Plate Tectonics and Associated Hazards 40 Marks

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Plate tectonics and Associated hazards Analyse the factors that cause differences in the hazards posed by volcanoes around the world. (40 Marks) Using case studies we can clearly see the differences in the hazards that volcanoes pose. A hazard is a situation that poses a level of threat to life, health, property or environment. The level of hazard posed by different volcanoes can very greatly, from a weak eruption with minimal impact that causes little damage, to a violent and life threatening explosion. Most of the sixty-plus volcanoes that erupt each year are low risk, however a combination of factors can cause a volcano to be a serious hazard. The factors causing these variations will be explained in this essay. The first factor that must be considered is the viscosity of the magma. This can determine how powerful an eruption is and what shape the volcano eventually becomes. Viscosity can be affected by three main factors, Firstly, the higher the temperature, the lower the density of the magma, causing it to flow more easily. Secondly, the greater the amount of dissolved gases in the magma, the less viscous it will be, and lastly the higher the silica content, the more viscous it will be. Thicker, more viscous magma has a greater potential for explosive eruptions and therefore represent the greatest potential hazards. The thickest type of magma is known as Acidic Magma. Its relatively low temperature, high silica content and leads to blockages and powerful eruptions. This can mean that the eruptions caused by thick magma can be less frequent and more difficult to predict, meaning that when an eruption does occur, it is usually with little or no warning, which can lead to catastrophic consequences as any nearby settlement will be relatively unprepared for the effects of a violent volcanic eruption. Furthermore, acidic magma is more likely to produce
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