What are the three different types of plate boundary and what are their relative motions?

Answer 1

The three main types of plate boundary are:

1. Convergent boundary
2. Divergent boundary
3. Transform boundary

At a convergent boundary the two plates are moving towards each other. Depending on the type of plate this can cause the formation of fold mountains (a process known as orogenesis - where a continental plate collides with a second continental plate), the formation of a subduction zone characterized by oceanic trenches and volcanic arcs (where oceanic crustal plates collide with and are forced under continental crustal plates). Occasionally in the same environment obduction can occur where small slivers of oceanic crust are forced up over the continental crust, thus being preserved.

At divergent boundaries the plates are moving away from each other and as such create tensile stress features such as normal faults. These can form horst and graben structures in the crust which under further extensional stress can become rift zones and ultimately form new mid oceanic ridges.

Transform faults are characterized by the parallel motion of the two differing plates (i.e. they slide past each other). Crust is neither created nor destroyed at transform boundaries, however there can be seismic activity.

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