NCERT Class 7 Social Science Chapter 22 Inside Our Earth Solutions to each chapter is provided in the list so that you can easily browse through different chapters NCERT Class 7 Social Science Chapter 22 Inside Our Earth and select need one. NCERT Class 7 Social Science Chapter 22 Inside Our Earth and After Question Answers Download PDF. NCERT SST Class 7 Solutions.
NCERT Class 7 Social Science Chapter 22 Inside Our Earth
Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 7 Social Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 7 Social Science Chapter 22 Inside Our Earth and After, NCERT Class 7 Social Science Textbook of Our Pasts – II: History, Social and Political Life – II: Civics, Our Environment: Geography. for All Chapters, You can practice these here.
Inside Our Earth
Chapter: 22
Our Environment [Geography]
QUESTIONS WITH ANSWERS
I. Answer the following questions:
Q.1. What are the three layers of the earth?
Ans: The earth is made up of three main layers-crust, mantle and the core.
(i) Crust
(a) It is the upper most layer of the earth’s surface.
(b) It is the thinnest of all three layers.
(c) It is about 35 km on the continental masses and only 5 km on the ocean floor.
(d) The main mineral constituents of this layer are – SIAL (i.e. silica and aluminium) and SIMA (silica and magnesium)
(ii) Mantle
(a) It is the second layer of the earth’s surface.
(b) It extends up to a depth of 2900 km below the crust.
(c) It has two parts – upper mantle and lower mantle.
(iii) Core
(a) It is the innermost layer of the earth.
(b) Its radius is about 3500 km.
(c) It is mainly made up of nickel and iron and is called nife (ni-nickel, fe-iron).
(d) The central core has very high temperature and pressure.
Q.2. What is a rock?
Ans: Any natural mass of mineral matter that makes up the earth’s crust is called rock.
Q.3. Name three types of rocks.
Ans: Three types of rocks:
(a) Primary Rocks or Igneous Rocks.
(b) Sedimentary Rocks.
(c) Metamorphic Rocks.
Q.4. How are extrusive and intrusive rocks formed?
Ans: When any volcano erupts molten lava flows out which rapidly cools down and solidifies into rocks. Thus rocks so formed are called extrusive rocks. These rocks are also called volcanic rocks.
Examples: Pumice and Basalt extrusive rocks have a very fine-grained structure.
Intrusive rocks are formed when magma cools and crystallizes with in the earth’s crust. These rocks are also called Plutonic rocks. Granite is one of the best examples of Intrusive rocks. Such rocks have larger grains.
Q.5. What do you mean by rock cycle?
Ans: The rock cycle is a continuous process in which rock changes from one kind into another.
Fig. Rock cycle
Q.6. What are the uses of rocks?
Ans: Uses of rocks:
(i) In ancient times rocks were used to make tools and weapons.
(ii) They are used in construction.
(iii) Rocks contain mineral, which are the raw material used in many industries.
(iv) Rocks are used for constructing roads.
(v) Rocks also contains fossil fuels which are the main sources of energy.
II. Tick the correct answer:
(i) The rock which is made up of molten magma is
(a) Igneous.
(b) Sedimentary.
(c) Metamorphic.
Ans: (a) Igneous.
(ii) 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.
(iv) Rocks which contain fossils are
(a) Sedimentary Rocks.
(b) Metamorphic Rocks.
(c) Igneous Rocks.
Ans: (a) Sedimentary Rocks.
(v) The thinnest layer of the earth is
(a) Crust.
(b) Mantle.
(c) Core.
Ans: (a) Crust.
III. Match the following:
Ans:
| (i) Core | (e) Innermost layer |
| (ii) Minerals | (d) Has definite chemical composition |
| (iii) Rocks | (b) Used for building roads and buildings |
| (iv) Clay | (a) Change into slate |
| (v) Sial | (c) Made of silicon and alumina |
IV. Give reasons:
(i) We cannot go to the centre of the earth.
