emissions.
01-06 Nov 2018 0530-0640 500 m SW --
02 Nov 2018 1523, 1703 500 m -- --
03 Nov 2018 0109 500 m -- Short (2-3 minutes) duration events. Ashfall reported in Coronado.
05 Nov 2018 0620 600 m NW --
06-11 Nov 2018 -- 500 m -- Low-level, continuous gas-and-ash emissions occasionally punctuated by energetic explosions that sent plumes as high as 500 m and caused ashfall in several areas downwind, including Cascajal de Coronado, Desamparados (35 km WSW), San Antonio, Guadalupe (32 km WSW), Sabanilla, San Pedro Montes de Oca, Moravia (31 km WSW), Heredia, and Coronado (San José, 35 km WSW). Weather prevented observations on 12 Nov.
13-19 Nov 2018 -- -- -- Periodic, passive ash emissions visible in webcam images or during cloudy conditions inferred from the seismic data.
22 Nov 2018 0710 100 m W --
23 Nov 2018 -- -- -- Frequent pulses of ash.
23-25 Nov 2018 -- 500 m -- Occasional Strombolian explosions ejected lava bombs deposited near the crater; residents of Cascajal de Coronado reported hearing several booming sounds.
26-27 Nov 2018 -- -- -- Passive emissions with small quantities of ash visible. Minor ashfall in San Jose (Cascajal de Coronado and Dulce Nombre), San Pedro Montes de Oca, and neighborhoods of Heredia.
28 Nov-03 Dec 2018 -- 500 m N, NW, SW Ashfall in Santo Domingo (36 km WSW) on 2 Dec.
05 Dec 2018 -- -- -- Minor emission.
06 Dec 2018 -- -- S Emission.
08 Dec 2018 0749 500 m NW --
09 Dec 2018 -- 1,000 m -- Ashfall in areas of Valle Central.
10 Dec 2018 -- -- -- Emissions periodically observed during periods of clear viewing. Ashfall in Moravia (31 km WSW) and Santa Ana, and residents of Heredia noted a sulfur odor.
11-12 Dec 2018 -- 500 m NW, SW The Tico Times stated some flights were delayed at San Jose airport, 67 km away.
13 Dec 2018 -- -- -- Pulsing ash emissions; ashfall in Guadalupe (32 km WSW) and Valle Central.
14-16 Dec 2018 -- -- W, SW Emissions with diffuse amounts of ash.
05-06 Jan 2019 0815 -- -- Increased after midnight on 6 Jan.
28 Jan-04 Feb 2019 -- -- -- Minor, sporadic ash emissions rose to low heights during most days.
01 Feb 2019 0640 1,500 m NW --
08 Feb 2019 0540 200 m -- Sporadic ash emissions for more than one hour.
11 Feb 2019 -- -- -- Very small ash emission.
13-15 Feb 2019 200-300 m NW, W, SW Almost continuous gas emissions with minor ash content.
15 Feb 2019 1330 1,000 m W --
18 Feb 2019 1310 500 m W --
21 Feb 2019 -- 300 m NW Frequent ash pulses.
22-24 Feb 2019 -- 300 m NW, SW Frequent ash emissions of variable intensity and duration. On 22 Feb ash fell in Santa Cruz (31 km WSW) and Santa Ana, and a sulfur odor was evident in Moravia.
28 Feb 2019 1050 500 m SW Ash pulses.

According to OVSICORI-UNA's annual summary for 2018, a slow decline in activity occurred after the volcano reached its highest emission rate during 2016. Activity during 2018 was consistent with an open system, generating frequent passive ash emissions. The volcano emitted ash on 58% of the days during the year. Some explosions were large enough to eject ballistics more than 400 m around the crater. Typical activity can be seen in a photo from 11 September 2018 (figure 50) and satellite imagery on 7 November 2018 (figure 51).

Figure (see Caption) Figure 50. Photo of an ash explosion at Turrialba taken on 11 September 2018. Courtesy of Red Sismologica Nacional (RSN: UCR-ICE), Universidad de Costa Rica.
Figure (see Caption) Figure 51. Sentinel-2 satellite image of an ash emission from Turrialba on 7 November 2018, taken in natural color (gamma adjusted). Courtesy of Sentinel Hub Playground.

During January into early February 2019, passive ash emissions continued irregularly and with less intensity and duration. Emissions sometimes lacked ash. In their report of 4 February 2019, OVSICORI-UNA indicated that passive ash emissions were weak and slow. For the rest of February, they characterized ash emissions as frequent, but of low intensity.

Seismic activity. On 1 November 2018 OVSICORI-UNA reported that seismicity remained high, and involved low-amplitude banded volcanic tremor along with long-period (LP) and volcano-tectonic (VT) earthquakes. In late January-early February 2019, OVSICORI-UNA reported that seismicity remained relatively stable, although a small increase was associated with the hydrothermal system. VT earthquakes were absent, and tremors had decreased in both energy and duration. The number of low-frequency LP volcanic earthquakes remained stable, although they had decreasing amplitudes. No explosions were documented, and emissions were weak and had short durations and very dilute ash content.

Thermal anomalies. No thermal anomalies were recorded during the reporting period using MODIS satellite instruments processed by MODVOLC algorithm. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected five scattered hotspots during September-October 2018, none during November-December 2018, and two during January-February 2019. All were within 2 km of the volcano and of low radiative power.

Gas measurements. Significant sulfur dioxide levels near the volcano were recorded by NASA's satellite-borne ozone instruments only on 29 September 2018 (both NPP/OMPS and Aura/OMI instruments) and on 11 February 2019 (Sentinel 5P/TROPOMI instrument). OVSICORI-UNA's gas measuring instruments were compromised in September 2018 through January 2019 due to vandalism. In early February, however, they detected hydrogen sulfide for the first time since 2016.

Geologic Background. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Red Sismologica Nacional (RSN) a collaboration between a) the Sección de Sismología, Vulcanología y Exploración Geofísica de la Escuela Centroamericana de Geología de la Universidad de Costa Rica (UCR), and b) the Área de Amenazas y Auscultación Sismológica y Volcánica del Instituto Costarricense de Electricidad (ICE), Costa Rica (URL: https://rsn.ucr.ac.cr/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); Costa Rica Star (URL: https://news.co.cr); The Tico Times (URL: https://ticotimes.net).


San Cristobal (Nicaragua) — April 2019 Citation iconCite this Report

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Weak ash explosions in January and March 2019

San Cristóbal has produced occasional weak explosions since 1999, with intermittent gas-and-ash emissions. The only reported explosion during the first half of 2018 was on 22 April, the first since November 2017 (BGVN 43:03). The current report covers activity between 1 August 2018 and 1 May 2019. The volcano is monitored by the Instituto Nicaragüense de Estudios Territoriales (INETER).

