Wednesday 9 November 2011

CBSE Class VII (7th) Geography -Chapter 2. Inside Our Earth

Question1. Answer the following questions.
Q(i). What are the three layers of the earth?
Answer.Crust, Mantle and Core are the three layers of the earth
Three Layers of the Earth

Q(ii). What is rock?
Answer. Any natural mass of mineral matter that makes up the earth’s crust is called rock.

Q(iii). Name three types of rocks?
Answer.There are three types of rocks:
1.Igneous rock.
2.Sedimentary rock.
3.Metamorphic rock.

Q(iv). How are extrusive and intrusive rock formed?
Answer. Extrusive rocks are formed due to rapid cooling and solidification of molten magma on the earth’s surface.
Intrusive rocks are formed when molten magma cools down deep inside the earth’s crust.

Q(v). What do you mean by a rock cycle?
Answer.The change of one type of rock into another type under certain conditions in a cyclic called a rock cycle.

Q(vi) What are the uses of rock?
Answer. Following are some uses of rocks:
1.They are used as fuels.
2.They are used in industries.
3.They are used in medicines.
4.They are used in fertilizers.

Q(vii) What are the metamorphic rocks?
Answer.The types of rocks formed when igneous and sedimentary rocks undergo heat and pressure are called metamorphic rocks.

Question2. Tick the correct answer.
Q(i)The rock which is made up of molten magma is.
(a)Igneous. (b) Sedimentary. (c) Metamorphic.


Q(ii) The innermost layer of the earth is.
(a)Crust. (b) Core. (c) Mantle.


Q(iii) Gold, petroleum and coal are example of.
(a)Rocks.(b) Minerals. (c) Fossils


Q(iv)Rock which contain of.
(a) Sedimentary rocks. (b) Metamorphic rocks. (c) Igneous rocks.

Answer.(a)Sedimentary rocks.

Q(v) The thinnest layer of the earth is.
(a)Crust. (b) Mantle. (c) Core.


Question 3.Match the following.
1Core(a)Change into slate.
2Minerals.(b)Used for roads and buildings.
3Rocks.(c)Made ofsilicaand alumina.
4Clay.(d)Has definite chemical compositon
5sial.(e)Innermost layer.


1Core(a)Innermost layer.
2Minerals.(b)Has definite chemical compositon.
3Rocks.(c)Used for roads and buildings.
4Clay.(d)Change into slate.
5sial.(e)Made of silicon and alumina.

Question4.Give Resons:
Q(i)We cannot go to the centre of the earth.
Answer: The radius of the earth is more than 6000 km. to reach the centre of ther earth, we have to dig a hole to this depth,which is impossible.

Q(ii). Sedimentary rocks are formed from sediment.
Answer: Rocks breakdown into small fragments under various conditions.These fragments,called sediments, are transported by wind and water. Layers of sediments are formed when loose sediments are compressed and hardened. These layers of sediments thus form sedimentary rocks.

Q(iii). Limestone is changed into marbles.
Answer. Ingenous and sedimentary rocks change their form under great pressure and temperature conditions to form metaphoric rocks. the same thing happens with limesone,which under the effect of heat and pressure chjange into marble, which is an example o fmetmorphic rocks.

Question 5. For fun.
Q(i)What are the minerals most commonly used in the following objects?


(ii) Identify some more objects made up of different minerals.
Answer. Some more objects:

3Electric wire.----copper,aluminium.