The Weekly Volcanic Activity Report: May 11 – 17, 2022

Weekly Volcanic Activity Report

New activity/unrest was reported for 4 volcanoes from May 11 – 17, 2022. During the same period, ongoing activity was reported for 23 volcanoes.

New activity/unrest: Awu, Sangihe Islands | Cleveland, Chuginadak Island (USA) | Krakatau, Sunda Strait | Reykjanes, Reykjanes Peninsula.

Ongoing activity: Aira, Kyushu (Japan) | Etna, Sicily (Italy) | Fuego, South-Central Guatemala | Great Sitkin, Andreanof Islands (USA) | Ibu, Halmahera | Karymsky, Eastern Kamchatka (Russia) | Katmai, Alaska | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island | Manam, Northeast of New Guinea | Merapi, Central Java | Pavlof, Alaska Peninsula, Alaska | Reventador, Ecuador | Rincon de la Vieja, Costa Rica | Ruapehu, North Island (New Zealand) | Sangay, Ecuador | Santa Maria, Southwestern Guatemala | Semeru, Eastern Java | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Northwestern Sumatra | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan).

New activity/unrest

Awu, Sangihe Islands

3.689°N, 125.447°E | Summit elev. 1318 m

PVMBG had raised the Alert Level for Awu to 2 (on a scale of 1-4) on 12 December 2021 because of a notable increase in the number of both shallow and deep volcanic earthquakes. Since then the number of shallow and deep volcanic earthquakes averaged 8 and 5 events per day, respectively. Gas emissions had not been visible, though weather conditions sometimes prevented views of the volcano. Another significant seismic increase was recorded on 9 May, with 88 shallow events and 147 deep events, and then again the following day with 90 shallow events and 203 deep events. At 1500 on 11 May a white emission was observed rising about 30 m above the crater rim. The Alert Level was raised to 3, and the public was warned to stay at least 3.5 km away from the summit crater.

Geological summary: The massive Gunung Awu stratovolcano occupies the northern end of Great Sangihe Island, the largest of the Sangihe arc. Deep valleys that form passageways for lahars dissect the flanks of the volcano, which was constructed within a 4.5-km-wide caldera. Powerful explosive eruptions in 1711, 1812, 1856, 1892, and 1966 produced devastating pyroclastic flows and lahars that caused more than 8000 cumulative fatalities. Awu contained a summit crater lake that was 1 km wide and 172 m deep in 1922, but was largely ejected during the 1966 eruption.

Cleveland, Chuginadak Island (USA)

52.825°N, 169.944°W | Summit elev. 1730 m

AVO reported that during 11-17 May elevated surface temperatures over Cleveland were identified in satellite images. No significant seismic or infrasound activity was detected. A continuous sulfur dioxide plume drifted 500 km during 15-16 May. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.

Geological summary: The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 it produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Krakatau, Sunda Strait

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

The Darwin VAAC reported that during 10-12 May ash plumes from Anak Krakatau rose to 2.4 km (8,000 ft) a.s.l. and drifted E, N, NW, and W based on satellite images and weather models. On 13 May satellite images showed a narrow ash plume drifting SE and E at an altitude of 2.4 km. Dense steam plume with minor ash content rose to 2.4 km and drifted NE, N, NW, and W during 14-16 May.

Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Reykjanes, Reykjanes Peninsula

63.817°N, 22.717°W | Summit elev. 140 m

The National Commissioner of the Icelandic Police declared a level of “uncertainty” for the Reykjanes Peninsula on 15 May, noting that the declaration meant that responders and agencies were to review their preparedness plans in response to recent increases in seismicity and deformation. IMO raised the Aviation Color Code for Reykjanes to Yellow on 16 May, stating that more than 3,000 earthquakes had been detected near Eldvörp in the Reykjanes/Svartsengi volcanic system during the past week. Nine earthquakes above M 3 and two earthquakes above M 4 were recorded during 15-16 May; the largest event was a M 4.3 which was recorded at 1738 on 15 May. The earthquakes were located at depths of 4-6 km. GPS and InSAR data detected inflation W of Thorbjörn during the previous two weeks, likely caused by a magmatic intrusion at 4-5 km depth.

Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E | Summit elev. 1117 m

JMA reported that a very small eruptive event was recorded at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 9-13 May. An eruptive event at 1141 on 15 May generated a plume that rose 1.2 km above the crater rim. 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.

