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AVCAN. Actualidad Volcánica
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 NOTICIAS
Actualidad
  Volcanología
Actualizado el
13/01/2011 19:24h
Enviado por Fernando Raja
el 2011-01-13 20:21:53
Smithsonian/USGS Weekly Volcanic Activity Report 5-11 January 2011

New Activity/Unrest: Etna, Sicily (Italy) / Kizimen, Eastern Kamchatka (Russia) / Manam, Northeast of New Guinea (SW Pacific).



Ongoing Activity: Bulusan, Luzon | Dukono, Halmahera | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Merapi, Central Java (Indonesia) | Pacaya, Guatemala | Reventador, Ecuador | Sakura-jima, Kyushu | San Cristóbal, Nicaragua | Santa María, Guatemala | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) | 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
 
After a few hours of quiescence on the evening of 3 January, very weak emissions of incandescent material (probably mostly hot gas with little or no solid material) resumed from the pit crater located on the lower E flank of Etna's Southeast Crater cone. Later that evening intense incandescence from the pit crater was reported by observers in the village of S. Alfio on the E flank of Etna. The emissions continued on 4 January at a rate of 4-6 events per hour, producing small plumes that appeared as thermal anomalies in thermal video footage. Activity ceased in the afternoon. Very weak emissions of incandescent material (probably again mostly hot gas) were observed on 5 January at the same rate as the previous day. A camera recorded white vapor plumes occasionally accompanied by some grayish-brown ash. Weak, intermittent incandescence from the pit crater was observed at night during 5-6 January. Emissions on 6 January occurred at a frequency of 3-4 events per hour, producing small plumes seen in thermal camera footage. That same day, intense degassing occurred from the W vent of Bocca Nuova (BN-1), and from the Northeast Crater, where pulsating emissions produced mushroom-shaped vapor plumes.
 
Starting in the late evening of 11 January, the seismic network recorded a slight increase in volcanic tremor amplitude. The amplitude peaked early on 12 January, and the source of the tremor shifted from a location N of the Northeast Crater towards the Southeast Crater. Weak Strombolian activity from the pit crater accompanied these changes on 11 January, and gradually became more intense on 12 January.
 
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.
 
 
 
KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m
 
KVERT reported that ash emissions from Kizimen had been essentially continuous during 31 December-7 January, producing ash plumes mostly below altitudes of 6-8 km (20,000-26,000 ft) a.s.l. reported by pilots or observed in satellite imagery. Seismicity remained high but variable and volcanic tremor continued to be recorded. A thermal anomaly over the volcano was observed in satellite imagery. On 5 January ash plumes drifted more than 500 km ENE. Ashfall was reported on the Komandorsky Islands, 350-500 km E. The Tokyo VAAC reported that ash continued to be observed in satellite imagery on 5 Janaury. According to information from KVERT and analyses of satellite imagery, a possible eruption on 6 January produced a plume that rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted E. Subsequent satellite images that same day showed continuing ash emissions. Ash plumes drifted NW on 9 January, and drifted NW again on 11 January, at an altitude of 2.7 km (9,000 ft) a.s.l. The Color Code remained at Red.
 
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.
 
 
 
MANAM Northeast of New Guinea (SW Pacific) 4.080°S, 145.037°E; summit elev. 1807 m
 
RVO reported that during 5-6 January low roaring from Manam's South Crater was heard and weak but steady crater incandescence was observed at night. Diffuse blue vapor was emitted from South Crater on 6 January. During 6-8 January white vapor rose from Main Crater and incandescence from both craters was observed at night. Diffuse brown ash plumes occasionally rose from South Crater on 7 January. The next day the Alert Level was lowered from Stage 3 to Stage 2. During 8-9 January Main Crater emitted white vapor and South Crater produced occasional gray ash plumes that drifted to the SE part of the island. Emissions from Main Crater turned to gray on 10 January. White-to-blue vapor plumes rose from South Crater. Both craters were incandescent at night during 8-10 January.
 
