Roundup of Global Volcanic Activity – Ongoing Activity for the week of 19 April – 25 April 2023
Ahyi – Mariana Islands (USA) : On 26 April both the Aviation Color Code and the Volcano Alert Level for Ahyi Seamount were lowered to Unassigned because signs of unrest had decreased, and no indication of submarine volcanic activity had occurred for at least four weeks. Observations of discolored water near the seamount were last identified in satellite images in late March 2023, and underwater activity based on acoustic signals had been negligible since early April 2023.
Aira – Kyushu (Japan) : JMA reported ongoing eruptive activity at Minamidake Crater during 17-24 April, with crater incandescence visible nightly. Two eruptive events on 17 April produced ash plumes that rose 1-1.5 km and drifted S. That same day sulfur dioxide emissions were somewhat high at 1,900 tons per day. Very small eruptive events occasionally occurred during 21-24 April.
Ambae – Vanuatu : Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that at 0730 on 19 April a plume consisting of steam, sulfur dioxide gas, and ash rose 695 m above Ambae’s summit and drifted E and SE, based on an image from a webcam located 22 km NE on the NE tip of Ambae Island, in Saratamata.
Cotopaxi – Ecuador : IG reported ongoing moderate eruptive activity at Cotopaxi during 18-25 April. Cloudy weather sometimes prevented webcam and satellite views, but daily emissions of steam-and-gas rising as high as 1.5 km were seen in webcam images. Small ash-and-gas emissions were visible during 21-22 April. An ash plume first seen at 0953 on 24 April rose up to 3 km above the summit and drifted NE. Later that afternoon and evening ash-and-gas emissions rose 350 m and drifted N. At 1600 the seismic station recorded a small secondary lahar that descended the Cutzalao/Agualongo drainage on the SW flank.
Ebeko – Paramushir Island (Russia) : KVERT reported that moderate activity at Ebeko was ongoing during 13-20 April and a thermal anomaly was identified in satellite images during 14-15 April. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), and satellite data, explosions during 14-16 April generated ash plumes that rose as high as 3.5 km (11,500 ft) a.s.l. and drifted 104 km NE. Weather clouds prevented satellite views on the other days of the week.
Fuego – South-Central Guatemala : INSIVUMEH reported that 4-12 explosions per hour were recorded at Fuego during 18-25 April, generating daily ash plumes that rose as high as 1 km above the crater rim and drifted as far as 65 km SW, S, SE, and E. Ashfall was recorded each day in areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), La Rochela, Santa Sofía (12 km SW), San Andrés Osuna, Ceilan, Finca La Asunción, Ceylon, El Zapote (10 km S), Aldeas, El Rodeo and other nearby communities. Daily block avalanches descended multiple drainages including the Santa Teresa, Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Honda, Las Lajas (SE), and El Jute (ESE), and often reached vegetated areas. Daily shock waves rattled structures in communities around the volcano and rumbling was often heard. Explosions ejected incandescent material as high as 350 m above the summit on most days. During 22-23 April the avalanches remobilized ash deposits causing a plume that rose 100 m and drifted S and SE. On 23 April lahars in the Ceniza drainage carried branches, tree trunks, and blocks 30 cm to 1.5 m in diameter.
Great Sitkin – Andreanof Islands (USA) : AVO reported that lava continued to slowly erupt at the summit of Great Sitkin during 19-25 April. Weather clouds often obscured satellite and webcam views during most of the week. Seismicity was low, and during 21-22 April only a few small events were detected. Satellite data last acquired on 14 April showed that the thick lava continued to expand towards the E and remained confined to the summit crater.
Karangetang – Sangihe Islands : PVMBG reported that the effusive eruption which began around 1700 on 8 February at Karangetang’s Main Crater (S crater) produced lava flows and lava avalanches that traveled as far as 2 km down the SW and S flanks in drainages leading to the Beha, Batang, Timbelang, Batuawang, and Kahetang rivers. Effusion ended on 1 April and avalanches of material were no longer detected. Seismic signals indicating effusion decreased and by 6 April were no longer being detected. Incandescence at both Main Crater and Crater II (N crater) was visible at night during 1-25 April. White gas plumes were seen rising as high as 200 m above the summit and drifted in multiple directions; weather clouds sometimes prevented views.
