Continental drift is a theory put forward by German
Scientist Alfred Wegener. It is a theory that has now been accepted by
most scientists around the world, although there were many sceptics when
it was first put forward.
Wegener put forward the idea that the reason
the huge continent of Pangea broke up was because of the 15 plates contained
in the earth's crust. These plates carry the continents we see today and
move centimetres every year in the direction they are travelling. These
plates are able to move because of the convection currents in the mantle.
This is huge amounts of boiling magma, which is pushed up from the core
of the earth and spreads out beneath these plates. By doing so, it pushes
the plates away from each other - a process known as 'sea-floor spreading'.
When this magma cools, it sinks, and so the plates are drawn together -
the proces of 'subduction'. If this magma is constantly rising and spreading
out beneath the plates, over millions of years, these plates are able to
travel large distances. The continuous rising of magma is what causes these
convection currents, and movements of continents around the globe.
When the plates move, they are able to move in
three directions - towards each other, away from each other, and into each
other. When these plates get so close that they actually collide, one plate
is often forced above the other, causing what is seen by us as a mountain
range. Mountain ranges such as the Himilayas and the Andes were the results
of collisions between plates.