Activity at the Plate Margins

Constructive Plate Boundary (Divergent)

• The two plates are moving apart- the earths core heats itself from within, the heat rises to the crust and moves outwards; friction drags the plates apart as the magma cools.
• Magma rises from the mantle into the gap created by the two plates moving apart, cooling to create new ocean or continental crust.
• If the boundary occurs underwater a mid-ocean ridge forms.For example, the mid-atlantic ridge where the eurasian and north american plates are moving apart.
• Underwater volcanoes erupt along these ridges and can build up over time to be above sea level e.g. Iceland along the mid-atlantic ridge.
• The plates do not move apart at the same pace which causes pressure to build up. When the pressure becomes too much then the plates crack creating earthquakes and also fault lines.
• As the plates keep moving apart, the crust between the parallel faults drops down to form a rift valley. For example, the East African Rift System that stretches from Mozambique to the Red Sea. It is formed because the Nubian and Somalian plates are diverging. Some parts of the system are hundreds of metres deep and thousands of metres wide.

Destructive Plate Boundary (Convergent)

• The two plates are moving towards each other
• Convection currents in the mantle move the two plates towards each other
• The more dense oceanic plate is forced under (subducts) the less dense continental plate forming a deep ocean trench e.g. Peru-Chile Trench in the…