7-3: 7-3: Theory of Plate TectonicsTheory of Plate Tectonics

Lithospheric tectonic plates float on Lithospheric tectonic plates float on asthenosphereasthenosphere

3 types of plate boundaries (fill in 3 types of plate boundaries (fill in Tectonic Plate BoundariesTectonic Plate Boundaries sheet) sheet)

• TransformTransform• DivergentDivergent• ConvergentConvergent

Animation of plate boundaries (website)

TransformTransform

• slide past each other slide past each other horizontally horizontally (opposite direction)(opposite direction)

ex: San Andreas fault (CA)ex: San Andreas fault (CA) may produce earthquakesmay produce earthquakes

San Andreas Fault (website)

California California (2 plates)(2 plates) San Andres Fault San Andres Fault

North American Plate

Pacific Plate

• DivergentDivergent—plates separate—plates separate ocean-ocean=sea-floor spreading ocean-ocean=sea-floor spreading

(mid-ocean ridge)(mid-ocean ridge) continent-continent=rift valleycontinent-continent=rift valley

East African Rift (from Ethiopia to East African Rift (from Ethiopia to Kenya)– divergent boundaryKenya)– divergent boundary

• ConvergentConvergent—collide—collide oceanic-oceanic plates oceanic-oceanic plates creates creates

island arch island arch (volcanic)(volcanic)

…………animation (website)animation (website) ocean-continent plates ocean-continent plates (denser (denser

ocean plate moves DOWN and ocean plate moves DOWN and continental plate folds upward) continental plate folds upward) creates creates trenchtrench (at subduction zone) (at subduction zone) and and volcanoesvolcanoes inland inland

…………animation animation (website)(website) continent-continent plates continent-continent plates creates creates

mountainsmountains

……..animation (website) ..animation (website)

Aleutian Islands (between Alaska Aleutian Islands (between Alaska and Russia)and Russia)

formed as 2 oceanic plates collidedformed as 2 oceanic plates collided

Mt. St. Helens (Washington state)Mt. St. Helens (Washington state) Created by ocean-continent collisionCreated by ocean-continent collision

Andes Andes Mountain Mountain (ocean-(ocean-

continent continent convergent convergent boundary)boundary)

Himalayas (Asia)Himalayas (Asia) formed as 2 continents collided (still growing)formed as 2 continents collided (still growing)

Other WebsitesOther Websites

http://www.pbs.org/wgbh/aso/http://www.pbs.org/wgbh/aso/tryit/tectonics/shockwave.html  tryit/tectonics/shockwave.html  (what happens at the plate (what happens at the plate boundaries!)boundaries!)

Summary of Plate Tectonics Summary of Plate Tectonics (Enchanted Learning)  (Enchanted Learning)  

                                                                    

plate tectonics online tutorialplate tectonics online tutorial

QuestionQuestion

Sea-floor spreading occurs at which Sea-floor spreading occurs at which of the following types of tectonic of the following types of tectonic plates?plates?• a. transforma. transform• b. convergentb. convergent• c. divergentc. divergent• d. strike-slipd. strike-slip

Possible causes of tectonic motion —Possible causes of tectonic motion —convection currentsconvection currents (website) in (website) in asthenosphereasthenosphere

tracking plate motion with GPS—tracking plate motion with GPS—plates move only a plates move only a few cm per few cm per yearyear

What features of Earth are produced What features of Earth are produced by the movement of lithospheric by the movement of lithospheric plates? plates?

>>mountains, >>mountains, volcanoes, volcanoes, volcanic islands, volcanic islands, rift valleysrift valleys

1. Earthquakes are MOST LIKELY to 1. Earthquakes are MOST LIKELY to occur at the occur at the bordersborders of _________. of _________. >>>>>lithospheric plates>>>>>lithospheric plates

2. The 2. The collisioncollision of two continental of two continental plates can produce _____________.plates can produce _____________. >>>>>>a mountain range (not a >>>>>>a mountain range (not a single mountain)single mountain)

3. Plate tectonics describes 3. Plate tectonics describes movements MAINLY in ___________.movements MAINLY in ___________. >>>>Earth crust (or lithosphere)>>>>Earth crust (or lithosphere)

4. Which ocean was produced by sea-floor 4. Which ocean was produced by sea-floor spreading between Africa and South spreading between Africa and South America?America? >>Atlantic>>Atlantic

5. As distance increases from a mid-ocean 5. As distance increases from a mid-ocean ridge, the rocks grow older or younger?ridge, the rocks grow older or younger? >>>>>older>>>>>older

6. The “ring of fire” helps scientists 6. The “ring of fire” helps scientists predict areas where ___________ are predict areas where ___________ are likely to occur. likely to occur. >>earthquakes and volcanoes>>earthquakes and volcanoes

7. Volcanoes can be produced by the 7. Volcanoes can be produced by the collisions of ____& _______ plates.collisions of ____& _______ plates.>>oceanic and oceanic OR >>oceanic and oceanic OR continental and oceaniccontinental and oceanic

More questionsMore questions

A A convection currentconvection current of magma is of magma is made up ofmade up of

a. a rising more dense liquid and a sinking a. a rising more dense liquid and a sinking less dense liquid.less dense liquid.

b. a rising less dense liquid and sinking b. a rising less dense liquid and sinking more dense liquid. more dense liquid.

c. liquids of the same density.c. liquids of the same density. d. solids of different densities.d. solids of different densities.

How do mid-ocean ridges support How do mid-ocean ridges support both the idea of continental drift and both the idea of continental drift and the theory of plate tectonics?the theory of plate tectonics?• a. Oceanic lithosphere is destroyed at a. Oceanic lithosphere is destroyed at

mid-ocean ridges.mid-ocean ridges.• b. New crust forms at mid-ocean ridges.b. New crust forms at mid-ocean ridges.• c. Tectonic plates collide at mid-ocean c. Tectonic plates collide at mid-ocean

ridges.ridges.• d. The crust at mid-ocean ridges is old d. The crust at mid-ocean ridges is old

oceanic lithosphere.oceanic lithosphere.