The Weekly Volcanic Activity Report: February 17 – 23, 2021

New activity/unrest was reported for 7 volcanoes from February 17 to 23, 2021. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest: Etna, Sicily (Italy) | Klyuchevskoy, Central Kamchatka (Russia) | Krysuvik, Iceland | Laguna del Maule, Central Chile-Argentina border | Pacaya, Guatemala | Raung, Eastern Java (Indonesia) | Sarychev Peak, Matua Island (Russia).

Ongoing activity: Aira, Kyushu (Japan) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Ibu, Halmahera (Indonesia) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island (Indonesia) | Merapi, Central Java (Indonesia) | Sabancaya, Peru | Semeru, Eastern Java (Indonesia) | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Whakaari/White Island, North Island (New Zealand).

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

Etna, Sicily (Italy)

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

INGV reported that a series of paroxysmal events separated by relative calm periods at Etna began on 16 February and continued at least through 23 February. The first episode began late on 16 February, characterized by gradually increasing Strombolian activity at the E vents of the Southeast Crater (SEC). Overflows of lava from the crater at 1805 caused a partial collapse of the cone and a pyroclastic flow that traveled 1.5 km along the W wall of the Valle de Bove. Lava fountains afterwards rose 500-600 m high. An eruptive plume rose several kilometers and drifted S, causing ashfall in areas as far as Syracuse, 60-80 km SSE. Lava flows advanced into the Valle de Bove and the Valle del Leone, and produced explosions in areas where they interacted with snow cover. Activity ended around 1900.

After a 30-hour pause the second paroxysmal episode began at 2330 on 17 February with overflows of lava from the eastern SEC vents. Lava fountaining began just after 0100 the next morning. Lava flows traveled towards the Valle de Bove, NE, SE, and SW. The eruption plume drifted SE, causing ashfall in Zafferana Etnea and Acireale. The lava fountains reached maximum heights of 600-700 m then ceased around 0140.

After another pause lasting about 32 hours, lava overflowed the SEC at around 0855 on 19 February. A rapid increase in explosive activity followed and lava fountaining began during 0945-0950. At 0953 lava fountains emerged from the S, or saddle, vent. At this time there were “fan-shaped” lava fountains rising from 4-5 vents orientated E-W. The eruption plume rose 10 km (32,800 ft) a.s.l. and drifted SE, again causing ashfall in downwind municipalities. Lava flowed S and towards the Valle de Bove causing explosions where they interacted with snow. Explosive activity ceased at 1110. Lab analysis of lava samples collected during 16-19 February eruptions showed that the magma was the most primitive over the past 20 years, meaning that the composition had changed little from its formation at depth and that it ascended quickly.

Weak Strombolian activity was visible in the late afternoon of 20 February. At 2230 a small lava flow descended a deep notch at the E end of the SEC and traveled towards the Valle de Bove. By 2300 the Strombolian activity had shifted to pulsating lava fountaining. Beginning at 0100 on 21 February more western vents became active and the E vents jetted lava 600-800 m high. Activity intensified at 0128 with jets of lava that rose more than 1 km high and were sustained for about 10 minutes. An eruption plume again rose to 10 km (32,800 ft) a.s.l. Beginning at 0200 the lava fountain became smaller, and at 0220 explosive activity ceased. Lava flowed SW and into the Valle de Bove.

Periodic ash emissions rose from both the S and E vents later than evening. Lava overflowed the SE crater just after 2230 and advanced 1 km towards the Valle de Bove. Lava fountains and Strombolian explosions occurred at multiple vents. Activity intensified at 0128 on 21 February and lava fountains rose 800-1,000 m above the SEC. Lava flowed from the S vent and an eruption plume rose several kilometers, but activity rapidly ceased at 0220. Lava flows continued to advance in the Valle de Bove; the longest flows were 3.5-4 km from the crater, between elevations of 1,700 and 1,800 m. During 0430-0515 very intense explosions from multiple SEC vents ejected incandescent bombs that fell as far as the base of the cone.

Weak Strombolian explosions at the SEC crater were visible late on 22 February. The frequency and intensity of the explosions increased and by 2210 material was ejected onto the flanks. By 2305 jets of lava were 300 m high, and by 2327 lava fountains rose from a second vent. Lava overflowed the crater at 2328 and headed towards the Valle de Bove. Within the first hour on 23 February lava fountains rose more than 1.5 km high and a sub-Plinian eruption plume had risen several kilometers above the summit, making this episode the most powerful and intense compared to the previous four. Lava overflowed the S vent and descended SW. Lava fountaining suddenly decreased at 0115 on 23 February, though lava flows continued to be fed. Strombolian activity again intensified at 0450, accompanied by ash emissions. Two lava flows formed and traveled SW and SE, the latter was longest and reached 1,700-1,800 m elevation. The activity ended at 1000.

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.

