Site formation

Sierra de Atapuerca is a karst system, i.e. it consists of a system of underground tunnels and ducts, some of which have become clogged and covered up- the case of the caves being dug in the Railway Cutting. The karst model in Sierra de Atapuerca is characteristically extensive underground forms (endokarst) and few open-air formations (exokarst). The exokarst forms in the Sierra include dolines and the odd gryke (a quite small groove or hollow separated by rock walls). The 3,700 metre long karst in Sierra de Atapuerca is the largest such system in the Duero River basin.

How did these channels form? How were they filled in? The Sierra bedrock is limestone, which dissolves in water. The limestone massif held underground water until the Arlanzón River valley was shaped and the water level subsided. At the same time, water filtered through cracks, dissolving the limestone and generating large cavities which at some point became exposed to the outside world, either because the crack gave rise to an entrance or because the roof caved in. When this happened, soil near the mouths of these cavities and water and wind-borne matter started to enter.

Animals and human beings came in and left food and tool remains there, which were then covered by more sediment. And so the caves started filling up, leaving us episodes from the lives of the groups which inhabited them, sandwiched between layers of sterile material soil. This is our direct contact with the past, some of the most valuable evidence preserved as a testimony of everyday life in prehistoric societies. Today, the physical landscape of Sierra de Atapuerca still contains the diversity and wealth enjoyed by Pleistocene humans.