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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

Heard (Australia) Thermal hotspots persist at Mawson Peak, lava flows visible in satellite data November 2017-September 2018

Krakatau (Indonesia) Strombolian, lava flow, and explosive activities resume, June-October 2018

Saunders (United Kingdom) Intermittent thermal pulses and satellite imagery hotspots during September 2016-September 2018

Karymsky (Russia) Thermal anomalies and ash explosions during August-September 2018

Nishinoshima (Japan) Quiescence interrupted by brief lava flow emission and small explosions in July 2018

Mayon (Philippines) Low activity during April-September with some ash plumes and ongoing crater incandescence

Kadovar (Papua New Guinea) Intermittent ash plumes; thermal anomalies in the crater and Coastal Vent through September 2018

Ketoi (Russia) Plume of uncertain composition reported based on satellite data one day in September

Sinabung (Indonesia) No significant ash plumes seen after 22 June 2018; minor ash in early July

Semeru (Indonesia) Small ash plumes in February, April, July, and August 2018; persistent thermal hotspot in the crater

Rincon de la Vieja (Costa Rica) Intermittent weak phreatic explosions during January-March and July-August 2018

Turrialba (Costa Rica) Ongoing variable ash emissions and crater incandescence through August 2018



Heard (Australia) — October 2018 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Thermal hotspots persist at Mawson Peak, lava flows visible in satellite data November 2017-September 2018

Remote Heard Island in the southern Indian Ocean is home to the snow-covered Big Ben stratovolcano, which has had confirmed intermittent activity since 1910. The nearest continental landmass, Antarctica, lies over 1,000 km S. Visual confirmation of lava flows on Heard are rare; thermal anomalies and hotspots detected by satellite-based instruments provide the most reliable information about eruptive activity. Thermal alerts reappeared in September 2012 after a four-year hiatus (BGVN 38:01), and have been intermittent since that time. Information comes from instruments on the European Space Agency's (ESA) Sentinel-2 satellite and MODVOLC and MIROVA thermal anomaly data from other satellite instruments. This report reviews evidence for eruptive activity from November 2017 through September 2018.

Satellite observations indicated intermittent hot spots at the summit through 12 December 2017. A few observations in January and February 2018 suggested steam plumes at the summit, but no significant thermal activity. An infrared pixel indicative of renewed thermal activity appeared again on 7 March, and similar observations were made at least twice each month in April and May. Activity increased significantly during June and remained elevated through September 2018 with multiple days of hotspot observations in satellite data each of those months, including images that indicated lava flowing in different directions from Mawson Peak. MODVOLC and MIROVA data also indicated increased thermal activity during June-September 2018.

Activity during October-December 2017. MIROVA thermal anomalies recorded during October 2017 indicated ongoing thermal activity at Heard (figure 32). This was confirmed by Sentinel-2 satellite imagery that revealed hotpots at the summit on ten different days in October (3, 6, 8, 13, 16, 21, 23, 26, 28, and 31), and included images suggesting lava flows descending from the summit in different directions on different days (figure 33).

Figure (see Caption) Figure 32. MODVOLC thermal alerts indicated significant thermal activity at Heard during October 2017 that tapered off during November. Intermittent signals appeared in December 2017, March, and April 2018, and a strong signal returned in June 2018 that continued through September. Courtesy of MIROVA.
Figure (see Caption) Figure 33. Sentinel-2 images of Heard Island's Big Ben volcano during October 2017 showed strong evidence of active effusive activity. a) 3 October 2017: at least three hot spots were visible through cloud cover at the summit and W of Mawson Peak, suggesting active lava flows. b) 6 October 2017: a small hot spot is visible at the peak with a small steam plume, and a larger hotspot to the NW suggested a still active lava flow. c) 16 October 2017: a small hotspot at the summit and larger hotspots W of the summit were indicative of ongoing flow activity. d) 23 October 2017: a steam plume drifted SE from a small summit hotspot and a larger hotspot to the W suggested a lava lake or active flow. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

The MODVOLC thermal alert data showed no further alerts for the year after 22 October 2017, and the MIROVA system anomalies tapered off in mid-November 2017. The Sentinel-2 satellite imagery, however, continued to record intermittent hotspots at and around Mawson Peak, the summit of Big Ben volcano, into December 2017 (figure 34). Hotspots were visible during six days in November (7, 15, 20, 25, 27, and 30) and three days during December (5, 7, and 12).

Figure (see Caption) Figure 34. Sentinel-2 images of Heard Island's Big Ben volcano showed reduced but ongoing thermal activity during November and December 2017. a) 7 November 2017: a steam plume drifts NE from a hotspot at Mawson Peak. b and c) 15 November and 12 December 2017: a small hotspot is distinct at the summit. d) 20 December 2017: a steam plume drifts east from the peak, but no clear hotspot is visible. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of ESA Sentinel Hub Playground.

Activity during January-May 2018. The satellite images during January and February 2018 were indicative of steam plumes at the summit, but distinct thermal signals reappeared on 7 and 12 March 2018 (figure 35). In spite of extensive cloud cover, the Sentinel-2 imagery also captured thermal signals twice each month in April (4 and 14) and May (9 and 14) (figure 36).

Figure (see Caption) Figure 35. Sentinel-2 images of Heard Island's Big Ben volcano showed only steam plumes at the summit during January and February, but hotspots reappeared in March 2018. a) 4 January 2018: a steam plume drifts SE from the summit under clear skies. b) 8 February 2018: a steam plume drifts SE from the summit adjacent to a large cloud on the N side of the volcano. c) 7 March 2018: the first hotspot in about three months is visible at the summit. d) 12 March 2018: a distinct hotspot is visible at Mawson Peak. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of ESA Sentinel Hub Playground.
Figure (see Caption) Figure 36. Sentinel-2 images of Heard Island's Big Ben volcano showed intermittent low-level thermal activity during April and May 2018. a) 4 April 2018: a small hotspot is visible at the summit through a hazy atmosphere. b) 9 May 2018: a distinct hotspot glows from the summit beneath cloud cover. Sentinel-2 images with Atmospheric Penetration view(bands 12, 11, and 8A), courtesy of ESA Sentinel Hub Playground.

Activity during June-September 2018. Thermal signals increased significantly in the satellite data during June 2018. The sizes of the thermal anomalies were bigger, and they were visible at least nine days of the month (3, 5, 8, 10, 15, 18, 23, 25, and 30). Five substantial thermal signals appeared during July (3, 10, 15, 18, and 28); images on 23 June and 3 July distinctly show a lava flow trending NE from the summit (figure 37). MODVOLC thermal alerts appeared in June 2018 on three days (2, 26, and 27) and on four days during July (7, 8, 9, 10) indicating increased activity during this time. The MIROVA thermal signals also showed a substantial increase in early June that peaked in mid-July and remained steady through September 2018 (figure 32).

Figure (see Caption) Figure 37. Sentinel-2 images of Heard Island's Big Ben volcano showed significantly increased thermal activity during June and July 2018. a) 8 June 2018: a substantial hotspot is visible through the cloud cover at the summit of Big Ben. b) 10 June 2018: the darker red hotspot at Mawson Peak was significantly larger than it was earlier in the year. c) 23 June 2018: the first multi-point hotspot since 31 October shows a distinct glow trending NE from the summit. d) 3 July 2018: a trail of hotspots defines a lava flow curving NNE from Mawson Peak. e) 18 July 2018: a second significant hotpot is visible a few hundred meters NE of the summit hotspot indicating a still active flow. f) 28 July 2018: the summit hotspot continued to glow brightly at the end of July, but no second hotspot was visible. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of ESA Sentinel Hub Playground.

Six images in August (2, 7, 9, 22, 27, 29) showed evidence of active lava at the summit, and suggested flows both NE and SE from the summit that were long enough to cause multiple hotspots (figure 38). During September and early October 2018 the satellite images continued to show multiple hotspots that indicated flow activity tens of meters SE from the summit multiple days of each month (figure 39).

Figure (see Caption) Figure 38. Sentinel-2 images of Heard Island's Big Ben volcano showed lava flow activity in two different directions from the summit during August 2018. a) 2 August 2018: lava flows NE from Mawson Peak while a steam plume drifts E from the summit. b) 9 August 2018: a second hotspot NE of the summit hotspot indicates continued flow activity in the same area observed on 2 August. c and d) 27 and 29 August 2018: a different secondary hotspot appeared SSE from the summit indicating a distinct flow event from the one recorded earlier in August. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of ESA Sentinel Hub Playground.
Figure (see Caption) Figure 39. Sentinel-2 images of Heard Island's Big Ben volcano in September and October 2018 showed hotspots indicating active flows SE of the summit on multiple days. a) 3 September 2018: a small hotspot at the summit and a larger hotspot SE of the summit indicated continued flow activity. b) 3 October 2018: a small steam plume drifted east from a small hotspot at the summit and a larger pair of hotspots to the SE indicated continued effusive activity. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of ESA Sentinel Hub Playground.

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

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


Krakatau (Indonesia) — October 2018 Citation iconCite this Report

Krakatau

Indonesia

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

All times are local (unless otherwise noted)


Strombolian, lava flow, and explosive activities resume, June-October 2018

Krakatau volcano in the Sunda Strait between Java and Sumatra, Indonesia experienced a major caldera collapse, likely in 535 CE, that formed a 7-km-wide caldera ringed by three islands (see inset figure 23, BGVN 36:08). Remnants of this volcano coalesced to create the pre-1883 Krakatau Island which collapsed during the 1883 eruption. The post-collapse cone of Anak Krakatau (Child of Krakatau), constructed within the 1883 caldera has been the site of frequent eruptions since 1927. The most recent event was a brief episode of Strombolian activity, ash plumes, and a lava flow during the second half of February 2017. Activity resumed in late June 2018 and continued through early October, the period covered in this report. Information is provided primarily 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 came from several social media sources and professional photographers.

After the brief event during February 2017, Anak Krakatau remained quiet for about 15 months. PVMBG kept the Alert Level at II, noting no significant changes until mid-June 2018. Increased seismicity on 18 June was followed by explosions with ash plumes beginning on 21 June. Intermittent ash emissions were accompanied by Strombolian activity with large blocks of incandescent ejecta that traveled down the flanks to the ocean throughout July. Explosions were reported as short bursts of seismic activity, repeating multiple times in a day, and producing dense black ash plumes that rose a few hundred meters from the summit. Similar activity continued throughout August, with the addition of a lava flow visible on the S flank that reached the ocean during 4-5 August. Generally increased activity in September resulted in the highest ash plumes of the period, up to 4.9 km altitude on 8 September; high-intensity explosions were heard tens of kilometers away during 9-10 September. PVMBG reported significantly increased numbers of daily explosions during the second half of the month. The thermal signature recorded in satellite data also increased during September, and a large SO2 plume was recorded in satellite data on 23 September.

Activity during June-July 2018. PVMBG noted an increase in seismic activity beginning on 18 June 2018. Foggy conditions hampered visual observations during 19-20 June, but on 21 June gray plumes were observed rising 100-200 m above the summit (figure 41). Two ash plumes were reported on 25 June; the first rose to about 1 km altitude and drifted N, and the second rose to 600 m altitude and drifted S (figure 42).

Figure (see Caption) Figure 41. Anak Krakatau began a new eruptive episode on 21 June 2018 with an ash plume that rose 200 m above the summit. Photo by undisclosed source, courtesy of Øystein Lund Andersen‏.
Figure (see Caption) Figure 42. The first of two ash plumes rose to about 1 km altitude and drifted N from Anak Krakatau on 25 June 2018; the first events after about 18 months of no activity were reported on 21 June. Courtesy of PVMBG (Eruption Information on Mt. Anak Krakatau, June 25, 2018).

Incandescence was observed at the summit during 1-2 July 2018, and two ash emissions were reported in VONA's (Volcano Observatory Notice for Aviation) on 3 July. PVMBG reported that during 4-5 July there were four additional ash-producing events, each lasting between 30 and 41 seconds. The last three of these events produced ash plumes that rose 300-500 m above the crater rim and drifted N and NW. The Darwin VAAC reported essentially continuous ash emissions during 3-9 July drifting generally W and SW at about 1.2 km altitude (figure 43). They were intermittently visible in satellite imagery when not obscured by meteoric clouds.

Figure (see Caption) Figure 43. A dense gray ash plume rose several hundred meters above Anak Krakatau on 7 July 2018 (local time) while large volcanic bombs traveled down the flanks. Photo by Sam Hidayat, courtesy of Øystein Lund Andersen‏.

Ash plumes were again observed by the Darwin VAAC in satellite imagery beginning on 13 July 2018 at 1.2 km altitude drifting NW. They were essentially continuous until they gradually decreased and dissipated early on 17 July, rising to 1.2-1.5 km altitude and drifting W, clearly visible in satellite imagery several times during the period. Satellite imagery revealed hotspots several times during July; they ranged from small pixels at the summit (9 July) to clear flow activity down the SE flank on multiple days (12, 19, and 24 July) (figure 44). In the VONA's reported by PVMBG during 15-17 July, they noted intermittent explosions that lasted around 30-90 seconds each. PVMBG reported a black ash plume 500 m above the summit drifting N during the afternoon of 16 July. The Darwin VAAC continued to report ash emission to 1.2-1.5 km altitude during 18-19 July, moving in several different directions; Strombolian activity sent incandescent ejecta in all directions on 19 July (figure 45). During 25-26 July the Darwin VAAC noted continuous minor ash emissions drifting SW at 1.2 km altitude, and a hotspot visible in infrared imagery.

Figure (see Caption) Figure 44. Sentinel-2 satellite imagery clearly documented the repeated thermal activity at Anak Krakatau throughout July 2018. a) 9 July 2018: a small hotspot was visible at the summit and an ash plume drifted NW. b) 12 July 2018: a much larger hotspot showed a distinct flow down the SE flank. c) 19 July 2018: even under partly cloudy skies, incandescent ejecta is visible on the S flank. d) 24 July 2018: incandescent lava had almost reached the SE coast. Sentinel-2 images with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 45. Strombolian activity sent incandescent ejecta down all the flanks and into the sea at Anak Krakatau on 19 July 2018, as seen from the island of Rakata (5 km SE). Courtesy of Reuters / Stringer.

Activity during August-early October 2018. A series of at least nine explosions took place on 2 August 2018 between 1333 and 1757 local time. They ranged from 13 to 64 seconds long, and produced ash plumes that drifted N. The Darwin VAAC reported minor ash observed in imagery at around 2 km altitude for much of the day. In a special report, PVMBG noted a black ash plume 500 m above sea level drifting N at 1757 local time. Continued explosive activity was reported by local observers during the early nighttime hours of 3 August (figure 46).

Figure (see Caption) Figure 46. A dark ash plume rose 100-200 m from Anak Krakatau during the early morning hours of 3 August 2018, and incandescent ejecta rolled down the flanks. Tens of explosions were heard in Serang (80 km E) and Lampung (80 km N). Courtesy of Sutopo Purwo Nugroho.

The Darwin VAAC reported continuous ash emissions rising to 1.8 km altitude and drifting E on 5 August, clearly visible in satellite imagery, along with a strong hotspot. The ash plume drifted SE then S the next day before dissipating. PVMBG reported incandescence visible during the nights of 5-15 August. Photographer Øystein Lund Andersen visited Krakatau during 4-6 August 2018 and recorded Strombolian activity, lava bomb ejecta, and a lava flow entering the ocean (figures 47-50).

Figure (see Caption) Figure 47. Strombolian explosions sent incandescent ejecta skyward, and blocks of debris down the flanks of Anak Krakatau on 5 August 2018 as captured in this drone photograph. Copyrighted photo by Øystein Lund Andersen‏, used with permission.
Figure (see Caption) Figure 48. Large volcanic bombs flew out from the summit vent of Anak Krakatau while a dark gray plume of ash rose a few hundred meters on 5 August 2018 in this drone photograph. Copyrighted photo by Øystein Lund Andersen‏, used with permission.
Figure (see Caption) Figure 49. A blocky lava flow traveled down the S flank of Anak Krakatau on 5 August 2018 in this closeup image taken by a drone. Copyrighted photo by Øystein Lund Andersen‏, used with permission.
Figure (see Caption) Figure 50. Views of Anak Krakatau from the SE showed Strombolian activity and incandescent lava (upper photo) and steam from the lava flowing into the ocean and dark ash emissions from the summit (lower photo) on 5 August 2018. Copyrighted photo by Øystein Lund Andersen‏, used with permission.

Emissions were reported intermittently drifting W on 11, 14, and 16 August at 1.2-1.5 km altitude. Video of explosions on 12 August with large bombs and dark ash plumes were captured by photographer James Reynolds (Earth Uncut TV). PVMBG reported black ash plumes drifting N at 500 m above the summit on 17 and 18 August after explosions that lasted 1-2 minutes each. The Darwin VAAC also reported ash plumes rising to 1.2 km altitude on 17-18 drifting NE. VONA's were issued during 22-23 August reporting at least three explosions that lasted 30-40 seconds and produced ash plumes that drifted N and NE. The Darwin VAAC reported the plume on 22 August as originating from a vent below the summit. PVMBG noted that a dark plume on 23 August drifted NE at about 700 m above the summit. During 27-30 August, the Darwin VAAC reported ash plumes intermittently visible in satellite imagery extending SW at 1.2-1.5 km altitude.

Ash plumes drifting N and NW were visible in satellite imagery during 3-4 September at 1.2-1.5 km altitude. The Darwin VAAC reported an ash plume moving NW and W at 4.9 km altitude on 8 September, the highest plume noted for the report period. The following day, the plume height had dropped to 1.5 km altitude, and was clearly observed drifting W in satellite imagery. A hotspot was reported on 12 September. During the night of 9-10 September PVMBG reported bursts of incandescent material rising 100-200 m above the peak, with explosions that rattled windows at the Anak Krakatau PGA Post, located 42 km from the volcano. Ash plumes continued to be observed through 13 September. The Darwin VAAC reported continuous ash emissions to 1.8 km altitude drifting W and NW on 16-17 September (figure 51). The ash plume was no longer visible on 18 September, but a hotspot remained discernable in satellite data through 20 September.

Figure (see Caption) Figure 51. On 16 September 2018 a dark ash plume rose several hundred meters above Anka Krakatau as incandescent lava flowing down the SE flank to the sea created steam plumes. Courtesy of Thibaud Plaquet.

PVMBG reported incandescence at the summit and gray and black ash plumes on 20 September that rose 500 m above the summit. A low-level ash emission was reported drifting S on 21 September and confirmed in the webcam. Four VONA's were issued that day, reporting explosions at 0221, 0827, 2241, and 2248, lasting from 72-115 seconds each. PVMBG subsequently reported observing 44 explosions with black ash plumes rising 100-600 m above the summit, and incandescence at night on 21 September. Ash emissions continued on 22 September at 1.5 km altitude, with a secondary explosion rising to 2.4 km altitude drifting W. The plume height was based on and infrared temperature measurement of 12 degrees C. Later in the day, an additional plume was observed in satellite imagery at 3.7 km altitude drifting N. PVMBG reported observations of 56 explosions, with 200-300 m high (above the summit) black ash plumes and incandescence at night on 22 September. Observations from nearby Rakata Island on 22 September indicated that tephra from incandescent explosions of the previous night mostly fell on the flanks, but some reached the sea. A lava flow on the SSE flank had also reached the ocean (figure 52).

Figure (see Caption) Figure 52. Activity at Krakatau during 22-23 September 2018 included substantial Strombolian explosions, a dark ash plume, lava flows, and large volcanic bombs traveling nearly to the ocean. Photo courtesy of Malmo Travel.

By 23 September 2018, a single plume was observed at 2.1 km altitude drifting WNW. A glow at the summit was visible in the webcam that day, and a hotspot was seen in satellite imagery the next day as observations of an ash plume drifting W at 2.1 km continued. A significant SO2 plume was captured in satellite data on 23 September (figure 53).

Figure (see Caption) Figure 53. A significant SO2 plume dispersed NW of Krakatau (lower right corner) on 23 September 2018 after a surge in activity was observed the previous two days. Courtesy of NASA Goddard Space Flight Center.

