GEOLOGY

Detailed explanation-1: -Magma contains dissolved gases, which provide the driving force that causes most volcanic eruptions. As magma rises towards the surface and pressure decreases, gases are released from the liquid portion of the magma (melt) and continue to travel upward and are eventually released into the atmosphere.

Detailed explanation-2: -While heat is what causes magma to rise to the surface, escaping gases provide the driving force for volcanic eruptions. The most common volcanic gas is steam. This is formed when water from within the Earth or rainwater soaking into the ground is absorbed by magma and then heated.

Detailed explanation-3: -As gas bubbles accumulate, the upward pressure increases, forcing cracks in the rocks to widen, often in the direction of Earth’s surface. For magma to erupt from a volcano, this upward pressure must exceed the downward pressure that is exerted by the eight-kilometer (five mile) thick load of rock overhead.