Relief of the Iberian Peninsula

Posted on Oct 27, 2024 in Geology

Morphostructural Unit Types

The Iberian Peninsula’s relief has three main features:

  1. Massive form: The peninsula has a large width from west to east coasts and a rectilinear shape.
  2. High average elevation: Its average elevation is only surpassed in Europe by Switzerland, with several high mountain ranges.
  3. Peripheral mountainous provision: A plateau surrounded by mountains limits the influence of the sea.

Types of Morphostructural Units:

  1. Skirting: Plains and plateaus of the Primary Era, formed as a result of the flattening or erosion of mountain ranges. Rocks are rigid and break. This type is found in the western half of the peninsula.
  2. Ancient Beds: Mountains of the Tertiary Era, formed from Paleozoic materials. They have soft, rounded peaks. Examples include the Central System, Montes de Toledo, Galician Massif, and the western part of the Cantabrian Mountains.
  3. Folding Ranges: Large mountain ranges of the Tertiary and Secondary Eras. There are two types: intermediate ranges (Iberian and eastern part of the Cantabrian Mountains) and alpine ranges (Pyrenees and Betic Cordillera). They have steep forms.
  4. Sedimentary Basins or Depressions: Sunken areas of the Tertiary Era filled with sediment. Examples include the depressions of the Duero, Tagus, and Guadiana rivers, and the alpine troughs of the Ebro and Guadalquivir rivers.

Evolution of Morphostructural Relief Units

  1. Precambrian Era: A band of slates and gneiss emerged from the sea, forming isolated elevations in the areas of the Central System and Montes de Toledo. These were later destroyed by erosion and covered by Paleozoic seas.
  2. Paleozoic Era: The Hercynian Orogeny occurred. Ridges of granite, slate, and quartzite emerged. The Hesperian Massif plateau tilted towards the Mediterranean. Several landmasses appeared and were subsequently destroyed.
  3. Mesozoic Era: A period of orogenic calm. Erosion and sedimentation prevailed. The Hercynian mountain ranges leveled, and the plateau tilted, allowing the sea to penetrate and deposit plastic materials. Sediments also accumulated in the Pyrenees and Betic zones.
  4. Tertiary Era: The Alpine Orogeny occurred. The Pyrenees and Betic Cordillera emerged by folding materials deposited in the Pyrenean and Betic troughs. Parallel to these, the Ebro and Guadalquivir depressions formed. The plateau tilted towards the Atlantic, and the Iberian, Cantabrian, and Sierra Morena ranges formed. The plateau experienced fractures and faults, resulting in horsts and grabens. The Galician Massif and the Central System and Montes de Toledo became horsts, while the Duero, Tagus, and Guadiana depressions became grabens, filling with sediment and forming gently sloping plains. Some areas experienced volcanic activity.
  5. Quaternary Era: Glaciation and the formation of river terraces began. Glaciation affected the highest mountain ranges, creating cirque and valley glaciers.

Rocky Areas and Relief Types

  1. Silica Area: Composed of Precambrian rocks, located in the west of the peninsula with ramifications in the Central System, Montes de Toledo, and Sierra Morena. Granite is the main rock. In mountains, it breaks into scree, while in lower areas, it forms granite tors.
  2. Limestone Area: Formed by sediments on the alpine folded side. Includes the Basque Mountains, parts of the Pyrenees, the Iberian Range, and the Subbética Cordillera. Limestone is hard but dissolves in water, resulting in karst landscapes with gorges, sinkholes, poljes, caves, and chasms.
  3. Shale Area: Composed of Tertiary and Quaternary sediments. Includes depressions and the Mediterranean coast. Reliefs are flat. Erosion is fast, and rivers open valleys. Badlands form in areas with alternating hot and dry periods with heavy rain.

Major Morphostructural Relief Units

Plateau

The fundamental unit of peninsular relief. It is a high plain, a remnant of the Hesperian Massif. It was deformed and partially destroyed during the Alpine Orogeny.

  1. Old Paleozoic Base: Located in the west. Composed of granite, slate, and quartzite. Includes peneplains and residual reliefs.
  2. Interior Ranges of the Plateau: Central System and Montes de Toledo, formed during the Alpine Orogeny. They have soft peaks.
  3. Sedimentary Basins of the Interior Plateau: Formed during the Alpine Orogeny. Include moors, fields, and hills.

Mountains Surrounding the Plateau

  1. Galician-Leonese Massif: Fractured and rejuvenated during the Alpine Orogeny. Composed of Paleozoic materials. Features rounded, low-rise mountains.
  2. Cantabrian Mountains: Two sectors: the western sector with Paleozoic materials and the eastern sector with secondary limestone.
  3. Iberian System: Intermediate range formed mostly by secondary material.
  4. Sierra Morena: Abrupt step separating the plateau from the Guadalquivir valley.

Depressions Outside the Plateau

  1. Ebro Depression: Enclosed by the Pyrenees, Iberian System, and Coastal-Catalan Range. Filled with sediments. Features somontanos, mesas, and badlands.
  2. Guadalquivir Depression: Parallel to the Betic Cordillera. Filled with sediments. Features gently rolling countryside, hills, and mesas.

Mountain Ranges Outside the Plateau

  1. Pyrenees: Includes the Axial Zone, Pre-Pyrenees, and Median Depression.
  2. Basque Mountains: Limestone mountains with low height and smooth forms.
  3. Coastal-Catalan Range: Transformation of the eastern Pyrenees. Divided into two parts: a northern half with Paleozoic materials and a southern half with secondary limestone.
  4. Betic Cordillera: Includes the Subbética Range, Penibética Range, and Intrabética Depression.

Coastal Relief

Atlantic Coast

  1. Cantabrian Coast: Straight coast with cliffs, rias, and small estuaries.
  2. Galician Rias: Flooded river valleys.
  3. South Atlantic Coast of Andalusia: Wetlands, coastal arrows, and dunes.

Mediterranean Coasts

  1. Betic Sector: Coastal cliffs, dune fields, lagoons, and marine terraces.
  2. Gulf of Valencia: Beaches, estuaries, deltas, and tombolos.
  3. Catalan Coast: Deltas and beaches with cliffs.

Island Relief

Balearic Islands

  1. Mallorca and Ibiza: Emerged fragments of the Subbética Mountains.
  2. Menorca: Linked to the Catalan Coastal Range.

Canary Islands

Volcanic islands formed during the Tertiary Era. Features volcanic cones, calderas, malpaíses, dikes, canyons, high cliffs, and beaches.