The Weekly Volcanic Activity Report: January 15 - 21, 2025

New activity/unrest

Ahyi, United States

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

Unrest at Ahyi Seamount continued through 17 January. Signals indicating activity, coming from the direction of Ahyi, were identified in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi) on 9 January. Satellite images showed a distinct plume of discolored water originating from the seamount on 10 January. 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 ocean surface ~18 km SE of the island of Farallon de Pajaros 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, 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.

Bardarbunga, Iceland

64.633°N, 17.516°W | Summit elev. 2000 m

The Icelandic Meteorological Office (IMO) reported that the seismic swarm that began at Bárdarbunga on 14 January in the NW part of the caldera did not escalate further. Only two earthquakes were recorded during 15-16 January, with magnitudes of 2.4 and 1.6, on each day respectively. At 1605 on 16 January the Aviation Color Code was lowered back to Green (the lowest color on a four-color scale).

Geological summary: The large central volcano of Bárðarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 km3, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system to the SW is also part of the Bárðarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárðarbunga potentially affect drainages in all directions.

Fentale, Ethiopia

8.985°N, 39.906°E | Summit elev. 2007 m

Satellite data analysis by the MIROVA team indicated that thermal anomalies over Fentale crater were visible during 13-14 January and progressively increased in size at least through 0020 on 21 January (local time). No cause of these anomalies has been identified. A visible satellite image showed a possible gas plume over the crater. A 14 January news article stated that the Fentale crater typically hosts a small lake and that billowing plumes rise above the summit. The article also noted that 10,000 people evacuated from Seganto and possibly a total of 54,000 had been evacuated from higher-risk areas. The earthquakes damaged schools, buildings, a factory, and roads.

Geological summary: Fentale is a volcanic complex at the N end of the Main Ethiopian Rift that includes a main stratovolcano and caldera with various subsidiary features. Products are primarily rhyolitic obsidian lava flows with minor tuffs. Welded pantelleritic ash flows accompanied formation of a 2.5 x 4.5 km elliptical summit caldera, with steep-sided walls, that trends WNW-ESE, perpendicular to the rift. Post-caldera vents lie along the same orientation. Lava flows that appear to be more recent are present on the NE and SW flanks, and even darker trachytic and obsidian lava flows occur on the caldera floor. An eruption during the 13th century destroyed an Abyssinian town and church to the south. In 1820 CE basaltic lava flows effused from a 4-km-long fissure on the S flank; lava also flowed onto the caldera floor. During 2015 there was a seismic swarm and deformation NE of Fentale, caused by a dike intrusion that Temtime et al. (2020) determined was about 6 km long (striking N29°E) and 2 m wide, with a depth range of 5.4-8 km below the surface (volume change of about 33 x 106 m³).

Grimsvotn, Iceland

64.416°N, 17.316°W | Summit elev. 1719 m

The Icelandic Meteorological Office (IMO) reported that floodwaters from a jökulhlaup originating from Grímsvötn’s subglacial lake peaked, likely on 15 January, then began to slowly decrease. The jökulhlaup was over by 20 January; both seismicity and water discharge levels in the Gígjukvísl river had returned to normal. The pressure decrease caused by the water volume loss from the subglacial lake did not trigger volcanic unrest. At 0948 on 20 January the Aviation Color Code was lowered back to Green (the lowest level on a four-color scale).

Geological summary: Grímsvötn, Iceland’s most frequently active volcano in recent history, lies largely beneath the vast Vatnajökull icecap. The caldera lake is covered by a 200-m-thick ice shelf, and only the southern rim of the 6 x 8 km caldera is exposed. The geothermal area in the caldera causes frequent jökulhlaups (glacier outburst floods) when melting raises the water level high enough to lift its ice dam. Long NE-SW-trending fissure systems extend from the central volcano. The most prominent of these is the noted Laki (Skaftar) fissure, which extends to the SW and produced the world’s largest known historical lava flow in 1783. The 15 km³ basaltic Laki lavas were erupted over 7 months from a 27-km-long fissure system. Extensive crop damage and livestock losses caused a severe famine that resulted in the loss of one-fifth of the population of Iceland.

Home Reef, Tonga

18.992°S, 174.775°W | Summit elev. -10 m

The Tonga Geological Services reported that analysis of satellite images showed no notable size changes at Home Reef during 2-17 January. A thermal anomaly persisted through 21 January, and during 19-21 January it was characterized as low to moderate. The Maritime Alert Level remained at Orange (the third level on a four-level scale), and mariners were advised to stay at least 2 nautical miles (3.7 km) away from the island. The Aviation Color Code remained at Yellow (the second level on a four-level scale), and the Alert Level for residents of Vava’u and Ha’apai remained at Green (the first level on a four-level scale).

