The Weekly Volcanic Activity Report: September 3-9, 2026

New activity/unrest: Karangetang, Indonesia | Krakatau, Indonesia | Sinabung, Indonesia | Villarrica, Chile.

Ongoing activity: Aira, Japan | Ambae, Vanuatu | Dukono, Indonesia | Great Sitkin, United States | Ibu, Indonesia | Kanlaon, Philippines | Kilauea, United States | Klyuchevskoy, Russia | Krasheninnikov, Russia | Kupreanof, United States | Lewotolok, Indonesia | Mayon, Philippines | Merapi, Indonesia | Nishinoshima, Japan | Purace, Colombia | Reventador, Ecuador | Sabancaya, Peru | Sangay, Ecuador| Semeru, Indonesia | Sheveluch, Russia.

New activity/unrest

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 3-9 September. Daily white 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. Daily rumbling sounds at various intensities were noted. 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.

Krakatau, Indonesia

6.1009°S, 105.4233°E; Elev. 285 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported ongoing Strombolian activity at Krakatau during 3-9 September, including an intense explosive and effusive phase that caused widespread ashfall and impacts. White, gray, and/or black ash plumes rose as high as 400 m above the summit and drifted W and NW during 3-4 September.

Webcam images at 0419 and at 0428 on 4 September showed incandescent material being ejected above the crater, though webcam images later that day at 2214, at 2242, and at 2253 showed what appeared to be lava fountaining and/or bright an intense ejections of lava. Continuous lava fountaining began at 2307, with sounds of rumbling and roaring along with felt vibrations were reported at the Pasauran Anak Krakatau Volcano Observation Post (50 km ESE) in the Serang Regency. As the eruption intensified there were explosion, rumbling, and booming sounds reported by residents across a large area as far as 200 km E, in Banten (80 km SE), and Lampung (170 km N); a bang was heard and windows and doors vibrated possibly as far as 700 km away according to a news article. The Darwin Volcanic Ash Advisory Centre (VAAC) noted that by 2330 ash plumes had risen to 13.7 km (45,000 ft) a.s.l. and drifted W, and 10 minutes later they had reached 14.6 km (48,000 ft) a.s.l. Webcams showed lava fountains rising 100-400 m above the vent and active lava flows, though ash-and-gas plumes, weather conditions, and darkness sometimes obscured webcam views. By 0050 on 5 September ash plumes had risen to 15.2 km (50,000 ft) a.s.l. and were fanning out to the W. Fountaining was last confirmed at 0100 on 5 September, before webcams were damaged by ejected volcanic material.

By 0150 on 5 September the Darwin VAAC noted that ash was still continuously rising to 15.2 km a.s.l. and drifting W, though ash at 5.5 km (18,000 ft) a.s.l. was drifting S. Within a few hours, by 0450, ash at 15.2 km a.s.l. was drifting W, ash at 6.1 km (20,000 ft) a.s.l. was drifting S, and ash at 5.5 km a.s.l. was drifting ESE. Ash continued to spread in these directions throughout the day. PVMBG reported that lava fountaining, active lava flows, and gas-and-ash emissions were continuous for 25 hours, stopping at 0004 on 6 September. By 1010 on 6 September the higher altitude portion of the ash plume, at 15.2 km, had detached and continued to drifted W, according to the VAAC. After the continuous phase ended, discrete Strombolian explosions were recorded at 0353, 0710, and 2023 on 6 September. Continuously emitted ash plumes were visible in satellite images during 6-7 September rising to 4.6 km (15,000 ft) a.s.l. and spreading E and SE; remnant ash clouds drifted W and E. By 1810 on 7 September the ash plume that had risen to 15.2 km a.s.l. was no longer discernable, though remnant ash at 4.6 km a.s.l. was visible drifting NW. Ash plumes rose to 1.8 km (6,000 ft) a.s.l. and drifted SW.

