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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

Sheveluch (Russia) Renewed activity with lava dome growth and ash explosions starting in late December 2018

Mayon (Philippines) Intermittent ash emissions; persistent summit incandescence, October 2018-April 2019

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

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

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

Semeru (Indonesia) Decreased activity after October 2018

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

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

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

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

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

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



Sheveluch (Russia) — May 2019 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Renewed activity with lava dome growth and ash explosions starting in late December 2018

Volcanism at Sheveluch has been ongoing for the past 20 years. Previous activity consisted of pyroclastic flows, explosions, moderate gas-and-steam emissions, and lava dome growth, according to the Kamchatka Volcanic Eruptions Response Team (KVERT). Between May 2018 and mid-December 2018 activity levels were low, with intermittent low-power thermal anomalies and gas-and-steam emissions. Activity increased in the second half of December 2018, remaining high through at least April 2019.

Activity intensified beginning in late December through April 2019, which included increased and more frequent thermal anomalies, according to KVERT and the MIROVA system (figure 50). On 30 December 2018, video data from KVERT showed explosions producing an ash cloud that rose up to 11 km altitude and drifted 244 km WSW and 35 km NE. Eruptive activity included incandescent lava flows and hot avalanches. The ash cloud that drifted WSW resulted in ashfall over Klyuchi Village (50 km SW) and Kozyrevsk (100 km SW).

Figure (see Caption) Figure 50. Thermal anomalies at Sheveluch increased in late December 2018, as seen on this MIROVA Log Radiative Power graph for the year ending 5 April 2019. The elevated thermal activity continued through March 2019. Courtesy of MIROVA.

Beginning in early January and going through April 2019, the lava dome at the northern part of the volcano continued to grow, extruding incandescent, viscous lava blocks (figure 51). Throughout these months, KVERT reported that satellite imagery and video data showed strong fumarolic activity, as well as strong gas-and-steam plumes containing some amount of ash; gas-and-steam plumes rose as high as 7 km. According to the KVERT Daily Reports on 3 and 4 January 2019, a gas-and-steam plume containing ash drifted NE up to about 600 and 400 km, respectively. Gas-and-steam plumes noted in the KVERT Daily Report, Weekly Releases, and Volcano Observatory Notice for Aviation (VONA), drifted 50-263 km in different directions. On 9 November 2018, the KVERT Daily Report recorded an ash plume drifting 461 km E from the volcano and on 26 December 2018, the KVERT Weekly Information Release recorded an ash cloud drifting 300 km NW. The KVERT Weekly Information Release reported that on 10 April 2019 an ash cloud drifted up to 1,300 km SE.

Figure (see Caption) Figure 51. Incandescent avalanches from the lava dome and an ash plume can be seen in this photo of Sheveluch on 22 February 2019. Photo by Yu. Demyanchuk; courtesy of the Institute of Volcanology and Seismology FEB RAS, KVERT.

Thermal anomalies based on MODIS satellite instruments analyzed using the MODVOLC algorithm were frequent beginning on 28 December 2018. In just three days in late December (28-31 December 2018) there were 34 thermal alerts. Hotspots were detected 21-27 days each month between January-April 2019. A majority of these hotspot pixels occurred within the summit crater.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far 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://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/).


Mayon (Philippines) — May 2019 Citation iconCite this Report

Mayon

Philippines

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

All times are local (unless otherwise noted)


Intermittent ash emissions; persistent summit incandescence, October 2018-April 2019

Steep-sloped and symmetrical Mayon has recorded historical eruptions back to 1616 that range from Strombolian fountaining to basaltic and andesitic flows, as well as large ash plumes, and devastating pyroclastic flows and lahars. A phreatic explosion with an ash plume in mid-January 2018 began the latest eruptive episode which included the growth of a lava dome with pyroclastic flows down the flanks and lava fountaining (BGVN 43:04). Activity tapered off during March; occasional ash emissions continued through August 2018. Minor ash emissions and summit incandescence were intermittent from October 2018-April 2019, the period covered in this report. Information is provided primarily by the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

Pyroclastic density currents were reported in early November 2018; ash plumes were produced from phreatic events a few times during both November and December 2018. Emissions produced SO2 anomalies during January-March 2019; a series of events in early March generated several small ash plumes. Satellite images showing a thermal anomaly at the summit were recorded multiple times each month from October 2018-April 2019 (figure 44).

Figure (see Caption) Figure 44. Small but distinct persistent thermal anomalies were recorded in satellite imagery from the summit of Mayon during October 2018-April 2019. Top left: 12 October 2018. Top right: 26 November 2018. Middle left: 11 December 2018. Middle right: 30 January 2019. Bottom left: 14 February 2019. Bottom right: 25 April 2019. All images are using the "Atmospheric penetration" filter (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Very little activity was reported at Mayon during October 2018. Steam plumes rose daily from 250-750 m above the summit before drifting with the prevailing winds and dissipating. Incandescence was observed at the summit most nights during the month, and seismicity remained low with only a few earthquakes reported. Leveling data obtained during 30 August-3 September indicated significant short-term deflation of the volcano relative to 17-24 July 2018. New leveling data obtained on 22-31 October indicated inflation of the SE quadrant and short-term deflation on the N flank relative to the 30 August-3 September data. The volcano remained inflated compared with 2010 baseline data. Electronic tilt data showed pronounced inflation of the mid-slopes beginning 25 June 2018.

Activity increased during November 2018. In addition to steam plumes rising to 750 m and an incandescent glow at the summit most nights, pyroclastic density currents and ash plumes were reported. The seismic monitoring network recorded pyroclastic density currents on 5 and 6 November. On 8 November around noontime, a small, short-lived brownish ash plume, associated with degassing, drifted WSW from the summit. A seismic event on the morning of 11 November was associated with a short-lived fountaining event that produced a brownish-gray ash plume that drifted SW. Another similar plume was reported on the morning of 12 November, also drifting SW before dissipating. Two phreatic events were observed on the morning of 26 November. They produced grayish to grayish-white ash plumes that rose 300-500 m above the summit before drifting SW. The following morning, another event produced a grayish ash plume 500 m above the summit that drifted SW. On 30 November a 1-minute-long ash emission event produced a grayish white plume that also drifted SW.

Steam plume emissions and incandescence at night continued at Mayon during December 2018. The seismic network recorded a four-minute-long event shortly after noon on 9 December that produced a grayish-brown ash plume which drifted W. Precise leveling data obtained on 8-13 December 2018 indicated a slight inflation of the volcano relative to 22-31 October 2018. A 30-second-long ash emission event in the afternoon on 18 December produced a brownish ash plume. Two phreatic events were observed on the morning of 27 December. They produced grayish to grayish-white ash plumes that rose 600 and 200 m above the summit, before drifting SW (figure 45).

Figure (see Caption) Figure 45. Ash plumes rose a few hundred m from the summit of Mayon on 27 December 2018. Courtesy of Twitter users "k i t" (left) and "georgianne" (right).

Very little surface activity except for white steam-laden plumes that crept downslope and drifted NW or SW was noted during January 2019. Incandescence at the summit, visible with the naked eye, became more frequent during February 2019, along with continued steam plumes. Precise leveling data obtained on 25 January-3 February 2019 indicated a slight deflation relative to 8-13 December 2018. However, continuous GPS and electronic tilt data showed inflation of the mid-slopes since June 2018. Small SO2 plumes were detected by the TROPOMI satellite instrument a few times during January-March 2019 (figure 46).

Figure (see Caption) Figure 46. Emissions of SO2 that exceeded 2 DU (Dobson Units) occurred a few times at Mayon during January-March 2019. Top left: 25 January. Top right: 16 February. Lower left: 4 March. Lower right: 15 March. Courtesy of NASA Goddard Space Flight Center.

Steam plumes rose 250-500 m above the summit and drifted generally W in early March 2019; incandescence continued daily at the summit. Phreatic events occurred on 7 and 8 March, producing ash plumes that rose 500 and 300 m from the summit before drifting SW (figure 47). Three more phreatic events occurred on the afternoon of 12 March; they produced light brown to grayish ash plumes that rose 500, 1,000, and 500 m, respectively, and drifted SW. Six phreatic events occurred throughout the day on 13 March, producing ash plumes that rose 200-700 m above the summit and drifted W. A single explosion the next day produced a 500-m-tall ash plume. The Tokyo VAAC reported an ash plume visible for several hours in satellite imagery drifting W at 3.7 km altitude on 13 March (UTC). An increase in the daily number of rockfall events from 1-2 per day to 5-10 per day was noted during the second half of March. Precise leveling data obtained on 20-26 March 2019 indicated a slight inflation relative to 25 January-3 February 2019.

Figure (see Caption) Figure 47. A small ash emission at Mayon was reported by PHIVOLCS on 8 March 3019; the plume rose 300 m from the summit and drifted SW. Courtesy of PHOVOLCS.

Steam plumes drifted SW or NW throughout April, rising 200-400 m from the summit. Incandescence could be observed at night for the first half of the month. Leveling data obtained during 9-17 April 2019 indicated a slight inflation relative to 20-26 March 2019. Seismicity remained low during the month with only occasional volcanic earthquakes and rockfall events. Lenticular clouds around the summit were observed (figure 48), but these are an unusual meteorological occurrence caused by weather conditions not related to volcanic activity.

Figure (see Caption) Figure 48. A double lenticular cloud surrounded the summit of Mayon early in the morning on 23 April 2019 and was captured by a local observer; it was not related to volcanic activity. Courtesy of Twitter user Ivan.

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/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Twitter user "Ivan", Naga City, Philippines (URL: https://twitter.com/ivanxlcsn); Twitter user "k i t", Legazpi City, Philippines (URL: https://twitter.com/jddmgc); Twitter user "georgianne", Costa Leona, Philippines (URL: https://twitter.com/xolovesgia_).


