The Weekly Volcanic Activity Report: December 10-16, 2025

New activity/unrest: Barren Island, India | Mayon, Philippines | Purace, Colombia | Semeru, Indonesia | Talang, Indonesia.

New activity/unrest

Barren Island, India

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

Satellite images showed that the lava flows on the N flank of Barren Island that began to be active in mid-November continued to be active in December. Satellite images acquired on 2, 5, 10, and 15 December showed that the lower half of the flows were hot and active. Thermal anomalies over two vents at the summit were also identified in the images, though weather clouds obscured the summit area on 15 December.

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

Mayon, Philippines

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

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing activity at Mayon during 11-15 December. The seismic network detected 6-17 daily rockfalls, one volcanic earthquake on 10 and 13 December and three volcanic earthquakes on 15 December. Gas plumes drifted WNW, WSW, and SW. Sulfur dioxide emissions averaged 307 tonnes per day on 10 December. The Alert Level remained at 1 (on a 0-5 scale); the public was warned to stay out of the 6-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Geologic summary: Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of 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 periods of andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic density currents 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.

Purace, Colombia

2.3095°N, 76.3948°W | Summit elev. 4650 m

The Servicio Geologico Colombiano (SGC) reported continuing eruptive activity at Puracé during 9-16 December. Seismicity was characterized by pulses of tremor, long-period signals indicating fluid movement, and periods of continuous tremor. The seismicity was located at depths less than 1 km and was related to internal movement of gases as well as emissions. Earthquakes indicating rock fracturing were located within 3 km of the crater at depths of 1-3 km. Gas-and-ash emissions, 2-15 per day, were associated with some seismic signals and visible in webcam images rising 700-800 m above the summit and drifting downwind. Significant sulfur dioxide emissions detected in satellite data dispersed within 300 m NE, NW, and W of the crater. Elevated temperatures in the crater area continued to be detected and were possibly associated with the emissions of hot gases. During 10-11 December minor ashfall and a weak sulfur odor was reported in Cristales (NW), in Pululó, Anambío (7 km NW), Coconuco (12 km WNW), Crucero de la Mina (6 km N), and the former Puracé police base to the N. Ashfall was reported in Cristales as well as in Río Negro (20 km SW) during 11-12 December, in Coconuco and in Río Negro during 12-13 December, and in Cristales and Chiliglo (11 km W) during 14-15 December. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public was warned to stay away from the crater.

Geologic summary: Puracé is an active andesitic volcano with a 600-m-diameter summit crater at the NW end of the Los Coconucos Volcanic Chain. This volcanic complex includes nine composite and five monogenetic volcanoes, extending from the Puracé crater more than 6 km SE to the summit of Pan de Azúcar stratovolcano. The dacitic massif which the complex is built on extends about 13 km NW-SE and 10 km NE-SW. Frequent small to moderate explosive eruptions reported since 1816 CE have modified the morphology of the summit crater, with the largest eruptions in 1849, 1869, and 1885.

Semeru, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 10-16 December, with daily eruptive events recorded by the seismic network. White-and-gray or gray ash plumes were observed almost daily rising 400-1,100 m above the summit and drifting in multiple directions; weather conditions prevented views on 14 December though eruptive events were detected. Incandescence at the summit on the upper SE flank was visible in several nighttime webcam images. The Alert Level remained at 3 (the second lowest level on a scale of 1-4) and the public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit on the SE flank along the Kobokan drainage, and 500 m from the banks of the Kobokan drainage as far as 17 km SE of the summit.

Geologic 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.

Talang, Indonesia

0.979°S, 100.681°E | Summit elev. 2575 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported increased seismicity at Talang starting in September 2024, and seismicity indicative of magma movement in December 2025. The seismic network recorded swarms of deep volcanic (VT) earthquakes on 8 April, on 25 July, on 23 September, and on 9 October 2025. Specifically, the 23 September swarm was more clustered beneath the crater area and located at shallower depths compared to the 8 April and 25 July swarms. During 1-9 December seismicity was characterized by 101 VT earthquakes, two felt earthquakes ranging I-III on the Modified Mercalli Intensity scale (MMI), and 14 deep tectonic earthquakes. A tectonic earthquake (M 4.7) at 0248 on 10 December was located about 222 km N; this was followed over about the next six hours by 227 VT earthquakes. At 1000 the Alert Level was raised to 2 (on a scale of 1-4) and visitors and tourists were warned to stay away 2 km from both South Crater and Main Crater. PVMBG noted that Talang, mainly consisting of the Talang Jantan cone and Talang Betina cone about 1 km W, was located along the central zone of the active Great Sumatran Fault and influenced by tectonic activity.

