1. Aim: How do Scientists read Rocks?

2. Vocabulary
Outcrop – a section of rock exposed on the surface that shows a geologic sequence.

3. I. Discovering Earth’s History
Uniformitarianism - the processes that we observe today are most likely the same processes that occurred millions of years ago.

4. *Does not tell us the actual age or use numbers to express time.
Relative dating - tells us the sequence in which events occurred.
*Does not tell us the actual age or use numbers to express time.

5. II. Three principles for Relative Dating:
A. Law of Superposition
Within an outcrop of undisturbed sedimentary rock, the oldest layers are at the bottom.

6. Which picture shows the
B. Law of Original Horizontality
Most sediments are deposited as horizontal beds (layers) and remain that way unless disturbed.
Which picture shows the
Law of Original Horizontality

7. Disturbed Rock Layers
Makes no sense without caption in book

8. C. Law of Cross-Cutting Relationships
A disrupted rock is older than the rock disrupting it.

9. Types of Cross-Cutting Relationships
Makes no sense without caption in book

10. III. Important Features
Volcanic Eruption –occur at one specific time and leaves a layers of ash which marks the time eruption.
Do not copy
K-T ash Boundary which marks the end of the Cretaceous Period and the beginning of the Paleogene Period. This layer is 65 million years old and below this layer, scientists find fossils of dinosaurs. Above this layer, there are no dinosaur fossils.

11. Unconformity (UNC)-
a gap in the
sedimentary rock
record. Usually
Caused by some
type of erosion.

12. The rock being metamorphosized
Contact Metamorphism – occurs as an igneous intrusion touches and metamorphosis's the surrounding rock.
Uses the law of cross-cutting relationships to describe the relative sequence.
Can you cause a metamorphosis of layer that does not exist yet?
Which comes first, the rock being metamorphosized or the magma? NO
The rock being metamorphosized

13. Closure 1: Place the letters in relative order using the notes as a guideline. Which letter comes first, second, third…
Answer: P, K, M, S, Intrusion R, erosion A (UNC), B, J, F.

14. Closure 2:
Relatively sequence the letters in the outcrop below. List which layer comes first, second, third…
Answers D C B F A E