The pictures display the origin of the convex shapes of the monoliths in Montserrat type relief. They were obtained near Montcau (Mura), 1st image in peak of Cortins and 2nd image in rocks of Coca. The red band is made of several thin layers of sandstone and clay which are much easier to erode than the thick and compact layers of conglomerates that wrap it. The erosion dig out the red band. The process may result in a rock shelter.
[photos by Florenci Vallès (1st) and Jordi Badia (2nd)]