The Weekly Volcanic Activity Report: January 12 – 18, 2022


New activity/unrest was reported for 4 volcanoes from January 12 to 18, 2022. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Barren Island, Andaman Islands (India) | Hunga Tonga-Hunga Ha'apai, Tonga Islands | Piton de la Fournaise, Reunion Island (France) | Wolf, Isla Isabela (Ecuador).

Ongoing activity: Aira, Kyushu (Japan) | Fuego, South-Central Guatemala | Great Sitkin, Andreanof Islands (USA) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island (Indonesia) | Merapi, Central Java (Indonesia) | Pavlof, Alaska Peninsula, Alaska | Rincon de la Vieja, Costa Rica | Semeru, Eastern Java (Indonesia) | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica | Whakaari/White Island, North Island (New Zealand) | 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

Barren Island, Andaman Islands (India)

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

The Darwin VAAC reported that during 1700-2200 on 8 January and 1200-1700 on 9 January ash plumes from Barren Island rose to 1.2 km (4,000 ft) a.s.l. and drifted W and WSW.

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

Hunga Tonga-Hunga Ha'apai, Tonga Islands

20.536°S, 175.382°W, Summit elev. 114 m

Large eruptions at Hunga Tonga-Hunga Ha'apai on both 14 and 15 January produced plumes that reached the stratosphere and caused significant regional effects. Activity on the 14th apparently removed approximately the middle third of the island that had been expanded over the previous few weeks, revealed by a Planet Lab image acquired at 1525 on 15 January. About two hours after that image was taken an even stronger eruption activity produced a stratospheric plume seen in satellite images, sent pressure waves across the atmosphere, and caused tsunami that traversed the Pacific. Following these explosions, a Sentinel image acquired on 17 January showed that most of the previous combined island had been destroyed, leaving only small parts of the NE island of Hunga Tonga (200 m long) and the SW island of Hunga Ha'apai (700 m long) above the ocean surface.

A sub-aerial eruption that began at 0420 on 14 January produced mushroom-shaped ash, steam, and gas plumes that rose as high as 20 km (65,600 ft) a.s.l., into the stratosphere, and expanded radially at the top of the plume to 240 m in diameter, according to the Tonga Geological Services (TGS). Geologists observing from a boat around 1700-1830 in the afternoon noted that the plume was about 5 km wide at its base, with Surtseyan pulses ejecting dark dense material into the air, and pyroclastic flows expanding over the ocean. The eruption plume drifted over the island groups of Tongatapu, ‘Eua, Ha’apai, and Vava’u, carrying an estimated sulfur dioxide mass of 0.05 Tg (50,000 tonnes) based on satellite data. Sulfur odors were reported in Tongatapu (70 km S), near the capital on Motutapu Island, and on ‘Eua (106 km SSE). Ashfall was reported on many islands, including Fonoi and Mango (75 km ENE). The Tonga Meteorological Services (TMS) issued tsunami warnings for areas including ‘otu Mu’omu’a in Ha’apai (Nomuka, Mango, Fonoifua), ‘Atataa, ‘Eueiki, and Tongatapu mo ‘Eua. At 2000 on 14 January a tsunami with a height of 20 cm was recorded by the Nuku’olofa tide gauge. TMS warned residents to stay away from low-lying coastal areas, beaches, and harbors. The Wellington VAAC noted that the eruption was intermittent during 0043-0604 on 15 January; plumes rose to altitudes of 14 km (45,900 ft) a.s.l. The Global Lightning Detection Network (GLD360) ground-based network detected 191,309 lightning events during a 21-hour period (0334 on 14 January-0134 on 15 January), or up to 30,000 events per hour; for comparison, during 22-28 December 2018 the partial collapse eruption of Krakatau generated 337,000 events. TGS noted that at 0720 on 15 January an eruption lasting 10-15 minutes sent an ash plume to 14 km (45,900 ft) a.s.l. that drifted E.

