Active volcanoes in the world: May 20 - 26, 2015

Active volcanoes in the world: May 20 - 26, 2015

New activity/unrest was observed at 6 volcanoes from May 20 - 26, 2015. During the same period, ongoing activity was observed at 23 volcanoes. 

New activity/unrest: Calbuco, Chile | Concepcion, Nicaragua | Kilauea, Hawaiian Islands (USA) | Piton de la Fournaise, Reunion Island (France) | Telica, Nicaragua | Wolf, Isla Isabela (Ecuador). 

Ongoing activity: Aira, Kyushu (Japan) | Batu Tara, Komba Island (Indonesia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Kerinci, Indonesia | Krakatau, Indonesia | Kuchinoerabujima, Ryukyu Islands (Japan) | Marapi, Indonesia | Papandayan, Western Java (Indonesia) | Popocatepetl, Mexico | Raung, Eastern Java (Indonesia) | Reventador, Ecuador | Santa Maria, Guatemala | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Sinabung, Indonesia | Slamet, Central Java (Indonesia) | Tengger Caldera, Eastern Java (Indonesia) | Ubinas, Peru | Villarrica, Chile | Zhupanovsky, Eastern Kamchatka (Russia).

New activity/unrest:

Calbuco, Chile
41.326°S, 72.614°W, Elevation 2003 m

OVDAS-SERNAGEOMIN reported that during 20-26 May activity at Calbuco fluctuated at low levels and continued to decline. Inclement weather prevented observations of the summit area on most days; white plumes were observed rising 300-400 m and drifting SE during 24-26 May, and incandescence at the crater was observed at night during 25-26 May. According to ONEMI, the number of evacuees within the 20-km evacuation zone remained at 6,685 on 26 May. The Alert Level remained at Orange (the second highest level on a four-color scale), and the 10-km-radius exclusion zone continued to be in effect.

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.

Concepcion, Nicaragua
11.538°N, 85.622°W, Elevation 1700 m

According to a 6 May news article, activity at Concepción had increased about three weeks prior and was characterized by fluctuating levels of seismicity and gas explosions. In a 8 May statement, INETER noted that seismic activity and gas explosions at Concepción had decreased since the day before; 15 gas explosions has been detected in a 24-hour period. By 24 May there had been a total of 987 gas explosions detected by the network since an unspecified date of increased activity.

Geologic summary: Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks of the volcano have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the north flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.

Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m

HVO reported that seismicity beneath Kilauea's summit, upper East Rift Zone, and Southwest Rift Zone was at background levels during 20-26 May. The summit tiltmeter network recorded fluctuating inflationary and deflationary tilt from the typical Halema'uma'u source. 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 be active with surface flows within 8.6 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.

Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Elevation 2632 m

OVPDLF reported that the eruption at Piton de la Fournaise that began on 17 May continued through 26 May. After a peak on 17 May, sulfur dioxide emissions fluctuated but had gradually decreased overall. Lava-flow rates estimated by satellite data had also fluctuated but showed an overall decrease from 24.2 cubic meters per second on 17 May to 2.5 cubic meters per second on 21 May. During 21-22 May observers reported large variations in activity, including increasing heights of the lava fountain (over 50 m high), collapsing parts of the newly formed cinder cone, and a new very fluid lava flow adjacent to the main flow. During an overflight on 23 May scientists observed a large blue sulfur dioxide plume above the vent, lower lava fountains, a smaller vent in the cone, and the presence of a lava tube about 200 m downstream of the vent. During 24-25 May activity remained unchanged; low lava fountains and low-level lava flows persisted.

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.

Telica, Nicaragua
12.602°N, 86.845°W, Elevation 1061 m

On 8 May INETER reported that activity at Telica had been increasing. Earthquakes SE of the volcano and seven small-intensity explosions had been detected during an unspecified period, although a M 2.4 earthquake had occurred at 1102 on 7 May. During 11-12 May there were 18 explosions, for a total of 64 since the increased activity began. An explosion at 0950 on 12 May was accompanied by small quantities of ash emissions. At 1223 an explosion generated a gas-and-ash plume and ejected hot rocks (pre-existing material) 400 m high and to the W. Minor ashfall was reported in El Realejo, Corinth, Posoltega, and Chichigalpa. Seismicity was at normal levels. By 1200 on 18 May a total of 421 small explosions had been detected (164 in the previous 24 hours); gas emissions were low. During 18-20 May reports noted that 31 small gas explosions had been detected; ash had not been detected since 17 May and activity was decreasing. During 21-22 May 16 small gas explosions occurred, for a total of 540 explosions. Gas explosions continued during 22-24 May. A few of the explosions ejected hot rock fragments and generated ash plumes. Ashfall was reported in Posoltega, Guanacastal, Quezalguaque, Chinandega, El Viejo, Chichigalpa, and El Realejo.

