Four Domains of the Earth
1. Lithosphere (solid land)
2. Hydrosphere (water)
3. Atmosphere (air)
4. Biosphere (life)
Lithosphere
Solid outer crust of the Earth
• Continents (7): Asia (largest), Africa, North America, South America, Antarctica, Europe, Australia (smallest)
• Highest point: Mount Everest (8848 m)
• Deepest point on land: Dead Sea (-399 m)
Hydrosphere
All water bodies (97% oceans, 3% fresh water)
• Oceans: Pacific (largest & deepest), Atlantic, Indian, Southern, Arctic (smallest)
• Mariana Trench (Pacific) – deepest point (-11,034 m)
Atmosphere
Blanket of air surrounding Earth
• Layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere
• Nitrogen 78%, Oxygen 21%, others 1%
Biosphere
Narrow zone where land, water, and air interact to support life
• Plant & animal kingdom
UPSC/SSC Must-Know Facts
- Asia – largest continent
- Australia – smallest continent
- Pacific – largest & deepest ocean
- Arctic – smallest ocean
- Mariana Trench – deepest point on Earth (-11,034 m)
- Mount Everest – highest point (8848 m)
- Dead Sea – lowest point on land
- 71% Earth surface = water → Blue Planet
- Oxygen (21%) essential for life
- Biosphere = interaction of three domains
Q1. Name the four major domains of the Earth and explain any two.
Answer: The four domains are Lithosphere, Hydrosphere, Atmosphere, and Biosphere.
• Lithosphere: Solid crust → continents & ocean floors
• Hydrosphere: All water bodies → oceans cover 71% of Earth
Q2. Why is the Earth called the ‘Blue Planet’?
Answer: Because more than 71% of the Earth’s surface is covered with water (mostly oceans), it appears blue from space.
Q3. Name the continents and oceans in order of their size.
Answer:
Continents: Asia > Africa > North America > South America > Antarctica > Europe > Australia
Oceans: Pacific > Atlantic > Indian > Southern > Arctic
Q4. What is Biosphere? Why is it important?
Answer: The narrow zone where lithosphere, hydrosphere, and atmosphere meet and support life. It is important because it sustains all living organisms.
Q5. Which is the deepest point on Earth and where is it located?
Answer: Mariana Trench in the Pacific Ocean (-11,034 m).