Systematic, seven years lasting monitoring of displacements on joints in a rock mass, combined with the first stage of geochemical monitoring of sandstone weathering, has enabled an insight into complex process of stability deterioration on the Prav?ice Rock Arch. The displacements are as reversible response of the rock mass to climatic influences in quasi-cycles, as well as irreversible deformations due to rock destruction. Deterioration of strength of sandstones by weathering is anthropogenically enhanced by atmospheric pollution. The model of the Arch formation from a long, slender rock rib, has stressed the crucial combination of selective weathering with rock falling, and postulates a hypothesis about geomorphologically short-live of the Arch, and about its Holocene Age. Regarding the model and monitoring results, probable scenario of the final collapse of the Arch stability has been proposed.