A larger, submarine eruption began at 1700 on 15 January. According to news reports and social media posts, residents in Nuku’alofa (65 km S) heard multiple loud booms and saw a large expanding eruption plume that eventually covered all of the Tongan islands. According to the Wellington VAAC the plume had risen to 15.2 km (50,000 ft) a.s.l. by 1819; the top of the plume as seen in satellite images was at least 600 km in diameter by 1903. During 1719-2300 there were almost 400,000 lightning events recorded in the plume by the GLD360 network, with 200,000 of those during 1800-1900. By 0343 on 16 January the plume had risen to 19.2 km (63,000 ft) a.s.l. Analysis of other satellite datasets suggested that the plume may have risen to 30 km (98,400) a.s.l. The sulfur dioxide mass of the plume was 0.4 Tg (400,000 tonnes) derived from satellite-based estimates; the cloud drifted W consistent with stratospheric winds. Significant ashfall was reported on populated islands of Tonga, 70-100 km E. News articles noted that some residents had difficulty breathing from the ash in the air.

Most domestic and international communications on the islands were severed due to a break in an underwater cable, and ashfall has delayed both damage assessment and relief assistance. An update on 18 January from the Government of Tonga provided details about the eruption and its effects, noting that tsunami warnings issued after the eruption began had triggered evacuations. Tsunami waves up to 2 m high, based on a news article, arrived on the W coasts of the Tongatapu, ‘Eua, and Ha’apai islands, and three people in Tonga were confirmed to have died as a result, with many others injured. Extensive damage was reported on Mango, Fonoifua, and Nomuka islands, and on the W part of Tongatapu. Aerial surveillance by the New Zealand Defence Force’s showed brown, damaged vegetation and landscapes, debris, and modified coastlines with sediment-laden waters. The Government of Tonga also noted that communications to the outer islands were accomplished with a patrol boat on 17 January, and limited communication with residents of Vava’u and Ha’apai was possible the next day. Evacuation efforts were underway for some remote islands. Ashfall contaminated fresh water supplies, hindered sea transportation and harbor access, and caused flights to be cancelled. According to a news report the small island of Atata, near Nuku’olofa, had been completely submerged. Tsunami warnings were also issued in several other countries surrounding the Pacific Ocean. Several news sources reported flooding and damage caused by the tsunamis at locations as far away as Peru (over 10,000 km), where it caused two deaths. Warnings were issued for the N and E coasts of New Zealand’s North Island and the Chatham Islands; multiple boats were destroyed. Thousands in Japan evacuated after tsunami warnings, and the waves there reached 80 cm, disrupting train services, flights, and damaging harbors and boats. In Anchorage, Alaska, the US National Weather Service reported maximum waves heights of 20-100 cm on Alaskan coastlines, and along the British Columbia coast waves were 16-29 cm on 15 January.

The explosions produced multiple pressure (shock) waves that rippled through surrounding weather clouds, though the pressure wave from the largest explosion propagated across the planet. The sonic boom from this wave was heard at great distances, including in Fiji (about 500 km NW), within about two hours in New Zealand (1,600-2,000 km), and within about nine hours in Alaska, USA (9,370 km NE). The pressure wave was also recorded by infrasound and weather instruments worldwide as it circled the Earth, with instruments picking up the wave a second time as it arrived from the opposite direction. Very small perturbances in the ocean waves recorded in the Caribbean, which some referred to as meteotsunamis, were likely generated by atmospheric disturbances from the pressure waves after they passed over South America.

Geological summary: The small islands of Hunga Tonga and Hunga Ha'apai cap a large seamount located about 30 km SSE of Falcon Island. The two linear andesitic islands are about 2 km long and represent the western and northern remnants of the rim of a largely submarine caldera lying east and south of the islands. Hunga Tonga reaches an elevation of about 114 m above sea level, and both islands display inward-facing sea cliffs with lava and tephra layers dipping gently away from the submarine caldera. A rocky shoal 3.2 km SE of Hunga Ha'apai and 3 km south of Hunga Tonga marks a historically active vent. Several submarine eruptions have occurred at Hunga Tonga-Hunga Ha'apai since the first historical eruption in 1912. An eruption that began in mid-December 2014 built a new island between the other two large islands.

