New activity/unrest was reported for 7 volcanoes between September 28 and October 4, 2016. In the same period, ongoing activity was reported for 13 volcanoes.
New activity/unrest: Colima, Mexico | Iya, Flores Island (Indonesia) | Katla, Iceland | Rinjani, Lombok Island (Indonesia) | Tengger Caldera, Eastern Java (Indonesia) | Tungurahua, Ecuador | Ubinas, Peru.
Ongoing activity: Bagana, Bougainville (Papua New Guinea) | Bulusan, Luzon (Philippines) | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Nevado del Ruiz, Colombia | Nevados de Chillán, Chile | Popocatepetl, Mexico | Santa Maria, Guatemala | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Turrialba, Costa Rica.
19.514°N, 103.62°W, Summit elev. 3850 m
The Unidad Estatal de Protección Civil de Colima reported that on 26 September seismicity at Colima increased, and crater incandescence was observed later that day. On 27 September small landslides originating from a new and growing lava dome traveled 100 m down the S flank. The exclusion zone was increased from 5 to 10 km in the Montegrande canyon; a 5-km exclusion zone was maintained in the other areas. According to news articles, incandescent landslides traveled down the S and SE flanks during 29 September-1 October. Gas-and-ash plumes rose 4 km and caused ashfall in nearby areas including La Becererra, La Yerbabuena, San Antonio, and El Jabali in the municipality of Comala, Montitlán in the municipality of Cuauhtémoc, and Juan Barragan in Tonila, Jalisco. On 1 October the Colima State government stated that the communities of La Yerbabuena (80 people) and La Becerrera (230 people) were preemptively evacuated, and the exclusion zone was extended to 12 km except on the Jalisco side (maintained at 7.5 km). A news article noted that Juan Barragan was also evacuated.
The Washington VAAC reported that on 29 September gas-and-steam emission possibly containing minor amounts of ash rose to an altitude of 4.9 km (16,000 ft) a.s.l. and drifted NW. On 30 September the webcam showed intense activity and crater incandescence, and gas-and-steam emissions that may have contained ash drifting WNW. An intense thermal anomaly was visible in short-wave infrared satellite images. Later that day an ash plume rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted 35 km W. Possible emissions with ash were recorded by the webcam on 1 October; weather clouds obscured views of the crater. An ash plume detected in satellite images drifted almost 40 km S and SW. Later that day the webcam recorded explosions and pyroclastic flows. On 2 October ash plumes rose to altitudes of 6.1-8.2 km (20,000-27,000 ft) a.s.l. and drifted SW and W. Emissions later that day were mostly comprised of gas and steam; seismicity decreased, though a thermal anomaly continued to be detected in satellite images. On 3 October ash plumes rose to altitudes of 5.5-6.4 km (18,000-21,000 ft) a.s.l. and drifted 25-40 km SW and SWW. Ashfall was reported in areas on the S and SW flanks. Based on webcam views ash emissions rose to an estimated altitude of 5.5 km (18,000 ft) a.s.l. and drifted S on 4 October.
Geological 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.
Iya, Flores Island (Indonesia)
8.897°S, 121.645°E, Summit elev. 637 m
PVMBG reported that during 1 July-29 September variable-density white plumes rose as high as 150 m above Iya. During most of that period seismicity was at normal levels characterized by deep and shallow volcanic earthquakes each detected at a rate of less than 10 events per day. Between 1550 and 1800 on 29 September, however, the seismic network detected 17 volcanic earthquakes. Since the number of volcanic earthquakes was significant and above normal levels, the Alert Level was raised to 2 (on a scale of 1-4), and the public was warned not to approach the crater within a 2-km radius.
Geological summary: Gunung Iya is the southernmost of a group of three volcanoes comprising a small peninsula south of the city of Ende on central Flores Island. The cones to the north, Rooja and Pui, appear to be slightly older than Iya and have not shown historical activity, although Pui has a youthful profile (a reported 1671 eruption of Pui was considered to have originated from Iya volcano). Iya, whose truncated southern side drops steeply to the sea, has had numerous moderate explosive eruptions during historical time.
63.633°N, 19.083°W, Summit elev. 1490 m
The Iceland Met Office (IMO) reported that an intense seismic swarm began at Katla on 29 September. The activity intensified again at 1202 on 30 September with tremor and several earthquakes M 3 or larger. The Aviation Color Code was raised to Yellow, the second highest level on a four-color scale. On 3 October IMO stated that the seismic swarm was the largest one in decades, though it appeared to be over. According to a news article from 3 October popular travel destinations near the glacier had been and remained closed to traffic.