On 24 September, PVMBG reported black ash plumes rising 1,000 m above the summit, incandescence at the summit, and lava flowing 300 m down the S flank observed in the webcam during the night. An ash plume was observed by the Darwin VAAC drifting WSW and then W on 25-26 September at 2.1 km altitude, lowering slightly to 1.8 km the following day, and to 1.2 km on 28 September. Continuous ash emissions were observed through 29 September. A new emission was reported on 30 September drifting SW at 1.8 km altitude. Ash emissions were observed daily by the Darwin VAAC from the 1st to at least 5 October at 2.1 km altitude drifting W. A large hotspot near the summit was noted on 3 October. The thermal activity at Anak Krakatau from late June into early October 2018, as recorded in infrared satellite data by the MIROVA project, confirmed the visual observations of increased activity that included Strombolian explosions, lava flows, ash plumes, and incandescent ejecta witnessed by ground observers during the period (figure 54).

Figure (see Caption) Figure 54. The MIROVA project graph of thermal activity at Krakatau from 12 February through early October 2018 showed the increasing thermal signature that appeared in late June at the onset of renewed explosive activity, the first since February 2017. Courtesy of MIROVA.

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 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 volcanoes, and left only a remnant of Rakata volcano. 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/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN); Øystein Lund Andersen? (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com); Reuters Latam (Twitter: @ReutersLatam, URL: http://www.reuters.com/); James Reynolds, Earth Uncut TV (Twitter: @EarthUncutTV, URL: https://www.earthuncut.tv/, Video: https://www.youtube.com/watch?v=UD3SLWtuPZs); Thibaud Plaquet (Instagram: tibomvm, URL: https://www.instagram.com/tibomvm/); Malmo Travel (Instagram: malmo.travel, URL: https://www.instagram.com/malmo.travel/).


Saunders (United Kingdom) — October 2018 Citation iconCite this Report

Saunders

United Kingdom

57.8°S, 26.483°W; summit elev. 843 m

All times are local (unless otherwise noted)


Intermittent thermal pulses and satellite imagery hotspots during September 2016-September 2018

Historical observations of eruptive activity on ice-covered Mount Michael stratovolcano on Saunders Island in the South Sandwich Islands were not recorded until the early 19th century at this remote site in the southernmost Atlantic Ocean. With the advent of satellite observation technology, indications of more frequent eruptive activity have become apparent. The last confirmed eruption evidenced by MODVOLC thermal alerts was during August-October 2015 (BGVN 41:02). Limited thermal anomaly data and satellite imagery since then have indicated intermittent activity through September 2018. Information for this report comes from MODVOLC and MIROVA thermal anomaly data and Sentinel-2, Landsat, and NASA Terra satellite imagery.

Evidence for thermal activity at Mount Michael tapered off in MIROVA data from October 2015 through January 2016. MODVOLC thermal alerts reappeared on 28 September 2016 and recurred intermittently through 6 January 2017. Low-level MIROVA thermal signals appeared in June and September-November 2017. During January-September 2018, evidence for some type of thermal or eruptive activity was recorded from either MODVOLC, MIROVA, or satellite imagery each month except for May and June.

Although MODVOLC thermal alerts at Mount Michael ended on 8 October 2015, the MIROVA radiative power data showed intermittent pulses of decreasing energy into early January 2016 (figure 10, BGVN 41:02). At a high-latitude, frequently cloud-covered site such as Saunders Island, this could be indicative of continued eruptive activity. A white plume in low resolution NASA's Terra satellite data was spotted drifting away from Saunders in April 2016, but no thermal activity was reported. The only high-confidence data available from April 2016 through May 2017 is from the MODVOLC thermal alert system, which recorded two thermal alerts on 28 September 2016, one the next day, one on 30 October, and eight alerts on four days in November. Activity continued into January 2017 with one alert on 17 December 2016, and six alerts on 2 and 6 January 2017 (figure 11).

Figure (see Caption) Figure 11. Seventeen MODVOLC thermal alerts between 28 September 2016 and 6 January 2017 were the best evidence available for eruptive activity on Saunders Island from April 2016 through May 2017. Courtesy of MODVOLC.

A low-level log radiative power MIROVA signal appeared in early June 2017; two more signals appeared in September 2017, one in early October and one in late November (figure 12). Additional signals plotted as more than 5 km from the source may or may not reflect activity from the volcano. Steam plumes were visible in NASA Terra satellite images drifting away from the island in August, October, and December 2017, but no thermal signatures were captured.

Figure (see Caption) Figure 12. The MIROVA log radiative power graph for Mount Michael on Saunders Island from 25 May-30 December 2017 showed intermittent heat sources that indicated possible eruptive activity each month except July and December. Location uncertainty makes the distinction between greater and less than 5 km summit distance unclear.

More sources of evidence for activity became available in 2018 with the addition of the Sentinel-2 satellite data during the months of February-April and September. Multiple thermal signals appeared from MIROVA in January 2018 (figure 13), and the first Sentinel-2 satellite image showed a distinct hotspot at the summit on 10 February (figure 14).

Figure (see Caption) Figure 13. MIROVA thermal data for January-September 2018 indicated intermittent thermal anomaly signals in January, March, April, and July-September (top). A Sentinel-2 image with a hotspot was captured on 23 September, the same day as the MIROVA thermal signal (bottom). Courtesy of MIROVA.
Figure (see Caption) Figure 14. A Sentinel-2 image of Saunders Island on 10 February 2018 revealed a distinct hotspot and small steam plume rising from the summit crater of Mount Michael. Sentinel-2 image with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

A MODVOLC thermal alert appeared on 26 March 2019 followed by a significant hotspot signal in Sentinel-2 imagery on 29 March (figure 15). The hotspot was still present along with a substantial steam plume on 3 April 2018. Sentinel-2 imagery on 11 April revealed a large steam plume and cloud cover, but no hotspot.

Figure (see Caption) Figure 15. Hotspots in Sentinel-2 imagery on 29 March and 3 April 2018 indicated eruptive activity at Mount Michael on Saunders Island. Sentinel-2 image with Atmospheric Penetration view (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

MIROVA thermal signals appeared in mid-July and mid-August 2018 (figure 13) but little satellite imagery was available to confirm any thermal activity. The next clear signal of eruptive activity was evident in a Sentinel-2 image as a hotspot at the summit on 23 September. A small MIROVA signal was recorded the same day (figure 13, bottom). A few days later, on 28 September 2018, a Landsat 8 image showed a clear streak of dark-gray ash trending NW from the summit of Mount Michael (figure 16).

Figure (see Caption) Figure 16. Satellite imagery confirmed eruptive activity at Mount Michael on Saunders Island in late September 2018. Top: a hotpot in a Sentinel-2 image on 23 September coincided with a MIROVA thermal signal (see figure 13); Bottom: A Landsat 8 image on 28 September has a distinct dark gray streak trending NW from the summit indicating a fresh ash deposit. The lighter gray area SW of the summit is likely a shadow. Sentinel-2 image with Atmospheric Penetration view, (bands 12, 11, and 8A), Landsat 8 image with pansharpened image processing, both courtesy of Sentinel Hub Playground.

Geologic Background. Saunders Island is a volcanic structure consisting of a large central edifice intersected by two seamount chains, as shown by bathymetric mapping (Leat et al., 2013). The young constructional Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater and a remnant of a somma rim to the SE. Tephra layers visible in ice cliffs surrounding the island are evidence of recent eruptions. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th century. A low ice-free lava platform, Blackstone Plain, is located on the north coast, surrounding a group of former sea stacks. A cluster of parasitic cones on the SE flank, the Ashen Hills, appear to have been modified since 1820 (LeMasurier and Thomson, 1990). Vapor emission is frequently reported from the summit crater. Recent AVHRR and MODIS satellite imagery has revealed evidence for lava lake activity in the summit crater.

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


Karymsky (Russia) — October 2018 Citation iconCite this Report

Karymsky

Russia

54.049°N, 159.443°E; summit elev. 1513 m

All times are local (unless otherwise noted)


Thermal anomalies and ash explosions during August-September 2018

The most recent eruptive period at Karymsky, on the Kamchatka Peninsula of Russia, began on 28 April 2018, with thermal anomalies, gas-and-steam emissions, and ash plumes observed through July 2018. The current report discusses activity through September 2018 (table 11). This report was compiled using information from the Kamchatka Volcanic Eruptions Response Team (KVERT).

KVERT reported ongoing thermal anomalies and intermittent ash plumes over Karymsky during August and September 2018 (table 11). Ash plumes drifted 50 km SE on 7 August, and 40 km S on 25 August. Stronger activity during 10-11 September consisted of continuous dense ash emissions along with explosions that sent plumes 5-6 km high which drifted 860 km NE. Incandescence photographed the next night was attributed to fumarolic activity (figure 41). Ash plumes were identified drifting 365 km E on 22-23 September. The last thermal anomaly was identified in satellite images on 28 September, and an ash plume was last visible on 30 September.

Table 11. Ash plumes and thermal anomalies at Karymsky, 1 August-30 September 2018. Clouds often obscured the volcano. Data compiled from KVERT reports.

Date Observations
01-07 Aug 2018 Thermal anomalies; ash plume drifted 50 km SE on 7 Aug.
08-14 Aug 2018 Thermal anomalies.
25-31 Aug 2018 Thermal anomalies; ash plume drifted 40 km S on 25 Aug.
01-07 Sep 2018 Thermal anomalies.
08-15 Sep 2018 Continuous ash emissions on 10 Sep. Explosions during 10-11 Sep with plumes rising 5-6 km that drifted 860 km NE.
16-23 Sep 2018 Thermal anomalies; ash plumes drifted 365 km E on 22-23 Sep.
24-30 Sep 2018 Thermal anomalies; ash plume on 30 Sep.
Figure (see Caption) Figure 41. Incandescence, attributed to fumarolic activity, was visible above the crater of Karymsky on 12 September 2018. Photo by D. Melnikov; courtesy of Institute of Volcanology and Seismology (IVS FEB RAS, KVERT).
Figure (see Caption) Figure 42. Sentinel-2 satellite imagery of Karymsky on 30 September 2018 showing a diffuse plume and thermal anomaly in the crater. Top: Natural color view (bands 4, 3, 2). Bottom: Short-wave Infrared view (bands 12, 8A, 4). Courtesy of Sentinel Hub Playground.

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were last observed on 31 July 2018. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected one hotspot in early August (moderate power), and two hotspots in late September (low power).

Geologic Background. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

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


Nishinoshima (Japan) — September 2018 Citation iconCite this Report

Nishinoshima

Japan

27.247°N, 140.874°E; summit elev. 25 m

All times are local (unless otherwise noted)


Quiescence interrupted by brief lava flow emission and small explosions in July 2018

Nishinoshima is an active volcano in the Ogasawara Arc, about 1,000 km S of Tokyo, Japan. After 40 years of dormancy, activity increased in November 2013 and has since formed an island. The eruption has continued with subaerial activity that largely consists of lava flows and small gas-and-ash plumes. This report covers November 2017 through July 2018, and summarizes activity noted in reports issued by the Japan Meteorological Agency, and images and footage taken by the Japan Coast Guard (JCG).

No eruptive activity at Nishinoshima had been noted since mid-August 2017, when lava was last entering the ocean. Activity recommenced on 12 July and a 200-m-long lava flow was confirmed on 13 July. The lava flow was accompanied by explosive activity that ejected blocks and bombs out to 500 m from the vent, plumes and water discoloration (figures 60, 61, and 62). An aerial survey by the JCG on 30 July showed that activity had ceased and the lava flow had reached 700 m in length, terminating 100 m from the ocean.

Figure (see Caption) Figure 60. Aerial photo of Nishinoshima taken on 18 July 2018. The photo shows the active lava flow emanating from the vent along with a gas plume, and water discoloration. A closer view of the lava flow is given in figure 61. The island is approximately 1.9 x 1.9 km in size. Courtesy of the Japan Coast Guard.
Figure (see Caption) Figure 61. A view of the active Nishinoshima vent and 200-m-long lava flow on 13 July 2018. The vent is also producing a dilute ash plume from the eastern side of the cone. Courtesy of the Japan Coast Guard.
Figure (see Caption) Figure 62. Screenshot from a thermal infrared video of the active Nishinoshima vent taken on 13 July 2018. The video shows explosions ejecting incandescent material onto the flanks of the cone and the active lava flow. Courtesy of the Japan Coast Guard.

After the July activity, Nishinoshima again entered a phase of quiescence with activity limited to fumaroles around the vent. Himawari-8 satellite observations noted no increased thermal output following the July 2018 eruption. Thermal anomalies detected by satellite-based MODIS instruments were identified by the MODVOLC system from during 12-21 July 2018.

Geologic Background. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Information Contacts: Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: http://www.kaiho.mlit.go.jp/info/kouhou/h29/index.html, http://www1.kaiho.mlit.go.jp/GIJUTSUKOKUSAI/kaiikiDB/kaiyo18-e1.htm); Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Mayon (Philippines) — October 2018 Citation iconCite this Report

Mayon

Philippines

13.257°N, 123.685°E; summit elev. 2462 m

All times are local (unless otherwise noted)


Low activity during April-September with some ash plumes and ongoing crater incandescence

Mayon is a frequently active volcano in the Philippines that produces ash plumes, lava flows, pyroclastic flows, and lahars. In early 2018, eruptive activity included lava fountaining that reached 700 m above the summit, and lava flows that traveled down the flanks and collapsed to produce pyroclastic flows (figure 39). Lava fountaining and lava flows decreased then ceased towards late March. Lava effusion was last detected on 18 March 2018, and the last pyroclastic flow for this eruptive episode occurred on 27 March 2018 (see BVGN 43:04). The hazard status for was lowered from alert level 4 to 3 (on a scale of 0 to 5) on 6 March 2018 due to decreased seismicity and degassing; the level was lowered again to 2 on 29 March. This report summarizes the activity during April through September 2018 and is based on daily bulletins issued by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and satellite data.

Figure (see Caption) Figure 39. Sentinel-2 thermal satellite images showing the lava flow activity at Mayon during January through March 2018. Three lava flow lobes flowed down the Mi-isi, Bonga-Buyuan, and Basud channels, and are shown in bright orange/red in these images. These are false color images created using bands 12, 11, 4, courtesy of Sentinel Hub Playground.

The hazard status remained on Alert level 2 (increasing unrest) throughout the reporting period. Activity was minimal with low seismicity (zero to four per day) and a total of 19 rockfall events throughout the entire period. White to light-brown plumes that reached a maximum of 1 km above the crater were observed almost every day from April through September (figure 40). Two short-lived light brown plumes were noted on 27 and 28 August and both reached 200 m above the crater.

Figure (see Caption) Figure 40. An emission of white steam-and-gas at Mayon and a dilute brown plume that reached 200 m above the crater was seen on 24 May 2018. Courtesy of PHIVOLCS.

On the days that sulfur dioxide was measured, the amount ranged from 436 to 2,800 tons per day (figure 41). Mayon remains inflated relative to 2010 baselines but the edifice has experienced deflation since 20 February, a period of inflation from 2-14 April, and slight inflation of the mid-slopes beginning 5 May, which then became more pronounced beginning 25 June. No other notable inflation or deflation was described throughout the reporting period.

Figure (see Caption) Figure 41. Measurements of sulfur dioxide output at Mayon during 1 April-30 September 2018. Data courtesy of PHIVOLCS.

Incandescence at the summit was observed almost every night (when weather permitted) from April through to the end of September 2018, and this elevated crater temperature is also seen in satellite thermal imagery (figure 42). Thermal satellite data showed a slight increase in output during April through to June, although not as high as the earlier 2018 activity, with a decline in thermal output starting in July (figure 43).

Figure (see Caption) Figure 42. Sentinel-2 thermal satellite image showing an elevated thermal signature in the crater of Mayon and a steam-and-gas plume on 15 May 2018. Similar indications of activity in the crater were frequently imaged on cloud-free days from April through September. This is a false color image created using bands 12, 11, 4, courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 43. Log radiative power MIROVA plot of MODIS thermal data for the year ending 11 October 2018 at Mayon. An elevated period of activity reflecting the lava flows in January through March is notable, followed by a second period of lower intensity activity during May into June, then a prolonged period of reduced activity through to the end of the reporting period; the August anomaly was not at the volcano. Courtesy of MIROVA.

Geologic Background. Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); 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).


Kadovar (Papua New Guinea) — October 2018 Citation iconCite this Report

Kadovar

Papua New Guinea

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

All times are local (unless otherwise noted)


Intermittent ash plumes; thermal anomalies in the crater and Coastal Vent through September 2018

The first confirmed eruption of Kadovar began on 5 January 2018 with dense ash plumes and steam and a lava flow. The eruption continued through February and then slowed during March (BGVN 43:04). This report describes notices of ash plumes from the Darwin Volcanic Ash Advisory Centre (VAAC) and satellite images during April through 1 October 2018.

According to the Darwin VAAC a pilot observed an ash plume rising to an altitude of 1.2 km on 10 June. The ash plume was not identified in satellite data. Another ash plume identified by a pilot and in satellite images rose to an altitude of 1.8 km on 20 June and drifted W. An ash plume was visible in satellite images on 28 September drifting SE at an altitude of 2.1 km. On 1 October an ash plume rose to 2.7 km and drifted W.

Infrared satellite data from Sentinel-2 showed hot spots in the summit crater and at the Coastal Vent along the W shoreline on 10, 15, and 25 April 2018; plumes of brown discolored water were streaming from the western side of the island (figure 18). Similar activity was frequently seen during clear weather in the following months. A steam plume was also often rising from the crater. The Coastal Vent cone was still hot on 8 August, but no infrared anomaly was seen in imagery from 28 August through September.

Figure (see Caption) Figure 18. Sentinel-2 natural color satellite image of Kadovar on 10 April 2018. The island is about 1.5 km in diameter. Steam can be seen rising from the summit and the Coastal Vent just off the western shore; both locations show thermal anomalies in infrared imagery. Discolored water plumes extend NE from the island. Courtesy of Sentinel Hub Playground.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Ketoi (Russia) — October 2018 Citation iconCite this Report

Ketoi

Russia

47.35°N, 152.475°E; summit elev. 1172 m

All times are local (unless otherwise noted)


Plume of uncertain composition reported based on satellite data one day in September

Gas-and-steam emissions were previously reported at Ketoi (figure 1) in January, July, and August 2013 (BGVN 40:09). Intense fumarolic activity originating from the same area, the N slope of Pallas Peak, was reported in 1981, 1987, and 1989. Based on a report from the Sakhalin Volcanic Eruption Response Team (SVERT) using Himawari-8 imagery, the Tokyo VAAC reported an ash plume on 21 September 2018 which drifted to the NE; however, evidence of the plume could not be confirmed by the VAAC from satellite imagery. The original VONA (Volcano Observatory Notice for Aviation) issued by SVERT noted a volcanic cloud without a specific mention of ash, but also remarked that thermal anomalies had been observed on 17 and 20 September.

Figure (see Caption) Figure 1. Natural color Sentinel-2 satellite image of Ketoi on 18 September 2018. A large freshwater lake can be seen SW of the Pallas Peak andesitic cone, which also hosts a crater lake. Lava flows originating from the younger cone extend primarily N to SW, and a white fumarolic area is immediately NE of the crater. The island is approximately 10 km in diameter. Courtesy of Sentinel Hub Playground.

Geologic Background. The circular, 10-km-wide Ketoi island, which rises across the 19-km-wide Diana Strait from Simushir Island, hosts of one of the most complex volcanic structures of the Kuril Islands. The rim of a 5-km-wide Pleistocene caldera is exposed only on the NE side. A younger 1172-m-high stratovolcano forming the NW part of the island is cut by a horst-and-graben structure containing two solfatara fields. A 1.5-km-wide freshwater lake fills an explosion crater in the center of the island. Pallas Peak, a large andesitic cone in the NE part of the caldera, is truncated by a 550-m-wide crater containing a brilliantly colored turquoise crater lake. Lava flows from Pallas Peak overtop the caldera rim and descend nearly 5 km to the SE coast. The first historical eruption of Pallas Peak, during 1843-46, was its largest.

