Landscapes and Landforms of Spain

Spain has a remarkable geomorphological diversity largely due to its geological and climatic variety. From the geological perspective, the Iberian Peninsula may be divided in two broad geological domains; the Iberian Massif in the western sector, and the mountains belts and Cenozoic basins related to Alpine tectonics in the eastern sector. The Iberian Massif (Variscan Spain) mainly consists of Paleozoic metamorphosed sedimentary formations intruded by plutonic rocks. This region is characterised by extensive planation surfaces locally interrupted by inselbergs, and includes outstanding examples of granitic landscapes. The Alpine Mountain Belts, related to the convergence between Europe, the Iberian microplate, and Africa, contain excellent examples of landscapes controlled by active tectonics. In these Alpine orogens, extensive limestone outcrops have favoured the development of outstanding poljes, dolines and karren fields Glacial landscapes are best developed in the Pyrenees, which still contain a number of active cirque glaciers. The Cenozoic Basins include some of the finest areas to examine stunning conglomerate monoliths, dramatic badlands, dune fields, deflation basins associated with lunette dunes and yardangs, and a wide variety of features related to evaporite dissolution. The Canarian Archipelago is a late Cenozoic chain of hot-spot-related volcanic islands located in the Atlantic Ocean west of the Sahara coast. The evolution of the Canaries is characterised by the growth of large volcanic edifices, punctuated by the development of giant landslides. The Teide volcano (3,718 m a.s.l.) in Tenerife rises more than 7 km above the adjacent abyssal plain. A total of 18 eruptions have been documented over the last 500 years, some of them with great societal impact; the 1730-1736 Timanfaya eruption covered more than 20 % of Lanzarote island. The around 10,000 km-long coastline of the Spanish territory display a wide variety of coastal landscapes, including rías, estuaries sequences of raised beaches, deltas, lagoons and spit bars, and dune fields.

The tectonic Guadalentín Depression is an elongated Quaternary sedimentary basin generated by a system of left-lateral strike-slip faults on the eastern Betic Cordillera. The Lorca-Alhama de Murcia fault (LAF) is the most relevant structure, controlling the 100-km-long western margin of the depression with a prominent mountain front. Climatic conditions are semiarid, and sedimentation is dominated by alluvial fans. The interaction between tectonics, alluvial sedimentation, and climate results in the development of widespread tectonic landforms and alluvial fan surfaces with different degree of calcrete development. The variable morpho-sedimentary arrangements record different styles of faulting and uplift history on the range front faults. Large fans occur associated with the main gaps and step-overs between the different fault segments bounding the Quaternary basin (e.g. Lorca Fan). Telescopic fan sedimentation under limited distal aggradation eventually turned into distal trenching throughout the late Holocene. This geomorphic evolution constitutes a good example of the transformation of the ancient main fan-feeding channel into a true fluvial channel (present-day Guadalentín River) linked to a well-preserved Late Bronze geoarcheological record.

The evolution of an incising drainage network controls regional geomorphic development, but is in turn controlled by four sets of dynamic factors. These are as follows: tectonics, including both regional epeirogenic uplift and more local tectonic deformation; climatic change, affecting variations in flood power and sediment supply; base level; and local factors such as river capture, related to the development of the drainage network itself. The geomorphology of four uplifted Neogene sedimentary basins in the eastern Betic Cordillera of Almería, Spain, demonstrates how these factors interact and operate over a range of temporal and spatial scales. The basins were marine basins until the early Pliocene, when differential epeirogenic uplift caused emergence and the initiation of the drainage networks; first in the Tabernas, then in the Sorbas, and finally in the Vera and Almería basins. The last two became terrestrial in the early Pleistocene. The modern landscape reflects the influence of differential regional uplift rates on the long-term dissectional history, operating regionally over the whole period of landform development. The extremes are represented on the one hand by the deeply dissected Tabernas basin and on the other hand by the centre of the Almeria basin, which is dominated by coalescent aggrading alluvial fans. The Quaternary climatic signal is another regional signal, expressed by the sediment-led terrace sequence, with aggradation occurring primarily during Pleistocene global glacials and incision during the interglacials. These regional signals are modified locally by the other factors. Local neotectonic deformation is particularly important in the Tabernas and Almeria basins. Base-level change induced by tectonic activity and by river capture is important locally throughout the area, but the effects of base-level change induced by Quaternary sea-level change are restricted to the coastal zone. River capture has had profound effects, modifying the drainage areas. The Vera basin has gained drainage area substantially, whereas that of the Almeria basin has decreased. The most important effects have been on base level and incision rates, especially in the Sorbas basin. The overriding long-term control on drainage development and therefore on landform dynamics has been the pattern of regional epeirogenic uplift, onto which the Quaternary climatically controlled aggradation/dissection sequence has been imposed. These are regional signals that have been modified locally by the more spatially and temporally restricted signals generated by base-level change and river capture.

