NCERT Solutions For Class 7 Geography Social Science Chapter 2 Inside Our Earth
Class 7 Geography Chapter 2:- Chapter 2 of Class 7 Geography, titled "Inside Our Earth," provides an in-depth exploration of the Earth's internal structure, which is fundamental to understanding the planet's physical characteristics. This chapter introduces students to the three primary layers of the Earth—the crust, mantle, and core—each with its distinct composition and properties. It further explains the formation and classification of rocks into igneous, sedimentary, and metamorphic types, detailing the processes that lead to their creation. Get the Chapter 2 of inside our earth class 7 Geography below.
Class 7 Geography Chapter 2 Questions and Answers
Q1. Answer the following questions:
(i) What are the three layers of the earth?
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The earth is composed of three distinct layers:
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Crust: This is the outermost layer of the earth where we live. It is the thinnest layer, varying in thickness from about 5 km under the oceans to about 30-50 km under the continents. The crust is made up of solid rocks and is rich in minerals and elements like silicon, aluminum, and oxygen.
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Mantle: Located beneath the crust, the mantle extends up to a depth of about 2,900 km. It is composed mainly of silicate minerals and is semi-solid, with its upper part capable of flowing slowly. This layer is responsible for the movement of tectonic plates.
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Core: The innermost layer of the earth, the core, is divided into two parts—the outer core, which is liquid, and the inner core, which is solid. The core is composed mainly of iron and nickel and is extremely hot, with temperatures reaching up to 5,000°C.
(ii) What is a rock?
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A rock is a natural mass of solid mineral matter that makes up the earth’s crust. Rocks can vary greatly in their composition, texture, size, and color. They are made up of one or more minerals and are classified based on their formation process and composition. The study of rocks, known as petrology, helps us understand the earth’s history and structure.
(iii) Name three types of rocks.
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The three main types of rocks are:
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Igneous Rocks: These rocks are formed from the solidification of molten magma or lava. They are classified into two types—extrusive igneous rocks, which form on the earth’s surface, and intrusive igneous rocks, which form below the surface.
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Sedimentary Rocks: These rocks are formed by the accumulation and compression of sediments over time. Sediments are small particles of rocks, minerals, and organic materials that are transported and deposited by wind, water, or ice. Sedimentary rocks often contain fossils.
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Metamorphic Rocks: These rocks are formed when existing igneous or sedimentary rocks are subjected to high temperatures and pressures, causing them to undergo physical and chemical changes. This process is known as metamorphism.
(iv) How are extrusive and intrusive rocks formed?
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Extrusive rocks are formed when molten lava erupts from a volcano and cools rapidly on the earth’s surface. Since the cooling happens quickly, these rocks have a fine-grained or glassy texture. An example of an extrusive rock is basalt, which is commonly found in volcanic regions.
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Intrusive rocks, on the other hand, are formed when molten magma cools and solidifies slowly beneath the earth’s surface. Due to the slow cooling process, these rocks have larger, visible crystals and a coarse-grained texture. Granite is a typical example of an intrusive rock and is widely used in construction.
(v) What do you mean by a rock cycle?
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The rock cycle is a continuous process through which rocks are transformed from one type to another over geological time due to various natural processes. This cycle explains how igneous rocks can break down into sediments, which then form sedimentary rocks. These sedimentary rocks can be subjected to heat and pressure to become metamorphic rocks. Finally, metamorphic rocks can melt to form magma, which upon cooling, forms new igneous rocks. This cycle illustrates the dynamic and interconnected nature of the earth’s crust.
(vi) What are the uses of rocks?
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Rocks have numerous uses in our daily lives and in various industries:
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Construction: Rocks such as granite, limestone, and sandstone are widely used in building houses, roads, and other infrastructure due to their strength and durability.
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Raw Materials: Rocks are sources of valuable minerals and metals like iron, copper, and gold, which are essential for manufacturing and industrial processes.
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Decoration: Marble, a metamorphic rock, is prized for its beauty and is used in sculptures and as a decorative material in buildings.
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Agriculture: Certain types of rocks, when ground into powder, are used as fertilizers to enrich soil with essential minerals.
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Recreation: Rocks and stones are also used in various games and recreational activities, such as skipping stones or creating stone art.
(vii) What are metamorphic rocks?
