The Weekly Volcanic Activity Report: December 7 – 13, 2022

New activity/unrest was reported for 5 volcanoes from December 7 to 13, 2022. During the same period, ongoing activity was reported for 15 volcanoes.

New activity/unrest: Ahyi, Mariana Islands (USA) | Fuego, South-Central Guatemala | Lascar, Northern Chile | Mauna Loa, Hawaiian Islands (USA) | Semeru, Eastern Java.

Ongoing activity: Aira, Kyushu (Japan) | Alaid, Kuril Islands (Russia) | Cotopaxi, Ecuador | Ebeko, Paramushir Island (Russia) | Great Sitkin, Andreanof Islands (USA) | Kilauea, Hawaiian Islands (USA) | Merapi, Central Java | Pavlof, Alaska Peninsula, Alaska | Sabancaya, Peru | San Miguel, Eastern El Salvador | Sheveluch, Central Kamchatka (Russia) | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Central Chile | Whakaari/White Island, North Island (New Zealand).

New activity/unrest

Ahyi, Mariana Islands (USA)

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

Unrest continued to be detected at Ahyi Seamount during 7-13 December. Wake Island hydrophone sensors detected daily signals consistent with explosions during 10-12 December. No signs of underwater plumes were visible in satellite images during 10-11 December; weather clouds obscured the area on 12 December. 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.

Fuego, South-Central Guatemala

14.473°N, 90.88°W | Summit elev. 3763 m

INSIVUMEH reported that the eruption at Fuego was ongoing during 7-13 December, though activity had notably intensified during 10-11 December. The seismic network recorded 4-10 explosions per hour during the week, with ash plumes rising as high as 1.2 km above the crater rim. The ash plumes generally drifted 10-20 km NW, W, and SW, causing daily ashfall in areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Finca Palo Verde, Sangre de Cristo (8 km WSW), San Pedro Yepocapa (8 km NW). Daily shock waves rattled structures in communities around the volcano. Daily block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Honda, Las Lajas (SE), and El Jute (ESE) drainages, often reaching vegetated areas. Strombolian explosions ejected incandescent material as high as 200 m above the summit on a few of the days.

Activity increased on 10 December. In a special report posted at 2241, INSIVUMEH noted that in the previous minutes multiple explosions of variable intensities produced ash plume that rose 1.2 km above the summit and drifted 30 km W and NW. Pulsating lava fountains rose as high as 500 m above the summit. A lava flow had traveled 800 m down the Ceniza drainage by the time the report was issued, and avalanches of material spalled from its front reached vegetated areas. At 2300 pyroclastic flows descended the Las Lajas drainage several kilometers. Dense ash plumes and pyroclastic flows down the Las Lajas drainage continued for at least an hour. Just before 0030 on 11 December pyroclastic flows traveled several kilometers down the Ceniza drainage on the SW flank. Lava fountains rose as high as 300 m. By 0640 dense ash plumes were rising over 1.2 km above the summit and the lava flow remained active. Avalanches of material from the advancing lava front descended to vegetated areas. Satellite images showed that ash clouds had spread NE, E, and SE, covering a wide area in the department of Sacatepéquez and the central and southern parts of the department of Guatemala. Activity decreased by the early afternoon; lava fountaining, dense ash emissions, and pyroclastic flows had all ceased before 1410.

Geological summary: Volcán Fuego, one of Central America’s most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala’s former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Lascar, Northern Chile

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

SERNAGEOMIN reported that an eruption at Láscar began at 1236 on 10 December with an explosive event that produced a dense ash plume and pyroclastic flows proximal to the crater. Hikers were near the crater and took video of the eruption. According to SEGEMAR the pyroclastic flows traveled short distances to the N and SE. The ash plume rose about 6 km above the crater rim and drifted SW. The event was coincident with a long-period earthquake detected by the seismic network. Later that day the Alert Level was raised to Yellow (the second lowest level on a four-color scale) and the public were warned to stay at least 5 km away from the crater. ONEMI declared an Alert Level Yellow (the middle level on a three-color scale) for San Pedro de Atacama (70 km NW). CKELAR noted that the thermal anomaly had intensified during the five days prior to the eruption along with increased sulfur dioxide gas emissions.

