The Weekly Volcanic Activity Report: October 6 - 12, 2021

The Weekly Volcanic Activity Report: October 6 - 12, 2021

New activity/unrest was reported for 2 volcanoes from October 6 to 12, 2021. During the same period, ongoing activity was reported for 12 volcanoes.

New activity/unrest: Kilauea, Hawaiian Islands (USA) | La Palma, Spain.

Ongoing activity: Aira, Kyushu (Japan) | Kadovar, Papua New Guinea | Karymsky, Eastern Kamchatka (Russia) | Lewotolok, Lembata Island (Indonesia) | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Pavlof, United States | Sabancaya, Peru | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan).

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, these reports are preliminary and subject to change as events are studied in more detail.

New activity/unrest

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Summit elev. 1222 m

HVO reported that the summit eruption at Kilauea continued in Halema`uma`u Crater during 6-12 October. At the beginning of the eruption, on 29 September, lava erupted from vents along the floor and from the W wall of the crater, though by 8 October only the W vent was active. Sulfur dioxide emissions remained high and were 5,300 tonnes per day on 8 October. A 10-m-wide, horseshoe-shaped spatter rampart had formed around the W vent and was open to the E where lava was feeding the lake. Lava fountains from the W vent were generally 12-15 m high but decreased to 4 m during 10-11 October. The total erupted volume was an estimated 15.9 million cubic meters on 8 October and the lake was as deep as 40 m on 12 October. The lava lake was not level; the W end was 2-3 m higher than the N and S parts of the lake and 5 m higher than the E end. Cooled and crusted parts of the lake’s surface overturned, or “foundered,” in all parts of the lake, though by 11 October foundering was not observed in the E. HVO noted that the central island (or raft) of cooler material from the 2020 eruption remained above the surface as the lava lake rose, and other smaller rafts had reemerged in the E and N parts of the lake. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

La Palma, Spain

28.57°N, 17.83°W, Summit elev. 2426 m

The eruption at La Palma continued during 6-12 October, characterized by Strombolian explosions, lava fountaining from multiple vents, advancing and branching lava flows, and daily ash emissions. Eruption details are based on official sources including PEVOLCA (Plan de Emergencias Volcánicas de Canarias) steering committee summaries. Seismicity continued to be elevated with most earthquakes located 10-15 km deep (though some deeper than 35 km) in the same area where the swarm first began on 11 September; dozens of events were felt by local residents and some were felt across the entire island.

The largest earthquake, at 0816 on 12 October, was a M 4.1 at a depth of 37 km. Sulfur dioxide emissions fluctuated at high levels between 4,522 and 21,868 tons per day. Sulfur dioxide plumes drifted in multiple directions; on 8 October they reached the Caribbean and on 12 October plumes were over northern Africa, Spain, and Portugal. The main cone had at least three effusive vents and another vent to the N was also active. Multiple collapses of parts of the cone sometimes sent large blocks of cooler lava rafting down the flows. The lava delta was fed by numerous streams of lava during most of the week. Plumes of steam containing hydrochloric acid rose from the edge of the lava delta and were quickly dissipated by the wind; local resident were not affected.

On 6 October a breakout lava flow from the W end of the main flow field traveled S between Los Guirres and El Charcó (previously evacuated), destroying crops and buildings. The flow covered about 0.4 square kilometers and was about 350 m from the coast. Ash plumes rose 3-3.2 km (10,000-10,500 ft) a.s.l. during 6-7 October. On 8 October a new vent formed on the main cone and ash plumes rose as high as 3.5 km (11,500 ft) a.s.l. Ash accumulation at the La Palma and Tenerife North (on Tenerife Island) airports caused a temporary shutdown of operations until the ash was removed. On 9 October a collapse of the N part of the cone sent a wide, multi-lobed flow carrying larger blocks NW over older flows that quickly advanced W along the N margins of the flow field, covering crops and destroying buildings in both Todoque and an industrial area. Ash plumes continued to rise from the vents; lightning was visible in the plume at times.

