1. Plate tectonics

2. Layers of the earth
From outside to inside: crust, mantle, outer core, inner core
Lithosphere = upper mantle & crust
The lithosphere acts as one layer

3. Plate tectonics Lithosphere is divided into several major plates
The plates can move and change shape and size
The plates are not exactly the same as continents.
Interaction of the plates is what we call plate tectonics

4. Plate tectonics
Plates move about 5 cm a year (the length your fingernail grows)
Plates move because of convection currents in the mantle.
Hot material moves up and cool material moves down

5. Effects of the Movement
Do you think moving 5 cm makes any difference in the Earth?
This small movement builds up great pressure.

7. Seafloor spreading Seafloor = floor at the bottom of the ocean
Seafloor spreading = rising magma forces the crust upward and apart, making new seafloor
All of the seafloor was made in the last 200 million years

8. Seafloor spreading

9. Effects of plate movement
Tectonic plates moving causes:
Earthquakes
Volcanoes
Mountain Building

10. What causes Earthquakes?

11. Evidence for plate tectonics
Earthquake patterns:
Earthquakes occur most often on plate boundaries

12. Evidence for plate tectonics
Paleomagnetism:
Scientists can see magnetic patterns in the seafloor
This allows us to see how new seafloor has formed over time

13. How can we find out the age of rocks at the bottom of the ocean?

14. Evidence for plate tectonics
Ocean Drilling:
Scientists can measure the age of the seafloor
This lets us see that new seafloor has formed from seafloor spreading recently