New activity/unrest was reported for 3 volcanoes between November 1 and 7, 2017. During the same period, ongoing activity was reported for 19 volcanoes.
New activity/unrest: Agung, Bali (Indonesia) | Aoba, Vanuatu | Kirishimayama, Kyushu (Japan).
Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Cleveland, Chuginadak Island (USA) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Langila, New Britain (Papua New Guinea) | Pacaya, Guatemala | Poas, Costa Rica | Popocatepetl, Mexico | Reventador, Ecuador | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica | Ulawun, New Britain (Papua New Guinea).
The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, notices of volcanic activity posted are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.
Agung, Bali (Indonesia)
8.343°S, 115.508°E, Elevation 2995 m
PVMBG reported that white plumes from Agung rose as high as 500 m above the crater rim during 1-7 November. The Alert Level remained at 3 (on a scale of 1-4), and the exclusion zones remained at 6 km, with an additional expansion to 7.5 km in the NNE, SE, S, and SW directions.
Geological summary: Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.
15.4°S, 167.83°E, Elevation 1496 m
Based on analyses of satellite and webcam images, and model data, the Wellington VAAC reported that during 6-7 November ash plumes from Aoba rose 2.1-4.3 km (7,000-14,000 ft) a.s.l. and drifted E, NW, W, and SW.
Geological summary: Aoba, also known as Ambae, is a massive 2500 cu km basaltic shield volcano that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes is located at the summit of the Hawaiian-style shield volcano within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. Post-caldera explosive eruptions formed the summit craters of Lake Voui (also spelled Vui) and Lake Manaro Ngoru about 360 years ago. A tuff cone was constructed within Lake Voui about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.
Kirishimayama, Kyushu (Japan)
31.934°N, 130.862°E, Elevation 1700 m
JMA reported that during 2-6 November activity at Shinmoedake (Shinmoe peak), a stratovolcano of the Kirishimayama volcano group, continued to be slightly elevated. White plumes rose 300-400 m above the crater rim. The Alert Level remained at 3 (on a scale of 1-5).
Geological summary: Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located, 1700-m-high Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported that sulfur dioxide flux at Aira Caldera’s Sakurajima volcano was just under 800 tons per day on 30 October. An explosion at Minamidake summit crater at 1221 on 31 October generated an ash plume that rose 1 km above the crater rim. The Alert Level remained at 3 (on a 5-level scale).
Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Elevation 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 3 November an ash plume from Bagana rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted NE.
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.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Elevation 1730 m
AVO reported that small explosions at Cleveland on 28 and 30 October partly destroyed the lava dome within the summit crater. Elevated surface temperatures were identified in satellite data during clear views during 1 and 5-7 November, possibly indicative of a lava flow in the crater. Otherwise no significant eruptive activity was recorded by seismic or infrasound sensors. The Aviation Color Coderemained at Orange and the Volcano Alert Level remained at Watch.
Geological 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.
Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Elevation 1229 m
Based on analyses of satellite imagery, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 1-7 November ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted N, NE, E, and ESE. Ash plumes drifted as far as 170 km during 4-5 November.
Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.
Ebeko, Paramushir Island (Russia)
50.686°N, 156.014°E, Elevation 1103 m
Based on observations by volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, explosions during 27 October-3 November generated ashplumes that rose as high as 2 km (6,600 ft) a.s.l. The Aviation Color Coderemained at Orange (the second highest level on a four-color scale).
Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.
14.473°N, 90.88°W, Elevation 3763 m
INSIVUMEH reported that during 2-3 November tremor at Fuego increased. Explosions (6-8 per hour) generated ash plumes that rose as high as 1.3 km above the crater and drifted 15 km W and SW. During 4-5 November there were 5-8 explosions per hour producing ash plumes that rose 1.2 km and drifted 10-15 km W and SW. Incandescent material was ejected 300 m above the crater, causing avalanches that were confined to the crater. The 11th effusive eruption phase in 2017 began on 5 November. Lava flowed 1-1.2 km W down the Seca drainage and 800 m SSW down the Ceniza drainage. Avalanches of material from the ends of the lava flows descended the flanks and reached vegetated areas. About 6-8 explosions per hour generated ash plumes that rose as high as 1.1 km and drifted 10-15 km W and SW. Ashfall was reported in areas downwind including Panimaché I and II (8 km SW), Santa Sofía (12 km SW), Morelia (9 km SW), and El Porvenir. The effusive phase ended on 7 November.
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, Elevation 1222 m
During 1-7 November HVO reported that the lava lake continued to rise, fall, and spatter in Kilauea’s Overlook crater. Webcams recorded incandescence from long-active sources within Pu'u 'O'o Crater and from a small lava pond in a pit on the W side of the crater. The 61G lava flow, originating from a vent on Pu'u 'O'o Crater's E flank, continued to enter the ocean at Kamokuna. Surface lava flows were active above and on the pali, and on the coastal plain.
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.
Langila, New Britain (Papua New Guinea)
5.525°S, 148.42°E, Elevation 1330 m
Based on analyses of satellite imagery and wind model data, the Darwin VAACreported that on 5 October an ash plume from Langila rose 3.7 km (12,000 ft) a.s.l.and drifted SE and ESE.
