***************************************************************************************
SI/USGS Weekly Volcanic Activity Report 21-27 April 2010
***************************************************************************************
SI/USGS Weekly Volcanic Activity Report
21-27 April 2010
Sally Kuhn Sennert - Weekly Report Editor
kuhns@si.edu
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Eyjafjallajökull, Southern Iceland | Reventador, Ecuador | Santa María, Guatemala | Tongkoko, Sulawesi
Ongoing Activity: | Bagana, Bougainville | Batu Tara, Komba Island (Indonesia) | Dukono, Halmahera | Fuego, Guatemala | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Llaima, Central Chile | Pagan, Mariana Islands (Central Pacific) | Sakura-jima, Kyushu | Sangay, Ecuador | Shiveluch, Central Kamchatka (Russia)
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 the summit eruption from Eyjafjallajökull continued during 21-27 April. The eruption rate on 21 April was inferred to have been an order of magnitude smaller than during the initial 72 hours of the eruption, having declined over the previous few days. Phreatomagmatic activity with some lava spatter occurred from the northernmost of two craters in the summit caldera, generating plumes to an altitude of 3 km (9,800 ft) a.s.l. that drifted S. The emission of lava flows likely began around 1200 evident by the onset of semi-continuous meltwater discharge, steaming from the N edge of the ice cauldron, and changes in tremor amplitude.
Similar activity continued for the next four days, although plumes sometimes rose to 6 km (19,700 ft) a.s.l. on 22 April. On 23 April changes in the wind direction pushed the plume NW, causing airports in SW Iceland to close. The next day, mild explosive activity ejected spatter 100 m above the crater and shockwaves were detected every few seconds; an ash plume rose 4 km (13,100 ft) a.s.l. and drifted SW. A depression in the ice, formed from lava flows that had advanced 400-500 m N of the crater, was 700 m long and steaming, especially at the edges.
The N crater was active on 25 April. The eruption plume height was unknown due to meteorological cloud cover at 5.3 km (17,400 ft) a.s.l.; minor ashfall was noted at two farms 10 km NW of the vents. Explosions were also heard at locations 10-15 km NW. On 26 April plumes rose to an average altitude of 4.8 km (15,700 ft) a.s.l. and drifted E. Radar data showed a tephra crater or cone continuously building on the N crater. The structure was approximately 150 m high and 200 m wide. According to news articles, flights from Iceland's airports resumed.
On 27 April NVC reported that the eruption plume was seen during an overflight, and rose to altitudes of 3-3.6 km (10,000-11,800 ft) a.s.l. and drifted WNW. Light ashfall was noted in inhabited areas between 32 and 45 km W. Scientists also saw that a new crater had formed in the SW part of the caldera; the rim was about 50 m lower than the surrounding ice surface. Ash plumes rose from the vent and spatter was ejected 100-200 m above the vent. The lava flow front had advanced 1 km N from the vents. Flights from Iceland's airports were again disrupted.
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/page/ies_forsida,
Associated Press
http://www.washingtonpost.com/wp-dyn/content/article/2010/04/26/AR2010042601237.html,
Iceland Review http://icelandreview.com/
REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m
The IG reported that on 20 April scientists conducting an overflight of Reventador saw steam-and-gas emissions. They also observed an explosion generate a pyroclastic flow that traveled 200 m down the S flank. Deposits from previous pyroclastic flows were seen on the same flank. Explosions generated steam-and-gas plumes with low ash content during 20-22 April. Weather clouds prevented views of the volcano in satellite imagery on 23 April, although a pilot reported that an ash plume rose to an altitude of 4.9 km (16,000 ft) a.s.l. On 26 April a steam-and-ash plume rose 500 m above the crater.
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
SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m
On 20 April, INSIVUMEH reported that explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose to altitudes of 2.8-3.4 km (9,200-11,200 ft) a.s.l. and drifted S and SE. On 26 April, ash explosions and pyroclastic flows generated ash plumes that rose to an altitude of 8.3 km (27,300 ft) a.s.l. and drifted NW and N. Ashfall was reported in Quetzaltenango (18 km WNW) and other areas to the W, NW, and N. According to news articles, schools in 10 communities were closed and flights were banned from within a 20-km-radius of the volcano.
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.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/,
Associated Press http://www.washingtonpost.com/wp-dyn/content/article/2010/04/27/AR2010042703058.html
TONGKOKO Sulawesi 1.52°N, 125.20°E; summit elev. 1149 m
Based on analyses of satellite imagery, the Darwin VAAC reported that on 23 April a possible ash plume from Tongkoko rose to an altitude of 10.7 km (35,000 ft) a.s.l.
Geologic Summary. The NE-most volcano on the island of Sulawesi, Tongkoko (also called Tangkoko) has a summit that is elongated in a NW-SE direction with a large deep crater that in 1801 contained a cone surrounded by lake water. The slightly higher Dua Saudara stratovolcano is located only 3 km to the SW of Tongkoko, and along with Tongkoko, forms the most prominent features of Gunung Dua Saudara National Park, a noted wildlife preserve. Eruptions occurred from the summit crater of Tongkoko in the 17th century and in 1801. The prominent, flat-topped lava dome Batu Angus originated on the E flank of Tongkoko in 1801, and, along with an adjacent E-flank vent, has been the source of all subsequent eruptions.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
Ongoing Activity
BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m
Based on analyses of satellite imagery, the Darwin VAAC reported that during 19-20, 23, 25, and 27 April ash plumes from Bagana rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and drifted 35-85 km S, SW, W, and NW.
