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

New activity/unrest: Kanlaon, Philippines | Poas, Costa Rica | Reykjanes, Iceland | Ulawun, Papua New Guinea.

New activity/unrest

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 1-7 April and a notable explosion on 8 April. The seismic network recorded 2-23 daily volcanic earthquakes, including 2-9 daily (except for 6 April) periods of volcanic tremor lasting two minutes to two hours and five minutes. Average daily sulfur dioxide emissions ranged from 1,283 to 2,725 tonnes per day. Moderate-to-voluminous gas-and-steam emissions that occasionally contained ash rose 100-600 m crater rim and drifted W, WSW, and SW. There were 2-9 periods of ash emissions during 1-5 April that each lasted 3 minutes to two minutes to two hours and five minutes.

A moderately-explosive eruption occurred at 0551 on 8 April and lasted for 56 minutes based on seismic data and visual observations. A voluminous gray ash plume slowly rose 4 km above the crater rim and drifted W and SW. Rumbling was heard and pyroclastic density currents traveled 1 km down the S flank. Large ballistic fragments were ejected a few hundred meters and set vegetation on fire on the upper E flank, near the summit. Minor ashfall was reported in the barangays including Roberto Salas Benedicto, La Granja, Haguimit, Nagasi, Yubo, Ara-al, San Miguel, and Cubay (La Carlota City), Mailum, Ilijan, and Binubuhan (Bago City), and Sag-ang and Mansalanao (La Castellana). Sulfur odors were notable in Cubay and less notable in areas as far as the Municipality of Hinigaran. According to a news article ashfall was widespread and recorded as far as 195 km W. About six domestic flights and one bound for Singapore were canceled. The Office of Civil Defense government offices, except those involved in disaster and emergency response, closed in La Carlota City along with face-to-face classes at all levels. Private establishments were encouraged to suspend work. Heavy ashfall in Ara-al within an hour of the eruption caused poor road visibility, and the river at the Najalin Bridge between Cubay and La Granja was contaminated with ashfall and there was poor visibly along the road in that area as well. Many of the residents that had evacuated within a 6-km radius due to increased eruptive activity in December 2024 remained in evacuation centers or elsewhere; the Disaster Response Operations Monitoring and Information Center (DROMIC) reported that as of 1800 on 19 April there were 8,315 people (2,607 families) spread across 22 evacuation centers and another 11,892 people (3,702 families) staying elsewhere. 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.

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 elevated levels of activity at Poás during 2-8 April. Inflation continued to be detected, though the rate of uplift had slowed. Sulfur dioxide emissions remained high; values over 2,200 tonnes per day (t/d) were identified in satellite data on 30 March and were followed by two days of values exceeding 1,000 t/d. Emissions recorded by a mobile Differential Optical Absorption Spectroscopy (DOAS) instrument averaged 5,300 ± 500 t/d on 1 April.

Phreatomagmatic events at Boca C occurred about every 4-12 minutes on most days during theweek. The events produced almost continuous gas, steam, and ash plumes that generally rose up to 500 m and mostly drifted SE, S, SW, W, and NW, though the plumes occasionally rose higher. Notably, gas, steam, and ash plumes rose to 1 km on 29 March, to 3 km at 1252 on 4 April, to heights greater than 1 km at 1701 on 6 April and at 0203 on 7 April, and to 1.5 km at 0218 and 0224 on 8 April. Ashfall was reported by residents through theweek; ashfall occurred on 4 April in Bajos del Toro (7 km WNW) and in areas to the S on 8 April including Poasito (7 km SW), San Juan Norte (9 km S), Savana Redonda (10 km SSE), San Pedro de Poás (14 km S), Poás (14 km S), Chilamate (16 km SSW), Pavas (16 km SE), Sabanilla (14 km SSE), Calle el Sitio 14 km S), Naranjo (16 km WSW), Cabuyal (8 km SW), Chilamate (16 km SSW), and Alajuela (20 km S). Explosions sometimes ejected incandescent blocks onto the crater floor. Weather conditions sometimes obscured views of the crater.

