Active volcanoes in the world: September 4 - September 10, 2013

Active volcanoes in the world: September 4 - September 10, 2013

During past seven days 8 volcanoes had new activity, ongoing activity was reported for 12 volcanoes. This report covers active volcanoes in the world from September 4 – September 10, 2013 based on Smithsonian/USGS criteria.

New activity/unrest: | Arenal, Costa Rica | Etna, Sicily (Italy) | Kliuchevskoi, Central Kamchatka (Russia) | Lokon-Empung, Sulawesi | Sakura-jima, Kyushu | Santa María, Guatemala | Suwanose-jima, Ryukyu Islands and Kyushu | Ubinas, Perú

Ongoing activity: | Batu Tara, Komba Island (Indonesia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Kizimen, Eastern Kamchatka (Russia) | Manam, Northeast of New Guinea (SW Pacific) | Popocatépetl, México | Rabaul, New Britain | Reventador, Ecuador | Shiveluch, Central Kamchatka (Russia) | Ulawun, New Britain | 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.

New activity

ARENAL, Costa Rica 
10.463°N, 84.703°W; summit elev. 1670 m

OVSICORI-UNA reported that plumes composed mainly of water vapor rose from the NE and SE edges of Arenal's Crater C on 8 and 9 September. Tremors indicative of hydrothermal and magmatic activity were detected on 8 September. The report noted that seismic and fumarolic activity had been very low in the past three years; however steam plumes associated with heavy rains had been frequent.

Geologic summary: Conical Volcan Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1,657-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. The earliest known eruptions of Arenal took place about 7,000 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. Arenal's most recent eruptive period began with a major explosive eruption in 1968. Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank.

ETNA, Sicily (Italy) 
37.734°N, 15.004°E; summit elev. 3330 m

Sezione di Catania - Osservatorio Etneo reported that a series of small and sporadic ash emissions from Etna's New Southeast Crater (NSEC) began during the morning of 3 September, marking the end of four months of complete quiescence. Weak Strombolian activity from NSEC was observed during the early morning of 6 September. At daybreak small ash puffs were emitted once or twice per hour. The same morning intense incandescence emanated from Bocca Nuova. The report stated that since early May only degassing from the summit craters was noted, along with usual bangs and rumblings from deep within the conduit of the Northeast Crater (NEC), which during the past few weeks had become more continuous and louder.

Geologic summary: Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BC. Historical lava flows cover much of the surface of this massive basaltic stratovolcano, the highest and most voluminous in Italy. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater. Flank eruptions, typically with higher effusion rates, occur less frequently and originate from fissures that open progressively downward from near the summit. A period of more intense intermittent explosive eruptions from Etna's summit craters began in 1995. The active volcano is monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) in Catania.

KLIUCHEVSKOI, Central Kamchatka (Russia) 
​56.057°N, 160.638°E; summit elev. 4850 m

KVERT reported that moderate seismic activity at Kliuchevskoi was detected during 30 August-6 September. A video camera recorded incandescence from the summit and WSW flank at night, and gas-and-steam plumes containing minor amounts of ash. Strombolian activity continued and a lava flow effused onto the SW flank. A large thermal anomaly from the lava dome was detected in satellite images.

The Aviation Color Code remained at Yellow.

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.

LOKON-EMPUNG, Sulawesi 
1.358°N, 124.792°E; summit elev. 1580 m

Based on ground reports from CVGHM, the Darwin VAAC reported that on 9 September an ash plume from Lokon-Empung rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted N. Ash was not detected in satellite images due to meteorological clouds. According to a news article an explosion at 0630 generated an ash plume that rose 1.5 km; the explosion was heard 10 km away. The VAAC noted that the next day ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. although ash was again not identified in satellite images.

Geologic summary: The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2.2 km apart) has a flat, craterless top. The morphologically younger Empung volcano has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.

SAKURA-JIMA, Kyushu 
31.585°N, 130.657°E; summit elev. 1117 m

JMA reported that 15 explosions from Sakura-jima's Showa Crater ejected tephra as far as 1,300 m during 2-6 September. Incandescence from the crater was visible some nights. An explosion at 1100 on 4 September generated an ash plume that rose 2.8 km and drifted S, causing ashfall in areas downwind including Arimuracho (4 km SSE). Tephra 4 cm in diameter was confirmed in an area 3 km S, and tephra 1 cm in diameter was reported 10 km SSE.