According to INETER, a series of explosions occurred on 9 January 2019 that lasted several hours. INETER stated that one explosion occurred at 1643; the Washington VAAC's first advisory stated that an explosion occurred at 1145 (local time). The weak explosions, which occurred after a period of heightened seismic activity, generated an ash plume that reached 200 m above the edge of the crater and drifted W. The Washington VAAC reported volcanic ash plumes on 10-11 January extending about 92 km SW, and on 24-25 January extending about 185 km WSW. A low-energy explosion was detected by the seismic network at 1550 on 4 March 2019. The event produced a gas-and-ash plume that rose 400 m above the crater rim and drifted SW.

Monitoring data reported by INETER (table 6) showed elevated levels of seismicity during October 2018 through January 2019. Sulfur dioxide was also measured at higher levels in January 2019.

Table 6. Monthly sulfur dioxide measurements and seismicity reported at San Cristóbal during August 2018-March 2019. "Most" indicates that type of seismicity was dominant that month. Data courtesy of INETER.

Month Average SO2 Total earthquakes Degassing-type earthquakes Volcano-tectonic (VT) earthquakes
Aug 2018 461 t/d 6,464 6,147 251
Sep 2018 893 t/d 9,659 9,586 73
Oct 2018 269 t/d 11,698 3,509 8,189
Nov 2018 -- 19,593 19,586 7
Dec 2018 -- 30,901 -- Most
Jan 2019 1,286 t/d 11,504 Most Very few
Feb 2019 695 t/d 3,470 Most Very few
Mar 2019 -- 3,882 Most Very few

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://webserver2.ineter.gob.ni/vol/dep-vol.html); 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).


Semisopochnoi (United States) — February 2019 Citation iconCite this Report

Semisopochnoi

United States

51.93°N, 179.58°E; summit elev. 1221 m

All times are local (unless otherwise noted)


Minor ash explosions during September and October 2018

The remote Semisopochnoi comprises the uninhabited volcanic island of the same name, ~20 km in diameter, in the Rat Islands group of the western Aleutians (figure 1). Plumes had been reported several times in the 18th and 19th centuries, and most recently observed in April 1987 from Sugarloaf Peak (SEAN 12:04). The volcano is dominated by an 8-km diameter caldera that contains a small lake (Fenner Lake) and a number of post-caldera cones and craters. Monitoring is done by the Alaska Volcano Observatory (AVO) using an on-island seismic network along with satellite observations and lightning sensors. An infrasound array on Adak Island, about 200 km E, may detect explosive emissions with a 13 minute delay if atmospheric conditions permit.

On 16 September 2018 increased seismicity was detected at 0831, prompting AVO to raise the Aviation Color Code (ACC) to Yellow and Volcano Alert Level (VAL) to Advisory. Retrospective analysis of satellite data acquired on 10 September revealed small ash deposits on the N flank of Mount Cerberus, possibly associated with two bursts of tremor recorded on 8 September (figure 5). This new information, coupled with intensifying seismicity and a strong tremor signal recorded at 1249 on 17 September, resulted in AVO raising the ACC to Orange and the VAL to Watch. Seismicity remained elevated on 18 September with nearly constant tremor recorded by local sensors. At the same time, no ash emissions were observed in cloudy satellite images and no eruptive activity was recorded on regional pressure sensors at Adak.

Figure (see Caption) Figure 1. Minor ash deposits can be seen on the south and west flanks of the N cone of Mount Cerberus, Semisopochnoi Island, in this ESA Sentinel-2 image from 1200 on 10 September 2018. Also note probable minor steam emissions obscuring the crater of the N cone. Image courtesy of AVO.

During 19-25 September 2018 seismicity remained elevated, alternating between periods of continuous and intermittent bursts of tremor. Tremor bursts at 1319 on 21 September and at 1034 on 22 September produced airwaves detected on a regional infrasound array on Adak Island; no ash emissions were identified above the low cloud deck in satellite data, and the infrasound detections likely reflected an atmospheric change instead of volcanic activity.

Seismicity remained elevated during 3-9 October 2018, with intermittent bursts of tremor. No volcanic activity was detected in infrasound or satellite data. On 11 October satellite data indicated partial erosion of a tephra cone in the crater of Cerberus's N cone. A crater lake about 90 m in diameter filled the vent. The data also suggested that the vent had not erupted since 1 October. Seismicity remained elevated and above background levels. The next day AVO lowered the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory, noting the recent satellite data results and lack of tremor recorded during the previous week. AVO reported that unrest continued during 11-24 October.

An eruptive event began at 2047 on 25 October 2018, identified based on seismic data; strong volcanic tremor lasted about 20 minutes and was followed by 40 minutes of weak tremor pulses. A weak infrasound signal was detected by instruments on Adak Island. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale) and Volcano Alert Level was raised to Watch (the second highest level on a four-level scale). A dense meteorological cloud deck prevented observations below 3 km, but a diffuse cloud was observed in satellite data rising briefly above the cloud deck, though it was unclear if it was related to eruptive activity. Tremor ended after the event, and seismicity returned to low levels.

Small explosions were detected by the seismic network at 2110 and 2246 on 26 October 2018, and 0057 and 0603 on 27 October. No ash clouds were identified in satellite data, but the volcano was obscured by high meteorological clouds. Additional small explosions were detected in seismic and infrasound data during 28-29 October; no ash clouds were observed in partly-cloudy-to-cloudy satellite images.

AVO reported on 31 October 2018 that unrest continued. Two small explosions were detected, one just before 0400 and the other around 1000. Satellite views were obscured by clouds at the time, and no ash clouds were observed. Unrest continued through 1 November, at which time the satellite link and the seismic line failed. On 21 November the ACC was lowered to Yellow and the VAL was lowered to Advisory.

Geologic Background. Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.

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/).


Asosan (Japan) — July 2019 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Multiple brief ash emission events during April and May 2019; minor ashfall in adjacent villages

Japan's 24-km-wide Asosan caldera on the island of Kyushu has been active throughout the Holocene. Nakadake has been the most active of 17 central cones within the caldera for 2,000 years. Historical eruptions have been primarily basaltic to basaltic-andesitic ash eruptions, with periodic Strombolian activity, all from Nakadake Crater 1. The most recent major eruptive episode began in late November 2014 and continued through 1 May 2016. Another eruption, with the largest ash plume in 20 years, occurred on 8 October 2016. Asosan remained quiet until renewed activity from Crater 1 began in mid-April 2019; it is covered in this report, through the end of June 2019. The Japan Meteorological Agency (JMA) provides monthly reports of activity; the Tokyo Volcanic Ash Advisory Center (VAAC) issues aviation alerts reporting on possible ash plumes.

