The Weekly Volcanic Activity Report: October 25 - 31, 2017

The Weekly Volcanic Activity Report: October 25 - 31, 2017

New/activity unrest was reported for 5 volcanoes between October 25 and 31, 2017. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest: Agung, Bali (Indonesia) | Aoba, Vanuatu | Kirishimayama, Kyushu (Japan) | Sarychev Peak, Matua Island (Russia) | Tinakula, Solomon Islands.

Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Cleveland, Chuginadak Island (USA) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Stromboli, Aeolian Islands (Italy) | Turrialba, Costa Rica | Ulawun, New Britain (Papua New Guinea) | Yasur, Vanuatu.

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

Agung, Bali (Indonesia)

8.343°S, 115.508°E, Summit elev. 2995 m

On 29 October PVMBG lowered the Alert level for Agung to 3 (on a scale of 1-4), noting a decline in activity, especially since 20 October. The thermal anomaly in the crater identified in satellite data was less intense in October than in September. Beginning on 20 October GPS data showed a slower deformation rate. Seismic signals decreased in number and amplitude, though low-frequency events continued to indicate magma movement. White fumarolic plumes rose as high as 500 m above the crater rim during 20-29 October; a comparison of video taken by drones on 20 and 29 October showed a relative decrease in the intensity of fumarolic emissions. BNPB stated that, despite the decreased Alert Level, the exclusion zones remained intact (at 6 km, and an additional expansion to 7.5 km in the NNE, SE, S, and SW directions). The number of evacuees was 133,457 (spread out in 385 shelters).

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.

Aoba, Vanuatu

15.4°S, 167.83°E, Summit elev. 1496 m

Based on analyses of satellite imagery and model data, the Wellington VAAC reported that on 29 October ash plumes from Aoba rose 6.1 km (20,000 ft) a.s.l. and drifted S and SE.

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, Summit elev. 1700 m

JMA reported that during 25-31 October activity at Shinmoedake (Shinmoe peak), a stratovolcano of the Kirishimayama volcano group, continued to be slightly elevated. White plumes rose 100-500 m above the crater rim, though weather clouds sometimes prevented visual observations. Almost daily field surveys revealed no particular changes in the fumarolic and fissure areas near the cracks on the W flank of Shinmoedake, nor to the thermally anomalous zone below the crack. Sulfur dioxide fluxes were as high as 200 tons/day. 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.

Sarychev Peak, Matua Island (Russia)

48.092°N, 153.2°E, Summit elev. 1496 m

SVERT reported that a thermal anomaly over Sarychev Peak was identified in satellite images on 29 October. Weather clouds prevented observations on the other days during 24-30 October. The Aviation Color Code remained at Green.

Geological summary: Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.

Tinakula, Solomon Islands

10.386°S, 165.804°E, Summit elev. 796 m

Based on satellite data and information from ground-based observers, the Wellington VAAC reported that during 25 October and the early part of 26 October a low-level eruption at Tinakula was ongoing. Ash emission rose 2.1 km (7,000 ft) a.s.l. and drifted S and SE. A news article from 1 November noted that significant ashfall had covered crops, and the water supplies for an estimated 11,500 people had been contaminated.

Geological summary: The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano that rises 3-4 km from the sea floor at the NW end of the Santa Cruz islands. Tinakula resembles Stromboli volcano in containing a breached summit crater that extends from the 851-m-high summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The satellitic cone of Mendana is located on the SE side. The dominantly andesitic Tinakula volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Frequent historical eruptions have originated from a cone constructed within the large breached crater. These have left the upper flanks of the volcano and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported that sulfur dioxide flux at Aira Caldera’s Sakurajima volcano was high at 1,000 and 1,400 tons per day on 23 and 27 October, respectively. Very small events at Minamidake summit crater were detected during 24-25 and 29-30 October. A thermally anomalous area on the SE flank, near Showa Crater, was identified on 25 October using a thermal camera. 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, Summit elev. 1855 m

Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 27 October an ash plume from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted E and 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, Summit elev. 1730 m

Based on satellite observations, AVO reported that the lava dome in Cleveland's summit crater continued to grow, and by 23 October it had dimensions of 140 x 110 m. A small, 30-second-long explosion was recorded at 1045 on 28 October in seismic and infrasound data. Weather conditions were overcast with clouds at approximately 4.6 km (15,000 ft) a.s.l.; no volcanic plumes associated with the explosion were identified in satellite images emerging above the cloud level. A small explosion was recorded at 0320 on 30 October, though no ash plume was observed rising above the weather clouds at 2.4 km (8,000 ft) a.s.l. in satellite data. Slightly elevated surface temperatures were detected the next day. The Aviation Color Code remained 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, Summit elev. 1229 m

Based on analyses of satellite imagery, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 25-31 October ash plumes from Dukono rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted NE, E, and SE.

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, Summit elev. 1103 m

Based on observations by volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, explosions during 20-27 October generated ash plumes that rose as high as 2 km (6,600 ft) a.s.l. 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, Summit elev. 1513 m

On 27 October KVERT reported that gas-and-steam activity at Karymsky continued, and that the last ash-bearing explosions occurred on 3 October. The Aviation Color Code was lowered to Green (the lowest 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, Summit elev. 1222 m

During 25-31 October 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 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.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m

Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosive activity at Sabancaya slightly decreased compared to the previous week; there was an average of 43 explosions recorded per day during 23-29 October. Seismicity was dominated by long-period events, with a relatively steady rate of signals indicating emissions and an increasing number of hybrid events. Gas-and-ash plumes rose 3.9 km above the crater rim and drifted 30 km NW, NE, E, and SE. The MIROVA system detected eight thermal anomalies. The sulfur dioxide flux was high, at 2,635 tons per day on 29 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, Summit elev. 3283 m

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 20-22 and 25 October. 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.

Sinabung, Indonesia

3.17°N, 98.392°E, Summit elev. 2460 m

Based on observations by PVMBG, satellite images, and model data, the Darwin VAAC reported that on 31 October ash plumes from Sinabung rose 4 km (13,000 ft) a.s.l.

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, Summit elev. 924 m

INGV reported that a strong explosive sequence began at the vents of Stromboli’s southern crater area (Area CS) at 1604 on 23 October. The explosions ejected coarse pyroclastic material onto the Pizzo Sopra la Fossa, and produced a dense ash plume that quickly dissipated to the SE.

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.

Turrialba, Costa Rica

10.025°N, 83.767°W, Summit elev. 3340 m

OVSICORI-UNA reported that events at Turrialba at 1030, 1105, and 1445 on 30 October generated ash plumes that rose 200-500 m above the crater rim and drifted NW, W, and SW. Ashfall was reported in the community of Pacayas (about 12 km SSW). OVSICORI-UNA noted that the ash emissions from the event at 1445 rose from the reddish 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 Britain (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 26-27 October ash plumes from Ulawun rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 130 km S and SE.

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.

Yasur, Vanuatu

19.532°S, 169.447°E, Summit elev. 361 m

On 31 October the Vanuatu Geohazards Observatory stated that the Alert Level for Yasur remained at 2 (on a scale of 0-4) and that, based on seismic data, explosions continued to be intense. VGO reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 395-m-radius permanent exclusion zone, and that volcanic ash and gas could reach areas impacted by trade winds.

Geological summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Source: GVP

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