According to the Comisión Nacional de Emergencias (CNE) on 8 April the Alert Level Orange for the Parque Nacional volcán Poás remained in effect as well as for the district of Toro Amarillo in the Canton of Sarchí due to activity at the crater, ashfall and sulfur odors impacting areas downwind, and a higher potential of lahars in drainages. The volcano’s 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 the eruption that began at 0945 on 1 April near the Sundhnúkur crater row, located between Stóra-Skógfell and Sýlingarfell within the Reykjanes volcanic system, was over at 1645 on that same day. Data collected during an overflight conducted by the Icelandic Institute of Natural History on 1 April indicated that about 0.4 million cubic meters of lava had erupted, making it the smallest eruption of the series that began in December 2023 and one sixth of the volume of the second smallest eruption that occurred in January 2024. The flow field was about 0.23 square kilometers and had an average thickness of 1.7 m. Some incandescence on the flow field was visible during 1-2 April as lava cooled. More than 25 cm of subsidence was detected at a GPS station in Svartsengi, though by 1450 on 2 April the rate had significantly slowed. Minor seismicity continued to be recorded, though the earthquake magnitudes had decreased. Several GPS stations recorded at most about 50 cm of movement or displacement in Grindavík, spread over several cracks visible throughout the town. At 1212 on 3 April the Aviation Color Code was lowered to Yellow (the second lowest level on a four-color scale). Subsidence was no longer measured. Deformation data indicated that the northernmost part of the intrusion, about 4 km N of Keilur, remained active, and inflation resumed in Svartsengi, during 3-4 April, though seismicity was decreasing.

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 activity at Ulawun was low during 1-7 April. Summit emissions were characterized as white, having variable densities, and containing small amounts of ash. The plumes drifted S and caused minor ashfall in areas within a few km to the S and SW of the volcano. Low rumbling noises were heard in those same areas on 1 and 4 April. Seismicity generally remained low. The seismic station (UULA), 2.8 km from the summit on the lower WSW flank, recorded small low- and high-frequency volcanic earthquakes, with low-frequency earthquakes being the dominant signal. Starting at about 0800 on 4 April the seismic signals quickly changed to continuous volcanic tremor and the tremor amplitude grew relatively rapidly. The tremor lasted about 5.5 hours, reverting to discrete seismic signals at around 1720. The station ceased being operational at around 1900. The two other seismic stations, UALB (5.6 km) and UULB (10 km NW), did not detect the seismicity due to their distance from the volcano and high levels of cultural noise that obscured signals. RVO noted that a team from the West New Britain Provincial Disaster Office had been conducting community awareness activities within 10 km of Ulawun since 27 March, so far visiting the Ulamona area (10 km NW), Navo, Noau, Voluvolu, Bakada, Sabalbala, Vamakuma, Bago, Kabaia, Soi, and Sohula care center.

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 28 March-5 April. A diffuse plume of discolored water in the vicinity of the seamount was last identified in a satellite image on 30 March, indicating possible submarine activity. No signals coming from the direction of Ahyi were identified in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi). 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 31 March-7 April. Nightly crater incandescence was visible in webcam images. Eruptive activity increased thisweekwith 21 eruptive events, 12 of which were explosions. An explosion at 2220 on 1 April ejected large blocks 300-500 m from the crater rim. Explosions at 0703 and 1922 on 2 April produced ash plumes that rose up to 1.9 km above the crater rim and ejected large blocks 300-900 m from the crater rim. Explosions at 1023, 1650, and 1937 on 4 April produced ash plumes that rose up to 1.5 km above the crater rim and ejected large blocks 800-1100 m from the crater rim. Explosions at 0027, 0643, 1524, and 2154 on 5 April produced ash plumes that rose up to 2.6 km above the crater rim and ejected large blocks 500-700 m from the crater rim. An explosion at 1148 on 7 April produced an ash plume that rose up to 2.9 km above the crater rim and ejected large blocks 600-900 m from the crater rim. Ash plumes rose straight up or drifted SE, S, or NE. 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.

