Because of the long half life of the radioactive atoms in nuclear waste, it must be isolated from contact with the hydrosphere and biosphere for at least 10,000 years. Therefore the disposal site must be in a setting in which frequency of natural disasters such as floods, earthquakes and volcanoes is extremely low. Deep burial of nuclear waste must take place in geological strata with minimal fracturing and low permeability. The regional water table must be far below the burial area, and the depth of burial must be far below the area influenced by surface erosion. The host rock should have good absorption properties, and be able to withstand heating by the radioactive decay of the waste.