Morphostructural Units: Formation and Evolution

Posted on Feb 4, 2025 in Geology

Morphostructural Units: Types

Types of Morphostructural Units

  1. Sockets: Formed on plains during the primary or Paleozoic era due to erosion of razed mountain ranges from that era’s orogenesis.
  2. Solid Ancient Mountains: Mountains formed in the Tertiary period by the re-emergence of a block from a plinth as a consequence of Alpine orogenic movements.
  3. Folding Ridges: Large mountain ridges that arose during the Tertiary orogeny due to the folding of sedimentary material, such as limestone deposited in the secondary period.
  4. Sedimentary Basins: Sunken areas or depressions formed in the Tertiary period and filled with sediments like limestone, clay, and sand.

Evolution of Morphostructural Units

  1. Archaic Era: A band emerged from northwest to southeast, formed by slates. Elevated areas also emerged in isolated locations from the central system and the Montes de Toledo.
  2. Primary and Paleozoic Era: The Hercynian orogeny occurred. Seas covered the peninsula, and the Hercynian mountain ranges formed from granite, slate, and quartzite. The Hesperian Massif rose in the west, and clumps of the Betica-Rif massif appeared in the southwest. All these became sockets.
  3. Secondary or Mesozoic Era: A period of calm prevailed with continuous leveling of the Hercynian mountain ranges. The slope of the plinth of the plateau towards the Mediterranean led to deep penetration of the sea.
  4. Tertiary Period: The Alpine orogeny occurred, resulting in:
    • Alpine ranges rising from materials deposited in depressions.
    • Prealpine depressions forming parallel to the new ranges.
    • The plateau being affected by the Alpine orogenesis.
  5. Quaternary Era: Glaciers formed, and fluvial terraces developed.
    • Mountain glaciers affected the highest areas, resulting in cirque and valley glaciers.
    • The epoch was characterized by the formation of fluvial terraces.

Areas of Dominant Rock Types

Area of Old Rocks (Precambrian and Primary)

Integrated by old Precambrian and primary rocks. These are mostly found in the western mainland and extend to the western part of the Cantabrian mountain range, the Montes de Toledo, and Sierra Morena. They are also located in other areas where remnants of ancient massifs remained: the axial Pyrenees and some sectors of the Iberian System, from the mountains and the Catalan Coastal Range, and the Penibetic System. The predominant rock in this area is granite. The molding is determined by the characteristics of this crystalline and rigid rock, which is susceptible to various forms of disturbance.

Area of Limestone Sediments

Formed by secondary sediments folded during the Tertiary period. The limestone soils form an inverted Z shape that extends through the Pyrenees, the Basque Mountains, the eastern part of the Cantabrian Mountains, the Iberian System, part of the Catalan Coastal Range, and the Subbetic Range. The prevailing rock is limestone, a hard rock that forms cracks or joints, but dissolves easily in rainwater, especially through the joints.

Area of Clay Sediments

Consisting of little resistant sedimentary materials (clay, marl, and gypsum) deposited in the late Tertiary and Quaternary periods. Covering a large part of the northern and southern sub-plateau depressions, the Ebro and Guadalquivir depressions, and the Mediterranean and coastal plains. The clay relief is basically horizontal because these areas were not affected by significant folding. Erosion is rapid due to the softness of the materials.