The Weekly Volcanic Activity Report: February 21 - 27, 2024

New activity/unrest was reported for 1 volcano from February 21 – 27, 2024. During the same period, ongoing activity was reported for 17 volcanoes.

New activity/unrest: Lewotolok, Lembata Island.

New activity/unrest

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued during 15-27 February. White-and-gray ash plumes generally rose 200-800 m above the summit though some rose as high as 1 km above the summit and were dense. The seismic network recorded 3,615 signals indicating emissions during 16-26 February, according to a news article. Avalanches were detected but not visually observed during 15-23 February, and seismicity fluctuated but the data indicated an upward trend. Explosions continued to be recorded but began to intensify, ejecting incandescent material as far as 500 m from the crater rim and producing taller ash plumes.

Lava flows advanced over the crater rim on 15 February and traveled 400 m from the vent down the S and SE flanks. The flows continued to advance and by 23 February the SE flow was 1 km long and the S flow was 600 m long. The public was warned to stay at least 2 km away from the summit and 3 km away on the S and SE flanks. According to news articles activity significantly increased during 24-26 February; ash plumes continued to rise as high as 1 km above the summit and avalanches of material descended the SE and S flanks as far as 1 km. The SE lava flow advanced relatively fast, reaching 2 km long by 26 February. At 1000 on 27 February PVMBG raised the Alert Level to 3 (on a scale of 1-4) and the exclusion zone on the S and SE flanks was increased to 4 km. Though evacuations were not mandatory in Jontona, there were plans to assist residents who chose to evacuate; the lava flow was 2 km from the village.

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.

Ongoing activity

Aira, Kyushu (Japan)

31.5772°N, 130.6589°E | Summit elev. 1117 m

JMA reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 17-26 February with nighttime crater incandescence. Very small eruptive events were recorded during 17-23 February. An explosion at 1734 on 24 February generated an ash plume that rose 400 m above the crater rim before entering weather clouds, and ejected blocks as far as 1.2 km away from the vent. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.

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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Bezymianny, Central Kamchatka (Russia)

55.972°N, 160.595°E | Summit elev. 2882 m

KVERT reported that a daily thermal anomaly over Bezymianny was identified in satellite images during 15-22 February. Dates are UTC; specific events are in local time where noted.

Geological summary: The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Dukono, Halmahera

1.6992°N, 127.8783°E | Summit elev. 1273 m

PVMBG reported that the eruption at Dukono was ongoing during 21-27 February. Daily gray-and-white ash plumes generally rose as high as 1.6 km above the summit and drifted in multiple directions; at 1050 on 24 February ash plumes rose to 2.7 km and drifted N according to a news article. The Alert Level remained at Level 2 (on a scale of 1-4), and the public was warned to remain outside of the 3-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, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. 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 explosive activity was ongoing at Ebeko during 15-22 February. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 16 and 18-20 February generated ash plumes that rose as high as 2.5 km (8,200 ft) a.s.l and drifted E and NW. Ashfall was reported in Severo-Kurilsk during 18-19 February. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are UTC; 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.

Fuego, South-Central Guatemala

14.473°N, 90.88°W | Summit elev. 3763 m

INSIVUMEH reported that eruptive activity continued at Fuego during 20-27 February. Explosions were recorded daily, averaging 5-11 per hour on most days, when counts were reported. The explosions generated gas-and-ash plumes that rose as high as 1.1 km above the crater rim and drifted as far as 30 km W, SW, and S. Explosions caused frequent block avalanches that descended various drainages including the Ceniza (SSW), Seca (W), Taniluyá (SW), and Las Lajas (SE), and sometimes reached vegetated areas. The explosions also ejected incandescent material 100-300 m above the summit on most of the days and ejected ballistics as far as 2 km during 20-21 February. Weak rumbling sounds and sho*k waves were frequently reported. Ashfall was reported on most days in areas downwind including Panimache I and II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), Sangre de Cristo (8 km W), Finca La Asunción (12 km SW), La Rochela (8 km SSW), Finca Ceilán (9 km S), San Andrés Osuna (11 km SSW), Siquinalá (21 km SSW), and Santa Lucía Cotzumalguapa (22 km SW).

