Roundup of Global Volcanic Activity – Ongoing Activity for the Week 21 April 2021 – 27 April 2021
Aira – Kyushu (Japan) : JMA reported that during 19-26 April incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. There was a total of 16 explosions, producing ash plumes that rose as high as 2.3 km above the summit and ejected bombs 1-1.3 km away from the crater. The sulfur dioxide emission rate was somewhat high at 1,800 tons per day on 21 April. An explosion at 0109 on 25 April produced what was initially thought to be a pyroclastic flow, triggering JMA to warn residents beyond a 2-km radius to be cautious and vigilant. Scientists conducting field observations later that day did not observe pyroclastic flow deposits or damaged vegetation, and concluded that the plume phenomenon was generated by winds. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.
Ebeko – Paramushir Island (Russia) : Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 16-18 and 22 April that sent ash plumes to 3 km (10,000 ft) a.s.l. and drifted NE, E, and SW. Ash fell in Severo-Kurilsk on 16 April. The Aviation colour Code remained at Orange (the second highest level on a four-colour scale).
Etna – Sicily (Italy) : INGV reported that during 19-25 April activity at Etna was mainly characterized by gas emissions rising from the summit craters, though inclement weather conditions often prevented visual observations. Bocca Nuova in particular produced frequent steam puffs. A strong explosion at 0030 on 25 April from the E vent of Southeast Crater (SEC) ejected incandescent material up to 350 m above the crater rim. An ash plume dispersed to the S.
Fuego – Guatemala : INSIVUMEH reported that 5-14 explosions were recorded per hour during 21-27 April at Fuego, generating ash plumes as high as 1.1 km above the crater rim. Shock waves rattled buildings around the volcano, especially in areas as far as 20 km W and SW. Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Las Lajas (SE), and Honda drainages, often reaching vegetated areas. Ashfall was reported on most days in several areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Sangre de Cristo (8 km WSW), and San Pedro Yepocapa (8 km NW). Explosions ejected incandescent material 100-400 m above the summit almost daily.
Kilauea – Hawaiian Islands (USA) : HVO reported that the W vent on the inner NW wall of Kilauea’s Halema`uma`u Crater continued to supply the lava lake during 21-27 April. Lava flowed at a low rate from the main vent into the lake through crusted-over channels and submerged inlets. The depth of the lake was about 226-227 m and lava continued to circulate in the W part, though the active area continued to shrink; the E half of the lake remained solidified. Lava sometimes overflowed the margins of the lake. The sulfur dioxide emission rate was 350, 550, 300, and 350 tons/day on 21, 22, 23, and 24 April, respectively. The rates were the lowest measured during the eruption, though elevated above the levels recorded in the months before the start of the eruption (20 December 2020). The Aviation colour Code remained at Orange and the Volcano Alert Level remained at Watch.
Krysuvik-Trolladyngja – Iceland : IMO reported that the fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 21-27 April. A M 4.1 earthquake was recorded at 2305 on 21 April about 6 km WSW of the fissures and followed by several aftershocks; it was the largest on the Reykjanes Peninsula since 15 March, before the eruption began. The average lava-flow rate was calculated by the University of Iceland’s Institute of Earth Sciences using photographs most recently collected during an overflight on 26 April. They reported that during the previous five days the flow rate from all of the active craters averaged just over 6 cubic meters per second; the average rate during the 38 days of the eruption was 5.6 cubic meters per second. The area of the flow field was 1.13 square kilometers, the total volume was over 18.4 million cubic meters, with an average thickness of just over 16 m. The Aviation colour Code remained at Orange due to the lack of ash and tephra emissions.
Lewotolok – Lembata Island (Indonesia) : PVMBG reported that the eruption at Lewotolok continued during 20-27 April. Black, gray, and white plumes rose as high as 1 km above the summit and drifted E, SE, and W on most days. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater.
Merapi – Central Java (Indonesia) : BPPTKG reported that the lava dome just below Merapi’s SW rim and the lava dome in the summit crater both continued to extrude lava during 16-22 April. The SW rim lava-dome volume was an estimated 1,069,600 cubic meters on 21 April, with a growth rate of about 11,900 cubic meters per day; the dome continued to shed material down the flank. A total of nine pyroclastic flows traveled a maximum of 1.8 km down the SW flank. Incandescent avalanches, recorded 144 times, traveled as far as 1.6 km down the SW flank and twice down the SE flank as far as 400 m. The volume of the summit lava dome was 1,794,000 cubic meters on 22 April. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 5 km away from the summit.
Pacaya – Guatemala : INSIVUMEH reported that during 20-21 April explosions at Pacaya’s Mackenney Crater generated minor gas-and-ash plumes that rose 250 m above the summit and drifted S and SW. The lava flow on the SW flank continued to be active, though did not advance. White gas plumes were visible the next day rising as high as 200 m. On 23 April lava effusion ceased. The lava flows on the SW flank remained hot and gas plumes rose from parts of the flow; no advancement was visible through 27 April. Gray-and-white emissions were visible during 24-27 April, rising 100-200 m above the summit and dispersing S and SW. Occasional minor explosions ejected incandescent material 50-150 m high during 26-27 April.
Semeru – Eastern Java (Indonesia) : PVMBG reported that during 21-22 and 24-25 April ash plumes from Semeru rose 500-700 m above the summit and drifted SW, S, and SE. The Alert Level remained at 2 (on a scale of 1-4), with a general exclusion zone of 1 km and extensions to 5 km in the SSE sector.
Sheveluch – Central Kamchatka (Russia) : KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 16-23 April. The Aviation colour Code remained at Orange (the second highest level on a four-colour scale).
Sinabung – Indonesia : PVMBG reported that the eruption at Sinabung continued during 21-27 April. Weather conditions sometimes prevented visual observations of the volcano, though white fumarolic plumes were visible almost daily rising as high as 700 m above the summit and drifted E and SE. Pyroclastic flows traveled 2 km on 21 April. Avalanches of material traveled 1 km E and SE during 23-24 April. Ash plumes rose 2 km above the summit on 24 April and to 1 km on 25 April, drifting ESE both days. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.
Stromboli – Aeolian Islands (Italy) : INGV reported that during 19-25 April activity at Stromboli was characterized by ongoing explosive activity from Area N (North Crater area) and in Area C-S (South-Central Crater area), though sometime weather conditions prevented visual observations. Explosions from two vents in the N1 vent (Area N) ejected lapilli and bombs 250 m high, and produced minor ash emissions. Explosions at N2 vents (Area N) averaged 11-14 events per hour. Periods of visible spattering were most notable on 24 April. Explosions from at least three vents in Area C-S occurred at a rate of 1-5 events per hour and ejected coarse material more than 250 m high.
Suwanosejima – Ryukyu Islands (Japan) : JMA reported that incandescence from Suwanosejima’s Ontake Crater was occasionally visible at night during 16-23 April. Five explosions generated ash plumes that rose as high as 1.7 km above the crater rim and ejected bombs 600 m away. The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.
Villarrica – Chile : SERNAGEOMIN reported that during 1-15 April gas-and-steam emissions with no or very small amounts of ash rose from Villarrica to heights less than 1.2 km above the crater rim. Crater incandescence was not visible at night and sulfur dioxide emissions were low. Observations from multiple sources suggested that the lava lake level was lower, decreasing the likelihood that material ejected by minor explosions would reach beyond 100 m from the crater. The Alert Level was lowered to Green on 23 April, the lowest level on a four-colour scale. ONEMI declared a “Preventative Early Warning” for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli, and the exclusion zone for the public of 100 m around the crater.