Physical geography

The Natural Park is located in the pre-coastal mountain range, somewhat decanted towards the central depression.

The material that forms predominantly is pinyolenca (conglomerate) rock from the Tertiary (Eocene). Alternating with layers of Pinyolenc appear discontinuous layers of red sandstones, more abundant the more to the west, towards the central depression. On the other hand, the thicker pebbles of pinyolenc have to be found in the east and south, where they can have diameters greater than one meter. All this great mass of sedimentary rocks was sedimented with a regime of heavy downpours and rivers with steep slopes, in a large delta.

The thickness of material exceeds one thousand meters. Subsequently the pebbles will cohere and adopt the current stone consistency. Much later, movements of the continental masses and sea level have made the sedimentary materials that have undergone erosion emerge, adopting enriscadas forms and with needles and monoliths. The infiltration of rainwater over millions of years has caused different karst phenomena: caves and chasms.
Among the most important caves include Manuel (the longest: 954 m), Mura caves (180 m visitable), the chasms include the Espluga (the deepest: 123 m) and Castellsapera.

(Source: Diputació de Barcelona)