The Weekly Volcanic Activity Report: August 27–September 2, 2025

New activity/unrest

Bagana, Papua New Guinea

6.137°S, 155.196°E | Summit elev. 1855 m

The Darwin Volcanic Ash Advisory Centre (VAAC) reported that ash plumes from Bagana were identified in satellite images rising to 2.1 km (7,000 ft) a.s.l. and drifting NW during 27-28 August.

Geologic summary: Bagana volcano, in a remote portion of central Bougainville Island, is frequently active. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although occasional explosive activity produces pyroclastic flows. Lava flows with tongue-shaped lobes up to 50 m thick and prominent levees descend the flanks on all sides.

Dempo, Indonesia

4.016°S, 103.121°E | Summit elev. 3142 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruptive event at Dempo was recorded at 1338 on 29 August and lasted nearly two minutes based on the seismic network. A diffuse white steam, gas, and ash plume rose 100 m above the summit and drifted N. The Alert Level remained at 2 (on a scale of 1-4), and the public were reminded to stay 1 km away from the crater and as far as 2 km on the N flank.

Geologic summary: Dempo is a stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3-km-wide amphitheater open to the north. The high point of the older Gunung Dempo crater rim is slightly lower, and lies at the SE end of the summit complex. The taller Marapi cone was constructed within the older crater. Remnants of seven craters are found at or near the summit, with volcanism migrating WNW over time. The active 750 x 1,100 m active crater cuts the NW side of the Marapi cone and contains a 400-m-wide lake at the far NW end. Eruptions recorded since 1817 have been small-to-moderate explosions that produced local ashfall.

Karymsky, Russia

54.049°N, 159.443°E | Summit elev. 1513 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that moderate activity continued at Karymsky during 21-28 August. Satellite images showed a weak thermal anomaly over the volcano on 22 and 26 August and ash plumes rising around 1.5 km above the summit were drifting 100 km E during 26-27 August; the volcano was quiet or obscured by clouds on the other days of the week. The Aviation Color Code remained at Orange (the third 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: Karymsky, the most active volcano of Kamchatka’s eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Krasheninnikov, Russia

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

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that the eruption at Krasheninnikov continued during 27 August-2 September. A daily large thermal anomaly over the volcano was identified in satellite images. 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).

Lokon-Empung, Indonesia

1.3644°N, 124.7992°E | Summit elev. 1580 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported increased seismicity at Lokon-Empung. During 1 August-1 September white steam-and-gas plumes rose as high as 10 m above the vent and seismicity was dominated by shallow volcanic earthquakes occurring at a rate of 1-37 per day. Seismicity increased during 0000-0600 on 2 September and was characterized by 35 shallow volcanic earthquakes, 25 earthquakes indicating emissions, and four deep volcanic earthquakes. Seismicity continued to intensify, and by 0221 on 3 September the seismic network had recorded a total of 143 shallow volcanic earthquakes, 72 earthquakes indicating emissions, and 15 deep volcanic earthquakes. Tiltmeter data indicated inflation during 17 August-2 September. No surficial changes were observed. The Alert Level was raised to 3 (on a scale of 1-4) at 1200 on 3 September and the public was warned to stay 2.5 km away from the crater.

Geologic summary: The Lokong-Empung volcanic complex, rising above the plain of Tondano in North Sulawesi, includes four peaks and an active crater. Lokon, the highest peak, has a flat craterless top. The morphologically younger Empung cone 2 km NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century. A ridge extending 3 km WNW from Lokon includes the Tatawiran and Tetempangan peaks. All eruptions since 1829 have originated from Tompaluan, a 150 x 250 m crater in the saddle between Lokon and Empung. These eruptions have primarily produced small-to-moderate ash plumes that sometimes damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.

Whakaari/White Island, New Zealand

37.52°S, 177.18°E | Summit elev. 294 m

GeoNet reported that a short-lived eruption occurred at Whakaari/White Island on 28 August. At 1015 a small eruption produced a dark ash plume with minor ash content that was visible in webcam images rising less than 1 km a.s.l. The plume drifted NE. After about 30 minutes the plume color turned white, indicating that the composition had changed to steam and gas. Occasional short-lived darker plumes containing ash were visible rising rose 700-800 m a.s.l. until around noon. The Volcanic Alert Level remained at 2 (on a scale of 0-5) and the Aviation Color Code remained at Yellow (the second lowest level on a four-color scale).

