The Weekly Volcanic Activity Report: December 9 - 15, 2020

The Weekly Volcanic Activity Report: December 9 - 15, 2020

New activity/unrest was reported for 5 volcanoes from December 9 to 15, 2020. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest: Barren Island, Andaman Islands (India) | Karymsky, Eastern Kamchatka (Russia) | Lewotolo, Lomblen Island (Indonesia) | Merapi, Central Java (Indonesia) | Telica, Nicaragua.

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Fuego, Guatemala | Kirishimayama, Kyushu (Japan) | Klyuchevskoy, Central Kamchatka (Russia) | Pacaya, Guatemala | Sabancaya, Peru | Santa Maria, Guatemala | Semeru, Eastern Java (Indonesia) | 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 23"00 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.

New activity/unrest

Barren Island, Andaman Islands (India)

12.278°N, 93.858°E, Summit elev. 354 m

The Darwin VAAC reported that on 8 December an ash plume from Barren Island rose to 1.8 km (6,000 ft) a.s.l. and drifted WSW.

Geological summary: Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Summit elev. 1513 m

At 2045 on 9 December explosions at Karymsky generated ash plumes that rose 6-7 km (19,700-23,000 ft) a.s.l. and drifted 60 km NW, prompting KVERT to raise the Alert Level to Orange (the second highest level on a four-color scale). Explosions continued the next day; ash plumes drifted 220 km NW, W, and SW. A thermal anomaly was identified in satellite images on 4, 8, and 10 December.

Geological 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.

Lewotolo, Lomblen Island (Indonesia)

8.274°S, 123.508°E, Summit elev. 1431 m

PVMBG reported that the eruption at Lewotolo continued during 9-15 December. Black, gray, and brown ash plumes were visible daily, rising as high as 1 km above the summit. Strombolian explosions were visible most nights ejecting material above the summit crater. 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.

Geological 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.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Summit elev. 2910 m

BPPTKG reported that during 4-10 December white emissions from Merapi rose as high as 400 m above the summit. Rock avalanches traveled around 200 m down the Lamat drainage on the W flank. A comparison of photos taken on 29 November and 8 December showed some morphological changes in the summit area; drone footage from 5 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).

Geological 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.

Telica, Nicaragua

12.606°N, 86.84°W, Summit elev. 1036 m

INETER reported that there were two small ash-and-gas explosions at Telica recorded during 8-9 December, making a total of 1,315 small explosions recorded since the latest activity began 30 November. Gas-and-ash plumes rose as high as 200 m above the crater rim.

Geological summary: Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported that during 7-14 December incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was often visible nightly and the sulfur dioxide emission rate remained high. Three explosions during 7-11 December produced ash plumes that rose as high as 2.4 km above the crater rim and ejected bombs 1.3-1.7 km away from the crater. An eruptive event at 0514 on 14 December produced a plume that rose 1.8 km and blended into weather clouds. The Alert Level remained at 3 (on a 5-level scale).

Geological 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.

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 8-14 December ash plumes from Dukono rose 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted in multiple directions. 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.

Geological 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.

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 8-9 December that sent ash plumes up to 3.5 km (11,500 ft) a.s.l. and drifted NE and SE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological 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.

Etna, Sicily (Italy)

37.748°N, 14.999°E, Summit elev. 3320 m

INGV reported that during 7-12 December activity at Etna was similar to the previous week, characterized by intra-crater Strombolian activity at Northeast Crater (NEC), and Strombolian activity, lava effusion, and pyroclastic flows at the Southeast Crater (SEC). Additionally, infrequent ash emissions at the Bocca Nuova (BN) craters and some explosions and minor ash emissions at the Voragine (VOR) were also recorded. Webcam views of activity was limited due to weather conditions; a field visit was made on 14 December.

Strombolian activity originated from the E and central vents at SEC ejected lava onto the inner crater walls. Occasional ash emissions dispersed quickly near the summit. Activity intensified at 2020 on 13 December and lava fountains formed around 2300. Collapses of the SW part of the SEC cone spurred a series of pyroclastic flows. At 2315 a small pyroclastic flow traveled down the SSW flank. A second pyroclastic flow began at 2316 and traveled 2 km down the SSW flank and covered Monte Frumento Supino cone (SSW). At 2330 a third and minor pyroclastic flow traveled SSW. Around the same time as the generation of the first two pyroclastic flows, two fissures opened on the SW flank of the SEC and produced lava flows to the S and SW until about 2350. A period of lava fountaining was visible during 0050-0110 and 0210-0223 on 14 December.

During a field inspection on 14 December scientists confirmed the partial cone collapses and noted that the two lava flows (S and SW) were cooling. The S lava flow had widened at the near the base of SEC and formed four lobes. One of the lobes continued on and stopped just NW of cones that had formed in 2002-2003. The SW flow traveled SSW, branched, curved around the W part of Monte Frumento Supino, and then stopped. Explosive activity from central SEC vent continued, with roaring and sporadic ash emissions. An explosion at 1352 formed an ash plume that rose about 4 km and drifted S. Strombolian explosions deposited material outside of the crater.

Geological 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.

