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AVO reported that slow lava effusion continued at Great Sitkin during 23-30 May. A sequence of small low-frequency earthquakes was recorded for several hours on 23 May but did not result in any observed change in eruptive activity. Several small earthquakes were recorded daily during 24-27 May. No changes to the flow field were identified in satellite images acquired on 23, 27, or 28 May. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 22-29 May and incandescence at the crater was visible nightly. Daily ash plumes from eruptive events rose as high as 1.6 km above the crater rim and drifted in multiple directions. Blocks were ejected as far as 300 m from the crater. At 2245 on 23 May an explosion generated an ash plume that rose 600 m and drifted S. The Alert Level remained at 3 (on a 5-level scale) and residents were warned to stay 2 km away from the crater.

Source: Japan Meteorological Agency (JMA)

KVERT reported that the eruption at Sheveluch was ongoing during 18-25 May. A thermal anomaly over the active crater and Karan lava dome area was identified in satellite images all week. Intense fumarolic activity at the active crater was likely associated with dome growth. 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

KVERT reported that moderate activity at Ebeko was ongoing during 18-25 May. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions during 23-25 May generated ash plumes that rose as high as 3.5 km (11,500 ft) a.s.l. and drifted S, SE, and E. A thermal anomaly was identified in satellite images on 24 May and ash plumes were visible drifting 75 km SE on 25 May. 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

JMA reported ongoing activity at both Minamidake Crater and Showa Crater (Aira Caldera?s Sakurajima volcano) during 22-29 May. Crater incandescence was observed nightly at Minamidake, and during 25-29 May at Showa; incandescence at Showa had not been visible since 5 March. The only eruptive event at Showa during this period was at 1125 on 22 May, when material was ejected 200-300 m from the crater and an ash plume rose 1.5 km above the crater rim. At 0610 on 24 May an explosion at Minamidake ejected material 300-500 m from the crater and generated an ash plume that rose 1.5 km above the crater and drifted to the SW. An eruptive event at 1327 on 25 May produced an ash plume that rose 2.3 km. On 26 May two explosions (at 0647 and 1441) and an eruptive event (1311) generated ash plumes that rose as high as 1.6 km and drifted N and S. The explosion at 1441 ejected blocks 500-700 m from the vent. An explosion at 1520 on 28 May ejected material 600-900 m from the crater and produced an ash plume that rose 2.3 km from the summit . The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from both craters.

Source: Japan Meteorological Agency (JMA)

IG reported that moderate eruptive activity continued at Cotopaxi during 23-30 May. Seismic activity was mainly characterized by long-period earthquakes and tremors associated with emissions that occurred almost daily; a total of three volcanic-tectonic earthquakes were recorded during the week. Weather clouds often hindered views, though gas-and-steam emissions were visible daily. During 23-24 May ash-and-gas emissions rose as high as 1 km above the summit and drifted W. On 26 May a period of continuous ash emissions was recorded with the plumes rising as high as 2 km above the summit and drifting NW and W. On 30 May ash plumes rose 1.2 km and drifted W; ashfall was reported in the Pastocalle parish of Latacunga canton (Cotopaxi Province). Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) ,Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)

BPPTKG reported that the eruption at Merapi (on Java) continued during 19-25 May and seismicity remained at elevated levels. The SW lava dome produced 236 minor lava avalanches that traveled as far as 2 km down the SW flank (upstream in the Bebeng and Boyong drainages). Morphological changes to the SW lava dome due to continuing collapses of material were evident in webcam and drone images. Based on a 17 May drone survey, the SW dome volume was an estimated 2,372,800 cubic meters and the dome in the main crater was an estimated 2,337,300 cubic meters. 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: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)

PVMBG reported that the eruption at Semeru continued during 24-30 May. Volcano Observatory Notices for Aviation (VONAs) that described ash emissions were issued throughout the week. Daily sometimes-dense ash plumes rose as high as 1 km above the summit and drifted S, SW, W, and N. The Alert Level remained at 3 (third highest 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.