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.

Mauna Loa, Hawaiian Islands (USA)

19.475°N, 155.608°W | Summit elev. 4170 m

HVO reported that activity at Mauna Loa’s Fissure 3 declined during 7-9 December and then ceased on 10 December. The main lava flow had only advanced a small distance during 6-7 December, at a rate of about 6 m per hour, possibly due to a significant breakout that had occurred about 4.5 km upslope of the flow front. Lava erupting from Fissure 3 was greatly reduced by the morning of 8 December. Lava overtopped channels near the vent but had not advanced farther than 4.4 km from the vent by 0930. The channel at lower elevations appeared to be drained and was likely no longer feeding the main flow which had stalled about 2.8 km from the Daniel K. Inouye Highway (Saddle Road). The sulfur dioxide emission rate had declined to 30,000 tonnes per day. By 1130 on 9 December low lava fountains at Fissure 3 fed flows that traveled as far as 2.65 km NE. By 0700 on 10 December a lava pond in the Fissure 3 vent was visible and fed short lava flows that stagnated at 2.6 km. Tremor levels were slowly declining and the sulfur dioxide emission rate was about 2,000 tonnnes per day. Lava was confined to the small pond by 1435 and gas emissions had significantly declined. HVO lowered the Volcano Alert Level to Watch (the second highest level on a four-level scale); the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

No activity was visible on the flow field overnight during 10-11 December, and by 0700 on 11 December the Fissure 3 vent was barely incandescent. Scientists observed no lava movement and only minor incandescence at the vent during an overflight in the early morning of 12 December. They heard a small explosion that accompanied a spray of spatter from the W end of the fissure. On 13 December HVO lowered the Volcano Alert Level to Watch and the Aviation Color Code to Yellow and noted that lava effusion at Fissure 3 had ceased on 10 December, sulfur dioxide emissions had decreased to near pre-eruption background levels, and volcanic tremor and earthquakes associated with the eruption were greatly diminished.

Geological summary: Massive Mauna Loa is a basaltic shield volcano that rises almost 9 km from the ocean floor to form the world’s largest Holocene volcano. Flank eruptions typically occur from the lengthy NE and SW rift zones, and from the Moku’aweoweo summit is caldera, which is within an older and larger 6 x 8 km caldera. Two of the youngest large debris avalanches documented in Hawaii traveled nearly 100 km from Mauna Loa; the second of the Alika avalanches was emplaced about 105,000 years ago (Moore et al., 1989). Almost 90% of the surface of the volcano is covered by lavas less than 4,000 years old (Lockwood and Lipman, 1987). Beginning about 1,500 years ago, a series of voluminous overflows from a summit lava lake covered about 25% of the volcano’s surface. Over the last 750 years, from shortly after the formation of Moku’aweoweo caldera until the present, an additional 25% of the volcano has been covered with lava flows, mainly from summit and NW rift zone vents.

Semeru, Eastern Java

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

BNPB reported that residents continued to be impacted by the collapses and large pyroclastic flows on Semeru’s SE flank on 4 December. As of 6 December, there were 781 people spread across 21 evacuation shelters and heavy ashfall prevented aid from easily reaching Pronojiwo Village, according to BNPB. Kajar Kuning was the worst affected village.

PVMBG reported that lava continued to erupt from the summit vent during 4-9 December, though activity generally declined. Ongoing thermal anomalies were identified in satellite images, though the intensity had decreased. The rate of deformation had declined based on tiltmeter data. Four pyroclastic flows moved as far as 6 km down the SE flanks, and avalanches of material traveled 300-500 m SE. At 0521 on 8 December a gray-to-white ash plume rose around 300 m above the summit and drifted N. At 0536 a gray ash plume rose 400 m and drifted N, as reported by a ground-based observer. A dense gray ash plume rose 500 m and drifted N at 0521 on 9 December. Later that day, at 1200, the Alert Level was lowered to 3 (the second highest level on a scale of 1-4) and the public was warned to stay at least 5 km away from the summit, as far as 13 km from the summer on the SE flanks, 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.

