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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 39, Number 11 (November 2014)

Managing Editor: Richard Wunderman

Etna (Italy)

January–13 June 2014: NSEC emits lava and 11 Feb landslide with ground-hugging reddish cloud

Fogo (Cape Verde)

Eruption of 23 November 2014 and aftermath

Korovin (United States)

Summary of activity during 1998-2007

Suwanosejima (Japan)

Periods with several eruptions per day during April 2013-December 2014



Etna (Italy) — November 2014 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


January–13 June 2014: NSEC emits lava and 11 Feb landslide with ground-hugging reddish cloud

Our last report on Etna covered activity through 31 December 2013 (BGVN 38:09) and described activity in terms of a series of paroxysms, including the emergence of a new South East Crater (NSEC; see figure 147 in BGVN 38:09).

This report covers subsequent activity from 1 January-13 June 2014 and summarizes first-hand accounts by Istituto Nazionale di Geofisica e Vulcanologia (INGV-Catania). The key events of this reporting interval were ongoing emissions of E-directed lavas from a vent area on the lower E flank of the NSEC. That same vent area at NSEC generated an unusual, reddish, ground-hugging cloud associated with a landslide on 11 February. It left a swath of pyroclastic deposits mapped for over 2 km.

A sketch map shows lava and pyroclastic emissions from October 2013 through February 2014 (figure 148). It thus gives an overview of Etna's products during the first part of this reporting interval (January through February 2014). Flows on figure 148 emitted during 2013 were discussed in the previous report (see map, figure 147, in BGVN 38:09). During January-February 2014 lava flows vented in an area on the NSEC's lower E flank. That same general area was the source of a landslide and pyroclastic deposits emplaced on 11 February 2014 (shaded in light tan with triangles or dots conveying coarser and finer deposits). The deposits were laid down by fast-moving, reddish, ground-hugging emissions.

Figure (see Caption) Figure 148. Map of Etna's summit area highlighting volcanic deposition during the interval October 2013 through 11 February 2014. Lavas of October 2013-December 2014 are shown in pale green; lavas of 14-16 December 2013, in light blue; lavas of 29 December 2013, in blue; lavas of 22 January-February 2014, in red. The 11 February 2014 pyroclastic deposits (tan) as mapped here stretch ~2.3 km W from their source at a depression (inside the hachured red line) on the lower E side of NSEC. These pyroclastic deposits are mapped into two adjacent map units on the basis of grain size. Both the pyroclastic deposits and the lava flows descended the steep W headwall of the broad valley called Valle del Bove. The valley's headwall area extends to ~2-3 km to the SE of NSEC before the slope gradient drops and the slope starts to make the transition to the valley floor. Courtesy of INGV (Etna Cartographic Laboratory).

Figure 148 also shows the important vent on NSEC's E flank (red hachured circle). Abbreviations for other summit vents: (SEC (Southeast crater), BN (Boca Nuova), VOR (Voragine), NEC (North East crater), as similarly defined in previous Bulletin reports). These other vents issued little in the way of deposits as late as the end of February 2014 (based on the map) and INGV reporting did not disclose much in the way of other deposits either.

Activity during January 2014. INGV reported that during 31 December 2013-1 January 2014 lava flows from a vent located on the NSEC continued to travel toward the N part of the Valle de Bove; the lava flows had been active since activity resumed on 29 December 2013. A 1 January web camera photo near midday showed a dense black plume emerging from NSEC. By 3 January 2014 the lava effusions stopped. Meanwhile at NEC during 4-13 January 2014 this vent released pulsating and almost continuous reddish ash emissions. Tremor remained at low amplitude into at least late January.

On the evening of 21 January after ~20 days absence (since an increase seen during 29-31 December 2013), strombolian emissions returned at NSEC. These emissions were weak. Sparse ash also discharged, barely rising over NSEC's rim.

Late on 22 January a small lava flow emerged from the vent on NSEC's upper E flank advancing over a few hundred meters in a few hours. This was the start of the lava flow shown in red on figure 148. Strombolian explosions ejected glowing pyroclasts onto NSEC's flanks. The explosions declined early on 23 January, and the lava flow stopped advancing. At 0105 that day a small puff emerging from the E base of the cone heralded the start of a new W-trending lava flow. On 26 January, strombolian emissions occurred and an ash plume drifted E. By evening the strombolian eruption declined in terms of both the amount of ash emitted and the eruptive intensity. The lava flow (red, figure 148) had by this time reached ~4 km long. Also, a new lava flow advanced on top of the earlier one.

Regarding NSEC, INGV reported that on 27-28 January it underwent a gradual but steady decrease of activity. Lava flows from two vents at the E base of the NSEC cone continued to effuse at a very low rate. Weather conditions almost entirely prevented visual and optical observations during early on 30 January until the evening of 3 February.

Activity during February 2014. Late on 3 February INGV noted a lava flow from one of the NSEC's vents along its E base remained active and had extended several hundred meters. Almost continuous ash emissions from NSEC began at about 1300 on 4 February and continued into the night; about 5-10 ash puffs were separated by steam emissions. Ash plumes drifted E. After sunset, jets of hot material were observed rising 100 m above the crater rim. At 2000 the ash emissions and injection of incandescent material ceased, but the lava flow continued and reached 1 km long. Into 5 February, lava escaped from one or two vents at the NSEC cone's E margin. Lava flows advanced several kilometers to the base of the Valle del Bove's W slope. On 6 February ash emissions ceased. Nevertheless, small Strombolian explosions ejected incandescent pyroclastic material 100 m above the crater. On 7 February Strombolian explosions ejected material onto the flanks of the NSEC; the next day ash puffs were observed.

INGV noted that the ongoing activity at NSEC that began 21 January 2014 represents a notable deviation from the behavior of the NSEC over the last three years. In the context of the last few decades of Etna activity, they viewed this as a completely normal eruptive occurrence. It is similar to emissive activity from January to March 2001 on the N flank of the old SEC, and other episodes of long duration observed in the past.

During 9-10, February activity continued to be characterized by Strombolian activity, periodic ash emissions, and advancing lava flows. On 9 February venting shifted to NSEC's W portion and included ash emissions. On 10 February at least one new eruptive vent opened upslope of the vents feeding the active flows.

At 0707 on 11 February a large, dense, reddish-brown ash cloud discharged from a lower E-flank vent area at NSEC (figure 149). Rather than rising much distance, the ash-charged cloud moved rapidly downslope. The cloud consisted of a dense hot avalanche or landslide that INGV also said looked very much like a pyroclastic flow. The ash laden cloud took about a minute to reach the base of the W wall of the Valle del Bove only stopping after it encountered less steep terrain. After this event, reddish brown ash emissions continued. The mapped portions of the 11 February pyroclastic deposits are shown on figure 148, but the ash cloud itself continued farther downslope (figure 149).

Figure (see Caption) Figure 149. The reddish ash cloud generated the morning of 11 February 2014 associated with a landslide and related eruption in the active vent area on the NSEC's E flank (upper left). This is a view from ~11 km E of NSEC (at Sant'Alfio, located on the Valle del Bove floor ~5.5 km from the closest point to the coast). Photo taken from INGV reporting on the 11 February event. They credit the photo to Casa di paglia Felcerossa-Permacultura.

Prior to the 11 February 2014 eruption, the area of collapse at the NSEC vent had contained unstable heated rock. In the past weeks, multiple vents in this area had been active. One vent near the E rim of the vent area was hot enough to glow. The presence of molten rock (e.g., magma and lava), hot gases, and the glowing vent were interpreted by INGV to have contributed to destabilizing the area that failed during the eruption.

Although the mapped area is smaller, the reddish cloud of 11 February expanded as it advanced over the lava field of 2008-2009, covering it almost entirely, and reaching the Valle del Bove with a front about 1 km wide. Shortly after reaching the level ground at the base of the W wall of the Valle del Bove, the flow stopped in an area about 3.5-4 km away from source vent. A cloud of ash rose up and drifted NE.

Lava flows also continued to erupt on 11 February. Those were associated with bluish clouds. During and after the 11 February event, the NSEC still generated persistent strombolian eruptions accompanied by small ash emissions. At 1800 on February 11 this was in progress, showing no change compared to the activity of the last days. During 11-12 February the amplitude of tremor remained slightly higher than normal but it dropped back to normal levels after that, and the average amplitudes generally remained at modest levels through mid-March.

NSEC's strombolian emissions slightly intensified on 12 February. An unstable part of the lower E flank of the vent that collapsed on 11 February continued to produce small collapses and reddish ash clouds. Lava continued to flow from the cone towards the Valle del Bove, and by nightfall had reached the base of the steep W wall of the valley. It then advanced on the flat land to the N of Mount Centenari (figure 148).

