1-1-1-1-1-1-1-1-1-1-1-1-1-1 From: "Kuhn, Sally" <KUHNS@xxxxxx> Smithsonian / USGS Weekly Volcanic Activity Report 16-22 December 2020 Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx) URL: https://volcano.si.edu/reports_weekly.cfm New Activity/Unrest: Cerro Hudson, Chile | Kilauea, Hawaiian Islands (USA) | Lewotolo, Lomblen Island (Indonesia) | Merapi, Central Java (Indonesia) | Ruapehu, North Island (New Zealand) Ongoing Activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Ibu, Halmahera (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Nishinoshima, Japan | Popocatepetl, Mexico | Reventador, Ecuador | Sangay, Ecuador | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Chile 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, these reports 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 about recent activity are published in issues of the Bulletin of the Global Volcanism Network. Note that 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 Cerro Hudson | Chile | 45.9°S, 72.97°W | Summit elev. 1905 m SERNAGEOMIN reported that a notable change in seismicity at Cerro Hudson was characterized by an increase in the frequency and magnitude of volcano-tectonic (VT), hybrid (HB), and long-period (LP) signals during 1-15 December. Two swarms of VT earthquakes were recorded during 10-11 December, with the largest event, a local M 2.9, located 4.7 km ESE of the calderaâ??s center at a depth of 4.6 km. The largest of five HB signals was a local M 3.1, located 4 km ESE at a depth of 4.3 km. The earthquake locations suggested a relatively shallow source SE of the caldera. No deformation or surficial changes were observed. The Alert Level was raised to Yellow (second highest level on a four-color scale) on 22 December, based on the increased seismicity. ONEMI warned the communities of Aysén and RÃo Ibáñez, declaring a status of â??Preventive Early Warningâ??, a level in between Green and Yellow. Geologic Summary. The ice-filled, 10-km-wide caldera of the remote Cerro Hudson volcano was not recognized until its first 20th-century eruption in 1971. It is the southernmost volcano in the Chilean Andes related to subduction of the Nazca plate beneath the South American plate. The massive volcano covers an area of 300 km2. The compound caldera is drained through a breach on its NW rim, which has been the source of mudflows down the RÃo de Los Huemeles. Two cinder cones occur N of the volcano and others occupy the SW and SE flanks. This volcano has been the source of several major Holocene explosive eruptions. An eruption about 6700 years ago was one of the largest known in the southern Andes during the Holocene; another eruption about 3600 years ago also produced more than 10 km3 of tephra. An eruption in 1991 was Chile's second largest of the 20th century and formed a new 800-m-wide crater in the SW portion of the caldera. Source: Servicio Nacional de GeologÃa y MinerÃa (SERNAGEOMIN) http://www.sernageomin.cl/ Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev. 1222 m HVO reported that a new eruption at Kilauea began on 20 December, after almost a month of pre-eruptive activity that included a dike intrusion. An earthquake swarm on 30 November centered in the middle of the caldera was recorded followed by periods of increased seismicity in the upper East Rift Zone. Spikes in seismicity began on 2 December; at 1745 earthquakes intensified beneath the S part of the caldera; tiltmeters simultaneously recorded accelerated deformation, resulting in about 8 cm of caldera floor uplift. The data suggested that a small intrusion had a volume equivalent to the amount of lava erupted in just 1-2 hours from Fissure 8 during the 2018 eruption. On 3 December seismcity and deformation decreased to pre-intrusion levels. On 17 December the number and duration of long-period seismic signals increased. An earthquake swarm and deformation were detected during the evening of 20 December. At about 2136 on 20 December an orange glow was evident in IR monitoring cameras, heralding a new eruption, and prompting HVO to raise the Volcano Alert Level to Warning and the Aviation Color Code to Red. Three fissures successively opened on the inner N, NW, and W walls of Halema`uma`u Crater; lava flows quickly boiled away the water lake, creating a vigorous steam plume, before the lava ponded at the bottom. Minor lava fountaining (25 m high) from the fissures was visible, with the tallest fountains reaching 50 m at the N fissure. Occasional blasts originated from the ponded lava. A M 4.4 earthquake beneath the S flank was recorded at 2236. A gas plume was seen rising from Halema`uma`u Crater and drifting SW at 0215 on 21 December. Later that morning HVO lowered the Volcano Alert Level to Watch and the Aviation Color Code to Orange. The accumulating lava in the crater rose at a rate of several meters per hour. Sulfur dioxide plumes drifted NW. By the morning of 22 December, the surface of the lava lake was about 134 m above the bottom of the crater, or 487 m below the crater rim, and rising 1 m/hour. An estimated 10 million cubic meters of lava had been erupted so far. Sulfur dioxide emission rates remained high, at around 30,000 tonnes/day. Lava effusion stopped at the NW vent during 0730-0800, and, along with the W vent, was inundated by the lava lake sometime before noon. Geologic Summary. