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Smithsonian/USGS Weekly Volcanic Activity Report 29 December 2010-4 January 2011
From: "Kuhn, Sally" <KUHNS@xxxxxx>
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Smithsonian/USGS Weekly Volcanic Activity Report
29 December 2010-4 January 2011
Sally Kuhn Sennert - Weekly Report Editor
New Activity/Unrest: | Etna, Sicily (Italy) | Kizimen, Eastern Kamchatka (Russia) | Manam, Northeast of New Guinea (SW Pacific) | Stromboli, Aeolian Islands (Italy)
Ongoing Activity: | Bezymianny, Central Kamchatka (Russia) | Bulusan, Luzon | Fuego, Guatemala | Gaua, Banks Islands (SW Pacific) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Machín, Colombia | Sakura-jima, Kyushu | Santa María, Guatemala | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) | Tengger Caldera, Eastern Java (Indonesia) | Tungurahua, Ecuador
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
ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m
INGV-CT reported that during the first few days of December gas emissions from a large pit crater on the lower E flank of Etna's Southeast Crater cone nearly ceased. On 22 December at 0446 a strong explosion occurred at the W vent of the Bocca Nuova (BN-1). This event generated an ash plume a few meters high, which then drifted NE, causing light ashfall in areas as far as the town of Linguaglossa (17 km NE). On 23 December bluish gas rose from a vent at the base of the W wall of the pit, at the base of the Southeast Crater cone. Bright incandescence was intermittently visible on video footage. Inclement weather prevented clear observations that day and during the next few days. On 29 December extremely small amounts of incandescent material emitted from the pit crater were observed using visible and thermal cameras. The brief emissions (2-6 second intervals) were jets of mainly hot gas that barely rose above the rim of the pit crater. Inclement weather again prevented observations of the crater during 30-31 December.
During the late afternoon on 2 January, strong incandescence at the pit crater evolved into vigorous Strombolian activity. Frequent Strombolian explosions (1-3 per minute) ejected coarse-grained incandescent material a few tens of meters above the rim of the pit. On a few occasions, incandescent bombs fell outside the pit's rim, mainly to the S and E. The activity continued into the early morning then decreased markedly. Negligible quantities of volcanic ash were produced.
Geologic Summary. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BC. Historical lava flows cover much of the surface of this massive basaltic stratovolcano, the highest and most voluminous in Italy. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater. Flank eruptions, typically with higher effusion rates, occur less frequently and originate from fissures that open progressively downward from near the summit. A period of more intense intermittent explosive eruptions from Etna's summit craters began in 1995. The active volcano is monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) in Catania.
Source: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV-CT) http://www.ct.ingv.it/index.php
KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m
KVERT reported that a thermal anomaly over Kizimen's lava dome was observed in satellite imagery during 29 December-1 January and that an explosive eruption that began on 13 December continued. On 31 December seismicity increased and volcanic tremor was detected. Explosions occurred sporadically for a period of about 20 minutes. Ash plumes detected in satellite imagery rose to an altitude of 8 km (26,200 ft) a.s.l. and drifted SW. Ashfall at least 1 mm thick occurred in multiple areas 225-275 km SSW, including Petropavlovsk-Kamchatsky, Yelizovo, Paratunka, and Nalychevo. On 1 January the Aviation Color Code was raised to Red. Ash plumes at an altitude of 4 km (13,100 ft) a.s.l. drifted 480-500 km SW; ash continued to accumulate in some areas. Seismic data indicated increased activity on 3 January. Explosions continued, and ash plumes drifted more than 200 km SE. A large and bright thermal anomaly was observed in satellite imagery.
Based on analysis of satellite imagery, the Tokyo VAAC reported that possible eruptions during 2-4 January produced plumes that rose to an altitude of 3-4.6 km (10,000-15,000 ft) a.s.l. and drifted S, E, and NE. Subsequent images on those same days showed ash emissions continuing, then dissipating.
