Plate Tectonics Chap. 17 Continental DriftContinental Drift Seafloor Spreading Theory of Plate Tectonics Causes of Plate Motion.

Plate TectonicsPlate TectonicsChap. 17Chap. 17Chap. 17Chap. 17

Continental Drift

Seafloor Spreading

Theory of Plate Tectonics

Causes of Plate Motion

Continental Drift

The End

Seafloor Spreading – 17.2

ObjectivesObjectives

• 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.I. Seeing the ocean floorSeeing the ocean floor

I.I. Seeing the ocean floorSeeing the ocean floorA.A. SonarSonar

I.I. Seeing the ocean floorSeeing the ocean floorA.A. SonarSonar

B.B. MagnetometerMagnetometer

II.II. Topography of Ocean FloorTopography of Ocean Floor

*See map on p. 912*See map on p. 912

II.II. Topography of Ocean FloorTopography of Ocean FloorA.A. Mountain ranges (oceanic Mountain ranges (oceanic

ridges)ridges)

These are associated with earthquakes These are associated with earthquakes and volcanosand volcanos

II.II. Topography of Ocean FloorTopography of Ocean FloorA.A. Mountain ranges (oceanic Mountain ranges (oceanic

ridges)ridges)

B.B. Canyons (deep-sea trenches)Canyons (deep-sea trenches)

*See map on p. 912*See map on p. 912

III.III. Rock StudiesRock StudiesA.A. Youngest rocks near ridgesYoungest rocks near ridges

III.III. Rock StudiesRock StudiesB.B. Old rocks (over 180 million Old rocks (over 180 million

years) cannot be found on years) cannot be found on seafloor. seafloor.

Continental rocks have been dates up to Continental rocks have been dates up to 3.8 billion years old.3.8 billion years old.

III.III. Rock StudiesRock StudiesC.C. Thin layer of sediment present Thin layer of sediment present

(thickness increases further (thickness increases further away from ridge).away from ridge).

III.III. Rock StudiesRock StudiesD.D. MagnetismMagnetism

Paleomagnetism is the study of the Paleomagnetism is the study of the Earth’s magnetic record.Earth’s magnetic record.

III.III. Rock StudiesRock StudiesD.D. MagnetismMagnetism

1. Magnetic reversals have occurred.

A change in the Earth’s A change in the Earth’s magnetic fieldmagnetic field

III.III. Rock StudiesRock StudiesD.D. MagnetismMagnetism

1. Magnetic reversals have occurred.

2. Basaltic rocks show these reversed fields.

III.III. Rock StudiesRock StudiesD.D. MagnetismMagnetism

3. Reversals are records in the seafloor.

III.III. Rock StudiesRock StudiesD.D. MagnetismMagnetism

4. Scientists created isochrons.

A line on a map that connects points of A line on a map that connects points of equal equal ..

III.III. Rock StudiesRock StudiesD.D. MagnetismMagnetism

4. Scientists created isochrons.

A line on a map that connects points of A line on a map that connects points of equal equal ageage..

IV.IV. Seafloor SpreadingSeafloor Spreading

IV.IV. Seafloor SpreadingSeafloor SpreadingA.A. Theory developed by Harry HessTheory developed by Harry Hess

IV.IV. Seafloor SpreadingSeafloor SpreadingA.A. Theory developed by Harry HessTheory developed by Harry Hess

B.B. Magma surfaces at ocean ridges, Magma surfaces at ocean ridges, forming new crust.forming new crust.

IV.IV. Seafloor SpreadingSeafloor SpreadingA.A. Theory developed by Harry HessTheory developed by Harry Hess

B.B. Magma surfaces at ocean ridges, Magma surfaces at ocean ridges, forming new crust.forming new crust.

