Volcanos

Roundup of Global Volcanic Activity – Ongoing Activity for the week 1 December – 7 December 2021

Aira – Kyushu (Japan) : JMA reported that incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 29 November-6 December. An eruptive event at 1702 on 2 December generated a plume that rose 1.3 km above the crater rim.

Etna – Sicily (Italy) : INGV reported that during 29 November-5 December eruptive activity at Etna was concentrated at the Northeast Crater (NEC) and the Southeast Crater (SEC), while only minor gas emissions rose from the Voragine and Bocca Nuova craters. Webcam images showed diffuse and discontinuous ash emissions from NEC on 1 December that quickly dissipated near the summit. On the morning of 4 December INGV staff working near the summit observed sporadic and diffuse ash emissions rising from SEC and quickly dissipating around the summit. During the afternoon and through the next day webcam images recorded Strombolian activity at SEC, in addition to the ash emissions.

Fuego – Guatemala : INSIVUMEH reported that 3-12 explosions per hour were recorded at Fuego during 30 November-7 December, generating ash plumes as high as 1 km above the crater rim and periodic shock waves that were felt in communities around the volcano. Ash plumes drifted as far as 25 km SW and W, causing almost daily ashfall in areas downwind, including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), and San Pedro Yepocapa (8 km NW). Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Las Lajas (SE), and El Jute drainages, often reaching vegetated areas. Explosions ejected incandescent material up to 100-200 m above the summit during 30 November-3 December. A new lava flow emerged during the morning of 5 December and lengthened to 400 m by the next day. During 5-6 December explosions ejected incandescent material 100 m above the summit.

Great Sitkin – Andreanof Islands (USA) : AVO reported that slow lava effusion at Great Sitkin likely continued during 1-7 December. Elevated surface temperatures at the summit were periodically detected through the week.

Grimsvotn – Iceland : The Icelandic Meteorological Office (IMO) reported that the jökulhlaup (glacial outburst flood) due to subsidence of the ice shelf in Grímsvötn’s caldera continued until 6 December. Subsidence of the ice shelf into the underlying lake had begun around 24 November in an area SE of Grímsfjall. Water from the lake drained from the E side of Skeiðarárjökull and from a channel in the middle of a trail into the Gígjukvísl River, causing rising waters first detected in that river overnight during 30 November-1 December. By 2 December the flow rate in the river was 930 meters per second, triple what was detected three days before, and 10 times the normal seasonal rate. Daily measurements showed that the flow rate continued to rise, likely peaking at 2,800 meters per second during the morning of 5 December; a second measurement later that day showed a lower discharge rate of 2,310 meters per second. The ice shelf continued to subside, though more slowly, and water turbulence in the lake had also decreased; the data indicated that the lake was mostly empty of water. A number of detected earthquakes were attributed to subsiding and breaking ice. By 6 December the ice shelf had subsided a total of about 77 m. At 0615 an M 2.3 earthquake was immediately followed by a M 3.6 one minute later. Five more earthquakes were recorded during 1500-2130, though all were below M 1. IMO raised the Aviation Color Code to Orange (the second highest level on a four-color scale) based on the increased seismicity during the previous few days, the larger events that morning, and considerations such as short run-up times seen before previous eruptions, and those past eruptions occasionally following flood events. Seismic tremor had decreased by the next day, and no signs of eruptive activity were indicated in gas or deformation data.

Karymsky – Eastern Kamchatka (Russia) : KVERT reported that on 25 November explosions at Karymsky generated ash plumes that rose as high as 6 km (19,700 ft) a.s.l. and drifted 30 km NW. A thermal anomaly was visible in satellite images during27-29 November. Explosions on 2 December produced ash plumes that rose up to 4 km (13,100 ft) a.s.l. and drifted 100 km ENE. Dates are based on UTC times.

Kilauea – Hawaiian Islands (USA) : HVO reported that lava effusion continued at a vent in the lower W wall of Kilauea’s Halema`uma`u Crater during 1-2 December. The rate of effusion sharply decreased, along with volcanic tremor levels, during 1600-1800 on 3 December. A small part of the vent cone collapsed at around 1700. No surface activity was observed on 5 December and most of the next day though weather conditions hindered visual confirmation; a few small hotspots around the vent were visible in thermal camera images. Lava was visible in the vent at about 1730 on 6 December and within 30 minutes was flowing into the lake. By 0300 on 7 December lava had covered the prior extent of the lava lake.

