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SI/USGS Weekly Volcanic Activity Report 5-11 May 2010
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SI/USGS Weekly Volcanic Activity Report
5-11 May 2010
Sally Kuhn Sennert - Weekly Report Editor
kuhns@si.edu
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Eyjafjallajökull, Southern Iceland | Ketoi, Kuril Islands (Russia) | Pagan, Mariana Islands (Central Pacific) | Reventador, Ecuador | Rinjani, Lombok Island (Indonesia) | Santa María, Guatemala
Ongoing Activity: | Aoba, Vanuatu (SW Pacific) | Bagana, Bougainville | Dukono, Halmahera | Gaua, Banks Islands (SW Pacific) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Popocatépetl, México | Sakura-jima, Kyushu | Sangay, Ecuador | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Tungurahua, Ecuador | Yasur, Vanuatu (SW Pacific)
The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.
Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source.
New Activity/Unrest
EYJAFJALLAJOKULL Southern Iceland 63.63°N, 19.62°W; summit elev. 1666 m
The Institute of Earth Sciences at the Nordic Volcanological Center (NVC) reported that during 5-11 May the eruption from Eyjafjallajökull continued to produce ash plumes from the summit vent. Based on analyses of imagery from weather satellites, scientific overflights, and pilot reports, ash plumes ranging in color from light gray to black rose to altitudes of 4-9 km (13,100-29,500 ft) a.s.l. and drifted ESE, SE, and S. The cinder cone in the summit crater continued to build and was near the level of the ice on the crater rim on 8 May.
On 5 and 6 May explosive activity increased and effusive activity decreased, resulting in higher eruption plumes and increased tephra fallout. The lava flow stopped advancing, and very little steam rose from the edges of the flow. Ashfall was reported in areas 55-70 km away during 5-8 May, and was "considerable" on 6 and 7 May. Ash was reported in a few areas within 12 km E and SSE during 9-10 May. According to new articles, ash plumes again caused flight disruptions during 5-11 May in several European countries, including Scotland, Ireland, Spain, and Portugal.
Geologic Summary. Eyjafjallajökull (also known as Eyjafjöll) is located west of Katla volcano. Eyjafjallajökull consists of an E-W-trending, elongated ice-covered basaltic-andesite stratovolcano with a 2.5-km-wide summit caldera. Fissure-fed lava flows occur on both the eastern and western flanks of the volcano, but are more prominent on the western side. Although the 1666-m-high 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 south flank from July-December 1999 was accompanied by increased seismic activity and was constrained by tilt measurements, GPS-geodesy and InSAR. The last historical eruption of Eyjafjallajökull prior to an eruption in 2010 produced intermediate-to-silicic tephra from the central caldera during December 1821 to January 1823.
Sources: Institute of Earth Sciences http://www.earthice.hi.is/,
Reuters
http://www.reuters.com/article/idUSTRE64568D20100507,
Agence France-Presse
http://www.google.com/hostednews/afp/article/ALeqM5iJMLS1IDqBS3FZlrffKUmdXC9JGA
KETOI Kuril Islands (Russia) 47.35°N, 152.475°E; summit elev. 1172 m
SVERT reported that increased fumarolic activity from Ketoi was noted in satellite imagery on 4 May.
Geologic Summary. The circular, 10-km-wide Ketoi island, which rises across the 19-km-wide Diana Strait from Simushir Island, hosts of one of the most complex volcanic structures of the Kuril Islands. The rim of a 5-km-wide Pleistocene caldera is exposed only on the NE side. A younger 1172-m-high stratovolcano forming the NW part of the island is cut by a horst-and-graben structure containing two solfatara fields. A 1.5-km-wide freshwater lake fills an explosion crater in the center of the island. Pallas Peak, a large andesitic cone in the NE part of the caldera, is truncated by a 550-m-wide crater containing a brilliantly colored turquoise crater lake. Lava flows from Pallas Peak overtop the caldera rim and descend nearly 5 km to the SE coast. The first historical eruption of Pallas Peak, during 1843-46, was its largest.
Source: Sakhalin Volcanic Eruption Response Team (SVERT) http://www.imgg.ru/rus/labs_vulcan_hazard.php
PAGAN Mariana Islands (Central Pacific) 18.13°N, 145.80°E; summit elev. 570 m
Steam and gas plumes from Pagan were seen in satellite imagery on 28 April (UTC) and 3 May; no unusual thermal activity was identified. A visitor to the island saw a minor ash emission on the morning of 3 May. The Aviation Color Code was raised to Yellow and the Volcano Alert Level was raised to Advisory on 6 May based on the recent satellite observations and confirmed minor ashfall on the island.
