NCERT Solutions for Class 7 for Social Science Geography Chapter 2 Inside Our Earth
1. Answer the following questions:
(i) What are the three layers of the earth?
Ans. The three layers of the earth are:
(ii) What is a rock?
Ans. Any natural mass of mineral matter that makes up the earth’s crust is called rock.
(iii) Name three types of rocks.
Ans. The three types of rocks are:
(a) Igneous Rocks
(b) Sedimentary Rocks, and
(c) Metamorphic Rocks
(iv) How are extrusive and intrusive rocks formed?
Ans. Rocks that are formed when molten magma solidifies on the earth’s crust are known as extrusive igneous rocks. Sometimes, the molten magma cools down deep inside the earth’s crust. The rocks so formed are known as intrusive igneous rocks.
(v) What do you mean by a rock cycle?
Ans. The process of transformation of rock from one type to another is known as rock cycle.
(vi) What are the uses of rocks?
Ans. Rocks are very useful to us. They are used for making roads, houses, buildings, bridges, etc. They are also used to make decorative items such as vases, boxes, statues, etc.
(vii) What are metamorphic rocks?
Ans. When igneous or sedimentary rocks are subjected to high temperature and pressure, they are converted into metamorphic rocks. For example, clay changes into slate and limestone into marble.
2. Tick the correct answer.
(i) The rock which is made up of molten magma is
(a) Igneous (b) Sedimentary (c) Metamorphic
(ii) The innermost layer of the earth is
(a) Crust (b) Core (c) Mantle
(iii) Gold, petroleum, and coal are examples of
(a) Rocks (b) Minerals (c) Fossils
(iv) Rocks which contain fossils are
(a) Sedimentary Rocks
(b) Metamorphic Rocks
(c) Igneous Rocks
(v) The thinnest layer of the earth is
(a) Crust (b) Mantle (c) Core
3. Match the following.
(i) Core (a) Earth’s surface
(ii) Minerals (b) Used for roads and buildings
(iii) Rocks (c) Made of silicon and alumina
(iv) Clay (d) Have definite chemical composition
(v) Sial (e) Innermost layer
(f) Changes into slate
(g) Process of transformation of the rock
(i) Core (e) Innermost layer
(ii) Minerals (d) Have definite chemical composition
(iii) Rocks (b) Used for roads and buildings
(iv) Clay (f) Changes into slate
(v) Sial (c) Made of silicon and alumina
5. Give reasons.
(i) We cannot go to the centre of the earth.
Ans. The centre of the earth is characterised by very high temperature and pressure, which does not allow the survival of any living being. Thus, it is impossible for anyone to reach the centre of the earth.
(ii) Sedimentary rocks are formed from sediments.
Ans. Rocks strike each other and are broken down into small sediments. These sediments are transported and deposited by natural agents like wind, water, etc. Overtime, these loose sediments are compressed and hardened to form rocks, which are known as sedimentary rocks.
(iii) Limestone is changed into marble.
Ans. When igneous and sedimentary rocks are subjected to high temperature and pressure, they are converted into metamorphic rocks. Limestone is a sedimentary rock, which after going through such a process is converted into marble, a metamorphic rock.
5. For fun.
(i) What are the minerals most commonly used in the following objects?
(a) Karhai - Aluminium
(b) Pan/Tava – Iron
(c) Ornaments – Gold
(d) Bell – Silver
(e) Hammer – Iron
(f) Lamp – Copper
(ii) Identify some more objects made up of different minerals.
Ans. Some other objects made up of minerals are:
(a) Pencil lead – Graphite
(b) Mirror – Quartz
(c) Trash can – Chromite
(d) Wires - Copper