The Weekly Volcanic Activity Report: April 27 – May 3, 2022

New activity/unrest was reported for 5 volcanoes from April 27 to May 3, 2022. During the same period, ongoing activity was reported 16 volcanoes.

New activity/unrest: Batu Tara, Komba Island | Gaua, Banks Islands (Vanuatu) | Karymsky, Eastern Kamchatka (Russia) | Krakatau, Sunda Strait | Ruapehu, North Island (New Zealand).

Ongoing activity: Aira, Kyushu (Japan) | Ambae, Vanuatu | Ambrym, Vanuatu | Dukono, Halmahera | Great Sitkin, Andreanof Islands (USA) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island | Manam, Northeast of New Guinea | Merapi, Central Java | Pavlof, Alaska Peninsula, Alaska | Semeru, Eastern Java | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Wolf, Isla Isabela (Galapagos) | Yasur, Vanuatu.

New activity/unrest

Batu Tara, Komba Island

7.791°S, 123.585°E, Summit elev. 633 m

PVMBG issued VONAs noting recent increased gas emissions at Batu Tara but no confirmed eruptions. Ground-based observers reported that at 1453 and 1617 on 28 April gas emissions rose 1-1.2 km above the summit and drifted W. At 0054 on 2 May gas emissions rose 500 m and drifted W. The Alert Level remained at 1 (on a scale of 1-4).

Geological summary: The small isolated island of Batu Tara in the Flores Sea about 50 km N of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy’s Stromboli volcano. Vegetation covers the flanks to within 50 m of the summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption, during 1847-52, produced explosions and a lava flow.

Gaua, Banks Islands (Vanuatu)

14.281°S, 167.514°E, Summit elev. 729 m

On 28 April the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported ongoing steam-and-gas emissions from Gaua’s Mt. Garet, and warned visitors that they may notice a sulfur odor near the cone. On 3 May local villages, especially in Naveto in the NE part of the island, heard a loud explosion and then saw a dense ash plume rising from Mt. Garet during 0900-0930. The Alert Level remained at 2 (on a scale of 0-5).

Geological summary: The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. The active Mount Garet (or Garat) cone in the SW part of the caldera has three pit craters across the summit area. Construction of Garet and other small cinder cones has left a crescent-shaped lake. The onset of eruptive activity from a vent high on the SE flank in 1962 ended a long period of dormancy.

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 on most days during 22-29 April. Explosions during 21-22 April produced ash plumes that rose as high as 5 km (16,400 ft) a.s.l. and drifted around 95 km E and SE. Explosions at 1410 on 28 April, local time, generated an ash plume that rose to 10 km (32,800 ft) a.s.l., was about 5 x 7 km at it’s top, and drifted WNW. The Aviation Color Code was raised to Red (the highest level on a four-color scale). By 1550 the ash cloud had spread to 28 x 34 km in size and had drifted almost 290 km WNW at an altitude of 9 km. The Aviation Color Code was lowered to orange because ash was no longer being emitted from the volcano. The plume had drifted more than 1,000 km before dissipating.

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.

Krakatau, Sunda Strait

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

PVMBG reported that only white gas plumes rose above Anak Krakatau during 27 April-4 May. Satellite images acquired on 27 April and 2 May showed incandescent lava flows in and around the crater and advancing into the sea. BNPB stated to residents and tourists that there should be no activity within 2 km of the volcano, and that residents within 5-7 km should restrict certain activities and prepare to evacuate if necessary. The Alert Level remained at 3 (on a scale of 1-4).

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.

Ruapehu, North Island (New Zealand)

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

On 2 May GeoNet reported that elevated unrest at Ruapehu continued during the previous week, consisting of lake water heating, volcanic gas output, and strong volcanic tremor. Variable tremor levels were characterized by bursts of strong tremor and short periods of weaker tremor. The lake water temperature had risen to 38 degrees Celsius. During an overflight scientists observed reduced upwelling in the lake over the Northern vents and additional upwelling over the main Central Vent, indicating that it was at least partially unblocked. A sulfur dioxide flux of 390 tonnes per day was measured during a flight on 28 April, the sixth highest amount since 2003. The sustained carbon dioxide and sulfur gas emissions, along with high tremor levels, continue to indicate that magma is driving this period of heightened unrest. At around 0945 on 3 May a steam plume was visible slowly rising as high as 1.5 km above the crater rim; it dissipated by 1030. The plume was not accompanied by seismic or acoustic signals, and weather conditions favored cloud formation. Scientists on an overflight that afternoon observed active upwelling and a slightly higher lake level, similar to observations the previous day. The lake temperature had risen to 39 degrees Celsius. Results from lake water chemistry analysis showed no indication that magma was interacting with the hydrothermal system beneath the lake. 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.

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) on 2 May. 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.

Ambae, Vanuatu

15.389°S, 167.835°E, Summit elev. 1496 m

On 28 April the Vanuatu Meteorology and Geo-Hazards (VMGD) reported that the cone in Ambae’s Lake Voui continued to produce steam and ash emissions. The Alert Level remained at 2 (on a scale of 0-5) and the public was warned to stay outside of the Danger Zone, defined as a 2-km radius around the active vents in Lake Voui, and away from drainages during heavy rains.

