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 Centro de Informação e Vigilância Sismovulcânica dos Açores (CIVISA) reported that on 1 April low-magnitude seismic activity was off the NW coast of Pico, in a NE-SW zone along the Faial-Pico channel, W of Madalena to N of Lagido, and encompassing the Cachorro Submarine Volcanic System. The earthquake depths ranged from 20 km deep to near surface. The seismicity was slightly above normal levels; on 9 April the Volcanic Alert Level was raised to V1 (the second lowest level on an 8-level scale) for the Faial-Pico channel.

Source: Centro de Informação e Vigilância Sismovulcânica dos Açores (CIVISA)

The Observatoire Volcanologique du Piton de la Fournaise (OVPF) reported that eruptive activity at Piton de la Fournaise resumed on 8 April. Low-amplitude continuous volcanic tremor that began on 3 April, beneath the ESE flank in the same location as during earlier eruptive phases, sharply decreased the evening of 7 April. Following the drop, gas pistoning (intermittent tremor phases) emerged and persisted through the next morning. At around 0530 on 8 April tremor amplitude significantly increased, and by 1315 had reached a higher level than on 2 April, prior to the cessation of the activity; concurrent gas emissions increased at the main cone, likely signaling lava at the surface. During an overflight later that afternoon a small lava lake in the cone was observed. Intermittent activity at the cone was characterized as periods of intense spattering and degassing followed by periods of calm with each period lasting around 10 minutes. At 0915 on 9 April a new vent was visible 180 m upflank of the cone. The new vent produced lava fountains while intermittent activity at the main cone ceased, though a lava lake persisted. A lava flow from the new vent descended the flank to around 700 m elevation with an estimated peak flow rate of 35 cubic meters per second. The flow rate average dropped to 10 cubic meters per second by 1800. By the morning of 20 April a cone had grown around the new vent that was breached, allowing for lava to move downslope and form a new flow field at the top of the Grandes Pentes. During 10-12 April lava fountains and spatter continued to build up the new cone while activity at the main cone was low, but produced significant gas emissions. Lava flow rates were as high as 15 cubic meters per second. The flow front did not significantly advance during 11-12 April and was between 1,345 and 1,370 m elevation. At 2310 on 12 April the tremor amplitude dropped sharply, indicating the end of the eruption. The Alert Level remained at 2.2 (on a 0-4 scale).

Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF)

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported an eruption at Poás on 10 April. An eruption signal was recorded on both seismic and acoustic instruments at 2243 that lasted for several minutes. Weather clouds and darkness prevented visual observations. Early on 11 April residents of Grecia reported minor amounts of ashfall on surfaces such as parked cars. 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 Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 6-12 April. An eruptive event on 9 April generated an ash plume that rose 1.5 km above the crater rim. Eruptive events at 0026, 1553, 1625, and 1648 on 10 April produced ash plumes that rose 1-1.5 km above the crater run and drifted NE and E. An ash plume from an explosion at 1204 on 11 April rose 3.4 km above the crater rim and drifted SE. Within an hour a moderate amount of ash fell in Kagoshima City (about 10 km W) and Tarumizu City (10 km SSE). An explosion at 0828 on 12 April generated an ash plume that rose 2.9 km above the crater rim and drifted S and NE. By 1400 moderate-to-heavy ashfall had fallen in Kagoshima City. 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 Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 9-14 April. Daily white-and-gray ash plumes rose 400-1,200 m above the summit and drifted 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 Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin?s summit crater during 8-14 April, with growth concentrated on the SW part of the flow. The seismic network recorded occasional small volcanic earthquakes and seismic signals from small rockfalls within the crater. Elevated surface temperatures were observed in satellite views during 11-14 April. 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 Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 8-14 April. The seismic network recorded 7-12 daily volcanic earthquakes during 8-11 April, including 1-5 daily periods of tremor lasting four minutes to two hours and 26 minutes. On 12 April there were 150 volcanic earthquakes and four periods of tremor (40 minutes to one hour and 40 minutes long), followed on 13 April by 102 volcanic earthquakes and two periods of tremor (33 and 56 minutes long). Sulfur dioxide emissions ranged from 610 to 2,470 tonnes per day. Emissions were visible daily that generally rose 400-1,200 m above the summit and drifted mainly SE, S, and SW. There were 1-5 daily periods of ash emissions recorded during 9-13 April. Five ash emissions occurred on 9 April with each lasting 5-47 minutes; one ash emission on 10 April lasted for two hours and 39 minutes; one ash emission on 11 April lasted for 54 minutes; three ash emissions on 12 April lasted for 47 minutes to just over two hours; and one ash emission on 13 April lasted for one hour and 13 minutes. 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 9-14 April. Activity at the S vent during 3-9 April including limited spattering, low dome fountains, and around 75 lava overflows. Beginning at 0225 on 9 April lava overflowed the N vent, followed by three more overflows. The last one began at 1008 and by 1110 had transitioned into a lava fountain. The fountain grew slowly and was about 100 m tall by 1200 and 190 m tall around 30 minutes later. An eruption plume rose 4.5 km (15,000 ft) a.s.l. and drifted N. At 1236 the Volcano Alert Level was raised to Warning (the highest level on a four-level scale) and the Aviation Color Code was raised to Red (the highest color on a four-color scale). By 1245 the fountain had reached a maximum height of 240 m. Tephra up to 25 cm in diameter fell within Hawai?i Volcanoes National Park, near Kilauea Military Camp, and into the adjacent Volcano Golf Course subdivision; ash and Pele?s hair was reported as far away as Kaumana (33 km NNE), just W of Hilo. Fountain height gradually dropped to 150 by late afternoon, the eruption plume was rising to 3 km (10,000 ft) a.s.l., and significantly less tephra fall was reported in areas to the NNE. Fountaining ended abruptly at 1941 after eight hours and 31 minutes of continuous activity at the N vent. The average effusion rate was 200 cubic meters per second; the highest peak was just over 390 cubic meters per second, occurring at around 1230. An estimated 7.5 million cubic meters of lava erupted and covered about 50 percent of the Halema?uma?u Crater floor. The S vent produced periodic gas jetting and flames. At 2002 the Volcano Alert Level was lowered to Advisory and the Aviation Color Code was lowered to Yellow. Both vents produced variable amounts of incandescence and gas emissions during 10-14 April.

