7-3: Theory of Plate Tectonics Lithospheric tectonic plates float on asthenosphere Lithospheric tectonic plates float on asthenosphere 3 types of plate boundaries (fill in Tectonic Plate Boundaries sheet) 3 types of plate boundaries (fill in Tectonic Plate Boundaries sheet) TransformTransform DivergentDivergent ConvergentConvergent Animation of plate boundaries Animation of plate boundaries (website)

Transform slide past each other horizontally (opposite direction)slide past each other horizontally (opposite direction) ex: San Andreas fault (CA) ex: San Andreas fault (CA) may produce earthquakes may produce earthquakes

San Andreas Fault San Andreas Fault (website)

California (2 plates) San Andres Fault North American Plate Pacific Plate

Divergent—plates separateDivergent—plates separate ocean-ocean=sea-floor spreading (mid-ocean ridge) ocean-ocean=sea-floor spreading (mid-ocean ridge) continent-continent=rift valley continent-continent=rift valley

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

Convergent—collideConvergent—collide oceanic-oceanic plates creates island arch (volcanic) oceanic-oceanic plates creates island arch (volcanic) ……animation (website) animation ocean-continent plates (denser ocean plate moves DOWN and continental plate folds upward) creates trench (at subduction zone) and volcanoes inland ocean-continent plates (denser ocean plate moves DOWN and continental plate folds upward) creates trench (at subduction zone) and volcanoes inland ……animation (website) animation continent-continent plates creates mountains continent-continent plates creates mountains …..animation (website) animation

Aleutian Islands (between Alaska and Russia) formed as 2 oceanic plates collided formed as 2 oceanic plates collided

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

Andes Mountain (ocean- continent convergent boundary)

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

Other Websites ryit/tectonics/shockwave.html (what happens at the plate boundaries!) ryit/tectonics/shockwave.html (what happens at the plate boundaries!) ryit/tectonics/shockwave.html ryit/tectonics/shockwave.html Summary of Plate Tectonics (Enchanted Learning) Summary of Plate Tectonics (Enchanted Learning) Summary of Plate Tectonics Summary of Plate Tectonics

plate tectonics online tutorial plate tectonics online tutorial plate tectonics online tutorial plate tectonics online tutorial

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

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

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

What features of Earth are produced by the movement of lithospheric plates? What features of Earth are produced by the movement of lithospheric plates? >>mountains, volcanoes, volcanic islands, rift valleys >>mountains, volcanoes, volcanic islands, rift valleys

1. Earthquakes are MOST LIKELY to occur at the borders of _________. >>>>>lithospheric plates >>>>>lithospheric plates 2. The collision of two continental plates can produce _____________. >>>>>>a mountain range (not a single mountain) >>>>>>a mountain range (not a single mountain) 3. Plate tectonics describes movements MAINLY in ___________. >>>>Earth crust (or lithosphere) >>>>Earth crust (or lithosphere)

4. Which ocean was produced by sea-floor spreading between Africa and South America? >>Atlantic >>Atlantic 5. As distance increases from a mid-ocean ridge, the rocks grow older or younger? >>>>>older >>>>>older

6. The “ring of fire” helps scientists predict areas where ___________ are likely to occur. >>earthquakes and volcanoes >>earthquakes and volcanoes 7. Volcanoes can be produced by the collisions of ____& _______ plates. >>oceanic and oceanic OR continental and oceanic >>oceanic and oceanic OR continental and oceanic

More questions A convection current of magma is made up of A convection current of magma is made up of a. a rising more dense liquid and a sinking less dense liquid. a. a rising more dense liquid and a sinking less dense liquid. b. a rising less dense liquid and sinking more dense liquid. b. a rising less dense liquid and sinking 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 both the idea of continental drift and the theory of plate tectonics? How do mid-ocean ridges support both the idea of continental drift and the theory of plate tectonics? a. Oceanic lithosphere is destroyed at mid-ocean ridges.a. Oceanic lithosphere is destroyed at 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 ridges.c. Tectonic plates collide at mid-ocean ridges. d. The crust at mid-ocean ridges is old oceanic lithosphere.d. The crust at mid-ocean ridges is old oceanic lithosphere.