Brief reminder of Part 1 (without mistake ) :
The structure of the Earth has several layers. At the centre is a solid core or ' seed ' with a radius of 1200 km and a depth of 6300 km. This seed floats in a liquid core that is driven by rapid convective movements that generate the Earth ' s magnetic field.
The Earth ' s mantle lies above the outer core and below the Earth ' s crust at a dept of 2900 km where the temperature is 3000°C.
The Earth ' s crust is a layer of compact rock that start at the surface of the Earth and sinks to a depth of 70 km, where the temperature can rise to 1000°C. It is craked in places and divided into pieces like a puzzle, these are the tectonic plates which are about 100 km thick. These pieces or plates, made up of large chunk of the Earth ' s outer shell, do not fit together very well. As a result, they are not fixe and float on the magma and move a few centimetres per year. The magma inside the Earth ' s mantle is in constant circular vertical motion.
In fact, when it is close to the core it is very hot and melts. Lighter, it rises to the surface while the magma neer the surface cools and hardens and sinnks back down. These curents cause the magma rocks to move and drag the plates above them. Thus, some of them move apart, others come closer together and slide under each other or colide, while others slide alongside each other. These movements craete mountain ranges, oceans or cause different types of movements, such as earthquakes, tsunamis, and volcanoes. |
