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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

Ol Doinyo Lengai (Tanzania) Multiple lava flows within the summit crater, September 2018-August 2019

Ulawun (Papua New Guinea) Explosions on 26 June and 3 August 2019 send plumes above 19 km altitude

Sarychev Peak (Russia) Ash plume on 11 August; thermal anomalies from late May to early October 2019

Asamayama (Japan) Ashfall from phreatic eruptions on 7 and 25 August 2019

Villarrica (Chile) Strombolian activity continued during March-August 2019 with an increase in July

Reventador (Ecuador) Daily ash emissions and incandescent block avalanches continue, February-July 2019

Raikoke (Russia) Short-lived series of large explosions 21-23 June 2019; first recorded activity in 95 years

Sinabung (Indonesia) Large ash explosions on 25 May and 9 June 2019

Semisopochnoi (United States) Small explosions detected between 16 July and 24 August 2019

Krakatau (Indonesia) Repeated Surtseyan explosions with ash and steam during February-July 2019

Tengger Caldera (Indonesia) Ash emissions on 19 and 28 July 2019; lahar on the SW flank of Bromo

Unnamed (Tonga) Submarine eruption in early August creates pumice rafts that drifted west to Fiji



Ol Doinyo Lengai (Tanzania) — September 2019 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)


Multiple lava flows within the summit crater, September 2018-August 2019

Frequent historical eruptions from Tanzania's Ol Doinyo Lengai have been recorded since the late 19th century. Located near the southern end of the East African Rift in the Gregory Rift Valley, the unique low-temperature carbonatitic lavas have been the focus of numerous volcanological studies; the volcano has also long been a cultural icon central to the Maasai people who live in the region. Following explosive eruptions in the mid-1960s and early 1980s the volcano entered a phase of effusive activity with the effusion of small, fluid, natrocarbonatitic lava flows within its active north summit crater. From 1983 to early 2007 the summit crater was the site of numerous often-changing hornitos (or spatter cones) and lava flows that slowly filled the crater. Lava began overflowing various flanks of the crater in 1993; by 2007 most flanks had been exposed to flows from the crater.

Seismic and effusive activity increased in mid-2007, and a new phase of explosive activity resumed in September of that year. The explosive activity formed a new pyroclastic cone inside the crater; repeated ash emissions reached altitudes greater than 10 km during March 2008, causing relocation of several thousand nearby villagers. Explosive activity diminished by mid-April 2008; by September new hornitos with small lava flows were again forming on the crater floor. Periodic eruptions of lava from fissures, spatter cones, and hornitos within the crater were witnessed throughout the next decade by scientists and others occasionally visiting the summit. Beginning in 2017, satellite imagery has become a valuable data source, providing information about both the thermal activity and the lava flows in the form of infrared imagery and the color contrast of black fresh lava and whiter cooled lava that is detectable in visible imagery (BGVN 43:10). The latest expeditions in 2018 and 2019 have added drone technology to the research tools. This report covers activity from September 2018 through August 2019 with data and images provided from satellite information and from researchers and visitors to the volcano.

Summary and data from satellite imagery. Throughout September 2018 to August 2019, evidence for repeated small lava flows was recorded in thermal data, satellite imagery, and from a few visits to or overflights of the summit crater by researchers. Intermittent low-level pulses of thermal activity appeared in MIROVA data a few times during the period (figure 187). Most months, Sentinel-2 satellite imagery generated six images with varying numbers of days that had a clear view of the summit and showed black and white color contrasts from fresh and cooled lava and/or thermal anomalies (table 27, figures 188-191). Lava flows came from multiple source vents within the crater, produced linear flows, and covered large areas of the crater floor. Thermal anomalies were located in different areas of the crater; multiple anomalies from different source vents were visible many months.

Figure (see Caption) Figure 187. Intermittent low-level pulses of thermal activity were recorded in the MIROVA thermal data a few times between 21 October 2018 and the end of August 2019. Courtesy of MIROVA.

Table 27. The number of days each month with Sentinel-2 images of Ol Doinyo Lengai, days with clear views of the summit showing detectable color contrasts between black and white lava, and days with detectable thermal anomalies within the summit crater. A clear summit means more than half the summit visible or features identifiable through diffuse cloud cover. Information courtesy of Sentinel Hub Playground.

Month Sentinel-2 Images Clear Summit with Lava Color Contrasts Thermal anomalies
Sep 2018 6 5 5
Oct 2018 7 4 3
Nov 2018 6 2 0
Dec 2018 5 1 1
Jan 2019 6 5 3
Feb 2019 6 5 6
Mar 2019 6 5 5
Apr 2019 6 1 0
May 2019 6 3 2
Jun 2019 6 3 3
Jul 2019 6 5 5
Aug 2019 6 5 3
Figure (see Caption) Figure 188. Sentinel-2 imagery of Ol Doinyo Lengai from September 2018 showed examples of the changing color contrasts of fresh black lava which quickly cools to whitish-brown (top row) and varying intensities and numbers of thermal anomalies on the same days (bottom row). It is clear that the color and thermal patterns change several times during the month even with only a few days of available imagery. Dates of images from left to right are 11, 16, and 21 September. The summit crater is 300 m across and 100 m deep. The top row is with Natural color rendering (bands 4, 3, 2) and the bottom row is with Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 189. Contrasting patterns of dark and light lava flows within the summit crater of Ol Doinyo Lengai on 1 (left) and 11 (right) October 2018 show how quickly new dark flows cool to a lighter color. The flow on 1 October appears to originate in the E part of the crater; the flow in the crater on 11 October has a source in the N part of the crater. These Sentinel-2 images use Natural color rendering (bands 4,3,2). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 190. A large flow at Ol Doinyo Lengai on 3 February 2019 filled most of the summit crater with lobes of black lava (top left) and generated one of the strongest thermal signatures of the period (top right) in these Sentinel-2 satellite images. On 20 March 2019, a small dark area of fresh material contrasted sharply with the surrounding light-colored material (bottom left); the thermal image of the same data shows a small anomaly near the dark spot (bottom right). The left column is with Natural color rendering (bands 4, 3, 2) and the right column is with Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 191. The dark lava spots at Ol Doinyo Lengai on 18 June 2019 (top left) and 28 July 2019 (top center) produced matching thermal anomalies in the Sentinal-2 imagery (bottom left and center). On days when the summit was partly obscured by clouds such as 27 August (top right), the strong thermal signal from the summit still confirmed fresh flow activity (bottom right). The top row is with Natural color rendering (bands 4, 3, 2) and the bottom row is with Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Information from site visits and overflights. Minor steam and gas emissions were visible from the summit crater during an overflight on 29 September 2018. Geologist Cin-Ty Lee captured excellent images of the W flank on 20 October 2018 (figure 192). The large circular crater at the base of the flank is the 'Oldoinyo' Maar (Graettinger, 2018a and 2018b). A view into the crater from an overflight that day (figure 193) showed clear evidence of at least five areas of dark, fresh lava. An effusive eruption was visible on the crater floor on 2 March 2019 (figure 194).

Figure (see Caption) Figure 192. A large maar stands out at the base of the SW flank of Ol Doinyo Lengai on 20 October 2018. Courtesy of Cin-Ty Lee (Rice University).
Figure (see Caption) Figure 193. A view into the summit crater of Ol Doinyo Lengai on 20 October 2018 shows clear evidence of recent flow activity in the form of multiple dark spots of fresh lava that has recently emerged from hornitos and fissures. The lava cools to a pale color very quickly, forming the contrasting background to the fresh flows. The summit crater is 300 m across and 100 m deep. Courtesy of Cin-Ty Lee (Rice University).
Figure (see Caption) Figure 194. A view into the crater floor at Ol Doinyo Lengai on 2 March 2019 showed a vent with both fresh (dark brown) and cooled (gray-white) carbonatite lavas and hornitos on the floor of the crater. The darkest material on the crater floor is from recent flows. Courtesy of Aman Laizer, Tanzania.

Research expedition in July-August 2019. In late July and early August 2019 an expedition, sponsored by the Deep Carbon Observatory (DCO) and led by researchers Kate Laxton and Emma Liu (University College London), made gas measurements, collected lava samples for the first time in 12 years, and deployed drones to gather data and images. The Ol Doinyo Lengai sampling team included Papkinye Lemolo, Boni Kicha, Ignas Mtui, Boni Mawe, Adadeus Mtui, Emma Liu, Arno Van Zyl, Kate Laxton, and their driver, Baraka. They collected samples by lowering devices via ropes and pulleys into the crater and photographed numerous active flows emerging from vents and hornitos on the crater floor (figure 195). By analyzing the composition of the first lava samples collected since the volcano's latest explosive activity in 2007, they hope to learn about recent changes to its underground plumbing system. A comparison of the satellite image taken on 28 July with a drone image of the summit crater taken by them the next day (figure 196) confirms the effectiveness of both the satellite imagery in identifying new flow features on the crater floor, and the drone imagery in providing outstanding details of activity.

Figure (see Caption) Figure 195. Researchers Kate Laxton and Emma Liu collected gas and lava samples at the summit of Ol Doinyo Lengai during their 26 July-4 August 2019 expedition. They sent gas sampling devices (small white "hamster ball" in center of left image) and lava sampling devices (right) down into the crater via ropes and pulleys. The crater is 300 m across and 100 m deep. Courtesy of Kate Laxton (University College London).
Figure (see Caption) Figure 196. A clear view by drone straight down into the crater at Ol Doinyo Lengai on 29 July 2019 provides valuable information about ongoing activity at the remote volcano. N is to the top. The summit crater is 300 m across and 100 m deep. The same configuration of fresh and cooled lava can be seen in Sentinel-2 imagery taken on 28 July 2019 (inset, N to the top). Courtesy of Emma Liu (University College London) and Sentinel Hub Playground.

With the drone technology, they were able to make close-up observations of features on the north crater floor such as the large hornito on the inner W wall of the crater (figure 197), an active lava pond near the center of the crater (figure 198), and several flows resurfacing the floor of the crater while they were there (figure 199). A large crack that rings the base of the N cone had enlarged significantly since last measured in 2014 (figure 200).

Figure (see Caption) Figure 197. A closeup view of the large hornito in the W wall of the Ol Doinyo Lengai summit crater on 26 July 2019 shows recent activity from the vent (dark material). See figure 197 for location of hornito against W wall. View is to the NW. Courtesy of Emma Liu (University College London).
Figure (see Caption) Figure 198. Incandescence from the lava pond in the center of the crater was still visible at 0627 on 29 July 2019 at Ol Doinyo Lengai; incandescence from the large hornito in the NW quadrant (behind the lava pond) had been visible when the researchers arrived at the summit at about 0500 that morning. The crater floor is continually resurfaced by ultra-low viscosity natrocarbonatite lava flows. The lava hydrates on contact with air within hours, changing color from black to grey/white in a very short time. View towards the N. Courtesy of Kate Laxton (University College London).
Figure (see Caption) Figure 199. On 30 July 2019 a lava flow from a hornito cluster resurfaced the NE quadrant of the crater floor at Ol Doinyo Lengai. The initial outbreak occurred at 0819, was vigorous, and ended by 0823. Lava continued to flow out of the hornito cluster at intervals throughout the day. Image facing NE, courtesy of Kate Laxton (University College London).
Figure (see Caption) Figure 200. The circumferential crack near the base of the N cone of Ol Doinyo Lengai is seen here being inspected by Emma Liu on 30 July 2019 where it intersects the Western Summit Trail. View is to the S. Significant widening of the crack is seen when compared with a similar image of the same crack from March 2014 (figure 172, BGVN 39:07). Local observers reported that the crack continued to widen after July 2019. Courtesy of Kate Laxton (University College London).

The color of the flows on the crater floor changed from grays and browns to blues and greens after a night of rainfall on 31 July 2019 (figure 201). Much of the lava pond surface was crusted over that day, but the large hornito in the NW quadrant was still active (figure 202), and both the pond and another hornito produced flows that merged onto the crater floor (figure 203).

