1. PLATE TECTONICS: PLATE BOUNDARIES

2. LAYERS OF THE EARTH Crust (brown/tan) Mantle (light & dark orange)
Core (yellow & white)

3. Beneath the lithosphere is the ASTHENOSPHERE
LAYERS OF THE EARTH
Lithosphere {
Crust and
upper mantle make up the LITHOSPHERE
rigid plates (OCEANIC & CONTINENTAL plates)
low temperature & pressure
Beneath the lithosphere is the ASTHENOSPHERE
plastic” mantle (flows, moves the plates)
higher temperature & pressure

4. PLATE TECTONICS the surface of the Earth is made of rigid plates
Size and position of plates can change over time
PLATE BOUNDARIES Edges of plates, where two plates “float” side-by-side, is where geologic activity takes place
Plates movement is from convection currents deep in the mantle

5. EARTH’S MAJOR PLATES:
Pacific, N. American, S. American, African, Eurasian, Indian, Antarctic

6. CONVECTION CURRENTS MOVE THE PLATES

7. CONVECTION CURRENTS MOVE THE PLATES
This continual movement (called convection currents) causes the crust to move in plate tectonics.

8. CONVECTION CURRENTS MOVE THE PLATES
Material in the mantle is heated by the radioactive core
it floats to the surface next to the crust
as it cools, it moves back down towards the core
7c Movement of matter among reservoirs is driven by Earth’s internal and external sources of energy

9. PLATE BOUNDARIES Divergent boundaries  plates move apart
Convergent boundaries  plates move together
Transform boundaries plates slide past  

10. DIVERGENT BOUNDARIES Make new crust
When two plates move apart and magma surfaces forming NEW crust (usually oceanic)
continental rift zones (landmass splits into two or more segments)
mid-ocean ridges (sea-floor is elevated)

11. DIVERGENT BOUNDARIES Make new crust
Rift valley continent-continent

12. DIVERGENT BOUNDARIES Make new crust: Sea Floor Spreading
Youngest rocks form at ridge
Older rocks are further from ridge
Oldest rocks are located at subduction zones

13. DIVERGENT BOUNDARIES Make new crust: Sea Floor Spreading
Every ~20,000 years the polarity of the Earth changes. This is change is reflected in the rocks, whose polarity is fixed once the magma is cooled.
As magma rises and cools, iron and magnesium minerals align themselves to the Earth’s magnetic field
“Magnetic Stripes” are formed
The Earth’s magnetic field reverses polarity
Magnetic stripes are mirrored on each side of the mid-ocean ridge

14. CONVERGENT BOUNDARIES plates colliding
Destroys old crust and forms new mountains
Three types of convergent boundaries

15. CONVERGENT BOUNDARIES plates colliding
Continent-continent convergence:
Folded mountains
Ex Himalayas Eurasian/Indian plates

16. CONVERGENT BOUNDARIES plates colliding: Subduction Zones
Subduction Zones: where ocean plates slide under another plate
Creates magma which moves upward, pushing up the land above it.
Magma/lava solidifies into intrusive/extrusive igneous rock
Heat from the magma can change the rock around it. Rock that recrystallizes without melting becomes metamorphic rock..
Denser oceanic plates always subduct beneath less dense continental plates

17. CONVERGENT BOUNDARIES plates colliding
Ocean-continent convergence:
Trench & Coastal Volcanoes
Andes Mountains Nazca & S.American plates

18. CONVERGENT BOUNDARIES plates colliding
Ocean-ocean convergence:
Trench & Island arc

19. When two plates slide past each other
TRANSFORM BOUNDARIES
When two plates slide past each other
no tearing or crushing - no damage occurs to the lithosphere
Faults –San Andreas Fault
Cause most earthquake damage

20. Summary of Plate Movements
Convection currents