The Weekly Volcanic Activity Report: March 26–April 1, 2025

New activity/unrest

Kirishimayama, Japan

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

The Japan Meteorological Agency (JMA) reported increasing unrest at Shinmoedake (Shinmoe peak, a stratovolcano of the Kirishimayama volcano group). The number of earthquakes with epicenters beneath Shinmoedake began increasing on 28 March. At around 0250 on 30 March a tiltmeter recorded 0.1 microradians of inflation. A volcanic tremor signal was detected at 0256 and lasted 10 minutes. At 0353 the Alert Level was raised to 3 (on a 5-level scale) and the public was warned to exercise caution within 4 km from Shinmoedake Crater. The number of earthquakes subsequently decreased after the inflation was detected. A field team that was deployed to the volcano observed nothing indicating increased activity. On 2 April the warning zone was reduced to 3 km.

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

Lewotobi, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Lewotobi Laki-laki significantly decreased after the more intense eruptive phase during 20-21 March, though ash plumes continued to be periodically observed. Minor incandescent at the summit was occasionally visible during 22-27 March, though absent during 28-30 March. Seismicity decreased overall; the number of earthquakes indicating emissions notably deceased, both low-frequency and volcanic earthquakes decreased, harmonic tremor fluctuated though was stable, and shallow volcanic earthquakes were not detected. The report warned that deposits of material especially on the WNW and NNE flanks increased the potential for lahars. During 25-26 March white plumes rose 100-500 m above the summit and drifted N and NE. On 26 March the exclusion zone was decreased to a radius of 6 km from the center of Laki-laki and 7 km in a semicircle clockwise from the SW to the NE. On 27 March white-and-gray plumes rose 100-300 m above the summit and drifted N and NE. During 28-30 March and 1 April white plumes rose 100-500 m above the summit and drifted in multiple directions. At 1200 on 30 March the Alert Level was lowered to 3 (on a scale of 1-4) and the public was warned to stay 6 km away from the center of Laki-laki. A white and gray plume rose 500 m above the summit on 31 March and drifted N and NE.

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

Lewotolok, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Lewotolok was ongoing during 26 March-1 April. White steam-and-gas plumes rose 100 m above the summit and drifted E on 26 March. Weather conditions obscured views during 27-30 March, though a nighttime webcam image on 29 March showed incandescent material being ejected above the summit. On 31 March white-and-gray ash plumes rose 100 m and drifted E and SE; a nighttime webcam image again showed incandescent material being ejected above the summit. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the vent and 2.5 km away on the S, SE, and W flanks.

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.

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 increasing activity at Poás in late March with continuing activity at least through 1 April. Significant inflation, phreatomagmatic activity, and volcanic emissions were ongoing. During 23-26 March, small-to-moderate phreatomagmatic explosions at the Boca A and Boca C vents were almost continuous, and they intensified on 24 March. The explosions generated gas-and-steam plumes that rose as high as 150 m and ejected jets of sediments and tephra; material up to 10 cm in diameter was occasionally deposited on the W crater rim. Volcanic gas emissions were very high and indicated that the water content was decreasing while emissions of more toxic gases was increasing. Sulfur dioxide emissions detected in satellite data were as high as 600 tons per day (t/d) on 25 March. Sistema Nacional de Áreas de Conservación (SINAC) closed the Parque Nacional volcán Poás on 25 March. During 25-26 March gas emissions were nearly constant and volcanic plumes drifted E.