Geologic Summary. Kizimen is an isolated, conical stratovolcano that is morphologically similar to Mount St. Helens prior to its 1980 eruption. The summit of Kizimen consists of overlapping lava domes, and blocky lava flows descend the flanks of the volcano, which is the westernmost of a volcanic chain north of Kronotsky volcano. The 2,376-m-high Kizimen was formed during four eruptive cycles beginning about 12,000 years ago and lasting 2,000-3,500 years. The largest eruptions took place about 10,000 and 8300-8400 years ago, and three periods of longterm lava-dome growth have occurred. The latest eruptive cycle began about 3,000 years ago with a large explosion and was followed by lava-dome growth lasting intermittently about 1,000 years. An explosive eruption about 1,100 years ago produced a lateral blast and created a 1.0 x 0.7 km wide crater breached to the NE, inside which a small lava dome (the fourth at Kizimen) has grown. A single explosive eruption, during 1927-28, has been recorded in historical time.
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
MANAM Northeast of New Guinea (SW Pacific) 4.080°S, 145.037°E; summit elev. 1807 m
RVO reported that on 25 December a new episode of eruptive activity from Manam's South Crater began and was characterized during 25-29 December by rising ash plumes and ejections of incandescent lava fragments. Although most of the material fell back into the crater, some was deposited around the summit area, and some larger fragments were deposited in the SW and SE valleys. The Main Crater produced white plumes occasionally laden with ash. Incandescence was visible on some nights.
On 30 December activity from South Crater increased and was reported by observers in Bogia, 20 km SSW, on the mainland. A dense ash plume rose 3 km above the summit crater and drifted NW. An observer at Tabele on the SW flank confirmed the eruption and also reported that three pyroclastic flows descended the SE valley, stopping by a few to several hundred meters from the coastline. The first and largest pyroclastic flow devastated a broad unpopulated area between Warisi and Dugulava villages. Ash plumes drifted NW and caused light ashfall in Tabele. RVO recommended an increase in the Alert Level to Stage 3. Later that day, ash emissions and incandescent fragment ejections diminished.
On 31 December, gray ash plumes rose 200-300 m above the South Crater and also above the Main Crater. Low booming sounds were noted and incandescence from the crater was observed at night. During 1-4 January eruptive activity continued from South Crater and gray-to-black ash plumes rose above the summit crater. Incandescence emanated from the crater. During 3-4 January incandescent fragments were ejected onto the flanks and rolled down the SE valley. White vapor rose from the Main Crater.
Geologic Summary. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys," regularly spaced 90 degrees apart, channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE avalanche valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded at Manam since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
Source: Rabaul Volcano Observatory (RVO)
STROMBOLI Aeolian Islands (Italy) 38.789°N, 15.213°E; summit elev. 924 m
INGV-CT reported that on 19 December a major explosion from a vent in the southern part of Stromboli's crater terrace occurred at 0956, coincident with an explosive sequence consisting of three discrete seismic events. During the last few days of December the "S1" vent produced frequent explosions of greater intensity than those of the preceding days. Jets rose 200 m above the crater terrace. On 27 December, the frequency of the explosions rose to 11-14 per hour. The "S1" vent is immediately next to the "S" vent, the source of the 19 December explosion.
Geologic Summary. Spectacular incandescent nighttime explosions at Stromboli volcano have long attracted visitors to the "Lighthouse of the Mediterranean."Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout historical time. The small, 926-m-high island of Stromboli is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The active summit vents are located at the head of the Sciara del Fuoco, a horseshoe-shaped scarp formed as a result of slope failure that extends to below sea level and funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded at Stromboli since Roman times.
Source: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV-CT) http://www.ct.ingv.it/index.php
Ongoing Activity
BEZYMIANNY Central Kamchatka (Russia) 55.978°N, 160.587°E; summit elev. 2882 m
KVERT reported that during 24-30 December seismicity did not exceed background levels. The temperature of thermal anomalies observed in satellite imagery during 23-24 and 27-28 December gradually increased. Gas-and-steam emissions were seen on 27 and 28 December; clouds prevented observations on the other days. The Aviation Color Code level remained at Yellow.