Galicia, in the NW of the Iberian Peninsula, is dominated by igneous rocks, mostly granitoids intruded during the Variscan orogeny. These granitoids can be grouped into four types: post- and syn-tectonic tonalite granites, and post- and syn-tectonic leucogranites. Granite landforms in Galicia have been largely controlled by endogenous features defined during their intrusion. Subsequently, tectonics associated with the Alpine orogeny between the Eocene and the beginning of the Late Miocene resulted in a dense network of faults and fractures. These structures delimit a heterogeneous mosaic of blocks in many cases formed by granite rocks, which were affected by differential tectonic movements during the Palaeogene, controlling the development of mountain ranges and depressions. However, the final subaerial exposure of the granite bedrock is mainly related to a wide range of erosion processes since Palaeogene times. In spite of the limited extent of the granitic outcrops in Galicia, they display a broad variety of landforms.

The Pedriza de Manzanares, located in the Guadarrama Range, Iberian Central System, is a Variscan massif formed by I-type peraluminous leucogranites intruded in the late Paleozoic (~307 ma). The morphostructure of the massif is largely the result of the reactivation of faults during the Alpine Orogeny (Paleogene–Pliocene) and the associated etching/exhumation processes. The former produced a stair-stepped topography (block faulting), and the latter gave rise to granitic domes and crests related to differential erosion. The domes, and to a lesser extent the crests with tors and widespread chaotic blocks, are the essential features of the landscape in the Pedriza de Manzanares. The low chemical weathering susceptibility of the granites in this area, together with the fracture system, favour the development of structural landforms. Moreover, on bare rock exposures, minor landforms formed by diverse weathering processes are frequent.

The sedimentary fill of the Ebro Cenozoic Basin, NE Spain, includes thick conglomerate successions in the marginal sectors associated with the surrounding Alpine orogens. These commonly cemented alluvial fan and fan delta conglomerates grade rapidly into less resistant fine-grained facies. Differential excavation of the basin fill, together with erosion processes controlled by vertical fractures in the massive and indurated conglomerates, has resulted in the development of monoliths, locally known as mallos, with vertical walls that may reach more than 300 m in height. The cemented and fractured conglomerates in some sectors of the Catalan margin of the basin, mostly composed of calcium carbonate, display features characteristic of well-developed karst terrains, including sinkholes, karst springs, and multilevel cave systems several kilometers long with spelothems.

Exokarst landforms, as well as caves and shafts, are common in the Tramuntana Range (Mallorca Island, western Mediterranean) owing to the presence of extensive limestone outcrops and suitable bioclimatic environmental conditions. The mountain range has excellent examples of polje-like depressions, dolines, karrenfields and karst gorges, especially in the northern sector. Karrenfields are the most remarkable landforms because of their morphological variety and widespread occurrence. They illustrate the impact of climatic gradients and soil erosion on their development and distribution.

The Sierra de Atapuerca caves are located in the southern flank of an anticline formed by Upper Cretaceous limestones and dolomites. These caves are mainly sub-horizontal passages or water table caves recording palaeodrainage from south to north, roughly parallel to the anticline axis. In the south, groundwater recharge is mainly associated with fractures at the contact between Mesozoic carbonates and the overlying Miocene marls, while the discharge area is located to the north, in the headwaters of the Pico River. The passages are arranged in three main levels interconnected by shafts and chambers. These cave levels are perched around +90, +70 and +60 m above the Arlanzón River, coinciding with the relative heights of fluvial terraces. Episodic fluvial downcutting led to the formation of successively lower karst levels and the entrenchment of the upper conduits under vadose conditions. Accessible dry caves were used by fauna and hominids, preserving an exceptional archaeo-palaeontological record spanning from ~1.2 Myr until the end of the Middle Pleistocene. The sites of Elefante, Gran Dolina, Galería and Sima de los Huesos have provided exceptional findings for understanding the first steps of human evolution in Europe. These sites relate to the occupation of the ancient cave entrances and areas inside the cave.

