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AS and A Level: Hazardous Environments
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Discuss the degree to which the theory of plate tectonics is supported by seismic and volcanic activity5 star(s)
Despite this evidence, his theory was initially rejected due to lack of explanation for how continents could move over the earth. However in 1948 a survey of the ocean floor found a ridge running north to south beneath the Atlantic Ocean. During the 1950's magnetic surveys of the ocean floor showed regular patterns of palaeomagnetic striping about the ridges. When lava erupts, iron rich minerals within it are aligned with the earth's magnetic field, this is fixed as the lava cools and they record the earth's polarity at the time they cool.
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Whereas seismicity is where the build up of pressure in the crust is released. Both volcanic and seismic activty when plotted on a map can be seen to follow certain patterns and it is this distribution that helps explain the plate theory. The distributions of earthquake events are found in broad, uneven belts around plate margins and it is the movement of the plates that cause the seismic events. Most of these earthquakes occur along destructive margins, where the heavier oceanic crust descends underneath continental crust. A build up of pressure here, where no subduction takes place for a space of time, eventually leads to a large slippage of the oceanic plate causing shockwaves
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The number of fatalities that result from volcanic and seismic natural hazards is related to the level of development in the country in which they occur. Discuss.4 star(s)
The magma formed from oceanic crust is less dense than (due to its high water content) the mantel and rises up through the vent (this can be seen in figure 1). The lava is generally acidic and is also viscous. This means that eruptions are usually, violent and unpredictable. At divergent plate boundaries the eruptions are from a crack. The eruptions are intermittent and not very violent as the lava has a low viscosity and acidity. Hot spots are volcanic regions where the underlying mantle is thought to have a higher temperature than the surrounding magma allowing it to rise up, hot spots may form island chains are arcs.
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Therefore most Cholera outbreaks occur in spring and autumn when ocean surface temperatures and algae blooms are at their highest. More algae mean more Copepods, and more Copepods mean more Cholera bacteria. The map on the left shows that the areas that Cholera is discovered in are situated below the Brandt line. This is because these areas are surrounded by warm oceans where the growth of algae will be high. Therefore the Cholera bacteria will occur in higher frequency in these areas. This is proven by the map of the world below, which shows the temperatures of the world's oceans.
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The hazards presented by volcanic activity have the greatest impact on the poorest members of the worlds population. To what extent do you agree with this view?3 star(s)
The eruptions of Soufriere Hills beginning in 1995 affected Montserrat's rich and poor inhabitants. As the mostly uninhabitable island's capital town Plymouth was covered in ash, lahars, and pyroclastic flows, many people were evacuated and the majority of the island's homes were destroyed, displacing 7000 people. As a British territory, residents were offered the chance to move to the UK, and similar offers were made from the US; but for the poorest people with little money this would have resulted in an even worse situation- and as Montserrat is formally classed as an LEDC this was the majority of the population- the GNI per capita is only $3,400.
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Floods happen when prolonged rain, intense storms, or meting snow release more water than rivers or land can contain, without causing damage, as a result they over-flow their banks, usually into low lying surrounding areas. More than one third of deaths caused by natural disasters are from serious cases of flooding. Some areas are more prone to flooding than others. For example; melt waters that originate in the mountainous regions of its neighbours India and Nepal regularly inundate the relatively low-lying nation of Bangladesh.
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Volcanic processes also can be found on or near subduction zones associated with destructive plate margins. The line of volcanoes, or 'ring of fire' that surrounds the Pacific Ocean is associated with plate subduction. This tends to be the most violent of all activity, potentially explosive, where it can be hazardous to the public. As do the types of hazards, which are categorised into primary and secondary. Primary hazards, created by the direct vulcanicity of the volcanoes, could include tephra, pyroclastic flows & volcanic gases.
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The primary earthquake hazard directly responsible for mortality is surface seismic waves which cause ground shaking. This poses a huge hazard as buildings and other structures collapse, killing or injuring their occupants. This was the case in Sichuan, China in 2008 where severe ground shaking was the direct cause of death, injury and the catastrophic destruction of hospitals, roads and other infrastructure. An estimated 5.4 million buildings collapsed and a further 21 million were damaged. In poorer areas such as rural China, buildings are compromised despite strict regulations due to poor quality construction work and corruption meaning the correct materials is not used.
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In December's tsunami in the Indian Ocean, an estimated 250,000-300,000 people were killed or are still missing, while millions of lives have been upturned, socially and economically, by its impact. A main reason for the huge death4 star(s)
Predict is defined as:-The skill of explaining new events based on observations or information. According to: - www.dpi.state.wi.us/standards/sciglos.html When looking at the different types of hazards to injure or kill people, or costing the most economic price, we consider such hazards as tsunamis and earthquakes. Recently, In December's tsunami in the Indian Ocean, an estimated 250,000-300,000 people were killed or are still missing, while millions of lives have been upturned, socially and economically, by its impact. A main reason for the huge death toll and such high economic damage was that the tsunami hadn't been predicted, and the people were not aware of its presence under the Indian Ocean.
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