Geologic summary: The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari (“The Dramatic Volcano”) and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

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 26 August-2 September. Nightly crater incandescence was visible in webcam images. There were 10 eruptive events recorded during 26-30 August that produced either discrete ash-and-gas plumes or periods of continuous ash-and-gas emissions. Ash plumes from the events rose as high as 2.4 km above the crater rim and drifted in multiple directions. Periods of continuous emissions occurred during 1602-1715 and 1917-2045 on 27 August, from 2256 on 28 August to 0430 on 29 August, and during 1300-1437, 1522-1730, and 1825-2125 on 30 August. 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.

Ambae, Vanuatu

15.389°S, 167.835°E | Summit elev. 1496 m

The Vanuatu Meteorology and Geohazards Department (VMGD) reported ongoing unrest at Ambae during the month of August based on seismic and satellite data, webcam images, and field observations. Sulfur dioxide emissions were identified in satellite images during 1, 3-9, 11-14, and 16-25 August. A low-level thermal anomaly was also detected in satellite images during 3, 7, 9-11, 13, and 16 August. Steam and/or gas emissions were visible in satellite and webcam observations during 5, 10-11, and 15 August. The Alert Level remained at 2 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone A, defined as a 2-km radius around the active vents in Lake Voui, and to stay away from drainages during heavy rains.

Geologic 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.

Ambrym, Vanuatu

16.25°S, 168.12°E | Summit elev. 1334 m

The Vanuatu Meteorology and Geohazards Department (VMGD) reported ongoing unrest at Ambrym during August. A weak thermal anomaly was detected in satellite images on 2 August. Steam emissions rising from Marum Crater on 5 August were reported based on field observations and webcam images. Seismic data confirmed ongoing unrest. The Alert Level remained at 2 (on a scale of 0-5). VMGD warned the public to stay outside of Permanent Danger Zone A, defined as a 1-km radius around Benbow Crater and a 2-km radius around Marum Crater, and to stay 500 m away from the ground cracks created by the December 2018 eruption.

Geologic summary: Ambrym is a large basaltic volcano with a 12-km-wide caldera formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have been frequently reported since 1774, though mostly limited to extra-caldera eruptions that would have affected local populations. Since 1950 observations of eruptive activity from cones within the caldera or from flank vents have occurred almost yearly.

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 27 August-2 September. Daily white-and-gray gas-and-ash plumes rose 100-600 m above the summit and drifted NW and E. 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.

Etna, Italy

37.748°N, 14.999°E | Summit elev. 3357 m

The Sezione di Catania – Osservatorio Etneo (INGV) reported that eruptive activity at Etna’s summit craters during 25-31 August was characterized by decreasing lava effusion at multiple vents. Strombolian activity and ash emissions occurred from SE Crater, and there were gas emissions at NE, Bocca Nuova, and Voragine craters. Strombolian activity of varying intensity at two vents at SE Crater ejected lava fragments that fell back into the crater and onto the flanks of the cone. The activity generated diffuse ash emissions that quickly dispersed around the summit area. Activity was observed through webcams and by observatory staff doing daily fieldwork in the summit area.

Lava effusion continued at a vent around 2,980 m elevation located along the N-S-trending fissure between Bocca Nuova and SE Crater. The flow field was complex with overlapping lava flows, lava tunnels, and ephemeral vents that produced secondary lava flows. The distal end of the flow field reached 2,250 m elevation and the longest flow was about 2 km. The flow field was estimated to be 560,000 square meters in area with a volume of about 1,700,000 cubic meters.

The vent located at 3,100 m elevation at the base of the saddle between Bocca Nuova Crater and SE Crater continued to effuse lava but at a slower rate by 27 August. Two lava flows reached at least 2,950 m elevation. During a field visit and drone overflight the morning of 29 August the vent was no longer effusing lava, and the flow field was cooling. The flow field was 840 m long, had an estimated area of 93,000 square meters, and erupted about 140,000 cubic meters of lava.

The vent on the S flank of SE Crater, at 3,200 m elevation, was active during most of the week with multiple lava flows advancing SW and S. On 27 August three aligned vents fed lava flows that branched into several small flows at the distal end of the flow field. On 29 August the most advanced flow front was traveling SE and reached 2,870 m elevation. The vents were inactive on 31 August and the lava flows were cooling. The flow field was 780 m long, had an estimated area of 150,000 square meters, and erupted about 310,000 cubic meters of lava.