Asosan remained quiet during 2017 and 2018 with steam plumes rising a few hundred meters from Crater 1 and low levels of SO2 emissions; a warm acidic lake was present within the crater. Fumarolic activity from two areas on the S and SW wall of the crater rim generated occasional thermal anomalies in satellite data and incandescence at night. A brief period of increased seismicity was reported in mid-March 2019. An increase in seismic amplitude on 14 April 2019 preceded a small explosion on 16 April; it produced an ash plume which rose 200 m above the crater rim and drifted NW. It was followed by additional small explosions on 19 April. A new explosion on 3 May produced minor ashfall in adjacent communities; ash emissions were reported multiple times during May with plumes reaching 1,400 m above the crater rim. No additional ash emissions were reported in June.

Activity during 2017 and 2018. JMA reported that no eruptions occurred during 2017. Amplitudes of volcanic tremor increased somewhat during March but were generally low for the rest of the year. The earthquake hypocenters were mostly located near the active crater at around sea level. SO2 emissions were slightly less than 1,000 tons per day (t/d) from January through April; for the rest of the year they ranged from 600 to 2,500 t/d. The Alert Level had been lowered from 2 to 1 on 7 February 2017 where it remained throughout the year. Steam plumes generally rose no more than 600 m above the active crater rim (figure 42). JMA noted that from January to June they often observed crater incandescence at night with a high-sensitivity surveillance camera; Sentinel-2 satellite images also captured thermal anomalies a few times (figure 43). The green lake inside the crater persisted throughout the year with water temperatures of 50-60°C. Two fumaroles were present with high-temperature gas emissions on the SW and S crater walls. Temperatures at the S crater wall were over 600°C from February to May; they decreased to 320-560°C during the rest of the year (figure 44). Sulfur deposits were visible around the SW crater wall fumarole during July.

Figure (see Caption) Figure 42. Steam plumes that rose around 600 m above Nakadake Crater 1 at Asosan were typical activity throughout 2017. Images taken with JMA webcam on 9 June (top left), 22 August (top right), 12 November (bottom left), and 20 December (bottom right) 2017. Courtesy of JMA (Aso volcano monthly activity reports, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 43. Sentinel-2 images captured thermal anomalies at the S rim of the green lake at Asosan's Nakadake Crater 1 on 16 February (left) and 27 May 2017 (right). JMA reported that incandescence was occasionally visible during the night from January-June from the same area. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 44. High-temperature gas and steam from fumaroles on the S wall of the Nakadake Crater 1 at Asosan on 24 August (top) and 17 November 2017 (bottom) were persistent all year, with temperatures ranging from 300 to over 600°C. The green lake inside the crater persisted throughout the year as well with water temperatures of 50-60°C. Courtesy of JMA (Aso volcano monthly activity reports, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).

The Alert Level did not change at Asosan during 2018, and no eruptions were reported. Sulfur dioxide emissions fluctuated between 400 and 1,800 t/d throughout the year. Steam plumes generally rose less than 500 m above the active crater (figure 45); incandescence was observed at night during May-October and sometimes observed in satellite imagery as thermal anomalies (figure 46). The temperature of the green lake inside the crater ranged from 58 to 75°C throughout the year. The thermal anomaly on the S wall of the crater was consistently in the 300-500°C range, and had a high temperature in April of 580°C; in December the high temperature had risen to 738°C (figure 47). A brief increase in the number of isolated tremors occurred during March, with 1,044 reported on 4 March, exceeding the previous maximum of 1,000 on 27 October 2014. Seismicity also increased briefly during June, with more than 400 events reported each day on 8, 18, and 20 June. The Minami Aso village Yoshioka fumarole zone, located about 5 km W of Nakadake Crater 1, continued to produce modest steam plumes throughout 2017 and 2018 (figure 48).

Figure (see Caption) Figure 45. Typical steam plumes at Asosan during 2018 rose around 500 m above the Nakadake Crater 1. Images are from 4 March (top left), 22 July (top right), 17 August (lower left), and 13 September 2018 (lower right). Courtesy of JMA (Aso volcano monthly activity reports, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 46. Nighttime incandescence was reported by JMA during May-October 2018 from the S rim of Nakadake Crater 1 at Asosan; Sentinel-2 satellite images (bands 12, 4, 2) captured thermal anomalies from the same area numerous times during 2018 including on 16 June (top left), 26 July and 19 September (middle row), and 18 and 23 November (bottom row). JMA photographed incandescence at night on 17 July 2018 at the S fumarole area (top right). Courtesy of Sentinel Hub Playground and JMA (Aso volcano Monthly Report for July 2018).
Figure (see Caption) Figure 47. The "Green Tea Pond" inside Nakadake Crater 1 at Asosan had temperatures that ranged from 58 to 75°C during 2018 (top row, 26 March 2018); the thermal anomaly on the S wall of the crater consistently had temperatures measured in the 300-500°C range and the SW fumarole area had somewhat lower temperatures (bottom row, 22 June 2018). Courtesy of JMA (monthly Asosan reports for March, May, and June 2018).
Figure (see Caption) Figure 48. The Minami Aso village Yoshioka fumarole zone, located about 5 km W of Nakadake Crater 1 at Asosan, continued to produce modest steam plumes throughout 2017 and 2018. It is shown here on 20 December 2017 (top) and 12 March 2018 (bottom). Courtesy of JMA (December 2017 and March 2018 monthly volcano reports).

Activity during 2019. Steam plumes rose to 800 m above the crater rim during January 2019. Overall activity increased slightly during February; SO2 emissions peaked at 2,200 t/d early in the month; they ranged from 800 to 1,800 t/d for most of the month. The amplitude of volcanic tremor also increased slightly during February. A further increase in tremor amplitude on 11 March 2019 prompted JMA to raise the Alert Level from 1 to 2 the following morning. Volcanic tremor amplitude decreased on 15 March; JMA determined that activity had decreased, and the Alert Level was lowered back to 1 on 29 March 2019. The amount of water in the crater decreased significantly between 27 February and 20 March, exposing part of the crater floor.

The surface temperature of the lake rose during the first part of 2019; it was 78°C in February and 84°C in March. Steam plumes rose to 1,200 m above the crater rim during March and April. SO2 emissions rose to 4,500 t/d on 12 March but dropped to a lower range of 1,300-2,400 for the rest of the month. Another surge in SO2 emissions on 12 April 2019 to 3,600 t/d prompted a special report from JMA the following day. SO2 emissions varied from about 1,700 to 4,100 t/d during the month; values remained high during the second half of the month. JMA noted that the color of the water in the lake inside Nakadake Crater 1 changed from green to gray after 4 April. Fountains of muddy water were periodically observed; they reached 15 m high on 9 April. The temperatures of both the lake (82°C) and around the two fumarole areas (S area about 530°C, SW area about 310°C) remained constant during April and similar to March.

