The Weekly Volcanic Activity Report: March 17 - 23, 2021

The Weekly Volcanic Activity Report: March 17 - 23, 2021

New activity/unrest was reported for 8 volcanoes from March 7 to 23, 2021. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Cleveland, Chuginadak Island (USA) | Etna, Sicily (Italy) | Krysuvik-Trolladyngja, Iceland | Pacaya, Guatemala | San Cristobal, Nicaragua | Semisopochnoi, Aleutian Islands (USA) | Taal, Luzon (Philippines) | Veniaminof, United States.

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Laguna del Maule, Central Chile-Argentina border | Lewotolok, Lembata Island (Indonesia) | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Raung, Eastern Java (Indonesia) | Reventador, Ecuador | Sangay, Ecuador | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Soufriere St. Vincent, St. Vincent | Suwanosejima, Ryukyu Islands (Japan).

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, these reports are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports about recent activity are published in issues of the Bulletin of the Global Volcanism Network.

New activity/unrest

Cleveland, Chuginadak Island (USA)

52.825°N, 169.944°W, Summit elev. 1730 m

AVO reported that on 10 March an earthquake at Cleveland was large enough to be recorded by seismometers 100 km away on Umnak Island. On 17 March volcanic gas emissions increased and elevated surface temperatures were identified in satellite images. The Aviation Color Code was raised to Yellow and the Volcano Alert Level was raised to Advisory.

Geological summary: The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 it produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Etna, Sicily (Italy)

37.748°N, 14.999°E, Summit elev. 3320 m

INGV reported continuing episodes of lava fountaining at Etna's Southeast Crater (SEC) on 15, 17, and 19 March, though weather conditions often prevented visual observations. Strombolian activity at SEC began at 2110 on 14 March and turned into lava fountaining at 0048 on 15 March. Lava traveled towards the Valle de Bove and an eruption plume drifted E. Lava fountaining ceased by 0343 and only weak Strombolian activity followed. The lava flows continued to advance.

Weak Strombolian activity at SEC on 17 March began to intensify at 0155 and changed into lava fountaining at 0319. An eruption plume drifted SE and lava flow advanced. Fountaining activity ceased at 0717 and was followed by explosive activity. By 1859 the lava flows had reached 2,200 m elevation. Explosions at SEC and the lava flow in the Valle de Bove were visible at 2142 on 18 March when the weather conditions allowed for partial visibility of the summit.

Explosive activity at SEC was visible at 0734 on 19 March. The activity intensified at 0915 and ash emissions were visible. Lava fountaining started at 0935 and an ash plume drifted ENE. Lava fountaining activity ceased at 1136 and changed to Strombolian activity which gradually decreased; by 1350 only sporadic explosions were visible along with minor ash emissions. Lava flows were noted late in the morning.

Geological summary: Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical 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 horseshoe-shaped 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.

Krysuvik-Trolladyngja, Iceland

63.917°N, 22.067°W, Summit elev. 360 m

IMO reported that a small eruption in the western part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, began at around 2045 on 19 March. The eruption was first visible in webcam images and confirmed by satellite data, and an orange glow in clouds on the horizon was seen from Reykjanesbaer and Grindavík (10 km SW). The Aviation Color Code was raised to Red. Reykjanesbraut, the main road from the capital region to Reykjanesbaer and the international airport at Keflavík, was closed.

A fissure, 500-700 m long, had opened on a slope in the Geldingadalur valley about 4.7 km N of the coast and just off the SE flank of Fagradalsfjall mountain. Small lava fountains rose as high as 100 m above the fissure, and by 1110 on 20 March, the lava had covered an area less than 1 square kilometer and was approximately 500 m across. The extrusion rate was an estimated 5 cubic meters per second. The Aviation Color Code was lowered to Orange because there was little to no ash production that would affect aircraft. Reykjanesbraut reopened, but Sudurstrandarvegur, the road along the S coastline, was closed between Grindavík and Thorlakshofn.

