Activity for the week of 26 April-2 May 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
| Central Java (Indonesia)
| 7.54°S, 110.446°E
| Elevation 2910 m
On 28 April, CVGHM observed a lava flow from Merapi traveling ~1.5 km SW to the Lamat River. On the 28th, seismicity was dominated by multiphase earthquakes. Signals from landslides, rockfalls, and low-frequency events were also recorded. According to news reports, around 27 April nearly 2,000 villagers were evacuated from Sidorejo and Tegalmulyo villages on the volcano's flanks. On the 27th, small amounts of ash fell in Gemer village about 5 km from Merapi's summit. Merapi remained at Alert Level 3 (on a scale of 1-4).
Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Reuters, People's Daily Online (China)
| 16.355°S, 70.903°W
| Elevation 5672 m
According to INGEMMET, on 22 April at 0715 an explosion began at Ubinas that produced an ash-and-gas plume that reached a height between 1 and 3 km above the volcano (or 21,900 and 28,450 ft a.s.l.). This was the highest rising plume since activity began in late March. Continuous emissions occurred until 1600. Ash and gas emitted during 20-22 April traveled as far as 60 km from the volcano mainly NW, W, and SW, and traces of ash reached the Arequipa airport. During 25 and 26 April, the volume of ash emitted from the volcano decreased significantly. Gas plumes rose between 200 and 700 m above the volcano's caldera (or 19,300 and 20,900 ft a.s.l.). The Alert Level was reduced from Orange to Yellow. Seismicity during 22-26 April was higher than normal. The Buenos Aires VAAC posted volcanic ash advisories during the report period.
Sources: Buenos Aires Volcanic Ash Advisory Center (VAAC), Instituto Geológico Minero y Metalúrgico (INGEMMET)
| Kyushu (Japan)
| 31.593°N, 130.657°E
| Elevation 1117 m
Based on information from JMA, the Tokyo VAAC reported that an explosion at Sakura-jima on 28 April produced an ash plume that rose to 2.1 km (7,000 ft) a.s.l. An explosion on 1 May produced a plume that rose to an unknown height.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
| United States
| 59.363°N, 153.43°W
| Elevation 1252 m
AVO reduced the Concern Color Code at Augustine from Orange to Yellow on 28 April. As of the 28th, instrumental and visual observations indicated that the growth of the summit lava dome and lava-flow emissions had stopped, or continued at very low rates. Seismic data showed that rockfalls and avalanches occurred at a diminished level. No changes were seen at the summit during the previous several weeks. AVO warned that despite the apparent cessation of lava-dome growth, the new dome and lava flows are still highly unstable, and rockfalls and avalanches are still occurring and may continue for several weeks or months.
Sources: US Geological Survey Alaska Volcano Observatory (AVO), Anchorage Volcanic Ash Advisory Center (VAAC)
| Andaman Islands (India)
| 12.278°N, 93.858°E
| Elevation 354 m
A plume emitted from Barren Island was visible on satellite imagery on 2 May at a height near 3.7 km (12,000 ft) a.s.l.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| Luzon (Philippines)
| 12.769°N, 124.056°E
| Elevation 1535 m
According to news reports, on 29 April at 1044 an explosion at Bulusan produced an ash plume that rose ~1.6 km above the volcano (or 10,400 ft a.s.l.). Ash fell on nearby villages. People are not permitted to enter within 4 km of the volcano's crater.
Sources: Agence France-Presse (AFP), INQ7.net
| 1.22°N, 77.37°W
| Elevation 4276 m
INGEOMINAS reported that Galeras remained at a critical state during 21 April to 1 May, with a partially solidified lava dome in the main crater and low levels of seismicity. The sulfur-dioxide flux continued at low levels. Galeras remained at Alert Level 2 (likely eruption in days or weeks).
Source: Servicio Geológico Colombiano (SGC)
| Eastern Kamchatka (Russia)
| 54.049°N, 159.443°E
| Elevation 1513 m
Intermittent eruptive activity continued at Karymsky during 21-28 April. Based on interpretations of seismic data, ash plumes rose to a height of ~3.8 km (12,500 ft) a.s.l. during the report week. Satellite imagery showed a large thermal anomaly at the volcano's crater, and numerous ash plumes and deposits extending 10-200 km SE and E of the volcano. Karymsky remained at Concern Color Code Orange.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 26 April to 2 May, lava from Kilauea continued to flow off of a lava delta into the ocean at the East Lae`apuki entry. No surface lava flows were visible on the Puluma pali fault scarp, as has been the case since 8 February. Continuous low-level volcanic tremor was recorded at Kilauea's summit, accompanied by a few small earthquakes. Volcanic tremor reached moderate levels at Pu`u `O`o. Small amounts of inflation and deflation occurred at the volcano.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| 23.37°S, 67.73°W
| Elevation 5592 m
Based on information from a significant meteorological forecast (SIGMET), the Buenos Aires VAAC reported that on 28 April a W-drifting ash cloud was observed at a height around 6.1-7.6 km (20,000-25,000 ft) a.s.l. The Aviation Color Code was at Red. Later that day activity was no longer observed and the Aviation Color Code was reduced to Green.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
| Papua New Guinea
| 4.08°S, 145.037°E
| Elevation 1807 m
Ash from Manam was observed on satellite imagery on 28 April at a height of ~3 km (10,000 ft) a.s.l.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| North Kermadec Ridge (New Zealand)
| 29.27°S, 177.92°W
| Elevation 516 m
Hydrothermal activity at Raoul Island's Green Lake crater had declined significantly as of 28 April and the lake water level continued to fall. The Alert Level at Raoul Island was reduced from 2 to 1 (some signs of volcano unrest), on a scale of 0-5.
| 12.702°N, 87.004°W
| Elevation 1745 m
Phreatomagmatic eruptions began at San Cristóbal on 21 April. Seismic tremor increased at the volcano that same day around 1300. Small explosions produced gas-and-ash plumes during 21-23 April that deposited small amounts of ash in nearby towns.
Source: Instituto Nicaragüense de Estudios Territoriales (INETER)
| 16.72°N, 62.18°W
| Elevation 915 m
Observations of Soufrière Hills during 21-28 April revealed that lava extrusion continued. Dome growth occurred over a sector extending SW to NE. The eastward facing lobe continued to grow on the NE side of the dome and a central spine was observed on 28 April. Small rockfalls and pyroclastic flows continued to initiate from the active E flank of the dome, adding to the talus in the upper reaches of the Tar River Valley. Rockfalls were accompanied by minor ash venting. Thermal images taken on 27 April indicated some very hot (in excess of 400°C) areas on the E flank of the dome. During the report period seismicity was dominated by rockfalls, as has been the case throughout the on-going phase of dome growth. The sulfur-dioxide flux averaged 520 metric tons per day, close to the long-term average for the entire eruption.
Sources: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)
| 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 26 April to 2 May, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. Seismicity continued as very small periodic earthquakes, recurring every few minutes, punctuated by occasional larger earthquakes. The active lava dome continued to build towards the W. 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 28 April-1 May, small-to-moderate explosions at Tungurahua produced gas, steam, and small amounts of ash. Seismicity was at relatively high levels. A plume rose to a maximum height of ~2 km above the volcano (or 23,050 ft a.s.l.) on 28 April.
Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG), Washington 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.
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.
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