Mountain Ranges of the Iberian Peninsula

The Galaico-Leonese Massif

The northwest corner of the Meseta Central, the Galaico-Leonese Massif, fractured and rejuvenated during the Alpine orogeny. It consists of Paleozoic materials and features rounded, low-lying mountains cut by faults. Its most prominent mountains are Segundera, Cabrera, and Ancares.

The Cantabrian Mountains

The Cantabrian Mountains have two sectors:

• The Asturian Massif: Composed of Paleozoic materials that were part of the Meseta Central and rejuvenated in the Alpine orogeny. Its western end features varying hardness of materials (slates and quartzites), while its eastern end consists of limestone.
• The eastern Cantabrian Mountains: Composed of Mesozoic limestone materials deposited by the sea and folded during the Alpine orogeny.

The Iberian System

Comprised mainly of Mesozoic materials, with Paleozoic materials present only in some sectors. The Iberian System has two sections:

• The northern third: Includes the highest peaks of the Cordillera (Urbión Peaks, 2235m).
• The Iberian System splits into two branches: the internal or Castilian branch with a cover of Mesozoic sedimentary material lining the old socket and the external or Aragonese branch with calcareous materials. Both are separated by a graben filled with Cenozoic material.

Sierra Morena

Sierra Morena is not a chain but an abrupt step between the Meseta Central and the Guadalquivir valley. Its origin is interpreted as a gigantic fault produced by the thrust that raised the Baetic Cordillera. The crag is Paleozoic, and its most prominent mountains are Madrona, Pedroches, and Aracena.

The Depressions

The Ebro and Guadalquivir depressions were Prealpina graves that, after the Tertiary Alpine orogeny, were situated between the massive old ranges and inlets within the continent. Cenozoic and Quaternary materials filled them, resulting in horizontal reliefs. Remnants of the ancient sea that covered them can be found in the marshes of the Guadalquivir.

Cordillera Costero-Catalana

The Cordillera Costero-Catalana is a transformation of the eastern Pyrenees, separated from them by faults. The northern half consists of Paleozoic materials, remnants of the old Hercynian massif. The southern half consists of limestone soils folded during the Alpine orogeny. The range is divided into two alignments: a low-lying coastal mountain range parallel to the coast and a higher inner littoral cordillera, separated by a longitudinal depression filled with Cenozoic and Quaternary materials.

The Pyrenees

The Pyrenees have a complex structure:

• The axial area: Paleozoic crag, the highest and steepest area (Montes Malditos with Aneto and Monte Perdido).
• The Pre-Pyrenees: Mesozoic limestone materials, less high.
• The median depression: A long, narrow depression separating the internal and external Pre-Pyrenees.
• The Basque Mountains: Mostly prolong the Pyrenees, featuring limestone crag and low altitude. The axial Pyrenees only emerges in the east. Its highest elevations are Aralar and Peña Gorbea.