Strombolian activity continued during 12-28 February. Lava emissions declined, but produced lava flows a few hundred meters long. Lava emissions continued also from an effusive vent from the interior of the portion of the recess formed 11 February, which continued through 17 February. On 15 February an explosion generated a vapor-and-ash plume, and was then followed by more explosions from the same area. Later on 15 February a small lava flow emerged from a new vent at the N base of the NSEC cone, which traveled 100 m towards the W wall of the Valle del Bove, and remained active the next day. During 16-17 February strombolian activity continued to produce small quantities of ash. Lava continued to flow from the vent at the base of the cone.

Activity during March 2014. During 1-10 March generally weak though persistent strombolian activity and diffuse ash emissions continued at NSEC. Tremor was generally low. An unstable part of the lower E flank of the cone that collapsed on 11 February (figure 150) continued to produce small collapses with reddish ash clouds, and thermal anomalies. Lava continued to flow from a vent on the lower part of the NSEC cone to the W wall of the Valle del Bove, and during 2-3 March the flows reached the base of the wall (figure 150).

Figure (see Caption) Figure 150. Glowing Etna lava flows seen from the SE on the evening of 3 March 2014. The flows continued to vent from the lower flank of the NSEC cone. The vent was in the same area associated with the collapse of 11 February 2014. Photo credit Turi Caggegi.

After several days of lava emissions from a vent on the lower part of the NSEC cone, during 5-6 March lava flows originated only from a higher vent and traveled 1.5 km towards the lower part of the W wall of the Valle del Bove. The lava flow fed by the vent on the inside of the unstable lower portion of the lower E flank remained active on 5 March. A second flow was fed a few hundred meters downslope , with an active front on the upper margin of the 2008-2009 lava field (directly to the NE, in the direction of Monte Simone and following the lava flow of 30-31 December 2013). On 8 March BN (Bocca Nuova) issued sporadic emissions of hot material with small amounts of volcanic ash.

INGV reported that during 12-25 March strombolian activity with occasional diffuse ash emissions continued from one or two vents at the base of Etna's NSEC cone. Lava flows originating from a vent on the upper wall traveled towards the upper part of the W wall of the Valle del Bove. Strombolian activity intensified during 18-22 March, producing more ash, and then decreased; no ash was emitted on 23 March. Lava flows originating from a vent on the upper wall traveled towards the upper part of the W wall of the Valle del Bove and also NE in the direction of Monte Simone. Tremor amplitude rose slightly on 24 March but declined on 26 March to low values similar to those seen prior to the episode of persistent NSEC eruptions that began on 21 January.

Strombolian activity at the NSEC cone ceased during the night of 26-27 March, after 64 days of persistent activity. Lava emissions from the lower side of the NSEC significantly decreased; on the evening of 28 March a small lava flow continued to advance but had stopped and was cooling the next day.

Activity during April 2014. During the night of 1-2 April emissions of minor lava flows from the NE base at NSEC cone decreased. Strombolian activity gradually intensified during the evening of 2 April, along with tremor, and then both decreased. Some collapses from the E flank of the NSEC cone took place that morning. Poor weather conditions prevented views of Etna for a few days, but by 7 April the lava flows had ceased and strombolian activity had sharply declined. No activity was observed on 8 April.

No eruptive activity at Etna was observed thereafter until the early hours of 22 April, when sporadic and weak strombolian activity resumed at the NSEC and continued for the next few days. Some explosions ejected incandescent pyroclastic material out of the crater and onto the upper S and SE flanks of the cone. A few small collapses occurred on the cone's unstable E flank. Late in the evening on 30 April the frequency and intensity of Strombolian explosions slightly increased. Degassing at the NEC also increased and thermal anomalies were detected by a camera.

Activity during May-13 June 2014. During the night of 2-3 May INGV attributed incandescence to weak, high-temperature gas emissions or strombolian explosions or both. The activity intensified on 4 May; some of the explosions ejected incandescent pyroclastic material high onto NSEC's S and SE flanks. Although tremor amplitude generally remained at low levels since early April; tremor on 1 May registered in episodes (banded tremor). Weak strombolian activity at NSEC continued through at least 10 June and no noteworthy eruptions were highlighted through 13 June.

Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it).


Fogo (Cape Verde) — November 2014 Citation iconCite this Report

Fogo

Cape Verde

14.95°N, 24.35°W; summit elev. 2829 m

All times are local (unless otherwise noted)


Eruption of 23 November 2014 and aftermath

This Bulletin report covers from June 1995 through February 2015. The interval's major volcanic event began on 23 November 2014 with the eruption of lavas. Fogo continued erupting through 8 February 2015, when the Observatório Vulcanológico de Cabo Verde (OVCV) stated that the eruption ceased.

The last eruption ended in May 1995 (BGVN 20:11). There was limited information for the multi-year interval between that eruption and the one in 2014. The data for this report came from two key sources: OVCV (generally posted on their Facebook page) and Fogo News (numerous articles, URL in Information contacts section). This report also contains a list of References at the end for cited sources.

Setting. Although the island of Fogo is ~25 km across and the greatest population density resides in coastal cities (red labels, figure 4), a small population also resides in the summit caldera where the venting took place. The spreading lava from the 2014 eruption covered ~4 km2 but did not escape the caldera.

Figure (see Caption) Figure 4. (Upper right) Index map showing Cape Verde islands with respect to the W edge of Africa and highlighting the island of Fogo (in black rectangle). (Below) Map of the island of Fogo showing some key towns and political subdivisions. Taken from Copernicus (2015).

A pre-eruption satellite image (figure 5) labels villages within Fogo's summit caldera (Cha caldera). The intracaldera cone Pico (Pico do Fogo) is also the highest point on the island. The villages of Portela and Bangaeira sat 4-5 km NW of Pico and had a collective population of ~1,000 residents in 2009. Lavas overrode both these villages during the 2014 eruption and buried the main N-S road across the caldera. Later maps and images show various aspects of the intra-caldera lavas.

Figure (see Caption) Figure 5. Image of Fogo's caldera captured by the Advanced Land Imager on NASA's EO-1 satellite on 10 June 2009. The summit area (Pico) is engulfed on the W by an 8-km-wide caldera (Cha caldera). The caldera's W crater wall, the headwall of a massive E-facing lateral-collapse structure, towers 1 km above the crater floor. At its base within the caldera lay the villages of Portela and Bangaeira, which were severely damaged if not destroyed by the 2014 eruption. Courtesy of NASA Earth Observatory-1 Team (NASA image created by Jesse Allen, using EO-1 ALI data provided by the NASA EO-1 Team; caption partially derived from information provided by Holli Riebeek).

For further information regarding Fogo's setting, the Copernicus website presents InSar (satellite radar-ranging) data and E-flank topography of high relevance had lavas escaped this part of the caldera (which did not occur in 2014).

Overview on the 2014 eruption. The 23 November 2014 eruption started at 1000 local time (LT). In years prior to the eruption, the CO2 fluxes remained low and fairly stable. During the interval from 23 November 2009 to April 2014, background CO2 typically stayed well below 150 tons per day (t/d). During the March-November 2014 interval emissions increased to fluxes of ~327 t/d. Residents felt earthquakes the night before the eruption. Lava streamed from a fissure in the caldera on Pico's outer WSW flank. The initial fissure vent emerged in a location near to the vent of the 1995 eruption, though materials apparently began to vent at multiple points along the fissure. Most of the available photos showed strombolian and perhaps vulcanian activity that fed lava flows (figures 6 and 7), but news reports also indicated explosions, lava fountains, and ash emissions. An ash plume from the eruption was visible 90 km W, at the capital, Praia, on the neighboring island of Santiago (Farge, 2014). Orders were issued to evacuate the villages of Portela and Bangaeira (Caesar, 2014), and to evacuate the Parque Natural de Fogo, a large park covering much of the central part of the island (Fogo News).

Figure (see Caption) Figure 6. A press photo taken on 28 November 2014 illustrating strombolian activity with spatter emerging from the fissure vent. Note the edifice constructed around the fissure vent area, the lava flowing around this edifice, and the rising plume. Courtesy of Boston.com; photo by Saulo Montrond (Reuters).
Figure (see Caption) Figure 7. Mário Moreira, a geophysicist at the Instituto Superior de Engenharia de Lisboa, Portugal, provided photos illustrating aspects of the 2014 Fogo eruption. (A) The fissure at the base of the Pico cone releasing a thin plume at an unstated time. (B) As seen at 2000 LT on 5 December 2014, an advancing molten-surfaced lava flow. There is a building with peaked roof in the foreground of the photo, providing an aid to gauge the scale of the lava flow. (C) Several vents opened along the original fissure, which developed a crater-shaped morphology. Courtesy of Mário Moreira.

