Environment

The Weekly Volcanic Activity Report: November 21


New activity/unrest was observed at 5 volcanoes between November 21 and 27, 2018. During the same period, ongoing activity was reported for 15 volcanoes.

New activity/unrest: Fuego, Guatemala | Karangetang, Siau Island (Indonesia) | Mayon, Luzon (Philippines) | Suwanosejima, Ryukyu Islands (Japan) | Veniaminof, United States.

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Krakatau, Indonesia | Kuchinoerabujima, Ryukyu Islands (Japan) | Merapi, Central Java (Indonesia) | Pacaya, Guatemala | Rincon de la Vieja, Costa Rica | Sabancaya, Peru | Sangay, Ecuador | Santa Maria, Guatemala | Semisopochnoi, United States | Sheveluch, Central Kamchatka (Russia) | 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

Fuego, Guatemala

14.473°N, 90.88°W, Elevation 3763 m

On 23 November INSIVUMEH reported that during the previous few days moderate explosions at Fuego generated shock waves that vibrated structures within 20 km. Ash plumes from the explosions rose 1.3 km above the cone in the summit crater and drifted 20 km W and SW, causing ashfall in areas downwind including Panimaché (8 km SW), El Porvenir (8 km ENE), Morelia (9 km SW), Santa Sofia (12 km SW), Sangre de Cristo (8 km WSW), Palo Verde Estate, and San Pedro Yepocapa (8 km NW). Incandescent material was ejected 150 m high, causing avalanches, some that traveled long distances in the Las Lajas (SE), Ceniza (SSW), and Seca (W) drainages and reached vegetated areas. During 24-25 November there were 12-15 weak-to-moderate explosions per hour, generating ash plumes that rose as high as 1.1 km and drifted 20-25 km W and SW. Shock waves continued to vibrate local structures, and ashfall was again reported in Panimaché, El Porvenir, Morelia, Santa Sofia, Sangre de Cristo, Palo Verde Estate, and San Pedro Yepocapa. Moderate-to-strong Vulcanian explosions on 26 November generated ash plumes that rose as high as 1.2 km and drifted N. The explosions were heard, and shock waves felt, mostly within 25 km, though some explosions were audible to residents of Guatemala City (city center is about 40 km ENE). Explosions continued the next day at a rate of 10-15 per hour. Ash plumes rose as high as 1.3 km and drifted 20-25 km W and SW. Incandescent material was ejected 200 m high, and avalanches of material descended multiple drainages. Ashfall was reported in areas downwind.

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.

Karangetang, Siau Island (Indonesia)

2.781°N, 125.407°E, Elevation 1797 m

PVMBG reported that at 1314 on 25 November an eruption at Karangetang produced an ash plume that rose at least 500 m above the crater rim; weather clouds prevented clear views of the plume. The Aviation Color Code was raised to Orange, though the Alert Level remained at 2 (on a scale of 1-4).

Geologic background: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. 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 has also produced pyroclastic flows.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E, Elevation 2462 m

PHIVOLCS reported that during 21-26 November white steam plumes periodically emitted from Mayon rose as high as 750 m and drifted WSW and SW. Crater incandescence was visible at night during 24-27 November. Two phreatic explosions were recorded during 0759 and 0805 on 26 November. The events generated grayish ash plumes that rose 300-500 m and drifted SW. 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, Elevation 796 m

JMA reported that 16 explosions at Suwanosejima’s Ontake Crater were recorded during 16-22 November. The highest ash plume rose 2 km, and material was ejected 300 m from the crater. Ashfall was reported in an area 4 km SSW on 17 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.

Veniaminof, United States

56.17°N, 159.38°W, Elevation 2507 m

Ash emissions from the cone in Veniaminof’s ice-filled summit caldera significantly increased overnight during 20-21 November, prompting AVO to raise the Aviation Color Code to Red and the Volcano Alert Level to Warning (the highest levels on four-level scales). Ash emissions rose to below 4.6 km (15,000 ft) a.s.l.and drifted more than 240 km SE. On 21 November observers and webcam views in Perryville (35 km SE) indicated continuous ash emissions through most of the day; ash plumes drifted SE, extending as far as 400 km by around 1445. A short eruptive pulse was recorded during 1526-1726, and then afterwards ash plumes rose to below 3 km (10,000 ft) a.s.l. Low-altitude ash emissions on 22 November drifted 100 km S. Minor ashfall was reported in Perryville. AVO lowered the Aviation Color Code and Volcano Alert Level to Orange and Watch, respectively, because of decreased ash emissions. Elevated thermal anomalies were identified in satellite data overnight, and incandescence was visible from a Perryville webcam, suggesting continuing lava effusion which had been obscured by the increased period of ash emissions. Lava effusion was persistent through 27 November.

