02. Inside Our Earth Class 7 Geography Chapter 2 Notes for CBSE and UPSC.

Welcome to Inside Our Earth Class 7 Geography Chapter 2 Notes for CBSE and UPSC.

Introduction – Inside of the Earth

Layers of the Earth

1. Crust
   • The crust is the Earth’s outermost layer, and it is crucial to our understanding of our planet’s structure.
   • It is divided into two primary types: continental and oceanic crust.
   • The continental crust is relatively thicker, measuring about 35 kilometers in depth, while the oceanic crust is thinner, approximately 5 kilometers thick.
   • The composition of the continental crust is predominantly silica and alumina, and it is often referred to as “sial” (si-silica, al-alumina).
   • On the other hand, the oceanic crust primarily consists of silica and magnesium, earning it the name “sima” (si-silica, ma-magnesium).
2. Mantle
   • The mantle is the layer located directly beneath the crust and extends to a depth of approximately 2900 kilometers.
   • It consists of semi-solid rock material that exhibits slow-flowing convection currents over geological timescales.
3. Core
   • The core is the Earth’s innermost layer, with a radius of approximately 3500 kilometers.
   • Composed primarily of nickel and iron, it is often referred to as “nife” (ni-nickel, fe-ferrous, i.e., iron).
   • The core is known for its extremely high temperatures and pressures.

Interesting Facts

• The deepest mine in the world, located in South Africa, reaches depths of approximately 4 kilometers, showcasing the remarkable depth of Earth’s interior exploration.
• The theoretical concept of reaching the center of the Earth is intriguing but impossible in practice. To reach it, one would need to dig a hole approximately 6000 kilometers deep on the ocean floor, which is beyond current technological capabilities.

Rocks and Minerals

Earth’s Crust Composition

1. Igneous Rocks
   • Igneous rocks are formed through the solidification of molten magma.
   • There are two main types: intrusive and extrusive.
   • Intrusive igneous rocks form deep within the Earth’s crust, where they cool slowly, resulting in large-grained structures (e.g., granite).
   • Extrusive igneous rocks, on the other hand, form on the Earth’s surface as magma rapidly cools, leading to fine-grained textures (e.g., basalt).
   • An exciting example is the Deccan Plateau, primarily composed of basalt rocks.
2. Sedimentary Rocks
   • Sedimentary rocks are the result of the compression and hardening of sediments over time.
   • These rocks can vary in appearance, color, size, and texture.
   • Sandstone, for instance, is formed from the consolidation of sand grains and often contains fossils, providing valuable insights into Earth’s history.
   • Sedimentary rocks are created through the transportation and deposition of loose sediments, which eventually become compacted and solidified.
3. Metamorphic Rocks
   • Metamorphic rocks undergo transformation from existing rocks due to high levels of heat and pressure.
   • This process changes their mineral composition and texture.
   • For example, clay can transform into slate, while limestone can metamorphose into marble.
   • The alteration of rocks under these conditions leads to the formation of unique textures and structures.

The Rock Cycle

• The rock cycle is a continuous geological process that encompasses the transformation of rocks from one type to another over time. It is a fundamental concept in understanding the dynamic nature of Earth’s surface.
• The cycle involves the formation of igneous, sedimentary, and metamorphic rocks, which are interconnected through various geological processes. These rocks can change from one type to another, creating a dynamic and ever-evolving Earth’s surface.

Keywords and Definitions

Important Keywords for Inside Our Earth Class 7 Geography Chapter 2 Notes for CBSE and UPSC.

1. Core

• Definition: The Earth’s innermost layer, primarily composed of nickel and iron.

2. Sial

• Definition: A term used to describe the composition of the continental crust, which consists mainly of silica and alumina.

3. Sima

• Definition: Refers to the composition of the oceanic crust, primarily composed of silica and magnesium.

4. Rock Cycle

• Definition: A continuous geological process that involves the transformation of rocks from one type to another over time, influenced by various geological forces and conditions.

5. Igneous Rocks

• Definition: Rocks formed from the solidification of molten magma. They can be intrusive (formed within the Earth’s crust) or extrusive (formed on the Earth’s surface).

6. Sedimentary Rocks

• Definition: Rocks formed from the compression and hardening of sediments over time. They often contain fossils and are created through the transportation and deposition of loose sediments. Learn more

7. Metamorphic Rocks

• Definition: Rocks formed from the alteration of existing rocks under heat and pressure, resulting in changes to their mineral composition and texture.

8. Crust

• Definition: The Earth’s outermost layer, with two primary types: continental and oceanic crust.

