ICSE Class 9 Answered

Crust

• The crust is the uppermost layer found on the surface of the Earth.
• It is the thinnest of all the layers and is about 35 km on the continental masses and only about 5 km on the ocean floor.
• Two main mineral constituents of the continental mass are silica and alumina. Therefore, continental crust is also called sial.
• The oceanic crust consists mainly of silica and alumina. Therefore, it is known as sima.

Mantle

• This layer of the Earth lies underneath the crust.
• It extends up to a depth of 2,900 km below the Earth’s crust.

Core

• It is innermost layer of the Earth with a radius of about 3500 km.
• It is called nife as it is made up of nickel and iron (ni-nickle; fe-ferrous or iron).
• There is very high temperature and pressure inside the Earth’s core.