Figure (see Caption) Figure 201. The active crater at Ol Doinyo Lengai is on the north side of and slightly below the topographic summit of the mountain (in the background). After overnight rain, lava flows on the crater floor turned various shades of greys, whites, blues, and greens on 31 July 2019. View to the SW, drone image. Courtesy of Emma Liu (University College London).
Figure (see Caption) Figure 202. A closeup view to the NW of the Ol Doinyo Lengai north crater on 31 July 2019 shows the blue and green tones of the hydrated lavas after the previous night's rains. The lava pond is at high-stand with much of the surface crusted over. The adjacent hornito is still active and breached to the NE. Courtesy of Emma Liu (University College London).
Figure (see Caption) Figure 203. Two fresh lava flows merge over the hydrated crater floor of the north crater at Ol Doinyo Lengai on 31 July 2019. One comes from a small hornito just out of view to the SW (lower right) and the other from the overflowing lava pond (left), merging in the SE quadrant. The colors of the two flows differ; the pond lava appears jet black, and the hornito lava is a lighter shade of brown. View to the SE, courtesy of Emma Liu (University College London).

On 1 August 2019 much of the crater floor was resurfaced by a brown lava that flowed from a hornito E of the lava pond (figure 204). Images of unusual, ephemeral features such as "spatter pots," "frozen jets," and "frothy flows" (figure 205) help to characterize the unusual magmatic activity at this unique volcano (figure 206).

Figure (see Caption) Figure 204. On 1 August 2019 at Ol Doinyo Lengai brown lava flowed from a hornito directly E of the lava pond (above the pond in figure 203) and resurfaced much of the S portion of the crater floor. At the far left of the image, the white (hydrated) lava jet aimed away from the hornito was solidified in mid-flow. View to the SE, courtesy of Emma Liu (University College London).
Figure (see Caption) Figure 205. Frothy pale-brown lava flowed across the SE quadrant of the crater floor (right) at Ol Doinyo Lengai on 4 August 2019 from an uncertain source between the adjacent hornito and lava pond which appears nearly crusted over. Spattering from a "spatter pot" (inset) and a small flow also headed NE from the hornito cluster E of the pond (behind pond). Courtesy of Kate Laxton (University College London).
Figure (see Caption) Figure 206. A view from the summit peak of Ol Doinyo Lengai on 4 August 2019 looking at the entire N cone and the swale between it and the peak. The crack shown in figure 201 rings the base of cone; the main summit trail intersects the crack near the bottom center of the cone. The researcher's campsite on the W flank (left) shows the scale of the cone. The East African Rift wall and Lake Natron are visible in the background on the left and right, respectively. Courtesy of Kate Laxton (University College London).

References: Graettinger, A. H., 2018a, MaarVLS database version 1, (URL: https://vhub.org/resources/4365).

Graettinger, A. H., 2018b, Trends in maar crater size and shape using the global Maar Volcano Location and Shape (MaarVLS) database. Journal of Volcanology and Geothermal Research, v. 357, p. 1-13. https://doi.org/10.1016/j.jvolgeores.2018.04.002.

Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Information Contacts: Cin-Ty Lee, Department of Earth, Environmental and Planetary Sciences, Rice University, 6100 Main St., Houston, TX 77005-1827, USA (URL: https://twitter.com/CinTyLee1, images at https://twitter.com/CinTyLee1/status/1054337204577812480, https://earthscience.rice.edu/directory/user/106/); Emma Liu, University College London, UCL Hazards Centre (Volcanology), Gower Street, London, WC1E 6BT, United Kingdom (URL: https://twitter.com/EmmaLiu31, https://www.ucl.ac.uk/earth-sciences/people/academic/dr-emma-liu); Kate Laxton, University College London, UCL Earth Sciences, Gower Street, London, WC1E 6BT, United Kingdom (URL: https://twitter.com/KateLaxton, https://www.ucl.ac.uk/earth-sciences/people/research-students/kate-laxton); Deep Carbon Observatory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, DC 20015-1305, USA (URL: https://deepcarbon.net/field-report-ol-doinyo-lengai-volcano-tanzania); 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/); Aman Laizer, Volcanologist, Arusha, Tanzania (URL: https://twitter.com/amanlaizerr, image at https://twitter.com/amanlaizerr/status/1102483717384216576).


Ulawun (Papua New Guinea) — September 2019 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Explosions on 26 June and 3 August 2019 send plumes above 19 km altitude

Typical activity at Ulawun consists of occasional weak explosions with ash plumes. During 2018 explosions occurred on 8 June, 21 September, and 5 October (BGVN 43:11). The volcano is monitored primarily by the Rabaul Volcano Observatory (RVO) and Darwin Volcanic Ash Advisory Centre (VAAC). This report describes activity from November 2018 through August 2019; no volcanism was noted during this period until late June 2019.

Activity during June-July 2019. RVO reported that Real-time Seismic-Amplitude Measurement (RSAM) values steadily increased during 24-25 June, and then sharply increased at around 0330 on 26 June. The RSAM values reflect an increase in seismicity dominated by volcanic tremor. An eruption began in the morning hours of 26 June with emissions of gray ash (figure 17) that over time became darker and more energetic. The plumes rose 1 km and caused minor ashfall to the NW and SW. Local residents heard roaring and rumbling during 0600-0800.

Figure (see Caption) Figure 17. Photograph of a small ash plume rising from the summit crater of Ulawun taken by a helicopter pilot at 1030 local time on 26 June 2019. According to the pilot, the amount of ash observed was not unusual. Image has been color adjusted from original. Courtesy of Craig Powell.

The Darwin VAAC issued several notices about ash plumes visible in satellite data. These stated that during 1130-1155 ash plumes rose to altitudes of 6.7-8.5 km and drifted W, while ash plumes that rose to 12.8-13.4 km drifted S and SW. A new pulse of activity (figures 17 and 18) generated ash plumes that by 1512 rose to an altitude of 16.8 km and drifted S and SE. By 1730 the ash plume had risen to 19.2 km and spread over 90 km in all directions. Ash from earlier ejections continued to drift S at an altitude of 13.4 km and W at an altitude of 8.5 km. RVO stated that RSAM values peaked at about 2,500 units during 1330-1600, and then dropped to 1,600 units as the eruption subsided.

Figure (see Caption) Figure 18. Photograph of Ulawun taken by a helicopter pilot at 1310 local time on 26 June 2019 showing a tall ash plume rising from the summit crater. Image has been color adjusted from original. Courtesy of Craig Powell.
Figure (see Caption) Figure 19. Photograph of Ulawun taken by a helicopter pilot at 1350 local time on 26 June 2019 showing a close-up view of the ash plume rising from the summit crater along with an area of incandescent ejecta. According to the pilot, this was the most active phase. Image has been color adjusted from original. Courtesy of Craig Powell.

According to RVO, parts of the ash plume at lower altitudes drifted W, causing variable amounts of ashfall in areas to the NW and SW. A pyroclastic flow descended the N flank. Residents evacuated to areas to the NE and W; a news article (Radio New Zealand) noted that around 3,000 people had gathered at a local church. According to another news source (phys.org), an observer in a helicopter reported a column of incandescent material rising from the crater, residents noted that the sky had turned black, and a main road in the N part of the island was blocked by volcanic material. Residents also reported a lava flow near Noau village and Eana Valley. RVO reported that the eruption ceased between 1800 and 1900. Incandescence visible on the N flank was from either a lava flow or pyroclastic flow deposits.

On 27 June diffuse white plumes were reported by RVO as rising from the summit crater and incandescence was visible from pyroclastic or lava flow deposits on the N flank from the activity the day before. The seismic station 11 km NW of the volcano recorded low RSAM values of between 2 and 50. According to the Darwin VAAC a strong thermal anomaly was visible in satellite images, though not after 1200. Ash from 26 June explosions continued to disperse and became difficult to discern in satellite images by 1300, though a sulfur dioxide signal persisted. Ash at an altitude of 13.7 km drifted SW to SE and dissipated by 1620, and ash at 16.8 km drifted NW to NE and dissipated by 1857. RVO noted that at 1300 on 27 June satellite images captured an ash explosion not reported by ground-based observers, likely due to cloudy weather conditions. The Alert Level was lowered to Stage 1 (the lowest level on a four-stage scale).

RSAM values slightly increased at 0600 on 28 June and fluctuated between 80 to 150 units afterwards. During 28-29 June diffuse white plumes continued to rise from the crater (figure 20) and from the North Valley vent. On 29 June a ReliefWeb update stated that around 11,000 evacuated people remained in shelters.

Figure (see Caption) Figure 20. Photograph of the steaming summit crater at Ulawun taken by a helicopter pilot at 0730 local time on 29 June 2019. Image has been color adjusted from original. Courtesy of Craig Powell.

According to RVO, diffuse white plumes rose from Ulawun's summit crater and the North Valley vent during 1-4 July and from the summit only during 5-9 July. The seismic station located 11 km NW of the volcano recorded three volcanic earthquakes and some sporadic, short-duration, volcanic tremors during 1-3 July. The seismic station 2.9 km W of the volcano was restored on 4 July and recorded small sub-continuous tremors. Some discrete high-frequency volcanic earthquakes were also recorded on most days. Sulfur dioxide emissions were 100 tonnes per day on 4 July. According to the United Nations in Papua New Guinea, 7,318 people remained displaced within seven sites because of the 26 June eruption.

Activity during August 2019. During 1-2 August RVO reported that white-to-gray vapor plumes rose from the summit crater and drifted NW. Incandescence from the summit crater was visible at night and jetting noises were audible for a short interval. RSAM values fluctuated but peaked at high levels. During the night of 2-3 August crater incandescence strengthened and roaring noises became louder around 0400. An explosion began between 0430 and 0500 on 3 August; booming noises commenced around 0445. By 0600 dense light-gray ash emissions were drifting NW, causing ashfall in areas downwind, including Ulamona Mission (10 km NW). Ash emissions continued through the day and changed from light to dark gray with time.

The eruption intensified at 1900 and a lava fountain rose more than 100 m above the crater rim. A Plinian ash plume rose 19 km and drifted W and SW, causing ashfall in areas downwind such as Navo and Kabaya, and as far as Kimbe Town (142 km SW). The Darwin VAAC reported that the ash plume expanded radially and reached the stratosphere, rising to an altitude of 19.2 km. The plume then detached and drifted S and then SE.

The Alert Level was raised to Stage 3. The areas most affected by ash and scoria fall were between Navo (W) and Saltamana Estate (NW). Two classrooms at the Navo Primary School and a church in Navo collapsed from the weight of the ash and scoria; one of the classroom roofs had already partially collapsed during the 26 June eruption. Evacuees in tents because of the 26 June explosion reported damage. Rabaul town (132 km NE) also reported ashfall. Seismicity declined rapidly within two hours of the event, though continued to fluctuate at moderate levels. According to a news source (Radio New Zealand, flights in and out of Hoskins airport in Port Moresby were cancelled on 4 August due to tephra fall. The Alert Level was lowered to Stage 1. Small amounts of white and gray vapor were emitted from the summit crater during 4-6 August. RVO reported that during 7-8 August minor emissions of white vapor rose from the summit crater.

Additional observations. Seismicity was dominated by low-level volcanic tremor and remained at low-to-moderate levels. RSAM values fluctuated between 400 and 550 units; peaks did not go above 700. Instruments aboard NASA satellites detected high levels of sulfur dioxide near or directly above the volcano on 26-29 June and 4-6 August 2019.

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed at Ulawun only on 26 June 2019 (8 pixels by the Terra satellite, 4 pixels by the Aqua satellite). The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected three anomalies during the reporting period, one during the last week of June 2019 and two during the first week of August, all three within 3 km of the volcano and of low to moderate energy.

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); 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/); 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); ReliefWeb (URL: https://reliefweb.int/); Radio New Zealand (URL: https://www.rnz.co.nz); phys.org (URL: https://phys.org); United Nations in Papua New Guinea (URL: http://pg.one.un.org/content/unct/papua_new_guinea/en/home.html).


Sarychev Peak (Russia) — November 2019 Citation iconCite this Report

Sarychev Peak

Russia

48.092°N, 153.2°E; summit elev. 1496 m

All times are local (unless otherwise noted)


Ash plume on 11 August; thermal anomalies from late May to early October 2019

Sarychev Peak, located on Matua Island in the central Kurile Islands of Russia, has had eruptions reported since 1765. Renewed activity began in October 2017, followed by a major eruption in June 2009 that included pyroclastic flows and ash plumes (BGVN 43:11 and 34:06). Thermal anomalies, explosions, and ash plumes took place between September and October 2018. A single ash explosion occurred in May 2019. Another ash plume was seen on 11 August, and small thermal anomalies were present in infrared imagery during June-October 2019. Information is provided by the Sakhalin Volcanic Eruption Response Team (SVERT) and the Tokyo Volcanic Ash Advisory Center (VAAC), with satellite imagery from Sentinel-2.

