1. Shake, Rattle, and Roll the Earth
Plate Tectonics, Volcanoes, and Earthquakes

2. A Review of the Earth’s Interior
1. Crust
Solid material
upper portion of lithosphere
2. Asthenosphere
plastic in nature (partly solid, partly liquid, allows it to flow)
lower portion of lithosphere
can flow very slowly with changes in heat
3. Mantle
layer below asthenosphere
more solid material
Outer core
liquid iron and nickel layer
less dense than inner core
allows certain seismic (earthquake) waves to pass through
5. Inner core
solid iron and nickel layer
more dense than outer core
blocks seismic (earthquake) waves

3. A quick review of p. 10
What is the density of the outer core?
At what temp is the Earth at a depth of 3000 km?
What is the pressure at the top of the inner core?

4. The Untold
Tragedies of
Continental
Drift

5. Theory of Continental Drift
1912 – Alfred Wegener proposes the theory
but has no way to explain how the continents move
what was his
evidence that
they did?

6. Wegener’s Evidence South America and Africa “fit” together
Pangea – the original supercontinent
movement of plates separated to create the
positions of present day continents
one reason why champosaurs could exist in Canada!
See ESRT page 8-9
Similar fossils found in Africa and South America
how could that happen?
Similar rock formations
Granite formations in Europe similar to those in US

8. Plate Tectonics Proves Wegener Right!
By the 1960’s
- Wegener’s theory finally accepted
- mechanism for crustal plate movement found
Theory of Plate Tectonics
a theory that describes the crust as being composed of interlocking plates
these plates move above the asthenosphere
they can :
move toward each other (converging boundaries)
move away from each other (divergent boundaries)
move past each other (transform boundaries)
Plate tectonics studies the formation and movement of these plates

9. Proof of Plate Tectonics
Earthquakes and Volcanoes
– occur where plates collide or separate
– not random in where they occur
Magnetism
- Earth’s N-S poles periodically “switch”
- some igneous rock contains iron
- a record of these switches occur in the rock
- surrounding the Mid-ocean ridges
(places where new crust is formed)
Heatflow measurements
- measurement are highest at areas of new sea floor
creation
- decreases as one moves away from these points

10. Plate Movement
The plates move due to the cooling and heating of the asthenosphere
Hotter material rises, cooler material sinks
Form convection cells
Drives the crustal plates across the surface of the Earth

11. What are plates made of? Two (2) types of tectonic crust
Continental crust
composed of felsic igneous rock
continental crust rides on top of the plates due to its lower density
Large amounts of granite
Oceanic Crust
Tend to slide under continental crust when they collide
composed of mafic igneous rock
Large amounts of basalt
Remember: felsic = low density; mafic = high density

12. Kinds of Plate Boundaries

13. Diverging Boundaries Regions of spreading centers
Places where two plates are moving apart
Most have mid ocean ridges
Ex: Mid Atlantic Ridge
Contains rift valleys - deep valleys where new material pushes aside older ocean crust
fault lines run perpendicular to the valleys at various points
earthquakes occur along the ridge

14. Hot magma rises
Pushes on either side of the mid ocean ridge

15. Sliding or Transform Boundaries
Places where plates move past each other
A fault is a break or crack in the crust where
plates move against each other
Ex: San Andreas Fault near San Francisco
average rate of movement is 5 cm/yr
some areas have not moved for over a
century – possible earthquake spots

16. The San Andreas Fault in California
Side ways movement of the plates
Can get caught – pressure builds – finally released as…

17. E A R T H Q U A K E

18. Homework for Earth Science
Tuesday Nite HW
Read pp 295 – 300
Write out and answer questions 1 – 7 p 300
Wednesday Nite HW
Read pp 301 – 304
Write out and answer questions 1 – 5 p 304
Thursday Nite HW
Read pp 305 – 308
Write out and answer questions 1 – 5 p 308
Friday – QUIZ ON Plate Tectonics

19. Converging Boundaries I – When Plates Collide
Places where two plates move toward each other
If both plates carry continents
A collision boundary forms
Continental collisions produce mountains, big and small
- Ex: Himalayan Mtns, Appalachian Mtns

20. Continent- Continent Collisions

21. Converging Boundaries II Subduction Zones
A place where one plate slides under an overriding plate
Deep sea trenches – characteristics of a subduction zone
Ex: Marianas Trench off Japan
when two oceanic plates collide
chains of volcanic islands form
Ex: Phillipines
Occurs when an oceanic plate and a continental plate
collide
a mountain chain forms on the continent
some may be volcanic
a trench forms in the ocean

22. A diagram of a subduction zone