La Palma – Spain : he eruption at La Palma continued during 1-7 December, characterized by Strombolian explosions and lava fountaining/jetting from multiple existing and new vents, advancing and sometimes branching lava flows, and almost daily ash emissions. Seismicity persisted at variable but elevated levels, with earthquake locations distributed at depths of 10-15 km and 30-40 km. Seismicity was intense at both levels during 30 November-2 December, though the intensity at deeper levels began to wane; in general, earthquake activity was low by the end of the week. Volcanic tremor levels fluctuated at medium to intense levels early in the week but by 3 December were also at low levels. Several vents in the main cone continued to effuse lava, eject tephra, and emit ash-and-gas plumes. Lava moved W through pre-existing lava channels, lava tubes, over older flows, and over new ground, increasing the flow field that consists of overlapping flows (numbered 1-12) and two lava deltas. Persistent Strombolian activity was sometimes intense at the NE-flank vent during 1-3 December, and lava continued to feed flow 8 and the N delta. Lava fountains rose 400-500 m above the vent on 2 December. A new pyroclastic cone had formed around the vent, though it was unstable, and blocks from collapses of parts of it were transported downslope by lava flows. The northernmost flow, flow 12, traveled over new ground in the Fronton area and then rejoined flow 8 downslope. The flows reached part of the Tacande highway on 3 December. The vents in the main cone were quieter, periodically emitting ash and gasses. A N-S-oriented crack opened in an area 100 m S of the main vent, likely from subsidence, because it was not hot or emitting gas. The NE vent was quiet by 4 December. On 3 December a new fissure opened on the SE of the main cone and produced Strombolian activity and fast-moving lava flows that traveled SW, along flow 10. The flow continued to advance W on 4 December, though at a slower rate as it moved over new ground in gaps between flows 3 and 11. Several new vents along an E-W fissure located W of Montaña del Cogote opened at noon on 4 December and produced multiple fast-moving lava flows. The flows descended SW over new ground, crossing into the municipalities of Tazacorte and Los Llanos de Aridane, destroying 60 homes. The flow joined flow 9, reached the sea cliff in the Las Hoyas area by 5 December, and descended the cliff the next day. During 6-7 December lava advanced W through multiple tubes and fed flows 1 and 2, and the S delta. The NE vent was quiet for a few days, but sporadic Strombolian activity and ash emissions had returned. Cracks and fractures in the upper part of the cone were visible. Several vents in the central and SE parts of the main cone also produced sporadic Strombolian activity and ash emissions. By 7 December lava had covered an estimated 11.82 square kilometers. The number of people that had evacuated and were staying in hotels had increased to 537. Gas and ash emissions periodically impacted island residents. Suspended ash and high concentrations of volcanic gases triggered a few air-quality alerts mostly affecting the W part of the island; authorities warned residents in some areas to stay indoors. Residents and essential personnel were occasionally barred from entering the exclusion zones to irrigate crops and remove ash from streets and buildings. Ash-and-gas plumes visible during 1-3 and 6-7 December rose as high as 3.5 km a.s.l.; volcanic plumes drifted W, SW, and SSW all week, away from the airport. Daily measurements indicated that sulfur dioxide emissions persisted at “high” levels, indicating values of 1,000 to 29,999 tons per day.

Lewotolok – Lembata Island (Indonesia) ; PVMBG reported that the eruption at Lewotolok continued during 1-7 December. Daily white-and-gray ash plumes that were sometimes dense rose as high as 800 m above the summit. Incandescent material was ejected from the vent on most days, and up to 300 m during 6-7 December, accompanied by roaring and rumbling. 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 no notable morphological changes to Merapi’s summit lava dome, though the dome just below the SW rim had decreased about 2 m in height during 26 November-2 December. The estimated dome volumes were 1.61 million cubic meters for the SW dome and almost 2.95 million cubic meters for the summit dome. The intensity of the seismic signals was higher than the week before. As many as 170 lava avalanches traveled a maximum of 2 km SW. Two pyroclastic flows traveled a maximum of 3 km SW on 1 December. In a VONA (Volcano Observatory Notice for Aviation), PVMBG stated that at 2104 on 1 December an ash plume rose 1 km above the summit and drifted E. According to BPPTKG a pyroclastic flow traveled 1.8 km down the Bebeng drainage on the SW flank at 1644 on 6 December. The event lasted two minutes and 40 seconds based on seismic data. The

Pavlof – United States : AVO reported that the eruption at Pavlof continued during 1-7 December, focused at a vent on the upper SE flank. Seismicity remained elevated and several daily explosions were detected using infrasound data. Elevated surface temperatures were observed in satellite data during 1-2 December, though cloud cover often prevented observations. No emissions were visible in mostly cloudy satellite and webcam views during 1-3 December. Minor ash emissions were visible in webcam images on 4 December and, based on webcam images and a pilot observation, the next day a diffuse ash plume rose as high as 3 km (10,000 ft) a.s.l. and drifted tens of kilometers beyond the volcano.

Santa Maria – Guatemala : INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 1-7 December. Avalanches generated by both lava effusion at the WSW part of Caliente dome and collapsing material descended the flanks in multiple directions, often reaching the base of the dome. Periodically the avalanches produced curtains of ash along their paths that dissipated near the volcano. Some of the avalanches were preceded by explosions detected by the seismic network and some were audible several kilometers away. During 2-3 and 6-7 December ash plumes rose 500 m above the summit and drifted 10 km NW and W, causing ashfall in areas downwind including San Marcos Palajunoj (8 km SW) and Loma Linda (6 km WSW). During 3-4 December ash-and-steam plumes rose 900 m and drifted SW and W.

Semisopochnoi – Aleutian Islands (USA) : AVO reported that low-level eruptive activity and elevated seismicity at Semisopochnoi’s North Cerberus crater continued during 1-7 December. Several daily explosions were detected in seismic and infrasound data. Weather clouds sometimes obscured satellite and webcam views of the volcano, though on most days low-level ash-and-steam plumes rising no higher than 1.5 km (5,000 ft) a.s.l. were visible mostly in webcam images. During 3-4 December a diffuse ash plume was identified in a satellite image drifting about 100 km E.

Sheveluch – Central Kamchatka (Russia) : KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 26 November-3 December.

Suwanosejima – Ryukyu Islands (Japan) : JMA reported that during 29 November-6 December about 47 explosions at Suwanosejima’s Ontake Crater produced eruption plumes that rose as high as 1.7 km above the crater rim and ejected blocks 600-700 m away from the crater. Plumes from non-explosive events rose as high has 2.3 km. Crater incandescence was visible nightly and ashfall was reported in Toshima village (4 km SSW).

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