Constructive Plate Boundaries

Divergent/Constructive boundaries

Form when two of the Earth’s plates move apart from one another. Convection currents that rise upwards towards the lithosphere move away from each other.

Example of a divergent plate boundary

North American and Eurasian plates, moving at a rate of 2.5cm per year.

Seafloor Spreading

When two oceanic plates are forced to separate from each other by convection currents. As plates are pulled apart, a gap develops, allowing magma from the mantle to rise through. This hardens into basalt rock and forms new ocean floor.

Seafloor spreading example

Mid-Atlantic Ridge, North American and Eurasian, beginning 130mil years ago. Volcanic Island, e.g. Iceland.

Rift Valleys

Landforms created when created when a continental plate is pulled apart by convection currents. This process is known as rifting

Rifting

Convection currents stretch land within a continent. This causes it to become thinner than surrounding land, creating a valley. Eventually the crust tears burst creating a new divergent boundary. E.g. The East African Ridge Valley

Lava

Molten rock that reaches the surface of the Earth

Seafloor Spreading

Harry Hess discovered that mid-ocean ridges form where 2 plates are pulled apart as a result of thermal convections currentd.