1. The Structure of the Earth
Earth’s Layers
The Structure of the Earth

3. Layers of the Earth
The layers of the Earth in order from the center out are.
Inner core
Outer core
Mantle
lower
Middle
upper
Asthenosphere
Lithosphere (crust)

4. The Crust The crust is the outermost layer of the Earth
Most widely studied and understood
Made up primarily of silicon and oxygen
Very thin when compared to the other layers
3-5 miles or 8 km thick under the oceanic crust
32 km or 25miles thick under the continental crust

5. The Crust The crust is the thinnest layer of the earth.
Oceanic crust
The mantle is the thickest layer of the Earth
Stretches from the lithosphere to the outer core

6. Continental Crust Composed mainly of granite
Thicker than oceanic crust (30-50 km)
Makes up only 25% of Earth’s surface
Less dense than oceanic crust

7. Oceanic Crust Oceanic crust is composed of primarily basalt
Basalt is much denser than the granite.
The less dense continents ride on the denser oceanic plates
Covered by water
Makes up 75% of Earth’s crust.
Thinner than the continental crust (5-10km)

8. The Lithosphere
The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the lithosphere.

9. Lithospheric Plates
The crust of the Earth is broken into many pieces called (lithospheric) plate.
The plates “float” on the soft, semi rigid asthenosphere

10. Mohorovicic Discontinuity
The imaginary line of discontinuity that separates the brittle crust of the earth from the mantle is the Mohorovicic Discontinuity or MOHO for short.
Boundary between the crust and the mantle in the earth.
Depth where seismic waves change velocity and there is also a change in chemical composition

11. MOHO

12. The Mantle The mantle is the thickest layer of Earth.
2,885 km thick, the mantle is 82% of Earth’s volume.
Upper mantle
Middle mantle
Asthenosphere
Lower mantle
Mesosphere (middle layer)
Mantle composition is an ultramafic rock called peridotite.
Solid rock layer between the crust and the core.

13. The Upper Mantle
The uppermost mantle is connected to the crust and forms the asthenosphere, which composes Earth's tectonic plates.
Part of the lithosphere

14. The Asthenosphere Middle Mantle
The asthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight
The movement of the middle mantle, asthenosphere, is the reason that the crustal plates of the Earth move.

15. Convection Currents
The middle mantle "flows" because of convection currents.
Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again
The cycle repeats over and over.
The molten rock below Earth’s surface is known as magma

16. The Lower Mantle
Called the Mesosphere because it is the middle layer of Earth.
“middle” sphere
2,250 km thick
lowest part of mantle

17. The Outer Core 1400 miles thick
It is so hot that the metals in it are all in the liquid state.
Composed of the melted metals of nickel and iron.
The flow of the inner core creates Earth’s magnetic field

18. Earth’s Magnetic Field
The flow of the fluid outer core around the solid inner core creates the Earth’s magnetic field

19. The Inner Core
The inner core of the Earth has extremely high temperatures and pressures
4, ,000 °C
3 million atmospheres
Pressure is so great that the metals are squeezed together and are not able.
forced to vibrate in place like a solid.
A ball of very hot metals.
Inner core dimensions
3,248 km radius
Composed of a sphere of hot, dense nickel and iron
1/3 of the Earth’s mass

20. Proof of Earth’s Structure
Seismic Waves: the waves that travel through the Earth’s interior during an earthquake.
Altered by the type of material that it travels through.
Timing and strength of seismic waves gives us a picture of Earth’s interior
Using the diagram which seismic wave travels through what type of substance?

21. Seismic Waves P-Waves S-Waves Travels through any substance
Compression wave
Any substance can be compressed
Solid, liquid, gas
S-Waves
Transverse, shear waves
Travels through solid only

22. Seismic Shadow Zone 104 -140 degrees from the epicenter
No direct P-waves
S-Waves are stopped entirely by the liquid core
P-Waves are bent

23. Think, Pair, Share
Write down the following question on a sheet of paper.
Have we ever seen part of the Mantle? Explain.
Include an illustration of the explanation.
Discuss the question with your partner and write the answer down.
Sit quietly until I say time is up