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); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sinabung (Indonesia) — September 2018 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


No significant ash plumes seen after 22 June 2018; minor ash in early July

Sinabung volcano is located in the Karo regency of North Sumatra, Indonesia. The current eruptive episode commenced in late 2013, after phreatic activity in 2010, producing ash plumes, lava domes and flows, and pyroclastic flows that caused evacuation and relocation of nearby communities. This report covers activity from April through early July, and is based on information provided by MAGMA Indonesia, the Darwin Volcanic Ash Advisory Center (VAAC), the Center for Volcanology and Geological Hazard Mitigation (CVGHM, also known as PVMBG), satellite data, and field photographs. Sinabung has been on Alert Level IV, the highest hazard status, since 2 June 2015.

The eruption has built a pyroclastic flow and lava fan to the SE (figure 60). This activity continued into 2018, with the last significant ash plume reported on 22 June (table 8). However, minor ash emissions continued at least through 5 July 2018.

Figure (see Caption) Figure 60. Satellite images showing Sinabung before and after the eruption with the newly-developed fan of pyroclastic flow, volcanic ash, and lava flow deposits. Top: Landsat-8 true color satellite image (pan-sharpened) acquired on 7 June 2013 before the eruption began. Bottom: Sentinel-2 natural color satellite image acquired on 16 July 2018, after the eruption ended. Courtesy of Sentinel Hub Playground.

Table 8. Summary of ash plumes (altitude and drift direction) and pyroclastic flows at Sinabung, April-June 2018. The summit is at 2,460 m elevation. Data courtesy of Darwin VAAC reports, MAGMA Indonesia VAAC reports, and CVGHM volcanic activity reports.

Date Ash plume altitude (km) Ash plume drift direction Pyroclastic flows
06 Apr 2018 7.5 W, S 3.5 km
12 Apr 2018 2.7 WNW Yes
19 Apr 2018 5.5 ESE 1 km
19 May 2018 3.2 NW --
20 May 2018 5.0 WNW --
15 Jun 2018 3.0 ESE --
22 Jun 2018 3.5 SE --

An eruption on 6 April 2018 at 1607 local time produced an ash plume that reached about 7.5 km above the summit. The eruption also produced pyroclastic flows that traveled about 3.5 km from the summit down the SE slope (figure 61). The eruption resulted in the closure of a nearby airport and ashfall affected hundreds of hectares of agricultural land. Two more notable ash plumes were reported on 12 and 19 April, to altitudes of about 2.7 and 5.5 km, respectively. A pyroclastic flow was reported during the 12 April eruption. Smaller ash and gas emissions occurred through the month.

Figure (see Caption) Figure 61. Eruption of Sinabung on 6 April 2018 at 1600 local time that produced an ash plume that reached over 5 km above the summit, and pyroclastic flows that reached about 3.5 km down the SE flank. Courtesy of Agence France-Presse via Straits Times.

Two ash plumes were recorded on 19 and 20 May, rising to about 3.2 and 5 km altitude, respectively. Throughout June small diffuse gas-and-ash plumes continued (figures 62 and 63). The last activity reported by the agencies was on the 15 and 22 June, when ash plumes reached 3 and 3.5 km altitude (figure 64). Activity after 22 June was limited to seismicity and ash, gas, and steam plumes to several hundred meters above the summit (figure 65). Although an elevated thermal signature was detected in Sentinel-2 satellite data on 30 August 2018, there were no reports of renewed activity.

Figure (see Caption) Figure 62. View of the Sinabung summit vent area during ash venting on 20 June 2018. This view from the SW shows the perched remains of the lava dome and collapse scar. Photo courtesy of Brett Carr, Lamont-Doherty Earth Observatory.
Figure (see Caption) Figure 63. Relatively consistent ash venting at Sinabung on 20 June 2018. This view shows the pyroclastic flow fan and the 2014 lava flow in the lower center of the photo. Drone photo courtesy of Brett Carr, Lamont-Doherty Earth Observatory.
Figure (see Caption) Figure 64. Small ash plume rising from Sinabung at 2106 on 22 June 2018. The ash plume reached about 1 km above the crater. Courtesy of BNPB (color adjusted).
Figure (see Caption) Figure 65. Minor ash venting at Sinabung on 5 July 2018. Photo courtesy of Brett Carr, Lamont-Doherty Earth Observatory.

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/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia ); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/, Twitter: https://twitter.com/id_magma); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Brett Carr, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY (URL: https://www.ldeo.columbia.edu/user/bcarr); Agence France-Presse (URL: http://www.afp.com/); Straits Times (URL: https://www.straitstimes.com).


Semeru (Indonesia) — September 2018 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Small ash plumes in February, April, July, and August 2018; persistent thermal hotspot in the crater

Semeru volcano is the tallest volcano in Java (figure 33) and one of the most active in Indonesia. The Mahameru summit area contains the active Jonggring-Seloko vent where activity consists of dome growth and regular ash plumes, along with pyroclastic flows, avalanches, and lava flows that travel down the SE-flank ravine. The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) Volcano Alert level for Semeru throughout the report period is II (on a scale of I-IV). The last Volcano Observatory Notice for Aviation (VONA) was issued on 9 January 2017, and the status has not changed during the reporting period. This report summarizes the activity from January to 24 August 2018 and is based on Volcano Ash Advisory Center (VAAC) ash advisories and satellite data.

Figure (see Caption) Figure 32. View looking NW at the quiet Mahameru summit area of Semeru on 24 August 2018 taken by a webcam courtesy of MAGMA Indonesia via Ø.L. Andersen's Twitter feed.

While there were no observatory activity reports issued, the Darwin VAAC issued reports for five events that produced ash plumes to altitudes ranging 3.4 to 4.9 km (table 22). MIROVA (Middle InfraRed Observation of Volcanic Activity) thermal data indicate near-consistent low-level thermal activity at Semeru after a period of no detected thermal anomalies in late January through early February. This supports the elevated thermal energy detected by Sentinel-2 satellite data at the Jonggring-Seloko vent and along the SE-flank ravine (figure 34). The MODVOLC algorithm detected 16 high-temperature hotspots through the reporting period, six in January, two in March, three in April, one in July, and two in August through to the 24th.

Table 22. Summary of ash plumes (altitude and drift direction) and pyroclastic flows at Semeru, January to 24 August 2018. The summit is at 3,657 m elevation. Data courtesy of Darwin VAAC report.

Date Altitude (km) Drift direction Other notes
24 Feb 2018 4.6 20 km ESE and WSW --
29 Apr 2018 3.4 NW Short-lived discrete eruption
20 Jul 2018 4.9 SW Minor discrete eruption
30-31 Jul 2018 4.3 W --
23-24 Aug 2018 4.3 W and SW --
Figure (see Caption) Figure 33. MIROVA plot of Log Radiative Power showing the relative thermal energy at Semeru ending September 2018. The detected thermal activity is more intense before mid-January 2018 when there was a gap in detected data before regular low-level activity resumed. Courtesy of MIROVA.
Figure (see Caption) Figure 34. Sentinel-2 false color thermal satellite images showing the persistent elevated thermal anomaly in the Jonggring-Seloko crater of Semeru from January through to 24 August 2018. Hot material can sometimes be identified in the SE-flank ravine. The larger central image is annotated with the major morphological features. False color (urban) images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

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

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


Rincon de la Vieja (Costa Rica) — September 2018 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Intermittent weak phreatic explosions during January-March and July-August 2018

The Rincón de la Vieja volcano complex has generated intermittent phreatic explosions since 2011; during 2017, weak phreatic explosions occurred during May, June, July, September, and October (BGVN 42:08 and 43:03). This activity continued through August 2018. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA).

According to OVSICORI-UNA, at 1758 on 9 January 2018, an explosion produced a plume that rose 1 km above the crater rim. On 12 January, OVSICORI-UNA reported some small phreatic explosions. The webcam detected weak explosions again in mid-February. Another weak explosion on 22 February confirmed the presence of a crater lake.

During the first week of March OVSICORI-UNA reported weak phreatic explosions of low amplitude that were only be detected by the webcam (figure 28), and not by seismic instruments. During the week of 5-11 March there were 2-4 weak phreatic explosions occurred per day, along with strong tremor on the 10th. Small eruptions were seen on unspecified days the week of 12-18 March.

Figure (see Caption) Figure 28. Webcam image of a phreatic explosion at Rincon de la Vieja on 3 March 2018. Courtesy of OVSICORI-UNA.

No phreatic activity was reported during the second half of March through June, though on 20 May a seismic swarm of about 30 earthquakes was recorded. After a tremor on 3 July, a possible weak phreatic explosion occurred on 4 July at 0044, followed by a pulse of tremor. On 28 July, at 1828, a small explosion followed by tremor was recorded.

On 3 August OVSICORI-UNA reported that two weak explosions occurred at dawn. On 14 August, another weak explosion began at 1828 and lasted three minutes. Foggy conditions prevented webcam views and an estimate of a plume height. Other weak explosions were recorded on 17 August at 1407 and 2015.

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

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


Turrialba (Costa Rica) — September 2018 Citation iconCite this Report

Turrialba

Costa Rica

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

All times are local (unless otherwise noted)


Ongoing variable ash emissions and crater incandescence through August 2018

This report summarizes activity at Turrialba during January-August 2018. Activity became more constant after September 2014, with cycles of explosions with numerous, sometimes persistent, weak and passive ash plumes and emissions usually rising no more than 500 m above the active crater. This activity continued during this reporting period (table 7). Most of the data were provided by monthly bulletins of the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) and alerts from the Washington Volcanic Ash Advisory Center (VAAC).

Table 7. Ash emissions at Turrialba, January-August 2018. Information was provided by OVSICORI-UNA, Washington VAAC, and RSN: UCR-ICE.

Date Time Max. Plume height above crater rim Drift Remarks
08 Jan 2018 0600 400-500 m NW --
08 Jan 2018 1319 400-500 m NE --
08 Jan 2018 2005 800 m SW --
09 Jan 2018 0630 300 m SW --
09 Jan 2018 1412 -- -- --
15 Jan 2018 0400 -- -- Ashfall in areas N of Pacayas (Pinos, Buenos Aires, and Santa Rosa de Oreamuno); sulfur odor noted in Santa Rosa de Oreamuno.
22 Jan 2018 0000 500 m NW --
26 Jan 2018 1101 100-200 m SW --
26 Jan 2018 1427 100-200 m SW --
30 Jan 2018 0920 100-200 m SW --
05 Feb 2018 0830 200 m SW --
06 Feb 2018 0730 1 km SW According to The Costa Rica Star, the activity continued for almost one hour; smaller explosion at 0832. Ashfall in several W-flank communities in San Jose (Goicoechea, Curridabat, Coronado) and Heredia.
27 Feb 2018 0800 100 m SW --
06 Mar 2018 2240 500 m NW Activity intensified around midnight with dense ash emissions and ejection of incandescent blocks, and remained elevated almost until 0300 on 7 March. At 1740 activity again intensified; emissions with increased ash volume occurred 1801-1820 drifting W.
08 Mar 2018 1515 300 m SW --
13 Mar 2018 0920 300 m NW --
23 Mar 2018 0605 100 m SW --
31 Mar 2018 1802 400 m SW --
01 Apr 2018 0838 500 m NW --
03 Apr 2018 0700 500 m NW --
05 Apr 2018 1230 500 m S --
09 Apr 2018 0609 300 m W --
11 Apr 2018 -- -- -- --
26 Apr 2018 0700 300 m W --
10 May 2018 -- -- -- Ashfall in La Pastora de Santa Cruz de Turrialba and Pacayas. No specific date: strong emissions of SO2, accompanied by vigorous fumarolic activity and jetting noises.
13 May 2018 0920 300-500 m -- Weak steam and gas, apparently no ash. Seismicity low, with low-amplitude long-period earthquakes and tremor. Continuous low-amplitude tremor.
21 May 2018 0900 -- -- --
28 May 2018 0930 300 m SE --
23 Jul-04 Aug 2018 -- 300 m NW, W, SW Series of weak, sporadic, and almost daily gas-and-ash emissions. On 24 July, ashfall in Coronado, Tibás (35 km WSW), Goicoechea (28 km WSW), Moravia (31 km WSW), and other areas in the Valle Central. On 31 July, ashfall in Tres Ríos (27 km SW). Sulfur odor occasionally reported.
02 Aug 2018 0023 1 km W --
02 Aug 2018 0700 300 m W --
04 Aug 2018 1600 300 m -- --
10 Aug 2018 -- -- W Pulsating, passive ash emissions. Strong sulfur odor in parts of Heredia (38 km W) and San José (36 km WSW) on 11 Aug.
27-28 Aug 2018 -- 200 m SW Continuous emissions.
30 Aug 2018 1340 200 m SW --
31 Aug-01 Sep 2018 -- 200 m SW, W Continuous gas-and-ash emissions.

According to an online news report (Q Costa Rica), a group of volcanologists called Volcanes sin Fronteras (Volcanos Without Borders) flew a drone over the volcano several times in December 2017 and first the two weeks of January 2018. On their Facebook page, they indicated that activity was dominated by intense degassing from the active crater, with sporadic explosions every 30-60 minutes, releasing gas and ash that rose to more than 300 m above the crater. They also observed phreato-magmatic explosions.

OVSICORI reported that pulses of ash emissions were common in January (figure 49), and incandescence was occasionally observed at night. Activity decreased after the middle of February, but strong incandescence was observed during early March.

Figure (see Caption) Figure 49. Webcam photo of an ash emission at Turrialba on 22 January 2018. Courtesy of Red Sismologica Nacional (RSN: UCR-ICE); published by the Costa Rica Star.

Eruptive activity resumed during the middle of May, but faded toward the end of the month to weak passive emissions, and finally ended. The volcano continued with a stable permanent Strombolian activity at the bottom of the crater. During June, the volcano was stable, with strong incandescence at night reflecting the presence of minor Strombolian activity that continued through at least early July.

On 3 July a weak explosion occurred and a thin layer of ash fell on the park ranger house and the Pica seismic station (2.5 km NW). A jet-like sound was heard on 4 July from a lookout. On 16 July incandescence continued at a low level. OVSICORI reported frequent weak ash emissions from 18 July through 2 August; the ash had a very low proportion of juvenile material and a high proportion of altered material. According to a news account (The Costa Rica Star) citing the RSN, persistent tremor accompanied these emissions, and a lahar descended the Toro Amarillo River on the W flank. Weak short-lived ash emissions resumed during the last half of August, and weak to moderate incandescence could still be observed.

Seismicity and deformation. During the first week of January, weak long-period (LP) earthquakes were recorded, but no volcanic-tectonic (VT) earthquakes or tremor. In February-April, weak VT earthquakes, a few LP earthquakes, and harmonic tremor were recorded. By May, seismic activity was almost non-existent, with VT signals below the crater and sporadic tremor. The latter disappeared by the end of May.

On 16 July, seismicity increased, particularly low-frequency earthquakes, to reach about 200 events the next day, but then decreased to normal on 18 July, with sporadic short tremor. During the last week of July, seismicity again increased until an internal explosion on 27 July, after which seismicity decreased. Tremor activity increased on 4 August, and by the middle of August, about 50 LP earthquakes per day were recorded, along with spasmodic tremor of low amplitude. This heightened activity continued during the following week.

Since June 2017, the volcano tended toward deflation, but then in early 2018 became stable until the middle of February, when inflation was recorded. By June, deformation was longer measured. No significant deformation was found in July or August.

Thermal anomalies. MODIS satellite instruments processed using the MODVOLC algorithm only recorded thermal anomalies on 22 March, 2 April, and 27 April (2 pixels). The MIROVA (Middle InfraRed Observation of Volcanic Activity) system recorded one hotspot during February, numerous hotspots between mid-March and mid-May, and only several hotspots after mid-May through the end of August. All recorded MIROVA anomalies were within 2.5 km of the volcano and of low radiative power.

Sulfur dioxide measurements. Significant sulfur dioxide levels near the volcano were recorded by NASA's satellite-borne ozone instruments between 30 March and 3 June, especially between 6-15 April.

According to OVSICORI, the CO2/SO2 ratio increased to a peak of 8 during the night of 21-22 January, then remained stable until the first week of February, when it decreased. By 20 February, the ratio was stable at about 4. The ratio was low during the middle of March, but rose on 29 March. On 10 April, the SO2 flow was normal (below 1000 t/d) and remained low until the middle of May, when CO2 levels increased. High CO2/SO2 levels were measured at the end of May, but decreased in early June. On 12 and 25 June, SO2 levels were about 400 and 500 tons/day, respectively. During early July, the ratio remained low at 4, with short periods of high measurements (about 10 on 5 July). The ratio remained stable throughout the rest of July. The ratio increased on 6 August during the last phase of eruptive activity, but then decreased to normal and stable levels for the rest of the month. Near the end of August, the two gas monitoring stations were vandalized.

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

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Red Sismologica Nacional (RSN: UCR-ICE), Universidad de Costa Rica and Instituto Costarricense de Electricidad (URL: http://rsn.ucr.ac.cr/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (URL: https://sO2.gsfc.nasa.gov/); Costa Rica Star (URL: https://news.co.cr); Q Costa Rica (URL: https://qcostarica.com).

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Bulletin of the Global Volcanism Network - Volume 43, Number 03 (March 2018)

Managing Editor: Edward Venzke

Ebeko (Russia)

Continuing frequent ash explosions through November 2017, typically to about 2 km altitude

Fournaise, Piton de la (France)

Second eruption of 2017; July-August, fissure with flows on the SE flank

Kilauea (United States)

Activity continues at Halema'uma'u lava lake, and at the East Rift Zone 61g flow, July-December 2017

Manam (Papua New Guinea)

Ash plumes and Strombolian explosions increase, March-May 2017

Poas (Costa Rica)

Increase in phreatic and phreato-magmatic explosions during April through August 2017

Rincon de la Vieja (Costa Rica)

Phreatic explosions during 29 September-22 October 2017

San Cristobal (Nicaragua)

Intermittent ash-bearing explosions during 2017; Ash plume drifts 250 km in August.

Sangay (Ecuador)

Eruptive episode of ash-bearing explosions and lava on SE flank, 20 July-26 October 2017

Suwanosejima (Japan)

Large explosions with ash plumes and Strombolian activity continue during 2017

Turrialba (Costa Rica)

Persistent explosions and ash emissions continue through 2017; small lava lake



Ebeko (Russia) — March 2018 Citation iconCite this Report

Ebeko

Russia

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

All times are local (unless otherwise noted)


Continuing frequent ash explosions through November 2017, typically to about 2 km altitude

Ebeko volcano is located on the remote N end of Paramushir Island in the Kuril Islands and contains many craters, lakes, and thermal features. Eruptions and ash plumes were observed at Ebeko in early July 2010 (BGVN 36:07). No additional activity was reported from Ebeko until October 2016, marking the start of the more recent eruptive cycle. New explosive eruptions accompanied by ash fall began on 20 October 2016 through April 2017 (BGVN: 42:08). Explosive eruptions, ash plumes, ash falls were observed and reported at a regular frequency during this reporting period from May through November 2017 (table 5). Eruptions were reported by observations from residents in the town of Severo-Kurilsk, located about 7 km E of Ebeko, by volcanologists and by satellite imagery. The Kamchatkan Volcanic Eruption Response Team (KVERT) is responsible for monitoring Ebeko, and is the primary source of information. The Aviation Color Code (ACC) remained at Orange throughout this reporting period. This color is the second highest level of the four color scale.

Table 5. Summary of activity at Ebeko volcano from May 2017 to November 2017. Aviation Color Code (ACC) is a 4-color scale. Data courtesy of KVERT.

