Class 7 Social Science Inside Our Earth Exam Notes

Read and download free pdf of Class 7 Social Science Inside Our Earth Exam Notes. Students and teachers of Class 7 Social Science can get free advanced study material, revision notes, sure shot questions and answers for Class 7 Social Science prepared as per the latest syllabus and examination guidelines in your school. Standard 7 students should download this study material which will give them more knowledge for all chapters in Social Science and all important topics which are scoring and can get you more marks. Students should also download free pdf of Chapter wise Notes for Class 7 Social Science prepared by school teachers as per the latest NCERT, CBSE, KVS books and syllabus issued this year and also download free worksheets and question papers available here to get higher scores in school exams and tests, also click here for more Study Material for Class 7 Social Science

Class 7 Social Science Inside Our Earth Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Introduction

The earth is the only planet in the solar system which supports life. It is a dynamic planet, In which changes are constantly taking place. The three realms of our earth are land (lithosphere), water (hydrosphere) and air (atmosphere). What lies in the interior of earth has always been a mystery for most of us.

 The earth is made up of concentric layers with one inside another (just like in an onion). Three main layers of the earth are the crust, the mantle and the core.

(1) The crust :-

(i) The outermost and thinnest of all the layers.

 (ii) It is also called lithosphere, as it is a sphere of solid rocks.

(iii) Its thickness is about 35-40 km on the continental masses and only about 5-10 km on the ocean floors.

(iv) The continental mass is made up of rocks and main mineral constitutents are silica and  alumina (SIAL).

(v) The main constituents of the rocks of the oceanic crust are silica and magnesium (SIMA).

 (vi) The crust forms less than one per cent of the radius of th earth.

(2) The Mantle :-

 (i) Lies just below the crust and it extends up to a depth of about 2900 km, below the crust.

 (ii) At the depth of about 100-250 km, the mantle is partially molten.

(iii) This region is known as the asthenosphere.

(iv) The temperature in the mantle increases with the increase in depth, and ranges between 870ºC (upper layer) and about 2200ºC (lower layer).

(v) The density of the mantle varies between 3 g per cm3 at the top and 4.5 g per cm3 at the bottom.

(3)  The Core :-

(i) The innermost layer of the earth and has a radius of about 3500 km.

(ii) It is the most inaccessible layer lying around the centre of the earth .

(iii) It is the heaviest part of the earth and is made up of nickel (Ni) and ferrous (Fe). Thus, it is alos called NIFE.

(iv) The estimated temperature is about 2200ºC to 5000ºC to.

(v) The layer is thought to be in the molten state, but the very high pressure keeps this layer firm and solid.

 (vi) The density varies from 5 g per cm3 to about 13.90 g per cm3.

→   ROCKS AND MINERALS

The lithosphere or the crust of the earth is made up of a large variety of rocks. The rocks are defined as any natural mass of mineral matter that makes up the crust of the earth. The rocks differ from one another in colour, structure, texture, mode of occurrence, etc. The scientists have recognised more than 2000 mineral elements in the rocks, but only a few are important. The crust of the earth contains more of silicon and aluminium.
 
According to the mode of formation, the rocks of the eath's crust are of the following three major types.
 
(1)  The Igneous rocks
 
(2)  The Sedimentary rocks
 
(3) The Metamorphic rocks

→   THE IGNEOUS ROCKS

(i)  The term 'igneous' has been derived from the Latin word 'ignis' which means fire. 
 
(ii)  The igneous rocks are associated with volcanic eruptions.
 
(iii) The hot molten material, called magma, is found at great depths in the interior of the earth. 
 
(iv) The magma is brought on the surface of the earth during the volcanic eruptions.
 
(v)  When the molten magma (now called lava) cools and solidifies, the igneous rocks are formed. 
 
(vi) These rocks were first to be formed and are called the primary rocks.
 
(vii) The igneous rocks are hard, smooth, finegrained, compact or have large crystals. (viii) These rocks do not have fossils of animals or plants.
 
(ix) The igneous rocks have silicate minerals and most of the metals, such as iron, aluminium, gold, etc. are found in them.
 
(x)  The igneous rocks are of two types –(A) The Extrusive Igneous rocks, and (B) The Intrusive igneous rocks.

