What do you know about the interior of the earth? [V. Imp.]
Our earth is made up of several concentric layers with one inside another. These layers are three in number—crust, mantle smd core.
Crust. It is the uppermost layer over the earth's surface. It is the thinnest of all the layers. It is about 35 km on the continential masses and only 5 km on the ocean floors.
The continental masses are made up of silica and alumina. It is thus called sial (si-silica and al-alumina). The oceanic crust mainly consists of silica and magnesium. It is thus called sima (si-silica and ma-magnesium).
Mantle:It is just beneath the crust.It extends up to a depth of 2900 km below the crust
Core:It is the innermost layer. Its radius is about 3500 km. It is mainly made up of nickel and iron and is known as nife (ni-nickel and fe-ferrous, Le., iron). The central core has very high temperature and pressure.
Give reasons:
(i) We cannot go to the centre of the earth.
(ii) Sedimentary rocks are formed from sediments.
(iii) Limestone is changed into marble.
Answer the following questions briefly.
(i) What are the three layers of the earth?
(ii) What is a rock?
(iii) Name three types of rocks.
(iv) How are extrusive and intrusive rocks formed?
(v) What do you mean by a rock cycle?
(vi) What are the uses of rocks?
(vii) What are metamorphic rocks?