Smithsonian / USGS Weekly Volcanic Activity Report

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday and averaging 16 reported volcanoes, this is not a comprehensive list of all eruptions this week, but rather a summary of activity that meet criteria discussed in the "Criteria and Disclaimers" section below.

Volcanic activity reported here is preliminary and subject to change. Carefully reviewed, detailed narratives over longer time periods are published as reports of the Bulletin of the Global Volcanism Network available through volcano profile pages.

Smithsonian / USGS Weekly Volcanic Activity Report for the week of 20 December-26 December 2023
Name	Country	Volcanic Region	Eruption Start Date	Report Status
Kanaga	United States	Aleutian Ridge Volcanic Arc	—	New
Lewotobi	Indonesia	Sunda Volcanic Arc	2023 Dec 23	New
Marapi	Indonesia	Sunda Volcanic Arc	2023 Dec 3	New
Reykjanes	Iceland	Iceland Neovolcanic Rift Volcanic Province	—	New
Aira	Japan	Ryukyu Volcanic Arc	2017 Mar 25	Continuing
Ebeko	Russia	Kuril Volcanic Arc	2022 Jun 11	Continuing
Etna	Italy	Sicily Volcanic Province	2022 Nov 27	Continuing
Great Sitkin	United States	Aleutian Ridge Volcanic Arc	2021 May 25	Continuing
Lewotolok	Indonesia	Sunda Volcanic Arc	—	Continuing
Mayon	Philippines	Eastern Philippine Volcanic Arc	—	Continuing
Merapi	Indonesia	Sunda Volcanic Arc	2020 Dec 31	Continuing
Nevado del Ruiz	Colombia	Northern Andean Volcanic Arc	2014 Nov 18	Continuing
Semeru	Indonesia	Sunda Volcanic Arc	2017 Jun 6	Continuing
Sheveluch	Russia	Eastern Kamchatka Volcanic Arc	1999 Aug 15	Continuing
Shishaldin	United States	Aleutian Ridge Volcanic Arc	—	Continuing
Suwanosejima	Japan	Ryukyu Volcanic Arc	2004 Oct 23	Continuing

All times are local unless otherwise stated.

Kanaga (United States) | 20 December-26 December 2023 | New Activity / Unrest Cite this Report

Kanaga
Aleutian Ridge Volcanic Arc

AVO reported that the rate of seismicity at Kanaga significantly declined after the explosion on 18 December and was slightly elevated with small daily earthquakes during 19-26 December. Satellite observations following the event showed a debris flow extending 1.5 km down the NW flank. Possible minor steaming was visible in a webcam image on 20 December. Weakly elevated surface temperatures were identified in satellite data during 23-26 December. The Volcano Alert Level remained at Advisory (the second level on a four-level scale) and the Aviation Color Code remained at Yellow (the second color on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

Lewotobi (Indonesia) | 20 December-26 December 2023 | New Activity / Unrest Cite this Report

Lewotobi
Sunda Volcanic Arc

PVMBG reported that an eruption at Lewotobi’s Laki-laki, the NW of two large adjacent stratovolcanoes, occurred at 0714 on 23 December and lasted about 24 minutes. The Aviation Color Code was raised to Orange (the third level on a four-color scale). Dense gray ash plumes rose 1-1.5 km above the summit and drifted N. The eruption was preceded by about a week of increased seismicity. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the active summit crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Marapi (Indonesia) | 20 December-26 December 2023 | New Activity / Unrest Cite this Report

Marapi
Sunda Volcanic Arc

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 20-26 December, though fog and rain occasionally prevented visual observations of the summit. White-and-gray ash plumes that were often dense rose as high as 1 km above the summit and drifted in multiple directions during 22-26 December. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay 3 km away from the summit crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Reykjanes (Iceland) | 20 December-26 December 2023 | New Activity / Unrest Cite this Report

Reykjanes
Iceland Neovolcanic Rift Volcanic Province

IMO reported that the eruption on the Reykjanes peninsula from fissures that had opened on 18 December near the older Sundhnúkagígar crater row, about 3 km NE of the town of Grindavík, had stopped by the morning of 21 December. There was a significant decrease in seismicity during 19-20 December, and by 1700 on 20 December lava was erupting from only two craters located at the central part of the fissure. Lava mainly flowed E, though to the N of Stóra-Skógfell a flow to the W continued to be fed but was no longer advancing. Eruptive activity declined later that night or early on 21 December and seismicity continued to decline. Scientists on an overflight during the morning of 21 December confirmed that no eruptive activity was visible and that lava effusion at the craters had ceased. Some areas on the lava-flow field were incandescent, and it was possible that lava continued to flow through tubes. At 1459 on 22 December IMO lowered the Aviation Color Code to Yellow (the second level on a four-color scale) noting that there were no active vents. A total of about 12 million cubic meters of lava had erupted, covering an area of about 3.4 square kilometers.

