Ongoing activity/unrest was observed at 3 volcanoes between July 13 and 19, 2016. Ongoing activity was reported for 17 volcanoes during the same period.
New activity/unrest: Kilauea, Hawaiian Islands (USA) | Manam, Papua New Guinea | Pacaya, Guatemala.
Ongoing activity: Alaid, Kuril Islands (Russia) | Bagana, Bougainville (Papua New Guinea) | Bristol Island, South Sandwich Islands (UK) | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Klyuchevskoy, Central Kamchatka (Russia) | Nevado del Ruiz, Colombia | Pavlof, United States | Sangay, Ecuador | Santa Maria, Guatemala | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Tengger Caldera, Eastern Java (Indonesia) | Turrialba, Costa Rica.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Summit elev. 1222 m
HVO reported that during 13-19 July the lava lake continued to rise and fall, circulate, and spatter in Kilauea's Overlook vent. Several incandescent vents on Pu'u 'O'o Crater's floor were evident in webcam images. The 61G lava flow, originating from a vent on Pu'u 'O'o Crater's E flank, continued to advance across the coastal plain. By midday on 15 July the lava flow was about 870 m from the ocean, advancing only 60 m since 12 July. A satellite image acquired on 17 July showed that the flow front was 820 m from the ocean. By the evening of 18 July the flow tip had stalled but breakouts were active a few hundred meters upslope.
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.
Manam, Papua New Guinea
4.08°S, 145.037°E, Summit elev. 1807 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 13 July an ash plume from Manam rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 55 km W.
Geological summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
14.381°N, 90.601°W, Summit elev. 2552 m
INSIVUMEH reported some weak explosions and fumarolic emissions at Pacaya during 16-18 July. Incandescence from the crater was visible at night or early in the morning.
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.
Alaid, Kuril Islands (Russia)
50.861°N, 155.565°E, Summit elev. 2285 m
KVERT reported that Strombolian activity at a new cinder cone in Alaid's summit crater was detected during 8-15 July, with lava flowing down the SW flank. Satellite images showed a thermal anomaly at the volcano during 7 and 11-13 July. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago and rises 3000 m from the floor of the Sea of Okhotsk. Numerous pyroclastic cones dot the lower flanks of basaltic to basaltic-andesite Alaid volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.
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 17-18 July ash plumes from Bagana rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted over 90 km W and NW.
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, roughly 1850-m-high cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.
Bristol Island, South Sandwich Islands (UK)
59.017°S, 26.533°W, Summit elev. 1100 m
The Buenos Aires VAAC reported that on 19 July a diffuse ash plume from Bristol Island's Mt. Sourabaya was visible in satellite images drifting 30 km NE. A persistent thermal anomaly was also identified in satellite data.
Geological summary: The 9 x 10 km Bristol Island near the southern end of the South Sandwich arc lies across Fortser's Passage from the Southern Thule Islands and forms one of the largest islands of the chain. Largely glacier-covered, it contains a horseshoe-shaped ridge at the interior extending northward from the highest peak, 1100-m-high Mount Darnley. A steep-sided flank cone or lava dome, Havfruen Peak, is located on the east side, and a young crater and fissure are on the west flank. Three large sea stacks lying off Turmoil Point at the western tip of the island may be remnants of an older now-eroded volcanic center. Both summit and flank vents have been active during historical time. The latest eruption, during 1956, originated from the west-flank crater, and deposited cinder over the icecap. The extensive icecap and the difficulty of landing make it the least explored of the South Sandwich Islands.
Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Summit elev. 742 m
SVERT reported that a thermal anomaly over Snow, a volcano of Chirpoi, was detected in satellite images on 13 July. The Aviation Color Code remained at Yellow.
Geological 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 and webcam images, the Washington VAAC reported that on 17 July an ash emission from Colima rose to an altitude of 4.9 km (16,000 ft) a.s.l., drifted just over 10 km NW, and quickly dissipated. The next day an ash plume rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted W.
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.
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 13-19 July ash plumes from Dukono rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted as far as 225 km NW, W, and SW.
