NCERT Solutions for Class 7 Geography Chapter 2 - Inside Our Earth

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Chapter 2 - Inside Our Earth Exercise 10

Solution 1

(i) The three layers of the Earth are the crust, the mantle and the core.

(ii) A rock is in effect any natural mass of mineral matter that constitutes the crust of the Earth.

(iii) The three types of rocks are as follows - 'igneous', 'sedimentary' and 'metamorphic'.

(iv) Extrusive rocks have a tendency to be formed when the molten magma from inside Earth turns up on the surface, cools down and sets. At the point when such liquid magma cools down gradually and solidifies within Earth's crust, intrusive rocks are formed.

(v) The change of one kind of rock into another, under specific conditions and in a cyclical way is alluded to as the rock cycle. For instance, igneous rocks, framed as an aftereffect of the cementing of molten magma, may separate into little particles, which might then be transported and saved to structure sedimentary rocks. Sedimentary and igneous rocks change into changeable rocks when subjected to heat and pressure. These changeable rocks might themselves get broken down to structure sedimentary rocks, or they may liquefy under extraordinary pressure and heat to become molten magma, which would then by and by set to structure igneous rocks.

(vi) Certain uses of rocks are as follows:

-  Construction of roads, houses and buildings.

-  Making of jewelery.

-  Cutting and drilling.

-  The mineral constituents of rocks are used in medicines, fuels, fertilisers and industrial purposes.

-  Animal and plant fossils help in scientific research.

(vii) Metamorphic rocks are those rocks that get formed when exposed to a great amount of sustained heat and pressure. Igneous and sedimentary rocks turn into metamorphic rocks when exposed to heat and pressure.

Solution 2

(i) – (a) Igneous

(ii) – (b) Core

(iii) – (b) Minerals

(iv) – (a) Sedimentary rocks

(v) – (a) Crust

Solution 3

(i) - (e) Innermost layer

(ii) - (d) Has definite chemical composition

(iii) - (b) Used for roads and buildings

(iv) - (a) Change into slate

(v) - (c) Made of silicon and alumina

Chapter 2 - Inside Our Earth Exercise 11

Solution 4

(i) The center of the Earth lies 6000 km below the ocean floor. It has extremely high temperature and pressure. It constitutes of molten magma and there is no oxygen for living organisms to survive on. Therefore, we cannot go to the centre of the earth.


(ii) Over time, big rocks tend to disintegrate into small fragments or sediments. These fragments are transported and deposited by elements like wind and water. These loose sediments tend to compress and harden over time and form layers over layers of rocks. These rocks are known as sedimentary rocks.


(iii) Limestone is a type of sedimentary rock. When it is exposed to sustained heat and pressure, it transforms into marble which is a metamorphic variety of rock.