Geologic Summary. Pagan Island, the largest and one of the most active of the Marianas Islands volcanoes, consists of two stratovolcanoes connected by a narrow isthmus. Both North and South Pagan stratovolcanoes were constructed within calderas, 7 and 4 km in diameter, respectively. The 570-m-high Mount Pagan at the NE end of the island rises above the flat floor of the caldera, which probably formed during the early Holocene. South Pagan is a 548-m-high stratovolcano with an elongated summit containing four distinct craters. Almost all of the historical eruptions of Pagan, which date back to the 17th century, have originated from North Pagan volcano. The largest eruption of Pagan during historical time took place in 1981 and prompted the evacuation of the sparsely populated island.
Source: Emergency Management Office of the Commonwealth of the Mariana Islands, Office of the Governor, United States Geological Survey Volcano Hazards Program http://volcano.wr.usgs.gov/nmi/activity/index.php
REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m
The IG reported that during 5-9 May observations of Reventador were not possible because of weather. The Washington VAAC reported that on 7 May an ash plume seen by a pilot rose to an altitude of 5.2 km (17,000 ft) a.s.l. Cloud cover prevented satellite observations of the area. On 8 May the IG noted a small lahar inside the caldera.
Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. Reventador has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera.
Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/,
Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
RINJANI Lombok Island (Indonesia) 8.42°S, 116.47°E; summit elev. 3726 m
Based on analysis of satellite imagery, the Darwin VAAC reported that on 5 May a possible ash plume from Rinjani rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted 150 km NW. The plume was not seen in imagery about six hours later. CVGHM advised the VAAC that intermittent activity could produce ash plumes to 1.5 km (5,000 ft) above the caldera.
Geologic Summary. Rinjani volcano on the island of Lombok rises to 3,726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the E, but the W side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak caldera. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the E end of the caldera. Historical eruptions at Rinjani dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake.
Source: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m
On 7 May, INSIVUMEH reported that explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose to altitudes of 2.9-3.4 km (9,500-11,200 ft) a.s.l. and drifted SW. Seismic stations recorded 17 explosions within 24 hours. On 10 May a white plume rose 75 m high. No explosions were noted.
Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large 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 westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/
Ongoing Activity
AOBA Vanuatu (SW Pacific) 15.40°S, 167.83°E; summit elev. 1496 m
On 11 May the Vanuatu Geohazards Observatory noted that there had been recent increases in activity from Aoba, starting with reports that local villagers saw a plume over the island in December 2009. Fluctuating gas emissions seen in satellite imagery were also noted at that time. Satellite imagery on 11 April revealed that sulfur dioxide emissions increased to a rate of more than 3,000 tons/day. Scientists flew over Aoba and confirmed increased gas emissions. They also noted two fumarolic zones in the SE part of Lake Manaro that were surrounded by discolored water. The Vanuatu Volcano Alert Level (VVAL) remained at 1 (on a scale of 0-4).
Geologic Summary. Aoba, also known as Ambae, is a massive 2500 cu km basaltic shield volcano that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes is located at the summit of the Hawaiian-style shield volcano within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. Post-caldera explosive eruptions formed the summit craters of Lake Voui (also spelled Vui) and Lake Manaro Ngoru about 360 years ago. A tuff cone was constructed within Lake Voui about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.
Source: Vanuatu Geohazards Observatory http://www.geohazards.gov.vu/
BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m
Based on analyses of satellite imagery, the Darwin VAAC reported that ash plumes from Bagana rose to altitudes of 2.4-3 km (8,000-10,000 ft) a.s.l. during 6 and 10-11 May and drifted 65 km W and SW.
Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m
The Darwin VAAC reported that during 4 and 8-10 May ash plumes from Dukono were seen in satellite imagery drifting 25-100 km NW, NE, and SE at an altitude of 3 km (10,000 ft) a.s.l. On 6 May a pilot reported that a significant plume rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted NW, but there was no confirmation of the plume in satellite imagery.
Geologic Summary. 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 N-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
GAUA Banks Islands (SW Pacific) 14.27°S, 167.50°E; summit elev. 797 m
On 11 May the Vanuatu Geohazards Observatory reported that field observations of Gaua revealed continued activity during April through the beginning of May. Significant emissions of gas and ash caused damage to vegetation around the crater and in areas on the NW, W, and SW parts of the island, the dominant wind directions. Lahars on the W part of the island were seen in April. Seismic data revealed that tremors had become more frequent since the beginning of the year. The Vanuatu Volcano Alert Level (VVAL) remained at 2 (on a scale of 0-4).
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.
Source: Vanuatu Geohazards Observatory http://www.geohazards.gov.vu/
KARYMSKY Eastern Kamchatka (Russia) 54.05°N, 159.45°E; summit elev. 1536 m
KVERT reported that during 30 April-7 May seismic activity from Karymsky was above background levels, suggesting that possible ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. Satellite imagery revealed a thermal anomaly over the volcano during 28 April-2 May. The Aviation Color Code level remained at Orange.
Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
During 5-11 May HVO reported that activity at Kilauea continued at the summit and the east rift zone. At the summit, episodic rising and falling of the lava-pool surface continued at the deep pit inset within the floor of Halema'uma'u crater; glow from the vent was visible. The plume of gas and ash from the summit vent drifted SW and W, dropping small amounts of ash, and occasionally Pele's hair and Pele's tears, downwind. The sulfur dioxide emission rate measured at the summit on 5 May was 880 tonnes/day.
At the east rift zone, lava flows that broke out of the TEB lava-tube system had advanced down the Pulama pali onto the coastal plain and headed S into the ocean. Lava also flowed along the highway, after covering the county viewing area on 5 May. Incandescence was sometimes seen from a vent low on the S wall of Pu'u 'O'o crater. On 9 May lava flows near the county viewing area stalled.
Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/
KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m
KVERT reported that during 30 April-7 May seismic activity from Kliuchevskoi was above background levels. Ground observations were prevented due to meteorological cloud cover. Satellite imagery revealed a large daily thermal anomaly from the volcano. Ash plumes drifted 125 km N on 2 May and 70 km W at an altitude of 5.5 km (18,000 ft) a.s.l. on 3 May. Gas-and-steam plumes drifted 55 km W and SW both days. Based on information from KEMSD, the Tokyo VAAC reported that on 10 May an eruption produced a plume that rose to an altitude of 6.1 km (20,000 ft) a.s.l. The Aviation Color Code level remained at Orange.
Geologic Summary. Kliuchevskoi is Kamchatka's highest and most active volcano. Since its origin about 7,000 years ago, the beautifully symmetrical, 4,835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. More than 100 flank eruptions, mostly on the NE and SE flanks of the conical volcano between 500 m and 3,600 m elevation, have occurred during the past 3,000 years. The morphology of its 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included major explosive and effusive events from flank craters.
Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m
CENAPRED reported emissions of steam and gas from Popocatépetl during 5-11 May. Plumes contained small amounts of ash on 7 May.
Geologic Summary. Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America's second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages.
Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
Based on information from JMA, the Tokyo VAAC reported that during 4-6 and 8-9 May explosions from Sakura-jima often produced plumes. Those plumes, along with ash plumes occasionally seen by pilots, rose to altitudes of 2.1-3.7 km (7,000-12,000 ft) a.s.l. and sometimes drifted N, NE, E, and SE.
Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SANGAY Ecuador 2.002°S, 78.341°W; summit elev. 5230 m
The Washington VAAC reported that on 6 May an ash plume from Sangay was seen by a pilot. Ash was not identified in satellite imagery, but a diffuse steam-and-gas plume was seen before weather clouds moved into the area.
Geologic Summary. The isolated Sangay volcano, located E of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. It has been in frequent eruption for the past several centuries. The steep-sided, 5,230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the E, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. Sangay towers above the tropical jungle on the E side; on the other sides flat plains of ash from the volcano have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The more or less constant eruptive activity has caused frequent changes to the morphology of the summit crater complex.
Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m
KVERT reported that during 30 April-7 May seismic activity from Shiveluch was above background levels and suggested that possible ash plumes rose to an altitude of 4.5 km (14,800 ft) a.s.l. Satellite imagery revealed a large daily thermal anomaly from the lava dome, and ash plumes that drifted about 18 km W on 3 May. The Aviation Color Code level remained at Orange.
Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. Intermittent explosive eruptions began in the 1990s from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m
MVO reported that activity at Soufrière Hills was low during 30 April-7 May. A pyroclastic flow traveled down the Tar River Valley on 3 May, stopping about 1 km before reaching the sea. The Hazard Level remained at 3.
Geologic Summary. 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. English's Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 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 Soufrière 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.
Source: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/
TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m
The IG reported that during 4-5 and 7-8 May lahars traveled down Tungurahua's N, W, and SW flanks. No activity from the crater was noted during 5-11 May, although meteorological cloud cover often prevented observations.
Geologic Summary. The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador's capital city, and is one of Ecuador's most active volcanoes. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/
YASUR Vanuatu (SW Pacific) 19.53°S, 169.442°E; summit elev. 361 m
On 11 May the Vanuatu Geohazards Observatory reported that, following an assessment of Yasur during 26-27 April, activity from the volcano remained high. Strong degassing and ash emissions from all three active vents were noted. Ash fell on the E and W parts of the island. New bombs were deposited around the crater rim and in areas near the vents. Explosions were heard and seen from surrounding villages. Satellite imagery and seismic data confirmed strong degassing and explosive activity. The Vanuatu Volcano Alert Level (VVAL) remained at 2 (on a scale of 0-4).
Geologic Summary. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Yasur is a mostly unvegetated pyroclastic cone with a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera in SE Tanna Island. It is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. Active tectonism along the Yenkahe horst accompanying eruptions of Yasur has raised Port Resolution harbor more than 20 m during the past century.
Source: Vanuatu Geohazards Observatory http://www.geohazards.gov.vu/
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