***************************************************************************** Bulletin of the Global Volcanism Network Volume 34, Number 10, October 2009 From: "Venzke, Ed" <VENZKEE@xxxxxx> ***************************************************************************** Bulletin of the Global Volcanism Network Volume 34, Number 10, August 2009 http://www.volcano.si.edu/ Gaua (Vanuatu) Eruptions during September-November 2009 cause ashfall and evacuations Tinakula (Santa Cruz Islands) Eruption suggested by satellite thermal data and confirmed in the field Ulawun (Papua New Guinea) Earthquake swarm followed by incandescence in June 2008 Batu Tara (Indonesia) Frequent ash plumes through October 2009 Egon (Indonesia) Update on the 15 April 2008 eruption and April-May 2008 seismicity Ibu (Indonesia) Ongoing dome growth during July-August 2009 Mayon (Philippines) Increased activity in mid-2009; November 2009 eruption Cleveland (USA) Two explosive ash emissions in June and October 2009 Soufriere Hills (Monserrat) A lull during late 2008 and intermittent high activity during late 2009 San Vicente (El Salvador) Landslide in November 2009 after heavy rains Fernandina (Ecuador) Thermal and gas analyses of April 2009 eruption Editors: Rick Wunderman, Edward Venzke, and Sally Kuhn Sennert Volunteer Staff: Paul S. Berger, Russell Ross, Hugh Replogle, Catie Carter, Ludmila Eichelberger, Robert Andrews, Margo Morell, Jacquelyn Gluck, and Stephen Bentley Gaua Vanuatu, SW Pacific 14.27°S, 167.50°E; summit elev. 797 m All times are local (= UTC + 11 hours) An eruption on Gaua Island in September 2009 was described in a report from the Vanuatu Geohazards unit (Vanuatu Department of Geology, Mines, and Water Resources, DGMWR) sent by Esline Garaebiti on 16 November. A later government report and several news reports extended into late November. According to the DGMWR, elevated volcanism in 1973 led to the evacuation of the entire island, which then was home to 600 people; Gaua Island now has more than 3,000 residents. News reports cited no fatalities and by the end of November hundreds of evacuees had moved to the safer E side of the island. Gaua island, round in shape, is ~ 20 km in diameter and lies in the N part of the archipelago (Banks Islands, Torba Province), ~ 100 km NE of the closest parts of the island Espiritu Santo (figure 1). The volcano is basaltic to andesitic in composition, and it contains a 6 x 9 km summit caldera that is ~ 700 m deep. Within the caldera sits Mount Garat (Gharat), a prominent cone that supports the summit and the crater complex that is the scene of the eruption. This caldera contains a large, crescent-shaped lake (Lake Letas) (Thery and Thery, 1995). Figure 1. Map of Vanuatu (formerly New Hebrides) showing major islands and province names. On this map Gaua island is labeled with its other name, Santa Maria. Inset shows Vanuatu with respect to other islands in this portion of the South Pacific. Ambrym volcano, S of Gaua at the E extent of Malampa province, sits on the island of the same name. Courtesy of Relief Web and from an original map by the Central Intelligence Agency. Activity during September-October 2009. Toward the end of September 2009, the island's inhabitants reported both strong degassing from Mount Garat's summit, gradual discoloration of the SW part of Lake Letas, and the strong smell of sulphur in the villages on the W coast. Mont Garat eruptions probably started on 27 September 2009. Around noon on 29 September 2009 a group of young men hunting close to the volcano witnessed a series of large explosions propelling an umbrella-shaped column of ash up to a height of ~ 3 km. They also noted a small pyroclastic flow limited to the W caldera. Due to prevailing E wind on that day, minor ashfalls were reported on the W part of Gaua. This explosive episode was also detected by the satellite-borne ozone monitoring instrument (OMI ) in measurements of sulfur dioxide (SO2) emissions the same day (figure 2). Figure 2. SO2 emissions recorded over and around Gaua at 0224 UTC on 29 September 2009 corresponding to the eruptive activity seen in the field. Note the higher, but normal, SO2 emission above Ambrym ~250 km farther S. Courtesy of DGMWR, with data provided by the OMI website. During 2-8 October 2009 a DGMWR team visiting the volcano found elevated SO2. They recorded an average flux of ~ 3,000 tons/day. They also noted an increase of the discolored area in Lake Letas (figures 3 and 4). Vegetation on NW part of the volcanic edifice, present in 2007, had been burned by acidic gases released from the volcano (figure 5). The team indicated that gas emissions had begun days to weeks earlier to cause such damage. Figure 3. Continuous degassing from the summit crater of Gaua. There are at least three active vents in the crater, one of which released a combination ash and gas. Photo taken 6 October 2009, courtesy S. Wallez. Figure 4. Strong discoloration was present at Gaua in the SW part of Lake Letas in 2003 (inset) and in 2009 (background). The 2003 photo showed discoloration with shades of green to pale yellow. The 2009 photo showed intense red-orange discoloration. Photos courtesy DGMWR (2003) and S. Wallez (2009). Figure 5. Views of Gaua's NW flank taken in the year 2007 and in November 2009, highlighting the almost complete loss of green vegetation. Photos courtesy of P. Bani, Research Institute for Development (IRD). The team installed a seismic station on 2 October 2009 to help track the volcanic activity. Many explosions were recorded during 10-11 October (figure 6), and on 13 October the seismic signals suggested strong volcanism as well as continuous degassing. Consequently the Alert Level was raised to 2 (on a scale of 0-4), advising the population not to venture close to the volcano and to stay out of potential drainages that might serve as flow paths. Figure 6. Seismic record from the Gaua seismic station illustrating that many explosions occurred between 1200 on 10 October 2009 and 1200 on 11 October 2009. Courtesy of DGMWR. Activity during November 2009. From the end of October to around 4 November, witnesses noted explosions with strong ash emissions (figure 7). A substantial ash plume, both reported by observers and confirmed by seismic recording, occurred on 31 October 2009. This was followed by ashfall in the NW part of the island, where 53 inhabitants were relocated to safer areas. Figure 7. Plumes released at Gaua on 3 November 2009. All three active vents emitted plumes, one a vigorous ash plume. Photo courtesy of Sylvain Todman, DGMWR. Gaua Bulletin No. 3 from DGMWR, dated 24 November 2009, reported a large explosion around 1400 on 18 November. The explosion produced very dense and high ash columns that blew W. The ash plumes from the 31 October and 18 November events photographed from the airport but were apparently not assessed for plume heights. Activity remained significant through at least 24 November. DGMWR recommended alert level 2 and noted the persisting danger of ashfalls and mudflows. News media reports and other data. Radio Australia News reported on 2 October 2009 that the last time the hazard concern was so high was in 1974 when volcanism led to inhabitants evacuated from the island for months. According to Radio Australia Net in an interview with Charles Bice (one of the Gaua Island community headmen), the early explosions had been heard by both residents and pilots on Air Vanuatu flights. During September-October, residents also found ash on their cabbage crops. A 26 November AFP report indicated that the Red Cross was dispensing containers and water purification tablets. It said the public had suffered respiratory problems and diaharrea. Rural water supplies often come from surface water, or from rainwater collected from areas such as roofs, and then stored in open drums or cisterns. These sources are often vulnerable to contamination from ashfall. A Vanuatu newspaper article by Len Garae printed after 18 November noted that by then the first phase of evacuation, aided by three ships, had taken ~ 159 villagers from the high-risk zone on the W side of the island to the E side of the island. The article stated that a larger eruption would mean evacuation of an additional 200 villagers on the island's W shoreline. An even more vigorous eruption would require inter-island ships to move residents to other islands. A Vanuatu news article emphasized three new explosion on 26 November and one on 27 November. It said that the additional villagers on the W side of the island were in the process of evacuating. Although yet to be confirmed elsewhere, the article said "the entire village of 'Waterfall' was destroyed by landslides." MODIS thermal alerts were absent during the 2009 eruption. A video shot in January 2003 from a low-flying helicopter showed fumarolic plumes rising from the summit craters. The video is available on YouTube from Geoff Mackley (http://www.youtube.com/user/geoffmackley). Reference: Thery, L., and Thery, J., 1995, Bathymetrie du lac Letas lle de GAUA (Banks) (Vanuatu), Port-Vila, Vanuatu: Institut Francais de Recherche Scientifique pour le Developpement en Cooperation, 1995. 