Active volcanoes in the world: February 18 - 24, 2015

Active volcanoes in the world: February 18 - 24, 2015

New activity was observed at 6 volcanoes from February 18 - 24, 2015. During the same period, ongoing activity was observed at 15 volcanoes.

New activity/unrest: Ambrym, Vanuatu | Chikurachki, Paramushir Island (Russia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Sinabung, Indonesia.

Ongoing activity: Aira, Kyushu (Japan) | Asosan, Kyushu (Japan) | Bardarbunga, Iceland | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Fogo, Cape Verde | Kilauea, Hawaiian Islands (USA) | Kuchinoerabujima, Ryukyu Islands (Japan) | Manam, Papua New Guinea | Ontakesan, Honshu (Japan) | Popocatepetl, Mexico | Reventador, Ecuador | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Zhupanovsky, Eastern Kamchatka (Russia).

New activity/unrest

Ambrym, Vanuatu
16.25°S, 168.12°E, Elevation 1334 m

On 21 February the Vanuatu Geohazards Observatory issued a notice reminding the public that a minor eruption was occurring at Ambrym from a new ventinside the caldera. The Alert Level was raised to 3 (on a new scale of 0-5). Hazardous areas were identified as being 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.

Chikurachki, Paramushir Island (Russia)
50.324°N, 155.461°E, Elevation 1781 m

KVERT noted that the eruption of Chikurachki that began on 16 February produced ash plumes during 16-18 February. Satellite images detected the ash plumes rising to altitudes of 7.5-8 km (24,600-26,200 ft) a.s.l. and drifting about 280 km W and E. No activity was detected during 19-22 February; the Aviation Color Code was lowered to Yellow. Chikurachki is not monitored with seismic instruments but is observed by ground-based means and satellite images.

Geologic summary: Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic plinian eruptions have occurred during the Holocene. Lava flows from 1781-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centers is located immediately to the south of Chikurachki, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

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

INSIVUMEH reported that during 19-20 February explosions at Fuego produced dense ash plumes that rose 650-1,250 m above the crater and drifted 12-15 km W, S, and SE. Shock waves from some of the explosions rattled structures in nearby areas including Panimache (8 km SW), Morelia (9 km SW), and Santa Sofía (12 km SW). Crater incandescence was visible at night and block avalanches that descended the Santa Teresa (W), Cenizas (SSW), Trinidad (S), and Las Lajas (SE) ravines. Ashfall was reported in Panimache and La Rochela. During 21-22 February explosions occurring at a rate of 5-7 per hour generated dense ash plumes that rose 550-850 m and drifted 10-15 km NE, W, and SW. Ash fell in Panimache I and II, Morelia, Santa Sofía, and Yepocapa (8 km NW). During 22-23 February explosions at a rate of 4-6 per hour were detected. Gray plumes rose 650-850 m and drifted 10-12 km. Explosions ejected tephra 100 m above the crater. Ashfall was again reported in nearby communities including Panimaché I and II, Morelia, Santa Sofía. Explosions continued to be detected during 23-24 February and incandescent material was ejected 100 m.

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 seismicity at Karymsky was detected during 13-20 February. Satellite images showed that the volcano was quiet or obscured by clouds. 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.

Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that during 13-20 February a Strombolian and Vulcanian eruption at Klyuchevskoy continued. Incandescence at the summit was visible and bombs were ejected 150 m above the crater. Explosions generated ash plumes that rose to altitudes of 5-8 km (16,400-26,200 ft) a.s.l.; ashfall was reported in Klyuchi Village (30 km NNE) during 13-16 February. A lava flow effused onto the E flank. Satellite images showed a daily, big, bright thermal anomaly over the volcano, and ash plumes drifted about 600 km mainly E, SE, and S. The Aviation Color Code remained at Orange.

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.

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

Based on satellite images and weather models, the Darwin VAAC reported that on 20 February an eruption from Sinabung generated ash plumes that rose to an altitude of 13.7 km (45,000 ft) a.s.l., drifted almost 540 km NW, and became detached. A lower-level eruption later that day produced an ash plume that rose to an altitude of 7.3 km (24,000 ft) a.s.l.

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.

