Peña Bermeja is a good geological observation point to appreciate the reliefs that have developed through river erosion over the last thirty million years, after the withdrawal of the immense sea that covered the entire territory. The cliffs of Peña Bermeja are common formations on the highest edges of the valleys, appearing in the limestones of the moorland that occupy the stratum located between the high plains and the slopes of impermeable marl and gypsum that fall towards the plain. In many places these limestone walls have been used to exploit stone quarries.