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
BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m
Based on analyses of satellite imagery, the Darwin VAAC reported that during 25-27 April ash plumes from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 45-85 km W and N.
Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern 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 north 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.
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 on 27 April an ash plume from Dukono was seen on satellite imagery drifting 45 km NW at an altitude of 3 km (10,000 ft) a.s.l.
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
FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m
On 26 April, INSIVUMEH reported that explosions from Fuego produced gray plumes that rose to altitudes of 4.3-4.6 km (14,100-15,100 ft) a.s.l. and drifted E. A few of the explosions produced avalanches around the volcano, and rumbling sounds were heard.
Geologic Summary. Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3,763-m-high Fuego and its twin volcano to the N, Acatenango. Construction of Meseta volcano continued until the late Pleistocene or early Holocene, after which growth of the modern Fuego volcano continued the southward migration of volcanism that began at Acatenango. Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows. The last major explosive eruption from Fuego took place in 1974, producing spectacular pyroclastic flows visible from Antigua.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/
KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m
KVERT reported that on 16 and 23 April seismic activity from Karymsky was at background levels. During 17-22 April, seismicity was above background levels and a thermal anomaly was seen in satellite imagery. On 17 and 18 April, seismic data suggested that ash plumes rose to an altitude of 2 km (6,500 ft) a.s.l. Ash plumes were seen in satellite imagery drifting 40-130 km SE on 17 and 21 April. 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 21-27 April 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 column continued at the deep pit inset within the floor of Halema`uma`u crater; glow from the vent was often visible. On most mornings the plume of gas and ash from the summit vent drifted SW, depositing small amounts of tephra near the vent. Sulfur dioxide emission rates measured at the summit during 21-23 April were in the 630-770 tonnes/day range.
At the east rift zone, lava flowed through tubes to supply a surface flow that had advanced down the Pulama pali and onto the coastal plain, heading SE along the east margin of the TEB flow field. The lava flowed through vegetation, causing small brush fires and minor methane bursts. On 22 April a second lava flow to the W was also active. Two days later, the first lava flow appeared to have stalled. The W flow continued to advance, and by 27 April was within the County Viewing Area.
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 16-23 April seismic activity from Kliuchevskoi was above background levels. Strombolian activity was noted and lava continued to flow down the flanks. Gas-and-steam plumes rose to an altitude of 5.7 km (18,700 ft) a.s.l. Satellite imagery revealed a large daily thermal anomaly from the volcano, and ash plumes that drifted about 45 km S on 18 April. Gas-and-steam plumes drifted 90-100 km E on 20 and 21 April. Based on information from the Yelizovo Airport (UHPP), the Tokyo VAAC reported that on 27 April an ash plume rose to an altitude of 7.9 km (26,000 ft) a.s.l. and drifted W. 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
LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m
On 26 April, SERNAGEOMIN reported that seismicity from Llaima had increased on 15 April and that tremor was detected. The Alert Level was raised to Yellow, (Level 4) on a three-color scale.
Geologic Summary. Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other to the SE. The massive 3,125-m-high, glacier-covered stratovolcano has a volume of 400 cu km. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following eruption of the 24 cu km Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7,200 years ago, construction of the present edifice began, characterized by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century.
Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/
PAGAN Mariana Islands (Central Pacific) 18.13°N, 145.80°E; summit elev. 570 m
A gas plume from Pagan was seen in satellite imagery on 21 and 22 April (UTC). The Volcano Alert Level and the Aviation Color Code remained "Unassigned." There are no monitoring instruments on Pagan, thus the levels "Green" or "Normal" do not apply because background activity is not defined. Monitoring is done by satellite and ground observers.
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
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
Based on information from JMA, the Tokyo VAAC reported that during 14-26 April explosions from Sakura-jima sometimes produced plumes identified in satellite imagery. Those plumes, along with ash plumes occasionally seen by pilots, rose to altitudes of 1.5-3.7 km (5,000-12,000 ft) a.s.l. and sometimes drifted in multiple directions.
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
Based on a pilot observation, the Washington VAAC reported that on 21 April an ash plume from Sangay rose to an altitude of 6.7 km (22,000 ft) a.s.l. Ash was not identified in satellite imagery, although weather clouds were present in 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 16-23 April seismic activity from Shiveluch was above background levels and ash plumes from hot avalanches rose to an altitude of 4 km (13,100 ft) a.s.l. Seismic data suggested that ash plumes rose 4-6.9 km (13,100-22,600 ft) a.s.l. during 15-17 and 20-21 April. An ash explosion on 18 April generated an ash plume that rose to an altitude of 7 km (23,000 ft) a.s.l. Satellite imagery revealed a large daily thermal anomaly from the lava dome, and ash plumes that drifted about 50-220 km SE on 18, 20, and 21 April. 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
__._,_.___
No comments:
Post a Comment