The Weekly Volcanic Activity Report: November 25 - December 1, 2020

The Weekly Volcanic Activity Report: November 25 - December 1, 2020

New activity/unrest was reported for 3 volcanoes from November 25 - December 1, 2020. Ongoing activity was reported for 12 volcanoes.

New activity/unrest: Lewotolo, Lomblen Island (Indonesia) | Merapi, Central Java (Indonesia) | Semeru, Eastern Java (Indonesia).

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Erta Ale, Ethiopia | Ibu, Halmahera (Indonesia) | Klyuchevskoy, Central Kamchatka (Russia) | Nishinoshima, Japan | Raung, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Telica, Nicaragua.

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

Lewotolo, Lomblen Island (Indonesia)

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

According to PVMBG continuous tremor at Lewotolo began to be recorded at 1943 on 26 November, and a series of volcanic earthquakes began at 1947. A new eruption started at 0557 on 27 November, producing dense blackish gray ash plumes that rose 500 m above the summit and drifted W. Incandescence at the summit was visible, and the emissions turned white around 0630. Seismicity slightly decreased after the eruption, though continuous tremor persisted for a period of time. Dense white plumes rose as high as 400 m and nighttime incandescence was noted during 27-28 November.

During the morning of 29 November seismicity again increased, characterized by six deep volcanic earthquakes; continuous tremor appeared around 0930. At 0945 a 10-minute eruption sent dense gray-to-black ash plumes 4 km above the summit that drifted W and NW at lower heights and SE and E near the top of the plume. Ashfall was reported in several surrounding villages and video posted on social media showed tephra falling on roofs in residential areas. According to BNPB, Badan Penanggulangan Bencana Daerah (BPBD) evacuated almost 4,500 residents from 26 villages to seven evacuation centers. At 1300, the Alert Level was raised to 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summer crater.

Ash plumes continued to rise on at least six more occasions, and around 1900 Strombolian activity was visible. A pungent sulfur odor was noted at the Lewotolo observation post. Satellite data showed that a sulfur dioxide plume had drifted over the N half of Australia by 30 November. Ash plumes continued to be emitted during 30 November-1 December, with dense white-and-gray ash plumes rising 700-2,000 m above the summit. Lava flows near the summit were visible and incandescent material traveled down the flanks.

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 20-26 November white emissions from Merapi rose as high as 750 m above the summit. Avalanches of material traveled down the flanks, as far as 1 km in the Lamat drainage (W flank) at 0648 on 22 November. A comparison of photos taken on 19 and 26 November showed morphology changes in the summit area from a collapse of part of the 1954 dome. Seismicity was higher than the previous week. Electronic Distance Measurement (EDM) data continued to measure a distance shortening between points in the NW at a rate of 11 cm per day. During overflights on 26 and 27 November BNPB and BPPTKG observers noted many new avalanche deposits on the NW, W, and SW flanks. As of 27 November, there were 2,318 people spread across 15 evacuation shelters, according to BNPB. 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.

Semeru, Eastern Java (Indonesia)

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

PVMBG reported that the eruption at Semeru continued during 1 October-30 November. White-and-gray ash plumes rose as high as 500 m above the summit and drifted in multiple directions. Rock avalanches were intermittently recorded starting on 19 October. A significant increase in the number rock avalanches was detected on 28 November. Pyroclastic flows originating from the ends of lava flows traveled 1 km down the SE flank. At 0123 on 1 December pyroclastic flows from the summit lava dome traveled 2-11 km down the Kobokan drainage on the SE flank. The Darwin VAAC initially reported ash plumes to 15 km (50,000 ft) a.s.l. but after further analysis noted that plumes rose to a lower altitude of 6.1 km (20,000 ft) a.s.l. and drifted SE. BNPB reported that the pyroclastic flows destroyed some mining machinery and impacted livestock, agricultural fields, and businesses. Some residents had evacuated and then returned to their homes; one person was missing. 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.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that during 23-30 November incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. Very small eruptive events were recorded. 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, and information from PVMBG, the Darwin VAAC reported that during 25 and 28-30 November ash plumes from Dukono rose to 2.1 km (7,000 ft) a.s.l. and drifted E and SE. 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 21-24 November that sent ash plumes up to 3 km (10,000 ft) a.s.l. and drifted NE, E, and SE. Ashfall was reported in Severo-Kurilsk during 23-24 November. 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.

Erta Ale, Ethiopia

13.6°N, 40.67°E, Summit elev. 613 m

Satellite data periodically showed possible thermal anomalies in Erta Ale’s N pit crater during 5 September-10 October; the crater was sometimes obscured by fumes through 29 November. A weak thermal anomaly may have been present in the S pit crater during 5 September-24 November, but was notably larger on 29 November.

Geological summary: Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Ibu, Halmahera (Indonesia)

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

PVMBG reported that at 1818 on 27 November a gray ash plume from Ibu rose 800 m and drifted W. 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.

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 20-27 November and lava advanced down the Apakhonchich drainage on the SE flank. A large bright thermal anomaly was identified daily in satellite images. During 20-21 and 23-26 November ash plumes drifted 186 km N, E, and 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.

Nishinoshima, Japan

27.247°N, 140.874°E, Summit elev. 25 m

The Japan Coast Guard reported that during an overflight of Nishinoshima on 24 August scientists observed white fumarolic plumes rising from multiple locations on the inner crater wall and the rim. The inner crater wall continued to be hot. The ocean water was brown around the W, S, and E parts of the island.

Geological 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.

Raung, Eastern Java (Indonesia)

8.119°S, 114.056°E, Summit elev. 3260 m

PVMBG reported that during 1-3 October dense gray plumes rose 50-300 m above Raung’s summit; neither eruptions nor gas emissions were visible afterwards, through 26 November. Seismicity decreased and deflation was recorded. The Alert Level was lowered to 1 (on a scale of 1-4) on 27 November, and the public was warned to stay away from the summer crater.

Geological summary: Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The unvegetated summit is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

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 20-27 November. 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 ash plumes rose as high as 500 m above Sinabung’s summit daily during 25 November-1 December. Block avalanches traveled 1 km down the flank on 1 December. 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.

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 20-27 November. A total of 34 explosions were recorded, ejecting bombs up to 700 m away from the crater and producing gray-and-white plumes that rose 1.4 km above the crater rim. The Tokyo VAAC noted that ash plumes drifted S and SE. Ashfall was reported in Toshima village (4 km SSW). Crater incandescence was visible from the morning of 20 November through 22 November. 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.

Telica, Nicaragua

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

INETER reported that ash-and-gas plumes rose from Telica on 30 November and drifted NE. Social media posts noted that around 50 ash-and-gas plumes rose 100-400 m above the crater rim during 30 November-1 December. Ash fell in Los Cocos (9 km SSW), El Panal (9 km SSW), Verónica Lacayo (10 km SW), Nuevo Belén, and pictures showed vegetation and buildings coated in ash.

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.

Source: GVP

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