Volcano World

Unrest continued to be detected at Ahyi Seamount during 30 November-6 December. Wake Island hydrophone sensors detected signals on most days and discolored water over the seamount was identified daily in satellite images. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Source: US Geological Survey

IG reported that the low-level eruption at Cotopaxi continued during 30 November-6 December. At 0841 on 30 November the seismic network recorded a signal associated with an emission. A gas plume with low ash content was visible in webcam images rising 600 m above the summit and drifting E. Earlier in the morning minor ashfall was reported in Latacunga, though the ashfall may have been the result of remobilized material previously deposited. Daily steam-and-gas emissions during 1-6 December rose as high as 1.5 km above the summit and drifted E, SE, S, and W. Daily sulfur dioxide emissions measured by satellite during 1-4 December averaged 119-4,000 tons per day. On 2 December IG noted that the heights of gas-and-steam emissions had increased in the past few weeks, corresponding to greater gas output. Thermal anomalies in the crater were visible in recent days; one was visible on 1 November, and two were visible on each of the days of 28 and 29 November. Servicio Nacional de Gestin de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Sources: Instituto Geofsico-Escuela Politcnica Nacional (IG) ,Servicio Nacional de Gestin de Riesgos y Emergencias (SNGRE)

INGV reported that a new vent, at the NE base of Etna?s SE Crater around 2,800 m elevation, was first seen at about 1800 on 27 November when weather conditions allowed for direct visual observations. The vent produced a lava flow that traveled 300 m E towards the Valle del Leone. Inclement weather conditions from 1000 on 28 November until the end of the next day prevented confirmation of continuing activity, though incandescent flashes in the clouds suggested ongoing effusion. The weather conditions improved on 30 November, and a second vent was observed, located upslope from the first at about 2,900 m elevation. A lava flow from the second vent had traveled about 450 parallel to and N of the first flow, reaching about 2,700 m elevation.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

HVO reported that the Northeast Rift Zone eruption at Mauna Loa continued during 30 November-6 December. Fissure 4, at the lowest elevation, produced lava flows that moved NE at a rate of about 60 m per hour during 30 November-1 December and crossed the Mauna Loa Weather Observatory Road overnight. A smaller slower lobe of lava traveled E but had stalled by the afternoon of 1 December. Fissure 4 was not very active during the morning of 2 December, and during an overflight on 3 December HVO geologists confirmed that it was no longer erupting and observed only glowing cracks in the vicinity. Fissure 3, at 3,510 m elevation, was the dominant source of the largest lava flow that continued to advance mainly N towards the Daniel K. Inouye Highway (Saddle Road) during the week. The main flow branched almost halfway down the flow field, but coalesced downslope an advanced as a single front. Lava fountains at the fissure were 20-25 m tall on 30 November, about 33 m tall during 3-4 December, and 40-100 m on 6 December. Molten lava bombs were sometimes ejected, which cooled at the base of the fissure and built a significant spatter rampart around the lava fountains. The rate of lava flow advancement was variable but generally trended down early in the week from 24-45 m per hour during 30 November-2 December to 6-13 m per hour during 3-5 December, as the lava-flow front reached flatter ground. As the flow rate slowed the flow front was widened and thickened. There were surges in the rate during 5-6 December with the lava flow typically advancing at 21 m per hour but moving up to 27.4 m per hour for shorter periods. Several small overflows were visible during 3-6 December near where the main lava flow branched, on the steeper slopes of the NE flank about halfway down the lava flow. By 0500 on 6 December the flow front was about 3.5 km from the highway; weather conditions hampered views of the eruption most of the day. The eruption produced volcanic gas plumes that rose to high altitudes and drifted W, generating vog in areas downwind. Pele's hair (strands of volcanic glass) fell in the Humu?ula Saddle area, and were also blown great distances, as far as far Laupahoehoe (59 km NW of Fissure 3), and the Mauna Kea Visitor Information Station. Hawai?i Volcanoes National Park had closed the Mauna Loa Road from Kipukapuaulu, and the closure extended to the summit caldera. Sulfur dioxide emission rates were high through the week with approximate rates of 180,000 tonnes per day on 1 December and 120,000 tonnes per day on 4 December. At 0180 on 4 December the Aviation Color Code was lowered to Orange (the second highest level on a four-color scale) because there was no current threat to aviation from significant volcanic ash emissions. The Federal Aviation Administration issued a temporary flight restriction extending from the surface to 1,500 ft (457 m) above ground level in the eruption area. The Volcano Alert Level remained at Warning (the highest level on a four-level scale) reflecting the ongoing lava-flow hazards.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

MARN reported that a total of 194 explosions were recorded at San Miguel during 15-29 November, with a daily average of 12 events. Gas, steam, and ash plumes generally rose 500 m above the crater rim, though plumes occasionally rose higher, particularly during 26-27 November as activity intensified. No explosions were detected during 30 November-6 December and seismicity decreased. MARN noted that those living within a 5 km radius should identify evacuation routes and to take preparation measures identified by the Sistema Nacional de Proteccin Civil.

