The Weekly Volcanic Activity Report: April 16–22, 2025

New activity/unrest

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 14-20 April with two episodes of Strombolian activity at SE Crater. The first episode began at 0900 on 15 April and progressively intensified until about 1130, when lava overflowed the crater and descended the SE flank; activity ceased at 1150. The lava flow was about 1.2 km long and reached 2,620 m elevation based on 17 and 18 April satellite images. The second episode began at 1905 on 18 April and progressively intensified until about 2330, with two lava flows overflowing the crater; one descended the SE flank along the same path as the 15 April flow, and the other descended the SW flank. Activity ceased at 0055 on 19 April.

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.

Klyuchevskoy, Russia

56.056°N, 160.642°E | Summit elev. 4754 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that Strombolian activity at Klyuchevskoy began on 20 April. Incandescence at the summit was first observed at 1004 and continued to intensify through the day. The Aviation Color Code was raised to Yellow (the second lowest level on a four-color scale) at 2232.

Geological summary: Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Kuchinoerabujima, Japan

30.443°N, 130.217°E | Summit elev. 657 m

The Japan Meteorological Agency (JMA) reported that the number of shallow volcanic earthquakes increased beneath an area near Kuchinoerabujima’s Furudake Crater with 100 earthquakes recorded during 7-16 April. No changes to geothermal areas located in and around both Shindake and Furudake craters were observed during a field survey conducted on 11 April. Sulfur dioxide emissions were low, averaging 20 tons per day on 11 April, and no ground deformation had been detected since November 2023. The Alert Level was raised to 2 (on a scale of 1-5) at 2325 on 16 April; the public was warned that ejected blocks may land within 1 km of both craters, and pyroclastic flows may affect areas within 2 km of the W flank of Shindake Crater.

Geological summary: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

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 frequent explosions and ash-and-gas plumes at Poás during 16-22 April. Weather clouds often prevented visual observations, though during daily periods of clearer weather the plumes were confirmed to have contained ash. Both seismic and acoustic data indicated that frequent small eruptions at varying intensities occurred through the week, a change from the continuous activity of the previous week; activity generally began decreasing on 11 April. Ash emissions rose around 200 m above the crater rim and drifted SW and WSW, primary from Boca C during the first part of the week, then from Boca A starting on 20 or 21 April. Incandescence at Boca A was sometimes visible during dark hours. Energetic explosions ejected blocks as high as the crater rim. Sulfur dioxide emissions measured by a Differential Optical Absorption Spectroscopy (DOAS) station averaged 230-439 tons per day (t/d), though the average was 1,217 t/d on 17 April.

Notably, a strong explosive phase began at 1414 on 21 April and lasted for five minutes. A dense ash plume from Boca A rose 4.5 km above the crater rim and drifted SW, and hot ballistics (around 250 degrees Celsius) were ejected to the W. Weather clouds prevented clear views of the plume. According to a news article ash, gas, and incandescent material were ejected. Ash fell across the Valle Central to the SW, including in Zarcero (18 km W), Grecia (16 km SW), Alajuela (20 km S), Heredia (28 km SE), and San José (33 km SE), and on social media residents posted photos of ashfall on the streets, cars, and homes. Lower-energy ash emissions continued through the rest of the day, generating brown ash plumes at 1554, 1628, and 1721. Small eruptive events were recorded on 22 April. That same day field measurements of the gas emissions using a DOAS instrument yielded an average that exceeded 1,000 t/d. 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.

Ulawun, Papua New Guinea

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

The Darwin Volcanic Ash Advisory Centre (VAAC) reported that a possible ash plume at Ulawun was observed by a pilot at 0730 on 21 April and rose to 3.7 km (12,000 ft) a.s.l. and drifted S. Weather clouds obscured satellite views.

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.

Whakaari/White Island, New Zealand

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

On 17 April GeoNet reported that during the previous few months gas-and-steam emissions at Whakaari/White Island more frequently contained ash. The webcams located at Whakatane and Te Kaha recorded an increase in ash content in the emissions during the last few weeks and minor amounts of ash were identified in satellite data as reported by the Wellington Volcanic Ash Advisory Center (VAAC). A hazy plume drifting downwind was visible from the mainland coast. Impact craters visible on the main crater floor during recent observation flights indicated that explosive activity had ejected rocks several hundreds of meters from the vent. Additionally, there were increases in temperatures (based on thermal infrared data) and sulfur dioxide emissions (detected by satellite and overflights). Recent activity was consistent with a low level of eruptive activity; the Volcanic Alert Level was raised to 3 (on a scale of 0-5) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale). GeoNet stated that the Alert Levels were reflective of the current level of activity, but there was uncertainty due to the current lack of consistent, usable, real-time monitoring data; GeoNet relies on remote cameras, satellite images, and periodic overflights to monitor Whakaari.

