1. KEY WORDS:
1. Stream: The ocean water current which flows speedily is called a stream.
2. Drift: The ocean water current which flows slowly is called a drift.
3. Ocean currents: Ocean water moves from one part to another in big streams constantly in a definite direction called ocean currents
4. Transpiration: Transpiration is the process in which plants release the water in the form of vapour through the leaves.
II. SHORT ANSWERS:
1. What do you think Hydrological cycle?
A.
1. Hydrological cycle is the circulation of water in different forms i.e., liquid, solid and gaseous phases.
2. It also refers to the continuous exchange of water between the oceans, atmosphere, land surface, sub surface and all the living organism.
2. What are the stages in the water cycle?
A.
There are six stages in the water cycle.
1. Evaporation,
2. Transportation,
3. Condensation,
4. Precipitation,
5. Run off, and
6. Groundwater
3. What are the differences between oceans and seas?
A.
Oceans:
1. Oceans are the large saline water bodies.
2. They are seperated by the continents.
3. They are not a part or branches of seas.
Seas:
1. Seas are small saline water bodies.
2. They are enclosed by land fully or partially.
3. They are the parts or branches of oceans.
4. Why is the Earth called the blue planet?
A.
1. On the surface of the planet Earth abundant water is called blue planet.
2. About 71% of the Earth is covered with water.
3. It's look in a blue colour from the outer space.
5. What is called panthalsa?
A.
Millions of years ago, oceans were combined together. The single super ocean was known as ‘panthalsa’.
6. What is the importance of Continental Shelf?
A
1. Fish wealth is more in this region.
2. Crude oil, natural gas are found here.
3. Building seaport is possible here.
7. What are called Isobaths?
A.
A line joining points on the sea bed at an equal vertical distance beneath the surface.
Sometimes referred to as depth contours.
8. What is called Isohaline?
A
A line joining the points in the ocean having the same degree of salinity.
9. Name the Highest Salinity in Water bodies?
A.
Highest Salinity in Water bodies:
1) Don Juan Pond – Antarctica – 440%0
2) Lake Retba – Senegal – 400%0
3) Lake Vanda – Antarctica – 350%0
10. What are called ocean currents?
A.
1. The general movement of the mass of water in a fairly defined direction over great distances is called ocean currents.
2. There are two types of ocean currents based on temperature are warm cold ocean currents.
3. There are two types of currents based on the speed are stream and drift.
11. Name lowest Salinity in Water bodies?
A
Lowest Salinity in Water bodies:
1) Baltic Sea – 10%0
2) Hudson Bay – 3-15%0
12. Where did the salt come from and is it the same salt you find on your dining room table?
A.
1. Most of the salt in the oceans come from land.
2. Over millions of years, rain, rivers and streams have washed over rocks containing the compound Sodium Chloride (NaCl), and carried it into the sea.
13. Describe about the Relief of the Ocean.
A.
Ocean floor is divided into four parts:
1. Continental Shelf:
a. It is the border zone between land and sea up to 200 mts depth.
b. It occupies about 7.6% of the ocean area.
c. It is very important for Fish wealth,
Crude oil, natural gas and building seaports.
2. Continental Slope:
a. The Continental slope is spread from 200 mts to 3,000 mts depth, with a complex relief.
b. It comprises of 15% of the ocean area.
c. These are formed by the process of erosion of glaciers and rivers.
3. Deep Sea plain (or) Abyssal Plain:
a. These are the flattest and smoothest regions of the world.
b. The depths vary between 3000-6000 mts.
c. It covers about 76.2% of the ocean basin.
4. Oceanic deeps (or) Trenches:
a. These are large narrow trenches that plunge as great ocean deeps to a depth of 6,000 mts.
b. They are found more close to the continents.
c. They are very significant in the study of plate movements.
14. What are the factors caused Ocean currents?
A.
Ocean currents are caused by:
1. Centrifugal Force:
a. The Centrifugal force at the equator is greater than that at the poles.
b. Because the equatorial water to move towards the poles.
2. Effect of Winds:
a. Due to the frictional gliding of winds, water is dragged along the wind direction.
b. Thus, a wind at the speed of 50 miles per hour, the velocity of current would be 0.75 miles per hour.
