The Weekly Volcanic Activity Report: February 7 - 13, 2024

New activity/unrest was reported for 4 volcanoes from February 7 to 13, 2024. During the same period, ongoing activity was reported for 21 volcanoes.

New activity/unrest: Ahyi, Mariana Islands (USA) | Lewotobi, Flores Island | Mayon, Luzon (Philippines) | Poas, Costa Rica.

New activity/unrest

Ahyi, Mariana Islands (USA)

20.42°N, 145.03°E; summit elev. -75 m

Signs of unrest at Ahyi Seamount continued. Plumes of discolored seawater in the vicinity of the seamount were occasionally observed in satellite images during 2-9 February. No additional signs of unrest were identified in data collected by regional seismic stations or remote underwater pressure sensors located near Wake Island (2,270 km E of Ahyi). 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).

Geological summary: Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the ocean surface ~18 km SE of the island of Farallon de Pajaros in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

Lewotobi, Flores Island

8.542°S, 122.775°E; summit elev. 1703 m

PVMBG reported that Lewotobi Laki-laki continued to erupt during 7-13 February. White emissions rose 30-700 m above the summit during 7 February, and 20–50 m above the summit during 8-11, and 13 February. A seismograph recorded eruptive events at 0807 on 7 February, 1858 on 9 February, 1806 on 10 February, and 1249 on 12 February. Dense, white to gray ash plumes rose 500-700 m above the summit and drifted N and NE during the eruptive events on 7 and 9 February. The Alert Level remained at 3 (the second highest level on a scale of 1-4) and the public was warned to stay outside of the exclusion zone, defined as a 4 km radius around Laki-laki crater, 5 km to the NNE, and 6 km on the NE flanks.

Geological summary: The Lewotobi “husband and wife” twin volcano (also known as Lewetobi) in eastern Flores Island is composed of the Lewotobi Lakilaki and Lewotobi Perempuan stratovolcanoes. Their summits are less than 2 km apart along a NW-SE line. The conical Lakilaki has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has erupted only twice in historical time. Small lava domes have grown during the 20th century in both of the crescentic summit craters, which are open to the north. A prominent flank cone, Iliwokar, occurs on the E flank of Perampuan.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E; summit elev. 2462 m

PHIVOLCS reported that unrest continued at Mayon during 7-13 February. Crater incandescence was visible daily. The seismic network recorded a few volcanic earthquakes and rockfall signals during the week. Moderate emissions were observed almost daily that rose as high as 500 m above the summit and drifted multiple directions. On 10 February sulfur dioxide gas emissions were measured at 1,875 tonnes per day. The Alert Level remained at 2 (on a 0-5 scale). Residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Geological summary: Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Poas, Costa Rica

10.2°N, 84.233°W; summit elev. 2697 m

OVSICORI-UNA reported that small, frequent phreatic eruptions at Poás continued during 6-13 February. Data from the monitoring network indicated that 50-600 phreatic explosive events per day were occurring, but only a few events ejected material more than 100 m. At 0107 on 6 February an eruptive event generated a column that rose at least 300 m above the crater. At 1221 on 8 February an event generated a column of steam-and-ash that rose 200 m above the crater, and a gas-and-steam column that rose over 1 km.

Geological summary: The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world’s most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

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 7–13 February with nighttime crater incandescence. An eruptive event at 0917 on 8 February produced an ash plume that rose 1.3 km above the crater. 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.

Cotopaxi, Ecuador

0.677°S, 78.436°W; summit elev. 5911 m

IG-EPN reported that a seismic station located on the W flank recorded high-frequency seismic signals associated with the descent of small to moderate-sized lahars at 1442 and 1430 on 8 and 10 February, respectively. The public was advised to stay away from areas near the Agualongo drainage and to not approach any channels, streams, or rivers within the vicinity of Parque Nacional Cotopaxi (Cotopaxi National Park). The Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at White (the lowest level on a four-color scale).

Geological summary: The symmetrical, glacier-covered, Cotopaxi stratovolcano is Ecuador’s most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend to its base. The modern edifice has been constructed since a major collapse sometime prior to about 5,000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. Strong eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. Smaller eruptions have been frequent since that time.