Ash-and-gas plumes fanned out in multiple directions during 4-8 September, moving SE to S across parts of Banten and west Java, including the capital of Jakarta (160 km E), and SW to NW over parts of Banten (77 km SE), Lampung, Bengkulu (430 km NW), West Sumatra, the southern Sunda Strait, and adjacent Indian Ocean. Nearly 3,000 flights were affected by re-routing, delays, or cancellations at multiple airports across the region; operations were suspended for various periods of time at eight domestic and international airports including Soekarno-Hatta International Airport (138 km E), Halim Perdanakusuma Airport (165 km E, Jakarta), Radin Inten II Airport (95 km NNW, Lampung), Husein Sastranegara Airport (255 km SSE, Bandung, West Java), Budiarto Airport (130 km ESE, Curug, Tangerang), Pondok Cabe Airport (150 km ESE, South Tangerang), Muhammad Taufik Kiemas Airport (190 km NW, Pesisir Barat, Lampung), and Atung Bungsu Airport (320 km NW, Pagar Alam, South Sumatra). The airports reopened on 8 September. Ashfall affected dozens of villages across the Banten and Lampung provinces, in Jakarta, and in other parts of west Java. Authorities advised residents in some areas to stay indoors and wear masks; in Lampung water was sprayed on several roadways to reduce the impact of ashfall.

Five eruptive events were recorded at 0508, 0534, 0749, 1134, and 1756 on 8 September and one was recorded at 1247 on 9 September, but none were visually observed. The Darwin VAAC noted that ash plumes rose 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted W and SW during those two days. According to a news report a group of five journalists and three crew members remained missing on 10 September after departing in a speed boat on 7 September to cover the eruption. 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.

Sinabung, Indonesia

3.17°N, 98.392°E; Elev. 2,460 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Sinabung was ongoing during 2-9 September. An eruptive event at 0720 on 2 September generated a gray-to-brown ash plume that rose 1 km above the summit and drifted E and SE. White-and-gray plumes rose as high as 500 m above the summit and drifted in multiple directions during 3-5 September. Dense white plumes were visible during the rest of the week, rising as high as 500 m above the summit and drifting in various directions. Seismicity continued to indicate magma movement and sulfur dioxide emissions remained at high levels.

The Badan Nacional Penanggulangan Bencana (BNPB) reported that there were approximately 208 families, or 650 people, that had evacuated as of 4 September; of that total 405 people were staying at the Jambur Arih Ersada shelter in Sukatepu. Recent ashfall had impacted agricultural fields though the extent of the damage was unknown. Local roads were sprayed with water to mitigate ashfall hazards. A drone overflight revealed no new lava domes at the summit and that the existing dome remained stable. At 1200 on 6 September the exclusion zone was lowered from 6 to 5 km on the SE flank but remained at 3 km from the summit in all other directions. A news report noted that by 7 September evacuees from Kuta Tengah had begun returning home. 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.

Villarrica, Chile

39.42°S, 71.93°W; Elev. 2,847 m

The Servicio Nacional de Geología y Minería (SERNAGEOMIN) and the Servicio Geológico Minero Argentino (SEGEMAR) reported that during August and the first few days of September seismic and surficial activity at Villarrica notably increased. An overall increase in seismic signals indicated lava lake activity. Concurrently with the increased seismicity, acoustic signals consistent with minor explosions were recorded as well as ballistic ejections, crater incandescence, and rising temperatures identified in satellite data. The data indicated a rise in the level of the lava lake and increasing activity. SERNAGEOMIN and SEGEMAR raised the Volcanic Alert Level to Yellow (the second lowest level on a four-level scale) on 4 and 5 September, respectively. The Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED) maintained the “Preventative Early Warning“ status for the communities of Villarrica, Pucón (16 km N), Curarrehue, and Panguipulli.

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 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.

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 31 August-7 September. Crater incandescence was visible in nighttime webcam images during 31 August-4 September. A total of 17 eruptive events produced ash plumes that rose as high as 1.7 km above the crater. Volcanologists conducted a field survey on 2 September and measured high sulfur dioxide emissions, averaging 2,800 tons per day. Very small eruptive events were recorded during 4-7 September. 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.

