Friday, May 14, 2010

Calbuco Volcano

Calbuco is a very explosive andesite stratovolcano located in southern Chile, in the Los Lagos Region, between Llanquihue Lake and Chapo Lake. The volcano and the surrounding area lie within Llanquihue National Reserve. It underwent edifice collapse in the late Pleistocene, producing a volcanic debris avalanche that reached the lake. The volcano has a truncated cone shape and is composed of blocky and lava flows interbedded with pyroclastic rocks. the main cone of Calbuco volcano consists of interbedded lavas and breccias. It includes a violent eruption that triggered a 3 cubic km rock-avalanche which traveled NNW.

Since 1837, Calbuco has erupted 9 times, with the latest one in 1972. One of the largest historical eruptions in southern Chile took place there in 1893–1894. Violent eruptions ejected 30-cm bombs to distances of 8 km from the crater, accompanied by voluminous hot lahars. Strong explosions occurred in April 1917, and a lava dome formed in the crater accompanied by hot lahars. Another short explosive eruption in January 1929 also included an apparent pyroclastic flow and a lava flow. The last major eruption of Calbuco, in 1961, sent ash columns 12–15 km high and produced plumes that dispersed mainly to the SE and two lava flows were also emitted. There was a minor, 4-hour eruption on August 26, 1972. Strong fumarolic emission from the main crater was observed on August 12, 1996.