On 24 November, according to the Toulouse Volcanic Ash Advisory Center (VAAC), a plume from Fogo mainly composed of sulfur dioxide extended over 220 km NW at ~9 km altitude. Lower altitude clouds contained ash.

An overview of the lava flow dispersal from the eruption is presented below, as a map with emplacement dates depicting the advancing flows (figure 8). The map was created on 25 December 2014, comparatively late in the eruption. The original map has been cropped to emphasize the lava flows, thus leaving Pico outside the area of view. At the scale of this map the summit would reside at the apex of the curving contours located along map's E margin (a spot off the map to the right and in the midst of the words "09 Dec.") The fissure vent resides in the spur of lava trending SW from the margin of Pico cone.

Figure (see Caption) Figure 8. A map produced on 25 December 2015 that summarizes the emplacement chronology of the Fogo lava flows. The dates of the flow mapping range from 29 November 2014 to 24 December 2012 and are keyed by color. Dates in the legend reflect estimates made based on satellite imagery. The data was not validated with in situ observations. The N-S distance between the horizontal lines across the map are ~2.5 km. Cropped and with simplified legend after Copernicus (2015).

The late stage advances seen in figure 8 (darkest red colors) roughly tripled the length of the W-trending lobe. A video on the Azores Volcanological & Geothermal Observatory website showed news footage of lava flows, which were steep-sided, rough-surfaced, and perhaps ~2-10 m high in some scenes.

That web page, and one called Culture Volcan presented an annotated still photo (figure 9) that highlighted the three lobes and the eruptive source. A key point is near the terminal end of the W lobe and the foot of the headwall, where there was a rural agricultural area with houses called Ilhéu de Losna. Culture Volcan noted damaged to farms and other infrastructure in that area. A photo not shown here showed an impressive pahoehoe lava flow that appeared to be crossing one of the farms.

Figure (see Caption) Figure 9. An annotated photo of the Cha caldera, with white dashes to accentuate flow margins, taken looking ~NNE along the curving headwall. Portela and Bangaeira appear in the distance. The photo was posted on 27 December 2014. The labels are in Portuguese and translate as follows: Cha caldera headwall or rampart ("Rempart de la Caldera de Cha"); N ("nord"); S ("sud"); W ("oust"); lava flow ("coulee"), eruptive fissure ("Fissure eruptive"). Photo credit to Montrond Theo (Involcan). Credit for editing and annotations to Culture Volcan. Posted as on the website of the Azores Volcanological & Geothermal Observatory.

An OVCV report noted that the eruption ended 8 February 2015 (a total of 77 days); and some ash columns approached 6 km in altitude. They estimated some lava flows grew as thick as 18-20 m.

Silva and others (2015) discussed the 2014 eruption chronology and presented the most complete (though still preliminary) picture of lava flow advance rates. The eruption vented on the E flank of the "1995 Pico Novo vent with the appearance of four eruptive vents" discharging gases, pyroclastic rocks, and lava. The N-directed lobe of lava associated with the destruction of Portela village included both aa and pahoehoe types. These advanced with average speeds of 1-3 to 8-10 m/hour with some cases of up to 20 m/hour (~0.3 m/min). At the vent, an initial hawaiian stage of fissure eruptions gave way to a later strombolian stage. The vent's main crater grew by the coalescence of small craters; three small vents released aa lava flows. One or two lava tubes developed. The site emitted loud explosions and strong rumbling.

A pahoehoe lava flow developed along the far end of the W-directed lobe (in the Ilhéu de Losna region, figure 9). It advanced at an average speed of 0.5 m/min. The flow here buried vineyards, other crops, and houses.

Uni-CV (Universidade de Cabo Verde) also reported that during 30-31 December, a gas-and-ash plume extended to 700-800 m above the cone drifting N and tephra was ejected 30-40 m above the vent's cone. The lava front near Ilhéu de Losna (to the W of Pico do Fogo) had stopped, while the N-directed lava front near the N part of the villages continued to flow slowly over roads and buildings. Uni-CV noted that the temperatures of the lava fronts gradually decreased.

According to Uni-CV (2015), during 1-11 January 2015, dense plumes rose to 400-1,500 m above the cone and tephra rose 200-400 m above the vent. During 8-12 January, explosions were followed by noises or bangs. On 12 January 2015, continuous explosions began at 0945, growing stronger, followed by eruptive pulses. A dense, dark plume rose 2 km in height and drifted E.

On 3 February 2015 OVCV scientists saw a bluish white discoloration of the air in the caldera, which they judged as the presence of ash. Explosions were heard 1 to 4 times per minute. The ash plume rose to 0.8-1.0 km above the vent area. Rock and spatter discharged.

Beginning at 1310 on 6 February 2015 scientists heard explosions at a rate of 2 to 3 per minute. The observers saw eruptive columns of brownish color that consisted of gases, tephra, and spatter that rose to 400-600 m in height above the vent. During 1345 to 1545, explosions intensified, sending out larger pyroclasts, and eruptive columns achieved heights above the crater of 1.2-1.5 km. The clouds blew NE and formed dense ash clouds. Around 1700 there occurred intervals of lowered intensity lasting a few minutes. A more energetic episode took place at 1745 on the 6th.

The 9 March 2015 report on the Uni-CV website contained numerous photos and thermal infrared images from fieldwork during early to middle February 2014. The photos showed numerous views of near vent lavas highlighting both their varied surface textures (from highly fragmental to smooth) along with temperatures up to ~700°C (measured on the basis of emissivity, atmospheric attenuation, and various inputs and assumptions in the processessing in the FLIR-brand camera). A satellite view highlights the 2014 vent area and its location perhaps ten's of meters E of the 1995 vent. Both the 2014 and 1995 vents trended NE. Other field photos revealed elongate cones constructed around the 2014 fissure vents. The inner rims of those vent-engulfing cones were encrusted with sulfur.

OVCV reported that on 8 February the eruption at Fogo had ended. SO2 emissions were almost undetectable on 8 February and continued to remain so at least through 11 February. During that period, the lava front had not moved, and only minor fumarolic activity was present at the edge of the new crater. Lava flow temperatures had dropped.

News, human impacts, and photos revealing diverse lava flow morphology. According to Fogo News, by 25 November the lava flow, which was more than 4 km in length, had destroyed much of Portella, Bangaeira and the park headquarters. Furthermore, the local (Fogo island) airport closed. Lava destroyed utility poles, hindering communications. Fogo News added that the Cape Verde government responded to the situation by creating a crisis cabinet.

On 30 November, the eruption, although quieter for a few days, resumed at dawn, according to Agencia Lusa (2014). Lava also closed the only alternative route between the Parque Natural de Fogo and the village of Portela. Travelling at ~20 m per hour, the flow destroyed dozens of homes, a large area of agricultural land, and the museum of the Parque.

A Fogo News story noted that by 2 December, the lava flow passing through Portela had destroyed the primary school, the Pedra Brabo hotel, and several additional houses. After 24 hours of remaining stagnant, the flow began again on 2 December, reportedly moving at ~9 m per hour. Furthermore, ashfall over pastures affected local livestock, especially goats. Ash emissions caused the cancellation of some flights from the island. The news also mentioned that on 6 December the lava flow rate had increased. By 8 December, the article said that about 90% of Bangaeira and 95% of Portela had been overtaken by the lava flow. After moving through the towns, the lava-flow front was ~300 m wide.

Based on a Fogo News article, Fogo volcanism decreased on 9 December. The lava flow stopped ~3.5 km from the settlement of Fernão Gomes (~5 km directly N of Pico do Fogo and just short of a steep downward slope to the towns of Cutelo Alto and Fonsaco, on the NE coast of Fogo). Gas and ash emissions also decreased and were mostly absent by 14 December. Even though the fissure vent's output was apparently low, the remaining buildings in the town of Bangaeira were overtaken by lava.

Fogo News noted that by 10 December volcanic ash had contaminated many water sources and ash had reached N of Sao Felipe on the W coast of Fogo, ~17 km SW of Pico do Fogo. As a result, the government flew in bottles of potable water.

The lava flow morphology as well as the societal impact is revealed below through a tiny sampling of available photos. The BBC (2014), and many news outlets prepared galleries on the Fogo eruption. Martin Rietze (2014) and Richard Roscoe documented portions of the eruption. Chrys Chrystello (2014) uploaded two videos to Youtube. The first one, posted on 24 November 2014, depicts plumes released from fissures and people evacuating their homes. The second one, posted on 26 November, showed evacuation, the movement of the lava flow across the caldera, and activity at night. Not depicted here are several photos and videos posted by OVCV (on its Facebook page).

