The Weekly Volcanic Activity Report: February 9 – 15, 2022

the-weekly-volcanic-activity-report-february-9-15-2022

New activity/unrest was reported for 4 volcanoes from February 9 to 15, 2022. During the same period, ongoing activity was reported for 22 volcanoes.

New activity/unrest: Krakatau, Sunda Strait | Langila, New Britain (Papua New Guinea) | Taal, Luzon (Philippines) | Tangkuban Parahu, Western Java.

Ongoing activity: Aira, Kyushu (Japan) | Davidof, Aleutian Islands (USA) | Dukono, Halmahera | Etna, Sicily (Italy) | Fuego, South-Central Guatemala | Great Sitkin, Andreanof Islands (USA) | Ibu, Halmahera | Kanlaon, Philippines | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island | Manam, Northeast of New Guinea | Merapi, Central Java | Nevado del Ruiz, Colombia | Pavlof, Alaska Peninsula, Alaska | Semeru, Eastern Java | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Whakaari/White Island, North Island (New Zealand) | 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

Krakatau, Sunda Strait

6.102°S, 105.423°E, Summit elev. 155 m

PVMBG reported that weather clouds and fog often obscured views of Anak Krakatau during 9-15 February. During periods of clear weather diffuse white plumes were rising as high as 50 m. 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 crater.

Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Langila, New Britain (Papua New Guinea)

5.525°S, 148.42°E, Summit elev. 1330 m

The Darwin VAAC reported that on 9 February ash plumes from Langila were visible in satellite images rising 4.3 km (14,000 ft) a.s.l. and drifting SW.

Geological summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower E flank of the extinct Talawe volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Taal, Luzon (Philippines)

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

PHIVOLCS reported that unrest at Taal continued during 8-15 February, with persistent low-level background tremor, hot volcanic fluids circulating in the crater lake, and daily gas-and-steam plumes that rose as high as 3 km above the lake and drifted mainly SW and W. Sulfur dioxide emissions continued to be elevated, averaging 8,686-10,270 tonnes/day on 8, 10, and 12 February.

Each day during 10-15 February the seismic network recorded as many as 33 volcanic earthquakes, 1-10 low-frequency volcanic earthquakes, and 2-24 episodes of volcanic tremor. One short-lived phreatomagmatic burst recorded at 1616 on 10 February produced a plume that rose 300 m from the lake and drifted SW. One hybrid event was recorded during 13-14 February. Tilt, continuous GPS, and InSAR data all indicated that Taal Volcano Island and the Taal region had begun deflating in October 2021. The Volcano Alert Level remained at a 2 (on a scale of 0-5). PHIVOLCS reminded the public that the entire Taal Volcano Island is a Permanent Danger Zone (PDZ) and warned against extended stays on Taal Lake.

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.

Tangkuban Parahu, Western Java

6.77°S, 107.6°E, Summit elev. 2084 m

PVMBG reported that during 30 January-13 February diffuse white steam-and-gas plumes from vents in Tangkuban Parahu's Ratu Crater did not rise above the crater rim. At 1143 on 12 February steam-and-gas venting from Ecoma Crater (within Ratu Crater) intensified, with bursts of emissions rising 100 m above a new vent. The emissions were less intense the next day, rising 20-60 m. Seismicity and deformation data, along with gas and temperature measurements, all indicated that the activity was the result of hydrothermal processes with no new magmatic intrusion. The Alert Level remained at 1 (on a scale of 1-4) and tourists were advised to avoid going into the crater.

Geological summary: Gunung Tangkuban Parahu is a broad stratovolcano overlooking Indonesia's former capital city of Bandung. The volcano was constructed within the 6 x 8 km Pleistocene Sunda caldera, which formed about 190,000 years ago. The volcano's low profile is the subject of legends referring to the mountain of the "upturned boat." The Sunda caldera rim forms a prominent ridge on the western side; elsewhere the rim is largely buried by deposits of the current volcano. The dominantly small phreatic eruptions recorded since the 19th century have originated from several nested craters within an elliptical 1 x 1.5 km summit depression.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that nighttime crater incandescence at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible during 7-11 February. Sulfur dioxide emissions were 700 tons per day, slightly low. An eruptive event at 1620 on 13 February produced a plume that rose 1 km above the crater rim. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.

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.

Davidof, Aleutian Islands (USA)

51.97°N, 178.33°E, Summit elev. 328 m

An earthquake swarm, either related to tectonic processes or volcanic unrest, began in the vicinity of Davidof on 24 January. The swarm continued at low levels during 9-13 February with small earthquakes recorded on most days. A shallow M 2.9 earthquake located 5 km N of the volcano was recorded on 11 February. 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.

