New activity/unrest was observed at 8 volcanoes from May 13 – 19, 2015. During the same period, ongoing activity was observed at 16 volcanoes.
New activity/unrest: Bulusan, Luzon (Philippines) | Calbuco, Chile | Chaiten, Chile | Etna, Sicily (Italy) | Hakoneyama, Honshu (Japan) | Kilauea, Hawaiian Islands (USA) | Lokon-Empung, Sulawesi (Indonesia) | Piton de la Fournaise, Reunion Island (France).
Ongoing activity: Aira, Kyushu (Japan) | Ambrym, Vanuatu | Batu Tara, Komba Island (Indonesia) | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Manam, Papua New Guinea | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Sinabung, Indonesia | Soputan, Sulawesi (Indonesia) | Turrialba, Costa Rica | Villarrica, Chile | Zhupanovsky, Eastern Kamchatka (Russia).
Bulusan, Luzon (Philippines)
12.77°N, 124.05°E, Elevation 1565 m
During 13-15 and 17-19 May PHIVOLCS reported that six or fewer volcanic earthquakes were recorded at Bulusan. Weak steam emissions were occasionally observed rising from the SW vent and from a vent on the upper NW flank; plumes drifted SW, WNW, or drifted downslope. PHIVOLCS maintained Alert Level 1, indicating abnormal conditions, and reminded the public of the 4-km radius Permanent Danger Zone (PDZ).
Geologic summary: Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. Bulusan lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of 1565-m-high Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.
Calbuco, Chile, 41.326°S
72.614°W, Elevation 2003 m
OVDAS-SERNAGEOMIN reported that during 13-19 May activity at Calbuco fluctuated at low levels and continued to decline. Inclement weather prevented daily observations of the summit area, although incandescence at the crater was observed during 17-18 May. According to ONEMI, the number of evacuees within the 20-km evacuation zone remained at 6,685 on 18 May. On 19 May the Alert Level was lowered to Orange (the second highest level on a four-color scale), and the exclusion zone was changed to a 10-km radius.
Geologic summary: Along with its neighbor Osorno, Calbuco is one of the most active volcanoes of the southern Chilean Andes. The isolated late-Pleistocene to Holocene andesitic volcano rises to 2003 m south of Lake Llanquihué in the Chilean lake district. Guanahuca, Guenauca, Huanauca, and Huanaque, all listed as synonyms of Calbuco (Catalog of Active Volcanoes of the World), are actually synonyms of nearby Osorno volcano (Moreno 1985, pers. comm.). The 2003-m-high Calbuco is elongated in a SW-NE direction and is capped by a 400-500 m wide summit crater. The complex evolution of Calbuco included edifice collapse of an intermediate edifice during the late Pleistocene that produced a 3 cu km debris avalanche that reached the lake. Calbuco has erupted frequently during the Holocene, and one of the largest historical eruptions in southern Chile took place from Calbuco in 1893-1894 and concluded with lava dome emplacement. Subsequent eruptions have enlarged the lava-dome complex in the summit crater.
42.833°S, 72.646°W, Elevation 1122 m
On 17 May, OVDAS-SERNAGEOMIN reported that seven hybrid earthquakes were detected beneath Chaitén at a depth of 1 km; the highest local magnitude recorded was 3.6. A second report on 19 May noted that seismicity had slightly increased during the previous few months, characterized by an increase in magnitude and occurrence of long-period events, volcano-tectonic events, and hybrid events. Thermal anomalies from the lava dome complex had also been detected although the report did not state when. The Alert Level was raised to Yellow, on a three-color scale.
Geologic summary: Chaitén is a small, glacier-free caldera with a compound Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. Early work had identified only a single explosive eruption during the early Holocene prior to the major 2008 eruption, but later work has identified multiple explosive eruptions throughout the Holocene. A rhyolitic, 962-m-high obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km away from the volcano to the north and south. The caldera is breached on the SW side by a river that drains to the bay of Chaitén, and the high point on its southern rim reaches 1122 m. The first historical eruption of Chaitén volcano beginning in 2008 produced major rhyolitic explosive activity and growth of a lava dome that filled much of the caldera.