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.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

JMA reported that four events at Minamidake crater (at Aira Caldera’s Sakurajima volcano) were recorded during 19-22 November, producing ash plumes that rose as high as 1.6 km above the crater rim. Material was ejected 500-700 m from the crater. Occasional, very small events occurred during 22-26 November. Crater incandescence was visible at night during 20-21 November, for the first time since 20 September, and continued through 26 November. 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.

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 21-27 November ash plumes from Dukono rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted NE, E, and SE.

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, Elevation 1103 m

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 15-23 November that sent ash plumes to 3.2 km (10,500 ft) a.s.l. Ash plumes drifted NE and S. 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.

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Elevation 1325 m

The Darwin VAAC reported that on 26 November an ash plume from Ibu was identified in satellite images rising to 1.8 km (6,000 ft) a.s.l. and drifting SE. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.

Geologic background: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Krakatau, Indonesia

6.102°S, 105.423°E, Elevation 813 m

PVMBG reported that events at Anak Krakatau were recorded at 0611 on 24 November, at 0810 on 25 November, and at 0900 and 1037 on 26 November, each lasting between 30 and 42 seconds. Ash plumes from the events rose 300-600 m and drifted NE and SW; the ash plumes from the 1037 event were dense and black. 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, Elevation 657 m

JMA reported that during 22-26 November intermittent events at Kuchinoerabujima’s Shindake Crater generated plumes that rose as high as 2.1 km above the crater rim. 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, Elevation 2910 m

PVMBG reported that during 16-22 November the lava dome in Merapi’s summit crater grew at a rate of 2,600 cubic meters per day, slower than the previous week. By 21 November the volume of the dome, based on photos taken from the SE, was an estimated 308,000 cubic meters. White emissions of variable density rose a maximum of 125 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.

Pacaya, Guatemala

14.382°N, 90.601°W, Elevation 2569 m

INSIVUMEH reported that during 24-27 November Strombolian explosions at Pacaya’s Mackenney Crater ejected material as high as 25 m above the crater rim. As many as three lava flows were active on the NW flanks, advancing towards Cerro Chino. Minor avalanches of material descended the SE flank during 26-27 November.

Geologic background: Eruptions from Pacaya, one of Guatemala’s most active volcanoes, are frequently visible from Guatemala City, the nation’s capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W, Elevation 1916 m

OVSICORI-UNA reported that at 0237 on 27 November a hydrothermal explosion at Rincón de la Vieja produced a plume of water vapor and gas that rose 600 m above the crater rim and drifted SW.

Geologic background: Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the “Colossus of Guanacaste,” it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

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 an average of 20 explosions per day occurred at Sabancaya during 19-25 November. Long-period seismic events were recorded, and hybrid earthquakes were infrequent and of low magnitude. Gas-and-ash plumes rose as high as 2.7 km above the crater rim and drifted 40 km NW and N. MIROVA detected six thermal anomalies, and on 22 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.

Sangay, Ecuador

2.005°S, 78.341°W, Elevation 5286 m

IG reported that since 8 August activity at Sangay was characterized by the extrusion of lava flows on the ESE flank and ash emissions that rose between 500 and 1,500 m and mainly drifted W and NW. Lava flows were 1-2 km long, though block avalanches from the flow fronts traveled additionally as far as 5 km. The seismic network recorded more than 50 signals per day indicating explosions. The activity continued at least through 21 November; the report noted that this phase has lasted longer than any other since 2015.

Geologic background: 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.

Santa Maria, Guatemala

14.757°N, 91.552°W, Elevation 3745 m

INSIVUMEH reported that during 24-27 November explosions at Santa María’s Santiaguito lava-dome complex generated ash plumes that rose 700-900 m and drifted SW, causing ashfall in Monte Claro. Avalanches of material descended the SE and NE flanks of the lava dome.

Geologic background: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semisopochnoi, United States

51.93°N, 179.58°E, Elevation 1221 m

AVO reported that no evidence of activity at Semisopochnoi had been detected since an explosion was recorded in infrasound data on 31 October. The satellite link for transmitting seismic data failed on 1 November, though no activity was observed in satellite or infrasound data since then. As a result, the Aviation Color Code was lowered to Yellow and Volcano Alert Level was lowered to Advisory (both are the second lowest levels on four-level scales) on 21 November.

Geologic background: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island’s northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that a weak thermal anomaly over Sheveluch was identified in satellite images during 16-17 and 19-20 November. The Aviation Color Coderemained 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, Elevation 3340 m

OVSICORI-UNA reported that at 0710 on 22 November an event at Turrialba generated an ash plume that rose 100 m above the crater rim and drifted W. The next day there were frequent pulses of ash. During 23-25 November occasional Strombolian explosions ejected lava bombs that were deposited near the crater; residents of Cascajal de Coronado reported hearing several booming sounds. Ash plumes rose as high as 500 m. During 26-27 November passive emissions with small quantities of ash were visible. Minor ashfall was reported in San Jose (Cascajal de Coronado and Dulce Nombre), San Pedro Montes de Oca, and neighborhoods of Heredia.

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.

Source: GVP



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