2. Warm-up 10/20 Describe what you think Earth was like just after it formed.

3. Early History of Earth Formation 4.6 billion years ago (bya) Nebular Theory Molten Volcanoes Collisions Atmosphere CO 2 Biological influence Pink in color Gradually cooled 3.9 bya oceans form Water from comets, planet Condensation led to rain Runoff brings minerals

4. Warm-up 10/21-22 Approximately how old is Earth? How do you think scientists determined that age?

5. Relative Dating Determining the relative order of past events. Estimate of age based on position ◦ Ryan Gosling was born after Matt McConaughey. Three ‘rules’

6. What order did the baker put down these layers of the cake? Purple! Blue! Yellow Red! Dark Pink! Light Pink! White!

7. #1: Law of Superposition (LOS) Bottom layer = Top layer = Placed last Placed first *When rocks are horizontal!

8. What happens if rock layers are not horizontal?

9. Layers deposited horizontally Rock is folded after cooling - Caused by pressure Bottom is still oldest. Top is still youngest. OLDEST YOUNGEST 2. Principle of Horizontality

10. Practice: Hold up the number Which is the oldest? Which layer is the youngest?

11. What happens if the rock layers are faulted?

12. 1. A fault is younger than any rock layer it cuts through. OLDEST 2 ND OLDEST 3 RD OLDEST YOUNGEST 3. Principle of Cross-Cutting Relationships

13. 2. An intrusion is younger than the rock layers it pushes through. OLDEST 2 ND OLDEST INTRUSION = YOUNGEST Intrusion – magma forces its way through the rock layers.

14. Practice!

15. Practice!

16. Tell the rock’s story…