Activity for the week of 19 April-25 April 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
| 23.37°S, 67.73°W
| Elevation 5592 m
Several phreatic explosions occurred at Lascar daily during 18-21 April. The explosions produced plumes of gas and small amounts of ash, with the highest rising plumes reaching 3 km above the volcano (or 28,200 ft a.s.l.) on the 18th and the 21st. Ash was deposited on the volcano's flanks as far as 3 km from the summit. There was no evidence of new magma reaching the surface and recorded seismicity was inferred to be related to shallow degassing. The Buenos Aires VAAC released volcanic ash advisory statements during the report period.
Sources: Buenos Aires Volcanic Ash Advisory Center (VAAC), Jorge Clavero-Chilean Geological Survey (Sernageomin) and Juan Cayupi-Chilean Emergency Office (ONEMI) via the Volcano Listserv
| Central Java (Indonesia)
| 7.54°S, 110.446°E
| Elevation 2910 m
During 21-25 April seismicity at Merapi remained at high levels, with several seismic signals recorded that were associated with rockfalls. The sulfur-dioxide flux from the volcano was 175 metric tons on 22 April. On 22 and 23 April, fumarolic emissions reached a maximum height of 400 m above the volcano (or 11,000 ft a.s.l.). On the 25th, two rockslides from lava-flow fronts were heard from nearby observatories. According to news reports, about 600 of the approximately 14,000 people living near the volcano had been evacuated by the 24th. Merapi remained at Alert Level 3 (on a scale of 1-4).
Sources: Associated Press, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Reuters
| 16.355°S, 70.903°W
| Elevation 5672 m
INGEMMET reported that gas and ash was emitted from Ubinas from 27 March to at least 19 April. On 13 April, ash emissions increased noticeably in comparison to the previous days, with ashfall in the villages of Ubinas, Querapi, and Sacuaya, and as far as 7 km from the volcano. Acid rain was also noted in these villages, particularly between 1400 and 1600 on 14 April. Explosions on 13 and 14 April were heard in nearby villages. At this time, the Alert Level at the volcano was Yellow. On the 19th, a lava dome was observed on the crater floor for the first time. It was incandescent, 60 m in diameter, and 4 m high. Explosions were heard as far as 6 km from the volcano and a plume composed of ash and lava fragments rose ~ 3 km above the volcano (or 28,450 ft a.s.l.). Plumes lasted for 6-7 hours and hazard statements suggested significant danger within 4 km of the crater. The Alert Level was raised to Orange. The Buenos Aires VAAC released volcanic ash advisory statements during the report period.
According to news reports, as of 19 April at least 1,000 people living N of the volcano suffered respiratory problems, dozens of livestock died and many more were ill after eating ash-covered grass, and water sources were polluted with ash. Dozens of people from Querapi, the town closest to the volcano, began to evacuate on 21 April. On 22 April, officials declared a state of emergency for the area near the volcano and sent aid for evacuees.
Sources: Agence France-Presse (AFP), Associated Press, Buenos Aires Volcanic Ash Advisory Center (VAAC), Instituto Geológico Minero y Metalúrgico (INGEMMET), Reuters
| 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 19 April generated a plume that rose to ~2.4 km (8,000 ft) a.s.l. and drifted NE.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
| United States
| 59.363°N, 153.43°W
| Elevation 1252 m
Eruptive activity continued at Augustine during 14-21 April, with seismicity, rates of rockfall signals, and visual observations indicating continued lava effusion. On 17 and 18 April, a flurry of signals associated with avalanches occurred that were larger than those seen in the previous few weeks. Based on aerial observations on the 19th, it seemed that an active rockfall and avalanche chute had developed near the margin of the new lava flow/dome complex in the NW summit area. A blanket of ash related to recent rockfalls in this area was visible on the volcano's SW flank. Augustine remained at Concern Color Code Orange.
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 low-level plume emitted from Barren Island was visible on satellite imagery on 19 April extending westward.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| 1.22°N, 77.37°W
| Elevation 4276 m
INGEOMINAS reported that Galeras remained at a critical state during 18-24 April, with a partially solidified lava dome in the main crater and low levels of seismicity. Galeras remained at Alert Level 2 (likely eruption in days or weeks).
Source: Servicio Geológico Colombiano (SGC)
| Hawaiian Islands (USA)
| 19.421°N, 155.287°W
| Elevation 1222 m
During 20-24 April, 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)
| North Kermadec Ridge (New Zealand)
| 29.27°S, 177.92°W
| Elevation 516 m
As of 21 April, hydrothermal activity at Raoul Island's Green Lake crater declined significantly and the lake level continued to fall. Recent earthquakes at or near the island were smaller and occurred less often than during the previous 3 weeks. Raoul Island remained at Alert Level 2 (minor eruptive activity).
| Eastern Java (Indonesia)
| 8.108°S, 112.922°E
| Elevation 3657 m
Based on information from a significant meteorological forecast (SIGMET), the Darwin VAAC reported that on 22 April an eruption at Semeru generated a plume that rose to ~4 km (13,000 ft) a.s.l. Ash was not visible on satellite imagery.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| 16.72°N, 62.18°W
| Elevation 915 m
Observations of Soufrière Hills' lava dome during 14-21 April suggested that lava extrusion continued. Growth occurred over a sector extending E to N, and on 18 April observers noted a smooth area of the dome resembling a whale's back. Numerous small rockfalls continued from the active eastern flanks of the lava dome, adding to the talus in the upper reaches of the Tar River Valley. Rockfalls were accompanied by minor ash venting. Due to unusual wind conditions, plumes were predominately transported N and NW, shifting to the E on 20 April. As a result of this process, light ashfall occurred over much of Montserrat.
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 20-24 April, 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 larger earthquakes were typically less than M 3 and occurred at an average rate of less than one per day. 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 19-23 April, small-to-moderate explosions at Tungurahua produced gas, steam, and small amounts of ash. Seismicity was at relatively high levels. Plumes rose to ~3 km above the volcano (or 26,300 ft a.s.l.) on 19 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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