🌍 Inside Our Earth

Understanding what lies beneath our feet helps explain earthquakes, volcanoes, mountains, minerals — everything. This chapter explains the structure of the earth and types of rocks in a simple way.

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1️⃣ Layers of the Earth — Crust, Mantle & Core

Think of Earth like a boiled egg:

• Egg shell → Crust
• Egg white → Mantle
• Egg yolk → Core

🌐 Crust

• The outermost layer
• Thinnest — only 5–30 km
• Made of SIAL (Silica + Aluminium)
• Continents & ocean floors rest here

🔥 Mantle

• Below the crust
• Extends up to 2,900 km
• Rocks are semi-molten
• Convection currents cause:
  • volcanoes
  • earthquakes
  • plate movement

☀️ Core

• Innermost & hottest part
• Made of NIFE (Nickel + Iron)
• Outer core → liquid
• Inner core → solid
• Generates Earth’s magnetic field

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2️⃣ What Is a Rock?

A rock is a naturally occurring solid made of minerals.

Examples: granite, basalt, sandstone, marble

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3️⃣ Minerals — The Building Blocks of Rocks

Minerals are naturally occurring chemical substances.

Examples: mica, quartz, feldspar, gold, diamond

Why minerals matter?

• Used in industries
• Used to extract metals
• Used in construction
• Foundation of economic growth

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4️⃣ Types of Rocks

Rocks keep changing — this is the Rock Cycle.

🟥 Igneous Rocks (Primary Rocks)

Formed when molten magma cools & solidifies.

Types:

• Intrusive: cools inside Earth (e.g., granite)
• Extrusive: cools on surface (e.g., basalt → Deccan Plateau)

🟫 Sedimentary Rocks

Formed from sediments deposited by wind, water, glaciers.
Over time, layers press & form rocks.

Examples: limestone, shale, sandstone

🟦 Metamorphic Rocks

Formed when existing rocks change due to heat & pressure.

Examples:

• Limestone → Marble
• Shale → Slate
• Coal → Diamond

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5️⃣ Rock Cycle

The rock cycle shows how each rock type transforms into another.

Magma 
 ↓ cools
Igneous Rock
 ↓ weathering & deposition
Sedimentary Rock
 ↓ heat & pressure
Metamorphic Rock
 ↓ melts
Magma again

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6️⃣ Minerals & Their Uses

• Gold → jewellery
• Coal → fuel, electricity
• Iron → machines, buildings
• Granite → construction
• Diamond → cutting tools + jewellery

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7️⃣ NCERT Diagram (Text Version)

Earth's Layers

---------------- Crust ----------------
--------------- Mantle ---------------
-------------- Outer Core ------------
-------------- Inner Core ------------

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📝 Chapter Summary

• Earth has three layers → crust, mantle, core
• Rocks are made of minerals
• Igneous, Sedimentary, Metamorphic are the three main rock types
• Rock cycle explains transformation
• Minerals are essential for industry & daily life

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💡 High-Yield for UPSC