1. Plate Boundaries

2.  Earth’s outer layer is divided into many strong, moving lithospheric plates lithospheric Tectonic Plates Plate Tectonics

3.  Lithosphere = Crust + rigid upper mantle  Asthenosphere = a weaker mantle layer beneath the lithosphere Asthenosphere Tectonic Plates

4. Subduction  Subduction – when one plate slides underneath another, forms trench  Ocean crust (basalt) is more dense/heavier than continental crust (granite)  Ocean crust subducts beneath continental crust and ocean crust

5. Mantle convection slab-pull & ridge-push Why Do the Plates Move? Internal Heat & Gravity

6. Convergent Plate Boundaries  Plates collide

7. Continent-Continent  Shallow earthquakes  No volcanoes  Large mountain ranges Convergent Plate Boundaries

8. Continent-Continent Himalayas

9. Ocean-Continent  Shallow to deep earthquakes Convergent Plate Boundaries Plate Tectonics  Rising magma forms a continental volcanic arcvolcanic arc  Trench forms  Subduction takes place

10. Convergent Plate Boundaries Plate Tectonics Ocean-Continent Andes Cascades

11. Ocean-Ocean  Shallow to deep earthquakes (subduction zone)subduction zone  Rising magma produces an island arc. Convergent Plate Boundaries Plate Tectonics  Trench forms from subduction

12. Convergent Plate Boundaries Plate Tectonics Ocean-Ocean Japan Aleutians

13. Divergent Plate Boundaries Plate Tectonics  Plates move apart

14. Divergent Plate Boundaries Plate Tectonics Mid-Ocean Ridge Mid-Atlantic Ridge  Shallow earthquakes, volcanism  Mid-ocean ridges with rift valleys

15. Divergent Plate Boundaries Plate Tectonics Continental Rift East Africa Rift  Shallow earthquakes  Volcanic activity may occur  Rifting apart of continental crust  Rifting valley forms

16. Transform Plate Boundaries Plate Tectonics  No volcanism  Plates slide by each other  Shallow earthquakes San Andreas Fault