Activity for the week of 12 October-18 October 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.
New Activity / Unrest
Dabbahu
| Ethiopia
| 12.595°N, 40.48°E
| Elevation 1401 m
Volcanic activity at Erta Ale discussed in the 5-11 October 2005 Weekly Volcanic Activity Report actually occurred at Dabbahu. The correct report is below.
A team of scientists visited the Da'Ure locality immediately adjacent to the NE flank of the Quaternary Dabbahu (or Boina) felsic complex on 4 and 5 October after receiving reports of volcanic activity there on 26 September. People in the area noted that on 26 September at about 1300 a very strong earthquake shook the area, and was followed by a dark column of "smoke" that rose high into the atmosphere and spread out to form a cloud, which darkened the area for 3 days and 3 nights. The scientists determined that a minor explosive eruption occurred from two semi-circular vents, producing ashfall that was ~5 cm thick near the vent. Ash deposits extended more than 500 m from the vent. Boulders emitted during the eruption were as large as 3 m and were deposited as far as 20 meters away. The scientists noted intense degassing from the vents, the scent of sulfur dioxide, and the sound of boiling water in the vents. As of about 10 October, the Addis Ababa University Geophysical Observatory reported that seismic activity in the area was continuing.
Source: Gezahegn Yirgu, Department of Earth Sciences, Addis Ababa University
Krummel-Garbuna-Welcker
| New Britain (Papua New Guinea)
| 5.416°S, 150.027°E
| Elevation 564 m
RVO reported that an eruption began at Garbuna on the afternoon of 16 October when "white vapor" rose above the volcano and a couple of felt earthquakes occurred. On 17 October, an eruption column rose 3-4 km above the volcano's summit (or 11,700-15,000 ft a.s.l.). At 1100 fine ash fell on the W and NW sides of the volcano, covering two plantations. Water sources originating from Garbuna were affected by the eruption. According to RVO, the volcano last erupted about 1,700 years ago.
Sources: Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC), The National
Ongoing Activity
Cleveland
| Chuginadak Island (USA)
| 52.825°N, 169.944°W
| Elevation 1730 m
After a brief ash burst at Cleveland on 7 October, no further eruptive activity was recorded at the volcano. On 10 October, AVO reduced the Concern Color Code from Orange to Yellow. AVO warned that although there were no additional ash bursts noted, they consider the volcano restless. Explosive ash-producing events could occur at any time and without warning (owing to the lack of local seismic monitoring). AVO continued to monitor the volcano using satellite imagery.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
Dukono
| Halmahera (Indonesia)
| 1.693°N, 127.894°E
| Elevation 1229 m
Explosions and pyroclastic ejections continued at Dukono during 10-16 October. Ash columns rose 100-950 m above the summit (or 4,200-7,000 ft a.s.l.) and mainly drifted SE. Seismicity was dominated by explosion earthquakes. Dukono remained at Alert Level 2.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)
Erebus
| Antarctica
| 77.53°S, 167.17°E
| Elevation 3794 m
According to the Mt. Erebus activity log, several "small- to medium-sized" eruptions occurred during 12-18 October, with a "very large" eruption occurring on 14 October. The eruption sizes were based on comparisons of seismic data for known Erebus eruptions.
Source: Mount Erebus Volcano Observatory
Karangetang
| Siau Island (Indonesia)
| 2.781°N, 125.407°E
| Elevation 1797 m
Gas was emitted from Karangetang's North and Batukole craters during 10-16 October. Seismicity was dominated by multiphase events, which decreased in number in comparison to the previous week. The number of deep volcanic earthquakes increased. Karangetang remained at Alert Level 3 (on a scale of 1-4).
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)
Kilauea
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
On 18 October, weak surface lava flows were visible at Kilauea and one cascade of lava flowed off of the western front of the East Lae`apuki delta. Background volcanic tremor was near normal levels at Kilauea's summit. Volcanic tremor was at moderate levels at Pu`u `O`o. During 11-18 October, small amounts of inflation and deflation occurred at the volcano.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
Montagu Island
| South Sandwich Islands (UK)
| 58.445°S, 26.374°W
| Elevation 1370 m
An ASTER satellite image from 23 September showed a 3.5-km-long lava flow extending from the summit of Montagu Island (Mt. Belinda) into the sea. This was the largest effusive event observed during the 4-year-old eruption. Based on MODVOLC alerts, the flow appeared to have started sometime between 10 and 14 September. A conspicuous 90-m-wide channel was visible ~1 km from the vent. The image also showed a steam plume at the location of the ocean entry, and an ash-rich plume extending NE from the volcano's summit.
