Inside Our Earth

KINGS

Chola

NEW KINGS

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Solarsystem

Earth is a dynamic planet which undergoes changes constantly inside and outside.

Internal Changes (Inside the Earth):

• Due to the heat and pressure from the Earth's interior.
• Movement of tectonic plates (massive pieces of the upper layer of the earth) causes earthquakes and volcanic eruptions.

External Changes (On the Surface):

• Caused by wind, water, ice, and human activities.

• Includes weathering, erosion, landslides, and floods.

• These natural forces change the shape of landforms like mountains, valleys, and rivers.

Describe the interior of the Earth and its main layers.

Earth is made up of several concentric layers, with one inside another.

1. Crust

• It is the outermost and thinnest layer of the Earth.

• It is about 35 km thick on land and 5 km on ocean floors.

• The continental crust is made of silica and alumina (called SIAL).

• The oceanic crust contains silica and magnesium (called SIMA).

2. Mantle

• Located just below the crust, it extends to a depth of 2900 km.
• It is made of hot, semi-solid rocks that can flow slowly.
• This slow movement is called mantle convection.
• It helps in the movement of Earth's plates.
• The mantle ranges in temperatures from 200 to 4000 degrees Celsius.
• It makes up 84% of earth's volume and 67% of mass. 

• The mantle is mainly made up of silicate minerals (Silicon-Oxygen compounds) that are rich in:

  • Iron (Fe)

  • Magnesium (Mg)

3. Core

• The innermost layer with a radius of about 3500 km.
• Composed of nickel and iron (NIFE- NICKEL AND FERROUS)
• Has extremely high temperature and pressure. (4000–5000℃)
• It makes up 15% of earth's volume.
• It contains two cores-Inner core and outer core.
• Outer core is made of liquid metal (mostly liquid iron and nickel).
• It is about 1200 km thick.
• The inner core stays solid because of very high pressure, even though it is extremely hot.
• It is about 2200 km thick.
• It is made of solid metal (mostly iron and nickel).
  
  

What are minerals?

Minerals are natural substances found inside the Earth.

They are not made by people.

They can be shiny, hard, colourful and used for making things like jewelry, tools, and buildings.

Eg. Eg. Gold – used in jewelry

Coal – used for fuel

Iron – used to make steel

Salt – used in food

Diamond – very hard and shiny

Item                              Mineral Used

Pencil (the tip)                 Graphite

Whiteboard markers        Colored pigments (minerals)

Window glass                Silica (from sand)

Chalk                               Limestone (Calcium carbonate)

Scissors/Stapler                Iron, Aluminum, or Steel

Desk legs (metal ones)       Iron or Aluminum

Electric wires                        Copper

Coins                                    Copper, Nickel

Paint on walls                Mineral-based pigments

Salt in lunchfood            Halite (rock salt)

What is a rock?

Answer:

A rock is a natural solid material that makes up the Earth’s crust.

It can be of different colours, sizes, and textures.

What are the different types of rocks?

Answer:

There are three main types of rocks:

Igneous rocks 

 Igneous rocks are formed when molten magma (hot, melted rock from inside the Earth) cools and becomes solid.

They are also called primary rocks because they are the first rocks to form on Earth.

There are two types of Igneous rocks:

🔹 I. Extrusive Igneous Rocks

Formed when molten lava (magma that comes out on the Earth’s surface) cools quickly.

Since it cools fast, the rock has very small or no visible grains.

Example: Basalt – The Deccan Plateau in India is made of basalt.

 II.Intrusive Igneous Rocks

Formed when magma cools slowly deep inside the Earth.

Slow cooling allows large grains (crystals) to form.

Example: Granite – It is used to make grinding stones and kitchen counters.

2. Sedimentary rocks

Sedimentary rocks are formed from small pieces of broken rocks called sediments. 

These sediments are created when rocks break down due to wind, water, heat, or ice. 

The tiny pieces are then carried by wind, rivers, or seas and are dropped or deposited in low areas like riverbeds, lakes, or oceans. 

Over a long time, these layers of sediments are pressed and hardened to form solid rocks. 

This slow process takes millions of years.

Sedimentary rocks are usually found in layers and may contain fossils, which are the remains of dead plants or animals.

Example: Sandstone (Grains of Sand), Limestone ( Shells, coral and other marine animal debris)

3. Metamorphic rocks – 

Metamorphic rocks are formed when igneous or sedimentary rocks are changed by great heat and pressure inside the Earth. 

This change happens deep underground and takes a very long time. 

The original rock does not melt, but its shape, texture, and structure change.

