The Weekly Volcanic Activity Report: February 23 – March 1, 2022

the-weekly-volcanic-activity-report-february-23-march-1-2022

New activity/unrest was reported for 3 volcanoes from February 23 to March 1, 2022. During the same period, ongoing activity was reported for 19 volcanoes.

New activity/unrest: Asosan, Kyushu (Japan) | Ontakesan, Honshu (Japan) | Telica, Sierra de los Marrabios.

Ongoing activity: Ambae, Vanuatu | Ambrym, Vanuatu | Davidof, Aleutian Islands (USA) | Etna, Sicily (Italy) | Great Sitkin, Andreanof Islands (USA) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Merapi, Central Java | Pavlof, Alaska Peninsula, Alaska | Sabancaya, Peru | Sangay, Ecuador | Semeru, Eastern Java | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica | Wolf, Isla Isabela (Galapagos) | Yasur, Vanuatu.

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

Asosan, Kyushu (Japan)

32.884°N, 131.104°E, Summit elev. 1592 m

JMA reported that the amplitude of volcanic tremor signals at Asosan increased at around 0500 on 24 February and then increased again around 0900. About 45 minutes later JMA raised the Alert Level to 3 (on a scale of 1-5) and warned the public to stay at least 2 km away from the crater. Tremor amplitude decreased at around 1540 on 27 February. White plumes continued to rise 700-800 m above the crater rim during 24-28 February.

Geological summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Ontakesan, Honshu (Japan)

35.893°N, 137.48°E, Summit elev. 3067 m

JMA reported that the number of volcanic earthquakes at Ontakesan began increasing at 1415 on 23 February. Four minutes later a volcanic tremor signal was detected along with uplift on the S flank. At 1635 JMA raised the Alert Level to 2 (on a scale of 1-5). The report warned the public to stay at least 1 km away from Crater 79-7 on the SW flank of the Kenga-mine summit. After a peak on 25 February, the number of daily volcanic earthquakes began to decline; there were two volcanic earthquakes recorded on 24 February, a total of 17 on 25 February, 4-5 per day during 26-28 February, and 3 on 1 March. During an overflight on 25 February scientists observed no changes in the fumarolic areas or other morphological changes on the volcano.

Geological summary: The massive Ontakesan stratovolcano, the second highest volcano in Japan, lies at the southern end of the Northern Japan Alps. Ascending this volcano is one of the major objects of religious pilgrimage in central Japan. It is constructed within a largely buried 4 x 5 km caldera and occupies the southern end of the Norikura volcanic zone, which extends northward to Yakedake volcano. The older volcanic complex consisted of at least four major stratovolcanoes constructed from about 680,000 to about 420,000 years ago, after which Ontakesan was inactive for more than 300,000 years. The broad, elongated summit of the younger edifice is cut by a series of small explosion craters along a NNE-trending line. Several phreatic eruptions post-date the roughly 7300-year-old Akahoya tephra from Kikai caldera. The first historical eruption took place in 1979 from fissures near the summit. A non-eruptive landslide in 1984 produced a debris avalanche and lahar that swept down valleys south and east of the volcano. Very minor phreatic activity caused a dusting of ash near the summit in 1991 and 2007. A significant phreatic explosion in September 2014, when a large number of hikers were at or near the summit, resulted in many fatalities.

Telica, Sierra de los Marrabios

12.606°N, 86.84°W, Summit elev. 1036 m

Based on satellite and webcam images, the Washington VAAC reported that during 21-24 and 27-28 February multiple ash emissions at Telica rose as high as 1.5 km (5,000 ft) a.s.l. and drifted as far as 55 km W, WSW, and SW.

Geological summary: Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Ongoing activity

Ambae, Vanuatu

15.389°S, 167.835°E, Summit elev. 1496 m

On 24 February the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that explosions at the cone in Ambae’s Lake Voui continued to produce steam and ash emissions. The Alert Level remained at 2 (on a scale of 0-5) and the public was warned to stay outside of the Danger Zone defined as a 2-km radius around the active vents in Lake Voui and away from drainages during heavy rains.

