Why Are Volcanos Violent

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Gas or its inability to escape is what causes volcanos to become violent. The longer gas is trapped, the more pressure builds up. The cause of gas building up is the result of the viscosity of the magma the gas is trapped in. Viscosity is the measure of the flow or how easily a liquid flows. If a liquid is viscous it is thick and will flow slowly like honey whereas a liquid that is nonviscous will flow like water. Think of the difference between a bowl of chili and a bowl of water in the microwave. When heated the chili will trap the gas causing the chili to explode all over the inside of the microwave and a bowl of water just boils and the steam escapes freely. The two factors that affect or control the viscosity are temperature and silicon and oxygen content. At lower temperatures magma is viscous and as the temperature rises the material becomes less viscous and flows more easily. The higher the silicon oxygen content, the higher the viscosity. Silicon and oxygen combine and form strands, chains and sheets which also makes flow more difficult. The location of the volcano also plays a big role in how destructive it will be. At divergent plate boundaries you have high mafic temperatures and very thin crust so gases are unable to get trapped. This forms a nonviolent shield volcano. When a shield volcano erupts the lava flows down the sides and does not build up to tap gasses and at convergent plate boundaries especially with subduction you have intermediate temperatures with lots of gas and water building up under continental crust that is very thick and holds pressure in. This is where more violent volcanos
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