Geological summary: Volcán Fuego, one of Central America’s most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala’s former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Gamalama, Halmahera

0.81°N, 127.3322°E | Summit elev. 1714 m

Although there was no eruptive activity reported at Gamalama, in a 23 February press release PVMBG noted that the number of daily deep volcanic earthquakes had significantly increased. A total of 14 deep volcanic earthquakes were recorded by the seismic network on 22 February, higher than the average of 2-3 events per day that had been recorded since January 2023. At 1623 on 22 February an observer saw a dense white-to-gray ash plume rising 400 m above the summit and drifting W. During 0000-0830 on 23 February the network recorded an additional four deep volcanic earthquakes as well as three events indicating emissions; dense white plumes were visible rising 100-400 m above the summit and drifting N. Seismicity before the increase, during 1-22 February, consisted of one tornillo earthquake, two harmonic earthquakes, one shallow volcanic earthquake, 34 deep volcanic earthquakes, two seismic events indicating floods or lahars, and 26 events indicating emissions. The Alert Level remained at 2 (on a scale of 1-4); visitors and residents were warned not to approach the crater within a 1.5-km radius.

Geological summary: Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia’s most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the extensive documentation of activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano; the S-flank Ngade maar formed after about 14,500–13,000 cal. BP (Faral et al., 2022). Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slow lava effusion continued in Great Sitkin’s summit crater during 21-27 February, confirmed by a 24 February satellite image. A few small volcanic earthquakes were recorded by the seismic network during 24-26 February. Weather clouds obscured satellite and webcam views during most of the week. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger 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 older edifice and produced a submarine debris avalanche. Deposits from this and an even 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. Eruptions have been recorded since the late-19th century.

Marapi, Central Sumatra

0.38°S, 100.474°E | Summit elev. 2885 m

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 21-27 February. White-and-gray gas-and-ash plumes rose 200-600 m above the summit and drifted in multiple directions on most days; white plumes rose 250 m and drifted SW, W, and NW on 27 February. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 4.5 km away from the active crater.

Geological summary: Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra’s most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi (on Java) continued during 16-22 February. Seismicity remained at high levels. The SW lava dome produced 145 lava avalanches that descended the S and SW flanks; three traveled S as far as 1 km down the upper part of the Boyong drainage and 142 traveled SW as far as 1.7 km down the upper part of the Bebeng drainage. Two pyroclastic flows traveled as far as 1.6 km down the SW flank. Morphological changes to the SW lava dome identified in webcam images were due to continuing effusion and collapses of material. 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.

Popocatepetl, Mexico

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

CENAPRED reported that eruptive activity continued at Popocatépetl during 21-27 February. The seismic network recorded daily periods of high-frequency, low-amplitude tremor that lasted from about 90 minutes to almost 22 hours. The Washington VAAC reported that daily ash plumes visible in webcam and satellite images generally rose to 5.2-6.7 km (17,000-22,000 ft) a.s.l. and drifted predominantly E, SE, S, and SW. The ash emissions were continuous for periods of time with remnant ash continuing to be visible in subsequent satellite images, drifting 75-140 km before dissipating. At 1151 on 24 February a dense ash plume rose to 7.6 km (25,000 ft) a.s.l. and drifted ENE; the plume was visible in satellite images the next day drifting almost 225 km SE. Several ash emissions lasting 1-2 hours each were visible in webcam and satellite images during 26-27 February.

Based on information from El Centro Nacional de Comunicación y Operación de Protección Civil (CENACOM), CENAPRED noted that minor ashfall was reported in Hueyapan (17 km SSW), Tetela del Volcán (20 km SW), and Jiutepec (59 km SW) in the state of Morelos on 21 February and in the municipalities of Jiutepec (60 km WSW), Atlatlahucán (30 km WSW), Cuautla (43 km SW), Tlaltizapan (65 km SW), and Ciudad Ayala in Morelos, and in Huaquechula (30 km SE) and Tlapanalá (39 km SE), Puebla, on 22 February. Minor ashfall was reported in the municipalities of Hueyapan, Yecapixtla (30 km SW) and Tetela del Volcán, Morelos; in Ixtacuixtla, Panotla, Tepetitla (36 km NE), Nativitas (40 km NE), Zacatelco (45 km NE), Santa Apolonia Teacalco (40 km NE), San Damián Texóloc (45km NE), Tetlahuaca (40 km NE), Zacatelco (45 km NE), Xicohtzingo (40 km ENE), Papalotla (62 km NNW), Tenancingo (47 km ENE), Santa Catarina Ayometla (47 km ENE), Magdalena Tlaltelulco (53 km NE), San Francisco Tetlanohcan (55 km NE), and Teolocholco (51 km ENE), Tlaxcala; in Iztacalco (62 km NW), Iztapalapa (59 km NW), and Coyoacán (65 km WNW), Mexico City; and finally in Atlautla (16 km W), Ayapango (21 km NW), Ecatzingo (15 km SW), Chalco (44 km NW), Tenango del Aire (29 km NW), Temamatla (32 km NW), Ozumba (18 km W), Tepetlixpa (20 km W), Tlalmanalco (30 km NW), and Amecameca (20 km NW), State of Mexico on 27 February. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale) and the public was warned to stay 12 km away from the crater.

