Plate Tectonics

1
Plate Tectonics
2
Plate Tectonics - Targets

• Describe tectonic plate movement, types of
  boundaries and boundary features.

3
Plate TectonicsPlate Movements7 major plates
usually named after continent or ocean which they
are on.
4
(No Transcript)
5
Plate Tectonics Vocab

• Lithosphere
• The rocky, rigid layer of the earth including the
  crust and the upper mantle
• Asthenosphere
• The plastic-like layer of the earth located
  beneath the lithosphere

6
Pieces of the lithosphere (plates) float on the
asthenosphere.

• Hot magma rises cooler magma sinks creating
  convection currents (like boiling water)

7

• Convection Current As a material heats (water,
  magma, etc.) it rises, as it rises it cools, as
  it cools it sinks, as it sinks it heats, as it
  heats it rises.
• It is a cycle that continues.

8
Basalt high density
Granite low density
What happens when two plates collide?
9
Plate Tectonics

• When plates collide or slide apart, volcanoes
  earthquakes occur.
• Most (90) volcanoes earthquakes occur in the
  Ring of Fire around the Pacific Ocean.

10
(No Transcript)
11
Continental drift - Pangaea
12
Is This Man Insane?

• Alfred Wegener (1880-1930)
• Created the Theory of Continental Drift around
  1912
• Was not the first to suggest the idea, but was
  the first to present and publish evidence
• Most Scientists did not agree with his theory
  until long after his death (until the 1960s)

13
Is This Man Insane?

• Why didnt other scientists agree?
• Even though Wegener had extensive evidence that
  the continents were once connected, he could not
  explain what made the continents move.
• He thought that the continents were moving
  through the ocean floor, like icebreakers plowing
  through ice sheets
• He believed centrifugal forces (earths spinning)
  and tidal forces (the pull of the moon and sun)
  were responsible for moving the continents

14
What evidence did Wegener Have?
1. Puzzle-like fit of the continents The
continental shelves of present-day continents
match up
15
What evidence did Wegener Have?

• 2. Fossils
• fossils of identical plants and animals found on
  opposite sides of the Atlantic
• fossils found in areas that indicate a climate
  utterly different from the climate of today
• fossils of tropical plants, such as ferns and
  cycads, are found today on the Arctic island of
  Spitsbergen and Antarctica

16
Fossils of Gondwanaland
17
Fossils from Pangaea Animation
18
What evidence did Wegener Have?

• 3. Mountains
• the Appalachian mountains of eastern North
  America match with the Scottish Highlands
• the distinctive rock strata of the Karroo system
  of South Africa are identical to those of the
  Santa Catarina system in Brazil

19
What evidence did Wegener Have?

• 4. Glacial Evidence
• Glacial straitions (created by glacial movement)
  are found in areas that are warm in the present
  day. (Africa and Australia)

20
(No Transcript)
21
What might the Earth look like in 50 million
years?
22
What might the Earth look like in 150 million
years?
23
What might the Earth look like in 250 million
years?
http//science.nasa.gov/headlines/y2000/ast06oct_1
.htm
24
Plate Tectonics Vocab

• Subduction
• when oceanic crust sinks into the mantle and is
  recycled
• Only occurs at Oceanic-Continental convergent and
  oceanic-oceanic convergent boundaries

25

• Paleomagnetism-
• Earths magnetic field has switched several times
  in history and is recorded in rocks
• Used to develop the theory of plate tectonics
• Shows a mirror image of magnetic strips on either
  side of mid-ocean ridges

26
5 Types of Plate Boundaries

• Convergent Boundaries
• Continental-continental convergent
• Oceanic-continental convergent
• Oceanic-oceanic convergent
• 2. Divergent Boundaries
• 3. Transform Boundaries

27
Continental-Continental Convergent (C-C)

• When two pieces of land collide, both are pushed
  upwards because of the low specific gravity of
  continental crust
• Results in landforms such as Mountains
  (Himalayas, Appalachians)
• Can cause earthquakes and very rare volcanism

28
Locations of C-C boundaries
The Rocky mountains.
The Appalachians mountains
The Himalayan mountains
29
Oceanic-Continental Convergent

• When oceanic crust and continental crust collide,
  the oceanic crust (higher density) subducts
  underneath the continental crust (lower density)
• Results in landforms such as
• Volcanic Mountains (Cascades Mountains in US,
  Andes Mountains in S. America)
• Trenches (Peru-Chile Trench)
• Commonly causes earthquakes and volcanism

30
(No Transcript)
31
Cascade Mountains
32
Oceanic-Oceanic Convergent

• When two pieces of oceanic crust collide, the
  older oceanic crust (higher density) subducts
  underneath the younger continental crust (lower
  density)
• Results in landforms such as
• Volcanic Island Arcs (Japan, Phillippines,
  Aleutian Islands)
• Trenches (Marianas trench, Japan Trench)
• Commonly causes earthquakes and volcanism

33
(No Transcript)
34
(No Transcript)
35
Locations of O-O Convergent Boundaries
36
Divergent Boundaries

• When magma comes to the surface at a rift or
  mid-ocean ridge, creating new crust and causing
  plates to move away from each other
• Results in landforms such as mountains, mid-ocean
  ridges (Mid-Atlantic Ridge), rift valleys
  (African Rift Valley), and islands (Iceland)
• Can cause earthquakes and volcanism

37
Divergent Boundaries on Land
38
Locations of Divergent Boundaries
39
Rift Valley in Iceland
40
Transform Boundaries

• Where two plates slide horizontally past each
  other with no vertical movement
• Same as Strike-slip and shear faults
• Results in landforms such as faults (San Andreas
  Fault)
• Can cause earthquakes and very rare volcanism

41
(No Transcript)
42
Locations of Transform Boundaries
San Andreas Fault
43
Amount of Movement
44
(No Transcript)
45
(No Transcript)
46
Evidence of continental drift magnetic reversals
Oldest Rocks
Youngest Rocks
47
Divergent boundary Example mid-ocean ridge
Convergent boundary Example Cascade mountains
(west USA)
48
Transform boundary Example San Andreas Fault, CA
Fault crack in Earths crust where movement
occurs.
49
Plate Boundaries
Where in the world can we find examples of each
boundary? What features would you expect at each
boundary?