ABSOLUTE AGE Absolute Dating Radiometric Dating Half Life Isotope Radioactive decay Carbon 14

ABSOLUTE DATING Process of establishing the age of an object by determining the number of years it has existed

Radiometric Dating Determining Age based on ratio of parent to daughter matter Parent – unstable radioactive isotope Daughter – stable isotope produced by the radioactive decay of the parent isotope The more daughter material there is the older the rock.

Parent to Daughter Decay

Radioactive Decay Unstable Isotope Decays A neutron converted into a proton, then an electron decays. The rate of decay is constant Isotope – atoms of the same element that have the same number of protons (+) but have different number of neutrons Half Life – time it takes one half of a radioactive sample to decay (become stable)

Radiometric Dating Carbon 14 dating Carbon normally found in 2 forms of stable isotopes, Carbon 12 and carbon 13. The radioactive isotope is Carbon 14. The half life of Carbon 14 is 5730 years. This is used to date things that have lived within the last 50,000 years Potassium to Argon – Half life of 1.3 billion years Used to date rocks older than 1.3 billion years Uranium to Lead – Half life of 4.5 billion years. Can be used for rocks older than 10 million years

Carbon 14 Dating process The carbon isotopes combine with oxygen to form the gas carbon dioxide, which is taken in by plants during photosynthesis. As long as a plant is alive, new carbon dioxide with a constant carbon 14 to 12 ratio is continually taken in. Animals that eat plants contain the same ratio. Plant or animal dies, no new carbon is taken in. Amount of carbon 14 begins to decrease as the plant or animals decays, and ratio of carbon 14 to 12 decreases.