The Weekly Volcano Activity Report: January 18 – 24, 2023

the weekly volcanic activity report

New activity/unrest was reported for 4 volcanoes from January 18 to 24, 2023. During the same period, ongoing activity was reported for 21 volcanoes.

New activity/unrest: Dieng Volcanic Complex, Central Java | Kilauea, Hawaiian Islands (USA) | Marapi, Central Sumatra | Semisopochnoi, Aleutian Islands (USA).

Ongoing activity: Ahyi, Mariana Islands (USA) | Aira, Kyushu (Japan) | Cotopaxi, Ecuador | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Great Sitkin, Andreanof Islands (USA) | Ibu, Halmahera | Krakatau, Sunda Strait | Lascar, Northern Chile | Lewotolok, Lembata Island | Merapi, Central Java | Nevado del Ruiz, Colombia | Pavlof, Alaska Peninsula, Alaska | Popocatepetl, Mexico | Reventador, Ecuador | Sangay, Ecuador | Semeru, Eastern Java | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Central Chile | Whakaari/White Island, North Island (New Zealand).

New activity/unrest

Dieng Volcanic Complex, Central Java

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

PVMBG reported that white gas plumes of varying densities rose as high as 80 m above the summit of the Dieng Volcanic Complex during 18-24 January. Carbon dioxide emission averages decreased from an average of 3,300 parts per million during 18-19 January to an average of 1,900 parts per million during 22-23 January. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 1 km away from Sileri Crater and 500 m away from the SE, S, and SW sectors of Timbang Crater.

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.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that lava continued to erupt in the E portion of Kilauea’s Halema’uma’u Crater floor during 17-24 January. Activity was concentrated in a large, perched lava lake, covering about 10 hectares in the E half of the crater by 17 January, and in a smaller lake to the W, in the basin of the 2021-2022 lava lake. One dominant lava fountain, 6-7 m high, was active in the E lake. Small daily overflows occurred along the margins of the E lake. 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 new coastline.

Marapi, Central Sumatra

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

PVMBG reported that the eruption at Marapi continued during 17-24 January. White-and-gray emissions rose as high as 500 m and drifted in various directions during 17-21 January; white steam plumes were visible 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.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported that eruptive activity at Semisopochnoi’s Mount Young was ongoing during 17-24 January. Seismicity was elevated with daily small local earthquakes and occasional weak tremor. Minor steam emissions were visible in webcam images during 17-19 January; no activity was identified in cloudy satellite views during the rest of the week. The Aviation Color Code remained at Orange (the second highest level on a four-color scale) and the Volcano Alert Level remained at Watch (the second highest level on a four-level scale).

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 (renamed Mount Young in 2023) was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank 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 Young, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active.

Ongoing activity

Ahyi, Mariana Islands (USA)

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

Unrest at Ahyi Seamount was occasionally detected during 17-24 January. Pressure sensors on Wake Island, 2,270 km E of Ahyi Seamount, detected one small signal during 22-23 January. No activity was observed in mostly cloudy satellite images. 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 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 (at Aira Caldera’s Sakurajima volcano) during 14-23 January. Crater incandescence was visible nightly. An explosion at 1215 on 18 January produced an ash plume that rose 1.4 km above the crater rim and ejected blocks as far as 1.1 km. Sulfur dioxide emissions were high at 1,400 tons per day. An explosion at 0659 on 19 January generated an ash plume that rose 1.3 km and ejected blocks 600-900 m and an explosion at 0307 on 21 January generated an ash plume that rose 1.6 km and ejected blocks as far as 1.1 km. Occasional very small eruptive events were recorded during 21-22 January. 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.

Cotopaxi, Ecuador

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

IG reported that the eruption at Cotopaxi continued during 18-24 January, characterized by daily emissions of steam, gas, and ash. The plumes were visible in webcam images and reported by the Washington VAAC, though sometimes weather conditions prevented observations. They rose as high as 2 km and drifted in various directions and caused ashfall in Chillos (33 km SW), Langualó, San Isidro Alto (20 km SW), and San Agustín del Callo (18 km WSW) during 17-18 January and in San Isidro Alto, Chillos and Langualó Chico during 18-19 January. 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 western Amazon basin. Smaller eruptions have been frequent since that time.

Ebeko, Paramushir Island (Russia)

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

KVERT reported that moderate activity at Ebeko was ongoing during 12-19 January. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions on 13 January generated ash plumes that rose as high as 3 km (10,000 ft) a.s.l. and drifted SE. A thermal anomaly was identified in satellite images on 13 and 16 January. 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 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.

