# NCERT Solutions for Class 11 Geography Chapter 28 - Water (Oceans)

##### Question 1:

Identify the element which is not a part of the Hydrological cycle:

1. Evaporation
2. Precipitation
3. Hydration
4. Condensation

(c). Hydration

##### Question 2:

The average depth of continental slope varies between:

1. 2–20 m
2. 200-2,000 m
3. 20-200 m
4. 2,000-20,000 m

(b). 200-2,000 m

##### Question 3:

Which one of the following is not a minor relief feature in the oceans?

1. Seamount
2. Atoll
3. Oceanic Deep
4. Guyot

(c). Oceanic Deep

##### Question 4:

Salinity is expressed as the amount of salt in grams dissolved in sea water per:

1. 10 gm
2. 1,000 gm
3. 100 gm
4. 10,000 gm

(b). 1000 gm

##### Question 5:

Which one of the following is the smallest oceans?

1. Indian Ocean
2. Arctic Ocean
3. Atlantic Ocean
4. Pacific Ocean

(c). Arctic Ocean

##### Question 6:

Why do we call the earth a Blue Planet?

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?

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.

##### Question 9:

What is a thermocline?

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?

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?

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?

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.