Date Plume Altitude Plume Distance Plume Direction Other Observations
23 Apr-26 Apr 2017 2.1 km 50 km NE ACC at Orange. Minor ashfall in Severo-Kurilsk reported on 25 April
07 May 2017 -- -- -- Satellite observation
08 May-09 May 2017 2.4-2.7 km -- S, NE Satellite observation
15 May 2017 2 km -- -- Explosions
23-24 May 2017 2 km -- -- Explosions
25 May-02 Jun 2017 -- -- -- Explosions
02 Jun-09 Jun 2017 -- -- -- Explosions
09 Jun-16 Jun 2017 -- -- -- Explosions
17, 21 Jun 2017 2 km -- -- Explosions
23 Jun-30 Jun 2017 2 km -- -- Explosions, ashfall in Severo-Kurilsk reported on 24 and 26 Jun
01, 04 Jul 2017 2.6 km -- -- Explosions
07 Jul-08 Jul 2017 1.5 km -- -- Explosions
31 Jul 2017 -- -- -- Weak thermal anomaly
01 Aug 2017 1.6 km -- -- Explosions
10 Aug 2017 -- -- -- Explosions
22 Aug 2017 2 km -- SW Explosions
28 Aug-29 Aug 2017 2.2 km -- -- Explosions, minor ashfall in Severo-Kurilsk
02 Sep 2017 4 km -- -- Explosions
03, 06-07 Sep 2017 2.1 km -- -- Explosions, minor ashfall in Severo-Kurilsk
13 Sep-14 Sep 2017 2.2 km -- -- Explosions
15 Sep-17 Sep 2017 3 km -- -- Explosions, minor ashfall in Severo-Kurilsk
24 Sep 2017 2 km -- -- Explosions
29-30 Sep, 01, 05 Oct 2017 1.5 km -- -- Explosions
06-07, 09, 12 Oct 2017 3 km -- -- Explosions, ashfall in Severo-Kurilsk reported on 7, 9, and 12 Oct
13-20 Oct 2017 2.5 km -- -- Explosions
20-27 Oct 2017 2 km -- -- Explosions
27 Oct-03 Nov 2017 2 km -- -- Explosions
05, 07-08 Nov 2017 2 km -- -- Explosions
16 Nov 2017 2 km -- -- Explosions
17-18, 20-21 Nov 2017 2 km -- -- Explosions, ashfall in Severo-Kurlisk reported on 22 Nov
25-26, 28-30 Nov 2017 2 km -- -- Explosions, ashfall in Severo-Kurlisk reported on 28 Nov

Explosives events, bursts of ash, ashfall, and ash plumes were reported throughout this period, and were quite variable in appearance (figures 12-16). Minor amounts of ash fell in Severo-Kurilsk on 25 April, 2-3, 6-7, 16, and 18 September, and 22 November. Ash plume altitudes during this reporting period ranged from 1.5 to 4 km; with the highest altitude of 4 km recorded on 2 September (table 5).

Figure (see Caption) Figure 12. Ash plume from an explosive event at Ebeko on 15 May 2017. Ash plume altitude reached 2 km. Photo by L. Kotenko, courtesy of Institute of Volcanology and Seismology IVS FEB RAS.
Figure (see Caption) Figure 13. Ash plume from an explosive event at Ebeko on 23 May 2017. Ash plume altitude reached 2 km. Photo by L. Kotenko, courtesy of Institute of Volcanology and Seismology IVS, FEB, RAS.
Figure (see Caption) Figure 14. Ash explosions from Ebeko on 10 August 2017 as seen from Severo-Kurilsk, 7 km E. Photo by V. Rashidov, courtesy of Institute of Volcanology and Seismology IVS FEB RAS.
Figure (see Caption) Figure 15. Ash bursts up to 2 km on 22 August 2017. Photo by T. Kotenk. Courtesy of Institute of Volcanology and Seismology IVS FEB RAS.
Figure (see Caption) Figure 16. Active crater of Ebeko volcano on 13 September 2017. Ash plume altitude reached 2.2 km. Photo by Ivan and Nataliya Cherkashiny. Courtesy of Institute of Volcanology and Seismology IVS FEB RAS.

MIROVA only identified two low-power thermal anomalies in the past year, one in late February 2017 and the other in late March 2017. A weak thermal anomaly was reported by KVERT on 31 July 2017.

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

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


Piton de la Fournaise (France) — March 2018 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


Second eruption of 2017; July-August, fissure with flows on the SE flank

Short pulses of intermittent eruptive activity have characterized Piton de la Fournaise, the large basaltic shield volcano on Reunion Island in the western Indian Ocean, for several thousand years. The most recent episode occurred during 31 January-27 February 2017 with an active vent located inside the Enclos caldera on the S flank, about 1 km SE of Château Fort and about 2.5 km ENE of Piton de Bert (BGVN 42:07). The next episode, discussed here, began on 14 July 2017 and lasted for about six weeks. Activity through February 2018 is covered in this report. Information is provided by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and satellite instruments.

A new fissure eruption began on 14 July 2017 on the S flank inside the caldera about 850 m W of Château Fort and lasted through 28 August. The fissure was initially 450 m long with seven active lava fountains. Within 48 hours the flow had reached its farthest extent, about 2.8 km from the fissure. Activity continued from the southernmost cone of the fissure with three active vents for a few weeks. Surface lava flows diminished, and activity was concentrated in lava tubes flowing SE from the cone with occasional breakouts and ephemeral vents along the flow field. The tremor signal briefly spiked with lava fountains on 16-17 August, and then ceased altogether on 28 August. A brief seismic swarm during 24 August-1 September led OVPF to conclude that magma had moved but did not open a new fissure. Inflation was intermittent through December, and then increased significantly during January before leveling off during February 2018.

Activity during June-July 2017. The brief seismic swarm of 17-18 May 2017 was followed by another brief increase in seismicity during the first few days of June 2017, but no surface eruption was reported. The inflation that occurred during the May event tapered off by early June. The volcano remained quiet until seismicity began increasing on 10 July 2017; this was accompanied by inflation recorded at the GPS stations as well. The observatory (OVPF) noted the beginning of seismic tremors, indicative of a new eruption, around 0050 on 14 July 2017. Webcams revealed that eruptive fissures opened on the S flank of the cone inside the Enclos caldera. A reconnaissance flight conducted later in the morning on 14 July indicated that the eruptive site was located 750 m SE of the Kala-Pele peak and 850 m W of Château Fort, about 2.2 km NE of Piton Bert (Figure 110).

Figure (see Caption) Figure 110. Location of the Piton de la Fournaise eruption that began on 14 July 2017. Courtesy of OVPF/IPGP (Bulletin d'activité du vendredi 14 juillet 2017 à 15h30 Heure locale).

By 0930 that morning, the fissure extended over a total length of approximately 450 m. Seven lava fountains with a maximum height of 30 m were active (figure 111). The fountain farthest downstream began to build a cone with two arms of flowing lava. Satellite measurements indicated an initial flow rate of about 22-30 m3/s at the beginning of the eruption.

Figure (see Caption) Figure 111. A new fissure opened on the S flank of the cone inside the Enclos caldera at Piton de la Fournaise on 14 July 2017. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du vendredi 14 juillet 2017 à 15h30 Heure locale).

The tremor intensity decreased significantly the following day; this was reflected in the decrease in the flow rates and the distribution of activity on the fissure. Only three lava fountains were active on 15 July 2017 near the downstream end of the fissure; they began to form two small cones with lava flows that merged into a single channel (figure 112). The fountains did not exceed 30 m in height. By 1400 on 15 July the flow front was 2.2 km SE from the fissure. Satellite instrument measurements suggested the flow rate had dropped to two m3/s. Sulfur dioxide anomalies were measured by the OMI satellite instrument during 14-16 July (figure 113).

Figure (see Caption) Figure 112. Lava emerged from two vents and merged into a single flow at the eruptive site at Piton de la Fournaise on 15 July 2017 at 1400 local time. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 15 juillet 2017 à 16h30 Heure locale).
Figure (see Caption) Figure 113. Sulfur dioxide anomalies were captured by the OMI instrument on the Aura satellite by NASA on 14 (left) and 16 (right) July 2017 at the beginning of the eruption at Piton de la Fournaise. Courtesy of NASA Goddard Space Flight Center.

Tremors fluctuated over the next few days with changes related to the growth and collapse of various the cones along the fissure. On 18 July, there were six active fountains (figure 114). The flow rate remained approximately 1-3 m3/s. Fountains reached 20 m high on 19 July and a third vent was visible forming on the N side of the main cone. During an overflight on 21 July, OVPF noted that all three vents were active, but lava was only flowing SE from the central one (figure 115). Lava tubes had begun to form downstream of the cone, with numerous breakouts creating small lateral expansion arms.

Figure (see Caption) Figure 114. Six fountains were active along the fissure zone on 18 July 2017 at Piton de la Fournaise. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mardi 18 juillet 2017 à 16h00 Heure locale).
Figure (see Caption) Figure 115. Lava flowed SE from the central vent of three in the fissure zone at Piton de la Fournaise on 21 July 2017. The magmatic gases are drifting SSE to the upper left of the image. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du vendredi 21 juillet 2017 à 16h30 Heure locale).

OVPF measured the flow dimensions on 22 July as 2.8 km long and 0.6 km wide (figure 116); the flow front had not advanced in the previous seven days. A fourth vent on the N side of the cone was periodically emitting ejecta, and two flows were active; one moving SE towards Château Fort and the other moving towards the SW inside a lava tube. On 24 July OVPF measured the flow rate as 1-4 m3/s, and the total volume of lava to date as 5.3 ± 1.9 million m3. On 25 July 2017, local observers reported that the main vent on the SE flank of the cone was visible, as well as a second vent on the N flank of the growing cone. The main lava channel was clearly visible downstream of the cone with frequent overflows (figure 117), and active flow continued inside the lava tubes.

Figure (see Caption) Figure 116. An outline of the active lava flow at Piton de la Fournainse on 22 July 2017. Base map courtesy of Google Earth. Annotations courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 22 juillet 2017 à 17h00 Heure locale).
Figure (see Caption) Figure 117. The main lava channel flowed SE from the eruptive vent at Piton de la Fournaise on 25 July 2017. Photo copyright by Cité du Volcan/Arthur Vaitilingom). Courtesy of OVPF/IPGP (Bulletin d'activité du mercredi 26 juillet 2017 à 16h00 Heure locale).

By 30 July the flow intensity had decreased to about half of its original flow rate. The cone continued to grow, but no surface lava flows were observed (figure 118). The main vent rarely produced ejecta. Active lava was flowing in tunnels with a few minor breakouts near the cone. The flow front remained 2.8 km from the eruptive vent.

Figure (see Caption) Figure 118. The eruptive vent of Piton de la Fournaise on 30 July 2017 showed no surface flows, but activity continued in lava tunnels. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du dimanche 30 juillet 2017 à 16h00 Heure locale).

Activity during August 2017-February 2018. The intensity of the tremors associated with the eruption continued to taper off into early August to levels below 20% of what they were at the beginning of the eruption, and this corresponded to a decrease in observed activity in the field. During an OVPF overflight on 2 August 2017 no flows or ejecta from the eruptive cone were seen, but a number of surface breakouts from lava tubes were still visible; the nearest to the cone was 520 m to the SE (figure 119). The main vent was completely blocked, but the smaller vent still had visible incandescence and strong degassing (figure 120).

Figure (see Caption) Figure 119. Lava tubes and small breakouts at Piton de la Fournaise on 2 August 2017 (N to the lower right). The breakouts were several hundred meters SE of the main vent. The eroded cone in the upper right is visible in the upper left of figure 115 showing the relative location compared with the main fissure. See also figure 121 for relative location. 1) A hornito formed from overpressure in an underlying lava tube. 2) A 20-m-long flow from a breakout over an active tunnel. 3) Two ephemeral vents had recently opened in the roof of the tunnel just prior to this photo being taken. 4-5-6) The longest breakout flow observed was 220 m long and began at an ephemeral vent located downstream of points 1, 2, and 3. The flow surface was 10 m wide near 4), spreading out and cooling farther downstream (5 and 6). Incandescent lava was still visible near the flow front (6) in two lobes. 7-8) Two other breakout flows from ephemeral vents 520 meters from the main vent were also visible, 50 and 180 m long, respectively. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 2 août 2017 à 16h30 Heure locale).
Figure (see Caption) Figure 120. Visible incandescence and strong degassing were apparent from the smaller vent at the eruptive site on 2 August 2017 at Piton de la Fournaise. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 2 août 2017 à 16h30 Heure locale).

Estimates of the flow rates during the first week of August were less than 1-2 m3/s, and the total lava volume emitted on the surface was measured at 7.2 +/- 2.3 million m3. A larger breakout from a tunnel on 5 August was visible in the OVPF webcams and fed a surface flow over several hundred meters for several hours. By 6 August 2017 the activity was focused mainly in lava tunnels with a few surface breakouts, although incandescence was visible from the small vent seen in imagery available in Google Earth (figure 121). Small ejecta was observed during 7-9 August from the remaining active small vent on the N flank of the cone (figure 122).

Figure (see Caption) Figure 121. Imagery from Google Earth captured on 6 August 2017 showed incandescence and degassing from the small vent at the S end of the fissure at Piton de la Fournaise (left plume), as well as degassing from surface breakouts along the still active lava tunnels to the SE. Courtesy of Google Earth.
Figure (see Caption) Figure 122. Only the small vent on the N side of the cone was still incandescent at Piton de la Fournaise on 9 August 2017. N is to the upper right. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 9 août 2017 à 17h00 Heure locale).

Observations made on 14 August 2017 indicated lava was still active in tunnels as pahoehoe flows were observed about 2 km from the active vent. A brief increase in seismic and surface activity occurred on 16 August. The Piton de Bert webcam captured short-lived lava fountains at the E edge of the eruptive cone. Seismic tremor intensity increased rapidly and then oscillated during 16-17 August. The minor inflation of the cone that had been observed since 1 August ceased by 18 August. Field measurements on 21 August demonstrated a significant decrease in flow activity since 12 August. The volcanic tremor signal was stable at a low level on 25 August; it decreased significantly on 27 August and disappeared altogether about 0300 local time on 28 August 2017, leading OVPF to conclude the eruptive phase had ended.

A number of indications led OVPF to conclude that two migrations of magma that did not reach the surface occurred between 16 August and 1 September. Increased seismicity began on 16 August and was accompanied by a measured increase in SO2; satellite measurements showed two areas of inflation SE of the active fissure between 7 and 25 August. A seismic swarm in the same area was recorded during 24 and 25 August (figure 123). Overflights by OVPF on 25 August did not identify any new fissures associated with the seismic events and inflation.

Figure (see Caption) Figure 123. A seismic swarm on 24 and 25 August 2017 at Piton de la Fournaise led OVPF to conclude that magma was moving beneath the surface in an area SE of the active fissure zone. Courtesy of and copyright by OVPF/IPGP (Bulletin mensuel du lundi 2 octobre 2017).

After the seismic swarm, the number of daily seismic events decreased to less than one per day by the end of September 2017. OVPF reported minor inflation during the second half of October along with a slight increase in seismicity. Inflation stabilized in November but increased again during January 2018 (figure 124). A gradual increase in shallow seismicity beneath the summit craters was recorded during the second half of February. It was accompanied by an increase in CO2 concentrations in the soil as well, which rose to some of the highest levels since measurements began in 2015.

Figure (see Caption) Figure 124. Deformation at Piton de la Fornaise from 14 July 2017 to 28 February 2018. The eruption of 14 July- 28 August 2017 is shown in yellow. The y-axis measures the change in length in centimeters of a N-S line crossing the Dolomieu crater between two GPS receivers. The raw data is shown in black and the blue line is the data smoothed over a week. A rise means elongation and therefore swelling of the volcano; conversely, a decrease indicates contraction and therefore deflation of the volcano. Courtesy of and copyright by OVPF/IPGP (Bulletin mensuel du jeudi 1 mars 2018).

Thermal anomaly data. The MIROVA project thermal anomaly record shows both the episodic nature of the activity and the cooling signature of the flows that continued beyond 28 August 2017 when OVPF noted the cessation of tremors associated with eruptive activity (figure 125). The MODVOLC thermal alerts first appeared on 13 July 2017 and continued persistently with multiple daily alerts until 23 August 2017.

Figure (see Caption) Figure 125. MIROVA thermal anomaly data for Piton de la Fournaise for the year ending 5 January 2018. The eruption of February 2017 had very little cooling after the tremors ceased at the end of February, but the July eruption had significant cooling evident for more than two months after the cessation of seismic tremors on 28 August 2017. Courtesy of MIROVA.

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

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise (OVPF), Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); 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/).


Kilauea (United States) — March 2018 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Activity continues at Halema'uma'u lava lake, and at the East Rift Zone 61g flow, July-December 2017

Hawaii's Kilauea volcano continued its eruptive activity, intermittent for thousands of years and continuous since 1983, throughout 2017. The summit caldera formed about 500 years ago, and the East Rift Zone (ERZ) has been active for much longer. Lava lakes were intermittent in and around Halema'uma'u crater at the summit until 1982. Lava has been continuously flowing from points along the ERZ since 1983, and the episode 61g flow was still vigorous through the end of 2017. A large explosion within Halema'uma'u Crater in March 2008 resulted in a new vent with a lava lake that has been continuously active through 2017.

The US Geological Survey's (USGS) Hawaii Volcano Observatory (HVO) has been monitoring and researching the volcano for over a century, since 1912. Quarterly Kilauea reports for July-December 2017, written by HVO scientists Carolyn Parcheta and Lil DeSmither, form the basis of this report. MODVOLC, MIROVA, and NASA Goddard Space Flight Center (GSFC) provided additional satellite information about thermal anomalies and SO2 plumes.

The lava lake inside the Overlook vent at Halema'uma'u Crater continued to rise and fall during the second half of 2017 with no significant lake level changes and a few periods of spattering. The lake level overall was lower at the end of the year than during much of the year, reflecting long-term deflation of the summit. There were no major explosive events from rockfalls, but smaller sloughs of veneer (thin layers of recently cooled lava that adhere to the vent walls) without accompanying explosions were common. Ongoing subsidence at Pu'u 'O'o, especially around the West Pit prompted moves of monitoring equipment, but little else changed at the cone.

The episode 61g lava flow continued with numerous surface breakouts from areas near the vent all the way down over the pali and into the ocean at the Kamokuna delta during July-December 2017. Changes in the subsurface flow in lava tubes contributed to changing locations of surface breakouts, which were still active at the end of the year. The lava flowing into the ocean at Kamokuna slowed and finally ended in November with changes occurring on the delta in the final weeks of its activity.

Activity at Halema'uma'u. For the second half of 2017, activity at the lava lake inside the Overlook crater continued with little change from January-June. The lake's surface circulation pattern was typical, with upwelling in the N and subsidence of the crust along the southern lake margin, but also around the entire edge of the lake depending on the upwelling location (figure 292). There were often "sinks" a few tens of meters from the SW edge of the lake where the crust folds in on itself and sinks, pulling material away from the wall. A noticeable lava veneer buildup often occurred on the southern margin, where the surface crust was most consistently subducting. Short-term spattering events lasted minutes to hours and occasionally altered the surface crust motion by creating localized subsidence. Throughout the period, spattering was often confined to a grotto at the SE sink. On most days, two or more spattering sites were active simultaneously.

Figure (see Caption) Figure 292. Commonly referenced features and geographic nomenclature at the Halema'uma'u lava lake which is inside the Overlook vent at Kilauea. Geographic directions are faded gray arrows inside the lake with white labels N, S, E, and W, and are distinct from nomenclature cardinal directions (black arrows) used in the text. Satellite image from DigitalGlobe taken on 20 October 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

The lava lake level generally rose and fell over periods of hours to days in response to gas-piston action and to inferred changes in summit lava pressure indicated by deflation-inflation (DI) events. There were a few periods with exceptions when the lake level remained constant for many days at a time, heating up the surrounding walls enough to produce thermal cracking and popping sounds. The total range of the lake level varied between 35 and 40 m during July-December 2017, with the highest level about 17 m below the rim in early September (elevation 1,020 m), and the lowest levels, about 57 m below the rim in late July and September (elevation 977 m) (figure 293).

