Spanish Geography: Relief, Plateaus, and Mountain Systems

Spanish Relief: Plateaus and Mountain Systems

The Interior Plateaus and Associated Mountains

The Northern Submeseta

The Northern Submeseta is primarily formed by the Duero River basin. It consists of very high-altitude territories with flat relief, largely unshaped by river erosion. Its geological composition includes Paleozoic rocks (in the West), calcareous sediments, clays, and Tertiary eroded mountain sediments.

The evolution of this region is a result of the Hercynian Orogeny, which formed high mountains. These mountains were subsequently eroded by the Alpine Orogeny. This hard core fractured, creating both sunken and elevated blocks. The plateau itself is inclined towards the Atlantic. An ancient inland lake formed sediments, which were later uplifted, creating horizontal territories during the Quaternary period.

The Sistema Central

The Sistema Central separates the two submesetas. This significant mountainous alignment runs from the southeast to the northwest. Its primary materials are granite and other igneous rocks. It represents an elevated Paleozoic basement area where igneous rocks from the Earth's interior fused. As these molten rocks approached the surface, they crystallized and hardened, forming the highest mountains, some of which retain remnants of glaciers from the Primary Era.

The Southern Submeseta

The Southern Submeseta has an altitude of 600-700 meters. Among its principal characteristics are its flat relief and strata. It is primarily formed by slate, limestone, and Hercynian basement rocks. This region originated from an inland Tertiary lake, whose sedimentary cover gave rise to horizontal folds.

The Montes de Toledo

The Montes de Toledo serve as the separation between the Tagus and Guadiana river basins. This mountainous alignment extends for over 200 km, with peaks reaching up to 1200 meters. It is formed by quartzite and solid slate materials. The range was fractured during the Hercynian Orogeny in the southern sub-plateau, exhibiting Alpine ramps due to subsequent erosion.

The Montes de León

Located in the northwestern corner of the Iberian Peninsula, the Montes de León are formed by fractured and uplifted hard rocks. These rocks, affected by the Alpine Orogeny, have relatively soft peaks, indicating the presence of an early peneplain. They are high mountains with soft tops, featuring characteristic horst and graben structures.

Peripheral Mountain Ranges

The Galician Massif (Macizo Galaico)

The Galician Massif is located in the northwestern corner, at the end of a medium-altitude peninsula. It is a mountainous massif composed of Paleozoic rocks. Part of its basement was leveled during the Tertiary period and subsequently affected by the Alpine Orogeny. It features flattened peaks, gentle relief, and distinct river valleys.

The Cantabrian Mountains (Cordillera Cantábrica)

The Cantabrian Mountains form a mountainous barrier parallel to the northern coast. Primarily formed by limestone, they represent a prolongation of the Tertiary massif and belong to the ancient Hercynian wing.

External Depressions

The Pyrenees

The Pyrenees form the natural frontier between Spain and France. They are primarily composed of quartzite, slate, and granite. This range was uplifted and folded during the Alpine Orogeny. The Pyrenees are characterized by steep peaks, significant elevation differences, and numerous small lakes.

The Ebro Depression

The Ebro Depression is triangular in shape and formed by basin sands and conglomerates. Its formation is closely linked to the Pyrenees during the Alpine Orogeny. Notable features include extensive river terraces.

The Guadalquivir Depression

The Guadalquivir Depression is a broad, triangular plain. It was formed by marine clay sedimentation and was submerged during the Tertiary period. It remains a remarkable geographical zone.