This document discusses methods for determining the relative age of rocks and fossils, including using the principle of superposition, where older rock layers are below younger ones, and looking at index fossils which lived during short, identifiable periods of time. It also briefly introduces the concept of absolute age dating using radiometric dating techniques, and contains exercises for students to practice determining relative age from a model geologic column by identifying the oldest and youngest layers and index fossils.

1. How do we find the relative
age of rocks and fossils?
Page 30

2. Remember when we did this?
Relative Age

3. How did we arrange
ourselves?
Relative Age

4. Relative Age: comparison of ages – is it
younger or older than the rocks/fossil
layers around it
oSuperposition – older rock is below
younger rock
oIndex Fossils – fossils of organisms that
lived for a relatively short period of time
Relative vs Absolute Age

5. Absolute age: how long since the
rock or fossil was formed
oFound using radiometric dating
Relative vs Absolute Age

6. SuperPosition

7. You Try!
Retrieved from here

8. You Try
Retrieved from here

9. Geologic Column
From Holt Science and Technology Georgia Earth Science

10. 1. How many layers are there in your
geologic column?
2. Which layer is oldest? Which layer is
youngest? How do you know?
3. What fossil is the oldest?
4. What fossils can be considered index
fossils? Why?
Reflection on Page 31