Plate Tectonics

Who is Alfred Wegner?

  • German Scientist
  • Hypothesized joining of continents: Pangea
  • Proposed geological boundary
  • Died during exploration at age 50
  • Body is preserved in the Greenland Glacier
  • He did not have a mechanism for why the continents moved.

Who is Harry Hess?

  • He lived 1906-1969
  • He was a geology professer at Princeton University.
  • Hypothesized sea floor spreading 

Name 3 types of plates.

  • Divergent
  • Convergent
  • Transform Fault 

What is a Divergent plate?

  • New lithosphere is forming 
  • Plates push apart

What is a Convergent Plate?

  • Subduction zones
  • Old oceanic lithosphere is being subducted into the mantle.
  • Plates push into one another.

What is a Transform Fault Boundary?


  • Plates move past one another 
  • Lithosphere neither thee created or subducted

What is a Divergent Plates?

  • Spreading centers
  • Tensional forces move lithosphere apart
  • Upwelling from mantle cause new sea floor
  • Most associated with oceanic ridge system 
  • 3 examples: Mid Atlantic
  • East Pacific Rise
  • Mid Indian Ocean
  • Continent may split land to create a continental rift.

What is aConvergent Boundaries?

  • Subduction Zone 
  • Oceanic- Continental 
  • Deep ocean trenches produced by oceanic lithosphere descending into mantle 
  • Partial mantle
  • Continental Volcanic (Andes, Cascades)
  • Oceanic- Oceanic 
  • 2 oceanic converge, one descends another
  • Volcanic Island Arc ( Aleutian Islands) Sustained subduction creates chain of volcanic structures.
  • Continental- Continental 
  • Buoyancy of lithosphere slabs inhibits subduction
  • Collison
  • Mountain Formation

What is a

Transform Fault Boundary



  • Grind past without creating or destroying lithosphere
  • Typically part of linear breaks in sea floor: known as fracture zones.
  • Mostly located within ocean basins ( Mendocino Fault)
  • Few cut through Continental Crust ( San Andreas)

Plate Tectonics

  • Ocean drilling 
  • Paleomagnetism 
  • – Polar Wandering
  • – Magnetic Reversals
  • Hot spots ( Hawaii)