Castelo Velho de Freixo de Numão. Geomorphological framework

Abstract

The Castelo Velho area stays at very special position because it corresponds to a kind of a crossroad where the large flat surface of the Meseta begins to be moved by the passage of a major tectonic accident (Vilariça fault) and simultaneously, carved by the down wearing erosion of the Douro and its tributaries. The major tectonic accident, active during the Quaternary, is underlined by the rigidity of the Vale da Vila and goes on towards the Vilariça graben, to the north, and towards Longroiva tectonic basin to the south. The site of Castelo Velho, dominating the Vale da Vila and the surface of Foz Côa, allows the observation of large areas, in particular a significant part of the Meseta, until Marofa mountain. In the pivotal position between the Western Highlands and the Meseta surface, this area also reflects a sharp change in climate due to the deep groove produced by the river system. This steep valley creates a special climatic area, the “Alto Douro” region, with a climate that contrasts with the surrounding plateau areas.