Figure (see Caption) Figure 293. Halema'uma'u lava lake level measurements for 2017 in meters above sea level at Kilauea. X-axis represents the count of the calendar days, 0 is 1 January 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

There were no significant explosive events triggered by rockfalls, but smaller collapses of veneer and the wall were common, particularly during deflationary phases when the lake level was low and exposed larger areas of the walls. A few larger collapses in September 2017 were big enough to change the geometry of the lake slightly (figure 294). The first, on 8 September at 1806 HST, was a collapse of the large ledge attached to the wall in the southern corner of the lake. This event produced a plume containing ash, a composite seismic event, and lake surface agitation. The following day, 9 September, there was another collapse at 0509. This involved an area of the E Overlook rim composed of mainly lithic deposits, directly above the Southeast sink, which produced a dusty plume, a composite seismic event, and lake surface agitation. On 12 September a thin slice of the southwest lake rim collapsed at 1420, producing a dusty plume, an agitated lake surface for about 10 minutes, and a composite seismic event.

Figure (see Caption) Figure 294. Small changes were visible in the geometry of the Overlook vent at Halema'uma'u from veneer and wall collapses in September 2017 at Kilauea. Left image taken 31 May 2017 by T. Orr shows the areas where the largest collapses took place in September 2017. A large shelf collapsed on 8 September, and the other two dates highlight areas where portions of the lake's lithic wall collapsed. The right photo was taken on 21 September 2017 by L. DeSmither. The photo views are looking SE. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

An interesting effect observed on two veneer collapses occurred on 24 October 2017 at 1617 and 1623. Both were silent events but were noticed because they visually depressed the lake as they fell in and sent a small "wave" propagating outward before spattering began a few seconds later. The wave did not make it more than half way across the lake in either case, and both spattering events lasted only a few minutes. Several veneer ledges built up and subsequently collapsed around the lakes perimeter but were most notable on the SW corner of the lake. Three collapses, on 5 December at 0400 and 7 December at 1856 and 2024, enlarged the NNE edge of the lake towards true N, but did not produce a spatter deposit or explosion (figure 295). Another rockfall occurred on the N margin of the lake on 23 December 2017 at 1552 and triggered a large spattering event.

Figure (see Caption) Figure 295. View from the SW time-lapse camera at Kilauea into the lava lake at Halema'uma'u showing the locations of two collapses in early December 2017 that expanded the Overlook vent towards the NNE. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Activity at Pu'u 'O'o. During July-December 2017, there were only minor changes in the main crater of Pu'u 'O'o as recorded by the PO webcam, PT webcam, and the West Pit time-lapse camera. Due to slight subsidence, altered ground, and widening cracks first noted in August, the West Pit time-lapse camera was relocated 20 m to the SE on 12 October, and roughly 25 m further back from the rim on 1 November after new crack expansion was observed.

During the month of August 2017 there was slight subsidence of the W portion of the crater floor, and around 20 August a crack opened up in the S embayment with three heat locations. There appeared to be slight subsidence of the E side of West Pit from the time-lapse imagery spanning 22 November to 12 December. This subsidence accelerated during 15-17 December, but then was slower through the end of the year. The deformation data confirmed subsidence at Pu'u 'O'o, but it seemed to be confined to the land bridge separating the main crater and the West Pit lava pond. The lava pond inside of the west pit rose slightly during the period from around an elevation of 847 m in early August to 849.5 m on 12 December when measured during site visits about every three weeks. A thick surface crust and sluggish plate motion was typical at the lava pond.

The time-lapse camera located on the E rim of the lava pond (through October) captured three rockfalls in July and two in August that disturbed the pond's surface. On 30 September 2017 a collapse of the west pit's SE rim also broke off a portion of the ledge below, as it was impacted by the falling rocks (figure 296). The collapse was large enough to agitate the pond surface for several tens of minutes, and produced a small step in the tilt at the POC tiltmeter.

Figure (see Caption) Figure 296. The West Pit lava pond time-lapse camera at Kilauea's Pu'u 'O'o crater captured the area of the rim that collapsed (circled in upper left corner) at 0054 HST on 30 September 2017. The larger circle shows where the lower ledge broke off as a result of the impact. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

The pond surface was also disturbed from rockfalls on 22, 28, and 31 October 2017. The first two events were on the N side of the West Pit rim, and the events on 31 October were on the S side of the rim. A small rockfall that triggered minor spattering was witnessed during an overflight on 1 November (figure 297). After 1 November, when the camera was moved away from the rim, it no longer had direct views of the pond. One of the E spillway spatter cones collapsed into the lava tube that was feeding the 61g flow on 20 November and provided a skylight into the tube for a day before it crusted over. On 12 December, a large talus pile on the NNE side of West Pit was evidence of rock falls near the original time-lapse camera site. The talus, likely resulting from several rock falls, piled up onto the lava coated bench.

Figure (see Caption) Figure 297. A rockfall witnessed at Kilauea's Pu'u 'O'o cone during a 1 November 2017 overflight. A small event on the W side of the pond triggered minor spattering. The surface of the pond had large plates with wide cracks. Left photo by L. DeSmither, right photo by C. Parcheta. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Activity at the East Rift Zone, episode 61g flow field. The 13 June 2017 breakout that had started on the upper flow field, approximately 1.1 km from the vent, was the largest area of active surface flows on the 61g flow during July-September. Ranging between 2.6–5.8 km from the vent, the breakout significantly expanded the upper flow fields western flow margin. This breakout remained active through the end of September (figure 298). On 26 June 2017 a breakout started near the top of Royal Gardens and quickly advanced down the pali, east of the main flow field. By 6 July the front of the breakout had extended 500 m beyond the pali base with fluid pahoehoe at the front, and a small a'a channel on the steep part of the pali. Slow advancement of the flow placed it approximately 1.5 km from the emergency road near the coast by 9 August before the flow front stalled. When mapped again on 15 August, the closest active flows were about 2.1 km uphill from the road. Intermittently during 1-20 September the breakout produced channelized flows on the steep part of the pali, sometimes as often as every 24 hours. By the end of September active surface flows had advanced to approximately 1.6 km from the emergency road (figure 298).

Figure (see Caption) Figure 298. Changes to the extent of Kilauea's active episode 61g flow field between 2 July and 28 September 2017, showing the flow margin expansion in red. The yellow line indicates the active lava tube beneath the surface flow. During this time, the flow field expanded an additional 165 hectares from the previous 1,007 hectares (as of 2 July), to a total of 1,172 hectares, increasing the flow field area by 16 percent. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

Two other breakouts that started near the episode 61g vent were also active during July-September 2017. The 5 March breakout, which had advanced downslope during its 4 months of activity, was weakly active on 10 July, with two small lava pads observed approximately 4.8 km from the vent. By the time of the overflight on 9 August, the breakout was inactive. On 26 July around 1025 HST, a new breakout started about 1.1 km from the vent and remained active through the end of September with flow activity located 1.1-2.5 km from the vent. On 27 August at roughly 0945 a breakout began on the steep part of the pali originating from the main 61g tube. By 1 September the breakout was at the base of the pali and spreading onto the coastal plain. A few other channels were reported on this area of the pali, and activity continued through the end of September with very little advancement across the coastal plain (figure 299).

Figure (see Caption) Figure 299. A view looking NW at the breakouts on the Pulama Pali and the coastal plain of Kilauea's East Rift Zone. The majority of the 61g surface flows that spread across the coastal plain were supplied by the 26 June 2017 breakout (right of the kipuka, green area, center right); the breakout that started on 27 August (left of the kipuka, steaming) supplied a smaller pad of flows closer to the base of the pali. A 'kipuka' is an Hawai'ian term for an "island" of land completely surrounded by one or more younger lava flows. Photo taken on 21 September 2017 by L. DeSmither. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

The 26 June 2017 breakout remained active and stable through the end of 2017, forming a tube from its breakout point to midway down the pali on the E side of the 61g flow. The area where breakouts from 5 March, 13 June, and 26 July occurred (1.1 km from vent) also remained intermittently active through the end of 2017 (figure 300).

Figure (see Caption) Figure 300. The lava flow field expansion for the 61g lava flow at Kilauea between 1 October and 31 December 2017. In addition to continued activity from the longer-lived breakouts fueling the expansion shown in red, nearly 90 known shorter-lived surface breakouts occurred, based on observations from webcams, overflights, and satellite data. Changes in the breakout locations are seen in the progression of orange, red, and purple dots after the 61g tube became blocked by a graben collapse on the delta near the end of September (see discussion in next section). The yellow lines indicate lava tube locations underneath the surface flow. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Numerous overflows originating on the sea cliff began in early October 2017. These breakouts occurred within 310 m of the sea cliff and persisted for nearly a month. There were also approximately 20 short-lived breakouts in October above the sea cliff, each lasting 1-3 days. They were located mostly in clusters on the upper flow field at 1, 2, and 3.5 km from the vent, along the top and base of the pali, and from the coastal tube.

An estimated 35 tube breakouts occurred during November 2017; they typically lasted 2- 10 days, and were located inland of the October breakouts. Locations of activity were in the upper flow field almost entirely between 2 and 3.5 km from vent, with three closer breakouts at 0.5, 0.8, and 1 km from vent. The two active tubes on the pali continued to have breakouts at the top and base of the cliff, but also started breakouts midway downslope (figure 301). At 0805 on 7 November, a viscous breakout occurred approximately 500 m above the sea cliff. The small breakout came directly from the 61g tube and lasted for roughly four and a half days. Another viscous breakout from the tube occurred approximately 950 m upslope of the sea cliff from 18-23 November. A week after that, a third viscous breakout occurred about 2 km from the sea cliff. By the end of November, there was no further breakout activity on the delta or the distal half of the coastal plain.

Figure (see Caption) Figure 301. A pali breakout from the 61g lava tube observed during a 20 November 2017 overflight at Kilauea. The photographer estimated the active breakout at tens of meters across. Photograph by C. Parcheta. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

During December 2017, an estimated 30 breakouts were recorded from the 61g flow tube, however these were often longer, lasting up to a week on the upper flow field, and with near perpetual breakouts on the pali throughout the month, which made quantifying the exact number difficult. A new breakout occurred 500 m from the 61g vent on 1 December and lasted through 20 December. This breakout, and the whole area between 500-1,200 m from the vent, poured lava onto the eastern upper flow field (figure 300). Most of the upper flow field activity was focused very close to the vent, between 350-800 m; additional activity also occurred at the 1 km location and a few continued breakouts were noted from the 2-3.5 km region. The coastal flow field activity was sluggish and mostly a result of the near-constant pali tube breakouts reaching the base. On 9 December a new voluminous breakout began near the top of the pali that burned through the kipuka near the center of the flow field (figures 302 and 303). This major breakout lasted through the end of the year and produced mostly 'a'a channels on the pali with pahoehoe at the pali base. Pali tube breakouts occurred at nearly every elevation but seemed to move higher up the slope as the month came to a close. Activity did not advance more than 400 m from the base of the pali.

Figure (see Caption) Figure 302. A small channel of lava burned through the kipuka on Kilauea's Pulama Pali on 21 December 2017. Figure 299 shows the kipuka on 21 September, still intact. Photograph by C. Parcheta. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).
Figure (see Caption) Figure 303. Close up of the 'a'a flow front near the base of the pali at Kilauea, which burned the remaining trees within the kipuka. Photograph by M. Patrick on 21 December 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Time series thermal maps of the 61g flow field overlaid on all of the tubes mapped from the field to date suggested to HVO scientists that some of the many breakouts during October-December 2017 may have come from reactivation of an earlier tube thought to be inactive since at least April 2017 (figure 304). Breakout locations coincided with the former tube trace, and happened at least five times between 21 September and 5 January 2018.

Figure (see Caption) Figure 304. A time series of thermal maps from overflights at Kilauea with all 61g tubes overlaid. Solid white lines are tubes active as of the image date, indicated by a thermal trace. Long dashed white line is the main (western) tube that became blocked at the end of September 2017. Dotted lines are older tubes from 2016 that were active when the 61g flow first crossed the coastal plain. These tubes were no longer noted in public maps by April 2017. In all thermal maps from October-December 2017, there was activity (indicated by black arrows) located above the older tube down the center of the flow field suggesting to HVO scientists that this tube may have been still producing breakouts from backlogged lava in the system. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Activity at the East Rift Zone, Kamokuna ocean entry. By the end of June 2017, flows from multiple breakouts had resurfaced the delta of the Kamokuna ocean entry, covering earlier cracks, and building up and steepening the delta's landward side. These surface breakouts continued into early July, but by 10 July several new cracks had appeared, two of which visibly spanned the width of the delta (figure 305). Slumping of the seaward half of the delta and expansion of the cracks was visible in time-lapse camera images until the end of September.

Figure (see Caption) Figure 305. The Kamokuna ocean entry delta at Kilauea with visible large coast-parallel cracks which span most of the delta's width. On the W (left) side of the delta, the largest crack has been partially buried by the 'a'a flow produced by the 19 August 2017 breakout which started on the sea cliff roughly 100 m inland (lighter in color). Photo taken on 1 September 2017 by L. DeSmither. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

On 19 August 2017 around 0405 HST a breakout started on the sea cliff approximately 100 m upslope of the ramp, and five minutes later lava was spilling over the sea cliff and onto the delta. The breakout point and the lava falls over the cliff were both on the W side of the 61g tube. The lava produced a small 'a'a flow on the delta (figure 305), during its short-lived activity that lasted roughly 9.5 hours. Late on 19 August, the time-lapse camera also captured two images of littoral explosions in the center of the delta that produced a large spatter deposit on the delta's surface.

Three more sea cliff breakouts started on 23 September 2017. The first was brief "firehose-like" activity that began in the early morning hours. Based on the delta surface flows it produced, activity lasted less than 24 hours. Later views of the cliff face revealed that the "firehose" came out of a narrow horizontal crack E of the ramp, that was less than a meter below the top of the cliff. Later that day, on the sea cliff near the ocean entry, two new breakouts started, one to the E and one to the W of the tube. The E breakout originated roughly 70 m upslope of the sea cliff, and the breakout point had been fractured and depressed. Its thin pahoehoe flow spread out behind the littoral cone and came close to the edge of the cliff but did not spill over. The W breakout was visible in the time-lapse camera images on 23 September from around noon until midnight, producing only a few small dribbles of lava over the sea cliff. The breakout point was roughly 100 m upslope of the sea cliff, and buried the breakout from 19 August with thick, viscous pahoehoe. By the end of September, surface flows again covered much of the delta until most of the cracks were obscured, and only the ramp and a small area of the eastern delta close to the sea cliff were still uncovered.

Beginning in late August 2017, the ocean entry plume started to fluctuate regularly, and the plume was often weak or would briefly shut down. A shatter ring (a raised rim depression that forms over active lava tubes) began forming near the front of the delta on 21 August. By 30 August, the repeated uplifting and subsidence of the delta had broken the surface flows and built up a large rubble pile. On 26 September 2017 a bulge formed on the back half of the delta where the slope was steepest (figure 306). This inflationary feature produced steam and a delta surface flow from a crack at its base.

Figure (see Caption) Figure 306. Changes at the Kamokuna ocean entry at Kilauea between 26 June (left) and 26 September 2017 (right). The delta grew about 1.62 hectares (4 acres) in size, but also thickened from multiple breakouts resurfacing the delta. The delta cracks are not visible in either photo because the delta had been newly resurfaced in both images. Photos taken by L. DeSmither. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

HVO scientists concluded that the bulge observed on 26 September 2017 was the result of the formation of a spreading-induced graben in the middle of the delta that obstructed the 61g tube between 23 and 26 September 2017 (figure 307, top row). During the first part of October, additional breakouts from the tube above the sea cliff produced lava falls that poured down on the W side of the tube (figure 307, middle row). A few breakouts in the latter half of October flowed to the E side of the tube (figure 307, bottom row). The delta did not expand much in area during October-December 2017, but it thickened greatly due to the added volume from the lava falls breakouts and several small sluggish breakouts on the delta. The maximum extent that the delta reached was a little over 4 hectares in October, and then it began to shrink from waves crumbling its edges. By the end of December, the delta had lost about 0.4 hectares (1 acre) of land.

Figure (see Caption) Figure 307. Activity at the Kamokuna ocean entry of Kilauea during September-October 2017. Top: before (left, 19 September 2017) and after (right, 26 September 2017) the graben formation induced by delta slumping. The yellow (left) and orange (right) lines indicate the topographic profile through the middle of the delta. Middle: Aerial photograph (left, C. Parcheta) and thermal image (right, M. Patrick) from a 12 October 2017 overflight showing the extent of lava falls both E and W of the tube. Once the tube became blocked, the whole delta was resurfaced by this outpouring of lava. Bottom: The last of the lava falls occurred on the E side of the tube. The western falls had solidified but were illuminated on the left in this image during the first activity of the eastern lava falls. Image taken by the Kamokuna time-lapse camera on 10 October 2017 at 1842. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

The ocean entry was thought to have fully ceased activity shortly after 12 November 2017. The plume had its first pause in activity on 23 September, and quickly resumed but with decreasing vigor. By 26 September the plume was noticeably weaker and beginning to show intermittent pauses, which continued and became more prolonged through 4 November. The following day (5 November) was the first day with no plume visible in the HPcam, and 6 November was the last day an ocean entry plume was visible in the HP webcam. Ocean entry was active and observed during field visits between 6-11 November, but its weak, diffuse plume was not visible to the HP camera. The time-lapse camera stopped taking photos during the end of the Kamokuna delta activity in the late afternoon on 11 November (figure 308). This malfunction was discovered during a field visit on 12 November; the batteries were replaced a week later. The last photo of known lava activity on the delta was taken on 12 November, and the delta was likely completely inactive within a day or two.

Figure (see Caption) Figure 308. Kamokuna delta at Kilauea on 11 November 2017 shortly before the edges began to crumble from the continuous wave action. Photograph by Kamokuna time-lapse camera. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

During a 12 December 2017 overflight, an HVO scientist witnessed a collapse of a small portion of the sea cliff east of the tube into a yellow talus pile on the back portion of the delta, removing the evidence of the lava falls.

Satellite thermal and SO2 data. In addition to field observations, satellite-based thermal and SO2 data provide important insights into the ongoing activity at Kilauea. The many MODVOLC thermal alerts issued during July-December 2017 show the varying intensity and locations through time of the many breakouts along the episode 61g flow field from near the vent at the base of Pu'u 'O'o all the way down to the Kamokuna ocean entry delta (figure 309).

Figure (see Caption) Figure 309. MODVOLC thermal alert pixels for the episode 61g lava flow at Kilauea during various weeks of July-December 2017. Green grid squares each represent 1 square km. Areas of activity discussed in the earlier text are labelled. Each image represents seven days of thermal alerts. Upper left: 2-8 July 2017, the 13 June breakout expands the upper flow field, and the front of the 26 June breakout has extended beyond the base of the pali. Upper right: 23-29 July 2017, the 26 July breakout appears about 1 km E of the vent, breakouts are active on the pali, and surface flows are active on the Kamokuna delta. Center left: 27 August-2 September 2017, extensive new breakouts along the base of the pali created multiple alerts in that area. Center right: 1-7 October 2017, abundant breakouts just above the delta create lava falls over the delta after the graben formed in late September. Lower left: 12-18 November 2017, many breakouts were observed near the vent and on the pali during November. Lower right: 17-23 December 2017, breakouts were focused on the upper slope and the pali where the kipukas burned up in December, and lava was no longer flowing into the ocean at the delta. Courtesy of HIGP, MODVOLC.

The MIROVA project thermal anomaly graph of distance from the summit also shows the multiple sources of heat at Kilauea and the migration of those sources over time (figure 310). The MIROVA center point for relative distances described here is about 10 km (0.1°) E of Halema'uma'u crater. The anomaly locations at about 10 km distance from this point correspond to both the lava pond at Pu'u 'O'o crater and the Halema'uma'u crater lava lake. Those about 20 km away correspond to the Kamokuna ocean entry. Anomalies that migrate over time between 10 and 20 km distance trace the movement of the many episode 61g flow breakouts between Pu'u 'O'o and the Kamokuna ocean entry during July-December 2017.