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 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 km2, destroying nearly 200 houses and adding new coastline to the island. Source: US Geological Survey Hawaiian Volcano Observatory (HVO) https://volcanoes.usgs.gov/observatories/hvo/ Lewotolo | Lomblen Island (Indonesia) | 8.274°S, 123.508°E | Summit elev. 1431 m PVMBG reported that the eruption at Lewotolo continued during 16-22 December. Gray-and-white ash plumes were visible daily, rising as high as 800 m above the summit. Strombolian explosions were visible most nights ejecting material 100-200 m above the summit crater. Rumbling was heard most days. The Alert Level was remained at 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summer crater. Geologic Summary. The Lewotolo (or Lewotolok) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Merapi | Central Java (Indonesia) | 7.54°S, 110.446°E | Summit elev. 2910 m BPPTKG reported that during 12-17 December white emissions from Merapi rose as high as 150 m above the summit. Rock avalanches traveled as far as 1.5 km down the Senowo drainage on the NW flank on 14 December. A comparison of photos taken on 11 and 15 December showed minor morphological changes in the summit area; drone video from 14 December revealed no new lava dome material in the summit crater. Seismic activity was less intense than the previous week. Electronic Distance Measurement (EDM) data continued to measure a distance shortening between points in the NW at a rate of 9 cm per day. The Alert Level remained at 3 (on a scale of 1-4). 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 north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities. Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG) http://www.merapi.bgl.esdm.go.id/ Ruapehu | North Island (New Zealand) | 39.28°S, 175.57°E | Summit elev. 2797 m GeoNet reported a warming trend of the crater lake water at Ruapehu, with a high temperature of 43 degrees Celsius. During an overflight to measure gas emissions the previous week, scientists observed that the lake was a uniform gray color (suggesting it is well mixed) and some water overflow at the lakeâ??s outlet. Gas output had increased in response to the heating cycle; the amounts of carbon dioxide (CO2) and sulfur gases (SO2 and H2S) in the plume were the largest measured in the past two decades. Short-lived pulses of volcanic tremor were coincident with gas emissions. The Volcanic Alert Level was raised to 2 and the Aviation Color Code was raised to Yellow on 21 December. Geologic Summary. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake (Te Wai a-moe), is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3,000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys. Source: GeoNet http://www.geonet.org.nz/ Ongoing Activity Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m JMA reported nightly incandescence from Minamidake Crater (at Aira Calderaâ??s Sakurajima volcano) during 14-21 December and that the sulfur dioxide emission rate remained high. Four explosions were recorded during 16-18 December. One of the explosions, at 1959 on 17 December, generated a plume that rose 3 km above the crater rim and ejected bombs 1.3-1.7 km away from the crater. Another explosion, at 0439 on 18 December, produced a plume that rose 1.8 km and ejected bombs 1-1.3 km away from the crater. The Alert Level remained at 3 (on a 5-level scale). Geologic Summary. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. 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: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/ Dukono | Halmahera (Indonesia) | 1.693°N, 127.894°E | Summit elev. 1229 m Based on satellite and wind model data, the Darwin VAAC reported that during 18-19 December ash plumes from Dukono rose to 2.1 km (7,000 ft) a.s.l. and drifted SE and E. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone. 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 north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time. Sources: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml; Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Ebeko | Paramushir Island (Russia) | 50.686°N, 156.014°E | Summit elev. 1103 m Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 11-12 and 15-17 December that sent ash plumes up to 3 km (10,000 ft) a.s.l. and drifted NE, SE, and S. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Geologic Summary. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php Etna | Sicily (Italy) | 37.748°N, 14.999°E | Summit elev. 3320 m INGV reported that strong activity at Etnaâ??s Southeast Crater (SEC) included fountaining and lava flows on 21 December. Tremor amplitude had gradually increased on 20 December but weather conditions prevented visual observations. During the morning of the 21st Strombolian activity occurred at three vents. By 0800 tremor amplitude suddenly increased, and by 1000 lava fountaining from at least two vents was observed in thermal camera images, along with an eruption plume to 3 km (10,000 ft) a.s.l. A lava flow emerged from the SW part of the cone, which had collapsed on 13 December, and traveled SW before branching W and E. A second flow from the NE side of the cone traveled E into the Valle del Bove. Lava fountaining ended around noon, with a simultaneous decrease in tremor amplitude. During the morning of 22 December a few small phreatic explosions were visible in webcam images, likely generated from the interaction of snow and lava. The front of the active SW flow reached 2,500 m elevation. By 1741 both flows were cooling down and no longer advancing. 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 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank. Source: Sezione di Catania - Osservatorio Etneo (INGV) http://www.ct.ingv.it/ Ibu | Halmahera (Indonesia) | 1.488°N, 127.63°E | Summit elev. 1325 m PVMBG reported that at 1826 on 19 December an ash plume from Ibu rose 400 m above the summit and drifted N. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side. Geologic Summary. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Karymsky | Eastern Kamchatka (Russia) | 54.049°N, 159.443°E | Summit elev. 1513 m KVERT reported that a thermal anomaly over Karymsky was visible during 11-12 and 17 December. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). 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 during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php Klyuchevskoy | Central Kamchatka (Russia) | 56.056°N, 160.642°E | Summit elev. 4754 m KVERT reported that Strombolian and sometimes Vulcanian activity at Klyuchevskoy continued during 11-18 December and lava advanced down the Kozyrevsky drainage on the S flank. A large bright thermal anomaly was identified daily in satellite images. A steam-and-gas plume with some ash rose to 6 km (19,700 ft) a.s.l. and drifted 120 km NE on 13 December. The Aviation Color Code remined at Orange (the second highest level on a four-color scale). Geologic Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 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 numerous major explosive and effusive eruptions from flank craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php Nishinoshima | Japan | 27.247°N, 140.874°E | Summit elev. 25 m JMA reduced the exclusion zone for Nishinoshima from a radius of 2.5 to 1.5 km around the summit crater on 18 December; eruptive activity ended in August. Fumarolic and high-temperature areas remained visible. Geologic Summary. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE. Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/ Popocatepetl | Mexico | 19.023°N, 98.622°W | Summit elev. 5393 m CENAPRED reported that each day during 16-22 December there were 112-231 steam-and-gas emissions from Popocatépetl, some of which contained minor amounts of ash. A gas, steam, and ash plume drifted SE on 22 December. The Alert Level remained at Yellow, Phase Two (middle level on a three-color scale). Geologic Summary. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time. Source: Centro Nacional de Prevencion de Desastres (CENAPRED) https://www.gob.mx/cenapred Reventador | Ecuador | 0.077°S, 77.656°W | Summit elev. 3562 m IG reported that a high level of activity continued to be recorded at Reventador during 16-22 December; adverse weather conditions sometimes prevented visual conformation. Seismicity was characterized by 40-109 daily explosions, volcano-tectonic and harmonic tremor events, and long-period earthquakes as well as signals indicating emissions. Gas, steam, and ash plumes, observed sometimes multiple times a day with the webcam or reported by the Washington VAAC, rose as high as 1 km above the summit crater and drifted mainly NW and W. Crater incandescence and incandescent blocks rolling 600 m down the NE and S flanks were observed nightly. The 450-m-long lava flow on the NE flank remained active but did not advance. Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It 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. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents. Source: Instituto GeofÃsico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/ Sangay | Ecuador | 2.005°S, 78.341°W | Summit elev. 5286 m IG reported a high level of activity at Sangay during 16-22 December. Seismicity was characterized by 20-127 daily explosions, occasional harmonic tremor, long-period earthquakes, and signals indicating emissions. Weather clouds often prevented visual observations of the volcano, but the Washington VAAC and IG webcams recorded daily ash plumes that rose as high as 2.4 km above the summit and drifted mainly NW, W, and SW. Seismic signals signifying lahars were recorded during 16-18 December. Geologic Summary. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex. Source: Instituto GeofÃsico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/ Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 11-18 December. On 22 December residents of Ust-Kamchatsk Village, 85 km SE, observed ash plumes rising to 8 km (26,200 ft) a.s.l. and drifting 42 km NE. The Aviation Color Code was raised to Red (the highest level on a four-color scale). Just over an hour later ash plumes rose 6.5-7.5 km (21,300-24,600 ft) a.s.l. and drifted 130 km E; the Aviation Color Code was lowered to Orange. Geologic Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php Suwanosejima | Ryukyu Islands (Japan) | 29.638°N, 129.714°E | Summit elev. 796 m JMA reported nighttime incandescence and intermittent eruptive activity at Suwanosejimaâ??s Ontake Crater during 11-18 December. A total of five explosions were recorded, ejecting bombs up to 500 m away from the crater and producing gray-and-white plumes that rose 1.6 km above the crater rim. Ashfall was reported in Toshima village (4 km SSW). The Alert Level remained at 2 (on a 5-level scale). Geologic Summary. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island. Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/ Villarrica | Chile | 39.42°S, 71.93°W | Summit elev. 2847 m POVI reported that four ash emissions at Villarrica were visible in webcam images on 16 December. SERNAGEOMIN stated that two ash pulses were associated with long-period (LP) events at 1146 and 1156 that same day; the first ash emission rose 160 m above the crater rim and drifted NW while the second rose 280 m and drifted 500 m NE. At 1716 on 17 December an ash emission associated with an LP event rose 720 m and drifted ESE. The Alert Level remained at Yellow, the second lowest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli, and the exclusion zone for the public of 500 m around the crater. Geologic Summary. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks. Sources: Proyecto Observación Villarrica Internet (POVI) http://www.povi.cl/ ; Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI) http://www.onemi.cl/; Servicio Nacional de GeologÃa y MinerÃa (SERNAGEOMIN) http://www.sernageomin.cl/ 1-1-1-1-1-1-1-1-1-1-1-1-1-1 ------------------------------