Geological summary: The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Ambrym, Vanuatu

16.25°S, 168.12°E, Summit elev. 1334 m

On 24 February the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that nighttime crater incandescence from Ambrym’s Benbow Crater was no longer visible, though steam emissions persisted. The Alert Level remained at 2 (on a scale of 0-5). VMGD warned the public to stay outside of the Permanent Danger Zone A, defined as a 1-km radius around Benbow Crater and a 2-km radius around Marum Crater, and additionally to stay 500 m away from the ground cracks created by the December 2018 eruption.

Geological summary: Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides Arc. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Davidof, Aleutian Islands (USA)

51.97°N, 178.33°E, Summit elev. 328 m

According to AVO the earthquake swarm that began on 24 January in the vicinity at Davidof continued at least through 1 March with a few small earthquakes recorded each day. The swarm was either related to tectonic processes or volcanic unrest. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.

Geological summary: A cluster of small islands between Segula and Little Sitkin in the western Aleutians, the largest of which is Davidof, are remnants of a stratovolcano that collapsed during the late Tertiary, forming a 2.7-km-wide caldera. The islands include Khvostof, Pyramid, Lopy, and Davidof; the latter three form the eastern rim of the mostly submarine caldera, sometimes referred to as the "Aleutian Krakatau." The islands were constructed above a roughly 100-m-deep submarine platform extending NW to Segula Island; the floor of the caldera lies 80 m below sea level. The islands are vegetated, but lava flows are recognizable, and Smith et al. (1978) suggested a possible Holocene age.

Etna, Sicily (Italy)

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

INGV reported that during 23-25 February activity at Etna’s Southeast Crater (SEC) was characterized by Strombolian activity and occasional ash emissions that rapidly dispersed to the SSW and SSE. At 1338 on 24 February a forceful ash emission from Northeast Crater drifted SSE. A diffuse ash emission rose from the same crater at 1642. Emissions at Bocca Nuova Crater consisted mainly of gas with occasional minor ash content during 21-27 February.

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.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slow lava effusion at Great Sitkin likely continued during 23 February-1 March and very low seismicity persisted. Weakly elevated surface temperatures at the summit were detected during 25-28 February. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 20 and 23-24 February. The volcano was either quiet or obscured by clouds on the other days during 18-25 February. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that lava effusion at the vent of the main cone in the lower W wall of Kilauea’s Halema`uma`u Crater continued at variable rates during 22 February-1 March. Effusion from the vent sometimes paused, including from the early afternoon on 23 February to 2115 on 27 February, from 1500 on 26 February to 1000 on 27 February, and again beginning at 0130 on 1 March. When the vent was active lava flowed S and W, into the W part of the lava lake. Lava occasionally oozed out from the margins of the lake. The lake level fluctuated through the week, likely reflecting the lava supply along with periods of inflation and deflation. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Merapi, Central Java

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

BPPTKG reported that both of Merapi’s two lava domes, situated just below the SW rim and in the summit crater, effused lava during 18-24 February. Based on analysis of drone data the volumes of the SW and central domes were an estimated 1.58 and 3.23 million cubic meters, respectively. Seismicity remained at high levels. In the SW-flank Bebeng drainage there were as many as 173 lava avalanches that traveled a maximum of 2 km and one pyroclastic flow that extended 1.8 km. Minor ashfall was reported in the Pakem District on 18 February. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-5 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.

Pavlof, Alaska Peninsula, Alaska

55.417°N, 161.894°W, Summit elev. 2493 m

AVO reported that the eruption at Pavlof was ongoing during 23 February-1 March. Lava effusion continued from a vent just E of the summit and sent a lava flow a short distance down the NE flank. Seismicity was higher with periods of tremor, and elevated surface temperatures were periodically identified in satellite images; both were consistent with continuing lava effusion. Small explosions were detected during 24 and 26-28 February. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Geological summary: The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Sabancaya, Peru

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

Instituto Geofísico del Perú (IGP) reported moderate levels of activity at Sabancaya during 21-27 February with a daily average of 35 explosions. Gas-and-ash plumes rose as high as 2.5 km above the summit and drifted NW, W, SW, and S. Three thermal anomalies originating from the lava dome in the summit crater were identified in satellite data. Minor inflation continued to be detected near 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.

Sangay, Ecuador

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

IG reported a high level of activity at Sangay during 22 February-1 March. Weather clouds and rain often prevented visual and webcam observations of the volcano, though daily ash-and-gas plumes were identified in satellite images by the Washington VAAC or in webcam views; plumes rose as high as 2 km above the volcano and drifted N, NW, W, and SW. Multiple daily thermal anomalies over the volcano were visible in satellite data.

