1. Section 17.4 Causes of plate motion
Earth Science
Section 17.4
Causes of plate motion

2. Objectives Explain the process of convection.
Summarize how convection in the mantle is related to the movements of tectonic plates.
Compare and contrast the processes of ridge push and slab pull.

3. Main Idea Convection currents in the mantle cause plate motions.
Convection is the transfer of energy via the movement of heated matter.

4. Vocabulary
ridge push
slab pull
convection

5. Convection Many scientists now think that:
large-scale motion in the mantle (Earth’s interior between the crust and the core)
drives the movement of tectonic plates.
Convection - the transfer of thermal energy by the movement of heated material from one place to another.

6. Convection The cooling of matter causes it to: A convection current.
contract slightly and increase in density.
The cooled matter then sinks as a result of gravity.
Warmed matter is then displaced and forced to rise.
This up-and-down flow produces a pattern of motion called
A convection current.

7. Convection Currents

8. Convection in the Mantle
Convection currents
develop in the mantle
move the crust
move outermost part of the mantle
transfer thermal energy from Earth’s interior to its exterior.

9. Convection in the Mantle
The rising material in a convection current
spreads out as it reaches the upper mantle
causes both upward and sideways forces
These forces
lift the crust
split the crust
at divergent plate boundaries.

10. Convection in the Mantle
The downward part of a convection current occurs where
A sinking force pulls tectonic plates downward
Occurs at convergent boundaries.

11. Ridge Push
Ridge push is the tectonic process associated with convection currents in Earth’s mantle that occurs when
the weight of an elevated ridge pushes oceanic plates
The force of the magma moving upward pushes oceanic plates
the plates move toward a subduction zone.

12. Slab Pull
Slab pull is the tectonic process associated with convection currents in Earth’s mantle that occurs as
the weight of the subducting plate pulls the trailing crust
The plate is pulled into a subduction zone.

13. The Result Move the tectonic plates Causing Continental Drift
The convection currents in the mantle, in combination with ridge push and slab pull:
Move the tectonic plates
Causing Continental Drift
Wegener was correct!!!!!