Satellite images from Sentinel-2 showed small white plumes from Sarychev Peak during clear weather on 4 and 14 August 2019 (figure 27); similar plumes were observed on a total of nine clear weather days between late June and October 2019. According to SVERT and the Tokyo VAAC, satellite data from HIMAWARI-8 showed an ash plume rising to an altitude of 2.7 km and drifting 50 km SE on 11 August. It was visible for a few days before dissipating. No further volcanism was detected by SVERT, and no activity was evident in a 17 August Sentinel-2 image (figure 27).

Figure (see Caption) Figure 27. Small white plumes were visible at Sarychev Peak in Sentinel-2 satellite images on 4 and 14 August 2019 (left and center). No activity was seen on 17 August (right). All three Sentinel-2 images use the "Natural Color" (bands 4, 3, 2) rendering; courtesy of Sentinel Hub Playground.

Intermittent weak thermal anomalies were detected by the MIROVA system using MODIS data from late May through 7 October 2019 (figure 28). Sentinel-2 satellite imagery from 28 June, 13 and 23 July, 9 August, and 21 October showed a very small thermal anomaly, but on 28 September a pronounced thermal anomaly was visible (figure 29). No additional thermal anomalies were identified from any source after 7 October through the end of the month.

Figure (see Caption) Figure 28. Thermal anomalies detected at Sarychev Peak by the MIROVA system (Log Radiative Power) using MODIS data for the year ending on 9 October 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 29. Sentinel-2 satellite images of Sarychev Peak on 23 June and 28 September 2019. A small thermal anomaly is visible on the eastern side of the crater on 23 June (left, indicated by arrow), while the thermal anomaly is more pronounced and visible in the middle of the crater on 28 September (right). Both Sentinel-2 satellite images use the "False Color (Urban)" (bands 12, 11, 4) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.

Information Contacts: Sakhalin Volcanic Eruption Response Team (SVERT), Institute of Marine Geology and Geophysics, Far Eastern Branch, Russian Academy of Science, Nauki st., 1B, Yuzhno-Sakhalinsk, Russia, 693022 (URL: http://www.imgg.ru/en/, http://www.imgg.ru/ru/svert/reports); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Asamayama (Japan) — September 2019 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Ashfall from phreatic eruptions on 7 and 25 August 2019

Asamayama (also known as Asama), located in the Kanto-Chubu Region of Japan, previously erupted in June 2015. Activity included increased volcanic seismicity, small eruptions which occasionally resulted in ashfall, and SO2 gas emissions (BGVN 41:10). This report covers activity through August 2019, which describes small phreatic eruptions, volcanic seismicity, faint incandescence and commonly white gas plumes, and fluctuating SO2 emissions. The primary source of information for this report is provided by the Japan Meteorological Agency (JMA).

Activity during October 2016-May 2019. From October 2016 through December 2017, a high-sensitivity camera captured faint incandescence at night accompanied by white gas plumes rising above the crater to an altitude ranging 100-800 m (figure 44). A thermal anomaly and faint incandescence accompanied by a white plume near the summit was observed at night on 6-7 and 21 January 2017. These thermal anomalies were recorded near the central part of the crater bottom in January, February, and November 2017, and in May 2019. After December 2017 the faint incandescence was not observed, with an exception on 18 July 2018.

Figure (see Caption) Figure 44. A surveillance camera observed faint incandescence at Asamayama in February 2017. Left: Onimushi surveillance camera taken at 0145 on 5 February 2017. Right: Kurokayama surveillance camera taken at 0510 on 1 February 2017. Courtesy of JMA (Monthly Report for February 2017).

Field surveys on 6, 16, and 28 December 2016 reported an increased amount of SO2 gas emissions from November 2016 (100-600 tons/day) to March 2017 (1,300-3,200 tons/day). In April 2017 the SO2 emissions decreased (600-1,500 tons/day). Low-frequency shallow volcanic tremors decreased in December 2016; none were observed in January 2017. From February 2017 through June 2018 volcanic tremors occurred more intermittently. According to the monthly JMA Reports on February 2017 and December 2018 and data from the Geographical Survey Institute's Global Navigation Satellite Systems (GNSS), a slight inflation between the north and south baseline was recorded starting in fall 2016 through December 2018. This growth become stagnant at some of the baselines in October 2017.

Activity during August 2019. On 7 August 2019 a small phreatic eruption occurred at the summit crater and continued for about 20 minutes, resulting in an ash plume that rose to a maximum altitude of 1.8 km, drifting N and an associated earthquake and volcanic tremor (figure 45). According to the Tokyo Volcanic Ash Advisory (VAAC), this plume rose 4.6 km, based on satellite data from HIMAWARI-8. A surveillance camera observed a large volcanic block was ejected roughly 200 m from the crater. According to an ashfall survey conducted by the Mobile Observation Team on 8 August, slight ashfall occurred in the Tsumagoi Village (12 km N) and Naganohara Town (19 km NE), Gunma Prefecture (figure 46 and 47). About 2 g/m2 of ash deposit was measured by the Tokyo Institute of Technology. Immediately after the eruption on 7 August, seismicity, volcanism, and SO2 emissions temporarily increased and then decreased that same day.

Figure (see Caption) Figure 45. Surveillance camera images of Asamayama showing the small eruption at the summit crater on 7 August 2019, resulting in incandescence and a plume rising 1.8 km altitude. Both photos were taken on 7 August 2019.Courtesy of JMA (Monthly Report for August 2019).
Figure (see Caption) Figure 46. A photomicrograph of fragmented ejecta (250-500 µm) from Asamayama deposited roughly 5 km from the crater as a result of the eruption on 7 August 2019. Courtesy of JMA (Monthly Report for August 2019).
Figure (see Caption) Figure 47. Photos of ashfall in a nearby town NNE of Asamayama due to the 7 August 2019 eruption. Courtesy of JMA (Daily Report for 8 August 2019).

Another eruption at the summit crater on 25 August 2019 was smaller than the one on 7 August. JMA reported the resulting ash plume rose to an altitude of 600 m and drifted E. However, the Tokyo VAAC reported that the altitude of the plume up to 3.4 km, according to satellite data from HIMAWARI-8. A small amount of ashfall occurred in Karuizawa-machi, Nagano (4 km E), according to interview surveys and the Tokyo Institute of Technology.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

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


Villarrica (Chile) — September 2019 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Strombolian activity continued during March-August 2019 with an increase in July

Villarrica is a frequently active volcano in Chile with an active lava lake in the deep summit crater. It has been producing intermittent Strombolian activity since February 2015, soon after the latest reactivation of the lava lake; similar activity continued into 2019. This report summarizes activity during March-August 2019 and is based on reports from the Southern Andes Volcano Observatory (Observatorio Volcanológico de Los Andes del Sur, OVDAS), part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile research group, and satellite data.

OVDAS-SERNAGEOMIN reported that degassing continued through March with a plume reaching 150 m above the crater with visible incandescence through the nights. The lava lake activity continued to fluctuate and deformation was also recorded. POVI reported sporadic Strombolian activity throughout the month with incandescent ejecta reaching around 25 m above the crater on 17 and 24 March, and nearly 50 m above the crater on the 20th (figure 76).

Figure (see Caption) Figure 76. A webcam image of Villarrica at 0441 on 20 March 2019 shows Strombolian activity and incandescent ejecta reaching nearly 50 m above the crater. People are shown for scale in the white box to the left in the blue background image that was taken on 27 March. Photos taken about 6 km away from the volcano, courtesy of POVI.

There was a slight increase in Strombolian activity reported on 7-8 April, with incandescent ballistic ejecta reaching around 50 m above the crater (figure 77). Although seismicity was low during 14-15 April, Strombolian activity produced lava fountains up to 70 m above the crater over those two days (figure 78). Activity continued into May with approximately 12 Strombolian explosions recorded on the night of 5-6 May erupting incandescent ejecta up to 50 m above the crater rim. Another lava fountaining episode was observed reaching around 70 m above the crater on 14 May (figure 79). POVI also noted that while this was one of the largest events since 2015, no significant changes in activity had been observed over the last five months. Throughout May, OVDAS-SERNAGEOMIN reported that the gas plume height did not exceed 170 m above the crater and incandescence was sporadically observed when weather allowed. SWIR (short-wave infrared) thermal data showed an increase in energy towards the end of May (figure 80).

Figure (see Caption) Figure 77. Strombolian activity at Villarrica on 7-8 April 2019 producing incandescent ballistic ejecta reaching around 50 m above the crater. Courtesy of POVI.
Figure (see Caption) Figure 78. Images of Villarrica on 15 April show a lava fountain that reached about 70 m above the crater. Courtesy of POVI.
Figure (see Caption) Figure 79. These images of Villarrica taken at 0311 and 2220 on 14 May 2019 show lava fountaining reaching 70-73 m above the crater. Courtesy of POVI.
Figure (see Caption) Figure 80. This graph shows the variation in short-wave infrared (SWIR) energy with the vertical scale indicating the number of pixels displaying high temperatures between 23 June 2018 and 29 May 2019. Courtesy of POVI.

Ballistic ejecta were observed above the crater rim on 17 and 20 June 2019 (figure 81), and activity was heard on 20 and 21 June. Activity throughout the month remained similar to previous months, with a fluctuating lava lake and minor explosions. On 15 July a thermal camera imaged a ballistic bomb landing over 300 m from the crater and disintegrating upon impact. Incandescent material was sporadically observed on 16 July. Strombolian activity increased on 22 July with the highest intensity activity in four years continuing through the 25th (figure 82).

Figure (see Caption) Figure 81. Ballistic ejecta is visible above the Villarrica crater in this infrared camera (IR940 nm) image taken on 17 June 2019. Courtesy of POVI.
Figure (see Caption) Figure 82. Strombolian activity at Villarrica on 22, 23, and 24 July with incandescent ballistic ejecta seen here above the summit crater. Courtesy of POVI.

On 6 August the Alert Level was raised by SERNAGEOMIN from Green to Yellow (on a scale of Green, Yellow, Orange, and Red indicating the greatest level of activity) due to activity being above the usual background level, including ejecta confirmed out to 200 m from the crater with velocities on the order of 100 km/hour (figure 83). The temperature of the lava lake was measured at a maximum of 1,000°C on 25 July. POVI reported the collapse of a segment of the eastern crater rim, possibly due to snow weight, between 9 and 12 August. The MIROVA system showed an increase in thermal energy in August (figure 84) and there was one MODVOLC thermal alert on 24 July.

Figure (see Caption) Figure 83. Observations during an overflight of Villarrica on 25 July 2019 showed that ballistic ejecta up to 50 cm in diameter had impacted out to 200 m from the crater. The velocities of these ejecta were likely on the order of 100 km/hour. The maximum temperature of the lava lake measured was 1,000°C, and 500°C was measured around the crater. Courtesy of SERNAGEOMIN.
Figure (see Caption) Figure 84. Thermal activity at Villarrica detected by the MIROVA system shows an increase in detected energy in August 2019. Courtesy of MIROVA.

Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); 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/).


Reventador (Ecuador) — August 2019 Citation iconCite this Report

Reventador

Ecuador

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

All times are local (unless otherwise noted)


Daily ash emissions and incandescent block avalanches continue, February-July 2019

The andesitic Volcán El Reventador lies east of the main volcanic axis of the Cordillera Real in Ecuador and has historical eruptions with numerous lava flows and explosive events going back to the 16th century. An eruption in November 2002 generated a 17-km-high eruption cloud, pyroclastic flows that traveled 8 km, and several lava flows. Eruptive activity has been continuous since 2008. Daily explosions with ash emissions and ejecta of incandescent blocks rolling hundreds of meters down the flanks have been typical for many years. Alameida et al. (2019) provide an excellent summary of recent activity (2016-2018) and monitoring. Activity continued during February-July 2019, the period covered in this report, with information provided by Ecuador's Instituto Geofisico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and infrared satellite data.

Persistent thermal activity accompanied daily ash emissions and incandescent block avalanches during February-July 2019 (figure 111). Ash plumes generally rose 600-1,200 m above the summit crater and drifted W or NW; incandescent blocks descended up to 800 m down all the flanks. On 25 February an ash plume reached 9.1 km altitude and drifted SE, causing ashfall in nearby communities. Pyroclastic flows were reported on 18 April and 19 May traveling 500 m down the flanks. Small but distinct SO2 emissions were detectible by satellite instruments a few times during the period (figure 112).

