NCERT Class 7 Geography Inside Our Earth

NCERT Class 7 Geography Inside Our Earth. Download NCERT Chapters and Books in pdf format. Easy to print and read. Copies of these textbooks may be downloaded and used as textbooks or for reference. Refer to other chapters and books at other links (NCERT now providing you soft copies of all textbooks of all subjects from class first to twelfth online). 

Inside Our Earth

The earth, our homeland is a dynamic planet. It is constantly undergoing changes inside and outside. Have you ever wondered what lies in the interior of the earth? What is the earth made up of?

INTERIOR OF THE EARTH

Just like an onion, the earth is made up of several concentric layers with one inside another (Fig. 2.1). 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 masses and only 5 km. on the ocean floors.

The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina). The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium) (Fig. 2.2). Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron). The central core has very high temperature and pressure.

ROCKS AND MINERALS

The earth’s crust is made up of various types of rocks. 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.

There are three major types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks. When the molten magma cools, 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. Can you imagine lava coming out from the volcanoes? 

Lava is actually fiery red molten magma coming out from the interior of the earth on its surface. When this 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. For example, basalt. The 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. Granite is an example of such a rock. Grinding stones used to prepare paste/powder of spices and grains are made of granite.

Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. These sediments 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. For example, sandstone is made from grains of sand. These rocks may als contain fossils of plants, animals and other microorganisms that once lived on them. Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure (Fig. 2.3). For example, clay changes into slate and limestone into marble.

Exercises

1. Answer the following questions.

(i) What are the three layers of the earth?

(ii) What is a rock?

(iii) Name three types of rocks.

(iv) How are extrusive and intrusive rocks formed?

(v) What do you mean by a rock cycle?

(vi) What are the uses of rocks?

(vii) What are metamorphic rocks?

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. Give reasons.

(i) We cannot go to the centre of the earth.

(ii) Sedimentary rocks are formed from sediments.

(iii) Limestone is changed into marble.


Please refer to attached file for NCERT Class 7 Geography Inside Our Earth

Tags: 

 


Click to View or Download pdf file
Click for more Social Science Study Material

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

Revised SOP preventive measures followed while conducting examinations

Revised SOP on preventive measures to be followed while conducting examinations to contain spread of COVID-19 issued by Ministry of Health & Family Welfare Examination centres are frequented by large number of students (as well as their parents) and staff till the...

Training of CBSE School Teachers on Olabs

Training of CBSE School Teachers on Olabs in collaboration with C-DAC Mumbai: OLabs is a platform jointly developed by the Ministry of Electronics and Telecommunications, Government of India, CDAC, and Amrita University to facilitate a virtual experience of CBSE...

National Online Painting Championship

The National Mission for Clean Ganga, Ministry of Jal Shakti in collaboration with Kalantar Art Trust is organizing KALANTAR-2020: National Online Painting Championship with the aim to provide a platform to youth and school children to demonstrate their artistic skills...

NEP Transforming India Quiz

As a part of Shikshak Parv celebration, an online quiz competition on National Education Policy 2020 will be organized by the Ministry of Education, Govt. of India, from 5 th September to 25th September 2020 in order to create awareness about NEP among all stakeholders...

TERI Green Olympiad 2020

Green Olympiad is a value driven project conducted by TERI (The Energy and Resources Institute) for school students annually since 1999. This Olympiad assesses the environment quotient of students and also enhances their understanding on issues related to sustainable...

Online Teacher Training Course on Competency based Education in DIKSHA

Competency is a set of skills, abilities, knowledge that helps an individual perform a given task in real life. Every learning should go into the imbibing of these skills to lead a productive and joyful life. The NATIONAL EDUCATION POLICY-2020 calls for shift towards...

×
Studies Today