NCERT Solutions Class 7 Social Science (Geography)
The NCERT Solutions in English Language for Class 7 Social Science (Geography – Our Environment) Chapter – 2 (Inside Our Earth) has been provided here to help the students in solving the questions from this exercise.
Chapter – 2 (Inside Our Earth)
Exercises
1. Answer the following questions.
(i) What are the three layers of the earth?
Answer – The three layers of the Earth are the crust, the mantle and the core.
(ii) What is a rock?
Answer – A rock refers to any natural mass of mineral matter that makes up the Earth’s crust.
(iii) Name three types of rocks.
Answer – The three types of rocks Igneous Rocks, Sedimentary Rocks and Metamorphic Rocks.
(iv) How are extrusive and intrusive rocks formed?
Answer – Extrusive rocks are formed when the molten magma present inside the Earth’s interior comes out onto the Earth’s surface, cools down and becomes solid. When molten magma cools down and solidifies deep within the Earth’s crust, intrusive rocks are formed.
(v) What do you mean by a rock cycle?
Answer – The process of transformation of rocks from one type to another, due to changes in certain conditions in a cyclic manner, is called a rock cycle.
(vi) What are the uses of rocks?
Answer – Some of the uses of rocks are as follows:
(i) To build houses and buildings.
(ii) Precious rocks, called gemstones, are often used to make jewellery.
(iii) To make tools for cutting and drilling purposes.
(iv) The fossilized remains of plants and animals present in rocks help in scientific research.
(v) The different minerals that make up different rocks are extracted and can be used as fuels, medicines, fertilizers, and industries.
(vii) What are metamorphic rocks?
Answer – Metamorphic rocks are the rocks that get formed under great heat and pressure. Igneous and sedimentary rocks, when subjected to heat and pressure, get transformed into metamorphic rocks.
2. Tick the correct answer.
(i) The rock which is made up of molten magma is
(a) Igneous
(b) Sedimentary
(c) Metamorphic
Answer – (a) Igneous
(ii) The innermost layer of the earth is
(a) Crust
(b) Core
(c) Mantle
Answer – (b) Core
(iii) Gold, petroleum and coal are examples of
(a) Rocks
(b) Minerals
(c) Fossils
Answer – (b) Minerals
(iv) Rocks which contain fossils are
(a) Sedimentary rocks
(b) Metamorphic rocks
(c) Igneous rocks
Answer – (a) Sedimentary rocks
(v) The thinnest layer of the earth is
(a) Crust
(b) Mantle
(c) Core
Answer – (a) Crust
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) Has definite chemical composition |
| (v) Sial | (e) Innermost layer |
| (f) Changes into slate | |
| (g) Process of transformation of the rock Rocks |
Answer –
| (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.
Answer – The centre of the earth is also called the core. It is the deepest layer of the earth hat is characterized by extremely high temperature and pressure. It consists of molten magma at earth’s centre that is so hot that it can melt anything that comes in its way. Thus, we cannot go to the centre of the earth.
(ii) Sedimentary rocks are formed from sediments.
Answer – When big rocks break down into small fragments (or sediments), the fragments are transported and deposited by factors like water and wind. The loose sediments compress and harden over the years to form layers and layers of rocks. These rocks are known as sedimentary rocks.
(iii) Limestone is changed into marble
Answer – Limestone is an example of a sedimentary rock. When it is subjected to conditions of extreme heat and pressure, it gets converted into marble, which is a metamorphic rock.
