vendredi, janv. 11, 2013
New seismic monitoring equipment has recently been installed by Sernageomin near Chillán volcano, one of Chile's most active volcanoes. First results of the monitoring confirmed that volcanic earthquakes - including some that are felt by local population - are common and frequent at the volcano, something that had long been known but never actually been measured. ... [details]
Nevados de Chillán volcanNevados de Chillán volcano in central Chile is one of the country's most active volcanoes. It is part of the Southern Volcanic Zone of the Andean Cordillera, and is composed by 3 overlapping stratovolcanoes located on a NNW-SSE-trending line.
Introduction:The complex cone of Nevados de Chillán sits on a basement of granitic intrusive rocks and Cenozoic lavas. Its main vents extend along a 10 km long NE trending ridge.
3 younger stratovolcanoes were constructed along a NNW-SSE line of 3 nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile.
The largest stratovolcano, dominantly andesitic, 3212-m-high Cerro Blanco (Volcán Nevado), is located at the NW end of the group.
3089-m-high Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end.
The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in altitude. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986, eventually exceeding its height by 20 m.
Source: GVP Nevados de Chillán volcano information
Based on satellite imagery, Nevados de Chillán volcano had an eruption in January 2009. An ash plume was detected that rose to 3.7-6.1 km (12,000-20,000 ft) altitude on 21-22 January and drifted 50-80 km SE.
Small eruptions occurred for over the week ending 27 August 2003, with ash columns up to heights of 500 m. The eruptions produced a new double crater in the saddle between the cones Nuevo (which erupted during 1906-1945) and Arrau (which erupted during 1973-1986). Eruptions occurred at Las Termas subcomplex.
The eruptions between 1861-65 occurred on the NW flank of Cerro Blanco subcomplex from the Santa Gertrudis cone and produced a new lava field.
The main phase of the eruption occurred during August 1861, in the height of the Austral winter, when seasonal snow covered the upper flanks of the volcano. Powerful strombolian explosions sent incandescent bombs high into the sky and could be seen at night from Chillan town 80 km to the west. At the same time, strong ash eruptions occurred and an earthquake was felt in Chillan. Ash fall turned water cloudy in Nuble River 20 km to the north. On 22 August 1861, lava flows were erupted. From February 1862 until 1863, strombolian explosions continued with small lava fountains near the vent.
K. Mee, H. Tuffen and J. S. Gilbert (2006) "Snow-contact volcanic facies and their use in determining past eruptive environments at Nevados de Chillán volcano, Chile", Bull. Volc., Volume 68, Number 4, 363-376
Cliquez ici pour recommander cette page à un ami