1. Layers of the Earth

2. The Earth’s Interior Most scientists agree that soon after Earth’s formation, Earth was a large ball of molten (melted) rock. As time passed, the molten materials cooled, hardened, and separated into layers.

3. Composition (What it is made of) Crust Mantle Core

4. The Crust Thin, outer layer that covers the planet 8 - 32 km thick 2 types of crust –O–Oceanic (very dense, made of basalt) –C–Continental (less dense, made of granite)

5. Oceanic and Continental Crust

6. The Mantle Middle layer Very thick layer (2900 km thick) Made of silicon, oxygen, iron, magnesium - solid that has the ability to flow = plasticity

7. The Core Central part of the planet Made of iron and nickel 1/3 of the earth’s mass Very hot - inner core = solid - outer core = liquid

8. Earth’s Layers How are the earth’s layers similar to an egg? Shell=crust Egg white=mantle Yolk=core

9. Physical Structure of the Earth (5 Layers) Lithosphere- rigid outer layer (crust) Asthenosphere- solid rock that flows slowly (like hot asphalt) Mesosphere- middle layer Outer Core- liquid layer Inner Core- solid, very dense

10. Do scientists travel to the inside of Earth to learn about the layers? High temperatures and tremendous pressure in the Earth’s interior would make traveling there and remaining alive impossible. Even the deepest oil wells are only a few kilometers deep, and the diameter of the Earth is 12,756 km.

11. So, how do we know about the layers? The study of behaviors of seismic waves has allowed geologists to piece together information about the parts of Earth that man has never seen directly. When earthquakes occur, vibrations are sent out through the Earth. These vibrations are called seismic waves.

12. Seismic Waves Seismic waves can travel along the surface of the Earth or through its interior. The waves speed up, slow down, or stop depending on the type of material (medium) that they are passing through. For example: S-waves are a type of seismic wave that can't go through liquid. Therefore, scientists know that the part of the Earth that S-waves can't penetrate is made up of liquid.