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-EPN reported that a moderate eruption at Reventador was ongoing during 21-27 February. Seismicity was characterized by 28-62 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Daily ash-and-gas plumes rose as high as 1.3 km above the crater rim and drifted in multiple directions, though weather conditions sometimes prevented views. Crater incandescence was occasionally visible during both overnight and morning hours; avalanches of incandescent material descended the flanks as far as 800 m from the summit on a few of the days and incandescent material was ejected 200 m above the crater during 23-24 February. A seismic signal indicating a lahar was recorded at 0015 on 24 February. Secretaría de Gestión de Riesgos maintained the Alert Level at Orange (the second highest level on a four-color scale).

Geological summary: Volcán El 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 stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have left extensive deposits on the scarp slope. The largest recorded 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.

Sangay, Ecuador

2.005°S, 78.341°W | Summit elev. 5286 m

IG-EPN reported that high levels of eruptive activity continued at Sangay during 20-27 February. The seismic network recorded 185-465 daily explosions. Gas plumes with low ash content rose 500-1,000 m above the summit and drifted SE during 20-21 February. Crater incandescence was occasionally visible and incandescent material descended the SE flank as far as 1 km during 20-23 February. Weather conditions prevented views during the rest of the week. Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at Yellow (the second highest level on a four-color scale).

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador’s volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within the open calderas of two previous edifices which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Santa Maria, Southwestern Guatemala

14.757°N, 91.552°W | Summit elev. 3745 m

INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava dome complex during 20-27 February with a lava extrusion at the Caliente dome. Incandescence from the dome was visible during most nights and early mornings, and occasional incandescence was also present along the upper part of the SW-flank lava flow. Daily explosions generated gas-and-ash plumes that rose 600-900 m above the summit and drifted W, SW, and S; the explosions occurred at a rate of 1-7 per hour on at least a few of the days. The explosions produced block avalanches on the dome’s W, SW, S, and E flanks and generated occasional, short-range pyroclastic flows that descended multiple flanks. Block avalanches from the margins of the upper part of the lava flow on the WSW flank were also occasionally visible. Ashfall occurred in Loma Linda (7 km W) and San Marcos Palajunoj (8 km SW) during 20-21 February and caused hazy conditions around the volcano during 22-23 February.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semeru, Eastern Java

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

PVMBG reported that eruptive activity continued at Semeru during 21-27 February. Daily gray-and-white ash plumes, often dense, rose 400-1,000 m above the summit and drifted in multiple directions. The Alert Level remained at 3 (the third highest level on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages 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 eruptive activity at Sheveluch continued during 15-22 February with a thermal anomaly identified in satellite images during 16, 18-19, and 22 February. On 19 February plumes of resuspended ash rose to 2.5 km (8,200 ft) a.s.l. and drifted about 55 km ESE. Weather clouds sometimes prevented views of the volcano. The Aviation Color Code remained at Orange (the third 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

JMA reported that the eruption at Suwanosejima’s Ontake Crater continued during 19-26 February. Crater incandescence was observed in webcam images nightly. Large blocks were sometimes ejected up to 400 m from the vent. Explosions were recorded at 0616 on 19 February, at 0604 and 2157 on 24 February, and at 1149 on 25 February; details of emissions were unknown. Eruptive events at 1702 and 2056 on 23 February produced ash plumes that rose at least 1 km above the crater rim and drifted S. Explosions at 2343 on 25 February and at 0431, 1402, 1910, and 1918 on 26 February produced ash plumes that rose 400-800 m above the crater rim and drifted S. The plume from the explosion at 1918 on 26 February rose to 800 m before entering into weather clouds. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 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 active summit craters. The summit is truncated by a large breached crater extending to the sea on the E 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 covered 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 an open collapse scarp extending 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.

Ubinas, Peru

16.345°S, 70.8972°W | Summit elev. 5608 m

Instituto Geofísico del Perú (IGP) reported that a lahar descended the Volcánmayo drainage on the SE flank at Ubinas at 1745 on 25 February and traveled towards the Ubinas River. The public was warned to stay away from the drainage and to avoid driving on the Querapi-Ubinas-Huarina highway.

Geological summary: The truncated appearance of Ubinas, Perú’s most active volcano, is a result of a 1.4-km-wide crater at the summit. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45°. The steep-walled, 150-m-deep summit crater contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one from about 1,000 years ago. Holocene lava flows are visible on the flanks, but activity documented since the 16th century has consisted of intermittent minor-to-moderate explosive eruptions.

References:

¹ Smithsonian Institution / US Geological Survey – Weekly Volcanic Activity Report, February 14 – 20, 2024 – Managing Editor: Sally Sennert.

Featured image credit: TW

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