Activity for the week of 20 September-26 September 2006
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
| 4.016°S, 103.121°E
| Elevation 3142 m
Increased seismicity at Dempo resulted in an elevation of the hazard status to Alert Level 2.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)
| United States
| 58.77°N, 153.672°W
| Elevation 2105 m
On the evening of 17 September the Alaska Volcano Observatory (AVO) received several reports of two discrete plumes rising from the Cape Douglas area, about 320 km SW of Anchorage. Retrospective analysis of data from the NEXRAD Doppler radar in King Salmon showed an unusual cloud starting at 1200 that day. The maximum cloud height determined by radar during the first hour of the event was 6 km (20,000 ft) a.s.l. The radar return from the cloud continued until at least 2145. A cloud of sulfur dioxide gas was observed by colleagues at the University of Maryland Baltimore County over the Cape Douglas/Fourpeaked region at 1500 using data collected by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite. On this basis all of the clouds were inferred to be volcanic in origin. Although satellite data did not detect ash during this event, AVO received reports of a trace of ashfall at Nonvianuk Lake outlet (110 km WNW) and near Homer (150 km NE).
Both fixed-wing and helicopter overflights in the Cape Douglas area 20 September confirmed the source of volcanic activity to be Fourpeaked volcano. AVO raised the Level of Concern Color Code from "Not Assigned" to YELLOW on 20 September. Fourpeaked and Douglas volcanoes are not monitored seismically. A 23 September observation flight conducted in relatively good weather permitted the first look at the summit since the event of 17 September. Observers saw a linear series of vents running N from the summit for about 1 km. Most of these vents were vigorously emitting steam and other volcanic gases. Gas measurements indicated abundant quantities of sulfur dioxide, hydrogren sulfide, and carbon dioxide.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
| Tonga Islands
| 18.992°S, 174.775°W
| Elevation -10 m
Reports have been received of large pumice rafts in the Fiji Islands. On 16 September observers aboard the M/V National Geographic Endeavour noted almost continuous rows of pumice that day as they traveled about 90 km east-southeast to Vatoa Island, where the pumice was present on the beaches. Large rafts of pumice were also passing through the northern Lau Group around Naitauba Island on 19 September. The source of the pumice is unknown at this time. [Later determined to be from Home Reef.]
Sources: David Cothran, M/V National Geographic Endeavour, David Forsythe, Naitauba Island, Fiji
| Costa Rica
| 10.2°N, 84.233°W
| Elevation 2708 m
On 26 September at least two phreatic eruptions occurred at Poás. One during the night of 25 September reached a height of at least 350 m above the warm acid lake, depositing rock fragments, mud, and water in the southern part of the inner crater and outside the western part of the crater. Material ejected that night reached Trojas de Sarchí, almost 10 km SW. A smaller eruption on the morning of 26 September was limited to the area of the lake, and formed green-yellow semicircular zones of mud and sulfur up to 75 m in diameter.
Source: Red Sismologica Nacional (RSN: UCR-ICE), Universidad de Costa Rica and Instituto Costarricense de Electricidad
| Solomon Islands
| 8.292°S, 156.52°E
| Elevation 335 m
Residents on Simbo Island reported feeling seven "earth tremors" on 21 September, and others in recent days. None of the events caused damage. The Solomon Islands Seismology Division does not have monitoring equipment on the island.
Source: Solomon Star
| Kyushu (Japan)
| 31.593°N, 130.657°E
| Elevation 1117 m
Based on information from JMA, the Tokyo VAAC reported eruptions at Sakura-jima on 20 and 21 September. A plume from the second eruption rose to 2.4 km (8,000 ft) a.s.l.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
| Andaman Islands (India)
| 12.278°N, 93.858°E
| Elevation 354 m
Indian Coast Guard officials noted in a news report on 23 September that the continuing eruption at Barren Island was decreasing in intensity. A surveillance report stated that there was less lava but more "smoke" coming from the volcano.
