The Meseta Central: Geology and Relief

The Meseta Central

The Meseta Central is a high plain located at an altitude of about 600-800 meters. It was formed primarily by the erosion of the Hesperian Massif, which emerged during the Hercynian orogeny. In the Tertiary Era, it was deformed, and the plateau was largely reshaped by the Alpine orogeny. Three main units can be distinguished:

A) The Old Paleozoic Basement

Today, it only occupies the western part of the peninsula. The erosion of Tertiary materials that covered the basement has exposed primary peneplains. These are elevations due to erosion or gently undulating surfaces. The peneplains feature inselbergs (very hard rocks). In areas where the peneplain contacts the sedimentary basins of the plateau, rivers create deep gorges.

B) The Interior Mountains

Within the plateau, the Central System and the Montes de Toledo were formed in the Tertiary Era by the uplift of some blocks of the Meseta's basement as a result of the Alpine orogeny.

• Central System: It is the highest part of the plateau and divides it in two. Its most prominent mountains are Somosierra, Guadarrama, Gredos, and Peña de Francia.
• Montes de Toledo: These are lower and divide the southern sub-plateau, separating the basins of the Tagus and Guadiana rivers. Its most important range is Guadalupe.

C) Internal Sedimentary Basins

The southern and northern sub-plateaus were formed in the Tertiary Era from the collapse of blocks of the Meseta's basement as a result of the Alpine orogeny. Lake basins were formed first, and then they were filled with Tertiary materials. Horizontal layers of soft Tertiary materials (clay, sand) and hard materials on top (limestone) resulted in páramos, campiñas, and cuestas.

• Páramos: These are flat, high structural surfaces with hard limestone layers, formed by fluvial erosion that carved U-shaped valleys. They are cut and separated by smaller hills, north and east of the northern sub-plateau and in the southern sub-plateau (La Alcarria, Mesa de Ocaña, and La Mancha).
• Campiñas: These are gently rolling lowlands crossed by rivers. Where páramos have been eroded, clays and marls of lower levels have surfaced. Witness hills (cerros testigos) are frequent, and tough terrain is found in the Tagus and Guadiana rivers.
• Cuestas: These are sloping areas between the páramos and the campiñas.

Northern Sub-Plateau

The northern sub-plateau basin is higher (800-850m), with a more uniform elevation. It encompasses part of the Duero watershed and is nearly enclosed by mountains.

Southern Sub-Plateau

The southern sub-plateau is lower (500-700m). It is divided in its middle by the Montes de Toledo into two hydrographic basins (Tagus and Guadiana) and opens towards the Atlantic Ocean.