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Question 1.
Which is the process through which water continuously changes its form?
(a) Water cycle
(b) Food cycle
(c) Rain
(d) All of these

Question 2.
Which water is salty?
(a) River water
(b) Pond water
(c) Rain water
(d) Sea water

Question 3.
Which one of the following is an artificial enclosure for keeping small house plants?
(a) Terrarium
(b) Thermosphere
(c) Climate
(d) Evaporation

Question 4.
Sea water contains
(a) 97.3% of salt
(b) 2% of salt
(c) 0.68% of salt
(d) 0.973% of salt

Question 5.
Which day of the year is celebrated as Water Day?
(a) 26 January
(b) 15 January
(c) 15 August
(d) 22 Marc

Question 6.
The movements that occur in oceans can be broadly called
(a) wave
(b) circulation
(c) water cycle
(d) all of these

Question 7.
Which is the Japanese word which means ‘Harbour Waves’?
(a) Tsunami
(b) Sea wave
(c) Ocean wave
(d) None of these

Question 8.
When did Tsunami strike the Indian ocean?
(a) 26 December, 2004
(6) 26 December, 2005
(c) 26 December, 2006
(d) 26 December, 2007

Question 9.
The largest Tsunami wave travels at the speed of
(a) more than 700 km per hour
(b) more than 500 km per hour
(c) more than 250 km per hour
(d) more than 100 km per hour

Question 10.
The rhythmic rise and fall of ocean water twice in a day is known as
(a) tide
(b) wave
(c) ocean current
(d) none of these

Question 11.
The Labrador and Gulf stream are the examples of:
(a) Tides
(b) Ocean currents
(c) Tsunami
(d) Waves

Match the contents of Column A with that of Column B

Fill in the blanks with appropriate words:

1. The major sources of fresh water are rivers and ……………

2. About ………….. % of water is present in the oceans and …………….. % as ice-caps.

3. The movements that occur in oceans are waves, …………. and ………….

4. …………. Point in the Andaman and Nicobar islands got submerged after the tsunami of 2004.

5. High tides help in ………….. and fishing.

6. …………. sea is the largest lake.

State whether the given statements are true or false.

1. We have about 0.68% of water as ground water.

2. Ocean water is calm and still.

3. Tsunami can be caused by underwater landslides.

4. Tides are highest on a full or new moon day.

5. Cold currents carry water from lower latitudes to poles.

6. Tides help in generating electricity.

Question 1.
When you think of water, what images came to your mind?
Answer:
Three states of water: solid, liquid and gaseous.

• Water running in rivers, canals, streams etc.
• Frozen and moving like glaciers.
• In the form of steam (evaporation)
• In the form of droplets (condensation)
• Falling as rainfall (Rainfall)
• As ground water/Water in taps.
• In the wells, ponds, pools etc

Question 2.
Where do the puddles of water vanish?
Answer:
Most of the water percolates into the ground.

• The sun’s heat evaporates the water as vapours. On cooling these vapours condenses and forms clouds
• Then this water may fall on land or sea as rain, snow or sleet.

Question 3.
What is water cycle?
Answer:
The continuous circulation of water between oceans, atmosphere and land is called water cycle.

Question 4.
What is a terrarium?
Answer:

• A terrarium is an artificial enclosure used for keeping small house plants.
• Our earth is like a terrarium.

Question 5.
Why is our earth like a terrarium?
Answer:
Our earth is like a terrarium as the water which existed centuries ago still exists. The water used to irrigate fields in Haryana might have in Amazon River centuries ago.

Question 6.
Name the sources of fresh water.
Answer:

• Rainfall, snow, rivers, ponds, springs and glaciers etc.
• Water from underground.

Question 7.
Why is sea water salty?
Answer:
There is a large amount of water in seas and oceans but it is salty or saline. It is because it contains a large amount of dissolved salts like sodium chloride or common salt.

Distribution of Water Bodies

Question 1.
Define salinity.
Answer:
Salinity is the amount of salt in grams present in 1000 grams of water. The average salinity of oceans is 35 parts per thousand (= 0.035%)

Question 2.
Discuss the distribution of water bodies.
Answer:

• Nearly 75% of the earth’s surface is covered with water.
• There is more water than land on the earth, still so many countries face water scarcity due to the fact that most of this water is salty or it is polluted beyond use.
• Moreover all the water on the earth is not available to us.
• The following table gives the distribution of water in percentage.

Question 3.
Why is water important to us? Suggest few ways to conserve water.
Answer:
Water is very necessary for us. Water alone can quench the thirst thirsty.
Water is needed for survival of plant and animal life.
Water is very essential and we should conserve it:

• By not wasting it during brushing, bathing, washing etc.
• By trapping the rain water by water shed development or rain water harvesting.
• By recycling water.
• By making check dams and bunds on the fields etc.

Question 4.
Swimmers can float in dead sea. Give reasons.
Answer:
Dead Sea in Israel has salinity of 45 parts per thousand and there the water is dense making it easier for swimmers to float.

Ocean Circulation

Question 1.
What is so magical or fascinating about sea?
Answer:
The continuous movement of ocean water is fascinating. The wet sand on beach, sea birds, the salty cool breeze, rhythmic movement of waves attracts one and all. On the other hand the water of ponds, lakes etc is calm.

