1. BFRB Pages

2. In order to study Plate Tectonics, we must first reorganize our layering system for the Earth:
Old System – 4 layers
Crust (rigid)
(rigid)
Mantle (putty like)
(semi rigid)
Outer core (liquid)
Inner core (solid)
New System – 5 layers
Lithosphere
Asthenosphere
Mantle
Outer Core
Inner Core

4. ESRT’s Page 10 - Cross Section of the Layers of the Earth/ Temperature Graph/ Pressure Graph

6. What is Plate Tectonics?
Earth’s surface is made up of moving, solid pieces called plates
(Reference Tables pg 5)
Plate tectonics is the study of the formation and movement of these plates
Earth’s plates are part of the lithosphere
The lithosphere is the crust and the upper part of the mantle

8. Properties of the Crust
Oceanic crust is mainly made of the igneous rock basalt
Continental crust is mainly made of the igneous rock granite
Oceanic crust is denser than continental crust (b/c basalt is MAFIC…remember?...ROCKS!)

10. How Plates Move… Asthenosphere - middle part of the mantle
Similar composition to the rigid upper mantle, but it is partially melted
This makes the asthenosphere like a very thick “liquid” (viscous)
(think VERY THICK MUD or SILLY PUTTY)
The “liquid” property of the asthenosphere allows it to flow very slowly

12. How Plates Move…cont’d
You can think of the lithospheric plates as “floating” on the asthenosphere
The heat from inside the Earth causes convection currents to form in the asthenosphere
Where convection currents rise, molten rock forces the plates apart
Where the convection currents are sinking, the plates are moving together

14. DIVERGENT BOUNDARY CONVERGENT BOUNDARY MOUNTAIN BUIDLING NEW ROCK
LIQUID HOT MAGMA
LIQUID HOT MAGMA

15. Alfred Wegener’s Theory of Continental Drift
In 1915, German geologist and meteorologist, Alfred Wegener, first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core
Wegener hypothesized that there was a gigantic supercontinent 200 MYA, which he named Pangaea, meaning "All-earth“
Wegener published this theory in his book, On the Origin of Continents & Oceans
Wegener

19. OK, so we’re saying that the lithospheric plates move around on top of the asthenosphere, but what evidence do we have of this Plate Movement?

20. Evidence of Plate Movement
1) “Puzzle-like” fit
The shape of the west coast of Africa and the east coast of South America seem to fit together like a puzzle
It is believed that they were once together, but moved apart over time (Theory of Continental Drift)

22. Evidence of Plate Movement
2) Geologic Evidence
Similar fossil remains in Africa and South America of a reptile that is found nowhere else in the world
Distinctive rocks were also found in Africa and South America in regions where the two continents were most likely joined together

26. Evidence of Plate Movement
3) The majority of earthquakes and volcanoes are found in belts that occur along plate boundaries (where the plates are moving together or apart)
Ex. the Pacific Ring of Fire

27. RING OF FIRE – PACIFIC PLATE

28. Evidence of Plate Movement
4) Magnetic polarity reversals are recorded in ocean floor rocks as the sea floor spreads apart
During certain periods in Earth’s history, the magnetic fields have reversed
Iron in the igneous rocks on the ocean floor would shift before the magma cooled and hardened
If the polarity changed, new magma would cool with minerals shifted in the opposite direction

31. Evidence of Plate Movement
5) Heat flowing out of the rocks (temperature) is greatest where the rocks are spreading apart (rising convection current)
Heat (temperature) decreases where the rocks are moving together
(sinking convection current)

32. ESRT’s Page 5 - Plate Tectonic Boundaries

34. 3 Main Types of Plate Boundaries
I Divergent Boundaries
II Transform Boundaries
III Convergent Boundaries
A. Collision (C-C)
B. Subduction (O-C) & (O-O)

35. Plate Boundaries
Divergent Boundaries- plates are moving apart at spreading centers
These boundaries form mid-ocean ridges or rises (like underwater mountain ranges)
In between the 2 peaks of the ridge are valleys called rift valleys
Ex. mid-Atlantic Ridge, East Pacific Ridge

36. (Overhead View)

37.                         
Mid-Atlantic Ridge

39. Plate Boundaries
Transform (Sliding) Boundary - 2 plates slide past each other
The sliding movement often causes earthquakes to occur along faults
A fault is nothing more than a crack in the Earth’s crust where movement has occurred
Ex. North American Plate and the Pacific Plate are sliding past each other along the San Andreas Fault in California

41.                         
Someday, Los Angeles will be North of San Francisco!!!!!

43. Convergent Boundaries - two plates are converging or coming together (2 main types)
                        

44. Type 1 Collision Boundary
(continental-continental) (C – C) - the two plates moving together are both continental crust plates
The collision causes the plates to form a single, larger continent and the crust is pushed upward into a mountain range
Ex. Himalayan Mountains (including Mt. Everest). The Indian Plate and the Eurasian Plate are still moving together, so Mt. Everest is still slowly getting taller!

45. Continental crust
Continental crust

47. Type 2
Subduction Boundary - one of the plates plunges under (subducts) the other
Occurs between two oceanic plates (O-O), or an oceanic and continental (O-C) plate
Most common characteristic is a
deep-sea trench VIF!!!!
These trenches are the deepest spots in the ocean
Ex - the Marianas Trench is approx. 35,000 feet deep! Mt. Everest could be put into the trench and the peak would still be about 1 mile below the ocean’s surface!

49. Continental crust
Oceanic crust

51. Subduction Boundaries cont’d
Because oceanic crust is denser than continental crust, the oceanic crust will always subduct underneath the continental
Volcanoes always seem to form at subduction boundaries
If two oceanic plates converge, volcanic islands will form (ex - Aleutian Islands in Alaska)
If one plate is continental and the other oceanic, the volcanoes will form along the edge of the continental crust (ex - Cascade Mountain Range on Western US)

52. Subduction Boundaries cont’d
When the oceanic crust gets buried deeper and deeper under the Earth, it begins to melt into “liquid hot” magma.
Since “liquid hot” magma is less dense than the solid rock surrounding it, it has to rise.
When it rises, it comes to the surface of the Earth and forms volcanoes.