Evaluate How Plate Tectonic Theory Helps Our Understanding of the Distribution of Seismic and Volcanic Events (40 Marks)

1194 Words Apr 23rd, 2013 5 Pages
Evaluate how Plate Tectonic Theory helps our Understanding of the Distribution of Seismic and Volcanic Events (40 marks)
The Plate Tectonic Theory developed in the late 1960’s, when people noticed how continents either side of the Atlantic Ocean seemed to almost fit together. Francis Bacon, an English Philosopher was aware of this as early as 1620. Topographical and geological evidence built up and allowed Alfred Wegener to publish a theory in 1912, suggesting that the continents were once all joined together in a supercontinent he called Pangaea. Wegener proposed that at some time, the land masses had drifted apart until they occupied their current positions on the globe. There was lots of evidence to support his theory including
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Subduction provided the mechanism for sea floor spreading, and the drifting of continents. The denser oceanic crust is created in some areas, and destroyed in others, and the less dense, more buoyant continental crust is not consumed. Central to the theory of plate tectonics is the idea that the higher temperatures at the earth’s core, and the heat released by radioactive decay of elements within the mantle, help to create convection currents. These zones of hotter, more liquid magma are thought to exhibit a continuous circulatory motion in the asthenoshphere that causes the crustal plates to move. They pull crust apart at spreading ridges and rift zones, and pull slabs of oceanic crust back down into the mantle at subduction zones. All plates are in motion of an average of 5-10cm per year but some can move up to 18cm per year.
Destructive plate margins also known as convergent boundaries, describe when two plates moving towards each other (continental and oceanic crust). This process involves the denser oceanic crust being subducted underneath the continental crust forming a subduction zone and oceanic trench. As it is subducted it melts due to heat and pressure. The heat sources are friction between the two plates and from earth’s interior. Melting of subducting plates creates magma which is lighter than the mantle and therefore rises resulting in

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