The Weekly Volcanic Activity Report: February 13 - 19, 2019

The Weekly Volcanic Activity Report: February 13 - 19, 2019

New activity/unrest was reported 5 volcanoes from February 13 to 19, 2019. During the same period, ongoing activity was reported for 15 volcanoes.

New activity/unrest: Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Piton de la Fournaise, Reunion Island (France) | Poas, Costa Rica | Tengger Caldera, Eastern Java (Indonesia).

Ongoing activity: Agung, Bali (Indonesia) | Aira, Kyushu (Japan) | Cleveland, Chuginadak Island (USA) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Kadovar, Papua New Guinea | Kerinci, Indonesia | Krakatau, Indonesia | Manam, Papua New Guinea | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Popocatepetl, Mexico | Sheveluch, Central Kamchatka (Russia) | Turrialba, Costa Rica.

New activity/unrest

Karangetang, Siau Island (Indonesia)

2.781°N, 125.407°E, Summit elev. 1797 m

PVMBG reported that during 13-19 February sometimes-dense white plumes rose as high as 400 m above the rim of Karangetang’s Main Crater. White emissions that were occasionally bluish rose mostly 50-150 m above Kawah Dua’s (North Crater) crater rim, though on 18 February the plumes were grayish and rose 200-300 m. Roaring sounds from the volcano were occasionally noted at an observation post. The Alert Level remained at 3 (on a scale of 1-4), and residents were warned to remain outside of the 2.5-km exclusion zone around the N and S craters, and additionally within 3 km WNW and 4 km NW.

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts has also produced pyroclastic flows.

Karymsky, Eastern Kamchatka (Russia)

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

KVERT reported that at 1427 on 16 February a satellite image captured an ash plume from Karymsky drifting 55 km SE at altitudes of 2.5-3 km (8,200-10,000 ft) a.s.l. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale). According to the Tokyo VAAC a possible ash plume on 17 February rose to 3.7 km (12,000 ft) a.s.l. and drifted SE. A weak ash plume drifting 117 km ESE was visible in satellite images on 18 February.

Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Piton de la Fournaise, Reunion Island (France)

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

OVPF reported that a seismic crisis began at Piton de la Fournaise at 1521 on 16 February accompanied by rapid deformation. The number of earthquakes sharply decreased at 1618 and deformation stopped at 1630. A second seismic crisis began at 0916 on 18 February, again accompanied by rapid deformation. Tremor commenced at 0948, coincident with at least eruptive fissures opening on the E flank of Dolomieu crater. Weather conditions prevented good views of the eruption site. Lava fountains rose less than 30 m above the vents, and after about an hour the longest lava flow reached 1,900 m elevation. Lava effusion ceased at 2200 on 18 February. A seismic crisis began at 1500 on 19 February, and tremor began to be recorded at 1700. Gas emissions were recorded by webcams for about an hour. During an overflight on 20 February the OVPF team observed a new eruption site located at 1,800 m elevation at the foot of Piton Madoré. One fissure opened and at 0620 only one lava fountain was active. The front of a lava flow reached 1,300 m elevation.

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

Poas, Costa Rica

10.2°N, 84.233°W, Summit elev. 2708 m

OVSICORI-UNA reported that since 8 February almost continuous emissions of gas has been recorded at Poás, with plumes rising as high as 1 km and drifting mainly SW. During 13-14 February the emissions contained ash; gas-and-ash plumes drifted SW, impacting areas downwind including Naranjo, Zarcero, and Grecia (16 km SW). Gas-and-ash emissions rose from the crater on 15 February, and gas emissions were recorded on 18 February.

Geological summary: The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Tengger Caldera, Eastern Java (Indonesia)

7.942°S, 112.95°E, Summit elev. 2329 m

PVMBG reported that at 0600 on 18 February an eruption at Tengger Caldera’s Bromo cone generated a dense white-and-brown ash plume that rose 600 m and drifted WSW. The Alert Level remained at 2 (on a scale of 1-4).

Geological 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.

