Active volcanoes in the world: September 10 - 16, 2014

Active volcanoes in the world: September 10 - 16, 2014

New activity/unrest was observed at 8 volcanoes from September 10 - 16, 2014. Ongoing activity was observed at 17 volcanoes.

New activity/unrest: Askja, Iceland  | Asosan, Kyushu (Japan)  | Bardarbunga, Iceland  | Kuchinoerabujima, Ryukyu Islands (Japan)  | Kusatsu-Shiranesan, Honshu (Japan)  | Mayon, Luzon (Philippines)  | Nishinoshima, Japan  | Slamet, Central Java (Indonesia)

Ongoing activity: Aira, Kyushu (Japan)  | Ambrym, Vanuatu  | Bezymianny, Central Kamchatka (Russia)  | Chirpoi, Kuril Islands (Russia)  | Copahue, Central Chile-Argentina border  | Fuego, Guatemala  | Karymsky, Eastern Kamchatka (Russia)  | Kilauea, Hawaiian Islands (USA)  | Pacaya, Guatemala  | Popocatepetl, Mexico  | Reventador, Ecuador  | Santa Maria, Guatemala  | Sheveluch, Central Kamchatka (Russia)  | Shishaldin, Fox Islands (USA)  | Tungurahua, Ecuador  | Ubinas, Peru  | Zhupanovsky, Eastern Kamchatka (Russia)

New activity/unrest

Askja, Iceland
65.03°N, 16.75°W  | Summit elev. 1516 m

IMO had maintained the Aviation Colour Code for Askja at Yellow since 28 August due to elevated seismicity and localized deformation. On 11 September the Colour Code was reduced to Green when seismicity had diminished significantly.

Geologic summary: Askja is a large basaltic central volcano that forms the Dyngjufjöll massif. It is truncated by three overlapping calderas, the largest of which is 8 km wide and may have been produced primarily from subglacial ring-fracture eruptions rather than by subsidence. A major rhyolitic explosive eruption from Dyngjufjöll about 10,000 years ago was in part associated with the formation of Askja caldera. Many postglacial eruptions also occurred along the ring-fracture. A major explosive eruption on the SE caldera margin in 1875 was one of Iceland's largest during historical time. It resulted in the formation of a smaller 4.5-km-wide caldera, now filled by Öskjuvatn lake, that truncates the rim of the larger central caldera. The 100-km-long Askja fissure swarm, which includes the Sveinagja graben, is also related to the Askja volcanic system, as are several small shield volcanoes such as Kollatadyngja. Twentieth-century eruptions have produced lava flows from vents located mostly near Öskjuvatn lake.

Asosan, Kyushu (Japan)
32.884°N, 131.104°E  | Summit elev. 1592 m

JMA reported that Alert Level 2 at Asosan continued during 8-16 September. A persistent white plume was observed 1,000 m above the crater.

Preliminary counts for volcanic earthquakes (394-564 per day) and tremor (80-174 per day) were reported during 8-15 September. Field surveys conducted on 9 and 12 September yielded elevated temperatures from fumaroles and the surface of the S crater wall.

Geologic summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 cu km of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

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

During 10-16 September, IMO maintained Aviation Colour Code Orange due to continued activity at Bárdarbunga’s Holuhraun eruptive fissure. Lava flows continued to advance at a consistent rate toward the E and W, and by 13 September, the lava field measured 24.5 km2. The main flow had entered the river bed of Jökulsá á Fjöllum and continued to follow its course; steam rose from the river where the lava was in contact but no explosive activity occurred. Persistent subsidence was detected from the Bárðarbunga caldera; approximately 23 m of total subsidence was measured during a survey on 14 September.

Seismicity persisted mainly around the caldera and the Dyngjujökull glacier. The largest earthquakes, M 5.5, M 5.3, and M 5.0, were detected on 10, 11, and 15 September respectively.

IMO reported continued elevated SO2 emissions during 10-16 September and issued warnings to the public in the municipality of Fjarðarbyggð on 13 September.

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.

