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why do volcanoes occur at constructive plate margins

There are a number of different types of 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 A section of the crust that makes up the Earth's landmasses. 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. An example of a constructive plate boundary is the mid-Atlantic Ridge. 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 A sudden shaking of the ground which releases energy. This occurs at the San Andreas Fault in California. plate. The plates move one another and this movement can cause earthquakes. As the plates collide, the oceanic plate is forced beneath the continental plate. This is known as. 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. 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. This is called a. Earthquakes can occur at collision margins. from one another. When this happens the magma from the mantle rises up to make (or construct) new land in the form of a.

The movement of the plates over the mantle can cause earthquakes. , the plates move past each other or are side by side moving at different speeds. As the plates move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy, causing an earthquake. The earthquakes at a conservative plate boundary can be very destructive as they occur close to the Earth s surface. There are no volcanoes at a conservative plate margin.

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