How does a convergent boundary occur?

Question

Leah Abbate · Accepted Answer

In essence, it is simple: to plates are in relative motion towards each other. The ‘why’ is more complex - please see below.

Plates move due to the movement of magma in the mantle beneath them. They are dragged from below by enormous plumes of semi-solid rock upwelling from the core/mantle boundary (in effect by convection currents.) The heat source for these convection currents is radioactive decay of the unstable (radioactive) nuclei in the core.

A diagram should help (though this one shows a constructive (divergent) boundary in the centre and two destructive (convergent) boundaries at the side):

It is generally true that the plate that descends is the denser of the two, and the one that remains on top is ‘crumpled’ up into a mountain range (called ‘fold mountains’, I believe) that will probably be tectonically active i.e. show both volcanoes and earthquakes. Again, a diagram provides a better picture than my words:

Hope this was of some use, if only to provoke further questions.

Nova Adams · Answer

undefined When two tectonic plates move in the direction of one another, they create a convergent boundary. This movement can lead to the collision of one plate and its subsequent subduction beneath the other, the formation of mountain ranges, or the formation of deep ocean trenches.