The Weekly Volcanic Activity Report: April 9-15, 2026

New activity/unrest: Pico, Portugal | Piton de la Fournaise, France | Poas, Costa Rica.

New activity/unrest

Pico, Portugal

38.47°N, 28.4°W; summit elev. 2351 m

The Centro de Informação e Vigilância Sismovulcânica dos Açores (CIVISA) reported that on 1 April low-magnitude seismic activity was off the NW coast of Pico, in a NE-SW zone along the Faial-Pico channel, W of Madalena to N of Lagido, and encompassing the Cachorro Submarine Volcanic System. The earthquake depths ranged from 20 km deep to near surface. The seismicity was slightly above normal levels; on 9 April the Volcanic Alert Level was raised to V1 (the second lowest level on an 8-level scale) for the Faial-Pico channel.

Geological summary: The conical Pico stratovolcano occupies the western end of Pico Island and is the highest volcano in the Azores. The dominantly basaltic edifice lies west of on an older linear volcano with numerous flank cones that forms most of the 46-km-long island. It was constructed over the Montanha volcanic complex on the eastern side of the island and is capped by a 500-m-wide summit crater that is overtopped by a small steep-sided cone. An eruption beginning in 1562 from the Sao Roque Piedade/Planalto da Achada fissure zone produced lava flows that reached the northern coast. Two fissures erupted on the NNW flank and SE flank of Pico volcano in 1718, with lavas reaching the north and south coasts. Lava flows from a fissure on the SE flank in 1720 reached the ocean.

Piton de la Fournaise, France

21.244°S, 55.708°E; summit elev. 2632 m

The Observatoire Volcanologique du Piton de la Fournaise (OVPF) reported that eruptive activity at Piton de la Fournaise resumed on 8 April. Low-amplitude continuous volcanic tremor that began on 3 April, beneath the ESE flank in the same location as during earlier eruptive phases, sharply decreased the evening of 7 April. Following the drop, gas pistoning (intermittent tremor phases) emerged and persisted through the next morning. At around 0530 on 8 April tremor amplitude significantly increased, and by 1315 had reached a higher level than on 2 April, prior to the cessation of the activity; concurrent gas emissions increased at the main cone, likely signaling lava at the surface. During an overflight later that afternoon a small lava lake in the cone was observed. Intermittent activity at the cone was characterized as periods of intense spattering and degassing followed by periods of calm with each period lasting around 10 minutes.

At 0915 on 9 April a new vent was visible 180 m upflank of the cone. The new vent produced lava fountains while intermittent activity at the main cone ceased, though a lava lake persisted. A lava flow from the new vent descended the flank to around 700 m elevation with an estimated peak flow rate of 35 cubic meters per second. The flow rate average dropped to 10 cubic meters per second by 1800. By the morning of 20 April a cone had grown around the new vent that was breached, allowing for lava to move downslope and form a new flow field at the top of the Grandes Pentes. During 10-12 April lava fountains and spatter continued to build up the new cone while activity at the main cone was low, but produced significant gas emissions. Lava flow rates were as high as 15 cubic meters per second. The flow front did not significantly advance during 11-12 April and was between 1,345 and 1,370 m elevation. At 2310 on 12 April the tremor amplitude dropped sharply, indicating the end of the eruption. The Alert Level remained at 2.2 (on a 0-4 scale).

Geological summary: Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three scarps formed at about 250,000, 65,000, and less than 5,000 years ago by progressive eastward slumping, leaving large embayments open to the E and SE. Numerous pyroclastic cones are present on the floor of the scarps and their outer flanks. Most recorded eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest scarp, which is about 9 km wide and about 13 km from the western wall to the ocean on the E. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Eruptions in 1708, 1774, 1776, 1800, 1977, and 1986 originated from fissures outside the scarps.

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 an eruption at Poás on 10 April. An eruption signal was recorded on both seismic and acoustic instruments at 2243 that lasted for several minutes. Weather clouds and darkness prevented visual observations. Early on 11 April residents of Grecia reported minor amounts of ashfall on surfaces such as parked cars. The Volcanic Alert Level remained at 2 (the second lowest level on a four-level 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.

