Download Plate Tectonics

Plate Tectonics
Chap. 17
Continental Drift
Seafloor Spreading
Theory of Plate Tectonics
Causes of Plate Motion
Continental Drift
The End
Seafloor Spreading – 17.2
Objectives
• Summarize the
evidence that led to
the discovery of
seafloor spreading.
• Explain the
significance of
magnetic patterns
on the seafloor.
• Explain the
process of seafloor
spreading.
I. Seeing the ocean floor
I. Seeing the ocean floor
A. Sonar
I. Seeing the ocean floor
A. Sonar
B. Magnetometer
II. Topography of Ocean Floor
*See map on p. 912
II. Topography of Ocean Floor
A. Mountain ranges (oceanic
ridges)
These are associated with earthquakes
and volcanos
II. Topography of Ocean Floor
A. Mountain ranges (oceanic
ridges)
B. Canyons (deep-sea trenches)
*See map on p. 912
III. Rock Studies
A. Youngest rocks near ridges
III. Rock Studies
B. Old rocks (over 180 million
years) cannot be found on
seafloor.
Continental rocks have been dates up to
3.8 billion years old.
III. Rock Studies
C. Thin layer of sediment present
(thickness increases further
away from ridge).
III. Rock Studies
D. Magnetism
Paleomagnetism is the study of the
Earth’s magnetic record.
III. Rock Studies
D. Magnetism
1. Magnetic reversals
have occurred.
A change in the Earth’s
magnetic field
III. Rock Studies
D. Magnetism
1. Magnetic reversals
have occurred.
2. Basaltic rocks show
these reversed fields.
III. Rock Studies
D. Magnetism
3. Reversals
are records
in the
seafloor.
III. Rock Studies
D. Magnetism
4. Scientists created isochrons.
A line on a map that connects points of
equal
.
III. Rock Studies
D. Magnetism
4. Scientists created isochrons.
A line on a map that connects points of
equal age.
IV. Seafloor Spreading
IV. Seafloor Spreading
A. Theory developed by Harry Hess
IV. Seafloor Spreading
A. Theory developed by Harry Hess
B. Magma surfaces at ocean ridges,
forming new crust.
IV. Seafloor Spreading
A. Theory developed by Harry Hess
B. Magma surfaces at ocean ridges,
forming new crust.
C. Crust is destroyed
at deep-sea
trenches
The End
Theory of Plate
Tectonics
I. Plates and Boundaries
I. Plates and Boundaries
A. Tectonic plates are named
(*diagram)
1. Pacific plate
7. Antarctic Plate
2. North American Plate
8. Arabian Plate
3. Eurasian Plate
9. Philipine Plate
4. African Plate
10. Caribbean Plate
5. South American Plate
11. Nazca Plate
6. Indian-Australian Plate
12. Cocos Plate
I. Plates and Boundaries
A. Tectonic plates are named
(*diagram)
B. Boundaries
Location where tectonic plates interact
I. Plates and Boundaries
A. Tectonic plates are named
(*diagram)
B. Boundaries
1. Divergent
Divergent Boundaries
Divergent Boundaries
 Plates are moving apart
Divergent Boundaries
 Plates are moving apart
 Causes thinning of the lithosphere
Divergent Boundaries
 Plates are moving apart
 Causes thinning of the lithosphere
 Often form on ocean floor
Divergent Boundaries




Plates are moving apart
Causes thinning of the lithosphere
Often form on ocean floor
Ex. Rift Valley in East Africa
I. Plates and Boundaries
A. Tectonic plates are named
(*diagram)
B. Boundaries
1. Divergent
2. Convergent
Convergent Boundaries
Convergent Boundaries
 Plates are moving together
Convergent Boundaries
 Plates are moving together
 Three types:
Convergent Boundaries
 Plates are moving together
 Three types:
1. Oceanic-oceanic
- one of the plates
undergoes subduction
Subduction
Process where one tectonic
plate slides below another.
