Long-term geological evolution has been described in Chapter 6 of NTB 24-17 (Nagra 2024i) and in the references therein. A short excerpt is given in the following paragraphs to contextualise the results from the perspective of safety assessment.

Recent tectonic deformation rates in Northern Switzerland are small compared with those in the geological past. The study of past geological evolution shows that deformation is preferentially accommodated by larger existing faults, which represent zones of weakness. Future deformation will thus most likely result in fault reactivation of existing faults. These are avoided when placing the disposal areas. If new faults were to develop cutting through the host rock, they are expected to be segmented and small in length and offset.

Future erosive processes (glacial and non-glacial) are expected to be comparable with those that occurred in the Quaternary period, but the rates are likely to be lower (no major drainage reorganisation, smaller glaciers, delay in glacial inception, and harder-to-erode rocks). Due to the great emplacement depth, the repository system is protected against future erosion. Excavation of the repository by either glacial or non-glacial (fluviatile) erosion processes within the next million years is not expected. Furthermore, a residual cover of at least 200 m, which ensures the self-sealing capacity of the host rock, is expected to remain present throughout the time period for assessment of one million years.

Climate change, glaciations, permafrost, and erosion can affect aquifer dynamics, including a shortening of the transport path along aquifers and the possibility of increased flow rates. Glacial loading may lead to overpressures in the host rock and to a temporarily increased hydraulic gradient and transport rates from the host rock towards the aquifers. However, mass transport is expected to remain diffusion dominated. Because of the buffering capacity of the host rock minerals, geochemical conditions will remain reducing.