The Weekly Volcanic Activity Report: September 10-16, 2026

New activity/unrest: Krakatau, Indonesia.

Ongoing activity: Aira, Japan | Dukono, Indonesia | Great Sitkin, United States | Ibu, Indonesia | Kanlaon, Philippines | Karangetang, Indonesia | Kilauea, United States | Klyuchevskoy, Russia | Krasheninnikov, Russia | Lewotolok, Indonesia | Mayon, Philippines | Merapi, Indonesia | Purace, Colombia | Rincon de la Vieja, Costa Rica | Sabancaya, Peru | Semeru, Indonesia | Sheveluch, Russia | Sinabung, Indonesia.

Other observations: Lewotobi, Indonesia

New activity/unrest

Krakatau, Indonesia

6.1009°S, 105.4233°E; Elev. 285 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported ongoing eruptive activity at Krakatau during 9-16 September. During 6-11 September there were 14 Strombolian eruptions reported. There was one eruption detected on a seismograph at 0047 on 9 September, but it was not visually confirmed. According to an analysis of a HIMAWARI-9 RGB image taken on that same day, an ash plume rose 2.1 km above the summit and drifted NW at 1000. As of 16 September the five journalists and three crew members of a missing ship had not been found. The Alert Level remained at 3 (on a scale of 1-4) and the public was advised to stay 3 km away from summit.

Geological summary: The renowned Krakatau (frequently misnamed as Krakatoa) volcano lies in the Sunda Strait between Java and Sumatra. Collapse of an older edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that volcano are preserved in Verlaten and Lang Islands; subsequently the Rakata, Danan, and Perbuwatan cones were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former Danan and Perbuwatan cones. Anak Krakatau has been the site of frequent eruptions since 1927.

Ongoing activity

Aira, Japan

31.5772°N, 130.6589°E; Elev. 1,117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 8-14 September. Crater incandescence was visible in nighttime webcam images during 11-14 September. An eruptive event at 1246 on 8 September generated an ash plume that rose 1.3 km above the crater rim and drifted S. Volcanologists conducted a field survey on 10 September and measured high sulfur dioxide emissions, averaging 2,100 tons per day. A total of eight eruptive events during 13-14 September produced ash plumes that rose as high as 2.5 km above the crater and ejected large blocks 600 m from the vent. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 1 km of both the Minimadake and Showa 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. 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; Elev. 1,273 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 10-15 September. White-and-gray ash plumes rose 200-1,100 m above the summit and drifted in different directions during 10-11 and 13-14 September; weather conditions obscured the summit on the other days or no plumes were emitted. 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.

Geological 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.

Great Sitkin, United States

52.076°N, 176.13°W; Elev. 1,740 m

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin’s summit crater during 10-15 September based on webcam and satellite images. Minor earthquakes were detected daily, likely associated with rockfalls on the growing dome. Weather clouds obscured webcam and satellite views during most of the week; though steaming at the lava dome was visible in webcam images and slightly elevated surface temperatures were identified in satellite data during 10-11 September. 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 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; Elev. 1,357 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ibu continued during 10-17 September, with daily eruptive events recorded by the seismic network. Gray or white-and-gray ash plumes rose as high as 800 m above the summit and drifted in multiple directions. Incandescence at the summit was visible in some 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.

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, 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.

Kanlaon, Philippines

10.4096°N, 123.13°E; Elev. 2,422 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 10-16 September. The seismic network recorded 0-9 daily volcanic earthquakes. Sulfur dioxide emissions ranged from 1,085 to 4,074 tonnes per day. Volcanic emissions generally rose as high as 900 m above the summit and drifted E, NE, and S on most days. A total of six ash emissions were recorded during 10-14 September, each lasting 38 to 88 minutes long. The Alert Level remained at 2 (on a scale of 0-5); the public was warned to stay out of the 4-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Geological summary: Kanlaon volcano (also spelled Canlaon) forms the highest point on the Philippine island of Negros. The massive andesitic stratovolcano is covered with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller but higher active vent, Lugud crater, to the south. Eruptions recorded since 1866 have typically consisted of phreatic explosions of small-to-moderate size that produce minor local ashfall.

Karangetang, Indonesia

2.781°N, 125.407°E; Elev. 1,797 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Karangetang’s North Crater (Kawah Dua) continued during 10-16 September. Daily white and white-and-gray plumes rose as high as 500 m above the summit and drifted in various directions. Incandescence at the North Crater and from lava flows and/or incandescent avalanches on the flanks was visible in some webcam images throughout the week. The Alert Level remained at 2 (on a scale of 1-4) and the public was advised to stay 1.5 km away from both craters, with an extension to 2.5 km on the NW and SW flanks of North Crater.

