NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth, here we are going to give you a summary of NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth with questions and answers from the textbook. In this chapter, we will study about the meaning of rocks, different layers of earth and how they help us. Your all doubts from the chapter of NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth of class 7 NCERT will be cleared from these explanations.
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Table of Contents
NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth: Introduction
Earth is made up of several concentric layers, with one inside another. Earth is a dynamic planet and always keeps on changing. We are going to look at a summary and NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth in details.
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Crust
The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km. on the continental area. The core is about 5 km. on the ocean floors.
The main mineral constituents of the continental mass are silica and alumina.It is thus called sial.The oceanic crust mainly consists of silica and magnesium. It is therefore called sima.
Mantle
Beneath the crust is the mantle which extends up to a depth of 2900 km.
Core
Innermost layer is called core. It has a radius of about 3500 km.
Mainly made up of nickel and iron and is called nife.
The central core has very high temperature and pressure.
Rocks and Minerals
Any natural mass of mineral matter that makes up the earth’s crust is called a rock. Rocks can be of different colour, size and texture.
Three major types of rocks are:
- Igneous rocks
- Sedimentary rocks
- Metamorphic rocks.
Primary rocks
Molten magma cools, and it becomes solid.
Rocks thus formed are called igneous rocks.
They are also called primary rocks.
There are two types of igneous rocks: intrusive rocks and extrusive rocks.
Molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure, such as basalt. Deccan plateau is made up of basalt rocks.
Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. Since they cool down slowly they form large grains. Such as Granite. Grinding stones are used to
- Prepare paste/powder of spices
- Grains are made of granite.
Sedimentary Rocks
Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. They are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks. Sandstone is made from grains of sand is such an example. These rocks may also contain fossils of plants, animals and other microorganisms that once lived on them.
Metamorphic Rocks
Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure.
One example is clay changes into slate and limestone into marble.
Rocks are very useful to us. The hard rocks are used for making roads, houses and buildings. One type of rock changes to another type under certain conditions in a cyclic manner. This process of transformation of the rock from one to another is known as the rock cycle.
Rocks are made up of different minerals. Minerals are naturally occurring substances. They have certain physical properties and definite chemical composition. Minerals are used as fuels. Such as, coal, natural gas and petroleum. They are also used in industries – iron, aluminium, gold, uranium, etc, in medicine, in fertilisers, etc.
NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth : Exercises
1. Answer the following questions.
(i) What are the three layers of the earth?
Ans. The three layers of the earth are:
- Crust
- Mantle
- Core
(ii) What is a rock?
Ans. Any natural mass of mineral matter that makes up the earth’s crust is called a rock.
(iii) Name three types of rocks.
Ans. three types of rocks are:
- Igneous
- Sedimentary
- Metamorphic
(iv) How are extrusive and intrusive rocks formed?
Ans. Molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks.
Molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks.
(v) What do you mean by a rock cycle?
Ans. One type of rock changes to another type under certain conditions in a cyclic manner. This process of transformation of the rock from one to another is known as the rock cycle.
(vi) What are the uses of rocks?
Ans. Rocks are used in making roads, houses and buildings. :
(vii) What are metamorphic rocks?
Ans. Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure.
One example is 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
Ans. (a) Igneous
More Questions
3. The innermost layer of the earth is
(a) Crust (b) Core (c) Mantle
Ans. (b) Core
(ii) Gold, petroleum and coal are examples of
(a) Rocks (b) Minerals (c) Fossils
Ans. (b) Minerals
(iii) Rocks which contain fossils are
(a) Sedimentary rocks (b) Metamorphic rocks (c) Igneous rocks
Ans. (a) Sedimentary rocks
(iv) The thinnest layer of the earth is
(a) Crust (b) Mantle (c) Core
Ans. (a) Crust
3. Match the following.
| COLUMN I | COLUMN II |
| (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) Has definite chemical composition |
| (v) Sial | (e) Innermost layer |
| (f) Changes into slate | |
| (g) Process of transformation of the rock |
| COLUMN I | COLUMN II |
| (i) Core | (e) Innermost layer |
| (ii) Minerals | (d) Has 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 |
4. Give reasons.
(i) We cannot go to the centre of the earth.
Ans. We cannot go to the centre of the earth because the temperature and pressure is very very high. Everything is molten in the core of the earth.
(ii) Sedimentary rocks are formed from sediments.
Ans. Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. They are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks. Thus, sedimentary rocks are formed from sediments.
(iii) Limestone is changed into marble.
Ans. Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure.
One example is clay changes into slate and limestone into marble.
NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth : Conclusion
All living beings on Earth are very lucky to be born here. None other planets have such a disciplined cycle, atmosphere than our own Earth. The layers of earth together keeps the Earth’ temperature and gravity in balance. It also provides us minerals and rocks for various purposes. Rocks are very important both for our health and building materials. Thus this is in conclusion, of NCERT Solutions Class 7 Social Science Chapter 2 Inside Our Earth. We will learn more about it higher classes.
