Much older than the Andes, having been formed in the Paleozoic and extensively eroded, the Sierra de Córdoba still manages to reach a height of 2880 metres at Mount Champaquí, east of Villa Dolores. The northern part, known as the Sierra de Norte, is considerably lower and less rugged. The mountains, when first built, formed the boundary between Gondwana and the then-expanding Pacific Ocean. They consist chiefly of metamorphic rocks such as quartzite, which were formed when large quantities of marine sediment were subject to enormous heat and pressure. In the Ordovician, there was extremely intense volcanism over the region, almost all of which is now completely eroded, forming the many salt lakes on the western side of the range, which is an elevated plateau leading to the foothills of the Andes.