Active volcanoes in the world: November 16 – 22, 2016

Between November 16 and 22, new activity was reported for 7 volcanoes. During the same period, ongoing activity was reported for 12 volcanoes.

New activity/unrest: Copahue, Central Chile-Argentina border | Kerinci, Indonesia | Langila, New Britian (Papua New Guinea) | Monowai, Tonga Ridge | Sabancaya, Peru | Ubinas, Peru | Zhupanovsky, Eastern Kamchatka (Russia).

Ongoing activity: Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Nevado del Ruiz, Colombia | Nevados de Chillan, Chile | Sangay, Ecuador | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica | Ulawun, New Britian (Papua New Guinea).

New activity/unrest

Copahue, Central Chile-Argentina border
37.856°S, 71.183°W, Summit elev. 2953 m

Based on satellite and webcam images, the Buenos Aires VAAC reported that during 16-18 and 21-22 November diffuse steam-and-ash plumes rose from Copahue to altitudes of 3.3-3.6 km (11,000-12,000 ft) a.s.l. and drifted NE, ENE, E, and WNW. On 17 November OVDAS-SERNAGEOMIN reported that activity continued to be dominated by weak Strombolian explosions likely from a pyroclastic cone forming on the floor of El Agrio crater. The Alert Level remained at Yellow; SERNAGEOMIN recommended no entry into a restricted area within 1.5 km of the crater.

Geological 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.

Kerinci, Indonesia
1.697°S, 101.264°E, Summit elev. 3800 m

Based on satellite data, the Darwin VAAC reported that during 16-19 and 21 November ash plumes from Kerinci rose to altitudes of 4.3-4.6 km (14,000-15,000 ft) a.s.l. and drifted NE, ENE, SE, and S. Plumes drifted almost 30 km on 17 November.

Geological summary: The 3800-m-high Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. Kerinci is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. The volcano contains a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. The frequently active Gunung Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Langila, New Britian (Papua New Guinea)
5.525°S, 148.42°E, Summit elev. 1330 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 16 November an ash plume from Langila rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted almost 30 km SE.

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.

Monowai, Tonga Ridge
25.887°S, 177.188°W, Summit elev. -132 m

GeoNet reported that on 16 November airplane passengers observed pumice floating in an area W of Minerva Reef, about 600 km SE of Fiji and 500 km SW of Tonga, where there are no known active submarine volcanoes. The nearest active submarine volcano is Monowai (400 km SE) which was active during 10-11 November, though it usually does not produce pumice rafts. Floating pumice was visible in satellite images during 15-16 November, extending more than 100 km. Analysts were not yet able to track the pumice to its source in older images. A larger pumice raft in October 2012 originated from Havre Seamount.

Geological summary: Monowai, also known as Orion seamount, rises to within 100 m of the sea surface about halfway between the Kermadec and Tonga island groups. The volcano lies at the southern end of the Tonga Ridge and is slightly offset from the Kermadec volcanoes. Small parasitic cones occur on the N and W flanks of the basaltic submarine volcano, which rises from a depth of about 1500 m and was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology. A large 8.5 x 11 km wide submarine caldera with a depth of more than 1500 m lies to the NNE. Numerous eruptions from Monowai have been detected from submarine acoustic signals since it was first recognized as a volcano in 1977. A shoal that had been reported in 1944 may have been a pumice raft or water disturbance due to degassing. Surface observations have included water discoloration, vigorous gas bubbling, and areas of upwelling water, sometimes accompanied by rumbling noises.

Sabancaya, Peru
15.78°S, 71.85°W, Summit elev. 5967 m

The Technical and Scientific Committee for volcanic risk management of the Arequipa region (comprised of five groups including IGP's OVS and INGEMMET's OVI) reported multiple explosions at Sabancaya during 16-18 and 20-21 November, and ash plumes that rose 2-4.2 km above the crater rim and drifted more than 40 km N, NE, S, and SW. The Buenos Aires VAAC stated that ash plumes visible in satellite and webcam images drifted SE on 19 November.

Geological summary: Sabancaya, located on the saddle between 6288-m-high Ampato and 6025-m-high 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 volcanoes, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. Both Nevado Ampato and Nevado Sabancaya are only slightly affected by glacial erosion and consist of a series of lava domes aligned along a NW-SW trend. The name of 5967-m-high Sabancaya (meaning "tongue of fire" in the Quechua Indian 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.

Ubinas, Peru
16.355°S, 70.903°W, Summit elev. 5672 m

The Comité Científico de Monitoreo Permanente del volcán Ubinas, made up of scientists from IGP's Observatorio Vulcanológico del Sur (OVS) and INGEMMET's Observatorio Vulcanológico (OVI), reported that at 1829 on 17 November an explosion at Ubinas generated an ash plume that rose 500 m above the crater rim and drifted W.

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.