The eruption continued during 21-23 March with a consistent extrusion rate. About three cones had formed along the fissure; the tallest and widest was situated at the higher part of the fissure. Lava flows, mainly from the largest cone, fanned out to the NW, W, and SW, and also flowed S and fanned out to the E. Spatter was ejected above the cones. Video captured by visitors showed parts of the largest cone collapsing and rebuilding. The IMO periodically issued warnings about weather conditions that would cause high concentrations of volcanic gases to settle near the eruption site, causing hazardous conditions for visitors. IMO noted that through the night of 22-23 March night sulfur dioxide levels in Reykjavík had increased, though not to unsafe levels.

Geological summary: The Krýsuvík-Trölladyngja volcanic system is described by the Catalogue of Icelandic Volcanoes as an approximately 50-km-long composite fissure swarm trending about N38°E, including a 30-km-long swarm of fissures, with no central volcano. It is one of the volcanic systems arranged en-echelon along the Reykjanes Peninsula west of Kleifarvatn lake. The Fagradalsfjall and Krýsuvík fissure swarms are considered splits or secondary swarms of the Krýsuvík-Trölladyngja volcanic system. Small shield volcanoes have produced a large portion of the erupted volume within the system. Several eruptions have taken place since the settlement of Iceland, including the eruption of a large basaltic lava flow from the Ogmundargigar crater row around the 12th century. The latest eruption, identified through tephrochronology, took place during the 14th century.

Pacaya, Guatemala

14.382°N, 90.601°W, Summit elev. 2569 m

INSIVUMEH reported periods of intense activity at Pacaya's Mackenney Crater during 17-18 March. Explosions produced dense ash plumes that rose 500-1,000 m above the crater rim and drifted 25-30 km S, SW, W, NW, and N. Incandescent material was ejected 300-500 m above the crater and fell within a 600 m radius of the crater. Lava flows on the S flank were 1.5 km long and set fire to vegetation at the advancing edge. Two new lava flows were visible; one traveled 400 m E and the other traveled 500 m S. Ashfall was reported in El Rodeo (4 km WSW), Patrocinio (about 5 km W), El Cedro (9 km NNW), San Francisco de Sales (5 km N), Amatitlán (12 km N), and Villa Nueva (16 km N).

Strong explosions during 21-23 March generated dense ash plumes that rose as high as 1.5 km above the summit. The plumes drifted 25-30 km NE, E, SE, and S, causing ashfall in Los Llanos, Los Pocitos (5 km S), Los Dolores (6 km SE), El Rodeo, Patrocinio, Mesías Alta and Mesías Baja, and Santa Elena Barillas (6 km ENE). Incandescent material was ejected 500 m above the crater and fell within 300-600 m of the crater. A lava flow on the SW flank was 1.5 km long, a flow on the S flank was 300 m long, and the E-flank lava flow had lengthened to 500 m. On 23 March ash plumes drifted 50 km NW, N, and NE, causing ashfall in Pepinal San Francisco de Sales, Los Pocitos, Los Dolores, Mesías Altas and Mesías Bajas, Santa Elena Barillas, Villa Nueva, and in the capital of Guatemala City (25-30 km NNE). Ash fell at Guatemala's international airport, Aeropuerto Internacional La Aurora, 50 km N of Pacaya, causing the airport to close. Soldiers swept ash off of the runway and incoming flights were diverted to El Salvador.

Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

San Cristobal, Nicaragua

12.702°N, 87.004°W, Summit elev. 1745 m

The Washington VAAC reported that on 19 March a notable ash cloud from San Cristóbal rose at least to 12.2 km (40,500 ft) a.s.l. and drifted over 80 km ENE based on satellite data, ash dispersion models, and weather models.

