The Weekly Volcanic Activity Report: January 17 - 23, 2024

New activity/unrest was reported for 4 volcanoes from January 17 to 23, 2024. During the same period, ongoing activity was reported for 12 volcanoes.

New activity/unrest: Ahyi, Mariana Islands (USA) | Grimsvotn, Iceland | Lewotobi, Flores Island | Marapi, Central Sumatra.

New activity/unrest

Ahyi, Mariana Islands (USA)

20.42°N, 145.03°E; summit elev. -75 m

Signs of unrest at Ahyi Seamount continued. Plumes of discolored water extending 4-4.5 km from the summit area were identified in satellite images during 21-23 January. No volcanic activity was identified in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi). 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.

Grimsvotn, Iceland

64.416°N, 17.316°W; summit elev. 1719 m

IMO lowered the Aviation Color Code for Grímsvötn to Green (the lowest level on a four-color scale) in a Volcano Observatory Notice for Aviation (VONA) issued at 1537 on 22 January. They noted that the jökulhlaup that had begun around 10 January had ended, and that there were no measurable signs of elevated activity.

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.

Lewotobi, Flores Island

8.542°S, 122.775°E; summit elev. 1703 m

PVMBG reported that the eruption at Lewotobi’s Laki-laki volcano was ongoing during 16-23 January. Dense white-and-gray or white, gray, and brown ash plumes rose as high as 1.5 km above the summit and drifted NW, N, NE, and E. Lava flows from the summit crater continued down the N flank and were almost 3.8 km long by 23 January, according to a news article. Lava avalanches and pyroclastic flows occasionally descended the N, NW, and SW flanks during the week; lava avalanches traveled at most 2 km down the SW flank on 16 January. The Alert Level remained at 4 (the highest level on a scale of 1-4) and the public was warned to stay outside of the exclusion zone, defined as a 5-km radius around Laki-laki Crater and 6 km from the crater on the N and NE flanks.

Geological summary: The Lewotobi “husband and wife” twin volcano (also known as Lewetobi) in eastern Flores Island is composed of the Lewotobi Lakilaki and Lewotobi Perempuan stratovolcanoes. Their summits are less than 2 km apart along a NW-SE line. The conical Lakilaki has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has erupted only twice in historical time. Small lava domes have grown during the 20th century in both of the crescentic summit craters, which are open to the north. A prominent flank cone, Iliwokar, occurs on the E flank of Perampuan.

Marapi, Central Sumatra

0.38°S, 100.474°E; summit elev. 2885 m

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 10-16 January. Plumes were not observed during 17-18 January. White-and-gray ash plumes rose 300-600 m above the summit and drifted in multiple directions during 19-22 January. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 4.5 km away from the active 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.

Ongoing activity

Aira, Kyushu (Japan)

31.5772°N, 130.6589°E; summit elev. 1117 m

JMA reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 15-22 January with nighttime crater incandescence. An explosion at 0505 on 18 January produced an ash plume that rose 800 m above the crater rim and merged into weather clouds and ejected material 300-500 m from the crater rim. A small eruptive event occurred at Showa Crater on 21 January. The Alert Level remained at 3 (on a 5-level scale), and the public was 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 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.

Bulusan, Luzon (Philippines)

12.769°N, 124.056°E; summit elev. 1535 m

PHIVOLCS reported increased seismicity at Bulusan in a special advisory. The seismic network recorded a total of 91 volcanic-tectonic earthquakes, associated with rock fracturing, located at depths of 2-4 km beneath the SW flank from 0138 on 22 January to 0130 on 23 January. Gas emissions characterized as weak-to-moderate rose from the summit crater and active vents. Both the SE and SW flanks have been inflated since February 2023 based on ground deformation data from continuous GPS and electronic tilt monitoring. The Alert Level remained at 1 (the second level on a scale of 0-5) and PHIVOLCS reminded the public not to enter the 4-km-radius Permanent Danger Zone (PDZ) and to be vigilant within the 2-km Extended Danger Zone (EDZ) on the SE flank.

