1. Relative Dating
Write on RIGHT Side

2. Relative dating: determining whether an object or event is older or younger than other objects
*Does not give us a rock’s age in years
RELATIVE DATING
Practice: Rate these phones from oldest (1) to youngest (3). How they look is a clue to their relative ages. Does this tell you the years that the phones were made?

3. How are undisturbed rock layers dated?
To find relative ages, scientists study layers of sedimentary rock.
Law of superposition states that the younger rocks lie above the older rocks if the layers have not been disturbed.

4. How are sedimentary rock layers disturbed?
By Tilting & Folding
Tilting: Earth’s forces move rock layers up or down unevenly
Folding: bending of rocks when they are squeezed together because stress is applied
By Faults & Intrusions
Fault: a break or crack in Earth’s crust where rocks can move
Intrusion: igneous rock that forms when magma is injected into rock and then cools
By Unconformities
Unconformity: when rock layers are eroded or sediment is not deposited for a long period of time

5. Page 171 in textbook Geologic Column
Geologic column: an ordered arrangement of rock layers that is based on the relative ages of rocks (oldest at the bottom). It is made by piecing together different rock sequences from different areas
Geologic Column
Page 171 in textbook

6. Reflection Turn to page 168 in your textbook Answer question 13
Cut out and glue/tape on the left side next to your notes
Turn to page 173 in your textbook
Answer questions 9, 10, &11
Cut out (include the picture) and glue/tape on left side next to your notes