Plate Boundaries

Types of Plate Boundaries

1. Destructive (Convergent) Plate Boundary

   • Formation: Occurs where two plates move towards each other.
   • Mechanism:
     • Driven by convection currents in the mantle.
     • Oceanic plate (more dense) moves towards the continental plate (less dense).
     • Oceanic plate subducts below the continental plate forming a subduction zone.
   • Effects:
     • Friction, increased pressure, and heat cause the subducting plate to melt.
     • Earthquakes occur from high pressure and seismic energy release in the subduction process.
     • The area of this occurrence is called the Benioff Zone.
     • Melting plates produce magma, leading to magma chambers and volcanic mountains.
     • Formation of fold mountains as the continental crust crumples above the oceanic plate.

2. Constructive (Divergent) Plate Boundary

   • Formation: Occurs where two plates move apart from each other in opposite directions.
   • Mechanism:
     • Cracks and fissures form, allowing magma to push through from the Earth's interior.
     • Magma rises to the surface, spreads, cools, and solidifies, creating new land.
   • Example: Mid-Atlantic Ridge.

3. Conservative (Transform) Plate Boundary

   • Formation: Occurs where two plates move alongside one another either in the same or opposite directions.
   • Mechanism:
     • Plates grind on each other and sometimes get locked together.
     • Pressure builds up over time and when released, sends strong seismic waves.
   • Effects:
     • Causes very strong earthquakes.
   • Example: San Andreas Fault.
   • Case Study: Christchurch Earthquake 2011.