The Weekly Volcanic Activity Report: November 8 - 14, 2023

New activity/unrest was reported for 1 volcano from November 8 to 14, 2023. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Reykjanes, Reykjanes Peninsula.

New activity/unrest

Reykjanes, Reykjanes Peninsula

63.817°N, 22.717°W | Summit elev.140 m

The Icelandic Meteorological Office (IMO) reported increased seismic activity and deformation caused by a magmatic dike intrusion with no surface eruption through 14 November in the eastern Reykjanes-Svartsengivolcanic system on the Reykjanes Peninsula, W of the Fagradalsfjall fissure system that produced lava flows during eruptions over the previous three years. Due to increased local seismicity recorded since 25 October, the onset of ground inflation on 27 October, geophysical models of the magma intrusion, and uncertainties associated with a possible eruption site, the National Police Commissioner evacuated approximately 4,000 residents from the coastal town of Grindavík on 10 November. IMO is responsible for volcano monitoring in Iceland, in coordination with scientists from the University of Iceland, and the Department of Civil Protection and Emergency Management.

An intense seismic swarm occurred during the night of 8-9 November; seven earthquakes (max. M 4.0) were centered in the area from Eldvörp to E ofSýlingarfell, with the largest measuring M 4.8 at 0046 on the 9th located Wof Mt. Þorbjörn. Ground uplift continued to be detected in GPS and satellite data, with the highest rates occurring NW of Þorbjörn. Geophysical models estimated the depth to the top of the intrusion was estimated to be ~800 m. On 10 November an intense seismic swarm at a depth of 5 km began near Sundhnjúkagigar, NE of Þorbjörn, around 0700 and increased further at 1500. More than 800 earthquakes were detected on 11 November at depths of 3-3.5 km and seismic activity migrated S towardsGrindavík. IMO attributed the shallow seismicity to the intrusion extending from Stóra-Skógsfell, ~6 km NNE of Grindavík, to beneath Grindavík, and offshore. Data acquired from satellite radar showed a graben-like are of deflation cutting through Grindavík. Analysis of COSMO-SkyMed (CSK) radar interferogram data from 3-11 November indicated that the intrusion was about 15 km long at a minimum depth of less than 1 km.

Geodetic models on 12 November showed that an area of inflation was located 3.5 km N of Grindavík, close to Sundhnúkur. Approximately 1,000 earthquakes, less than M 3.0, were detected N of Grindavík at 3-5 km depths between 0000 and 1230 on 12 November. On 13 November, the size and intensity of earthquakes decreased, when approximately 900 earthquakes were detected at depths of 2-5 km between 0000 and 1620 in the area betweenSundhnúkur and Grindavík. During 12-13 November, calculations estimated that the magma inflow to the intrusion was 75 cubic meters per second. Between 0000 and 1240 on 14 November, 700 earthquakes occurred at depths of 3-5 km along the intrusion; the largest was M 3.1. After IMO installed two Differential Optical Absorption Spectrometers (DOAS, remote sensing gas instruments) on Húsafell, one of them detected SO2 at the graben-like feature between Sundhnúkagígar and Grindavík, but the source was unknown. Additional GPS stations have also been installed to monitor deformation.

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/Svartsengivolcanic 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.

Ongoing activity

Aira, Kyushu (Japan)

31.5772°N, 130.6589°E | Summit elev. 1117 m

JMA reported ongoing activity at Minamidake Crater (Aira Caldera’sSakurajima volcano) during 8-14 November. Sulfur dioxide emissions averaged2,700 tons per day measured on 6 November. A total of 15 explosions were recorded during 6-10 November, and a total of 8 during 10-13 November. At 2240 on 11 November an ash plume rose as high as 1.2 km above the crater rim and drifted SE and SW, large blocks were ejected 400 m from the summit crater, and crater incandescence was observed. At 2053 on 13 November an explosion generated an ash plume that rose 400 m above the crater and drifted SW. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.

Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan’s most active. The eruption of the voluminous Ito pyroclastic flow accompanied the 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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Dukono, Halmahera

1.6992°N, 127.8783°E | Summit elev. 1273 m

PVMBG reported that the eruption at Dukono was ongoing from 8-14 November. Daily dense white-and-gray or gray-to-black ash plumes rose as high as 1 km above the summit and drifted ENE, E, SE, and S. Roaring and thumping noises were heard from 8-9 November and on 13 November. The AlertLevel remained at Level 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, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. MalupangWariang, 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 | Summitelev. 1103 m

KVERT reported that moderate explosive activity at Ebeko was ongoing during 8-14 November. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are UTC; specific events are in local time where noted.

Geological summary: The flat-topped summit of the central cone of Ebekovolcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along an 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. 3357 m

INGV-OE reported that eruptive activity continued at Etna from 8-14 November. Lava fountaining began on 12 November at 1700 UTC and ended at 1930 UTC; an eruptive column rose to 4.5 km a.s.l. At 1940, a pyroclastic flow originated from the SE Crater area and traveled SSE. Effusive lava flowed SE, S, and SW from the SE Crater area and began to cool. The seismic network recorded high-amplitude tremor mainly localized to the SE Crater between 1800 and 1900 on 12 November. The average amplitude of the tremor signals decreased drastically and returned to baseline levels by 2000. Deviations in deformation measurements also returned to normal.

Geological summary: Mount Etna, towering above Catania on the island of Sicily, has one of the world’s longest documented records of 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 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, South-Central Guatemala

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

INSIVUMEH reported that eruptive activity continued at Fuego during 8-14 November. Weak and moderate explosions were recorded daily; the number of explosive events averaged 1-8 per hour during 8-9, 11-12, and 14 November, counts were not reported for 10 and 13 November. Daily explosions produced gas-and-ash plumes that rose to 4-4.8 km a.s.l. (300-1,100 m above the summit) and drifted as far as 30 km SW and W. Fine ashfall was reported in areas downwind such as Panimaché I and II (8 km SW), Morelia (9 km SW), Santa Sofía, and Yepocapa (12 km SW) on 8 November; Morelia, Santa Sofía, and Panimache (8 km SW) on 10 November; Panimaché I and II, Morelia, SantaSofía, El Porvenir (11 km SW), Finca Palo Verde (10 km WSW), Sangre deCristo (8 km W), and Yepocapa on 12 November; Panimache, Morelia, SantaSofía, and Yucales (12 km SW) on 13 November; and Panimaché I y II, Morelia, Santa Sofía, El Porvenir, Sangre de Cristo, Finca Palo Verde, andYepocapa on 14 November. Additionally, explosions produced faint rumbles, shockwaves, pulses of incandescent ejecta up to 100 m above the crater, and weak and moderate avalanches that descended the El Jute (ESE), Las Lajas(SE), Ceniza (SSW), and Seca (W) drainages.

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 Mesetadates back to about 230,000 years and continued until the late Pleistocene or early Holocene. The collapse of Meseta may have produced the massive Occuintla 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.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W | Summitelev. 1740 m

AVO reported that slow lava effusion likely continued at Great Sitkinduring 8-14 November. Views of the summit were obscured by weather clouds during most days; however, satellite radar observations on 8 November indicated continued surface growth concentrated on the E area of the summit lava flow. Seismicity was low with only a few local earthquakes recorded by the seismic network during the week. The Volcano Alert Level remained at watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8x 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 of 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.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued from 8-14 November. White-and-gray ash plumes rose 50-500 m above the summit and drifted N, W, and NW on 10 and 13 November. White steam-and-gas plumes rose 50-400 m and drifted W and NW on the other days during the week. Incandescent material being ejected above the summit was observed on 9 and 12 November; on the 12th it was captured in a webcam image at 0357. According to Antara News the local Mountain Monitoring Officer also noted that many of the explosions on 13 November were accompanied by rumbling or thumping noises, and crater incandescence was still observed. The AlertLevel remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the summit crater.