Dukono, Halmahera

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

Based on satellite and wind model data, the Darwin VAAC reported that on 13 February ash plumes from Dukono rose to 2.1 km (7,000 ft) a.s.l. and drifted SW. 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.

Etna, Sicily (Italy)

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

INGV reported that a notable eruption at Etna’s Southeast Crater (SEC) occurred during 9-10 February and changed the morphology of the cone. The eruption began with incandescence from explosive activity within SEC that was visible in webcam images at night during 9-10 February. Sporadic ash emissions rose above the crater. Lava began to effuse at 1520 on 10 February and flows descended WSW. Strombolian activity varied in intensity and frequency, though at 1700 there was a clear intensification. Lava flows continued to be fed and had descended S and SE to 2,900 m elevation. Strombolian activity transitioned to lava fountaining at around 2140, with fountains rising 1-1.5 km high, and ash plumes rising to 12 km (39,400 ft) a.s.l. and drifting W. Two pyroclastic flows, visible at 2140 and 2219, traveled a few hundred meters SE towards the Valle del Bove. At 2226 a larger pyroclastic flow expanded 1.6 km S and SE and covered the northernmost 2002-2003 craters, reaching 2,750 m elevation, and damaging a hut along the way. Lava fountaining ceased at 2300. The ash plume slowly dispersed W over the next few hours and the lava flow continued to be fed, reaching 2,850 m elevation. A new deep scarp opening to the SSW was formed during the eruption, overprinting the smaller breach that was on the SW crater rim. The new scarp was about 500 m long and had variable widths of 100-190 m. Weak and sporadic explosive activity continued from the lower part of the scarp. Tephra fell in areas to the NW (particularly at Maletto, 15 km NW) and as far as Sant’Agata di Militello (50 km NW) and Capo d'Orlando (50 km NNW), along the Tyrrhenian coast. At 1125 on 11 February a small vent opened at the SE base of the SEC, emitted ash, and produced a short, thick lava flow that traveled a few tens of meters SE.

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.

Fuego, South-Central Guatemala

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

In a special bulletin, INSIVUMEH reported that an effusive period at Fuego began on 9 February, producing lava flows than descended the Ceniza drainage on the SSW flank. There were 2-9 explosions per hour recorded during 8-9 and 1-15 February, generating ash plumes that rose as high as 1.1 km above the crater rim. The ash plumes mainly drifted 10-15 km N, NE, S, SW, and W causing almost daily ashfall in areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Sangre de Cristo (8 km WSW), and La Rochela. Periodic shock waves rattled structures in communities around the volcano. Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), and Taniluyá (SW) drainages. Explosions ejected incandescent material up to 100-300 m above the summit. The effusive activity intensified by 14 February with periods of elevated activity lasting minutes to hours. Strombolian explosions increased in frequency and intensity, gas emissions increased, and incandescence from the crater was visible at night through the early morning of 15 February. Peaks in seismic RSAM data mirrored the peaks in activity. Lava flows traveled as far as 200 m down the Ceniza drainage and produced block avalanches from the flow front.

Geological summary: Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slow lava effusion at Great Sitkin continued during 9-15 February, though cloudy conditions often prevented satellite and webcam views. Seismicity remained slightly above background levels, and elevated surface temperatures were periodically identified in satellite images. A steam plume was occasionally visible in webcam images. 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.

Ibu, Halmahera

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

PVMBG reported that the eruption at Ibu continued during 9-15 January. Gray-and-white ash plumes rose 200-1,000 m above the summit and drifted W and E. Strong rumbling sounds were heard during 8-9 January and minor ashfall was reported in a populated area just W of the volcano. The Alert Level remained at a 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, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Kanlaon, Philippines

10.412°N, 123.132°E, Summit elev. 2435 m

PHIVOLCS issued a special notice for Kanlaon on 9 February, noting localized earthquake activity on the lower NW flank. There were 11 very shallow earthquakes, with local magnitudes of M 0.9-2.1, recorded by the seismic network between 2012 on 8 February and 0900 on 9 February. Ground deformation data from continuous GPS and tilt measurements indicated slight inflation of the middle and upper flanks of the volcano since mid-October 2021; EDM and electronic tilt data reflected short-term deflation on the SE flank since December 2021 and January 2022, respectively. The Alert Level remained at 1 (on a scale of 0-5) and PHIVOLCS reminded the public to remain outside of the 4-km-radius Permanent Danger Zone.

Geological summary: Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.