 (A) The Extrusive Igneous rocks :-

 (i)   Formed by the cooling of molten lava on the surface of the earth.

 (ii)  The hot lava cools down rapidly and becomes solid.

 (iii) These rocks are smooth and have a fine grained structure, such as basalt.

(v)  The Deccan plateau of India is made up of basalt rocks.

 (B) The Intrusive Igneous rocks :-

 (i)   Formed when the hot molten magma cools down and solidifies deep inside the crust of the earth. 

 (ii)  The slow rate of cooling forms coarse textured hard rocks with large crystals, such as granite.

 (iii) The grinding stones are generally made of granite.

→   THE SEDIMENTARY ROCKS

 (i)   When the igneous rocks are exposed on the earth's surface, they are broken down by the agents of weathering into small fragments. The small fragments, called sediments, are carried away and deposited by the agents of gradation, such as rivers, glaciers, wind and sea waves.

 (ii)  The  loose  deposited  sediments  are  compressed  and  hardened  due  to  the  weight  of  new  layers  of sediments. The sediments are cemented together to form sedimentary rocks. The sedimentary rocks are the  secondary  rocks  as  they  are  formed  by  the  solidification  of  sediments  derived  from  igneous, sedimentary or metamorphic rocks.

 (iii) The sedimentary rocks are softer than the igneous rocks and may also contain fossils of plants, animals and other organisms that once lived on them.

 (iv) These rocks are mostly formed under water and have horizontal layers.

 (v)  The sedimentary rocks are most widespread and cover about 75 percent of the surface area of the earth.

  (vi) These rocks can create extensive landforms.

 (vii) Coal and petroleum are the most important products derived from the sedimentary rocks.

 (viii) Sandstone is made from grains of stone.

→    THE METAMORPHIC ROCKS

 (i)   The term 'metamorphic' has been derived from 'metamorphose', which means change in form. The rocks which were once igneous and sedimentary can change under great heat and pressure into metamorphic rocks.

 (ii)  The minerals in the rocks may change their composition and texture under high temperature and pressure. 

 (iii) For Example, the limestone can change into marble and clay can change into slate.

 (iv) The metamorphic rocks are generally hard and have high specific gravity.

→    SIGNIFICANCE OF ROCKS

(i)   The rocks are of great use as they are composed of various minerals. (ii)  Soils are derived from the weathering of rocks.

(iii) Almost all types of building materials needed for making roads, houses, buildings, bridges, etc. are derived from rocks.

(iv) Rocks are a source of metals like iron, copper, gold, silver, etc.

(v)  Some minerals are used as fossil fuels such as coal and petroleum. (vi) They are also used in industries-Iron, Aluminium.

→     ROCK CYCLE

(i)   The change of one type of rock into another type of rock under certain conditions in a cyclic manner is called the rock cycle.

(ii)  The hot molten magma cools and solidifies to form igneous rocks.

(iii) The different agents of weathering break the igneous rocks into small fragments.

(iv) These small fragments of igneous rocks are carried and deposited by the agents of gradation to form sedimentary rocks.

(v)  The igneous and sedimentary rocks thus formed can be subjected to great heat and pressure. 

(vi) This can change them into metamorphic rocks.

(vii) At many places, the great heat and pressure can melt the metamorphic rocks to form the molten magma. 

(viii) This molten magma can cool down and become to form igneous rocks again.

 ♦  The rock cycle derives energy from inside the earth and also from the Sun.

 ♦   The rock material of the earth is never lost in the rock cycle.

 ♦   The rock cycle on the earth's surface has neither a beginning nor an end

→   ROCK DISTRIBUTION IN INDIA

(i)   Granite is found in Rajasthan, Madhya Pradesh, Chota Nagpur Plateau, Karnataka. Tamil Nadu Andhra Pradesh and Deccan trap region (Maharashtra).

(ii)  Sandstone occurs in Vindhyachal and Aravali ranges. Limestone occurs widely in peninsular India. Coal mines occur in the basins of rivers Godavari. Mahanadi and Damodar, Marble is found in Rajasthan . The Indo-Ganetic plain is of sedimentary accumulation.

