Question 1:
Identify the element which is not a part of the Hydrological cycle:
- Evaporation
- Precipitation
- Hydration
- Condensation
Answer:
(c). Hydration
Question 2:
The average depth of continental slope varies between:
- 2–20 m
- 200-2,000 m
- 20-200 m
- 2,000-20,000 m
Answer:
(b). 200-2,000 m
Question 3:
Which one of the following is not a minor relief feature in the oceans?
- Seamount
- Atoll
- Oceanic Deep
- Guyot
Answer:
(c). Oceanic Deep
Question 4:
Salinity is expressed as the amount of salt in grams dissolved in sea water per:
- 10 gm
- 1,000 gm
- 100 gm
- 10,000 gm
Answer:
(b). 1000 gm
Question 5:
Which one of the following is the smallest oceans?
- Indian Ocean
- Arctic Ocean
- Atlantic Ocean
- Pacific Ocean
Answer:
(c). Arctic Ocean
Question 6:
Why do we call the earth a Blue Planet?
Answer:
Planet Earth is often called water planet or blue planet, because of abundance of water on its surface. The water bodies cover 71 per cent of earth's surface, 60.7 per cent of the total area lies in the northern hemisphere and 80.9 per cent in the southern hemisphere. If we take into account only the water surface of the earth, then 43 per cent lies in the northern hemisphere and 57 per cent in ther southern hemisphere.
Question 7:
What is a continental margin?
Answer:
The continental shelf forms the edge of the continents. The continental margin is the zone of the ocean floor that separates the thin oceanic crust from thick continental crust. Together, the continental shelf, continental slope, and continental rise are called continental margin.
Question 8:
List out the deepest trenches of various oceans.
Answer:
Question 9:
What is a thermocline?
Answer:
The temperature-depth profile of the ocean water shows that the temperature decreases with increasing depth. The second layer of ocean water, from where there is a rapid decrease of temperature, is called the thermocline.
Question 10:
When you move into the ocean, what thermal layers would you encounter? Why the temperature varies with depth?
Answer:
The temperature structure of oceans can be
described as a three-layer system from surface to the
bottom.
(a) The first layer represents the top layer of warm
oceanic water and it is about 500m thick with
temperatures ranging between 20° and 25° C.
(b) The second layer called the thermocline layer and
is characterised by rapid decrease in temperature with
increasing depth. The thermocline is 500 -1,000 m thick.
(c) The third layer is very cold and extends upto the
deep ocean floor.
Question 11:
What is salinity of water?
Answer:
The degree of saltness of water is called Salinity. Salinity is the term used to define the total content of dissolved salts in sea water. It is an important property of ocean water. Along with ocean water, rainwater also contains salts, which makes it salty.
Question 11:
How are various elements of Hydrological cycle interlinked?
Answer:
Water through evaporation, from ocean reaches
as water vapour into atmosphere. This water vapour
returns to land in the form of rainfall. This is known as
Hydrological Cycle. The Hydrological cycle is expressed
mathematically as :
RF = RO + ET
Rainfall = Run off + Evatranspiration
Question 12:
Examine the factors that control the distribution of temperature of the oceans.
Answer:
Temperature of the oceans. Water warms
up and cools down much more slowly than the land.
Therefore, the temperature of the ocean water varies
from place to place, both at the surface and at great
depths. The variation of temperature of the oceans
depends upon the following factors :
1. Latitude. In general, the temperature of ocean
water decreases away from the equator. The highest
temperature 26° C is found on the equator. The
temperature decreases polewards. At 70° latitude, the
temperature of ocean water is only 5° C.
2. Prevailing winds. The prevailing winds
displace the upper surface of the ocean water so that
the cooler water from below comes up. This upwelling
of water decreases the temperature. Due to upwelling
of water by trade winds temperature is lower on the
eastern than on the western coast.
3. Ocean currents. Ocean currents tend to equalise
the temperature of the oceans. Warm currents raise
the temperature, while cold currents lower the
temperature of ocean water.
N. W. Europe experiences a winter temperature of
5°C due to warm Gulf stream current but Eastern parts
of Canada have a temperature of 2° C due to cold Labrador
current.
4. Location of land-masses. Location of landmasses
affects the temperature of small enclosed seas.
A temperature of 30° C is recorded in Red Sea located
in tropical region. But in Baltic Sea, located high
latitudes, temperature of ocean water is only 5° C.
5. Salinity. The temperature of ocean water varies
with salinity. The greater the salinity, the higher is
the temperature.
6. Depth of the Ocean. Generally, the water
temperature decreases with depth, but the rate of
decrease of temperature is not equal at all depths. The
temperature falls from 15° C to 2° C between the
surface and the depth of 1800 metres. Between 1800
metres and 4000 metres, the temperature decreases
from 2° C to 1.6° C.
7. Location of submarine ridges. The
submarine ridges do not allow the mixing of water at
depths in adjacent seas. The temperature of the
enclosed sea is different from that of the open seas.