Scientists determine the composition of Earth's interior layers by measuring seismic waves from earthquakes. The speed and ability of different types of waves to travel through solids and liquids provides information about what materials exist in Earth's core and where transitions between layers occur. Earth has a solid inner core of iron and nickel surrounded by a liquid outer core, with a mantle divided into lithosphere and asthenosphere, and an outer crust made of oceanic or continental plates.

1. • What does the inside of the
Earth look like?

2. How do we determine the composition of the
Earth?
• Scientists cannot see the interior so they must
use other ways to figure it out!
• Earthquakes have many different types of waves
• These waves travel at different speeds
through solids and liquids
• Some waves don’t travel at all through liquids.
• Measuring these waves tells us what is in the
Earth’s core and where the materials change.

4. Earth Layers
• The Earth is divided into four main
layers.
*Inner Core
*Outer Core
*Mantle
*Crust

5. The Earth’s Crust
• The crust is the thinnest layer on Earth
• There are two types of crust
• Oceanic crust – made mostly of the igneous rock
basalt. Found under the ocean. Relatively thin.
• Continental crust – made mostly of granite. Found
under the continents. Relatively thick.

6. Special parts of the Crust
• Lithosphere
• Crust is the upper part of the lithosphere
• Broken up into large plates
• Asthenosphere
• Upper part of mantle, below lithosphere
• 130 – 160 km thick
• Cooler part of the mantle that the
lithospheric plates slide on top of.

9. The Earth’s Mantle
• Located directly above the outer core
• Starts below the crust
• Is the largest layer
• 80% of the Earth’s volume & 68% of Earth’s mass

10. The Earth’s Mantle
• Composed of more iron than the crust.
• Density, pressure, and temperature all increase
the deeper you go in the mantle
• Temperature ranges from 870 C – 2200 C

12. Special layers of the mantle
• Lithosphere – crust plus the upper, solid
part of the mantle. Forms plates.
• Asthenosphere – just under the
lithosphere. Slow moving “Silly putty”
layer on which the lithospheric plates
slid. (Solid rock that flows very slowly.)

14. Currents in the Mantle

15. The Earth’s Core
The Earth’s Core
• Composed of the inner and outer core
• Both are made of iron and nickel

16. • How do scientists know that
there is a solid inner core?

18. The Earth’s Outer Core
The Outer Core - Liquid
• Surrounds the inner core
• Temperature ranges from 2200 C – 5000 C
near inner core
• Molten (liquid) iron and nickel

20. The Earth’s Inner Core
The Inner Core - Solid
• Temperature reaches 5000 C
• Solid iron and nickel
• Usually both would be liquid but are solid in the
core because of the incredible pressure
• The solid core is the source of Earth’s magnetic
field

21. What do
you know
about these
layers?