Primordial heat refers to the heat left over from the initial formation of the Earth from gravitational collapse of dust and gas in the solar nebula. Radiogenic heat refers to the heat generated within Earth by the radioactive decay of isotopes such as uranium, thorium, and potassium.

1. Earth’s Layers
Geology Unit

2. 1. Identify the different layers
of Earth.
2. Describe the layers and
function of Earth’s interior.
3. Explain how heat affects
the composition and transfer of
materials within each layer.

3. DEFINE…
• Crust
• Continental Crust
• Oceanic Crust
• Mantle
• Lithosphere
• Asthenosphere
• Outer Core
• Inner Core
• Density
• Volume
• Convection Currents

4. Three Layers
• The Crust
• The
Mantle
• The Core

5. The Crust
• The surface of Earth.
• The thinnest layer.
• Made of solid rock.
• Contains all the
mountains, rocks,
water, soil and land
features.
• Contains the
lithosphere, oceanic
crust and continental
crust. 5 – 25 miles
thick

6. Lithosphere
• Made from the Crust and Upper Mantle.
• “Litho” means “stone” in Greek.
• This is the layer in which we live because it contains the
oceanic and continental crust.

7. Crust
Lithosphere

8. Oceanic versus
Continental Crust
• Oceanic Crust:
• Below the ocean
• Consists of basalt
• Very dense
• Continental Crust:
• Forms and contains the
large landmasses
• Consists of granite
• Less dense
5 – 25 miles thick
3 - 5 miles thick

9. The Mantle • Divided into two parts:
• Upper mantle
• Lower mantle.
• Most of the mantle is
solid rock.
• The lower mantle rock
is softer.
• It makes up 85% of the
Earth’s mass.
• Temperatures can
reach up to 870 C.
1,800 miles thick

10. Asthenosphere
• Zone in the
Upper Mantle.
• Lithosphere floats
on top of it.
• Consists of hot,
plastic rock.
• “Asthens” means
“weak” in Greek.

11. Crust
Lithosphere
Asthenosphere

12. Transfer of Heat
• Radiation – The transfer of energy through space,
such as the transfer of heat from the Sun.
• Conduction – The transfer of heat within a material
or between two materials that are touching.
• Convection – The transfer of heat by the movement
of currents within a fluid.

13. •REMEMBER:
• Volume is THE AMOUNT
OF SPACE AN OBJECT
TAKES UP. If a liquid is
heated to a gas, it will take
up more space than
before.

14. Convection Currents
• Density = Mass
Volume
• What are Convection Currents???
The process of liquid heating and cooling in between the
mantle and outer core of the Earth.
• When a liquid is heated, the particles spread apart. This is
due to the fact that their energy is being converted into kinetic
energy (the energy of movement). Once these molecules
spread out, their volume increases causing their density to
decrease. Therefore, the hot liquid floats to the top and the
cooler water, which has decreased in volume and increased
in density, sinks to the bottom.
• This process occurs, repeatedly, in the mantle due to the heat
from the core and mantle.

15. Convection Currents
Takes place
between the
Mantle and the
Outer Core.
Since the density of the
liquid decreased, it
floated up, towards the
surface.

16. The Core
• The Core is Divided into
two parts:
• Outer Core
• Inner Core
Inner Core
Outer Core

17. Outer vs. Inner Core
• Outer Core – only liquid layer!
• Made up of liquid iron and nickel.
• This layer creates the Earth’s
magnetic field.
• Temperatures can reach up to
2,200 C.
• Inner Core
• The center of Earth.
• Made up of scorching-hot iron and
nickel. This layer stays solid
though due to intense pressure.
• This layer may also contain
oxygen, sulfur and silicon.
• Temperatures range between
9,000 C and 13,000 C.

18. Evidence
How do Scientists know about the interior of the
Earth?
Two forms of evidence:
• Direct evidence from rock samples
• Indirect evidence from seismic waves

19. Review…
Can you name the
different layers of the
Earth??
Number a piece of
paper 1 -5 and write
the name of each
layer.
4
5
3
2
1

20. Review…
1. Inner Core
2. Outer Core
3. Lower Mantle
4. Upper Mantle
5. Crust
4
5
3
2
1

21. Define the following terms:
1. Primordial Heat
2. Radiogenic Heat