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)
 
 
Ongoing Activity
 
 
BULUSAN Luzon 12.770°N, 124.05°E; summit elev. 1565 m
 
During 4-10 January, PHIVOLCS reported that 2-8 daily volcanic earthquakes at Bulusan were detected by the seismic network. Clouds usually prevented observations, but on 5 or 6 January steam was seen rising from a known NW thermal vent. The Tokyo VAAC reported that on 6 and 7 January ash was observed according to notices from the Manila airport (RPLL). The Alert Level remained at 1 (on a scale of 0-5).
 
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.
 
 
 
DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m
 
Based on analyses of satellite imagery, the Darwin VAAC reported that during 5-7 January ash plumes from Dukono rose to altitudes of 2.4-3.7 km (8,000-12,000 ft) a.s.l. and drifted 65-130 km W.
 
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.
 
 
 
FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m
 
INSIVUMEH reported that during 5-6 January explosions from Fuego produced ash plumes that rose 500-800 m above the crater and drifted 10 km S and SW. The explosions caused windows and roofs to rattle in areas 6 km away. Fine ashfall was reported in communities downwind including Panimaché (6 km SW), Morelia (7 km SW), and Yepocapa (8 km WNW). Incandescence from the crater was observed at night. On 8 January, the Washington VAAC reported multiple gas-and-ash plumes that rose to an altitude of 5.2 km (17,000 ft) a.s.l. were observed in satellite imagery. During 10-11 January INSIVUMEH again reported that explosions produced ash plumes that rose 500-800 m above the crater and shock waves that were detected as far away as 7 km. Plumes drifted 15 km W and block avalanches descended a few drainages.
 
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.
 
 
 
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 on 1 and 5 January, suggesting that possible ash plumes rose to an altitude of 3.8 km (12,500 ft) a.s.l. Seismic activity did not exceed background levels on the other days during 31 December-7 January. A thermal anomaly was detected daily in satellite imagery. An ash plume drifting 140 km SE was also seen in imagery on 2 January. Based on a pilot observation, the Tokyo VAAC reported that on 5 January an ash plume rose to an altitude of 4.6 km (15,000 ft) a.s.l.
 
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.
 
 
 
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
 
During 5-11 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 SW, NE, and N deposited ash and fresh spatter nearby.
 
At the east rift zone, lava that broke out of the Quarry tube at a saddle between two rootless shields around 610 m elevation, continued to advance in two branches, E and W. At the lowest elevation of the E branch lava advanced along Highway 130 near Kalapana. One part of the W branch entered the ocean on 6 January at a location about 2 km SW of the end of Highway 130. Lava flows fed by an 8-m-high cone on the N portion of the Pu'u 'O'o crater floor covered and recovered the E crater floor. The web camera also recorded incandescence from a small fume-producing vent in the E wall of the crater. On 10 January the sides of the cone seemingly gave way and lava poured into two active flows that traveled toward the W portion of 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.
 
 
 
MERAPI Central Java (Indonesia) 7.542°S, 110.442°E; summit elev. 2968 m
 
According to a news article, lahars on Merapi's flanks that occurred on 3 and 9 January caused damage to houses, farms, and infrastructure in multiple villages in the Magelang district, 26 km WNW of Merapi. One death and one injury were reported. On 9 January, the Red Cross evacuated people trapped in their homes in the Sirihan village. An estimated 3,000 people live in the flooded area, but the number of people evacuated was unknown.
 
Geologic Summary. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately N of the major city of Yogyakarta. The steep-sided modern Merapi edifice, its upper part unvegetated due to frequent eruptive activity, was constructed to the SW of an arcuate scarp cutting the eroded older Batulawang volcano. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated and inhabited lands on the volcano's western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory (MVO).
 
Source: IRIN
 
 
PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m
 
INSIVUMEH reported that during 5-6 January steam-and-gas plumes, white and blue in color, rose 200 m above Pacaya's MacKenney cone. Seismic activity was consistent with gas emissions.
 