The Cenozoic sedimentary fill of Calatayud Graben, an intramontane basin within the Iberian Chain, includes an evaporitic sequence around 500 m thick with significant halite and glauberite units in the subsurface. Interstratal dissolution of the salt-bearing evaporites has generated megacollapse structures covering up to 12 km² in which Neogene sediments have subsided as much as 200 m. The Quaternary alluvium related to the present-day fluvial systems shows sharp changes in thickness locally reaching more than 100 m. The thickened terrace deposits fill basins several kilometres long generated by dissolution-induced synsedimentary subsidence. The area offers the opportunity to examine excellent exposures of subsidence structures and paleosinkholes that illustrate the mechanisms involved in sinkhole development (sagging, collapse, and suffosion). Dissolution and hydrocompaction subsidence has caused extensive structural damage in Calatayud city, including outstanding historical buildings. On November 2003, a collapse sinkhole undermined the foundation of a five-storey building, leading to its demolition, involving around 5 million euro of direct losses.

The gypsum karst of Sorbas is one of the most well-known gypsiferous areas in the world from the speleological point of view. The Yesares formation comprises an alternating sequence of gypsum and marly strata deposited during the Messinian salinity crisis. The development of the cave systems is closely linked to this alternation of sediments. The caves have been mainly formed by erosion of the marl units, whilst gypsum dissolution was especially active during the initial stages. On the surface, striking karst landforms are found, such as gypsum tumuli, a great variety of dolines formed by different mechanisms, several types of karren, as well as a 30-m-high gypsum scarp. Proto-conduits on the ceilings of the galleries, as well as some sedimentary features, provide evidence of the initial phreatic speleogenetic phases. In addition, the gypsum caves of Sorbas have a great deal of speleothems, some of them unique worldwide (e.g. gypsum balls, hollow stalagmites, gypsum trees and trays, and deflated stalagmites). The protection of the gypsum karst of Sorbas, due to the wide variety of surface and subsurface geomorphological features, should be considered of top priority for the administration.

Gallocanta Lake, covering 14.5 km², is the greatest ephemeral saline lake in Europe. It is located in the Iberian Chain, NE Spain, in the bottom of a karst polje. The Gallocanta saline lake formed once Jurassic limestones were almost completely corroded, and the floor of the depression was underlain by Triassic clays and evaporites. The late Quaternary evolution of the lake can be reconstructed from the deposits underlying the lake bottom and from different levels of lacustrine terraces located in its downwind side. Different phases of flooding and desiccation can be deduced from both sources of data. The current dynamics of the lake is controlled by water-level fluctuations and wind action. Wind-driven waves and longshore currents transport sediments to the downwind zone and generate barrier islands, spits and submerged bars, with a dynamic behaviour very similar to that of marine coastal environments. Lake segmentation due to cuspate foreland growth has divided the original lake into minor ones. Segmentation is still active at present and tends to isolate a minor lacustrine body. Progressively decreasing rainfall, together with sediment supply to the lake, enhanced by extensive agricultural practices in the basin, have frequently led to lake desiccation over the last decades. Extensive polygonal soils and salt crusts cover the bottom during drying-up periods.

The E–W trending Cantabrian Mountains, with peaks more than 2,600 m a.s.l., are located along the northern coast of the Iberian Peninsula. After the development of south-verging structures during the Alpine Orogeny, the Cantabrian Mountains were arranged as an asymmetrical relief deeply dissected by the fluvial network, with steep rivers flowing into the Cantabrian Sea in the north and less steep rivers draining towards the Duero Tertiary Basin to the south. The area shows a high geomorphic diversity, including relict Quaternary glacial and periglacial landforms, as well as features related to slope instability, fluvial and karstic processes. This work summarizes the geomorphological features of two different protected areas of the Cantabrian Mountains designated as Picos de Europa: the Picos de Europa National Park and the Picos de Europa Regional Park. Both are representative areas of the high-mountain landscapes of the northern and southern sectors of the Cantabrian Mountains. Moreover, the former hosts good examples of underground alpine karst.

