6.11. In addition to providing a description of the present day characteristics of a site, the site characterization programme should collate and interpret information in support of models describing the past evolution of the site. This should include an investigation of the long term stability of the geosphere in response to past environmental and climatic changes at the surface and the effects of tectonics, including faulting, rock fracturing and volcanism. Palaeohydrogeological studies are particularly relevant in this regard. The timescale for consideration of such changes should be at least comparable to the future timescale of interest in the safety assessment. Such information may be used in support of scenarios for the future natural evolution of the site and for evaluating the relevance of features, events and processes that could affect the performance of the disposal system, including interactions between the natural and engineered elements.