1. Chapter 28
THE CHANGING EARTH

2. The Layers of Earth

3. The Layers of Earth Crust- a thin surface covering the Earth.
2 kinds: Oceanic & Continental
What is a crack in the crust called??
Mantle- a thick molten layer between the core and the crust
Outer Core- molten iron, nickel, and oxygen
Inner Core- solid iron and nickel
The core’s temperature ranges between 2,000 oC and 5,000 oC…hot, hot, hot!

4. The Surface of Earth
Is there a pattern???
YES!!!

5. Continental Drift How is this possible?
The idea that the continents were once one landmass; a “super-continent” named Pangea
How is this possible?

6. mantle convection Heat transferred from the core to the
mantle produces a slow convection
of the material in the mantle
Thermal Convection Demo

7. Sea Floor Spreading
Mid-Ocean Ridges: mountain ranges on the ocean floor
The closer you get to a ridge, the younger the ocean floor.
Scientists concluded that the “new” land must be coming up through the ocean ridges

8. Plate Tectonics
Earth's outer layer is made up of tectonic plates, which are moving
explains the how and why behind mountains, volcanoes, and earthquakes

9. Plate Boundaries The area called where 2 plates meet

10. Divergent Plates
Plates are moving apart, allowing molten material to rise up and create new crust
Mid-ocean ridges
Sites of earthquakes and volcanoes

11. Convergent Plates Occurs when two plates approach each other
Subduction: one plate slides under another
Often the site of volcanoes
Collision can also occur between approaching plates
Mountains form

12. Convergent Plates
Subduction:
Collision:

13. Transform Plates Occurs when 2 plates slide past each other
No crust is created or destroyed
Earthquakes
What “famous” transform plate boundary is located in the US?

14. Review of Boundaries
Define each term. Have the students as a class mimic the movement of divergent, convergent, and transform boundaries using their hands. Use the hyperlinks as visuals while discussing each type of plate boundary.

15. Fault Def. Zone of weakness or a break in the Earth’s crust.
Ex. The San Andreas Fault

16. Earthquakes in the US: SAN ANDREAS FAULT
A well known transform boundary where the Pacific plate and North American plate meet
Average rate of motion across the San Andreas Fault is 2 in./yr. (3 million years L.A. will be next to S.F.)

17. Earthquakes in the US: OTHER FAULT LINES
Do EQ’s occur anywhere else in the US?
YES!...it’s been a while, but there are other fault lines in the US.
New Madrid fault in Midwest
250 miles long
Last major EQ in 1895
Eastern US
Last major EQ in 1886
Why would an EQ be so damaging in these areas today?

18. Earthquakes
Def. Vibrations of the earth’s crust from rock movement of plates along faults
As plates move, they stretch/compress, and stress builds up
When the rocks break or change shape, they release stored energy in the form of movement
LIKE A RUBBER BAND!
This creates seismic waves that move through Earth

21. Richter scale
A scale (1-10) used to measure the energy given off by earthquakes.
Ex San Fransisco – 7.1 on the Richter Scale (67 deaths, 4000 injuries, and 6 Billion Dollars of damage.)

22. Where do Earthquakes Occur?
Along plate boundaries, faults

23. Facts & Figures: Earthquakes
Largest EQ recorded in the US: 9.2
Largest in world: 9.5
500,000 detectable EQ’s each year.
More damage is caused indirectly from the EQ, not the EQ itself.
10,000 EQ’s will develop in southern California this year. However, most will not be felt
Powerful EQ’s rocked the Midwest in the 1800’s. One recorded a magnitude of over 8 and caused church bells to ring in Boston Massachusetts
Deadliest EQ: China in 1557, killing 830,000 people