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

Tinakula

Solomon Islands

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

Figure (see Caption) Figure 33. The number and intensity of MIROVA thermal anomalies increased at Tinakula during April and May 2019. After a short pause, they returned at the end of June. Courtesy of MIROVA.
Figure (see Caption) Figure 34. Sentinel-2 satellite images captured thermal anomalies at the summit and on the W flank of Tinakula during April and May 2019 suggesting the presence of an incandescent flow down the W scarp. Top row: 7 and 22 April 2019 (bands 12, 8, 4). Bottom row: 27 April and 12 May 2019 (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

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

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


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

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Heard (Australia) — April 2019 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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


Semeru (Indonesia) — April 2019 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Decreased activity after October 2018

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

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

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

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

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

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

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

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

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


Dukono (Indonesia) — April 2019 Citation iconCite this Report

Dukono

Indonesia

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

All times are local (unless otherwise noted)


Numerous ash explosions from October 2018 through March 2019

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

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

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

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

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

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


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

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Occasional weak phreatic explosions continue through February 2019

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

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

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

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

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

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

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

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


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

Turrialba

Costa Rica

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

All times are local (unless otherwise noted)


Frequent passive ash emissions continue through February 2019

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

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

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

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

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

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

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

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

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

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

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Red Sismologica Nacional (RSN) a collaboration between a) the Sección de Sismología, Vulcanología y Exploración Geofísica de la Escuela Centroamericana de Geología de la Universidad de Costa Rica (UCR), and b) the Área de Amenazas y Auscultación Sismológica y Volcánica del Instituto Costarricense de Electricidad (ICE), Costa Rica (URL: https://rsn.ucr.ac.cr/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Costa Rica Star (URL: https://news.co.cr); The Tico Times (URL: https://ticotimes.net).


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

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Weak ash explosions in January and March 2019

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

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

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

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

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

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://webserver2.ineter.gob.ni/vol/dep-vol.html); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html).


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

Semisopochnoi

United States

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

All times are local (unless otherwise noted)


Minor ash explosions during September and October 2018

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

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

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

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

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

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

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

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

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

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


Asosan (Japan) — July 2019 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

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Bulletin of the Global Volcanism Network - Volume 35, Number 03 (March 2010)

Managing Editor: Richard Wunderman

Eyjafjallajokull (Iceland)

Fissure eruption and lava flows from E flank on 20 March

Fournaise, Piton de la (France)

Seismicity and eruptions January 2009 and November 2009-January 2010

Santa Maria (Guatemala)

Continuing frequent ash explosions through 2008-2009

Sheveluch (Russia)

Near-constant dome growth during May 2008 through March 2010

Soufriere Hills (United Kingdom)

Lava dome growth continuing; pyroclastic flows reached the ocean

Stromboli (Italy)

Explosions and lava flows in 2009; recent reports on 2007 eruption

Telica (Nicaragua)

Incandescent crater floor areas seen in November 2009 and March 2010



Eyjafjallajokull (Iceland) — March 2010 Citation iconCite this Report

Eyjafjallajokull

Iceland

63.633°N, 19.633°W; summit elev. 1651 m

All times are local (unless otherwise noted)


Fissure eruption and lava flows from E flank on 20 March

During March 2010, the Icelandic Meteorological Office (IMO) and the Nordic Volcanological Center of the University of Iceland's Institute of Earth Sciences (IES) reported the first eruption of Eyjafjallajökull volcano in southern Iceland since 1823. The following was mostly condensed from a multitude of reports on the EIS and IMO websites, and only discusses activity through the start of the explosive summit phase. Many of the satellite images featured here came from the NASA Earth Observatory.

From 20 March to 12 April 2010 the eruption's first phase occurred from a fissure 9 km ENE of the summit, an area named Fimmvörðuháls, located between the Eyjafjallajökull and Mýrdalsjökull icecaps (figure 1). These vents on the lower E slopes were snow-covered but not under the year-round icecap found at higher elevations. Lava flows filled gullies, and quickly melted adjacent winter snow, creating small steam plumes. After apparent cessation of the fissure activity on or about 12 April, a second phase of the eruption began on 14 April (figures 2 and 3, table 1), generating ash plumes that blew E to Europe and resulted in a 20-80% decrease of airline flights for as much as a week (Wall and Flottau, 2010). As of late May the eruption continued, with occasional plumes that restricted air travel in parts of Europe.

Figure (see Caption) Figure 1. Map of southern Iceland showing Eyjafjallajökull and Katla volcanoes, towns, and locations of monitoring instruments. The Mýrdalsjökull icecap overlies Katla. ("Jökull" translates to "glacier" or "icecap" in English). Index map showing some eruptive centers is from Laursen (2010). Base map courtesy of IMO.
Figure (see Caption) Figure 2. Approximately N-looking interpretive cross-section cartoon drawn between Eyjafjallajökull and Katla. The eruption of 20 March was located at Fimmvörðuháls. Starting on 14 April, eruptions took place at the summit caldera. Notice the thin upper layer (blue on colored versions) representing glacial ice and the inferred common linkage at ~ 2 km depth below sea level of the conduits feeding the two active vent areas. Courtesy of Páll Einarsson (IES).
Figure (see Caption) Figure 3. ASTER image of the Eyjafjallajökull-Fimmvörðuháls vents at 1350 local time on 19 April. The image shows both visible information and heat signatures from areas of anomalously high thermal infrared (IR) radiation (for colored versions, yellow is hottest, red, cooler). For the Fimmvörðuháls the thermal signature shows the extent of lava flows no longer extruding but still hot. At the summit, the vent is clearly active, with a thermal signature and a dense white plume blowing SSE. ASTER is the Advanced Spaceborne Thermal Emission and Reflection Radiometer flying on NASA's Terra satellite. Courtesy of Rob Simmon, the U.S./Japan ASTER Science Team, and Holli Riebeek, NASA Earth Observatory.

Table 1. Preliminary data regarding the 2010 eruption of Eyjafjallajökull, which started at an E-flank vent (Fimmvörðuháls) and then later shifted to the ice-covered summit caldera. The grain sizes of the second phase of the eruption were quantified by The Environment Agency of Iceland; other data courtesy of IMO and IES.

Dates Activity Rock type and description
20 Mar-12 Apr 2010 Fissure eruptions of lava flows at Fimmvörðuháls. Alkali-olivine basalt (~47.7 wt % SiO2). Euhedral plagiclase, olivine, and clinopyroxene phenocrysts seem to be in equilibrium with magma.
14 Apr 2010 and later Explosions from the summit caldera of Eyjafjallajökull. Ash clouds, initially up to ~11 km altitude. Trachyandesite (56.7-59.6 wt % SiO2). Grain size from sample at Mýrdalssandur (50 km from vent): 24%, under 10 ?m (as aerosol); 33% , 10-50 ?m; 20% , 50-146 ?m; 23%, 146-294 ?m. Fluorine: 850 mg/kg (19 April).

Precursory observations. The IES website contained a list of scientific papers and publications including several noting restlessness at Fimmvörðuhálsat in recent years (see Further References below). The IES reports noted that the Fimmvörðuháls eruption followed weeks of high seismicity and deformation (figure 4).

Figure (see Caption) Figure 4. (top) Map of the southern Iceland GPS (Global Positioning System) network, including stations THEY, SKOG, STE1, and STE2. (bottom) Displacement measurements for selected continuous/semi-continuous GPS stations around Eyjafjallajökull from early July 2009 to early March 2010. Inset photograph is of station SKOG. Courtesy of IES.

In general terms, GPS data indicated that permanent station Thorvaldseyri (THEY; S of the volcano, figure 4) started moving S in late December 2009. In the weeks prior to the eruption, there was rapid deformation at Skogaheidi (SKOG; S of the volcano) and Steinsholt (STE1 and STE2; N of the volcano). IES identified three distinct phases in the GPS data. First, at the end of December, the southward motion of THEY. Second, at the beginning of February 2010, displacement at THEY changed to SW as SKOG began E displacement. Third, after 5 March, STE2 displaced rapidly NW and up. Scientists noticed a trend after 4 March at continuous GPS sites installed within 12 km of the eruptive site; all showed deformation at rates of up to a centimeter a day.

Seismic tremor began around 2230 on 4 March, and around that time, signal sources rose slowly towards the surface. Compared to the weeks prior to the eruption, seismicity increased rather slowly immediately prior to the eruption. However, as the eruption onset neared, geophysicists saw both the depth of earthquakes decrease and the locations of earthquakes move from the area under the summit towards the Fimmvörðuháls site.

According to Laursen (2010) "Eyjafjallajökull's so-far-unpredictable behavior offers a perfect example of the challenge facing volcanologists. Before this spring's first eruption...GPS stations on the volcano had wandered several centimeters in May of 2009 and again in December, signs that rising magma was stretching the skin of the volcano in advance of an eruption. In mid-February...Steinunn Jakobsdóttir, a geophysicist at IMO, was tracking tremors ~ 5 kilometers below Eyjafjallajökull's surface. But officials didn't order evacuations because the seismic hints weren't that dire. 'Usually when an eruption starts, a low-frequency [seismic signal] is rising when the magma is coming to the surface,' says Jakobsdóttir. Although seismic tracking placed magma closer to the surface on 19 March, this low-frequency signal was absent, so civil authorities kept the alert level at its lowest setting. But the next night, southern Icelanders reported a dark cloud glowing red above the mountain: The volcano had experienced a small eruption, one that led authorities to evacuate farmers living in its floodplains."

Eruption from Fimmvörðuháls. Late on 20 March 2010 an eruption began at Fimmvörðuháls, an area around 1,000 m elevation in a ~ 2-km-wide pass of ice-free land between Eyjafjallajökull and Mýrdalsjökull. Initially detected visually, the eruption was seen at 2352 that day as a red cloud above the site.

The eruption broke out with Hawaiian-style fire fountains (figure 5) on a ~ 500-m-long, NE-oriented fissure (at 63° 38.1' N, 19° 26.4' W). Lava flowed a short distance from the eruptive site and a minor eruption plume rose to less than 1 km altitude and blew W. Tephra fall was minor or insignificant.

Figure (see Caption) Figure 5. Image of fissure eruption at Eyjafjallajökull taken 21 March 2010 by Sigrún Hreinsdóttir. Courtesy of IES.

Airborne observers during 0400-0700 on 21 March described a short eruptive fissure with fire fountaining from 10-12 vents reaching up to ~ 100 m height. Eruption tremor rose slowly until reaching a maximum at around 0700-0800 that day. No further lengthening of the fissure was detected. Lava was still limited to the immediate surroundings of the eruptive craters (runouts of less than few hundred meters). Minor ashfall occurred within a few kilometers W.

On 22 March, observations made from the ground showed lava extrusion from a series of closely-spaced vents. Prevailing E winds led to maximum scoria accumulation on a linear rim W of the NE-trending fissure. A'a lava flowed over the steep Hrunagil canyon rim creating spectacular 'lava falls.'

During 23-31 March, lava steadily issued at the initial craters, with gradual focusing towards fewer vents. Lava advanced N into the Hrunagil and Hvannárgil valleys, with continuation of intermittent lava falls (figures 6-8). Lava descending gullies generated zones of frothy rock. Extensive steam plumes occurred when advancing lava encountered water and snow. Two or three plumes were observed (one at the eruptive craters, others more pronounced in front of the advancing lava). Meltwater descended in batches into rivers valleys, and seismometers recorded relatively steady eruption tremor.

