1. Earth’s Internal Processes
Section 3
Earth’s Interior

2. Inside the Earth Scientists learn about the interior by:
Drilling a hole 200 m into the oceanic crust
Studying the behavior of seismic waves
Earth’s interior is not the same throughout
Earthquake waves arrive at different times

3. Earthquake Observations
A boundary that marks a density change between layers is called a discontinuity.

4. Think – Pair - Share
Why do you think that scientists attempted to drill through oceanic crust instead of continental crust?

5. Earthquake Observations
Seismic recording stations like ours record seismic wave data.
Waves refract when they encounter sharp changes in density.

6. Shadow Zones P- and S- waves spread out from an epicenter
Waves travel through 105 degrees of arc
Shadow Zone – “dead zone” between 105 and 140 degrees
From 140 to 180 degrees only P-waves are recorded

7. Earth’s Interior 3
Shadow Zones

8. Earth’s Core Shadow zones reveal
A layer in the interior may be absorbing waves
S-waves turn into P- like waves
S-waves travel only through solids
Outer core may be a liquid

9. Inner Core P-waves are refracted as they pass through the inner core
Inner core must be denser than outer core
Pressure of outer core keeps the inner core solid
Outer core remains liquid because of the high temperatures

10. Composition of Layers Layers become denser with depth
Lithosphere – crust & upper mantle
Rocky materials – mostly silicates
Asthenosphere – weaker layer under lithosphere
Plasticlike layer
Mantle – divided into upper and lower
Made of silicates

11. Composition (con’t) Core – divided into outer and inner
Mostly nickel and iron
Earth may have formed from meteorite- like material
Material was forced together by gravity and melted
Densest materials are in the core, less dense ones float on the surface

12. .

13. Post PowerPoint What do scientists know about Earth’s interior?
How do they know this?

14. Question 1 Answer Section Check What is Earth’s core made of?
Earth’s core is primarily made of metallic material such as iron and nickel.

15. Question 2 Section Check
Earth’s internal layers become _______ with depth.
A. cooler
B. darker
C. denser
D. lighter

16. Section Check
Answer
The answer is C.

17. Question 3 Answer Section Check
Why can’t S-waves penetrate the liquid outer core?
Answer
S-wave only travel through solids. This suggests that the outer core is in a liquid state.