The Weekly Volcanic Activity Report: April 3 - 9, 2024

New activity/unrest was reported for 6 volcanoes from April 3 to 9, 2024. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest

Atka Volcanic Complex, Andreanof Islands (USA)

52.331°N, 174.139°W | Summit elev. 1518 m

AVO lowered the Volcano Alert Level for the Atka volcanic complex to Normal (the lowest level on a four-level scale) and the Aviation Color Code to Green (the lowest color on a four-color scale) at 0734 on 9 April. The report noted that activity at the volcano had decreased following the small explosion at the summit crater of Korovin on 27 March, one of the volcanoes at the complex. Though occasional small earthquakes and weak volcanic tremor continued to be recorded, the activity was at background levels.

Geological summary: The Atka Volcanic Complex consists of a central shield and Pleistocene caldera and four notable volcanic cones. A major explosive dacitic eruption accompanied formation of the caldera about 500,000 to 300,000 years ago; approximately half of the caldera rime remains, open towards the NW. The Sarichef cone, ~5 km ESE of the caldera rim, retains a symmetrical profile, unlike most other heavily eroded features outside the caldera to the S and W. The Kliuchef stratovolcano grew within the caldera and exhibits five eruptive vents striking NE, including two at the summit, that have been active in the Holocene. A 700-m-diameter crater 1 km NE of the summit may have been the source vent for a large 1812 CE eruption. Hot springs and fumaroles are located on the flanks of Kliuchef and in a glacial valley to the SW. The most frequently active volcano of the complex is Korovin, at the NE tip of Atka Island about 5 km N of Kliuchef. An 800-m-diameter crater on the SE side of the summit contains a deep circular pit that sometimes contains a crater lake thought to be the source of phreatic ash explosions. The smaller Konia cone, slightly offset to the E, lies between Kliuchef and Korovin. Most of the lava flows in the complex are basaltic, though some dacitic flows are also present.

Barren Island, Andaman Islands (India)

12.278°N, 93.858°E | Summit elev. 354 m

Eruptive activity at Barren Island continued according to notices from the Darwin VAAC. Ash plumes identified in satellite images during 2-3 April rose 0.9-1.5 km (3,000-5,000 ft) a.s.l. and drifted SW and W. Weather conditions prevented views on 4 April. A thermal anomaly over the summit was identified in Sentinel data on 30 March and 4 April.

Geological summary: Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Etna, Sicily (Italy)

37.748°N, 14.999°E | Summit elev. 3357 m

A small vent at Etna’s Southeast Crater began emitting unprecedented quantities of volcanic gas puffs that formed vortex rings during the evening of 2 April. INGV issued a Volcano Observatory Notice for Aviation (VONA) at 2016 on 2 April raising the Aviation Color Code to Yellow (the second highest color on a four-color scale) due to increased signs of unrest. The Aviation Color Code was raised to Orange at 2030 because explosive activity at the summit craters was visible in webcam images; ash emissions were not produced.

A series of six explosive events were recorded by the seismic network during 1501-1510 on 7 April. Coincident with the seismic signals a four-minute-long, dense ash emission from Bocca Nuova Crater rose to 5 km a.s.l., or about 1.6 km above the summit, and quickly dispersed to the S. A VONA issued at 1018 on 9 April noted sporadic activity at the summit craters.

Geological summary: Mount Etna, towering above Catania on the island of Sicily, has one of the world’s longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Fernandina, Isla Fernandina (Galapagos)

0.37°S, 91.55°W | Summit elev. 1476 m

Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that during 2 March-1 April an estimated 44 million cubic meters of lava had erupted at Fernandina, making the current eruption the largest in the last 15 years, surpassed only by the 2009 eruption. Fissure 13, located just below the crater rim on the upper SE flank, continued to be active during 2-9 April; the rate of lava effusion was about five cubic meters per second at least through 4 April, though the advancement rate of the distal end of the lava flow was variable. Sulfur dioxide emissions were generally at moderate levels, fluctuating between about 100 and 1,000 tons per day, though emissions were as high as around 1,650 tons per day on 4 April. Daily thermal anomalies over the lava flow continued to be detected and were variable in both number and intensity. The lava flows continued to advance down the flank and by 4 April were about 13.2 km long and about 1.3 km from the coastline. Based on observations from the Dirección del Parque Nacional Galápagos, the Ministerio del Ambiente, and Agua y Transición Ecológica the flows reached the ocean on 7 April. An 8 April satellite image showed plumes of gas and steam rising from the ocean entry.