On 26 March activity again intensified; during clear conditions ash and bombs were observed being ejected 200 m from the vents and the gas-and-steam plumes contained an increase in ash content. During 27-28 March frequent-to-continuous explosions at Boca C produced gas-and-ash plumes that rose 300-400 m and drifted SW. An explosion at 1558 on 28 March generated a gas-and-ash plume that rose 500 m and drifted W. Activity decreased during the morning of 29 March; small but frequent eruptive events ejected material as high as 50 m and volcanic plumes containing low amounts of ash drifted W. Activity increased in the evening, and during 2030-2315 incandescent bombs were ejected from the vents. A volcanic plume rose 500 m and drifted SW at 2210, and an explosion at 2051 generated a volcanic plume that rose 1 km and drifted W. Ash deposits more than 5 mm deep were observed at the visitor overlook. Significant sulfur dioxide emissions were detected in satellite data. During 30 March-1 April eruptive activity was almost continuous, sulfur dioxide emissions remained high, and ash plumes mainly drifted SW. At 0052 on 31 March a high-energy eruptive event ejected incandescent blocks and material more than 600 m high and generated a gas-and-ash plume that drifted SW and W. Volcanic plumes rose 200 m and drifted NW almost an hour later. Comisión Nacional de Emergencias (CNE) announced an Alert Level Orange for the national park and district of Toro Amarillo in the Canton of Sarchí (including the Desagüe and Agrio river basins) due to increased activity in the crater, ashfall and sulfur odors impacting areas downwind, and a higher potential of lahars in drainages. On 1 April incandescent blocks continued to be ejected from the vents, sometimes as high as 400 m, and ash plumes drifted SW. The Alert Level remained at 3 (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest color on a four-color scale).

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

Reykjanes, Iceland

63.817°N, 22.717°W | Summit elev. 140 m

The Icelandic Meteorological Office (IMO) reported that an earthquake swarm at the Sundhnúkur crater row began at 0630 on 1 April, located between Stóra-Skógfell and Sýlingarfell within the Reykjanes volcanic system. Monitoring data showed related deformation, and pressure changes were detected in boreholes. IMO raised the Aviation Color Code to Orange (the second highest level on a four-color scale) at 0657 noting that magma was moving, and an eruption may begin within an hour or so. GPS signals indicated that magma was moving both NE and S towards Grindavík, and the intrusion was about 11 km long; emergency responders in Grindavík reported felt earthquakes and observed signs of deformation. According to a news report residents from about 40 occupied homes in Grindavík were evacuated; eight people decided to not evacuate. A M 4 earthquake was felt in Reykjavík.

A NE-SW-trending fissure opened at around 0945, just N of the protective barrier built around Grindavík, and by 1000 had grown to 500 m long. Lava fountains developed along the fissure and gas plumes rose about 2 km above the fissure. By 1024 the fissure had extended S and was erupting lava a few hundred meters inside the barrier, between the barrier and Grindavík; lava flowed slowly S. The Aviation Color Code was raised to Red at 1024 and then back to Orange at 1054; no ash was detected in the emissions. The fissure continued to extend S and by 1235 it was 1.2 km long and comprised of five segments. The nearest house was 500 m S. Seismicity continued to be detected along the length of the intrusion and was most intense at the N end, which extended more than 3 km beyond the extent of previous eruptive fissures. Lava traveled mainly NW at the N end of the fissure, mostly W and to a lesser extent to the E at the central portion of the fissure, and S from the S end of the fissure in the area between the barrier and the town. The Blue Lagoon spa area closed for the day according to a news report. Eruptive activity significantly decreased during 1340-1440, though seismicity was ongoing at both the N and S ends of the intrusion. Activity continued to decrease and by 1500 no activity was visible; drone and webcam recordings indicated only minor activity. Seismicity at the S end of the intrusion, near Grindavík, had decreased. Seismicity at the N end continued at a similar intensity and shifted even further N; earthquakes were located almost 9 km more N than the northernmost eruption fissure during the August 2024 eruption. The largest earthquakes was around a M 3 and was felt in Vogar, 7 km NW of the activity.

Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.