Ans: We cannot go to the centre of the earth as, to reach there we will have to dig a hole of 6000 km. Moreover at the centre, core has very high temperature and pressure.
(ii) Sedimentary rocks are formed from sediments.
Ans: Over the period of several thousand years, sediments carried by the agent of gradation like water, ice, winds and the sea are deposited in layers over the earth. The sediment may consist of weathered and fragmented rocks, minerals, microorganisms and plants and animal remains. As deposition of sediments builds up, the pressure exerted by the upper layers, squeezes the sediments into layered rocks called sedimentary rocks.
(iii) Limestone is changed into marble.
Ans: Limestone is a sedimentary rock. It changed into marble due to high heat and pressure for even longer period of time and formed into a metamorphic rock.
V. For Fun:
(i) What are the minerals most commonly used in the following objects?
(ii) Identify some more objects made up of different minerals.
Ans: (i) Iron, stainless steel, brass, gold and aluminium are the different types of minerals which are commonly used in these objects.
(ii) Bell, lamp and ornaments.
SOME OTHER IMPORTANT QUESTIONS FOR EXAMINATION
Very Short Answer Type Questions
Q.1. Name a dynamic planet.
Ans: Our homeland i.e., earth is a dynamic planet.
Q.2. Where is the deepest mine in the world?
Ans: The deepest mine in the world, is in South Africa.
Q.3. To reach to the centre of the earth (which is not possible!) how deep hole need to be dug on the ocean floor?
Ans: 6000 km deep hole will have to be dug.
Q.4. What is the radius of the earth?
Ans: The radius of the earth is 6371 km.
Q.5. How much crust forms the volume of the earth?
Ans: The crust forms only 0.5 per cent of the volume of the earth.
Q.6. What are fossils?
Ans: The remains of the dead plants and animals trapped in the layers of rocks are called fossils.
Q.7. How rocks are classified?
Ans: There are three major types of rocks. They are classified as igneous rocks, sedimentary rocks and metamorphic rocks.
Q.8. What are primary rocks?
Ans: When the molten magma cools, it becomes solid. Thus rocks so formed are called igneous rocks. These are also called primary rocks.
Q.9. How are primary rocks classified?
Ans: Primary rocks are classified as intrusive rocks and extrusive rocks.
Q.10. What are sediments?
Ans: Rocks roll down, crack and hit each, they are broken down into small fragments known as sediments.
Q.11. Define the concept minerals.
Ans: Naturally occurring substances that have a definite chemical composition are called Minerals.
Q.12. How is magma formed?
Ans: Magma is formed due to great pressure and temperature, form molten materials in metamorphic rocks.
Q.13. How is the earth’s interior structured?
Ans: The earth’s interior is structured into layers.
Q.14. How is crust separated from the mantle?
Ans: The crust is separated from the mantle by the ‘Mohorovicic Discontinuity’.
Q.15. What is metamorphism?
Ans: Combination of pressure and heat changes the form of igneous and sedimentary rocks without melting. This change is known as metamorphism.
Q.16. Give two examples of sedimentary rocks.
Ans: Sandstone, limestone and chalk are some examples of sedimentary rocks.
Q.17. What happens when igneous rocks and sedimentary rocks go under pressure and heat?
Ans: They turn into metamorphic rocks.
Q.18. Why sedimentary rocks are called derived rocks?
Ans: Sedimentary rocks are called derived rocks because these are derived by denudation of rocks by the various agents of erosion.
Q.19. What are two minerals of ‘Sima’?
Ans: Two minerals of ‘Sima’ are Silica and Magnesium.
Q.20. What is the earth made of?
Ans: The earth is made of rocks.
Q.21. What is Alumina?
Ans: It is another major mineral forming the crust.
Q.22. What does the word igneous mean?
Ans: The word igneous mean ‘fire’.
Q.23. Name the rocks which contain fossils.
Ans: Sedimentary rocks.
Q.24. Why are igneous rocks called primary rocks?