Klyuchevskoy, Central Kamchatka (Russia)

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

KVERT reported that during 1100-1150 on 18 February a new vent opened on Klyuchevskoy’s lower NW flank, near Erman glacier at elevations of 2,500-2,700 m, based on satellite images. Snowfall in the area of Klyuchi during 18-19 February inhibited webcam views. Bright incandescence was visible in webcam images beginning at 0323 on 21 February, likely indicating an advancing lava flow. On 23 February the Kamchatka Volcanological Station team reported that lava was flowing from two vents and bombs were being ejected 50 m high. A lahar along the Krutenkaya River was visible in an area 7 km E of Klyuchi Village (30 km NNE). Bright incandescence over the two flank vents was identified in satellite and video images on 24 February. KVERT raised the Aviation Color Code to Orange (the second highest level on a four-color scale).

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.

Krysuvik, Iceland

63.883°N, 22.083°W, Summit elev. 360 m

IMO raised the Aviation Color Code for Krýsuvík to Yellow on 24 February based on recent increased seismicity. Intense seismic activity had been detected for the previous few days and since midnight through the generation of the report at 1107 more than 500 earthquakes had been recorded. At 1005 a M 5.7 earthquake occurred 5 km W of Krýsuvík and at 1027 a M 4.2 was located in Nupshlidarhals, less than 1 km NW of Krýsuvík. The seismic unrest was unusual for the area in the context of the unrest in the Reykjanes peninsula that began in January 2020.

Geological summary: The Krysuvík volcanic system (also spelled Krisuvik) consists of a group of NE-SW-trending basaltic crater rows and small shield volcanoes cutting the central Reykjanes Peninsula west of Kleifarvatn lake. Several eruptions have taken place since the settlement of Iceland, including the eruption of a large lava flow from the Ogmundargigar crater row around the 12th century. The latest eruption took place during the 14th century.

Laguna del Maule, Central Chile-Argentina border

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

SERNAGEOMIN reported that during 1-16 February the seismic network at Laguna del Maule recorded a total of 533 volcano-tectonic earthquakes. Two earthquake swarms were recorded during 15-16 February; the largest events were local magnitude 3.1, and were located 9.1 and 8.8 km SW of the lake at a depth of 1.9 km. The epicenters were near the area producing anomalous carbon dioxide emissions. Swarms were recorded in June and December 2020, and January and February 2021, with the largest events occurring during the most recent swarm.

The highest rate of inflation during the previous 30 days was 2.3 cm/month, recorded at a station closest to the center of deformation. The highest horizontal displacement was an estimated 1.4 cm/month from a station just SW of the center. InSAR data mostly showed agreement in the magnitude and distribution of the ground-based deformation data. Overall, the deformation rates were higher than maximum averages. On 22 February the Alert Level was raised to Yellow, the second lowest level on a four-color scale. ONEMI declared 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.

Pacaya, Guatemala

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

INSIVUMEH reported that seismicity at Pacaya increased around 0900 on 18 February. Incandescent material was ejected 200 m above Mackenney Crater and explosions produced gas-and-ash plumes that rose 450 m and drifted mostly NE and S. An active lava flow on the SSW flank was 1.1 km long and generated hot block avalanches from the flow front. A lava flow emerged on the SW flank on 19 February. During 19-20 February periods of increased activity lasted 3-5 hours; moderate-to-loud explosions were accompanied by rumbling and sounds resembling trains. Ballistics were ejected 300- 500 m from the crater and ash plumes rose as high as 450 m and drifted SW. Ashfall was reported in areas downwind including El Rodeo and El Patrocinio. A lava flow on the S flank was 800 m long and produced incandescent blocks from the flow front that descended 500 m.

Strombolian activity increased on the morning of 20 February but fluctuated throughout the day. Ash plumes, that were dense during periods of heightened activity, rose 450 m and drifted 10-25 km S, SW, and W. As it grew darker lava fountains were visible rising 300-400 m and ballistics were ejected as far as 500 m from the crater. The lava flow on the S flank had lengthened to 1.1 km. Strombolian explosions continued during 21-22 February, ejecting incandescent material 100-175 m high. Ash plumes rose 450-800 m above the summit and drifted possibly as far as 15 km NW, W, and SW, causing ashfall in areas downwind including San Francisco de Sales, El Cedro, El Rodeo, and El Patrocinio. Ballistics were ejected as far as 500 m from the crater. Blocks from the front of the lava flow descended 300 m. Weak explosions during 22-23 February ejected incandescent material as high as 100 m above the summit. A 900-m-long lava flow was active on the SSW flank. Ash plumes drifted 5 km S.

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.

Raung, Eastern Java (Indonesia)

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

PVMBG reported that daily gray and sometimes black ash plumes rose 200-1,200 m above Raung’s summit during 17-23 February. Ash plumes were sometimes dense and drifted mainly N, NE, 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.

Sarychev Peak, Matua Island (Russia)

48.092°N, 153.2°E, Summit elev. 1496 m

SVERT noted that thermal anomalies over Sarychev Peak were identified in satellite images during 9-10 and 12-14 February. KVERT reported on 19 February that the effusive eruption was over, though lava continued to advance in the summit crater and a thermal anomaly remained visible. KVERT lowered the Aviation Color Code to Green (the lowest level on a four-color scale).