Eruptive activity continued during 10-13 December. At 0653 on 10 December a dense white-to-gray ash plume rose about 700 m above the summit and drifted N. White-and-gray ash plume were visible at 0652 on 11 December and 0727 on 12 December rising at least 500 m and drifting S and SW, respectively.

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.

Ongoing activity

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 5-12 December consisting of a few eruptive events and three explosions. Crater incandescence was visible nightly. Explosions produced ash plumes that rose as high as 2.7 km above the crater rim and ejected large blocks as far as 1.1 km away. Sulfur dioxide emissions were high at 2,800 tons per day on 6 December. 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.

Alaid, Kuril Islands (Russia)

50.861°N, 155.565°E | Summit elev. 2285 m

KVERT reported that the eruption at Alaid was ongoing during 1-8 December. A thermal anomaly was identified in satellite images on 2 and 8 December; weather clouds obscured observations on the other days. 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 highest and northernmost volcano of the Kuril Islands, Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached open to the south. This basaltic to basaltic-andesite volcano is the northernmost of a chain constructed west of the main Kuril archipelago. Numerous pyroclastic cones are present the lower flanks, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest reported in the Kuril Islands.

Cotopaxi, Ecuador

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

IG reported that the low-level eruption at Cotopaxi continued during 7-13 December characterized by steam-and-gas emissions and occasional ash emissions. Sulfur dioxide emissions measured by satellite almost daily averaged 665-2,745 tons per day. Steam-and-gas emissions observed during 7-10 December rose as high as 2 km above the crater rim and drifted SW, W, and NW. Ash emissions during 0758-0816 on 8 December rose 1 km and drifted WNW. The Washington VAAC issued three advisories noting that ash rose 800-1,100 m and drifted W. A tremor signal that started at 0832 on 9 December was probably related to gas-and-ash emissions, though cloudy weather conditions prevented visual confirmation. During the night of 9-10 December several steam-and-ash emissions were identified in satellite images rising as high as 1.1 km and drifting NW. Minor ashfall was reported in Conocoto-Pichincha in the morning of 10 December. At 0930 on 11 December the seismic stations recorded a signal related to gas-and-ash emissions that rose 2 km and drifted W. Ash fell in Control Caspi, located at the S entrance to Parque Nacional Cotopaxi. Several gas-and-steam emissions with low ash content were visible that afternoon and during the morning of 12 December rising as high as 500 m and drifting W. 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 1-8 December. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions during 1-2 and 7 December generated ash plumes that rose to 2.5 km (8,200 ft) a.s.l. and drifted NE. The volcano was quiet or obscured by weather clouds on the other days of the week. 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.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slow lava effusion continued at Great Sitkin during 27 November-11 December based on satellite images. Cloud cover mostly prevented satellite and webcam observations during 7-12 December. Seismicity remained at low levels. 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.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that lava continued to effuse from a vent in the lower W wall of Kilauea’s Halema`uma`u Crater during 6-8 December and entered the lava lake, though the eruption rate had diminished, and the floor of the crater had deflated. The eruption ceased on 9 December. During 10-12 December the lake crusted over, no incandescence was visible, and sulfur dioxide emissions had decreased to near pre-eruption background levels. On 13 December HVO lowered the Volcano Alert Level to Advisory (the second lowest level on a four-level scale) and the Aviation Color Code to Yellow (the second lowest 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.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi continued during 2-8 December and seismicity remained at high levels. The SW lava dome produced two lava avalanches that traveled as far as 1.6 km down the SW flank (upstream in the Kali Bebeng drainage). No significant morphological changes to the central and SW lava domes were evident. 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.