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.

Ongoing activity

Aira, Japan

31.5772°N, 130.6589°E | Summit elev. 1117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 14-21 April. Nightly crater incandescence was visible at Minamidake Crater in webcam images, and very small eruptive events were recorded during 14-18 April. On 17 April sulfur dioxide emissions averaged 900 tons per day. 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 10-17 April and that there were occasional avalanches of hot material. 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 mainly the E flank, and crater incandescence was often visible during dark hours. Ash plumes generated from these avalanches on most days rose as high as 3.1 km above the summit and drifted NNW, NW, W, and E. 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.

Bulusan, Philippines

12.769°N, 124.056°E | Summit elev. 1535 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported increased seismicity at Bulusan. Seismicity recorded from 0300 on 12 April until 2200 on 21 April consisted of 94 weak volcano-tectonic earthquakes indicating rock fracturing, another four low-frequency volcanic earthquakes indicating fluid movement. The earthquake locations were within 20 km depth, with about half characterized as shallow. Weak-to-moderate gas emissions rose from the summit crater and active vents. The Alert Level remained at 0 (the lowest level on a scale of 0-5).

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

Dukono, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Dukono continued during 16-22 April. White-and-gray ash plumes that were sometimes dense rose 600-1,500 m above the crater rim and drifted in multiple directions. Occasional rumbling and banging sounds were heard during 19-20 April. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Geological summary: 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.

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 16-22 April. Small daily earthquakes were detected by the seismic network. Inflation of the lava flow and minor advancement at the E and SE margins were visible in radar data from 17 April. Minor steaming at the lava flow was visible on 21 April. Weather clouds often obscured 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.

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 16-22 April. Daily dense gray ash plumes rose 300-600 m above the summit and drifted in multiple directions. Nighttime crater incandescence was visible in a webcam images on 16, 18, and 21 April. 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 16-22 April. The seismic network recorded 1-16 daily volcanic earthquakes and two periods of volcanic tremor (34 and 42 minutes long) on 15 April. Daily sulfur dioxide emissions ranged from 1,170 to 3,078 tonnes per day. Gas-and-steam emissions that occasionally contained ash generally rose as high as 200 m above the crater rim and drifted SW, W, and WNW. There were two ash emissions on 15 April (20 and 70 minutes long), and another on 20 April (31 minutes long); voluminous gas-and-ash plumes rose 600 m above the rim and drifted SW on 20 April. 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.

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 two vents along the SW margin of Halema’uma’u Crater, continued at variable levels during 16-22 April. Both the N and S vents were strongly incandescent and produced gas emissions on 16 April. Later that evening at around 2110 incandescence at the N vent intensified and began to eject spatter at intervals of 10-20 seconds. Spatter bursts increased in size and frequency, and at around 2130 dome fountains 3-5 m high had formed. A lava pond in the crater rose and was visible at 2145, and by 2201 lava overflowed the crater and traveled short distances (up to 100 m) on the crater floor. Sulfur dioxide emissions were elevated. The activity ceased at 2321. Incandescence from the S vent disappeared when the N vent overflowed but returned once the flows ceased. Both the N and S vents were strongly incandescent and produced gas emissions during 17-20 April.

