The Earth is composed of three major spheres that interact with each other:

1. Lithosphere (Land)
2. Atmosphere (Air)
3. Hydrosphere (Water)

These together make Earth a life-supporting planet.

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🪨 1. LITHOSPHERE (LAND SPHERE)

📌 Definition:

The Lithosphere is the outermost solid layer of the Earth, consisting of the crust and the upper part of the mantle.

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📊 Structure of Lithosphere:

1. Crust

• Thin outer layer
• Thickness:
  • Oceanic: 5–10 km
  • Continental: 30–70 km
• Made of silica and alumina (SIAL)

2. Upper Mantle

• Lies below the crust
• Contains semi-molten rocks
• Helps in plate movement

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🌎 Types of Crust:

1. Continental Crust

• Thick and less dense
• Composed mainly of granite

2. Oceanic Crust

• Thin and dense
• Composed mainly of basalt

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🌋 Tectonic Plates:

• Lithosphere is divided into large plates
• These plates float on the asthenosphere
• Plate movements cause:
  • Earthquakes
  • Volcanoes
  • Mountain formation

Types of Plate Boundaries:

1. Convergent (plates collide)
2. Divergent (plates move apart)
3. Transform (plates slide past each other)

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🏞️ Landforms:

• Mountains
• Plateaus
• Plains
• Valleys

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⭐ Importance:

• Provides land for living organisms
• Source of minerals and natural resources
• Supports agriculture and human settlements

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🌫️ 2. ATMOSPHERE (AIR SPHERE)

📌 Definition:

The Atmosphere is the layer of gases surrounding the Earth, held by gravity.

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🌬️ Composition of Atmosphere:

• Nitrogen – 78%
• Oxygen – 21%
• Argon – 0.93%
• Carbon dioxide – 0.03%
• Other gases (neon, helium, etc.)

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🌍 Layers of Atmosphere:

1. Troposphere

• Lowest layer (up to ~12 km)
• Weather occurs here
• Contains 75% of atmospheric mass

2. Stratosphere

• 12–50 km above Earth
• Contains ozone layer
• Temperature increases with height

3. Mesosphere

• 50–80 km
• Coldest layer
• Meteors burn here

4. Thermosphere

• 80–400 km
• Very high temperature
• Ionosphere present (radio communication)

5. Exosphere

• Outermost layer
• Gradually merges into space

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🌦️ Functions of Atmosphere:

• Provides oxygen for respiration
• Protects Earth from harmful UV rays
• Maintains Earth’s temperature
• Helps in weather and climate formation
• Burns meteors before reaching Earth

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🌡️ Important Concepts:

• Greenhouse Effect
• Air Pressure
• Winds (global circulation)
• Weather vs Climate

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💧 3. HYDROSPHERE (WATER SPHERE)

📌 Definition:

The Hydrosphere includes all forms of water on Earth, whether in liquid, solid, or gaseous state.

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🌊 Distribution of Water:

• Oceans (Saltwater) – 97%
• Freshwater – 3%
  • Glaciers – 69%
  • Groundwater – 30%
  • Surface water – 1%

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💦 Forms of Water:

• Liquid → Rivers, lakes, oceans
• Solid → Ice caps, glaciers
• Gas → Water vapor

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🔄 Water Cycle (Hydrological Cycle):

1. Evaporation – Water turns into vapor
2. Condensation – Vapor forms clouds
3. Precipitation – Rain, snow, etc.
4. Runoff – Water flows into rivers/oceans
5. Infiltration – Water enters the ground

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🌊 Major Water Bodies:

• Oceans
• Seas
• Rivers
• Lakes
• Glaciers
• Groundwater

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⭐ Importance:

• Essential for all living organisms
• Regulates Earth’s temperature
• Supports marine ecosystem
• Important for agriculture and industry

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🔗 INTERRELATION OF SPHERES

🌍 How They Work Together:

• Atmosphere + Hydrosphere → Rainfall
• Lithosphere + Hydrosphere → Soil formation
• All three → Support life (Biosphere)

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📚 ADDITIONAL CONCEPTS (ADVANCED)

🌱 Biosphere:

• Zone where life exists
• Combination of lithosphere, atmosphere, and hydrosphere

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🌏 Earth System:

Earth works as an interconnected system where:

• Energy flows (from Sun)
• Matter cycles (water cycle, carbon cycle)

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🎯 EXAM-IMPORTANT POINTS

• Lithosphere = Land (crust + upper mantle)
• Atmosphere = 5 layers
• Hydrosphere = 71% of Earth surface
• Ozone layer → Stratosphere
• Weather → Troposphere
• Water cycle = continuous process
• Plate tectonics → cause earthquakes & volcanoes