That’s why they are called metamorphic, which means “changed form.”

For example, clay can change into slate, and limestone can turn into marble. 

Schist, a form of rock, is formed from mudstone. 

FAMOUS MONUMENTS WITH THE TYPE OF ROCK USED TO BUILD THEM

Taj Mahal (India) – Made of white marble (Metamorphic)

Statue of Liberty (USA) – Base made of granite (Igneous)

Red Fort (India) – Made of red sandstone (Sedimentary)

Qutub Minar (India) – Made of red sandstone and marble

Gateway of India (Mumbai) – Made of yellow basalt and reinforced concrete (Igneous)

Rock Cycle

• The process of transformation of the rock from one to another is known as the rock cycle.

→ When the molten magma cools; it solidifies to become igneous rock.

→ These igneous rocks are broken down into small particles by various agents such as weathering, temperature, wind etc. and are transported and deposited to form sedimentary rocks.

→ These smaller grains of rocks keep moving towards basins and lower regions and gradually form sedimentary rocks.

→ When the igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks.

→ The metamorphic rocks which are still under great heat and pressure melt down to form molten magma.

→ This molten magma again can cool down and solidify into igneous rocks.

Note: These processes take hundreds and thousands of years.

Metamorphic rocks on Earth can become molten magma through a process called melting, which occurs when the rocks are subjected to extreme heat and pressure deep within the Earth's crust or mantle. Here’s how it works:

1. Subduction Zones: When tectonic plates move, one plate may slide beneath another in a process called subduction. As the metamorphic rocks are pushed deeper into the Earth's interior, they are exposed to intense heat from the surrounding molten material and extreme pressure.

2. Heat and Pressure: The heat comes from the Earth's interior, where temperatures can rise to thousands of degrees. The pressure from the overlying rocks is so great that the metamorphic rocks begin to melt, transforming them into molten magma.

3. Magma Formation: This molten material, which is now magma, can eventually rise through the Earth's crust, cooling and solidifying to form igneous rocks once it reaches the surface.

Gold

Diamond
Aluminum

What is a Mineral?

• A mineral is a naturally occurring substance.

• It has a specific physical property (like color, hardness, or shine).

• It also has a definite chemical composition.

• Minerals are found in the earth’s crust.

• Examples of Minerals:

  Gold, Silver, Diamond – used in jewellery.

  Iron, Copper, Aluminium – used in industries.

  Coal, Petroleum – used as fuels 

Minerals Used in Daily Life:

• Salt (Halite) – for cooking

• Graphite – used in pencils

• Fluorite – used in toothpaste and glassmaking

• Gypsum – used in making chalk and plaster

• Zinc – Used in batteries, medicine, and sunscreen.

• Calcite – Used in chalk, toothpaste, and building materials.

QUESTION ANSWERS

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

Answer:The three layers of the earth are :-

Crust: It is the uppermost layer of the Earth's surface.

Mantle: The layer between Crust and Core.

Core: It is the innermost layer of the Earth surface.

(ii) What is a rock?

Answer:Any natural mass of mineral matter that makes up the earth's crust is called a rock. Rocks can be of different colour, sizes and textures.

(iii) Name three types of rocks.

Answer:The three major types of rocks are:-

Igneous rocks

Sedimentary rocks

Metamorphic rocks.

(iv) How are extrusive and intrusive rocks formed?

Answer: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.

Example - Basalt.

When the molten magma cools down deep inside the earth's crust. Solid rocks so formed are called intrusive igneous rocks.

Example- Granite.

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

Answer:The process of transformation of the rock from one to another is known as the rock cycle.

(vi) What are the uses of rocks?

Answer:The hard rocks are used for making roads, houses and buildings.

(vii) What are metamorphic rocks?

Answer:Metamorphic rocks are those which are formed when the igneous and sedimentary rocks change their form under great heat and pressure.

(i) Core	(e) Innermost layer
(ii) Minerals	(d) Has definite chemical composition
(iii) Rocks	(b) Used for roads and buildings
(iv) Clay	(f) Changes into slate
(v) Sial	(c) Made of silicon and alumina

Question 4:Give reasons.

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

Answer:We cannot go to the centre of the Earth because :-

• the temperature and pressure at the centre of the Earth is very high.
• To reach the centre of the earth one will have to dig a hole 6000km deep on the ocean floor which is quite impossible.

(ii) Sedimentary rocks are formed from sediments.

Answer: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 also contain fossils of plants, animals and other microorganisms that once lived on them.

(iii) Limestone is changed into marble.