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.

Semeru, Eastern Java

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

PVMBG reported that eruptions at Semeru recorded at 0605 on 24 February, 0538, 0557, and 0755 on 25 February, 0535 on 27 February, and 0555 on 29 February generated ash plumes that rose 500-700 m above the summit and drifted N and SW. The Alert Level remained at 3 (on a scale of 1-4). The public was warned to stay at least 500 m away from Kobokan drainages within 17 km of the summit, along with other drainages originating on Semeru, 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.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported that low-level eruptive activity at Semisopochnoi's North Cerberus cone continued during 23 February-1 March. Seismicity was elevated with low-level tremor and daily small explosions. Weather clouds sometimes prevented satellite and webcam views of the volcano, though low ash clouds from the summit were visible on most days. Ash deposits on the N flank were visible in a few webcam images. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

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 18-25 February. The Aviation Color Code remained at Orange (the second highest 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 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.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Summit elev. 924 m

INGV reported that during 21-27 February activity at Stromboli was characterized by ongoing explosions from three vents in Area N (North Crater area) and three vents in Area C-S (South-Central Crater area). Explosions from Area N vents (N1 and N2) averaged 2-5 events per hour; explosions from the N1 vent ejected lapilli and bombs 80-150 m high and those at two N2 vents ejected material less than 80 m high. N2 produced weak and occasional spattering. No explosions occurred at the S1 and C vents in Area C-S; low-intensity explosions at the two S2 vents occurred at a rate of 4-9 per hour and ejected coarse material no higher than 80 m.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that 13 explosions were recorded at Suwanosejima's Ontake Crater during 21-28 February. The explosions produced ash plumes that rose as high as 2.2 km above the crater rim and ejected blocks 300-400 m away from the crater. Ashfall was reported in Toshima village (3.5 km SSW) and crater incandescence was visible nightly. The Alert Level remained at 3 and the public was warned to stay 2 km away from the crater.

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.

Turrialba, Costa Rica

10.025°N, 83.767°W, Summit elev. 3340 m

OVSICORI-UNA reported that a point of incandescence on the SW wall of Turrialba’s Cráter Oeste was visible on 23 February and was coincident with the area of strongest gas emissions. At 1955 on 27 February an eruption produced a diffuse ash plume that rose 300 m above the summit and drifted NE. Rumbling heard on 28 February was sometimes coincident with minor ash emissions.

Geological summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Wolf, Isla Isabela (Galapagos)

0.02°N, 91.35°W, Summit elev. 1710 m

IG reported that the eruption at Wolf continued during 23 February-1 March. Daily thermal alert counts, as high as around 253, indicated active and advancing lava flows on the SE flank.

Geological summary: Wolf, the highest volcano of the Galápagos Islands, straddles the equator at the north end of the archipelago's largest island, Isabela. The 1710-m-high edifice has steeper slopes than most other Isabela volcanoes, reaching angles up to 35 degrees. A 6 x 7 km caldera, at 700 m one of the deepest of the Galápagos Islands, is located at the summit. A prominent bench on the west side of the caldera rises 450 above the caldera floor, much of which is covered by a lava flow erupted in 1982. Radial fissures concentrated along diffuse rift zones extend down the north, NW, and SE flanks, and submarine vents lie beyond the north and NW fissures. Similar unvegetated flows originating from a circumferential chain of spatter and scoria cones on the eastern caldera rim drape the forested flanks to the sea. The proportion of aa lava flows at Volcán Wolf exceeds that of other Galápagos volcanoes. An eruption in in 1797 was the first documented historical eruption in the Galápagos Islands.

Yasur, Vanuatu

19.532°S, 169.447°E, Summit elev. 361 m

The Vanuatu Meteorology and Geohazards Department (VMGD) reported that activity at Yasur continued at a high level of “major unrest,” as defined by the Alert Level 2 status (the middle level on a scale of 0-4). Ash-and-gas emissions and loud explosions continued to be recorded, with bombs falling in and around the crater. The public was reminded not to enter the restricted area within 600 m around the cone, defined by Danger Zone A on the hazard map.

Geological summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Reference:

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 February-1 March 2022 Managing Editor: Sally Kuhn Sennert

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