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

PVMBG reported that the eruption at Lewotolok continued during 24-30 May. Daily white-to-gray plumes of variable densities rose as high as 800 m above the summit and drifted E, NE, N, and NW. At 2037 on 27 May a webcam image showed an explosion of incandescent material above the summit. At 0613 on 29 May a dense gray-and-black ash plume rose 800 m above the summit and drifted NE and E. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the summit crater in all directions.

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

INSIVUMEH reported that 1-3 weak explosions per hour were recorded at Fuego on most days during 24-30 May. The explosions generated ash plumes that rose between 450-750 m above the summit. The plumes drifted as far as 10 km SE on 26 and 30 May, 10 km SE and S on 27 May, and 6 km SE and S on 29 May. Ashfall was reported in El Zapote (10 km SSE), La Rochela (8 km SSW), and San Andrés Osuna (12 km SSW) on 26 and 30 May. Minor crater incandescence was occasionally visible during some nights and early mornings. Minor lahars descended the Ceniza drainage on 25 and 28 May and a weak-to-moderate lahar descended the Santa Teresa on 29 May. Both lahars consisted of hot volcanic material, branches, tree trunks, and volcanic blocks as large as 1.5 m in diameter.

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

OVSICORI-UNA reported that phreatic explosions continued at Rincón de la Vieja during 24-30 May. Moderate phreatic events at 1815 and 1830 on 24 May produced voluminous gas-and-steam plumes possibly containing some lake sediments that rose about 2.5 km above the crater rim. Aerial photos from that day showed fairly low lake water levels. The water was a milky gray color and was convecting, partly due to of subaqueous fumaroles. White deposits comprised of altered rocks blanketed the active crater from eruptive activity in recent days. A strong phreatic explosion at 1435 on 25 May produced an ash, gas, and steam plume that drifted NW. Small phreatic events were recorded at 2230 on 25 May and at 0453 and 0704 on 26 May. During a 26 May overflight the lake water level was observed to have significantly dropped compared to 24 May. Phreatic eruptions were recorded at 1357 and 2348 on 26 May and at 0221 and 0632 on 27 May. An energetic eruption at 2135 on 27 May ejected incandescent material and generated a plume mainly comprised of water vapor that rose 3.5-4 km above the crater rim. A significant lahar descended the Pénjamo River and possibly other drainages. On 29 May OVSICORI-UNA noted that the volcano was very active with frequent explosive eruptions. At 0244 an explosion ejected incandescent material and generated a lahar in the Pénjamo River.

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

INGV reported that during 23-24 May activity at Etna was characterized by weak intra-crater explosive activity at the SE Crater and minor incandescence at Bocca Nuova Crater based on webcam images. A drone survey of the lava flows and tephra deposits emplaced during the 21 May paroxysmal eruption was conducted on 27 May. Lava flows had traveled 2.3 km, reaching 2,650 m elevation. During a field inspection on 28 May volcanologists observed gas emissions rising from Bocca Nuova and fumarolic activity at both Voragine Crater and NE Crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

On 28 May the Observatoire Volcanologique de Goma (OVG) reported that the lava flows on Nyamulagira?s upper W flank had begun to cool and solidify. By 29 May seismicity had returned to levels similar to those recorded before the 17 May increase in activity. Lava effusion continued but was confined to the summit crater; incandescence above the crater was periodically visible.

Source: Observatoire Volcanologique de Goma (OVG)