Ans: Igneous rocks are called primary or basic rocks because all other rocks are directly or indirectly formed from them.
Q.25. How are Metamorphic rocks formed?
Ans: Metamorphic rocks are formed from igneous or sedimentary rocks due to intense heat and pressure.
Short Answer Type Questions
Q.1. Write a short note about the structure of the crust of the earth.
Ans: (a) Crust is the uppermost layer of the earth’s surface.
(b) It is the thinnest of all the layers.
(c) It is about 35 km on the continental masses and only 5 km on the ocean floor.
(d) The main mineral constituents of crust are SIAL (i.e. silica and aluminium) and SIMA (i.e. silica of magnesium).
Q.2. How the second layer of the earth is divided? Write in brief about its division.
Ans: The mantle is the second layer of the earth. It is divided into two parts:
(i) Upper Mantle. and
(ii) Lower Mantle.
(i) The Upper Mantle is made up of solid rocks. Here, the temperature goes up to about 2270°C.
(ii) The Lower Mantle is made up of semi-plastic or plastic materials. Such materials change under extreme pressure and temperature conditions.
Q.3. Which is the deepest and most inaccessible zone of the earth? Write a brief description about it.
Ans: Core is the deepest and the most in accessible zone of the earth. It has the following features:
(a) It is the innermost layer of the earth.
(b) It has a radius of about 3500 kms.
(c) It is mainly made up of nickel and iron and is called nife.
(d) The central core has very high temperature and pressure.
Q.4. What is the earth’s crust is made up of?
Ans: The earth’s crust is made up of different kinds of rocks. A rock is natural mass of mineral matter that makes up the earth’s crust and of different colour, size and texture. There are three different types of rocks. These are igneous rocks, sedimentary rocks and metamorphic rocks.
Q.5. How are igneous rocks classified?
Ans: Igneous rocks are classified into two categories. These are Intrusive igneous rocks and Extrusive igneous rocks.
Intrusive igneous rocks are formed by the cooling of magma below the earth’s surface. For example, Granite, Diorite, Gabbro, etc. When the magma comes out during a volcanic eruption, it cools and solidifies on the earth’s surface and leads to the formation of extrusive igneous rocks. For example, Basalt, Obsidian, etc.
Q.6. How are sedimentary rocks formed? Explain.
Ans: Formation of sedimentary rocks can be explained as follows:
(a) Rocks roll down, crack and hit each other (due to the forces of nature like running water, moving ive, winds and waves) and are broken into small fragments.
(b) These smaller particles called sediments are transported and deposited by wind, water etc.
(c) These loose sediments are compressed and hardened to form layers of rocks called sedimentary rocks e.g. sandstone is made of grains of sand.
Long Answer Type Questions
Q.1. Differentiate between the different types of rocks.
Ans: There are three types of rocks:
Q.2. What are minerals? Write about them in brief.
Ans: Minerals: Naturally occurring substances that have a definite chemical composition are called minerals.
(i) A mineral contains only one ore and has an atomic structure.
(ii) A mineral is a natural inorganic compound found in rocks.
(iii) There are about 2,000 types of known minerals.
Q.3. Describe any four points of importance of rocks.
Ans: Importance of rocks:
(i) They are the most essential and abundant elements on the earth’s crust.
(ii) All fossil fuels, gems, diamonds, precious stones, etc., are derived from rocks.
(iii) Rocks are used for construction of roads, buildings and many other structures.
(iv) Rocks are essential for all living things.
(v) Soil is derived from weathered rock material.
Q.4. How rocks are different from minerals?
Ans: Rocks are different from minerals in the following manner:
Q.5. What is the difference between crust and core?
Ans:
Q.6. Distinguish between mantle and core.
Ans:
Q.7. Distinguish between Intrusive Igneous Rocks and Extrusive Igneous Rocks.
Ans:
Higher Order Thinking Skill
Q.1. Rock cycle is a continuous process. Explain how?
