Morphostructural Units of Relief in the Iberian Peninsula and Canary Islands

Posted on Apr 26, 2024 in Geography

Morphostructural Units of Relief

The Plateau

The peninsular fundamental unit of relief consists of high plains, remnants of the Hesperian Massif, primarily shaped by the Hercynian orogeny and later eroded and deformed during the Alpine orogeny. Within the plateau, we can differentiate:

The Old Basement

  • Composed of granite, slate, and quartzite, primarily found in the west.
  • Features peneplains (smooth surfaces with minimal elevation differences), montes islas (isolated hills), and mountain ranges like the Central System and Montes de Toledo.

Tertiary Alpine Orogeny Formations

  • Composed of granite, slate, and gneiss, with softer peaks.
  • Includes the Central System, dividing the plateau into two, with prominent mountains like Somosierra, Guadarrama, Gredos, Peña de Francia, and Gata.
  • Includes the Montes de Toledo, of lower altitude, dividing the southern sub-plateau, with Sierra Guadalupe being the most important.

Sedimentary Basins of the Plateau Interior

  • Formed during the Tertiary Alpine orogeny, resulting in moors, meadows, and hills.
  • Moors are small plateaus with flat surfaces capped by resistant limestone layers.
  • Countryside refers to gently rolling lowlands traversed by rivers.
  • Slopes are steep areas between moors and countryside.
  • The northern sub-plateau basin is higher and more uniform, belonging to the Duero watershed.
  • The southern sub-plateau basin is lower and divided by the Montes de Toledo into the Tagus and Guadiana river basins.

Mountainous Rim of the Plateau

Formed during the Tertiary by block rejuvenation or folding of materials deposited during the Secondary, these include:

  • The Galician-Leonese Massif: rejuvenated during the Alpine orogeny, featuring rounded, low-lying mountains.
  • The Cantabrian Mountains: divided into a western sector with Paleozoic materials and an eastern sector with Secondary limestone materials.
  • The Iberian System: formed by materials deposited on the eastern edge of the plateau, folded during the Alpine orogeny.
  • Sierra Morena: an abrupt step separating the plateau from the Guadalquivir valley, characterized by dark, rocky vegetation.

Depressions Associated with the Plateau

These are the Ebro and Guadalquivir depressions, pre-Alpine basins filled with sediments and characterized by nearly horizontal reliefs.

The Ebro Basin

  • Enclosed by the Pyrenees, Iberian System, and Coastal Range – Catalana.
  • Filled with marine and continental deposits, resulting in foothills, plains, mallos (rocky towers), and hoyas (badlands).

The Guadalquivir Depression

  • Parallel to the Betic Cordilleras, featuring gently rolling countryside, mesas, and mountains.

Mountain Ranges Associated with the Plateau

Formed during the Alpine orogeny, these include:

  • The Pyrenees: with an axial zone of Paleozoic rocks, Pre-Pyrenees with softer shapes, and a mean depression separating them.
  • The Basque Mountains: an extension of the Pyrenean foothills, with low-lying limestone mountains.
  • The Coastal Range – Catalana: a transformation of the eastern Pyrenees, divided into a northern Paleozoic and southern limestone half.
  • The Betic Cordilleras: with the Subbética Cordillera featuring folded and thrust nappes, the Penibética ridge with higher elevations, and the Intrabético Depression with badlands landscapes.

Origin of the Canary Islands

The Canary Islands are of volcanic origin, with several theories proposed for their formation:

  • Continental Drift Theory: suggests the islands are fragments of the African continent.
  • Seabed Expansion Theory: proposes the islands formed due to the expansion of the ocean floor.
  • Plate Tectonics Theory: suggests the islands formed as South America and Africa separated, creating the Atlantic Ocean.