The Weekly Volcanic Activity Report: March 1 – 7, 2023

the weekly volcanic activity report

New activity/unrest was reported for 5 volcanoes from March 1 – 7, 2023. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Aniakchak, Alaska Peninsula, Alaska | Karangetang, Sangihe Islands | Suwanosejima, Ryukyu Islands (Japan) | Tanaga, Andreanof Islands (USA) | Trident, Alaska.

Ongoing activity: Ahyi, Mariana Islands (USA) | Aira, Kyushu (Japan) | Atka Volcanic Complex, Andreanof Islands (USA) | Cotopaxi, Ecuador | Dieng Volcanic Complex, Central Java | Ebeko, Paramushir Island (Russia) | Great Sitkin, Andreanof Islands (USA) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island | Marapi, Central Sumatra | Merapi, Central Java | Nevado del Ruiz, Colombia | Papandayan, Western Java | Semeru, Eastern Java | Sheveluch, Central Kamchatka (Russia) | Takawangha, Andreanof Islands (USA).

New activity/unrest

Aniakchak, Alaska Peninsula, Alaska

56.88°N, 158.17°W | Summit elev. 1341 m

AVO reported that the earthquake swarm at Aniakchak was ongoing with 120 earthquakes located during 25 February-3 March. Magnitudes were as high as M3.1 and several earthquakes had magnitudes between M2 and M3. The earthquakes were located at shallow depths (less than 5 km) and below the S part of the caldera and to the E of the volcano. Daily, small, shallow earthquakes with magnitudes as high as M2.7 were recorded during 4-7 March. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: One of the most dramatic calderas of the Aleutian arc, the 10-km-wide Aniakchak caldera formed around 3,400 years ago during a voluminous eruption in which pyroclastic flows traveled more than 50 km N to the Bering Sea and also reached the Pacific Ocean to the south. At least 40 explosive eruptions have been documented during the past 10,000 years, making it the most active volcano of the eastern Aleutian arc. A dominantly andesitic pre-caldera volcano was constructed above basement Mesozoic and Tertiary sedimentary rocks that are exposed in the caldera walls to elevations of about 610 m. The ice-free caldera floor contains many pyroclastic cones, tuff cones, maars, and lava domes. Surprise Lake on the NE side drains through The Gates, a steep-walled breach on the east side of the 1-km-high caldera rim that was the site of the catastrophic draining of a once larger lake about 1850 years BP. Vent Mountain and Half Cone are two long-lived vents on the south-central and NW caldera floor, respectively. The first and only confirmed historical eruption took place in 1931 from vents on the west and SW caldera floor.

Karangetang, Sangihe Islands

2.781°N, 125.407°E | Summit elev. 1797 m

According to PVMBG the eruption at Karangetang’s Main Crater (S crater) continued during 1-7 March. Nighttime webcam images posted with daily reports showed flows of incandescent material descending the flanks, though incandescence decreased towards the end of the week. The Alert Level remained at 3 (on a scale of 1-4) and the public was advised to stay 2.5 km away from Main Crater with an extension to 3.5 km on the S and SE flanks.

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia’s most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; the collapse of lava flow fronts has produced pyroclastic flows.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that the number of explosions at Suwanosejima’s Ontake Crater began to increase on 2 February and further increased on 2 March. Activity intensified and a total of 25 explosions were recorded during 1-5 March. Ash plumes rose as high as 1.4 km above the crater rim and large blocks were ejected as far as 500 m from the vent. Crater incandescence was visible at night. Occasional ashfall and rumbling noises were reported in Toshima village (3.5 km SSW). Since large blocks could be ejected further than the restricted zone of 1 km, JMA raised the Alert Level to 3 (on a 5-level scale) at 0640 on 5 March and warned the public to stay 2 km away from the crater. Explosions continued during 5-7 March. Ash plumes rose as high as 2 km above the crater rim and large blocks were ejected as far as 500 m.

Geological summary: The 8-km-long 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. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded 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 open 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.

Tanaga, Andreanof Islands (USA)

51.885°N, 178.146°W | Summit elev. 1806 m

At 2215 on 7 March AVO raised the Aviation Color Code for Tanaga to Yellow and the Volcano Alert Level to Advisory due to increased seismicity. Earlier that afternoon, starting at about 1330, seismicity began to increase and by around 2045 earthquakes were occurring at a rate of 2-3 per minute. The events were located at shallow depths and the largest events were M2-3.

