1. Warm-up Week 13 Day 2 Describe Convection in your own words.
How is the crust destroyed at convergent boundaries?
How does the ocean floor grow bigger?

2. Warm-up Week 13 Day 2 Describe Convection in your own words.
Which type of plate boundary does each scenario represent?
Nick punches Mr. J in the face.
You cut your finger and a scab forms.
Handshake at the end of a soccer game.

3. “Testing Plate Tectonics”
9.4 & 9.5

4. Paleomagnetism Magnetic field. Study of changes in
“Paleo” = ancient
“Magne” = stone
“Net” = collection
“ism” = process
Magnetic field.
Study of changes in
earth’s magnetic field

5. Heat & Magnets Too hot! Cool again… ↓ magnetism. ↑ magnetism.
Points toward poles.
Compass!

6. Polarity?! How magnetic? Normal polarity Reverse polarity
Same direction as today
Reverse polarity
Opposite direction

7. Seafloor spreading
Youngest  ridge.
Oldest  farther.

8. Magnetic Reversals in Seafloor Spreading

9. Hot Spots. Tube of mantle rising toward crust. Plates move above.
Heat up.
Volcanoes.
Mountains & Islands.

10. Recall: Convection… Convection causes plates to move. Cycle of heat
Unequal tempo
Swirls liquid mantle
Plates float on top.
Plate move with “current”
Convection causes plates to move.

11. Q: What makes things move?
Pushes!
Pulls!
“FORCES”

12. Q: What makes plates move?
Ridge-Push
Divergent boundary
Creation of Ocean ridge
“Pushes” crust out of the way
Caused by gravity!
Slab-Pull
Convergent boundary
Subduction
“Pulls” crust along with it!