Geologically speaking, the Chaco is an up to 3000 m deep trough, created by the Andean upfolding. During millions of years the Chaco-trough* was filled by sediments from the Andes, with water acting as a means of transport for the weathering materials. Over long periods of accumulation in the Chaco-trough, strong shifts occured, during which rock was pushed to the surface - tectonic upheavals** emerged. Among them, the Cerro Leon, a mountain formation with an extension of approximately 40 square kilometres. The highest elevation is about 600 m. Rock enthusiasts can appreciate beautiful layers of submontane deposits comprising of quartzite and sandstone.

* Putzer: "Geologie von Paraguay" (Geology of Paraguay), publ. by Gebrüder Borneträger, Berlin 1962

** Seibert: "Farbatlas Südamerika" (Colour Atlas South America), publ. by E. Ulmer, Stuttgart 1996