1. Layers of the Earth
Chapter 8 Section 1

2. Landforms Plateau- raised, flat land Gorge- deep crack in the plateau
Mountains-
Plains- flatlands with very few trees
Valleys- the land between two mountains
Many landforms are hidden by water.

3. Earth’s layers
Atmosphere- the gases that we breathe, weather occurs here, and it acts as an insulator protecting Earth
Crust- Outermost solid layer
Thickness varies
Continental crust- soil and rocks we live on km
Oceanic Crust- soil and rocks underneath the water km
Thinnest layer
Mantle-Below the crust
Thickest part of Earth
Outer portion is solid like the crust and the inner portion is so hot that the rock can flow like a liquid

4. Earth’s layers Core- Divided into the inner and outer core
Temperature s about 7,000 degrees Celsius
Outer core is liquid
Inner core is solid

5. Earth’s Crust 46.6 % is oxygen 27.7 % is silicon
The other elements are aluminum, iron, calcium, sodium, potassium, magnesium and trace other elements

6. Earth’s plates Lithosphere- the crust and the upper mantle
The lithosphere is broken into plates
There are about 20 tectonic plates that are all different sizes and shapes
They may be made of continental and oceanic crust

7. How does Earth plates help shape Landforms
Chapter 8 Section 2

8. Continental Drift
In 1912, Alfred Wegener suggested a reason for why the coastlines of certain continents looked like they fit together at one time.
He felt that the continents were all joined about 225 million years ago.
He called this Super continent- Pangaea- meaning all Earth

9. Continental Drift
Wegener thought all the continents were joined at one time and slowly drifted apart.
Proof for the Continental Drift Theory
The coastlines fit together like puzzle pieces
Plant and animal fossils found on West Coast of Africa matched those found on the East Coast of South America
Rock layers on W coast of Africa matched rock layers on E. coast South America

10. Problems
Wegener could not explain what forces moved the continents apart.
It was not until much later that scientist figured out the forces pulling the continents apart. They had to look to the seafloor.

11. Seafloor Spreading Harry Hess- 1960
He noticed that new seafloor forms at ocean ridges.
The magma rises and forms a ridge which pushes the old seafloor away
The magma rises when the plates pull apart

12. Convection current Arthur Holmes- 1930’s
He noticed that when you heat liquids the particles move faster and the hot liquid rises.
The hot liquid will eventually cool and sink down
This process of heating and cooling is a convection current.
Convection currents move the plates because the molten rock in the mantle rises then cools.

13. Final Proof of Continental Drift
Scientists studied the magnetism of the rocks near the Mid ocean Ridge
They saw that in some places the magnetism faced north while in some places it faced south.
Every half-million years the pattern flips. This proves that old rock is pushed from the newly formed rock at the Mid- ocean ridge

14. How do scientist explain Earth’s Features
Chapter 8 Lesson 3

15. Theory of Plate tectonics
Earth’s lithosphere is broken into 20 plates
The continents and the ocean floor make up the surfaces of the moving plates
The plates can move in one of 3 ways
Toward one and another
Away from one and another
Sliding past each other
The plates move about 2 cm each year

16. 50 million years from now
The plates will have begun to move back together
Another Pangaea like continent is expected

17. Plate boundaries A plate boundary is the area where two plates form.
A spreading boundary- where two plates move apart
Huge valleys can form
Responsible for sea floor spreading
Caused the Mid- Atlantic Ridge

18. Fracture Boundaries
At a fracture boundary- the plate slides past each other
A fault- a break in the Earth’s crust is made
Responsible for strong earthquakes

19. Colliding boundaries
Colliding boundaries occur when two plates push against each other.
1. One plate could slide beneath another- subduction zone and volcanoes occur
2. The two plates collide making mountains
It is also possible to have earthquakes and ocean trenches at this boundary

20. What Causes earthquakes and volcanoes
Chapter 8 Section 4

21. Earthquakes Plate movement occurs slowly so you can’t see or feel it.
The rocks jagged edges catch and pressure builds up
If the pressure is too strong then an earthquake happens

22. Earthquakes The point underground of an earthquake is the FOCUS
The point directly above the focus on Earth’s surface is the EPICENTER
The energy of an earthquake is carried in waves
The waves can move up or down
The waves can move back and forth
The waves can roll or move in a circular fashion

23. Earthquake magnitude
The greatest damage occurs near the focus and epicenter
As the waves move out- they lose energy
Almost all the largest earthquakes have occurred in California and Alaska
The boundary between the Pacific Plate and the North American plate

24. Richter Scale
The magnitude of an earthquake is measured on the Richter scale
Each increase of 1 on the Richter scale means a 31 times more energy is released

25. Volcanoes
A volcano- an opening in the surface of one of Earth’s plates through which magma rises.
Ash cloud- tiny bits of rock spew out the opening
Crater- steep-sided depression at the top of a volcano
Caldera-crater that is at least 1.6 km wide

26. Volcanoes Most often occur when one plate sinks beneath another
Most volcanoes occur on the ocean floor

27. Detecting an Earthquake or volcano
Seismometers- detect shaking or tremors in Earth’s crust
Magma rising or Earth’s plates moving
Tiltmeter- detects changes in the slope of the land
Seismograph- records the movement or tremors at faults