Katmai – Alaska : AVO reported that during the morning of 23 April, strong NW winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes dispersed unconsolidated ash up to 1.8 km (6,000 ft) a.s.l. to the SE across Shelikof Strait to Kodiak Island. The ash was originally deposited during the Novarupta-Katmai eruption in 1912.
Lewotolok – Lembata Island : PVMBG reported that the eruption at Lewotolok was ongoing during 19-25 April. On 19, 21, and 23 April white-and-gray plumes rose 200-700 m and drifted E, NE, N, and NW. White steam-and-gas plumes of variable densities were seen during 20, 22, and 24-25 April rising as high as 500 m above the summit and drifting SW, W, and NW. Crater incandescence was visible in webcam images posted with the reports during 21-22 April.
Merapi – Central Java : BPPTKG reported that the eruption at Merapi (on Java) continued during 19-25 April and seismicity remained at high levels. The SW lava dome produced more than 80 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 were evident in webcam images due to continuing collapses of material.
Reventador – Ecuador : IG reported that the eruption at Reventador was ongoing during 19-25 April. Seismic activity was not characterized due to technical problems. Steam, gas, and ash plumes were observed in IG webcam images and described in Washington VAAC advisories on most days; weather conditions occasionally prevented views. The plumes rose as high as 1.6 km above the summit and drifted E, SE, W, and SW. Crater incandescence was visible at night during 20-21 April.
Sabancaya – Peru : Instituto Geofísico del Perú (IGP) reported moderate levels of activity at Sabancaya during 17-23 April with a daily average of 31 explosions. Gas-and-ash plumes rose as high as 2.5 km above the summit and drifted NW, W, SW, and S. Six thermal anomalies originating from the lava dome in the summit crater were identified in satellite data.
Santa Maria – Southwestern Guatemala : INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 18-25 April. Effusion from the Caliente dome complex fed lava flows that descended the San Isidro and Zanjón Seco drainages on the W and SW flanks; the main lava flow was 4.3 km long and remained active. Incandescence from the dome and the lava flows was frequently visible at night. Daily avalanches descended multiple flanks of the dome and were also occasionally generated from the lava-flow front and margins. Daily weak or weak-to-moderate explosions recorded by the seismic network generated ash plumes that rose as high as 1 km above the complex and drifted mainly S and SW. During 18-19 April ash fall was reported in Finca El Faro (6.7 km S). On 21 April quiet rumbling sounds were barely heard on nearby farms.
Semeru – Eastern Java : PVMBG reported that the eruption at Semeru continued during 18-25 April and frequent Volcano Observatory Notices for Aviation (VONAs) describing ash emissions were issued through the week. On 19 April at 0710 and 0829 dense white-and-gray ash plumes rose 800-1,000 m above the summit and drifted S. On 20 April at 0616, 0619, 0805, and 0902 white-and-gray variable density ash plumes rose 300-1,000 m and drifted N and NW. At 0534 on 21 April a white-to-brown ash plume rose 600 m and drifted NE and at 0640 a dense white-and-gray ash plume rose 700 m and drifted SW. On 23 April at 0448, 0553, 0643, and 0731 gray ash plumes of variable densities rose 400-1,000 m and drifted SE, S, SW, and W. On 25 April at 0519, 0710, and 0756 dense gray ash plumes rose 500-800 m and drifted NW, W, and SW.
Semisopochnoi – Aleutian Islands (USA) : AVO reported that low-level unrest continued at Semisopochnoi during 18-25 April. Daily periods or bursts of tremor and occasional low-frequency earthquakes were detected during the week. Small explosions were detected in seismic and infrasound data during 18-19 and 24-25 April. Cloudy weather prevented webcam and satellite views on most days. Possible recent ash deposits on Mount Young’s crater rim were visible in clear webcam images during 22-23 April, and steam emissions from the active N crater were visible during 22-25 April.
Suwanosejima – Ryukyu Islands (Japan) : JMA reported that the eruption at Suwanosejima’s Ontake Crater continued during 17-24 April. No explosions were recorded, but eruptive activity produced periodic ash plumes and ejected blocks as far as 300 m from the vent. On 17 April ash plumes rose 1-1.5 km above the crater rim and drifted E and SE, and on 18 April an ash plume rose 2 km and drifted N. Ashfall was reported in Toshima village (3.5 km SSW) during 17-21 April. On 23 April an ash plume rose 1.1 km and drifted SW.