A destructive plate margin forms when an oceanic and continental plate move towards each other. The lighter, thicker continental plate is subducted by the heavier, denser oceanic plate. The oceanic plate melts as it sinks below the continental plate due to friction in the subduction zone and the heat of the mantle. The crust becomes molten magma. This may be forced to the surface of the earth causing a volcanic eruption.
One explanation for plate movement at a destructive plate margin is slab pull. Oceanic plates are heavy so gravity, acts upon them, pulling them down.
Alternatively, convection currents under the Earth’s crust transfer heat, which rises through the surface and cools back down. These convection currents are thought to cause the oceanic and continental plate to move towards each other.
A cross-section of a destructive plate margin
The movement of the oceanic plate is not smooth. Due to friction, the plate gets stuck. Pressure then builds up. The plate will eventually slip causing an earthquake.
The continental plate is crumpled by the pressure and forms fold mountains.
Destructive plate margins occur where an oceanic and continental plate move towards each other. Examples below include the Pacific Plate and Eurasian Plate and the Nazca Plate and the South American Plate.
A map to show the Earth’s plates
Find out about conservative and constructive plate margins.