1. Relative Dating

2. I. Relative Dating
Relative Dating is when you give the age of a rock or fossil compared to another rock or fossil.
Example: Rock A is OLDER than Rock B.
An actual age in years is not determined.

3. II. Rules of Relative Dating
Law of Superposition: When sedimentary rock layers are deposited, younger layers are on top of older deposits.

4. Rules of Relative Dating
2. Law of Original Horizontality: Sedimentary rock layers are deposited horizontally. If they are tilted, folded, or broken, it happened later.

5. Rules of Relative Dating
3. Law of Cross-Cutting Relationships: If an igneous intrusion or a fault cuts through existing rocks, the intrusion/fault is YOUNGER than the rock it cuts through

6. III. Correlation
Rock layers in different places are linked or matched up by the rocks and fossils in the layers.

7. IV. Unconformity
When rock has been eroded, so you have a missing section of time in the rock record.

8. Why are some of the layers tilted
Why are some of the layers tilted? What happened to the top of the folded rocks? The missing rock layers is called an _unconformity.

9. Index Fossils
Some species of organisms only lived for a short period of time before they became extinct. Fossils are the preserved physical remains of deceased organisms that are at least 10,000 years old
NOTE: Most organisms DO NOT become fossils after death
NOTE: The formation of fossils is a RARE event
Trilobite: Index fossil for the Paleozoic Era
Age: mya

10. If you use radiometric dating to get an age for the fossil, then you know that the rock the fossil is found in is also that age.
We can tell if one fossil is older than another based on which
layer we find it in. (Deeper layers-older. Shallow layers-younger)

11. Fossil B lived 10 million years ago – 2 million years ago.
Fossil A lived 20 million years ago- 8 million years ago.
What do you know about the age of the rock containing both fossils?

12. What is “B”?
Place the layers in order from oldest to youngest

13. Put the events in order

14. Put the events in order