1. Tuesday, April 2nd Warm-Up Agenda Homework
Choose ONE question:
What is an index fossil?
How do index fossils show us the relative age of rock layers?
What can index fossils be used to help prove?
Agenda
Notes on Absolute Age, Radioactive Dating and Ice Cores
Homework
Part 2 Vocab – Due Friday 4/5

2. Absolute Age and Radioactive Dating

3. Absolute Age of Rocks
How can scientists determine the exact age of rocks?

4. Absolute Age of Rocks
How can scientists determine the exact age of rocks?
Radioactive Dating
The process of measuring the known rate of decay of radioactive materials contained in the rocks.

5. Radioactive Decay
Radioactive Decay - the process in which a radioactive isotope tends to break down into stable atoms of the same element or another element.

6. What are Isotopes?
Isotope - an atom that has a different number of neutrons than stable atoms of the same element.
Carbon 12
Carbon 14

7. Carbon Dating Video

8. Radioactive Decay - Isotopes
Parent Isotope - The original radioactive element. Daughter Isotope - The stable isotope that results from radioactive decay of the parent isotope.

9. Half-Life
Half-Life - The time needed for half of a sample of radioactive substance to undergo radioactive decay.
The time it takes for the Parent Isotope to break down into the Daughter Isotope.

10. Half-Life Activity Using the scissors, cut the piece of paper in half.
Every time you cut the paper, that is one Half-Life.
See how many times you can cut the paper in half.

11. Half-Life of Different Elements

12. Calculating Half-Life
Time (years)
% of Carbon-14
100% 1
5730
50% 2 3 4 5

13. Calculating Half-Life
Time (years)
% of Carbon-14
100% 1
5730
50% 2
11460
25% 3 4 5

14. Calculating Half-Life
Time (years)
% of Carbon-14
100% 1
5730
50% 2
11460
25% 3
17190
12.5% 4 5

15. Calculating Half-Life
Time (years)
% of Carbon-14
100% 1
5730
50% 2
11460
25% 3
17190
12.5% 4
22920
6.25% 5

16. Calculating Half-Life
Time (years)
% of Carbon-14
100% 1
5730
50% 2
11460
25% 3
17190
12.5% 4
22920
6.25% 5
28650
3.125%

17. Calculating Half-Life
Example: Carbon-14 has a Half-Life of 5730 years.
How many years old would a fossil be if it contained 6.25% of Carbon-14?