The Weekly Volcanic Activity Report: April 16-22, 2026

New activity/unrest: Dempo, Indonesia | Pico, Portugal | Poas, Costa Rica | Rincon de la Vieja, Costa Rica.

New activity/unrest

Dempo, Indonesia

4.016°S, 103.121°E; Elev. 3,142 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that a phreatic eruption at Dempo was recorded at 1145 on 15 April which seismic data showed lasted nearly 14 minutes. A dense white plume rose around 3.5 km above the summit and drifted NE. 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.

Geological 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.

Pico, Portugal

38.47°N, 28.4°W; Elev. 2,351 m

The Centro de Informação e Vigilância Sismovulcânica dos Açores (CIVISA) reported that the low-magnitude seismic activity off the NW coast of Pico had decreased and was near baseline levels. The area of seismicity wa in a NE-SW zone along the Faial-Pico channel, W of Madalena to N of Lagido, and encompassing the Cachorro Submarine Volcanic System. On 21 April the Volcanic Alert Level was lowered to V0 (the 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.

Poas, Costa Rica

10.2°N, 84.233°W; Elev. 2,697 m

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported that an eruption signal at Poás recorded at 2244 on 10 April originated from a known fumarolic field at the W edge of the lake along the crater floor and wall area. A low-temperature thermal anomaly had been present there in 2022, but had been progressively covered by meters of tephra deposits during 2024 and 2025 eruptions. A section of that inner W wall, as high as 23 m above the floor, collapsed and sent material into the lake. The landslide led to a rapid decompression of gas beneath the surface, producing a gas-and-ash plume that caused minor ashfall and a sulfur odor in Grecia (17 km SW) and neighboring San Pedro. The collapse and eruption sequence lasted about two minutes based on seismic data, and was followed by a period of sustained seismic tremor likely associated with continuous gas emissions at the newly exposed fumarolic field. Weather clouds prevented views at the time of the event. Scientists conducted a drone overflight on 14 April and observed that the crater lake had risen by 3 m, with ash and lapilli deposits scattered across the crater floor and the W crater rim. The volume of the landslide was estimated at 70,000 cubic meters. The lake remained very hot at 71 degrees Celsius (compared to 75 degrees Celsius on 8 April) and active convection cells were particularly notable over Boca A. During 15-16 April emissions were visible rising from Boca A, Boca B, and the fumarolic field W of the lake. A 16 April news article stated that monitoring instruments did not detect major changes in seismicity or deformation before or after the 10 April event. 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.

Rincon de la Vieja, Costa Rica

10.8314°N, 85.3364°W; Elev. 1,729 m

The Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported minor eruptive events at Rincón de la Vieja during 15-22 April. Small phreatic eruptions were recorded at 2236 on 14 April, at 0054 on 15 April, and at 0414 on 16 April; weather conditions obscured views of the events. A short eruption at 1206 on 17 April ejected an ash plume that rose 500 m above the crater rim and a steam-and-gas plume that rose as high as 2 km above the crater rim. Another event was recorded at 2318 on 19 April but not visually observed due to darkness. A minor eruption at 2024 on 20 April was also not visible. The Alert Level remained at Level 2, Yellow, the second lowest level on a four-level scale.

Geological summary: Rincón de la Vieja is a volcanic complex in the Guanacaste Range of NW Costa Rica. Sometimes referred to as the Rincon de la Vieja-Santa María Volcanic Complex, it consists of a slightly arcuate 20-km-long ridge of 12 craters and pyroclastic cones constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the “Colossus of Guanacaste,” it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. The Santa María cone, the highest peak of the complex, is located on the E side of the ridge and has a lake within the 400-m-diameter crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous reported eruptions possibly dating back to the 16th century, have been from the active crater, near the center of the complex, with an acidic 300-m-diameter lake.