Geological summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.
14.382°N, 90.601°W, Elevation 2569 m
INSIVUMEH reported that during 4-7 November Strombolian explosions at Pacaya’s Mackenney cone ejected material as high as 40 m above the crater rim.
Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.
Poas, Costa Rica
10.2°N, 84.233°W, Elevation 2708 m
OVSICORI-UNA reported that an event at Poás at 0915 on 6 November generated a plume that rose 300 m above the crater rim.
Geological summary: The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.
19.023°N, 98.622°W, Elevation 5426 m
Each day during 1-7 November CENAPRED reported 200-361 emissions from Popocatépetl, some of which contained ash. Crater incandescence was noted almost nightly. Increased seismicity at 0146 on 3 November coincided with a period of Strombolian activity that ended at 0535; gas, water vapor, and ash emissions rose from the carter and incandescent material was ejected 500 m onto the flanks. An explosion was detected at 1027. On 4 November explosions were detected at 0145 and 0608. Following the second explosion a continuous gas plume with minor ash drifted WSW. Beginning at 0735 ashfall was reported in municipalities of Yecapixtla (31 km SW) and Zacualpan de Amilpas (30 km SW), in the state of Morelos. A Strombolian period began at 1029 and lasted for 80 minutes, causing ashfall in Tetela del Volcán (20 km SW). Explosions at 1440 and 2231 ejected incandescent material 200 m onto the flanks. Another explosion was recorded at 0411 on 5 November. An explosion at 1653 on 6 November generated a gas-and-ash plume that rose 2.5 km above the crater rim and drifted SW. Fragments were ejected 500 m onto the flanks. An explosion at 0100 on 7 November generated a gas-and-ash plume that rose almost 2 km above the crater rim and drifted SW. 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.
0.077°S, 77.656°W, Elevation 3562 m
IG reported that during the last week of October the intensity of explosions at Reventador slightly increased; ash plumes, generated from 4-5 explosions per hour, rose to more than 2.5 km above the crater rim and had a higher ash content. Plumes typically drifted W, but also occasionally S and N. Loud “cannon shot” sounds accompanying some explosions were heard in nearby towns. IGvolcanologists conducting fieldwork on 23 and 25 October noted strong explosions producing “cannon shots” that vibrated windows in Hostería Reventador, 7.2 km away. On 27 October ash plumes rose as high as 4.9 km. During 30-31 October ashfall was reported in multiple towns in the Napo Province to the S, mainly due to a change in wind direction and not increased activity.
Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.
15.787°S, 71.857°W, Elevation 5960 m
Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosive activity at Sabancaya increased compared to the previous week; there was an average of 57 daily explosions during 30 October-5 November. Seismicity was dominated by long-period events, with signals indicating emissions. Gas-and-ash plumes rose 3.8 km above the crater rim and drifted 40 km N, NE, and E. The MIROVA system detected five thermal anomalies. The sulfur dioxide flux was high, at 3,996 tons per day, on 30 October. The report noted that the public should not to approach the crater within a 12-km radius.
Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 26-30 October and 1-2 November. Explosions on 2 November generated ash plumes that rose 8 km (26,200 ft) a.s.l. and drifted NE. 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, Elevation 2460 m
Based on observations by PVMBG, satellite and webcam images, and model data, the Darwin VAAC reported that during 2 and 5-7 November ash plumes from Sinabung rose 3.4-4.9 km (11,000-16,000 ft) a.s.l. and drifted E, ESE, and SSE.
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 andesitic-to-dacitic edifice 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.
Stromboli, Aeolian Islands (Italy)
38.789°N, 15.213°E, Elevation 924 m
INGV reported that a 3-minute-long explosive sequence began at the central vents of Stromboli’s southern crater area (Area CS) at 2129 on 1 November. The explosions ejected coarse pyroclastic material onto the Sciara del Fuoco, in the direction of Pizzo Sopra la Fossa, and produced a dense ash plume that quickly dissipated to the S. Seismicity returned to normal levels after the events.
Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small, 924-m-high island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period from about 13,000 to 5000 years ago was followed by formation of the modern Stromboli edifice. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5000 years ago as a result of the most recent of a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.
Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Elevation 796 m
Based on JMA notices and satellite data, the Tokyo VAAC reported explosions at Suwanosejima during 31 October, and 1, 3, and 5 November; plumes rose 1.5 km (5,000 ft) a.s.l. and drifted NW and W.
Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
The Washington VAAC reported that an ash emission from Turrialba was observed in webcam images on 4 November. Ash was not identified in satellite images, though weather cloud cover was increasing and may have obscured views.
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.
Ulawun, New Britain (Papua New Guinea)
5.05°S, 151.33°E, Elevation 2334 m
Based on analyses of satellite imagery, the Darwin VAAC reported that on 3 November an ash plumes from Ulawun rose to an altitude of 3 km (10,000 ft) a.s.l.and drifted NNE, though a RVO report noted only vapor emissions.
Geological summary: The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m is unvegetated. A prominent E-W-trending escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.