The Weekly Volcanic Activity Report: November 14 - 20, 2018

The Weekly Volcanic Activity Report: November 14 - 20, 2018

New activity/unrest was reported for 3 volcanoes between November 14 and 20, 2018. During the same period, ongoing activity was reported for 13 volcanoes.

New activity/unrest: Fuego, Guatemala | Mayon, Luzon (Philippines) | Suwanosejima, Ryukyu Islands (Japan).

Ongoing activity: Aira, Kyushu (Japan) | Ambrym, Vanuatu | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Kadovar, Papua New Guinea | Krakatau, Indonesia | Kuchinoerabujima, Ryukyu Islands (Japan) | Merapi, Central Java (Indonesia) | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Turrialba, Costa Rica | Veniaminof, United States | 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

Fuego, Guatemala

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

INSIVUMEH and CONRED reported that activity at Fuego increased on 18 November, heralding the fifth effusive phase of 2018. Incandescent material was ejected 200-300 m above the crater rim and a lava flow in the Ceniza (SSW) drainage reached 2.5 km in length. Avalanches of material from the lava flow reached vegetated areas. Explosions occurring at a rate of 8-17 per hour generated ash plumes that rose at least 1.2 km and drifted 20-25 km W and SW. Ashfall was reported in areas downwind including Morelia (9 km SW), Santa Sofia (12 km SW), Sangre de Cristo (8 km WSW), Panimaché I and II (8 km SW), and Finca Palo Verde. Volcanic material also accumulated in the Taniluyá (SW) and Seca (W) drainages causing increased risk of avalanches. Later that day explosions became stronger, and incandescent material was ejected 400 m high. Ashfall continued to be reported in local communities. CONRED reported that a portion of National Route 14 was closed, and evacuations began in some local areas.

Strombolian activity continued to intensify on 19 November with stronger explosions and increased seismicity. Incandescent material was ejected as high as 1 km above the crater. Ash plumes rose as high as 3.2 km and drifted 20-60 km W, SW, and NE. Pyroclastic flows descended the Seca drainage, and, along with ash emissions from the crater, caused ashfall in multiple areas including Santa Sofia, Sangre de Cristo, Panimaché I and II, and Finca Palo Verde. The lava flow in the Ceniza drainage advanced to 3 km long and produced avalanches from the flow front. Avalanches of tephra also descended the Seca, Ceniza, Taniluyá, Las Lajas, and Honda (E) drainages, reaching vegetated areas. CONRED noted that 3,925 people had been evacuated.

INSIVUMEH noted that the effusive phase was over at 1800 on 19 November, having lasted for 32 hours. Explosions continued during 19-20 November, generating ash plumes which rose 0.8-1 km and drifted 10-15 km NW, W, and SW. Ash fell in areas downwind including El Porvenir (8 km ENE), Morelia, Santa Sofia, Sangre de Cristo, Panimaché I and II, and Finca Palo Verde. Incandescent material was ejected 100-300 m high, casing avalanches, some that traveled long distances. Some explosions generated shock waves that rattled nearby structures.

Geologic background: 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.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E, Summit elev. 2462 m

PHIVOLCS reported that during 14-20 November white steam plumes emitted from Mayon drifted downslope and then in multiple directions. Crater incandescence was visible at night. The Alert Level remained at 2 (on a 0-5 scale) and PHIVOLCS reminded residents to stay away from the 6-km-radius Permanent Danger Zone and the 7-km Extended Danger Zone on the SSW and ENE flanks.

Geologic background: Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer-term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E, Summit elev. 796 m

JMA reported that four explosions at Suwanosejima’s Ontake Crater were recorded during 9-16 November. The highest ash plume rose 2 km, the first time a plume from Ontake Crater rose that high since 4 April. Material was ejected 700 m from the crater. Ashfall was reported in an area 4 km SSW on 15 November. The Alert Level remained at 2 (on a 5-level scale).

Geologic background: 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.


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Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that an explosion at Minamidake crater (at Aira Caldera’s Sakurajima volcano) was recorded at 0043 on 14 November, producing a large ash cloud that rose over 4 km above the crater rim. Incandescent material was ejected more than 1 km from the crater. The report noted that this was the first occurrence of an ash plume rising above 4 km since 16 July 2018. Two events occurred during 16-19 November with the larger plume rising 1.6 km into the clouds. The Alert Level remained at 3 (on a 5-level scale).

Geologic background: 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.