A large increase in the amplitude of volcanic tremor early on 14 April 2019 prompted JMA to raise the Alert Level from 1 to 2 later in the day. The epicenters of the earthquakes were very shallow, located within 1 km beneath the crater. A small eruption occurred at 1828 on 16 April at Nakadake Crater 1; it produced a gray and white plume that rose 200 m above the crater rim and was the first eruption since 8 October 2016 (figure 49). Incandescence was observed inside the crater on 3 and 17 April. The amplitude of seismic tremors decreased on 18 April. Three very small eruptions on 19 April produced ash and steam plumes that rose 500 m above the crater rim. During a site visit that day JMA measured a high-temperature area that produced incandescence from the bottom of the crater at night (figure 50).

Figure (see Caption) Figure 49. The first eruption since October 2016 at Nakadake Crater 1 at Asosan on 16 April 2019 sent an ash plume 200 m above the crater rim (top). Incandescent gas appeared on the crater floor the next day (bottom). Courtesy of JMA (Aso volcano monthly activity reports, April 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 50. Three small explosions on 19 April 2019 at Asosan's Nakadake Crater 1 produced small ash emissions that rose 500 m above the crater rim (top). A strong thermal signal also appeared from the bottom of the crater. Courtesy of JMA (Aso volcano monthly activity reports, April 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).

A new eruption began at 1540 on 3 May that lasted until 0620 on 5 May (figure 51). Initially the ash plume rose 600 m above the crater rim, but a few hours later the volume of ash increased, and the plume reached 2 km above the crater rim for a brief period. Incandescence was visible from the webcam. The Tokyo VAAC reported the ash plume at 3 km altitude drifting SE on 3 May. Later in the day it rose to 3.7 km altitude and drifted SW. During a field survey the following day (4 May) JMA reported a steam and ash plume rising from the center of the active crater. The infrared thermal imaging camera recorded the temperature of the plume at about 500°C (figure 52).

Figure (see Caption) Figure 51. An explosion at Asosan's Nakadake Crater 1 on 3 May 2019 produced an ash plume that reached 2 km above the crater rim (top) and incandescence visible from the webcam (bottom). Courtesy of JMA (Aso volcano monthly activity reports, April 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 52. During a site visit on 4 May 2019, staff from JMA witnessed an ash and steam plume rising from the bottom of Nakadake Crater 1 at Asosan (top). The infrared thermal imaging camera recorded the temperature of the plume at about 500°C (bottom). Courtesy of JMA (Aso volcano monthly activity reports, May 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).

Ash fell on the S flank, and a small amount of ashfall on 4 May was confirmed by evidence on a car windshield in Takamori Town (6 km S), Kumamoto Prefecture (figure 53). Ashfall was also reported in Takamori-machi, Minami Aso village (9 km SW), and part of Yamato-cho (25 km SW), also in the Kumamoto Prefecture. SO2 emissions were measured as high as 4,000 t/d on 4 May. Additional explosions with ash plumes were reported from Asosan on 9, 12-16, 29, and 31 May; the plumes rose from 200 to 1,400 m above the crater rim but were not visible in satellite imagery. The TROPOMI instrument on the Sentinel-5 satellite captured SO2 plumes on 3 and 26 May 2019 (figure 54).

Figure (see Caption) Figure 53. Ashfall was reported on 4 May 2019 in Takamori Town, Kumamoto Prefecture, from the eruption at Asosan's Nakadake Crater 1 on 3 May 2019. Courtesy of JMA (Aso volcano monthly activity reports, May 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 54. Plumes of SO2 from Asosan were recorded by the TROPOMI instrument on the Sentinel-5P satellite on 3 (left) and 26 (right) May 2019. Courtesy of NASA Goddard Space Flight Center.

Steam plumes rose to 1,700 m above the crater rim during June 2019 (figure 55). During field visits on 6 and 25 June diffuse ash emissions were observed rising from the center of the active crater, but they did not extend significantly above the crater rim (figure 56). The maximum temperature of the plume was measured at about 340°C with a thermal imaging camera. Almost all of the water in the crater bottom had evaporated since early May; incandescence continued to be observed within the crater at night with the high-resolution webcam (figure 57).

Figure (see Caption) Figure 55. Steam plumes rose to 1,700 m above the crater rim at Asosan's Nakadake Crater 1 on 10 June 2019. Courtesy of JMA (Aso volcano monthly activity reports, June 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 56. Plumes of gas and minor ash were visible at Asosan's Nakadake Crater 1 during site visits by JMA on 6 (left) and 25 (right) June 2019. Courtesy of JMA (Aso volcano monthly activity reports, June 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).
Figure (see Caption) Figure 57. Incandescent gas was visible from the vent at Asosan's Nakadake Crater 1 on 18 (left) and 25 (right) June 2019. Courtesy of JMA (Aso volcano monthly activity reports, June 2019, Fukuoka District Meteorological Observatory, Regional volcano monitoring and warning center).

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

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


Nyamuragira (DR Congo) — May 2019 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Lava lake reappears in central crater in April 2018; activity tapers off during April 2019

The Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo is part of the western branch of the East African Rift System. Nyamuragira (or Nyamulagira), a high-potassium basaltic shield volcano on the W edge of VVP, includes a lava field that covers over 1,100 km2 and contains more than 100 flank cones in addition to a large central crater (see figure 63, BGVN 42:06). A lava lake that had been active for many years emptied from the central crater in 1938. Numerous flank eruptions were observed after that time, the most recent during November 2011-March 2012 on the NE flank. This was followed by a period of degassing with unusually SO2-rich plumes from April 2012 through April 2014 (BGVN 42:06). The lava lake reappeared during July 2014-April 2016 and November 2016-May 2017, producing a strong thermal signature. After a year of quiet, a new lava lake appeared in April 2018, reported below (through May 2019) with information provided by the Observatoire Volcanologique de Goma (OVG), MONUSCO (the United Nations Organization working in the area), and satellite data and imagery from multiple sources.

Fresh lava reappeared inside the summit crater in mid-April 2018 from a lava lake and adjacent spatter cone. Satellite imagery and very limited ground-based observations suggested that intermittent pulses of activity from both sources produced significant lava flows within the summit crater through April 2019 when the strength of the thermal signal declined significantly. Images from May 2019 showed a smaller but persistent thermal anomaly within the crater.

Activity from October 2017-May 2019. Indications of thermal activity tapered off in May 2017 (BGVN 42:11). On 20 October 2017 OVG released a communication stating that a brief episode of unspecified activity occurred on 17 and 18 October, but the volcano returned to lower activity levels on 20 October. There was no evidence of thermal activity during the month. The volcano remained quiet with no reports of thermal activity until April 2018 (figure 73).

