1. Absolute Dating

2. 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

3. 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?

4. 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

5. 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

6. 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

7. 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!

8. 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)

9. 0.5 Half lives
0.5 x 10,000 = 5,000 years old

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

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