The Weekly Volcanic Activity Report: September 5 – 11, 2018

New activity/unrest was reported for 3 volcanoes between September 5 and 11, 2018. During the same period, ongoing activity was reported for 11 volcanoes.

New activity/unrest: Etna, Sicily (Italy) | Krakatau, Indonesia | Veniaminof, United States.

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Sabancaya, Peru | Sangay, Ecuador | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Stromboli, Aeolian Islands (Italy) | Turrialba, Costa Rica.

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.

New activity/unrest

Etna, Sicily (Italy)

37.748°N, 14.999°E, Elevation 3295 m

INGV reported that during 3-9 September activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), and New Southeast Crater (NSEC). A few Strombolian explosions at NSEC were recorded on 5 September; an explosion at 0536 generated an ash plume that produced local ashfall around the vent and in the Valle del Bove, and quickly dispersed. A similar but less intense event occurred earlier that day, at 0316. Similar Strombolian events continued during 6-9 September, at intervals of a few hours. Strombolian activity at the N vent (BN-1) in Bocca Nuova occurred at 3-5-minute intervals, ejecting incandescent material that fell within the crater confines. Gas emissions were sometimes punctuated with ash emissions. Intense degassing was characteristic of the second vent (BN-2). Strombolian activity occurred at NEC, and a few times explosions were accompanied by ash emissions.

Geological summary: Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank. This volcano is located within the Mount Etna, a UNESCO World Heritage property.

Krakatau, Indonesia

6.102°S, 105.423°E, Elevation 813 m

Based on satellite data, the Darwin VAAC reported that on 8 September ash plumes from Anak Krakatau rose to altitudes of 4.9-5.5 km (16,000-18,000 ft) a.s.l.and drifted W and NW. During 9-10 September ash plumes rose to 1.5 km (5,000 ft) a.s.l. and drifted W. The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were warned not to approach the volcano within 2 km of the crater.

Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927. This volcano is located within the Ujung Kulon National Park, a UNESCO World Heritage property.

Veniaminof, United States

56.17°N, 159.38°W, Elevation 2507 m

On 4 September low-level ash emissions (less than 3 km or 10,000 ft a.s.l.) from Veniaminof were evident in webcam images and confirmed by observers in Perryville (35 km S), prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. Seismicity was elevated. During 4-6 September pulsating, low-altitude ash plumes were visible from a Perryville webcam and reported by a pilot, and a small thermal anomaly was visible in satellite data. On 7 September the thermal signal increased, suggesting lava fountaining at the summit. Webcam images the next day showed minor ash or steam near the summit cone. Ash deposits on the snowfield formed a “V” shape from the summit, extending to the SSW and SE. On 9 September a lava flow, about 800 m long, was identified on the S flank in satellite data. Witnesses aboard a ferry passing Veniaminof early the next morning noted lava fountaining and an active lava flow. Lava flows continued on 11 September, though were confined to the summit caldera.

Geological summary: Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

JMA reported that there were two events and four explosions at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 3-10 September, with ashplumes rising as high as 1.7 km above the crater rim. Crater incandescence was occasionally visible at night. An explosion at 0304 on 9 September ejected material as far as 700 m. 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.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Elevation 1229 m

Based on satellite data, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 5-10 September ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted SSE, SE, 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.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E, Elevation 1103 m

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 31 August-7 September that sent ash plumes to 4.5 km (14,800 ft) a.s.l. Ash plumes were identified in satellite images drifting about 75 km N and S on 31 August and 4 September, and a thermal anomaly over the volcano was visible during 4-5 September. The Aviation Color Code remained 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.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Elevation 1513 m

KVERT reported that a thermal anomaly over Karymsky was identified in satellite images on 31 August and 5 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Elevation 1222 m

HVO reported that during 5-11 September weak lava activity at Kilauea’s Fissure 8 was characterized by occasional incandescence; during 9-10 September a small collapse pit formed and exposed hot material underneath. Seismicity and ground deformation remain low at the summit, and aftershocks from the M 6.9 earthquake in early May were located along faults on the south flank. The combined rate of sulfur dioxide emission from the summit and the LERZ (<1,000 tonnes/day) were lower than any time since late 2007. A series of small collapses at Pu'u 'O'o Crater during 8-10 September generated visible brown plumes. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Geological summary: Kilauea, which overlaps the E 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 km2, destroying nearly 200 houses and adding new coastline to the island. This volcano is located within the Hawaiian Islands, a UNESCO World Heritage property.

Sabancaya, Peru

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 explosions at Sabancaya averaged 17 per day during 3-9 September. Hybrid earthquakes were infrequent and of low magnitude. Gas-and-ash plumes rose as high as 3.5 km above the crater rim and drifted 50 km SW, E, and NE. The MIROVA system detected seven thermal anomalies, and on 3 September the sulfur dioxide gas flux was high at 2,380 tons/day. The report noted that the public should not 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.

Sangay, Ecuador

2.005°S, 78.341°W, Elevation 5286 m

Based on satellite images and wind model data, the Washington VAAC reported that during 5-8 and 10 September ash emissions from Sangay rose to 4.3-6.7 km (14,000-22,000 ft) a.s.l. and drifted at least 170 km W. A thermal anomaly was visible on 5 September.

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic 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. This volcano is located within the Sangay National Park, a UNESCO World Heritage property.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Elevation 3657 m

Based on analysis of satellite images and wind model data, the Darwin VAAC reported that during 6-7 September ash plumes from Semeru rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted SW.

Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. This volcano is located within the Bromo Tengger Semeru-Arjuno, a UNESCO Biosphere Reserve property.

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 data during 1-7 September. 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 km3 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.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Elevation 924 m

INGV reported that during 3-9 September activity at Stromboli was characterized by ongoing Strombolian activity and degassing from multiple vents within the crater terrace. Explosions mainly from two vents (N1 and N2) in Area N (north crater area, NCA) and three vents (C, S1, and S2) in Area C-S (South Central crater area) occurred at a rate of 2-15 per hour. Low-to-medium-intensity explosions from the N1 vent ejected lapilli and bombs mixed with ash as high as 120 m. Explosions of variable intensity at the N2 vent ejected tephra 150 m high. Vent C produced gas emissions, and periodic low-intensity explosions ejected tephra 80 m high. Incandescent material from S1 jetted 120 m above the crater. Low-intensity explosions at S2 ejected tephra less than 80 m high.

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 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 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. This volcano is located within the Isole Eolie (Aeolian Islands), a UNESCO World Heritage property.

Turrialba, Costa Rica

10.025°N, 83.767°W, Elevation 3340 m

OVSICORI-UNA reported that passive gas-and-ash emissions from Turrialba were continuous during 27 August-5 September, with plumes rising 100 m above the vent. Emissions on 6 September were mostly gas, punctuated by small and sporadic ash plumes. At 1210 on 10 September an event produced an ash plume that rose 300 m above the crater rim and drifted NW.

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 edifice covers an area of 500 km2. 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.

Source: GVP