Volcanos

Roundup of Global Volcanic Activity – New Activity for the Week 14 April 2021 – 20 April 2021

Karymsky – Eastern Kamchatka (Russia) : KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 9-12 April; weather conditions obscured views during 13-16 April. An explosion at 1745 on 11 April produced ash plumes that rose to 4 km (13,100 ft) a.s.l. and drifted 112 km SSE. The Aviation colour Code remained at Orange (the second highest level on a four-colour scale).

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 14-20 April. Lava flowed from about eight vents and the flow field continued to expand; on 14 April a new hiking trail (“A”) had been covered. Volcanic gas emissions were at dangerous levels during 14-15 April so the eruption site was closed to the public. At about 1500 on 17 April a new vent was confirmed to have opened. It was small and close to another crater, possibly the one that had opened on 13 April. Lava was not flowing from the northernmost crater (the first that had opened outside Geldingadalur) during 18-20 April. The eruption had been ongoing for 30 days by 17 April. Based on a report from University of Iceland’s Institute of Earth Sciences, the average lava-flow rate during the first 17 days of the eruption was 4.5-5 cubic meters per second but had increased to 7 cubic meters per second over the previous 13 days. During 12-18 April the flow rate was closer to 8 cubic meters per second, a slight increase over the recent average. By 19 April the area of the flow field was 0.9 square kilometers and the total volume was over 14 million cubic meters. IMO warned visitors that new fissures could open without adequate visible warning, especially in an area by Litla-Hrút, just S of Keilir, `where seismicity was concentrated. They also warned of increased gas emissions hazards. The Aviation colour Code remained Orange due to the lack of ash and tephra emissions.

Piton de la Fournaise – Reunion Island (France) : OVPF reported that the eruption at Piton de la Fournaise continued during 14-20 April. Lava fountaining was visible from both cones on most days, though sometimes inclement weather prevented visual observations of the eruption site. During an overflight on 16 April scientists observed that the most distal part of the lava flows had stopped advancing. The larger and more northern cone was 28 m high. The cone at a lower elevation, about 100 m away, had two vents. The smaller cone fed lava flows that traveled though tubes and emerged after 100 m, continuing to advance as many surficial breakout flows. The total length of the flow field was about 3.5 km and the maximum width was 750 m. Sulfur dioxide emissions gradually increased between 400 and 859 tonnes per day during 9-12 April, peaked at 4,054 tonnes per day on 13 April, and then dropped to 2,100 tonnes per day on 14 April. OVPF estimated lava-flow rates based on the gas-emission rates, noting that weather conditions could affect the accuracy of the measurements. They estimated that the average flow rate in cubic meters per second was 20 during 9-10 April, an average of 24 with a maximum value of 59 on 13 April, 12.5 on 14 April, and 6.5-8.3 during 16-19 April. The Alert Level was raised to 2-2.

Soufriere St. Vincent – St. Vincent : University of the West Indies Seismic Research Centre (UWI-SRC) and National Emergency Management Organisation (NEMO) reported that the explosive eruption at Soufrière St. Vincent (often simply referred to as “La Soufriere”) continued during 14-20 April, though at a decreasing frequency. Explosions and pyroclastic flows were reported on 13 April, as well as lahars in the Sandy Bay area. During 14 April seismicity continued to be characterized by episodes of tremor, about 13-15 hours apart, separated by swarms of small, long-period (LP) earthquakes. An episode of tremor that began at 1135 was associated with increased explosive activity, though the emissions were gas rich and less energetic than previous events. Another episode of tremor began at 0230 on 15 April along with increased venting. Almost constant swarms of long-period and hybrid events were recorded through the day, punctuated by three brief episodes (less than 30 minutes) of low-level tremor. An episode of tremor began at 2100 and lasted 40 minutes, and was possibly associated with a minor increase in venting. For the first time sulfur dioxide emissions were successfully measured by ground-based instruments; scientists recorded 809 tons per day from a Coast Guard boat along the W coast. Periods of tremor and near-constant swarms of LP and hybrid events were recorded on 16 April. An explosion at 0615 on 16 April generated an ash plume that rose about 8 km (26,200 ft) a.s.l. and drifted W. A three-minute period of high-level tremor started at the same time and was flowed by over two hours of lower-level tremor. Sulfur dioxide emissions were again measured from the W coast, yielding a flux of 460 tons per day. The rate of LP and hybrid events dropped significantly at 2000. Sulfur dioxide plumes reached India. Occasional satellite images of the summit showed a series of changes to the new crater, centered in the SW part of the summit crater. By 17 April an Institut de Physique du Globe de Paris scientist reported that the crater was about 900 m N to S, at least 750 m E to W, and about 100 m deep based on RADAR data. Several vents were either visible or inferred from points of emissions. Sulfur dioxide emissions were 232 and 391 tons per day on 17 and 18 April, respectively. A period of high tremor began at 1649 on 18 April. An explosion produced an ash plume that rose to 8 km (26,200 ft) a.s.l. and drifted S and SW. This explosion occurred 52 hours after the last one and was the 30th since the explosive phase started. The period of tremor lasted until about 2100 and was followed by ongoing small LP and hybrid events. The rates of those events dropped again, at around 0100 on 19 April. One rockfall was detected by the seismic network at 0139, and two were noted the next day. At 0400 on 20 April a lahar was detected by the seismic network and lasted for 30 minutes; it possibly traveled down the SE flank. During 15-19 April NEMO reported details about the people that have evacuated. The total number of displaced people was 12,775 by 19 April, with 6,208 people in 85 public shelters and 6,567 people (1,800 families) in private shelters. There were no casualties caused by the eruption.

Semisopochnoi – Aleutian Islands (USA) : AVO reported that an eruption at Semisopochnoi continued during 14-20 April. Sulfur dioxide emissions were identified in satellite images during 13-14 April. An explosion was recorded by the regional infrasound network at 0417 on 14 April, though weather cloud cover as high as 4 km (13,000 ft) a.s.l. prevented satellite confirmation of an ash plume. Ash emissions began during the morning of 15 April and continued through the day, drifting more than 350 km SE at altitudes as high as 6 km (20,000 ft) a.s.l. They did not decrease in intensity, so at 1915 AVO raised the Aviation colour Code to Red and the Volcano Alert Level to Warning. Sustained ash emissions continued on 16 April, though the plume rose as high as 3 km (10,000 ft) a.s.l. and winds pushed it N. Explosions were detected through the night and early in the morning. Minor ash deposits around the volcano were visible. Eruptive activity declined during 16-17 April; one clear satellite view suggested that activity had declined or ceased. At 1249 on 17 April AVO lowered the Aviation colour Code to Orange and the Volcano Alert Level to Watch. Several explosions were recorded during 17-19 April though weather clouds obscured views. Volcanic plumes were visible just above the weather cloud deck (situated at 3 km (10,000 ft) a.s.l.) and drifted S during 19-20 April. A few darker (possibly ash rich) plumes were visible in satellite data at 0700 and 1150 on 19 April and on 20 April.

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