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The point at which two plates meet is called a plate boundary or margin.

Destructive plate boundaries

At a destructive plate boundary - also known as a convergent plate boundary - the plates are moving towards one another. It usually involves an oceanic plate and a continental plate. This movement can cause earthquakes and volcanoes. An example of this plate boundary or margin is where the Nazca and South American plates are converging.

As the plates collide, the oceanic plate is forced beneath the continental plate. This is known as subduction and results in the formation of an ocean trench. This happens because the oceanic plate is denser (heavier) than the continental plate. When the plate sinks into the mantle it melts to form magma. The pressure of the magma builds up beneath the Earth's surface. The magma escapes through weaknesses in the rock and rises up through a composite volcano, also known as a stratovolcano. The volcanic eruptions are often violent, with lots of steam, gas and ash.

If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains.

Landforms associated with destructive plate boundaries

Large scale landforms at a destructive plate boundary include super volcanoes, such as the Campi Flegrei volcano in Italy - where the Eurasian plate and the African Atlantic plate are moving towards each other along the Mediterranean sea.

Small scale landforms created at a destructive plate margin include cinder cones, eg Parícutin, México. Cinder cones are the simplest type of volcano, built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone.