1. Earth Science: Plate Tectonics

2. How do we see inside the Earth?
Waves
Seismic waves
Seismology
Study & measurement of seismic waves
What do we know that produces seismic waves?

4. Two main types of waves
“P” Waves
“S” waves

5. P-waves “P” or Primary waves Longitudinal Compress and expand Fastest
Travel through all mediums ( solid, liquid and air)

6. “S” Waves “S” or Secondary waves Transverse
Vibrate up and down / side to side
Slower than “P” waves
Only travel through solids

8. Layers of the Earth

9. The Crust Surface layer Like an eggshell Thin Brittle Can crack
Two regions:
Oceanic (Basalt rock)
Continental (granite rock)
Crust is less dense than the mantle
Like ice on water; the crust floats on the mantle

10. The Mantle

11. The Mantle Rocky Like the crust Silicon Oxygen
Iron, magnesium, calcium are heavier elements
Mantle is denser
How does the Earth’s crust add to the density of the mantle?
Weight bearing down on the mantle…it compresses the minerals, increasing the pressure and squeezing them into rocks.

12. The Mantle Higher temperature Why? Increased pressure
Decay of radioactive elements

13. Layers of The Mantle Upper mantle Lithosphere Asthenosphere
Rigid rock upper portion of upper mantle
Asthenosphere
Lies beneath lithosphere and “flows” like plastic
It is solid…silly putty
Lower mantle

14. The Core Two layers: inner and outer core 15% Earth’s volume
30% Earth’s mass
2x as dense as the Earth’s mantle
Why?
Made of metallic iron
Inner core is VERY hot!
Some places as hot as the surface of the sun!

15. The Inner Core Solid Iron How?
Pressure from Earth keeps Iron packed tightly; doesn’t allow it’s atoms to flow

16. The Outer Core Outer Core Liquid Iron Less pressure
Flows and spins as Earth rotates
Creates convection currents
Affects Earth’s surface
Produces electrical charge
Possibly responsible for Earth’s magnetic field

17. Magnetosphere

18. Convection Currents What are convection currents?
Current of heat flows from core to crust
This sets up a convection current in the mantle

19. Effects of Convection Currents
When the current comes at a weaker part of the crust, for example at a volcano, magma comes above the earth's surface.
This is called plate tectonics.
The movement of these plates goes very slowly.
The bumping of two tectonic plates causes an earthquake.
The convection current along the bottom of the crust causes the moving of the tectonic plates.

20. Continental Drift & Tectonic Plates
Wegner’s Hypothesis on Continental Drift
The World’s continents are in motion
At one time, the continents were joined together as one…
This was known as Pangea
They fit together like a jigsaw puzzle

21. What caused the continents to separate?

22. Continental Drift
Wegner’s theory that proposed the landmass known as Pangea started breaking up
Separated into two parts: Laurasia and Gondwanaland
Wegner’s theory of the separation of Pangea was supported by fossil, biological, climatological and geological evidence

23. Seafloor Spreading Seafloor is not permanent
Constantly renewing itself
Mid Atlantic Ridge (longest & tallest mountain range in the world, center of the Atlantic Ocean)
Forms islands: Iceland and Azore
There are rifts in the mountains

25. Plate tectonics Continents move because they are embedded in plates
The plates shuffle or move atop of the Earth’s surface
Plates move in different directions and different speeds from each other
There are nine large plates and several smaller plates

27. Plate Boundaries Divergent Boundaries Plates move away from each other
Comes from rock in athenosphere
Partially melted
The rock partially melts = lava
It was magma before it left the surface of the Earth

28. Convergent boundaries
Plates move toward each other

31. Transform fault boundaries
Plates slide past each other

34. Earthquakes Devastating Stress (force) applied to rock
Stress causes strain
Eventually the rock cannot bend anymore
It breaks and releases stored energy
The released energy ( Seismic Waves) travel out in all directions

35. Earthquakes cont The initiating site of the seismic wave: focus
The point at Earth’s surface directly above the focus: epicenter
Measured on a Richter Scale ( the incraments are ten fold in magnitude…

38. Tsunami
Seismic sea wave
Created by an earthquake