What is the inside of Earth made of?

• The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km. on the continental masses and only 5 km. on the ocean floors. The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina). 
• The oceanic crust mainly consists of silica and magnesium. it is therefore called sima (si-silica and ma-magnesium). Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust.
• The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron).

Further Reading:

• Inside Our Earth
• Geography Notes