New activity/unrest was observed at 5 volcanoes from January 13 – 19, 2016. During the same period, ongoing activity was reported for 17 volcanoes.
New activity/unrest: Egon, Flores Island (Indonesia) | Masaya, Nicaragua | Nevados de Chillán, Chile | San Miguel, El Salvador | Zhupanovsky, Eastern Kamchatka (Russia).
Ongoing activity: Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Copahue, Central Chile-Argentina border | Cotopaxi, Ecuador | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Lokon-Empung, Sulawesi (Indonesia) | Momotombo, Nicaragua | Paluweh, Indonesia | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Tengger Caldera, Eastern Java (Indonesia) | Ubinas, Peru | Yasur, Vanuatu.
Egon, Flores Island (Indonesia)
8.676°S, 122.455°E, Summit elev. 1661 m
PVMBG reported that during 1-12 January seismicity at Egon was dominated by shallow volcanic tremor, harmonic tremor, and signals indicating emissions. Seismicity had increased on 15 December 2015, and then fluctuated through 11 January. RSAM increased significantly on 12 January due to an earthquake detected at 0936. PVMBG noted that the pattern of seismicity was similar to that observed before a phreatic eruption on 15 April 2008. The Alert Level was raised to 2 (on a scale of 1-4) and residents were advised to stay at least 3 km away from the crater.
On 20 January BNPB reported that activity increased again, prompting the PVMBG to raise the Alert Level to 3. The report noted that access to the Mapitara district was closed due to a strong sulfur dioxide odor in that area, and that 927 people living within 3 km of the volcano had been evacuated (501 people refused to evacuate). Diffuse white plumes rose as high as 50 m above the crater.
Geologic summary: Gunung Egon volcano sits astride the narrow waist of eastern Flores Island. The barren, sparsely vegetated summit region has a 350-m-wide, 200-m-deep crater that sometimes contains a lake. Other small crater lakes occur on the flanks of the 1703-m-high volcano, which is also known as Namang. A lava dome forms the southern 1671-m-high summit. Solfataric activity occurs on the crater wall and rim and on the upper southern flank. Reports of historical eruptive activity prior to explosive eruptions beginning in 2004 were inconclusive. A column of "smoke" was often observed above the summit during 1888-1891 and in 1892. Strong "smoke" emission in 1907 reported by Sapper (1917) was considered by the Catalog of Active Volcanoes of the World (Neumann van Padang, 1951) to be an historical eruption, but Kemmerling (1929) noted that this was likely confused with an eruption on the same date and time from Lewotobi Lakilaki volcano.
11.984°N, 86.161°W, Summit elev. 635 m
INETER reported that the lava lake in Masaya's Santiago crater continued to be active during 13-18 January. RSAM values indicated low to moderate seismicity.
Geologic summary: Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.
Nevados de Chillán, Chile
36.863°S, 71.377°W, Summit elev. 3212 m
Servicio Nacional de Geología and Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) reported that at 1755 on 8 January a phreatic explosion at Nevados de Chillán generated a short-duration ash emission and was associated with a long-period seismic event. At least one phreatic explosion occurred on 9 January, generating ash emissions. During an overflight that same day volcanologists observed a new crater on the E flank of the Volcán Nuevo lava-dome complex, about 40 m from the edge of the crater. The Alert Level remained at Yellow, the middle level on a three-color scale.
Geologic summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes of Chile. 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, 3212-m-high Cerro Blanco (Volcán Nevado), is located at the NW end of the group, and 3089-m-high 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 altitude. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986, eventually exceeding its height by 20 m.
San Miguel, El Salvador
13.434°N, 88.269°W, Summit elev. 2130 m
SNET reported that at 0520 on 12 January a gas-and-ash plume from San Miguel rose 400-800 m above the crater and drifted WSW, causing ashfall in San Jorge, Caseríos, La Piedra, Moritas, and La Placita. Gas-and-ash emissions continued through the rest of the day; ashfall was also later reported in San Rafael Oriente, Alegría, and Berlín en Usulután. Seismicity declined during 12-14 January. Gas plumes with minor to no ash content rose as high as 300 m. On 14 January seismicity stabilized above background levels, and gas emissions were observed. The next day local observers reported a millimeter of ash deposited in Las Cruces, on the N flank. A webcam recorded gas emissions rising 400 m and drifting N throughout the morning. Gas emissions during 17-18 January were weak, only rising 150 m, and RSAM values gradually declined. At 0900 on 18 January the emission plume became dark and drifted SW.
Geologic summary: The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit of the 2130-m-high volcano rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit, also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the north, NE, and SE sides. The SE-flank lava flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.
Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Summit elev. 2899 m
Based on visual observations, KVERT reported that at 1636 on 19 January an explosion at Zhupanovsky generated an ash plume that rose to altitudes of 7-8 km (23,000-26,200 ft) a.s.l. and drifted 20 km E. The Aviation Color Code was raised to Orange (the second highest on a four-color scale).
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.
Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Summit elev. 742 m
SVERT reported that satellite images detected a thermal anomaly over Snow, a volcano of Chirpoi, during 12-13 and 17 January. The Aviation Color Code remained at Yellow.
Geologic summary:Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.
19.514°N, 103.62°W, Summit elev. 3850 m
Based on satellite images, wind data, webcam images, and notices from the Mexico City MWO, the Washington VAAC reported that during 14-19 January ash plumes from Colima rose to altitudes of 4.3-6.7 km (14,000-22,000 ft) a.s.l. and drifted NE, E, SE, and S.
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.
Copahue, Central Chile-Argentina border
37.856°S, 71.183°W, Summit elev. 2953 m
Based on a SIGMET and webcam views, the Buenos Aires VAAC reported that on 13 and 16 January continuous gas-and-steam plumes from Copahue contained minor amounts of ash and drifted SE.
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.
0.677°S, 78.436°W, Summit elev. 5911 m
IG reported that at 1336 on 13 January a seismic station on Cotopaxi's W flank recorded an hour-long signal caused by a lahar. Preliminary results indicated that the peak flow rate was around 40 m3/s with a volume of about 50,000 m3; the lahar was the largest recorded at the volcano since the current eruption began. Lahars also descended the Agualongo River, leaving deposits on the bridge that crosses the river.
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)
1.693°N, 127.894°E, Summit elev. 1229 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 13-19 January ash plumes from Dukono rose to altitudes of 2.1 km (7,000 ft) a.s.l. and drifted 35-120 km S, SW, W, and WNW.
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.
14.473°N, 90.88°W, Summit elev. 3763 m
INSIVUMEH reported that approximately 1-2 explosions every four hours were detected at Fuego during 14-15 January. Ash plumes rose 450-650 m above the crater and drifted N and NE. During 16-17 January, 4-5 explosion per hour were detected, generating ash plumes that rose 750 m and drifted 12 km NE. Block avalanches descended the flanks in multiple directions. There were 26 explosions during 18-19 January, with some generating shock waves and jet engine sounds. Ash plumes rose 550-850 m and drifted 10-12 km S, SW, and W. Three lava flows in the Trinidad, Las Lajas, and Santa Teresa drainages were at most 2 km 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.
Karangetang, Siau Island (Indonesia)
2.78°N, 125.4°E, Summit elev. 1784 m
Based on observations conducted at the Karangetang Volcano Observation Post in the village of Salili, PVMBG reported that during 6-20 January the lava dome was incandescent at night. Variable amounts of white and blue emissions rose as high as 100 m above Main Crater. RSAM values had been stable since 27 December 2015. The Alert Level remained at 3 (on a scale of 1-4); visitors and residents were warned not to approach Karangetang within a 4-km radius. Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 14 January a steam-and-ash plume rose to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted over 35 km W. The next day an ash-and-steam plume rose to an altitude of 2.7 (9,000 ft) a.s.l. and drifted almost 20 km SW.
Geologic 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 moderate explosive activity at Karymsky continued during 8-14 January. Satellite images detected a thermal anomaly during 11-14 January. 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 13-19 January. The lava lake continued to circulate and spatter in the Overlook vent. Webcams recorded multiple incandescent outgassing vents within Pu'u 'O'o Crater and high on the northeast rim. Several small and brief lava flows erupted onto the crater floor on 14 January. The June 27th NE-trending lava flow continued to be active within 6 km NE of Pu'u 'O'o Crater, burning some areas of forest.
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.
Lokon-Empung, Sulawesi (Indonesia)
1.358°N, 124.792°E, Summit elev. 1580 m
Although inclement weather sometimes obscured views of Lokon-Empung's Tompaluan Crater, PVMBG reported that during 6-13 January observers at the post in Kakaskasen Tomohon (North Sulawesi, 4 km from the crater) saw white plumes rising as high as 150 m above the crater. Seismicity fluctuated, and was dominated by shallow volcanic earthquakes and signals indicating emissions. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists were reminded not to approach the crater within a radius of 2.5 km.
Geologic summary: The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2 km apart), has a flat, craterless top. The morphologically younger Empung volcano to the NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred. A ridge extending WNW from Lokon includes Tatawiran and Tetempangan peak, 3 km away.
