Activity for the week of 17 August-23 August 2005
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.
Ongoing Activity
Anatahan
| Mariana Islands (USA)
| 16.35°N, 145.67°E
| Elevation 790 m
During 17-22 August, eruptive activity continued at Anatahan with ash plumes rising to heights of ~7.9 km (26,000 ft) a.s.l. Volcanic tremor and sporadic long-period earthquakes continued to occur at the volcano.
Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program
Bagana
| Bougainville (Papua New Guinea)
| 6.137°S, 155.196°E
| Elevation 1855 m
During 15-21 August, volcanic activity at Bagana remained at low levels. Variable amounts of thick "white vapor" were emitted from the summit crater. During several nights, dull-to-moderately bright incandescence was visible. On the 20th, lava flowed from volcano's main crater. Incandescent lava avalanches occasionally originated from unstable areas of the lava flow.
Source: Rabaul Volcano Observatory (RVO) via the Darwin Volcanic Ash Advisory Center
Barren Island
| Andaman Islands (India)
| 12.278°N, 93.858°E
| Elevation 354 m
A pilot reported a plume from Barren Island on 18 August at a height of ~3 km (10,000 ft) a.s.l. Ash was not visible on satellite imagery. Barren Island began erupting on 28 May.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
Colima
| Mexico
| 19.514°N, 103.62°W
| Elevation 3850 m
During 17- 22 August, small explosions at Colima produced low-level ash plumes. The largest events occurred on 21 and 22 August, producing plumes that drifted W. Due to the threat of lahars forming on the volcano's flanks, Universidad de Colima advised avoiding the ravines of La Lumbre, San Antonio, Monte Grande (in Colima state), and La Arena (in Jalisco state).
Source: Centro Universitario de Estudios e Investigaciones de Vulcanologia - Universidad de Colima
Cotopaxi
| Ecuador
| 0.677°S, 78.436°W
| Elevation 5911 m
A seismic anomaly that began at Cotopaxi in late July continued through 14 August. During this period, there was an increase in the number of long-period earthquakes in comparison to previous months. The earthquakes were less than M 3 and occurred at depths between 1 and 2 km below the volcano. Several of the earthquakes correlated with increases in the volume of fumarole emissions in the crater. No carbon dioxide was detected when measurements were made during 8-14 August.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG)
Galeras
| Colombia
| 1.22°N, 77.37°W
| Elevation 4276 m
During 19-21 August, 30 volcano-tectonic earthquakes were recorded at Galeras. The earthquakes occurred 3-4 km NW of the volcano's active cone, near the towns of Santa Bárbara, Nariño, and La Florida. About five earthquakes felt by nearby populations occurred at depths of 8-6 km, with the largest (M 4.7) occurring at a depth of 6 km on 21 August. No significant deformation was observed at the volcano during the report period, and gas emission continued from the main and secondary craters.
Source: Servicio Geológico Colombiano (SGC)
Kilauea
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 17-22 August, lava from Kilauea entered the sea at the East Lae`apuki area, and surface lava flows were sometimes visible on the Pulama Pali fault scarp and the coastal flat. By 22 August, surface lava on the W branch of the PKK lava flow was no longer visible. Background volcanic tremor was around normal levels at Kilauea's summit. Volcanic tremor was at moderate levels at Pu`u `O`o. Small periods of inflation and deflation occurred at the volcano during the report period.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
Langila
| New Britain (Papua New Guinea)
| 5.525°S, 148.42°E
| Elevation 1330 m
RVO reported that moderate levels of volcanic activity occurred at Langila's Crater 2 during 15-21 August. The activity was marked by occasional sub-continuous forceful emissions of ash. The resultant ash clouds rose as high as 1 km above the volcano (or ~7,600 ft a.s.l.) before drifting N and NW and depositing fine ash in villages along the island's coast. On the evening of the 18th, strong projections of incandescent lava fragments were seen. During the report period, there was no activity at Crater 3 and seismicity was low at the volcano. Based on a pilot report, the Darwin VAAC reported that ash from Langila was visible on 23 August at a height between 3 and 4.6 km (10,000 and 15,000 ft) a.s.l. No ash was visible on satellite imagery.
Sources: Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC)
Manam
| Papua New Guinea
| 4.08°S, 145.037°E
| Elevation 1807 m
According to RVO, during 15-21 August low-level volcanic activity continued at Manam. On the 15th, ash was emitted from Southern Crater. The Darwin VAAC reported that a low-level plume from Manam was visible on satellite imagery on 22 August. Manam remained at Alert Level "Stage 1," which indicates low levels of activity.