Geological summary: Katla volcano, located near the southern end of Iceland's eastern volcanic zone, is hidden beneath the Myrdalsjökull icecap. The subglacial basaltic-to-rhyolitic volcano is one of Iceland's most active and is a frequent producer of damaging jökulhlaups, or glacier-outburst floods. A large 10 x 14 km subglacial caldera with a long axis in a NW-SE direction is up to 750 m deep. Its high point reaches 1380 m, and three major outlet glaciers have breached its rim. Although most historical eruptions have taken place from fissures inside the caldera, the Eldgjá fissure system, which extends about 60 km to the NE from the current ice margin towards Grímsvötn volcano, has been the source of major Holocene eruptions. An eruption from the Eldgjá fissure system about 934 CE produced a voluminous lava flow of about 18 cu km, one of the world's largest known Holocene lava flows. Katla has been the source of frequent subglacial basaltic explosive eruptions that have been among the largest tephra-producers in Iceland during historical time and has also produced numerous dacitic explosive eruptions during the Holocene.
Rinjani, Lombok Island (Indonesia)
8.42°S, 116.47°E, Summit elev. 3726 m
Based on data from the Mount Rinjani National Park, BNPB reported that as many as 1,023 tourists were on Rinjani when it erupted on 27 September; officially only 464 people were registered to make the 3-day trek to the volcano and back. Officials began the evacuation of tourists that day. According to a news article, 44 trekkers had still not returned to the entrance points by 1 October. The Alert Level remained at 2 (on a scale of 1-4); the public was warned not to approach the crater within a 3-km radius.
Geological summary: Rinjani volcano on the island of Lombok rises to 3726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the east, but the west side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak (Samalas) caldera. The caldera formed during one of the largest Holocene eruptions globally in 1257 CE, which truncated Samalas stratovolcano. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the east end of the caldera. Historical eruptions dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake.
Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Summit elev. 2329 m
Based on analyses of satellite images and information from PVMBG, the Darwin VAAC reported that on 29 September and 1 October ash plumes from Tengger Caldera’s Bromo cone rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted E and SE.
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.
1.467°S, 78.442°W, Summit elev. 5023 m
IG reported that during 27 September-4 October seismic activity at Tungurahua remained at moderate levels, characterized by 1-8 long-period earthquakes and up to three volcano-tectonic events per day. An hour-long period of tremor was recorded on 1 October. Minor fumarolic emissions rose above the crater rim.
Geological 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
According to IGP's Observatorio Vulcanológico del Sur (OVS) seismicity at Ubinas increased during 9-14 September, characterized by an increased number of volcano-tectonic and hybrid events. Volcano-tectonic vents also became more intense. A small thermal anomaly was detected on 20 September. According to a news article, an "exhalation" occurred at 1921 on 2 October, and was followed by explosions detected at 2250 that same day, and 0424 and 0552 on 3 October. The largest explosion, at 2250 on 2 October, emitted a dense ash plume that rose 1.7 km and drifted 10 km NE and NW, causing ashfall in Santa Rosa de Phara and Yanapuqui.
Geological 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.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Summit elev. 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 29 September-2 October ash plumes from Bagana rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 45-65 km SE and W.
Geological summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical 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 flanks on all sides.
Bulusan, Luzon (Philippines)
12.77°N, 124.05°E, Summit elev. 1565 m
PHIVOLCS reported that during 0650-1240 on 1 October voluminous white-to-grayish emissions rose 200 m from vents on Bulusan's SE flank and drifted SE. Minor amounts of ash fell in the barangays of San Rafael, San Roque, and San Jose, in the municipality of Bulusan. The Alert Level remained at 1, indicating abnormal conditions and a 4-km-radius Permanent Danger Zone (PDZ).
Geological summary: Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. Bulusan lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of 1565-m-high Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.
Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Summit elev. 1229 m
Based on analyses of satellite imagery, information from PVMBG, and model data, the Darwin VAAC reported that during 28-29 September and 1-4 October ash plumes from Dukono rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted SW, S, and E.
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.