Etna, Sicily (Italy)

37.748°N, 14.999°E | Summit elev. 3357 m

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 16-22 January, though the rate notably fluctuated. Lava effusion progressively decreased during 16-17 January and had possibly ceased by the late afternoon of 17 January. Effusion restarted in the early hours of 18 January, generating two lava flows. One of the flows traveled NE along the W edge of the lava field, and the other traveled E onto the steep W wall of Valle del Bove, reaching the base of the wall on 20 January. The effusion rate decreased on 21 January and the again increased during the evening. Late on 22 January a new lava flow descended the Valle del Bove, almost reaching the base of the W wall at around 2,200 m elevation.

Geological summary: Mount Etna, towering above Catania on the island of Sicily, has one of the world’s longest documented records of 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 caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slightly elevated surface temperatures at Great Sitkin were identified in satellite images on 18 January, suggesting continuing lava effusion at a low rate primarily to the S and E. A few small earthquakes were detected on most days by the local seismic network. No activity was observed in mostly cloudy satellite and web camera images during 19-24 January. 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: 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 17-24 January. Daily white-and-gray plumes of variable densities rose 200-1,000 m above the summit and drifted in multiple directions. 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.

Krakatau, Sunda Strait

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

PVMBG reported that the eruption at Anak Krakatau intensified at the end of the week during 17-23 January. White steam-and-gas plumes rose as high as 200 m above the summit and drifted NE, E, and S. Strombolian activity was visible in webcam images at 0041, 0043, and 0450 on 23 January. At 0607 and 0701 dense gray ash plumes rose 300 m above summit and drifted E. At 0758, 0759, 0808, and 0928 dense gray-to-black ash plumes rose 200-500 m and drifted SE. Webcam photos showed progressively intensifying Strombolian activity at 1919, 1958, and 2113 on 24 January. A dense gray ash plume rose 300 m and drifted E at 1957. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 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 edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that 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 caused more than 36,000 fatalities, most as a result of 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.

Lascar, Northern Chile

23.37°S, 67.73°W | Summit elev. 5592 m

SERNAGEOMIN reported that after the 19 December 2022 eruption at Láscar, activity levels had returned to baseline. During 1-15 January sulfur dioxide emissions detected by a Differential Absorption Optical Spectroscopy (DOAS) instrument located 6 km ESE of the crater measured an average value of around 483 tonnes per day, with a maximum value of 881 tonnes per day on 13 January. These values were at normal levels. Occasional low-level thermal anomalies were identified in satellite images and corresponded to passive degassing from the vents in the summit crater. The maximum height of white gas plumes was 1.4 km above the crater rim, recorded on 11 January. On 19 January the Alert Level was lowered to Green (the lowest level on a four-color scale) and the public were warned to stay at least 700 m away from the crater. ONEMI reported that a “Preventive Early Warning” was declared for San Pedro de Atacama (70 km NW).

Geological summary: Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok was ongoing during 17-24 January. Nighttime webcam images captured almost daily showed incandescent material being ejected above the summit crater. White steam-and-gas plumes were visible on most days rising as high has 250 m above the summit. Emissions during 18-20 January were white-and-gray and rose as high as 400 m and drifted NE and E. 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.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi continued during 12-19 January and seismicity remained at high levels. The SW lava dome produced three lava avalanches that traveled as far as 1.2 km down the SW flank (upstream in the Kali Bebeng drainage). Avalanche sounds were heard on six occasions. 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 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

Servicio Geológico Colombiano (SGC) reported that at 0710 on 23 January an ash cloud rose from Nevado del Ruiz and drifted NW, causing ashfall in the municipality of Manizales (27 km NW). The ash emission occurred simultaneously with a seismic signal that indicated moving fluids within the volcano’s conduit. 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 has ended. No explosions had been detected since 11 December and seismicity had decreased to background levels. Weakly elevated surface temperatures and minor steaming from the recently active vent continue to be observed intermittently in satellite and webcam images, consistent with the cooling of previously erupted lava. On 19 January AVO lowered the Volcano Alert Level to Normal (the lowest level on a four-level scale) and the Aviation Color Code to Green (the lowest level on a four-color scale).

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.

Popocatepetl, Mexico

19.023°N, 98.622°W | Summit elev. 5393 m

CENAPRED reported that there were 94-206 steam-and-gas emissions, sometimes containing ash, rising from Popocatépetl each day during 17-24 January. The plumes drifted N, NE, and N. Minor ashfall was reported in the municipalities of Domingo Arenas, San Nicolas de los Ranchos, Santiago Xalizintla, in the town of San Mateo Ozolco in Calpan, state of Puebla and in the municipalities of Tlaxcala and Papalotla, state of Tlaxcala on 17 January. On 21 January an ash plume rose as high as 3 km and drifted NNE and one minor explosion was detected. Four explosions were recorded during 21-22 January and six were recorded during 23-24 January. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale).