Geological summary: Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, large amounts of floating pumice, and an ephemeral 500 x 1,500 m island, with cliffs 30-50 m high that enclosed a water-filled crater. In 2006 an island-forming eruption produced widespread dacitic pumice rafts that drifted as far as Australia. Another island was built during a September-October 2022 eruption.

Ibu, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 16-22 January. Daily gray or white-and-gray ash plumes that were often dense rose as high as 1.5 km above the summit and drifted mainly NW, W, and SW. Webcam images posted with the reports often showed incandescence at the summit or being ejected above the summit of the inner active cone.

BNPB reported that following the increase in the Alert Level to the highest level the government issued a decree leading to the coordination of an emergency response and a task force, and that would be in effect for a two-week period. An emergency response team implemented the evacuation of resident in five villages that were deemed at a higher risk for impacts from the eruption. A total of 221 people were evacuated during 16-17 January, though more than 3,000 people were in higher risk locations; on 16 January residents were evacuated from Sangaji Nyeku, the closest village to the summit at 3.7 km, and on 17 January residents were evacuated from the villages of Sosangaji, Tuguis, Togoreba Sungi, Borona, and Todoke. Farmers harvesting nutmeg will be allowed to return to their gardens during daytime hours. According to a news report about 644 people had evacuated by 20 January. The Alert Level remained at 4 (the highest level on a four-level scale) and the public was advised to stay 5 km away from the active crater and 6 km away from the N crater wall opening.

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.

Kilauea, United States

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

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea’s Kaluapele summit caldera continued during 15-21 January from both a N and S vent along the SW margin of Halema’uma’u Crater. Webcam images showed continuous incandescence from the N vent overnight during 14-15 January. Low-level continuous lava spattering from the N vent was visible starting at 0540 on 15 January and was followed by a slow-moving lava flow from the N vent at around 0915. Low-level lava fountaining began at around 0955 and flows from the vent increased in size. By 1053 lava flows had covered about 10 percent of the crater floor and the lava fountain was reaching heights of 60 m. Lava fountaining and flows from the S vent began at 1140. During the afternoon field crews onsite observed fountains 90-100 m high from the N vent and 40-50 m high from the S vent. Both fountains were active overnight during 15-16 January. During the morning of 16 January field crews reported fountain heights of 50 m and 40 m from the N and S vents, respectively. Parts of the S vent collapsed at about 0825 causing the fountain height to decrease by half. Lava flows were confined to the SW part of the crater floor, near the vents.

Lava fountains persisted during 16-17 January, occasionally rising as high as 45 m. Lava oozed out of cracks in cooler lava covering the crater floor. Pele’s hair was reported in nearby communities including Uekahuna Overlook, the Kilauea Visitor’s Center, the Volcano Golf Course subdivision, Volcano Village, and Ohia Estates. Tephra fell at Uekahuna Overlook and within the closed area of the National Park. Both the N and S vents had built cones that were 30-35 m tall by the morning of 17 January. Lava fountaining continued during 17-18 January, but the fountains remained below the crater rims. Lava ooze-outs on the crater floor continued to be visible. The N vent ceased erupting at around 0945 on 18 January; lava from the S vent continued to flow from the S vent at a lower rate for an additional 20 minutes, stopping at about 1010. Incandescence at the vents persisted overnight during 18-19 January and lava on the crater floor overturned an exposed molten lava. The crater floor was almost entirely dark by the evening of 19 January. Incandescence from the N vent remained strong at least through the morning of 21 January. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color 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.

Ontakesan, Japan

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

The Japan Meteorological Agency (JMA) reported increased seismic unrest at Ontakesan. The number of small volcanic earthquakes with epicenters near the summit had increased in mid-December 2024 and further increased in January 2025, most notably on 16 January. Volcanic earthquake totals of 5-8 per day were recorded during 10, 12-13, and 15 January. There were 24 and 19 volcanic earthquakes recorded on 11 and 14 January, respectively. Seismicity escalated on 16 January, with 27 volcanic earthquakes. The Alert Level was raised to 2 (on a scale of 1-5) at 2200 on 16 January and the public was warned to stay 1 km away from Jigokudani Crater. Deformation data did not show any ground movement.

A total of 8-13 daily volcanic earthquake were recorded during 17-20 January. On 21 January the deformation network recorded summit inflation and the number of volcanic earthquakes significantly increased to 273 by 1900. Fumarolic activity remained at normal levels; white emissions from Jigokudani Crater rose 200 m.

