Spain’s Geography: Relief, Geology, and Coastal Features

Posted on Dec 17, 2024 in Geology

Spanish Geographical Area

Spain is a medium-sized country located in the Northern Hemisphere’s temperate zone. Its territory includes:

Mainland Spain: It occupies an original position between two continents, Europe and Africa, and between two bodies of water, the Atlantic Ocean and the Mediterranean Sea. This situation, between air masses of different origins, has created a variety of climates, water, vegetation, and soils, and a geopolitical crossroads between different civilizations.
Balearic Islands: Located in the Mediterranean Sea, comprising the islands of Mallorca, Menorca, Ibiza, Formentera, and Cabrera.
Canary Islands: Situated in the Atlantic Ocean, 100km from the coast of Africa. Formed by La Palma, El Hierro, La Gomera, Tenerife, Gran Canaria, Fuerteventura, Lanzarote, and some smaller islands.
Ceuta and Melilla: Located in the north of Africa.

The Spanish territory has great natural diversity due to its wide range of reliefs and climate change. This results in an unequal distribution of natural resources and economic activities. Depending on the area, some land uses dominate, leading to a plurality of human landscapes.

Peninsular Relief

The relief is the set of forms presented by the Earth’s surface. Features:

Solid Shape: Straight coasts, not just a rugged coastline.
High average altitude (660m) due to the presence of high mountains, and the interior is made up of a core of uplands.
Peripheral mountain layout around the plateau: The influence of the sea stops and causes strong contrasts between the coast and the peninsular interior.

Morphostructural Unit Types

Sockets: Plains and plateaus formed in the Primary or Paleozoic era as a result of the erosion of the ranges encountered in the orogeny of the same era. They are very rigid; thus, with no fold orogenic thrusts, they break. Located in the western half of the peninsula.
Old Beds: Mountains formed during the Tertiary period by the new lift in a block of a base because of the pressures of the Alpine orogeny. In the Plateau, the Central System, and Montes de Toledo.
Cordilleras of folding: Large mountain elevations encountered in the orogenic Alpine Tertiary age due to the folding of sedimentary materials deposited in the sea during the Secondary era.
- Intermediate Cordilleras: Formed by the folding of material deposited in the sea on the edges of the sockets (Iberian System).
- Alpine mountain ranges: Formed by the bonding of materials deposited in geosynclinal or long and deep trenches (Pyrenees).
Sedimentary basins: Sunken areas formed in the Tertiary period, which were filled with sediments, mainly clay and limestone.
- Basins: Formed by the collapse of a block or socket because of the pressures of Alpine orogenesis (Tajo).
- Pre-Alpine Depressions: Formed by decompression following the lifting of the Cordilleras, which led to the collapse of certain sectors or from shallow trenches that remained on the side of the geosyncline when the Alpine ranges rose (depression of the Ebro and Guadalquivir).

Geological Evolution of the Peninsula

Divided into phases:

In the Archaic era or Precambrian (4000-600 million years ago), a mountain band emerged from the sea, consisting of slate and gneiss, which included all of the current Galicia.
In the Primary or Paleozoic era (600-225 million years ago), the Hercynian orogeny took place. Hercynian mountain ranges emerged, consisting of silicon materials. In the northeast appeared beds of Aquitaine, Catalano-Balearic, and Ebro. All were destroyed by erosion during the Primary era and converted into sockets.
During the Secondary or Mesozoic era (225-68 million years ago), the predominant period was erosion and sedimentation. The continued erosion wore down the Hercynian reliefs. The sediment deposited materials, mainly limestone, in areas covered by the sea.
During the Tertiary era (68-1.7 million years ago), the Alpine orogeny occurred, which caused large changes in topography.
- Alpine ranges rose by folding materials deposited in the Pyrenean and Betic troughs between ancient massifs, which acted as buffers. The Pyrenees and the Betic mountain ranges emerged.
- Pre-Alpine depressions formed in parallel with the new mountain ranges: the depression of the Ebro and the Guadalquivir.
- The plateau was affected by the Alpine orogenesis: It leaned toward the Atlantic and formed the mountainous eastern and southern edges of the plateau. At its eastern edge, folded materials deposited by the sea in the Secondary era, causing the eastern part of the Cantabrian Mountains and the Iberian system.
- The base of the Paleozoic Plateau consists of rigid materials, experienced fractures, and faults. The failures resulted in a Germanic block structure consisting of raised or sunken blocks. The uplifted blocks formed the mountain ridge north of the Plateau and mountain ranges of the plateau. The depression created inside hollow blocks or sedimentary basins of the plateau also led to volcanic activity.
During the Quaternary era (1.7 million years ago to date), the most striking phenomena are:
- Glaciers affected the highest mountain ranges:
  - Glacier circus: Ice dams at the headwaters of the valleys. The melting ice and break the wall rocks, expanding and creating a sheer circus form.
  - Valley Glaciers: Rivers of ice. They are formed when the thickness of ice on the circus is large, then the lower layers of the ice move out of the circus and spread down the valley. Rock fragments containing ice widen the valley into a U-shape. There are also areas where the ice is melted and formed lakes.
- The river terraces are flat strips high at the margins of a river. Its origin is due to the Quaternary climatic alternations.

