Active volcanoes in the world: August 20 - August 26, 2014

Active volcanoes in the world: August 20 - August 26, 2014

New activity/unrest was observed at 1 volcano from August 20 - August 26, 2014. Ongoing activity was observed at 20 volcanoes.

New activity/unrest: Bardarbunga, Iceland

Ongoing activity: Aira, Kyushu (Japan)  | Bagana, Bougainville (Papua New Guinea)  | Batu Tara, Komba Island (Indonesia)  | Dukono, Halmahera (Indonesia)  | Fuego, Guatemala  | Kilauea, Hawaiian Islands (USA)  | Kuchinoerabujima, Ryukyu Islands (Japan)  | Kusatsu-Shiranesan, Honshu (Japan)  | Mayon, Luzon (Philippines)  | Pacaya, Guatemala  | Popocatepetl, Mexico  | Reventador, Ecuador  | Sabancaya, Peru  | San Miguel, El Salvador  | Santa Maria, Guatemala  | Sheveluch, Central Kamchatka (Russia)  | Shishaldin, Fox Islands (USA)  | Tungurahua, Ecuador  | Ubinas, Peru  | Zhupanovsky, Eastern Kamchatka (Russia)

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 on these pages are preliminary and subject to change as events are studied in more detail.

New activity/unrest

Bardarbunga, Iceland
64.63°N, 17.53°W, Summit elev. 2009 m

During 20-26 August the Icelandic Met Office reported ongoing high rates of seismic activity at Bárdarbunga volcano. Global Postioning System and seismic data indicated that an intrusive dike had increased from 25 to 40 km in length E, NE, and N of the volcano over the past week. During 22-26 August several earthquakes in the 4.7-5.7 magnitude range had been detected at or near the volcano. On 23 August seismic tremor indicated a small lava-eruption 150-400 m beneath the Dyngjujökull glacier, prompting a change in the Aviation Color Code to Red. On 24 August observations from an overflight indicated there was no eruption and the Aviation Color Code was changed to Orange. On 26 August the location of the seismicity was located primarily along the 10 km long tip of the dike that extended 5 km beyond the glacier margin.

Geologic summary: The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.

Ongoing activity

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m

During 20-26 August JMA reported 17 explosions from Showa Crater at Aira Caldera’s Sakurajima volcano that were accompanied by volcanic earthquakes and volcanic tremor, and which ejected ballistics 500-800 m away. On 20-24 August clear incandescence was visible using high-sensitivity camera at night. On 20-26 August the Tokyo VAAC reported explosions with plumes that rose to an altitude of 1.2-2.7 km (4,000-9,000 ft) a.s.l. and drifted NE and N, though volcanic ashcould not be identified in satellite data. The Alert Level remained at 3 (on a scale of 1-5).

Geologic 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)
6.14°S, 155.195°E, Summit elev. 1750 m

During 25-26 August the Darwin VAAC reported ash plumes at Bagana that rose 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted 65-120 km W and WNW. TheAviation Color Code remained at Orange.

Geologic summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical, roughly 1750-m-high lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is frequent and is 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 volcano's flanks on all sides.

Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E, Summit elev. 748 m

Based on analyses of satellite data, the Darwin VAAC reported an ash plume from Batu Tara on 26 June that drifted 35-55 km NW and W. The Aviation Color Code remained at Orange.

Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (fomerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.

Dukono, Halmahera (Indonesia)
1.68°N, 127.88°E, Summit elev. 1335 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 20-21 August a low-level plume from Dukono rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 37 km NW and N.