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
INSIVUMEH reported that on 15 July activity at Fuego increased, characterized by eight explosions per hour detected by the seismic network and ash plumes that rose 1.1 km above the crater. Ash fell on the W and SW flanks. During 17-19 July there were 3-6 explosions per hour detected. Ash plumes rose as high as 850 m above the crater and drifted at least 12 km W and SW, causing ashfall in areas downwind including Yepocapa (8 km N), Sangre de Cristo (8 km WSW), and Panimaché I and II (8 km SW). Some explosions generated shock waves that rattled nearby homes and sounds resembling jet engines were heard every 3-8 minutes. Incandescent material was ejected 100-200 m high, and 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.
Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 8-15 July. Volcanic bombs were ejected 200-300 m above the summit crater and 50 m above a cinder cone, and landed in the Apakhonchich drainage on the SE flank. A lava flow traveled down the Apakhonchich drainage. Satellite images showed a large and intense daily thermal anomaly at the volcano, and ash plumes drifting 170 km NE during 11-12 July. The Aviation Color Code was raised to 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 during 12-18 July seismicity at Nevado del Ruiz slightly increased as compared to levels the week before. Several episodes of “drumbeat” earthquakes were recorded during 13, 15, and 16-17 July. These signals were low energy and indicated a growing lava dome. Significant amounts of water vapor and gas rose from the crater. Gas, steam, and ash plumes rose at most 500 m above the crater rim and drifted NW on 13, 14, 16, and 17 July. 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.
Pavlof, United States
55.417°N, 161.894°W, Summit elev. 2493 m
AVO reported that seismic activity at Pavlof remained elevated during 13-19 July. A steam plume was visible in satellite images and reported by observers in Sand Point (90 km E) on 18 July. The next day persistent steam plumes with occasional minor ash-producing explosions were observed in satellite views. The Aviation Color Code remained at Yellow and Volcano Alert Level remained at Advisory.
Geological summary: The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.
2.005°S, 78.341°W, Summit elev. 5286 m
Based on satellite images and wind data, the Washington VAAC reported that on 16 July a possible ash plume from Sangay rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted 22 km SW.
Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. The dominantly andesitic volcano has been in frequent eruption for the past several centuries. The steep-sided, 5230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.
Santa Maria, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m
INSIVUMEH reported that at 1330 on 15 July an explosion at Santa María's Santiaguito lava-dome complex generated an ash plume that rose 2.4 km and drifted NW. Gas plumes rose from the complex during 17-18 July. At 0235 on 19 July an explosion generated avalanches and a pyroclastic flow that traveled SE down Caliente dome. An ash plume rose 1 km and drifted SW.
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 8-15 July 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. 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, model data, and ground reports from PVMBG, the Darwin VAAC reported that during 15-16 and 19 July ash plumes from Sinabung rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted NW, W, and SW.
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.
Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Summit elev. 796 m
Based on JMA notices, satellite-image analyses and pilot observations, the Tokyo VAAC reported that during 18-19 July ash plumes from Suwanosejima rose to altitudes of 1.8-2.7 km (6,000-9,000 ft) a.s.l. and drifted NE.
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.
Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Summit elev. 2329 m
Based on satellite images, wind data, and information from PVMBG, the Darwin VAAC reported that during 13-16 and 19 July ash plumes from Tengger Caldera's Bromo cone rose to altitudes of 2.1-3.3 km (7,000-11,000 ft) a.s.l. and drifted over 45 km NW, SW, and SE. BNPB reported that the Abdul Rachman Saleh Airport in Malang (26 km W) closed again due to ash, from 2307 on 15 July to 0900 on 16 July; six flights were diverted and two were cancelled. Minor amounts of ash fell in the communities of Probolinggo (35 km NE) and Lumajang (36 km SW). The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were reminded not to approach the crater within a radius of 1 km.
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.
Turrialba, Costa Rica
10.025°N, 83.767°W, Summit elev. 3340 m
OVSICORI-UNA reported that at 1330 on 13 July Turrialba produced a weak ash emission that rose 100 m and drifted W.
Geological summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 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.