Figure 10 shows three press photos posted online on 2 December. According to the captions, Portela village residents sat in the foreground, meaning that they watched as the lava flow advanced over their community. They also tried to salvage materials from the destroyed infrastructure.

Figure (see Caption) Figure 10. Three press photos relating to the human dimensions of the Fogo eruption. The buildings, about to be destroyed, also give a sense of the size and scope of the hackly surfaced lavas. The three photos were undated, but were posted online on 2 December 2014. Courtesy of Boston.com. Photo credit (all photos) to Joao Relvas/EPA.

Judging from the photos in figure 10, the thicker areas of lava stood higher than single story buildings. In these photos the encroaching lava front and the flow tops both appear strongly fragmental in nature, composed of blocks of diverse sizes. The lower photo in figure 10 suggests that the depicted flow front had angles of repose up to on the order of ~45 degrees. In the various photos of figure 10, the molten component of the lava flow, is not clearly apparent on the flow's exposed surface or sprouting out of the fragmental flow.

Figure 11, by contrast, depicts a compact lava flow that is clearly composed of a comparatively thin body that came right through the wall and large door in this building. The flow surface, in this case, is nearly devoid of fragmental material and the comparatively smooth upper surfaces contrast with those in the lava flows seen in figure 10. The article also noted a lack of injuries or deaths from the eruption, despite the obvious catastrophic destruction

Figure (see Caption) Figure 11. A photo from the Fogo eruption. Smith (2014) stated that, "Lava began to ravage the only building left standing in the village of Portela on the island of Fogo, Cape Verde." Photo credit: Nicolau Centeio/EPA.

Although, there were no fatalities, 1,076 people were displaced by the 2014 eruption. Map Action (2014), a UK-based charity, issued a map of the Fogo refugee situation (figure 12). They said that, by 11 December, the lava had covered a few square kilometers and that there were three Internally Displaced Person (IDP) shelters existing in areas well outside the caldera.

Figure (see Caption) Figure 12. Map stating conditions as of 11 December 2014. By this point, Portela and Bangaeira had both been invaded by the lava flows. The vent producing the lava is the blue square in the center; the Pico cone's summit area is shown as a red triangle. The lava flow during 29 November to 7 December (light orange slashed region) reached ~5 km in length. During 8-9 December, an area of new lava flows stretched another ~1 km in length (darker orange slashed region). There were three official IDP shelters (blue tents): Mosteiros (169 inhabitants), Achada das Furnas (404 inhabitants), and Monte Grande (360 inhabitants). Source: Map Action (2014).

In an assessment report that was released on 16 December 2014, Relief Web said that: "A volcan[ic] eruption [on] Fogo Island, in Cabo [Cape] Verde, began on 23 November and continues as of 16 December 2014. The eruption has had direct impact on the people living in Chã das Caldeiras, the volcano crater area. 1076 people have been evacuated from the area, of which 929 have been relocated in temporary accommodation [centers] and in houses built in the aftermath of the 1995 eruption, while the remaining are sheltered in host families' homes. The affected people are a predominantly rural community, whose subsistence largely depends on agriculture and livestock. As of 16 December, national authorities report that lava has destroyed over 230 buildings, including the national park headquarters, wine and jam production facilities, a primary school, a hotel, churches, 100% of Portela and Bangaeira infrastructure, as well as more than 429 hectares [4.29 km2] of land, of which 120 hectares [1.2 km2] were agricultural land, resulting in great material and economic loss for the affected people and leaving many without a source of income."

During March 2015 online news sources showed residents in the process of road construction and building excavation.

Technical data. The average daily value of carbon dioxide fluxes at Fogo from 23 November 2009 through 2014 was compiled by four groups (figure 13). The fluxes steadily increased during the interval. Values were typically well below 150 tons per day (t/d) and had a long-term trend near 117 t/d. In March 2014, fluxes increased to 327 metric tons per day (t/d). The CO2 fluxes wavered and reached a high of ~350 t/d by a few days before the eruption. According to OVCV, the increase in CO2 suggested that pressure in Fogo's volcanic hydrothermal system had escalated, and that an eruption would soon occur.

Figure (see Caption) Figure 13. Diffuse CO2 fluxes at Fogo in metric tons per day (t/d) from 23 November 2009 to 23 November 2014. The red arrow depicts the date of the eruption ("Erupção"), 23 November 2014. The computation of the blue errors bars and the measurement techniques were unspecified (although similar measurements for late November behavior noted below stemmed from mini-DOAS measurements). Courtesy of OVCV, Uni-CV, Instituto Volcanológico de Canarias (INVOLCAN), and Tenerife con Cabo Verde (joint between Tenerife, Canary Islands and Cape Verde).

Soil-gas radon measurements were taken during 20-21 April 2013 by project MAKAVOL (which is run jointly by the government of Tenerife, Canary Islands and the University of Cape Verde [Uni-CV]). According to the first measurements from the geochemical station FOGO-1 in Cha caldera, the soil-gas radon (222Rn) emissions were in the range of 20-160 Bq/m3, only slightly more than the natural amount in the atmosphere (~37 Bq/m3). Bulletin editors found few if any additional radon measurements leading up to the 2014 eruption.

Between 23 November 2014 through 10 January 2015, INVOLCAN (2015) published a chart showing the weekly average of daily SO2 fluxes from Fogo (figure 14). A substantial atmospheric SO2 increase from 23 November through the first week of December 2014 was also depicted on OMI satellite imagery (see separate section below), when SO2 fluxes reached a peak of ~25 kilotons (kt). The Uni-CV (2015) also reported in situ measurements of SO2 levels; they fluctuated between 869 and 2430 t/d, during 30-31 December 2014 and 1-2 January 2015.

Figure (see Caption) Figure 14. Weekly average of daily SO2 emissions ("Emisión de SO2") from Fogo, based on optical remote sensing technology (mini-DOAS). The SO2 peaked at 10,900 t/d during the eruption's first week (23-29 November). Courtesy of INVOLCAN (2015), with minor revisions by Bulletin editors.

The mini-DOAS optical remote sensing in figure 14 was also used in late November to measure the gas content of plumes, according to the OVCV. Their measurements indicated the eruption around this time released 12,000 t/d of SO2, 23,000 t/d of H2O, and 10,000 t/d of CO2 . On 30 November, the molar ratios of CO2:SO2 and H2O:SO2 were 1:5 and 8:5, respectively. According to Hernández and others (2015), other molar ratios were CO2:H2O = 0.3 and SO2:H2S = 7.5. (For more details on pre-eruption gas emissions, see Dionis and others (2015).)

According to a report by Uni-CV discussing the 8-11 February 2015 interval, their data on sulfur dioxide (SO2) monitoring were provided for civil protection, to help improve crisis management. They requested that their data not be reproduced except for reporting by the team involved in the data collection (INVOLCAN / ITER and Uni-CV). That said, we provide a brief summary and cite a few broad comments. SO2 fluxes emerging from the vent dropped to near zero during 8-11 February, one factor in determining the end of the eruption the 8th. Those low fluxes were measured by vehicle-mounted mini-DOAS insturments. From 28 November the team, with interagency support, conducted 366 measurements. One or more field trips to the vent area described conditions there during early and middle February.

According to the Uni-CV report issued 9 March 2015, during 25 January to 1 February 2015 the SO2 flux decreased. Shortly after that the fluxes rose somewhat (to several hundred tons per day

After 7 February 2015, temperatures in the vent area of both the fumaroles and at the base of the cone had decreased significantly (table 1). The temperature difference at the two distances are a well known effect associated with absorption of infrared energy as it passes through the atmosphere.

Table 1. The temperatures of the cone base and the fumaroles from 7 to 9 February 2015. Courtesy of Uni-CV (2015).

Date Sensors Temperature at cone's base (°C) Temperature of fumarole (°C)
07 Feb 2015 ~2 km away 288 144
08 Feb 2015 ~2 km away 92 138
09 Feb 2015 ~2 km away 89 136
07 Feb 2015 ~1 km away 309 175
08 Feb 2015 ~1 km away 138 165
09 Feb 2015 ~1 km away 132 169

MODVOLC. MODIS thermal infrared sensors, aboard the Aqua and Terra satellites and processed by the MODVOLC algorithm, found hotspots infrequently at Fogo between 2001 and mid-2014; these hotspots were on the N flanks of Fogo, and thus were probably not associated with volcanic activity. On 23 November 2014, the number of hotspots increased dramatically. Hotspots were recorded daily, and many had a large number of pixels (for example, 19 pixels from the Aqua satellite on 25 November 2014).

By the end of December 2014, the number of hotspots declined. During January 2015, hotspots were recorded on a total of 11 days. Only one hotspot was observed in February (7 February), and none in March.

