techtonics

• earthquake = sudden and violent period on ground shaking caused by sudden release of energy from the earth's interior
• earthquakes normally occur at plate boundaries, where plates are moving past each other
• oceanic crust :

  under ocean

  more dense

  5km thick

  made of basalt
• continental crust :

  under land

  less dense

  60km thick

  made of granite
• earth layers

  inner core

  outer core

  mantle

  crust
• inner core is solid and is made of iron and nickel