Geological summary: Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic “overturned soup bowl” profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Poas, Costa Rica

10.2°N, 84.233°W | Summit elev. 2697 m

OVSICORI-UNA reported continuing emissions at Poás during 3-9 April. Vents on the nearly dry crater floor vigorously emitted plumes of gas and steam; ash was present in the plumes during 3-5 April and absent on the rest of the days. The plumes rose a few hundred meters above the crater rim and mainly drifted W, SW, and S and were often detected downwind in residential areas of Heredia and El Valle Central. Incandescence was visible from Boca A and Boca C during 3-4 April, and at Boca A during 4-5 April. A sulfur odor was reported in Heredia and El Valle Central during 3-4 April and in Sarchí on 9 April. Weather conditions sometimes prevented visual observations.

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.

Reykjanes, Reykjanes Peninsula

63.817°N, 22.717°W | Summit elev. 140 m

IMO reported that the eruption along the fissure within the Reykanes volcanic system continued during 3-9 April. Two cones produced lava flows during the beginning of the week, but by 8 April only the larger, main cone was active. Lava flowed mostly S and the flows thickened near the crater and slightly to the S where the flows were most active. On 7 April lava filled the main crater, overflowed the crater rim, and cascaded down the cone’s flank. Part of N crater rim collapsed at 2130 causing lava to flow N; the lava built up a mound, blocking the path, and by the next day most of the lava again flowed S.

The average lava effusion rate decreased from about 6.6 cubic meters per second during 27 March-3 April to about 3.6 cubic meters per second during 3-8 April. During an overflight on 8 April observers confirmed that there had been a gradual decrease in the intensity of the eruption. The lava-flow field was an estimated 6.14 square kilometers with an approximate volume of 31.1 million cubic meters. Concurrent with a decrease in eruption intensity, inflation had accelerated. Seismicity continued to be at low levels and was concentrated between Sylingarfell and Stóra-Skógfell, and in the W part of Grindavík. Sulfur dioxide emissions continued to be high around the eruption site and were detected in residential areas downwind. On 3 April the Civil Protection Emergency Level was lowered to the middle level on a three-level scale. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.

Ongoing activity

Ahyi, Mariana Islands (USA)

20.42°N, 145.03°E | Summit elev. -75 m

Signs of unrest at Ahyi Seamount had not been observed in satellite images since 27 March when an area of discolored water was present near the seamount. Both the Aviation Color Code and the Volcano Alert Level were lowered to Unassigned at 0346 on 10 April due to the absence of activity and the lack of local monitoring stations.

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.

Dukono, Halmahera

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

PVMBG reported that the eruption at Dukono was ongoing during 3-9 April. Gray-and-white ash plumes rose as high as 1 km above the summit and drifted SW, S, and SE during 3 and 7-9 April. According to the Darwin VAAC an ash plume rose to 2.4 km (8,000 ft) a.s.l., or about 1.6 km above the summit, and drifted SW on 4 April. Plumes were either absent or not observed due to weather conditions on the other days. 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 28 March-4 April. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 28-29 March and 1 and 3-4 April generated ash plumes that rose as high as 4.5 km (14,800 ft) a.s.l. and drifted S and SE. A thermal anomaly was identified in satellite images on 29 March and 4 April; on other days there was no activity or weather conditions prevented views. 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 1-9 April. Explosions were recorded daily, averaging 2-10 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 NW, W, and SW. Explosions caused frequent, daily block avalanches that descended various drainages including the Ceniza (SSW), Seca (W), Taniluyá (SW), and Las Lajas (SE), and sometimes reached vegetated areas. Weak rumbling sounds and shock waves were reported on most days. Ashfall was reported in areas downwind during 4-7 April including El Porvenir (11 km SW), El Rodeo, Finca Palo Verde, Sangre de Cristo (8 km WSW), Yepocapa (8 km NW), Santa Sofía (12 km SW), Los Yucales (12 km SW), Panimaché I and II (8 km WSW), and Morelia (9 km SW); ash possibly fell in La Soledad (11 km N), Acatenango (8 km E), Parramos (18 km NNE), and other nearby communities during 4-5 April. The explosions also ejected incandescent material up to 300 m above the summit during 5-6 April. In the afternoon of 8 April lahars descended the Las Lajas and Ceniza drainages, carrying tree branches, trunks, and blocks as large as 1.5 m in diameter.

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.

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 3-9 April. Slightly elevated surface temperatures were identified in satellite images during 2-3 April. Seismicity was low with a few small daily earthquakes recorded by the seismic network; the network was not operational during 8-9 April. Weather clouds fully or partly 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.