17 p. : ill., maps; 28 cm. Series-Sciences de la terre geologie-geophysique ; no. 10 (in French and English) Geologic Summary. The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. Construction of the historically active cone of Mount Garat (Gharat) and other small cinder cones in the SW part of the caldera has left a crescent-shaped caldera lake. The symmetrical, flat-topped Mount Garat cone is topped by three pit craters. The onset of eruptive activity from a vent high on the SE flank of Mount Garat in 1962 ended a long period of dormancy. Information Contacts: E. Garaebiti, S. Todman, C. Haruel, D. Charley, D. Nakedau, J. Cevuard, and A. Worwor, Department of Geology, Mines and Water Resources (DGMWR), Geohazards Unit, Vanuatu (URL: http://www.geohazards.gov.vu/); P. Bani, Institut de recherche pour la developpment (IRD), Noumea, New Caledonia (URL: http://www.ird.nc/); OMI (Ozone Monitoring Instrument) Sulfur Dioxide Group, Joint Center for Earth Systems Technology, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA (http://so2.umbc.edu/omi/); Relief Web (URL: http://www.reliefweb.in); Agence France-Press (AFP) (URL: http://www.afp.com/); Radio Australia News (URL: http://www.radioaustralianews.net.au); The Independent/L'Indepednant, Vanuatu (URL: http://www.independent.vu/); Geoff Mackley, PO Box 12926, Penrose, Auckland 1135, New Zealand (http://www.youtube.com/user/geoffmackley, http://www.geoffmackley.com/). Tinakula Santa Cruz Islands, SW Pacific 10.38°S, 165.80°E; summit elev. 851 m All times are local (= UTC + 11 hours) MODIS/MODVOLC satellite thermal alerts data for Tinakula (table 1) suggests continuing eruptive activity during the period mid-June 2007 through early December 2009; however, these data lack validation by field observations. Similar intermittent alerts have been detected since mid-February 2005 (BGVN 31:03, 32:03, and 32:07). Table 1. MODIS/MODVOLC satellite thermal alerts measured at Tinakula during the period mid-June 2007 through early December 2009 (continued from table in BGVN 32:07). Note particularly the number of alerts recorded at 0230 on 15 February 2009 (5 pixels), indicating a possible eruption resulting in thermal anomalies covering an area of 5 to 7.5 km2. Courtesy of the Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System. Date Time Pixels Satellite (UTC) 24 Sep 2007 1140 2 Terra 19 Oct 2007 1430 1 Aqua 09 Nov 2007 1150 1 Terra 19 Sep 2008 1130 1 Terra 26 Sep 2008 1140 1 Terra 04 Nov 2008 1145 1 Terra 29 Nov 2009 1440 2 Aqua 15 Feb 2009 0230 5 Aqua 04 May 2009 1205 1 Terra 12 Aug 2009 1140 1 Terra 14 Aug 2009 1125 1 Terra A possible observation of eruptive activity was found on a website by Clark Berge dated 22 September 2009: "A tall plume of steam and smoke streams from the top of a majestic cone rising direct from the sea.... During my visit to Temotu Province last week ... we circled [Tinakula in a motorized canoe], which seemed lush and harmless until we rounded a point and saw the steep black face of stone. Boulders were detaching themselves and bounding down the cliff amid a shower of sparks. I quickly realized the stones were glowing red!" Geologic Summary. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano that rises 3-4 km from the sea floor at the NW end of the Santa Cruz islands. Tinakula resembles Stromboli volcano in containing a breached summit crater that extends from the 851-m-high 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 Tinakula 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 of the volcano and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated. Information Contacts: 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://hotspot.higp.hawaii.edu/); Clark Berge (URL: http://brclarkberge.blogspot.com/2009/09/tinakula-volcanoe.html). Ulawun New Britain, Papua New Guinea 5.05°S, 151.33°E; summit elev. 2,334 m Aactivity at Ulawun since early 2007 has consisted primarily of low-frequency earthquakes and white vapor emissions, with ash reported on 1 May and 25 December 2007 (BGVN 33:03). No additional activity was reported by the Rabaul Volcano Observatory (RVO) until a seismic swarm preceded observations of glow on 13-14 June 2008. Incandescence was seen again in mid-May 2009. RVO reported that increased seismic activity at Ulawun consisting of high-frequency volcano-tectonic (VT) earthquakes began on 7 June 2008. After peaking at 22 events on 12 June, the daily totals dropped and fluctuated between one and seven events per day, although totals of 14-15 events occurred on 14, 29, and 30 June. Some of the VT earthquakes were felt, including three on 30 June. Low-frequency earthquakes continued to occur as well, but remained within background levels; daily totals were between 257 and 775. Summit activity was very low and consisted of variable amounts of white vapor. Bluish vapor was observed on some days during 16-21 June. Other reported activity included low roaring noises on 1, 2, 12, and 14 June, and summit glow on the 13th and 14th. On 22 June noises heard in villages to the NE accompanied some of the earthquakes. On 28 June an earthquake accompanied by a booming noise was felt in nearby areas. White vapor plumes were emitted during 2-6 July, and occasional roaring noises were reported during 1-3 July. Additional reports by RVO in February and April 2009 noted that the volcano remained quiet, only releasing white vapor, with no reports of glow at night. Seismicity was moderate to low in February until power problems disabled the instrument. The number of seismic events that month fluctuated between 400 and 950 before declining to a range of 250-300 during 20-24 February. Low-frequency events dominated the record, although some high-frequency activity was recorded at a daily rate of 1-6 events. Ulawun remained quiet throughout September and October 2009. Summit activity was dominated by weak to moderate volumes of white vapor, and seismicity was generally low. During September, daily totals for high-frequency volcano-tectonic events ranged between 0 and 7, and low-frequency earthquakes were registered at a rate of 167-547. For the month of October, daily totals for high-frequency volcano-tectonic events were as high as 11, and the number of low-frequency earthquakes ranged between 74 and 404. Geologic Summary. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. Ulawun volcano, also known as the North Son, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m of the 2334-m-high Ulawun volcano is unvegetated. A prominent E-W-trending escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and eastern flanks. A steep-walled valley cuts the NW side of Ulawun volcano, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater. Information Contacts: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea (Email: hguria@xxxxxxxxxxxxx). Batu Tara Lesser Sunda Islands, Indonesia 7.792°S, 123.579°E; summit elev. 748 m Batu Tara has been active since January 2007, with thermal anomalies and occasional low-level ash plumes at least through 24 November 2009. This report discusses activity since our previous report (BGVN 34:01), which covered activity through 10 March 2009. Since 10 March 2009, the eruption of low-level ash plumes has continued at least through 24 November 2009. Many reports of Batu Tara plumes came from the Darwin Volcanic Ash Advisory Centre (table 2). Table 2. Summary of Volcanic Ash Advisories for Batu Tara reported by the Darwin Volcanic Ash Advisory Centre (VAAC) during 11 March 2009-24 November 2009. Many of these plumes were described as ash plumes. This table continues the table in BGVN 34:01. Courtesy of the Darwin VAAC. Date (2009) Plume top Plume drift direction(s) altitude (km) and extent 11 Mar 2.1 N, NW 20 Mar 2.4 NW 25-27 Mar 2.1 ~30-110 km NW 05-06 Apr 2.4 40-210 km W 11-12, 14 Apr 1.8-2.4 35-90 km W, NW 15-16 Apr 1.8-2.4 35-75 km W, NW 24-25, 28 Apr 3.0 Up to 110 km in variable directions 29-30 Apr, 03-04 May 2.4-3.0 45-185 km W, NW 05 May 2.4 55 W 14-19 May 3.0 35-75 km W, NW, N 20 May 3.0 65 km NW 26 May 2.4 55 km NW 27 May-02 Jun 2.4 25-75 km NW, W, SW 03-08 Jun 2.4 40-75 km NW, W, SW 09 Jun -- 140 km W 10-16 Jun 1.5-2.4 25-185 km SW, NW, N, NE 25-30 Jun 1.5 35-130 km SW, W, NW 01-07 Jul 1.5-2.4 35-110 km W, NW, N. 08 Jul 2.4 55 km W, NW 12-14 Jul 1.5 25-55 km W, NW, and N. 15-18 Jul 1.5 20-55 km in multiple directions 23 Jul 2.4 55 km W 27-28 Jul 1.5 Up to 150 km NW 29-31 Jul 1.5 Up to 37 km NW, N 04-07 Aug 1.5-2.1 45-90 km W, NW, N 12-13, 15-17 Aug 1.5-3.0 5-110 km W, NW, N 19, 21-25 Aug 1.5 35-150 km W, WNW, NW 26 Aug-01 Sep 1.5-2.4 15-55 km W, NW, N 02-08 Sep 1.5 10-55 km W, NW 09-11, 14-15 Sep 1.5 25-45 km W, NW 16-19, 21-22 Sep 1.5 20-65 km W, NW, N, NE 23-29 Sep 1.5-2.4 15-75 km W, NW 30 Sep-03, 05-06 Oct 2.4 25-75 km W, NW, N 06 Oct 2.4 65 km W 14-16 Oct 1.8 25-185 km W, N 27 Oct 2.1 65 km W, NW 24 Nov 2.4 90 km NW NASA's Earth Observatory described the scene from an image taken on 30 April 2009 (figure 8). "In this true-color picture, Batu Tara looks like a small, smoking speck in the Flores Sea. Initially blowing toward the NW, the volcanic plume changes direction multiple times, forming a large question-mark shape, mingling with clouds in the N. When volcanic gases mingle with oxygen and moisture in the presence of sunlight, vog, or volcanic smog, often results. The off-white color and diffuse shape of the volcanic plume in the N are suggestive of vog." MODVOLC recorded thermal alerts at Batu Tara on 26 and 29 May, and 3 July 2009. Figure 8. Image of plume from Batu Tara taken on 30 April 2009 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. Plume extends W and NW. Courtesy NASA Earth Observatory. Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km N of Lembata (fomerly Lomblen) Island contains a scarp on the E side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies N of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow. Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); 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), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/). Egon Lesser Sunda Islands, Indonesia 8.67°S, 122.45°E; summit elev. 1,703 m All times are local (= UTC + 8 hours) Since the eruption of 28 January 2004, Egon has frequently undergone phreatic eruptions without any significant increase in volcanic tremor or earthquakes. Our last report on Egon (BGVN 33:08) summarized the gradual decline of activity during April-May 2008. This report overlaps with the earlier one but benefits from better report translation. The closest large city to Egon is Maumere (Flores), ~ 25 km WNW. The Center of Volcanology and Geological Hazard Mitigation (CVGHM) provided additional information on the April-May 2008 disturbances (BGVN 33:08). A spike in the volcano's activity took place on 6-7 April 2008 (table 3). Reports noted a subsequent decrease in earth movements. On 4-15 April 2008 thin white smoke was seen rising ~ 25-50 m above the crater. This emission was considered a daily activity; however seismicity became evident. Table 3. Seismicity and observations of activity at Egon during 5-28 April 2009. "--" indicates no data reported. Courtesy of CVGHM. Date Deep Volcanic Shallow Volcanic Tremor Duration Earthquakes (VA) Earthquakes (VB) (seconds) Observations 05 Apr 2008 3 0 -- Usual daily occurrence of hot air blasts and whitish smoke 06 Apr 2008 38 93 -- Hot air blasts and "whitish smoke," rising 25-50 m 07 Apr 2008 15 2 -- Hot air blasts and "whitish smoke," rising ~35 m 08-14 Apr 2008 6 3 -- Hot air blasts and "whitish smoke," rising ~25 m above the crater and a significant decrease in volcanic quakes 15 Apr 2008 -- -- 1290 s Ash plume to 4,000 m height 20 Apr 2008 -- -- 1073.5 s Ash plume to 2,000 m height 24 Apr 2008 -- -- 91 s Ash plume to 850 m height 28 Apr 2008 -- -- 60.5 s Ash plume to 75 m height On 15 April 2008 a phreatic eruption occurred and CVGHM raised the Alert Level to 3 ("Saga" - on a scale of 1-4). Visual observations indicated that the ash column rose ~ 4,000 m above the crater; however the ash was not identifiable from satellite survey due to cloud cover. The eruption was accompanied by a "grumbling" sound. An ash/cinder cloud reached the city of Maumere (Flores), ~ 20 km WNW. Because of the height of eruptive plume, authorities at Waioti Airport serving Maumere were alerted. The emergency response team, together with the district government of Sikka (Flores) onsite at the villages closest to the eruption, reported that ~ 600 persons from local villages evacuated; they reported no fatalities. The Darwin Volcanic Ash Advisory Center (VAAC) issued two alerts of the volcanic activity at Egon, on 15 and 16 April 2008. Between 15 April and 11 May 2008, four explosive tremor events were recorded (table 3). Land deformation in the vicinity of the volcano stabilized after 27 April 2008. During 15 April-10 May 2008, 1-2 deep volcanic earthquakes occurred daily. Between 25 April to 10 May, shallow volcanic earthquakes decreased from 6-20 daily to 1-10 daily. During that time, tremors caused by hot air blasts continued to be recorded, reaching a rather high total range of around 6-47 events per day. The higher values are comparatively large; a normal stasis condition is considered to be a ~ 1-9 hot air blast signals per day. On 12 May 2008, hot air tremors had amplitudes of 2 mm and durations of 5-11 seconds. Whitish smoke could frequently be seen reaching a height of only 10 m above the peak. On 13 May, CVGHM downgraded the hazard status to Alert Level 2 (Waspada). For the rest of May 2008 and for more than a year, Egon's was relatively quiet. From 4 March to 12 July 2009, type-A earthquakes were recorded at a rate of 1-2 events per day; type-B earthquakes, 1-3 events per day; (except on 6 May when six were recorded). During that interval there were 1-9 hot air blast earthquakes per day and the hot air blasts of smoke were generally whitish in color and were rose to ~ 10 m over the peak. Eruptive earthquakes were absent. Although tremor was still recorded (with an amplitude of 0.5-4 mm), since 4 March 2009, earth movements have decreased. On 17 July 2009, the CGVHM. downgraded the hazard status to Alert Level 1 (Normal). MODVOLC review of activity shows no thermal indicators of volcanic activity. Geologic Summary. Gunung Egon volcano sits astride the narrow waist of eastern Flores Island. The barren, sparsely vegetated summit region has a 350-m-wide, 200-m-deep crater that sometimes contains a lake. Other small crater lakes occur on the flanks of the 1703-m-high volcano, which is also known as Namang. A lava dome forms the southern 1671-m-high summit. Solfataric activity occurs on the crater wall and rim and on the upper southern flank. Reports of historical eruptive activity prior to explosive eruptions beginning in 2004 were inconclusive. A column of "smoke" was often observed above the summit during 1888-1891 and in 1892. Strong "smoke" emission in 1907 reported by Sapper (1917) was considered by the Catalog of Active Volcanoes of the