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 30-31 March and 1-3 April. The volcano was obscured by weather clouds on the other days of theweek. According to the Institute of Volcanology and Seismology (IVS) of the Far Eastern Branch of the Russian Academy of Sciences (FEB RAS), occasional ash plumes rose as high as 1.2 km above the summit and drifted NE and E. On most days, incandescent debris avalanches descended the SE flank and summit incandescence was visible during dark hours. 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 continued during 2-8 April. White-and-gray ash plumes rose 400-3,300 m above the crater rim and drifted in multiple directions. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Geological summary: 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.

Etna, Italy

37.748°N, 14.999°E | Summit elev. 3357 m

The Sezione di Catania – Osservatorio Etneo (INGV) reported continuing activity at Etna during 31 March-6 April. Weather clouds occasionally obscured views of the summit area, though direct field observations occurred during 2-4 April. Minor, discontinuous Strombolian activity began at SE Crater at 2100 on 2 April and progressively intensified. From about 2250 on 2 April to 0050 on 3 April Strombolian activity was intense and ejected material onto the flanks of the cone. The activity slowly decreased and by 0600 explosions were no longer visible in webcam images. During the morning of 2 April ash emissions rose from Voragine Crater as high as 3.5 km a.s.l. and drifted mainly SE. A field team observed ashfall on the snow in the summit area. Ash emissions were again observed on 4 April. Minor and sporadic red ash emissions at Bocca Nuova Crater were observed during the weekby INGV-OE personnel in the field.

Geological summary: Mount Etna, towering above Catania on the island of Sicily, has one of the world’s longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Gede, Indonesia

5.93°S, 106.07°E | Summit elev. 595 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported an increase in seismicity at Gede on 1 April. During March plumes (likely steam) rose 50-100 m above the rim of Wadon Crater and an average of 0-1 daily deep volcanic earthquakes were detected by the seismic network. The network recorded 47 deep volcanic earthquakes on 1 April. Seismicity decreased the next day, and no deep volcanic earthquakes were detected during 2-6 April. Plumes continued to rise as high as 100 m above the crater rim. One tornillo earthquake was recorded on 6 April. According to a news article the Balai Besar Taman Nasional Gunung Gede Pangrango (TNGGP) (the Gede national park) had already closed the volcano to climbers months before for unstated reasons and was scheduled to reopen on 3 April; the closure was extended to 7 April as a precaution due to the increased seismicity. The Alert Level remained at 1 (on a scale of 1-4) and the public was warned to stay 600 m away from Wadon Crater. The last eruption occurred in 1957 at Ratu Crater.

Geological summary: Gede volcano on the NW tip of Java is of Quaternary age and is located about 280 km from the trench (van Bemmelen 1949b). The Gede Salak volcanic complex consists of pyroclastic flows on its western flanks and lava flows on its eastern flanks (Kurniawan et al., 2011). Mt. Gede is also surrounded by Plio-Quaternary tuffs (Banten Tuffs) ranging from 0.07 to 0.1 Ma in age (Pramumijoyo and Sebrier, 1991). Kurniawan et al. (2011) suggest that these Tuffs came from the calderas of the nearby Rawa Dano volcanic complex but gravity anomalies in the region suggest that neither Gede nor its nearby volcanoes could have been responsible for these ignimbrites and instead suggest a pre-existing caldera in the Sunda Straight was responsible (Nishimura et al., 1986).

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 1-8 April. Small daily earthquakes were detected by the seismic network. Slightly elevated surface temperatures were observed in satellite data during 3-4 and 6-9 April. Weather clouds often obscured satellite and webcam views of the volcano. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an older edifice and produced a submarine debris avalanche. Deposits from this and an even older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Eruptions have been recorded since the late-19th century.

Home Reef, Tonga

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

On 4 April the Tonga Geological Services reported that thermal anomalies at Home Reef were identified in satellite images during the previous two weeks; the anomalies were at mostly low levels, though they were occasionally characterized as moderate. A decrease in activity was detected in infrasound data. A lava dome just SW of the central part of the island was visible in a 26 March satellite image; this 80 m W-E, 100 m N-S feature had not changed in size since the previous view. Discolored water surrounding the island. The Maritime Alert Level remained at Orange (the third level on a four-level scale), and mariners were advised to stay at least 2 nautical miles (3.7 km) away from the island. The Aviation Color Code remained at Yellow (the second level on a four-level scale), and the Alert Level for residents of Vava’u and Ha’apai remained at Green (the first level on a four-level scale).