Geologic summary: Talang is part of a large volcanic edifice just NW of Dibawah Lake. An older volcanic peak, Pasar Arbaao, is ~1.5 km W. The steep-sided Talang cone exhibits fumarolic activity but has no crater; it appears to have grown within a larger caldera. Recorded eruptions have mostly involved small-to-moderate explosive activity, first documented in the 19th century, that originated from a series of small craters in a valley on the NE flank.

Ongoing activity

Aira, Japan

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

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 8-15 December with five eruptive events and four explosions. Ash plumes rose as high as 2.2 km above the crater rim and large blocks were ejected as far as 600 m from the vent. Nightly crater incandescence was visible in webcam images. Eruptive events during 8-11 December produced ash plumes that rose as high as 2.2 km above the crater rim and drifted E and SE. Explosions at 1014 on 10 December and at 1334 and at 1606 on 13 December generated ash plumes that rose 500-1,800 m above the crater rim and drifted S and N. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 2 km of both the Minimadake and Showa craters.

Geologic 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 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, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 10-16 December. Daily white-and-gray gas-and-ash plumes rose as high as 1.3 km above the summit and drifted in multiple directions. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Geologic summary: The Dukono complex in northern Halmahera is on an edifice with a broad, low profile containing multiple peaks and overlapping craters. Almost 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 Gunung Mamuya cone, 10 km NE. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also had reported eruptions.

Fuego, Guatemala

14.4748°N, 90.8806°W | Summit elev. 3799 m

The Instituto Nacional de Sismología, Vulcanologia, Meteorologia e Hidrología (INSIVUMEH) reported that eruptive activity at Fuego continued during 9-16 December. Daily Strombolian explosions recorded by the seismic network, at rates of 4-11 per hour, generated gas-and-ash plumes that rose as high as 1.1 km above the summit and drifted as far as 40 km NW, W, and SW. Occasional rumbling sounds, shock waves, and/or sounds associated with gas emissions were reported. Explosions occasionally ejected incandescent material as high as 200 m above the summit and showered the upper flanks with incandescent material. Ashfall was reported in areas to the W during 11-12 December.

Geologic 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 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, United States

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

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin’s summit crater during 9-16 December. Small earthquakes were detected by the seismic network along with occasional rockfall signals. Elevated surface temperatures consistent with lava effusion were identified in satellite views during 9-10 and 12-16 December. Minor steaming from the lava flow was visible in clear webcam views during 14-15 December. Weather clouds sometimes obscured satellite and webcam views. 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).

Geologic summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger 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 older edifice and produced a submarine debris avalanche. Deposits from this and an even 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. Eruptions have been recorded since the late-19th century.

Ibu, Indonesia

1.4941°N, 127.6324°E | Summit elev. 1357 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 10-16 December. Daily white-to-gray or gray ash plumes rose 200-1,000 m above the summit and drifted in multiple directions; weather conditions occasionally prevented visual confirmation. Incandescence at the summit was visible in a few nighttime webcam images. The Alert Level remained at 2 (the second lowest level on a four-level scale) and the public was advised to stay 2 km away from the active crater and 3.5 km away from the N crater wall opening.

Geologic 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, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and 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. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Katmai, United States

58.279°N, 154.9533°W | Summit elev. 2047 m

The Alaska Volcano Observatory (AVO) reported that on 10 and 12 December strong winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes dispersed unconsolidated ash up to 1.8 km (6,000 ft) a.s.l. to the SE. The ash was originally deposited during the Novarupta-Katmai eruption in 1912. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).

Geologic summary: Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. The edifice had four NE-SW-trending summits, most of which were truncated by the 1912 collapse. Two or more large explosive eruptions took place during the late Pleistocene. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene, but Holocene lava flows from a flank vent descend the SE flank of the SW edifice into the Katmai River canyon. The steep walled young caldera has a jagged rim that rises 500-1,000 m above the caldera floor and contains a deep lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916.

Kilauea, United States

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

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea’s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema’uma’u Crater, continued at variable levels during 9-16 December. Incandescence at the S vent was visible during dark hours but incandescent at the N vent persisted through 12 December and was absent or very minor during the rest of the week. Tremor was continuous with irregular peaks that during 12-16 December were related to gas pistoning. 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).

Geologic summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Krasheninnikov, Russia

54.596°N, 160.27°E | Summit elev. 1816 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that eruptive activity at Krasheninnikov continued during 4-11 December. A large thermal anomaly over the volcano was identified in satellite images on all days except 9 December when weather clouds obscured views. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates and times are provided in Coordinated Universal Time (UTC); specific events are indicated in local time where specified.

Geologic summary: The late Pleistocene to Holocene Krasheninnikov volcano is comprised of two overlapping stratovolcanoes within a 9 x 10 km Pleistocene caldera. Young lava flows from summit and flank vents descend both into the caldera and down its outer flanks, and older flows that covered much of the SE caldera rim extended downslope at least 7 km. Tephra deposits from the caldera-forming eruption directly overlie a 39,000 years before present (BP) tephra thought to be associated with the formation of Uzon caldera (Florenskii, 1988). The intra-caldera stratovolcanoes are situated along a NE-SW-trending fissure that has also produced zones of Holocene cinder cones extending 15-20 km beyond the caldera. Construction of the southern edifice began about 11,000 years BP and lasted for about 4,500 years; it has a summit crater about 800-900 m wide. The northern edifice was constructed during a cycle of similar length that began about 6,500 years ago; it has a summit crater about 1.5 km wide, within which is low cone with an 800-m-wide crater containing another small cone. An eruptive cycle during about 600-400 years BP (1350-1550 CE) produced the Pauk lava cone in the crater of the northern cone and the Yuzhny lava flow on SW flank outside the caldera, followed by the Molodoy flow from the upper SW flank (Ponomareva, 1987; Ponomareva and Tsyurupa, 1985; Ponomareva and Braitseva, 1990).

Lewotolok, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Lewotolok was ongoing during 10-16 December. Daily white plumes rose as high as 500 m above the summit of the cone and drifted in various directions. A few nighttime webcam images showed incandescence at the summit. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the summit and 2.5 km away on the SSE and W flanks.

Geologic 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-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.

Marapi, Indonesia

0.38°S, 100.474°E | Summit elev. 2885 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive events at Marapi (on Sumatra) were recorded at 0445 on 11 December and at 1654 on 15 December, but were not visually observed due to weather conditions. At 1637 on 14 December an ash plume rose 1.2 km above the crater rim and drifted N. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the active crater.

Geologic summary: Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra’s most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Merapi, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Merapi continued during 10-16 December. The SW lava dome produced 10 lava avalanches that traveled as far as 2 km SW down the Bebeng drainage on 10 December and 2-16 per day that traveled 1.7-2 km down the Sat/Putih drainage during 11-12, 14, and 16 December. 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.

Geologic 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.

Ruang, Indonesia

2.3058°N, 125.3671°E | Summit elev. 703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ruang had decreased following the 17 and 30 April 2024 eruptions. During September-December 2025 white emissions decreased in height to 10-50 m above the summit. Volcanic seismicity was generally low; during the previous three months seismicity was dominated by distant tectonic earthquakes, with 0-3 deep volcanic (VT) earthquakes per day. The Alert Level was lowered to 1 (the lowest level on a scale of 1-4) at 1000 on 10 December and the public was warned to stay 500 m away from the active crater.

Geologic summary: Ruang volcano is the southernmost volcano in the Sangihe Island arc, north of Sulawesi Island; it is not the better known Raung volcano on Java. The 4 x 5 km island volcano is across a narrow strait SW of the larger Tagulandang Island. The summit contains a crater partially filled by a lava dome initially emplaced in 1904. Explosive eruptions recorded since 1808 have often been accompanied by lava dome formation and pyroclastic flows that have damaged inhabited areas.

Sheveluch, Russia

56.653°N, 161.36°E | Summit elev. 3283 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported continuing eruptive activity at Sheveluch’s “300 years of RAS” dome on the SW flank of Old Sheveluch and at the Young Sheveluch dome during 4-11 December. Ash plumes and clouds drifted as far as 250 km N during 5-7 December. A thermal anomaly was identified in satellite images during 6-8 and 11 December; the volcano was obscured by weather clouds on the other days. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC; specific events are in local time where noted.