Figure (see Caption) Figure 73. Sentinel-2 satellite images (bands 12, 4, 2) indicated no thermal activity at Nyamuragira on 19 November (top left), 14 December 2017 (top right) and 18 January 2018 (bottom). However, Nyiragongo (about 13 km SE) had an active lava lake with a gas plume drifting SW on 18 January 2018 (bottom right). Courtesy of Sentinel Hub Playground.

OVG reported the new lava emissions beginning on 14 April 2018 as appearing from both the lava lake and a small adjacent spatter cone (figure 74). The first satellite image showing thermal activity at the summit appeared on 18 April 2018 (figure 75) and coincided with the abrupt beginning of strong MIROVA thermal signals (figure 76). MODVOLC thermal alerts also first appeared on 18 April 2018. An image of the active crater taken on 9 May 2018 showed the lake filled with fresh lava and two adjacent incandescent spatter cones (figure 77).

Figure (see Caption) Figure 74. Fresh lava reappeared at Nyamuragira's crater during April 2018 from the lava lake (left) and the adjacent small spatter cone (right). Courtesy of OVG (Republique Democratique du Congo, Ministere de la Recherche Scientifique, Observatoire Volcanologique de Goma, Direction Generale Goma, Rapport Avril 2018).
Figure (see Caption) Figure 75. The first satellite image (bands 12, 4, 2) indicating renewed thermal activity at the Nyamuragira crater appeared on 18 April 2018; the signal remained strong a few weeks later on 3 May 2018. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 76. A strong thermal signal appeared in the MIROVA graph of Log Radiative Power on 18 April 2018 for Nyamuragira, indicating a return of the lava lake at the summit crater. Courtesy of MIROVA.
Figure (see Caption) Figure 77. Fresh lava filled the lake inside the crater at Nyamuragira on 9 May 2018. Two spatter cones were incandescent with gas emissions. Courtesy of OVG (Republique Democratique du Congo, Ministere de la Recherche Scientifique, Observatoire Volcanologique de Goma, Direction Generale Goma, Rapport Mai 2018).

Satellite images confirmed that ongoing activity from the lava lake remained strong during June -September 2018 (figure 78). A mission to Nyamuragira was carried out by helicopter provided by MONUSCO on 20 July 2018; lava lake activity was observed along with gas emissions from the small spatter cone (figure 79). OVG reported increased volcanic seismicity during 1-3 and 10-17 September 2018, and also during October, located in the crater area, mostly at depths of 0-5 km.

Figure (see Caption) Figure 78. Sentinel-2 satellite images (bands 12, 4, 2) confirmed that ongoing activity from the lava lake at Nyamuragira remained strong during June-September 2018, likely covering the crater floor with a significant amount of fresh lava. Image are from 12 June (top left), 7 July (top right), 17 July (middle left), 22 July (middle right), 11 August (bottom left), and 20 September (bottom right). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 79. The crater at Nyamuragira on 20 July 2018 had an active lava lake and adjacent incandescent spatter cone with gas emissions. Courtesy of OVG (Republique Democratique du Congo, Ministere de la Recherche Scientifique, Observatoire Volcanologique de Goma, Direction Generale Goma, Rapport Juillet 2018).

Personnel from OVG and MONUSCO (United Nations Organization Stabilization Mission in DR Congo) made site visits on 11 October and 2 November 2018 and concluded that the level of the active lava lake had increased during that time (figure 80). On 2 November OVG measured the height from the base of the active cone to the W rim of the crater as 58 m (figure 81).

Figure (see Caption) Figure 80. OVG scientists reported a rise in the lake level between site visits to the Nyamuragira crater on 11 October (top) and 2 November 2018 (bottom). Top image courtesy of MONUSCO and Culture Vulcan, bottom image courtesy of OVG (Republique Democratique du Congo, Ministere de la Recherche Scientifique, Observatoire Volcanologique de Goma, Direction Generale Goma, Rapport Octobre 2018).
Figure (see Caption) Figure 81. On 2 November 2018 scientists from OVG measured the height from the base of the active cone to the W rim of the crater as 58 m. Courtesy of OVG (Republique Democratique du Congo, Ministere de la Recherche Scientifique, Observatoire Volcanologique de Goma, Direction Generale Goma, Rapport Octobre 2018).

Seismicity remained high during November 2018 but decreased significantly during December. Instrument and access issues in January 2019 prevented accurate assessment of seismicity for the month. The lava lake remained active with periodic surges of thermal activity during November 2018-March 2019 (figure 82). Multiple images show incandescence in multiple places within the crater, suggesting significant fresh overflowing lava.

Figure (see Caption) Figure 82. The active lava lake at Nyamuragira produced strong thermal signals from November 2018 through March 2019 that were recorded in Sentinel-2 satellite images (bands 12, 4, 2). Several images suggest fresh lava cooling around the rim of the crater in addition to the active lake. A relatively cloud-free day on 19 November 2018 (top left) revealed no clear thermal signal, but a strong signal was recorded on 29 November (top right) despite significant cloud cover. Images from 13 and 28 January 2019 (second row) both showed evidence of incandescent lava in multiple places within the crater. The thermal signal was smaller and focused on the center of the crater on 12 and 27 February 2019 (third row). Images taken on 9 and 19 March 2019 clearly showed incandescent material at the center of the crater and around the rim (bottom row). Courtesy of Sentinel Hub Playground.

On 12 April 2019 a Ukrainian Aviation Unit supported by MONUSCO provided support for scientists visiting the crater for observations and seismic analysis. Satellite data confirmed ongoing thermal activity into May, although the strength of the signal appeared to decrease (figure 83). MODVOLC thermal alerts ceased after 8 April, and the MIROVA thermal data also confirmed a decrease in the strength of the thermal signal during April 2019 (figure 84).

Figure (see Caption) Figure 83. Sentinel-2 satellite data (bands 12, 4, 2) confirmed ongoing thermal activity at Nyamuragira into May 2019. The thermal anomalies on 18 April (left) and 3 May (right) 2019 were smaller than those recorded during previous months. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 84. The MIROVA graph of thermal activity (log radiative power) at Nyamuragira from 16 July 2018 through April 2019 showed near-constant levels of high activity through April 2019 when it declined. This corresponded well with satellite and ground-based observations. Courtesy of MIROVA.

Geologic Background. Africa's most active volcano, Nyamuragira, is a massive high-potassium basaltic shield about 25 km N of Lake Kivu. Also known as Nyamulagira, it has generated extensive lava flows that cover 1500 km2 of the western branch of the East African Rift. The broad low-angle shield volcano contrasts dramatically with the adjacent steep-sided Nyiragongo to the SW. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Historical eruptions have occurred within the summit caldera, as well as from the numerous fissures and cinder cones on the flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu.