Figure (see Caption) Figure 310. The MIROVA project thermal anomaly graph of distance from the summit shows the multiple sources of heat at Kilauea and the migration of those sources from 1 June 2017-15 January 2018. The MIROVA center point for relative distances described here is about 10 km (0.1°) E of western Halema'uma'u crater. The anomaly locations at about 10 km distance (y-axis) correspond to both the lava pond at Pu'u 'O'o crater and the Halema'uma'u crater lava lake. Those about 20 km away correspond to the Kamokuna ocean entry. Anomalies that migrate over time between 10 and 20 km distance trace the movement of the many episode 61g flow breakouts between Pu'u 'O'o and the Kamokuna ocean entry during July-December 2017.

Kilauea emits significant SO2 that is recorded by both ground-based and satellite instruments. Sulfur dioxide emissions exceeded density levels of two Dobson Units (DU) multiple times every month during the period (figure 311). Increases in SO2 flux are caused by many factors including increases in the number and size of surface lava breakouts as well as activity at the summit crater.

Figure (see Caption) Figure 311. Sulfur dioxide emissions generally exceeded density levels of two Dobson Units (DU) multiple times every month at Kilauea and are recorded daily in satellite data. Increases in SO2 emissions are caused by many factors including increases in the number and size of surface lava breakouts as well as activity at the summit crater. A few of the SO2 plumes captured by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite with DU greater than 2 during July-December 2017 are shown. The prevailing winds on Hawaii blow from NE to SW, so plumes generally drift SW. UR: 23 July 2017, UL: 12 September 2017, LR: 9 October 2017 and LL: 28 December 2017. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: http://hvo.wr.usgs.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Manam (Papua New Guinea) — March 2018 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Ash plumes and Strombolian explosions increase, March-May 2017

Manam is a basaltic-andesitic stratovolcano that lies 13 km off the northern coast of mainland Papua New Guinea; it has a 400-year history of recorded evidence for recurring low-level ash plumes and occasional Strombolian emissions, lava flows, pyroclastic avalanches, and large ash plumes. Activity during 2016 included only two episodes of ash emissions, during early March and mid-July, but persistent thermal activity (strongest between March and July 2016) was intermittent throughout the year (BGVN 42:03). Activity from January 2017-January 2018, discussed below, included increased Strombolian activity, lava flows, and ash emissions during February-May 2017 that led to evacuations and concern for local residents. Information about Manam is primarily provided by Papua New Guinea's Rabaul Volcano Observatory (RVO), part of the Department of Mineral Policy and Geohazards Management (DMPGM). This information is supplemented with aviation alerts from the Darwin Volcanic Ash Advisory Center (VAAC). MODIS thermal anomaly satellite data is recorded by the University of Hawai'i's MODVOLC thermal alert recording system, and the Italian MIROVA project; sulfur dioxide monitoring is done by instruments on satellites managed by NASA's Goddard Space Flight Center.

Summary of 2017 activity. A strong surge in thermal activity beginning in mid-February 2017 lasted through mid-June. Low levels of intermittent activity continued for the rest of 2017, with a short-lived increase during late December 2017 and early January 2018 (figure 35). Strong multi-pixel daily MODVOLC thermal alerts began on 17 February and continued through 29 May 2017. Plumes of SO2 were detected with satellite instruments in late February, early March, and during the second half of May.

Figure (see Caption) Figure 35. The MIROVA project Log Radiative Power signal for Manam increased significantly during late February 2017 and remained elevated through mid-June. Significant ash plumes and Strombolian activity were reported from early March-late May, after which only a few low-level ash plumes were reported through the end of 2017. Log Radiative Power graph of the year ending 17 January 2018. The occasional points shown in black indicate thermal sources located more than 5 km from the summit, and are likely unrelated to volcanic activity. Courtesy of MIROVA.

The first report of ash emissions in 2017 was on 2 March. Activity increased in late March, and again during the second half of April. Most of the many ash plume events that took place during May rose to 2-5 km altitude, but on 4 and 26 May they rose to over 12 km altitude. Ash plumes were noted on only two days during June, and none during July. Minor low-level ash emissions resumed in early and mid-August. The final VAAC report of 2017 was issued on 2 September.

RVO reported incandescent activity, Strombolian explosions, lava and pyroclastic flows, and ash emissions during February-May 2017 from both the Main and Southern craters (figures 36 and 37), and steam-and-gas emissions throughout the year. Activity during late February to mid-April occurred at both craters; most of the activity during late April and May came from Southern Crater. The events of mid-May caused ashfall across the island. Lava flows and pyroclastic flows in mid-April and mid-May led to evacuations from several villages. Incandescence was observed once from Southern Crater in November and once from Main Crater in December.

Figure (see Caption) Figure 36. Activity at Main Crater of Manam during 2017. The five graphs represent the rate (right y-axis) and intensity (left y-axis) of various activity at the volcano. Steam-and-gas emissions were observed throughout the year (bottom graph; green bars, blue circles). Explosions were heard during mid-February-April (second from bottom graph; blue bars, green circles). Ash emissions were reported from mid-February through April, and at the end of May (middle graph; purple bars, black crosses). Incandescence was observed from mid-February-April, once at the end of May and once in early December (second from top graph; black bars, red x's). Incandescent bombs, lava flows or pyroclastic flows were observed during mid-February-April and at the end of May (top graph; red bars, black diamonds). Courtesy of Steve Saunders, RVO.
Figure (see Caption) Figure 37. Activity at Southern Crater of Manam during 2017. The five graphs represent the rate (right y-axis) and intensity (left y-axis) of various activity at the volcano. Steam-and-gas emissions were observed throughout the year (bottom graph; green bars, blue circles). Explosions were heard during February-May and in mid-July (second from bottom graph; blue bars, green circles). Ash emissions were reported from mid-January through May (middle graph; purple bars, black crosses). Incandescence was observed in early January, from late January-May, and once in early November (second from top graph; black bars, red x's). Incandescent bombs, lava flows, or pyroclastic flows were observed from mid-February-mid May (top graph; red bars, black diamonds). Courtesy of Steve Saunders, RVO.

Activity during February-March 2017. After a break during much of December 2016, low-to-moderate pulses of thermal anomalies were recorded briefly by the MIROVA project early in January 2017 (BGVN 42:03, figure 34). Activity increased again in mid-February with stronger MIROVA anomalies and multi-pixel MODVOLC thermal alerts. Sulfur dioxide plumes were released on 25 February and 4 March 2017 (figure 38).

Figure (see Caption) Figure 38. Sulfur dioxide emissions from Manam increased in late February 2017 along with increased thermal activity. SO2 plumes were captured by the OMI instrument on the Aura satellite on 25 February 2017 (left) and 4 March 2017 (right). Another emission, partly obscured, on 4 March is likely from Bagana on Bougainville Island to the SE. Courtesy of NASA Goddard Space Flight Center.

MODVOLC thermal alerts were issued on 13 days during March, many days had 3-6 alerts. The Darwin VAAC issued the first Volcanic Ash Advisory of 2017 on 2 March based on a pilot report of ash extending N of the volcano at 3 km altitude. The next report, on 20 March, indicated an ash plume visible in satellite imagery moving NE at 2.4 km altitude. It extended 80 km E of the summit the following day. Mostly-steam emissions with minor ash content were reported on 23 March, extending 75 km SE at the same altitude.

Activity during April 2017. Intense multi-pixel MODVOLC thermal alerts continued into April 2017; days with multiple alerts included 2, 14, 22-23, and 25-26 April. RVO released a Volcano Information Bulletin on 16 April 2017 noting a sudden increase in RSAM values beginning on 15 April, and indicating that a small-to-moderate eruption was ongoing from Main Crater. Incandescence was visible during most nights of April from both Main and Southern craters. RSAM values increased by two orders of magnitude during 16-17 April (figure 39). During that night, a brief report from Dugulava village on the SE side of the island indicated that large incandescent lava fragments were falling into valleys to the N and SW, accompanied by loud explosions. Strombolian activity at Southern Crater increased on 18 April, and was accompanied by emissions of dark ash plumes that rose a few hundred meters above the crater and drifted NW. Two small pyroclastic flows were channeled into valleys on the SE and SW flanks, and terminated at about 1,000 m elevation. Strombolian activity subsided by late afternoon, but weak gray ash emissions continued. At Main Crater, white-gray ash plumes continued with bursts of incandescence at about 5-minute intervals.

Figure (see Caption) Figure 39. A spike in RSAM values during 16-17 April 2017 coincided with increased Strombolian activity from Southern Crater at the summit of Manam. Courtesy of RVO-DMPGM (Volcano Information Bulletin-No. 06-042017, Issue Date: 19th April 2017).

RVO reported that activity diminished after 18 April but continued at low levels through 21 April; explosions were still heard from both Main and Southern Craters. Both craters were incandescent, but only Southern Crater ejected incandescent tephra, which became briefly intense during the morning of 20 April. Pale gray-to-brown plumes containing minor amounts of ash rose from both craters and drifted SE. RSAM values began to rise again on 22 April, and Strombolian activity continued during 22-24 April (figure 40). According to a news article from 25 April (The National) the Alert Level was raised to Stage 3, and an official on the island noted that evacuations of women and children had begun to Bogia, about 16 km SW on the mainland.

Figure (see Caption) Figure 40. An explosion at Manam on 22 April 2017. Incandescence at the summit and steam emissions are visible beneath the meteoric clouds. Photo: USGS/Landsat-8 OLI. Courtesy of Radio New Zealand.

The Darwin VAAC reported an ash plume at 4.6 km altitude extending about 35 km SE from the summit on 24 April. The next day, an ash plume was observed drifting a similar distance SW at 3 km altitude. The drift direction changed to WSW then W during 26 April, and the plume was last observed about 65 km from the summit. Infrared imagery indicated ongoing activity at the summit.

Strombolian activity and strong, dark-gray ash emissions continued during 24-25 April; activity declined for a few days before the next pulse began during the early morning of 28 April with Strombolian explosions that were heard at the Bogia Government Station. Most of the lava fell back into the crater, but some traveled down the SW and SE valleys, and minor amounts of ash fell on the SE and W parts of the island.

A pulse of moderately-high Strombolian activity occurred from Southern Crater during the early morning of 30 April 2017. The episode lasted about two hours and produced a small pyroclastic flow that was channeled into the SW valley and stopped at about 200 m elevation. Ejected incandescent lava fragments landed mostly within the crater, but some traveled down the SW and SE valleys. Ash and scoria up to 40 mm in diameter fell on the E side of the island in Abaria and Boakure.

Activity during May 2017. The strongest thermal activity of the year was recorded during May 2017. MODVOLC thermal alerts were issued on 4, 5, 9, 13, 14, 17, 18, 25, and 29 May, with 21 alerts issued on 18 May and a single alert on 29 May that was the last issued for the year. RVO reported a Strombolian event from Southern Crater, lasting from about 1700 on 4 May to 0700 the following morning. A lava flow descended into the SW valley to 600 m above sea level, and minor amounts of ash fell in areas stretching between Warisi to the E, Dugulaba on the S, and Boda and Baliab on the NW parts of the island.

The Darwin VAAC reported an ash plume drifting E at 3 km altitude late on 4 May 2017 (UTC). About an hour later, they reported a much higher altitude ash plume moving S from the summit at 12.5 km altitude, in addition to continuous ash moving E at 3 km altitude. The high-level ash plume dissipated after about five hours, but the lower-level emission continued to be visible in satellite imagery drifting E, then NE at least 25 km from the summit through 7 May, after which activity subsided. RVO reported steam-and-gas emissions from Southern Crater on 13 May. Incandescent lava fragments were ejected during the early morning of 14 May, generating a lava flow that traveled down the SW valley to an elevation of 600-700 m.

The next VAAC report, on 14 May 2017, noted an ash plume drifting NW at 4.6 km altitude 35 km from the summit. Later in the day, they reported another short-lived ash plume that rose to 5.5 km altitude drifting almost 100 km W, and a large hotspot over the summit. The lower-altitude plume lasted for another day before dissipating. RVO reported light gray to dark gray ash plumes during 15-18 May. The Darwin VAAC reported multiple plumes moving W at 2.1-2.4 km altitude on 17 May, and continuous emissions extending WNW on 18 May. RVO reported explosive activity on 18 May; a small lava flow traveled down the SW valley, but not as far as the 13-14 May flow. A weak ash emission, which dissipated after a few hours, was reported on 19 May drifting W at 2.7 km altitude. The Darwin VAAC reported that a substantial ash emission on 26 May 2017 was seen in satellite images drifting 55-75 km W at 12.2 km altitude. A second plume from a continuous lower-level eruption was reported later in the day rising to 4.6 km altitude. Both plumes dissipated by the end of the day. Sulfur dioxide emissions were captured by satellite instruments on 18 and 27 May (figure 41).

Figure (see Caption) Figure 41. SO2 plumes from Manam were captured on 18 (left) and 27 (right) May 2017 by the OMI instrument on the Aura satellite. Eruptive activity was reported by RVO and ash emissions were reported by the Darwin VAAC on 18 May, and a large ash emission was reported by the Darwin VAAC on 26 May. Courtesy of NASA Goddard Space Flight Center.

Activity during June-December 2017. Activity decreased significantly after May 2017 and was low for the remainder of the year. RVO noted weak-to-moderate steam plumes on the rare clear-weather days during June; there was no observed incandescence, and very low seismicity. The Darwin VAAC reported an ash plume that rose to 5.5 km altitude and drifted W on 6 June. Later in the day the plume extended WNW at about 2.4 km altitude. It was last observed early on 7 June before dissipating. No further ash emissions were noted by the Darwin VAAC or RVO until 5 August 2017 when the Darwin VAAC observed minor ash emissions moving NW at 2.1 km altitude. The emissions were visible that day and the next before dissipating. A new ash emission was reported late on 7 August, drifting W at 1.8 km altitude for about 8 hours before dissipating early the next day. Another minor plume on 12 August briefly extended 35 km NW at 2.1 km altitude. During 21-22 August, a similar plume was seen at the same altitude. A minor ash emission on 1 September, which also rose to 2.1 km altitude, was only visible for a few hours before dissipating, and was the last emission reported in 2017.

RVO noted incandescence at Southern Crater once in early November, and once at Main Crater in early December. The MIROVA data showed a cluster of thermal anomalies during late December2017 and early January 2018 (figure 35) suggesting a renewed pulse of thermal activity during that time.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

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/); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Radio New Zealand (URL: http://www.radionz.co.nz); The National (URL: http://www.thenational.com.pg).


Poas (Costa Rica) — March 2018 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Increase in phreatic and phreato-magmatic explosions during April through August 2017

Recent activity at Poás has been characterized by intermittent phreatic explosions from the hyperacid lake (figure 118). Explosions were noted in June-August 2016 (BGVN 42:03), but there were no reports explosions since then through March 2017. This report summarizes activity from April 2017 through March 2018. During this period, activity increased substantially during April-August 2017 and thereafter waned. No explosions were reported during 7 November 2017-31 March 2018. Information below was primarily drawn from reports issued by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA).

Figure (see Caption) Figure 118. Landsat imagery of Poás taken 11 April 2016. Courtesy of Digital Globe and Google Earth.

Activity during April 2017. According to OVSICORI-UNA, activity increased substantially at the beginning of 2017, with significant increases in seismicity, steam-and-gas emissions, and surface deformation. Seismicity included numerous long-period (LP) earthquakes, more than 200 daily events between the end of March and the beginning of April, and weak explosions since 30 March. Deformation was characterized by inflation, with a vertical increase of more than 1 cm in a three-month period and an increase of 3 mm horizontally between two sites S and N of the crater separated by 1,570 m.

Gas emissions dramatically shifted toward a more magmatic composition, particularly after 30 March. Sulfur dioxide measurements on 4 April were about an order of magnitude greater than those on 28 March (~180 ± 65 tonnes/day (t/d) vs. ~19 ± 8 t/d), with the dome contributing 25% and the lake 75% of the flow. The increased flow was accompanied by the emergence of new fumaroles that may have contributed to the warming of the lake (which went from 35 to 40°C in just one week). In April, the lake quickly changed from a milky green color to a milky gray color, which suggested that emissions of magmatic gases from vents beneath the lake may have increased. The dome is on the S side of the crater lake and was formed during phreatomagmatic activity between 1953 and 1955; it has been a site of persistent fumarolic degassing for the last 200 years.

OVSICORI-UNA reported that a strong 40-minute phreatic explosion from an area between the lava dome and the hot lake occurred on 12 April 2017, starting at 1830. A plume of steam, altered rocks, sediments, and gases was produced; the height of the column could not be determined due to poor visibility. Ash fell around the crater and in Bajos del Toro (7 km WNW). The water level in the Desague River, with headwaters at the S part of the crater, increased by 2 m. According to news articles (Tico Times, The Costa Rica Star), the National Emergency Commission evacuated residents living near the river. The Poás Volcano National Park closed the next day and has remained closed through March 2018.

On 13 April, at 1546, an eight-minute-long explosion produced a plume that rose 500 m above the crater rim. The event rendered a webcam on the N rim inoperable. Explosions at 0758 (strong) and 1055 on 14 April generated plumes that rose to an undetermined height.

A 10-minute-long event that began at 0810 on 15 April again produced a plume of unknown height. Frequent (2-3 events per hour) small, short-lived, phreatic explosions were recorded by seismographs during 15-16 April. A plume that rose 500 m followed an explosion at 0946 on 16 April. Later that day, at 1350, an event generated a plume that rose 1 km. A news article (The Costa Rica Star) reported that boulders as large as 2 m in diameter fell in an area 30 m away from a tourist trail, breaking a water pipe. Rocks also damaged fences and concrete floors in viewing areas. Small, frequent, and short-lived phreatic explosions continued to be recorded through 18 April. A video posted by a news outlet (The Costa Rica Star) showed an explosion ejecting incandescent material.

According to OVSICORI-UNA, on 20 April a dense steam plume rose from a vent in the newly-forming pyroclastic cone at the site of the old dome in the hot lake. Sulfur dioxide levels increased from 1,000 t/d on 13 April to 2,500 t/d on 20 April. During 20-22 April Strombolian activity ejected tephra that fell around the vent within a 300-m radius. Gas-and-ash plumes rose 200 m above the vent. The Cruz Roja (Red Cross) in Grecia reported ashfall in Alajuela (20 km S), Fraijanes (8 km SE), San Miguel (40 km SSE), Carbonal (8.5 km SSW), Cajón (11 km SSW), San Francisco, San Roque (23 km SSE), and San Juan Norte de Poás (8.5 km S). Explosions at 1316 and 1603 on 22 April produced plumes of unknown height. Several more explosions were recorded that day; an event at 2212 was very intense, ejecting bombs large distances. An event at 1215 on 23 April generated a plume of unknown height.

Figure (see Caption) Figure 119. Photo showing location of the acid lake and dome at Poás during or after April 2017. The dotted line follows the outline of the great lake that covered the entire bottom of the caldera during the first half of the last century. Courtesy of OVSICORI-UNA. Borde de Antiguo lago is "Edge of the Ancient Lake"; Tercio norte: Lago is "north third of the lake"; domo is "dome"; Tercio sur: Playón o Angiguo lago is "South Tercio: Playón or Angiguo lake; Fumarola abril 2017 is "fumarole in April 2017; sector de fumarolas 2005-2006 is "sector of fumaroles 2005-226. Courtesy of OVSICORI-UNA (El Domo y el Lago Caliente en el Volcán Poás: Estructuras Básicas para Comprender las Erupciones Actuales. Nota técnica: 16 de abril de 2017).

Activity during May 2017. OVSICORI-UNA reported that large explosions were seismically recorded at 0621 on 1 May and at 1724 on 6 May, though poor visibility prevented visual confirmation of the events. On 10 May, ash emissions were observed. Gas emissions were measured by an instrument mounted on a drone, revealing a gas plume rich in sulfur dioxide and low in carbon dioxide. Deformation was high, with vertical inflation of 3 cm since February.