Etna, Sicily (Italy)

37.748°N, 14.999°E | Summit elev. 3320 m

INGV reported that at around 1900 on 12 May new vents opened along the N flank of Etna’s Southeast Crater (SEC) and produced ash emissions that rose to 3.5 km (11,500 ft) a.s.l. and drifted SW. Lava flowed from the vents and traveled to the N base of the crater. Lava effusion continued over the next several days, and by 17 May the flow had descended ENE into Valle del Leone, reaching 2,300-2,400 m elevation. Discontinuous Strombolian activity of variable intensities occurred at SEC; during more intense phases ash emissions were visible, though the plumes dissipated rapidly.

Geological summary: Mount Etna, towering above Catania, Sicily’s second largest city, has one of the world’s longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Fuego, South-Central Guatemala

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

INSIVUMEH reported that 2-9 explosions per hour were recorded at Fuego during 10-17 May, generating ash plumes that rose as high as 1.1 km above the crater rim. The ash plumes drifted 10-15 km E, SE, S, 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), Finca Palo Verde, Finca la Asunción, El Zapote (10 km S), Ceylon, Yucales (12 km SW), El Porvenir (8 km ENE), Alotenángo (8 km ENE), San Miguel Dueñas (10 km NE), San Sebastián, and La Rochela. Daily shock waves rattled structures in communities around the volcano and occasional rumbling was heard. Block avalanches descended the flanks in all directions, but most commonly were visible in the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Honda, and Las Lajas (SE) drainages. Daily explosions ejected incandescent material 100-350 m above the summit.

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.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that minor advancement of the lava flows at Great Sitkin indicated continuing slow lava effusion during 10-17 May. Daily elevated surface temperatures were identified in satellite data. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Ibu, Halmahera

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

PVMBG reported that the eruption at Ibu continued during 11-17 May. Daily gray-and-white ash plumes of variable densities generally rose 200-800 m above the summit and drifted mainly W and N. Eruptive events at 0903 and 1807 on 14 May and at 1759 on 15 May produced ash plumes that rose 0.8-1 km above the summit and drifted W and SW. At 1646 on 16 May dense gray ash plumes rose around 2.5 km and drifted W. The Alert Level remained at a 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side.

Geological summary: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Karymsky, Eastern Kamchatka (Russia) 

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

KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 6-13 May. Explosions on 12 May generated ash plumes that rose as high as 6 km (19,700 ft) a.s.l. by 1120 local time and drifted about 30 km NW. Explosions on 14 May produced ash plumes that rose to 5.7 km (18,700 ft) a.s.l. by 0940 local time and drifted 28 km NE. 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: 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.

Katmai, Alaska

58.28°N, 154.963°W | Summit elev. 2047 m

AVO reported that on 13 May strong winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes blew unconsolidated ash SE towards Kodiak Island at an altitude up to 1.8 km (6,000 ft) a.s.l. The ash was originally deposited during the Novarupta eruption in 1912. The Volcano Alert Level remained at Normal and the Aviation Color Code remained at Green.

Geological summary: Prior to 1912, Mount Katmai was a compound stratovolcano with four NE-SW-trending summits, most of which were truncated by caldera collapse in that year. Two or more large explosive eruptions took place from Mount Katmai during the late Pleistocene. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene in age, but Holocene lava flows from a flank vent descend the SE flank of the SW stratovolcano into the Katmai River canyon. Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km wide caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. The steep walled young caldera has a jagged rim that rises 500-1000 m above the caldera floor and contains a 250-m-deep, still-rising lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916. Post-1912 glaciers have formed on a bench within Katmai caldera.

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 10-17 May, entering the active lava lake and flowing onto the crater floor. By 10 May the total volume of erupted lava was an estimated 77 million cubic meters, and the lake which had risen a total of 106 m since 29 September 2021. The surface of the lava lake was active all week, though the height of the lake was high and relatively stable. Breakouts of lava occurred along the NE and NW margins of the lake during 10-11 May, and more notably from the E margins the rest of the week. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

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.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued during 10-17 May. An increase in gas emissions along with continuing ash emissions was observed on 14 and 17 May. The ash emissions rose to 1-2.4 km above the summit and drifted W, N, and NE. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater and 4 km away from the crater on the SE flank.

