Unit 4.1 ~ Plate Tectonics

 The Layers of Earth

  • The core is radioactive and hot which drives convection.

 Convection

  • Convection occurs in the upper mantle in a slow, creeping motion. It breaks the lithosphere into plates and moves them

Oceanic - Continental

  • Oceanic crust is denser than continental and subducts below
  • Subduction creates trenches and cracks
  • Magma seeps through cracks and creates volcanoes
  • Causes earthquakes and volcanoes

 

Oceanic - Oceanic

  • Both crusts are basalt
  • Older crust is denser due to more sediments
  • Creates volcanic island arcs (Japan and Aleutian Islands in Alaska)
  • Causes tsunamis and earthquakes

 

Continental-Continental

  • Both crusts are granite
  • Same density so push up
  • Little subduction
  • Happens in
    • Himalaya Mountains between India and Nepal

 

Divergent

  • Crusts pull apart and magma rises to fill gap
  • Magma hardens when cooled by ocean water
  • Creates underwater mountain ranges
  • Mid-ocean ridges in
    • Iceland, African Rift Valley

 

Transform

  • 2 plates slip past earth other 
  • Some called strike-slip faults
  • San Andreas fault in California between Pacific and North American plates

 

Hot Spot Volcanoes

  • Occur in the middle of plates where crust cracks and magma seeps up

  • Hawaiian Islands on Pacific Plate

  • Yellowstone hot spot on N. Amer. plate - flat volcano

   

  Rock Cycle