4.1

1
4.1 4.2 Plate Tectonics
2

• As explorers began bringing back information
  about the world, map makers began to notice the
  coastlines of continents could possibly be
  matched up
• Where the continents once touching????
• This led to the formation of a hypothesis.

3
Continental Drift

• Hypothesis that continents had moved.
• Pangaea single landmass
• Panthalassa all seas

4
Evidence for Continental Drift

• Fossils of plants and animals in areas that would
  have been joined in Pangaea
• Similar age and types of rocks
• South America (Brazil) and Africa

5
Evidence of Continental Drift

• 3) Sea floor Spreading
• Mid Ocean Ridges
• 4) Paleomagnetism

6
3) Seafloor spreading

• Newest rock is found at mid ocean ridges
• The mid ocean ridges are breaks where magma flows
  up from with in the earth forming new rock.
• Ocean floor is moving away from these rifts

7
Journal Seafloor spreading

• Where is the newest (youngest) oceanic rock found
  in the diagram?
• Where is the oldest oceanic rock found in the
  diagram?

A
B
C
8
(No Transcript)
9
Journal

• In your own words, describe seafloor spreading

10
4) Paleomagnetism

• As magma solidifies, the iron in it aligns with
  earths magnetic field.
• As earths poles switched, the iron bands
  polarity switched as well.
• There is a pattern on each
• side of a mid ocean ridge which
• shows that the sides where
• formed at the same time and
• then spread out!

11
(No Transcript)
12
The Theory of Plate Tectonics

• Describes continental movement and proposes an
  explanation
• 2 types of Crust Oceanic Continental which make
  up the lithosphere
• Below the lithosphere is the asthenosphere which
  had the ability to flow.

13
The Theory of Plate Tectonics

• The pieces of lithosphere float on top of the
  asthenosphere

14
What causes plate motion???

• Convection Currents warm material rising, cool
  material sinking
• Based on density differences
• Less dense materials rise (warm magma)
• More dense materials sink (cool magma)

15
(No Transcript)
16
What causes plate motion???

• In plate tectonics,
• cycle of warm magma rising up to the lithosphere
  where it cools and solidifies
• The new lithosphere moves away from the mid ocean
  ridges
• It cools and becomes more dense
• It eventually is subducted into the asthenosphere

17
3 main types of Plate Boundaries

• Divergent
• Convergent
• Transform/ Transverse
• Journal
• What does the word diverge mean?
• What does the word converge mean?

18
Journal Boundaries

• Divergent Convergent Transform/
• 
  Transverse

19
Divergent Boundaries

• Two plates moving away from each other
• Forms
• Rift Valley (Continental/Continental)
• Mid Ocean Ridges (Oceanic/Oceanic)

20
Convergent Boundaries

• The direct collision of two plates
• Oceanic-Continental
• Form subduction zones and volcanoes
• Continental-Continental
• Form mountains
• Oceanic-Oceanic
• Form Island arcs

21
(No Transcript)
22
Transform/Transverse Boundaries

• When two plates move past each other
• Form Faults
• Can you name a famous local fault???

23
(No Transcript)
24
Microplate Terranes

• Continents are a patchwork of terranes
• Terranes pieces of lithosphere
• Own geological history
• Separated by faults at its boundaries
• Own magnetic properties

25
On a separate piece of paper.

• Quiz yourself
• Name and describe the 3 types of plate
  boundaries.
• At what type of boundary would island arcs be
  found?
• What is the evidence for continental drift?