Question 2.
Which movements occur in oceans?
Answer:The movements of oceans are categorized as tides, currents and waves.

Waves

Question 1.
What are sea waves?
Ans,
Sea Waves:

• When the water on the surface of the ocean rises and falls alternately, they are called waves.
• When we are playing throw ball on the beach and the ball falls into the water, it begins to go up and down.
• It is fun that the ball gets washed back to the shore by the waves.

Question 2.
How are Tsunamis formed? How do they cause destruction?
Answer:
Tsunami is a Japanese word meaning harbour waves.

• Winds blowing at high speed during a storm form huge waves.
• An earthquake, volcanic eruption or underwater landslides can shift large amount of ocean water.
• These tidal waves called Tsunami may be as high as 15 m. It travels at a speed of more than 700 km/hr.
• The areas near the coasts get submerged and it leads to earthquakes also.

Question 1.
Briefly write about the sequence of events leading to Tsunami of 2004 in the Indian Ocean.
Answer:
Tsunami of 26 December 2004 was the result of the earthquake that had its epicentre close to western boundary of Sumatra. It caused havoc in the Indian Ocean.

• Due to the earthquake measuring 9.0 on Richter scale the Indian plate went under Burma plate.
• The ocean floor was displaced by about 10-20 m. Huge mass of ocean water flowed to fill the gap.
• After thrusting the Indian plate and Burma plate, this water rushed back towards the coastline.
• Tsunami at the speed of 800km /hr washed some of the islands in the Indian Ocean.
• As the wave moved away from the epicentre of earthquake the speed declined 700-900km/hr to 70-80km/hr.
• Waves travelled up to a depth of 3 km from the coast:

Question 4.
What were the effects of the Tsunami?
Ans.
Tsunami caused severe destruction.

• Some of the islands of Indian Ocean were completely washed away.
• Indira point in Andaman got completely submerged.
• More than 10,000 people were killed and more than a lakh of houses were affected.
• Coastal areas of Tamil Nadu. Kerala, Puducherry, Andhra Pradesh and the Andaman and Nicobar islands were worst affected.

Question 5.
Can such an event be predicted in advance?
Answer:
Earthquake cannot be predicted in advance but it is possible to give 3-4 hour notice of potential Tsunami. Such system are there in Pacific Ocean but not in Indian Ocean. Seismic activity and Tsunami threat is higher in the Pacific.

Question 6.
Why was the Tsunami of December 26, 2004 very devastating?
Answer:

• The Tsunami that ravaged the South and South-east Asian coasts in December 2004 was the most devastating Tsunami in the last several hundred years.
• The large damage caused to life and property was primarily a result of the following:
• lack of monitoring,
• the early warning systems, and
• lack of knowledge among the coast dwellers of the Indian ocean.
• The first indication that Tsunami is approaching was the rapid withdrawal of water from the coastal region.
• It was followed by destructive wave.
• When this happened on the coast, instead of people going to high ground, they started assembling at the coast to view the miracle.
• It resulted in a large casualty of curious onlookers when the gigantic wave-tsunami struck.

Tides

Question 1.
What are tides?
Answer:
The rhythmic rise and fall of ocean water twice a day is called a tide. When water rises to its highest level and covers much of the ocean it is called high tide. During low tide the water falls to its lowest level and recedes from the shore.

Question 2.
Explain Spring and Neap Tides.
Answer:
During the full moon and new moon days, the sun, the moon and the earth are in the same liNe.

• On this day the tides are highest.
• These tides are called Spring Tides.
• But when the moon is in its first and last quarter, the ocean waters get drawn in diagonally opposite direction by the gravitational pull of the sun and the earth.
• It results in low tides.
• These tides are called Neap Tides.

Question 3.
Describe the importance of tides to man.
Answer:

• High tides help in navigation.
• They raise the water level close to the shores.
• This helps the ships to arrive at the harbour more easily.
• The high tides also help in fishing.
• Many more fish come closer to the shore during the high tides.
• This enables fishermen to get a plentiful catch.
• The rise and fall of water due to tides is used to generate electricity in some places like the gulf of Khambant.

Ocean Currents

Question 1.
What are Ocean currents?
Answer:
Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. They may be warm or cold currents:

• Warm currents originate near equator and move towards poles. They bring about warm temperatures over land surfaces, for example Gulf stream.
• Cold currents originate near poles and move towards tropical or lower latitudes. They bring about coolness over land surfaces, for example Labrador current.

Question 2.
Explain the advantages and disadvantages of ocean currents to man.
Answer:
The ocean currents influence the temperature conditions of the coastal areas.

• Warm currents increase the temperature over land surface.
• The areas where warm and cold currents meet, provide the best fishing grounds of the world.
• Seas Around Japan and the eastern coast of North America are such examples.
• The areas where a warm and cold current meet, also experience foggy weather making it difficult for navigation.

Question 3.
Seas around Japan are good fishing ground but difficult for navigation. Give reasons.
Answer:
Cold and warm currents meet and create good fishing grounds around Japan and Eastern Coast of North America.