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.
πͺ¨ 1. LITHOSPHERE (LAND SPHERE)
π Definition:
The Lithosphere is the outermost solid layer of the Earth, consisting of the crust and the upper part of the mantle.
π Structure of Lithosphere:
1. Crust
- Thin outer layer
- Thickness:
- Oceanic: 5β10 km
- Continental: 30β70 km
- Made of silica and alumina (SIAL)
2. Upper Mantle
- Lies below the crust
- Contains semi-molten rocks
- Helps in plate movement
π Types of Crust:
1. Continental Crust
- Thick and less dense
- Composed mainly of granite
2. Oceanic Crust
- Thin and dense
- Composed mainly of basalt
π 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)
ποΈ Landforms:
- Mountains
- Plateaus
- Plains
- Valleys
β Importance:
- Provides land for living organisms
- Source of minerals and natural resources
- Supports agriculture and human settlements
π«οΈ 2. ATMOSPHERE (AIR SPHERE)
π Definition:
The Atmosphere is the layer of gases surrounding the Earth, held by gravity.
π¬οΈ Composition of Atmosphere:
- Nitrogen β 78%
- Oxygen β 21%
- Argon β 0.93%
- Carbon dioxide β 0.03%
- Other gases (neon, helium, etc.)
π Layers of Atmosphere:
1. Troposphere
- Lowest layer (up to ~12 km)
- Weather occurs here
- Contains 75% of atmospheric mass
2. Stratosphere
- 12β50 km above Earth
- Contains ozone layer
- Temperature increases with height
3. Mesosphere
- 50β80 km
- Coldest layer
- Meteors burn here
4. Thermosphere
- 80β400 km
- Very high temperature
- Ionosphere present (radio communication)
5. Exosphere
- Outermost layer
- Gradually merges into space
π¦οΈ Functions of Atmosphere:
- Provides oxygen for respiration
- Protects Earth from harmful UV rays
- Maintains Earthβs temperature
- Helps in weather and climate formation
- Burns meteors before reaching Earth
π‘οΈ Important Concepts:
- Greenhouse Effect
- Air Pressure
- Winds (global circulation)
- Weather vs Climate
π§ 3. HYDROSPHERE (WATER SPHERE)
π Definition:
The Hydrosphere includes all forms of water on Earth, whether in liquid, solid, or gaseous state.
π Distribution of Water:
- Oceans (Saltwater) β 97%
- Freshwater β 3%
- Glaciers β 69%
- Groundwater β 30%
- Surface water β 1%
π¦ Forms of Water:
- Liquid β Rivers, lakes, oceans
- Solid β Ice caps, glaciers
- Gas β Water vapor
π Water Cycle (Hydrological Cycle):
- Evaporation β Water turns into vapor
- Condensation β Vapor forms clouds
- Precipitation β Rain, snow, etc.
- Runoff β Water flows into rivers/oceans
- Infiltration β Water enters the ground
π Major Water Bodies:
- Oceans
- Seas
- Rivers
- Lakes
- Glaciers
- Groundwater
β Importance:
- Essential for all living organisms
- Regulates Earthβs temperature
- Supports marine ecosystem
- Important for agriculture and industry
π INTERRELATION OF SPHERES
π How They Work Together:
- Atmosphere + Hydrosphere β Rainfall
- Lithosphere + Hydrosphere β Soil formation
- All three β Support life (Biosphere)
π ADDITIONAL CONCEPTS (ADVANCED)
π± Biosphere:
- Zone where life exists
- Combination of lithosphere, atmosphere, and hydrosphere
π Earth System:
Earth works as an interconnected system where:
- Energy flows (from Sun)
- Matter cycles (water cycle, carbon cycle)
π― EXAM-IMPORTANT POINTS
- Lithosphere = Land (crust + upper mantle)
- Atmosphere = 5 layers
- Hydrosphere = 71% of Earth surface
- Ozone layer β Stratosphere
- Weather β Troposphere
- Water cycle = continuous process
- Plate tectonics β cause earthquakes & volcanoes
