Notes For All Chapters – Geography Class 6
1. What is the Hydrosphere?
- The hydrosphere includes all the water bodies on Earth.
- It consists of oceans, seas, rivers, lakes, reservoirs, and groundwater.
- 97.7% of Earth’s water is found in oceans.
2. Major Oceans of the World
| Ocean | Area (sq. km.) |
|---|---|
| Pacific Ocean | 166,240,977 |
| Atlantic Ocean | 86,557,402 |
| Indian Ocean | 73,426,163 |
| Southern Ocean | 20,327,000 |
| Arctic Ocean | 13,224,479 |
- The Pacific Ocean is the largest and deepest ocean.
- The Atlantic Ocean is used most for trade and transport.
- The Indian Ocean is important for monsoons and marine trade.
- The Southern and Arctic Oceans have extremely cold temperatures.
3. Why is Ocean Water Salty?
Ocean water contains salt and minerals that make it salty.
Sources of salt in oceans:
- Rivers bring minerals and salts into the ocean.
- Volcanoes under the sea release gases and minerals.
- Dead plants and animals in the ocean decompose and release minerals.
The Dead Sea has the highest salinity (332 parts per thousand).
4. Importance of Oceans
1) Source of Food
- Oceans provide fish, prawns, crabs, and other seafood.
- Marine animals are also used for fertilizers and medicines.
2) Control Climate
- Oceans absorb and release heat, affecting weather and monsoons.
- Coastal areas have a moderate climate because of ocean winds.
3) Rain and Water Cycle
- Oceans are the main source of rain through evaporation and clouds.
- Rainwater fills rivers, lakes, and groundwater, which returns to oceans.
4) Transport and Trade
- Ships and boats use oceans for cheap and efficient transport.
- Many countries like Spain, Norway, and Japan depend on ocean trade.
5) Natural Resources
- Oceans provide oil, natural gas, salt, iron, manganese, cobalt, and pearls.
- In some places, ocean water is converted into drinking water (e.g., Dubai).
6) Protection and Biodiversity
- Mangrove forests grow near coastal areas and protect land from storms.
- Oceans support plankton, fish, whales, corals, and other marine life.
5. What are Ocean Currents?
- Ocean currents are continuous movements of ocean water.
- Warm currents move from the Equator to the Poles (make areas warmer).
- Cold currents move from the Poles to the Equator (make areas cooler).
Effect on Climate:
- Warm currents increase temperatures in colder regions.
- Cold currents cool down hot coastal areas.
6. Difference Between Coastal and Inland Climate
| Feature | Coastal Climate (Near the sea) | Inland Climate (Far from the sea) |
|---|---|---|
| Temperature | Moderate, does not change much | Extreme, very hot or very cold |
| Day-Night Difference | Small | Large |
| Example | Mumbai, Chennai | Nagpur, Delhi |
7. Ocean Transport
- Waterways are cheaper and can carry heavy goods over long distances.
- Ships transport coal, crude oil, minerals, and food grains.
- Ocean currents help ships move faster and save fuel.
8. Ocean Pollution and Its Effects
Causes of Ocean Pollution:
- Oil spills from ships pollute ocean water.
- Dumping of industrial waste and sewage into the sea.
- Plastic and garbage thrown into oceans harm marine life.
- Overfishing reduces fish populations.
- Cutting of mangrove forests destroys coastal ecosystems.
Effects of Ocean Pollution:
- Marine animals like whales, turtles, and dolphins are in danger.
- Polluted oceans cause climate changes and rising sea levels.
- Water pollution affects fisheries and human health.
Ways to Reduce Ocean Pollution:
- Stop dumping plastic and chemicals into oceans.
- Protect mangrove forests to save marine life.
- Use eco-friendly fishing and transport methods.
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