The Weekly Volcanic Activity Report: May 21-27, 2026

New activity/unrest: Dukono, Indonesia | Nevado de Longavi, Chile | Sinabung, Indonesia | Titan Ridge, Papua New Guinea.

New activity/unrest

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 30 April-6 May. Ash plumes in various combinations of white, gray, and black rose 300-1,600 m above the summit and drifted in multiple directions on most days; white plumes rose 300 m above the summit on 23 May. 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.

Nevado de Longavi, Chile

36.1959°S, 71.1641°W; Elev. 3,175 m

The Servicio Geológico Minero Argentino (SEGEMAR) reported that Observatorio Volcánico de los Andes del Sur (OVDAS) monitoring stations near Nevado de Longaví recorded a volcano-tectonic (VT) earthquake at 0149 on 20 May associated with rock fracturing inside the volcano. The earthquake was followed by a swarm of 110 events over the next three hours. VT events were recorded later that morning at 0822, at 0834, and at 0921. The Servicio Nacional de Geología y Minería (SERNAGEOMIN) and Servicio Nacional de Prevención y Respuesta ante Desastres (SENAPRED) stated that during 20-22 May more than 400 VT earthquakes had been recorded, with four having a local magnitude greater than 3; the largest VT earthquake was a local M 4.3 recorded at 0049 on 20 May. The data indicated a seismic source located 4-5 km SW of the crater at a depth of around 3 km. In addition, the seismic network detected several events attributed to fluid dynamics, including five long-period earthquakes and one tremor event, all of which were low energy. Though there is no record of observed eruptive activity at the volcano, the seismic episode was above known baseline activity for the number of events, their magnitude, and the energy released. At 1817 on 22 May SERNAGEOMIN raised the Alert Level to Yellow (the second lowest level on a four-color scale). SENAPRED declared “Preventative Early Warning” for the communities of Longaví (53 km WNW), Linares (55 km NW), and Colbún (60 km NNW), and a 3 km restricted access perimeter around the crater. The Argentine Observatory of Volcanic Surveillance (OAVV) of SEGEMAR also raised the Alert Level to Yellow (the second lowest level on a four-color scale) the next day.

Geological summary: The conical Nevado de Longaví is a late-Pleistocene to Holocene, dominantly andesitic stratovolcano constructed over a basement of Tertiary volcaniclastic and granitic rocks. Two edifice-collapse events modified the E and SW flanks of a pre-Holocene edifice, and Holocene activity has been concentrated at the summit and on the E flanks. Andesitic-to-dacitic lava domes occupy the summit region. The latest eruptions produced a lava dome in the upper part of the collapse scarp and summit region that partially collapsed to the E, forming block-and-ash flow deposits. Fumarolic activity has been reported.

Sinabung, Indonesia

3.17°N, 98.392°E; Elev. 2,460 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that increased seismicity began at Sinabung at 2353 on 21 May when the seismic network recorded continuous tremors with a maximum amplitude of 4 mm. The tremors persisted at least through 22 May and were accompanied by low-frequency earthquakes, hybrid earthquakes, and earthquakes indicating emissions all of which were rarely recorded. Daily white plumes rose as high as 500 m above the summit and drifted in various directions during 21-27 May. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the summit and 3.5 km on the SE flank.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Titan Ridge, Papua New Guinea

3.03°S, 147.78°E; Elev. -1,300 m

The Rabaul Volcano Observatory (RVO) reported that the eruption at Titan Ridge, previously identified as the Central Bismarck Sea volcano, decreased during 21-28 May. Hydroacoustic data indicated that the eruption was ongoing, though the number of events had declined. Steam plumes were visible in satellite images rising from the two vents and drifting W and NW during 21-25 May, though they were less vigorous. Pumice continued to rise to the surface, though the pumice rafts were smaller. Minor amounts of ash in the plumes indicated that pumice pieces were degassing at the surface. A M 5.7 earthquake occurred just N of the eruption site at 2008 on 22 May; it was the first recorded since 17 May and did not appear to have changed the eruption characteristics. Thermal anomalies around the base of the plumes were identified in Middle Infrared Observations of Volcanic Activity (MIROVA) hot-spot detection system during 22-24 May. The plumes had significantly decreased during 25-28 May and were characterized as a narrow, wispy fume drifting a few kilometers NW when visible among weather clouds. Some pumice was still being generated and formed rafts that spread SW, W, and NW, but they were much smaller. A small thermal anomaly was identified on 27 May. RVO warned ships to avoid the pumice rafts.

