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 Wednesday, 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 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.

Sources: CBS News,Disaster Response Operations Monitoring and Information Center (DROMIC),Office of Civil Defense ,Philippine Institute of Volcanology and Seismology (PHIVOLCS)

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 the week. 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 the week; 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).

Sources: Comisión Nacional de Prevención de Riesgos y Atención de Emergencias (CNE),Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

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.

Source: Icelandic Meteorological Office (IMO)

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.

Source: Rabaul Volcano Observatory (RVO)

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).

Source: US Geological Survey

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 this week with 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.

Source: Japan Meteorological Agency (JMA)

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 the week. 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.

Sources: Institute of Volcanology and Seismology (IVS) of the Far Eastern Branch of the Russian Academy of Sciences (FEB RAS),Kamchatkan Volcanic Eruption Response Team (KVERT)

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.

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

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 week by INGV-OE personnel in the field.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

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.

Sources: Antara News,Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

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).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

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).

Source: Tonga Geological Services, Government of Tonga