Spain occupies most of the Iberian Peninsula and includes two island archipelagos, a handful of North African territories, and one of the most geographically varied landscapes in Europe. Ringed by mountains, split by rivers, home to glaciers and semi-arid badlands within the same national borders, the country’s physical geography has shaped everything from its water politics to its patterns of rural settlement. What makes Spain’s geography particularly interesting is how many of its landscapes exist in tension with one another: wet versus dry, high versus low, ancient rock versus young volcanic soil.
A Peninsula Built by Collisions and Rotations
The Iberian Peninsula sits at the junction of the African and Eurasian tectonic plates, and its geology reflects tens of millions of years of compression, rotation, and rifting. During the late Jurassic and Cretaceous periods, the landmass that would become Iberia underwent a complex sequence of movements relative to Europe, including a roughly 35-degree counter-clockwise rotation during the Aptian stage of the Early Cretaceous. That rotation, combined with subduction and mountain-building processes, helped create the Pyrenees along the French border and contributed to the overall structural framework of the peninsula.1Earth-Science Reviews. Mesozoic rotation of Iberia: Subduction in the Pyrenees?
The result is a landmass dominated by its central plateau, the Meseta, which covers much of interior Spain at an average elevation of about 600 to 700 meters. The Meseta is not flat tableland in any dramatic sense, but its high, relatively level interior gives Spain one of the highest average elevations in Europe. This plateau is bounded and bisected by mountain ranges: the Cantabrian Mountains to the north, the Sistema Central splitting the Meseta into northern and southern halves, the Sierra Morena marking the southern edge, and the Iberian Range along the eastern flank.
In the northeast, the Ebro Basin forms a large interior depression bounded by the Pyrenees to the north (where peaks exceed 3,000 meters), the Cantabrian Range to the northwest, the Iberian Range to the south (with summits in the 2,000 to 2,300 meter range), and the Catalan Prelittoral Range to the east.2Journal of Hydrology. Estimating rainfall erosivity from daily precipitation records: A comparison among methods using data from the Ebro Basin (NE Spain) This enclosed valley produces its own distinct climate, shielded from moist Atlantic air by mountains on nearly every side.
Volcanism You Might Not Expect
Most people associate Spain with beaches or bullfighting rings, not volcanic craters. But the country has volcanic landscapes on both the mainland and the islands. La Garrotxa, in the northeastern corner of Catalonia between the towns of Olot and Girona, is the youngest zone of monogenetic volcanism on the Iberian Peninsula, related to the broader Neogene-Quaternary European Rift system. The field contains more than 50 eruptive vents scattered across about 600 square kilometers, many of them well-preserved cinder cones now covered in dense beech forest.3Tectonophysics. Volcano-structural analysis of La Garrotxa Volcanic Field (NE Iberia): Implications for the plumbing system The last eruptions occurred roughly 11,000 years ago, making this geologically recent and, in theory, not extinct.
Then there are the Canary Islands, which are far more obviously volcanic. Mount Teide on Tenerife rises to 3,718 meters, making it the highest peak in all of Spain and the highest point in the Atlantic islands. Teide’s volcanic origin creates unusual ecological layering: a stable temperature inversion at about 2,000 meters causes surface soil temperatures to peak near 70°C just below the tree line, rather than decreasing linearly with elevation as you would expect. This inversion pushes the Canary Island pine tree line unusually low, down to about 2,000 to 2,100 meters.4Flora. Altitudinal change in soil and foliar nutrient concentrations and in microclimate across the tree line on the subtropical island mountain Mt. Teide (Canary Islands)
Rivers, Floods, and Water Wars
Spain’s major rivers drain in different directions according to the tilt of the landscape. The Ebro flows east into the Mediterranean. The Tagus, Duero, Guadiana, and Guadalquivir flow west or southwest toward the Atlantic. This asymmetry matters enormously because the Atlantic-facing basins receive more rainfall from westerly weather systems, while the Mediterranean basins are often chronically short of water.
Historical flood records illustrate this split vividly. Between roughly 1400 and 1500 and again from 1850 to 1910, the Atlantic river basins experienced large floods driven by intense frontal systems arriving from the west and northwest. In a contrasting pattern between about 1290 and 1400, flooding actually shifted eastward: it decreased in Atlantic basins while increasing in the Ebro and Júcar basins along the Mediterranean side of the country.5Geological Society, London, Special Publications. Climate change and flood sensitivity in Spain These oscillations show how Spain’s geography channels weather systems into distinct regional outcomes.