Ulawun, Papua New Guinea

5.05°S, 151.33°E | Summit elev. 2334 m

The Rabaul Volcano Observatory (RVO) reported that at 0800 on 27 March a dense, dark-gray ash plume rose 2-3 km above the Ulawun’s summit and drifted S. Two seismic stations, located 10 km NW and 6 km from the volcano, indicated that seismicity remained low, though small, low-frequency earthquakes within background noise were detected by both stations. Increase seismicity was detected at the station 10 km NW in Real-time Seismic-Amplitude Measurement (RSAM) data 1-2 hours before the eruptive event, peaked about 30 minutes after the event, and then decreased to near-background levels about three hours later. RVO noted that the ash event was likely over, though seismic data suggested that there was a low probability that small ash plumes could sometimes occur. Continuous low rumbling was heard on 28 March. During 28 March-1 April activity was low and diffuse plumes contained ash but over the week changed to only white steam plumes.

Operations were restored at the third, and primary, seismic station (UULA) 2.8 km from the summit, on the lower WSW flank, on 28 March. The station immediately began recording small low- and high-frequency volcanic earthquakes, with low-frequency earthquakes being the dominant signal. Both the number and magnitude of both types of earthquakes increased on 1 April.

Geological summary: The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea’s most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Ongoing activity

Ahyi, United States

20.42°N, 145.03°E | Summit elev. -75 m

Unrest at Ahyi Seamount may have continued during 21-28 March. A diffuse plume of discolored water in the vicinity of the seamount was last identified in a satellite image on 15 March, indicating possible submarine activity. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the ocean surface ~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 | Summit elev. 1117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 24-31 March. Nightly crater incandescence was visible in webcam images. An explosion at 1145 on 25 March generated an ash plume that rose 2.5 km above the crater rim and drifted E. The explosion ejected large blocks 500-700 m from the vent. Another explosion occurred at 2127 on 27 March. On 28 March sulfur dioxide emissions were very high at 3,100 tons per day. Eruptive events at 1213 and 1236 on 25 March and at 1447 on 30 March generated ash plumes that rose 1-1.3 km above the crater rim and drifted E or SE. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from 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 | Summit elev. 1496 m

On 27 March the Vanuatu Meteorology and Geohazards Department (VMGD) reported that steam and/or gas emissions from the active vents at Ambae were ongoing during March based on satellite images and webcam images. Sulfur dioxide emissions were detected in satellite data. Seismic data also confirmed ongoing unrest. The Alert Level remained at 2 (on a scale of 0-5), and the public was warned to stay outside of the Danger Zone, defined as a 2-km radius around the active vents in Lake Voui, and 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.

Awu, Indonesia

3.689°N, 125.447°E | Summit elev. 1318 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that seismicity at Awu had increased. During March fluctuating levels of emissions rose as high as 200 m above the lava dome on the main crater floor and did not indicate an increase in activity. Tiltmeter data continued to show an inflationary trend. On 28 March there was an increase in the number of low-frequency earthquakes, indicating fluid movement at depth, and was accompanied by a relatively high number of shallow volcanic earthquakes. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the crater’s center.

Geological summary: The massive Gunung Awu stratovolcano occupies the northern end of Great Sangihe Island, the largest of the Sangihe arc. Deep valleys that form passageways for lahars dissect the flanks of the volcano, which was constructed within a 4.5-km-wide caldera. Powerful explosive eruptions in 1711, 1812, 1856, 1892, and 1966 produced devastating pyroclastic flows and lahars that caused more than 8000 cumulative fatalities. Awu contained a summit crater lake that was 1 km wide and 172 m deep in 1922, but was largely ejected during the 1966 eruption.

Bezymianny, Russia

55.972°N, 160.595°E | Summit elev. 2882 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that a thermal anomaly over Bezymianny was identified in satellite images during 20-27 March. According to the Institute of Volcanology and Seismology (IVS) of the Far Eastern Branch of the Russian Academy of Sciences (FEB RAS), incandescent debris avalanches descended the SE and/or E flanks and daily summit incandescence was visible during dark hours. An ash plume generated from a debris avalanche rose 100 m above the summit and drifted NE on 21 March. Weather conditions occasionally obscured webcam and satellite views. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). 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.

