New activity/unrest was observed at 6 volcanoes from April 1 - 7, 2015. During the same period, ongoing activity was observed at 17 volcanoes.
New activity/unrest: Batu Tara, Komba Island (Indonesia) | Chirinkotan, Kuril Islands (Russia) | Semisopochnoi, United States | Tungurahua, Ecuador | Turrialba, Costa Rica | Villarrica, Chile.
Ongoing activity: Aira, Kyushu (Japan) | Ambrym, Vanuatu | Asosan, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Kuchinoerabujima, Ryukyu Islands (Japan) | Popocatepetl, Mexico | Reventador, Ecuador | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Sinabung, Indonesia | Zhupanovsky, Eastern Kamchatka (Russia).
Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E | Elevation 748 m
According to the Darwin VAAC a pilot observed an ash plume in the vicinity of Batu Tara on 7 April. The plume drifted NW at an altitude of 3 km (10,000 ft) a.s.l.
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.
Chirinkotan, Kuril Islands (Russia)
48.98°N, 153.48°E | Elevation 724 m
SVERT reported that on 5 April a thermal anomaly over Chirinkotan was detected in satellite images. Cloud cover prevented views of the volcano on the other days during 31 March-6 April. The Aviation Color Code remained at Yellow.
Geologic summary: The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.
Semisopochnoi, United States
51.93°N, 179.58°E | Elevation 1221 m
On 25 March AVO reported that seismicity at Semisopochnoi that had begun in January continued and had increased over the previous few days. Brief periods of tremor were also detected. AVO raised the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory. The elevated seismicity, characterized by discrete fairly small earthquakes beneath the center of the island, continued to be detected through 7 April.
Geologic summary: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.
1.467°S, 78.442°W | Elevation 5023 m
IG reported that, although cloud cover often prevented visual observations of Tungurahua’s crater during 1-5 April, minor steam emissions were occasionally seen. On 6 April at 0356 tremor began to be detected and was associated with steam-and-ash emissions which rose 1 km above the crater. Noises were reported at 0730 and ashfall was reported in Cahuaji (8 km SW), Chacauco (NW), Manzano (8 km SW), and Punzupal Alto. Later that day an ash plume drifted W. Emissions in the early afternoon rose no higher than 1 km. On 7 April cloud cover prevented views of the crater most of the day; ashfall was reported in Palitahua (6 km SSW), and a water vapor-and-ash plume rose 1 km and drifted NW. Two explosions were detected by the seismic network.
Geologic summary: Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.
Turrialba, Costa Rica
10.025°N, 83.767°W | Elevation 3340 m
OVSICORI-UNA reported that at 1307 on 3 April a small ash eruption occurred at Turrialba, causing ashfall in nearby areas including Silvia and La Central (2 km SW). At 1124 on 5 April an eruption generated an ash plume that rose 500 m and caused ashfall in Curridabat (31 km WSW), Granadilla (29 km WSW), San Pedro, Desamparados (35 km WSW), Aserrí (40 km SW), San Sebastián (37 km WSW), and Escazú (42 km WSW). Gas-and-vapor plumes rose from the crater at 0800 on 6 April.
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 that during 31 March-4 April small Strombolian explosions at Villarrica continued, and seismicity slightly and steadily increased. During 4-5 April pulsating emissions of water vapor and ash rose 700 m above the crater. Strombolian explosions sometimes ejected material outside the crater, onto the flanks, at distances no greater than 200 m. Pulsating gas-and-ash emissions continued at a lower level during 6-7 April. Nighttime incandescence from the crater was occasionally observed, and seismicity decreased. 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.
Aira, Kyushu (Japan)
31.593°N, 130.657°E | Elevation 1117 m
JMA reported that 20 explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 30 March-3 April. Incandescence from the crater was periodically visible at night, and inflation continued to be detected. The Alert Level remained at 3 (on a scale of 1-5). Based on JMA notices, the Tokyo VAAC reported that explosions during 1-2, 5, and 7 April generated plumes which rose to altitudes of 1.5-3.4 km (5,000-11,000 ft)a.s.l. and drifted E and NE. Pilots observed ash plumes that rose to an altitude of 3 km (10,000 ft) on 1 April and 1.5 km (5,000 ft) a.s.l. on 7 April.
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 7 April the Vanuatu Geohazards Observatory issued a statement reminding residents and visitors that Ambrym remained active. The Alert Level remained at 2 (on a new 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.
Asosan, Kyushu (Japan)
32.884°N, 131.104°E | Elevation 1592 m
JMA reported that, based on seismic data, the eruption from Asosan’s Nakadake Crater that began on 25 November 2014 continued during 30 March-3 April. A plume rose 900 m above the crater rim and incandescence from the vent was observed at night. Field surveys confirmed that rumbling originated from the active vent. High-amplitude tremor continued. The Alert Level remained at 2 (on a scale of 1-5).
Geologic summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 cu km of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E | Elevation 1855 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 1-2 April an ash plume from Bagana drifted 75 km SE and NE.
Geologic summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical, roughly 1850-m-high 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 volcano's flanks on all sides. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.