Geologic Summary. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. Pacaya is a complex volcano constructed on the southern rim of the 14 x 16 km Pleistocene Amatitlan caldera. A cluster of dacitic lava domes occupies the caldera floor. The Pacaya massif includes the Cerro Grande lava dome and a younger volcano to the SW. Collapse of Pacaya volcano about 1,100 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (MacKenney cone) grew. During the past several decades, activity at Pacaya has consisted of frequent Strombolian eruptions with intermittent lava flow extrusion on the flanks of MacKenney cone, punctuated by occasional larger explosive eruptions.
 
 
 
REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m
 
Based on a pilot observation, the Washington VAAC reported that on 4 January an ash plume from Reventador rose to an altitude of 5.2 km (17,000 ft) a.s.l. Cloud cover prevented clear satellite observations of the volcano. A subsequent report stated that IG noted low seismicity, no reports of ashfall, and that satellite imagery showed no ash emissions.
 
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.
 
 
 
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
 
Based on information from JMA, the Tokyo VAAC reported that during 7-8 January explosions from Sakura-jima produced plumes that rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted E and SE. On 8 January, pilots reported that ash plumes rose to altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted 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.
 
 
 
SAN CRISTOBAL Nicaragua 12.702°N, 87.004°W; summit elev. 1745 m
 
Based on analyses of satellite imagery, the Washington VAAC reported that on 6 January a gas-and-steam plume from San Cristóbal, possibly containing ash, drifted 25 km SW. The VAAC noted a METAR weather notice stating that “smoke” was observed.
 
Geologic Summary. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1,745-m-high youngest cone, San Cristóbal itself (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km to the west of San Cristóbal; it and the eroded Moyotepe volcano, 4 km to the NE of San Cristóbal, are of Pleistocene age. Volcán Casita contains an elongated summit crater and lies immediately E of San Cristóbal; Casita was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the San Cristóbal complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.
 
 
 
SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m
 
INSIVUMEH reported that during 5-6 January explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose 400-500 m above Caliente dome and drifted SW. Based on analyses of satellite imagery, the Washington VAAC reported that on 8 January a gas plume possibly containing ash drifted less than 30 km SSW. During 10-11 January, INSIVUMEH reported that explosions produced ash plumes that rose as high as 600 m above the dome and drifted SW and W. Avalanches descended the S and E flanks.
 
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.
 
 
 
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 31 December-7 January. A bright thermal anomaly over the volcano was observed daily in satellite imagery. Seismic data showed that possible ash plumes rose to an altitude of 5 km (16,400 ft) a.s.l. on 2 January. That same day an explosion generated ash plumes that rose to an altitude of 8 km (26,000 ft) a.s.l. and were observed in satellite imagery drifting 92 km S. Moderate gas-and-steam activity was visually observed during 2 and 5-6 January. 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.
 
 
 
SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m
 
MVO reported that during 31 December 2010-7 January 2011 activity from the Soufrière Hills lava dome was at a low level. A small lahar descended the Belham valley (NW) on 5 January. Gas measurements on 6 January indicated that the ratio of hydrochloric acid to sulfur dioxide was 0.29, a ratio similar to those measured over the last few months and consistent with no lava extrusion. Helicopter observations that same day showed marked acid rain damage in the Spring (W) and Gingoes (SW) ghaut areas, up to 3 km from the lava dome. Cloudy weather prevented observations of the lava dome. 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.
 
 
 
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 during 11-12 January. 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.
 
 
 
TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m
 
On 5 January IG reported that, after moderately-sized explosions during 24-25 December, activity at Tungurahua had decreased. IG noted that during this time seismicity decreased and explosions had not occurred, deflation was detected, sulfur dioxide emissions gradually reduced, and decreases in the amount of ash present in plumes was noted. Although cloudy weather often prevented observations during 5-11 January, steam plumes were occasionally observed and rose above the crater to low heights.
 
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.
 
 
 
 
Sally Kuhn Sennert - Weekly Report Editor


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