Activity for the week of 17 August-23 August 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
| Bougainville (Papua New Guinea)
| 6.137°S, 155.196°E
| Elevation 1855 m
Based on analyses of satellite imagery, the Darwin VAAC reported that on 21 August an ash plume from Bagana rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 93 km SW.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| Chuginadak Island (USA)
| 52.825°N, 169.944°W
| Elevation 1730 m
AVO reported that during 17-23 August cloud cover over Cleveland prevented observations of the summit crater. On 21 August AVO noted that a weak, 1-pixel thermal anomaly was observed in a recent satellite view during a cloud break. 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 3320 m
Sezione di Catania - Osservatorio Etneo reported that eight days after the preceding episode, Etna's New SE Crater was the site of another paroxysmal eruptive episode on the morning of 20 August, the eleventh event of this type since the beginning of 2011. The event began on 18 August with increased gas emissions from New SE Crater. On 19 August a powerful explosion ejected incandescent bombs and produced a small ash plume. The event was followed by a few more minor explosions, all accompanied by an increase in volcanic tremor amplitude and focal shift from the NE Crater toward the New SE Crater. Throughout the day small dilute ash was emitted. During the evening weak Strombolian activity commenced, with small explosions occurring about every 30 minutes.
On 20 August weak but continuous incandescence due to lava emissions appeared in the crater. Strombolian activity intensified, and lava overflowed the rim through a breach in the E crater rim traveling towards the Valle del Bove. Almost five hours later lava fountaining generated heavy fallout of large pyroclastics onto the flanks of the cone. Dense plumes of gas and tephra rose 5-6 km from the crater and drifted SW, causing ash- and lapilli-fall in areas such as Paternò (22 km SSW), Ragalna (13 km SSW), and Biancavilla (16 km SW). Closer to the crater, in the Torre del Filosofo area to the S, clasts up to several tens of centimeters in diameter landed on the ground.
Light brown dust clouds appeared in an area on the lower E flank of the cone, where a small depression had formed a few hours after the 12 August event. Shortly thereafter, the continuous, intense ejection of pyroclastics onto the flanks of the cone generated avalanches resembling pyroclastic flows, which descended a few hundred meters beyond the base of the cone, mainly towards the S. In the meantime, the lower portion of the E flank of the cone began to slide and collapse under the push of lava from within the channel. A new lava flow issued from the collapsed area, taking a more southerly path than the lava emitted until then, and divided into numerous branches. Lava fountaining slowed later in the evening and eventually ceased, followed by ash emissions from the crater for a few minutes. A series of ash explosions lasted for five minutes in the early morning on 21 August. The morphological changes affecting the pyroclastic cone surrounding the New SE Crater were significant. Besides the collapse on the lower E flank of the cone, the S and NE rims of the cone had grown in height.
Source: Sezione di Catania - Osservatorio Etneo (INGV)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 17-23 August, HVO reported that lava continued to trickle onto the collapsed floor of Kilauea's Pu'u 'O'o' crater and some spattering occurred from various areas on the floor. The only activity on the W flank was observed during 17-20 August; a small lava flow from the base of the N pond rim near the Kamoamoa fissures and a larger flow from the N flow branch were both active. During 20-21 August a small amount of lava emitted from a vent on the S crater floor flowed a short distance. Later, lava started issued in larger quantities from another source on the S part of the floor that quickly filled in a low trench. Lava continued to flow onto the crater floor during the next two days.
During 17-18 August lava flowed onto the floor of the vent inset within the E wall of Halema'uma'u Crater. By the next day a persistent spattering source at the W edge of the cavity pushed the lava surface sluggishly from W to E. During 19-21 August drain-and-fill cycles were observed; the highest level of the lava surface was below the inner ledge 75 m below Halema'uma'u Crater floor.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| Papua New Guinea
| 4.08°S, 145.037°E
| Elevation 1807 m
RVO reported that the summit area of Manam was obscured by atmospheric clouds on most days during 1-19 August. When the summit was clear to viewers on the mainland, 15-20 km away from Manam, both vents were emitting white vapor plumes. Main Crater produced light-gray ash clouds during 13 and 17-18 August, and bright, steady incandescence was visible on most clear nights. Weak incandescence was visible from Southern Crater on some nights. People living on the island reported occasional noises from both craters on 3 and 11 August. Seismicity during the reporting period was dominated by volcanic tremors. Discrete high-frequency volcano-tectonic earthquakes were also recorded. RVO noted that high-frequency volcano-tectonic earthquakes are not very common for Manam. An electronic tiltmeter located about 4 km SW from the summit craters continued to show inflation towards the summit area.
Based on analysis of satellite imagery, the Darwin VAAC reported that during 18-21 August ash plumes rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted 45-90 km NW and W.
Sources: Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC)
| New Britain (Papua New Guinea)
| 4.271°S, 152.203°E
| Elevation 688 m
RVO reported that white vapor plumes rose from Rabaul caldera's Tavurvur cone during 15-19 August. No volcano-related seismicity was recorded. The rate of uplift from GPS measurements on Matupit Island had increased from the end of July.