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Summit elev. 2899 m

KVERT reported that at 1429 on 20 November a webcam recorded ash plumes from Zhupanovsky rising to altitudes of 6-8 km (19,700-26,200 ft) a.s.l. and drifted 73 km E. The Aviation Color Code was raised from Green to Orange, the second highest level on a 4-color scale. KVERT noted that conditions were quiet after the eruption; on 22 November the Aviation Color Code was lowered to Yellow.

Geological 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.

Ongoing activity

Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Summit elev. 1229 m

Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 16 and 18-22 November ash plumes from Dukono rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted in multiple directions.

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.

Fuego, Guatemala
14.473°N, 90.88°W, Summit elev. 3763 m

INSIVUMEH reported that during 16-17 and 19 November explosions at Fuego generated ash plumes that rose 650-950 m above the crater rim and drifted 12 km W, SW, and S. Incandescent material was ejected as high as 200 m causing minor avalanches confined to the crater. The 15th Strombolian episode in 2016 began on 20 November. Lava fountains rose as high as 300 m and fed three lava flows which traveled 1 km S down the Trinidad drainage, 2 km SSW down the Ceniza drainage, and 2.5 km SE down the Las Lajas drainage. Explosions generated ash plumes that rose as high as 1.3 km and drifted 15 km S and SW. Ashfall was reported in areas downwind including Morelia (9 km SW), Santa Sofía (12 km SW), and Panimaché I and II (8 km SW). Lava fountains continued to rise 300 m above the crater rim on 21 November and avalanches of material descended the Santa Teresa (W) and Taniluyá (SW) drainages. Ash plumes rose 1.3 km and drifted 20 km S, SW, and W, causing ashfall again in Morelia, Santa Sofía, and Panimaché I and II. INSIVUMEH noted that on 22 November the Strombolian eruptive phase had ended. Ash plumes continued to be generated, rising as high as 1.8 km and drifting more than 10 km S and SW.

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 16-22 November 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 7.5 m below the Halema’uma’u floor. 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 near Kamokuna at the easternmost lava delta.

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 on 17 November an ash plume from Klyuchevskoy visible in satellite images rose to an altitude of 5 km (16,400 ft) a.s.l. and drifted almost 60 km WNW. The Aviation Color Code remained at Yellow.

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

Based on information from the Bogota MWO, the Washington VAAC reported on 16 November an ash plume from Nevado del Ruiz rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted NE. Weather clouds prevented satellite views.

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 Chillan, Chile
36.863°S, 71.377°W, Summit elev. 3212 m

The Buenos Aires VAAC reported that on 18 November an ash puff from Nevados de Chillán was recorded by the webcam. SERNAGEOMIN reported that two explosions, detected at 0536 on 18 November, generated a plume that rose 1.2 km above the crater rim.

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.

Sangay, Ecuador
2.005°S, 78.341°W, Summit elev. 5286 m

Based on satellite images and wind data, the Washington VAAC reported that during 16-17 November ash plumes from Sangay rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted as far as 290 km SE.

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.

Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m

KVERT reported that during 11-18 November lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence, ash explosions with ash plumes as high as 6 km (19,700 ft) a.s.l., and hot avalanches. Satellite images showed a daily thermal anomaly over the dome, and ash plumes that drifted as far as 170 km E on 12 and 15 November. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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.

Sinabung, Indonesia
3.17°N, 98.392°E, Summit elev. 2460 m

Based on satellite images, wind data, ground reports from PVMBG, and the Jakarta MWO, the Darwin VAAC reported that on 20 November ash plumes from Sinabung rose to altitudes of 3.3-3.9 km (11,000-13,000 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 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.

Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Summit elev. 796 m

Based on JMA notices and satellite-image analyses, the Tokyo VAAC reported that during 16-17 November explosions at Suwanosejima generated ash plumes that rose to an altitude over 1.2 km (4,000 ft) a.s.l. and drifted S. During 20-21 November ash plumes rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted E.

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, Summit elev. 3340 m

OVSICORI-UNA reported that tremor and ash emissions at Turrialba ceased on 17 November. Tremor amplitude increased at 0140 on 19 November, though weather clouds prevented visual confirmation of correlating emissions. By 0800 tremor amplitude was low and some long-period events were recorded. Low emissions were mostly white, indicating gas, water vapor, and minor amounts of ash. A small quantity of ash fell in Cartago and Paraíso de Cartago (25 km SW). Tremor amplitude remained low on 20 November. A thin layer of ash deposits were reported in Ipis de Goicoechea, 27 km SW of the crater.

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 Britian (Papua New Guinea)
5.05°S, 151.33°E, Summit elev. 2334 m

Based on analyses of satellite imagery, the Darwin VAAC reported that during 16-18 November ash plumes from Ulawun rose to altitudes of 2.7-3 km (9,000-10,000 ft) a.s.l. and drifted over 30 km SE, SW, and W.

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. Ulawun 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 of the 2334-m-high Ulawun volcano 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 eastern flanks. A steep-walled valley cuts the NW side of Ulawun volcano, 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.

Source: GVP