Active volcanoes in the world: September 3 - 9, 2014

Active volcanoes in the world: September 3 - 9, 2014

New activity/unrest was observed at 8 volcanoes from September 3 - 9, 2014. Ongoing activity was observed at 15 volcanoes.

New activity/unrest: Asosan, Kyushu (Japan)  | Bardarbunga, Iceland  | Barren Island, Andaman Islands (India)  | Kilauea, Hawaiian Islands (USA)  | Kusatsu-Shiranesan, Honshu (Japan)  | Manam, Papua New Guinea  | Rabaul, New Britian (Papua New Guinea)  | Suwanosejima, Ryukyu Islands (Japan)

Ongoing activity: Aira, Kyushu (Japan)  | Bezymianny, Central Kamchatka (Russia)  | Fuego, Guatemala  | Karymsky, Eastern Kamchatka (Russia)  | Kuchinoerabujima, Ryukyu Islands (Japan)  | Pacaya, Guatemala  | Poas, Costa Rica  | 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

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

JMA reported that Alert Level 2 at Asosan continued during 1-8 September. A small eruption occurred on 1 September from Nakadake crater, generating an off-white plume that suggested a small amount of ash; the plume rose 1,200 m above the crater. Incandescence from the crater was detected with a camera on 2 September. Volcanic earthquakes (48-92 per day) and tremor (429-500 per day) was detected during 1-4 September.

On 6 September a small eruption occurred from Nakadake crater that generated a plume 600 m above the rim. Elevated SO2 (1,200 tons/day) was detected during a field survey (the previous measurement on 21 August was 1,000 tons/day). Volcano-tectonic earthquakes (55-129 per day) and tremor (401-463 per day) was detected during 5-7 September.

Tokyo VAAC issued advisories based on JMA reports of eruptions on 1 and 6 September, though no volcanic ash was visible in satellite images.

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 3-9 September the Icelandic Met Office reported ongoing lava effusion, high gas emissions, and elevated seismicity from Bárdarbunga’s Holuhraun lava field. On 3 September, the lava flow continued advancing ENE and covered 7.2 km2. Field observations determined that ash production was almost negligible. Radar images provided measurements of a 0.5-1 km wide depression that had formed within the Dyngjujökull glacier (located ~2 km S of the eruption site).

On 4 September there was no decline in effusive activity and the lava field had an aerial extent of 10.8 km2. There were no obvious changes on the Dyngjujökull glacier.

Two new eruptive fissures were observed south of the main eruption site on 5 September. These sites were less effusive and were located ~2 km away from the Dyngjujökull glacier. The eruption also continued from the original fissure and generated a ~460 m high steam plume. During a surveillance flight, the depression within Dyngjujökull glacier appeared to have grown deeper. On 6 September large changes were observed from the overlying glacier of Bárdarbunga (Vatnajökull glacier); a large area subsided that corresponded to deformation of the caldera floor. There were no signs of an eruption from the caldera. Two depressions were noted on the Dyngjujökull glacier, suggesting that small, short sub-glacial eruptions may have occurred.

The fissure eruption continued during 6-7 September and lava effusion was 100-200 m3/s on 7 September. Activity from the S fissures was less than that of the N fissure which had been active since the beginning of the eruption. The advancing lava flow reached the W main branch of the Jökulsá á Fjöllum river. No explosive activity due to lava and river water interaction was observed, but steam rose from the area.

During 8-9 September activity was no longer detected from the southernmost fissure. Lava continued to advance and interact with the Jökulsá á Fjöllum river. The extent of the lava flow reached 19 km2 and gas emissions remained high.

The London VAAC reported no ash plumes associated with the fissure eruptions. The Aviation Color Code remained at Orange.

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.

Barren Island, Andaman Islands (India)
12.278°N, 93.858°E, Summit elev. 354 m

The Darwin VAAC released an advisory on 9 September based on a Sigmet and noted ash observations from Barren Island at 1428 that day. The low-level plume was not identifiable in satellite images.