World (Neumann van Padang, 1951) to be a historical eruption, but Kemmerling (1929) noted that this was likely confused with an eruption on the same date and time from Lewotobi Lakilaki volcano. Information Contacts: Center of Volcanology and Geological Hazard Mitigation, Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/). Ibu Halmahera, Indonesia 1.488°N, 127.63°E; summit elev. 1,325 m All times are local (= UTC + 9 hours) Thermal anomalies detected by satellites (MODVOLC thermal alerts) through June 2009 suggested continued growth of a lava dome in the crater (BGVN 34:05). The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that prior to 11 July 2009, white and gray plumes from Ibu rose ~ 600 m above the crater rim. After 11 July, the plumes were gray and rose only ~ 400 m above the crater rim. Ash from the gray plumes fell on areas within a 3-km radius of Ibu. Observers noted an increase of eruptive activity after mid-July. During the period 27 July to 3 August, the total number of eruptive events showed a tendency to increase. Each eruptive earthquake was then followed by the expulsion of lava that reached the upper slopes. Plumes seen during 15 July to 4 August 2009 were grayish-white and reached a height of ~ 300-400 m above the crater rim. The lava extrusions accompanied rather strong rumbling noises on five occasions. The incandescent material was seen coming from the summit on 2 August 2009, and lava flows were seen. Later that day, a thunderous sound was followed by incandescence at the summit. On 3 August, incandescent material was ejected as high as 20 m above the crater. The total of explosion earthquakes increased from the 20-49 events of mid-July to 50-80 events during 27 July to 4 August. Villagers in Desa Duono, Going, and Sanghaji noted strong rumbling sounds. No volcanic earthquakes were recorded during that time frame. On 4 August 2009, 82 volcanic earthquakes were recorded. Each eruptive earthquake was followed by the expulsion of lava which reached the upper slopes. The observation post in the village of Duono, 5 km NW of Ibu, reported that the lava dome continued to grow. As a result, local residents were advised to prepare for times when they needed to wear masks that cover both the nose and the mouth. Visitors and tourists were asked to remain at least 2 km from the crater. Geologic Summary. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the western flank. A group of maars is located below the northern and western flanks of the volcano. Only a few eruptions have been recorded from Ibu in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998. Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); 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://hotspot.higp.hawaii.edu/). Mayon Luzon, Philippines 13.257°N, 123.685°E; summit elev. 2,462 m All times are local (= UTC + 8 hours) On 10 August 2008 an explosion and resulting ash plume followed weeks of increased activity and summit incandescence (BGVN 34:02). According to a Philippine Information Agency (PIA) Daily News Reader press release, the 10 August eruption was followed by an M 5.8 earthquake on 15 August and a series of aftershocks that continued through at least 20 August. On 10 July 2009, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) noted increased activity beginning in June 2009. According to PHIVOLCS, there was a rise in low-frequency volcanic earthquakes, a ground uplift of ~ 1 cm, moderate steam emissions, and summit incandescence. An 8 July overflight discovered the crater contained a "cone-shaped pile of hot, steaming old rocks." The fresh deposits were possibly from a previous eruption, and may have been the source of the glow in the crater. The Alert Level for Mayon was raised from 1 (low level unrest) to 2 (unrest which could lead to more ash explosions or eventually to hazardous magmatic eruptions). According to a 6 August 2009 article from the Philippine Daily Inquirer, resident PHIVOLCS volcanologist Eduardo Laguerta reported that the number of earthquakes at Mayon had decreased by early August 2009. However, the Inquirer reported that SO2 emissions had increased, with a maximum of 1,977 tons per day on 6 August, compared to 500 tons per day when there is no activity. PHIVOLCS reported that 11 earthquakes were detected during 14-15 September, with steam plumes drifting NW and ENE. On 15 September, three ash explosions produced a brownish ash plume that rose 700 m above the crater and drifted SW. On 28 October a minor explosion produced a brownish ash plume that rose 600 m above the crater and drifted NE, preceded by 13 volcanic earthquakes over the previous 24-hour period. On 11 November 2009 another ash eruption occurred at 0158 that lasted for ~ 3 minutes and ejected incandescent rock fragments seen from nearby villages. The explosion was accompanied by rumbling sounds and light ashfall in surrounding areas to the SW, W, and NW. According to the Inquirer, a second explosion was recorded at 0702, with an ash plume reaching 300 m above the crater. The Inquirer reported that residents in Daraga township to the S were ordered to evacuate early, but that further mass evacuations would not be ordered until the Alert Level was raised to Level 3. An aviation ash advisory from the Tokyo VAAC noted continuous ash erupting in MTSAT-IR satellite imagery at 0800 on 11 November. A 21 November 2009 article from Vox Bikol confirmed that as of 17 November, Mayon continued to exhibit summit incandescence and emit fluctuating amounts of SO2. Due to the continuing unrest PHIVOLCS installed additional seismic monitoring equipment, including three sets of broadband instruments from the Japan International Cooperating Agency (JICA). A news article from Vox Bikol stated that PHIVOLCS did not observe summit incandescence during 2-3 December due to heavy cloud cover, but as of 4 December 2009 ground deformation and moderate steam emissions were continuing. PHIVOLCS continued to enforce the 6-km-radius Permanent Danger Zone (PDZ) and the 7-km-radius Extended Danger Zone (EDZ) on the SE flank, and urged residents to avoid river channels that are prone to lahars. Geologic Summary. Beautifully symmetrical Mayon volcano, which rises to 2,462 m above the Albay Gulf, is the Philippines' most active volcano. The structurally simple volcano has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. The historical eruptions of this basaltic-andesitic volcano 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. Mayon's most violent eruption, in 1814, killed more than 1,200 people and devastated several towns. Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); Philippine Daily Inquirer, (URL: http://www.inquirer.net/); Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Vox Bikol (URL: http://www.voxbikol.com/); Philippine Information Agency (URL: http://www.pia.gov.ph/). Cleveland Aleutian Islands, United States 52.825°N, 169.944°W; summit elev. 1,730 m As previously reported (BGVN 33:11) , the Alaska Volcano Observatory (AVO) had raised the aviation color code for Cleveland on 24 December 2008 to Yellow and the alert level to Advisory, following a thermal anomaly near the summit that was present for two days. The anomaly was occasionally observed into early January 2009. On 2 January, a short-lived ash explosion produced an ash plume that rose ~ 6 km and drifted ~ 240 km ESE before dissipating. A small explosive eruption on 25 June 2009 sent an ash cloud rose to an estimated altitude of 4.6 km, which quickly detached from the volcano and drifted S. Another small and brief explosive eruption occurred on 2 October. A small detached ash cloud rose to maximum altitudes of 4.6-6.1 km and drifted ~ 600 km NE, dispersing over the Bering Sea. No further activity was detected through 19 October, so the Alert Levels were lowered to "Unassigned." Cleveland is not monitored by a real-time seismic network, thus the levels "Green" or "Normal" do not apply because background activity is not defined. Geologic Summary. Beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1,730-m-high Mount Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name for Mount Cleveland, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks of the volcano. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mount Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks. Information Contacts. 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, P.O. Box 757320, Fairbanks, AK 99775-7320, USA (Email: eisch@xxxxxxxxxxxxxxxxxx), and the Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (Email: cnye@xxxxxxxxxxxxxxxxx). Soufriere Hills Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 915 m Dome collapse at Soufriere Hills (figure 9) and an eruption on 28 July 2008 was followed by dome regrowth (BGVN 33:10). During October through 4 December 2008, low-level activity included occasional earthquakes and explosion, lahars, and small pyroclastic flows. The current report describes activity from 5 December 2008 through 10 December 2009, primarily based on information provided by the Montserrat Volcano Observatory (MVO). Activity was intermittent during 2009 (table 4), with high-level activity resuming in November and continuing through at least 11 December. Figure 9. Visible satellite imagery showing Soufriere Hills and the southern part of Montserrat on 24 June 2006. Courtesy of Google Earth, with data provided by Europa Technologies and DigitalGlobe. Table 4. Ash plumes or plumes that may have contained ash from Soufriere Hills between 5 December 2008 and 2 December 2009. Courtesy Washington Volcanic Ash Advisory Center (VAAC), based on analysis of satellite imagery, information from MVO, and pilot reports. Date Ash plume height, Remarks flow direction 13 Dec 2008 4.6-5.2 km 14 Dec 2008 1.8 km, W 15 Dec 2008 2.4-3 km, SW 16 Dec 2008 S Thermal anomaly 19-23 Dec 2008 4.3 km, various Thermal anomalies on 19 and 21 Dec 24 Dec 2008 3 km Caused by pyroclastic flow 26-30 Dec 2008 2.1-4.9 km, Thermal anomalies on 27 Dec various (28 and 30 Dec) Thermal anomaly 03 Jan 2009 2.4-10.7 km, various 04 Jan 2009 W, WSW 25 Feb 2009 W Caused by pyroclastic flow 06 Apr 2009 2.7-4.9 km, NW 24 May 2009 -- Caused by pyroclastic flow 04-06 Oct 2009 3.4-5.5 km, W, WNW 23-25 Oct 2009 W Caused by pyroclastic flows 24 Nov 2009 6.1 km Caused by pyroclastic flows 02 Dec 2009 4.6-6.1 km Caused by pyroclastic flows Activity during December 2008. Subsequent to the four explosions between 2-5 December 2008, the MVO reported that seismicity from the lava dome remained elevated. The volcano continued to inflate and discharge lava and ash during December 2008. Frequent pulses of ash rose from multiple places on the NW face of the lava dome and from a low on the dome behind Gages Mountain (as seen from Salem). A series of pyroclastic flows and rockfalls descended the Gages Valley and other valleys during December 2008, at least two reaching Plymouth (~ 5 km W). Significant lava dome growth on the SW flank was observed. Photographs showed that most of the growth had taken place since 8 December; lava was filling in the area between the lava dome and Chance's Peak. Initial calculations suggested that the dome grew at a rate of 1 m^3/s during this time. During the last two weeks of December 2008, the lava dome was characterized by increased lava extrusion, rockfalls, and pyroclastic flows. Lava extrusion on the N, W, and SW sides of the dome continued and incandescence on the dome was visible at night when weather was favorable. On 22 December, the Hazard Level was increased to 4 (on a scale 1-5) due to the repeated occurrences of pyroclastic flows in the lower part of Tyers Ghaut. On 24 December, a large pyroclastic flow that reached Plymouth, and possibly the sea, generated an ash plume that rose to an altitude of 3 km. Ashfall was reported in areas 6-7 km NW. Large incandescent blocks, deposited by rockfalls and pyroclastic flows, were visible on multiple occasions at night in the lower parts of Tyers Ghaut. Fires triggered by surges were visible in the neighboring valley. Activity during January-May 2009. On 2-3 January 2009, activity from the lava dome increased drastically. On 2 January, an energetic pyroclastic flow and associated surge traveled down Tyers Ghaut (NW) and reached the upper part of Belham River. On 3 January, after a period of elevated seismicity, two explosions produced large ash plumes that rose to altitudes greater than 10.7 km. Ashfall affected most of the island at elevations of 1.2 km and above. The explosions had significant "jet components" that rose to at least 500 m above the dome. In-column collapses resulted in pyroclastic flows that traveled W and reached Plymouth (~ 5 km W). According to news articles, about 70 people were evacuated from an area about 6-8 km NW. According to MVO, the level of seismic activity decreased dramatically after 3 January. It increased slightly in early February, with occasional rockfalls, and several small pyroclastic flows. On 19 February 2009, the Hazard Level was lowered to 3. Seismic activity remained low during March through May. Occasionally, lahars caused by heavy rainfall descended through multiple river valleys. Thermal images of a pyroclastic flow on 25 February 2009, and other videos, can be viewed on the MVO YouTube channel (http://www.youtube.com/user/montserratvolcanoobs). In mid-May 2009, activity from the Soufriere Hills lava dome increased slightly, but generally remained at a low level. Tectonic earthquakes were noted on 16, 18, 20, and 21 May at depths less than 3 km beneath the lava dome. Two possible explosions were detected on 21 May. The second and larger signal was followed by an ash plume that drifted W over Gages Mountain. During 21-22 May, a strong smell of sulfur dioxide was noted from Salem (6 km NW) to Woodlands (1 km N of Salem). Heavy rainfall caused erosion of the lava dome and hot pyroclastic flow deposits; steam plumes occasionally laden with ash occurred periodically from the base of Tyre's ghaut. Lahars traveled down multiple river valleys on 18 May. Activity during May-December 2009. Between the latter part of May and 4 October 2009, activity remained low with only periodic rockfalls and small pyroclastic flows. On 4 October 2009, a short volcano-tectonic earthquake swarm from the Soufriere Hills lava dome was detected. A period of tremor and vigorous ash venting followed about an hour later. The resulting ash plume drifted WNW across the island and out to sea, causing ashfall in Old Towne and Olveston. The seismic signals indicated no explosive activity or pyroclastic flows, but only two rockfalls after the ash-venting event. On 5 October, intermittent ash venting continued (figure 10), and ash fell S of inhabited areas. Early on 7 October, the ash-venting events from the lava dome ceased after a total of 13 had occurred. The last three were associated with small pyroclastic flows that traveled about 500 m down Tyers Ghaut to the NNW. Figure 10. Earth Observatory natural-color satellite photo of Soufriere Hills acquired on 6 October 2009. The photo shows an ash plume extending W, a day after eruptive activity resumed on 5 October. According to the U.S. Air Force Weather Agency, ash rose to 3.6 km and extended 280 km. Courtesy NASA Earth Observatory (image by Jeff Schmaltz, MODIS Rapid Response, NASA Goddard Space Flight Center). By mid-October 2009, activity from the Soufriere Hills lava dome rose to a high level. A new lava dome, first reported on 9 October, continued to grow. The new lava dome summit was about 60 m above the old dome structure. Seismicity was high and cycles of low-level tremor occurred at regular intervals. Over 1,200 rockfalls were detected and pyroclastic flows traveled down every major drainage valley except the Tar River valley to the E, resulting in ash plumes (figure 11). Heavy rainfall caused a lahar in the Belham Valley to the NW on 14 October. On 16 October, several large pyroclastic flows descended the White River to the S and reached the sea. Moderate-sized pyroclastic flows traveled 3 km NE down Tuitts Ghaut and White Bottom Ghaut, and a few smaller pyroclastic