Figure (see Caption) Figure 6. EO-1 ALI satellite image with annotations indicating path of lava flows from the Fimmvörðuháls vent, 24 March 2010. Note N arrow and scale at lower left. Courtesy of Robert Simmon, NASA Earth Observatory.
Figure (see Caption) Figure 7. Photo showing lava falls developed when lava flows encountered steep canyon walls, 1 April 2010. Courtesy of Sigrún Hreinsdóttir, IES.
Figure (see Caption) Figure 8. Map showing Fimmvörðuháls fissures and the distribution of new scoria and lava at various points in time during 21 March-7 April 2010. Table indicates cumulative areal extent of the deposits. Courtesy of EIS and Icelandic Coast Guard.

On the evening of 31 March, scientists noted the opening of a new short fissure immediately N of the previous one. This change may have been a response to changes at shallow depth in the feeder channel. Eruption tremor remained unchanged. During 31 March-6 April, lava discharged in both the old and new eruptive craters in a manner similar to before. Pronounced 'lava falls' returned to Hvannárgil valley.

During 1-2 April 2010 a team from the Italian Instituto Nazionale di Geofisica e Vulcanologia (INGV) working in collaboration with the scientists from IES conducted gas measurements at Fimmvörðuháls (Burton and others, 2010). Three measurement techniques were used: open-path FTIR (Fourier transform infrared spectroscopy), DOAS (differential optical absorption spectroscopy), and a sulfur dioxide (SO2) imaging system. The FTIR spectrometer uses infrared radiation emitted from the erupting lavas as a source for absorption spectrometry of gases emitted from the explosive vents. Spectra are analyzed using a single-beam retrieval, which allows pathlength estimates of H2O, CO2, SO2, HCl, and HF. Favorable wind conditions allowed traverse measurements under the gas plume with a DOAS spectrometer for SO2 flux estimates.

The investigators found that the SO2 gas flux was ~ 3,000 metric tons per day. Approximately 70% of the SO2 flux was produced by the fissure that opened 31 March, with ~ 30% emitted by the fissure that had opened on 21 March. The overall HF flux was ~ 30 tons per day. Gas compositions emitted from the two fissures were broadly similar and rich in H2O (over 80% by mole), less than 15% CO2, and less than 3% SO2. The SO2/HCl ratio varied at the 31 March fissure on 1 and 2 April (25% and 5%, respectively).

On 5 April, eruption tremor (at 1-2 Hz recorded at the nearest seismic station, Godabunga) began to gradually decline. By 7 April lava emissions had stopped from the original craters, but continued at the 31 March fissure.

When IES surveyed the new landscape on 7 April (figure 9), they found 1.3 km2 of new lava, an average thickness of new lava there of 10-12 m, and an estimated volume of eruptive material of 22-24 x 106 m3. From this they computed an average emission rate of ~ 15 m3/s. The tallest new cone reached an elevation 1,067 m, ~ 82 m above the previous ground surface. Another cone with a rim at 1,032 m elevation was 47 m above the previous surface and the vent area glowed red.

Figure (see Caption) Figure 9. The Fimmvörðuháls as surveyed and photographed by Freysteinn Sigmundsson and Eyjólfur Magnússon on 7 April 2010. Values shown are elevations and those in parentheses refer to the approximate net gain in elevation due to fresh deposits on the pre-eruption surface. Courtesy of IES.

By 9 April, after little change in deformation rates during the eruption, time series at continuous GPS stations N of the volcano showed sudden change, partly jumping back to pre-eruptive levels. On 11 April, eruption tremor also approached pre-eruptive levels, but visual observation revealed eruptive activity in late afternoon. Seismic tremor on 12 April reached a minimum.

Eruption from the summit caldera. The second, more explosive eruptive phase, began on 14 April 2010 at the subglacial, central summit caldera. This phase was preceded by an earthquake swarm from around 2300 on 13 April to 0100 on 14 April. Meltwater started to emanate from the icecap around 0700 on 14 April and an eruption plume was observed later that morning. The exact conditions at the summit were unknown due to cloud cover obscuring the volcano, but on 15 April an overflight imaged the erupting caldera using radar (figure 10).

Figure (see Caption) Figure 10. This 15 April radar image of the Eyjafjallajökull eruption depicts the otherwise hidden scene at the cloud-covered summit caldera. The glacial snow and ice had deformed and melted, forming circular depressions (ice cauldrons) in the icecap's surface. Flooding from the melting glacier had led to the various features on and below the glacier to the N and S (illustrated by labels). The data were acquired via aircraft by the Icelandic Coast Guard during 1700-1800 on 15 April 2010. The glacier margin and surface contours came from a 2004 investigation. Courtesy of Icelandic Coast Guard and IES.

The 15 April radar image helped depict a series of vents along a 2-km-long, N-oriented fissure. Both on top of and from below, meltwater flowed down the N and S slopes. Jokulhlaups (floods of meltwater also carrying considerable debris) reached the lowlands around the volcano with peak flow around noon on 14 April, causing destruction of roads, infrastructure, and farmlands. Residents had earlier been evacuated from hazardous areas. Tephra fall began in SE Iceland. That evening, a second jokulhlaup emanated from the icecap down the Markarfljot valley, which trends E-W along the N margin of the volcano and contains extensive outwash from surrounding glaciers.

On 15 April the ash plume reached a maximum altitude of over 8 km. E-blown ash began to arrive over mainland Europe closing airspace over the British Isles and large parts of Northern Europe. Ash generation continued at a similar level. Meltwater emerged from the glacier in pulses. Debris-charged jokulhlaups were seen in the evening.

Chemical analyses of mid-April ash samples revealed fluorine-rich intermediate eruptive products with silica content of ~ 58%. The initial lavas erupted at Fimmvörðuháls had silica contents of ~ 48% (table 1).

References. Burton, M., Salerno, G., La Spina, A., Stefansson, A., and Kaasalainen, H., 2010, Gas composition and flux report, IES web site.

Laursen, L., 2010, Iceland eruptions fuel interest in volcanic gas monitoring: Science, v. 328, no. 5977, p. 410-411.

Sigmarsson, O., Óskarsson, N., Þórðarson, Þ., Larsen, and G., Höskuldsson, Á, 2010, Preliminary interpretations of chemical analysis of tephra from Eyjafjallajökull volcano (report on the IES website).

Wall, R., and Flottau, J., 2010. Out of the ashes: Rising losses and recriminations rile Europe's air transport sector: Aviation Week & Space Technology, v. 172, no. 16, p.23-25.

Further References. Dahm, T., and Brandsdóttir, B., 1997, Moment tensors of micro-earthquakes from the Eyjafjallajökull volcano in South Iceland: Geophysical Journal International, v. 130, no.1, p. 183-192, DOI:10.1111/j.1365-246X.1997.tb00997.x.

Guðmundsson, M.T., and Gylfason, A.G., 2004, H?ttumat vegna eldgosa og hlaupa frá vestanverðum Mýrdalsjökli og Eyjafjallajökli. Háskólaútgáfan og Ríkislögreglustjórinn [Volcanic risk assessment run from Mýrdalsjökli and Eyjafjallajökull measurements]: University of Iceland and the National Police, 230 p.

Hjaltadottir, S., K. S. Vogfjord and R. Slunga, 2009, Seismic signs of magma pathways through the crust at Eyjafjallajokull volcanoe, South Iceland: Icelandic Meteorological Office report, VI 2009-013 (http://www.vedur.is/media/vedurstofan/utgafa/skyrslur/2009/VI_2009_013.pdf).

Hooper, A., Pedersen, R., and Sigmundsson, F., 2009, Constraints on magma intrusion at Eyjafjallajökull and Katla volcanoes in Iceland, from time series SAR interferometry, p. 13-24 in Bean, C.J., Braiden, A.K., Lokmer, I., Martini, F., and O'Brien, G.S., eds., The VOLUME project - Volcanoes: Understanding subsurface mass movement: School of Geological Sciences, University College Dublin.

Larsen, G., 1999, Gosi í Eyjafjallajökli 1821-1823 [The eruption of the Eyjafjallajökull volcano in 1821-1823]: Science Institute Research Report RH-28-99, Reykjavík, 13 p.

Pedersen, R., Sigmundsson, F., and Einarsson, P., 2007, Controlling factors on earthquake swarms associated with magmatic intrusions; Constraints from Iceland: Journal of Volcanology and Geothermal Research, v. 162, p. 73-80.

Pedersen, R., and Sigmundsson, F., 2004, InSAR based sill model links spatially offset areas of deformation and seismicity for the 1994 unrest episode at Eyjafjallajökull volcano, Iceland: Geophysical Research Letters, v. 31, L14610 doi: 10.1029/2004GL020368.

Pedersen, R., and Sigmundsson, F., 2006, Temporal development of the 1999 intrusive episode in the Eyjafjallajökull volcano, Iceland, derived from InSAR images: Bulletin Volcanology, v. 68, p. 377-393.

Sigmundsson, F., Geirsson, H., Hooper, A. J., Hjaltadottir, S., Vogfjord, K. S., Sturkell, E. C., Pedersen, R., Pinel, V., Fabien, A., Einarsson, P., Gudmundsson, M. T., Ofeigsson, B., and Feigl, K., 2009, Magma ascent at coupled volcanoes: Episodic magma injection at Katla and Eyjafjallajökull ice-covered volcanoes in Iceland and the onset of a new unrest episode in 2009: Eos (Transactions of the American Geophysical Union), v. 90, no. 52, Fall Meeting Supplement, Abstract V32B-03.

Sturkell, E., Einarsson, P., Sigmundsson, F., Hooper, A., Ófeigsson, B.G., Geirsson, H., and Ólafsson, H., 2009, Katla and Eyjafjallajökull volcanoes, p. 5-12 in Schomacker, A., Krüger. J., and Kjr, K.H., eds., The Mrdalsjökull Ice cap, Iceland - Glacial processes, sediments and landforms on an active volcano: Developments in Quaternary Sciences, v. 13.

Geologic Background. Eyjafjallajökull (also known as Eyjafjöll) is located west of Katla volcano. It consists of an elongated ice-covered stratovolcano with a 2.5-km-wide summit caldera. Fissure-fed lava flows occur on both the E and W flanks, but are more prominent on the western side. Although the volcano has erupted during historical time, it has been less active than other volcanoes of Iceland's eastern volcanic zone, and relatively few Holocene lava flows are known. An intrusion beneath the S flank from July-December 1999 was accompanied by increased seismic activity. The last historical activity prior to an eruption in 2010 produced intermediate-to-silicic tephra from the central caldera during December 1821 to January 1823.