Ongoing activity

Ahyi, United States

20.437°N, 145.03°E; Elev. -55 m

The US Geological Survey reported that a point source plume of discolored water near Ahyi Seamount was visible in satellite images on 10 April and a diffuse plume of discolored water was visible in satellite images on 13 April. No signals were detected in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi), nor were there any other indicators suggesting significant unrest. 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.

Aira, Japan

31.5772°N, 130.6589°E; Elev. 1,117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 13-21 April. Crater incandescence was visible in nighttime webcam images. An explosion at 0449 on 13 April generated an ash plume that rose around 1.2 km above the crater rim and ejected blocks as far as 1.2 km from the vent. Sulfur dioxide emissions were high, averaging 2,800 tons per day on 16 April. Explosions at 2003 and at 2330 on 18 April, at 0112 on 19 April, and at 0503 on 20 April generated ash plumes that rose 400-2,300 m above the crater rim and drifted W and SW. The explosions ejected blocks 300-1,200 m from the vent. By 0600 on 19 April minor ashfall was reported in Kagoshima City (about 10 km W), Satsumasendai City (42 km NW), Hioki City (25 km WNW), Ichikikushikino City (40 km NW), and Aira City (17 km N). Ash plumes from eruptive events at 2018 on 18 April and at 0622 on 20 April rose 1.4 and 1.5 km above the vent and drifted W and SW, respectively. An explosion at 1545 on 21 April generated a moderately large ash plume that rose 2.7 km above the crater rim and drifted SE and ejected blocks 500-700 m from the vent. Ash plumes were continuously emitted, rising to 1.3 km above the crater rim and drifting S at 1615, and decreasing to 800 m above the crater rim before ending at 1720. An eruptive event at 2221 generated an ash plume that rose 2.4 km above the crater rim. Moderately heavy ashfall was reported in Kagoshima City during 1545-2300 on 21 April. 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.

Ambae, Vanuatu

15.389°S, 167.835°E; Elev. 1,496 m

On 22 April the Vanuatu Meteorology and Geohazards Department (VMGD) reported that the eruption at Ambae was ongoing. Seismic activity had decreased but continued to be characterized by continuous volcanic tremor and volcanic-seismic events. Plumes of gas, steam, and/or ash were identified in satellite images rising from the crater. At night summit incandescence was observed by residents of Ambae and nearby islands, and was visible in webcam views. The Alert Level remained at 3 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone B, defined as a 3-km radius around the active vents in Lake Voui, and to stay away from drainages during heavy rains.

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

Bulusan, Philippines

12.769°N, 124.056°E; Elev. 1,535 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported increased seismicity at Bulusan in a 22 April advisory, with a total of 101 volcano-tectonic (VT) earthquakes recorded by the seismic network during 0450-1330 that same day. The VT earthquakes were associated with rock fracturing with most of the events located at depths of 2.5 km or less beneath the N edifice. Weak-to-moderate gas emissions rose from the summit crater and active vents; sulfur dioxide emissions were at low levels averaging 75 tonnes per day on 9 April. The Alert Level remained at 1 (the second lowest level on a scale of 0-5). The public was reminded not to enter the 4-km-radius Permanent Danger Zone (PDZ) and to be vigilant within the 2-km Extended Danger Zone (EDZ) on the SE flank. Pilots were warned not to fly close to the summit because ash from phreatic eruptions could be hazardous to aircraft.

Geological summary: Luzon’s southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

Dukono, Indonesia

1.6992°N, 127.8783°E; Elev. 1,273 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 16-22 April. Daily white-and-gray ash plumes rose 300-2,00 m above the summit and drifted in multiple directions. Weak rumbling sounds were often heard at the observation post, 11 km N, on 16 April and occasional explosions were heard at the post on 22 April. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Geological summary: The Dukono complex in northern Halmahera is on an edifice with a broad, low profile containing multiple peaks and overlapping craters. Almost continuous explosive eruptions, sometimes accompanied by lava flows, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the Gunung Mamuya cone, 10 km NE. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also had reported eruptions.

