1. TOPIC XIII: Interpreting Geologic History

2. Putting rocks or geological events in a
Dating rock layers and geologic events can be done with two methods:
1. RELATIVE DATING-
Putting rocks or geological events in a
chronological order. Which rock came first?
It is RELATIVE because-
Youngest -
Oldest -)

3. 2. ABSOLUTE DATING-
Finding -.
This is determined -
Trilobite

4. Absolute Dating

5. PRINCIPLE OF UNIFORMITY
With each of these methods geologists rely on one important assumption about the past
PRINCIPLE OF UNIFORMITY-
“-”.
The geological processes -
EXAMPLES: erosion-
By looking at characteristics of rocks, geologists can make -

6. CORRELATION

7. CORRELATION-
Matching the age of rocks and geologic events in
different -
There are four ways that geologists can correlate ROCK FORMATIONS (-):
1. “WALKING THE OUTCROP”:
An OUTCROP -
If the rock formation is exposed an individual can -.
Most OUTCROPS -

9. 2. SIMILARITY OF ROCKS-
Rock formations are separated
they can -.
The problem is -

10. 3.BEST METHOD OF CORRELATION!! USE OF INDEX FOSSILS-
A FOSSIL -
INDEX FOSSIL a fossil has to meet two criteria:
Lived over a large -
b) Lived for a -

12. 4. VOLCANIC ASH-
When a volcano erupts -
This ash may -
The ash will then -
Useful because volcanic ash could cover large areas in a –
(days to weeks) and –
Good TIME MARKER!!

13. Volcanic Ash