Based on information from JMA, the Tokyo VAAC reported that during 4-10 September explosions generated plumes that rose to altitudes of 2.4-4.3 km (8,000-14,000 ft) a.s.l., and most days drifted N, NE, E, S, and SW. On 6 and 8 September pilots observed ash plumes that rose to altitudes of 3-4.6 km (15,000 ft) a.s.l.; plumes drifted NE on 8 September.

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 was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago 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 4,850 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.

SANTA MARIA, Guatemala 
14.756°N, 91.552°W; summit elev. 3772 m

INSIVUMEH reported that at 1405 on 5 September a lahar descended Santa María's Nima I drainage on the S flank carrying mostly fine sediment and 50-cm-diameter blocks, but also a small percentage of blocks 1-2 m in diameter. During 5-10 September white plumes rose 200-500 m and drifted W, SW, E, and NE. A few weak avalanches descended the S part of the active crater of the Santiaguito lava-dome complex. On 10 September another lahar traveled down the Nima I drainage, carrying blocks up to 3 m in diameter. The lahar was 15 m wide, 6 m deep, and had a sulfur odor.

Geologic summary: Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large 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, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

SUWANOSE-JIMA, Kyushu
29.635°N, 129.716°E; summit elev. 799 m

According to the Tokyo VAAC, the JMA reported that during 5-6 September explosions from Suwanose-jima generated ash plumes that rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted NW and N.

Geologic summary: The 8-km-long, spindle-shaped island of Suwanose-jima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. Only about 50 persons live on the sparsely populated island. 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. Suwanose-jima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from On-take (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 On-take 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.

UBINAS, Perú 
16.355°S, 70.903°W; summit elev. 5672 m

According to a news source, IGP reported that a seventh phreatic explosion from Ubinas occurred just after 1800 on 4 September; six explosions were recorded between 1 and 3 September. The explosion caused alarmed residents of Querapi, 4 km S, to temporarily leave their homes and congregate in the town square.

Geologic summary: A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives 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 Peru. The upper slopes of the stratovolcano, composed primarily of Pleistocene andesitic lava flows, 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 extend 10 km from the volcano. Widespread Plinian pumice-fall deposits from Ubinas include some of Holocene age. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor explosive eruptions.

Ongoing activity

BATU TARA, Komba Island (Indonesia) 
7.792°S, 123.579°E; summit elev. 748 m

Based on analyses of satellite imagery and wind data, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that on 5 September an ash plume from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 75 km W.

Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly 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.

FUEGO, Guatemala 
14.473°N, 90.880°W; summit elev. 3763 m

INSIVUMEH reported that during 4-6 September explosions from Fuego generated ash plumes that rose 800-850 m and drifted 10-12 km W and SW. Block avalanches descended the Ceniza (SSW) drainage. During 5-6 September explosions produced shock waves that rattled structures in villages 10 km away.

On 6 September the number and magnitude of explosions increased; rumbling and shock waves were reported 12 km away. Ash plumes rose 750 m and drifted 10 km W and SW. During 7-10 September explosions generated ash plumes that rose 250-400 m; plumes drifted 7 km W and NW on 7 September. Incandescent material was ejected 100 m high and then formed small avalanches. On 9 September heavy rain was followed by lahars in the Las Lajas and El Jute drainages which carried blocks 2 m in diameter. During 9-10 September ash plumes drifted 6 km E and SE.

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) 
54.05°N, 159.45°E; summit elev. 1536 m

KVERT reported that moderate seismic activity at Karymsky was detected during 30 August-6 September. Weak ash explosions likely occurred. Satellite images detected no activity or were obscured by clouds. 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) 
19.421°N, 155.287°W; summit elev. 1222 m

During 4-10 September 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 47-56 m below the Halema'uma'u crater floor. 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. Short lava flows issued from one or more of the NE spatter cones four times during 8-9 September.

The 3.2-km-long 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. Peace Day activity, fed by lava tubes extending from Pu'u 'O'o, consisted of some breakouts on the pali and coastal plain.