The mismatch between where rain falls and where people farm has produced one of the most contentious pieces of infrastructure in the country: the Tagus-Segura Aqueduct. Built in the 1970s and operational since 1979, this massive water transfer was designed to move up to 650 cubic hectometers per year from the Tagus headwaters in central Spain to the Segura basin in the arid southeast, one of the most water-stressed areas on the Mediterranean.6Journal of Hydrology: Regional Studies. Multi-objective optimal design of interbasin water transfers: The Tagus-Segura aqueduct (Spain) It has been a flashpoint for political conflict ever since, with donor-basin communities arguing that the transfer reduces river flow and causes salinization in the Tagus headwaters, while recipient communities in the southeast depend on it to sustain irrigated agriculture and drinking water supplies.7Journal of Hydrology: Regional Studies. Multi-objective optimal design of interbasin water transfers: The Tagus-Segura aqueduct (Spain)
From Glaciers to Semi-Arid Badlands
Few countries can claim both active glaciers and a landscape that has served as a stand-in for the Sahara in Hollywood films, but Spain manages it. The Pyrenees host the southernmost glaciers in Europe, though they are disappearing fast. Between 2011 and 2020, the total glacierized area in the Pyrenees shrank by about 23%, and ice thickness dropped by an average of 6.3 meters, with no sign that the rate of loss was slowing.8Geophysical Research Letters. Toward an Ice‐Free Mountain Range: Demise of Pyrenean Glaciers During 2011–2020 The mass-balance years of 2021-22 and 2022-23 were especially brutal, with prolonged heat waves and reduced snow cover hitting these already tiny glaciers, none of which covers even half a square kilometer.9Regional Environmental Change. Pyrenean glaciers are disappearing fast: state of the glaciers after the extreme mass losses in 2022 and 2023
At the opposite extreme, the Tabernas basin in Almería province, in the southeast, is often called Europe’s only true desert. Its badland landscape is the result of tectonic uplift since the Pliocene, which created steep relief, combined with soft Tortonian-age sedimentary rock that erodes easily under the predominantly arid climate.10Landscapes and Landforms of Spain. Badlands in the Tabernas Basin, Betic Chain The area has been used as a filming location for countless Westerns and desert adventure films precisely because the terrain looks nothing like what most people imagine when they think of Spain.
The mountainous northern and northwestern regions, meanwhile, sit firmly in the Atlantic climate zone: green, wet, and heavily forested. The Cantabrian Mountains produce a sharp rain shadow, so that towns on the north coast might receive well over a thousand millimeters of rain per year, while places just over the ridge on the Meseta side get less than half that. The Picos de Europa, a limestone massif within the Cantabrian range, host deep karst cave systems within one of Spain’s most-visited national parks.11Geoheritage. Karst Cave Geoheritage in Protected Areas: Characterisation and Proposals of Management of Deep Caves in the Picos de Europa National Park (Spain)
The Balearic Islands and Coastal Karst
Spain’s Mediterranean islands, the Balearics, have their own geological character. Mallorca, the largest, has flat eastern and southern lowlands built on Upper Miocene reef limestone. Groundwater moving through these carbonates, mixed with seawater along the coast, has carved out extraordinary cave systems. Cova des Pas de Vallgornera, at more than 74 kilometers in surveyed length, is one of the longest caves in Europe. Its layout varies dramatically depending on the type of reef rock: spongework mazes and collapse chambers dominate where the original reef front stood, while joint-guided tunnels characterize the former back-reef zones. Three different agents shaped the system: coastal mixing of fresh and salt water, drainage of rainwater percolating through the rock, and hypogene recharge linked to local geothermal activity.12International Journal of Speleology. Geologic constraints and speleogenesis of Cova des Pas de Vallgornera, a complex coastal cave from Mallorca Island (Western Mediterranean)
Karst landscapes are not limited to the islands. Much of Mediterranean Spain is underlain by limestone, and the Strait of Gibraltar, where Spain nearly touches Morocco across just 14 kilometers of water, plays its own role in Spain’s geography. The strait governs the exchange between the Atlantic Ocean and the Mediterranean Sea. Tidal mixing over the Camarinal Sill within the strait returns an average of about 16% of the nutrients flowing out of the Mediterranean back into it, a figure that fluctuates between 4% and 35% depending on tidal strength.13Progress in Oceanography. Analysis of mixing and biogeochemical effects induced by tides on the Atlantic–Mediterranean flow in the Strait of Gibraltar through a physical–biological coupled model That nutrient cycling affects marine productivity across the western Mediterranean, connecting Spain’s narrowest geographic pinch point to the broader ecology of the sea.
Dehesas, Wetlands, and Ecological Signatures
Two of Spain’s most distinctive ecosystems owe their character to the interplay between its climate and its soils. The dehesa is a savanna-like landscape of scattered holm oaks created through centuries of agroforestry. Traditional uses range across sheep and pig grazing, extensive cereal farming, acorn production for fattening pigs, firewood, charcoal, bee-keeping, and hunting. The term “dehesa” refers both to this multi-use land system and to the parkland landscape it produces.14Landscape and Urban Planning. Land manager attitudes toward management, regeneration, and conservation of Spanish holm oak savannas (dehesas) Covering large swaths of western Spain, particularly in Extremadura and parts of Castilla y León, dehesas are open woodlands where the structure of vegetation varies with land use. Grazed plots, cropped plots, and plots that have been abandoned and overtaken by shrubs each handle soil moisture differently; encroached (shrub-invaded) plots consistently showed lower soil water availability than grazed or cropped ones.15CATENA. Effect of land-use on soil water dynamic in dehesas of Central–Western Spain The implication is that abandoning these landscapes can actually worsen drought stress on the remaining trees.