Satellite-based SO2 emissions. Based on the OMI satellite, the 23 November eruption caused a substantial atmospheric SO2 mass increase through the first week of December 2014 (figure 15). Total SO2 mass reached a peak of ~25 kilotons.

Figure (see Caption) Figure 15. Preliminary OMI satellite data on daily total SO2 masses in the atmosphere between 8 November 2014 and 31 December 2014. According to the chart, the SO2 peaked between 26 November and 3 December at ~25 kt. These automated measurements could have been overestimated or underestimated based on factors such as cloud cover, row anomalies, and the altitude of the plume. Courtesy of Simon Carn and the NASA MEASURES website.

References. Agência Lusa, 2014, Erupções vulcânicas da ilha do Fogo evoluem para "estado crítico", 30 November 2014, Observador (URL: http://observador.pt/2014/11/30/erupcoes-vulcanicas-da-ilha-fogo-evoluem-para-estado-critico/) [accessed in March 2015]

BBC, 2014, In pictures: Pico do Fogo volcano in Cape Verde erupts, 2 December 2014, British Broadcasting Company (URL: http://www.bbc.com/news/world-africa-30291041) [accessed in March 2015]

Caesar, Chris, 2014, Cape Verde Evacuations Are Underway Following Volcano Eruption, 23 November 2014, Boston.com (URL: http://www.boston.com/news/local/massachusetts/2014/11/23/cape-verde-evacuations-are-underway-following-volcano-eruption/MqqLEMCSab9qYGqlw1F5qL/story.html) [accessed in March 2015]

Chrystello, Chrys, 2014, YouTube (URL: https://www.youtube.com/user/chryschrystello/) [accessed in March 2015]

Copernicus, 2015, Fogo Island-Cape Verde, Volcanic eruption 23 November 2014 (23/11/2014) [Grading map, detail 01, Monit 12, Activation ID, EMSR-111, Product number 01FogoIsland, v1.]. Copernicus, (URL: emergency.copernicus.eu/mapping/)

Dionis, SM; Melián, G; Rodríguez, F; Hernández, PA; Padrón, E; Pérez, NM; Barrancos, J; Padilla, G; Sumino, H; Fernandes, P; Bandomo, Z; Silva, S; Pereira, J; Semedo, H, 2015, Diffuse volcanic gas emission and thermal energy release from the summit crater of Pico do Fogo, Cape Verde, 27 January 2015, Bulletin of Volcanology (URL: http://link.springer.com/article/10.1007/s00445-014-0897-4) [accessed in April 2015]

Farge, Emma, 2014, Cape Verde orders evacuation after Fogo volcano erupts, 23 November 2014, Reuters (URL: http://www.reuters.com/article/2014/11/23/us-caboverde-volcano-idUSKCN0J70SN20141123) [accessed in March 2015]

Hernández, PA; Melián, G; Dionis, SM; Barrancos, J; Padilla, G; Padrón, E; Silva, S; Fernandes, P; Cardoso, N; Pérez, NM; Rodríguez, F; Asensio-Ramos, M; Calvo, D; Semedo, H; Alfama, V, 2015, Chemical composition of volcanic gases emitted during the 2014-15 Fogo eruption, Cape Verde, EGU General Assembly 2015 (URL: http://meetingorganizer.copernicus.org/EGU2015/EGU2015-9577.pdf) [accessed in April 2015]

INVOLCAN, 2015, Nota de Prensa: Científicos del INVOLCAN continúan en Cabo Verde colaborando en el seguimiento de la erupción de Fogo, 11 January 2015 (URL: http://www.involcan.org/wp-content/uploads/2015/02/11_01_2015_Nota-de-prensa.pdf) [accessed in April 2015]

Lusa, 2014, Erupção na ilha cabo-verdiana do Fogo era "previsível", 23 November 2014, Diário de Notícias (URL: http://www.dn.pt/inicio/globo/interior.aspx?content_id=4256685) [accessed in March 2015]

Map Action, 2014, Cape Verde - Fogo Island: Shelters location (as of 11 Dec 2014), 16 December 2014 (URL: http://mapaction.org/map-catalogue/mapdetail/3671.html) [accessed in March 2015]

Rietze, Martin, 2014, Youtube, (URL: https://www.youtube.com/channel/UC5LzAA_nyNWEUfpcUFOCpJw) [accessed in March 2015]

Roscoe, Richard, 2015, Fogo Volcano, Photovolcanica (URL: http://photovolcanica.com/VolcanoInfo/Fogo/Fogo.html, https://www.youtube.com/user/Photovolcanica) [accessed in March 2015]

Silva, S, Cardoso, N., Alfama, V., Cabral, J., Semedo, H., Pérez, NM, Dionis, S, Hernández, PA, Barrancos, J, Melián, GV, Pereira, JM, and Rodríguez, F., 2015, Chronology of the 2014 volcanic eruption on the island of Fogo, Cape Verde; Geophysical Research Abstracts, Vol. 17, EGU 2015-13378 (Poster), 2015 EGU General Assembly 2015

Smith, Jennifer, 2014, Local Cape Verdeans join to support volcano victims--'Catastrophic' destruction by volcano spurs those in Mass. to help victims, The Boston Globe (URL: www.bostonglobe.com)

Uni-CV, 2015, Fórum para reconstrução da ilha do Fogo, Universidade de Cabo Verde (URL: http://www.unicv.edu.cv/index.php/arquivo-destaque/4038-2-dia-da-erupcao-equipa-da-uni-cv-faz-relatorio-do-desenvolver-da-erupcao) [accessed in March 2015]

Geologic Background. The island of Fogo consists of a single massive stratovolcano that is the most prominent of the Cape Verde Islands. The roughly circular 25-km-wide island is truncated by a large 9-km-wide caldera that is breached to the east and has a headwall 1 km high. The caldera is located asymmetrically NE of the center of the island and was formed as a result of massive lateral collapse of the ancestral Monte Armarelo edifice. A very youthful steep-sided central cone, Pico, rises more than 1 km above the caldera floor to about 100 m above the caldera rim, forming the 2829 m high point of the island. Pico, which is capped by a 500-m-wide, 150-m-deep summit crater, was apparently in almost continuous activity from the time of Portuguese settlement in 1500 CE until around 1760. Later historical lava flows, some from vents on the caldera floor, reached the eastern coast below the breached caldera.

Information Contacts: Observatório Vulcanológico de Cabo Verde (OVCV), Departamento de Ciência e Tecnologia, Universidade de Cabo Verde (Uni-CV), Campus de Palmarejo, Praia, Cape Verde (URL: https://www.facebook.com/pages/Observatorio-Vulcanologico-de-Cabo-Verde-OVCV/175875102444250); Universidade de Cabo Verde (Uni-CV), Av. Santo Antao, Praia, Cape Verde (URL: http://www.unicv.edu.cv/); Copernicus (The European Earth Observation Programme) (URL: http://emergency.copernicus.eu/); Cabildo Insular de Tenerife, Plaza de España, 1, 38003 Santa Cruz de Tenerife, Spain (URL: http://www.tenerife.es/); Instituto Volcanológico de Canarias (INVOLCAN), Parque Taoro, 22 38400, Puerto de la Cruz, Tenerife, Spain (URL: http://www.involcan.org/); Toulouse Volcanic Ash Advisory Centre (VAAC) (URL: http://www.meteo.fr/vaac/); Montrand Theo (URL: https://www.facebook.com/montrond.theo); Volcanological and Geothermal Observatory of the Azores, Ladeira da Mãe de Deus, 9501-855 Ponta Delgada, Portugal (URL: http://www.uac.pt/); Culture Volcan (URL: http://laculturevolcan.blogspot.com/2014/12/leruption-du-volcan-fogo-pourrait-etre.html); Mário Moreira, Instituto Superior de Engenharia de Lisboa, Portugal; Hawai’i Institute of Geophysics and Planetology (HIGP), MODVOLC alerts team, University of Hawai’i at Manoa, 1680 East-West Road, Post 602, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA MEASURES, Goddard Space Flight Center (URL: https://so2.gsfc.nasa.gov/); and Simon Carn, Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, MI 49931 USA (URL: https://so2.gsfc.nasa.gov/); Fogo News (URL: http://www.fogonews.com/); and Boston.com (URL: http://www.bostonglobe.com/).


Korovin (United States) — November 2014 Citation iconCite this Report

Korovin

United States

52.381°N, 174.166°W; summit elev. 1518 m

All times are local (unless otherwise noted)


Summary of activity during 1998-2007

Korovin is a stratovolcano located on Atka Island in the central Aleutian Islands; its most recent reported activity ended in 2007. This report summarizes and contains new information on activity from 1998 to 2007 by drawing on information primarily from the Alaska Volcano Observatory (AVO) and their cited publications. Much of the summary takes the form of a table at the end of the report.