Ongoing activity

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

JMA reported that 10 explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 16-20 February. Incandescence from the crater was visible at night on 19 February, and inflation continued to be detected. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 18-24 February plumes rose to altitudes of 1.8-4.6 km (6,000-15,000 ft) a.s.l. and drifted in multiple directions.

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.

Asosan, Kyushu (Japan)
32.884°N, 131.104°E, Elevation 1592 m

JMA reported that, based on seismicity and infrasound data, the eruption from Asosan’s Nakadake Crater that began on 25 November 2014 continued during 16-20 February. Plumes rose 900 m above the crater and high-amplitude tremor continued to be detected. 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.

Bardarbunga, Iceland
64.63°N, 17.53°W, Elevation 2009 m

During 17-19 February, Icelandic Met Office reported continued activity at Bárdarbunga’s Holuhraun eruptive fissure, though the overall intensity of the eruption continued to decrease. Only one active vent was present in the crater, and the lava level in that crater continued to sink. The eruption plume rose no more than 1 km above the ground and drifted NE, and the lava channel was crusted over beyond the uppermost 200-300 m. The lava tube continued to feed the N and NE parts of Holuhraun, inflating the lava field. The reduced effusion rate was no longer able to sustain active breakouts in an area 17-18 km ENE from the vent. A 24 February report noted that the rate of subsidence was less than 2 cm per day and lava flows decreased substantially. Seismic activity continued to decrease although it was still considered to be strong.

Geologic summary: The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.

Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Elevation 742 m

SVERT reported that satellite images over Snow, a volcano of Chirpoi, showed gas-and-steam emissions on 19 February and a thermal anomaly on 21 February. Cloud cover obscured views on other days during 16-23 February. 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.

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

Based on satellite images, Mexico City MWO, METAR and Colima Tower notices, pilot observations, and a webcam, the Washington VAAC reported that during 18-24 February multiple gas-and-ash plumes per day from Colima rose to altitudes of 5.5-7.3 km (18,000-24,000 ft) a.s.l. and drifted in multiple directions. Ash drifted as far as 350 km SE (on 19 February).

In a 24 February bulletin, the Unidad Estatal de Protección Civil reported that the number and size of lava-block collapses at Colima remained low during the previous week. Lava flows showed no evidence of movement. Explosive activity was low to moderate and generated plumes that rose 2-3 km and drifted downwind. Ashfall in nearby areas was persistent. Residents were warned not go within 5 km of the volcano.

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.

Fogo, Cape Verde
14.95°N, 24.35°W, Elevation 2829 m

The Observatório Vulcanológico de Cabo Verde (OVCV) reported that on 8 February the eruption at Fogo had ended; sulfur dioxide emissions were almost undetectable on 8 February and continued to remain so at least through 11 February. During that period, pahoehoe flows remained stagnant and only minorfumarolic activity was present at the edge of the new crater. In addition, since 7 February, temperatures of the fumaroles and of an area at the base of the cone had decreased significantly.

Geologic summary: The island of Fogo consists of a single massive stratovolcano that is the most prominent of the Cape Verde Islands. The roughly circular 25-km-wide island is truncated by a large 9-km-wide caldera that is breached to the east and has a headwall 1 km high. The caldera is located asymmetrically NE of the center of the island and was formed as a result of massive lateral collapse of the ancestral Monte Armarelo edifice. A very youthful steep-sided central cone, Pico, rises more than 1 km above the caldera floor to about 100 m above the caldera rim, forming the 2829 m high point of the island. Pico, which is capped by a 500-m-wide, 150-m-deep summit crater, was apparently in almost continuous activity from the time of Portuguese settlement in 1500 CE until around 1760. Later historical lava flows, some from vents on the caldera floor, reached the eastern coast below the breached caldera.

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

During 19-24 February HVO reported that Kilauea’s 27 June NE-trending lava flow continued to be active with several small breakouts across the interior and edges of the lobes, upslope of the leading front. These breakouts included a lobe extending to the N, about 1.6 km upslope from Highway 130, and a lobe on the S side of the flow, about 870 m upslope of Malama Market. The most northern lobe of lava remained about 500 m above Highway 130, near police and fire stations. At Pu'u 'O'o Crater, glow emanated from several outgassing openings in the crater floor. The circulating lava lake occasionally rose and fell in the deep pit within Halema'uma'u Crater. Gas emissions remained elevated.