9. Mantle

• Definition: The layer located directly beneath the crust, composed of semi-solid rock material that exhibits slow-flowing convection currents over geological timescales.

10. Minerals

• Definition: Naturally occurring substances with specific physical properties and chemical compositions. They are used in various applications, including fuels, industries, medicine, and more.

Important Questions

Important Questions for Inside Our Earth Class 7 Geography Chapter 2 Notes for CBSE and UPSC.

Frequently Asked Questions (FAQs)

1. What are the three primary layers of the Earth?

Answer: The three primary layers of the Earth are the crust, mantle, and core.

2. How are igneous rocks classified, and can you provide examples?

Answer: Igneous rocks are classified into two main types: intrusive (formed deep within the Earth’s crust) and extrusive (formed on the Earth’s surface). Examples include granite (intrusive) and basalt (extrusive).

3. What is the rock cycle, and how does it work?

Answer: The rock cycle is a continuous geological process in which rocks change from one type to another over time. It involves the formation of igneous, sedimentary, and metamorphic rocks, interconnected through various geological processes.

4. What are metamorphic rocks, and how are they formed?

Answer: Metamorphic rocks are rocks formed from the alteration of existing rocks under heat and pressure. This process results in changes to their mineral composition and texture.

5. What are the primary uses of rocks in our daily lives?

Answer: Rocks serve various purposes in our lives, including construction materials for roads and buildings. They are also essential in traditional games and activities.

6. What is the composition of the Earth’s core?

Answer: The Earth’s core is primarily composed of nickel and iron, making it “nife” (ni-nickel and fe-ferrous, i.e., iron).

7. What percentage of the Earth’s volume does the crust represent?

Answer: The crust represents only 1 percent of the Earth’s volume, with the mantle and core making up the majority.

8. Can you explain the difference between intrusive and extrusive igneous rocks?

Answer: Intrusive igneous rocks form deep inside the Earth’s crust, where they cool slowly, resulting in large-grained structures. Extrusive igneous rocks form on the Earth’s surface as magma rapidly cools, leading to fine-grained textures.

9. What are sediments, and how do they contribute to the formation of sedimentary rocks?

Answer: Sediments are small particles created when rocks roll down, crack, and hit each other, breaking into small fragments. These particles are transported and deposited by wind, water, etc. Over time, they compress and harden to form sedimentary rocks.

10. How does the rock cycle illustrate the dynamic nature of Earth’s surface?

Answer: The rock cycle demonstrates that rocks change from one type to another over time, influenced by various geological forces and conditions. It shows the continuous transformation of igneous, sedimentary, and metamorphic rocks, highlighting the dynamic nature of Earth’s surface.

Multiple Choice Questions (MCQs) with Answers

1. What are igneous rocks primarily formed from?

• (a) Sediments
• (b) Molten magma
• (c) Existing rocks
• Answer: (b) Molten magma

2. Which type of rock forms rapidly on the Earth’s surface?

• (a) Intrusive igneous rocks
• (b) Sedimentary rocks
• (c) Extrusive igneous rocks
• Answer: (c) Extrusive igneous rocks

3. What is the main composition of the Earth’s core?

• (a) Silica and alumina
• (b) Nickel and iron
• (c) Silica and magnesium
• Answer: (b) Nickel and iron

4. Which layer of the Earth is primarily composed of nickel and iron?

• (a) Mantle
• (b) Core
• (c) Crust
• Answer: (b) Core

5. What is the primary characteristic of intrusive igneous rocks?

• (a) Fine-grained structure
• (b) Formation on the Earth’s surface
• (c) Slow cooling and large grains
• Answer: (c) Slow cooling and large grains

6. Which type of rock is formed from the alteration of existing rocks under heat and pressure?

• (a) Sedimentary rocks
• (b) Metamorphic rocks
• (c) Igneous rocks
• Answer: (b) Metamorphic rocks

7. What is the primary use of rocks in construction?

• (a) Making jewelry
• (b) Building roads and houses
• (c) Fuel source
• Answer: (b) Building roads and houses

8. What is the thinnest layer of the Earth?

• (a) Mantle
• (b) Crust
• (c) Core
• Answer: (b) Crust

9. What are sediments?

• (a) Solid rocks
• (b) Loose particles broken from rocks
• (c) Molten magma
• Answer: (b) Loose particles broken from rocks

10. What does the rock cycle illustrate?

• (a) The transformation of water into ice
• (b) The continuous change of rocks from one type to another
• (c) The formation of clouds
• Answer: (b) The continuous change of rocks from one type to another

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This was the end of Inside Our Earth Class 7 Geography Chapter 2 Notes for CBSE and UPSC.

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