flows descended Tyers Ghaut to the N. Extensive ash clouds rose to an altitude of 6 km and drifted WNW, resulting in multiple minor ashfall in inhabited areas. Venting on 6 October 2009 can be seen on the YouTube channel for the Government Information Unit of Montserrat (http://www.youtube.com/user/GIUGOV). Lahars traveled NW down the Belham valley. Figure 11. Photo of Soufriere Hills taken from the International Space Station on 11 October 2009. Photo shows ash and steam plume extending W. Gray deposits that include pyroclastic flows and lahars are visible extending from the volcano toward the coastline. Courtesy NASA Earth Observatory. During the last week of October 2009, seismicity decreased slightly. However, numerous pyroclastic flows, some of which produced ash plumes, occurred in most of the major drainage valleys. Rockfalls were concentrated in the S. Heavy rainfall continued to cause lahars in the Belham Valley. On 29 October, a 40-m-high spine was seen protruding from the summit. Changes in lava-dome morphology seen on 30 October, and occurrences of pyroclastic flows traveling NE, indicated that growth was concentrated in the central part of the lava dome. By 30 October, activity was again at a high level. Hybrid earthquakes were recorded for the first time since the renewal of activity in early October. Numerous pyroclastic flows occurred in most of the major drainage valleys. The frequency of pyroclastic flows increased on 5 November and particularly vigorous flows occurred in Tuitt's Ghaut to the NE. Ash fell in inhabited areas on a few occasions. Lahars descended the Belham Valley several times. Good views of the lava dome on 9 and 10 November revealed that recent lava-dome growth was concentrated on the WSW side, immediately NE of Chances Peak; intense incandescence and rockfalls were noted at night. Ash fell across the Montserrat on 11 November, and about 6-8 km NW in Salem, Old Towne, Olveston, and Woodlands on 12 November. One pyroclastic flow nearly reached the sea at Kinsale village (WSW). By mid-November, activity from the Soufriere Hills lava dome consisted of ash venting along with semi-continuous rockfalls and pyroclastic flows that were concentrated on the W flank. Ashfall occurred across many areas of the island. On 19 November, heavy ashfall occurred to the NW between Old Towne and Brades. Views of the lava dome on 16 November showed that the dome height had decreased because of collapses and that a deep channel had developed NE of Chances Peak. Pyroclastic flows in the Gages Valley (W) continued down Spring Ghaut and Aymer's Ghaut, and spread onto the alluvial fan below St. Georges Hill. On 21 November 2009, activity returned to a high level. Periods of tremor were detected on 23 November. Lava extrusion during this period shifted from the W side of the lava dome to the summit region. As a result, abundant pyroclastic flows traveled NE down Tuitt's Ghaut on 23 November for the first time in several weeks. On 24 November there was a period of 120 minutes of continuous pyroclastic flow activity, followed by 90 minutes of semi-continuous activity. The pyroclastic flows traveled W down Gages Valley and into Spring Ghaut, and NE down Tuitt's Ghaut and Whites Bottom Ghaut reaching Tuitt's village. Associated ash plumes rose to an altitude of 6.1 km. On 26 November, a pyroclastic flow that descended the Tar River valley was caused by collapse of part of the old, pre-2009 lava dome. Ashfall occurred in Old Towne and parts of Olveston. Incandescent material seen in a photograph taken at night on 29 November traveled down the flanks of the lava dome in several areas. High-level activity from the lava dome continued through the first half of December 2009. Dome growth was concentrated on the N side, which has led to approximately 100 m of lateral growth of the lava dome in a northward direction. This growth has increased the available material for the formation of pyroclastic flows. Pyroclastic flows down the N flank became more abundant and their runout distance steadily increased. Pyroclastic flows also occurred to the NE and W, and one reached within 200 m of the sea. Ash vented from the S part of the lava dome. On 10 December 2009, a large pyroclastic flow traveled down Tyers Ghaut. This pyroclastic flow reached to below the west end of Lees village in the Dyers river, some 3.5 km from the lava dome. This event prompted MVO to raise the Hazard Level from 3 to 4. The higher Hazard Level signifies that larger pyroclastic flows moving down the Belham valley are a more likely possibility. According to MVO, larger pyroclastic flows could be formed by a partial dome collapse which could involve several million cubic meters of material. Helicopter observations have shown that the head of Tuitt's Ghaut down to the junction with Whites Bottom Ghaut is full of pyroclastic flow deposits such that there is now a continuous surface across from Farrell's plain. The head of Tyers Ghaut is also now nearly full. This means that future pyroclastic flows are likely to be less confined by topography and will spread more readily across the N flanks of the volcano. Thermal anomalies. MODIS satellite imagery recorded many thermal anomalies during December 2008, a smaller number in January 2009, none in February 2009, one in March 2009, and none during April through 10 October 2009. Beginning on 11 October through 11 December 2009, MODIS recorded a large number of thermal anomalies. Geologic Summary. The complex, dominantly andesitic Soufriere 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. English's Crater, a 1-km-wide crater breached widely to the east, was formed during an eruption about 4000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufriere Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat 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, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/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://hotspot.higp.hawaii.edu/); U.S. Air Force Weather Agency (AFWA)/XOGM, Offutt Air Force Base, NE 68113, USA (Email: Charles.Holliday@xxxxxxxxxxx). San Vicente El Salvador 13.595°N, 88.837°W; summit elev. 2,182 m All times are local (= UTC - 6 hours) During 7-8 November 2009, heavy rains caused landslides and flooding in areas NE to NW of San Vicente in central El Salvador (figure 12), resulting in flooded rivers, buried homes and car, and casualties. The most recent volcanic activity consisted of lava flows that were covered by an eruption of neighboring Ilopango volcano in 260 AD. According to the USGS, previous earthquake-and rainfall-triggered landslides and lahars occurred in 1774, 1934, 1996, and 2001. In 1774, a lahar on the NE flank affected the town of San Vicente. The 1934 lahar on the N flank destroyed the town of Tepetitan, more than 6 km from the summit. In 1996, landslides and lahars on the S flank damaged the major roadway between Tecoluca (17 km NW) and Zacatecoluca (6 km SSW). On 13 February 2001, a M 6.6 earthquake caused more than 25 landslides on the N and NW flanks of the volcano that reportedly killed 39 people. However, no subsequent volcanic activity occurred from San Vicente, San Miguel, San Salvador, or Santa Ana volcanoes. Figure 12. Location map of San Vicente volcano in the Departamento of San Vicente, in El Salvador. The country is divided into 14 Departamentos; five of these were affected by the 7-8 November events. The capital is San Salvador, 40 km WNW of San Vicente. Frequent and heavy rains on 7 November 2009 and into the next morning caused landslides, lahars, and flooding in the major drainages around the northern flanks of San Vicente. Servicio Nacional de Estudios Territoriales (SNET) reported that debris flows traveled up to 7 km away, severely affecting roads and towns. Loss of life and property were particularly severe in Verapaz, population ~ 3,000, (about 6 km NW of the summit) and Guadalupe (5 km NW from the summit, on the flanks), although damage was reported in several areas, including in the capital of San Salvador, 40 km WNW. According