Geologic summary: Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. The morphology of a fresh pyroclastic cone that was constructed in the center of the caldera has varied during the course of historical eruptions. Lava flows fill much of the caldera floor and have reached the sea along the western coast during historical eruptions.

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

During 3-9 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 on 2 September, 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 3-9 September little change was recorded from Pu`u `O`o; glow was visible overnight above several outgassing openings in the crater floor. On 3 September HVO raised the Volcano Alert Level from Watch to Warning due to the advancement of the June 27th lava flow. By that afternoon the NE trending lava flow had reached ~13.2 km from the vent, placing the active flow front 1.3 km from the E boundary of the Wao Kele o Puna Forest Reserve. The lava flow continued to generate smoke and localized fires as it spread through the forest, and as of 9 September had advanced ~800 m.

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 Halema'uma'u 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.

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

During 29 August-5 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 (0-5 per day) and tremor has not been detected.

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.

Manam, Papua New Guinea
4.08°S, 145.037°E, Summit elev. 1807 m

The Darwin VAAC released advisories on 6 September and noted ash seen in satellite images of Manam at 1032 and 1132. The plume reached 2,100 m (7,000 ft) a.s.l. and drifted ~27 km NW.

Geologic summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys," regularly spaced 90 degrees apart, channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE avalanche valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded at Manam since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Rabaul, New Britian (Papua New Guinea)
4.271°S, 152.203°E, Summit elev. 688 m

During 31 August-5 September, Rabaul caldera’s Tavurvur cone remained quiet and no nighttime incandescence was observed. Variable amounts of white vapor were visible rising from the summit as well as traces of blue vapor. A few short-duration rumbling noises were heard during 30-31 August, and seismicity remained very high and dominated by small, low-frequency earthquakes. However, earthquakes decreased from 80 events per hour to 15 events per hour at 0300 on 31 August. Less than 10 earthquakes were detected during 1-2 September; a slight increase in low-frequency earthquakes was detected during 4-5 September.

Geologic summary: The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims of Rabaul. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Summit elev. 796 m

Tokyo VAAC released ash advisories for Suwanosejima during 3-4 and 9 September based on JMA reports. Ash drifted NE and N at 1,800-5,500 m (6,000-18,000 ft) a.s.l. on 3 September. On 4 September, an ash plume at 5,500 m (18,000 ft) a.s.l. was observed. JMA also reported a 2,100 m (7,000 ft) a.s.l. ash plume on 9 September at 2233.

Geologic summary: 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 persons live on the island.

Ongoing activity

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

During 1-9 September JMA maintained Alert Level 3 for Aira Caldera’s Sakurajima volcano. There were 23 explosions were recorded from Showa crater from 1 to 4 September; during 5-7 September there were 18 explosions.

During 3-7 September JMA reported ash eruptions, causing the Tokyo VAAC to issue regular advisories; however, ash was not visible in satellite images. At 0437 on 9 September, ash was visible in satellite images and reached 3,300 m (11,000 ft) a.s.l. drifting S. On 2 and 3 September, ballistics reached 1,300-1,800 m above the crater. Nighttime incandescence was detected during 4-5 September from Showa crater. Volcanic earthquakes and tremor were detected during 1-8 September.

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.

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

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

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.

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

On 2 September INSIVUMEH seismically detected a lahar flowing through Fuego’s Taniluyá drainage (SW flank). Observations determined a width of 75 m and height of 2.5 m. The flow cut the road between Santa Lucia Cotzulmaguapa and the communities of Morelia, Santa Sofía, and Panimaché I and II. Lahars were also detected within Río Ceniza (SSW) and Santa Teresa (W).

