analyse the factors that cause differences in the hazards posed by volcanoes around the world (40 marks)

1351 Words Oct 22nd, 2013 6 Pages
analyse the factors that cause differences in the hazards posed by volcanoes around the world (40 marks)

A hazard is a situation that poses a level of threat tolife, 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 voilent 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
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Furthermore, violent eruptions caused by an intense build up of presssure can lead to hazards such as Tephra and even Lava bombs, which aaare fragments of volcanic rock and lava blasted up into the air. Thesecould pose a life threatening risk to an urban population if it is within reach of the tephra ejected by the volcano. The fact that over 80% of the world's active volcanoes occur at destructive plate boundaries, including the Pacific Ring of Fire, means that the hazards posed by these volcanoes are very serious due to their explosiveness and unpredictability as a result of the acidic lava which is fromed there.

Another factor affecting the hazards posed by a volcano is the materials ejecte when it erupts. Non-explosive eruptions such as those which produce mainly basaltic lava flows, do not usuallyrepresent a particularly serious hazard to people, although they will destroy farmland an buildings. A greater hazard is posed when large quantities of very fluid lava are released, such as when part of acrater collapses, and there is a real danger to people. However, it is whn an eruption is explosive that the greatest risk to people is posed. As the magma is usually very viscous, there is not usually much lava, and so any that is produced cools and solidifies quickly.But features of these eruptions such as ash clouds, pyroclastic flows, lahars and tsunamis, are severe hazards. An ash cloud can reach 20km in jiust 30 minutes, and can be carried hundreds

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