Compare the physical causes of tectonic hazards at contrasting plate boundaries

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Compare the physical causes of tectonic hazards at contrasting plate boundaries

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A tectonic hazard is a physical occurrence resulting from movement in the earth’s crust which has the potential to cause loss of life or property’ (Digby) these tectonic hazards include Volcanoes, earthquakes, or tsunamis and have varying impacts depending on the severity of the physical causes. Tectonic hazards usually occur at plate boundaries where either continental or oceanic crust meet and are either converging, diverging, or sliding past each other. However, intra plate tectonic hazards also occur and there are various other physical causes which are suggested to cause tectonic hazards, these include things such as soil liquefaction, the type of magma, geology of the land around, and the climate of the area. This essay will look at several different plate boundaries, including the 1995 Kobe earthquake in Japan which took place on a destructive boundary, the 1989 San Francisco earthquake on a conservative plate, and the mid Atlantic ridge which is a constructive boundary which causes the 2012 E15 eruption in Iceland.

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Heat rising and falling in the mantle creates convection currents, which are generated by radioactive decay in the core, these currents cause plates to move, and when one oceanic plate moves towards a continental plate, the oceanic plate sinks and is destroyed because it is denser than the continental plate which rises above. These types of plate boundaries often cause earthquakes and volcanoes due to the subduction which causes friction and heat. An example of this is the 1995 Kobe earthquake in Japan. This took place in south central Japan, in the second most populated and industrialised area after Tokyo. The Philippine plate was subducted under the Eurasian plate causing an earthquake with a magnitude of 7.2 (BBC news). There were several other physical causes which made this earthquake a severe hazard, the location of the centre of the earthquake was only 16km below the surface of the land, this shallow focus meant that a lot of energy was released near the surface creating a very large and long shake lasting about 20s, resulting in the area being more affected than if the earthquake had a deep focus. Kobe also suffered a lot of land damage due to soil liquefaction, this is where saturated soil loses its stiffness, usually due to the shaking of an earthquake, which causes it to behave like a liquid due to the increase in pore water pressures, the effects can be extremely damaging as buildings loose all their support and therefore a lot of infrastructure is destroyed, in Kobe this was a particular problem as the crumbling infrastructure causes lots of fires to start, endangering even more people than the earthquake. This soil liquefaction also had a secondary hazard of landslides which were dangerous in the mountainous area.

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Destructive margin

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Conservative margin

Conservative margins, or transform fault boundaries, are when two plates are moving sideways past each other, so land is neither formed nor destroyed. most transform faults appear on the sea floor as deep valleys, however the San Andreas Fault in California is one of few which is exposed to land, due to the pacific plate grinding past the north American plate, roughly at the same rate as finger nails grow.  As a result of a slip along the San Andreas Fault the plates caused the Loma Prieta quake of 89, this was because ...

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