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 6-12 April. An eruptive event on 9 April generated an ash plume that rose 1.5 km above the crater rim. Eruptive events at 0026, 1553, 1625, and 1648 on 10 April produced ash plumes that rose 1-1.5 km above the crater run and drifted NE and E. An ash plume from an explosion at 1204 on 11 April rose 3.4 km above the crater rim and drifted SE. Within an hour a moderate amount of ash fell in Kagoshima City (about 10 km W) and Tarumizu City (10 km SSE). An explosion at 0828 on 12 April generated an ash plume that rose 2.9 km above the crater rim and drifted S and NE. By 1400 moderate-to-heavy ashfall had fallen in Kagoshima City. 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.

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 9-14 April. Daily white-and-gray ash plumes rose 400-1,200 m above the summit and drifted multiple directions. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

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 8-14 April, with growth concentrated on the SW part of the flow. The seismic network recorded occasional small volcanic earthquakes and seismic signals from small rockfalls within the crater. Elevated surface temperatures were observed in satellite views during 11-14 April. Weather clouds often prevented webcam and satellite observations. 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.

Kanlaon, Philippines

10.4096°N, 123.13°E; summit elev. 2422 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 8-14 April. The seismic network recorded 7-12 daily volcanic earthquakes during 8-11 April, including 1-5 daily periods of tremor lasting four minutes to two hours and 26 minutes. On 12 April there were 150 volcanic earthquakes and four periods of tremor (40 minutes to one hour and 40 minutes long), followed on 13 April by 102 volcanic earthquakes and two periods of tremor (33 and 56 minutes long). Sulfur dioxide emissions ranged from 610 to 2,470 tonnes per day. Emissions were visible daily that generally rose 400-1,200 m above the summit and drifted mainly SE, S, and SW.

There were 1-5 daily periods of ash emissions recorded during 9-13 April. Five ash emissions occurred on 9 April with each lasting 5-47 minutes; one ash emission on 10 April lasted for two hours and 39 minutes; one ash emission on 11 April lasted for 54 minutes; three ash emissions on 12 April lasted for 47 minutes to just over two hours; and one ash emission on 13 April lasted for one hour and 13 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; summit elev. 1222 m

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea’s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema’uma’u Crater, continued at variable levels during 9-14 April. Activity at the S vent during 3-9 April including limited spattering, low dome fountains, and around 75 lava overflows. Beginning at 0225 on 9 April lava overflowed the N vent, followed by three more overflows. The last one began at 1008 and by 1110 had transitioned into a lava fountain. The fountain grew slowly and was about 100 m tall by 1200 and 190 m tall around 30 minutes later. An eruption plume rose 4.5 km (15,000 ft) a.s.l. and drifted N. At 1236 the Volcano Alert Level was raised to Warning (the highest level on a four-level scale) and the Aviation Color Code was raised to Red (the highest color on a four-color scale). By 1245 the fountain had reached a maximum height of 240 m. Tephra up to 25 cm in diameter fell within Hawai’i Volcanoes National Park, near Kilauea Military Camp, and into the adjacent Volcano Golf Course subdivision; ash and Pele’s hair was reported as far away as Kaumana (33 km NNE), just W of Hilo. Fountain height gradually dropped to 150 by late afternoon, the eruption plume was rising to 3 km (10,000 ft) a.s.l., and significantly less tephra fall was reported in areas to the NNE. Fountaining ended abruptly at 1941 after eight hours and 31 minutes of continuous activity at the N vent. The average effusion rate was 200 cubic meters per second; the highest peak was just over 390 cubic meters per second, occurring at around 1230. An estimated 7.5 million cubic meters of lava erupted and covered about 50 percent of the Halema’uma’u Crater floor. The S vent produced periodic gas jetting and flames. At 2002 the Volcano Alert Level was lowered to Advisory and the Aviation Color Code was lowered to Yellow. Both vents produced variable amounts of incandescence and gas emissions during 10-14 April.

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.

Krasheninnikov, Russia

54.596°N, 160.27°E; summit elev. 1816 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 8-14 April. A near-daily thermal anomaly was identified in satellite images. Satellite images showed small thermal anomalies along the active lava flow on the ENE flank on 11 April. 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).

