Mountain ranges affect climate, the network of rivers, soils and their erosion, bioregions, and even human economies insofar as they rely on natural resources. The Andalusian terrain offers a range of altitudes and slopes. Andalusia has the Iberian peninsula’s highest mountains and nearly 15 percent of its terrain over 1,000 metres (3,300 ft). The picture is similar for areas under 100 metres (330 ft) (with the Baetic Depression), and for the variety of slopes.
The Atlantic coast is overwhelmingly beach and gradually sloping coasts; the Mediterranean coast has many cliffs, above all in the Malagan AxarquÃa and in Granada and AlmerÃa. This asymmetry divides the region naturally into Upper Andalusia (two mountainous areas) and Lower Andalusia (the broad basin of the Guadalquivir).
The Sierra Morena separates Andalusia from the plains of Extremadura and Castile–La Mancha on Spain’s Meseta Central. Although sparsely populated, this is not a particularly high range, and its highest point, the 1,323-metre (4,341 ft) peak of La Bañuela in the Sierra Madrona, lies outside of Andalusia. Within the Sierra Morena, the gorge of Despeñaperros forms a natural frontier between Castile and Andalusia.
The Baetic Cordillera consists of the parallel mountain ranges of the Cordillera Penibética near the Mediterranean coast and the Cordillera Subbética inland, separated by the Surco Intrabético. The Cordillera Subbética is quite discontinuous, offering many passes that facilitate transportation, but the Penibético forms a strong barrier between the Mediterranean coast and the interior. The Sierra Nevada, part of the Cordillera Penibética in the Province of Granada, has the highest peaks in Iberia: El Mulhacén at 3,478 metres (11,411 ft) and El Veleta at 3,392 metres (11,129 ft).
Lower Andalusia, the Baetic Depression, the basin of the Guadalquivir, lies between these two mountainous areas. It is a nearly flat territory, open to the Gulf of Cádiz in the southeast. Throughout history, this has been the most populous part of Andalusia.