The Rocky and Relief Types

Silica Area

Integrated by ancient rocks of Precambrian and Primary. It is located in eastern Spain. The predominant rock is granite, a rigid crystalline rock that alters, creating different types of granite relief.

Granite is chemically altered by water depth: Its crystals break down and transform into pardoamarillentas sands.
The granite is altered from the joints or fractures in the rock. Forms differ according to altitude:
- In high mountain areas, the water seeps through the rock fractures. The result is the formation of sharp peaks, jagged and steep scree, or accumulations of fragments of broken rocks at the foot of the mountains.
- In the lower elevations, if the joints are parallel, granite flakes or disintegrates slowly and creates a gently undulating landscape of rounded forms, called domes. If the joints are perpendicular, it forms into balls that can be stacked on each other, forming berrocal. Sometimes the balls are on the slopes or at the foot of the mountains, forming a granitic chaos.

Limestone Area

It has an inverted Z-shape and is located in the Pyrenean foothills and the Cordillera Subbética. The dominant rock is limestone, a hard rock that fractures or joints and cracks form that is readily soluble in water. It results in a karst relief.

Characteristic forms:

Pencil or Lenar: Grooves or cavities separated by partitions formed by the passage of water where they store water.
The gorges, ravines, or hoces: Narrow and deep valleys, surrounded by steep slopes, caused by rivers.
The poljes: Elongated depressions with a horizontal background. They are wholly or partly covered by water; sewers or wells disappear and continue circulating underground.
The sinkholes or torcas: Large cavities formed in places where water stagnates. They can join with other forms called uvala cavities.
The caves: Formed by filtering the water through the cracks in the ground. Usually, stalactites form from water deposited on the ceiling, and stalagmites form from water deposited on the ground.
The potholes: Narrow openings that connect the surface with the underground galleries.

Clay Area

Composed of clay rocks from the Tertiary and Quaternary eras. It is located in the basins of the northern and southern sub-plateau, in the depressions of the Ebro and Guadalquivir. The predominant rock is clay, resulting in a horizontal relief. Its rapid erosion generates two types of relief:

The countryside: Gently undulating plains formed when the rivers open valleys that separate horizontal structures.
Gullies: Formed in areas with long dry periods and alternating heat, and no plant protection exists.

The relief caused by differential erosion acts differentially, giving rise to different relief as the provision of strata.

When the strata are horizontal, open river valleys separate large platforms, called páramo, having a horizontal top formed by a hard stratum with concave flanks. The sides are eroded further. The páramo is reduced and eventually becomes a witness hill, and antecerro when the stratum disappears.
When the strata are gently inclined and alternating hard and soft materials, slopes are formed. The retreat of slopes by erosion also leads to witness hills and antecerros.
When the layers are folded and composed of alternating hard and soft materials, they give rise to relief:
- Apalachense: Formed over a mountainous Hercynian. Found in the Cantabrian mountains, in the Montes de Toledo, and Sierra Morena.
- Jurassic: Ridges formed in youth are made of limestone. Found on the Iberian, the Pyrenees, and the Betic Cordillera.