CENAPRED reported that during 23-30 May activity at Popocatépetl consisted of seismic tremors, very few minor and moderate explosions, near-constant emissions of steam, gas, and sometimes ash, and ejections of incandescent material. Overall activity slightly decreased during the week. A total of approximately 140 hours of high-frequency tremors of variable duration and intensity were recorded. A M 1.2 volcano-tectonic earthquake was recorded at 0340 on 24 May. Less than two hours later, at 0503, a minor explosion generated an ash plume that rose to 1 km above the summit and ejected incandescent material onto the flanks. A moderate explosion occurred at 1343. The Washington VAAC reported continuous ash emissions that rose 8.5-10.7 km (28,000-35,000 ft) a.s.l. and drifted SE. Ashfall was reported in Nealtican (21 km E), San Pedro Cholula (34 km E), San Andrés Cholula (36 km E), Tzicatlacoyan (65 km E), Tianguismanalco (22 km SE), Atlixco (25 km SE), Huaquechula (30 km SE), Ocoyucan (33 km SE), San Diego La Mesa Tochimiltzingo (39 km SE), San Juan Atzompa (71 km SE), Tehuitzingo (85 km SE), Tepexi de Rodríguez (88 km SE), Atzitzihuacán (23 km S), and Tilapa (48 km S). Emissions were sometimes continuous during the night of 24 May into the early morning of 25 May; the plumes drifted SE and were occasionally visible in webcam images. According to the VAAC ash emissions rose 7.6-8.5 km (25,000-28,000 ft) a.s.l. and drifted S, SSE, and SE. Ashfall was reported at 0045 in Atlixco, San Pedro Cholula, and the capital of Puebla. Minor ashfall was reported at 0600 in the municipality of Tetela del Volcan of Estado de Morelos. Incandescent material was ejected onto the flanks close to the crater on 25 May. The Secretary of Navy (SEMAR) conducted a drone flight during the morning of 25 May to collect information about crater activity for the Comité Científico Asesor (CCA), or Scientific Advisory Committee. During a meeting on 26 May that included the CCA, CENAPRED, CNPC, and other agencies it was shared that the drone footage of the crater showed no new lava dome, and that ash and incandescent material had significantly filled in the inner crater. Periods of continuous or nearly continuous ash emissions were recorded during 26-30 May and incandescent material was sometimes ejected short distances from the crater rim. At 1726 on 26 May a minor explosion generated steam, gas, and ash plume and ejected incandescent material. At 1926 on 29 May a minor explosion was recorded. During 26-30 May ash, steam, and gas emissions rose 5.2-7.9 km (17,000-26,000 ft) a.s.l. and drifted SE, E, and ESE according to the VAAC. Ashfall was reported in Nopalucan (87 km NE), San Pedro Cholula (34 km E), Cuautlancingo (38 km E), Puebla Capital, Amozoc (61 km E), Chietla (56 km S), Tlapanalá (39 km SE), Nopalucan (87 km NE), Tepexco (43 km S), Chila de la Sal (104 km S), Chila de las Flores (144 km SE), Tulcingo del Valle (111 km S), Atzala (53 km S), Xochiltepec (53 km SE), Yecapixtla (30 km SW), Amecameca (18 km NW), Atlixco, Atzitzihuacán (23 km S), Ayapango (21 km NW), San Pedro Benito Juárez (10-12 km SE), Acatlán de Osorio, Tlacotepec (110 km SE), Ecatzingo (15 km SW), Tochimilco (16 km SSE), Hueyapan (17 km SW), Tetela del Volcán, Tianguismanalco (22 km SE), Atlixco, Tenango del Aire (29 km NW), Huaquechula, Chautla (36 km NE), and Zacualpan (31 km SW). The eruption continued to impact residents. Air quality alerts were issued in Puebla on a few of the days during the first part of the week. According to the government of Puebla on 25 May the Ministry of Health warned residents to protect themselves from airborne ash with protective clothing and to stay inside when possible due to a reported increase in illnesses relating to ash exposure. By 26 May over one million students were able to return to classrooms.

Sources: Centro Nacional de Prevencion de Desastres (CENAPRED),Coordinación Nacional de Protección Civil (CNPC) ,Gobierno de Puebla, Cuenta Oficial de la Coordinación General de Protección Civil del Estado de Puebla

IG reported a high level of activity at Sangay during 23-30 May, though weather clouds sometimes prevented visual observations. There were 304-600 daily explosions recorded by the seismic network; no data was reported on 28 May. Ash plumes were seen in webcam images and reported by the Washington VAAC almost daily. On 23 May incandescent material extending 1.8 km down the SE flank was visible in webcam images. On 24 May pyroclastic flows descending 200 m were visible in between somewhat-dense weather clouds. An ash plume rose 300 m and drifted W. On 25 May ash plumes rose as high as 2 km and drifted NE and SE. Ash emissions were visible in webcam images at 1734 and were continuous for a period of time. Crater incandescence was visible overnight during 25-27 May and ash plumes that rose 500-800 m drifted SW and NW during 26-27 May. Incandescence from the lava flow on the SE flank was noted overnight during 28-29 May. The VAAC reported that at 0610 on 29 May ash plumes were visible in satellite images drifting W at 30,000 ft a.s.l., or 3.9 km above the summit, and drifting N at 40,000 ft a.s.l., or 6.9 km above the summit. Several pyroclastic flows descending the SE flank were visible in webcam images at 0615. At 1730 ashfall was reported in Cebadas Parish (Chimborazo province). Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) ,Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)

