During past seven days 8 volcanoes had new activity, ongoing activity was reported for 14 volcanoes. This report covers active volcanoes in the world from August 14 – August 20, 2013 based on Smithsonian/USGS criteria.
New activity/unrest:|Ambrym, Vanuatu|Gaua, Vanuatu | Iliwerung, Lesser Sunda Islands | Ketoi, Kuril Islands | Kliuchevskoi, Kamchatka Peninsula | Kverkfjöll, Iceland (northeastern) | Sakura-jima, Ryukyu Islands and Kyushu | White Island, New Zealand
Ongoing activity: |Batu Tara, Lesser Sunda Islands | Chirinkotan, Kuril Islands | Chirpoi, Kuril Islands | Fuego, Guatemala | Karymsky, Kamchatka Peninsula | Kilauea, Hawaiian Islands | Kizimen, Kamchatka Peninsula | Manam, Northeast of New Guinea | Pacaya, Guatemala | Pagan, United States | Popocatépetl, México | Shiveluch, Kamchatka Peninsula | Tolbachik, Kamchatka Peninsula | Veniaminof, Alaska Peninsula
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 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.
Summit elev. 1334 m
According to NASA's Earth Observatory, a satellite image acquired on 9 August showed steam-and-gas plumes rising from Ambrym’s Benbow cone and from the active lava lake in Mbwelesu Crater (one of three active sub-craters of the Marun cone).
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.
Summit elev. 797 m
On 14 August the Vanuatu Geohazards Observatory reported that activity at Gaua had increased since June; volcanic tremor levels increased slightly and ash plume emissions continued. The Alert Level remained at 1 (on a scale of 0-4).
Geologic summary: The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. Construction of the historically active cone of Mount Garat (Gharat) and other small cinder cones in the SW part of the caldera has left a crescent-shaped caldera lake. The symmetrical, flat-topped Mount Garat cone is topped by three pit craters. The onset of eruptive activity from a vent high on the SE flank of Mount Garat in 1962 ended a long period of dormancy.
ILIWERUNG, Lesser Sunda Islands (Indonesia)
Summit elev. 1018 m
CVGHM reported that observers at a post 590 m a.s.l. and 6 km away from Iliwerung reported that diffuse fumarolic emissions from the crater were visible during the mornings from 1 to 19 August. Seismicity fluctuated during the month, but 81 shallow volcanic earthquakes were detected between 1606 and 1741 on 19 August, compared to a total of 30 the previous 18 days. The Alert Level was raised to 2 (on a scale of 0-4).
At 0714 on 20 August an eruption from the submarine SE flank vent, Hobal, ejected dense white plumes 2 km a.s.l. that drifted S. Incandescence at sea level was observed at 0746, and the water around the eruption site turned yellow. Fishermen and tourists were not permitted within a 2-km-radius of Hobal.
Geologic summary:Constructed on the southern rim of the Lerek caldera, Iliwerung forms a prominent south-facing peninsula on Lembata (formerly Lomblen) Island. Craters and lava domes have formed along N-S and NW-SE lines on the complex volcano; during historical time vents from the summit to the submarine SE flank have been active. The Iliwerung summit lava dome was formed during an eruption in 1870. In 1948 Iligripe lava dome grew on the eastern flank at 120 m altitude. Beginning in 1973-74, when three ephemeral islands were formed, submarine eruptions began on the lower SE flank at a vent named Hobal; several other eruptions took place from this vent before the end of the century.
KETOI, Kuril Islands (Russia)
Summit elev. 1172 m
SVERT reported that a thermal anomaly over Ketoi's Pallas Peak was detected in satellite images on 12 August. The Aviation Color Code remained at Yellow.