(iii) Rocks have great economic value. The cotton soil found in the Deccan trap is a product of extrusive igneous rocks. Other soils like alluvium are also result of disintegrated rocks. Stones used in construction of houses and roads, dams, etc. are all rock products. Rocks are source of previous and useful metals. Iron ore, bauxite, copper, lead, zinc and gold are found in igneous rocks. Non-metallic minerals include sulphur which is used for medicinal purposes. Coal and Petroleum are important sources of energy.

 

Please click on below link to download pdf file for Class 7 Social Science Inside Our Earth Exam Notes.

Tags: 

 


Click to View or Download pdf file
Click for more Social Science Study Material
Class 7 Social Science Water Exam Notes
Class 7 Social Science Understanding Media Exam Notes
Class 7 Social Science Understanding Advertising Exam Notes
Class 7 Social Science Tribes Nomads and settled communities Exam Notes
Class 7 Social Science Tracing Changes Through A thousand Year Exam Notes
Class 7 Social Science Towns Traders and Craftspersons Exam Notes
Class 7 Social Science The Mughal Empire Exam Notes
Class 7 Social Science The Making of Regional Cultures Exam Notes
Class 7 Social Science The Delhi Sultanate Exam Notes
Class 7 Social Science Struggles For Equality Exam Notes
Class 7 Social Science Rulers and buildings Exam Notes
Class 7 Social Science Role Of The Government In Health Exam Notes
Class 7 Social Science Our Environment Exam Notes
Class 7 Social Science Our Changing Earth B Exam Notes
Class 7 Social Science Our Changing Earth A Exam Notes
Class 7 Social Science On Equality Exam Notes
Class 7 Social Science New Kings and Kingdoms Exam Notes
Class 7 Social Science Natural Vegetation and Wild Life Exam Notes
Class 7 Social Science Markets Around us Exam Notes
Class 7 Social Science Life In The Temperature Grasslands Exam Notes
Class 7 Social Science Life In Desserts Exam Notes
Class 7 Social Science Inside Our Earth Exam Notes
Class 7 Social Science Human Environment Settlement Transport and Communication Exam Notes
Class 7 Social Science Human Environment Interactions Exam Notes
Class 7 Social Science How The State Government Works Exam Notes
Class 7 Social Science Gender and the Role of women Exam Notes
Class 7 Social Science Eighteenth Century Political Formations Exam Notes
Class 7 Social Science Devotional Paths to the Divine Exam Notes
Class 7 Social Science Air Exam Notes Set B
Class 7 Social Science Air Exam Notes Set A
Class 7 Social Science A Shirt in the Market Exam Notes

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

CBSE Board Examination Scheme of Assessment 2021 2022

A. Academic session to be divided into 2 Terms with approximately 50% syllabus in each term: The syllabus for the Academic session 2021-22 will be divided into 2 terms by following a systematic approach by looking into the interconnectivity of concepts and topics by...

CBSE Class 12 Evaluation Criteria 2021

SUMMARY OF THE POLICY FOR TABULATION OF MARKS FOR CLASS XII BOARD EXAMINATIONS 2021   1(a) Due to cancellation of the Board examinations, the assessment of theory portion of 80/70/60/50/30 marks will be done by the school based on the following:     Class...

Moderation of Marks Class 11 and 12 Board Exams

The portal for moderation and finalization of results for Class-12 is being opened from 16.07.2021 to 22.07.2021. As Board has to declare the result latest by 31.07.2021, schools have been requested to follow the schedule strictly and complete the moderation within...

FAQs on Policy for Tabulation of Marks for Class 10 Board Exams

ON POLICY Question.1 How CBSE will declare the result of Class-X? Answer. Results of Class X Board will be declared on the basis of an objective criterion developed by the Board vide Notification no.CBSE/CE/2021 dated 01.05.2021. Question.2. If any candidate is not...

CBSE asks schools to load Class 12 Internal Assessment Marks

This has a reference to the letter no CBSE/COORD/2021 dated 11.02.2021 regarding conduct of the School-Based Assessment (Internal Assessment/Practical/ Project) of Class-XII and uploading the marks by 11.06.2021. It has been observed that some schools have not been...

×
Studies Today