to the Pan American Health Organization (PAHO), the rate of rainfall at San Vicente volcano was 81 mm/hour, for a total of 355 mm in a 24-hour period. Five of the 14 Departamentos were affected by events caused by the rainfall: San Vicente, La Paz, La Libertad, San Salvador, and Cuscatlan. On 9 November an eyewitness living in Verapaz noted in media reports that, "It was about two in the morning when the rain started coming down harder, and the earth started shaking... The next thing I knew I was lying among parts of the walls of my house." Another resident stated, "I started to hear roaring noises and the ground began to shake. Then my windows broke and lots of mud came in..." According to news articles, about 300 houses were flooded when a river in the town overflowed. Extensive damage was done to roads (figure 13), water and power sevices, and croplands in Verapaz. Figure 13. A resident walks through an area hit by a landslide after torrential rains in Verapaz, El Salvador, on 9 November 2009. Photo by Yuri Cortez, AFP/Getty Images. In the capital of San Salvador, eyewitnesses described an area of 8 km^2 that had been covered by rocks, mud, and debris, and that many houses and hamlets had completely disappeared. At least six bridges were swept away and landslides blocked major and secondary roads, cutting communication and hindering clean-up efforts. Based on information from PAHO, the number of people in shelters peaked on 16 November at 15,090. As of 22 November, 198 people had died, 77 were missing, and 5,759 remained in shelters. The estimated number of affected people was 75,000. Geologic Summary. The twin peaks of San Vicente volcano, also known as Chichontepec, rise dramatically to the SE of Lake Ilopango. The modern andesitic stratovolcano was constructed within the Pleistocene La Carbonera caldera, whose rim is visible only on its SW side. San Vicente volcano, the second highest in El Salvador, grew within the caldera to form a paired volcano with summit craters oriented along a WSW-ENE line. The northern and southern flanks are covered by lava flows from the central vent, but lava flows on the eastern side originated from a vent on the upper flank. Volcanism has continued into the Holocene, but the latest lava flows are covered by deposits from the major ca. 260 AD eruption from neighboring Ilopango volcano. Reports of historical eruptions in 1643 and 1835 are false (Catalog of Active Volcanoes of the World; Sapper, 1917), but numerous hot springs and fumaroles are found on the northern and western flanks of the volcano. Information Contacts: Servicio Nacional de Estudios Territoriales (SNET), Km. 5 1/2 carretera a Santa Tecla y Calle las Mercedes, contiguo a Parque de Pelota, Edificio SNET, Apartado Postal 27, Centro de Gobierno, El Salvador 2283-2246 (URL: http://www.snet.gob.sv/); Pan American Health Organization (PAHO) - El Salvador, 73 Avenida Sur No. 135, Colonia Escalon, San Salvador, El Salvador (URL: http://devserver.paho.org/els/); Associated Press (URL: http://www.ap.org/); Los Angeles Times, 202 West 1st Street, Los Angeles, CA 90012, USA (URL: http://www.latimes.com/); BBC News (URL: http://news.bbc.co.uk/). Fernandina Galapagos Islands, Ecuador 0.37°S, 91.55°W; summit elev. 1,476 m All times are local (= UTC - 6 hours) Silvana Hidalgo and Patricia Mothes of the Ecuador Instituto Geofisco, Escuela Politecnica Nacional (IG-EPN) (Geophysical Institute, National Polytechnic School) sent an informal report on gas and temperature measurements during the final stage of the April 2009 eruption of Fernandina (Bourquin and others, 2009). Our last report on Fernandina in April 2009 (BGVN 34:04) discussed this eruption. The following information came from that document. The 2009 Fernandina volcano eruption, beginning 11 April 2009, was characterized by an extensive lava outpouring on the SW flank and sulfur dioxide (SO2) gas emission. First eyewitnesses reported an eruptive column on the morning of 11 April. Thermal and SO2 anomalies were shown by MODIS and AURA satellites, respectively. Rangers from the Galapagos National Park Service (GPNS) found the active eruptive fissure during a flight on 13 April 2009 (figure 14) . That fissure was near the 2005 eruptive fissure (BGVN 30:04). The 2009 fissure was ~ 200 m long and 10 m wide, and ejected lava fountains 15 m high. A gas and ash plume drifted SW, and a steam plume rose where the lava flow poured into the ocean (figure 15). Figure 14. Aerial photograph taken 13 April 2009 of the eruptive fissure seen as a horizontal band with a curtain of lava fountains during the Fernandina eruption. Courtesy of Oscar Carvajal, GNPS ranger; from (Bourquin and others, 2009). Figure 15. Aerial photograph taken 13 April 2009 of the steam plume caused by lava flowing into the ocean during the Fernandina eruption. Courtesy of Oscar Carvajal, GNPS ranger; from (Bourquin and others, 2009). During a flight on the morning of 15 April, personnel from the GNPS verified that the eruption continued, but with lower intensity than in the days before. Three vents discharging lava at ~ 400 m elevation on the SW flank along a radial fissure were active, feeding a lava flow up to 10 m wide. During 15-16 April, gas-and-steam plumes from Fernandina drifted up to 555 km W. The images recorded by the OMI (ozone monitoring instrument) satellite-borne platform showed a drastic decrease of activity after 16 April and a new increase on the 23 April (there was no data between 19 and 23 April due to a satellite update). This decrease in the eruption intensity correlated with a drop in the number of thermal alerts detected by MODIS satellite. The eruption ended on 28 April 2009. A field campaign was conducted by IGEPN from 27 April to 5 May 2009 to compare ground results with satellite data. Measurements of the SO2 associated with the eruption were conducted 29-30 April. At this time the eruption was nearing completion; the scientists were unable to make field measurements of the high SO2 fluxes during the earlier, more vigorous eruption phase. SO2 measurements. The SO2 measurements were carried on using a mobile-DOAS (differential optical absorption spectroscopy) instrument composed of a small, upward-looking telescope, connected by optical fiber to a spectrometer and a GPS (global positioning system) receiver (figure 16). The measurements were performed during several traverses around the eruption vent using a small boat supplied by the Galapagos National Park. One traverse along the W side (downwind side) of the island, conducted on 29 April 2009, found a SO2 flux maximum measurement of 2,997 tons/day. On 30 April, a traverse along the S and SW side of the island measured 527 tons/day. The IG-EPN report gave more detailed data on all measurements in support of the SO2 program made during the 2-day survey. Figure 16. Shaded relief map [digital elevation model (DEM)] of Fernandina Island including the NW part of Isabela to the E. The labeled lines correspond to the small boat traverses done on 29-30 April 2009 to measure environmental properties for SO2 flux analyses . Courtesy of Bourquin and others, 2009. Ozone monitoring instrument (OMI) satellite images showed degassing from 11-16 April 2009, with the higher SO2 values on 12 and 14 April. This degassing was associated with ash emission observed with MODIS satellite (shown in BGVN 34:04). From 17-19 April almost no SO2 was visible in the satellite images. After 4 days without data, satellite images showed a high SO2 emission on 23 April, increasing until 25 April when the eruption began its decline. After this date, and for the days when the field measurements were conducted, little SO2 was present in the atmosphere. Thermal measurements. The team made measurements using a forward looking infrared (FLIR) thermal camera during a flight over the zone covered by the fresh lava flows (figure 17, table 5). These measurements, associated with post eruption satellite images, allowed an estimation of the area covered by the eruption products. Figure 17. High-resolution satellite image after the April 2009 Fernandina eruption identifying individual lava flows and other points of interest. Courtesy of Bourquin and others (2009). Table 5. Description of points of interest at Fernandina from comparison of satellite thermal images and lava flow photographs. Location numbers in the first column correspond to the numbered points in figure 17. Courtesy of Bourquin and others (2009). Location Date of event number Comments 1 1995 eruption (radial fissure) Upper vents at elevation of ~1,000 and ~750 m with the associated lava flows. 