Seismicity persisted in the Grindavík, Sundhnúksgígar, and Svartsengi regions, was variable daily, though low overall. Ground deformation data from GPS and satellite-based measurements indicated that magma accumulation beneath the Svartsengi region continued. A new hazard assessment and updated map went into effect on 22 December; the areas around the fissure were reduced from very high to high, and the assessment for Grindavík was unchanged (remaining “considerable”).

Source: Icelandic Meteorological Office (IMO)

Aira (Japan) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Aira
Ryukyu Volcanic Arc

JMA reported ongoing activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 18-25 December, with incandescence at the crater observed nightly. Small eruptive events were occasionally recorded on 18 December. Sulfur dioxide emissions were high, averaging 2,700 tons per day on 20 December. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.

Source: Japan Meteorological Agency (JMA)

Ebeko (Russia) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Ebeko
Kuril Volcanic Arc

KVERT reported that moderate explosive activity was ongoing at Ebeko during 14-21 December. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 18-21 December generated ash plumes that rose as high as 2.5 km (8,200 ft) a.s.l and drifted SE 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Etna (Italy) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Etna
Sicily Volcanic Province

INGV reported that a seismic swarm at Etna was recorded during 1508-1517 on 21 December. Coincident with the swarm, light-gray ash emissions rose from Bocca Nuova Crater during 1513-1520 and drifted S, rapidly dissipating. At 0217 on 23 December a strong explosion at SE Crater ejected coarse material onto the flanks and produced an ash plume that was dispersed by wind. At 1223 a strong explosion at the same crater produced an ash plume that rapidly dissipated.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

Great Sitkin (United States) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Great Sitkin
Aleutian Ridge Volcanic Arc

AVO reported that a 20 December radar image of Great Sitkin showed continuing growth of a thick flow in the summit crater; effusion likely continued during 20-26 December. Weather clouds often obscured views of the volcano. Minor steaming was identified in satellite data during 22-23 December. Elevated surface temperatures were identified in satellite data and minor steaming was seen in webcam images during 24-25 December. Seismicity was low. 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).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

Lewotolok (Indonesia) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Lewotolok
Sunda Volcanic Arc

PVMBG reported that the eruption at Lewotolok continued during 20-26 December. White-and-gray ash plumes rose 500-700 m during 21-23 December and drifted E, NW, and W. White steam-and-gas plumes rose 100-600 m above the summit on the other days and drifted W, NW, NE, and E. Incandescent lava was occasionally ejected about the vent. 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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Mayon (Philippines) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Mayon
Eastern Philippine Volcanic Arc

PHIVOLCS characterized activity at Mayon as “decreased unrest” during 19-26 December. The seismic network recorded 0-6 daily volcanic earthquakes and a total of two rockfall events during 21-24 December. Emissions were visible daily, rising as high as 500 m above the summit and drifting NW, W, and SW. The Tokyo VAAC reported that at 0852 on 23 December an ash emission was identified in a satellite image rising to 2.4 km (8,000 ft) a.s.l. and drifting WSW based on satellite data and information from PHIVOLCS. The Alert Level remained at 2 (on a 0-5 scale). Residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Tokyo Volcanic Ash Advisory Center (VAAC)

Merapi (Indonesia) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Merapi
Sunda Volcanic Arc

BPPTKG reported that the eruption at Merapi (on Java) continued during 15-21 December. The SW lava dome produced a total of 147 lava avalanches that descended the S and SW flanks; 26 traveled S as far as 1.6 km down the upper part of the Boyong drainage, 120 traveled SW as far as 1.7 km down the upper part of the Bebeng drainage, and one traveled 1.2 km down the Putih/Sat drainage on the WSW flank. Morphological changes to the SW lava dome were identified in webcam images due to continuing collapses of material. The intensity of earthquakes indicating avalanches and hybrid events significantly decreased during the week. 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.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)

Nevado del Ruiz (Colombia) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Nevado del Ruiz
Northern Andean Volcanic Arc

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued at low-to-moderate levels during 19-25 December. Seismic events indicating rock fracturing increased in both number an intensity. These events were located in areas up to 11 km in various directions from Arenas Crater, though mainly on the E flank, at depths of 1-9 km. The seismic activity was most notable during 24-25 December; earthquakes at 1402, 1403, and 1715 on 24 December and at 0813 on 25 December were felt in parts of La Cabaña and the Lagunilla River drainage in the department of Tolima. Seismicity associated with activity at the lava dome had also intensified, beginning at 2301 on 24 December. Ash-and-gas emissions were seismicity detected during the week as well as occasionally visible in webcam images. The maximum height of the ash-and-gas emissions was 1.9 km above the summit, recorded on 22 December. Emissions drifted SE during the first part of the week and SW and NW during the second part of the week, generating ashfall near the volcano and occasionally in Manizales (27 km NW). The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)

