The Weekly Volcanic Activity Report: August 24 - 30, 2022

New activity/unrest was reported for 5 volcanoes from August 24 – 30, 2022. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Chikurachki, Paramushir Island (Russia) | Nevados de Chillan, Central Chile | Ofu-Olosega, American Samoa (SW Pacific) | Semisopochnoi, Aleutian Islands (USA) | Ta’u, American Samoa (SW Pacific).

New activity/unrest

Chikurachki, Paramushir Island (Russia)

50.324°N, 155.461°E | Summit elev. 1781 m

KVERT reported that during 23-25 August occasional ash plumes from Chikurachki rose as high as 2 km (6,600 ft) a.s.l. and drifted about 20 km E. A thermal anomaly was identified in satellite images on 25 August. 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.

Geological summary: Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is a relatively small cone constructed on a high Pleistocene edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic Plinian eruptions have occurred during the Holocene. Lava flows have reached the sea and formed capes on the NW coast; several young lava flows are also present on the E flank beneath a scoria deposit. The Tatarinov group of six volcanic centers is located immediately to the south, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov centers are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of an eruption around 1690 CE from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Nevados de Chillan, Central Chile

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

SERNAGEOMIN reported that on 29 August an explosion at Dome 4 in Nevados de Chillán’s Nicanor Crater produced a plume with a high tephra content that rose 2 km above the crater rim and drifted S. The explosion also generated a pyroclastic flow that descended less than 500 m on the E and SE flanks. 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.

Ofu-Olosega, American Samoa (SW Pacific)

14.175°S, 169.618°W | Summit elev. 639 m

Data from seismometers recently installed on Tutuila, Ta’u, and Ofu-Olosega islands of American Samoa to monitor an ongoing seismic swarm indicated that the events were related to Ta’u Island and not Ofu-Olosega. HVO lowered the Volcano Alert Level to Normal and the Aviation Color Code to Green on 26 August. The report warned residents of Ofu-Olosega that they could still be significantly affected by events that may take place on or around Ta’u Island.

Geological summary: The two triangle-shaped islands of Ofu and Olosega in eastern Samoa, with a combined length of 6 km, are separated by a narrow strait. The islands are formed by two eroded, coalescing basaltic shield volcanoes whose slopes dip to the east and west. Steep cliffs up to 600-m high truncate the northern and southern sides of the islands. The narrow, steep-sided ridge forming the eastern tip of Ofu Island consists of a dike complex. The shield volcano on Ofu is cut on the north by the A’ofa caldera; bathymetry suggests that a caldera may also exist on the Sili shield volcano of Olosega. The Nu’utele tuff cone, forming a small crescent-shaped island immediately off the west end of Ofu Island, is Holocene in age. A submarine eruption took place in 1866 at the opposite end of the two islands, 3 km SE of Olosega, along the ridge connecting Olosega with Ta’u Island.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported ongoing low-level seismicity and steam emissions at Semisopochnoi during 23-30 August. Satellite images were mostly cloudy; steam emissions were seen almost daily in webcam images. 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.

Ta’u, American Samoa (SW Pacific)

14.23°S, 169.454°W | Summit elev. 931 m

HVO reported that an earthquake swarm in the Manu’a Islands of American Samoa continued to be felt by residents of Ta’u Island and Ofu-Olosega islands during 24-30 August. Three advanced seismometers were installed beginning the second week of August, one on Ofu Island and two on Ta’u, and by 26 August the data indicated that the source of the activity was related to Ta’u Island. Around 30 earthquakes per hour were recorded each day. At 2033 on 23 August an earthquake widely felt by residents of the Manu’a islands and Tutuila Island was characterized as producing light-to-moderate shaking (a maximum Intensity of V on the Modified Mercalli Intensity Scale); the estimated M 3-3.5 event was the largest recorded since the new instruments were installed. The largest earthquakes recorded during 25-26 August had estimated magnitudes between 3 and 4 and were felt by residents of Manu’a. An estimated M 2.8 event was strongly felt at 0932 on 27 August. Numerous events were felt during 27-28 August, but none were reported during 28-30 August. Booming noises had been reported and investigated for weeks; scientists confirmed that they were related to the earthquakes, noting that the sound waves generated by some earthquakes could produce sounds audible to humans. No signs of ground cracking, landslides, rockfalls, or other activity that could have caused the sounds were seen. The Volcano Alert Level remained at Advisory and the Aviation Color Code remained at Yellow.

Geological summary: The 10-km-wide Ta’u Island, located at the E end of the Samoan islands, is ringed by sea cliffs. It is the emergent portion of the large Lata shield volcano. A major flank collapse event around 22 ka resulted in the steep scarps on the southern side of the island. Two smaller shields were constructed along rift zones at the NW and NE tips of the island. The NW corner of the island has a tuff-cone complex that ejected large dunite xenoliths and coral blocks. Numerous Holocene post-caldera cones occur at the summit and on the flanks.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported low but continuing activity from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 22-29 August. Small eruptive events were recorded throughout the week, and nighttime incandescence was visible from the crater was visible during 26-29 August. 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.

Dukono, Halmahera

1.693°N, 127.894°E | Summit elev. 1229 m

PVMBG reported that almost daily white plumes from Dukono rose as high as 200 m above the summit and drifted SW, W, and NW. During 27-18 August dense white, gray, and brown ash plumes rose as high as 1 km above the summit and drifted SW and W. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E | Summit elev. 1103 m

KVERT reported that moderate activity at Ebeko was ongoing. A thermal anomaly over the volcano was identified in satellite images during 18-19, 22, and 25 August. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions generated ash plumes that rose up to 3 km (10,000 ft) a.s.l. during 19 and 22-25 August and drifted N and E. 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.

Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Erta Ale, Ethiopia

13.6°N, 40.67°E | Summit elev. 613 m

Thermal anomalies of variable intensities at Erta Ale’s N and S pit craters were periodically identified in satellite images during August. On 1 August there were two anomalies in the S pit crater and none in the N pit crater. Images were cloudy on 6 and 11 August. On 16 August two anomalies were again visible in the S pit crater while one large anomaly occupied the N crater. Translucent weather clouds obscured views on 21 August, though two anomalies were visible in the S pit crater. Dense weather clouds covered the N pit crater on 26 August and obscured the S pit crater, though one anomaly was visible.

Geological summary: The Erta Ale basaltic shield volcano is the most active in Ethiopia, with a 50-km-wide edifice that rises more than 600 m from below sea level in the barren Danakil depression. It is the namesake and most prominent feature of the Erta Ale Range. The volcano includes a 0.7 x 1.6 km elliptical summit crater hosting steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera usually also holds at least one long-term lava lake that has been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W | Summit elev. 1740 m

AVO reported that slow lava effusion at Great Sitkin probably continued during 24-30 August with lava around the vent likely thickening. Weather clouds often obscured satellite and webcam views during most of the week; elevated surface temperatures were occasionally visible. Seismicity was very low. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Karymsky, Eastern Kamchatka (Russia)

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

KVERT reported that the eruption at Karymsky continued during 18-25 August. A thermal anomaly over the volcano was identified in satellite images during 18-19, 22, and 24-25 August. 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.

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.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that lava continued to effuse from a vent in the lower W wall of Kilauea’s Halema`uma`u Crater during 24-30 August, entering the lava lake and flowing onto the crater floor. Part of the lake was continuously active. The lake level mostly remained within the bounding levees, though daily breakouts were visible along the margins. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E | Summit elev. 4754 m

Strong winds re-suspended ash from the E flank of Klyuchevskoy and created plumes that were visible in satellite images drifting more than 205 km E during 25-26 August. KVERT raised the Aviation Color Code to Orange on 26 August; plumes were not visible the next day so the Aviation Color Code was lowered back to Green.

Geological summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka’s highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Lewotolok, Lembata Island

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

PVMBG reported that the Strombolian eruption at Lewotolok continued during 23-30 August. Daily white emissions rose as high as 700 m above the summit and drifted in multiple directions. Photos posted with daily reports showed crater incandescence and occasional Strombolian activity. 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 and 4 km away from the crater on the SE flank.

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

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

BPPTKG reported that the eruption at Merapi continued during 19-25 August. Seismicity intensified compared to the previous week; in particular the number of deep volcanic earthquakes increased and indicated magmatic activity at depths less than 1.5 km. As many as 19 lava avalanches traveled down the Bebeng drainage on the SW flank, reaching a maximum distance of 1.8 km. Photo analyses showed no height changes at the SW and central lava domes, though some changes at the SW dome were observed due to avalanche activity. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 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.

Pavlof, Alaska Peninsula, Alaska

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

AVO reported that a minor eruption at a vent on Pavlof’s upper E flank was ongoing during 23-30 August, though there was no evidence of lava effusion. Seismic tremor persisted. A small ash emission rose to about 4 km (12,000 ft) a.s.l. on 24 August and was seen by passing aircraft. Sulfur dioxide emissions were also detected that same day. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

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.

Popocatepetl, Mexico

19.023°N, 98.622°W | Summit elev. 5393 m

CENAPRED reported that there were 15-75 steam-and-gas emissions, sometimes containing minor amounts of ash, rising from Popocatépetl each day during 23-30 August. A moderate explosion was detected at 0117 on 30 August. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale).

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Reventador, Ecuador

0.077°S, 77.656°W | Summit elev. 3562 m

IG characterized the ongoing eruption at Reventador as moderate during 23-30 August. Gas-and-ash plumes, observed with webcams or reported by the Washington VAAC, rose as high as 1.6 km above the summit and drifted in multiple directions. Crater incandescence was visible on most nights and often during early morning hours. Incandescent blocks were visible rolling 500 m down the NE flank during 24-25 August and 600 m down all flanks during 28-29 August.

Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Semeru, Eastern Java

8.108°S, 112.922°E | Summit elev. 3657 m

PVMBG reported that the eruption at Semeru continued during 23-30 August. Eruptive events at 0735 on 26 August, 0606 and 0628 on 27 August, 0623 on 28 August, and 0618 on 29 August produced ash plumes that rose 500-600 m above the summit and drifted N, W, and SW. The Alert Level remained at 3 (on a scale of 1-4). The public was warned to stay at least 5 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.

Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that the ongoing eruption at Sheveluch was characterized by explosions, hot avalanches, and lava-dome extrusion during 18-25 August. A daily thermal anomaly was identified in satellite images during 18-19, 21, and 23-25 August. Ash plumes drifted 190 km SE and 150 km E on 19 and 25 August, respectively. 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.

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. 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 occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. 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.

Suwanosejima, Ryukyu Islands (Japan)

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

At 2151 on 28 August a large eruptive event at Suwanosejima’s Ontake Crater ejected large bombs 800 m above the vent and produced an eruption plume that rose into overhead weather clouds. Crater incandescence was visible in webcam images overnight. By 0900 on 29 August three more explosions were recorded and produced ash plumes that rose as high as 1.3 km above the vent. The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.

Geological summary: The 8-km-long 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. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded 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 open 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 – August 24 – 30, 2022 – Managing Editor: Sally Kuhn Sennert

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