Information Contacts: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Sturlugata 7, Askja, 101 Reykjavík, Iceland (URL: http://www.earthice.hi.is/page/ies_volcanoes) [contributors:Páll Einarsson, ásta Rut Hjartardóttir, Magnus Tumi Gudmundsson, Freysteinn Sigmundsson, Niels Oskarsson, Gudrun Larsen, Sigrun Hreinsdottir, Rikke Pedersen, Ingibjörg Jónsdóttir]; Icelandic Meteorological Office (IMO), Bústaðavegur 9, 150 Reykjavík, Iceland (URL: http://en.vedur.is/) [contributors:Steinunn Jakobsdóttir, Kristin S. Vogfjord, Sigurlaug Hjaltadottir, Gunnar B. Gudmundsson, Matthew J. Roberts]; The Environment Agency of Iceland, Sudurlandsbraut 24, 108 Reykjavik, Iceland (URL: http://english.ust.is/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); London Volcanic Ash Advisory Centre, Met Office, FitzRoy Road, Exeter, Devon EX1 3PB, United Kingdom (URL: http://www.metoffice.gov.uk/aviation/vaac/).


Piton de la Fournaise (France) — March 2010 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)


Seismicity and eruptions January 2009 and November 2009-January 2010

Eruptions from Piton de la Fournaise resumed in September 2008 after more than 16 months of quiet (BGVN 34:02). Eruptive episodes inside Dolomeiu crater, as reported by the Observatoire Volcanologique du Piton de la Fournaise (OVPDLF), took during 21 September-2 October and on 28 November 2008, with a third that began on 15 December and continued into January 2009. This report presents observations from January 2009 through January 2010.

Eruptions during 21 September 2008-4 February 2009. Eruptive phases in September, November, and December 2008 were previously described (BGVN 34:02). OVPDLF reported that the episode that began on 14 December 2008 ended on 4 February 2009. During that eruption two vents were active; lava flowed to the bottom of Dolomieu crater through lava tubes and caused the crust over the pooled area to rise. Some incandescence was noted at night and at dawn. Eruption tremor was irregular until 1 January, when it suddenly stopped. Tremor gradually rose over the next few days, but to a relatively low level, where it remained steady until slowly dropping again in early February (figure 79). Lava flows from this eruption covered an area of approximately 420 x 220 m, with a thickness of 75 m (figure 80).

Figure (see Caption) Figure 79. Tremor at Piton de la Fournaise, 14 December 2008-5 February 2009. Courtesy of OVPDLF.
Figure (see Caption) Figure 80. Cumulative lava flows in Dolomieu crater at Piton de la Fournaise during the September 2008-February 2009 eruption. Flows covered 420 x 220 m to a depth of 75 m. Courtesy of OVPDLF.

Activity during October 2009-January 2010. The OVPDLF reported three eruptions from the summit region at the Dolomieu crater's W wall adjacent to Bory crater between November 2009 and January 2010. The flows traveled to the E down the steep cliff toward the crater floor. These eruptions began on 5 November 2009, lasting about two days; on 14 December 2009, lasting 6 hours; and on 2 January 2010, lasting 10 days.

During 5-13 October 2009, OVPDLF reported increased seismicity (figure 81). Seismicity from 14 to 17 October indicated deformation on the N side of, and rockfalls within, the Dolomieu crater. On 18 October another seismic crisis was noted along with deformation on the N and S sides of the Dolomieu crater. Aerial observations on 19 October revealed a small new fumarole in the crater. Unspecified changes in the chemical composition of the gases were also noted. On 20 October rockfalls occured in greater number and longer duration than in previous days.

Figure (see Caption) Figure 81. A graph showing the number of volcano-tectonic earthquakes/day registered between 1 July 2009 and 26 January 2010 at Piton de la Fournaise. Horizontal bars indicate eruptions. Courtesy OVPDLF.

On 4 November 2009 a magnitude 3 earthquake at 0604 was felt by some residents of the southern part of the island. Such a magnitude is uncommon at this volcano. Seismologists at the Observatory located the earthquake at 750 m below sea level, under the southwestern edge of the Dolomieu crater. Later that day, 167 earthquakes of lesser magnitude followed. The focal depths rose to ~ 1 km above sea level with epicenters below the summit.

OVPDLF reported that 30 minutes after an intense seismic event on 5 November, a tremor signal characteristic of the beginning of an eruption occurred, and a vent opened inside the southern part of the Dolomieu crater. Within another 30 minutes, a fissure on the upper SE flank propagated E, and a second fissure opened on the E flank.

Lava fountains ~ 20 m high and flows were emitted from both fissures. The glowing lava was visible from the edge of the Enclos Fouqué and from the road in the Grand Brulé. Beginning around 1500, there was a gradual decrease in the intensity of the eruption. At 0645 on 6 November, a reconnaissance was conducted by a helicopter supplied by the National Gendarmerie, which confirmed that two fissures were open in the S side, S and E of the Dolomieu summit crater. Each emitted a lava flow descending to ~ 1,970 m elevation. As of 0730 that day, the lava ceased flowing, with a gradual decrease in the intensity of the eruption tremor.

At 1730 on 14 December a seismic event preceded a rise in summit deformation (8 cm horizontal). Eruptive tremor began at 1830, and an eruption began at 1845. A system of sub-parallel fissures along the summit of Dolomieu crater fed lava flows on the S slope of the volcano, inside the Enclos Fouqué. A second fissure system opened on the E flank of the Dolomieu summit crater at 2025, and lava flows advanced down the eastern slope. This eruption ended at 0040 after a gradual decrease in magma supply. On 15 December, a visible degassing in the S and SE fissures was associated with low-intensity eruptive tremor. All of the lava flows were confined to high portions of the S and SE slopes.

Fissure-fed fountaining sent lava flows down the S flank on 14 December 2009. Another seismic event on 29 December was characterized by numerous earthquakes up to M 3 in the area W and NW of Dolomieu crater at depths of 1.1-2.2 km below the summit. Deformation was also detected. OVPDLF reported decreased seismicity and fewer landslides within Dolomieu crater on 30 and 31 December.

On 2 January 2010 a fissure eruption near the top of the W crater rim (figure 82) was preceded by a seismic event and another 3 cm of horizontal deformation. Lava fountains rose a few tens of meters high and sent lava flows into Dolomieu crater, and ash and gas plumes rose above Piton de la Fournaise. Large landslides also occurred in Bory crater (W). During 2-3 January, seismicity and the number of landslides decreased. A series of ash plumes was noted through 12 January.

Figure (see Caption) Figure 82. Dolomieu crater on 2 January from its W rim showing lava flows and fountains. The dense gray plume was attributed to collapse along the steep crater wall. Courtesy of OVPDLF.

As of 4 January, the lava flows covered about 80% of the crater floor. Lava fountaining was still visible during 5-7 January and continued to erupt from a vent along a fissure high on the SW Dolomieu crater wall. The vent produced lava fountains and flows that pooled in the bottom of the crater. On 7 January the vent closed, but the previously erupted lava continued to flow for the next few days (figure 83). Seismicity decreased on 12 January and only minor gas emissions persisted. Figure 82 shows the lava flow along the axis where extensive glowing flows were visible. Some flows around this time were fed by lava tubes.

Figure (see Caption) Figure 83. A photo taken on the morning of 7 January 2010 of the lava vent flows from the W wall adjacent to Bory crater at Piton de la Fournaise. Courtesy of Undervol, OVPDLF.

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: Laurent Michon and Patrick Bachélery, Laboratoire GéoSciences Réunion, Institut de Physique du Globe de Paris, Université de La Réunion, CNRS, UMR 7154-Géologie des Systèmes Volcaniques, La Réunion, France; Guillaume Levieux, Thomas Staudacher, and Valérie Ferrazzini, Observatoire Volcanologique du Piton de la Fournaise (OVPDLF), Institut de Physique du Globe de Paris, 14 route nationale 3, 27ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr/ovpf/actualites-ovpf/).


Santa Maria (Guatemala) — March 2010 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Continuing frequent ash explosions through 2008-2009

Ongoing volcanism, including ash explosions, pyroclastic flows, avalanches, and lahars had continued through November 2007 at Santa Maria (BGVN 32:10). Subsequent activity has been closely monitored by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), with input from the Washington Volcanic Ash Advisory Center (VAAC).

Activity during 2008. On 11 January 2008, INSIVUMEH reported constant avalanches of blocks from the lava flows on the W and SW flanks of Santa María's Santiaguito lava dome complex. Weak-to-moderate explosions produced ash plumes that rose to altitudes of 4.1-4.5 km and drifted SW. On 6 February, weak explosions generated white columns of water and steam and ash that rose ~ 200 m above the crater rim. There were also a few avalanches onto the W flank lava flow. Degassing on 8 February was characterized by steam and gray plumes of fine ash on the SW flank. A significant magmatic explosion that threw fine ash up to ~ 5 km altitude and drifted ~ 4 km to the SW was followed by weak explosions of steam and ash. Avalanches of blocks from the crater rim on 12 February reached the lava flows on the S and SW flanks. Two moderate explosions expelled gray ash up to ~ 4 km altitude that dispersed to the SW.

The Washington VAAC (based on satellite imagery) reported that ash "puffs" from the Santiaguito lava dome complex rose ~ 4.5 km and drifted SW on 1 April, and then rose ~ 4 km and drifted W on 2 April. During 3-7 April, small explosions produced ash plumes; ashfall was reported in surrounding areas. This was followed on 15 April by three explosions expelling ash 300-900 m above the volcano and dispersing 5 km to the SW. Constant avalanches occurred to the W and SW. On 18 April another volcanic ash emission was reported by the Washington VAAC which rose to ~ 4.8 km, drifted SW, and extended ~ 30 km. More weak to moderate explosions occurred on 21 April which expelled gray ash clouds 300-800 m above the crater rim that drifted E. This activity was repeated on 25 April; the Washington VAAC reported an ash emission which rose to ~ 4.8 km and drifted ~ 13 km SW. On 28 April explosions sent ash plumes to an altitude of 4.1 km that drifted W.

Based on observations of satellite imagery, the Washington VAAC reported that ash puffs from the Santiaguito complex drifted NW on 13 May. On 22 May, two explosions were heard and gray ash emissions rose ~ 300-600 m above the crater rim and drifted S and SW, depositing ash in the Palajunoj area. Avalanches of blocks on the SW flanks were seen and heard. A lahar descended the Nima I River to the S on 25 May.

