The Weekly Volcanic Activity Report: October 23 - 29, 2019

The Weekly Volcanic Activity Report: October 23 - 29, 2019

New activity/unrest was reported for 4 volcanoes from October 23 - 29, 2019. During the same period, ongoing activity was reported for 12 volcanoes.

New activity/unrest: Klyuchevskoy, Central Kamchatka (Russia) | Kuchinoerabujima, Ryukyu Islands (Japan) | Pavlof, United States | Shishaldin, Fox Islands (USA). 

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Kanlaon, Philippines | Karangetang, Siau Island (Indonesia) | Krakatau, Indonesia | Nevados de Chillan, Chile | Piton de la Fournaise, Reunion Island (France) | Sabancaya, Peru | Sangeang Api, Indonesia | Sheveluch, Central Kamchatka (Russia) | White Island, North Island (New Zealand).

New activity/unrest

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Summit elev. 4754 m

A small amount of ash began to be visible in gas-and-steam emissions at Klyuchevskoy beginning at 1020 on 24 October, prompting KVERT to raise the Aviation Color Code to Yellow (the second lowest level on a four-color scale). Later that day video images showed an ash plume rising as high as 6 km (19,700 ft) a.s.l. and drifting 40 km NE. The Aviation Color Code was raised to Orange. KVERT and the Tokyo VAAC noted that during 25-28 October ash plumes rose to 5.5 km (18,000 ft) a.sl. and drifted 15-20 km SE, E, and NW. A weak thermal anomaly over the volcano was identified on 18 and 24 October.

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.

Kuchinoerabujima, Ryukyu Islands (Japan)

30.443°N, 130.217°E, Summit elev. 657 m

A large shallow earthquake at Kuchinoerabujima was recorded at 2133 on 27 October, prompting JMA to raise the Alert Level to 3 (the middle level on a scale of 1-5) within a few hours. The report also stated that the number of volcanic earthquakes had increased on 18 October. A large earthquake was also detected on 18 October but had occurred at a slightly deeper location (below the W part of Shindake Crater) than the 27 October event.

Geological summary: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. The youngest cone, centrally-located Shindake, formed after the NW side of Furudake was breached by an explosion. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Pavlof, United States

55.417°N, 161.894°W, Summit elev. 2493 m

AVO reported that after a small explosion at Pavlof was recorded on 19 October and before 25 October clear satellite and webcam views did not show any deposits associated with the event. Weakly elevated surface temperatures and a small steam plume were occasionally visible. No other activity was detected during 26-29 October. The Aviation Color Code remained at Yellow and the 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.

Shishaldin, Fox Islands (USA)

54.756°N, 163.97°W, Summit elev. 2857 m

Pilot and local observations as well as webcam views all indicated that the incandescence at Shishaldin’s summit crater was from low-level Strombolian activity during 21-22 October. Seismicity and infrasound signals were consistent with low-level eruptive activity, and a steam plume was persistent. By 23 October lava had filled the crater and during 23-24 October overflowed the N crater rim. A 200-m-long lava flow on the N flank melted snow and caused a lahar which traveled 2.9 km and stopped at about 1,230 m elevation. A smaller lava flows caused a 1-km-long lahar to descend the NE flank. Spatter accumulated around the crater rim and melted snow. On 25 October AVO noted that trace ash deposits had extended at least 8.5 km SE.

Low-level eruptive activity continued during 26-29 October. Seismicity remained elevated, with periods of high-amplitude tremor. Small explosions were recorded during 27-28 October. A satellite image from 28 October showed a 850-m-long SWIR anomaly on the NW flank from a lava flow. A central spatter cone was visible. Spatter deposits on the snow at the upper flanks was evident, and tephra deposits extended about 2.5 km N. The lahar on the NW flank branched extensively at lower elevations and was at least 5 km long. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that two eruptive events at Minamidake crater (at Aira Caldera’s Sakurajima volcano) recorded during 25-28 October generated plumes that rose 1.2 km. 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, Summit elev. 1229 m

Based on satellite and wind model data, and information from PVMBG, the Darwin VAAC reported that during 23-29 October ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

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

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 18, 20-21, and 23 October that sent ash plumes up to 3 km (10,000 ft) a.s.l. Ash plumes drifted N, E, and SE. A weak thermal anomaly was identified in satellite images on 20 October. 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.

Kanlaon, Philippines

10.412°N, 123.132°E, Summit elev. 2435 m

On 25 October PHIVOLCS lowered the Alert Level for Kanlaon to 0 (on a scale of 0-5) noting that volcanic activity had declined to baseline levels in June and had continued to be low.

Geological summary: Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.

