A layer of hard rock, most likely a several meters thick conglomerate layer, makes the flat summits in tabular geomorphology. The erosion of the soft rocks just below, most likely mudstones, outlines the resistant rock layer on top (1st photo, on the left, from the summit of Collbaix [Manresa]).
The summit rock layer can build shelters, as the one seen in 2nd photo, on top of slope of El Puig (Rajadell).
As the basement is lost, the hard rock layer of the summit is projected out until roughly poligonal as a result of former crevices, enormous blocks of rock fall down (3rd photo, in Rajadell).
All conglomerate blocks spreading through the slopes fell down from top layer. These landscapes are known as chaos of blocks in geomorphology. Additional blocks will fall in the future. The images are taken near Cal Miralles (Rajadell) (4th photo), in the slope of El Puig (Rajadell) (5th photo) and in the south slope of Santa Cecília de Grevalosa (Castellfollit del Boix) hermitage (6th photo).
Even some block may roll until the bottom of the valley, like the one made of sandstone and conglomerate that bridges the stream of Mura near Mas Ventaiol (El Pont de Vilomara i Rocafort) (7th photo).
[photos Jordi Badia (1st and 6th) and Florenci Vallès (2nd, 3rd, 4th, 5th and 7th)]