Source: The Hindu
| Eastern Kamchatka (Russia)
| 54.049°N, 159.443°E
| Elevation 1513 m
Seismic data and satellite observations reported by KVERT indicate that moderate ash eruptions were continuing from Karymsky during 16-22 September. There have been 40-200 weak shallow earthquakes recorded each day. A thermal anomaly over the crater was noted on 18-19 September. Based on visual observations, volcanologists in the area on 19 September estimated ash explosions to have reached altitudes of 2.3 km (7,500 ft) a.s.l. Ash plumes extending 16-40 km SW and SE were noted at satellite images on 18-19 September.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
Throughout 20-26 September Kilauea continued to erupt from the Pu`u `O`o vent on the East Rift Zone. Summit inflation centered in the south part of the caldera also continued. Lava was flowing through the PKK lava tube from its source on the SW flank of Pu`u `O`o to the ocean. About 1 km S of Pu`u `O`o, the Campout flow branches off from the PKK tube. The PKK and Campout systems feed two widely separated ocean entries named East Lae`apuki and East Ka`ili`ili, respectively. Activity during this period included numerous small breakouts from the Campout flow, new skylights along the PKK tube, and variable activity at the ocean entries. At Pu`u `O`o, intermittent lava incandescence reflected on gas plumes was visible from the usual four vents (East Pond, January, South Wall Complex, and Drainhole).
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| Luzon (Philippines)
| 13.257°N, 123.685°E
| Elevation 2462 m
Surface activity at Mayon consisted of incandescent lava fragments rolling down the slopes and glow coming from the summit crater. Moderate white steam emissions continued from the summit. The number of daily volcanic earthquakes was low during 20-24 September, with 1-3 events per day. On the 25th there were 14 earthquakes recorded. There were also 114 tremor episodes that day, also a high for the week ending on 26 September. Sulfur dioxide flux remained above normal, between 1,200 and 2,200 metric tons/day.
Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)
| Eastern Java (Indonesia)
| 8.108°S, 112.922°E
| Elevation 3657 m
Based on satellite imagery, the Darwin VAAC issued multiple aviation ash advisories for Semeru during 20-21 September. Plumes were initially reported to be near 11 km (36,000 ft) a.s.l. and drifting SW. The later reports noted a plume at 4.9 km (16,000 ft) a.s.l. extending about 90 km W.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| 16.72°N, 62.18°W
| Elevation 915 m
MVO reported that during 15-22 September the lava dome at Soufrière Hills continued to grow at a moderate rate, slower than earlier in the month. Growth appears to have occurred predominantly in the summit area and on the S and E sides of the dome. The vent situated in the Gages Wall is still active, with minor explosive activity seen during an observation flight on 19 September. An intense 30-minute episode of volcanic tremor on 19 September was accompanied by rockfall activity that caused minor pyroclastic flows down the N and NE flanks of the lava dome. On 22 September the volume of the dome was about 80 million cubic meters. Seismicity was dominated by rockfalls with a significant drop in earthquake activity relative to the previous reporting period. The alert level was reduced to 3 (on a scale of 0-5) on 21 September. Aviation ash advisories during this period noted continuous ash emissions.
Sources: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)
| United States
| 46.2°N, 122.18°W
| Elevation 2549 m
Lava continued to extrude onto the crater floor during 20-26 September with low seismicity, generating occasional rockfalls as talus sloughed off the flanks of the growing dome.
Source: US Geological Survey Cascades Volcano Observatory (CVO)
| Ryukyu Islands (Japan)
| 29.638°N, 129.714°E
| Elevation 796 m
On 20 September the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite caught Suwanose-jima in the process of emitting volcanic ash and steam. The volcano's emissions blew N, gradually fanning out over the ocean, with a grayish tinge that distinguished it from nearby white clouds. Aviation ash advisories for this eruption issued by the Tokyo VAAC based on satellite imagery, pilot reports, and JMA, noted that the plume rose to 2.1 km (7,000 ft) a.s.l. and extended about 80 km N.
Sources: NASA Earth Observatory, Tokyo Volcanic Ash Advisory Center (VAAC)
| 1.467°S, 78.442°W
| Elevation 5023 m
During 20-26 September seismicity remained low, as Tungurahua continued to generate ash eruptions. Ash rose 2 km above summit (23,000 ft a.s.l.) on the afternoon of 21 September. Moderate ash emissions occurred again on 22 September. Three more ash emissions on 23 September caused ashfall in Penipe; one plume rose 3 km above the summit (26,000 ft a.s.l.), and another 4 km (29,500 ft a.s.l.). Ash plumes were seen again on 25 September.
Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG), Washington Volcanic Ash Advisory Center (VAAC)
| 16.355°S, 70.903°W
| Elevation 5672 m
Based on pilot reports, the Buenos Aires VAAC issued aviation ash advisories for Ubinas on 24 and 25 September. The continuous ash emissions were rising as high as 9 km (30,000 ft) a.s.l. and drifting SSE.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
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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