By 10 October the flow field was 1,520 m wide, and covered 4.9-5.7 square kilometers, depending on the source of the estimates. Between 726 and 1,323 buildings had been engulfed by lava and more than 1.3 square kilometers of crops were lost. About 6,000 people had been evacuated. A partial collapse of the cone allowed the inner lava lake to spill out, sending flows and very large cooled blocks downslope. Ash plumes rose 3.5 km a.s.l. and caused ashfall to the S. Video showed lava fountains rising 500 m above the vent late that night. By 11 October the lava delta had grown mainly to the N and S, and was an estimated 0.34 square kilometers in size, though flows feeding it had slowed. Dense dark ash plumes were seen rising from the main vents. The most northern flow had continued to advance and was 300 m from the coast. The flows overtook a concrete plant, prompting authorities to instruct residents in El Paso and Los Llanos de Aridane to remain indoors and take measures to reduce exposure to toxic fumes. On 12 October the advancing northern flow caused the pre-emptive evacuation of the La Laguna area, totaling 700-800 people. The flow continued to cover crops and was 200 m from the coast, but had slowed. The lockdown for El Paso and Los Llanos de Aridane was lifted after air quality improved. Ash plumes from the main vent rose 3.5 km a.s.l. The Alert Level remained at Red (the highest level on a four-color scale) for affected communities.

Geological summary: The 47-km-long wedge-shaped island of La Palma, the NW-most of the Canary Islands, is composed of two large volcanic centers. The older northern one is cut by the massive steep-walled Caldera Taburiente, one of several massive collapse scarps produced by edifice failure to the SW. The younger Cumbre Vieja, the southern volcano, is one of the most active in the Canaries. The elongated volcano dates back to about 125,000 years ago and is oriented N-S. Eruptions during the past 7,000 years have formed abundant cinder cones and craters along the axis of Cumbre Vieja, producing fissure-fed lava flows that descend steeply to the sea. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas. The southern tip of the island is mantled by a broad lava field emplaced during the 1677-1678 eruption. Lava flows also reached the sea in 1585, 1646, 1712, 1949, and 1971.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported that incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 4-11 October. The sulfur dioxide emission rate was 400 tons per day on 5 October. An explosion at 0517 on 8 October ejected material 600-900 m away from the crater and produced an eruption plume that was obscured by weather clouds. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.

Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Kadovar, Papua New Guinea

3.608°S, 144.588°E, Summit elev. 365 m

Based on satellite and wind model data, the Darwin VAAC reported that during 8-9 October ash plumes from Kadovar rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted W and NW.

Geological summary: The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that a thermal anomaly over Karymsky was identified in satellite images on 7 October. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Lewotolok, Lembata Island (Indonesia)

8.274°S, 123.508°E, Summit elev. 1431 m

PVMBG reported that the eruption at Lewotolok continued during 6-12 October. White-and-gray plumes generally rose as high as 800 m above the summit and drifted in multiple directions. A VONA stated that on 7 October and ash plume rose 1.9 km above the summit and drifted W. Rumbling and banging sounds were reported daily. Incandescent material was ejected daily as far as 300 m away from the vent in multiple directions, though during 5-6 October incandescent material was ejected as far as 1 km SE. BNPB noted that 25-26 eruptive events per day were sometimes recorded before activity increased in October. 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.

Geological summary: The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Summit elev. 2910 m

BPPTKG reported minor morphological changes to Merapi’s SW lava dome, located just below the SW rim and in the summit crater, and no changes to the summit crater dome during 1-7 October. The SW dome grew about 3 m taller had an estimated volume of 1.679 million cubic meters, and the summit lava dome had an estimated volume of 2.854 million cubic meters. As many as 76 lava avalanches traveled a maximum of 2 km SW. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-5 km away from the summit based on location.

Geological summary: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Nevados de Chillan, Chile

36.868°S, 71.378°W, Summit elev. 3180 m

SERNAGEOMIN reported continuing explosive and effusive activity at Nevados de Chillán’s Nicanor Crater during 16-30 September though weather conditions often prevented visual confirmation. Explosions generated plumes with low ash content that rose as high as 1.1 km above the crater rim. A new lava dome (Dome 3) in the crater was first identified on 15 September and was 27 x 40 m, elongated NW-SE, and 990 square meters in area. The dome formation was preceded by a decrease in the extrusion rates and temperatures of the L5 and L6 lava flows. By 24 September growth at Dome 3 reached 36 x 43 m and covered 2,137 square meters. Dome 4 was first visible on 29 September, adjacent to Dome 3 on the NE side, and produced a new lava flow (L7) that traveled 50 m down the flank between the L5 and L6 flows. The L5 lava flow also began to advance.

