Plate Tectonics (AQA A Level Geography)

Where oceanic plates collide, subduction leads to increased friction and melting. The less dense material begins to rise through the crust, creating a series of volcanic islands.

Radioactive elements beneath the crust cause intense heating, often away from plate boundaries. As the volcano breaks through the crust and crust moves, an arc is formed.

As plates diverge, magma is forced to the surface. After subsequent underwater eruptions, eventually island arcs are formed along ridges, such as in the Mid Atlantic.

As continental plates collide, enormous pressure is exerted and folding occurs. Where folding occurs in coastal locations, some land can be cut off by the sea leading to arc formation.

At constructive plate boundaries, convection currents cause plates to pull apart. This generates both seismic and volcanic activity.

At conservative plate margins, plates are pulled alongside each other. This generates seismic activity after a period of pressure build-up.

At destructive margins gravity forces lithosphere to descend into the mantle. The collision with the other plate causes both shallow and deep seismic activity.

At constructive plate margins, plates are pulled apart leading to the formation of rift valleys. These valleys continue to widen and generate significant seismic activity.

Opposing convection currents lead to the divergence of plates. As plates pull apart magma intrudes leading to the formation of ridges.

As plates slide past each other, fault lines emerge which, following the build-up of substantial pressure, lead to the development of major earthquakes.

Subduction occurs where two plates converge. Subduction can lead to the formation of features such as deep sea trenches and island arcs.

Radioactive decay is the main process. As the plate slides over the place experiencing the decay, the magma is forced through the plate leading to the formation of island chains.