3. Precipitation:
a. The equatorial areas receive the greatest rainfall. Hence, the sea level is higher.
b. As a result, water moves north and south from the equator.
4. Solar Energy:
a. The ocean water is about 8 cm higher in level near the equator than in the middle latitudes because water to expand by solar energy.
b. This causes a very slight gradient and water tends to flow down the slope.
5. Other causes:
Salinity, density differences, melting of ice also affect the ocean currents.
15. In which ways oceans are being exploited by us, today?
A.
1. Today, oceans have also fallen victim
to our exploitation.
2. Many large fish like whales have been
disappearing.
3. Oceans have also become dumping ground for plastic and other forms toxic waste.
16. Describe about the salinity of the ocean water?
A.
1. Most of the salt in the oceans come from land.
2. Over millions of years, rain, rivers and streams have washed over rocks containing the compound Sodium Chloride (NaCl), and carried it into the sea.
3. Salinity is the term used to define the total content of dissolved salts in sea water.
4. It is usually expressed as parts per thousand (%0) or PPT.
5. The average salinity of the oceans is 35%0.
6. Salinity of the ocean water changes because evaporation, precipitation, fresh water from the rivers, freezing and thawing of ice etc.,
17. Write about the temperature of the ocean water?
A.
1. The ocean temperature is influenced by latitudes, winds, ocean currents, unequal distribution of land and change of seasons.
2. Normally, the temperature in the
oceans varies from – 2°C to 29°C.
3. Vertical distribution of temperature decreases one goes deep inside the ocean.
4. The fall in temperature is very steep for the first kilometre.
5. After that, there is a steady decline upto a depth of 5 kilometres.
6. The temperature is steady at about 2°C.
18. Give reasons for the low salinity of Baltic sea.
A.
1. Baltic sea is enclosed by Scandinavian peninsula and Finland.
2. Many rivers influx large fresh water resulting lower salinity.
III. IMPROVE YOUR LEARNING:
1. Find the odd one out and give an explanation for your choice.
I) a) evaporation b) condensation c) salination d) precipitation
A.
Salination (c) is odd one, remaining all related to the water cycle
II) a) tectonics b) centrifugal force c) solar energy d) precipitation
A.
Tectonics (a) is odd one, Remaining all are the factors that affect ocean currents.
2. Correct the false statements.
a) Ocean trenches can be located near the continents
b) Relief features of the oceans are like plains
c) Most salt in the seas is washed into it from land over centuries
d) Temperature of ocean water remains the same across the globe
A.
False statements (b) and (d)
b) Relief features of the oceans are Continental shelf, Continental slope, Trenches, Deep sea plains and Ridges.
d) Temperature of ocean water varies from place to place across the globe.
3. Do you think that the description of blue planet is accurate? Describe any one way in which your activity impacts its oceans.
A.
Yes , I do think that the description of blue planet is accurate,
1. Three fourths of the earth's surface is covered with water bodies (71%) and when looked from the space our earth appears blue .
2. This is largely due to the earth's atmosphere being blue and blue light is scattered in all directions.
3. The huge oceans also reflects the atmospheric blue colour.
4. Why are there differences in the salinity of oceans?
A.
Factors affecting salinity of the Ocean:
1. Evaporation and precipitation.
2. In coastal regions, by the fresh water flow from rivers and in Polar regions, by the process of freezing and thawing of ice.
3. Winds by transferring water to other areas.
4. The ocean currents.
5. How is human life dependent upon oceans?
A.
1. It is strange that most life on earth is found under water bodies.
2. Oceans are source of food like fishes and salt are found in abundance.
3. Chlorine, fluorine, iodine and mineral oil are also extracted from oceans.
4. They are used for generation of water power. 5. Some rare gems and pearls are found here.
6. Oceans largely contribute to the weather phenomena through hydrological cycle.
7. They are used as trade routes for international trade.
6. Observe the map 1 on page 35 and write down the names of a few warm and cold currents.
A.