During 3-9 September INSIVUMEH reported that white fumarolic plumes rose 300-600 m above Fuego’s summit. Weak-to-moderate ash explosions occurred each day and generated plumes 500-800 m high; ash plumes drifted up to 15 km away with prevailing winds. Moderate rumbling was heard and shockwaves caused roofs to shake on some houses near the volcano. On 3 and 5-9 September incandescent plumes were observed 75-150 m above the crater. Weak avalanches were channeled into the drainages of Ceniza (SSW), Trinidad (S), Taniluyá (SW), Santa Teresa, Las Lajas, and Honda during 9 September.

During 3-4 and 6-9 September fine gray ash from explosions fell over the areas of Yepocapa (8 km WNW), Sangre de Cristo (8 km WSW), Panimaché I and II (8 km SW), Morelia (10 km SW), Santa Sofía (12 km SW), Yucales (12 km SW), Porvenir (8 km ENE), and others.

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 5 September. On 3 September satellite data showed an ash plume at 4,000 m (13,100 ft) a.s.l. that extended about 9 km WSW. The volcano was quiet or obscured by clouds on the other days of week.

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.

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

During 1-8 September, JMA reported that Alert Level 3 conditions persisted at Kuchinoerabujima, but no eruptive activity was observed. Seismicity increased during 3-5 September; tremor was occasionally detected. Based on webcamera images, white plumes were visible rising 400 m from the crater during 1-5 September and to 200 m during 5-8 September. Tremor was not detected during 5-8 September and JMA noted that poor weather conditions due to a typhoon were affecting the seismic network.

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.

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

During 3-9 September INSIVUMEH reported that a weak fumarolic plume was frequently visible rising to 50 m above the summit. The plume tended to drift 400-500 m E and SW. On 4 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.

Poas, Costa Rica
10.2°N, 84.233°W, Summit elev. 2708 m

OVSICORI-UNA reported that three consecutive phreatic eruptions occurred within the crater lake of Poás on 27 August, each within 2 minutes of the previous one. One explosion generated a plume up to 200 m above the surface of the lake. Based on seismic energy released, this event was similar to the eruption on 1 June, one of the largest of the year which partially destroyed a gas-measuring station.

OVSICORI-UNA noted that phreatic eruptions from Poás tended to occur impulsively, have short durations (within 5-10 seconds), and frequently lack precursory activity.

Geologic summary: The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

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

During 3-9 September CENAPRED maintained Alert Level Yellow Phase 2 for Popocatepetl. Nighttime incandescence from the crater was visible during this time period. Low-intensity exhalations were observed during 24-hour periods with consecutive daily counts: 15, 1, 5, 17, 30, 12 and 22. On 4 and 5 September, three and four VT earthquakes were detected, respectively, with an average magnitude 1.7. Small pulses of steam and gas drifted WSW during the mornings of 5 and 6 September.

On 7 September, steam and gas emissions were accompanied by 15 minutes of harmonic tremor. At 0315 incandescent tephra was ejected. An ash plume was observed reaching 1 km above the summit and drifting WNW.

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 3-9 September IG reported moderate activity including explosions, long-period earthquakes, harmonic tremor, and tremor at Reventador. While cloud cover frequently limited observations, on 5-8 September steam emissions were observed with small quantities of ash. In the morning of 5 September an explosion generated a plume and ejected blocks from the crater that fell ~500 m below the summit on the W flank. A thermal camera detected an explosion on the following day that also included ballistics. Rumbling sounds were heard in the morning of 7 September, and that evening a 1 km plume was observed. The following morning a vapor plume persisted from the summit, and in the afternoon it contained a small amount of ash.

The MODIS sensor onboard the Terra satellite detected thermal anomalies from the region of Reventador’s summit during 4-6 September.

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 3-9 September INSIVUMEH reported white fumarolic plumes rising 200-300 m above Santa Maria’s active cone, Santiaguito. The active lava flow on the E flank continued to generate ash plumes and incandescence. On 4 September fine ash dispersed W over the area of Palajunoj (18 km SSW). On 6 September INSIVUMEH observed the lava flow advancing within the Nima 1 drainage.