Etna, Sicily (Italy)
37.734°N, 15.004°E, Elevation 3330 m
INGV reported that the new episode at Etna’s New Southeast Crater (NSEC) that began on 12 May continued the next day. At 0410 on 13 May a series of small collapses accompanied the opening of three vents, along a fracture oriented E-W, below the E rim of NSEC, one of which effused a small lava flow. At 0800 a fracture at the vent propagated 200 m from the rim down the cone within 10 minutes. This event was accompanied by collapses, along with reddish ash ejection onto the summit area and the high S flank. Strombolian activity increased that night and was characterized by almost continuous Strombolian explosions, sometimes accompanied by ash emissions. This activity continued during 14-15 May. Ash plumes rose a few hundred meters and dispersed with the wind; minor ashfall was reported in areas from the S to the NE. A single lava flow traveled NE towards Mt. Rittman, and then E towards Mt. Simone where it formed two branches. One branch approached the base of the N wall of the Valle del Bove while the other traveled W to a distance 5 km from NSEC. Activity decreased on 15 May and ceased on 16 May.
Geologic 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 at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater (the latter formed in 1978). 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.
Hakoneyama, Honshu (Japan)
35.233°N, 139.021°E, Elevation 1438 m
JMA reported that during 14-17 May seismicity at Hakoneyama remained high. Inclinometer data showed variations related to seismicity, and vigorous steaming from the hot springs was observed. The Alert Level remained at 2 (on a 5-level scale). According to a news article, the ground level in the Owakudani hot spring area had risen 12 cm during 17 April-15 May; the deformation occurred in an area 200 m in diameter. The article also noted that 471 earthquakes were recorded on 15 May, the highest number ever recorded there in one day.
Geologic summary: Hakoneyama volcano is truncated by two overlapping calderas, the largest of which is 10 x 11 km wide. The calderas were formed as a result of two major explosive eruptions about 180,000 and 49,000-60,000 years ago. Scenic Lake Ashi lies between the SW caldera wall and a half dozen post-caldera lava domes that were constructed along a SW-NE trend cutting through the center of the calderas. Dome growth occurred progressively to the south, and the largest and youngest of these, Kamiyama, forms the high point of Hakoneyama. The calderas are breached to the east by the Hayakawa canyon. A phreatic explosion about 3000 years ago was followed by collapse of the NW side of Kamiyama, damming the Hayakawa valley and creating Lake Ashi. The latest magmatic eruptive activity about 2900 years ago produced a pyroclastic flow and a lava dome in the explosion crater, although phreatic eruptions took place as recently as the 12-13th centuries CE. Seismic swarms have occurred during the 20th century. Lake Ashi, along with major thermal areas in the caldera, forms a popular resort area SW of Tokyo.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m
HVO reported that the circulating lava lake in the pit within Kilauea's Halema'uma'u Crater started to drop on 9 May and as of 15 May was about 50 m lower than the raised vent rim. The lake-level drop was accompanied by a change from inflation of the summit area to deflation centered near Halema'uma'u Crater. In addition, on 13 May, the focus of deformation changed to the S part of Kilauea's summit caldera and upper Southwest Rift Zone (SWRZ), where rapid and localized inflationary tilt was recorded. Seismicity shifted from Kilauea's summit and the upper East Rift Zone (ERZ) to the S part of the summit; seismicity at the upper SWRZ continued. The number of earthquakes increased on 15 May. The data suggest that magma had moved into a shallow area beneath the S part of the caldera and upper SWRZ. During 16-18 May rates of tilting slowed, and seismicity at the summit and SWRZ remained above background levels but had decreased. By 19 May seismicity rates at the summit were normal and tilit had decreased slightly. The lava lake remained about 45-50 m below the crater floor.
Nighttime incandescence suggested an active lava pond in an isolated vent W of Pu'u 'O'o Crater. The June 27th NE-trending lava flow continued to have active surface flows within 8 km NE of Pu'u 'O'o.
Geologic summary: Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea 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 sq km, destroying nearly 200 houses and adding new coastline to the island.
Lokon-Empung, Sulawesi (Indonesia)
1.358°N, 124.792°E, Elevation 1580 m
PVMBG reported that during 6-13 May observers of Lokon-Empung noted white plumes rising 25-50 m above Tompaluan Crater, although inclement weather often prevented observations. Seismicity fluctuated but slightly decreased overall. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists were reminded not to approach Tompaluan Crater within a radius of 2.5 km. Based on ground observations, the Darwin VAAC reported that an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. on 20 May. Inclement weather prevented satellite views of the volcano.
Geologic summary: The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2.2 km apart), has a flat, craterless top. The morphologically younger Empung volcano has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.
Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Elevation 2632 m
OVPDLF reported that during 4-16 May the number and magnitude of earthquakes at Piton de la Fournaise increased, and inflation was detected at the base of the summit cone. Gas emissions intensified; specifically hydrogen sulfide emissions increased on 5 May after a peak of sulfur dioxide values on 3 May. A seismic crisis was detected on 17 May. Between 1100 and 1230 the network detected 200 volcano-tectonic events, and then at 1250 a more intense seismic crisis began. Significant deformation at the crater rim was detected and a few minutes later, at 1345, an eruption started outside and SE of Dolomieu crater in the Castle crater area. Visual confirmation occurred 15 minutes later as clouds moved away. Volcanologists observed the area and noted lava fountains from three fissures, and two lava flows. A very large gas plume emitted during the first few hours of the eruption rose 3.6-4 km altitude and drifted NW. The fissure furthest W stopped issuing lava fountains before midnight. On 18 May only one fissure was active and the SSW-drifting gas plume was much smaller. Hydrogen sulfide emissions continued to be high, and carbon dioxide emissions increased. Lava fountains from a single vent along the second fissure, further E, rose 40-50 m. The lava flow had traveled 4 km, reaching an elevation of 1.1 km. Three field observations occurred on 19 May; scientists observed lava fountains 20-30 m high, and the advancing lava flow which had traveled 750 m in the previous day, reaching 1 km elevation.
Geologic 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.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported 31 explosions during 11-18 May from Showa Crater at Aira Caldera’s Sakurajima volcano, some that ejected tephra as far as 1,800 m. Incandescence from the crater was visible at night on 11 May. The next day a very small explosion at Minami-Dake Crater generated a 200-m-high plume. Three larger explosions from Showa Crater, at 2104 and 2200 on 13 May, and 0416 on 14 May, generated ash plumes that rose as high as 3.5 km. Tephra, about 2 cm in diameter, and ashfall reported in Kagoshima Kurokami was attributed to the explosion at 2104 on 13 May. During 15-18 May ash plumes rose as high as 3 km twice, except from an explosion at 1732 on 17 May, an event that produced a 3.8-km-high ash plume. The Alert Level remained at 3 (on a 5-level scale).
Geologic 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.
16.25°S, 168.12°E, Elevation 1334 m
On 18 May the Vanuatu Geohazards Observatory issued a statement reminding residents and visitors that Ambrym remained active. The Alert Level remained at 2 (on a scale of 0-5). Areas deemed hazardous were near and around the active vents (Benbow, Maben-Mbwelesu, Niri-Mbwelesu and Mbwelesu), and in downwind areas prone to ashfall.
Geologic 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 1900 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 caldera 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.
Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E, Elevation 748 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 16-19 May ash plumes from Batu Tara rose to an altitude of 2.5 km (8,000 ft) a.s.l. and drifted 35-95 km W and NW.
Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km N of Lembata (fomerly 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 748-m-high 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.
Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Elevation 742 m
SVERT reported that satellite images over Snow, a volcano of Chirpoi, detected a thermal anomaly on 12 and 16 May. Cloud cover obscured views on other days during 13-18 May. The Aviation Color Code remained at Yellow.
Geologic summary: Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.
19.514°N, 103.62°W, Elevation 3850 m
Based on satellite images, webcam views, and wind models, the Washington VAAC reported that on 16 May an ash plume rose from Colima to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted 95 km ESE before dissipating. A thermal anomaly was also visible. Ash emissions later that day also dissipated within 95 km ESE.
Geologic summary: The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.
Dukono, Halmahera (Indonesia)
1.68°N, 127.88°E, Elevation 1335 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 17-19 May ash plumes from Dukono rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 45-75 km E and NW.
Geologic 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.
14.473°N, 90.88°W, Elevation 3763 m
INSIVUMEH reported that during 14-15 May the number and intensity of explosions at Fuego was high. During 14-17 May ash plumes rose 450-750 m above the crater and drifted 10-12 km W and SW. Shock waves from some explosions rattled nearby houses on the W and SW flanks, including in Morelia, Panimache, and Sangre de Cristo. Ashfall was reported in Panimache, Morelia, and Santa Sofía. Incandescent tephra was ejected 150-200 m above the crater and block avalanches descended multiple drainages. In a special report from 18 May, INSIVUMEH stated that hours after of an effusive eruption that ended at 1730 observers noted ash plumes drifting 10 km and a S-flank lava flow. The report also stated that inclement weather had hindered views during the previous few days. During 18-19 May explosions generated ash plumes that rose 550-750 m and drifted 10 km W and SW. Ash fell in Morelia, Panimache I and II, and Santa Sofía. Incandescent tephra was ejected 150 m above the crater and block avalanches descended multiple drainages.
