Layers of the Earth

1. Layers of the Earth For third and forth graders By Jennie Lahr Student at Northern Michigan University

2. Introduction • The earth has four main layers • Crust • Mantle • Outer Core • Inner Core

3. The Earth’s Crust • Very thin compared to the other three layers • Oceanic crust is about 3-5 miles thick under the oceans • Continental crust is about 25 miles thick under the continents • Crust of the Earth is broken into many pieces called plates

4. Notice how thin the Earth’s crust is in comparison to the other layers.

5. The Earth’s Mantle • The mantle is the layer located directly under the crust • It is the largest layer of the Earth, 1800 miles thick • Composed of very hot, dense rock

6. The Earth’s Outer Core • Is located about 1800 miles beneath the crust • The outer core is about 1400 miles thick • It is composed of the melted metals nickel and iron • Temperature varies from 4000 degrees F to 9000 degrees F

7. This diagram focuses in on the outer core.

8. The Earth’s Inner Core • The inner core begins about 4000 miles beneath the crust • It is about 800 miles thick • Temperatures may reach 9000 degrees F • The pressures are 45,000,000 pounds per square inch (this is 3,000,000 times the air pressure on you at sea level) • Temperatures and pressures are so great that liquids are forced into solids

9. This diagram shows all the main layers of the Earth and their characteristics.

10. How do we know there are 4 layers • P waves (primary waves) • S waves (secondary waves) • P waves pass through the center of the earth and S waves can not because of the liquid outer core • Explanation of P and S waves • In depth explanation of interior waves (this site is recommended for children in middle school and higher)