Convergent Boundaries
 Plates are moving together
 Three types:
1. Oceanic-oceanic
- one of the plates
undergoes subduction
- some of the magma
returns to the surface
forming volcanic islands
and a trench
Convergent Boundaries
 Plates are moving together
 Three types:
2. Oceanic-continental
- Denser oceanic crust goes
under continental crust.
Convergent Boundaries
 Plates are moving together
 Three types:
2. Oceanic-continental
- Denser oceanic crust goes
under continental crust.
- Produces a trench and
volcanoes
Convergent Boundaries
 Plates are moving together
 Three types:
3. Continental-continental
- two continental plates
collide, forming a
mountain range.
Convergent Boundaries
 Plates are moving together
 Three types:
3. Continental-continental
- two continental plates
collide, forming a
mountain range.
- Ex. Himalayas
I. Plates and Boundaries
A. Tectonic plates are named
(*diagram)
B. Boundaries
1. Divergent
2. Convergent
3. Transform
Transform Boundaries
Transform Boundaries
 Plates are sliding past each
other.
Transform Boundaries
 Plates are sliding past each
other.
 No new crust formed, nor is
crust destroyed.
Transform Boundaries
 Plates are sliding past each
other.
 No new crust formed, nor is
crust destroyed.
 Characterized by shallow
earthquakes.
Transform Boundaries
 Plates are sliding past each
other.
 No new crust formed, nor is
crust destroyed.
 Characterized by shallow
earthquakes.
 Ex. San Andreas, California.
The End
Causes of Plate
Motion
I. Mantle Convection
I. Mantle Convection
A. Warmer materials move _____.
I. Mantle Convection
A. Warmer materials move _____.
B. Cooler materials move _____.
I. Mantle Convection
A. Warmer materials move _____.
B. Cooler materials move _____.
C. This creates a circular
movement.
II. Slab motion
II. Slab motion
A. At a ______ boundary new rock
causes the plate to be pushed.
(This is ridge push)
II. Slab motion
A. At a ______ boundary new rock
causes the plate to be pushed.
(This is ridge push)
B. At a ______ boundary the old
rock is pulled underneath
another layer. (This is slab pull).
III. Other questions
III. Other questions
A. How do mantle convection currents
originate?
III. Other questions
A. How do mantle convection currents
originate?
B. Are these currents permanent?
III. Other questions
A. How do mantle convection currents
originate?
B. Are these currents permanent?
C. How deep do these currents reach?
III. Other questions
A. How do mantle convection currents
originate?
B. Are these currents permanent?
C. How deep do these currents reach?
D. Does a downward convection cause a
subduction zone, or does a
subduction zone cause a downward
current?
The End
Image Sources
A.
http://www.manatee.k12.fl.us/sites/elementary/palmasola/
pshwgif4con1.htm
Image Sources
G.
H.
I.
Dead Sea. http://jan.ucc.nau.edu/~shand/image_archive.htm
http://www.gc.maricopa.edu/earthsci/imagearchive/
White Cliffs of Dover, England.
http://www.calstatela.edu/faculty/acolvil/geo_time.html
J.
Bituminous coal, Pittsburg mine.
http://www.appaltree.net/aba/coalspecs.htm
K. Gneiss. http://geology.csupomona.edu/alert/metamorphic/metaclass.htm
L. Schist.
http://gaia.busanedu.net/~creative/2002/cyber/rock/pages/30313_schist_cen
tral_museum.htm
M. Biotite Gneiss.
http://gaia.busanedu.net/~creative/2002/cyber/rock/pages/30469_biotie_gne
iss_kbise.htm
N. Quartzite. http://www.gc.maricopa.edu/earthsci/imagearchive/quartzite.htm
O. Quartzite. http://www.dragonlogic.com/Presentations/Slide_35.html
P. Marble.
http://gaia.busanedu.net/~creative/2002/cyber/rock/pages/30615_marble_kb
ise.htm
Q. Kyanite with garnet.
http://www.millenniumminerals.com/gemstones/kyanite.html