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 on 10 February. The volcano was either quiet or obscured by clouds on the other days during 4-11 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 9-15 February. Effusion had paused, but restarted at 0120 on 9 February when lava again began entering the lava lake. The lake level fluctuated through the week, likely reflecting variable lava supply along with periods of inflation and deflation. Effusion from the W vent paused during around 0900-1100 on 11 February. 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.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued during 8-15 February. Daily white-and-gray ash plumes rose as high as 1.2 km above the summit and drifted E and W. Incandescent material was ejected 300-350 m in multiple directions, and rumbling and weak banging noises were heard. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater and 4 km away from the crater on the SE flank.

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.

Manam, Northeast of New Guinea

4.08°S, 145.037°E, Summit elev. 1807 m

The Darwin VAAC reported that on 14 February ash plumes from Manam rose to 2.4 (8,000 ft) a.s.l. and drifted SE.

Geological summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical basaltic-andesitic stratovolcano to its lower flanks. These valleys channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Merapi, Central Java

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

BPPTKG reported no significant morphological changes at Merapi’s lava domes, located just below the SW rim and in the summit crater, during 4-10 February. Seismicity remained at high levels. In the SW-flank Bebeng drainage there were as many as 133 lava avalanches that traveled a maximum of 2 km and three pyroclastic flows that extended 2 km. Ashfall was reported in multiple areas within about 20 km to the S, SE, and E including the Cangkringan, Sleman and Musuk districts. 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.

Nevado del Ruiz, Colombia

4.892°N, 75.324°W, Summit elev. 5279 m

On 15 February Servicio Geológico Colombiano’s (SGC) reported that during the previous week seismicity at Nevado del Ruiz was at similar levels to the weeks before, characterized by periods of continuous volcanic tremor, harmonic tremor, long-period events, and very-long-period earthquakes, indicating movement of fluids. These earthquakes occurred in the vicinity of Arenas Crater. Additional earthquake signals indicating rock fracturing were located at Arenas Crater and in areas to the SE and had decreased in size and frequency since the previous week. Two periods of “drumbeat” seismicity, indicting growth of the lava dome, were recorded on 10 February. Gas-and-ash emissions were periodically visible in webcam images. A small explosion on 11 February generated an ash plume that rose above the crater. According to the Washington VAAC an ash plume rose to 7 km (23,000 ft) a.s.l. and drifted N at 1130 that same day. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

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

Pavlof, Alaska Peninsula, Alaska

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

AVO reported that the eruption at Pavlof was ongoing during 8-15 February with lava effusion from a vent on the upper SE flank feeding lava flows on the E flank. Seismicity was elevated with periods of tremor and elevated surface temperatures were identified in satellite images; both were consistent was continuing lava effusion. 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.

Semeru, Eastern Java

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

PVMBG reported that the eruption at Semeru continued during 8-15 February, though weather conditions sometimes hindered views. Crater incandescence was visible during 8-9 February. Daily eruptive events produced white-and-gray plumes that rose as high as 500 m above the summit and sometimes drifted SE and N. 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 9-15 February. Seismicity was elevated with low-level tremor, and several small explosions were detected daily in both seismic and infrasound data, through 13 February. Steam and low-level ash emissions likely occurred daily, though due to weather clouds they were not confirmed in satellite and webcam images during 13-14 February. 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 4-11 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.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that five explosions were recorded at Suwanosejima's Ontake Crater during 7-14 February. The explosions produced ash plumes that rose as high as 2 km above the crater rim and ejected large blocks 300-400 m from the crater. Ashfall was reported in Toshima village (3.5 km SSW) during 11-14 February. 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.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E, Summit elev. 294 m

On 15 February GeoNet reported that technicians recently repaired and upgraded equipment, improving the transmission of seismic and webcam data from Whakaari/White Island. The report noted that minor ash emissions from the active vents continued to be seen in webcam images. The lake had deepened due to recent wet weather conditions and mud geysering from one of the main craters was visible; mud geysering was common at the volcano during periods when the lake water was higher. The Volcanic Alert Level remained at 2 and the Aviation Color Code remained at Yellow.

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.

Wolf, Isla Isabela (Galapagos)

0.02°N, 91.35°W, Summit elev. 1710 m

IG reported that the eruption at Wolf continued during 8-15 February. Daily thermal alert counts, anywhere from a few to over three hundred, 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 Wellington VAAC reported that during 12-13 February ash emissions from Yasur were visible in webcam and satellite images rising to 900 m (3,000 ft) a.s.l. and drifting S and SW.

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, 2 February-8 February 2022 Managing Editor: Sally Kuhn Sennert

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