mercredi, avril 28, 2010
The Chilean geological service SERNAGEOMIN raised the alert level of Llaima volcano from 3 to 4 on 25 April because of ‘the occurrence of earthquakes with high energy levels and tremor signals with durations of up to 20 minutes’, a volcanologist reported to a llocal newspaper. ... [details]
dimanche, avril 05, 2009
A new eruption started at Llaima volcano on 4 April 09. Lava fountains and stormbolian activity from the summit vents fed lava flows travelling down the slope of the volcano. [details]
Llaima volcanLlaima stratovolcano is one of Chile's largest and most active volcanoes. It is located 90 km S of Callaqui in the Araucanía Region of southern-central Chile, in the Conguillio National Park about 80 km from the city of Temuco.
It is one of the volcanoes with the most known historic eruptions in South America. Its eruptions are brief episodes with spectacular lava fountains, strombolian activity and lava flows. Eruptions often occur along NNE trending fissures.
Introduction:Llaima contains two main historically active craters, one at the summit and the other, Pichillaima, to the SE. The volcano is dominantly basaltic-to-andesitic and has a volume of 400 cubic km.
About 7200 years ago, activity at Llaima became less explosive and more effusive. Following the end of an explosive phase, the construction of the present edifice began, which consists primarily of lava flows. It overlaps an 8-km-wide caldera that formed about 13,200 years ago, after a violent eruption that deposited the 24 km3 Curacautín Ignimbrite.
Llaima has over 40 flank vents that have formed cinder cones. Its eruptions are characterized by strombolian, hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century.
April 2009 eruption
Llaima volcano erupted on Friday 3 April 2009 following several months of low seismic activity. On 2 April at 16:00 h local time, amplitude and frequency of long period earthquakes increased to 45 to 60 per hour and remained constant until 6pm on 3 April, when it evelved into continuous low frequency seismic tremor. The seismic increase during 2-3 April was associated with weak vapour emissions.
From 20:30 h on 3 April, eyewitnesses reported glow in the main crater. At 21:00 h, tremor increased, and at 22:45 h weak strombolian explosions occurred from the main crater.
Until 06:00 h on 4 April, moderate strombolian explosions occurred every 1-3 seconds from 2 vents in the crater. Incandescent bombs were ejected up to 700 m above the crater. Muddy water was observed in drainage ravines, and a lahar warning was sent out.
Source: GVP monthly reports
Llaima volcano erupted again on 1 January 2008, producing lava fountains, lava flows and ash. The eruption persisted on fluctuating levels throughout the year. On 10 July, powerful strombolian eruptions reaching a height of 500 m above the crater. An exclusion zone was placed around the volcano, and residents were evacuated. 3 ash eruptions occurred on 21 August, sending ash to 11,000 ft (ca. 4 km) altitude.
Ash eruptions at Llaima volcano sent an ash plume to 17,000 ft (ca. 6 km) altitude on 8 August 2007.
In early January 2003, an increase in ground temperature at Llaima volcano started to melt snow and ice in the north and south craters, exposing bare rock at the summit and Pichillaima crater.
3 ash eruptions occurred on 10 April, causing ash fall on the N slope of Captrén. On 11 April, a helicopter overflight discovered impact craters from bombs on the snow and ash fall on the glaciers on the NE, E, SE, and SW flanks of Llaima, extending to up to 4 km.
Small ash eruptions occurred at Llaima volcano in April 1998.
Small phreatic or phreatomagmatic ash eruptions occurred at Llaima volcano during March-September 1997 and were detected by seismographs.
1995 ash eruptions
Llaima volcano started small ash eruptions on 13 October 1995. During the night of 20-21 October, a stronger explosion occurred from the main crater and deposited ash in a 12 km long area towards the SW from the summit.
1994 May 17 explosive eruption - large ash plume & destructive lahars
A powerful vulcanian ash eruption eruption began at Llaima volcano on 17 May 1994. A 5 km tall ash plume was erupted, reaching 8 km altitude and extended 300 km ESE. Ash fall occurred in the towns of Zapala and Cutral-Co, in the Neuquén Province, Argentina.
Lava flows underneath the glaciated summit melted ice and snow and caused devastating lahars. One reached the town of Vilcún (43 km W of Llaima), and destroyed 5 bridges across the Rio Calbuco, and left 59 people straded.
Source: GVP monthly reports
3 small summit eruptions occurred at Llaima volcano between 23 August and 2 September 1992.
A small explosion occurred on 25 February 1990, followed by a sustained fountain of glowing ash. Small lahars were detected on the east flank. ...plus
Llaima volcano had a strong eruption from its central crater on 20 April 1984. The eruptions were visible from Temuco, 70 km W of the volcano. People living in the immediate surroundings of the volcano were evacuated.
1979 ash eruptions
Eruptions began at Llaima volcano on 15 October 1979. An ash plume of 1 km height above the crater was produced. On 24 November, 2 explosions sent ash up to 2 km above the summit.
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