Dukono, Indonesia

1.6992°N, 127.8783°E | Summit elev. 1273 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Dukono was ongoing during 26 March-1 April. Daily dense white-and-gray or gray ash plumes rose as high as 2.5 km above the crater rim and drifted in multiple directions. Rumbling and banging sounds were sometimes accompanied by strong booms during 26-28 March. 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: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-less 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 N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

East Epi, Vanuatu

16.6797°S, 168.3893°E | Summit elev. 833 m

On 27 March the Vanuatu Meteorology and Geohazards Department (VMGD) reported that minor unrest continued at East Epi during March. No activity was observed above the ocean surface by communities of Epi and neighboring islands, though signs of continuing volcanic unrest was detected in seismic data. The Alert Level remained at 1 (on a scale of 0-5) and the public was warned to stay outside of the Danger Zone, defined as a 2-km radius around the active submarine vent.

Geological summary: The submarine East Epi group of basaltic and dacitic cones are located within a possible 10-km-diameter caldera off the NE coast of southern Epi Island in Vanuatu. Three cones (1-1.5 basal diameter), known as Epi A, Epi B (or Cioan), and Epi C, are located along the northern rim of the inferred caldera, though Beier et al. (2018) suggest an alternate to the post-caldera formation model. A few smaller cones are south of Epi B. Ephemeral islands were formed during eruptions at Epi B in 1920 and 1953. Explosive activity was reported in 1958 and 1960, discolored water was often seen during 1971-1974 and 1988, a new vent was detected in 1979, and explosive activity occurred in 1999, 2002, 2004, and 2023. The summit was at 34 m below sea level at the time of a 2001 survey, and a research cruise in 2013 (R/V Sonne SO-229; Haase et al, 2013) sampled six cones, including “very fresh pumice and lava bombs” from Epi B and “relatively old-looking” material from the others. The SO-229 cruise also recovered rhyodacitic pumice with mafic streaks, similar to that sampled by previous cruises, and described Epi B as “covered by massive blocks of pumice.”

Gaua, Vanuatu

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

On 27 March the Vanuatu Meteorology and Geohazards (VMGD) reported that volcanic emissions consisting of steam and/or gas continued to be emitted at Gaua based on satellite images. Sulfur dioxide gas was detected in the emissions on 1 March. The Alert Level remained at 2 (on a scale of 0-5) and the public was warned to stay away from the main cone.

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

Great Sitkin, United States

52.076°N, 176.13°W | Summit elev. 1740 m

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin’s summit crater during 26 March-1 April. Small daily earthquakes were detected by the seismic network. Slightly elevated surface temperatures were observed in satellite data during most of the week. Typical minor steaming from the vent region was visible in webcam images during 25-26 March and 30-31 March. 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.

Ibu, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 26 March-1 April. Daily dense gray ash plumes rose 300-1,200 m above the summit and drifted in multiple directions. Incandescence at the summit was visible in several webcam images posted with the reports. The Alert Level remained at 3 (the second highest level on a four-level scale) and the public was advised to stay 4 km away from the active crater and 5 km away from the N crater wall opening.

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

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 25 March-1 April. The seismic network recorded 6-23 daily volcanic earthquakes, including one period of volcanic tremor lasting one hour and 26 minutes on 29 March and one period of volcanic tremor lasting seven minutes on 31 March. Average daily sulfur dioxide emissions ranged from 1,665 to 3,302 tonnes per day. Moderate-to-voluminous, gas-and-steam emissions that occasionally contained ash generally rose 100-750 m crater rim and drifted W, WSW, and SW; weather conditions obscured views on 28 and 30 March. A period of ash emissions during 1524-1845 on 31 March produced voluminous plumes that rose up to 1.5 km above the crater rim and drifted W. According to a news article minor ashfall was reported in the barangays of Sag-ang in La Castellana (15 km SW) and Ara-al (7 km W) in La Carlota City, along with Binubuhan (17 km WNW), Ilijan (10 km NW), Ma-ao (17 km NW), and Mailum (11 km NW) in Bago City, Quintia. Ash emissions during 0557-0614, 0759-1001, 1028-1041, and 1140-1224 on 1 April rose 300-500 m above the crater rim and drifted SW. The Alert Level remained at 3 (on a scale of 0-5); the public was warned to stay 6 km away from the summit and pilots were warned not to fly close to the volcano.

