Relief Formation and Landscapes of the Iberian Peninsula
Relief of the Iberian Peninsula
The relief found in the Iberian Peninsula is the result of a series of orogenic stages and erosion that have alternated over millions of years. There are three types of Iberia: siliceous, limestone, and clay.
Siliceous Iberia
First, in siliceous Iberia, there are Precambrian and Paleozoic materials (the oldest in the Peninsula). These are igneous or magmatic rocks (resulting from cooling lava) and metamorphic rocks (formed from the transformation of igneous and sedimentary rocks, as these are under pressure and high temperatures, making them the hardest and most compact). According to their formation, igneous rocks can be distinguished into two types: extrusive (solidified on the outside), such as basalt, and intrusive (solidified inside), forming batholiths, such as granite.
In the Primary or Paleozoic Era (570 million years ago), the Iberian Peninsula, as a result of the Hercynian orogeny (active magmatism), formed the first solid landmasses: Hesperian, Aquitaine, Ebro, Catalano-Balear, and Betic-Rif.
This Iberia is located in the western base of the plateau (remnants of the Hesperian Massif are found), the northwest (Galician Massif, fractured during the Alpine orogeny), the western sector of the Cantabrian Mountains (up to the Picos de Europa), the Central System, the Montes de Toledo, Sierra Morena, the Axial Pyrenees (like Aneto), and the Penibaetic System. Discontinuous patches can also be found in the old Paleozoic massifs, which were eroded over time in the Mesozoic Era. There are also areas of post-Alpine volcanism in Olot (Girona), Campo de Calatrava (Ciudad Real), between the Betic-Rif and Cabo de Gata (Almería), and in the mouth of the Ebro River.
Morphogenetic systems sculpt definitive forms, related to the prevailing climate of each area and time, and the succession of climatic phases that give us the final outcome of current modeling.
With respect to landscape, which is the result of morphogenetic systems, we can distinguish temperate and cold regions. In cold areas (highest summits of the Pyrenees), the system is given by the periglacial process of gelifraction or cryoclastia: water enters the joints, freezes, expands, and the pressure generated fractures the rock, leaving angular edges. The result of this process is vertical walls, needles, scree (sheets of debris), and cliffs.
In contrast, in temperate zones, with the pluvial system, the temperature does not drop to 0°C. The water breaks down the minerals in the granite, leading to rounded peaks and scree.
Limestone Iberia
Limestone Iberia is formed by sediments from the Mesozoic Era (a calm orogenic period) and folded during the Cenozoic Era, which gave rise to the Alpine Orogeny. This orogeny affected both old and solid materials that had been sedimenting at the foot of the massifs and folded the deposited material. The limestone soils form an “inverted Z” that extends through the pre-Pyrenees, the Basque Mountains (formed as a result of the Pyrenees), the eastern sector of the Cantabrian Mountains (formed by subduction), the Iberian System, part of the Coastal-Catalan Range, and the Subbaetic Range.
The material is predominantly limestone, a hard rock that forms cracks and fractures that easily dissolve in rainwater. This originates a complex relief, shaped by karst features, resulting in surface forms (lapies and dolines) and subterranean forms (potholes and caves). It gives rise to the pluvial system (Basque Mountains). The river water models relief in their mouths, forming estuaries. There is no permanent ice, but there is stormwater modeling.
Clay Iberia
These materials have not been subjected to high pressures or high temperatures. They were formed following the Hercynian orogeny and are composed of tough, little sedimentary material deposited in the late Cenozoic and Quaternary periods. Sedimentary rocks are formed by the erosion of other existing rocks and the sedimentation of remains from erosion. This includes part of the depressions of the northern and southern sub-plateaus, the depressions of the Ebro (where the Ebro Massif was raised in the Paleozoic Era and collapsed in the Cenozoic Era, disappearing and being covered with water, closed off from the sea), the Guadalquivir, and the Mediterranean coastal plains (areas where rain is usually not normal, but when it does, it forms grooves).
The clay relief is basically horizontal, as these are areas not affected by subsequent folding. Its erosion is quick and easy due to the softness of the materials. The rivers open valleys that separate horizontal structures, which are soon eroded, resulting in gently undulating relief (gullies and badlands, mesas, buttes, and inselbergs).
In this Iberia, orogenic calm occurs. There is a change in the relief, arising from subsequent erosion and sedimentation on the sides, creating peneplains (mountains flattened by erosion).