1. Relative Dating of Rocks Layers

2. Age of Earth Early 1900s: 6000 years old Today: 4.6 billion years old
How did scientist come up with this number?
Relative Age Dating
Absolute Age Dating

3. Developed the principle of uniformitarianism
James Hutton (1700s)
Developed the principle of uniformitarianism
processes occurring today have been occurring since Earth formed.

4. 1) Relative Age Dating
Comparing one rock layer to another.
Sequences the order of events
No exact dates
Easy comparison of fossil ages

5. Geologic Principles
Original Horizontality – sedimentary rocks are deposited in horizontal layers.

6. Superposition – in an undisturbed rock sequence:
Oldest rock layers are at the bottom
Youngest layers are on top

7. Law of Superposition L U M X S Which layer is the oldest?
Which layer is the youngest?
Would the fossils in rock layer “U” be older or younger the fossils in rock layer “X”?
How do you know?