Activity for the week of 27 October-2 November 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
| 64.416°N, 17.316°W
| Elevation 1719 m
According to scientists from the Institute of Earth Sciences at the University of Iceland and the Icelandic Meteorological Office, an eruption began at the subglacial Grímsvötn volcano on 1 November around 2100. The eruption was preceded by both long-term and short-term precursors, and was triggered by the release of overburden pressure associated with a glacial outburst flood (jokulhlaup), originating from the Grímsvötn subglacial caldera lake.
Seismicity originally increased at the volcano in mid-2003, about the same time uplift exceeded a maximum reached in 1998: the last eruption at Grímsvötn occurred within the volcano's caldera beginning on 18 December 1998 and resulted in a catastrophic flood. Additional uplift and expansion of the volcano since mid-2003 suggested the approaching failure of the volcano. Seismicity further increased in late October 2004, and on 26 October high-frequency tremor indicated increased water flow from the caldera lake and suggested that a glacial outburst flood was about to begin. On 29 October, the amount of discharge increased in the Skeidara River. About 3 hours before the eruption began an intense swarm of volcanic earthquakes started, changing to continuous low-frequency tremor at the onset of the eruption. The release in overburden pressure associated with the outburst flood triggered the eruption. The amount of drop in water level in the Grímsvötn caldera at the onset of the eruption is uncertain, but was probably on the order of 10-20 m, corresponding to a pressure change of 0.1-0.2 MPa at the volcano's surface. This modest pressure change triggered the eruption because internal pressure in the Grímsvötn shallow magma chamber was high after continuous inflow of magma to the volcano since 1998.
The London VAAC reported that the ash plume produced from the eruption reached a height of ~12.2 km a.s.l. According to news articles, the eruption occurred in an unpopulated region so no evacuations were needed, but air traffic was diverted away from the region.
Observations on 2 November revealed that the eruption was occurring from a circular vent ~1 km in diameter in the SE part of the volcano's crater. The ice thickness in this part of the Grímsvötn caldera was ~200 m prior to the eruption. On 3 November, eruptive activity occurred in pulses, resulting in a changing eruption column height from 8-9 km to 13-14 km above the volcano. The ash fall sector extended at least 150 km from the eruption site. The distal ash plume was observed in Norway, Finland, and Sweden.
Sources: Associated Press, Institute of Earth Sciences, Reuters, London Volcanic Ash Advisory Centre (VAAC)
| Papua New Guinea
| 4.08°S, 145.037°E
| Elevation 1807 m
The eruption that began at Manam on 24 October continued through at least 31 October. According to RVO, during 27-28 October there were occasional emissions of ash-laden brown clouds and projections of incandescent lava from Manam's Southern Crater. Fine ash from the eruptions traveled NW, and was deposited between the villages of Jogari and Baliau. Main Crater released occasional weak-to-moderate emissions of white vapor, and sometimes brown ash. Weak, fluctuating incandescence was visible from the crater at night. During 28-29 October, at Southern Crater there were occasional emissions of moderate, thick, dark ash-laden clouds that rose above normal atmospheric clouds. The ash clouds drifted NW, depositing ash between the villages of Yassa and Baliau. The Alert Level at Manam was at Stage 1. By 31 October, the eruption at Main Crater consisted of Strombolian activity, with ash and scoria emissions. Scoria of ~1 cm diameter and ash was deposited in Warisi village on the SE side of the island. Small pyroclastic flows were generated and fresh lava flowed into the NE valley. The lava flow followed the Boakure side of the valley, covering older flows from the 1992-1994 eruption. Beginning on the morning of the 31st, the amount of continuous volcanic tremor increased to moderate-to-high levels, so the Alert Level was increased to Stage 2. Villagers near the four main valleys near Manam were advised to remain away from the volcano.
The Darwin VAAC reported that a SE-drifting plume from Manam was visible on satellite imagery on 31 October during 0813-1449 at a height of ~13.7 km a.s.l. The Aviation Color Code was at Red, the highest level. According to a news report, about 4,000 villagers living near the volcano were moved to safer areas. Reportedly, "about 1 ft [0.3 m] of ash with hot pumice" landed on the roofs of houses, and ash drifted as far W as Wewak, ~100 km from Manam Island. On 2 November around 2325 a possible eruption may have produced a plume to a height of ~7.6 km a.s.l. that drifted SE.
Sources: Darwin Volcanic Ash Advisory Centre (VAAC), Rabaul Volcano Observatory (RVO), The Sydney Morning Herald
| Luzon (Philippines)
| 14.002°N, 120.993°E
| Elevation 311 m
PHIVOLCS raised the Alert Level at Taal from 0 to 1 (on a scale of 0-5) on 29 October due to an increase in seismicity at the volcano. The seismic network at Taal began to record significant volcanic earthquakes on 23 September. In general, through 29 October the number of earthquakes increased, with a maximum of 13 earthquakes recorded on 15 October. Initial epicenter locations were in the vicinity of Main Crater and to the NNW near Binintiang Malaki and to the SSE near Calauit. No significant changes in thermal and steam emissions were observed. PHIVOLCS recommended appropriate vigilance by the public when visiting the island and noted that Main Crater was off-limits to visitors because of the potential for sudden steam explosions and high concentrations of noxious gases.
Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)
| 19.514°N, 103.62°W
| Elevation 3850 m
During 27 October to 1 November, block-lava flows continued to travel down Colima's N, W, NW, and S flanks as they have since 30 September. Several explosions occurred daily. By 1 November, the block-lava flows on the N flank reached about 1,800 m long and about 200 m wide, and on the WNW flank block-lava reached about 600 m long and 200 m wide at its widest point. During the report period, block-and-ash flows spilling from the fronts of the advancing block-lava flows on the W flank 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 28-29 October, several weak explosions at Fuego sent plumes to a maximum height of 300 m above the volcano and volcanic bombs were sometimes thrown ~75 m above the volcano's crater. In addition, avalanches of incandescent volcanic material traveled ~600 m towards the ravine of the Ceniza River.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 28-31 October, surface lava was 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 weak at Kilauea's summit and essentially no tremor was recorded. Tremor remained at moderate levels at Pu`u `O`o. During the report period, no significant deformation occurred.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| South Sandwich Islands (UK)
| 58.445°S, 26.374°W
| Elevation 1370 m
According to NASA's Earth Observatory News website, the IKONOS satellite acquired an image of Montagu Island (Mount Belinda) on 1 October that showed a steaming vent, and dark basaltic tephra covering ice surfaces N of the lava that erupted down the volcano's N flank. A steam plume drifted N, and light colored clouds surrounded the S side of the crater.
Source: NASA Earth Observatory
| 14.757°N, 91.552°W
| Elevation 3745 m
During 28-29 October, weak-to-moderate explosions occurred at Santa María's Santiaguito lava-dome complex, producing gas-and-ash plumes to ~800 m above the volcano. Some explosions were followed by collapses of the lava dome in the crater of Caliente dome. Pyroclastic flows traveled down the volcano's NE and SW flanks after some collapses. The Washington VAAC reported on 31 October that satellite imagery showed a possible ash-bearing plume at a height of ~4.5 km a.s.l.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Washington Volcanic Ash Advisory Center (VAAC)
| 16.72°N, 62.18°W
| Elevation 915 m
Volcanic and seismic activity at Soufrière Hills continued to be at elevated levels during 22-29 October. The seismic network recorded one volcano-tectonic and 40 hybrid earthquakes. Like the previous week, the increased hybrid earthquake activity was thought to be related to heavy rainfall during the report period. In association with the heavy rainfall, minor mudflow activity was recorded and observed in the Belham River. An observation flight over the volcano on 28 October revealed the continued existence of standing water in the explosion pit produced by the 3 March 2004 event and no evidence of a re-start of lava-dome growth.
Source: Montserrat Volcano Observatory (MVO)
| United States
| 46.2°N, 122.18°W
| Elevation 2549 m
According to CVO, during 28 October to 1 November, seismicity at St. Helens remained at a low level compared to early in the unrest. The seismicity during the report period was consistent with a continuing, slow rise of magma driving uplift of the crater floor and feeding a surface extrusion of lava. The overall low rates of seismicity and gas emission suggested that the lava reaching the surface was gas poor, thereby reducing the probability of highly explosive eruptions in the near term. Field work conducted on 27 October revealed several new observations. A new GPS (Global Positioning System) station on the southern part of the new lava dome moved downward and SE. A GPS station near the summit of the old lava dome had moved northward about 7 cm since 20 October. Thermal imaging showed an elongate band of elevated surface temperature, locally as great as 775° C along the W face of the new lava dome coincident with the area of exposed newly extruded lava. Gas-emission rates measured that day were similar to recent previous measurements (SO2 at about 250 tons per day, CO2 at about 300 tons per day, H2S at about 2 tons per day). In addition, samples of lava-dome rock similar in appearance to the rock of the older lava dome were collected from two localities in the vicinity of the exposed new lava. Overall, the results indicated that the character and rise of magma continued as it has over the past few weeks. CVO reported on 29 October that GPS, LIDAR (LIght Detection and Ranging), and photogrammetric measurements, in combination with visual observations over several days suggested that the lava-dome complex was spreading outward at its margins, similar to the expected behavior of a viscous lava flow. St. Helens remained at Volcano Advisory (Alert Level 2); aviation color code Orange.
Source: US Geological Survey Cascades Volcano Observatory (CVO)
| 1.467°S, 78.442°W
| Elevation 5023 m
During 27 October to 1 November, volcanic activity at Tungurahua was at moderate levels, with several explosions producing plumes of gas, steam, and ash. On 27 October an explosion produced an ash column to a height of ~3.5 km above the volcano. During the evening ash fell in the towns of Baños, Runtún, and El Salado. Explosions on 31 October also deposited small amounts of ash in Bilbao and Motilone.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG)
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.
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