Figure (see Caption) Figure 111. The thermal energy at Reventador persisted throughout 4 November 2018 through July 2019, but was highest in April and May. Courtesy of MIROVA.
Figure (see Caption) Figure 112. Small SO2 plumes were released from Reventador and detected by satellite instruments only a few times during February-July 2019. Columbia's Nevada del Ruiz produced a much larger SO2 signal during each of the days shown here as well. Top left: 26 February; top right: 27 February; bottom left: 3 April; bottom right: 4 April. Courtesy of NASA Goddard Space Flight Center.

The Washington VAAC issued multiple daily ash advisories on all but two days during February 2019. IGEPN reported daily ash emissions rising from 400 to over 1,000 m above the summit crater. Incandescent block avalanches rolled 400-800 m down the flanks on most nights (figure 113). Late on 8 February the Washington VAAC reported an ash plume moving W at 5.8 km altitude extending 10 km from the summit. Plumes rising more than 1,000 m above the summit were reported on 9, 13, 16, 18, 19, and 25 February. On 25 February the Washington VAAC reported an ash plume visible in satellite imagery drifting SE from the summit at 9.1 km altitude that dissipated quickly, and drifted SSE. It was followed by new ash clouds at 7.6 km altitude that drifted S. Ashfall was reported in San Luis in the Parish of Gonzalo Díaz de Pineda by UMEVA Orellana and the Chaco Fire Department.

Figure (see Caption) Figure 113. Emission of ash from Reventador and incandescent blocks rolling down the cone occurred daily during February 2019, and were captured by the COPETE webcam located on the S rim of the caldera. On 1 February (top left) incandescent blocks rolled 600 m down the flanks. On 13 February (top right) ash plumes rose 800 m and drifted W. On 16 February (bottom left) ash rose to 1,000 m and drifted W. On 18 February (bottom right) the highest emission exceeded 1,000 m above the crater and was clearly visible in spite of meteoric clouds obscuring the volcano. Courtesy of IGEPN (Daily reports 2019-32, 44, 47, and 49).

Ash plumes exceeded 1,000 m in height above the summit almost every day during March 2019 and generally drifted W or NW. The Washington VAAC reported an ash plume visible above the cloud deck at 6.7 km altitude extending 25 km NW early on 3 March; there were no reports of ashfall nearby. Incandescent block avalanches rolled 800 m down all the flanks the previous night; they were visible moving 300-800 m down the flanks most nights throughout the month (figure 114).

Figure (see Caption) Figure 114. Ash plumes and incandescent block avalanches occurred daily at Reventador during March 2019 and were captured by the COPETE webcam on the S rim of the caldera. On 3 March (top left) a possible pyroclastic flow traveled down the E flank in the early morning. Ash plumes on 17 and 18 March (top right, bottom left) rose 900-1,000 m above the summit and drifted W. On 23 March (bottom right) ash plumes rose to 1,000 m and drifted N while incandescent blocks rolled 600 m down the flanks. Courtesy of IGEPN (Daily reports 2019 62, 76, 77, and 82).

During April 2019 ash plume heights ranged from 600 to over 1,000 m above the summit each day, drifting either W or NW. Incandescent avalanche blocks rolled down all the flanks for hundreds of meters daily; the largest explosions sent blocks 800 m from the summit (figure 115). On 18 April IGEPN reported that a pyroclastic flow the previous afternoon had traveled 500 m down the NE flank.

Figure (see Caption) Figure 115. Ash plumes and incandescent block avalanches occurred daily at Reventador during April 2019. On 3 April, ash emissions were reported drifting W and NW at 1,000 m above the summit (top left). On 14 April ash plumes rose over 600 m above the summit crater (top right). The 3 and 14 April images were taken from the LAVCAM webcam on the SE flank. Incandescent block avalanches descended 800 m down all the flanks on 15 April along with ash plumes rising over 1,000 m above the summit (bottom left), both visible in this image from the COPETE webcam on the S rim of the caldera. A pyroclastic flow descended 500 m down the NE flank on 17 April and was captured in the thermal REBECA webcam (bottom right) located on the N rim of the caldera. Courtesy of IGEPN (Daily reports 2019-93, 104, 105, and 108).

On most days during May 2019, incandescent block avalanches were observed traveling 700-800 m down all the flanks. Ash plume heights ranged from 600 to 1,200 m above the crater each day of the month (figure 116) they were visible. A pyroclastic flow was reported during the afternoon of 19 May that moved 500 m down the N flank.

Figure (see Caption) Figure 116. Even on days with thick meteoric clouds, ash plumes can be observed at Reventador. The ash plumes reached 1,000 m above the crater on 8 May 2019 (top left). The infrared webcam REBECA on the N rim of the caldera captured a pyroclastic flow on the N flank on the afternoon of 19 May (top right). Strong explosions on 23 May sent incandescent blocks and possible pyroclastic flows at least 800 m down all the flanks (bottom left). Ash plumes reached 1,000 m above the summit on 27 May and drifted W (bottom right). Images on 8, 23, and 27 May taken from the COPETE webcam on the S rim of the caldera. Courtesy of IGEPN (Daily Reports 2019-128, 140, 143, and 147).

Activity diminished somewhat during June 2019. Ash plumes reached 1,200 m above the summit early in June but decreased to 600 m or less for the second half of the month. Meteoric clouds prevented observation for most of the third week of June; VAAC reports indicated ash emissions rose to 5.2 km altitude on 19 June and again on 26 June (about 2 km above the crater). Incandescent blocks were reported traveling down all of the flanks, generally 500-800 m, during about half of the days the mountain was visible (figure 117). Multiple VAAC reports were also issued daily during July 2019. Ash plumes were reported by IGEPN rising over 600 m above the crater every day it was visible and incandescent blocks traveled 400-800 m down the flanks (figure 118). The Darwin VAAC reported an ash emission on 9 July that rose to 4.9 km altitude as multiple puffs that drifted W, extending about 35 km from the summit.

Figure (see Caption) Figure 117. Activity diminished slightly at Reventador during June 2019. Incandescent material was visible on the N flank from infrared webcam REBECA on the N rim of the caldera on 6 June (top left). On 7 June ash rose over 1,000 m above the summit and drifted N and W (top right) as seen from the COPETE webcam on the S rim of the caldera. Incandescent block avalanches rolled 600 m down all the flanks on 8 June (bottom left) and were photographed by the LAVCAM webcam located on the SE flank. An ash plume rose to 1,000 m on 25 June and was photographed from the San Rafael waterfall (bottom right). Courtesy of IGEPN (Daily Reports 2019-157, 158, 159, and 176).
Figure (see Caption) Figure 118. Daily explosive activity was reported at Reventador during July 2019. On 9 and 10 July ash plumes rose over 600 m and drifted W and incandescent blocks descended 800 m down all the flanks (top row), as seen from the LAVCAM webcam on the SE flank. On 27 July many of the large incandescent blocks appeared to be several m in diameter as they descended the flanks (bottom left, LAVCAM). On 1 August, a small steam plume was visible on a clear morning from the CORTESIA webcam located N of the volcano. Courtesy of IGEPN Daily reports (2019-190, 191, 208, and 213).

References: Almeida M, Gaunt H E, and Ramón P, 2019, Ecuador's El Reventador volcano continually remakes itself, Eos, 100, https://doi.org/10.1029/2019EO117105. Published on 18 March 2019.

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

Information Contacts: Instituto Geofísico (IG-EPN), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); 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/).


Raikoke (Russia) — August 2019 Citation iconCite this Report

Raikoke

Russia

48.292°N, 153.25°E; summit elev. 551 m

All times are local (unless otherwise noted)


Short-lived series of large explosions 21-23 June 2019; first recorded activity in 95 years

Raikoke in the central Kuril Islands lies 400 km SW of the southern tip of Russia's Kamchatcka Peninsula. Two significant eruptive events in historical times, including fatalities, have been recorded. In 1778 an eruption killed 15 people "under the hail of bombs" who were under the command of Captain Chernyi, returning from Matua to Kamchatka. This prompted the Russian military to order the first investigation of the volcanic character of the island two years later (Gorshkov, 1970). Tanakadate (1925) reported that travelers on a steamer witnessed an ash plume rising from the island on 15 February 1924, observed that the island was already covered in ash from recent activity, and noted that a dense steam plume was visible for a week rising from the summit crater. The latest eruptive event in June 2019 produced a very large ash plume that covered the island with ash and dispersed ash and gases more than 10 km high into the atmosphere. The volcano is monitored by the Sakhalin Volcanic Eruption Response Team, (SVERT) part of the Institute of Marine Geology and Geophysics, Far Eastern Branch of the Russian Academy of Sciences (IMGG FEB RAS) and the Kamchatka Volcanic Eruption Response Team (KVERT) which is part of the Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences (IVS FEB RAS).

A brief but intense eruption beginning on 21 June 2019 sent major ash and sulfur dioxide plumes into the stratosphere (figures 1 and 2); the plumes rapidly drifted over 1,000 km from the volcano. Strong explosions with dense ash plumes lasted for less than 48 hours, minor emissions continued for a few more days; the SO2, however, continued to circulate over far eastern Russia and the Bering Sea for more than three weeks after the initial explosion. The eruption covered the island with centimeters to meters of ash and enlarged the summit crater. By the end of July 2019 only minor intermittent steam emissions were observed in satellite imagery.

Figure (see Caption) Figure 1. On the morning of 22 June 2019, astronauts on the International Space Station captured this image of a large ash plume rising from Raikoke in the Kuril Islands. The plume reached altitudes of 10-13 km and drifted E during the volcano's first known explosion in 95 years. Courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 2. A large and very dense SO2 plume (measuring over 900 Dobson Units (DU)) drifted E from Raikoke in the Kuril Islands on 22 June 2019, about 8 hours after the first known explosion in 95 years. Courtesy of NASA Goddard Space Flight Center.

Summary of 2019 activity. A powerful eruption at Raikoke began at 1805 on 21 June 2019 (UTC). Volcano Observatory Notices for Aviation (VONA's) issued by KVERT described the large ash plume that rapidly rose to 10-13 km altitude and extended for 370 km NE within the first two hours (figure 3). After eight hours, the plume extended 605 km ENE; it had reached 1,160 km E by 13 hours after the first explosion (figure 4). The last strong explosive event, according to KVERT, producing an ash column as high as 10-11 km, occurred at 0540 UTC on 22 June. SVERT reported a series of nine explosions during the eruption. Over 440 lightning events within the ash plume were detected in the first 24 hours by weather-monitoring equipment. The Japanese Ministry of Transportation reported that almost 40 planes were diverted because of the ash plume (figure 5).

Figure (see Caption) Figure 3. A dense ash plume drifted E from Raikoke on 22 June 2019 from a series of large explosions that lasted for less than 24 hours, as seen in this Terra satellite image. The plume was detected in the atmosphere for several days after the end of the eruptive activity. Courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 4. The ash plume from Raikoke volcano that erupted on 21 June 2019 drifted over 1,000 km E by late in the day on 22 June, as seen in this oblique, composite view based on data from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite. Courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 5. Numerous airplanes were traveling on flight paths near the Raikoke ash plume (black streak at center) early on 22 June 2019. The Japanese Ministry of Transportation reported that almost 40 planes were diverted because of the plume. Courtesy of Flightradar24 and Volcano Discovery.

On 23 June (local time) the cruise ship Athena approached the island; expedition member Nikolai Pavlov provided an eyewitness account and took remarkable drone photographs of the end of the eruption. The ship approached the W flank of the island in the late afternoon and they were able to launch a drone and photograph the shore and the summit. They noted that the entire surface of the island was covered with a thick layer of light-colored ash up to several tens of centimeters thick (figure 6). Fresh debris up to several meters thick fanned out from the base of the slopes (figure 7). The water had a yellowish-greenish tint and was darker brown closer to the shore. Dark-brown steam explosions occurred when waves flowed over hot areas along the shoreline, now blanketed in pale ash with bands of steam and gas rising from it (figure 8). A dense brown ash plume drifted W from the crater, rising about 1.5 km above the summit (figure 9).