Karangetang, Siau Island (Indonesia)

2.781°N, 125.407°E, Summit elev. 1797 m

PVMBG reported that during 21-27 October lava continued to effuse from Karangetang’s Main Crater (S), traveling as far as 1.8 km down the Nanitu, Pangi, and Sense drainages on the SW and W flanks. Incandescence from both summit craters was visible at night. Sometimes dense white plumes rose to 500 m above the summit. The Alert Level remained at 2 (on a scale of 1-4).

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Krakatau, Indonesia

6.102°S, 105.423°E, Summit elev. 813 m

PVMBG reported that during 21-27 October diffuse white plumes rose as high as 100 m above Anak Krakatau’s active vent. As many as three eruptive events per day during 25-27 October generated ash plumes that rose as high as 200 m above the vent. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km-radius hazard zone from 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 or 535 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, and left only a remnant of Rakata. 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.

Nevados de Chillan, Chile

36.868°S, 71.378°W, Summit elev. 3180 m

ONEMI and SERNAGEOMIN reported that during 22-24 October white-to-gray plumes from Nevados de Chillán’s Nicanor Crater rose as high as 1.3 km above the rim and drifted SE. Explosions ejecting incandescent material onto the flank were visible at night. A new lava flow from the crater had begun to effuse on 16 October and continued to very slowly advance on the NE flank. Diffuse white plumes rose from the crater on 25 and 29 October; cloudy weather obscured views in between those dates. The volcano Alert Level remained at Orange, the second highest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián, and stated that the public should stay at least 3 km away from the crater on the SW flank and 5 km away on the ENE flank.

Geological summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. 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, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. 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 elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

Piton de la Fournaise, Reunion Island (France)

21.244°S, 55.708°E, Summit elev. 2632 m

OVPF reported that inflation began to be detected at Piton de la Fournaise on 11 October and a seismic crisis was recorded on 21 October. A second seismic crisis began at 0415 on 25 October accompanied by rapid deformation. Volcanic tremor began at 1440, signaling the arrival of magma to the surface; the eruption area was not visible in webcam views. Field observers first saw two active fissures at the S part of l’Enclos Fouqué at an elevation of 1,400 m. Several lava flows were identified, with the front of the longest flow reaching an area 2 km upstream from National Road RN2 by 1700. Tremor intensity began to decline around three hours after the start of the eruption and continued to decline through the morning of 26 October. That same morning there was one active vent producing 10-20-m-high lava fountains. Downstream of piton Tremblet the flow forked and by 1700 on 26 October the leading toe was about 250 m from RN2. On 27 October tremor intensity fluctuated concurrently with the variable intensity of cone formation. The cone had grown to 10 m high and lava was ejected 20 m above the cone rim. Only one lava flow was active and was 200 m long; the flow near RN2 had not progressed. The eruption ceased at 1630.

Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Sabancaya, Peru

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

Instituto Geofísico del Perú (IGP) reported that an average of 48 low-to-medium intensity explosions per day occurred at Sabancaya during 21-27 October. Gas-and-ash plumes rose as high as 2.5 km above the summit and drifted W, SW, and S. There were 15 thermal anomalies identified in satellite data. The report noted that the lava dome in the summit crater had been slowing extruding since February and filling in the N part of the crater, though the rate of the extrusion had increased in recent months. On 26 October Observatorio Vulcanológico del INGEMMET (OVI) conducted a drone overflight and captured video of the lava dome. The estimated volume of the lava dome was 4.6 million cubic meters based on the footage. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of 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.

Sangeang Api, Indonesia

8.2°S, 119.07°E, Summit elev. 1912 m

The Darwin VAAC reported that during 26-28 October multiple discrete ash emissions from Sangeang Api rose to 2.1-2.7 km (7,000-9,000 ft) a.s.l. and dissipated rapidly to the NW, WNW, and W. A thermal anomaly was visible in satellite images on 26 October. The Alert Level remained at 2 (on a scale of 1-4).

Geological summary: Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, Doro Api and Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512, most of them during in the 20th century.

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 18-25 October. Resuspended ash drifted 110 km SE during 19-20 October. Explosions recorded on 21 October generated ash plume that rose to 10-11 km (32,800-36,100 ft) a.s.l. and drifted 1,300 km SE. 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.

White Island, North Island (New Zealand)

37.52°S, 177.18°E, Summit elev. 321 m

GeoNet reported that sulfur dioxide emissions and the level of volcanic tremor both increased at White Island over the past several months, and were at the highest levels since 2016. The report noted that the changes could be related to a variety of processes, including an increased level of unrest, though the level of hazards on the island remained unchanged; the Volcanic Alert Level remained at 1 (the second lowest level on a 0-5 scale) and the Aviation Color Code remained at Green. The crater lake level continued to rise and impact surface activity around vents, creating small-scale geysering, on the W side of the crater floor.

Geological summary: Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.

Source: GVP

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