Fuego, Guatemala

14.473°N, 90.88°W, Summit elev. 3763 m

INSIVUMEH reported that 3-15 explosions were recorded per hour during 8-15 December at Fuego, generating ash plumes as high as 1.1 km above the crater rim that drifted 10-25 km generally S, SW, and W. Shock waves rattled buildings within 20 km of the summit. Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), El Jute, Las Lajas (SE), and Honda drainages; avalanches sometimes reached vegetated areas. Incandescent material was occasionally ejected 100-200 m. Ashfall was reported most days in several areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Finca Palo Verde, Santa Sofía (12 km SW), El Porvenir (8 km ENE), San Pedro Yepocapa (8 km NW), and Sangre de Cristo (8 km WSW).

Geological summary: Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Kirishimayama, Kyushu (Japan)

31.934°N, 130.862°E, Summit elev. 1700 m

JMA noted that no eruption had occurred at Shinmoedake (Shinmoe peak, a stratovolcano of the Kirishimayama volcano group) since 28 June 2018. Volcanic earthquakes with hypocenters just below Shinmoedake had increased around 17 November 2019, fluctuated afterwards, and then began a decreasing trend in mid-October 2020. Sulfur dioxide levels were generally low, deformation data showed no changes, and both fumarolic and geothermal area activity remained stable. The Alert Level was lowered to 1 (on a scale of 1-5) on 11 December.

Geological summary: Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Summit elev. 4754 m

KVERT reported that Strombolian and Vulcanian activity at Klyuchevskoy continued during 4-7 December and lava advanced down the Kozyrevsky drainage on the S flank. A large bright thermal anomaly was identified daily in satellite images. Steam-and-gas plumes with some ash rose to 7 km (23,000 ft) a.s.l. and drifted 130 km NW and NE. The Aviation Color Code remined at Orange (the second highest level on a four-color scale).

Geological 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.

Pacaya, Guatemala

14.382°N, 90.601°W, Summit elev. 2569 m

INSIVUMEH reported that on 9 December a new lava flow emerged from a vent S of Cerro Chino, NNW of Pacaya’s summit, and traveled as far as 250 m WSW. The branched lava flow which had opened in October on the WSW flank was active, with lengths between 400 and 600 m. Avalanches of material from the new flow and the SW-flank lava flows descended 100 m. Strombolian explosions from the cone in Mackenney Crater were visible on most days during 9-15 December and ejected material as high as 150 m above the vent. Gray ash plumes were occasionally visible drifting S, SW, and W at generally low altitudes. On 12 December strong winds picked up ash deposits and created ash curtains that drifted 1.5 km away and dispersed. Lava flows on the SW flank varied in length between 500 m and 1,000 m. The NW-flank lava flow ceased effusing by 13 December.

Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 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. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported a daily average of 54 explosions at Sabancaya during 7-13 December. Gas-and-ash plumes rose as high as 2.8 km above the summit and drifted NW, W, and SW. Eight thermal anomalies over the crater were identified in satellite data. Minor inflation continued to be detected in areas N of Hualca Hualca (4 km N) and on the SE flank. INGEMMET stated that ashfall was noted in the towns of Cabanaconde (22 km NW), Pinchollo (20 km N), and Madrigal (20 km NE) during 9-10 December. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Santa Maria, Guatemala

14.757°N, 91.552°W, Summit elev. 3745 m

INSIVUMEH reported that during 9-15 December explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose as high as 900 m above the complex. The extrusion of blocky lava at the WSW part of Caliente dome generated block-and-ash flows that descended the NW, WSW, SW, and E flanks often reaching the base of the complex. The activity increased at 0430 on 11 December with notable avalanches of material and block-and-ash flows lava dome traveling down the W and SW flanks. Ash plumes drifted 15 km SW, causing ashfall in areas downwind including Finca Montebello, Loma Linda, and San Marcos Palajunoj. Activity remained elevated at least through 13 December; ash plumes drifted as far as 20 km W, SW, and S, and pyroclastic flows descended the flanks.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive 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 vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Summit elev. 3657 m

PVMBG reported that the eruption at Semeru continued during 9-15 December. Incandescent material was ejected 50-100 m above the summit on 9 December and rock avalanches descended the Kobokan drainage 500 m on the SE flank. Explosions were recorded by the seismic network during 10-12 December but they could not be visually confirmed due to weather conditions. On 13 December a pyroclastic flow originating from the end of a lava flow traveled 1.5 km down the Kembar drainage (S flank), reaching a maximum distance of 3.5 km from the crater. The next day a pyroclastic flow traveled 3.5 km down the Kobokan drainage. Rock avalanches from the end of a lava flow traveled 300-1,500 m down both drainages during 14-15 December. The Alert Level remained at 2 (on a scale of 1-4), with a general exclusion zone of 1 km and extensions to 4 km in the SSE sector.

Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

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 4-11 December. The lava block, named “Dolphin,” which had emerged in the E part of the summit lava dome, was absent in an 8 December photo of the volcano. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological 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.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E, Summit elev. 796 m

JMA reported nighttime incandescence and intermittent eruptive activity at Suwanosejima’s Ontake Crater during 4-11 December. A total of 20 explosions were recorded, ejecting bombs up to 500 m away from the crater and producing gray-and-white plumes that rose 1.5 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).

Geological 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.

Villarrica, Chile

39.42°S, 71.93°W, Summit elev. 2847 m

POVI reported that during an over-flight of Villarrica on 9 December scientists observed a small lava lake, 10-15 m in diameter, partially covered by floating black solidified lava. 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 of 500 m around the crater.

Geological 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.

Source: GVP


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