EMS- Managing natural hazards, page no 141

What are plate boundaries: A plate boundary is a three-dimensional surface or zone across which there is a significant change in the velocity (speed or direction) of motion of one lithospheric plate relative to the adjacent lithospheric plate. There are three types of plate boundary:

The three types of plate boundaries:

• Constructive{divergent}: Divergent boundaries are the zones where two tectonic plates are moving away from one another. Divergent boundaries are constructive boundaries because new crust is generated by magma pushing up from the mantle as the plates pull away from each other.

• Destructive{convergent}: where plates are moving towards each other and old crust is either dragged down into the mantle at a subduction zone or pushed upwards to form mountain ranges.

• Conservative: A Conservative plate boundary is where two crustal plates slide past each other, and the movement of the plates is parallel to the plate margin. The plates move with relative horizontal movement which is either sinistral (left) or dextral (right).

  
  

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