Geological summary: The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported that satellite data showed minor ash deposits on Semisopochnoi's flanks and a possible gas cloud on 14 March. Two small explosions on 19 March, at 0350 and 0534, were recorded by regional infrasound sensors and prompted AVO to raise the Aviation Color Code and the Volcano Alert Level to Orange and Watch, respectively. A small explosion at 0230 on 21 March was followed by a series of smaller explosions. A volcanic gas cloud was visible in satellite data during the previous day. Three small explosions were detected during 22-23 March, though high weather cloud cover, at 9.1 km (30,000 ft) a.s.l., prevented satellite confirmation; no ash was visible above the cloud deck.

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

Taal, Luzon (Philippines)

14.002°N, 120.993°E, Summit elev. 311 m

PHIVOLCS reported that at Taal during 16-23 March there were 36-193 daily volcanic earthquakes and 27-156 daily periods of volcanic tremor with variable durations (1-15 minutes). Three hybrid earthquakes were recorded each day on 18 and 19 March. Diffuse steam plumes from fumarolic vents in Main Crater rose as high as 100 m. Daily measurements of sulfur dioxide emissions were 603-1,184 tonnes per day. The Alert Level remained at 2 (on a scale of 0-5). PHIVOLCS strongly recommended no entry onto the island, and access to the Main Crater and Daang Kastila fissure (along the walking trail) was strictly prohibited.

Geological summary: Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all historical eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones that have grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.

Veniaminof, United States

56.17°N, 159.38°W, Summit elev. 2507 m

AVO reported that the eruption at Veniaminof continued during 17-23 March. Low surface temperatures were visible in satellite images along with steam-and-gas plumes. Low-level tremor was recorded in local seismic data. During the morning of 21 March small explosions were identified using seismic data and infrasound sensors in Chignik Lagoon. A volcanic gas cloud drifted SE at or below 1.5 km (5,000 ft) a.s.l. Small explosions were detected again during 21-23 March. Sulfur dioxide plumes were identified in satellite data. Minor ash emissions rose hundreds of meters and rapidly dissipated, though on 23 March a pilot saw an ash plume rise to 3 km (10,000 ft) a.s.l. Satellite data during 22-23 March showed highly elevated surface temperatures and subsidence of the glacial ice over the flank vent where lava was erupting. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Geological summary: Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that during 15-22 March incandescence from Minamidake Crater (at Aira Caldera's Sakurajima volcano) was visible nightly. An explosion on 15 March produced an eruption plume that rose 1.5 km above the crater rim and ejected bombs 500-700 m away from the crater. The explosions on 20 March generated plumes that rose as high as 1.6 km. The sulfur dioxide emission rate was 1,800 tons per day on 12 March. The Alert Level remained at 3 (on a 5-level scale).

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

Dukono, Halmahera (Indonesia)

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

Based on satellite and wind model data, the Darwin VAAC reported that during 16-23 March ash plumes from Dukono rose to 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

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

Ebeko, Paramushir Island (Russia)

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

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 12-15 and 18-19 March that sent ash plumes to 2.6 km (8,500 ft) a.s.l. and drifted E, NE, and NW. Ashfall was reported in Severo-Kurilsk on 12 March. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that two vents on the inner NW wall of Kilauea's Halema`uma`u Crater continued to supply the lava lake during 17-23 March. Lava flowed from both the main vent and a vent several meters NE into the lake through submerged inlets. Another lava flow emerged from about halfway up the cone structure starting at 0220 on 16 March, but had ended by the next day.

The depth of the western part of the lake rose from about 221 m to 223 m and lava continued to circulate in that part. The E half of the lake remained solidified and lower that the W half, with the crusted E half expanding towards the W. The sulfur dioxide emission rate was 650, 700, and 1,100 tons/day on 17, 18, and 19 March, respectively. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

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

Klyuchevskoy, Central Kamchatka (Russia)

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

KVERT reported that the Strombolian eruption from vents on Klyuchevskoy's lower NW flank continued during 12-19 March. A large, bright thermal anomaly over the vents was identified in satellite images. Kamchatka Volcanological Station scientists visited the eruption site on 16 March and observed decreased activity. A small lava flow effused from a vent at the W base of the cone and lava flowed from the N side. Every few seconds material was ejected as high as 100 m above the cone's rim. On 22 March the cinder cone was weakly incandescent and lava effusion continued to be observed in webcam images. The temperature of the thermal anomaly identified in satellite data also significantly decreased. The Aviation Color Code was lowered to Yellow (the second lowest level on a four-color scale) on 22 March. Two days later, on 24 March, the Aviation Color Code was lowered to Green (the lowest level); weak incandescence from the cone and flows visible in webcam images reflected cooling.