Geologic summary: Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of 1061-m-high Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately SE of Telica, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Wolf, Isla Isabela (Ecuador)
0.02°N, 91.35°W, Elevation 1710 m

According to IG the seismic station located on Fernandina Island recorded several events at Wolf (on Isabela Island) starting at 2350 on 24 May. The most significant signal occurred at 0058 on 25 May, corresponding to an explosion and the start of an eruption. At 0215 the Washington VAAC detected an ash plume that rose to an altitude of 10.7 km (35,000 ft) a.s.l. and drifted 65 km SW. At 0345 one ash plume drifted 250 km ENE at an altitude of 15.2 km (50,000 ft) a.s.l., and another drifted 250 km S at an altitude of 13.7 km (45,000 ft) a.s.l. Starting at 0428 the Hawai'i Institute of Geophysics and Planetology (HIGP) reported intense thermal anomalies on Wolf's SE flank based on MODIS satellite data. Galapagos National Park staff reported an arcuate fissure along the upper SSE rim and several lava flows descending the flanks. Later that day the VAAC noted a smaller ash emission that drifted 150 km SW, and a bright thermal anomaly that had persisted. Satellites detecting sulfur dioxide showed that the cloud was sulfur-dioxide rich and ash poor; ~100-200 kt of sulfur dioxide had been emitted during the first 13 hours of the eruption.

Geologic 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.

Ongoing activity:

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m

JMA reported 19 explosions during 18-25 May from Showa Crater at Aira Caldera’s Sakurajima volcano, some that ejected tephra as far as 1,300 m, and incandescence from the crater was occasionally visible at night. During 21-22 May explosions generated ash plumes that rose 3-4.3 km above the crater. 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.

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 21-22 May ash plumes from Batu Tara rose to an altitude of 2.5 km (8,000 ft) a.s.l. and drifted over 80 km W.

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.

Colima, Mexico
19.514°N, 103.62°W, Elevation 3850 m

Based on satellite images, the Washington VAAC reported that on 21 May an ash plume rose from Colima to an altitude below 4.9 km (16,000 ft) a.s.l. and drifted W.

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 75 km 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.

Fuego, Guatemala
14.473°N, 90.88°W, Elevation 3763 m

INSIVUMEH reported that activity at Fuego remained high during 21-26 May. Explosions produced ash plumes that rose 800 m above the crater and drifted 8-10 km W and SW. Ash fell in nearby areas including Panimache I and II, Morelia, and Santa Sofía. Homes within a 10-km radius vibrated from explosions. Incandescent material was ejected 150-200 m above the crater and incandescent block avalanches descended the Cenizas (SSW) and Trinidad (S) ravines.

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 15-22 May. Satellite images detected a thermal anomaly during 15-16 May and anash plume drifting 27 km W on 16 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.

Kerinci, Indonesia
1.697°S, 101.264°E, Elevation 3800 m

PVMBG reported that during 1 February-21 May 2015 white plumes from Kerinci rose 50-150 m and drifted E and W. Seismicity during 1-21 May was dominated by signals indicating emissions (100-110 per day on average) as well as volcanic earthquakes (1 per day on average). 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.

Geologic summary: The 3800-m-high Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. Kerinci is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. The volcano contains a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. The frequently active Gunung Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Krakatau, Indonesia
6.102°S, 105.423°E, Elevation 813 m

PVMBG reported that during 22 April-25 May diffuse white plumes rose 25 m above Anak Krakatau, although foggy weather often prevented observations. Seismicity was high during May, and continued to be dominated by shallow and deep volcanic earthquakes, and signals indicating emissions. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were warned not to approach the volcano within 1 km of the crater.

Geologic 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 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 volcanoes, and left only a remnant of Rakata volcano. 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.