Geological summary: Tanaga volcano, the second largest volcanic center of the central Aleutians, is central and highest of three youthful stratovolcanoes oriented along a roughly E-W line at the NW tip of Tanaga Island. Ridges to the east and south represent the rim of an arcuate caldera formed by the collapse of an ancestral edifice during the Pleistocene. Most Holocene eruptions originated from Tanaga volcano itself, which consists of two large cones, the western of which is the highest, constructed within a caldera whose 400-m-high rim is prominent to the SE. At the westernmost end of the complex is conical Sajaka, a double cone that may be the youngest of the three volcanoes. Sajaka One volcano collapsed during the late Holocene, producing a debris avalanche that swept into the sea, after which the Sajaka Two cone was constructed within the collapse scarp.

Trident, Alaska

58.236°N, 155.1°W | Summit elev. 1864 m

AVO reported that the earthquake swarm at Trident was ongoing during 1-7 March. Daily small earthquakes with magnitudes less than 1 were recorded at a rate of about 1-5 per day. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: The Trident stratovolcano cluster was named for the three prominent peaks that were the most visible features at the summit prior to 1953. The andesitic-dacitic group consists of four overlapping stratovolcanoes and numerous flank lava domes, including Falling Mountain and Mt. Cerberus on the far west flank. The summit complex is located 3-5 km SE of Novarupta volcano and merges along a ridge to the NE with Katmai. The three oldest Trident volcanoes are glaciated and Pleistocene in age, while the youngest, Southwest Trident, was formed during historical time. Eruptions migrated through time from the NE to the SW. In 1953 a new lava dome began growing on the SW flank of Trident I volcano. A series of thick andesitic lava flows erupted between 1953 and 1968, forming a cone with 400-800 m of local relief. Periodic explosions took place until 1974, and the current summit contains a 350-m-wide crater. Some of the distal lava flows from the West Trident stratovolcano collapsed into the Novarupta vent during its 1912 eruption.

Ongoing activity

Ahyi, Mariana Islands (USA)

20.42°N, 145.03°E | Summit elev. -75 m

Unrest at Ahyi Seamount continued during 1-7 March. Plumes of discolored water above the seamount were visible in satellite images during 1-2 and 4 March. Pressure sensors on Wake Island, 2,270 km E of Ahyi Seamount, did not detect activity. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the Northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area of the seamount, followed by an upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

Aira, Kyushu (Japan)

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

JMA reported ongoing eruptive activity at Minamidake Crater and Showa Crater (at Aira Caldera’s Sakurajima volcano) during 27 February-6 March. Incandescence was visible nightly at Minamidake and during 3-6 March at Showa. Explosions at Minamidake were recorded on 28 February and 1, 3, and 4 March, and non-explosive eruptive events were occasionally recorded. Eruption plumes rose as high as 2.8 km above the Minamidake Crater rim and large blocks were ejected as far as 1.3 km from the vent. Non-explosive eruptive events were occasionally recorded at Showa during 27 February-2 March and four explosions occurred during 3-6 March. Eruption plumes rose as high as 2.7 km above the Showa rim and large blocks were ejected 500-800 m from the vent. Sulfur dioxide emissions were extremely high at 3,500 tons per day on 2 March. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from both craters.

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 the 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.

Atka Volcanic Complex, Andreanof Islands (USA)

52.331°N, 174.139°W | Summit elev. 1518 m

On 2 March AVO changed both the Aviation Color Code and Volcano Alert Level for the Atka Volcanic Complex to Unassigned, due to a data outage. The loss of data flow from seismic stations made AVO unable to assess whether the volcano is at its normal background state.

Geological summary: The Atka Volcanic Complex consists of a central shield and Pleistocene caldera with several post-caldera volcanoes. A major dacitic explosive eruption accompanied the formation of the caldera about 500,000 to 300,000 years ago. The most prominent of the post-caldera stratovolcanoes are Kliuchef and Sarichef, both of which may have been active in historical time. Sarichef has a symmetrical profile, but the less eroded Kliuchef is the source of most if not all historical eruptions. Kliuchef may have been active on occasion simultaneously with the Korovin volcano to the north. Hot springs and fumaroles are located on the flanks of Mount Kliuchef and in a glacial valley SW of Kliuchef. Korovin, at the NE tip of Atka Island, is the most frequently active volcano of the complex and contains a double summit with two craters. The NW summit has a small crater, but the 1-km-wide crater of the SE cone has an open cylindrical vent of widely variable depth that sometimes contains a crater lake or a high magma column. A fresh-looking cinder cone lies on the flank of the partially dissected Konia volcano, located on the SE flank of the dominantly basaltic Korovin. Some late-stage dacitic lava flows are present on both Korovin and Konia.