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.

Karymsky, Russia

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

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported moderate levels of activity at Karymsky during 20-27 March. Thermal anomalies over the volcano were identified in satellite images on 21 March; weather clouds obscured views on the other days. On 30 March, KVERT lowered the Aviation Color Code from Orange (the third level on a four-color scale) to Yellow (the second level on a four-color scale), noting that eruptive activity was last observed on 12 November 2024. Dates are based on UTC times; specific events are in local time where noted.

Geological summary: Karymsky, the most active volcano of Kamchatka’s eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Katmai, United States

58.279°N, 154.9533°W | Summit elev. 2047 m

The Alaska Volcano Observatory (AVO) reported that on 31 March strong winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes dispersed unconsolidated ash up to 1.2 km (4,000 ft) a.s.l. to the SE. The ash was originally deposited during the Novarupta-Katmai eruption in 1912. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).

Geological summary: Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. The edifice had four NE-SW-trending summits, most of which were truncated by the 1912 collapse. Two or more large explosive eruptions took place during the late Pleistocene. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene, but Holocene lava flows from a flank vent descend the SE flank of the SW edifice into the Katmai River canyon. The steep walled young caldera has a jagged rim that rises 500-1,000 m above the caldera floor and contains a deep lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916.

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, from vents along the SW margin of Halema’uma’u Crater, continued at variable levels during 25 March-1 April. After a few days of no lava effusion from the N and S vents, activity resumed on 25 March. Eight cycles of rising lava in the N vent and small spatter fountaining were recorded during 0927-1155, with each cycle lasting 5-10 minutes and ending with lava draining back into the vent. At 1204 a more dynamic cycle began at the N vent with vigorous dome fountaining 10-20 m high and overflows of lava that extended onto the crater floor. Intermittent activity at the S vent also sent lava onto the crater floor. The cycles at the N vent continued through the day and by 0936 on 26 March nearly 100 cycles had been counted. Lava covered about 20 percent of the crater floor.

The cycles began to transition to lava fountaining at 1000 on 26 March, and by 1020 both vents were producing sustained fountains that rose more than 180 m. By 1045 fountains at the S vent were rising 180-210 m while N vent fountains were rising about half as high. Fountains at the S vent rose as high as 305 m during 1100-1200 and again at around 1330. Just after 1330 the S vent fountain began to incline, or bend over, with fountaining directed toward the SE. The inclined fountaining reappeared intermittently through the afternoon hours, with a maximum inclination approaching 45 degrees. By 1730 S vent fountains was vertical again with sustained heights of 150-215 m. Activity at the N vent ceased at around 1200 and fountaining at the S vent stopped at 1910. Lava flows covered 80-90 percent of the crater floor. Pele’s Hair and tephra was reported on surfaces in areas within Hawai’i Volcanoes National Park and surrounding communities. Sulfur dioxide gas emissions were estimated to be 50,000 tons per day during the periods of intense lava fountaining.

During 27-31 March spots of orange glow on the crater floor were visible at night, though diminished each day as the erupted lava cooled. Incandescent from the N vent was absent possibly due to being infilled with tephra and spatter from the S vent. A small opening in the S vent degassed and weakly glowed weakly during 27-28 March, was dark for a few nights, then was sporadically incandescent during 30-31 March.