14.473°N, 90.88°W, Summit elev. 3763 m
Based on INSIVUMEH reports, CONRED stated that beginning at 0730 on 27 September loud explosions at Fuego generated ash plumes that rose 1 km above the crater rim and drifted more than 15 km W and SW. After about 36 hours of elevated activity, the 13th Strombolian episode in 2016, Fuego returned to more normal levels. On 28 September there were 4-6 explosions per hour recorded, producing ash plumes that rose 550-650 m and drifted 8-12 km W and SW. Lava flows in the Las Lajas (SE) and Santa Teresa (W) drainages had stalled. Explosions during 30 September-1 October and 3-4 October generated ash plumes that rose as high as 1.1 km and drifted 7-13 km W, SW, and S. During 3-4 October explosions produced shock waves and ashfall in Morelia (10 km SW). Incandescent material was ejected 300 m high, and block avalanches reached vegetated areas.
Geological 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.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Summit elev. 1222 m
During 28 September-4 October HVO reported that the lava lake continued to rise and fall, circulate, and spatter in Kilauea’s Overlook vent. The lake level rose as high as 10 m below the Halema'uma'u floor (on 1 October), and was sometimes visible from the Jaggar Museum (NW rim of Kilauea Caldera). Webcams recorded incandescence from long-active sources within Pu'u 'O'o Crater. The 61G lava flow, originating from a vent on Pu'u 'O'o Crater's E flank, continued to enter the ocean at multiple locations near Kamokuna. Scattered breakouts were active 2 km inland from the coast.
Geological 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 are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.
Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 23-30 September. Ash emissions rose from the summit crater and from the cinder cone in the Apakhonchich drainage on the E flank. A lava flow traveled down the Apakhonchich drainage. Satellite images showed a large and bright daily thermal anomaly at the volcano. During 23-24 September explosions generated ash plumes that rose as high as 6 km (19,700 ft) a.s.l. and drifted 165 km in multiple directions. The Aviation Color Code remained at Orange.
Geological summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.
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 a webcam recorded an ash plume rising from Nevado del Ruiz at 0558 on 29 September. Based on information from the Bogota MWO, the Washington VAAC reported on the same day that an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted WSW. Later that day ASHTAM reports indicated an ash emission to an altitude of 8.5 km (28,000 ft) a.s.l. and drifted 13 km S, though cloud cover prevented webcam and satellite image views. An ash emission reported by the Bogota MWO rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted NE on 3 October. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).
Geological 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.
Nevados de Chillán, Chile
36.863°S, 71.377°W, Summit elev. 3212 m
Based on webcam images and pilot observations, the Buenos Aires VAAC reported that on 3 October an ash emission from Nevados de Chillán drifted SE.
Geological 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.
19.023°N, 98.622°W, Summit elev. 5426 m
Each day during 28 September-4 October CENAPRED reported 125-389 steam, gas, and ash emissions from Popocatépetl. Cloud cover often prevented observations, though gas-and-steam plumes were visible daily. Crater incandescence was visible on some nights. An explosion at 0929 on 29 September produced a plume that drifted NW. Explosions were also detected at 1813 on 30 September, 1300 on 3 October, and 0231 and 0647 on 4 October. The Alert Level remained at Yellow, Phase Two.
Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 CE, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.
Santa Maria, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m
INSIVUMEH reported that during 30 September-1 October and 3-4 October explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose 1.1 km above the complex and drifted SE, S, and SW. Local ashfall was reported in areas including in San Marcos (10 km SW), Palajunoj (18 km SSW), Loma Linda (6 km WSW), El Nuevo Palmar (12 km SSW), and Las Marías.
Geological summary: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 23-30 September lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Satellite images showed a daily thermal anomaly over the dome. Re-suspended ash formed a plume that drifted about 100 km SE and E during 28-29 September. The Aviation Color Code remained at Orange.
Geological 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
Based on satellite images and ground reports from PVMBG, the Darwin VAAC reported that during 28-29 September ash plumes from Sinabung rose to altitudes of 3.6-3.9 km (12,000-13,000 ft) a.s.l. and drifted E.
Geological 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.
Turrialba, Costa Rica
10.025°N, 83.767°W, Summit elev. 3340 m
OVSICORI-UNA reported that continuous ash emissions of varying intensity rose from Turrialba during 26-29 September. On the morning of 30 September emissions reduced and rose passively no more than 100 m above the crater. Tremor was constant but had a low amplitude. Later that day intermittent gas, steam, and ash plumes rose as high as 500 m and drifted W and SW. Intermittent eruptions during 2-3 October produced ash plumes that rose no higher than 1 km and drifted S, SSW, SW, and NNE. Ashfall and a sulfur odor were reported in multiple areas downwind. Activity increased at 0823 on 3 October, with almost continuous emissions rising at most 1 km, and continued steadily through 4 October.
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 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.