On 3 June, a Special Bulletin was issued to warn of the potential high water conditions in the Nimá I, Nimá II, San Isidro, Drum, Samala, rivers as a result of heavy rains in the area. On 5 June, avalanches were heard on the flanks of the volcano and overflows into the Samal and Mulu Rivers were reported. A lahar on 9 June about 15 m wide and up to 2 m deep descended the Nima I River, carrying blocks up to 1 m in diameter, and smelling of sulfur.

During the morning of 19 June, six weak-to-moderate explosions produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted SW and S. An incandescent lava flow accompanied by constant avalanches of blocks descended the SW flank. On 20 June, five weak-to-moderate explosions expelled gray ash up to ~ 600-800 m above the crater, spreading to the SW over the area of Palajunoj. The lava flow to the SW continued and incandescent lava could be seen at night, accompanied by constant avalanches of blocks and fine ash. A lahar traveled S down the Nima I river, carrying blocks up to 1 m in diameter. These conditions continued through 24 June.

On 4 July, an explosion produced an ash plume that rose to an altitude of 3.3 km and drifted SW. A lahar traveled S down the Nima I River, carrying tree limbs and blocks up to 50 cm in diameter. On 7-8 July, sounds resembling avalanches descending the flanks were reported; visual observations were hindered due to cloud cover. On 22 July seismic stations detected a lahar in the Nima I river. Explosions observed on 23, 28, and 29 July from the Caliente cone produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted SW and W. Ashfall was reported in areas downwind. A lava flow and avalanches of blocks descended the SW flank. On 28 July, weak pyroclastic flows also traveled down the SW flank.

During 21-26 August, explosions from the Caliente cone, part of the Santiaguito complex, produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted S, SW, and W. Constant degassing from the crater was noted.

On 10 September seismic stations detected a lahar in the Nima I River. The lahar, about 18 m wide and up to 2 m deep, carried blocks and smelled of sulfur. During 11-16 September, explosions produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted SW; on 18 September, the Washington VAAC reported that an ash plume rose to an altitude of 4.3 km and drifted SSW. On 24 September explosions produced ash plumes that rose to altitudes of 2.8 km and drifted SW. Avalanches of material from lava flows descended the SW flank.

On 11 and 15 November, the Washington VAAC reported that ash puffs drifted SW. On 12 December, explosions from the Caliente dome produced an ash plume that rose to an altitude of 3.2 km and drifted SW; the Washington VAAC reported a plume to an altitude of 5.8 km. On 16 December, two ash puffs drifted W and WNW at altitudes of 4.3-4.6 km. The Washington VAAC again reported that during 17-20 and 22 December ash plumes drifted SW, W, and NW; plumes rose to an altitude of 5.8 km. On 22 December, white plumes drifted SW and avalanches occurred from the crater rim. On 23 December a small ash plume drifted NW and explosions resulted in pyroclastic flows. Ash plumes rose to an altitude of 3.3 km and drifted S and SW. On 25 December a puff of ash drifted WNW.

Activity during 2009. Activity continued into 2009 and the Washington VAAC reported that two small ash plumes drifted ESE on 1 January. During 4-5 January, gas and steam plumes possibly containing some ash drifted SW and WSW. On 5 and 6 January fumarolic plumes drifted 100 m above the crater. Five explosions produced ash plumes that rose to altitudes of 2.8-3 km and drifted W and SE. A few avalanches originating from a lava flow descended the W flank. Explosions during 30 January-3 February produced plumes that rose to altitudes of 2.6-3.2 km and drifted W, SW, and S. Avalanches that were periodically incandescent descended the S and W flanks of Caliente lava dome.

The Washington VAAC reported that on 4 February multiple ash puffs drifted W. Explosions on 6 February produced plumes that rose to altitudes of 2.8-3.1 km and also drifted SW. Ashfall was reported in areas downwind. Ash puffs on 12 February drifted WSW and W. On 16-17 February, explosions produced ash plumes that rose to altitudes of 2.7-3.3 km and drifted SW. Small pyroclastic flows on 16 February descended the SE flank and reached the Nima I River. Incandescent avalanches were noted on 17 February and fumarolic plumes drifted SW.

On 18 February, a dense ash plume drifted W, and on the 20th an explosion sent an ash plume to an altitude of 3.2 km that drifted E. On 24 February, an explosion produced a white plume that rose 500 m above the summit and drifted SW. Incandescence was seen SW of Caliente dome. On 26-27 February and 2 March, explosions produced ash plumes that rose to altitudes of 2.8-3.4 km and drifted SW. Ashfall was reported in nearby areas. Avalanches were seen SW of the Caliente dome.

Based on satellite imagery, the Washington VAAC reported that during 4-6 March ash plumes drifted W. On 6 and 10 March, ash plumes rose to 2.8-3.4 km and drifted SW, NW, and N. Ashfall was reported in areas downwind. On 12, 16, and 17 March, explosions produced ash plumes that rose to altitudes of 2.7-3.5 km and drifted E and SW. A few avalanches originated from an active lava flow and traveled down the SW flank. On 12 March an ash plume drifted S, and on 15 March, an ash plume rose to an altitude of 3 km and drifted SW and WSW.

During 24-28 April explosions produced ash plumes that drifted 5-8 km WSW, although the number of explosions had decreased during the previous few weeks. On 5, 8, and 9 June ash plumes rose to altitudes of 2.8-3.3 km and drifted SW. Gas plumes that were sometimes gray rose ~ 300-600 m above the Caliente dome, and avalanches descended the S and W flanks. On 26 and 29 June explosions produced ash plumes that rose to altitudes of 2.9-3.3 km and drifted W and SW.

On 26 June, the seismic network detected a lahar that traveled S down the Nima I River. Steam plumes and a sulfur odor rose from the deposits. The lahar was 15 m wide and 1 m thick at the toe, and carried blocks up to 1.5 m in diameter. On 2 July lahars descended both the Nimá I and Nimá II rivers, carrying tree branches and blocks 50-75 cm in diameter. The lahars were 15 and 20 m wide.

On 6 July, explosions produced ash plumes that rose to altitudes of 2.8-3.2 km and drifted W. On 31 July and 3 August, explosions produced ash plumes, and the Caliente lava dome was incandescent. On 3 August, ash plumes rose to an altitude of 3.1 km and drifted W. Fumarolic plumes rose 200 m above the dome and rumbling noises were occasionally heard.

On 28 August, another explosion was noted. On 1 September, fumarolic plumes rose 150 m above Caliente dome and drifted SW and avalanches descended the SW flank of the dome. On 14 September an explosion produced an ash plume that rose to an altitude of 3.3 km. The plume drifted SW and caused ashfall. Avalanches went to the SW.

The Washington VAAC reported that on 22 October multiple ash plumes drifted less than 20 km SW. On 23 and 26 October, explosions produced ash plumes that rose above Caliente dome to altitudes of 3-3.3 km. The plumes drifted W and SE and caused ashfall. Avalanches descended the SW flank of the dome. Degassing sounds resembling airplane engines were also heard.

On 6 November, an explosion produced a plume that rose 900 m and drifted SW. The Washington VAAC reported that on 8 November a small gas plume possibly containing ash drifted less than 10 km SSW. Another small plume was seen later that day. On 13 November, a plume drifted SW. Avalanches descended the SW flank of the dome and the Washington VAAC reported that on 16 November multiple ash plumes drifted WSW.

On 20 November, two explosions produced an ash plume that drifted SW. Avalanches descended the SW flank of the dome. An explosion on 24 November produced an ash plume the rose to an altitude of 3.3 km and drifted SE. Ashfall was reported in areas downwind.

On 11, 14, and 15 December, explosions produced ash plumes that rose to altitudes of 2.8-3.5 km and drifted W and SW. Avalanches occasionally descended the SE flank of the dome. On 15 December, explosions generated pyroclastic flows that descended the E and SW flanks. On 30 December explosions produced ash plumes that rose to altitudes of 3-3.4 km and drifted W and SW. The Washington VAAC reported that ash plumes seen on satellite imagery drifted more than 30 km WSW. Avalanches occasionally descended the SW flank of the dome.

Activity during January-April 2010. Incandescent avalanches traveled down the SW flanks on 8 January 2010. A few explosions on 5 and 11-12 January produced ash plumes that rose to altitudes of 3.1-3.4 km and drifted S, SE, and SW. Avalanches from a lava flow descended the W flank of the dome. On 21 January ashfall was reported in areas near the Santiaguito complex. The next day an explosion produced an ash plume that rose to an altitude of 3.2 km and drifted SW. An ash plume seen on satellite imagery drifted less than 10 km.

On 2 and 4 March, explosions produced ash plumes that rose to altitudes of 2.7-3.1 km and drifted E and NE. Ash fell in areas downwind. Ash fell in inhabited areas downwind. The Washington VAAC reported that on 8 March an ash plume was seen in satellite imagery drifting WNW. On 29 March, explosions produced ash plumes that rose to altitudes of 3-3.3 km and drifted W over inhabited areas. Avalanches from a lava flow descended the SW flank. On 30 March a diffuse ash plume was seen in satellite imagery.

On 20 April, explosions produced ash plumes that rose to altitudes of 2.8-3.4 km and drifted S and SE. On 26 April, ash explosions and pyroclastic flows generated ash plumes that rose to an altitude of 8.3 km and drifted NW and N. Ashfall was reported in Quetzaltenango (18 km WNW) and other areas to the W, NW, and N. According to news articles, schools in 10 communities were closed and flights were banned within a 20-km-radius of the volcano.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanología, Meteorología, e Hidrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié; 21-72, Zona 13, Guatemala City, Guatemala (URL: http://www.conred.org/).


Sheveluch (Russia) — March 2010 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Near-constant dome growth during May 2008 through March 2010

Volcanism at Shiveluch that has been almost continuous since 1980 remained so from May 2008 through March 2010. During that time the lava dome was active and frequently growing, and produced moderate and weak explosions (figure 18). The most active phases took place during July-October 2008, March-April 2009, and November-December 2009 (figure 19).

Figure (see Caption) Figure 18. (top) A panoramic view Shiveluch looking N on 27 August 2009. The "Young Shiveluch" lava dome is degassing. (bottom) A photo taken at night on 15 September 2009 from the same perspective as the photo on left, showing lava traveling down the dome's S flank. Both photos taken from Kliuchi by Yuri Demyanchuk, IVS RAS.
Figure (see Caption) Figure 19. Plots for Shiveluch indicating the number the thermal anomaly pixels from satellite observations (top plot) and numbers of earthquakes originating in or adjacent to the dome (lower plot) during May 2008 to March 2010. The arrows show the observed explosions during good visibility. The ash cloud icons indicate the most significance events (ash plumes extending more then 50 km based on satellite images). Data from KB GS RAS.