Information Contacts: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; Katcho Karume, Director; Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MONUSCO, United Nations Organization Stabilization Mission in the DR Congo (URL: https://monusco.unmissions.org/en/, Twitter: @MONUSCO); Cultur Volcan, Journal d'un volcanophile (URL: https://laculturevolcan.blogspot.com), Twitter: @CultureVolcan).


Tengger Caldera (Indonesia) — May 2019 Citation iconCite this Report

Tengger Caldera

Indonesia

7.942°S, 112.95°E; summit elev. 2329 m

All times are local (unless otherwise noted)


New explosions with ash plumes from Bromo Cone mid-February-April 2019

The 16-km-wide Tengger Caldera in East Java, Indonesia is a massive volcanic complex with numerous overlapping stratovolcanos (figure 11). Mount Bromo is a pyroclastic cone that lies within the large Sandsea Caldera at the northern end of the complex (figure 12) and has erupted more than 20 times during each of the last two centuries. It is part of the Bromo Tengger Semeru National Park (also a UNESCO Biosphere Reserve) and is frequently visited by tourists. The last eruption from November 2015 to November 2016 produced hundreds of ash plumes that rose as high as 4 km altitude; some of them drifted for hundreds of kilometers before dissipating and briefly disrupted air traffic. Only steam and gas plumes were observed at Mount Bromo from December 2016 to February 2018 when a new series of explosions with ash plumes began; they are covered in this report with information provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC). Copyrighted ground and drone-based images from Øystein Lund Andersen have been used with permission of the photographer.

Figure (see Caption) Figure 11. The Tengger Caldera viewed from the north Mount Bromo issuing steam in the foreground and Semeru volcano in the background on 30 September 2018. Courtesy of Øystein Lund Andersen, used with permission.
Figure (see Caption) Figure 12. Aerial view of the Bromo Cone in Tengger Caldera seen from the west on 30 September 2018. Courtesy of Øystein Lund Andersen, used with permission.

PVMBG lowered the Alert Level at Bromo on 21 October 2016 from III to II near the end of an eruptive episode lasting nearly a year. The last VAAC report was issued on 12 November 2016 (BGVN 41:12) noting that the last ash emission had been observed the previous day drifting NW at 3 km altitude. Throughout 2017 and 2018 Bromo remained at Alert Level II, with no unusual activity described by PVMBG. During 1-2 September 2018, a wildfire in the Bromo Tengger Semeru National Park burned 65 hectares of savannah (figure 13); the fire produced 12 MODVOLC thermal alerts around the Tengger Caldera rim. No reports of increased volcanic activity were issued by PVMBG during the period.

Figure (see Caption) Figure 13. A wall of fire in the Bromo Tengger Semeru National Park savanna during 1-2 September 2018 produced thermal alerts that were not related to volcanic activity at the Bromo Cone in Tengger Caldera. Image courtesy of the park authority, reported by Mongabay. MODVOLC thermal alerts courtesy of Hawai'i Institute of Geophysics and Planetology (HIGP).

After slightly more than two years of little activity other than gas and steam plumes, ash emissions resumed from the Bromo Cone on 18 February 2019. After a brief pause, a new explosion on 10 March marked the beginning of a series of near-daily ash emissions that lasted for the rest of March, producing ash plumes that rose to altitudes ranging from 3.0 to 5.2 km and drifted in many different directions. A new series of ash emissions began on 6 April, rising to 3 km and also drifting in multiple directions. Ash emission density decreased during the month; plumes were only rising a few hundred meters above the summit by the end of April and consisted of mostly steam and moderate amounts of ash.

Activity during February-April 2019. PVMBG reported that at 0600 on 18 February 2019 an eruption at Tengger Caldera's Bromo Cone generated a dense white-and-brown ash plume that rose 600 m and drifted WSW. The plume was not visible in satellite imagery, according to the Darwin VAAC. The Alert Level remained at 2 (on a scale of 1-4). After a few weeks of quiet a new explosion on 10 March (local time) produced a white, brown, and gray ash plume that rose 600 m above the summit; the plume was visible in satellite imagery extending SW. Increased tremor amplitude was also reported on 10 March. A new emission the next morning produced similar ash plumes that drifted S, SW, and W at 3 km altitude. On the morning of 12 March (local time) a continuous ash plume was observed in satellite imagery at 3.4 km altitude drifting SW. The plume drifted counterclockwise towards the S, E, and NE throughout the day and continued to drift NE and SE on 13 March. The altitude of the plume was reported at 4.3 km later that day based on a pilot report.

Continuous brown, gray, and black ash emissions were reported by PVMBG during 14-19 March at altitudes ranging from 3 to 3.9 km; they drifted generally NE to NW. Ashfall was noted around the crater and downwind a short distance. The Darwin VAAC reported continuous ash emissions to 5.2 km altitude drifting SE on 20 March. It was initially reported by a pilot and partially discernable in satellite imagery before dissipating. Ongoing ash emissions of variable densities and colors ranging from white to black were intermittently visible in satellite imagery and confirmed in webcam and ground reports at around 3.0 km altitude during 21-25 March (figures 14-17). Ashfall impacted the closest villages to Bromo, including Cemara Lawang (30 km NW), which was covered by a thin layer of ash. A few trees in the area were toppled over by the weight of the ash. The plume altitude increased slightly on 26 March to 3.7-3.9 km, drifting N and NE. The higher altitude plume dissipated early on 28 March, but ash emissions continued at 3.0 km for the rest of the day.

Figure (see Caption) Figure 14. Ash drifted NNE from the Bromo Cone in Tengger Caldera on 23 March 2019. Courtesy of Øystein Lund Andersen (drone image), used with permission.
Figure (see Caption) Figure 15. Ash drifted N from the Bromo Cone in Tengger Caldera on 23 March 2019. The Batok Cone is on the right, Segera Wedi is behind Bromo, and Semeru is in the far background. Courtesy of Øystein Lund Andersen, used with permission.
Figure (see Caption) Figure 16. A few trees toppled from ashfall in the vicinity of the Bromo Cone in Tengger Caldera on 24 March 2019. Courtesy of Øystein Lund Andersen, used with permission.
Figure (see Caption) Figure 17. Ash plumes from the Bromo Cone in Tengger Caldera on 24 March 2019 caused ashfall in communities as far as 30 km away. View is from the floor of the Sandsea Caldera. Courtesy of Øystein Lund Andersen, used with permission.