Piton de la Fournaise, Reunion Island (France)

21.244°S, 55.708°E, Summit elev. 2632 m

OVPF reported that the eruption at Piton de la Fournaise continued during 10-16 January. Weather clouds often obscured views of the vent, though visual observations were made daily. Lava was sometimes ejected above the crater rim. The lava lake periodically rose and overflowed the cone during 10-13 January, sending flows down the flanks, and several breakouts of lava were visible on the flow field. The flow on the S margin of the field slowly advanced to the S wall of Enclos Fouqué. Activity decreased for a period of time during 14-15 January. Activity increased again during 15-16 January, though no overflows of the lake were recorded and lava was only periodically ejected above the rim. Some small vegetation fires were visible near the base of the caldera wall. Tremor decreased and the eruption ceased at 0210 on 17 January.

Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Wolf, Isla Isabela (Ecuador)

0.02°N, 91.35°W, Summit elev. 1710 m

On 13 January IG reported that the eruption at Wolf was continuing, but at decreasing levels. Lava from at least three fissures had traveled about 16.5 km SE, and covered an estimated 7.4 square kilometers, but had not reached the coast. Daily counts of thermal anomalies were in the hundreds but had progressively decreased in quantity and intensity in recent days, interpreted as a decrease in the effusion rate and cooling flows. Notices of ash-and-gas plumes were issued by the Washington VAAC on 7-8 January, noting that plumes decreased from 2.6 km to 300 m above the vent. Additionally, sulfur dioxide emissions decreased from 60,000 tons per days recorded on 7 January to 8,100 tons per day on 12 January. Seismicity also trended downward.

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.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 10-17 January. Seismic data showed a decreasing number of volcanic earthquakes. 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.

Fuego, South-Central Guatemala

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

INSIVUMEH reported that 6-13 explosions per hour were recorded at Fuego during 12-18 January, generating ash plumes that rose as high as 1.1 km above the crater rim. The ash plumes mainly drifted 10-20 km S and SW 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. Ash plumes drifted as far as 20 km E and NE during 14-16 January. Daily, periodic shock waves rattled structures in communities around the volcano. Block avalanches descended the flanks in all directions, but most commonly were visible in the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Honda, and Las Lajas (SE) drainages, often reaching vegetated areas. Explosions ejected incandescent material up to 150-350 m above the summit during 12-16 January.

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 12-18 January, though cloudy conditions prevented satellite and webcam confirmation. Seismicity was very low and small events were occasionally recorded. Steam emissions were observed in webcam views during 14-15 January. 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 increased explosive activity at Karymsky and a thermal anomaly visible in satellite images during 7-8 and 11-12 January. Explosions during 11-13 January produced ash plumes that drifted almost 130 km in various directions. 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 resumed at the vent in the lower W wall of Kilauea’s Halema`uma`u Crater at around 1840 on 11 January. The level of the lava lake had increased 13 m by about 0300 on 12 January, slightly surpassing the level prior to the pause that began on 10 January; the lake has risen a total of 70 m since the beginning of the eruption. During 12-14 January the lake was active and lava oozed out along the crusted-over E margins. A surge in lava effusion at the vent was recorded at 0545 on 15 January, coincident with a peak in summit inflation. Effusion had paused by the afternoon, though minor activity at the vent on the N side of the spatter cone, minor overturns of the lake, and small oozes of lava at the lake’s margins persisted. The lake level dropped 10 m by the morning of 16 January. Small overturns of the crusted lake were visible during 16-17 January. By 18 January the lake was completely crusted over and a small wispy plume rose from the vent. 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 (Indonesia)

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

PVMBG reported that the eruption at Lewotolok continued during 11-16 January. Ash plumes rose as high as 700 m above the summit and drifted E, SE, and W during 11-14 January. Incandescent material ejected up to 300-700 m SE from the vent was accompanied by rumbling and banging noises. Eruption noises persisted through 16 January but weather prevented visual confirmation of activity during 15-16 January. 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.

