Absolute Dating

What is Absolute Dating? Determining the actual age, in numbers of years, of something (rock, object, event). How do you do it? Index Fossils Radioactive isotopes Atoms of the same element that have different # of neutrons

Index Fossils The fossil remains of an organism that lived in a particular geologic age, used to identify or date the rock in which it is found. 10 MY 15 MY 17 MY How old?

Radioactive Isotopes Radioactive isotopes are isotopes that are unstable and break down into other stable isotopes by a process called radioactive decay. Stable Unstable Unstable

Radioactive Isotopes The radioactive isotope is called the parent isotope, and the stable isotope formed by its breakdown is called the daughter isotope. Stable Daughter Unstable Parent Unstable Parent

Radioactive Isotopes HALF LIFE Half-life is the time needed for half of a sample of a radioactive element to undergo radioactive decay and form daughter isotopes. 100,000 years 100,000 years HALF LIFE

Radiometric Dating Scientists use lots of different radioactive elements that have different half-lives (Carbon-14, Uranium/Lead, Argon) If trying to date something young (thousands of years), an element with a short half-life is chosen Carbon-14 has a half-life of 5,730 years If trying to date something old (millions or billions of years), an element with a long half-life is chosen. Uranium-238 has a half-life of 4.5 billions years!

Practice #1 Calculate the age of this sample if the half-life of ‘Purpleandgreenballium’ is 10,000 years Parent Isotopes _______________ Total # Isotopes = 75% (Look at graph)

0.5 Half lives 0.5 x 10,000 = 5,000 years old

Practice #2 Calculate the age of this sample if the half-life of ‘Greenandpurplespherium’ is 1,000,000 years Answer = 2,000,000 years

Practice #3 Calculate the age of this sample if the half-life of ‘Shinycolorfulatomsium’ is 33,574,000 years Answer = 100,722,000 years