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

Ibu, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 2-7 April. Daily dense gray ash plumes rose 300-1,000 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.

Katmai, United States

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

The Alaska Volcano Observatory (AVO) reported that during 6-7 and 9 April strong winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes dispersed unconsolidated ash up to 1.5-1.8 km (5,000-6,000 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 1-8 April. Weak spattering at the N vent that had begun on 31 March changed to low lava fountaining and lava pond activity that ceased at 2122 on 1 April. Lava fountaining began at the S vent around 0800 on 1 April and rapidly increased in height, with fountains rising to 245 m. Volcanic gas emissions were elevated; during the period of high fountaining, sulfur dioxide emission rates were 50,000 tonnes per day along Highway 11, just NW of Halema’uma’u Crater. Small pumice, ash, and Pele’s hair fell on Highway 11, leaving deposits about 1 cm thick, and in closed areas of Hawai’i Volcanoes National Park. The fountain heights dropped significantly to 90 m by 0950 on 2 April and then ceased at 1203. Small spattering at the S vent was observed later in the afternoon. Lava covered about 50 percent of the crater floor.

Incandescence at the S vent was visible during 3-5 April and at the N vent during 4-7 April. During 3-7 April a dense white gas plume rose from the vents and bright sulfur deposits were visible on the vent cones. Lava flows were periodically active on the E crater floor. Incandescence at the S vent intensified at around 2120 on 7 April, indicating rising lava in the cone. Lava overflowed the vent at 2215 and spread across the crater floor. Low spatter fountains rising 5-30 m were visible at 0250 on 8 April. Spattering and activity at a lava pond in the N vent was visible at around 0400. 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.

Lewotobi, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Lewotobi Laki-laki continued during 2-8 April. Dense gray ash plumes rose 300-1,200 m above the summit during 4-6 and 8 April and mainly drifted N, NE, and E, and occasionally SW. Minor incandescent at the summit was occasionally visible in webcam images posted with the daily reports. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 6 km away 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 | Summit elev. 1431 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Lewotolok was ongoing during 2-8 April. White steam-and-gas plumes rose as high as 120 m above the summit of the cone and drifted NE, E, and SE on most days; white-and-gray plumes rose 30 m and drifted E on 3 April. Nighttime webcam images accompanying the daily reports often showed incandescent material being ejected above the summit, as far as 600 m from the vent during 3-4 April. Rumbling was heard on 3 April and a lava flow was visible, but it remained confined to the crater. 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.

Marapi, Indonesia

0.38°S, 100.474°E | Summit elev. 2885 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Marapi’s Verbeek Crater (on Sumatra) continued during 2-8 April. An eruptive event at 2233 on 1 April was recorded by the seismic network but not observed. At 0625 on 2 April a gray ash plume rose 350 m above the summit and drifted NE and at 1604 a dense gray ash plume rose 1 km above the summit and drifted E. On 3 April at 1804 a dense gray ash plume rose 400 m and drifted E. At 0712 on 3 April an eruptive event that lasted one minute and nine seconds produced an ash plume that rose 1.5 km above the summit and drifted E. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the active crater.

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

Merapi, Indonesia

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

The Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG) reported that the eruption at Merapi (on Java) continued during 28 March-4 April. Seismicity was at higher levels than the previousweek. The SW lava dome produced 28 lava avalanches that traveled as far as 1.8 km SW down the Bebeng drainage, 50 that traveled as far as 1.8 km SW down the Krasak drainage, and 37 that traveled as far as 1.8 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.

