1. 9.4 Testing Plate Tectonics
I. Evidence for Plate Tectonics
9.4 Testing Plate Tectonics
 A) Paleomagnetism is the natural remnant magnetism in rock bodies
1) Normal polarity—when rocks show the same magnetism as today’s magnetism
2) Reverse polarity—when rocks show the opposite magnetism

2. Polarity of the Ocean Crust

3. 9.4 Testing Plate Tectonics
I. Evidence for Plate Tectonics
9.4 Testing Plate Tectonics
 3) The discovery of strips is among the strongest evidence of seafloor spreading.

4. 9.4 Testing Plate Tectonics
Evidence for Plate Tectonics
9.4 Testing Plate Tectonics
B) Earthquake/ Volcano Patterns
Scientists found a close link between earthquakes and volcanoes with the plate boundaries.

5. The Pacific Ring of Fire
Evidence for Plate Tectonics
The Pacific Ring of Fire

7. 9.4 Testing Plate Tectonics
Evidence for Plate Tectonics
9.4 Testing Plate Tectonics
C) Ocean Drilling
1) The youngest oceanic crust is at the ridge crest, and the oldest oceanic crust is at the continental margins.

9. 9.4 Testing Plate Tectonics
Evidence for Plate Tectonics
9.4 Testing Plate Tectonics
D) Hot Spots
1) hot spot is a concentration of heat in the mantle producing magma that rises to Earth’s surface

10. 9.5 Mechanisms of Plate Motion
Causes of Plate Motion
9.5 Mechanisms of Plate Motion
 Scientists generally agree that convection in the mantle is the basic driving force for plate movement.
Convective flow is the motion of matter resulting from changes in temperature.

11. 9.5 Mechanisms of Plate Motion
Causes of Plate Motion
9.5 Mechanisms of Plate Motion
 Mantle Convection
The unequal distribution of heat within Earth causes the thermal convection in the mantle that ultimately drives plate motion.

12. 9.5 Mechanisms of Plate Motion
Causes of Plate Motion
ridge push
"gravity sliding" off of MORs
should be important for plates with lots of MOR boundary (e.g., African)
slab pull
cold, dense sub-ducting slab pulls plate with it
important for plates with lots of subduction zone boundaries (e.g., Pacific