Great Sitkin, United States

52.076°N, 176.13°W; Elev. 1,740 m

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin’s summit crater during 15-22 April. Lava-dome growth was concentrated on the SW part of the flow, though a small lobe advanced to the SE. The seismic network recorded frequent rockfalls within the crater from the growing dome. Weather clouds 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.

Home Reef, Tonga

18.992°S, 174.775°W; Elev. -10 m

The Tonga Geological Services reported that no significant activity was detected at Home Reef during 4-18 April, though weak thermal anomalies continued to be identified in satellite images. An 11 April satellite image showed plumes of discolored water around the island, indicative of underwater activity, and a diffuse gas plume from the crater drifting SE. The Aviation Color Code remained at Yellow (the second lowest level on a four-level scale, the Maritime Alert Level remained at Red (the highest 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

1.4941°N, 127.6324°E; Elev. 1,357 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ibu continued during 16-22 April, with daily eruptive events recorded by the seismic network. Gray ash plumes rose 300-800 m above the summit and drifted in multiple directions. 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.

Geological summary: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Kanlaon, Philippines

10.4096°N, 123.13°E; Elev. 2,422 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 14-22 April. The seismic network recorded 12-53 daily volcanic earthquakes, including 1-7 daily periods of tremor lasting three minutes to just over one hour. Sulfur dioxide emissions ranged from 680 to 2,313 tonnes per day. Emissions were visible daily that generally rose 350-1,100 m above the summit and drifted mainly WNW, W, and SW. There were 1-5 periods of ash emissions almost daily; none were visible on 20 April. The ash emissions each lasted for eight minutes to two hours and 25 minutes. At 0543 on 14 April and at 0548 on 22 April ash emissions visible in webcam images rose 600 m and 500 m above the summit, respectively, and drifted SW. The Alert Level remained at 2 (on a scale of 0-5); the public was warned to stay out of the 4-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

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

Kilauea, United States

19.421°N, 155.287°W; Elev. 1,222 m

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea’s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema’uma’u Crater, continued at variable levels during 15-22 April. Incandescence at the S vent was visible nightly in webcam images along with several daily periods of intense flaming caused by the ignition of volcanic gases escaping the vent. The N vent emitted gases and was faintly incandescent during 16-17 and 19-20 April. The N vent produced three lava overflows starting at 1946 on 20 April, prompting HVO to raise the Volcano Alert Level to Watch (the second highest level on a four-level scale) and the Aviation Color Code to Orange (the second highest color on a four-color scale) at 2116. The overflows ended by midnight, but strong incandescence at both vents remained visible overnight during 20-21 April along with periods of intense flaming at the S vent. An intense spatter burst at 2300 on 21 April ejected lava a short distance from the N vent.

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.

Laguna del Maule, Chile

36.058°S, 70.492°W; Elev. 2,162 m

According to a Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED) 20 April report, the Servicio Nacional de Geología y Minería (SERNAGEOMIN) noted that no changes at Laguna del Maule were detected during 1-15 April. In general, seismicity was unchanged compared to the second half of March and no surficial activity was observed. Inflation continued to be detected but the trend remained stable. The Alert Level was lowered to Green (the lowest level on a three-color scale). SENAPRED maintained “Preventative Early Warning” for San Clemente which had been in effect since 6 August 2025. The public was warned to stay 2 km away from the center of the activity due to the potential for anomalous carbon dioxide emissions. The Argentine Observatory of Volcanic Surveillance (OAVV) of the Servicio Geológico Minero Argentino (SEGEMAR) announced on 22 April that they also lowered the Alert Level to Green (the lowest level on a four-color scale).

Geological summary: The Laguna del Maule volcanic complex includes a 15 x 25 km caldera with a cluster of small stratovolcanoes, lava domes, and pyroclastic cones of Pleistocene-to-Holocene age. The caldera lies mostly on the Chilean side of the border, but partially extends into Argentina. Fourteen Pleistocene basaltic lava flows were erupted down the upper part of the Maule river valley. A cluster of Pleistocene cinder cones was constructed on the NW side of Maule lake in the northern part of the caldera. The latest activity produced an explosion crater on the E side of the lake and a series of Holocene rhyolitic lava domes and blocky lava flows that surround it.