Unrest at Ahyi Seamount continued during 21-30 May. Underwater events were detected by pressure sensors on Wake Island (2,270 km E) at least during 24-25 and 28-30 May. The events were possibly related to underwater explosions or earthquakes at the volcano. No activity was visible in cloudy or partly cloudy satellite images. 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

Webcam images of Karangetang published in PVMBG daily reports periodically showed incandescence at Main Crater (S crater) and from material on the flanks of Main Crater during 23-30 May. Incandescence at the summit was most intense in the webcam images from 2332 on 26 May and 2304 on 29 May; the material on the flanks was brightest in the 29 May image. White gas-and-steam plumes were visible on most days rising as high as 150 m above the summit and rifting in various directions. The Alert Level remained at 3 (on a scale of 1-4) and the public were advised to stay 2.5 km away from Main Crater with an extension to 3.5 km on the S and SE flanks. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 2.5 km away from the craters on the S and SW flanks and 1.5 km away on the other flanks.

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

KVERT reported that eruptive activity at Bezymianny was generally characterized by lava effusion, gas-and-steam emissions, lava dome incandescence, and hot avalanches that traveled down the flanks during 24-30 May. A persistent thermal anomaly was identified daily in satellite data. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

PVMBG reported that Dukono continued to erupt during 24-30 May. Daily explosions were recorded by the seismic network. White-and-gray plumes of variable densities rose as high as 450 m above the summit and drifted E. The Alert Level remained at Level 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

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

IG reported that the eruption at Reventador was ongoing during 23-30 May. Seismicity was characterized by 28-43 daily explosions, long-period earthquakes, harmonic tremors, and emission-related tremors. Daily gas-and-ash emissions rose as high has 1 km above the crater and drifted SW, W, NW, and NE. On most nights incandescent blocks were seen rolling 500-1,000 m down the flanks; incandescence at the crater and on the upper flanks was also periodically visible. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Orange (the second highest level on a four-color scale).

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) ,Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)

MARN reported that seismicity at San Miguel was detected on 23 May and remained elevated. At 1647 on 27 May an explosion generated a gas-and-ash plume that rose 700 m; seismicity decreased afterwards. Sulfur dioxide emissions were as high as 400 tons per day that same day based on measurements from an instrument located on the W flank, and then decreased to 268 and below 100 tons per day on 28 and 29 May, respectively. MARN warned the public to stay at least 3 km away from the crater.

Source: Ministerio de Medio Ambiente y Recursos Naturales (MARN)

INGV reported ongoing activity at Stromboli during 22-28 May. The Strombolian activity was centered at two vents in Area N (one each at craters N1 and N2), within the upper part of the Sciara del Fuoco, and from four vents in Area C-S (South-Central Crater) in the crater terrace. Low-intensity explosions at a rate of 3-7 per hour from Area N ejected mainly coarse material (bombs and lapilli) from N2, with mainly ash emissions from N1 as high as 80 m above the vents. Low- to medium-intensity explosions at an average rate of 2-7 per hour from the two vents in sector S2 (Area C-S) ejected a mix of coarse material and ash. During 27-28 May intense gas emissions at S1 sometimes contained coarse material. Intense spattering and occasionally weak explosions of coarse material was observed in sector C (Area C-S).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

GeoNet reported that earthquake activity and ground deformation at Taupo declined during January-April and returned to background levels in May. The Volcanic Alert Level was lowered to 0 (the lowest level on a six-level scale) on 30 May and the Aviation Color Code remained at Green (the lowest level on a four-color scale). Unrest at the volcano started in early May 2022; during the year there were just over 1,800 earthquakes located beneath the volcano along with ground deformation both on the lake floor and around the lake.

Source: GeoNet