Geological summary: Luzon’s southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

Dukono, Halmahera

1.6992°N, 127.8783°E; summit elev. 1273 m

PVMBG reported that the eruption at Dukono was ongoing during 17-23 January. Gray-and-white ash plumes rose 100-1,800 m above the summit and drifted S and SE during 18-19 and 22-23 January; emissions were not observed on the other days. The Alert Level remained at Level 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, 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, Paramushir Island (Russia)

50.686°N, 156.014°E; summit elev. 1103 m

KVERT reported that moderate explosive activity was ongoing at Ebeko during 11-18 January. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 12 and 17-18 January generated ash plumes that rose as high as 3.5 km (11,500 ft) a.s.l and drifted NE and E. 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.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W; summit elev. 1740 m

AVO reported that the eruption of lava at Great Sitkin’s summit lava dome continued during 16-23 January, confirmed by a few radar images acquired during the week. Effusion was concentrated at the center of the dome with minimal advancement at the margins of the flow. Weakly elevated surface temperatures were identified in satellite data during 16-18 January. Local webcams and seismic data communications were offline due to a storm-related power failure. The Volcano Alert Level remained at Watch (the third highest level on a four-level scale) and the Aviation Color Code remained at Orange (the third highest color 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 Ibu continued to erupt during 17-23 January. Daily white-and-gray or gray-to-brown ash emissions rose 200-1,300 m above the summit and drifted S, SW, and W. On 17 January banging and rumbling sounds were heard at the observation post and glass in the building shook. Minor amounts of ash fell in local areas to the NW, W, and SW of the volcano during 17-19 January. The Alert Level remained at a 2 (the second highest level on a four-level scale), with the public advised to stay outside of the 2 km hazard zone and 3.5 km away from the N area of the active crater.

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.

Lewotolok, Lembata Island

8.274°S, 123.508°E; summit elev. 1431 m

PVMBG reported that the eruption at Lewotolok continued during 17-23 January. White gas-and-steam plumes rose 300 m above the summit and drifted NE, E, and SE during 17-20 January; emissions were not visible on the other days. Incandescent material was occasionally ejected above the vent, sometimes as high as 400 m. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the 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 (on Java) continued during 12-18 January. Seismicity remained at high levels. The SW lava dome produced a total of 88 lava avalanches that descended the S and SW flanks; five traveled S as far as 1.2 km down the upper part of the Boyong drainage and 83 traveled SW as far as 1.6 km down the upper part of the Bebeng drainage. Four pyroclastic flows descended the Bebeng drainage as far as 2.4 km. Morphological changes to the SW lava dome identified in webcam images were due to continuing collapses of material. 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.

Semeru, Eastern Java

8.108°S, 112.922°E; summit elev. 3657 m

PVMBG reported that eruptive activity continued at Semeru during 17-23 January. Dense gray ash plumes rose 700 m above the summit and drifted N and NE at 0016 on 18 January and 300 m above the summit and drifted NE at 0136 on 23 January. The Alert Level remained at 3 (the third highest level on a scale of 1-4). Eruptive events were recorded at 0922 on 19 January and at 1540 on 22 January, though emissions were not observed. 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, Central Kamchatka (Russia)

56.653°N, 161.36°E; summit elev. 3283 m

KVERT reported that the eruption at Sheveluch continued during 11-18 January. A thermal anomaly was identified in satellite images during 11-15 and 17 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, 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 16-22 January and crater incandescence was observed nightly. The Alert Level was lowered to 2 at 1100 on 19 January because the probability of material being ejected more than 1 km laterally had decreased. There were seven explosions detected from 1759 on 19 January to 1222 on 22 January. Details about the plumes were reported for two of them and unknown for the remaining ones; on 21 January an explosion at 1632 produced an ash plume that rose 1 km above the crater rim and drifted SE and an explosion at 2215 produced an ash plume that rose 600 m above the crater rim before merging into weather clouds. The public was 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

POVI reported that Strombolian activity at Villarrica was visible on 22 January in webcam images from a new camera located W of the volcano. Incandescent material was ejected above the crater rim. The Volcanic Alert level remained at Yellow (the third level on a four-level scale) according to SERNAGEOMIN.

Geological summary: The glacier-covered Villarrica stratovolcano, in the northern Lakes District of central Chile, is ~15 km south of the city of Pucon. A 2-km-wide caldera that formed about 3,500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesite cone at the NW margin of a 6-km-wide Pleistocene caldera. More than 30 scoria cones and fissure vents are present on 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. Eruptions documented since 1558 CE 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.

References:

¹ Smithsonian Institution / US Geological Survey – Weekly Volcanic Activity Report, January 17 – 23, 2024 – Managing Editor: Sally Sennert

Featured image credit: TW

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