After just a few days of quiet, new ash emissions rising to 3.0 km altitude and drifting SE were reported by both PVMBG (from the webcam) and the Darwin VAAC on 6 April 2019. By the next day the continuous ash emissions were drifting N, then E during 8-10 April, and S during 11 and 12 April. A new emission seen in the webcam was reported by the Darwin VAAC on 15 April (UTC) that rose to 3.0 km and drifted W. Ash plumes were intermittently visible in either webcam or satellite imagery until 17 April rising 500-1,000 m above the crater; from 19-25 April only steam plumes were reported rising 300-500 m above the summit. A minor ash emission was reported from the webcam on 26 April that rose to 3.0 km altitude and drifted NE for a few hours before dissipating. PVMBG reported medium density white to gray ash plumes that rose 400-600 m above the crater for the remainder of the month.

Geologic Background. The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com); Mongabay, URL: https://news.mongabay.com/2018/09/fires-tear-through-east-java-park-threatening-leopard-habitat/.

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Bulletin of the Global Volcanism Network - Volume 43, Number 05 (May 2018)

Managing Editor: Edward Venzke

Bagana (Papua New Guinea)

Intermittent ash plumes and thermal anomalies continue through 15 April 2018

Dieng Volcanic Complex (Indonesia)

Phreatic explosion on 1 April 2018 at Sileri Crater

Ibu (Indonesia)

Ongoing thermal anomalies from dome growth in the summit crater through April 2018

Karangetang (Indonesia)

Small ash plume and incandescence seen on 2 February 2018

Kikai (Japan)

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

Klyuchevskoy (Russia)

Intermittent moderate gas, steam, and ash plumes during December 2017-February 2018

Pacaya (Guatemala)

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

Reventador (Ecuador)

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

Santa Maria (Guatemala)

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

Sheveluch (Russia)

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



Bagana (Papua New Guinea) — May 2018 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)


Intermittent ash plumes and thermal anomalies continue through 15 April 2018

Bagana is a relatively remote volcano on Bougainville Island that is poorly monitored except by satellite. The most recent eruptive phase began on or before early 2000 with intermittent ash plumes and thermal anomalies (BGVN 41:04, 41:07, 42:08). During the period 13 June 2017-15 April 2018, this same pattern of activity continued. Intermittent ash plumes rose to 2.1-2.4 km altitude (table 6). Plume activity was especially elevated during August 2017. Satellite data indicate that both plume activity and thermal alerts had decreased markedly by the beginning of March 2018.

Table 6. Summary of ash plumes from Bagana reported during 14 June 2017-15 April 2018. Courtesy of the Darwin Volcanic Ash Advisory Centre (VAAC).

Date Max Plume Altitude (km) Plume Drift
14 Jun 2017 2.1 65 km SW, W, NW
22, 25 Jun 2017 2.1 NW
02 Jul 2017 2.1 W
16 Jul 2017 2.1 W
23 Jul 2017 2.1 W
01 Aug 2017 2.1 W
05-08 Aug 2017 2.1 Multiple
09-10, 13 Aug 2017 2.4 W, NW (120 km W on 13 Aug)
24-28 Aug 2017 2.1-2.4 WNW, W, SW
31 Aug 2017 2.1 N, W, SW
11-12 Sep 2017 2.1 NW
27 Oct 2017 2.1 E, NE
03 Nov 2017 2.4 NE
15-17 Nov 2017 2.1 N, SW, SSW, W
25-26 Dec 2017 2.4 NE
07-08 Feb 2018 2.4 NE
26-27 Feb 2018 2.1 WNW
02 Mar 2018 2.4 NE
14-15 Apr 2018 2.1-2.4 110 km SW

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed 0-3 days each month during June-November 2017, seven days in December 2017, one day in January 2018, and two days in February 2018. More than two pixels were recorded on 4-5 and 9 December (up to five pixels), 31 January (4 pixels), and 4 February (5 pixels).

The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, recorded a moderate number of thermal alerts within 5 km of the volcano from June through late November 2017, except for a decrease between mid-September and mid-October (figure 29). Activity rose sharply during the end of November through early December and again during the first half of January before tapering off, a pattern inconsistent with the reported ash plumes. Few hotspots were detected between mid-February through 15 April, a pattern consistent with the MODVOLC data.

Figure (see Caption) Figure 29. Thermal anomalies at Bagana shown on a MIROVA plot (Log Radiative Power) for the year ending 27 April 2018. Courtesy of MIROVA.

Sulfur dioxide anomalies since June 2016 above 2.5 Dobson Units (Ozone Monitoring Instrument, OMI) or above 1.6 Dobson Units (Ozone Mapping and Profiler Suite, OMPS) occurred in 2016 on 4 and 6 July, 10-11 October, 11 November, and 3 December. Similar emissions were detected in 2017 on 30 January, 3 and 19 March, 15 April, 5 August, and 2 and 7 December. The satellite data showed high levels of SO2 in 2018 on 8 and 24 February, and 29 March.

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/); MIROVA, a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Dieng Volcanic Complex (Indonesia) — May 2018 Citation iconCite this Report

Dieng Volcanic Complex

Indonesia

7.2°S, 109.879°E; summit elev. 2565 m

All times are local (unless otherwise noted)


Phreatic explosion on 1 April 2018 at Sileri Crater

Dieng has had a history of intermittent phreatic explosions. In 2017, explosions occurred on 30 April, 24 May, and 2 July (BGVN 42:10). Another phreatic explosion occurred on 1 April 2018. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

PVMBG reported that a phreatic explosion at the Sileri Crater lake (Dieng Volcanic Complex) occurred at 1342 on 1 April 2018, ejecting mud and material 150 m high, and up to 200 m in multiple directions. The event was preceded by black emissions that rose 90 m, and then diffuse white emissions that rose 150 m. The report noted that few tourists were in the area due to rainy weather; visitors are not permitted within 200 m of the crater rim.

According to a news report (The Jakarta Post) that cited an official of the National Disaster Management Agency (BNPB), no toxic gases such as carbon dioxide, hydrogen sulfide, or sulfur dioxide were detected in the explosion.

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

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


Ibu (Indonesia) — May 2018 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


Ongoing thermal anomalies from dome growth in the summit crater through April 2018

Ongoing activity at Ibu volcano from April through August 2017 consisted primarily of intermittent ash explosions (BGVN 42:10). Based on data and reports through April 2018, the eruption that began on 5 April 2008 appeared to be continuing. Monitoring of the volcano is the responsibility of the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Center for Volcanology and Geological Hazard Mitigation (CVGHM). Additional data below come from the Darwin Volcanic Ash Advisory Centre (VAAC) notices, with infrared MODIS data analyzed by the MODVOLC and MIROVA systems.

There were no reports of ash plumes from September 2017 through early March 2018. Although the summit area is often covered in fog, on 7-8 March ash plumes were observed rising 300-600 m above the crater rim and drifting W and S (table 3). Additional eruption plumes with ash were reported on 20 and 30 April. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2-3.5 km away from the active crater.

