The Earth’s structure
The earth is made up of 3 main layers, the crust, the mantle and the core. The crust is the
outer layer, the core is the inner layer and in between there is the mantle.
1. The Crust
It is the layer on which we live as the continents and the oceans rest on it. It is made
of solid material and floats on the Mantle. Its thickness varies depending upon the
type of materials of which it is made. Therefore Oceanic crust is about 6 to 11km
thick, while Continental crust is about 30 km thick.
2. The Mantle
It consists of materials which are softer and denser. It is in a semi-molten state as part
of the material is in the form of magma. It is about 2,900km thick and temperature
can range from 500 to 3000ºC. The mantle is divided into the inner mantle and the
outer mantle.Convection currents in the mantle causes the movements of tectonic
plates at the surface.
3. The Core
It is the innermost part of the earth. Temperature is extremely high here. It is a dense
ball of iron and nickel. It is divided into 2 parts, the Outer core and the Inner core.
The Outer Core:
It is in a molten (liquid) state due to composition (mainly iron) and extreme
temperature (4000-5000ºC). It is about 2,200 km thick.
The Inner Core:
It is the centre of the earth, and is about 1,250 km thick.
It mainly consists of iron, nickel and some lighter elements (probably sulphur,
carbon, oxygen, silicon and potassium). Though the temperature in the inner core is
about 5000-6000 ºC, it is in a solid state because of the high pressure at the centre of
the earth.
More info:
http://ontwikkel.thinkquest.nl/~ll125/en/struct.htm
http://www.didcotgirls.oxon.sch.uk/depts/geog/bcs_geography/earth_structure.htm