The Almodôvar area is situated in an area of transition between the Alentejo peneplain, in the northernmost part of the municipality, and the hills of the Serra do Caldeirão to the south of its territory.
The mountains in the park are erosional remnants of resistant igneous rocks that remained after an ancient Mesozoic peneplain surface was uplifted in the Cenozoic to form a plateau, and subsequently dissected via millions of years of erosion by wind, water and glacial ice.
The Acasta Gneiss in the Canadian Shield in the Northwest Territories, Canada is composed of the Archaean igneous and gneissic cores of ancient mountain chains that have been exposed in a glacial peneplain.