Reventador, Ecuador

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

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that eruptive activity continued at Reventador during 1-8 April. Seismicity included 52-127 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Multiple daily ash-and-gas plumes rose as high as 1.3 km above the crater rim and drifted mainly NW, W, and SW. Webcams recorded multiple nightly instances of incandescent material descending the flanks as far as 1.2 km below the crater rim. On 2 April pyroclastic flows traveled 250 m down the SE flank and 700 m down the S flank. A pyroclastic flow traveled 500 m down the flank on 3 April. Secretaría de Gestión de Riesgos maintained the Alert Level at Orange (the second highest level on a four-color scale).

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

Sangay, Ecuador

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

The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that moderate levels of eruptive activity continued at Sangay during 1-8 April. The seismic network recorded 36-185 daily explosions. Weather clouds obscured views most of theweek, but on most of the days several gas-and-ash plumes were visible rising as high as 2 km above the summit and drifting SW. Crater incandescence was often visible during dark hours. 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.

Santa Maria, Guatemala

14.757°N, 91.552°W | Summit elev. 3745 m

The Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología (INSIVUMEH) reported ongoing, high-level eruptive activity at Santa Maria’s Santiaguito dome complex during 2-8 April with continuing lava extrusion at Caliente dome. Daily explosions, as many as five per hour when reported, generated gas-and-ash plumes that rose as high as 1.2 km above the dome and possibly drifted as far as 40 km N, NW, W, and SW. Effusion of blocky lava and collapses of material produced block avalanches that were sometimes heard several kilometers away; these mainly descended the SE, S, SW, and W flanks. Collapsed material sometimes produced short pyroclastic flows that descended the flanks in all directions. Incandescence was visible at Caliente dome and upper part of the SW flank lava flow. Ashfall was forecast for areas downwind on most days. Ashfall was reported in Finca El Patrocinio (8 km SW), San Marcos (10 km SW), Loma Linda (7 km W), Palajunoj (17 km SSW), Llanos de Pinal, and other nearby communities during 2-3 April, from Calahuaché (8 km SSE) to Viejo Palmar (11 km S) and Loma Linda during 6-7 April, and forecasted for areas downwind on most other days.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semeru, Indonesia

8.108°S, 112.922°E | Summit elev. 3657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 2-8 April, with multiple eruptive events recorded daily by the seismic network. Dense white-and-gray ash plumes rose 400-900 m above the summit and drifted in multiple directions; plumes were not visible on 2 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 27 March-3 April. Thermal anomalies over the domes were identified in satellite images during 30-31 March and 1-3 April; 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.

Stromboli, Italy

38.789°N, 15.213°E | Summit elev. 924 m

The Sezione di Catania – Osservatorio Etneo (INGV) reported that eruptive activity continued at Stromboli during 31 March-6 April. Webcam images showed Strombolian activity at four vents in Area N within the upper part of the Sciara del Fuoco and from at least two vents in Area C-S (South-Central Crater) on the crater terrace. The vents in Area N continued to produce low- to medium-intensity explosions at a rate of 8-12 events per hour, ejecting lapilli and bombs less than 150 m above the vents. Minor and discontinuous spattering at the N2 vent was intense for short periods on 31 March and 2 April. Explosions at the vents in Area C-S ejected tephra above the vent at a rate of 1-5 events per hour. The Alert Level remained at Yellow (the second lowest level on a four-level scale).

Geological summary: Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the “Lighthouse of the Mediterranean” in the NE Aeolian Islands. This volcano has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

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 31 March-7 April. Incandescence was observed nightly in webcam images. An explosion at 2050 on 1 April generated an ash plume that rose 600 m above the crater and ejected large blocks as far as 200 m from the vent. 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.

Whakaari/White Island, New Zealand

37.52°S, 177.18°E | Summit elev. 294 m

The Wellington VAAC reported that low-level steam-and-gas emissions from Whakaari/White Island contained minor amounts of ash during 1-2 and 6 April. The emissions rose 0.9-1.8 km (3,000-6,000 ft) a.s.l. and drifted S and SE based on webcam and satellite images.

Geological summary: The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari (“The Dramatic Volcano”) and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

References:

¹ Smithsonian Institution / US Geological Survey – GVP – Weekly Volcanic Activity Report April 2–8, 2025 –
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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