Lesson 5.5: The Theory of Plate Tectonics

​Lesson 5.5: The Theory of Plate Tectonics

Multiple Choice

Which feature forms the longest mountain range on Earth?

• The mid-ocean Ridges

• The deep-ocean trenches

• The Rockies

• The Andes

Multiple Choice

Which process adds more crust to the ocean floor

• Suction

• Sea-floor Spreading

• Subduction

• Magnetic Stripe

Multiple Choice

Where does Subduction Occur?

• Along the middle of some Ocean Floors

• Down the middle of Mountain Ranges

• On Continents

• At Deep-Ocean trenches

​Key Concepts:

• Explain the Theory of Plate Tectonics

​What are tectonic plates?

• Plates: Uneven pieces of the Earth's Lithosphere

  • Move over the Mantle

  • Meet at boundaries and move in three ways

Ohio Grade 8 | Lesson 5.5

​The ways plates move

• ​Divergent Boundaries: plates move away from each other

• Convergent Boundaries:​ Plates move towards each other

• Transform Boundaries: Plates slip past each other​

Ohio Grade 8 | Lesson 5.5

​The Theory of Plate Tectonics

• ​Earth's Plates are in slow constant motion, driven by convection in the mantle

  • Explains the formation, movement, and subduction of Earth's plates​

Ohio Grade 8 | Lesson 5.5

​Mantle Convection and Plate Motion

• As convection currents move in the mantle, the tectonic plate sits on top and moves with the current

• Plate movement is measured with satellites

  • Plates move about 1 to 12 centimeters a year

  • As they move, the shapes and size of the oceans change

  • Evidence shows that multiple super continents have existed before Pangea​

Ohio Grade 8 | Lesson 5.5

Multiple Choice

True or False: Earth's plates meet at boundaries

• True

• False

Multiple Choice

What is the motion of Earth's plates like?

• Fast and in stages

• Slow and in stages

• Fast and constant

• Slow and Constant

Multiple Choice

True or False: Ocean Currents move the Earth's plates

• True

• False

​Divergent Boundaries

• Faults are created at boundaries where convection currents pull plates apart and push them together

• Divergent Boundaries

  • When Plates move away, they can create massive cracks in the crust

    • When under water, mid-ocean ridges form

    • When on land a deep rift valley forms​

Ohio Grade 8 | Lesson 5.5

​Convergent Boundaries

• Plates collide together

  • the denser plate sinks while the less dense plate rises​

    • Oceanic crust more dense and it sinks to the mantle

    • Continental crust raises up and forms mountains

  • When plates with the same density collide, the crust squeezes into high mountains

Ohio Grade 8 | Lesson 5.5

​Transform Boundaries

• Plates slide past each other in opposite directions

  • two jagged edges can get "caught" on each other and lock in place together

  • eventually enough force will break the two plates apart

• Crust is neither created or destroyed

• Mainly where Earthquakes occur​

  • The San Andreas Fault​

Ohio Grade 8 | Lesson 5.5

Multiple Choice

Which theory describes the motion of and force driving Earth's plates?

• The First law of Motion

• The Third Law of Motion

• Continental Drift

• Plate Tectonics

Multiple Choice

The San Andreas fault is an example of which kind of boundary

• transform

• divergent

• oceanic

• convergent

Multiple Choice

Which feature forms at convergent boundaries?

• Mountain Range

• Trench

• Rift Valley

• Mid-Ocean Ridge