Geological summary: The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Ambrym, Vanuatu

16.25°S, 168.12°E, Summit elev. 1334 m

The Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that incandescence from Ambrym’s Benbow Crater was visible during 25 January-3 February from a lava flow that had effused from a new vent on the NW part of the crater floor. Recent observations indicated that gas and ash was no longer being emitted from the crater, and seismicity had decreased and stabilized. The Alert Level was lowered to 1 (on a scale of 0-5) on 28 April. VMGD warned the public to stay outside of Permanent Danger Zone A, defined as a 1-km radius around Benbow Crater and a 2-km radius around Marum Crater, and additionally to stay 500 m away from the ground cracks created by the December 2018 eruption.

Geological summary: Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides Arc. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Dukono, Halmahera

1.693°N, 127.894°E, Summit elev. 1229 m

Based on satellite and wind model data, the Darwin VAAC reported that during 27-29 April and 2-3 May ash plumes from Dukono rose to 2.1 km (7,000 ft) a.s.l. and drifted E, NE, N, and NW. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slow lava effusion at Great Sitkin likely continued during 27 April-3 May; no significant seismic activity was detected and weather clouds obscured webcam and satellite views. 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.

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 26 April-3 May, entering the active lava lake and flowing onto the crater floor. Roiling and spattering in the SE part of the lake was visible during 26-27 April. The surface of the lava lake was active all week, and the height of the lake fluctuated; the lake occasionally overflowed the rim, sending lava onto the crater floor. Daily breakouts occurred along the margins of the crater rim. 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 26 April-4 May. Daily white-and-gray ash plumes rose 50-600 m above the summit and drifted in multiple directions. Images of the volcano showed incandescent material being ejected above the crater rim. 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 on 1 May ash plumes from Manam rose to 2.7 km (9,000 ft) a.s.l. and drifted SE and ESE based on information from RVO, satellite images, and weather models. During 2-3 May low-level ash emissions rose to 2.1 km (7,000 ft) a.s.l. and drifted ESE.

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 that the eruption at Merapi continued during 22-28 April. The heights and morphologies of the SW lava dome and the central lava dome were unchanged from the previous week, and seismicity remained at high levels. As many as 102 lava avalanches traveled a maximum of 2 km, mostly down the Bebeng drainage on the SW flank. 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 26 April-3 May, though weather conditions sometimes prevented visual observations. Seismic tremor persisted and elevated surface temperatures were identified in satellite images almost daily. A short lava flow had descended the E flank during 26-28 April and was about 500 m long. Steaming from the active vent was visible during 30 April-2 May. 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.

Semeru, Eastern Java

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

PVMBG reported that the eruption at Semeru continued during 26 April-3 May. Almost daily ash plumes were visible rising 300-700 m above the summit that drifted W, SW, and E. Ash plumes were recorded at 0523 and 0557 on 28 April, 0502 and 0649 on 29 April, 0621 on 30 April, 0704 on 2 May, and 0922 on 3 May. A pyroclastic flow from the end of the lava flow descended the SE flank at 0630 on 1 May and produced ash plumes that rose as high as 500 m above the summit. 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 26 April-3 May. Tremor continued to be detected by the seismic network. Weather clouds obscured views of the volcano on most days, though occasional views during 27-29 May revealed new ash deposits on the flanks. 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 22-29 April, 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.

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 25 April-2 May. Eruption plumes rose as high as 800 m above the crater rim and crater incandescence was occasionally visible. One explosion, recorded in Toshima village (3.5 km SSW), generated an ash plume that rose 1.3 km and into weather clouds. 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.

Wolf, Isla Isabela (Galapagos)

0.02°N, 91.35°W, Summit elev. 1710 m

IG reported that thermal anomalies over Wolf were periodically identified in satellite images during 26 April-3 May, indicating active lava flows.

Geological summary: Wolf, the highest volcano of the Galápagos Islands, straddles the equator at the north end of the archipelago’s largest island, Isabela. The 1710-m-high edifice has steeper slopes than most other Isabela volcanoes, reaching angles up to 35 degrees. A 6 x 7 km caldera, at 700 m one of the deepest of the Galápagos Islands, is located at the summit. A prominent bench on the west side of the caldera rises 450 above the caldera floor, much of which is covered by a lava flow erupted in 1982. Radial fissures concentrated along diffuse rift zones extend down the north, NW, and SE flanks, and submarine vents lie beyond the north and NW fissures. Similar unvegetated flows originating from a circumferential chain of spatter and scoria cones on the eastern caldera rim drape the forested flanks to the sea. The proportion of aa lava flows at Volcán Wolf exceeds that of other Galápagos volcanoes. An eruption in in 1797 was the first documented historical eruption in the Galápagos Islands.

Yasur, Vanuatu

19.532°S, 169.447°E, Summit elev. 361 m

On 28 April Vanuatu Meteorology and Geohazards Department (VMGD) reported that activity at Yasur continued at a high level of “major unrest,” as defined by the Alert Level 2 status (the middle level on a scale of 0-4). Ash-and-gas emissions and loud explosions continued to be recorded, with bombs falling in and around the crater. The public was reminded to not enter the restricted area within 600 m around the cone, defined by Danger Zone A on the hazard map.

Geological summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Reference:

Smithsonian / US Geological Survey – Weekly Volcanic Activity Report – April 27 – May 3, 2022 – Managing Editor: Sally Kuhn Sennert

Featured image credit: TW