Smithsonian/USGS Weekly Volcanic Activity Report 28 September-4 October 2011
From: "Kuhn, Sally" <KUHNS@xxxxxx>
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Smithsonian/USGS Weekly Volcanic Activity Report
28 September-4 October 2011
Sally Kuhn Sennert - Weekly Report Editor
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Hierro, Canary Islands (Spain) | Krakatau, Indonesia | Nabro, Eritrea | Rincón de la Vieja, Costa Rica | Shiveluch, Central Kamchatka (Russia) | Villarrica, Central Chile
Ongoing Activity: | Cleveland, Chuginadak Island | Etna, Sicily (Italy) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Kizimen, Eastern Kamchatka (Russia) | Puyehue-Cordón Caulle, Central Chile | Sakura-jima, Kyushu | Santa María, Guatemala
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.
Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source.
New Activity/Unrest
HIERRO Canary Islands (Spain) 27.73°N, 18.03°W; summit elev. 1500 m
Instituto Geográfico Nacional (IGN) reported a drastic increase in the seismic activity at Hierro during 27 September-3 October, with more than 1,100 new seismic events detected, 83 of them felt by residents, with a maximum intensity value of IV using EMS-98 (European Macroseismic Scale). Most of the hypocenters were located offshore, SW of the island, at around 14 km depth. The maximum magnitude recorded during this week was 3.8. The total number of located events had reached more than 9,300 since the anomalous activity began on 16 July. The superficial deformation measured by the GPS network had reached 35 mm.
Geologic Summary. The triangular island of Hierro is the SW-most and least studied of the Canary Islands. The massive Hierro shield volcano is truncated by a large NW-facing escarpment formed as a result of gravitational collapse of El Golfo volcano about 130,000 years ago. The steep-sided 1500-m-high scarp towers above a low lava platform bordering 12-km-wide El Golfo Bay, and three other large submarine landslide deposits occur to the SW and SE. Three prominent rifts oriented NW, NE, and south at 120 degree angles form prominent topographic ridges. The subaerial portion of the volcano consists of flat-lying Quaternary basaltic and trachybasaltic lava flows and tuffs capped by numerous young cinder cones and lava flows. Holocene cones and flows are found both on the outer flanks and in the El Golfo depression. Hierro contains the greatest concentration of young vents in the Canary Islands. Uncertainty surrounds the report of an historical eruption in 1793.
Source: Instituto Geográfico Nacional (IGN) http://www.ign.es/ign/layout/volcaVolcanologia.do
KRAKATAU Indonesia 6.102°S, 105.423°E; summit elev. 813 m
CVGHM reported that seismicity from Anak Krakatau in 2011, as late as 10 July, consisted of 20-30 volcanic-earthquake events per day and shallow events ranged from 120 to 135 events per day. Hundreds of events per day were detected during swarms. On 10 July, the seismic equipment was damaged by Krakatau's activity but was again operational in mid-September. During 18-30 September seismic events reached 4-5 events per minute. Visual observations in 2011 until 13 September indicated occasional explosive eruptions that would eject material and produce ash plumes. During 14-30 September fumarolic activity from the crater and in the fumarolic fields was visible. The Alert Level was increased to 3 (on a scale of 1-4) on 30 September based on an increase in seismic activity and widespread fumarolic activity.
Geologic Summary. Renowned Krakatau volcano lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 AD, resulted in a 7-km-wide caldera. Remnants of this volcano formed Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. The post-collapse cone of Anak Krakatau (Child of Krakatau), constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan, has been the site of frequent eruptions since 1927.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://www.vsi.esdm.go.id/
NABRO Eritrea 13.37°N, 41.70°E; summit elev. 2218 m
According to NASA's Earth Observatory, satellite images of Nabro acquired on 28 September showed heat from the vent in the central crater, and from an area 1.3 km S of the vent that indicated an active lava flow. A small and diffuse plume rose from the vent. A region of seemingly thicker black ash (that completely covered the sparse vegetation) was noted S of the crater and thinner layers of ash (with some areas of visible vegetation) flanked either side of the region.
Geologic Summary. The 2218-m-high Nabro stratovolcano is the highest volcano in the Danakil depression of northern Ethiopia and Eritrea. Located at the SE end of the Danakil Alps, Nabro lies in the Danakil horst. Nabro is the most prominent and NE-most of three volcanoes with large summit calderas aligned in a NE-SW direction SW of Dubbi volcano. These three volcanoes, along with Sork Ale volcano, collectively comprise the Bidu volcanic complex. The complex Nabro stratovolcano is truncated by nested calderas, 8 and 5 km in diameter. The larger caldera is widely breached to the SW. Nabro was constructed primarily of trachytic lava flows and pyroclastics. Post-caldera rhyolitic obsidian domes and basaltic lava flows were erupted inside the caldera and on its flanks. Some very recent lava flows were erupted from NNW-trending fissures transverse to the trend of the Nabro volcanic range.