Atka volcanic complex. According to Myers and others (2002) Korovin is a part of the 360 km2 Atka volcanic complex, found on the northern part of Atka Island. It is the largest modern complex within the central Aleutians (Myers and others, 2002). The ancestral Atka volcano, in the complex, was described as a large shield volcano consisting of basaltic and basaltic andesite flows, which was subsequently surrounded by a series of satellite vents (Myers and others, 2002).

A caldera forming eruption at the Atka shield volcano occurred ~300,000-500,000 years ago, creating a 5-km-diameter caldera. Associated with that event was the eruption of a large dacitic flow, called Big Pink. Regarding the composition of Big Pink, Myers and others (2002) said, "It consists of pumiceous and glassy units but is not associated with any ash flows." After the caldera formation, the volcanic centers of Korovin, Kliuchef, Konia and Sarichef formed. Figure 4 is a topographic map showing the location of these four volcanic centers and the location of the Atka caldera. These structures all comprise the Atka volcanic complex.

Figure (see Caption) Figure 4. Topographical map of the northern part of Atka Island, located in the central Aleutian Islands. The map highlights the locations of the Atka caldera, the Korovin, Kliuchef and Sarichef volcanoes and the Konia vent, which all comprise the Atka volcanic complex. Image created by the Alaska Volcano Observatory (AVO) and U.S Geological Survey (USGS) using BigTopo 7 software and AllTopo 7. Image taken from the AVO website.

Korovin volcano. Korovin is located 21 km NE from the town of Atka (figure 4). It is the largest and tallest volcano of the post-caldera volcanic centers within the Atka volcanic complex. According to Myers and others (2002), Korovin shows little evidence of glaciation, unlike Kliuchef, located ~5 km S of Korovin. Regarding Korovin' edifice and age, Myers and others (2002) say "Its uneroded form suggests the volcano is mostly Holocene in age."

Korovin has a basal diameter of ~7 km and two summit vents located 0.6 km apart (Myers and others, 2002). The NW summit vent has a small crater and is the lower of the two vents. The SE summit has a 1 km wide crater, with steep walls and a depth of several hundred meters (Myers and others, 2002). The SE summit crater sometimes contains a crater lake and is considered Korovin's active crater. Figure 5 is an aerial photo of Korovin, highlighting its two summit vents.

Figure (see Caption) Figure 5. Photograph of Korovin volcano taken from an aircraft flying at 9.1 km altitude on 5 August 2007. The view is oblique and from the N (i.e. looking S). Steam is rising from the active crater (SE crater). The summit of Kliuchef volcano is partially visible at the top of the image; it sits ~5 km S of Korovin. Photograph taken by Burke Mees, Alaska Airlines. Photograph from McGimsey and others (2011).

During the summer of 2004, AVO installed a network of seismic stations throughout the northern part of Atka Island. Data from the network was accessible in March 2005; however, it wasn't until December 2005 that Korovin was considered seismically monitored. On 2 December 2005, Korovin was also officially assigned the Level of Concern Color Code Green after "a sufficient period of background seismicity had been recorded" (McGimsey and others, 2007). Before, AVO had listed Korovin as UA (unassigned) during periods when no significant activity was noted. AVO assigns volcanoes UA when there is no real-time seismic network in the area that can be used to define background levels of seismicity.

In addition to being seismically monitored, Korovin is also monitored through ground-based, aerial, and satellite imagery and photographs. Korovin and its plumes are often photographed by residents of Atka village (figures 6 and 7), which are then sent to the AVO. Figure 8 provides examples of photos of Korovin taken from satellites. Images from figures 6-8 furnish various kinds of evidence, from steaming (i.e. non-eruptive cases, figure 7), ash-bearing plumes (figure 6), and the result of ash-bearing eruptions (ash on the snow surface seen in satellite views, figure 8). Evidence of these kinds is summarized in next section.

Figure (see Caption) Figure 6. Photographs showing the progression of a steam plume that developed over Kovorin around 1900 on 23 February 2005. Plume was observed drifting to the E, and ash was seen falling out near the base of the plume. These photos were taken in Atka village and are courtesy of Louis and Kathleen Nevzoroff. Photos were taken from McGimsey and others (2008).
Figure (see Caption) Figure 7. Photograph of a steam column rising from Korovin on 27 July 2007. Steam was estimated to reach ~215-245 m above the crater. The photo was captured by Louis Nevzoroff from Atka village. Taken from McGimsey and others (2011).
Figure (see Caption) Figure 8. Two satellite photographs showing ash deposits on the upper E flank of Korovin in 2002 (top) and 2004 (bottom). The source of these ash deposits is thought to be intermittent, minor phreatic eruptions through the hot, roiling lake within the SE summit crater of Korovin (McGimsey and others, 2007). Top image was taken on 5 July 2002 and produced by the Image Analysis Laboratory, NASA Johnson Space Center. Bottom image was captured on 4 July 2004 and is an Ikonos near-infrared color composite, copyrighted by Space Imaging LLC. Both images originally published in McGimsey and others (2008).

Activity during 1998-2007. During this interval (table 1), activity ranged from eruptive cases to those that were considered non eruptive.

Activity was often reported to AVO by Atka village residents and pilots in the area. Korovin was also monitored through satellite imagery, when weather conditions were favorable. During this interval, the highest plumes were observed on 30 June 1998 and reached an altitude of ~9.1 km. As activity varied, the Aviation Color Code (ACC), the Volcanic Activity Alert Level (VAAL), and the Level of Concern Color Code (LCCC) were changed to reflect Korovin's activity status.

AVO presented general information on reported activity from 1998-2007 on their website. For each of the events within this interval, AVO cited information from several sources, some of which included the following: McGimsey and others (2003), which discussed activity in 1998; McGimsey and others (2008), which discussed 2005 activity; Neal and others (2009) that looked at 2006 activity; and McGimsey and others (2011) that detailed 2007 activity. AVO also referenced several past Bulletin reports, which highlighted Korovin activity (BGVN 23:06, and 31:02).

Our summary in table 1 summarizes the following: (1) the basic information on Korovin's activity from the AVO website and (2) additional information from some of AVO's cited references. Greater detail can be found on AVO's website and in their cited references.

Table 1. Condensed descriptions of key events during both eruptive and non-eruptive periods during 1987-2007. The data sources are stated in the table. The Remarks column generally contains the following: (1) "AVO:" This presents a very brief synopsis of the summary that AVO provides on each of their Korovin reported activity web pages (as accessed in May 2015). (2) Below that, we present a succinct timeline of Korovin activity created using on information found in some of AVO's cited references. The 2005 activity is in two sections to highlight different periods of activity during that year; 2006-2007 is considered one period of activity. Where AVO cited references are augmented by past Bulletin reports, the information has been [bracketed]. Times are all local, unless otherwise stated. The term 'resident(s)' refers to resident(s) of Atka village. Abbreviations used are as follows: Village Public Safety Officer, VPSO; above sea level, a.s.l., and Interferometric synthetic aperture radar, InSAR; Aviation Color Code, ACC; Volcanic Activity Alert Level, VAAL; Level of Concern Color Code, LCCC; unassigned activity (UA); and satellite-based Ozone Monitoring Instrument, OMI.

Date Remarks
1998

AVO: Eruption started, 30 June 1998 ±1 month. Eruption end, 30 June 1998 ± 7 days

McGimsey and others (2003):

Eruption start / stop dates: 30 June / 8 July

"…, the timing of this activity remains poorly constrained; intermittent ash may, in fact, have occurred weeks or prior to June 30."

10 May- Pilot observed ash on SE slope. Pilot had seen no ash the previous week and speculated the ash was deposited a few days prior to May 10

28 June-Individual reported a dark ash plume over Korovin

30 June-VPSO in Atka village reported two separate clouds, first at ~0730 and second at ~0830. Second cloud rose ~9.1 km and was tinted orange. VPSO said events "produced dustings of ash in Atka". AVO received 2 pilot reports: (1) at 1115, noted volcanic cloud reached ~4.9 km a.s.l., (2) at 1720, cloud to 9.1 km near Korovin

2 July- Resident reported a 'rusty' cloud, ~4.9 km a.s.l. moving SE

3 July- Pilot reported profuse steam from summit crater and ash on S, SE and E flanks. Thin trail of ash extended SW towards Atka village

8 July- AVO noted minor, weakly ash-bearing clouds over Korovin with satellite images

2002

AVO: Eruption started, July 2002 ±1 month. Considered a questionable eruption

McGimsey and others (2008):

5 July- Satellite photo of ash deposits on upper E flank of Korovin (figure 8, top). "Intermittent, minor phreatic eruptions through a hot, roiling lake in the south summit crater of Korovin [is] the probable source."