Cotopaxi, Ecuador

0.677°S, 78.436°W | Summit elev. 5911 m

IG reported that the eruption at Cotopaxi continued from 28 February-7 March. Several daily ash, gas, and steam plumes rose as high as 1.5 km above the summit from 28 February-2 March and drifted W and SW. Minor ashfall was reported in Mulaló parish (Colcas-Ticatilín) of the Latacunga canton during the afternoon of 28 February. Steam-and-gas emissions were visible rising as high as 700 m and drifting SW and W during 3-7 March. Minor ashfall was reported in Mulaló parish on 5 March. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Geological summary: The symmetrical, glacier-covered, Cotopaxi stratovolcano is Ecuador’s most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend to its base. The modern edifice has been constructed since a major collapse sometime prior to about 5,000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. Strong eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and the western Amazon basin. Smaller eruptions have been frequent since that time.

Dieng Volcanic Complex, Central Java

7.2°S, 109.879°E | Summit elev. 2565 m

On 6 March PVMBG lowered the Alert Level for the Dieng Volcanic Complex to 1 (on a scale of 1-4) due to decreased carbon dioxide emissions. During the first half of January, carbon dioxide emissions were elevated at Timbang Crater and then significantly increased in mid-January; recent measurements indicated a decreasing trend. On 22 February a mobile instrument measured 112,000 ppm CO2 at the crater, though the concentration dropped to 9,200 ppm at a distance of less than 10 m from the crater rim. Measurements at the multi-gas station indicated a concentration of 1,500-1,900 parts per million (ppm). The public was warned to stay 500 m away from Sileri Crater and to stay out of Timbang Crater, and to take caution when digging in the ground as gasses could be released from the soil.

Geological summary: The Dieng plateau in the highlands of central Java is renowned both for the variety of its volcanic scenery and as a sacred area housing Java’s oldest Hindu temples, dating back to the 9th century CE. The Dieng Volcanic Complex consists of multiple stratovolcanoes and more than 20 small Pleistocene-to-Holocene craters and cones over a 6 x 14 km area. Prahu stratovolcano was truncated by a large Pleistocene caldera, which was subsequently filled by a series of cones, lava domes, and craters, many containing lakes. Lava flows cover much of the plateau, but observed activity has been restricted to minor phreatic eruptions. Gas emissions are a hazard at several craters and have caused fatalities. There are abundant thermal features and high heat flow across the area.

Ebeko, Paramushir Island (Russia)

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

KVERT reported that moderate activity at Ebeko was ongoing from 23 February-2 March. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions during 24 and 26-27 February and on 2 March generated ash plumes that rose as high as 4 km (13,100 ft) a.s.l. and drifted E. Ashfall was reported in Severo-Kurilsk on 27 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 flat-topped summit of the central cone of the Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

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 1-7 March. Satellite images and web camera views were cloudy. Seismicity was low. 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 of 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.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that the eruption on the floor of Kilauea’s Halema’uma’u Crater continued during 1-6 March but at a decreased rate. The western lake in the basin of the 2021-2022 lava lake remained weakly active; a few lava flows were visible on 1 March. A small amount of lava circulated within the lake and there were intermittent crustal overturns, but the lake was mostly crusted over and the active area got substantially smaller through the week; by 5 March the lake was completely crusted over. Minor lava ooze-outs were visible on 6 March, and the eruption had paused by 7 March. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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 a new coastline.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok was ongoing during 1-7 March. White-and-gray plumes rose as high as 400 m above the summit and drifted E and SE on 2 and 7 March. On most of the other days, white gas plumes were seen rising as high as 100 m and drifting E and SE. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 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.

Marapi, Central Sumatra

0.38°S, 100.474°E | Summit elev. 2885 m

PVMBG reported that the eruption at Marapi (on Sumatra) continued during 1-7 March. On 2 March white steam-and-gas plumes rose 100 m from the summit and drifted NW, SW, and E, and on 4 March white-and-gray plumes rose 200 m and drifted N and NE; weather clouds prevented visual observations on the other days. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the crater.

