Exploring Spain’s Mountain Ranges: Pyrenees, Basque Mountains, Catalan Coastal Ranges, and Baetic System
Exploring Spain’s Mountain Ranges
The Pyrenees
Location:
The Pyrenees mountain range stretches between the Bay of Biscay and Cape Creus, forming a natural border between Spain and France. Its central region presents a formidable barrier, gradually descending towards the west. The central Pyrenees span 150km, exhibiting a notable lack of symmetry and narrowing towards the ends.
Geological Evolution:
The Pyrenees were formed during the Tertiary Period due to the erosion of the Spanish plateau and the Aquitaine massif.
Lithology and Structural Units:
Several distinct structural units comprise the Pyrenees, running from north to south:
- Axial Zone: The backbone of the Pyrenees, composed of Paleozoic materials like granite and slate. The highest peaks in this zone are adorned with glaciers, meadows, and dense forests.
- Inner Mountain Ranges: Flanking the axial zone, these ranges consist of limestone soils and feature sharp peaks exceeding 2,000 meters, such as the Collarada and Turbón.
- Intermediate Depression: This longitudinal depression, including the Berdún Channel, is characterized by Tertiary marl and drained by the Aragon River. Key towns like Jaca and Sabiñánigo are located here.
- Outer Ranges: Composed of limestone, these ranges reach heights between 1,500 and 2,500 meters and include the Sierra de Leyre, Loarre, and Guara.
Landforms:
The Pyrenees exhibit a Jurassic relief, with mountains forming anticlines and depressions occupying synclines. During the Quaternary Period, intense glacial activity sculpted the landscape, carving cirques and U-shaped valleys like Ordesa. These glacial processes also created numerous lakes. The eastern Pyrenees, near the Catalan Coastal Range, feature around 40 small volcanic cones and lava flows.
Basque Mountains
Location:
Situated between the Cantabrian Mountains and the Pyrenees, the Basque Mountains are a collection of ranges defined by peaks like Gorbea and Aitxuri, reaching heights of around 1,500 meters.
Geological Evolution:
The formation of the Basque Mountains is closely linked to the uplift of the Pyrenees.
Lithology:
The Basque Mountains are characterized by Mesozoic terrain, featuring alternating limestones and a formation known as flysch, which consists of thin layers of marl and sandstone tightly folded together.
Landforms:
The Basque Mountains present a complex network of saw-like ridges without a clear direction. The terrain gradually softens and becomes hillier towards the coast.
Catalan Coastal Ranges
Location and Units:
The Catalan Coastal Ranges form a mountain barrier parallel to the coastline, effectively isolating the Ebro basin from the sea and influencing its continental climate. The ranges connect with the Iberian System in the south and are separated from the Pyrenees by the Empordà depression in the north. Several units make up the Catalan Coastal Ranges:
- Coastal Range: Spanning 150 km and reaching heights between 500 and 800 meters, this range is divided into several blocks, including the Massif de les Gavarres, Montnegre, and Garraf.
- Pre-littoral Depression: This area of rolling hills is densely populated and cultivated, encompassing regions like La Selva, Vallès, Penedès, and Camp de Tarragona.
- Pre-littoral Range: The main line of this range includes Montseny, Montserrat, Prades Mountains, and Ports de Tortosa-Beseit.
Geological Evolution:
The northern section of the Catalan Coastal Ranges is a remnant of the ancient Hercynian massif, also found in Menorca and Sardinia. The southern part was uplifted during the Alpine orogeny, with Mesozoic sediments folding and thrusting over the older massif. The pre-littoral depression is a graben, formed by faults and filled with Tertiary sedimentary materials.
Lithology:
The northern zone consists mainly of Paleozoic granites and shales, while the southern zone is dominated by folded Mesozoic limestones. Tertiary and Quaternary materials are found in the pre-littoral depression and the contact zone with the Ebro basin.
Landforms:
The northern zone features flattened summits due to erosion, while the southern zone exhibits more rugged relief. The pre-littoral depression is characterized by rolling hills sculpted from Tertiary and Quaternary sediments.
The Baetic System
Location and Units:
The Baetic System displays a complex arrangement of fold lines, divided into two main systems:
- Penibaetic System: Running along the coast and reaching the highest elevations, this system includes ranges like the Sierras de Almijara, Tejeda, Nevada, Baza, and Filabres.
- Subbaetic System: Located north of the Penibaetic System, this system comprises ranges such as Grazalema, Ubrique, Mágina, Cazorla, Segura, and Espuña, with altitudes ranging from 1,500 to 2,000 meters.
Geological Evolution:
The Baetic System’s formation is complex and linked to the Rif massif in Africa. Downward folding created the current structure, which was then pushed by the African block, overriding the Iberian massif and forming the Penibaetic System.
Lithology:
The Baetic System is composed of Paleozoic materials flanked by Triassic limestones and other sediments. The intra-Baetic depression is filled with Miocene and Pliocene clays and loams.
Landforms:
The Penibaetic System exhibits remnants of glaciation and volcanic activity. The Subbaetic System is characterized by significant karst phenomena, such as the Torcal de Antequera.