Sources: Ministerio de Medio Ambiente y Recursos Naturales (MARN),Proteccin Civil de El Salvador

PVMBG reported that the eruption at Semeru was ongoing the past month, culminating in a collapse of lava causing notable pyroclastic flows and ash plumes on 4 December. During 1 November-2 December an average of 88 daily white-and-gray ash plumes of variable densities were visually observed rising as high as 1.5 km above the summit. Pyroclastic flows, seen twice, traveled as far as 4.5 km down the flank. Deformation data showed inflation and thermal anomalies indicated hot lava-dome material at the summit. A white-to-gray ash plume rose around 500 m above the summit and drifted S on 3 December. At 0246 on 4 December material collapsed on the SE flank, producing a series of pyroclastic flows that mainly traveled 5-13 km SE and S, and as far as 19 km in those same directions, according to BNPB. The pyroclastic flows overtook the Gladak Perak Bridge, 13 km SE of the summit, which connected residents of Pronojiwo (13 km SE) and Lumajang (32 km ESE) and appeared to be under construction based on pictures posted on social media. Dense dark-gray ash plumes rose along the pyroclastic flows up to 1.5 km above the summit and drifted SE and S. The ash plumes caused dark conditions and limited visibility, especially in Kajar Kuning (12 km SE) where residents reported dense ashfall and heavy rain. Ejected incandescent material was deposited as far as 8 km from the summit, and ashfall was reported in areas 12 km SE. Pyroclastic flows were ongoing at least through 0951, traveling 5-7 km down the flanks. At 1200 PVMBG raised the Alert Level to 4 (the highest level on a scale of 1-4) and warned the public to stay at least 8 km away from the summit, and 500 m from Kobokan drainages within 17 km of the summit, along with other drainages originating on Semeru, including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards. A total of 1,979 people were evacuated to 11 centers, a public kitchen was established, and thousands of masks were distributed to minimize respiratory health risks due to volcanic ash.

Sources: Badan Nacional Penanggulangan Bencana (BNPB) ,Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

GeoNet reported that a strong M 5.6 earthquake occurred beneath Taupo on 30 November. The event was widely felt and caused a small tsunami in the lake. Lake water inundated the shore at several locations, mostly along the N shore, traveling inland as far as 40 m at Wharewaka Point (along the NE shore). Both the earthquake and the tsunami caused minor local damage. The instrument at Horomatangi recorded 250 mm of horizontal ground movement towards the SE, the largest movement ever recorded at that location. Other onshore stations recorded smaller movements of around 10-20 mm. More than 600 aftershocks were located by 7 December, though the magnitude and rate of the events had begun to decline. The largest aftershock was an M 4.5 and two other M 4 events were also recorded. Earthquakes larger than M 5 beneath Lake Taupo had occurred only four times since 1952, including a M 5 event that occurred on 4 September 2019 as part of a previous period of volcanic unrest. GeoNet noted that there had been 17 previous episodes of unrest at Taupo over the previous 150 years, some more notable than the current episode, and many others before written records. None resulted in an eruption, with the last eruption occurring around 232 CE. The Volcanic Alert Level remained at 1 (the second lowest level on a six-level scale) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).

Source: GeoNet

SERNAGEOMIN reported that on 1 December weather conditions were clear, allowing for good visual observations of the Villarrica summit. Ejected incandescent material was visible rising 80-220 m above the crater rim. The report noted that gas emissions and high-temperature thermal anomalies had been continuous during the previous few days. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the public was warned that material could be ejected within 500 m of the crater. ONEMI remained the Alert Level Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucn (16 km N), Curarrehue, and the commune of Panguipulli.

Sources: Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI) ,Servicio Nacional de Geologa y Minera (SERNAGEOMIN)

JMA reported ongoing eruptive activity at Minamidake Crater (at Aira Caldera?s Sakurajima volcano) consisting of a few eruptive events and two explosions. Crater incandescence was visible nightly, sometimes characterized as incandescent flashes. An explosion at 0340 on 2 December produced an ash plume that rose as high as 3.2 km above the crater rim and ejected large blocks as far as 1.1 km from the vent. The second explosion, recorded at 1929 on 3 December, produced an ash plume that rose as high as 3 km and ejected large blocks 1-1.3 km away. Webcam video of the event showed incandescent material ejected above the crater and lightning in the ash plume. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.

Sources: Japan Meteorological Agency (JMA) ,Treasure Official Channel

KVERT reported that the eruption at Alaid was ongoing during 25 November-1 December. A daily thermal anomaly was identified in satellite images. Ash plumes drifted 220 km SE during 25-26 November. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)