Geography Notes Chapter 6 Importance of Oceans Class 6 Maharashtra Board

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

• 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:

1. Rivers bring minerals and salts into the ocean.
2. Volcanoes under the sea release gases and minerals.
3. 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

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:

1. Oil spills from ships pollute ocean water.
2. Dumping of industrial waste and sewage into the sea.
3. Plastic and garbage thrown into oceans harm marine life.
4. Overfishing reduces fish populations.
5. 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.