Lewotobi, Indonesia

8.542°S, 122.775°E; summit elev. 1703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported periodic ash plumes at Lewotobi Laki-laki during 9-14 April. Daily white plumes rose as high as 500 m above the summit and drifted in multiple directions. Gray ash plumes recorded at 0724 and 2216 on 10 April, at 1958 on 12 April, and at 0824 on 13 April rose 100-500 m above the summit and drifted N, NE, S, and SW; an even was recorded at 1115 on 11 April but weather conditions prevented visual confirmation. Multiple ash plumes were visible on 14 April (at 0245, 0522, 0821, 1448, 1756, 1819, and 2107) rose 400-800 m above the summit and drifted W and SW. Minor incandescence at the summit was visible in a webcam image corresponding to the ash plume at 0245. The Alert Level remained at 2 (the second lowest level on a scale of 1-4) and the exclusion zone was a radius of 4 km from the center of Laki-laki.

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

Mayon, Philippines

13.257°N, 123.685°E; summit elev. 2462 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that the eruption at Mayon continued during 8-14 April, characterized by lava effusion, pyroclastic density currents (PDCs), incandescent rockfalls, ash plumes, and occasional minor Strombolian activity. Emissions were visible daily, rising 200-1,000 m above the summit and drifting in different directions. Each day the seismic network recorded 169-287 rockfalls, 0-3 PDCs, and 34-254 volcanic earthquakes. There were 5-36 periods of volcanic tremor, each lasting between one and 36 minutes. Daily measurements of sulfur dioxide emissions averaged 1,536-2,428 tonnes per day. The lava flows did not advance in the Mi-isi (S), Basud (E), and Bonga (SE) drainages, remaining 1.3, 3.8, and 3.2 km long, respectively. Minor Strombolian activity and short periods of lava fountaining were recorded daily.

The number of evacuees did not change compared to the previous week; by 1800 on 14 April a total of 4,020 people (1,105 families) were staying in 12 evacuation shelters, and an additional 85 people (26 families) were staying with friends or relatives, according to the Disaster Response Operations Monitoring and Information Center (DROMIC). The Alert Level remained at 3 (on a 0-5 scale) and residents were 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; summit elev. 2910 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Merapi (on Java) continued during 9-14 April with occasional lava avalanches produced by the active lava dome on the upper SW flank. White plumes rose as high as 525 m above the summit on most days and drifted in different directions. On 9 April two lava avalanches descended the Sat/Putih drainage (W flank) as far as 1.5 km and two pyroclastic flows were detected by the seismic network. There were 15 lava avalanches that descended the Krasak drainage (W flank) as far as 1.5 km. On 11 April two pyroclastic flows traveled 1.5 km down the Boyong (S) drainage and 14 lava avalanches traveled as far as 2 km down the Sat/Putih drainage. The next day, on 12 April, one pyroclastic flow traveled 2 km down the Sat/Putih drainage and 26 lava avalanches descended the same drainage as far as 2 km. On 13 April one pyroclastic flow traveled 2 km down the Boyong drainage and four lava avalanches descended the Sat/Putih drainage as far as 1.7 km. Nine lava avalanches traveled as far as 1.7 km down the Krasak drainage on 14 April. 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.

Reventador, Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that eruptive activity at Reventador continued at a high level during 8-14 April. Seismicity included 58-90 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Ash-and-gas plumes were not visible in webcam images due to weather conditions but were identified in satellite images on most or all days, rising 700-1,500 m above the crater rim and drifting mainly NW, W, and WSW, but sometimes in other directions. Thermal anomalies were identified in satellite images on a few of the days. 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 8-14 April. Seismic data was not available due to transmission problems. Daily ash-and-gas plumes visible in webcam views, satellite images, and reported by the Washington Volcanic Ash Advisory Center rose 500-2,400 m above the crater rim and drifted in multiple directions. Almost nightly there were several observations of incandescent material descending the flanks as far as 1.3 km, particularly to the NW; weather conditions sometimes prevented views. 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; summit elev. 3657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 9-14 April, with daily eruptive events recorded by the seismic network. Daily white-to-gray and gray ash plumes were visible generally rising 300-2,500 m above the summit and drifting in multiple directions. According to news reports and PVMBG, pyroclastic flows periodically descended the Kobokan drainage on the SE flank. Pyroclastic flows descended the SE flank 4.5 km at 1730 on 7 April, 2.5 km at 1737 on 9 April, 2.5 km on 11 April, and 3 km at 0522 on 14 April. Incandescent material descending the SE flank was visible in a webcam image at 2314 on 13 April. The Alert Level remained at 3 (the second lowest level on a scale of 1-4) and the public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit on the SE flank along the Kobokan drainage, and 500 m from the banks of the Kobokan drainage as far as 17 km SE of the summit.