Geological summary: SOFAR signals resembling those produced at known submarine eruptions were recorded in January 1972 in the central Bismarck Sea (Johnson et al., 1981). The source of the signals was at the junction of two segments of the N margin of the South Bismarck plate. The more easterly of these segments is a transform fault, whereas the more westerly is an area of oblique active seafloor spreading. The signals were detected by a seismic station on nearby Manus Island, as well as at hydrophone stations on Wake and Midway Islands in the central Pacific. During the eruption in 2026 the “Titan Ridge” name was proposed by local residents. The general story of the Titan (pronounced Tee-Tahn) people is that their island home got devastated and reduced to the Circular Reef (~40 km SSW) due to an uncertain natural phenomenon); they drifted for awhile before they settled, and most of the Titan villages are now mainly along the south coast of Manus Island.

Ongoing activity

Aira, Japan

31.5772°N, 130.6589°E; Elev. 1,117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 18-25 May. Crater incandescence was visible in nighttime webcam images during the first half of the week. An eruptive event at 0519 on 22 May generated an ash plume that rose 1.6 km above the crater rim and drifted E. 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.

Asamayama, Japan

36.406°N, 138.523°E; Elev. 2,568 m

The Japan Meteorological Agency (JMA) reported declining unrest at Asamayama. Deformation, notably on the W flank, stagnated in May 2024. Sulfur dioxide emissions began decreasing in June 2025 and by December of that year had reached low levels. The number of shallow volcanic earthquakes had been declining since July 2025. The average number of earthquakes per day overall decreased from around 30 in March 2026 to below 30 by May. The Alert Level was lowered to 1 (on a scale of 1-5) at 1100 on 22 May and the public was warned that eruptive products could impact areas within 500 m of the crater.

Geological summary: Asamayama, Honshu’s most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asamayama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has observed activity dating back at least to the 11th century CE. Maekake has had several major Plinian eruptions, the last two of which occurred in 1108 (Asamayama’s largest Holocene eruption) and 1783 CE.

Bezymianny, Russia

55.972°N, 160.595°E; Elev. 2,882 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that lava effusion at Bezymianny continued on 21 May, accompanied by gas-and-steam emissions and small hot lava avalanches. Pyroclastic flow deposits on the E flank were visible in satellite data. At 0310 on 21 May the Aviation Color Code was lowered to Yellow (the second lowest level on a four-level scale). A daily thermal anomaly was identified in satellite images during 21-27 May. Ash plumes from an explosive eruption at 1820 on 18 May had drifted more than 1,500 km NW and SW by 21 May and around 2,850 km ESE by 23 May. Dates are reported in UTC; specific events are in local time where noted.

Geological summary: The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

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 20-27 May. Small earthquakes associated with lava dome growth and rockfalls were detected in seismic data on most days. Weather clouds often prevented webcam and satellite observations, though slightly elevated surface temperatures were visible in satellite images during 22-23 May. 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 volcanic activity was detected at Home Reef during 18 April-22 May. Thermal anomalies detected by the Middle Infrared Observations of Volcanic Activity (MIROVA) hot-spot detection system were persistently low. The Aviation Color Code was lowered to Green (the lowest level on a four-level scale), the Maritime Alert Level was lowered to Orange (the second highest level on a four-level scale) with advice to stay at least 1 nautical mile (1.8 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 21-27 May, with daily eruptive events recorded by the seismic network. Daily gray ash plumes rose 200-800 m above the summit and drifted NE, E, and SE. Incandescence at the summit was visible in some nighttime webcam images. The Alert Level remained at 2 (the second lowest level on a four-level scale) and the public was advised to stay 2 km away from the active crater and 3.5 km away from the N crater wall opening.

