Roundup of Global Volcanic Activity – New Activity for the Week 29 September – 5 October 2021

Kilauea – Hawaiian Islands (USA) : Seismicity abruptly increased below Kilauea’s summit at about 1400 on 29 September. Around 30 minutes later the earthquakes became more intense, frequent, and shallower, and deformation patterns rapidly changed. The data suggested an upward movement of magma that prompted HVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch at 1509. A new eruption was identified at 1521 when incandescence from Halema`uma`u Crater became visible in webcam views; HVO raised the Aviation Color Code to Red and the Volcano Alert Level to Warning. Fissures opened along the bottom of Halema`uma`u Crater floor and produced lava fountains and flows. A photo taken at 1615 showed a large plume comprised of steam, carbon dioxide, and sulfur dioxide rising from the fissures. Measurements just after the eruption started showed sulfur dioxide emissions of around 85,000 tonnes/day. At about 1640 another fissure with several vents opened on the inner W wall of the crater and produced low lava fountains and flows that descended to the crater floor. The vent expanded by 1709. Lava from both fissures pooled on the solidified lava lake surface and quickly began to overturn and create a lava lake. Tephra was deposited in areas SW of the crater and collected by HVO scientists for analysis. The tallest lava fountain was near the S end of the lava lake and rose 20-25 m during the night of 29-30 September. During a helicopter overflight around 0730 on 30 September scientists determined that the lake was about 980 m E-W and 710 m N-S, covering an estimated 52 hectares. The W wall vent was visible, and several fountains were rising from the fissure in the central part of the lake. Sulfur dioxide emission rates remained high, estimated at around 20,000 tonnes/day. Overnight during 30 September-1 October fountains rose as high as 15 m at the dominant vent in the W wall. Less vigorous fountaining persisted at other vents, though fewer were active. The lake had risen 24 m by the morning of 1 October, adding 4 m in the past day. Cooled and crusted parts of the lake’s surface overturned, or “foundered.” Sulfur dioxide emission rates remained high, estimated at around 12,900 tonnes per day. The lake had risen another 2 m by the morning of 2 October; fountains were 7 m tall at the main W wall vent and 1-2 m at the southern vents. Fountains occasionally rose as high as 50-60 m in bursts. Pumice, Pele?s hair, and fragments of volcanic glass were deposited downwind. The sulfur dioxide emission rate on 3 October was again high at 14,750 tonnes/day. The W vent was again the most vigorous during 3-4 October with sustained lava fountains to 10-15 m with occasional bursts up to 20 m. The lake rose 3 m, past the base of the W vent where a 12-m-high spatter cone had formed, and continued to founder in spots. Lava fountains rose 5-10 m from the vents in the S and central portions of the lake, including along a fissure 35-42 m long, with occasional larger bursts. The lake was not level and generally higher near the location of the vents; the W end was 1-2 m higher than the E, and S end was about 1 m higher than the N. By 4 October ledges about 20 m wide separated the N and E parts of the active lava lake from the crater wall and were lower than the lake surface; the N, E, and S margins of the lake were perched about 3 m above the surrounding ledge. The sulfur dioxide emission rate remained elevated but had decreased to 7,000-9,000 tonnes/day. HVO lowered the Aviation Color Code to Orange and the Volcano Alert Level to Watch at 1652. On 5 October lava fountaining from the W vent was unchanged while fountains from the other vents rose 1-5 m. The lake rose 1 more meter.

La Palma – Spain : The eruption at La Palma continued during 29 September-5 October, characterized by Strombolian explosions, lava fountaining from multiple vents, lava flows, and daily ash emissions. Seismicity continued to be elevated with earthquakes located mainly 10-15 km deep (though some were 25-40 km deep) in the same area where the swarm first began on 11 September; dozens of events were felt by residents. Within the first eight days of the eruption, 21-27 September, an estimated 50 million cubic meters of material had been erupted. Just before midnight on 28 September the lava reached the ocean, producing a steam-and-gas plume; within 45 minutes the lava created a 50-m-high delta. The sulfur dioxide flux was as high as 16,760 tons per day. On 29 September the PEVOLCA (Plan de Emergencias Volcánicas de Canarias) steering committee restated that the 2.5 km and maritime exclusion zones around the vents and ocean entry, respectively, remained in effect; residents were periodically allowed to collect belongings and care for animals and crops. The lava covered almost 4.8 square kilometers, burying or damaging 744 buildings. There were 185 evacuees in a local hotel. Ash plumes continued to rise from the active vents, and IGN noted a decrease in plume altitude to 3.5 km (11,500 ft) a.s.l. on 29 September and then a rise to 5 km (16,400 ft) a.s.l. the next day. Lava continued flowing to the sea along the same path. The lava delta had grown three times in size by 30 September to an estimated 0.17 square kilometers; the furthest edge of the delta was 450 m from the coast, it had spread laterally 600-800 m, and was as thick as 24 m. PEVOLCA lifted access restrictions for residents of Tazacorte, San Borondón, Marina Alta, Marina Baja, and La Condesa (nearly 4,000 people); they had previously been warned to stay indoors to minimize coming into contact with potentially toxic gas plumes generated from the ocean entry. Restrictions for other residents living near the margins of the flows were also lifted. Two vents opened about 600 m NW of the main cone on 1 October and within two days had formed small cones. Lava from the vents traveled W and joined the main flow field downslope. The lava delta had extended 540 m from the coastline. Ash plumes rose to 3-5 km a.s.l. and drifted S on 2 October, and sulfur dioxide emissions were 3,401 tons per day. By 3 October an estimated 946 houses had been completely demolished and 128 had been partially damaged. The width of the flow field was a maximum of 1,250 m and lava tubes were identified in satellite images. The lava delta had developed four lobes being fed by multiple flows and had an estimated area of 0.32 square kilometers. In the afternoon the frequency and intensity of explosive activity increased and bombs were ejected as far as 800 m. Lava fountains rose hundreds of meters and ash plumes rose as high as 4.5 km (14,800 ft) a.s.l. The sulfur dioxide emission rate reached 16,000 tons per day. During 1900-1945 one of the new cones collapsed, which allowed the inner lava lake to spill out, sending flows downslope carrying blocks from the destroyed portion of the cone. Ash plumes rose as high as 4.5 km a.s.l. and explosions ejected bombs on 5 October according to a news report. Some explosions produced dense black plumes that billowed as they rose above the vent.

Nyiragongo – DR Congo : According to a news article the scientific director of GVO stated that lava had returned to Nyiragongo’s crater on 18 September. Notable thermal anomalies were visible in Sentinel satellite images on 29 September and 4 October.

Vulcano – Aeolian Islands (Italy) : INGV reported that hydrothermal activity at Vulcano increased in July, and notably more in September. Specifically, temperatures of the fumaroles on the crater rim and on the inner flank had increased along with the amounts of carbon dioxide and sulfur dioxide in the emissions. The highest temperature of 340 degrees Celsius was along the rim. The temperature and salinity of groundwater measured near the base of La Fossa cone were both elevated, and outgassing from ground sites was noted. On 13 September the seismic network detected a significant increase in microseismcity linked to hydrothermal processes. Additionally, very-long-period events were also recorded for the first time in 15 years when instrumentation able to detect the signals was installed. Deformation on the N side of the cone was first identified in mid-August and totaled 1 cm of uplift by mid-September. The report stated that new seismic stations and instruments to measure carbon dioxide emissions had been added to the monitoring network, and a thermal camera pointing at the fumarolic field was planned.

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