The Weekly Volcanic Activity Report: May 2 - 8, 2018

The Weekly Volcanic Activity Report: May 2 - 8, 2018

New activity/unrest was reported for 6 volcanoes between May 2 and 8, 2018. During the same period, ongoing activity was reported for 11 volcanoes.

New activity/unrest: Ibu, Halmahera (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Marapi, Indonesia | Osorno, Chile | Piton de la Fournaise, Reunion Island (France).

Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Cleveland, Chuginadak Island (USA) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Pacaya, Guatemala, Sabancaya, Peru | Santa Maria, Guatemala | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan).

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, notices of volcanic activity posted are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.

New activity/unrest

Ibu, Halmahera (Indonesia)

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

At 0622 on 5 May an eruption at Ibu generated an ash plume that rose at least 600 m above the crater rim and drifted N and NE, based on information from the Darwin VAAC and PVMBG. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the 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, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. 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. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Karymsky, Eastern Kamchatka (Russia)

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

Based on satellite data, KVERT reported that during 28 April and 2-3 May explosions at Karymsky generated ash plumes that rose as high as 5.5 km (18,000 ft) and drifted 150 km NE and SE. A weak thermal anomaly over the volcano was visible on 3 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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.

Kilauea, Hawaiian Islands (USA)

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

On 2 May HVO noted that the intrusion of magma into Kilauea’s lower East Rift Zone (ERZ) continued, with deformation and frequent earthquakes (many felt by residents). Small cracks formed on some of the roads in and adjacent to Leilani Estates. Seismicity at Pu'u 'O'o Crater remained elevated after floor collapses which began on 30 April. Short-lived ash plumes periodically rose from the crater. The lava flows on the pali near the Royal Gardens subdivision were sluggish. Deflation at the summit accelerated around midday, accompanied by a drop in the level of the lava lake.

On 3 May the intensity of the ERZ seismicity decreased slightly, and the eastward migration of hypocenters slowed or ceased; deformation continued. The lava level in Overlook crater dropped over 30 m, though spattering in the lake continued. At 1030 ground shaking from a M 5 earthquake S of Pu'u 'O'o caused rockfalls and possibly a collapse in the crater; an ash plume rose from the crater and drifted SW. More ground cracks in the E part of Leilani Estates formed that afternoon; hot white and blue fumes rose from the cracks. Lava spatter and gas bursts began erupting from 150-m-long fissures just after 1700 and ended around 1830. Lava flows spread less than 10 m, and strong sulfur dioxide odors were noted. The lava lake in the Overlook Crater dropped an additional 37 m.

By the morning of 4 May three fissures were active; fissure 2 opened at 0100 and fissure 3 opened around 0600. Spatter was ejected as high as 30 m and lava flows were traveling short distances. Large, loud bubble bursts occurred at fissure 3. Ash plumes from intermittent collapses at Pu'u 'O'o continued to rise above the crater, and the 61 G lava flow was no longer being fed. A M 6.9 earthquake occurred at 1233, centered on the S flank. Fissures 4 and 5 opened at 1039 and 1200, respectively, and by 1600 there were six, each several hundred meters long. The sixth fissure was on the E edge of the subdivision. The Hawaii Emergency Management Agency stated that multiple agencies were assisting with the mandatory evacuation of residents (about 1,700) in the Leilani Estates and Lanipuna Gardens subdivisions. A temporary flight restriction was declared for most of lower Puna. The report noted dangerously high concentrations of sulfur dioxide.

Based on satellite InSAR data, the summit caldera floor subsided about 10 cm during 23 April-5 May. Corresponding to this deflationary trend, the summit lava lake in Overlook crater had dropped to about 128 m below the crater rim since 30 April. Summit seismicity increased during 4-5 May coincident with the M 6.9 earthquake; about 152 events (M 2-3) were recorded. Rockfalls from the inner crater walls produced ash plumes that rose above the Halema'uma'u crater rim on 5 May. New ground cracks on Highway 130 opened on 5 May, and at dawn fissure 7 formed. By mid-afternoon fissure 7 stopped erupting, and the 8th fissure opened at 2044 near fissures 2 and 7. Lava fountains from fissure 8 rose as high as 70 m, and in other areas were as high as 100 m. A lava flow from fissure 7 traveled 260 m NE. The lava lake in Overlook Crater continued to drop.

The eruption from one or two fissures was continuous during 5-7 May, and ‘a’a lava flows from fissure 8 advanced 0.9 km NNE by 1000 on 6 May. HVO warned that poor air quality from sulfur dioxide gas emissions, and smoke plumes from burning asphalt and houses was a health concern. Strong gas emissions rose from the fissures during 6-7 May, though lava effusion was minimal overnight. New cracks crossed Highway 130 west of the eruption site, and some others widened. The level of the summit lava lake continued to drop, and by 7 May was 220 m below the crater rim. Two new fissures emerged on 7 May. The first (fissure 11) opened at about 0930 in a forested area SW of Leilani Estates, and was active for about three hours. The second (fissure 12) opened at about 1220 between fissures 10 and 11. By 1515 both new fissures were active, and the W end of fissure 10 was robustly steaming. According to a news article, lava had covered an area about 36,000 square meters.

Lava effusion at night during 7-8 May was minimal, and by around 0700 on 8 May the ERZ eruption had paused. The fissure system was about 4 km long and continued to strongly emit gas. Ash plumes generated by falling rocks in Overlook crater continued to produced ash plumes. On 8 May the Office of the Mayor stated that 35 structures had been destroyed, and lava covered. HVO maps show the locations and numbers of the fissures.

