Geographical Units of the Iberian Peninsula

Plateau and Inner Units

Central Plateau

The Central Plateau, at an average altitude of 800m, is a sedimentary basin primarily drained by the Duero River. Its southern part, at around 600m elevation, is divided by the Montes de Toledo, separating the Tagus and Guadiana river basins.

Central System

The Central System divides the plateau into two sectors, running in a Northeast-Southwest direction. It was formed during the Alpine movements and subsequent Tertiary uplift, characterized by hard materials and significant faulting.

Montes de Toledo

The Montes de Toledo divide the southern sub-plateau into the Tagus and Guadiana river basins. This low mountain range, with peaks reaching approximately 1600m (e.g., in Badajoz and Cáceres), is primarily formed by shale and granite. Its main tectonic alignment is Appalachian.

Peripheral Mountain Ranges

Galician Massif and Mountains of León

The Galician Massif and Mountains of León represent the oldest solid part of the Iberian Peninsula, situated within the ancient Hesperian Massif. They form a set of heavily eroded mountains composed of hard materials, generally aligned East-West. Altitude increases from West to East, reaching maximum heights in the forested areas of León. Along the coast, old river valleys are abundant, some of which have been invaded by the sea. In León, the mountains surrounding Lake Sanabria, of Alpine origin, are particularly notable.

Iberian System

The Iberian System is located east of the plateau, running in a Northwest-Southeast direction. It is divided into two sectors:

• Northern Sector: Characterized by primary materials, with the Sierra de Urbión (Duero basin) standing out.
• Southern Sector: Features limestone materials, with the Albarracín and Javalambre basins forming a significant karstic relief.

The system is separated by the Jalón River and forms the Jiloca tributary, which is an important contributor to the Ebro River.

Sierra Morena

The Sierra Morena runs in a Southeast-Northwest direction and is known for its raw materials and metallic mineral deposits. Notable areas include Aracena, Guadalcanal, Sierra Madroña, and Hornachuelos. It is a relatively low-lying range, with peaks around 1300m. The Despeñaperros Pass is the main communication route from the plateau to the Guadalquivir Valley. Towards the valley, it forms a significant escarpment, often referred to as the “Guadalquivir step.”

Units Outside the Plateau

Basque Mountains

The Basque Mountains are situated between the Cantabrian coast and the Pyrenees. They are predominantly of lower-to-middle altitude, where Jurassic limestone materials form a distinct tectonic configuration.

Pyrenees

The Pyrenees form the natural isthmus connecting the Iberian Peninsula and the European continent. Running in an East-West longitudinal direction, their rugged configuration makes communication difficult. Three main mountain ranges can be distinguished:

• Axial Pyrenees: Located in the center, formed by siliceous materials, and home to the maximum height, Aneto (3404m).
• Inner Pre-Pyrenees
• Outer Pre-Pyrenees

The Pre-Pyrenees are separated by a series of valleys of varying widths, such as the Berdún basin. Glacial features are prominent throughout the Pyrenees, especially in the Axial Pyrenees, with abundant small alpine lakes (known as ibones).