Geologic Summary. Prior to its noted 1955-56 eruption, Bezymianny volcano had been considered extinct. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. That eruption, similar to the 1980 event at Mount St. Helens, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
BULUSAN Luzon 12.770°N, 124.05°E; summit elev. 1565 m
Based on notices from the Manila airport (RPLL), the Tokyo VAAC reported that on 29 and 30 December ash from Bulusan was observed. PHIVOLCS noted that inclement weather prevented views of the summit area during 29-31 December. Eight volcano-tectonic earthquakes were detected by the seismic network during 30-31 December.
Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed within the 11-km-diameter dacitic Irosin caldera, which was formed more than 36,000 years ago. A broad, flat moat is located below the prominent SW caldera rim; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.
Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m
INSIVUMEH reported that during 29-30 December explosions from Fuego, almost constant at times, produced dense ash plumes that rose 600-800 m above the crater and drifted 8 km W and SW. Avalanches occurred on the flanks. The Washington VAAC reported that several small emissions observed in satellite imagery drifted W on 1 January. INSIVUMEH noted that during 3-4 January explosions generated ash plumes that rose 800-1,000 m above the crater and fanned out towards the S and SW. The plumes drifted almost 15 km and caused ashfall in areas downwind, including Panimaché (6 km SW), Morelia (7 km SW), and Santa Sofia (12 km SW). Incandescence from the crater was observed at night.
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.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/,
Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
GAUA Banks Islands (SW Pacific) 14.27°S, 167.50°E; summit elev. 797 m
On 21 December, the Vanuatu Geohazards Observatory reported that volcanic activity from Gaua had been low since September. Recent observations indicated that the near-vent vegetation and vegetation exposed to trade winds on the W side of the island was again growing. Seismic data showed a decreasing number of events. The Alert Level was lowered to 1 (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 seismic activity at Karymsky was above background levels during 23-26 December and did not exceed background levels during 27-30 December. Seismic data suggested that possible ash plumes rose to an altitude of 4.3 km (14,100 ft) a.s.l. Thermal anomalies were detected in satellite imagery during 23-24 December; cloud cover prevented views on the other days. The Aviation Color Code level remained at Orange.
Based on a Yelizovo Airport (UHPP) notification, the Tokyo VAAC reported that on 31 December an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted E.
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.
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
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
During 29 December-4 January, HVO reported that activity at Kilauea continued from the summit caldera and the east rift zone. At the summit caldera, the level of the lava-pool surface in the deep pit within Halema'uma'u crater circulated and remained mostly stable at approximately 120 m below the crater floor, periodically rising several meters higher. Nighttime incandescence was visible from the Jaggar Museum on the NW caldera rim. A plume from the vent that drifted mainly SW deposited ash and fresh spatter nearby.
At the east rift zone, lava that broke out of the Quarry tube onto the surface, at a saddle between two rootless shields at around the 610 m elevation, continued to advance in two branches. The lava flow at the lowest elevation advanced E beyond Kalapana by 3 January. Incandescence from a small spatter cone on the north-central part of Pu'u 'O'o crater floor continued. Lava from that cone flowed SE, NE, and W. Lava from a second spatter cone, located on the NW edge of the crater, was active on the crater floor. Weak incandescence was also visible from a small, fume-producing vent in the E wall of the crater, and from other various areas on the crater floor.
