1. L.O: SWBAT describe the shadow zones.
Do Now: Questions 1-3

2. How do we know about the interior of our Earth?
If we have only been able to drill to a depth of about 12 km (7.5 miles) …
How do we know about the interior of our Earth?
Geologists study seismic information (earthquake waves) and meteorites to infer the composition of our Earth.

3. 1. HOW seismic waves BEHAVE:
The velocity of seismic waves change speed as they pass through different materials.
*P-waves pass through solids and liquids.
*S-waves only pass through solids.
S-waves “disappear” when they hit a liquid.

4. Earthquake always generate both P-waves & S-waves.
The seismic waves go in all directions away from the earthquake’s epicenter

5. The seismic waves should be picked up by seismographs all over the world…but..

6. Some places only get the P-waves.
other places, called “shadow zones” don’t pick up any earthquake waves!
Some places only get the P-waves.

7. Why?

8. the p-waves are refracted (deflected away)
by the core.
the s-waves disappear because they
are absorbed by the liquid outer core

9. * definition: Shadow zone: places that don’t receive seismic waves because the P-waves are refracted by the outer core and S-waves are absorbed by it

10. #2 METEORS
Meteors (and asteroids) are left-over material from the formation of the solar system

11. Meteors are made of iron & nickel
Meteors are made of iron & nickel. we infer that Earth’s interior is also made of iron & nickel, because Earth’s core & meteors formed at the same time 4.5 billion years ago.

12. Diamonds have helped us make inferences about Earth’s interior too!
Millions of atmospheres of pressure is needed to turn carbon into a diamond, so we can infer that Earth’s interior pressure must be millions of atmospheres strong!
Diamonds can only form under very intense pressure. This gives us clues about the pressure deep inside Earth.