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

Purace, Colombia

2.32°N, 76.4°W | Summit elev. 4650 m

The Servicio Geologico Colombiano (SGC) reported that seismic tremor at Puracé increased at 2356 on 19 January with events located in the NW part of the Los Coconucos volcanic chain. An ash emission rose 1.4 km above the Curiquinga crater rim and drifted SW, causing a notable sulfur odor in the towns of Puracé (11 km NW) and Coconuco (12 km WNW), along with ashfall in Coconuco, Timbío (34 km WNW), Popayán (30 km NW), and Sotará (23 km W). The emission was detected by pressure sensors, was visible in webcam images, and was observed by nearby residents. A significant increase in sulfur dioxide emissions was detected in satellite data and from instruments at the summit. Deformation was also detected at the Puracé and Curiquinga craters. On 20 January SGC noted that four vents producing gas emissions had been identified based on webcam images and reports by residents: two at Puracé and two new vents in Curiquinga. The Alert Level remained at Yellow (the second lowest level on a four-color scale).

Geological summary: Puracé in Colombia consists of an andesitic stratovolcano with a 500-m-wide summit crater constructed over a dacitic shield volcano. It lies at the NW end of a volcanic massif opposite Pan de Azúcar stratovolcano, 6 km SE. A NW-SE-trending group of seven cones and craters, Los Coconucos, lies between the two larger edifices. Frequent explosive eruptions in the 19th and 20th centuries have modified the morphology of the summit crater. The largest eruptions occurred in 1849, 1869, and 1885.

Ongoing activity

Aira, Japan

31.5772°N, 130.6589°E | Summit elev. 1117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 13-20 January. Nightly crater incandescence was visible in webcam images. On 14 January sulfur dioxide emissions were high, averaging 2,300 tons per day. Explosions at 0223 and 0440 on 15 January, at 0626 on 17 January, at 0837, 9090, 1427, and 1526 on 19 January, and at 0842 on 20 January produced ash plumes that rose 300-2,000 m above the crater rim and drifted SE and E. Most of the explosions ejected large blocks 500-1,300 m from the crater rim. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 1 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 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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Dukono, Indonesia

1.6992°N, 127.8783°E | Summit elev. 1273 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Dukono was ongoing during 15-21 January. White-and-gray ash plumes rose 100-800 m above the crater rim and drifted E on most days; emissions were not visible on 19 January possibly in part due to weather conditions. Occasional thumping noises were reported on 20 January. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Ebeko, Russia

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

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that moderate activity was ongoing at Ebeko during 9-16 January. An explosion on 13 January generated an ash plume that rose as high as 2.5 km (8,200 ft) a.s.l. and drifted SE, according to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E). Satellite images indicated that the volcano was quiet or obscured by weather clouds. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are UTC; 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.

Erta Ale, Ethiopia

13.601°N, 40.666°E | Summit elev. 585 m

Satellite images of Erta Ale on 7, 17, and 22 January showed thermal anomalies over the N and S pit crater vent areas.

Geological summary: The Erta Ale basaltic shield volcano in Ethiopia has a 50-km-wide edifice that rises more than 600 m from below sea level in the Danakil depression. The volcano includes a 0.7 x 1.6 km summit crater hosting steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera usually also holds at least one long-term lava lake that has been active since at least 1967, and possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Great Sitkin, United States

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

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick lava flow in Great Sitkin’s summit crater during 14-21 January. The local seismic network continued to detect small earthquakes associated with the ongoing eruption. Mostly cloudy satellite and webcam images prevented clear observations, though steaming from the lava flow was visible during 14-15 January. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger 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 older edifice and produced a submarine debris avalanche. Deposits from this and an even 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. Eruptions have been recorded since the late-19th century.

Kanlaon, Philippines

10.4096°N, 123.13°E | Summit elev. 2422 m

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 14-21 January. The seismic network recorded 4-17 daily volcanic earthquakes that included 1-5 periods of volcanic tremor lasting five minutes to one hour and 36 minutes; volcanic tremor was not detected on 17 January. Average daily sulfur dioxide emissions ranged from 2,302 to 5,222 tonnes per day. Weather clouds prevented views on 14 and 17 January. There were 2-5 periods of ash emissions during 15-16 and 18-21 January, each as short as two minutes and as long as three hours and seven minutes. Gas-and-steam emissions and those occasionally containing ash rose as high as 300 m above the summit and drifted SW and W. Plumes were voluminous on 21 January.