Semeru (Indonesia) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Semeru
Sunda Volcanic Arc

PVMBG reported that eruptive activity continued at Semeru during 20-26 December. Daily white-and-gray ash plumes that were sometimes dense generally rose 400-800 m above the summit and drifted S, SW, and W, though at 0512 on 25 December an ash plume rose as high as 1 km. The Alert Level remained at 3 (third highest 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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Sheveluch (Russia) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Sheveluch
Eastern Kamchatka Volcanic Arc

KVERT reported that the eruption at Sheveluch continued during 14-21 December. A daily thermal anomaly 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Shishaldin (United States) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Shishaldin
Aleutian Ridge Volcanic Arc

AVO reported that unrest continued at Shishaldin during 20-26 December. Seismicity was slightly elevated and consisted of small low-frequency earthquakes and tremor. Minor steaming was visible in a webcam image during 20-21 December. 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).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

Suwanosejima (Japan) | 20 December-26 December 2023 | Continuing ActivityCite this Report

Suwanosejima
Ryukyu Volcanic Arc

JMA reported that the eruption at Suwanosejima's Ontake Crater continued during 18-25 December. No explosions were detected, though large blocks were ejected as far as 200 m from the vent. Eruption plumes rose as high as 1,200 m above the crater rim during 24-25 December and drifted S and SE. Ashfall was reported in Toshima village (3.5 km SSW), though dates were not specified. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 1 km away from the crater.

Source: Japan Meteorological Agency (JMA)

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Criteria & Disclaimers

Criteria

The Weekly Volcanic Activity Report does not necessarily include all volcanic activity that occurred on Earth during the week. More than a dozen volcanoes globally have displayed more-or-less continuous eruptive activity for decades or longer, and such routine activity is typically not reported here. Moreover, Earth's sea-floor volcanism is seldom reported even though in theory it represents the single most prolific source of erupted material. The Weekly Volcanic Activity Report summarizes volcanic activity that meets one or more of the following criteria:

- A volcano observatory raises or lowers the alert level at the volcano.
- A volcanic ash advisory has been released by a volcanic ash advisory center (VAAC) stating that an ash cloud has been produced from the volcano.
- A verifiable news report of new activity or a change in activity at the volcano has been issued.
- Observers have reported a significant change in volcanic activity. Such activity can include, but is not restricted to, pyroclastic flows, lahars, lava flows, dome collapse, or increased unrest.

Volcanoes are included in the "New Activity/Unrest" section of the Weekly Volcanic Activity Report if the activity occurs after at least 3 months of quiescence. Once a volcano is included in the "New Activity/Unrest" section, updates will remain in that section unless the activity continues for more than 1 month without escalating, after which time updates will be listed in the "Continuing Activity" section. Volcanoes are also included in the "New Activity/Unrest" section if the volcano is undergoing a period of relatively high unrest, or increasing unrest. This is commonly equal to Alert Level Orange on a scale of Green, Yellow, Orange, Red, where Red is the highest alert. Or alert level 3 on a scale of 1-4 or 1-5.

It is important to note that volcanic activity meeting one or more of these criteria may occur during the week, but may not be included in the Weekly Volcanic Activity Report because we did not receive a report.

Disclaimers

1. The Weekly Volcanic Activity Report is intended to provide timely information about global volcanism on a weekly basis. Consequently, the report is generated rapidly by summarizing volcanic reports from various sources, with little time for fact checking. The accuracy of the Weekly Volcanic Activity Report is dependent upon the quality of the volcanic activity reports we receive. Reports published in the Bulletin of the Global Volcanism Network are cover longer time periods and are more carefully reviewed, although all of the volcanoes discussed in the Weekly Volcanic Activity Report are not necessarily reported in the Bulletin. Because of our emphasis on rapid reporting on the web we have avoided diacritical marks. Reports are updated on the Weekly Volcanic Activity Report web page as they are received, therefore information may be included regarding events that occurred before the current report period.

2. Rapidly developing events lead to coverage that is often fragmentary. Volcanoes, their eruptions, and their plumes and associated atmospheric effects are complex phenomena that may require months to years of data analysis in order to create a comprehensive summary and interpretation of events.

3. Preliminary accounts sometimes contain exaggerations and "false alarms," and accordingly, this report may include some events ultimately found to be erroneous or misleading.

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