During 17-23 May, plumes consisted mainly of gas and steam, sometimes including solid material, that rose no more than 1 km above the vent. During 25-26 May, ashfall was reported in some communities around the volcano. Small phreatic explosions were recorded sporadically during 27-30 May.

Activity during June 2017. An explosion reported by OVSICORI-UNA at 1200 on 2 June generated a plume consisting of steam, gases, and minor amounts of ash that rose 600 m above the crater. Another event recorded at 1353 could not be confirmed visually due to weather conditions. An event at 0858 on 6 June generated a plume that rose 1 km.

During 7-8 June, the webcam recorded strong emissions of steam, magmatic gases, and particulates. A sulfur odor was reported in Alajuela, San Ramon (24 km WSW), and Barva (23 km SSE), and incandescence in the area of the crater was recorded at night. OVSICORI-UNA noted that during 8-9 June, a plume of steam, magmatic gases, and particulates rose from two vents; the lake had evaporated and exposed the vents. A minor sulfur odor was reported on the campus of the Universidad Nacional in Heredia. Explosions at 1610 and 1750 on 11 June generated plumes that rose 300 and 600 m above the crater, respectively. Plumes from the vents rose 1 km during 12-13 June. A sulfur odor was noted in Quesada (26 km ENE), Santa Ana (30 km SSE), San José de Alajuela, and San Juanillo Naranjo.

Gas emissions during 13-15 June rose no higher than 500 m above the crater rim and drifted N. During breaks in weather, observers near the crater on 16 June noted ash emissions rising less than 1 km above the crater rim and drifting N. Ash emissions from events at 1340 on 18 June, and 1100 and 1350 on 20 June, rose less than 1 km.

During 20-25 June, plumes of reddish-colored ash, water vapor, and magmatic gases were recorded rising as high as 500 m above two vents during 20-21 June. Magmatic gases and steam plumes rose as high as 1 km above the vents the rest of the period.

Webcams recorded intense incandescence at night during 28-29 June from the bottom of the crater. A sulfur odor was noted in San Rafael de Poás (12 km SSW) and Vara Blanca (10 km ESE). An event at 1115 on 19 June generated a plume that rose 1 km above the vents. An event at 1450 may have generated a plume, but poor visibility did not allow for confirmation.

Activity during July-December 2017. According to OVSICORI-UNA, frequent, but weak Strombolian activity during 1-4 July ejected incandescent material that fell around vent A (Boca Roja). Plumes of steam, magmatic gases, and particulates rose at most 500 m from the vents.

During 4-9 July, plumes of steam, magmatic gases, and aerosols rose 200-600 m above vents A (Boca Roja) and B (Boca Azufrada). Minor incandescence from the bottom of the crater was observed during 4-5 July, and a strong sulfur odor was reported in some areas of Alajuela and Heredia. During 5-7 July, grayish-red ash emissions rose intermittently from vent A, and on 7 July a loud "jet" sound was noted in Mirador. A strong sulfur odor and minor ashfall was reported in some areas of Alajuela. An event at 1450 on 10 July generated a plume that rose 300 m.

OVSICORI-UNA reported that during 12-17 July, gas plumes rose as high as 1 km above vents A and B and drifted SW and NW. From 19 through 24 July plumes of steam, magmatic gases, and aerosols were emitted from vent A, and plumes of steam, gases, and abundant yellow particles of native sulfur rose from vent B. Plumes rose 300-500 m above the vents and drifted W and SW.

On 1 August an event passively produced a plume that rose 500 m above the crater. Incandescence from the bottom of the crater was recorded at night by the webcams. Sulfur dioxide was emitted at a rate of 1,000-1,500 t/d. Activity on 3 August was similar to that in July, except that plumes rose as high as 1 km above the vents. Gas plumes continued to rise from the vents and drift SW and NW at least through 8 August. OVSICORI-UNA reported additional explosions on 22 August (1517 local), 24 August (0920 and 0930), 29 August (0945), 13 September (0820), and 6 November (0915) that rose 300-600 m above the crater rim.

Seismicity. During May and June, some volcano-tectonic (VT) and LP earthquakes were recorded, and tremor levels generally ranged from low-to-moderate amplitude, although higher tremor levels were sometimes detected during 22-30 May. The tremor amplitude often corresponded to the vigor of emissions of steam, magmatic gases, and material from fumarolic vents. Seismic activity was not identified after 30 June, except for a single report that indicated that during 11-14 August seismographs detected low-amplitude tremor, some VT earthquakes, and high-frequency signals indicating gas emissions.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); National Emergency Commission (CNE) (Comisión Nacional de Prevención de Riesgos y Atención de Emergencias (CNE) (URL: http://www.cne.go.cr); Tico Times (URL: http://www.ticotimes.net/); The Costa Rica Star (URL: https://news.co.cr/).


Rincon de la Vieja (Costa Rica) — March 2018 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Phreatic explosions during 29 September-22 October 2017

During the first half of 2017, phreatic explosions at Rincón de la Vieja occurred on 23 May, 11-12 June (however, clouds obscured visible observations), 18 and 23 June, and 5 July (BGVN 42:08). This report describes activity from 6 July through December 2017. Information comes from the Observatorio Vulcanológico Sismológica de Costa Rica-Universidad Nacional (OVSICORI-UNA).

After a small phreatic explosion on 5 July 2017, there were no further reports of any explosions until 29 September when OVSICORI-UNA reported that at 0848 a small phreatic explosion produced a plume that rose 1 km above the crater rim (figure 27); material also flowed down the S flank.

Figure (see Caption) Figure 27. Webcam image of a phreatic explosion at Rincón de la Vieja on 29 September 2017. Courtesy of OVSICORI-UNA (color adjusted).

According to OVSICORI-UNA, events on 3 October at 0848 and 1445 generated plumes that rose 700 m and 1,500 m, respectively. OVSICORI-UNA also reported that on 9 October at 1048, a small explosion produced a plume that rose 700 m above the crater rim. According to news reports (The Costa Rica Star and CRHoy.com) quoting OVSICORI-UNA, an explosion on 22 October at 0640 generated a steam-and-gas plume that rose about 1 km above the crater. There were no further reports of an explosion through the end of December.

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

Information Contacts: Observatorio Vulcanológico Sismológica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/, https://www.facebook.com/OVSICORI/); CRHoy.com (URL: http://www.crhoy.com/); The Costa Rica Star (URL: https://news.co.cr/).


San Cristobal (Nicaragua) — March 2018 Citation iconCite this Report

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Intermittent ash-bearing explosions during 2017; Ash plume drifts 250 km in August.

Nicaragua's San Cristóbal volcanic complex has exhibited sporadic eruptive activity dated back to the early 16th century. More consistent modern record keeping has documented short-lived eruptive episodes every year since 1999. Small explosions with intermittent gas-and-ash emissions are typical. Three single-day explosive events were reported in 2015; a series of explosions on 5 March 2015 generated a 500 m high ash plume, 41 explosions on 6 June 2015 ejected ash 200 m above the summit, and the first of two explosions on 12 June 2015 sent an ash plume 2,000 m above the summit. The next eruption did not occur until 22 April 2016 when 11 explosions were recorded, with the largest sending an ash plume 2,000 m above the summit. Activity from July 2016-December 2017 is covered in this report. Information is provided by the Instituto Nicaragüense de Estudios Territoriales (INETER), and the Washington Volcanic Ash Advisory Center (VAAC).

Following little activity during the remainder of 2016 after the 22 April explosions, small explosions with minor ash were reported in February, March, and April 2017. Significant explosions during 18-19 August sent ash plumes over 200 km W and deposited ash in numerous communities. Seismicity was high during October-December 2017, but ash-bearing explosions were only reported on 7 and 11 November.

After the 22 April 2016 explosions, San Cristóbal remained quiet for the remainder of 2016. In the month's they were measured, 45-72 degassing-type seismic events were recorded. During a field visit on 29 November 2016, new landslides around the crater rim, both inside the crater and down the outer flanks, were observed. These were interpreted by INETER scientists as resulting from a major tectonic earthquake that occurred offshore in mid-November that was felt in nearby Chinandega (16 km SW), and not from volcanic activity.

Seismic activity increased slightly in January 2017 with 100 degassing events recorded. INETER reported 15 small ash-and-gas explosions during 18-19 February and 153 degassing events. There were no reports of ashfall in the nearby communities. Only 27 degassing seismic events were reported in March; three small gas explosions with minor ash occurred on 16, 25, and 28 March 2017.

Eight small explosions with gas and minor ash took place during April 2017 on days 13, 15, 16 and 19, but no damage was reported in nearby communities. Very low values of SO2 (averaging 147 tons/day) were measured at the end of April 2017, far less than values of 854 and 642 measured in September and October 2016. Degassing-type seismic events increased sharply beginning on 20 April, totaling 1,931 events; they remained elevated through 25 April.

Volcano-tectonic (VT) earthquakes increased significantly to 235 recorded events during May, from values in the single digits earlier in the year. Minor fumarolic activity occurred at the S side of the summit crater on 27 May 2017 (figure 33). Two small gas explosions were recorded on 20 and 27 May, but no ash emissions were reported. A significant increase to 2,349 degasification-type earthquakes was reported during June 2017; slightly fewer (1,981) were reported during July.

Figure (see Caption) Figure 33. Minor fumarolic activity was observed at the S side of the summit crater at San Cristóbal during a field visit by INETER on 27 May 2017. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Mayo 2017).

Significant explosions early on 18 August 2017 were observed from Chinandega with notable gas and ash emissions (figure 34), and ashfall was deposited around the region (figure 35). Communities affected by the ashfall were located to the W and SW of the volcano and included Belén, La Mora, La Bolsa, El Viejo (18 km WSW), La Grecia, Realejo (25 km SW) and Corinto (30 km SW). Ash plumes rose between 300 and 600 m above the crater rim and drifted W and SW. Additional explosions occurred the next day but had ceased by 20 August.

Figure (see Caption) Figure 34. Explosion and ash plume at San Cristóbal at 1330 on 18 August 2017. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Agosto, 2017).
Figure (see Caption) Figure 35. Ash was collected by INETER scientists from the 18 August 2017 explosion at San Cristóbal. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Agosto, 2017).

A small plume was noted in satellite imagery by the Washington VAAC on 18 August 2017 moving NW. Later imagery showed gas and ash drifting W at an estimated altitude of 2.1 km. It extended approximately 265 km W of the summit before dissipating. Ground measurements of SO2 made during 18-20 August showed increases to a peak of 3,519 metric tons per day on 19 August before dropping back to more typical background values below 700 t/d. INETER scientists used GOES and AVHRR satellite images to identify the maximum extent of the ash plume from the eruptive event. The ash cloud covered the area W of San Cristóbal, approximately 2,960 Km2, and extended more than 80 km offshore, with a total length of 125 km and a maximum width of 33 km (figure 36). Seismometers recorded 3,880 degassing-type seismic events during August 2017. Seismicity decreased slightly during September 2017 to 2,604 measured events, of which 2,415 were degassing-type, 187 were VT events, and two explosions were recorded on 1 September, but no ashfall was reported.

Figure (see Caption) Figure 36. The extent of the ash plume from the 18-20 August 2017 eruptive episode at San Cristóbal, identified in satellite imagery by INETER scientists. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Agosto, 2017).

An order-of-magnitude increase in seismicity occurred during October-December 2017, with the monthly totals of the numbers of events ranging from 17,000-21,000 (figure 37). INETER reported a series of 14 explosions during the evening of 7 November. Ashfall was reported to the W in Los Farallones, San Agustín, La Mora, El Naranjo and the city of Chinandega. The Washington VAAC subsequently reported an ash plume that models suggested rose to 6.7 km and drifted W on 11 November.

Figure (see Caption) Figure 37. Numbers of daily seismic events at San Cristóbal during October-December 2017. Event types include VT (volcano-tectonic), degasification, and tremor. Note scale in each graph as different symbols and colors are used for the same type each month. Total seismic events for October (top) was 17,815, November (middle) was 19,206, and December (bottom) was 20,925. Ash bearing explosions were reported by INETER on 7 November, and the Washington VAAC reported an ash plume on 11 November that possibly rose to 6.7 km altitude and drifted W. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Octubre, Noviembre, Diciembre, 2017).

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html).


Sangay (Ecuador) — March 2018 Citation iconCite this Report

Sangay

Ecuador

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

All times are local (unless otherwise noted)


Eruptive episode of ash-bearing explosions and lava on SE flank, 20 July-26 October 2017

Periodic eruptive activity at Ecuador's remote Sangay has included frequent explosions with ash emissions and occasional andesitic block lava flows. Eruptive activity from late March to mid-November 2016 included multiple ash emissions and persistent thermal signals through July 2016 (BGVN 42:08). A new episode of ash emissions and thermal anomalies, that began on 20 July 2017 (BGVN 42:08) and lasted through late October 2017, is covered in this report. Subsequent activity through February 2018 included a single ash-emission event near the end of the month. Information is provided by Ecuador's Instituto Geofísico (IG) and the Washington Volcanic Ash Advisory Center (VAAC); thermal data from the MODIS satellite instrument is recorded by the University of Hawaii's MODVOLC system and the Italian MIROVA project.

The first ash plume of the latest eruptive episode at Sangay was reported on 20 July 2017. VAAC reports were issued on 20 and 21 July, eleven days in August, six days in September, and on 13 October. Thermal activity first appeared in a MIROVA plot during the last week of July and continued through 26 October. Multiple MODVOLC thermal alerts were issued between 2 August and 19 October. IG reported that low-energy ash emissions rising 1 km or less above the summit crater were typical throughout the period. They also repeatedly noted two distinct thermal hot spots in satellite data. A single ash emission on 25 February 2018 was the only additional activity through the end of February 2018.

Activity during July-October 2017. The Washington VAAC reported an ash emission on 20 July 2017 that rose to 8.2 km altitude and drifted about 80 km W. A plume was reported on 1 August by the Guyaquil MWO near the summit at about 5.3 km altitude, but was obscured by clouds in satellite imagery. The following day an ash plume was observed at 7.6 km altitude centered about 15 km NW of the summit. An ash emission was reported on 6 August, but was not visible in satellite imagery. The MWO reported an ash emission on 12 August at 6.4 km altitude moving SW, but no ash was detected in satellite imagery under partly cloudy conditions. The Washington VAAC observed an ash plume on 13 August extending around 50 km SW at 6.1 km altitude and a well-defined hotpot. IG reported an ash emission drifting W on 16 August, but clouds obscured satellite views of the plume. Hotspots continued to be observed in shortwave infrared (SWIR) imagery. The Washington VAAC reported an ash plume at 8.2 km altitude on 17 August. The imagery showed an initial puff moving NW followed by several smaller puffs. On 19 August, the Guayaquil MWO reported an ash plume at 5.8 km altitude drifting SW. The next day, another explosion was reported with ash rising again to 5.8 km and drifting W, and a hotspot was observed in satellite imagery.

The Washington VAAC reported a possible ash plume extending 30 km SW of the summit at 7 km altitude on 22 August. It had dissipated the next day, but they noted that a hotspot was visible in SWIR imagery. The next ash plume was reported by the MWO on 1 September at 5.2 km altitude but was not observed in satellite imagery. The next day, the Washington VAAC observed an ash plume at 6.1 km altitude extending 15 km NW of the summit. The Guayaquil MWO reported an ash plume to 7.3 km altitude on 6 September. On 20 September, a possible ash plume could be seen in GOES-16 imagery extending about 150 km W from the summit at 6.1 km altitude. Another plume extended 15 km SW from the summit later in the day at the same altitude. By the end of the day, continuous ash emissions were reported drifting W at 5.8 km altitude. The following day, occasional ash emissions were still reported drifting W and dissipating within 35 km of the summit. A new emission late on 21 September sent an ash plume 25 km W of the summit at 6.1 km altitude. Possible ongoing emissions were reported on 22 September, but not visible in satellite imagery. After three weeks of quiet, the Washington VAAC reported an ash emission on 13 October drifting S at 6.1 km altitude along with a bright hot spot visible for part of the day. This was the last report of ash emissions for 2017.

The eruption that began on 20 July 2017 was characterized by explosions from the central crater and lava emissions from the Ñuñurco dome on the E side of the summit. IG reported two areas of hot spots visible in thermal images during August and September. Around 65 seismic explosions and 25 long-period events were recorded daily during most of this time, along with a few harmonic tremors. Low-energy ash emissions rising 1 km or less above the summit crater were typical. Ashfall was reported to the SW and NW in Culebrillas (75 km SW), and Licto (35 km NW). New lava flows were interpreted to be on the ESE flank by IG based on the repeated hot spots visible in satellite imagery and darkened areas in the snow in the webcam images (figure 20).

Figure (see Caption) Figure 20. A dark streak in the snow near the summit (left side, arrow) of Sangay indicates recent ejecta of blocks or flows on the upper ESE flank of the cone on 1 October 2017. View is from the ECU911 webcam located in Huamboya, 40 km E. Courtesy of IG-EPN (Informe Especial del Volcán Sangay, 2017-2, Continúa la erupción, se observan dos ventos, 4 de octubre del 2017).

Thermal activity measured from satellite instruments support the interpretation of significant lava emissions as blocks or flows at Sangay during late July-October 2017. The MODVOLC system reported 11 thermal alerts beginning on 14 August, 15 during September, and 13 between 3 and 19 October. A similar signal of thermal activity was recorded by the MIROVA system during the same period (figure 21).

Figure (see Caption) Figure 21. The MIROVA project graph of thermal anomalies in MODIS data from Sangay for the year ending on 17 November 2017 (lower graph) clearly shows the period of increased heat flow between late July and late October. The last anomaly appeared on 26 October 2017 (upper graph). Courtesy of MIROVA.

Activity on 25 February 2018. The Washington VAAC reported an ash plume rising to 6.1 km altitude and drifting NE from the summit on 25 February 2018. The plume was visible 170 km NE before dissipating by the end of the day.

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

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


Suwanosejima (Japan) — March 2018 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Large explosions with ash plumes and Strombolian activity continue during 2017

Suwanosejima, an andesitic stratovolcano in Japan's northern Ryukyu Islands, was intermittently active for much of the 20th century, producing ash plumes, Strombolian explosions, and ash deposits. Continuous activity since October 2004 (figure 24) has consisted generally of multiple ash plumes most months rising hundreds of meters above the summit to altitudes between 1 and 3 km, and tens of reported explosions. The rate of activity began increasing during 2014; the frequency of explosions and the height of the plumes have continued to increase through 2017, which is covered in this report. Information is provided primarily by the Japan Meteorological Agency (JMA), and the Tokyo Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 24. Eruptive history at Suwanosejima from January 2003-December 2017. Black bars represent the height of the emissions in meters above the crater rim, gray volcanoes indicate an explosion, usually accompanied by an ash plume, and the red volcanoes represent large explosions with ash plumes. Courtesy of JMA (Suwanosejima volcanic activity report, December 2017).

Activity at Suwanosejima has been persistent and generally increasing during 2014-2017 (figure 25). During 2017, ash emissions rose from a few hundred to nearly 3 km above the Ontake crater rim. Large explosions were reported 32 times by JMA, including 12 during August. Most explosions sent ash emissions to less than 1,000 m above the crater rim, but the highest ash plume, on 3 August 2017, rose 2.8 km above the crater rim, and was the highest recorded since observations began in 2003. Incandescence was observed at the crater from a thermal camera throughout the year and was witnessed locally many times. Many of the explosions, large and small, were heard in the nearby village. Ashfall was confirmed in the village to the SSW on nine different occasions during the year.

Figure (see Caption) Figure 25. Eruptive history at Suwanosejima for 2014-2017. Black bars represent height of steam, gas, or ash plumes in meters above crater rim, gray arrows or volcanoes represent an explosion, usually accompanied by an ash plume, red arrows or volcanoes represent a large explosion with an ash plume, red bars or orange diamonds indicate incandescence observed in webcams. From top to bottom: Eruptive activity during 2014, 2015, 2016, and 2017. Courtesy of JMA (Suwanosejima volcanic activity reports, December 2014, 2015, 2016, and 2017).