Lewotobi, Flores Island

8.542°S, 122.775°E | Summit elev. 1703 m

PVMBG reported that white-and-gray plumes rose 50-200 m above the summit of Lewotobi’s Laki-laki volcano and drifted N, NE, and E on 6 and 9 April. White plumes rose as high as 300 m above the summit and drifted in multiple directions on 3, 5, and 7 April; no plumes were visible on 4 April. The Alert Level remained at 2 (the second lowest level on a scale of 1-4) and the public was warned to stay outside of the exclusion zone, defined as a 2-km radius around Laki-laki crater, 3 km to the NNE, and 5 km on the NE flanks.

Geological summary: The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the “husband and wife”). Their summits are less than 2 km apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued during 3-9 April. White-and-gray ash plumes rose as high as 350 m above the summit and drifted E and SE on 4 and 7 April. White emissions rose as high as 600 m above the summit and drifted in multiple directions on the other days. The Alert Level remained at 3 (on a scale of 1-4) and the residents of Lamawolo, Lamatokan, and Jontona were warned to stay 2 km away from the vent and 3 km away from the vent on the S and SE flanks.

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 3-9 April. White-and-gray ash plumes rose 250-1,500 m above the summit and drifted in multiple directions during 3-5 and 8-9 April. White steam-and-gas plumes rose 250-300 m above the summit and drifted E and SE during 6-7 April.

Lahars generated by intense rainfall were detected by the seismic network during 1400-1530 on 5 April. The lahars originated in multiple drainages on Marapi and damaged homes and infrastructure in parts of the Agam and Tanah Datar regencies including Bukik Batabuah and Aia Angek, and villages in the districts of Sungai Pua, Candung, and Batipuah. According to news articles at least two pulses of lahars damaged the Bukittinggi-Padang highway, causing it to be impassible for several hours. The lahars infiltrated about 65 hectares of rice fields, damaged 72 houses, and affected 38 businesses. In some areas, cars were stranded and some motorists were trapped, smaller roads were blocked, gas stations were impacted, and a few farm animals were swept away. About 270 residents were affected, and at least 68 were evacuated. Some residents were taken to the hospital, but no fatalities were reported. Based on field observations during 5-6 April authorities identified several rivers that had shallowed due to deposited material from the lahars and needed to be dredged so that they could flow normally and not cause further flooding. Efforts to remove the lahar and debris deposits such as tree trunks and branches was underway. 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 29 March-4 April. Seismicity remained at high levels. The SW lava dome produced 49 lava avalanches that traveled as far as 1.8 km down the SW flank. One pyroclastic flow traveled 1.7 km SW down the upper part of the Bebeng drainage. Morphological changes to the SW lava dome were due to continuing effusion and collapses of material. The volume of the SW dome was an estimated 2,054,600 cubic meters and the dome in the main crater was an estimated 2,358,200 cubic meters based on a 30 March drone survey and webcam images. The highest temperature of the SW dome was 243 degrees Celsius, lower than the previous measurement. 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.

Reventador, Ecuador

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

IG-EPN reported that a moderate eruption at Reventador was ongoing during 2-9 April. Seismicity was characterized by 46-78 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Ash-and-gas plumes rose as high as 1.1 km above the crater rim and drifted NW, W, and SW during 2-4 and 7 April. Weather conditions sometimes prevented views; emissions were not visible on the other days of the week. Avalanches of incandescent material were visible most overnights, descending the flanks as far as 800 m from the summit. 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 2-9 April. The seismic network recorded 1,106 explosions during 2-3 April and 20-411 daily explosions during the rest of the week. Gas-and-ash plumes rose 300-1,000 m above the summit and drifted SW on most days; weather conditions often hindered views during the week. Incandescent material descended the SE flank as far as 600 m during 2-3 April. 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 1-9 April with a lava extrusion and avalanches 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 parts of the lava flow on the WSW, S, and SE flanks. Daily explosions (1-7 per hour on some days) generated gas-and-ash plumes that mainly rose 600-900 m above the summit and drifted as far as 20 km NW, W, and SW. The explosions produced block avalanches on the dome’s flanks and generated occasional, short-range pyroclastic flows that mainly descended E, SE, and SW flanks. Block avalanches from the dome and the margins of the upper part of the lava flow were also sometimes visible. Rumblings were occasionally heard. Ashfall was reported in San Marcos Palajunoj (8 km SW), Loma Linda (7 km W), Llanos de Pinal, and other nearby communities during 4-5 April.

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 3-9 April. Daily white-and-gray ash plumes rose 400-800 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 28 March-4 April with a daily thermal anomaly identified in satellite images. On 29 March a plume of resuspended ash drifted 65 km E. 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.

References:

Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – April 3 – 9, 2024 – Managing Editor: Sally Sennert.

Featured image credit: TW

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