“Using case studies, explain why people live in hazardous volcanic environments and how the impact of hazards vary.”

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“Using case studies, explain why people live in hazardous volcanic environments and how the impact of hazards vary.”

Many volcanic regions on Earth are densely populated. The people who choose to live in these areas face a major hazard from volcanic eruptions. I will use case studies of volcanic regions that had devastating effects and created a natural disaster, such as the eruption of Unzen in Japan in 1792 and the eruption of El Chichon in Mexico in 1982. I will discuss how the principal hazards from eruptions, such as deadly pyroclastic flows, lahars (mudflows) and tsunami (tidal waves) affect people's lives and property. I will also discuss why people choose to live in such a hazardous environment.

     Volcanoes affect people in many ways, some are good some are not. When a volcano erupts, houses, buildings, roads, and fields can get covered with ash. As long as you can get the ash off your house may not collapse, but often the people leave because of the ash and are not around to continually clean off their roofs. If the ashful is really heavy it can make it impossible to breathe.

Lava flows are almost always too slow to run over people, but they can certainly run over houses, roads, and any other structures. These two features alone could destroy any settlement near the volcano, leaving whole communities with no homes to return to.

Pyroclastic flows are mixtures of hot gas and ash, and they travel very quickly down the slopes of volcanoes. They are so hot and choking that if you are caught in one it will kill you. They are also so fast that trying to out run them would be futile, they can reach speeds of 100-200 km/hour. If a volcano that is known for producing pyroclastic flows and is looking like it may erupt soon, the most sensible thing to do is evacuate before it does erupt.

Some of the good ways that volcanoes affect people include producing spectacular scenery, and producing very rich soils for farming.

     Volcanoes expel many different substances when they erupt. Water vapour, the most common gas released by volcanoes, causes few problems. Sulphur dioxide, carbon dioxide and hydrogen are released in smaller amounts. Carbon monoxide, hydrogen sulphide, and hydrogen fluoride are also released but this is rarely more than 1 per cent of the total composition.

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Gases pose the greatest hazard close to the vent where concentrations are greatest. Away from the vent the gases quickly diffuse into the air. Long term exposure to volcanic fumes may aggravate existing respiratory problems. It may also cause headaches and fatigue in healthy people. The gases also limit visibility, when they become trapped by atmospheric conditions.

      The greatest beneficial effect that volcanoes have on the environment is to provide nutrients to the surrounding soil. Volcanic ash often contains minerals that are beneficial to plants, and if it is very fine ash it is able to ...

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