Geologic summary: Mount Etna, towering above Catania on the island of Sicily, has one of the world’s longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Fuego, 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 26 August-2 September. Daily Strombolian explosions were recorded by the seismic network at rates of 5-13 per hour when reported. The explosions generated daily gas-and-ash plumes that rose as high as 1.1 km above the summit and drifted 10-30 km NW, W, and SW. Rumbling sounds, shock waves, and/or sound associated with gas emissions were reported daily. On most days, explosions ejected incandescent material 150-300 m above the summit and occasionally showered the upper flanks with incandescent material. Block avalanches descended the flanks, sometimes reaching vegetated areas. Ashfall was reported in areas downwind including Panimache I and II (8 km SW), Finca Palo Verde (10 km WSW), Yepocapa (12 km SW), and Sangre de Cristo (8 km W) during 28-29 August and in Yepocapa during 31 August-1 September.

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.

Gaua, Vanuatu

14.281°S, 167.514°E | Summit elev. 729 m

The Vanuatu Meteorology and Geohazards (VMGD) reported that unrest continued at Gaua during August. Sulfur dioxide emissions were identified in satellite images on 3 August and steam and/or gas emissions were visible in satellite images rising from the vent during 3-5 and 12 August. The Alert Level remained at 2 (on a scale of 0-5) and the public was warned to stay away from the main cone.

Geologic summary: The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km summit caldera. Small vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; littoral cones were formed where these lava flows reached the ocean. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. The active Mount Garet (or Garat) cone in the SW part of the caldera has three pit craters across the summit area. Construction of Garet and other small cinder cones has left a crescent-shaped lake. The onset of eruptive activity from a vent high on the SE flank in 1962 ended a long period of dormancy.

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 27 August-2 September. Satellite data indicated that the flow was advancing S, with some rockfalls occurring along the S and E margins. Small daily earthquakes were detected by the seismic network, including signals probably caused by the small rockfalls. Weather clouds mostly obscured satellite and webcam views; elevated surface temperatures were identified in satellite data during 27-28 August and 1-2 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).

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

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 20-26 August. Daily dense gray or white-and-gray ash plumes rose 300-700 m above the summit and drifted NE and E. 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.

Kelimutu, Indonesia

8.77°S, 121.82°E | Summit elev. 1639 m

Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported another significant increase in the lake water temperature at Kelimutu’s Crater II (Tiwu Koofai Nuwamuri). The temperature of the lake water rose from 34.2 degrees Celsius (C) on 26 August to 36.4 degrees C on 29 August. A strong sulfur odor accompanied the temperature increase along with the appearance of gas-and-steam on the lake’s surface. The color of the lake water had not changed, remaining light blue. There was no significant change in seismicity. The Alert Level remained at 1 (on a scale of 1-4) and the public was advised to limit activities near the craters, not approach the lake water, and to not spend the night in the craters.

Geologic summary: Kelimutu is a small, but well-known, Indonesian compound volcano in central Flores Island with three summit crater lakes of varying colors. The western lake, Tiwi Ata Mbupu (Lake of Old People) is commonly blue. Tiwu Nua Muri Kooh Tai (Lake of Young Men and Maidens) and Tiwu Ata Polo (Bewitched, or Enchanted Lake), which share a common crater wall, are commonly colored green and red, respectively, although lake colors periodically vary. Active upwelling, probably fed by subaqueous fumaroles, occurs at the two eastern lakes. The scenic lakes are a popular tourist destination and have been the source of minor phreatic eruptions in historical time. The summit is elongated 2 km in a WNW-ESE direction; the older cones of Kelido (3 km N) and Kelibara (2 km S).

Kick ’em Jenny, Grenada

12.3°N, 61.64°W | Summit elev. -185 m

The University of the West Indies (UWI) Seismic Research Centre (SRC) and the National Disaster Management Agency (NaDMA) reported a period of increased seismicity at Kick ’em Jenny during 27-30 August. A seismic swarm began at around 1000 on 27 August and by 0800 on 28 August the seismic network had recorded around 800 tremors. The largest events were M 2.2-2.4; no reports were received of felt earthquakes in Grenada. Seismicity began to decline through the day. During 1200 on 28 August and 0830 on 29 August the network recorded 72 events, or an average of 3-4 per hour, reflecting decreasing unrest. The largest events were M 1.4-1.8. Unrest further declined and by 1200 on 30 August only one or two tremors per hour were detected. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the maritime exclusion zone did not change from the radius of 1.5 km.