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)
55.130°N, 160.32°E; summit elev. 2376 m

KVERT reported that during 30 August-6 September 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 on 2 and 5 September; 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) 
4.080°S, 145.037°E; summit elev. 1807 m

RVO reported that after a small eruption from Manam's Southern Crater during 27-28 August, activity subsided. Diffuse gray-brown ash plumes, emitted at short intervals, rose from the crater during 29-30 August, and crater incandescence was noted. Seismicity declined and was at a low level by the end of the day on 31 August.

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.

POPOCATEPETL, México 
19.023°N, 98.622°W; summit elev. 5426 m

CENAPRED reported that during 4-10 September seismicity at Popocatépetl indicated continuing emissions of water vapor, gas, and small amounts of ash; cloud cover sometimes prevented observations of the crater. Incandescence from the crater was observed on most nights. Steam, gas, and ash plumes drifted SE on 8 September and NW on 9 September. 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.

RABAUL, New Britain 
4.271°S, 152.203°E; summit elev. 688 m

RVO reported that during 1-31 August low-level activity at Rabaul caldera's Tavurvur cone consisted of pale gray plumes with variable but mostly minor ash content. Intervals between emissions ranged from tens of seconds to hours. Ash plumes rose as high as 1 km and drifted NW, causing ashfall mainly in a narrow band between the E part of old Rabaul town (3-5 km NW) and Namanula Hill, and further downwind towards Nonga area. Malaguna No. 1 and other parts of Rabaul town were also affected. Most noises were associated with forceful emissions and were short in duration. Seismicity was high and dominated by ash-emission events.

Ash plume characteristics were similar during 1-5 September, although the interval time between emissions ranged from tens of seconds to tens of minutes. Plumes rose 50 m and were immediately blown NW by strong winds which re-suspended older ash deposits in widespread areas including Rabaul town. Residents of Rabaul town reported a chlorine odor; RVO noted that the odor, although uncommon, did not represent an increase in activity.

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. 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 E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. 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.

REVENTADOR, Ecuador 
0.077°S, 77.656°W; summit elev. 3562 m

IG reported that seismicity remained elevated at Reventador during 4-10 September. Although cloud cover often prevented observations, ash plumes were occasionally observed rising from the lava dome. On 6 September IG staff observed 1-km-long deposits from a pyroclastic flow that had descended the S flank after an explosion.  Ash plumes rose 1-2 km above the lava dome during 6-7 September, and minor ash emissions were noted on 9 September. 

Geologic summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. Reventador 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.

SHIVELUCH, Central Kamchatka (Russia)
56.653°N, 161.360°E; summit elev. 3283 m

Based on visual observations and analyses of satellite data, KVERT reported that during 30 August-6 September a viscous lava flow effused onto the N and NW flanks of Shiveluch's lava dome, accompanied by hot avalanches, incandescence, and fumarolic activity. A thermal anomaly was detected daily in satellite images. 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.

ULAWUN, New Britain
5.05°S, 151.33°E; summit elev. 2334 m

RVO reported that activity at Ulawun was low during 4-31 August; emissions from the summit crater consisted of white vapor until 16 August, and were gray during 17-31 August. Emissions were more energetic on 24 August, rising 200 m. A single booming noise and weak incandescence was also reported that day. RSAM values fluctuated but decreased overall.

Geologic summary: The symmetrical basaltic to andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. Ulawun rises above the N coast of New Britain opposite Bamus volcano. The upper 1,000 m of the 2,334-m-high volcano is unvegetated. A steep-walled valley cuts the NW side of the volcano, and a flank lava-flow complex lies to the S of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

VENIAMINOF, Alaska Peninsula 
56.17°N, 159.38°W; summit elev. 2507 m

AVO reported continuous seismic tremor at Veniaminof during 4-10 September, and elevated surface temperatures detected in satellite images consistent with lava effusion and fountaining. Cloud cover sometimes prevented web cam views (from Perryville, 32 km SSE) of the intracaldera cone, although on 4 September a diffuse ash plume was observed rising several hundred feet above the cone and drifting E. On 7 September the web cam recorded a plume more steam-rich than in recent days. No ash emissions were visible in web cam images on 10 September. 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.

Source: GVP

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