1. THE MECHANISMS OF PLATE MOTION
PLATE TECTONICS
THE MECHANISMS OF PLATE MOTION

2. WHAT CAUSES
PLATE MOTION?

3. THE DRIVING MECHANISM “CONVECTION CURRENTS”
Driving force of Plate Tectonics
Thermal Convection Flow in mantle
Caused by differences in density
Warm less dense material rises
Cooler more dense material sinks

4. THE DRIVING MECHANISM “CONVECTION CURRENTS”
Heat Sources
Heat Gradient & Gravity
Contraction causes temperature & pressure to increase with depth
Decay of radioactive elements
Core heating of Mantle
Matierial rises towards the surface
Spreads out and drags the lithosphere with it

5. Whole-Mantle Convection
Ocean lithospheric slabs sink into lower mantle
Provides downward arm of convection flow
Hot mantle plumes at mantle-core boundary move heat toward surface

6. Mechanisms of Plate Motion - Causes
Slab-Pull - Descending Plates:
Cooling, older and more dense crust sinks and pulls the trailing lithospheric plate along
Cooling, Older and more dense slab of ocean crust sinks at a subduction zone through Asthenosphere pulling trailing lithosphere with it

7. Mechanisms of Plate Motion - Causes
Ridge (slab)-Push - Gravity:
Elevated ridge system push plates
Ocean slab thickens and becomes more dense as it cools causing it to slide down the sides of the ocean ridges under the influence of gravity, pushing lithosphere ahead of it

8. Plate Motion Mechanisms Hot Mantle Plumes
Caused by CONVECTION CURRENTS
Extends from mantle-core boundary
Produce Volcanic hot spots
Spreads out laterally under the lithosphere
Heated mantle material rises & spreads out moving the slabs with it

9. THE END

10. Tectonic Settings and Volcanic Activity