Activity for the week of 5 April-11 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
| United States
| 59.363°N, 153.43°W
| Elevation 1252 m
Low-level eruptive activity continued at Augustine during 31 March to 4 April, although it was at lower levels than in previous weeks. The seismic network continued to record signals that were associated with occasional hot block-and-ash flows, rock avalanches, rockfalls, and lava flows. Small and dilute ash clouds resulting from these processes were likely confined to the immediate vicinity of the volcano. Satellite imagery continued to show a thermal anomaly at the volcano's summit. Airborne sulfur-dioxide gas measurements revealed continued magmatic gas emissions. Low-light camera observations indicated that activity was restricted mainly to the summit lava dome. Augustine remained at Concern Color Code Orange.
Sources: US Geological Survey Alaska Volcano Observatory (AVO), Anchorage Volcanic Ash Advisory Center (VAAC)
Ol Doinyo Lengai
| 2.764°S, 35.914°E
| Elevation 2962 m
On Frederick Belton's Ol Doinyo Lengai website, information was compiled about the activity that began around 30 March. According to the site, a bush pilot reported that a lava flow and lava fountains were emitted on the 30th, but there were no ash emissions. A steam plume was visible that may have been mistakenly described as ash in news reports. According to an observer in Tanzania, on 4 April a very large lava flow was visible on the volcano's W flank. The lava flow was over 1 km long and had traveled down the flank of the volcano and into a gorge. There were no signs that the flow was still hot. Photographs revealed that another lava flow may have traveled W of the volcano on 3 or 4 April. On 7 or 8 April, active lava was contained within a new lava lake. Contrary to news reports, a local tour operator stated that there were no evacuations from villages near the volcano.
Source: Ol Doinyo Lengai (Fred Belton)
| 16.355°S, 70.903°W
| Elevation 5672 m
Based on information from the Perúvian Volcanologic Observatory, the Buenos Aires VAAC reported that ash emitted from Ubinas reached 6.1-9.1 km (20,000-30,000 ft) a.s.l. on 6 April around 1220. No ash was visible on satellite imagery. The Aviation Color Code for the volcano was at Red, the highest level. At 1900 on the 6th a plume was observed at 6.1-7.3 km (20,000-24,000 ft) a.s.l. and drifting NE. The Aviation Color Code was subsequently reduced to Orange. On 8 April the VAAC received a report that volcanic activity had ceased, so the Aviation Color Code was reduced to Green, the lowest level. On the 9th, a significant meteorological forecast (SIGMET) was issued for an ash cloud at a height of 6.1-7.3 km (20,000-24,000 ft) a.s.l. that was drifting SW. The Aviation Color Code was increased to Red until 11 April. On the 11th volcanic activity reportedly ceased, so the code was again decreased to Green.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
| Andaman Islands (India)
| 12.278°N, 93.858°E
| Elevation 354 m
Based on information from a pilot report and satellite imagery, the Darwin VAAC reported that an ash plume was emitted from Barren Island during 5-6 April. The plume did not rise higher than 4.6 km (15,000 ft) a.s.l.
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 5-10 April, with a partially solidified lava dome in the main crater. Decreases were observed in various measured parameters at the volcano, including seismicity, deformation, gas emissions, and temperatures. According to INGEOMINAS, most of the explosive eruptions at Galeras in the past 17 years occurred when parameters were at similarly low levels. In addition, the current lava dome has a significantly greater volume than the dome that was destroyed during an eruption in 1992. Also, the volume of magma in the interior of the volcanic system is greater than during 1989-1993. 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 5-11 April, lava from Kilauea continued to flow off of a lava delta into the ocean at the East Lae`apuki entry. Background volcanic tremor was at normal levels at Kilauea's summit. Small, shallow earthquakes continued beneath the summit area and upper E rift zone. Volcanic tremor reached moderate levels at Pu`u `O`o. Slight inflation and deflation occurred at the volcano.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
| Central Java (Indonesia)
| 7.54°S, 110.446°E
| Elevation 2910 m
According to a news article, authorities banned mountain climbing on 10 April at Merapi due to increased activity. There were reports that the amount of tremor had increased and that lava was seen flowing near Pasar Bubar village, ~350 m from the volcano's crater.
Source: Deutsche Presse-Agentur
| Costa Rica
| 10.2°N, 84.233°W
| Elevation 2708 m
On 1 April, clear weather allowed OVSICORI-UNA staff to visit Poás for the first time since explosions occurred during 24-26 March. They confirmed that Laguna Caliente at the volcano's summit had widened, and that sediments and blocks from the lake's bottom and surrounding walls were ejected during the explosions. The lava dome's (or pyroclastic cone's) N wall was greatly fractured and a 40 x 7 x 8 m segment of the wall was gone. In addition, a 40 x 4 x 6 m chunk of the SE wall of the lake was missing and must have been destroyed during the explosions. They also found that the lake was light gray due to large quantities of suspended sediments, had a temperature of 54 degrees Celsius, had a pH of 0.63, and the lake level had decreased in comparison to the level before the explosions.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)
| North Kermadec Ridge (New Zealand)
| 29.27°S, 177.92°W
| Elevation 516 m
Seismicity continued to decline at Raoul Island through 7 April. In addition, Green Lake's water level began to recede, ending the water-level increase that had occurred in response to the 17 March eruption. Raoul Island remained at Alert Level 2 (minor eruptive activity).
| 16.72°N, 62.18°W
| Elevation 915 m
Low extrusion rates occurred at Soufrière Hills' lava dome at the beginning of the interval 31 March to 7 April. Continued lava-dome growth was focused E, with a lava lobe growing in that direction and the majority of rockfalls and pyroclastic flows occurring in the SE to NE sector. Photographs taken on 6 April clearly showed slightly elevated extrusion rates with lobe development on the E side of the dome. One moderate-sized pyroclastic flow occurred around 1030 on 2 April, resulting in minor ashfall to the W of the island. During the report period, the sulfur-dioxide flux averaged 578 metric tons per day. The hydrogen chloride to sulfur dioxide ratio was 2.3 and 2.6 on 4 and 5 April, respectively.
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 5-10 April, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. Small earthquakes occurred once every several minutes, and GPS (global positioning system) data showed that solidified dacite lava continued to extrude slowly. 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 4-10 April, small-to-moderate explosions at Tungurahua consisted of gas, steam, and small amounts of ash. Plumes rose to ~3 km above the volcano (or 26,300 ft a.s.l.) on 9 April. Ash fell in the Baños, Guadalupe, Choglontus, Bilbao, and Manzano sectors. Around 1500 on the 9th, several lahars traveled down gorges mainly on the W side of the volcano, disrupting traffic along the Baños-Penipe highway.
Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG), Washington Volcanic Ash Advisory Center (VAAC)
| New Britain (Papua New Guinea)
| 5.05°S, 151.33°E
| Elevation 2334 m
A small low-level plume emitted from Ulawun was visible on satellite imagery extending W on 9 April.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
| United States
| 56.17°N, 159.38°W
| Elevation 2507 m
During 31 March to 7 April, low-altitude ash emissions occurred from Veniaminof and seismicity remained at low levels. On 6 April, a pilot reported an ash plume at a height of ~3 km (10,000 ft) a.s.l. The Concern Color Code remained at Yellow.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
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.
3. Preliminary accounts sometimes contain exaggerations and "false alarms," and accordingly, this report may include some events ultimately found to be erroneous or misleading.
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