Source: NASA Earth Observatory http://earthobservatory.nasa.gov/
RINCON DE LA VIEJA Costa Rica 10.830°N, 85.324°W; summit elev. 1916 m
On 30 September, OVSICORI-UNA reported phreatic eruptions from Rincón de la Vieja's active crater during the previous six weeks. A well-documented event on 16 September ejected sediment that covered sections of the upper N walls. Some of the material was washed down the flanks and caused changes in water quality along the main creeks and major rivers up to 18 km away from the source. The death of several fish species was noted the next day and sediment deposits 10-15 cm deep were sampled 2 km N of the active crater. Scientists conducting fieldwork during 27-29 September observed that the hot lake was convecting and grayish in color due to the suspended sediments. Preliminary deformation and temperature measurements did not indicate any significant changes.
Geologic Summary. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Rincón de la Vieja, sometimes known as the "Colossus of Guanacaste," has an estimated volume of 130 cu km and contains at least 9 major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the Rincón complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 cu km Río Blanca tephra about 3500 years ago was the last major magmatic eruption from the volcano. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent crater containing a 500-m-wide acid lake (known as the Active Crater) located ENE of Von Seebach crater.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/
SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m
KVERT reported that seismic activity at Shiveluch was moderate during 23-30 September, and indicated that possible ash plumes rose to an altitude of 4.6 km (15,100 ft) a.s.l. during 23 and 26-27 September. Ground-based observers noted that ash plumes rose to altitudes of 5.5 and 4.5 km (18,000 and 14,800 ft) a.s.l. on 23 and 27 September, respectively. Ash plumes observed in satellite imagery during 23-24 September drifted 45 km E. Seismicity increased on 3 October. Ash plumes rose to altitudes of 6-9 km (19,700-29,500 ft) a.s.l. during 3-5 October. Ground-based observers noted on 5 October a brightly incandescent lava dome, which was also detected as a large and bright thermal anomaly in satellite imagery. The Aviation Color Code was raised to Red.
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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
VILLARRICA Central Chile 39.42°S, 71.93°W; summit elev. 2847 m
According to Projecto Observación Visual Volcán Villarrica (POVI), an image from 17 September showed the inner SSW wall of the crater covered with snow and ice, and a thin layer of ash. A rapid rise in the level of the lava lake (in a pit about 40 m wide) on 19 September caused much of the snow and ice to melt, especially on the southern inner wall. Strombolian explosions from the crater were observed on 26 September, and tephra deposits on the E edge of the crater were noted. On 27 September incandescence from the lava lake were reflected in the cloud cover above.
Geologic Summary. Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide caldera formed during the late Pleistocene, more than 0.9 million years ago. A 2-km-wide postglacial caldera is located at the base of the presently active, dominantly basaltic-to-andesitic cone at the NW margin of the Pleistocene caldera. About 25 scoria cones dot Villarrica's flanks. Plinian eruptions and pyroclastic flows have been produced during the Holocene from this dominantly basaltic volcano, but historical eruptions have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Lahars from the glacier-covered volcano have damaged towns on its flanks.
Source: Projecto Observación Visual Volcán Villarrica (POVI) http://www.povi.cl/
Ongoing Activity
CLEVELAND Chuginadak Island 52.825°N, 169.944°W; summit elev. 1730 m
AVO reported that during 27-28 September and 30 September-1 October thermal anomalies over Cleveland's summit lava dome were detected in satellite images and suggested that the lava dome continued to slowly grow. Clouds obscured views on 29 September and during 2-3 October. Elevated surface temperatures were detected by satellite in partly cloudy images acquired during 3-4 October. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange. No current seismic information was available because Cleveland does not have a real-time seismic network.
Geologic Summary. Symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/
ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m
Sezione di Catania - Osservatorio Etneo reported that the fifteenth paroxysmal eruptive episode of 2011 took place at the New SE Crater of Etna during the evening of 28 September. That morning, noises originated from the New SE Crater. At 1600 volcanic tremor amplitude started to increase, and rhythmic ash emissions that rose from a vent located within the crater were occasionally accompanied by small Strombolian explosions. Starting at 1930 Strombolian activity progressively increased both in the intensity and frequency of explosions, and eventually became continuous. Bombs and scoria were ejected well beyond the crater rim. A small amount of lava flowed through the notch in the SE flank of the volcano at 2115 and was soon followed by explosions from a vent within the same area. The Strombolian activity waned for a few minutes then rapidly increased, forming a sustained lava fountain that rose as high as 800 m. At 2133 and 2134 two powerful explosions originating from a vent on the E rim of the crater created shock waves visible in the clouds above the crater and ejected large bombs hundreds of meters away. Lava fountains 100-150 m high commenced from a vent on the N base of the New SE Crater cone at 2136. The vent emitted a small lava flow soon after. At 2155 activity from all vents decreased, and between 2205 and 2210 all explosive activity ceased. Lava continued to flow until 2330.