2 2005 eruption (circumferential fissure) Upper vents with the associated lava flows. 3 2009 eruption (radial fissure) Upper vents at elevation of ~550 m covering part of the 1995 eruptive fissure and lava flows; vents displayed activity during the first overflight (13 April 2009) (figure 18); maximum apparent temperature measured with the thermal camera was 179.3°C. 4 2009 eruption (radial fissure) Upper vents at elevation of ~700 m located to W of 1995 eruptive fissure; vents active during the first flight (13 April 2009); maximum apparent temperature measured with the thermal camera was 67°C. 5 2009 eruption Dark grey patch not observed on images previous to April 2009 eruption; might correspond to a short-life vent with small lavas. 6 2009 eruption (radial fissure) Principal vents at elevation of ~500 m; last visual observation of incandescence was on 29 April 2009 during; measurements with the thermocouple in a 50 cm crack and greater-than-30-m-long crack gave maximum temperature of 970°C. 7 2009 eruption Area covered by principal April 2009 lava flows that reached the sea; maximum apparent temperature measured with the thermal camera was 131.9°C. 8 1995 eruption (radial fissure) influence 2009 lava flow Principal 1995 vent; during the first part of 2009 eruption, lava flowed W to this vent and reached the ocean; after a while, it changed its course and flowed E to the vent but never reached the ocean. 9 1995 lava field and 2009 lava flow SE lobe of the 2009 lava flow borders 1995 lava field and ends 1,800 m before entering into the ocean; maximum apparent temperature measured with the thermal camera was 70.9°C (figure 19). 10 2009 eruption April 2009 lava flows entered into the ocean the first days of the eruption; this region of the lava flows is 800 m-wide (figure 20); maximum apparent temperature measured with the thermal camera was 132°C. 11 1995 eruption 1995 eruption lava field. Figure 18. Aerial photo showing the upper fissure and the principal vents of the April 2009 Fernandina eruption. Courtesy of Bourquin and others (2009). Figure 19. Photograph of SE lava flow (area 9) from the April 2009 Fernandina eruption. Area number 11 corresponds to the 1995 eruption lava field. Courtesy of Bourquin and others (2009). Figure 20. Photograph of lava flow entering the ocean on the SW coast (area 10) from the April 2009 Fernandina eruption. Courtesy of Bourquin and others (2009). Estimation of the area covered. The area covered by the April 2009 Fernandina volcano eruption was estimated using (1) thermal images taken with the infrared camera FLIR during the overflight of 1 May 2009, (2) QUICKBIRD satellite image (browse image visible; 11 May 2009), (3) ASTER satellite image (16 May 2009), (4) photographs taken by the personal of IGEPN and GNPS during the overflight of 1 May 2009, and (5) a Digital Elevation Model (DEM) provided by the IGEPN. Thanks to the strong thermal contrast between the new products and the older lava flows, it was possible to map precisely the limits of April 2009 eruption. The thermal contrast information was stacked on the satellite images and the area has been calculated with the help of the DEM (figure 21). The area covered by the April 2009 eruption is of about 6.7 km^2 which is a value similar to the 1995 eruption (6.5 km^2; Rowland and others, 2003). Unfortunately no thickness measurements are available for the April 2009 lava flows. Nevertheless, considering the similarities between both eruptions, IGEPN scientists used the average thickness calculated by Rowland and others (2003) for the 1995 eruption (8.5 +- 2 m), to calculate the 2009 eruption volume. It gives an approximate volume of 57 +- 13 million^ m^3 of lava emitted. This volume is equivalent to those of 1995 and 1988 but the emission rates were drastically different. This estimation has to be taken carefully as no thickness measurement was done during the fieldwork. Figure 21. Map of Fernandina showing the extent of the April 2009 lava flows extending down the SW flank to the ocean. Courtesy of Bourquin and others (2009). Satellite thermal data. As shown in BVGN 34:04, from 11 April to 22 June 2009 MODVOLC detected 789 hot-spots on Fernandina Island with 725 during the time of the eruption and 64 after it. The number of thermal alerts was the highest for 12 April and then decreased until the end of the eruption. At least three episodes of high effusion occurred, during 11-14, 16-19, and 28 April. Comparing these observations with the OMI satellite images, the first two effusive episodes were accompanied by high SO2 emissions, but not the last one. This could be due to an artifact on the OMI satellite image for 28 April. The decreasing number of thermal alerts after 28 April is thought to illustrate the cooling of the lava flows, as they are not associated with SO2 emissions. Eruption photos. The smugmug.com website shows a number of photos of the April 2009 Fernandina eruption from offshore. According to the website, the vessel carrying the photographers was restricted from sailing to visit the side of Fernandina Island where the volcano was erupting in mid-April. On 19 April the vessel was given permission by the Galapagos National Park to see the volcano. The boat anchored ~ 1.6 km offshore and the photographers boarded small boats to get within ~ 90 m of where the lava was pouring into the sea (figures 22 and 23). Figure 22. Night photo of the ocean entry area at Ferandina taken 19 April 2009. In this photo a small boat is apparent in the right midground, with siloutees of people highlighed by incandescene in the background. Courtesy of smugmug; the photographer's name was not specified on that website. Figure 23. Photo of the ocean entry area at Fernandina taken 19 April 2009. In this photo the red-orange lava about to enter the ocean is apparent at right and at elevation on the left appears a a fountain jets towards the night sky. Courtesy of smugmug; the photographer's name was not specified on that website. References: Bourquin, J., Hidalgo, S., Bernard, B., Ramon, P., Vallejo, S., and Parmigiani, A, 2009, April 2009 Fernandina volcano eruption, Galapagos Islands, Ecuador: SO2 and thermal field measurements compared with satellite data: Informal report, Instituto Geofisco Escuela Politecnica Nacional (IGEPN). Rowland, S.K., Harris, A.J.L., Wooster, M.J., Amelung, F., Garbeil, H., Wilson, L, and Mouginis-Mark, P.J., 2003, Volumetric characteristics of lava flows from interferometric radar and multispectral satellite data: The 1995 Fernandina and 1998 Cerro Azul eruptions in the western Galapagos: Bulletin of Volcanology, v. 65, no. 5, p. 311-330. Geologic Summary. Fernandina, the most active of Galapagos volcanoes and the one closest to the Galapagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galapagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 cu km section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake. Information Contacts: Silvana Hidalgo and Patricia Mothes, Instituto Geofisco Escuela Politecnica Nacional (IGEPN) (Geophysical Institute, National Polytechnic School), Casilla 1701-2759, Quito, Ecuador (Email: shidalgo@xxxxxxxxxxxx and pmothes@xxxxxxxxxxxx; URL: http://www.igepn.edu.ec/); 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://hotspot.higp.hawaii.edu/); SmugMug (URL: http://www.smugmug.com; http://www.wildphotopics.com/Travel-International/Galapagos-Islands-and-Quito/Fernandina-Island-La/8109366_9nVGc/1/528644840_CChcM). ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