Table 3. Monthly summary of reported ash plumes and MODIS thermal anomalies from Ibu for August 2017-April 2018. The direction of drift for the ash plume through each month is highly variable. Data from Darwin VAAC, PVMBG, and MODVOLC.

Month Plume Altitude (km) Plume Drift Days with MODVOLC Alert Pixels
Sep 2017 -- -- 4
Oct 2017 -- -- 5
Nov 2017 -- -- 4
Dec 2017 -- -- 4
Jan 2018 -- -- 4
Feb 2018 -- -- 2
Mar 2018 1.6-1.9 W, S 2
Apr 2018 1.8-1.9 E, S 3

Thermal anomalies identified by the MIROVA system using MODIS satellite data (figure 12) show that activity has been ongoing and almost continuous during May 2017-April 2018. Anomalies for the same time period detected and mapped using MODVOLC (figure 13, table 3) appear to be centered towards the north part of the crater and possibly extending down the N flank. This may indicate eruptive activity similar to that reported by PVMBG in June-December 2013 (BGVN 38:11) where the lava dome grew above the crater rim and sent incandescent material over a low notch in the rim and down a river valley towards Duono village, about 5 km NW.

Figure (see Caption) Figure 12. Thermal anomalies at Ibu shown on a MIROVA plot (Log Radiative Power) for the year ending 3 May 2018. Courtesy of MIROVA.
Figure (see Caption) Figure 13. A contour map showing MODVOLC thermal alert pixels at Ibu for the year ending 3 May 2018. Pixels are centered at the north crater rim and down the N flank. Courtesy of Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System.

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

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


Karangetang (Indonesia) — May 2018 Citation iconCite this Report

Karangetang

Indonesia

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

All times are local (unless otherwise noted)


Small ash plume and incandescence seen on 2 February 2018

Eruptive activity at Karangetang between June 2014 and March 2016 included intermittent ash plumes, lava flows, pyroclastic flows, and persistent thermal anomalies from a slowly growing lava dome (BGVN 42:02) south of the highest summit (figure 16). Activity since mid-March 2016 has been low, with only a few notable events consisting of a possible ash plume on 10 May 2017, a strong sulfur dioxide emission on 10 October 2017, and a small ash explosion on 2 February 2018. Information was mainly provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC).

Figure (see Caption) Figure 16. Satellite image of the summit area of Karangetang on 27 June 2012. The active dome is steaming, with the fumarolic plume curving towards the NE. Dark-colored recent lava flows are noticeable. The higher inactive summit is about 500 m N and 20 m higher than the active dome. Courtesy of DigitalGlobe and Google Earth.

Based on analyses of satellite imagery, wind data, and ground-based visual observations, the Darwin VAAC reported that on 10 May 2017 a gas-and-steam plume apparently containing ash rose to an altitude of 3.6 km and drifted over 35 km SE. The Aviation Color Code was briefly raised to Orange.

According to a news account (Antara News) that quoted the chief of the volcano's observatory post, "sulfuric smoke" rose 200 m on 10 October 2017. The official stated that this was natural activity for the volcano and also indicated that several types of tremor had occurred the previous day. A small SO2 anomaly near the volcano was detected on 11 October 2017, registering 2.1 Dobson Units on the Aura satellite Ozone Monitoring Instrument.

In a Volcano Observatory Notice for Aviation (VONA) issued on 2 February 2018, PVMBG reported an explosion, crater incandescence, and an ash plume that rose 600 m above the summit. The Aviation Color Code was raised from Unassigned to Yellow.

No MODVOLC thermal anomalies were detected during the reporting period. The MIROVA system, however, detected twelve scattered low-power thermal anomalies in the year ending on 26 April 2018. One of the thermal anomalies occurred around 10 October.

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/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Antara News (URL: https://en.antaranews.com/).


Kikai (Japan) — May 2018 Citation iconCite this Report

Kikai

Japan

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Klyuchevskoy (Russia) — May 2018 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Intermittent moderate gas, steam, and ash plumes during December 2017-February 2018

Klyuchevskoy has been active for many decades, alternating between eruptive and less active periods. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters. The current eruptive period began in late August 2015. Lava effusion ended in early November 2016 but explosive activity continued to be observed through October 2017 (BGVN 42:11) and into mid-February 2018 as described below. The Kamchatkan Volcanic Eruption Response Team (KVERT) is responsible for monitoring, and is the primary source of information. The Aviation Color Code remained at Orange through April 2018.

Strong gas-and-steam activity was observed on 2-5 December 2017. Ash plumes rose to an altitude of 5.5 km and extended for about 180 km (figure 26). Emissions were reported at 2300 on 5 December 2017 with plumes extending 170 km E. Gas-and-steam and ash plumes extended for approximately 95 km to the E and SW on 7 and 13 December, respectively. On 16-19 December the gas-steam and ash plumes extended approximately 140 km E, and on 22-25 December they reached about 220 km E.

Figure (see Caption) Figure 26. Photo of Klyuchevskoy showing a gas-and-steam plume on 3 December 2017. Courtesy of Yu. Demyanchuk (IVS FEB RAS, KVERT).

Moderate eruptive activity continued into January and February 2018. On 1, 3, and 4 January gas-and-steam plumes with ash extended approximately 150 km downwind. The plume extended to 160 km N, W, and E on 5, 6, and 8-10 January (figures 27 and 28). On 12 and 17-18 January, the plume extended to 120 km W and E. The Tokyo VAAC reported that on 18 February an ash plume rose to an altitude of 5.2 km and extended SW. No further reports of ash plumes were reported through April 2018.

Figure (see Caption) Figure 27. Gas-and-steam plume with minor ash content rising from Klyuchevskoy on 6 January 2018. Courtesy of Yu. Demyanchuk (IVS FEB RAS, KVERT).
Figure (see Caption) Figure 28. Close-up satellite image of a small plume of gas, steam, and ash rising from Klyuchevskoy on 10 January 2018 taken by the Operational Land Imager (OLI) on Landsat 8. Courtesy of NASA Earth Observatory, with imagery by Joshua Stevens and Jeff Schmaltz, using Landsat data from the U.S. Geological Survey.

A weak thermal anomaly was detected over the volcano on 5, 6, 11, 16, and 22, December 2017; and on 3, 6, 8, 11, 12, 15 and 17 January 2018. The number of MIROVA thermal anomalies detected also increased in the first half of January 2018; most were low to slightly moderate in intensity.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); 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 Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Pacaya (Guatemala) — May 2018 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Reventador (Ecuador) — May 2018 Citation iconCite this Report

Reventador

Ecuador

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IGEPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Martin Rietze (URL: http://mrietze.com/web16/Ecuador17.htm).


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

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html).


Sheveluch (Russia) — May 2018 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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