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; summit elev. 3283 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported continuing eruptive activity at the lava domes along the N crater floor of Young Sheveluch (on the SW flank of Old Sheveluch) during 8-14 April. Growth continued along the N part of the main lava dome. An explosive event on 8 April produced an ash plume that drifted 1,600 km NE during 8-9 April. Explosions on 12 April generated ash plumes that rose up to 8.3 km (27,200 ft) a.s.l. and drifted 135 km NW. 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.

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 3-10 April. Incandescence was observed nightly in webcam images. Eruptive events produced plumes that rose as high as 700 m above the crater rim. 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 eruptive activity at Taal during 8-14 April. The seismic network recorded 1-7 daily volcanic earthquakes; additionally, there was a two-minute period of tremor on 10 April and another tremor period lasting one hour and 32 minutes on 11 April. Daily gas-and-steam emissions were diffuse, rising as high as 800 m above the crater rim and generally drifting NW, W, and SW. A minor phreatomagmatic event occurred during 1020-1022 on 9 April, ejected dark material above the lake’s surface, and produced a plume that rose 300 m. Sulfur dioxide emissions averaged 732 tonnes per day that same day. A one-minute phreatomagmatic event on 10 April ejected dark material above the lake’s surface, and produced a plume that rose 300 m. 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.

Ahyi, United States

20.437°N, 145.03°E; summit elev. -55 m

The US Geological Survey reported that a 300-400 m long submarine plume of discolored water over Ahyi Seamount was visible in an 8 April satellite image. The last time a similar plume was visible in satellite imagery was on January 9, though persistent cloud cover and limited availability of high-quality satellite images made it difficult to monitor such occurrences consistently. No signals were detected in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi). Both the Aviation Color Code and the Volcano Alert Level remained at Unassigned.

Geological summary: Ahyi seamount is a large conical submarine volcano ~18 km SE of the island of Farallon de Pajaros in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

Atka Volcanic Complex, United States

52.331°N, 174.139°W; summit elev. 1518 m

The Alaska Volcano Observatory (AVO) reported that seismic activity, sulfur dioxide emissions, and thermal anomalies at the Atka volcanic complex had declined to background levels over the past few weeks. At 1547 on 13 April the Volcano Alert Level was lowered to Normal (the lowest level on a four-level scale) and the Aviation Color Code was lowered to Green (the lowest color on a four-color scale).

Geological summary: The Atka Volcanic Complex consists of a central shield and Pleistocene caldera and four notable volcanic cones. A major explosive dacitic eruption accompanied formation of the caldera about 500,000 to 300,000 years ago; approximately half of the caldera rime remains, open towards the NW. The Sarichef cone, ~5 km ESE of the caldera rim, retains a symmetrical profile, unlike most other heavily eroded features outside the caldera to the S and W. The Kliuchef stratovolcano grew within the caldera and exhibits five eruptive vents striking NE, including two at the summit, that have been active in the Holocene. A 700-m-diameter crater 1 km NE of the summit may have been the source vent for a large 1812 CE eruption. Hot springs and fumaroles are located on the flanks of Kliuchef and in a glacial valley to the SW. The most frequently active volcano of the complex is Korovin, at the NE tip of Atka Island about 5 km N of Kliuchef. An 800-m-diameter crater on the SE side of the summit contains a deep circular pit that sometimes contains a crater lake thought to be the source of phreatic ash explosions. The smaller Konia cone, slightly offset to the E, lies between Kliuchef and Korovin. Most of the lava flows in the complex are basaltic, though some dacitic flows are also present.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – GVP – April 9-15, 2026 – 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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