12.422°N, 86.54°W, Summit elev. 1297 m
INETER reported that at 1209 on 12 January a large explosion at Momotombo ejected incandescent material onto the flanks and generated an ash plume that rose 4 km above the crater. Tephra was deposited on the E, NE, N, and NW flanks. Ash plumes drifted downwind and caused ashfall in the communities of Flor de Piedra, La Concha (40 SSE), Amatistán, Guacucal (40 km N), La Palma, Puerto Momotombo (10 km WSW), La Sabaneta, Mira Lago, Asentamiento Miramar, Pancasán, René Linarte, Raúl Cabezas, and Betania. At around 0500 on 15 January strong volcanic tremor was accompanied by small explosions in the crater; ejected ash and incandescent tephra were deposited on the W flank. Seismicity decreased during 16-17 January.
Geologic summary: Momotombo is a young, 1297-m-high stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows from Momotombo have flowed down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms a 391-m-high island offshore in Lake Managua. Momotombo has a long record of strombolian eruptions, punctuated by occasional larger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after an April 10, 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the southern flank of the volcano.
8.32°S, 121.708°E, Summit elev. 875 m
PVMBG reported that observers at a post located in Kampung Ropa, Keliwumbu Village, noted that during 30 December 2015-13 January 2016 diffuse white plumes rose as high as 150 m above Paluweh. Seismicity remained relatively stable, and was characterized by shallow and deep volcanic earthquakes, and signals indicating emissions and avalanches. The Alert Level remained at 2 (on a scale of 1-4). Residents and tourists were reminded not to approach the summit within a radius of 1.5 km.
Geologic summary: Paluweh volcano, also known as Rokatenda, forms the 8-km-wide island of Paluweh north of the volcanic arc that cuts across Flores Island. Although the volcano rises about 3000 m above the sea floor, its summit reaches only 875 m above sea level. The broad irregular summit region contains overlapping craters up to 900 m wide and several lava domes. Several flank vents occur along a NW-trending fissure. The largest historical eruption occurred in 1928, when strong explosive activity was accompanied by landslide-induced tsunamis and lava dome emplacement.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 8-15 January lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Explosions on 9 January generated ash plumes that rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted W. Satellite images detected a daily and intense thermal anomaly over the dome, and ash plumes that drifted 200 km W during 9-10 January. 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.
3.17°N, 98.392°E, Summit elev. 2460 m
PVMBG reported that during 4-14 January inclement weather sometimes prevented visual observations of Sinabung and the growing lava dome in the summit crater. As many as 192 hot avalanches and 12 pyroclastic flows traveled 0.5-3 km ESE. Ash plumes from a total of 40 events rose as high as 3 km. Seismicity consisted of avalanche and pyroclastic-flow signals, low-frequency and hybrid events, tremor, tectonic events, and volcanic earthquakes. Seismicity fluctuated at high levels, although it had declined compared to the previous week, and indicated lava-dome growth. The Alert Level remained at 4 (on a scale of 1-4), indicating that people within 7 km of the volcano in the SSE sector, and within 6 km in the ESE sector, should evacuate.
Based on information from PVMBG and satellite images, the Darwin VAAC reported that during 13-15 and 17-19 January ash plumes from Sinabung rose to altitudes of 3-4.3 km (10,000-14,000 ft) a.s.l. and drifted NW, W, and SW.
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.
Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Summit elev. 2329 m
Based on satellite and webcam images, the Darwin VAAC reported that during 13-19 January ash plumes from Tengger Caldera's Bromo cone rose to an altitude of 3.6-4.2 km (12,000-14,000 ft) a.s.l. and drifted 15-160 km NW, W, SW, and S.
Geologic summary: The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.
16.355°S, 70.903°W, Summit elev. 5672 m
Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 12-18 January the seismic network at Ubinas recorded an increase in the number and magnitude of long-period earthquakes and a decrease in volcano-tectonic events. Thermal anomalies were detected on 13 and 15 January. At 0640 on 15 January a plume rose 500 m above the crater's base. At 1253 an explosion generated an ash plume that rose 3 km above the crater's base and drifted S and SW. The report noted that this was the first explosive event since 5 November 2015.
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.
19.53°S, 169.442°E, Summit elev. 361 m
On 14 January, the Vanuatu Geohazards Observatory stated that the Alert Level for Yasur remained at 2 (on a scale of 0-4) and that explosions had become more intense. VGO reminded residents and tourists that hazardous areas were near and around the volcanic crater, and that volcanic ash and gas could reach areas impacted by trade winds.
Geologic summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.
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