The lava flow emitted from the SE flank of the cone reached the lower portion of the W slope of the Valle del Bove, somewhat SW of Monte Centenari. Ash plumes drifted SW and light ashfall occurred on the S flank of Etna, including in the towns of Nicolosi (14 km S) and Catania (27 km S).
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.
Source: Sezione di Catania - Osservatorio Etneo http://www.ct.ingv.it/
KARYMSKY Eastern Kamchatka (Russia) 54.05°N, 159.45°E; summit elev. 1536 m
KVERT reported that seismic activity continued at a moderate level at Karymsky during 23-30 September and indicated that possible ash plumes rose to an altitude of 4.5 km (14,800 ft) a.s.l. Satellite imagery showed a thermal anomaly on the volcano on 24 September and ash plumes that drifted 80 km SE during 28-29 September. 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
During 28 September-4 October, HVO reported that the lava lake circulated and periodically rose and fell in the deep pit within Kilauea's Halema'uma'u crater. Almost daily measurements indicated that the gas plume from the vent continued to deposit variable amounts of ash and occasionally fresh spatter nearby.
At the E rift zone, the fissure that formed on 21 September on the upper E flank of Pu'u 'O'o continued to feed lava flows on 28 September that traveled along the edges of a low lava ridge. Most of the active lava spread out at higher elevations S and W of Pu'u Halulu (1.3 km NE of Pu'u 'O'o). Lava activity resumed from two sources on the E edge of the Pu'u 'O'o Crater floor and continued to spread W within the crater. During an overflight on 29 September, geologists observed that the fissure fed scattered active lava flows within 1.8 km on the SE flank of the cone. During 2-3 October lava from the E-crater floor source covered the crater floor. On 4 October active lava was confined to a small lake on the E side of the crater floor.
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.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/
KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m
KVERT reported that during 23-30 September seismicity at Kizimen remained high with 1,200-1,600 earthquakes recorded daily. A large thermal anomaly on the volcano was detected daily in satellite images. A large lava flow on the NE flank continued to effuse and strong fumarolic activity was observed. 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
PUYEHUE-CORDON CAULLE Central Chile 40.590°S, 72.117°W; summit elev. 2236 m
Based on seismicity during 28 September-4 October, OVDAS-SERNAGEOMIN reported that the eruption from the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, continued at a low level. Plumes visible in satellite images drifted 30-300 km NW, NE, E, and SE during 28 September-3 October. Plumes were also observed with an area camera to rise as high as 4 km during 30 September-4 October. The Alert Level remained at Red.
Geologic Summary. The Puyehue-Cordón Caulle volcanic complex (PCCVC) is a large NW-SE-trending late-Pleistocene to Holocene basaltic-to-rhyolitic transverse volcanic chain SE of Lago Ranco. The 1799-m-high Pleistocene Cordillera Nevada caldera lies at the NW end, separated from Puyehue stratovolcano at the SE end by the Cordón Caulle fissure complex. The Pleistocene Mencheca volcano with Holocene flank cones lies NE of Puyehue. The basaltic-to-rhyolitic Puyehue volcano is the most geochemically diverse of the PCCVC. The flat-topped, 2236-m-high Puyehue volcano was constructed above a 5-km-wide caldera and is capped by a 2.4-km-wide summit caldera of Holocene age. Lava flows and domes of mostly rhyolitic composition are found on the eastern flank of Puyehue. Historical eruptions originally attributed to Puyehue, including major eruptions in 1921-22 and 1960, are now known to be from the Cordón Caulle rift zone. The Cordón Caulle geothermal area, occupying a 6 x 13 km wide volcano-tectonic depression, is the largest active geothermal area of the southern Andes volcanic zone.
Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
Based on information from JMA, the Tokyo VAAC reported that during 28 September-3 October explosions from Sakura-jima produced plumes that rose to altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted in multiple directions. On 30 September and during 1-2 October pilots observed ash plumes that rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and mostly drifted NE, E, and ESE.
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.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m
INSIVUMEH reported that on 29 September a lahar 28 m wide and 2 m deep traveled down Santa María's Rio Nima II drainage, carrying 2-m-wide blocks and tree branches. During 29-30 September and 3-4 October explosions from the Santiaguito lava dome complex produced gray ash plumes that rose 1 km above the crater and drifted 15 km E and SW. Avalanches from the lava-flow fronts descended the flanks. During 3-4 October avalanches from the lava dome occasionally generated pyroclastic flows; lava flows were active on the SW and SE flanks.
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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/inicio.html
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Sally Kuhn Sennert
SI/USGS Weekly Volcanic Activity Report Editor
Global Volcanism Program
http://www.volcano.si.edu/reports/usgs/
Smithsonian Institution, National Museum of Natural History
Department of Mineral Sciences, MRC-119
Washington, D.C., 20560
Phone: 202.633.1805Fax: 202.357.2476
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