Answer:Igneous and sedimentary rocks can be changed into metamorphic rocks under great heat and pressure.
Limestone is an igneous rock and it can be changed into marble under heat and pressure.

Question 5:For Fun:

(I). What are the minerals most commonly used in the following objects?

(ii) Identify some more objects made up of different minerals.

Answer:(I). Karhai - Iron

Ornaments- Gold

Pan/Tawa- Iron

Bell- Bronze

Hammer- Iron

Lamp- Bronze

Answer:(ii) Copper is used in the manufacture of electrical wire, copper pipes for water, copper cookware.

Salt used in our foods is made up of sodium and chlorine.

Chalks used in schools is a limestone.

Chalkboards are made up of slate.

Ceramics cups is made up of clay mudstone.

Graphite in pencils.

Door knobs and handles of Iron.

Diamond jewllery.

Collect pictures of some monuments and find out which are the rocks used to build them. Two pictures have been collected for you.

 

Answer:

Humayun's tomb : The structure is of dressed stone clad in red sandstone with white and black inlaid marble borders.

Qutub Minar: made up of red sandstone and white marble.

Hawa Mahal of Jaipur: Built from red and pink sandstone.

India Gate: is made up of Sandstones.

Source: https://www.champstreet.com/ncert-solutions/class-7/social-science/geography/chapter-2/inside-our-earth.jsp

https://www.youtube.com/watch?v=VvXTM368oGU

Uses of Rocks in Our Day-to-Day Life:

1. Building Materials:
   Rocks like granite, limestone, and sandstone are used to build houses, roads, bridges, and monuments.

2. Making Tools and Utensils:
   In the past, people used rocks to make tools. Even today, grinding stones and mortars are made from rocks.

3. Decoration:
   Marble and granite are used for flooring, statues, and decorative pieces.

4. Energy Production:
   Some rocks, like coal, are used to produce electricity and heat.

5. Jewelry and Ornaments:
   Precious stones like diamonds, rubies, and emeralds are types of rocks used to make jewelry.

6. Manufacturing:
   Rocks provide minerals used to make products like glass, cement, and ceramics.

7. Soil Formation:
   Weathered rocks break down into soil, which is essential for growing plants.

QUIZ SESSION

1. What is the uppermost layer over the earth’s surface called?
2. What are the main mineral constituents of the continental mass?
3. What is the thickness of the oceanic crust?
4. What lies just beneath the crust of the earth?
5. What is the innermost layer of the earth called?
6. What is the core mainly made up of?
7. What is a rock?
8. How are igneous rocks formed?
9. What are the two types of igneous rocks?
10. What is the Deccan plateau made up of?
11. What are smaller particles of rocks called?
12. How are sedimentary rocks formed?
13. What type of rocks can contain fossils?
14. What changes igneous and sedimentary rocks into metamorphic rocks?
15. What is the process of transformation of rocks from one type to another called?
16. What is the main use of hard rocks?
17. What does the word “igneous” mean in Latin?
18. Which rock is an example of an intrusive igneous rock?
19. What is the radius of the earth?
20. What are fossils?
21. What percentage of the earth’s volume is made up of the mantle?
22. Which type of rock is marble?
23. Which type of rock is sandstone?
24. Which rock is made up of grains of sand?
25. What are minerals?
26. What type of rock changes into marble under heat and pressure?
27. What type of rock changes into slate under heat and pressure?
28. Where is the deepest mine in the world locate? Name it 
29. What are the three layers of the earth?
30. What is the term for the molten magma that comes out of volcanoes and solidifies on the earth’s surface?
31. It states that every adult in a country, irrespective of their wealth and the communities she/he belongs to, has one vote.
32. Who is the father of the Indian Constitution?
33. Which is the autobiographical work of Om Prakash Valmiki?
34. Which state was the first state in India to introduce mid day meal scheme and in 2001?
35. What was the name of the official policy of racial discrimination followed in South Africa for many years?
36. Who was the famous Mauryan king who ruled most of India?
37.  Who is known as the "Napoleon of India"?
38. What you meant by "Prashasti"?
39. The most famous and longest-ruling kingdom in Tamil Nadu.
40. Who founded the Mughal Empire in India?
41. Which ruler is shown on this gold coin who was known for his love of music and poetry?
    
    
    
42. This king ruled Delhi and built the Qutub Minar. His name starts with 'Q'. Who is he?
43. This famous Mughal ruler is known for starting a new religion called Din-i-Ilahi. Who is he?
44. Which battle did Babur win to establish the Mughal Empire in India?
45. Which famous Mughal emperor had a group of 'Nine Gems' or 'Navratnas' in his court?