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 during 2 and 4-5 April. Cloud cover obscured views on other days during 31 March-6 April. 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, Mexico City MWO, Colima Observatory notices, webcam views, and local media the Washington VAAC reported multiple ashemissions per day from Colima during 1-3 and 5-7 April. A small ash puff drifted 13 km E on 1 April. The next day an ash plume rose to an altitude of 6.4 km (21,000 ft) a.s.l. and drifted N. Ash emissions on 3 April drifted N, NE, E, and SE. On 5 April ash plumes rose to altitudes of km (14,000-23,000 ft) a.s.l. and drifted 20-40 km NNE and SW. The next day an ash plume rose to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted SW. On 7 April an ash cloud drifted almost 20 km 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 2-3 April ash plumes from Dukono rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 35-65 km NE. During 6-7 April ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 35-45 km SW and N.
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.
Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E | Elevation 1513 m
KVERT reported that during 27 March-3 April moderate activity at Karymsky continued. Satellite images detected ash plumes drifting 150 km NE and SW during 27 and 29-30 March, and a thermal anomaly over the volcano on 29 March. 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.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W | Elevation 1222 m
During 1-7 April HVO reported that Kilauea’s 27 June NE-trending lava flow continued to be active with three areas of breakouts within and along the flow-field margins. The three main areas of breakouts were the 21 February breakout on the flank of Pu'u 'O'o, the 9 March breakout near the forested cone of Kahauale'a (burning trees were visible), and a relatively small forked breakout 5-6 km farther NE of Pu'u 'O'o. The circulating lava lake occasionally rose and fell in the deep pit within Halema'uma'u Crater. Gas emissions remained elevated. During an overflight on 3 April geologists observed a small collapse pit had formed sometime since the previous overflight (possibly on 18 March based on tilt data) in the W portion of Pu'u 'O'o Crater. The opening was about 27 m in diameter but the chamber below was much larger. The floor of the collapse pit was about 80 m in diameter, about 24 m below the pit rim and hosted two active lava ponds.
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.
Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E | Elevation 4754 m
On 6 April KVERT reported that the Aviation Color Code for Klyuchevskoy was lowered to Green, noting that the explosive eruption had finished on 24 March. KVERT speculated that the continuing high seismicity reflected rebuilding of the magmatic system. Moderate gas-and-steam activity continued.
Geologic 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.
Kuchinoerabujima, Ryukyu Islands (Japan)
30.443°N, 130.217°E | Elevation 657 m
JMA reported that no eruptions occurred from Kuchinoerabujima during 30 March-3 April, although the level of activity remained elevated. White plumes rose 1 km above Shindake Crater, and incandescence from the crater was observed at night. Volcanic earthquakes were detected; tremor was absent. Fumarolicactivity in a crack in W part of the crater was observed during a field survey on 30 March. In addition the temperature of a thermal anomaly in the W part continued to rise. 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.
19.023°N, 98.622°W | Elevation 5426 m
CENAPRED reported that during 1-7 April the seismic network at Popocatépetl recorded 101-191 daily emissions except during 3-4 and 6-7 April when only 37 and 53 were detected, respectively. Cloud cover often prevented observations of the crater, although ash plumes and nighttime crater incandescence were often noted. On 3 April multiple ash plumes rose 1-3 km above the crater. A period of harmonic tremor, that began at 1039 and ended at 1338, was accompanied by continuous emissions of steam with small amounts of ash. During 3-4 April explosions generated ash plumes that rose as high as 2 km; ashfall was reported in Tetela and Ocuituco. More explosions on 4 April generated ash plumes that rose 0.5-2 km and drifted SW. During 4-6 April explosions ejected incandescenttephra 100-700 m onto the flanks, and produced steam, gas, and ash plumes that rose 1.2-2 km and sometimes drifted W. Episodes of tremor were detected on 5 April. At 0754 on 7 April an episode of explosions and tremor began. Steam, gas, and ash plumes rose from the crater and material was ejected short distances from the crater. 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.
0.077°S, 77.656°W | Elevation 3562 m
During 1-7 April IG reported moderate seismic activity including explosions, long-period earthquakes, harmonic tremor, and occasional tremor at Reventador; cloud cover often prevented visual observations. During 1-2 and 6 April incandescence from the crater and a lava flow on the SW flank were visible with the aid of an infrared camera. On 3 April a steam plume rose 600 m above the crater and drifted NW. The next day a steam-and-ash plume rose 500 m and drifted W. On 6 April a steam-and-ash plume rose 1 km and drifted NW.
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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E | Elevation 3283 m
KVERT reported that during 27 March-3 April lava-dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, andfumarolic activity. A strong explosion on 29 March generated ash plumes that rose to an altitude of 10 km (32,800 ft) a.s.l. and drifted more than 155 km W. A daily thermal anomaly was also visible 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 during 1-7 April indicating that low-level eruptive activity confined to the summit crater likely continued. Highly elevated surface temperatures in the crater were detected during 1-3 April, suggesting the presence of lava within the crater. 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
Based on PVMBG notices, BNPB reported that activity at Sinabung increased on 1 April. Seismicity increased. Pyroclastic flows traveled 3.5 km S and producedash plumes that rose 2 km and drifted SW. Avalanches were detected and incandescent lava was observed at night. On 2 April pyroclastic flows traveled 4 km S and 1 km SE. Avalanches continued. 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 5 km on the S and 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.
Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E | Elevation 2899 m
KVERT reported that a moderate explosive eruption at Zhupanovsky continued during 27 March-3 April. Satellite images detected a thermal anomaly over the volcano on 26 and 30 March, and 2 April. 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.