Question

write one reason behind the formation of volcanic eruption ​

Answer 1

Answer:

Volcanoes erupt when molten rock called magma rises to the surface. Magma is formed when the earth's mantle melts. ... If magma is thick, gas bubbles cannot easily escape and pressure builds up as the magma rises. When the pressure is too much an explosive eruption can happen, which can be dangerous and destructive

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Answer 2

There are several different causes for a volcano to erupt which all fundamentally come down to a  pressure change within the volcano which forces the magma to overflow the chamber it is held in.

The most common type of eruption is caused by the movement of tectonic plates.

When one is pushed under the other the magma, sediment and seawater is forced into the chamber which eventually overflows and the volcano erupts spewing lava into the sky.

This kind of eruption produces sticky, thick lava at temperatures from 800 to 1,000C.

The second type of eruption caused by tectonic plates is  when the plates move away from each other allowing magma to rise and fill the the gap, which can cause a gentle explosion of thin lava of temperatures between 800 to 1,200C.

Decreasing temperatures can cause old magma to crystallise and sink to the bottom of the chamber and this movement can force fresh liquid magma up and out - similar to dropping a brick in a bucket of water.

Finally a decrease in external pressure can trigger an eruption as it may minimise the volcano's ability to hold back by increasing the pressures inside the magma chamber.

This kind of eruption can be caused by natural events such as typhoons, which decrease rock density, and glacial melting on the top of the volcano which alters the molten rock composition