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia’s most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Kilauea, United States

19.421°N, 155.287°W; Elev. 1,222 m

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kīlauea’s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halemaʻumaʻu Crater, continued at variable levels during 10-15 September. Occasional incandescence and flames were observed in webcams images from all three eruptive vents (S, W, and N) at Halemaʻumaʻu Crater. On 10 September overflows were less frequent, slower, shorter in duration (less than 10 minutes), not fed by a dome fountain, and did not travel as far from the N vent. Overflows during the morning of 11 September were more vigorous and lasted longer than 10 minutes. Several of these were fed by dome fountains that were 5-10 m tall. They also traveled farther from the N vent compared to those from the 10th.

There were 104 lava overflows from the N vent during 7-12 September, with the last one starting at 0727 on 12 September. Occasional spattering and flames were observed from the W vent and less frequently from the S vent; more energetic spatter and large flames were noted during drainback events. Each overflow during 11-12 September averaged about 20 minutes, separated by periods of about 10-15 minutes. The size and vigor of the dome fountains in the N vent gradually doubled in size to 10-15 m high on 12 September.

Intermittent spatter bursts were visible at the N vent during the early morning of 13 September and increased in intensity throughout the day. Around noon, the bursts began depositing spatter that started to build a small cone on the rim of the N vent. During the afternoon, effusive activity began to cool within the upper regions of the conduit. There were distinct Strombolian eruptions reported throughout the night, characterized by large, individual spatter bursts. A seismic swarm consisting of shallow earthquakes occurred during 2115-2125 on 13 September.

Eruptive activity significantly slowed at 0600 on 14 September; no lava flows were observed after 12 September. By the afternoon of 14 September, the small cone around the N vent measured 11-12 m tall. Just before 2100, cracks on and near the base of the NW wall of Halemaʻumaʻu Crater erupted lava just N of the vent complex. This was the same area where the short seismic swarm occurred the previous day. No fountaining was associated with these new vents, which began to feed a small lava flow in the NW corner of the crater floor. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code at Orange (the second highest color on a four-color scale).

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the Island of Hawai\`i. 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 Halema\`uma\`u 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.

Klyuchevskoy, Russia

56.056°N, 160.642°E; Elev. 4,754 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that a thermal anomaly over Klyuchevskoy was identified in satellite images on most days during 10-15 September; weather clouds occasionally obscured views. The Aviation Color Code was lowered to Yellow (the second lowest level on a four-color scale) on 9 September. Dates are based on UTC; specific events are in local time where noted.

Geological summary: Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Krasheninnikov, Russia

54.596°N, 160.27°E; Elev. 1,816 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that lava flows at Krasheninnikov continued to effuse onto the E flank of the Northern Cone during 10-15 September. A daily large thermal anomaly was identified in satellite images. Gas-and-steam emissions sometimes contained ash. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale). Dates and times are provided in Coordinated Universal Time (UTC); events are in local time only where specified.

Geological 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; Elev. 1,431 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported continuing eruptive activity at Lewotolok during 10-16 September. Daily gray ash plumes rose 100-700 m above the summit and drifted NW, W, and SW. The lava flows on the SSE and NE flanks did not advance, remaining at 1.8 km and 1.1 km long, respectively. During 11-13 September a new lava flow traveled 300-700 m down the SE flank, over older flows. Webcam images from 9, 11, and 13-16 September showed incandescent material being ejected above the summit and onto the flanks. The Alert Level remained at 2 (on a scale of 1-4). The public was warned to stay 2 km away from the summit with an extension to 3 km on the S and SE flanks.

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-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.

Mayon, Philippines

13.257°N, 123.685°E; Elev. 2,462 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported ongoing ash emissions and unrest at Mayon during 9-16 September. Each day the seismic network recorded 2-38 volcanic earthquakes; one rockfall was detected on 6 September. Sulfur dioxide emissions (SO₂) generally averaged 500-5,363 tonnes per day (t/d). Emissions rose 100-750 m above the crater and drifted in different directions on 12, 13, 15, and 16 September. A total of three ash emissions, each lasting one minute long, were recorded on 14 and 15 September. One ash emission, lasting 46 seconds, was reported on 16 September. The Alert Level remained at 2 (on a 0-5 scale) and the public was 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 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.

Merapi, Indonesia

7.54°S, 110.446°E; Elev. 2,910 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Merapi (on Java) continued during 10-16 September with lava avalanches produced by the active lava dome on the upper SW flank. The seismic network recorded as many as 43 lava avalanches that traveled as far as 2 km down the Sat/Putih drainage on the SW flank during 10-11, 13, and 15-16 September and one lava avalanche that traveled as far as 1.5 km down the Krasak drainage on the SW flank on 13 and 16 September. On 14 September as many as 25 lava avalanches were reported on the SW flank, affecting the Sat/Putih, Bebeng, and Krasak drainages. On 16 September there were seven lava avalanches reported on the SW flank affecting the Sat/Putih and Krasak drainages. 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 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.

