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. 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. 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.
This situation provides a more varied range of tectonic settings than do constructive plate boundaries. Firstly, and in contrast to constructive plate boundaries, destructive plate boundaries are asymmetrical with regard to plate speeds, age and large-scale structures.
Secondly, whereas true constructive boundaries occur almost invariably in oceanic lithosphere, destructive boundaries also affect continental lithosphere - they can occur entirely within continental lithosphere. Consequently, there are three possible types of destructive plate boundary:. In addition to the disappearance of old lithosphere, destructive boundaries associated with ocean-ocean subduction and ocean-continent subduction are also characterised by:.
The sea floor slopes into the trenches from both the landward and oceanward sides. They are continuous for many hundreds of kilometres, occurring both adjacent to continents and wholly within oceans;. Earthquakes can occur as deep as km;. As you work through this course you will need various resources to help you complete some of the activities. Making the decision to study can be a big step, which is why you'll want a trusted University.
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Request an Open University prospectus There are four main types of plate boundary. These are constructive, destructive, conservative and collision margins. Find out more about constructive plate margins. A destructive plate boundary occurs when an oceanic plate is forced under or subducts a continental plate.
Find out more about destructive plate margins. Find out more about conservative plate margins. Take our plate margins or landforms at plate margins quiz to test your knowledge. If you've found the resources on this page useful please consider making a secure donation via PayPal to support the development of the site.
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