Kuchinoerabujima, Ryukyu Islands (Japan)
30.443°N, 130.217°E, Elevation 657 m

JMA reported that no eruptions occurred from Kuchinoerabujima during 18-22 May, although the level of activity remained elevated. White plumes rose 600 m above Shindake Crater, and incandescence from the W part of the crater was observed at night. Volcanic earthquakes were detected; tremor was absent. Fumarolic activity in a crack in W part of the crater was observed during a field survey. The Alert Level remained at 3 (on a scale of 1-5).

Geologic summary: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyus, 15 km west of Yakushima. Furutake, Shintake, and Noike were erupted from south to north, respectively, to form a composite cone that is parallel to the trend of the Ryukyu Islands. The highest peak, Furutake, reaches only 657 m above sea level. The youngest cone, 640-m-high Shintake, was formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Marapi, Indonesia
0.381°S, 100.473°E, Elevation 2891 m

PVMBG reported that during February-25 May diffuse white plumes rose as high as 300 m above Marapi, although inclement weather often prevented observations. Seismicity fluctuated. 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.

Geologic 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.

Papandayan, Western Java (Indonesia)
7.32°S, 107.73°E, Elevation 2665 m

PVMBG reported that during 22 April-25 May seismicity at Papandayan was dominated by shallow volcanic earthquakes but also consisted of volcanic earthquakes, low-frequency earthquakes, tremor, and local and remote tectonic earthquakes. Visual monitoring occurred from the Pakuwon Village post; observers noted white plumes rising at most 30 m above the crater. The Alert Level remained at 2 (on a scale of 1-4); residents and tourists were reminded not to approach the craters within a 1-km radius.

Geologic summary: Papandayan is a complex stratovolcano with four large summit craters, the youngest of which was breached to the NE by collapse during a brief eruption in 1772 and contains active fumarole fields. The broad 1.1-km-wide, flat-floored Alun-Alun crater truncates the summit of Papandayan, and Gunung Puntang to the north gives the volcano a twin-peaked appearance. Several episodes of collapse have given the volcano an irregular profile and produced debris avalanches that have impacted lowland areas beyond the volcano. A sulfur-encrusted fumarole field occupies historically active Kawah Mas ("Golden Crater"). After its first historical eruption in 1772, in which collapse of the NE flank produced a catastrophic debris avalanche that destroyed 40 villages and killed nearly 3000 persons, only small phreatic eruptions had occurred prior to an explosive eruption that began in November 2002.

Popocatepetl, Mexico
19.023°N, 98.622°W, Elevation 5426 m

CENAPRED reported that during 20-26 May the seismic network at Popocatépetl recorded 40-307 daily emissions consisting of water vapor, gas, and sometimes ash; cloud cover often prevented visual observations. Nighttime crater incandescence was noted every night; sometimes the incandescence would become more intense with accompanying emissions. A small explosion at 0023 on 21 May generated a plume with low ash content that rose 800 m and drifted SW. During 22-24 May ash plumes rose 0.5-2.5 km and drifted SW. Ashfall was reported in Ocuituco (24 km SW) on 22 May. From 1702 to 1955 on 25 May a series of explosions accompanied by tremor ejected steam, gas, and ash plumes that drifted SSE. Explosions were detected on 26 May; ashfall was rpeorted in Tetela del Volcán (20 km SW).The Alert Level remained at Yellow, Phase Two.

Geologic summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 CE, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.

Raung, Eastern Java (Indonesia)
8.125°S, 114.042°E, Elevation 3332 m

PVMBG reported that, during infrequent times of clear weather during February-21 May 2014, gray and gray-to-brown plumes were observed rising as high as 300 m above Raung's crater rim. Rumbling was frequently heard at the observation post. Crater incandescence was observed during February and on 12 April. Seismicity fluctuated and was dominated by tremor. The Alert Level remained at 2 (on a scale of 1-4); residents and tourists were reminded not to approach the craters within a 2-km radius.

Geologic summary: Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The 3332-m-high, unvegetated summit of Gunung Raung is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the west flank produced a large debris avalanche that traveled 79 km from the volcano, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and west, respectively.