Purace, Colombia

2.3095°N, 76.3948°W; Elev. 4,650 m

The Servicio Geologico Colombiano (SGC) reported intensifying eruptive activity at Puracé during 10-15 September. Signals associated with fluid movement dominated the seismicity and were characterized as tremor-type signals located beneath Puracé volcano at depths less than 1 km. Seismic activity associated with rock fracturing (volcano-tectonic earthquakes) continued to be recorded, but a majority of signals were located in an area 10-22 km NE of Puracé at depths of 7-17 km. Some of these earthquakes were felt by residents, with the largest (M 3.1) recorded at 1022 on 10 September. Sulfur dioxide flux stayed above the average baseline levels and soil carbon dioxide concentrations rose throughout the reporting period. Slow ground deformation persisted in an area between the Puracé, Piocollo, and Curiquinga volcanoes.

Ash plumes rose as high as 1.2 km above the summit and drifted NW during 10-13 September; the highest event occurred at 0859 on 13 September, according to several nearby communities, including Río Blanco. Two ash plumes were recorded on 14 and on 15 September drifting NW, but could not be visually confirmed due to cloud cover. Ashfall was reported in Cristales and Loma Linda on 10 September and in Hato Viejo, Hispala, 20 de Julio, and Coconuco on 13 September. The Alert Level remained at Orange (the second highest level on a four-color scale).

Geological 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.

Rincon de la Vieja, Costa Rica

10.8314°N, 85.3364°W; Elev. 1,729 m

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported that a total of 67 small phreatic eruptions at Rincón de la Vieja were recorded daily by the seismic and infrasound networks during 6-16 September. One of the eruptive events at 1032 on 6 September generated a lahar; secondary lahars were recorded on 5 and 6 September after heavy rainfall. On 13 September the sulfur dioxide flux exceeded 6,000 tonnes per day. The Alert Level remained at 3 (Caution) and the Aviation Color Code remained Orange.

Geological summary: Rincón de la Vieja is a volcanic complex in the Guanacaste Range of NW Costa Rica. Sometimes referred to as the Rincon de la Vieja-Santa María Volcanic Complex, it consists of a slightly arcuate 20-km-long ridge of 12 craters and pyroclastic cones 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. The Santa María cone, the highest peak of the complex, is located on the E side of the ridge and has a lake within the 400-m-diameter crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous reported eruptions possibly dating back to the 16th century, have been from the active crater, near the center of the complex, with an acidic 300-m-diameter lake.

Sabancaya, Peru

15.787°S, 71.857°W; Elev. 5,960 m

The Instituto Geofísico del Perú’s (IGP) Centro Vulcanológico Nacional (CENVUL) reported continuing eruptive activity at Sabancaya during 7-13 September. The seismic network detected 41 seismic events associated with the movement of magmatic fluids, along with earthquakes indicating internal rock fracturing; no volcanic explosions occurred during the period. Gas, steam, and ash emissions periodically rose as high as 500 m above the summit and drifted less than 10 km E and SE. Moderate sulfur dioxide (SO₂) emissions averaged 753 tons per day, and 6 thermal anomalies (each 3 MW or less) associated with the lava dome were identified. The Alert Level remained at Orange (the third level on a four-color scale) and the public was warned to stay outside of a 12 km radius from the summit.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning “tongue of fire” in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of observed eruptions date back to 1750 CE.

Semeru, Indonesia

8.108°S, 112.922°E; Elev. 3,657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 10-16 September, with daily eruptive events recorded by the seismic network. White-and-gray ash plumes rose 200-1,000 m above the summit and drifted in multiple directions on most days; no emissions were visible during 10-11 September. The Alert Level remained at 3 (the second highest level on a scale of 1-4) and the public was warned to stay at least 5 km away from the Jonggring Saloko Crater 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.

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, Russia

56.653°N, 161.36°E; Elev. 3,283 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported continuing lava effusion and explosive activity at the lava domes along the N crater floor of Young Sheveluch (on the SW flank of Old Sheveluch) during 9-15 September. A thermal anomaly was identified in satellite images on 11, 13, and 15 September; weather clouds occasionally obscured views. 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.

Geological 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.

Sinabung, Indonesia

3.17°N, 98.392°E; Elev. 2,460 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Sinabung was ongoing during 10-16 September. White plumes were visible during the week, rising as high as 600 m above the summit and drifting in multiple directions. The Alert Level remained at 3 (the second highest level on a scale of 1-4).

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.

Lewotobi, Indonesia

8.542°S, 122.775°E; Elev. 1,703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the Alert Level was lowered to 2 (on a scale of 1-4) at Lewotobi Laki-Laki on 16 September, and the public was warned to stay 4 km away from the center of Laki-Laki.

Geological summary: The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the “husband and wife”). Their summits are less than 2 km
apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava
domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – GVP – September 10-16, 2026 – Managing Editor: Sally Sennert