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 no significant morphological changes at Merapi’s lava domes, located just below the SW rim and in the summit crater, during 6-13 January. The intensity of the seismic signals remained at high levels. As many as 123 lava avalanches traveled a maximum of 2.2 km SW down the Bebeng drainage, and four pyroclastic flows traveled a maximum of 2.5 km SW. 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 elevated seismicity at Pavlof during 12-18 January was characterized by daily periods of tremor. Elevated surface temperatures consistent with lava effusion near the vent and the active lava flow on the SE flank were identified in satellite images almost daily; weather clouds prevented views for periods of time during 12-13 January. 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.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W, Summit elev. 1916 m

OVSICORI-UNA reported that at 0024 on 13 January a two-minute eruption was recorded at Rincón de la Vieja, though weather clouds prevented visual confirmation. Residents to the N heard the eruption and felt vibrations, and lahars were seen in the Rio Azul. Small eruptive events were recorded at 1153 on 15 January and 1243 on 18 January, but plumes were not visible due to weather clouds.

Geological summary: Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Semeru, Eastern Java (Indonesia)

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

PVMBG reported that the eruption at Semeru continued during 12-17 January. White steam plumes that were sometimes dense rose as high as 1 km above the summit almost daily, and crater incandescence was visible nightly. Incandescent avalanches traveled as far as 500 m down the Kobokan drainage on the SE flank during 11-12 January. White-and-gray ash plumes rose 300 m during 14-15 January. At 1020 on 16 January a collapse from the end of the active lava flow in the Kobokan drainage produced a pyroclastic flow, and an ash plume that rose 1.5 km and drifted N. An eruptive event at 0534 on 17 January generated an ash plume that a ground observer reported rising 400 m. 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 and elevated seismicity at Semisopochnoi's North Cerberus cone continued during 12-18 January. A small explosion was recorded by local seismic and infrasound sensors during 12-13 January. The weather was mostly cloudy, though low-level ash clouds were occasionally visible in webcam images during 12-15 January. Steam emissions were visible in 15-16 January 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 8-14 January. Intense steam-and-gas emissions with ash were visible during 6-7 and 9-11 January; plumes rose as high as 5 km (16,400 ft) a.s.l. and drifted 175 km W. 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 incandescence at Suwanosejima's Ontake Crater was visible nightly during 10-17 January. There were 157 explosions recorded, producing ash plumes that rose as high as 2 km above the crater rim and ejected material up to 800 m away from the crater. Eruption sounds were heard in Toshima village (4 km SSW). Volcanologists observed ash-and-steam plumes rising from the crater during an overflight on 17 January. 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 incandescence from Turrialba’s West Crater was visible overnight during 15-16 January. Eruptive events were recorded at 2126 and 2132 on 17 January; the second event was stronger and produced an ash-and-gas plume that rose 1 km above the crater. Ashfall and a sulfur odor were reported by residents in Coronado, Tres Rios (30 km SW), Alajuela (50 km W), and Santa Ana (46 km WSW). At 1115 on 18 January an eruptive event produced a plume that rose 300 m and drifted SW.

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.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E, Summit elev. 294 m

On 18 January GeoNet reported results from an overflight of Whakaari/White Island the week before, noting a significant decrease of temperatures at the active vent area and a small decrease in gas emissions. Temperatures in the main vent area were as high as 191 degrees Celsius, a decrease from a high value of 516 measured in December. Gas emissions had slightly decreased since December; both sulfur dioxide and carbon dioxide gas emission rates were slightly below the 10-year average. Both the gas-emission and temperature data were consistent with a degassing magma body below the surface. Very minor ash emissions continued to be visible with deposits only extending around the active vents. The water in the lake had receded likely due to recent dry weather conditions. 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.

Yasur, Vanuatu

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

The Wellington VAAC reported that on 15 January intermittent low-level ash plumes from Yasur rose 1.5 km (5,000 ft) a.s.l. and drifted SE. Ashfall was reported in nearby villages. A Sentinel satellite image acquired that same day showed a strip of ash deposits in areas to the NW. Continuous, low-level ash plumes were visible in satellite and webcam images on 17 and 18 January rising to 1.5 km a.s.l. and drifting SE and W, respectively.

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.


Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 January-18 January 2022 Managing Editor: Sally Kuhn Sennert

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