Activity during January-April 2017. There were no large explosions at Suwanosejima during January 2017, but occasional minor ash emissions rose as high as 1,300 m above the Ontake crater rim. Incandescence was visible from the webcam on most clear nights. Ashfall was reported in the village 4 km S on 17 and 26 January. The Tokyo VAAC reported ash emissions four times in January. Ash plumes rose to 1.2 km altitude and drifted SE on 4 January; to 1.8 km and drifted W on 5 January; to 1.2 km and drifted S on 16-17 January; and to 2.1 km and drifted SE on 25 January.

In contrast with January, five large explosions were reported by JMA during February 2017. The first, on 9 February, sent an ash plume to 700 m above the crater rim. An ash emission on 18 February rose to 1,200 m above the rim (figure 26). People in the nearby village reported hearing explosions on 18, 20, 27, and 28 February. The largest explosions occurred during 27-28 February when ejecta was scattered 600 m from the crater rim. The Tokyo VAAC reported ash emissions drifting SE several times: on 9 February at 1.5 km altitude, on 16 and 17 February at 1.8 km, and during 27-28 February at 1.5 km.

Figure (see Caption) Figure 26. An ash emission from Suwanosejima was captured by the 'Campground' webcam on 18 February 2017. Courtesy of JMA (Suwanosejima volcanic activity report, February 2017).

Intermittent ash emissions occurred during March 2017, but no large explosive events were reported. Ejecta was scattered around the edge of the crater on 4 March and an ash plume rose 1,000 m. Small ash plumes were noted rising 900 m on 12 and 15 March; explosions were heard in the village on 14 and 16 March, and ashfall was reported there on 25 March. Incandescence was observed at the summit intermittently throughout the month. During a field survey on 21 and 22 March, JMA noted minor thermal anomalies at the Ontake Crater, the N slope of the Ontake crater, and just above the coastline on the E flank (figure 27). The Tokyo VAAC reported ash emissions three times during March; on 3 March ash plumes rose to 1.5-1.8 km altitude and drifted SE and on both 28 and 31 March they rose to 1.8 km altitude and drifted SE and E.

Figure (see Caption) Figure 27. Thermal anomalies were apparent from the Ontake crater (upper left), the north slope of the crater (upper right), and just above the coastline on the E flank (lower left) in this thermal image of Suwanosejima taken on 22 March 2017 from the NE. Courtesy of JMA (Suwanosejima volcanic activity report, March 2017).

Only minor ash emissions and occasional incandescence was reported during April 2017. Two emission events on 1 April sent ash plumes to 1,200 m above the crater rim. A tremor that lasted nine minutes occurred on 11 April and a small seismic swarm was recorded on 13 April. Small explosions were also reported on 17 and 19 April, with the 19 April event heard at the nearby village; another small explosion was reported on 30 April. There were no reports issued by the Tokyo VAAC.

Activity during May-August 2017. Activity increased slightly during May 2017; two large explosions were recorded by JMA. A small explosion was reported on 1 May, and the highest plume rose to 1,900 m above the crater rim on 10 May during a larger event. Incandescence was observed from the local village on 16 May, and explosions were heard from the village on 16 and 18 May, and again on 28 and 29 May; no ashfall was reported. The Tokyo VAAC reported ash emissions on 7, 8, and 10 May. On 7 May they reported an ash plume located 45 km S at 1 km altitude extending SW. A few hours later ash extended N at 1.5 km. An explosion on 8 May sent an ash plume to 2.1 km where it remained stationary over the volcano for much of the day before dissipating. A higher ash plume was reported on 10 May at 2.7 km altitude drifting E.

Small ash explosions occurred at Ontake Crater on 8 and 21 June 2017, but there were no larger explosive events. Ash plume heights rose to only 600 m above the crater rim, and occasional nighttime incandescence was reported. No reports were issued by the Tokyo VAAC. JMA reported that the highest ash plume during July rose 2.1 km above the summit crater on 17 July, but no large explosions were recorded. Incandescence was observed intermittently throughout the month. A small explosion on 2 July sent an ash plume to 1.9 km above the crater rim. Intermittent ash emissions were noted during 17-19, 22 and 25 July. The Tokyo VAAC reported ash emissions during 2 and 16-18 July. They reported the plumes on 2 July at 1.8-2.4 km altitude, extending N for most of the day. A new explosion on 16 July sent an ash plume to 2.7 km altitude that drifted E. Intermittent ash emissions continued to drift E through 18 July at altitudes ranging from 1.8-2.1 km.

Activity increased substantially during August 2017; JMA reported 12 large explosions, nine of which occurred during the last week. Ashfall was reported in the nearby village on 2 August. The highest plume of the month was reported on 3 August, 2.8 km above the crater rim. Explosions were heard in the village on 3 and 19 August. A small explosion was reported on 12 August. Large explosions occurred on 19, 20, and 24 August in addition to the nine events during the last week. A single MODVOLC thermal alert was reported on 18 August, and the MIROVA system reported thermal anomalies during several days of the last week of the month (figure 28). The Washington VAAC reported ash on 1 August that rose to 2.4 km altitude and drifted SW. A higher plume on 3 August rose to 3.7 km and drifted W. They reported another ash plume that first rose to 3.0 km on 24 August; subsequent emissions that day were drifting NE at 2.1-2.4 km altitude. A new plume on 25 August extended E at 2.4 km. Continuing ash emissions from multiple explosions during 28-31 August rose to 1.2-3.0 km altitude and drifted SE.

Figure (see Caption) Figure 28. Log Radiative Power plot from the MIROVA project for Suwanosejima for 24 May 2017-15 February 2018 shows increased thermal activity during late August 2017, and intermittent pulses of activity from late May-September. Courtesy of MIROVA.

Activity during September-December 2017. Four large explosions were recorded during the first week of September 2017, after which a number of smaller ash emission events were reported. Ashfall was reported four times in the nearby village on 2, 4, 29, and 30 September. The Tokyo VAAC reported explosions on 1, 4, 6, and 29 September. The ash plume from the explosion on 6 September rose to 1.5 km altitude and drifted E; on 29 September, it rose to 2.4 km altitude, also drifting E.

JMA reported four large explosions during October 2017. Two explosions occurred on 11 October; one of the ash plumes rose 1,900 m above the crater rim (figure 29). Explosions were heard in the nearby village on 12 and 31 October, and ashfall was reported on 13 October. During the large explosion of 31 October incandescent ejecta was scattered around the crater rim and the ash plume rose 1,900 m. The Tokyo VAAC reported an explosion with ash on 10 October (UTC) that rose to 2.7 km altitude and remained stationary until dissipating a few hours later. They noted that the explosion on 31 October produced a plume that rose over 1.5 km and drifted NW.

Figure (see Caption) Figure 29. An ash plume from an explosion on 11 October 2017 rises 1.9 km above the Ontake crater of Suwanosejima. Courtesy of JMA (Suwanosejima volcanic activity report, October 2017).

JMA reported five large explosions during November 2017. Incandescent ejecta was seen around the crater rim during the explosion of 1 November, and the plume rose to 2 km above the rim. Loud explosions were heard from the nearby village on 3, 5, 6, 15, and 16 November, and ashfall was reported there on 14, 15, and 20 November. A small explosion was reported on 10 November; intermittent explosions with ash plumes rising 700 m were observed on 20 and 21 November. The Tokyo VAAC reported ash plumes at 1.5 km drifting W on 1 and 5 November, and at 1.8 km altitude drifting NW on 10 November, the last VAAC report issued for 2017.

Only small explosions were reported from Ontake crater during December 2017. The highest plume rose 700 m above the crater rim. Small explosions were heard a number of times in the nearby village on 8-9, 11-13, and 26-30 December. JMA scientists visiting during 8-10 December heard intermittent explosions and witnessed incandescence visible to the naked eye. They also observed ashfall in the village on the morning of 10 December. During a field survey on 14 December, no significant changes were noted from the previous survey in March 2017 (figures 30 and 31).

Figure (see Caption) Figure 30. The summit of Suwanosejima with steam rising from Ontake Crater taken from the W on 14 December 2017. Courtesy of JMA (Suwanosejima volcanic activity report, December 2017).
Figure (see Caption) Figure 31. Steam rises from the Ontake Crater of Suwanosejima viewed from the E on 14 December 2017. Courtesy of JMA (Suwanosejima volcanic activity report, December 2017).

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); 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/); 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/).


Turrialba (Costa Rica) — March 2018 Citation iconCite this Report

Turrialba

Costa Rica

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

All times are local (unless otherwise noted)


Persistent explosions and ash emissions continue through 2017; small lava lake

A phreatic eruption at Turrialba in January 2010 heralded a series of brief eruptions during subsequent years. Explosions and emissions containing ash increased in 2015 and 2016 (BGVN 42:06). The current report indicates that increased activity continued during 2017. The information below comes from the Observatorio Vulcanologico y Sysmologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) unless otherwise indicated.

Frequent ash emissions, both passive and explosive events, rose the heights of less than 1 km above the crater and were blown downwind, causing ashfall in communities within about 40 km, and a sulfur odor at greater distances. Fumarolic plumes described as consisting of water vapor, aerosols, and magmatic gases were also common from the West Crater. Volcanic seismicity was variable, often corresponding to changes in activity.

Activity during January-June 2017. During the first part of January, no explosions took place. Based on webcam and satellite views, the Washington Volcanic Ash Advisory Center (VAAC) reported that on 22 January, an ash plume rose to an altitude of 4 km and drifted E. The VAAC reported ongoing ash emissions on 27 January.

On 1 February, OVSICORI-UNA reported that since 27 January the seismic network had recorded variable-amplitude, discontinuous tremor indicative of moving pressurized volcanic fluid. Passive emissions of ash were observed during 1-2 February, rising as high as 500 m above the crater. Ashfall was reported in the area of the capital, San Jose (about 37 km WSW), including Desamparados, Calle Blancos, and Tres Ríos (27 km WSW), and a sulfur odor was noted in San Pablo Heredia (35 km W). An explosion at 0900 on 4 February generated an ash plume that rose 300 m and drifted W. Almost continuous ash emissions rose at most 500 above the crater during 4-5 February and drifted WSW (figure 48).

Figure (see Caption) Figure 48. An ash explosion from Turrialba on 4 February 2017 at 1145, taken by an RSN camera at the summit. Courtesy of RSN:UCR-ICE (Resumen de la Actividad Sismica y Eruptiva del Volcan Turrialba, 03 de febrero de 2017).

OVSICORI-UNA reported that at 1610 on 8 February, an ash plume rose 300 m and drifted N. An event at 1531 on 10 February also produced an ash plume, but inclement weather prevented observations. During 11-12 February, variable amplitude tremor was detected, and at night hot blocks ejected from the vent landed in Central Crater. Several events on 13 February (at 0255, 0305, 0415, and 1459) produced ash plumes that rose as high as 1 km and drifted N, NW, and W. Small ejections of incandescent material fell around the active crater during the early morning. On 14 February continuous emissions of gas and steam with low ash content were visible. A strong sulfur odor was reported in San Pablo de Oreamuno (25 km SW). High-amplitude tremor remained constant during 15-16 February and sporadic gas emissions with minor amounts of ash drifted S and E; occasional ballistics were ejected from the crater. During 16-17 February tremor amplitude decreased and sporadic gas emissions with low ash content rose no higher than 300 m and drifted NW and SW. Similar emissions were observed during 20-21 February, drifting NW and NE.

Weak gas emissions during 20-21 March sometimes contained small amounts of ash that rose no higher than 100 m above the crater rim and drifted SW. Volcanic tremor had medium and variable amplitude, and a few low-frequency (LF) earthquakes were recorded. A weak ash emission was visible during 1800-1940 on 25 March. Periods of more intense crater incandescence, from possible Strombolian activity, corresponded to higher tremor amplitude during 0330-0530 on 26 March. Later that day a small plume with minor ash rose 500 m above the crater and drifted S and SE. An event at 0752 on 28 March generated an ash plume that rose 300 m and drifted S.

Ash-and-gas plumes rose 500 m above the crater during 31 March-1 April, and ashfall was reported at the Juan Santamaría airport (48 km W). Ash plumes rose 500 m at 1700 on 2 April, and 200 m at 0601 on 4 April. A passive ash emission occurred on 16 April. An event at 0751 on 17 April generated a plume containing minor amounts of ash that rose 500 m above the crater and drifted SW. On 18 April, a diffuse plume consisting of gas and sometimes ash rose 1 km above the crater and drifted W.

An event at 1700 on 5 May generated a weak ash plume that rose 500 m above the crater and drifted SW. Two short-amplitude events occurred at 1702 and 1820, though it was uncertain if they were associated with an explosion. During 5-7 May volcano-tectonic (VT) and long-period (LP) earthquakes were detected, as well as variable-amplitude tremor. At 1250 on 6 May, an event produced a plume that rose 300 m and drifted W. Passive ash emissions occurred between 1250 and 1730 on 6 May, and at 1000 on 7 May, that rose no higher than 1 km. At 0902 on 9 May an event generated an ash plume that rose 500 m and drifted NW.

An explosion on 10 May was followed by weak and passive ash emissions. Several LP earthquakes were recorded, and inflation continued. Gas measurements indicated a sulfur dioxide flux of 1,000 tonnes/day, and a high carbon dioxide/sulfur dioxide ratio. An event at 0900 on 12 May generated a plume, though poor visibility prevented a height estimate. An event at 0730 on 14 May generated a plume that rose 500 m above the crater rim and drifted N. Low-amplitude tremor was detected during 15-16 May, and a discontinuous ash plume rose no more than 500 m and drifted N and NW.

Ash emissions observed during 17-23 May rose as high as 1 km above the vent. Ashfall was reported in El Tapojo and Juan Viñas (15 km SSE) during 17-18 May, and in Capellades (along with a strong sulfur odor) during 19-20 May. During 23-30 May, tremor amplitude fluctuated from low to high levels, often corresponding to emission characteristics; periods of VT and LP events were also recorded. During 24-26 May several passive ash emissions rose no higher than 500 m above the vent and drifted NW and SW. Frequent and small explosions during 26-27 May generated ash plumes that rose higher than 500 m above the vent and ejected material higher than 200 m and no farther than 100 m towards Central Crater. Small explosions during 27-29 May produced ash plumes that rose 300-500 m. Fumarolic plumes during 30-31 May occasionally contained ash that rose no higher than 300 m above the crater rim and drifted NW.

On 3 June at 1930 an event produced an ash plume that rose 300 m and drifted SW. During 7-13 June, tremor amplitude fluctuated from low to medium levels and periods of small VT events and many small-amplitude LP events were also recorded. Fumarolic plumes rose as high as 1 km above the vent and drifted mainly NW, W, and SW. Gas emissions during 14-15 June sometimes containing ash rose no higher than 300 m above the crater. Events at 0620 and 1405 on 16 June generated ash plumes that rose 500 m and drifted NW, and 200 m and drifted S, respectively. Passive ash emissions during 19-20 June rose as high as 1 km and drifted in multiple directions. During 20-25 June fumarolic plumes rose as high as 1 km above the crater; the gases were strongly incandescent the night of 22-23 June.

Drone observations on 29 June 2017. According to an RSN:UCR-ICE report and meeting abstract (Ruiz and others, 2017), government officials flew a drone over the volcano on 29 June 2017. The observations showed profound changes in the morphology of the active crater since a previous overflight on 30 March 2016. In March 2016, the active crater exhibited internal landslides, an accumulation of materials at the foot of the W wall, and a ring of fumaroles surrounding a small opening that constituted the point of ash emission. The active crater was narrow and had an oblong shape, with a longer axis in the E-W direction.

During the recent overflight, the active crater was deeper and wider, elliptical, with its longest axis in the SW-NE direction, coincident with the preferential direction of explosions. In the N and NE sectors of the crater floor ash and blocks had accumulated. The most significant feature of the crater's central sector was an opening with a major axis of about 50 m across from which incandescent material was observed; the group believed this incandescence originated in the small lava lake from which passive ash emissions or small explosions arise. The authors stated that lava was present on the crater floor, forming a small lava pool (15 x 25 m).

Activity during July-December 2017. During 29 June-11 July seismicity was characterized by low-to-medium amplitude tremor and a small number of low-amplitude VT and LP events. Fumarolic plumes and occasional ash rose as high as 1 km above the West Crater fumaroles. Incandescence from the main crater was recorded at night. Minor ashfall and a sulfur odor was reported in areas of San José including Rancho Redondo, Goicoechea, Moravia, San Pedro Montes de Oca, Guadalupe, and Coronado, and in San Rafael and Barva (Heredia). Parque Nacional Volcán Turrialba staff reported that ash was deposited between La Silvia and La Picada farms. Events at 1325 on 10 July and 1545 on 11 July generated plumes that rose 300 and 500 m above the crater rim, respectively.

Daily explosions over 12-17 July produced gas and ash plumes that rose 200-500 m and generally drifted NW, W, and SW. Multiple events on 15 July caused ashfall in Sabanilla de Montes de Oca (30 km WSW), Ipis (27 km SW), El Carmen de Guadalupe, Purral (26 km WSW), Guadalupe (32 km WSW), and Tibás (35 km WSW). A sulfur dioxide odor was also reported in San José (36 km WSW), Tibás, Guadalupe, Escazú (42 km WSW), and Puriscal (65 km WSW). During 19-24 July fumarolic plumes rose as high as 500 m, and on most nights incandescence emanated from West Crater. The emissions contained ash during 20-22 July; minor ash fell in Coronado (San José) on 20 July, and in Sabanilla de Montes de Oca on 22 July.

Events on 26 July, 9 August (1607), 21 August (1012), 24 August (0715), 28 August (1025), 5 September (0820 and 1550), 11 September (0730), 13 September (0820 and 1555), 14 September (0600), 18 September (0703), 25 September (1112), and 26 September (0910) produced plumes that rose 100-500 m above the crater rim and drifted NW, SW, N, and W.

During 27 September-1 October and on 3 October, daily events generated plumes that rose as high as 1 km above the crater rim and drifted NW, W, SW, and S. On 30 September explosions ejected hot material out of West Crater and minor ashfall was reported in Coronado (San José). On 3 October, ash fell in Santa Cruz (7 km SE), Las Verbenas, Santa Teresita, Calle Vargas, Guayabito, and La Isabel.

Events on 6 October (0815), 9 October (1040), 11 October (0927), and 20 October (0825) produced plumes that rose 50-300 m above the crater rim and drifted NW and N. Events at 1030, 1105, and 1445 on 30 October generated ash plumes that rose 200-500 m above the crater rim and drifted NW, W, and SW. Ashfall was reported in the community of Pacayas (about 12 km SSW).

The Washington VAAC reported that an ash emission was observed in webcam images on 4 November; ash was not identified in satellite images, though weather cloud cover was increasing and may have obscured views. According to OVSICORI-UNA, another ash emission began before 0730 on 13 November and intensified around 0830, generating an ash plume that rose 500 m above the crater rim and drifted SW. A small event at 1319 on 1 December generated a weak ash plume that rose 50 m above the crater rim and drifted SW.

Reference. Ruiz, P., Mora, M., Soto, G.J., Vega, P., Barrantes, R., 2017. Geomorphological mapping using drones into the eruptive summit of Turrialba volcano, Costa Rica. University of Costa Rica. Abstract V23A-0455, AGU Fall meeting of American Geophysical Union, New Orleans, 12 Dec 2017.

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

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Red Sismologica Nacional (RSN) a collaboration between a) the Sección de Sismología, Vulcanología y Exploración Geofísica de la Escuela Centroamericana de Geología de la Universidad de Costa Rica (UCR), and b) the Área de Amenazas y Auscultación Sismológica y Volcánica del Instituto Costarricense de Electricidad (ICE), Costa Rica (URL: http://www.rsn.ucr.ac.cr/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html).

Atmospheric Effects

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

View Atmospheric Effects Reports

Special Announcements

Special announcements of various kinds and obituaries.

View Special Announcements Reports

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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