Geologic 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. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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

During 20-26 August, INSIVUMEH reported that weak to moderate explosions at Fuego expelled blocks up to 800 m above the rim. On most days white plumes rose 200-600 m above the crater and drifted SW and W and on 25 August the white plume rose to 4.2 km (13,800 ft) above the crater. Ash plumes rose 4.1-4.6 km (13,500-15,100 ft) a.s.l. and drifted 10-15 km NE, W, S and SW. Ashfall was reported in villages Morelia (9 km SW), Panimaché (8 km SW), Panimaché II, Sangre de Cristo (8 km WSW), and Hagia Sophia. On most days rumbling was heard around the volcano and rattled structures near the volcano on 24 August. On 21 and 25 August were jet engine like sounds lasting 1-4 minutes. Weak to moderate avalanches of blocks were channeled into the canyons Las Lajas (SE), Trinidad (S), Ceniza (SSW), Taniluyá (SW), Santa Teresa and Honda.

Geologic summary: 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.

Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Summit elev. 1222 m

During 20-26 August HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater. Gas emissions remained elevated. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas; smaller particles may have been dropped several kilometers away. On 23 August part of the deep inner ledge surrounding the lava lake collapsed, disrupting the lava lake surface for a short time.

During 20-26 August glow was visible overnight above several outgassing openings in Pu`u `O`o's crater floor and on 20-21 August glow was visible at skylights along the June 27th flow lava tube. On 22 August observations during a helicopter flight showed the June 27th flow had poured into a deep, large crack of Kilauea’s east rift zone and produced a line of steaming that advanced eastward. On 25 August an overflight confirmed that lava in the crack had returned to the surface, creating a small, isolated pad of lava. On 26 August the farthest portion of this new pad of lava was about 11.4 km from the vent on Pu`u `O`o and about 3.1 km from the eastern boundary of the Wao Kele o Puna Forest Reserve. A separate branch of the June 27th flow continued to advance into a different section of forest northeast of Pu`u `O`o and was 7.3 km from the vent on 25 August.

Geologic 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 of Kilauea 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.

Kuchinoerabujima, Ryukyu Islands (Japan)
30.443°N, 130.217°E, Summit elev. 657 m

JMA reported that during 20-26 August there were few episodes of volcanic tremor and volcanic earthquakes, with no explosions at Kuchinoerabujima. On most days a white plume rose 20-400m above the crater rim. The Alert Level for Kuchinoerabujima remained at 3 (on a scale of 1-5).

Geologic summary: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyus, 15 km west of Yakushima. Furutake, Shintake, and Noike were erupted from south to north, respectively, to form a composite cone that is parallel to the trend of the Ryukyu Islands. The highest peak, Furutake, reaches only 657 m above sea level. The youngest cone, 640-m-high Shintake, was 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.

Kusatsu-Shiranesan, Honshu (Japan)
36.618°N, 138.528°E, Summit elev. 2165 m

On 20-22 August JMA reported volcanic earthquakes continuing at Kusatsu-Shiranesan’s crater, although decreased from early August and tremor was absent. The Alert Level remains at 2 (on a scale of 1-5).

Geologic summary: The summit of Kusatsu-Shiranesan volcano, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the east, south and SW flanks. The latest eruptive stage began about 14,000 years ago. All historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries.

Mayon, Luzon (Philippines), 13.257°N, 123.685°E, Summit elev. 2462 m

During 20-26 PHIVOLCS reported no incandescence at Mayon, despite the emergence of a summit dome, slight ground deformation, and increased volcanic gas emission. On most days seismic instruments recorded a few rock falls and sparse earthquakes. During 20-25 August observers noted moderate emission of white steam plumes that drifted SW, WSW, NE, ENE, and SSW. The Alert Level remained at 2 (on a scale of 0-5).

Geologic summary: Beautifully symmetrical Mayon volcano, which rises to 2462 m above the Albay Gulf, is the Philippines' most active volcano. The structurally simple volcano has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions at this basaltic-andesitic volcano 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. Mayon's most violent eruption, in 1814, killed more than 1200 people and devastated several towns.

Pacaya, Guatemala
14.381°N, 90.601°W, Summit elev. 2552 m

INSIVUMEH reported that during 20-26 August white and blueish white fumarolic plumes rose 50-150 m above Mackenney Crater at Pacaya and drifted 500-800 m S and SW. On 25 August small bursts of gray ash rose 300-700 m above the crater and drifted S.