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

Kanlaon, Philippines

10.4096°N, 123.13°E; Elev. 2,422 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 20-27 May. The seismic network recorded 6-33 daily volcanic earthquakes, including 1-7 daily periods of volcanic tremor lasting 1-21 minutes each. Sulfur dioxide emissions ranged from 491 to 1,788 tonnes per day. Daily volcanic emissions rose 300-700 m above the summit and drifted W, WSW, and SW. During 20 and 22-25 May there were 2-7 daily periods of ash emissions lasting as short as one minute to as long as one hour and 32 minutes. Specifically, the webcam recorded ash emissions at 1601 on 22 May rising 400 m above the crater rim and drifting SW, at 0659 on 24 May rising 300 m above the crater rim and drifting SW, and at 1037 on 25 May rising 400 m above the crater rim and drifting WSW. 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 20-27 May. Nighttime incandescence was persistent at both the N and S vents, though it was stronger at the S vent during the first part of the week. During a helicopter overflight on 22 May HVO geologists observed active lava deep within both vents. The Volcano Alert Level remained at Advisory (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: 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.

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 21-27 May. White plumes rose as high as 100 m above the summit and drifted in multiple directions on most days. At 1956 on 23 May a white-and-gray ash plume rose 200 m above the summit of the main cone and drifted NW. At the same time a webcam image showed incandescent material being ejected above the summit and falling onto the upper cone’s flanks. Beginning at 1900 on 25 May the seismic network recorded a sequence of “drumbeat” signals, characterized by a series of hybrid/multi-phase earthquakes with relatively uniform waveforms and inter-event intervals. The sequence persisted for about an hour with the intervals between signals lengthening with time before ceasing. A spike in Real-time Seismic Amplitude Measurements (RSAM) data was recorded as a result of the drumbeat sequence. Rumbling was heard at the observation post (6 km SW) on 26 May. White-and-gray plumes rose 50 m above the summit and drifted E. Incandescent material descending the flanks of the cone was visible in a webcam image at 1939 that same day. 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.

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 20-27 May, 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 900 m above the summit and drifting mainly WNW, W, WSW, and SW. Each day the seismic network recorded 286-351 rockfalls, 0-8 PDCs, and 27-57 volcanic earthquakes. The earthquake counts included 4-20 daily periods of volcanic tremor, each lasting between one minute to two hours and 25 minutes. Daily measurements of sulfur dioxide emissions averaged 988-2,615 tonnes per day. The lava flows did not advance in the Basud (E) and Bonga (SE) drainages, remaining 3.8 and 3.2 km long, respectively. Lava flows in the Mi-isi drainage extended another 100 m to 1.8 km by 24 May.

The number of evacuees fluctuated; by 1800 on 26 May a total of 3,974 people (1,088 families) were staying in 12 evacuation shelters, and an additional 137 people (40 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; Elev. 2,910 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Merapi (on Java) continued during 21-27 May with occasional lava avalanches produced by the active lava dome on the upper SW flank. White plumes rose as high as 650 m above the summit on most days. There were 2-10 daily lava avalanches that traveled as far as 2 km down the Sat/Putih drainage (W flank). 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.

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 20-27 May. The seismic network recorded 10-53 long-period events per day, though 148 long-period events were detected during 26-27 May. The signals were accompanied by steam-and-gas emissions that sometimes contained ash and drifted mostly E and SE. In addition, the seismic network recorded a period of tremor that lasted just over two hours during 23-24 May and one volcano-tectonic earthquake at 0136 on 25 May. According to the Washington Volcanic Ash Advisory Center (VAAC) ash plumes visible in webcam and satellite images during 25-27 May rose to 6.1 km (20,000 ft) a.s.l. (as high as 400 m above the summit) and drifted S, SSE, and SE. 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.