Geological summary: Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that during 15-22 February incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. An explosion on 16 February generated an eruption plume that rose 1 km above the crater rim and ejected bombs 1-1.3 km away from the crater. That same day the sulfur dioxide emission rate was extremely high, at 4,300 tons per day. An ash plume from an explosion at 2253 on 21 February rose 1.6 km and entered weather clouds. Large bombs were ejected 800-1,100 m away from the crater. 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.

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, 14-15, and 17 February that sent ash plumes to 2.1 km (6,900 ft) a.s.l. and drifted E and SE. Ashfall was reported in Severo-Kurilsk on 15 February and a thermal anomaly was identified in satellite images on 17 February. 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.

Fuego, Guatemala

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

INSIVUMEH reported that 4-12 explosions were recorded per hour during 17-23 February at Fuego, generating ash plumes as high as 1.1 km above the crater rim. Shock waves rattled buildings around the volcano. Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Las Lajas (SE), and Honda drainages, often reaching vegetated areas. Ashfall was reported on most days in several areas downwind including Morelia (9 km SW), Panimaché I (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), and San Pedro Yepocapa (8 km NW). Notably, on 17 February ash plumes drifted as far as 50 km E, causing ashfall in local communities as well as in Guatemala City (city center is about 40 km ENE). Ash plumes drifted 40 km SW on 18 February. Curtains of old ash deposits remobilized by strong winds were observed during 19-21 February. Incandescent material was ejected 100-400 m above the summit during 19-22 February.

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.

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Summit elev. 1325 m

PVMBG reported that on most days during 17-23 February gray-and-white ash plume from Ibu were seen rising 200-800 m above the summit and drifting in multiple directions. Weather conditions sometimes hindered observations. The report stated that during 16-17 February there were a total of 88 eruptive events. 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 active crater and 3.5 km away on the N side.

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, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. 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. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that a vent on the inner NW wall of Kilauea’s Halema`uma`u Crater continued to supply the lava lake during 17-23 February. The depth of the western part of the lake fluctuated between 215 and 218 m and the lake surface actively overturned at “plate” boundaries. The sulfur dioxide emission rate was elevated at 1,000 tons/day on 19 February.

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.

Lewotolok, Lembata Island (Indonesia)

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

PVMBG reported that the eruption at Lewotolok continued during 16-23 February; weather conditions sometimes hindered visual observations. Gray-and-white ash plumes rose 50-500 m above the summit and drifted E and SE. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summer 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 2021 lava dome just below Merapi’s SW rim and the new lava dome in the summit crater both continued to grow during 12-18 February. The 2021 lava dome volume was an estimated 397,500 cubic meters on 17 February, with a growth rate of about 25,200 cubic meters per day; it was 258 m long, 133 m wide, and 30 m high. The summit lava dome was an estimated 426,000 cubic meters, with a growth rate of about 10,000 cubic meters per day; it was 160 m long, 120 m wide, and 50 m high. Seismicity was less intense than the previous week. Electronic Distance Measurement (EDM) data showed no notable deformation. PVMBG noted that foggy conditions often prevented visual observations during 18-23 February, though sometimes white emissions were observed rising up to 400 m above the summit. 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.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported a daily average of 71 explosions at Sabancaya during 15-21 February. Gas-and-ash plumes rose as high as 3.2 km above the summit and drifted in multiple directions. Ten thermal anomalies originating from the lava dome in the summit crater were identified in satellite data. Minor inflation continued to be detected in areas N of Hualca Hualca (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

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.

Semeru, Eastern Java (Indonesia)

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

PVMBG reported that the eruption at Semeru continued during 17-23 February, though weather conditions often prevented visual confirmation. At 0601 on 17 February an ash plume rose 300 m and drifted N. A white-and-gray ash plume rose 100 m and drifted N, NE, and E on 18 February. The Alert Level remained at 2 (on a scale of 1-4), with a general exclusion zone of 1 km and extensions to 4 km in the SSE sector.

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.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported that no significant activity at Semisopochnoi was recorded after several ash deposits were visible in satellite images during 6-7 February. On 19 February the Aviation Color Code and the Volcano Alert Level were lowered to Yellow/Advisory, respectively.

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.

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 February. 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 17-23 February, though weather conditions sometimes prevented visual confirmation. White plumes rose as high as 1 km above the summit and drifted in multiple directions. On 21 February pyroclastic flows traveled as far as 2 km down the E and SE flanks. 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.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported intermittent eruptive events at Suwanosejima’s Ontake Crater during 12-19 February. These events produced ash plumes that rose as high as 1.5 km above the crater rim and ejected bombs 300 m away from the crater. 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.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E, Summit elev. 294 m

GeoNet reported that beginning around 0220 on 19 February a series of short-lived, low-energy steam explosions at Whakaari/White Island were recorded for about 100 minutes by local seismic and acoustic instruments. Webcam images were dark due to the time of day; no trace ash deposits were visible. Tremor had begun around 2100 the night before and then ceased at 0550 when the steam explosions ended. Visual observations and gas flux measurements taken during an overflight on 18 February showed no changes compared to the previous month. The Volcanic Alert Level remained at 1 and the Aviation Color Code remained at Green.

Geological summary: The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Source: GVP