Lascar, Chile

23.37°S, 67.73°W; Elev. 5,592 m

The Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED) and Servicio Nacional de Geología y Minería (SERNAGEOMIN) reported decreasing activity at Láscar during 1-15 April. Seismicity decreased to baseline levels, gas plume rose to low heights, and sulfur dioxide emissions fluctuated at low or baseline levels. Low-level thermal anomalies persisted. The Alert Level was lowered to Green (the lowest level on a four-color scale) and the public were warned to stay at least 5 km away from the crater. The Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED noted that that a “Preventive Early Warning” remained in effect for San Pedro de Atacama (70 km NW). The Argentine Observatory of Volcanic Surveillance (OAVV) of the Servicio Geológico Minero Argentino (SEGEMAR) announced on 22 April that they also lowered the Alert Level to Green (the lowest level on a four-color scale).

Geological summary: Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Lewotobi, Indonesia

8.542°S, 122.775°E; Elev. 1,703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported periodic ash plumes at Lewotobi Laki-laki during 15-22 April. Periodic ash plumes were visible in webcam images and detected by the seismic network. A few dense gray ash plumes on 15 and 17 April rose 300-600 m above the crater rim and drifted SW, W, N, and NE. An eruptive event was recorded on 19 April but not visually observed. Ash plumes on 21 April rose as high as 1 km above the crater rim and drifted in multiple directions. Multiple ash plumes on 22 April rose as high as 1.7 km above the crater rim and drifted SW and W. Minor incandescence at the summit was visible in a few webcam images. 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.

Lewotolok, Indonesia

8.274°S, 123.508°E; Elev. 1,431 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported ongoing eruptive activity at Lewotolok during 15-23 April. White-and-gray ash plumes rose as high as 300 m above the summit and drifted NW, W, and SW during 15-27, 19, and 21-22 April; white plumes were visible on 18 April and no emissions were observed on 20 April. A webcam image from 2007 on 15 April showed incandescent material being ejected above the summit and onto the flanks. Summit incandescence was visible in a webcam image from 0210 on 23 April. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the summit.

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.

Marapi, Indonesia

0.38°S, 100.474°E; Elev. 2,885 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Marapi (on Sumatra) continued during 16-22 April. White plumes rose as high as 200 m above the summit on most days and drifted in multiple directions. An eruptive event at 0843 on 16 April generated an ash plume that rose 1.6 km above the summit and drifted NE. 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.

Mayon, Philippines

13.257°N, 123.685°E; Elev. 2,462 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that the eruption at Mayon continued during 14-21 April, characterized by lava effusion, pyroclastic density currents (PDCs), incandescent rockfalls, ash-and-gas plumes, and occasional minor Strombolian activity. Emissions were visible daily, rising as high as 1 km above the summit and drifting mainly SW and W. Each day the seismic network recorded 267-440 rockfalls, 0-5 PDCs, and 41-123 volcanic earthquakes. Additionally, there were 9-35 daily periods of volcanic tremor, each lasting between one minute and just over one hour, and on 16 April there were 22 periods of harmonic tremor lasting 5-35 minutes. Near daily measurements of sulfur dioxide emissions averaged 1,132-2,257 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 notably change compared to the previous week; by 1800 on 20 April a total of 4,021 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.

Planchon-Peteroa, Chile

35.223°S, 70.568°W; Elev. 3,977 m

According to a Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED) report on 20 April, the Servicio Nacional de Geología y Minería (SERNAGEOMIN) noted that no surficial changes in gas emissions, thermal anomalies, or deformation had been detected at Planchón-Peteroa during 1-15 April. The lakes in the active craters were stable. Seismicity was characterized by low-energy earthquakes indicating fluid movement within the system. The Alert Level was lowered to Green (the lowest level on a three-color scale). SENAPRED stated that the communities of Molina (66 WNW), Curicó (68 km NW), Romeral (75 km NW), and Teno (68 km NW) continued to be under a “Preventive Early Warning” (since 18 July 2025) and that a security perimeter 4 km from the craters was in effect.