Pavlof, Alaska Peninsula, Alaska

55.417°N, 161.894°W | Summit elev. 2493 m

AVO reported that seismic tremor and a few low-frequency earthquakes at Pavlof indicated continuing unrest during 7-13 December; one explosion was recorded on 7 December. No explosions or lava flow activity was detected in seismic, infrasound, satellite, or webcam data during the rest of the week. The report noted that events on 3 December resulted in the erosion of a narrow, 2-km-long gully beneath the ice below the vent. 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 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.

Sabancaya, Peru

15.787°S, 71.857°W | Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported moderate levels of activity at Sabancaya during 5-11 December with a daily average of 40 explosions. Gas-and-ash plumes rose as high as 2 km above the summit and drifted SW, S, and NE. Two thermal anomalies originating from the lava dome in the summit crater were identified in satellite data. Minor inflation continued to be detected near Hualca Hualca (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning “tongue of fire” in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

San Miguel, Eastern El Salvador

13.434°N, 88.269°W | Summit elev. 2130 m

On 7 December MARN reported that activity at San Miguel had decreased. No explosions had been recorded since 29 November and seismicity had decreased. Sulfur dioxide emissions were below the baseline of 300 tons per day.

Geological summary: The symmetrical cone of San Miguel, one of the most active volcanoes in El Salvador, rises from near sea level to form one of the country’s most prominent landmarks. A broad, deep, crater complex that has been frequently modified by eruptions recorded since the early 16th century caps the truncated unvegetated summit, also known locally as Chaparrastique. Flanks eruptions of the basaltic-andesitic volcano have produced many lava flows, including several during the 17th-19th centuries that extended to the N, NE, and SE. The SE-flank flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. Flank vent locations have migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that the ongoing eruption at Sheveluch during 2-8 December was generally characterized by explosions, hot avalanches, lava-dome extrusion, and strong fumarolic activity. A daily thermal anomaly was identified in satellite images. Collapses generated hot avalanches and ash plumes that drifted 60 km NE and E during the week. 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.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E | Summit elev. 924 m

INGV reported that lava continued to flow from the vent that opened on 4 December just downslope of the N2 vent in Stromboli’s Area N. The flow had descended the Sciara del Fuoco and reached the coast by around 1700 on 4 December. By 7 December only the top third of the flow was active while the rest of the flow was cooling. The flow was last confirmed to be active in webcam images on 8 December, but afterwards the webcam stream was interrupted. Explosions at three vents in Area N ejected coarse material (bombs and lapilli) less than 80 m high at a rate of 1-7 explosions per hour during 5-11 December.

Geological summary: Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the “Lighthouse of the Mediterranean” in the NE Aeolian Islands. This volcano has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

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 5-12 December and crater incandescence was visible nightly. No explosions were recorded. Eruption plumes rose as high as 1.7 km above the crater rim and blocks were ejected as far as 200 m from the vent. Ashfall was occasionally reported in Toshima village (3.5 km SSW). 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 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 during an overflight of Villarrica on 6 December scientists observed intense gas emissions from the lava lake and tephra deposits on the S and SE flanks, as far as 500 m from the crater. During 7-12 December seismicity slightly increased, whitish, low-altitude gas plumes were emitted, and incandescence from the crater was sometimes visible. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the public was warned that material could be ejected within 500 m of the crater. ONEMI remained the Alert Level 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 12 December GeoNet reported continuing unrest at Whakaari/White Island characterized by minor-to-moderate gas-and-steam emissions and low levels of gas. During an overflight on 6 December sulfur dioxide gas emissions averaged around 273 tonnes per day and carbon dioxide emissions averaged around 787 tonnes per day, levels similar to those last measured on 14 October. The lake level had decreased. No signs of ash emissions or other eruptive activity were recorded. 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.

References:

Smithsonian / US Geological Survey Weekly Volcanic Activity Report – December 7 – 13, 2022 –
Managing Editor: Sally Kuhn Sennert