Geologic summary: Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. 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 Acatenango. In contrast to 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.
Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Elevation 1513 m
KVERT reported that moderate activity at Karymsky likely continued during 8-15 May. The Aviation Color Code remained at Orange.
Geologic 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.
Manam, Papua New Guinea
4.08°S, 145.037°E, Elevation 1807 m
Based on observations of satellite imagery and wind data analyses, the Darwin VAAC reported that on 13 May an ash plume from Manam drifted over 35 km NE at an altitude of 3 km (10,000 ft) a.s.l.
Geologic 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 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche 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 historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical 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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that during 8-15 May lava-dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, and fumarolic activity. A daily thermal anomaly was also detected in satellite images. The Aviation Color Code remained at Orange.
Geologic summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km 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.
Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Elevation 2857 m
AVO reported that seismicity at Shishaldin continued to be elevated over background levels 13-19 May, indicating that low-level eruptive activity confined to the summit crater likely continued. On 15 May a low-level vigorous gas-and-steam plume possibly containing ash was recorded by the webcam. Elevated surface temperatures were detected in satellite images. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geologic summary: The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.
3.17°N, 98.392°E, Elevation 2460 m
PVMBG reported that foggy weather prevented visual observations of Sinabung during 4-12 May, except for a few clearer periods on some days. On 4 May dense white-to-gray plumes rose 700 m above the summit. During 7-11 May white plumes rose as high as 700 m. Lava from the dome traveled 1 km S on 10 May. A pyroclastic flow originating from the lava dome traveled 3 km S on 12 May, and produced ash plumes mainly obscured by fog. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tectonic events, and volcanic earthquakes; levels declined overall. The Alert Level remained at 3 (on a scale of 1-4). Visitors and tourists were prohibited from approaching the crater within a radius of 6 km on the S, 5 km on the SE flanks, and 3 km in the other directions.
Geologic 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, 2460-m-high andesitic-to-dacitic volcano is at the southern end of the four overlapping summit craters. 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.
Soputan, Sulawesi (Indonesia)
1.108°N, 124.73°E, Elevation 1784 m
PVMBG reported that during 6-13 May white plumes were observed rising as high as 100 m above Soputan even though inclement weather sometimes obscured crater views. Seismicity fluctuated; volcanic earthquakes continued to be recorded. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists were advised not to approach the craters within a radius of 4 km, or 6.5 km on the WSW flank.
Geologic summary: The small Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano rises to 1784 m and is located SW of Sempu volcano. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
OVSICORI-UNA reported that an ash emission from Turrialba occurred at 1520 on 14 May and drifted W. An eruption that started at 1018 on 18 May, and lasted for 23 minutes, generated an ash plume that rose 400 m above the crater and drifted NW. Another ash emission from a 25-minute-long eruption, which began at 1350, rose 500 m and drifted NW. At 1549 a third ash emission drifted NNW at an unknown altitude due to cloudy conditions.
Geologic summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.
39.42°S, 71.93°W, Elevation 2847 m
OVDAS-SERNAGEOMIN reported no significant changes at Villarrica during 6-12 May. Activity was characterized by weak and infrequent Strombolian explosions from the lava lake, diffuse gas emissions with occasional ash, nighttime crater incandescence, and decreasing seismicity. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public was warned to stay outside of a 5-km radius around the crater and away from drainages.
Geologic summary: Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot Villarrica's flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano have been produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 sq km of the volcano, and lahars have damaged towns on its flanks.
Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Elevation 2899 m
KVERT reported that weak activity continued at Zhupanovsky during 8-15 May. Satellite images detected a weak thermal anomaly over the volcano on 14 May; cloud cover prevented observations on the other days. The Aviation Color Code remained at Orange.
Geologic summary: The Zhupanovsky volcanic massif consists of four overlapping stratovolcanoes along a WNW-trending ridge. The elongated volcanic complex was constructed within a Pliocene-early Pleistocene caldera whose rim is exposed only on the eastern side. Three of the stratovolcanoes were built during the Pleistocene, the fourth is Holocene in age and was the source of all of Zhupanovsky's historical eruptions. An early Holocene stage of frequent moderate and weak eruptions from 7000 to 5000 years before present (BP) was succeeded by a period of infrequent larger eruptions that produced pyroclastic flows. The last major eruption took place about 800-900 years BP. Historical eruptions have consisted of relatively minor explosions from the third cone.
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