Purace, Colombia

2.3095°N, 76.3948°W; Elev. 4,650 m

The Servicio Geologico Colombiano (SGC) reported ongoing low-level eruptive activity at Puracé during 19-25 May. Seismic activity associated with rock fracturing processes was mainly located beneath Piocollo and Puracé volcanoes at depths of 1-3 km; the level of seismicity was similar to the previous week. A thermal anomaly continued to be detected in satellite images within the crater of Puracé and in the fumarolic field along its outer rim. Sulfur dioxide emissions rates notably increased. Continuous tremor levels associated with fluid movement and emissions intensified, with signals located beneath both Puracé and Piocollo at depths less than 3 km. Gas-and-ash emissions rose as high as 3 km above the summit and drifted NW and W. Ashfall was reported in the rural communities of Campamento, Cristales, Cobaló, 20 de Julio, Anambío, Pisanrabo, and San Juan (Puracé municipality), and in the district of Paletará, the urban zone, and in the municipal seat of Coconuco. Ashfall reports also came in from the Piedra de León sector in the municipality of Sotará and from certain sectors of the city of Popayán. The Alert Level remained at Yellow (the second lowest level on a four-color scale).

Geological summary: Puracé is an active andesitic volcano with a 600-m-diameter summit crater at the NW end of the Los Coconucos Volcanic Chain. This volcanic complex includes nine composite and five monogenetic volcanoes, extending from the Puracé crater more than 6 km SE to the summit of Pan de Azúcar stratovolcano. The dacitic massif which the complex is built on extends about 13 km NW-SE and 10 km NE-SW. Frequent small to moderate explosive eruptions reported since 1816 CE have modified the morphology of the summit crater, with the largest eruptions in 1849, 1869, and 1885.

Reventador, Ecuador

0.077°S, 77.656°W; Elev. 3,562 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that eruptive activity at Reventador continued at a high level during 20-27 May. Seismicity included 64-84 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Ash-and-gas plumes, sometimes multiple per day, were visible in webcam and satellite images and reported by the Washington Volcanic Ash Advisory Center (VAAC) on most days. The ash plumes rose 500-1,200 m above the crater rim and drifted W and NW. Incandescent blocks were also visible during dark hours on most days rolling as far as 1 km down the flanks. Thermal anomalies were often identified in satellite images. Weather clouds sometimes obscured views. On 21 and 26 May small-to-moderate secondary lahars descended the Marker River on the S flank. Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at Orange (the second highest level on a four-color scale).

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

Sabancaya, Peru

15.787°S, 71.857°W; Elev. 5,960 m

The Instituto Geofísico del Perú’s (IGP) Centro Vulcanológico Nacional (CENVUL) reported continuing eruptive activity at Sabancaya during 18-24 May. The seismic network detected 81 seismic events related to the movement of magmatic fluids and additional earthquakes indicating rock fracturing. No explosions were recorded. Gas, steam, and ash plumes periodically rose as high as 1.7 km above the crater rim and drifted less than 10 km NE, E, and SE. Thermal anomalies on the crater floor were identified in satellite images. The Alert Level remained at Orange (the third level on a four-color scale) and the public was warned to stay outside of a 12 km radius from the summit.

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

Sangay, Ecuador

2.005°S, 78.341°W; Elev. 5,286 m

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that the eruption continued at Sangay during 20-27 May. The seismic network recorded 54 explosions during 20-21 May and 178-356 daily explosions during the rest of the week. Ash-and-gas plumes were visible in webcam views, satellite images, and reported by the Washington Volcanic Ash Advisory Center on most days rising 600-900 m above the crater rim and drifting S, SW, W, and 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; Elev. 3,657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 21-27 May, with daily eruptive events recorded by the seismic network. Daily white-to-gray or gray ash plumes rose 300-1,000 m above the summit and drifted in multiple directions. Incandescent material on the upper SE flank was visible at 0443 on 21 May in a webcam image. 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

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – GVP – May 21-27, 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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