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

Laguna del Maule, Central Chile-Argentina border

36.058°S, 70.492°W, Summit elev. 2162 m

SERNAGEOMIN reported that during 1-15 March the seismic network at Laguna del Maule recorded a total of 123 volcano-tectonic earthquakes. The largest event was a local M 2.4 located 8.2 km WSW of the lake, at a depth of 4.4 km. One tremor event was also recorded. Recent carbon dioxide emission measurements showed an upward trend and that the area of anomalous emissions had expanded. Deformation rates were higher than maximum averages. The Alert Level remained at Yellow, the second lowest level on a four-color scale. ONEMI maintained a Yellow Alert for San Clemente and recommended restricted access within a radius of 2 km from the center of elevated carbon dioxide emissions.

Geological summary: The 15 x 25 km wide Laguna del Maule caldera contains a cluster of small stratovolcanoes, lava domes, and pyroclastic cones of Pleistocene-to-Holocene age. The caldera lies mostly on the Chilean side of the border, but partially extends into Argentina. Fourteen Pleistocene basaltic lava flows were erupted down the upper part of the Maule river valley. A cluster of Pleistocene cinder cones was constructed on the NW side of the Maule lake, which occupies part of the northern portion of the caldera. The latest activity produced an explosion crater on the E side of the lake and a series of Holocene rhyolitic lava domes and blocky lava flows that surround it.

Lewotolok, Lembata Island (Indonesia)

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

PVMBG reported that the Strombolian eruption at Lewotolok continued during 17-23 March. Daily gray-and-white ash plumes rose as high as 700 m above the summit and drifted mainly E and SE. Incandescent material was ejected 300 m E of the summit on 20 March. The next day incandescent material was ejected 100 m above the summit and as far as 200 m E. On 22 March explosions ejected incandescent material 250-350 m SE. The eruptive events were accompanied by rumbling and banging sounds. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summit crater.

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

Merapi, Central Java (Indonesia)

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

BPPTKG reported that the lava dome just below Merapi's SW rim and the lava dome in the summit crater both continued to grow during 12-18 March. The 2021 lava-dome volume was an estimated 840,000 cubic meters on 18 March, with a growth rate of about 12,900 cubic meters per day, and continued to shed material down the flank. A total of three pyroclastic flows traveled a maximum of 1 km down the SW flank. Incandescent avalanches, recorded 211 times, traveled as far as 1.2 km down the SW flank. The summit lava dome had grown to 65 m tall and had an estimated volume of 950,000 cubic meters with a growth rate of 12,800 cubic meters per day. The Alert Level remained at 3 (on a scale of 1-4), and the public were warned to stay 5 km away from the summit.

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

Nevados de Chillan, Chile

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

SERNAGEOMIN reported that activity at Nevados de Chillán's Nicanor Crater was ongoing with sporadic gas-and-ash emissions and continuing lava effusion during 1-15 March. Explosions produced eruption plumes that rose as high as 1.3 km above the crater rim, and sometimes ejected material as far as 160 m onto the NE flank. The L5 lava flow on the N flank was about 925 m long and 80 m wide at the distal end, and continued to slowly advance. The Alert Level remained at Yellow, the second lowest level on a four-color scale. ONEMI stated that Alert Level Yellow (the middle level on a three-color scale) remained in place for the communities of Pinto and Coihueco, noting that the public should stay at least 2 km away from the crater.

