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Explain plate tectonics theory and the relationship between plate margins and global distribution of earthquakes and volcanic eruptions (6 Marks)


Plate tectonic theory is the theory that the earth’s structure is made up of different layers, the crust, mantle, outer core and inner core. Each of those layers display different compositions and characteristics which all contribute to plate tectonic theory.The outer layer of the earth is the outer crust, that we live on. The way that land in currently distributed on earth has not always this way. Together the underlying convection current of the mantel later and the outer plates drifted apart from each other from one super continent (Pangea) to how we know the distribution of continental land to be today. There are 9 main tectonic plates and 10 minor ones.The inner core layer is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C. The inner core layer heats up the intermediate mantle layer, causing a convection current in the liquid of the mantle. The outer layer, or the crust are like solid objects floating on top of the moving liquid layer of the mantle. This means that the circular convection current of the mantle causes the outer crust to move. This movement can be divergent, convergent or conservative. Divergent plate boundaries are when tectonic activity causes plates to move away from each other. This is also known as constructive plate boundary because they often occur between oceanic plates and can lead to formation of new land as the mantle is exposed to the outer surface and solidify to form land. Divergent boundaries form volcanic islands, which occur when the plates move apart to produce gaps that molten lava rises to fill.The second type of plate boundary is convergence, this is where two continental plates collide. Between a boundary of an oceanic and continental plate, the dense oceanic plate will subduct under the less dense plate. Where the denser oceanic plate subducts, it results in oceanic trenches, the deepest trench is the Mariana trench, also associated with an active volcanic arch. The third main type of plate boundary is the transform plate boundary, also known as conservative plate boundary. This occurs where plates slide past each other in opposite directions, or in the same direction but at different speeds.Friction is eventually overcome, and the plates slip past in a sudden movement. The shockwaves created produce an earthquake.The best known example of this plate boundary is the San Andreas fault line which forms between the Pacific plate and the North American plate. strike slip fault may occur when the displacement is vertical, causing an earthquake if on land or a tsunami if in the ocean.