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.

Manam, Northeast of New Guinea

4.08°S, 145.037°E | Summit elev. 1807 m

The Darwin VAAC reported that during 13-16 May ash plumes from Manam rose to 2.4-3.7 km (8,000-12,000 ft) a.s.l. and drifted NE, SW, and W based on satellite images and weather models.

Geological summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country’s most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical basaltic-andesitic stratovolcano to its lower flanks. These valleys channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island’s shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Merapi, Central Java

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

BPPTKG reported no significant morphological changes at Merapi’s summit lava dome during 6-12 May, though the height of the dome below the SW rim had increased by around 2 m. As many as 92 lava avalanches traveled a maximum of 2 km, mostly down the Bebeng drainage on the SW flank. Two pyroclastic flows traveled 2 km down the Bebeng drainage. Seismicity remained high. 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 the eruption at a vent on Pavlof’s upper E flank was ongoing during 10-17 May, and seismic tremor persisted. Daily elevated surface temperatures were identified in satellite images consistent with the effusion of short lava flows on the upper flank. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

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.

Reventador, Ecuador

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

IG reported that a high level of activity continued at Reventador during 10-17 May, though cloudy weather conditions sometimes prevented visual observations, particularly during 14-15 May. Gas-and-ash plumes, often observed multiple times a day as reported by the Washington VAAC, rose as high as 1 km above the summit and drifted mainly NW and W. Incandescence from the crater and incandescent blocks rolling 600 m down the flanks was visible during 10-13 May. During the morning of 17 May a new lava flow descended the NE flank.

Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W | Summit elev. 1916 m

On 13 May OVSICORI-UNA reported that 23 small phreatic explosions at Rincón de la Vieja were recorded during the previous week. Eruptive events at 2328 on 10 May and 0700 on 11 May were recorded by the seismic network through darkness and cloudy weather conditions prevented visual confirmation. Tremor levels decreased significantly on 12 May.

Geological summary: Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the “Colossus of Guanacaste,” it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Ruapehu, North Island (New Zealand)

39.28°S, 175.57°E | Summit elev. 2797 m

On 17 May GeoNet reported that elevated unrest at Ruapehu continued, though at reduced levels. During the previous two weeks the level of volcanic tremor declined from strong to moderate. The lake water temperature decreased from a peak of 41 degrees Celsius on 8 May to 37 degrees Celsius. A gas measurement flight on 13 May confirmed continuing high levels of gas emissions, though at values lower than measured two weeks prior; sulfur dioxide and carbon dioxide flux rates at 179 and 1,658 tonnes per day, respectively. Lake upwelling over the northern vent area was also visible during the overflight. The Volcanic Alert Level remained at 2 (on a scale from 0-5) and the Aviation Color Code remained at Yellow.

Geological summary: Ruapehu, one of New Zealand’s most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the NW-flank Murimoto debris-avalanche deposit. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. The broad summait area and flank contain at least six vents active during the Holocene. Frequent mild-to-moderate explosive eruptions have been recorded from the Te Wai a-Moe (Crater Lake) vent, and tephra characteristics suggest that the crater lake may have formed as recently as 3,000 years ago. Lahars resulting from phreatic eruptions at the summit crater lake are a hazard to a ski area on the upper flanks and lower river valleys.

Sangay, Ecuador

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

IG reported a high level of activity at Sangay during 10-17 May. Weather clouds and rain often prevented visual and webcam observations of the volcano, though almost daily ash-and-gas plumes were identified in satellite images by the Washington VAAC; plumes rose as high as 1.5 km above the volcano and drifted W. Almost daily, multiple daily thermal anomalies over the volcano were visible in satellite data. The seismic network detected signals indicating lahars or possible lahars during 13-17 May.

