How old is the Earth Part -2

How old is the Earth Part -2

Beneath the Earth's crust lies a much thicker layer called the mantle, a layer which man has never reached, even in his deepest drilling. Boreholes have been sunk to depths of nearly 8 km. (5 miles) in the search for oil. 

The mantle is about 2,800 km. (1750 miles) thick and forms about three-quarters of the whole Earth. 

It consists of solid rock at temperatures which vary from about 870°C (1600°F) near the crust to over 2200°C (4000°F) at its greatest depths.

Beneath the mantle lies the Earth's core, a great ball which may consist of molten iron under enormous pressure perhaps 20,000 tons per square inch. 

It is this central core that is the source of the Earth's magnetic field since the liquid iron in it generates its own electricity.