The Weekly Volcanic Activity Report: December 30, 2020 - January 5, 2021

The Weekly Volcanic Activity Report: December 30, 2020 - January 5, 2021

New activity/unrest was reported for 4 volcanoes from December 30, 2020 to January 5, 2021. During the same period, ongoing activity was reported for 15 volcanoes.

New activity/unrest: Kilauea, Hawaiian Islands (USA) | Merapi, Central Java (Indonesia) | Soufriere St. Vincent, St. Vincent | Suwanosejima, Ryukyu Islands (Japan).

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Kadovar, Papua New Guinea | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Lewotolo, Lomblen Island (Indonesia) | Pacaya, Guatemala | Santa Maria, Guatemala | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Ubinas, Peru | 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

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Summit elev. 1222 m

HVO reported that lava effusion from a vent on the inner NW wall of Kilauea’s Halema`uma`u Crater continued to feed a growing lava lake during 30 December-5 January. A cone had formed over the remaining active vent, which was one of three that had opened at the beginning of the eruption. Lava sometimes spattered from vents at the top of a cone and flowed down into the lake through a crusted-over channel; during 2-5 January a dome fountain was visible near the lake’s margin, formed by upwelling of lava as in entered the lake at a partially submerged inlet.

The lake deepened from 181 m on 30 December to 191 m by 4 January, and the lake volume was an estimated 26 million cubic meters by 4 January. An island of cooler, solidified lava continued to float around on the lava lake’s surface, and by 4 January the island’s surface was 1-2 m above the surface of the lava lake. Over the week the island was joined by less than a dozen other small islands of cooled and solidified material that also moved around, though they mostly remained in the eastern part of the lake. The lava lake was also becoming perched as overflows of lava onto the narrow edge formed around the lake’s margins continued to build a levee; by 3 January the lake was perched about 1 m above the margin. Sulfur dioxide emissions fluctuated between 3,000 and 6,500 tonnes/day. Seismicity remained elevated but stable.

Geological 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.

Merapi, Central Java (Indonesia)

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

BPPTKG reported that during 25-31 December rock avalanches traveled as far as 1.5 km down Merapi’s NW flank in the Senowo drainage. A comparison of photos taken on 24 and 30 December showed minor morphological changes in the summit area. Seismic activity was more 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 14 cm per day. Incandescence from the crater was visible at night on 31 December, possibly signifying the emergence of lava. At 1952 on 4 January avalanches on the SW flank were recorded by webcams and heard at the Merapi Babadan observation post, and were coincident with the appearance of another incandescent area. That same day BNPB noted that 1,115 residents remained in evacuation centers. Descending incandescent material was visible on the upper SW flank during 1847-1911 on 5 January. The Alert Level remained at 3 (on a scale of 1-4), and the public were warned to stay 5 km away from the summit.

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.

Soufriere St. Vincent, St. Vincent

13.33°N, 61.18°W, Summit elev. 1220 m

The Seismic Research Centre at the University of the West Indies (UWI-SRC) and National Emergency Management Organisation (NEMO) of St. Vincent and the Grenadines reported that during an overflight at 1600 on 31 December scientists confirmed that the new lava dome on the WSW edge of Soufrière St. Vincent’s 1979 lava dome continued to grow. Steam from the dome was visible from Belmont Observatory through 4 January. The Alert Level remained at Orange (the second highest level on a four-color scale).

Geological summary: Soufrière St. Vincent is the northernmost and youngest volcano on St. Vincent Island. The NE rim of the 1.6-km wide summit crater is cut by a crater formed in 1812. The crater itself lies on the SW margin of a larger 2.2-km-wide caldera, which is breached widely to the SW as a result of slope failure. Frequent explosive eruptions after about 4,300 years ago produced pyroclastic deposits of the Yellow Tephra Formation, which cover much of the island. The first historical eruption took place in 1718; it and the 1812 eruption produced major explosions. Much of the northern end of the island was devastated by a major eruption in 1902 that coincided with the catastrophic Mont Pelée eruption on Martinique. A lava dome was emplaced in the summit crater in 1971 during a strictly effusive eruption, forming an island within a lake that filled the crater. A series of explosive eruptions in 1979 destroyed the 1971 dome and ejected the lake; a new dome was then built.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that two explosions, on 29 and 30 December, were recorded at Suwanosejima’s Ontake Crater. Crater incandescence was visible at night during 1-4 January, and eruption plumes rose as high as 1.2 km above the crater rim. The Alert Level remained at 3 (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.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that during 28 December-4 January incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was often visible nightly. The sulfur dioxide emission rate remained high. Four explosions were recorded during 28 December-1 January; an explosion at 1614 on 29 December generated ash plumes that rose as high as 3.5 km above the crater rim and ejecting bombs 1.3-1.7 km away from the crater. Very small eruptive events were recorded during 2-4 January. 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 1-2 January ash plumes from Dukono rose to 2.1 km (7,000 ft) a.s.l. and drifted NE, E, and SW. 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 25 and 30-31 December; ash plumes rose up to 3.1 km (10,200 ft) a.s.l. and drifted in multiple directions. 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.