Figure (see Caption) Figure 6. The entire surface of the island of Raikoke was covered with a thick layer of light-colored ash up to several tens of centimeters thick on 23 June 2019 when photographed by drone from the cruise ship Athena about 36 hours after the explosions began. View is of the W flank. Photo by Nik Pavlov; courtesy of IVS FEB RAS.
Figure (see Caption) Figure 7. Fresh ash and volcanic debris up to several meters thick coated the flanks of Raikoke on 23 June 2019 after the large explosive eruption two days earlier. View is by drone of the W flank. Photo by Nik Pavlov; courtesy of IVS FEB RAS.
Figure (see Caption) Figure 8. The 21 June 2019 eruption of Raikoke covered the island in volcanic debris. The formerly vegetated areas (left, before eruption) were blanketed in pale ash with bands of steam and gas rising all along the shoreline (right, on 23 June 2019) less than two days after the explosions began. The open water area between the sea stack and the island was filled with tephra. Photos by Nik Pavlov; courtesy of IVS FEB RAS.
Figure (see Caption) Figure 9. At the summit of Raikoke on 23 June 2019, a dense brown ash plume drifted W from the crater, rising about 1.5 km, two days after a large explosive eruption. Drone photo by Nik Pavlov; courtesy of IVS FEB RAS.

Early on 23 June, the large ash cloud continued to drift E and then NE at an altitude of 10-13 km. At that altitude, the leading edge of the ash cloud became entrained in a large low pressure system and began rotating from SE to NW, centered in the area of the Komandorskiye Islands, 1,200 km NE of Raikoke. By then the farthest edge of ash plume was located about 2,000 km ENE of the volcano. Meanwhile, at the summit and immediately above, the ash plume was drifting NW on 23 June (figures 9 and 10). Ashfall was reported (via Twitter) from a ship in the Pacific Ocean 40 km from Raikoke on 23 June. Weak ashfall was also reported in Paramushir, over 300 km NE the same day. KVERT reported that satellite data from 25 June indicated that a steam and gas plume, possibly with some ash, extended for 60 km NW. They also noted that the high-altitude "aerosol cloud" continued to drift to the N and W, reaching a distance of 1,700 km NW (see SO2 discussion below). By 27 June KVERT reported that the eruption had ended, but the aerosols continued to drift to the NW and E. They lowered the Aviation Alert Level to Green the following day.

Figure (see Caption) Figure 10. The brown ash plume from Raikoke was drifting NW on 23 June 2019 (left), while the remnants of the ash from the earlier explosions continued to be observed over a large area to the NE on 25 June (right). The plume in the 23 June image extends about 30 km NW; the plume in the 25 June image extends a similar distance NE. Natural color rendering (bands 4, 3, 2) of Sentinel-2 imagery, courtesy of Sentinel Hub Playground.

Tokyo and Anchorage VAAC Reports. The Tokyo VAAC first observed the ash plume in satellite imagery at 10.4 km altitude at 1850 on 21 June 209, just under an hour after the explosion was first reported by KVERT. About four hours later they updated the altitude to 13.1 km based on satellite data and a pilot report. By the evening of 22 June the high-level ash plume was still drifting ESE at about 13 km altitude while a secondary plume at 4.6 km altitude drifted SE for a few more hours before dissipating. The direction of the high-altitude plume began to shift to the NNW by 0300 on 23 June. By 0900 it had dropped slightly to 12.2 km and was drifting NE. The Anchorage VAAC reported at 2030 that the ash plume was becoming obscured by meteorological clouds around a large and deep low-pressure system in the western Bering Sea. Ash and SO2 signals in satellite imagery remained strong over the region S and W of the Pribilof Islands as well as over the far western Bering Sea adjacent to Russia. By early on 24 June the plume drifted NNW for a few hours before rotating back again to a NE drift direction. By the afternoon of 24 June, the altitude had dropped slightly to 11.6 km as it continued to drift NNE.

The ash plume was still clearly visible in satellite imagery late on 24 June. An aircraft reported SO2 at 14.3 km altitude above the area of the ash plume. The plume then began to move in multiple directions; the northern part moved E, while the southern part moved N. The remainder was essentially stationary, circulating around a closed low-pressure zone in the western Bering Sea. The ash plume remained stationary and slowly dissipated as it circulated around the low through 25 June before beginning to push S (figure 11). By early on 26 June the main area of the ash plume was between 325 km WSW of St. Matthew Island and 500 km NNW of St. Lawrence Island, and moving slowly NW. The Anchorage VAAC could no longer detect the plume in satellite imagery shortly after midnight (UTC) on 27 June, although they noted that areas of aerosol haze and SO2 likely persisted over the western Bering Sea and far eastern Russia.

Figure (see Caption) Figure 11. This RGB image created from a variety of spectral channels from the GOES-17 (GOES-West) satellite shows the ash and gas plume from Raikoke on 25 June 2019. The brighter yellows highlight features that are high in SO2 concentration. Highlighted along the bottom of the image is the pilot report over the far southern Bering Sea; the aircraft was flying at an altitude of 11 km (36,000 feet), and the pilot remarked that there were multiple layers seen below that altitude which had a greyish appearance (likely volcanic ash). Courtesy of NOAA and Scott Bachmeier.

Sulfur dioxide emissions. A very large SO2 plume was released during the eruption. Preliminary total SO2 mass estimates by Simon Carn taken from both UV and IR sensors suggested around 1.4-1.5 Tg (1 Teragram = 109 Kg) that included SO2 columns within the ash plume with values as high as 1,000 Dobson Units (DU) (figure 12). As the plume drifted on 23 and 24 June, similar to the ash plume as described by the Tokyo VAAC, it moved in a circular flow pattern as a result of being entrained in a low-pressure system in the western Bering Sea (figure 13). By 25 June the NW edge of the SO2 had reached far eastern Russia, 1,700 km from the volcano (as described by KVERT), while the eastern edges reached across Alaska and the Gulf of Alaska to the S. Two days later streams of SO2 from Raikoke were present over far northern Siberia and northern Canada (figure 14). For the following three weeks high levels of SO2 persisted over far eastern Russia and the Bering Sea, demonstrating the close relationship between the prevailing weather patterns and the aerosol concentrations from the volcano (figure 15).

Figure (see Caption) Figure 12. A contour map showing the mass and density of SO2 released into the atmosphere from Raikoke on 22 June 2019. Courtesy of Simon Carn.
Figure (see Caption) Figure 13. Streams of SO2 from Raikoke drifted around a complex flow pattern in the Bering Sea on 23 and 24 June 2019. Data from TROPOMI instrument on the Sentinel-5P satellite, courtesy of NASA Goddard Space Flight Center and Simon Carn.
Figure (see Caption) Figure 14. SO2 plumes from Raikoke dispersed over a large area of the northern hemisphere in late June 2019. By 25 June (top) the SO2 plumes had dispersed to far eastern Russia, 1,700 km from the volcano, while the eastern edges reached across Alaska and the Gulf of Alaska to the S. By 27 June (bottom) streams of SO2 were present over far northern Siberia and northern Canada, and also continued to circulate in a denser mass over far eastern Russia. Data from TROPOMI instrument on the Sentinel-5P satellite, courtesy of NASA Goddard Space Flight Center and Simon Carn.
Figure (see Caption) Figure 15. For the first two weeks of July 2019, high levels of SO2 from the 21 June 2019 eruption of Raikoke persisted over far eastern Russia and the Bering Sea entrained in a slow moving low-pressure system, demonstrating the close relationship between the prevailing weather patterns and the aerosol concentrations from the volcano. Data from TROPOMI instrument on the Sentinel-5P satellite, courtesy of NASA Goddard Space Flight Center.

Changes to the island. Since no known activity had occurred at Raikoke for 95 years, the island was well vegetated on most of its slopes and the inner walls of the summit crater before the explosion (figure 16). The first clear satellite image after the explosion, on 30 June 2019, revealed a modest steam plume rising from the summit crater, pale-colored ash surrounding the entire island, and new deposits of debris fans extending out from the NE, SW, and S flanks. Part of a newly enlarged crater was visible at the N edge of the old crater. Two weeks later only a small steam plume was present at the summit, making the outline of the enlarged crater more visible; the extensive shoreline deposits of fresh volcanic material remained. A clear view into the summit crater on 23 July revealed the size and shape of the newly enlarged summit crater (figure 17).

Figure (see Caption) Figure 16. Changes at Raikoke before and after the 21 June 2019 eruption were clear in Sentinel-2 satellite imagery. The island was heavily vegetated on most of its slopes and the inner walls of the summit crater before the explosion (top left, 3 June 2019). The first clear satellite image after the explosion, on 30 June 2019 revealed a steam plume rising from the summit crater, pale-colored ash surrounding the entire island, and new deposits of debris fans extending out from the NE, SW, and S flanks (top right). Part of a newly enlarged crater was visible at the N edge of the old crater. Two weeks later only a small steam plume was present at the summit, making the outline of the enlarged crater more visible; the extensive shoreline deposits of fresh volcanic material remained (bottom right, 13 July 2019). A clear view into the summit crater on 23 July revealed the new size and shape of the summit crater (bottom left). Natural Color rendering (bands 4, 3, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 17. Sentinel-2 satellite imagery of the summit crater of Raikoke before (left) and after (right) the explosions that began on 21 June 2019. The old crater rim is outlined in red in both images. The new crater rim is outlined in yellow in the 23 July image. Natural Color rendering (bands 4, 3, 2), courtesy of Sentinel Hub Playground.

References: Gorshkov G S, 1970, Volcanism and the Upper Mantle; Investigations in the Kurile Island Arc, New York: Plenum Publishing Corp, 385 p.

Tanakadate H, 1925, The volcanic activity in Japan during 1914-1924, Bull Volc. v. 1, no. 3.

Geologic Background. A low truncated volcano forms the small barren Raikoke Island, which lies 16 km across the Golovnin Strait from Matua Island in the central Kuriles. The oval-shaped basaltic island is only 2 x 2.5 km wide and rises above a submarine terrace. An eruption in 1778, during which the upper third of the island was said to have been destroyed, prompted the first volcanological investigation in the Kuril Islands two years later. Incorrect reports of eruptions in 1777 and 1780 were due to misprints and errors in descriptions of the 1778 event (Gorshkov, 1970). Another powerful eruption in 1924 greatly deepened the crater and changed the outline of the island. Prior to a 2019 eruption, the steep-walled crater, highest on the SE side, was 700 m wide and 200 m deep. Lava flows mantle the eastern side of the island.

Information Contacts: Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Sakhalin Volcanic Eruption Response Team (SVERT), Institute of Marine Geology and Geophysics, Far Eastern Branch, Russian Academy of Science, Nauki st., 1B, Yuzhno-Sakhalinsk, Russia, 693022 (URL: http://www.imgg.ru/en/, http://www.imgg.ru/ru/svert/reports); Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); 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); NOAA, Cooperative Institute for Meteorological Satellite Studies (CIMSS), Space Science and Engineering Center (SSEC), University of Wisconsin-Madison, 1225 W. Dayton St. Madison, WI 53706, (URL: http://cimss.ssec.wisc.edu/); Simon Carn, Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA (URL: http://www.volcarno.com/, Twitter: @simoncarn); Scott Bachmeier, Cooperative Institute for Meteorological Satellite Studies (CIMSS), Space Science and Engineering Center (SSEC), University of Wisconsin-Madison, 1225 W. Dayton St. Madison, WI 53706; Flightradar24 (URL: https://www.flightradar24.com/51,-2/6); Volcano Discovery (URL: http://www.volcanodiscovery.com/).


Sinabung (Indonesia) — August 2019 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


Large ash explosions on 25 May and 9 June 2019

Indonesia's Sinabung volcano in north Sumatra has been highly active since its first confirmed Holocene eruption during August and September 2010. It remained quiet after the initial eruption until September 2013, when a new eruptive phase began that continued uninterrupted through June 2018. Ash plumes often rose several kilometers, avalanche blocks fell kilometers down the flanks, and deadly pyroclastic flows traveled more than 4 km repeatedly during the eruption. After a pause in eruptive activity from July 2018 through April 2019, explosions took place again during May and June 2019. This report covers activity from July 2018 through July 2019 with information provided by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), referred to by some agencies as CVGHM or the Indonesian Center of Volcanology and Geological Hazard Mitigation, the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB). Additional information comes from satellite instruments and local news reports.

After the last ash emission observed on 5 July 2018, activity diminished significantly. Occasional thermal anomalies were observed in satellite images in August 2018, and February-March 2019. Seismic evidence of lahars was recorded almost every month from July 2018 through July 2019. Renewed explosions with ash plumes began in early May; two large events, on 24 May and 9 June, produced ash plumes observed in satellite data at altitudes greater than 15 km (table 9).

