This area of the Natural Monument of Pedras Ruivas preserves testimonies of how the last and current climate cycle evolved, namely sediments, fossils, coastal platforms and larger scale geoforms.

Despite the cliffs that dominate the landscape is organized in a very choppy way, as a result of the abrasion on the very dense fracture network, some stand out whose tops, flattened at an altitude of 5 m, reveal an ancestral beach level, from the last interglacial, outside the reach of the current sea. This origin is certified by the ichnofossils of Paracentrotus lividus, sea urchin housing cavities, organisms tolerant to rapid variation in abiotic conditions such as salinity, partial pressure of oxygen and temperature resulting from a tidal cycle, but without resistance to desiccation. Therefore, the marine occupation of these levels is determined, 125 thousand years ago, at a time when the sea level would be about 20 cm above the current. The difference of about 4.8 m observed is explained by seismic crises, a subject developed in the Natural Monument Alcantilado de Montedor.

From the climatic evolution that followed, from climatic cooling to glaciation, the lake sediments that constitute one of the layers of sediments that cover the coastal platform up to the water line, which are dark brown, are preserved and witnessed. This sedimentary unit was deposited in depressions of the ancestral coastal platforms, with reduced depth, between 18000 and 11000 years ago, forming an environment of a swampy lagoon. This lagoon lasted in the landscape for about 7 thousand years and would be supplied by spring melting waters from the snows of the local slopes. From microscopic data, pollens and spores of freshwater algae were identified, which prove the existence of a confined environment away from direct marine influence.