During the two years discussed, there were many short-lived ash plumes (1-3 km above the dome), ash clouds produced by rockfalls and avalanches, and strong explosions that generated long-distance plumes (those with 'ash cloud' symbols above the arrows, figure 19). The large explosive eruptions of 26 April and 23 June 2009 sent respective ash plumes to 510 km and 754 km distances (table 8). The day after the earlier event, there was clear visibility on 27 April (figure 20).

Table 8. Significant explosions and ash plumes recorded at Shiveluch from May 2008 to March 2010. Plumes lower than ~1.2 km above the dome and seen for less than 10 km from the vent were omitted. Data courtesy of KVERT.

Date Plume altitude (m) Plume extension (km)
14 May 2008 5800 --
20 May 2008 5500 --
27 May 2008 3600 --
25 Jun 2008 4200 --
13 Sep 2008 6500 100 km NE
28 Sep 2008 5000 --
01 Oct 2008 -- 70 km S, W
14 Oct 2008 6000 --
16 Oct 2008 4500 --
19 Oct 2008 -- 30 km E
20 Oct 2008 -- 62 km E
05-06 Nov 2008 4000 --
04 Dec 2008 -- 25 km NE
17 Jan 2009 -- 10 km E
20 Jan 2009 4500 --
25 Feb 2009 5500 --
04 Mar 2009 4700 --
10 Mar 2009 6000 --
24 Mar 2009 7500 --
27-29 Mar 2009 -- 10 km SE
04 Apr 2009 4500 --
05 Apr 2009 -- 10 km E
15, 22 Apr 2009 4000 --
25 Apr 2009 6700 50 km SE
26 Apr 2009 5000 510 km SE
27-29 Apr 2009 5000 107-120 km NE
13 May 2009 5000 --
22 May 2009 4000 --
10 Jun 2009 7700 --
11 Jun 2009 4500 140 km SW
13-14 Jun 2009 5500-6100 --
18 Jun 2009 5700 --
20 Jun 2009 5000 --
23 Jun 2009 -- 754 km S
24 Jun 2009 -- 28 km NW
25 Jun 2009 -- 95 km
03 Jul 2009 -- 20 km SE
18 Jul 2009 -- 34 km E
24 Jul 2009 5000 --
27 Jul 2009 5000 10 km E
02 Aug 2009 -- 23 km E
15 Aug 2009 4500 --
31 Aug 2009 -- 107 km E
02 Sep 2009 -- 20 km S
11 Sep 2009 15000 --
18-19 Sep 2009 5000-5500 --
20 Sep 2009 -- 30 km NW
22 Sep 2009 4500 70 km SW
29 Sep 2009 -- 45 km E
02-03 Oct 2009 -- 30-60 km SE
30 Oct 2009 -- 255 km E
04-05 Nov 2009 4200-4500 --
10 Mar 2010 5500 --
11 Mar 2010 -- 10 km E
Figure (see Caption) Figure 20. Strong explosion on 26 April 2009 at Shiveluch produced a pyroclastic flow on the S slope and a resulting ash plume that extended 120 km to the NE. Photo by Yuri Demyanchuk, IVS RAS.

KVERT noted that on 11 September 2009 there were strong explosions. Based on interpretations of seismic data, the inferred ash plumes that day rose to an altitude greater than 15 km above sea level. The seismic network then detected 8 minutes of signals interpreted as pyroclastic flows from the lava dome; resulting plumes rose to an altitude of ~ 15 km. Cloud cover prevented visual observations. Ten more events characterized as ash explosions and either pyroclastic flows or avalanches were detected. Seismicity then decreased during 11-12 September. A visit during clear visibility on 13 September revealed fresh pyroclastic-flow deposits (figure 21).

Figure (see Caption) Figure 21. The light area on this 13 September 2009 photo represents fresh pyroclastic-flow deposits on Shiveluch. The deposits covered the apron and extended 5 km S. Dotted-line indicates the approximate profile of the lava dome of Young Shiveluch. Photo by Yuri Demyanchuk, IVS RAS.

Seismicity. Extended intervals of low-level seismicity were detected at the dome in May and June 2008, during May to October 2009, and to some extent from January through March 2010 (figure 19, bottom). A plot of regional seismicity during December 2009-5 April 2010 in a 70-km-diameter circle around Shiveluch (figure 22) indicates SW-dipping epicenters that rise to shallow depths under Shiveluch (and similarly for other volcanoes in the Kliuchevskoi group).

Figure (see Caption) Figure 22. Regional seismicity recorded during 19 December 2009 to 4 April 2010, presented in three panels. (a) A map of the region showing location and depths of earthquakes (white line is trace of cross-section AB), and the 70-km-diameter circle enclosing Shiveluch with epicenters of earthquakes plotted in (c). (b) Earthquakes projected onto the vertical plane of cross section AB. (c) Histogram showing Shiveluch's daily earthquakes with respect to time (bar height shows class (Ks) from seismic amplitude, after S.A. Fedotov), ascending curve is the cumulative number of earthquakes. Courtesy of KB GS RAS.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanology and Seismology (IV&S) Far East Division, Russian Academy of Sciences (FED RAS), Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS), Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs, http://www.emsd.ru/~ssl/monitoring/main.htm); Yuri Demyanchuk, IV&S FED RAS; Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), the Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and the Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Soufriere Hills (United Kingdom) — March 2010 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Lava dome growth continuing; pyroclastic flows reached the ocean

Montserrat Volcano Observatory (MVO) reported a strong increase in dome growth at Soufrière Hills (figure 82) and energetic explosive activity, including pyroclastic flows and substantial ash clouds, during the 6 months ending early April 2010 (the end of this reporting interval). Energetic extrusions were particularly noteworthy during January and February 2010 (table 69). From mid-December 2009 through early April 2010 there was continuing seismicity and gas emissions (table 70) as well as weekly ash emissions and pyroclsatic flows (table 71). Partial dome collapse on 11 February 2010 led to a plume that rose to ~15 km altitude.

Figure (see Caption) Figure 82. Map of Montserrat showing the pre-eruption topography of Soufrière Hills. The black circle shows the location of the MVO. The approximate outline of the Tar River delta in July 2004 is shown. Courtesy of Wadge and others (2005).

Table 69. Key features of the five Vulcanian explosions that occurred at Soufriere Hills in January and February 2010. Units in valley columns are pyroclastic-f low runout distances in kilometers. From Cole and others (2010) with due credit to Washington Volcanic Ash Advisory Center (VAAC) for satellite and aviation-based plume altitude estimates.

Date Time (local) Lapilli Fallout Plume White's Bottom Ghaut Tar River Valley Farrells Plain Tyers Ghaut/Belham Valley Gages Gingoes Ghaut White River
08 Jan 2010 1449-1500 No: Ash from PFs 7.6 km (25,000 ft) 4.7 2 2 5.8 4 2.6 1.5
10 Jan 2010 0128-0135 Not known 6.7 km (22,000 ft) >2 -- 1.5 2.5 3 -- --
10 Jan 2010 2027-2031 Yes: pumice 5.5 km (18,000 ft) 1.5 2 -- -- -- -- --
05 Feb 2010 1349-1356 Yes: non-pumiceous 6.7 km (22,000 ft) 1.5 2 1.5 2 4 1.5 1.5
08 Feb 2010 1957-2003 Not known 4.6 km (15,000 ft) -- -- -- -- 3.5 -- --

Table 70. Soufrière Hills seismicity and gas measurements from weekly reports between 4 December 2009 and 19 March 2010. MVO seismicity terminology as follows: Rockfall signals (featureless, high-frequency events, which correlate to large rockfalls from the dome); Volcano-tectonic (high frequencies >5 Hz, often impulsive P-phases and usually clear S-phases); Long-period (generally phaseless events with predominant frequency ~1 Hz); Hybrid (repetitive transient events of intermediate frequency, 3-5 Hz, without discernible S-phases; initial high-frequency waveforms at some stations) (MVO, 1996). Numbers refer to the total over the period indicated. Hydrochloric acid/sulfur dioxide ratios (HCl/SO2) are derived from Fourier Transform Infrared (FTIR) gas measurements. Cycles of activity refer to rockfalls, ash venting, and pyroclastic flows. "--" indicates that data was not reported. Courtesy of MVO.

Date Rockfall signals Long-period EQ's Volcano-tectonic EQ's Hybrid EQ's Observations
04 Dec-11 Dec 2009 957 207 3 6 Activity (pyroclastic flow, ash venting, rock falls, etc.) continued in cycles more irregular in time in the last few days; 10 Dec-hazard level raised from 3 to 4.
11 Dec-18 Dec 2009 977 134 3 58 Cycles of activity continue, varying between 5 and 6 hours; intensity of cycles decreased slightly through the week, however an increase in intensity occurred after about 1600 on 17 Dec.
18 Dec-24 Dec 2009 594 154 3 25 Cycles of activity with periods between 6 and 7 hours; heavy ashfall NW Montserrat.
24 Dec-31 Dec 2009 270 52 -- 6 Cycles of activity with periods between 6 and 8 hours.
31 Dec-08 Jan 2010 135 73 1 16 Cycles of activity with periods between 8 and 10 hours; ashfall in Old Towns, Salem, Olveston, Woodlands.
08 Jan-15 Jan 2010 68 25 2 10 Three explosions occurred during the week (1449 on 8 Jan, and 0128 and 2027 on 10 Jan), each accompanied by seismic signals that lasted 11, 7, and 4 minutes, respectively; ash plumes reached altitudes of 7.6, 6.7, and 5.5 km, respectively.
15 Jan-22 Jan 2010 196 38 -- 18 Cycles of activity with 6-8-hour periods; several houses buried and set on fire in Kinsale; ash clouds associated with pyroclastic flows reached 3-km altitude. Hybrid swarm of seven larger quakes on 20 Jan.
22 Jan-29 Jan 2010 565 113 2 18 Cycles of activity with periods between 5 and 7 hours; 25 Jan-heavy rain caused vigorous steaming of hot pyroclastic flows.
29 Jan-05 Feb 2010 552 87 6 64 Cycles of activity with periods between 7 and 12 hours. On 5 Feb a 30-m-high pyramidal-shaped extrusion was first seen; although it temporarily put the summit elevation at 1,170 m, it was destroyed by an explosion at 1349 that day; resulting pyroclastic surges moved NW across the sea near Plymouth.
05 Feb-12 Feb 2010 512 141 4 82 Two explosions on 5 and 8 Feb; 11 Feb-partial dome collapse, plume rose to altitude of ~15.2 km.
12 Feb-19 Feb 2010 53 34 1 4 17 Feb data consistent with quite slow extrusion of lava; MVO not yet able to make observations into the deep crater at the dome summit. HCl/SO2 = 0.76 (17 Feb).
19 Feb-26 Feb 2010 11 -- -- 6 23 Feb-hazard level lowered from 4 to 3. HCl/SO2 = 0.74 (19 Feb); 0.7 (22 Feb).
26 Feb-05 Mar 2010 7 1 -- 9 Swarm of 7 hybrids on 4 Mar. HCl/SO2 = 0.81 (1 Mar); 0.71 (2 Mar); 0.98 (4 Mar).
05 Mar-12 Mar 2010 47 9 2 7 Hybrid swarm of 6 on 11 Mar
12 Mar-19 Mar 2010 41 3 -- 7 17 Mar- SO2 flux 2,315 tons/day. HCl/SO2 = 0.6
19 Mar-26 Mar 2010 28 3 1 3 Avg. SO2 flux 342 tons/day
26 Mar-02 Apr 2010 17 -- -- 1 Avg. SO2 flux 194 tons/day
02 Apr-09 Apr 2010 9 1 3 3 3-day avg. SO2 flux 376 tons/day

Table 71. Brief summary of dome emissions compiled from MVO reports, 4 December 2009-1 April 2010. Date entries indicated with a * are discussed in the text. Courtesy of MVO.