Ambae, Vanuatu

15.389°S, 167.835°E; Elev. 1,496 m

The Wellington Volcanic Ash Advisory Center (VAAC) reported that ash plumes at Ambae were identified in satellite images rising 2.1 km (7,000 ft) a.s.l. and drifting SE on 6 September. The Alert Level remained at 3 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone B, defined as a 3-km radius around the active vents in Lake Voui, and to stay away from drainages during heavy rains.

Geological summary: The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone with numerous scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

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 3-9 September. White-and-gray ash plumes rose 300-800 m above the summit and drifted NW, N, and E during 6-7 September; weather conditions obscured views on the other days or there were no plumes. 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 3-9 September based on webcam and satellite images. The flow gradually expanded E as confirmed by radar data. 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 weakly elevated surface temperatures were identified in satellite data during 4-5 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 3-9 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 2-9 September. The seismic network recorded 0-11 daily volcanic earthquakes. Sulfur dioxide emissions ranged from 852 to 2,257 tonnes per day. Volcanic emissions generally rose as high as 500 m above the summit and drifted E on most days; observations were obscured during 3-5 September. Two ash plumes, lasting 15 minutes and two hours and 44 minutes, were recorded on 7 September. One of the ash plumes was visible in webcam images at 0109 rising 500 m above the summit and drifting E. At 1802 on 9 September a grayish ash plume rose 500 m above the summit and drifted NE; ash emissions lasted for 38 minutes. 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.

Kilauea, United States

19.421°N, 155.287°W; Elev. 1,222 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 2-9 September. Semi-continuous or continuous incandescence at the N vent was observed in webcams during 2-7 September. Overnight during 6-7 September the N vent produced occasional flames and low-level spatter that rose just above the rim. Incandescence at both the S and W vents was also periodically observed. At 1245 on 7 September lava overflowed the N vent, prompting HVO to raise the Volcano Alert Level to Watch (the second highest level on a four-level scale) and the Aviation Color Code to Orange (the second highest color on a four-color scale) 15 minutes later. There were 28 additional lava overflows, with the last starting at 0727 on 9 September. Each overflow lasted from 15 minutes to about two hours, separated by periods of about 15 minutes to eight hours. The overflows became progressively more vigorous and fed by a dome fountain that rose 5-10 m. The lava flows formed two lobes advancing around 1 km SW and NE.

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 3-9 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: 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 ENE and E flanks of the Northern Cone during 3-9 September. A daily large thermal anomaly was identified in satellite images. Small temperature anomalies along the active lava flows on the ENE flank were visible in satellite images from 3 and 8 September. 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).

Kupreanof, United States

56.011°N, 159.797°W; Elev. 1,895 m

The Alaska Volcano Observatory (AVO) reported that the number of earthquakes, the intensity of steam emissions, and measured sulfur dioxide emissions at Kupreanof had declined in the past month. The Volcano Alert Level and the Aviation Color Code were both changed to Unassigned at 1431 on 8 September, rather than Green and Normal, respectively, due to insufficient ground-based monitoring data. The temporary monitoring station installed near Kupreanof during the summer of 2026 provided seismic data, infrasound data, gas measurements, and web camera images on an intermittent basis due to the conservation of battery power; the frequency of data acquisition may be increased if activity warrants. Kupreanof was also monitored by satellite data, remote infrasound and lightning networks, and visual observations from nearby pilots and mariners.

Geological summary: Kupreanof is the largest and NE-most of a group of five relatively closely spaced Quaternary volcanic centers opposite Stepovak Bay. A debris flow or block-and-ash flow with possible juvenile fragments descended a late-Pleistocene valley south of the volcano. This stratovolcano displays vigorous fumarolic activity, and although a “grayish-brown ash horizon” extending 15 km was reported by a pilot in 1987 after emissions from a SSW-flank solfatara field, the cause of this event is uncertain.