Geological summary: The Lewotolok (or Lewotolo) 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-meter 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.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E | Summit elev. 2462 m

PHIVOLCS reported that slow lava effusion at Mayon’s summit crater continued during 8-14 November. The lengths of the lava flow in the Mi-Isi(S), Bonga (SE), and Basud (E) drainages remained at 2.8 km, 3.4 km, and 1.1 km, respectively. Collapses at the lava dome produced rockfalls and occasional pyroclastic density currents (PDCs, or pyroclastic flows) that descended the flanks as far as 4 km; There were 0-10 daily PDC events. Seismic stations recorded 73-157 rockfall events each day and 12- 127 tremor events that lasted 1-39 minutes during 8 and 11-14 November. There were 14, 3, and 46 volcanic earthquakes on 8, 9, and 14 November, respectively. Sulfur dioxide emissions, measured almost daily, averaged between 715 and 2,295 tonnes per day, with the highest value recorded on 13 November. The Alert Level remained at 3 (on a 0-5 scale) and residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ).PHIVOLCS recommended that civil aviation authorities advise pilots to avoid flying close to the summit.

Geological summary: Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano in the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer-term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi (on Java) continued from 3-9 November. The SW lava dome produced a total of 79 lava avalanches that descended the flanks; 74 traveled as far as 2 km down the upper Bebengdrainage, with another four going up to 1.5 km down the upper part of the Wyong drainage and one reaching 1.5 km down the upper Sat/Putih drainage. Morphological changes to the SW lava dome were due to continuous collapses of material. Seismicity remained at elevated levels. The Alert level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit, based on location.

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 the 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 YoungMerapi edifice, its upper part unvegetated due to frequent activity, began of the earlier collapse scarp. Pyroclastic flows and lahars accompanying the 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.

Popocatepetl, Mexico

19.023°N, 98.622°W | Summit elev. 5393 m

CENAPRED reported that eruptive activity continued at Popocatépetl during 8-14 November. Long-period events totaling 9-156 per day were accompanied by steam-and-gas plumes, and sometimes ash, that drifted NNE or NNW. Periods of low-amplitude and high-frequency volcanic tremors were recorded; between 284-1,323 minutes daily. According to the Washington VAAC, ash plumes rose as high as 6.4 km (21,000 ft) a.s.l., about 1 km above the summit, and drifted N, W, NW, and NNW during 8-9 November. During 10-13 November theVAAC reported ash plumes that rose as high as 6.7 km (22,000 ft) a.s.l. anddrifted N, NNW, NE, NW and NNW. On 13 November an M 1.5 volcano-tectonic(VT) earthquake was detected at 0339, and light ashfall was reported inAmecameca (19 km NW), Cocotitlán (34 km NW), and Tenango del Aire (101 km W), State of Mexico, and Ocuituco (22 km SW), State of Morelos. On 14 November ash plumes rose as high as 6 km (20,000 ft) a.s.l. and drifted N, NE, and SE, and light ashfall was reported in Cuernavaca, Morelos (64 kmW). The Alert Level remained at Yellow, Phase Two (the second level on a three-color scale) and the public was warned to stay 12 km away from the crater.

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late Pleistocene to Holocene El Frailecone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since pre-Columbian times.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W | Summit elev.1916 m

OVSICORI-UNA reported continued unrest at Rincón de la Vieja during 8-14 September. Small phreatic eruptions were detected at 1113 on 7 November and 0722 on 8 November. The previous week a total of 10 steam-and-gas exhalations were recorded, and the average SO2 flux was 334 tonnes/day, which is the highest value measured in recent years. At 0136 on 12 November and 0415 on 14 November small gas emissions were detected. The Alert Level remained at Level 3, Orange, the third level on a four-level scale.

Geological summary: Rincón de la Vieja, the largest volcano in NW Costa Rica is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the “Colossus of Guanacaste,” it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Santa Maria, Southwestern Guatemala

14.757°N, 91.552°W | Summitelev. 3745 m

INSIVUMEH reported that eruptive activity continued at the Santa Santiago lava dome complex from 8-14 November. Extrusion at the Caliente dome continued, with growth concentrated toward the WSW. Degassing activity was observed during most days; white and blue gas-and-steam plumes rose to 400 m above the lava dome and drifted SW. Daily weak to moderate explosions produced gas-and-ash plumes to 3.2-3.5 km a.s.l. (700-1,000 m above the dome complex) that drifted SW and W; sometimes areas around the volcano appeared hazy due to ashfall. Block avalanches descended the SE, S, and SW flanks, and some were accompanied by small pyroclastic flows. Incandescence from the lava dome and flow was observed in the crater during most nights and early mornings.