Date Dome Activity Location of pyroclastic flows (PF) and rockfalls (RF) (runout distance from dome)
11 Dec-31 Dec 2009 Hottest and most active areas located on NW flank. Whites Ghaut to Whites Bottom Ghaut to the sea (4 km); Tyres Ghaut (~1-2 km); Gages valley (~2 km); Tar River valley; Gingoes Ghaut; Farrells plain, Dyers village (~2.5 km), Spring Ghaut.
31 Dec-08 Jan 2010 Growth on N side; 2 January-40-m high, 150-m wide lobe of lava extruded onto dome. Whites Ghaut, Farrells plain, Tyers Ghaut.
08 Jan-15 Jan 2010 * NE flank; 2 Jan-40-m high, 150-mwide lobe of lava extruded onto N summit of dome; 11 Jan-dome growth resumed on top, central part of dome. 8 Jan-collapsing fountain of tephra generated PF down Whites Bottom Ghaut, Tuitts Ghaut (within several hundred meters of the sea), Tyers Ghaut, Belham valley, Tar River valley; 10 Jan-explosion produced PF down Whites Bottom and Tuitts Ghaut, Tyers Ghaut, Gages valley.
15 Jan-22 Jan 2010 * 18 Jan-partial dome collapse on W side of dome. 18 Jan-PF reached sea down Aymers Ghaut (Gages valley to Spring Ghaut to Aymers Ghaut); houses inundated/burned in Kinsale.
22 Jan-29 Jan 2010 Dome growth on SE side of summit; NE side of summit has steep, vertical walls; NW part more rounded. Increase in PF in Tar River valley (several reached sea); Whites Ghaut; heavy rain on 25 caused vigorous steaming of hot PF in Belham valley; some lahars formed.
29 Jan-05 Feb 2010 5 Feb-central W part of lava dome grew to altitude of ~1,070 m. Gages valley to Spring Ghaut (~2-3 km; head of Springs Ghaut neearly full of PF deposits), Whites Ghaut.
05 Feb-12 Feb 2010 * W side of dome; 9 Feb-activity shifted to N side of dome; 11 Feb-partial dome collapse, scar ~300 m wide on N flank of volcano (MVO-"largest event for volcano since May 2006"). 5 Feb-volcanian explosion sent PF to Plymouth and into sea ~500 m, Tyers Ghaut (~2 km), Whites Ghaut, plume to ~8.4 km altitude; 8 Feb-small vulcanian explosion generated PF down Gages valley (over 2 km altitude), plume to ~5 km drifted E and ENE to Antigua; 11 Feb-PF reached on E side of island (coastline extended E ~650 meters at airport), Tyers Ghaut into Belham valley.
12 Feb-19 Feb 2010 Low activity, some incandescence on dome. PF deposits ~15 m thick in Trant's region, PF razed many buildings in Harris and Streatham.
19 Feb-26 Feb 2010 Low activity. --
26 Feb-05 Mar 2010 26 Feb-crater at summit of dome less than 100 m deep and ~200 m wide. 4 Mar-Tar River valley.
05 Mar-12 Mar 2010 * Moderate activity. 8-9 Mar-rainfall caused degradation of dome; Gages valley (~2 km).
12 Mar-19 Mar 2010 * Low activity; some incandescence on 14 Mar. --
19 Mar-26 Mar 2010 Low activity. 25 Mar-Spring Ghaut (~2 km).
26 Mar-02 Apr 2010 Low activity. --
02 Apr-09 Apr 2010 Low activity; some incandescence on dome. Lahars in Farm River and Trant's area.

MVO issued a synthesis to the Scientific Advisory Committee (SAC) on volcanism between 15 August 2009 and 28 February 2010 (Cole and others, 2010). That report figures heavily in the following summary, but the included tables and comments also came from MVO reports, and there is a section on satellite thermal monitoring. Two similar earlier reports were published in 2009 (Robertson and others, 2009 and Stewart and others, 2009).

Since the dome remained active and at the same time represented the volcano's highest point, the summit elevation varied. The historical value of 915 m was a high point on the crater rim. Cole and others (2010) noted that the dome's summit was 1,050 m in September 2009, with the elevation being 1,130 m on 29 January 2010. Some taller heights involved blocky spines that did not last.

Extrusive Phase 5 activity. Extrusive Phase 4 finished on 3 January 2009 and was followed by 10 months of comparative inactivity with intermittent small pyroclastic flows and ash venting 5-7 October (BGVN 34:10). Phase 5 occurred from 4 October 2009 to 11 February 2010 (figure 83). Seismic records enabled MVO to subdivide this phase into three episodes of inferred dome growth as follows: 9 October-20 November 2009 (Episode 1); 20 November 2009-8 January 2010 (Episode 2); and 8 January-11 February 2010 (Episode 3). Cole and others (2010) noted that "A characteristic feature of Phase 5 dome growth has been the simultaneous occurrence of PFs in more than one direction, sometimes on the opposite side of the lava dome." Throughout Phase 5, ash often fell on inhabited areas.

Figure (see Caption) Figure 83. Rockfall and pyroclastic flow data from the Phase 5 interval (3 October 2009 to 14 February 2010) at Soufriere Hills. Pyroclastic flows were observed by MVO staff, mainly during work hours, with each assigned to one of six drainages (flow directions) and to one of three sizes (the symbol size is proportional to the PF's size). Daily counts of rockfalls and long-period earthquakes and rockfalls (LP/RF) were determined by inspection of seismic signals (from station MBFL located at MVO). From Cole and others (2010).

Phase 5 began with a swarm of 24 volcano-tectonic (VT) earthquakes and ash venting. Gas fluxes had been low for two days prior to the onset of activity. The dome variously grew to the S, W, and N, and pyroclastic flows traveled in many directions. The eruptive style was described as "ash venting" rather than "explosions" due to the mild character of the associated seismic signals and the absence of ballistic fragments. Fallout deposits included comparatively coarse, well-sorted ash.

October dome growth mostly occurred on the S, with shed material filling the upper part of the SW flank's White River and covering what had stood as a protective wall for material traveling WSW. As a result, for the first time, substantial pyroclastic flows entered the WSW flank's Gingoes and Aymer's Ghauts, reaching the sea there with runout distances of over 4 km in those drainages.

Cyclic episodes of tremor occurred particularly during episode 2. On 23 November tremor occurred all day; it then waned and began to appear in cycles at 4-hour intervals, initially with signals of long-period and hybrid earthquakes. The tremor appeared associated with increased venting lasting 0.5-2 hours with plume heights to 5 km altitude. At 0640 on 10 December 2009, a large pyroclastic flow traveled down Tyers (Tyres) Ghaut and reached ~3.5 km from the lava dome.

Vigorous Vulcanian explosions occurred on five occasions during January-February 2010 (table 69), episode 3. All of these involved collapsing ash columns, producing fountain collapse pyroclastic flows that typically descended more than one ghaut. One explosion on 8 January, the largest by volume during January-February, sent a pyroclastic flow ~ 6 km down the Belham Valley. Two more Vulcanian explosions occurred during the night on 10 January.

Dome collapse of 11 February 2010. A large dome collapse took place in the early afternoon of 11 February, one day after a shift in dome-growth direction, and had several pulses. The collapse comprised 40-50 million cubic meters of material, and represented roughly 20% of the dome's total volume. A collapse scar ~ 300 m wide developed on the N flank of the dome. The collapse ended with vertically-directed explosions that created a new crater behind the collapsed part of the dome.

The collapse produced large pyroclastic flows and surges, mainly to the N and NE, that extended the E coastline (between Trants and Spanish Point), adding ~1 km2 of new land. Two smaller flows also traveled NW and entered the Belham Valley.

A large ash column resulted from the collapse that reached ~15 km altitude, causing extensive ashfall on Guadeloupe (~60 km SE) and other parts of the eastern Caribbean. After 11 February, both seismicity and surface activity quieted but deep deformation returned. Gas measurements also indicated that the system remained active.

Pyroclastic flows traveled N and NE toward the old airport. The extensive pyroclastic-flow deposits extended the coastline 300-400 m out to sea. The coastal area impacted extended from Whites Bottom Ghaut to Trants Bay, just N of the old Bramble airport (figures 84 and 85). The effects were clearly visible on the NE flanks. Some flows, ~ 15 m thick, reached the sea at Trant's Bay. These flows extended the island's coastline up to 650 m to the E.

Figure (see Caption) Figure 84. Two false-color satellite images, taken nearly 3 years apart at Soufriere Hills highlight the impact of the dome collapse of 11 February 2010. The image on the right is from 21 February 2010; the image on the left is from 17 March 2007. In colored versions of this image, red areas are vegetated, clouds are white, blue/black areas are ocean water, and gray areas are flow deposits. The large collapse scar on the N flank of the dome is visible (arrow). Several of the ghauts (valleys) on the SW side can be seen to have been nearly filled by pyroclastic flow deposits between October 2009 and February 2010. Images courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 85. Taken one week after the events of 11 February 2010 at Soufrière Hills, this aerial photograph shows the new pyroclastic flows at Spanish Point. Courtesy of MVO.

Towards the end of the collapse there was an energetic pyroclastic flow directed N over Streatham and Harris. This sent flows over the Harris Ridge into Bugby Hole and down the Farm River (~3.5 km from the dome) for the first time. The flows razed many buildings in both Harris and Streatham down to their foundations, and trees were felled by pyroclastic surges in the Gun Hill area and at the head of Farm River in Bugby Hole.