Major Morphostructural Units of Peninsular Relief

The relief is distributed along the Peninsular Plateau. This zone is divided into two sectors by the Central System: the central plains and the southern sub-plateau north. The Plateau is the fundamental unit of relief Peninsula. It is a plain located about 600-800 meters altitude, formed in the Primary era. Three different units:

The old basement in today is just west of the peninsula; erosion has deleted Tertiary materials that covered the base, exposing the primary silicon materials: granite, slate, and quartzite. The relief is made by erosional peneplain or gently rolling hills and rugged island, or residual reliefs made of more resistant rocks. In the contact zone of peneplain with sedimentary basins of the Plateau, deep gorges are created by rivers to snap on hard materials.
The mountain ranges, the Central System, and the Montes de Toledo. Formed in the Tertiary era by the removal of some blocks of the base of the plateau as a result of the Alpine orogeny. Its material is granite, slate, and gneiss. The Central System is higher and divides the plateau in half. Its most prominent mountains are Somosierra, Guadarrama, Gredos, Peña de Francia, and Gata. The Montes de Toledo are lower and divide the southern sub-plateau in two, separating the basins of the Tajo and Guadiana. Its most important mountain is Guadalupe.
The interior sedimentary basins were formed in the Tertiary era of the Alpine orogeny.
- The moors are flat and high structural surfaces consist of hard limestone strata.
- The countryside is gently rolling lowlands traversed by rivers, formed where the moors.
- The slopes are steep areas between the moors and the countryside.

The northern sub-plateau basin is higher, more uniform, because all of it belongs to one of the Duero basins. The basin of the southern sub-plateau is lower, is rugged and the Toledo Mountains, which divide into two basins of the Tajo and Guadiana.

The Mountain Ridges of the Plateau

The Galician-Leonese Massif formed in the Tertiary era by lifting the northwest corner of the Plateau during the Alpine orogeny. Its materials are Paleozoic. It presents mountains surrounded by low buildings. Its hills are Segundera Cabrera and The Ancares.
The Cantabrian mountain range has two distinct areas:
- The West, the Asturian Massif, formed in the Tertiary era by the uplift of this sector of the Plateau during the Alpine orogeny.
- The east, the Cantabrian Mountain, was formed in the Tertiary era by the folding of secondary materials deposited by the sea on the edge of the Plateau.
The Iberian was formed in the Tertiary era by the folding of secondary materials deposited by the sea on the eastern edge of the base of the plateau. Two sectors:
- The northern third, including the higher elevations of the mountains.
- From the southeast of the Iberian Soria, it splits into two branches: the interior or Castilian and exterior or Aragonese. Both are separated by a rift valley.
Sierra Morena is an abrupt step that separates the plateau of the Guadalquivir valley.

External Depressions of the Plateau

The Ebro basin is parallel to the Pyrenees and is closed for the Iberian and the Coastal Range-Catalana.
- The foothills are flat land, slightly sloping hills between external and central depression. Consisting of conglomerates, coarse and hard, transported by rivers from the mountainous landscape. In them, the erosion has created mallets and sinkholes. The mallets are rock towers formed from vertical fractures. The pits are depressions on soft materials.
- In the center of the depression, the strata are horizontal, alternately hard limestone and clay, marl, and soft casts.
The depression of the Guadalquivir is parallel to the Betic Cordilleras.

Outer Ridges of the Plateau

The Pyrenees, Structure:
- The axis is the old solid Hercynian of Aquitaine, where the higher altitude of the mountains.
- The Prepyrenees found south of the Axial zone. Alignments are divided into two parallel to the axis: the indoor and outdoor ranges.
- The median depression is a long, narrow depression between the marly interior and exterior pre-Pyrenean mountains.
The Basque mountains preface the Pyrenean foothills.
The Cordillera Costero-Catalana is a transformation of the eastern Pyrenees, separated by faults. It is divided into two teams: one along the coast, low height, and a higher internal. Separated by a longitudinal depression or graben.
The Betic Cordilleras are structured in: the mountains Penibética (along the coast); range Subbética (inside) and depression Intrabético (between Penibética and Betic Cordilleras).

