Destructive Margin

• What is subduction?


  The process of one tectonic plate sliding beneath another.
• What are the arrows like in a destructive plate margin?

  Moving towards each other
• What plate boundary is this?

  Destructive

  
• Volcanoes forming at destructive margins:


  • As plates move towards each other, the oceanic (denser) plate sinks below the continental (lighter) plate and melts in the subduction zone.
  • Hot magma rises up through the overlying mantle and crust, and some can eventually erupt producing volcanoes.
  • The magma becomes increasingly viscous/sticky as it rises to the surface producing composite volcanoes which are steep sided and have violent eruptions with ash falls
• Earthquakes forming at destructive plate margins:


  • As the two plates converge, pressure builds up.
  • The rocks eventually fracture causing an earthquake.
  • Most happen at shallow depths below the surface where the plates collide.
  • They also occur at greater depth, in the lower part of the subduction zone
• Which plate boundary do composite volcanoes form?


  Destructive plate boundary
• Give an example of a composite volcano and its characteristics:


  Mount St. Helens

  -Tall steep sided formed by layers of ash and lava

  -Eruptions of thick sticky acid lava

  -Eruptions tend to be violent