Activity for the week of 28 September-4 October 2011
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 / Unrest
| 27.73°N, 18.03°W
| Elevation 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.
Source: Instituto Geográfico Nacional (IGN)
| 6.102°S, 105.423°E
| Elevation 155 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.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)
| 13.37°N, 41.7°E
| Elevation 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.
Source: NASA Earth Observatory
Rincon de la Vieja
| Costa Rica
| 10.83°N, 85.324°W
| Elevation 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.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)
| Central Kamchatka (Russia)
| 56.653°N, 161.36°E
| Elevation 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| 39.42°S, 71.93°W
| Elevation 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.
Source: Proyecto Observación Villarrica Internet (POVI)
| Kyushu (Japan)
| 31.593°N, 130.657°E
| Elevation 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.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
| Chuginadak Island (USA)
| 52.825°N, 169.944°W
| Elevation 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.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
| Sicily (Italy)
| 37.748°N, 14.999°E
| Elevation 3295 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).
Source: Sezione di Catania - Osservatorio Etneo (INGV)
| Eastern Kamchatka (Russia)
| 54.049°N, 159.443°E
| Elevation 1513 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 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.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| Eastern Kamchatka (Russia)
| 55.131°N, 160.32°E
| Elevation 2334 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| 40.59°S, 72.117°W
| Elevation 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.
Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)
| 14.757°N, 91.552°W
| Elevation 3745 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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)
Criteria & Disclaimers
The Weekly Volcanic Activity Report does not necessarily include all volcanic activity that occurred on Earth during the week. More than a dozen volcanoes globally have displayed more-or-less continuous eruptive activity for decades or longer, and such routine activity is typically not reported here. Moreover, Earth's sea-floor volcanism is seldom reported even though in theory it represents the single most prolific source of erupted material. The Weekly Volcanic Activity Report summarizes volcanic activity that meets one or more of the following criteria:
- A volcano observatory raises or lowers the alert level at the volcano.
- A volcanic ash advisory has been released by a volcanic ash advisory center (VAAC) stating that an ash cloud has been produced from the volcano.
- A verifiable news report of new activity or a change in activity at the volcano has been issued.
- Observers have reported a significant change in volcanic activity. Such activity can include, but is not restricted to, pyroclastic flows, lahars, lava flows, dome collapse, or increased unrest.
Volcanoes are included in the "New Activity/Unrest" section of the Weekly Volcanic Activity Report if the activity occurs after at least 3 months of quiescence. Once a volcano is included in the "New Activity/Unrest" section, updates will remain in that section unless the activity continues for more than 1 month without escalating, after which time updates will be listed in the "Continuing Activity" section. Volcanoes are also included in the "New Activity/Unrest" section if the volcano is undergoing a period of relatively high unrest, or increasing unrest. This is commonly equal to Alert Level Orange on a scale of Green, Yellow, Orange, Red, where Red is the highest alert. Or alert level 3 on a scale of 1-4 or 1-5.
It is important to note that volcanic activity meeting one or more of these criteria may occur during the week, but may not be included in the Weekly Volcanic Activity Report because we did not receive a report.
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