Geologic summary: The circular, 10-km-wide Ketoi island, which rises across the 19-km-wide Diana Strait from Simushir Island, hosts of one of the most complex volcanic structures of the Kuril Islands. The rim of a 5-km-wide Pleistocene caldera is exposed only on the NE side. A younger 1172-m-high stratovolcano forming the NW part of the island is cut by a horst-and-graben structure containing two solfatara fields. A 1.5-km-wide freshwater lake fills an explosion crater in the center of the island. Pallas Peak, a large andesitic cone in the NE part of the caldera, is truncated by a 550-m-wide crater containing a brilliantly colored turquoise crater lake. Lava flows from Pallas Peak overtop the caldera rim and descend nearly 5 km to the SE coast. The first historical eruption of Pallas Peak, during 1843-46, was its largest.
KLIUCHEVSKOI, Kamchatka Peninsula (Russia)
Summit elev. 4835 m
Based on seismic data from the Kamchatka Branch of Geophysical Services (KBGS; Russian Academy of Sciences), KVERT reported that a Strombolian eruption from Kliuchevskoi began at 1830 on 15 August. Video images recorded incandescence from the crater that night, and gas-and-steam plumes containing minor amounts of ash rising as high as 6 km (19,700 ft) a.s.l. and drifting NE during 15-16 August. Satellite images detected a large, bright thermal anomaly during 15-16 August. The Aviation Color Code was raised to Yellow, the second lowest of a four-color scale. Gas-and-steam plumes containing minor amounts of ash rose to an altitude of 5.5 km (18,000 ft) a.s.l. during 16-17 August. Incandescence from the crater at night and a thermal anomaly in satellite images continued to be reported during 17-19 August.
Geologic summary: Kliuchevskoi is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. Kliuchevskoi rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred at Kliuchevskoi during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of its 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.
KVERKFJOLL, northeastern Iceland
Summit elev. 1929 m
On 15 August park rangers noted unusually high water in the Volgu River, which originates from a water-filled depression called Gengissig in a geothermal area of Kverkfjöll; the high water destroyed a walking bridge. The next day an overflight of the area by members of National Commissioner of the Icelandic Police (NCIP), the Icelandic Meteorological Office (IMO), and the Institute of Earth Sciences revealed that Gengissig was empty and that a phreatic explosion had deposited streaks of dark material on the rock and snow.
Geologic summary: Kverkfjöll is a large subglacial volcano at the NE end of the Vatnajökull icecap. Two elliptical ice-filled calderas, 8 x 5 km in diameter, have been identified. An associated fissure swarm can be traced 60 km to the NE. A half dozen ridges of subglacially erupted pillow lavas are now exposed and extend beyond the glacial icecap to the NE. Subglacial historical eruptions have been recorded since the mid-17th century. Several other historical eruptions once attributed to Kverkfjöll are now thought to have originated from Bárdarbunga volcano to the west.
SAKURA-JIMA, Ryukyu Islands and Kyushu (Japan)
Summit elev. 1117 m
JMA reported that 24 explosions at Sakura-jima's Showa Crater were detected during 12-19 August and ejected tephra as far as 1.8 km. Incandescence from the crater was observed on 14 August. A very small eruption from Minami-dake Crater occurred on 16 August, producing an ash plume that rose 200 m.
An explosion from Showa Crater on 18 August generated a large ash plume that rose 5 km above the crater and drifted NW. A small pyroclastic flow traveled SE. According to news sources, the 50-minute-long eruption produced ashfall in the central and northern parts of Kagoshima (10 km W), causing train delays and poor visibility for car drivers. The event was the 500th explosion this year.
Geologic summary: Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km wide Aira 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 Sakura-jima 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 Kita-dake summit cone ended about 4850 years ago, after which eruptions took place at Minami-dake. 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.
WHITE ISLAND, New Zealand
Summit elev. 321 m
The GeoNet Data Centre reported that a small eruption from White Island occurred at 1023 on 20 August and continued for about 10 minutes. The eruption ejected mud and rocks short distances, and generated a voluminous steam plume (visible from the Bay of Plenty coast), that rose 4 km a.s.l. and then slowly dispersed. Weather radar observations showed that a minor amount of ash was present in the plume. The Volcano Alert Level was raised to 2 (on a scale of 0-5) and the Aviation Colour Code was raised to Red (on a four-color scale). Later that day the Aviation Colour Code was lowered to Orange.
