1. Composition of the Earth

2. Earth Layers The earth isn’t a solid sphere
It is made of 4 major layers
Crust
Mantle
Outer core
Inner core

3. Crust “outer skin” Continental crust is about 70km thick
Oceanic crust is about 10 km thick
(this is why so much ocean drilling occurs)

4. Mantle About 2900 km thick Made of mostly Iron, Silicon and Magnesium
Asthenosphere is
the upper part of
the mantle
Very viscous

5. Outer Core
Approx 2100 km thick
Made of molten Iron and Nickel

6. Inner Core Approx 1300 km radius Solid ball of Iron and Nickel
Extremely hot
Stays a solid due to very high pressure

7. Quick check T/F – all layers are made of solid rock
T/F – thickest layer is the mantle
T/F – Inner core is made of liquid Iron and nickel
T/F – Outer core is made of silicon and oxygen

8. Answers F – all layers are made of solid rock
T – thickest layer is the mantle
F – Inner core is made of liquid Iron and nickel
F – Outer core is made of silicon and oxygen

9. Plate Movement
Caused by convection currents in the mantle

10. Definitions Trench – steep walled valley where 2 plates meet
Slab pull – plates subducting pulls the rest of the plate with it
Ridge Push – new forming rock pushes plate away from spreading centre

11. Definitions
Spreading Centre – area where plates move apart from each other
Rift Valley – a spreading centre that occurs on land

12. Types of Movement

13. Collisions at Plate Boundaries
Divergent
Pulling apart (spreading)
New rock is often formed here

14. Collisions at Plate Boundaries
Convergent
Plates come together
Often subduction occurs (one slides under the other)
**More on this in a moment**

15. Collisions at Plate Boundaries
Transform
Plates slide past each other
Produces earthquakes
Eg. San Andreas Fault

17. Convergent Boundaries
There are three different types of convergent boundaries
These depend on what type of plates come together
Oceanic-continental
Oceanic-oceanic
Continental-continental

18. Oceanic-Continental
The oceanic plate subducts beneath the continental plate
Eg. Coastal BC
The Juan de Fuca (oceanic) plate subducts under the North American (continental) plate
This causes coastal mountains and land volcanoes

19. Oceanic-Oceanic One plate will subduct beneath another
Volcanic activity and possible islands form

20. Continental-Continental
Plates are not likely to subduct
They push on each other and form mountains