Reventador, Ecuador
0.077°S, 77.656°W, Elevation 3562 m

During 20-26 May IG reported moderate-to-high seismic activity including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions at Reventador; cloud cover sometimes prevented visual observations. A lava flow on the SW flank advanced during 20-21 May. During 24-25 May ash plumes rose 600-800 m and drifted SW, although at 1730 on 25 May a water vapor plume with moderate ash content rose 1.5 km and drifted SW.

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

Santa Maria, Guatemala
14.756°N, 91.552°W, Elevation 3772 m

INSIVUMEH reported that a moderate explosion at Caliente cone, part of Santa María's Santiaguito lava-dome complex, generated an ash plume that rose 600 m and drifted SW; ashfall was reported in La Florida and Monte Claro. During 23-24 May explosions produced ash plumes that rose 500 m and drifted SE and E. Ash fell in the Palajunoj area and Monte Claro. Small explosions and avalanches were detected during 24-26 May.

Geologic 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, Elevation 3283 m

KVERT reported that during 15-22 May lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity. A thermal anomaly was detected in satellite images during 15-19 May. 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 20-26 May indicating that low-level eruptive activity confined to the summit crater likely continued. Elevated surface temperatures were periodically 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.

Sinabung, Indonesia
3.17°N, 98.392°E, Elevation 2460 m

PVMBG reported that foggy weather often prevented visual observations of Sinabung during 19-25 May, except for a few clearer periods on some days. White plumes rose as high as 800 m during 19-20 and 22-24 May. Lava from the lava dome was active as far as 1.5 km S during 21-23 May. On 24 May a pyroclastic flow traveled 2 km down the S flank and produced an ash plume that rose 500 m. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tectonic events, and volcanic earthquakes; RSAM values increased due to an increase of avalanche signals. 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.

Slamet, Central Java (Indonesia)
7.242°S, 109.208°E, Elevation 3428 m

PVMBG reported that during 21 April-21 May dense white plumes rose as high as 700 m above Slamet's crater. Seismicity consisted of emission signals and tremor; RSAM values fluctuated. The Alert Level remained at 2 (on a scale of 1-4). Residents and tourists were warned to not approach the crater within a radius of 2 km.

Geologic summary: Slamet, Java's second highest volcano at 3428 m and one of its most active, has a cluster of about three dozen cinder cones on its lower SE-NE flanks and a single cinder cone on the western flank. It is composed of two overlapping edifices, an older basaltic-andesite to andesitic volcano on the west and a younger basaltic to basaltic-andesite one on the east. Gunung Malang II cinder cone on the upper E flank on the younger edifice fed a lava flow that extends 6 km E. Four craters occur at the summit of Gunung Slamet, with activity migrating to the SW over time. Historical eruptions, recorded since the 18th century, have originated from a 150-m-deep, 450-m-wide, steep-walled crater at the western part of the summit and have consisted of explosive eruptions generally lasting a few days to a few weeks.

Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Elevation 2329 m

PVMBG reported that during 1 April-25 May white plumes from Tengger Caldera's Bromo cone rose 50 m above the crater. A sulfur dioxide odor was noted at the Bromo observation post. Seismicity was dominated by tremor, but also included volcanic earthquakes. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were warned not to approach the crater within a radius of 1 km.

Geologic summary: The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.

Ubinas, Peru
16.355°S, 70.903°W, Elevation 5672 m

Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 19-26 May long-period earthquakes continued at the same rate while volcano-tectonic and hybrid events increased. Overall the dominant signal was spasmodic tremor associated with ash-and-steam emissions. While conducting fieldwork during 19-22 May, OVS staff observed persistent water vapor, gas, and ash emissions that rose 400 m. At 1051 and 1213 on 24 May ash plumes rose as high as 1.2 km and drifted NE and E.

Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Villarrica, Chile
39.42°S, 71.93°W, Elevation 2847 m

OVDAS-SERNAGEOMIN reported no significant changes at Villarrica during 20-26 May. Seismicity had significantly decreased, although the data continued to indicate small explosions and degassing from the lava lake. Deformation data suggested inflation during 24-26 May. 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

On 16 May KVERT reported that the explosive eruption that began at Zhupanovsky on 6 June 2014 ended at the beginning of April 2015. The last ash plume occurred on 3 April, although weak thermal anomalies continued to be detected. The Aviation Color Code was lowered to Yellow. On 20 May an ash plume drifted 470 km E.

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.

Source: GVP

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