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 the construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguitolava-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

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

PVMBG reported that eruptive activity continued at Semeru from 8-14 November. White emissions rose 100-200 m above the vent on 8-9 November, but weather conditions prevented visual observations during the rest of the week. The Alert Level remained at 3 (third highest on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

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 an 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 | Summitelev. 3283 m

KVERT reported that the eruption at Sheveluch continued from 8-14 November. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskayavolcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old StaryShiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Monodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. 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.

Shishaldin, Fox Islands (USA)

54.756°N, 163.97°W | Summit elev.2857 m

AVO reported that eruptive activity continued at Shishaldin from 8-14 November. Seismicity remained elevated; the seismic network recorded ongoing tremor events and small, low-frequency earthquakes. On 8 November, infrasound sensors detected signals associated with small explosions, and a sulfur dioxide plume was detected by satellite sensors; material ejected during the explosions likely remained confined within the summit crater. Elevated surface temperatures of the summit crater were detected in satellite data during the nights of 11-13 November. Gas-and-steam emissions were occasionally seen in webcam and satellite images; views were obscured by weather clouds most days.

Geological summary: The symmetrical glacier-covered Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. It is the westernmost of three large stratovolcanoes in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning “mountain which points way when I am lost.” Constructed atop an older glacially dissected edifice, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century. A steam plume often rises from the summit crater.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E | Summitelev. 796 m

JMA reported that the eruption at Suwanosejima’s Ontake Crater continued during 6-13 November. An eruptive event at 1423 on 11 November produced a column of ash that rose as high as 1.2 km above the crater rim. Ashfall was reported 3.5 km SW of Mitake crater. Incandescence was observed around the crater during most nights. Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 1 km away from the crater.

Geological summary: The 8-km-long 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 crate extending to the sea on the east flank that was formed by edifice collapse. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded 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 Otakecollapsed, forming a large debris avalanche and creating the open Sakuchicaldera, 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.

Taal, Luzon (Philippines)

14.0106°N, 120.9975°E | Summit elev. 311 m

PHIVOLCS reported that the increased unrest at Taal continued from 8-14 November. Daily pronounced upwelling of gases and hot fluids in the lake generated steam-and-gas plumes that rose as high as 1 km above the crater and drifted SW. Sulfur dioxide emissions were 5282-11,499 tonnes per day(t/d); the highest being recorded on 9 November. The Alert Level remained at 1 (on a scale of 0-5), and PHIVOLCS reminded the public that the entire Taal Volcano Island was a Permanent Danger Zone (PDZ).

Geological summary: Taal is one of the most active volcanoes in the Philippines and has produced some powerful eruptions. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160m, with several submerged eruptive centers. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.

Villarrica, Central Chile

39.42°S, 71.93°W | Summit elev. 2847 m

Explosive activity at Villarrica continued during 8-14 November, according to POVI. Webcam images from 0215 on 8 November showed bright crater incandescence, and at 2314 on 12 November and 0109 on 13 November webcam images showed low-level Strombolian-type explosive activity at the summit. The Volcanic Alert Level remained at Yellow (the third level on a four-level scale) according to SERNAGEOMIN.

Geological summary: The glacier-covered Villarrica stratovolcano, in the northern Lakes District of central Chile, is ~15 km south of the city of Pucon. A 2-km-wide caldera that formed about 3,500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesite cone at the NW margin of a 6-km-wide Pleistocene caldera. More than 30 Scoria cones and fissure vents are present on 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 been issued from summit and flank vents. Eruptions documented since 1558 CE 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.

References:

Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – November 8 – 14, 2023 – Managing Editor: Sally Sennert.

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