Sources: Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC)
Mauna Loa
| Hawaiian Islands (USA)
| 19.475°N, 155.608°W
| Elevation 4170 m
HVO reported on 21 August that extension across Mauna Loa's summit had resumed over the previous few weeks after pausing for much of July. Seismicity remained at low levels at the volcano.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
Ol Doinyo Lengai
| Tanzania
| 2.764°S, 35.914°E
| Elevation 2962 m
During a trip to Ol Doinyo Lengai by Fred Belton during 19 July to 9 August, three eruptions occurred at cone T58C on 20 and 21 July, one of which lasted 20 hours. No further eruptions were observed through 9 August. The most recent eruption prior to 20 July occurred on 9 July when large lava flows completely covered the campsite in the E part of the crater. Photos indicated that there may have been infrequent activity at the volcano at least as long ago as 15 May. No new cones had formed at the volcano since 15 July 2004 when T58C was created.
Source: Ol Doinyo Lengai (Fred Belton)
Rabaul
| New Britain (Papua New Guinea)
| 4.271°S, 152.203°E
| Elevation 688 m
Rabaul caldera's active Tavurvur cone continued to emit ash during 15-21 August, although there was a slight decline in the frequency of emissions in comparison to earlier weeks. Ash plumes rose 800-1,500 m above the volcano (or 4,900-7,200 ft a.s.l.) and drifted N and NW, occasionally depositing ash on the E part of Rabaul Town and in areas farther downwind. Projected incandescent lava fragments were visible at night. Seismicity was at moderate-to-high levels, with most earthquakes associated with ash emissions and explosions. Ground-deformation measurements from GPS and tide-gauge instruments fluctuated, however the general trend showed a slow rate of uplift. As a safety precaution, people were discouraged from venturing within 1 km of the erupting vent.
Source: Rabaul Volcano Observatory (RVO) via the Darwin Volcanic Ash Advisory Center
Reventador
| Ecuador
| 0.077°S, 77.656°W
| Elevation 3562 m
Volcanic activity continued at Reventador during 18-21 August, with ash plumes rising to a maximum height of ~5.8 km (19,000 ft) a.s.l. on 18 August. A hotspot was occasionally visible on satellite imagery during the report period.
Source: Washington Volcanic Ash Advisory Center (VAAC)
Sarigan
| Mariana Islands (USA)
| 16.708°N, 145.78°E
| Elevation 538 m
A seismic swarm that began at Sarigan on 9 August tapered off on 18 August.
Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program
Soufriere Hills
| Montserrat
| 16.72°N, 62.18°W
| Elevation 915 m
Volcanic and seismic activity remained at elevated levels at Soufrière Hills during 12-19 August. Periodic ash venting continued, with a vigorous episode occurring on 18 August at 1800. On 16 August, the presence of a small blocky lava dome with talus slopes was confirmed. There was some ash venting from the dome, but no significant rockfalls were seen. The daily recorded sulfur-dioxide flux averaged 570 metric tons per day (t/d), above the long-term eruption average of 500 t/d.
Source: Montserrat Volcano Observatory (MVO)
St. Helens
| United States
| 46.2°N, 122.18°W
| Elevation 2549 m
Growth of the new lava dome inside the crater of Mount St. Helens continued during 17-22 August accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. Growth of the lava dome continued to spawn rockfalls, which produced ash plumes that occasionally rose above the rim. A large rockfall on 21 August at 2056 generated a bright glow of hot rock and a thick ash plume that temporarily affected radio transmissions from instruments in the crater. St Helens remained at Volcano Advisory (Alert Level 2); aviation color code Orange.
Source: US Geological Survey Cascades Volcano Observatory (CVO)
Tungurahua
| Ecuador
| 1.467°S, 78.442°W
| Elevation 5023 m
During 17-22 August, volcanic activity at Tungurahua remained at low levels with small emissions of steam, gas, and variable ash content. On 21 and 22 August, ash fell in the town of Bilbao 8 km W of the volcano.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG)
Ulawun
| New Britain (Papua New Guinea)
| 5.05°S, 151.33°E
| Elevation 2334 m
Volcanic activity remained at low levels at Ulawun during 15-21 August, with steam emitted from the summit crater. Seismicity was at low levels, consisting of small low-frequency earthquakes.
Source: Rabaul Volcano Observatory (RVO) via the Darwin Volcanic Ash Advisory Center
Witori
| New Britain (Papua New Guinea)
| 5.576°S, 150.516°E
| Elevation 724 m
Pago was quiet during 15-21 August, with only steam emissions occurring from the upper vents of the fissure system. Seismicity was at low levels.
Source: Rabaul Volcano Observatory (RVO) via the Darwin Volcanic Ash Advisory Center
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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