Ans: Rock cycle is a continuous process, as rocks go through a cycle of transformation. This can further be explained as follows:
(a) When magma cools, it solidifies to become igneous rocks.
(b) These igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks.
(c) When the igneous and sedimentary rocks are subjected to heat and pressure, they change into metamorphic rocks.
(d) The metamorphic rocks which are still under great heat and pressure melt down to form molten magma.
(e) This molten magma can again cool down and solidify into igneous rocks and this cycle goes on.
Q.2. How are minerals useful for mankind?
Ans: Minerals are useful for mankind as some minerals like coal, natural gas and petroleum are used as fuel or energy. They are also used in industries. Iron, aluminium, gold, uranium, etc. are used in medicine and also in fertilizer etc.
Q.3. Place the following words under the correct heading:
Sandstone, Marble, Limestone, Granite, Slate, Dileto, Basalt, Quartzite, coal
| Igneous | Sedimentary | Metamorphic |
| _______ | _______ | _______ |
| _______ | _______ | _______ |
| _______ | _______ | _______ |
Ans: Igneous: Granite, Basalt, Dolomite.
Sedimentary: Sandstone, Limestone, Coal.
Metamorphic: Marble, Slate, Quartzite.
Q.4. What are the uses of Minerals?
Ans: (a) They are used as fuels such as – coal, natural gas and petroleum.
(b) They are also used in industries like – iron, gold, uranium etc.
(c) They are used in medicines.
(d) They are also used as fertilizers.
Value Based Questions
Q.1. Why rocks are useful (valuable) for human beings?
Ans: Rocks are useful for human beings as,
(i) They provide us valuable materials for the construction of roads, buildings, etc.
(ii) They help in the formation of fossil fuels which are used as major sources of energy.
Q.2. Why rock formation is a slow process?
Ans: Formation of rocks is a slow process because:
(a) Climate breaks the parent rocks into many smaller pieces.
(b) Topography or elevation helps in weathering of the rocks.
(c) Plants, animals and organisms help in weathering of rocks.
For all these processes, time factor plays a major role.
OBJECTIVE TYPE QUESTIONS
Q.1. Draw the diagram of the interior of the earth with proper labelling of its layers.
Ans:
Q.2. Look at the picture given below and write what kind of material is used to construct them.
Ans: These are two historic monuments of India. Red Fort is in Delhi while Taj Mahal is in Agra The Red Fort is made of red marble while Taj Mahal is made of white marble.
Q.3. Write true and false for each of the following statements:
1. The deepest mine in the world is in South Africa.
Ans: True.
2. The innermost layer is the core with a radius of about 4500 km.
Ans: False.
3. The process of transformation of the rock from one to another is known as the rock formation.
Ans: False.
4. The uppermost layer over the earth’s surface is called the mantle.
Ans: False.
5. Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust.
Ans: True.
Multiple Choice Questions
Choose the correct option:
1. The upper crust over continent is known as _______.
(a) Rock.
(b) Mentle.
(c) Layer.
(d) Crust.
Ans: (d) Crust.
2. Where is deepest mine in the world?
(a) South America.
(b) South Africa.
(c) North America.
(d) Canada.
Ans: (b) South Africa.
3. Rocks containing metals in large quantities are called _______.
(a) Fossil.
(b) Ore.
(c) Magma.
(d) Minerals.
Ans: (d) Minerals.
4. _______ is the hardest mineral.
(a) Basalt.
(b) Granite.
(c) Diamond.
(d) Quartzite.
Ans: (c) Diamond.
5. Nickel founds in _______.
(a) Crust.
(b) Inner core.
(c) Outer core.
(d) Mantle.
Ans: (c) Outer core.
6. Victoria Memorial in Kolkata is made up of _______.
(a) Marble.
(b) Granite.
(c) Sandstone.
(d) None of these.
Ans: (a) Marble.
7. Which of these used as fuels?
(a) Coal.
(b) Natural gas.
(c) Petroleum.
(d) All of these.
Ans: (d) All of these.
