The Northern Plateau (Meseta Norte) is constituted by Paleozoic sockets. At the beginning of the Mesozoic Era, once the Hercynian folding that raised the current Central Europe and the Gallaeci zone of Spain, the deposited materials were dragged by the erosive action of the rivers.

During the alpine orogeny, the materials that formed the plateau broke through multiple points. From this fracture rose the mountains of León, with mountains of not much height and, constituting the spine of the Plateau (Meseta), the Cantabrian Mountains and the Sistema Central, formed by materials such as granite or metamorphic slates.

The karst complex of Ojo Guareña, consisting of 110 km of galleries and its caves formed in carbonatic materials of Coniacian which are situated on a level of impermeable marls, is the second largest of the peninsula.

This geological configuration has allowed upwellings of mineral-medicinal or thermal water, used now or in the past, in Almeida de Sayago, Boñar, Calabor, Caldas de Luna, Castromonte, Cucho, Gejuelo del Barro, Morales de Campos, Tresacasas, Valdelateja and Villarijo, among other places.