The Weekly Volcanic Activity Report: July 2

New activity/unrest was reported for 3 volcanoes from July 2 to 8, 2025. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Kirishimayama, Japan | Lewotobi, Indonesia | Lewotolok, Indonesia.

New activity/unrest

Kirishimayama, Japan

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

The Japan Meteorological Agency (JMA) reported that eruptive activity continued at Shinmoedake (Shinmoe peak, a stratovolcano of the Kirishimayama volcano group) during 2-8 July. The number of volcanic earthquakes with epicenters directly beneath Shinmoedake had been fluctuating since late October 2024, though the rates continue to be high. Beginning at 1025 on 27 June continuous gas-and-ash plumes with variable densities rose to various heights above the vents on the crater floor, at least through 9 July. The plumes generally rose 300-2,800 m above the crater rim, and occasionally higher, and drifted in various directions, causing periodic ashfall in areas downwind. On 2 July a large amount of ash fell in Makizonocho (14 km SW), Kirishima City, obscuring the white lines on the roads. At 1349 on 3 July the plumes rose 5 km above the crater rim and drifted S; the taller plume was associated with rumbling sounds. During a field survey in Kobayashi City that same day observers heard loud rumbling, and a notable amount of ash again fell in Makizonocho. At 1640 on 4 July plumes rose 3.3 km above the crater rim. Ashfall during 3-4 July was confirmed in Kagoshima City, Kirishima City, Yusui (16 km WNW), Aira City 931 km SW), Minamisatsuma City, and Hioki City (55 km SW) in Kagoshima Prefecture. On 7 July sulfur dioxide emissions averaged 900 tons per day. 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.

Geological 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 that an explosive eruption from Lewotobi Laki-laki at 1105 on 7 July was accompanied by loud booming sounds. A dense gray-to-black ash plume rose to around 18 km above the summit and drifted NE, N. and NW. Photos of the eruption showed pyroclastic flows descending the N and NE flanks as far as 5 km. The eruption lasted about six and a half minutes based on seismic data. According to the Badan Nacional Penanggulangan Bencana (BNPB) ashfall was reported in several villages in the Wulanggitang District including Nawakote, Klatanlo, Hokeng Jaya, Boru, and Pululera. A smaller explosion at 1519 generated a dense gray ash plume that rose around 1 km above the summit and drifted W. Another significant event at 1932 produced a dense gray-to-black ash plume that rose about 13 km above the summit and drifted W and NW. Incandescent material descending multiple flanks was visible in a webcam image starting at 1944.

News outlets reported that some flights from the El Tari Kupang Airport to Frans Seda Maumere Airport, along with a few dozen international flights, were cancelled. The Komodo International Airport, around 300 km W, was closed during 7-8 July. The Alert Level remained at 4 (on a scale of 1-4) and on 25 June the exclusion zone was reduced to 6 km from the center of Laki-laki and 7 km in a semicircle clockwise from the SW to the NE.

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

Lewotolok, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Lewotolok intensified during 27 June-2 July, with activity that included taller white, gray, and black ash plumes that rose 1.2 km above the summit. Incandescent material was ejected in all directions, as far as 1.5 km N and ENE, and caused vegetation fires on the N and NE flanks. Rumbling and booming sounds were reported. At 2000 on 2 July the Alert Level as raised to 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit. Daily gray, white-to-gray, or gray-to-black ash plumes rose 400-700 m above the summit of the cone and drifted NW, W, and SW during 2-8 July. Clear nighttime webcam images showed incandescent material both at the summit cone and being ejected above the cone. Lava flows on the flanks of the main volcano edifice were also incandescent.

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.

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 30 June-7 July. Nightly crater incandescence was visible in webcam images. One small eruptive event was recorded on 30 June. On 2 July sulfur dioxide emissions were slightly high, averaging 1,500 tons per day. Eruptive events during 6-7 July produced ash plumes that rose as high as 3 km above the crater rim. Plumes were continuously emitted during 1346-2310 on 6 July and during 0224-0840 on 7 July. 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.

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.

Asosan, Japan

32.8849°N, 131.085°E | Summit elev. 1592 m

The Japan Meteorological Agency (JMA) reported that the amplitude of volcanic tremors at Asosan began to increase at around 1150 on 4 July, signaling an increasing unrest. Sulfur dioxide gas emissions were low, averaging 300-600 tons per day. White plumes rose 300 m above the crater rim. At 1300 the Alert Level was raised to 2 (on a scale of 1-5) and the public was warned to stay at least 1 km away from Nakadake Crater.

Geological summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan’s most active volcanoes. It was the location of Japan’s first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu’s most popular tourist destinations.

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 2-8 July. Daily white-and-gray or gray-to-black gas-and-ash plumes rose 600-1,600 m above the summit and drifted NW and E. Faint booming and rumbling was heard by residents and at the observation post, 10-11 km N, during 4-5 July. Ashfall was reported in areas downwind including at the Mamuya Village Observation post and in Tobelo City (15 km ENE); more ash fell in areas of Tobelo City during 6-7 July. 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 | 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 2-8 July. Lava-flow advancement was concentrated at the SW and SE margins based on a 3 July radar image. Small daily earthquakes were detected by the seismic network, including signals probably caused by small rockfalls from the steep flanks. Slightly elevated surface temperatures consistent with lava effusion were observed in clear satellite views during 1-2 and 4-5 July. Diffuse steaming from the known active portions of the lava flow was observed in satellite images during 7-8 July. 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.

