This area of the Natural Monument of the Alcantilado de Montedor, preserves reddish sandstone, consolidated in hematite (iron oxide), relics of 71 thousand years ago, a wide dune field. This lithostratigraphic unit, called Sands of Ronca de Montedor, consolidated in hot and humid weather, a period in which the sea level would be about 40 m below the current one and the coastline more than 10 km from this location.