Uranium is present in many different rocks and minerals, usually in the form of uranium-238.Radioactive dating is a method of dating rocks and minerals using radioactive isotopes.
The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.Radioactive decay is a natural process and comes from the atomic nucleus becoming unstable and releasing bits and pieces.Volcanic rocks – such as tuff and basalt – can be used in dating because they are formed at a particular moment in time, during an eruption.Sedimentary rocks are rarely useful for dating because they are made up of bits of older rocks.This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.
those that form during chemical reactions without breaking down).Purpose: to establish the nature and rate of landscape evolution by determining the relative or absolute times when soil or rock surfaces where exposed by erosion, deglaciation or tectonism; constructed by deposition or tectonism; or exposed at the surface prior to burial by sediments or extrusive rock.Relative (floating) age: is known only with respect to other landforms or surfaces; the chronology floats in time until referenced to an absolute date.For geological purposes, this is taken as one year.Love-hungry teenagers and archaeologists agree: dating is hard. The applicability, accuracy and usefulness of each method deserve scrutiny.