Some warm currents:
1. Equatorial current.
2. Gulf stream.
3. North Pacific current.
4. Brazil current.
Some cool currents:
1. Labrador current.
2. Greenland current.
3. West wind drift.
4. East wind drift.
7. Read the para ‘Ocean as a Resource’ on page 33 and comment on it.
Ocean as a Resource: Most life on earth is under the water. Human beings still have not finished identifying all the different forms of life in the oceans. Human beings have depended on oceans for their food and livelihood from the ancient times. Oceans provided abundant food resources like fish and salt. We also use the sand, gravel, etc. for our industries or housing. Humans extract minerals like chlorine, fluroine, iodine from it. Ocean waves are used for generating power. Ocean floor is mined for oils. Oceans also provide us with gems and pearls. For centuries, we have created our civilisations on its shores and traded across with each other travelling on them.
A.
1. The ocean is one of earth's most valuable natural resources.
2. It provides food in the form of fish and shell fish.
3. It is used for transportation - both travelling and shipping.
4. It provides a treasured source of recreation for humans.
5. It is mined for minerals and drilled for crude oil.
IV. CHOOSE THE CORRECT ANSWERS:
*. ................ is the largest ocean ( )
A) Atlantic
B) The Arctic
C) The Indian
D) The Pacific
*River water contains ......... sodium chloride( )
A) 3.5 %
B) 3 %
C) 2 %
D) 9.2 %
*A line joining points on the sea bed at an equal vertical distance beneath the surface ( )
A) Isobar
B) Isotherm
C) Isohyets
D) Isobaths
*Lowest salinity is in ( )
A) Great salt lake
B) Lake Van
C) Baltic sea
D) Red sea
*The salinity of Baltic sea is ( )
A) 330%o
B) 238%o
C) 10%o
D) 240%o.
* .......... Oceanic temperature range is ( )
A) -2°C to 29°C
B ) 2°C to 29°C
C ) -4° C to 35°C
D) none
* .......% of total water on the earth is saline ocean water ( )
A) 68.7%
B) 2.75%
C) 97.25%
D) 29.9%
* ...............is a cyclic resource ( )
A) Water
B) Air
C) Coal
D) Wind
*Largest continental shelf present in. ( )
A) Pacific ocean
B) Arctic ocean
C) Atlantic ocean
D ) Indian ocean
*The line, joining the points in the ocean having the same degree of salinity ( )
A) Isobar
B) Isohyets
C) Isohaline
D) Isobaths
*. ............ ocean separates America from Europe and Africa ( )
A) The Atlantic ocean
B) The Pacific ocean
C) The Indian ocean
D) The Antarctic ocean
*. ................. is the smallest ocean ( )
A) The Atlantic
B) The Arctic
C) The Antarctic
D) The India
*The Highest salinity is in ............. ( )
A) Don Juan Pond
B) Kolleru lake
C) Dal lake
D) Lake sambar
* ......... is average salinity of the oceans ( )
A) 3.5%
B) 35 %o
C) 35 %
D) 3.5 %o
* ............... consists the highest salinity ( )
A) Dead sea
B) Lake van
C) Baltic sea
D) Don Juan Pond
* ....... are the flattest and smoothe regions of the world ( )
A) The Continental shelf
B) The Continental slope
C) Deep Sea plains
D) Oceanic deeps
*Releasing water vapor to the air by plants is called ( )
A) precipitation
B) condensation
C) transpiration
D) precipitation
*Forming tiny droplets and clouds by water vapor is called .............. ( )
A) transpiration
B) condensation
C) evaporation
D) evapotranspiration
*. .............% of the total amount of fresh water on the earth is in lakes, reservoirs and river systems. ( )
A) 29.9%
B) 68.7%
C) 0.26%
D) 2.75%
* .......... is expressed as parts per thousand (PPT) or %o. ( )
A) Salinity of ocean
B) Density of ocean
C) distance of oceans
D) Pressure on oceans
*First successful worldwide deep sea exploration was conducted with ( )
A) Java
B) Naves
C) Horizon
D) Challenger
* ............. occupies more ocean area ( )
A) Continental shelf
B) Continental slope
C) Deep sea plain
D) Trenches