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador’s volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Santa Maria, Southwestern Guatemala

14.757°N, 91.552°W, Summit elev. 3745 m

INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 10-17 May. Incandescence from Caliente crater and the lava flows on the W and SW flanks was visible nightly and during some early mornings. The lava flows continued to advance in the San Isidro channel, and produced block avalanches from the ends and sides of the flows that descended the S, SW, and S flanks. Ash from these avalanches fell in areas on and around the volcano.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semeru, Eastern Java

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

PVMBG reported that the eruption at Semeru continued during 11-17 May. An eruptive event at 0608 on 14 May generated an ash plume that rose 200 m and drifted N. Another event recorded at 0634 on 17 May produced an ash plume that rose 300 m and drifted SW. The Alert Level remained at 3 (on a scale of 1-4). The public was warned to stay at least 500 m away from Kobokan drainages within 17 km of the summit, along with other drainages originating on Semeru, including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported that low-level eruptive activity at Semisopochnoi’s North Cerberus cone continued during 10-17 May. Seismicity continued to be elevated with intermittent tremor detected by the seismic network. Several daily explosions were recorded in infrasound and seismic data. Daily low-level ash emissions were visible in clear satellite images and webcam views. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island’s northern part. The three-peaked Mount Cerberus was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank of Cerberus appear younger than those on the south side. Other post-caldera volcanoes include the symmetrical Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 6-13 May, and lava-dome extrusion continued. 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 1300 km3 volcano is one of Kamchatka’s largest and most active volcanic structures. 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 dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. 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.

Sinabung, Northwestern Sumatra

3.17°N, 98.392°E | Summit elev. 2460 m

PVMBG lowered the Alert Level for Sinabung to 2 (on a scale of 1-4) on 11 May, noting that data showed stability at the volcano. During 1 January-17 May gas emissions were frequently visible and detected by instruments; daily averages of sulfur dioxide emissions from passive degassing were below 250 tons per day, though a high value of about 4,000 tons per day was recorded in January, and white plumes of varying densities rose as high as 500 m above the summit. During the previous four months deformation data showed a downward trend and indicated deflation, and the number of deep and shallow volcanic earthquakes signals generally declined. Growth of the SE part of the lava dome continued at a low rate as indicated by low numbers of earthquake signals caused by fluid movement. Avalanches of material were indicated by seismic signals though not visually confirmed. The public was warned to stay at least 3 km away from the summit and 4.5 km on the SE flank.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Stromboli, Aeolian Islands (Italy)

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

INGV reported that during 9-15 May activity at Stromboli was characterized by ongoing explosions from three vents in Area N (North Crater area) and two vents in Area C-S (South-Central Crater area). During 9-13 May explosions from Area N vents (N1 and N2) averaged 2-4 events per hour; explosions from the N1 vent ejected lapilli and bombs mixed with ash 80-150 m high and those at two N2 vents ejected material less than 80 m high. No explosions occurred at the S1 and C vents in Area C-S; low- to medium-intensity explosions at the two S2 vents occurred at a rate of 0-5 per hour and ejected coarse material 80-150 m high.

A sequence of six major explosions occurred at S1 and S2 in Area C-S during 1643-1647 on 13 May. The first, and most energetic, occurred at 1643 and ejected an abundant amount of coarse material 300 m high. The material fell in areas to the E and SE, and at Pizzo Sopra la Fossa (an area atop the volcano about 100 m above the crater terrace). The second explosion was lower in intensity but also ejected coarse material. The third through the sixth explosion all ejected ash. Deposits from the explosions seen during a field visit the next day were found as far at 450 m elevation, and impacts from ballistics were found along the switchbacks up the Liscione between 700 and 830 m elevation. Decimeter to meter-sized bombs were observed near 850 m elevation. Elongated tephra, centimeter to decimeter in size, was seen near Pizzo Sopra la Fossa. The CS vent area had deepened and the vents were elongated towards the central part. After the sequence of explosions on 13 May, through 15 May, explosive activity at N1, N2, and Area C-S was low.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the “Lighthouse of the Mediterranean.” Stromboli, the NE-most of the Aeolian Islands, 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 horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend 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 eruptive activity continued to be recorded at Suwanosejima’s Ontake Crater during 9-16 May. Eruption plumes rose as high as 1 km above the crater rim and material was ejected 400 m above the vent; no explosions were recorded. Ash fell in Toshima village (3.5 km SSW) during 13-16 May. The Alert Level remained at 3 and the public was warned to stay 2 km away from the crater.

Geological summary: The 8-km-long, spindle-shaped 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. Suwanosejima, one of Japan’s most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical 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 horseshoe-shaped 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.

Reference:

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 May-17 May 2022. Managing Editor: Sally Kuhn Sennert

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