1. Determining Relative Age
Chapter 8 - 1
Determining Relative Age

2. Age of the Earth 4.6 billion years old
James Hutton was 1st to determine this
Scottish physician and farmer

3. Uniformitarianism
Same forces that change the Earth today changed it years ago
Present is the key to the past

4. Rate of processes may change

5. Earth’s Age Before Hutton most believed Earth was 6,000 years old
Many believed that all features formed at the same time

6. Processes that change the Earth today are very slow
Millions of years would have to have passes to get what we have today

7. Relative Age Layers of rock show events
Indicates that one layer of rock is older than another
Nothing about age

9. Law of Superposition
A layer of sedimentary rock is older than the layer above it
It is younger than the layer below it

10. Principle of Original Horizontality
Rock generally forms in horizontal layers
Unless disturbed

11. Rocks that are not horizontal have been tilted or deformed
Sedimentary rocks

12. Graded Bedding
Larger particles should be at the bottom of the rock layer

13. Cross - Beds Sandy sediments formed curved beds
Tops of layers erode before new form
Curved at bottom and cut off at top

15. Ripple Marks
Crests of ripple marks point up

16. Unconformities
A break in the geologist record
Missing parts

17. Nonconformity
Stratified rock rests on unstratified rock

18. Angular Conformity
Layers are tilted

19. Disconformity
Boundary between order and newer layer is missing

20. Crosscutting Relationships
Fault or igneous intrusion are older than the rock it cut through