1. Earth Structure

2. Review of Density…
Density is an expression of the relative heaviness of a substance
mass per unit volume
grams per cubic centimeter (g/cm3)
The density of pure water is 1g/cm3.
Granite rock is about 2.7 times denser at 2.7g/cm3.

3. Formation of the Earth
The most dense material (Iron and Nickel) settled to the core (center)
Less dense matter (Silicates) formed the vast interior of the Earth (mantle).
The least dense material (Granite and Basalt) formed the Earth’s solid stony crust.
Volcanic eruptions continued through the crust.

4. Formation of the Earth Continued…
With each eruption, gases, water vapor, ash and lava (molten material) were brought to the surface.
The water vapor and gases formed the atmosphere.
As the Earth cooled the water vapor turned to water and the rains started.
The oceans formed from runoff. This also supplied the ocean with the mineral content it has today.

5. IGNEOUS ROCKS
Formed from molten material including volcanic lava, ash, or bombs as well as magma below Earth’s surface

6. TYPES OF IGNEOUS ROCKS
BASALT
GRANITE

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

8. Earth’s Layers
How are the earth’s layers similar to an egg?

9. The Crust Outer layer 5-25 miles thick Broken into pieces - plates
2 types of crust
Oceanic
more dense – 2.9g/cm2
made of basalt
Continental
least dense – 2.8g/cm2
made of granite

10. Oceanic and Continental Crust

11. The Mantle Middle layer Very thick Largest layer Upper Mantle –
“Floats on plastic”
3.3 g/cm3
Plastic Mantle –
3.5 g/cm3

12. The Core Made mostly of iron 1/3 of the earth’s mass Very hot
The most dense
Divided into 2:
The outer core
made up of liquid iron and nickel
density of 11.8g/cm3
The inner core
made up of solid iron and nickel
density of 16.0g/cm3

13. Physical Structure of the Earth (5 Layers)
Crust (less than 1% of the total volume of the Earth)
Lithosphere
rigid outer layer (crust)
Plate in the “plate tectonic theory”
Asthenosphere
solid rock that flows slowly (like hot asphalt)
“plastic” layer
Mantle (83% of the total volume of the Earth)
Mesosphere
middle layer (mantle)
Core (16% of the total volume of the Earth)
Outer Core
liquid
Inner Core
solid, very dense

15. Density Layering The overall density of the Earth is 5.5g/cm3
The crust changes continually to balance the amount of lighter and denser material.
Erosion and glacial melting decreases the density of the crust.
Volcanic eruption will increase the density.

16. Seismic waves
Evidence of distinct layers in the Earth with different densities comes from the observations of seismic waves (the vibrations generated by earthquakes and explosions)
As seismic waves move through the Earth, wave patterns may change indicating the waves were:
Reflected: bounced back due to extreme density
Refracted: directional change
Measuring the changes in the velocity of these waves as they travel through the Earth provides information on the number of layers and the thickness and composition of the layers.

18. -Original Subduction Zone
Ocean
Solid mantle=
Lithosphere
Continental Crust
Oceanic crust
Continental Crust
Solid Mantle
Solid Mantle
Plastic Mantle
Plastic mantle =
Asthenosphere
Label the following:
-Continental Crust
-Ocean
-Oceanic Crust
-Solid Mantle
-Plastic Mantle
-Original Subduction Zone
-New Subduction Zone