Volcanos

Roundup of Global Volcanic Activity – Ongoing Activity for the Week 28 April 2021 – 4 May 2021

Aira – Kyushu (Japan) : JMA reported that during 26 April-3 May incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. There was a total of 10 explosions, producing ash plumes that rose as high has 2.4 km above the summit and ejected bombs 1.3-1.7 km away from the crater. 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 22-24 April that sent ash plumes to 3 km (10,000 ft) a.s.l. and drifted NE and SW. The Aviation colour Code remained at Orange (the second highest level on a four-colour scale).

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 28 April-4 May through a submerged inlet. The depth of the lake was about 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 and comprised about 93 percent of the total area, based on thermal measurements acquired on 16 April. The sulfur dioxide emission rate was 250 and 475 tons/day on 30 April and 2 May, respectively, continuing a downward trend that began in mid-April; the recent rates suggested that the effusion rate had also decreased. 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 28 April-4 May. According to a news source, activity at the S vent of the fifth cone, which had opened on 13 April with N and S vents, intensified at around 2030 on 26 April. Fountaining became more explosive and lava was jetted 40-50 m high. The lava-flow rate significantly increased; lava flowed S then E and descended a valley into Meradalir. By 29 April activity had intensified at the fifth cone where lava ejections reached 250 m high, but had ceased at the others. By 1 May lava flows had traveled N in Meradalir and connected to the flows that had previously descended into the valley from a fissure that opened on 5 April. IMO noted that fountaining at the vent was steady until around 0000-0100 on 2 May when it became more pulsating. Resting periods of 1-2 minutes were punctuated by intense fountaining reaching 100-150 m high for periods of 8-12 minutes. Gas plumes with minor amounts of ash rose 800-900 m a.s.l. A news source noted that on 2 May lava fountains rose over 300 m, the highest to date, and were seen from Reykjavik. Ejecta set fire to vegetation on the hill to the S of the vent, causing a smoke plume. The Aviation colour Code remained at Orange due to the lack of ash and tephra emissions.

Lewotolok – Lembata Island (Indonesia) : PVMBG reported that white plumes from Lewotolok rose as high as 500 m and drifted SE, SW, and W on most days during 27 April-3 May. Gray-and-white plumes rose 500 m and drifted W on 30 April and 2 May. 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 23-29 April. The SW rim lava dome had an estimated volume of 1,141,850 cubic meters on 28 April, with a growth rate of about 11,900 cubic meters per day, and continued to shed material down the flank. A total of 12 pyroclastic flows traveled a maximum of 2 km down the SW flank. Incandescent avalanches, recorded 113 times, traveled as far as 2 km down the SW flank. The volume of the summit lava dome was 1,794,000 cubic meters on 28 April, unchanged from the previous week. Electronic Distance Measurement (EDM) data showed a distance shortening between points in the NW at a rate of 0.5 cm per day, indicating inflation. 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 27-29 April occasional explosions at Pacaya’s Mackenney Crater ejected incandescent material as high as 250 m above the summit. On 27 April a lava flow emerged from a new fissure on the upper SE flank traveled 200 m. At around 0500 on 29 April the seismic network recorded signals indicating a change from mostly explosive to mostly effusive activity. At around 0645 a new fissure opened on the N flank, producing a lava flow that rapidly traveled N towards Cerro Chino and then turned S and spread W and SW. Explosive activity at the fissure was minor during 29-30 April. By 3 May the flow was almost 2.1 km long, and continued to advanced W and SW at least through 4 May.

Semeru – Eastern Java (Indonesia) : PVMBG reported that at 0740 on 28 April an ash plume from Semeru rose 600 m above the summit and drifted SW. The next day, at 0550, an ash plume rose 400 m and drifted S. 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 23-30 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 28 April-4 May. Weather conditions sometimes prevented visual observations of the volcano, though white fumarolic plumes were visible almost daily rising as high as 500 m above the summit and drifted in multiple directions. At 0728 on 28 April an ash plume rose 1 km and drifted SSW. At 1810 an ash plume rose 1 km and drifted SSE and an incandescent avalanche descended 1.5 km down the SSE flank. At 2346 an ash plume rose 1.5 km and drifted W and SW, and another incandescent rockfall traveled 1.5 km SSE. Eruptive events produced ash plumes that rose 500-1,000 m above the summit during 30 April-1 May. Avalanches of material traveled as far as 1.5 km E and 1 km SE during 1-3 May. 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.

Soufriere St. Vincent – St. Vincent : University of the West Indies Seismic Research Centre (UWI-SRC) reported that seismicity at Soufrière St. Vincent (often simply referred to as “La Soufriere”) remained low during 28 April-4 May, with a few long-period, hybrid, and volcano-tectonic earthquakes recorded daily. Multiple significant lahars were generated by rainfall during 28-29 April. Lahars likely descended all valleys in the Red and Orange zones, and some were hot and visibly steaming. Trees brought down by lahars were swept to the sea; floating logs created hazardous conditions for small boats along the coastline. UWI-SRC and the National Emergency Management Organisation (NEMO) both warned the public to stay away from drainages and areas prone to flooding, and noted that lahars have caused notable erosion and damage to drainages and parts of the coastline. Smaller lahars were recorded during the mornings of 30 April and 1 May. Multiple lahars were detected in likely all the volcano’s drainages for a period of about six hours on 3 May, with the most intense lahars occurring during 1100-1200. Sulfur dioxide emissions were measured from a boat near the W coast, yielding a flux of 1,036 tons per day. Photos showed people in Sandy Bay shoveling off ash from rooftops on 4 May. The volcano Alert Level remained at Red.

Suwanosejima – Ryukyu Islands (Japan) : JMA reported that 45 explosions at Suwanosejima’s Ontake Crater produced eruption plumes that rose as high as 1.7 km above the crater rim during 23-30 April. Large volcanic bombs were ejected 400 m from the crater. Nighttime crater incandescence was visible during 24-25 April. The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.

Taal – Luzon (Philippines) : PHIVOLCS reported that unrest at Taal continued during 27 April-4 May. Low-level background tremor that had begun at 0905 on 8 April continued, along with 2-26 daily low-frequency events and 5-37 daily volcanic earthquakes during 28 April-2 May. One hybrid event was detected during 28-29 April. Diffuse steam plumes from fumarolic vents in Main Crater rose 5-10 m on most days. Average daily sulfur dioxide emission rates were in the 1,452-3,191 tonnes per day range. Upwelling of hot volcanic fluids in the crater lake was accompanied by steam plumes that were 300-600 m tall on 27 April, 30 April, and 4 May. The Alert Level for Taal remained at 2 (on a scale of 0-5). PHIVOLCS strongly recommended no entry onto the island, and access to the Main Crater and Daang Kastila fissure (along the walking trail) was strictly prohibited.

Whakaari/White Island – North Island (New Zealand) : GeoNet reported that a brief period of low-energy tremor and acoustic signals was recorded at Whakaari/White Island beginning at 2230 on 29 April. During an overflight on 30 April scientists did not observe new deposits near the active vent or thermal anomalies at the active vent area. Gas-emission rates had been relatively unchanged since March. The brief period of increased activity was likely caused by a series of low-energy subterranean explosions, similar to activity observed in mid-February and early-mid March. Seismic tremor remained at background levels. The Volcanic Alert Level remained at 1 and the Aviation colour Code remained at Green.

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