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 8-14 April. A near-daily thermal anomaly was identified in satellite images. Satellite images showed small thermal anomalies along the active lava flow on the ENE flank on 11 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)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported periodic ash plumes at Lewotobi Laki-laki during 9-14 April. Daily white plumes rose as high as 500 m above the summit and drifted in multiple directions. Gray ash plumes recorded at 0724 and 2216 on 10 April, at 1958 on 12 April, and at 0824 on 13 April rose 100-500 m above the summit and drifted N, NE, S, and SW; an even was recorded at 1115 on 11 April but weather conditions prevented visual confirmation. Multiple ash plumes were visible on 14 April (at 0245, 0522, 0821, 1448, 1756, 1819, and 2107) rose 400-800 m above the summit and drifted W and SW. Minor incandescence at the summit was visible in a webcam image corresponding to the ash plume at 0245. The Alert Level remained at 2 (the second lowest level on a scale of 1-4) and the exclusion zone was a radius of 4 km from the center of Laki-laki.

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

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that the eruption at Mayon continued during 8-14 April, characterized by lava effusion, pyroclastic density currents (PDCs), incandescent rockfalls, ash plumes, and occasional minor Strombolian activity. Emissions were visible daily, rising 200-1,000 m above the summit and drifting in different directions. Each day the seismic network recorded 169-287 rockfalls, 0-3 PDCs, and 34-254 volcanic earthquakes. There were 5-36 periods of volcanic tremor, each lasting between one and 36 minutes. Daily measurements of sulfur dioxide emissions averaged 1,536-2,428 tonnes per day. The lava flows did not advance in the Mi-isi (S), Basud (E), and Bonga (SE) drainages, remaining 1.3, 3.8, and 3.2 km long, respectively. Minor Strombolian activity and short periods of lava fountaining were recorded daily. The number of evacuees did not change compared to the previous week; by 1800 on 14 April a total of 4,020 people (1,105 families) were staying in 12 evacuation shelters, and an additional 85 people (26 families) were staying with friends or relatives, according to the Disaster Response Operations Monitoring and Information Center (DROMIC). The Alert Level remained at 3 (on a 0-5 scale) and residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ). PHIVOLCS recommended that civil aviation authorities advise pilots to avoid flying close to the summit.

Sources: Disaster Response Operations Monitoring and Information Center (DROMIC),Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Merapi (on Java) continued during 9-14 April with occasional lava avalanches produced by the active lava dome on the upper SW flank. White plumes rose as high as 525 m above the summit on most days and drifted in different directions. On 9 April two lava avalanches descended the Sat/Putih drainage (W flank) as far as 1.5 km and two pyroclastic flows were detected by the seismic network. There were 15 lava avalanches that descended the Krasak drainage (W flank) as far as 1.5 km. On 11 April two pyroclastic flows traveled 1.5 km down the Boyong (S) drainage and 14 lava avalanches traveled as far as 2 km down the Sat/Putih drainage. The next day, on 12 April, one pyroclastic flow traveled 2 km down the Sat/Putih drainage and 26 lava avalanches descended the same drainage as far as 2 km. On 13 April one pyroclastic flow traveled 2 km down the Boyong drainage and four lava avalanches descended the Sat/Putih drainage as far as 1.7 km. Nine lava avalanches traveled as far as 1.7 km down the Krasak drainage on 14 April. 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.

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