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.

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

JMA reported that no eruptions occurred from Kuchinoerabujima during 16-20 January, although the level of activity remained elevated. White plumes rose 600 m above the crater. Low-level seismicity continued and tremor was absent. 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.

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 24 February ash plumes from Manam rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted almost 40 km W.

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.

Ontakesan, Honshu (Japan)
35.893°N, 137.48°E, Elevation 3067 m

JMA reported that cloud cover mostly prevented visual observations of Ontakesan during 13-20 February; white plumes rose 50-200 m above the crater rim. Seismicity remained low. The Alert Level remained at 3 (on a scale of 1-5).

Geologic summary: The massive Ontakesan stratovolcano, the second highest volcano in Japan, lies at the southern end of the Northern Japan Alps. Ascending this volcano is one of the major objects of religious pilgrimage in central Japan. It is constructed within a largely buried 4 x 5 km caldera and occupies the southern end of the Norikura volcanic zone, which extends northward to Yakedake volcano. The older volcanic complex consisted of at least four major stratovolcanoes constructed from about 680,000 to about 420,000 years ago, after which Ontakesan was inactive for more than 300,000 years. The broad, elongated summit of the younger edifice is cut by a series of small explosion craters along a NNE-trending line. Several phreatic eruptions post-date the roughly 7300-year-old Akahoya tephra from Kikai caldera. The first historical eruption took place in 1979 from fissures near the summit. A non-eruptive landslide in 1984 produced a debris avalanche and lahar that swept down valleys south and east of the volcano. Very minor phreatic activity caused a dusting of ash near the summit in 1991 and 2007. A significant phreatic explosion in September 2014, when a large number of hikers were at or near the summit, resulted in many fatalities.

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

CENAPRED reported that during an overflight of Popocatépetl on 17 February volcanologists observed dome number 55, 150 in diameter, at the bottom of the inner crater (formed in July 2013) which was 100 m below the floor of the main crater. Each day during 18-24 February the seismic network recorded between 47 and 166 low-intensity events, accompanied by steam-and-gas emissions that visibly contained minor amounts of ash most days. Incandescence from the crater was noted some nights. On 18 February five explosions generated plumes that rose no more than 1 km and drifted NE. A series of small explosions detected during 0844-1300 was accompanied by periods of harmonic tremor. On 21 February there were 22 small explosions, some of which ejected tephra 200 m onto the NE flank. Another series of small explosions, detected from 2221 on 22 February to 0220 on 23 February, were again accompanied by periods of harmonic tremor. Steam, gas, and ash plumes drifted SW on 24 February. 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.

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

During 18-24 February IG reported moderate seismic activity including explosions, long-period earthquakes, harmonic tremor, and tremor at Reventador; cloud cover often prevented visual observations. On 19 February observers confirmed the presence of a 1-km-long lava flow that had been advancing down the SW flank since 11 February. A diffuse steam plume with minor amounts of ash rose 1 km and drifted SW. On 21 February steam-and-ash emissions rose 600 m and drifted NW. Vapor plumes with minor amounts of ash rose 500 m and drifted SW on 24 February.

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 13-20 February lava-dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, andfumarolic activity. Strong explosions on 16 and 17 February generated ash plumes that rose to an altitude of 8 km (26,200 ft) a.s.l. and drifted 180 km NW. A thermal anomaly over the dome was detected daily. 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 18-24 February. Cloud cover often prevented webcam and satellite-image views of the volcano. Weakly elevated surface temperatures were detected in satellite images during 22-24 February. Low-level eruptive activity confined to the summit crater likely continued. 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.

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Elevation 2899 m

KVERT reported that a moderate explosive eruption at Zhupanovsky continued during 13-20 February. Satellite images detected a thermal anomaly over the volcano during 14-15 and 18 February. Ash clouds rose to altitudes of 3-3.5 km (10,000-11,500 ft) a.s.l. and drifted over 200 km W during 15-16 February and SE during 17-19 February. 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.

Source: GVP

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