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Continental Drift

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Convection currents in the mantle. Scientists generally agree that convection occurring in the mantle is the basic driving force for plate movement. – PowerPoint PPT presentation

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Title: Continental Drift


1
Continental Drift
2
Continental Drift Theory
  • Proposed by Alfred Wegener in 1912
  • 250 million years ago, all of the continents were
    combined into one super-continent called
    Pangaea

The continents gradually drifted apart to where
they are today.
3
Plate Tectonics

4
Earths Major Plates
  • Eurasian Caribbean
  • Australian-Indian South American
  • Pacific African
  • Juan de Fuca Antarctic North American

5
Earths Major Plates
6
2 TYPES OF CRUST
1) OCEANIC - under ocean - thin -
very dense
2) CONTINENTAL - less dense
7
Theory of Plate Tectonics
  • Movement leads to the formation of volcanoes,
    earthquakes, ocean trenches, mountain formations,
    etc.
  • Plates move 1-10 cm per year

8
  • New Technology Supports Continental Drift Theory

Earthquakes and volcanoes occur in concentrated
areas. This suggests that the crust is divided
into pieces.
9
In about the late 1940s, Sonar was invented.
10
Bats use it!
11
Sonar brought Wegners theory back to life!
12
Sonar made it possible for us to observe the
ocean floor.
13
Soon, scientists observed a large mountain chain
running down the center of the Atlantic ocean.
14
They quickly found that the ridge ran around the
world!
15
Sea- floor Spreading
  • The longest chain of mountains in the world is
    the Mid-Ocean Ridge.
  • The mid-ocean ridge extends into all of Earths
    oceans.

16
Sea- floor Spreading
  • At this ridge, the molten material rises from the
    mantle and erupts (much like a volcano).
  • Molten material spreads out, pushing older rock
    to both sides of the ridge.

17
Sea Floor Spreading-
Makes the mid ocean ridge.
Animation
http//www.wwnorton.com/college/geo/egeo2/content/
animations/2_1.htm
18
Evidence - Drilling Samples
  • The Glomar Challenger did a drilling sample and
    found rocks that are farther away from the ridge
    are the older of the rocks. The younger ones were
    in the center of the ridge.

19
The further from the Mid Ocean Ridge the rocks
are, the older they are newer rocks in center
of ridge
20
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21
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22
What causes the plates to move?
Convection currents in the mantle. Scientists
generally agree that convection occurring in the
mantle is the basic driving force for plate
movement.
Utube
23
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24
Animation
25
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26
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28
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29
DIVERGENT PLATE BOUNDRY
  • 2 plates move AWAY from each other
  • Forms volcanoes (mid-ocean ridge), cause of
    seafloor spreading and rift valleys.

30
DIVERGENT PLATE BOUNDRY
  • 2 plates move AWAY from each other
  • Forms volcanoes (mid-ocean ridge), cause of
    seafloor spreading and rift valleys.

Sea floor spreading
Rift valley
31
If new crust is being added to Earths surface,
is Earth getting bigger?
32
CONVERGENT PLATE BOUNDRYS
  • 2 plates move toward each other (COLLIDING)
  • Three things can happen depending on what type of
    crust is colliding.
  • Oceanic to Continental (Subduction)
  • Continental to Continental
  • (Mountains Form)
  • 3. Oceanic to Oceanic
  • (Subduction)

33
Continental-Continental
  • Crust on continents have the same density, so
    they push against each other forming mountains.
  • EX Himalayan mountain range

http//www2.nature.nps.gov/GEOLOGY/usgsnps/pltec/c
ontvscont289x153.gif
34
Continental/Continental Convergence
Found- India (Mt. Everest)
35
Continental-Ocean
  • More dense crust of ocean is pulled beneath
    (subducted) the less dense continental crust.
  • Forms trench in ocean
  • Forms volcanoes on land

Subduction zone
animation
http//www2.nature.nps.gov/GEOLOGY/usgsnps/pltec/c
ontvsocn288x157.gif
36
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37
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38
What is subduction?
  • Subduction is the process by which the ocean
    floor sinks beneath the continental crust and
    back into the mantle.
  • Seen in the US on the Pacific Coast.

39
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40
The Ring of Fire has over 400 volcanoes , both
active and dormant. Most of the worlds
earthquakes also occur around this Ring of
Fire.
41
Oceanic/Oceanic Convergence
Found- Alaska (Aleutian Islands)
42
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44
TRANSFORM
  • 2 plates SLIDING HORIZONTALLY past each other
  • Forms earthquakes

45
Transform plates sliding horizontally past each
other.
Found- California (San Andreas Fault) Produces
earthquakes!!
All plates
46
Hawaiian Islands
How they are formed In action
47
Tsunami
How they are formed
Japan 2011
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