Geological summary: Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra’s most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi (on Java) continued from 24 February-2 March and seismicity remained at high levels. The SW lava dome produced two lava avalanches that traveled as far as 1 km down the SW flank (upstream in the Bebeng and Boyong drainages). No significant morphological changes to the central and SW lava domes were evident in webcam images. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 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 the Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with a 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 the 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

Servicio Geológico Colombiano (SGC) reported that seismicity at Nevado del Ruiz began increasing on 27 February characterized by events indicating fluid movement. The elevated seismicity was sustained. On 4 March the intensity of the signals intensified and was associated with mostly continuous ash emissions with occasional pulses. Ashfall was reported in Manizales (27 km NW). 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.

Papandayan, Western Java

7.32°S, 107.73°E | Summit elev. 2665 m

PVMBG issued a special report based on recent observations of Papandayan. The number of shallow volcanic earthquakes had increased in January and although the numbers fluctuated, low-frequency earthquakes also increased overall during January and February. Webcam images from the camera in the parking area showed incandescence emanating from Kawah Baru during the night on 22 February. A team of PVMBG scientists inspected the crater during 2100-2300 on an unspecified date to identify the source of the incandescence. They observed intense emissions rising from Kawah Baru, heard a faint rumbling, and detected a strong sulfur odor, but did not see incandescence. Gas plumes rose 300 m from a solfatara. The color of the lake in Kawah Baru was greenish. Rumbling sounds from both the Kawah Mas and Kawah Baru solfatara complexes varied from weak to strong and gas emissions were sometimes intense. Solfatara temperatures were variable at Kawah Mas, Kawah Manuk, and Kawah Baru with a maximum temperature of 123.8 degrees Celsius. Sulfur dioxide gas concentrations were high at a distance of 500 m from the solfatara complexes. Based on the field observations PVMBG concluded that conditions at Papandayan were relatively normal. The Alert Level remained at 1 (on a scale of 1-4) and tourists were advised to stay 500 m away from the active craters.

Geological summary: Papandayan is a complex stratovolcano with four large summit craters, the youngest of which was breached to the NE by collapse during a brief eruption in 1772 and contains active fumarole fields. The broad 1.1-km-wide, flat-floored Alun-Alun crater truncates the summit of Papandayan, and Gunung Puntang to the north gives a twin-peaked appearance. Several episodes of collapse have created an irregular profile and produced debris avalanches that have impacted lowland areas. A sulfur-encrusted fumarole field occupies historically active Kawah Mas (“Golden Crater”). After its first historical eruption in 1772, in which the collapse of the NE flank produced a catastrophic debris avalanche that destroyed 40 villages and killed nearly 3000 people, only small phreatic eruptions had occurred prior to an explosive eruption that began in November 2002.

Semeru, Eastern Java

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

PVMBG reported that the eruption at Semeru continued during 1-7 March. Weather clouds sometimes prevented views of the volcano, though on most days no emissions were visible. On 6 March white-and-gray ash plumes rose as high as 200 m above the summit and drifted N and NE. The Alert Level remained at 3 (on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 100 m away from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid 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.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that the ongoing eruption at Sheveluch was generally characterized by explosions, hot avalanches, lava-dome extrusion, and strong fumarolic activity. A daily thermal anomaly was identified in satellite images from 23 February-2 March. At 1150 on 5 March local time video images showed an ash plume generated by hot avalanches rising 5.5 km a.s.l. (just over 2.2 km above the summit) and drifting 5 km NE. 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 the Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. 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 occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. 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.

Takawangha, Andreanof Islands (USA)

51.873°N, 178.006°W | Summit elev. 1449 m

AVO reported that the earthquake swarm at Takawangha that began in November 2022 was ongoing with 120 earthquakes located from 25 February-3 March. The number of events per day was highest on 28 February and 1 March, with over 50 earthquakes located on each of those days. Three earthquakes had magnitudes greater than 3, occurred at shallow depths of less than 6 km, and were located about 6 km E of the volcano. During 3-7 March small daily earthquakes with magnitudes less than M2 occurred in the vicinity of the volcano. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: Takawangha is a youthful volcano with an ice-filled caldera on northern Tanaga Island, near the western end of the Andreanof Islands. It lies across a saddle from the historically active Tanaga volcano to the west; older, deeply eroded volcanoes lie adjacent to the east. The summit of the dominantly basaltic to the basaltic-andesite volcano is largely ice-covered, with the exception of five Holocene craters that during the last few thousand years produced explosive eruptions and lava flows that reached the lower flanks. No historical eruptions are known, although radiocarbon dating indicates explosive eruptions have occurred within the past several hundred years.

References:

Smithsonian / US Geological Survey Weekly Volcanic Activity Report – March 1 – 7, 2023 – Managing editor: Sally Kuhn Sennert

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