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Metamorphic rocks are formed from the transformation of existing igneous or sedimentary rocks through heat, pressure, or chemically active fluids over long periods. This process, known as metamorphism, alters the mineral composition and structure of the original rock, creating a new type of rock with different properties. For example, shale, a sedimentary rock, can transform into slate, while limestone can metamorphose into marble. Metamorphic rocks are typically harder and more resistant to weathering than their original forms.
Read More: class 7 geography chapter 1
Q2. Tick the correct answer:
(i) The rock made up of molten magma is:
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(a) Igneous
(ii) The innermost layer of the earth is:
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(b) Core
(iii) Gold, petroleum, and coal are examples of:
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(b) Minerals
(iv) Rocks which contain fossils are:
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(a) Sedimentary rocks
(v) The thinnest layer of the earth is:
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(a) Crust
Q3. Match the following:
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Core - (e) Innermost layer
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Minerals - (d) Has a definite chemical composition
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Rocks - (b) Used for roads and buildings
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Clay - (f) Changes into slate
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Sial - (c) Made of silicon and alumina
Q4. Give reasons:
(i) We cannot go to the center of the earth.
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We cannot go to the center of the earth because the conditions there are extreme. The temperature at the core can reach up to 5,000°C, and the pressure is so high that it would crush any human or equipment. Moreover, the materials in the core are in a molten state due to the intense heat, making it impossible for humans to survive or for any known technology to withstand these conditions.
(ii) Sedimentary rocks are formed from sediments.
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Sedimentary rocks are formed through the accumulation of sediments, which are small fragments of rocks, minerals, and organic materials. These sediments are transported by natural agents like wind, water, and ice, and are deposited in layers over time. As more layers accumulate, the weight of the overlying sediments compresses the lower layers, causing them to harden and cement together, forming sedimentary rocks. This process can take millions of years, and these rocks often contain fossils, which provide important clues about the earth's past.
(iii) Limestone is changed into marble.
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Limestone, a sedimentary rock composed mainly of calcium carbonate, can transform into marble, a metamorphic rock, through the process of metamorphism. When limestone is subjected to intense heat and pressure, the mineral grains within it recrystallize, leading to the formation of a denser and more crystalline rock—marble. This transformation enhances the durability and aesthetic appeal of the rock, making marble a popular material for sculptures, buildings, and decorative purposes.
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Class 7 Geography Chapter 2 Summary
Chapter 2 of Class 7 Geography, titled "Inside Our Earth," provides a comprehensive overview of the Earth's internal structure and the processes that shape it. The chapter begins by introducing the three main layers of the Earth: the crust, mantle, and core. The crust is the outermost layer where we live, the mantle lies beneath it, and the core is the innermost part of the Earth, consisting of a liquid outer core and a solid inner core.
The chapter also covers the types of rocks found within the Earth's crust, categorizing them into igneous, sedimentary, and metamorphic rocks. Igneous rocks are formed from molten magma, sedimentary rocks are formed from compressed sediments, and metamorphic rocks are created when existing rocks transform due to heat and pressure.
Furthermore, the chapter discusses the rock cycle, which describes the continuous transformation of rocks from one type to another over time. This cycle illustrates the dynamic nature of the Earth's surface, where rocks are constantly being formed, broken down, and reformed.
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Inside Our Earth Class 7 FAQs
Q1. What are the three layers of the Earth?
Ans. The three layers of the Earth are the crust, mantle, and core. The crust is the outermost layer, the mantle lies beneath it, and the core is the innermost part of the Earth.
Q2. What is the composition of the Earth's crust?
Ans. The Earth's crust is composed mainly of solid rocks, including various minerals. It is rich in elements such as silicon, aluminum, and oxygen.
Q3. What is the difference between extrusive and intrusive igneous rocks?
Ans. Extrusive igneous rocks are formed when molten lava cools and solidifies on the Earth's surface, while intrusive igneous rocks are formed when magma cools and solidifies beneath the Earth's surface.
Q4. How are sedimentary rocks formed?
Ans. Sedimentary rocks are formed from the accumulation and compression of sediments, which are small particles of rocks, minerals, and organic materials. These sediments are deposited over time and solidify to form sedimentary rocks.
Q5. What is the rock cycle?
Ans. The rock cycle is the continuous process through which rocks are transformed from one type to another due to various natural processes like melting, cooling, erosion, and compression.