The eruption continued to impact residents. The National Disaster Risk Reduction and Management Council (NDRRMC) report issued at 0800 on 21 January stated that 9,869 people (3,117 families) were spread across 23 evacuation centers and another 8,376 people (2,648 families) were staying elsewhere. The Alert Level remained at 3 (on a scale of 0-5); the public was warned to stay 6 km away from the summit and pilots were warned not to fly close to the volcano.

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

Karymsky, Russia

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

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported moderate levels of activity at Karymsky during 9-16 January. A weak thermal anomaly over the volcano was identified in satellite images. The Aviation Color Code remained at Orange (the third 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.

Lewotobi, Indonesia

8.542°S, 122.775°E | Summit elev. 1703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity continued at Lewotobi Laki-laki during 15-21 January. White-and-gray ash plumes that were sometimes dense rose as high as 1.5 km above the summit and drifted in multiple directions on 16 and 20 January. White gas-and-steam plumes rose as high as 500 m above the summit and drifted in multiple directions on 19 and 21 January. Emissions were not visible on the other days. Incandescence at the crater was periodically visible in a webcam images. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 5 km away from the center of Laki-laki and 6 km in a semicircle counterclockwise from the NE to the SW.

Geological summary: The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the “husband and wife”). Their summits are less than 2 km apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan.

Merapi, Indonesia

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

The Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG) reported that the eruption at Merapi (on Java) continued during 10-16 January. Seismicity was less intense than the previous week. The SW lava dome produced 29 lava avalanches that traveled as far as 1.9 km SW down the Bebeng drainage, 12 that traveled as far as 1.9 km SW down the Krasak drainage, and 13 that traveled as far as 1.7 km SW down the Sat/Putih drainage. Morphological changes at the SW dome were caused by continuing effusion and collapses of material. No significant morphological changes at the summit dome were visible. 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’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 14-20 January. Seismic data indicated that events associated with fluid movement increased in both number and intensity compared to the previous week, but the frequency of pulsating ash-and-gas emissions decreased slightly. Webcam images confirmed some ash emissions and higher-temperature ejecta were associated with some of these events. Notably, at 2145 on 15 January and at 1957 on 20 January, gas-and-ash plumes rose 1.4-2 km above the summit and drifted NW, W, and SW, causing ashfall in Villamaría (28 km NW) and Manizales (28 km NW). Seismicity associated with rock fracturing decreased in both number and magnitude compared to the previous week. The earthquakes with magnitudes less than 1 were located below Arenas Crater and the N, NE, SSE, and SSW flanks within 9 km, and had depths of 1-6 km. Low-to-moderate-energy thermal anomalies on the crater floor were identified in satellite data when weather permitted. Sulfur dioxide emissions detected in satellite data were higher than the previous weeks and charactered as significant. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

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.

Semeru, Indonesia

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity continued at Semeru during 15-21 January with several daily eruptive events recorded by the seismic network. Gray or white-and-gray ash plumes rose 400-1000 m above the summit and drifted in multiple directions during 15-19 January. Emissions were not observed during 20-21 January. The Alert Level remained at 2 (the second lowest level 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, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages 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, Russia

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

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that lava extrusion may have continued at Sheveluch’s “300 years of RAS” dome on the SW flank of Old Sheveluch and at the Young Sheveluch dome during 9-16 January. Daily thermal anomalies over the domes were identified in satellite images. Plumes of resuspended ash drifted 74 km SE during 13-14 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 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, Japan

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

The Japan Meteorological Agency (JMA) reported that eruptive activity at Suwanosejima’s Ontake Crater continued during 13-20 January. Crater incandescence was observed nightly in webcam images. A total of six explosions were recorded and large blocks were sometimes ejected as far as 300 m from the crater. Explosions at 2300 on 13 January, at 0153 and 0346 on 14 January, at 2023 on 17 January, and at 0832 and 1759 on 73 January generated ash plumes that rose 800-1,000 m and drifted SE and E. The plumes sometimes rose into weather clouds. Eruptive events on 13, 18, and 20 January produced ash plumes that rose 1-1.1 km above the crater rim and drifted SE. Occasional rumbling and ashfall were reported within 1 km of the crater according to the Suwanosejima Branch Office in Toshima village (3.5 km SSW). The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 1.5 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 active summit craters. The summit is truncated by a large breached crater extending to the sea on the E 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 covered 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 an open collapse scarp extending 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.

References:

¹ Smithsonian Institution / US Geological Survey Weekly Volcanic Activity Report – January 15 – 21, 2025 – Managing Editor: Sally Sennert.

Rishika Yadav

Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.

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