The Earths Layers
- Core = dense rocks containing iron and nickle alloys + divided up into solid inner core and a molten outer core. temp = 5000*C +
- Mantle = molten and semi molten rocks containing lighter elements, such as silicon and oxygen.
- Crust = even lighter because of the elements that are present => most abundangt being silicon, oxygen, aluminium, potassium, and sodium.
- Crust varies in thickness: beneath ocean = 6-10km thich, beneath continents = 30-4-km. Under highest mountain rages = upto 70km thick.
- The theory of plate tectonics has retained this simple threefold division, but new research has suggested that the crust and the upper mantle should be divides into the lithosphere and the asthenosphere.
- Lithosphere = crust and rigid upper section of the mantle + = approx 80-90km thick.
- It is divided into seven very large plates and a number of smaller ones.
- Plates = divided into 2 catagories: oceanic + continental => depending on the material from which they are made.
- Below lithosphere = semi-molten asthenosphere, on which the plates float + move.
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