GCSE AQA GEOGRAPHY B: THE RESTLESS EARTH: PLATE MARGINS

The Restless Earth

The Earth is made up with different layers: 

Solid core - made of iron and nickel, which is solid due to high temperatures, with an extreme amount of pressure

Outer core - which faces slgihtly less pressure

The Mantle - a zone of molten sillicates and other materials. Molten so it moves, the source of this is the Earth's intense inner heat which sets up convection currents.

The Crust- this can be of two types, oceanic and continental and lies at the surface of the Earth.

Oceanic Crust - denser, newer, thinner

Continental Crust - less dense, older, thicker

Convection Currents- heat currents in the molten magma that move the crust very slowly

Plate Margin - the edges of the plates where they are either sliding over eachother, colliding, moving apart or subducting under eachother.

Plate Margins

There are four types of plate margin: conservative, destructive, collisional, constructive

Destructive 

This is when the denser oceanic plate is pushed towards the less dense continental plate by convection currents under the Earth's surface. The oceanic plate subducts under the continental plate at what is called the subduction zone, creating a deep oceanic trench. It is the oceanic crust which sinks into the mantle because it is heavier / more dense. As it descends the friction, increasing temperature and increasing pressure from the mantle melt the plate. Some of this molten magma can work its way through the continental crust in fissures and cracks and collects in magma chambers. This is often some distance from the margin where magma can eventually re-emerge at the surface to create a range of mountains. The movement…