C.C. Crust is destroyedCrust is destroyedat deep-sea at deep-sea trenchestrenches

The End

Theory of Plate Tectonics

I.I. Plates and BoundariesPlates and Boundaries

I.I. Plates and BoundariesPlates and BoundariesA.A. Tectonic plates are named Tectonic plates are named

(*diagram)(*diagram)

1. Pacific plate

2. North American Plate

3. Eurasian Plate

4. African Plate

5. South American Plate

6. Indian-Australian Plate

7. Antarctic Plate

8. Arabian Plate

9. Philipine Plate

10. Caribbean Plate

11. Nazca Plate

12. Cocos Plate

I.I. Plates and BoundariesPlates and BoundariesA.A. Tectonic plates are named Tectonic plates are named

(*diagram)(*diagram)

B.B. BoundariesBoundaries

Location where tectonic plates interactLocation where tectonic plates interact

I.I. Plates and BoundariesPlates and BoundariesA.A. Tectonic plates are named Tectonic plates are named

(*diagram)(*diagram)

B.B. BoundariesBoundaries1. Divergent

Divergent Boundaries

Divergent BoundariesPlates 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.I. Plates and BoundariesPlates and BoundariesA.A. Tectonic plates are named Tectonic plates are named

(*diagram)(*diagram)

B.B. BoundariesBoundaries1. 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

SubductionSubduction

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.I. Plates and BoundariesPlates and BoundariesA.A. Tectonic plates are named Tectonic plates are named

(*diagram)(*diagram)

B.B. BoundariesBoundaries1. 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.I. Mantle ConvectionMantle Convection

I.I. Mantle ConvectionMantle ConvectionA.A. Warmer materials move _____.Warmer materials move _____.

I.I. Mantle ConvectionMantle ConvectionA.A. Warmer materials move _____.Warmer materials move _____.

B.B. Cooler materials move _____.Cooler materials move _____.

I.I. Mantle ConvectionMantle ConvectionA.A. Warmer materials move _____.Warmer materials move _____.

B.B. Cooler materials move _____.Cooler materials move _____.

C.C. This creates a circular This creates a circular movement.movement.

II.II. Slab motionSlab motion

II.II. Slab motionSlab motionA.A. At a ______ boundary new rock At a ______ boundary new rock

causes the plate to be pushed. causes the plate to be pushed. (This is (This is ridge pushridge push))

II.II. Slab motionSlab motionA.A. At a ______ boundary new rock At a ______ boundary new rock

causes the plate to be pushed. causes the plate to be pushed. (This is (This is ridge pushridge push))

B.B. At a ______ boundary the old At a ______ boundary the old rock is pulled underneath rock is pulled underneath another layer. (This is another layer. (This is slab pullslab pull). ).

III.III. Other questionsOther questions

III.III. Other questionsOther questionsA.A. How do mantle convection currents How do mantle convection currents

originate?originate?

III.III. Other questionsOther questionsA.A. How do mantle convection currents How do mantle convection currents

originate?originate?

B.B. Are these currents permanent?Are these currents permanent?

III.III. Other questionsOther questionsA.A. How do mantle convection currents How do mantle convection currents

originate?originate?

B.B. Are these currents permanent?Are these currents permanent?

C.C. How deep do these currents reach?How deep do these currents reach?

III.III. Other questionsOther questionsA.A. How do mantle convection currents How do mantle convection currents

originate?originate?

B.B. Are these currents permanent?Are these currents permanent?

C.C. How deep do these currents reach?How deep do these currents reach?

D.D. Does a downward convection cause a Does a downward convection cause a subduction zone, or does a subduction zone, or does a subduction zone cause a downward subduction zone cause a downward current?current?

The End

Image SourcesImage SourcesA. http://www.manatee.k12.fl.us/sites/elementary/

palmasola/pshwgif4con1.htm

Image SourcesImage SourcesG. Dead Sea. http://jan.ucc.nau.edu/~shand/image_archive.htmH. http://www.gc.maricopa.edu/earthsci/imagearchive/I. White Cliffs of Dover, England.

http://www.calstatela.edu/faculty/acolvil/geo_time.htmlJ. Bituminous coal, Pittsburg mine.

http://www.appaltree.net/aba/coalspecs.htmK. Gneiss. http://geology.csupomona.edu/alert/metamorphic/metaclass.htmL. Schist.

http://gaia.busanedu.net/~creative/2002/cyber/rock/pages/30313_schist_central_museum.htm

M. Biotite Gneiss. http://gaia.busanedu.net/~creative/2002/cyber/rock/pages/30469_biotie_gneiss_kbise.htm

N. Quartzite. http://www.gc.maricopa.edu/earthsci/imagearchive/quartzite.htmO. Quartzite. http://www.dragonlogic.com/Presentations/Slide_35.htmlP. Marble.

http://gaia.busanedu.net/~creative/2002/cyber/rock/pages/30615_marble_kbise.htm

Q. Kyanite with garnet. http://www.millenniumminerals.com/gemstones/kyanite.html