Table 9. Summary of activity at Sinabung during July 2018-July 2019. Steam plume heights from PVMBG daily reports. VONA reports issued by Sinabung Volcano Observatory, part of PVMBG. Satellite imagery from Sentinel-2. Lahar seismicity from PVMBG daily and weekly reports. Ash plume heights from VAAC reports. Pyroclastic flows from VONA reports.

Month Steam Plume Heights (m) Dates of VONA reports Satellite Thermal Anomalies (date) Seismicity indicating Lahars (date) Ash Plume Altitude (date and distance) Pyroclastic flows
Jul 2018 100-700 -- -- -- -- --
Aug 2018 50-700 -- 30 1, 20 -- --
Sep 2018 100-500 -- -- 1st week, 12, 29 -- --
Oct 2018 50-1,000 -- -- 1 -- --
Nov 2018 50-350 -- -- 14 -- --
Dec 2018 50-500 -- -- 30 -- --
Jan 2019 50-350 -- -- -- -- --
Feb 2019 100-400 -- 6, 21 -- -- --
Mar 2019 50-300 -- 3, 8 27 -- --
Apr 2019 50-400 -- -- 2, 4, 11 -- --
May 2019 200-700 7, 11, 12, 24, 26, 27 (2) -- 4, 14 7 (4.6 km), 24 (15.2 km), 25 (6.1 km) --
June 2019 50-600 9, 10 -- -- 9 (16.8 km), 10 (3.0 km) 9-3.5 km SE, 3.0 km S
July 2019 100-700 -- -- 10, 12, 14, 16, 4th week -- --

No eruptive activity was reported after 5 July 2018 for several months, however Sentinel-2 thermal imagery on 30 August indicated a hot spot at the summit suggestive of eruptive activity. The next distinct thermal signal appeared on 6 February 2019, with a few more in late February and early March (figure 66, see table 9).

Figure (see Caption) Figure 66. Sentinel-2 satellite imagery on 30 August 2018, 6 February, and 8 March 2019 showed distinct thermal anomalies suggestive of eruptive activity at Sinabung, although no activity was reported by PVMBG. Images rendered with Atmospheric Penetration, bands 12, 11, and 8A. Courtesy of Sentinel Hub Playground.

PVMBG reported the first ash emission in 11 months early on 7 May 2019. They noted that an ash plume rose 2 km above the summit and drifted ESE. The Sinabung Volcano Observatory (SVO) issued a VONA (Volcano Observatory Notice for Aviation) that described an eruptive event lasting for a little over 40 minutes. Ashfall was reported in several villages. The Jakarta Post reported that Karo Disaster Mitigation Agency (BPDB) head Martin Sitepu said four districts were affected by the eruption, namely Simpang Empat (7 km SE), Namanteran (5 km NE), Kabanjahe (14 km SE), and Berastadi (12 km E). The Darwin VAAC reported the ash plume at 4.6 km altitude and noted that it dissipated about six hours later (figure 67). The TROPOMI SO2 instrument detected an SO2 plume shortly after the event (figure 68).

Figure (see Caption) Figure 67. Images from the explosion at Sinabung on 7 May 2019. Left and bottom right photos by Kopi Cimbang and Kalak Karo Kerina, courtesy of David de Zabedrosky. Top right photo courtesy of Sutopo Purwo Nugroho, BNPB.
Figure (see Caption) Figure 68. The TROPOMI instrument on the Sentinel-5P satellite captured an SO2 emission from Sinabung shortly after the eruption on 7 May 2019. Courtesy of NASA Goddard Space Flight Center.

On 11 May 2019 SVO issued a VONA reporting a seismic eruption event with a 9 mm amplitude that lasted for about 30 minutes; clouds and fog prevented visual confirmation. Another VONA issued the following day reported an ash emission that lasted for 28 minutes but again was not observed due to fog. The Darwin VAAC did not observe the ash plumes reported on 11 or 12 May; they did report incandescent material observed in the webcam on 11 May. Sutopo Purwo Nugroho of BNPB reported that the 12 May eruption was accompanied by incandescent lava and ash, and the explosion was heard in Rendang (figure 69). The Alert Level had been at Level IV since 2 June 2015. Based on decreased seismicity, a decrease in visual activity (figure 70), stability of deformation data, and a decrease in SO2 flux during the previous 11 months, PVMBG lowered the Alert Level from IV to III on 20 May 2019.

Figure (see Caption) Figure 69. Incandescent lava and ash were captured by a webcam at Sinabung on 12 May 2019. Courtesy of Sutopo Purwo Nugroho, BNPB.
Figure (see Caption) Figure 70. The summit of Sinabung emitted only steam and gas on 18 May 2019, shortly before PVMBG lowered the Alert Level from IV to III. Courtesy of PVMBG (Decreased G. Sinabung activity level from Level IV (Beware) to Level III (Standby), May 20, 2019).

A large explosion was reported by the Darwin VAAC on 24 May 2019 (UTC) that produced a high-altitude ash plume visible in satellite imagery at 15.2 km altitude moving W; the plume was not visible from the ground due to fog. The Sinabung Volcano Observatory reported that the brief explosion lasted for only 7 minutes (figure 71), but the plume detached and drifted NW for about 12 hours before dissipating. The substantial SO2 plume associated with the event was recorded by satellite instruments a few hours later (figure 72, left). Another six-minute explosion late on 26 May (UTC) produced an ash plume that was reported by a ground observer at 4.9 km altitude drifting S (figure 72, right). About an hour after the event, the Darwin VAAC observed the plume drifting S at 6.1 km altitude; it had dissipated four hours later. Sumbul Sembiring, a resident of Kabanjahe, told news outlet Tempo.com that ash had fallen at the settlements. Two more explosions were reported on 27 May; the first lasted for a little over 12 minutes, the second (about 90 minutes later, 28 May local time) lasted for about 2.5 minutes. No ash plumes were visible from the ground or satellite imagery for either event.

Figure (see Caption) Figure 71. A brief but powerful explosion at Sinabung in the early hours of 25 May 2019 (local time) produced a seven-minute-long seismic signal and a 15.2-km-altitude ash plume. Courtesy of MAGMA Indonesia and Volcano Discovery.
Figure (see Caption) Figure 72. Two closely spaced eruptive events occurred at Sinabung on 24 and 26 May UTC (25 and 27 May local time). The 24 May event produced a significant SO2 plume recorded by the TROPOMI instrument a few hours afterwards (left), and a 15.2-km-altitude ash plume only recorded in satellite imagery. The event on 26 May produced a visible ash plume that was reported at 6.1 km altitude and was faintly visible from the ground (right). SO2 courtesy of NASA Goddard Space Flight Center, photograph courtesy of PVMBG and Øystein Lund Andersen.

An explosion on 9 June 2019 produced an ash plume, estimated from the ground as rising to 9.5 km altitude, that drifted S and E; pyroclastic flows traveled 3.5 km SE and 3 km S down the flanks (figure 73). The explosion was heard at the Sinabung Observatory. The Darwin VAAC reported that the eruption was visible in Himawari-8 satellite imagery, and reported by pilots, at 16.8 km altitude drifting W; about an hour later the VAAC noted that the detached plume continued drifting SW but lower plumes were still present at 9.1 km altitude drifting W and below 4.3 km drifting SE. They also noted that pyroclastic flows moving SSE were sending ash to 4.3 km altitude. Three hours later they reported that both upper level plumes had detached and were moving SW and W. After six hours, the lower altitude plumes at 4.3 and 9.1 km altitudes had dissipated; the higher plume continued moving SW at 12.2 km altitude until it dissipated within the next eight hours. Instruments on the Sentinel-5P satellite captured an SO2 plume from the explosion drifting W across the southern Indian Ocean (figure 74).

Figure (see Caption) Figure 73. A large explosion at Sinabung on 9 June 2019 produced an ash plume that rose to 16.8 km altitude and also generated pyroclastic flows (foreground) that traveled down the S and SE flanks. Left image courtesy of Sutopo Purwo Nugroho, Head of the BNPB Information and Public Relations Data Center. Right image photo source PVMBG/Mbah Rono/ Berastagi Nachelle Homestay, courtesy of Jaime Sincioco.
Figure (see Caption) Figure 74. An SO2 plume from the 9 June 2019 explosion at Sinabung drifted more than a thousand kilometers W across the southern Indian Ocean. Courtesy of Sentinel Hub and Annamaria Luongo.

The SVO reported continuous ash and gas emissions at 3.0 km altitude moving ESE early on 10 June; it was obscured in satellite imagery by meteoric clouds. There were no additional VONA's or VAAC reports issued for the remainder of June or July 2019. An image on social media from 20 June 2019 shows incandescent blocks near the summit (figure 75). PVMBG reported that emissions on 25 June were white to brownish and rose 200 m above the summit and drifted E and SE.

Figure (see Caption) Figure 75. Incandescent blocks at the summit of Sinabung were visible in this 20 June 2019 image taken from a rooftop terrace in Berastagi, 13 km E. Photo by Nachelle Homestay, courtesy of Jaime Sincioco.

PVMBG detected seismic signals from lahars several times during the second week of July 2019. News outlets reported lahars damaging villages in the Karo district on 11 and 13 July (figure 76). Detik.com reported that lahars cut off the main access road to Perbaji Village (4 km SW), Kutambaru Village (14 km S), and the Tiganderket connecting road to Kutabuluh (17 km WNW). In addition, Puskesmas Kutambaru was submerged in mud. Images from iNews Malam showed large boulders and rafts of trees in thick layers of mud covering homes and roads. No casualties were reported.

Figure (see Caption) Figure 76. Lahars on 11 and 13 July 2019 caused damage in numerous villages around Sinabung, filling homes and roadways with mud, tree trunks, and debris. No casualties were reported. Courtesy of iNews Malam.

Geologic Background. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

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/); 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/); The Jakarta Post (URL: https://www.thejakartapost.com/news/2019/05/07/mount-sinabung-erupts-again.html); Detikcom (URL: https://news.detik.com/berita/d-4619253/hujan-deras-sejumlah-desa-di-sekitar-gunung-sinabung-banjir-lahar-dingin); iNews Malam (URL: https://tv.inews.id/, https://www.youtube.com/watch?v=uAI4CpSb41k); Tempo.com (URL:https://en.tempo.co/read/1209667/mount-sinabung-erupts-on-monday-morning); David de Zabedrosky, Calera de Tango, Chile (Twitter: @deZabedrosky, URL: https://twitter.com/deZabedrosky/status/1125814504867160065/photo/1, https://twitter.com/deZabedrosky/status/1125814504867160065/photo/2); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Øystein Lund Andersen? (Twitter: @OysteinLAnderse, URL: https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com image at https://twitter.com/OysteinLAnderse/status/1132849458142572544); Jaime Sincioco, Phillipines (Twitter: @jaimessincioca, URL: https://twitter.com/jaimessincioco); Annamaria Luongo, University of Padua, Venice, Italy (Twitter: @annamaria_84, URL:https://twitter.com/annamaria_84).


Semisopochnoi (United States) — September 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)


Small explosions detected between 16 July and 24 August 2019

The remote island of Semisopochnoi in the western Aleutians is dominated by a caldera measuring 8 km in diameter that contains a small lake (Fenner Lake) and a number of post-caldera cones and craters. A small (100 m diameter) crater lake in the N cone of Semisopochnoi's Cerberus three-cone cluster has persisted since January 2019. An eruption at Sugarloaf Peak in 1987 included an ash plume (SEAN 12:04). Activity during September-October 2018 included increased seismicity and small explosions (BGVN 44:02). The primary source of information for this reporting period of July-August 2019 comes from the Alaska Volcano Observatory (AVO), when there were two low-level eruptions.

Seismicity rose above background levels on 5 July 2019. AVO reported that data from local seismic and infrasound sensors likely detected a small explosion on 16 July. A strong tremor on 17 July generated airwaves that were detected on an infrasound array 260 km E on Adak Island. In addition to this, a small plume extended 18 km WSW from the Cerberus vent, but no ash signals were detected in satellite data. Seismicity decreased abruptly on 18 July after a short-lived eruption. Seismicity increased slightly on 23 July and remained elevated through August.

On 24 July 2019 AVO reported that satellite data showed that the crater lake was gone and a new, shallow inner crater measuring 80 m in diameter had formed on the crater floor, though no lava was identified. Satellite imagery indicated that the crater of the Cerberus N cone had been replaced by a smooth, featureless area of either tephra or water at a level several meters below the previous floor. Satellite imagery detected faint steam plumes rising to 5-10 km altitude and minor SO2 emissions on 27 July. Satellite data showed a steam plume rising from Semisopochnoi on 18 August and SO2 emissions on 21-22 August. Ground-coupled airwaves identified in seismic data on 23-24 August was indicative of additional explosive activity.

