1. Layers of the Earth
Using a laser pointer, briefly highlight and describe the layers of the earth’s interior. Also highlight the fact that the earth has oceanic and continental crust.

2. CRUST/LITHOSPHERE thinnest layer floating on mantle
is cool and solid
between km thick
floating on mantle
Oceanic Crust: km thick
Continental Crust ~ 40 km thick

3. Mantle/Athenosphere average thickness is about 2880 km
solid but very hot
behaves like plastic, flowing and circulating slowly without breaking

4. Core radius ~ 3470 km half of the Earth’s diameter
metallic - made of iron and nickel
outer core - liquid
inner core -solid

5. Supercontinent Pangea – all lands Similar Reptiles and insects
Tropical forests
coal deposits
Discuss the theory of Pangea and show animation (click on link).
Tens of Millions of years ago!

6. Pangaea
Wegener revived the early idea of continental drift, contending that all of the present-day continents were connected,
side-by-side, as long ago as the Carboniferous (~300 Myr).
He called the supercontinental mass Pangaea,
Greek for ‘all lands’.

7. Today’s Continents
As soon as maps of the globe became available, people wondered about the arrangement of the continents and oceans. Hundreds of years later, valid explanations were constructed.

8. The crust and lithosphere are broken up into 25 Plates
USGS

9. Movement of the Plates:
Continental Drift
Evidence
How it works

10. Continental Drift: Fossil Evidence
Mesosaurus: purely freshwater reptile
Glossopteris: seeds too large to be effectively wind-transported

11. Continental Drift: Rock Ages
Rock ages showed strong correlation across the Atlantic, as did mountain ranges of similar age

12. Continental Drift: Geometry evidence
shape of the continents
eg. the shape of the west coast of Africa and the east coast of South America are remarkably similar and were perhaps once joined

13. More Evidence:Mantle Convection
Materials that can flow tend to lose thermal energy by the convection process. This explains circulation in a pot of water that is being heated from below in the same way it describes the convection currents in the Earth’s mantle.

14. Where convection rises sea floor spreading takes place.
Mantle Convection
Giant convection cells within the upper mantle drag the plates along laterally.
Where convection rises sea floor spreading takes place.
Where the convection cells descend they drag crust down, causing subduction

15. How does it work? Plates – pieces of the lithosphere
Plates fit closely together along cracks called
Plate Boundaries
Convection Currents  movement
Explain that the lithosphere is broken into pieces called plates. The place where the pieces fit together are the boundaries. Using a laser pointer, explain the theory that plate movement is caused by convection currents in the mantle.

17. Here is another version of the Rock Cycle

18. Mechanisms of Plate Tectonics:

19. Mechanisms of Plate Tectonics:2
Ridge-Push
RIDGE 1
TRENCH
MANTLE 3
drag
convective flow of mantle

20. Sea Floor Spreading
Hot material rose at the oceanic ridges, thus explaining the high heat flow and volcanic activity, and why the ocean floor is bulged up at the ridges.
The logical next step is that where continent and ocean meet, at the trenches, ocean crust is being returned to the mantle at the same rate it is being generated at the ridges.

21. Types of Boundaries Divergent Convergent Sliding
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.

22. To summarize……

23. C Sliding B Convergent A Divergent
plates are moving apart
new crust is created
Magma is coming to the surface
plates are coming together
crust is returning to the mantle
plates are slipping past each other
crust is not created or destroyed

24. C Sliding B Convergent A Divergent
Plates move against each other
Stress builds up
Stress is released
earthquake
2 continental plates  mountain range
Continental crust
 rift valley
Oceanic crust  mid-ocean ridge C
Sliding B
Convergent A
Divergent
2 oceanic plates or
oceanic + continental
subduction

25. DIVERGENCE: Sea Floor Spreading
Sea floor spreading, leads to continental drift
*This hypothesis makes a number of testable predictions.*

26. * Taking magnetic stratigraphy back in time is paleomagnetism. *
Magnetic Reversals
Interestingly, the polarity of the magnetic field shifts every Myr. That means rocks formed over time will record either ‘normal’ magnetic orientation (like today), or ‘reversed’. This leads to alternating bands of normal and reversed magnetism.
We are apparently headed into a polarity reversal, to be complete in ~3000 yr.
* Taking magnetic stratigraphy back in time is paleomagnetism. *

27. Paleomagnetism and Sea Floor Spreading
The magnetic stripes as products of steady creation of new ocean crust over geologic time.

28. Oceanic Ridges

29. The ridge is a Divergent Plate Margin and divergence takes place by Sea Floor Spreading.
From
New crust is added from upwelling magma (molten rock) from the upper mantle.
Older crust is pushed laterally away from the ridge axis – so that the sea floor spreads away from the ridge axis.

30. CONVERGENCE: Oceanic Crust – Continental Crust
The denser oceanic crust descends beneath lighter continental crust.
Coastal mountain chains develop due to compressive forces and volcanics (e.g., the Andes of South America).
Magma material rises from descending slab and builds volcanoes in
the rising
mountains.

31. CONVERGENCE: Oceanic Crust-Oceanic Crust
The oldest, densest crust normal descends beneath the younger crust.
Volcanic islands develop at the surface of the over-riding crust (forming Island Arcs) - e.g. Hawaii

32. Continental Crust-Continental Crust
CONVERGENCE:
Continental Crust-Continental Crust
Neither plate subducts (both too light).
Compressive forces driving plates fold and thrust the continental margins forming an extensive mountain belt (e.g., the Himalayan Mountains).

33. SLIDING: Slip-Strike Faults
Plate margins along which the plates slip by each other. Termed: Slip-Strike Faults/Transform Faults
On either side of a fault plate motions are in opposite directions.

34. The Big Picture
Remind students to look for their assigned boundaries and write down information to describe them.