Activity for the week of 20 October-26 October 2004
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
| Papua New Guinea
| 4.08°S, 145.037°E
| Elevation 1807 m
Based on information from JMA, a pilot report, and satellite imagery, the Darwin VAAC reported that an eruption began at Manam on 24 October around 1125, producing a plume to a maximum height of about 15 km (a height of ~6 km was reported in news articles). Preliminary reports from RVO stated that pyroclastic flows traveled down the valley SE of the volcano. The aviation color code was at Red, the highest value. According to RVO, low-level eruptive activity occurred at the volcano after the 24 October eruption and was decreasing by 26 October. News articles reported that authorities advised the evacuation of ~3000 people living near the volcano to safer parts of the island.
Sources: Darwin Volcanic Ash Advisory Centre (VAAC), The Courier-Mail News, Associated Press
| United States
| 46.2°N, 122.18°W
| Elevation 2549 m
During 21-26 October, the new lava dome inside the emerging dome of St Helens continued to grow, and seismicity remained at low levels compared to early in the unrest. Geological and thermal-imaging observations on 20 October confirmed that both the area of uplift, and the new lava extrusion increased in size noticeably since last seen on 14 October. In addition, the area of uplift and intense deformation continued to move southward and was nearing the crater wall. About 0.3 m of new snow with a light dusting of ash covered much of the uplift, except for the new lava extrusion, which was steaming heavily. The new lava extrusion, which occupies the western part of the uplift, was about 275 m long by 75 m wide, 70 m high, and had a volume of almost 1.5 million cubic meters. Its maximum temperature was about 600 degrees C. Low levels of carbon dioxide, sulfur dioxide, and hydrogen sulfide were recorded on the 20th, an observation which did not rule out the continued rise of magma from depth. On 21 October a new protrusion that had a maximum temperature of about 650 degrees C.
Analyses of samples from the new lava dome collected on 20 October suggested that since lava first appeared on 11 October it has been rising more rapidly from depth and not spending much more than a few days at shallow levels before being extruded onto the surface. Reviews of several lines of evidence confirmed that the average rate of volume change for the deformed area and new lava dome between late September and mid-October was about 8 cubic meters (a typical dump-truck full) per second. According to CVO, a substantial part of that change must be magma, which suggests a rate similar to that for many other lava-dome-building eruptions.
Source: US Geological Survey Cascades Volcano Observatory (CVO)
| Mariana Islands (USA)
| 16.35°N, 145.67°E
| Elevation 790 m
On 27 September, the first long-period seismic events since July 2004 were recorded at Anatahan. Only a few, small events were recorded. Beginning on 12 October, several periods of small, rather regularly spaced long-period events were recorded at intervals of 4 to 15 seconds. This seismicity began several hours after the onset of a series of intense tropical depressions and storms. On 18 October, people in Saipan smelled H2S during very hazy visibility, but no plume was detected on satellite imagery by the Washington VAAC.
Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program
| 19.514°N, 103.62°W
| Elevation 3850 m
During 22-26 October, block-lava flows continued to travel down Colima's N, NW, W, and S flanks as they have since 30 September. On the 26th, the block-lava flows on the N flank reached a length of ~1,800 m and a width of 200 m, and on the WNW flank the block-lava reached a length of ~600 m and a width of 200 m. On the 22nd, the volcano's gas output included 840 metric tons of sulfur dioxide. During the report period, block-and-ash flows spilling from the fronts of the advancing block-lava flows reached ~ 2 km from the summit.
Source: Centro Universitario de Estudios e Investigaciones de Vulcanologia - Universidad de Colima
| 14.473°N, 90.88°W
| Elevation 3763 m
During 21-22 October, several weak explosions at Fuego sent plumes to a maximum height of ~300 m above the volcano. In addition, avalanches of incandescent volcanic material traveled towards the ravines of Taniluyá and Ceniza on the volcano's flanks. The avalanches originated from two areas about 20 m below the S edge of Fuego's crater.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 21-24 October, patches of incandescent lava were visible on the PKK lava flow on the Pulama pali fault scarp and all vents in the crater of Pu`u `O`o were incandescent. Seismicity was at low levels at Kilauea's summit and essentially no tremor was recorded there. Tremor was at moderate levels at Pu`u `O`o. During the report period, there were episodes of inflation and deflation.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| 14.757°N, 91.552°W
| Elevation 3745 m
During 21-22 October, weak-to-moderate explosions occurred at Santa María's Santiaguito lava-dome complex. Some explosions were followed by collapses of the SW edge of the lava dome in the crater of Caliente Dome. On 22 October two pyroclastic flows traveled down the volcano's flank. The Washington VAAC reported that hot spots and plumes possibly containing ash were occasionally visible on satellite imagery on 21 October.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Washington Volcanic Ash Advisory Center (VAAC)
| Central Kamchatka (Russia)
| 56.653°N, 161.36°E
| Elevation 3283 m
During 15-22 October, seismicity at Shiveluch was above background levels, with shallow earthquakes occurring beneath the active lava dome. Based on interpretations of seismic data, ash-and-gas explosions possibly produced plumes to 6.5 km a.s.l. In addition, avalanches of hot material may have occurred during the week. KVERT reported seeing a new lava flow at Shiveluch's lava dome around 26 October. Shiveluch remained at Concern Color Code Orange.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| Fox Islands (USA)
| 54.756°N, 163.97°W
| Elevation 2857 m
On 26 October, AVO lowered the Concern Color Code at Shishaldin from Yellow to Green. Volcanic tremor at the volcano had remained at a relatively constant and low level for more than a month. No new satellite observations indicative of significant activity in the summit crater had been received by AVO, and there had been no recent reports of ash emissions or ash on the snow near the summit. The low-level seismic tremor that continued to be recorded at the volcano was considered to be representative of the background rate of activity at Shishaldin.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
| 16.72°N, 62.18°W
| Elevation 915 m
Seismic activity at Soufrière Hills was at elevated levels during 15-22 October in comparison to previous weeks. The seismic network recorded four rockfall events and 49 hybrid earthquakes, and one volcano-tectonic earthquake. MVO scientists thought that increased hybrid earthquake activity was related to heavy rainfall during the week. The sulfur dioxide gas flux varied from 250 to 1,100 metric tons per day during the report period. Mudflows were recorded during 15, 19, and 21 October.
Source: Montserrat Volcano Observatory (MVO)
| 1.467°S, 78.442°W
| Elevation 5023 m
Volcanic and seismic activity at Tungurahua during 21-26 October were at relatively low levels, characterized by a few long-period earthquakes, tremor, and small explosions. Emissions mainly consisted of steam, gas, and ash.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG)
| United States
| 56.17°N, 159.38°W
| Elevation 2507 m
AVO lowered the Concern Color Codeat Veniaminof on 26 October from Yellow to Green. Seismicity, which had been associated with ash emissions that occurred during the summer of 2004, decreased to levels that indicated ash, ash-and-steam, or steam emissions were no longer occurring on a regular basis. Since early September, no ash emissions were seen on the web camera and no evidence of ash was visible on satellite imagery. Also, AVO had received no recent reports of ash from pilots or ground observers. AVO considered the intermittent, low-level seismic tremor that continued to be recorded at the volcano to be part of the background activity. They reported that steaming from the intracaldera cone may still occur.
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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