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Horcones and Cerro Aconcagua

by Lisa-Maria Kogler and Martin Mergili

General information

With a summit elevation of 6962 m, Cerro Acocagua is the highest peak of the Andes - and also worldwide except for Asia. Located at approx. 32° Southern latitude, it is at a similar position as the Himalayas on the Northern Hemisphere. Even though the Aconcagua has a volcanic structure in its interior, it is - in contrast to many other mountains in the Andes - not a volcano. This can be explained by the following theory: the subduction angle at which the oceanic Nazca Plate is pushed beneath the continental South American Plate is relatively flat in this area, which does not favour volcanic activity. In the early stages of evolution of the mountain, the subduction angle was still steeper, so that today's Aconcagua was a volcano at the beginning. Therefore it is characterized by volcanic rocks. Today, the interior structure of the Aconcagua is volcanic, but the mountain is detached from the source of magma. A closer look at the title image reveals a flat, but undulating hilly terrain in the foreground. Now, the question is how this landform could have developed. At least two hypotheses do exist about its formation.


The mysterious mounds of Horcones

Christina would now like to tell you something about the undulating landscape in front of Aconcagua, in which she is standing right a the moment. You will need some skills in the German language to understand everything Christina says.

On the one hand, the mounds could consist of glacial deposits (till) dating back to the end of the last ice age. On the other hand, there is the hypothesis that the landscape was formed by at least two huge prehistoric rock avalanches, originating from the slopes of Cerro Aconcagua. The available evidence clearly favours the second possibility.

Movie: Peter Mathis and Gregor Offenthaler | Speaker: Christina Hauck


How the rock avalanches could have looked like

Martin has developed a computer programme with which he thinks to be able to calculate the propagation of rock avalanches, using a flow model. You can now initiate a rock avalanche from the southern face of Cerro Aconcagua by clicking on the release area highlighted in brown colour.

Simulation models can help us to get a certain impression on how landslides could have moved. However, model results never represent reality, but in the best case a reasonable approximation of reality. This is particularly true in those cases where the initial conditions are hardly known, such as here. Therefore, the visualization only shows how the prehistoric rock avalanches from Cerro Aconcagua could have looked like, without claiming to exactly reproduce one of the two inferred events.

This computation was performed with the software r.avaflow. Input data derived from SRTM V4 data. Background: Landsat 5 True Color Composite. Points and road mapped from OpenStreetMap.

References and links

Fauqué, L., Hermanns, R., Hewitt, K., Rosas, M., Wilson, C., Baumann, V., Lagorio, S. & Di Tommaso, I. (2009). Mega-deslizamientos de la pared sur del Cerro Aconcagua y su relación con depósitos asignados a la glaciación Pleistocena. Revista de la Asociación Geológica Argentina, 65(4), 691-712 [Access source]

Wikipedia article on the Aconcagua [Access source]

Spanish-language info table on site