A berrocal is the landscape that results from the slow erosive process known as chemical meteorisation; this is caused by the chemical components of the atmosphere acting statically to destroy the granitic rocks, and is characterised by the formation of a large number of rounded blocks, boulders, “mushroom rocks” and “tors” scattered all over the surface of the batholiths. The granitic rocks have been superficially eroded following the fracture planes (diaclases) enlarged by the action of the atmospheric water that attacks and breaks up the minerals that make up the granite (quartzes, feldspars, and micas) to shape the berrocal over time. In Extremadura berrocales are known as berruecos or barruecos.
The granites of the Berrocal de Peraleda are essentially fine-grained with two micas, although others can also be found with large crystals of orientated feldspars and lodes of aplites, pegmatites, and quartzes. They are related to the numerous parallel fracture lines in a northeast-southwest direction that limit and compartmentalise the interior of this huge batholith, which are made use of by the streams that originate on the Sierra de la Breña and flow into the nearby River Tajo. Tertiary materials from the Pliocene age (rañas) have been deposited on these granites; they consist of clays, sands, and quartzite boulders from the sierras of Las Villuercas. The rañas platforms of El Madroñal, the Dehesa Boyal (common grazing ground), Las Cuevas, and Las Porquerizas are significant; they are separated from each other by the encasing of the river network along the fracture lines.