Ambrym, Vanuatu

16.25°S, 168.12°E, Summit elev. 1334 m

On 15 November the Vanuatu Meteorology and Geo-hazards Department (VMGD) reported that the lava lakes in Ambrym’s Benbow and Marum craters continued to be active during October and November, and produced substantial and sustained gas-and-steam emissions. The Alert Level remained at 2 (on a scale of 0-5); the report reminded the public to stay outside of the Permanent Danger Zone defined as a 1-km radius from Benbow Crater and a 2.7-km radius from Marum Crater.

Geologic background: Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Summit elev. 1229 m

Based on satellite data and wind model data, the Darwin VAAC reported that during 14-15 and 19-20 November 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.

Geologic background: 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 9-15 November that sent ash plumes to 4.5 km (14,800 ft) a.s.l. Ash plumes drifted E. A weak thermal anomaly was identified in satellite data during 12-13 November. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geologic background: 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.

Kadovar, Papua New Guinea

3.608°S, 144.588°E, Summit elev. 365 m

The Darwin VAAC reported that discrete, low-level events at Kadovar regularly occurred on 14 November based on satellite data. Ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted E.

Geologic background: The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.

Krakatau, Indonesia

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

PVMBG reported that seven events at Anak Krakatau were recorded between 0840 on 14 November and 0601 on 15 November. Each event lasted for 33-175 seconds, based on the seismic data, and produced ash plumes that rose 0.3-1 km above the crater rim and drifted N, ENE, and E. A 212-second-long event at 0524 on 16 November generated a dense black ash plume that rose 600 m and drifted NE. An event at 0532 lasted 207 seconds and generated an ash plume that rose 300 m and drifted NE. 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.

Geologic background: 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.

Kuchinoerabujima, Ryukyu Islands (Japan)

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

JMA reported that intermittent events at Kuchinoerabujima’s Shindake Crater had been recorded since 21 October, and crater incandescence began to be periodically visible on 6 November. Ash plumes rose as high as 1.2 km above the crater rim during 12-19 November and, according to the Tokyo VAAC, drifted in multiple directions. During fieldwork on 14 and 15 November observers noted no changes to the thermal areas in the crater. The Alert Level remained at 3 (on a scale of 1-5).

Geologic background: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km west 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 Shintake, formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake 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.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Summit elev. 2910 m

PVMBG reported that during 9-15 November the lava dome in Merapi’s summit crater grew at a rate of 2,400 cubic meters per day, slower than the previous week. By 14 November the volume of the dome, based on photos from the SE sector, was an estimated 290,000 cubic meters. White emissions of variable density rose a maximum of 200 m above the summit. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone.

Geologic background: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

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 an average of 20 explosions per day occurred at Sabancaya during 12-18 November. Long-period seismic events were recorded, and hybrid earthquakes were infrequent and of low magnitude. Gas-and-ash plumes rose as high as 3 km above the crater rim and drifted 40 km NW, SW, and S. MIROVA detected seven thermal anomalies, and on 13 November the sulfur-dioxide gas flux was high at 3,000 tons per day. The report noted that the public should not approach the crater within a 12-km radius.

Geologic background: 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 explosions at Sheveluch on 9 November generated ash plumes that drifted as far as 460 km E. A weak thermal anomaly was identified in satellite images during 9-11 and 15 November. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geologic background: 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.

Turrialba, Costa Rica

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

OVSICORI-UNA reported that periodic, passive ash emissions at Turrialba continued to be visible in webcam images or during cloudy conditions inferred from the seismic data during 13-19 November.

Geologic background: 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.

Veniaminof, United States

56.17°N, 159.38°W, Summit elev. 2507 m

AVO reported that the eruption from the cone in Veniaminof’s ice-filled summit caldera, continued at low levels during 14-20 November. Satellite and webcam data showed elevated surface temperatures from minor lava spattering and lava effusion. Relatively continuous low-amplitude tremor was recorded. Steam and diffuse ash plumes were periodically identified in webcam and satellite images; plumes rose as high as 4.9 km (16,000 ft) a.s.l. on 16 November. Recent satellite data showed that the lava flows had traveled as far as 1.2 km from the vent. Fractures in the ice sheet adjacent to the lava flow continued to grow due to meltwater flowing beneath the ice sheet. The Aviation Color Code remained at Orange (the second highest level on a four-color scale) and the Volcano Alert Level remained at Watch (the second highest level on a four-level scale).

Geologic background: 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.

Yasur, Vanuatu

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

On 15 November the Vanuatu Meteorology and Geo-hazards Department (VMGD) reported that ongoing explosions at Yasur were sometimes strong during October and November, based on visual observations and seismic data. The Alert Level remained at 2 (on a scale of 0-4). VMGD 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.

Geologic background: 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

Comments

Carol Harrison 18 days ago

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