2004

AVO: Eruption started, June 2004 ±1 month. Considered a questionable eruption

McGimsey and others (2008):

4 July- Satellite photograph shows ash deposits on upper E flank of Korovin (figure 8, bottom). Same explanation as 5 July 2002

Neal and others (2009):

7 July- Korovin photographed with ash covering the snow on its E flank. According to the caption of the photograph, "The deposit may be the result of phreatic explosions or vigorous wind remobilization of ash from within the summit crater."

19 July- Aerial photograph of Korovin showing ash deposited around the crater vent. The caption for the photograph states, "At times, a shallow body of gray, turbid water partially fills the inner crater and, in 2004, was observed roiling. Phreatic explosions from this water-rich, high-temperature system may be responsible for the occasional localized ash-fall deposits seen on the upper flanks of Korovin."

2005

AVO: Eruption started, 23 February. Eruption end, 7 May ± 14 days. Considered a questionable eruption.

McGimsey and others (2008):

23 February- Clear day. Residents noted minor steaming around 1200. Around 1900, residents observed dark cloud rising several thousand feet and drifting E (figure 6). Ash seen falling out near base of plume. Minutes later, three or four smaller gray puffs seen. No other activity seen that night. In satellite imagery, small steam plume with minor ash noticed. Height of plume estimated at ~3 km.

24 February- LCCC was raised from UA (unassigned) to Yellow

4 March- LCCC reduced from Yellow to UA

19 March- Pilot report noted steam rising several thousand feet above Korovin

Early May- Observational data showed roiling lake in SE crater emptied. Visible glow.

2005

AVO: Seismicity without confirmed eruption, start / end: 13 September

McGimsey and others (2008):

13 September- Long sequence of strong seismicity. Sequence began with two small local events, then ~30 minutes of weak tremor, and then ~20 weak local events. Nothing unusual noted in satellite images from this time.

2006-2007

AVO: Non-eruptive activity started, 16 January 2006 and ended September 2007 ± 2 months.

Neal and others (2009):

16 January 2006- Background seismic activity increased

17-18, 21 Jan and 21-22 Feb- burst of tremor-like signals

22 February 2006- LCCC increased from Green to Yellow

Early March- Seismicity stabilized and then decreased

8 March- LCCC downgraded from Yellow to Green

July- Increased number of earthquakes in vicinity of Korovin

September and October- Increased tremor episodes

19 October- SE crater lake disappeared by this date and absent for rest of 2006. Lake present on 12 September (satellite data).

29 October- White vapor plumes rose several hundred meters above Korovin and coincided with ~5-min of strong tremor

5 November 2006- Strongest earthquake swarm recorded by seismic network

6 November- Yellow ACC and an Advisory VAAL declared

18 November- dark-gray ash on E flank of SE crater observed in ASTER satellite images. Ash was not present in image from 21 November. ASTER satellite imagery showed warm spots in Korovin crater

Late November 2006- Significant deformation in latter half of 2006. Circular pattern of uplift, as much as 5 cm noted through July and October InSAR data. November-December- Seismicity high; strong, short-lived signals. Low-frequency tremor bursts.

11, 21 and 24 December 2006- Residents photographed large, white-vapor plumes rising from Korovin. One resident noted that he saw ash falling below the plume he reported. Ash was not verified on the ground

End of 2006-No ash detected in atmosphere or on ground through satellite data. Rise in ground temperature also not detected

McGimsey and others (2011):

Beginning of 2007- ACC, Yellow, and VAAL, Advisory due to increased activity in 2006. High seismicity from 2006 continued into 2007. Inflation (uplift) in N part of Atka Island that began in June 2006 totaled 9-10 cm and began to taper off in 2007

11 January 2007- M3.5 earthquake considered large for volcano-generated seismicity.

23 January- Series of tremor bursts

24 January- Resident took pictures of steam column rising from SE crater and reported similar steam columns rose ~300 m every 15-80 minutes

14 February 2007- Pilot reported a steam plume extending 1.5-2.4 km over Korovin

3 March- Residents photograph ash deposit on W flank. Residents observed steam from SE summit vent. Flurry of low-frequency seismicity in morning

May, June & August- Episodes of tremor lasted several days

27 July 2007- Steam plumes observed by residents (figure 7)

5 August- OMI detected small SO2 cloud, 300 km N of Cleveland volcano. Based on wind dispersal models, cloud believed to be from Korovin. Aerial photo (figure 5) showed steam rising from SE crater

20 August- OMI detected small emission of SO2 from Korovin

7 September- ACC/VAAL downgraded to Green/Normal due to decreasing trends in seismicity and uplift

October-December 2007- uneventful

References. Alaska Volcano Observatory, the U.S. Geological Survey, BigTopo 7, and AllTopo 7, Topographic shaded relief image of the northern part of Atka Island (Image 2906), accessed on 14 April 2005, (URL: http://www.avo.alaska.edu/images/image.php?id=2906).

McGimsey, R. G., Neal, C. A., and Girina, O., 2003, 1998 volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Open-File Report OF 03-0423, 35 pp, (URL: http://pubs.usgs.gov/of/2003/of03-423/).

McGimsey, R.G., Neal, C.A., Dixon, J.P., and Ushakov, S., 2008, 2005 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2007-5269, 94 pp, (URL: http://pubs.usgs.gov/sir/2007/5269/).

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

Myers, J.D., Marsh, B. D., Frost, C. D. and Linton, J.A., 2002, Petrologic constraints on the spatial distribution of crustal magma chambers, Atka Volcanic Center, central Aleutian arc, Contributions to Mineralogy and Petrology, vol. 143, issue 5, pp. 567-586, DOI 10.1007/s00410-002-0356-7 (URL: http://link.springer.com/article/10.1007/s00410-002-0356-7).

Neal, C.A., McGimsey, R.G., Dixon, J.P., Manevich, A., and Rybin, A., 2009, 2006 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2008-5214, 102 pp, (URL: http://pubs.usgs.gov/sir/2008/5214/).

Geologic Background. Korovin, the most frequently active volcano of the large volcanic complex at the NE tip of Atka Island, contains a 1533-m-high double summit with two craters located along a NW-SE line. The NW summit has a small crater, but the 1-km-wide crater of the SE cone has an unusual, open cylindrical vent of widely variable depth that sometimes contains a crater lake or a high magma column. A fresh-looking cinder cone lies on the flank of partially dissected Konia volcano, located on the SE flank. The volcano is dominantly basaltic in composition, although some late-stage dacitic lava flows are present on both Korovin and Konia.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.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; Game McGimsey, AVO.


Suwanosejima (Japan) — November 2014 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Periods with several eruptions per day during April 2013-December 2014

This report covers activity at Suwanose-jima from 1 April 2013 to 31 December 2014. The previous Bulletin report (BGVN 38:04) detailed near-continuous tremor, a few earthquakes, and occasional ash plumes and eruptions during July 2012 through April 2013. This reporting period includes continuous tremor, intervals with several explosions per day, and plumes rising up to 5.5 km altitude. The data was gathered primarily from two key sources: the Tokyo Volcanic Ash Advisory Center (VAAC) and the Japan Meteorological Agency (JMA), who publishes monthly reports on Japanese volcanic activity (URL in Information contacts section).

The map in figure 17 highlights the location of the Otake crater (elevation of 796 m, also called Ontake crater), which was the source of the plumes, explosions, and other activity at Suwanose-jima during this reporting interval. The map was published by the JMA and also depicts the locations of monitoring sites for the volcano.

Figure (see Caption) Figure 17. A map indicating monitoring sites and topography, with a contour interval of 20 m. The Otake crater is located in the center of the island. Seismometers (circles), infrasonic microphones (circles with crosses), tiltmeters (triangles), GPS (stars), and visual cameras (binoculars) were situated on the nearby slopes by several agencies. The Disaster Prevention Research Institute (DPRI) utilizes the light blue units, the JMA the red units, and the Geospatial Information Authority of Japan (GSI) the orange unit. Source: Iguchi and Ito (date unknown) with slight changes by Bulletin editors.

Activity during 2013. According to the JMA (monthly reports), the Alert Level at Suwanose-jima constantly remained at 2 (on an increasing scale of 1-5). At night, high-sensitivity cameras regularly observed weak crater glow. A series of almost-continuous tremors began on 28 September 2012 and persisted through 2013.

During the month of April, the JMA noted that the tremor lasted for a total of 677 hours and 50 minutes. On 13 April 2013, the Otake crater had a minor eruption with plumes rising to 0.7 km above the crater.

The Otake crater did not erupt during May and June 2013. In May, white plumes generally rose to 0.2-0.3 km above the crater; the tallest plume reached 0.5 km. There was "no remarkable change in plume activity" in June, according to the JMA. During the month of May, a nearly continuous tremor lasted for a total duration of 704 hours and 54 minutes. It stopped on 1 June 2013 and then resumed on 12 June.