Geologic summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. Pacaya is a complex basaltic volcano 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 volcano 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 at Pacaya 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.

Popocatepetl, Mexico
19.023°N, 98.622°W, Summit elev. 5426 m

CENAPRED reported that during 20-26 August steam-and-gas emissions with minor ash rose 100-800 m above Popocatépetl’s crater and drifted NW and W. On 25-26 August the emissions had a low intensity explosive component. On most nights incandescence was observed, increasing with larger emissions. On 23 August slight amounts of ash were reported northwest of the volcano in the communities of Amecameca, Ozumba, and Tlalmanalco. On most days there was only partial visibility due to cloud cover, and on 25-26 August heavy cloud cover was reported. On 24 August the Washington VAAC reported emissions but ash was not detected by satellite. The Alert Level remained at to Yellow, Phase Two.

Geologic summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 CE, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.

Reventador, Ecuador
0.077°S, 77.656°W, Summit elev. 3562 m

During 20-26 August IG reported moderate to high volcanic activity at Reventador, including explosions, long-period earthquakes, harmonic tremor, and tremor. On 20 August ash plumes, observed through partly cloudy skies, remained near the volcano. On 26 August in the morning hours emissions of water vapor were reported above the crater drifting SW. The volcano was obscured by clouds the other days of the week. On 24 August the Washington VAAC reported an emission with light ash to 6 km (20,000 ft) a.s.l. identified by wind and satellite data, seismic detection, and pilot report.

Geologic summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Sabancaya, Peru
15.78°S, 71.85°W, Summit elev. 5967 m

IGP reported that on 24-25 August an increase in volcano-tectonic and long-period earthquakes, and during 23-25 August there was a slight increase in white to blueish white fumarolic emissions that rose 500-1500 m above the summit of Sabancaya. On 25 August during the night instruments detected a sequence of explosive events that lasted 82 seconds. On 26 August INGEMMET reported long-period, volcano-tectonic, and hybrid earthquakes. White to light gray plumes rose 100-1300 m above the summit drifting SE.

Geologic summary: Sabancaya, located on the saddle between 6288-m-high Ampato and 6025-m-high 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 volcanoes, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. Both Nevado Ampato and Nevado Sabancaya are only slightly affected by glacial erosion and consist of a series of lava domes aligned along a NW-SW trend. The name of 5967-m-high Sabancaya (meaning "tongue of fire" in the Quechua Indian 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.

San Miguel, El Salvador
13.434°N, 88.269°W, Summit elev. 2130 m

On 20-26 August SNET reported low seismic activity at San Miguel. On most days short pulses of white and whitish gray steam plumes were observed at the summit.

Geologic summary: The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit of the 2130-m-high volcano rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit of the towering volcano, which is also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the north, NE, and SE sides. The SE-flank lava flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Santa Maria, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m

On 20-25 August, INSIVUMEH reported lava flowing towards Upper Nima Canyon I and incandescence within the Santiaguito crater at night. On most days collapses of the lava flow generate fine ash that drifts up to 700 m SW, S, and SE. Fumarolic degassing plumes rose 100-200 m above the crater and drifted up to 2.9 km SW, S, and SE.

Geologic summary: 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 of Volcán Santa María 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.

Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m

KVERT reported that during 15-21 August lava-dome extrusion onto Sheveluch’s SE flank was accompanied by moderate ash explosions, incandescence of the dome summit, hot avalanches, and fumarolic activity. Satellite data showed a thermal anomaly over the lava dome on 18-19 August. The volcano was obscured by clouds the other days of week. The Aviation Color Code remained at Orange.

Geologic 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.

Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Summit elev. 2857 m

AVO reported that during 20-26 August low-level eruptive activity continued at Shishaldin volcano. A steam and gas plume was visible in web camera and satellite images occasionally during the week. On 20 August satellite images showed a steam plume extending 60 km N of the volcano. On 23 August a pilot reported a steam-and-ash plume rose about 300 m (1,000 ft) above the summit and drifted NE. On 20-22 and 26 August elevated surface temperatures at the summit were detected in clear satellite views. Infrasound sensors located in Dillingham and on Akutan Island detected sound waves from the direction of Shishaldin that were consistent with low-level eruptive activity. No significant activity noted in seismic data. The Aviation Color Code remained at Orange and theVolcano Alert Level remained at Watch.

Geologic 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.

Tungurahua, Ecuador
1.467°S, 78.442°W, Summit elev. 5023 m

During 20-26 August IG reported that moderate to high eruptive activity continued at Tungurahua, including volcanic tremor, explosions, and long-period earthquakes. On most days explosions described as “canon like” blasts, roars, and “gunfire” were heard near the volcano and rattled windows in the town of Baños on 21 August. On most days ash plumes rose 1.5-5 km (4,900-16,400 ft) above the crater rim and drifted W and SW. On 22-23 August views through intermittent clouds showed blocks falling on the E flank of the volcano and on 24-25 August incandescent blocks fell 1-1.5 km below the crater rim. On 23-26 ashfall was reported in several areas, including Bilbao, Chacauco, Mocha, Choglontus, Tisaleo, and El Manzano. On 26 August muddy water was observed after rains in Mapayacu Gorge. On most days the Washington VAAC reported ongoing and continuous emissions. On 21 August the Washington VAAC reported emissions rose to 6 km (20,000 ft) a.s.l. and on 24 August emissions rose to 8.5 km (28,000 ft) a.s.l. On 26 August short duration explosions were reported.

Geologic summary: Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major volcanic edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Ubinas, Peru
16.355°S, 70.903°W, Summit elev. 5672 m

During 20-26 August INGEMMET reported that the eruption of Ubinas was continuing. During 20-25 August water vapor, gas, and minor ash plumes rose 200-1800 m above the crater and drifted E, NE, and S. On 21 August an explosion was followed by an ash plume that rose 4.2 km (13,800 ft) above the summit and drifted S and expelled incandescent blocks up to 2 km from the crater, primarily on the S flank. The explosion was heard up to 10 km from the volcano. On 22 August an ash plume rose to 1.8 km (5,900 ft) and drifted E and NE. On 21-22 August ashfall was reported in the towns of Querapi, Ubinas, Escacha, Tonohaya, and Yalahua.

Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I volcano was followed by construction of Ubinas II volcano beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Zhupanovsky, Eastern Kamchatka (Russia)
53.59°N, 159.147°E, Summit elev. 2958 m

KVERT reported that during 15-21 August that moderate explosive eruption continued at Zhupanovsky. Satellite data showed a thermal anomaly over the volcano on 16-17 August. On 18 and 15 August the volcano was obscured by clouds. The Tokyo VAAC reported ash plumes rose to 3-4.5 km (10,000-15,000 ft)a.s.l. and drifted S and SSE. On August 19 KVERT reported that satellite data showed ash plumes drifted 51 km S of the volcano and on August 20 that ash plumes rose to 3 km (9800 ft) a.s.l. and drifted 110 km SSE.

Geologic summary: The Zhupanovsky volcanic massif consists of four overlapping stratovolcanoes along a WNW-trending ridge. The elongated volcanic complex was constructed within a Pliocene-early Pleistocene caldera whose rim is exposed only on the eastern side. Three of the stratovolcanoes were built during the Pleistocene, the fourth is Holocene in age and was the source of all of Zhupanovsky's historical eruptions. An early Holocene stage of frequent moderate and weak eruptions from 7000 to 5000 years before present (BP) was succeeded by a period of infrequent larger eruptions that produced pyroclastic flows. The last major eruption took place about 800-900 years BP. Historical eruptions have consisted of relatively minor explosions from the third cone.

Source: GVP

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