Analyse the factors that causes differences in the hazards posed by volcanoes around the world (40 marks)

A hazard can be define as something which poses a level of threat the life, health, property or environment, a volcano can compromise all these things through the many hazards volcanoes presents. Such as lahars, flash flooding, landslides, pyroclastic flows, ash clouds and many others. There are factors which can influence the severity of the hazard and cause differences in them and can be classified into different categories, such as physical, economic, political and social.

One physical factor which causes differences in a volcanic hazard is the steepness of the volcano. If the volcanoes sides are of a steep gradient then the lava from the volcano would flow must faster than if the sides were a steady gradient. Mount Nyiragongo for example had extremely steep sides, 50 degrees at some points. This, combined with the low viscosity of the basaltic lava, saw lava speeds of up to 60 miles per hour. The hazard of a lava flow in Nyiragongo was much greater than if the volcano had steady sloping sides. The type of lava also influences the hazard, if the lava is ryolytic then it has a high viscosity due to its high silica content and its low temperature (only between 650-750 Celsius). Therefore it won’t flow very fast, minimising the impact of the hazard, whereas if it is basaltic like Mount Nyiragongo then it will flow extremely fast, intensifying the hazard.

The type of lava also affects how explosive the volcanic eruption is; if the lava is of low viscosity such as basaltic lava then the eruption will not be that explosive, usually the eruption will be of Hawaiian type. Whereas more viscous lava such as andesitic and ryolitic, the eruption is more likely to have a higher VEI, such as Chaiten, Chile in 2008. Therefore lava creates many differences in