Fuego, Guatemala

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

INSIVUMEH reported that 3-15 explosions were recorded per hour during 29 December-5 January at Fuego, generating ash plumes as high as 1.1 km above the crater rim that drifted 7-30 km generally N, NW, W, SW, and S. Shock waves rattled buildings around the volcano and were detected as far as 25 km away. Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), El Jute, Las Lajas (SE), and Honda drainages, often reaching vegetated areas. Incandescent material was ejected 100-300 m above the summit almost daily. 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), Yucales, La Soledad (11 km N), San Miguel Dueñas (10 km NE), and San Pedro Yepocapa (8 km NW).

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.

Kadovar, Papua New Guinea

3.608°S, 144.588°E, Summit elev. 365 m

Based on satellite and wind model data, the Darwin VAAC reported that on 3 January two ash puffs from Kadovar rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted SW.

Geological summary: The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Karymsky, Eastern Kamchatka (Russia)

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

KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 24-28 December. Explosions on 26 and 30 December produced ash plumes that rose 4-5 km (13,100-16,400 ft) a.s.l. and drifted 70 km NW. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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.

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 25 December-1 January 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 6 km (19,700 ft) a.s.l. and drifted 250 km in multiple directions. Kamchatka Volcanological Station observers reported that at about 1720 on 2 January a landslide descended the Apakhonchich drainage on the SE flank, producing a cloud of ash that rose about 1 km and quickly drifted SE. 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.

Lewotolo, Lomblen Island (Indonesia)

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

PVMBG reported that a Strombolian eruption at Lewotolo continued during 30 December-5 January. Gray-and-white ash plumes were visible daily, rising as high as 1 km above the summit. Rumbling and banging sounds were reported almost daily, and incandescent material was ejected as far as 1 km SE from the crater during 30-31 December and 4-5 January. Strombolian explosions ejected material 100-200 m above the summit crater during 1-5 January. 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.

Pacaya, Guatemala

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

INSIVUMEH reported that Strombolian activity and lava effusion continued at Pacaya during 29 December-5 January. Explosions from the cone in Mackenney Crater ejected material as high as 300 m above the vent and away from the crater. Lava flows on the SW and W flanks were active and varied in length between 400 and 650 m; the lava flow on the SW flank had numerous branches. Activity was most notable on 1 January; gas-and-ash plumes rose 100-300 m above the summit and drifted 10 km NW, and explosions that were sometimes strong rattled nearby houses.

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.

Santa Maria, Guatemala

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

INSIVUMEH reported that during 29 December-5 January explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose 800-900 m above the complex. Plumes sometimes drifted about 1 km SW. The extrusion of blocky lava at Caliente dome generated block-and-ash flows that descended the NW, W, SW, and E flanks, often reaching the base of the complex. Ashfall on the flanks was noted almost daily, though during 1-2 January ashfall was also reported in Loma Linda (6 km WSW) and San Marcos Palajunoj (8 km SW).

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 incandescent material ejected 50 m above Semeru’s summit was visible most nights during 30 December-5 January. Cloudy weather often obscured visual observations during the daytime. A pyroclastic flow traveled 3.5 km down the Kobokan drainage on the SE flank on 31 December. Incandescent material from the ends of lava flows descended 300-1,000 m, reaching a maximum distance of 550-1,250 m from the crater during 1-3 January. 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.

According to BNPB, observers at the Gunungsawur Observatory, 12 km SE of Semeru, recorded heavy rain around the volcano on 30 December, resulting in multiple lahars. At 0939 a lahar in the Koboan River drainage on the SE flank was seen and also recorded by the post’s seismic station. A lahar detected at 0950 was followed by an increase in water flow in the Curah Koboan, Rejali Bondeli, and Regoyo watersheds. At 1111 the seismic station recorded a lahar and accompanying pyroclastic flow that traveled 3.5 km down the Curah Koboan drainage. At 1130 lahars in Curah Koboan drainage damaged bamboo stalls owned by a local resident in Sumberwuluh Village (15 km SE).

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 25 December-1 January. A strong explosion on 29 December generated ash plumes that rose as high as 7 km (23,000 ft) a.s.l. and drifting 250 km W. 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.

Sinabung, Indonesia

3.17°N, 98.392°E, Summit elev. 2460 m

PVMBG reported that white-and-gray plumes generally rose as high as 500 m above Sinabung’s summit during 30 December-5 January. Avalanches of material traveled 500-1,200 m down the E and SE flanks each day. Three eruptive events recorded on 4 January (at 0854, 1150, and 1412) produced dense gray ash plumes that rose 700-1,000 m above the summit and drifted N, NW, and W. Three eruptive events were detected the next day as well. The first, at 0825, generated an ash plume that rose 800 m above the summit. Ash emissions were not visible from the second and third events, recorded at 2027 and 2108. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Ubinas, Peru

16.355°S, 70.903°W, Summit elev. 5672 m

Instituto Geofísico del Perú (IGP) reported that at 1659 on 31 December and at 1746 on 1 January low-volume lahars descended the Volcánmayo drainage on Ubinas’s SE flank and damaged parts of the highway linking Arequipa, Querapi, Ubinas, and Huarina. The Alert Level remained at Yellow (the second lowest level on a four-color scale).

Geological summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Perú's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one of Holocene age about 1,000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Villarrica, Chile

39.42°S, 71.93°W, Summit elev. 2847 m

POVI reported that during an overflight of Villarrica on 2 January scientists observed an incandescent vent at the bottom of the crater that had a solidified lava bridge connecting across a partially crusted-over top. 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, the commune of Panguipulli, and the exclusion zone for the public 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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