Home Reef, Tonga

18.992°S, 174.775°W | Summit elev. -10 m

The Tonga Geological Services reported that activity at Home Reef continued during 21 June-5 July. Discolored water around the island was visible in clear satellite images on 26 June and 1 July. The crater was about 210 m N-S and 120 m E-W. Fresh dark deposits surrounded the vent in the first image and lighter deposits around the same area were visible in the second image. The activity could not be accurately characterized due to the images being low resolution. No thermal anomalies nor ash emissions were detected in satellite data. The Aviation Color Code remained at Yellow (the second lowest level on a four-level scale, the Maritime Alert Level remained at Orange (the third level on a four-level scale) with advice to stay at least 2 nautical miles (3.7 km) from the island, and the Alert Level for residents of Vava’u and Ha’apai remained at Green (the first level on a four-level scale).

Geological summary: Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, large amounts of floating pumice, and an ephemeral 500 x 1,500 m island, with cliffs 30-50 m high that enclosed a water-filled crater. In 2006 an island-forming eruption produced widespread dacitic pumice rafts that drifted as far as Australia. Another island was built during a September-October 2022 eruption.

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 2-8 July. Daily dense gray or white-to-gray ash plumes rose 300-700 m above the summit and drifted in multiple directions. Nighttime crater incandescence was visible in some webcam images. The Alert Level remained at 3 (the second highest level on a four-level scale) and the public was advised to stay 4 km away from the active crater and 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.

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 and intermittent spatter at two vents along the SW margin of Halema’uma’u Crater, continued at variable levels during 2-8 July. Nighttime incandescence at the N vent was visible every night, with intermittent lava spattering and jetting at the same vent visible during 3-7 July. Rockfalls from spatter deposits on the crater wall exposed areas of incandescence. Two short overflows of lava at the N vent occurred at around 1830 on 7 July. Cycles of minor lava spattering, lava jetting, and gas flames were visible during 7-8 July. 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: 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.

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 2-8 July. Daily white plumes rose as high as 150 m above the summit and drifted NE, E, and SE. An eruptive event was recorded at 1359 om 6 July though 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.

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

Merapi, Indonesia

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

The Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG) reported that the eruption at Merapi (on Java) continued during 27 June-3 July. Seismic levels were similar to the previous week. The SW lava dome produced eight lava avalanches that traveled as far as 2 km SW down the Bebeng drainage, five that traveled as far as 1.5 km SW down the Krasak drainage, and 56 that traveled as far as 2 km W down the Sat/Putih drainage. Small morphological changes to the SW lava dome resulted from continuing effusion and minor collapses. 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.

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 2-8 July. Uplift ceased to be detected in the past few weeks and no significant deformation was detected during the current week. Strong incandescence at Boca A vent was observed and the level of the hyperacid lake over Boca C had stabilized. Minor ashfall was reported in areas downwind on 3 July. The Alert Level remained at 2 (the second lowest level on a four-level scale) and the Aviation Color Code remained at Yellow (the second lowest color on a four-color scale).

Geological 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.

Rainier, United States

46.853°N, 121.76°W | Summit elev. 4392 m

The Cascades Volcano Observatory (CVO) reported that a small seismic swarm at Rainier began at 0129 on 8 July. By the 0926 the seismic network recorded hundreds of earthquakes at rates up to several per minute. The earthquakes were located at depths of 2-6 km below the summit; the largest earthquake, a M 1.7, was detected at 0452. No earthquakes were felt, no deformation was detected, and no anomalous signals were detected at infrasound monitoring stations. CVO noted that seismicity is typically about 9 earthquakes per month, plus swarms once or twice per year, but with much smaller numbers of events per swarm. The last large swarm at Rainier had over 1,000 earthquakes over three days in 2009 (120 located), had an earthquake with a maximum magnitude of 2.3. Past swarms have been attributed to circulation of fluids interacting with preexisting faults. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest color on a four-color scale).

Geological summary: Mount Rainier is a heavily glaciated andesitic volcano in the Puget Sound region. Large Holocene mudflows from collapse have reached as far as the Puget Sound lowlands. The present summit was constructed within a large crater breached to the NE, formed by collapse during a major explosive eruption about 5,600 years ago that deposited the widespread Osceola Mudflow. Rainier has produced eruptions throughout the Holocene, including about a dozen during the past 2,600 years; the largest of these occurred about 2,200 years ago. The present summit cone is capped by two overlapping craters. Extensive hydrothermal alteration of the upper portion of the volcano has contributed to its structural weakness; an active thermal system has caused periodic melting on flank glaciers and produced an elaborate system of steam caves in the summit icecap. Reported uncertain 19th-century eruptions, including a possible but not confirmed phreatic eruption in 1894, have not left identifiable deposits.