The eruption originated in the active crater area that had been ejecting small amounts of mud in recent weeks. A short period of strong volcanic tremor was detected the previous morning, but it was not clear if it was related to the eruption.
Geologic summary: Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The 321-m-high island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE of White Island. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred at White Island throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.
BATU TARA, Lesser Sunda Islands (Indonesia)
Summit elev. 748 m
Based on analyses of satellite imagery and wind data, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that on 16 August an ash plume from Batu Tara rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted 130 km W.
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.
CHIRINKOTAN, Kuril Islands (Russia)
Summit elev. 724 m
Based on analysis of satellite images, SVERT reported that a possible thermal anomaly from Chirinkotan was observed on 12 August. The Aviation Color Code remained at Yellow.
Geologic summary: The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.
CHIRPOI, Kuril Islands (Russia)
Summit elev. 742 m
SSVERT reported that a thermal anomaly from Snow, a volcano of Chirpoi, was detected in satellite images on 12 August, along with gas-and-steam emissions. Cloud cover prevented observations during 13-18 August. The Aviation Color Code remained at Yellow.
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. Two volcanoes on Chirpoi Island have been historically active. 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.
Summit elev. 3763 m
INSIVUMEH reported that explosions from Fuego during 13-14 August generated ash plumes that drifted 10 km W and SW. Three lava flows were active; one of the flows traveled SW. Five explosions during 14-15 August ejected incandescent material 100 m high, and generated ash plumes that rose 300 m and drifted 6 km. Lava flows were 150 and 300 m long in the Taniluya (SW) and Ceniza (SSW) drainages, respectively. The next day explosions produced ash plumes that rose 550 m and drifted 10 km W. On 17 August 30-m-wide lahars carrying blocks traveled down the Las Lajas, Ceniza, and El Jute (SE) drainages. During 17-18 August explosions that were heard generated ash plumes that rose 200-300 m and drifted 7 km W. Lava flows in the Taniluya and Ceniza drainages were each 400 m long.
During 18-19 August the flow rate increased; the lava flows were 600 and 800 m long in the Taniluya and Ceniza drainages, respectively. Incandescent blocks from the lava-flow fronts rolled down the flanks and reached vegetated areas. Explosions during 19-20 August ejected incandescent material as high as 150 m, and generated ash plumes that rose 400 m.
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 3,763-m-high Fuego and its twin volcano to the N, Acatenango. Construction of Meseta volcano continued until the late Pleistocene or early Holocene, after which growth of the modern Fuego volcano continued the southward migration of volcanism that began at Acatenango. Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows. The last major explosive eruption from Fuego took place in 1974, producing spectacular pyroclastic flows visible from Antigua.
KARYMSKY, Eastern Kamchatka (Russia)
Summit elev. 1536 m
KVERT reported that moderate seismic activity at Karymsky was detected during 9-17 August. Based on seismic interpretation, possible ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. on 15 August and to an altitude of 4 km (13,100 ft) a.s.l. the other days of the week. Satellite imagery showed a weak thermal anomaly on the volcano on 15 August; cloud cover prevented observations on the other days. The Aviation Color Code remained at Orange.
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 about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-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. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996.
KILAUEA, Hawaii (USA)
Summit elev. 1222 m
During 14-20 August HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater; the lake level was as high as 36 m below the Halema'uma'u crater floor on 16 and 18 August. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas.
At Pu'u 'O'o Crater, glow emanated from spatter cones on the N and S portions of the crater floor. The Kahauale’a 2 lava flow, fed by the NE spatter cone, was active with scattered break-out flows and burned the forest N of Pu'u 'O'o. On 18 August on 1330 the E flank of the N spatter cone apparently burst, causing lava flows to sporadically rush from the cone and cover a large part of the crater floor by the next morning. Peace Day activity, fed by lava tubes extending from Pu'u 'O'o, consisted of some breakouts on the pali and coastal plain, and an ocean entry outside of the National Park boundary to the E.
Geologic summary: Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 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.