Ongoing activity

Agung, Bali (Indonesia)

8.343°S, 115.508°E, Summit elev. 2997 m

PVMBG reported that an explosive event at Agung was recorded at 0434 on 14 February, causing ashfall in Bugbug village, 20 km SE. Crater incandescence was recorded at night by webcams in Karangasem City (16 km SE). The Alert Level remained at 3 (on a scale of 1-4) with the exclusion zone set at a 4-km radius.

Geological summary: Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

Aira, Kyushu (Japan)

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

JMA reported that 12-18 February incandescence was visible from Minamidake crater (at Aira Caldera’s Sakurajima volcano), and two events and two explosions were recorded. One of the explosions occurred at 0624 on 14 February, producing a plume that rose 1.5 km above the crater rim and ejecting material 500-700 m from the crater. An explosion on 17 February generated a plume that rose 2.3 km above the crater rim and ejected material 1-1.3 km from the crater. The Alert Level remained at 3 (on a 5-level scale).

Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Cleveland, Chuginadak Island (USA)

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

AVO reported that unrest at Cleveland continued during 13-19 February, though no activity was detected in seismic or infrasound data. Elevated surface temperatures were identified in satellite images; weather clouds sometimes prevented views of the volcano. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Dukono, Halmahera (Indonesia)

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

Based on satellite data, wind model data, and ground-based observations, the Darwin VAAC reported that during 13-19 February ash plumes from Dukono rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted S and SW. The Alert Level remained at 2 (on a scale of 1-4), and visitors were warned to remain outside of the 2-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Ebeko, Paramushir Island (Russia)

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

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 8-15 February that sent ash plumes to 2.5 km (8,200 ft) a.s.l. Ash fell in Severo-Kurilsk on 11 February. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Etna, Sicily (Italy)

37.748°N, 14.999°E, Summit elev. 3295 m

On 19 February INGV summarized Etna’s fissure eruption that occurred high on the SE flank during 24-27 December 2018, noting that 3-4 million cubic meters of lava erupted and covered an area of 1 square kilometer. After the event seismicity gradually decreased. The last significant event was a ML 4.1 recorded on 8 January 2019; afterwards seismicity was characterized as frequent events with modest magnitudes. Since the beginning of January ash emissions intermittently rose mainly from Northeast Crater (NEC) and more sporadically from Bocca Nuova. News sources noted that the Catania Airport (Aeroporto di Catania – Sicilia) was closed during 26-27 January. Preliminary assessments of some of the ash deposits showed they contained no juvenile material. During 11-17 February ash emissions of variable intensity rose from NEC and were notable on 14 and 18 February. Volcanic tremor amplitude did not significantly vary compared to the previous week, having average values overall. The Catania Airport announced the partial closure of airspace and flight delays during 17-18 February due to ash emissions.

Geological summary: Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Kadovar, Papua New Guinea

3.608°S, 144.588°E, Summit elev. 365 m

Based on satellite data and wind model data, the Darwin VAAC reported that on 16 February ash plumes from Kadovar rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted ESE.

Geological summary: The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.

Kerinci, Indonesia

1.697°S, 101.264°E, Summit elev. 3800 m

PVMBG reported that at 1309 on 13 February an observer noted a brownish-white ash plume rising 400 m above Kerinci’s crater rim and drifting NE. The Alert Level remained at 2 (on a scale of 1-4).

Geological summary: Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is 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. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, 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, Summit elev. 813 m

PVMBG reported that a brief explosive event at Anak Krakatau was recorded at 0026 on 14 February, though weather conditions prevented clear views of the event. During 15-17 February diffuse white plumes rose 50 m above the summit. At 1402 on 18 February another short-lived event produced an ash plume that rose about 500 m above the summit and drifted S and SW. The Alert Level remained at 3 (on a scale of 1-4), and residents were warned to remain outside of the 5-km radius hazard zone from the crater.

Geological 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.

Manam, Papua New Guinea

4.08°S, 145.037°E, Summit elev. 1807 m

Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 15 February an ash plume from Manam rose to an altitude of 4.9 km (16,000 ft) a.s.l. and drifted E.