Dukono, Halmahera

1.6992°N, 127.8783°E; summit elev. 1273 m

PVMBG reported that Dukono continued to erupt during 7-13 February. Gray-and-white emissions rose 650-1900 m above the summit during 7-10 February; emissions were not observed during 11-13 February due to fog. The Alert Level remained at Level 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, 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 continued at Ebeko during 1-8 February. According to volcanologists in Severo-Kurilsk (Paramushir Island, approximately 7 km E), explosions ejected ash as high as 4.5 km a.s.l during 5-6, and 8 February; ash plumes drifted SE and E. Satellite data acquired by KVERT showed the ash plume produced on 6 February extended as far as 11 km SE. The Aviation Color Code remained at Orange (the third color 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 7-13 February. Explosions were recorded daily, between 3-10 per hour. The explosions generated gas-and-ash plumes that rose as high as 1.0 km above the crater rim and drifted as far as 20 km in multiple directions. Explosions caused frequent block avalanches that descended various drainages including the Ceniza (SSW), Seca (W), Taniluyá (SW), Honda (E), and Las Lajas (SE) and reached vegetated areas. The explosions also ejected incandescent material as high as 400 m above the summit and weak rumbling sounds and shockwaves were reported daily. On 7 February fine ashfall was reported in Panimaché I (8 km SW), Morelia (9 km SW), Finca La Asunción (12 km SW), La Rochela (8 km SSW), and other nearby communities.

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.

Gareloi, Aleutian Islands (USA)

51.79°N, 178.794°W; summit elev. 1573 m

AVO raised the Volcano Alert Level for Gareloi to Advisory (the second level on a four-level scale) and the Aviation Color Code to Yellow (the second color on a four-color scale) at 1310 on 12 February due to increased seismic activity. Seismic unrest began at 0915 on 12 February; the local seismic network recorded ongoing tremor during 12-13 February. Persistent degassing activity from a fumarole field located on the S crater continued. No additional surficial activity was observed in partly cloudy satellite and webcam images.

Geological summary: The 8 x 10 km Gareloi Island, the northernmost volcano of the Delarof Group at the western end of the Andreanof Islands, consists of a stratovolcano with two summits and a prominent SE-trending fissure. The fissure was formed during an eruption in 1929 and extends from the southern summit to the sea. Steep sea cliffs that are cut into rocks of an older, eroded center are found on the SW coast, and submarine deposits of three debris avalanches produced by edifice collapse are found offshore. Young lava flows cover the older volcano from the summit to the coast along three broad axes trending NW, ENE, and S. The 1929 eruption originated from 13 craters along a 4-km-long fissure. Phreatic explosions were followed by the ejection of glassy pumice, lapilli, scoria, and older blocks, as well as by the emission of four short, steep lava flows, one of which reached the SE coast.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W; summit elev. 1740 m

AVO reported that slow lava effusion continued at Great Sitkin summit crater during 7-13 February. Few small volcanic earthquakes were recorded by the seismic network on most days, and low-frequency earthquakes (LFs) were recorded during 10-11 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 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.

Ibu, Halmahera

1.488°N, 127.63°E; summit elev. 1325 m

PVMBG reported that Ibu continued to erupt during 7-13 February. White and gray emissions rose 200-1500 m above the summit daily. Eruptive events were detected by a seismograph on 8 and 10 February. Dense, gray ash emissions rose as high as 1.5 km above the summit and drifted E, SW, and W. Eruption column heights were not observed during 12 February. The Alert Level remained at 2 (the second highest level on a four-level scale), with the public advised to stay outside of the 2 km radius hazard zone and 3.5 km away from the N area of the active crater.

Geological summary: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Lewotolok, Lembata Island

8.274°S, 123.508°E; summit elev. 1431 m

PVMBG reported that Lewotolok continued to erupt during 7-13 February. White emissions rose 5-100 m above the summit during 7 February, and 50-100 m above the summit during 10 and 13 February. A seismograph recorded explosive eruptive events at 1754 on 8 February, and 1657 on 9 February; white to gray ash plumes rose approximately 300-500 m above the summit and drifted E and SE. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 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.

