The Earth is divided into three main layers based on their composition and density: 1. The crust is the solid, outermost layer made of silica and oxygen. It varies in thickness from 5-60 km. 2. Below the crust lies the mantle, the largest layer made of hot, soft rock reaching 2900 km thick. It is divided into the upper and lower mantle. 3. The innermost layer is the core, separated into a liquid outer core made mostly of iron and responsible for Earth's magnetic field, and a solid inner core of iron and nickel.

1. Earth’s Layers
SC Standard 8-3.1 Summarize the 3
layers of Earth on the basis of relative
position , density and composition.

2. Earth is divided into 3 basic
layers:
1. Crust
2. Mantle
3. Core
These layers are then
subdivided into smaller layers.

3. CRUST :
•Is the outermost layer on the earth.
(EGG SHELL)
•Thickness varies. Under mountains
it can be as thick as 60 km and less
than 5 km under the ocean.
•It is the least dense of all the layers.
(lightest layer)
•It is made up of silicon and oxygen.

4. 2 TYPES OF CRUST :
• Oceanic crust is
very dense, made
of Basalt.
• Continental crust
is less dense,
made of Granite.

5. GRANITE
BASALT

6. MANTLE :
• Located below the crust. (Egg
White)
• It is the largest layer (about 2900
km thick). Rock layers are
movable. (plastic)
• Hot soften rocks made up of more
magnesium and iron.
• Density increases with depth due
to increase in pressure.

7. MANTLE : Divided into 2 parts
• Upper mantle
• Lower mantle.
• Contains the “Moho” (Mohorovicic
discontinunity)

8. CORE : (Egg Yolk)
• Located below the Mantle.
• It is divided into 2 layers
Outer Core
Inner Core

9. Outer Core :
• is liquid and is made up of mostly
iron (easily magnetized)
• The movement of materials in the
liquid O.C. is inferred to be the
cause of Earth’s magnetic field!
(highlight in your notes)
• The O.C. is about 2250 km thick.

10. Inner Core :
• Is the center of the Earth – 1200
km thick.
• It’s solid iron and nickel. Most
dense layer (heaviest) (highlight in
notes)
• The increased pressure
causes the I.C. to be solid

11. In your notes lets draw together a diagram of the Earth.
CRUST
MANTLE
OUTER CORE
INNER CORE

13. Look at the sub-layers of the mantle
LITHOSPHERE:
• This is the “crunchy” layer of the Earth.
• It includes the crust and the very
uppermost part of the upper Mantle
ASTHENOSPHERE:
• Soft – can bend like plastic, layer in the
upper portion of the mantle
• It is located right below the Lithosphere.
Lithosphere floats on this layer (like jello)

14. Lithosphere
CRUST Asthenosphere
MANTLE
OUTER CORE
INNER CORE

15. In Review:
1.What are the 3 main layers of the Earth?
Crust, Mantle, Core
2.Which layer is the least dense?
Crust
3.Which core layer is solid iron and nickel?
Inner core
4.What is the name given to the “crunchy” layer of
the crust and uppermost part of the mantle?
Lithosphere
5. The motion in this layer is the reason Earth has
a magnetic field.
Outer core