Coastal Landforms of Mainland

The coastal landforms:

Capes: Outgoing coast deep into the sea, and the gulfs, incoming deep sea to the coast.
Cliffs: These are coasts that enter the sea with an outstanding source. They created sea erosion in the lower caves, sea arches, to pierce the bottom and stacks to discard the top of the arc.
Beaches: Flat expanses and low slopes of sand, gravel, or pebbles, situated at sea level. They consist of continental and marine sediments.
Rasas: Marine erosion platforms parallel to the coast that have been elevated above sea level. They can spread, constituting saws. Low levels have flat shapes, and high ones are attacked by erosion and are not flat.
Rías: Incoming coastal displayed the invasion by the Sea of the final stretch of a river valley. They may be due to sea level rise or fall in the continental crust.
Marshes: Mud plains. Shallow bays are formed, which are filled with sediments carried by rivers that cross them and with those provided by the sea, which covers at high tide and left uncovered at low tide.
Spits: Sand bars that extend straight and sandy coastline into the bay. Its end is usually curved toward the ground. The arrows are formed by the sand transport from the coast into the bay. If the arrow gets to close the front, it is called a barrier island.
Albuferas: Salty coastal lagoons separated from the sea by a sandy cord that closes the bay. They are usually converted into wetlands.
Tómbolo: Sand bars linking the coast rocky islets. They can be double.
Deltas: Coastal outgoing formed when the river contributes more sediment than it can redistribute the sea because it is a body of water without current.
Dunes: Sand mounds typical of sandy shores. They are formed by the transport and accumulation of sand by the wind, set by the vegetation.

The Atlantic Coast

The Cantabrian coast is straight. Its major accidents are the cliffs and shallows. There are also estuaries, sandy beaches, and some raffles.
The Galician coast is the most articulate of Spain. Resulting from the invasion by the sea from the river valleys in the numerous open fractures Galician Massif.
The Atlantic coast of Andalusia has major accidents such as spits and dune fields.

The Mediterranean Coast

The Betic sector is between the Rock of Gibraltar and Cape La Nao. It has sections from the Betic Cordillera cliffs that are parallel to the coastline and stretches of coastal low forming a narrow coastal plain created by generous contributions from the Betic Cordillera. Frequent sand dunes, lagoons, and marine terraces are found.
The Gulf of Valencia is characterized by broad, sandy beaches and lagoons, the bazaars, and small deltas.
The Catalan coast consists of coastal cliffs, beaches, and some small coastal plains and deltas.

The Balearic Archipelago

Mallorca, three sets: The Sierra de Tramuntana in the north of limestone and is the Puig Mayor. The Llevant, limestone. The central depression or Pla is clay and soft relief.
Ibiza and Formentera, with a limestone mountainous north of Ibiza, a massive east of Formentera (Mola), and between them a plain.
Menorca, two sets. The northern half has Paleozoic mountain ranges, low height, and smooth shapes. The southern half is flat, of limestone and Mesozoic, and they are separated by a fault.

Balearic coasts are steep in areas where mountainous terrain reaches the sea.

The Canary Islands

The volcanic cones are conical elevations open at the top. They were formed by volcanic material clutter around the emission mouth, like ash or small stones. Assets include Palma, Lanzarote.
Boilers: Large circular craters caused by the explosion or collapse of a volcano. Famous boiler explosion Bandama (Gran Canaria).
Badlands: Rough terrain quickly formed to solidify the lava flows in waves or blocks.
Dams and rocks: Magma emission lines have been filled by lava and have been exposed by differential erosion. They form when the tube is a horizontal crack and rocks when the vertical stack of a volcanic cone, but can also be formed only by newer rocks to erosion.
The ravines are narrow valleys, steep and short-haul, created by the engagement of the streams in the volcanic soil. Formed in a time of climate more humid than today, allowing the existence of water currents is likely to cause severe erosion.
The high cliffs are characteristic of ancient massifs. The cliffs of less size sit on the materials of recent eruptions.
Beaches: In the western islands are stretches of songs because of the close coastal shelf; in the eastern islands, the largest width of the coastal shelf allows for sandy beaches.