Plate Boundaries

• Plate Boundaries


  • Transform
  • Convergent
  • Divergent
• Convergent Plate Boundary


  Two tectonic plates collide towards each other, one plate eventually slides beneath the other, this process is called subduction
• Converging oceanic plates


  • Form trenches
  • Become sources of earthquakes
• Subduction


  1. Leading edge of subducted plate reaches mantle

  2. Melts and turns into magma

  3. Molten material rises to surface

  4. Creates volcanic island arc parallel to trench
• Types of Convergent Plate Boundary

  • Oceanic-Continental
  • Ocean-Ocean
  • Continental-Continental
• Oceanic-Continental Convergent Plate Boundary

  • One plate is oceanic
  • Large volcanoes found in lines that outline the subduction zone
  • Earthquakes also happen in these zones
• Ocean-Ocean Convergent Plate Boundary

  • One plate (oceanic crust and Lithospheric mantle) is pushed, or subducted, under the other
  • Mixes with overlying mantle
  • Addition of water to hot mantle lowers crust's melting point
  • Leads to formation of magma
• Continental-Continental Convergent Plate Boundary

  • Two plates collide
  • Have a density lower than the mantle which prevent subduction
  • Create mountains
• Layers of Earth


  • Oceanic crust
  • Lithosphere
  • Asthenosphere
  • Continental crust
• Divergent Plate Boundary


  Region where crustal plates are moving away from each other and in opposite directions
• Divergent Plate Boundaries


  • Happen at mid-ocean ridges (seafloor spreading)
  • Happen at rifted continental margins
  • Form submarine mountain ranges called oceanic spreading ridges
• Transform Fault or Transform Boundary


  Fault along a plate boundary where the motion is predominantly horizontal, two plates are sliding past each other
• Structures crossing Transform Boundary

  • Offset split into pieces and carried in opposite directions
• Types of Transform Plate Boundaries

  • Ridge-Ridge Boundaries
  • Trench-Trench Boundaries
  • Ridge-Trench Boundaries
• Ridge-Ridge Boundaries


  • Mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics
  • Uplifting of ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary
• Trench-Trench Boundaries


  • Trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle
  • Causes the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression
• Ridge-Trench Boundaries


  • Trench is a deep elongated cavity bordering a continent or an island arc, formed when one tectonic plate slides beneath another
  • Ridge is underwater mountain range that criss-crosses the oceans and is formed by rising magma in a zone where two plates are moving apart