Raung, Indonesia

8.119°S, 114.056°E | Summit elev. 3260 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Raung continued during 2-8 July. Gray or white-and-gray ash plumes rose 400-1,000 m above the crater rim and drifted S and SW during 2, 4-5, and 7 July. Incandescence at the summit was sometimes visible in webcam images. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater.

Geological summary: Raung, one of Java’s most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The unvegetated summit is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

Reventador, Ecuador

0.077°S, 77.656°W, Summit elev. 3562 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that eruptive activity continued at Reventador during 1-8 July. Seismicity included 70-112 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Multiple daily ash-and-gas plumes rose 400-700 m above the crater rim and drifted mainly NW, W, and SW. Webcams recorded multiple nightly instances of incandescent material descending the flanks as far as 1.1 km below the crater rim. 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.

Sangay, Ecuador

2.005°S, 78.341°W | Summit elev. 5286 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that the eruption continued at Sangay during 1-8 July. The seismic network recorded 48-94 explosions each day. Ash-and-gas plumes were observed in webcam and/or satellite images rising as high as 1.2 km above the summit and drifting mainly, NW, W, and SW, though weather clouds sometimes obscured views; plumes were not observed during 3-4 July. The surveillance camera network recorded several instances of incandescent material descending the flanks as far as 1 km during 5-7 July. 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 | Summit elev. 3657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 2-8 July, often with multiple daily eruptive events recorded by the seismic network. Emissions were not visually observed most of the week. Dense white-and-gray ash plumes rose 400-1,000 m above the summit and drifted NE, N, W, and SW during 2 and 6-7 July. 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.

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.

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 30 June-7 July. Incandescence was observed nightly in webcam images. Six explosions were recorded during the week, at 0806 on 30 July, at 0752 and 1608 on 1 July, at 0206 on 2 July, and at 1327 and 2038 on 6 July. The explosions produced ash plumes that rose as high as 2 km above the crater rim and drifted W, SE, and E; some of the plumes were not visible. Ashfall was reported by the Suwanosejima Branch of the Toshima Village Office (3.5 km SSW) on 30 June and 6 July. Eruptive events during 30 June and 6-7 July generated ash plumes that rose as high as 2 km above the crater rim and drifted W, SE, and E. 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.

Geological 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.

Taal, Philippines

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

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported increased seismicity at Taal. No volcanic earthquakes were recorded by the seismic network during 1-4 July, but two low-frequency volcanic earthquakes were detected on 5 July. A distinct increase in volcanic tremor began at 0337 on 6 July and continued at elevated levels through the day. Low levels of sulfur dioxide had been emitted in June with daily averages of 478 tonnes per day (t/d) on 2 July and 377 t/d on 4 July. Daily gas-and-steam emissions rose as high as 1.8 km above the crater rim and drifted mainly NE, though emissions became noticeably absent around the same time as increased seismicity. PHIVOLCS warned that the increased seismicity and lack of emissions may indicated a blockage and increased pressurization, potentially leading to a phreatic event. The Alert Level remained at 1 (on a scale of 0-5); PHIVOLCS reminded the public that the entire Taal Volcano Island (TVI) was a Permanent Danger Zone (PDZ) and recommended that the Main Crater and areas along the Daang Kastila fissure should remain prohibited. Pilots were warned to avoid flying over TVI.

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

Yellowstone, United States

44.43°N, 110.67°W | Summit elev. 2805 m

The Yellowstone Volcano Observatory (YVO) reported that a small hydrothermal eruption occurred at Black Diamond Pool, in Yellowstone’s Biscuit Basin thermal area, at 2018 on 3 July based on webcam images. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest color on a four-color scale).

Geological summary: The Yellowstone Plateau volcanic field developed through three volcanic cycles spanning two million years that included some of the world’s largest known eruptions. Eruption of the over 2,450 km3 Huckleberry Ridge Tuff about 2.1 million years ago created the more than 75-km-long Island Park caldera. The second cycle concluded with the eruption of the Mesa Falls Tuff around 1.3 million years ago, forming the 16-km-wide Henrys Fork caldera at the western end of the first caldera. Activity subsequently shifted to the present Yellowstone Plateau and culminated 640,000 years ago with the eruption of the over 1,000 km3 Lava Creek Tuff and the formation of the present 45 x 85 km caldera. Resurgent doming subsequently occurred at both the NE and SW sides of the caldera and voluminous (1000 km3) intracaldera rhyolitic lava flows were erupted between 150,000 and 70,000 years ago. No magmatic eruptions have occurred since the late Pleistocene, but large hydrothermal events took place near Yellowstone Lake during the Holocene. Yellowstone is presently the site of one of the world’s largest hydrothermal systems, including Earth’s largest concentration of geysers.

References:

1 Smithsonian Institution / US Geological Survey – GVP – Weekly Volcanic Activity Report –July 2–8, 2025 – Managing Editor: Sally Sennert

The Weekly Volcanic Activity Report: July 2–8, 2025