Geological summary: Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Marapi, Indonesia

0.38°S, 100.474°E, Summit elev. 2885 m

On 2 May at 0703 an eruption at Marapi produced a dense, gray ash plume that rose 4 km above the crater rim and drifted SE. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were advised not to enter an area within 3 km of the summit.

Geological summary: Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Osorno, Chile

41.105°S, 72.496°W, Summit elev. 2659 m

Servicio Nacional de Geología and Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) raised the Alert Level for Osorno to Yellow (the second lowest level on a four-color scale) on 8 May, due to a gradual increase in the number and magnitude of seismic events recorded during 1-30 April. Earthquakes were concentrated on the NNW flank. The largest of the 294 total events was a M 3, located 2 km NW of the crater at a depth of 3.3 km.

Geological summary: The symmetrical, glacier-clad Osorno volcano forms a renowned landmark that towers over Todos los Santos and Llanquihué lakes. It was constructed over a roughly 250,000-year-old eroded stratovolcano, La Picada, that has a mostly buried 6-km-wide caldera. La Picada underlies Osorno on the NE and has postglacial maars and scoria cones. The 2652-m-high dominantly basaltic to basaltic-andesite Osorno is one of the most active volcanoes of the southern Chilean Andes, and contains two small dacitic lava domes on the NW and SSE flanks. Flank scoria cones and fissure vents, primarily on the west and SW sides, have produced lava flows that reached Lago Llanquihué. Frequent explosive eruptions including pyroclastic flows and surges have occurred during the past 14,000 years. Historical eruptions have originated from both summit and flank vents, producing basaltic and andesitic lava flows that have entered both Llanquihué and Todos los Santos lakes.

Piton de la Fournaise, Reunion Island (France)

21.244°S, 55.708°E, Summit elev. 2632 m

OVPF reported that the eruption at Piton de la Fournaise which began on 27 April from fissures at Rivals Crater continued through 8 May. Spattering was weak at the highest-elevation vent of the three. During fieldwork on 3 May scientists observed spattering from the central vent. Lava breakouts frequently occurred from a well-developed lava tube originating at the central vent. During 5-7 May activity was mainly confined to the lava tube, though the lava-flow front had not significantly advanced. The central vent had completely closed over by 6 May. Fires on and at the foot of the rampart were reported on 7 May. Tremor intensity had decreased during the previous few days but stabilized on 8 May.

Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that there were seven events and 15 explosions at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 1-7 May. Tephra was ejected as far as 1.3 km from the crater, and ash plumes rose as high as 2.8 km above the crater rim. The Alert Level remained at 3 (on a 5-level scale).

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.

Bagana, Bougainville (Papua New Guinea)

6.137°S, 155.196°E, Summit elev. 1855 m

Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 8 May a possible ash plume from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted W.

Geological summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Cleveland, Chuginadak Island (USA)

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

AVO reported that a small explosion at Cleveland was detected in seismic and infrasound data at 2149 on 4 May. The event produced a small ash cloud that rose as high as 6.7 km (22,000 ft) a.s.l. and drifted SE. The Aviation Color Code and the Volcano Alert Level were raised to Orange/Watch. No additional significant activity led AVO to the lower the levels back to Yellow/Advisory on 6 May.

Geological summary: The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped 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 Cleveland 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.

Dukono, Halmahera (Indonesia)

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

Based on analyses of satellite imagery, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 2-8 May ash plumes from Dukono rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and drifted NE and E.

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.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E, Summit elev. 1103 m

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 1-3 May that sent ash plumes as high as 2.8 km (9,200 ft) a.s.l. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Summit elev. 4754 m

Based on webcam and satellite observations KVERT reported that at 1150 on 8 May an ash plume from Klyuchevskoy rose to altitudes of 5-5.5 km (16,400-18,000 ft) a.s.l. and drifted 105 km SSE. The Aviation Color Code was raised to Orange.

Geological summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Pacaya, Guatemala

14.382°N, 90.601°W, Summit elev. 2569 m

INSIVUMEH reported that during 1-2 May Strombolian explosions at Pacaya’s Mackenney Crater ejected material as high as 50 m above the crater rim. A 500-m-long lava flow advanced NW towards Cerro Chino. Nighttime crater incandescence was visible, and rumbling was heard in areas within 2-3 km. Activity increased on 4 May, with explosions ejecting tephra as high as 80 m. The lava flow continued to advance and by 6 May was 600 m long. Strombolian explosions ejected material 15 m above the crater rim, and nighttime incandescence continued to be present.

Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Sabancaya, Peru

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

Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosive activity at Sabancaya increased compared to the previous week; explosions averaged 25 per day during 30 April-6 May. The number of long-period events and signals indicating emissions increased. Gas-and-ash plumes rose as high as 2 km above the crater rim and drifted 40 km N, NE, and E. The MIROVA system detected four thermal anomalies, and on 6 May the sulfur dioxide gas flux was high at 2,662 tons/day. The report noted that the public should not approach the crater within 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.

Santa Maria, Guatemala

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

INSIVUMEH reported that explosions at Santa María's Santiaguito lava-dome complex, detected by the seismic network during 1-2 and 5-6 May, generated ash plumes that rose 600-700 m and drifted SW. Avalanches of material descended the SE flank of the lava dome.

Geological summary: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 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 westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that a weak thermal anomaly over Sheveluch was identified in satellite images on 28 and 30 April and 2 May. The Aviation Color Code remained at Orange.

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

The Tokyo VAAC reported explosions at Suwanosejima on 2 and 4 May, based on JMA notices and satellite data.

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 of the volcano 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.

Source: GVP

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