INSIVUMEH reported that a strong lahar was detected by the seismic network and observed within Río Nima 1 on 7 September. Fines and blocks (up to 40 m) were mobilized, and 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 Sheveluch continued and maintained Alert Level Orange during the week of 5 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.

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 3-7 September. When weather conditions were favorable, satellite images detected elevated surface temperatures. Observations were restricted on 8-9 September due to cloudy conditions.

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 3-9 September IG reported moderate-to-high activity from Tungurahua. Explosions were observed most days during clear conditions, but also heard during episodes of rumbling during 4-6 September.

On 3 September gray and black ashfall was reported in the areas of Manzano (8 km SW), Choglontus (13 km WSW), Tisaleo (29 km NW), Quero Alto (20 km NW), and Quinchicoto. In the afternoon a pyroclastic flow descended 500 m from the crater and explosions were detected during 1700-1900. Ashfall was also noted on 5 September in the towns of Manzano and Palitahua (6 km SSW). At 1210 an ash plume reached 1,500 m above the crater and drifted both W and E.

In the morning of 6 September an incandescent plume was observed rising from the summit. Ash drifted W and later SW, and 0.5 mm of black ash accumulated in the areas of Penipe (15 km SW), Puela (8 km SW), Pillate (8 km W), Galán (WNW), and to the S of Quero (20 km NW). The following day ashfall was reported in Palitagua (SW), Manzano, and Bilbao (8 km W).

The MODIS sensor onboard the Aqua satellite detected a thermal anomaly from the region of Tungurahua’s summit on 7 September.

On 8 September cloudy conditions persisted, but in the afternoon an ash plume was visible drifting NW; ashfall was reported from Cevallos (23 km NW), Quero, Mocha (25 km W), Pillate, and Tisaleo. Black ashfall was reported in the area of Pillate on the following day.

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 3-9 September IGP reported that the eruption of Ubinas was continuing. During 3-4 and 9 September, steam plumes from fumaroles occasionally rose from the summit. Seismicity was generally low but dominated by tremor. Two exhalations of ash were observed on 5 September, the first at 0858 generated an ash plume up to 1,000 m above the summit which dispersed S. The second plume occurred at 1327 and dispersed ash 500 m above the summit that dispersed N.

A total of five explosions were detected on 8 September, the strongest occurred at 0850 and produced a 1,200 m plume; the second explosion expelled ash to heights between 1,300 and 1,900 m; ashfall was noted in areas S.

The Buenos Aires VAAC reported Aviation Color Code Orange on 8 and 9 September when visible images revealed a narrow plume of steam and ash drifting SE. By 0400 on 9 September, the emissions contained water vapor, gas, and light ash, and reached an altitude of 7,300 m (24,000 ft) a.s.l..

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)
53.589°N, 159.15°E, Summit elev. 2899 m

According to KVERT, the moderate explosive eruption of Zhupanovsky continued and Alert Level Orange was maintained through 8 September. On 1 September visual data detected an ash plume to an altitude of 3,500 m (11,500 ft) a.s.l. drifting NW of the volcano. Satellite data showed ash plumes at 3,500-4,000 m (11,500-13,100 ft) a.s.l. that extended about 85 km in various directions on 28 and 30 August and 1-4 September. Persistent thermal anomalies were detected from the summit area based on satellite images.

KVERT reported three ash plumes drifting SW on 7 September. The plumes were 10 km, 38 km, and 72 km long at 2,500-3,000 m (8,200-9,840 ft) a.s.l. On 8 September, satellite images revealed an ash plume extending 52 km SW from the volcano.

According to the Tokyo VAAC, ash plumes and possible ash plumes were detected by satellite images during 29 August-9 September with the exception of 5 and 6 September. Plume heights were 2,700-11,600 m (9,000-38,000 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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