On the opposite end of the moisture spectrum, the Doñana wetlands in southwestern Spain, at the mouth of the Guadalquivir River, form one of Europe’s most important bird habitats. The seasonal flooding of these temporary wetlands dominates the area’s carbon cycle: because the flooded area is four to seven times larger than the permanent water features, the temporary wetlands contribute an order of magnitude more to daily carbon exchange with the atmosphere during the flood period.16PLOS ONE. Contribution of Doñana Wetlands to Carbon Sequestration Doñana is not just a wildlife refuge; it is a massive seasonal carbon pump driven by geography and hydrology.
Soil Erosion and the Reshaping of the Southeast
Spain has some of the worst soil erosion in Europe. More than 22 million hectares, roughly 44% of the country’s land area, experience erosion rates above 12 tonnes per hectare per year, which exceeds the estimated tolerance for soil formation in Mediterranean environments. Within that area, over 9 million hectares lose more than 50 tonnes per hectare annually. The numbers are especially stark for certain crops: woody dryland plantings like vineyards, almond orchards, and olive groves see erosion rates around 9.5 kilograms per square meter per year, compared to about 3.6 for herbaceous dryland crops and 2.1 for scrubland and pasture.17Geomorphology. Vegetation and soil erosion under a semi-arid Mediterranean climate: a case study from Murcia (Spain) The irony is that some of Spain’s most economically important crops are the ones stripping soil the fastest.
The southeastern coast has also been transformed by intensive greenhouse horticulture. The province of Almería hosts the largest continuous greenhouse area in the world, reaching about 26,000 hectares by 2007. Visible from space as a white scar on the landscape, these plastic-covered greenhouses have had an unexpected climatic side effect: a local cooling trend of about 0.3°C per decade between 1983 and 2006, running against the regional and global warming trend. The cooling is attributed to the increase in surface reflectivity (albedo) created by all that white plastic bouncing sunlight back into the atmosphere.18Journal of Geophysical Research: Atmospheres. Surface temperature cooling trends and negative radiative forcing due to land use change toward greenhouse farming in southeastern Spain19Environmental Science & Technology. Mesoscale Climatic Simulation of Surface Air Temperature Cooling by Highly Reflective Greenhouses in SE Spain It is one of the clearest examples anywhere on Earth of human land use generating measurable local climate change through albedo rather than greenhouse gas emissions.
The water needed to sustain this greenhouse agriculture, much of it supplied via the Tagus-Segura transfer and desalination plants, has downstream consequences. The Mar Menor, one of the largest coastal lagoons on the Mediterranean, sits adjacent to Almería’s intensive agricultural zone. A 20-kilometer sandy bar called La Manga separates the lagoon from the open sea, crossed by five narrow channels. Urbanization along La Manga has altered water flow through those channels, changing coastal dynamics. Meanwhile, the conversion of surrounding land from dry crops to intensively irrigated fields, made possible largely by the Tagus-Segura water transfer, has sent agricultural runoff flooding into the lagoon and triggered algal blooms that have devastated its ecosystem in recent years.20WIT Press. THE ENVIRONMENTAL IMPACTS OF LAND TRANSFORMATION IN THE COASTAL PERIMETER OF THE MAR MENOR LAGOON (SPAIN)
The Emptying Interior
Spain’s geography has always pushed population toward the coasts and a few major inland cities, but in recent decades the imbalance has accelerated. About 42% of Spanish municipalities have seen population declines, and an estimated 45,000 people leave rural communities each year. The regions hardest hit between 1996 and 2021 were Asturias (losing about 90% of its rural population), Castilla y León (about 88%), Extremadura (about 86%), and Aragón (about 78%). The average age of rural farmers in Spain is 61.21Preprints.org. The Problem of Rural Depopulation in Spain. Towards a Sustainable, Person-Centred Model of Repopulation
This depopulation is not random. It maps almost perfectly onto Spain’s physical geography. The areas losing people fastest are the high, interior regions of the Meseta and the mountainous northern provinces: places where the terrain is difficult, the climate extreme (bitterly cold winters in Castilla y León, hot summers in Extremadura), and the soils less productive without heavy irrigation. Spain even has a name for the phenomenon: “la España vacía,” or “empty Spain.” A band of territory stretching from Aragón through both Castillas and down into Extremadura has population densities comparable to parts of Scandinavia, despite sitting in a Mediterranean country. The mountains, the aridity, and the tilt of Spain’s economic geography toward coastal cities like Barcelona, Valencia, and Málaga have combined to drain the interior of working-age residents, leaving behind an aging population and a landscape increasingly given back to scrub and forest.
Vegetation patterns on Spain’s mountains underscore the ecological complexity that this human retreat is reshaping. The mountain ranges display two geographically opposed gradients: a Mediterranean-to-Euro-Siberian transition running broadly north to south, layered on top of the Atlantic-to-continental gradient running west to east.22PubMed. Equilibrium of vegetation and climate at the European rear edge. A reference for climate change planning in mountainous Mediterranean regions As rural land management fades, forests are expanding into formerly grazed hillsides, wildfire fuel loads are growing, and the landscape is being remade not by geological time but by the quiet arithmetic of demographics.