The Earth is composed of three major spheres that interact with each other:
- Lithosphere (Land)
- Atmosphere (Air)
- Hydrosphere (Water)
These together make Earth a life-supporting planet.
🪨 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.
📊 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
🌎 Types of Crust:
1. Continental Crust
- Thick and less dense
- Composed mainly of granite
2. Oceanic Crust
- Thin and dense
- Composed mainly of basalt
🌋 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:
- Convergent (plates collide)
- Divergent (plates move apart)
- Transform (plates slide past each other)
🏞️ Landforms:
- Mountains
- Plateaus
- Plains
- Valleys
⭐ Importance:
- Provides land for living organisms
- Source of minerals and natural resources
- Supports agriculture and human settlements
🌫️ 2. ATMOSPHERE (AIR SPHERE)
📌 Definition:
The Atmosphere is the layer of gases surrounding the Earth, held by gravity.
🌬️ Composition of Atmosphere:
- Nitrogen – 78%
- Oxygen – 21%
- Argon – 0.93%
- Carbon dioxide – 0.03%
- Other gases (neon, helium, etc.)
🌍 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
🌦️ 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
🌡️ Important Concepts:
- Greenhouse Effect
- Air Pressure
- Winds (global circulation)
- Weather vs Climate
💧 3. HYDROSPHERE (WATER SPHERE)
📌 Definition:
The Hydrosphere includes all forms of water on Earth, whether in liquid, solid, or gaseous state.
🌊 Distribution of Water:
- Oceans (Saltwater) – 97%
- Freshwater – 3%
- Glaciers – 69%
- Groundwater – 30%
- Surface water – 1%
💦 Forms of Water:
- Liquid → Rivers, lakes, oceans
- Solid → Ice caps, glaciers
- Gas → Water vapor
🔄 Water Cycle (Hydrological Cycle):
- Evaporation – Water turns into vapor
- Condensation – Vapor forms clouds
- Precipitation – Rain, snow, etc.
- Runoff – Water flows into rivers/oceans
- Infiltration – Water enters the ground
🌊 Major Water Bodies:
- Oceans
- Seas
- Rivers
- Lakes
- Glaciers
- Groundwater
⭐ Importance:
- Essential for all living organisms
- Regulates Earth’s temperature
- Supports marine ecosystem
- Important for agriculture and industry
🔗 INTERRELATION OF SPHERES
🌍 How They Work Together:
- Atmosphere + Hydrosphere → Rainfall
- Lithosphere + Hydrosphere → Soil formation
- All three → Support life (Biosphere)
📚 ADDITIONAL CONCEPTS (ADVANCED)
🌱 Biosphere:
- Zone where life exists
- Combination of lithosphere, atmosphere, and hydrosphere
🌏 Earth System:
Earth works as an interconnected system where:
- Energy flows (from Sun)
- Matter cycles (water cycle, carbon cycle)
🎯 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