Activity for the week of 29 September-5 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
| Lombok Island (Indonesia)
| 8.42°S, 116.47°E
| Elevation 3726 m
Based on information from DVGHM, the Darwin VAAC reported that an eruption at Rinjani on 1 October at 0530 produced a plume to ~600 m above the volcano's summit. No ash was visible on satellite imagery. The volcano was at Aviation Color Code Orange. Visual observations revealed that eruptions on 5 October reached ~4.5 km a.s.l. A news article reported that hikers were banned from climbing the volcano, but the evacuation of villagers near the volcano was deemed unnecessary by local officials.
Sources: Darwin Volcanic Ash Advisory Centre (VAAC), The Jakarta Post
| United States
| 46.2°N, 122.18°W
| Elevation 2549 m
Shortly before noon on 1 October, Mount St. Helens emitted a plume of steam and minor ash from an area of new crevasses that had opened in a portion of the crater glacier between the headwall of the 1980 crater and the lava dome. This marked the first eruption from Mount St. Helens since a series of phreatic explosions during 1989-1991. The area of the new vent, located at the southern base of the lava dome, had become increasingly crevassed and uplifted over the previous few days. The event lasted from 11:57 to 12:21 PDT and created a pale-gray cloud that reached an altitude of about 9700 ft (from pilot reports) and drifted SW. USGS scientists making thermal measurements witnessed the emission and noted that the clouds were not particularly hot. Blocks of rock and ice ejected by the event fell in the crater and rim areas. The emission was accompanied by an abrupt drop in seismicity, which remained at low levels.
Prior to the eruption, on 29 September CVO raised the Alert level to 2 (out of 3) due to a significant increase in seismicity overnight. The Volcano Alert was raised to the highest level on 2 October due to a change in the type of seismic signals (50-minute-long tremor) that occurred immediately after a small steam emission at 1215 that day. A small 2-minute-long eruption occurred around noon on 4 October from the vent just S of the lava dome, sending a steam and minor ash plume to an altitude of about 3 km. It drifted SW accompanied by minor ashfall in areas close to the volcano.
During the evening of 3 October, seismicity increased until a steam (and possibly ash) emission around 2240. The plume barely rose to the crater rim. On 4 October, there were 30- and 10-minute-long steam-and-ash emissions at 0943 and 1410, respectively. The larger emission dusted roads SE of the volcano with ash. The maximum thickness of the ash at 8 km distance was 0.2 mm. Neither event generated earthquakes or an explosion signal. CVO scientists inferred that the eruption occurred because hot rock was pushed up into the glacier, melted ice, and generated the steam. On 5 October earthquake energy slowly increased to previous high values.
Shortly after 9:00 a.m. PDT on 5 October, the most vigorous steam and ash emission of the current period of activity began. The emission originated from the same vent as have others this past week, as well as from another nearby new vent in the intensely deforming area on the south side of the 1980-86 lava dome. Steam clouds billowed from the crater for more than one hour. Ash content varied with intensity of steam jetting from the vent, and ash plumes at times billowed above the 1980 crater rim. For the first time, ash content was sufficient that it was detected by National Weather Service Doppler Radar. Steam and ash clouds reached about 12,000 feet and drifted NNE. Media reports indicated that a light dusting of ash fell in Morton, Randle, and Packwood, Washington, towns ~30 miles N of the volcano. There were no reports of ash falling at greater distances.
Following the 5 October steam-and-ash eruption, seismicity dropped to a low level and remained low. Low-level tremor observed following the eruption also gradually declined. Lack of earthquake and rockfall signals suggested that deformation of the uplift area on the south side of the 1980-86 lava dome had slowed. Brief visual observations the morning of 6 October from Coldwater Visitor Center showed weak steam emissions from the crater. Because the USGS inferred that the vigorous unrest of the past few days had lessened and that the probability of an imminent eruption that would endanger life and property was significantly less than at any time since 2 October, the alert level was lowered to Volcano Advisory (Alert Level 2).
Source: US Geological Survey Cascades Volcano Observatory (CVO)
| 19.514°N, 103.62°W
| Elevation 3850 m
A new growing lava dome was sighted in Colima's summit crater on 28 September, following three days of vigorous fumarolic emissions. Starting on 30 September, block-and-ash flows moved down the volcano's W, WNW, and N flanks. Blocks of lava began to travel down the volcano's N and WNW flanks around 1 October, reaching lengths of ~300 m on the N flanks and ~100 m on the WNW. On 5 October, block-and-ash flows continued to travel as far as 2 km, and about 30 small explosions produced plumes to a maximum height of 400 m above the volcano.
Source: Centro Universitario de Estudios e Investigaciones de Vulcanologia - Universidad de Colima
| 14.473°N, 90.88°W
| Elevation 3763 m
During 30 September to 4 October several explosions occurred at Fuego, producing ash plumes to a maximum height of 2 km above the volcano. On 30 September, lava avalanches traveled towards Santa Teresa and Taniluya ravines. On 1 October, incandescent lava bombs were hurled ~100 m above the volcano.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 30 September to 5 October, patches of incandescence were visible at the PKK lava flow on the Pulama pali scarp and all vents in the crater of Pu`u `O`o were incandescent. During the report period, seismicity was weak at Kilauea's summit, with essentially no tremor recorded. Tremor was moderate at Pu`u `O`o. In addition, small amounts of inflation and deflation occurred.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
Piton de la Fournaise
| Reunion Island (France)
| 21.244°S, 55.708°E
| Elevation 2632 m
The main recent eruption phase at Piton de la Fournaise began on 13 August 2004 and stopped on 2 September. It was followed by two minor phases from the main vent on the volcano's E flank; these, in turn, ceased on 3 October around 0300.
Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF)
| 14.757°N, 91.552°W
| Elevation 3745 m
During 30 September to 4 October moderate explosions at Santa María's Santiaguito lava-dome complex produced ash-and-gas plumes to a maximum height of 1 km above the volcano. Some explosions were accompanied by avalanches of volcanic material down the S side of Caliente dome. Explosions on 4 October produced small 3-minute-long pyroclastic flows to the SW.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)
| 16.72°N, 62.18°W
| Elevation 915 m
Volcanic and seismic activity at Soufrière Hills during 24 September to 1 October remained slightly elevated, as has been the case for several weeks. The seismic network recorded three rockfalls, one long-period earthquake, and eight hybrid earthquakes. Sulfur-dioxide flux ranged between 200 and 540 metric tons per day, with a weekly average of 340 metric tons.
Source: Montserrat Volcano Observatory (MVO)
| 1.467°S, 78.442°W
| Elevation 5023 m
During 29 September to 5 October seismic and volcanic activity at Tungurahua were at relatively low levels, with the occurrence of occasional small explosions of gas, steam, and ash and some long-period earthquakes.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG)
| United States
| 56.17°N, 159.38°W
| Elevation 2507 m
During 24 September to 1 October, low-level tremor and intermittent small tremor bursts may have occurred at Veniominof, but high winds in the area made analysis of seismic records inconclusive. The winds were strong enough to produce an overshadowing effect on seismic records that could hide evidence of low-level tremor. If the tremor episodes continued, they likely represented low-level ash-and-steam emissions similar to those observed over the previous 4 months. Cloudy conditions obscured views of the volcano in web camera and satellite data. Veniaminof remained at Concern Color Code Yellow.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
News Feeds and Google Placemarks
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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.
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