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 7-13 February. White and gray gas-and-ash plumes rose as high as 700 m above the summit and drifted in multiple directions. On 10 February at 1651, PVMBG reported that an ash plume rose 700 m above the summit and drifted SW. According to the Darwin VAAC ash plumes rose over 700 m above the crater on most days and drifted N, E, SSW, and SW, though weather conditions sometimes prevented identification in satellite data. 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 2-8 February. Seismicity remained at high levels. The SW lava dome produced 184 lava avalanches that descended the S and SW flanks: one traveled S as far as 1.5 km down the upper part of the Boyong drainage and 183 traveled SW as far as 1.7 km down the upper part of the Bebeng drainage. One pyroclastic flow descended the Bebeng drainage, traveling as far as 1.6 km. 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.

Nevado del Ruiz, Colombia

4.892°N, 75.324°W; summit elev. 5279 m

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that unstable eruptive activity at Nevado del Ruiz continued during 30 January–6 February. Seismic events indicating rock fracturing remained similar to the previous week in both number of events and seismic energy released. These events were mainly located in areas up to 5 km to the NE, SE, S, and SW of Arenas Crater, and at depths of 1-7 km. The largest event, a M 1.1, occurred at 0648 on 2 February and was located about 2 km SSE of the crater and at a depth of 4 km. Seismicity associated with gas-and-ash emissions remained at similar numbers as the previous week but were more intense, and several ash emissions were observed through cameras. On 5 February an ash plume rose to a maximum height of 1.8 km above the summit. Sulfur dioxide emissions varied but continued at a low level overall. The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Geological summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America’s deadliest eruption.

Reventador, Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

IG-EPN reported that moderate eruptive activity continued at Reventador during 7-13 February. The seismic station recorded 27-45 daily explosive events, long-period earthquakes, episodes of harmonic tremor, and episodes of tremor associated with active degassing events. Several ash-and-gas plumes rose as high as 1.7 km above the crater rim and drifted N, SW, WSW, WNW, and NW; weather clouds often prevented visual monitoring of crater activity. The webcam monitoring system occasionally recorded episodes of crater incandescence during the night and early morning hours. Incandescent material was ejected up to 200 m above the crater during the night of 8 February, and avalanches of incandescent material descended multiple flanks as far as 600 m from the summit during 7-9 February. Secretaría de Gestión de Riesgos (SGR) 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.

Sabancaya, Peru

15.787°S, 71.857°W; summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported that moderate levels of eruptive activity continued at Sabancaya during 5-11 February. The monitoring network recorded a daily average of 33 explosions that often ejected gas-and-ash emissions as high as 2 km above the summit crater; ash plumes drifted less than 10 km downwind. The seismic network recorded seismic signals associated with the movement of magma and gases; counts ranged between 17 and 69 events per day. Thermal anomalies over the lava dome in the summit crater were identified in daily processed satellite data. Deformation monitoring data indicated slight inflation of the area near the Hualca Hualca sector (4 km N) continued. The Alert Level remained at Orange (the third level on a four-color scale) and the public was reminded to stay at least 12 km away from the summit crater in all directions.

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.

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 7-13 February. Reported seismicity consisted of 132-458 daily counts of explosive events. Weather clouds prevented views of summit crater activity during 7-9 February. During the morning of 8 February, small pyroclastic flows descended a ravine on the SW flank. Ash-and-gas plumes were observed in webcam images and sometimes satellite images acquired by the GOES-16 satellite during 10-11 and 12-13 February; plumes rose as high as 1.5 km above the crater and drifted SW, WSW, and W. Degassing activity was observed in GOES-16 satellite images during 11-12 February; gas plumes rose as high as 1.8 km above the crater and drifted SW and W. Continuous emissions consisting of gas and low amounts of ash were observed in webcam images at 1645 on 12 February; the emissions rose as high as 2.2 km above the crater and drifted WSW. The webcam monitoring system occasionally recorded episodes of crater incandescence during the night and early morning hours. Avalanches of incandescent material descended the SW flank as far as 1.5 km from the summit during the nights and early mornings of 7-8, 9-10, and 12-13 February. 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 7-13 February with lava extrusion at the Caliente dome. Weak, moderate, and sometimes abundant degassing was observed daily and rose as high as 200 m above the crater. Incandescence from the dome and upper lava flow was visible during most nights and early mornings. Daily explosions generated gas-and-ash plumes that rose as high as 900 m above the dome and drifted S, SW, W, and NW. The explosions produced block avalanches around the dome and along the SE, S, SW, and W flanks. Explosions generated short-range pyroclastic flows that descended the E and SE flanks on 9 February and the S, SW, and W flanks on 12 February. On 8 February ashfall was observed in the direct vicinity of the volcano.

