1. Daily Review #1 What happens in radioactive decay? Define half-life.
The element chaparralium has a half-life of 24,000 years. If a fossil contains 25% of the original amount of chaparralium, how old is this fossil? Explain how you arrived at this answer.
What do you think happened to create the rock in this picture?

2. Relative vs. Absolute Dating
Definition
Example
Relative
Order of events
X is older/younger than Y
Less specific
Three major techniques

3. Law of Superposition What order were the layers of the cake put down?
How are rocks similar?
Oldest…
Youngest…
When layers are horizontal

4. What if the layers aren’t horizontal?

5. Principle of Horizontality
Rock forms layers horizontally
If not horizontal
Happened after rock cooled
Folding
Caused by pressure

6. Cross-Cutting Occur after rocks form Faults Caused by earthquakes
Shift rock layers

7. Cross-Cutting cont.
Intrusions
Magma invades cracks
Cools into rock

8. Tell the rock’s story…

9. Mapping Interior No drilling past crust Seismographs Earthquakes
Wave speed effected by density and thickness
Study times to pick up seismic waves

10. Composition of Earth 3 layers Crust Based on compounds present
Density differences
Crust
Outermost
5-100 km
Thinnest layer
Types
Continental
Oceanic

11. Mantle Middle layer 2900 km thick Never visited Conclusions based on
Observations on Earth surface
Pushes to surface
Oceanic volcanoes

12. Core Center Radius of 3430 km Mostly Fe, some Ni 1/3 of Earth’s mass
Very little O, Si, Al, Mg
1/3 of Earth’s mass

13. Physical Structure Lithosphere Asthenosphere Solid, outer layer Crust
Upper mantle
Asthenosphere
Solid, slow flowing rock
Mantle

14. Outer core
Liquid layer
Inner core
Center
Solid, dense

15. Daily Review #2 Tell the rock’s story…
Review quiz – make corrections

16. Plate Tectonics Plates Divisions of lithosphere Moving on
asthenosphere
Plate Tectonics

17. Wegener – Continental Drift Theory
Early 1900s
Once single landmass - Pangaea
Broke up – Laurasia, Gondwana
Drifted to present location

18. Daily Review #3 Put in order of age: Gondwana, Pangaea, South America
Sketch the layers of the Earth and label the asthenosphere, lithosphere, outer core, inner core, mantle and crust
Fill in the boxes on your layers of the Earth worksheet
Composition = if it contains any specific elements (you will not fill this in for all boxes)
Thickness = rank from thinnest to thickest

19. Continental Drift Evidence
For Wegener
Fitting together of continents
Similar things on distant continents
Fossils
Rocks

20. How would you explain this evidence?

21. Sea-Floor Spreading Evidence for continental drift Mid-ocean ridges
Tectonic plates moving separating
New magma rises
Form new oceanic crust
Older crust pushed away

22. Magnetic Reversals Evidence for continental drift Molten rock
Magnetic minerals
Align with magnetic field
Magnetic field reverses
177 times in 85 million years
Last 600,000 years ago
Recorded in rock
Similar pattern to age of rocks

23. Causes for Plate Tectonics
Convection
Cools
Asthenosphere
More dense
Heated rock
Expands and rises

24. New material pushed up at ridges Subduction zone
Pushes older material away
Subduction zone
Denser plate sinks
Pulls rest of plate