Geologic summary: Kick ’em Jenny, an active submarine volcano 8 km off the N shore of Grenada, rises 1,300 m from the sea floor. Recent bathymetric surveys have shown evidence for a major arcuate collapse structure, which was the source of a submarine debris avalanche that traveled more than 15 km W. Bathymetry also revealed another submarine cone to the SE, Kick ’em Jack, and submarine lava domes to its S. These and subaerial tuff rings and lava flows at Ile de Caille and other nearby islands may represent a single large volcanic complex. Numerous eruptions have occurred since 1939, mostly documented by acoustic signals. Prior to the 1939 eruption, when an eruption cloud rose 275 m above the ocean and was witnessed by a large number of people in northern Grenada, there had been no written mention of the volcano. Eruptions have involved both explosive activity and the quiet extrusion of lava flows and lava domes in the summit crater; deep rumbling noises have sometimes been heard onshore. Recent eruptions have modified the morphology of the summit crater.

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 at vents with craters along the SW margin of Halema’uma’u Crater, continued at variable levels during 27 August-2 September. Minor incandescence at the N vent was intermittently visible during 27-30 August but intensified overnight during 30-31 August, indicating that lava was nearing the surface. Spattering at the N vent began at around 2000 on 31 August and by the early morning on 1 September the surface of the lava pond within the vent had risen to the point of being almost visible in a webcam view.

At around 2030 on 1 September gas-pistoning cycles began, with lava continuing to fill the N crater. Brief overflows of lava down the crater flanks were visible at 0043 and 0045 on 2 September. Several more vigorous and cyclic overflows occured at 0258, 0312, 0233, 0358, 0411, and 0425; each cycle lasted 6-17 minutes and was followed by minor drain-backs of 1-2 m. At 0521 the overflows became continuous and low dome fountains were visible. The dome fountains intensified at 0635; lava fountains soon grew to 100 m high and were inclined 45 degrees NW. By 0711 the fountains were 150 m high and arcing about 150 m across. At around 0820 the fountains turned slightly counterclockwise to the NNE. Sulfur dioxide emission rates were estimated to be at least 50,000 tonnes/day, a typical rate during periods of fountaining. Fountaining was continuous for 13.4 hours from the N vent, and during this time both the S and middle vents were also active. The N vent ceased erupting at 1949 and the S and middle vents ceased erupting at 2001, after a few minutes of lava jetting. Lava output averaged more than 200 cubic meters per second and produced over 9.6 million cubic meters of lava, the highest output so far during this eruption for one of these short fountaining episodes. Lava flows covered 40-50 percent of the caldera floor. 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.

Kirishimayama, Japan

31.934°N, 130.862°E | Summit elev. 1700 m

The Japan Meteorological Agency (JMA) reported that activity continued at Shinmoedake (Shinmoe peak, a stratovolcano of the Kirishimayama volcano group) during 26 August-2 September. Fumarolic plumes rose as high as 100 m above the fissures on the W flank. The number of volcanic earthquakes located beneath Shinmoedake, first detected in late October 2024, continued to be frequent; a short-duration volcanic tremor was detected around 0800 on 31 August. At 0453 on 28 August an ash plume rose 5.5 km above the crater rim and drifted S. Significant ashfall reported in areas downwind, including in Kirishima City (21 km SW) and Miyakonojo City (30 km SE), was enough to obscure the lines on some roads. Ashfall was also reported in Soo City (32 km SSE) and Kanoya City (60 km S). Ash plumes were continuous through the morning and early afternoon; the plumes rose 4.5 km above the crater rim and drifted S at 0523, then rose to 3.7 km at 0900 before stopping at 1450. A period of ash emissions was recorded from 1823 on 28 August to 0830 on 29 August, with ash plumes rising 700-1,300 m above the crater rim and occasionally drifting N. Continuous ash plumes rose as high as 600 m above the crater rim and drifted N during 0542-0830 on 30 August. At 1323 on 30 August an ash plume rose 300 m above the crater rim ana drifted NW. The Alert Level remained at 3 (on a 5-level scale) and the public was warned to exercise caution within 3 km from Shinmoedake Crater.

Geologic summary: Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

Lewotobi, Indonesia

8.542°S, 122.775°E | Summit elev. 1703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported continuing activity at Lewotobi Laki-laki during 27 August-2 September. Daily white gas-and-steam plumes rose as high as 1 km above the summit and drifted SW, W, N, and NE. Ash plumes were visible during 27-29 August rising 500-1,600 m above the summit and drifting in the same directions as the gas-and-steam plumes. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 6 km away from the center of Laki-laki.

Geologic 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.