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

Raung, Eastern Java (Indonesia)

8.119°S, 114.056°E, Summit elev. 3260 m

PVMBG reported that daily gray-and-white ash plumes rose 300-900 m above Raung's summit during 16-23 March. Ash plumes drifted mainly N, E, and S. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Geological summary: Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The unvegetated summit is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

Reventador, Ecuador

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

IG reported that a high level of activity continued to be recorded at Reventador during 16-23 March; adverse weather conditions sometimes prevented visual confirmation. Seismicity was characterized by 31-81 daily explosions, volcano-tectonic and harmonic tremor events, and long-period earthquakes as well as signals indicating emissions. Gas, steam, and ash plumes were often observed multiple times a day with the webcam or reported by the Washington VAAC; they rose as high as 1.5 km above the summit crater and drifted mainly NE, E, and SW. Crater incandescence and incandescent blocks rolling at least down the N, NE, and E flanks were observed nightly.

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

Sangay, Ecuador

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

IG reported a high level of activity at Sangay during 17-23 March. Seismicity was characterized by daily explosions, long-period earthquakes, and signals indicating emissions. Weather clouds and rain often prevented visual observations of the volcano, though based on the Washington VAAC, webcam images, and observer reports, ash plumes were noted most days rising as high as 1.5 km above the summit and drifting mainly N, W, and SW. A seismic station recorded occasional debris flows during 17-19 March. No ashfall was reported by residents.

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 horseshoe-shaped 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 sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less 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.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 12-19 March. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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

Sinabung, Indonesia

3.17°N, 98.392°E, Summit elev. 2460 m

PVMBG reported that the eruption at Sinabung continued during 16-23 March. Weather conditions often prevented visual observations of the volcano, particularly during the end of the week. Avalanches were detected daily by the seismic network and observed traveling 500-1,500 m down the E and SE flanks during 16-18 March. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Soufriere St. Vincent, St. Vincent

13.33°N, 61.18°W, Summit elev. 1220 m

University of the West Indies Seismic Research Centre (UWI-SRC) and National Emergency Management Organisation (NEMO) reported that the lava dome in Soufrière St. Vincent's main crater continued to slowly grow during 17-23 March, expanding to the N and S. A team visited the dome on 19 and 23 March to make observations, take measurements, and maintain monitoring equipment. Gas-and-steam continued to rise from the top of the dome as well as along the contact between the old and new domes. As of 19 March the dome was 105 m tall, 912 m long, 243 m wide, and had an estimated volume of 13.13 million cubic meters. The Alert Level remained at Orange (the second highest level on a four-color scale).

Geological summary: Soufrière St. Vincent is the northernmost and youngest volcano on St. Vincent Island. The NE rim of the 1.6-km wide summit crater is cut by a crater formed in 1812. The crater itself lies on the SW margin of a larger 2.2-km-wide caldera, which is breached widely to the SW as a result of slope failure. Frequent explosive eruptions after about 4,300 years ago produced pyroclastic deposits of the Yellow Tephra Formation, which cover much of the island. The first historical eruption took place in 1718; it and the 1812 eruption produced major explosions. Much of the northern end of the island was devastated by a major eruption in 1902 that coincided with the catastrophic Mont Pelée eruption on Martinique. A lava dome was emplaced in the summit crater in 1971 during a strictly effusive eruption, forming an island within a lake that filled the crater. A series of explosive eruptions in 1979 destroyed the 1971 dome and ejected the lake; a new dome was then built.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that the seismic network for Suwanosejima's Ontake Crater detected a total of 11 explosions during 12-19 March. These events produced eruption plumes that rose as high as 1.7 km above the crater rim and ejected bombs up to 700 m away from the crater. Incandescence from the crater was occasionally visible at night. The Alert Level remained at 2 (on a 5-level scale).

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

Source: GVP

Comments

Karen 5 months ago

You should add the ASH ADVISORY REPORT to your weekly Volcanic Report https://www.volcanodiscovery.com/news/vaac/latest-reports.html

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