Plate boundaries

There are a number of different types of plate boundary.

Destructive plate boundary

A destructive plate boundary is sometimes called a convergent or tensional plate margin. This occurs when oceanic and continental plates move together. The oceanic plate is forced under the lighter continental plate. Friction causes melting of the oceanic plate and may trigger earthquakes. Magma rises up through cracks and erupts onto the surface.

An example of a destructive plate boundary is where the Nazca plate is forced under the South American Plate.

Destructive plates may force plates underneath one another and cause volcanoes or earthquakes

Collision zones

Collision zones form when two continental plates collide. Neither plate is forced under the other, and so both are forced up and form fold mountains.

At a collision plate boundary, the crust is forced together and the intense pressure causes fold mountains to form

Constructive plate boundary

A constructive plate boundary, sometimes called a divergent plate margin, occurs when plates move apart. Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed.

An example of a constructive plate boundary is the mid-Atlantic Ridge.

At a constructive plate margin, new crust is created by magma rising through the gap created by the plates moving apart.

Conservative plate boundary

A conservative plate boundary, sometimes called a transform plate margin, occurs where plates slide past each other in opposite directions, or in the same direction but at different speeds.

Friction is eventually overcome and the plates slip past in a sudden movement. The shockwaves created produce an earthquake.

This occurs at the San Andreas Fault in California.

At a conservative plate margin, plates slide past each other causing friction and earthquakes.
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