1. Inside the Earth

2. The layered Earth Crust Mantle Core
These layers differ by temperature, density, composition and pressure

3. How do we know it’s not just solid rock?
The overall density of the Earth is much higher than the density of the rocks we find on the surface. (This tells us that there must be denser material inside)
Seismic and sound waves do not travel at a constant speed when going through the earth. Changes in speed and direction of waves mean they hit material of different density

4. The Crust Outer layer: we step on it! 5-100 km thick 2 types of crust
Oceanic (very dense, made of basalt)
Continental (less dense, made of granite)

5. Oceanic and Continental Crust
The oceanic crust is thinner than the continental crust but is much denser. It sinks into the layer underneath

6. The Mantle Middle layer thickest layer
Heat is transferred through this layer from the hot core to the cooler crust
Able to flow slowly due to convection currents
Flowing part called the asthenosphere

7. The Core Made mostly of iron and nickel 1/3 of the earth’s mass
Very hot
Radioactivity creates the energy that flows as heat to the other layers

8. To review

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

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

11. The crust is cracked
Earth’s crust is broken into about 19 pieces called TECTONIC PLATES
These plates move on top of the asthenosphere

12. Tectonic plates All of earth’s plates are moving and have always moved
Alfred Wegener was the first to provide evidence of the moving landmasses in a theory he called CONTINENTAL DRIFT

13. Evidence that the continents can move
From matching fossils on continents now far removed from each other.

14. More evidence From the precise, non-random location of earthquakes
Age of the ocean floor, showing a pattern of old and young rocks