New activity/unrest was observed at 2 volcanoes from October 14 – 20, 2015. During the same period, ongoing activity was reported for 19 volcanoes.
New activity/unrest: Copahue, Central Chile-Argentina border | Fuego, Guatemala
Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Batu Tara, Komba Island (Indonesia) | Cleveland, Chuginadak Island (USA) | Colima, Mexico | Concepcion, Nicaragua | Cotopaxi, Ecuador | Dukono, Halmahera (Indonesia) | Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Nevado del Ruiz, Colombia | Piton de la Fournaise, Reunion Island (France) | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Sinabung, Indonesia | Tungurahua, Ecuador | Ubinas, Peru | White Island, North Island (New Zealand)
Copahue, Central Chile-Argentina border
37.856°S, 71.183°W, Summit elev. 2953 m
According to the Buenos Aires VAAC, the webcam recorded weak emissions of steam, gas, and possibly minor amounts of ash rising from Copahue during 16-18 October.
Geologic summary: Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.
14.473°N, 90.88°W, Summit elev. 3763 m
INSIVUMEH reported that during 13-14 October lava fountains periodically rose 150 above Fuego's crater, producing a 300-m-long lava flow in the Santa Teresa (W) drainage. Weak explosions generated ash plumes that rose 750 m above the crater. During 16-17 October cloud cover prevented visual observations; explosions were heard and shock waves were detected. During 19-20 October ash plumes from explosions rose 550 m high. The lava flow was 500 m long.
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.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m
JMA reported that during 13-16 October small scale explosions occurred at Showa Crater, at Aira Caldera’s Sakurajima volcano. The Alert Level remained at 3 (on a 5-level scale).
Geologic summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Summit elev. 1855 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 16-20 October ash plumes from Bagana rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted 20-95 km N, NE, E, and SE.
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.
Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E, Summit elev. 748 m
Based on analysis of satellite imagery and wind data, the Darwin VAAC reported that during 14-19 October ash plumes from Batu Tara rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted 45-130 km WSW and W.
Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km N of Lembata (fomerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption, during 1847-52, produced explosions and a lava flow.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Summit elev. 1730 m
AVO reported that strongly elevated temperatures at Cleveland had not been detected since 18 August, and moderately elevated temperatures have been observed with decreasing regularity since then (30 September was the most recent instance). In addition, explosive activity, as detected by infrasound, last occurred on 6 August. Due to the declining activity and indications that lave effusion likely had stopped, AVO lowered the Level of Concern Color Code to Yellow and the Volcano Alert Level to Advisory on 14 October.
Geologic summary: 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. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mount 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 for Mount Cleveland, 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.
19.514°N, 103.62°W, Summit elev. 3850 m
The Unidad Estatal de Protección Civil de Colima reported that on 6 October scientists conducted an overflight of Colima and noted that the summit crater was 200 m wide and 50 m deep. Explosions had excavated parts of the crater, exposing the inner wall stratigraphy in the W and N parts of the crater. Fumarolic plumes rose from vents outside of the crater and from the SE interior. Weaker fumarolic activity was present in the NE and W sectors. An explosion on 5 October had produced a small pyroclastic flow that had traveled 2.1 km down the flanks. The report reminded the public to stay at least 5 km away from the crater, and 12 km away in the Montegrande drainage. Based on satellite images, wind data, webcam views, and notices from the Mexico City MWO, the Washington VAAC reported that during 13-16 and 18-19 October ash plumes from Colima rose to altitudes of 5.5-6.7 km (15,000-22,000 ft) a.s.l. and drifted SW and NW.
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.
11.538°N, 85.622°W, Summit elev. 1700 m
Based on seismic data, INETER reported that a lahar at Concepción detected between 1210 and 1305 on 14 October impacted local communities. Material was deposited in the streets of La Chirca (N), La Unión (SE), and Los Ramos (SE).
Geologic summary: Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks of the volcano have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the north flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.
0.677°S, 78.436°W, Summit elev. 5911 m
IG reported that during 14-20 October cloud cover sometimes obscured views of Cotopaxi although emissions were observed daily. Gas, steam, and ash plumes rose as high as 2 km above the crater and drifted W, NW, N, and E. Small lahars descended the NW flank during 14-15 October, and a small lahar traveled down the Agualongo gorge on 16 October. Ashfall was reported during 16-17 and 19-20 October in Ticatilín, Lasso (60 km N), Chasqui (48 km NNW), Agualongo, Mariscal Sucre (50 km NNW), Rumipamba, San Fernando (58 km NNW), Selva Alegre (54 km NNW), Rumiñahui (61 km N), Vallecito, Aloasí (23 km NW), Aloag (28 km NW), Jambelí, El Chaupi (24 km WNW), Tanicuchi (25 km SW), and Maldonado.
Geologic summary: Symmetrical, glacier-clad Cotopaxi stratovolcano is Ecuador's most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend as far as the base of Cotopaxi. The modern conical volcano has been constructed since a major edifice collapse sometime prior to about 5000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions of Cotopaxi, and lahars have frequently devastated adjacent valleys. The most violent historical eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. The last significant eruption of Cotopaxi took place in 1904.