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/).


Krakatau (Indonesia) — August 2019 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 813 m

All times are local (unless otherwise noted)


Repeated Surtseyan explosions with ash and steam during February-July 2019

Krakatau volcano in the Sunda Strait between Java and Sumatra, Indonesia experienced a major caldera collapse around 535 CE; it formed a 7-km-wide caldera ringed by three islands. Remnants of this volcano joined to create the pre-1883 Krakatau Island which collapsed during the major 1883 eruption. Anak Krakatau (Child of Krakatau), constructed beginning in late 1927 within the 1883 caldera (BGVN 44:03, figure 56), was the site of over 40 smaller episodes until 22 December 2018 when a large explosion and tsunami destroyed most of the 338-m-high edifice (BGVN 44:03). Subsequent activity from February-July 2019 is covered in this report with information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, referred to as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG). Aviation reports are provided by the Darwin Volcanic Ash Advisory Center (VAAC), and photographs from several social media sources.

The cyclical nature of the growth and destruction of Krakatau was made apparent again in the explosive events of 22 December 2018-6 January 2019, when much of the island of Anak Krakatau was destroyed in a series of events that included a deadly tsunami from a flank collapse, a Vulcanian explosion, and several days of Surtseyan phreatomagmatic activity (figure 83) (Gouhier and Paris, 2019). Due to the location of the volcano in the middle of Sunda Strait, surrounded by coastal communities, damage from the tsunami was once again significant; over 400 fatalities and 30,000 injuries were reported along with damage to thousands of homes, businesses, and boats (figure 84) (BGVN 44:03). After a small explosion on 8 January 2019, the volcano remained quiet until 14 February when a new seismic event was recorded. Intermittent explosions increased in frequency and continued through July 2019; images of Surtseyan explosions with ejecta and steam rising a few hundred meters were occasionally captured by authorities patrolling the Krakatau Islands Nature Preserve and Marine Nature Reserve (KPHK), and by a newly installed webcam.

Figure (see Caption) Figure 83. The dramatic morphologic changes of Anak Krakatau before and after the explosive events of 22 December 2019-6 January 2019 were apparent in these Planet Labs, Inc. images published by the BBC. Left: Planet Lab's Dove satellite captured this clear image of the 338-m-high cone with a summit crater on 17 December 2018. Center: The skies cleared enough on 30 December to reveal the new crater in place of the former cone after the explosions and tsunami of 22-23 December, and multiple subsequent explosions. Right: Surtseyan explosions continued daily through 6 January; Planet Labs captured this event on 2 January 2019. Courtesy of BBC and Planet Labs, Inc.
Figure (see Caption) Figure 84. The location of Anak Krakatau in the middle of Sunda Strait surrounded by populated coastal communities (left) places great risk on those communities from explosive events and tsunamis at the volcano, such as what occurred during the 22 December 2018-6 January 2019 destruction of Anak Krakatau. The village of Tanjung in South Lampung (right) was especially hard hit. Map courtesy of BBC News, and photo courtesy of Daily Mail.

Three explosions were reported on 14, 18, and 23 February. No ash plume was observed on 14 February. The event on 18 February produced a dense gray ash plume that rose 720 m and drifted SSW. On 23 February the plume was white and rose 500 m, drifting ENE. During most days, no emissions were observed; occasional plumes of steam rose 50-100 m above the crater. Authorities visited the island on 15 February and observed the new crater lake and ash-covered flank of the remnant cone (figure 85 and 86).

Figure (see Caption) Figure 85. The denuded slope and new crater at Anak Krakatau on 15 February 2019. Bright orange discoloration of the water on the W side of the volcano is from recent iron-rich discharge. The new summit was measured at 155 m high. Verlaten Island is in the background. Courtesy of Sutopo Purwo Nugroho, BNPB.
Figure (see Caption) Figure 86. The new crater at Anak Krakatau on 15 February 2019. Fumarolic activity is visible in the narrow strip between the crater and the bay; bright orange discoloration of the water on the W side of the volcano is from recent iron-rich discharge. Courtesy of Sutopo Purwo Nugroho, BNPB.

Activity increased during March 2019 with 14 seismic events recorded. Four events on 14 March were reported, with durations ranging from 30 seconds to 4 minutes; neither ash nor steam plumes were reported from these events. Events on 16, 17, and 18 March produced N-drifting white steam plumes that were reported at altitudes of 1.2 km, 650 m, and 350 m, respectively (figure 87). Multiple additional explosions were reported on 24, 30, and 31 March; dense white plumes drifted NE on 30 and 31 March. Nearby rangers for the KPHK who witnessed the explosions on 30 March reported material rising 500-1,000 m above the crater (figure 88). The duration of the seismic events associated with the explosions ranged from 40 seconds to 5 minutes during the second half of March. PVMBG lowered the Alert Level from III to II on 25 March, noting that while explosions continued, the intensity and frequency had decreased; none of the explosions were heard at the Pasauran-Banten (SE) or Kalianda-Lampung (NE) stations that were each about 50 km away.

Figure (see Caption) Figure 87. An eruption at Krakatau on 18 March 2019 produced a steam plume that rose several hundred meters, barely visible from a community across the strait. Courtesy of Oystein Anderson and PVMBG.
Figure (see Caption) Figure 88. White steam and dark ejecta were observed at Anak Krakatau during an explosion on 30 March 2019 by the local patrol team from BKSDA Bengkulu-Ministry of LHK, which manages the Krakatau Islands Nature Preserve and Marine Nature Reserve. Courtesy of Krakatau Islands KPHK.

Although the number of reported seismic events increased significantly during April and May 2019, with 22 VONA's issued during April and 41 during May, only a single event had witnessed evidence of ejecta on 3 April (figure 89). The KPHK patrol that monitors conditions on the islands observed the first plant life returning on Sertung Island (5 km W of Anak Krakatau) on 5 April 2019, emerging through the several centimeters of fresh ash from the explosions and tsunami in late December and early January (figure 90). A 200-m-high steam plume was observed on 14 April, and plumes drifted NE and E on 27 and 29 April.

Figure (see Caption) Figure 89. Rangers for KPHK photographed a Surtseyan explosion with tephra and steam at Anak Krakatau on 3 April 2019. Courtesy of Krakatau Islands KPHK.
Figure (see Caption) Figure 90. A new plant on nearby Sertung Island emerges on 5 April 2019 through several centimeters of fresh ash from the Anak Krakatau explosions of December 2018 and January 2019. Courtesy of Krakatau Islands KPHK.

Members of an expedition to the island on 4 May 2019 photographed the still-steaming lake inside the new crater and the eroding ash-covered slopes (figure 91). Only the explosions on 10 and 17 May produced visible steam plumes that month, to 300-350 m high. By 15 May 2019 a new station had been installed at Anak Krakatau by PVMBG (figure 92). Four separate seismic events were recorded that day. Fog covered the island on a daily basis, and very few visible steam plumes were reported throughout April and May. The durations of the explosion events ranged from 30 seconds to 13 minutes (on 10 May); most of the events lasted for 1-2 minutes.

Figure (see Caption) Figure 91. Members of an expedition photographed the water-filled crater and ash-laden slopes of Anak Krakatau on 4 May 2019. Top image is looking S with Rakata island in the background, bottom image is looking W from the flank of the cone remnant. Photo by Galih Jati, courtesy of Volcano Discovery.
Figure (see Caption) Figure 92. By 15 May 2019 a new seismic station had been installed at Anak Krakatau by PVMBG. Four separate seismic events were recorded on 15 May 2019. Courtesy of Krakatau Islands KPHK.

Nine explosive events were reported during June 2019, but none produced visible steam or ash plumes until 25 June when a PVMBG webcam placed on Anak Krakatau captured a video of a Surtseyan event that lasted for about one minute. Dark gray ejecta shot tens of meters into the air over the lake, accompanied by billowing steam plumes which soon engulfed the webcam (figure 93). The other explosive events during March-July were likely similar, but frequent fog and the short-lived nature of the events made visual evidence scarce from webcams located 50 km away. During July there were 21 VONAs issued reporting similar seismic events that lasted from 30 seconds to 5 minutes; no plumes or sounds were seen or heard.

Figure (see Caption) Figure 93. Dark gray ejecta and billowing steam plumes were captured by a newly installed PVMBG webcam during an explosion at Anak Krakatau on 25 June 2019. The water-laden ash rose tens of meters and scattered ejecta around the island. See Information Contacts for a link to the video. Courtesy of Devy Kamil Syahbana and PVMBG.

Satellite imagery provided solid evidence that activity at Anak Krakatau during February-July 2019 included underwater venting. Dark orange submarine plumes were visible drifting away from the SW flank of the volcano near the new crater multiple times each month (figure 94). The patterns of the plumes varied in size and intensity, suggesting repeated injections of material into the water. The thermal activity showed a marked decline from the period prior to the large explosions and tsunami on 22-23 December 2018. Very little thermal activity was reported during January-March 2019, it increased moderately during April-July 2019 (figure 95).

Figure (see Caption) Figure 94. Dark orange plumes were visible in the seawater around Anak Krakatau during February-July 2019, strongly suggesting submarine discharges from the volcano. Top left: On 2 February 2019 the plume was discharging to the SW and visible in the water for nearly 10 km. Top center and right: on 29 March and 3 April the brightest areas of discharge were off the immediate SW flank; the plumes were drifting both NW and SE around the island. By 28 May (bottom left) the discharge was concentrated close to the SW flank with multiple underwater plumes suggesting several emission points. The only satellite image evidence suggesting a subaerial eruption appeared on 9 June (bottom center) when a dense steam plume rising and possible ejecta in the crater were visible. By 27 July (bottom right), discharge was still visible from the underwater vents on the SW flank, and the gradual filling in of the embayment on the W flank, when compared with the 2 February image, was clear. The island is about 2 km in diameter. Sentinel-2 satellite images with natural color rendering (bands 4,3,2) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 95. Thermal activity dropped abruptly at Anak Krakatau after the major flank collapse, explosions, and tsunami on 22-23 December 2018; it remained quiet through March and increased modestly during April-July 2019. Courtesy of MIROVA.

References: Gouhier, M, and Paris, R, 2019, SO2 and tephra emissions during the December 22, 2018 Anak Krakatau flank-collapse eruption, Volcanica 2(2): 91-103. doi: 10.30909/vol.02.02.91103.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Krakatau Islands KPHK, Conservation Area Region III Lampung, BKSDA Bengkulu-Ministry of LHK, (URL: https://www.instagram.com/krakatau_ca_cal); 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/); BBC News, (URL: https://www.bbc.com, article at https://www.bbc.com/news/science-environment-46743362); Planet Labs Inc. (URL: http://www.planet.com/); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN, image at https://twitter.com/Sutopo_PN/status/1101007655290589185/photo/1); Øystein Lund Andersen? (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com, image at https://twitter.com/OysteinLAnderse/status/1107479025126039552/photo/1); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/), images at https://www.volcanodiscovery.com/krakatau/news/80657/Krakatau-volcano-Indonesia-activity-update-and-field-report-increasing-unrest.html; Devy Kamil Syahbana, Volcanologist, Bandung, Indonesia, (URL: https://twitter.com/_elangtimur, video at https://twitter.com/_elangtimur/status/1143372011177033728); The Daily Mail (URL: https://www.dailymail.co.uk, article at https://www.dailymail.co.uk/sciencetech/article-6910895/FORTY-volcanoes-world-potential-Anak-Krakatoa-eruptions.html) published 11 April 2019.


Tengger Caldera (Indonesia) — August 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)


Ash emissions on 19 and 28 July 2019; lahar on the SW flank of Bromo

The Mount Bromo pyroclastic cone within the Tengger Caldera erupts frequently, typically producing gas-and-steam plumes, ash plumes, and explosions (BGVN 44:05). Information compiled for the reporting period of May-July 2019 is from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

The eruptive activity at Tengger Caldera that began in mid-February continued through late July 2019, including white-and-brown ash plumes, ash emissions, and tremors. During the months of May through June 2019, white plumes rose between 50 to 600 m above the summit. Satellite imagery captured a small gas-and-steam plume from Bromo on 5 June (figure 18). Low-frequency tremors were recorded by a seismograph from May through July 2019.

