Morphostructural Units of the Iberian Peninsula’s Relief
Relief Configuration of the Iberian Peninsula
The configuration of the Iberian Peninsula’s relief is characterized by three basic features:
- Massive Form: This is due to the peninsula’s large width and generally straight coastline, with few significant indentations. This limits the influence of the sea inland.
- High Average Altitude: At 660 meters, this is due to the presence of high mountains. The interior of the peninsula is composed of an extensive upland core, the Meseta Central (Plateau).
- Peripheral Mountain Arrangement: The mountains surrounding the plateau limit the influence of the sea.
Types of Morphostructural Units
Morphostructural units refer to the forms and internal arrangement of the relief. The structure results from tectonic movements within the Earth, causing upheavals, subsidence, and displacement of the Earth’s crust, and creating the basic layout of the relief. The form is due to the subsequent action of external agents (water, ice, wind, etc.) that erode, transport, and deposit the relief materials.
In the Iberian Peninsula, we find the following units:
- Sockets (Zócalos): These are plains and plateaus formed in the Paleozoic Era due to the erosion of mountain ranges created during the orogenesis of that era. The materials are Paleozoic siliceous rocks (granite, quartzite, etc.). They are very rigid; therefore, with new orogenic activity, they do not fold but fracture. Currently, they present predominantly horizontal reliefs, occupying large areas in the western half of the peninsula.
- Ancient Massifs (Macizos Antiguos): These are mountains formed in the Tertiary Period by the uplift of a block of a socket due to the pressures of the Alpine orogeny. Their materials are also Paleozoic. Currently, they have rounded and flattened tops, being elevated erosion surfaces. Examples include the Central System, Montes de Toledo, and the Galician Massif.
- Folded Mountain Ranges (Cordilleras de Plegamiento) (Alpine Orogeny): These are large mountain ranges formed during the Alpine orogeny of the Tertiary Period by the folding of sedimentary materials deposited by the sea during the Mesozoic Era. They currently have steep slopes and rugged forms because erosion has not yet softened them. There are two types:
- Intermediate mountain ranges, formed by the folding of material deposited by the sea on the edge of the baseboard (Iberian System, Cantabrian Mountains).
- Alpine mountain ranges, formed by the folding of materials deposited in trenches or geosynclines (Pyrenees, Betic Mountains).
- Sedimentary Basins (Cuencas Sedimentarias): These are sunken areas formed in the Tertiary Period that were filled with sediment. They now present horizontal or gently sloping reliefs. There are two types:
- Basins formed by the collapse of a socket due to the pressures of Alpine orogenesis (depressions of the Duero, Tagus, and Guadiana rivers).
- Pre-Alpine depressions, located on either side of the Alpine ranges. These are caused by the collapse of certain sectors after the uplift of the mountain ranges or from shallow trenches that remained on both sides of the geosyncline upon the rise of the Alpine ranges.
- Germanic Mountain Ranges (Cordilleras Germánicas): postdate the Alpine Orogeny. They are formed by sedimentary basins whose materials fold. Examples: Sistema Central, Montes de Toledo.