How does a convergent boundary occur?

1 Answer
Jan 23, 2018

Answer:

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

Explanation:

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):

enter image source here

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:

http://worldlywise.pbworks.com/w/page/25833576/Unit%202%20Section%20B%20-%20Causes%20and%20effects%20of%20volcanoes%20and%20responses%20to%20them

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