1. Inside the Earth Earth’s Structure

2. Earth’s Layered Structure
Earth’s interior consists of three major zones defined by their chemical composition—
the crust,
mantle,
and core.

3. Review of Earth’s Interior
Chemical Classification
Crust -
Continental Crust:
Mostly granite
Average thickness 30km
Oceanic Crust:
Mostly basalt
Average thickness 5 – 8 km
Denser than continental crust
Thin, rocky outer layer

4.                                                                                             
Divisions in the Earth's Interior

5. Inside the Earth’s Interior
Mantle
Approximately 2900 km thick
870o to 2200o
Composed of silicon, oxygen, iron and magnesium
Upper layer contains the asthenosphere

6. Inside Earth’s Interior
Core
Approximately 3550 km thick
2200o to 5000o
Composed of iron and nickel
Tremendous pressure

9. Earth’s Layered Structure

10. Inside Earth’s Interior
Physical Classification: 5 layers based on physical traits
Lithosphere:
Crust and uppermost part of mantle
Rigid layer of rock
“Litho” means stone
Approximately 100 km thick

11. Lithosphere
The Earth’s crust and upper mantle are broken into sections called plates
Plates move around on top of the mantle like rafts

12. 2 Types of Plates
Ocean plates - plates below the oceans made up of mostly basalt
Continental plates - plates below the continents made up of mostly granite

14. Inside Earth’s Interior
Asthenosphere:
Upper mantle – higher temperature and pressure
Soft rock that the lithosphere floats on
“Asthenes” means weak
Convection currents in the asthenosphere cause plates to move
Mesosphere
Rest of mantle which is solid material due to high pressure

16. Earth’s Outer Core At the center of Earth is the core.
The core is made mostly of iron and nickel and possibly smaller amounts of lighter elements, including sulfur and oxygen.
The core is about 4,400 miles (7,100 kilometers) in diameter, slightly larger than half the diameter of Earth and about the size of Mars.
The outermost 1,400 miles (2,250 kilometers) of the core are liquid.
Currents flowing in the core are thought to generate Earth's magnetic field.

17. Earth’s Inner Core
Geologists believe the innermost part of the core, about 1,600 miles (2,600 kilometers) in diameter, is made of a similar material as the outer core, but it is solid.
The inner core is about four-fifths as big as Earth's moon.
Earth gets hotter toward the center. Geologists believe the temperature of Earth's outer core is about 6700 to 7800 degrees F (3700 to 4300 degrees C). The inner core may be as hot as 12,600 degrees F (7000 degrees C)--hotter than the surface of the sun. But, because it is under great pressures, the rock in the center of Earth remains solid.

19. How deep is deep?
The deepest mine in the world, a gold mine in South Africa, reaches a depth of 3.8 km.
You would have to travel 1600 times that to reach the Earth’s center.
6,000 km

20. Exploring the Earth
Geologist use two main types of evidence to learn about the Earth’s interior.
Direct evidence from rock samples.
Indirect evidence from seismic waves.

21. Rock Samples
Rocks from inside Earth give geologists clues about Earth’s structure.

22. Rock Samples
Geologists have drilled holes as deep as 12 km into Earth.
The drills bring up samples of rocks to study.
Geologists can make inferences.
In addition, forces inside the Earth blast rock to the surface from depths of more than 100 km.
These rocks provide information about the interior.

23. Finding Indirect Evidence
Seismic Waves
Primary Waves (P waves)
Back and Forth motion
First to arrive after earthquake
Can travel through liquid and solids
Secondary Waves (S waves)
Up and Down motion
Cannot travel through liquid

24. Seismic Waves Paths Through the Earth
S Waves
P Waves

25. Finding Indirect Evidence
The denser the rock the more quickly the wave will travel
As P waves travel from one type of material to another the waves bend or refract
S waves stop at the outer core indicating that it must be liquid

26. Finding Indirect Evidence
The Moho
The name of the boundary between the mantle and the crust. Named for Andrija Mohorovicic
An area where seismic waves suddenly speed up (due to rock density)

27. Shadow Zone
Absence of P waves from about 105 degrees to 140 degrees around the globe from an earthquake
Can be explained if Earth contains a core composed of materials unlike the overlying mantle

28. Earth’s Interior Showing P and S Wave Paths