Weak spattering began at the N vent at 1720 on 31 March. The spattering became continuous and by 1800 low lava fountains rose 5-10 m. The lava level in the vent gradually rose and overflowed at 2257, sending lava onto the crater floor. Incandescence from the S vent was visible overnight during 31 March-1 April and minor spattering was first observed by field crews at 0830 on 1 April. By 0944 lava covered only five percent of the crater floor. Fountaining at the S vent began and rapidly increased, rising to over 70 m by 1040 and exceeding 215 m by 1050. Low dome fountaining and overflows continue from the N vent. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Lopevi, Vanuatu

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

On 27 March the Vanuatu Meteorology and Geohazards Department (VMGD) reported that during the previous month small fumarolic steam plumes were continuously emitted at Lopevi’s summit crater based on recent photos and webcam images. Low-level thermal anomalies were identified in satellite images on 19 and 24 March. Seismic data confirmed continuing unrest. The Alert Level remained at 2 (on a scale of 0-4).

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

Merapi, Indonesia

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

The Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG) reported that the eruption at Merapi (on Java) continued during 21-27 March. Seismicity was at higher levels than the previous week. The SW lava dome produced 23 lava avalanches that traveled as far as 1.9 km SW down the Bebeng drainage, 20 that traveled as far as 2 km SW down the Krasak drainage, and 26 that traveled as far as 2 km W down the Sat/Putih drainage. Slight morphological changes to the SW lava dome resulted from minor collapses of material. 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.

Nevado del Ruiz, Colombia

4.892°N, 75.324°W | Summit elev. 5279 m

The Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 25-31 March. Seismic data indicated that events associated with fluid movement decreased in both number and intensity compared to the previous week, though long-duration signals slightly increased. Some of the seismic events were associated with pulsating ash emissions; webcam images confirmed these ash emissions, including some with higher-temperature ejecta. Gas plumes rose as high as 1 km above the summit; at 1744 on 25 March a gas-and-ash plume rose as high as 1.9 km above the summit as it drifted SW and W. Seismicity associated with rock fracturing decreased in both number and magnitude compared to the previous week. The earthquakes were mainly located below Arenas Crater, the NE and SW flanks within 4 km, and the W and NW flanks within 14 km, with depths of 1-10 km. Low-energy thermal anomalies on the crater floor were identified in satellite data. Sulfur dioxide emissions detected in satellite data continued to be significant. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Geological summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America’s deadliest eruption.

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 26 March-1 April, with multiple eruptive events recorded daily by the seismic network. Daily dense white-and-gray or gray-to-black ash plumes rose 300-800 m above the summit and drifted N, NE, E, and S. Incandescence at the summit was visible in webcam images from 1 April. The Alert Level remained at 2 (the second lowest level on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Sheveluch, Russia

56.653°N, 161.36°E | Summit elev. 3283 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that lava extrusion may have continued at Sheveluch’s “300 years of RAS” dome on the SW flank of Old Sheveluch and at the Young Sheveluch dome during 20-27 March. Thermal anomalies over the domes were identified in satellite images during 21-22 and 25-26 March; weather clouds obscured views on the other days. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; 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 24-31 March. Incandescence was observed nightly in webcam images. An eruptive event at 0927 on 29 March generated an ash plume that rose 1.5 km above the summit and drifted SE. Then at 1740 on 29 March an explosion generated an ash plume that rose 1 km into weather clouds. The Alert Level remained at 2 (the second level on a five-level scale) and the public was warned to stay at least 1.5 km away from 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.

Yasur, Vanuatu

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

On 27 March the Vanuatu Meteorology and Geohazards Department (VMGD) reported that activity at Yasur continued at a level of “major unrest,” as defined by the Alert Level 2 status (on a scale of 0-5). Satellite and webcam images indicated that explosions continued, producing emissions of gas, steam, and/or ash. Sulfur dioxide gas emissions and low-level thermal anomalies were identified in satellite images. Seismic data confirmed continuing volcanic activity with explosions that were occasionally strong. The report warned that ejected material from explosions could fall in and around the crater. The public was reminded to not enter the restricted area within 600 m around the boundaries of the Permanent Exclusion Zone, defined by Danger Zone A on the hazard map.

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

References:

¹ Smithsonian Institution / US Geological Survey – Weekly Volcanic Activity Report March 26–April 1, 2025 – GVP – 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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