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

During 8-16 September JMA reported that Alert Level 3 conditions persisted at Kuchinoerabujima, but no eruptive activity was observed. Low-level seismicity continued and tremor was absent. White plumes were visible on webcamera images rising 800 m from the crater during 8-12 September and to 600 m during 13-16 September. A field survey on 12 September measured SO2 emissions that were similar to pre-eruptive levels (300 tons/day).

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

During 5-12 September JMA maintained Alert Level 2 for Kusatsu-Shiranesan due to continued unrest. GPS measurements indicated inflation, although thermal anomalies had been absent since July. Volcanic earthquakes continued at a low level (a maximum of 3 per day) and tremor was absent.

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

PHIVOLCS reported Mayon’s earthquakes, rockfall events, and an inflationary trend from leveling surveys on 15 September. A noticeable escalation occurred later that day, including 39 rockfall events and 32 low-frequency volcanic earthquakes. Crater glow became visible around 2000 and PHIVOLCS released an informational bulletin at 2200 announcing Alert Level 3. On 16 September incandescent rockfalls spread to the upper reaches of Bonga Gully on the SE flank.

News reports highlighted the evacuation orders announced by the governor of Albay province, which included the 6 km permanent danger zone surrounding the volcano; an assisted evacuation was enforced for the 6-8 km extended danger zone. In an interview with the press, the governor noted that some residents had already fled their homes in Guinobatan (11.8 km SW) on the evening of 15 September.

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.

Nishinoshima, Japan
27.247°N, 140.874°E  | Summit elev. 25 m

The Tokyo VAAC reported an ash plume from Nishinoshima that rose to an altitude of about 3,000 km (10,000 ft) a.s.l. and drifted S on 16 September.

The University of Hawaii reported that satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS) resulted in frequent MODVOLC alerts for Nishinoshima, as recently as 11 September.

Geologic summary: The small island of Nishinoshima was recently enlarged when it was joined to several new islands that formed during an eruption in 1973-74. Water discoloration has been observed on several occasions since. The 700-m-wide island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Slamet, Central Java (Indonesia)
7.242°S, 109.208°E  | Summit elev. 3428 m

PVMBG reported explosive activity from Slamet during 4-12 September. During the past week, activity peaked with incandescent explosions; rumbling sounds were heard by scientists at the Slamet observation post. On 11 September the largest ash plume was observed (200-1,500 m above the summit) and incandescent plumes reached 400 m above the summit. Seismicity was dominated by emissions and explosion signals. Deformation data indicated that relatively little pressure was accumulating due to magma movement. PVMBG maintained the Alert Level 3 (on a scale of 1-4).

Geologic summary: Slamet, Java's second highest volcano at 3428 m and one of its most active, has a cluster of about three dozen cinder cones on its lower SE-NE flanks and a single cinder cone on the western flank. It is composed of two overlapping edifices, an older basaltic-andesite to andesitic volcano on the west and a younger basaltic to basaltic-andesite one on the east. Gunung Malang II cinder cone on the upper E flank on the younger edifice fed a lava flow that extends 6 km E. Four craters occur at the summit of Gunung Slamet, with activity migrating to the SW over time. Historical eruptions, recorded since the 18th century, have originated from a 150-m-deep, 450-m-wide, steep-walled crater at the western part of the summit and have consisted of explosive eruptions generally lasting a few days to a few weeks.

Ongoing activity

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

During 8-16 September JMA maintained Alert Level 3 for Aira Caldera’s Sakurajima volcano. Volcanic earthquakes and tremor were detected during this time period. There were 12 explosions that ejected tephra up to 1,300 m above Showa crater. Sustained eruptions from the crater were recorded on 10 and 11 September and nighttime incandescence was detected during 11-16 September.

During 10-16 September JMA reported ash eruptions, causing the Tokyo VAAC to issue regular advisories; however, ash was not visible in satellite images.

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.

Ambrym, Vanuatu
16.25°S, 168.12°E  | Summit elev. 1334 m

On 11 September, the Vanuatu Geohazards Observatory reported increased seismicity from Ambrym and raised the Alert Level from 1 to 2 (on a scale of 0-4).

Geologic summary: 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.