At around 0745 on 20 April a narrow lava flow was produced from the S vent. Lava fountaining to 2-3 m began soon after, and by 0915 lava flows had traveled about 1 km across the crater floor. After brief pauses during 0930-0943 and 1030-1050, followed by lava flows being fed by 5-m-high dome fountains. Lava flows and dome fountaining resumed after another break during 1110-1222, and then again ceased at 1244. Small gas-pistoning events occurred every 3-5 minutes and were superimposed upon the longer cycles of activity. Intermittent spattering at the N vent began at around 0130 on 22 April and increased in frequency. Lava overflowed the S vent at 0320, and by 0330 lava fountaining was occurring at both vents. Lava overflowed the N vent at 0347. By 0436 the fountain at the S vent was over 200 m high and the N vent fountain was more than 50 m high, feeding lava flows that cascaded down the vent flanks and onto the crater floor. Lava fountains at the N vent slightly grew through the day, rising as high as 60 m. The activity abruptly ceased at 1328, after lava had covered about 30 percent of the crater floor. 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 16-22 April. Dense gray ash plumes rose 2.5-3.5 km above the summit on 16 April and drifted multiple directions. Ash plumes during 17-18 April rose 500-700 m above the summit and drifted mainly N and NE; weather clouds sometimes obscured views. Multiple ash plumes per day were recorded during 19-22 April. Ash plumes rose as high as 3 km and drifted in multiple directions. An eruptive event that was recorded at 2359 on 20 April ejected incandescent material onto the upper flanks. According to a news report, the event was accompanied by a loud banging sound heard at the Lewotobi Laki-laki observation post, 4.9 km WSW. On 22 April ash-and-gas plumes were continuously emitted from approximately 1000 at least through 1554; dense gray ash plumes rose 1.3-1.5 km above the summit and drifted W and NW, though weather clouds sometimes obscured views. 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 16-22 April. White steam-and-gas plumes rose as high as 100 m above the summit of the cone and drifted E and SE. Ash plumes rose 400 m above the summit and drifted SE on 17 April. Nighttime webcam images showed either incandescence at the summit or 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.

Marapi, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity from Verbeek Crater at Marapi (on Sumatra) continued during 16-22 April. Ash plumes rose 200-1,000 m above the summit and drifted NE, E, SE, and S on 16, 19, and 21 April. An explosion was recorded at 2141 on 21 April but was not visually confirmed due to weather cloud cover. According to a news report a resident Padang Panjang City (11 km SW) said that the explosion was so loud that it shook the windows. A webcam image at 2212 on 21 April 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 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 11-17 April. Seismicity remained at high levels. The SW lava dome produced 46 lava avalanches that traveled as far as 2 km SW down the Bebeng drainage, 30 that traveled as far as 2 km SW down the Krasak drainage, and 46 that traveled as far as 2 km W down the Sat/Putih drainage. Small morphological changes to the SW lava dome resulted from continuing effusion and 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.

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 16-22 April, with multiple daily eruptive events recorded by the seismic network. White-and-gray ash plumes rose 500-1,300 m above the summit and drifted in multiple directions; ash plumes were not visible on 18 April. Incandescence at the summit was visible in a 17 April webcam image. 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 10-17 April. Daily thermal anomalies over the domes were identified in satellite images. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC 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 14-21 April. Incandescence was observed nightly in webcam images. Eruptive activity generated emissions that rose 400 m above the crater rim. Ashfall was reported by the Suwanosejima Branch of the Toshima Village Office (3.5 km SSW). The Alert Level remained at 2 (the second level on a five-level scale) and the public was warned to be cautious within 1.5 km of the crater.

Geological summary: The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two active summit craters. The summit is truncated by a large breached crater extending to the sea on the E flank that was formed by edifice collapse. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded eruption took place in 1813-14, when thick scoria deposits covered residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed, forming a large debris avalanche and creating an open collapse scarp extending to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Yakedake, Japan

36.227°N, 137.587°E | Summit elev. 2455 m

The Japan Meteorological Agency (JMA) lowered the Alert Level for Yakedake to 1 (on a scale of 1-5) at 1100 on 18 April, noting that seismicity has remind at low levels after a period of elevated seismicity was recorded during 3-9 March. JMA warned climbers to be alert to any changes at the volcano and to wear a helmet.

Geological summary: Yakedake rises above the popular resort of Kamikochi in the Northern Japan Alps. The small dominantly andesitic stratovolcano, one of several Japanese volcanoes named Yakedake or Yakeyama (“Burning Peak” or “Burning Mountain”), was constructed astride a N-S-trending ridge between the older volcanoes of Warudaniyama and Shirataniyama. Akandanayama, about 4 km SSW, is a stratovolcano with lava domes that was active into the Holocene. A 300-m-wide crater is located at the summit, and explosion craters are found on the SE and N flanks. Frequent small-to-moderate phreatic eruptions have occurred during the 20th century. On 11 February 1995, a hydrothermal explosion in a geothermal area killed two people at a highway construction site.

References:

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