Dating rock
w:Relative dating is based on the Principal of w:Original horizontality, Lateral Continuity, w:Law of superposition and Faunal Succession and is described as the theory that layers of sedimentary rock are layed in the order of older at the bottom to younger at the top. And the occurance of a species who live for short periods of time and can unit different strata localities into a specific time period.
w:Absolute dating, by using radiation via w:isotopes to analyse w:radioactive decay. This is good to analyse recently fossilised organisms via C-14. For longer periods the sediment itself must be analysed, this would give a date for the original material, like an ignious rock formation that is eroded but not the present sedimentary rock.
w:Optically stimulated luminescence, uses the last time that light from the sun reached the material. This only works for burried material
w:Radiometric dating uses radioactive decay like w:Uranium-thorium dating the time since burial that the w:uranium has decayed to w:thorium.