It was unclear whether there was any new dome growth within the crater during the week after the collapse. Night-time views of the dome revealed several small points of incandescence. Observations of the crater at the summit of the dome on 26 February found that it was then 50-100 m deep and ~200 m wide (figure 86). There was no newly extruded lava visible inside the crater.

Figure (see Caption) Figure 86. Views of the inside of the new crater at the summit of the Soufrière Hills dome taken on 26 February 2010. The dark material on the left is the deposit of a fresh rockfall that probably occurred a few days before the photograph was taken. Courtesy of MVO.

Heavy rain on 8-9 March caused vigorous steaming of the hot 11 February deposits (figure 87). Strong geysering was visible at Trants near the old Bramble airport, with ash and steam fountaining occurring. In addition, lahars traveled down several drainages, including the Belham valley. Small spots of incandescence on the dome were visible again on 14 March. Occasional small pyroclastic flows and rockfalls were still occurring mainly from the western and southern parts of the dome.

Figure (see Caption) Figure 87. Heavy rainfall on 8 and 9 March 2010 triggered a series of small to moderate sized pyroclastic flows. These were derived from the old dome and collapse scar. Pyroclastic flows continued to form as small amounts of cooled lava were shed from the surface. Courtesy of MVO.

MODVOLC Thermal Alerts. According to the Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, no satellite thermal alerts were measured over Soufrière Hills between 29 March 2007 and 3 December 2008. Satellite thermal alerts were measured almost daily during 11 October 2009 through 15 February 2010. An isolated thermal alert was measured on 10 March 2010. Previously shorter periods of thermal alerts were measured during 11-29 March 2007 and 3 December 2008-3 January 2009.

References. Cole, P., Bass, V., Christopher, C., Fergus, M., Gunn, L., Odbert, H., Simpson, R., Stewart, R., Stinton, A., Stone, J., Syers, R., Robertson, R., Watts, R., and Williams, P., 2010, Report to the Scientific Advisory Committee on Montserrat Volcanic Activity, Report on Activity between 15 August 2009 and 28 February 2010, Open File Report OFR 10-01a, Prepared for SAC 14: 22-24 March 2010. Montserrat Volcano Observatory (MVO).

Robertson, R., Babal, L., Bass, V., Christopher, T., Chardot, L., Fergus, M., Fournier, N., Higgins, M., Joseph, E., Komorowski, J.-C., Odbert, H., Simpson, R., Smith, P., Stewart, R., Stone, J., Syers, R., Tsaines, B., and Williams, P., 2009, Report for the Scientific Advisory Committee on Montserrat Volcanic Activity, Prepared for SAC 13: 7-9 September 2009, MVO Open File Report 09/03.

Stewart, R., Bass, V., Chardot, L., Christopher, T., Dondin, F., Finizola, A., Fournier, N., Joseph, E., Komorowski, J.-C., Legendre, Y., Peltier, A., Robertson, R., Syers, R., and Williams, P., 2009, Report for the Scientific Advisory Committee on Montserrat Volcanic Activity, Prepared for SAC12: 9-11 March 2009, MVO Open File Report 09/01.

Wadge, G., Macfarlane, D.G., Robertson, D.A., Hale, A.J., Pinkerton, H., Burrell, R.V., Norton, G.E., and James, M.R., 2005, AVTIS: a novel millimetre-wave ground based instrument for volcano remote sensing: J. Volcanology and Geothermal Research, v. 146, no. 4, p. 307-318.

MVO, 1996, MVO/VSC Open Scientific Meeting, 27 November 1996, Seismicity of Montserrat Soufrière Hills Volcano Eruption, July 1995-November 1996 (URL: http://www.geo.mtu.edu/volcanoes/west.indies/soufriere/govt/meetings/nov1996/02.html).

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

Information Contacts: Montserrat Volcano Observatory (MVO), Fleming, Montserrat, West Indies (URL: http://www.mvo.ms/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/).


Stromboli (Italy) — March 2010 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Explosions and lava flows in 2009; recent reports on 2007 eruption

Sonia Calvari of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) reported that the 2007 eruptive episode at Stromboli started on 27 February and finished on 2 April (BGVN 32:04) Additional details about this eruption can be found in Barberi and others (2009) and Calvari and others (2010). Eruptions later in 2007 and during 2008 will be reported in a later issue; summaries of activity in 2009 and January 2010 are included below.

Activity during 2009. The summit activity in 2009 was very unusual, producing four or five intracrater lava flows. Lava within the crater depression was extruded on 22-25 April, 3 May, and 30 August 2009. On 8 November a major explosion from the vents in the central crater fragmented and destroyed part of the E flank of the cinder cone there. The explosion produced an eruptive column over 350 m high that drifted SE and was soon followed by a lava flow from the widened central vent. The lava flow spread within the crater depression for a few minutes and reached a maximum distance of ~ 60 m. After the 8 November explosion, activity returned to background levels.

Strong seismic activity was recorded on 24 November 2009. Observers saw an explosive eruption cloud and the emission of a lava flow. Ejecta fallout affected the summit area, particularly the Pizzo sopra la Fossa, where numerous volcanic bombs landed. Also affected was the eastern downwind flank, where a layer of pumice was deposited on the beach. The fallout of incandescent material caused some vegetation fires on the E flank. After this explosive activity, seismicity returned to the level previously observed.

Activity during January 2010. According to the INGV website, at 1912 UTC on 4 January 2010, the network of surveillance cameras recorded an explosion that affected the central vent area. During a first phase, coarse pink pyroclastic materials (bombs and possibly lithic particles) were erupted from the entire crater terrace. A second phase followed with the emission of a small ash plume. Beginning at 0757 UTC on 7 January, the IR camera located on the Pizzo sopra la Fossa showed spattering lava in the central portion of the crater, leading to a series of lava flows; the lava stopped around 0100 UTC on 8 January. At 1448 UTC on 10 January, the INGV network of surveillance cameras recorded a strong explosion that affected the N portion of the crater, causing a major fallout of volcanic bombs at Pizzo sopra la Fossa and high on the NE part of the volcano.

References. Barberi, F., Rosi, M., and Scendone, R. (eds), 2009, The 2007 eruption of Stromboli: Journal of Volcanology and Geothermal Research, v. 182, no. 3-4, p. 123-280.

Calvari, S., Lodato, L., Steffke, A., Cristaldi, A., Harris, A.J.L., Spampinato, L., and Boschi, E., 2010, The 2007 Stromboli eruption: Event chronology and effusion rates using thermal infrared data: Journal Geophysical Research, Solid Earth, 115, B4, B04201, doi:10.1029/2009JB006478.

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

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


Telica (Nicaragua) — March 2010 Citation iconCite this Report

Telica

Nicaragua

12.606°N, 86.84°W; summit elev. 1036 m

All times are local (unless otherwise noted)


Incandescent crater floor areas seen in November 2009 and March 2010

Telica exhibited extensive degassing and sporadic ash explosions during 2006-2008 (BGVN 34:08). Activity since then had decreased to a relatively low level, but degassing was continuing. This report discusses activity in 2009 and January-February 2010 based on reports from the Instituto Nicarag?ense de Estudios Territoriales (INETER) and from fieldwork by Mel Rodgers (University of South Florida) in November 2009 and March 2010.

INETER publishes a monthly bulletin on earthquakes and volcanic activity in Nicaragua. For Telica, most of the monthly data consists of in-field temperature measurements. An observation camera situated 20 km from the crater has not been functional for more than a year. The seismic instrument at Telica was frequently out of order during 2009.

On 20 May 2009, the sulfur dioxide output in the crater ranged from 106-251 tons per day. The maximum temperature of the crater was about 90-112°C in April and May 2009, but rose to 201°C in July, 251°C in August, and 302-317°C during September through November 2009. The maximum temperature of four fumaroles was also measured, which generally ranged from 67-72°C. These temperatures decreased in June 2009 and increased in August 2009 (to 76-105°C). The temperature of fumarole 4 decreased to 59°C in October; gas emission at that fumarole ceased altogether in November.

Visits in November 2009 and March 2010. Mel Rodgers detailed observations during fieldwork at the volcano in November 2009 and March 2010 conducted with Diana Roman (University of South Florida), Peter La Femina and Halldor Geirsson (Pennsylvania State University), and Alain Morales (INETER). On 24-25 November 2009, the group observed a set of elongated fractures flanking the crater floor through which incandescence and/or lava were clearly visible. A high concentration of gas and a steady gas-and-vapor plume were also observed in the crater. Multiple vigorous fumaroles were observed on the W side of the crater close to the top of the crater wall, and an intermittent jetting noise that appeared to be coming from the crater floor was audible from their position at the crater rim. A broadband seismometer was installed and, during the 24-hour visit, a high rate of long-period (LP) seismicity was recorded.

On 15 March 2010, the researchers returned and again observed incandescence within the crater. Incandescence was clearly visible through a C-shaped crack or skylight, SE of the 25 November 2009 location (figures 17 and 18). A high concentration of gas and a steady gas-and-vapor plume in the crater continued and vigorous degassing of the fumaroles on the crater floor was observed (figure 19). Intermittent jetting noises and rockfalls were audible coming from the crater, and at 2202 UTC a loud, low popping noise from the crater was heard. Data retrieved from the single station installed in November 2009 showed a high rate of LP seismicity from November 2009-March 2010.

Figure (see Caption) Figure 17. Photograph taken 25 November 2009 of Telica volcano showing the relative locations of the 25 November 2009 incandescent fracture (right) and the later 15 March 2010 incandescent crack/skylight (left). Courtesy of Mel Rodgers.
Figure (see Caption) Figure 18. Photograph taken 15 March 2010 showing incandescence visible in the C-shaped crack/skylight at Telica volcano. Courtesy of Mel Rodgers.
Figure (see Caption) Figure 19. Photograph taken 15 March 2010 showing a view of the entire Telica crater floor. Locations of sightings of incandescence and of vigorous gas jets are indicated. Courtesy of Mel Rodgers.

A successful installation of the TESAND (Telica Seismic and Deformation) network was completed in March 2010. This network, consisting of six broadband seismometers and eight high-rate (1 Hz) continuous global positioning system stations, will be deployed for 3 years to document background LP seismicity and magmatic processes associated with quiescent volcanism.

According to the Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, no satellite thermal alerts were measured over Telica during 2008, 2009, and through 30 April 2010.

Geologic Background. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Information Contacts: Instituto Nicaraguense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua; Mel Rodgers, University of South Florida; Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822 (URL: http://modis.higp.hawaii.edu/).

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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