Relative dating vs absolute dating worksheet

22-May-2014 11:53

Throughout the history of life, different organisms have appeared, flourished and become extinct.Many of these organisms have left their remains as fossils in sedimentary rocks.Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence.The method of reading the order is called stratigraphy (layers of rock are called strata).Suppose you find a fossil at one place that cannot be dated using absolute methods.That fossil species may have been dated somewhere else, so you can match them and say that your fossil has a similar age.Others measure the subatomic particles that are emitted as an isotope decays.Some measure the decay of isotopes more indirectly.

Most absolute dates for rocks are obtained with radiometric methods.Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.These rates of decay are known, so if you can measure the proportion of parent and daughter isotopes in rocks now, you can calculate when the rocks were formed.These use radioactive minerals in rocks as geological clocks.

The atoms of some chemical elements have different forms, called isotopes.Each isotope is identified with what is called a ‘mass number’.