Water

Water Cycle

• Water is present in rivers, lakes, oceans, etc.
• Sun’s heat causes evaporation of water into vapour.
• When water vapour cools, it condenses and forms clouds.
• It falls back to land or sea as rain, snow or sleet.

→ The process of continuous change in water’s form and circulation between oceans, atmosphere and land is called the water cycle.

Terrarium

→ A terrarium is an artificial enclosure for keeping small house plants.

• Fresh water sources: rivers, ponds, springs, glaciers.
• Oceans and seas contain salty water due to dissolved salts like sodium chloride (common salt).

Distribution of Water Bodies

Saline Water

→ Oceans: 97.3%

Fresh Water

• Ice-caps: 2.0%
• Ground Water: 0.68%
• Fresh Water Lakes: 0.0009%
• Inland Seas and Salt Lakes: 0.0009%
• Atmosphere: 0.0019%
• Rivers: 0.0001%

Ocean Circulation

→ Ocean water is always in motion. Movements are broadly categorized as:

• Waves
• Tides
• Currents

Waves

→ When water on the surface of the ocean rises and falls alternately, they are called waves.

→ Earthquakes, volcanic eruptions, underwater landslides can cause huge tidal waves called tsunamis.

• The largest tsunami ever recorded was 150 m high.
• These waves can travel faster than 700 km/h.
• The 2004 tsunami caused massive damage in coastal India, submerging Indira Point in the Andaman & Nicobar Islands.

Tides

→ The rhythmic rise and fall of ocean water twice daily is called a tide.

• High Tide: Water rises to cover much of the shore.
• Low Tide: Water falls to its lowest level and recedes.

Cause of Tides

→ Gravitational pull of the sun and moon causes tides.

→ Water closer to the moon is pulled strongly, causing high tide.

Spring Tide

→ During full and new moon days, the sun, moon and Earth are aligned. This results in the highest tides.

Neap Tide

→ During the first and last quarter of the moon, sun and Earth pull water in different directions, causing low tides.

Importance of Tides

• High tides help ships reach the harbour easily.
• Help in fishing as more fish come near the shore.
• Used to generate electricity in some places.

Ocean Currents

→ Ocean currents are continuous streams of water moving in definite directions.

Types of Ocean Currents

• Warm Ocean Currents: Originate near the equator, move toward poles. Example: Gulf Stream.
• Cold Ocean Currents: Originate from polar areas and flow toward lower latitudes. Example: Labrador Current.

Importance of Ocean Currents

• Influence temperature of coastal areas.
• Regions where warm and cold currents meet are rich in marine life (e.g., Japan, east coast of North America).
• These regions may also have foggy weather, making navigation difficult.

MCQs

1. March 22 is celebrated as World

(a) Earth Day

(b) Environment Day

(c) Water Day

(d) Soil Day

► (c) Water Day

2. During a____ , the ____ blowing at very high speed form huge waves. These may cause tremendous destruction.

(a) Rain, Winds

(b) Storm, Winds

(c) Winds, Storm

(d) Rain, Storm

► (b) Storm, Winds

3. Dead sea in

(a) Jordan

(b) Lebanon

(c) Egypt

(d) Israel

► (d) Israel

4. Amazon river is in

(a) Australia

(b) South America

(c) Europe

(d) Africa

► (b) South America

5. How much percentage of saline water is available on earth surface

(a) 97.5

(b) 98.2

(c) 95.2

(d) 93.5

► (a) 97.5

6. The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the

(a) Liquid cycle

(b) Ocean cycle

(c) Ice cycle

(d) Water cycle

► (d) Water cycle

7. The rhythmic rise and fall of ocean water twice in a day is called a

(a) Wave

(b) Wind

(c) Tide

(d) Current

► (c) Tide

8. ____ are streams of water flowing constantly on the ocean surface in definite directions

(a) High tides

(b) Ocean currents

(c) Wind

(d) Wave

► (b) Ocean currents

9. The major sources of freshwater are as follows except

(a) Ocean

(b) Rivers

(c) Ponds

(d) Glaciers

► (a) Ocean

10. ___ are formed when winds scrape across the ocean surface.

(a) Currents

(b) Waves

(c) Air

(d) Tides

► (b) Waves

11. Indira point was in

(a) Kerala

(b) Lakshadweep

(c) Tamil Nadu

(d) Andaman and Nicobar islands

► (d) Andaman and Nicobar islands

12. What fraction of earth is covered by water

(a) Three-fourth

(b) One-fourth

(c) One-half

(d) One-third

► (a) Three-fourth

13. Tsunami is a

(a) French word

(b) Indian word

(c) Chinese word

(d) Japanese word

► (d) Japanese word

14. Which ocean is the largest?

(a) Arctic

(b) Atlantic

(c) Indian

(d) Pacific

► (d) Pacific

15. The Labrador Ocean current is ___ current while the Gulf Stream is a ___ current

(a) cold, warm

(b) cold, cold

(c) warm, warm

(d) warm, cold

► (a) cold, warm

16. Which river is the longest river in the world

(a) Darling

(b) Ganga

(c) Nile

(d) Amazon

► (c) Nile

17. Following are the movements that occur in oceans except

(a) Tides

(b) Waves

(c) Currents

(d) Wind

► (d) Wind

18. The tsunami of ___ caused widespread damage in the coastal areas of India

(a) 2002

(b) 2001

(c) 2004

(d) 1999

► (c) 2004