The Ordesa and Monte Perdido National Park was created in 1918 and enlarged in 1982 to highlight and protect spectacular high mountain relief dominated by limestone. Alpine tectonics resulted in the piling-up of south-verging thrust sheets leading to the thick sedimentary successions exposed in impressive vertical cliffs. The presence of massive limestones has favoured the development of deep canyons and karst landforms, including karren, dolines, and caves with large shafts. Quaternary glaciations contributed to increase the geomorphic diversity, forming cirques and stunning U-shaped valleys. Small glaciers from the Little Ice Age still remain on the north-facing slopes of the Monte Perdido. Periglacial processes in the most elevated areas of the National Park, as well as erosion in thick soils developed on marly limestone have produced unique geomorphological features.

This work presents the general geomorphological setting of the Maladeta Massif and a more specific analysis on two outstanding aspects of this Alpine area: (1) the main lithostructural features and their relation with active deformation processes (active faults and deep-seated landslides) and (2) the glacial geomorphology of the massif, focusing on the recent recessional pattern (1981–2005) of the glacial masses (glaciers and glacierets). Historical surface and volume losses in the ice bodies are assessed, together with the climatic and topographic factors that have controlled the shrinkage of glaciers at regional and local scales.

The Tremedal Massif is an inlier of Paleozoic rocks that protrudes around 300 m over an extensive planation surface cut across Mesozoic formations. It reaches 1,920 m a.s.l. at Caimodorro and has a continental climate characterised by a large number of days with minimum temperatures below freezing point (80–100 days per year). The massif displays a concordant topography controlled by nearly cylindrical folds mainly developed on quartzites and shales. Differential erosion has produced synclinal valleys underlain by shales and steep quartzite ridges on the intervening anticlines. Frost shattering acting on the quartzites, affected by widely spaced jointing, has produced laterally continuous block slopes on the lower part of the hillslopes. The block slopes developed on both valley sides grade into striking block streams up to 2.5 km long along the valley bottoms. The block slopes, underlain by soft shales, display solifluction lobes and benches, suggesting that the formation of the streams is related to the progressive downhill displacement of the boulder deposits in the slopes. The block slopes and streams are relict landforms as the lichens covering the weathered surface of the boulders and the development of tree cover reveal. These periglacial deposits record a period in the Late Quaternary during which frost shattering processes were much more intense, and the slopes were essentially devoid of tree vegetation, probably due to colder and drier conditions.

The complex badland landscape at Tabernas results from a combination of relief amplitude generated by tectonic uplift since the Pliocene and reactivated several times during the Pleistocene, the properties of the Tortonian sedimentary rocks and a predominantly arid climate. The landscape is dominated by deep incision of the main river systems, which continues in part of the headwater tributaries, and characterized by contrasting slope morphologies and a variety of microecosystems. The Tabernas badlands exhibit a diversity of landforms resulting from the combination of multi-age soil surface components that allow a variety of processes to operate at different rates. These are dominated by rilling and shallow mass movements on south-facing hillslopes. On old surfaces and north-facing hillslopes, where biological components are present, overland flow with variable infiltration capacity and low erosion rates prevail. Incision in the gully bottoms occurs in the most active areas.

From a geological perspective, deltas are ephemeral geomorphic systems whose development is controlled by the sensitive equilibrium between fluvial sediment supply, global sea level, wave-induced energy and regional subsidence. Once this equilibrium is lost, the delta may start to retreat and eventually disappear. The ephemeral character of deltas is a serious threat to their lands, as well as to the economic activities developed in these areas for centuries. This is the case of the Ebro Delta, the third largest delta in the Mediterranean area, which is extensively used for agriculture and includes a Natural Park with special significance for migrating birds. Historically, the geomorphological features of the Ebro Delta have been controlled by the discharge of the Ebro River that used to supply large amounts of sediment during flood events. This sediment is redistributed along the coast in response to wave-induced sedimentary dynamics. However, the construction of dams during the twentieth century has drastically changed the equilibrium responsible for the previous morphological evolution of the delta. Nowadays, after the drastic reduction in sediment supply to the delta, the wave-induced processes cause strong erosion during storm events and rapid littoral drift affecting the shape of coastal landforms. This chapter shows the morphological evolution of the Ebro delta over the last 8000 years in response to the deceleration of Holocene sea-level rise, along with its most recent evolution and the predicted future morphology of delta according to the climate change scenario of the IPCC.