KIZIMEN, Eastern Kamchatka (Russia)
Summit elev. 2376 m
KVERT reported that during 9-17 August moderate seismic activity continued at Kizimen. Video and satellite data showed that lava continued to extrude from the summit, producing incandescence, strong gas-and-steam activity, and hot avalanches on the W and E flanks. A thermal anomaly was detected in satellite images during 10-12 August; cloud cover obscured views on the other days. The Aviation Color Code remained at Orange.
Geologic summary: Kizimen is an isolated, conical stratovolcano that is morphologically similar to Mount St. Helens prior to its 1980 eruption. The summit of Kizimen consists of overlapping lava domes, and blocky lava flows descend the flanks of the volcano, which is the westernmost of a volcanic chain north of Kronotsky volcano. The 2,376-m-high Kizimen was formed during four eruptive cycles beginning about 12,000 years ago and lasting 2,000-3,500 years. The largest eruptions took place about 10,000 and 8300-8400 years ago, and three periods of longterm lava-dome growth have occurred. The latest eruptive cycle began about 3,000 years ago with a large explosion and was followed by lava-dome growth lasting intermittently about 1,000 years. An explosive eruption about 1,100 years ago produced a lateral blast and created a 1.0 x 0.7 km wide crater breached to the NE, inside which a small lava dome (the fourth at Kizimen) has grown. A single explosive eruption, during 1927-28, has been recorded in historical time.
MANAM, Northeast of New Guinea (SW Pacific)
Summit elev. 1807 m
Based on a pilot observation, the Darwin VAAC reported that on 19 August an ash plume from Manam rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted 65 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. 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.
Summit elev. 2552 m
INSIVUMEH reported that during 7-8 August white vapor plumes rose 200 m above Pacaya and drifted E. On 9 August seismicity increased, and Strombolian explosions ejected tephra 200 m above MacKenney Crater and onto the flanks, 400 m away from crater. The next day the number and magnitudes of explosions increased, and seismic signals indicating fluid movement were recorded. Tephra was again ejected 400 m away from MacKenney Crater, causing small avalanches of volcanic material on the flanks. On 12 August fumarolic plumes rose 50 m. Cloud cover prevented observations of the crater on 13 August; however, the seismic network recorded a few gas explosions and tremor.
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 volcano constructed on the southern rim of the 14 x 16 km Pleistocene Amatitlan caldera. A cluster of dacitic lava domes occupies the caldera floor. The Pacaya massif includes the Cerro Grande lava dome and a younger volcano to the SW. Collapse of Pacaya volcano about 1,100 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. During the past several decades, activity at Pacaya has consisted of frequent Strombolian eruptions with intermittent lava flow extrusion on the flanks of MacKenney cone, punctuated by occasional larger explosive eruptions.
PAGAN, United States
Summit elev. 570 m
The seismic network at Pagan recorded tremor and small discrete earthquakes during 9-16 August, indicating low-level unrest. A steam-and-gas plume was visible in satellite images during periods of clear weather and from web-camera images. A small explosion with a relatively high amplitude seismic component and small infrasound component occurred at 0010 on 12 August. The data suggested that degassing increased about 30 sec after the event. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.
Geologic summary: Pagan Island, the largest and one of the most active of the Mariana Islands volcanoes, consists of two stratovolcanoes connected by a narrow isthmus. Both North and South Pagan stratovolcanoes were constructed within calderas, 7 and 4 km in diameter, respectively. The 570-m-high Mount Pagan at the NE end of the island rises above the flat floor of the northern caldera, which may have formed less than 1000 years ago. South Pagan is a 548-m-high stratovolcano with an elongated summit containing four distinct craters. Almost all of the historical eruptions of Pagan, which date back to the 17th century, have originated from North Pagan volcano. The largest eruption of Pagan during historical time took place in 1981 and prompted the evacuation of the sparsely populated island.