Sources: Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts Team, British Antarctic Survey
San Miguel
| El Salvador
| 13.434°N, 88.269°W
| Elevation 2130 m
SNET reported that activity had not changed at San Miguel after small clusters of earthquakes occurred at the volcano during 27 September to about 14 October. During a visit to the volcano on 13 October small rockfalls were seen, but there were no significant changes in the crater and sulfur-dioxide emissions were very weak.
Source: Servicio Nacional de Estudios Territoriales (SNET)
Sangay
| Ecuador
| 2.005°S, 78.341°W
| Elevation 5286 m
An ash plume emitted from Sangay was visible on satellite imagery on 16 October around 0645. The plume moved SSW very slowly, corresponding to a possible height of ~6.7 km (22,000 ft) a.s.l. By 0900 the plume was too thin to be visible on satellite imagery and thunderstorms developed in the area, further obscuring the ash cloud.
Source: Washington Volcanic Ash Advisory Center (VAAC)
Santa Ana
| El Salvador
| 13.853°N, 89.63°W
| Elevation 2381 m
During 12-17 October, seismicity was relatively stable and there were low-level gas emissions at Santa Ana. Storms on 12 October caused the generation of lahars that traveled towards Coatepeque.
Source: Servicio Nacional de Estudios Territoriales (SNET)
Saunders
| South Sandwich Islands (UK)
| 57.8°S, 26.483°W
| Elevation 843 m
The first MODVOLC alerts at Mount Michael since May 2003 recently began, indicating an increased level of activity in the island's summit crater (and presumed lava lake). The alerts occurred on 3, 5, and 6 October.
Sources: Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts Team, British Antarctic Survey
Soufriere Hills
| Montserrat
| 16.72°N, 62.18°W
| Elevation 915 m
Volcanic and seismic activity at Soufrière Hills remained at elevated levels during 7-14 October. Lava-dome growth mostly occurred on the W side of the dome, which was largely obscured by clouds and steam. Observations suggested that the lava-dome growth rate increased, with preliminary calculations suggesting a rate of at least 2 cubic meters per second. Incandescence was visible at the lava dome on a video camera at night. The sulfur-dioxide flux averaged 580 metric tons per day (t/d), above the long-term eruption average of 500 t/d. The hydrogen-chloride versus sulfur-dioxide ratio increased to about 1.
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 12-18 October, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. There were no significant changes in seismicity or deformation during the report period. During the previous few weeks, a prominent linear feature developed on the disintegrating "whaleback" that grew during the previous spring and summer and was currently located E of the actively growing part of the new lava dome. A digital elevation model of the active lava dome, which was created from aerial photographs taken on 10 August, showed that the volume had grown to 62 million cubic meters. The average rate of growth during late July and early August was about 2 cubic meters per second, a rate that typified most of 2005. St Helens remained at Volcano Advisory (Alert Level 2); aviation color code Orange.
Source: US Geological Survey Cascades Volcano Observatory (CVO)
Stromboli
| Aeolian Islands (Italy)
| 38.789°N, 15.213°E
| Elevation 924 m
A plume emitted from Stromboli that may have contained ash was visible on satellite imagery on 14 October at a height around 1.8-2.4 km (6,000-8,000 ft) a.s.l. The plume extended ~10 km NW of the volcano.
Source: Toulouse Volcanic Ash Advisory Centre (VAAC)
Tanaga
| Andreanof Islands (USA)
| 51.885°N, 178.146°W
| Elevation 1806 m
Elevated seismic activity below young volcanic vents on Tanaga Island continued during 7-14 October, although the rate of small earthquakes reduced slightly in comparison to the previous week. The activity that began at Tanaga on 1 October was at the highest level recorded since the seismic network was installed in 2003, so the Concern Color Code remained at Yellow.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
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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