Bezymianny, Central Kamchatka (Russia)
55.972°N, 160.595°E  | Summit elev. 2882 m

KVERT maintained Alert Level Yellow during the week of 12 September for Bezymianny. Weak seismic activity continued, and according to video data, moderate gas and steam activity occurred, although the volcano was frequently obscured by clouds. Satellite data showed a weak thermal anomaly over the volcano during 4-5 and 11 September.

Geologic summary: Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E  | Summit elev. 742 m

During 1 to 16 September thermal anomalies were detected from Chirpoi in satellite images when clear conditions permitted. On 4 September SVERT increased the Aviation Color Code from Green to Yellow due to renewed activity including thermal anomalies. Gas-and-steam plumes were visible on 11 and 15-16 September.

Geologic summary: Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.

Copahue, Central Chile-Argentina border
37.856°S, 71.183°W  | Summit elev. 2953 m

On 14 September SERNAGEOMIN reported elevated seismicity from Copahue. A seismic swarm occurred during 1200-1900 comprising 389 LP earthquakes; epicenters were within the crater area and hypocenters were at depths less than 3 km. SERNAGEOMIN noted that this unrest was similar to that from May and October 2013. Web cameras located nearby captured a persistent vapor plume that reached ~250 m above the crater and drifted ~700 m ENE. The Alert Level remained at Yellow.

Geologic summary: Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

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

During 10-16 September INSIVUMEH reported that white fumarolic plumes rose 200-600 m above Fuego’s summit. Variable explosions generated ash plumes 500-1,00 m above the summit; during 24-hour periods there were daily counts of 28, 32, 21, 12, 0, 8, and 11. The lava flow was active within the Ceniza drainage (SSW) on 13 September and had extended 100 m.

Moderate rumbling was heard and shockwaves caused roofs to shake on some houses near the volcano. On 10-13, 15, and 16 September incandescent plumes were observed 100-200 m above the crater.

Weak avalanches were frequently channeled into the drainages of Ceniza, Trinidad (S), Taniluyá (SW), Santa Teresa (W), Las Lajas (SE), and Honda (E) during 10-16 September.

During 10-13 and 15 September fine gray ash from explosions fell over the areas of Sangre de Cristo (8 km WSW), Panimaché I and II (8 km SW), Morelia (10 km SW), Santa Sofía (12 km SW), and others. During 14 September ashfall was reported in Yepocapa (8 km WNW), Panimaché, Sangre de Cristo, Morelia, and others. During 16 September ashfall was reported in Alotenango (8 km ENE), Antigua (18 km NE), Ciudad Vieja (13.5 km NE), and other areas.

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.

Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E  | Summit elev. 1513 m

KVERT reported that moderate-to-weak seismic activity continued at Karymsky and maintained Yellow Alert during the week of 12 September. On 10 September satellite data showed an ash plume at that extended about 100 km SE. The volcano was quiet or obscured by clouds on the other days of week.

According to the Tokyo VAAC, ash plumes were detected by satellite images during 10 and 16 September. Plume heights were 2,100-3,000 m (7,000-10,000 ft) a.s.l..

Geologic summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

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

During 10-16 September HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater, remaining 50-60 m below the Overlook Crater rim. Elevated gas emissions were detected during the week of 9 September, with amounts of 3,300-6,700 tonnes per day, and persisted through this reporting period. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas; smaller particles may have fallen several kilometers away.

During 10-16 September little change was recorded from Pu`u `O`o; glow was visible overnight above several outgassing openings in the crater floor. By 16 September the NE-trending lava flow extended 15.5 km from the vent, placing the active flow front within the NW portion of the Kaohe Homesteads, a vacant forested portion of the subdivision. The flow had advanced at an average rate of 215 m/day between 12 and 15 September and continued to generate smoke and localized fires as it spread through the forest.

The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

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.

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

During 10-16 September INSIVUMEH reported that a weak fumarolic plume was frequently visible rising 50-75 m above the summit of Pacaya. The plume tended to drift 500-600 m S, SW, and W. On 14 September, B-type earthquakes were detected associated with gas emissions.