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Reventador, Ecuador

0.077°S, 77.656°W | Summit elev. 3562 m

IG described the ongoing eruption at Reventador as moderate during 17-24 January. Daily seismicity was characterized by explosions, long-period earthquakes, periods of harmonic tremor, and signals that indicated emissions. The daily count of explosions ranged from 22-96; seismic data transmission was interrupted during 22-23 January. Although weather clouds often prevented observations of the summit, daily gas, steam, and ash plumes were observed in IG webcam images and described in Washington VAAC volcanic activity notifications almost daily. The plumes rose as high as 2.2 km above the volcano and drifted in multiple directions. Crater incandescence was visible nightly and incandescent blocks were ejected onto the flanks sometimes in all directions; incandescent blocks were also visible rolling as far as 800 m down the flanks. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Orange (the second highest level on a four-color scale).

Geological summary: Volcán El Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor about 1,300 m to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the scarp. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Sangay, Ecuador

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

IG reported a high level of activity at Sangay during 17-24 January, which included daily explosions, long-period earthquakes, and gas, steam, and ash emissions. The daily count of explosions ranged from 53-122, though seismic data transmission was sometimes interrupted. Almost daily gas, steam, and ash plumes were either observed in IG webcam images or described in Washington VAAC volcanic activity notifications; weather clouds often prevented observations of the summit. The plumes rose as high as 1.5 km above the volcano and drifted in multiple directions. Multiple thermal anomalies were identified in satellite images on most days. Crater incandescence from the crater and from material on the SE flank was visible at night during 21-22 January. 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 isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador’s volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within the open calderas of two previous edifices which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Semeru, Eastern Java

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

PVMBG reported that the eruption at Semeru continued during 17-24 January. Daily dense white-and-gray ash plumes generally rose 500-800 m above the summit and drifted N, NE, SE, and S. Ash plumes rose as high as 1 km and drifted SE at 0628 on 19 January. 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, and 500 m 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.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that the ongoing eruption at Sheveluch during 12-19 January was generally characterized by explosions, hot avalanches, lava-dome extrusion, and strong fumarolic activity. A daily thermal anomaly was identified in satellite images. Explosions on 19 January produced ash plumes that were identified in satellite images rising as high as 10 km (32,800 ft) a.s.l. and drifting W at 1240 local time. KVERT raised the Aviation Color Code to Red (the highest level on a four-color scale). In a Volcano Observatory Notice for Aviation (VONA) posted at 1635 local time KVERT noted that no additional plumes were identified in satellite images. The Aviation Color Code was lowered to Orange. 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 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.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that the eruption at Suwanosejima’s Ontake Crater continued during 16-23 January. No explosions were recorded, though eruption plumes rose as high as 1.2 km above the crater rim and blocks were ejected as far as 300 m from the vent. Ashfall was occasionally reported in Toshima village (3.5 km SSW). JMA noted that the number of explosions began decreasing in mid-October 2022 and the last explosion was recorded on 16 November. Additionally, plume heights had occasionally risen higher than 2 km above the crater rim during October-November 2022, but starting in December the heights had generally been at or below 1 km. Other data had also indicated low levels of activity; the probability of material being ejected more than 1 km away from the crater had decreased. The Alert Level was lowered to 2 (on a 5-level scale) on 24 January, and residents were warned to stay 1 km away from the crater.

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.

Villarrica, Central Chile

39.42°S, 71.93°W | Summit elev. 2847 m

SERNAGEOMIN reported that the eruption at Villarrica was ongoing during 17-24 January. Daily minor Strombolian explosions from a vent on the crater floor ejected incandescent material that generally rose as high as 100 m above the crater rim and fell back down in and around the crater. On 19 January POVI noted that lava was ejected as high as 140 m above the crater rim and onto the W and SW flanks. Explosion noises were heard on 19 and 22 January in areas within a radius of 10 km. The Alert Level remained at Yellow (the second lowest level on a four-color scale). ONEMI maintained the Alert Level at Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli.

Geological summary: Glacier-clad Villarrica, one of Chile’s most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E | Summit elev. 294 m

On 24 January GeoNet reported continuing unrest at Whakaari/White Island characterized by minor-to-moderate gas-and-steam emissions and low levels of gas. The activity was confirmed during an overflight on 16 January. Sulfur dioxide gas emissions were low, averaging around 33 tonnes per day, and carbon dioxide emissions were moderate, averaging around 705 tonnes per day; the gas levels had declined compared to the 6 December 2022 measurements. No notable changes to the lake were visible aside from minor fluctuations of the lake level. No signs of ash emissions or other eruptive activity were observed. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcanic Alert Level remained at 2 (on a scale of 0-5).

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.


Smithsonian / US Geological Survey Weekly Volcanic Activity Report – January 18 -24, 2023 – Managing Editor: Sally Kuhn Sennert


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