Spanish Peninsular Relief: Formation and Characteristics
Characteristics of the Spanish Peninsular Relief
The relief is the set of forms presented by the Earth’s surface, which are dynamically constructed and destroyed. It is solid-form and determined by the width and extension of the coast. The rectilinear layout offers few refuges for navigation. The high average altitude is due to the extensive existence of a central plateau, and mountain ranges that cross the peninsular territory. The average altitude is 660m, with some areas reaching 1300m, making communications difficult.
Peripheral provision of the mainland relief: This makes access difficult between the coast and the plateau. The diversity of the relief is due to the geological formation and the variety of climates, which creates distinct natural units.
Primary or Paleozoic Era
The first peninsular lands were the ancient granitic Galician massif, while the other space was covered by marine waters. There were great pressures and extremely high temperatures caused by the movement of the Earth’s crust, called the Hercynian orogeny. The material layers that were formed were abundant in siliceous rocks, such as granite and slate.
Secondary or Mesozoic Era
The Hercynian reliefs were eroded and transported by wind and water. Coarse materials (limestone or sandstone) formed marine deposits. Due to the high temperatures and the weight of the strata, the rock became limestone.
Cenozoic Era
Tertiary Period
Due to a meteorite impact and the instability of tectonic plates, there was a rupture. Orogenies were formed, which, due to the hardness and stiffness of the plates, fractured and dislocated. In jagged areas, deep depressions and grabens were formed. These movements are seen in the mountain ranges that cross the Meseta. The collision of plates along with the folding of sedimentary materials formed the Alpine mountain ranges.
Quaternary Period
Relief erosion of rivers and glaciers contributed alluvial material to the Guadalquivir and Ebro depressions. Sedimentation and the filling of low areas formed coastal plains.
The Plateau
- North sub-plateau: Surrounded by mountains and crossed by the Duero River. The western slope between the peneplain and the plateau is steep, and the rivers are embedded.
- South sub-plateau: Consists of two plateaus separated by the Toledo Mountains. It has a gentle inclination towards the Atlantic, draining into the plain of La Mancha.
Units Related to the Meseta
- Old Paleozoic base: Part of the western part of the plateau, which is a gentle peneplain in the lands of Salamanca and Extremadura, where the old materials (granite, slate) are uncovered.
- Sedimentary rock: The ancient base is sunken and buried under sedimentary materials. Clay and sand are abundant in the lower strata, while the upper layer is limestone, found in the barren fields.
- Reliefs in the interior of the plateau: Mountainous system formed during the Tertiary period in the Alpine orogeny, when the ancient base was uplifted and fractured, known as fracture tectonics.
- Mountainous edges of the plateau: During the Alpine orogeny, when some plates of the Earth’s crust were pressed, the ancient base was fractured into blocks.
The Mountainous Interior of the Plateau
- The Central System: Between the mountains of the Central System, the blocks are sunken, and valleys are open. Snowy, high mountain passes make communications difficult (the major port is Somosierra).
- The Toledo Mountains: Divide the southern sub-plateau and drain the waters of the Tagus River. They consist of a series of mountains of modest altitude.