Source: Rabaul Volcano Observatory (RVO)
| Kyushu (Japan)
| 31.593°N, 130.657°E
| Elevation 1117 m
Based on information from JMA, the Tokyo VAAC reported that during 17-22 August explosions from Sakura-jima often produced plumes that rose to altitudes of 1.2-2.4 km (4,000-8,000 ft) a.s.l. and drifted E. On 18 August, a pilot observed an ash plume that rose to an altitude of 1.8 km (6,000 ft) a.s.l.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
| Halmahera (Indonesia)
| 1.693°N, 127.894°E
| Elevation 1229 m
Based on analyses of satellite imagery, the Darwin VAAC reported that during 18-21 August ash plumes from Dukono rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 110-150 km NE and N.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| Eastern Kamchatka (Russia)
| 54.049°N, 159.443°E
| Elevation 1513 m
KVERT reported that during 12-19 August moderate seismic activity continued at Karymsky, indicating that possible ash plumes rose to an altitude of 4.2 km (13,800 ft) a.s.l. A thermal anomaly on the volcano was detected by satellite during 14 and 17-18 August; cloud cover prevented observations on the other days. The Aviation Color Code remained at Orange.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| Eastern Kamchatka (Russia)
| 55.131°N, 160.32°E
| Elevation 2334 m
KVERT reported that during 12-19 August seismicity from Kizimen was above background levels and weak volcanic tremor continued to be detected. Video images showed an occasional steam plume that rose to an altitude of 3 km (9,800 ft) a.s.l. and fumarolic activity on 14 August. A lava flow on the E flank was active. Satellite images showed a large bright thermal anomaly on the volcano all week and a gas-and-steam plume that drifted 57 km NNE on 15 August. The Aviation Color Code remained at Orange.
Based on analyses of satellite imagery, the Tokyo VAAC reported that a possible eruption on 20 August produced a plume that rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted E. Subsequent images that day showed that continuing ash emissions had later dissipated.
Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Tokyo Volcanic Ash Advisory Center (VAAC)
| 40.59°S, 72.117°W
| Elevation 2236 m
During 16-23 August, OVDAS-SERNAGEOMIN reported that seismic activity indicated the eruption from the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, continued at a low level. Cloudy weather mostly prevented satellite and camera observations of the eruption during 16-17 August, however a mostly white plume was observed by an area camera rising 2 km above the crater on 16 August. A plume that was sometimes gray rose 2.5 km above the crater on 18 August. A plume observed in satellite imagery that same day drifted 200 km NW. A period of harmonic tremor that lasted about 25 minutes may have indicated lava emission. Incandescence was observed at night during 18-19 August.
On 19 August a camera recorded a mostly white plume that rose 2 km above the crater. Satellite imagery showed a plume drifting 270 km NW. During an overflight, conducted by ONEMI in collaboration with the Air Force, scientists observed a white plume rising 1.4 km that was dark gray for the first few meters above the vent. Solidified lava filled up a depression around Cordón Caulle; no active lava flows were noted. On 20 August a plume that was mostly white rose 2.5 km above the crater. Two explosive events caused the plume to rise 4 km and contain a higher concentration of ash. Satellite imagery showed a plume drifting 200 km WNW on 20 August, and 500 km SE and NW on 21 August. A white plume that rose 2 km above the crater was observed on 22 August. Satellite imagery showed a very diffuse plume drifting E. The Alert Level remained at Red.
Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)
| 12.702°N, 87.004°W
| Elevation 1745 m
The Washington VAAC reported that on 21 August emissions of gas and light ash from San Cristóbal were possibly detected in satellite imagery drifting 35 km WNW. Ash was not detected in subsequent images.
Source: Washington Volcanic Ash Advisory Center (VAAC)
| Central Kamchatka (Russia)
| 56.653°N, 161.36°E
| Elevation 3283 m
KVERT reported that seismic activity at Shiveluch was moderate during 12-19 August, and indicated that possible ash plumes rose to an altitude of 6.8 km (22,300 ft) a.s.l. on 13 August and to an altitude of 7.8 km (25,600 ft) a.s.l. on 15 August. Ash plumes may have risen to an altitude of 5 km (16,400 ft) a.s.l. on the other days. Gas-and-steam plumes containing ash observed in satellite imagery drifted 30 km SW on 12 August. Ground-based observers noted that an ash plume rose to an altitude of 6.5 km (21,300 ft) a.s.l. on 16 August. The Aviation Color Code remained at Orange.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
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.
1. The Weekly Volcanic Activity Report is intended to provide timely information about global volcanism on a weekly basis. Consequently, the report is generated rapidly by summarizing volcanic reports from various sources, with little time for fact checking. The accuracy of the Weekly Volcanic Activity Report is dependent upon the quality of the volcanic activity reports we receive. Reports published in the Bulletin of the Global Volcanism Network are monthly, and more carefully reviewed, although all of the volcanoes discussed in the Weekly Volcanic Activity Report are not necessarily reported in the Bulletin. Because of our emphasis on rapid reporting on the web we have avoided diacritical marks. Reports are updated on the Weekly Volcanic Activity Report web page as they are received, therefore information may be included regarding events that occurred before the current report period.
2. Rapidly developing events lead to coverage that is often fragmentary. Volcanoes, their eruptions, and their plumes and associated atmospheric effects are complex phenomena that may require months to years of data analysis in order to create a comprehensive summary and interpretation of events.
3. Preliminary accounts sometimes contain exaggerations and "false alarms," and accordingly, this report may include some events ultimately found to be erroneous or misleading.
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