Geological 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.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Summit elev. 2910 m

PVMBG reported that during 8-17 February the volume of the lava dome in Merapi’s summit crater was about the same as the previous week, and there were no apparent morphological changes. Most of the extruded lava did not add to the dome volume but instead fell into the upper parts of the Gendol River drainage and the SE flank. Incandescent avalanches traveling down the SE flank were visible at night. At 0858 on 11 February a pyroclastic flow traveled 400 m down the Gendol drainage. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone.

Geological summary: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Nevados de Chillan, Chile

36.868°S, 71.378°W, Summit elev. 3180 m

ONEMI and SERNAGEOMIN reported that during 5-12 February growth of the lava dome in Nevados de Chillán’s Nicanor Crater was very slow (10.8 cubic meters per hour). White water vapor emissions, occasionally grayish from included tephra, rose as high as 1.7 km and drifted SE and NE. Crater incandescence was recorded by a webcam each day. At 0109 on 15 February an explosive event partially destroyed the lava dome and ejected incandescent material onto areas near the crater. The Alert Level remained at Orange, the second highest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián.

Geological summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

Popocatepetl, Mexico

19.023°N, 98.622°W, Summit elev. 5393 m

CENAPRED reported that each day during 13-19 February there were 20-140 steam-and-gas emissions from Popocatépetl, some of which contained ash. Seismicity began to increase at 2100 on 14 February coincident with the onset of Strombolian activity. Incandescent material was ejected 1.5 km onto the flanks, and gas-and-ash plumes rose as high as 2 km above the carter rim and drifted SW. The phase lasted for about seven hours. Explosions were recorded at 1528, 1602, 1824, and 1935 on 14 February and at 0409 on 15 February. Ashfall was reported in areas downwind including Tetela del Volcán (20 km SW), Zacualpan (31 km SW), Jonacatepec (43 km SW), Cuautla (43 km SW), Ocuituco (24 km SW), Yecapixtla (31 km SW), and in Tochimilco (16 km SSE).

During 0044-0606 on 16 February Strombolian activity ejected incandescent material that fell back into the crater. Gas-and-ash plumes rose 1 km and drifted SE. A period of harmonic tremor began at 1600, accompanied by emissions of water vapor and gas that rose 1.5 km. By 1830 ejected incandescent fragments were visible and fell onto flanks 400 m from the crater. Plumes rose 2 km and drifted NNE. Seismicity decreased by 2100 and material was no longer being ejected above the crater rim, though crater incandescence remained visible. There were at least 14 explosions detected on 17 February; the more significant events were recorded at 0438, 0457, 0719, 0821, and 0956, generating plumes that rose 2 km and drifted NNE. Minor ashfall was reported in areas downwind including Tlaxco (85 km NE) and Xalostoc, Nativitas (40 km NE), Hueyotlipan (57 km NNE), Amaxac de Guerrero (60 km NE), Tepetitla de Lardizábal (37 km NE), Texoloc, and Tlaxcala (51 km NE). An explosion at 0704 on 18 February produced a plume that rose 2 km and drifted NNE. An explosion was detected at 0613 on 19 February. On 20 February CENAPRED noted growth of lava dome #82. The Alert Level remained at Yellow, Phase Two (middle level on a three-color scale).

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 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 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 Pre-Columbian time.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that during 8-15 February Sheveluch’s lava dome continued to grow, extruding blocks on the N side, and producing hot avalanches and fumarolic plumes. A thermal anomaly was identified in satellite images daily. Video and satellite data recorded gas-and-steam plumes with variable ash content rising to 4 km (13,100 ft) a.s.l. and drifting in multiple directions. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Turrialba, Costa Rica

10.025°N, 83.767°W, Summit elev. 3340 m

OVSICORI-UNA reported that during 13-15 February a period of almost continuous gas emissions with minor ash content rose 200-300 m above the rim of Turrialba’s active vent. The plumes drifted NW, W, and SW. An event at 1330 on 15 February produced a plume that rose 1 km and drifted W. During the morning of 18 February a plume with low ash content rose from the vent. An event at 1310 generated a plume that rose 500 m and drifted W.

Geological 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 edifice covers an area of 500 km2. 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.

Source: GVP

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