The Weekly Volcanic Activity Report: October 21 – 27, 2020

New activity/unrest was reported for 3 volcanoes from October 21 to 27, 2020. During the same period, ongoing activity was​ reported for 14 volcanoes.

New activity/unrest: Bezymianny, Central Kamchatka (Russia) | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia).

Ongoing activity: Bulusan, Luzon (Philippines) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Great Sitkin, Andreanof Islands (USA) | Ibu, Halmahera (Indonesia) | Langila, New Britain (Papua New Guinea) | Reykjanes, Iceland | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Stromboli, Aeolian Islands (Italy) | 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

Bezymianny, Central Kamchatka (Russia)

55.972°N, 160.595°E, Summit elev. 2882 m

Based on Tokyo VAAC notices, KVERT reported that an explosive eruption at Bezymianny began at 0822 on 22 October and produced a large ash cloud that rose as high as 9 km (29,500 ft) a.s.l. The Aviation Color Code was raised to Red, the highest level on a four-color scale. The ash cloud identified in satellite images was 100 x 200 km in size. KVERT noted that by 1519 the eruption was over. A large ash cloud was still visible, though it had dropped to lower altitudes of 5-5.5 km (16,400-18,000 ft) a.s.l. and split into a N part (57 x 105 km) and a S part (36 x 67 km). The clouds shiftied direction and drifted as far as 811 km NW and SE. The Aviation Color Code was lowered to Orange. On 23 October a thermal anomaly over the summit was identified in satellite images and growth of a lava dome was noted. The Aviation Color Code was lowered to Yellow.

Geological summary: Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Karymsky, Eastern Kamchatka (Russia)

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

A new eruption at Karymsky that began on 21 October prompted KVERT to raise the Aviation Color Code to Orange (the second highest level on a four-color scale). A thermal anomaly was identified in satellite images. During 21-23 October explosions produced ash plumes that rose as high as 6 km (19,700 ft) a.s.l. and drifted 380 km SE. An ash cloud, 30 x 60 km in area, was identified in satellite images 530 km SE from the volcano.

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 activity at Klyuchevskoy continued during 16-23 October and lava advanced down the Apakhonchich drainage on the SE flank. A large bright thermal anomaly was identified daily in satellite images and on 18 October an ash plume drifted 90 km E. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale) on 8 October.

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.

Ongoing activity

Bulusan, Luzon (Philippines)

12.769°N, 124.056°E, Summit elev. 1535 m

On 26 October PHIVOLCS lowered the Alert Level for Bulusan to 0, indicating normal conditions, though warnings remained to not enter the 4-km-radius Permanent Danger Zone (PDZ). The decision was based on monitoring data that showed sulfur dioxide flux remaining below detection levels since 2018, deformation continuing a deflationary trend since May 2019, and the frequency of volcanic earthquakes declining to baseline levels (0-2 earthquakes/day) beginning in late September 2020. Very diffuse white plumes rose from the summit vents.

Geological summary: Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

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 21-27 October ash plumes from Dukono rose to 2.1 km (7,000 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 16-23 October that sent ash plumes up to 3.5 km (11,500 ft) a.s.l. and drifted N, NE, and SE. Ash fell in Severo-Kurilsk during 20-22 October. A thermal anomaly over the volcano was visible in satellite data on 22 October. 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 19-25 October activity at Etna was characterized by intra-crater Strombolian activity at Northeast Crater (NEC), Strombolian activity at the New Southeast Crater (NSEC) cone, and gas emissions at the Voragine (VOR) and Bocca Nuova (BN) craters. During a helicopter overflight along the W side on 23 October scientists observed Strombolian explosions at NSEC that produced ash emissions and ejected shreds of lava out of the crater. Both the frequency and intensity of explosions was variable. There were several thermal anomalies on the NEC crater floor, and some on the floor of the BN crater. An ash plume from NSEC rose to 4.5 km a.s.l. and drifted SSE. The report noted that, based on drone footage from the beginning of the month, the NSEC vent was 190 m long in the NW direction and 140 m wide in the NE direction.

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.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W, Summit elev. 1740 m

AVO reported that seismicity at Great Sitkin had decreased during the previous several months and had returned to background levels by 21 October. Additionally, eruptive activity or unusual surface temperatures had not been observed in clear satellite images. The Aviation Color Code was lowered to Green and the Volcano Alert Level was lowered to Normal.

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Summit elev. 1325 m

PVMBG reported that during 21-26 October ash plumes rose 200-800 m above Ibu’s summit and drifted N, NE, and E. 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.

Geological 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.

Langila, New Britain (Papua New Guinea)

5.525°S, 148.42°E, Summit elev. 1330 m

Based on analyses of satellite imagery and wind model data, the Darwin VAAC reported that on 22 and 24 October ash plumes from Langila rose 2.1 km (7,000 ft) a.s.l. and drifted S and N, respectively. Ash plumes rose to 1.8 km (6,000 ft) a.s.l. and drifted NW on 25 October.

Geological summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower E flank of the extinct Talawe volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Reykjanes, Iceland

63.85°N, 22.566°W, Summit elev. 140 m

IMO reported that a M 5.6 earthquake was recorded at 1343 on 20 October beneath Nupshlidarhals, a hill about 5 km W of the geothermal area in Seltun. This was the largest earthquake since 2003 recorded in the Reykjanes peninsula. There were about 1,700 aftershocks recorded in the following 24-hour period. IMO received reports of rockfalls in steep areas and increased gas odors in the vicinity of Graenavatn at Nupshlidarhals. Four landslides were noted near the epicenter; some existing ground cracks were displaced and new cracks had formed in Krysuvikurbjarg. On 26 October IMO stated that seismic activity had significantly decreased in recent days; about 180 earthquakes below M 2.2 had been detected during the previous two days.

Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.

Semeru, Eastern Java (Indonesia)

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

PVMBG that gray-and-white ash plumes rose 500 m above Semeru’s summit and drifted S and SW during 22-24 October. The Alert Level remained at 2 (on a scale of 1-4).

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 16-23 October. 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 plumes rose as high as 500 m above Sinabung’s summit on most days during 20-27 October; foggy conditions sometimes prevented visual observations. On 23 October white-and-gray ash plumes rose as high as 1 km and drifted in multiple directions. Pyroclastic flows traveled 1.5-2.5 km down the E and SE flanks on 25 October. According to a news article ash plumes drifted SE of the volcano twice that same day, causing some local residents to evacuate. The report noted that a lava dome in the summit crater continued to grow. 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.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Summit elev. 924 m

INGV reported that during 19-25 October activity at Stromboli was characterized by ongoing explosive activity from Area N (north crater area) and in Area C-S (south-central crater area). Explosions from two vents at the N1 vent (Area N) ejected lapilli and bombs 80-150 m high, and produced ash emissions. Explosions at two N2 vents ejected a mix of coarse and fine material at a frequency of 5-10 events per hour. Explosions from vents in Area C-S also ejected both coarse and fine material 250 m high at a frequency of 1-3 events per hour.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

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 16-23 October. Three explosions were recorded; an explosion at 0439 on 17 October produced a grayish-white ash plume that rose 1.4 km above the crater rim. 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

SERNAGEOMIN reported that a long-period (LP) event and associated explosion were recorded by Villarrica’s seismic network at 1041 on 23 October. An ash plume rose 180 m. 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.

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