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 3-9 September. Daily gray ash plumes rose 400-800 m above the summit and drifted in multiple directions. The lava flows on the SSE and NE flanks did not advance, remaining at 1.8 km and 1.1 km long, respectively. During 4-5 September a new lava flow traveled 500 m down the NE flank, over older flows. A webcam image from 2136 on 6 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 unrest at Mayon during 2-8 September. Each day the seismic network recorded 5-14 volcanic earthquakes; one rockfall was detected on 6 September. Sulfur dioxide emissions (SO₂) generally averaged 4,095-6,931 tonnes per day (t/d) but peaked at a very high rate of 8,165 t/d on 3 September. SO₂ emissions had averaged 4,196 t/d since the Alert level was lowered to 2 on 5 August. 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 3-9 September with lava avalanches produced by the active lava dome on the upper SW flank. The seismic network recorded as many as nine lava avalanches per day that traveled as far as 2 km down the Sat/Putih drainage on the SW flank during 3-6 September. 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.

Nishinoshima, Japan

27.2439°N, 140.8797°E; Elev. 160 m

The Japan Meteorological Agency (JMA) lowered the warning level for Nishinoshima at 1100 on 8 September and warned the public to be cautious within 1 km of the summit crater. Steam emissions within the crater were observed during an overflight on 17 August 2026. Eruptive activity last occurred on 4 October 2023.

Geological summary: The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Multiple eruptions between 2013 and 2023 completely covered the previous exposed surface and continued to enlarge the island. The island is the summit of a massive submarine volcano that has prominent peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the ocean surface 9 km SSE.

Purace, Colombia

2.3095°N, 76.3948°W; Elev. 4,650 m

The Servicio Geologico Colombiano (SGC) reported intensifying eruptive activity at Puracé during 2-9 September. Signals associated with fluid movement dominated the seismicity and were characterized as tremor-type signals located beneath Puracé volcano at depths less than 4 km. Seismic activity associated with rock fracturing (volcano-tectonic earthquakes) continued to be recorded, but a majority of signals were located in an area 10-19 km NE of Puracé at depths of 6-12 km. Some of these earthquakes were felt by residents; the largest earthquake, a M 4.1 recorded at 2058 on 6 September, was felt by residents in the municipalities of Puracé, Totoró, and Popayán. 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. As many as five daily ash emissions were recorded by the seismic network, though adverse weather conditions often prevented visual confirmation. Ashfall was reported in Cristales and Loma Linda during 3-4 September. Ash plumes rose as high as 600 m above the summit and drifted N and NW during 4-5 September, followed by plumes to 200 m that drifted NW during 5-6 September. An ash plume at 1531 on 7 September rose 450 m above the summit and drifted NW. Five ash plums during 8-9 September rose as high as 1.5 km above the summit and drifted NW. Ashfall was reported in Cristales and 20 de Julio, municipality of Puracé. 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.

Reventador, Ecuador

0.077°S, 77.656°W; Elev. 3,562 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that eruptive activity at Reventador continued at a high level during 3-9 September. Seismicity included 67-80 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Daily ash-and-gas plumes were visible rising 200-1,000 m above the crater rim and drifting mainly NW, W, and SW. Incandescent blocks were visible during dark hours each day rolling as far as 1.1 km down the flanks and sometimes being ejected from the summit onto the flanks. Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at Orange (the second highest level on a four-color scale).

Geological summary: Volcán El Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have left extensive deposits on the scarp slope. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

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 31 August-6 September. The seismic network detected 51 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 1.4 km above the summit and drifted less than 10 km E and SE. Moderate sulfur dioxide (SO₂) emissions averaged 968 tons per day, and 11 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.

Sangay, Ecuador

2.005°S, 78.341°W; Elev. 5,286 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that activity at Sangay continued to be low. The seismic network recorded 4-11 daily explosions during 1-4 September. Weather conditions sometimes obscured webcam and satellite views, though no emissions were visible when conditions were clear or partially clear. IG-EPN switched to weekly summaries of activity on 4 September. The Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at Yellow (the second highest level on a four-color scale).

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador’s volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within the open calderas of two previous edifices which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

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 3-9 September, with daily eruptive events recorded by the seismic network. White-and-gray ash plumes rose 300-1,000 m above the summit and drifted in multiple directions on most days; no emissions were visible during 8-9 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 2-9 September. A thermal anomaly was identified in satellite images on most days; 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.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – GVP – September 3-9, 2026 – Managing Editor: Sally Sennert