Geologic summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. 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 occur on its outer flanks. The Molodoy 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, United States

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

The Alaska Volcano Observatory (AVO) reported that on 13 December strong winds in the vicinity of Shishaldin dispersed unconsolidated ash up to 2.7 km (9,000 ft) a.s.l. to the SSW. This phenomenon was not the result of recent volcanic activity and occurs during times of strong winds and dry snow-free conditions. The Anchorage Volcanic Ash Advisory Center and AVO reported that plumes of unconsolidated ash were visible in satellite images the next day, rising to the same altitude. Lower-level plumes of unconsolidated ash were also visible the week before, on 6 December, rising to 1.2 km (4,000 ft) a.s.l. The Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale) and the Aviation Color Code remained at Yellow (the second lowest level on a four-color scale).

Geologic summary: The symmetrical glacier-covered Shishaldin in the Aleutian Islands is the westernmost of three large stratovolcanoes in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning “mountain which points the way when I am lost.” Constructed atop an older glacially dissected edifice, it is largely basaltic in composition. Remnants of an older edifice 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 covered 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.

Stromboli, Italy

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

The Sezione di Catania – Osservatorio Etneo (INGV) reported that eruptive activity continued at Stromboli during 8-14 December. Webcam images showed Strombolian activity from five vents in Area N within the upper part of the Sciara del Fuoco, and from at least two vents in Area C-S (South-Central Crater) on the crater terrace. The vents in Area N (two in sector N1 and three in sector N2) continued to produce low- to medium-intensity explosions at a rate of 10-21 per hour, ejecting lapilli and bombs less than 150 m above the vents. Spattering at N2 was visible and intense for long periods of time. Low- to medium-intensity explosions ejected tephra from two vents in Area C-S at a rate of 0-3 times per hour. Intense spattering at the S vent at N2 began during the late morning of 14 December. An abundant amount of spatter accumulated and extended a few hundred meters down the upper portion of the Sciara del Fuoco. The flow was visible for a few hours. The Alert Level remained at Yellow (the second lowest level on a four-level scale) according to the Dipartimento della Protezione Civile.

Geologic summary: Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the “Lighthouse of the Mediterranean” in the NE Aeolian Islands. This volcano 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 scarp that formed about 5,000 years ago due to a series of slope failures which extends 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, Japan

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

The Japan Meteorological Agency (JMA) reported that eruptive activity at Suwanosejima’s Ontake Crater continued during 5-12 December. Incandescence was observed nightly in webcam images. An eruptive event on 12 December generated an ash plume that rose 600 m above the cater rim. Ashfall was reported in Toshima Village (3.5 km SSW) that same day. The Alert Level remained at 2 (the second level on a five-level scale) and the public was warned to be cautious within 1.5 km of the crater.

Geologic summary: The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two active summit craters. The summit is truncated by a large breached crater extending to the sea on the E 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 covered 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 an open collapse scarp extending 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.

Westdahl, United States

54.516°N, 164.65°W | Summit elev. 1563 m

The Anchorage Volcanic Ash Advisory Center (VAAC) reported that during 14-15 December plumes of unconsolidated ash in the vicinity of Westdahl were visible in satellite images rising to 1.8 km (6,000 ft) a.s.l. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).

Geologic summary: Westdahl is a broad glacier-covered volcano occupying the SW end of Unimak Island. Two peaks protrude from the summit plateau, and a new crater formed in 1978 cuts the summit icecap. The volcano has a somewhat of a shield-like morphology and forms one of the largest volcanoes of the Aleutian Islands. The sharp-topped, conical Pogromni stratovolcano, 6 km N, rises several hundred meters higher than Westdahl, but is moderately glacially dissected and presumably older. Many satellitic cones of postglacial age are located along a NW-SE line cutting across the summit of Westdahl. Some of the historical eruptions attributed to the eroded Pogromni may have originated instead from Westdahl (Miller et al. 1998). The first historical eruption occurred in 1795. An 8-km-long fissure extending east from the summit produced explosive eruptions and lava flows in 1991.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – GVP – December 10-16, 2025 – Managing Editor: Sally Sennert

Teo Blašković

I'm a dedicated researcher, journalist, and editor at The Watchers. With over 20 years of experience in the media industry, I specialize in hard science news, focusing on extreme weather, seismic and volcanic activity, space weather, and astronomy, including near-Earth objects and planetary defense strategies. You can reach me at teo /at/ watchers.news.

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