KVERT reported that over the past few weeks a minor amount of ash was present in Karymsky’s gas-and-steam plumes and trace ash deposits were visible on the surrounding snow. A very weak thermal anomaly was identified in satellite data on 6 April. The Tokyo VAAC reported that on 18 April an ash plume rose to 1.5 km (5,000 ft) a.s.l. and drifted SE based on satellite data and information from UHPP (Petropavlovsk-Kamchatsky Airport). The Aviation Color Code was raised to Yellow (the second lowest level on a four-color scale) on 19 April.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Tokyo Volcanic Ash Advisory Center (VAAC)

PVMBG reported that during 13-19 April dense gray eruption plumes from Anak Krakatau rose as high as 50 m above the crater rim, and white plumes rose 25-100 m above the summit. Satellite data acquired on 15 April revealed new lava flows from the 10-11 April eruption covering the vent and extending the coastline W. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km-radius hazard zone from the crater.

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

An increased number of volcanic earthquakes over a few days prompted PVMBG to issue a VONA on 15 April and raise the Aviation Color Code for Lokon-Empung to Yellow (the second lowest on a four-color scale). The volcano Alert Level remained at 2 (on a scale of 1-4). Residents and tourists were reminded not to approach the crater within a radius of 1.5 km.

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

PVMBG reported that the eruption at Semeru continued during 1-16 April. Eruptive events produced gray ash plumes that rose 400-600 m above the summit. Additionally, gray-to-white gas plumes from Jonggring-Seloko Crater rose 200-400 m; incandescent material was ejected 10-20 m above the crater. Incandescent lava flows traveled 500-1,000 m down the Kembar, Bang, and Kobokan drainages (on the S flank). At 0608 on 17 April a pyroclastic flow descended 2 km along the Bang drainage. Ash plumes drifted N, SE, and SW during 15-16 and 20-21 April. The Alert Level remained at 2 (on a scale of 1-4), and the public was reminded to stay outside of the general 1-km radius from the summit and 4 km on the SSE flank.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC)

JMA reported that during 13-20 April incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. The seismic network occasionally recorded very small eruptive events and three explosions. Ash plumes rose as high as 2.5 km above the crater rim. The sulfur dioxide emission rate was high at 1,700 and 2,000 tons/day on 14 and 17 April, respectively. The Alert Level remained at 3 (on a 5-level scale).

Source: Japan Meteorological Agency (JMA)

JMA reported that eruptive activity at Asosan was recorded during 13-20 April. Gray-white ash plumes rose 800-1,100 m above the crater rim and caused ashfall in areas downwind. The sulfur dioxide emission rate was somewhat high at 1,600 and 1,200 tons per day on 14 and 16 April, respectively. The Alert Level remained at 2 (on a scale of 1-5).

Source: Japan Meteorological Agency (JMA)

KVERT reported that a thermal anomaly over Bezymianny was identified in satellite images during 10-17 April. Gas-and-steam emissions persisted. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Based on satellite and wind model data, the Darwin VAAC reported that during 15-21 April ash plumes from Dukono rose to 2.1 km (7,000 ft) a.s.l. and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Sources: Darwin Volcanic Ash Advisory Centre (VAAC), Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions on 13 April that sent ash plumes up to 2.5 km (8,200 ft) a.s.l. Ash plumes drifted SE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

KVERT reported that Strombolian activity at Klyuchevskoy was visible during 10-17 April along with a bright thermal anomaly identified in satellite images. Gas-and-steam plumes with some ash rose to 6 km (19,700 ft) a.s.l. and drifted 200 km S and E on those same days. The Aviation Color Code remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

JMA reported that during 13-20 April very small eruptive events at Kuchinoerabujima’s Shindake Crater produced grayish-white plumes that rose 600 m above the crater rim. An event at 0147 on 20 April generated a grayish-white plume that rose 800 m and drifted SE. The Alert Level remained at 3 (the middle level on a scale of 1-5).

Source: Japan Meteorological Agency (JMA)

PVMBG reported relatively quiet conditions at Merapi during 13-19 April. White plumes of variable densities rose as high as 300 m above the crater that had formed on 10 April. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to stay outside of the 3-km exclusion zone.

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

ONEMI and SERNAGEOMIN reported that an explosive event at Nevados de Chillán’s Nicanor Crater recorded at 1333 on 21 April was associated with a long-period earthquake signal. The explosion produced a gas-and-ash plume that rose 2.4 km above the vent and drifted SE. The Alert Level remained at Yellow, the second lowest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián, and stated that the public should stay at least 3 km away from the crater on the SW flank and 5 km away on the ENE flank.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI)

OVSICORI-UNA reported periodic hydrothermal explosions at Rincón de la Vieja during 15-21 April. At 0306 on 15 April a phreatic eruption was recorded by the seismic network; weather conditions prevented visual confirmation, though local residents reported lahars in the Pénjamo, Azufrada, and Azul rivers. A steam plume from a phreatic event at 0929 on 18 April rose 200 m above the crater rim. Several small events were detected during the morning of 19 April but none produced plumes that rose above the rim. At 1014 a phreatic eruption ejected water and sediment 300 m above the crater rim and onto the flank, and produced a steam-and-gas plume that rose 1.5 km above rim. A lahar followed the activity. During 20-21 April several low-energy puffs of gas-and-steam were recorded. A low-energy event at 0626 on 21 April generated a steam plume that rose 1 km above the crater rim.

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

Instituto Geofísico del Perú (IGP) reported that a daily average of 11 explosions occurred at Sabancaya during 13-19 April. Gas-and-ash plumes rose as high as 3.9 km above the summit and drifted NW, S, and SE. There were eight thermal anomalies identified in satellite data, originating from the lava dome in the summit crater. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Source: Instituto Geofísico del Perú (IGP)

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 10-17 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

On 16 April AVO reported that seismicity at Shishaldin had decreased during the past two weeks, though it remained slightly above background levels. Additionally, satellite images showed no new lava nor changes in the crater area, and a decrease in surface temperatures. The Volcano Alert Level was lowered to Advisory and the Aviation Color Code was lowered to Yellow.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

JMA reported that during 10-17 April incandescence from Suwanosejima’s Ontake Crater was visible nightly. Small eruptions occasionally occurred, along with an explosion on 15 April, producing gray-white plumes that rose as high as 1 km above the crater rim; plumes drifted N on 15 April. Rumbling sounds were noted in a village 4 km SSW. The Alert Level remained at 2 (on a 5-level scale).

Sources: Japan Meteorological Agency (JMA), Tokyo Volcanic Ash Advisory Center (VAAC)

On 16 April GeoNet reported that data collected from Whakaari/White Island came from instrumentation on the island only, including seismic stations, webcams, and sulfur dioxide gas emission sensors; no overflights had been conducted over the past three weeks. GeoNet concluded that there were no significant changes in sulfur dioxide flux, seismicity remained low, and the active vents area appeared unchanged since early March. High temperatures from the vent area were apparent at night. The Volcanic Alert Level remained at 2 and the Aviation Color Code remained at Yellow.

Source: GeoNet