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 7-13 February. White emissions rose 100-200 m above the summit and drifted multiple directions during 8-9 February. Several ash emissions were reported throughout the week and rose 500-1,000 m above the summit and drifted 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 the eruption at Sheveluch continued during 1-8 February characterized by powerful degassing activity observed from the Karan dome, and thermal anomalies identified in satellite images during 1-3 and 6-7 February. 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.

Shishaldin, Fox Islands (USA)

54.756°N, 163.97°W; summit elev. 2857 m

AVO raised the Volcano Alert Level for Shishaldin to Watch (the third level on a four-level scale) and the Aviation Color Code to Orange (the third color on a four-color scale) at 1246 on 11 February due to a slight increase in volcanic activity. Minor ash emissions were observed in a webcam image timestamped at 0925 on 11 February. The low-level ash cloud extended from the summit crater and draped over the N flank. AVO posited that since seismic signals typically associated with surficial mass flows were recorded at the same time as the ash emission event, a collapse event of previously deposited material on the upper area of the cone could have occurred. After the minor ash episode occurred, weather clouds obscured views of the summit and there was no evidence of ash in satellite images.

Geological summary: The symmetrical glacier-covered Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. It is the westernmost of three large stratovolcanoes in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning “mountain which points the way when I am lost.” Constructed atop an older glacially dissected edifice, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century. A steam plume often rises from the summit crater.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E; summit elev. 924 m

INGV reported that eruptive activity continued at Stromboli during 2-11 February. Webcam images showed Strombolian activity at two vents in Area N (one at N1 and one at N2), within the upper part of the Sciara del Fuoco, and from one vent at S2 in Area C-S (South-Central Crater) in the crater terrace. At Area N, low intensity explosive activity was observed from sectors N1 and N2 with the eruption of coarse material (bombs and lapilli) as high as 80 m above the vents. The average frequency of explosions from this area was 3-4 events per hour. At Area C-S, low to high intensity explosive activity was observed from sector S2 with the eruption of coarse and fine material (bombs, lapilli, and ash) as high as 150 m above the vent. The average explosions rate was 5-10 events per hour. On 9 February an explosive sequence was observed at sector S2 of Area C-S. Starting at 2055, the initial and highest energy explosion ejected coarse material onto the slopes of the crater terrace; ash emissions rose higher than 350 m above the vent and drifted E. Two lesser explosions followed, ejecting material approximately 150 m above the vent. The three events were then followed by some low-intensity explosions that ejected ash less than 80 m above the vent. The total duration of the sequence was about 4 minutes. The Dipartimento della Protezione Civile maintained the Alert Level at Yellow (the second highest level on a four-level scale).

Geological summary: Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the “Lighthouse of the Mediterranean” in the NE Aeolian Islands. This volcano 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 scarp that formed about 5,000 years ago due to a series of slope failures which extends 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 the eruption at Suwanosejima’s Ontake Crater continued during 5-12 February. Crater incandescence was observed in thermal webcam images. A total of two eruptions were reported; large volcanic blocks were ejected as far as 500 m away from the vent. The eruptions recorded at 1147 on 6 February and 1314 on 12 February produced ash plumes that rose 1 km above the crater rim before drifting SE and S, respectively. Seismicity consisted of a few volcanic earthquakes detected in the W area of the island, and episodes of tremor that occurred at the same time as the eruptive events. The Alert Level remained at 2 (on a 5-level scale), and the public was warned to stay at least 1 km away from Ontake crater in all directions.

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.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – February 7 – 13, 2024 – Managing Editor: Sally Sennert. Written by JoAnna G. Marlow.

Featured image credit: The Watchers

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