Lewotolok, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Lewotolok was ongoing during 27 August-2 September. White-to-gray ash plumes rose 200-500 m above the summit of the cone and drifted W during 27 and 29-30 August. A nighttime webcam image at 2142 on 29 August showed incandescent material being ejected above the cone and onto the flanks. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit.

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.

Lopevi, Vanuatu

16.507°S, 168.346°E | Summit elev. 1413 m

The Vanuatu Meteorology and Geohazards Department (VMGD) reported that seismic data confirmed continuing unrest at Lopevi during August. Low-level thermal anomalies identified in satellite images during 3, 6-7, and 15 August. Small fumarolic steam plumes were continuously emitted from the summit crater during 6-7, 9, and 11 August based on a webcam images and observation photos. The Alert Level remained at 2 (on a scale of 0-4).

Geologic summary: The small 7-km-wide conical island of Lopevi, known locally as Vanei Vollohulu, is one of Vanuatu’s most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily along a NW-SE-trending fissure that cuts across the island, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1413-m-high volcano date back to the mid-19th century. The island was evacuated following major eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast.

Marapi, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Marapi (on Sumatra) continued during 27 August-2 September. Gray-to-white ash plumes rose as high as 800 m above the crater rim and drifted N, NE, and SE on 27, 29, and 31 August. Two eruptive events recorded on 27 and 29 August were not visually observed. 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.

Poas, Costa Rica

10.2°N, 84.233°W | Summit elev. 2697 m

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported continuing gas-and-steam emissions with occasional minor amounts of ash at Poás during 27 August-2 September. Variable incandescence at Boca A vent continued to be visible at night. At 1230 on 2 September a gray steam-and-gas plume with a moderate amount of ash rose 500 m above the crater rim and drifted W. A few hours later, at 1703, a light-gray steam-and-gas plume with minor ash content rose 300 m above the crater rim. The Volcanic Alert Level remained at 2 (the second lowest level on a four-level scale).

Geologic summary: The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world’s most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

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 27 August-2 September, sometimes with multiple daily eruptive events recorded by the seismic network. White-and-gray or gray ash plumes rose 200-900 m above the summit and drifted W, SW, and S on 27 and 31 August and during 1-2 September. The Alert Level remained at 2 (the second lowest level on a scale of 1-4). The public was warned to stay at least 3 km away from the summit in all directions, 8 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 13 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

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.

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 21-28 August. Thermal anomalies over the domes were identified in satellite images on 21, 24, and 27 August; weather clouds obscured views 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.

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 25-31 August. Webcam images showed Strombolian activity at four 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 continued to produce low- to medium-intensity explosions at a rate of 9-17 events per hour, ejecting lapilli and bombs less than 150 m above the vents. Low- to medium-intensity explosions at the vents in Area C-S occurred at a rate of 0-5 times per hour. 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 25 August-1 September. Incandescence was observed nightly in webcam images. Eruptive events during 25-31 August produced ash plumes that rose as high as 2.4 km above the crater rim and either rose straight up or drifted N. Ash-and-gas emissions were continuous from 2034 on 27 August to 0830 on 28 August, and again from 0911 on 28 August to 0500 on 29 August. Explosions at 1722 on 26 August and at 1047 on 1 September produced ash plumes that rose 1.5 km above the crater rim and 1.8 km above the crater rim and drifted N, respectively. Minor ashfall was reported in Toshima Village (3.5 km SSW). 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.

Yasur, Vanuatu

19.532°S, 169.447°E | Summit elev. 361 m

The Vanuatu Meteorology and Geohazards Department (VMGD) reported that activity at Yasur continued at a level of “major unrest,” as defined by the Alert Level 2 status (on a scale of 0-5) during August. Field photos and webcam images indicated that explosions continued, producing emissions of gas, steam, and/or ash during 1-17, 20-23, and 25-28 August. Sulfur dioxide gas emissions were identified in satellite images during 1-4, 6-14, 16-19, and 22-27 August, and low-level thermal anomalies were identified during 3-7, 10-13, 21, and 25-26 August. Seismic data confirmed continuing volcanic activity with explosions that were occasionally strong. The report warned that ejected material from explosions could fall in and around the crater. The public was reminded to not enter the restricted area within 600 m around the boundaries of the Permanent Exclusion Zone, defined by Danger Zone A on the hazard map.

Geologic summary: Yasur has exhibited essentially continuous Strombolian and Vulcanian activity at least since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island in Vanuatu, this pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide open feature associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

References:

¹ Smithsonian Institution / US Geological Survey – GVP – Weekly Volcanic Activity Report – August 27–September 2, 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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