Geography - The Earth & Tectonic Plates: Geography Exam Tips

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Get Unlimited Access to GCSE Tutor Videos & Online Revision Here for £19.99: http://www.revisionapp.co.uk/product/online-gcse-revision. Our planet Earth is divided up into four layers: the inner core, outer core, mantle and crust. The solid inner core is made up of blazing hot iron and nickel, and is surrounded by the liquid outer core. The mantle is made up mostly of magma, or molten rock, and the crust is the layer we live and walk on. The crust is also made up of Earth's tectonic plates, which move constantly over the mantle, and occasionally collide. This is how earthquakes and volcanoes occur.

Land is carried by what is known as the continental crust, and water by the oceanic crust. The plates of the Earth's crust move in different directions. The plates move apart at divergent or constructive boundaries. Likewise, if they move together the boundary is known as convergent or destructive. Earthquakes and volcanoes are most likely to occur at these boundaries; hefty chunks of the Earth are crashing into each other! These plate boundaries are areas of high seismic activity, which means that it is an area more likely to experience earthquakes, or the after-effects of earthquakes, such as tsunamis.

The motion of the tectonic plates is caused by convection currents. These are caused by radioactive decay in the core of the Earth, and result in hot currents rising and cold currents falling. As the plates move apart, the molten magma from the mantle very slowly begins to emerge. This is quickly cooled into igneous rock, but the magma keeps erupting. Most of these constructive boundaries occur under the ocean, so the magma cools very quickly. Over time, this builds into a massive pile of cooled magma, or a volcano. These piles can sometimes be so large that they erupt out of the sea and form islands.

When two plates move together, in a destructive boundary, it is usually an oceanic plate and a continental plate. As the oceanic plate is denser, when the two collide it is forced underneath the continental plate, melting as it goes. This creates shuddering earthquakes, and can even trigger a volcanic eruption if the magma is under enough pressure. The force of this collision is so great that whole mountains are crushed together, which is known as folding. This pushes the mountains upwards. Some of the highest mountains on the planet are fold mountains, and the extreme forces present in a destructive boundary, effectively an earthquake, caused them all.
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plate tectonics, earthquakes, and volcanoes

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