Doñana Natural Park is a good global example of the sedimentary filling of a broad tidal estuary during the Mid-Late Holocene, after the last postglacial sea-level rise. The timing of this rise is not well defined yet in the Gulf of Cádiz, since the oldest evidence of coastal sedimentation, located at the right bank of the mouth of the old Guadalquivir Estuary, dates back to ca. 5,000 years ago. The first evolutionary stages of the embayment indicate an obvious marine influence, dominated by waves and storms from the SW. Since ca. 4,000 years ago, protection provided by the growing coastal spit barrier of Doñana favored the development of a sheltered marsh dominated by tides and fluvial currents. About 2,200 years ago, since the time Romans controlled the area, the estuary was dominated by marshlands with a wide lagoon at its mouth (Lacus Ligustinus), and the current landscape of Doñana started to form. The evolution of the last 2,000 years includes the quick and continuous growth of coastal barriers by longshore drift, the origin of the present-day marshland landscape and the development of dune fields migrating inland towards the wetlands.

Raised beaches along the Cantabrian coast are related to erosion surfaces, locally known as rasas, affected by tectonic uplift. The higher surfaces, probably of Pliocene age, have a maximum relative height of 285 m above mean sea level (MSL). Generally, they have gentle seaward slopes and highly variable lateral and longitudinal distribution. They reach 20 km in maximum width in central Asturias, and the lower levels cover smaller areas. Two W-E-oriented zones may be differentiated along the coast: Burela-Nalón (107 km) and Nalón-France (365 km). Two or three levels of rasas were generated in the first sector, which gradually merge into one towards the west. In the Nalón-France zone, 12 levels have been recognised. These geomorphic surfaces are apparently slightly deformed, although some authors proposed that they are strongly faulted. Some aggradation and fluvial terraces, abrasion surfaces, as well aeolian sand deposits, can be correlated with rasa levels. Other old deposits disconnected from the rasas were generated associated with exposed and estuarine beaches and may include slope deposits less than 1.0 m thick. Most beach and aeolian dune deposits are siliciclastic, with a limited proportion of bioclastic sands and debris. Relevant pending issues to be resolved are the numerical age of the rasas and their possible correlation with erosion surfaces, eustatic changes and uplift, considering that neotectonic activity is thought to be low and localised. The most recent marine terraces have not been uplifted and are affected by a general recession due to sea-level rise.

The Olot Volcanic Field (OVF) records the youngest eruptions (0.5–0.01 Ma) of the Catalan Volcanic Zone (CVZ), associated with the post-Alpine European intraplate rift. Magma reached the surface through a fault system cross-cutting the Catalan Transversal Range, producing about 50 monogenetic volcanoes built up by strombolian and/or phreatomagmatic activity. The volcanic cones have maximum and average basal widths of 1,290 and 500 m, respectively. Maximum and mean heights are 189–100 m, respectively. Given the age of the eruptions, the primary volcanic landforms are well preserved and geomorphic features related to erosional processes are rare. Lava flows emerging from most of the volcanoes flowed along river valleys, reaching up to 10 km in length and locally generating volcanic dams.