Geological summary: Planchón-Peteroa is an elongated complex volcano along the Chile-Argentina border with several overlapping calderas. Activity began in the Pleistocene with construction of the basaltic andesite to dacitic Volcán Azufre, followed by formation of the basaltic and basaltic andesite Volcán Planchón, 6 km N. About 11,500 years ago much of Azufre and part of Planchón collapsed, forming the massive Río Teno debris avalanche, which traveled 95 km to reach Chile’s Central Valley. Subsequently, Volcán Planchón II was formed. The youngest volcano, andesitic and basaltic andesite Volcán Peteroa, consists of scattered vents between Azufre and Planchón, and and contains a small steaming crater lake. Reported eruptions from the complex have been dominantly explosive, although lava flows were emplaced in 1837 and 1937.

Popocatepetl, Mexico

19.023°N, 98.622°W; Elev. 5,393 m

The Centro Nacional de Prevención de Desastres (CENAPRED) reported that eruptive activity was low at Popocatépetl during 15-22 April. The seismic network recorded 2-22 long-period events per day, accompanied by steam-and-gas emissions that drifted in multiple directions. In addition, the seismic network recorded a few volcano-tectonic earthquakes during the week. According to the Washington Volcanic Ash Advisory Center (VAAC) previously deposited ash was re-suspended by winds and drifted SW on 19 April. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale) and the public was warned to stay 12 km away from the crater.

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Sabancaya, Peru

15.787°S, 71.857°W; Elev. 5,960 m

The Instituto Geofísico del Perú’s (IGP) Centro Vulcanológico Nacional (CENVUL) reported continuing eruptive activity at Sabancaya during 14-22 April. The seismic network detected 3-22 daily earthquakes indicating the movement of magma and gases. As many as four daily thermal anomalies were identified in satellite images during 15-19 April; none were detected on the other days. Gas, steam, and ash plumes rose 500-1,900 m above the summit and drifted in multiple directions during 15-19 April. Gas-and-steam emissions rose as high as 100 m above the summit and drifted in multiple directions on 21 April. Weather conditions obscured views on 20 and 22 April. The Alert Level remained at Orange (the third level on a four-color scale) and the public was warned to stay outside of a 12 km radius from the summit.

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

Semeru, Indonesia

8.108°S, 112.922°E; Elev. 3,657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 15-22 April, with daily eruptive events recorded by the seismic network. Daily white-to-gray and gray ash plumes were visible rising 300-1,200 m above the summit and drifting N, NE, S, and SW. An eruptive event at 0706 on 19 April generated an ash plume that rose 1 km above the summit and a news report stated that a pyroclastic flow went 4km down the Kobokan drainage on the SE flank. Another news report noted that students from Supiturang Village continued to attend class in a temporary learning space as they waited to be relocated to a different school; their school had been damaged by an eruption in January. On 23 April a news article stated that the Semeru hiking trail within the Taman Nasional Bromo Tengger Semeru (Bromo Tengger Semeru National Park) was reopening the next day to allow a set number of climbers per day to descend the volcano on the main climbing route. The climbing route closed on 19 November 2025 due to eruptive activity. 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; Elev. 3,283 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 15-22 April. Growth continued along the N part of the main lava dome. A daily thermal anomaly was identified in satellite images. 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; Elev. 796 m

The Japan Meteorological Agency (JMA) reported that eruptive activity at Suwanosejima’s Ontake Crater continued during 10-17 April. Incandescence was observed nightly in webcam images. Eruptive events produced plumes that rose as high as 600 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; Elev. 311 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that a weak phreatic eruption at Taal occurred at 1910 on 21 April and generated an eruption plume that rose 100 m above the lake’s surface. 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.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – GVP – April 16-22, 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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