Dukono, Halmahera (Indonesia)
1.68°N, 127.88°E, Summit elev. 1335 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 14-20 October ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted 30-150 km NE, NNE, 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.
Karangetang, Siau Island (Indonesia)
2.78°N, 125.4°E, Summit elev. 1784 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 18 October ash plumes from Karangetang rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 75-95 km NE.
Geologic summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. The 1784-m-high stratovolcano contains five summit craters along a N-S line. Karangetang 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 moderate explosive activity at Karymsky continued during 9-16 October. Satellite images showed a thermal anomaly over the volcano on 11 October. 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, Summit elev. 1222 m
HVO reported that seismicity beneath Kilauea's summit, upper East Rift Zone, and Southwest Rift Zone was at background levels during 14-20 October. The lava lake continued to circulate and spatter in the Overlook vent; small rockfalls into the lake during 14-15 October caused brief spattering and lake-surface agitation. The June 27th NE-trending lava flow continued to be active within 2.2-6.3 km NE of Pu'u 'O'o Crater.
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.
Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Summit elev. 5279 m
Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 13-19 October seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 0.9 and 8.5 km. The largest event was recorded at 2328 on 13 October, a local M 1.8, near Arenas Crater at a depth of 2.7 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.8 km and drifted NW on 17 October. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").
Geologic summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers >200 sq km. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.
Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Summit elev. 2632 m
OVPDLF reported that on 12 October there was a strong increase in tremor intensity at Piton de la Fournaise, with values reaching or exceeding those detected during the first few hours of the beginning of the eruption (24 August). A strong increase in sulfur dioxide emissions was also detected by a ground-based DOAS (Differential Optical Absorption Spectrometer); values on 2 October were 205 tonnes per day (t/d) and values on 12 October were 1,990 t/d. A satellite-based sensor recorded 1,138 t/d during 13-14 October which was twice the amount measured on 24 August. The satellite-based lava-flow rate on 14 October was 12 m³/s (±4 m³/s), consistent with model data. Strain measurements showed deflation. Several small ephemeral vents across the lava field produced lava flows, and in many instances hornitos were present at these vents. A hornito SW of the cone ejected spatter during 13-14 October. Activity continued to increase on 17 October. The cone continued to grow; the base was 100 m in diameter and it was about 40 m high. Parts of the cone rim continued to collapse, and a notch in the rim allowed for periodic lava-lake overflows.
Geologic summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 9-16 October lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity, dome incandescence, and hot avalanches. Satellite images detected a daily thermal anomaly over the dome. An ash plume drifted 44 km SW on 9 Ocotber. 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, Summit elev. 2857 m
AVO reported that seismicity at Shishaldin continued to be elevated over background levels during 14-20 October, indicating that low-level eruptive activity confined to the summit crater continued. Cloud cover often prevented satellite and webcam observations; weakly elevated surface temperatures were detected in satellite images on 16 October. 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, Summit elev. 2460 m
Based on satellite images and information from PVMBG, the Darwin VAAC reported that on 16 October an ash plume from Sinabung rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted 45 km SW. On 20 October ash plumes rose to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted 55 km N.
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.
1.467°S, 78.442°W, Summit elev. 5023 m
IG reported that seismicity decreased after a period of Strombolian activity at Tungurahua detected during 1900-2100 on 11 October; explosions were detected at 2015, 2110, and 2248. An explosion at 2318 on 13 October ejected blocks onto the W flank. Ashfall was reported in Choglontus (13 km WSW) the next morning. Cloud cover often prevented views of the summit area during 14-20 October. Ash fell in Cotaló (8 km NW), Bilbao (8 km W), and Choglontus on 19 October. Later that day a steam-and-ash emission rose 500 m above the crater and drifted W. Ashfall was reported in Manzanó (8 km SW) on 20 October.
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.
16.355°S, 70.903°W, Summit elev. 5672 m
Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 13-19 October seismicity at Ubinas fluctuated; moderate levels of seismicity were detected near the beginning of the period but then declined during the second half of the week. Thermal anomalies were detected during 13-14 October. Five explosions generated ash plumes that rose 2 km above the crater on 15 October.
Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.
White Island, North Island (New Zealand)
37.52°S, 177.18°E, Summit elev. 321 m
On 14 October the GeoNet Data Centre reported a recent slight intensification of activity at White Island. Increased amounts of CO2 emitted from one of the large accessible fumaroles was detected on 1 October along with a temperature increase. SO2 emissions at the volcano also increased. On 8 October volcanic tremor magnitude strengthened and became banded (the signal disappeared and reappeared every few hours), commonly noted during eruptions and periods of unrest. The Volcanic Alert Level remained at 1 and the Aviation Colour Code remained Green.
Geologic summary: Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The 321-m-high island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE of White Island. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred at White Island throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.
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