Summit elev. 5426 m
CENAPRED reported that during 14-20 August seismicity at Popocatépetl indicated continuing emissions; cloud cover sometimes prevented observations of the crater. Incandescence from the crater was observed and occasionally intensified with some emissions. On 14 August a period of tremor was accompanied by an ash emission that drifted W. Ashfall was reported in the towns of Ozumba (18 km W), Tepetlixpa (20 km W), Atlautla (17 km W), and Ecatzingo (15 km SW) in the State of México. Later that day an ash plume rose 1 km above the crater and drifted W. Gas-and-steam plumes were observed during 15-16 August. A period of tremor on 17 August was accompanied by an ash plume that rose 1.5 km and drifted WSW. Ash fell in Tetela del Volcán (20 km SW), Ocuituco (24 km SW), Yecapixtla (31 km SW), Tlayacapan (40 km WSW), Cuautla (43 km SW), Ayala (45 km SW), and Cuernavaca (65 km WSW). On 18 August high-frequency, low-amplitude tremor was accompanied by an ash emission that rose 1.2 km and drifted SW. On 19 August minor steam-and-gas emissions drifted W. During 19-20 August emissions likely contained small amounts of ash but cloud cover prevented confirmation. The Alert Level remained at to Yellow, Phase Two.
Geologic summary: Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America's second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages.
SHIVELUCH, Central Kamchatka (Russia)
Summit elev. 3283 m
Based on visual observations and analyses of satellite data, KVERT reported that during 9-17 August a viscous lava flow effused onto the NW flank of Shiveluch's lava dome, accompanied by hot avalanches, incandescence, and fumarolic activity. Satellite images detected a thermal anomaly during 9-12, 14, and 16-17 August; cloud cover prevented observations on the other days. Explosions generated ash plumes that rose to altitudes of 5-7 km (16,400-23,000 ft) a.s.l. and drifted E and NE. The Aviation Color Code remained at Orange.
Geologic summary: The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. Intermittent explosive eruptions began in the 1990s from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964.
TOLBACHIK, Central Kamchatka (Russia)
Summit elev. 3682 m
KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 9-17 August that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and weak gas-and-steam plumes were observed. A thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.
Geologic summary: The massive Tolbachik basaltic volcano is located at the southern end of the dominantly andesitic Kliuchevskaya volcano group. The Tolbachik massif is composed of two overlapping, but morphologically dissimilar volcanoes. The flat-topped Plosky Tolbachik shield volcano with its nested Holocene Hawaiian-type calderas up to 3 km in diameter is located east of the older and higher sharp-topped Ostry Tolbachik stratovolcano. The summit caldera at Plosky Tolbachik was formed in association with major lava effusion about 6500 years ago and simultaneously with a major southward-directed sector collapse of Ostry Tolbachik volcano. Lengthy rift zones extending NE and SSW of the volcano have erupted voluminous basaltic lava flows during the Holocene, with activity during the past two thousand years being confined to the narrow axial zone of the rifts. The 1975-76 eruption originating from the SSW-flank fissure system and the summit was the largest historical basaltic eruption in Kamchatka.
VENIAMINOF, Alaska Peninsula
Summit elev. 2507 m
AVO reported that during 13-15 August seismic tremor at Veniaminof was high, and persistent elevated surface temperatures consistent with lava effusion were visible on satellite imagery. During 16-17 August the high levels of tremor became sustained; seismicity remained high through 20 August. Very high surface temperatures were detected in images during 16-17 August; only weak thermal signals were evident through the cloud cover in satellite data during 17-18 August. Clear views on 18 August from the FAA web-camera in Perryville (32 km SSE) showed minor ash emissions. During a helicopter overflight on 19 August geologists observed two active lava flows from the cone, and lava flowing passively over ice at the foot of the cone. Elevated surface temperatures were detected in satellite data during 19-20 August. Clear web-camera views showed minor ash emissions rising to an altitude of 3.7 (12,000 ft) a.s.l. and drifting W and then SSE, just past the caldera rim. The Volcano Alert Level remained at Watch and the Aviation Color code remained at Orange.
Geologic summary: Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the N, is deeply notched on the W by Cone Glacier, and is covered by an ice sheet on the S. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which reaches an elevation of 2,156 m and rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.