Plate Tectonics

Convection Currents

The plate tectonics that make up the Earth’s crust are not stationery lumps of rock, they are continually moving at around 2-3cm per year.  The position of the plates as they are today is shown in the map below.

They ‘float’ on the magma beneath them in the mantle, which acts like a conveyor belt for the plates due to the convection currents that occur within the molten rock.  At the surface, the plates are dragged in different directions depending on the direction the convection currents are flowing in.

The heat from the core causes the mantle to be heated at its base.  The hot rock rises gradually towards the crust.  As it rises, it moves further away from its heat source at the core and starts to cool down.  When it reaches the crust, it is forced out sideways because it cannot easily pass through the solid rock above it.  It continues to cool and as it cools, it begins to sink back down towards the core.  As it reaches the solid outer core, it is again forced sideways because it cannot pass through the solid iron/nickel layer and at the same time it is heated up once again and rises to the surface.  This process ofheating, rising, cooling and sinking forms currents within the magma called convection currents.

Continental Drift

Before the World looked as it does today, it was all one large supercontinent called Pangea…