The Teide Volcano rises 3,718 m a.s.l. and 7,500 m above the seafloor and is the world’s third-highest volcanic structure. The last eruptions of this active volcanic system occurred in the Early Middle Ages in the Teide stratocone summit and in the western rift zone in 1909. The explicitness of the Teide’s volcanism led von Buch and von Humboldt to abandon Neptunism in favour of Plutonism, a crucial step in the progress of modern geology and volcanology. The Teide volcanic complex comprises a spectacular volcanic system that includes mafic eruptions from active rift zones and a pair of felsic stratocones encircled by peripheral lava domes. This volcanic system is nested within the depression originated by a giant landslide that occurred about 200 ka ago. The gravitational collapse favoured the emplacement of shallow felsic magma chambers under the main stratovolcanoes, interacting with the deeper mafic magmas that feed the rift zones. This led to a continuous compositional progression in a bimodal basanite–phonolite series, with the mafic terms at the distal ends of the rifts and the felsic component in the central stratocones. Compositional differences are reflected in the diversity of eruptive mechanisms and in the variety of volcanic landforms and structures and their associated landscapes. The Teide Volcano was included in the UNESCO World Heritage List in 2007 as a site of extraordinary natural beauty and exceptional geological values, which provides highly significant evidence helping to understand geological processes in the evolution of oceanic volcanic islands.

Eruptions resumed in 1730 in Lanzarote Island after a prolonged period of volcanic repose, probably encompassing the entire Holocene. This historical eruption involved about 3–5 km³ of basaltic pyroclasts and lavas, covering some 225 km² (one third of the island). The accumulation of volcanic products had a strong impact on the landscape of this Miocene oceanic island. This was the second largest effusive basaltic event in recorded history, surpassed only by the 1783 Lakagigar eruption in Iceland. The central part of Lanzarote was mantled by lapilli-derived soils and aeolian sands, which provided a strongly contrasting ground for the basaltic products of the 1730 eruption. After the initial phase of the eruption, the style changed and new vents were controlled by a 15-km-long volcano–tectonic zip-like eastwards-progressing fissure, with the first vents opening offshore west of the island. This abrupt modification may explain the progression of this eruption, from the average duration of historical Canarian eruptions (a few months), towards an exceptionally prolonged period of about six years. Besides duration, other outstanding features of the 1730–1736 eruption include the tholeiitic composition of lavas and the length of flows and lava tubes, particularly in the final stages. Initially, the eruption had a catastrophic impact on the resources of the island, since most of the farmland was covered by lavas and lapilli. However, agriculture significantly improved after the eruption with the introduction of dry farming, using lapilli cover as a new mulching technique.

Relatively small landslides of the order of millions of m³ are frequent geological features, while giant landslides or mega-landslides up to thousands of km³ are rare and mainly related to the development of oceanic islands, principally in the initial shield stages. They were first documented in the Hawaiian Islands, but are also extraordinarily well represented in the Canary Islands, where they have been comprehensively studied onshore (pre- and post-collapse processes and the evolution of nested volcanism) and offshore (characteristics and extent of the debris avalanche deposits). Mega-landslides are important processes in the development of oceanic islands and their geomorphological features, particularly valleys and calderas, spectacular landscapes, which constitute relevant natural and economic resources.

Spain is the country with the largest surface of protected natural areas in the European Union (around 27 % of the territory). This is due to some peculiar biogeographic factors, as well as to the high diversity (geodiversity) and uniqueness of the Spanish geomorphological landscapes. This chapter deals with the preservation of this important geomorphological heritage, which must be analyzed in a broader context of nature conservation and within the framework of geoconservation guiding principles. Nature conservation and geoconservation had a promising beginning in Spain during the first decades of the twentieth century, but due to historical ups and downs, this policy was not continued. The environmental movement during the sixties and seventies, together with the democratization of the country, led to a promising shift in nature conservation, but with minor changes regarding geological and geomorphological heritage management. During the last few years, scientific societies, universities, and other related groups have positively influenced the Spanish politicians and the public, resulting in significant advances in geoconservation. Nowadays, the Spanish geomorphological heritage is managed by regional governments through a complicate set of national, regional, and sectoral regulations. Additionally, the participation in international programs of nature conservation, such as those promoted by UNESCO (World Heritage Sites, Biosphere Reserves, and Geoparks), as well as some local and private initiatives, has recently undergone an important development.

An overview of the main geomorphic hazards in Spain is presented. For each one of the processes analysed (floods, landslides, sinkholes, and coastal hazards), a brief description of their distribution, socioeconomic effects, and main causes is given. The main lines of research undertaken in recent times on these hazards, including development of new tools or techniques, are discussed. Finally, legislation and land-use planning measures for mitigation of risks due to such processes are described.