The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Thursday, these notices are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of eruptions during the week, but rather a summary of activity that meet selected criteria. Carefully reviewed, detailed reports are published in the Bulletin of the Global Volcanism Network.

The Washington Volcanic Ash Advisory Center (VAAC) reported that on 26 April a diffuse ash plume from Masaya was visible in satellite and webcam images rising to 1.5 km (5,000 ft) a.s.l. and drifting less than 20 km E.

Source: Washington Volcanic Ash Advisory Center (VAAC)

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported eruptive activity at Poás during 22-29 April. Gas emissions across the lake and from the new fumarolic field along the inner W wall were visible during 22-23 April. A phreatic/Surtseyan eruption at Boca A at 1524 on 27 April ejected jets of dark material above the lake?s surface and produced a steam plume that rose around 100 m. A second eruptive event the next day, on 28 April, lasted around one minute and consisted of three explosive pulses based on acoustic data. The event produced an eruption plume that rose 400 m and ejected ballistics to the SE that landed on the upper crater terrace. The Volcanic Alert Level remained at 2 (the second lowest level on a four-level scale).

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

The Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported minor eruptive events at Rincón de la Vieja during 23-29 April. A phreatic eruption at 1140 on 23 April produced a steam-and-gas plume that rose 100 m above the crater rim. Gas-and-steam plumes rose 500 m vertically above the crater rim due to lack of wind throughout the day on 24 April. A moderate ash eruption recorded at 0302 on 27 April was the most energetic event so far in 2026. The Alert Level remained at Level 2, Yellow, the second lowest level on a four-level scale.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 24-27 April. Crater incandescence was visible in nighttime webcam images. Very small eruptive events were periodically detected. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 2 km of both the Minimadake and Showa craters.

Source: Japan Meteorological Agency (JMA)

The eruption at Ambae continued during 24-25 April based on reports from the Wellington Volcanic Ash Advisory Center (VAAC). On 24 April sulfur dioxide emissions were identified in satellite images alongside a plume visible in webcam images; weather clouds prevented confirmation of ash. Weather clouds continued to obscure views for a few subsequent images. A diffuse ash plume was identified in a satellite image at 0915 on 25 April drifting SE at an altitude at or below 2.4 km (8,000 ft) a.s.l. The Alert Level remained at 3 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone B, defined as a 3-km radius around the active vents in Lake Voui, and to stay away from drainages during heavy rains.

Sources: Vanuatu Meteorology and Geohazards Department (VMGD),Wellington Volcanic Ash Advisory Center (VAAC)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 23-29 April. Daily white-and-gray ash plumes rose 400-1,400 m above the summit 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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Instituto Nacional de Sismología, Vulcanologia, Meteorologia e Hidrología (INSIVUMEH) reported that eruptive activity at Fuego continued during 22-29 April. Daily Strombolian explosions recorded by the seismic network, at rates of 5-13 per hour when reported, generated gas-and-ash plumes that rose as high as 1.1 km above the summit and drifted as far as 40 km in different directions. Rumbling sounds, shock waves, and/or sounds associated with gas emissions were reported daily. Explosions occasionally ejected incandescent material as high as 300 m above the summit. Incandescent block avalanches descended the Seca (W), Taniluyá (SSW), Ceniza (SSW), Las Lajas (SE), Santa Teresa (W), and Trinidad (SSW) drainages, sometimes reaching vegetated areas. Ashfall was reported in areas downwind including in El Rodeo (10 km SSE), El Zapote (10 km SSE), La Reunión (7 km SE), and Alotenango (8 km ENE) during 22-23 April, on the W and SW flanks during 27-28 April, and in Panimaché I and II (8 km SW), Finca La Asunción (12 km SW), Morelia (10 km SW), El Porvenir (11 km SW), and their surrounding areas.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin?s summit crater during 22-29 April. Lava-dome growth and rockfalls were concentrated on the E and S parts of the flow. The rockfalls were recorded daily by the seismic network. Weather clouds often prevented webcam and satellite observations. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ibu continued during 23-29 April, with daily eruptive events recorded by the seismic network. Daily gray or white-to-gray ash plumes rose 300-700 m above the summit and drifted in multiple directions. The Alert Level remained at 2 (the second lowest level on a four-level scale) and the public was advised to stay 2 km away from the active crater and 3.5 km away from the N crater wall opening.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 22-29 April. The seismic network recorded 7-54 daily volcanic earthquakes, including 2-5 daily periods of tremor lasting three minutes to just over one hour. Sulfur dioxide emissions ranged from 1,162 to 2,098 tonnes per day. Emissions were visible daily that generally rose 300-1,800 m above the summit and drifted in multiple directions. There were 2-11 daily periods of ash emissions, each lasting for three minutes to just over one hour. At 1723 on 24 April, at 0832 on 25 April, and at 1830 on 26 April ash plumes visible in webcam images rose 800 m, 300 m, and 1,200 m above the summit, respectively, and drifted W and SW. The Alert Level remained at 2 (on a scale of 0-5); the public was warned to stay out of the 4-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea?s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema?uma?u Crater, continued at variable levels during 22-29 April. Three lava overflows at the N vent were recorded during 20-21 April. Overflows at the S vent on 22 April were followed by low dome fountaining. Low fountaining at the N vent began at 0100 on 23 April; over the following 30 minutes activity decreased at the S vent and increased at the N vent. At 0134 a sharp increase in seismic tremor and deflation detected by summit tiltmeters marked the start of the high fountaining at the N vent. The fountains grew steadily until peak heights were reached at 0300; the main part of the fountains rose to at least 220 m, with diffuse areas of tephra at the top of the fountain occasionally going above 300 m. An eruption plume rose to 6 km (20,000 ft) a.s.l. and drifted S and SW. No significant tephra fallout was reported at visitor areas of Hawai?i Volcanoes National Park or on county roads, but Pele's hair and fine ash was reported falling in communities at the S end of the island. After their peak, fountain height gradually decreased and were about 100 m high just before abruptly ending at 1001, after 8.5 hours in total of continuous lava fountaining. At 1013 the Volcano Alert Level was lowered to Advisory and the Aviation Color Code was lowered to Yellow due to reduced ground and aviation hazards. The average effusion rate was 170 cubic meters per second; the highest peak was just over 300 cubic meters per second, occurring at around 0300. An estimated 5.2 million cubic meters of lava erupted and covered about 50 percent of the Halema?uma?u Crater floor. Gas jetting and flames at the S vent were periodically visible during the fountaining episode at the N vent. Variable incandescence and occasional flaming at both vents were visible during 24-29 April. The lava flows on the crater floor were incandescent and spread E during 24-25 April; only a few glowing spots on the flow field were visible during the rest of the week as the lava cooled. Seismic tremor with bursts of tremor every 1-10 minutes likely associated with gas pistoning cycles in the eruptive vents persisted. Earthquake activity at the summit was low.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that lava flows at Krasheninnikov continued to effuse onto the ENE and E flanks of the Northern Cone during 22-29 April. A large daily thermal anomaly was identified in satellite images. Satellite images showed small thermal anomalies along the active lava flow on the ENE flank on 23 and 26 April; the flows were obscured by either volcanic or weather clouds on 28 April. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale). Dates and times are provided in Coordinated Universal Time (UTC); events are in local time only where specified.

Sources: Copernicus,Kamchatkan Volcanic Eruption Response Team (KVERT)