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/
MACHIN Colombia 4.48°N, 75.392°W; summit elev. 2650+ m
According to INGEOMINAS, Observatory Vulcanológico and Sismológico de Manizales reported a period of increased seismicity from Cerro Machín on 31 December. A total of 346 volcano-tectonic events no stronger than M 2.1 were located S and SW of the main lava dome. On 1 January seismicity again increased, and at the time of the report, 367 events had been detected. The low-magnitude events were located S and SW of the main dome at depths between 2.5 and 4.5 km. The largest event, M 2.3, was located S of the dome at a depth of about 3.3 km and felt by residents near the volcano and in the municipality of Cajamarca, 14 km WSW. The Alert level remained at III (Yellow; "changes in the behavior of volcanic activity").
Geologic Summary. The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the S and contains three forested lava domes. Voluminous pyroclastic flows traveled up to 40 km from the volcano during eruptions in the mid-to-late Holocene perhaps associated with formation of the caldera. Late-Holocene eruptions produced block-and-ash flows that traveled through the breach in the caldera rim to the W and S. The latest known eruption of Volcán Cerro Machín took place about 800 years ago.
Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co//
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
Based on information from JMA, the Tokyo VAAC reported that on 2 January a plume from Sakura-jima rose to an altitude of 1.8 km (6,000 ft) a.s.l. An explosion was noted the next day. An explosion on 5 January produced a plume that rose to an altitude of 1.2 km (4,000 ft) a.s.l. and drifted E.
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
SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m
INSIVUMEH reported that during 29-30 December a few explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose 300-600 m above Caliente dome and drifted S and SE. Ashfall was reported in local villages downwind. The Washington VAAC reported that several small emissions observed in satellite imagery drifted W on 1 January. During 3-4 January, INSIVUMEH reported that explosions produced ash plumes that rose 700 m above the complex and drifted SW. Avalanches descended the W part of the dome.
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/,
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 moderate seismic activity from Shiveluch was detected during 24-30 December. Ash explosions on 24 December produced ash plumes that rose to altitudes as high as 4.5 km (14,800 ft) a.s.l. A bright thermal anomaly over the volcano was observed in satellite imagery during 24 and 27-28 December. Moderate gas-and-steam activity was visually observed on 24 and 28 December. 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 during 24-31 December activity from the Soufrière Hills lava dome was at a low level. Rockfalls or small pyroclastic flows detected by the seismic network occurred in the 11 February collapse scar on the N side of the volcano. Clouds prevented clear views of the lava dome. Lahars associated with heavy rains descended multiple drainages on 30 December. 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/
SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m
Based on information from JMA, the Tokyo VAAC reported an explosion from Suwanose-jima on 29 December. Details of a possible resulting plume were not reported.
Geologic Summary. The 8-km-long, spindle-shaped island of Suwanose-jima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. Only about 50 persons live on the sparsely populated island. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanose-jima, one of Japan's most frequently active volcanoes, was in a state of intermittent Strombolian activity from On-take, the NE summit crater, that began in 1949 and lasted nearly a half century. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, after which the island was uninhabited for about 70 years. The SW crater produced lava flows that reached the western coast in 1813, and lava flows reached the eastern coast of the island in 1884.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
TENGGER CALDERA Eastern Java (Indonesia) 7.942°S, 112.95°E; summit elev. 2329 m
Based on analyses of satellite imagery, the Darwin VAAC reported that on 30 December an ash plume from Tengger Caldera's Bromo cone rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted about 95 km E.
Geologic Summary. The 16-km-wide Tengger caldera in eastern Java is located at the northern end of a volcanic massif extending from Semeru volcano. The massive Tengger volcanic complex consists of five overlapping stratovolcanoes, each truncated by a caldera. The most recent is the 9 x 10 km wide Sandsea caldera, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most frequently visited and most active volcanoes. More than 50 mild-to-moderate explosive eruptions have occurred since 1804.
Source: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m
Although storm clouds occasionally prevented observations of the summit area, IG reported that steam plumes were observed almost daily during 29 December-4 January. Incandescence from the crater was occasionally observed at night. On 30 December a steam-and ash plume rose 500 m above the crater and drifted W. On 2 January a small explosion produced an ash plume that also rose 500 m above the crater and drifted W.
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/
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