On 9 July 2013, a pilot reported an ash plume to 1.5 km altitude. However, the Tokyo VAAC was unable to detect ash in satellite images. Continuous tremor occurred from mid-June to 15 July and from 24 to 30 July. On 29 July, an earthquake occurred near Suwanose-jima, with a magnitude of 3.2 and a seismic intensity of 2 (an increasing scale of 0-7).

The International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) conducted a field trip to the volcano during 15 and 18 July 2013 (figure 18). They found the volcano quiet, releasing only short, white plumes.

Figure (see Caption) Figure 18. Photos taken from 16-18 July during a field trip associated with the IAVCEI 2013 Scientific Assembly. Additional photos can be found on Volcano Discovery. (Top) Otake crater, facing NE. A thin, white plume rises from the crater and is shown in greater detail in the zoomed photo on the upper right. (Bottom, left) Crater from which the 1813 subplinian Bunka eruption originated. (Bottom, middle) Flank of old cinder cone within the rift zone. The ground in this area was covered by spatter agglutinate from the 1813 eruption. (Bottom, right) Scoria and ash deposits in the NE cliff of the island. Source: Pfeiffer (2013), labeled by Bulletin editors.

On 25 August 2013 at 1904 LT, the Otake crater erupted, and intermittent explosive eruptions continued from 26 August onwards. On 27 August, plumes rose to ~1.2 km altitude and drifted NE/SE. On 28 August, ash plumes beginning at 0910 LT rose to altitudes of 1.8-2.1 km, drifting NE and 3-3.7 km altitude, drifting E/NW. There was a total of 16 explosive eruptions during August. The above crater height of the resultant grayish white plumes generally ranged from 0.5-0.8 km, with the tallest plumes reaching ~1.5 km above the crater. Tremor occurred near continuously during 2-4, 11-14, and 25-31 August. Satellites utilized by the VAAC detected ash on 29 August, and from 30 August to 1 September, they detected explosions as well.

During September 2013, the Otake crater erupted explosively six times. Explosions occurred from 5-6 September with ash plumes rising to 1.8-2.1 km altitude, beginning at 0655 LT on the 5th and drifting NNW. On 12 September, ash plumes rose to 1.8 km altitude, drifting NW. During 29-30 September, ash plumes rose to 1.5 km altitude, drifting W and volcanic blocks were scattered around the crater on the 29th. Plumes in September generally rose above the crater to less than 1 km and the maximum height was 1.4 km. Earthquakes were felt near to Suwanose-jima on 10, 21, and 26 September 2013. The seismic intensity was 1 and tremor occurred intermittently.

During October, minor explosions occurred at the Otake crater during 13-15 and 21-22 October. Gray plumes from those eruptions generally rose above the crater to less than 0.6 km, with a maximum height of 1 km above the crater. Earthquakes were felt near the volcano on 9 October 2013. The seismic intensity was 2 and tremor occurred intermittently. On 21 October, an ash plume rose to 1.5 km altitude, heading S.

On 27 November 2013, the Otake crater erupted explosively 7 times, causing a scattering of volcanic projectiles around the crater. The eruption formed a plume that rose 1.8 km altitude, drifting E. In addition, Otake erupted occasionally throughout the month, with gray plumes above the crater generally rising to less than 0.6 km and a maximum plume height of 1 km. Tremor occurred intermittently.

Between 26 and 31 December 2013, Otake erupted 247 times, according to the JMA December 2013 report. From 27-28 December, plumes from Suwanose-jima rose to ~1.5 km altitude, drifting SE. On 28 December, small amounts of ashfall were observed [in the village ~4 km SSW] of Otake. According to the village administration, air shocks rattled windows and sliding doors from 28-29 December and crater glow was observable at night. On 29 December 2013, 125 explosions occurred, along with tremor and airshocks from about 0000 to 0300 LT. This indicated "consecutive eruptions," according to the JMA, with gray plumes rising to 0.6 km above the crater. The eruption ejected volcanic projectiles around the crater.

Activity during 2014. Information for activity during May, July, and October 2014 was unavailable, with an absence of VAAC reports for these intervals. During January, the Otake crater exploded 23 times, with volcanic projectiles scattering around the crater. The Tokyo VAAC noted explosions during 1-3 and 6 January. Between 1 and 2 January, explosions formed plumes to 0.9-1.8 km altitude, drifting SE. The explosions were heard in [the] village until the 3rd. During 8 to 9 January, explosions generated plumes, which rose to 1.2 km altitude and drifted NE/SE. The VAAC noted an explosion on 24 January, generating a plume that rose to 1.8 km altitude. Minor ashfall was observed on 1, 6, and 23 January.

During February 2014, the Otake crater exploded 7 times (on 2, 12, 19, and 23-24 February), with plumes reaching a maximum height of 1.2 km above the crater. On 2 February, the explosion at 1638 LT formed an ash plume to 1.8-3 km altitude that blew SE/SSE. On 12 February, the generated plume rose to 1.2 km altitude and drifted SE, and on 14 February, a plume rose to an altitude of 1.8 km altitude. During 23 to 24 February, plumes rose to 1.8 km altitude and drifted E. Volcanic seismicity for February was high and tremor occurred occasionally.

On 1 March 2014, the Otake crater erupted explosively. All other eruptions during March were minor and sporadic in occurrence. Plumes rose to a maximum height of 0.8 km above the crater. The volcanic seismicity was high and tremor occurred occasionally.

On 29 April, the Otake crater erupted explosively twice and the resulting plumes rose to 1.2 km altitude, heading E. All other eruptions during April were once again minor and sporadic in occurrence. Plumes reached a maximum height of 0.8 km above the crater.

During June 2014, the Otake crater erupted several times, with explosions on 18 June at 2246 LT, on 19 June at 1734 LT with a plume heading E, and on 20 June at 0933 LT. VAAC satellite imagery did not indicate any ash within the plumes.

Between 28 August and 1 September, eruptions resulted in ash plumes rising to 1.8-2.7 km altitude and drifting S, SE, E, and NE. Several eruptions occurred during the first week of September, with ash plumes rising to 1.8-5.5 km altitude on 3 September beginning at 1109 LT, 5.5 km altitude on 4 September at 1833 LT, and 2.1 km altitude on 9 September at 2233 LT.

On 14 November 2014, the Tokyo VAAC reported an explosion, with a plume rising to 1.8 km altitude and drifting SE.

Explosions at Suwanose-jima on 7 December 2014 formed plumes rising to 1.5-1.8 km altitude, drifting E/SE. On 14 December, plumes rose to 1.8 km altitude. and drifted SE.

SO2 emissions. Morita and others (2013) conducted an analysis of SO2 emissions at Suwanose-jima between 20 January and 7 May 2013. Using a UV spectrometer, Ocean Optics USB2000+, they obtained 3 to 15 minute long scans from between 0800 and 1700 LT. The average daily SO2 emission rate was ~700 tons/day (t/d), and ranged between 300 and 1300 t/d. These emission numbers are comparable to those at Suwanose-jima between 1975 and 2006, when the SO2 fluctuated between 300 and 1,130 t/d (Mori and others, 2013). The researchers also found positive correlations between seismic amplitude and released puffs with associated increases in SO2 emissions.

References. Iguchi, M., Ito, K., date unknown, 97. Suwanosejima, Japan Meteorological Agency (URL: http://www.data.jma.go.jp/svd/vois/data/tokyo/STOCK/souran_eng/volcanoes/097_suwanosejima.pdf) [accessed in April 2015]

Mori, T., Shinohara, H., Kazahaya, K., Hirabayashi, J., Matsushima, T., Mori, T., Ohwada, M., Masanobu, O., Iino, H., Miyashita, M., 2013, Time-averaged SO2 fluxes of subduction-zone volcanoes: Example of a 32-year exhaustive survey for Japanese volcanoes, 16 August 2013, Journal of Geophysical Research: Atmospheres (URL: http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50591/full)

Morita, M., Mori, T., Iguchi, M., Nishimura, T., 2013, Continuous monitoring of sulfur dioxide emission rate at Suwanosejima volcano, Japan, Fall 2013, American Geophysical Union (URL: http://adsabs.harvard.edu/abs/2013AGUFM.V43B2875M)

Pfeiffer, T., 2013, Excursion to Suwanose-jima volcano (Tokara Islands, Japan) - photos from the IAVCEI 2013 field trip A3, July 2013, Volcano Discovery (URL: http://www.volcanodiscovery.com/suwanosejima/photos/july2013/fieldtrip.html) [accessed in April 2015]

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

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

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/).