On 5 October the L5 and L7 lava flows advanced and nighttime incandescence from both flows increased. Incandescence from the crater was visible in webcam images at night during 8-9 October. On 9 October a long-period earthquake was recorded at 0706 on 9 October; an associated emission rose more than 240 m above the vent and drifted NW. The Alert Level remained at Yellow, the second lowest level on a four-color scale. ONEMI stated that Alert Level Yellow (the middle level on a three-color scale) remained in place for the communities of Pinto and Coihueco, noting that the public should stay at least 2 km away from the crater.

Geological summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The dominantly andesitic Cerro Blanco (Volcán Nevado) stratovolcano is located at the NW end of the massif. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The Volcán Nuevo lava-dome complex formed during 1906-1945 on the NW flank of Viejo. The Volcán Arrau dome complex was then constructed on the SE side of Volcán Nuevo between 1973 and 1986, and eventually exceeded its height. Smaller domes or cones are present in the 5-km valley between the two major edifices.

Pavlof, United States

55.417°N, 161.894°W, Summit elev. 2493 m

AVO reported that seismicity at Pavlof remained elevated during 6-12 October. Two explosions were recorded by infrasound network during 6-7 October. Mostly cloudy conditions obscured satellite and webcam images most days. The Volcano Alert Level and Aviation Color Code remained at Watch and Orange, respectively.

Geological summary: The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported a daily average of 27 explosions at Sabancaya during 4-10 October. Gas-and-ash plumes rose as high as 2 km above the summit and drifted in multiple directions. One thermal anomaly originating from the lava dome in the summit crater was identified in satellite data. Minor inflation continued to be detected near Hualca Hualca (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Semisopochnoi, Aleutian Islands (USA)

51.93°N, 179.58°E, Summit elev. 1221 m

AVO reported that eruptive activity at Semisopochnoi's North Cerberus crater continued during 6-12 October. Seismicity remained elevated and a few explosions per day were detected in infrasound data. Although weather clouds often prevented webcam and satellite views, discontinuous, low-level ash emissions were visible rising to altitudes up to 3 km (10,000 ft a.s.l.) and drifting E during 8-9 October. Low-level ash emissions were also visible in webcam images during 9-12 October. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked Mount Cerberus was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank of Cerberus appear younger than those on the south side. Other post-caldera volcanoes include the symmetrical Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Summit elev. 3283 m

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 1, 4, and 6-7 October. Plumes of resuspended ash drifted 200 km SE during 6-7 October. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Summit elev. 924 m

INGV reported that during 4-10 October activity at Stromboli was characterized by ongoing explosive activity from three vents in Area N (North Crater area) and six vents in Area C-S (South-Central Crater area). Explosions from two vents in the N1 vent (Area N) ejected lapilli and bombs 80 m high, and produced minor ash emissions. Explosions at two N2 vents (Area N) averaged 3-8 events per hour and ejected material less than 80 m high. Explosions from the S1 and S2 vents in Area C-S were sporadic and occurred at a rate of 4-8 per hour; coarse material was ejected 150 m high. Gas emissions rose from the C vent.

A short explosive event at the N2 vents began at 1617 on 6 October. Notably, a large explosion ejected tephra radially beyond the crater terrace as far as the upper part of the Sciara del Fuoco, and incandescent material rolled down to the coast. An ash cloud was produced, though it quickly dissipated. A small lava overflow from the vents followed but it did not travel past the upper part of the Sciara del Fuoco.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E, Summit elev. 796 m

JMA reported that 52 explosions at Suwanosejima's Ontake Crater produced eruption plumes that rose as high as 2.4 km above the crater rim during 4-11 October. Large volcanic bombs were ejected as far as 1.1 km from the crater. Crater incandescence was visible nightly. The Alert Level remained at 3 and the public was warned to stay 2 km away from the crater.

Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Reference:

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 October-12 October 2021. Managing Editor: Sally Kuhn Sennert.


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