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

During 10-16 September CENAPRED maintained Alert Level Yellow Phase 2 for Popocatepetl. Nighttime incandescence from the crater was visible during this time. Low-intensity exhalations were observed during 24-hour periods with consecutive daily counts of 31, 5, 7, 36, 64, 36, and 1. VT earthquakes of magnitude 1.9 and 2.2 was detected on 11 and 13 September, respectively. Weather conditions frequently prevented visual observations.

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

IG reported moderate volcanic activity including explosions, long-period earthquakes, and tremor at Reventador during 10-16 September. On 10 September continuous steam with minor ash plumes rose 1,000 m above the summit and drifted NW. Cloudy conditions frequently obscured views of the summit.

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.

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

During 10-16 September INSIVUMEH reported white fumarolic plumes rising 150-500 m above Santa Maria’s active cone, Santiaguito. The active lava flow on the E flank continued to generate ash plumes and incandescence. On 14 September INSIVUMEH observed that the lava flow advancing within the Nimá 1 drainage had reached a total of 3,500 m from the summit.

INSIVUMEH reported hot lahars in the drainages of Cabello de Ángel and Río Nimá 1 on 11 September. Tree trunks and branches were entrained and the flow was 20 m wide and 2 m deep. Moderate vibrations could be felt from the ground as it passed the observatory; sulfur odors were also noticed.

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 the explosive and effusive eruption of Shiveluch continued and maintained Alert Level Orange during the week of 12 September. Activity was dominated by lava dome growth on the SE flank, moderate ash explosions, fumarolic activity, and hot avalanches. Satellite data showed a persistent thermal anomaly from the dome region during 4-5, 7 and 11 September. Remobilized ash was observed in a dust plume on 11 September that rose 1-2 km (3,280-6,562 ft) a.s.l. and drifted SE.

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 low-level seismicity and eruptive activity continued from Shishaldin during 10-16 September. Observations were frequently restricted due to cloudy conditions, although elevated temperatures were observed on 15 September in one satellite image.

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

IG reported moderate volcanic activity including explosions, long-period earthquakes, and tremor at Tungurahua during 10-16 September. On 10 September a minor ash plume was visible drifting SE from the summit. Ahfall was reported in the area of Quero (20 km NW) and Tisaleo (29 km NW) on 10 September. In the morning of 11 September, small explosions were reported that generated rockfalls on the flanks. Moderate rainfall on 12 and 15 September generated lahars within the NW drainages of Achupashal and La Pampa. Light ashfall was reported from Cusúa (~8 km NW of the summit) on 16 September and, during clear viewing conditions, snowfall was noted on Tungurahua’s upper flanks. Cloudy conditions frequently obscured views of the summit.

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 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, 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 10-16 September IGP reported that the eruption of Ubinas was continuing and maintained Alert Level Orange. On 10 September there were 15 explosions with plumes 900-1,700 m above the crater and 10 exhalation events; on 11 September there was one explosion with a plume 3,000 m above the crater and 8 exhalation events (600-900 m above the crater). There were no explosions or exhalations during 12-16 September, although seismicity (LP, VT, and hybrid earthquakes) continued except on 13 September when hybrid earthquakes were absent.

Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It 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 was followed by construction of Ubinas II 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 about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E  | Summit elev. 2899 m

KVERT reported ashfall from Zhupanovsky in the area of IVS FEB RAS (Petropavlovsk-Kamchatsky) during 1100-1300 on 7-8 September. The moderate explosive eruption continued and Alert Level Orange was maintained through the week of 12 September. According to visual data, ash plumes extended about 50 and 70 km S and SE of the volcano on 10 and 11 September, respectively. Persistent thermal anomalies were detected from the summit area based on satellite images during 4-5 and 10-11 September.

Satellite data showed ash plumes up to 3.5-4.0 km (11,500-13,100 ft) a.s.l. mainly during 9-11 September, and ash plumes drifted about 1,113 km SE and S.

According to the Tokyo VAAC, ash plumes were detected by satellite images during 10-16 September with the exception of 15 September. Plume heights were 2,400-3,700 m (8,000-12,000 ft) a.s.l..

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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