why+volcanic+eruptions+occur


 * __ Why volcanic eruptions occur __**

 The Earth’s __[|mantle]__ is around 30km from beneath your feet. It’s a region of superhot rock that goes down all the way to the Earth’s core. The mantle is so hot that it slowly melts rock to create a slow moving substance called __[|magma]. __ The magma is light enough to rise upwards and collect in __[|magma chambers]__. After a while the magma pushes through the fissures and vents in the Earth’s crust. This process has then created a volcanic eruption. Magma comes out of the volcano and is called lava when it gets out of the volcano. When the magma has risen to the surface of the volcano, it explodes and flows down the sides of the volcano. Magma happens to be less dense than the rock surrounding it, so it attempts to float to the surface. If the magma contains dissolved gasses and water, when the magma reaches the surface of the volcano the water and dissolved gasses will instantly expand into steam and gas, causing a violent eruption. There are three main factors that will trigger a volcanic eruption. These are the buoyancy of the magma, the pressure from the exsolved gases in the magma and the injection of a new batch of magma into a magma chamber already filled up.

 When the rock inside the Earth melts, its mass remains the same, though its volume increases, producing magma that is actually less dense than the rock surrounding it. The magma rises towards the surface because of the buoyancy of the magma. The density of the magma between where the magma was created and the surface is less than that of the surrounding and overlying rocks. The magma will then reach the opening of the volcano and erupt . In addition to this, when new magma enters a magma chamber that is already full, it is possible that the volcano will erupt. The newly produced magma can be of the same or different composition. Either way, the new magma causes some of the existing magma to rise to the surface and erupt.

__** Bibliography: **__ [] [|http://www.universetoday.com/77111/why-do-volcanoes-erupt/] []



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