Plate Tectonics

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Evaluate how plate tectonics theory helps our understanding of the distribution of seismic and volcanic events.

Plate tectonics is a relatively new theory that was developed by Alfred Wegner in 1912 who came up with the idea of Pangea which tells us about the structure of the earth. The earths structure consists of a crust which varies in thickness from 5 to 10 km beneath the oceans to 70 km under continents. The lithosphere is the next part which consists of the crust and the upper mantle and is where plate tectonics are formed. The mantle is the widest section of the earth because it is 2900km thick. Also the rocks in the upper part of the mantle are solid and sit on top of the asthenosphere. The core is made up of two parts the inner core which is semi-liquid and consists mostly of iron and the outer core which is solid and made up of iron-nickel alloy.

Volcanoes occur mainly at destructive plate margins. Destructive margins occur when a continental plate converges with an oceanic plate but oceanic-oceanic convergences do also occur. When a oceanic plate collides with the continental plate because the oceanic plate is denser the lighter continental plate the oceanic plate will subduct underneath. The bending of the oceanic plate is where the two plates have collided and is where you will find an ocean trench for example the marianas trench located the Pacific Ocean, just east of the 14 Mariana Islands near Japan. As the two plates collide the continental land mass is uplifted and compressed which forms fold mountains such as the Andes. Then the oceanic plate will begin to melt at depths of 100km and will be destroyed by 700km and this is known as the Benioff zone. When the oceanic plate melts it creates magma which is less dense than the surronding asthenosphere. As a result plumes begin to rise through fault lines and cracks and then eventually the magma…...

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