1. Composition and Physical Layers of the Earth
Plate tectonics
Composition and Physical Layers of the Earth

2. Composition
The Earth is composed of three main layers based on the differences in chemical make up
1. the crust
2. the mantle
3. the core

3. Composition of the Earth’s crust
Continental crust (found on land) is made up mostly of granite rock.
Oceanic crust (found under the oceans) is made up mostly of basalt rock
Basalt rock is more dense than Granite rock
The crust is less than 1% of the Earth’s total mass

4. Composition of the Earth’s mantle
The Earth has an upper mantle and a lower mantle.
The upper mantle is partially melted (molten) and contains iron and silicon metal compounds
The lower mantle is completely molten and also contains iron. Magnesium, silicon and oxygen are also present.

5. Composition of the earths core
The Earth has an inner core and an outer core
They both contain large quantities of the element iron and small amounts of the elements nickel, sulfur and oxygen

6. Cool fact!
The solid inner core of the Earth spins faster than the rest of the planet.
The Earth’s outer core is hot liquid iron and other minerals that conduct electricity .
The combination of the spinning inner core and the electrical moving outer core generates the Earth’s magnetic field!

7. Physical layers
The earth is also separated into 5 physical layers based on differences in temperature and pressure
1. Lithosphere
2. Asthenosphere
3. Mesosphere
4. Outer core
5. Inner core

8. Earth Physical Layers
* Differences in pressure and temperature cause STRESS which separates the Earth into physical layers.
For example if rock gets hot enough it will melt and become a liquid but if we put enough pressure on the liquid rock it can be come a solid again

9. Lithosphere Outermost physical layer of the earth
Called the Rock sphere
Consists of the crust and the upper part of the mantle
This layer makes up the “Tectonic Plates”!
15 – 300 km thick
Why do you think the thickness varies?

10. Asthenosphere Called the weak sphere
It is the “soft” layer of the mantle
The “tectonic plates” move on top of this layer
250 km thick

11. Mesosphere
Strong lower part of the mantle
2,550 km thick

12. Outer Core Liquid molten iron Conducts electricity
Continuously moving by convection.
- remember studying convection in weather?
2,200 km thick

13. Inner core Solid iron Spins faster than the rest of the planet
Why is the inner core solid and the outer core liquid when they are both made up of the same element iron?

14. How do we know about these Layers?
Seismic waves (vibrations) created by earthquakes travel at different speeds depending on the density of each layer
The denser the material the faster the waves travel

15. Let’s review!!
What are the layers of the earth that are described by their composition?
What are the two types of crust?
What type of rock is found on each type of crust?
Which type of rock is most dense?

16. Review continued! What causes stress in the Earth’s layers?
What are the five physical layers of the earth?
Which physical layer makes up the tectonic plates?
Which layer is soft and the plates move on top of it?
Which layer is liquid, has strong magnetism and conducts electricity?

17. Pictures cited http://www.yorku.ca/esse/veo/earth/image/1-2-10.JPG