Volcanic field Descabezado Grande - Cerro Azul

by Martin Mergili

Those who take a flight between Santiago and the southern parts of Chile, and who have managed to get a window seat on the eastern side, will recognize a 30 x 20 km large bright spot in the Andean mountain landscape at the latitude of Talca. This bright spot represents a volcanic field producing, besides lava, a lot of pyroclastic material rich in silicium dioxide, and therefore bright in colour. The most prominent summits in the centre of the field are the 3953 m high stratovolcano Descabezado Grande with its ice-filled crater (wich can be recognized in the title image), and Cerro Azul approximately seven kilometres farther south. In the 20th Century, however, Volcanic hazards were rather emerging from Volcán Quizapú, representing a lateral cone of Cerro Azul.

The eruption of Volcán Quizapú

The bright spot in the landscape is well recognizable in this photo. The most recent large eruption in this place happened in 1932, when the Volcán Quizapú on the right side of the main summit produced a highly explosive plinian eruption. Pyroclastic material (primarily ash) was transported over long distances all the way to Buenos Aires and parts of Uruguay. According to some (but not all) sources, this was one of the strongest volcanic eruptions worldwide throughout the 20th century. The forested areas in the foreground belong to the National Reserve Altos de Lircay.

In the contribution on stratovolcanoes you can trigger a plinian eruption by yourself.

At which time of the year did Volcán Quizapú most likely erupt in 1932?

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This volcano is located in an area where the climate still shows some similarities to mediterranean climates. This means that westerly winds prevail during winter time, whereas southeasterly tradewinds are common during summer time. These broad-scale patterns can certainly be superimposed by finer-scale wind systems. However, clear, broad-scale westerly winds are necessary to transport a significant amount of volcanic ash over 1000 km eastward, as it was observed in this case. Such conditions are rather to be expected during winter time.

Indeed, the eruption occurred on 2 June 1932 - at the onset of the Southern-hemispheric winter.

In this context you can also try to solve the task on the Puyehue-Cordón Caulle volcano.

Hildreth, W. & Drake, R.E. (1992): Volcán Quizapu, Chilean Andes. Bulletin of Volcanology 54(2): 93-125 [Access source]

Rovere, E.I., Violante, R.A., Rodriguez, E., Osella, A. & De la Vega, M. (2012): Aspectos tefrológicos de la erupción del volcá,n Quizapú de 1932 en la región de la Laguna Llancanelo, Payenia (Mendoza, Argentina). Latin American Journal of Sedimentology and Basin Analysis 19(2): 105-124 [Access source]

Ruprecht, P., Bergantz, G.W., Cooper, K.M. & Hildreth, W. (2012): The crustal magma storage system of Volcán Quizapu, Chile, and the effects of magma mixing on magma diversity. Journal of Petrology 53(4): 801-840 [Access source]

Stone, J.B. (2015): The volcanoes of southern Chile

The Volcán Descabezado Grande in the Global Volcanism Program of the Smithsonian Institution [Access source]

Spanish Wikipedia article on the Volcán Descabezado Grande [Access source]