Figure (see Caption) Figure 18. Sentinel-2 satellite image showing a small gas-and-steam plume rising from the Bromo cone (center) in the Tengger Caldera on 5 June 2019. Thermal (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

According to PVMBG and a Volcano Observatory Notice for Aviation (VONA), an ash eruption occurred on 19 July 2019; however, no ash column was observed due to weather conditions. A seismograph recorded five earthquakes and three shallow volcanic tremors the same day. In addition, rainfall triggered a lahar on the SW flank of Bromo.

On 28 July the Darwin VAAC reported that ash plumes originating from Bromo rose to a maximum altitude of about 3.9 km and drifted NW from the summit, based on webcam images and pilot reports. PVMBG reported that lower altitude ash plumes (2.4 km) on the same day were also recorded by webcam images, satellite imagery (Himawari-8), and weather models.

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/).


Unnamed (Tonga) — November 2019 Citation iconCite this Report

Unnamed

Tonga

18.325°S, 174.365°W; summit elev. -40 m

All times are local (unless otherwise noted)


Submarine eruption in early August creates pumice rafts that drifted west to Fiji

Large areas of floating pumice, termed rafts, were encountered by sailors in the northern Tonga region approximately 80 km NW of Vava'u starting around 9 August 2019; the pumice reached the western islands of Fiji by 9 October (figure 7). Pumice rafts are floating masses of individual clasts ranging from millimeters to meters in diameter. The pumice clasts form when silicic magma is degassing, forming bubbles as it rises to the surface, which then rapidly cools to form solid rock. The isolated vesicles formed by the bubbles provide buoyancy to the rock and in turn, the entire pumice raft. These rafts are spread and carried by currents across the ocean; rafts originating in the Tonga area can eventually reach Australia. This report summarizes the pumice raft eruption from early August 2019 using witness accounts and satellite images (acquisition dates are given in UTC). Pending further research, the presumed source is the unnamed Tongan seamount (volcano number 243091) about 45 km NW of Vava'u, the origin of an earlier pumice raft produced during an eruption in 2001.

Figure (see Caption) Figure 7. The path of the pumice from the unnamed Tongan seamount from 9 August to 9 October 2019 based on eye-witness accounts and satellite data discussed below, as well as additional Aqua/MODIS satellite images from NASA Worldview. Blue Marble MODIS/NASA Earth Observatory base map courtesy of NASA Worldview.

The first sighting of pumice was around 1430 on 9 August NW of Vava'u in Tonga (18° 22.068' S, 174° 50.800' W), when Shannon Lenz and Tom Whitehead on board SV Finely Finished initially encountered isolated rocks and smaller streaks of pumice clasts. The area covered by rock increasing to a raft with an estimated thickness of at least 15 cm that extended to the horizon in different directions, and which took 6-8 hours to cross (figure 8). There was no sulfur smell and the sound was described as a "cement mixer, especially below deck." There was also no plume or incandescence observed. Their video, posted to YouTube on 17 August, showed a thin surface layer of cohesive interconnected irregular streaks of pumice with the ocean surface still visible between them. Later footage showed a continuous, undulating mass of pumice entirely covering the ocean surface. Larger clasts are visible scattered throughout the raft. The pumice raft was visible in satellite imagery on this day NW of Late Island (figure 9). By 11 August the raft had evolved into a largely linear feature with smaller rafts to the SW (figure 10). Approximately four hours later, about 15 km to the WSW, Rachel Mackie encountered the pumice. Initially the pumice was "ribbons several hundred meters long and up to 20m wide. It was quite fine and like a slick across the surface of the water." By 2130 they were surrounded by the pumice, and around 25 km away the smell of sulfur was noted.

Figure (see Caption) Figure 8. The pumice raft from the unnamed Tongan seamount on 9 August 2019 taken by Shannon Lenz and Tom Whitehead on board SV Finely Finished. The photos show the pumice raft extending to the horizon in different directions. Scattered larger clasts protrude from the relatively smooth surface that entirely obscures the ocean surface. Courtesy of Shannon Lenz and Tom Whitehead via noonsite.
Figure (see Caption) Figure 9. The pumice raft from the unnamed Tongan seamount on 9 August 2019 (UTC) can be seen NW of Late Island of Tonga in this Aqua/MODIS satellite image. The dashed white line encompasses the visible pumice. The location of the pumice in this image is shown in figure 7. Courtesy of NASA WorldView.
Figure (see Caption) Figure 10. The Sentinel-2 satellite first imaged the pumice from the unnamed Tongan seamount on 11 August 2019 (UTC). This image indicates the pumice distribution with the main raft towards the W and the easternmost area of pumice approximately 45 km away. The eastern tip of the pumice area is located approximately 30 km WNW of Lake islands in Tonga. The location of the pumice in this image is shown in figure 7. Natural color (bands 4, 3, 2) Sentinel-2 satellite image courtesy of Sentinel Hub Playground.

Michael and Larissa Hoult aboard the catamaran ROAM encountered the raft on 15 August (figure 11). They initially saw isolated clasts ranging from marble to tennis ball size (15-70 mm) at 18° 46′S, 174° 55'W. At around 0700 UTC (1900 local time) they noted the smell of sulfur at 18° 55′S, 175° 21′W, and by 0800 UTC they were immersed in the raft with visible clasts ranging from marble to basketball (25 cm) sizes. At this point the raft was entirely obscuring the ocean surface. On 16 and 21 August the pumice continued to disperse and drift NW (figures 12 and 13). On 20 August Scott Bryan calculated an average drift rate of around 13 km/day, with the pumice on this date about 164 km W of the unnamed seamount.

Figure (see Caption) Figure 11. Images of pumice from the unnamed Tongan seamount encountered by Michael and Larissa Hoult aboard the catamaran Roam on 15 August. Left: Larissa takes photographs with scale of pumice clasts; top right: a closeup of a pumice clast showing the vesicle network preserving the degassing structures of the magma; bottom left: Michael holding several larger pumice clasts. The location of their encounter with the pumice is shown in figure 7. Courtesy of SailSurfROAM.
Figure (see Caption) Figure 12. The pumice from the unnamed Tongan seamount (volcano number 243091) on 16 August 2019 UTC. The location of the pumice in this image is shown in figure 7. Natural color (bands 4, 3, 2) Sentinel-2 satellite image courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 13. On 21 August 2019 (UTC) the pumice from the unnamed Tongan seamount (volcano number 243091) had drifted at least 120 km WNW of Late Island in Tonga. The location of the pumice in this image is shown in figure 7. Natural color (bands 4, 3, 2) Sentinel-2 satellite image courtesy of Sentinel Hub Playground.

An online article published by Brad Scott at GeoNet on 9 September reported the preliminary size of the raft to be 60 km2, significantly smaller than the 2012 Havre seamount pumice raft that was 400 km2. Satellite identification of pumice-covered areas by GNS scientists showed the material moving SSW through 14 August (figure 14).

Figure (see Caption) Figure 14. A compilation of mapped pumice raft extents from 9 August (red line) through to 14 August (dark blue) from Suomi NPP, Terra, Aqua, and Sentinel-2 satellite images. The progression of the pumice raft is towards the SW. Courtesy of Salman Ashraf, GNS Science.

On 5 September the Maritime Safety Authority of Fiji (MSAF) issued a notice to mariners stating that the pumice was sighted in the vicinity of Lakeba, Oneata, and Aiwa Islands and was moving to the W. On 6 September a Planet Labs satellite image shows pumice encompassing the Fijian island of Lakeba over 450 km W of the Tongan islands (figure 15). The pumice entered the lagoon within the barrier reef and drifted around the island to continue towards the W. The pumice was imaged by the Landsat 8 satellite on 26 September as it moved through the Fijian islands, approximately 760 km away from its source (figure 16). The pumice is segmented into numerous smaller rafts of varying sizes that stretch over at least 140 km. On 12 September the Fiji Sun reported that the pumice had reached some of the Lau islands and was thick enough near the shore for people to stand on it.

Figure (see Caption) Figure 15. Planet Labs satellite images show Lakeba Island to the E of the larger Viti Levu Island in the Fiji archipelago. The top image shows the island on 7 July 2019 prior to the pumice raft from the unnamed Tongan seamount. The bottom image shows pumice on the sea surface almost entirely encompassing the island on 6 September. The location of the pumice in this image is shown in figure 7. Courtesy of Planet Labs.
Figure (see Caption) Figure 16. Landsat 8 satellite images show the visible extent of the unnamed seamount pumice on 26 September 2019 (UTC), up to approximately 760 km from the Tongan islands. The pumice seen here extends over a distance of 140 km. The top image shows the locations of the other three images in the white boxes, with a, b, and c indicating the locations. White arrows point to examples of the light brown pumice rafts in these images, seen through light cloud cover. The island in the lower right is Koro Island, the island to the lower left is Viti Levu, and the island to the top right is Vanua Levu. The location of the pumice in this image is shown in figure 7. Landsat 8 true color-pansharpened satellite images courtesy of Sentinel Hub.

Pumice had reached the Yasawa islands in western Fiji by 29 September and was beginning to fill the eastern bays (figure 17). By 9 October bays had been filled out to 500-600 m from the shore, and pumice had also passed through the islands to continue towards the W (figure 18). At this point the pumice beyond the islands had broken up into linear segments that continued towards the NW.

Figure (see Caption) Figure 17. These Sentinel-2 satellite images show the pumice from the unnamed Tongan seamount drifting towards the Yasawa islands of Fiji. The 24 September 2019 (UTC) image shows the beaches without the pumice, the 29 September image shows pumice drifting westward towards the islands, and the 9 October image shows the bays partly filled with pumice out to a maximum of 500-600 m from the shore. These islands are approximately 850 km from the Tongan islands. The Yasawa islands coastline impacted by the pumice shown in these images stretches approximately 48 km. The location of the pumice in this image is shown in figure 7. Sentinel-2 natural color (bands 4, 3, 2) satellite images courtesy of Sentinel Hub.
Figure (see Caption) Figure 18. This Sentinel-2 satellite image acquired on 9 October 2019 (UTC) shows expanses of pumice from the unnamed Tongan seamount that passed through the Yasawa islands of Fiji and was continuing NWW, seen in the center of the image. The location of the pumice in this image is shown in figure 7. Sentinel-2 natural color (bands 4, 3, 2) satellite images courtesy of Sentinel Hub.

Geologic Background. A submarine volcano along the Tofua volcanic arc was first observed in September 2001. The newly discovered volcano lies NW of the island of Vava'u about 35 km S of Fonualei and 60 km NE of Late volcano. The site of the eruption is along a NNE-SSW-trending submarine plateau with an approximate bathymetric depth of 300 m. T-phase waves were recorded on 27-28 September 2001, and on the 27th local fishermen observed an ash-rich eruption column that rose above the sea surface. No eruptive activity was reported after the 28th, but water discoloration was documented during the following month. In early November rafts and strandings of dacitic pumice were reported along the coast of Kadavu and Viti Levu in the Fiji Islands. The depth of the summit of the submarine cone following the eruption determined to be 40 m during a 2007 survey; the crater of the 2001 eruption was breached to the E.

Information Contacts: GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/); Salman Ashraf, GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/, https://www.geonet.org.nz/news/8RnSKdhaWOEABBIh0bHDj); Brad Scott, New Zealand GeoNet Project, a collaboration between the Earthquake Commission and GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.geonet.org.nz/, https://www.geonet.org.nz/news/8RnSKdhaWOEABBIh0bHDj); Scott Bryan, School of Earth, Environmental & Biological Sciences, Science and Engineering Faculty, Queensland University of Technology, R Block Level 2, 204, Gardens Point (URL: https://staff.qut.edu.au/staff/scott.bryan); Shannon Lenz and Tom Whitehead, SV Finely Finished (URL: https://www.noonsite.com/news/south-pacific-tonga-to-fiji-navigation-alert-dangerous-slick-of-volcanic-rubble/, YouTube: https://www.youtube.com/watch?v=PEsHLSFFQhQ); Michael and Larissa Hoult, Sail Surf ROAM (URL: https://www.facebook.com/sailsurfroam/); Rachel Mackie, OLIVE (URL: http://www.oliveocean.com/, https://www.facebook.com/rachel.mackie.718); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/); Fiji Sun (URL: https://fijisun.com.fj/2019/09/12/pumice-menace-hits-parts-of-lau-group/).

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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, 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/).