Types of Plate Margin

Destructive Plate Margins 

• Convection currents in the mantle cause the plates to move together
• If one plate is made of oceanic crust and the other is made of continental crust, the denser oceanic crust sinks under the lighter continental crust in a process know as subduction. 
• Great pressure is exerted and and the oceanic crust is destroyed.
• If two continental crusts meet each other, they collide rather than one sinking beneath the other. This collision boundary is a different type of destructive margin. 

Constructive Plate Margins

• When plates move apart a constructive plate boundary results. This usually happens under oceans.
• As these oceanic plates pull away from each other, cracks and fractures form between the plates where there is no solid crust. 
• Magma forces its way into the cracks and makes its way to the surface to form volcanoes. 
• New land is formed as the plates pull apart. 

Conservative Plate Margins

• At conservative plate margins, the plates are sliding past each other.
• They are moving in a similar (but not the same) direction at slightly different angles and speeds. 
• As one plate is moving faster than the other and in a slightly different direction, they tend to get stuck. 
• Eventually the build up of pressure causes them to be released. 
• This sudden release of pressure causes an earthquake.
• At a conservative plate margin, crust is neither being destroyed or made. With no source of magma, volcanoes are absent.